Tests of Lorentz Symmetry in Single Beta Decay

Low-energy experiments studying single beta decay can serve as sensitive probes of Lorentz invariance that can complement interferometric searches for deviations from this spacetime symmetry. Experimental signatures of a dimension-three operator for Lorentz violation which are unobservable in neutrino oscillations are described for the decay of polarized and unpolarized neutrons as well as for measurements of the spectral endpoint in beta decay

Reproducibility of a Titanium Plasma Vacuum Spark Discharge

The results of an extensive operation of a Vacuum Spark plasma using Titanium electrodes in a 120 ns 150 kA discharge are presented. The hot spots are found to form with a regular spacing in a zippering Z-pinch plasma, which forms close to the cathode and extends to approximately two thirds of the anode separation over a period of a few ns. The axis of the discharge is well defined by an initial plasma from a Nd:YAG laser focussed onto the cathode electrode surface. The statistics of the formation of the hot spots are given for the life of one anode electrode. Between one and three hotspots form and the favored positions are at 1.5 and 3.0 mm from the cathode and the strongest emission, as observed in a filtered X-ray pinhole camera, comes from the hot spot closest to the cathode. The emission spectra resolved between 50 and 350 \AA shows a wide range of Ti ionization which allows the temperatures of the anode blow off plasma, the Z-pinch and the hot spot plasma to be distinguished. These results are compared with filtered PIN diode signals and filtered pinhole images.Comment: 5 pages, 4 figure

Carbonatos en suelos de la zona oriental de Gran Canaria

The study of three soil profiles in the aridic-xeric zone of Las Palmas island showed that: petrocalcic horizons are formed in pyroclastic episodes; these horizons are generally thick; the xeric zone frequently have polycyclic profiles and their carbonates have complex mineralogy; underlain basaltic rocks are scantly altered, and their joints are frequently filled by carbonates. These facts suggest that the development of these profiles is mostly Pleistocene, and the diffuse carbonates accumulation in depth obstructs the assessment of carbonatation processes

Avaliação de reativos padrões para provas de Imunodifusão Radial. Controle in vitro de vacinas antirrábicas

The RID assay is one of the in vitro methods used for in-process control in the production of rabies vaccines for veterinary use. It has been shown to be very useful for determining antigen concentration in the final bulk product. The work presented in this paper, including the production and standardization of candidate standard reagents for use in the Radial Immunodiffusion Assay (RID) was carried out at the Pan American Institute for Food Protection and Zoonoses (INPPAZ/PAHO/WHO). The study was completed with the cooperation of the Faculty of Veterinary Sciences, National University of La Plata (NULP), Argentina, where the validation of the proposed standards and the quality control of samples from 28 different batches of rabies vaccines produced with Pasteur strain rabies virus (PV) in BHK cells were performed. The activity of the vaccines was determined by in vivo (NIH) and in vitro (RID)assays. The results of the candidate reagents for the reagent standardization tests showed stability, sensitivity and reproducibility. The Relative Potency the 1.2 between the problem vaccines and the reference vaccine was estimated by variance and regression analysis. The results of our validation study show that the INPPAZ (PAHO/WHO) is capable of producing and distributing the above-mentioned standard reagents, as well as of providing support for the incorporation of the RID technique (sensitive, rapid and inexpensive) to the laboratories that manufacture rabies vaccines in Latin America and the Caribbean.A prova de Imunodifusão Radial (IDR) é um método in vitro conveniente para determinar a concentração de antígenos no produto final como um todo, de vacinas anti-rábicas para uso veterinário. Os reativos padrões candidatos para uso na prova IDR, proposta para o controle de processo de vacinas de cultivo celular, elaboradas na América Latina e Caribe, foram produzidos e padronizados no Instituto Panamericano de Proteção de Alimentos e Zoonoses (INPPAZ). A validação dos padrões e o controle de qualidade de 28 lotes de vacinas anti-rábicas, de diferentes procedências, foram realizados na Faculdade de Ciências Veterinárias da Universidade de La Plata, Argentina (UNLP). Todas as vacinas foram elaboradas com virus rábico cepa Pasteur (PV) em células BHK e sua atividade foi determinada através de provas in vivo (NIH) e in vitro (IDR). Os resultados dos reativos, candidatos para as provas de padronização, demonstraram estabilidade, sensibilidade e reprodutibilidade. Por análise de variância e de regressão foi estimada a potência relativa de 1.2 entre as vacinas problemas e a vacina de referência. Os resultados deste estudo de validação indicam que o INPPAZ, está em condições de elaborar e distribuir os reativos padrões acima mencionados e apoiar a adoção da técnica de IDR (sensível, rápida, econômica) pelos laboratórios de produção de vacinas anti-rábicas da América Latina e Caribe

