1,569 research outputs found

    Морфологічні аспекти реакції тиротропів аденогіповіза, як наслідок хронічної інтоксикації малими дозами пестициду 2,4 Д

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    В работе представлены результаты исследований структурно-функциональных изменений тиротропных клеток аденогипофиза в условиях пестицидной интоксикации различной длительности.In this work we prove the presente the results of structural estimation of the functional state of the adenohypophysis in different periods of pesticide intoxication increase

    Weak-field approximation of effective gravitational theory with local Galilean invariance

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    We examine the weak-field approximation of locally Galilean invariant gravitational theories with general covariance in a (4+1)(4+1)-dimensional Galilean framework. The additional degrees of freedom allow us to obtain Poisson, diffusion, and Schr\"odinger equations for the fluctuation field. An advantage of this approach over the usual (3+1)(3+1)-dimensional General Relativity is that it allows us to choose an ansatz for the fluctuation field that can accommodate the field equations of the Lagrangian approach to MOdified Newtonian Dynamics (MOND) known as AQUAdratic Lagrangian (AQUAL). We investigate a wave solution for the Schr\"odinger equations.Comment: 15 page

    Critical temperature for the two-dimensional attractive Hubbard Model

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    The critical temperature for the attractive Hubbard model on a square lattice is determined from the analysis of two independent quantities, the helicity modulus, ρs\rho_s, and the pairing correlation function, PsP_s. These quantities have been calculated through Quantum Monte Carlo simulations for lattices up to 18×1818\times 18, and for several densities, in the intermediate-coupling regime. Imposing the universal-jump condition for an accurately calculated ρs\rho_s, together with thorough finite-size scaling analyses (in the spirit of the phenomenological renormalization group) of PsP_s, suggests that TcT_c is considerably higher than hitherto assumed.Comment: 5 pages, 6 figures. Accepted for publication in Phys. Rev.

    Distribution of forensic marker allelic frequencies in pernambuco, Northestern Brazil

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    7siPernambuco is one of the 27 federal units of Brazil, ranking seventh in the number of inhabitants. We examined the allele frequencies of 13 short tandem repeat loci (CFS1PO, D3S1358, D5S818, D7S820, D8S1179, D13S317, D16S539, D18S51, D21S11, FGA, TH01, vWA, and TPOX), the minimum recommended by the Federal Bureau of Investigation and commonly used in forensic genetics laboratories in Brazil, in a sample of 609 unrelated individuals from all geographic regions of Pernambuco. The allele frequencies ranged from 5 to 47.2%. No significant differences for any loci analyzed were observed compared with other publications in other various regions of Brazil. Most of the markers observed were in Hardy-Weinberg equilibrium. The occurrence of the allele 47.2 (locus FGA) and alleles 35.1 and 39 (locus D21S11), also described in a single study of the Brazilian population, was observed. The other forensic parameters analyzed (matching probability, power of discrimination, polymorphic information content, paternity exclusion, complement factor I, observed heterozygosity, expected heterozygosity) indicated that the studied markers are very informative for human forensic identification purposes in the Pernambuco population.openopenSantos, S.M.; Souza, C.A.; Rabelo, K.C.N.; Souza, P.; Moura, R.R.; Oliveira, T.C.; Crovella, S.Santos, S. M.; Souza, C. A.; Rabelo, K. C. N.; Souza, P.; Moura, R. R.; Oliveira, T. C.; Crovella, Sergi

    Evaluation of the AR4 CMIP3 and the AR5 CMIP5 model and projections for precipitation in northeast Brazil

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    This article compares the sensitivity of IPCC CMIP3-AR4 and CMIP5-AR5 models used on the latest reports from the Intergovernmental Panel on Climate Change (IPCC) in representing the annual average variations (austral summer and autumn) on three regions in Northeastern Brazil (NNEB) for the periods 1979–2000 using the CMAP (Climatology Merged Analysis of Precipitation) data as reference. The three areas of NNEB chosen for this analysis were the semiarid, eastern, and southern regions. The EOF analysis was performed to investigate how the coupled models resolve the temporal variability of the spatial modes in the Tropical Atlantic Sea Surface Temperature (SST), which drives the interannual variations of the rainfall in the Northeastern Brazil. CMIP3-AR4 and CMIP5-AR5 models presented a good representation of the annual cycle of precipitation. Results from correlation and mean absolute error analysis indicate that both CMIP3 and CMIP5 models produce large errors and barely capture the interannual rainfall variance during austral summer and autumn in Northeast Brazil, this features is closely related to the poor representation of the modes of SST variability in the Tropical Atlantic Ocean. For the summer and autumn rainfall projections (2040–2070) in the semiarid region, there was no convergence between the CMIP3 and CMIP5 models. During the summer and autumn in the eastern sector, both the CMIP3 and CMIP5 models projected rainfall above the mean for the 2040–2070 period

    Magnetic and pair correlations of the Hubbard model with next-nearest-neighbor hopping

