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  • Inorganic Chemistry  (83,671)
  • General Chemistry  (77,717)
  • LUNAR AND PLANETARY EXPLORATION  (14,409)
  • Meteorology
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  • 1
    Publication Date: 2024-02-26
    Description: Identifcation of ontogenetic age classes plays an important role in the felds of zoology, palaeontology and archaeology, where accurate age classifcations of (sub)fossil remains are a crucial component for the reconstruction \nof past life. Textural ageing\xe2\x80\x94the identifcation of age-related bone surface textures\xe2\x80\x94provides a size-independent \nmethod for age assessment of vertebrate material. However, most of the work so far is limited to qualitative results. \nWhile qualitative approaches provide helpful insights on textural ageing patterns, they are heavily subject to observer \nbias and fall short of quantitative data relevant for detailed statistical analyses and cross-comparisons. Here, we present a pilot study on the application of 3D surface digital microscopy to quantify bone surface textures on the long \nbones of the grey heron (Ardea cinerea) and the Canada goose (Branta canadensis) using internationally verifed \nroughness parameters. Using a standardised measuring protocol, computed roughness values show a strong correlation with qualitative descriptions of textural patterns. Overall, higher roughness values correspond to increased numbers of grooves and pits and vice versa. Most of the roughness parameters allowed distinguishing between diferent \nontogenetic classes and closely followed the typical sigmoidal animal growth curve. Our results show that bone \ntexture quantifcation is a feasible approach to identifying ontogenetic age classes.
    Keywords: General Physics and Astronomy ; General Environmental Science ; General Biochemistry ; Genetics and Molecular Biology ; General Materials Science ; General Chemistry ; Roughness ; Surfaces ; Taphonomy ; Topography ; Bone ; Ontogeny ; Digital microscopy
    Repository Name: National Museum of Natural History, Netherlands
    Type: info:eu-repo/semantics/article
    Format: application/pdf
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  • 2
    Publication Date: 2022-06-02
    Description: This work refers to an interdisciplinary study on the archaeological site of Pyrgi, an Etruscan harbour still under excavation, located on the Lazio’s coast in Santa Severa, in the province of Rome. The objective of the research is to assess the main cause of the floods and the time the water stays in the site to determine if the floods are periodic phenomena over time or random events for guarantee a correct conservation of the site . The study is based on the combined use of geomatic technologies, meteorological and climatic models, and hydrogeological knowledge.
    Keywords: Geomatic ; Hydrogeology ; Meteorology ; Coastal Cultural Heritage ; Pyrgi
    Language: English
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  • 3
    Publication Date: 2022-12-12
    Description: Isentropic analysis in this country originated with a particular purpose in view, namely as a means of using moisture distribution to determine flow patterns in the atmosphere It revealed, very successfully, certain theoretically anticipated patterns. Subsequently it has come into general use in connection with upper-air analysis but for the most part its application is dominated by the original particular purpose. A rather different approach is to use isentropic analysis in a more purely descriptive fashion as the principal tool for upper-air analysis. This demands that an isentropic chart represent synoptically as much useful information as possible and that all phases of its preparation receive due care.
    Keywords: Upper air temperature ; Meteorology
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
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  • 4
    Publication Date: 2022-02-10
    Description: Abstract
    Description: Integrated water vapor above Iquique airport from March 2018 to March 2019 measured with Microwave radiometer HATPRO-FOGHAT. Retrieval is based on 20 Years of Radiosonde Data from Antofagasta. Radiosonde data has been preprocessed with a relative humidity threshold of 90% for cloud formation.
    Keywords: Climatology/Meteorology/Atmosphere ; Meteorology ; Remote Sensing ; Integrated water vapor (IWV)
    Type: Dataset , Dataset
    Format: NetCDF
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  • 5
    Publication Date: 2022-02-10
    Description: Abstract
    Description: Liquid water path above Iquique airport from March 2018 to March 2019 measured with Microwave radiometer HATPRO-FOGHAT. Retrieval is based on 20 Years of Radiosonde Data from Antofagasta. Radiosonde data has been preprocessed with a relative humidity threshold of 80% for cloud formation.
    Keywords: Climatology/Meteorology/Atmosphere ; Meteorology ; Remote Sensing ; Cloud liquid water path (LWP)
    Type: Dataset , Dataset
    Format: NetCDF
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  • 6
    Publication Date: 2022-02-10
    Description: Abstract
    Description: Liquid water path above Iquique airport from March 2018 to March 2019 measured with Microwave radiometer HATPRO-FOGHAT. Retrieval is based on 20 Years of Radiosonde Data from Antofagasta. Radiosonde data has been preprocessed with a relative humidity threshold of 85% for cloud formation.
    Keywords: Climatology/Meteorology/Atmosphere ; Meteorology ; Remote Sensing ; Cloud liquid water path (LWP)
    Type: Dataset , Dataset
    Format: NetCDF
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  • 7
    Publication Date: 2022-02-10
    Description: Abstract
    Description: Integrated water vapor above Iquique airport from March 2018 to March 2019 measured with Microwave radiometer HATPRO-FOGHAT. Retrieval is based on 20 Years of Radiosonde Data from Antofagasta. Radiosonde data has been preprocessed with a relative humidity threshold of 95% for cloud formation.
    Keywords: Climatology/Meteorology/Atmosphere ; Meteorology ; Remote Sensing ; Integrated water vapor (IWV)
    Type: Dataset , Dataset
    Format: NetCDF
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  • 8
    Publication Date: 2022-02-10
    Description: Abstract
    Description: Liquid water path above Iquique airport from March 2018 to March 2019 measured with Microwave radiometer HATPRO-FOGHAT. Retrieval is based on 20 Years of Radiosonde Data from Antofagasta. Radiosonde data has been preprocessed with a relative humidity threshold of 90% for cloud formation.
    Keywords: Climatology/Meteorology/Atmosphere ; Meteorology ; Remote Sensing ; Cloud liquid water path (LWP)
    Type: Dataset , Dataset
    Format: NetCDF
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  • 9
    Publication Date: 2022-02-10
    Description: Abstract
    Description: Liquid water path above Iquique airport from March 2018 to March 2019 measured with Microwave radiometer HATPRO-FOGHAT. Retrieval is based on 20 Years of Radiosonde Data from Antofagasta. Radiosonde data has been preprocessed with a relative humidity threshold of 95% for cloud formation.
    Keywords: Climatology/Meteorology/Atmosphere ; Meteorology ; Remote Sensing ; Cloud liquid water path (LWP)
    Type: Dataset , Dataset
    Format: NetCDF
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  • 10
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    Frontiers Media SA
    Publication Date: 2024-04-04
    Description: The Frontiers in Chemistry Editorial Office team are delighted to present the inaugural “Frontiers in Chemistry: Rising Stars” article collection, showcasing the high-quality work of internationally recognized researchers in the early stages of their independent careers. All Rising Star researchers featured within this collection were individually nominated by the Journal’s Chief Editors in recognition of their potential to influence the future directions in their respective fields. The work presented here highlights the diversity of research performed across the entire breadth of the chemical sciences, and presents advances in theory, experiment and methodology with applications to compelling problems. This Editorial features the corresponding author(s) of each paper published within this important collection, ordered by section alphabetically, highlighting them as the great researchers of the future. The Frontiers in Chemistry Editorial Office team would like to thank each researcher who contributed their work to this collection. We would also like to personally thank our Chief Editors for their exemplary leadership of this article collection; their strong support and passion for this important, community-driven collection has ensured its success and global impact.
    Keywords: Green and Sustainable Chemistry ; Analytical Chemistry ; Theoretical and Computational Chemistry ; Polymer Chemistry ; Medicinal and Pharmaceutical Chemistry ; Organic Chemistry ; Nanoscience ; Catalysis and Photocatalysis ; Supramolecular Chemistry ; Electrochemistry ; Inorganic Chemistry ; Chemical Biology ; thema EDItEUR::P Mathematics and Science::PD Science: general issues
    Language: English
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  • 11
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    Frontiers Media SA
    Publication Date: 2024-04-04
    Description: This eBook is a collection of articles from a Frontiers Research Topic. Frontiers Research Topics are very popular trademarks of the Frontiers Journals Series: they are collections of at least ten articles, all centered on a particular subject. With their unique mix of varied contributions from Original Research to Review Articles, Frontiers Research Topics unify the most influential researchers, the latest key findings and historical advances in a hot research area! Find out more on how to host your own Frontiers Research Topic or contribute to one as an author by contacting the Frontiers Editorial Office: frontiersin.org/about/contact
    Keywords: parameter estimation ; superior collicullus ; Electroencephalography ; Ostrinia furnacalis ; excitable media ; Avian song system ; Meteorology ; thema EDItEUR::P Mathematics and Science::PD Science: general issues
    Language: English
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  • 12
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    Springer Nature | Palgrave Macmillan
    Publication Date: 2024-04-04
    Description: Climate Change; Climate Forecasting; Energy Industry; Climate Risk Management; Meteorology
    Keywords: Climate Change ; Climate Forecasting ; Energy Industry ; Climate Risk Management ; Meteorology ; bic Book Industry Communication::P Mathematics & science::PH Physics ; thema EDItEUR::P Mathematics and Science::PH Physics
    Language: English
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  • 13
    Publication Date: 2023-06-16
    Description: Global navigation satellite system (GNSS) remote sensing of the troposphere, called GNSS meteorology, is already a well-established tool in post-processing applications. Real-time GNSS meteorology has been possible since 2013, when the International GNSS Service (IGS) established its real-time service. The reported accuracy of the real-time zenith total delay (ZTD) has not improved significantly over time and usually remains at the level of 5–18 mm, depending on the station and test period studied. Millimeter-level improvements are noticed due to GPS ambiguity resolution, gradient estimation, or multi-GNSS processing. However, neither are these achievements combined in a single processing strategy, nor is the impact of other processing parameters on ZTD accuracy analyzed. Therefore, we discuss these shortcomings in detail and present a comprehensive analysis of the sensitivity of real-time ZTD on processing parameters. First, we identify a so-called common strategy, which combines processing parameters that are identified to be the most popular among published papers on the topic. We question the popular elevation-dependent weighting function and introduce an alternative one. We investigate the impact of selected processing parameters, i.e., PPP functional model, GNSS selection and combination, inter-system weighting, elevation-dependent weighting function, and gradient estimation. We define an advanced strategy dedicated to real-time GNSS meteorology, which is superior to the common one. The a posteriori error of estimated ZTD is reduced by 41%. The accuracy of ZTD estimates with the proposed strategy is improved by 17% with respect to the IGS final products and varies over stations from 5.4 to 10.1 mm. Finally, we confirm the latitude dependency of ZTD accuracy, but also detect its seasonality.
    Description: H2020 Marie Skłodowska-Curie Actions http://dx.doi.org/10.13039/100010665
    Keywords: ddc:526 ; GNSS ; Meteorology ; Real time ; ZTD
    Language: English
    Type: doc-type:article
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  • 14
    Publication Date: 2022-02-25
    Description: Abstract
    Description: Classification of the state of the atmospheric boundary layer at Diego Aracena Aitport, Iquique, Chile. Profiles of vertical and horizontal wind speed and backscatter coefficient (measured with a Doppler Wind Lidar) as well as thermal stratification at the surface (Thermo-Hygrometers at ~1m and ~2m height) are used to identify height regions without and with turbulence, clouds and precipitation . In a second step the sources of this turbulence are identified (clouds, surface heating or wind shear). For details of the method see Manninen, A., T. Marke, E. O'Connor, and M. Tuononen, 2018: Atmospheric boundary layer classification with Doppler lidar, J. Geophys. Res. , 123, DOI:10.1029/2017JD028169. For daily plots see: http://tiny.cc/iqq_cn_bl_class
    Keywords: Climatology/Meteorology/Atmosphere ; Meteorology ; Remote Sensing ; LiDAR ; Stratocumulus ; Wind ; Clouds
    Type: Dataset , Dataset
    Format: NetCDF
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  • 15
    Publication Date: 2022-02-10
    Description: Abstract
    Description: Wind profiles from March 2018 - MArch 2019 from Doppler Wind Lidar installed at Iquique airport.Wind speed and direction were derived from the VAD-24 scans performed every 15minutes. Error estimates (variables delta_* in the netcdf files) are based on turbulence from vertical stare measurements.
