A cation counterflux supports lysosomal acidification

Lysosomes lose cations to balance the influx of protons as the organelle acidifies

Wave attenuation model for dephasing and measurement of conditional times

Inelastic scattering induces dephasing in mesoscopic systems. An analysis of previous models to simulate inelastic scattering in such systems is presented and also a relatively new model based on wave attenuation is introduced. The problem of Aharonov-Bohm(AB) oscillations in conductance of a mesoscopic ring is studied. We have shown that conductance is symmetric under flux reversal and visibility of AB oscillations decay to zero as function of the incoherence parameter, signalling dephasing. Further wave attenuation is applied to a fundamental problem in quantum mechanics, i.e., the conditional(reflection/transmission) times spent in a given region of space by a quantum particle before scattering off from that region.Comment: 8 pages, 6 figures. Based on presentations by A. M. J and C. B at the 2nd Winter Institute on Foundations of Quantum theory, Quantum Optics and QIP held at S N Bose National Centre for Basic Sciences, Kolkata, India, from January 2-11, 200

Complexidade e escala na investigação da eficácia do ensino: reflexões do estudo MET

Researchers and policymakers in the US and beyond increasingly seek to identify teaching qualities that are associated with academic achievement gains for K-12 students through effectiveness studies. Yet teaching quality varies with academic content and social contexts, involves multiple participants, and requires a range of skills, knowledge, and dispositions. In this essay, we address the inescapable tension between complexity and scale in research on teaching effectiveness. We provide five recommendations to study designers and analysts to manage this tension to enhance effectiveness research, drawing on our recent experiences as the first external analysts of the Measures of Effective Teaching (MET) study. Our recommendations address conceptual framing, the measurement of teaching (e.g., observation protocols, student surveys), sampling, classroom videoing, and the use and interpretation of value-added models.Investigadores y legisladores en los Estados Unidos y en otros países buscan identificar las cualidades de la enseñanza que se asocian con incrementos de desempeño académico para alumnos de primaria y secundaria a través de estudios de eficacia. Sin embargo, la calidad de la enseñanza varía según el contenido académico y los contextos sociales, involucra a múltiples participantes y requiere una variedad de habilidades, conocimientos y disposiciones. En este ensayo, abordamos la ineludible tensión entre la complejidad y la escala en la investigación sobre la eficacia de la enseñanza. Proveemos cinco recomendaciones a los diseñadores de estudios y analistas para manejar esta tensión y mejorar la investigación de eficacia, aprovechando nuestras experiencias recientes como los primeros analistas externos del estudio Measures of Effective Teaching (MET). Nuestras recomendaciones abordan el marco conceptual, la medición de la enseñanza (por ej., protocolos de observación, encuestas de estudiantes), el muestreo, el video en el aula y el uso e interpretación de modelos de valor agregado.Pesquisadores e legisladores nos Estados Unidos e em outros países buscam identificar as qualidades de ensino associadas ao aumento do desempenho acadêmico de alunos do ensino fundamental e médio por meio de estudos de eficácia. No entanto, a qualidade do ensino varia de acordo com o conteúdo acadêmico e os contextos sociais, envolve múltiplos participantes e requer uma variedade de habilidades, conhecimentos e disposições. Neste ensaio, abordamos a tensão inescapável entre complexidade e escala na pesquisa sobre a eficácia do ensino. Fornecemos cinco recomendações para projetistas e analistas de estudo para gerenciar essa tensão e melhorar a pesquisa sobre eficácia, alavancando nossas experiências recentes como os primeiros analistas externos do estudo Measures of Effective Teaching (MET). Nossas recomendações abordam a estrutura conceitual, a medição do ensino (por exemplo, protocolos de observação, pesquisas com estudantes), amostragem, vídeo em sala de aula e o uso e interpretação de modelos de valor agregado

Early Adoption of Dabigatran and Its Dosing in US Patients With Atrial Fibrillation: Results From the Outcomes Registry for Better Informed Treatment of Atrial Fibrillation

