Design, fabrication, and tests of a metallic shell tile thermal protection system for space transportation

A thermal protection tile for earth-to-orbit transports is described. The tiles consist of a rigid external shell filled with a flexible insulation. The tiles tend to be thicker than the current Shuttle rigidized silica tiles for the same entry heat load but are projected to be more durable and lighter. The tiles were thermally tested for several simulated entry trajectories

The Allocation of Public School Expenditures

While the Serrano v Priest decisions and Proposition 13 effectively rendered California school district budgets exogenous, intra-district resource allocation remains largely at the discretion of school district administrations. As a result, Serrano v Priest and Proposition 13 alleviate concerns about the potentially endogenous relationship between student body composition and inter-district resource disparity and allow us to focus on consistently estimating the effect of classroom versus non-classroom spending. We find that teaching expenditures have a positive effect on student performance while nonteaching expenditures have a negative effect. Either the reallocation of $100 from administrative to classroom spending, with no change in overall expenditures, or an$100 increase aimed directly at the classroom moves the average California high school approximately 5 percentage points higher in the state test score rankings. These results are similar across grade levels (elementary, middle and high schools) and subject areas (mathematics, reading, language, spelling, social studies, and science). Our results suggest that both current and future educational expenditures should be targeted towards the classroom.school spending; test scores

RESOURCE ALLOCATION IN JOINT PUBLIC-PRIVATE AGRICULTURAL RESEARCH

Federal technology transfer legislation has encouraged increased collaboration between the public and private sectors, including joint research ventures known as Cooperative Research and Development Agreements (CRADAs). While several economically important technologies have been developed through CRADAs, there is concern that CRADA may divert public research from its central research missions. This study compares the pattern of research resource allocation for CRADA projects at the U.S. Department of Agriculture with research priorities of public and private intramural agricultural research. The findings suggest that CRADAs have attracted considerable private co-financing of joint research projects, and may have enabled public research to concentrate more resources on research areas where private incentives are relatively weak.agricultural research, CRADA projects, research priorities, technology transfer, Research and Development/Tech Change/Emerging Technologies,

School Size and the Distribution of Test Scores

After forty years of school consolidation, the preponderance of the evidence, including the results presented in this paper, suggest that the race to reap returns to scale and specialization in education may have come at a high price. This paper uses newly available STAR test score data from California to explore the relationship between school size and the distribution of test scores across elementary, middle, and high schools. We find that school size has a statistically significant and economically large impact on school performance. For example, the probability that an average suburban high school is dominated by low scorers rises from 47% to 71% as the school grows from 200 to 800 students per grade.school size, test scores

Trypanosoma cruzi expresses a plant-like ascorbate-dependent hemoperoxidase localized to the endoplasmic reticulum.

In most aerobic organisms hemoperoxidases play a major role in H(2)O(2)-detoxification, but trypanosomatids have been reported to lack this activity. Here we describe the properties of an ascorbate-dependent hemoperoxidase (TcAPX) from the American trypanosome Trypanosoma cruzi. The activity of this plant-like enzyme can be linked to the reduction of the parasite-specific thiol trypanothione by ascorbate in a process that involves nonenzymatic interaction. The role of heme in peroxidase activity was demonstrated by spectral and inhibition studies. Ascorbate could saturate TcAPX activity indicating that the enzyme obeys Michaelis-Menten kinetics. Parasites that overexpressed TcAPX activity were found to have increased resistance to exogenous H(2)O(2). To determine subcellular location an epitope-tagged form of TcAPX was expressed in T. cruzi, which was observed to colocalize with endoplasmic reticulum resident chaperone protein BiP. These findings identify an arm of the oxidative defense system of this medically important parasite. The absence of this redox pathway in the human host may be therapeutically exploitable

Retention and application of Skylab experiences to future programs

The problems encountered and special techniques and procedures developed on the Skylab program are described along with the experiences and practical benefits obtained for dissemination and use on future programs. Three major topics are discussed: electrical problems, mechanical problems, and special techniques. Special techniques and procedures are identified that were either developed or refined during the Skylab program. These techniques and procedures came from all manufacturing and test phases of the Skylab program and include both flight and GSE items from component level to sophisticated spaceflight systems

Shell tile thermal protection system

A reusable, externally applied thermal protection system for use on aerospace vehicles subject to high thermal and mechanical stresses utilizes a shell tile structure which effectively separates its primary functions as an insulator and load absorber. The tile consists of structurally strong upper and lower metallic shells manufactured from materials meeting the thermal and structural requirements incident to tile placement on the spacecraft. A lightweight, high temperature package of insulation is utilized in the upper shell while a lightweight, low temperature insulation is utilized in the lower shell. Assembly of the tile which is facilitated by a self-locking mechanism, may occur subsequent to installation of the lower shell on the spacecraft structural skin

Influence of blade aerodynamic model on prediction of helicopter rotor aeroacoustic signatures

Brown’s vorticity transport model has been used to investigate how the local blade aerodynamic model influences the quality of the prediction of the high-frequency airloads associated with blade–vortex interactions, and thus the accuracy with which the acoustic signature of a helicopter rotor can be predicted. The vorticity transport model can accurately resolve the structure of the wake of the rotor and allows significant flexibility in the way that the blade loading can be represented. The Second Higher-Harmonic Control Aeroacoustics Rotor Test was initiated to provide experimental insight into the acoustic signature of a rotor in cases of strong blade–vortex interaction. Predictions of two models for the local blade aerodynamics are compared with the test data. A marked improvement in accuracy of the predicted high-frequency airloads and acoustic signature is obtained when a lifting-chord model for the blade aerodynamics is used instead of a lifting-line-type approach. Errors in the amplitude and phase of the acoustic peaks are reduced, and the quality of the prediction is affected to a lesser extent by the computational resolution of the wake, with the lifting-chord model producing the best representation of the distribution of sound pressure below the rotor