9,844 research outputs found
Scheming in Dimensional Regularization
We consider the most general loop integral that appears in non-relativistic
effective field theories with no light particles. The divergences of this
integral are in correspondence with simple poles in the space of complex
space-time dimensions. Integrals related to the original integral by
subtraction of one or more poles in dimensions other than D=4 lead to
nonminimal subtraction schemes. Subtraction of all poles in correspondence with
ultraviolet divergences of the loop integral leads naturally to a
regularization scheme which is precisely equivalent to cutoff regularization.
We therefore recover cutoff regularization from dimensional regularization with
a nonminimal subtraction scheme. We then discuss the power-counting for
non-relativistic effective field theories which arises in these alternative
schemes.Comment: 12 pages, additional text in opening section, version to be published
in J. Phys.
Estimativa da habilidade materna em éguas da raça pantaneira através do tempo de mamada.
Este trabalho teve como objetivo estimar a habilidade materna em éguas da raça Pantaneira através do tempo de mamada. Utilizaram-se 30 éguas com potro ao pé com idade média de 7 ,2::t 1,92 ano. Nove observadores foram distribuídos em turnos de 6h/dia, anotando-se o tempo da mamada, horário, clima, égua, sexo do potro, interrupção da mamada realizada pelo potro/égua. Não houve associação entre o tempo de mamada e o horário (manhã ou tarde), bem como horário e interrupção da mamada, independente do potro ou a égua interromper a mamada. Observou-se tempo médio de mamada (n=746) de 1,14 :t 0,59 minutos com coeficiente de variação de 42%. Houve associação (X2, P=O,OOl) entre ordem do parto e tempo da mamada, evidenciando que a habilidade materna das éguas primíparas é inferior as demais éguas com idade superior a 4,5 anos ou mais de duas crias, decrescendo após os sete anos ou mais de cinco partos
Descrição de sistemas de criação tradicionais de ovinos da Nhecolândia, Pantanal, MS.
Este trabalho tem como objetivo principal resgatar o conhecimento empírico sobre o sistema de criação tradicional de ovinos no Pantanal, caracterizando-o e descrevendo-o a partir de oito fazendas da sub-região da Nhecolândia, Pantanal, MS. Devido a crescente demanda do mercado por carne ovina, os produtores do Pantanal podem diversificar a produção animal. A região apresenta potencial para a produção de ovelhas pantaneiras para cruzamentos no planalto, produção de cordeiros (orgânicos), produção de subsistência da fazenda, entre outros. Para tanto, há a necessidade de desenvolver práticas sustentáveis de manejo da ovinocultura no Pantanalbitstream/item/80589/1/CT94.pd
Nano-porosity in GaSb induced by swift heavy ion irradiation
Nano-porous structures form in GaSb after ion irradiation with 185 MeV Au ions. The porous layer formation is governed by the dominant electronic energy loss at this energy regime. The porous layer morphology differs significantly from that previously reported for low-energy, ion-irradiated GaSb. Prior to the onset of porosity, positron annihilation lifetime spectroscopy indicates the formation of small vacancy clusters in single ion impacts, while transmission electron microscopy reveals fragmentation of the GaSb into nanocrystallites embedded in an amorphous matrix. Following this fragmentation process, macroscopic porosity forms, presumably within the amorphous phase.The authors thank the Australian Research Council for
support and the staff at the ANU Heavy Ion Accelerator
Facility for their continued technical assistance. R.C.E. acknowledges the support
from the Office of Basic Energy Sciences of the U.S. DOE
(Grant No. DE-FG02-97ER45656)
Elaboração participativa de indicadores sócio-culturais em fazendas no Pantanal.
Para construir uma ferramenta para avaliação da sustentabilidade das fazendaspantaneiras, há a necessidade de definir indicadores sócio-culturais apropriados à realidade local. Este trabalho teve como objetivo definir indicadores sociais mínimos para fazendas no Pantanal à partir de levantamentos da literatura, conhecimentos de especialistas locais e questionamentos à moradores e trabalhadores locais. Foram entrevistados 12 peões de seis fazendas do Pantanal a partir da seguinte questão: ?o que significa uma fazenda boa no Pantanal para você??
