116 research outputs found
Proton conductivity through polybenzimidazole composite membranes containing silica nanofiber mats
The quest for sustainable and more efficient energy-converting devices has been the focus of researchers′ efforts in the past decades. In this study, SiO2 nanofiber mats were fabricated through an electrospinning process and later functionalized using silane chemistry to introduce different polar groups −OH (neutral), −SO3H (acidic) and −NH2 (basic). The modified nanofiber mats were embedded in PBI to fabricate mixed matrix membranes. The incorporation of these nanofiber mats in the PBI matrix showed an improvement in the chemical and thermal stability of the composite membranes. Proton conduction measurements show that PBI composite membranes containing nanofiber mats with basic groups showed higher proton conductivities, reaching values as high as 4 mS·cm−1 at 200 °C
Eclipsing Binaries as Astrophysical Laboratories: Internal Structure, Convective Core Overshooting and Evolution of the B-star Components of V380 Cygni
New photometric solutions have been carried out on the important eccentric
eclipsing system V380 Cygni (B1.5II-III + B2V) from UBV differential
photoelectric photometry obtained by us. The photometric elements obtained from
the analysis of the light curves have been combined with the spectroscopic
solution recently published by Popper & Guinan and have led to the physical
properties of the system components. The effective temperature of the stars has
been determined by fitting IUE UV spectrophotometry to Kurucz model atmospheres
and compared with other determinations from broad-band and intermediate-band
standard photometry. The values of mass, absolute radius, and effective
temperature, for the primary and secondary stars are: 11.1+/-0.5 Mo, 14.7+/-0.2
Ro, 21350+/-400 K, and 6.95+/-0.25 Mo, 3.74+/-0.07 Ro, 20500+/-500 K,
respectively. In addition, a re-determination of the system's apsidal motion
rate has been done from the analysis of 12 eclipse timings obtained from 1923
to 1995. Using stellar structure and evolutionary models with modern input
physics, tests on the extent of convection in the core of the more massive star
of the system have been carried out. Both the analysis of the log g-log Teff
diagram and the apsidal motion study indicate a star with a larger convective
core, and thus more centrally condensed, than currently assumed. This has been
quantified in form of an overshooting parameter with a value of 0.6+/-0.1.
Finally, the tidal evolution of the system (synchronization and circularization
times) has also been studied.Comment: 23 pages, 5 figures, version accepted for publication in Ap
Far Ultraviolet Absolute Flux of alpha Virginis
We present the far ultraviolet spectrum of alpha Virginis taken with EURD
spectrograph on-board MINISAT-01. The spectral range covered is from ~900 to
1080 A with 5 A spectral resolution. We have fitted Kurucz models to IUE
spectra of alpha Vir and compared the extension of the model to our wavelengths
with EURD data. This comparison shows that EURD fluxes are consistent with the
prediction of the model within 20-30%, depending on the reddening assumed. EURD
fluxes are consistent with Voyager observations but are ~60% higher than most
previous rocket observations of alpha Vir.Comment: 13 pages, 4 figures. Submitted to The Astrophysical Journa
ABORDAGEM DAS CONFIGURAÇÕES: DIMENSÕES DO INDIVÍDUO, EMPREENDIMENTO E CONTEXTO EM EMPRESAS NO ESTÁGIO INICIAL
A presente pesquisa teve como objetivo analisar as configurações empreendedoras em empresas no estágio inicial. Trata-se de uma pesquisa exploratória e descritiva com coleta de dados por levantamento, com uma amostra por conveniência de 62 empresas. O questionário foi composto por 48 (quarenta e oito) questões subdivididas em três seções: a primeira seção continha dados demográficos; na segunda seção as questões versavam sobre o empreendimento: setor de atuação, abrangência de atuação, idade da empresa, porte e número de funcionários; e na terceira seção havia 40 (quarenta) questões fechadas sobre as variáveis determinantes das configurações empreendedoras. Para analisar tais configurações, foi feita uma análise fatorial e análise de agrupamentos, considerando as dimensões: indivíduo, empreendimento e contexto. Foram formados três clusters, com características que delimitavam configurações empreendedoras distintas. Todas as empresas apresentaram uma percepção bastante semelhante sobre a dimensão indivíduo. As empresas do cluster 1, apresentaram porcentagens menores em relação ao projeto e contexto. As empresas do cluster 2 parecem perseguir alta motivação para a abertura do negócio. As empresas do cluster 3 mostram o alto lócus de controle, o que representa a participação dominante do empreendedor, com foco no controle do indivíduo
The LMC eclipsing binary HV 2274: fundamental properties and comparison with evolutionary models
We are carrying out an international, multi-wavelength program to determine
the fundamental properties and independent distance estimates of selected
eclipsing binaries in the LMC and SMC. Eclipsing binaries with well-defined
double-line radial velocity curves and light curves provide valuable
information on orbital and physical properties of their component stars. The
study of stars in the LMC and SMC where the metal abundances are significantly
lower than solar provides an important opportunity to test stellar atmosphere,
interior and evolution models, and opacities. For the first time, we can also
measure direct M-L relations for stars outside our Galaxy. In this paper we
concentrate on the determination of the orbital and physical properties of HV
2274 from analyses of light curves and new radial velocity curves formed from
HST/GHRS observations. From UV/optical spectrophotometry of HV 2274 obtained
with HST/FOS, the temperatures and the metallicity of the stars were found, as
