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Search Results: 1 - 10 of 489318 matches for " V. M. Gray "
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Salinidad y el nivel del agua como factores en la distribución de la vegetación en la ciénaga del NW de Campeche, México
Víctor Rico Gray,Mónica Palacios Ríos
Acta botánica mexicana , 1996,
Abstract: El objetivo de este estudio fue establecer si la presencia de ciertas asociaciones vegetales (i.e., tular, manglar de Avicennia germinans, manglar de Rhizophora mangle, manglar mixto, asociación Rhizophora-Eleocharis) se relaciona con diferencias significativas de factores abióticos (i.e., nivel de agua superficial y salinidad del agua). El estudio se desarrolló en la región de los petenes, a lo largo de la costa NW de Campeche, México. Se encontró que la salinidad se incrementa con la sequía y disminuye rápidamente con las lluvias. El manglar de Rhizophora tuvo la mayor concentración de sales en el a o y la menor el tular. Para cada asociación, la salinidad fue significativamente mayor al finalizar la época seca que al terminar las lluvias. El nivel de agua disminuye al avanzar la sequía, se incrementa en junio con las precipitaciones pluviales y en julio se acerca a su máxima expresión. Sin embargo, encontramos diferencias significativas entre todas las asociaciones. Los resultados indican que la presencia de cada una de las comunidades estudiadas corresponde a condiciones específicas en términos de los factores abióticos considerados y sugieren que las altas salinidades del final de la temporada de sequía y la prolongada inundación durante la estación de lluvias, son determinantes para el establecimiento de las especies en las comunidades.
Influence of sweeping detonation-wave loading on shock hardening and damage evolution during spallation loading in tantalum
Gray G.T.,Hull L.M.,Livescu V.,Faulkner J.R.
EPJ Web of Conferences , 2012, DOI: 10.1051/epjconf/20122602004
Abstract: Widespread research over the past five decades has provided a wealth of experimental data and insight concerning the shock hardening, damage evolution, and the spallation response of materials subjected to square-topped shock-wave loading profiles. However, fewer quantitative studies have been conducted on the effect of direct, in-contact, high explosive (HE)-driven Taylor wave (unsupported shocks) loading on the shock hardening, damage evolution, or spallation response of materials. Systematic studies quantifying the effect of sweeping-detonation wave loading are yet sparser. In this study, the shock hardening and spallation response of Ta is shown to be critically dependent on the peak shock stress and the shock obliquity during sweeping-detonation-wave shock loading. Sweeping-wave loading is observed to: a) yield a lower spall strength than previously documented for 1-D supported-shock-wave loading, b) exhibit increased shock hardening as a function of increasing obliquity, and c) lead to an increased incidence of deformation twin formation with increasing shock obliquity.
Ancient Skeletal Evidence for Leprosy in India (2000 B.C.)
Gwen Robbins, V. Mushrif Tripathy, V. N. Misra, R. K. Mohanty, V. S. Shinde, Kelsey M. Gray, Malcolm D. Schug
PLOS ONE , 2009, DOI: 10.1371/journal.pone.0005669
Abstract: Background Leprosy is a chronic infectious disease caused by Mycobacterium leprae that affects almost 250,000 people worldwide. The timing of first infection, geographic origin, and pattern of transmission of the disease are still under investigation. Comparative genomics research has suggested M. leprae evolved either in East Africa or South Asia during the Late Pleistocene before spreading to Europe and the rest of the World. The earliest widely accepted evidence for leprosy is in Asian texts dated to 600 B.C. Methodology/Principal Findings We report an analysis of pathological conditions in skeletal remains from the second millennium B.C. in India. A middle aged adult male skeleton demonstrates pathological changes in the rhinomaxillary region, degenerative joint disease, infectious involvement of the tibia (periostitis), and injury to the peripheral skeleton. The presence and patterning of lesions was subject to a process of differential diagnosis for leprosy including treponemal disease, leishmaniasis, tuberculosis, osteomyelitis, and non-specific infection. Conclusions/Significance Results indicate that lepromatous leprosy was present in India by 2000 B.C. This evidence represents the oldest documented skeletal evidence for the disease. Our results indicate that Vedic burial traditions in cases of leprosy were present in northwest India prior to the first millennium B.C. Our results also support translations of early Vedic scriptures as the first textual reference to leprosy. The presence of leprosy in skeletal material dated to the post-urban phase of the Indus Age suggests that if M. leprae evolved in Africa, the disease migrated to India before the Late Holocene, possibly during the third millennium B.C. at a time when there was substantial interaction among the Indus Civilization, Mesopotamia, and Egypt. This evidence should be impetus to look for additional skeletal and molecular evidence of leprosy in India and Africa to confirm the African origin of the disease.
