1,303 research outputs found

    Synthesis of aminodiarylamines in the thieno[3,2-b]pyridine series and effects on tumor cell growth inhibition, cell cycle and apoptosis

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    Several series of compounds that include the thienopyridine scaffold have been reported as inhibitors of known cancer therapeutic targets or as inhibitors of cell proliferation in tumor cell lines [1,2]. Our research group has already synthesized several thieno[3,2-b]pyridine derivatives by Pd-catalyzed C-C (Suzuki and Sonogashira) and C-N (Buchwald-Hartwig) couplings and some of them have presented tumor cell growth inhibitory activity in cell lines [3- 5]

    SU(4) Instantons on Calabi-Yau Threefolds with Z_2 x Z_2 Fundamental Group

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    Structure group SU(4) gauge vacua of both weakly and strongly coupled heterotic superstring theory compactified on torus-fibered Calabi-Yau threefolds Z with Z_2 x Z_2 fundamental group are presented. This is accomplished by constructing invariant, stable, holomorphic rank four vector bundles on the simply connected cover of Z. Such bundles can descend either to Hermite-Yang-Mills instantons on Z or to twisted gauge fields satisfying the Hermite-Yang-Mills equation corrected by a non-trivial flat B-field. It is shown that large families of such instantons satisfy the constraints imposed by particle physics phenomenology. The discrete parameter spaces of those families are presented, as well as a lower bound on the dimension of the continuous moduli of any such vacuum. In conjunction with Z_2 x Z_2 Wilson lines, these SU(4) gauge vacua can lead to standard-like models at low energy with an additional U(1)_{B-L} symmetry. This U(1)_{B-L} symmetry is very helpful in naturally suppressing nucleon decay.Comment: 68 pages, no figure

    Einstein energy associated with the Friedmann -Robertson -Walker metric

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    Following Einstein's definition of Lagrangian density and gravitational field energy density (Einstein, A., Ann. Phys. Lpz., 49, 806 (1916); Einstein, A., Phys. Z., 19, 115 (1918); Pauli, W., {\it Theory of Relativity}, B.I. Publications, Mumbai, 1963, Trans. by G. Field), Tolman derived a general formula for the total matter plus gravitational field energy (P0P_0) of an arbitrary system (Tolman, R.C., Phys. Rev., 35(8), 875 (1930); Tolman, R.C., {\it Relativity, Thermodynamics & Cosmology}, Clarendon Press, Oxford, 1962)); Xulu, S.S., arXiv:hep-th/0308070 (2003)). For a static isolated system, in quasi-Cartesian coordinates, this formula leads to the well known result P0=g(T00T11T22T33) d3xP_0 = \int \sqrt{-g} (T_0^0 - T_1^1 -T_2^2 -T_3^3) ~d^3 x, where gg is the determinant of the metric tensor and TbaT^a_b is the energy momentum tensor of the {\em matter}. Though in the literature, this is known as "Tolman Mass", it must be realized that this is essentially "Einstein Mass" because the underlying pseudo-tensor here is due to Einstein. In fact, Landau -Lifshitz obtained the same expression for the "inertial mass" of a static isolated system without using any pseudo-tensor at all and which points to physical significance and correctness of Einstein Mass (Landau, L.D., and Lifshitz, E.M., {\it The Classical Theory of Fields}, Pergamon Press, Oxford, 2th ed., 1962)! For the first time we apply this general formula to find an expression for P0P_0 for the Friedmann- Robertson -Walker (FRW) metric by using the same quasi-Cartesian basis. As we analyze this new result, physically, a spatially flat model having no cosmological constant is suggested. Eventually, it is seen that conservation of P0P_0 is honoured only in the a static limit.Comment: By mistake a marginally different earlier version was loaded, now the journal version is uploade

    Magnetic Field Amplification in Galaxy Clusters and its Simulation

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    We review the present theoretical and numerical understanding of magnetic field amplification in cosmic large-scale structure, on length scales of galaxy clusters and beyond. Structure formation drives compression and turbulence, which amplify tiny magnetic seed fields to the microGauss values that are observed in the intracluster medium. This process is intimately connected to the properties of turbulence and the microphysics of the intra-cluster medium. Additional roles are played by merger induced shocks that sweep through the intra-cluster medium and motions induced by sloshing cool cores. The accurate simulation of magnetic field amplification in clusters still poses a serious challenge for simulations of cosmological structure formation. We review the current literature on cosmological simulations that include magnetic fields and outline theoretical as well as numerical challenges.Comment: 60 pages, 19 Figure

    Measurement of the ttbar Production Cross Section in ppbar Collisions at sqrt(s)=1.96 TeV using Lepton + Jets Events with Lifetime b-tagging

