Temperature effects on the calculation of the functional derivative of Tc with respect to α2F(ω).

The functional derivative of the superconducting transition temperature Tc with respect to the electron-phonon coupling function [Formula: see text] permits identifying the frequency regions where phonons are most effective in raising Tc. This work presents an analysis of temperature effects on the calculation of the δTc/δα2F(ω) and µ* parameters. The results may permit establishing that the variation of the temperature in the δTc/δα2F(ω) and µ* parameter allows establishing patterns and conditions that are possibly related to the physical conditions in the superconducting state, with implications on the theoretical estimation of the Tc.

Assessment of surface and electrical properties of the TiO2@zeolite hybrid materials.

Degradation of pollutants in aqueous medium is of high interest due to the impact on environment and human health, therefore, design and study of the physico-chemical properties of photocatalysts for water remediation are of major significance. Among properties of photocatalyst, those related to the surface and electrical mechanism are crucial to the photocatalyst´s performance. Here we report the chemical and morphological characteristics of TiO2@zeolite photocatalyst by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) respectively, and a coherent electrical conduction mechanism was proposed based on data obtained from assisted laser impedance spectroscopy (ALIS), in which the zeolite was synthesized from recycled coal fly ash. The results obtained by SEM and XPS verified the presence of spherical particles of TiO2 anatase with presence of Ti3+ state. ALIS results showed that impedance of the entire system increases when the amount of TiO2 increases and the samples with lower capacitive performance allowed a larger transfer of the charges between the solid-liquid interface. All results showed that higher photocatalytic performance of TiO2 growth over hydroxysodalite with 8.7 wt% and 25 wt% of TiO2 can be explained in terms of the morphology of TiO2 and the interactions between substrate-TiO2 mainly.

Cooper-pair distribution function [Formula: see text] for superconducting [Formula: see text] and [Formula: see text].

Cooper-pair distribution function, [Formula: see text], is a recent theoretical proposal that reveals information about the superconductor state through the determination of the spectral regions where Cooper pairs are formed. This is built from the well-established Eliashberg spectral function and phonon density of states, calculated by first-principles. From this function is possible to obtain the [Formula: see text] parameter, which is proportional to the total number of Cooper pairs formed at a critical temperature [Formula: see text]. Herein, we reported [Formula: see text] function of the compressed [Formula: see text] and [Formula: see text] high-[Formula: see text] conventional superconductors, including the effect of stable sulfur isotopes in [Formula: see text]. [Formula: see text] suggests that the vibration energy range of 10-70 meV is where the Cooper pairs are possible for these superconductors, pointing out the possible importance of the low-energy region on the electron-phonon superconductivity. This has been confirmed by the fact that a simple variation in the low-frequency region induced for the substitution of S atoms in [Formula: see text] by its stable isotopes can lead to important changes in [Formula: see text]. The results also show proportionality between [Formula: see text] parameter and experimental or theoretical [Formula: see text] values.

Cooper Pairs Distribution function for bcc Niobium under pressure from first-principles.

In this paper, we report Cooper Pairs Distribution function [Formula: see text] for bcc Niobium under pressure. This function reveals information about the superconductor state through the determination of the spectral regions for Cooper-pairs formation. [Formula: see text] is built from the well-established Eliashberg spectral function and phonon density of states, calculated by first-principles. [Formula: see text] for Nb suggests that the low-frequency vibration region [Formula: see text] is where Cooper-pairs are possible. From [Formula: see text], it is possible to obtain the [Formula: see text] parameter, which is proportional to the total number of Cooper-Pairs formed at a temperature [Formula: see text]. The [Formula: see text] parameter allows an approach to the understanding of the Nb [Formula: see text] anomalies, measured around 5 and 50 GPa.

The higher superconducting transition temperatureTcand the functional derivative ofTcwithα2F(ω) for electron-phonon superconductors.

This work presents an analysis of the functional derivative of the superconducting transition temperatureTcwith respect to the electron-phonon coupling functionα2F(ω) [δTc/δα2F(ω)] andα2F(ω) spectrum of H3S (Im3̄m), in the pressure range where the high-Tcwas measured (155-225 GPa). The calculations are done in the framework of the Migdal-Eliashberg theory. We find for this electron-phonon superconductor, a correlation between the maximums ofδTc/δα2F(ω) andα2F(ω) with its higherTc. We corroborate this behavior in other electron-phonon superconductors by analyzing data available in the literature, which suggests its validity in this type of superconductors. The correlation observed could be considered as a theoretical tool that in an electron-phonon superconductor, allows describing qualitatively the proximity to its highestTc, and determining the optimal physical conditions (pressure, alloying or doping concentration) that lead to the superconductor reaching its highestTcpossible.

