ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • American Meteorological Society  (7,601)
  • Annual Reviews
  • 2000-2004  (10,167)
  • 1
    facet.materialart.
    Unknown
    American Meteorological Society
    In:  Journal of Climate, 16 . pp. 2717-2734.
    Publication Date: 2018-07-24
    Description: Synoptic-scale variability in the air–sea turbulent fluxes in the areas of midlatitudinal western boundary currents is analyzed. In the Gulf Stream area, ocean–atmosphere fluxes on synoptic time- and space scales are clearly coordinated with the propagating synoptic-scale atmospheric transients. The statistical analysis of 6-hourly resolution sea level pressure and surface turbulent fluxes from the NCEP–NCAR reanalysis for the period from 1948 to 2000 in the area of strong sea surface temperature gradients in the Gulf Stream gives strong proof for the association between the propagating cyclones and synoptic patterns of surface turbulent fluxes. It is shown that sea–air interaction in this area is controlled by the sharpness of surface temperature gradients in the ocean and by the intensity of the advection of the air masses in different parts of cyclones during the cold-air and warm-air outbreaks. A simple parameter based on the joint consideration of the characteristics of sea surface temperature and sea level pressure fields is used to characterize the synoptic variability of air–sea turbulent fluxes. The effectiveness of the relationship between surface temperature and surface pressure on one side and air–sea flux anomalies on the other vary from year to year in phase with variability in the frequencies of deep atmospheric cyclones in the Gulf Stream area. The limits of applicability of the approach, its sensitivity to higher-resolution sea surface temperature data, and the possibility of its further applications are discussed.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    facet.materialart.
    Unknown
    American Meteorological Society
    In:  Journal of Physical Oceanography, 32 . pp. 1112-1116.
    Publication Date: 2018-04-06
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    facet.materialart.
    Unknown
    American Meteorological Society
    In:  Journal of Climate, 15 . pp. 3043-3057.
    Publication Date: 2018-07-24
    Description: Zonally symmetric fluctuations of the midlatitude westerly winds characterize the primary mode of atmospheric variability in the Southern Hemisphere during all seasons. This is true not only in observations but also in an unforced 15 000-yr integration of a coarse-resolution (R15) coupled ocean–atmosphere model. Here it is documented how this mode of atmospheric variability, known as the Southern Annular Mode (SAM), generates ocean circulation and sea ice variations in the model integration on interannual to centennial timescales that are tightly in phase with the SAM. The positive phase of the SAM is associated with an intensification of the surface westerlies over the circumpolar ocean (around 60°S), and a weakening of the surface westerlies farther north. This induces Ekman drift to the north at all longitudes of the circumpolar ocean, and Ekman drift to the south at around 30°S. Through mass continuity, the Ekman drift generates anomalous upwelling along the margins of the Antarctic continent, and downwelling around 45°S. The anomalous flow diverging from the Antarctic continent also increases the vertical tilt of the isopycnals in the Southern Ocean, so that a more intense circumpolar current is also closely associated with positive SAM. In addition, the anomalous divergent flow advects sea ice farther north, resulting in an increase in sea ice coverage. Finally, positive SAM drives increases in poleward heat transport at about 30°S, while decreases occur in the circumpolar region. Ocean and sea ice anomalies of the opposite sign occur when the SAM is negative. The ocean and sea ice fluctuations associated with the SAM constitute a significant fraction of simulated ocean variability poleward of 30°S year-round. The robustness of the mechanisms relating the SAM to oceanic variability suggests that the SAM is likely an important source of large-scale variability in the real Southern Hemisphere ocean.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    Publication Date: 2018-04-10
    Description: Comparisons are made between a time series of meteorological surface layer observational data taken on board the R/V Knorr, and model analysis data from the European Centre for Medium-Range Weather Forecasting (ECMWF) and the National Centers for Environmental Prediction (NCEP). The observational data were gathered during a winter cruise of the R/V Knorr, from 6 February to 13 March 1997, as part of the Labrador Sea Deep Convection Experiment. The surface layer observations generally compare well with both model representations of the wintertime atmosphere. The biases that exist are mainly related to discrepancies in the sea surface temperature or the relative humidity of the analyses. The surface layer observations are used to generate bulk estimates of the surface momentum flux, and the surface sensible and latent heat fluxes. These are then compared with the model-generated turbulent surface fluxes. The ECMWF surface sensible and latent heat flux time series compare reasonably well, with overestimates of only 13% and 10%, respectively. In contrast, the NCEP model overestimates the bulk fluxes by 51% and 27%, respectively. The differences between the bulk estimates and those of the two models are due to different surface heat flux algorithms. It is shown that the roughness length formula used in the NCEP reanalysis project is inappropriate for moderate to high wind speeds. Its failings are acute for situations of large air–sea temperature difference and high wind speed, that is, for areas of high sensible heat fluxes such as the Labrador Sea, the Norwegian Sea, the Gulf Stream, and the Kuroshio. The new operational NCEP bulk algorithm is found to be more appropriate for such areas. It is concluded that surface turbulent flux fields from the ECMWF are within the bounds of observational uncertainty and therefore suitable for driving ocean models. This is in contrast to the surface flux fields from the NCEP reanalysis project, where the application of a more suitable algorithm to the model surface-layer meteorological data is recommended
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    facet.materialart.
    Unknown
    American Meteorological Society
    In:  Journal of Climate, 17 (22). pp. 4463-4472.
    Publication Date: 2017-08-23
    Description: On seasonal time scales, ENSO prediction has become feasible in an operational framework in recent years. On decadal to multidecadal time scales, the variability of the oceanic circulation is assumed to provide a potential for climate prediction. To investigate the decadal predictability of the coupled atmosphere–ocean general circulation model (AOGCM) European Centre-Hamburg model version 5/Max Planck Institute Ocean Model (ECHAM5/MPI-OM), a 500-yr-long control integration and “perfect model” predictability experiments are analyzed. The results show that the sea surface temperatures (SSTs) of the North Atlantic, Nordic Seas, and Southern Ocean exhibit predictability on multidecadal time scales. Over the ocean, the predictability of surface air temperature (SAT) is very similar to that of SST. Over land, there is little evidence of decadal predictability of SAT except for some small maritime-influenced regions of Europe. The AOGCM produces predictable signals in lower-tropospheric temperature and precipitation over the North Atlantic, but not in sea level pressure.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 6
    facet.materialart.
    Unknown
    American Meteorological Society
    In:  Journal of Physical Oceanography, 32 . pp. 687-701.
    Publication Date: 2018-04-06
    Description: The quasi-decadal salinity fluctuations in the upper 300 m of the Labrador Sea are investigated by partitioning all available salinity station data since 1948 by region and bottom depth. There are major freshwater anomalies in the early 1970s (the Great Salinity Anomaly), mid-1980s, and early 1990s. These vary in amplitude throughout the region, being least on the shelf and greatest over the slope region near the Labrador Current. The Labrador Sea cannot be considered a simple conduit for freshwater anomalies originating in the East Greenland Current. There is evidence that local processes modulate the anomaly. The freshwater anomalies in the Labrador Current are approximately twice as large as those in the East Greenland Current. The Baffin Island Current flowing southward through the western Davis Strait is the only local source of freshwater with sufficient volume to account for this increase. The propagation speed, 2–3 cm s−1, of the anomaly along the Labrador Sea margin is much less than the advection speed indicating a highly damped system. The connection of the North Atlantic Oscillation (NAO) with these quasi-decadal salinity fluctuations is most obvious in the Labrador Sea interior, where increased surface buoyancy flux during positive NAO drives deep convective mixing and thus terminates the fresh surface anomalies. Less clear are the processes by which NAO-forced changes of lateral freshwater flux modulate the salinity along the margin. The authors propose a feedback mechanism where, during years of low wind speed, freshwater accumulates offshore of the slope front in the surface layer. The increased upper-layer buoyancy prohibits further mixing, and low salinities persist.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 7
    facet.materialart.
    Unknown
    American Meteorological Society
    In:  Journal of Physical Oceanography, 32 (3). pp. 891-902.
    Publication Date: 2018-04-06
    Description: The so-called equatorial stacked jets are analyzed with ship-board observations and moored time series from the Atlantic Ocean. The features are identified and isolated by comparing vertical wavenumber spectra at the equator with those a few degrees from the equator. Mode-filtering gives clear views of the jets in meridional sections, the typical extent being ±1° in latitude. The vertical structure can be well described (explaining 82% of the variance) by N−1-stretched cosines, with a Gaussian amplitude tapering in the vertical. The stretched wavelengths are somewhat variable. Fitting jets of a fixed (stretched) wavelength to four moored sensors in the depth range 1300–1900 m, allows one to track the vertical phase of the jets with an rms error of 30°–45°. The resulting fit from a 20-month moored time series shows long periods of unchanging jet conditions and intermittent times of high variability. There is no significant vertical propagation on these timescales nor a seasonal reversal. Using a composite from many different experiments, interannual variability is visible, however. A possible mechanism for the stacked jets is inertial instability, resulting from background meridional shears at the equator. A condition is that the Ertel potential vorticity becomes zero somewhere, due to meridional asymmetries in the zonal flows. The ship-board observations show that this may be approximately fulfilled by the instantaneous zonal low-mode flows at various depths, resulting from an excess of zonal momentum south of the equator most of the time. Inertial instability should act to redistribute this zonal momentum, and our mooring data show indeed persistent northward momentum flux, but not at the depth levels expected. The momentum transport might suggest that the jets can also flux or mix other properties across the equator.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 8
    facet.materialart.
    Unknown
    American Meteorological Society
    In:  Journal of Climate, 17 (11). pp. 2255-2258.
    Publication Date: 2017-08-23
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 9
    facet.materialart.
