Showing papers by "University of Nevada, Reno published in 1999"

Sensing the ups and downs of Las Vegas: InSAR reveals structural control of land subsidence and aquifer-system deformation

Abstract: Land subsidence in Las Vegas, Nevada, United States, between April 1992 and December 1997 was measured using spaceborne interferometric synthetic aperture radar. The detailed deformation maps clearly show that the spatial extent of subsidence is controlled by geologic structures (faults) and sediment composition (clay thickness). The maximum detected subsidence during the 5.75 yr period is 19 cm. Comparison with leveling data indicates that the subsidence rates declined during the past decade as a result of rising ground-water levels brought about by a net reduction in ground-water extraction. Temporal analysis also detects seasonal subsidence and uplift patterns, which provide information about the elastic and inelastic properties of the aquifer system and their spatial variability.

Two-Step Estimation of a Censored System of Equations

Abstract: A consistent two-step estimation procedure is proposed for a system of equations with limited dependent variables. Monte Carlo simulation results suggest the procedure outperforms an existing two-step method.

Improving the nutrient composition of plants to enhance human nutrition and health1

Abstract: Plant foods contain almost all of the mineral and organic nutrients established as essential for human nutrition, as well as a number of unique organic phytochemicals that have been linked to the promotion of good health. Because the concentrations of many of these dietary constituents are often low in edible plant sources, research is under way to understand the physiological, biochemical, and molecular mechanisms that contribute to their transport, synthesis and accumulation in plants. This knowledge can be used to develop strategies with which to manipulate crop plants, and thereby improve their nutritional quality. Improvement strategies will differ between various nutrients, but generalizations can be made for mineral or organic nutrients. This review focuses on the plant nutritional physiology and biochemistry of two essential human nutrients, iron and vitamin E, to provide examples of the type of information that is needed, and the strategies that can be used, to improve the mineral or organic nutrient composition of plants.

The biochemical and molecular basis for photosynthetic acclimation to elevated atmospheric CO2

Abstract: Amax, maximum CO2 assimilation rate CAB, genes encoding chlorophyll a/b binding proteins Ci, intercellular CO2 concentration PGK, the gene encoding 3-phosphoglycerate kinase PRK, the gene encoding phosphoribulokinase PSAB, the gene encoding the 83 kDa apoprotein of the PSI reaction centre PSBA, the gene encoding the D1 protein of photosystem II RBCS, genes encoding the Rubisco small subunit protein RBCL, the gene encoding the Rubisco large subunit protein Rubisco, ribulose-1,5-bisphosphate carboxylase/ oxygenase SBP, the gene encoding sedoheptulose-1,5-bisphosphatase There have been many recent exciting advances in our understanding of the cellular processes that underlie photosynthetic acclimation to rising atmospheric CO2 concentration. Of particular interest have been the molecular processes that modulate photosynthetic gene expression in response to elevated CO2 and the biochemical processes that link changes in atmospheric CO2 concentration to the production of a metabolic signal. Central to this acclimation response is a reduction in ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) protein content. Studies indicate that this reduction results from species-dependent variation in the differential use and temporal control of molecular processes. We present a model for the control of Rubisco protein accumulation that emphasizes the role of subunit message translation as well as the abundance of subunit messages as components of the acclimation response. Many studies indicate that photosynthetic acclimation to elevated CO2 results from adjustments in leaf carbohydrate signalling. The repression of photosynthetic gene expression is considered to occur primarily by hexokinase functioning as a hexose flux sensor that ultimately affects transcription. Leaf hexoses may be produced as potential sources of signals primarily by sucrose cycling and secondarily by starch hydrolysis. An increased rate of sucrose cycling is suggested to occur at elevated CO2 by enhanced provision of sucrose to leaf acid invertases. Additionally, sink limitations that accentuate photosynthetic acclimation may result from a relative decrease in the export of leaf sucrose and subsequent increase in cellular sucrose levels and sucrose cycling.

Affect and favorable work outcomes: two longitudinal tests of the happy–productive worker thesis

Abstract: This research examined relationships between alternative measures of affect and supervisory performance ratings. The first study showed that dispositional rather than state affect significantly predicted supervisory ratings of performance over time. Since the measures of affect differed on both content and temporal dimensions, a follow-up study was conducted to explicate the results. The second study found that a pleasantness-based measure of dispositional affect (Berkman, 1971a) again predicted rated performance over time, but activation-based measures of both dispositional and state affect (using PANAS scales) were not predictive of supervisory evaluations of performance. The implications of these findings in terms of research on affect and the longstanding pursuit of the happy–productive worker are discussed. Copyright © 1999 John Wiley & Sons, Ltd.

