79 research outputs found
Accurate masses and radii of normal stars: modern results and applications
This paper presents and discusses a critical compilation of accurate,
fundamental determinations of stellar masses and radii. We have identified 95
detached binary systems containing 190 stars (94 eclipsing systems, and alpha
Centauri) that satisfy our criterion that the mass and radius of both stars be
known to 3% or better. To these we add interstellar reddening, effective
temperature, metal abundance, rotational velocity and apsidal motion
determinations when available, and we compute a number of other physical
parameters, notably luminosity and distance. We discuss the use of this
information for testing models of stellar evolution. The amount and quality of
the data also allow us to analyse the tidal evolution of the systems in
considerable depth, testing prescriptions of rotational synchronisation and
orbital circularisation in greater detail than possible before. The new data
also enable us to derive empirical calibrations of M and R for single (post-)
main-sequence stars above 0.6 M(Sun). Simple, polynomial functions of T(eff),
log g and [Fe/H] yield M and R with errors of 6% and 3%, respectively.
Excellent agreement is found with independent determinations for host stars of
transiting extrasolar planets, and good agreement with determinations of M and
R from stellar models as constrained by trigonometric parallaxes and
spectroscopic values of T(eff) and [Fe/H]. Finally, we list a set of 23
interferometric binaries with masses known to better than 3%, but without
fundamental radius determinations (except alpha Aur). We discuss the prospects
for improving these and other stellar parameters in the near future.Comment: 56 pages including figures and tables. To appear in The Astronomy and
Astrophysics Review. Ascii versions of the tables will appear in the online
version of the articl
Pressure-induced radial collapse in few-wall carbon nanotubes: A combined theoretical and experimental study
Brazilian authors acknowledge funding from CNPq (grant 307317/2010-2, INCT NanoBioSimes) and Central AnalĂtica-UFC/CT-INFRA-FINEP/PrĂł-Equipamentos-CAPES/CNPq-SisNano-MCTI (grant 402284/2013-5). R. S. Alencar is also in debt to Coordenação de Aperfeiçoamento de Pessoal de NĂvel Superior under the grant No. 99999.004227/2014-00 for financial support. Alexander Soldatov (University of Lulea, Sweden) is warmly acknowledged for discussions on the RBM Raman spectra interpretation at the collapse region
Social determinants of leprosy in a hyperendemic State in North Brazil
OBJECTIVE To identify the socioeconomic, demographic, operational, and health service-related factors associated with the occurrence of leprosy in a hyperendemic State in North Brazil. METHODS This is an ecological study based on secondary data from the Sistema de Informações de Agravos de Notificação in municipalities of the State of Tocantins from 2001 to 2012. Units of analysis were the 139 municipalities of the State. Negative binomial log linear regression models were used to estimate incidence rate ratios. RESULTS In bivariate analysis, the incidence rate ratios were significantly higher for municipalities with higher income ratio of the poorest 20.0% (1.47; 95%CI 1.19–1.81) and better Municipal Human Development Index (1.53; 95%CI 1.14–2.06). In multivariate analysis, the incidence rate ratios were significantly higher in municipalities with higher proportion of immigrants (1.31; 95%CI 1.11–1.55) and higher proportion of households with waste collection (1.37; 95%CI 1.11–1.69). There was a significant reduction in the incidence rate ratio with increased coverage of the Bolsa FamĂlia Program (0.98; 95%CI 0.96–0.99). CONCLUSIONS Control programs need to focus on activities in municipalities of greater social vulnerability with intersectoral investment for the improvement of the living conditions of the population.OBJETIVO Identificar fatores socioeconĂ´micos, demográficos, operacionais e de serviços de saĂşde associados Ă ocorrĂŞncia da hansenĂase em um estado hiperendĂŞmico do norte do Brasil. MÉTODOS Estudo ecolĂłgico com dados secundários do Sistema de Informações de Agravos de Notificação em municĂpios do estado do Tocantins de 2001 a 2012. As unidades de análise foram os 139 municĂpios do estado. Modelos de regressĂŁo log linear binomial negativa foram utilizados para estimar as razões de taxas de incidĂŞncia. RESULTADOS Na análise bivariada, a razĂŁo de taxa de incidĂŞncia foi significativamente maior para os municĂpios com maior razĂŁo de renda dos 20,0% mais pobres (1,47; IC95% 1,19–1,81) e melhor ĂŤndice de Desenvolvimento Humano Municipal (1,53; IC95% 1,14–2,06). Na mĂşltipla, a razĂŁo de taxa de incidĂŞncia foi significativamente superior em municĂpios com maior concentração de imigrantes (1,31; IC95% 1,11–1,55) e proporção de domicĂlios com coleta de lixo (1,37; IC95% 1,11–1,69). Houve redução significativa da razĂŁo de taxa de incidĂŞncia com o aumento da cobertura do programa bolsa famĂlia (0,98; IC95% 0,96–0,99). CONCLUSĂ•ES Os programas de controle precisam focar as atividades em municĂpios de maior vulnerabilidade social com investimentos intersetoriais para a melhoria das condições de vida da população
Genetic Structure, Linkage Disequilibrium and Signature of Selection in Sorghum: Lessons from Physically Anchored DArT Markers
Population structure, extent of linkage disequilibrium (LD) as well as signatures of selection were investigated in sorghum using a core sample representative of worldwide diversity. A total of 177 accessions were genotyped with 1122 informative physically anchored DArT markers. The properties of DArTs to describe sorghum genetic structure were compared to those of SSRs and of previously published RFLP markers. Model-based (STRUCTURE software) and Neighbor-Joining diversity analyses led to the identification of 6 groups and confirmed previous evolutionary hypotheses. Results were globally consistent between the different marker systems. However, DArTs appeared more robust in terms of data resolution and bayesian group assignment. Whole genome linkage disequilibrium as measured by mean r2 decreased from 0.18 (between 0 to 10 kb) to 0.03 (between 100 kb to 1 Mb), stabilizing at 0.03 after 1 Mb. Effects on LD estimations of sample size and genetic structure were tested using i. random sampling, ii. the Maximum Length SubTree algorithm (MLST), and iii. structure groups. Optimizing population composition by the MLST reduced the biases in small samples and seemed to be an efficient way of selecting samples to make the best use of LD as a genome mapping approach in structured populations. These results also suggested that more than 100,000 markers may be required to perform genome-wide association studies in collections covering worldwide sorghum diversity. Analysis of DArT markers differentiation between the identified genetic groups pointed out outlier loci potentially linked to genes controlling traits of interest, including disease resistance genes for which evidence of selection had already been reported. In addition, evidence of selection near a homologous locus of FAR1 concurred with sorghum phenotypic diversity for sensitivity to photoperiod
Topical Application of Activity-based Probes for Visualization of Brain Tumor Tissue
Several investigators have shown the utility of systemically delivered optical imaging probes to image tumors in small animal models of cancer. Here we demonstrate an innovative method for imaging tumors and tumor margins during surgery. Specifically, we show that optical imaging probes topically applied to tumors and surrounding normal tissue rapidly differentiate between tissues. In contrast to systemic delivery of optical imaging probes which label tumors uniformly over time, topical probe application results in rapid and robust probe activation that is detectable as early as 5 minutes following application. Importantly, labeling is primarily associated with peri-tumor spaces. This methodology provides a means for rapid visualization of tumor and potentially infiltrating tumor cells and has potential applications for directed surgical excision of tumor tissues. Furthermore, this technology could find use in surgical resections for any tumors having differential regulation of cysteine cathepsin activity
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