29 research outputs found
Structural, electrical, and optical properties of CuGaSe2 rf sputtered thin films
Thin films of CuGaSe2 have been produced by rf sputtering. Compositional, structural, electrical, and optical properties are strongly influenced by growthtemperature. At substrate temperatures lower than 300â°C amorphous or poorly crystalline Seâexcess films are obtained, showing high resistivity (â103 Ωâcm) and optical transitions at 1.62, 1.80, and 2.4 eV (values lower than the singleâcrystal counterparts). At the higher growthtemperatures,polycrystalline films are obtained (average grain size 0.7 ÎŒm) with lower values of resistivity (1 Ωâcm), and optical transitions at 1.68, 1.90, and 2.55 eV (very close to the singleâcrystal values). A hopping conduction mechanism has been detected at the lower measuringtemperature (T150 K). Structural and compositional characteristics are used to explain the behavior observed in the electrical and optical properties
Role of deep levels and interface states in the capacitance characteristics of allâsputtered CuInSe2/CdS solar cell heterojunctions
Allâsputtered CuInSe2/CdS solar cellheterojunctions have been analyzed by means of capacitanceâfrequency (CâF) and capacitanceâbias voltage (CâV) measurements. Depending on the CuInSe2 layer composition, two kinds of heterojunctions were analyzed: type 1 heterojunctions (based on stoichiometric or slightly Inârich CuInSe2 layers) and type 2 heterojunctions (based on Cuârich CuInSe2 layers). In type 1 heterojunctions, a 80âmeV donor level has been found. Densities of interface states in the range 101 0â101 1 cm2âeVâ 1 (type 1) and in the range 101 2â101 3 cmâ 2âeVâ 1 (type 2) have been deduced. On the other hand, doping concentrations of 1.6Ă101 6 cmâ 3 for stoichiometric CuInSe2 (type 1 heterojunction) and 8Ă101 7 cmâ 3 for the CdS (type 2 heterojunction) have been deduced from CâVmeasurements
A methodological approach an the design and fabrication of an abrasive wear machine and construction according to ASTM-G65 standard
Este artĂculo trata sobre el diseño y construcciĂłn de una mĂĄquina para la mediciĂłn del desgaste abrasivo basado en la norma ASTM G65 [1]. El diseño toma como consideraciĂłn lo expuesto por la norma y es complementado con metodologĂas de diseño y desarrollo concurrente de producto. En el diseño conceptual se establece las especificaciones iniciales requeridas; para el diseño funcional se formulan las funciones que la mĂĄquina debe realizar para cada requerimiento, las alternativas de diseño son evaluadas por el mĂ©todo de criterios ponderados, permitiendo establecer la mejor alternativa de diseño conceptual y funcional. Por Ășltimo en la fase de diseño de detalle se definen los materiales y el dimensionamiento de las piezas estableciendo un factor de seguridad en los elementos que ameriten, para la fabricaciĂłn y puesta en funcionamiento de equipo se usan procesos de mecanizado y de soldadura.Abstract: This article discusses the design and construction of a machine for measuring the abrasive wear based
on the ASTM G65. The design takes as its consideration the norm and is complemented with design
methodologies and concurrent product development. The design concept provides the specifications
required, and for the functional design makes the functions that the machine must be made for each
feature, these methods are evaluated by of weighted criteria, allowing to establish the best option for
conceptual design and functional. In the detailed design phase defines the material and sizing of parts
providing a safety factor in elements that warrant for the manufacture and operation of process equipment
used for welding
CuInSe2 thin films produced by rf sputtering in Ar/H2 atmospheres
Structural, compositional, optical, and electrical properties of CuInSe2thin filmsgrown by rf reactive sputtering from a Se excess target in Ar/H2 atmospheres are presented. The addition of H2 to the sputtering atmospheres allows the control of stoichiometry of films giving rise to remarkable changes in the film properties. Variation of substrate temperature causes changes in film composition because of the variation of hydrogen reactivity at the substrate. Measurements of resistivity at variable temperatures indicate a hopping conduction mechanism through gap states for films grown at low temperature (100â250â°C), the existence of three acceptor levels at about 0.046, 0.098, and 0.144 eV above valence band for films grown at intermediate temperature (250â350â°C), and a pseudometallic behavior for film grown at high temperatures (350â450â°C). Chalcopyrite polycrystalline thin films of CuInSe2 with an average grain size of 1 ÎŒm, an optical gap of 1.01 eV, and resistivities from 10â 1 to 103 Ωâcm can be obtained by adding 1.5% of H2 to the sputtering atmosphere and by varying the substrate temperature from 300 to 400â°C
Un anĂĄlisis sobre la percepciĂłn que tiene los estudiantes de pedagogĂa sobre la responsabilidad social universitaria
