Competitive Impacts of Means-Tested Vouchers on Public School Performance: Evidence from Louisiana

Given the significant growth rate and geographic expansion of private school choice programs over the past two decades, it is important to examine how traditional public schools respond to the sudden injection of competition for students and resources. Although prior studies of this nature have been limited to Florida and Milwaukee, using multiple analytic strategies this paper examines the competitive impacts of the Louisiana Scholarship Program (LSP) to determine its achievement impacts on students in affected public schools. Serving 4,954 students in its first year of statewide expansion, this targeted school voucher program provides public funds for low-income students in low-performing public schools to enroll in participating private schools across the state of Louisiana. Using (1) a school fixed effects approach and (2) a regression discontinuity framework to examine the achievement impacts of the LSP on students in affected public schools, this competitive effects analysis reveals neutral to positive impacts that are small in magnitude. Policy implications are discussed.

A Novel Experimental Technique to Simulate Shock Behaviour and Bursting Failure of Roadways

Rockburst is a sudden and dynamic failure of rock that can cause serious injury to miners and damage to the underground excavations. Stress path, dynamic disturbance, and support system play important and different roles in the generation processes of rockbursts, resulting rockbursts with variety of reasons and failure modes. A test facility that was capable of simulating such factors was developed to study shock behaviour and bursting failure of roadways. The results demonstrate that the modeled roadway was in good condition and retained a shock resistance capacity after three drop loads. Until the acceleration amplitude increased to a certain level at the time of the fourth dynamic loading, sudden bursting failure of modeled roadway occurred. Many large fragments ejected from the upper and middle regions of the roadway, accompanied with loud noise. A deep pit was observed after the bursting failure. The axial of the fan-shaped pit had an angle above the vertical. In addition, shock behaviour of the modeled roadway had been changed by the anchor-net support. Significant differences appeared between the acceleration signals measured in two roadway sections with and without the anchor-net support. The acceleration magnitude of the supported roadway section was strongly reduced by the presence of the anchor-net support. Even when the unsupported roadway section underwent a sudden injection failure, the roadway with anchor-net support was in good condition. This study may eventually lead to a methodology for studying the rockbursting resistance capacity of underground roadways.

The Formation of Debris Flow Dams: Geomorphic Setting and Influential Factors

Temporary dams can be formed by the sudden injection of debris flow into main stream for some favorable geomorphologic and hydraulic conditions, which would result in extensive inundations upstream and catastrophic floods downstream due to dam breach and consequently dramatic changes of channel and valley. Expeditious means of assessing potential of dam-forming are necessary, particularly in geological active regions. The complete blockages or dam-forming significantly relate to the discharge ratio and velocity ratio between tributary and main stream, bulk density of debris flow, confluent angles and evenness degree of grain sizes.

Spectral Turn-Over of Radio Arc Filaments at 43 GHz: Magnetic Tubes of 4000-yr Old in the Galactic Center

The origin of the straight magnetic filaments in the Radio Arc near the Galactic Center is still controversial: either if they are permanent structure of constant configuration for a galactic-time scale, or they are temporary structure of short life time such as due to a sudden injection of cosmic rays or to sudden shock compression. Measurement of life time of the radio emitting cosmic ray electrons consisting the filaments is one of the crucial methods besides a time variation measurement of the fine structure of the filaments.In order to investigate possible spatial variation of spectral index at higher frequencies in the filaments, which might give information about the life time of cosmic ray electrons, we have performed high-resolution radio continuum observations at 43 GHz of the GO.18-0.04 region of the radio Arc near the galactic center using the Nobeyama Millimeter-wave Array. A detailed description of this work is given in Sofue et al. (1992).

Interaction between cardiac chambers and thoracic pressure in intact circulation

A comprehensive model that describes the interaction between the cardiovascular system (CVS) and the intrathoracic pressure (ITP) based on a lumped parameter vascular representation and a time-varying elastance concept for the four cardiac chambers is presented. Special attention is given to two possible mechanisms of interventricular interaction; the constraining effects of the pericardium and direct interventricular interaction that results from the fact that the two ventricles share a common interventricular septum. The response of the CVS to positive and negative perturbations in the ITP and to injection of fluid into the pericardium was simulated and compared with experimental literature data. The results show that 1) the total heart volume is relatively constant throughout the cycle both for ITP of 0 and +15 mmHg, which is consistent with experimental data in dogs, thus suggesting that intrinsic properties of the cardiac chambers rather than a restricting pericardium is the mechanism for that observation. 2) The pericardium has a major role in modifying the transient and steady-state response to a step decrease in the ITP with a transient decrease in left ventricle (LV) end-diastolic volume followed by gradual increase afterwards. 3) The response to sudden injection of fluid into the pericardial space is a larger transient decrease in right ventricle than LV volume, which is consistent with experimental data. 4) Transmission across the septum has a relatively minor role in modifying the response of the CVS to negative pressure. Thus the model reasonably predicts the effects of intrathoracic and pericardial pressures on the circulation in a reflex-blocked animal and provides a means for placing multiple potential mechanisms in proper hierarchial order with regard to contributions to LV and overall CVS function.