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  • American Association for the Advancement of Science (AAAS)
  • American Meteorological Society
  • 2005-2009  (20,678)
  • 1995-1999  (16,015)
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  • 1
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    Aegean Sea Water Masses during the Early Stages of the Eastern Mediterranean Climatic Transient (2007)
    American Meteorological Society
    Details
    Publication Date: 2021-06-08
    Description: The Aegean water masses and circulation structure are studied via two large-scale surveys performed during the late winters of 1988 and 1990 by the R/V Yakov Gakkel of the former Soviet Union. The analysis of these data sheds light on the mechanisms of water mass formation in the Aegean Sea that triggered the outflow of Cretan Deep Water (CDW) from the Cretan Sea into the abyssal basins of the eastern Mediterranean Sea (the so-called Eastern Mediterranean Transient). It is found that the central Aegean Basin is the site of the formation of Aegean Intermediate Water, which slides southward and, depending on their density, renews either the intermediate or the deep water of the Cretan Sea. During the winter of 1988, the Cretan Sea waters were renewed mainly at intermediate levels, while during the winter of 1990 it was mainly the volume of CDW that increased. This Aegean water mass redistribution and formation process in 1990 differed from that in 1988 in two major aspects: (i) during the winter of 1990 the position of the front between the Black Sea Water and the Levantine Surface Water was displaced farther north than during the winter of 1988 and (ii) heavier waters were formed in 1990 as a result of enhanced lateral advection of salty Levantine Surface Water that enriched the intermediate waters with salt. In 1990 the 29.2 isopycnal rose to the surface of the central basin and a large volume of CDW filled the Cretan Basin. It is found that, already in 1988, the 29.2 isopycnal surface, which we assume is the lowest density of the CDW, was shallower than the Kassos Strait sill and thus CDW egressed into the Eastern Mediterranean.
    Description: Published
    Description: 1841-1859
    Description: JCR Journal
    Description: reserved
    Keywords: Aegean Sea ; Water Masses ; 03. Hydrosphere::03.03. Physical::03.03.03. Interannual-to-decadal ocean variability
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 2
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    Gulf Stream Variability in Five Oceanic General Circulation Models (2008)
    American Meteorological Society
    Details
    Publication Date: 2021-06-01
    Description: Five non-eddy-resolving oceanic general circulation models driven by atmospheric fluxes derived from the NCEP reanalysis are used to investigate the link between the Gulf Stream (GS) variability, the atmospheric circulation, and the Atlantic meridional overturning circulation (AMOC). Despite the limited model resolution, the temperature at the 200-m depth along the mean GS axis behaves similarly in most models to that observed, and it is also well correlated with the North Atlantic Oscillation (NAO), indicating that a northward (southward) GS shift lags a positive (negative) NAO phase by 0–2 yr. The northward shift is accompanied by an increase in the GS transport, and conversely the southward shift with a decrease in the GS transport. Two dominant time scales appear in the response of the GS transport to the NAO forcing: a fast time scale (less than 1 month) for the barotropic component, and a slower one (about 2 yr) for the baroclinic component. In addition, the two components are weakly coupled. The GS response seems broadly consistent with a linear adjustment to the changes in the wind stress curl, and evidence for baroclinic Rossby wave propagation is found in the southern part of the subtropical gyre. However, the GS shifts are also affected by basin-scale changes in the oceanic conditions, and they are well correlated in most models with the changes in the AMOC. A larger AMOC is found when the GS is stronger and displaced northward, and a higher correlation is found when the observed changes of the GS position are used in the comparison. The relation between the GS and the AMOC could be explained by the inherent coupling between the thermohaline and the wind-driven circulation, or by the NAO variability driving them on similar time scales in the models.
    Description: This research was supported by the PREDICATE project of the European Community, and for M. Bentsen by the Research Council of Norway through RegClim, NOClim, and the Programme of Supercomputing.
    Description: Published
    Description: 2119–2135
    Description: 3.7. Dinamica del clima e dell'oceano
    Description: JCR Journal
    Description: reserved
    Keywords: ocean modelling ; gulf stream variability ; 03. Hydrosphere::03.01. General::03.01.03. Global climate models
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 3
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    Effects of Land-Surface-Vegetation on theboreal summer surface climate of a GCM (2007)
    American Meteorological Society
    Details
    Publication Date: 2020-11-19
    Description: A land surface model (LSM) has been included in the ECMWF Hamburg version 4 (ECHAM4) atmospheric general circulation model (AGCM). The LSM is an early version of the Organizing Carbon and Hydrology in Dynamic Ecosystems (ORCHIDEE) and it replaces the simple land surface scheme previously included in ECHAM4. The purpose of this paper is to document how a more exhaustive consideration of the land surface–vegetation processes affects the simulated boreal summer surface climate. To investigate the impacts on the simulated climate, different sets of Atmospheric Model Intercomparison Project (AMIP)-type simulations have been performed with ECHAM4 alone and with the AGCM coupled with ORCHIDEE. Furthermore, to assess the effects of the increase in horizontal resolution the coupling of ECHAM4 with the LSM has been implemented at different horizontal resolutions. The analysis reveals that the LSM has large effects on the simulated boreal summer surface climate of the atmospheric model. Considerable impacts are found in the surface energy balance due to changes in the surface latent heat fluxes over tropical and midlatitude areas covered with vegetation. Rainfall and atmospheric circulation are substantially affected by these changes. In particular, increased precipitation is found over evergreen and summergreen vegetated areas. Because of the socioeconomical relevance, particular attention has been devoted to the Indian summer monsoon (ISM) region. The results of this study indicate that precipitation over the Indian subcontinent is better simulated with the coupled ECHAM4–ORCHIDEE model compared to the atmospheric model alone.
    Description: Published
    Description: 255–278
    Description: 3.7. Dinamica del clima e dell'oceano
    Description: JCR Journal
    Description: partially_open
    Keywords: Land Atmosphere interactions ; Global climate models ; 01. Atmosphere::01.01. Atmosphere::01.01.02. Climate
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 4
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    Using Temperature–Salinity Relations in a Global Ocean Implementation of a Multivariate Data Assimilation Scheme (2008)
    American Meteorological Society
    Details
    Publication Date: 2017-04-04
    Description: In this paper results from the application of an ocean data assimilation (ODA) system, combining a multivariate reduced-order optimal interpolator (OI) scheme with a global ocean general circulation model (OGCM), are described. The present ODA system, designed to assimilate in situ temperature and salinity observations, has been used to produce ocean reanalyses for the 1962–2001 period. The impact of assimilating observed hydrographic data on the ocean mean state and temporal variability is evaluated. A special focus of this work is on the ODA system skill in reproducing a realistic ocean salinity state. Results from a hierarchy of different salinity reanalyses, using varying combinations of assimilated data and background error covariance structures, are described. The impact of the space and time resolution of the background error covariance parameterization on salinity is addressed.
    Description: This work has been funded by the ENACT Project (Contract EVK2-CT2001-00117) for A. Bellucci and P. Di Pietro, and partially by the ENSEMBLES Project (Contract GOCE-CT-2003-505539) for A. Bellucci.
    Description: Published
    Description: 3785-3807
    Description: 3.7. Dinamica del clima e dell'oceano
    Description: JCR Journal
    Description: reserved
    Keywords: ocean modelling ; data assimilation ; reanalysis ; upper ocean variability ; temperature ; Salinity ; 03. Hydrosphere::03.01. General::03.01.04. Ocean data assimilation and reanalysis
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 5
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    Atmospheric horizontal resolution affects tropical climate variability in coupled models (2008)
    American Meteorological Society
    Details
    Publication Date: 2017-04-04
    Description: The effect of horizontal resolution on tropical variability is investigated within the modified SINTEX model, SINTEX-F, developed jointly at INGV, IPSL and at the Frontier Research System. The horizontal resolutions T30 and T106 are investigated in terms of the coupling characteristics, frequency and variability of the tropical ocean-atmosphere interactions. It appears that the T106 resolution is generally beneficial even if it does not eliminate all the major systematic errors of the coupled model. There is an excessive shift west of the cold tongue and ENSO variability, and high resolution has also a somewhat negative impact to the variability in the East Indian Ocean. A dominant two-year peak for the NINO3 variabilty in the T30 model is moderated in the T106 as it shifts to longer time scale. At high resolution new processes come into play, as the coupling of tropical instability waves, the resolution of coastal flows at the Pacific Mexican coasts and improved coastal forcing along the coast of South America. The delayed oscillator seems the main mechanism that generates the interannual variability in both models, but the models realize it in different ways. In the T30 model it is confined close to the equator, involving relatively fast equatorial and near-equatorial modes, in the high resolution, it involves a wider latitudinal region and slower waves. It is speculated that the extent of the region that is involved in the interannual variability may be linked to the time scale of the variability itself.
    Description: This research was partially supported by the Italy–USA Cooperation Program of the Italian Ministry of Environment and by the EU projects ENSEMBLES and DYNAMITE.
    Description: Published
    Description: 730-750
    Description: 3.7. Dinamica del clima e dell'oceano
    Description: JCR Journal
    Description: reserved
    Keywords: coupled models ; tropical variability ; ENSO system ; 03. Hydrosphere::03.01. General::03.01.03. Global climate models
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 6
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    The influence of Tropical Indian Ocean SST on the Indian summer monsoon (2007)
    American Meteorological Society
    Details
    Publication Date: 2017-04-04
    Description: The Indian Summer Monsoon (ISM) is one of the main components of the Asian summer monsoon. It is well known that one of the starting mechanisms of a summer monsoon is the thermal contrast between land and ocean and that sea surface temperature (SST) and moisture are crucial factors for its evolution and intensity. The Indian Ocean, therefore, may play a very important role in the generation and evolution of the ISM itself. A coupled general circulation model, implemented with a high resolution atmospheric component, appears to be able to simulate the Indian summer monsoon in a realistic way. In particular, the features of the simulated ISM variability are similar to the observations. In this study, the relationships between ISM and Tropical Indian Ocean (TIO) SST anomalies are investigated, as well as the ability of the coupled model to capture those connections. The recent discovery of the Indian Ocean Dipole Mode (IODM) may suggest new perspectives in the relationship between ISM and TIO SST. A new statistical technique, the Coupled Manifold, is used to investigate the TIO SST variability and its relation with the Tropical Pacific Ocean (TPO). The analysis shows that the SST variability in the TIO contains a significant portion that is independent from the TPO variability. The same technique is used to estimate the amount of Indian rainfall variability that can be explained by the Tropical Indian Ocean SST. Indian Ocean SST anomalies are separated in a part remotely forced from the Tropical Pacific Ocean variability and a part independent from that. The relationships between the two SSTA components and the Indian monsoon variability are then investigated in detail.
    Description: Published
    Description: 3083-3105
    Description: 3.7. Dinamica del clima e dell'oceano
    Description: JCR Journal
    Description: reserved
    Keywords: Indian Ocean ; monsoon ; 01. Atmosphere::01.01. Atmosphere::01.01.02. Climate
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 7
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    Marine Environment and Security for the European Area (MERSEA) - Towards operational oceanography (2007)
    American Meteorological Society
    Details
    Publication Date: 2017-04-04
    Description: An assessment of the present European operational marine monitoring and forecasting systems shows how observations, atmospheric forcing fields and ocean models combine to make useful oceanographic products possible.
    Description: Published
    Description: 1081-1090
    Description: open
    Keywords: MARINE ENVIRONMENT ; 03. Hydrosphere::03.01. General::03.01.05. Operational oceanography
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 8
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    Interannual to Decadal Climate Predictability in the North Atlantic: A Multi-Model-Ensemble Study (2007)
    American Meteorological Society
    Details
    Publication Date: 2017-04-04
    Description: Ensemble experiments are performed with five coupled atmosphere–ocean models to investigate the potential for initial-value climate forecasts on interannual to decadal time scales. Experiments are started from similar model-generated initial states, and common diagnostics of predictability are used. We find that variations in the ocean meridional overturning circulation (MOC) are potentially predictable on interannual to decadal time scales, a more consistent picture of the surface temperature impact of decadal variations in the MOC is now apparent, and variations of surface air temperatures in the North Atlantic Ocean are also potentially predictable on interannual to decadal time scales, albeit with potential skill levels that are less than those seen for MOC variations. This intercomparison represents a step forward in assessing the robustness of model estimates of potential skill and is a prerequisite for the development of any operational forecasting system.
    Description: Published
    Description: 1195-1203
    Description: JCR Journal
    Description: reserved
    Keywords: Decadal Climate ; North Atlantic ; 03. Hydrosphere::03.01. General::03.01.03. Global climate models ; 03. Hydrosphere::03.02. Hydrology::03.02.05. Models and Forecasts ; 03. Hydrosphere::03.03. Physical::03.03.03. Interannual-to-decadal ocean variability
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 9
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    Tropospheric Comparisons of Vaisala Radiosondes and Balloon-Borne Frost-Point and Lyman-α Hygrometers during the LAUTLOS-WAVVAP Experiment (2008)
    American Meteorological Society
    In:  EPIC3Journal of Atmospheric and Oceanic Technology, American Meteorological Society, 25(2), pp. 149-166, ISSN: 0739-0572
    Details
    Publication Date: 2019-07-17
    Description: The accuracy of all types of Vaisala radiosondes and two types of Snow White chilled-mirror hygrosondes was assessed in an intensive in situ comparison with reference hygrometers. Fourteen nighttime reference comparisons were performed to determine a working reference for the radiosonde comparisons. These showed that the night version of the Snow White agreed best with the references [i.e., the NOAA frost-point hygrometer (FPH) and University of Colorado cryogenic frost-point hygrometer (CFH)], but that the daytime version had severe problems with contamination in the humid upper troposphere. Since the RS92 performance was superior to the other radiosondes and to the day version of the Snow White, it was selected to be the working reference. According to the reference comparison, the RS92 has no bias in the mid- and lower troposphere, with deviations 〈±5% in relative humidity (RH). In the upper troposphere, the RS92 has a 5% RH wet bias, which is partly due to the RS92 time lag error and the termination of the heating cycle. It was shown that the time lag effects relating to Vaisala radiosondes can be corrected. Because these were nighttime comparisons, they can be considered to be free from solar radiation effects. Neither the radiosondes nor the Snow White succeeded in reproducing reference class hygrometer profiles in the stratosphere. According to the 29 radiosonde intercomparisons, the RS92 and the modified RS90 (FN) had the best mutual agreement and no bias. The disagreement is largest (〈±10% RH) at low temperatures (T ≪ −30°C), where the FN underestimated (overestimated) in high (low) ambient RH. In comparison with the RS92, the RS90 had a semilinearly increasing wet bias with decreasing temperature, where the bias was 10% RH at −60°C. The RS80-A suffers from a large temperature-dependent dry bias in high RH conditions, being over 30% RH at −60°C and 5% RH near 0°C. The RS80-A dry bias can be almost totally removed with the correction algorithm by Leiterer et al., which was chosen as the best available. The other approach tested tends to overcorrect in high RH conditions when T 〈 −50°C. For T 〉 −30°C it is ineffective and does not correct the RS80-A dry bias in high ambient RH.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 10
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    The Teleconnection between the Western Indian and the Western Pacific Oceans (2005)
    American Meteorological Society
    Details
    Publication Date: 2021-05-19
    Description: In this study we show a teleconnection pattern relating Outgoing Longwave Radiation (OLR) anomalies over the western Pacific Ocean and sea surface temperature anomalies (SSTA) over the western Indian Ocean over two seasons (Sept-Oct-Nov and Dec-Jan-Feb) at zero lag from observations and atmospheric general circulation model (AGCM) integrations. This teleconnection pattern suggests that a positive SSTA in Sept-Oct-Nov (SON) and Dec-Jan-Feb (DJF) seasons over the western Indian Ocean increases the contemporaneous positive OLR anomalies over the western Pacific Ocean. This teleconnection pattern is also simulated by the Center for Ocean-Land- Atmosphere studies (COLA) AGCM forced with observed SST’s. From the experimental COLA AGCM runs (wherein the Pacific Ocean SST variability is suppressed except for the climatological annual cycle) it is diagnosed that the interannual variability of OLR over the western Pacific Ocean persists because of this teleconnection. In relation to this teleconnection pattern it is shown that there is a significant linear response of the SON and DJF equatorial zonal wind anomaly over the Pacific Ocean to contemporaneous SSTA over the western Indian Ocean which is comparable to that of the eastern and western Pacific Oceans. The experimental AGCM runs clearly show that this response of the equatorial zonal wind anomaly to the western Indian Ocean forcing shifts westward towards the Indian Ocean in the absence of Pacific SST variability.
