School Choice in the District of Columbia: Saving Taxpayers Money, Increasing Opportunities for Children

Members of Congress and President Bush have put forth proposals that would establish school voucher programs in the District of Columbia. Those programs would allow pupils to use vouchers to attend the parochial or private school of their parents' choice. Could private schools increase the range of academic options in the nation's capital by educating students currently attending District of Columbia public schools? An analysis of the private and parochial schools in the metropolitan Washington, D.C., area reveals the following: Private schools in Washington and sur-rounding areas charge less on average than the D.C. public school system spends per pupil.The D.C. public school system, which has suffered from overspending and budget deficits in the last few years, could find its enrollment reduced by almost 10 percent as a result of a voucher program.Private schools in Washington could immediately accommodate about 2,925 students now attending public or charter schools. Allowing all independent and parochial schools in the Washington metro area to participate in a school choice program could add almost 3,500 more spaces, since there are more than 6,000 seats available in local, nonpublic schools

Obtention d'alliages réfractaires SiCxNy(O) par dépôt chimique à oartir d'une gazeuse Si(CH3)4-NH3

By pure thermal CVD from Si(CH/sub 3/)/sub 4/NH/sub 3/ mixtures SiC/sub x/N/sub y/(O) films have been prepared at 1475 K. Using electron microprobe analysis a continuous composition variation between SiC and Si/sub 3/N/sub 4/ is shown. The difficulty of quantitative analysis due to the conductivity of the samples is underlined. By selecting the right conditions, precise measurements were obtained. These films have an optical energy band gap in the range 2.2-4.1 eV and a constant photoluminescence peak. The film structure is discussed and these materials may be probably ascribed to an alloy phas

Tests of mode coupling theory in a simple model for two-component miscible polymer blends

We present molecular dynamics simulations on the structural relaxation of a simple bead-spring model for polymer blends. The introduction of a different monomer size induces a large time scale separation for the dynamics of the two components. Simulation results for a large set of observables probing density correlations, Rouse modes, and orientations of bond and chain end-to-end vectors, are analyzed within the framework of the Mode Coupling Theory (MCT). An unusually large value of the exponent parameter is obtained. This feature suggests the possibility of an underlying higher-order MCT scenario for dynamic arrest.Comment: Revised version. Additional figures and citation

Wake deviation of yawed wind turbine by Large-Eddy Simulation

International audienceKeywords: Large Eddy Simulation, yaw and wake interaction According to the current energetic and environmental challenges, maximizing the electric power generated in windfarms is a societal concern. New strategies such as involving wind turbine yaw angle seem relevant to reduce wake interaction and associated power losses [1]. Therefore, yawed turbine aerodynamics is modified and remains a challenging investigation topic. Since experimental data on actual windfarm scales are not affordable and given the constant growth of computational resources, high order numerical simulations tend to be a promising approach [2]. The goal of this study is to evaluate a highly resolved numerical model under yaw condition in a wind tunnel before applying it to actual windfarm. The blade modeling is performed using an Actuator Line Method [3] (ALM), coupled to the low Mach-number massively-parallel finite-volume Large-Eddy Simulation (LES) flow solver on unstructured meshes, called YALES2 [4] [5]. The Blind Test 5 experimental configuration led at NTNU [6], gathering numerous experimental data, is reproduced in this study. After the study of a yawed turbine wake interaction with downstream turbine the study of a single yawed turbine (+30 o and 0 o) will be presented. The computational domain of these cases will be the NTNU wind tunnel, involving a turbulence grid aiming to create a fully turbulent sheared inflow [6]. The grid will be modeled using multiple Actuator Lines (to mimic the turbine blades) with dedicated polars [7] [8]. Each computational case is performed on a unstructured mesh with around 150.10 6 tetrahedra. An instantaneous velocity field of the yawed turbine wake interaction is presented on Figure 1. Figure 1: Instantaneous streamwise velocity field of wake interaction between two turbines in the NTNU wind tunnel with unstructured mes

Hyper high NA achromatic interferometer for immersion lithography at 193nm

International audienceAn apparatus for immersion interferometric lithography is described here where the interfering beams are created by illuminating a first diffraction grating followed by a second diffraction grating recombining the diffracted beams onto the photo-resist plane. The main advantage of this system is to be achromatic: thus it is possible to use a basic commercial ArF excimer laser as the exposure source. We present here the calculations made to evaluate the different parameters that can influence the depth-of-focus in the immersion configuration. As the set-up is mainly based on the two diffraction gratings, it matters to properly design it. The purpose of this paper is to show the optimization made on the diffraction gratings in taking into account their fabrication process since they are fabricated using the capabilities of the silicon line available in our laboratory. On one hand, calculations have been done to determine the second grating period as a function of the first grating period and the ”immersion NA”. By simply adding a fluid to a “dry” system, we will indeed be able to improve the depth of focus but not the resolution. In playing with the diffraction grating periods, we are able to benefit from the introduction of the immersion fluid. We have performed simulations in order to optimize the grating diffraction efficiency as a function of the etch depth and the fractional linewidth. Finally we report on first results obtained with the achromatic immersion interferometer. The apparatus was used with a 193 nm GAM excimer laser to print resist patterns having a period of 100 nm with excellent contrast

