Laser-writing of ring-shaped waveguides in BGO crystal for telecommunication band

We report on the fabrication of ring-shaped waveguides operating at the telecommunication band in a cubic Bi4Ge3O12 (BGO) crystal by using technique of femtosecond laser writing. In the regions of laser written tracks in BGO crystal, positive refractive index is induced, resulting in so-called Type I configuration. The modal profiles are within the designed track cladding with ring-shaped geometries, which are analogous to circular optical lattices. The homogenous guidance along both TE and TM polarizations has been obtained at telecommunication wavelength of 1.55 μm. Both straight and S-curved waveguiding structures have been produced with ring-shaped configurations. This work paves the way to fabricate complex photonic networks for telecommunications by using ring-shaped waveguides in compact chips.National Natural Science Foundation of China (NSFC) (61775120); Junta de Castilla y León (Project SA046U16); Spanish Ministerio de Economía y Competitividad (MINECO, FIS2013-44174-P, FIS2015-71933-REDT)

Background studies and shielding effects for the TPC detector of the CAST experiment

Sunset solar axions traversing the intense magnetic field of the CERN Axion Solar Telescope (CAST) experiment may be detected in a Time Projection Chamber (TPC) detector, as X-rays signals. These signals could be masked, however, by the inhomogeneous background of materials in the experimental site. A detailed analysis, based on the detector characteristics, the background radiation at the CAST site, simulations and experimental results, has allowed us to design a shielding which reduces the background level by a factor of ~4 compared to the detector without shielding, depending on its position, in the energy range between 1 and 10 keV. Moreover, this shielding has improved the homogeneity of background measured by the TPC.Comment: 14 pages, 5 figures, accepted in New Journal of Physic

Chirality in Bare and Passivated Gold Nanoclusters

Chiral structures have been found as the lowest-energy isomers of bare (Au$_{28}$ and Au$_{55}) and thiol-passivated (Au$_{28}(SCH$_{3})$_{16}$and Au$_{38}(SCH_{3})_{24}) gold nanoclusters. The degree of chirality existing in the chiral clusters was calculated using the Hausdorff chirality measure. We found that the index of chirality is higher in the passivated clusters and decreases with the cluster size. These results are consistent with the observed chiroptical activity recently reported for glutahione-passivated gold nanoclusters, and provide theoretical support for the existence of chirality in these novel compounds.Comment: 5 pages, 1 figure. Submitted to PR

Complejo enteritis mucoide del conejo, 2: Interrelación causal de las aflatoxinas y el C. perfringens.

Se realizan 3 ensayos biológicos para esclarecer el papel del Clostridium perfringens y de aflatoxinas en el complejo enteritis mucoide del conejo, para los 2 primeros ensayos se utilizan 24 animales de 40 días de edad, 12 conejos por ensayo, distribuídos al azar en grupos de 3 animales por jaula, para administrarles vía oral aflatoxina B1 en las siguientes concentraciones: 50, 100, 150 y 350 p.p.b. El experimento dura 20 días. En el tercer ensayo, a 9 conejos se les administra vía oral cantidades conocidas de toxinas C. perfringens. No se demuestra la presencia de C. perfringens en el contenido gastrointestinal de gazapos desde el nacimiento hasta los 40 días, momento a partir del cual se observa un incremento progresivo del mismo. Las observaciones clínicas y las alteraciones macro y microscópicas encontradas en los 2 grupos de conejos que recibieron 50 p.p.b. de aflatoxina B1, permiten determinar que al menos la aflatoxina actúa como causa predisponente de la enfermedad, facilitando la proliferación de otros microorganismos en el tubo digestivo como el C. perfringens y el E. coli, los cuales vendrían a complicar el cuadro clínico-patológico. Los grupos de animales que recibieron concentraciones de la micotoxina superiores a 100 p.p.b. desarrollaron un cuadro de aflatoxicosis entre sub-aguda y crónica. En caso de presentarse un brote de la enfermedad, se aconseja cambiar de inmediato el alimento, adicionando a la nueva dieta antibióticos tipo clortetaciclinaCunicultur

Resistance and inactivation kinetics of bacterial strains isolated from the Non-chlorinated and chlorinated effluents of a WWTP

The microbiological quality of water from a wastewater treatment plant that uses sodium hypochlorite as a disinfectant was assessed. Mesophilic aerobic bacteria were not removed efficiently. This fact allowed for the isolation of several bacterial strains from the effluents. Molecular identification indicated that the strains were related to Aeromonas hydrophila, Escherichia coli (three strains), Enterobacter cloacae, Kluyvera cryocrescens (three strains), Kluyvera intermedia, Citrobacter freundii (two strains), Bacillus sp. and Enterobacter sp. The first five strains, which were isolated from the non-chlorinated effluent, were used to test resistance to chlorine disinfection using three sets of variables: disinfectant concentration (8, 20 and 30 mg·L−1), contact time (0, 15 and 30 min) and water temperature (20, 25 and 30 °C). The results demonstrated that the strains have independent responses to experimental conditions and that the most efficient treatment was an 8 mg·L−1 dose of disinfectant at a temperature of 20 °C for 30 min. The other eight strains, which were isolated from the chlorinated effluent, were used to analyze inactivation kinetics using the disinfectant at a dose of 15 mg·L−1 with various retention times (0, 10, 20, 30, 60 and 90 min). The results indicated that during the inactivation process, there was no relationship between removal percentage and retention time and that the strains have no common response to the treatmentsThe work of SM-H was supported by a graduate scholarship (number 217745) that was kindly provided by CONACyT, Mexico. Some chemical reagents were generously provided by the Administration of the B.A. in Biology at UAEH, Mexico. We thank the Instituto Tecnológico de Estudios Superiores de Monterrey, Hidalgo campus, for allowing us to sample from its WWTP. The authors recognize Jose A. Rodriguez-Ávila for his comments on the procedure for analyzing inactivation kineticsS

