Showing papers by "University of Nevada, Reno published in 2003"

Effect of estrogen plus progestin on global cognitive function in postmenopausal women: the Women's Health Initiative Memory Study: a randomized controlled trial.

Abstract: ContextObservational studies have suggested that postmenopausal hormone treatment may improve cognitive function, but data from randomized clinical trials have been sparse and inconclusive The Women's Health Initiative Memory Study (WHIMS) is an ancillary study of the Women's Health Initiative (WHI) hormone therapy trials On July 8, 2002, the estrogen plus progestin therapy in the WHI trial was discontinued because of certain increased health risks for womenObjectiveTo determine whether estrogen plus progestin therapy protects global cognitive function in older postmenopausal womenDesign, Setting, and ParticipantsA randomized, double-blind, placebo-controlled clinical trial, WHIMS is an ancillary study of geographically diverse, community-dwelling women aged 65 years or older from 39 of 40 clinical centers within the WHI estrogen plus progestin trial that started in June 1995 Of 4894 eligible postmenopausal women aged 65 years or older and free of probable dementia at baseline, 4532 (926%) were enrolled in the estrogen plus progestin component of WHIMS A total of 4381 participants (967%) provided at least 1 valid cognitive function score between June 1995 and July 8, 2002InterventionsParticipants received either 1 daily tablet containing 0625 mg of conjugated equine estrogen with 25 mg of medroxyprogesterone acetate (n = 2145) or matching placebo (n = 2236)Main Outcome MeasureGlobal cognitive function measured annually with the Modified Mini-Mental State ExaminationResultsThe Modified Mini-Mental State Examination mean total scores in both groups increased slightly over time (mean follow-up of 42 years) Women in the estrogen plus progestin group had smaller average increases in total scores compared with women receiving placebo (P = 03), but these differences were not clinically important Removing women by censoring them after adjudicated dementia, mild cognitive impairment, or stroke, and nonadherence to study protocol, did not alter the findings Prior hormone therapy use and duration of prior use did not affect the interpretation of the results, nor did timing of prior hormone therapy initiation with respect to the final menstrual period More women in the estrogen plus progestin group had a substantial and clinically important decline (≥2 SDs) in Modified Mini-Mental State Examination total score (67%) compared with the placebo group (48%) (P = 008)ConclusionsAmong postmenopausal women aged 65 years or older, estrogen plus progestin did not improve cognitive function when compared with placebo While most women receiving estrogen plus progestin did not experience clinically relevant adverse effects on cognition compared with placebo, a small increased risk of clinically meaningful cognitive decline occurred in the estrogen plus progestin group

Agency costs, ownership structure and corporate governance mechanisms

Abstract: In this paper, we extend the work of Ang et al. [J. Finance 55 (1999) 81] to large firms. We find that managerial ownership is positively related to asset utilization but does not serve as a significant deterrent to excessive discretionary expenses. Outside block ownership may only have a limited effect on reducing agency costs. Furthermore, smaller boards serve the same role, but independent outsiders on a board do not appear to protect the firm from agency costs. Thus, this paper reports complementary evidence to Ang, Cole and Lin. In large publicly traded corporations, managerial ownership significantly alleviates principal–agent conflicts even in the presence of other agency deterrent mechanisms.

Ecological Effects of Nitrogen Deposition in the Western United States

Abstract: In the western United States vast acreages of land are exposed to low levels of atmospheric nitrogen (N) deposition, with interspersed hotspots of elevated N deposition downwind of large, expanding metropolitan centers or large agricultural operations. Biological response studies in western North America demonstrate that some aquatic and terrestrial plant and microbial communities are significantly altered by N deposition. Greater plant productivity is counterbalanced by biotic community changes and deleterious effects on sensitive organisms (lichens and phytoplankton) that respond to low inputs of N (3 to 8 kilograms N per hectare per year). Streamwater nitrate concentrations are elevated in high-elevation catchments in Colorado and are unusually high in southern California and in some chaparral catchments in the southwestern Sierra Nevada. Chronic N deposition in the West is implicated in increased fire frequency in some areas and habitat alteration for threatened species. Between hotspots, N deposition is too low to cause noticeable effects or has not been studied.

