Showing papers by "University of Nevada, Reno published in 1993"

Seismicity Remotely Triggered by the Magnitude 7.3 Landers, California, Earthquake

Abstract: The magnitude 7.3 Landers earthquake of 28 June 1992 triggered a remarkably sudden and widespread increase in earthquake activity across much of the western United States. The triggered earthquakes, which occurred at distances up to 1250 kilometers (17 source dimensions) from the Landers mainshock, were confined to areas of persistent seismicity and strike-slip to normal faulting. Many of the triggered areas also are sites of geothermal and recent volcanic activity. Static stress changes calculated for elastic models of the earthquake appear to be too small to have caused the triggering. The most promising explanations involve nonlinear interactions between large dynamic strains accompanying seismic waves from the mainshock and crustal fluids (perhaps including crustal magma).

Binge eating disorder: its further validation in a multisite study.

Abstract: Binge eating disorder (BED) is a new eating disorder that describes the eating disturbance of a large number of individuals who suffer from recurrent binge eating but who do not regularly engage in the compensatory behaviors to avoid weight gain seen in bulimia nervosa. This multisite study of BED involved 1,785 subjects drawn from 18 weight control programs, 942 subjects from five nonpatient community samples, and 75 patients with bulimia nervosa. Approximately 29% of subjects in weight control programs met the criteria for BED. In the nonpatient community samples BED was more common than purging bulimia nervosa. The validity of BED was supported by its strong association with (1) impairment in work and social functioning, (2) overconcern with body/shape and weight, (3) general psychopathology, (4) significant amount of time in adult life on diets, (5) a history of depression, alcohol/drug abuse, and treatment for emotional problems.

The ‘flickering switch’ of late Pleistocene climate change

Abstract: POLAR ice contains a unique record of past climate variations; previous Greenland ice cores have documented relatively warm ‘interstadial’ periods during the last glaciation and short (centuryscale) returns to colder conditions during the glacial to interglacial warming (see, for example, ref. 1). These climate features have also been observed to varying degrees in ocean sediment cores2–4 and terrestrial pollen and insect records5–7. Here we report electrical conductivity measurements from a new Greenland ice core, which confirm these previous observations, and also reveal a hitherto unrecognized mode of rapid climate variation. Fluctuations in ice conductivity on the scales of <5–20 years reflect rapid oscillations in the dust content of the atmosphere. This ‘flickering’ between two preferred states would seem to require extremely rapid reorganizations in atmospheric circulation.

NG-nitro L-arginine methyl ester and other alkyl esters of arginine are muscarinic receptor antagonists.

Abstract: Analogues of L-arginine with modifications at the terminal guanidino nitrogen and/or the carboxyl terminus of the molecule have been widely used for their ability to inhibit the production of nitric oxide and are thought to be competitive antagonists of nitric oxide synthase. The present studies were designed to test the possibility that these agents are also muscarinic receptor antagonists. Acetylcholine produced concentration-dependent contraction of endothelium-denuded rabbit coronary artery as well as isolated strips of canine colonic smooth muscle. The arginine analogue NG-nitro L-arginine methyl ester (L-NAME, 100 microM) but not NG-monomethyl L-arginine (L-NMMA, 100 microM) significantly shifted these contractile relations to the right, an effect that was not reversed by addition of 1 mM L-arginine. In radioligand binding studies using the muscarinic radioligand [3H]quinuclidinyl benzilate and tissues known to contain differing contributions of M1, M2, and M3 muscarinic receptors, addition of increasing concentrations of L-NAME resulted in a monophasic competition of binding with affinities (Ki) ranging from 68 microM in endothelium to 317 microM in whole aorta. Addition of the hydrolysis-resistant guanosine 5'-triphosphate analogue GTP gamma S (100 microM) had no effect on L-NAME competition of [3H]quinuclidinyl benzilate binding. Addition of L-NAME in radioligand binding competition studies using the agonist carbachol did not result in an alteration of the receptor's affinity for agonist, confirming the competitive nature of the interaction of L-NAME with the muscarinic receptor.(ABSTRACT TRUNCATED AT 250 WORDS)