    Description: Published
    Keywords: Sea surface temperature ; Atmospheric conditions ; Teleconnections
    Repository Name: AquaDocs
    Type: Journal Contribution , Refereed , Article
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  • 11
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    The Role of the Land Surface Background State in Climate Predictability (2005)
    American Meteorological Society
    Details
    Publication Date: 2021-05-19
    Description: Skill in ensemble-mean dynamical seasonal climate hindcasts with a coupled land-atmosphere model and specified observed sea surface temperature is compared to that for long multi-decade integrations of the same model where the initial conditions are far removed from the seasons of validation. The evaluations are performed for surface temperature and compared among all seasons. Skill is found to be higher in the seasonal simulations than the multi-decadal integrations except during boreal winter. The higher skill is prominent even beyond the first month when the direct influence of the atmospheric initial state elevates model skill. Skill is generally found to be lowest during the winter season for the dynamical seasonal forecasts, equal to that of the long integrations, which show some of the highest skill during winter. The reason for the differences in skill during the non-winter months is attributed to the severe climate drift in the long simulations, manifest through errors in downward fluxes of water and energy over land and evident in soil wetness. The drift presses the land surface to extreme dry or wet states over much of the globe, into a range where there is little sensitivity of evaporation to fluctuations in soil moisture. Thus, the land-atmosphere feedback is suppressed, which appears to lessen the model’s ability to respond correctly over land to remote ocean temperature anomalies.
    Description: Center for Ocean-Land-Atmosphere Studies
    Description: Published
    Keywords: Atmosphere-ocean system
    Repository Name: AquaDocs
    Type: Journal Contribution , Refereed , Article
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  • 12
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    A Shallow-CISK-Deep-Equilibrium Mechanism for The Interaction Between Large-Scale Convection and Large-Scale Circulations In The Tropics (2005)
    American Meteorological Society
    Details
    Publication Date: 2021-05-19
    Description: In this paper, the circulations driven by deep heating and shallow heating are investigated through analytically solving a set of linear equations and examining circulations simulated by a dry primitive equation model. Special emphasis is placed on the low-level mass (moisture) convergence associated with the forced circulation and the maintenance of the shallow and deep heat sources. It is found that the forced circulation driven by shallow heating is more likely to be trapped horizontally near the heating area but relatively extended in the vertical. As a consequence, diabatic heating can not balance adiabatic cooling due to upward motion. At the levels slightly above the top of the heating, a negative vertical gradient of temperature perturbation appears. For the atmosphere driven by deep heating, however, the temperature perturbation cannot accumulate because the heating signals propagate away very fast, allowing an approximate equilibrium between the convective diabatic heating and adiabatic cooling due to upward motion. The converged moisture associated with circulation driven by shallow heating exceeds the amount needed to maintain the heat source. However, the circulation driven by deep heating does not feed back effectively to the moisture convergence, and thus can not be self-sustaining.
    Description: Center for Ocean-Land-Atmosphere Studies - Calverton
    Description: Published
    Keywords: Atmospheric circulation
    Repository Name: AquaDocs
    Type: Journal Contribution , Refereed , Article
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  • 13
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    Accuracy of a pulse-coherent acoustic Doppler profiler in a wave-dominated flow (2007)
    American Meteorological Society
    Details
    Publication Date: 2022-05-25
    Description: This paper is not subject to U.S. copyright. The definitive version was published in Journal of Atmospheric and Oceanic Technology 21 (2004): 1448–1461, doi:10.1175/1520-0426(2004)021〈1448:AOAPAD〉2.0.CO;2.
    Description: The accuracy of velocities measured by a pulse-coherent acoustic Doppler profiler (PCADP) in the bottom boundary layer of a wave-dominated inner-shelf environment is evaluated. The downward-looking PCADP measured velocities in eight 10-cm cells at 1 Hz. Velocities measured by the PCADP are compared to those measured by an acoustic Doppler velocimeter for wave orbital velocities up to 95 cm s−1 and currents up to 40 cm s−1. An algorithm for correcting ambiguity errors using the resolution velocities was developed. Instrument bias, measured as the average error in burst mean speed, is −0.4 cm s−1 (standard deviation = 0.8). The accuracy (root-mean-square error) of instantaneous velocities has a mean of 8.6 cm s−1 (standard deviation = 6.5) for eastward velocities (the predominant direction of waves), 6.5 cm s−1 (standard deviation = 4.4) for northward velocities, and 2.4 cm s−1 (standard deviation = 1.6) for vertical velocities. Both burst mean and root-mean-square errors are greater for bursts with ub ≥ 50 cm s−1. Profiles of burst mean speeds from the bottom five cells were fit to logarithmic curves: 92% of bursts with mean speed ≥ 5 cm s−1 have a correlation coefficient R2 〉 0.96. In cells close to the transducer, instantaneous velocities are noisy, burst mean velocities are biased low, and bottom orbital velocities are biased high. With adequate blanking distances for both the profile and resolution velocities, the PCADP provides sufficient accuracy to measure velocities in the bottom boundary layer under moderately energetic inner-shelf conditions.
    Description: This work was funded by the U.S. Geological Survey as part of the Southwest Washington Coastal Erosion Study
    Repository Name: Woods Hole Open Access Server
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  • 14
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    Geophysics: Singing icebergs (2005)
    American Association for the Advancement of Science (AAAS)
    In:  EPIC3Science, American Association for the Advancement of Science (AAAS), 310(5752), pp. 1299-1299, ISSN: 0036-8075
    Details
    Publication Date: 2023-06-13
    Description: 〈jats:p〉Sustained harmonic tremor signals were recorded by the seismographs of the German Neumayer Base seismological network in western Dronning Maud Land, Antarctica. These tremor episodes, lasting up to 16 hours, were recorded up to 820 kilometers from the source. Their spectra show narrow peaks with fundamental frequencies ranging from 0.5 to 6 hertz, more than 30 integer harmonic overtones, and frequency gliding, resembling volcanic tremor. Frequency‐wave number analysis suggested a moving source, which was recognized as iceberg B-09A traveling along the coast of eastern Antarctica. The most probable tremor sources are fluid-flow‐induced vibrations inside the iceberg's tunnel/crevasse systems.〈/jats:p〉
    Repository Name: EPIC Alfred Wegener Institut
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  • 15
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    Stochastic Lagrangian Models of Turbulent Diffusion (1996)
    American Meteorological Society
    Details
    Publication Date: 1996-08-01
    Description: No Abstract available.
    Print ISSN: 0065-9401
    Electronic ISSN: 1943-3646
    Topics: Geography , Geosciences , Physics
    Published by American Meteorological Society
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  • 16
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    Dynamical Diagnosis: A Comparison of Quasigeostrophy and Ertel Potential Vorticity (2008)
    American Meteorological Society
    Details
    Publication Date: 2008-11-01
    Description: Advances in computer power, new forecasting challenges, and new diagnostic techniques have brought about changes in the way atmospheric development and vertical motion are diagnosed in an operational setting. Many of these changes, such as improved model skill, model resolution, and ensemble forecasting, have arguably been detrimental to the ability of forecasters to understand and respond to the evolving atmosphere. The use of nondivergent wind in place of geostrophic wind would be a step in the right direction, but the advantages of potential vorticity suggest that its widespread adoption as a diagnostic tool on the west side of the Atlantic is overdue. Ertel potential vorticity (PV), when scaled to be compatible with pseudopotential vorticity, is generally similar to pseudopotential vorticity, so forecasters accustomed to quasigeostrophic reasoning through the height tendency equation can transfer some of their intuition into the Ertel-PV framework. Indeed, many of the differences between pseudopotential vorticity and Ertel potential vorticity are consequences of the choice of definition of quasigeostrophic PV and are not fundamental to the quasigeostrophic system. Thus, at its core, PV thinking is consistent with commonly used quasigeostrophic diagnostic techniques.
    Print ISSN: 0065-9401
    Electronic ISSN: 1943-3646
    Topics: Geography , Geosciences , Physics
    Published by American Meteorological Society
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  • 17
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    Ensemble Synoptic Analysis (2008)
    American Meteorological Society
    Details
    Publication Date: 2008-11-01
    Description: Synoptic and mesoscale meteorology underwent a revolution in the 1940s and 1950s with the widespread deployment of novel weather observations, such as the radiosonde network and the advent of weather radar. These observations provoked a rapid increase in our understanding of the structure and dynamics of the atmosphere by pioneering analysts such as Fred Sanders. The authors argue that we may be approaching an analogous revolution in our ability to study the structure and dynamics of atmospheric phenomena with the advent of probabilistic objective analyses. These probabilistic analyses provide not only best estimates of the state of the atmosphere (e.g., the expected value) and the uncertainty about this state (e.g., the variance), but also the relationships between all locations and all variables at that instant in time. Up until now, these relationships have been determined by sampling in time by, for example, case studies, composites, and time-series analysis. Here the authors propose a new approach, ensemble synoptic analysis, which exploits the information contained in probabilistic samples of analyses at one or more instants in time. One source of probabilistic analyses is ensemble-based state-estimation methods, such as ensemble-based Kalman filters. Analyses from such a filter may be used to study atmospheric phenomena and the relationships between fields and locations at one or more instants in time. After a brief overview of a research-based ensemble Kalman filter, illustrative examples of ensemble synoptic analysis are given for an extratropical cyclone, including relationships between the cyclone minimum sea level pressure and other synoptic features, statistically determined operators for potential-vorticity inversion, and ensemble-based sensitivity analysis.
    Print ISSN: 0065-9401
    Electronic ISSN: 1943-3646
    Topics: Geography , Geosciences , Physics
    Published by American Meteorological Society
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  • 18
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    Closed Anticyclones of the Subtropics and Midlatitudes: A 54-Yr Climatology (1950–2003) and Three Case Studies (2008)
    American Meteorological Society
    Details
    Publication Date: 2008-11-01
    Description: The pioneering large-scale studies of cyclone frequency, location, and intensity conducted by Fred Sanders prompt similar questions about lesser-studied anticyclone development. The results of a climatology of closed anticyclones (CAs) at 200, 500, and 850 hPa, with an emphasis on the subtropics and midlatitudes, is presented to assess the seasonally varying distribution and hemispheric differences of these features. To construct the CA climatology, a counting program was applied to twice-daily 2.5° NCEP–NCAR reanalysis 200-, 500-, and 850-hPa geopotential height fields for the period 1950–2003. Stationary CAs, defined as those CAs that were located at a particular location for consecutive time periods, were counted only once. The climatology results show that 200-hPa CAs occur preferentially during summer over subtropical continental regions, while 500-hPa CAs occur preferentially over subtropical oceans in all seasons and over subtropical continents in summer. Conversely, 850-hPa CAs occur preferentially over oceanic regions beneath upper-level midocean troughs, and are most prominent in the Northern Hemisphere, and over midlatitude continents in winter. Three case studies of objectively identified CAs that produced heal waves over the United States, Europe, and Australia in 1995, 2003, and 2004, respectively, are presented to supplement the climatological results. The case studies, examining the subset of CAs than can produce heat waves, illustrate how climatologically hot continental tropical air masses produced over arid and semiarid regions of the subtropics and lower midlatitudes can become abnormally hot in conjunction with dynamically driven upper-level ridge amplification. Subsequently, these abnormally hot air masses are advected downstream away from their source regions in conjunction with transient disturbances embedded in anomalously strong westerly jets.
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    An Empirical Perspective on Cold Fronts (2008)
    American Meteorological Society
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    Publication Date: 2008-11-01
    Description: Oklahoma Mesonetwork data are used to illustrate important atmospheric features that are not well shown by the usual synoptic data. For example, some shifts of wind from south to north that are shown as cold fronts on synoptic charts are not cold fronts by any plausible definition. As previously discussed by Fred Sanders and others, such errors in analysis can be reduced by knowledge of the wide variety of weather phenomena that actually exists, and by more attention to temperatures at the earth's surface as revealed by conventional synoptic data. Mesoscale data for four cases reinforce previous discussions of the ephemeral nature of fronts and deficiencies in the usual analyses of cold fronts. One type of misanalyzed case involves post-cold-frontal boundary layer air that is warmer than the prefrontal air. A second type is usually nocturnal, with a rise of local temperature during disruption of an inversion and a wind shift with later cooling that accompanies advection of a climatological gradient of temperature.
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    Back to Norway: An Essay (2008)
    American Meteorological Society
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    Publication Date: 2008-11-01
    Description: The advent of the polar front theory of cyclones in Norway early in the last century held that the development of fronts and air masses is central to understanding midlatitude weather phenomena. While work on fronts continues to this day, the concept of air masses has been largely forgotten, superseded by the idea of a continuum. The Norwegians placed equal emphasis on the thermodynamics of airmass formation and on the dynamical processes that moved air masses around; today, almost all the emphasis is on dynamics, with little published literature on diabatic processes acting on a large scale. In this essay, the author argues that a lack of understanding of large-scale diabatic processes leads to an incomplete picture of the atmosphere and contributes to systematic errors in medium- and long-range weather forecasts. At the same time, modern concepts centered around potential vorticity conservation and inversion lead one to a redefinition of the term "air mass" that may have some utility in conceptualizing atmospheric physics and in weather forecasting.
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    Linking Weather and Climate (2008)
    American Meteorological Society
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    Publication Date: 2008-11-01
    Description: Historically, the atmospheric sciences have tended to treat problems of weather and climate separately. The real physical system, however, is a continuum, with short-term (minutes to days) “weather” fluctuations influencing climate variations and change, and, conversely, more slowly varying aspects of the system (typical time scales of a season or longer) affecting the weather that is experienced. While this past approach has served important purposes, it is becoming increasingly apparent that in order to make progress in addressing many socially important problems, an improved understanding of the connections between weather and climate is required. This overview summarizes the progress over the last few decades in the understanding of the phenomena and mechanisms linking weather and climate variations. The principal emphasis is on developments in understanding key phenomena and processes that bridge the time scales between synoptic-scale weather variability (periods of approximately 1 week) and climate variations of a season or longer. Advances in the ability to identify synoptic features, improve physical understanding, and develop forecast skill within this time range are reviewed, focusing on a subset of major, recurrent phenomena that impact extratropical wintertime weather and climate variations over the Pacific–North American region. While progress has been impressive, research has also illuminated areas where future gains are possible. This article concludes with suggestions on near-term directions for advancing the understanding and capabilities to predict the connections between weather and climate variations.
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    Fred Sanders' Roles in the Transformation of Synoptic Meteorology, the Study of Rapid Cyclogenesis, the Prediction of Marine Cyclones, and the Forecast of New York City's “Big Snow” of December 1947 (2008)
    American Meteorological Society
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    Publication Date: 2008-11-01
    Description: Fred Sanders' career extended over 55 yr, touching upon many of the revolutionary transformations in the field of meteorology during that period. In this paper, his contributions to the transformation of synoptic meteorology, his research into the nature of explosive cyclogenesis, and related advances in the ability to predict these storms are reviewed. In addition to this review, the current status of forecasting oceanic cyclones 4.5 days in advance is presented, illustrating the progress that has been made and the challenges that persist, especially for forecasting those extreme extratropical cyclones that are marked by surface wind speeds exceeding hurricane force. Last, Fred Sanders' participation in a forecast for the historic 1947 snowstorm (that produced snowfall amounts in the New York City area that set records at that time) is reviewed along with an attempt to use today's operational global model to simulate this storm using data that were available at the time. The study reveals the predictive limitations involved with this case based on the scarcity of upper-air data in 1947, while confirming Fred Sanders' forecasting skills when dealing with these types of major storm events, even as a young aviation forecaster at New York's LaGuardia Airport.
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    Finescale Radar Observations of a Dryline during the International H2O Project (IHOP_2002) (2008)
    American Meteorological Society
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    Publication Date: 2008-11-01
    Description: A case study of a double dryline on 22 May 2002 is presented. Mobile, 3-mm-wavelength Doppler radars from the University of Massachusetts and the University of Wyoming (Wyoming cloud radar) were used to collect very fine resolution vertical-velocity data in the vicinity of each of the moisture gradients associated with the drylines. Very narrow (50–100 m wide) channels of strong upward vertical velocity (up to 8 m s–1) were measured in the convergence zone of the easternmost dryline, larger in magnitude than reported with previous drylines. Distinct areas of descending motion were evident to the east and west of both drylines. Radar data are interpreted in the context of other observational platforms available during the International H2O Project (IHOP-2002). a variational ground-based mobile radar data processing technique was developed and applied to pseudo-dual-Doppler data collected during a rolling range-height indicator deployment. It was found that there was a secondary (vertical) circulation normal to the easternmost moisture gradient; the circulation comprised an easterly component near-surface flow to the east, a strong upward vertical component in the convergence zone, a westerly return, flow above the convective boundary layer, and numerous regions of descending motion, the most prominent approximately 3–5 km to the east of the surface convergence zone.
