Measurement Methods of Electron Emission Over a Full Range of Sample Charging

The electron emission properties of a material subject to incident radiation flux are key parameters in determining to what equilibrium charge a spacecraft will established under given environmental conditions. However, there is a complex relation between these emission properties and the charge built up in spacecraft insulators. Complex modeling codes have been developed to predict the potential a spacecraft will adopt as a consequence of its interaction with the space plasma. These require correct models of the electron yields as a function of charge to accurately predict the both the charge build up and the equilibrium potential of spacecraft components. This paper focuses on different methods appropriate to determine the fundamental electronic material property of total electron yield as the materials accumulates charge. Three methods for determining the uncharged total yield are presented: (i) The DC Continuous Beam Method is a relatively easy and accurate method appropriate for conductors and semi-conductors with maximum total electron yield σmaxρ\u3c106 \u3eΩ-cm. (ii) The Pulse-Yield Method seeks to minimize the effects of charging and is applicable to materials with σmaxρ up to \u3e1024 Ω-cm. (iii) The Yield Decay Method is a very difficult and time consuming that uses a combination of measurement and modeling to measure the most difficult materials with σmax\u3e4 and ρ up to \u3e1024 Ω-cm. Data for high purity polycrystalline Au, Kapton HN, and polycrystalline aluminum oxide ceramic are presented. These data demonstrate the relative strengths and weaknesses of each method, but more importantly show that the methods described herein are capable of reliably measuring the total electron yield of almost any spacecraft material

Moyamoya phenomenon after radiation for optic glioma

Journal ArticleThe role of radiotherapy in the management of patients with optic pathway glioma is controversial. In a series of patients with optic pathway glioma treated at The Hospital for Sick Children in Toronto, five children were encountered who developed moyamoya phenomenon after radiotherapy. A retrospective review of the medical records was undertaken in order to assess the relationship between optic pathway glioma, neurofibromatosis type 1 (NF1), radiation therapy, and moyamoya disease. Forty-seven patients with optic pathway glioma were operated on at The Hospital for Sick Children between 1971 and 1990. The moyamoya phenomenon did not occur in any of the 19 patients not receiving radiotherapy. Among the 28 patients who received radiotherapy, five developed moyamoya disease (two of 23 without NF1 and three of five with NF1). There was a statistically significant relationship between radiotherapy and moyamoya disease when the analysis was stratified according to the presence of NF1 (Mantel-Haensel chisquared test 15.23, p<0.01). The high incidence of moyamoya disease (three of five cases, or 60%) in patients with NF1 who have undergone radiotherapy suggests a synergistic relationship that should be considered when formulating a treatment plan for NF1 patients with optic pathway glioma

Design of a real-time wind turbine simulator using a custom parallel architecture

The design of a new parallel-processing digital simulator is described. The new simulator has been developed specifically for analysis of wind energy systems in real time. The new processor has been named: the Wind Energy System Time-domain simulator, version 3 (WEST-3). Like previous WEST versions, WEST-3 performs many computations in parallel. The modules in WEST-3 are pure digital processors, however. These digital processors can be programmed individually and operated in concert to achieve real-time simulation of wind turbine systems. Because of this programmability, WEST-3 is very much more flexible and general than its two predecessors. The design features of WEST-3 are described to show how the system produces high-speed solutions of nonlinear time-domain equations. WEST-3 has two very fast Computational Units (CU's) that use minicomputer technology plus special architectural features that make them many times faster than a microcomputer. These CU's are needed to perform the complex computations associated with the wind turbine rotor system in real time. The parallel architecture of the CU causes several tasks to be done in each cycle, including an IO operation and the combination of a multiply, add, and store. The WEST-3 simulator can be expanded at any time for additional computational power. This is possible because the CU's interfaced to each other and to other portions of the simulation using special serial buses. These buses can be 'patched' together in essentially any configuration (in a manner very similar to the programming methods used in analog computation) to balance the input/ output requirements. CU's can be added in any number to share a given computational load. This flexible bus feature is very different from many other parallel processors which usually have a throughput limit because of rigid bus architecture

Expression of thrombospondin in the adult nervous system

Thrombospondin (TSP) is an extracellular matrix molecule that has been previously associated with neural development and neurite outgrowth in vitro. Little is known, however, about the expression of TSP in the adult nervous system. In this study, TSP localization was examined in nervous tissue from adult mouse, goldfish, newt, and adult and juvenile Xenopus. TSP was associated with neurons in the brains of all species examined. TSP was present in central nerve tracts capable of regeneration, such as the goldfish, Xenopus, and newt optic nerves, but was absent from tracts not capable of regeneration, such as the mouse optic nerve. TSP was also present in the neuropil of goldfish and newt spinal cord, but was restricted to motor neurons in mice and adult Xenopus. In addition, TSP was observed in sciatic nerves of mice, Xenopus, and newt. These results indicate a correlation between the presence of TSP and the potential for successful nerve regeneration across a wide range of animal classes. © Wiley-Liss, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50059/1/903400109_ftp.pd

