2,571 research outputs found

    Supernova pencil beam survey

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    Type Ia supernovae (SNe Ia) can be calibrated to be good standard candles at cosmological distances. We propose a supernova pencil beam survey that could yield between dozens to hundreds of SNe Ia in redshift bins of 0.1 up to z=1.5z=1.5, which would compliment space based SN searches, and enable the proper consideration of the systematic uncertainties of SNe Ia as standard candles, in particular, luminosity evolution and gravitational lensing. We simulate SNe Ia luminosities by adding weak lensing noise (using empirical fitting formulae) and scatter in SN Ia absolute magnitudes to standard candles placed at random redshifts. We show that flux-averaging is powerful in reducing the combined noise due to gravitational lensing and scatter in SN Ia absolute magnitudes. The SN number count is not sensitive to matter distribution in the universe; it can be used to test models of cosmology or to measure the SN rate. The SN pencil beam survey can yield a wealth of data which should enable accurate determination of the cosmological parameters and the SN rate, and provide valuable information on the formation and evolution of galaxies. The SN pencil beam survey can be accomplished on a dedicated 4 meter telescope with a square degree field of view. This telescope can be used to conduct other important observational projects compatible with the SN pencil beam survey, such as QSOs, Kuiper belt objects, and in particular, weak lensing measurements of field galaxies, and the search for gamma-ray burst afterglows.Comment: Final version, to appear in ApJ, 531, #2 (March 10, 2000). 22 pages including 5 figures. Improved presentatio

    A New Local Temperature Distribution Function for X-ray Clusters: Cosmological Applications

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    (abridged) We present a new determination of the local temperature function of X-ray clusters. We use a new sample comprising fifty clusters for which temperature information is now available, making it the largest complete sample of its kind. It is therefore expected to significantly improve the estimation of the temperature distribution function of moderately hot clusters. We find that the resulting temperature function is higher than previous estimations, but agrees well with the temperature distribution function inferred from the BCS and RASS luminosity function. We have used this sample to constrain the amplitude of the matter fluctuations on cluster's scale of 8Ω03−1h−18\sqrt[3]{\Omega_0}^{-1}h^{-1}Mpc, assuming a mass-temperature relation based on recent numerical simulations. We find σ8=0.6±0.02\sigma_8 = 0.6\pm 0.02 for an Ω0=1\Omega_0 = 1 model. Our sample provides an ideal reference at z∌0z \sim 0 to use in the application of the cosmological test based on the evolution of X-ray cluster abundance (Oukbir & Blanchard 1992, 1997). Using Henry's sample, we find that the abundance of clusters at z=0.33z = 0.33 is significantly smaller, by a factor larger than 2, which shows that the EMSS sample provides strong evidence for evolution of the cluster abundance. A likelihood analysis leads to a rather high value of the mean density parameter of the universe: Ω=0.92±0.22\Omega =0.92 \pm 0.22 (open case) and Ω=0.86±0.25\Omega =0.86 \pm 0.25 (flat case), which is consistent with a previous, independent estimation based on the full EMSS sample by Sadat et al.(1998). Some systematic uncertainties which could alter this result are briefly discussed.Comment: 31 pages, 12 figures, mathches the version published in Astronomy and Astrophysic

    Bringing Background into the Foreground: Making All Classes Equal in Weakly-supervised Video Semantic Segmentation

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    Pixel-level annotations are expensive and time-consuming to obtain. Hence, weak supervision using only image tags could have a significant impact in semantic segmentation. Recent years have seen great progress in weakly-supervised semantic segmentation, whether from a single image or from videos. However, most existing methods are designed to handle a single background class. In practical applications, such as autonomous navigation, it is often crucial to reason about multiple background classes. In this paper, we introduce an approach to doing so by making use of classifier heatmaps. We then develop a two-stream deep architecture that jointly leverages appearance and motion, and design a loss based on our heatmaps to train it. Our experiments demonstrate the benefits of our classifier heatmaps and of our two-stream architecture on challenging urban scene datasets and on the YouTube-Objects benchmark, where we obtain state-of-the-art results.Comment: 11 pages, 4 figures, 7 tables, Accepted in ICCV 201

