1,008 research outputs found

    Introduction to the Special Issue on Natural Language and Learning Machines

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    1. Introduction The interaction between machine learning and natural language processing (NLP) research underlies most of the progress made in NLP for the last few decades (Cardie and Mooney 1999; Fung and Roth 2005). Machine Learning has been the common framework for the birth and development of most paradigms, discoveries and achievements in statistical natural language processing. At the international level the AAAI Fall symposiums in 1990 (Jacobs 1990) and 1992 (Goldman 1992) and the IBM ..

    Evolved Galaxies at z > 1.5 from the Gemini Deep Deep Survey: The Formation Epoch of Massive Stellar Systems

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    We present spectroscopic evidence from the Gemini Deep Deep Survey (GDDS) for a significant population of color-selected red galaxies at 1.3 < z < 2.2 whose integrated light is dominated by evolved stars. Unlike radio-selected objects, the z > 1.5 old galaxies have a sky density > 0.1 per sq. arcmin. Conservative age estimates for 20 galaxies with z > 1.3; = 1.49, give a median age of 1.2 Gyr and = 2.4. One quarter of the galaxies have inferred z_f > 4. Models restricted to abundances less than or equal to solar give median ages and z_f of 2.3 Gyr and 3.3, respectively. These galaxies are among the most massive and contribute approximately 50% of the stellar mass density at 1 < z < 2. The derived ages and most probable star formation histories suggest a high star-formation-rate (300-500 solar masses per year) phase in the progenitor population. We argue that most of the red galaxies are not descendants of the typical z=3 Lyman break galaxies. Galaxies associated with luminous sub-mm sources have the requisite star formation rates to be the progenitor population. Our results point toward early and rapid formation for a significant fraction of present day massive galaxies.Comment: 12 pages, 2 figures, 1 table, Accepted for publication, ApJ Letter

    Cosmic Star Formation History and its Dependence on Galaxy Stellar Mass

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    We examine the cosmic star formation rate (SFR) and its dependence on galaxy stellar mass over the redshift range 0.8 < z < 2 using data from the Gemini Deep Deep Survey (GDDS). The SFR in the most massive galaxies (M > 10^{10.8} M_sun) was six times higher at z = 2 than it is today. It drops steeply from z = 2, reaching the present day value at z ~ 1. In contrast, the SFR density of intermediate mass galaxies (10^{10.2} < M < 10^{10.8} M_sun) declines more slowly and may peak or plateau at z ~ 1.5. We use the characteristic growth time t_SFR = rho_M / rho_SFR to provide evidence of an associated transition in massive galaxies from a burst to a quiescent star formation mode at z ~ 2. Intermediate mass systems transit from burst to quiescent mode at z ~ 1, while the lowest mass objects undergo bursts throughout our redshift range. Our results show unambiguously that the formation era for galaxies was extended and proceeded from high to low mass systems. The most massive galaxies formed most of their stars in the first ~3 Gyr of cosmic history. Intermediate mass objects continued to form their dominant stellar mass for an additional ~2 Gyr, while the lowest mass systems have been forming over the whole cosmic epoch spanned by the GDDS. This view of galaxy formation clearly supports `downsizing' in the SFR where the most massive galaxies form first and galaxy formation proceeds from larger to smaller mass scales.Comment: Accepted for publication in ApJ

    Nutrition in chronic inflammatory conditions: Bypassing the mucosal block for micronutrients

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    Nutritional Immunity is one of the most ancient innate immune responses, during which the body can restrict nutrients availability to pathogens and restricts their uptake by the gut mucosa (mucosal block). Though this can be a beneficial strategy during infection, it also is associated with non‐communicable diseases—where the pathogen is missing; leading to increased morbidity and mortality as micronutritional uptake and distribution in the body is hindered. Here, we discuss the acute immune response in respect to nutrients, the opposing nutritional demands of regulatory and inflammatory cells and particularly focus on some nutrients linked with inflammation such as iron, vitamins A, Bs, C, and other antioxidants. We propose that while the absorption of certain micronutrients is hindered during inflammation, the dietary lymph path remains available. As such, several clinical trials investigated the role of the lymphatic system during protein absorption, following a ketogenic diet and an increased intake of antioxidants, vitamins, and minerals, in reducing inflammation and ameliorating disease

