2,023 research outputs found
Free-ranging, Northern Bobwhite Submissions to the Southeastern Cooperative Wildlife Disease Study (1982-2015)
There are concerns regarding population declines of northern bobwhite (Colinus virginianus) over the past 4 decades (Palmer et al. 2011). Infectious and noninfectious diseases are among the limiting factors that potentially influence bobwhite demographics (Applegate 2014). The last update of diseases of bobwhite was presented at the Second National Quail Symposium in 1982 (Davidson et al. 1982). Since that report, scientists at the Southeastern Cooperative Wildlife Disease Study (SCWDS) have examined 133 wild bobwhites from 13 states. The SCWDS is a cooperative between states and the University of Georgia and obtains cases from the cooperating states. In this update, we focus on the diagnostic testing results from wild birds and exclude other cases that were examined during this period. We searched the SCWDS database for all bobwhite cases 1985–2016 and examined the individual case reports for 133 wild bobwhite quail. During this period, the majority of cases originated from Florida, Georgia, and Kansas, where research was being conducted on bobwhite populations. A diagnosis could not be clearly identified in all cases and some otherwise healthy bobwhites were submitted for screening; therefore, we have narrowed the focus of this report to a subset of 78 bobwhites. Wild bobwhites that were submitted by SCWDS state cooperators had an approximately even distribution between male and female birds (26 F: 19 M; 2 unknown sex). Adults (20 F, 10 M) predominated over juvenile birds (6 F, 7 M, 2 unknown sex). Trauma (physical injury) was the diagnosis in 17 female and 38 male bobwhites submitted during this period. Three each of male and female birds were considered to have no health problems. Some of the most frequent findings in diagnosed bobwhites were possible Physaloptera sp. infection (n = 9, 17.0%), avian pox (n = 7, 14.9%), intoxication (lead and carbamate; n = 5, 10.6%), corneal opacity (n = 4, 8.5%), Sarcocystis sp. infection (n = 3, 6.4%), and fungal pneumonia (n = 2, 4.25%). Some parasitic infections (e.g., coccidiosis) were thought to be associated with mortality based on necropsy and laboratory findings while a number of the parasites were determined to be incidental findings (e.g., Sarcocystis and Physaloptera) based on necropsy and laboratory findings. Corneal opacity was found in 4 birds, but the cause was not determined. The most striking findings were that trauma (e.g., physical injury) or avian pox were among the most common causes of mortality in free-ranging quail. Iatrogenic (researcher) causes of mortality (n = 5, 10.6%) associated with complications from radiotransmitters and small mammal trapping also occurred. This latter urges careful consideration among bobwhite researchers. The cause of population declines in bobwhites are likely multifactorial. We hope that morbidity and mortality investigations can provide some insight into potential limiting factors for bobwhites and assist wildlife managers with population management decisions
Train Crew Reduction for Increased Productivity of Rail Transit
With the increases in wages since the 1950s, labor costs have become the dominÂant portion of operating costs for transit agencies. Efforts to increase producÂtivity of operating labor have been particularly successful on rail transit systems. For example, development of high-capacity articulated cars, provision of separated rights-of-way and introduction of self-service fare collection have resulted in an approximately 20-fold increase in productivity of light rail transit systems.
The report shows that while the modern rail transit systems (e.g. Lindenwold Line, San Francisco BART, Atlanta\u27s MARTA) have one-person train crews and thus very high productivity, most older streetcar, rapid transit and regional rail systems still have obsolete, inefficient labor practices.
A systematic analysis of alternative ways of performing different duties shows that on many existing transit systems productivity of operating labor can be substantially increased through rather modest efforts. This has been illustrated in two actual cases. The greatest potential benefits from introduction of modern operating methods exist on regional rail systems. Existing rapid transit is another mode on which labor productivity can be substantially increased. Cooperation of labor unions should be obtained by retaining jobs through increased service frequency, or by passing on a portion of the savings to the operating employees in form of increased wages for increased duties
Foraging behavior and Doppler shift compensation in echolocating hipposiderid bats, I-Iipposideros bicolor and I-Iipposideros speoris
1. Two hipposiderid bats,H. bicolor andH. speoris, were observed in their natural foraging areas in Madurai (South India). Both species hunt close together near the foliage of trees and bushes but they differ in fine structure of preferred hunting space:H. bicolor hunts within the foliage, especially whenH. speoris is active at the same time, whereasH. speoris never flies in dense vegetation but rather in the more open area (Fig. 1, Table 1).
2. Both species emit CF/FM-sounds containing only one harmonic component in almost all echolocation situations. The CF-parts of CF/FM-sounds are species specific within a band of 127–138 kHz forH. speoris and 147–159 kHz forH. bicolor (Tables 2 and 3).
3. H. speoris additionally uses a complex harmonic sound during obstacle avoidance and during laboratory tests for Doppler shift compensation.H. bicolor consistently emits CF/FM-sounds in these same situations (Fig. 2).
4. Both hipposiderid bats respond to Doppler shifts in the returning echoes by lowering the frequency of the emitted sounds (Fig. 3). However, Doppler compensations are incomplete as the emitted frequencies are decreased by only 55% and 56% (mean values) of the full frequency shifts byH. speoris andH, bicolor, respectively.
