Showing papers by "University of Nevada, Reno published in 1997"

Object-oriented application frameworks

Abstract: Computing power and network bandwidth have increased dramatically over the past decade However, the design and implementation of complex software remains expensive and error-prone Much of the cost and effort stems from the continuous rediscovery and re-invention of core concepts and components across the software industry In particular, the growing heterogeneity of hardware architectures and diversity of operating system and communication platforms makes it hard to build correct, portable, efficient, and inexpensive applications from scratch Object-oriented (OO) application frameworks are a promising technology for reifying proven software designs and implementations in order to reduce the cost and improve the quality of software A framework is a reusable, ``semi-complete'' application that can be specialized to produce custom applications [Johnson:88] In contrast to earlier OO reuse techniques based on class libraries, frameworks are targeted for particular business units (such as data processing or cellular communications) and application domains (such as user interfaces or real-time avionics) Frameworks like MacApp, ET++, Interviews, ACE, Microsoft's MFC and DCOM, JavaSoft's RMI, and implementations of OMG's CORBA play an increasingly important role in contemporary software development

Molecular identification of a volume-regulated chloride channel

Abstract: A volume-regulated chloride current ( I Cl.vol) is ubiquitously present in mammalian cells, and is required for the regulation of electrical activity, cell volume, intracellular pH, immunological responses, cell proliferation and differentiation. However, the molecule responsible for I Cl.vol has yet to be determined1,2,3. Although three putative chloride channel proteins expressed from cloned genes (P-glycoprotein4, p I Cln (ref. 5) and ClC-2 (ref. 6)) have been proposed to be the molecular equivalent of I Cl.vol, neither P-glycoprotein nor p I Cln is thought to be a chloride channel or part thereof7,8, and the properties of expressed ClC-2 channels differ from native I Cl.vol (refs. 3, 6). Here we report that functional expression in NIH/3T3 cells of a cardiac clone of another member of the ClC family, ClC-3, results in a large basally active chloride conductance, which is strongly modulated by cell volume and exhibits many properties identical to those of I Cl.vol in native cells1,2,3,9,10,11,12,13. A mutation of asparagine to lysine at position 579 at the end of the transmembrane domains of ClC-3 abolishes the outward rectification and changes the anion selectivity from I− > Cl− to Cl− > I− but leaves swelling activation intact. Because ClC-3 is a channel protein belonging to a large gene family of chloride channels3,14, these results indicate that ClC-3 encodes I Cl.vol in many native mammalian cells.

The contribution of burnout to work performance.

Abstract: While the notion that ‘burnout’ is related to a decline in work performance is widely recognized, empirical support for this relationship is lacking. The present study, composed of human services personnel, is the first to empirically test the relationships among Maslach's three dimensions of burnout and work performance. A negative relationship was established between one dimension of burnout, emotional exhaustion, and subsequent work performance. However, the results failed to establish relationships among work performance, depersonalization and diminished personal accomplishment. These results provide further support for emotional exhaustion as a key component of the burnout experience. Future directions and implications of these findings are introduced. © 1997 John Wiley & Sons, Ltd.

Attentional requirements in a 'preattentive' feature search task

Abstract: It is commonly assumed that certain features are so elementary to the visual system that they require no attentional resources to be perceived. Such 'preattentive' features are traditionally identified by visual search performance, in which the reaction time for detecting a feature difference against a set of distractor items does not increase with the number of distractors. This suggests an unlimited capacity for the perception of such features. We provide evidence to the contrary, demonstrating that detection of differences in a simple feature such as orientation is severely impaired by additionally imposing an attentionally demanding rapid serial visual presentation task involving letter identification. The same visual stimuli exhibit non-increasing reaction time versus set-size functions. These results demonstrate that attention can be critical even for the detection of so-called 'preattentive' features.