The microhardness indentation load/size effect in rutile and cassiterite single crystals

Abstract: The microhardness indentation load/size effect (ISE) on the Knoop microhardness of single crystals of TiO2 and SnO2 has been investigated. Experimental results have been analysed using the classical power law approach and from an effective indentation test load viewpoint. The Hays/Kendall concept of a critical applied test load for the initiation of plastic deformation was considered, but rejected to explain the ISE. A proportional specimen resistance (PSR) model has been proposed that consists of the elastic resistance of the test specimen and frictional effects at the indentor facet/specimen interface during microindentation. The microhardness test load, P, and the resulting indentation size, d, have been found to follow the relationship $$P = a_1 d + a_2 d^2 = a_1 d + (P_c /d_0^2 ) d^2$$ The ISE is a consequence of the indentation-size proportional resistance of the test specimen as described by a 1. a 2 is found to be related to the load-independent indentation hardness. It consists of the critical indentation load, P c, and the characteristic indentation size, d o.

The mobility of zirconium and other immobile' elements during hydrothermal alteration

Abstract: Development of zircon and other Zr phases in hydrothermal deposits indicates that Zr can be highly mobile in these systems. Mobility is most common in, but not restricted to, F-rich hydrothermal systems related to alkalic, F-rich igneous suites; these suites can range from peralkaline through metaluminous to peraluminous. A few examples are neither alkalic nor F rich. Three locations in the Trans-Pecos Magmatic Province, Texas, U.S.A., demonstrate this hydrothermal Zr mobility. All three igneous systems are alkalic and F rich but vary in alkali/Al ratios. Peralkaline rhyolites and trachytes in the Christmas Mountains contain as much as 2100 ppm Zr, mostly in aegirine or arfvedsonite; zircon is rare or absent

Behavioural constraints and conservation biology: Conspecific attraction and recruitment

Abstract: Wildlife managers have devoted considerable time and research to determine how animals judge the suitability and quality of their habitat. These analyses typically center on habitat characteristics and often produce equivocal results. An additional method of habitat assessment is to examine the extent to which animals, and particularly birds, use conspecifics as cues to establishing breeding and feeding territories. Conspecifics can be indicators of habitat quality, or they might intrinsically affect reproductive success. Here we discuss the implications of conspecific attraction for biologists who wish to conserve endangered species that are living in fragmented habitats.

Electrical conductivity measurements from the GISP2 and GRIP Greenland ice cores

Abstract: THE direct-current electrical conductivity of glacial ice depends on its acidity1–3, and can also indicate changes in climate, as ice formed in cold, dusty periods has a high concentration of alkaline dust1,4,5, which significantly reduces the conductivity6,7 compared to warmer, less dusty periods. Here we present electrical conductivity records for the Greenland Ice Sheet Project 2 (GISP2) and Greenland Ice-core Project (GRIP) ice cores, drilled 28 km apart to enable direct comparison of the results. The upper parts of both records are consistent with previous evidence from other Greenland cores4,8–12 for a stable Greenland climate during the Holocene, and a series of warm events punctuating the last glacial period. However, there is a significant discrepancy between the two records in the bottom 10% of the cores, calling into question recent reports of climate variability in the last interglacial4,8 and the penultimate glaciation8. At this stage, it is too early to say what exactly is causing the discrepancy, although ice flow may have introduced some discontinuities into the records. Further work will be necessary to establish how much climatic information it will eventually be possible to extract from the lower parts of the two cores.

Atomic force microscopy of long DNA: imaging in air and under water

Abstract: We have obtained striking atomic force microscopy images of the intact lambda bacteriophage genome and of several lambda restriction fragments both in air and under water. The DNA is unstained and the images are stable under continuous scanning for up to 30 min. Measured contour lengths of fully imaged restriction fragments and intact lambda DNA are accurate to within a few percent. The key to this development is the use of a process for binding unmodified double-stranded DNA to chemically treated mica surfaces. This procedure leads to strong DNA attachment and yields high-quality images that are stable under repeated scanning, even with the sample submerged in water. This allows normal hydration conditions to be maintained during scanning and in addition leads to a general improvement of image quality. Both the lateral resolution and the contrast increase by a factor of approximately 3 under water.