5. The differences in Doppler shift compensation, echolocating and hunting behavior suggest thatH. speoris is less specialized on echolocation with CF/FM-sounds thanH. bicolor
Discordant Alternans Mechanism for Initiation of Ventricular Fibrillation In Vitro
Background: Ventricular tachyarrhythmias are often preceded by short sequences of premature ventricular complexes. In a previous study, a restitution-based computational model predicted which sequences of stimulated premature complexes were most likely to induce ventricular fibrillation in canines in vivo. However, the underlying mechanism, based on discordant-alternans dynamics, could not be verified in that study. The current study seeks to elucidate the mechanism by determining whether the spatiotemporal evolution of action potentials and initiation of ventricular fibrillation in in vitro experiments are consistent with model predictions. Methods and Results: Optical mapping voltage signals from canine right-ventricular tissue (n=9) were obtained simultaneously from the entire epicardium and endocardium during and after premature stimulus sequences. Model predictions of action potential propagation along a 1-dimensional cable were developed using action potential duration versus diastolic interval data. The model predicted sign-change patterns in action potential duration and diastolic interval spatial gradients with posterior probabilities of 91.1%, and 82.1%, respectively. The model predicted conduction block with 64% sensitivity and 100% specificity. A generalized estimating equation logistic-regression approach showed that model-prediction effects were significant for both conduction block (P \u3c 1x10E-15, coefficient 44.36) and sustained ventricular fibrillation (P=0.0046, coefficient, 1.63) events. Conclusions: The observed sign-change patterns favored discordant alternans, and the model successfully identified sequences of premature stimuli that induced conduction block. This suggests that the relatively simple discordant-alternans-based process that led to block in the model may often be responsible for ventricular fibrillation onset when preceded by premature beats. These observations may aid in developing improved methods for anticipating block and ventricular fibrillation
Electron and hole transmission through superconductor - normal metal interfaces
We have investigated the transmission of electrons and holes through
interfaces between superconducting aluminum (Tc = 1.2 K) and various normal
non-magnetic metals (copper, gold, palladium, platinum, and silver) using
Andreev-reflection spectroscopy at T = 0.1 K. We analyzed the point contacts
with the modified BTK theory that includes Dynes' lifetime as a fitting
parameter G in addition to superconducting energy gap 2D and normal reflection
described by Z. For contact areas from 1 nm^2 to 10000 nm^2 the BTK Z parameter
was 0.5, corresponding to transmission coefficients of about 80 %, independent
of the normal metal. The very small variation of Z indicates that the
interfaces have a negligible dielectric tunneling barrier. Fermi surface
mismatch does not account for the observed transmission coefficient.Comment: 9 pages, 4 figures, submitted to Proceedings of the 19th
International Conference on Magnetism ICM2012 (Busan 2012
Low urine pH and acid excretion do not predict bone fractures or the loss of bone mineral density: a prospective cohort study
<p>Abstract</p> <p>Background</p> <p>The acid-ash hypothesis, the alkaline diet, and related products are marketed to the general public. Websites, lay literature, and direct mail marketing encourage people to measure their urine pH to assess their health status and their risk of osteoporosis.</p> <p>The objectives of this study were to determine whether 1) low urine pH, or 2) acid excretion in urine [sulfate + chloride + 1.8x phosphate + organic acids] minus [sodium + potassium + 2x calcium + 2x magnesium mEq] in fasting morning urine predict: a) fragility fractures; and b) five-year change of bone mineral density (BMD) in adults.</p> <p>Methods</p> <p>Design: Cohort study: the prospective population-based Canadian Multicentre Osteoporosis Study. Multiple logistic regression was used to examine associations between acid excretion (urine pH and urine acid excretion) in fasting morning with the incidence of fractures (6804 person years). Multiple linear regression was used to examine associations between acid excretion with changes in BMD over 5-years at three sites: lumbar spine, femoral neck, and total hip (n = 651). Potential confounders controlled included: age, gender, family history of osteoporosis, physical activity, smoking, calcium intake, vitamin D status, estrogen status, medications, renal function, urine creatinine, body mass index, and change of body mass index.</p> <p>Results</p> <p>There were no associations between either urine pH or acid excretion and either the incidence of fractures or change of BMD after adjustment for confounders.</p> <p>Conclusion</p> <p>Urine pH and urine acid excretion do not predict osteoporosis risk.</p
Triton, a new species-level database of Cenozoic planktonic foraminiferal occurrences
Planktonic foraminifera are a major constituent of ocean floor sediments, and thus have one of the most complete fossil records of any organism. Expeditions to sample these sediments have produced large amounts of spatiotemporal occurrence records throughout the Cenozoic, but no single source exists to house these data. We have therefore created a comprehensive dataset that integrates numerous sources for spatiotemporal records of planktonic foraminifera. This new dataset, Triton, contains >500,000 records and is four times larger than the previous largest database, Neptune. To ensure comparability among data sources, we have cleaned all records using a unified set of taxonomic concepts and have converted age data to the GTS 2020 timescale. Where ages were not absolute (e.g. based on biostratigraphic or magnetostratigraphic zones), we have used generalised additive models to produce continuous estimates. This dataset is an excellent resource for macroecological and macroevolutionary studies, particularly for investigating how species responded to past climatic changes
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