Guidelines for More Accurate Determination and Interpretation of Effective Lifetime from Measured Quasi-Steady-State Photoconductance

Presented at the 11th Workshop on Crystalline Silicon Solar Cell Materials and Processes; Estes Park, Colorado; August 19-22, 2001

Operation Epsilon: Science, History, and Theatrical Narrative

In 1945, shortly after VE day, the Anglo-American forces rounded up ten renowned nuclear scientists and interned them at Farm Hall, an estate near Cambridge, England. All the rooms on the estate had been bugged. The conversations of the scientists were recorded on wax discs and translated. Information regarding both the scientists' research and anything else that might be of interest to the Anglo-American military was sent to Washington and London. The internship lasted from July to January. During that time, America dropped the atomic bomb on Hiroshima and Nagasaki, and Otto Hahn was awarded the Nobel Prize for his discovery of fission. The men's responses to those events are a part of the transcript. The entire operation had the code name Operation Epsilon. The full transcripts were declassified only in 1993. They were published in England under the title Operation Epsilon: The Farm Hall Transcripts and in the states as Hitler's Uranium Club, superbly edited by Jeremy Bernstein. Besides Hahn, the other scientists were Werner Heisenberg, Max Von Laue, Karl Friederich Von Weizsacker, Paul Harteck, Karl Wirtz, Kurt Diebner Horst Korsching, and Erich Bagge. Bagge and Diebner were the only members of the Nazi party

Scattering of a Baseball by a Bat

A ball can be hit faster if it is projected without spin but it can be hit farther if it is projected with backspin. Measurements are presented in this paper of the tradeoff between speed and spin for a baseball impacting a baseball bat. The results are inconsistent with a collision model in which the ball rolls off the bat and instead imply tangential compliance in the ball, the bat, or both. If the results are extrapolated to the higher speeds that are typical of the game of baseball, they suggest that a curveball can be hit with greater backspin than a fastball, but by an amount that is less than would be the case in the absence of tangential compliance.Comment: Accepted for publication in American Journal of Physic

The Dynamics of Urban Agriculture in Hanoi, Vietnam

In many developing countries, urban agriculture makes a significant contribution to the livelihoods of urban populations, in providing food security and income generation. In Hanoi, Vietnam’s capital city, urban agriculture is a longstanding feature, but rapid urban growth is leading to greater competition over land use, such that this practice is being increasingly threatened by conversion to non-agricultural urban uses.  The quality and safety of foodstuffs grown in urban areas is of growing concern to both consumers and producers in developing country cities such as Hanoi, where a large share of the city’s food supply is grown within the urban area. Government support has encouraged urban producers to modernize and invest in safer growing practices. However, in Hanoi, as indeed elsewhere, there is an urgent need to recognise the significance of urban agriculture in future planning strategies. Drawing upon recent field-based research in Hanoi, which examined local actors’ knowledge and perceptions of changes in urban agriculture within the city, the paper identifies key trends and underlying environmental and socio-economic factors, and considers the future sustainability of the practice.Dans de nombreux pays en voie de développement, l’agriculture urbaine représente une contribution significative à la subsistance des populations urbaines, en assurant leur sécurité alimentaire et en générant des revenus. À Hanoi, la capitale du Vietnam, l’agriculture urbaine n'est pas une nouveauté, mais la rapidité de la croissance urbaine intensifie la concurrence pour l'utilisation du sol, et la réaffectation du sol à des fins non agricoles fait peser une menace de plus en plus lourde sur cette pratique. La qualité et la sécurité des produits alimentaires cultivés dans les zones urbaines préoccupent de plus en plus les consommateurs et les producteurs dans les villes des pays en voie de développement telles que Hanoi, où une large part de l’approvisionnement de la ville est cultivée dans la zone urbaine. Le gouvernement a encouragé les producteurs urbains à se moderniser et à investir dans des pratiques de culture plus sûres. Mais, à Hanoi comme ailleurs, il est urgent que les futures stratégies de planification reconnaissent l’importance de l’agriculture urbaine. Une étude récente menée sur le terrain à Hanoi examine la connaissance et la perception que les acteurs locaux ont des changements survenus dans l’agriculture urbaine. Cette étude identifie les tendances clés et les facteurs environnementaux et socioéconomiques sous-jacents, et examine la pérennité de cette pratique dans le futur.En muchos países en vías de desarrollo, la agricultura urbana brinda una contribución significativa al modo de vida de las poblaciones urbanas, permitiendo asegurar una alimentación sana y generar ingresos. En Hanoi, la capital de Vietnam, la agricultura urbana es una característica presente desde hace mucho tiempo, pero el rápido crecimiento urbano está conduciendo a una mayor competencia en la utilización del terreno, tanto que esta práctica se ve cada vez más amenazada por la conversión a utilizaciones urbanas no agrícolas. La calidad y la seguridad de los alimentos cultivados en áreas urbanas es una preocupación creciente tanto para los consumidores como para los productores en las ciudades en países en vía de desarrollo, como Hanoi, donde una buena proporción de los alimentos de la ciudad son cultivados dentro de la zona urbana. El apoyo gubernamental ha alentado a los productores urbanos a modernizarse e invertir en prácticas de cultivo más seguras. Sin embargo, en Hanoi como en otras partes, existe la urgente necesidad de reconocer la importancia de la agricultura urbana en las estrategias de planificación futuras. Basándose en investigaciones de campo reciente en Hanoi, que examinaron el conocimiento de los actores locales y su percepción del cambio en la agricultura urbana dentro de la ciudad, este artículo identifica las tendencias claves y los factores ambientales y socioeconómicos subyacentes, y considera la futura sostenibilidad de la práctica

