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## CONTRIBUTION TO THE THEORY OF PERMEABILITY OF MEMBRANES FOR ELECTROLYTES

Michaelis, L.
Fonte: The Rockefeller University Press Publicador: The Rockefeller University Press
Tipo: Artigo de Revista Científica
Publicado em 04/01/1926 Português
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On page 39, Vol. viii, No. 2, September 18, 1925, multiply the right-hand side of formula (2) by the factor See PDF for Equation. On page 44, immediately after formula (1) the text should be continued as follows: Let us suppose a membrane to be separated by two solutions of KCl of different concentrations K1 and K2 and these concentrations and the corresponding concentrations of K+ within the membrane, which are in equilibrium with the outside solutions, to be so high that the H+ ions may be neglected. When a small electric current flows across the system, practically the K+ ions alone are transferred and that in a reversible manner. Therefore the total P.D. is practically See PDF for Equation This P.D. is composed of two P.D.'s at the boundaries and the diffusion potential within the membrane. Suppose the immobility of the anions is not absolute but only relative as compared with the mobility of the cations, KCl would gradually penetrate into the membrane to equal concentration with the outside solution on either side and no boundary potential would be established. In this case the diffusion P.D. within the membrane is the only P.D., amounting to See PDF for Equation but, V being practically = 0, it would result that See PDF for Equation So the definitive result is the same as in the former case. Now cancel the printed text as far as page 48...

## Propagation of uncertainties and multimodality in the impact problem of two elastic bodies

Buezas, Fernando Salvador; Rosales, Marta Beatriz; Sampaio, Rubens
Fonte: Elsevier Publicador: Elsevier
Tipo: info:eu-repo/semantics/article; info:ar-repo/semantics/artículo; info:eu-repo/semantics/publishedVersion Formato: application/pdf
Português
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An uncertainty quantification study is carried out for the problem of the frontal collision of two elastic bodies. The time of contact and the resultant force function involved during the collision are the quantities of interest. If the initial conditions and the mechanical and geometrical properties were known, the response prediction would be deterministic. However, if the data contains any uncertainty, a stochastic approach becomes appropriate. Based on the Principle of Maximum Entropy (PME), and under certain restrictions on the parameter values, we derive the probability density function (PDF) for each of the stochastic parameters to construct a probabilistic model. Two cases are dealt with: one of a collision involving two spheres and another of a collision of two discs. In the first case, a parameter involving geometry and material properties is assumed stochastic. Since a functional relationship exists, the propagation of the uncertainty of the time of contact can be done symbolically. However, the interaction force function can only be computed from the solution of a nonlinear ordinary differential equation. Given the PDF of the parameter, the problem of uncertainty propagation is tackled using Monte Carlo simulations. The comparison of both approaches yields an excellent agreement. With respect to the collision of two discs...

## Mercado de Trabalho: Conjuntura e Análise: n. 30, Maio. 2006

Brasil. Instituto de Pesquisa Econômica Aplicada (Ipea); Brasil. Ministério do Trabalho e Emprego (MTE)
Fonte: Instituto de Pesquisa Econômica Aplicada (Ipea) Publicador: Instituto de Pesquisa Econômica Aplicada (Ipea)
Tipo: Mercado de trabalho: conjuntura e análise
Português
Relevância na Pesquisa
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O boletim Mercado de trabalho: conjuntura e análise tem periodicidade semestral e traz uma análise conjuntural do Mercado de trabalho, acompanhada de indicadores e seções temáticas que abordam tanto considerações mais técnicas como questões de cunho político-institucional.; n. 30, 40 p.; parte 1: Apresentação de conjuntura, arquivo pdf; parte 2: Análise do mercado de trabalho, arquivo pdf; parte 3: Nota Técnica: Desigualdade de rendimento do trabalho no Brasil no período pós-real, arquivo pdf; parte 4: Nota Técnica: O dilema do financiamento orçamentário das políticas públicas de emprego, arquivo pdf

## Mercado de Trabalho: Conjuntura e Análise: n. 32, mar. 2007

Brasil. Instituto de Pesquisa Econômica Aplicada (Ipea); Brasil. Ministério do Trabalho e Emprego (MTE)
Fonte: Instituto de Pesquisa Econômica Aplicada (Ipea) Publicador: Instituto de Pesquisa Econômica Aplicada (Ipea)
Tipo: Mercado de trabalho: conjuntura e análise
Português
Relevância na Pesquisa
148.29727%
O boletim Mercado de trabalho: conjuntura e análise tem periodicidade semestral e traz uma análise conjuntural do Mercado de trabalho, acompanhada de indicadores e seções temáticas que abordam tanto considerações mais técnicas como questões de cunho político-institucional.; n. 32, ca. 30 p.; parte 1: Apresentação da conjuntura, arquivo pdf; parte 2: Análise do mercado de trabalho, arquivo pdf; parte 3: Nota técnica: A evolução do mercado de trabalho metropolitano segundo a leitura da nova metodologia da pesquisa mensal de emprego no período de março de 2002 a dezembro de 2006, arquivo pdf; parte 4: Indicadores e previsões Ipea, em 6 arquivos pdf

