467 research outputs found
Plasmodium species mixed infections in two areas of Manhiça District, Mozambique
We compared the distribution patterns of individual Plasmodium species and mixed-species infections in two geographically close endemic areas, but showing environmental differences. Comparisons concerned circulating Plasmodium infections in both human and mosquito vector populations in the dry and wet seasons, at a micro-epidemiological level (households). Both areas revealed a very high overall prevalence of infection, all year-round and in all age groups. Plasmodium falciparum was the predominant species, being found in the vast majority of infected individuals regardless of the presence of other species. Plasmodium malariae and Plasmodium ovale occurred almost exclusively in mixed infections. Seasonal variation in P. malariae prevalence was observed in one area but not in the other. A decrease in P. malariae prevalence concurred with a marked increase of P. falciparum prevalence. However this was strongly dependent on age and when analysing infections at the individual level, a different pattern between co-infecting species was unveiled. Regarding transmission patterns, in both areas, P. falciparum gametocytes predominated in single infections regardless of age and P. malariae gametocyte carriage increased when its overall prevalence decreased
Thermochemistry and kinetics of the trans-N2H2+N reaction
AbstractThermochemical and kinetics properties of the hydrogen abstraction and addition processes of the trans-N2H2+N reaction were computed using high-level ab initio and DFT approximation methods with aug-cc-pVXZ (X=T,Q) basis set. The CCSD (T)/CBS//BB1K/aug-cc-pVTZ results for classical barrier height are 13.1 and 15.0kcal/mol for the abstraction and addition reactions, respectively. The thermal rate constants were calculated using the dual-level direct dynamics by variational transition state theory with the BB1K potential energy surface and thermochemical properties corrected with the CCSD (T)/CBS//BB1K/aug-cc-pVTZ results. The rate constants calculated show that the variational and tunneling effects play a relevant role only for the abstraction reaction
Quasinormal modes of a Schwarzschild black hole surrounded by free static spherically symmetric quintessence: Electromagnetic perturbations
In this paper, we evaluated the quasinormal modes of electromagnetic
perturbation in a Schwarzschild black hole surrounded by the static spherically
symmetric quintessence by using the third-order WKB approximation when the
quintessential state parameter in the range of . Due to
the presence of quintessence, Maxwell field damps more slowly. And when at
, it is similar to the black hole solution in the ds/Ads
spacetime. The appropriate boundary conditions need to be modified.Comment: 6 pages, 3 figure
Flame retardants: Polybrominated diphenyl ethers
Para melhorar a qualidade de vida do Homem foram desenvolvidos durante as Ășltimas dĂ©cadas muitos produtos quĂmicos, como por exemplo os retardantes de chama. Estes compostos sĂŁo adicionados a uma grande variedade de materiais cuja finalidade Ă© evitar ou retardar a propagação de incĂȘndios.Os Ă©teres difenĂlicos polibromados (PBDEs, Polybrominated Diphenyl Ethers) pertencem ao grupo de retardantes de chama bromados. Estes compostos sĂŁo misturados com os polĂmeros e tendem a libertarem-se por acção do tempo, do calor e da luz para o meio ambiente. Os PBDEs sĂŁo compostos lipofĂlicos e sĂŁo classificados como poluentes orgĂąnicos persistentes (POPs, Persistent Organic Pollutants) por serem persistentes, tĂłxicos e bioacumulĂĄveis. Por serem POPs, os PBDEs ganharam relevo nos estudos efetuados em diversas matrizes ambientais e no Homem (fluidos fsisiolĂłgicos, tecidos, ĂłrgĂŁos), com o objetivo de estudar e identificar a sua ocorrĂȘncia, assim como, evitar a sua dispersĂŁo.Este artigo tem como objetivo abordar o problema dos retardantes de chama, mais concretamente dos PBDEs, no que se refere Ă sua utilização, propriedades fĂsico-quĂmicas, toxicidade e ocorrĂȘncia no meio ambiente, dando enfase aos estudos e problemas em Portugal. To improve the quality of life of people have been developed during the last decades many chemicals such as flame retardants. These compounds are added to a wide variety of materials whose purpose is to prevent or slow the spread of fire.Polybrominated diphenyl ethers (PBDEs) belong to the group of brominated flame retardants. These compounds are blended with polymers and tend to free themselves by weathering, heat and light to the environment. PBDEs are lipophilic compounds and are classified as persistent organic pollutants (POPs) to be persistent, bioaccumulative and toxic. As belonging to the class of POPs, PBDE gained importance in the studies on various environmental matrices and in humans (physiological fluids, tissues, organs) in order to study and identify their occurrence, as well as to prevent its spread.This article aims to address the problem of flame retardants, in particular of PBDE in relation to its use, physico-chemical properties, toxicity and incidence on the environment, and studies focusing on the problems in Portugal
Schwarzschild black hole surrounded by quintessence: Null geodesics
We have studied the null geodesics of the Schwarzschild black hole surrounded
by quintessence matter. Quintessence matter is a candidate for dark energy.