Amplificación del efecto destructivo de los desprendimientos rocosos por deslizamiento sobre suelos volcánicos (Tenerife y Madeira)

This work provides geomorphological and geotechnical observations on the amplification of the destructive behaviour of rock falls developed in rocky slopes with a soil rich in organic matter, which are both exposed to high rainfall regimes. The determinant factor of this process would be related to the low geotechnical quality that the organic matter gives to the soil, which experience a sudden change in its fabric related to the dynamic load, similar to those observed in the quick clays in the fjords of Norway

PVDF/TiO2 nanocomposites prepared by solution blow spinning: surface properties and their relation with S. Mutans adhesion

Thermoplastic nanocomposite materials with potential bactericide properties were prepared and their surface properties and adhesion to Streptococcus mutans, S. mutans, were characterized. Solution blow spinning was successfully used to prepare films with a fiber-like structure on the surface of nanocomposites based on Polyvinylidene fluoride, PVDF, filled with well dispersed TiO2 nanoparticles. PVDF/TiO2 nanocomposites were prepared varying the nanoparticles content (0%, 1%, 2%, 5% and 10% by weight). In order to understand the influence of the presence of TiO2 nanoparticles and the final surface properties on the adhesion of S. mutans to the materials, a deep characterization was carried out focusing on the morphology, roughness, surface free energy from contact angle measurements and cell adhesion by single cell force spectroscopy. It was observed that the uniform dispersion of the nanofiller arose from nanoparticles embedded in the polymer when fibers were created during the blow spinning process. TiO2 content influenced the topography of the films probably due to a direct effect on the solvent evaporation rate. Although this factor greatly conditioned the roughness of the samples and therefore the surface free energy, S. mutant adhesion on the substrates under study was concluded to be more dependent on the specific interactions with the surface polar groups of the material.Authors gratefully acknowledge financial support of Ministerio de Economía y Competitividad (grant number MAT2014-59116-C2). Furthermore, the authors greatly appreciate The Ministerio de Educación Cultura y Deporte of Spain in the frame of "Modalidad A del Programa de estancias de movilidad de profesores e investigadores en centros extranjeros de enseñanza superior e investigación" for granting the research proposal of Javier González-Benito (Ref.: PR2015-00018) to do short stay at the National Institute of Standards and Technology, NIST (USA)

Algoritmos generales para simuladores de cirugía laparoscópica

Recent advances in fields such as modeling of deformable objects, haptic technologies, immersive technologies, computation capacity and virtual environments have created the conditions to offer novel and suitable training tools and learning methods in the medical area. One of these training tools is the virtual surgical simulator, which has no limitations of time or risk, unlike conventional methods of training. Moreover, these simulators allow for the quantitative evaluation of the surgeon performance, giving the possibility to create performance standards in order to define if the surgeon is well prepared to execute a determined surgical procedure on a real patient. This paper describes the development of a virtual simulator for laparoscopic surgery. The simulator allows the multimodal interaction between the surgeon and the surgical virtual environment using visual and haptic feedback devices. To make the experience of the surgeon closer to the real surgical environment a specific user interface was developed. Additionally in this paper we describe some implementations carried out to face typical challenges presented in surgical simulators related to the tradeoff between real-time performance and high realism; for instance, the deformation of soft tissues are simulated using a GPU (Graphics Processor Unit) -based implementation of the mass-spring model. In this case, we explain the algorithms developed taking into account the particular case of a cholecystectomy procedure in laparoscopic surgery.Recientes avances en áreas tales como modelación computacional de objetos deformables, tecnologías hápticas, tecnologías inmersivas, capacidad de procesamiento y ambiente virtuales han proporcionado las bases para el desarrollo de herramientas y métodos de aprendizaje confiables en el entrenamiento médico. Una de estas herramientas de entrenamiento son los simuladores quirúrgicos virtuales, los cuales no tienen limitaciones de tiempo o riesgos a diferencia de los métodos convencionales de entrenamiento. Además, dichos simuladores permiten una evaluación cuantitativa del desempeño del cirujano, dando la posibilidad de crear estándares de desempeño con el fin de definir en qué momento un cirujano está preparado para realizar un determinado procedimiento quirúrgico sobre un paciente. Este artículo describe el desarrollo de un simulador virtual para cirugía laparoscópica. Este simulador permite la interacción multimodal entre el cirujano y el ambiente virtual quirúrgico usando dispositivos de retroalimentación visual y háptica. Para hacer la experiencia del cirujano más cercana a la de una ambiente quirúrgico real se desarrolló una interfaz cirujano-simulador especial. Adicionalmente en este artículo se describen algunas implementaciones que solucionan los problemas típicos cuando se desarrolla un simulador quirúrgico, principalmente relacionados con lograr un desempeño en tiempo real mientras se sacrifica el nivel de realismo de la simulación: por ejemplo, la deformación de los tejidos blandos simulados usando una implementación del modelo masa-resorte en la unidad de procesamiento gráfico. En este caso se describen los algoritmos desarrollados tomando en cuenta la simulación de un procedimiento laparoscópico llamado colecistectomía

