Enhancement by polydispersity of the biaxial nematic phase in a mixture of hard rods and plates

The phase diagram of a polydisperse mixture of uniaxial rod-like and plate-like hard parallelepipeds is determined for aspect ratios $\kappa=5$ and 15. All particles have equal volume and polydispersity is introduced in a highly symmetric way. The corresponding binary mixture is known to have a biaxial phase for $\kappa=15$, but to be unstable against demixing into two uniaxial nematics for $\kappa=5$. We find that the phase diagram for $\kappa=15$ is qualitatively similar to that of the binary mixture, regardless the amount of polydispersity, while for $\kappa=5$ a sufficient amount of polydispersity stabilizes the biaxial phase. This provides some clues for the design of an experiment in which this long searched biaxial phase could be observed.Comment: 4 pages, 5 eps figure files, uses RevTeX 4 styl

A constitutive model for analyzing martensite formation in austenitic steels deforming at high strain rates

This study presents a constitutive model for steels exhibiting SIMT, based on previous sem inal works, and the corresponding methodology to estimate their parameters. The model includes temperature effects in the phase transformation kinetics, and in the softening of each solid phase through the use of a homogenization technique. The model was validated with experimental results of dynamic tensile tests on AISI 304 sheet steel specimens, and their predictions correlate well with the experimental evidence in terms of macroscopic stress strain curves and martensite volume fraction formed at high strain rates. The work shows the value of considering temperature effects in the modeling of metastable austen itic steels submitted to impact conditions. Regarding most of the works reported in the lit erature on SIMT, modeling of the martensitic transformation at high strain rates is the distinctive feature of the present paper.The researchers of the University Carlos III of Madrid are indebted to the Comunidad Autónoma de Madrid (Project CCG10 UC3M/DPI 5596)) and to the Ministerio de Ciencia e Innovación de España (Project DPI/2008 06408) for the financial support received which allowed conducting part of this work. The authors express their thanks to Mr. Philippe and Mr. Tobisch from the company Zwick for the facilities provided to perform the tensile tests at high strain rates.Publicad

Experimental and numerical analysis of the martensitic transformation in AISI 304 steel sheets subjected to perforation by conical and hemispherical projectiles

In this work, an experimental and numerical analysis of the martensitic transformation in AISI 304 steel sheets subjected to perforation by conical and hemispherical projectiles is conducted. Experiments are performed using a pneumatic gas gun for with the impact velocities in the range of 35 m/s < V-0 < 200 m/s. Two target thicknesses are examined, t(1) = 0.5 mm and t(2) = 1.0 mm. The experimental setup enabled the determination of the impact velocity, the residual velocity and the failure mode of the steel sheets. The effect of the projectile nose shape on the target's capacity for energy absorption is evaluated. Moreover, martensite is detected in all the impacted samples, and the role played by the projectile nose shape on the transformation is highlighted. A three-dimensional model is developed in ABAQUS/Explicit to simulate the perforation tests. The material is defined via the constitutive model developed by Zaera et al. (2012) to describe the strain-induced martensitic transformation occurring in metastable austenitic steels at high strain rates. The finite element results are compared with the experimental evidence, and satisfactory matching is observed over the entire range of impact velocities tested and for both projectile configurations and target thicknesses considered. The numerical model succeeds in describing the perforation mechanisms associated with each projectile-target configuration analyzed. The roles played by impact velocity, target thickness and projectile nose shape on the martensitic transformation are properly captured.The researchers of the University Carlos III of Madrid are in debted to the Comunidad Autónoma de Madrid (Project CCG10 UC3M/DPI 5596) and to the Ministerio de Ciencia e Innovación de España (DPI2011 24068) for the financial support received which allowed conducting part of this work

Capital social, metas del milenio y desarrollo local : el caso de la Iniciativa de Carapeguá en Desarrollo, Paraguay

¿Puede lo global y lo local generar una sinergia catalizadora del desarrollo comunitario en forma sostenible? ¿Puede la aplicación de la "caja de herramientas" de la gerencia social fortalecer el capital social, que a su vez impulsará el desarrollo local? ¿Puede la capacitación en gerencia social ser un elemento articulador y catalizador del desarrollo local? El objetivo a corto plazo del programa fue el de fortalecer el capital social local para catalizar una estrategia de desarrollo local sostenible, que mejore las condiciones de vida de la población en forma consistente con los objetivos de desarrollo del milenio. Para evaluar el impacto del programa sobre el capital social, se presentan y analizan las acciones y procesos del programa que pudieron haber impactado sobre los distintos elementos que constituyen el acervo de capital social de una comunidad