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    We present a measurement of the top quark pair (ttˉt\bar{t}) production cross section (σttˉ\sigma_{t\bar{t}}) in ppˉp\bar{p} collisions at s=1.96\sqrt{s}=1.96 TeV using 230 pb1^{-1} of data collected by the D0 experiment at the Fermilab Tevatron Collider. We select events with one charged lepton (electron or muon), missing transverse energy, and jets in the final state. We employ lifetime-based b-jet identification techniques to further enhance the ttˉt\bar{t} purity of the selected sample. For a top quark mass of 175 GeV, we measure σttˉ=8.61.5+1.6(stat.+syst.)±0.6(lumi.)\sigma_{t\bar{t}}=8.6^{+1.6}_{-1.5}(stat.+syst.)\pm 0.6(lumi.) pb, in agreement with the standard model expectation.Comment: 7 pages, 2 figures, 3 tables Submitted to Phys.Rev.Let

    Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector

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    A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results

    Epidemiological situation of bovine brucellosis in the State of São Paulo, Brazil

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    Realizou-se um estudo para caracterizar a situação epidemiológica da brucelose bovina no Estado de São Paulo. O Estado foi estratificado em sete circuitos produtores de bovinos, e 150 rebanhos com atividade reprodutiva foram aleatoriamente selecionados em cada um deles. No total, foram amostrados 1.073 rebanhos. Foram aletoriamente coletadas amostras de soro de 10 ou 15 fêmeas bovinas com idade ³24 meses, totalizando 8.761 animais. Os soros foram submetidos a um protocolo de testes em série, tendo o teste do antígeno acidificado tamponado como método de triagem e o da fixação de complemento como confirmatório. A prevalência estimada de rebanhos com pelo menos um animal soropositivo foi de 9,7% [7,8-11,6%], enquanto a prevalência estimada de animais soropositivos foi de 3,8% [0,7-6,9%], no Estado. Em cada rebanho foi aplicado um questionário epidemiológico para avaliar o grau de associação de possíveis fatores de risco (odds ratio, OR) com a doença. Propriedades com 87 ou mais bovinos (OR= 2,25) e compra de reprodutores (OR= 1,56) foram as variáveis mais associadas à condição de foco de brucelose. ____________________________________________________________________________________________________________ ARQUIVOA study to characterize the epidemiological situation of bovine brucellosis in the State of São Paulo was carried out. The state was stratified in seven cattle production regions and 150 herds with reproductive activity were randomly selected within each one. A total of 1,073 herds were sampled. In a second stage, 10 or 15 cows older than 24 month age (in herds with <100 cows and herds ≥100 cows, respectively) were bled at random. A total of 8,761 animals were bled. Sera were tested using a serial testing procedure with the Rose Bengal test as the screening method and the Complement Fixation as the confirmatory method. The estimated prevalence of herds with at least one positive animal was 9.7% [7.8-11.6%], whereas the estimated prevalence of positive cattle was 3.8% [0.7-6.9%] in São Paulo State. An epidemiological questionnaire was applied in each farm, allowing the evaluation of the association of selected risk factors with the disease. The characteristics associated with the brucellosis infected herds were farms with more than 87 bovines (OR= 2.25) and introduction of breeding cattle (OR= 1.56)

    Measurement of D*+/- meson production in jets from pp collisions at sqrt(s) = 7 TeV with the ATLAS detector

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    This paper reports a measurement of D*+/- meson production in jets from proton-proton collisions at a center-of-mass energy of sqrt(s) = 7 TeV at the CERN Large Hadron Collider. The measurement is based on a data sample recorded with the ATLAS detector with an integrated luminosity of 0.30 pb^-1 for jets with transverse momentum between 25 and 70 GeV in the pseudorapidity range |eta| < 2.5. D*+/- mesons found in jets are fully reconstructed in the decay chain: D*+ -> D0pi+, D0 -> K-pi+, and its charge conjugate. The production rate is found to be N(D*+/-)/N(jet) = 0.025 +/- 0.001(stat.) +/- 0.004(syst.) for D*+/- mesons that carry a fraction z of the jet momentum in the range 0.3 < z < 1. Monte Carlo predictions fail to describe the data at small values of z, and this is most marked at low jet transverse momentum.Comment: 10 pages plus author list (22 pages total), 5 figures, 1 table, matches published version in Physical Review

    Estimating the global conservation status of more than 15,000 Amazonian tree species

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    Estimates of extinction risk for Amazonian plant and animal species are rare and not often incorporated into land-use policy and conservation planning. We overlay spatial distribution models with historical and projected deforestation to show that at least 36% and up to 57% of all Amazonian tree species are likely to qualify as globally threatened under International Union for Conservation of Nature (IUCN) Red List criteria. If confirmed, these results would increase the number of threatened plant species on Earth by 22%. We show that the trends observed in Amazonia apply to trees throughout the tropics, and we predict thatmost of the world&#8217;s >40,000 tropical tree species now qualify as globally threatened. A gap analysis suggests that existing Amazonian protected areas and indigenous territories will protect viable populations of most threatened species if these areas suffer no further degradation, highlighting the key roles that protected areas, indigenous peoples, and improved governance can play in preventing large-scale extinctions in the tropics in this century
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