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West Texas (west + texas)

Distribution by Scientific Domains

Earth and Environmental Science	50%
Medical Sciences	33%

Selected Abstracts

A method for establishing the critical threshold for aeolian transport in the field

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 10 2004
John E. Stout
Abstract A basic feature of any wind-eroding surface is its threshold , the wind speed at which sediment transport is initiated. A new method was developed and tested that allows for the rapid determination of threshold under natural wind conditions in the ,eld. A mathematical expression that relates saltation activity and relative wind strength was reformulated so that threshold may be calculated from measurements of saltation activity and the mean and standard deviation of wind speed. To test the new method and determine its usefulness, a ,eld experiment was performed within a region of low-relief dunes on the Southern High Plains of West Texas. The experimental system consisted of a 2-m meteorological tower and a piezoelectric saltation sensor. It was found that during periods of active aeolian activity, threshold values could be calculated every 5 minutes. This new method allows for routine monitoring of surface threshold conditions in the ,eld. Example threshold calculations are presented and they demonstrate that the method works well. Published in 2004 by John Wiley & Sons, Ltd. [source]

Inverted clast stratigraphy in an eolian archaeological environment

GEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 7 2002
Brenda J. Buck
Understanding the geomorphic history of eolian basins is important in interpreting the archaeological record and human responses to past environments. One hundred forty soil profiles were excavated and described in southern New Mexico and West Texas. Seven major late Quaternary stratigraphic units were found: La Mesa, eolian Jornada (I, II), eolian Isaacks' Ranch, eolian Organ (I, II, and III), Historical Blowsand, and the playa deposits of Petts Tank and Lake Tank. Each unit represents a period of landscape instability, eolian erosion, and concurrent deposition, followed by landscape stability and soil formation. Eolian erosion can form local surficial lag deposits if materials larger than the competence of the wind are present. However, erosional processes alone cannot explain the presence of older clasts at the surface with intact, younger deposits underneath. We propose a combination of processes: deflation in eolian windows, followed by lateral movement of clasts over areas that have not been deflated. The effects of these processes on artifact stratigraphy and archaeological interpretations could be significant. © 2002 Wiley Periodicals, Inc. [source]

The creation of an asymmetric hydraulic fracture as a result of driving stress gradients

GEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2009
T. Fischer
SUMMARY Hydraulic fracture stimulation is frequently performed in hydrocarbon reservoirs and geothermal systems to increase the permeability of the rock formation. These hydraulic fractures are often mapped by hypocentres of induced microearthquakes. In some cases microseismicity exhibits asymmetry relative to the injection well, which can be interpreted by unequal conditions for fracture growth at opposite sides of the well or by observation effects. Here we investigate the role of the lateral change of the minimum compressive stress. We use a simple model to describe the relation among the lateral stress gradient, the mean viscous pressure gradients in the fracture wings, the fracture geometry, and the net pressure in the fracture. Our model predicts a faster fracture growth in the direction of decreasing stress and a limited growth in the opposite direction. We derive a simple relationship to estimate the lateral stress gradient from the injection pressure and the shape of the seismic hypocentre cloud. The model is tested by microseismic data obtained during stimulation of a Canyon Sands gas field in West Texas. Using a maximum likelihood method we fit the parameters of the asymmetric fracture model to the space,time pattern of hypocentres. The estimated stress gradients per metre are in the range from 0.008 to 0.010 times the bottom-hole injection overpressure (8,10 kPa m,1 assuming the net pressure of 1 MPa). Such large horizontal gradients in the order of the hydrostatic gradient could be caused by the inhomogeneous extraction of gas resulting in a lateral change of the effective normal stress acting normal to the fracture wall. [source]

The Combined Effects of Participatory Styles of Elderly Patients and Their Physicians on Satisfaction

HEALTH SERVICES RESEARCH, Issue 2 2004
K. Tom Xu
Objectives. To test whether concordance or discordance of patient participation between patients and physicians is associated with higher satisfaction, and to examine the effects of patients' and physicians' participatory styles on patients' satisfaction with their physicians. Data. Data collected in the Texas Tech 5000 Survey of elderly patients in West Texas were used. Patient satisfaction with their physicians was measured by a single item from the Consumer Assessment of Health Plans (CAHPS), representing patients' ratings of their physicians. Patient participation was measured by an index derived from a three-item instrument and physicians' participatory decision-making (PDM) style was measured by a three-item instrument developed by the Medical Outcomes Study. Methods. An ordered logit multivariate regression was used to investigate the effects of patients' and physicians' participatory styles on satisfaction with physicians. The interaction between patients' participation and physicians' participatory styles was also included to examine the dependency of the two variables. Results. Controlling for confounding factors, a higher PDM score was associated with a higher rating of patient satisfaction with physicians. A higher patient participation score was related to a lower physician satisfaction rating. The combined effect of patients' and physicians' participation styles indicated that for a low patient participation score, a high PDM score was not needed to produce high satisfaction. The greater the discordance in this direction, the higher the satisfaction. However, with a high patient participation score, only an extremely high PDM score would produce relatively high satisfaction. Conclusions. The current study supports the discordance hypothesis. Participatory physicians and patient,physician communications concerning patient participation can promote higher satisfaction. [source]

Rietveld analysis of X-ray powder diffraction patterns as a potential tool for the identification of impact-deformed carbonate rocks

METEORITICS & PLANETARY SCIENCE, Issue 11 2009
Sarah A. Huson
Entire XRD patterns, single peak profiles and Rietveld refined parameters of carbonate samples from the Sierra Madera impact crater, west Texas, unshocked equivalent samples from 95 miles north of the crater and the Mission Canyon Formation of southwest Montana and western Wyoming were used to evaluate the use of X-ray powder diffraction as a potential tool for distinguishing impact deformed rocks from unshocked and tectonically deformed rocks. At Sierra Madera dolostone and limestone samples were collected from the crater rim (lower shock intensity) and the central uplift (higher shock intensity). Unshocked equivalent dolostone samples were collected from well cores drilled outside of the impact crater. Carbonate rocks of the Mission Canyon Formation were sampled along a transect across the tectonic front of the Sevier and Laramide orogenic belts. Whereas calcite subjected to significant shock intensities at the Sierra Madera impact crater can be differentiated from tectonically deformed calcite from the Mission Canyon Formation using Rietveld refined peak profiles, weakly shocked calcite from the crater rim appears to be indistinguishable from the tectonically deformed calcite. In contrast, Rietveld analysis readily distinguishes shocked Sierra Madera dolomite from unshocked equivalent dolostone samples from outside the crater and tectonically deformed Mission Canyon Formation dolomite. [source]

Interdisciplinary Collaboration: A Study in Progress

PUBLIC HEALTH NURSING, Issue 4 2002
Carol Boswell R.N., Ed.D.
A multidisciplinary, multi-institutional collaborative effort was initiated to address the perspectives of health care literacy in an urban/rural area of west Texas. This article presents the mechanisms utilized in the development and implementation of this collaborative process. Individuals within multiple institutions realized the importance of working together to address health care issues. As a result of this consortium development, an initial endeavor addressing health care literacy and functional health status was initiated. The development of the consortium and the project is presented in this article to provide a model for consortium development applicable to other professions. [source]