Development and Evaluation of a Tutorial to Improve Students' Understanding of a Lock-in amplifier

A lock-in amplifier is a versatile instrument frequently used in physics research. However, many students struggle with the basic operating principles of a lock-in amplifier which can lead to a variety of difficulties. To improve students' understanding, we have been developing and evaluating a research-based tutorial which makes use of a computer simulation of a lock-in amplifier. The tutorial is based on a field-tested approach in which students realize their difficulties after predicting the outcome of simulated experiments involving a lock-in amplifier and check their predictions using the simulated lock-in amplifier. Then, the tutorial provides guidance and strives to help students develop a coherent understanding of the basics of a lock-in amplifier. The tutorial development involved interviews with physics faculty members and graduate students and iteration of many versions of the tutorial with professors and graduate students. The student difficulties with lock-in amplifiers and the development and assessment of the research-based tutorial to help students develop a functional understanding of this device are discussed.Comment: Currently under review for Phys Rev ST PER. arXiv admin note: text overlap with arXiv:1601.0128

Preeminent role of the Van Hove singularity in the strong-coupling analysis of scanning tunneling spectroscopy for two-dimensional cuprates

In two dimensions the non-interacting density of states displays a Van Hove singularity (VHS) which introduces an intrinsic electron-hole asymmetry, absent in three dimensions. We show that due to this VHS the strong-coupling analysis of tunneling spectra in high-$T_c$ superconductors must be reconsidered. Based on a microscopic model which reproduces the experimental data with great accuracy, we elucidate the peculiar role played by the VHS in shaping the tunneling spectra, and show that more conventional analyses of strong-coupling effects can lead to severe errors.Comment: 5 pages, 4 figure

Pairwise and higher-order correlations among drug-resistance mutations in HIV-1 subtype B protease

<p>Abstract</p> <p>Background</p> <p>The reaction of HIV protease to inhibitor therapy is characterized by the emergence of complex mutational patterns which confer drug resistance. The response of HIV protease to drugs often involves both primary mutations that directly inhibit the action of the drug, and a host of accessory resistance mutations that may occur far from the active site but may contribute to restoring the fitness or stability of the enzyme. Here we develop a probabilistic approach based on connected information that allows us to study residue, pair level and higher-order correlations within the same framework.</p> <p>Results</p> <p>We apply our methodology to a database of approximately 13,000 sequences which have been annotated by the treatment history of the patients from which the samples were obtained. We show that including pair interactions is essential for agreement with the mutational data, since neglect of these interactions results in order-of-magnitude errors in the probabilities of the simultaneous occurence of many mutations. The magnitude of these pair correlations changes dramatically between sequences obtained from patients that were or were not exposed to drugs. Higher-order effects make a contribution of as much as 10% for residues taken three at a time, but increase to more than twice that for 10 to 15-residue groups. The sequence data is insufficient to determine the higher-order effects for larger groups. We find that higher-order interactions have a significant effect on the predicted frequencies of sequences with large numbers of mutations. While relatively rare, such sequences are more prevalent after multi-drug therapy. The relative importance of these higher-order interactions increases with the number of drugs the patient had been exposed to.</p> <p>Conclusion</p> <p>Correlations are critical for the understanding of mutation patterns in HIV protease. Pair interactions have substantial qualitative effects, while higher-order interactions are individually smaller but may have a collective effect. Together they lead to correlations which could have an important impact on the dynamics of the evolution of cross-resistance, by allowing the virus to pass through otherwise unlikely mutational states. These findings also indicate that pairwise and possibly higher-order effects should be included in the models of protein evolution, instead of assuming that all residues mutate independently of one another.</p

Sudden unexpected death in children with epilepsy: the many faces of fungal pathogenicity

