Nonmesonic Weak Decay of Λ\Lambda Hypernuclei within a Nuclear Matter Formalism

The nonmesonic weak decay of $\Lambda$ hypernuclei using nonrelativistic nuclear matter is studied. As the basic building block we use the Polarization Propagator Method developed by Oset and Salcedo. It is shown that the exact calculation of exchange terms is required. Using the Local Density Approximation we evaluate the nonmesonic decay width for $^{12}_{\Lambda}C$ and compare the result with a finite nucleus calculation, obtaining a qualitative agreement.Comment: 28 pages, 3 figure

Kinematical and nonlocality effects on the nonmesonic weak hypernuclear decay

We derive in detail the transition potential for nonmesonic lambda-hypernuclear decay in a one-meson-exchange model involving the full pseudoscalar and vector meson octets and including two effects that have been systematically omitted in the literature. These are the kinematical effects due to the difference between the lambda and nucleon masses and the first-order nonlocality corrections. Numerical results for $^{12}_\Lambda$C and $^5_\Lambda$He are presented and they show that the combined kinematical plus nonlocal corrections have an appreciable influence on the partial decay rates. However, this is somewhat diminished in the main decay observables: the total nonmesonic rate, the neutron-to-proton branching ratio, and the asymmetry parameter. The latter two still cannot be reconciled with the available experimental data. The existing theoretical predictions for the sign of the asymmetry parameter in $^5_\Lambda$He are confirmed.Comment: 36 pages; LaTeX2e; 1 eps figure. Changes: 2 more tables and 14 new references added; effects on asymmetry parameter calculated; discussions expanded; more definite conclusions reache

Fijación interna versus percutánea en fracturas diafisarias de metacarpianos: estudio de casos-controles

Objetivos: comparación de resultados clínicos de fijación interna versus fijación percutánea. Material y Métodos: estudio retrospectivo de casos y controles de 58 fracturas de metacarpianos (43 pacientes). Se incluyeron las fracturas diafisarias, sin afectación articular. Se excluyeron si había afectación del pulgar o de falanges, fracturas abiertas o más de 3 fracturas en la misma mano. Un total de 26 fracturas fueron tratadas con fijación interna y 32 con percutánea. Con un seguimiento medio de 2,5 años (rango, 1-4), se valoró la función mediante movilidad activa total (MAT), fuerza, DASH, EAV de dolor y resultado radiográfico. Resultados: con ambos tratamientos los resultados fueron satisfactorios. El tiempo de consolidación y alineación radiográfica fueron similares. Todas las valoraciones clínicas, objetivas y subjetivas, fueron mejores en el grupo de fijación interna, así como la tasa de retorno a las actividades previas. En el grupo de fijación interna hubo un caso de pseudoartrosis que fue reoperado y otro de déficit de movilidad. En el grupo percutáneo hubo 4 casos con déficit de movilidad. Discusión y conclusiones: ambas técnicas ofrecen resultados adecuados, pero con la fijación interna se obtuvieron mejores resultados respecto a movilidad, fuerza, mayor facilidad para realización de las actividades previas y retorno a las laborales y deportivas, a pesar de las complicaciones inherentes a la cirugía abiertaObjectives: comparison of outcomes with internal fixation versus percutaneous fixation. Material and Methods: retrospective case-control study of 58 metacarpal fractures (43 patients). Shaft fractures without joint involvement were included. Exclusion criteria were involvement of the thumb or phalange, open fracture, or more than 3 fractures in the same hand. There were 26 fractures treated with internal fixation and 32 with percutaneous fixation. With a mean follow-up of 2,5 years (range, 1-4), functional evaluation was performed by total active motion (TAM), strength grip, DASH, pain VAS, and radiographic results. Results: satisfactory outcomes were obtained with both treatments. Consolidation time and radiographic alignment were similar. All clinical objective and subjective assessments were better in the internal fixation group, as well as the rate of return to previous activities. In the internal fixation group, there was one case with nonunion, which was reoperated, and other with lack of motion. In the percutaneous group, there were 4 cases with mobility deficits. Discussion and conclusions: satisfactory results were offered by both methods, but better outcomes were obtained by internal fixation with regard to motion, strength, best facility for previous activities, and return to work and sport activities. All this was spite of the inherent complications of open surger