    Unknown
    American Meteorological Society
    In:  Journal of Physical Oceanography, 31 . pp. 1287-1303.
    Publication Date: 2018-04-06
    Description: A general circulation ocean model has been used to study the formation and propagation mechanisms of North Atlantic Oscillation (NAO)-generated temperature anomalies along the pathway of the North Atlantic Current (NAC). The NAO-like wind forcing generates temperature anomalies in the upper 440 m that propagate along the pathway of the NAC in general agreement with the observations. The analysis of individual components of the ocean heat budget reveals that the anomalies are primarily generated by the wind stress anomaly-induced oceanic heat transport divergence. After their generation they are advected with the mean current. Surface heat flux anomalies account for only one-third of the total temperature changes. Along the pathway of the NAC temperature anomalies of opposite signs are formed in the first and second halves of the pathway, a pattern called here the North Atlantic dipole (NAD). The response of the ocean depends fundamentally on Rt = (L/υ)/τ, the ratio between the time it takes for anomalies to propagate along the NAC [(L/υ) 10 years] compared to the forcing period τ. The authors find that for NAO periods shorter than 4 years (Rt 〉 1) the response in the subpolar region is mainly determined by the local forcing. For NAO periods longer than 32 years (Rt 〈 1); however, the SST anomalies in the northeastern part of the NAD become controlled by ocean advection. In the subpolar region maximal amplitudes of the temperature response are found for intermediate (decadal) periods (Rt 1) where the propagation of temperature anomalies constructively interferes with the local forcing. A comparison of the NAO-generated propagating temperature anomalies with those found in observations will be discussed.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 10
    Publication Date: 2017-07-20
    Description: Sea surface temperature (SST) observations in the North Atlantic indicate the existence of strong multidecadal variability with a unique spatial structure. It is shown by means of a new global climate model, which does not employ flux adjustments, that the multidecadal SST variability is closely related to variations in the North Atlantic thermohaline circulation (THC). The close correspondence between the North Atlantic SST and THC variabilities allows, in conjunction with the dynamical inertia of the THC, for the prediction of the slowly varying component of the North Atlantic climate system. It is shown additionally that past variations of the North Atlantic THC can be reconstructed from a simple North Atlantic SST index and that future, anthropogenically forced changes in the THC can be easily monitored by observing SSTs. The latter is confirmed by another state-of-the-art global climate model. Finally, the strong multidecadal variability may mask an anthropogenic signal in the North Atlantic for some decades.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 11
    facet.materialart.
    Unknown
    American Meteorological Society
    In:  Journal of Physical Oceanography, 34 (11). pp. 2398-2412.
    Publication Date: 2018-04-11
    Description: In the eastern South Pacific Ocean, at a depth of about 200 m, a salinity minimum is found. This minimum is associated with a particular water mass, the “Shallow Salinity Minimum Water” (SSMW). SSMW outcrops in a fresh tongue (Smin) centered at about 45°S. The Smin appears to emanate from the eastern boundary, against the mean flow. The watermass transformation that creates SSMW and Smin is investigated here. The Smin and SSMW are transformed from saltier and warmer waters originating from the western South Pacific. The freshening and cooling occur when the water is advected eastward at the poleward side of the subtropical gyre. Sources of freshening and cooling are air–sea exchange and advection of water from south of the subtropical gyre. A freshwater and heat budget for the mixed layer reveals that both sources equally contribute to the watermass transformation in the mixed layer. The freshened and cooled mixed layer water is subducted into the gyre interior along the southern rim of the subtropical gyre. Subduction into the zonal flow restricts the transformation of interior properties to diffusion only. A simple advection/diffusion balance reveals diffusion coefficients of order 2000 m2 s−1. The tongue shape of the Smin is explained from a dynamical viewpoint because no relation to a positive precipitation–evaporation balance was found. Freshest Smin values are found to coincide with slowest eastward mixed layer flow that accumulates the largest amounts of freshwater in the mixed layer and creates the fresh tongue at the sea surface. Although the SSMW is the densest and freshest mode of water subducted along the South American coast, the freshening and cooling in the South Pacific affect a whole range of densities (25.0–26.8 kg m−3). The transformed water turns northward with the gyre circulation and contributes to the hydrographic structure of the gyre farther north. Because the South Pacific provides most of the source waters that upwell along the equatorial Pacific, variability in South Pacific hydrography may influence equatorial Pacific hydrography. Because one-half of the transformation is found to be controlled through Ekman transport, variability in wind forcing at the southern rim of the subtropical gyre may be a source for variability of the equatorial Pacific.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 12
    facet.materialart.
    Unknown
    American Meteorological Society
    In:  Journal of Physical Oceanography, 32 (12). pp. 3346-3363.
    Publication Date: 2018-04-06
    Description: Experiments with a suite of North Atlantic general circulation models are used to examine the sources of eddy kinetic energy (EKE) in the Labrador Sea. A high-resolution model version (112°) quantitatively reproduces the observed signature. A particular feature of the EKE in the Labrador Sea is its pronounced seasonal cycle, with a maximum intensity in early winter, as already found in earlier studies based on altimeter data. In contrast to a previously advanced hypothesis, the seasonally varying eddy field is not related to a forcing by high-frequency wind variations but can be explained by a seasonally modulated instability of the West Greenland Current (WGC). The main source of EKE in the Labrador Sea is an energy transfer due to Reynolds interaction work (barotropic instability) in a confined region near Cape Desolation where the WGC adjusts to a change in the topographic slope: Geostrophic contours tend to converge upstream of Cape Desolation, such that the topographically guided WGC narrows as well and becomes barotropically unstable. The eddies spawned from the WGC instability area, dominating the EKE in the interior Labrador Sea, are predominantly anticyclonic with warm and saline cores in the upper kilometer of the water column, while the few cyclones originating as well from the instability area show a more depth-independent structure. Companion experiments with a ⅓° model exhibit the strength of the WGC, influenced by either changes in the wind stress or heat flux forcing, as a leading factor determining seasonal to interannual changes of EKE in the Labrador Sea
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 13
    facet.materialart.
    Unknown
    American Meteorological Society
    In:  Journal of Physical Oceanography, 34 . pp. 1548-1570.
    Publication Date: 2018-04-11
    Description: The deep circulation and related transports of the southern Labrador Sea are determined from direct current observations from ship surveys and a moored current-meter array. The measurements covered a time span from summer 1997 to 1999 and show a well-defined deep boundary current extending approximately out to the 3300-m depth contour and weak reverse currents farther offshore. The flow has a strong barotropic component, and significant baroclinic flow is only found in the shallow Labrador Current at the shelf break and associated with a deep core of Denmark Strait Overflow Water. The total deep-water transport below σΘ = 27.74 kg m−3 was 26 ± 5 Sv (Sv ≡ 106 m3 s−1) comprising Labrador Sea Water (LSW), Gibbs Fracture Zone Water (GFZW), and Denmark Strait Overflow Water (DSOW). Intraseasonal variability of the flow and transport was high, ranging from 15 to 35 Sv, and the annual means differed by 17%. A seasonal cycle is confined to the shallow Labrador Current; in its deeper part, where the mean flow is still strong, no obvious seasonality could be detected. The transport of the interior anticyclonic recirculation was estimated from lowered acoustic Doppler current profiler stations and geostrophy, yielding about 9 Sv. Thus, the net deep-water outflow from the Labrador Sea was about 17 Sv. The baroclinic transport of GFZW and DSOW referenced to the depth of the isopycnal σΘ = 27.80 kg m−3 is only about one-third of the total transport in these layers. Longer-term variations of the total transports are not represented well by the baroclinic contribution.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 14
    facet.materialart.
    Unknown
    American Meteorological Society
    In:  Journal of Climate, 17 (22). pp. 4301-4315.
    Publication Date: 2017-08-23
    Description: Simulations and seasonal forecasts of tropical Pacific SST and subsurface fields that are based on the global Consortium for Estimating the Circulation and Climate of the Ocean (ECCO) ocean-state estimation procedure are investigated. As compared to similar results from a traditional ENSO simulation and forecast procedure, the hindcast of the constrained ocean state is significantly closer to observed surface and subsurface conditions. The skill of the 12-month lead SST forecast in the equatorial Pacific is comparable in both approaches. The optimization appears to have better skill in the SST anomaly correlations, suggesting that the initial ocean conditions and forcing corrections calculated by the ocean-state estimation do have a positive impact on the predictive skill. However, the optimized forecast skill is currently limited by the low quality of the statistical atmosphere. Progress is expected from optimizing a coupled model over a longer time interval with the coupling statistics being part of the control vector.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 15
    Publication Date: 2016-09-07
    Description: A multi-model ensemble-based system for seasonal-to-interannual prediction has been developed in a joint European project known as DEMETER (Development of a European Multimodel Ensemble Prediction System for Seasonal to Interannual Prediction). The DEMETER system comprises seven global atmosphere–ocean coupled models, each running from an ensemble of initial conditions. Comprehensive hindcast evaluation demonstrates the enhanced reliability and skill of the multimodel ensemble over a more conventional single-model ensemble approach. In addition, innovative examples of the application of seasonal ensemble forecasts in malaria and crop yield prediction are discussed. The strategy followed in DEMETER deals with important problems such as communication across disciplines, downscaling of climate simulations, and use of probabilistic forecast information in the applications sector, illustrating the economic value of seasonal-to-interannual prediction for society as a whole.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 16
    facet.materialart.
    Unknown
    American Meteorological Society
    In:  Journal of Physical Oceanography, 32 . pp. 573-584.