Surface decoration of catanionic vesicles with superparamagnetic iron oxide nanoparticles: a model system for triggered release under moderate temperature conditions

International audienceWe report the design of new catanionic vesicles decorated with iron oxide nanoparticles, which could be used as a model system to illustrate controlled delivery of small solutes under mild hyperthermia. Efficient release of fluorescent dye rhodamine 6G was observed when samples were exposed to an oscillating magnetic field. Our system provides direct evidence for reversible permeability upon magnetic stimulation

Prevalence of sensorineural hearing loss in children and adolescents with diabetes mellitus

To establish the prevalence of sensorineural hearing loss (SNHL), as well as the predisposing risk factors, in children and adolescents with type 1 diabetes mellitus (T1DM) attending the Service of Endocrino-Pediatrics and Otolaryngology Department of the ‘‘Dr. José Eleuterio González’’ University Hospital and the Materno-Infantil Hospital, from January 2011 to December 2012. Material and methods: A total of 84 children with T1DM, with ages between 6 and 18 years old, were studied. Values of glycated hemoglobin (HbA1c) were assessed and Tonal audiometry and Speech audiometry tests were performed. Results: A total of 84 patients with a diagnosis of T1DM were studied, out of which 12 (14.3%) presented SNHL. Fifty percent of patients with hearing loss were in the age range of 10---13 years old. Regarding time of evolution with the disease (T1DM), 33% of patients with more than 5 years with T1DM presented SNHL, and nearly 88.9% of the patients with less than 5 years with T1DM presented normal hearing (p = 0.011). Moreover, 65.47% of the patients presented complications due to poor glycemic control at some point in the evolution of their disease. All (100%) diabetic patients with SNHL and 91% of the patients without SNHL had HbA1c values greater than 6%. In patients with hearing impairments, 83.3% suffered mild and 16.4% suffered moderate hearing loss. Most presented bilateral hearing loss, with the right ear dominating. Acute frequencies, mainly 8000 kHz, were the most affected

Laryngeal amyloidosis: An uncommon cause of dysphonia

Introduction: Amyloidosis is used to describe a range of disorders deined by extracellular deposition of abnormal protein ibrils. The larynx is the most common site of localized amyloidosis in the head and neck region and constitutes less than 1% of benign laryngeal lesions. Hoarseness is the most common symptom. Objective: Prospective clinical evaluation of patients with localized laryngeal amyloidosis. Clinical cases: Presented are 4 cases of patients with localized laryngeal amyloidosis who were treated at the Otolaryngology and Head and Neck Surgery Department at the “Dr. José Eleuterio González” University Hospital in Monterrey, Mexico. Three patients underwent phonomicrosurgery by direct microlaryngoscopy with the removal of the amyloid implantation using a cold knife excision with great results. In each patient the major site of involvement was the supraglottis with a small focus on the false vocal cord. A medical work-up, including a complete blood count (CBC), a basic metabolic panel, urinalysis, liver function test, chest X-ray and physical examination were performed to rule out the presence of systemic disease; no amyloidosis or signs of systemic disease were found. Congo red staining conirms the diagnosis of amyloidosis in all surgical specimens. Conclusions: In laryngeal amyloidosis, the treatment should be directed toward the improvement of the voice and the maintenance of the airway

The Sigma 13 (10-14) twin in alpha-Al2O3: A model for a general grain boundary

The atomistic structure and energetics of the Sigma 13 (10-14)[1-210] symmetrical tilt grain boundary in alpha-Al2O3 are studied by first-principles calculations based on the local-density-functional theory with a mixed-basis pseudopotential method. Three configurations, stable with respect to intergranular cleavage, are identified: one Al-terminated glide-mirror twin boundary, and two O-terminated twin boundaries, with glide-mirror and two-fold screw-rotation symmetries, respectively. Their relative energetics as a function of axial grain separation are described, and the local electronic structure and bonding are analysed. The Al-terminated variant is predicted to be the most stable one, confirming previous empirical calculations, but in contrast with high-resolution transmission electron microscopy observations on high-purity diffusion-bonded bicrystals, which resulted in an O-terminated structure. An explanation of this discrepancy is proposed, based on the different relative energetics of the internal interfaces with respect to the free surfaces