Joint resummation in electroweak boson production

We present a phenomenological application of the joint resummation formalism to electroweak annihilation processes at measured boson momentum Q_T. This formalism simultaneously resums at next-to-leading logarithmic accuracy large threshold and recoil corrections to partonic scattering. We invert the impact parameter transform using a previously described analytic continuation procedure. This leads to a well-defined, resummed perturbative cross section for all nonzero Q_T, which can be compared to resummation carried out directly in Q_T space. From the structure of the resummed expressions, we also determine the form of nonperturbative corrections to the cross section and implement these into our analysis. We obtain a good description of the transverse momentum distribution of Z bosons produced at the Tevatron collider.Comment: 27 pages, LaTeX, 8 figures as eps files. Some additions to earlier version, this version as published in Phys. Rev. D66 (2002) 01401

Spin structure of the nucleon: QCD evolution, lattice results and models

The question how the spin of the nucleon is distributed among its quark and gluon constituents is still a subject of intense investigations. Lattice QCD has progressed to provide information about spin fractions and orbital angular momentum contributions for up- and down-quarks in the proton, at a typical scale \mu^2~4 GeV^2. On the other hand, chiral quark models have traditionally been used for orientation at low momentum scales. In the comparison of such model calculations with experiment or lattice QCD, fixing the model scale and the treatment of scale evolution are essential. In this paper, we present a refined model calculation and a QCD evolution of lattice results up to next-to-next-to-leading order. We compare this approach with the Myhrer-Thomas scenario for resolving the proton spin puzzle.Comment: 11 pages, 6 figures, equation (9) has been corrected leading to a revised figure 1b. Revision matches published versio

Measurement of the differential cross section for the production of an isolated photon with associated jet in ppbar collisions at sqrt(s)=1.96 TeV

The process ppbar -> photon + jet + X is studied using 1.0 fb^-1 of data collected by the D0 detector at the Fermilab Tevatron ppbar collider at a center-of-mass energy sqrt(s)=1.96 TeV. Photons are reconstructed in the central rapidity region |y_gamma|<1.0 with transverse momenta in the range 30<Pt_gamma<400 GeV while jets are reconstructed in either the central |y_jet|15 GeV. The differential cross section d^3sigma/dPt_gamma dy_gamma dy_jet is measured as a function of Pt_gamma in four regions, differing by the relative orientations of the photon and the jet in rapidity. Ratios between the differential cross sections in each region are also presented. Next-to-leading order QCD predictions using different parameterizations of parton distribution functions and theoretical scale choices are compared to the data. The predictions do not simultaneously describe the measured normalization and Pt_gamma dependence of the cross section in any of the four measured regions.Comment: 13 pages, 10 figure

Ocorrência de ixodidae parasitos de capivara (Hydrochoerus hydrochaeris linnaeus, 1766) na estação ecológica do Taim, Rio Grande - RS, Brasil Occurence of ixodidae parasites of capybara (Hydrochoeurus hydrochaeris linnaeus, 1766) in the ecologic area of Taim, Rio Grande - RS, Brazil

O objetivo deste trabalho foi identificar as espécies de carrapatos observadas sobre capivaras na Estação Ecológica do Taim, Rio Grande- RS, Brasil. Foram examinadas 27 capivaras encontradas mortas por atropelamento na BR 471, em seu trecho que corta a Estação, sendo cole lados 497 carrapatos das espécies Amblyomma cooperi (=A. lutzi; = A. ypisilophorum), Amblyomma triste, Amblyomma tigrinum e ninfas do gênero Amblyomma. A. cooperi representou 68,41% dos carrapatos identificados, com uma freqüência de parasitismo de 92,60% dos hospedeiros, enquanto A. triste representou 24,75% dos carrapatos em 44,43% dos hospedeiros e A. tigrinum foi coletado em 14,81% dos hospedeiros, totalizando 1,21% dos carrapatos. As ninfas de Amblyomma sp. foram cotetadas em 18,51% dos hospedeiros apresentando um percentual de 5,63% do total de carrapatos. A relação macho : fêmea apresentou valores de 2,3 : 1 e 2 : l para o A. cooperi e A. triste, respectivamente. Todos hospedeiros apresentavam-se parasitados, com uma média de 18,4 carrapatos, variando de 1 a 64 carrapatos coletados por hospedeiro.<br>The aim of this article was the identification ofthe tick species observed on capybara in wildlife in the Ecologic Area of Taim, Rio Grande - RS; Brazil. Twenly seven capybaras found dead by trample in the road BR 471 in the Ecologic Area, wereexamined ticks coilected of the species Amblyomma cooperi (= A. lutzi and = A. ypisilophorum), Amblyomma triste, Amblyomma tigrinum and ninphs of the Genus Amblyomma. Amblyomma cooperi represented 68.41% of the ticks with a frequency of parasitism of 92.60% of the hosts; Amblyomma triste species represented 24.75% of the collected ticks m 44.43% of the hosts; Amblyomma tigrinum species were coilected m 14.81% of the hosts from a total of 1.21% of the found ticks and, the nimphs of Amblyomma were coilected in 18.51% of the hosts per forming 5.63% of the ali ticks coilected. The relation mate .female showed values of 2.3:1 and 2:1 to A. cooperiand and A. triste, respectivety. All examined hosts were found wiih ticks, with a mean of 18.4 ticks per host