    Keywords: Climatology/Meteorology/Atmosphere ; Meteorology ; Remote Sensing ; LiDAR ; Wind speed ; Wind direction
    Type: Dataset , Dataset
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  • 16
    Publication Date: 2022-05-25
    Description: During cruise 102 of the R/V Atlantis-II in the Joint Air-Sea Interaction Project (JASIN), surface meteorological data were gathered by Woods Hole Oceanographic Institution personnel from two moored buoys and from the ship. One buoy (JASIN W2/WHOI 651) carried a Vector Averaging Wind Recorder (VAWR) and a Vector Measuring Wind Recorder (VMWR); these instruments provided 18 days of intercomparison data and 38 days of meteorological data from 30 July to 6 September 1978. The other buoy (JASIN H2) carried a VMWR and gave 25 total days of data from 16 July to 10 August, and from 26 August to 1 September. A PET computer, hardwired to sensors positioned on the ship, displayed data that were logged during both legs of the cruise. Manual data were gathered by the science watches. This report describes the PET system, and displays and compares all the data. VAWR hourly meteorological data are listed for the 38 day period. Scientific interpretation of these data, such as calculations of heat fluxes, will be published separately.
    Description: Prepared for the National Science Foundation under Grants OCE77-25803 and OCE76-80174, and for the Office of Naval Research under Contract N00014-76-C-0197; NR 083-400 to the Woods Hole Oceanographic Institution.
    Keywords: Joint Air-Sea Interaction Project ; Meteorology ; Ocean-atmosphere interaction ; Atlantis II (Ship : 1963-) Cruise AII102
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
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  • 17
    Publication Date: 2022-05-26
    Description: Includes Errata
    Description: Time-series of monthly averages of latent, sensible and radiational heat fluxes and momentum fluxes at the surfaces of the North and South Atlantic Oceans were calculated from ship weather observations. These fluxes, together with values of meteorological variables have been averaged over entire Marsden squares (10X10° squares) for all months from January 1948 through December 1972. The method of computing fluxes from ship weather observations, listing of variables averaged, addition of sea-ice coverage of sub-polar regions, correction of albedos for the presence of sea ice, correction of infrared radiational exchange for humidity conditions of the upper atmosphere, and format of the data on magnetic tapes are described. Statistics of the fluxes and variables have been computed. Standard data tapes containing these time series and statistics are available.
    Description: Prepared for Climate Dynamics Research Program~ Division of Atmospheric Sciences, National Science Foundation under Grant ATM 77-01475 A01.
    Keywords: Meteorology ; Climatology
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
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  • 18
    Publication Date: 2022-05-26
    Description: The Northwest Tropical Atlantic Station (NTAS) was established to address the need for accurate air-sea flux estimates and upper ocean measurements in a region with strong sea surface temperature anomalies and the likelihood of significant local air–sea interaction on inter-annual to decadal timescales. The approach is to maintain a surface mooring outfitted for meteorological and oceanographic measurements at a site near 15N, 51W by successive mooring turnarounds. These observations are used to investigate air–sea interaction processes related to climate variability. The NTAS Ocean Reference Station (ORS NTAS) is supported by the National Oceanic and Atmospheric Administration’s (NOAA) Ocean Observing and Monitoring Division. This report documents recovery of the NTAS-15 mooring and deployment of the NTAS-16 mooring. Both moorings used Surlyn foam buoys as the surface element. These buoys were outfitted with two Air–Sea Interaction Meteorology (ASIMET) systems. Each system measures, records, and transmits via Argos satellite the surface meteorological variables necessary to compute air–sea fluxes of heat, moisture and momentum. The upper 160 m of the mooring line were outfitted with oceanographic sensors for the measurement of temperature, salinity and velocity. The mooring turnaround was done by the Upper Ocean Processes Group of the Woods Hole Oceanographic Institution (WHOI), onboard R/V Endeavor (cruise EN590). The cruise took place between January 21 and February 8 2017. The NTAS-16 mooring was deployed on January 30, and the NTAS-15 mooring was recovered on January 31. A 24-hour intercomparison period was conducted on January 29 in front of the NTAS 15 buoy, and again on February 1 in front of the NTAS 16 buoy. During the inter-comparisons, data from instrumentation on the buoys, telemetered through Argos satellite system, and the ship’s meteorological and oceanographic measurements were monitored while the ship was stationed 0.2 nm downwind of the buoys. This report describes these operations, as well as other work done on the cruise and some of the pre-cruise buoy preparations. Other operations during EN590 consisted in the recovery and deployment of the Meridional Overturning Variability Experiment (MOVE) Pressure Inverted Echo Sounders (PIES) at two MOVE arrays (MOVE 1 in the east, and MOVE 3 in the west near Guadeloupe). Acoustic downloads of data from (PIES) and subsurface mooring (MOVE1, 3 and 4) were also conducted. MOVE is designed to monitor the integrated deep meridional flow in the tropical North Atlantic.
    Description: Funding was provided by the National Oceanic and Atmospheric Administration under Grant No. NA14OAR4320158.
    Keywords: Hydrography ; Oceanographic instruments ; Meteorology ; Endeavor (Ship: 1976-) Cruise EN590
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
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  • 19
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2017-02-10
    Description: Author: Jake Yeston
    Keywords: Inorganic Chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 20
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2017-01-27
    Description: Author: Jake Yeston
    Keywords: Inorganic Chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 21
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2017-01-27
    Description: Polynitrogens have the potential for ultrahigh-performing explosives or propellants because singly or doubly bonded polynitrogens can decompose to triply bonded dinitrogen (N2) with an extraordinarily large energy release. The large energy content and relatively low activation energy toward decomposition makes the synthesis of a stable polynitrogen allotrope an extraordinary challenge. Many elements exist in different forms (allotropes)—for example, carbon can exist as graphite, diamond, buckyballs, or graphene. However, no stable neutral allotropes are known for nitrogen, and only two stable homonuclear polynitrogen ions had been isolated until now—namely, the N3− anion (1) and the N5+ cation (2). On page 374 of this issue, Zhang et al. (3) report the synthesis and characterization of the first stable salt of the cyclo-N5− anion, only the third stable homonuclear polynitrogen ion ever isolated. Author: Karl O. Christe
    Keywords: Inorganic Chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 22
    Publication Date: 2021-05-19
    Description: Basic data concerning the sources of coastal marine pollution of both urban and industrial origin in Tunisia are presented as well as basic information regarding the relationship between marine pollution and oceanography, topography and hydrology and human activity. This study will serve as a basis for more precise measurements of degrees of pollution and for monitoring the coastal marine pollution in Tunisia.
    Description: Dans ce travail ont été rassemblées les données de base concernant les sources de pollution marine côtière en Tunisie, pollution d'origines urbaine et industrielle, ainsi que les informations de base relatives, d’une part, à l’océanographie, la topographie et l’hydrologie et, d’autre part, aux activités humaines en relation avec la pollution du milieu marin. Ce travail constitue un inventaire a priori des sources de pollution et servira de base à des mesures précises des degrés de pollution et de surveillance de la pollution marine côtière en Tunisie.
    Description: Published
    Keywords: Meteorology ; Oceanology ; Sea water ; Pollutants ; Pollution effects ; Marine
    Repository Name: AquaDocs
    Type: Journal Contribution , Refereed
    Format: pp 53-95
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  • 23
    Publication Date: 2022-05-26
    Description: Meteorological data have been gathered from a moored surface buoy at 34°N, 70°W in the Long Term Upper Ocean Study (LOTUS) experiment. The meteorological results from the first year of LOTUS are encouraging; the data returned from redundant sensors agree closely. Surface heat fluxes calculated from the observations show the annual cycle of heat transfer to the mixed layer. This report documents the meteorological sensors on the LOTUs-3 (May 1982-october 1982) and LOTUS-4 (November 1982-March 1983) surface buoys. It describes in detail the telemetry of the meteorological data via the ARGOS satellite system. The measurements returned from LOTUS-3 are presented and evaluated. Monthly heat fluxes at the sea surface are computed using the bulk formulas and compared with the long-term means. The errors in the heat fluxes have been estimated.
    Description: Prepared for the Office of Naval Research under Contract N00014-76-C-0197; NR 083-400.
    Keywords: Meteorology ; Oceanus (Ship : 1975-) Cruise OC119 ; Oceanus (Ship : 1975-) Cruise OC129 ; Endeavor (Ship: 1976-) Cruise EN97
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
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  • 24
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2016-04-15
    Description: The United States has fallen behind Europe in adopting a modern weather balloon system. Twice a day, hundreds of hydrogen- or helium-filled balloons lift off from stations around the world, carrying temperature, pressure, and humidity sensors that provide crucial information for weather forecast models. But for more than three-quarters of the world's 800 balloon stations, the information is streamed in an antiquated alphanumeric format; these stations have failed to meet a 2014 deadline to upgrade to a new, more powerful binary format. Moreover, many forecasters who use balloon data have also failed to switch over, and are now facing data gaps as nations turn off the old, alphanumeric streams. The U.S. Global Forecast System, for example, does not incorporate the new, binary data. Author: Eric Hand
    Keywords: Meteorology
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 25
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2016-09-09
    Description: Author: Jake Yeston
    Keywords: Inorganic Chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 26
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2016-11-11
    Description: Author: Jake Yeston
    Keywords: Inorganic Chemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 27
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    Woods Hole Oceanographic Institution
    Publication Date: 2022-05-26
    Description: This report presents meteorological data recorded by the MR on the three deployments of Tropic Heat moorings, within 1.5 degrees north and south of the equator at approximately 134°W and 140°W. Parameters recorded included vector averaged wind speed and direction, air and sea temperatures, insolation, barometric pressure, and relative humidity although not all parameters were recorded on all deployments . The deployments were all nominally six months . Data recovery was poor because of instrument and mooring failures.
    Description: Funding was provided by the National Science Foundation under grant Number OCE 83-1 0982.
    Keywords: Buoys ; Meteorology
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
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  • 28
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    Woods Hole Oceanographic Institution
    Publication Date: 2022-05-26
    Description: This report presents meteorological data from three deployments of SEQUAL moorings SS and S6 (nominal positions 0°N, 24°W and 0°N, 15°W) and also from a post SEQUAL deployment at SEQUAL mooring site S2 at 0°N, 28°W. Parameters recorded include vector averaged wind speed and direction, air and sea surface temperatures, insolation, barometric pressure and relative humidity although not all parameters were recorded on all deployments. All deployments were nominally six months.
    Description: Funding was provided by the National Science Foundation under grant Numbers OCE 81-22061 and OCE 82-111 08.