Prevalence of cardiovascular diseases among older adults : the cardiovascular health study

Abstract: The Cardiovascular Health Study is a population-based longitudinal study of 5,201 adults aged 65 years and older. Prevalences of myocardial infarction, angina pectoris, congestive heart failure, peripheral artery disease, stroke, and transient ischemic attack were ascertained between June 1989 and May 1990 in participants recruited from Forsyth County, North Carolina; Washington County, Maryland; Sacramento County, California; and Pittsburgh, Pennsylvania. A medical history was taken to obtain self-reports of prevalent disease. For all participants, use of nitrates was ascertained to document angina, electrocardiograms were used to document prevalent myocardial infarction, and ankle-arm blood pressure studies were used to document peripheral artery disease. Self-reports of disease that were not confirmed by examination findings were further investigated by examination of medical records. Reported disease that was confirmed by examination findings or by medical records was classified as "definite." Disease that was documented by examination, but not reported by the participant, was classified as "unreported." The prevalence rates of definite myocardial infarction and angina were 11% and 15%, respectively, among men aged 65-69 years, 18% and 17% among men aged 80-84 years, 4% and 8% among women aged 65-69 years, and 3% and 13% among women aged 80-84 years. Twenty-three percent of men and 38% of women with electrocardiographic evidence of myocardial infarction did not report it. These results suggest that prevalent disease estimates based only on self-report may underestimate the prevalence of cardiovascular diseases in older Americans.

The frictional component of the indentation size effect in low load microhardness testing

Abstract: The role of friction between the microhardness indenter and the test specimen is addressed through the analysis of dry (unlubricated) and lubricated tests on iron by Atkinson and Shi. Quantitative evaluation through a proportional specimen resistance model accurately describes the results. It suggests that friction is a major portion of the observed hardness increase at low test loads, the indentation size effect. The ISE is related to the surface-area-to-volume ratio of the indentation, which is inversely related to the indentation dimension.

Some applied implications of a contemporary behavior-analytic account of verbal events.

Abstract: Behavior analysts have always intended to develop the principles adequate to the analysis ofcomplex human behavior. Unlike some other wings of the animal learning tradition, behavior analysts were never interested in "the behavior of rats for its own sake" (Skinner, 1938, p. 441). Rather, the hope was that the analysis of relatively simple nonhuman behaviors in relatively simple environments would pay off as a research strategy (see S. Hayes & L. Hayes, 1992). Whether this strategy would actually work was an empirical matter, because we "can neither assert nor deny continuity or discontinuity" (Skinner, 1938, p. 442), but in fact it worked amazingly well. The extension of behavior-analytic principles derived from the study of nonhumans to human conduct has led to the development of interventions that have had a powerful impact on many areas of human concern. Skinner (1938) at first worried that his approach might not be sufficient for the analysis of verbal behavior. By 1957 he was convinced that a straightforward operant analysis worked there as well. But now, over 35 years later, Skinner's analysis ofverbal events has become increasingly threadbare. Holes have emerged, on both empirical and theoretical grounds. As a result, the analysis of verbal events from a behavior-analytic viewpoint is more open to alternatives. Skinner's analysis, after all, was never the behavior-analytic account-it was only a behavior-analytic account. The need for an adequate behavioranalytic account of verbal events is perhaps felt the most among clinical radical behaviorists. This wing of the applied arena is distinguishable on the one hand

Amplification of nitric oxide signaling by interstitial cells isolated from canine colon.

