Population structure, long-term connectivity, and effective size of mutton snapper (Lutjanus analis) in the Caribbean Sea and Florida Keys

Genetic structure and average long-term connectivity and effective size of mutton snapper (Lutjanus analis) sampled from offshore localities in the U.S. Caribbean and the Florida Keys were assessed by using nuclear-encoded microsatellites and a fragment of mitochondrial DNA. No significant differences in allele, genotype (microsatellites), or haplotype (mtDNA) distributions were detected; tests of selective neutrality (mtDNA) were nonsignificant after Bonferroni correction. Heuristic estimates of average long-term rate of migration (proportion of migrant individuals/generation) between geographically adjacent localities varied from 0.0033 to 0.0054, indicating that local subpopulations could respond independently of environmental perturbations. Estimates of average longterm effective population sizes varied from 341 to 1066 and differed significantly among several of the localities. These results indicate that over time larval drift and interregional adult movement may not be sufficient to maintain population sustainability across the region and that there may be different demographic stocks at some of the localities studied. The estimate of long-term effective population size at the locality offshore of St. Croix was below the minimum threshold size considered necessary to maintain the equilibrium between the loss of adaptive genetic variance from genetic drift and its replacement by mutation. Genetic variability in mutton snapper likely is maintained at the intraregional level by aggregate spawning and random mating of local populations. This feature is perhaps ironic in that aggregate spawning also renders mutton snapper especially vulnerable to overexploitation

Summer melt regulates winter glacier flow speeds throughout Alaska

pre-printPredicting how climate change will affect glacier and ice sheet flow speeds remains a large hurdle toward accurate sea level rise forecasting. Increases in surface melt rates are known to accelerate glacier flow in summer, whereas in winter, flow speeds are believed to be relatively invariant. Here we show that wintertime flow speeds on nearly all major glaciers throughout Alaska are not only variable but are inversely related to melt from preceding summers. For each additional meter of summertime melt, we observe an 11% decrease in wintertime velocity on glaciers of all sizes, geometries, climates, and bed types. This dynamic occurs because interannual differences in summertime melt affect how much water is retained in the subglacial system during winter. The ubiquity of the dynamic indicates it occurs globally on glaciers and ice sheets not frozen to their beds and thus constitutes a new mechanism affecting sea level rise projections

Pointlike constituent quarks and scattering equivalences

In this paper scattering equivalences are used to simplify current operators in constituent quark models. The simplicity of the method is illustrated by applying it to a relativistic constituent quark model that fits the meson mass spectrum. This model requires a non-trivial constituent quark current operator to fit the pion form factor data. A model with a different confining interaction, that has the identical spectrum and can reproduce the measured pion form factor using only point-like constituent quark impulse currents is constructed. Both the original and transformed models are relativistic direct-interaction models with a light-front kinematic subgroup.Comment: 12 pages, 6 figures, corrected caption on fig

False-negative upper extremity ultrasound in the initial evaluation of patients with suspected subclavian vein thrombosis due to thoracic outlet syndrome (Paget-Schroetter syndrome)

