1,544 research outputs found
Compositon of Tantalum Nitride Thin Films Grown by Low-Energy Nitrogen Implantation: A Factor Analysis Study of the Ta 4f XPS Core Level
Tantalum nitride thin films have been grown by in situ nitrogen implantation
of metallic tantalum at room temperature over the energy range of 0.5-5keV.
X-ray photoelectron spectroscopy (XPS) and Factor Analysis (FA) have been used
to characterise the chemical composition of the films. The number of the
different Ta-N phases formed during nitrogen implantation, as well as their
spectral shape and concentrations, have been obtained using principal component
analysis (PCA) and iterative target transformation factor analysis (ITTFA),
without any prior assumptions. According to FA results, the composition of the
tantalum nitride films depends on both the ion dose and ion energy, and is
mainly formed by a mixture of metallic tantalum, beta-TaN0.05, gamma-Ta2N and
cubic/hexagonal TaN phases.Comment: 24 pages, 5 figures submitted to Applied Physics
Nitric oxide synthase blockade and body fluid volumes
Fil: Balaszczuk, A.M.. Instituto Universitario de Ciencias de la Salud. Fundación Barceló; Argentina.Fil: Arranz, C. Instituto Universitario de Ciencias de la Salud. Fundación Barceló; Argentina.The influence of chronic nitric oxide synthase inhibition with NGnitro- L-arginine methyl ester (L-NAME) on body fluid distribution was studied in male Wistar rats weighing 260-340 g. Extracellular, interstitial and intracellular spaces, as well as plasma volume were measured after a three-week treatment with L-NAME (»70 mg/kg per 24 h in drinking water). An increase in extracellular space (16.1 ± 1.1 vs 13.7 ± 0.6 ml/100 g in control group, N = 12, P<0.01), interstitial space (14.0 ± 0.9 vs 9.7 ± 0.6 ml/100 g in control group, P<0.001) and total water (68.7 ± 3.9 vs 59.0 ± 2.9 ml/100 g, P<0.001) was observed in the L-NAME group (N = 8). Plasma volume was lower in L-NAMEtreated rats (2.8 ± 0.2 ml/100 g) than in the control group (3.6 ± 0.1 ml/ 100 g, P<0.001). Blood volume was also lower in L-NAME-treated rats (5.2 ± 0.3 ml/100 g) than in the control group (7.2 ± 0.3 ml/100 g, P<0.001). The increase in total ratio of kidney wet weight to body weight in the L-NAME group (903 ± 31 vs 773 ± 45 mg/100 g in control group, P<0.01) but not in total kidney water suggests that this experimental hypertension occurs with an increase in renal mass. The fact that the heart weight to body weight ratio and the total heart water remained constant indicates that, despite the presence of high blood pressure, no modification in cardiac mass occurred. These data show that L-NAME-induced hypertension causes alterations in body fluid distribution and in renal mass
4U 1626-67 as seen by Suzaku before and after the 2008 torque reversal
Aims. The accretion-powered pulsar 4U 1626-67 experienced a new torque
reversal at the beginning of 2008, after about 18 years of steadily spinning
down. The main goal of the present work is to study this recent torque reversal
that occurred in 2008 February.
Methods. We present a spectral analysis of this source using two pointed
observations performed by Suzaku in 2006 March and in 2010 September.
Results. We confirm with Suzaku the presence of a strong emission-line
complex centered on 1 keV, with the strongest line being the hydrogen-like Ne
Ly-alpha at 1.025(3) keV. We were able to resolve this complex with up to seven
emission lines. A dramatic increase of the intensity of the Ne Ly-alpha line
after the 2008 torque reversal occurred, with the equivalent width of this line
reaching almost the same value measured by ASCA in 1993. We also report on the
detection of a cyclotron line feature centered at ~37 keV. In spite of the fact
that an increase of the X-ray luminosity (0.5-100 keV) of a factor of ~2.8
occurred between these two observations, no significant change in the energy of
the cyclotron line feature was observed. However, the intensity of the ~1 keV
line complex increased by an overall factor of ~8.