Abstract: The effects of nitric oxide (NO) on intracellular Ca2+ concentration ([Ca2+]i) were studied in enzymatically dispersed interstitial cells (ICs) and smooth muscle cells (SMCs) isolated from canine colon. [Ca2+]i was monitored by using fluo-3 and video fluorescence imaging techniques. Exogenous NO caused an increase in [Ca2+]i in ICs and a decrease in [Ca2+]i in SMCs. Effects of NO on ICs were not blocked by removal of extracellular Ca2+ but were blocked by ryanodine, suggesting that NO caused release of Ca2+ from intracellular stores. When [Ca2+]i was elevated in an IC by micropressure ejection of Bay K 8644, [Ca2+]i decreased in nearby SMCs, suggesting release of a diffusible substance. The diffusible substance may be NO or an NO-related substance based on blockade of transmission by NG-nitro-L-arginine methyl ester, NG-monomethyl-L-arginine, or oxyhemoglobin. The elevation of [Ca2+]i in ICs by NO, which, in turn, might cause further release of NO and elevation of [Ca2+]i, suggests a positive feedback and amplification mechanism in these cells. Elevation of [Ca2+]i in SMCs had no effect on adjacent SMCs. Our data suggest that ICs may play a central role in amplification of NO signaling and propagation of inhibitory wave fronts.

Regulation of Ca2+ channels by cAMP and cGMP in vascular smooth muscle cells.

Abstract: Whole-cell Ca2+ channel currents in rabbit portal vein cells were recorded using the amphotericin B-perforated patch-clamp technique at 35 degrees C. This technique allowed recording of stable inward currents in the absence of run-down for more than 30 minutes. Depolarizing voltage steps from a holding potential of -70 mV elicited voltage-dependent inward currents. The voltage dependence of inward currents measured in either 2.5 mmol/L Ba(2+)- or 2.5 mmol/L Ca(2+)-containing solution were very similar. However, maximum Ba2+ current (obtained at around +10 mV) was approximately 1.5-fold larger than maximum Ca2+ current. Changing the holding potential from -70 to -40 mV decreased inward currents but did not shift the voltage dependence significantly. Inward currents were also completely blocked by the dihydropyridine Ca2+ channel blocker, nicardipine (10 mumol/L), suggesting the presence of predominantly L-type Ca2+ channels in rabbit portal vein cells. Isoproterenol caused small increases in the amplitude of Ba2+ currents in a concentration-dependent manner (10 nmol/L to 1 mumol/L), which were reversed with propranolol. Forskolin (1 mumol/L) or 8-bromo-cAMP (0.1 mmol/L) also caused small increases in the amplitude of Ba2+ currents, suggesting that the stimulatory actions of isoproterenol are importantly linked to the production of cAMP. Higher concentrations of of isoproterenol (10 mumol/L) or forskolin (10 mumol/L) caused a transient increase in Ba2+ currents followed by f decrease in current amplitude. Higher doses of 8-bromo-cAMP (1 mmol/L) and low doses of 8-bromo-cGMP (0.1 mmol/L) inhibited Ba2+ currents, increased the rate of current inactivation, and produced a negative voltage shift in steady-state availability. These results indicate that low concentrations of intracellular cAMP produce modest increases in Ca2+ channel activity, whereas cGMP and higher concentrations of cAMP result in inhibition of Ca2+ channel activity in vascular smooth muscle cells. The observed similarities of cGMP and high concentrations of cAMP on Ba2+ current amplitude, kinetics, and steady-state inactivation suggest mediation by a common mechanism, possibly involving activation of cGMP-dependent protein kinase.

Estimating Yield Distributions with a Stochastic Trend and Nonnormal Errors

Abstract: Randomness in crop yields can be decomposed into two broad modeling focuses: the estimation of the mean or central tendency of the distribution and the dispersion around that central tendency. We propose modeling the central tendency of the distribution with a stochastic trend model and allowing for nonnonnality within the stochastic trend through an inverse hyperbolic sine distribution. Results are consistent with this construction. First, residuals around the stochastic trend model are found to be non normal. Second, the inverse hyperbolic sine modification of the stochastic trend model corrects both skewness and kurtosis of corn yields.