    Keywords: Meteorology ; Buoys
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
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  • 29
    Publication Date: 2015-09-19
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Ostrander, Chris E -- Lautenbacher, Conrad C -- England -- Nature. 2015 Sep 17;525(7569):321. doi: 10.1038/525321d.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉University of Hawaii at Manoa, Honolulu, Hawaii, USA. ; GeoOptics, Dunwoody, Georgia, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26381978" target="_blank"〉PubMed〈/a〉
    Keywords: *International Cooperation ; Meteorology ; Oceanography/*standards ; *Oceans and Seas ; Pacific Islands ; Pacific Ocean ; United States
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 30
    Publication Date: 2021-05-19
    Description: Published
    Description: Mécanismes hydologiques
    Description: Climat
    Keywords: Meteorology ; Hydrology
    Repository Name: AquaDocs
    Type: Journal Contribution , Non-Refereed , Article
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  • 31
    Publication Date: 2021-05-19
    Description: Continuous measurements were taken of oceanographic and meteorological parameters for two stations of the Global Ocean Observing System of the Southwest Caribbean, framed in the INAP project. The response of the surface layer, to atmospheric events, allowed to differentiate the pass of two cold fronts by Johnny Cay station (San Andres Island) and the arrival of the “Veranillo” in the sensors of Tesoro Island (Islas del Rosario, Cartagena). The cold fronts produced a decrease in the atmospheric pressure, air temperature, caused radical changes in wind direction and speed followed by precipitation. This situation lowered the sea surface temperature, the surface layer pH and rose momentarily the sea level. The “Veranillo” came to Archipelago of Rosario generating a strong increase in wind speed and solar radiation. The response in the sea surface layer was evident through a significant increase in sea level.
    Description: INVEMAR
    Description: Published
    Description: Veranillo; INAP
    Keywords: Meteorology ; Oceanography ; Cold fronts
    Repository Name: AquaDocs
    Type: Journal Contribution , Refereed , Article
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  • 32
    Publication Date: 2021-01-30
    Description: Observing System and the WMO Information System (EC-WG/WIGOS-WIS-4) was held at the WMO Secretariat in Geneva, Switzerland, from 10 to 11 February 2011. The session was chaired by Prof A. D. Moura (Brazil), Third Vice-President of WMO. EC-WG/WIGOS-WIS reviewed and endorsed the following WIGOS documents to be submitted to the sixteenth Congress (Cg-XVI): (a) Report on the Integration between the WMO Observing Systems (Appendix II); (b) WIGOS Test of Concept Development and Implementation Plan (WDIP) (Appendix III); (c) WIGOS Concept of Operations (CONOPS) (Appendix IV); (d) WIGOS Development and Implementation Strategy (WDIS) (Appendix V). Furthermore, EC-WG/WIGOS-WIS-4 formulated its recommendations on the WIGOS implementation in the form of Draft Resolution 11.3/1 (Cg-XVI) – Implementation of the WMO Integrated Global Observing System (WIGOS) (Appendix VII). When discussing the individual Agenda Items, particular attention was given to pre-Congress actions, on the enhancement of communication on WIGOS matters.
    Description: Supported by World Meteorological Organization.
    Description: Document available in English.
    Description: Published
    Keywords: Meteorology ; Marine meteorology
    Repository Name: AquaDocs
    Type: Report , Non-Refereed
    Format: 92
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  • 33
    Publication Date: 2021-01-30
    Description: The second session of the Executive Council Working Group on the WMO Integrated Global Observing System and the WMO Information System (EC-WG/WIGOS-WIS) was held at the WMO Secretariat in Geneva, Switzerland, from 6 to 8 May 2009, and was chaired by Prof A. Divino Moura (Brazil), Third Vice-President of the WMO and Chair of EC WG. EC-WG/WIGOS-WIS was briefed on major deliberations of the first session of its Subgroup on the WMO Integrated Global Observing System (SG-WIGOS-1) Geneva, Switzerland, 10 - 13 November 2008; the CBS Technical Conference on WIGOS (TECO-WIGOS) (Dubrovnik, Croatia, 23-24 March 2009); and the fourteenth session of the Commission for Basic Systems (CBS-XIV) (Dubrovnik, Croatia, 25 March - 2 April 2009). EC-WG/WIGOS-WIS was briefed on the status of: (a) Implementation of the WIS Project and its Implementation Plan; (b)nWIGOS Pilot and Demonstration Projects; (c) Review of the WIGOS Concept of Operation (CONOPS); (d) Implementation of WIGOS Development and Implementation Plan (WDIP) and its corresponding update; (e) Monitoring of the implementation of WIGOS and WIS through Rolling Requirements Review; (f) Revision of WMO Technical Regulations related to WIGOS and WIS implementation. Based on the outcomes of the consideration of the individual Agenda Items, EC-WG/WIGOS-WIS articulated its guidance, advice and recommendations regarding the further development of the implementation of WIS, WIGOS concept, coordination of WIGOS and WIS plans; it agreed on the versions of CONOPS (Appendix II) and WDIP (Appendix III) to be submitted to EC-LXI for consideration and endorsement.
    Description: Supported by World Meteorological Organization.
    Description: Document available in English.
    Description: Published
    Keywords: Meteorology ; UNESCO ; Marine meteorology
    Repository Name: AquaDocs
    Type: Report , Non-Refereed
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  • 34
    Publication Date: 2021-01-30
    Description: WMO/ IOC
    Description: Document available in English
    Description: Published
    Description: management
    Keywords: Meteorology ; Marine meteorology
    Repository Name: AquaDocs
    Type: Report , Non-Refereed
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  • 35
    Publication Date: 2021-01-30
    Description: The first session of the Subgroup on the WMO Integrated Global Observing System (EC-WG/SG-WIGOS-1) of the Executive Council Working Group on the WMO Integrated Global Observing System (WIGOS) and the WMO Information System (WIS) was held at the WMO Secretariat in Geneva, Switzerland, from 10 to 13 November 2008, and was chaired by Dr John Nash (UK), the President of the Commission for Instruments and Methods of Observation (CIMO) and Chair of the Subgroup. Main attention of the SG-WIGOS was focused on the status of WIGOS Pilot and Demonstration Projects and their potential input for the update of WIGOS Concept of Operations (CONOPS) and WIGOS Development and Implementation Plan (WDIP); on the elaboration of the WIGOS Integration Levels; on a review of needs and potential problems of WMO co-sponsored observing systems; and update of CONOPS and WDIP. SG-WIGOS discussed a scope, time frame and role of WIGOS Pilot Projects. When doing that, guidance from Cg-XV were taken into account that Pilot Projects should be designed to test concepts, identify problem areas and to help in elaborating WDIP by inputs from respective technical commission.
    Description: Supported by World Meteorological Organization.
    Description: Document available in English.
    Description: Published
    Keywords: Meteorology ; Marine meteorology
    Repository Name: AquaDocs
    Type: Report , Non-Refereed
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  • 36
    Publication Date: 2021-05-19
    Description: The third session of the Executive Council Working Group on the WMO Integrated Global Observing System and the WMO Information System (EC-WG/WIGOS-WIS) was held at the WMO Secretariat in Geneva, Switzerland, from 24 to 26 March 2010. The session was chaired by Prof A. Divino Moura (Brazil), Third Vice-President of the WMO and Chair of EC WG. EC-WG/WIGOS-WIS reviewed major deliberations of the second session of its Subgroup on WIGOS (SG-WIGOS-2, Geneva, Switzerland, 19-23 October 2009), and the sixth session of the Inter-Commission Group on WIS (ICG-WIS, Seoul, Republic of Korea, 22-26 February 2010) and developed appropriate proposals and recommendations. EC-WG/WIGOS-WIS further considered: (a) Report on the WIGOS Projects (Status, Evaluation, Lessons Learned); (b) WIGOS Concept of Operations (CONOPS); (c) WIGOS Test of Concept Development and Implementation Plan (WDIP); (d) WIGOS Development and Implementation Strategy (WDIS); (e) Report on the integration between the WMO observing systems. Based on the outcomes of the discussion under individual Agenda Items, EC-WG/WIGOS-WIS formulated recommendations on the further development and implementation of the WIGOS concept, the implementation of WIS, and the enhanced coordination of WIS and WIGOS activities. EC WG decided to submit the updated versions of CONOPS (Appendix II), WDIP (Appendix IV) and WDIS (Appendix V) to EC-LXII for consideration and endorsement.
    Description: Supported by World Meteorological Organization.
    Description: Document available in English.
    Description: Published
    Keywords: Meteorology ; Marine meteorology
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    Type: Report , Non-Refereed
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  • 37
    Publication Date: 2021-05-19
    Description: Un resumen de datos meteorológicos e hidrológicos para la Bahía de Santa Marta, Caribe colombiano. Se presentan datos de precipitación, temperatura y salinidad del agua superficial para la Bahía de Santa Marta, Caribe colombiano, para el periodo de noviembre 1978 a mayo 1982. Se obtienen generalizaciones de los patrones anuales incluyendo datos ya publicados (Muller, 1979). A partir de mediciones adicionales de la variación de la temperatura del agua y de la salinidad durante el día, valores preliminares de cuantos de luz, junto con datos disponibles sobre contenido y saturación de oxigeno, pH, alcalinidad, estabilidad, dirección y velocidad del viento, horas de luz, temperatura del aire y descarga del Río Manzanares, se hace una caracterización cuantitativa de las estaciones seca y húmeda que se observan en el área investigada.
    Description: Data on rainfall, water surface temperature and salinity from the Bay of Santa Marta, Colombian Caribbean, are presented for the period November 1978 to May 1982. Including data already published (Müller, 1979) generalizations of the anual patterns are obtained. Additional measurements of the variation of water temperature and salinity in the course of one day, preliminary values of light quanta, together with available data on oxygen contení and saturation, pH, alcalinity, stability, wind direction and velocity, hours of sunshine, air temperature, and water discharge of the river Manzanares permitted a quantitative characterization of the dry and rainy season which can be observed in the área of investigad on.
    Description: Published
    Description: hydrological cycle
    Keywords: Physical oceanography ; Meteorology ; Meteorology ; Physical oceanography
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    Type: Journal Contribution
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  • 38
    Publication Date: 2021-05-19
    Description: Durante los años 1965 a 1967 se realizaron estudios micrometeorológicos en la región xerofítica de Santa Marta. Las condiciones meteorológicas durante el tiempo de las investigaciones están descritas por los datos sobre las temperaturas y las precipitaciones, por los climatogramas y por un diagrama de la economía hídrica del suelo de 1966. La temperatura promedia del año 1966 fue 27,7° C, las precipitaciones oscilaron entre 378 y 750 milímetros anuales. En el suelo hay carencia de agua durante la mayor parte del año. Los estudios micrometeorológicos se llevaron a cabo en dos sitios, uno situado en un cardonal y el otro en la región de un bosque de galería. Los cardonales y las regiones del bosque de galería forman dos extremos respecto a la economía hídrica de la vegetación. Por la capa vegetal más cerrada y las mejores condiciones edáficas y orográficas, el microclima en el bosque de galería tiene una tendencia menor a situaciones extremas que el mismo en el cardonal. Se comunican numerosos datos sobre las temperaturas y la humedad del aire, las velocidades de las brisas y la evaporación dependientes tanto de las estaciones del año como del nivel del sobre el suelo.