Origen y rutas de dispersión de los mangles: una revisión con énfasis en las especies de América
Víctor Rico Gray
Acta botánica mexicana , 1993,
Abstract: El objetivo de esta revisión es resumir la información disponible referente al registro fósil de las especies de mangle, así como presentar y discutir las teorías acerca de su origen y rutas de dispersión, haciendo énfasis en las especies americanas. Se sugiere que los géneros Rhizophora y Avicennia se originaron durante el Eoceno en la región Indo-Malaya, dispersándose posteriormente hacia América a través del antiguo Mar de Tetis. Al cerrarse éste durante el Oligoceno, otros géneros no tuvieron acceso al Océano Atlántico. La llegada a las costas americanas del Océano Pacífico se realizó cuando Norte y Sudamérica eran continentes separados. Los géneros Conocarpus, Laguncularia y Pelliciera se originaron en el oeste de Gondwana y no han salido significativamente de su área de distribución original.
Cholesterol Levels and Statin Use in Patients With Coronary Heart Disease Treated in Primary Care Settings
Patrick J. O’Connor, MD, MPH,Richard J. Gray, MD,Michael V. Maciosek, PhD,Kelly M. Fillbrandt, BS
Preventing Chronic Disease , 2005,
Abstract: Introduction Therapy with 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors, or statins, has proven to be effective in the treatment of lipid disorders. However, statin therapy continues to be underused, even though statins are a relatively safe and well-tolerated class of agents. In this study, we assessed trends in lipid control in patients with heart disease who receive most of their health care in primary care clinics. The objective was to determine whether systems of care implemented within a large medical group are associated with improved treatment and control of dyslipidemia in a high-risk group of coronary heart disease patients. Methods All adults with heart disease in a Minnesota medical group (N = 2947) were identified using diagnosis and procedure codes related to coronary heart disease (sensitivity = 0.85; positive predictive value = 0.89) in 1996. Study subjects were observed from 1995 to 1998. Subjects had a baseline and follow-up test for low-density lipoprotein cholesterol and high-density lipoprotein cholesterol. Changes between baseline and follow-up measurements and trends in the use of statins and other lipid-active agents among the study subjects were analyzed. Results Among 1388 subjects with two or more eligible lipid measurements, mean low-density lipoprotein cholesterol improved from 137.6 mg/dL to 111.0 mg/dL (P < .001), and mean high-density lipoprotein cholesterol improved from 42.3 mg/dL to 46.3 mg/dL (P < .001). The percentage of patients with low-density lipoprotein cholesterol ≤100 mg/dL rose from 12.5% to 39.8% (P < .001), and the percentage with high-density lipoprotein cholesterol ≥40 mg/dL rose from 52.5% to 67.6% (P < .001). In multivariate models, statin use was identified as the main factor that contributed to the improvement in low-density lipoprotein cholesterol (P < .001). Men had greater decreases in low-density lipoprotein cholesterol than women after adjusting for other variables (P < .001). Statin use rose from 24.3% at baseline to 69.6% at follow-up. The statin discontinuation rate was 8.3% for baseline statin users and 12.2% for subjects who used statins at any time during the study period. Conclusion Investment in better heart disease care for patients in primary care clinics led to major improvement in lipid control over 30 months, primarily due to increased statin use. Improvements in low-density lipoprotein cholesterol and high-density lipoprotein cholesterol were sufficient to substantially reduce risk of subsequent major cardiovascular events.