Belief heterogeneity and survival in incomplete markets
In complete markets economies (Sandroni [16]), or in economies with Pareto optimal outcomes (Blume and Easley [10]), the market selection hypothesis holds, as long as traders have identical discount factors. Traders who survive must have beliefs that merge with the truth. We show that in incomplete markets, regardless of traders’ discount factors, the market selects for a range of beliefs, at least some of which do not merge with the truth. We also show that impatient traders with incorrect beliefs can survive and that these incorrect beliefs impact prices. These beliefs may be chosen so that they are far from the truth
A perturbative solution for gravitational waves in quadratic gravity
We find a gravitational wave solution to the linearized version of quadratic
gravity by adding successive perturbations to the Einstein's linearized field
equations. We show that only the Ricci squared quadratic invariant contributes
to give a different solution of those found in Einstein's general relativity.
The perturbative solution is written as a power series in the
parameter, the coefficient of the Ricci squared term in the quadratic
gravitational action. We also show that, for monochromatic waves of a given
angular frequency , the perturbative solution can be summed out to give
an exact solution to linearized version of quadratic gravity, for
.
This result may lead to implications to the predictions for gravitational
wave backgrounds of cosmological origin.Comment: 9 pages, to appear in CQ
Spin Transfer from a Ferromagnet into a Semiconductor through an Oxide barrier
We present results on the magnetoresistance of the system Ni/Al203/n-doped
Si/Al2O3/Ni in fabricated nanostructures. The results at temperature of 14K
reveal a 75% magnetoresistance that decreases in value up to approximately 30K
where the effect disappears. We observe minimum resistance in the antiparallel
configurations of the source and drain of Ni. As a possibility, it seems to
indicate the existence of a magnetic state at the Si/oxide interface. The
average spin diffusion length obtained is of 650 nm approximately. Results are
compared to the window of resistances that seems to exist between the tunnel
barrier resistance and two threshold resistances but the spin transfer seems to
work in the range and outside the two thresholds
Epidemiological Study of Mycobacterium bovis Infection in Buffalo and Cattle in Amazonas, Brazil.
Bovine Tuberculosis (BTB) is an endemic disease in about one hundred countries, affecting the economy causing a decrease in productivity, condemnation of meat, and damaging the credibility on international trade. Additionally, Mycobacterium bovis the major causative agent for BTB can also infect humans causing a variety of clinical presentations. The aim of this study was to determine BTB prevalence and the main risk factors for theMycobacterium bovis prevalence in cattle and buffalos in Amazonas State, Brazil. Tissue samples from 151 animals (45 buffalo and 106 cattle from five herds with buffalo only, 22 herds with cattle only, and 12 herds with buffalo and cattle) were obtained from slaughterhouses under State Veterinary Inspection. M. bovis were isolated on Stonebrink medium. The positive cultures were confirmed by polymerase chain reaction (PCR) testing. The apparent herd and animal prevalence rates were 56.4 and 5.40%, respectively. Regarding animal species, the apparent prevalence rates were 3% in cattle and 11.8% in buffalo. Generalized Linear Mixed Models (GLMM) with random effect were used to assess the association with risk factors on the prevalence. Species (buffalo), herds size (>100 animals) and the presence of both species (buffalo and cattle) in the herd were the major risk factors for the infection by Mycobacterium bovis in the region. The findings reveal an urgent need for evidence-based effective intervention to reduce BTB prevalence in cattle and buffalo and prevent its spread to the human population. Studies are needed to understand why buffalo are more likely to be infected by M. bovis than cattle in Amazon. Recommendations for zoning, use of data from the inspection services to generate information regarding BTB focus, adoption of epidemiological tools, and discouragement of practices that promote the mixing of cattle and buffalo, were made
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