Background: Dabigatran is a novel oral anticoagulant approved for thromboprophylaxis in atrial fibrillation. Adoption patterns of this new agent in community practice are unknown. Methods and Results: We studied patterns of dabigatran use among patients enrolled in the Outcomes Registry for Better Informed Treatment of Atrial Fibrillation (ORBIT‐AF) Registry between June 2010 and August 2011 and followed for 12 months. Among 9974 atrial fibrillation patients included, 1217 (12%) were treated with dabigatran during the study. Overall, patients receiving dabigatran were younger (median age 72 versus 75 years, P<0.0001), more likely to be white (92% versus 89%, P=0.005), more likely to have private insurance (33% versus 25%, P<0.0001), and less likely to have prior cardiovascular disease (4% versus 33%, P<0.0001). They had more new‐onset atrial fibrillation (8.8% versus 4.1%, P<0.0001), lower CHADS2 scores (estimated risk based on the presence of congestive heart failure, hypertension, aged ≥75 years, diabetes mellitus, and prior stroke or transient ischemic attack; mean 2.0 versus 2.3, P<0.0001), and lower Anticoagulation and Risk Factors in Atrial Fibrillation scores (mean 2.4 versus 2.8, P<0.0001). More than half (n=14/25, 56%) of patients with severe kidney disease were not prescribed reduced dosing, whereas 10% (n=91/920) with preserved renal function received lower dosing. Among patients not on dabigatran at baseline, 8% had dabigatran initiated during follow‐up. Patient education was significantly associated with switching from warfarin to dabigatran (adjusted odds ratio for postgraduate 1.73, P=0.007), whereas antiarrhythmic drug use significantly correlated with de novo adoption of dabigatran (adjusted odds ratio 2.4, P<0.0001). Conclusions: Patients receiving dabigatran were younger and at a lower risk of stroke and bleeding. Patients appeared to drive switching from warfarin, whereas clinical characteristics influenced de novo start of dabigatran. These data suggest cautious early uptake of dabigatran, and more careful attention to dosing adjustments is warranted. Clinical Trial Registration URL: Clinicaltrials.gov. Unique identifier: NCT01165710

On positivity of Ehrhart polynomials

Ehrhart discovered that the function that counts the number of lattice points in dilations of an integral polytope is a polynomial. We call the coefficients of this polynomial Ehrhart coefficients, and say a polytope is Ehrhart positive if all Ehrhart coefficients are positive (which is not true for all integral polytopes). The main purpose of this article is to survey interesting families of polytopes that are known to be Ehrhart positive and discuss the reasons from which their Ehrhart positivity follows. We also include examples of polytopes that have negative Ehrhart coefficients and polytopes that are conjectured to be Ehrhart positive, as well as pose a few relevant questions.Comment: 40 pages, 7 figures. To appear in in Recent Trends in Algebraic Combinatorics, a volume of the Association for Women in Mathematics Series, Springer International Publishin

Invasive Aspergillosis after Pandemic (H1N1) 2009

We report 2 patients with invasive aspergillosis after infection with pandemic (H1N1) 2009. Influenza viruses are known to cause immunologic defects and impair ciliary clearance. These defects, combined with high-dose corticosteroids prescribed during influenza-associated adult respiratory distress syndrome, may be novel risk factors predisposing otherwise immunocompetent patients to invasive aspergillosis

Investigating Childhood Leukemia in Churchill County, Nevada

BACKGROUND: Sixteen children diagnosed with acute leukemia between 1997 and 2002 lived in Churchill County, Nevada, at the time of or before their illness. Considering the county population and statewide cancer rate, fewer than two cases would be expected. OBJECTIVES: In March 2001, the Centers for Disease Control and Prevention led federal, state, and local agencies in a cross-sectional, case-comparison study to determine if ongoing environmental exposures posed a health risk to residents and to compare levels of contaminants in environmental and biologic samples collected from participating families. METHODS: Surveys with more than 500 variables were administered to 205 people in 69 families. Blood, urine, and cheek cell samples were collected and analyzed for 139 chemicals, eight viral markers, and several genetic polymorphisms. Air, water, soil, and dust samples were collected from almost 80 homes to measure more than 200 chemicals. RESULTS: The scope of this cancer cluster investigation exceeded any previous study of pediatric leukemia. Nonetheless, no exposure consistent with leukemia risk was identified. Overall, tungsten and arsenic levels in urine and water samples were significantly higher than national comparison values; however, levels were similar among case and comparison groups. CONCLUSIONS: Although the cases in this cancer cluster may in fact have a common etiology, their small number and the length of time between diagnosis and our exposure assessment lessen the ability to find an association between leukemia and environmental exposures. Given the limitations of individual cancer cluster investigations, it may prove more efficient to pool laboratory and questionnaire data from similar leukemia clusters