The first lady geologist,or collector par excellence?     

Cynthia V. Burek 《Geology Today》2001,17(5):192-194

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CROP RESPONSE TO CLIMATE CHANGE IN THE SOUTHERN GREAT PLAINS: A SIMULATION STUDY*     

Cynthia Rosenzweig 《The Professional geographer》1990,42(1):20-37

This study utilizes global climate models and crop growth models to estimate the potential agricultural effects of climate change caused by a doubling of atmospheric carbon dioxide for the southern Great Plains. Projected climate changes cause simulated wheat and corn yields to decrease in the study area. Decreases in modeled grain yields are caused primarily by temperature increases which shorten the duration of crop life cycle and curtail the harvestable biomass production. While physiological effects of carbon dioxide and changing cultivars offer some hope of climate change mitigation, detrimental consequences to regional crop production, including need for increased irrigation, are suggested.  相似文献   

Making the Subterranean Visible: Security,Tunnels, and the United States–Mexico Border     

Cynthia Sorrensen 《Geographical review》2014,104(3):328-345

The number of unauthorized tunnels discovered through the U.S.–Mexico border has risen dramatically since the mid‐1990s. These tunnels are problematic for the state because the subterranean border is both less visible and more difficult to monitor and control than is the surface border. In this era of heighten security, the debate on secure borders has intensified. As a result, the need to demonstrate security success at both the national and the agency level has risen. Efforts to make tunnel discoveries (and security) visible are made within border‐security agencies and within national discourse and legislation. These efforts spatially fix tunnels to the border in ways that obscure fuller a understanding of drug trafficking in general. This paper employs archival research, content analysis, and informal interviews with security‐enforcement agents to consider the material presence of tunnels within border landscapes.  相似文献   

Compositional limits and analogs of monoclinic triple-chain silicates     

David M. Jenkins  Geoffrey J. Gilleaudeau  Cynthia Kawa  Jaclyn M. Dibiase  Maria Fokin 《Contributions to Mineralogy and Petrology》2012,164(2):229-244

Growing recognition of triple-chain silicates in nature has prompted experimental research into the conditions under which they can form and the extent of solid solution that is feasible for some key chemical substitutions. Experiments were done primarily in the range of 0.1–0.5 GPa and 200–850 °C for durations of 18–1,034 h. A wide range of bulk compositions were explored in this study that can be classified broadly into two groups: those that are Na free and involve various possible chemical substitutions into jimthompsonite (Mg₁₀Si₁₂O₃₂(OH)₄), and those that are Na bearing and involve chemical substitutions into the ideal end-member Na₄Mg₈Si₁₂O₃₂(OH)₄. Numerous attempts to synthesize jimthompsonite or clinojimthompsonite were unsuccessful despite the type of starting material used (reagent oxides, magnesite + SiO₂, talc + enstatite, or anthophyllite). Similarly, the chemical substitutions of F⁻ for OH⁻, Mn²⁺, Ca²⁺, or Fe²⁺ for Mg²⁺, and 2Li⁺ for Mg²⁺ and a vacancy were unsuccessful at nucleating triple-chain silicates. Conversely, nearly pure yields of monoclinic triple-chain silicate could be made at temperatures of 440–630 °C and 0.2 GPa from the composition Na₄Mg₈Si₁₂O₃₂(OH)₄, as found in previous studies, though its composition is most likely depleted in Na as evidenced by electron microprobe and FTIR analysis. Pure yields of triple-chain silicate were also obtained for the F-analog composition Na₄Mg₈Si₁₂O₃₂F₄ at 550–750 °C and 0.2–0.5 GPa if a flux consisting of Na-halide salt and water in a 2:1 ratio by weight was used. In addition, limited chemical substitution could be documented for the substitutions of 2 Na⁺ for Na⁺ + H⁺ and of Mg²⁺ + vacancy for 2Na⁺. For the former, the Na content appears to be limited to 2.5 cations giving the ideal composition of Na_2.5Mg₈Si₁₂O_30.5(OH)_5.5, while for the latter substitution the Na content may go as low as 1.1 cations giving the composition Na_1.1Mg_9.4Si₁₂O_31.9(OH)_4.1 based on a fixed number of Si cations. Further investigation involving Mg for Na cation exchange may provide a pathway for the synthesis of Na-free clinojimthompsonite. Fairly extensive solid solution was also observed for triple-chain silicates made along the compositional join Na₄Mg₈Si₁₂O₃₂(OH)₄–Ca₂Mg₈Si₁₂O₃₂(OH)₄ where the limit of Ca substitution at 450 °C and 0.2 GPa corresponds to Na_0.7Ca_1.8Mg_7.8Si₁₂O_31.9(OH)_4.1 (with the OH content adjusted to achieve charge balance). Aside from the Na content, this composition is similar to that observed as wide-chain lamellae in host actinolite. The relative ease with which Na-rich triple chains can be made experimentally suggests that these phases might exist in nature; this study provides additional insights into the range of compositions and formation conditions at which they might occur.  相似文献   

