17,639 research outputs found

    The WFCAM Multi-wavelength Variable Star Catalog

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    Stellar variability in the near-infrared (NIR) remains largely unexplored. The exploitation of public science archives with data-mining methods offers a perspective for the time-domain exploration of the NIR sky. We perform a comprehensive search for stellar variability using the optical-NIR multi-band photometric data in the public Calibration Database of the WFCAM Science Archive (WSA), with the aim of contributing to the general census of variable stars, and to extend the current scarce inventory of accurate NIR light curves for a number of variable star classes. We introduce new variability indices designed for multi-band data with correlated sampling, and apply them for pre-selecting variable star candidates, i.e., light curves that are dominated by correlated variations, from noise-dominated ones. Pre-selection criteria are established by robust numerical tests for evaluating the response of variability indices to colored noise characteristic to the data. We find 275 periodic variable stars and an additional 44 objects with suspected variability with uncertain periods or apparently aperiodic variation. Only 44 of these objects had been previously known, including 11 RR~Lyrae stars in the outskirts of the globular cluster M3 (NGC~5272). We provide a preliminary classification of the new variable stars that have well-measured light curves, but the variability types of a large number of objects remain ambiguous. We classify most of the new variables as contact binary stars, but we also find several pulsating stars, among which 34 are probably new field RR~Lyrae and 3 are likely Cepheids. We also identify 32 highly reddened variable objects close to previously known dark nebulae, suggesting that these are embedded young stellar objects. We publish our results and all light-curve data as the WFCAM Variable Star Catalog.Comment: 21 pages, 11 figure

    A Comment on Quantum Distribution Functions and the OSV Conjecture

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    Using the attractor mechanism and the relation between the quantization of H3(M)H^{3}(M) and topological strings on a Calabi Yau threefold MM we define a map from BPS black holes into coherent states. This map allows us to represent the Bekenstein-Hawking-Wald entropy as a quantum distribution function on the phase space H3(M)H^{3}(M). This distribution function is a mixed Husimi/anti-Husimi distribution corresponding to the different normal ordering prescriptions for the string coupling and deviations of the complex structure moduli. From the integral representation of this distribution function in terms of the Wigner distribution we recover the Ooguri-Strominger-Vafa (OSV) conjecture in the region "at infinity" of the complex structure moduli space. The physical meaning of the OSV corrections are briefly discussed in this limit.Comment: 27 pages. v2:reference and footnote adde

    Efficient computation of hashes

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    The sequential computation of hashes at the core of many distributed storage systems and found, for example, in grid services can hinder efficiency in service quality and even pose security challenges that can only be addressed by the use of parallel hash tree modes. The main contributions of this paper are, first, the identification of several efficiency and security challenges posed by the use of sequential hash computation based on the Merkle-Damgard engine. In addition, alternatives for the parallel computation of hash trees are discussed, and a prototype for a new parallel implementation of the Keccak function, the SHA-3 winner, is introduced

    5D Attractors with Higher Derivatives

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    We analyze higher derivative corrections to attractor geometries in five dimensions. We find corrected AdS_3xS^2 geometries by solving the equations of motion coming from a recently constructed four-derivative supergravity action in five dimensions. The result allows us to explicitly verify a previous anomaly based derivation of the AdS_3 central charges of this theory. Also, by dimensional reduction we compare our results with those of the 4D higher derivative attractor, and find complete agreement.Comment: 18 pages, harvma

    A search for RFLP markers to identify genes for aluminum tolerance in maize.