La responsabilidad social universitaria (RSU) es entendida como las formas de gestionar de manera Ă©tica la universidad, considerando su visiĂłn y misiĂłn como punto de partida para orientar sus valores, compromiso social y transparencia en la que participan toda la comunidad acadĂ©mica. Este sentido, el objetivo es interpretar la percepciĂłn que tienen un grupo de once (11) participantes sobre la RSU que fomenta la universidad como parte de esa polĂtica social. El trabajo se desarrollĂł bajo un enfoque cualitativo con perspectiva construccionista, en la que se interpretan de los datos que fueron recolectados mediante una entrevista de 14 preguntas guĂas. Los resultados evidencian que los estudiantes tienen una opiniĂłn difusa sobre las estrategias de la universidad para promover la Responsabilidad Social Universitaria. Se concluye que se debe informar y concientizar a todos los integrantes de la comunidad universitaria sobre los beneficios que tiene este fenĂłmeno en el desarrollo de la sociedad
Atrasentan and renal events in patients with type 2 diabetes and chronic kidney disease (SONAR): a double-blind, randomised, placebo-controlled trial
Background: Short-term treatment for people with type 2 diabetes using a low dose of the selective endothelin A receptor antagonist atrasentan reduces albuminuria without causing significant sodium retention. We report the long-term effects of treatment with atrasentan on major renal outcomes. Methods: We did this double-blind, randomised, placebo-controlled trial at 689 sites in 41 countries. We enrolled adults aged 18â85 years with type 2 diabetes, estimated glomerular filtration rate (eGFR)25â75 mL/min per 1·73 m 2 of body surface area, and a urine albumin-to-creatinine ratio (UACR)of 300â5000 mg/g who had received maximum labelled or tolerated reninâangiotensin system inhibition for at least 4 weeks. Participants were given atrasentan 0·75 mg orally daily during an enrichment period before random group assignment. Those with a UACR decrease of at least 30% with no substantial fluid retention during the enrichment period (responders)were included in the double-blind treatment period. Responders were randomly assigned to receive either atrasentan 0·75 mg orally daily or placebo. All patients and investigators were masked to treatment assignment. The primary endpoint was a composite of doubling of serum creatinine (sustained for â„30 days)or end-stage kidney disease (eGFR <15 mL/min per 1·73 m 2 sustained for â„90 days, chronic dialysis for â„90 days, kidney transplantation, or death from kidney failure)in the intention-to-treat population of all responders. Safety was assessed in all patients who received at least one dose of their assigned study treatment. The study is registered with ClinicalTrials.gov, number NCT01858532. Findings: Between May 17, 2013, and July 13, 2017, 11 087 patients were screened; 5117 entered the enrichment period, and 4711 completed the enrichment period. Of these, 2648 patients were responders and were randomly assigned to the atrasentan group (n=1325)or placebo group (n=1323). Median follow-up was 2·2 years (IQR 1·4â2·9). 79 (6·0%)of 1325 patients in the atrasentan group and 105 (7·9%)of 1323 in the placebo group had a primary composite renal endpoint event (hazard ratio [HR]0·65 [95% CI 0·49â0·88]; p=0·0047). Fluid retention and anaemia adverse events, which have been previously attributed to endothelin receptor antagonists, were more frequent in the atrasentan group than in the placebo group. Hospital admission for heart failure occurred in 47 (3·5%)of 1325 patients in the atrasentan group and 34 (2·6%)of 1323 patients in the placebo group (HR 1·33 [95% CI 0·85â2·07]; p=0·208). 58 (4·4%)patients in the atrasentan group and 52 (3·9%)in the placebo group died (HR 1·09 [95% CI 0·75â1·59]; p=0·65). Interpretation: Atrasentan reduced the risk of renal events in patients with diabetes and chronic kidney disease who were selected to optimise efficacy and safety. These data support a potential role for selective endothelin receptor antagonists in protecting renal function in patients with type 2 diabetes at high risk of developing end-stage kidney disease. Funding: AbbVie
Non-invasive diagnostic tests for Helicobacter pylori infection
BACKGROUND: Helicobacter pylori (H pylori) infection has been implicated in a number of malignancies and non-malignant conditions including peptic ulcers, non-ulcer dyspepsia, recurrent peptic ulcer bleeding, unexplained iron deficiency anaemia, idiopathic thrombocytopaenia purpura, and colorectal adenomas. The confirmatory diagnosis of H pylori is by endoscopic biopsy, followed by histopathological examination using haemotoxylin and eosin (H & E) stain or special stains such as Giemsa stain and Warthin-Starry stain. Special stains are more accurate than H & E stain. There is significant uncertainty about the diagnostic accuracy of non-invasive tests for diagnosis of H pylori. OBJECTIVES: To compare the diagnostic accuracy of urea breath test, serology, and stool antigen test, used alone or in combination, for diagnosis of H pylori infection in symptomatic and asymptomatic people, so that eradication therapy for H pylori can be started. SEARCH METHODS: We searched MEDLINE, Embase, the Science Citation Index and the National Institute for Health Research Health Technology Assessment Database on 4 March 2016. We screened references in the included studies to identify additional studies. We also