4,036 research outputs found
The use of computer-generated color graphic images for transient thermal analysis
Color computer graphics techniques were investigated as a means of rapidly scanning and interpreting large sets of transient heating data. The data presented were generated to support the conceptual design of a heat-sink thermal protection system (TPS) for a hypersonic research airplane. Color-coded vector and raster displays of the numerical geometry used in the heating calculations were employed to analyze skin thicknesses and surface temperatures of the heat-sink TPS under a variety of trajectory flight profiles. Both vector and raster displays proved to be effective means for rapidly identifying heat-sink mass concentrations, regions of high heating, and potentially adverse thermal gradients. The color-coded (raster) surface displays are a very efficient means for displaying surface-temperature and heating histories, and thereby the more stringent design requirements can quickly be identified. The related hardware and software developments required to implement both the vector and the raster displays for this application are also discussed
Neutrinos, Axions and Conformal Symmetry
We demonstrate that radiative breaking of conformal symmetry (and
simultaneously electroweak symmetry) in the Standard Model with right-chiral
neutrinos and a minimally enlarged scalar sector induces spontaneous breaking
of lepton number symmetry, which naturally gives rise to an axion-like particle
with some unusual features. The couplings of this `axion' to Standard Model
particles, in particular photons and gluons, are entirely determined (and
computable) via the conformal anomaly, and their smallness turns out to be
directly related to the smallness of the masses of light neutrinos.Comment: 10 pages, 2 figures, expanded version, to be published in EPJ
Crystallographic disorder and electron scattering on structural two-level systems in ZrAs1.4Se0.5
Single crystals of ZrAs1.4Se0.5 (PbFCl type structure) were grown by chemical
vapour transport. While their thermodynamic and transport properties are
typical for ordinary metals, the electrical resistivity exhibits a shallow
minimum at low temperatures. Application of strong magnetic fields does not
influence this anomaly. The minimum of the resistivity in ZrAs1.4Se0.5
apparently originates from interaction between the conduction electrons and
structural two-level systems. Significant disorder in the As-Se substructure is
inferred from X-ray diffraction and electron microprobe studies
Estudo de prevalência do Cassava Commom Mosaic VÃrus (CsCMV) e do Cassava Vein Mosaic Virus (CsVMV) na região produtora do Estado da Bahia.
A mandioca (Manihot esculenta Crantz) é uma das principais fontes de energia na dieta humana dos paÃses tropicais. Por ser propagada vegetativamente, através de partes caulinares (ramas ou manivas) (RODRIGUES et al., 2008), a dispersão de doenças sistêmicas, como as causadas por viroses, podem levar a degenerescência das manivas (COSTA; KITAJIMA, 1972). Em relação aos vÃrus de maior importância econômica no Brasil, destacam-se o mosaico das nervuras - Cassava vein mosaic virus (CsVMV), e o mosaico comum - Cassava common mosaic virus CsCMV (CHUMBINHO et al, 2010). Trabalho realizados no inÃcio da década passada consideram o mosaico das nervuras, CsVMV, como sendo um vÃrus de ampla abrangência geográfica, sendo prevalente, principalmente, no ecossistema do semiárido nordestino. Esse efeito não está somente associado à s severas manifestações produzidas, mas também pela influência negativa na qualidade dos produtos obtidos (CHIGERU et al., 2003). Além da transmissão por material propagativo, o CsVMV é transmitido por ferramentas utilizadas para o corte das manivas. Observações de campo têm indicado que a manifestação severa da doença em variedades suscetÃveis pode causar perdas de produção que variam de 10 a 20%, prejudicando a qualidade do produto, devido à redução de 10 a 50% nos teores de amido (FUKUDA, 1993). Os sintomas caracterizam-se pela presença de cloroses intensas entre as nervuras primárias e secundárias, nas plantas afetadas. Em casos severos da doença é comum observar um forte retorcimento do limbo foliar (OTSUBO et al., 2003). O CsCMV, mosaico comum, pertencente a famÃlia Flexiviridae e gênero Potexvirus (SOARES et al., 2009), não possui vetor conhecido, logo entende-se que sua disseminação ocorre mecanicamente (COLARICCIO et al., 2009). O Cassava common mosaic vÃrus - CsCMV é classificado como uma Potexvirus e possui uma partÃcula semiflexuosa de 15 nm × 495 nm (Kitajima et al., 1965). O genoma é constituÃdo de uma fita única de RNA senso positiva (ssRNA) de 