Searching for Spellcheckers: What Kids Want, What Kids Need

Misspellings in queries used to initiate online searches is an everyday occurrence. When this happens, users either rely on the search engine’s ability to understand their query or they turn to spellcheckers. Spellcheckers are usually based on popular dictionaries or past query logs, leading to spelling suggestions that often better resonate with adult users because that data is more readily available. Based on an educational perspective, previous research reports, and initial analyses of sample search logs, we hypothesize that existing spellcheckers are not suitable for young users who frequently encounter spelling challenges when searching for information online. We present early results of our ongoing research focused on identifying the needs and expectations children have regarding spellcheckers

Modern foraminifera, δ\u3csup\u3e13\u3c/sup\u3eC, and bulk geochemistry of central Oregon tidal marshes and their application in paleoseismology

We assessed the utility of δ13C and bulk geochemistry (total organic content and C:N) to reconstruct relative sea-level changes on the Cascadia subduction zone through comparison with an established sea-level indicator (benthic foraminifera). Four modern transects collected from three tidal environments at Siletz Bay, Oregon, USA, produced three elevation-dependent groups in both the foraminiferal and δ13C/bulk geochemistry datasets. Foraminiferal samples from the tidal flat and low marsh are identified by Miliammina fusca abundances of \u3e 45%, middle and high marsh by M. fusca abundances of \u3c 45% and the highest marsh by Trochamminita irregularis abundances \u3e 25%. The δ13C values from the groups defined with δ13C/bulk geochemistry analyses decrease with an increasing elevation; − 24.1 ± 1.7‰ in the tidal flat and low marsh; − 27.3 ± 1.4‰ in the middle and high marsh; and − 29.6 ± 0.8‰ in the highest marsh samples. We applied the modern foraminiferal and δ13C distributions to a core that contained a stratigraphic contact marking the great Cascadia earthquake of AD 1700. Both techniques gave similar values for coseismic subsidence across the contact (0.88 ± 0.39 m and 0.71 ± 0.56 m) suggesting that δ13C has potential for identifying amounts of relative sea-level change due to tectonics

Quantitative chest computerized tomography and FEV1 equally identify pulmonary exacerbation risk in children with cystic fibrosis

