Anisotropic enhancement of Yb3+ luminescence by disordered plasmonic networks self-assembled on RbTiOPO4 ferroelectric crystals.

Increasing Yb3+ absorption efficiency is currently desired in a number of applications including bio-imaging, photovoltaics, near infrared driven photocatalysis or ultra-short pulsed solid-state lasers. In this work, silver nanoparticles, which are connected forming disordered networks, have been self-assembled on Yb3+ doped RbTiOPO4 crystals to produce a remarkable enhancement of Yb3+ absorption, and hence in the photoluminescence of this ion. The results are interpreted taking into account the near-field response of the plasmonic networks, which display strong amplification of the electric field at the maximum of Yb3+ excitation at around 900 nm, together with the anisotropic character of the Yb3+ transitions in RbTiOPO4. We show that in the near field regime, the scattering of the plasmonic networks produces additional polarization field components to those of the incident field, which allows access to the largest transition dipolar moment of Yb3+ ions in RbTiOPO4. As a result, a much more efficient route for Yb3+ excitation takes place at the immediacy of the plasmonic networks. This work provides fundamental insights for improving the optical properties of rare earth ions by the suitable design of metallic nanoparticle arrangements, and constitutes a promising step towards the development of new multifunctional solid-state lasers.

Rare earth doped ring-shaped luminescent micro-composites on patterned ferroelectrics.

Ferroelectric domain patterns are used as templates on which rare earth doped high refractive index nanoparticles activated with trivalent rare earth ions (RE(3+)) are selectively assembled on domain surfaces with a specific polarization. Two-dimensional luminescent heterostructures, with sizes and geometries defined by the ferroelectric patterning are achieved. The process of incorporation and consolidation of the optically active nanoparticles into the alternate domain structures leads to luminescent ring-shaped arrangements with innovative geometries and to a micrometer spatial control of the trivalent rare earth ion emitters. Multicolor emission systems and the possibility of chromatic switching at the micrometer scale among the three different compounds forming the two dimensional structure is demonstrated.

Coherent light generation from a Nd:SBN nonlinear laser crystal through its ferroelectric phase transition.

In this Letter we have used the optical pump induced thermal loading to drive Nd(3+) a doped Sr(0,47)Ba(0.53)(Nb)(3))(2) laser crystal during laser operation through its ferroelectric phase transition. We demonstrate that lasing is possible below, at, and above phase transition. For temperatures close to (approximately 105 degrees C) the spatial distribution of laser radiation is remarkably affected. This feature, which leads to a laser gain depression, can be explained in terms of the strong temperature dependence of the thermo-optic coefficient during phase transition. Additionally, the visible radiation generated by intracavity self-frequency doubling disappears when the phase transition is undergone, showing a bistable behavior. The results provide fundamental information on physical parameters along the phase transition and will stimulate further work in the fields of nonlinear optics, optical switching, and data storage.

Escabiosis: revisión y actualización / Scabies: checking and update

La sarna o escabiosis es una ectoparasitosis producida por Sarcoptes scabiei. Existen dos formas clínicas, la típica y la llamada sarna noruega, con lesiones hiperqueratósicas generalizadas y con un gran potencial para provocar brotes en situaciones de hacinamiento. La infestación es más frecuente en aquellas circunstancias en que existe un contacto prolongado con los afectados. En ocasiones, esta enfermedad plantea problemas diagnósticos y terapéuticos, dependiendo de la edad y situación del sujeto. El tratamiento se basará en el uso correcto de escabicidas, medidas higiénicas y la realización de una adecuada profilaxis en todos los sujetos conviventes (AU)

An investigation of documentation submitted by university students to verify their learning disabilities.

To become eligible for support services at the postsecondary level, students with learning disabilities (LD) must submit documentation to verify the existence of a specific LD. The documentation submitted over a 5-year period by 415 students to a large public research university that offers a comprehensive program for students with LD was examined. An analysis of the documentation indicates that serious problems exist in the type and quality of evaluation reports. Problems include flaws in the comprehensiveness of the assessments, and the use of questionable instruments for this population. Recommendations for establishing guidelines for acceptable documentation are offered.

Paraguayan National Blood Pressure Study: prevalence of hypertension in the general population.

Stroke and cardiovascular disease are major causes of death in Paraguay but no information is available on the distribution of blood pressure (BP) and the extent of hypertension in the general population. The aim of this study, which was the first comprehensive national survey in a country in South America, was to determine the prevalence of hypertension to ascertain the need for a national programme for the control of high BP. The study design was a cross-sectional survey. A multi-stage sampling process was used to identify areas within districts covering the five main regions of the country. Alternate houses were visited by eight survey teams within these areas; 9880 adults aged 18-74 years answered a questionnaire and had measurements of height, weight and BP (twice) according to a standard protocol. Using a modified WHO definition of hypertension, 39.1% of women and 26.8% of men had raised BP (mild, moderate or severe hypertension). More women than men had borderline hypertension (17.5% vs 8.3%) and mild hypertension (32.8% vs 20.8%), whereas about 6% of both sexes had moderate or severe hypertension. Prevalence increased markedly with age, such that more than one quarter of the sample > 60 years of age had moderate or severe hypertension. Both systolic and diastolic pressure showed a consistent increase with body mass index (P < or = 0.001). Almost half the subjects with measured moderate or severe hypertension were unaware that they had raised BP. Hypertension is a major health problem in Paraguay such that a national programme of detection and treatment may be warranted.