Figural aftereffects in the perception of faces

Abstract: We examined figural aftereffects in images of human faces, for which changes in configuration are highly discriminable. Observers either matched or rated faces before or after viewing distorted images of faces. Prior adaptation strongly biases face perception by causing the original face to appear distorted in a direction opposite to the adapting distortion. Aftereffects transferred across different faces and were similar for upright or inverted faces, but were weaker when the adapting and test faces had different orientations (e.g., adapt inverted and test upright). Thus the aftereffects depend on which images are distorted, and not simply on the type of distortion introduced. We further show that the aftereffects are asymmetric, for adapting to the original face has little effect on the perception of a distorted face. This asymmetry suggests that adaptation may play an important normalizing role in face perception. Our results suggest that in normal viewing, figural aftereffects may strongly influence form perception and could provide a novel method for probing properties of human face perception.

The Impact of Acceptance versus Control Rationales on Pain Tolerance

Abstract: Acceptance approaches, which have been receiving increased attention within behavior therapy, seek to undermine the linkage between private events and overt behavior, rather than attempting to control the form or frequency of private events per se Research comparing control versus acceptance strategies is limited The present study examined the behavioral and subjective impact of a control-based versus acceptance rationale, using a cold pressor task Subjects in the acceptance group demonstrated greater tolerance of pain compared to the control-based and placebo groups Only the control-based rationale targeted the subjective experience of pain but it did not differ across rationales Results confirmed that acceptance was effective in manipulating the believability of reason giving, a key process measure By encouraging individuals to distance themselves from their private events, acceptance methods may help reduce the use of emotional reasons to explain behavior and hence shift concern from moderating thoughts and feelings to experiencing the consequences of one’s action Acceptance is a promising new technique Its effect is all the more surprising given that it teaches principles (eg, “thoughts do not cause behavior”) that run counter both to the popular culture and to the dominant approaches within empirical clinical intervention

Metapopulation structure of bull trout: influences of physical, biotic, and geometrical landscape characteristics

Abstract: Metapopulation structure of species in fragmented landscapes is ultimately the result of spatial variability in demographic processes. While specific information on demographic parameters is desirable, a more practical approach to studying metapopulations in fragmented landscapes may begin with analyses of species' occurrence in relation to large-scale habitat variability. Here, we analyzed occurrence of stream-living bull trout (Salvelinus confluentus) in relation to physical, biotic, and geometrical characteristics of habitats. Bull trout occurrence was analyzed at several spatial (10 x m) scales. Data were from nested sampling of 720 sites (10 m), 179 reaches (10 2 m), and 81 patches ($10 3 m) of stream habitats within the Boise River basin of central Idaho. Based on previous findings, patches were defined as stream catchments with suitable conditions for spawning and rearing of bull trout (.1600 m elevation). Patch-scale bull trout occurrence was significantly related to patch area and isolation (stream distance between occupied patches). Lack of spatial autocorrelation between patches indicated that isolation effects were more likely the result of limited interaction among habitats (such as dispersal), rather than of correlated envi- ronmental conditions. A third factor, human disturbance in the form of roads, was associated with reduced bull trout occurrence at the patch-scale. Analyses of occurrence among reaches within occupied patches showed bull trout may select larger (.2 m width) stream habitats. Occurrence of bull trout was not associated with nonnative brook trout (Salvelinus fontinalis) at large (patch), intermediate (reach), or small (site) spatial scales. Definition of a meta- population structure for bull trout in the Boise River basin was complicated by uncertainties in the frequency and magnitude of dispersal. From the distribution of patch sizes and isolation among occupied patches, we suggest that the metapopulation is a complex mosaic of several elements found in conceptual models. This complexity poses a challenge to empirical and theoretical attempts to study stream-living bull trout. Future work to define the structure of bull trout metapopulations must relate temporal and spatial patterns of patch occupancy with complex patterns of dispersal that likely interact with habitat spatial struc- ture, life history variability, and the historical context of regional climate changes. Results of this work suggest that conservation of bull trout should involve protection of larger, less isolated, and less disturbed (as indexed by road densities) habitats that may serve as im- portant refugia or sources of recolonization. Bull trout populations in smaller, isolated, and more disturbed habitats may be at risk of extinction. Finally, metapopulation structure implies the existence of suitable, but presently unoccupied habitat, which should be managed carefully to facilitate potential natural recolonization or reintroductions of bull trout.

