Observation of Scaling Violations in Scaled Momentum Distributions at HERA

Charged particle production has been measured in deep inelastic scattering (DIS) events over a large range of $x$ and $Q^2$ using the ZEUS detector. The evolution of the scaled momentum, $x_p$, with $Q^2,$ in the range 10 to 1280 $GeV^2$, has been investigated in the current fragmentation region of the Breit frame. The results show clear evidence, in a single experiment, for scaling violations in scaled momenta as a function of $Q^2$.Comment: 21 pages including 4 figures, to be published in Physics Letters B. Two references adde

D* Production in Deep Inelastic Scattering at HERA

This paper presents measurements of D^{*\pm} production in deep inelastic scattering from collisions between 27.5 GeV positrons and 820 GeV protons. The data have been taken with the ZEUS detector at HERA. The decay channel $D^{*+}\to (D^0 \to K^- \pi^+) \pi^+$ (+ c.c.) has been used in the study. The $e^+p$ cross section for inclusive D^{*\pm} production with $5<Q^2<100 GeV^2$ and $y<0.7$ is 5.3 \pms 1.0 \pms 0.8 nb in the kinematic region {$1.3<p_T(D^{*\pm})<9.0$ GeV and $| \eta(D^{*\pm}) |<1.5$}. Differential cross sections as functions of p_T(D^{*\pm}), $\eta(D^{*\pm}), W$ and $Q^2$ are compared with next-to-leading order QCD calculations based on the photon-gluon fusion production mechanism. After an extrapolation of the cross section to the full kinematic region in p_T(D^{*\pm}) and $\eta$(D^{*\pm}), the charm contribution $F_2^{c\bar{c}}(x,Q^2)$ to the proton structure function is determined for Bjorken $x$ between 2 $\cdot$ 10$^{-4}$ and 5 $\cdot$ 10$^{-3}$.Comment: 17 pages including 4 figure

Avaliação do efeito trombogênico da perfusão regional intravenosa com gentamicina em equinos

The distal end of the horse is often affected by septic processes that are difficult to treat. The intravenous regional perfusion of antimicrobials is a treatment option for these processes, increasing the local concentration of the drug using small doses, and is currently widely used, but still presenting various issues. The aim of this study was to evaluate the possible complications of the technique, using gentamicin at a dose of 2.2mg/kg in the cephalic vein of horses. Fifteen healthy horses were assigned to three groups of 5 animals. Group 1, tourniquet group (TG), group 2, tourniquet and 40mL of physiologic saline solution (SPG) and group 3, tourniquet and 2.2mg/kg gentamicin completed to 40mL by the addition of physiologic saline solution (ASG). The perfused limb was evaluated by thermography and ultrasound Duplex color over time. The data were analyzed by Tukey's and Dunnett's method, and the accepted significance level was P<0.05. All groups showed thrombotic score zero and there was no significant difference between groups in the average diameter of the vein and member temperatures. The intravenous regional antibiosis with 2.2mg/kg of gentamicin as a single dose did not affect the development of thrombosis in the cephalic vein.A extremidade distal dos equinos é frequentemente afetada por processos sépticos de difícil tratamento. A perfusão regional intravenosa de antimicrobianos é uma opção de tratamento para esses processos, pois aumenta a concentração do fármaco no local mediante pequenas doses. Entretanto, apesar de ser muito utilizada recentemente, ainda apresenta várias questões. O objetivo deste trabalho foi avaliar as possíveis complicações da técnica, com o uso da gentamicina na dose de 2,2mg/kg na veia cefálica de equinos. Utilizaram-se 15 equinos hígidos divididos aleatoriamente em três grupos de cinco animais: grupo somente com torniquete (GT), grupo que recebeu 40mL de solução fisiológica (GSF) e grupo que recebeu gentamicina na dose de 2,2mg/kg, acrescida de solução fisiológica até completar o volume de 40mL (GSG). O membro perfundido foi avaliado por termografia e ultrassonografia duplex em cores ao longo do tempo. Os dados foram submetidos à análise pelos testes de Tukey e de Dunnett, e o nível de significância adotado foi de P<0,05. Todos os grupos apresentaram escore trombótico zero, e não houve diferença significativa entre os grupos quanto ao diâmetro médio da veia e da temperatura dos membros. A antibiose intravenosa regional com 2,2mg/kg de gentamicina, em dose única, não acarretou o desenvolvimento de trombose na veia cefálicaFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Universidade Estadual Paulista FMVZUniversidade Estadual Paulista FMV

Measurement of the reaction γ∗p→ϕp\gamma^*p \rightarrow \phi p in deep inelastic e+pe^+p scattering at HERA

The production of phi mesons in the reaction e(+)p --> e(+)phi p (phi --> K+K-), for 7 phi p cross section rises strongly with W. This behaviour is similar to that previously found for the gamma*p --> rho(0)p cross section. This strong dependence cannot be explained by production through soft pomeron exchange, It is, however, consistent with perturbative QCD expectations, where it reflects the rise of the gluon momentum density in the proton at small x. The ratio of sigma(phi)/sigma(rho(0)), which has previously been determined by ZEUS to be 0.065 +/- 0.013 (stat.) in photoproduction at a mean W of 70 GeV, is measured to be 0.18 +/- 0.05 (stat.) +/- 0.03 (syst.) at a mean Q(2) of 12.3 GeV2 and mean W of approximate to 100 GeV and is thus approaching at large Q(2) the value of 2/9 predicted from the quark charges of the vector mesons and a flavour independent production mechanism

Observation of Events with an Energetic Forward Neutron in Deep Inelastic Scattering at HERA

In deep inelastic neutral current scattering of positrons and protons at the center of mass energy of 300 GeV, we observe, with the ZEUS detector, events with a high energy neutron produced at very small scattering angles with respect to the proton direction. The events constitute a fixed fraction of the deep inelastic, neutral current event sample independent of Bjorken x and Q2 in the range 3 · 10-4 \u3c xBJ \u3c 6 · 10-3 and 10 \u3c Q2 \u3c 100 GeV2

Atomic Species Associated with the Portevin–Le Chatelier Effect in Superalloy 718 Studied by Mechanical Spectroscopy

In many Ni-based superalloys, dynamic strain aging (DSA) generates an inhomogeneous plastic deformation resulting in jerky flow known as the Portevin--Le Chatelier (PLC) effect. This phenomenon has a deleterious effect on the mechanical properties and, at high temperature, is related to the diffusion of substitutional solute atoms toward the core of dislocations. However, the question about the nature of the atomic species responsible for the PLC effect at high temperature still remains open. The goal of the present work is to answer this important question; to this purpose, three different 718-type and a 625 superalloy were studied through a nonconventional approach by mechanical spectroscopy. The internal friction (IF) spectra of all the studied alloys show a relaxation peak P718 (at 885 K for 0.1 Hz) in the same temperature range, 700 K to 950 K, as the observed PLC effect. The activation parameters of this relaxation peak have been measured, Ea(P718){\thinspace}={\thinspace}2.68{\thinspace}{\textpm}{\thinspace}0.05 eV, $\tau$0{\thinspace}={\thinspace}2{\textperiodcentered}10-15 {\textpm} 1 s as well as its broadening factor $\beta${\thinspace}={\thinspace}1.1. Experiments on different alloys and the dependence of the relaxation strength on the amount of Mo attribute this relaxation to the stress-induced reorientation of Mo-Mo dipoles due to the short distance diffusion of one Mo atom by exchange with a vacancy. Then, it is concluded that Mo is the atomic species responsible for the high-temperature PLC effect in 718 superallo