Ionic polymer–metal composites: II. Manufacturing techniques

Abstract: This paper, the second in a series of four review papers to appear in this journal, presents a detailed description of various techniques and experimental procedures in manufacturing ionic polymer–metal composites (IPMCs) that, if fully developed, can be used as effective biomimetic sensors, actuators and artificial muscles as well as fully electroded with embedded electrodes for fuel cells. The performance of IPMCs manufactured by different manufacturing techniques are presented and compared. In particular, a number of issues such as force optimization using the Taguchi design of experiment technique, effects of different cations on electromechanical performance of IPMCs, electrode and particle size and distribution control, manufacturing cost minimization approaches, scaling and three-dimensional (3D) muscle production issues and heterogeneous composites by physical loading techniques are also reviewed and discussed.

Isochoric heating of solid-density matter with an ultrafast proton beam.

Abstract: A new technique is described for the isochoric heating (i.e., heating at constant volume) of matter to high energy-density plasma states (>10{sup 5} J/g) on a picosecond timescale (10{sup -12} sec). An intense, collimated, ultrashort-pulse beam of protons--generated by a high-intensity laser pulse--is used to isochorically heat a solid density material to a temperature of several eV. The duration of heating is shorter than the timescale for significant hydrodynamic expansion to occur, hence the material is heated to a solid density warm dense plasma state. Using spherically-shaped laser targets a focused proton beam is produced and used to heat a smaller volume to over 20 eV. The technique described of ultrafast proton heating provides a unique method for creating isochorically heated high-energy density plasma states.

Interpreting Dimensions of Consumer Trust in E-Commerce

Abstract: Consumer trust in an Internet vendor is an issue commanding ever more attention. Based on an extensive review of literature, this paper proposes dimensions of trust in an Internet vendor. These are competence, integrity and benevolence. Competence refers to a company's ability to fulfill promises made with the consumers. Integrity suggests that a company acts in a consistent, reliable, and honest manner. Benevolence is the ability of a company to hold consumer interests ahead of its own self-interest and indicates sincere concern for the welfare of the customers. In a further analysis various sources where trust might reside are also identified. Drawing on the literature in marketing and general management, the sources of trust are classified as characteristics of the consumer, the firm, the website and the interaction between the consumer and the firm. Given the dimensions and sources of trust, a path model for developing consumer trust in E-commerce is suggested. This research makes a contribution to the development of a theoretical understanding of trust in E-commerce. Although the concepts presented in this paper can be used to carry out further empirical research, they can also be used by practitioners to identify particular trust characteristics for realizing the potential of business to consumer E-commerce venture.

Fractal mobile/immobile solute transport

Abstract: [1] A fractal mobile/immobile model for solute transport assumes power law waiting times in the immobile zone, leading to a fractional time derivative in the model equations. The equations are equivalent to previous models of mobile/immobile transport with power law memory functions and are the limiting equations that govern continuous time random walks with heavy tailed random waiting times. The solution is gained by performing an integral transform on the solution of any boundary value problem for transport in the absence of an immobile phase. In this regard, the output from a multidimensional numerical model can be transformed to include the effect of a fractal immobile phase. The solutions capture the anomalous behavior of tracer plumes in heterogeneous aquifers, including power law breakthrough curves at late time, and power law decline in the measured mobile mass. The MADE site mobile tritium mass decline is consistent with a fractional time derivative of order γ = 0.33, while Haggerty et al.'s [2002] stream tracer test is well modeled by a fractional time derivative of order γ = 0.3.

A comparative study of control techniques for PWM rectifiers in AC adjustable speed drives

Abstract: Four control techniques for pulse-width modulation (PWM) rectifiers in AC adjustable speed drives are presented. In particular, the so-called virtual-flux oriented control (VFOC) and virtual-flux based direct power control (VF-DPC) schemes are described and compared with their voltage based counterparts. These are the voltage oriented control (VOC) and voltage-based direct power control (V-DPC) techniques. Theoretical background is provided, and results of computer simulations and laboratory experiments are given, documenting advantages and disadvantages of the individual control strategies.