Introduction to special issue on international geographies of HIV/AIDS     

Cynthia K. Pope  Ezekiel Kalipeni 《GeoJournal》2012,77(4):445-448

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Trace element geochemical evolution and groundwater origin in North Rukuru–Songwe alluvial aquifer of northern Malawi     

Harold Wilson Tumwitike Mapoma  Xianjun Xie  Yapeng Zhu  Yaqing Liu  Gertrude Cynthia Sitolo-Banda 《Environmental Earth Sciences》2016,75(10):877

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The contribution of women to Welsh geological research and education up to 1920     

Cynthia V. Burek 《Proceedings of the Geologists' Association. Geologists' Association》2014

The importance of Welsh geology to the development of the science of geology and the stratigraphic column is underestimated and indeed the contribution of women to this process is largely overlooked. This paper explores the scientific contribution and the role that women played to the investigation of Welsh stratigraphy. The work of Gertrude Elles, Ethel Skeat, Ethel Wood and Margaret Crosfield, the so-called Newnham quartet of palaeontologists, and the educational contribution of Dilys Davies, the first female to study geology at Newnham College, Cambridge and of Annie Greenly to the work of her husband Edward Greenly on Anglesey is discussed. Catherine Raisin also contributed work on the metamorphic rocks of Wales and her work is examined. Without their contributions, Welsh stratigraphy would not be as advanced as it is today especially in the use of graptolite identification for correlation. However, scientific research was not the only contribution and other roles such as illustrators, proof readers, field assistants and teachers will also be examined against the background of the time. The fact that there were few higher education institutions in Wales at the time admitting women to geology is a significant factor for geological research. The contribution of female researchers to this research development is largely forgotten by both researchers, educators and the general public. This paper hopes to rectify these omissions.  相似文献   

Early science results from the Cosmic Origins Spectrograph     

Cynthia S. Froning 《Astrophysics and Space Science》2011,335(1):267-272

The Cosmic Origins Spectrograph (COS) is an ultraviolet spectrograph installed on the Hubble Space Telescope during Servicing Mission Four. COS covers 1150–3200 Å at spectral resolutions up to R～18,000. COS is the most sensitive UV spectrograph to have flown on HST. In this paper, I present science results from the first nine months of COS science operations, focusing on how COS has enabled probes of cosmic origins, from star and planet formation to the large scale structure of the modern universe.  相似文献   

Qualitative Methods for Research on Mapmaking and Map Use     

Trudy A. Suchan  Cynthia A. Brewer 《The Professional geographer》2000,52(1):145-154

Contemporary cartographic research on mapmaking and map use has a broad mandate and, as a consequence, researchers need a broad suite of methods. Consistent with research developments in other geographic subdisciplines, cartographic researchers now use qualitative methods. They offer the advantage of bringing research closer to the problem‐solving realms of mapmakers and map users. Our purpose here is to discuss an array of qualitative methods for mapmaking and map use. Questionnaires, interviews, and protocol methods are used to gather verbal data about mapmaking and map use. Ethnographies produce data from direct observation of mapmakers and users. Maps also are sources for document analysis. We use examples of published cartographic research to elaborate on each of these methods.  相似文献   

Paleoenvironmental dynamics in central-eastern Brazil during the last 23 000 years: tropical peatland record in the Cerrado biome     

Camila Rodrigues Costa  Cynthia Fernandes Pinto da Luz  Ingrid Horák-Terra  Plínio Barbosa de Camargo  Uidemar Morais Barral  Carlos Victor Mendonça-Filho  Thamyres Sabrina Gonçalves  Alexandre Christófaro Silva 《第四纪科学杂志》2023,38(1):61-75

The Cerrado biome is the second largest in Brazil, but the evolution of the Cerrado during the late Quaternary is not yet fully known. This study identifies paleoenvironmental changes during the last 23 000 years, based on a tropical mountain peatland record, in the Serra do Espinhaço Meridional in central-eastern Brazil. A multi-proxy approach was used that involved palynological analysis, stable isotopes (δ¹³C, δ¹⁵N), geochemistry, radiocarbon dating and multivariate statistics derived from a peatland core from Rio Preto (Minas Gerais state). The study reveals a very humid and cold climate during the late Pleistocene, with an increase in temperature and decrease in humidity at the Pleistocene–Holocene transition. During this period there was strong instability in the landscape (episodes of erosion). At the beginning of the Holocene there was a reduction in humidity with greater landscape stability. The current sub-humid climatic conditions seem to have been established in the mid-/late Holocene, with periods of landscape instability. Our findings agree with other Cerrado records that contradict previously established hypotheses, such as the Amazonian Refuge and the Pleistocene Arc.  相似文献