    Publication Date: 2018-04-06
    Description: Fifteen profiling floats were injected into the deep boundary current off Labrador. They were ballasted to drift in the core depth of Labrador Sea Water (LSW) at 1500-m depth and were deployed in two groups during March and July/August 1997. Initially, for about three months, the floats were drifting within the boundary current, and the flow vectors were used to determine the mean horizontal structure of the Deep Labrador Current, which was found to be about 100 km wide with an average core speed of 18 cm s−1. North of Flemish Cap the boundary current encounters complicated topography around “Orphan Knoll,” and there the LSW outflow splits up into different routes. One obvious LSW path is eastward through the Charlie Gibbs Fracture Zone and another route is a narrow recirculation toward the central Labrador Sea. A surprising result was that none of the floats were able to follow the boundary current southward to the Grand Banks area and exit into the subtropics. Trajectories and temperature profiles of the eastward drifting floats indicate the importance of the North Atlantic Current for dispersing the floats, even at the level of LSW.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 17
    facet.materialart.
    Unknown
    American Meteorological Society
    In:  Journal of Physical Oceanography, 32 . pp. 3020-3038.
    Publication Date: 2018-04-09
    Description: The ventilation of the permanent thermocline of the Southern Hemisphere gyres is quantified using climatological and synoptic observational data. Ventilation is estimated with three independent methods: the kinematic method provides subduction rates from the vertical and horizontal fluxes through the base of the mixed layer, the water age uses in situ age distribution of thermocline waters, and the annual-mean water mass formation through air–sea interaction is calculated. All three independent estimates agree within their error bars, which are admittedly large. The subduction rates are mainly controlled through their vertical and lateral components with only minor transient eddy contributions. The vertical transfer, derived from Ekman pumping, ventilates over most of the areas of the subtropical gyres, while lateral transfer occurs mainly along the Subtropical and Subantarctic Fronts, where it injects mode and intermediate waters. For the permanent thermocline the overall ventilation of the South Atlantic is about 21 Sv (Sv ≡ 106 m3 s−1). Of this, lateral transfer contributes 10 Sv, mainly in the Brazil–Malvinas confluence zone and to the northeast of Drake Passage. The effective vertical transfer at the bottom of the mixed layer is only two-thirds of the Ekman pumping due to strong northward forcing of the mixed layer itself. The Indian Ocean is ventilated at a rate of 35 Sv with equal lateral and vertical contributions. The South Pacific's overall ventilation is 44 Sv of which the lateral input contributes little more than half. West of 130°W, the South Pacific is ventilated through Ekman pumping and with only minor lateral transfer. In the east lateral transfer dominates between 10° and 20°S and along the Subantarctic Front in a narrow density range. Combining overall transports with earlier estimates for the Northern Hemisphere gives a ventilation of the World Ocean's permanent thermocline of about 160 Sv. Analysis of atmospheric reanalysis air–sea flux data reveals an overall increase in the formation of thermocline waters for all three Southern Hemisphere oceans.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 18
    facet.materialart.
    Unknown
    American Meteorological Society
    In:  Journal of Physical Oceanography, 34 (3). pp. 566-581.
    Publication Date: 2018-04-11
    Description: Two major water masses dominate the deep layers in the Mariana and Caroline Basins: the Lower Circumpolar Water (LCPW), arriving from the Southern Ocean along the slopes north of the Marshall Islands, and the North Pacific Deep Water (NPDW) reaching the region from the northeastern Pacific Ocean. Hydrographic and moored observations and multibeam echosounding were performed in the East Mariana and the East Caroline Basins to detail watermass distributions and flow paths in the area. The LCPW enters the East Mariana Basin from the east. At about 13°N, however, in the southern part of the basin, a part of this water mass arrives in a southward western boundary flow along the Izu–Ogasawara–Mariana Ridge. Both hydrographic observations and moored current measurements lead to the conclusion that this water not only continues westward to the West Mariana Basin as suggested before, but also provides bottom water to the East Caroline Basin. The critical throughflow regions were identified by multibeam echosounding at the Yap Mariana Junction between the East and West Mariana Basins and at the Caroline Ridge between the East Mariana and East Caroline Basins. The throughflow is steady between the East and West Mariana Basins, whereas more variability is found at the Caroline Ridge. At both locations, throughflow fluctuations are correlated with watermass property variations suggesting layer-thickness changes. The total transport to the two neighboring basins is only about 1 Sverdrup (1Sv ≡ 106 m3 s−1) but has considerable impact on the watermass structure in these basins. Estimates are given for the diapycnal mixing that is required to balance the inflow into the East Caroline Basin. Farther above in the water column, the high-silica tongue of NPDW extends from the east to the far southwestern corner of the East Mariana Basin, with transports being mostly southward across the basin.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 19
    Publication Date: 2018-04-11
    Description: The current system east of the Grand Banks was intensely observed by World Ocean Circulation Experiment (WOCE) array ACM-6 during 1993–95 with eight moorings, reaching about 500 km out from the shelf edge and covering the water column from about 400-m depth to the bottom. More recently, a reduced array by the Institut für Meerskunde (IfM) at Kiel, Germany, of four moorings was deployed during 1999–2001, focusing on the deep-water flow near the western continental slope. Both sets of moored time series, each about 22 months long, are combined here for a mean current boundary section, and both arrays are analyzed for the variability of currents and transports. A mean hydrographic section is derived from seven ship surveys and is used for geostrophic upper-layer extrapolation and isopycnal subdivision of the mean transports into deep-water classes. The offshore part of the combined section is dominated by the deep-reaching North Atlantic Current (NAC) with currents still at 10 cm s−1 near the bottom and a total northward transport of about 140 Sv (Sv ≡ 106 m3 s−1), with the details depending on the method of surface extrapolation used. The mean flow along the western boundary was southward with the section-mean North Atlantic Deep Water outflow determined to be 12 Sv below the σθ = 27.74 kg m−3 isopycnal. However, east of the deep western boundary current (DWBC), the deep NAC carries a transport of 51 Sv northward below σθ = 27.74 kg m−3, resulting in a large net northward flow in the western part of the basin. From watermass signatures it is concluded that the deep NAC is not a direct recirculation of DWBC water masses. Transport time series for the DWBC variability are derived for both arrays. The variance is concentrated in the period range from 2 weeks to 2 months, but there are also variations at interannual and longer periods, with much of the DWBC variability being related to fluctuations and meandering of the NAC. A significant annual cycle is not recognizable in the combined current and transport time series of both arrays. The moored array results are compared with other evidence on deep outflow and recirculation, including recent models of different types and complexity.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 20
    facet.materialart.
    Unknown
    American Meteorological Society
    In:  Journal of the Atmospheric Sciences, 60 . pp. 152-165.
    Publication Date: 2018-04-16
    Description: A new mechanism is proposed that explains two key features of the observed El Niño–Southern Oscillation (ENSO) phenomenon—its irregularity and decadal amplitude changes. Using a low-order ENSO model, the authors show that the nonlinearities in the tropical heat budget can lead to bursting behavior characterized by decadal occurrences of strong El Niño events. La Niña events are not affected, a feature that is also seen in ENSO observations. One key result of this analysis is that decadal variability in the Tropics can be generated without invoking extratropical processes or stochastic forcing. The El Niño bursting behavior simulated by the low-order ENSO model can be understood in terms of the concept of homoclinic and heteroclinic connections. It is shown that this new model for ENSO amplitude modulations and irregularity, although difficult to prove, might explain some features of ENSO dynamics seen in more complex climate models and the observations.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 21
    facet.materialart.
    Unknown
    American Meteorological Society
    In:  Journal of Atmospheric and Oceanic Technology, 19 (5). pp. 794-807.
    Publication Date: 2017-01-25
    Description: Lowered acoustic Doppler current profilers (LADCPs) have matured from an experimental instrument to an operational hydrographic tool to study ocean dynamics. The data processing, however, is still in a rather primitive state. First, a method to estimate bottom-track velocities using the standard water profile data was developed. Then inverse solutions are presented that enhance the standard data processing by adding external constraints such as bottom-referenced velocity profiles. Depending on the depth of the profile and the ADCP range the inclusion of bottom-track data can reduce the local velocity errors by a significant factor. The least squares framework also allows for simplified error analysis of the LADCP system and some of the trade-offs are discussed.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 22
    facet.materialart.
    Unknown
    American Meteorological Society
    In:  Journal of Atmospheric and Oceanic Technology, 17 . pp. 1439-1443.
    Publication Date: 2018-07-04
    Description: The World Ocean Circulation Experiment has established Lagrangian observations with neutrally buoyant floats as a routine tool in the study of deep-sea currents. Here a novel variant of the well-proven RAFOS concept for seeding floats at locations where they can be triggered on a timed basis is introduced. This cost-effective method obviates the need to revisit sites with a high-priced research vessel each time floats are to be deployed. It enables multiple Lagrangian time series, for example, for the observation of intermediate point sources of water masses, which are independent but have identical start points. This can be done even in environmentally challenging regions such as below the ice. The successfully tested autonomous float park concept does not rely on a release carousel moored on the seafloor. Instead, a second release was added to the standard RAFOS float for optional delay of regular drift missions. A float park can easily be installed by a conductivity–temperature–depth recorder system with a slightly modified rosette sampler.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 23
    facet.materialart.
    Unknown
    American Meteorological Society
    In:  Journal of Physical Oceanography, 31 (3). pp. 765-776.