Pi-K Scattering in Full QCD with Domain-Wall Valence Quarks

We calculate the pi+ K+ scattering length in fully-dynamical lattice QCD with domain-wall valence quarks on MILC lattices with rooted staggered sea-quarks at a lattice spacing of b=0.125 fm, lattice spatial size of L =2.5 fm and at pion masses of m_pi=290, 350, 490 and 600 MeV. The lattice data, analyzed at next-to-leading order in chiral perturbation theory, allows an extraction of the full pi K scattering amplitude at threshold. Extrapolating to the physical point gives m_pi a_3/2 = -0.0574 (+- 0.0016)(+0.0024 -0.0058) and m_pi a_1/2 = 0.1725 (+- 0.0017)(+0.0023 -0.0156) for the I=3/2 and I=1/2 scattering lengths, respectively, where the first error is statistical and the second error is an estimate of the systematic due to truncation of the chiral expansion.Comment: 14 pages, 9 figure

Nonmesonic weak decay spectra of Λ4^4_\LambdaHe

To comprehend the recent Brookhaven National Laboratory experiment E788 on $^4_\Lambda$He, we have outlined a simple theoretical framework, based on the independent-particle shell model, for the one-nucleon-induced nonmesonic weak decay spectra. Basically, the shapes of all the spectra are tailored by the kinematics of the corresponding phase space, depending very weakly on the dynamics, which is gauged here by the one-meson-exchange-potential. In spite of the straightforwardness of the approach a good agreement with data is acheived. This might be an indication that the final-state-interactions and the two-nucleon induced processes are not very important in the decay of this hypernucleus. We have also found that the $\pi+K$ exchange potential with soft vertex-form-factor cutoffs $(\Lambda_\pi \approx 0.7$ GeV, $\Lambda_K \approx 0.9$ GeV), is able to account simultaneously for the available experimental data related to $\Gamma_p$ and $\Gamma_n$ for $^4_\Lambda$H, $^4_\Lambda$He, and $^5_\Lambda$He.Comment: 12 pages, 4 figures, 1 table, submitted for publication; v2: major revision, 18 pages, one author added, table, figures and bibliography change

Mathematical models for multicontainer loading problems

This paper deals with the problem of a distribution company that has to serve its customers by putting first the products on pallets and then loading the pallets onto trucks. We approach the problem by developing and solving integer linear models. We start with basic models, that include the essential features of the problem, such as respecting the dimensions of the truck, and not exceeding the total weight capacity and the maximum weigh capacity on each axle. Then, we add progressively new conditions to consider the weight and volume of pallet bases and to include other desirable features for the solutions to be useful in practice, such as the position of the center of gravity and the minimization of the number of pallets.The models have been tested on a large set of real instances involving up to 46 trucks and kindly provided to us by a distribution company. The results show that in most cases the optimal solution can be obtained in small running times. Moreover, when optimality cannot be proven, the gap is very small, so we obtain high quality solutions for all the instances that we tested

Egg yolk IgY antibodies: A therapeutic intervention against group A rotavirus in calves

Bovine group A rotavirus (RVA) is considered the major cause of diarrhea in intensively reared neonatal calves. Chicken egg yolk antibodies (IgY) are efficient in protecting neonatal calves from RVA diarrhea; however, the value of this intervention in calves once diarrhea has appeared is unclear. The aim of the present study was to evaluate the application of RVA-specific IgY as a passive treatment in those cases. The experimental groups were: G1 = RVA-specific IgY treatment; G2 = no Ab treatment; and G3 = colostrum deprived + no Ab treatment. IgY treatment significantly reduced virus shedding, diarrhea duration and severity compared to G2 and G3 calves. However, it caused a partial suppression of systemic Ab responses to RVA that could be associated with less severe diarrhea. The oral treatment with IgY for 7 days was associated with significantly higher antibody secreting cell responses in the calves compared with other groups of animals.Fil: Vega, Celina Guadalupe. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Virología; ArgentinaFil: Bok, Marina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Virología; ArgentinaFil: Saif, L.. Ohio State University; Estados UnidosFil: Fernandez, F.. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Virología; ArgentinaFil: Parreño, Gladys Viviana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Virología; Argentin

On-site detection of equid alphaherpesvirus 3 in perineal and genital swabs of mares and stallions