Influence of the Nanostructure of Palladium Mesoparticles on the Kinetics of Molecular Oxygen Electroreduction

The effect of the nanostructure of electrodeposited palladium mesoparticles on the oxygen electroreduction reaction (oerr) in acid media is studied by electrochemical techniques combined with scanning tunneling microscopy, tapping-mode atomic force microscopy, and scanning electron microscopy. Palladium mesoparticles supported on highly oriented pyrolytic graphite (HOPG) exhibit a remarkable electrocatalytic enhancement, i.e., a decrease in the cathodic overvoltage on the order of 0.25 V, as compared to polycrystalline palladium electrodes. For a similar particle size, the largest electrocatalytic activity is obtained by use of quasi-twodimensional (2D) ramified palladium particles and electrodeposited palladium charges exceeding 3 mC cm-2. For these particles, experimental results show that the electrocatalytic enhancement of the oerr can be related to the combined influence of the nanostructure of 2D branching on the HOPG and traces of oxygen-containing adsorbates that induces local perturbation of electronic states at palladium mesoparticles. The 2D nature of surfaces increases markedly the reversibility of the first two-electron-transfer step of the oerr.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

LA COMUNIDAD EDUCATIVA Y LA GESTIÓN ESCOLAR DE LAS ESCUELAS DE PANAMÁ ESTE.

Most Latin American countries tended to neglect the configuration functions of the education system, to focus on service delivery routines. The result was that, because of the profound changes in the macro-social structures, the educational system entered an accelerated process of deconfiguration, derived from the loss of effectiveness. The impacts of a globalization that would transform daily practices, organizational forms and then question all the assumptions on which the praxis of educators and administrators is raised were still incipient. In recent years, school management has separated administrative activities from technical, teaching and pedagogical activities, concentrating the former in the hands of managers (general administration), which confirms the existence of a group of homologous actions with a high rational and common to a bank, a department store or a hospital, where operational programs of material, financial and human resources are managed, as well as the control of an adequate functioning of services and processes. And it is that Fayol (1987) needed the conviction that, through the application of its principles of scientific administration, the action of all people and of any service could be rationalized, ensuring a regular, predictable, optimal and efficient operation.En esos tiempos, la mayoría de los países latinoamericanos tendieron a desatender las funciones de configuración del sistema educativo, para centrarse en las rutinas de prestación del servicio. El resultado fue que, a raíz de los profundos cambios en las estructuras macro sociales, el sistema educativo ingresó en un acelerado proceso de desconfiguración, derivado de la pérdida de eficacia. Aun eran incipientes los impactos de una globalización que transformaría las prácticas cotidianas, las formas organizativas y luego cuestionaría todos los supuestos sobre los que se levanta la praxis de los educadores y de los administradores. La gestión escolar en estos años ha separado las actividades administrativas de las actividades técnicas, docentes y pedagógicas, concentrando las primeras en manos de los directivos (administración general), lo que confirma la existencia de un grupo de acciones homólogas con un alto enfoque racional y comunes a un banco, una tienda de departamentos o un hospital, donde maniobran programas operativos de recursos materiales, financieros y humanos, así como el control de un adecuado funcionamiento de los servicios y procesos. Y es que Fayol (1987) precisaba el convencimiento de que, a través de la aplicación de sus principios de administración científica, se podría racionalizar la acción de todas las personas y de cualquier servicio, asegurando un funcionamiento regular, previsible, óptimo y eficiente