Nutritional genomics: manipulating plant micronutrients to improve human health.

Abstract: The nutritional health and well-being of humans are entirely dependent on plant foods either directly or indirectly when plants are consumed by animals. Plant foods provide almost all essential vitamins and minerals and a number of other health-promoting phytochemicals. Because micronutrient concentrations are often low in staple crops, research is under way to understand and manipulate synthesis of micronutrients in order to improve crop nutritional quality. Genome sequencing projects are providing novel approaches for identifying plant biosynthetic genes of nutritional importance. The term "nutritional genomics" is used to describe work at the interface of plant biochemistry, genomics, and human nutrition.

Development and plasticity of interstitial cells of Cajal.

Abstract: Interstitial cells of Cajal (ICC) are the pacemakers in gastrointestinal (GI) muscles, and these cells also mediate or transduce inputs from the enteric nervous system. Different classes of ICC are involved in pacemaking and neurotransmission. ICC express specific ionic conductances that make them unique in their ability to generate and propagate slow waves in GI muscles or transduce neural inputs. Much of what we know about the function of ICC comes from developmental studies that were made possible by the discoveries that ICC express c-kit and proper development of ICC depends upon signalling via the Kit receptor pathway. Manipulating Kit signalling with reagents to block the receptor or downstream signalling pathways or by using mutant mice in which Kit or its ligand, stem cell factor, are defective has allowed novel studies into the specific functions of the different classes of ICC in several regions of the GI tract. Kit is also a surface antigen that can be used to conveniently label ICC in GI muscles. Immunohistochemical studies using Kit antibodies have expanded our knowledge about the ICC phenotype, the structure of ICC networks, the interactions of ICC with other cells in the gut wall, and the loss of ICC in some clinical disorders. Preparations made devoid of ICC have also allowed analysis of the consequences of losing specific classes of ICC on GI motility. This review describes recent advances in our knowledge about the development and plasticity of ICC and how developmental studies have contributed to our understanding of the functions of ICC. We have reviewed the clinical literature and discussed how loss or defects in ICC affect GI motor function.

Probabilistic Seismic Hazard Analysis without the Ergodic Assumption

Abstract: INTRODUCTION An ergodic process is a random process in which the distribution of a random variable in space is the same as the distribution of that same random variable at a single point when sampled as a function of time. An ergodic assumption is commonly made in probabilistic seismic hazard analysis (PSHA). A regression analysis is used to obtain a mean curve to predict ground motion as a function of magnitude and distance (and sometimes other parameters). The standard deviation of this ground-motion regression is determined mainly by the misfit between observations and the corresponding predicted ground motions at multiple stations for a small number of well recorded earthquakes. Thus, the standard deviation of the ground-motion regression is dominantly related to the statistics of the spatial variability of the ground motions. An ergodic assumption is made when PSHA treats that spatial uncertainty of ground motions as an uncertainty over time...

Multidimensional advection and fractional dispersion.

Abstract: Extension of the fractional diffusion equation to two or three dimensions is not as simple as extension of the second-order equation. This is revealed by the solutions of the equations: unlike the Gaussian, the most general stable vector cannot be generated with an atomistic measure on the coordinate axes. A random combination of maximally skewed stable variables on the unit sphere generates a stable vector that is a general model of a diffusing particle. Subsets are symmetric stable vectors that have previously appeared in the literature and the well-known multidimensional Brownian motion. A multidimensional fractional differential operator is defined in the process.

Religious Conversion and Personality Change

Abstract: The question of whether religious conversion causes changes in someone's personality is examined in light of two bodies of literature—the research on personality change and the research on conversion. When the theory and research on personality change is applied to the question of whether conversion causes such change, the answer depends on what level of personality is of concern. Research on the relation between religious conversion and a variety of behavioral, attitudinal, emotional, and lifestyle variables is consistent with this conclusion. Although conversion seems to have minimal effect on elemental functions such as the Big Five traits or temperaments, it can result in profound, life transforming changes in mid-level functions such as goals, feelings, attitudes, and behaviors, and in the more self-defining personality

Lessons from exemplary colleges of education: Factors affecting technology integration in preservice programs

Abstract: This study focused on efforts in four colleges of education deemed exemplary in their approaches to prepare preservice teachers to use technology. The study addressed one over-arching question: What are the important pieces of the puzzle that make up the current technology integration efforts at these exemplary sites? Data were gathered during the 1997–98 academic year. Findings suggest that there is a web of enabling factors that supports student learning opportunities and desired technology-related outcomes for preservice teachers. The informed leadership of deans and other administrative and faculty leaders appears to be especially critical to sustain and expand technology-integration efforts. Leadership issues, along with a wide range of other factors, are systematically examined across the four case studies. The authors conclude that while each of the four cases is unique, many of the recommended practices explored in this study would likely prove beneficial if employed in other settings.