    Description: During the years 1965 to 1967 micrometeorological studies were conducted in the region of Santa Marta xerophytic. Weather conditions during the time of the research are described by the data on temperatures and rainfall, by climatogram and a diagram of the ground water economy of 1966. The average temperature of 1966 was 27.7 ° C, precipitation ranged between 378 and 750 millimeters per year. On the floor there is a shortage of water during most of the year. Micrometeorological studies were conducted at two sites, one located in a cardonal and the other in the region of a gallery forest. The cactus and gallery forest regions are two extremes on the water economy of vegetation. For more closed vegetation cover and the best soil conditions and terrain, the microclimate in the gallery forest has less tendency to extremes in the same cardonal. They communicate numerous data on temperatures and humidity, the speeds of the winds and evaporation dependent both seasons as on level ground.
    Description: Published
    Keywords: Meteorology ; Meteorology
    Repository Name: AquaDocs
    Type: Journal Contribution
    Format: pp.45-75
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  • 39
    Publication Date: 2022-05-26
    Description: Originally issued as Reference No. 60-33, series later renamed WHOI-
    Description: The study is based upon the concept that climatology cannot be divorced from the dynamics of weather. An attempt is made to outline the meteorological framework of this region of the tropics. The rainfall of Trinidad is then discussed within this framework. The mean annual distribution of rainfall over the island forms a basis for the discussion of monthly distributions. Seasonal variation is pointed out and related to broad scale migrations of the subtropical anticyclones and the equatorial trough. The dual rainfall maximum occurring during the wet season is, in turn, related to the synoptic scale patterns of this season. Distribution is then examined with reference to the moist layer, wind direction and speed. Diurnal distribution is treated in detail and the mechanisms giving rise to the well-defined distribution patterns are discussed. Finally some attention is paid to shower amounts and distribution. In conclusion the rainfall of the island is summarized by relating the seasonal variations to the broadscale meteorological background and the actual distribution to the local scale influences.
    Keywords: Rain and rainfall ; Meteorology
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
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  • 40
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    Nature Publishing Group (NPG)
    Publication Date: 2010-05-14
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Earle, Sylvia -- England -- Nature. 2010 May 13;465(7295):165. doi: 10.1038/465165a.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉US National Oceanic and Atmospheric Administration, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20463723" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Climate ; *Conservation of Natural Resources ; *Ecology ; *Ecosystem ; *Marine Biology ; Meteorology ; *Motion Pictures as Topic ; Oceans and Seas ; Population Density
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 41
    Publication Date: 2021-05-19
    Description: Published
    Description: Echo-sounder
    Keywords: Meteorology ; Meteorology ; Fishing nets
    Repository Name: AquaDocs
    Type: Report , Non-Refereed
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  • 42
    Publication Date: 2022-05-25
    Description: The 1991 Acoustic Surface Reverberation Experiment (ASREX 91) took place in November and December off the coast of British Columbia. As part of this experiment, three moorings were deployed to characterize the environmental background. The moorings consisted of a meteorological/oceanographic mooring designed to measure surface meteorology, current and temperature in the upper 120 meters, and nondirectional wave parameters and two wave moorings which were instrumented with pitch-roll buoys to characterize the directional wave spectrum. This report presents results from these three moorings. The conditions seen during the experiment were extremely rough, with wind speeds at 3.4m above the water surface reaching a maximum of 22 m/s and wave heights reaching a maximum of over 10 meters. The air-sea flux of heat was strongly cooling, and the mixed layer deepened over the course of the experiment from approximately 40 to approximately 70 meters. Spectra of the temperature showed a strong semidiurnal tidal signal associated with temperature excursions of several degrees C. The velocity signal showed strong inertial oscilations with amplitudes of 30-50 cm/s. Weaker low-frequency and semidiurnal tidal signals were also seen. The waves were very strong with significant wave heights of 5-6 meters persisting for up to 2 weeks at a time. Waves were generally out of the south or the west.
    Description: Funding was provided by the Ocean Acoustics Program (Code 324OA) of the Office of Naval Research under contract N00014-91-J-1891.
    Keywords: North Pacific ; Meteorology ; Oceanography ; Moored instrument measurements ; Thomas G. Thompson (Ship) Cruise TN4 ; Thomas G. Thompson (Ship) Cruise TN5
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
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  • 43
    Publication Date: 2022-05-26
    Description: The Third Acoustic Surface Reverberation Experiment (AS REX III) took place from December 1993 to March 1994 at Site L (34°N, 70°W) in the mid-Atlantic. As part of this experiment, two moorings were deployed to measure the environmental background. A meteorological and oceanographic mooring was deployed to characterize the surface wind stress, buoyancy flux, and the current and temperature structure over the top 500 meters. A Seatex Wavescan buoy was deployed to characterize the directional wave spectrum. This report presents results from these moorings. Wind speeds up to 25 m/s were seen, with significant heat losses (up to 1050 W/m2) when cold continental air moved out over the warm Atlantic. The wave heights ranged up to 8 m, with significant wave heights of several meters persisting for relatively long periods. Wave height and period, nondirectional spectra, directional spectra and a typology of wave events are presented and related to surface forcing.
    Description: Funding was provided by the Office of Naval Research through Grant No. NOOOl4-91-J-1891.
    Keywords: Meteorology ; Oceanography ; Moored instrument measurements ; Mid-Atlantic ; Knorr (Ship : 1970-) Cruise ; Edwin Link (Ship) Cruise
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
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  • 44
    Publication Date: 2022-05-26
    Description: An array of moorings at four sites at a mid-shelf location in the mid-Atlantic Bight was deployed for a period of 10 months beginning in August 1996 as part of the Coastal Mixing and Optics Experiment (CMO), funded by the Office of Naval Research (ONR). The purpose of this array is to gather information to help identify and understand the vertical mixing processes influencing the evolution of the stratification over the shelf. The observations from this moored array will be used to investigate changes in the stratification in response to atmospheric forcing, surface gravity wave variabilty, surface and bottom boundary layer mixing, current shear, internal waves, and advection. This report describes the primary mooring deployments carried out by the Upper Ocean Processes (UOP) Group on the R/V Oceanus, sailing out of Woods Hole during July, August, and September of 1996.
    Description: Funding was provided by the Office of Naval Research through Grant No. N00014-95-1-0339.
    Keywords: North Atlantic ; Meteorology ; Oceanography ; Moored instrument measurements ; Oceanus (Ship : 1975-) Cruise OC284 ; Coastal Mixing and Optics (CMO) Experiment
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
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  • 45
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    Massachusetts Institute of Technology and Woods Hole Oceanographic Institution
    Publication Date: 2022-05-26
    Description: The physical processes which result in the formation of clouds and the production of precipitation have been described by numerous meteorologists. The genetical classification has been summarized by Petterssen as follows: (1) Clouds and precipitation types which form in unstable air masses, (2) Clouds and precipitation types which form in stable air masses, (3) Clouds and precipitation types which form in connection with quasi-horizontal inversions in the free atmosphere, and (4) Frontal clouds and precipitation forms. In general, the procedure adopted for the forecasting of these meteorological elements can also be subdivided into the same four categories. Since the distribution of the elements in the atmosphere is never constant with time, the problem of forecasting cloudiness and precipitation is sometimes diffcult. A detailed discussion of qualitative and quantitative prognostic methods can be found in various standard meteorological texts. However, present methods are not entirely adequate and it is the aim of this investigation to contribute to the solution of the forecast problem. This study has been divided into two main sections, viz., (1) Clouds and precipitation types which occur at frontal surfaces as the result of frontal lifting, and (2) Clouds and precipitation types which occur within air masses as the result of horizontal convergence within the wind field. (1) Frontal Surfaces. In a recent study of fronts and frontogenesis, Petterssen and Austin have investigated the processes that tend to create wind shear, or vorticity, along fronts. It was found that, in general, an increase or decrease in shear is accompanied by a change in the vertical velocity field at a front. Since cloudiness and precipitation arise from the ascending velocities at frontal surfaces, the possibility of forecasting the change in horizontal shear at a front will be investigated. Furthermore, it has been shown that the vertical velocity of either air mass at a frontal surface can be determined from the velocity of the front and the horizontal wind velocity. The wind velocities in the free atmosphere can be obtained with a reasonable degree of accuracy, but the front velocity cannot always be evaluated with the same accuracy. Because it is important to determine the magnitude or at least the sign of the vertical velocities, a kinematical study will be made of the displacement of frontal surfaces. (2) Horizontal Convergence. In 1931 Giao published an explanation of the origin of clouds and precipitation in the vicinity of moving cyclones, without introducing the concept of frontal surfaces. Giao claimed that most condensation phenomena could be attributed to the cooling produced by local pressure changes and the horizontal convergence which arises from the meridional component of the wind velocity. The conclusions are conveniently summarized by Haurwitz, together with a short discussion of Giao's theory. Since some systems of clouds and precipitation types may result solely from convergence in the horizontal flow, an attempt wil be made to evaluate this effect quantitatively.
    Keywords: Clouds ; Precipitation ; Meteorology
    Repository Name: Woods Hole Open Access Server
    Type: Book
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  • 46
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    Publication Date: 2021-01-30
    Description: The Fifth EUMETSAT User Forum in Africa was organised in Dakar, Senegal, by EUMETSAT, the World Meteorological Organization (WMO) and the Ministry of Equipment and Transport of the Republic of Senegal. The Forum was held from 30 September to 4 October 2002 with over 160 participants representing most African and European countries. Representatives of the following African Intergovernmental Regional Associations were present: Economic Community of West African States (ECOWAS), Intergovernmental Authority on Development (IGAD), Intergovernmental Oceanographic Commission of UNESCO (IOC) and Southern Africa Transport and Communications Commission (SATCC), Communauté Economique et Monétaire de l'Afrique Centrale (CEMAC), as well as representatives of the European Commission and the Food and Agriculture Organisation of the UN (FAO).
    Description: EUMETSAT
    Description: Published
    Keywords: Meteorology
    Repository Name: AquaDocs
    Type: Proceedings Paper , Non-Refereed
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  • 47
    Publication Date: 2022-05-25
    Description: To investigate vertical mixing processes influencing the evolution of the stratification over continental shelves a moored array was deployed on the New England shelf from August 1996 to June 1997 as part of the Office of Naval Research's Coastal Mixing and Optics program. The array consisted of four mid-shelf sites instrumented to measure oceanic (currents, temperature, salinity, pressure, and surface gravity wave spectra) and meteorological (winds, surface heat flux, precipitation) variables. This report presents a description of the moored array, a summary of the data processing, and statistics and time-series plots summarizing the data. A report on the mooring recovery cruise and a summary of shipboard CTD surveys taken during the mooring deployment are also included.
    Description: Funding was provided by the Office of Naval Research under Contract No. N00014-95-1-0339.
    Keywords: Meteorology ; Oceanography ; North Atlantic ; Moored instrument measurements ; Ocean-atmosphere interaction ; Oceanic mixing ; Oceanus (Ship : 1975-) Cruise OC305
    Repository Name: Woods Hole Open Access Server
    Type: Technical Report
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  • 48
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    In:  Eos Trans. AGU, Prague, Wiley, vol. 82, no. 20, pp. 222 & 225, pp. B09404, (ISSN: 1340-4202)
    Publication Date: 2001
    Keywords: Statistical investigations ; Earthquake risk ; 3344 ; Meteorology ; and ; atmospheric ; dynamics ; Paleoclimatology ; 1620 ; Global ; change ; Climate ; dynamics ; (3309) ; climate ; changes ; 6309 ; Policy ; sciences ; Decision ; making ; under ; uncertainty ; advice
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  • 49
    Electronic Resource
    Electronic Resource
    Springer
    International journal of biometeorology 44 (2000), S. 198-203 
    ISSN: 1432-1254
    Keywords: Keywords Urban heat island ; Coastal city ; Meteorology ; Aveiro (Portugal)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Abstract  This project arose from the need to study the phenomenon of the urban heat island, since only by recognising this phenomenon can we moderate it to improve the human and urban environments. Not only big cities develop urban heat islands. This study detected the presence and recorded the characteristics of an urban heat island in the small coastal city of Aveiro, Portugal. The study was developed through the scheduled measurements of air temperature and the analysis of the geographical, meteorological and urban conditions. The form and intensity of Aveiro’s heat island are a response to the interaction of three principal factors: the urban morphology (the hottest zones in the city are those with the tallest and the highest density of buildings, without green spaces and with intense generation of heat from traffic, commerce and services); the meteorological conditions (the intensity of the island is at its maximum when the sky is totally clear and there is no wind, and at its minimum in those situations when there is atmospheric instability, such as wind, cloud and precipitation); and the proximity of the coastal lagoon (which borders the city to the west and northwest and moderates seasonal temperatures. The urban heat island influences the comfort and health of its inhabitants, thus urban planning is very important in the moderation and prevention of this phenomenon.
