84 research outputs found
Photonuclear reactions of actinides in the giant dipole resonance region
Photonuclear reactions at energies covering the giant dipole resonance (GDR)
region are analyzed with an approach based on nuclear photoabsorption followed
by the process of competition between light particle evaporation and fission
for the excited nucleus. The photoabsorption cross section at energies covering
the GDR region is contributed by both the Lorentz type GDR cross section and
the quasideuteron cross section. The evaporation-fission process of the
compound nucleus is simulated in a Monte-Carlo framework. Photofission reaction
cross sections are analyzed in a systematic manner in the energy range of
10-20 MeV for the actinides Th, U and Np.
Photonuclear cross sections for the medium-mass nuclei Cu and Zn,
for which there are no fission events, are also presented. The study reproduces
satisfactorily the available experimental data of photofission cross sections
at GDR energy region and the increasing trend of nuclear fissility with the
fissility parameter for the actinides.Comment: 4 pages including 2 tables and 1 figur
Non-vacuum Solutions of Bianchi Type VI_0 Universe in f(R) Gravity
In this paper, we solve the field equations in metric f(R) gravity for
Bianchi type VI_0 spacetime and discuss evolution of the expanding universe. We
find two types of non-vacuum solutions by taking isotropic and anisotropic
fluids as the source of matter and dark energy. The physical behavior of these
solutions is analyzed and compared in the future evolution with the help of
some physical and geometrical parameters. It is concluded that in the presence
of isotropic fluid, the model has singularity at and represents
continuously expanding shearing universe currently entering into phantom phase.
In anisotropic fluid, the model has no initial singularity and exhibits the
uniform accelerating expansion. However, the spacetime does not achieve
isotropy as in both of these solutions.Comment: 20 pages, 5 figures, accepted for publication in Astrophys. Space Sc
Some anisotropic universes in the presence of imperfect fluid coupling with spatial curvature
We consider Bianchi VI spacetime, which also can be reduced to Bianchi types
VI0-V-III-I. We initially consider the most general form of the energy-momentum
tensor which yields anisotropic stress and heat flow. We then derive an
energy-momentum tensor that couples with the spatial curvature in a way so as
to cancel out the terms that arise due to the spatial curvature in the
evolution equations of the Einstein field equations. We obtain exact solutions
for the universes indefinetly expanding with constant mean deceleration
parameter. The solutions are beriefly discussed for each Bianchi type. The
dynamics of the models and fluid are examined briefly, and the models that can
approach to isotropy are determined. We conclude that even if the observed
universe is almost isotropic, this does not necessarily imply the isotropy of
the fluid (e.g., dark energy) affecting the evolution of the universe within
the context of general relativity.Comment: 17 pages, no figures; to appear in International Journal of
Theoretical Physics; in this version (which is more concise) an equation
added, some references updated and adde
Bianchi type II models in the presence of perfect fluid and anisotropic dark energy
Spatially homogeneous but totally anisotropic and non-flat Bianchi type II
cosmological model has been studied in general relativity in the presence of
two minimally interacting fluids; a perfect fluid as the matter fluid and a
hypothetical anisotropic fluid as the dark energy fluid. The Einstein's field
equations have been solved by applying two kinematical ans\"{a}tze: we have
assumed the variation law for the mean Hubble parameter that yields a constant
value of deceleration parameter, and one of the components of the shear tensor
has been considered proportional to the mean Hubble parameter. We have
particularly dwelled on the accelerating models with non-divergent expansion
anisotropy as the Universe evolves. Yielding anisotropic pressure, the fluid we
consider in the context of dark energy, can produce results that can be
produced in the presence of isotropic fluid in accordance with the \Lambda CDM
cosmology. However, the derived model gives additional opportunities by being
able to allow kinematics that cannot be produced in the presence of fluids that
yield only isotropic pressure. We have obtained well behaving cases where the
anisotropy of the expansion and the anisotropy of the fluid converge to finite
values (include zero) in the late Universe. We have also showed that although
the metric we consider is totally anisotropic, the anisotropy of the dark
energy is constrained to be axially symmetric, as long as the overall energy
momentum tensor possesses zero shear stress.Comment: 15 pages; 5 figures; matches the version published in The European
Physical Journal Plu
The seesaw mechanism at TeV scale in the 3-3-1 model with right-handed neutrinos
We implement the seesaw mechanism in the 3-3-1 model with right-handed
neutrinos. This is accomplished by the introduction of a scalar sextet into the
model and the spontaneous violation of the lepton number. We identify the
Majoron as a singlet under symmetry, which makes it
safe under the current bounds imposed by electroweak data. The main result of
this work is that the seesaw mechanism works already at TeV scale with the