Gut permeability to lactulose and mannitol differs in treated Crohn's disease and celiac disease patients and healthy subjects

The gut barrier monitors and protects the gastrointestinal tract from challenges such as microorganisms, toxins and proteins that could act as antigens. There is evidence that gut barrier dysfunction may act as a primary disease mechanism in intestinal disorders. The aim of the present study was to evaluate the barrier function towards sugars after the appropriate treatment of celiac disease and Crohn's disease patients and compare the results with those obtained with healthy subjects. Fifteen healthy volunteers, 22 celiac disease patients after 1 year of a gluten-free diet, and 31 Crohn's disease patients in remission were submitted to an intestinal permeability test with 6.0 g lactulose and 3.0 g mannitol. Six-hour urinary lactulose excretion in Crohn's disease patients was significantly higher than in both celiac disease patients (0.42 vs 0.15%) and healthy controls (0.42 vs 0.07%). Urinary lactulose excretion was significantly higher in celiac disease patients than in healthy controls (0.15 vs 0.07%). Urinary mannitol excretion in Crohn's disease patients was the same as healthy controls (21 vs 21%) and these values were significantly higher than in celiac disease patients (10.9%). The lactulose/mannitol ratio was significantly higher in Crohn's disease patients in comparison to celiac disease patients (0.021 vs 0.013) and healthy controls (0.021 vs 0.003) and this ratio was also significantly higher in celiac disease patients compared to healthy controls (0.013 vs 0.003). In spite of treatment, differences in sugar permeability were observed in both disease groups. These differences in the behavior of the sugar probes probably reflect different mechanisms for the alterations of intestinal permeability

Difilobotriasis humana en la Patagonia, Argentina Human diphyllobothriasis in Patagonia, Argentina

OBJETIVO: El objetivo del trabajo fué detectar hospedadores humanos en la zona andino patagónica argentina, teniendo en cuenta las prácticas de pesca desportiva y la importancia de los salmónidos dentro de la zona. MATERIAL Y METODO: Entre 1986 y 1995 se implementaron Campañas de Información en los laboratorios de Análisis Clínicos de la región andinopatagónica argentina, destinadas a lograr una detección más eficiente de la difilobotriasis, a través de análisis coproparasitológicos. RESULTADOS: Adicionalmente, se confeccionaron planillas destinadas a recoger información sobre las características de la infección, del tratamiento y del paciente. Durante este período se detectaron 13 nuevos casos humanos, por identificación directa del parásito o por la presencia de huevos en materia fecal. Las características de las infecciones responden a las descriptas para el género Diphyllobothrium. CONCLUSIONES: En la región, los salmónidos son los peces predilectos en la pesca deportiva. Estos peces, frecuentemente parasitados con larvas, constituyen la principal fuente de contagio para el hombre al ser consumidos insuficientemente cocidos o ahumados en frío.<br>OBJECTIVE: In view of the amateur fishing practices and the importance of salmonids in the region the study sets out to detect human hosts in the Andean-Patagonian zone. MATERIAL AND METHOD: Information campaigns were carried out by Clinical Analysis Laboratories of Andean Patagonia between 1986 and 1995 to detect diphyllobothriasis more efficiently by means of coproparasitological analysis. RESULTS: Further, forms were prepared for the collection of information about infection, treatment and the characteristics of the human host. During this period 13 new cases were registered either through direct identification of the parasite or through the presence of eggs in the faeces. The characteristics of infection are similar to those described for the genus Diphyllobothrium. CONCLUSIONS: The favourite game fish in Andean Patagonia are salmonids. This fish, often infected with plerocercoids, when eaten insufficiently cooked or cold smoked, constitutes the main source of human infection