    Publication Date: 2018-04-06
    Description: The authors derive a string function that describes the propagation of large-scale, potentially large amplitude, baroclinic energy anomalies in a two-layer ocean with variable topography and rotation parameter. The generality of the two-layer results allows results for the 1-layer, 1.5-layer, inverted 1.5-layer, lens, and dome models to be produced as limiting-cases. The string function is a scalar field that acts as a streamfunction for the propagation velocity. In the linear case the string function is simply c2o/f, where co is the background baroclinic shallow water wave speed, and typically describes propagation poleward on the eastern boundaries, westward (with some topographic steering) over the middle ocean, and equatorward on the western boundaries. In the more general nonlinear case, the string function is locally distorted by the anomaly. In the fully nonlinear examples of a lens or dome, there is no rest or background string function; the string function is generated entirely by the disturbance and propagation is due to asymmetric distribution of the anomalous mass over the string function contours. It is shown that conventional beta/topographic propagation results (e.g., beta drift of eddies, the Nof speed of cold domes) can be obtained as limiting cases of the string function. The string function provides, however, more general propagation velocities that are also usually simpler to derive. The first baroclinic mode string function for the global oceans is calculated from hydrographic data. The westward propagation speeds in the ocean basins as derived from the meridional gradient of the string function are typically two to five times faster than those expected from standard theory and agree well with the propagation speeds observed for long baroclinic Rossby waves in the TOPEX/Poseidon data.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 24
    facet.materialart.
    Unknown
    American Meteorological Society
    In:  Journal of Climate, 15 (2). pp. 216-225.
    Publication Date: 2018-07-24
    Description: Empirical orthogonal function (EOF) analyses (rotated or not) are widely used in climate research. In recent years there have been several studies in which EOF analyses were used to highlight potential physical mechanisms associated with climate variability. For example, several SST modes were identified such as the “Tropical Atlantic Dipole,” the “Tropical Indian Ocean Dipole,” and different SLP modes in the Northern Hemisphere winter. In this note it is emphasized that caution should be used when trying to interpret these statistically derived modes and their significance. Indeed, from a synthetic example it is shown that patterns derived from EOF analyses can be misleading at times and associated with very little climate physics.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 25
    facet.materialart.
    Unknown
    American Meteorological Society
    In:  Journal of Climate, 13 (4). pp. 777-792.
    Publication Date: 2018-07-24
    Description: Analyses of annual mean sea surface temperatures (SST) from observations for the period 1903–94 and four different general circulation models (GCMs) were conducted. The two dominant EOFs of all datasets are characterized by two patterns, which are centered in the trade wind zones, at roughly 15°N and 15°S, respectively. The two patterns are uncorrelated at any lag and the time spectra of the corresponding principle components are consistent with red noise. The SST variability is strongly correlated with wind stress anomalies in the trade wind zones. The correlations between the wind stress and the SST, as well as the correlation between the net heat flux and the SST anomalies are consistent with the assumption that the variability of the upper tropical Atlantic Ocean is forced by the atmosphere. Dynamic feedbacks of the tropical Atlantic Ocean are less important. The variability in the trade wind zones shows a weak correlation with the ENSO mode in the tropical Pacific.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 26
    facet.materialart.
    Unknown
    American Meteorological Society
    In:  Journal of Climate, 13 (11). pp. 1809-1813.
    Publication Date: 2018-07-24
    Description: Most global climate models simulate a weakening of the North Atlantic thermohaline circulation (THC) in response to enhanced greenhouse warming. Both surface warming and freshening in high latitudes, the so-called sinking region, contribute to the weakening of the THC. Some models even simulate a complete breakdown of the THC at sufficiently strong forcing. Here results are presented from a state-of-the-art global climate model that does not simulate a weakening of the THC in response to greenhouse warming. Large-scale air–sea interactions in the Tropics, similar to those operating during present-day El Niños, lead to anomalously high salinities in the tropical Atlantic. These are advected into the sinking region, thereby increasing the surface density and compensating the effects of the local warming and freshening.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 27
    facet.materialart.
    Unknown
    American Meteorological Society
    In:  Journal of Climate, 13 (6). pp. 1173-1194.
    Publication Date: 2018-07-24
    Description: Connections between the tropical and midlatitude Pacific on decadal timescales are examined using a 137-yr run of a fully coupled ocean–atmosphere general circulation model. It is shown that the model does a credible job of simulating both ENSO-scale and decadal-scale variability, and that there are statistically significant correlations between the midlatitudes and Tropics on decadal timescales. Three physical mechanisms linking the regions are examined: 1) Oceanic advection along isopycnal surfaces from the midlatitude subduction regions to the Tropics, 2) coastally trapped or Kelvin wave propagation between the Tropics and midlatitudes, and 3) near-simultaneous communication between the regions affected by changes in the atmosphere. It is found that communication via the atmosphere explains the strongest correlations found in the model. Further evidence is presented that is consistent with the idea that midlatitude sea surface temperature anomalies drive changes in the trade wind system that alter the east–west slope of the tropical thermocline, thereby effecting decadal-timescale changes in ENSO activity.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 28
    facet.materialart.
    Unknown
    American Meteorological Society
    In:  Journal of Climate, 13 (8). pp. 1371-1383.
    Publication Date: 2018-07-24
    Description: The interannual variability of the Indian Ocean SST is investigated by analyzing data from observations and an integration of a global coupled GCM (CGCM) ECHO-2. First, it is demonstrated that the CGCM is capable of producing realistic tropical climate variability. Second, it is shown that a considerable part of the interannual variability in Indian Ocean SST can be described as the response to interannual fluctuations over the Pacific related to ENSO. Although the Indian Ocean region also exhibits ENSO-independent interannual variability, this paper focuses on the ENSO-induced component only. Large-scale SST anomalies of the same sign as those observed in the eastern equatorial Pacific Ocean during ENSO extremes develop in the entire tropical and subtropical Indian Ocean with a time lag of about 4 months. This lead–lag relationship is found in both the observations and the CGCM. Using the CGCM output, it is shown that the ENSO signal is carried into the Indian Ocean mainly through anomalous surface heat fluxes.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 29
    facet.materialart.
    Unknown
    American Meteorological Society
    In:  Bulletin of the American Meteorological Society, 81 (2). pp. 313-318.
    Publication Date: 2016-09-07
    Description: The Coupled Model Intercomparison Project (CMIP) was established to study and intercompare climate simulations made with coupled ocean-atmosphere-cryosphere-land GCMs. There are two main phases (CMIP1 and CMIP2), which study, respectively, 1) the ability of models to simulate current climate, and 2) model simulations of climate change due to an idealized change in forcing (a 1% per year CO2 increase). Results from a number of CMIP projects were reported at the first CMIP Workshop held in Melbourne, Australia, in October 1998. Some recent advances in global coupled modeling related to CMIP were also reported. Presentations were based on preliminary unpublished results. Key outcomes from the workshop were that 1) many observed aspects of climate variability are simulated in global coupled models including the North Atlantic oscillation and its linkages to North Atlantic SSTs, El Niño-like events, and monsoon interannual variability; 2) the amplitude of both high- and low-frequency global mean surface temperature variability in many global coupled models is less than that observed, with the former due in part to simulated ENSO in the models being generally weaker than observed, and the latter likely to be at least partially due to the uncertainty in the estimates of past radiative forcing; 3) an El Niño-like pattern in the mean SST response with greater surface warming in the eastern equatorial Pacific than the western equatorial Pacific is found by a number of models in global warming climate change experiments, but other models have a more spatially uniform or even a La Niña-like, response; 4) flux adjustment, by definition, improves the simulation of mean present-day climate over oceans, does not guarantee a drift-free climate, but can produce a stable base state in some models to enable very long term (1000 yr and longer) integrations-in these models it does not appear to have a major effect on model processes or model responses to increasing CO2; and 5) recent multicentury integrations show that a stable surface climate can be attained without flux adjustment (though still with some systematic simulation errors).
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 30
    facet.materialart.
    Unknown
    American Meteorological Society
    In:  Journal of the Atmospheric Sciences, 57 (8). pp. 1132-1140.
    Publication Date: 2018-04-16
    Description: The response of the Max Planck Institutes ECHAM3 atmospheric general circulation model to a prescribed decade-long positive anomaly in sea surface temperatures (SSTs) over the North Atlantic is investigated. Two 10-yr realizations of the anomaly experiment are compared against a 100-yr control run of the model with seasonally varying climatological SST using a model spatial resolution of T42. In addition to the time-mean response, particular attention is paid to changes in intraseasonal variability, expressed in terms of North Atlantic?European weather regimes. The model regimes are quite realistic. Substantial differences are found in the 700-mb geopotential height field response between the two decadal realizations. The time-mean response in the first sample decade is characterized by the positive (zonal) phase of the North Atlantic oscillation (NAO); this response can be identified with changes in the frequency of occurrence of certain weather regimes by about one standard deviation. (Preliminary results of this numerical experiment were reported at the Atlantic Climate Variability Workshop held at the Lamont?Doherty Earth Observatory of Columbia University, Palisades, New York, 24?26 September 1997.) By contrast, the second SST anomaly decade shows a localized trough centered over the British Isles; it projects less strongly onto the models intrinsic weather regimes. The control run itself exhibits pronounced decade-to-decade variations in the weather regimes frequency of occurrence as well as in its NAO index. The two 10-yr anomaly experiments are insufficient, in length and number, to identify a robust SST response above this level of intrinsic variability.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 31
    facet.materialart.
    Unknown
    American Meteorological Society
    In:  Journal of Physical Oceanography, 31 (4). pp. 1031-1053.