Statistical modeling of collision-induced dissociation thresholds

Abstract: Analysis of the energy dependence of the cross sections for collision-induced dissociation reactions has permitted the determination of quantitative thermodynamic information for a variety of ionic clusters. As such clusters become larger, the rate at which the decomposition occurs becomes comparable to the instrumental time available for observing the reaction. A method for incorporating statistical theories for energy-dependent unimolecular decomposition in this threshold analysis is reviewed and updated. The revision relies on the fact that for most ionic clusters, the transition state is a loose association of the products that can be located at the centrifugal barrier. This permits a straightforward estimation of the molecular parameters needed in statistical theories for the transition state. Further, we also discuss several treatments of the adiabatic rotations of the dissociating cluster. The various models developed here and previously are compared and used to analyze a series of data for Li+(ROH...

Pattern recognition using neural networks: theory and algorithms for engineers and scientists

Abstract: Part I FUNDAMENTALS OF PATTERN RECOGNITION 0. Basic Concepts of Pattern Recognition 1. Decision Theoretic Algorithms 2. Structural Pattern Recognition Part II INTRODUCTORY NEURAL NETWORKS 3. Artificial Neural Network Structures 4. Supervised Training via Error Backpropogation: Derivations 5. Acceleration and Stabilization of Supervised Gradient Training of MLPs Part III ADVANCED FUNDAMENTALS OF NEURAL NETWORKS 6. Supervised Training via Strategic Search 7. Advances in Network Algorithms for Recognition 8. Using Hopfield Recurrent Neural Networks Part IV NEURAL, FEATURE, AND DATA ENGINEERING 9. Neural Engineering and Testing of FANNs 10. Feature and Data Engineering

Artificial neural networks improve the accuracy of cancer survival prediction

Abstract: BACKGROUND The TNM staging system originated as a response to the need for an accurate, consistent, universal cancer outcome prediction system. Since the TNM staging system was introduced in the 1950s, new prognostic factors have been identified and new methods for integrating prognostic factors have been developed. This study compares the prediction accuracy of the TNM staging system with that of artificial neural network statistical models. METHODS For 5-year survival of patients with breast or colorectal carcinoma, the authors compared the TNM staging system's predictive accuracy with that of artificial neural networks (ANN). The area under the receiver operating characteristic curve, as applied to an independent validation data set, was the measure of accuracy. RESULTS For the American College of Surgeons' Patient Care Evaluation (PCE) data set, using only the TNM variables (tumor size, number of positive regional lymph nodes, and distant metastasis), the artificial neural network's predictions of the 5-year survival of patients with breast carcinoma were significantly more accurate than those of the TNM staging system (TNM, 0.720; ANN, 0.770; P < 0.001). For the National Cancer Institute's Surveillance, Epidemiology, and End Results breast carcinoma data set, using only the TNM variables, the artificial neural network's predictions of 10-year survival were significantly more accurate than those of the TNM staging system (TNM, 0.692; ANN, 0.730; P < 0.01). For the PCE colorectal data set, using only the TNM variables, the artificial neural network's predictions of the 5-year survival of patients with colorectal carcinoma were significantly more accurate than those of the TNM staging system (TNM, 0.737; ANN, 0.815; P < 0.001). Adding commonly collected demographic and anatomic variables to the TNM variables further increased the accuracy of the artificial neural network's predictions of breast carcinoma survival (0.784) and colorectal carcinoma survival (0.869). CONCLUSIONS Artificial neural networks are significantly more accurate than the TNM staging system when both use the TNM prognostic factors alone. New prognostic factors can be added to artificial neural networks to increase prognostic accuracy further. These results are robust across different data sets and cancer sites. Cancer 1997; 79:857-62. © 1997 American Cancer Society.

INFERRING PHYLOGENIES FROM mtDNA VARIATION: MITOCHONDRIAL-GENE TREES VERSUS NUCLEAR-GENE TREES REVISITED.