Epilepsy is one of the most prevalent neurological diseases worldwide. the mortality rates are considerably higher in people with epilepsy than would be expected in a healthy population and sudden unexpected death in epilepsy (SUDEP) is the most frequent epilepsy-related category of death. Most children had seizures before the occurrence of the fatal event and autonomic dysfunction has been proposed as mechanisms of sudden death in this population. Is this sense, we raise the question whether is there a possible relationship between SUDEP in children and fungal pathogenicity. Indeed, the role of fungal pathogenicity in the establishment of epilepsy and even in cases of SUDEP has an interesting role in this scenario. Moreover, maternal infections during pregnancy have been associated with an increased risk for several brain disorders, however, this fact is still considered uncertain with respect to epilepsy.Based on this information and considering that maternal-fetal yeast infection is directly associated with an increased risk for epilepsy in childhood and that some patients have medically intractable epilepsy, the chances of these children suffering a fatal event cannot be overlooked by healthcare professionals. Thus, as exact knowledge regarding this association is lacking, some possibilities could be evaluated, and more emphasis on translational research would contribute to further progress to the knowledge of SUDEP. (C) 2012 Elsevier B.V. All rights reserved.Universidade Federal de São Paulo, Escola Paulista Med UNIFESP EPM, Disciplina Neurol Expt, São Paulo, BrazilUniversidade Federal de São Paulo, Escola Paulista Med UNIFESP EPM, Dept Psicobiol, São Paulo, BrazilUniversidade Federal de São Paulo, Escola Paulista Med UNIFESP EPM, Disciplina Doencas Infecciosas, Dept Med, São Paulo, BrazilUPM, Neurobiol Lab, Programa Posgrad Disturbios Desenvolvimento, São Paulo, BrazilUniversidade Federal de São Paulo, Escola Paulista Med UNIFESP EPM, Disciplina Neurol Expt, São Paulo, BrazilUniversidade Federal de São Paulo, Escola Paulista Med UNIFESP EPM, Dept Psicobiol, São Paulo, BrazilUniversidade Federal de São Paulo, Escola Paulista Med UNIFESP EPM, Disciplina Doencas Infecciosas, Dept Med, São Paulo, BrazilWeb of Scienc

A systematic review of measures of self-reported adherence to unsupervised home-based rehabilitation exercise programmes, and their psychometric properties

BACKGROUND: Adherence is an important factor contributing to the effectiveness of exercise-based rehabilitation. However, there appears to be a lack of reliable, validated measures to assess self-reported adherence to prescribed but unsupervised home-based rehabilitation exercises. OBJECTIVES: A systematic review was conducted to establish what measures were available and to evaluate their psychometric properties. DATA SOURCES: MEDLINE, EMBASE, PsycINFO CINAHL (June 2013) and the Cochrane library were searched (September 2013). Reference lists from articles meeting the inclusion criteria were checked to ensure all relevant papers were included. STUDY SELECTION: To be included articles had to be available in English; use a self-report measure of adherence in relation to a prescribed but unsupervised home-based exercise or physical rehabilitation programme; involve participants over the age of 18. All health conditions and clinical populations were included. DATA EXTRACTION: Descriptive data reported were collated on a data extraction sheet. The measures were evaluated in terms of eight psychometric quality criteria. RESULTS: 58 studies were included, reporting 61 different measures including 29 questionnaires, 29 logs, two visual analogue scales and one tally counter. Only two measures scored positively for one psychometric property (content validity). The majority of measures had no reported validity or reliability testing. CONCLUSIONS: The results expose a gap in the literature for well-developed measures that capture self-reported adherence to prescribed but unsupervised home-based rehabilitation exercises

Effective action and density functional theory

The effective action for the charge density and the photon field is proposed as a generalization of the density functional. A simple definition is given for the density functional, as the functional Legendre transform of the generator functional of connected Green functions for the density and the photon field, offering systematic approximation schemes. The leading order of the perturbation expansion reproduces the Hartree-Fock equation. A renormalization group motivated method is introduced to turn on the Coulomb interaction gradually and to find corrections to the Hartree-Fock and the Kohn-Sham schemes.Comment: New references and a numerical algorithm added, to appear in Phys. Rev. B. 30 pages, no figure