2 × 106 Da, com capsÃdio constituÃdo por uma única proteÃna de 21 kDa de massa molecular (Nolt et al.,1991). Os sintomas apresentados em mandiocas infectadas por esse vÃrus são de mosaico no limbo foliar, presença de áreas cloróticas que são muitas vezes limitados pela as veias e a doença pode causar perdas de rendimento em mais de 30%. Por essa razão, alguns trabalhos apontam para a importância do cuidado que se deve ter na seleção do material de plantio, pois essas medidas podem ajudar a erradicar ou reduzir a doença a um nÃvel econômico significativamente secundário. O objetivo do presente trabalho foi detectar, avaliar e identificar a prevalência do CsCMV e do CsVMV em diversas variedades de mandioca cultivadas nas principais regiões produtoras de mandioca do estado da Bahia
Exact One Loop Running Couplings in the Standard Model
Taking the dominant couplings in the standard model to be the quartic scalar
coupling, the Yukawa coupling of the top quark, and the SU(3) gauge coupling,
we consider their associated running couplings to one loop order. Despite the
non-linear nature of the differential equations governing these functions, we
show that they can be solved exactly. The nature of these solutions is
discussed and their singularity structure is examined. It is shown that for a
sufficiently small Higgs mass, the quartic scalar coupling decreases with
increasing energy scale and becomes negative, indicative of vacuum instability.
This behavior changes for a Higgs mass greater than 168 GeV, beyond which this
couplant increases with increasing energy scales and becomes singular prior to
the ultraviolet (UV) pole of the Yukawa coupling. Upper and lower bounds on the
Higgs mass corresponding to new physics at the TeV scale are obtained and
compare favourably with the numerical results of the one-loop and two-loop
analyses with inclusion of electroweak couplings.Comment: 5 pages, LaTeX, additional references and further discussion in this
version. Accepted for publication in Canadian Journal of Physic
Computing Black Hole entropy in Loop Quantum Gravity from a Conformal Field Theory perspective
Motivated by the analogy proposed by Witten between Chern-Simons and
Conformal Field Theories, we explore an alternative way of computing the
entropy of a black hole starting from the isolated horizon framework in Loop
Quantum Gravity. The consistency of the result opens a window for the interplay
between Conformal Field Theory and the description of black holes in Loop
Quantum Gravity.Comment: 9 page
Radiative pion capture by a nucleon
The differential cross sections for and are computed up to in heavy baryon chiral perturbation
theory (HBChPT). The expressions at and have no free
parameters. There are three unknown parameters at , low energy
constants of the HBChPT Lagrangian, which are determined by fitting to
experimental data. Two acceptable fits are obtained, which can be separated by
comparing with earlier dispersion relation calculations of the inverse process.
Expressions for the multipoles, with emphasis on the p-wave multipoles, are
obtained and evaluated at threshold. Generally the results obtained from the
best of the two fits are in good agreement with the dispersion relation
predictions.Comment: 24 pages, Latex, using RevTe
One-loop effects of extra dimensions on the WW\gamma and WWZ vertices
The one-loop contribution of the excited Kaluza-Klein (KK) modes of the
gauge group on the off-shell and vertices is
calculated in the context of a pure Yang-Mills theory in five dimensions and
its phenomenological implications discussed. The use of a gauge-fixing
procedure for the excited KK modes that is covariant under the standard gauge
transformations of the group is stressed. A gauge-fixing term and the
Faddeev-Popov ghost sector for the KK gauge modes that are separately invariant
under the standard gauge transformations of are presented. It is
shown that the one-loop contributions of the KK modes to the off-shell
and vertices are free of ultraviolet divergences and
well-behaved at high energies. It is found that for a size of the fifth
dimension of , the one-loop contribution of the KK modes to
these vertices is about one order of magnitude lower than the corresponding
standard model radiative correction. This contribution is similar to the one
estimated for new gauge bosons contributions in other contexts. Tree-level
effects on these vertices induced by operators of higher canonical dimension
are also investigated. It is found that these effects are lower than those
generated at the one-loop order by the KK gauge modes.Comment: 19 pages, 9 figures. Some typos were correcte
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