2,355 research outputs found
An accelerated closed universe
We study a model in which a closed universe with dust and quintessence matter
components may look like an accelerated flat Friedmann-Robertson-Walker (FRW)
universe at low redshifts. Several quantities relevant to the model are
expressed in terms of observed density parameters, and
, and of the associated density parameter related
to the quintessence scalar field .Comment: 11 pages. For a festschrift honoring Alberto Garcia. To appear in
Gen. Rel. Gra
Curvature of the universe and the dark energy potential
The flatness of an accelerating universe model (characterized by a dark
energy scalar field ) is mimicked from a curved model that is filled
with, apart from the cold dark matter component, a quintessencelike scalar
field . In this process, we characterize the original scalar potential
and the mimicked scalar potential associated to the scalar
fields and , respectively. The parameters of the original model are
fixed through the mimicked quantities that we relate to the present
astronomical data, such that the equation state parameter and the
dark energy density parameter .Comment: References 7 and 8 have been corrected: (7) Riess et al. 1998, AJ,
116, 1009 and (8) Perlmutter et al. 1999, ApJ, 517, 56
Tachyon warm inflationary universe model in the weak dissipative regime
Warm inflationary universe model in a tachyon field theory is studied in the
weak dissipative regime. We develop our model for an exponential potential and
the dissipation parameter =constant. We describe scalar and
tensor perturbations for this scenario.Comment: 9 pages, accepted by European Physical Journal
Classificação de cultivares de brássicas com relação à resistência à traça-das-crucíferas e à presença de glucosinolatos.
O objetivo deste trabalho foi avaliar o efeito de cultivares de repolho e de couve na biologia da traça-das-crucíferas; analisar a composição química das plantas, em relação aos glucosinolatos e aplicar a análise multivariada na classificação das cultivares. Foram utilizadas as cultivares: de repolho verde Chato-de-quintal e o híbrido Midori; de repolho roxo Roxo precoce e o híbrido Roxo TPC00682; e de couve-manteiga Geórgia (padrão de suscetibilidade) e Geórgia híbrido HS20. Foram avaliadas as características biológicas da praga: viabilidade e duração das fases larval e pupal, razão sexual, fecundidade das fêmeas, longevidade dos adultos e duração e viabilidade da fase de ovo, tendo-se calculado o potencial reprodutivo corrigido (PRC). Obtiveram-se as correlações entre os parâmetros pelo método de Pearson, e realizaram-se análises multivariadas de agrupamento e de componentes principais. Em cromatógrafo líquido, avaliaram-se a presença de sinigrina e de outros glucosinolatos nas plantas. A cultivar Geórgia e os híbridos HS20 e Roxo foram classificados como altamente suscetíveis; 'Roxo precoce' e 'Midori' como suscetíveis e, 'Chato-de-quintal' como moderadamente resistente à Plutella xylostella. As análises multivariadas proporcionam melhor classificação das cultivares, em razão do grau de resistência apresentado. Os materiais genéticos avaliados não apresentam a substância secundária sinigrina
Preservação de acessos de cucurbitáceas no Banco Ativo de Germoplasma (BAG) da Embrapa Semi-Árido - condicões atuais.
Como objetivo inicial testar a viabilidade do uso da sílico gel azul como dessecante em sementes de acessos previamente armazenados
Metabólitos de defesa induzidos em plantas de soja pelo ataque de Bemisia tabaci biótipo B, em condições de campo.
Poster
Emergent Universe with Exotic Matter in Brane World Scenario
In this work, we have examined the emergent scenario in brane world model for
phantom and tachyonic matter. For tachyonic matter field we have obtained
emergent scenario is possible for closed, open and at model of the universe
with some restriction of potential. For normal scalar field the emergent
scenario is possible only for closed model and the result is identical with the
work of Ellis et al [2], but for phantom field the emergent scenario is
possible for closed, open and at model of the universe with some restriction of
potential
Implicação do ácido salicílico na indução de compostos de defesa no controle da ferrugem asiática da soja.
Poster
Biologia da lagarta-da-soja em dieta enriquecida com diferentes concentrações de rutina e genistina.
Polymeric ionic liquid nanoparticle emulsions as a corrosion inhibitor in anticorrosion coatings
In this contribution, we report the facile preparation of cross-linked polymerizable ionic liquid (PIL)-based nanoparticles via thiol–ene photopolymerization in a miniemulsion. The synthesized PIL nanoparticles with a diameter of about 200 nm were fully characterized with regard to their chemical structures, morphologies, and properties using different techniques, such as Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, and transmission electron microscopy. To gain an in-depth understanding of the physical and morphological structures of the PIL nanoparticles in an emulsion, small-angle neutron scattering and ultra-small-angle neutron scattering were used. Neutron scattering studies revealed valuable information regarding the formation of cylindrical ionic micelles in the spherical nanoparticles, which is a unique property of this system. Furthermore, the PIL nanoparticle emulsion was utilized as an inhibitor in a self-assembled nanophase particle (SNAP) coating. The corrosion protection ability of the resultant coating was examined using potentiodynamic polarization and electrochemical impedance spectroscopy. The results show that the PIL nanoparticle emulsion in the SNAP coating acts as an inhibitor of corrosion and is promising for fabricating advanced coatings with improved barrier function and corrosion protection.Mona Taghavikish, Surya Subianto, Naba Kumar Dutta, Liliana de Campo, Jitendra P. Mata, Christine Rehm, and Namita Roy Choudhur
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