West Texas A&M University

About: West Texas A&M University is a education organization based out in Canyon, Texas, United States. It is known for research contribution in the topics: Population & Raman spectroscopy. The organization has 929 authors who have published 1704 publications receiving 28642 citations.

The Arecibo Legacy Fast ALFA Survey: the α.40 H I source catalog, its characteristics and their impact on the derivation of the H I mass function

Abstract: We present a current catalog of 21 cm H I line sources extracted from the Arecibo Legacy Fast Arecibo L-band Feed Array (ALFALFA) survey over ~2800 deg^2 of sky: the α.40 catalog. Covering 40% of the final survey area, the α.40 catalog contains 15,855 sources in the regions 07^h30^m < R.A. < 16^h30^m, +04° < decl. <+16°, and +24° < decl. <+28° and 22^h < R.A. < 03^h, +14° < decl. <+16°, and +24° < decl. < + 32°. Of those, 15,041 are certainly extragalactic, yielding a source density of 5.3 galaxies per deg^2, a factor of 29 improvement over the catalog extracted from the H I Parkes All-Sky Survey. In addition to the source centroid positions, H I line flux densities, recessional velocities, and line widths, the catalog includes the coordinates of the most probable optical counterpart of each H I line detection, and a separate compilation provides a cross-match to identifications given in the photometric and spectroscopic catalogs associated with the Sloan Digital Sky Survey Data Release 7. Fewer than 2% of the extragalactic H I line sources cannot be identified with a feasible optical counterpart; some of those may be rare OH megamasers at 0.16 < z < 0.25. A detailed analysis is presented of the completeness, width-dependent sensitivity function and bias inherent of the α.40 catalog. The impact of survey selection, distance errors, current volume coverage, and local large-scale structure on the derivation of the H I mass function is assessed. While α.40 does not yet provide a completely representative sampling of cosmological volume, derivations of the H I mass function using future data releases from ALFALFA will further improve both statistical and systematic uncertainties.

Physical Activity and Stroke Risk A Meta-Analysis

Abstract: Background and Purpose— Whether physical activity reduces stroke risk remains controversial. We used a meta-analysis to examine the overall association between physical activity or cardiorespiratory fitness and stroke incidence or mortality. Methods— We searched MEDLINE from 1966 to 2002 and identified 23 studies (18 cohort and 5 case-control) that met inclusion criteria. We estimated the overall relative risk (RR) of stroke incidence or mortality for highly and moderately active individuals versus individuals with low levels of activity using the general variance–based method. Results— The meta-analysis documented that there was a reduction in stroke risk for active or fit individuals compared with inactive or unfit persons in cohort, case-control, and both study types combined. For cohort studies, highly active individuals had a 25% lower risk of stroke incidence or mortality (RR=0.75; 95% CI, 0.69 to 0.82) compared with low-active individuals. For case-control studies, highly active individuals had a 6...

E-leadership: Implications for theory, research, and practice

Abstract: In this article we review literature to build a broad understanding of what constitutes e-leadership in organizations. We propose a framework based on Adaptive Structuration Theory that could be used to study how Advanced Information Technology could influence and is influenced by leadership. According to our framework, the effects of Advanced Information Technology emerge from their interaction with organizational structures of which leadership is a part. Furthermore, organizational structures, including leadership, may themselves be transformed as a result of interactions with Advanced Information Technology. We use our Adaptive Structuration Theory–based framework to pool relevant results and suggestions from a diverse array of literature to provide recommendations for developing a research agenda on e-leadership.