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    The objective of this study was to identify restriction fragment length polymorphism (RFLP) markers linked to QTLs that control aluminum (Al) tolerance in maize. The strategy used was bulked segregation analysis (BSA) and the genetic material utilized was an F2 population derived from a cross between the Al-susceptible inbred line L53 and Al-tolerant inbred line L1327. Both lines were developed at the National Maize and Sorghum Research Center - CNPMS/EMBRAPA. The F2 population of 1554 individuals was evaluated in a nutrient solution containing a toxic concentration of Al and relative seminal root length (RSRL) was used as a phenotype measured tolerance. The RSRL frequency distribution was continuous, but skewed towards Al-susceptible individuals. Seedlings of the F2 population which scored the highest and the lowest RSRL values were transplanted to the field and subsequently selfed to obtain F3 families. Thirty F3 families (15 Al-susceptible and 15 Al-tolerant) were evaluated in nutrient solution, using an incomplete block design, to identify those with the smallest variances for aluminum tolerance and susceptibility. Six Al-susceptible and five Al-tolerant F3 families were chosen to construct one pool of Al-susceptible individuals, and another of Al-tolerant, herein refered as "bulks", based on average values of RSRL and genetic variance. One hundred and thirteen probes were selected, with an average interval of 30 cM, covering the 10 maize chromosomes. These were tested for their ability to discriminate the parental lines. Fifty-four of these probes were polymorphic, with 46 showing codominance. These probes were hybridized with DNA from the two contrasting bulks. Three RFLPs on chromosome 8 distinguished the bulks on the basis of band intensity. DNA of individuals from the bulks was hybridized with these probes and showed the presence of heterozygous individuals in each bulk. These results suggest that in maize there is a region related to aliminum tolerance on chromosome 8

    Cold gel-like emulsions of lactoferrin subjected to ohmic heating

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    Ohmic heating is a technique that has gained increasing attention because of its capacity to produce uniform heating, and claimed electrical influence on the functional and technological properties of treated protein dispersions. The aim of this work was to evaluate the influence of ohmic heating on the properties of cold gel-like emulsions, comparing them with those obtained by conventional heating. The effect of ohmic and conventional heating on physical and structural properties of lactoferrin was also addressed. Ohmic heating treatment resulted in less pronounced aggregation of lactoferrin, when compared to conventional heating. An increase of particle size, turbidity, intrinsic and extrinsic fluorescence values and a decrease of dichroic signal after heat treatment indicated an increase of protein interactions. Emulsions produced from heat-treated lactoferrin showed gel-like behavior which was related to the emulsifying capacity of lactoferrin, combined with the emulsification method and the heat pre-treatment applied to the protein. Rheological and microstructural properties were intrinsically related to the heat treatment of the protein since ohmic heating produced gel-like emulsions with a less rigid structure. These emulsions could be interesting for food applications containing heat-sensitive ingredients.Authors would like to thank National Council for Scientific and Technological Development (CNPq) for the PhD fellowship (140271/ 2014-7) and for the research grant (307168/2016-6). This study was also supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/ 04469/2013 unit and COMPETE 2020 (POCI-01-0145-FEDER-006684) and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded byEuropean Regional Development Fund under the scope of Norte2020 - Programa Operacional Regional do Norte. Ricardo N. Pereira gratefully acknowledge to FCT the financial grant with reference SFRH/BPD/81887/2011. We also acknowledge Synlait Milk Ltd. for the donation of lactoferrin samples.info:eu-repo/semantics/publishedVersio

    Use of RFLPs to identify genes for aluminium tolerance in maize.

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    The objective of this study was to identify restriction fragment length polymorphism (RFLP) markers linked to quantitative trait loci that control. Al tolerance in maize. The strategy used was bulked segregant analysis, which is based on selecting for bulk bred true F2 individuals. The genetic material used consisted of an F2 population derived from a cross between Al susceptible (L53) and Al tolerant (L1327) maize inbred lines, Both lines were developed in the maize breeding programme of the Centro Nacional de Pesquisa de Milho e Sorgo. The relative seminal root length (RSRL) index was used as the phenotypic measure of tolerance. The frequency distribution of RSRL showed continuous distribution, which is typical of a quantitatively inherited character, with a tendency towards Al susceptible individuals. The estimated heritability was found to be 60%. This moderately high heritability value suggests that, although the caracter has a quantitative nature, it may be controlled by a small number of genes, Those seedlings of the F2 population that stored the highest and lowest values for RSRL were subsequently selfed to obtain the F3 families. These falmilies were evaluated in nutrient solution to identify those that were not segregating. On the basis of the results, five individuals were chosen for each bulk. Sixty-five probes were selected at an average interval 0f 30 cM, covering all ten maize chromosomes. For the hybridization work, a non-radioctive labelling system, using dig-dUTP and alkaline phosphatase, proved to be quite efficient and reliable, resulting in Southern blots with good resolution and allowing the menbranes to be stripped and reprobed as least three times. Twenty-three markers showed a co-dominant effect, identifying 40 RFLP loci that could distinguish the parental inbred lines. These 23 probes are now being hybridized with DNA from the two contrasting bulks. Also, a search for other informative markers is being carried out to increase genome coverage
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