21,643 research outputs found
A dense micro-cluster of Class 0 protostars in NGC 2264 D-MM1
We present sensitive and high angular resolution (~1") 1.3 mm continuum
observations of the dusty core D-MM1 in the Spokes cluster in NGC 2264 using
the Submillimeter Array. A dense micro-cluster of seven Class 0 sources was
detected in a 20" x 20" region with masses between 0.4 to 1.2 solar masses and
deconvolved sizes of about 600 AU. We interpret the 1.3 mm emission as arising
from the envelopes of the Class 0 protostellar sources. The mean separation of
the 11 known sources (SMA Class 0 and previously known infrared sources) within
D-MM1 is considerably smaller than the characteristic spacing between sources
in the larger Spokes cluster and is consistent with hierarchical thermal
fragmentation of the dense molecular gas in this region.Comment: Accepted for publication in the Astrophysical Journal Letter
Deepwater and Other Sharks of the U.S. Atlantic Ocean Exclusive Economic Zone
Fifty-one deepwater and other shark species of the U.S. Exclusive Economic Zone in the Atlantic Ocean and Gulf of Mexico, which currently are not included in any Federal fishery management plan, are described, with a focus on primary distribution. Many of these shark species are not well known, while others which are more common may be of particular interest. Owing to concerns regarding possible
increases in fishing effort for some of these species, as well as possible increases in bycatch rates as other fisheries move farther offshore, it is important that these
sharks be considered in marine ecosystem management efforts. This will necessitate a better understanding of their biology and distribution. Primary distribution maps are included, based on geographic information system (GIS) analyses of both published and unpublished data, and a review of the literature. The most recent systematic classification and nomenclature for these species is used
Cardiovascular consequences of cortisol excess
Cushing's syndrome is a consequence of primary or, more commonly, secondary oversecretion of cortisol. Cardiovascular disease is the major cause of morbidity and mortality in Cushing's syndrome, and excess risk remains even in effectively treated patients. The cardiovascular consequences of cortisol excess are protean and include, inter alia, elevation of blood pressure, truncal obesity, hyperinsulinemia, hyperglycemia, insulin resistance, and dyslipidemia. This review analyses the relationship of cortisol excess, both locally and at tissue level, to these cardiovascular risk factors, and to putative mechanisms for hypertension. Previous studies have examined correlations between cortisol, blood pressure, and other parameters in the general population and in Cushing's syndrome. This review also details changes induced by short-term cortisol administration in normotensive healthy men
Ground Beetles (Coleoptera: Carabidae) Inhabiting Stands of Reed Canary Grass Phalaris Arundinacea on Islands in the Lower Chippewa River, Wisconsin
We used pitfall traps to assess ground beetle diversity (Coleoptera:Carabidae) on two islands in the lower Chippewa River, Eau Claire County, Wisconsin, with rapidly expanding populations of reed canary grass, Phalaris arundinaceae. We collected 233 individuals belonging to 17 species over four, 3-9 day sampling periods, May-August 1994. All species have been documented in Wisconsin and most are considered habitat generalists. Agonum fidele, A. extensicolle, Anisodactylus harrisii and Bembidion quadrimaculatum oppositum comprised 70% of all species collected. Seven species were common to both islands, with 13 species collected on Canarygrass Island and 11 species on Ski Jump Island. Carabid species diversity (Shannonâs H=2.01) was greatest on Canarygrass Island
Circadian and Metabolic Effects of Light: Implications in Weight Homeostasis and Health
Daily interactions between the hypothalamic circadian clock at the suprachiasmatic nucleus (SCN) and peripheral circadian oscillators regulate physiology and metabolism to set temporal variations in homeostatic regulation. Phase coherence of these circadian oscillators is achieved by the entrainment of the SCN to the environmental 24-h light:dark (LD) cycle, coupled through downstream neural, neuroendocrine, and autonomic outputs. The SCN coordinate activity and feeding rhythms, thus setting the timing of food intake, energy expenditure, thermogenesis, and active and basal metabolism. In this work, we will discuss evidences exploring the impact of different photic entrainment conditions on energy metabolism. The steady-state interaction between the LD cycle and the SCN is essential for health and wellbeing, as its chronic misalignment disrupts the circadian organization at different levels. For instance, in nocturnal rodents, non-24 h protocols (i.e., LD cycles of different durations, or chronic jet-lag simulations) might generate forced desynchronization of oscillators from the behavioral to the metabolic level. Even seemingly subtle photic manipulations, as the exposure to a "dim light" scotophase, might lead to similar alterations. The daily amount of light integrated by the clock (i.e., the photophase duration) strongly regulates energy metabolism in photoperiodic species. Removing LD cycles under either constant light or darkness, which are routine protocols in chronobiology, can also affect metabolism, and the same happens with disrupted LD cycles (like shiftwork of jetlag) and artificial light at night in humans. A profound knowledge of the photic and metabolic inputs to the clock, as well as its endocrine and autonomic outputs to peripheral oscillators driving energy metabolism, will help us to understand and alleviate circadian health alterations including cardiometabolic diseases, diabetes, and obesity.Fil: Plano, Santiago AndrĂ©s. Pontificia Universidad CatĂłlica Argentina "Santa MarĂa de los Buenos Aires". Instituto de Investigaciones BiomĂ©dicas. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Oficina de CoordinaciĂłn Administrativa Houssay. Instituto de Investigaciones BiomĂ©dicas; ArgentinaFil: Casiraghi, Leandro Pablo. Universidad Nacional de Quilmes. Departamento de Ciencia y TecnologĂa. Laboratorio de CronobiologĂa; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; ArgentinaFil: Garcia Moro, Paula. Universidad Nacional de Quilmes. Departamento de Ciencia y TecnologĂa. Laboratorio de CronobiologĂa; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; ArgentinaFil: Paladino, Natalia. Universidad Nacional de Quilmes. Departamento de Ciencia y TecnologĂa. Laboratorio de CronobiologĂa; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; ArgentinaFil: Golombek, Diego AndrĂ©s. Universidad Nacional de Quilmes. Departamento de Ciencia y TecnologĂa. Laboratorio de CronobiologĂa; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; ArgentinaFil: Chiesa, Juan JosĂ©. Universidad Nacional de Quilmes. Departamento de Ciencia y TecnologĂa. Laboratorio de CronobiologĂa; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; Argentin
Fractional charge perspective on the band-gap in density-functional theory
The calculation of the band-gap by density-functional theory (DFT) methods is
examined by considering the behavior of the energy as a function of number of
electrons. It is found that the incorrect band-gap prediction with most
approximate functionals originates mainly from errors in describing systems
with fractional charges. Formulas for the energy derivatives with respect to
number of electrons are derived which clarify the role of optimized effective
potentials in prediction of the band-gap. Calculations with a recent functional
that has much improved behavior for fractional charges give a good prediction
of the energy gap and also for finite systems.
Our results indicate it is possible, within DFT, to have a functional whose
eigenvalues or derivatives accurately predict the band-gap
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