OBJECTIVE: To assess the utilization and consequences of upper extremity Duplex ultrasound in the initial diagnostic evaluation of patients with suspected subclavian vein (SCV) thrombosis and venous thoracic outlet syndrome (VTOS). METHODS: A retrospective single-center review was conducted for patients that underwent primary surgical treatment for VTOS between 2008 and 2017, in whom an upper extremity ultrasound had been performed as the initial diagnostic test (n = 214). Clinical and treatment characteristics were compared between patients with positive and false-negative ultrasound studies. RESULTS: There were 122 men (57%) and 92 women (43%) that had presented with spontaneous idiopathic arm swelling, including 28 (13%) with proven pulmonary embolism, at a mean age of 30.7 ± 0.8 years (range 14-69). Upper extremity ultrasound had been performed 23.8 ± 12.2 days after the onset of symptoms, with confirmation of axillary-SCV thrombosis in 169 patients (79%) and negative results in 45 (21%). Of the false-negative ultrasound study reports, only 8 (18%) acknowledged limitations in visualizing the central SCV. Definitive diagnostic imaging (DDI) had been obtained by upper extremity venography in 175 (82%), computed tomography angiography in 24 (11%), and magnetic resonance angiography in 15 (7%), with 142 (66%) undergoing catheter-directed axillary-SCV thrombolysis. The mean interval between initial ultrasound and DDI was 48.9 ± 14.2 days with no significant difference between groups, but patients with a positive ultrasound were more likely to have DDI within 48 hours than those with a false-negative ultrasound (44% vs 24%; P = .02). At the time of surgical treatment, the SCV was widely patent following paraclavicular decompression and external venolysis alone in 74 patients (35%). Patch angioplasty was performed for focal SCV stenosis in 76 (36%) and bypass graft reconstruction for long-segment axillary-SCV occlusion in 63 (29%). Patients with false-negative initial ultrasound studies were significantly more likely to require SCV bypass reconstruction than those with a positive ultrasound (44% vs 25%; P = .02). CONCLUSIONS: Duplex ultrasound has significant limitations in the initial evaluation of patients with suspected SCV thrombosis, with false-negative results in 21% of patients with proven VTOS. This is rarely acknowledged in ultrasound reports, but false-negative ultrasound studies have the potential to delay definitive imaging, thrombolysis, and further treatment for VTOS. Initial false-negative ultrasound results are associated with progressive thrombus extension and a more frequent need for SCV bypass reconstruction at the time of surgical treatment

The Detectability of Pair-Production Supernovae at z < 6

Nonrotating, zero metallicity stars with initial masses 140 < M < 260 solar masses are expected to end their lives as pair-production supernovae (PPSNe), in which an electron-positron pair-production instability triggers explosive nuclear burning. Interest in such stars has been rekindled by recent theoretical studies that suggest primordial molecular clouds preferentially form stars with these masses. Since metal enrichment is a local process, the resulting PPSNe could occur over a broad range of redshifts, in pockets of metal-free gas. Using the implicit hydrodynamics code KEPLER, we have calculated a set of PPSN light curves that addresses the theoretical uncertainties and allows us to assess observational strategies for finding these objects at intermediate redshifts. The peak luminosities of typical PPSNe are only slightly greater than those of Type Ia, but they remain bright much longer (~ 1 year) and have hydrogen lines. Ongoing supernova searches may soon be able to limit the contribution of these very massive stars to < 1% of the total star formation rate density out to z=2 which already provides useful constraints for theoretical models. The planned Joint Dark Energy Mission satellite will be able to extend these limits out to z=6.Comment: 12 pages, 6 figures, ApJ in press; slightly revised version, a few typos correcte

Reusing Data and Metadata to Create New Metadata Through Machine-Learning & Other Programmatic Methods

Recent improvements in natural language processing (NLP) enable metadata to be created programmatically from reused original metadata or even the dataset itself. Transfer-learning applied to NLP has greatly improved performance and reduced training data requirements. In this talk, well compare machine-generated metadata to human-generated metadata and discuss characteristics of metadata and data archives that affect suitability for machine-learning reuse of metadata. Where as human-generated metadata is often populated once, populated from the perspective of data supplier, populated by many individuals with different words for the same thing, and limited in length, machine-generated metadata can be updated any number of times, generated from the perspective of any user, constrained to a standardized set of terms that can be evolved over time, and be any length required. Machine-learning generated metadata offers benefits but also additional needs in terms of version control, process transparency, human-computer interaction, and IT requirements. As a successful example, well discuss how a dataset of abstracts and associated human-tagged keywords from a standardized list of several thousand keywords were used to create a machine-learning model that predicted keyword metadata for open-source code projects on code.nasa.gov. Well also discuss a less successful example from data.nasa.gov to show how data archive architecture and characteristics of initial metadata can be strong controls on how easy it is to leverage programmatic methods to reuse metadata to create additional metadata

Academic Pre‐Orientation Program for Dental Students: Beginning and End of Program Evaluations, 1998–2016

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/153572/1/jddjde018039.pd