    Gemini Deep Deep Survey VI: Massive Hdelta-strong galaxies at z=1

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    We show that there has been a dramatic decline in the abundance of massive galaxies with strong Hdelta stellar absorption lines from z=1.2 to the present. These ``Hdelta-strong'', or HDS, galaxies have undergone a recent and rapid break in their star-formation activity. Combining data from the Gemini Deep Deep and the Sloan Digital Sky Surveys to make mass-matched samples (M*>=10^10.2 Msun), with 25 and 50,255 galaxies, respectively), we find that the fraction of galaxies in an HDS phase has decreased from about 50% at z=1.2 to a few percent today. This decrease in fraction is due to an actual decrease in the number density of massive HDS systems by a factor of 2-4, coupled with an increase in the number density of massive galaxies by about 30 percent. We show that this result depends only weakly on the threshold chosen for the Hdelta equivalent width to define HDS systems (if greater than 4 A) and corresponds to a (1+z)^{2.5\pm 0.7} evolution. Spectral synthesis studies of the high-redshift population using the PEGASE code, treating Hdelta_A, EW[OII], Dn4000, and rest-frame colors, favor models in which the Balmer absorption features in massive Hdelta-strong systems are the echoes of intense episodes of star-formation that faded about 1 Gyr prior to the epoch of observation. The z=1.4-2 epoch appears to correspond to a time at which massive galaxies are in transition from a mode of sustained star formation to a relatively quiescent mode with weak and rare star-formation episodes. We argue that the most likely local descendants of the distant massive HDS galaxies are passively evolving massive galaxies in the field and small groups.Comment: 16 pages, 12 figures, 3 tables, uses emulateapj.sty; updated to match the version accepted by ApJ. One figure added, conclusions unchange

    Corruption et investissement externe direct au Brésil

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     O Brasil até 2010 ficou entre os 10 principais países receptores de IED, mas de 2010 a 2014, perdeu posições no ranking dos países receptores de IED. Um dos fatores econômicos que os investidores analisam na escolha do país receptor é a corrupção, que é um dos principais desafios enfrentados pelo Brasil. O presente trabalho tem como objetivo analisar a percepção de executivos de empresas multinacionais sobre o quanto a corrupção influenciou no IED do Brasil no período de 2010 a 2014. Para tanto, utilizou-se uma metodologia de pesquisa em duas partes complementares. Na primeira foram realizadas entrevistas com dois executivos de multinacionais de capital estrangeiro. Na segunda foram enviados questionários para multinacionais de capital estrangeiro atuantes no Brasil. Após a análise dos dados coletados de ambas as pesquisas percebeu-se que a corrupção é um fator condicionante para a entrada de IED no país e que o Brasil precisa combater e controlar a corrupção, pois a mesma afeta a qualidade dos serviços prestados, a infraestrutura e o investimento global no país

    Dyspnea perception during the inspiratory resistive loads test in obese subjects waiting bariatric surgery

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    Identifcation of low dyspnea perception is relevant, since this condition is signifcantly associated with worse outcomes. We investigated dyspnea perception during the inspiratory resistive loads test on obese subjects waiting bariatric surgery in comparison with normal subjects. Secondarily, we analysed the proportion of obese subjects with low, moderate and high dyspnea perception. This observational study included subjects with body mass index (BMI)≥35kg/m2, compared to healthy subjects with BMI ≥18 and <25kg/m2. Subject underwent clinical evaluation, inspiratory test with progressive resistive loads and spirometry. We studied 23 obese subjects (mean BMI=51.9±9.3kg/ m2) and 25 normal subjects (mean BMI=24.3±2.3kg/m2). With the increase magnitude of resistive loads there was a signifcant increase in dyspnea score (p<0.001) and progressive increase of the generated inspiratory pressure (p<0.001), but there was no diference between the groups in terms of dyspnea score (p=0.191) and no interaction efect (p=0.372). Among the obese subjects, 4 individuals were classifed as low perception, 11 as moderate and 8 as high. In conclusion, the degree of dyspnea perception during the inspiratory progressive resistive loads test did not difer between obese and normal subjects. Among obese subjects, only 17% were classifed as low dyspnea perception
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