The effect of Mn2Sb2 and Mn2Sb secondary phases on magnetism in (GaMn)Sb thin films.

In this work, a detailed study of structural, electrical and magnetic characterization of (GaMn)Sb diluted magnetic semiconductors (DMS) is presented. (GaMn)Sb thin films were grown by DC magnetron co-sputtering method as an innovative procedure to fabricate III-V DMS. The presence of unusual Mn2Sb2 and Mn2Sb secondary phases, induced by substrate temperature and deposition time, were revealed through XRD measurements. Magnetization measurements allow determining crossover between a paramagnetic-like to a ferromagnetic-like behavior controlled by secondary phases. It was found that both, the magnetic remanence and magnetic coercivity, increases with substrate temperature. Interestingly, the magnetic response is paramagnetic at lower deposition times and substrate temperatures, and XRD measurements suggest the absence of Mn2Sb and Mn2Sb2 in secondary phases. For longer deposition times or higher substrate temperature, XRD shows the presence of Mn2Sb2 and Mn2Sb phases and ferromagnetic-like behavior. The DC resistivity of our samples was characterized and the carrier density was determined by Hall measurements and, in contrast with the reported in other studies, found them to be a p-type semiconductor with carrier densities as big as one order of magnitude larger than reported values. From the ferromagnetic-like samples, evidence of an anomalous Hall-effect in the sample was found, with higher magnetic saturation and a anomalous Hall conductivity of 2380 S/cm. All the results point to a contribution of the secondary phases to the overall magnetic response of the samples used, and suggest the importance of studying the formation of secondary phases in the growth of DMS, especially, for the case of (GaMn)Sb where Mn ion can have multiple oxidation states.

Clinical predictors of methicillin-resistant Staphylococcus aureus in nosocomial and healthcare-associated pneumonia: a multicenter, matched case-control study.

The situations in which coverage for methicillin-resistant Staphylococcus aureus (MRSA) in the empirical treatment of nosocomial pneumonia (NP) or severe healthcare-associated pneumonia (HCAP) is needed are poorly defined, particularly outside intensive care units (ICUs). Our aim was to characterize if the risk of MRSA NP/HCAP can be defined by clinical variables. We designed an observational, retrospective, multicenter, case-control study to analyze the association between defined clinical variables and risk of MRSA NP/HCAP in non-ICU patients using conditional multivariable logistic regression. Cases and controls (1:2) with microbiological diagnosis were included. Controls were matched for hospital, type of pneumonia (NP or HCAP), and date of isolation. A total of 140 cases (77 NP and 63 HCAP) and 280 controls were studied. The variables associated with the risk of MRSA pneumonia were: (i) respiratory infection/colonization caused by MRSA in the previous year [odds ratio (OR) 14.81, 95% confidence interval (CI) 4.13-53.13, p < 0.001]; (ii) hospitalization in the previous 90 days (OR 2.41, 95% CI 1.21-4.81, p = 0.012); and (iii) age (OR 1.02, 95% CI 1.001-1.05, p = 0.040). The area under the receiver operating characteristic (ROC) curve for the multivariable model was 0.72 (95% CI 0.66-0.78). The multivariate model had a sensitivity of 74.5% (95% CI 65.3-83.6), a specificity of 63.3% (95% CI 56.0-70.6), a positive predictive value of 52.5% (95% CI 43.9-61.2), and a negative predictive value of 82.0% (95% CI 75.3-88.8) for the observed data. Clinical predictors of MRSA NP/HCAP can be used to define a low-risk population in whom coverage against MRSA may not be needed.

Simvastatin exerts antiproliferative and differentiating effects on MG63 osteoblast-like cells: Morphological and immunocytochemical study.

