Adensamentos periódicos do rebanho bovino de corte no Pantanal e seus reflexos na eficiência reprodutiva: um relato.

Os adensamentos consistem em promover, periodicamente, rodeios (agrupar o rebanho de cria), sob a hipótese de que a aproximação de touros e vacas conduz a um maior índice de prenhez. Este trabalho teve como objetivo relatar a experiência de um estudo realizado para averiguar se essa pratica tem, efetivamente, o efeito esperado, bem como relatar as dificuldades encontradas. Foi conduzido numa propriedade particular representativa do Pantanal de Rio Verde de Mato Grosso, MS, no período de 1987 a 1990. Utilizaram-se 766 vacas neloradas e 46 touros da raça Nelore, mantidos em duas invernadas (pastagem nativa) de, aproximadamente, 1.500 hectares cada, cuja lotação foi de 3 hectares/unidade animal e a relação touro/vaca foi de 1:16. O ensaio envolveu dois tratamentos (T1 e T2). O T1 obedeceu ao manejo tradicional da região (testemunha). No T2, o rebanho foi submetido a adensamentos a cada 21 dias, durante a estação de monta (setembro a março). O adensamento consistiu em levar todo o gado para um piquete a parte, com 19 hectares, mantendo-o por 48 horas. Os resultados obtidos não são conclusivos por falta de controle das condições experimentais. Discutem-se as dificuldades encontradas nesse ensaio, bem como são apresentadas sugestões para futuros trabalhos a serem conduzidos na região.bitstream/item/139369/1/cir-tec-28.pd

Electrostatic extraction of cold molecules from a cryogenic reservoir

We present a method which delivers a continuous, high-density beam of slow and internally cold polar molecules. In our source, warm molecules are first cooled by collisions with a cryogenic helium buffer gas. Cold molecules are then extracted by means of an electrostatic quadrupole guide. For ND$_3$ the source produces fluxes up to $(7 \pm ^{7}_{4}) \times 10^{10}$ molecules/s with peak densities up to $(1.0 \pm ^{1.0}_{0.6}) \times 10^9$ molecules/cm$^3$. For H$_2$CO the population of rovibrational states is monitored by depletion spectroscopy, resulting in single-state populations up to $(82 \pm 10)$.Comment: 4 pages, 4 figures, changes to the text, updated figures and reference

Probing the dynamics of quasicrystal growth using synchrotron live imaging

The dynamics of quasicrystal growth remains an unsolved problem in condensed matter. By means of synchrotron live imaging, facetted growth proceeding by the tangential motion of ledges at the solid-melt interface is clearly evidenced all along the solidification of icosahedral AlPdMn quasicrystals. The effect of interface kinetics is significant so that nucleation and free growth of new facetted grains occur in the melt when the solidification rate is increased. The evolution of these grains is explained in details, which reveals the crucial role of aluminum rejection, both in the poisoning of grain growth and driving fluid flow

Creation and manipulation of entanglement in spin chains far from equilibrium

We investigate creation, manipulation, and steering of entanglement in spin chains from the viewpoint of quantum communication between distant parties. We demonstrate how global parametric driving of the spin-spin coupling and/or local time-dependent Zeeman fields produce a large amount of entanglement between the first and the last spin of the chain. This occurs whenever the driving frequency meets a resonance condition, identified as "entanglement resonance". Our approach marks a promising step towards an efficient quantum state transfer or teleportation in solid state system. Following the reasoning of Zueco et al. [1], we propose generation and routing of multipartite entangled states by use of symmetric tree-like structures of spin chains. Furthermore, we study the effect of decoherence on the resulting spin entanglement between the corresponding terminal spins.Comment: 10 pages, 8 figure

Numerical study of lattice index theorem usingimproved cooling and overlap fermions

We investigate topological charge and the index theorem on finite lattices numerically. Using mean field improved gauge field configurations we calculate the topological charge Q using the gluon field definition with ${\cal O}(a^4)$-improved cooling and an ${\cal O}(a^4)$-improved field strength tensor $F_{\mu\nu}$. We also calculate the index of the massless overlap fermion operator by directly measuring the differences of the numbers of zero modes with left- and right--handed chiralities. For sufficiently smooth field configurations we find that the gluon field definition of the topological charge is integer to better than 1% and furthermore that this agrees with the index of the overlap Dirac operator, i.e., the Atiyah-Singer index theorem is satisfied. This establishes a benchmark for reliability when calculating lattice quantities which are very sensitive to topology.Comment: 15 pages, 1 figure