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    The Application of Fred Sanders' Teaching to Current Research on Extreme Cold-Season Precipitation Events in the Saint Lawrence River Valley Region (2008)
    American Meteorological Society
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    Publication Date: 2008-11-01
    Description: Fred Sanders' teaching and research contributions in the area of quasigeostrophic theory are highlighted in this paper. The application of these contributions is made to the topic of extreme cold-season precipitation events in the Saint Lawrence valley in the northeastern United States and southern Quebec. This research focuses on analyses of Saint Lawrence valley heavy precipitation events. Synoptic- and planetary-scale circulation anomaly precursors are typically identified several days prior to these events. These precursors include transient upper-level troughs, strong moisture transports into the region, and anomalously large precipitable water amounts. The physical insight of Fred Sanders' work is used in the analysis of these composite results. Further details of this insight are provided in analyses of one case of heavy precipitation.
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    The Sanders Barotropic Tropical Cyclone Track Prediction Model (SANBAR) (2008)
    American Meteorological Society
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    Publication Date: 2008-11-01
    Description: Sanders designed a barotropic tropical cyclone (TC) track prediction model for the North Atlantic TC basin that became known as the Sanders barotropic (SANBAR) model. It predicted the streamfunction of the deeplayer mean winds (tropical circulation vertically averaged from 1000 to 100 hPa) that represents the vertically averaged tropical circulations. Originally, the wind input for the operational objective analysis (OA) consisted of winds measured by radiosondes and 44 bogus winds provided by analysis at the National Hurricane Center (NHC), which corresponded to the vertically averaged flow over sparsely observed tropical, subtropical, and midlatitude oceanic regions. The model covered a fixed regional area and had a grid size of ~ 154 km. It estimated the initial storm motion solely on the basis of the large-scale flow from the OA, not taking into account the observed storm motion. During 1970, the SANBAR model became the first dynamical TC track model to be run operationally at NHC. Track forecasts of SANBAR were verified from the 1971 TC season when track model verifications began at NHC until its retirement after the 1989 Atlantic TC season. The average annual SANBAR forecast track errors were verified relative to Climatology and Persistence (CLIPER), the standard no-skill track forecast. Comparison with CLIPER determines the skill of track forecast methods. Verifications are presented for two different versions of the SANBAR model system used operationally during 1973–84 and 1985–89. In homogeneous comparisons (i.e., includes only forecasts for the same initial times) for the former period, SANBAR's track forecasts were slightly better than CLIPER at 24–48-h forecast intervals; however, from 1985 to 1989 the average SANBAR track forecast errors from 24–72 h were ~10% more skillful than homogeneous CLIPER track forecasts.
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    Surface Potential Temperature as an Analysis and Forecasting Tool (2008)
    American Meteorological Society
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    Publication Date: 2008-11-01
    Description: In the last decade, Fred Sanders was often critical of current surface analysis techniques. This led to his promoting the use of surface potential temperatures to distinguish between fronts, baroclinic troughs, and non-frontal baroclinic zones, and to the development of a climatology of surface baroclinic zones. In this paper, criticisms of current surface analysis techniques and the usefulness of surface potential temperature analyses are discussed. Case examples are used to compare potential temperature analyses and current National Centers for Environmental Prediction analyses. The 1-yr climatology of Sanders and Hoffman is reconstructed using a composite technique. Annual and seasonal mean potential temperature analyses over the continental United States, southern Canada, northern Mexico, and adjacent coastal waters are presented. In addition, gridpoint frequencies of moderate and strong potential temperature gradients are calculated. The results of the mean potential temperature analyses show that moderate and strong surface baroclinic zones are favored along the coastlines and the slopes of the North American cordillera. Additional subsynoptic details, not found in Sanders and Hoffman, are identified. The availability of the composite results allows for the calculation of potential temperature gradient anomalies. It is shown that these anomalies can be used to identify significant frontal baroclinic zones that are associated with weak potential temperature gradients. Together the results and reviews in this paper show that surface potential temperature analyses are a valuable forecasting and analysis tool allowing analysts to distinguish and identify fronts, baroclinic troughs, and nonfrontal baroclinic zones.
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    Surface Boundaries of the Southern Plains: Their Role in the Initiation of Convective Storms (2008)
    American Meteorological Society
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    Publication Date: 2008-11-01
    Description: The nature of the different types of surface boundaries that appear in the southern plains of the United States during the convectively active season is reviewed. The following boundaries are discussed: fronts, the dryline, troughs, and outflow boundaries, The boundaries are related to their environment and to local topography. The role these boundaries might play in the initiation of convective storms is emphasized. The various types of boundary-related vertical circulations and their dynamics are discussed. In particular, quasigeostrophic and semigeostrophic dynamics, and the dynamics of solenoidal circulations, density currents, boundary layers, and gravity waves are considered. Miscellaneous topics pertinent to convective storms and their relationship to surface boundaries such as along-the-boundary variability, boundary collisions, and the role of vertical shear are also discussed. Although some cases of storm initiation along surface boundaries have been well documented using research datasets collected during comprehensive field experiments, much of what we know is based only on empirical forecasting and nowcasting experience. It is suggested that many problems relating to convective-storm formation need to be explored in detail using real datasets with new observing systems and techniques, in conjunction with numerical simulation studies, and through climatological studies.
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    Strong Surface Fronts over Sloping Terrain and Coastal Plains (2008)
    American Meteorological Society
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    Publication Date: 2008-11-01
    Description: This paper begins with a review of basic surface frontogenesis concepts with an emphasis on fronts located over sloping terrain adjacent to mountain barriers and fronts located in large-scale baroclinic zones close to coastlines. The impact of cold-air damming and differential diabatic heating and cooling on frontogenesis is considered through two detailed case studies of intense surface fronts. The first case, from 17 to 18 April 2002, featured the westward passage of a cold (side-door) front across coastal eastern New England in which 15°–20°C temperature decreases were observed in less than one hour. The second case, from 28 February to 4 March 1972, featured a long-lived front that affected most of the United States from the Rockies to the Atlantic coast and was noteworthy for a 50°C temperature contrast between Kansas and southern Manitoba, Canada. In the April 2002 case most of New England was initially covered by an unusually warm, dry air mass. Dynamical anticyclogenesis over eastern Canada set the stage for a favorable pressure gradient to allow chilly marine air to approach coastal New England from the east. Diabatic cooling over the chilly (5°–8°C) waters of the Gulf of Maine allowed surface pressures to remain relatively high offshore while diabatic heating over the land (31°–33°C temperatures) enabled surface pressures to fall relative to over the ocean. The resulting higher pressures offshore resulted in an onshore cold push. Frontal intensity was likely enhanced prior to leaf out and grass green-up as virtually all of the available insolation went into sensible heating. The large-scale environment in the February–March 1972 case favored the accumulation of bitterly cold arctic air in Canada. Frontal formation occurred over northern Montana and North Dakota as the arctic air moved slowly southward in conjunction with surface pressure rises east of the Canadian Rockies. The arctic air accelerated southward subsequent to lee cyclogenesis–induced pressure falls ahead of an upstream trough that crossed the Rockies. The southward acceleration of the arctic air was also facilitated by dynamic anticyclogenesis in southern Canada beneath a poleward jet-entrance region. Frontal intensity varied diurnally in response to differential diabatic heating. Three types of cyclogenesis events were observed over the lifetime of the event: 1) low-amplitude frontal waves with no upper-level support, 2) low-amplitude frontal waves that formed in a jet-entrance region, and 3) cyclones that formed ahead of advancing upper-level troughs. All cyclones were either nondeveloping or weak developments despite extreme baroclinicity, likely the result of large atmospheric static stability in the arctic frontal zone and unfavorable alongfront stretching deformation. Significant frontal–mountain interactions were observed over the Rockies and the Appalachians.
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    The Fiftieth Anniversary of Sanders (1955): A Mesoscale Model Simulation of the Cold Front of 17–18 April 1953 (2008)
    American Meteorological Society
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    Publication Date: 2008-11-01
    Description: Over 50 yr have passed since the publication of Sanders' 1955 study, the first quantitative study of the structure and dynamics of a surface cold front. The purpose of this chapter is to reexamine some of the results of that study in light of modern methods of numerical weather prediction and diagnosis. A simulation with a resolution as high as 6-km horizontal grid spacing was performed with the fifth-generation-Pennsylvania State University-National Center for Atmospheric Research (PSU-NCAR) Mesoscale Model (MM5), given initial and lateral boundary conditions from the National Centers for Environmental Precipitation-National Center for Atmospheric Research (NCEP-NCAR) reanalysis project data from 17 to 18 April 1953. The MM5 produced a reasonable simulation af the front, albeit its strength was not as intense and its movement was not as fast as was analyzed by Sanders. The vertical structure of the front differed from that analyzed by Sanders in several significant ways. First, the strongest horizontal temperature gradient associated with the cold front in the simulation occurred above a surface-based inversion, not at the earth's surface. Second, the ascent plume at the leading edge of the front was deeper and more intense than that analyzed by Sanders. The reason was an elevated mixed layer that had moved over the surface cold front in the simulation, allowing a much deeper vertical circulation than was analyzed by Sanders. This structure is similar to that of Australian cold fronts with their deep, well-mixed, prefrontal surface layer. These two differences between the model simulation and the analysis by Sanders may be because upper-air data from Fort Worth, Texas, was unavailable to Sanders. Third, the elevated mixed layer also meant that isentropes along the leading edge of the front extended vertically. Fourth, the field of frontogenesis of the horizontal temperature gradient calculated from the three-dimensional wind differed in that the magnitude of the maximum of the deformation term was larger than the magnitude of the maximum of the tilting term in the simulation, in contrast to Sanders' analysis and other previously published cases. These two discrepancies may be attributable to the limited horizontal resolution of the data that Sanders used in constructing his cross section. Last, a deficiency of the model simulation was that the postfrontal surface superadiabatic layer in the model did not match the observed well-mixed boundary layer. This result raises the question of the origin of the well-mixed postfrontal boundary layer behind cold fronts. To address this question, an additional model simulation without surface fluxes was performed, producing a well-mixed, not superadiabatic, layer. This result suggests that surface fluxes were not necessary for the development of the well-mixed layer, in agreement with previous research. Analysis of this event also amplifies two research themes that Sanders returned to later in his career, First, a prefrontal wind shift occurred in both the observations and model simulation at stations in western Oklahoma. This prefrontal wind shift was caused by a lee cyclone departing the leeward slopes of the Rockies slightly equatorward of the cold front, rather than along the front as was the case farther eastward. Sanders' later research showed how the occurrence of these prefrontal wind shifts leads to the weakening of fronts. Second, this study shows the advantage of using surface potential temperature, rather than surface temperature, for determining the locations of the surface fronts on sloping terrain.
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    Must Surprise Snowstorms be a Surprise? (2008)
    American Meteorological Society
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    Publication Date: 2008-11-01
    Description: Today, even with state-of-the-art observational, data assimilation, and modeling systems run routinely on supercomputers, there are often surprises in the prediction of snowstorms, especially the “big ones,” affecting coastal regions of the mid-Atlantic and northeastern United States. Little did the author know that lessons from Fred Sanders' synoptic meteorology class at the Massachusetts Institute of Technology (1967) would later (late 1980s) inspire him to pursue practical issues of predictability in the context of the development of ensemble prediction systems, strategies, and applications for providing information on the inevitable case-dependent uncertainties in forecasts. This paper is a brief qualitative and somewhat colloquial overview, based upon this author's personal involvement and experiences, intended to highlight some basic aspects of the source and nature of uncertainties in forecasts and to illustrate the sort of value added information ensembles can provide in dealing with uncertainties in predictions of East Coast snowstorms.
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    Perspectives on Fred Sanders' Research on Cold Fronts (2008)
    American Meteorological Society
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    Publication Date: 2008-11-01
    Description: One characteristic of Fred Sanders' research is his ability to take a topic that is believed to be well understood by the research community and show that interesting research problems still exist. Among Sanders' considerable contributions to synoptic meteorology, those concerned with surface cold fronts have been especially influential. After a brief historical review of fronts and frontal analysis, this chapter presents three stages in Sanders' career when he performed research on the structure, dynamics, and analysis of surface cold fronts. First, his 1955 paper, "An investigation of the structure and dynamics of an intense surface frontal zone," was the first study to discuss quantitatively the dynamics of a surface cold front. In the 1960s, Sanders and his students further examined the structure of cold fronts, resulting in the unpublished 1967 report to the National Science Foundation, "Frontal structure and the dynamics of frontogenesis." For a third lime in his career, Sanders published several papers (1995–2005) revisiting the structure and dynamics of cold fronts. His 1967 and 1995–2005 work raises the question of the origin and dynamics of the surface pressure trough and/or wind shift that sometimes precedes the temperature gradient (hereafter called a prefrontal trough or prefrontal wind shift, respectively). Sanders showed that the relationship between this prefrontal feature and the temperature gradient is fundamental to the strength of the front. When the wind shift is coincident with the temperature gradient, frontogenesis (strengthening of the front) results; when the wind shift lies ahead of the temperature gradient, frontolysis (weakening of the front) results. a number of proposed mechanisms for the formation of prefrontal troughs and prefrontal wind shifts exist. Consequently, much research remains to be performed on these topics.
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    Meteorology of the Southern Hemisphere (1998)
    American Meteorological Society
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    Publication Date: 1998-12-01
    Description: No Abstract available.
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    Uncertainty and Inference for Verification Measures (2007)
    American Meteorological Society
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    Publication Date: 2007-06-01
    Description: When a forecast is assessed, a single value for a verification measure is often quoted. This is of limited use, as it needs to be complemented by some idea of the uncertainty associated with the value. If this uncertainty can be quantified, it is then possible to make statistical inferences based on the value observed. There are two main types of inference: confidence intervals can be constructed for an underlying “population” value of the measure, or hypotheses can be tested regarding the underlying value. This paper will review the main ideas of confidence intervals and hypothesis tests, together with the less well known “prediction intervals,” concentrating on aspects that are often poorly understood. Comparisons will be made between different methods of constructing confidence intervals—exact, asymptotic, bootstrap, and Bayesian—and the difference between prediction intervals and confidence intervals will be explained. For hypothesis testing, multiple testing will be briefly discussed, together with connections between hypothesis testing, prediction intervals, and confidence intervals.
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    Relationships between Marine Stratus Cloud Optical Depth and Temperature: Inferences from AVHRR Observations (2007)
    American Meteorological Society
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    Publication Date: 2007-05-15
    Description: Studies using International Satellite Cloud Climatology Project (ISCCP) data have reported decreases in cloud optical depth with increasing temperature, thereby suggesting a positive feedback in cloud optical depth as climate warms. The negative cloud optical depth and temperature relationships are questioned because ISCCP employs threshold assumptions to identify cloudy pixels that have included partly cloudy pixels. This study applies the spatial coherence technique to one month of Advanced Very High Resolution Radiometer (AVHRR) data over the Pacific Ocean to differentiate overcast pixels from the partly cloudy pixels and to reexamine the cloud optical depth–temperature relationships. For low-level marine stratus clouds studied here, retrievals from partly cloudy pixels showed 30%–50% smaller optical depths, 1°–4°C higher cloud temperatures, and slightly larger droplet effective radii, when they were compared to retrievals from the overcast pixels. Despite these biases, retrievals for the overcast and partly cloudy pixels show similar negative cloud optical depth–temperature relationships and their magnitudes agree with the ISCCP results for the midlatitude and subtropical regions. There were slightly negative droplet effective radius–temperature relationships, and considerable positive cloud liquid water content–temperature relationships indicated by aircraft measurements. However, cloud thickness decreases appear to be the main reason why cloud optical depth decreases with increasing temperature. Overall, cloud thickness thinning may explain why similar negative cloud optical depth–temperature relationships are found in both overcast and partly cloudy pixels. In addition, comparing the cloud-top temperature to the air temperature at 740 hPa indicates that cloud-top height generally rises with warming. This suggests that the cloud thinning is mainly due to the ascending of cloud base. The results presented in this study are confined to the midlatitude and subtropical Pacific and may not be applicable to the Tropics or other regions.