Abstract: The paper by Moore (1995) provided a theoretical basis for preferring mitochondrial-DNA(mtDNA) gene trees over nuclear-gene trees when estimating species phylogenies. This commentary examines conditions that contradict Moore's analysis, suggesting that mtDNA-gene trees for clades exhibiting female philopatry and male dispersal, or a polygynous mating system, may be less reliable indicators of a species phylogeny than nuclear-gene trees. Moore (1995) provides a clear discussion of the differences between gene trees and species trees. The fundamental reason for this distinction is that new alleles, or haplotypes, can originate at any point in time and are not constrained to begin evolutionary divergence at the time of speciation. Indeed, the fact that mutation generates polymorphism within a species is the foundation of population genetics. This point alone allows true branch lengths on a gene tree to differ from true branch lengths on the species tree for the same set of taxa. Of greater concern is that the true branching topology of a gene tree can also differ from that of the species tree when polymorphisms are maintained for long periods relative to internodal distances on the species tree (Moore 1995, fig. 1). If polymorphisms are resolved relatively quickly by the extinction and fixation of alternative alleles (i.e., lineage sorting sensu Avise et al. 1987), then the topology of the species tree will be imposed on the gene tree, because homologous gene sequences will coalesce in the most recent common ancestor of any two species. If, however, ancient polymorphisms coexisted for periods longer than the time between speciation events then the order of speciation may not be reflected in the gene phylogeny. This is expected because loss of particular lineages from descendant taxa should be random with respect to the age of the lineage. The loss of genetic lineages over a time period that includes a speciation event can occur by subsampling of ancestral polymorphisms in the original descendant population or by the subsequent extinction of alleles in descendant taxa. For the purpose of data analysis, undersampling extant intrataxonomic variation also mimics the effects of lineage sorting. Two strategies have been suggested to deal with the potential discordance between gene trees and species trees. The first recommends the simultaneous analysis of multiple unlinked genes (Pamilo and Nei 1988; Wu 1991). This strategy, however, is based on the assumption that the pattern of loss of alleles in descendant taxa is not correlated across loci. Although this may often be the case, there are also circumstances that would invalidate this assumption. For example, the subsampling of ancestral alleles during speciation may not be independent across unlinked loci if genetic variation was geographically structured in the ancestor (Hoelzer and Melnick 1994). Even when this critical assumption is true, the number of unlinked genes that must be examined to give one confidence in the topology can be prohibitive (Moore 1995). The second strategy, which is promoted by Moore (1995), is to use a gene that exhibits short coalescence times. This will maximize the chance that the historical durations of polymorphism retention will not exceed internodal distances on the species tree. Moore (1995) goes on to show that mtDNA is expected to exhibit a coalescence time that is 25% as long as for nuclear genes. This assertion is based on the expectation that effective population size of mtDNA (Nemit) is one-fourth that of nuclear genes (Nenuc) because the mitochondrial genome is both haploid and transmitted only through females. In a random mating population with an equal number of males and females, there will be four times more nuclear-gene copies passed on to the next generation because the nuclear genome is diploid, and alleles are contributed by both sexes. This is an excellent point with important implications for our interpretations of results in molecular systematics and our choices of approach to future studies; however, there are also other factors that can increase Nemit relative to Nenuc. Consideration of these factors shows that Nem it can exceed Nenuc and render a mtDNA tree a less reliable estimate of the species phylogeny than a nuclear-gene tree.

Fluorometric assessments of mitochondrial function and viability in cryopreserved bovine spermatozoa.

Abstract: Mitochondrial function and sperm viability were quantified in samples of cryopreserved bovine spermatozoa from 12 bulls using fluorometric techniques. The active mitochondria of the spermatozoa were fluorescently stained using three different fluorophores: rhodamine 123 (R123), 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolyl-carbocyan ine iodide (JC-1) or MitoTracker Green FM (MITO). The stained spermatozoa, and companion aliquots that had been stained with SYBR-14 (a living-cell nucleic acid stain) and propidium iodide to assess viability, were quantified using flow cytometry. The resulting fluorescent measurements of mitochondrial function were compared with microscopic assessments of progressive sperm motility immediately after thawing, with motility after 3-h incubation at 37 degrees C, and with the fluorescent assessment of sperm viability. Staining with either R123 or MITO resulted in a single green population. In contrast, the JC-1 staining of mitochondria produced both green and red-orange populations of spermatozoa and sometimes a progressive gradient between the two populations. The ability of JC-1 to discriminate between mitochondria exhibiting high membrane potential from those having low to medium membrane potential provided a more rigorous estimate of metabolic function than the other two fluorescent stains. Overall, the three fluorometric measurements of mitochondrial function were highly correlated with each other, with the SYBR-14 assessment of viability, and with the microscopic estimates of motility.