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    A combination of analytical approaches and quantum Monte Carlo simulations is used to study both magnetic and pairing correlations for a version of the Hubbard model that includes second-neighbor hopping t=0.35tt^{\prime }=-0.35t as a model for high-temperature superconductors. Magnetic properties are analyzed using the Two-Particle Self-Consistent approach. The maximum in magnetic susceptibility as a function of doping appears both at finite % t^{\prime } and at t=0t^{\prime }=0 but for two totally different physical reasons. When t=0t^{\prime }=0, it is induced by antiferromagnetic correlations while at t=0.35tt^{\prime }=-0.35t it is a band structure effect amplified by interactions. Finally, pairing fluctuations are compared with % T -matrix results to disentangle the effects of van Hove singularity and of nesting on superconducting correlations. The addition of antiferromagnetic fluctuations increases slightly the dd-wave superconducting correlations despite the presence of a van Hove singularity which tends to decrease them in the repulsive model. Some aspects of the phase diagram and some subtleties of finite-size scaling in Monte Carlo simulations, such as inverted finite-size dependence, are also discussed.Comment: Revtex, 8 pages + 15 uuencoded postcript figure

    A Simple Model for the DNA Denaturation Transition

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    We study pairs of interacting self-avoiding walks on the 3d simple cubic lattice. They have a common origin and are allowed to overlap only at the same monomer position along the chain. The latter overlaps are indeed favored by an energetic gain. This is inspired by a model introduced long ago by Poland and Sheraga [J. Chem. Phys. {\bf 45}, 1464 (1966)] for the denaturation transition in DNA where, however, self avoidance was not fully taken into account. For both models, there exists a temperature T_m above which the entropic advantage to open up overcomes the energy gained by forming tightly bound two-stranded structures. Numerical simulations of our model indicate that the transition is of first order (the energy density is discontinuous), but the analog of the surface tension vanishes and the scaling laws near the transition point are exactly those of a second order transition with crossover exponent \phi=1. Numerical and exact analytic results show that the transition is second order in modified models where the self-avoidance is partially or completely neglected.Comment: 29 pages, LaTeX, 20 postscript figure

    Problems with Time-Varying Extra Dimensions or "Cardassian Expansion" as Alternatives to Dark Energy

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    It has recently been proposed that the Universe might be accelerating as a consequence of extra dimensions with time varying size. We show that although these scenarios can lead to acceleration, they run into serious difficulty when taking into account limits on the time variation of the four dimensional Newton's constant. On the other hand, models of ``Cardassian'' expansion based on extra dimensions which have been constructed so far violate the weak energy condition for the bulk stress energy, for parameters that give an accelerating universe.Comment: 8 pages, minor changes. To appear in Physical Review

    Could thermal fluctuations seed cosmic structure?

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    We examine the possibility that thermal, rather than quantum, fluctuations are responsible for seeding the structure of our universe. We find that while the thermalization condition leads to nearly Gaussian statistics, a Harrisson-Zeldovich spectrum for the primordial fluctuations can only be achieved in very special circumstances. These depend on whether the universe gets hotter or colder in time, while the modes are leaving the horizon. In the latter case we find a no-go theorem which can only be avoided if the fundamental degrees of freedom are not particle-like, such as in string gases near the Hagedorn phase transition. The former case is less forbidding, and we suggest two potentially successful ``warming universe'' scenarios. One makes use of the Phoenix universe, the other of ``phantom'' matter.Comment: minor corrections made, references added, matches the version accepted to PR

    Ethnoichthyology Of The Indigenous Truká People, Northeast Brazil

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    Historically, fishing is an important activity for riverine communities established along the São Francisco River, including indigenous communities. In the present study, we researched fishing activities in two villages of the Truká ethnic group, both located in the State of Pernambuco along the sub-middle section of the São Francisco River, Northeast Brazil. We recorded the richness and uses of the fished species and the ecological knowledge on these species, the fishing techniques employed and the perception of the indigenous people regarding current environmental impacts on the São Francisco River that influence local fishing. Method: The information was obtained through interviews with 33 Truká fishers (27 men and six women), including 17 interviewees from Central Village (Cabrobó) and 16 from Tapera Village (Orocó). Results: Using five fishing techniques, the interviewees caught 25 fish species, including 21 native and four exotic species. All species are used as food, and two species are used in traditional Truká medicine. The interviewees revealed that fishing currently has less importance in their subsistence. They indicated that this situation is occurring because of several factors, such as the introduction of exotic species, pollution and urbanization, that have impacted the São Francisco River, resulting in a decline of fishing resources. Nevertheless, we found that the indigenous people who are still fishing have a broad knowledge of the habitat and ecology of the target fishing. Conclusion: Although fishing is declining in importance among the Truká, we found that the individuals who are still practicing this activity have a broad knowledge about the habitat and ecology of the target species and apply that knowledge to fishing methods. Knowledge about the ecology of the species and the environmental impacts that have affected them can support basic research on local fish populations and research investigating the environmental impacts, resource management and sustainable exploitation of fisheries resources. © 2016 Santos and Nóbrea Alves.12
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