1,721 research outputs found

    Reply to "Comment on 'Scalar-tensor gravity coupled to a global monopole and flat rotation curves' "

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    In Brans-Dicke theory of gravity we explain how the extra constant value in the formula for rotation velocities of stars in a galactic halo can be obtained due to the global monopole field. We argue on a few points of the preceding Comment and discuss improvement of our model.Comment: 4 pages, RevTeX4 fil

    Effective Vortex Mass from Microscopic Theory

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    We calculate the effective mass of a single quantized vortex in the BCS superconductor at finite temperature. Based on effective action approach, we arrive at the effective mass of a vortex as integral of the spectral function J(ω)J(\omega) divided by ω3\omega^3 over frequency. The spectral function is given in terms of the quantum-mechanical transition elements of the gradient of the Hamiltonian between two Bogoliubov-deGennes (BdG) eigenstates. Based on self-consistent numerical diagonalization of the BdG equation we find that the effective mass per unit length of vortex at zero temperature is of order m(kfξ0)2m (k_f \xi_0)^2 (kfk_f=Fermi momentum, ξ0\xi_0=coherence length), essentially equaling the electron mass displaced within the coherence length from the vortex core. Transitions between the core states are responsible for most of the mass. The mass reaches a maximum value at T0.5TcT\approx 0.5 T_c and decreases continuously to zero at TcT_c.Comment: Supercedes prior version, cond-mat/990312

    Sediment transport rate-based model for rainfall-induced soil erosion

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    http://www.sciencedirect.com/science/article/B6VCG-4TP7HC2-1/2/2a6275ceb0176f80cedfb5efe5ef248

    Multiplicity of 5' Cap Structures Present on Short RNAs

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    Most RNA molecules are co- or post-transcriptionally modified to alter their chemical and functional properties to assist in their ultimate biological function. Among these modifications, the addition of 5' cap structure has been found to regulate turnover and localization. Here we report a study of the cap structure of human short (<200 nt) RNAs (sRNAs), using sequencing of cDNA libraries prepared by enzymatic pretreatment of the sRNAs with cap sensitive-specificity, thin layer chromatographic (TLC) analyses of isolated cap structures and mass spectrometric analyses for validation of TLC analyses. Processed versions of snoRNAs and tRNAs sequences of less than 50 nt were observed in capped sRNA libraries, indicating additional processing and recapping of these annotated sRNAs biotypes. We report for the first time 2,7 dimethylguanosine in human sRNAs cap structures and surprisingly we find multiple type 0 cap structures (mGpppC, 7mGpppG, GpppG, GpppA, and 7mGpppA) in RNA length fractions shorter than 50 nt. Finally, we find the presence of additional uncharacterized cap structures that wait determination by the creation of needed reference compounds to be used in TLC analyses. These studies suggest the existence of novel biochemical pathways leading to the processing of primary and sRNAs and the modifications of their RNA 5' ends with a spectrum of chemical modifications

    Simcluster: clustering enumeration gene expression data on the simplex space

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    Transcript enumeration methods such as SAGE, MPSS, and sequencing-by-synthesis EST &#x22;digital northern&#x22;, are important high-throughput techniques for digital gene expression measurement. As other counting or voting processes, these measurements constitute compositional data exhibiting properties particular to the simplex space where the summation of the components is constrained. These properties are not present on regular Euclidean spaces, on which hybridization-based microarray data is often modeled. Therefore, pattern recognition methods commonly used for microarray data analysis may be non-informative for the data generated by transcript enumeration techniques since they ignore certain fundamental properties of this space.&#xd;&#xa;&#xd;&#xa;Here we present a software tool, Simcluster, designed to perform clustering analysis for data on the simplex space. We present Simcluster as a stand-alone command-line C package and as a user-friendly on-line tool. Both versions are available at: http://xerad.systemsbiology.net/simcluster.&#xd;&#xa;&#xd;&#xa;Simcluster is designed in accordance with a well-established mathematical framework for compositional data analysis, which provides principled procedures for dealing with the simplex space, and is thus applicable in a number of contexts, including enumeration-based gene expression data

    Biopython: freely available Python tools for computational molecular biology and bioinformatics

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    Summary: The Biopython project is a mature open source international collaboration of volunteer developers, providing Python libraries for a wide range of bioinformatics problems. Biopython includes modules for reading and writing different sequence file formats and multiple sequence alignments, dealing with 3D macro molecular structures, interacting with common tools such as BLAST, ClustalW and EMBOSS, accessing key online databases, as well as providing numerical methods for statistical learning. Availability: Biopython is freely available, with documentation and source code at www.biopython.org under the Biopython license. Contact: All queries should be directed to the Biopython mailing lists, see www.biopython.org/wiki/[email protected]

    Paprikateelt in de gesloten kas: resultaten bij Themato in 2006

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    Een gesloten kas is meer dan een kas waar de luchtramen gesloten blijven. Hij wordt verwarmd door het inblazen van warme lucht in plaats van door buisrailverwarming. Gekoeld wordt er door het inblazen van koude lucht in plaats van het openen van de ramen. Met het koelen van de kaslucht wordt tegelijkertijd warmte ”geoogst”. Deze wordt in de grond opgeslagen om later weer te gebruiken. Ook kan er actief ontvochtigd worden wanneer de relatieve luchtvochtigheid te hoog is. En wellicht het belangrijkste punt: het CO2-gehalte kan zo hoog als gewenst gerealiseerd worden. Verlies van CO2 door luchting vindt niet meer plaats
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