Here, we have done a detailed analysis of the geodesics and exact solutions are
presented in terms of Jacobi-elliptic integrals for all possible energy and
angular momentum of the photons. The circular orbits of the photons are studied
in detail. As an application of the null geodesics, the angle of deflection of
the photons are computed.Comment: 25 pages, 20 figures. typos corrected and some of the notation
change
Duality Orbits, Dyon Spectrum and Gauge Theory Limit of Heterotic String Theory on T^6
For heterotic string theory compactified on T^6, we derive the complete set
of T-duality invariants which characterize a pair of charge vectors (Q,P)
labelling the electric and magnetic charges of the dyon. Using this we can
identify the complete set of dyons to which the previously derived degeneracy
formula can be extended. By going near special points in the moduli space of
the theory we derive the spectrum of quarter BPS dyons in N=4 supersymmetric
gauge theory with simply laced gauge groups. The results are in agreement with
those derived from field theory analysis.Comment: LaTeX file, 22 page
Numerical simulations for performance optimization of a few-cycle terawatt NOPCPA system
We present a systematic numerical design and performance study of an ultra-broadband noncollinear optical parametric chirped pulse amplification (NOPCPA) system. Using a split-step Fourier approach, we model a three-stage amplifier system which is designed for the generation of 7 fs pulses with multi-terawatt peak intensity. The numerical results are compared with recent experimental data. Several important aspects and design parameters specific to NOPCPA are identified, and the values of these parameters required to achieve optimal working conditions are investigated. We identify and analyze wavelength-dependent gain saturation effects, which are specific to NOPCPA and have a strong influence on the parametric amplification process. © Springer-Verlag 2007
New Polynomial Cases of the Weighted Efficient Domination Problem
Let G be a finite undirected graph. A vertex dominates itself and all its
neighbors in G. A vertex set D is an efficient dominating set (e.d. for short)
of G if every vertex of G is dominated by exactly one vertex of D. The
Efficient Domination (ED) problem, which asks for the existence of an e.d. in
G, is known to be NP-complete even for very restricted graph classes.
In particular, the ED problem remains NP-complete for 2P3-free graphs and
thus for P7-free graphs. We show that the weighted version of the problem
(abbreviated WED) is solvable in polynomial time on various subclasses of
2P3-free and P7-free graphs, including (P2+P4)-free graphs, P5-free graphs and
other classes.
Furthermore, we show that a minimum weight e.d. consisting only of vertices
of degree at most 2 (if one exists) can be found in polynomial time. This
contrasts with our NP-completeness result for the ED problem on planar
bipartite graphs with maximum degree 3
Measurement of the branching fraction
The branching fraction is measured in a data sample
corresponding to 0.41 of integrated luminosity collected with the LHCb
detector at the LHC. This channel is sensitive to the penguin contributions
affecting the sin2 measurement from The
time-integrated branching fraction is measured to be . This is the most precise measurement to
date
Model-independent search for CP violation in D0âKâK+ÏâÏ+ and D0âÏâÏ+Ï+Ïâ decays
A search for CP violation in the phase-space structures of D0 and View the MathML source decays to the final states KâK+ÏâÏ+ and ÏâÏ+Ï+Ïâ is presented. The search is carried out with a data set corresponding to an integrated luminosity of 1.0 fbâ1 collected in 2011 by the LHCb experiment in pp collisions at a centre-of-mass energy of 7 TeV. For the KâK+ÏâÏ+ final state, the four-body phase space is divided into 32 bins, each bin with approximately 1800 decays. The p-value under the hypothesis of no CP violation is 9.1%, and in no bin is a CP asymmetry greater than 6.5% observed. The phase space of the ÏâÏ+Ï+Ïâ final state is partitioned into 128 bins, each bin with approximately 2500 decays. The p-value under the hypothesis of no CP violation is 41%, and in no bin is a CP asymmetry greater than 5.5% observed. All results are consistent with the hypothesis of no CP violation at the current sensitivity
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