11,083 research outputs found

    Electron-impact excitation of diatomic hydride cations I: HeH+^+, CH+^+, ArH+^+

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    {\bf R}-matrix calculations combined with the adiabatic nuclei approximation are used to compute electron-impact rotiational excitation rates for three closed-shell diatomic cations, HeH+^+, CH+^+, ArH+^+. Comparisons with previous studies show that an improved treatment of threshold effects leads to significant changes in the low temperature rates, furthermore the new calculations suggest that excitation of CH+^+ is dominated by ΔJ=1\Delta J =1 transitions as is expected for cations with a large dipole moment. A model for ArH+^+ excitation in the Crab Nebula is presented which gives results consistent with the observations for electron densities in the range 2−3×1032-3\times 10^3~cm−3^{-3}.Comment: MNRAS submitted 7 pages, 9 figure

    Detection of flour or farina from Triticum aestivum in macaroni by starch-gel electrophoresis of water-soluble proteins

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    A water-soluble protein component, A, has been found which appears without exception at a higher concentration in Triticum aestivum than in T. durum. Quantitation of A is achieved by referring the height of densitogram peak A to the height of peak B, which corresponds to a second component that is present in all varieties studied from both species. Extreme valúes of peak height ratio (PHR) in both species are tentatively established. On the basis of these valúes, the máximum and minimum possible contents of T. aestivum in a mixture are expressed as a function of PHR. All the varieties of T. aestivum studied are detected when they contribute more than 60% to the mixture. In over 90% of all possible binary combinations between varieties of T. aestivum and T. durum, the máximum proportion of undetected T. aestivum has been 30%

    A seven square degrees survey for galaxy-scale gravitational lenses with the HST imaging archive

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    We present the results of a visual search for galaxy-scale gravitational lenses in nearly 7 square degrees of Hubble Space Telescope (HST) images. The dataset comprises the whole imaging data ever taken with the Advanced Camera for Surveys (ACS) in the filter F814W (I-band) up to August 31st, 2011, i.e. 6.03 square degrees excluding the field of the Cosmic Evolution Survey (COSMOS) which has been the subject of a separate visual search. In addition, we have searched for lenses in the whole Wide Field Camera 3 (WFC3) near-IR imaging dataset in all filters (1.01 square degrees) up to the same date. Our primary goal is to provide a sample of lenses with a broad range of different morphologies and lens-source brightness contrast in order estimate a lower limit to the number of galaxy-scale strong lenses in the future Euclid survey in its VIS band. Our criteria to select lenses are purely morphological as we do not use any colour or redshift information.The final candidate selection is very conservative hence leading to a nearly pure but incomplete sample. We find 49 new lens candidates: 40 in the ACS images and 9 in the WFC3 images. Out of these, 16 candidates are secure lenses owing to their striking morphology, 21 more are very good candidates, and 12 more have morphologies compatible with gravitational lensing but also compatible with other astrophysical objects. It is therefore insensitive to cosmic variance and allows to estimate the number of galaxy-scale strong lenses on the sky for a putative survey depth, which is the main result of the present work. Because of the incompleteness of the sample, the estimated lensing rates should be taken as lower limits. Using these, we anticipate that a 15 000 square degrees space survey such as Euclid will find at least 60 000 galaxy-scale strong lenses down to a limiting AB magnitude of I = 24.5 (10-sigma) or I = 25.8 (3-sigma).Comment: 13 pages, 12 figures, Accepted for publication in MNRA

    Many parameter Hoelder perturbation of unbounded operators

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    If u↦A(u)u\mapsto A(u) is a C0,αC^{0,\alpha}-mapping, for 0<α≤10< \alpha \le 1, having as values unbounded self-adjoint operators with compact resolvents and common domain of definition, parametrized by uu in an (even infinite dimensional) space, then any continuous (in uu) arrangement of the eigenvalues of A(u)A(u) is indeed C0,αC^{0,\alpha} in uu.Comment: LaTeX, 4 pages; The result is generalized from Lipschitz to Hoelder. Title change

    Entropy of complex relevant components of Boolean networks

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    Boolean network models of strongly connected modules are capable of capturing the high regulatory complexity of many biological gene regulatory circuits. We study numerically the previously introduced basin entropy, a parameter for the dynamical uncertainty or information storage capacity of a network as well as the average transient time in random relevant components as a function of their connectivity. We also demonstrate that basin entropy can be estimated from time-series data and is therefore also applicable to non-deterministic networks models.Comment: 8 pages, 6 figure
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