well as the interstellar extinction of the system. The values of mass, absolute
radius, and effective temperature, for the primary and secondary stars are:
12.2(7) Mo, 9.9(2) Ro, 23000(180) K, and 11.4(7) Mo, 9.0(2) Ro, 23110(180) K,
respectively. The age of the system (17(2) Myr), helium abundance (Y=0.26(3))
and a lower limit of the convective core overshooting parameter of 0.2 were
obtained from fitting the stellar data with evolution models. The apsidal
motion analysis corroborates that some amount of convective overshooting
(0.2-0.5) is needed.Comment: 39 pages, 9 figures, accepted for publication in Ap
An Integrated TCGA Pan-Cancer Clinical Data Resource to Drive High-Quality Survival Outcome Analytics
For a decade, The Cancer Genome Atlas (TCGA) program collected clinicopathologic annotation data along with multi-platform molecular profiles of more than 11,000 human tumors across 33 different cancer types. TCGA clinical data contain key features representing the democratized nature of the data collection process. To ensure proper use of this large clinical dataset associated with genomic features, we developed a standardized dataset named the TCGA Pan-Cancer Clinical Data Resource (TCGA-CDR), which includes four major clinical outcome endpoints. In addition to detailing major challenges and statistical limitations encountered during the effort of integrating the acquired clinical data, we present a summary that includes endpoint usage recommendations for each cancer type. These TCGA-CDR findings appear to be consistent with cancer genomics studies independent of the TCGA effort and provide opportunities for investigating cancer biology using clinical correlates at an unprecedented scale. Analysis of clinicopathologic annotations for over 11,000 cancer patients in the TCGA program leads to the generation of TCGA Clinical Data Resource, which provides recommendations of clinical outcome endpoint usage for 33 cancer types
Pan-Cancer Analysis of lncRNA Regulation Supports Their Targeting of Cancer Genes in Each Tumor Context
Long noncoding RNAs (lncRNAs) are commonly dys-regulated in tumors, but only a handful are known toplay pathophysiological roles in cancer. We inferredlncRNAs that dysregulate cancer pathways, onco-genes, and tumor suppressors (cancer genes) bymodeling their effects on the activity of transcriptionfactors, RNA-binding proteins, and microRNAs in5,185 TCGA tumors and 1,019 ENCODE assays.Our predictions included hundreds of candidateonco- and tumor-suppressor lncRNAs (cancerlncRNAs) whose somatic alterations account for thedysregulation of dozens of cancer genes and path-ways in each of 14 tumor contexts. To demonstrateproof of concept, we showed that perturbations tar-geting OIP5-AS1 (an inferred tumor suppressor) andTUG1 and WT1-AS (inferred onco-lncRNAs) dysre-gulated cancer genes and altered proliferation ofbreast and gynecologic cancer cells. Our analysis in-dicates that, although most lncRNAs are dysregu-lated in a tumor-specific manner, some, includingOIP5-AS1, TUG1, NEAT1, MEG3, and TSIX, synergis-tically dysregulate cancer pathways in multiple tumorcontexts
Pan-cancer Alterations of the MYC Oncogene and Its Proximal Network across the Cancer Genome Atlas
Although theMYConcogene has been implicated incancer, a systematic assessment of alterations ofMYC, related transcription factors, and co-regulatoryproteins, forming the proximal MYC network (PMN),across human cancers is lacking. Using computa-tional approaches, we define genomic and proteo-mic features associated with MYC and the PMNacross the 33 cancers of The Cancer Genome Atlas.Pan-cancer, 28% of all samples had at least one ofthe MYC paralogs amplified. In contrast, the MYCantagonists MGA and MNT were the most frequentlymutated or deleted members, proposing a roleas tumor suppressors.MYCalterations were mutu-ally exclusive withPIK3CA,PTEN,APC,orBRAFalterations, suggesting that MYC is a distinct onco-genic driver. Expression analysis revealed MYC-associated pathways in tumor subtypes, such asimmune response and growth factor signaling; chro-matin, translation, and DNA replication/repair wereconserved pan-cancer. This analysis reveals insightsinto MYC biology and is a reference for biomarkersand therapeutics for cancers with alterations ofMYC or the PMN
Genomic, Pathway Network, and Immunologic Features Distinguishing Squamous Carcinomas
This integrated, multiplatform PanCancer Atlas study co-mapped and identified distinguishing
molecular features of squamous cell carcinomas (SCCs) from five sites associated with smokin
Spatial Organization and Molecular Correlation of Tumor-Infiltrating Lymphocytes Using Deep Learning on Pathology Images
Beyond sample curation and basic pathologic characterization, the digitized H&E-stained images
of TCGA samples remain underutilized. To highlight this resource, we present mappings of tumorinfiltrating lymphocytes (TILs) based on H&E images from 13 TCGA tumor types. These TIL
maps are derived through computational staining using a convolutional neural network trained to
classify patches of images. Affinity propagation revealed local spatial structure in TIL patterns and
correlation with overall survival. TIL map structural patterns were grouped using standard
histopathological parameters. These patterns are enriched in particular T cell subpopulations
derived from molecular measures. TIL densities and spatial structure were differentially enriched
among tumor types, immune subtypes, and tumor molecular subtypes, implying that spatial
infiltrate state could reflect particular tumor cell aberration states. Obtaining spatial lymphocytic
patterns linked to the rich genomic characterization of TCGA samples demonstrates one use for
the TCGA image archives with insights into the tumor-immune microenvironment
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