    Publication Date: 2018-04-06
    Description: Observations from the WOCE PCM-1 moored current meter array east of Taiwan for the period September 1994 to May 1996 are used to derive estimates of the Kuroshio transport at the entrance to the East China Sea. Three different methods of calculating the Kuroshio transport are employed and compared. These methods include 1) a “direct” method that uses conventional interpolation of the measured currents and extrapolation to the surface and bottom to estimate the current structure, 2) a “dynamic height” method in which moored temperature measurements from moorings on opposite sides of the channel are used to estimate dynamic height differences across the current and spatially averaged baroclinic transport profiles, and 3) an “adjusted geostrophic” method in which all moored temperature measurements within the array are used to estimate a relative geostrophic velocity field that is referenced and adjusted by the available direct current measurements. The first two methods are largely independent and are shown to produce very similar transport results. The latter two methods are particularly useful in situations where direct current measurements may have marginal resolution for accurate transport estimates. These methods should be generally applicable in other settings and illustrate the benefits of including a dynamic height measuring capability as a backup for conventional direct transport calculations. The mean transport of the Kuroshio over the 20-month duration of the experiment ranges from 20.7 to 22.1 Sv (1 Sv ≡ 106 m3 s−1) for the three methods, or within 1.3 Sv of each other. The overall mean transport for the Kuroshio is estimated to be 21.5 Sv with an uncertainty of 2.5 Sv. All methods show a similar range of variability of ±10 Sv with dominant timescales of several months. Fluctuations in the transport are shown to have a robust vertical structure, with over 90% of the transport variance explained by a single vertical mode. The moored transports are used to determine the relationship between Kuroshio transport and sea-level difference between Taiwan and the southern Ryukyu Islands, allowing for long-term monitoring of the Kuroshio inflow to the East China Sea.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 32
    facet.materialart.
    Unknown
    American Meteorological Society
    In:  Journal of Physical Oceanography, 31 (11). pp. 3214-3229.
    Publication Date: 2018-04-06
    Description: A densely spaced hydrographic survey of the northern Irminger Basin together with satellite-tracked near-surface drifters confirm the intense mesoscale variability within and above the Denmark Strait overflow. In particular, the drifters show distinct cyclonic vortices over the downslope edge of the outflow plume. Growing perturbations such as these can be attributed to the baroclinic instability of a density current. A primitive equation model with periodic boundaries is used to simulate the destabilization of an idealized dense filament on a continental slope that resembles the northeastern Irminger Basin. Unstable waves evolve rapidly if the initial temperature profile is perturbed with a sinusoidal anomaly that exceeds a certain cutoff wavelength. As the waves grow to large amplitudes isolated eddies of both signs develop. Anticyclones form initially within the dense filament and are rich in overflow water. In contrast, cyclones form initially with their center in the ambient water but wrap outflow water around their center, thus containing a mixture of both water types. The nonlinear advection of waters that were originally located within the front between both water masses contributes most significantly to the stronger intensification of the cyclones in comparison with anticyclones. The frontal waters carry positive relative vorticity into the center of the cyclone. The process bears therefore some resemblance to atmospheric frontal cyclogenesis. After saturation there is a bottom jet of overflow water that is confined by counterrotating eddies: anticyclones upslope and cyclones downslope of the overflow core. The parameter dependence of the maximum growth rate is studied, and the implications of eddy-induced mixing for the water mass modification is discussed.
    Type: Article , PeerReviewed
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 33
    ISSN: 1056-3466
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract We assess the environmental health impact and policy implications of the widespread addition of methyl tert-butyl ether (MTBE) as a chemical that is used as an oxygenate to much of the gasoline supply in the United States. Initial concerns about short-term and long-term adverse health consequences following the substantial increase in MTBE use in the winter of 1992-1993 have been supplemented by the discovery in 1996 of what is now relatively widespread contamination of groundwater. We identify 14 governmental initiatives during the 10-year period 1989-1999 in which the potential adverse consequences of MTBE were considered and a nearly identical research agenda was proposed. The lessons from the ongoing MTBE episode show that: (a) research should precede rather than follow environmental health policy decisions; (b) the extent of potential human and environmental exposure should be an important criterion in determining the amount of information needed before making an environmental policy decision; (c) a better understanding of nonspecific human symptoms associated with environmental exposures is needed; (d) the boundaries between the US Environmental Protection Agency program offices should be as porous as the boundaries between environmental media; (e) the US Environmental Protection Agency needs to focus more on public health rather than on legal approaches to environmental management; (f) it is more difficult to remove a chemical once it is in commerce than it is to prevent its use; (g) resolution of uncertainty is best accomplished through research rather than through repetitive review; and (h) better tools are needed to evaluate risk/risk trade-offs. The ongoing replacement of MTBE by other, less well studied oxygenates such as tertiary amyl methyl ether indicates that these environmental public policy lessons have not been learned.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 34
    ISSN: 1056-3466
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The interdependency of aircraft technological systems, the global reach of the aviation transport industry, and the uncertainty surrounding potential atmospheric effects have made defining the relationship between aviation and environmental impact an arduous task. Air travel continues to experience the fastest growth of all modes of transport, and although the energy intensity of the aviation transport system continues to decline, fuel use and total emissions have steadily risen. This trend, which represents a conflict between growth and environmental impact, has motivated the aircraft manufacturing and airline industries, the scientific community, and governmental bodies to consider what pace of emissions reduction is acceptable. This paper analyzes the historical influence of aircraft performance on cost to examine the potential pace of future efficiency improvements and emissions reduction. Technological and operational influences on aircraft energy intensity are quantified and correlated with direct operating cost and aircraft price using analytical and statistical models built upon historical data for US airlines. The energy intensity reduction potential and economic characteristics of future aircraft are also projected, through extrapolations of historical trends in aircraft technology and operations.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 35
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    ISSN: 1056-3466
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Over the past 20 years, a new scientific discipline based on direct measurement of human exposure to environmental pollutants has developed. The fundamental principle of the new science is to "measure where the people are." This has required developing small, lightweight, quiet personal monitors for volatile organic compounds and other pollutants. A second principle has been to measure body burden, particularly exhaled breath, whenever possible to determine the relationship between exposure and dose. Studies employing the new monitors and breath measurements have overturned accepted ideas about the sources of most volatile organic pollutants. The main sources turn out surprisingly often to be small, close to the person, and completely unregulated. These findings should result in major changes in our approach to environmental regulation; however, powerful forces of resistance would need to be overcome.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 36
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    ISSN: 1056-3466
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Civilization's advances during the twentieth century are closely bound with an unprecedented rise of energy consumption in general, and of hydrocarbons and electricity in particular. Substantial improvements of all key nineteenth-century energy techniques and introduction of new extraction and transportation means and new prime movers resulted in widespread diffusion of labor-saving and comfort-providing conversions and in substantially declining energy prices. Although modern societies could not exist without large and incessant flows of energy, there are no simple linear relationships between the inputs of fossil fuels and electricity and a nation's economic performance and social accomplishments. International comparisons show a variety of consumption patterns and a continuing large disparity between affluent and modernizing nations. The necessity of minimizing environmental impacts of energy use, particularly those with potentially worrisome global effects, is perhaps the greatest challenge resulting from the twentieth century's energy advances.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 37
    ISSN: 1056-3466
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Theoretical considerations and empirical data suggest that existing technologies and procedures can improve indoor environments in a manner that significantly increases productivity and health. The existing literature contains moderate to strong evidence that characteristics of buildings and indoor environments significantly influence rates of communicable respiratory illness, allergy and asthma symptoms, sick building symptoms, and worker performance. Whereas there is considerable uncertainty in the estimates of the magnitudes of productivity gains that may be obtained by providing better indoor environments, the projected gains are very large. For the United States, the estimated potential annual savings and productivity gains are $6 to $14 billion from reduced respiratory disease, $1 to $4 billion from reduced allergies and asthma, $10 to $30 billion from reduced sick building syndrome symptoms, and $20 to $160 billion from direct improvements in worker performance that are unrelated to health. Productivity gains that are quantified and demonstrated could serve as a strong stimulus for energy efficiency measures that simultaneously improve the indoor environment.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 38
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    ISSN: 1056-3466
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Low environmental damage is one of the main justifications for continued efforts to reduce energy consumption and to shift to cleaner sources such as solar energy, especially now that supply security has slipped from public consciousness. In recent years there has been much progress in the analysis of environmental damages, in particular thanks to the ExternE (External Costs of Energy) Project of the European Commission. This paper presents a summary of the methodology and key results for the external costs of the major energy technologies. Even though the uncertainties are large, the results provide substantial evidence that the classic air pollutants (particles, NOx and SOx) from fossil fuels impose significant public health costs, comparable to the cost of global warming from CO2 emissions.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 39
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    ISSN: 1056-3466
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: The evolution from an electrochemist was motivated by a growing conviction that Indian science and technology should be reoriented. A cell was created in the Indian Institute of Science in 1974 to initiate and promote work of rural relevance as a weapon against poverty. Surveys led to a detailed empirical study of energy consumption patterns in villages and to the design and construction of rural energy centers. The lessons from this village work are described. The principal outcome of the collaboration with J. Goldemberg (Brazil), T.B. Johansson (Sweden), and R.H. Williams (United States) was the book Energy for a Sustainable World that contributed significantly to the new paradigm for energy. The application of this paradigm resulted in a detailed electricity demand scenario for the South Indian state of Karnataka. Following mandatory retirement from the Indian Institute of Science, the International Energy Initiative (IEI) was set up in 1991 as a Southern-conceived, Southern-led, Southern-located South-North partnership. Persisting personal concerns about the ethical implications of science resurfaced through opposition to India's nuclear tests in 1998 and a visit to the concentration camps at Auschwitz. The associated human dimensions of energy were emphasized in the acceptance speech at Goteborg of the Volvo Environment Prize 2000. The penultimate endgame involved retirement.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 40
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    ISSN: 1056-3466