    Gun Violence and Human Rights

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    This article challenges the prevailing narrative regarding gun rights in the United States by viewing them through the lens of human rights. In doing so, it makes five central claims. First, that the U.S. gun violence crisis implicates the rights enshrined in human rights treaties and customary international law. Second, that the U.S. government is responsible for addressing these rights violations. Third, that the U.S. government’s failure to do so is violative of its international human rights obligations. Fourth, that the Second Amendment does not pose a legal bar to the sorts of government actions that would meet this obligation. And, fifth, that both international and domestic remedies are available to those harmed by the U.S. government’s inaction

    Comparison of Knee-High and Thigh-High Graduated Compression Stockings in Preventing Deep Vein Thrombosis in Patients with Hemorrhagic Stroke

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    Background: Deep Vein Thrombosis (DVT) is a common complication in patients with hemorrhagic stroke. Prophylaxis and treatment of DVT in these patients is very difficult because there are some limitations regarding the use of anticoagulant drugs. Objectives: The purpose of this study was to compare the effectiveness of knee-high and thigh-high graduated compression stockings in preventing DVT in patients with hemorrhagic stroke. Methods: In this clinical trial, 88 patients with hemorrhagic stroke were randomly assigned to two groups to receive either thighhigh or knee-high graduated compression stockings as prophylaxis for DVT. The prevalence of DVT was studied using clinical symptoms and Doppler ultrasound. Chi-square and Mann Whitney U tests were used to analyze the data. Results: In the thigh-high stockings group, 11 patients (26.8%) and in the knee-high stockings group, 18 patients (38.3%) were affected by DVT during the study. However, no significant difference was observed between the two groups (P = 0.25). Conclusions: There was no significant difference between the two groups in the incidence of DVT. Therefore, either knee-high or thigh-high stockings can be used as prophylaxis, depending on patients’ will, cost and ease of use

    Effect of Ginger on Relieving Nausea and Vomiting in Pregnancy: A Randomized, Placebo-Controlled Trial

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    Background: Nausea and vomiting are common and unpleasant complications in pregnancy. Although many alternative therapists support the use of ginger for nausea and vomiting of pregnancy, there is currently insufficient clinical evidence to support its use in this condition Objectives: The present study was performed to assess the effectiveness of ginger in the treatment of nausea and vomiting in pregnancy. Patients and Methods: This seven-day clinical trial was performed on 120 eligible pregnant women with symptoms of mild to moderate nausea and vomiting before 16 weeks gestation. They were divided into; ginger, placebo and control groups, by block randomization. Women were asked to record their nausea and vomiting for three days, and then participants received either ginger capsules, or a placebo for four days. No intervention was done with the control group. Data measure was self-recorded symptoms according to the Rhodes Index. Data were analyzed by ANOVA, ANCOVA, Kruskal-Wallis, Chi-square, and Fisher’s exact test, for the quantitative and qualitative variables. Results: There were no statistical differences in the baseline demographics between the three groups apart from age of marriage and wanted or unwanted pregnancy. An ANCOVA test (covariance test) showed significant differences in mean scores after the intervention in the three groups (P < 0.001). Conclusions: Ginger was effective for the relief of mild to moderate nausea and vomiting in pregnant women at less than 16 weeks gestation

    High Redshift Supernovae in the Hubble Deep Field

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    Two supernovae detected in the Hubble Deep Field using the original December 1995 epoch and data from a shorter (63000 s in F814W) December 1997 visit with HST are discussed. The supernovae (SNe) are both associated with distinct galaxies at redshifts of 0.95 (spectroscopic) from Cohen etal. (1996) and 1.32 (photometric) from the work of Fernandez-Soto, Lanzetta, and Yahil (1998). These redshifts are near, in the case of 0.95, and well beyond for 1.32 the greatest distance reported previously for SNe. We show that our observations are sensitive to SNe to z < 1.8 in either epoch for an event near peak brightness. Detailed simulations are discussed that quantify the level at which false events from our search phase would start to to arise, and the completeness of our search as a function of both SN brightness and host galaxy redshift. The number of Type Ia and Type II SNe expected as a function of redshift in the two HDF epochs are discussed in relation to several published predictions and our own detailed calculations. A mean detection frequency of one SN per epoch for the small HDF area is consistent with expectations from current theory.Comment: 62 pages, 17 figures, ApJ 1999 in pres
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