926 research outputs found
Diel variations in chlorophyll a, phytoplancton primary production and enviromental factors from Ubatuba region (Lat. 23Âș30'S Long. 45Âș06'W)
A series of experiments with natural phytoplankton populations was carried out to study the diel variation of chlrophyll a, primary production and some environmental factors. Samples were collected from surface over a period of 24 hours and always from one fixed station located in Flamengo Inlet, Ubatuba region, southern Brazil The experiments were performed in situ and simulated conditions to verify the patterns of diel cycles of both biotic and abiotic factors. The results obtained showed that diel variations were markedly pronounced mainly in relation to primary production and chlorophyll a. Diel variations of biological factors seems to be due to exogenous and endogenous phenomena
Phenomenological viability of orbifold models with three Higgs families
We discuss the phenomenological viability of string multi-Higgs doublet
models, namely a scenario of heterotic orbifolds with two Wilson lines,
which naturally predicts three supersymmetric families of matter and Higgs
fields. We study the orbifold parameter space, and discuss the compatibility of
the predicted Yukawa couplings with current experimental data. We address the
implications of tree-level flavour changing neutral processes in constraining
the Higgs sector of the model, finding that viable scenarios can be obtained
for a reasonably light Higgs spectrum. We also take into account the tree-level
contributions to indirect CP violation, showing that the experimental value of
can be accommodated in the present framework.Comment: 31 pages, 12 figures. Comments and references added. Final version to
be published in JHE
Phenomenology of the General NMSSM with Gauge Mediated Supersymmetry Breaking
We investigate various classes of Gauge Mediated Supersymmetry Breaking
models and show that the Next-to-Minimal Supersymmetric Standard Model can
solve the mu-problem in a phenomenologically acceptable way. These models
include scenarios with singlet tadpole terms, which are phenomenologically
viable, e.g., in the presence of a small Yukawa coupling <~ 10^{-5}. Scenarios
with suppressed trilinear A-terms at the messenger scale lead naturally to
light CP-odd scalars, which play the r\^ole of pseudo R-axions. A wide range of
parameters of such models satisfies LEP constraints, with CP-even Higgs scalars
below 114 GeV decaying dominantly into a pair of CP-odd scalars.Comment: 24 pages, 6 figures, typos corrected, reference adde
Nonlinear Modulation of Multi-Dimensional Lattice Waves
The equations governing weakly nonlinear modulations of -dimensional
lattices are considered using a quasi-discrete multiple-scale approach. It is
found that the evolution of a short wave packet for a lattice system with cubic
and quartic interatomic potentials is governed by generalized Davey-Stewartson
(GDS) equations, which include mean motion induced by the oscillatory wave
packet through cubic interatomic interaction. The GDS equations derived here
are more general than those known in the theory of water waves because of the
anisotropy inherent in lattices. Generalized Kadomtsev-Petviashvili equations
describing the evolution of long wavelength acoustic modes in two and three
dimensional lattices are also presented. Then the modulational instability of a
-dimensional Stokes lattice wave is discussed based on the -dimensional
GDS equations obtained. Finally, the one- and two-soliton solutions of
two-dimensional GDS equations are provided by means of Hirota's bilinear
transformation method.Comment: Submitted to PR
Effects of Impurity Content on the Sintering Characteristics of Plasma-Sprayed Zirconia
Yttria-stabilized zirconia powders, containing different levels of SiO2 and Al2O3, have been plasma sprayed onto metallic substrates. The coatings were detached from their substrates and a dilatometer was used to monitor the dimensional changes they exhibited during prolonged heat treatments. It was found that specimens containing higher levels of silica and alumina exhibited higher rates of linear contraction, in both in-plane and through-thickness directions. The in-plane stiffness and the through-thickness thermal conductivity were also measured after different heat treatments and these were found to increase at a greater rate for specimens with higher impurity (silica and alumina) levels. Changes in the pore architecture during heat treatments were studied using Mercury Intrusion Porosimetry (MIP). Fine scale porosity (<_50 nm) was found to be sharply reduced even by relatively short heat treatments. This is correlated with improvements in inter-splat bonding and partial healing of intra-splat microcracks, which are responsible for the observed changes in stiffness and conductivity, as well as the dimensional changes
Spontaneous CP Violation in Non-Minimal Supersymmetric Models
We study the possibilities of spontaneous CP violation in the Next-to-Minimal
Supersymmetric Standard Model with an extra singlet tadpole term in the scalar
potential. We calculate the Higgs boson masses and couplings with radiative
corrections including dominant two loop terms. We show that it is possible to
satisfy the LEP constraints on the Higgs boson spectrum with non-trivial
spontaneous CP violating phases. We also show that these phases could account
for the observed value of epsilonK.Comment: 21 pages, 7 Figures in Encapsulated Postscrip
Anticorpos lĂticos induzidos por infecção pelo Trypanosoma cruzi reconhecem epitopos presentes nas formas tripomastigotas e epimastigotas do parasita
Sera of Chaga's disease patients containing anti-T. cruzi lytic antibodies were submitted to affinity chromatography using Sepharose 4B conjugated with antigen extracted from epimasiigote or trypomasiigote forms of the parasite. Epimastigotes were obtained from culture at the exponential growth phase and the trypomastigotes from blood of infected and immunosuppressed mice. Antigen of both parasite forms was obtained by sonication of the parasites followed by centrifugation. Both antigens were then conjugated to activated Sepharose 4B. Affinity chromatography was performed by passing sera from chagasic patients through an immunoadsorbent column containing either epimasiigote or trypomasiigote antigens. Antibodies bound to the column were eluted with cold 0,2 M glycine buffer pH 2,8. The eluted antibodies were analysed regarding their isotype and lytic activity. The results showed that anti-T. cruzi lytic antibodies present in sera from chagasic patients are mainly located in the IgG isotype and recognize epitopes present in both trypomasiigote and epimastigote forms. A brief report of this work has already been published12.Soro de pacientes com doença de Chagas na fase crĂŽnica foram submetidos a cromatografia de afinidade com Sepharose 4B conjugada com um extrato antigĂȘnico obtido de formas epimastigotas ou tripomastigotas de T. cruzi: os epimastigotas foram obtidos de cultura na fase exponencial de crescimento e os tripomastigotas de sangue de camundongos infectados e imunossuprimidos. Os antĂgenos de ambas formas parasitĂĄrias foram obtidos por tratamento dos parasitas por ultra-som, seguido de centrifugação. A cromatografia de afinidade foi feita passando-se os soros chagĂĄsicos atravĂ©s de uma coluna de imunoadsorvente contendo antĂgenos de epimastigotas ou tripomastigotas. Os anticorpos foram eluĂdos da coluna com tampĂŁo glicina 0,2 M pH 2,8 a 4°C. Os anticorpos eluidos foram analisados quanto ao seu isotipo e atividade lĂtica. Os resultados mostraram que os anticorpos anti-T. cruzi com atividade lĂtica presentes em soros chagĂĄsicos estĂŁo localizados no isotipo IgG e reconhecem epitopos presentes tanto nos tripomastigotas quanto nos epimastigotas
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