585 research outputs found
Bianchi type I space and the stability of inflationary Friedmann-Robertson-Walker space
Stability analysis of the Bianchi type I universe in pure gravity theory is
studied in details. We first derive the non-redundant field equation of the
system by introducing the generalized Bianchi type I metric. This non-redundant
equation reduces to the Friedmann equation in the isotropic limit. It is shown
further that any unstable mode of the isotropic perturbation with respect to a
de Sitter background is also unstable with respect to anisotropic
perturbations. Implications to the choice of physical theories are discussed in
details in this paper.Comment: 5 pages, some comment adde
Friedmann Equation and Stability of Inflationary Higher Derivative Gravity
Stability analysis on the De Sitter universe in pure gravity theory is known
to be useful in many aspects. We first show how to complete the proof of an
earlier argument based on a redundant field equation. It is shown further that
the stability condition applies to Friedmann-Robertson-Walker spaces
based on the non-redundant Friedmann equation derived from a simple effective
Lagrangian. We show how to derive this expression for the Friedmann equation of
pure gravity theory. This expression is also generalized to include scalar
field interactions.Comment: Revtex, 6 pages, Add two more references, some typos correcte
Metabolism of alcaligenes denitrificans in biofilm vs planktonic cells
Aims: To compare the effect of phosphorous concentration (200 mg P 1-1 and 20 mg P 1-1) on
the denitrifying efficiency of Alcaligenes denitrificans when in the form of planktonic cells or in the form of a biofilm, and to select the most adequate C/N ratio.
Methods and Results: Two types of assays were carried out: with planktonic cells and with
cells in biofilm form. Anoxic bottles with the appropriate C/N and phosphorous concentration
were incubated at 30°C and submitted to orbital shaking at 150 rev min-1. The specific activity
of cells in biofilm form, in terms of substrate consumption, was significantly higher than cells in
planktonic form. With regard to the effect of increasing phosphorous concentration, an increase
in specific activity was also only evident when the cells were in biofilm form.
Conclusions: The two forms showed different performances and phosphorous concentration
only markedly affected the biofilm form.
Significance and Impact of the Study: The importance of the C/N/P ratio in the
denitrification process is demonstrated. As there was no report in the literature about the
stoichiometric relationship of heterotrophic denitrification with citrate, its stoichiometry,
including the requirement for cell synthesis, was determined.Instituto de Biotecnologia e QuĂmica Fina (IBQF).
PRAXIS XXI
Musculação Na Educação FĂsica Escolar: Uma ExperiĂȘncia No Ensino MĂ©dio Noturno
The study aimed to plan, apply and evaluate the teaching unit âweight trainingâ to a class of 3rd year high school night of a public school of MaringĂĄâPR. It's an experience report with 19 students, in three stages: âpresentations and initial investigationsâ with the presentation of the project and implementation of the initial questionnaire, âget hands dirtyâ application of a teaching unit consists in 10 classes based on the curriculum guidelines of basic education in the State of ParanĂĄ and âevaluating actionsâ by means of a final questionnaire. It was concluded that students show interest and motivation in practicing weight training at extracurricular environment and in studying and experiencing new contents in Physical Education lessons from the experience. © 2015 ColĂ©gio Brasileiro de CiĂȘncias do Esporte38217117
Floristic variations in a woody plant community along a trail in a Semideciduous Seasonal Forest, Viçosa, Minas Gerais State, Brazil
Potent and Broad-Spectrum Antimicrobial Activity of Analogs from the Scorpion Peptide Stigmurin
Scorpion venom constitutes a rich source of biologically active compounds with high potential for therapeutic and biotechnological applications that can be used as prototypes for the design of new drugs. The aim of this study was to characterize the structural conformation, evaluate the antimicrobial activity, and gain insight into the possible action mechanism underlying it, for two new analog peptides of the scorpion peptide Stigmurin, named StigA25 and StigA31. The amino acid substitutions in the native sequence for lysine residues resulted in peptides with higher positive net charge and hydrophobicity, with an increase in the theoretical helical content. StigA25 and StigA31 showed the capacity to modify their structural conformation according to the environment, and were stable to pH and temperature variation-results similar to the native peptide. Both analog peptides demonstrated broad-spectrum antimicrobial activity in vitro, showing an effect superior to that of the native peptide, being non-hemolytic at the biologically active concentrations. Therefore, this study demonstrates the therapeutic potential of the analog peptides from Stigmurin and the promising approach of rational drug design based on scorpion venom peptide to obtain new anti-infective agents.publishersversionpublishe
Quenching of chlorophyll fluorescence induced by silver nanoparticles
The interaction between chlorophyll (Chl) and silver nanoparticles (AgNPs) was evaluated by analyzing the optical behavior of Chl molecules surrounded by different concentrations of AgNPs (10, 60, and 100 nm of diameter). UVâVis absorption, steady state and time-resolved fluorescence measurements were performed for Chl in the presence and absence of these nanoparticles. AgNPs strongly suppressed the Chl fluorescence intensity at 678 nm. The Stern-Volmer constant (KSV) showed that fluorescence suppression is driven by the dynamic quenching process. In particular, KSV was nanoparticle size-dependent with an exponential decrease as a function of the nanoparticle diameter. Finally, changes in the Chl fluorescence lifetime in the presence of nanoparticles demonstrated that the fluorescence quenching may be induced by the excited electron transfer from the Chl molecules to the metal nanoparticles
Comparison of methods for determination of nutrient digestibility of a dry kibble diet for ocelots
Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment
This paper describes an analysis of the angular distribution of W->enu and
W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with
the ATLAS detector at the LHC in 2010, corresponding to an integrated
luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and
the missing transverse energy, the W decay angular distribution projected onto
the transverse plane is obtained and analysed in terms of helicity fractions
f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV
and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw
> 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour,
are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017
+/- 0.030, where the first uncertainties are statistical, and the second
include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables,
revised author list, matches European Journal of Physics C versio
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