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  • 50
    ISSN: 1434-193X
    Keywords: Triplet recombination ; Electron transfer ; Radical ions ; Photochemistry ; Terpenes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The triphenypyrylium tetrafluoroborate (TPT)-sensitized reactions of several terpene donor molecules, including sabinene (1), α-phellandrene (4), α-terpinene (5) and γ-terpinene (6) give rise to significantly different products than reactions induced by other electron-transfer sensitizers, such as 1,4-dicyanobenzene (DCB). The divergent reactions require decidedly different key intermediates; the products obtained with TPT can be explained by dissociative recombination of the intermediate radical-radical cation pair in the triplet state, generating donor-derived biradicals.
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  • 51
    ISSN: 1434-193X
    Keywords: Azides ; Cleavage reactions ; Cycloadditions ; Nitrogen heterocycles ; Polycycles ; Ring expansion ; Synthetic methods ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---2-Alkyl-1-methylquinazolinium hexafluorophosphates 9 are deprotonated by sodium or potassium hydride to afford solutions of 2-alkylidenedihydroquinazolines 10, which were investigated by NMR spectroscopy. Trapping with methanesulfonyl azide (5a) of 10 in situ or subsequent treatment with trifluoromethanesulfonyl azide (5b) gives mixtures of colourless (15) and intensely yellow N-sulfonylimino-1,4-benzodiazepines 16 along with products due to cleavage of the exocyclic double bond of 10, viz. 11 and 13. The ethylidene compound 10b yields the bicyclic products 18 and 19, apparently by complex sequences of reactions that are triggered by removal of the acidic proton at C-2 of 16b and 16f. The structures of the products are based on spectroscopic evidence and X-ray diffraction analyses performed on 15b, 16d, 16e, and 19.
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  • 52
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1589-1593 
    ISSN: 1434-193X
    Keywords: Azaallenium ions ; Azaallylium ions ; Iminium ion ; Kinetics ; Linear Free Energy Relationships ; Ab initio calculations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The rate constants for the reactions of the 2-azaallenium ion 1b+, the 2-azaallylium ion 2a+ and the iminium ion 3+ with different nucleophiles were determined by 1H NMR spectroscopy. By correlation with the Linear Free Enthalpy Relationship (LFER) lg k20°C = s (E + N), developed by Mayr and Patz, the electrophilicity parameters E(1b+) = -3.7, E(2a+) ≍ -16 and E(3+) = -10.43 were obtained. They show that the relative reactivities of these ions are approximately 1012:1:106. Quantum chemical calculations (ab initio, DFT) of the methyl anion affinities for the ions 1b+,2a+ and3+ are in agreement with the experimental E values. The X-ray structure of 3+·CF3SO3- is reported for the first time; it shows no strong interaction between the cation and the anion.
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  • 53
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1595-1601 
    ISSN: 1434-193X
    Keywords: Oxazoline N-oxide ; Cycloadditions ; Cycloadditions ; Lactams ; Thienamycin ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---[3+2] Cycloaddition between a camphor-derived oxazoline N-oxide 9 and the γ,δ-unsaturated enamino ester 11 afforded the single adduct 6. A stereoselective reduction of the enamino ester side chain allowed the control of the absolute configuration of the two additional asymmetric centres. Nitrogen protection and oxidative hydrolysis of the resulting product 13, followed by further functional group manipulations, led to the β-lactam derivative 1, a known precursor of the β-methylthienamycin derivative2a.
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  • 54
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1603-1607 
    ISSN: 1434-193X
    Keywords: Boron ; Cyclotrimerizations ; Nitrogen heterocycles ; Macrocycles ; Subphthalocyanines ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The regioselective preparation of ortho-substituted subphthalocyanides was achieved employing 3-substituted phthalonitrile derivatives as starting materials. A mechanistic proposal has been outlined.Supporting information for this article is available on the WWW under //http://www.wiley-vch.de/contents/jc_2046/2000/99525_s.pdf or from the author.
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  • 55
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    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1609-1615 
    ISSN: 1434-193X
    Keywords: Terpenoids ; Natural products ; Total synthesis ; Cyclizations ; Rearrangements ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A new route for the synthesis of 2,7- and 7-functionalized labdanes starts from (R)-carvone (1). 11-Nordrim-7-en-9-one (15) is an appropriate starting material for the total synthesis of hispanone (21), a biologically active furolabdane isolated from the Mediterranean medicinal plant Ballota saxatilis.
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  • 56
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    Liebigs Annalen 2000 (2000), S. 1623-1626 
    ISSN: 1434-193X
    Keywords: Iridoid glucoside ; (8S)-Kingiside ; (8S)-Loganin ; (8S)-7-Ketologanin ; Asymmetric synthesis ; Natural products ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The tetraacetyl derivative 8 of the naturally occurring kingiside (8a) was prepared from aucubin (1). Intermediates in the synthesis were (8S)-tetraacetyl loganin (6) and (8S)-tetraacetyl-7-ketologanin (7), whose free (8R)-epimers occur in many different plants (Caprifoliaceae, Loganiaceae). The 13C NMR spectrum allows the structure to be unequivocally identified.
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  • 57
    ISSN: 1434-193X
    Keywords: Tetrakis(dimethylamino)naphthalenes ; Basicity ; Hydrogen bonds ; Cyclicvoltammetry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---For comparison to the recently described 2,3,6,7-tetrakis(dimethylamino)naphthalene (1) the three isomers 2,3, and 4 were synthesized. The basicities of this group of isomers are strongly dependent upon the different mutual orientations of the pairs of dimethylamino substituents: only the isomers 3 and, partially, 4, both with dimethylamino groups in adjacent peri-positions of the naphthalene, are strong “proton sponges”. For the isomers 1 and 2 with the same number and kind of twofold dimethylamino substituents in neighbouring ortho-positions, however, no significant basicity increase is observed. To explain this difference between the two groups of isomers it is suggested that in the ortho-pairs of 1 and 2 the C-N bonds diverge considerably, leading to an increased N···N distance and consequently to less stable [N···H···N]+ hydrogen bonds in contrast to the parallel C-N bonds in the peri-substituted isomers 3 and 4. X-ray crystal structure analyses of the bases and of some of the salts derived therefrom were solved and are discussed. Cyclic voltammetry indicates that 1 to 4 are strong electron donors, reacting easily to radical cations or dications which with suitable acids have been obtained as salts.
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  • 58
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    Liebigs Annalen 2000 (2000), S. 1677-1683 
    ISSN: 1434-193X
    Keywords: Radicals ; Cyclizations ; Pyridinethione ; Tetrahydrofurans ; Asymmetric synthesis ; Thiazolethione ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The trisubstituted functionalized tetrahydrofurans 10, 11, 16, 18, and 19 were photochemically prepared from 2,3-syn- and 2,3-anti-configuredN-(3-benzoyloxy-5-hexen-2-oxy)thiazole-2(3H)-thione anti-6, pyridinethiones 7, anti-8, and BrCCl3. The formation of tetrahydrofurans was achieved by an efficient and highly regioselective alkoxyl radical cyclization (5-exo-trig). The 2,3-anti substituted intermediates 9 and 12 cyclize stereoselectively whereas a 2,3-syn-configured O-radical affords both possible diastereomeric addition products in equal amounts. The cyclized tetrahydrofuryl methyl radicals were trapped with the bromine atom donor BrCCl3 to afford the bromomethyl-substituted cyclic ethers 10, 11, 18, and 19 in excellent yields. The utility of this reaction was stressed by conversion of one of the newly prepared tetrahydrofurans in a two-step synthesis into (+)-allo-muscarine (+)-20.Supporting information for this article is available on the WWW under //http://www.wiley-vch.de/contents/jc_2046/2000/99590_s.pdf or from the author.
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  • 59
    ISSN: 1434-193X
    Keywords: Thioketones ; Thiocarbonyl ylides ; Cycloadditions ; Cycloreversions ; Sulfur heterocycles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Reactions of diaryl thioketones with diazomethane at room temperature afford 4,4,5,5-tetraaryl-1,3-dithiolanes; the scope of this surprising 2:1 interaction has been studied for decades (Schönberg Reaction). The clue to the mechanism was our observation that the stoichiometry is 1:1 at -78 °C, and 2,5-dihydro-2,2-diaryl-1,3,4-thiadiazoles are formed as primary [2+3] cycloadducts. They lose N2 at -45 °C in first-order reactions generating diaryl thioketone S-methylides which can be intercepted by thioketones (→1,3-dithiolanes), multiple CC bonds, or acids HX. In the absence of trapping reagents, the elusive intermediates either dimerize furnishing 2,2,3,3-tetraaryl-1,4-dithianes or give rise to 2,2-diarylthiiranes by electrocyclization. Beyond thiobenzophenone and diazomethane, our main model reaction, the studies involve fluorene-9-thione, 4,4-dimethoxy- and 4,4-dichlorothiobenzophenone. The ring of 2,5-dihydro-2,2-diphenyl-1,3,4-thiadiazole (8) is opened by LDA at -78 °C and derivatives of anion 12 are obtained. - In summa: The Schönberg reaction consists of two 1,3-dipolar cycloadditions, linked by a 1,3-dipolar cycloreversion.
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  • 60
    ISSN: 1434-193X
    Keywords: Conjugation ; Boron ; Sensors ; Cyclic voltammetry ; Polymers ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---New electropolymerizable aromatic compounds (i.e. pyrrole, thiophene, aniline) bearing boronic acid and ester substituents have been synthesized and their electrochemical behavior has been investigated. Functionalized polythiophene and polypyrrole films could be anodically generated in acetonitrile, whereas the polyaniline derivative was electroformed in an acidic aqueous solution. The electrochemical responses of some of these materials were changed when fluoride ions were added to the electrolytic solutions. The strongest modifications, caused by binding of fluoride by the immobilized boron, were observed for the polypyrrole derivative in hydroorganic media.
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  • 61
    ISSN: 1434-193X
    Keywords: Heterocycles ; Zinc ; Palladium ; Catalysts ; Sulfur ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Organozinc halides derived from Grignard reagents behave differently in their reaction with ethyl (±±)-(2RS,3SR)-tetrahydro-4-methylene-2-phenyl-3-(phenylsulfonyl)furan-3-carboxylate (3) according to the hybridisation of the carbon ligand. During the development of short multi-component reactions for the synthesis of diverse functionalized ethyl 2,5-dihydrofuran-3-carboxylates it was discovered that aryl and vinyl zinc halides undergo clean reaction with 3 in the presence of Pd(PPh3)4. In contrast, when alkyl zinc halides are reacted with 3 in the presence of Pd(PPh3)4, reductive desulfonation of 3 is observed. Remarkably, in the absence of a transition metal catalyst, the allylic substitution of 3 with alkyl zinc halides proceeds cleanly and in moderate to good yield.