Background: Chest computerized tomography (CT) scores are associated with the frequency of future pulmonary exacerbations in people with cystic fibrosis (CF). However, cut-off values to identify children with mild lung disease with different risks for frequent future pulmonary exacerbations have not been identified. Methods: Chest CT scans were assessed using the Brody score for participants of the Pulmozyme Early Intervention Trial (PEIT) and Wisconsin Randomized Clinical Trial of CF Newborn Screening (WI RCT). We determined the area under the receiver operating characteristic (ROC) curve for Brody scores and forced expiratory volume in 1 s (FEV1) to compare with the frequency of pulmonary exacerbations up to 10 years later. Results: There were 60 participants in the PEIT with mean (SD) age 10.6 (1.7) years at the time of the CT and 81 participants in the WI RCT with mean age 11.5 (3.0) years. The Brody score cut-off that best identified children at-risk for ≥0.3 annual pulmonary exacerbations was 3.6 in the PEIT and 2.1 in the WI RCT. There were no statistical differences between ROC curves for the Brody CT score and FEV1 % predicted in either study (P ≥ 0.4). Conclusions: CT score cut-off values that identify children with CF with mild lung disease at different risks for frequent pulmonary exacerbations over an extended follow up period are similar in separate cohorts. Brody scores and FEV1 % predicted have similar abilities to identify these children, suggesting that FEV1 % predicted alone may be adequate for predicting future frequency of pulmonary exacerbations

The effect of exercise induced hyperthermia on muscle fibre conduction velocity during sustained isometric contraction

This study investigated the effect of dynamic exercise in a hot environment on muscle fibre conduction velocity (MFCV) of the knee extensors during a sustained isometric contraction. Seven trained male cyclists (mean [±SD], age, and V_ O2max were 35 ± 9.9 and 57.4 ± 6.6 ml kg1 min1) cycled for 50 min at 60% of peak power output in either: (1) 40 C (HOT); or (2) 19 C (NEUTRO); and (3) remained passive in 40 C (PASS). Post-intervention a 100 s maximal sustained isometric contraction (SMC) of the knee extensors was performed. Rectal temperature increased (p < 0.01) for both HOT and NEUTRO with PASS unchanged and with HOT rising higher (p < 0.01) than NEUTRO (38.6 ± 0.4 vs. 37.6 ± 0.4 C). Muscle temperature increased (p < 0.01) for all three conditions with HOT rising the highest (p < 0.01) (40.3 ± 0.5 vs. 38.3 ± 0.3 and 37.6 ± 1.3 C for NEUTRO and PASS, respectively). Lactate showed higher accumulation (p < 0.01) for HOT than NEUTRO (6.9 ± 2.3 vs. 4.2 ± 2.1 mmol l1). During SMC the torque, electromyography root mean squared (RMS) and MFCV all significantly (p < 0.01) declined. Only in HOT did MFCV decline significantly (p < 0.01) less than torque and RMS (9.9 ± 6.2% vs. 37.5 ± 17.8% and 37.6 ± 21.4%, respectively). In conclusion, during exercise induced hyperthermia, reduced motor unit recruitment as opposed to slower conducting properties of the muscle fibre appears to be responsible for the greater reduction in torque output

Regional differences in the evolution of lung disease in children with cystic fibrosis

Progression of lung disease is a major event in children with cystic fibrosis (CF), but regional differences in its evolution are unclear. We hypothesized that regional differences occur beginning in early childhood. We examined this issue by evaluating 132 patients followed in the Wisconsin Neonatal Screening Project between 1985 and 2010. We scored chest x-rays obtained every 1–2 years with the Wisconsin chest x-ray system, in which we divided the lungs into quadrants, and gave special attention to ratings for bronchiectasis (BX) and nodular/branching opacities. We compared the upper and lower quadrant scores, and upper right and left quadrant scores, as patients aged using a multivariable generalized estimation equation (GEE) model. We did a confirmatory analysis for a subset of 81 patients with chest computerized tomography (CT) images obtained in 2000 and scored using the Brody scoring system. The chest x-ray analysis shows that the upper quadrants have higher BX (p<0.001) and nodular/branching opacities (p<0.001) scores than the lower quadrants. CT analysis likewise reveals that the upper quadrants have more BX (p=0.02). Patients positive for mucoid PA showed significantly higher BX scores than patients with nonmucoid PA (p= 0.001). Chest x-ray scoring also revealed that the upper right quadrant has more BX (p< 0.001) than the upper left quadrant, and CT analysis was again confirmatory (p< 0.001). We conclude that pediatric patients with CF develop more severe lung disease in the upper lobes than the lower lobes in association with mucoid PA infections and also have more severe lung disease on the right side than on the left side in the upper quadrants. A variety of potential explanations such as aspiration episodes may be clinically relevant and provide insights regarding therapies