The Young Solar Analogs Project: I. Spectroscopic and Photometric Methods and Multi-year Timescale Spectroscopic Results
R. O. Gray,J. M. Saken,C. J. Corbally,M. M. Briley,R. A. Lambert,V. A. Fuller,I. M. Newsome,M. F. Seeds,Y. Kahvaz
Physics , 2015,
Abstract: This is the first in a series of papers presenting methods and results from the Young Solar Analogs Project, which began in 2007. This project monitors both spectroscopically and photometrically a set of 31 young (300 - 1500 Myr) solar-type stars with the goal of gaining insight into the space environment of the Earth during the period when life first appeared. From our spectroscopic observations we derive the Mount Wilson $S$ chromospheric activity index ($S_{\rm MW}$), and describe the method we use to transform our instrumental indices to $S_{\rm MW}$ without the need for a color term. We introduce three photospheric indices based on strong absorption features in the blue-violet spectrum -- the G-band, the Ca I resonance line, and the Hydrogen-$\gamma$ line -- with the expectation that these indices might prove to be useful in detecting variations in the surface temperatures of active solar-type stars. We also describe our photometric program, and in particular our "Superstar technique" for differential photometry which, instead of relying on a handful of comparison stars, uses the photon flux in the entire star field in the CCD image to derive the program star magnitude. We present time series plots of our spectroscopic data for all four indices, and carry out extensive statistical tests on those time series demonstrating the reality of variations on timescales of years in all four indices. We also statistically test for and discover correlations and anti-correlations between the four indices. We discuss the physical basis of those correlations. As it turns out, the "photospheric" indices appear to be most strongly affected by continuum emission. We thus anticipate that these indices may prove to be useful proxies for monitoring continuum emission in the near ultraviolet.
Hormonal Regulation of Plant Growth and Development
William M. Gray
PLOS Biology , 2012, DOI: 10.1371/journal.pbio.0020311
Abstract:
Measurement of the b-jet cross-section with associated vector boson production with the ATLAS experiment at the LHC
Gray Heather M.
EPJ Web of Conferences , 2012, DOI: 10.1051/epjconf/20122812050
Abstract: A measurement of the cross-section for vector boson production in association with jets containing b-hadrons is presented using 35 pb-1 of data from the LHC collected by the ATLAS experiment in 2010. Such processes are not only important tests of pQCD but also large, irreducible backgrounds to searches such as a low mass Higgs boson decaying to pairs of b-quarks when the Higgs is produced in association with a vector boson. Theoretical predictions of the V+b production rate have large uncertainties and previous measurements have reported discrepancies. Cross-sections measured using in the electron and muon channels will be shown. Comparisons will be made to recent theoretical predictions at the next-to-leading order in αS.
Hormonal Regulation of Plant Growth and Development
William M Gray
PLOS Biology , 2004, DOI: 10.1371/journal.pbio.0020311
Abstract:
The Pd(100)-(SQRT(5) x SQRT(5) R27^o)-O surface oxide revisited
M. Todorova,E. Lundgren,V. Blum,A. Mikkelsen,S. Gray,J. Gustafson,M. Borg,J. Rogal,K. Reuter,J. N. Andersen,M. Scheffler
Physics , 2003, DOI: 10.1016/S0039-6028(03)00873-2
Abstract: Combining high-resolution core-level spectroscopy (HRCLS), scanning tunneling microscopy (STM) and density-functional theory (DFT) calculations we reanalyze the Pd(100)-(SQRT(5) x SQRT(5) R27^o)-O surface oxide phase. We find that the prevalent structural model, a rumpled PdO(001) film suggested by previous low energy electron diffraction (LEED) work (M. Saidy et al., Surf. Sci. 494, L799 (2001)), is incompatible with all three employed methods. Instead, we suggest the two-dimensional film to consist of a strained PdO(101) layer on top of Pd(100). LEED intensity calculations show that this model is compatible with the experimental data of Saidy et al.
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