Equine coital exanthema (ECE) is an infectious, venereally transmitted muco-cutaneous disease affecting mares and stallions, caused by equid alphaherpesvirus 3 (EHV3). Diagnostic tools for rapid identification of EHV3 are of primary importance to diminish the risk of EHV3 dissemination at the time of breeding. In the last years, it has been shown that the performance of the insulated-isothermal polymerase chain reaction (iiPCR) is comparable to virus isolation, nested PCR and real-time PCR (qPCR) in detecting pathogens of various animal species. Analytical sensitivity and specificity of the iiPCR were compared with a qPCR, using a plasmid containing the target region of the EHV3 glycoprotein G gene and an Argentinian EHV3 isolate (E/9283/07 C3A). In order to evaluate the diagnostic performance of the iiPCR, nucleic acids of 85 perineal and genital swabs (PGS) of mares and stallions were extracted by tacoTM mini and tested by both techniques. EHV3 was detected in 46 and 45 of the 85 PGS by the iiPCR and qPCR, respectively. There was almost perfect agreement between the two diagnostic methods (98.82%; 95% CI: 95.03–100%; κ = 0.98). The iiPCR had a limit of detection of 95.00% at 6 genome equivalents per reaction and a detection endpoint for viral DNA comparable to that of the qPCR, and did not react with six non-targeted equine pathogens. The iiPCR represents a sensitive and specific method for the rapid on-site diagnosis of EHV3 infection. Its routinely implementation in breeding facilities, and artificial insemination and embryo transfer centers, will contribute to prevent the dissemination of this venereal, highly contagious disease in horses.Fil: Vissani, María Aldana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria; ArgentinaFil: Tordoya, Maria Silvia. Instituto Nacional de Tecnología Agropecuaria; ArgentinaFil: Tsai, Y.-L.. GeneReach; Estados UnidosFil: Lee, P.-Y.A.. GeneReach; Estados UnidosFil: Shen, Y.-H.. GeneReach; Estados UnidosFil: Lee, F.-C.. GeneReach; Estados UnidosFil: Wang, H.-T.T.. GeneReach; Estados UnidosFil: Parreño, Gladys Viviana. Instituto Nacional de Tecnología Agropecuaria; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Barrandeguy, María Edith. Instituto Nacional de Tecnología Agropecuaria; Argentina. Universidad del Salvador. Escuela de Veterinaria; Argentin

Natural history of a visceral leishmaniasis outbreak in highland Ethiopia

In May 2005, visceral leishmaniasis (VL) was recognized for the first time in Libo Kemken, Ethiopia, a highland region where only few cases had been reported before. We analyzed records of VL patients treated from May 25, 2005 to December 13, 2007 by the only VL treatment center in the area, maintained by Médecins Sans Frontières-Ethiopia, Operational Center Barcelona-Athens. The median age was 18 years; 77.6% were male. The overall case fatality rate was 4%, but adults 45 years or older were five times as likely to die as 5-29 year olds. Other factors associated with increased mortality included HIV infection, edema, severe malnutrition, pneumonia, tuberculosis, and vomiting. The VL epidemic expanded rapidly over a several-year period, culminating in an epidemic peak in the last third of 2005, spread over two districts, and transformed into a sustained endemic situation by 2007

Relativistic Treatment of Hypernuclear Decay

We compute for the first time the decay width of lambda-hypernuclei in a relativistic mean-field approximation to the Walecka model. Due to the small mass difference between the lambda-hyperon and its decay products---a nucleon and a pion---the mesonic component of the decay is strongly Pauli blocked in the nuclear medium. Thus, the in-medium decay becomes dominated by the non-mesonic, or two-body, component of the decay. For this mode, the lambda-hyperon decays into a nucleon and a spacelike nuclear excitation. In this work we concentrate exclusively on the pion-like modes. By relying on the analytic structure of the nucleon and pion propagators, we express the non-mesonic component of the decay in terms of the spin-longitudinal response function. This response has been constrained from precise quasielastic (p,n) measurements done at LAMPF. We compute the spin-longitudinal response in a relativistic random-phase-approximation model that reproduces accurately the quasielastic data. By doing so, we obtain hypernuclear decay widths that are considerably smaller---by factors of two or three---relative to existing nonrelativistic calculations.Comment: Revtex: 18 pages and 4 postscript figure