A New Deal for Global Health R&D? The Recommendations of the Consultative Expert Working Group on Research and Development (CEWG)

John-Arne Røttingen and Claudia Chamas, chairs of the the Consultative Expert Working Group on Research and Development (CEWG), summarize their recent report recommending to the World Health Assembly that a global health R&D treaty be developed

Low-fluence Electron Yields of Highly Insulating Materials

Electron-induced electron yields of high-resistivity high-yield materials - ceramic polycrystalline aluminum oxide and polymer polyimide (Kapton HN) - were made by using a low-fluence pulsed incident electron beam and charge neutralization electron source to minimize charge accumulation. Large changes in the energy-dependent total yield curves and yield decay curves were observed, even for incident electron fluences of \u3c 3 fC/mm2. The evolution of the electron yield as charge accumulates in the material is modeled in terms of electron recapture based on an extended Chung-Everhart model of the electron emission spectrum. This model is used to explain the anomalies measured in highly insulating high-yield materials and to provide a method for determining the limiting yield spectra of uncharged dielectrics. The relevance of these results to spacecraft charging is also discussed

Lunar Atmosphere and Dust Environment Explorer Integration and Test

Integration and test (I&T) of the Lunar Atmosphere and Dust Environment Explorer (LADEE) is presented. A collaborative NASA project between Goddard Space Flight Center and Ames Research Center, LADEE's mission is to explore the low lunar orbit environment and exosphere for constituents. Its instruments include two spectrometers, a dust detector, and a laser communication technology demonstration. Although a relatively low-cost spacecraft, LADEE has I&T requirements typical of most planetary probes, such as prelaunch contamination control, sterilization, and instrument calibration. To lead to a successful mission, I&T at the spacecraft, instrument, and observatory level must include step-by-step and end-to-end functional, environmental, and performance testing. Due to its compressed development schedule, LADEE I&T planning requires adjusting test flows and sequences to account for long-lead critical-path items and limited spares. A protoflight test-level strategy is also baselined. However, the program benefits from having two independent but collaborative teams of engineers, managers, and technicians that have a wealth of flight project experience. This paper summarizes the LADEE I&T planning, flow, facilities, and probe-unique processes. Coordination of requirements and approaches to I&T when multiple organizations are involved is discussed. Also presented are cost-effective approaches to I&T that are transferable to most any spaceflight project I&T program

Soluble Trace Elements and Total Mercury in Arctic Alaskan Snow

Ultraclean field and laboratory procedures were used to examine trace element concentrations in northern Alaskan snow. Sixteen soluble trace elements and total mercury were determined in snow core samples representing the annual snowfall deposited during the 1993-94 season at two sites in the Prudhoe Bay oil field and nine sites in the Arctic National Wildlife Refuge (Arctic NWR). Results indicate there were two distinct point sources for trace elements in the Prudhoe Bay oil field- a source associated with oil and gas production and a source associated with municipal solid-waste incineration. Soluble trace element concentrations measured in snow from the Arctic NWR resembled concentrations of trace elements measured elsewhere in the Arctic using clean sample-collection and processing techniques and were consistent with deposition resulting from widespread arctic atmospheric contamination. With the exception of elements associated with sea salts, there were no orographic or east-west trends observed in the Arctic NWR data, nor were there any detectable influences from the Prudhoe Bay oil field, probably because of the predominant easterly and northeasterly winds on the North Slope of Alaska. However, regression analysis on latitude suggested significant south-to-north increases in selected trace element concentrations, many of which appear unrelated to the sea salt contribution.Des techniques ultra-propres utilisées sur le terrain et en laboratoire ont permis d'étudier les concentrations en éléments traces dans la neige de l'Alaska septentrional. Seize éléments traces solubles et le mercure total ont été mesurés dans des carottes de neige représentant la chute nivale annuelle de la saison 1993-94 à deux emplacements du champ pétrolifère de Prudhoe Bay et à neuf emplacements du refuge faunique national Arctique. Les résultats révèlent qu'il existe deux sources ponctuelles distinctes d'éléments traces découverts dans le champ pétrolifère de Prudhoe Bay, l'une reliée à la production de pétrole et de gaz et l'autre reliée à l'incinération des déchets municipaux solides. Les concentrations en éléments traces solubles mesurées dans la neige du refuge faunique national Arctique s'apparentaient aux concentrations en éléments traces mesurées ailleurs dans l'Arctique à l'aide de techniques propres de prélèvement et de traitement des carottes. Ces concentrations correspondent bien à des dépôts engendrés par une pollution atmosphérique généralisée dans l'Arctique. À l'exception des éléments associés aux sels marins, on n'a observé aucune tendance orographique ou est-ouest dans les données du refuge faunique national Arctique, de même qu'on n'a pas décelé d'influences perceptibles dues au champ pétrolifère de Prudhoe Bay, probablement en raison des vents prédominants d'est et du nord-est sur le versant nord de l'Alaska. L'analyse de régression sur la latitude suggère cependant une augmentation importante en allant du sud au nord dans les concentrations en certains éléments traces, dont beaucoup ne semblent pas reliées à l'apport de sel marin

First Report of NRG Oncology/Radiation Therapy Oncology Group 0622: A Phase 2 Trial of Samarium-153 Followed by Salvage Prostatic Fossa Irradiation in High-Risk Clinically Nonmetastatic Prostate Cancer After Radical Prostatectomy.

