2,830 research outputs found

    The Variation of Integrated Star IMFs among Galaxies

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    The integrated galaxial initial mass function (IGIMF) is the relevant distribution function containing the information on the distribution of stellar remnants, the number of supernovae and the chemical enrichment history of a galaxy. Since most stars form in embedded star clusters with different masses the IGIMF becomes an integral of the assumed (universal or invariant) stellar IMF over the embedded star-cluster mass function (ECMF). For a range of reasonable assumptions about the IMF and the ECMF we find the IGIMF to be steeper (containing fewer massive stars per star) than the stellar IMF, but below a few Msol it is invariant and identical to the stellar IMF for all galaxies. However, the steepening sensitively depends on the form of the ECMF in the low-mass regime. Furthermore, observations indicate a relation between the star formation rate of a galaxy and the most massive young stellar cluster in it. The assumption that this cluster mass marks the upper end of a young-cluster mass function leads to a connection of the star formation rate and the slope of the IGIMF above a few Msol. The IGIMF varies with the star formation history of a galaxy. Notably, large variations of the IGIMF are evident for dE, dIrr and LSB galaxies with a small to modest stellar mass. We find that for any galaxy the number of supernovae per star (NSNS) is suppressed relative to that expected for a Salpeter IMF. Dwarf galaxies have a smaller NSNS compared to massive galaxies. For dwarf galaxies the NSNS varies substantially depending on the galaxy assembly history and the assumptions made about the low-mass end of the ECMF. The findings presented here may be of some consequence for the cosmological evolution of the number of supernovae per low-mass star and the chemical enrichment of galaxies of different mass.Comment: 27 pages, accepted for publication by Ap

    Extrahepatic Biliary Papillomatosis Occurring After Removal of a Dysplastic Gall Bladder

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    A case is presented of a woman who developed obstructive jaundice secondary to dysplastic mucinous papillomatosis two years after she had undergone cholecystectomy and exploration of the common bile duct. The gall bladder was dysplastic. It is suggested that the dysplastic glands removed from the common bile duct at the second operation either represented seedlings from dysplastic areas of the gall bladder or were a manifestation of dysplastic field change

    CCD photometric and mass function study of 9 young Large Magellanic Cloud star clusters

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    We present CCD photometric and mass function study of 9 young Large Magellanic Cloud star clusters namely NGC 1767, NGC 1994, NGC 2002, NGC 2003, NGC 2006, SL 538, NGC 2011, NGC 2098 and NGC 2136. The BVRI data reaching down to V ~ 21 mag, are collected from 3.5-meter NTT/EFOSC2 in sub-arcsec seeing conditions. For NGC 1767, NGC 1994, NGC 2002, NGC 2003, NGC 2011 and NGC 2136, broad band photometric CCD data are presented for the first time. Seven of the 9 clusters have ages between 16 to 25 Myr while remaining two clusters have ages 32±432\pm4 Myr (NGC 2098) and 90±1090\pm10 Myr (NGC 2136). For 7 younger clusters, the age estimates based on a recent model and the integrated spectra are found to be systematically lower (\sim 10 Myr) from the present estimate. In the mass range of 212\sim 2 - 12 MM_{\odot}, the MF slopes for 8 out of nine clusters were found to be similar with the value of γ\gamma ranging from 1.90±0.16-1.90\pm0.16 to 2.28±0.21-2.28\pm0.21. For NGC 1767 it is flatter with γ=1.23±0.27\gamma = -1.23\pm0.27. Mass segregation effects are observed for NGC 2002, NGC 2006, NGC 2136 and NGC 2098. This is consistent with the findings of Kontizas et al. for NGC 2098. Presence of mass segregation in these clusters could be an imprint of star formation process as their ages are significantly smaller than their dynamical evolution time. Mean MF slope of γ=2.22±0.16\gamma = -2.22\pm0.16 derived for a sample of 25 young (100\le 100 Myr) dynamically unevolved LMC stellar systems provide support for the universality of IMF in the intermediate mass range 212M\sim 2-12 M_{\odot}.Comment: To appear in MNRA

    Draft Genome Sequence for Desulfovibrio africanus Strain PCS.

