Hypervelocity dust particle impacts observed by the Giotto Magnetometer and Plasma Experiments

We report thirteen very short events in the magnetic field of the inner magnetic pile‐up region of comet Halley observed by the Giotto magnetometer experiment together with simultaneous plasma data obtained by the Johnstone plasma analyzer and the ion mass spectrometer experiments. The events are due to dust impacts in the milligram range on the spacecraft at the relative velocity between the cemetery dust and the spacecraft of 68 km/sec. They are generally consistent with dust impact events derived from spacecraft attitude perturbations by the Giotto camera [Curdt and Keller, private communication]. Their characteristic shape generally involves a sudden decrease in magnetic field magnitude, a subsequent overshoot beyond initial field values and an asymptotic approach to the initial field somewhat reminiscent of the magnetic field signature after the AMPTE releases in the solar wind. These observations give a new way of analyzing ultra‐fast dust particles incident on a spacecraft

Conversation I

Documento PDF, 24 páginasGuía de estudio para el curso Conversation I, código 5009, que imparte la Escuela de Ciencias Sociales y Humanidades de la UNED.Universidad Estatal a Distancia de Costa Ric

Los ultrasonidos y la calidad de la madera estructural : aplicación a Pinus pinaster Ait.

Los resultados de este trabajo muestran que el valor de la medida de la velocidad de propagación de los ultrasonidos se ve modificada por la distancia de medida y por el ángulo que forma la dirección de medida con la inclinación de las fibras, debiendo ser corregida cuando se trabaja con piezas de madera de tamaño estructural. Asimismo, se observa una buena relación entre las características determinadas por la técnica ultrasónica y los ensayos de flexión estática y rotura, e indica que esta técnica no destructiva se puede utilizar con garantías en P. pinaster para llevar a cabo una clasificación resistente de la madera, aportando un rendimiento mayor que con la clasificación visual, UNE 56.544.____________________________________The results of this work show that the value of velocity measurement of ultrasounds wave is modified by the distance of transducers and by the angle formed by the direction of measurement with the grain angle, having to be corrected when works with wood pieces of structural size. Also, a good relation between the characteristics determined by the ultrasonic technique and the tests of static flexion is observed, showing that this nondestructive technique can be used with guarantees in P. pinaster to carry out a resistant classification of wood, obtaining a greater yield than the visual grading, UNE 56.544

Pain-induced adaptations in the claustro-cingulate pathway.

Persistent pain is a prevalent medical concern correlating with a hyperexcitable anterior cingulate cortex (ACC). Its activity is modulated by inputs from several brain regions, but the maladjustments that these afferent circuits undergo during the transition from acute to chronic pain still require clarification. We focus on ACC-projecting claustrum (CLAACC) neurons and their responses to sensory and aversive stimuli in a mouse model of inflammatory pain. Using chemogenetics, in vivo calcium imaging, and ex vivo electrophysiological approaches, we reveal that suppression of CLAACC activity acutely attenuates allodynia and that the claustrum preferentially transmits aversive information to the ACC. With prolonged pain, a claustro-cingulate functional impairment develops, which is mediated by a weakened excitatory drive onto ACC pyramidal neurons, resulting in a diminished claustral influence on the ACC. These findings support an instrumental role of the claustrum in the processing of nociceptive information and its susceptibility to persistent pain states

Synthesis, Characterization and Evaluation of the Cytotoxicity of Ni-Doped Zn(Se,S) Quantum Dots