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    Analyzing Monthly Extreme Sea Levels with a Time-Dependent GEV Model (2007)
    American Meteorological Society
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    Publication Date: 2007-05-01
    Description: A statistical model to analyze different time scales of the variability of extreme high sea levels is presented. This model uses a time-dependent generalized extreme value (GEV) distribution to fit monthly maxima series and is applied to a large historical tidal gauge record (San Francisco, California). The model allows the identification and estimation of the effects of several time scales—such as seasonality, interdecadal variability, and secular trends—in the location, scale, and shape parameters of the probability distribution of extreme sea levels. The inclusion of seasonal effects explains a large amount of data variability, thereby allowing a more efficient estimation of the processes involved. Significant correlation with the Southern Oscillation index and the nodal cycle, as well as an increase of about 20% for the secular variability of the scale parameter have been detected for the particular dataset analyzed. Results show that the model is adequate for a complete analysis of seasonal-to-interannual sea level extremes providing time-dependent quantiles and confidence intervals.
    Print ISSN: 0739-0572
    Electronic ISSN: 1520-0426
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    Characterization of the Interannual and Intraseasonal Variability of West African Vegetation between 1982 and 2002 by Means of NOAA AVHRR NDVI Data (2007)
    American Meteorological Society
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    Publication Date: 2007-04-01
    Description: The interannual and intraseasonal variability of West African vegetation over the period 1982–2002 is studied using the normalized difference vegetation index (NDVI) from the Advanced Very High Resolution Radiometer (AVHRR).The novel independent component analysis (ICA) technique is applied to extract the main modes of the interannual variability of the vegetation, among which two modes are worth describing. The first component (IC1) describes NDVI variability over the Sahel from August to October. A strong photosynthetic activity over the Sahel is related to above-normal convection and rainfall within the intertropical convergence zone (ITCZ) in summertime and is partly associated with colder (warmer) SST in the eastern tropical Pacific (the Mediterranean). The second component (IC2) depicts a dipole pattern between the Sahelian and Guinean regions during the northern summer followed by a southward-propagating signal from October to December. It is associated with a north–south dipole in convection and rainfall induced by variations in the latitudinal location of the ITCZ as a response to the occurrence of the tropical Atlantic dipole.The analysis of the intraseasonal variability of the Sahelian vegetation relies on the analysis of the seasonal marches and their main phenological stages. Green-up usually starts in early July and shows a very low year-to-year variability, while senescence ends by mid-November and is prone to larger interannual variability. Six types of vegetative seasonal marches are discriminated according to variations in the timing of phenological stages as well as in the greening intensity. These types appear to be strongly dependent on rainfall distribution and amount, particularly those recorded in late August. Finally, year-to-year memory effects are highlighted: NDVI recorded during the green-up phase in year j appears to be strongly related to the maximum NDVI value recorded at year j − 1.
    Print ISSN: 0894-8755
    Electronic ISSN: 1520-0442
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    Scaling Analysis of the Sea Surface Temperature Anomaly in the South China Sea (2007)
    American Meteorological Society
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    Publication Date: 2007-04-01
    Description: Based on the data of optimum interpolation sea surface temperature (OISST), the temporal correlations of the sea surface temperature anomaly (SSTA) in the South China Sea (SCS) are studied by using the rescaled range analysis (R/S) and detrended fluctuation analysis (DFA). The results show that the scaling exponents of SSTAs are larger than 0.8. This finding indicates that the SSTAs in the SCS exhibit persistent long-range time correlation of the fluctuations and the interval spreads over a wide period, from about 1 month to 4.5 yr (4∼235 weeks). In addition, the “degree” of the correlations depends very much on the geographic locations: near to the coastal regions, the value is small, while far from the coastline, the value is relatively larger. This means that SSTAs in the central SCS are smoother than those of the coastal regions. The persistence of SST in the SCS may be used as a “minimum skill” to assess the ocean models and to evaluate their performance.
    Print ISSN: 0739-0572
    Electronic ISSN: 1520-0426
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    Lake-Breeze Fronts in the Salt Lake Valley (2007)
    American Meteorological Society
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    Publication Date: 2007-02-01
    Description: Winds at the Salt Lake City International Airport (SLC) during the April–October period from 1948 to 2003 have been observed to shift to the north (up-valley direction) between late morning and afternoon on over 70% of the days without precipitation. Lake-breeze fronts that develop as a result of the differential heating between the air over the nearby Great Salt Lake and that over the lake’s surroundings are observed at SLC only a few times each month. Fewer lake-breeze fronts are observed during late July–early September than before or after that period. Interannual fluctuations in the areal extent of the shallow Great Salt Lake contribute to year-to-year variations in the number of lake-breeze frontal passages at SLC. Data collected during the Vertical Transport and Mixing Experiment (VTMX) of October 2000 are used to examine the structure and evolution of a lake-breeze front that moved through the Salt Lake Valley on 17 October. The onset of upslope and up-valley winds occurred within the valley prior to the passage of the lake-breeze front. The lake-breeze front moved at roughly 3 m s−1 up the valley and was characterized near the surface by an abrupt increase in wind speed and dewpoint temperature over a distance of 3–4 km. Rapid vertical mixing of aerosols at the top of the 600–800-m-deep boundary layer was evident as the front passed.
    Print ISSN: 1558-8424
    Electronic ISSN: 1558-8432
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    Numerical and Experimental Investigation of the Neutral Atmospheric Surface Layer (2007)
    American Meteorological Society
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    Publication Date: 2007-01-01
    Description: This study combines the experimental measurements with large-eddy simulation (LES) data of a neutral planetary boundary layer (PBL) documented by a 60-m tower instrumented with eight sonic anemometers, and a high-resolution Doppler lidar during the 1999 Cooperative Atmospheric and Surface Exchange Study (CASES-99) experiment. The target of the paper is (i) to investigate the multiscale nature of the turbulent eddies in the surface layer (SL), (ii) to explain the existence of a −1 power law in the velocity fluctuation spectra, and (iii) to investigate the different nature of turbulence in the two sublayers within the SL, which are the eddy surface layer (ESL; lower sublayer of the SL lying between the surface and about 20-m height) and the shear surface layer (SSL; lying between the ESL top and the SL top). The sonic anemometers and Doppler lidar prove to be proper instruments for LES validation, and in particular, the Doppler lidar because of its ability to map near-surface eddies.This study shows the different nature of turbulence in the ESL and the SSL in terms of organized eddies, velocity fluctuation spectra, and second-order moment statistics. If quantitative agreement is found in the SSL between the LES and the measurements, only qualitative similarity is found in the ESL due to the subgrid-scale model, indicating that the LES captures part of the physics of the ESL. The LES helps explain the origin of the −1 power-law spectral subrange evidence in the velocity fluctuation spectra computed in the SL using the CASES-99 dataset: strong interaction between the mean flow and the fluctuating vorticities is found in the SL, and turbulent production is found to be larger than turbulent energy transfer for k1z 〉 1 (k1 being the longitudinal wavenumber and z the height), which is the condition of the −1 power-law existence.
    Print ISSN: 0022-4928
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    The Influence of Precipitation Variability and Partial Irrigation within Grid Cells on a Hydrological Simulation (2007)
    American Meteorological Society
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    Publication Date: 2007-06-01
    Description: The effects of natural and anthropogenic heterogeneity on a hydrological simulation are evaluated using a distributed biosphere hydrological model (DBHM) system. The DBHM embeds a biosphere model into a distributed hydrological scheme, representing both topography and vegetation in a mesoscale hydrological simulation, and the model system includes an irrigation scheme. The authors investigated the effects of two kinds of variability, precipitation variability and the variability of irrigation redistributing runoff, representing natural and anthropogenic heterogeneity, respectively, on hydrological processes. Runoff was underestimated if rainfall was placed spatially uniformly over large grid cells. Accounting for precipitation heterogeneity improved the runoff simulation. However, the negative runoff contribution, namely, the situation that mean annual precipitation is less than evapotranspiration, cannot be simulated by only considering the natural heterogeneity. This constructive model shortcoming can be eliminated by accounting for anthropogenic heterogeneity caused by irrigation water withdrawals. Irrigation leads to increased evapotranspiration and decreased runoff, and surface soil moisture in irrigated areas increases because of irrigation. Simulations performed for the Yellow River basin of China indicated streamflow decreases of 41% due to irrigation effects. The latent heat flux in the peak irrigation season [June–August (JJA)] increased 3.3 W m−2 with a decrease in the ground surface temperature of 0.1 K for the river basin. The maximum simulated increase in the latent heat flux was 43 W m−2, and the ground temperature decrease was 1.6 K in the peak irrigation season.
    Print ISSN: 1525-755X
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    An Assessment of Marine Surface Winds from the Australian Bureau of Meteorology Numerical Weather Prediction Systems (2007)
    American Meteorological Society
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    Publication Date: 2007-06-01
    Description: A method for routinely verifying numerical weather prediction surface marine winds with satellite scatterometer winds is introduced. The marine surface winds from the Australian Bureau of Meteorology’s operational global and regional numerical weather prediction systems are evaluated. The model marine surface layer is described. Marine surface winds from the global and limited-area models are compared with observations, both in situ (anemometer) and remote (scatterometer). A 2-yr verification shows that wind speeds from the regional model are typically underestimated by approximately 5%, with a greater bias in the meridional direction than the zonal direction. The global model also underestimates the surface winds by around 5%–10%. A case study of a significant marine storm shows that where larger errors occur, they are due to an underestimation of the storm intensity, rather than to biases in the boundary layer parameterizations.
    Print ISSN: 0882-8156
    Electronic ISSN: 1520-0434
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    Monsoon Dynamics with Interactive Forcing. Part I: Axisymmetric Studies (2007)
    American Meteorological Society
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    Publication Date: 2007-05-01
    Description: The applicability of axisymmetric theory of angular momentum conserving circulations to the large-scale steady monsoon is studied in a general circulation model with idealized representations of continental geometry and simple physics. Results from an aquaplanet setup with localized subtropical forcing are compared with a continental case. It is found that the meridional circulation that develops is close to angular momentum conserving for cross-equatorial circulation cells, both in the aquaplanet and in the continental cases. The equator proves to be a substantial barrier to boundary layer meridional flow; flow into the summer hemisphere from the winter hemisphere tends to occur in the free troposphere rather than in the boundary layer. A theory is proposed to explain the location of the monsoon; assuming quasiequilibrium, the poleward boundary of the monsoon circulation is collocated with the maximum in subcloud moist static energy, with the monsoon rains occurring near and slightly equatorward of this maximum. The model results support this theory of monsoon location, and it is found that the subcloud moist static energy distribution is determined by a balance between surface forcing and advection by the large-scale flow.
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    Fully Nonlinear Statistics of Wave Crest Elevation Calculated Using a Spectral Response Surface Method: Applications to Unidirectional Sea States (2007)
    American Meteorological Society
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    Publication Date: 2007-01-01
    Description: This paper concerns the calculation of the probability of exceedance of wave crest elevation. The statistics have been calculated for broadbanded, unidirectional, deep-water sea states by incorporating a fully nonlinear wave model into a spectral response surface method. This is a novel approach to the calculation of statistics and, as all of the calculations are performed in the probability domain, avoids the need for long time-domain simulations. Furthermore, in contrast to theoretical distributions, the broadbanded, fully nonlinear nature of the sea state can be considered. The results have been compared with those of fully nonlinear time-domain simulations and are shown to be in good agreement. The results indicate that in unidirectional seas the crest elevations of the largest waves can be much higher than would be predicted by linear or second-order theory. Hence, the occurrence of locally long crested sea states offers a possible explanation for the formation of freak or rogue waves.
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    Variability in the Environmental Factors Driving Evapotranspiration from a Grazed Rangeland during Severe Drought Conditions (2007)
    American Meteorological Society
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    Publication Date: 2007-04-01
    Description: Nearly one-half of the earth’s terrestrial surface is susceptible to drought, which can have significant social, economic, and environmental impacts. Therefore, it is important to develop better descriptions and models of the processes linking the land surface and atmosphere during drought. Using data collected during the International H2O Project, the study presented here investigates the effects of variations in the environmental factors driving the latent heat flux (λE) during drought conditions at a rangeland site located in the panhandle of Oklahoma. Specifically, this study focuses on the relationships of λE with vapor pressure deficit, wind speed, net radiation, soil moisture content, and greenness fraction. While each of these environmental factors has an influence, soil moisture content is the key control on λE. The role of soil moisture in regulating λE is explained in terms of the surface resistance to water vapor transfer. The results show that λE transitioned between being water or energy limited during the course of the drought. The implications of this on the ability to understand and model drought conditions and transitions into or out of droughts are discussed.
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    Intercomparison Study of the Land Surface Process Model and the Common Land Model for a Prairie Wetland in Florida (2006)
    American Meteorological Society
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    Publication Date: 2006-12-01
    Description: Common Land Model (CLM) and Land Surface Process (LSP) model simulations are compared to measured values for a 13-day dry-down period with a rapidly decreasing near-surface water table for a marsh wetland community in Florida. LSP was able to provide reasonable estimates without any modifications to the model physics. To obtain reasonable simulations using CLM, the baseline TOPMODEL baseflow generation and the bottom drainage mechanisms were not employed and the lower layers were allowed to remain saturated. In addition, several of CLM’s default wetland vegetation parameters were replaced with grassland parameters. Even after these modifications, CLM underestimated soil water storage. However, both model-simulated soil temperatures showed very good agreement as compared to measured temperatures, capturing both the soil warming during the study period and the diurnal fluctuations. Modeled surface energy fluxes also agreed well with measured values. LSP’s inability to consistently capture latent heat fluxes appears to be linked to its canopy resistance scaling functions. Other minor issues were that CLM’s rooting depth greatly exceeded observed depths and that CLM did not move water in the vadose zone from lower to upper layers during the nighttime as observed in the measurements. Overall, these results suggest that LSP can be applied to characterize a marsh dry down, but that minor modifications could greatly improve results. CLM demonstrated considerable potential, but requires some changes to model physics and default parameters prior to application to wetlands at a subgrid scale.
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    Autonomous Underwater Vehicle Measurements of Surface Wave Decay and Directional Spectra in the Marginal Sea Ice Zone* (2007)
    American Meteorological Society
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    Publication Date: 2007-01-01
    Description: In March 2003 several autonomous underwater vehicle (AUV) missions were carried out under sea ice in the western Bellingshausen Sea. Data from the upward-looking acoustic Doppler current profiler (ADCP) on the “Autosub” AUV indicate a strongly oscillating horizontal velocity of the ice due to ocean swell. Swell period, height, direction, and directional spread have been computed every 800 m from the ice edge to 10 km inward for three missions. Exponential, period-dependent attenuation of waves propagating through sea ice was observed. Mean period increased with distance from the ice edge. The wave field refracted during propagation. The directional wave spread does not seem to relate to distance from the ice edge, although higher frequencies tended to be more spread. If suitably deployed, an ordinary ADCP may be used with this technique to study both scalar and directional properties of waves in open or ice-covered water.
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    Swell and Slanting-Fetch Effects on Wind Wave Growth (2007)
    American Meteorological Society
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    Publication Date: 2007-04-01
    Description: Wind-sea generation was observed during two experiments off the coast of North Carolina. One event with offshore winds of 9–11 m s−1 directed 20° from shore normal was observed with eight directional stations recording simultaneously and spanning a fetch from 4 to 83 km. An opposing swell of 1-m height and 10-s period was also present. The wind-sea part of the wave spectrum conforms to established growth curves for significant wave height and peak period, except at inner-shelf stations where a large alongshore wind-sea component was observed. At these short fetches, the mean wave direction θm was observed to change abruptly across the wind-sea spectral peak, from alongshore at lower frequencies to downwind at higher frequencies. Waves from another event with offshore winds of 6–14 m s−1 directed 20°–30° from shore normal were observed with two instrument arrays. A significant amount of low-frequency wave energy was observed to propagate alongshore from the region where the wind was strongest. These measurements are used to assess the performance of some widely used parameterizations in wave models. The modeled transition of θm across the wind-sea spectrum is smoother than that in the observations and is reproduced very differently by different parameterizations, giving insights into the appropriate level of dissipation. Calculations with the full Boltzmann integral of quartet wave–wave interactions reveal that the discrete interaction approximation parameterization for these interactions is reasonably accurate at the peak of the wind sea but overpredicts the directional spread at high frequencies. This error is well compensated by parameterizations of the wind input source term that have a narrow directional distribution. Observations also highlight deficiencies in some parameterizations of wave dissipation processes in mixed swell–wind-sea conditions.
