Spontaneous Breaking of Translational Invariance in One-Dimensional Stationary States on a Ring

We consider a model in which positive and negative particles diffuse in an asymmetric, CP-invariant way on a ring. The positive particles hop clockwise, the negative counterclockwise and oppositely-charged adjacent particles may swap positions. Monte-Carlo simulations and analytic calculations suggest that the model has three phases; a "pure" phase in which one has three pinned blocks of only positive, negative particles and vacancies, and in which translational invariance is spontaneously broken, a "mixed" phase with a non-vanishing current in which the three blocks are positive, negative and neutral, and a disordered phase without blocks.Comment: 7 pages, LaTeX, needs epsf.st

Poverty comparisons with absolute poverty lines estimated from survey data

"The objective of measuring poverty is usually to make comparisons over time or between two or more groups. Common statistical inference methods are used to determine whether an apparent difference in measured poverty is statistically significant. Studies of relative poverty have long recognized that when the poverty line is calculated from sample survey data, both the variance of the poverty line and the variance of the welfare metric contribute to the variance of the poverty estimate. In contrast, studies using absolute poverty lines have ignored the poverty line variance, even when the poverty lines are estimated from sample survey data. Including the poverty line variance could either reduce or increase the precision of poverty estimates, depending on the specific characteristics of the data. This paper presents a general procedure for estimating the standard error of poverty measures when the poverty line is estimated from survey data. Based on bootstrap methods, the approach can be used for a wide range of poverty measures and methods for estimating poverty lines. The method is applied to recent household survey data from Mozambique. When the sampling variance of the poverty line is taken into account, the estimated standard errors of Foster-Greer- Thorbecke and Watts poverty measures increase by 15 to 30 percent at the national level, with considerable variability at lower levels of aggregation." -- Authors' AbstractPoverty measurement, Surveys -- Statistical methods, Household surveys, Poverty lines

Estimating utility-consistent poverty lines

"With the focus of international development resources increasingly turned toward poverty reduction, the demand for reliable empirical estimates of poverty levels has grown dramatically... This paper contributes to the poverty measurement literature by introducing an information theoretic approach to assuring the utility consistency of poverty lines. Even though the philosophical roots of information theory and the links between information theory and other estimation criteria fill volumes, the actual practical application of the approach is quite straightforward." From TextPoverty lines ,Poverty alleviation ,Development projects Evaluation ,measurement ,Entropy estimation ,

Yang-Lee Theory for a Nonequilibrium Phase Transition

To analyze phase transitions in a nonequilibrium system we study its grand canonical partition function as a function of complex fugacity. Real and positive roots of the partition function mark phase transitions. This behavior, first found by Yang and Lee under general conditions for equilibrium systems, can also be applied to nonequilibrium phase transitions. We consider a one-dimensional diffusion model with periodic boundary conditions. Depending on the diffusion rates, we find real and positive roots and can distinguish two regions of analyticity, which can identified with two different phases. In a region of the parameter space both of these phases coexist. The condensation point can be computed with high accuracy.Comment: 4 pages, accepted for publication in Phys.Rev.Let

Polycomb group protein complexes exchange rapidly in living Drosophila

Fluorescence recovery after photobleaching (FRAP) microscopy was used to determine the kinetic properties of Polycomb group (PcG) proteins in whole living Drosophila organisms (embryos) and tissues (wing imaginal discs and salivary glands). PcG genes are essential genes in higher eukaryotes responsible for the maintenance of the spatially distinct repression of developmentally important regulators such as the homeotic genes. Their absence, as well as overexpression, causes transformations in the axial organization of the body. Although protein complexes have been isolated in vitro, little is known about their stability or exact mechanism of repression in vivo. We determined the translational diffusion constants of PcG proteins, dissociation constants and residence times for complexes in vivo at different developmental stages. In polytene nuclei, the rate constants suggest heterogeneity of the complexes. Computer simulations with new models for spatially distributed protein complexes were performed in systems showing both diffusion and binding equilibria, and the results compared with our experimental data. We were able to determine forward and reverse rate constants for complex formation. Complexes exchanged within a period of 1-10 minutes, more than an order of magnitude faster than the cell cycle time, ruling out models of repression in which access of transcription activators to the chromatin is limited and demonstrating that long-term repression primarily reflects mass-action chemical equilibria

Poverty Comparisons with Endogenous Absolute Poverty Lines

The objective of measuring poverty is usually to make comparisons over time or between two or more groups. Comm on statistical inference methods are used to determine whether an apparent difference in measured poverty is statistically significant. Studies of relative poverty have long recognized that when the poverty line is calculated from sample survey data, both the variance of the poverty line and the variance of the welfare metric contribute to the variance of the poverty estimate. In contrast, studies using absolute poverty lines have ignored the poverty line variance, even when the poverty lines are estimated from sample survey data. Including the poverty line variance could either reduce or increase the precision of poverty estimates, depending on the s pecific characteristics of the data. This paper presents a general procedure for estimating the standard error of poverty measures when th e poverty line is estimated from survey data. Based on bootstrap methods, the approach can be used for a wide range of poverty measures and methods for estimating poverty lines. The method is applied to recent household survey data from Mozambique. When the sampling variance of the poverty line is taken into account, the estimated standard errors of the headcount and the poverty gap at the national level increase by 27 and 29 percent respectively.poverty measurement, bootstrap, Mozambique, Food Security and Poverty, I32, C13, 012,

Comment on `Measurement of the π+p⃗\pi^+ \vec p analyzing power at 68.3 MeV'

We comment on a recent paper by Weiser et al. [Phys. Rev. C {\bf 54}, 1930 (1996)]. The authors have performed a single-energy analysis of $\pi^+ p$ scattering data at 68.3 MeV, finding a value for the $S_{31}$ phase shift about 1^o smaller than found in the Karlsruhe-Helsinki (KH) partial-wave analysis. The authors use this result to argue for a dispersion relation analysis using recently measured data, so that their effect on the $\pi NN$ coupling constant (f^2) and $\Sigma$ amplitude can be determined. We note that these tasks were accomplished prior to the submission of the above paper. We clarify the effect of this new analyzing power data on f^2 and the $\Sigma$ amplitude.Comment: 5 pages of text. Revised according to Referee suggestion