outcome that the right-handed neutrino masses lie in the electroweak scale, in
the range from MeV to tens of GeV. This window provides a great opportunity to
test their appearance at current detectors, though when we contrast our results
with some previous analysis concerning detection sensitivity at LHC, we
conclude that further work is needed in order to validate this search.Comment: about 13 pages, no figure
Primers microssatélites validados em tilápia do nilo no gene da aromatase cerebral (Cyp19b)
Aromatase cytochrome P450 is an enzyme that is responsible for a key step in the biosynthesis of estrogens, which is linked to reproduction. This enzyme is a product of the gene Cyp19 and catalyzes the formation of estrogen from androgen. Estrogen is essential for the development of the gonads and various other physiological processes, ranging from normal growth to reproductive behavior. This study aimed at validation of primers for microsatellite locus in the regulatory region of gene Cyp19b in Oreochromis niloticus. Thirty samples of three strains were analyzed: Chitralada and Supreme from larviculture Aquabel, and GIFT from the State University of Maringá (Paraná, Brazil). After extraction of DNA, the samples were subjected to PCR using primers designed to flank a microsatellite region. After confirmation of amplification, the samples were subjected to electrophoretic separation in the apparatus Origins (Elchrom Scientific, USA) to identify the alleles. A polymorphism in the regulatory region of Cyp19b was identified in the three strains. Three alleles, ranging from 123 to 141 bp, were observed. The primers for amplification of microsatellite in the regulatory region of gene Cyp19b were efficient and, therefore, they may be used for identification of mutations in this region in typical microsatellite analysis. Studies are being conducted to correlate the effect of temperature with the alleles observed in the animals sampled and the resulting sex ratio.A aromatase citocromo P450 é uma enzima que é responsável por um passo chave na biossíntese de estrogênio que está ligado à reprodução. Esta enzima é um produto do gene Cyp19 e catalisa a formação de estrogênio a partir de androgênio. O estrogênio é essencial para o desenvolvimento das gônadas e diversos processos fisiológicos, que vão desde o crescimento normal até o comportamento reprodutivo. Este estudo teve como objetivo a validação de primers para locus microssatélite presente na região regulatória do gene Cyp19b de Oreochromis niloticus. Trinta amostras de três linhagens: Chitralada e Supreme da larvicultura Aquabel e GIFT da Universidade Estadual de Maringá – PR foram analisadas. Após a extração de DNA as amostras foram submetidas a PCR utilizando os primers desenhados para flanquear a região microssatélite. Após a confirmação da amplificação as amostras foram submetidas à separação eletroforética no aparato Origins (Elchrom Scientific, USA) para identificação dos alelos. Foi verificada a existência um polimorfismo na região promotora de Cyp19b nas três linhagens. Observamos três alelos, variando entre 123 e 141 pb. Os primers para a amplificação de microssatélite na região regulatória do gene Cyp19b foram eficientes e, portanto, seu uso para identificação de mutações nesta região pode ser empregada na análise típica de microssatélite. Estudos estão sendo conduzidos para correlacionar o efeito da temperatura com os alelos observados nos animais amostrados e a proporção de sexo resultante. 
Hubble expansion and structure formation in the "running FLRW model" of the cosmic evolution
A new class of FLRW cosmological models with time-evolving fundamental
parameters should emerge naturally from a description of the expansion of the
universe based on the first principles of quantum field theory and string
theory. Within this general paradigm, one expects that both the gravitational
Newton's coupling, G, and the cosmological term, Lambda, should not be strictly
constant but appear rather as smooth functions of the Hubble rate. This
scenario ("running FLRW model") predicts, in a natural way, the existence of
dynamical dark energy without invoking the participation of extraneous scalar
fields. In this paper, we perform a detailed study of these models in the light
of the latest cosmological data, which serves to illustrate the
phenomenological viability of the new dark energy paradigm as a serious
alternative to the traditional scalar field approaches. By performing a joint
likelihood analysis of the recent SNIa data, the CMB shift parameter, and the
BAOs traced by the Sloan Digital Sky Survey, we put tight constraints on the
main cosmological parameters. Furthermore, we derive the theoretically
predicted dark-matter halo mass function and the corresponding redshift
distribution of cluster-size halos for the "running" models studied. Despite
the fact that these models closely reproduce the standard LCDM Hubble
expansion, their normalization of the perturbation's power-spectrum varies,
imposing, in many cases, a significantly different cluster-size halo redshift
distribution. This fact indicates that it should be relatively easy to
distinguish between the "running" models and the LCDM cosmology using realistic
future X-ray and Sunyaev-Zeldovich cluster surveys.Comment: Version published in JCAP 08 (2011) 007: 1+41 pages, 6 Figures, 1
Table. Typos corrected. Extended discussion on the computation of the