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    Distribution of Energy Spectra, Reynolds Stresses, Turbulence Production, and Dissipation in a Tidally Driven Bottom Boundary Layer (2007)
    American Meteorological Society
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    Publication Date: 2007-06-01
    Description: Seven sets of 2D particle image velocimetry data obtained in the bottom boundary layer of the coastal ocean along the South Carolina and Georgia coast [at the South Atlantic Bight Synoptic Offshore Observational Network (SABSOON) site] are examined, covering the accelerating and decelerating phases of a single tidal cycle at several heights above the seabed. Additional datasets from a previous deployment are also included in the analysis. The mean velocity profiles are logarithmic, and the vertical distribution of Reynolds stresses normalized by the square of the free stream velocity collapse well for data obtained at the same elevation but at different phases of the tidal cycle. The magnitudes of 〈u′u′〉, 〈w′w′〉, and −〈u′w′〉 decrease with height above bottom in the 25–160-cm elevation range and are consistent with the magnitudes and trends observed in laboratory turbulent boundary layers. If a constant stress layer exists, it is located below 25-cm elevation. Two methods for estimating dissipation rate are compared. The first, a direct estimate, is based on the measured in-plane instantaneous velocity gradients. The second method is based on fitting the resolved part of the dissipation spectrum to the universal dissipation spectrum available in Gargett et al. Being undervalued, the direct estimates are a factor of 2–2.5 smaller than the spectrum-based estimates. Taylor microscale Reynolds numbers for the present analysis range from 24 to 665. Anisotropy is present at all resolved scales. At the transition between inertial and dissipation range the longitudinal spectra exhibit a flatter than −5/3 slope and form spectral bumps. Second-order statistics of the velocity gradients show a tendency toward isotropy with increasing Reynolds number. Dissipation exceeds production at all measurement heights, but the difference varies with elevation. Close to the bottom, the production is 40%–70% of the dissipation, but it decreases to 10%–30% for elevations greater than 80 cm.
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    Dispersive Fluxes between the Coastal Ocean and a Semienclosed Estuarine Basin (2007)
    American Meteorological Society
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    Publication Date: 2007-06-01
    Description: Scalar exchange between San Francisco Bay and the coastal ocean is examined using shipboard observations made across the Golden Gate Channel. The study consists of experiments during each of the following three “seasons”: winter/spring runoff (March 2002), summer upwelling (July 2003), and autumn relaxation (October 2002). Within each experiment, transects across the channel were repeated approximately every 12 min for 25 h during both spring and neap tides. Velocity was measured from a boat-mounted ADCP. Scalar concentrations were measured at the surface and from a tow-yoed SeaSciences Acrobat. Net salinity exchange rates for each season are quantified with harmonic analysis. Accuracy of the net fluxes is confirmed by comparison with independently measured values. Harmonic results are then decomposed into flux mechanisms using temporal and spatial correlations. In this study, the temporal correlation of cross-sectionally averaged salinity and velocity (tidal pumping flux) is the largest part of the dispersive flux of salinity into the bay. From the tidal pumping flux portion of the dispersive flux, it is shown that there is less exchange than was found in earlier studies. Furthermore, tidal pumping flux scales strongly with freshwater flow resulting from the density-driven movement of a tidally trapped eddy and stratification-induced increases in ebb–flood frictional phasing. Complex bathymetry makes salinity exchange scale differently with flow than would be expected from simple tidal asymmetry and gravitational circulation models.
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    Performance of a New Generation of Acoustic Current Meters (2007)
    American Meteorological Society
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    Publication Date: 2007-02-01
    Description: As part of a program aimed at developing a long-duration, subsurface mooring, known as Ultramoor, several modern acoustic current meters were tested. The instruments with which the authors have the most experience are the Aanderaa RCM11 and the Nortek Aquadopp, which measure currents using the Doppler shift of backscattered acoustic signals, and the Falmouth Scientific ACM, which measures changes in travel time of acoustic signals between pairs of transducers. Some results from the Doppler-based Sontek Argonaut and the travel-time-based Nobska MAVS are also reported. This paper concentrates on the fidelity of the speed measurement but also presents some results related to the accuracy of the direction measurement. Two procedures were used to compare the instruments. In one, different instruments were placed close to one another on three different deep-ocean moorings. These tests showed that the RCM11 measures consistently lower speeds than either a vector averaging current meter or a vector measuring current meter, both more traditional instruments with mechanical velocity sensors. The Aquadopp in use at the time, but since updated to address accuracy problems in low scattering environments, was biased high. A second means of testing involved comparing the appropriate velocity component of each instrument with the rate of change of pressure when they were lowered from a ship. Results from this procedure revealed no depth dependence or measurable bias in the RCM11 data, but did show biases in both the Aquadopp and Argonaut Doppler-based instruments that resulted from low signal-to-noise ratios in the clear, low scattering conditions beneath the thermocline. Improvements in the design of the latest Aquadopp have reduced this bias to a level that is not significant.
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    Spectral Energy Fluxes in Geostrophic Turbulence: Implications for Ocean Energetics (2007)
    American Meteorological Society
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    Publication Date: 2007-03-01
    Description: The energy pathways in geostrophic turbulence are explored using a two-layer, flat-bottom, f-plane, quasigeostrophic model forced by an imposed, horizontally homogenous, baroclinically unstable mean flow and damped by bottom Ekman friction. A systematic presentation of the spectral energy fluxes, the mean flow forcing, and dissipation terms allows for a comprehensive understanding of the sources and sinks for baroclinic and barotropic energy as a function of length scale. The key new result is a robust inverse cascade of kinetic energy for both the baroclinic mode and the upper layer. This is consistent with recent observations of satellite altimeter data over the South Pacific Ocean. The well-known forward cascade of baroclinic potential and total energy was found to be very robust. Decomposing the spectral fluxes into contributions from different terms provided further insight. The inverse baroclinic kinetic energy cascade is driven mostly by an efficient interaction between the baroclinic velocity and the barotropic vorticity, the latter playing a crucial catalytic role. This cascade can be further enhanced by the baroclinic mode self-interaction, which is only present with nonuniform stratification (unequal layer depths). When model parameters are set such that modeled eddies compare favorably with observations, the inverse baroclinic kinetic energy cascade is actually much stronger than the well-known inverse cascade in the barotropic mode. The upper-layer kinetic energy cascade was found to dominate the lower-layer cascade over a wide range of parameters, suggesting that the surface cascade and time mean density stratification may be sufficient for estimating the depth-integrated cascade from ocean observations. This may find useful application in inferring the kinetic to gravitational potential energy conversion rate from satellite measurements.
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    Suppression of volcanism during rapid extension in the basin and range province, united states (1998)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1998-01-09
    Description: Continental extension and volcanism are generally thought to be complementary. Stratigraphic and structural data from some highly extended parts of the Basin and Range province reveal instead that rapid extension appears to have suppressed volcanism. This relation may reflect enhanced crystallization of midcrustal magmas during extension resulting from exsolution of magmatic volatiles, increased interaction of magmas with meteoric water, and dispersal of magma into smaller bodies. Some rift environments may thus be characterized by voluminous synextensional plutonism with little or no concomitant volcanism.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Gans -- Bohrson -- New York, N.Y. -- Science. 1998 Jan 2;279(5347):66-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Geological Sciences and Institute for Crustal Studies, University of California, Santa Barbara, CA 93106, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9417024" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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    Bimetallic system for nitrogen fixation: ruthenium-assisted protonation of coordinated N2 on tungsten with H2 (1998)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1998-01-28
    Description: Treatment of the tungsten dinitrogen complex cis-[W(N2)2(PMe2Ph)4] (Me = methyl, Ph = phenyl) with an equilibrium mixture of [RuCl(dppp)2]X and trans-[RuCl(eta2-H2)(dppp)2]X [X = BF4, PF6, or OSO2CF3; dppp = 1,3-bis(diphenylphosphino)propane] under 1 atmosphere of dihydrogen at 55 degrees Celsius for 24 hours gave NH3 in moderate yield. The same reaction in the presence of acetone produced acetone azine in high yield. None of these reactions proceeded in the absence of dihydrogen.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Nishibayashi -- Iwai -- Hidai -- New York, N.Y. -- Science. 1998 Jan 23;279(5350):540-2.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry and Biotechnology, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113, Japan.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9438842" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
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    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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    Driving the growth cone (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-09-28
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Caroni, P -- New York, N.Y. -- Science. 1998 Sep 4;281(5382):1465-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Friedrich Miescher Institute, Basel, Switzerland. caroni@fmi.ch〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9750116" target="_blank"〉PubMed〈/a〉
    Keywords: Acetylcholine/physiology ; Animals ; Axons/*physiology ; Brain-Derived Neurotrophic Factor/physiology ; Calcium/metabolism ; Cell Movement ; Cyclic AMP/*physiology ; Cyclic GMP/*physiology ; Glycoproteins/physiology ; Nerve Growth Factors/physiology ; Neurons/*physiology ; Neurotrophin 3 ; Semaphorin-3A ; Signal Transduction ; Tumor Suppressor Proteins
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    Metastasis in eggs (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-10-17
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Sikorski, R -- Peters, R -- New York, N.Y. -- Science. 1998 Sep 18;281(5384):1823.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9776688" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Blood Vessels/physiology ; Chick Embryo ; *Chorion/blood supply ; Humans ; Metalloendopeptidases/metabolism ; *Neoplasm Metastasis ; Neoplasm Seeding ; *Polymerase Chain Reaction ; Receptors, Cell Surface/metabolism ; Receptors, Urokinase Plasminogen Activator ; Tumor Cells, Cultured
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    Activity-dependent cortical target selection by thalamic axons (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-07-24
    Description: Connections in the developing nervous system are thought to be formed initially by an activity-independent process of axon pathfinding and target selection and subsequently refined by neural activity. Blockade of sodium action potentials by intracranial infusion of tetrodotoxin in cats during the early period when axons from the lateral geniculate nucleus (LGN) were in the process of selecting visual cortex as their target altered the pattern and precision of this thalamocortical projection. The majority of LGN neurons, rather than projecting to visual cortex, elaborated a significant projection within the subplate of cortical areas normally bypassed. Those axons that did project to their correct target were topographically disorganized. Thus, neural activity is required for initial targeting decisions made by thalamic axons as they traverse the subplate.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Catalano, S M -- Shatz, C J -- EY02838/EY/NEI NIH HHS/ -- EY06491/EY/NEI NIH HHS/ -- New York, N.Y. -- Science. 1998 Jul 24;281(5376):559-62.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Howard Hughes Medical Institute and Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3200, USA. scatalan@cco.caltech.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9677198" target="_blank"〉PubMed〈/a〉
    Keywords: Action Potentials/drug effects ; Animals ; Auditory Cortex/cytology/embryology ; Axons/*physiology/ultrastructure ; Carbocyanines ; Cats ; Dendrites/ultrastructure ; Geniculate Bodies/cytology/*embryology ; Neural Pathways ; Tetrodotoxin/pharmacology ; Visual Cortex/cytology/*embryology
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    Structural basis for a Ca2+-sensing function of the metabotropic glutamate receptors (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-03-28
    Description: The metabotropic glutamate receptors (mGluRs) are widely distributed in the brain and play important roles in synaptic plasticity. Here it is shown that some types of mGluRs are activated not only by glutamate but also by extracellular Ca2+ (Ca2+o). A single amino acid residue was found to determine the sensitivity of mGluRs to Ca2+o. One of the receptors, mGluR1alpha, but not its point mutant with reduced sensitivity to Ca2+o, caused morphological changes when transfected into mammalian cells. Thus, the sensing of Ca2+o by mGluRs may be important in cells under physiological condition.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kubo, Y -- Miyashita, T -- Murata, Y -- New York, N.Y. -- Science. 1998 Mar 13;279(5357):1722-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Neurophysiology, Tokyo Metropolitan Institute for Neuroscience, Musashidai 2-6, Fuchu, Tokyo 183-8526, Japan. ykubo@tmin.ac.jp〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9497291" target="_blank"〉PubMed〈/a〉
    Keywords: Actins/ultrastructure ; Amino Acid Sequence ; Animals ; Binding Sites ; Brain/metabolism ; CHO Cells ; Calcium/*metabolism/pharmacology ; Cell Size ; Cricetinae ; Cyclic AMP/metabolism ; G Protein-Coupled Inwardly-Rectifying Potassium Channels ; Glutamic Acid/metabolism/pharmacology ; Molecular Sequence Data ; Oocytes ; Point Mutation ; Potassium Channels/metabolism ; *Potassium Channels, Inwardly Rectifying ; Rats ; Receptors, Metabotropic Glutamate/chemistry/genetics/*metabolism ; Recombinant Fusion Proteins/metabolism ; Second Messenger Systems ; Transfection ; Xenopus laevis
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    Long-range electrostatic trapping of single-protein molecules at a liquid-solid interface (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-09-11
    Description: The motion of single, dye-labeled protein molecules was monitored at various pH and ionic strengths within the 180-nanometer-thick evanescent-field layer at a fused-silica surface. Below the isoelectric point, molecules partitioning into the excitation region increased in number but maintained a random spatial distribution, implying that surface charge can influence the charged protein at distances beyond that of the electrical double-layer thickness. The residence times of the molecules in the interfacial layer also increased below the isoelectric point. However, immobilization on the solid surface for extended periods was not observed. Histograms of residence times exhibit nearly identical asymmetry as the corresponding elution peaks in capillary electrophoresis. These results are a direct verification of the statistical theory of chromatography at the single-molecule level, with the caveat that long-range trapping rather than adsorption is the dominant mechanism.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Xu, X H -- Yeung, E S -- New York, N.Y. -- Science. 1998 Sep 11;281(5383):1650-3.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Ames Laboratory-U.S. Department of Energy and Department of Chemistry, Iowa State University, Ames, IA 50011, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9733506" target="_blank"〉PubMed〈/a〉
    Keywords: Chemistry, Physical ; Chromatography ; Concanavalin A/*chemistry ; Diffusion ; Electrophoresis, Capillary ; Fluorescence ; Hydrogen-Ion Concentration ; Isoelectric Point ; Osmolar Concentration ; Physicochemical Phenomena ; Proteins/*chemistry ; Rhodamines ; Static Electricity
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    Spatial organization of transcription elongation complex in Escherichia coli (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-07-17
    Description: During RNA synthesis in the ternary elongation complex, RNA polymerase enzyme holds nucleic acids in three contiguous sites: the double-stranded DNA-binding site (DBS) ahead of the transcription bubble, the RNA-DNA heteroduplex-binding site (HBS), and the RNA-binding site (RBS) upstream of HBS. Photochemical cross-linking allowed mapping of the DNA and RNA contacts to specific positions on the amino acid sequence. Unexpectedly, the same protein regions were found to participate in both DBS and RBS. Thus, DNA entry and RNA exit occur close together in the RNA polymerase molecule, suggesting that the three sites constitute a single unit. The results explain how RNA in the integrated unit RBS-HBS-DBS may stabilize the ternary complex, whereas a hairpin in RNA result in its dissociation.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Nudler, E -- Gusarov, I -- Avetissova, E -- Kozlov, M -- Goldfarb, A -- GM49242/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1998 Jul 17;281(5375):424-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biochemistry, New York University Medical Center, New York, NY 10016, USA. evgeny.nudler@med.nyu.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9665887" target="_blank"〉PubMed〈/a〉