In Vivo Chaperone Activity of Heat Shock Protein 70 and Thermotolerance

Abstract: Heat shock protein 70 (Hsp70) is thought to play a critical role in the thermotolerance of mammalian cells, presumably due to its chaperone activity. We examined the chaperone activity and cellular heat resistance of a clonal cell line in which overexpression of Hsp70 was transiently induced by means of the tetracycline-regulated gene expression system. This single-cell-line approach circumvents problems associated with clonal variation and indirect effects resulting from constitutive overexpression of Hsp70. The in vivo chaperone function of Hsp70 was quantitatively investigated by using firefly luciferase as a reporter protein. Chaperone activity was found to strictly correlate to the level of Hsp70 expression. In addition, we observed an Hsp70 concentration dependent increase in the cellular heat resistance. In order to study the contribution of the Hsp70 chaperone activity, heat resistance of cells that expressed tetracycline-regulated Hsp70 was compared to thermotolerant cells expressing the same level of Hsp70 plus all of the other heat shock proteins. Overexpression of Hsp70 alone was sufficient to induce a similar recovery of cytoplasmic luciferase activity, as does expression of all Hsps in thermotolerant cells. However, when the luciferase reporter protein was directed to the nucleus, expression of Hsp70 alone was not sufficient to yield the level of recovery observed in thermotolerant cells. In addition, cells expressing the same level of Hsp70 found in heat-induced thermotolerant cells containing additional Hsps showed increased resistance to thermal killing but were more sensitive than thermotolerant cells. These results suggest that the inducible form of Hsp70 contributes to the stress-tolerant state by increasing the chaperone activity in the cytoplasm. However, its expression alone is apparently insufficient for protection of other subcellular compartments to yield clonal heat resistance to the level observed in thermotolerant cells.

Genetic algorithms and method of moments (GA/MOM) for the design of integrated antennas

Abstract: This paper introduces a novel technique for efficiently combining genetic algorithms (GAs) with method of moments (MoM) for integrated antenna design and explores a two example applications of the GA/MoM approach. Integral to efficient GA/MoM integration is the use of direct Z-matrix manipulation (DMM). In DMM a "mother" structure is selected and its corresponding impedance or Z-matrix is filled only once prior to beginning the GA optimization process. The GA optimizer then optimizes the design by creating substructures of the mother structure as represented by the corresponding subsets of the original mother Z-matrix. Application of DMM with GA/MoM significantly reduces the total optimization time by eliminating multiple Z-matrix fill operations. DMM also facilitates the use of matrix partitioning and presolving to further reduce the optimization time in many practical cases. The design of a broad-band patch antenna with greater than 20% bandwidth and a dual-band patch antenna are presented as examples of the utility of GA/MoM with DMM. Measured results for the dual-band antenna are compared to numerical results. Excellent agreement between numerical and measured results is observed.

Summertime transport of current‐use pesticides from California's Central Valley to the Sierra Nevada Mountain Range, USA

Abstract: Aricultural activity in California's Central Valley may be an important source of pesticides that are transported in the air to the Sierra Nevada Mountain Range, USA. Pesticides applied to this intensive crop production area may volatilize under warm temperatures typical of the valley and be transported through the atmosphere to be deposited in the cooler, higher elevation regions of the Sierra Nevada Mountains. To determine the extent of summertime atmospheric transport of pesticides to this region, high-volume air, dry deposition, and surface water samples were collected in the Central Valley and at different elevations in California's Sequoia National Park. Results revealed that the highest residue concentrations were those of compounds with heavy summertime agricultural use. A significant drop in pesticide concentrations in both air and water samples was observed within a few 100-m elevation from the valley; however, levels remained relatively constant between ∼500 and 2,000 m. Water concentrations from two areas above 3,000 m contained levels less than a tenth as high as those at lower elevations. Possible effects of the pesticides were estimated using measured water concentrations to calculate total exposure of three aquatic species to organophosphate insecticides. Aggregate exposure calculations showed concentrations were well below 96-h LC50 values for rainbow trout and stonefly but concentrations may be harmful to amphipods.

