29,184 research outputs found
Absence of Gluonic Components in Axial and Tensor Mesons
A quarkonium-gluonium mixing scheme previously developed to describe the
characteristic of the pseudoscalar mesons is applied to axial and tensor
mesons. The parameters of the model are determined by fitting the eigenvalues
of a mass matrix. The corresponding eigenvectors give the proportion of light
quarks, strange quarks and glueball in each meson. However the predictions of
the model for branching ratios and electromagnetic decays are incompatible with
the experimental results. These results suggest the absence of gluonic
components in the states of axial and tensor isosinglet mesons analyzed here.Comment: 12 page
Magnetic phases evolution in the LaMn1-xFexO3+y system
We have investigated the crystal structure and magnetic properties for
polycrystalline samples of LaMn1-xFexO3+y, in the whole range x=0.0 to x=1.0,
prepared by solid state reaction in air. All samples show the ORT-2
orthorhombic structure that suppresses the Jahn-Teller distortion, thus
favoring a ferromagnetic (FM) superexchange (SE) interaction between
Mn^{3+}-O-Mn^{3+}. For x=0.0 the oxygen excess (y ~ 0.09) produces vacancies in
the La and Mn sites and generates a fraction around 18% of Mn^{4+} ions and 82%
of the usual Mn^{3+} ions, with possible double exchange interaction between
them. The Fe doping in this system is known to produce only stable Fe^{3+}
ions. We find an evolution from a fairly strong FM phase with a Curie
temperature T_{C} ~ 160 K, for x=0.0, to an antiferromagnetic (AFM) phase with
T_{N} = 790 K, for x=1.0, accompanied by clear signatures of a cluster-glass
behavior. For intermediate Fe contents a mixed-phase state occurs, with a
gradual decrease (increase) of the FM (AFM) phase, accompanied by a systematic
transition broadening for 0.2 < x < 0.7. A model based on the expected exchange
interaction among the various magnetic-ion types, accounts very well for the
saturation-magnetization dependence on Fe doping.Comment: 27 pages, 9 figure
Manejo e controle de plantas infestantes em fruteiras tropicais.
A produção agrícola brasileira é a cada dia demandada para oferecer produtos de qualidade ao consumidor, produzidos por sistemas de produção agrícolas economicamente viáveis, energeticamente eficientes e ecologicamente sustentáveis que protejam e conservem os recursos naturais e o meio ambiente.Palestra
Fast gates for ion traps by splitting laser pulses
We present a fast phase gate scheme that is experimentally achievable and has an operation time more than two orders of magnitude faster than current experimental schemes for low numbers of pulses. The gate time improves with the number of pulses following an inverse power law. Unlike
implemented schemes which excite precise motional sidebands, thus limiting
the gate timescale, our scheme excites multiple motional states using discrete
ultra-fast pulses.We use beam-splitters to divide pulses into smaller components
to overcome limitations due to the finite laser pulse repetition rate. This provides
gate times faster than proposed theoretical schemes when we optimize a practical
setup
The Two-Component Virial Theorem and the Physical Properties of Stellar Systems
Motivated by present indirect evidences that galaxies are surrounded by dark
matter halos, we investigate whether their physical properties can be described
by a formulation of the virial theorem which explicitly takes into account the
gravitational potential term representing the interaction of the dark halo with
the barionic or luminous component. Our analysis shows that the application of
such a ``two-component virial theorem'' not only accounts for the scaling
relations displayed, in particular, by elliptical galaxies, but also for the
observed properties of all virialized stellar systems, ranging from globular
clusters to galaxy clusters.Comment: 13 pages, 2 figures, LaTeX, corrected few typos. This version matches
the published versio
Protocolo modificado para extração de DNA do gênero Pestalotiopsis.
Objetivou-se com este trabalho modificar o protocolo de extração de DNA do gênero Pestalotiopsis. Foram obtidos 200 mg de micélio de 11 isolados de Pestalotiopsis sp. O protocolo de extração proposto por Joshi (2009) foi modificado e testado retirando-se o fenol no processo de desproteinização do DNA. A quantidade de DNA genômico extraído foi quantificada em fotodocumentador e a qualidade do DNA final foi avaliada em gel 0,9% de agarose e em reações de marcadores RAPD. A metodologia sem o emprego do fenol proporcionou quantidade satisfatória (32,55 a 49,92 ng/µL) e pureza de DNA para caracterização molecular do fungo. O protocolo modificado, portanto, pode ser utilizado para extrair DNA do gênero Pestalotiopsis com eficiência do método e segurança para os usuários
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