20,203,149 research outputs found

    Surgery and the Spectrum of the Dirac Operator

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    We show that for generic Riemannian metrics on a simply-connected closed spin manifold of dimension at least 5 the dimension of the space of harmonic spinors is no larger than it must be by the index theorem. The same result holds for periodic fundamental groups of odd order. The proof is based on a surgery theorem for the Dirac spectrum which says that if one performs surgery of codimension at least 3 on a closed Riemannian spin manifold, then the Dirac spectrum changes arbitrarily little provided the metric on the manifold after surgery is chosen properly.Comment: 23 pages, 4 figures, to appear in J. Reine Angew. Mat

    Static and dynamic semantics of NoSQL languages

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    We present a calculus for processing semistructured data that spans differences of application area among several novel query languages, broadly categorized as "NoSQL". This calculus lets users define their own operators, capturing a wider range of data processing capabilities, whilst providing a typing precision so far typical only of primitive hard-coded operators. The type inference algorithm is based on semantic type checking, resulting in type information that is both precise, and flexible enough to handle structured and semistructured data. We illustrate the use of this calculus by encoding a large fragment of Jaql, including operations and iterators over JSON, embedded SQL expressions, and co-grouping, and show how the encoding directly yields a typing discipline for Jaql as it is, namely without the addition of any type definition or type annotation in the code

    Study of CP violation in Dalitz-plot analyses of B0 --> K+K-KS, B+ --> K+K-K+, and B+ --> KSKSK+

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    We perform amplitude analyses of the decays B0K+KKS0B^0 \to K^+K^-K^0_S, B+K+KK+B^+ \rightarrow K^+K^-K^+, and B+KS0KS0K+B^+ \to K^0_S K^0_S K^+, and measure CP-violating parameters and partial branching fractions. The results are based on a data sample of approximately 470×106470\times 10^6 BBˉB\bar{B} decays, collected with the BABAR detector at the PEP-II asymmetric-energy BB factory at the SLAC National Accelerator Laboratory. For B+K+KK+B^+ \to K^+K^-K^+, we find a direct CP asymmetry in B+ϕ(1020)K+B^+ \to \phi(1020)K^+ of ACP=(12.8±4.4±1.3)A_{CP}= (12.8\pm 4.4 \pm 1.3)%, which differs from zero by 2.8σ2.8 \sigma. For B0K+KKS0B^0 \to K^+K^-K^0_S, we measure the CP-violating phase βeff(ϕ(1020)KS0)=(21±6±2)\beta_{\rm eff} (\phi(1020)K^0_S) = (21\pm 6 \pm 2)^\circ. For B+KS0KS0K+B^+ \to K^0_S K^0_S K^+, we measure an overall direct CP asymmetry of ACP=(45+4±2)A_{CP} = (4 ^{+4}_{-5} \pm 2)%. We also perform an angular-moment analysis of the three channels, and determine that the fX(1500)f_X(1500) state can be described well by the sum of the resonances f0(1500)f_0(1500), f2(1525)f_2^{\prime}(1525), and f0(1710)f_0(1710).Comment: 35 pages, 68 postscript figures. v3 - minor modifications to agree with published versio

    Dried chicory root (Cichorium intybus L.) as a natural fructan source in rabbit diet: effects on growth performance, digestion and caecal and carcass traits

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    [EN] Three experimental diets were formulated including (per kg) 100 g oats (control diet), 50 g chicory root (Chicory 5 diet) or 100 g chicory root (Chicory 10 diet) at the expense of oats. The diets differed with respect to starch and fructan contents. In the performance trial, 120 Hyplus rabbits were randomly allocated to three groups (two rabbits per cage) and fed one of the three experimental diets between 31 and 73 days of age. At the end of the trial period, 20 rabbits per treatment were slaughtered and used for evaluation of carcass traits. In addition, the coefficients of total tract apparent digestibility (CTTAD) of the diets and caecal traits were determined from 45 to 49 days of age in 10 rabbits per treatment. The diets did not differ significantly in terms of weight gain, feed intake, feed conversion ratio, health status or carcass traits of rabbits. The CTTADs of crude protein (P=0.041) and ether extract (P=0.006) were lower in rabbits fed the Chicory 10 diet than in rabbits fed the control diet. The CTTAD of starch (P<0.001) was lower, whereas that of fructans (P<0.001) higher, in rabbits fed the diets based on chicory root. The caecum weight (P=0.037), the weight of its contents (P=0.025) and the lactic acid (P=0.028) concentration were higher in rabbits fed the Chicory 10 diet than in control rabbits. On the contrary, rabbits fed with the chicory diets showed lower caecal pH (P=0.048) than rabbits fed the control diet. There was a tendency towards a lower caecal dry matter content and higher total VFA concentration in rabbits fed the chicory diets. It may be concluded that chicory root can serve as a natural source of inulin-type fructans in rabbit feed. Diet supplementation with 10% dried chicory root beneficially affected the caecal fermentative activity in the rabbits, without significant reductions in the nutritive value of the diet, growth performance or carcass quality.Financial support for this study was provided by the institutional research project MZE 0002701404Volek, Z.; Marounek, M. (2011). Dried chicory root (Cichorium intybus L.) as a natural fructan source in rabbit diet: effects on growth performance, digestion and caecal and carcass traits. World Rabbit Science. 19(3):143-150. https://doi.org/10.4995/wrs.2011.850SWORD14315019