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  • 62
    ISSN: 1434-193X
    Keywords: Self-assembly ; Vapor-pressure osmometry ; Resorcin[4]arenes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Resorcin[4]arene tetracarboxylic acids 5,6 (A) and resorcin[4]arene tetrapyridines 2,3 (P) self-assemble in chloroform solution to form stable heterotopic AP dimers. Data from NMR titration and dilution experiments, as well as from vapor-pressure osmometry (VPO), indicate that the AP dimer is formed with an association constant greater than 107 M-1. Solid-solution extraction experiments are indicative of the formation of a 2:1 trimer (A2P), while self-associated homotopic species (A2 and A3) can be detected by NMR and VPO. Analysis of the heterotopic noncovalent assembly process over a range of compositions shows that these other species are much less stable than the AP heterodimer, which is the exclusive species at an A/P concentration ratio of 1:1 (〉 99.7% of the total at 10 mM).
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  • 63
    ISSN: 1434-193X
    Keywords: Sulfoxides ; β-Amino sulfones ; Mannich type reaction ; Lithium perchlorate ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The LiClO4-mediated one-pot reaction of aldehydes with (trimethylsilyl)dialkyl amines and the lithium salt of sulfoxides or sulfones, affords the corresponding β-(dialkylamino) sulfoxides and β-(dialkylamino) sulfones in high yields. The aminosulfoxidation reaction of aliphatic or aromatic aldehydes lacks diastereoselectivity, but the diastereomeric sulfoxides can be separated by HPLC or column chromatography for further use.
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  • 64
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    Liebigs Annalen 2000 (2000), S. 1741-1744 
    ISSN: 1434-193X
    Keywords: Bridged pyranose derivatives ; Ring enlargement ; Carbenes ; Glycosides ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Addition of dichlorocarbene to the glycal (±±)-2 followed by cyclopropyl-allyl rearrangement leads to the chloro-2H-pyran (±±)-4. Oxidation of (±±)-4 and reduction of the obtained hydroxypyranone (±±)-5 gave the methyl pyranoside (±±)-6. The relative configuration of (±±)-6 was established by X-ray structural analysis of the corresponding acetate (±±)-7. The synthesis of the optically active starting materials (+)-2 and (-)-2 is also reported.
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  • 65
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    Liebigs Annalen 2000 (2000), S. 1745-1758 
    ISSN: 1434-193X
    Keywords: CMP-Neu5Ac analogues ; Enzyme inhibitors ; Substrate analogues ; Transition state analogues ; Transferases ; Carbohydrates ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Quinic acid was transformed into phosphitamides 16, 25, and 36, which could be readily linked to 5′-O-unprotected cytidine derivative 17. Ensuing oxidation of the obtained phosphite triesters with tBuO2H and hydrogenolytic de-O-benzylation furnished the corresponding phosphate diesters 18, 26, and 38. Base catalyzed removal of acetyl protecting groups, and methyl ester hydrolysis furnished CMP-Neu5Ac analogues 1d, 1e, and 2. Quinic acid was also transformed into 1,2-unsaturated diallyl α-hydroxymethyl-phosphate derivatives (R)- and (S)-46, which on reaction with cytidine phosphitamide 47 afforded the phosphite triesters. Subsequent oxidation with tBuO2H and then treatment with NEt3 gave phosphate diester derivatives (R)- and (S)-48. Deallylation, acetyl group removal, and methyl ester hydrolysis furnished (R)- and (S)-3, respectively. Treatment of (R)- and (S)-48 with DBU as a base led to acetic acid elimination, thus yielding, after de-O-allylation, acetyl group cleavage, and ester hydrolysis, diene derivative (E)-4. Donor substrate analogues 1d and 1e exhibited good α(2-6)-sialyltransferase inhibition (Ki: 2.0·10-4 and 2.0·10-5 M). However, transition state analogues (R)-, and particularly (S)-3 showed excellent inhibition properties (Ki: 1.6·10-6 and 2.7·10-7 M).
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  • 66
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    Liebigs Annalen 2000 (2000), S. 1759-1765 
    ISSN: 1434-193X
    Keywords: Cyclitols ; Aminocyclitols ; Glycosidase inhibitors ; α-Mannosidase inhibitors ; Deoxygenation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Three deoxy derivatives 2-4 of the α-mannosidase inhibitor mannostatin A (1) were synthesized, and their inhibition of Jack bean α-mannosidase was evaluated in order to elucidate the roles of each of the three hydroxyl groups of the inhibitor. The 1- and 2-deoxy derivatives 2 and 3 retained some inhibitory activity, although reduced by a factor of about 100 relative to the parent, whereas it was completely lost with the 3-deoxy derivative 4. Structure and activity relationships are discussed in the light of these findings.
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  • 67
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    Liebigs Annalen 2000 (2000), S. 1767-1772 
    ISSN: 1434-193X
    Keywords: Circular dichroism ; Conformation analysis ; s-Triazines ; Chiral auxiliaries ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---CD data of the optically pure 2-[(R)-1-(9-anthryl)ethylamino]-4-chloro-6-[(R)-1-(1-naphthyl)ethylamino]-1,3,5-triazine, 2[(R)-1-(9-anthryl)ethylamino]-4,6-bis[(R)-1-(1-naphthyl)ethylamino]-1,3,5-triazine, 2,4-bis[(R)-1-(9-anthryl)ethylamino]-6-chloro-1,3,5-triazine are presented. The analysis of the CD spectra by means of the nonempirical DeVoe approach has afforded the complete conformational characterisation of the three s-triazine derivatives, allowing us to establish how the conformation of these derivatives depends on the nature of the substituent 1-arylethylamino groups.
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  • 68
    ISSN: 1434-193X
    Keywords: Cycloadditions ; Carbenes ; Nitrones ; Nitrilimines ; Pyrazolines ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The reaction of tert-butylalkynyl chromium Fischer carbene complex 1 with nitrones 2 affords β-enamino-ketoaldehydes 4 by the light-promoted rearrangement of the corresponding [3+2] cycloadduct carbene complexes 3. On the other hand, [3+2] cycloaddition of chiral nonracemic Fischer alkenyl carbene complexes 19 with nitrilimines 10 yields enantiomerically pure Δ2-pyrazolines with high regio- and diastereoselectivity.
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  • 69
    ISSN: 1434-193X
    Keywords: Asymmetric synthesis ; Zinc ; Transition structures ; QM/MM computations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Trimethylsilyl substitutions of the fenchyl alcohols [(1R,2R,4S)-exo-(2-Ar)-1,3,3-trimethylbicyclo[2.2.1]heptan-2-ol, Ar = 2-methoxyphenyl (1) and Ar = 2-(dimethylaminomethyl)phenyl (2)] yield the chiral ligands 3 [Ar = 2-methoxy-3-(trimethylsilyl)phenyl] and 4 [Ar = 2-(dimethylaminomethyl)3-(trimethylsilyl)phenyl]. Increased reactivities and enantioselectivities in diethylzinc additions to benzaldehyde are obtained from 3 (63% ee R) and 4 (93% ee S), relative to 1 (26% ee S) and 2 (73% ee S). X-ray crystal structures of 3 and of its methylzinc complex 3-Zn reveal out-of-plane bending of the methoxy groups as major geometrical consequences of the trimethylsilyl substitutions. Analyses of QM/MM ONIOM μ-O transition-structure models for 1, 2, 3, and 4 show that trimethylsilyl-induced distortions of methoxy and of dimethylaminomethyl groups explain the observed increased enantioselectivities.
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  • 70
    ISSN: 1434-193X
    Keywords: Palladium ; exo-π-Allylpalladium complexes ; Allylic alkylation ; Spiro compounds ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The palladium(0)-catalyzed alkylation of 2,3-bis(acetoxymethyl)bicyclo[2.2.1]hepta-2,5-diene 1 with malonate-type enolates as nucleophiles is investigated. A monoalkylated product is formed first, and undergoes (depending on the nucleophile used) a second intramolecular reaction leading to spirocyclopropane-annulated bicyclo[2.2.1]heptene derivatives 5. The formation of endo spirobicyclic cyclopropanes adducts as major isomer is rationalized by assuming formation of an intermediate exo-(π-allyl)palladium complex.
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  • 71
    ISSN: 1434-193X
    Keywords: Ketones ; Reductions ; Micelles ; Cobalt ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Operationally simple and environmentally benign procedures have been developed to selectively reduce different α,β-unsaturated ketones, 4,4-dimethylcyclohex-2-ene-1-one (1), isophorone (2), benzylideneacetone (3), chalcone (4) by NaBH4 or by the system NaBH4 + CoCl2. Alternative reaction media to the extensively used MeOH have been explored, and new procedures take advantage of the acceleration and chemoselectivity induced by water or by aqueous micellar solutions. It was possible to selectively and quantitatively afford pure products of 1,2 and of 1,4 reduction as well as the totally reduced compounds (yield and selectivity 〉 90%) by simple changes in the experimental conditions.
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  • 72
    ISSN: 1434-193X
    Keywords: C-Glycosides ; Conformation analysis ; Molecular dynamics ; Selectins ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The conformational behavior of the C-glycosyl analogue of sialyl-α-(2→3)-galactose, synthesized as a glycosidase inhibitor, has been studied using a combination of NMR spectroscopy (J and NOE data) and molecular dynamics calculations. The obtained results show that the population distribution of conformers with respect to the orientation about the pseudo-glycosidic linkages is mainly controlled by steric interactions. This is in contrast to findings made for O-glycosides. In these natural compounds, the conformational behavior about the glycosidic linkage Φ is mainly governed by the exo-anomeric effect.
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  • 73
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    Liebigs Annalen 2000 (2000), S. 1815-1820 
    ISSN: 1434-193X
    Keywords: Asymmetric synthesis ; Palladium-catalysed couplings ; Palladacycles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Chiral C2-symmetric N-benzylazetidines have been conveniently prepared from optically pure anti-1,3-diols without loss of enantiomeric purity. N-Debenzylation led to the corresponding N-unsubstituted azetidines, which were then subjected to palladium-catalysed coupling reactions with aryl bromides to afford chiral N-arylazetidines. (R,R)-N-Benzyl-2,4-dimethylazetidine has been employed in the synthesis of a new cyclopalladated complex, which can be used, for instance, as a chiral recognition agent for phosphorus ligands.
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  • 74
    ISSN: 1434-193X
    Keywords: Cyclizations ; Spiro compounds ; Nucleosides ; Isomerizations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Syntheses of the spiro nucleosides 2′-deoxyhydantocidin 3a and its 1′-epimer 3b are described. The newly developed route involves a Horner-Wadsworth-Emmons condensation of the phosphonate 16 with the erythrose derivative 15 affording a mixture of six isomers which was fully assigned by NMR spectroscopy. The mixture was directly converted into the final compounds in an efficient base-catalyzed cyclization reaction. A base-catalyzed interconversion between the two isomers was observed.
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  • 75
    ISSN: 1434-193X
    Keywords: Benzodiazepines ; Heterocycles ; Azeto[1,2-a]-1,5-benzodiazepines ; Cyclizations ; Cycloadditions ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The reaction of o-phenylenediamine (4) with one, two or three equivalents of p-substituted 3-dimethylaminopropiophenone hydrochlorides 5a-e was studied. 4-Aryl-2,3-dihydro-1H-1,5-benzodiazepine derivatives 6a-e were obtained in good yields, along with the 1:2-adducts 7c-e and the unexpected 1:3-adducts rac-8c-e. The type of adduct formed is determined by the molar ratio of the reactants 4 and 5 and by the nature of the substituent in the para position of the propiophenone 5.