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract From modest beginnings in the 1960s, environmental economics has grown to be a major subdiscipline of economics. It combines traditional work in the field of welfare economics and the theory of economic growth with more recent perspectives on the political economy of choosing policy instruments and the philosophy of sustainable development. The central tenets are that environmental problems have their roots in the failure of economic systems to maximize human well-being, that environmental quality matters for human well-being and for more traditionally oriented economic growth objectives, and that efficient policy can be achieved through incentive design.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 41
    ISSN: 1056-3466
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Students of public policy sometimes envision an idealized policy process where competent data collection and incisive analysis on both sides of a debate lead to reasoned judgments and sound decisions. Unfortunately, numbers that prove decisive in policy debates are not always carefully developed, credibly documented, or correct. This paper presents four widely cited examples of numbers in the energy field that are either misleading or wrong. It explores the origins of these numbers, how they missed the mark, and how they have been misused by both analysts and the media. In addition, it describes and uses a three-stage analytical process for evaluating such statistics that involves defining terms and boundaries, assessing underlying data, and critically analyzing arguments.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 42
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    ISSN: 1056-3466
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Fossil fuels play a crucial role in satisfying growing world energy demands, but their continued use could cause irreparable harm to the environment. Unless virtually all anthropogenic carbon dioxide is captured, either at the source or subsequently from the air, and disposed of safely and permanently, fossil fuels may have to be phased out over the next few decades. Sequestration of waste carbon dioxide will require methods that can safely store several trillion tons of carbon dioxide. Long-term storage of a gaseous substance is fraught with uncertainty and hazards, but carbonate chemistry offers permanent solutions to the disposal problem. Carbonates can be formed from carbon dioxide and metal oxides in reactions that are thermodynamically favored and exothermic, which result in materials that can be safely and permanently kept out of the active carbon stocks in the environment. Carbonate sequestration methods require the development of an extractive minerals industry that provides the base ions for neutralizing carbonic acid.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 43
    ISSN: 1056-3466
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Technical change in the energy sector is central for addressing long-term environmental issues, including climate change. Most models of energy, economy, and the environment (E3 models) use exogenous assumptions for this. This is an important weakness. We show that there is strong evidence that technical change in the energy sector is to an important degree induced by market circumstances and expectations and, by implication, by environmental policies such as CO2 abatement. We classify the main approaches to modeling such induced technical change and review results with particular reference to climate change. Among models with learning by doing, weak responses are only obtained from models that are highly aggregated (lack technological diversity) and/or that equate rates of return to innovation across sectors. Induced technical change broadens the scope of efficient policies toward mitigation, including not just research and development and aggregated market instruments but a range of sectoral-based policies potentially at divergent marginal costs. Furthermore, to the extent that cleaner technologies induced by mitigation diffuse globally, a positive spillover will result that will tend to offset the substitution-based negative spillover usually hypothesized to result from the migration of polluting industries. Initial explorations suggest that this effect could also be very large.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 44
    ISSN: 1056-3466
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The cement industry contributes about 5% to global anthropogenic CO2 emissions, making the cement industry an important sector for CO2-emission mitigation strategies. CO2 is emitted from the calcination process of limestone, from combustion of fuels in the kiln, as well as from power generation. In this paper, we review the total CO2 emissions from cement making, including process and energy-related emissions. Currently, most available data only includes the process emissions. We also discuss CO2 emission mitigation options for the cement industry. Estimated total carbon emissions from cement production in 1994 were 307 million metric tons of carbon (MtC), 160 MtC from process carbon emissions, and 147 MtC from energy use. Overall, the top 10 cement-producing countries in 1994 accounted for 63% of global carbon emissions from cement production. The average intensity of carbon dioxide emissions from total global cement production is 222 kg of C/t of cement. Emission mitigation options include energy efficiency improvement, new processes, a shift to low carbon fuels, application of waste fuels, increased use of additives in cement making, and, eventually, alternative cements and CO2 removal from flue gases in clinker kilns.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 45
    ISSN: 1056-3466
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract During the period 1995-1999, the President's Committee of Advisors on Science and Technology (PCAST) produced three major energy studies, at President Clinton's request. The panels that conducted these studies were broadly constituted from the academic, industrial, and NGO (nongovernmental organization) sectors, and their recommendations were unanimous. These efforts (a) helped lay the foundation for several major energy initiatives of the second Clinton term, including the Climate Change Technology Initiative, the Nuclear Energy Research Initiative, and the International Clean Energy Initiative; (b) helped launch energy R&D activities on methane hydrates and geological sequestration of carbon dioxide; and (c) strengthened related activities, such as the Partnership for a New Generation of Vehicles, the Partnership for Advancing Technologies in Housing, the fossil power Vision-21 Program, and the National Bioenergy Initiative. Federal budgets for research, development, demonstration, and deployment of advanced energy technologies have increased substantially over the past four years, but they still fall short of PCAST's recommendations; and a number of the PCAST recommendations on matters other than budget have yet to be fully implemented. The PCAST energy studies demonstrate the possibility of forging consensus around key energy issues and provide a foundation on which, it is hoped, the continuing pursuit of a coherent national policy on energy innovation will be able to build.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 46
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    ISSN: 1056-3466
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: FAUST: Ich fuhl's, vergebens hab' ich alle Schatze Des Menschengeists auf mich herbeigerafft, Und wenn ich mich am Ende niedersetze, Quilt innerlich doch keine neue Kraft; Ich bin nicht um ein Haar breit hoher, Bin dem Unendlichen nicht naher. Goethe's Faust, Part I, lines 1810-15. 1 A dedication to research in the physical sciences together with the circumstances of World War II, led me into theoretical and observational studies of the global physical climate. For all practical purposes, I was on my own when working in Cambridge and London, England, and I went whereever my interests led me. I organized three atmospheric observatories (two in England). I have also worked at many astronomical observatories. As time progressed, I became increasingly involved in studies of atmospheric radiation as a controlling factor for the Earth's climate. I am often taken to be a specialist in atmospheric radiation, but I have never regarded it as more than an important element in climate studies. But radiative transfer and global questions did not become important for climate science until later, and in the 1950s and 1960s I found myself drawn to studies of planetary atmospheres as an arena in which my skills were of central importance. Mars and Venus were the focus of my work for many years, and I was partly responsible for launching the Pioneer Venus mission, which placed probes into the Venus atmosphere in 1978. Much later, the experience I gained in space instrumentation and in the structure of atmospheres led me back to climate science, where I started. Then my interest was in observing the climate and testing the credibility of climate predictions. I still maintain some activity in this field. Outside these research activities, I created a Center for Earth and Planetary Physics at Harvard University to take over the activities of the Blue Hill Observatory, when that Observatory ceased to be a viable facility. The purpose of the Center was to teach earth science in the context of the discipline of physical science. The Center had some notable achievements but eventually had to give way to requirements for environmental sciences in the University, a change that I regret. During my active life in the United States, I invested a great deal of effort in support of the work of the National Research Council (NRC), including many years spent on report review. I am increasingly troubled by the postmodern view of science that appears to dominate these activities. But that may be no more than a biased rosy view of the past with its exciting early experiences and hopes.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 47
    ISSN: 1056-3466
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract This paper explores how long-term energy forecasts are created and why they are useful. It focuses on forecasts of energy use in the United States for the year 2000 but considers only long-term predictions, i.e., those covering two or more decades. The motivation is current interest in global warming forecasts, some of which run beyond a century. The basic observation is that forecasters in the 1950-1980 period underestimated the importance of unmodeled surprises. A key example is the failure to foresee the ability of the United States economy to respond to the oil embargos of the 1970s by increasing efficiency. Not only were most forecasts of that period systematically high, but forecasters systematically underestimated uncertainties. Long-term energy forecasts must make assumptions about both technologies and social systems. At their most successful, they influence how people act by showing the consequences of not acting. They are useful when they provide insights to energy planners, influence the perceptions of the public and the energy policy community, capture current understanding of underlying physical and economic principles, or highlight key emerging social or economic trends. It is true that at best we see dimly into the future, but those who acknowledge their duty to posterity will feel impelled to use their foresight upon what facts and guiding principles we do possess. Though many data are at present wanting or doubtful, our conclusions may be rendered so far probable as to lead to further inquiries... (1), p. 4.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 48
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    ISSN: 1056-8700
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Physics
    Notes: Abstract A fundamental perspective can be achieved by targeting single cells for analysis with the goal of deconvoluting complex biological functions. However, single-cell studies have their own difficulties, such as minute volumes and sample amounts. Quantitative chemical analysis of single cells has emerged as a powerful new area in recent years due to several technological advancements. The development of microelectrodes has allowed the measurement of redox-active species as a function of cellular dynamics. This miniaturization trend is also evident in the separation sciences with the application of small column separations to single cells. Desorption ionization methods with mass spectrometric detection have shown single-cell capability owing to numerous technological developments. Finally, fluorescence imaging has also progressed to the point where single-cell dynamics can be probed by native fluorescence utilizing either single or multiple photon excitation. The results of these studies are reviewed with an emphasis on the quantitation of single-cell dynamics.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 49
    ISSN: 1056-8700
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Physics
    Notes: Abstract Species and tissue-specific isozymes of phosphorylase display differences in regulatory properties consistent with their distinct roles in particular organisms and tissues. In this review, we compare crystallographic structures of regulated and unregulated phosphorylases, including maltodextrin phosphorylase (MalP) from Escherichia coli, glycogen phosphorylase from yeast, and mammalian isozymes from muscle and liver tissues. Mutagenesis and functional studies supplement the structural work and provide insights into the structural basis for allosteric control mechanisms. MalP, a simple, unregulated enzyme, is contrasted with the more complicated yeast and mammalian phosphorylases that have evolved regulatory sites onto the basic catalytic architecture. The human liver and muscle isozymes show differences structurally in their means of invoking allosteric activation. Phosphorylation, though common to both the yeast and mammalian enzymes, occurs at different sites and activates the enzymes by surprisingly different mechanisms.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 50