    Afterglow upper limits for four short duration, hard spectrum gamma-ray bursts

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    We present interplanetary network localization, spectral, and time history information for four short-duration, hard spectrum gamma-ray bursts, GRB000607, 001025B, 001204, and 010119. All of these events were followed up with sensitive radio and optical observations (the first and only such bursts to be followed up in the radio to date), but no detections were made, demonstrating that the short bursts do not have anomalously intense afterglows. We discuss the upper limits, and show that the lack of observable counterparts is consistent both with the hypothesis that the afterglow behavior of the short bursts is like that of the long duration bursts, many of which similarly have no detectable afterglows, as well as with the hypothesis that the short bursts have no detectable afterglows at all. Small number statistics do not allow a clear choice between these alternatives, but given the present detection rates of various missions, we show that progress can be expected in the near future.Comment: 19 pages, 4 figures; Revised version, accepted by the Astrophysical Journa

    Hadronic effects in leptonic systems: muonium hyperfine structure and anomalous magnetic moment of muon

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    Contributions of hadronic effects to the muonium physics and anomalous magnetic moment of muon are considered. Special attention is paid to higher-order effects and the uncertainty related to the hadronic contribution to the hyperfine structure interval in the ground state of muonium.Comment: Presented at PSAS 2002 (St. Petersburg

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    Shrinking a large dataset to identify variables associated with increased risk of Plasmodium falciparum infection in Western Kenya

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    Large datasets are often not amenable to analysis using traditional single-step approaches. Here, our general objective was to apply imputation techniques, principal component analysis (PCA), elastic net and generalized linear models to a large dataset in a systematic approach to extract the most meaningful predictors for a health outcome. We extracted predictors for Plasmodium falciparum infection, from a large covariate dataset while facing limited numbers of observations, using data from the People, Animals, and their Zoonoses (PAZ) project to demonstrate these techniques: data collected from 415 homesteads in western Kenya, contained over 1500 variables that describe the health, environment, and social factors of the humans, livestock, and the homesteads in which they reside. The wide, sparse dataset was simplified to 42 predictors of P. falciparum malaria infection and wealth rankings were produced for all homesteads. The 42 predictors make biological sense and are supported by previous studies. This systematic data-mining approach we used would make many large datasets more manageable and informative for decision-making processes and health policy prioritization

    ClaimChain: Improving the Security and Privacy of In-band Key Distribution for Messaging

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    The social demand for email end-to-end encryption is barely supported by mainstream service providers. Autocrypt is a new community-driven open specification for e-mail encryption that attempts to respond to this demand. In Autocrypt the encryption keys are attached directly to messages, and thus the encryption can be implemented by email clients without any collaboration of the providers. The decentralized nature of this in-band key distribution, however, makes it prone to man-in-the-middle attacks and can leak the social graph of users. To address this problem we introduce ClaimChain, a cryptographic construction for privacy-preserving authentication of public keys. Users store claims about their identities and keys, as well as their beliefs about others, in ClaimChains. These chains form authenticated decentralized repositories that enable users to prove the authenticity of both their keys and the keys of their contacts. ClaimChains are encrypted, and therefore protect the stored information, such as keys and contact identities, from prying eyes. At the same time, ClaimChain implements mechanisms to provide strong non-equivocation properties, discouraging malicious actors from distributing conflicting or inauthentic claims. We implemented ClaimChain and we show that it offers reasonable performance, low overhead, and authenticity guarantees.Comment: Appears in 2018 Workshop on Privacy in the Electronic Society (WPES'18

    The zCOSMOS 20k Group Catalog

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    We present an optical group catalog between 0.1 < z < 1 based on 16,500 high-quality spectroscopic redshifts in the completed zCOSMOS-bright survey. The catalog published herein contains 1498 groups in total and 192 groups with more than five observed members. The catalog includes both group properties and the identification of the member galaxies. Based on mock catalogs, the completeness and purity of groups with three and more members should be both about 83% with respect to all groups that should have been detectable within the survey, and more than 75% of the groups should exhibit a one-to-one correspondence to the "real" groups. Particularly at high redshift, there are apparently more galaxies in groups in the COSMOS field than expected from mock catalogs. We detect clear evidence for the growth of cosmic structure over the last seven billion years in the sense that the fraction of galaxies that are found in groups (in volume-limited samples) increases significantly with cosmic time. In the second part of the paper, we develop a method for associating galaxies that only have photo-z to our spectroscopically identified groups. We show that this leads to improved definition of group centers, improved identification of the most massive galaxies in the groups, and improved identification of central and satellite galaxies, where we define the former to be galaxies at the minimum of the gravitational potential wells. Subsamples of centrals and satellites in the groups can be defined with purities up to 80%, while a straight binary classification of all group and non-group galaxies into centrals and satellites achieves purities of 85% and 75%, respectively, for the spectroscopic sample.Comment: 26 pages, 21 figures, published in ApJ (along with machine-readable tables
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