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  • 76
    ISSN: 1434-193X
    Keywords: Cup-shaped PAHs ; Host-guest compounds ; Host-guest chemistry ; Cyclizations ; Semiempirical calculations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Cyclotrimerisation of benzo-polycyclic bromostannylalkenes 8a-d with Cu(NO3)2·3H2O in THF affords benzotri(benzonorbornadienes) 3a-d as a mixture of the syn and anti isomers. The ratio of syn to anti is close to the 1:3 statistical value in most cases (i.e. in cyclotrimers 3a,b,d), but highly in favour of the anti isomer in 3c, where steric hindrance by the methoxy groups plays an important role in the stereochemistry of the cyclotrimerisation. The substrates for the cyclotrimerisation, i.e. the bromostannyl alkenes 8a-d, were prepared from bromoalkenes 7a-d by treatment with base (LDA) and quenching with trimethyltin chloride. In turn, bromoalkenes 7a-d were prepared from alkenes 5a-d by radical bromination-elimination. The reaction conditions used were designed to minimise Wagner-Meerwein rearrangements that would lead to unwanted bromo isomers. The cup-shaped syn cyclotrimers 3a-d exhibit high electron density within the cavity as determined by AM1 semiempirical calculations of their electrostatic potential surfaces and are valuable substrates for supramolecular chemistry. As an example, it is shown that fullerene C60 is drawn into solution in acetonitrile by complexation with both the syn and anti trimer of benzonorbornadiene 3a.
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  • 77
    ISSN: 1434-193X
    Keywords: Carbene complexes ; Enamines ; Metallatrienes ; Cyclopentadienes ; Dihydropyrroles ; spiro-Tetrahydropyrroles ; Iminium carbonylmetalates ; Dimetallapolyenes ; Tungsten ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Reactions of the [(1-alkynyl)carbene]tungsten complex (CO)5W=C(OEt)C≡CPh (1) with 1-aminocyclohexenes 2a-c and 7a-c afford different types of products depending on the amino substituents and the reaction conditions. (4-Aminocyclobutenyl)carbene complexes B have been shown to be generated in the first reaction step through a [2+2] cycloaddition. These are key intermediates and afford cross-conjugated tungstatrienes E, (conjugated) 1-tungsta-1,3,5-hexatrienes G, or (non-conjugated) 1-tungsta-1,3,6-heptatrienes F by following competing reaction pathways. Cross-conjugated 1-tungstatrienes 3 have been isolated in 52-74% yield by performing the reactions of 1-aminobenzocyclohexenes 2a-c with compound 1 in pentane. In dichloromethane instead of pentane, (conjugated) 1-tungsta-1,3,5-hexatrienes 4 are obtained, which subse-quently undergo fragmentation to give cyclopentadienes 6 (by π-cyclization) and dihydropyrroles (by α-cyclization) in a molar ratio dependent on the nature of the amino substituents. (Non-conjugated) 1-tungsta-1,3,6-heptatrienes 10 are generated upon reaction of 1-aminocyclohexenes 7a-c with compounds 1, which are transformed into cyclopentadienes 12 via conjugated 1-tungsta-1,3,5-hexatrienes 9 as intermediates. Reactions of 1-tungsta-1,3,6-heptatrienes 10 with the (1-alkynyl)carbene complex 1 afford dinuclear compounds 14, which subsequently yield indenes 15 (by two successive π-cyclization steps) and spiro-tetrahydropyrroles 16 (by both a π-cyclization and an α-cyclization step), depending on the steric bulk of the amino substituent.
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  • 78
    ISSN: 1434-193X
    Keywords: Allyl alcohols ; Organocerium reagents ; Alkenes ; Addition reactions ; Cerium ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Alkylcerium reagents add to the multiple bonds of allyl and propargyl alcohols in good yields and under mild conditions. The double bond can be reduced with lithium aluminum hydride in the presence of cerium trichloride. The regiochemistry of the attack depends on electronic factors.
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  • 79
    ISSN: 1434-193X
    Keywords: Amidines ; Chiral bases ; N-Acyliminium ions ; Enantioselective catalysis ; Chiral pool ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The synthesis of four enantiopure hydroxyamidines is described. One amidine was obtained from (S)-pyroglutamic acid. Its key step involved the addition of phenylmagnesium bromide to the corresponding ester, affording the tertiary alcohol without detectable racemization. The second amidine was obtained by coupling of an (S)-malic acid derived N-acyliminium ion with β-naphthol. The other amidines were obtained from an (S)-serine-derived imide which was reduced to two diastereomeric lactams that were eventually transformed into the corresponding amidines.
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  • 80
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 155-163 
    ISSN: 1434-193X
    Keywords: Macrocycles ; Cyclizations ; Strained compounds ; Ketophosphonate ; Iodoalkyne ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Two strategies have been explored to build the highly strained eleven-membered ring 2, a potential precursor for the biosynthetic key intermediate of the protoilludane family: an intramolecular Horner-Wadsworth-Emmons olefination and an intramolecular Nozaki-Hiyama-Kishi type-ring closure.
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  • 81
    ISSN: 1434-193X
    Keywords: Neutral anion receptor ; Hydrogen bonds ; Urea moieties ; Donor-acceptor systems ; Macrocycles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The synthesis of macrocyclic and acyclic cleft-like anion receptors in which four hydrogen bond donating urea moieties are present in a preorganized fashion is described. NMR spectroscopy shows the complex formation with H2PO4- and Cl -. Cleft-like receptors bind H2PO4- in a 2:1 guest-host stoichiometry (Ka = 107M-2) in DMSO, whereas Cl - is bound in a 1:1 stoichiometry (Ka = 103M-1). The macrocyclic receptors form a 1:1 complex with H2PO4- (Ka = 103M-1 in DMSO) with a 100-fold selectivity for H2PO4- over Cl -.
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  • 82
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 193-198 
    ISSN: 1434-193X
    Keywords: Nucleophilic substitutions ; Azulenes ; Hydroxylation ; Amination ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Hydroxylation of azulenes with tert-butylhydroperoxide proceeds efficiently at the 6-position when the former contain electron-withdrawing substituents in the five-membered ring. Similarly, VNS amination of azulenes proceeds with 4-amino-1,2,4-triazole; its anion, being an active nucleophile, also reacts with unsubstituted azulene. A variety of transformations of 6-hydroxyazulenes, such as substitution of the corresponding sulfonates with nitrogen, oxygen, sulfur, carbon nucleophiles and halogens, and the Claisen rearrangement of allylic ethers, is reported.
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  • 83
    ISSN: 1434-193X
    Keywords: Heterocycles ; Carbohydrates ; Imidazolidines ; Oxazolidines ; Spiro compounds ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Prochiral 1,3-dihydroxyacetone forms racemic oxazolidine- and oxazoline-type spiro[4.4]nonanes upon reactions with potassium (thio)cyanate and cyanamide. In contrast, 1,3-diaminoacetone yields only the corresponding spiro-bisimidazolidinethione under similar conditions together with monocyclic by-products, but the spiro-bisimidazolidinone is accessible by reaction of 1,3-dichloroacetone with urea. The resolution of the racemic spiro-bisoxazolidinethione 2a was achieved by using brucine as the resolving agent.
    Additional Material: 1 Ill.
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  • 84
    ISSN: 1434-193X
    Keywords: Homogeneous catalysis ; Palladium ; Acetoxylation ; Acryloxylation ; Addition reactions ; Cyclooctadiene ; Cyclooct-4-enone ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Palladium-catalyzed acryloxylation of several cycloalkenes in the presence of the Pd(OAc)2/p-benzoquinone/MnO2 catalytic system is reported. This oxidation reaction yields allylic acrylates as the sole products through the intermediacy of an η3-allyl complex. However, with 1,5-cyclooctadiene (3), cyclooct-4-enone (4) is the major reaction product. Its formation results from oxidation, which is also observed in the palladium-catalyzed acetoxylation of 3. It has been shown that this is the result of a 1,2-trans addition (acryloxy-palladation), followed by a β-hydride elimination, which yields an enol acrylate or acetate. A second Markovnikov-oriented 1,2-trans-acryloxy-palladation on the latter yields a palladium complex, rearrangement of which gives 4.
    Additional Material: 1 Ill.
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  • 85
    ISSN: 1434-193X
    Keywords: Amino acids ; coupling ; N-Substituted amide ; Cyclizations ; Cyclic dipeptides ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A short synthesis of new, functionalized seven-membered ring cyclic dipeptides is described. After the coupling of N-protected β-amino acids to N-substituted α-amino tert-butyl esters, the protective groups of the terminal functions were removed and the cyclization took place diastereoselectively in the presence of the coupling agent BOP. Amide substitution was found to be effective in promoting the cyclization of linear dipeptides.
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  • 86
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 275-280 
    ISSN: 1434-193X
    Keywords: Radical reactions ; Substituent effects ; Nitrogen heterocycles ; Dihydropyridines ; Pyrrolines ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A set of allene-tethered benzoyloximes (5) has been treated with nBu3SnH. Depending on their substitution pattern, a wide range of compounds has been obtained. If the stannyl radical adds on the allene, the C-centred radical thus formed undergoes either a 5-exo ring closure to give the cyclopentene derivatives 7 or a 6-endo ring closure onto the N atom to give the dihydropyridines 8. If the stannyl radical adds on the benzoyl moiety, an iminyl radical is formed which leads to the 3H-pyrroles 9 and the alkylidene-pyrrolines 10. Steric effects as well as polar effects are the factors governing the reaction course.Supporting information for this article is available on the WWW under //http://www.wiley-vch.de/contents/jc_2046/2000/99373_s.pdf or from the author.
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  • 87
    ISSN: 1434-193X
    Keywords: Antibiotics ; Configuration determination ; Heterocycles ; Hongoquercin A ; Terpenoids ; Total synthesis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---(±)-Hongoquercin A (1), the racemate of an antibacterial fungal metabolite, has been synthesized starting from geranylacetone (2) and ethyl orsellinate (ethyl 2,4-dihydroxy-6-methylbenzoate, 5). The structure (±)-1 has been confirmed by X-ray analysis of its ethyl ester (±)-10. Synthesis of the naturally occurring (+)-hongoquercin A from (-)-sclareol (11) established its configuration as depicted in 1.
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  • 88
    ISSN: 1434-193X
    Keywords: Carbohydrates ; Amino sugars ; Protecting groups ; Glycosylations ; Trichloroacetimidates ; Oligosaccharides ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The N-DMM-Protected lactosamine derivative 2 was readily transformed into the corresponding glycosyl donor 4 and into acceptor 5. A TMSOTf-catalyzed glycosidation afforded the derived tetrasaccharide 6 which led to glycosyl donor 9. Reaction of 9 with lactose derivative 10 as acceptor gave the desired hexasaccharide 11. Cleavage of all protective groups and N-acetylation afforded the target molecule 1b (lacto-N-neohexaose). Glycosylation of acceptor 10 with donor 4 furnished tetrasaccharide 16 which, employing standard procedures, gave acceptor 18. Glycosylation of 18 with donor 9 furnished, under standard conditions, octasaccharide 19. Cleavage of all protective groups and N-acetylation afforded the target molecule 1c (lacto-N-neooctaose). Both 1b and 1c were obtained in good overall yields.