Quantum dots (QDs) are semiconductor nanocrystals with desirable optical properties for biological applications, such as bioimaging and drug delivery. However, the potential toxicity of these nanostructures in biological systems limits their application. The present work is focused on the synthesis, characterization, and evaluation of the toxicity of water-stable Ni-doped Zn(Se,S) QDs. Also, the study of nondoped nanostructures was included for comparison purposes. Ni-doped nanostructures were produced from zinc chloride and selenide aqueous solutions in presence of 3-mercaptopropionic acid and Ni molar concentration of 0.001 M. In order to evaluate the potential cytoxicity of these doped nanostructures, human pancreatic carcinoma cells (PANC-1) were used as model. The cell viability was monitored in presence of Ni-doped Zn(Se,S) QDs at concentrations ranging from 0 μg/mL to 500 μg/mL and light excited Ni-doped Zn(Se,S) nanostructures were evaluated at 50 μg/mL. Results suggested that Ni-doped Zn(Se,S) nanostructures were completely safe to PANC-1 when concentrations from 0 μg/mL to 500 μg/mL were used, whereas non-doped nanostructures evidenced toxicity at concentrations higher than 200 μg/mL. Also, Ni-doped Zn(Se,S) QDs under light excitation do not evidence toxicity to PANC-1. These findings suggest strongly that Zn(Se,S) nanostructures doped with nickel could be used in a safe manner in light-driving biological applications and drug delivery

Creativity, pedagogical, and educational innovation: analysis of the perception of a group of Chilean teachers

Este estudio se circunscribe al ámbito de la educación, la didáctica y la metodología en el trabajo de aula. Se analizan los resultados de una investigación con enfoque cuantitativo, que tuvo por objetivo identificar la percepción y experiencias acerca de la creatividad, innovación pedagógica y educativa -estas dos últimas nociones no siempre claras y distinguibles en la teoría y los estudios empíricos- en un grupo de docentes que recién inicia su proceso de formación en un programa de postgrado de Magíster en Didáctica, dictado por la Escuela de Educación del Campus Los Ángeles de la Universidad de Concepción, de la provincia y región de Biobío, Chile. La investigación tuvo un alcance descriptivo y como principal técnica de recolección de datos se utilizó un cuestionario de opinión con preguntas abiertas. Los principales hallazgos señalan que el profesorado en general y en un porcentaje mayoritario valora la creatividad, entiende el concepto de innovación pedagógica, pero tiene dificultades para identificar la diferencia entre esta última y la innovación educativa debido a su amplitud conceptual. Además, los resultados señalan que si bien el profesorado cree que la innovación es necesaria y tiene buena predisposición a ella en el ámbito de su labor pedagógica-docente, no siempre se generan las condiciones favorables para su implementación en los establecimientos educativos.This study is circumscribed to the scope of education, didactics, and classroom methodology. The results of an investigation with a quantitative approach will be analyzed, whose aim was to identify the perception and experiences related to creativity, as well as to pedagogical and educational innovation - the two latter concepts not always clear and distinguishable in theory and empirical studies. The research was done in a group of teachers who were just beginning their training process in a Graduate Degree in Didactics, taught in the School of Education at the Los Angeles Campus of the Universidad de Concepción, in the region of Biobío, Chile. The investigation had a descriptive approach and the main method for data collection was an opinion questionnaire with open questions. The main findings show that teachers in general and in a high percentage appreciate creativity, understand the concept of pedagogical innovation, but have difficulties to identify the difference between the latter and educational innovation due to its conceptual breadth. Furthermore, the results show that while teachers believe that innovation is necessary and that they are willing to do it in their pedagogical teaching activity, favorable conditions to implement it in schools are not always generated

The ‘CheA’ and ‘CheY’ domains of Myxococcus xanthus FrzE function independently in vitro as an autokinase and a phosphate acceptor, respectively

AbstractFrzE is a chemotaxis protein in Myxococcus xanthus which has sequence homology to two different chemotaxis proteins of enteric bacteria, CheA (autokinase) and CheY (phosphate acceptor) [Proc. Natl. Acad. Sci. USA 87 (1990) 5898–5902]. It was also shown that a recombinant FrzE protein was autophosphorylated when incubated in the presence of ATP and Mn2+ [J. Bacteriol. 172 (1990) 6661–6668]. In this study, we further investigated the biochemical properties of FrzE. Two recombinant proteins were produced: one containing only the ‘CheA’ domain of FrzE and the second only the ‘CheY’ domain. The CheA domain polypeptide contained the autokinase activity which was absent from the CheY domain polypeptide. The phosphorylated CheA domain polypeptide as well as the intact FrzE protein were able to transfer phosphate groups to the CheY domain peptide. These results indicate that FrzE has structural as well as functional homologies to CheA and CheY in a single polypeptide