School Choice and Student Achievement. Evidence from Poland

The impact of school choice on education quality is one of the most hotly contested issues in education economics. We contribute to the debate by investigating the effect of concentration of local education markets and the number of schools in the city on the average achievements of 9th grade students in Polish middle schools. We find the evidence that the increased availability of choice leads to higher performance, although this relationship holds only until a certain threshold is reached. As the number of schools in the city reaches four, the marginal benefit from further widening of the market falls to zero, or even becomes negative. Besides the influence on the average achievement in the city, the increased school choice leads to higher differentiation among schools. In contrast to the previous result, here we do not observe any threshold, and the effect seems to be independent of scale.school choice, school competition, educational quality, school differentiation

Is Large More Effective than Small is Beautiful? Size and Performance of Primary Schools in Poland

We investigate the size-related features of the production function of Polish primary schools. The interplay of small schools ineffectiveness and of organizational and social difficulties appearing in large schools implies that the relationship between school size and student achievement is non-linear, with the optimal size crucially dependent on the social characteristics of the served population (such as average income per capita). Busing is found to have negative effect on performance, related to average distance of student transportation. The findings present several challenges to consolidation policies on quality ground, quite independent of the more common cost considerations.school production function, educational achievement, school size, class size, school consolidation

School Choice and Student Achievement. Evidence from Poland

The impact of school choice on education quality is one of the most hotly contested issues in education economics. We contribute to the debate by investigating the effect of concentration of local education markets and the number of schools in the city on the average achievements of 9th grade students in Polish middle schools. We find the evidence that the increased availability of choice leads to higher performance, although this relationship holds only until a certain threshold is reached. As the number of schools in the city reaches four, the marginal benefit from further widening of the market falls to zero, or even becomes negative. Besides the influence on the average achievement in the city, the increased school choice leads to higher differentiation among schools. In contrast to the previous result, here we do not observe any threshold, and the effect seems to be independent of scale

School Choice and Student Achievement. Evidence from Poland

The impact of school choice on education quality is one of the most hotly contested issues in education economics. We contribute to the debate by investigating the effect of concentration of local education markets and the number of schools in the city on the average achievements of 9th grade students in Polish middle schools. We find the evidence that the increased availability of choice leads to higher performance, although this relationship holds only until a certain threshold is reached. As the number of schools in the city reaches four, the marginal benefit from further widening of the market falls to zero, or even becomes negative. Besides the influence on the average achievement in the city, the increased school choice leads to higher differentiation among schools. In contrast to the previous result, here we do not observe any threshold, and the effect seems to be independent of scale

A discrete geometric approach for simulating the dynamics of thin viscous threads

We present a numerical model for the dynamics of thin viscous threads based on a discrete, Lagrangian formulation of the smooth equations. The model makes use of a condensed set of coordinates, called the centerline/spin representation: the kinematical constraints linking the centerline's tangent to the orientation of the material frame is used to eliminate two out of three degrees of freedom associated with rotations. Based on a description of twist inspired from discrete differential geometry and from variational principles, we build a full-fledged discrete viscous thread model, which includes in particular a discrete representation of the internal viscous stress. Consistency of the discrete model with the classical, smooth equations is established formally in the limit of a vanishing discretization length. The discrete models lends itself naturally to numerical implementation. Our numerical method is validated against reference solutions for steady coiling. The method makes it possible to simulate the unsteady behavior of thin viscous jets in a robust and efficient way, including the combined effects of inertia, stretching, bending, twisting, large rotations and surface tension

Towards spectrally selective catastrophic response

We study the large-amplitude response of classical molecules to electromagnetic radiation, showing the universality of the transition from linear to nonlinear response and breakup at sufficiently large amplitudes. We demonstrate that a range of models, from the simple harmonic oscillator to the successful Peyrard-Bishop-Dauxois type models of DNA, which include realistic effects of the environment (including damping and dephasing due to thermal fluctuations), lead to characteristic universal behavior: formation of domains of dissociation in driving force amplitude-frequency space, characterized by the presence of local boundary minima. We demonstrate that by simply following the progression of the resonance maxima in this space, while gradually increasing intensity of the radiation, one must necessarily arrive at one of these minima, i.e., a point where the ultrahigh spectral selectivity is retained. We show that this universal property, applicable to other oscillatory systems, is a consequence of the fact that these models belong to the fold catastrophe universality class of Thom's catastrophe theory. This in turn implies that for most biostructures, including DNA, high spectral sensitivity near the onset of the denaturation processes can be expected. Such spectrally selective molecular denaturation could find important applications in biology and medicine

Calcium binding to a disordered domain of a type III-secreted protein from a coral pathogen promotes secondary structure formation and catalytic activity

Strains of the Gram-negative bacterium Vibrio coralliilyticus cause the bleaching of corals due to decomposition of symbiotic microalgae. The V. coralliilyticus strain ATCC BAA-450 (Vc450) encodes a type III secretion system (T3SS). The gene cluster also encodes a protein (locus tag VIC_001052) with sequence homology to the T3SS-secreted nodulation proteins NopE1 and NopE2 of Bradyrhizobium japonicum (USDA110). VIC_001052 has been shown to undergo auto-cleavage in the presence of Ca2+ similar to the NopE proteins. We have studied the hitherto unknown secondary structure, Ca2+-binding affinity and stoichiometry of the "metal ion-inducible autocleavage" (MIIA) domain of VIC_001052 which does not possess a classical Ca2+-binding motif. CD and fluorescence spectroscopy revealed that the MIIA domain is largely intrinsically disordered. Binding of Ca2+ and other di- and trivalent cations induced secondary structure and hydrophobic packing after partial neutralization of the highly negatively charged MIIA domain. Mass spectrometry and isothermal titration calorimetry showed two Ca2+-binding sites which promote structure formation with a total binding enthalpy of -110 kJ mol(-1) at a low micromolar K-d. Putative binding motifs were identified by sequence similarity to EF-hand domains and their structure analyzed by molecular dynamics simulations. The stoichiometric Ca2+-dependent induction of structure correlated with catalytic activity and may provide a "host-sensing" mechanism that is shared among pathogens that use a T3SS for efficient secretion of disordered proteins

Optimization of hierarchical structure and nanoscale enabled plasmonic refraction for window electrodes in photovoltaics

An ideal network window electrode for photovoltaic applications should provide an optimal surface coverage, a uniform current density into and/or from a substrate, and a minimum of the overall resistance for a given shading ratio. Here we show that metallic networks with quasi-fractal structure provides a near-perfect practical realization of such an ideal electrode. We find that a leaf venation network, which possesses key characteristics of the optimal structure, indeed outperforms other networks. We further show that elements of hierarchal topology, rather than details of the branching geometry, are of primary importance in optimizing the networks, and demonstrate this experimentally on five model artificial hierarchical networks of varied levels of complexity. In addition to these structural effects, networks containing nanowires are shown to acquire transparency exceeding the geometric constraint due to the plasmonic refraction