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  • 89
    ISSN: 1434-193X
    Keywords: Sharpless asymmetric dihydroxylation ; Asimilobin ; Tetrahydrofuran ring ; Wittig reactions ; Annonaceous acetogenins ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The most efficient method for the synthesis of the trans/threo/trans-bis(tetrahydrofuran) (THF) ring unit was established, and the first total synthesis of (-)-asimilobin and its diastereomer was then accomplished in twelve and fourteen steps, respectively, from trans-1,5,9-decatriene, by a convergent route with a Wittig reaction as the key step. By virtue of these synthetic results, the absolute configuration of the bis(THF) unit in naturally occurring asimilobin should be corrected.
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  • 90
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 381-385 
    ISSN: 1434-193X
    Keywords: Enynes ; Macrocycles ; Coordination chemistry ; Crown compounds ; Radicals ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The complex molecular structure and interesting activation mechanisms of naturally occurring enediynes have inspired the synthesis of a variety of simpler model systems to mimic their properties. While in most model compounds nucleophilic attack, isomerization or bioreduction are used to activate the unsaturated system for diradical cyclization, some attempts have been made to employ metal-ion coordination for this purpose. Significant enhancement of the thermal reactivity has been achieved by metal-ion induced conformational and electronic changes of suitably substituted enediynes, such as 1, 5, 6, 17 and 18. Enediyne activation by stoichiometric or catalytic formation of vinylidene complexes, such as 22, from terminal alkynes has also been investigated. This paper summarizes recent results pursuing the activation of enediyne diradical cyclization by metal ions.
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  • 91
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 419-423 
    ISSN: 1434-193X
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The first enantioselective synthesis of enantiomerically pure (-)-wine lactone, (-)-1a, a fragrance constituent of various white wines, and its epimer (+)-1b, was carried out. The key steps are allylic substitution of (±)-2-cyclohexen-1-yl acetate (2) with dimethylmalonate using palladium complexes of phosphanyldihydrooxazol L1 or of the phosphanylcarboxylic acid L2 as catalyst, subsequent decarboxylation, iodolactonization and elimination, furnishing enantiomerically pure bicyclic lactone (+)-7 in 47% overall yield. The diastereoselective introduction of methyl groups by SN2′-type substitution with an organocopper compound and by enolate alkylation gave lactone (-)-1a in 43% overall yield from (+)-7.
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  • 92
    ISSN: 1434-193X
    Keywords: Aplykurodins ; Marine steroids ; C-C coupling ; Cyclic peroxides ; Lactonization ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---An approach to the synthesis of aplykurodins, ichthyotoxic marine lactones, is presented. The carbon framework was derived from vitamin D3 by conversion of the readily accessible allyl alcohol 13 to the protected Grundmann's hydroxy ketone 22 and subsequent introduction of the C2 side chain through a Pd0-promoted coupling. Highly stereoselective hetero Diels-Alder reaction with O21 produced the key intermediate peroxide 25. Functional group transformations, coupled with a series of chemo- and stereoselective reactions, finally resulted in the synthesis of the unnatural analogue 17,18-dihydro-3,9-di-epi-aplykurodinone B (6).
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  • 93
    ISSN: 1434-193X
    Keywords: Zeolites ; Radical ions ; Ring opening ; Electron transfer ; Oxidations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Incorporation of trans-1,2-diphenylcyclopropane (1) and its 3,3-D2-isotopomer into the channels of a redox-active pentasil zeolite (Na-ZSM-5) resulted in the formation of exo,exo-1,3-diphenylallyl radical (2•) and its 2-D1 isotopomer, respectively. This conversion requires oxidation, ring opening, and deprotonation, in an unspecified sequence. The allyl radical 2• is also formed upon incorporation of trans-1,3-diphenylpropene (3). A comparison with the solution photochemistry, in the presence or absence of added base, shows the conversion of 1 into 2• to be a zeolite-specific reaction. Incorporation of arylcyclopropanes 9 (R = H, OCH3) into ZSM-5 generated trans-propenylbenzene radical cations 10•+ (R = H, OCH3); the 2,2-D2 isotopomer of 9 (R = OCH3) gave rise to three different isotopomers of 10•+ (R = OCH3).
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  • 94
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 485-490 
    ISSN: 1434-193X
    Keywords: Calixarenes ; Tripodal cryptand ; Extraction abilities ; Cations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The tripodal calixcryptands have been one of the scarcely explored fields in calixarene chemistry due to the difficulties in their preparation. The strategy presented in this paper shows that novel tripodal calixcryptands can be conveniently prepared by directly treacing p-tert-butylcalix[n]arenes (n = 4, 6) with a multi-functional polypode reagent, e.g. 1,1,1-tris(tosyloxyethoxyethoxymethyl)propane or tetrakis(tosyloxyethoxyethoxymethyl)methane, under selected conditions. The first example of 1,2,4-tripodal calix[6]cryptands has been prepared. Novel calix[6]crown and doublecalix[4]arenes were co-prepared. The extraction abilities of these novel calixcryptands toward several alkali metal ions, ammonium and alkylammonium ions are presented.
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  • 95
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 521-525 
    ISSN: 1434-193X
    Keywords: Allyl aryl sulfones ; Nitroarenes ; Condensation reaction ; Lewis acids ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Allyl aryl sulfones 2 react with aryl nitrocompounds 1 in a DBU/MgCl2 system giving the 4-arylsulfonyl quinolines 3. Some mechanistic aspects of the reaction are discussed. Application of this reaction to the formal total synthesis of the natural product (-)Eupolauramine is described.
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  • 96
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 527-538 
    ISSN: 1434-193X
    Keywords: Furans ; Pyrans ; Dihydropyran-2-ylidenes ; Ring closure ; Addition reaction ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---On treatment with base the pentynones 8a-f undergo anionic addition reactions of the resulting enolate species to the alkyne moiety and afford the 2,5-disubstituted furans 10a-f in yields ranging from 10-91%. The proposed mechanism involves the 2-methylene-dihydrofurans 11 as intermediates which tautomerize to yield the observed products. In the case of the α-picolyl derivative 8g both possible enolates 12 and 13 are formed which are subsequently transformed to the products 10g and 14g, respectively. Starting with the hexynones 9a-e an analogous reaction takes place with the formation of the pyran derivatives 15 and 16 in comparable yields. Under the same reaction conditions the n-butyl ketone 9f gives rise to two isomeric compounds, namely the 4H-pyran 16f and the cyclohexenone 17. This result is explained by assuming initial formation of two isomeric enolates which react either by O- or C-attack on the carbon-carbon triple bond.
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  • 97
    ISSN: 1434-193X
    Keywords: Alkylations ; Deaminated AdoHcy ; Decarboxylated AdoHcy ; Mitsunobu reaction ; Nucleosides ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---5′-Acetylthio-5′-deoxy-2′,3′-O-isopropylideneadenosine (8) was directly prepared from commercially available 2′,3′-O-isopropylideneadenosine (7) and thioacetic acid under Mitsunobu conditions in almost quantitative yield. In situ cleavage of the acetylthio function of 8 followed by coupling with different alkyl bromides proceeded with high yields. Deprotection of the obtained 5′-thionucleosides yielded the S-adenosyl-L-homocysteine analogues decarboxylated AdoHcy (11), deaminated AdoHcy (14) and 5′-[3-(cyano)propylthio]-5′-deoxyadenosine (16) in good overall yields. Direct deprotection of the thionucleoside 8 delivered 5′-thio-5′-deoxyadenosine (18) in excellent yield. In addition, binding constants of these AdoHcy analogues and the DNA methyltransferase M·HhaI were determined in a fluorescence assay.
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  • 98
    ISSN: 1434-193X
    Keywords: Amino ketones ; Homogeneous catalysis ; Aziridination ; Copper ; Enols ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A series of acyclic and cyclic enol derivatives 1 has been transformed into the corresponding α-amino-functionalized ketones 2 by means of enantioselective catalytic aziridination with chiral Cu complexes, prepared in situ from [Cu(MeCN)4]PF6 and the optically active ligands 3, by using (N-tosylimino)iodobenzene (PhINTs) as a nitrogen source. The best enantioselectivities (ee values of up to 52%) have been achieved for the electronically deactivated enol acetate 1aδ, but the incorporation of steric bulk and the substitution pattern at the enol double bond do not improve the ee values. The cyclic substrates react considerably less readily (only up to 45% conversion) compared to their acyclic counterparts (complete consumption). A transition structure is suggested for the asymmetric Cu-catalyzed aziridination of the enol acetate 1aδ in the presence of the chiral ligand 3b that could account for the sense of the (R)-configured product 2a.
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  • 99
    ISSN: 1434-193X
    Keywords: Porphyrins ; Chiral auxiliaries ; Macrocycles ; Pyrethroids ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Esters, N,N-disubstituted amides, and a N-acylurea derived from the enantiopure industrial intermediate (1R)-cis-hemicaronaldehydic acid (or biocartol) are convenient synthons for the preparation of a series of chiroporphyrins by condensation with pyrrole. These chiral meso-tetracyclopropylporphyrins are obtained exclusively as the D2-symmetric α,β,α,β atropisomer, generally in low to moderate yields (2-20%), and in the urea case in excellent yield (60%). Hydrolysis of the urea substituents affords a chiroporphyrin with mono-N-substituted amide groups. 1H-NMR spectroscopy indicates that the ester, amide, and urea stereogenic groups sit on the porphyrin close to the metal binding site and restrict substrate or ligand access along a C2-symmetric groove. This structural feature of chiroporphyrins and of their metal complexes is of high potential interest in asymmetric catalysis and chiral recognition.
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  • 100
    ISSN: 1434-193X
    Keywords: Cyclophanes ; Molecular recognition ; Molecular shuttles ; Rotaxanes ; Template-directed synthesis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Two dumbbell-shaped compounds (8 and 11), each composed of two polyether chains intercepted by a 1,4-dioxybenzene recognition site, terminated by tetraarylmethane-based stoppers, and emanating from a central 9,10- or a 2,6-dioxyanthracene unit, have been synthesized. Two [2]rotaxanes (9 · 4 PF6 and 12 · 4 PF6) have been prepared by interlocking these dumbbell-shaped compounds (8 and 11) with a bipyridinium-based tetracationic cyclophane (15 · 4 PF6) - namely, cyclobis(paraquat-p-phenylene). A [3]rotaxane (10 · 8 PF6) incorporating two cyclophane components (15 · 4 PF6) was also obtained when the 9,10-dioxyanthracene-containing dumbbell-shaped compound (8) incorporating two 1,4-dioxybenzene recognition sites was employed. The 1H-NMR spectroscopic investigation of the [2]rotaxanes (9 · 4 PF6 and 12 · 4PF6) revealed that the cyclophane component encircles one of the two 1,4-dioxybenzene recognition sites in the 9,10-dioxyanthracene-containing [2]rotaxane (9 · 4 PF6) and the 2,6-dioxyanthracene unit in the other [2]rotaxane (12 · 4 PF6). These structures have been confirmed by UV/Vis and electrochemical experiments. Comparison with the spectroscopic properties of simple model compounds shows the presence of electronic interactions which lead to (i) the occurrence of very efficient energy transfer processes in the dumbbell-shaped components and (ii) perturbations in the absorption spectra with appearance of two charge-transfer absorption bands and complete luminescence quenching in the [2]rotaxanes. For the 2,6-dioxyanthracene-containing [2]rotaxane (12 · 4 PF6), it has been demonstrated that the cyclophane can be displaced from the dioxyanthracene to the 1,4-dioxybenzene station upon electrochemical oxidation.
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