    Keywords: Binding Sites ; DNA, Bacterial/chemistry/*metabolism ; DNA-Directed RNA Polymerases/chemistry/*metabolism ; Escherichia coli/*genetics/metabolism ; Idoxuridine/metabolism ; Models, Genetic ; Nucleic Acid Conformation ; Nucleic Acid Heteroduplexes/*metabolism ; Protein Binding ; RNA, Bacterial/chemistry/*metabolism ; Templates, Genetic ; *Transcription, Genetic ; Ultraviolet Rays
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    Supramolecular structure of the Salmonella typhimurium type III protein secretion system (1998)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1998-05-09
    Description: The type III secretion system of Salmonella typhimurium directs the translocation of proteins into host cells. Evolutionarily related to the flagellar assembly machinery, this system is also present in other pathogenic bacteria, but its organization is unknown. Electron microscopy revealed supramolecular structures spanning the inner and outer membranes of flagellated and nonflagellated strains; such structures were not detected in strains carrying null mutations in components of the type III apparatus. Isolated structures were found to contain at least three proteins of this secretion system. Thus, the type III apparatus of S. typhimurium, and presumably other bacteria, exists as a supramolecular structure in the bacterial envelope.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kubori, T -- Matsushima, Y -- Nakamura, D -- Uralil, J -- Lara-Tejero, M -- Sukhan, A -- Galan, J E -- Aizawa, S I -- New York, N.Y. -- Science. 1998 Apr 24;280(5363):602-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biosciences, Teikyo University, 1-1 Toyosatodai, Utsunomiya 320, Japan.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9554854" target="_blank"〉PubMed〈/a〉
    Keywords: Bacterial Outer Membrane Proteins/analysis ; Bacterial Proteins/*analysis/chemistry/*metabolism/ultrastructure ; Cell Membrane/chemistry/ultrastructure ; Centrifugation, Density Gradient ; Macromolecular Substances ; Membrane Proteins/*analysis/chemistry/ultrastructure ; *Membrane Transport Proteins ; Microscopy, Electron ; Microscopy, Immunoelectron ; Porins/analysis ; Salmonella typhimurium/*chemistry/metabolism/*ultrastructure
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    Structural basis of plasticity in T cell receptor recognition of a self peptide-MHC antigen (1998)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1998-03-21
    Description: The T cell receptor (TCR) inherently has dual specificity. T cells must recognize self-antigens in the thymus during maturation and then discriminate between foreign pathogens in the periphery. A molecular basis for this cross-reactivity is elucidated by the crystal structure of the alloreactive 2C TCR bound to self peptide-major histocompatibility complex (pMHC) antigen H-2Kb-dEV8 refined against anisotropic 3.0 angstrom resolution x-ray data. The interface between peptide and TCR exhibits extremely poor shape complementarity, and the TCR beta chain complementarity-determining region 3 (CDR3) has minimal interaction with the dEV8 peptide. Large conformational changes in three of the TCR CDR loops are induced upon binding, providing a mechanism of structural plasticity to accommodate a variety of different peptide antigens. Extensive TCR interaction with the pMHC alpha helices suggests a generalized orientation that is mediated by the Valpha domain of the TCR and rationalizes how TCRs can effectively "scan" different peptides bound within a large, low-affinity MHC structural framework for those that provide the slight additional kinetic stabilization required for signaling.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Garcia, K C -- Degano, M -- Pease, L R -- Huang, M -- Peterson, P A -- Teyton, L -- Wilson, I A -- AI42266/AI/NIAID NIH HHS/ -- AI42267/AI/NIAID NIH HHS/ -- R01 CA58896/CA/NCI NIH HHS/ -- New York, N.Y. -- Science. 1998 Feb 20;279(5354):1166-72.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Molecular Biology and the Skaggs Institute of Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9469799" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Crystallization ; Crystallography, X-Ray ; H-2 Antigens/*chemistry/*immunology/metabolism ; Ligands ; Mice ; Mice, Transgenic ; Models, Molecular ; Mutation ; Oligopeptides/*chemistry/immunology/metabolism ; Protein Conformation ; Protein Structure, Secondary ; Receptors, Antigen, T-Cell, alpha-beta/*chemistry/*immunology/metabolism ; Recombinant Proteins
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    Identification of alpha-dystroglycan as a receptor for lymphocytic choriomeningitis virus and Lassa fever virus (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-12-16
    Description: A peripheral membrane protein that is interactive with lymphocytic choriomeningitis virus (LCMV) was purified from cells permissive to infection. Tryptic peptides from this protein were determined to be alpha-dystroglycan (alpha-DG). Several strains of LCMV and other arenaviruses, including Lassa fever virus (LFV), Oliveros, and Mobala, bound to purified alpha-DG protein. Soluble alpha-DG blocked both LCMV and LFV infection. Cells bearing a null mutation of the gene encoding DG were resistant to LCMV infection, and reconstitution of DG expression in null mutant cells restored susceptibility to LCMV infection. Thus, alpha-DG is a cellular receptor for both LCMV and LFV.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Cao, W -- Henry, M D -- Borrow, P -- Yamada, H -- Elder, J H -- Ravkov, E V -- Nichol, S T -- Compans, R W -- Campbell, K P -- Oldstone, M B -- AG 00080/AG/NIA NIH HHS/ -- AI 09484/AI/NIAID NIH HHS/ -- DK09712/DK/NIDDK NIH HHS/ -- etc. -- New York, N.Y. -- Science. 1998 Dec 11;282(5396):2079-81.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Division of Virology, Department of Neuropharmacology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9851928" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Animals ; Arenavirus/metabolism ; Cell Line ; Cytoskeletal Proteins/chemistry/genetics/*metabolism ; Dystroglycans ; Lassa virus/*metabolism/physiology ; Lymphocytic choriomeningitis virus/*metabolism/physiology ; Membrane Glycoproteins/chemistry/genetics/*metabolism ; Mice ; Molecular Sequence Data ; Mutation ; Receptors, Virus/chemistry/*metabolism ; Recombinant Fusion Proteins/metabolism ; Virus Replication
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    Isotopic evidence for the Cretaceous-Tertiary impactor and its type (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-10-30
    Description: High-precision mass spectrometric analysis of chromium in sediment samples from the Cretaceous-Tertiary (K-T) boundary coincident with the extinction of numerous organisms on Earth confirms the cosmic origin of the K-T phenomenon. The isotopic composition of chromium in K-T boundary samples from Stevns Klint, Denmark, and Caravaca, Spain, is different from that of Earth and indicates its extraterrestrial source. The chromium isotopic signature is consistent with a carbonaceous chondrite-type impactor. The observed differences in the chromium isotopic composition among various meteorite classes can serve as a diagnostic tool for deciphering the nature of impactors that have collided with Earth during its history.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Shukolyukov, A -- Lugmair, G W -- New York, N.Y. -- Science. 1998 Oct 30;282(5390):927-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093-0212, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9794759" target="_blank"〉PubMed〈/a〉
    Keywords: Chromium/analysis ; Chromium Isotopes/*analysis ; Denmark ; *Earth (Planet) ; Geologic Sediments/*chemistry ; Mass Spectrometry ; *Meteoroids ; Spain
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    Induced massive star formation in the trifid nebula? (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-10-17
    Description: The Trifid nebula is a young (10(5) years) galactic HII region where several protostellar sources have been detected with the infrared space observatory. The sources are massive (17 to 60 solar masses) and are associated with molecular gas condensations at the edges or inside the nebula. They appear to be in an early evolutionary stage and may represent the most recent generation of stars in the Trifid. These sources range from dense, apparently still inactive cores to more evolved sources, undergoing violent mass ejection episodes, including a source that powers an optical jet. These observations suggest that the protostellar sources may have evolved by induced star formation in the Trifid nebula.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Cernicharo -- Lefloch -- Cox -- Cesarsky -- Esteban -- Yusef-Zadeh -- Mendez -- Acosta-Pulido -- Garcia Lopez RJ -- Heras -- New York, N.Y. -- Science. 1998 Oct 16;282(5388):462-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉J. Cernicharo, Instituto de Estructura de la Materia, Dpto. Fisica Molecular, Consejo Superior de Investigaciones Cientificas, (CSIC), Serrano 123, 28006 Madrid, Spain. B. Lefloch, Instituto de Estructura de la Materia, Dpto. Fisica Molecu.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9774270" target="_blank"〉PubMed〈/a〉
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    Plutonium-fission xenon found in Earth's mantle (1998)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1998-05-19
    Description: Data from mid-ocean ridge basalt glasses indicate that the short-lived radionuclide plutonium-244 that was present during an early stage of the development of the solar system is responsible for roughly 30 percent of the fissiogenic xenon excesses in the interior of Earth today. The rest of the fissiogenic xenon can be ascribed to the spontaneous fission of still live uranium-238. This result, in combination with the refined determination of xenon-129 excesses from extinct iodine-129, implies that the accretion of Earth was finished roughly 50 million to 70 million years after solar system formation and that the atmosphere was formed by mantle degassing.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kunz -- Staudacher -- Allegre -- New York, N.Y. -- Science. 1998 May 8;280(5365):877-80.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉J. Kunz, Institut de Physique du Globe de Paris, Laboratoire de Geochimie et Cosmochimie, Centre National de la Recherche Scientifique URA 1758, 4 place Jussieu, F-75252 Paris Cedex 05, France. T. Staudacher, Institut de Physique du.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9572726" target="_blank"〉PubMed〈/a〉
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    Quantitation of HIV-1-specific cytotoxic T lymphocytes and plasma load of viral RNA (1998)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1998-04-16
    Description: Although cytotoxic T lymphocytes (CTLs) are thought to be involved in the control of human immunodeficiency virus-type 1 (HIV-1) infection, it has not been possible to demonstrate a direct relation between CTL activity and plasma RNA viral load. Human leukocyte antigen-peptide tetrameric complexes offer a specific means to directly quantitate circulating CTLs ex vivo. With the use of the tetrameric complexes, a significant inverse correlation was observed between HIV-specific CTL frequency and plasma RNA viral load. In contrast, no significant association was detected between the clearance rate of productively infected cells and frequency of HIV-specific CTLs. These data are consistent with a significant role for HIV-specific CTLs in the control of HIV infection and suggest a considerable cytopathic effect of the virus in vivo.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Ogg, G S -- Jin, X -- Bonhoeffer, S -- Dunbar, P R -- Nowak, M A -- Monard, S -- Segal, J P -- Cao, Y -- Rowland-Jones, S L -- Cerundolo, V -- Hurley, A -- Markowitz, M -- Ho, D D -- Nixon, D F -- McMichael, A J -- MO1-RR00102/RR/NCRR NIH HHS/ -- U01AI41534/AI/NIAID NIH HHS/ -- Wellcome Trust/United Kingdom -- New York, N.Y. -- Science. 1998 Mar 27;279(5359):2103-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institute of Molecular Medicine, Nuffield Department of Medicine, Oxford OX3 9DS, UK.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9516110" target="_blank"〉PubMed〈/a〉
    Keywords: Anti-HIV Agents/therapeutic use ; CD4 Lymphocyte Count ; Coloring Agents ; Cytopathogenic Effect, Viral ; Cytotoxicity, Immunologic ; Flow Cytometry ; Gene Products, gag ; Gene Products, pol ; HIV Infections/drug therapy/*immunology/*virology ; HIV-1/genetics/*physiology ; HLA-A Antigens ; Humans ; Lymphocyte Count/*methods ; Oligopeptides ; RNA, Viral/*blood ; Sensitivity and Specificity ; T-Lymphocytes, Cytotoxic/*immunology ; Viral Load ; Viremia
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    Gas-phase ionic reactions: dynamics and mechanism of nucleophilic displacements (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-04-02
    Description: Nucleophilic displacement reactions (the SN2 reaction) of ions in the gas phase are a prototypical reaction system that allows a study of dynamics, mechanisms, and structure-energy relations. This article reviews aspects of the kinetics (especially the applicability of statistical reaction rate theory), the relation of structure and reactivity, and the effects of small numbers of solvent molecules on the reaction and compares the behavior of the ionic reaction in the gas phase with that in solution.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Chabinyc -- Craig -- Regan -- Brauman -- New York, N.Y. -- Science. 1998 Mar 20;279(5358):1882-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉M. L. Chabinyc, C. K. Regan, and J. I. Brauman are in the Department of Chemistry, Stanford University, Stanford, CA 94305-5080, USA. S. L. Craig is in the Central Research and Development Department, E. I. DuPont de Nemours and Company, Incorporated〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9506930" target="_blank"〉PubMed〈/a〉
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    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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    Which of our genes makes us human? (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-09-28
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Gibbons, A -- New York, N.Y. -- Science. 1998 Sep 4;281(5382):1432-4.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9750111" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Chromosome Mapping ; *Chromosomes, Human ; Gene Expression ; *Genome ; *Genome, Human ; Hominidae/*genetics ; *Human Characteristics ; Humans ; Mutation ; Pan troglodytes/genetics ; *Sequence Analysis, DNA ; Sialic Acids/chemistry/physiology ; Species Specificity
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    Induction of lens differentiation by activation of a bZIP transcription factor, L-Maf (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-04-29
    Description: After the vertebrate lens is induced from head ectoderm, lens-specific genes are expressed. Transcriptional regulation of the lens-specific alphaA-crystallin gene is controlled by an enhancer element, alphaCE2. A gene encoding an alphaCE2-binding protein, L-maf(lens-specific maf), was isolated. L-maf expression is initiated in the lens placode and is restricted to lens cells. The gene product L-Maf regulates the expression of multiple genes expressed in the lens, and ectopic expression of this transcription factor converts chick embryonic ectodermal cells and cultured cells into lens fibers. Thus, vertebrate lens induction and differentiation can be triggered by the activation of L-Maf.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Ogino, H -- Yasuda, K -- New York, N.Y. -- Science. 1998 Apr 3;280(5360):115-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma 630-0101, Japan.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9525857" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Animals ; Basic-Leucine Zipper Transcription Factors ; Cell Differentiation ; Cells, Cultured ; Chick Embryo ; Crystallins/genetics ; DNA, Complementary ; DNA-Binding Proteins/chemistry/genetics ; Ectoderm ; Enhancer Elements, Genetic ; Eye Proteins/genetics ; G-Box Binding Factors ; *Gene Expression Regulation, Developmental ; Genes, Reporter ; Intermediate Filament Proteins/genetics ; Lens, Crystalline/*cytology/*embryology/metabolism ; Maf Transcription Factors ; Molecular Sequence Data ; Promoter Regions, Genetic ; Recombinant Fusion Proteins/metabolism ; Transcription Factors/chemistry/genetics/*metabolism ; *Transcription, Genetic ; Transcriptional Activation ; Transfection
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    Role of IQGAP1, a target of the small GTPases Cdc42 and Rac1, in regulation of E-cadherin- mediated cell-cell adhesion (1998)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1998-08-07
    Description: The small guanosine triphosphatases (GTPases) Cdc42 and Rac1 regulate E-cadherin-mediated cell-cell adhesion. IQGAP1, a target of Cdc42 and Rac1, was localized with E-cadherin and beta-catenin at sites of cell-cell contact in mouse L fibroblasts expressing E-cadherin (EL cells), and interacted with E-cadherin and beta-catenin both in vivo and in vitro. IQGAP1 induced the dissociation of alpha-catenin from a cadherin-catenin complex in vitro and in vivo. Overexpression of IQGAP1 in EL cells, but not in L cells expressing an E-cadherin-alpha-catenin chimeric protein, resulted in a decrease in E-cadherin-mediated cell-cell adhesive activity. Thus, IQGAP1, acting downstream of Cdc42 and Rac1, appears to regulate cell-cell adhesion through the cadherin-catenin pathway.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kuroda, S -- Fukata, M -- Nakagawa, M -- Fujii, K -- Nakamura, T -- Ookubo, T -- Izawa, I -- Nagase, T -- Nomura, N -- Tani, H -- Shoji, I -- Matsuura, Y -- Yonehara, S -- Kaibuchi, K -- New York, N.Y. -- Science. 1998 Aug 7;281(5378):832-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Division of Signal Transduction, Nara Institute of Science and Technology, Ikoma 630-0101, Japan.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9694656" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Cadherins/*metabolism ; *Cell Adhesion ; Cell Cycle Proteins/*metabolism ; Cell Membrane/metabolism ; Cytoskeletal Proteins/metabolism ; GTP Phosphohydrolases/*metabolism ; GTP-Binding Proteins/*metabolism ; GTPase-Activating Proteins ; L Cells (Cell Line) ; Mice ; Mutation ; Proteins/*metabolism ; Recombinant Fusion Proteins/metabolism ; Recombinant Proteins/metabolism ; *Trans-Activators ; alpha Catenin ; beta Catenin ; cdc42 GTP-Binding Protein ; rac GTP-Binding Proteins
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    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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    Evidence against a significant younger dryas cooling event in new zealand (1998)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1998-08-07
    Description: Pollen records of deglacial sequences from northwest Nelson, New Zealand, demonstrate that there was no significant temperature decline associated with the Younger Dryas in New Zealand. Records of glacial advances at this time were either the product of increased snow accumulation under enhanced precipitation regimes or random variation rather than the result of a regional thermal decline. This finding supports those models of Younger Dryas initiation that require neither enhanced westerly circulation nor significant thermal decline in the Southern Hemisphere.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Singer -- Shulmeister -- McLea -- New York, N.Y. -- Science. 1998 Aug 7;281(5378):812-4.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Research School of Earth Sciences, Victoria University, Post Office Box 600, Wellington, New Zealand.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9694650" target="_blank"〉PubMed〈/a〉