The history of a quiet-Sun magnetic element revealed by IMaX/SUNRISE

Isolated flux tubes are considered to be fundamental magnetic building blocks of the solar photosphere. Their formation is usually attributed to the concentration of magnetic field to kG strengths by the convective collapse mechanism. However, the small size of the magnetic elements in quiet-Sun areas has prevented this scenario from being studied in fully resolved structures. Here we report on the formation and subsequent evolution of one such photospheric magnetic flux tube, observed in the quiet Sun with unprecedented spatial resolution (0\farcs 15 - 0\farcs 18) and high temporal cadence (33 s). The observations were acquired by the Imaging Magnetograph Experiment (IMaX) aboard the \textsc{Sunrise} balloon-borne solar observatory. The equipartition field strength magnetic element is the result of the merging of several same polarity magnetic flux patches, including a footpoint of a previously emerged loop. The magnetic structure is then further intensified to kG field strengths by convective collapse. The fine structure found within the flux concentration reveals that the scenario is more complex than can be described by a thin flux tube model with bright points and downflow plumes being established near the edges of the kG magnetic feature. We also observe a daisy-like alignment of surrounding granules and a long-lived inflow towards the magnetic feature. After a subsequent weakening process, the field is again intensified to kG strengths. The area of the magnetic feature is seen to change in anti-phase with the field strength, while the brightness of the bright points and the speed of the downflows varies in phase. We also find a relation between the brightness of the bright point and the presence of upflows within it.Comment: 13 pages. Accepted in ApJ. Animation 1 can be viewed and downloaded from: http://spg.iaa.es/downloads.as

The parasitic turbellarian Urastoma cyprinae (Platyhelminthes: Urastomidae) from blue mussel Mytilus galloprovincialis in Spain: occurrence and pathology

8 pages, 8 figures, 2 tables.The turbellarian Urastoma cyprinae (Graff, 1882) Graff, 1903 was found inhabiting the mantle cavity between the lamellae of the demibranchs of mussels Mytilus galloprovincialis Lamarck cultured in Galicia (NW Spain). Heavily infested mussels were recognized by the presence of white spots in the gills. The affected area exhibited disarrangement of the gill filaments. The space between 2 lameliae was considerably reduced and the blood sinuses were wider in the unhealthy area than in the healthy area. The turbellarian also induced a heavy infiltration by blood cells and subsequent necrosis of the gill tissues. Routine parasitological studies showed that this parasite was first detected in the Galician region in early 1989. In 1993, U. cyprinae appeared to be present in the 3 main production rias in the Galician region, affecting both natural beds and rafted mussels. U. cyprinae could be considered a potential threat to mussel culture.J.A.F.R. acknowledges the Diputación de Pontevedra, Spain, and Xunta de Galicia, for his research fellowship in the IIM-CSIC. J.C.M. was supported by a grant of the CONACyT frorn Mexico.Peer reviewe

La integración de la educación ambiental en la ESO : datos para la reflexión

We present in this paper the analysis and principal results of a research carried out among 438 teachers and 126 headmasters. The issues concern the situation of environmental education in Obligatory Secondary School. The purpose of the study was to identify teacher and headmaster's opinions, perceptions and feelings about the situation of environmental education in their centres

Ethnic Differences in Physiological Responses to Fear Conditioned Stimuli

The idea that emotional expression varies with ethnicity is based largely on questionnaires and behavioral observations rather than physiological measures. We therefore compared the skin conductance responses (SCR) of Hispanic (Puerto Rican) and White non-Hispanic subjects in a fear conditioning and fear extinction task. Subjects were recruited from two sites: San Juan, Puerto Rico (PR), and Boston, Massachusetts (MA), using identical methods. A total of 78 healthy subjects (39 from PR, 39 from MA) were divided by sex and matched for age and educational level. Females from the two sites did not differ in their SCRs during any experimental phase of fear conditioning (habituation, conditioning, or extinction). In contrast, PR males responded significantly to the conditioned stimulus than MA males or PR females. Subtracting ethnic differences observed during the habituation phase (prior to conditioning) eliminated differences from subsequent phases, suggesting that PR males are elevated in their response to novelty rather than fear learning. Our findings suggest that, in addition to sex differences, there are ethnic differences in physiological responses to novel stimuli at least in males, which could be relevant for the assessment and treatment of anxiety disorders

Temperature measurements on ES steel sheets subjected to perforation by hemispherical projectiles

In this paper is reported a study on the behaviour of ES mild steel sheets subjected to perforation by hemispherical projectiles. Experiments have been conducted using a pneumatic cannon within the range of impact velocities 5m/s<=V0<=60m/s. The experimental setup allowed evaluating initial velocity, failure mode and post-mortem deflection of the plates. The tests have been recorded using high speed infrared camera. It made possible to obtain temperature contours of the specimen during impact. Thus, special attention is focussed on the thermal softening of the material which is responsible for instabilities and failure. Assuming adiabatic conditions of deformation, the increase of temperature may be related to the plastic deformation. The critical strain leading to target-failure is evaluated coupling temperature measurements with numerical simulations and with analytical predictions obtained by means of the Rusinek-Klepaczko constitutive relation [Rusinek, A., Klepaczko, J.R. Shear testing of sheet steel at wide range of strain rates and a constitutive relation with strain rate and temperature dependence of the flow stress. Int J Plasticity. 2001; 17, 87-115]. It has been estimated that the process of localization of plastic deformation which leads to target-failure involves local values close to for the boundary value problem approached. Subsequently, this failure strain level has been applied to simulate the perforation process and the numerical results obtained show satisfactory agreement with the experiments in terms of ballistic limit, temperature increase and failure mode of the target.The researchers of the University Carlos III of Madrid are indebted to the Comunidad Autónoma de Madrid (Project CCG08 UC3M/MAT 4464) and to the Ministerio de Ciencia e Innovación de España (Project DPI/2008 06408)Publicad