Phase prediction, microstructure and high hardness of novel light-weight high entropy alloys

Guided by CALPHAD modeling, low-density and multiphase three novel High Entropy Alloys (HEAs), Al40Cu15Cr15Fe15Si15, Al65Cu5Cr5Si15Mn5Ti5 and Al60Cu10Fe10Cr5Mn5Ni5Mg5 were produced by large scale vacuum die casting. A mixture of simple and complex phases was observed in the as-cast microstructures, which demonstrates good agreement with CALPHAD results. The measured densities varied from 3.7 g/cm3 to 4.6 g/cm3 and microhardness from 743 Hv to 916 Hv. Finally, the hardness of all the light-weight HEAs (LWHEAs) with densities below 4.6 g/cm3 manufactured to date were reviewed. The hardness of Al40Cu15Cr15Fe15Si15 and hardness to density ratio of Al65Cu5Cr5Si15Mn5Ti5 are the highest of all LWHEAs reported up to date.This work has been partially funded by the Basque government through the Project Elkartek: KK-2017/0000

Time-dependent Feshbach method to study resonant photoionization of He with ultrashort laser pulses

ABSTRACT: A time-dependent Feshbach formalism is proposed to study the resonant photoionization of the helium atom using ultrashort laser pulses. This spectral method consist in solving the time-dependent Schr¨odinger equation by expanding the time-dependent wavepacket in terms of eigenfunctions defined in two orthogonal halfspaces: a bound-like resonant Q and a non-resonant scattering-like P. The latter eigenfunctions for the projected Hamiltonians QHQ and PHP are not indeed eigenfunctions of the total Hamiltonian, so that the electrostatic coupling QHP acts as a leaking operator Q→P responsible for the temporal decay of resonances into the underlying continuum, keeping the physical insight of the Fano-Feshbach time independent formalisms. This method allows not only for accurate descriptions of the resonance parameters (energies, widths and Fano shape parameters) but also for the temporal evolution of the photodynamics involved in the resonant photoionization when using short laser pulses. We illustrate the performance of the method by analyzing the temporal formation of i) the one-photon ionization cross section below the second ionization threshold and the buildup of Fano profiles and ii) the up-down asymmetry of photoelectron angular distributions resulting from interferences of S-, P- and D-waves after simultaneous photoexcitation and decay of the lowest 1Se, 1Po and 1De resonant states, by using two sequential laser pulses with XUV harmonic frequencies separated by a time delay

Computation of resonant states using explicitly correlated coordinates in Be-like atomic systems

ABSTRACT: We present an efficient computational method to obtain accurate values for energy positions and widths of autoionizing states in Be-like atomic systems. The two-active (outer) electron wavefunction is expanded in terms of Hylleraas-type correlated configurations. The interaction with the 1s2 frozen core is represented through a model potential and the unphysical 1sn` series of virtual core states are removed by using a Phillips-Kleinman pseudopotential projector. A novel feature is that all matrix elements can be written in closed form. We illustrate the performance of our approach in computing doubly-excited states in Be and Ne6+ by using the stabilization method

El efecto osteoinductor de la matriz de los aloinjertos : estudio experimental en cultivos de osteoblastos humanos

Se ha realizado un estudio del efecto que produce el aloinjerto óseo sobre los osteoblastos humanos en cultivo. Para ello se han realizado cultivos de osteoblastos humanos y se les ha añadido un fragmento de aloinjerto sometido a esterilización por autoclave y conservación mediante congelación. Como medidas del efecto del aloinjerto sobre los osteoblastos se han tomado la curva de proliferación, la determinación de propéptido aminoterminal de procolágeno I, como marcador de la formación de matriz ósea y la determinación de interleucina6 como marcador de activación osteoclástica. Como resultados más importantes, se ha encontrado que durante la primera semana del experimento predominan los fenómenos de reabsorción ósea caracterizados por una disminución del número de osteoblastos y de los niveles de propéptido aminoterminal de procolágeno I y un aumento de los niveles de interleucina6. Por el contrario, la segunda semana del experimento esta tendencia se invierte y predominan los fenómenos de formación óse

Intervention Project on Emotional Education in El Milagro Community (Iquitos, Peru)

En los últimos años, la educación ha incorporado la educacional emocional como complemento al desarrollo del potencial cognitivo del estudiante, existiendo en la actualidad programas, pautas de actuación y recursos encaminados a favorecer la resolución de conflictos y dificultades mediante la compresión y gestión de las emociones. En este sentido, se presentaun proyecto de intervención socioeducativa sobre educación emocional dirigido a estudiantes, familiares y docentes en un Colegio Agropecuario de Educación Secundaria, situado en la Comunidad “El Milagro” en la región de Iquitos, Perú. Los objetivos del proyecto pretenden dar respuesta a una serie de necesidades y problemáticas (adicciones, embarazos precoces, bajo rendimiento académico, absentismo escolar, etc.), surgidas en el centro educativo y en su entorno. El proyecto plantea un conjunto de actividades (debates, video-fórum, role-playing, biodanza, etc.), que ofrece espacios de reflexión e intercambio de ideas y concepciones relacionadas con diversas temáticas como la sexualidad, autoconcepto, resiliencia, etc. La evaluación del proyecto realizada a través de diferentes técnicas de análisis y recogida de la información como la observación, entrevistas informales y cuestionarios permitió conocer el nivel de satisfacción de los participantes, así como la eficacia, la eficiencia y el grado de consecución de los objetivos propuestos.In recent years, education has incorporated emotional education as a complement to the development of the student's cognitive potential. Currently, there are programs, action guidelines and resources aimed at favoring the resolution of conflicts and difficulties through the understanding and management of emotions. In this sense, a socio-educational intervention project on emotional education is presented to students, family members and teachers in an Agricultural College of Secondary Education, located in the community "El Milagro" in the region of Iquitos, Peru. The objectives of the project are intended to respond to a series of needs and problems (addictions, early pregnancies, low academic performance, school absenteeism, etc.), arising in the school and its environment. The project proposes a set of activities (discussion, video-forum, role-playing, biodance, etc.), which offers spaces for reflection and exchange of ideas and concepts related to various topics such as sexuality, self-concept, resilience, etc. The evaluation of the project carried out through different techniques of analysis and collection of information such as observation, informal interviews and questionnaires allowed to know the level of satisfaction of the participants, as well as the effectiveness, efficiency and degree of achievement of the objectives proposed

