Multiple Quantum Well AlGaAs Nanowires

This letter reports on the growth, structure and luminescent properties of individual multiple quantum well (MQW) AlGaAs nanowires (NWs). The composition modulations (MQWs) are obtained by alternating the elemental flux of Al and Ga during the molecular beam epitaxy growth of the AlGaAs wire on GaAs (111)B substrates. Transmission electron microscopy and energy dispersive X-ray spectroscopy performed on individual NWs are consistent with a configuration composed of conical segments stacked along the NW axis. Micro-photoluminescence measurements and confocal microscopy showed enhanced light emission from the MQW NWs as compared to non-segmented NWs due to carrier confinement and sidewall passivation

Visible light reduces C. elegans longevity.

The transparent nematode Caenorhabditis elegans can sense UV and blue-violet light to alter behavior. Because high-dose UV and blue-violet light are not a common feature outside of the laboratory setting, we asked what role, if any, could low-intensity visible light play in C. elegans physiology and longevity. Here, we show that C. elegans lifespan is inversely correlated to the time worms were exposed to visible light. While circadian control, lite-1 and tax-2 do not contribute to the lifespan reduction, we demonstrate that visible light creates photooxidative stress along with a general unfolded-protein response that decreases the lifespan. Finally, we find that long-lived mutants are more resistant to light stress, as well as wild-type worms supplemented pharmacologically with antioxidants. This study reveals that transparent nematodes are sensitive to visible light radiation and highlights the need to standardize methods for controlling the unrecognized biased effect of light during lifespan studies in laboratory conditions

A Calibrated Time Domain Envelope Measurement System for the Behavioral Modeling of Power Amplifiers

This paper presents a set-up which enables the generation and the calibrated time domain measurements of complex envelopes of modulated signals at both ports of non linear microwave power amplifiers. The architecture of the characterization tool is given. Examples of error corrected time domain envelopes at the input / output RF ports of a 36 dBm output power – 30dB power gain L-band SSPA are shown. Futhermore, the use of this characterization tool and a suitable processing of measurement data are applied to a novel measurement based behavioral modeling approach of non linear devices accounting for memory effects

Anisotropic Hall Effect in Single Crystal Heavy Fermion YbAgGe

Temperature- and field-dependent Hall effect measurements are reported for YbAgGe, a heavy fermion compound exhibiting a field-induced quantum phase transition, and for two other closely related members of the RAgGe series: a non-magnetic analogue, LuAgGe and a representative, ''good local moment'', magnetic material, TmAgGe. Whereas the temperature dependent Hall coefficient of YbAgGe shows behavior similar to what has been observed in a number of heavy fermion compounds, the low temperature, field-dependent measurements reveal well defined, sudden changes with applied field; in specific for $H \perp c$ a clear local maximum that sharpens as temperature is reduced below 2 K and that approaches a value of 45 kOe - a value that has been proposed as the $T = 0$ quantum critical point. Similar behavior was observed for $H \| c$ where a clear minimum in the field-dependent Hall resistivity was observed at low temperatures. Although at our base temperatures it is difficult to distinguish between the field-dependent behavior predicted for (i) diffraction off a critical spin density wave or (ii) breakdown in the composite nature of the heavy electron, for both field directions there is a distinct temperature dependence of a feature that can clearly be associated with a field-induced quantum critical point at $T = 0$ persisting up to at least 2 K.Comment: revised versio

Dengue una enfermedad emergente y re-emergente en América

El Dengue es una enfermedad infecciosa, producida por un arbovirus cuyo único reservorio es el hombre. El virusutiliza como vector biológico al mosquito Aedes aegypti o al mosquito Aedes albopictus. La sintomatología se presentahabitualmente como un cuadro febril denominado dengue clásico, que se caracteriza por fiebre alta de presentaciónaguda, de duración limitada (2 a 7 días), con intenso malestar general, acompañado de erupción cutánea. Puedepresentar síntomas hemorrágicos de escasa intensidad, como petequias y sangramiento gingival. El tratamiento essintomático y el paciente mejora completamente en aproximadamente 7 días. Esta forma de dengue no producemortalidad. Sin embargo, existen otras presentaciones de la enfermedad que pueden llegar a manifestaciones graves deltipo hemorrágicas con muerte, lo que se presenta en el 5% de los enfermos. El dengue es un problema creciente desalud pública, que afecta a más de 100 países en el mundo, con más de 50 millones de casos informados cada año. Loscuatro tipos de dengue, están circulando en América, donde los casos aumentaron en los últimos años en formaexplosiva. Si bien, en Chile continental no se ha documentado la existencia del mosquito vector del dengue de formaendémica, si se ha hecho en Chile Insular, más específicamente en Isla de Pascua, donde desde el año 1999, seincorporó a la lista de enfermedades de declaración obligatoria (D.S. Nº 158) estableciendo su vigilancia. Los factoresque han llevado a la emergencia de esta enfermedad son principalmente el cambio climático, que ha modificado elnicho ecológico de los mosquitos de la familia Aedes. También la urbanización, la falta de control del vector, las fallasen infraestructura básica y el pobre saneamiento ambiental. La intervención primaria de salud pública ha ido por la líneadel uso de insecticidas para el control del vector y la detección temprana de casos. No existe aún una vacuna efectiva,sin embargo, actualmente se están realizando esfuerzos en esta materia