Planejamento urbano em tempos de pandemia: Mudanças em quatro cidades latino-americanas

A pandemia de Covid-19 exigiu do Estado políticas públicas capazes de reverter o grave cenário em áreas tão determinantes para a qualidade de vida e condições sociais como o planejamento urbano e a mobilidade. Junto com a pandemia vieram medidas de isolamento social, o crescimento do comércio eletrônico, as mudanças comportamentais no uso de transporte público, a condução de processos participativos de forma virtual, o esvaziamento dos edifícios corporativos, o home office e o fechamento do comércio tradicional, entre outras transformações ocorridas. Nesse contexto surgiram iniciativas governamentais inovadoras no campo do planejamento urbano e ordenamento territorial cuja compreensão é fundamental para a implementação de um Grande Impulso para a sustentabilidade. A presente pesquisa possui natureza exploratória e buscou identificar e compreender iniciativas governamentais no campo do planejamento urbano de quatro cidades: Bogotá, Buenos Aires, Cidade do México e São Paulo, após o surgimento da pandemia de Covid-19, em especial de tipo regulatório. Inclui a revisão dos planos de ordenamento territorial, a regulação do uso e ocupação do solo, em especial a reconversão de imóveis e flexibilização normativa, o uso do espaço público, o licenciamento urbanístico e os planos urbanísticos setoriais. Os achados contribuem para alcançar cidades mais inclusivas, sustentáveis e inteligentes.Resumo .-- Introdução .-- I. Estrutura regulatória nacional e o papel dos municípios na política urbana .-- II. Revisão dos planos de ordenamento territorial durante a pandemia .-- III. Alterações das regras de parcelamento, uso e ocupação do solo durante a pandemia .-- IV. Planos urbanísticos setoriais .-- V. Simplificação do licenciamento urbanístico .-- VI. Considerações finais

Planificación urbanística en tiempos de pandemia: Cambios en cuatro ciudades latinoamericanas

Las múltiples crisis ocasionadas por la pandemia de enfermedad por coronavirus (COVID-19) tuvieron profundas consecuencias que exigieron redefinir el papel del Estado para que fuera capaz de actuar e innovar en dicho contexto, aumentando su capacidad para implementar políticas públicas que sirvieran para revertir la grave situación. La necesidad de aplicar medidas de aislamiento social, el crecimiento del comercio electrónico, los cambios de comportamiento en el uso del transporte público, la realización de procesos participativos de forma virtual, la desocupación de los edificios corporativos, la generalización del teletrabajo y el cierre del comercio tradicional, entre otras transformaciones, obligaron a buscar iniciativas gubernamentales innovadoras en el ámbito del urbanismo y el ordenamiento territorial. Esta investigación tiene carácter exploratorio y busca conocer las iniciativas gubernamentales desarrolladas en las ciudades latinoamericanas en materia de planificación urbana, especialmente los cambios legislativos, tras la irrupción de la pandemia de COVID-19. A partir de un estudio de casos múltiples, que incluye São Paulo, Bogotá, Buenos Aires y la Ciudad de México, se identifican las tendencias generales en el ámbito de la administración pública municipal y se contribuye a la formulación de posibles vías que conduzcan a ciudades más inclusivas, igualitarias y sostenibles.Resumen .-- Ingtroducción .-- I. La estructura normativa nacional y el papel de los municipios en la política urbana .-- II. Revisión de los planes de ordenamiento territorial durante la pandemia .-- III. Cambios en las normas de parcelación, uso y ocupación del suelo durante la pandemia .-- IV. Planos urbanísticos sectoriales .-- V. Simplificación de la concesión de licencias urbanísticas .-- VI. Consideraciones finales