Complete Feshbach-type projection method to compute autoionizing states in Li-like atomic systems

ABSTRACT: A fully ab initio method of solution to compute autoionizing states in Li-like atomic systems based on the application of the Feshbach projection formalism is proposed. Applications of the Feshbach formalism, which in principle is a complete many-particle theory, to systems of more than two-active electrons are very scarce due to the limitations imposed by the practical construction of correct projection operators P and Q inherent to the theory. We include rigorously all the ingredients required by the Feshbach theory in order to compute accurate resonance parameters for the lowest autoionizing states of Li and Ne7+, for the 2Se, 2Po and 2De symmetries

Evaluación de un índice para cuantificar sequías hidrológicas utilizando series sintéticas que incluyen variaciones temporales generadas por distintos procesos

Fil: Vicario, Leticia. Instituto Nacional del Agua-Centro de la Región Semiárida; Argentina.Fil: Vicario, Leticia. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Centro de Estudios y Tecnología del Agua; Argentina.Fil: García, Carlos M. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Centro de Estudios y Tecnología del Agua; Argentina.Fil: García, Carlos M. Universidad Nacional de Córdoba. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina.Fil: Bertoni, Juan Carlos. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina.Las sequías hidrológicas se manifiestan con una reducción en variables que cuantifican la disponibilidad hídrica en distintos cuerpos de agua y tiene importantes efectos negativos en el aspecto socio-económico de una región, por lo que es relevante contar con metodologías precisas para su detección y cuantificación. Una de las metodologías utilizadas para analizar sequías hidrológicas es el índice SDI (Streamflow Drought Index). La utilización del índice SDI requiere de series de datos de caudal de alta calidad y longitud suficiente. Las series históricas de caudales registradas presentan variaciones temporales generadas por distintos procesos que podrían afectar os resultados provistos por el índice: variaciones en su tendencia temporal; fluctuaciones de baja frecuencia; fluctuaciones de alta frecuencia (interanual) y fluctuaciones aleatorias. En este trabajo se evalúa al índice SDI utilizando series sintéticas que incluyen las distintas variaciones temporales citadas previamente. Las series sintéticas generadas presentan parámetros estadísticos similares a una serie histórica de caudales observados en un curso fluvial de la región pampeana central de Argentina. En este trabajo se observa que el índice SDI permite identificar y caracterizar las sequías hidrológicas aun cuando las series presenten distintas variaciones temporales utilizando intervalos de agregación de 9 y 12 meses.http://fich.unl.edu.ar/hidrollanuras2014/blog/2014/10/16/trabajos-publicados/Fil: Vicario, Leticia. Instituto Nacional del Agua-Centro de la Región Semiárida; Argentina.Fil: Vicario, Leticia. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Centro de Estudios y Tecnología del Agua; Argentina.Fil: García, Carlos M. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Centro de Estudios y Tecnología del Agua; Argentina.Fil: García, Carlos M. Universidad Nacional de Córdoba. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina.Fil: Bertoni, Juan Carlos. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina.Otras Ingeniería Civi

Feshbach projection approach to study plasma effects on doubly excited autoionizing states in helium

ABSTRACT: We have implemented a method based on the Feshbach formalism along with an explicitly correlated configuration interactionmethod to perform a systematic study on the behavior of resonance parameters (energies and lifetimes) of the autoionizing states of plasma-embedded He 1,3Se, 1,3Po, and 1,3De, as a function of the screening strength. In particular, we study the evolution of the lowest states in the series located below the He+(N = 2) ionization threshold in the unscreened case. At variance with one-electron atoms (where shape resonance widths vary monotonically with the screening strength) the evolution of the Auger width with respect to screening is found to be different for each series represented by (K,T )A pseudoquantum numbers until resonances merge into the upper electronic continuum, when crossing the He+(2s) threshold. We conclude from our ab initio calculations that, although resonances pertaining to the same (K,T )A series share a similar tendency in their widths against the screening strength, general propensity rules for the robustness of lifetimes, based on the isomorphic series in the (K,T )A classification, cannot be established in plasma embedded helium

Feshbach-like study of He resonant states in Debye plasmas using explicitly correlated wave functions

ABSTRACT: We present a study on the 1;3Se, 1;3Po and 1;3De He resonant states below the He+ (N=2) threshold under the in uence of a plasma environment, when the Debye screening length is varied. The interaction between all charged particles is modeled with Yukawa-like screened Coulomb potentials. We make use of the Feshbach projector method to characterize resonant states, implemented by using explicitly correlated CI-wave functions