## On calibration of some distance scales in astrophysics

Vukotic, B.; Jurkovic, M.; Urosevic, D.; Arbutina, B.
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
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We present a method for distance calibration without using standard fitting procedures. Instead we use random resampling to reconstruct the probability density function (PDF) of calibration data points in the fitting plane. The resulting PDF is then used to estimate distance-related properties. The method is applied to samples of radio surface brightness to diameter (\Sigma-D) data for the Galactic supernova remnants (SNRs) and planetary nebulae (PNe), and period-luminosity (PL) data for the Large Magellanic Cloud (LMC) fundamental mode classical Cepheids. We argue that resulting density maps can provide more accurate and more reliable calibrations than those obtained by standard linear fitting procedures. For the selected sample of the Galactic SNRs, the presented PDF method of distance calibration results in a smaller average distance fractional error of up to $\approx 16$ percentage points. Similarly, the fractional error is smaller for up to $\approx 8$ and $\approx 0.5$ percentage points, for the samples of Galactic PNe and LMC Cepheids, respectively. In addition, we provide a PDF-based calibration data for each of the samples.; Comment: 11 pages, 3 figures, corrected for mistakenly considering working data as absolute instead of apparent magnitude...

## Roughness distributions for 1/f^alpha signals

Antal, T.; Droz, M.; Gyorgyi, G.; Racz, Z.
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
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The probability density function (PDF) of the roughness, i.e., of the temporal variance, of 1/f^alpha noise signals is studied. Our starting point is the generalization of the model of Gaussian, time-periodic, 1/f noise, discussed in our recent Letter [T. Antal et al., PRL, vol. 87, 240601 (2001)], to arbitrary power law. We investigate three main scaling regions, distinguished by the scaling of the cumulants in terms of the microscopic scale and the total length of the period. Various analytical representations of the PDF allow for a precise numerical evaluation of the scaling function of the PDF for any alpha. A simulation of the periodic process makes it possible to study also non-periodic signals on short intervals embedded in the full period. We find that for alpha=<1/2 the scaled PDF-s in both the periodic and the non-periodic cases are Gaussian, but for alpha>1/2 they differ from the Gaussian and from each other. Both deviations increase with growing alpha. That conclusion, based on numerics, is reinforced by analytic results for alpha=2 and alpha->infinity. We suggest that our theoretical and numerical results open a new perspective on the data analysis of 1/f^alpha processes.; Comment: 12 pages incl. 6 figures, with RevTex4...

## What regulates the velocity distribution of interstellar clouds?

Ricotti, Massimo; Ferrara, Andrea
Tipo: Artigo de Revista Científica
Publicado em 08/04/2002 Português
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## A collaborative theoretical and experimental study of the structure and electronic excitation spectrum of the BAr and B(Ar)2 complexes

Alexander, Millard H.; Walton, Andrew; Yang, Moonbong; Yang, Xin; Hwang, Eunsook; Dagdigian, Paul J.
Tipo: Artigo de Revista Científica
Publicado em 23/01/1997 Português
Relevância na Pesquisa
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We report the investigation of the 3s <- 2p transition in the BAr2 cluster. In a supersonic expansion of B atoms entrained in Ar, at high beam source backing pressures we observe several features in the fluorescence excitation spectrum which cannot be assigned to the BAr diatom. Using BAr(X, B) potential energy curves which reproduce our experimental observations on this molecule and an Ar-Ar interaction potential, we employ a pairwise additive model, along with variational and diffusion Monte-Carlo treatments of the nuclear motion, to determine the lowest vibrational state of the BAr2 cluster. A subsequent simulation of the fluorescence excitation spectrum reproduces nearly quantitatively the strongest feature in our experimental spectrum not assignable to BAr. Because of the barrier in the BAr(B 2Sigma+) potential energy curve, the 3s <- 2p transition in the BAr2 cluster is predicted to have an asymmetric profile, as is found experimentally.; Comment: a pdf file (5 kB) containing the abstract can be retrieved as ftp://mha-ibm2.umd.edu/pub/publications/BAr2.abs.pdf a pdf file (325 kB) containing the entire manuscript can be retrieved as ftp://mha-ibm2.umd.edu/pub/publications/BAr2.ms.pdf To appear in J. Chem. Phys. 106 (1997) 8 April issue.