The Pharmacology of Ryanodine and Related Compounds

Abstract: The goal of this review has been to describe the current state of the pharmacology of ryanodine and related compounds relative to the vertebrate RyRs. Resolution of questions concerning the molecular properties of RyR channel function and the contributions made by the RyR isoforms to cellular signaling in a variety of tissues will require the production of new pharmacological agents directed against these proteins. Novel naturally occurring ryanodine congeners have been identified, and significant advances have been made in developing chemical approaches that permit the structure of ryanodine to be derivatized in selective ways. Moreover, several of these changes have yielded compounds that differ in their binding affinities and in their abilities to modify the properties of the RyR channels. These advances give substance to the possibility of designing the required pharmacological agents based on rational design changes of the structure ryanodine.

Neuronal release of soluble nucleotidases and their role in neurotransmitter inactivation

Abstract: Efficient control of synaptic transmission requires a rapid mechanism for terminating the actions of neurotransmitters. For amino acids and monoamines, this is achieved by their uptake into the cell by specific high-affinity transporters; acetylcholine is first broken down in the extracellular space and then choline is taken up by the cell. Because ATP is hydrolysed to adenosine by membrane-bound enzymes (ectonucleotidases) that are present in most tissues, it has been assumed that these enzymes terminate the neurotransmitter actions of ATP in the brain and in the periphery. We show here, however, that stimulation of sympathetic nerves innervating the guinea-pig vas deferens releases not only neuronal ATP, but also soluble nucleotidases that break down this ATP to adenosine, indicating that inactivation of ATP is increased by nerve activity. This release of specific nucleotidases together with ATP represents a new mechanism for terminating the actions of a neurotransmitter.

Nonlinear ground-motion amplification by sediments during the 1994 Northridge earthquake

Abstract: It has been known since at least 1898 (ref 1) that sediments can amplify earthquake ground motion relative to bedrock For the weak ground motion accompanying small earthquakes, the amplification due to sediments is well understood in terms of linear elasticity (Hooke's law)2, but there has been a long-standing debate regarding the amplification associated with the strong ground motion produced by large earthquakes The view of geotechnical engineers, based largely on laboratory studies, is that Hooke's law breaks down at larger strains causing a reduced (nonlinear) amplification Seismologists, on the other hand, have tended to remain sceptical of this nonlinear effect, mainly because the relatively few strong-motion observations seemed to be consistent with linear elasticity Although some recent earthquake studies have demonstrated nonlinear behaviour under certain circumstances3,4, the significance of nonlinearity for the type of stiff-soil sites found in the greater Los Angeles region remains unresolved5 Here we report that ground-motion amplification due to sediments for the main shock of the 1994 Northridge earthquake was up to a factor of two less than the amplification observed for its aftershocks These observations imply significant nonlinearity in such amplification, and bring into question the use of measurements of weak ground motion to predict the strong ground motion at sedimentary sites

Interstitial cells of Cajal in the guinea-pig gastrointestinal tract as revealed by c-Kit immunohistochemistry