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    ISSN: 1056-8700
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Physics
    Notes: Abstract Atomic resolution structure determinations of proteins by X-ray crystallography are formidable multidisciplinary undertakings, requiring protein construct design, expression and purification, crystallization trials, phase determination, and model building. Modern mass spectrometric methods can greatly facilitate these obligate tasks. Thus, mass spectrometry can be used to verify that the desired protein construct has been correctly expressed, to define compact domains in the target protein, to assess the components contained within the protein crystals, and to screen for successful incorporation of seleno-methionine and other heavy metal reagents used for phasing. In addition, mass spectrometry can be used to address issues of modeling, topology, and side-chain proximity. Here, we demonstrate how rational use of mass spectrometry assists and expedites high resolution X-ray structure determination through each stage of the process of protein crystallography.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 51
    ISSN: 1056-8700
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Physics
    Notes: Abstract Proteins are designed to function in environments crowded by cosolutes, but most studies of protein equilibria are conducted in dilute solution. While there is no doubt that crowding changes protein equilibria, interpretations of the changes remain controversial. This review combines experimental observations on the effect of small uncharged cosolutes (mostly sugars) on protein stability with a discussion of the thermodynamics of cosolute-induced nonideality and critical assessments of the most commonly applied interpretations. Despite the controversy surrounding the most appropriate manner for interpreting these effects of thermodynamic nonideality arising from the presence of small cosolutes, experimental advantage may still be taken of the ability of the cosolute effect to promote not only protein stabilization but also protein self-association and complex formation between dissimilar reactants. This phenomenon clearly has potential ramifications in the cell, where the crowded environment could well induce the same effects.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 52
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    ISSN: 1056-8700
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Physics
    Notes: Abstract The mammalian thioredoxins are a family of small (approximately 12 kDa) redox proteins that undergo NADPH-dependent reduction by thioredoxin reductase and in turn reduce oxidized cysteine groups on proteins. The two main thioredoxins are thioredoxin-1, a cytosolic and nuclear form, and thioredoxin-2, a mitochondrial form. Thioredoxin-1 has been studied more. It performs many biological actions including the supply of reducing equivalents to thioredoxin peroxidases and ribonucleotide reductase, the regulation of transcription factor activity, and the regulation of enzyme activity by heterodimer formation. Thioredoxin-1 stimulates cell growth and is an inhibitor of apoptosis. Thioredoxins may play a role in a variety of human diseases including cancer. An increased level of thioredoxin-1 is found in many human tumors, where it is associated with aggressive tumor growth. Drugs are being developed that inhibit thioredoxin and that have antitumor activity.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 53
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    ISSN: 1056-8700
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Physics
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 54
    ISSN: 1056-8700
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Physics
    Notes: Abstract The first crystal structures of intact T cell receptors (TCRs) bound to class I peptide-MHC (pMHCs) antigens were determined in 1996. Since then, further structures of class I TCR/pMHC complexes have explored the degree of structural variability in the TCR-pMHC system and the structural basis for positive and negative selection. The recent determination of class II and allogeneic class I TCR/pMHC structures, as well as those of accessory molecules (e.g., CD3), has pushed our knowledge of TCR/pMHC interactions into new realms, shedding light on clinical pathologies, such as graft rejection and graft-versus-host disease. Furthermore, the determination of coreceptor structures lays the foundation for a more comprehensive structural description of the supramolecular TCR signaling events and those assemblies that arise in the immunological synapse. While these telling photodocumentaries of the TCR/pMHC interaction are composed mainly from static crystal structures, a full description of the biological snapshots in T cell signaling requires additional analytical methods that record the dynamics of the process. To this end, surface plasmon resonance (SPR), isothermal titration calorimetry (ITC), and ultracentrifugation (UC) have furnished both affinities and kinetics of the TCR/pMHC association. In the past year, structural, biochemical, and molecular biological data describing TCR/pMHC interactions have sublimely coalesced into a burgeoning well of understanding that promises to deliver further insights into T cell recognition. The coming years will, through a more intimate union of structural and kinetic data, allow many pressing questions to be addressed, such as how TCR/pMHC ligation is affected by coreceptor binding and what is the mechanism of TCR signaling in both early and late stages of T cell engagement with antigen-presenting cells.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 55
    ISSN: 1056-8700
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Physics
    Notes: Abstract During the course of their biological function, proteins undergo different types of structural rearrangements ranging from local to large-scale conformational changes. These changes are usually triggered by their interactions with small-molecular-weight ligands or other macromolecules. Because binding interactions occur at specific sites and involve only a small number of residues, a chain of cooperative interactions is necessary for the propagation of binding signals to distal locations within the protein structure. This process requires an uneven structural distribution of protein stability and cooperativity as revealed by NMR-detected hydrogen/deuterium exchange experiments under native conditions. The distribution of stabilizing interactions does not only provide the architectural foundation to the three-dimensional structure of a protein, but it also provides the required framework for functional cooperativity. In this review, the statistical thermodynamic linkage between protein stability, functional cooperativity, and ligand binding is discussed.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 56
    ISSN: 1056-8700
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Physics
    Notes: Abstract The field of computational cell biology has emerged within the past 5 years because of the need to apply disciplined computational approaches to build and test complex hypotheses on the interacting structural, physical, and chemical features that underlie intracellular processes. To meet this need, newly developed software tools allow cell biologists and biophysicists to build models and generate simulations from them. The construction of general-purpose computational approaches is especially challenging if the spatial complexity of cellular systems is to be explicitly treated. This review surveys some of the existing efforts in this field with special emphasis on a system being developed in the authors' laboratory, Virtual Cell. The theories behind both stochastic and deterministic simulations are discussed. Examples of respective applications to cell biological problems in RNA trafficking and neuronal calcium dynamics are provided to illustrate these ideas.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 57
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    ISSN: 1056-8700
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Physics
    Notes: Abstract Structural and thermodynamic characterizations of a variety of intra- and intermolecular interactions stabilizing/destabilizing protein systems represent a major part of multidisciplinary efforts aimed at solving the problems of protein folding and binding. To this end, volumetric techniques have been successfully used to gain insights into protein hydration and intraglobular packing. Despite the fact that the use of volumetric measurements in protein-related studies dates back to the 1950s, such measurements still represent a relatively untapped yet potentially informative means for tackling the problems of protein folding and binding. This notion has been further emphasized by recent advances in the development of highly sensitive volumetric instrumentation that has led to intensifying volumetric investigations of protein systems. This paper reviews the volumetric properties of proteins and their low-molecular-weight analogs, in particular, discussing the recent progress in the use of volumetric data for studying conformational transitions of proteins as well as protein-ligand, protein-protein, and protein-nucleic acid interactions.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 58
    ISSN: 1056-8700
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Physics
    Notes: Abstract This review focuses on cofactor-ligand and protein-protein interactions within the photosystem I reaction center. The topics include a description of the electron transfer cofactors, the mode of binding of the cofactors to protein-bound ligands, and a description of intraprotein contacts that ultimately allow photosystem I to be assembled (in cyanobacteria) from 96 chlorophylls, 22 carotenoids, 2 phylloquinones, 3 [4Fe-4S] clusters, and 12 polypeptides. During the 15 years that have elapsed from the first report of crystals to the atomic-resolution X-ray crystal structure, cofactor-ligand interactions and protein-protein interactions were systematically being explored by spectroscopic and genetic methods. This article charts the interplay between these disciplines and assesses how good the early insights were in light of the current structure of photosystem I.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 59
    ISSN: 1056-8700
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Physics
    Notes: Abstract The past decade has witnessed increasingly detailed insights into the structural mechanism of the bacteriorhodopsin photocycle. Concurrently, there has been much progress within our knowledge pertaining to the lipids of the purple membrane, including the discovery of new lipids and the overall effort to localize and identify each lipid within the purple membrane. Therefore, there is a need to classify this information to generalize the findings. We discuss the properties and roles of haloarchaeal lipids and present the structural data as individual case studies. Lipid-protein interactions are discussed in the context of structure-function relationships. A brief discussion of the possibility that bacteriorhodopsin functions as a light-driven inward hydroxide pump rather than an outward proton pump is also presented.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 60
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    ISSN: 1056-8700
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Physics
    Notes: Views of how cell membranes are organized are presently changing. The lipid bilayer that constitutes these membranes is no longer understood to be a homogeneous fluid. Instead, lipid assemblies, termed rafts, have been introduced to provide fluid platforms that segregate membrane components and dynamically compartmentalize membranes. These assemblies are thought to be composed mainly of sphingolipids and cholesterol in the outer leaflet, somehow connected to domains of unknown composition in the inner leaflet. Specific classes of proteins are associated with the rafts. This review critically analyzes what is known of phase behavior and liquid-liquid immiscibility in model systems and compares these data with what is known of domain formation in cell membranes.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 61
    ISSN: 1523-9829
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Technology , Medicine
    Notes: Abstract Hydrogels are cross-linked hydrophilic polymers that can imbibe water or biological fluids. Their biomedical and pharmaceutical applications include a very wide range of systems and processes that utilize several molecular design characteristics. This review discusses the molecular structure, dynamic behavior, and structural modifications of hydrogels as well as the various applications of these biohydrogels. Recent advances in the preparation of three-dimensional structures with exact chain conformations, as well as tethering of functional groups, allow for the preparation of promising new hydrogels. Meanwhile, intelligent biohydrogels with pH- or temperature-sensitivity continue to be important materials in medical applications.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 62
    ISSN: 1056-8700
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Physics
    Notes: Emerging methods in cryo-electron microscopy allow determination of the three-dimensional architectures of objects ranging in size from small proteins to large eukaryotic cells, spanning a size range of more than 12 orders of magnitude. Advances in determining structures by "single particle" microscopy and by "electron tomography" provide exciting opportunities to describe the structures of subcellular assemblies that are either too large or too heterogeneous to be investigated by conventional crystallographic methods. Here, we review selected aspects of progress in structure determination by cryo-electron microscopy at molecular resolution, with a particular emphasis on topics at the interface of single particle and tomographic approaches. The rapid pace of development in this field suggests that comprehensive descriptions of the structures of whole cells and organelles in terms of the spatial arrangements of their molecular components may soon become routine.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 63