Physical, Emotional, and Behavioral Reactions to Breaking Up: The Roles of Gender, Age, Emotional Involvement, and Attachment Style:

Abstract: Associations between gender, age, emotional involvement, and attachment style and reactions to romantic relationship dissolution were studied in a survey of more than 5,000 Internet respondents. It was hypothesized that individual reactions to breakups would be congruent with characteristic attachment behaviors and affect-regulation strategies generally associated with attachment style. Attachment-related anxiety was associated with greater preoccupation with the lost partner, greater perseveration over the loss, more extreme physical and emotional distress, exaggerated attempts to reestablish the relationship, partner-related sexual motivation, angry and vengeful behavior, interference with exploratory activities, dysfunctional coping strategies, and disordered resolution. Attachment-related avoidance was weakly and negatively associated with most distress/proximity-seeking reactions to breakups and strongly and positively associated with avoidant and self-reliant coping strategies. Security (low scores on the anxiety and avoidance dimensions) was associated with social coping strategies (e.g., using friends and family as "safe havens"). Attachment insecurity, particularly anxiety, was associated with using drugs and alcohol to cope with loss.

A Reservoir of Nitrate Beneath Desert Soils

Abstract: A large reservoir of bioavailable nitrogen (up to approximately 10(4) kilograms of nitrogen per hectare, as nitrate) has been previously overlooked in studies of global nitrogen distribution. The reservoir has been accumulating in subsoil zones of arid regions throughout the Holocene. Consideration of the subsoil reservoir raises estimates of vadose-zone nitrogen inventories by 14 to 71% for warm deserts and arid shrublands worldwide and by 3 to 16% globally. Subsoil nitrate accumulation indicates long-term leaching from desert soils, impelling further evaluation of nutrient dynamics in xeric ecosystems. Evidence that subsoil accumulations are readily mobilized raises concern about groundwater contamination after land-use or climate change.

Rapid ecological and behavioural changes in carnivores: the responses of black bears (Ursus americanus) to altered food

Abstract: Many areas have experienced disproportionate increases in the number of conflicts between large carnivores and humans, and this is especially true in western North America where urban sprawl has encroached into regions that have historically contained large carnivores. Yet, globally there is a paucity of studies of temporal changes in behavioural and ecological parameters of carnivores associated with human-induced perturbations at the same location. We capitalized on the extent to which human population growth and its coincident food stores offer a quasi-experimental setting to test hypotheses about the impact of novel food resources. Using black bears Ursus americanus and garbage, measures of behaviour and ecology were contrasted between individuals living in urban– wildland interface (‘experimental’) and in wildland (‘control’) settings at the interface of the Sierra Nevada Range and the Great Basin Desert in the western United States. A temporal dimension was included by comparing our data to those from the same population lacking areas of human encroachment 10–15 years earlier. Specifically, an examination was made of the impacts of garbage on bear time budgets, patterns of activity, and den chronology. Individuals at urban interface areas relative to wildland conspecifics were: (1) active for significantly fewer h per day (8.5 vs 13.3 h; P < 0.01); (2) shifted their activities to nocturnal periods (P < 0.001); (3) entered dens significantly later and remained in them for significantly fewer days (P < 0.05). Our results are contrasted with selected carnivores from sites where attendant changes in behaviour and ecology have accompanied landscape changes associated with human activity. Our findings suggest alterations in carnivore ecology may be rapid and occur within shorter periods than had been previously assumed.

The effect of queen pheromones on worker honey bee ovary development.

Abstract: We report results that address a long-standing controversy in honey bee biology, the identity of the queen-produced compounds that inhibit worker honey bee ovary development. As the honey bee is the only organism for which identities have been proposed for any pheromone that regulates reproduction, the resolution of its identity is of broad significance. We examined the effects of synthetic honey bee queen mandibular pheromone (QMP), four newly identified queen retinue pheromone components, and whole-queen extracts on the ovary development of caged worker bees. The newly identified compounds did not inhibit worker ovary development alone, nor did they improve the efficacy of QMP when applied in combination. QMP was as effective as queen extracts at ovary regulation. Caged workers in the QMP and queen extract treatments had better developed ovaries than did workers remaining in queenright colonies. We conclude that QMP is responsible for the ovary-regulating pheromonal capability of queens from European-derived Apis mellifera subspecies.