BACKGROUND AND OBJECTIVE: Current evidence suggests that statins exert an anabolic effect on bone and may therefore impact on osteogenic differentiation and proliferation. These effects can be useful for their use in guided bone regeneration. The objective of this study was to determine the in vitro effects of simvastatin on the differentiation and proliferation of MG63 human osteoblast tumor cells. MATERIAL AND METHODS: MG63 human osteosarcoma cells were cultured in the presence of simvastatin or solvent alone for 72 hours, and their proliferation was assessed by MTT assay. Cells from the culture were prepared for light, transmission and scanning electron microscopy studies. immunocytochemical was used to analyze the differentiation and proliferation markers Musashi-1, Ki-67, CD56 and CD44. RESULTS: Cultured MG63 control cells showed spheroid morphology with numerous secretion vesicles accumulated on the surface, observing no cytoplasmic projections with intercellular connections. However, cells cultured with simvastatin had a polygonal and spindle-shaped morphology, with cytoplasmic projections that interconnected cells. There were numerous microvilli-like filamentous projections on the surface with no defined pattern. At 72 hours of culture, CD56, Ki-67 and Musashi-1 expression was significantly reduced (P < .001) in simvastatin-treated cells. CD44 expression was intense in both groups and was not affected by simvastatin treatment. CONCLUSION: MG63 cells cultured with simvastatin for 72 hours undergo morphological and surface changes. Simvastatin treatment exerts antiproliferative and differentiating effects on these cells as well as promoting recovery of cellular homeostasis.

Synthesis and characterization of porous silicon as hydroxyapatite host matrix of biomedical applications.

In this work, porous-silicon samples were prepared by electrochemical etching on p-type (B-doped) Silicon (Si) wafers. Hydrofluoric acid (HF)-ethanol (C2H5OH) [HF:Et] and Hydrofluoric acid (HF)-dimethylformamide (DMF-C3H7NO) [HF:DMF] solution concentrations were varied between [1:2]-[1:3] and [1:7]-[1:9], respectively. Effects of synthesis parameters, like current density, solution concentrations, reaction time, on morphological properties were studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM) measurements. Pore sizes varying from 20 nm to micrometers were obtained for long reaction times and [HF:Et] [1:2] concentrations; while pore sizes in the same order were observed for [HF:DMF] [1:7], but for shorter reaction time. Greater surface uniformity and pore distribution was obtained for a current density of around 8 mA/cm2 using solutions with DMF. A correlation between reflectance measurements and pore size is presented. The porous-silicon samples were used as substrate for hydroxyapatite growth by sol-gel method. X-ray diffraction (XRD) and SEM were used to characterize the layers grown. It was found that the layer topography obtained on PS samples was characterized by the evidence of Hydroxyapatite in the inter-pore regions and over the surface.

Nosocomial pneumonia caused by methicillin-resistant Staphylococcus aureus treated with linezolid or vancomycin: A secondary economic analysis of resource use from a Spanish perspective / Neumonía nosocomial causada por Staphylococcus aureusresistente a meticilina tratada con linezolid o vancomicina: análisis económico secundario del uso de recursos sanitarios desde una perspectiva Española

OBJECTIVES: Adopting a unique Spanish perspective, this study aims to assess healthcare resource utilization (HCRU) and the costs of treating nosocomial pneumonia (NP) produced by methicillin-resistant Staphylococcus aureus (MRSA) in hospitalized adults using linezolid or vancomycin. An evaluation is also made of the renal failure rate and related economic outcomes between study groups. DESIGN: An economic post hoc evaluation of a randomized, double-blind, multicenter phase 4 study was carried out. Scope: Nosocomial pneumonia due to MRSA in hospitalized adults. PARTICIPANTS: The modified intent to treat (mITT) population comprised 224 linezolid- and 224 vancomycin-treated patients. INTERVENTIONS: Costs and HCRU were evaluated between patients administered either linezolid or vancomycin, and between patients who developed renal failure and those who did not. Primary endpoints: Analysis of HCRU outcomes and costs. RESULTS: Total costs were similar between the linezolid- (€17,782 ± €9,615) and vancomycin-treated patients (€17,423 ± €9,460) (P = .69). The renal failure rate was significantly lower in the linezolid-treated patients (4% vs. 15%; P<.001). The total costs tended to be higher in patients who developed renal failure (€19,626 ± €10,840 vs. €17,388 ± €9,369; P = .14). Among the patients who developed renal failure, HCRU (days on mechanical ventilation: 13.2 ± 10.7 vs. 7.6 ± 3.6 days; P = .21; ICU stay: 14.4 ± 10.5 vs. 9.9 ± 6.6 days; P = .30; hospital stay: 19.5 ± 9.5 vs. 16.1 ± 11.0 days; P = .26) and cost (€17,219 ± €8,792 vs. €20,263 ± €11,350; P = .51) tended to be lower in the linezolid- vs. vancomycin-treated patients. There were no statistically significant differences in costs per patient-day between cohorts after correcting for mortality (€1000 vs. €1,010; P = .98). CONCLUSIONS: From a Spanish perspective, there were no statistically significant differences in total costs between the linezolid and vancomycin pneumonia cohorts. The drug cost corresponding to linezolid was partially offset by fewer renal failure adverse events

OBJETIVOS: Analizar la utilización de recursos sanitarios (URS) y los costes de la neumonía nosocomial por Staphylococcus aureus resistente a meticilina en adultos hospitalizados tratados con linezolid o vancomicina. También se evaluó el porcentaje de fallo renal entre dichos pacientes. DISEÑO: Análisis post-hoc de un ensayo clínico fase IV multicéntrico, aleatorizado, doble ciego. Ámbito: Pacientes adultos, hospitalizados con neumonía nosocomial por Staphylococcus aureusresistente a meticilina. PARTICIPANTES: Pacientes tratados con linezolid (224) o vancomicina (224). INTERVENCIONES: Desde la perspectiva española se compararon costes y URS entre pacientes tratados con linezolid o vancomicina y entre los que desarrollaron fallo renal y los que no. Principales variables de interés Análisis de costes y URS. RESULTADOS: Los costes totales fueron similares (p = 0,69) en los pacientes tratados con linezolid (17.782 ± 9.615€) o vancomicina (17.423 ± 9.460 €). La tasa de fallo renal fue significativamente menor en los tratados con linezolid (4 vs. 15%, p < 0,001). Los costes totales fueron mayores en aquellos que desarrollaron fallo renal (19.626 ± 10.840€ vs. 17.388 ± 9.369€, p = 0,14). La URS (días de ventilación mecánica: 13,2 ± 10,7 vs. 7,6 ± 3,6, p = 0,21; días en UCI: 14,4 ± 10,5 vs. 9,9 ± 6,6, p = 0,30; días de hospitalización: 19,5 ± 9,5 vs. 16,1 ± 11,0, p = 0,26) y los costes totales (17.219 ± 8.792€ vs. 20.263 ± 11.350€, p = 0,51) tendieron a ser inferiores en los pacientes tratados con linezolid que desarrollan fallo renal. Tras corregir el análisis por mortalidad, los costes diarios por paciente fueron similares (1.000 vs. 1.010€; p = 0,98). CONCLUSIONES: Desde la perspectiva española, no hubo diferencias en la URS y los costes entre los pacientes con neumonía tratados con linezolid o vancomicina. El coste de linezolid fue contrarrestado por la menor incidencia de fallo renal

Nosocomial pneumonia caused by methicillin-resistant Staphylococcus aureus treated with linezolid or vancomycin: A secondary economic analysis of resource use from a Spanish perspective.

OBJECTIVES: Adopting a unique Spanish perspective, this study aims to assess healthcare resource utilization (HCRU) and the costs of treating nosocomial pneumonia (NP) produced by methicillin-resistant Staphylococcus aureus (MRSA) in hospitalized adults using linezolid or vancomycin. An evaluation is also made of the renal failure rate and related economic outcomes between study groups. DESIGN: An economic post hoc evaluation of a randomized, double-blind, multicenter phase 4 study was carried out. SCOPE: Nosocomial pneumonia due to MRSA in hospitalized adults. PARTICIPANTS: The modified intent to treat (mITT) population comprised 224 linezolid- and 224 vancomycin-treated patients. INTERVENTIONS: Costs and HCRU were evaluated between patients administered either linezolid or vancomycin, and between patients who developed renal failure and those who did not. PRIMARY ENDPOINTS: Analysis of HCRU outcomes and costs. RESULTS: Total costs were similar between the linezolid- (€17,782±€9,615) and vancomycin-treated patients (€17,423±€9,460) (P=.69). The renal failure rate was significantly lower in the linezolid-treated patients (4% vs. 15%; P<.001). The total costs tended to be higher in patients who developed renal failure (€19,626±€10,840 vs. €17,388±€9,369; P=.14). Among the patients who developed renal failure, HCRU (days on mechanical ventilation: 13.2±10.7 vs. 7.6±3.6 days; P=.21; ICU stay: 14.4±10.5 vs. 9.9±6.6 days; P=.30; hospital stay: 19.5±9.5 vs. 16.1±11.0 days; P=.26) and cost (€17,219±€8,792 vs. €20,263±€11,350; P=.51) tended to be lower in the linezolid- vs. vancomycin-treated patients. There were no statistically significant differences in costs per patient-day between cohorts after correcting for mortality (€1000 vs. €1,010; P=.98). CONCLUSIONS: From a Spanish perspective, there were no statistically significant differences in total costs between the linezolid and vancomycin pneumonia cohorts. The drug cost corresponding to linezolid was partially offset by fewer renal failure adverse events.

Complementary clinical effects of red complex bacteria on generalized periodontitis in a caucasian population.

OBJECTIVES: To relate five periodontopathogenic bacteria, including the red complex, to the severity, extent, and inflammation of the periodontal lesion in Caucasian patients with generalized aggressive and chronic periodontitis and to explore whether tobacco use is associated with a specific bacterial profile. MATERIALS AND METHODS: A cross-sectional and analytic study was conducted in patients with aggressive and chronic periodontitis. Data were gathered on socio-demographic and periodontal variables, and RH-PCR was used to determine subgingival bacterial profile. Linear and logistic regression analyses were performed. RESULTS: The study included 60 patients with aggressive and 123 with chronic periodontitis. Total red complex bacteria count was higher in aggressive periodontitis, mainly due to T. denticola (P = 0.015). In both periodontitis types, models showed an association between T. forsythia count and probing depth (B = 0.157, P = 0.030) and between T. denticola count and higher bleeding scores (B = 2.371, P = 0.027). Smoking did not affect the red complex bacteria count in either disease. CONCLUSIONS: The prevalence of red complex bacteria was similar between aggressive and chronic periodontitis, but their count was higher in the former. In both diseases, T. forsythia was associated with greater severity and T. denticola with more severe bleeding. Tobacco smoking was not associated with the presence of red complex bacteria in either disease.

Oral bacteria in placental tissues: increased molecular detection in pregnant periodontitis patients.

OBJECTIVES: The objective of this study was to identify the DNA of oral bacteria in placental samples from women with and without periodontitis who had or had not had preterm births and/or low birthweight (PB/LBW) neonates. METHODS: Data were gathered from 57 puerperal women in relation to socio-demographic, gynaecological, and periodontal variables and to placental histomorphology. Fifty-seven biopsies, 28 from mothers with periodontitis, were taken aseptically from preterm placentas (n = 36) and from full-term placentas (n = 21). Total DNA was extracted, and the presence of 15 oral bacteria was assessed using Nested-PCR. RESULTS: The placentas from women with periodontitis showed a higher prevalence of periodontopathogens compared to those from women without periodontitis (P = 0.009). Samples showed low prevalences of Actinomyces israelii, Parvimonas micra and Tannerella forsythia. An association was found between Eikenella corrodens in placenta and periodontitis (P = 0.002). The most ubiquitous bacterium, Fusobacterium nucleatum, was more prevalent in mothers with periodontitis and PB/LBW (P = 0.033). Porphyromonas gingivalis, Treponema denticola, Prevotella intermedia and Aggregatibacter actinomycetemcomitans were not detected. CONCLUSIONS: These results, along with previous findings, show that oral bacteria may be normally present in the placenta, however, the levels of certain oral pathogens in the placenta would highly depend on the mother's periodontal state.

Application of a topical vapocoolant spray decreases pain at the site of initial intradermal anaesthetic injection during ultrasound-guided breast needle biopsy.

AIM: To assess whether the application of a topical vapocoolant spray immediately prior to initial intradermal anaesthetic injection during ultrasound-guided breast biopsy decreases pain at the site of the initial injection. MATERIALS AND METHODS: In this institutional review board-approved, Health Insurance Portability and Accountability Act (HIPAA)-compliant study, 50 women aged 49.1 ± 1.6 years (mean ± standard error) were recruited and provided written informed consent. Participants served as their own controls and were blinded as to whether a topical vapocoolant spray or a placebo was used immediately prior to the initial local anaesthetic injection at two separate biopsy sites. With the exception of the application of vapocoolant or placebo, the entire ultrasound-guided procedure was performed according to a routine protocol. Participants recorded pain at initial injection site on a visual analogue scale. General linear mixed models for repeated measures analysis of variance and a 0.05 significance level were used. RESULTS: Application of topical vapocoolant spray was shown to significantly decrease pain at the site of initial intradermal anaesthetic injection as compared to placebo (p<0.001). Treatment effect was independent of age of the subject, race/ethnicity, operator, type of biopsy device, and histopathology result. No complications from vapocoolant spray use were reported. CONCLUSION: Application of a topical vapocoolant spray immediately prior to initial intradermal anaesthetic injection during ultrasound-guided breast biopsy significantly decreases pain at the site of the initial injection and could contribute to improve the patient's overall procedural experience.

Effect of root planing on surface topography: an in-vivo randomized experimental trial.

BACKGROUND AND OBJECTIVE: The root surface topography exerts a major influence on clinical attachment and bacterial recolonization after root planing. In-vitro topographic studies have yielded variable results, and clinical studies are necessary to compare root surface topography after planing with current ultrasonic devices and with traditional manual instrumentation. The aim of this study was to compare the topography of untreated single-rooted teeth planed in vivo with a curette, a piezoelectric ultrasonic (PU) scraper or a vertically oscillating ultrasonic (VOU) scraper. MATERIAL AND METHODS: In a randomized experimental trial of 19 patients, 44 single-rooted teeth were randomly assigned to one of four groups for: no treatment; manual root planing with a curette; root planing with a PU scraper; or root planing with a VOU scraper. Post-treatment, the teeth were extracted and their topography was analyzed in 124 observations with white-light confocal microscopy, measuring the roughness parameters arithmetic average height, root-mean-square roughness, maximum height of peaks, maximum depth of valleys, absolute height, skewness and kurtosis. RESULTS: The roughness values arithmetic average height and root-mean-square roughness were similar after each treatment and lower than after no treatment ( p < 0.05). Absolute height was lower in the VOU group than in the untreated ( p = 0.0026) and PU (p = 0.045) groups. Surface morphology was similar after the three treatments and was less irregular than in the untreated group. Values for the remaining roughness parameters were similar among all treatment groups ( p > 0.05). CONCLUSION: Both ultrasonic devices reduce the roughness, producing a similar topography to that observed after manual instrumentation with a curette, to which they appear to represent a valid alternative.

Acute myocardial infarct size is related to periodontitis extent and severity.

Cardiovascular disease has been associated with 40% of deaths in high-income countries and 28% in lower-income countries. The relationship between periodontitis and acute myocardial infarction is well documented, but it has not been established whether the extent and severity of periodontitis influence the infarct size. This cross-sectional and analytic study was designed to investigate the association of chronic periodontitis extent and severity with acute myocardial infarct size as indicated by serum cardiac troponin I and myoglobin levels. Sociodemographic, periodontal, cardiologic, and hematologic variables were gathered in 112 consecutive patients with myocardial infarction. The extent (Arbes Index) and severity (Periodontal Inflammatory Severity Index) of the chronic periodontitis were significantly associated with troponin I levels after controlling for sociodemographic and clinical confounders (change in R (2) = .041, p < .02, and R (2) = .031, p = .04). However, only the extent index accounted for levels of myoglobin (change in R (2) = .030, p < .05), total leukocytes (change in R (2) = .041 p < .02), and neutrophils (change in R (2) = .059, p < .01). Mediated regression analysis showed that leukocytes and neutrophils may underlie these observed relationships of chronic periodontitis with troponin I and myoglobin. To our knowledge, this study contributes the first research data demonstrating that the extent and severity of periodontitis is positively associated with acute myocardial infarct size as measured by serum troponin I and myoglobin levels.

Efecto Hall y estudio de fotovoltaje superficial transiente (SPV) en películas delgadas de Cu3BiS3 / Hall effect and transient surface photovoltage (SPV) study of Cu3BiS3 thin films / Efeito Hall e estudo de foto voltagem superficial transiente (SPV) em películas delgadas de Cu3BiS3

Se presentan las propiedades eléctricas del compuesto Cu3BiS3 depositado por co-evaporación. Este es un nuevo compuesto que puede tener propiedades adecuadas para ser utilizado como capa absorbente en celdas solares. Las muestras fueron caracterizadas a través de medidas de efecto Hall y fotovoltaje superficial transiente (SPV). A través de medidas de efecto Hall se encontró que la concentración de portadores de carga n es del orden de 10(16) cm-3 independiente de la relación de masas de Cu/Bi. También se encontró que la movilidad de este compuesto (μ del orden de 4 cm²V -1s-1) varía de acuerdo con los mecanismos de transporte que la gobiernan en dependencia con la temperatura. A partir de las medidas de SPV se encontró alta densidad de defectos superficiales, defectos que son pasivados al superponer una capa buffer sobre el compuesto Cu3BiS3.

Here, we present the electrical properties of the compound Cu3BiS3 deposited by co-evaporation. This new compound may have the properties necessary to be used as an absorbent layer in solar cells. The samples were characterized by Hall effect and transient surface photovoltage (SPV) measurements. Using Hall effect measurements, we found that the concentration of n charge carriers is in the order of 10(16) cm³ irrespective of the Cu/Bi mass ratio. We also found that the mobility of this compound (μ in the order of 4 cm² V-1s-1) varies according to the transport mechanisms that govern it and are dependent on temperature. Based on the SPV, we found a high density of surface defects, which can be passivated by superimposing a buffer layer over the Cu3BiS3 compound.

Apresentam-se as propriedades elétricas do composto Cu3BiS3 depositado por co-evaporação. É um composto novo que pode ter as propriedades adequadas para ser utilizado como capa absorvente em células solares. As amostras foram caracterizadas através de medidas do efeito Hall e foto voltagem superficial transiente (SPV). Através de medidas do efeito Hall se encontro que a concentração de portadores de carga n é da ordem de 10(16) cm³ independentemente da relação de massas de Cu/Bi. Também se encontrou que a mobilidade des composto (μ da ordem de 4 cm²V -1s-1) varia de acordo com os mecanismos de transporte que a governam em dependência com a temperatura. Partindo das medidas de SPV se encontrou uma alta densidade de defeitos superficiais, defeitos que são passivados a sobrepor uma capa buffer sobre o composto Cu3BiS3.

Procesos hopping a través del modelo difusional en materiales nanocristalinos usados para aplicaciones fotovoltaicas / Hopping processes in nanocrystalline materials used for photovoltaic applications using a diffusion model / Processos Hopping através do modelo de difusão em materiais nanocristalinos utilizados para aplicações fotovoltaicas

Se presentan los modelos de hopping de rango variable (variable range hopping; VRH), vecinos cercanos (nearest neighbor hopping; NNH) y barreras de potencial presentes en las fronteras de grano; como mecanismos de transporte eléctrico predominantes en los materiales semiconductores para aplicaciones fotovoltaicas. Las medidas de conductividad a oscuras en función de temperatura fueron realizadas para región de bajas temperaturas entre 120 y 400 K con Si y compuestos Cu3BiS2 y Cu2ZnSnSe4. Siguiendo la teoría de percolación, se obtuvieron parámetros hopping y la densidad de estados cerca del nivel de Fermi, N(E F), para todas las muestras. A partir de los planteamientos dados por Mott para VRH, se presentó el modelo difusional, que permitió establecer la relación entre la conductividad y la densidad de estados de defecto o estados localizados en el gap del material. El análisis comparativo entre modelos, evidenció, que es posible obtener mejora hasta de un orden de magnitud en valores para cada uno de los parámetros hopping que caracterizan el material.

Here, we present variable range hopping (VRH) models, nearest neighbor hopping (NNH) and potential barriers present at the grain boundaries, as well as mechanisms of electrical transport predominant in semiconductor materials for photovoltaic applications. We performed dark conductivity measures according to temperature for low temperature regions between 120 and 400 K in Si and Cu3BiS2 and Cu2ZnSnSe4 compounds. Using the percolation theory, we obtained hopping parameters and the density of states near the Fermi, N(E F) level for all samples. Using the approach by Mott for VRH, we obtained the diffusion model, which established the relationship between conductivity and density of defect states or localized gap states of the material. The comparative analysis between models evidenced that it is possible to obtain improvement of an order of magnitude in the values of each of the hopping parameters that characterize the material.

Apresentam-se os modelos de hopping de categoria variável (variable range hopping; VRH), vizinhos próximos (nearest neighbor hopping, NNH) e barreiras de potenciais presentes nas fronteiras de grãos; como mecanismo de transporte elétrico predominantes nos materiais semicondutores para aplicações fotovoltaicas. As medidas de condutividade no escuro em função da temperatura foram realizadas para região de baixas temperaturas entre 120 e 400 K com Si e compostos Cu3BiS2 e Cu2ZnSnSe4. Seguindo a teoria da percolação obtiveram-se parâmetros hopping e a densidade de estados próximos do nível Fermi[BO1] N(E F) para toda a amostra. A partir das abordagens seguidas por Mott para VRH, apresentou-se o modelo de difusão, que permitiu estabelecer a relação entre a condutividade e a densidade de estados de defeito ou estados localizados no gap do material. A análise comparativa dos modelos mostrou que é possível obter melhoria até de uma amplitude de magnitude em valores para cada um dos parâmetros hopping que caracterizam o material.