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    Desulfovibrio africanus strain PCS is an anaerobic sulfate-reducing bacterium (SRB) isolated from sediment from Paleta Creek, San Diego, CA. Strain PCS is capable of reducing metals such as Fe(III) and Cr(VI), has a cell cycle, and is predicted to produce methylmercury. We present the D. africanus PCS genome sequence

    Analysis of Box Culvert to Reduce Stress Values

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    At the time of construction of roads, highways a structure is placed (commonly used) to transfer the traffic, rain water, drainage from one side to another of the road is called a culvert placed beneath the road. Due to the structural use, multiple loads are placed on the box causing various types of stress which occurs on it. The paper tries to reduce the stress occurred in the box by flaring the box partially

    Multibiometric Authentication System Processed by the Use of Fusion Algorithm

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    The present day authentication system is mostly uni-model i.e having only single authentication method which can be either finger print, iris , palm veins ,etc. Thus these models have to contend with a variety of problems such as absurd or unusual data, non-versatility; un authorized attempts, and huge amount of error rates. Some of these limitations can be reduced or stopped by the use of multimodal biometric systems that integrate the evidence presented by several sources of information. This paper converses a multi biometric based authentication system based on Fusion algorithm using a key. Our work mainly focuses on the fusion algorithm, i.e fusion of finger and palm print out of which the greatest features from the above two traits are taken into account. With minimum possible features the fusion of the both the traits is carried out. Then some key is generated for multi biometric authentication. By processing the test image of a person, the identity of the person is displayed with his/her own image. By the fusion algorithm, it is found that it has less computation time compared to the existing algorithms. By matching results, we validate and authenticate the particular individual

    Context Free Grammar (CFG) Analysis for simple Kannada sentences

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    When Computational Linguistic is concerns Kannada is lagging far behind compared to Telugu and Tamil. Writing the grammar production for any south Indian language is bit difficult. Because the languages are highly inflected with three gender forms and two number forms. This paper is an effort to write Context Free Grammar for simple Kannada sentences. Kannada Language being one of the major Dravidian languages of India and it has 27th place in most spoken language in the world. But still it does not yet have computerized grammar checking methods for a given Kannada sentence. Thus, this paper highlights the process of generating context free grammar for simple Kannada sentences

    A Raman study of the Charge-Density-Wave State in A0.3_{0.3}MoO3_3 (A = K,Rb)

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    We report a comparative Raman spectroscopic study of the quasi-one-dimensional charge-density-wave systems \ab (A = K, Rb). The temperature and polarization dependent experiments reveal charge-coupled vibrational Raman features. The strongly temperature-dependent collective amplitudon mode in both materials differ by about 3 cm, thus revealing the role of alkali atom. We discus the observed vibrational features in terms of charge-density-wave ground state accompanied by change in the crystal symmetry. A frequency-kink in some modes seen in \bb between T = 80 K and 100 K supports the first-order lock-in transition, unlike \rb. The unusually sharp Raman lines(limited by the instrumental response) at very low temperatures and their temperature evolution suggests that the decay of the low energy phonons is strongly influenced by the presence of the temperature dependent charge density wave gap.Comment: 13 pages, 7 figure

    Viruses and Drug Resistant Bacteria in Groundwater of Southeastern Minnesota

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    ABSTRACT-Karst topography of soils in southeastern Minnesota is responsible for the formation of sinkholes, subsurface cracks, and underground rivers which may enhance the transportation of surface contaminants into groundwater. The present study was conducted to determine the presence of human pathogenic viruses, coliforms, fecal coliforms and coliphages in private rural wells of this area. The occurrence of drug resistance in bacteria isolated from groundwater also was studied. Coliform bacteria were detected at least once from 22 of the 26 sites sampled over 34 months. Water from 10 sites yielded drug-resistant indicator bacteria; 25 of 38 (65.8 percent) total coliforms and 9 of27 (33.3 percent) fecal coliforms tested were found to carry drug resistance. Human enteric viruses were detected by DNA hybridization and/or virus isolation techniques in nine samples from seven different sites, some in the absence of fecal coliforms. Of the 161 samples tested for coliphages, 13 samples from seven sites were found positive. On two occasions, coliphages were isolated from samples in which coliforms were absent. These findings indicate that potential public health problems exist in this region

    Complete Genome Sequence of Pelosinus fermentans JBW45, a Member of a Remarkably Competitive Group of Negativicutes in the Firmicutes Phylum.

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    The genome of Pelosinus fermentans JBW45, isolated from a chromium-contaminated site in Hanford, Washington, USA, has been completed with PacBio sequencing. Nine copies of the rRNA gene operon and multiple transposase genes with identical sequences resulted in breaks in the original draft genome and may suggest genomic instability of JBW45
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