The electroweak chiral Lagrangian reanalyzed

In this paper we reanalyze the electroweak chiral Lagrangian with particular focus on two issues related to gauge invariance. Our analysis is based on a manifestly gauge-invariant approach that we introduced recently. It deals with gauge-invariant Green's functions and provides a method to evaluate the corresponding generating functional without fixing the gauge. First we show, for the case where no fermions are included in the effective Lagrangian, that the set of low-energy constants currently used in the literature is redundant. In particular, by employing the equations of motion for the gauge fields one can choose to remove two low-energy constants which contribute to the self-energies of the gauge bosons. If fermions are included in the effective field theory analysis the situation is more involved. Even in this case, however, these contributions to the self-energies of the gauge bosons can be removed. The relation of this result to the experimentally determined values for the oblique parameters S, T, and U is discussed. In the second part of the paper we consider the matching relation between a full and an effective theory. We show how the low-energy constants of the effective Lagrangian can be determined by matching gauge-invariant Green's functions in both theories. As an application we explicitly evaluate the low-energy constants for the standard model with a heavy Higgs boson. The matching at the one-loop level and at next-to-leading order in the low-energy expansion is performed employing functional methods.Comment: 44 pages, Revtex. v2: Sections II and III interchanged. New section II now self-contained. Discussions improved in sections I, II, V.C and VI. Conclusions unchanged. Published versio

Gauge-invariant Green's functions for the bosonic sector of the standard model

There are many applications in gauge theories where the usually employed framework involving gauge-dependent Green's functions leads to considerable problems. In order to overcome the difficulties invariably tied to gauge dependence, we present a manifestly gauge-invariant approach. We propose a generating functional of appropriately chosen gauge-invariant Green's functions for the bosonic sector of the standard model. Since the corresponding external sources emit one-particle states, these functions yield the same S-matrix elements as those obtained in the usual framework. We evaluate the generating functional for the bosonic sector of the standard model up to the one-loop level and carry out its renormalization in the on-shell scheme. Explicit results for some two-point functions are given. Gauge invariance is manifest at any step of our calculation.Comment: 29 pages, Revtex. v2: Discussions improved, conclusions unchanged. Some references added. v3: Published versio

Improved photobiological H-2 production in engineered green algal cells

Oxygenic photosynthetic organisms use solar energy to split water (H2O) into protons (H+), electrons (e(-)), and oxygen. A select group of photosynthetic microorganisms, including the green alga Chlamydomonas reinhardtii, has evolved the additional ability to redirect the derived H+ and e(-) to drive hydrogen (H-2) production via the chloroplast hydrogenases HydA1 and A2 (H(2)ase). This process occurs under anaerobic conditions and provides a biological basis for solar-driven H-2 production. However, its relatively poor yield is a major limitation for the economic viability of this process. To improve H-2 production in Chlamydomonas, we have developed a new approach to increase H+ and e(-) supply to the hydrogenases. In a first step, mutants blocked in the state 1 transition were selected. These mutants are inhibited in cyclic e(-) transfer around photosystem I, eliminating possible competition for e(-) with H(2)ase. Selected strains were further screened for increased H-2 production rates, leading to the isolation of Stm6. This strain has a modified respiratory metabolism, providing it with two additional important properties as follows: large starch reserves ( i.e. enhanced substrate availability), and a low dissolved O-2 concentration (40% of the wild type (WT)), resulting in reduced inhibition of H2ase activation. The H-2 production rates of Stm6 were 5 - 13 times that of the control WT strain over a range of conditions ( light intensity, culture time, +/- uncoupler). Typically, similar to 540 ml of H-2 liter(-1) culture ( up to 98% pure) were produced over a 10-14-day period at a maximal rate of 4 ml h(-1) ( efficiency = similar to 5 times the WT). Stm6 therefore represents an important step toward the development of future solar-powered H-2 production systems

The motor development of orphaned children with and without HIV: Pilot exploration of foster care and residential placement

<p>Abstract</p> <p>Background</p> <p>The AIDS epidemic has lead to an increase in orphaned children who need residential care. It is known that HIV leads to delayed motor development. However, the impact of place of residence on motor function has not been investigated in the South African context. The aim of the study was therefore to establish if children in institutionalised settings performed better or worse in terms of gross motor function than their counterparts in foster care. A secondary objective was to compare the performance of children with HIV in these two settings with those of children who were HIV negative.</p> <p>Methods</p> <p>Forty-four children both with and without HIV, were recruited from institutions and foster care families in Cape Town. The Peabody Development Motor Scale (PDMS II) was used to calculate the total motor quotient (TMQ) at baseline and six months later. Comparisons of TMQ were made between residential settings and between children with and without HIV.</p> <p>Results</p> <p>Twenty-one children were infected with HIV and were significantly delayed compared to their healthy counterparts. Antiretroviral therapy was well managed among the group but did not appear to result in restoration of TMQ to normal over the study period. HIV status and place of residence emerged as a predictor of TMQ with children in residential care performing better than their counterparts in foster care. All children showed improvement over the six months of study.</p> <p>Conclusions</p> <p>Foster parents were well supported administratively in the community by social welfare services but their children might have lacked stimulation in comparison to those in institutional settings. This could have been due to a lack of resources and knowledge regarding child development. The assumption that foster homes provide a better alternative to institutions may not be correct in a resource poor community and needs to be examined further.</p