585 research outputs found

    Units of relativistic time scales and associated quantities

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    This note suggests nomenclature for dealing with the units of various astronomical quantities that are used with the relativistic time scales TT, TDB, TCB and TCG. It is suggested to avoid wordings like "TDB units" and "TT units" and avoid contrasting them to "SI units". The quantities intended for use with TCG, TCB, TT or TDB should be called "TCG-compatible", "TCB-compatible", "TT-compatible" or "TDB-compatible", respectively. The names of the units second and meter for numerical values of all these quantities should be used with out any adjectives. This suggestion comes from a special discussion forum created within IAU Commission 52 "Relativity in Fundamental Astronomy"

    Effect of Platelet-activating Factor on in vitro and in vivo Interleukin-6 Production

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    The aim of the present study was to investigate the possible effect of platelet-activating factor (PAF), by comparison with interleukin-1β and polyriboinositic/polyribocytidylic (poly I–C) acid, on IL-6 production by L 929 mouse fibroblasts. At concentrations above 1 μM PAF, the production of IL-6 by mouse fibroblasts was enhanced in a dose dependent fashion. At 5 μM PAF, the peak increase (60.1 ± 19.4 U/ml) was similar to that induced by 50 μg/ml poly I–C (60.0 ± 35.0 U/ml) and higher than the one evoked by 100 U/ml IL-1β (3.8 ± 1.8 U/ml). The increase of 11-6 activity induced by 5 μM PAF was maximal after a 22 h incubation period with L 929 cells. Lyso-PAF (5 μM) also increased IL-6 activity from fibroblasts to a similar extent compared with 5 μM PAF. In addition, the IL-6 activity induced by 5 μM PAF was still observed when the specific PAF antagonist, BN 52021 (10 μM), was added to the incubation medium of L 929 cells. The result suggests that the production of IL-6 by L 929 cells evoked by PAF in vitro is not receptor mediated. The in vivo effect of PAF on IL-6 production was also investigated in the rat. Two hours after intravenous injection of PAF (2 to 4 μg/kg), a dramatic increase of IL-6 activity in rat serum was observed, this effect being dose dependent. The increase of IL-6 induced by 3 μg/kg PAF was not observed when the animals were treated with the PAF antagonist, BN 52021 (1 to 60 mg/kg0. These results demonstrate that PAF modulates IL-6 production and that the in vivo effect is receptor mediated

    Hereditary sensory and autonomic neuropathy type IV and orthopaedic complications

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    SummaryHereditary sensory and autonomic neuropathy type IV (HSAN-IV) is a very rare autosomal recessive disorder characterized by recurrent episodes of unexplained fever, extensive anhidrosis, total insensitivity to pain, hypotonia, and mental retardation. The most frequent complications of this disease are corneal scarring, multiple fractures, joint deformities, osteomyelitis, and disabling self-mutilations. We reported the case of a 12-year-old boy. The goal was to discuss our decision-making and compare this case with cases described in the literature

    Deterministic Hydrological Model For Flood Risk Assessment Of Mexico City

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    Mexico City is facing problems of flooding in some areas at certain times of the year, causing important losses and damages on properties and residents including some casualties. Therefore, it is important to carry out a flood risk assessment in the catchment of Mexico City and estimate damages of probable flood events. However, limited data of observed discharges and water depths in the main rivers of the city are available, and this represents an obstacle for the understanding of flooding in Mexico City. The objective of the developed tool is to provide an efficient support to management of the flood processes by predicting the behavior of the catchment for different rainfall events and flood scenarios. The capability of a model based on MIKE SHE modeling system for the Mexico City catchment was evaluated by comparing the observed data and the simulation results during a year after a careful development based on the most important parameters for characterizing the processes. Significant and operational results (\u3e0.75 for Nash Sutcliffe coefficient) have been obtained on one of the major sub-catchments of the Mexico basin. These results demonstrate the interest to implement a deterministic hydrological model for assessing flood risks in a dense urban environment where data availability is limited. In addition, three methods for flood map creation are proposed to assist flood risk management