## A quasi-Gaussian approximation for the probability distribution of correlation functions

Wilking, Philipp; Schneider, Peter
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
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Context. Whenever correlation functions are used for inference about cosmological parameters in the context of a Bayesian analysis, the likelihood function of correlation functions needs to be known. Usually, it is approximated as a multivariate Gaussian, though this is not necessarily a good approximation. Aims. We show how to calculate a better approximation for the probability distribution of correlation functions, which we call "quasi-Gaussian". Methods. Using the exact univariate PDF as well as constraints on correlation functions previously derived, we transform the correlation functions to an unconstrained variable for which the Gaussian approximation is well justified. From this Gaussian in the transformed space, we obtain the quasi-Gaussian PDF. The two approximations for the probability distributions are compared to the "true" distribution as obtained from simulations. Additionally, we test how the new approximation performs when used as likelihood in a toy-model Bayesian analysis. Results. The quasi-Gaussian PDF agrees very well with the PDF obtained from simulations; in particular, it provides a significantly better description than a straightforward copula approach. In a simple toy-model likelihood analysis, it yields noticeably different results than the Gaussian likelihood...

## Quantum magnetism in two dimensions: From semi-classical Neel order to magnetic disorder

Richter, J.; Schulenburg, J.; Honecker, A.
Tipo: Artigo de Revista Científica
Publicado em 23/12/2004 Português
Relevância na Pesquisa
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This is a review of ground-state features of the s=1/2 Heisenberg antiferromagnet on two-dimensional lattices. A central issue is the interplay of lattice topology (e.g. coordination number, non-equivalent nearest-neighbor bonds, geometric frustration) and quantum fluctuations and their impact on possible long-range order. This article presents a unified summary of all 11 two-dimensional uniform Archimedean lattices which include e.g. the square, triangular and kagome lattice. We find that the ground state of the spin-1/2 Heisenberg antiferromagnet is likely to be semi-classically ordered in most cases. However, the interplay of geometric frustration and quantum fluctuations gives rise to a quantum paramagnetic ground state without semi-classical long-range order on two lattices which are precisely those among the 11 uniform Archimedean lattices with a highly degenerate ground state in the classical limit. The first one is the famous kagome lattice where many low-lying singlet excitations are known to arise in the spin gap. The second lattice is called star lattice and has a clear gap to all excitations. Modification of certain bonds leads to quantum phase transitions which are also discussed briefly. Furthermore, we discuss the magnetization process of the Heisenberg antiferromagnet on the 11 Archimedean lattices...

## Nonparametric tests of structure for high angular resolution diffusion imaging in Q-space

Olhede, Sofia C.; Whitcher, Brandon
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
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High angular resolution diffusion imaging data is the observed characteristic function for the local diffusion of water molecules in tissue. This data is used to infer structural information in brain imaging. Nonparametric scalar measures are proposed to summarize such data, and to locally characterize spatial features of the diffusion probability density function (PDF), relying on the geometry of the characteristic function. Summary statistics are defined so that their distributions are, to first-order, both independent of nuisance parameters and also analytically tractable. The dominant direction of the diffusion at a spatial location (voxel) is determined, and a new set of axes are introduced in Fourier space. Variation quantified in these axes determines the local spatial properties of the diffusion density. Nonparametric hypothesis tests for determining whether the diffusion is unimodal, isotropic or multi-modal are proposed. More subtle characteristics of white-matter microstructure, such as the degree of anisotropy of the PDF and symmetry compared with a variety of asymmetric PDF alternatives, may be ascertained directly in the Fourier domain without parametric assumptions on the form of the diffusion PDF. We simulate a set of diffusion processes and characterize their local properties using the newly introduced summaries. We show how complex white-matter structures across multiple voxels exhibit clear ellipsoidal and asymmetric structure in simulation...

## Reconstruction of the One-point Distribution of Convergence from Weak Lensing by Large-scale Structure

Zhang, Tong-Jie; Pen, Ue-Li
Tipo: Artigo de Revista Científica
Português
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Weak lensing measurements are starting to provide statistical maps of the distribution of matter in the universe that are increasingly precise and complementary to cosmic microwave background maps. The probability distribution (PDF) provides a powerful tool to test non-Gausian features in the convergence field and to discriminate the different cosmological models. In this letter, we present a new PDF space Wiener filter approach to reconstruct the probability density function of the convergence from the noisy convergence field. We find that for parameters comparable to the CFHT legacy survey, the averaged PDF of the convergence in a 3 degree field can be reconstructed with an uncertainty of about 10%, even though the pointwise PDF is noise dominated.; Comment: 21 pages, 8 figures, accepted for publication in ApJ, added some discussions

## The Arecibo Galaxy Environments Survey - Description and Early Results

Minchin, R. F.; Auld, R.; Davies, J. I.; Catinella, B.; Cortese, L.; Linder, S.; Momjian, E.; Muller, E.; O'Neil, K.; Rosenberg, J.; Sabatini, S; Schneider, S. E.; Stage, M.; van Driel, W.; team, for the AGES