Influence of supplementation on behavior of grazing cattle

Abstract: supplemental starch decreased ( P .lo) or decreased (P .lo) this response. Different types tices that modify behaviors to control feed intake, and timing of starch-based supplements produced improve efficiency, or reduce stress could be major variable results; however, increasing the level of contributions to the livestock industry. Dormant grasses are usually deficient

Williams syndrome: Autosomal dominant inheritance

Abstract: Williams syndrome (WS) usually occurs sporadically. Few familial cases of Williams syndrome have been described, and those reports have often lacked photographic documentation. We describe 3 families, including a 3-year-old boy and his 34-year-old father, a 2-year-old girl and her 30-year-old mother, and a 3-year-old girl and her 31-year-old mother. None of these patients has supravalvular aortic stenosis or chromosome abnormalities. In all 3 families, the parent with Williams syndrome was diagnosed after the identification of the syndrome in the affected child.

Criteria for prognostic factors and for an enhanced prognostic system

Abstract: The American Joint Committee on Cancer proposes the following criteria for evaluating putative prognostic factors: they must be (1) significant, (2) independent, and (3) clinically important. Furthermore, we suggest the criteria for selecting a prognostic system that includes TNM and new prognostic factors. These criteria are: (1) easy for physicians to use; (2) provides predictions for all types of cancer; (3) provides the most accurate relapse and survival predictions at diagnosis and for every year lived for each patient; (4) provides group survival curves, where the grouping can be by any variable including outcome and therapy; (5) accommodates missing data and censored patients and is tolerant of noisy and biased data; (6) makes no a priori assumptions regarding the type of data, the distribution of the variables, or the relationships among the variables; (7) can test putative prognostic factors for significance, independence, and clinical importance; (8) accommodates treatment information in the evaluation of prognostic factors; (9) accommodates new putative prognostic factors without changing the model; (10) accommodates emerging diagnostic techniques; (11) provides information regarding the importance of each predictive variable; and (12) is automatic.

A small highly basic protein is encoded in overlapping frame within the P gene of vesicular stomatitis virus.

Abstract: Vesicular stomatitis virus (VSV) has served for several decades as the prototype rhabdovirus and a model RNA virus. Extensive studies upheld the original view of VSV genetics with simply five genes (N, P, M, G, and L), each encoding a single unique protein. We now report the first unambiguous demonstration of the existence of an additional unique protein encoded in an overlapping frame within the virus P gene. Experiments using antipeptide sera specific for the predicted second open reading frame have demonstrated the synthesis of two N-terminally nested forms of the protein in virus-infected cells. The major form is 55 amino acids in length, whereas the minor form has 10 additional N-terminal amino acids. Ribosome initiation of synthesis of these proteins appears to occur at AUG codons, 68 and 41 bases, respectively, downstream of the P protein AUG initiation codon. The proteins are found in the cytoplasm of the infected cell but are undetectable in purified virions, consistent with their being nonstructural proteins. Both the major and minor forms of the protein are highly basic and arginine rich, reminiscent of the C and C' proteins encoded in overlapping frame close to the 5' terminus of the P mRNA of several paramyxoviruses. The potential to encode small, highly basic proteins within the P mRNA 5' terminus is highly conserved among the vesiculoviruses.

Power spectra of a PWM inverter with randomized pulse position

Abstract: Random pulse width modulation in static power converters results in the partial transfer of power from the discrete spectrum of the output voltage to the continuous spectrum, with advantageous effects on the operation of the supplied electromechanical systems. In this paper, a random PWM technique with randomized pulse position for three-phase voltage-controlled inverters is analyzed. Closed-form equations for the discrete and continuous power spectra of the line-to-line and line-to-neutral voltages of the inverter have been derived and confirmed by experiments. Presented theory opens the way to numerical optimization of the voltage spectra of randomly modulated inverters. >

Photoinhibition as a control on photosynthesis and production of Sphagnum mosses.