L-Ferritin Binding to Scara5 : A New Iron Traffic Pathway Potentially Implicated in Retinopathy

Iron is essential in the retina because the heme-containing enzyme guanylate cyclase modulates phototransduction in rods and cones. Transferrin endocytosis is the classical pathway for obtaining iron from the blood circulation in the retina. However, the iron storage protein ferritin has been also recently proposed as an iron carrier. In this study, the presence of Scara5 and its binding to L-ferritin was investigated in the retina. Our results showed that Scara5, the specific receptor for L-ferritin, was expressed in mouse and human retinas in many cell types, including endothelial cells. Furthermore, we showed that intravenously injected ferritin crossed the blood retinal barrier through L-ferritin binding to Scara5 in endothelial cells. Thus, suggesting the existence of a new pathway for iron delivery and trafficking in the retina. In a murine model of photoreceptor degeneration, Scara5 was downregulated, pointing out this receptor as a potential player implicated in retinopathy and also as a possible therapeutic target

Determinación de trihalometanos en aguas de consumo humano por microextracción en fase sólida- cromatografía de gases en Pereira, Colombia

La desinfección del agua con cloro, genera subproductos como los trihalometanos (THM´s), a los cuales se les atribuyen propiedades cancerígenas y con un potencial efecto adverso en el sistema reproductivo. El nivel máximo permitido de THM´s en Estados Unidos es 80 µg/L, mientras que en Colombia es 200 µg/L. En este estudio un método simple, rápido y libre de solventes fue estandarizado para la determinación de THM´s  en aguas para consumo humano utilizando microextracción en fase sólida con espacio de cabeza combinada con cromatografía de gases con detector de microcaptura de electrones  (HS-SPME-GC-mECD) y utilizado para la cuantificación de THM´s en aguas de consumo humano. Fueron estudiados parámetros experimentales así como el tiempo de adsorción, la temperatura de adsorción y desorción, la agitación de la muestra y la adición de NaCl. Se determinaron los límites de detección y cuantificación del método y se realizó el análisis de los trihalometanos de 75 muestras de agua de la planta de tratamiento de Aguas y Aguas de la ciudad de Pereira. Las condiciones optimizadas fueron 20 min de extracción a 37 °C en presencia de 25% de NaCl y con una agitación de 200 rpm; con  tiempo de desorción de 4 min a 250 °C. El rango lineal de 5-100 mg/L fue establecido con una desviación estándar relativa (%RSD) en el rango 6,1-10,1 %. Los límites de detección estuvieron en el rango 3,8-7,8 mg/L. El promedio de la concentración de THM´s fue de 55,5 mg/L el cual cumple con los límites máximos permitidos en la regulación internacional y nacional.Water disinfection with chlorine generates byproducts such as trihalomethanes (THM’s), to which cancer risk and a potential adverse effect on the reproductive system properties are attributed. The maximum permitted level of THM’s in the United States is 80- 100 µg/L, while in Colombia it is 200 µg/L. In this study a simple, fast and solvent-free method was developed for the determination of THM’s in drinking water using solid phase microextraction in combination with head space gas chromatography microcapture electron detector (HS-SPME-GC-µECD) and used for quantification of THM’s in drinking water. Experimental parameters such as extraction time, extraction temperature, desorption temperature, magnetic stirring, and addition of salt were studied. Limits of detection and quantification were determined and the analysis of THM´s in 75 samples of water from the treatment plant of Pereira city were performed. Optimized conditions were 20 min extraction at 37 °C in the presence of 25% NaCl and with stirring at 200 rpm; with a desorption time of 4 min at 250 °C. Linear range of 5-100 µg/L was established with a relative standard deviation (% RSD) in the range 6.1-10.1%. Detection limits ranged from 3.8 to 7.8 µg/L. Average concentration of THMs was 55.5 µg/L which was within International and National requirements

Estrategia de intervención sobre riesgo reproductivo preconcepcional

An intervention strategy was carried out in the office No. 4 of Niceto Pérez, from January to December 2012, in order to modify the knowledge that women have of some essential aspects of preconceptional reproductive risk. The study universe consists of 110 women belonging to the mentioned office; a sample of 45 is selected. A data emptying sheet designed by the author is drawn up which collects the necessary information according to the proposed tasks. Taking into account the population of childbearing age, it is given a program of educational activities, with prior informed consent. It is possible to increase the knowledge about preconceptional reproductive risk in women of fertile age studied, obtaining 95% of the women with knowledge in the subject in question. 100% knows about the risks.Se realiza una estrategia de intervención en el consultorio No. 4 de Niceto Pérez, en el período comprendido de enero a diciembre 2012, con la finalidad de modificar los conocimientos que tienen las féminas, de algunos aspectos esenciales del riesgo reproductivo preconcepcional. El universo de estudio está constituido por 110 mujeres pertenecientes al consultorio mencionado, de las cuales se selecciona una muestra de 45. Se confecciona  una planilla de vaciamiento de datos diseñada por el autor que recoge la información necesaria de acuerdo a las tareas propuestas. Teniendo en cuenta la población en edad fértil, se le imparte un programa de actividades educativas, con previo consentimiento informado. Se logra elevar los conocimientos sobre riesgo reproductivo preconcepcional en mujeres en edad fértil estudiadas obteniendo el 95 % de las mujeres con conocimiento en el tema en cuestión. El 100 % conoce sobre los riesgos.