Operator Ordering in Quantum Radiative Processes

In this work we reexamine quantum electrodynamics of atomic eletrons in the Coulomb gauge in the dipole approximation and calculate the shift of atomic energy levels in the context of Dalibard, Dupont-Roc and Cohen-Tannoudji (DDC) formalism by considering the variation rates of physical observables. We then analyze the physical interpretation of the ordering of operators in the dipole approximation interaction Hamiltonian in terms of field fluctuations and self-reaction of atomic eletrons, discussing the arbitrariness in the statistical functions in second order bound-state perturbation theory.Comment: Latex file, 12 pages, no figures, includes PACS numbers and minor changes in the text with the addition of a new sectio

Electrostatic theory for imaging experiments on local charges in quantum Hall systems

We use a simple electrostatic treatment to model recent experiments on quantum Hall systems, in which charging of localised states by addition of integer or fractionally-charged quasiparticles is observed. Treating the localised state as a compressible quantum dot or antidot embedded in an incompressible background, we calculate the electrostatic potential in its vicinity as a function of its charge, and the chemical potential values at which its charge changes. The results offer a quantitative framework for analysis of the observations.Comment: 4 pages, 3 figure

A eubacterial origin for the human tRNA nucleotidyltransferase?

tRNA CCA-termini are generated and maintained by tRNA nucleotidyltransferases. Together with poly(A) polymerases and other enzymes they belong to the nucleotidyltransferase superfamily. However, sequence alignments within this family do not allow to distinguish between CCA-adding enzymes and poly(A) polymerases. Furthermore, due to the lack of sequence information about animal CCA-adding enzymes, identification of corresponding animal genes was not possible so far. Therefore, we looked for the human homolog using the baker's yeast tRNA nucleotidyltransferase as a query sequence in a BLAST search. This revealed that the human gene transcript CGI-47, (\#AF151805) deposited in GenBank is likely to encode such an enzyme. To identify the nature of this protein, the cDNA of the transcript was cloned and the recombinant protein biochemically characterized, indicating that CGI-47 encodes a bona fide CCA-adding enzyme and not a poly(A) polymerase. This confirmed animal CCA-adding enzyme allowed us to identify putative homologs from other animals. Calculation of a neighbor-joining tree, using an alignment of several CCA-adding enzymes, revealed that the animal enzymes resemble more eubacterial ones than eukaryotic plant and fungal tRNA nucleotidyltransferases, suggesting that the animal nuclear cca genes might have been derived from the endosymbiotic progenitor of mitochondria and are therefore of eubacterial origin

In vivo magnetic resonance imaging of mesenchymal stem cells in myocardial infarction

Background - We investigated the potential of magnetic resonance imaging (MRI) to track magnetically labeled mesenchymal stem cells (MR-MSCs) in a swine myocardial infarction (MI) model. Methods and Results - Adult farm pigs (n=5) were subjected to closed-chest experimental MI. MR-MSCs (2.8 to 16×107 cells) were injected intramyocardially under x-ray fluoroscopy. MRIs were obtained on a 1.5T MR scanner to demonstrate the location of the MR-MSCs and were correlated with histology. Contrast-enhanced MRI demonstrated successful injection in the infarct and serial MSC tracking was demonstrated in two animals. Conclusion - MRI tracking of MSCs is feasible and represents a preferred method for studying the engraftment of MSCs in MI

Ground state of a polydisperse electrorheological solid: Beyond the dipole approximation

The ground state of an electrorheological (ER) fluid has been studied based on our recently proposed dipole-induced dipole (DID) model. We obtained an analytic expression of the interaction between chains of particles which are of the same or different dielectric constants. The effects of dielectric constants on the structure formation in monodisperse and polydisperse electrorheological fluids are studied in a wide range of dielectric contrasts between the particles and the base fluid. Our results showed that the established body-centered tetragonal ground state in monodisperse ER fluids may become unstable due to a polydispersity in the particle dielectric constants. While our results agree with that of the fully multipole theory, the DID model is much simpler, which offers a basis for computer simulations in polydisperse ER fluids.Comment: Accepted for publications by Phys. Rev.