Interstitial cells of Cajal generate electrical slow waves in the murine stomach

Abstract: 1. The gastric corpus and antrum contain interstitial cells of Cajal (ICC) within the tunica muscularis. We tested the hypothesis that ICC are involved in the generation and regeneration of electrical slow waves. 2. Normal, postnatal development of slow wave activity was characterized in tissues freshly removed from animals between birth and day 50 (D50). Slow wave amplitude and frequency increased during this period. Networks of myenteric ICC (IC-MY) were present in gastric muscles at birth and did not change significantly in appearance during the period of study as imaged by confocal immunofluorescence microscopy. 3. IC-MY networks were maintained and electrical rhythmicity developed in organ culture in a manner similar to normal postnatal development. Electrical activity was maintained for at least 48 days in culture. 4. Addition of a neutralizing antibody (ACK2) for the receptor tyrosine kinase, Kit, to the culture media caused progressive loss of Kit-immunoreactive cells. Loss of Kit-immunoreactive cells was associated with loss of slow wave activity. Most muscles became electrically quiescent after 3-4 weeks of exposure to ACK2. 5. In some muscles small clusters of Kit-immunoreactive IC-MY remained after culturing with ACK2. These muscles displayed slow wave activity but only in the immediate regions in which Kit-positive IC-MY remained. These data suggest that regions without Kit-immunoreactive cells cannot generate or regenerate slow waves. 6. After loss of Kit-immunoreactive cells, the muscles could not be paced by direct electrical stimulation. Stimulation with acetylcholine also failed to elicit slow waves. The data suggest that the generation of slow waves is an exclusive property of IC-MY; smooth muscle cells may not express the ionic apparatus necessary for generation of these events. 7. We conclude that IC-MY are an essential element in the spontaneous rhythmic electrical and contractile activity of gastric muscles. This class of ICC appears to generate slow wave activity and may provide a means for regeneration of slow waves.

Cellular and molecular basis for electrical rhythmicity in gastrointestinal muscles.

Abstract: ▪ Abstract Regulation of gastrointestinal (GI) motility is intimately coordinated with the modulation of ionic conductances expressed in GI smooth muscle and nonmuscle cells. Interstitial cells of Cajal (ICC) act as pacemaker cells and possess unique ionic conductances that trigger slow wave activity in these cells. The slow wave mechanism is an exclusive feature of ICC: Smooth muscle cells may lack the basic ionic mechanisms necessary to generate or regenerate slow waves. The molecular identification of the components for these conductances provides the foundation for a complete understanding of the ionic basis for GI motility. In addition, this information will provide a basis for the identification or development of therapeutics that might act on these channels. It is much easier to study these conductances and develop blocking drugs in expression systems than in native GI muscle cells. This review focuses on the relationship between ionic currents in native GI smooth muscle cells and ICC and their mol...

Natural selection on thermogenic capacity of high-altitude deer mice.

Abstract: Adaptive explanations that rely on physiological arguments are common, but tests of hypotheses about the significance of whole-animal physiological performance (e.g., aerobic capacities) are rare. We studied phenotypic selection on the thermogenic capacity (i.e., maximal rate of oxygen consumption [VO2 max] elicited via cold exposure) of high-altitude (~3800 m) deer mice (Peromyscus maniculatus). A high VO2 max equates to a high capacity for heat production and should favor survival in the cold environments prevalent at high altitude. Strong directional selection favored high VO2 max, at least in one year. The selection for increased VO2 max is consistent with predictions derived from incorporating our physiological data into a biophysical model. During another year, we found weak evidence of selection for decreased body mass. Nonlinear selection was not significant for any of the selection episodes we studied. The strong directional selection for VO2 max that we observed suggests that-given ample genetic variation-aerobic metabolism and perhaps endothermy may have evolved rapidly on the geological time scale.

Obesity correlates with gastroesophageal reflux.

Abstract: Thirty morbidly obese patients presenting forbariatric surgery were evaluated for symptomatic andobjective evidence of gastroesophageal reflux Sixteenpatients had heartburn while 14 were asymptomatic All underwent esophageal function testing;manometry was performed in all patients, pH monitoringin 28 Patients with esophageal pH < 4 for more than5% of observed time weighed more than those with normal acid exposure, 1652 vs 1298 kg (P <001), and had significantly higher body mass indices,565 vs 483 kg/m2 (P < 005) Similarly,morbidly obese patients with abnormal reflux scores weighed significantly more and hadgreater body mass indices than patients with normalscores (P < 005) Lower esophageal sphincterpressure was higher in patients with normal esophagealacid exposure than in those with abnormal findings,155 vs 125 mm Hg (P < 005) This studydemonstrates a correlation between both weight and bodymass index with gastroesophageal reflux