Normal ordering and boundary conditions in open bosonic strings

Boundary conditions play a non trivial role in string theory. For instance the rich structure of D-branes is generated by choosing appropriate combinations of Dirichlet and Neumann boundary conditions. Furthermore, when an antisymmetric background is present at the string end-points (corresponding to mixed boundary conditions) space time becomes non-commutative there. We show here how to build up normal ordered products for bosonic string position operators that satisfy both equations of motion and open string boundary conditions at quantum level. We also calculate the equal time commutator of these normal ordered products in the presence of antisymmetric tensor background.Comment: 7 pages no figures, References adde

Normal ordering and boundary conditions for fermionic string coordinates

We build up normal ordered products for fermionic open string coordinates consistent with boundary conditions. The results are obtained considering the presence of antisymmetric tensor fields. We find a discontinuity of the normal ordered products at string endpoints even in the absence of the background. We discuss how the energy momentum tensor also changes at the world-sheet boundary in such a way that the central charge keeps the standard value at string end points.Comment: In this revised version we clarify the issue of consistency between supersymmetry and boundary conditions and stress the fact that we are considering flat space. we also add two more reference

Performance of Nellore steers in Panicum maximum pastures.

O objetivo do trabalho foi avaliar o ganho de peso médio diário (GMD) de novilhos Nelore, a taxa de lotação(TL) e o ganho de peso por área (GA) em pastagens de três cultivares de Panicum maximum. O experimento foi conduzido em Planaltina, Distrito Federal, Brasil, durante 248 dias, divididos em período chuvoso (140 dias) e período seco (108 dias). Os tratamentos experimentais foram as cultivares Zuri, Tamani e Massai manejadas em lotação rotacionada em ciclos de pastejo de 28 dias (21 dias de descanso e 7 dias de pastejo) na estação chuvosa e 56 dias (42 dias de descanso e 14 dias de pastejo) na estação seca. Os ajustes na taxa de lotação foram conduzidos considerando a mesma oferta de forragem entre tratamentos. O GMD (novilhos desmamados de 216 kg de peso vivo) foi de 0,352, 0,391 e 0,254kg/cabeça para as cultivares Zuri, Tamani e Massai, respectivamente. O GMD diminuiu no período seco, mas permaneceu maior para Zuri e Tamani. O maior desempenho individual foi associado a valores mais elevados de proteína bruta e digestibilidade da forragem, especialmente para a cultivar Tamani. A TL foi mais elevada para Massai e Zuri em ambas as estações do ano, enquanto o GA foi semelhante entre os trata-mentos. Embora a cultivar Tamani tenha proporcionado lotação mais baixa, o GA foi parcialmente compensado por valores ele-vados de GMD. A cultivar Zuri conseguiu aliar maior desempenho individual com alta lotação

Principais doenças e parasitas que ocorrem no rebanho ovino de Roraima.

Ovino. Consideracoes gerais. Aquisicao de animais. Instalacoes. Aprisco. Bebedouros. Pediluvio. Local de isolamento. Doencas infecto-contagiosas. Linfadenite caseosa. Pododermatite. Necrotica. Mamite. Ectima contagioso. Ceraconjuntivite. Ceratite. Tumores de olhos. Doencas parasitarias. Miiase. Helmintos gastrintestinais.bitstream/item/64864/1/CPAFRR-DOCUMENTOS-01-PRINCIPAIS-DOENCAS-E-PARASITAS-QUE-OCORREN-NO-REBANHO-OVINO-DE-RORAIMA-FL-11.pd

Characterization of the CBC2 readout ASIC for the CMS strip-tracker high-luminosity upgrade

The CMS Binary Chip 2 (CBC2) is a full-scale prototype ASIC developed for the front-end readout of the high-luminosity upgrade of the CMS silicon strip tracker. The 254-channel, 130 nm CMOS ASIC is designed for the binary readout of double-layer modules, and features cluster-width discrimination and coincidence logic for detecting high-PT track candidates. The chip was delivered in January 2013 and has since been bump-bonded to a dual-chip hybrid and extensively tested. The CBC2 is fully functional and working to specification: we present the result of electrical characterization of the chip, including gain, noise, threshold scan and power consumption, together with the performance of the stub finding logic. Finally we will outline the plan for future developments towards the production version

Alternatives in polymerization contraction stress management

Polymerization contraction stress of dental composites is often associated with marginal and interfacial failure of bonded restorations. The magnitude of the stress depends on the composite's composition (filler content and matrix composition) and its ability to flow before gelation, which is related to the cavity configuration and curing characteristics of the composite. This article reviews the variations found among studies regarding the contraction stress testing method, contraction stress values of current composites, and discusses the validity of contraction stress studies in relation to results from microleakage tests. The effect of lower curing rates and alternative curing routines on contraction stress values is also discussed, as well as the use of low elastic modulus liners. Moreover, studies with experimental Bis-GMA-based composites and recent developments in low-shrinkage monomers are described