Patterns of apparent extirpation among isolated populations of pikas (ochotona princeps) in the great basin

Abstract: We conducted exploratory analyses to examine the relative roles played by natural and anthropogenic influences on persistence of a montane mammal. We revisited historical locations of pikas (Ochotona princeps) within the hydrographic Great Basin during summers of 1994–1999. Seven of 25 populations (28%) reported earlier in the 20th century appeared to have experienced recent extirpations. We assessed causative agents of faunal change using several alternative, but not mutually exclusive, hypotheses. Higher probability of persistence was correlated with greater area of talus habitat at local and mountain-range scales, higher elevation, more easterly longitude, more southern latitude, lack of livestock grazing, greater distance to primary roads, and wilderness management. However, only area of habitat in the mountain range, maximum elevation of talus habitat, and distance to primary roads appeared in the most parsimonious model of persistence when we used Akaike's information criterion model-select...

Factors Affecting Science Teaching Efficacy of Preservice Elementary Teachers

Abstract: (2003). Factors Affecting Science Teaching Efficacy of Preservice Elementary Teachers. Journal of Science Teacher Education: Vol. 14, No. 3, pp. 177-192.

Self‐consistency in reference frames, geocenter definition, and surface loading of the solid Earth

Abstract: [1] Crustal motion can be described as a vector displacement field, which depends on both the physical deformation and the reference frame. Self-consistent descriptions of surface kinematics must account for the dynamic relationship between the Earth's surface and the frame origin at some defined center of the Earth, which is governed by the Earth's response to the degree-one spherical harmonic component of surface loads. Terrestrial reference frames are defined here as “isomorphic” if the computed surface displacements functionally accord with load Love number theory. Isomorphic frames are shown to move relative to each other along the direction of the load's center of mass. The following frames are isomorphic: center of mass of the solid Earth, center of mass of the entire Earth system, no-net translation of the surface, no-net horizontal translation of the surface, and no-net vertical translation of the surface. The theory predicts different degree-one load Love numbers and geocenter motion for specific isomorphic frames. Under a change in center of mass of surface load in any isomorphic frame, the total surface displacement field consists not only of a geocenter translation in inertial space, but must also be accompanied by surface deformation. Therefore estimation of geocenter displacement should account for this deformation. Even very long baseline interferometry (VLBI) is sensitive to geocenter displacement, as the accompanying deformation changes baseline lengths. The choice of specific isomorphic frame can facilitate scientific interpretation; the theory presented here clarifies how coordinate displacements and horizontal versus vertical motion are critically tied to this choice.

Distribution of the vanilloid receptor (VR1) in the gastrointestinal tract

Abstract: The gastrointestinal (GI) tract responds to a variety of stimuli through local and centrally mediated pathways. Changes in the intestinal microenvironment are sensed by vagal, spinal, and intrinsic primary afferent fibers. Sensory nerve endings located close to the lumen of the GI tract respond to pH, chemical composition of lumenal contents, or distortion of the mucosa. Afferents within the muscle layers are thought to be tension sensitive, whereas those located within the myenteric plexus are also thought to respond to changes in chemical composition and humoral substances. Subpopulations of these afferent fibers are activated by capsaicin. However, the exact location of these nerves is currently not known. The vanilloid receptor (VR1) is a nonselective cation channel that is activated by capsaicin, acid, and temperature. Antibodies to VR1 make it possible to determine the location of these afferents, their morphology, and their relationships with enteric nerves and other cell types in the GI tract. VR1-like immunoreactivity was observed on nerves within myenteric ganglia and interganglionic fiber tracts throughout the GI tract. VR1 nerves were also observed within the muscle layers and had an irregular profile, with varicose-like swellings along their lengths. Blood vessels within the GI wall had VR1-immunoreactive nerve fibers associated with them. VR1-like nerves and other immunopositive cells were also observed within the mucosa. In summary, VR1-like immunoreactivity was found in several locations within the GI tract and may provide sensory integration of chemical, physical, or inflammatory stimuli. VR1-like fibers appear to be predominantly spinal in origin, but a few vagal VR1-like fibers exist in the stomach.