Helmintos animais em vestígios arqueológicos humanos: revisão de zoonoses no passado

The authors present a review of records of intestinal parasitic helminths from animals in human archaeological remains, reported since the emergence of paleopathological studies. The objective was to relate paleoparasitological findings to geographic, biotic, and abiotic factors from the environment in which the prehistoric populations lived, and understand some aspects related to the process of human dispersion and biological and cultural evolution. Modification of eating habits and the incorporation of new cultural practices are analyzed from the perspective of zoonoses from prehistory to the present day, especially in Brazilian indigenous populations. Three tables identifying the helminths, their natural hosts, dates, and sites of archaeological findings complete this review. In conclusion, various zoonoses known today have occurred since antiquity, and these data, combined with studies on the emergence and reemergence of diseases, could make possible to compose scenarios for the future.São revistos os registros de ocorrência de helmintos intestinais parasitos de animais em vestígios arqueológicos humanos, relatados desde o surgimento dos estudos paleopatológicos. Busca-se relacionar os achados em paleoparasitologia com fatores geográficos, bióticos e abióticos do ambiente em que as populações pré-históricas viviam, e com aspectos do processo de dispersão e evolução biológica e cultural humana. A modificação de hábitos alimentares e a incorporação de novas práticas culturais são analisadas sob o ponto de vista das zoonoses desde a pré-história até a atualidade, em especial em populações indígenas brasileiras. Três tabelas identificando os helmintos, seus hospedeiros naturais, datações e local dos achados arqueológicos complementam esta revisão. Conclui-se que várias zoonoses conhecidas hoje ocorrem desde a antiguidade e que estes dados, combinados a estudos de emergência e reemergência de doenças, podem auxiliar a compor cenários para o futuro

Psychometric Evaluation of the IBD-Specific Anxiety Scale: A Novel Measure of Disease-Related Anxiety for Adolescents With IBD

Anxiety related to pediatric inflammatory bowel disease (IBD) is a common comorbidity; yet, this construct is understudied because of lack of available valid measurement. Objective: The present study will report the preliminary validation of the 20-item IBD-Specific Anxiety Scale (IBD-SAS) in a large, geographically diverse sample of adolescents aged 12-18 years with IBD. Method: A total of 281 adolescents, ages 12-18 (M = 14.8, SD = 1.78; 51% male), completed the IBD-SAS along with measures of IBD-related quality of life, anxiety, depressive symptoms, and disease activity. Factor structure was assessed using exploratory and confirmatory factor analyses (EFA and CFA). Results: EFA (Sample 1; n = 141) yielded one-, two-, three- and four-factor models. The CFA (Sample 2; n = 140) demonstrated that a four-factor model was superior to three- and two-factor model for the amended scale. In total, the IBD-SAS showed excellent internal consistency (Cronbach's à = .95) and was most strongly associated with health-related quality of life. Moderate to strong associations were observed between IBD-SAS and general measures of anxiety and depressive symptoms, and IBD disease activity providing additional support that health-specific anxiety is a valid and distinct construct. Conclusions: Based on the results of this study, the IBD-SAS displayed adequate psychometric properties and can meaningfully contribute to the assessment of IBD-specific anxiety in adolescents diagnosed with IBD, thus filling an empirical and clinical need in this population

A Geography of Risk: Structural Racism and Coronavirus Disease 2019 Mortality in the United States

Coronavirus disease 2019 (COVID-19) is disproportionately burdening racial and ethnic minority groups in the United States. Higher risks of infection and mortality among racialized minorities are a consequence of structural racism, reflected in specific policies that date back centuries and persist today. Yet our surveillance activities do not reflect what we know about how racism structures risk. When measuring racial and ethnic disparities in deaths due to COVID-19, the Centers for Disease Control and Prevention statistically accounts for the geographic distribution of deaths throughout the United States to reflect the fact that deaths are concentrated in areas with different racial and ethnic distributions from those of the larger United States. In this commentary, we argue that such an approach misses an important driver of disparities in COVID-19 mortality, namely the historical forces that determine where individuals live, work, and play, and that consequently determine their risk of dying from COVID-19. We explain why controlling for geography downplays the disproportionate burden of COVID-19 on racialized minority groups in the United States. Finally, we offer recommendations for the analysis of surveillance data to estimate racial disparities, including shifting from distribution-based to risk-based measures, to help inform a more effective and equitable public health response to the pandemic

MCHO – A new indicator for insulation conditions in transmission lines

AbstractConventionally monitoring operating conditions of a power transmission line is accomplished by periodic inspections along this line. This monitoring allows corrective maintenance by finding faults during the inspection. But in more efficient maintenance, predictive techniques that are characterized by real-time monitoring should be employed. Such predictive techniques allow for verifying the working status of the line by using normal working models to detect faults and fault models for diagnosis. This paper presents a study that used a mathematical model appropriate for application to predictive maintenance of transmission line segments at low cost, without the need for sensors distributed along the line, and presenting a new indicator of transmission line operation conditions. By tracking the leakage current of transmission lines, this model allows for estimating the current line insulation status. Once the current line insulation status is known, it is possible to compare it against other future status and verify the progress of the insulation conditions of that line. The model uses a new indicator, called MCHO, which can detect and diagnose both normal and abnormal operating conditions of a power transmission line. This new indicator is the capacitance of the harmonic frequencies of the transmission line leakage current. The model was validated through measurements obtained on a stretch of transmission line