linearly extrapolated density threshold above which structures collapse in
time-varying vacuum models. One appendix, a few references and one figure
adde
Economic and climatic models for estimating coffee supply
O objetivo deste trabalho foi estimar a oferta cafeeira por meio da calibração de modelos estatÃsticos, com variáveis econômicas e climáticas, das principais regiões produtoras do Estado de São Paulo. As regiões estudadas foram Batatais, Caconde, Cássia dos Coqueiros, Cristais Paulista, EspÃrito Santo do Pinhal, MarÃlia, Mococa e Osvaldo Cruz. Foram utilizados dados de oferta cafeeira, variáveis econômicas (crédito rural, crédito rural na agricultura e valor da produção) e variáveis climáticas (temperatura do ar, precipitação pluvial, evapotranspiração potencial, deficiência e excedente hÃdrico) de cada região, para o perÃodo de 2000–2014. Os modelos foram calibrados com uso de técnicas de regressão linear múltipla, e todas as combinações possÃveis foram testadas para a seleção das variáveis. A oferta cafeeira foi a variável dependente, e as demais, as independentes. A acurácia e a precisão dos modelos foram analisadas pelo erro percentual médio e pelo coeficiente de determinação ajustado, respectivamente. As variáveis que mais influenciam a oferta cafeeira são o valor de produção e a temperatura do ar. É possÃvel estimar a oferta cafeeira com regressões lineares múltiplas por meio de variáveis econômicas e elementos climáticos. Os modelos mais acurados são os calibrados para estimar a oferta cafeeira das regiões de Cássia dos Coqueiros e Osvaldo Cruz.The objective of this work was to estimate the coffee supply by calibrating statistical models with economic and climatic variables for the main producing regions of the state of São Paulo, Brazil. The regions were Batatais, Caconde, Cássia dos Coqueiros, Cristais Paulista, EspÃrito Santo do Pinhal, MarÃlia, Mococa, and Osvaldo Cruz. Data on coffee supply, economic variables (rural credit, rural agricultural credit, and production value), and climatic variables (air temperature, rainfall, potential evapotranspiration, water deficit, and water surplus) for each region, during the period from 2000–2014, were used. The models were calibrated using multiple linear regression, and all possible combinations were tested for selecting the variables. Coffee supply was the dependent variable, and the other ones were considered independent. The accuracy and precision of the models were assessed by the mean absolute percentage error and the adjusted coefficient of determination, respectively. The variables that most affect coffee supply are production value and air temperature. Coffee supply can be estimated with multiple linear regressions using economic and climatic variables. The most accurate models are those calibrated to estimate coffee supply for the regions of Cássia dos Coqueiros and Osvaldo Cruz
Quantifying the impact of gut microbiota on inflammation and hypertensive organ damage
AIMS: Hypertension (HTN) can lead to heart and kidney damage. The gut microbiota has been linked to HTN, although it is difficult to estimate its significance due to the variety of other features known to influence HTN. In the present study, we used germ-free (GF) and colonized (COL) littermate mice to quantify the impact of microbial colonization on organ damage in HTN. METHODS AND RESULTS: Four-week-old male GF C57BL/6J littermates were randomized to remain GF or receive microbial colonization. HTN was induced by subcutaneous infusion with angiotensin (Ang) II (1.44 mg/kg/d) and 1% NaCl in the drinking water; sham-treated mice served as control. Renal damage was exacerbated in GF mice, whereas cardiac damage was more comparable between COL and GF, suggesting that the kidney is more sensitive to microbial influence. Multivariate analysis revealed a larger effect of HTN in GF mice. Serum metabolomics demonstrated that the colonization status influences circulating metabolites relevant to HTN. Importantly, GF mice were deficient in anti-inflammatory fecal short-chain fatty acids (SCFA). Flow cytometry showed that the microbiome has an impact on the induction of anti-hypertensive myeloid-derived suppressor cells and pro-inflammatory Th17 cells in HTN. In vitro inducibility of Th17 cells was significantly higher for cells isolated from GF than conventionally raised mice. CONCLUSIONS: Microbial colonization status of mice had potent effects on their phenotypic response to a hypertensive stimulus, and the kidney is a highly microbiota-susceptible target organ in HTN. The magnitude of the pathogenic response in GF mice underscores the role of the microbiome in mediating inflammation in HTN. TRANSLATION PERSPECTIVE: To assess the potential of microbiota-targeted interventions to prevent organ damage in hypertension, an accurate quantification of microbial influence is necessary. We provide evidence that the development of hypertensive organ damage is dependent on colonization status and suggest that a healthy microbiota provides anti-hypertensive immune and metabolic signals to the host. In the absence of normal symbiotic host-microbiome interactions, hypertensive damage to the kidney in particular is exacerbated. We suggest that hypertensive patients experiencing perturbations to the microbiota, which are common in CVD, may be at a greater risk for target-organ damage than those with a healthy microbiome
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