The Only Stable State of O2- Is the X 2Πg Ground State and It (Still!) Has an Adiabatic Electron Detachment Energy of 0.45 eV

Abstract: The ultraviolet photoelectron spectrum of O2- exhibits 29 resolved vibronic transitions to the three low-lying electronic states of neutral O2 (X 3Σg-, a 1Δg, b 1Σg+) from the X 2ΠJ (J = 3/2 and 1/2) spin−orbit states of the anion. A Franck−Condon simulation, using the established molecular constants of the neutral oxygen states, matches every observed feature in the spectrum. The 0−0 origin transition is unambiguously assigned, yielding the electron affinity EA0(O2) = 0.448 ± 0.006 eV. The derived bond dissociation energy is D0(O2-) = 395.9 ± 0.6 kJ/mol. Coupled-cluster theory at the CCSD(T)/aug-cc-pVTZ level is used to determine the potential energy curves of O2 and of O2- in its ground state and two excited states, in both the electronically bound and unbound regions. Stabilization methods are employed to characterize the anion curves at bond lengths where their electronic energies lie above that of the ground-state neutral. The calculations confirm that the O2- X 2Πg ground state is adiabatically stab...

Evolving questions and paradigm shifts in endoplasmic-reticulum-associated degradation (ERAD).

Abstract: ER-associated degradation (ERAD) is a component of the protein quality control system, ensuring that aberrant polypeptides cannot transit through the secretory pathway. This is accomplished by a complex sequence of events in which unwanted proteins are selected in the ER and exported to the cytosol for degradation by the proteasome. Given that protein quality control can be essential for cell survival, it is not surprising that ERAD is linked to numerous disease states. Here we review the molecular mechanisms of ERAD, its role in metabolic regulation and biomedical implications, and the unanswered questions regarding this process.

Using black bears to test ideal-free distribution models experimentally

Abstract: Models on the distribution of animals are invaluable in understanding how individuals and, ultimately, populations respond to ecological processes. Rarely, have they been applied to conservation issues at a landscape level. We capitalized on the distribution of a previously unavailable novel food resource, found at the juxtaposition of urban and wildland areas, to test the generality of ideal-free distribution (IFD) models using a mammalian carnivore, the black bear (Ursus americanus). The primary question we addressed was whether an increase in the prevalence of individuals in a geographical region reflects a population increase or a landscape level redistribution. Combining spatial and temporal data sets with empirically obtained information spanning 12‐15 years, we contrasted demographic, lifehistory, and reproductive parameters between individuals at urban‐wildland interface (experimental) and wildland (control) areas at the interface of the Sierra Nevada Range and Great Basin Desert in western North America. Bears were expected to respond to natural versus artificially clumped resources according to an IFD model. Evidence only partially supported this idea because individuals in urban areas had densities 3 times the historical values from the same area, sex ratios were 4.25 times more skewed toward males, bears had 30% larger body mass, home ranges were reduced by 90% for males and 70% for females, and bears entered dens significantly later than wildland conspecifics. However, females in urban-interface areas gave birth to 3 times the number of cubs, although only half as many dispersed successfully relative to wildland females. Further, urban-interface females had a higher proportion (0.57) of potential reproductive years, in which they had young, compared with wildland females (0.29). We present evidence suggesting that bears in Nevada and in the Lake Tahoe basin conform primarily to an ideal-despotic distribution model. Our findings on population reallocation, rather than demographic increase, reemphasize how knowledge about correlates of individual performance and distribution over time helps to understand the extent to which humans change ecosystems, whether their actions are intentional or not.

Factors controlling concentration, export, and decomposition of dissolved organic nutrients in the Everglades of Florida