    ISSN: 1056-8700
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Physics
    Notes: Topoisomerases are enzymes that use DNA strand scission, manipulation, and rejoining activities to directly modulate DNA topology. These actions provide a powerful means to effect changes in DNA supercoiling levels, and allow some topoisomerases to both unknot and decatenate chromosomes. Since their initial discovery over three decades ago, researchers have amassed a rich store of information on the cellular roles and regulation of topoisomerases, and have delineated general models for their chemical and physical mechanisms. Topoisomerases are now known to be necessary for the survival of cellular organisms and many viruses and are rich clinical targets for anticancer and antimicrobial treatments. In recent years, crystal structures have been obtained for each of the four types of topoisomerases in a number of distinct conformational and substrate-bound states. In addition, sophisticated biophysical methods have been utilized to study details of topoisomerase reaction dynamics and enzymology. A synthesis of these approaches has provided researchers with new physical insights into how topoisomerases employ chemistry and allostery to direct the large-scale molecular motions needed to pass DNA strands through each other.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 64
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    ISSN: 1523-9829
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Technology , Medicine
    Notes: Abstract Two-dimensional viewing of three-dimensional anatomy by conventional ultrasound limits our ability to quantify and visualize a number of diseases and is partly responsible for the reported variability in diagnosis. Over the past two decades, many investigators have addressed this limitation by developing three-dimensional imaging techniques, including three-dimensional ultrasound imaging. In this paper we describe the development of a number of three-dimensional ultrasound imaging systems that make use of B mode, color Doppler, and power Doppler. In these systems, the conventional ultrasound transducer is scanned mechanically or by a freehand technique. The ultrasound images are digitized and then reconstructed into a three-dimensional volume, which can be viewed and manipulated interactively by the diagnostician with a variety of image-rendering techniques. These developments as well as future trends are discussed with regard to their applications and limitations.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 65
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    ISSN: 1523-9829
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Technology , Medicine
    Notes: Abstract Electrical shock trauma tends to produce a very complex pattern of injury, mainly because of the multiple modes of frequency-dependent tissue-field interactions. Historically, Joule heating was thought to be the only cause of electrical injuries to tissue by commercial-frequency electrical shocks. In the last 15 years, biomedical engineering research has improved the understanding of the underlying biophysical injury mechanisms. Besides thermal burns secondary to Joule heating, permeabilization of cell membranes and direct electroconformational denaturation of macromolecules such as proteins have also been identified as tissue-damage mechanisms. This review summarizes the physics of tissue injury caused by contact with commercial-frequency power lines, as well as exposure to lightning and radio frequency (RF), microwave, and ionizing radiation. In addition, we describe the anatomic patterns of the resultant tissue injury from these modes of electromagnetic exposures.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 66
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    ISSN: 1523-9829
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Technology , Medicine
    Notes: Abstract We review some of the most recent advances in the area of wavelet applications in medical imaging. We first review key concepts in the processing of medical images with wavelet transforms and multiscale analysis, including time-frequency tiling, overcomplete representations, higher dimensional bases, symmetry, boundary effects, translational invariance, orientation selectivity, and best-basis selection. We next describe some applications in magnetic resonance imaging, including activation detection and denoising of functional magnetic resonance imaging and encoding schemes. We then present an overview in the area of ultrasound, including computational anatomy with three-dimensional cardiac ultrasound. Next, wavelets in tomography are reviewed, including their relationship to the radon transform and applications in position emission tomography imaging. Finally, wavelet applications in digital mammography are reviewed, including computer-assisted diagnostic systems that support the detection and classification of small masses and methods of contrast enhancement.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 67
    ISSN: 1523-9829
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Technology , Medicine
    Notes: Abstract The goal of the Image Guided Therapy Program, as the name implies, is to develop the use of imaging to guide minimally invasive therapy. The program combines interventional and intraoperative magnetic resonance imaging (MRI) with high-performance computing and novel therapeutic devices. In clinical practice the multidisciplinary program provides for the investigation of a wide range of interventional and surgical procedures. The Signa SP 0.5 T superconducting MRI system (GE Medical Systems, Milwaukee, WI) has a 56-cm-wide vertical gap, allowing access to the patient and permitting the execution of interactive MRI-guided procedures. This system is integrated with an optical tracking system and utilizes flexible surface coils and MRI-compatible displays to facilitate procedures. Images are obtained with routine pulse sequences. Nearly real-time imaging, with fast gradient-recalled echo sequences, may be acquired at a rate of one image every 1.5 s with interactive image plane selection. Since 1994, more than 800 of these procedures, including various percutaneous procedures and open surgeries, have been successfully performed at Brigham and Women's Hospital (Boston, MA).
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 68
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    ISSN: 1523-9829
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Technology , Medicine
    Notes: Abstract Interrogation of tissue with light offers the potential for noninvasive chemical measurement, and penetration with near-infrared wavelengths (750-1000 nm) is greater than with visible light. Specific absorption by clinically relevant compounds such as oxy- and deoxyhemoglobin and the intracellular respiratory enzyme cytochrome oxidase enable in vivo measurement of these to be performed safely and conveniently. This is the basis of in vivo near-infrared spectroscopy (ivNIRS). Multiple scattering of the interrogating beam by tissues leads to an optical path that is considerably longer than the simple physical pathlength and this complicates the analysis. Modeling of photon propagation through tissues with, for example, finite element and Monte Carlo methods, is assisting in improving the ivNIRS methodology. Instrumentation has advanced from simple continuous wave approaches, through time-resolved methods based on either time-domain or frequency-domain approaches, to spatially resolved measurement based on diffuse reflectance. Initial clinical applications were for monitoring the brain in the neonate and fetus and muscle in adults. Currently, use in adults and children for neurological assessments are of growing interest.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 69
    ISSN: 1523-9829
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Technology , Medicine
    Notes: Abstract Recent studies suggest that there are multiple regulatory pathways by which chondrocytes in articular cartilage sense and respond to mechanical stimuli, including upstream signaling pathways and mechanisms that may lead to direct changes at the level of transcription, translation, post-translational modifications, and cell-mediated extracellular assembly and degradation of the tissue matrix. This review focuses on the effects of mechanical loading on cartilage and the resulting chondrocyte-mediated biosynthesis, remodeling, degradation, and repair of this tissue. The effects of compression and tissue shear deformation are compared, and approaches to the study of mechanical regulation of gene expression are described. Of particular interest regarding dense connective tissues, recent experiments have shown that mechanotransduction is critically important in vivo in the cell-mediated feedback between physical stimuli, the molecular structure of newly synthesized matrix molecules, and the resulting macroscopic biomechanical properties of the tissue.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 70
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    ISSN: 1523-9829
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Technology , Medicine
    Notes: Thomas A. McMahon (1943-1999) was a pioneer in the field of biomechanics. He made primary contributions to our understanding of terrestrial locomotion, allometry and scaling, cardiac assist devices, orthopedic biomechanics, and a number of other areas. His work was frequently characterized by the use of simple mathematical models to explain seemingly complex phenomena. He also validated these models through creative experimentation. McMahon was a successful inventor and also published three well-received novels. He was raised in Lexington, Massachussetts, attended Cornell University as an undergraduate, and earned a PhD at MIT. From 1970 until his death, he was a member of the faculty of Harvard University, where he taught biomedical engineering. He is fondly remembered as a warm and gentle colleague and an exemplary mentor to his students.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 71
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    ISSN: 1523-9829
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Technology , Medicine
    Notes: Abstract It long has been known that mechanical forces play a role in the development of the cardiovascular system, but only recently have biomechanical engineers begun to explore this field. This paper reviews some of this work. First, an overview of the relevant biology is discussed. Next, a mechanical theory is presented that can be used to model developmental processes. The theory includes the effects of finite volumetric growth and active contractile forces. Finally, applications of this and other theories to problems of cardiovascular development are discussed, and some future directions are suggested. The intent is to stimulate further interest among engineers in this important area of research.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 72
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    ISSN: 1523-9829
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Technology , Medicine
    Notes: Abstract Medical imaging has been used primarily for diagnosis. In the past 15 years there has been an emergence of the use of images for the guidance of therapy. This process requires three-dimensional localization devices, the ability to register medical images to physical space, and the ability to display position and trajectory on those images. This paper examines the development and state of the art in those processes.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 73
    ISSN: 1523-9829
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Technology , Medicine
    Notes: Abstract This is the second of two chapters (the first chapter appeared in the Annual Review of Biomedical Engineering, 2000, 2:55-81) dealing with some 60 years of accumulated knowledge in the field of impact biomechanics. The regions covered in the first chapter were the head, neck, and thorax. In this chapter, the abdomen, pelvis, and lower extremities are discussed. The thoracolumbar spine is not covered because of length limitations and the low frequency of injury to this area from automotive accidents. Again, in the cited results, the reader needs to be keenly aware of the wide variation in human response and tolerance. This is due primarily to the large biological variations among humans and to the effects of aging. Average values that are useful in design cannot be applied to individuals.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 74
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    ISSN: 1523-9829
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Technology , Medicine
    Notes: Abstract The heart requires a large amount of energy to sustain both ionic homeostasis and contraction. Under normal conditions, adenosine triphosphate (ATP) production meets this demand. Hence, there is a complex regulatory system that adjusts energy production to meet this demand. However, the mechanisms for this control are a topic of active debate. Energy metabolism can be divided into three main stages: substrate delivery to the tricarboxylic acid (TCA) cycle, the TCA cycle, and oxidative phosphorylation. Each of these processes has multiple control points and exerts control over the other stages. This review discusses the basic stages of energy metabolism, mechanisms of control, and the mathematical and computational models that have been used to study these mechanisms.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 75
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    ISSN: 1523-9829
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff