Construcción de medidor de potencia óptica de alta exactitud para fibras ópticas

En este trabajo se describe el diseño y la implementación de un medidor de potencia óptica – MPO – para uso en el área de fibras ópticas de telecomunicaciones. El dispositivo opera en el intervalo de longitud de onda de 950 nm a 1 650 nm usando un fotodiodo de arseniuro de indio-galio – InGaAs – y su respuesta en potencia fue linealizada de 0.07 mW a 0.70 mW. El ingreso de haz de luz se realiza por medio de fibra óptica de telecomunicaciones y la medición está basada en un fotodiodo estabilizado en temperatura, amplificador de transimpedancia, amplificación de tensión, conversión digital y comunicación inalámbrica de datos operada por microcontrolador. El prototipo descrito fue probado como referencia de medición de potencia acoplada a fibra en condiciones de laboratorio de metrología con incertidumbre de medición inferior a 2.2% para las longitudes de onda de 1 310 nm, 1 550 nm y 1 625 nm

Comparative Study of Zn2Ti3O8 and ZnTiO3 Photocatalytic Properties for Hydrogen Production

In the present work, zinc titanates (ZTO) as photocatalysts were synthesized, characterized, and evaluated aiming to study their photocatalytic properties for hydrogen production under visible-light irradiation and employing MeOH (methanol) and TEOA (Triethanolamine) as sacrificial agents. ZTO were synthesized by modified Pechini method. Characterization of materials consisted in TGA, XRD, TEM, EELS, BET, and UV–Vis. Surface interaction studies consisted of FT-IR spectroscopy and determination of MeOH and TEOA adsorption–desorption capacities on the ZTO by TGA. Zinc titanates were evaluated as photocatalyst for H2 production using an artificial visible light and monitored by GC. TGA results led to establish calcination temperatures of 550 °C (Zn2Ti3O8) and 700 °C (ZnTiO3) to reach their crystalline phases. XRD analysis of sample cds-ZTO found cubic Zn2Ti3O8 and traces of the ZnO crystalline phase, while p-ZTO exhibited a mixture of cubic and hexagonal ZnTiO3 crystalline phases. Surface area for cds-ZTO was 88 m2/g, while ZnTiO3 had 13 m2/g. Photocatalytic H2 production for cds-ZTO and p-ZTO using TEOA as sacrificial agent showed the highest photocatalytic activities generating 548 and 441 µmolH2/h.gcat. TEOA adsorption–desorption capacity was found superior on cds-ZTO and p-ZTO than that for MeOH on both samples

Tumor Surface Regularity at MR Imaging Predicts Survival and Response to Surgery in Patients with Glioblastoma.

Purpose To evaluate the prognostic and predictive value of surface-derived imaging biomarkers obtained from contrast material-enhanced volumetric T1-weighted pretreatment magnetic resonance (MR) imaging sequences in patients with glioblastoma multiforme. Materials and Methods A discovery cohort from five local institutions (165 patients; mean age, 62 years ± 12 [standard deviation]; 43% women and 57% men) and an independent validation cohort (51 patients; mean age, 60 years ± 12; 39% women and 61% men) from The Cancer Imaging Archive with volumetric T1-weighted pretreatment contrast-enhanced MR imaging sequences were included in the study. Clinical variables such as age, treatment, and survival were collected. After tumor segmentation and image processing, tumor surface regularity, measuring how much the tumor surface deviates from a sphere of the same volume, was obtained. Kaplan-Meier, Cox proportional hazards, correlations, and concordance indexes were used to compare variables and patient subgroups. Results Surface regularity was a powerful predictor of survival in the discovery (P = .005, hazard ratio [HR] = 1.61) and validation groups (P = .05, HR = 1.84). Multivariate analysis selected age and surface regularity as significant variables in a combined prognostic model (

How do energy balance-related behaviors cluster in adolescents?

BJECTIVES: To delineate the clustering of energy balance-related behaviors in adolescents and investigate whether these behaviors are associated with the household socioeconomic status and parental education level. METHODS: Two cross-sectional studies assessed information on sedentary behavior, physical activity, sugar-sweetened beverages and fruit and vegetable consumption, and sleep duration by self-reported questionnaires in adolescents (12.5-17.5years old) from Maringa/Brazil (BRACAH Study; n=682) and ten European cities (HELENA Study; n=1252) from nine different countries. Gender-specific cluster analyses were performed separately for each study, applying a combination of hierarchical and non-hierarchical methods. RESULTS: Girls showed equivalent behaviors: Sedentary; Active; Unhealthy Eating; Healthy Eating; while boys differed (Brazilian: Sedentary; Active; Healthy Eating; European: Sedentary; Healthy; Unhealthy Eating). In Brazil, we found no association between socioeconomic status and parental education. In European girls, the high socioeconomic status and both parents' university degree were associated with Healthy Eating. In European boys, the high socioeconomic status was associated with Unhealthy Eating, and the mothers' university degree was associated with the Healthy cluster. CONCLUSIONS: Adolescents show Sedentary behavior, regardless of their sex, country of origin, or socioeconomic condition