Structure and Organic Matter Storage in Agricultural Soils

Abstract: Introduction Analysis of Soil Organic Matter Storage in Agroecosystems, M.R. Carter Mechanisms and Processes Soil Architecture and Distribution of Organic Matter, M.J. Kooistra and M. van Noordwijk Formation of Soil Aggregates and Accumulation of Soil Organic Matter, J.M. Tisdall Carbon in Primary and Secondary Organomineral Complexes, B.T. Christensen Storage of Soil Carbon in the Light Fraction and Macroorganic Matter, E.G. Gregorich and H.H. Janzen Impact of Climate, Soil Type, and Management Aggregation and Organic Matter Storage in Cool, Humid Agricultural Soils, D.A. Angers and M.R. Carter Aggregation and Organic Matter Storage in Meso-Thermal, Humid Soils, R.J. Haynes and M.H. Beare Aggregation and Organic Matter Storage in Sub-Humid and Semi-Arid Soils, R.C. Dalal and B.J. Bridge Aggregation and Organic Matter Storage in Kaolinitic and Smectitic Tropical Soils, C. Feller, A. Albrecht, and D. Tessier Organic Carbon Storage in Tropical Hydromorphic Soils, H.W. Scharpenseel, E.-M. Pfeiffer, and P. Becker-Heidmann Assessment of Soil Organic Matter Storage Conservation Strategies for Improving Soil Quality and Organic Matter Storage, D.L. Karlen and C.A. Cambardella Models to Evaluate Soil Organic Matter Storage and Dynamics, W.J. Parton, D.S. Ojima, and D.S. Schimel Methods to Characterize and Quantify Organic Matter Storage in Soil Fractions and Aggregates, M.R. Carter and E.G. Gregorich Index

Long-term experiments for sustainable nutrient management in China. A review

Abstract: China is facing one of the largest challenges of this century to continue to increase annual cereal production to about 600 Mt by 2030 to ensure food security with shrinking cropland and limited resources, while maintaining or improving soil fertility, and protecting the environment. Rich experiences in integrated and efficient utilization of different strategies of crop rotation, intercropping, and all possible nutrient resources accumulated by Chinese farmers in traditional farming systems have been gradually abandoned and nutrient management shifted to over-reliance on synthetic fertilizers. China is now the world's largest producer, consumer and importer of chemical fertilizers. Over- application of nitrogen (N) is common in intensive agricultural regions, and current N-uptake efficiency was reported to be only 28.3, 28.2 and 26.1% for rice, wheat and maize, respectively, and less than 20% in intensive agricultural regions and for fruit trees or vegetable crops. In addition to surface and groundwater pollution and greenhouse gas emissions, over-application of N fertilizers has caused significant soil acidification in major Chinese croplands, decreasing soil pH by 0.13 to 2.20. High yield as a top priority, small-scale farming, lack of temporal synchronization of nutrient supply and crop demand, lack of effective extension systems, and hand application of fertilizers by farmers are possible reasons leading to the over-application problems. There is little doubt that current nutrient management practices are not sustainable and more efficient management systems need to be developed. A review of long-term experiments conducted around the world indicated that chemical fertilizer alone is not enough to improve or maintain soil fertility at high levels and the soil acidification problem caused by over- application of synthetic N fertilizers can be reduced if more fertilizer N is applied as NO − relative to ammonium- or urea-based N fertilizers. Organic fertilizers can improve soil fertility and quality, but long-term application at high rates can also lead to more nitrate leaching, and accumulation of P, if not managed well. Well-managed combination of chemical and organic fertilizers can overcome the disadvantages of applying single source of fertilizers and sustainably achieve higher crop yields, improve soil fertility, alleviate soil acidification problems, and increase nutrient-use efficiency compared with only using chemical fertilizers. Crop yield can be increased through temporal diversity using crop rotation strategies compared with continuous cropping and legume-based cropping systems can reduce carbon and nitrogen losses. Crop yield responses to N fertilization can vary significantly from year to year due to variation in weather conditions and indigenous N supply, thus the commonly adopted prescriptive approach to N management needs to be replaced by a responsive in-season management approach based on diagnosis of crop growth, N status and demand. A crop sensor-based in-season site-specific N management strategy was able to increase N- uptake efficiency by 368% over farmers' practices in the North China Plain. Combination of these well-tested nutrient management principles and practices with modern crop management technologies is needed to develop sustainable nutrient management systems in China that can precisely match field-to-field and year-to-year variability in nutrient supply and crop demand for both single crops and crop rotations to not only improve nutrient-use efficiency but also increase crop yield and protect the environment. In addition, innovative and effective extension and service-providing systems to assist farmers in adopting and applying new management systems and technologies are also crucially important for China to meet the grand challenge of food security, nutrient-use efficiency and sustainable development.