Conclusions. Our results favor a scenario in which the neutron star in 4U
1626-67 accretes material from a geometrically thin disk during both the
spin-up and spin-down phases.Comment: 7 pages, 5 figures and 2 tables. Accepted in A&
Obesity dependent metabolic signatures associated with nonalcoholic fatty liver disease progression
Our understanding of the mechanisms by which nonalcoholic fatty liver disease (NAFLD) progresses from simple steatosis to steatohepatitis (NASH) is still very limited. Despite the growing number of studies linking the disease with altered serum metabolite levels, an obstacle to the development of metabolome-based NAFLD predictors has been the lack of large cohort data
from biopsy-proven patients matched for key metabolic features such as obesity. We studied 467 biopsied individuals with normal liver histology (n=90) or diagnosed with NAFLD (steatosis, n=246; NASH, n=131), randomly divided into estimation (80% of all patients) and validation (20% of all patients) groups. Qualitative determinations of 540 serum metabolite variables were performed using ultra-performance liquid chromatography coupled to mass spectrometry (UPLCMS). The metabolic profile was dependent on patient body-mass index (BMI), suggesting that the
NAFLD pathogenesis mechanism may be quite different depending on an individual’s level of obesity. A BMI-stratified multivariate model based on the NAFLD serum metabolic profile was used to separate patients with and without NASH. The area under the receiver operating characteristic curve was 0.87 in the estimation and 0.85 in the validation group. The cutoff (0.54)
corresponding to maximum average diagnostic accuracy (0.82) predicted NASH with a sensitivity of 0.71 and a specificity of 0.92 (negative/positive predictive values = 0.82/0.84). The present data, indicating that a BMI-dependent serum metabolic profile may be able to reliably distinguish NASH from steatosis patients, have significant implications for the development of
NASH biomarkers and potential novel targets for therapeutic intervention
Grain Sorting Effects on Geochemical Characteristics of Sulfide Mine Tailings: a Case Study
The geochemical evolution of a sulfide mine tailings impoundment in SW Spain was studied. The impoundment was selected because of its small size and its tailings deposition system with a simple discharge point. The objective of this study was to test the hypothesis that mineral segregation associated to hydraulic sorting has significant effects on the geochemical characteristics and the long term weathering. Tailings samples were collected along depth profiles in three sampling points (proximal, central and distal to the point of discharge), and characterized by color, grain size, pH, acid-base account and chemical elements concentration, with the help of routine XRD analysis. Three vertical zones were identified: an upper oxidized zone, a transition intermediate zone, and an unoxidized zone. The analytical results indicate a segregation pattern in the unoxidized tailings based on differences in size and density of tailings grains. Near the discharge point, tailings were coarser and rich in pyrite, whereas the proportion of silicates increased from proximal to distal points. This results in a clear zoning which has consequences on geochemical and mineralogical evolution under weathering, showing substantial differences in the depth of the oxidation front, the acid generation and neutralization capacity, the formation of Fe secondary phases (jarosite) and the total content of the sulfide-related elements (Fe, As, Zn, Cu, Pb and Cd). The results of the study can serve to improve the theoretical bases for the development of conceptual models for predicting environmental impacts associated with sulfide tailings impoundments. Recently, the impoundment has been covered with a soil cover. This fact offers the possibility of new research on its evolution under new conditions
Earth Occultation Imaging of the Low Energy Gamma-Ray Sky with GBM
The Earth Occultation Technique (EOT) has been applied to Fermi's Gamma-ray
Burst Monitor (GBM) to perform all-sky monitoring for a predetermined catalog
of hard X-ray/soft gamma-ray sources. In order to search for sources not in the
catalog, thus completing the catalog and reducing a source of systematic error
in EOT, an imaging method has been developed -- Imaging with a Differential
filter using the Earth Occultation Method (IDEOM). IDEOM is a tomographic
imaging method that takes advantage of the orbital precession of the Fermi
satellite. Using IDEOM, all-sky reconstructions have been generated for ~sim 4
years of GBM data in the 12-50 keV, 50-100 keV and 100-300 keV energy bands in
search of sources otherwise unmodeled by the GBM occultation analysis. IDEOM
analysis resulted in the detection of 57 sources in the 12-50 keV energy band,
23 sources in the 50-100 keV energy band, and 7 sources in the 100-300 keV
energy band. Seventeen sources were not present in the original GBM-EOT catalog
and have now been added. We also present the first joined averaged spectra for
four persistent sources detected by GBM using EOT and by the Large Area
Telescope (LAT) on Fermi: NGC 1275, 3C 273, Cen A, and the Crab
The development of the enterprising motivation in tourism students. A comparative analysis between grade and postgraduate students
Increasing the number of entrepreneurs and the quality of the entrepreneurship, it is the key thing because its positive influences over the economic activity. For this reason, it turns out essential to understand the factors that determine this phenomenon. This paper develops a model that includes those factors which allows acting on the enterprising intention of the students in the field of tourism. It has been decided on a theoretical approach based on the basics of the intentional theory from a perspective of higher education. A survey with a sample of 122 tourism students has been used ? including both graduates and students. Our analysis suggests that curricular and extracurricular activities have a different effect in the intentions, attitudes and capacities for the business? project development. On the other hand, our results show a weak impact of these activities in the business? competences
Crowdsourcing malaria parasite quantification: an online game for analyzing images of infected thick blood smears
Background: There are 600,000 new malaria cases daily worldwide. The gold standard for estimating the parasite burden and the corresponding severity of the disease consists in manually counting the number of parasites in blood smears through a microscope, a process that can take more than 20 minutes of an expert microscopist’s time.
Objective: This research tests the feasibility of a crowdsourced approach to malaria image analysis. In particular, we investigated whether anonymous volunteers with no prior experience would be able to count malaria parasites in digitized images of thick blood smears by playing a Web-based game.
Methods: The experimental system consisted of a Web-based game where online volunteers were tasked with detecting parasites in digitized blood sample images coupled with a decision algorithm that combined the analyses from several players to produce an improved collective detection outcome. Data were collected through the MalariaSpot website. Random images of thick blood films containing Plasmodium falciparum at medium to low parasitemias, acquired by conventional optical microscopy, were presented to players. In the game, players had to find and tag as many parasites as possible in 1 minute. In the event that players found all the parasites present in the image, they were presented with a new image. In order to combine the choices of different players into a single crowd decision, we implemented an image processing pipeline and a quorum algorithm that judged a parasite tagged when a group of players agreed on its position.
Results: Over 1 month, anonymous players from 95 countries played more than 12,000 games and generated a database of more than 270,000 clicks on the test images. Results revealed that combining 22 games from nonexpert players achieved a parasite counting accuracy higher than 99%. This performance could be obtained also by combining 13 games from players trained for 1 minute. Exhaustive computations measured the parasite counting accuracy for all players as a function of the number of games considered and the experience of the players. In addition, we propose a mathematical equation that accurately models the collective parasite counting performance.
Conclusions: This research validates the online gaming approach for crowdsourced counting of malaria parasites in images of thick blood films. The findings support the conclusion that nonexperts are able to rapidly learn how to identify the typical features of malaria parasites in digitized thick blood samples and that combining the analyses of several users provides similar parasite counting accuracy rates as those of expert microscopists. This experiment illustrates the potential of the crowdsourced gaming approach for performing routine malaria parasite quantification, and more generally for solving biomedical image analysis problems, with future potential for telediagnosis related to global health challenges
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