    Backgrounds and sensitivity of the NEXT double beta decay experiment

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    NEXT (Neutrino Experiment with a Xenon TPC) is a neutrinoless double-beta (ßß0¿ßß0¿) decay experiment that will operate at the Canfranc Underground Laboratory (LSC). It is an electroluminescent high-pressure gaseous xenon Time Projection Chamber (TPC) with separate read-out planes for calorimetry and tracking. Energy resolution and background suppression are the two key features of any neutrinoless double beta decay experiment. NEXT has both good energy resolution (<1% FWHM) at the Q value of 136Xe and an extra handle for background identification provided by track reconstruction. With the background model of NEXT, based on the detector simulation and the evaluation of the detector radiopurity, we can determine the sensitivity to a measurement of the ßß2¿ßß2¿ mode in NEW and to a ßß0¿ßß0¿ search in NEXT100. In this way we can predict the background rate of 5×10-4 counts/(keV kg yr)5×10-4 counts/(keV kg yr), and a sensitivity to the Majorana neutrino mass down to 100 meV after a 5-years run of NEXT100

    Molecular Systematics of the Deep-Sea Hydrothermal Vent Endemic Brachyuran Family Bythograeidae: A Comparison of Three Bayesian Species Tree Methods

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    Brachyuran crabs of the family Bythograeidae are endemic to deep-sea hydrothermal vents and represent one of the most successful groups of macroinvertebrates that have colonized this extreme environment. Occurring worldwide, the family includes six genera (Allograea, Austinograea, Bythograea, Cyanagraea, Gandalfus, and Segonzacia) and fourteen formally described species. To investigate their evolutionary relationships, we conducted Maximum Likelihood and Bayesian molecular phylogenetic analyses, based on DNA sequences from fragments of three mitochondrial genes (16S rDNA, Cytochrome oxidase I, and Cytochrome b) and three nuclear genes (28S rDNA, the sodium–potassium ATPase a-subunit ‘NaK’, and Histone H3A). We employed traditional concatenated (i.e., supermatrix) phylogenetic methods, as well as three recently developed Bayesian multilocus methods aimed at inferring species trees from potentially discordant gene trees. We found strong support for two main clades within Bythograeidae: one comprising the members of the genus Bythograea; and the other comprising the remaining genera. Relationships within each of these two clades were partially resolved. We compare our results with an earlier hypothesis on the phylogenetic relationships among bythograeid genera based on morphology. We also discuss the biogeography of the family in the light of our results. Our species tree analyses reveal differences in how each of the three methods weighs conflicting phylogenetic signal from different gene partitions and how limits on the number of outgroup taxa may affect the results

    Limits on the Stochastic Gravitational Wave Background from the North American Nanohertz Observatory for Gravitational Waves

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    We present an analysis of high-precision pulsar timing data taken as part of the North American Nanohertz Observatory for Gravitational waves (NANOGrav) project. We have observed 17 pulsars for a span of roughly five years using the Green Bank and Arecibo radio telescopes. We analyze these data using standard pulsar timing models, with the addition of time-variable dispersion measure and frequency-variable pulse shape terms. Sub-microsecond timing residuals are obtained in nearly all cases, and the best root-mean-square timing residuals in this set are ~30-50 ns. We present methods for analyzing post-fit timing residuals for the presence of a gravitational wave signal with a specified spectral shape. These optimally take into account the timing fluctuation power removed by the model fit, and can be applied to either data from a single pulsar, or to a set of pulsars to detect a correlated signal. We apply these methods to our dataset to set an upper limit on the strength of the nHz-frequency stochastic supermassive black hole gravitational wave background of h_c (1 yr^-1) < 7x10^-15 (95%). This result is dominated by the timing of the two best pulsars in the set, PSRs J1713+0747 and J1909-3744.Comment: To be submitted to Ap
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