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    Coupling of Ras and Rac guanosine triphosphatases through the Ras exchanger Sos (1998)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1998-02-07
    Description: The Son of Sevenless (Sos) proteins control receptor-mediated activation of Ras by catalyzing the exchange of guanosine diphosphate for guanosine triphosphate on Ras. The NH2-terminal region of Sos contains a Dbl homology (DH) domain in tandem with a pleckstrin homology (PH) domain. In COS-1 cells, the DH domain of Sos stimulated guanine nucleotide exchange on Rac but not Cdc42 in vitro and in vivo. The tandem DH-PH domain of Sos (DH-PH-Sos) was defective in Rac activation but regained Rac stimulating activity when it was coexpressed with activated Ras. Ras-mediated activation of DH-PH-Sos did not require activation of mitogen-activated protein kinase but it was dependent on activation of phosphoinositide 3-kinase. These results reveal a potential mechanism for coupling of Ras and Rac signaling pathways.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Nimnual, A S -- Yatsula, B A -- Bar-Sagi, D -- CA09176/CA/NCI NIH HHS/ -- CA28146/CA/NCI NIH HHS/ -- CA55360/CA/NCI NIH HHS/ -- New York, N.Y. -- Science. 1998 Jan 23;279(5350):560-3.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Molecular Genetics and Microbiology, State University of New York at Stony Brook, Stony Brook, NY 11794, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9438849" target="_blank"〉PubMed〈/a〉
    Keywords: Actins/metabolism ; Animals ; COS Cells ; Calcium-Calmodulin-Dependent Protein Kinases/metabolism ; Cell Cycle Proteins/metabolism ; Cell Line ; Cell Membrane/ultrastructure ; Enzyme Activation ; GTP Phosphohydrolases/*metabolism ; GTP-Binding Proteins/*metabolism ; Guanine Nucleotide Exchange Factors ; Guanosine Diphosphate/metabolism ; Guanosine Triphosphate/metabolism ; Humans ; JNK Mitogen-Activated Protein Kinases ; Membrane Proteins/chemistry/*metabolism ; *Mitogen-Activated Protein Kinases ; Proteins/metabolism ; Proto-Oncogene Proteins ; Recombinant Fusion Proteins/metabolism ; Retroviridae Proteins, Oncogenic/chemistry ; Signal Transduction ; Son of Sevenless Proteins ; Transfection ; cdc42 GTP-Binding Protein ; rac GTP-Binding Proteins ; ras Guanine Nucleotide Exchange Factors ; ras Proteins/*metabolism
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    'Monogamous' gibbons really swing (1998)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1998-05-23
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Gibbons, A -- New York, N.Y. -- Science. 1998 May 1;280(5364):677-8.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9599145" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; *Behavior, Animal ; Female ; *Hylobates ; Male ; *Sexual Behavior, Animal ; *Social Behavior
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    Essential role of CED-4 oligomerization in CED-3 activation and apoptosis (1998)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1998-08-28
    Description: Control of the activation of apoptosis is important both in development and in protection against cancer. In the classic genetic model Caenorhabditis elegans, the pro-apoptotic protein CED-4 activates the CED-3 caspase and is inhibited by the Bcl-2-like protein CED-9. Both processes are mediated by protein-protein interaction. Facilitating the proximity of CED-3 zymogen molecules was found to induce caspase activation and cell death. CED-4 protein oligomerized in cells and in vitro. This oligomerization induced CED-3 proximity and competed with CED-4:CED-9 interaction. Mutations that abolished CED-4 oligomerization inactivated its ability to activate CED-3. Thus, the mechanism of control is that CED-3 in CED-3:CED-4 complexes is activated by CED-4 oligomerization, which is inhibited by binding of CED-9 to CED-4.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Yang, X -- Chang, H Y -- Baltimore, D -- CA51462/CA/NCI NIH HHS/ -- New York, N.Y. -- Science. 1998 Aug 28;281(5381):1355-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9721101" target="_blank"〉PubMed〈/a〉
    Keywords: *Apoptosis ; Apoptosis Regulatory Proteins ; Biopolymers ; *Caenorhabditis elegans Proteins ; Calcium-Binding Proteins/*chemistry/genetics/*metabolism ; *Caspases ; Cell Line ; Chemistry, Physical ; Cysteine Endopeptidases/*metabolism ; Cysteine Proteinase Inhibitors/pharmacology ; Enzyme Activation ; Enzyme Precursors/metabolism ; HeLa Cells ; Helminth Proteins/*chemistry/genetics/*metabolism ; Humans ; Mutation ; Oligopeptides/pharmacology ; Physicochemical Phenomena ; Proto-Oncogene Proteins/metabolism ; Proto-Oncogene Proteins c-bcl-2/metabolism ; Recombinant Fusion Proteins/metabolism ; Tacrolimus/pharmacology ; Transfection ; bcl-X Protein
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    Dendritic integration and its role in computing image velocity (1998)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1998-09-22
    Description: The mechanisms underlying visual motion detection can be studied simultaneously in different cell compartments in vivo by using calcium as a reporter of the spatiotemporal activity distribution in single motion-sensitive cells of the fly. As predicted by the Reichardt model, local dendritic calcium signals are found to indicate the direction and velocity of pattern motion but are corrupted by spatial pattern properties. The latter are canceled out by spatial integration, thus leading to a purely directional selective output signal in the axon. These findings attribute a specific computational task to the dendrites of visual interneurons and imply a functional interpretation of dendritic morphology.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Single, S -- Borst, A -- New York, N.Y. -- Science. 1998 Sep 18;281(5384):1848-50.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Friedrich-Miescher-Laboratory of the Max-Planck-Society, Spemannstrasse 37-39, D-72076 Tuebingen, Germany.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9743497" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Axons/metabolism/physiology ; Calcium/*metabolism ; Calcium Channels/metabolism ; Dendrites/metabolism/*physiology/ultrastructure ; Diptera/physiology ; Female ; Interneurons/physiology ; Membrane Potentials ; *Motion Perception ; Photoreceptor Cells, Invertebrate/*physiology
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    Integrated optoelectronic devices based on conjugated polymers (1998)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1998-06-20
    Description: An all-polymer semiconductor integrated device is demonstrated with a high-mobility conjugated polymer field-effect transistor (FET) driving a polymer light-emitting diode (LED) of similar size. The FET uses regioregular poly(hexylthiophene). Its performance approaches that of inorganic amorphous silicon FETs, with field-effect mobilities of 0.05 to 0.1 square centimeters per volt second and ON-OFF current ratios of 〉10(6). The high mobility is attributed to the formation of extended polaron states as a result of local self-organization, in contrast to the variable-range hopping of self-localized polarons found in more disordered polymers. The FET-LED device represents a step toward all-polymer optoelectronic integrated circuits such as active-matrix polymer LED displays.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Sirringhaus -- Tessler -- Friend -- New York, N.Y. -- Science. 1998 Jun 12;280(5370):1741-4.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge CB3 0HE, UK.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9624049" target="_blank"〉PubMed〈/a〉
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    Structure and function in the nucleus (1998)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1998-05-09
    Description: Current evidence suggests that the nucleus has a distinct substructure, albeit one that is dynamic rather than a rigid framework. Viral infection, oncogene expression, and inherited human disorders can each cause profound and specific changes in nuclear organization. This review summarizes recent progress in understanding nuclear organization, highlighting in particular the dynamic aspects of nuclear structure.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lamond, A I -- Earnshaw, W C -- 073915/Wellcome Trust/United Kingdom -- Wellcome Trust/United Kingdom -- New York, N.Y. -- Science. 1998 Apr 24;280(5363):547-53.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biochemistry, University of Dundee, Dundee DD1 4HN, Scotland, UK. a.i.lamond@dundee.ac.uk〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9554838" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Cell Nucleolus/physiology/ultrastructure ; Cell Nucleus/chemistry/*physiology/*ultrastructure ; Chromatin/physiology ; Chromosomes/physiology ; *Drosophila Proteins ; Euchromatin ; Gene Expression Regulation ; Heterochromatin/physiology ; Humans ; Insect Proteins/chemistry/physiology ; Interphase ; Neoplasm Proteins/chemistry/physiology ; *Nuclear Proteins ; Polycomb Repressive Complex 1 ; Polycomb-Group Proteins ; Repressor Proteins/chemistry/physiology ; Ribonucleoproteins, Small Nuclear/analysis/physiology ; Transcription Factors/chemistry/physiology ; Tumor Suppressor Proteins
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    Anthropologists probe genes, brains at annual meeting (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-05-09
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Gibbons, A -- New York, N.Y. -- Science. 1998 Apr 17;280(5362):380-1.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9575083" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; *Anthropology, Physical ; Biological Evolution ; Brain/*anatomy & histology ; Computer Simulation ; DNA, Mitochondrial/genetics ; Female ; *Genetics, Population ; *Hinduism/history ; History, Ancient ; Hominidae/*anatomy & histology ; Humans ; India ; Male ; Models, Anatomic ; Y Chromosome/genetics
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    Calibrating the mitochondrial clock (1998)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1998-01-24
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Gibbons, A -- New York, N.Y. -- Science. 1998 Jan 2;279(5347):28-9.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9441404" target="_blank"〉PubMed〈/a〉
    Keywords: DNA Fingerprinting ; DNA, Mitochondrial/*genetics ; *Evolution, Molecular ; Forensic Medicine ; Humans ; *Mutation ; Point Mutation ; *Polymorphism, Genetic
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    Secretion of thiols and disulfide bond formation: retraction (1998)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1998-03-21
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Sitia, R -- Ceriotti, A -- Cabibbo, A -- Fassina, G -- Ruvo, M -- New York, N.Y. -- Science. 1998 Feb 27;279(5355):1288-9.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9508700" target="_blank"〉PubMed〈/a〉
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    Oxygen reservoirs in the early solar nebula inferred from an allende CAI (1998)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1998-10-17
    Description: Ultraviolet laser microprobe analyses of a calcium-aluminum-rich inclusion (CAI) from the Allende meteorite suggest that a line with a slope of exactly 1.00 on a plot of delta17O against delta18O represents the primitive oxygen isotope reservoir of the early solar nebula. Most meteorites are enriched in 17O and 18O relative to this line, and their oxygen isotope ratios can be explained by mass fractionation or isotope exchange initiating from the primitive reservoir. These data establish a link between the oxygen isotopic composition of the abundant ordinary chondrites and the primitive 16O-rich component of CAIs.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Young -- Russell -- New York, N.Y. -- Science. 1998 Oct 16;282(5388):452-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉E. D. Young, Department of Earth Sciences, University of Oxford, Parks Road, Oxford, OX1 3PR, UK. E-mail: ed.young@earth.ox.ac.uk S. S. Russell, Department of Mineralogy, Natural History Museum, Cromwell Road, London SW7 5BD, UK. E-mail: sar.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9774267" target="_blank"〉PubMed〈/a〉
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    Role of phosphorylation in regulation of the assembly of endocytic coat complexes (1998)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1998-08-07
    Description: Clathrin-mediated endocytosis involves cycles of assembly and disassembly of clathrin coat components and their accessory proteins. Dephosphorylation of rat brain extract was shown to promote the assembly of dynamin 1, synaptojanin 1, and amphiphysin into complexes that also included clathrin and AP-2. Phosphorylation of dynamin 1 and synaptojanin 1 inhibited their binding to amphiphysin, whereas phosphorylation of amphiphysin inhibited its binding to AP-2 and clathrin. Thus, phosphorylation regulates the association and dissociation cycle of the clathrin-based endocytic machinery, and calcium-dependent dephosphorylation of endocytic proteins could prepare nerve terminals for a burst of endocytosis.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Slepnev, V I -- Ochoa, G C -- Butler, M H -- Grabs, D -- De Camilli, P -- CA46128/CA/NCI NIH HHS/ -- NS36251/NS/NINDS NIH HHS/ -- New York, N.Y. -- Science. 1998 Aug 7;281(5378):821-4.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Howard Hughes Medical Institute and Department of Cell Biology, Yale University School of Medicine, 295 Congress Avenue, New Haven, CT 06510, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9694653" target="_blank"〉PubMed〈/a〉
    Keywords: Adaptor Protein Complex alpha Subunits ; Adaptor Protein Complex beta Subunits ; Adaptor Proteins, Vesicular Transport ; Adenosine Triphosphate/metabolism ; Animals ; Binding Sites ; Carbazoles/pharmacology ; Chromatography, Affinity ; Clathrin/*metabolism ; Cyclosporine/pharmacology ; Dimerization ; Dynamin I ; Dynamins ; *Endocytosis ; Enzyme Inhibitors/pharmacology ; GTP Phosphohydrolases/*metabolism ; Indole Alkaloids ; Membrane Proteins/*metabolism ; Nerve Tissue Proteins/*metabolism ; Phosphoric Monoester Hydrolases/*metabolism ; Rats ; Recombinant Fusion Proteins/metabolism ; src Homology Domains
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    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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    Oxygen reservoirs in the early solar nebula inferred from an Allende CAI (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-10-17
    Description: Ultraviolet laser microprobe analyses of a calcium-aluminum-rich inclusion (CAI) from the Allende meteorite suggest that a line with a slope of exactly 1.00 on a plot of delta (17)O against delta (18)O represents the primitive oxygen isotope reservoir of the early solar nebula. Most meteorites are enriched in (17)O and (18)O relative to this line, and their oxygen isotope ratios can be explained by mass fractionation or isotope exchange initiating from the primitive reservoir. These data establish a link between the oxygen isotopic composition of the abundant ordinary chondrites and the primitive (16)O-rich component of CAIs.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Young, E D -- Russell, S S -- New York, N.Y. -- Science. 1998 Oct 16;282(5388):452-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Earth Sciences, University of Oxford, UK. ed.young@earth.ox.ac.uk〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9841405" target="_blank"〉PubMed〈/a〉
    Keywords: *Meteoroids ; *Oxygen ; Oxygen Isotopes ; *Solar System
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    Fluorescent, sequence-selective peptide detection by synthetic small molecules (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-02-28
    Description: Small organic sensor molecules were prepared that bind and signal the presence of unlabeled tripeptides in a sequence-selective manner. Sequence-selective peptide binding is a difficult problem because small peptides are highly flexible and there are no clear rules for designing peptide-binding molecules as there are for the nucleic acids. The signaling system involved the application of fluorescence energy transfer and provided large, real-time fluorescence increases (300 to 500 percent) upon peptide binding. With it, these sensors were sensitive enough to detect unlabeled cognate peptides both in organic solution and in the solid state at low micromolar concentrations.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Chen, C T -- Wagner, H -- Still, W C -- New York, N.Y. -- Science. 1998 Feb 6;279(5352):851-3.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, Columbia University, New York, NY 10027, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9452382" target="_blank"〉PubMed〈/a〉
    Keywords: Binding Sites ; Energy Transfer ; Fluorescence ; Microspheres ; Oligopeptides/*analysis/metabolism ; Peptide Library ; Peptides, Cyclic/*chemical synthesis/chemistry/metabolism ; Polystyrenes ; Spectrometry, Fluorescence
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    Bid for better beef gives Japan a leg up on cattle (1999)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1999-01-05
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Normile, D -- New York, N.Y. -- Science. 1998 Dec 11;282(5396):1975-6.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9874644" target="_blank"〉PubMed〈/a〉
    Keywords: Animal Husbandry/*methods ; Animals ; Blastocyst ; Cattle/embryology/*genetics ; Cell Differentiation ; Cells, Cultured ; *Cloning, Organism ; Embryo Transfer/veterinary ; Fallopian Tubes/cytology ; Female ; Japan ; *Nuclear Transfer Techniques ; Oocytes ; Ovarian Follicle/cytology ; Pregnancy
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    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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    The HIV-1 envelope glycoproteins: fusogens, antigens, and immunogens (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-06-25
    Description: The human immunodeficiency virus-type 1 (HIV-1) envelope glycoproteins interact with receptors on the target cell and mediate virus entry by fusing the viral and cell membranes. The structure of the envelope glycoproteins has evolved to fulfill these functions while evading the neutralizing antibody response. An understanding of the viral strategies for immune evasion should guide attempts to improve the immunogenicity of the HIV-1 envelope glycoproteins and, ultimately, aid in HIV-1 vaccine development.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Wyatt, R -- Sodroski, J -- AI 31783/AI/NIAID NIH HHS/ -- AI 39420/AI/NIAID NIH HHS/ -- AI28691/AI/NIAID NIH HHS/ -- etc. -- New York, N.Y. -- Science. 1998 Jun 19;280(5371):1884-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Cancer Immunology/AIDS, Dana-Farber Cancer Institute, Department of Pathology, Harvard Medical School, Boston, MA 02115, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9632381" target="_blank"〉PubMed〈/a〉