Abstract: Interstitial cells of Cajal (ICC) of various morphologies have been described in the gastrointestinal (GI) tracts of mammals. Different classes of ICC are likely to have different functional roles. ICC of the mouse GI tract have been shown to express c-kit, a proto-oncogene that codes for a receptor tyrosine kinase. We have studied the distribution of ICC within the guinea pig GI tract using antibodies to c-Kit protein and immunohistochemical techniques. c-Kit-like immunoreactivity revealed at least 6 types of ICC: (1) intramuscular ICC (IC-IM1) that lie within the muscle layers of the esophagus, stomach, and cecum, (2) ICC within the myenteric plexus region (IC-MY1) in the corpus, antrum, small intestine, and colon,(3) ICC that populate the deep muscular plexus of the small intestine (IC-DMP), (4) ICC at the submucosal surface of the circular muscle layer in the colon (IC-SM), (5) stellate ICC that are closely associated with the myenteric plexus (IC-MY2) and orientated toward the longitudinal muscle layer in the colon, and (6) branching intramuscular ICC (IC-IM2) in the proximal colon within the circular and longitudinal muscle layers. c-Kit immunohistochemistry appears to be an excellent and selective technique for labeling ICC of the guinea-pig GI tract. Labeling of these cells at the light-microscopic level provides an opportunity for characterizing the distribution, density, organization, and relationship between ICC and other cell types.

Mutations in transcriptional regulator ATRX establish the functional significance of a PHD-like domain

Abstract: Mutations in transcriptional regulator ATRX establish the functional significance of a PHD-like domain.

Individual Variation in Mammals

Abstract: The study of individual variation offers an underexploited wealth of opportunities for mammalogists. This paper addresses recent developments in the study of both intra- and inter-individual variation. After reviewing several methods (e.g., intraclass correlation, product-moment correlation, and confirmatory factor analysis) for quantifying intra-individual consistency or repeatability, we discuss how these measures of repeatability can serve as guides for appropriately defining traits and how they may be helpful in ensuring that appropriate statistical models are used (e.g., in accounting for measurement errors in regression analyses). We discuss three aspects of inter-individual variation; phenotypic selection, alternative individual strategies and phenotypic integration, and quantitative genetic analyses. The value of these approaches for studying inter-individual variation is illustrated with recent examples from the literature. Finally, we discuss how many field studies of mammals may be well poised to exploit the unique insights that can be gained from studying individual variation.

Space vector PWM technique with minimum switching losses and a variable pulse rate [for VSI]

Abstract: A novel randomized control strategy for three-phase voltage source inverters, based on voltage space vectors, is described. An implicit asymmetrical modulating function results in switching losses in the inverter being reduced by about half in comparison with those using the classic space vector pulsewidth PWM method. The pulse rate is varied within individual 60/spl deg/ sectors of the vector plane, so that the power spectra of the output voltage are spread over a wide frequency range and acquire a continuous part. Relevant theoretical analyses, computer simulations and experimental results are presented.

Phosphorylation of the 27-kDa heat shock protein via p38 MAP kinase and MAPKAP kinase in smooth muscle

Abstract: The 27-kDa heat shock protein (HSP27) is expressed in a variety of tissues in the absence of stress and is thought to regulate actin filament dynamics, possibly by a phosphorylation/dephosphorylati...

Nearly synchronous climate change in the Northern Hemisphere during the last glacial termination

Abstract: The climate of the North Atlantic region underwent a series of abrupt cold/warm oscillations when the ice sheets of the Northern Hemisphere retreated during the last glacial termination (17.7–11.5kyr ago). Evidence for these oscillations, which are recorded in European terrestrial sediments as the Oldest Dryas/Bolling/Older Dryas/Allerod/Younger Dryas vegetational sequence1,2, has been found in Greenland ice cores3,4. The geographical extent of many of these oscillations is not well known5,6, but the last major cold event (the Younger Dryas) seems to have been global in extent7,8,9,10. Here we present evidence of four major oscillations in the hydrological balance of the Owens basin, California, that occurred during the last glacial termination. Dry events in western North America occurred at approximately the same time as cold events recorded in Greenland ice, with transitions between climate regimes in the two regions taking place within a few hundred years of each other. Our observations thus support recent climate simulations which indicate that cooling of the North Atlantic Ocean results in cooling of the North Pacific Ocean11 which, in turn, leads to a drier climate in western North America12.