Cálculo de constantes ópticas de películas delgadas de Cu3BiS3 a través del método de Wolfe / Calculation of the optical constants of Cu3BiS3 thin films using the Wolfe method / Calculou-se de constantes óticas de películas finas de Cu3BiS3 através do método de Wolfe

Se calculó la obtención de las constantes ópticas usando el método de Wolfe. Dichas contantes: coeficiente de absorción (α), índice de refracción (n) y espesor de una película delgada (d), son de importancia en el proceso de caracterización óptica del material. Se realizó una comparación del método del Wolfe con el método empleado por R. Swanepoel. Se desarrolló un modelo de programación no lineal con restricciones, de manera que fue posible estimar las constantes ópticas de películas delgadas semiconductoras, a partir únicamente, de datos de transmisión conocidos. Se presentó una solución al modelo de programación no lineal para programación cuadrática. Se demostró la confiabilidad del método propuesto, obteniendo valores de α = 10378.34 cm-1, n = 2.4595, d =989.71 nm y Eg = 1.39 Ev, a través de experimentos numéricos con datos de medidas de transmitancia espectral en películas delgadas de Cu3BiS3.

Using the Wolfe method, we calculated the procurement of optical constants. These constants, absorption coefficient (α), refraction index of (n) and thin film thickness (d ), are significant in the optical characterization of the material. We compared the Wolfe method with the method employed by R. Swanepoel. To estimate the optical constants of semiconductor thin films, we developed a constrained nonlinear programming model, based solely, on known transmission data. Ultimately, we presented a solution to this nonlinear programming model for quadratic programming. Through numerical experiments and transmittance spectral data of Cu3BiS3 thin films, we obtained values of a= 10378.34 cm-1, n = 2.4595, d =989.71 nm and Eg= 1.39 Ev, demonstrating the reliability of the proposed method.

Calculou-se a obtenção de constantes óticas utilizando o método de Wolfe. Estas constantes: coeficiente de absorção (α), índice de refração (n) e espessura de uma película fina (d), são importantes no processo de caracterização ótica do material. Realizou-se uma comparação do método de Wolfe com o método utilizado por R. Swanepoel. Desenvolveu-se um modelo de programação não linear com restrições, de modo que foi possível estimar as constantes óticas de películas finas semicondutores, a partir unicamente, de dados de transmissão conhecidos. Apresentou-se uma solução ao modelo de programação não linear para programação quadrática. Mostrou-se a confiabilidade do método proposto, obtendo valores de α = 10378.34 cm-1, n = 2.4595, d =989.71 nm y Eg = 1.39 Ev, através de experiências numéricas com dados de medidas de transmissão espectral em películas finas de Cu3BiS3.

Laparoscopy-assisted transvaginal resection of sigmoid cancer.

OBJECTIVE: To investigate the feasibility and safety of laparoscopy-assisted transvaginal resection of sigmoid cancer. METHODS: From 2009 to 2011 we performed 21 laparoscopy-assisted transvaginal resections of sigmoid cancers. RESULTS: The resected tumours were T1(6), T2(7) and T3(8). The median number of resected lymph nodes was 15. Median operative time was 150 min and no conversion to open technique was necessary. A total of eighteen patients tolerated a liquid diet 24 h after surgery. The average VAS pain score (0 = no pain, 10 = unbearable pain) was 1.8 after 24 h and 1.1 after 48 h. One patient experienced a postoperative ileus, two patients had vaginal spotting with serous flow and three patients suffered urinary tract infections. One patient developed a hernia at the umbilical trocar site that was operated on. None of the sexually active patients reported any differences in sexual activity pre-op and postop on a postoperative questionnaire. After a median of 25 (10-41) months of follow-up, all patients are alive and well, with no evidence of recurrent disease. CONCLUSION: Laparoscopy-assisted transvaginal resection of sigmoid cancer is feasible and safe in a selected group of patients.