    Keywords: AIDS Vaccines/chemistry/immunology ; Animals ; Gene Products, env/chemistry/immunology/*physiology ; HIV Antibodies/biosynthesis ; HIV Antigens/immunology ; HIV Envelope Protein gp41/physiology ; HIV Infections/*immunology ; HIV-1/chemistry/immunology/*physiology ; Humans ; Membrane Fusion ; Receptors, HIV/metabolism
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    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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    Anterior cingulate cortex, error detection, and the online monitoring of performance (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-05-23
    Description: An unresolved question in neuroscience and psychology is how the brain monitors performance to regulate behavior. It has been proposed that the anterior cingulate cortex (ACC), on the medial surface of the frontal lobe, contributes to performance monitoring by detecting errors. In this study, event-related functional magnetic resonance imaging was used to examine ACC function. Results confirm that this region shows activity during erroneous responses. However, activity was also observed in the same region during correct responses under conditions of increased response competition. This suggests that the ACC detects conditions under which errors are likely to occur rather than errors themselves.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Carter, C S -- Braver, T S -- Barch, D M -- Botvinick, M M -- Noll, D -- Cohen, J D -- K08MH01306/MH/NIMH NIH HHS/ -- R01MH52864/MH/NIMH NIH HHS/ -- New York, N.Y. -- Science. 1998 May 1;280(5364):747-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Western Psychiatric Institute and Clinic, School of Medicine, University of Pittsburgh, 3811 O'Hara Street, Pittsburgh, PA 15213, USA. cscarter+@pitt.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9563953" target="_blank"〉PubMed〈/a〉
    Keywords: Brain Mapping ; Cognition/*physiology ; Frontal Lobe/*physiology ; Gyrus Cinguli/*physiology ; Humans ; Magnetic Resonance Imaging
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    A receptor/cytoskeletal movement triggered by costimulation during T cell activation (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-12-18
    Description: During T cell activation, the engagement of costimulatory molecules is often crucial to the development of an effective immune response, but the mechanism by which this is achieved is not known. Here, it is shown that beads attached to the surface of a T cell translocate toward the interface shortly after the start of T cell activation. This movement appears to depend on myosin motor proteins and requires the engagement of the major costimulatory receptor pairs, B7-CD28 and ICAM-1-LFA-1. This suggests that the engagement of costimulatory receptors triggers an active accumulation of molecules at the interface of the T cell and the antigen-presenting cell, which then increases the overall amplitude and duration of T cell signaling.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Wulfing, C -- Davis, M M -- New York, N.Y. -- Science. 1998 Dec 18;282(5397):2266-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Howard Hughes Medical Institute and Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA 94305, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9856952" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Antigen Presentation ; Antigen-Presenting Cells/immunology ; Antigens, CD/*metabolism ; Antigens, CD28/metabolism ; Antigens, CD86 ; Biotinylation ; CHO Cells ; Calcium/metabolism ; Cricetinae ; Cytoskeleton/*physiology ; Intercellular Adhesion Molecule-1/metabolism ; *Lymphocyte Activation ; Lymphocyte Function-Associated Antigen-1/metabolism ; Membrane Glycoproteins/metabolism ; Mice ; Microspheres ; Molecular Motor Proteins/physiology ; Myosins/physiology ; Phosphatidylinositol 3-Kinases/metabolism ; Receptors, Antigen, T-Cell/immunology ; Signal Transduction ; T-Lymphocytes/*immunology/metabolism/ultrastructure ; Tumor Cells, Cultured
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    Femtosecond dynamics of electron localization at interfaces (1998)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1998-01-16
    Description: The dynamics of two-dimensional small-polaron formation at ultrathin alkane layers on a silver(111) surface have been studied with femtosecond time- and angle-resolved two-photon photoemission spectroscopy. Optical excitation creates interfacial electrons in quasi-free states for motion parallel to the interface. These initially delocalized electrons self-trap as small polarons in a localized state within a few hundred femtoseconds. The localized electrons then decay back to the metal within picoseconds by tunneling through the adlayer potential barrier. The energy dependence of the self-trapping rate has been measured and modeled with a theory analogous to electron transfer theory. This analysis determines the inter- and intramolecular vibrational modes of the overlayer responsible for self-trapping as well as the relaxation energy of the overlayer molecular lattice. These results for a model interface contribute to the fundamental picture of electron behavior in weakly bonded solids and can lead to better understanding of carrier dynamics in many different systems, including organic light-emitting diodes.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Ge -- Wong -- Lingle Jr -- McNeill -- Gaffney -- Harris -- New York, N.Y. -- Science. 1998 Jan 9;279(5348):202-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, University of California, Berkeley, CA 94720, USA, and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9422687" target="_blank"〉PubMed〈/a〉
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    Court hears fight over safety of lab (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-12-05
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Normile, D -- New York, N.Y. -- Science. 1998 Oct 9;282(5387):213, 215.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9841381" target="_blank"〉PubMed〈/a〉
    Keywords: *Communicable Diseases ; *Containment of Biohazards ; Expert Testimony ; Laboratories/*legislation & jurisprudence/standards ; *Safety ; Tokyo ; World Health Organization
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    Automating a mouse (1998)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1998-06-06
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Sikorski, R -- Peters, R -- New York, N.Y. -- Science. 1998 May 15;280(5366):1101.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9616082" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Gene Library ; Gene Targeting ; *Genetic Techniques ; Genetic Vectors ; Mice ; Mice, Knockout/*genetics ; Mutagenesis, Insertional ; Sequence Analysis, DNA ; *Stem Cells
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  • 92
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    Cholinergic switching within neocortical inhibitory networks (1998)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1998-08-14
    Description: Differential actions of acetylcholine on the excitability of two subtypes of interneurons in layer V of the rat visual cortex were examined. Acetylcholine excited low-threshold spike (LTS) cells through nicotinic receptors, whereas it elicited hyperpolarization in fast spiking (FS) cells through muscarinic receptors. Axons of LTS cells were mainly distributed vertically to upper layers, and those of FS cells were primarily confined to layer V. Thus, cortical cholinergic activation may reduce some forms of intralaminar inhibition, promote intracolumnar inhibition, and change the direction of information flow within cortical circuits.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Xiang, Z -- Huguenard, J R -- Prince, D A -- NS 06477/NS/NINDS NIH HHS/ -- NS 07280/NS/NINDS NIH HHS/ -- NS 12151/NS/NINDS NIH HHS/ -- etc. -- New York, N.Y. -- Science. 1998 Aug 14;281(5379):985-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Neurology and Neurological Sciences, Stanford University Medical Center, Stanford, CA 94305, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9703513" target="_blank"〉PubMed〈/a〉
    Keywords: Acetylcholine/*physiology ; Animals ; Hexamethonium/pharmacology ; In Vitro Techniques ; Interneurons/physiology ; Membrane Potentials ; Muscarinic Antagonists/pharmacology ; Nerve Net/*physiology ; *Neural Inhibition ; Nicotinic Antagonists/pharmacology ; Patch-Clamp Techniques ; Rats ; Rats, Sprague-Dawley ; Receptors, Nicotinic/physiology ; Scopolamine Hydrobromide/pharmacology ; Visual Cortex/cytology/*physiology
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    Mismatch repair co-opted by hypermutation (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-03-21
    Description: Mice homozygous for a disrupted allele of the mismatch repair gene Pms2 have a mutator phenotype. When this allele is crossed into quasi-monoclonal (QM) mice, which have a very limited B cell repertoire, homozygotes have fewer somatic mutations at the immunoglobulin heavy chain and lambda chain loci than do heterozygotes or wild-type QM mice. That is, mismatch repair seems to contribute to somatic hypermutation rather than stifling it. It is suggested that at immunoglobulin loci in hypermutable B cells, mismatched base pairs are "corrected" according to the newly synthesized DNA strand, thereby fixing incipient mutations instead of eliminating them.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Cascalho, M -- Wong, J -- Steinberg, C -- Wabl, M -- 1R01 GM37699/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1998 Feb 20;279(5354):1207-10.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Microbiology and Immunology, University of California, San Francisco, CA 94143-0670, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9469811" target="_blank"〉PubMed〈/a〉
    Keywords: *Adenosine Triphosphatases ; Alleles ; Amino Acid Sequence ; Animals ; B-Lymphocytes/immunology ; Base Composition ; Base Sequence ; Cloning, Molecular ; Crosses, Genetic ; *DNA Repair ; *DNA Repair Enzymes ; *DNA-Binding Proteins ; Female ; Gene Rearrangement ; *Genes, Immunoglobulin ; Heterozygote ; Immunoglobulin Heavy Chains/chemistry/genetics ; Immunoglobulin Variable Region/chemistry/*genetics ; Immunoglobulin lambda-Chains/chemistry/genetics ; Male ; Mice ; Mice, Knockout ; Molecular Sequence Data ; *Mutation ; Proteins/*genetics/physiology
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    New potential for human embryonic stem cells (1998)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1998-12-05
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Gearhart, J -- New York, N.Y. -- Science. 1998 Nov 6;282(5391):1061-2.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Gynecology and Obstetrics, Johns Hopkins Medicine, Baltimore, MD 21287, USA. gearhart@jhmi.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9841453" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Blastocyst/*cytology ; *Cell Culture Techniques ; Cell Differentiation ; *Cell Line ; Cell Lineage ; *Embryo Research ; Embryo, Mammalian/*cytology ; Federal Government ; Germ Cells/*cytology ; Government Regulation ; Guidelines as Topic ; Humans ; Major Histocompatibility Complex ; Mice ; Research Support as Topic ; Risk Assessment ; Stem Cell Transplantation ; Stem Cells/*cytology ; Transplantation Immunology ; United States
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    Detection of atomic deuterium in the upper atmosphere of Mars (1998)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1998-06-11
    Description: High-resolution spectroscopy of Mars' atmosphere with the Hubble Space Telescope revealed the deuterium Lyman alpha line at an intensity of 23 +/- 6 rayleighs. This measured intensity corresponds to HD/H2 = 1.5 +/- 0.6 x 10(-4), which is smaller by a factor of 11 than HDO/H2O. This indicates that fractionation of HD/H2 relative to that of HDO/H2O is not kinetically controlled by the rates of formation and destruction of H2 and HD but is thermodynamically controlled by the isotope exchange HD + H2O left and right arrow HDO + H2. Molecular hydrogen is strongly depleted in deuterium relative to water on Mars because of the very long lifetime of H2 (1200 years). The derived isotope fractionation corresponds to an estimate of a planetwide reservoir of water ice about 5 meters thick that is exchangeable with the atmosphere.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Krasnopolsky, V A -- Mumma, M J -- Gladstone, G R -- New York, N.Y. -- Science. 1998 Jun 5;280(5369):1576-80.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physics, Catholic University of America, Washington, DC 20064, USA. VKras@lepvx3.gsfc.nasa.gov〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9616115" target="_blank"〉PubMed〈/a〉
    Keywords: Atmosphere ; Deuterium/*analysis ; *Extraterrestrial Environment ; Hydrogen/*analysis ; Ice ; *Mars ; Temperature ; *Water
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    Science in Southeast Asia (1998)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1998-03-21
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉New York, N.Y. -- Science. 1998 Mar 6;279(5356):1465-82.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9508721" target="_blank"〉PubMed〈/a〉
    Keywords: Asia, Southeastern ; *Science
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    A preorganized active site in the crystal structure of the Tetrahymena ribozyme (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-12-05
    Description: Group I introns possess a single active site that catalyzes the two sequential reactions of self-splicing. An RNA comprising the two domains of the Tetrahymena thermophila group I intron catalytic core retains activity, and the 5.0 angstrom crystal structure of this 247-nucleotide ribozyme is now described. Close packing of the two domains forms a shallow cleft capable of binding the short helix that contains the 5' splice site. The helix that provides the binding site for the guanosine substrate deviates significantly from A-form geometry, providing a tight binding pocket. The binding pockets for both the 5' splice site helix and guanosine are formed and oriented in the absence of these substrates. Thus, this large ribozyme is largely preorganized for catalysis, much like a globular protein enzyme.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Golden, B L -- Gooding, A R -- Podell, E R -- Cech, T R -- New York, N.Y. -- Science. 1998 Oct 9;282(5387):259-64.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Howard Hughes Medical Institute, Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309-0215, USA. bgolden@petunia.colorado.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9841391" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Base Pairing ; Base Sequence ; Binding Sites ; Catalysis ; Crystallography, X-Ray ; Guanosine/metabolism ; Introns ; Magnesium/metabolism ; Manganese/metabolism ; *Models, Molecular ; Molecular Sequence Data ; *Nucleic Acid Conformation ; Phosphates/metabolism ; RNA Splicing ; RNA, Catalytic/*chemistry/metabolism ; Tetrahymena thermophila/*genetics
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 98
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    Dismissal of faculty (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-12-05
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Soslau, G -- Rottenberg, H -- Stearns, M -- New York, N.Y. -- Science. 1998 Oct 23;282(5389):627-8.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9841412" target="_blank"〉PubMed〈/a〉
    Keywords: Academic Medical Centers/manpower/*organization & administration ; *Faculty ; *Faculty, Medical ; Pennsylvania ; Schools, Medical/manpower/*organization & administration
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 99
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    Expansion of the allelic exclusion principle? (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-04-16
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Chess, A -- New York, N.Y. -- Science. 1998 Mar 27;279(5359):2067-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Whitehead Institute for Biomedical Research, Massachusetts Institute of Technology, Cambridge, MA 02142, USA. chess@wi.mit.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9537917" target="_blank"〉PubMed〈/a〉
    Keywords: *Alleles ; Animals ; CD4-Positive T-Lymphocytes/*immunology ; DNA Replication ; *Gene Expression Regulation ; Genes, Immunoglobulin ; Interleukin-2/*genetics ; Lymphocyte Activation ; Mice ; Polymerase Chain Reaction ; Receptors, Antigen, T-Cell/metabolism ; Signal Transduction ; Transcription, Genetic
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 100
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    Magnetic Field and Plasma Observations at Mars: Initial Results of the Mars Global Surveyor Mission (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-03-13
    Description: The magnetometer and electron reflectometer investigation (MAG/ER) on the Mars Global Surveyor spacecraft has obtained magnetic field and plasma observations throughout the near-Mars environment, from beyond the influence of Mars to just above the surface (at an altitude of approximately 100 kilometers). The solar wind interaction with Mars is in many ways similar to that at Venus and at an active comet, that is, primarily an ionospheric-atmospheric interaction. No significant planetary magnetic field of global scale has been detected to date (〈2 x 10(21) Gauss-cubic centimeter), but here the discovery of multiple magnetic anomalies of small spatial scale in the crust of Mars is reported.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Acuna -- Connerney -- Wasilewski -- Lin -- Anderson -- Carlson -- McFadden -- Curtis -- Mitchell -- Reme -- Mazelle -- Sauvaud -- d'Uston -- Cros -- Medale -- Bauer -- Cloutier -- Mayhew -- Winterhalter -- Ness -- New York, N.Y. -- Science. 1998 Mar 13;279(5357):1676-80.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉M. H. Acuna, J. E. P. Connerney, P. Wasilewski, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA. R. P. Lin, Space Sciences Laboratory and Department of Physics, University of California, Berkeley, CA 94720, USA. K. A. Anderson, C. W. Carlson, J. McFadden, D. W. Curtis, D. Mitchell, Space Sciences Laboratory, University of California, Berkeley, CA 94720, USA. H. Reme, C. Mazelle, J. A. Sauvaud, C. d'Uston, A. Cros, J. L. Medale, Centre d'Etude Spatiale des Rayonnements, 31209 Toulouse Cedex, France. S. J. Bauer, University of Graz and Space Research Institute, A-8010 Graz, Austria. P. Cloutier, Department of Space Physics and Astronomy, Rice University, Houston, TX 77005, USA. M. Mayhew, National Science Foundation, Arlington, VA 22230, USA. D. Winterhalter, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA. N. F. Ness, Bartol Research Institute, University of Delaware, Newark, DE 19716, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9497279" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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