3,532 research outputs found

    Models of the SL9 Impacts II. Radiative-hydrodynamic Modeling of the Plume Splashback

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    We model the plume "splashback" phase of the SL9 collisions with Jupiter using the ZEUS-3D hydrodynamic code. We modified the Zeus code to include gray radiative transport, and we present validation tests. We couple the infalling mass and momentum fluxes of SL9 plume material (from paper I) to a jovian atmospheric model. A strong and complex shock structure results. The modeled shock temperatures agree well with observations, and the structure and evolution of the modeled shocks account for the appearance of high excitation molecular line emission after the peak of the continuum light curve. The splashback region cools by radial expansion as well as by radiation. The morphology of our synthetic continuum light curves agree with observations over a broad wavelength range (0.9 to 12 microns). A feature of our ballistic plume is a shell of mass at the highest velocities, which we term the "vanguard". Portions of the vanguard ejected on shallow trajectories produce a lateral shock front, whose initial expansion accounts for the "third precursors" seen in the 2-micron light curves of the larger impacts, and for hot methane emission at early times. Continued propagation of this lateral shock approximately reproduces the radii, propagation speed, and centroid positions of the large rings observed at 3-4 microns by McGregor et al. The portion of the vanguard ejected closer to the vertical falls back with high z-component velocities just after maximum light, producing CO emission and the "flare" seen at 0.9 microns. The model also produces secondary maxima ("bounces") whose amplitudes and periods are in agreement with observations.Comment: 13 pages, 9 figures (figs 3 and 4 in color), accepted for Ap.J. latex, version including full figures at: http://oobleck.tn.cornell.edu/jh/ast/papers/slplume2-20.ps.g

    NRG approach to the transport through a finite Hubbard chain connected to reservoirs

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    We study the low-energy properties of a Hubbard chain of finite size N_C connected to two noninteracting leads using the numerical renormalization group (NRG) method. The results obtained for N_C = 3 and 4 show that the low-lying eigenstates have one-to-one correspondence with the free quasi-particle excitations of a local Fermi liquid. It enables us to determine the transport coefficients from the fixed-point Hamiltonian. At half-filling, the conductance for even N_C decreases exponentially with increasing U showing a tendency towards the development of a Mott-Hubbard gap. In contrast, for odd N_C, the Fermi-liquid nature of the low-energy states assures perfect transmission through the Kondo resonance. Our formulation to deduce the conductance from the fixed-point energy levels can be applied to various types of interacting systems.Comment: One typo found in Eq.(3) in previous version has been correcte

    Targeted Therapy for Metastatic Renal Carcinoma: An Update

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    Conventional chemotherapy is associated with poor outcomes in metastatic renal cell carcinoma (RCC). Advances in the understanding of tumor molecular biology and the implementation of new drugs that target these molecular pathways have increased the arsenal against advanced RCC and improved outcomes in these patients. Herein, we briefly describe the latest data on targeted therapies used in the treatment of advanced renal cell carcinoma. Search strategy was performed according to PRISMA guidelines. Abstracts of relevant studies published in PubMed between 2000 and 2014 were analyzed by two authors. Abstracts were selected if they were published in English, data reported was of phase II or III clinical trials, and outcomes followed FDA approval.  If consensus between the two authors was achieved, they were included in the review. Key words used were “target therapy” and “metastatic renal cell carcinoma”. The results of the studies analyzed in this review support the benefits of targeted therapy in metastatic RCC. These include improved progression-free survival, overall survival, and quality of life as well as reduced toxicities compared to immunotherapy. The improvement in outcomes in metastatic RCC makes these drugs a preferred option as a primary treatment for these patients.

    Composición química y actividad antifúngica del látex de Argemone mexicana (Cardo Santo)

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    Ecuador cuenta con una amplia diversidad de especies vegetales que han sido usadas como medicina tradicional, entre ellas la especie Argemone mexicana (Cardo Santo), la cual se encuentra distribuida en varias zonas de la sierra central, el látex es usado en forma tópica, de manera directa y en emplastos, debido a que presenta propiedades antifúngicas. El presente trabajo de investigación se enfoca en la caracterización e identificación de las especies químicas presentes en el látex de dicha especie, para lo cual se obtuvieron dos extractos (acuoso y etanólico). Se realizaron cortes en la planta y mediante jeringuillas esterilizadas, se extrajo el látex para su posterior caracterización por medio de un tamizaje fitoquímico (análisis químico referencial) y la técnica de CG-EM (cromatografía de gases acoplado a espectrometría de masas). Paralelamente, se realizaron pruebas de bioactividad, mediante la técnica de Kirby Bauer, con las cepas de hongos Botrytis cinerea y Cladoosporium spp, y con dos medios de cultivo (agar PDA y Saoubourad), donde se logró comprobar la actividad antifúngica del extracto acuoso del látex a concentraciones de 10 µl y 20 µl del extracto, mediante la observación evidente de la formación de halos de inhibición bien definidos. Utilizando los metabolitos secundarios identificados por cromatografía de gases-detector de masas se realizó una comparación de sus estructuras químicas y bioactividad con trabajos similares reportados en la literatura, lo que permitió atribuirle la actividad antifúngica a los compuestos identificados, pudiendo ser responsables de la actividad biológica observada.Ecuador has a wide diversity of plant species that have been used as traditional medicine, including the Argemone mexicana specie (Cardo Santo), which is distributed in various areas of the central highlands, latex is used topically, directly and in plasters, because it has antifungal properties. The present research work focuses on the characterization and identification of the chemical species present in the latex of said species, for which two extracts (aqueous and ethanolic) were obtained. Cuts were made in the plant and the latex was extracted using sterilized syringes for its subsequent characterization by means of a phytochemical screening (referential chemical analysis) and GC-MS technique (gas chromatography coupled to mass spectrometry). At the same time, bioactivity tests were carried out, using the Kirby Bauer technique, in the strains of fungi Botrytis cinerea and Cladoosporium spp, and with two culture media (PDA and Saubourad agar), where it was possible to verify the antifungal activity of the aqueous extract of the latex at concentrations of 10 µl and 20 µl of the extract, through the evident observation of the formation of well-defined inhibition halos. Using the secondary metabolites identified by gas chromatography-mass detector, a comparison of their chemical structures and bioactivity with similar works reported in the literature was made, which allowed attributing the antifungal activity to the identified compounds that could be responsible for the observed biological activity.&nbsp