Abstract: Water draining from the Everglades marshes of southern Florida containshigh concentrations of dissolved organic C (DOC), N (DON), and in somelocations, P (DOP). These dissolved organic nutrients carry over 90% of the Nand organic C, and about 25% of the P exported downstream in the Everglades.Ourobjectives were to describe the most important aspects of the origin and fateofdissolved organic matter (DOM) in the Everglades, and to describe the processescontrolling its concentration and export. Concentrations of dissolved organicnutrients are influenced by local plant production, decomposition, and sorptionequilibrium with peat. The drained peat soils of the Everglades AgriculturalArea and the more productive marshes of the northern Everglades produce some ofthe highest concentrations of DOC and DON in the Everglades watershed. Inportions of the marshes of the northern Everglades, P enrichment was correlatedwith higher local DOC and DON concentrations and greater production of solubleplant matter. Microbial degradation of Everglades DOM was very slow; less than10% of the DOC was lost after 6 months of incubation in the laboratory andsupplements of inorganic nutrients failed to speed the decomposition. Exposureto solar radiation increased the subsequent decay rate of the remaining DOC(25%in 6 mo.). Solar radiation alone mineralized 20.5% of the DOC, 7%of the DON, and degraded about 50% of the humic substances over 21 days insterile porewater samples and thus degraded DOM faster than microbialdegradation. The humic substances appeared to inhibit biodegradation of theother fractions of the DOC since hydrophilic organic acids decomposed fasterwhen isolated from the humic substances.The fate of DOC and DON is closely linked as indicated by a generally narrowrange of C/N ratios. In contrast, high concentrations of DOP were associatedwith P enrichment (at least in pore water). The DOC was composed of about 50%humic substances, 33% hydrophilic acids, and 15% hydrophilic neutralsubstances,typical of DOC from other environments, despite the fact that it originatesfroma neutral to slightly alkaline peatland. Despite high exports of DON (3.9g m−2 y−1 from one area), themarshes of the northern Everglades are a sink for DON on a landscape scale. Theagricultural fields of the Everglades Agricultural Area, however, exported netquantities of DON. High concentrations of DOC desorbed from the agriculturalsoils when water with no DOC was added. Sorption experiments indicated thathighconcentrations of dissolved organic matter flowing into the marshes from theEverglades Agricultural Area could suppress the further desorption ofadditionalsoluble organic matter through physicochemical mechanisms. While biologicalfactors, plant production and microbial decomposition are important inproducingpotentially soluble organic nutrients, physicochemical sorption equilibria,hydrology, and degradation by solar radiation are also likely to control theexport of this material on the landscape scale.

Explosives: a microsensor for trinitrotoluene vapour.

Abstract: Sensing devices designed to detect explosive vapours are bulky, expensive and in need of technological improvement — dogs remain the most effective detectors1 in the fight against terrorism and in the removal of land-mines2,3. Here we demonstrate the deflagration of trinitrotoluene (TNT) in a small localized explosion on an uncoated piezoresistive microcantilever. This explosive-vapour sensor, which has a detection capability that is comparable to that of a dog, should enable extremely sensitive, miniature detection devices to be used on a large scale.

Toward a New Sexual Selection Paradigm: Polyandry, Conflict and Incompatibility (Invited Article)

Abstract: Darwin's recognition that male-male competition and female choice could favor the evolution of exaggerated male traits detrimental to survival set the stage for more than a century of theoretical and empirical work on sexual selection. While this Darwinian paradigm represents one of the most profound insights in biology, its preoccupation with sexual selection as a directional evolutionary force acting on males has diverted attention away from the selective processes acting on females. Our understanding of female reproduction has been further confounded by discreet female mating tactics that have perpetuated the illusion of the monogamous female and masked the potential for conflict between the sexes. With advances in molecular techniques leading to the discovery that polyandry is a pervasive mating strategy, recognition of these shortcomings has brought the study of sexual selection to its current state of flux. In this paper, we suggest that progress in two key areas is critical to formulation of a more inclusive, sexual selection paradigm that adequately incorporates selection from the female perspective. First, we need to develop a better understanding of male x female and maternal x paternal genome interactions and the role that polyandry plays in providing females with non-additive genetic benefits such as incompatibility avoidance. Consideration of these interaction effects influencing natural selection on females is important because they can complicate and even undermine directional sexual selection on males. Secondly, because antagonistic coevolution maintains a balance between opposing sides that obscures the conflict itself, many more experimental evolution studies and interventionist investigations (e.g. gene knockouts) are needed to tease apart male manipulative adaptations and female counter-adaptations. It seems evident that the divisiveness and controversy that has plagued sexual selection theory since Darwin first proposed the idea has often stalled progress in this important field of evolutionary biology. What is now needed is a more pluralistic and integrative approach that considers natural as well as sexual selection acting on females, incorporates multiple sexual selection mechanisms, and exploits advances in physiology and molecular biology to understand the mechanisms through which males and females achieve reproductive success.