conducted citation searches of relevant studies, most recently on 4 December 2016. We did not restrict studies by language or publication status, or whether data were collected prospectively or retrospectively. SELECTION CRITERIA: We included diagnostic accuracy studies that evaluated at least one of the index tests (urea breath test using isotopes such as13C or14C, serology and stool antigen test) against the reference standard (histopathological examination using H & E stain, special stains or immunohistochemical stain) in people suspected of having H pylori infection. DATA COLLECTION AND ANALYSIS: Two review authors independently screened the references to identify relevant studies and independently extracted data. We assessed the methodological quality of studies using the QUADAS-2 tool. We performed meta-analysis by using the hierarchical summary receiver operating characteristic (HSROC) model to estimate and compare SROC curves. Where appropriate, we used bivariate or univariate logistic regression models to estimate summary sensitivities and specificities. MAIN RESULTS: We included 101 studies involving 11,003 participants, of which 5839 participants (53.1%) had H pylori infection. The prevalence of H pylori infection in the studies ranged from 15.2% to 94.7%, with a median prevalence of 53.7% (interquartile range 42.0% to 66.5%). Most of the studies (57%) included participants with dyspepsia and 53 studies excluded participants who recently had proton pump inhibitors or antibiotics.There was at least an unclear risk of bias or unclear applicability concern for each study.Of the 101 studies, 15 compared the accuracy of two index tests and two studies compared the accuracy of three index tests. Thirty-four studies (4242 participants) evaluated serology; 29 studies (2988 participants) evaluated stool antigen test; 34 studies (3139 participants) evaluated urea breath test-13C; 21 studies (1810 participants) evaluated urea breath test-14C; and two studies (127 participants) evaluated urea breath test but did not report the isotope used. The thresholds used to define test positivity and the staining techniques used for histopathological examination (reference standard) varied between studies. Due to sparse data for each threshold reported, it was not possible to identify the best threshold for each test.Using data from 99 studies in an indirect test comparison, there was statistical evidence of a difference in diagnostic accuracy between urea breath test-13C, urea breath test-14C, serology and stool antigen test (P = 0.024). The diagnostic odds ratios for urea breath test-13C, urea breath test-14C, serology, and stool antigen test were 153 (95% confidence interval (CI) 73.7 to 316), 105 (95% CI 74.0 to 150), 47.4 (95% CI 25.5 to 88.1) and 45.1 (95% CI 24.2 to 84.1). The sensitivity (95% CI) estimated at a fixed specificity of 0.90 (median from studies across the four tests), was 0.94 (95% CI 0.89 to 0.97) for urea breath test-13C, 0.92 (95% CI 0.89 to 0.94) for urea breath test-14C, 0.84 (95% CI 0.74 to 0.91) for serology, and 0.83 (95% CI 0.73 to 0.90) for stool antigen test. This implies that on average, given a specificity of 0.90 and prevalence of 53.7% (median specificity and prevalence in the studies), out of 1000 people tested for H pylori infection, there will be 46 false positives (people without H pylori infection who will be diagnosed as having H pylori infection). In this hypothetical cohort, urea breath test-13C, urea breath test-14C, serology, and stool antigen test will give 30 (95% CI 15 to 58), 42 (95% CI 30 to 58), 86 (95% CI 50 to 140), and 89 (95% CI 52 to 146) false negatives respectively (people with H pylori infection for whom the diagnosis of H pylori will be missed).Direct comparisons were based on few head-to-head studies. The ratios of diagnostic odds ratios (DORs) were 0.68 (95% CI 0.12 to 3.70; P = 0.56) for urea breath test-13C versus serology (seven studies), and 0.88 (95% CI 0.14 to 5.56; P = 0.84) for urea breath test-13C versus stool antigen test (seven studies). The 95% CIs of these estimates overlap with those of the ratios of DORs from the indirect comparison. Data were limited or unavailable for meta-analysis of other direct comparisons. AUTHORS' CONCLUSIONS: In people without a history of gastrectomy and those who have not recently had antibiotics or proton ,pump inhibitors, urea breath tests had high diagnostic accuracy while serology and stool antigen tests were less accurate for diagnosis of Helicobacter pylori infection.This is based on an indirect test comparison (with potential for bias due to confounding), as evidence from direct comparisons was limited or unavailable. The thresholds used for these tests were highly variable and we were unable to identify specific thresholds that might be useful in clinical practice.We need further comparative studies of high methodological quality to obtain more reliable evidence of relative accuracy between the tests. Such studies should be conducted prospectively in a representative spectrum of participants and clearly reported to ensure low risk of bias. Most importantly, studies should prespecify and clearly report thresholds used, and should avoid inappropriate exclusions