    Search for right-handed W bosons in top quark decay

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    We present a measurement of the fraction f+ of right-handed W bosons produced in top quark decays, based on a candidate sample of ttˉt\bar{t} events in the lepton+jets decay mode. These data correspond to an integrated luminosity of 230pb^-1, collected by the DO detector at the Fermilab Tevatron ppˉp\bar{p} Collider at sqrt(s)=1.96 TeV. We use a constrained fit to reconstruct the kinematics of the ttˉt\bar{t} and decay products, which allows for the measurement of the leptonic decay angle θ\theta^* for each event. By comparing the cosθ\cos\theta^* distribution from the data with those for the expected background and signal for various values of f+, we find f+=0.00+-0.13(stat)+-0.07(syst). This measurement is consistent with the standard model prediction of f+=3.6x10^-4.Comment: Submitted to Physical Review D Rapid Communications 7 pages, 3 figure

    Measurement of Semileptonic Branching Fractions of B Mesons to Narrow D** States

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    Using the data accumulated in 2002-2004 with the DO detector in proton-antiproton collisions at the Fermilab Tevatron collider with centre-of-mass energy 1.96 TeV, the branching fractions of the decays B -> \bar{D}_1^0(2420) \mu^+ \nu_\mu X and B -> \bar{D}_2^{*0}(2460) \mu^+ \nu_\mu X and their ratio have been measured: BR(\bar{b}->B) \cdot BR(B-> \bar{D}_1^0 \mu^+ \nu_\mu X) \cdot BR(\bar{D}_1^0 -> D*- pi+) = (0.087+-0.007(stat)+-0.014(syst))%; BR(\bar{b}->B)\cdot BR(B->D_2^{*0} \mu^+ \nu_\mu X) \cdot BR(\bar{D}_2^{*0} -> D*- \pi^+) = (0.035+-0.007(stat)+-0.008(syst))%; and (BR(B -> \bar{D}_2^{*0} \mu^+ \nu_\mu X)BR(D2*0->D*- pi+)) / (BR(B -> \bar{D}_1^{0} \mu^+ \nu_\mu X)\cdot BR(\bar{D}_1^{0}->D*- \pi^+)) = 0.39+-0.09(stat)+-0.12(syst), where the charge conjugated states are always implied.Comment: submitted to Phys. Rev. Let

    Measurement of the B0_s semileptonic branching ratio to an orbitally excited D_s** state, Br(B0_s -> Ds1(2536) mu nu)

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    In a data sample of approximately 1.3 fb-1 collected with the D0 detector between 2002 and 2006, the orbitally excited charm state D_s1(2536) has been observed with a measured mass of 2535.7 +/- 0.6 (stat) +/- 0.5 (syst) MeV via the decay mode B0_s -> D_s1(2536) mu nu X. A first measurement is made of the branching ratio product Br(b(bar) -> D_s1(2536) mu nu X).Br(D_s1(2536)->D* K0_S). Assuming that D_s1(2536) production in semileptonic decay is entirely from B0_s, an extraction of the semileptonic branching ratio Br(B0_s -> D_s1(2536) mu nu X) is made.Comment: 7 pages, 2 figures, LaTeX, version with minor changes as accepted by Phys. Rev. Let

    Measurement of the Lifetime Difference in the B_s^0 System

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    We present a study of the decay B_s^0 -> J/psi phi We obtain the CP-odd fraction in the final state at time zero, R_perp = 0.16 +/- 0.10 (stat) +/- 0.02 (syst), the average lifetime of the (B_s, B_sbar) system, tau (B_s^0) =1.39^{+0.13}_{-0.16} (stat) ^{+0.01}_{-0.02} (syst) ps, and the relative width difference between the heavy and light mass eigenstates, Delta Gamma/Gamma = (Gamma_L - Gamma_H)/Gamma =0.24^{+0.28}_{-0.38} (stat) ^{+0.03}_{-0.04} (syst). With the additional constraint from the world average of the B_s^0$lifetime measurements using semileptonic decays, we find tau (B_s^0)= 1.39 +/- 0.06 ~ps and Delta Gamma/\Gamma = 0.25^{+0.14}_{-0.15}. For the ratio of the B_s^0 and B^0 lifetimes we obtain tau(B_s^0)/tau(B^0)} = 0.91 +/- 0.09 (stat) +/- 0.003 (syst).Comment: submitted to Phys. Rev. Lett. FERMILAB-PUB-05-324-

    Differential branching fraction and angular analysis of the decay B0→K∗0μ+μ−

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    The angular distribution and differential branching fraction of the decay B 0→ K ∗0 μ + μ − are studied using a data sample, collected by the LHCb experiment in pp collisions at s√=7 TeV, corresponding to an integrated luminosity of 1.0 fb−1. Several angular observables are measured in bins of the dimuon invariant mass squared, q 2. A first measurement of the zero-crossing point of the forward-backward asymmetry of the dimuon system is also presented. The zero-crossing point is measured to be q20=4.9±0.9GeV2/c4 , where the uncertainty is the sum of statistical and systematic uncertainties. The results are consistent with the Standard Model predictions
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