Abstract: The effect of high light intensity on photosynthesis and growth of Sphagnum moss species from Alaskan arctic tundra was studied under field and laboratory conditions. Field experiments consisted of experimental shading of mosses at sites normally exposed to full ambient irradiance, and removal of the vascular plant canopy from above mosses in tundra water track habitats. Moss growth was then monitored in the experimental plots and in adjacent control areas for 50 days from late June to early August 1988. In shaded plots total moss growth was 2–3 times higher than that measured in control plots, while significant reductions in moss growth were found in canopy removal plots. The possibility that photoinhibition of photosynthesis might occur under high-light conditions and affect growth was studied under controlled laboratory conditions with mosses collected from the arctic study site, as well as from a temperate location in the Sierra Nevada, California. After 2 days of high-light treatment (800 μmol photons m−2 s−1) in a controlled environmental chamber, moss photosynthetic capacity was significantly lowered in both arctic and temperate samples, and did not recover during the 14-day experimental period. The observed decrease in photosynthetic capacity was correlated (r2=0.735, P<0.001) with a decrease in the ratio of variable to maximum chlorophyll fluorescence (Fv/Fm) in arctic and temperate mosses. This relationship indicates photoinhibition of photosynthesis in both arctic and temperate mosses at even moderately high light intensities. It is suggested that susceptibility to photoinhibition and failure to photoacclimate to higher light intensities in Sphagnum spp. may be related to low tissue nitrogen levels in these exclusively ombrotrophic plants. Photoinhibition of photosynthesis leading to lowered annual carbon gain in Sphagnum mosses may be an important factor affecting CO2 flux at the ecosystem level, given the abundance of these plants in Alaskan tussock tundra.

mtDNA diversity in rhesus monkeys reveals overestimates of divergence time and paraphyly with neighboring species.

Abstract: Reconstructions of the human-African great ape phylogeny by using mitochondrial DNA (mtDNA) have been subject to considerable debate. One confounding factor may be the lack of data on intraspecific variation. To test this hypothesis, we examined the effect of intraspecific mtDNA diversity on the phylogenetic reconstruction of another Plio-Pleistocene radiation of higher primates, the fascicularis group of macaque (Macaca) monkey species. Fifteen endonucleases were used to identify 10 haplotypes of 40-47 restriction sites in M. mulatta, which were compared with similar data for the other members of this species group. Interpopulational, intraspecific mtDNA diversity was large (0.5%-4.5%), and estimates of divergence time and branching order incorporating this variation were substantially different from those based on single representatives of each species. We conclude that intraspecific mtDNA diversity is substantial in at least some primate species. Consequently, without prior information on the extent of genetic diversity within a particular species, intraspecific variation must be assessed and accounted for when reconstructing primate phylogenies. Further, we question the reliability of hominoid mtDNA phylogenies, based as they are on one or a few representatives of each species, in an already depauperate superfamily of primates.

Cache site selection by chipmunks (Tamias spp.) and its influence on the effectiveness of seed dispersal in Jeffrey pine (Pinus jeffreyi).

Abstract: The effectiveness of Jeffrey pine (Pinus jeffreyi) seed dispersal performed by seed-caching yellow pine chipmunks (Tamias amoenus) and lodgepole chipmunks (Tamias speciosus) was compared to that of wind dispersal in the Sierra Nevada of western Nevada. Wind-dispersed seeds typically fall under or near the parent tree. Chipmunks removed 90 and 97% of 1064 radioactive seeds from each of two simulated wind-dispersed seed shadows in less than 24 h. "Wind-dispersed" seeds were deployed within 12 m of the two "source" trees, but chipmunk caches were found from 2-69 m from the trees. Chipmunks carried nearly all seeds away from source trees, greatly reducing the density of seeds under and near source trees. Caches contained from 1-35 seeds and most were buried 7-21 mm deep. Chipmunks cached in open bitterbrush shrubland with mineral soils much more than expected and cached in closed-canopy Jeffrey pine and lodgepole pine forests with thick needle litter much less than expected. Many Jeffrey pine seedlings and saplings grow in the bitterbrush habitat and few grow in the pine forests. Ten and 20% of the original caches survived until April, the time of seed germination, at the two sites. The movement of wind-dispersed seeds is random relative to environmental variables important in seedling survival, and the wind in coniferous forests cannot quickly bury seeds. The quality of seed dispersal rendered by chipmunks was superior to that provided by the wind because the chipmunks quickly harvested seeds on the ground, moved them away from source trees, and buried them in the ground in habitats and microhabitats where they were more likely to establish new seedlings. The increased quality of seed dispersal provided by animals relative to the wind may help explain why over twenty species of pines have evolved seeds and cones that are adapted for dispersal by seed-caching animals.