PURPOSE: To investigate the utility of 153Sm lexidronam (Quadramet) in the setting of men with prostate cancer status post radical prostatectomy who develop biochemical failure with no clinical evidence of osseous metastases. PATIENTS AND METHODS: Trial NRG Oncology RTOG 0622 is a single-arm phase 2 trial that enrolled men with pT2-T4, N0-1, M0 prostate cancer status post radical prostatectomy, who meet at least 1 of these biochemical failure criteria: (1) prostate-specific antigen (PSA) \u3e 1.0 ng/mL; (2) PSA \u3e 0.2 ng/mL if Gleason score 9 to 10; or (3) PSA \u3e 0.2 ng/mL if N1. Patients received 153Sm (2.0 mCi/kg intravenously × 1) followed by salvage external beam radiation therapy (EBRT) to the prostatic fossa (64.8-70.2 Gy in 1.8-Gy daily fractions). No androgen deprivation therapy was allowed. The primary objective was PSA response within 12 weeks of receiving 153Sm. The secondary objectives were to: (1) assess the completion rate for the regimen of 153Sm and EBRT; (2) evaluate the hematologic toxicity and other adverse events (AEs) at 12 and 24 weeks; and (3) determine the freedom from progression rate at 2 years. RESULTS: A total of 60 enrolled eligible patients were included in this analysis. Median follow-up was 3.97 years. A PSA response was achieved in 7 of 52 evaluable patients (13.5%), compared with the 25% hypothesized. The 2-year freedom from progression rate was 25.5% (95% confidence interval 14.4%-36.7%), and the biochemical failure rate was 64.4% (95% CI 50.5%-75.2%). Samarium-153 was well tolerated, with 16 (of 60) grade 3 to 4 hematologic AEs and no grade 5 hematologic AEs. Radiation therapy was also well tolerated, with no grade 3 to 5 acute radiation therapy-related AEs and 1 grade 3 to 4 and no grade 5 late radiation therapy-related AEs. CONCLUSIONS: Trial NRG Oncology RTOG 0622 did not meet its primary endpoint of PSA response, although the regimen of 153Sm and salvage EBRT was well tolerated. Although the toxicity profile supports study of 153Sm in high-risk disease, it may not be beneficial in men receiving EBRT

Efficacy of a Carbon Fiber Orthotic Toe-Off Brace in Adults with Cerebral Palsy

Purpose/Hypothesis : This pilot study evaluated the effects of a unique carbon fiber ankle/foot orthosis for individuals diagnosed with foot drop (“Toe-Off” design, Allard USA, Inc). We hypothesized that use of this brace would be useful for adults with cerebral palsy (CP) as evidenced by improved gait characteristics including gait endurance and balance. Number of Subjects : A convenience sample of 4 patients, between the ages of 29 and 55, with diagnoses of cerebral palsy, was successfully recruited from United Cerebral Palsy (UCP) of Suffolk (Central Islip, NY). All individuals received regular physical therapy at UCP prior to and throughout the study. Materials/Methods : Patients were assessed wearing their standard plastic orthotics (Pretest) and then fitted for their new carbon fiber bracing. Patients returned for testing at Day 1, Week 4, and Week 8 post-initiation wearing the new brace. At each testing session, patients were evaluated with the Berg Balance test, the GaitRite walkway system for gait analysis, a Six Minute Walk test for endurance, and an orthotic questionnaire incorporating quality of life measures including domains for: a) ease of wearing; b) ease of functional movement, and c) quality of life responses. At week 20, patients were re-evaluated with the Six Minute Walk test and questionnaire. All data was assessed using non-parametric statistical comparisons using SPSS software. Results : No significant differences between the use of standard plastic and carbon fiber composite bracings were noted in any of the parameters measured which can be partially explained by the small sample size and the greater than normal variability in the dataset. However, overall Berg Balance scores increased for all test intervals following Pretest measures. In addition, patients reported a general increase in satisfaction in the new orthotics whether discussing ease of use, ability to negotiate the environment, or with respect to quality of life. Conclusions : In this pilot trial assessing the use of a carbon fiber “Toe-off” brace for adults with CP, this bracing appears comparable in efficacy to that of conventional plastic orthotics. However, given the variation in response to testing and the encouraging self-reported satisfaction with the new brace in this patient population, future trials of this paradigm are recommended with an increased sample size. Clinical Relevance : Technological advances of orthotic bracing has recently lead to the use of carbon fiber composites due to the increased tensile properties of this material compared to those of conventional plastic bracing. Little has been established in the efficacy for using this type of bracing in adults with CP with foot drop. Future studies with larger sample size are necessary in order to increase the strength of statistical analysis given the variability typical of this patient population