Role of surface states on the sensing properties of In0.5Ga0.5As surface quantum dots

Self-assembled uncapped III-V semiconductor quantum dots (QD) have recently emerged as good candidates to develop sensor devices due to their exceptional sensitivity to changes in the surrounding environment. Previous studies report that the external ambient conditions greatly influence the optical and electrical properties of In0.5Ga0.5As surface QD (SQD)2. Furthermore, it was found different electrical response depending on the two- or threedimensional nature of the surface. Surface quantum well (SQW) conductivity suffers a negligible variation when changing the external atmosphere, whereas SQDs conductivity shows a significant increment3 Surface states are generally proposed to be responsible for such effect, although this is still under discussion. In the case of the SQDs, this effect is enhanced by the high surface to volume ratio compared to SQWs

Synthesis and Antiproliferative Activity of Sulfa-Michael Adducts and Thiochromenes Derived from Carbohydrates

The Michael addition reactions of carbohydrate-derived nitroalkenes with ethyl thioglycolate and 2-mercaptobenzyl alcohol were studied. Reactions were conducted under mild, solvent-free conditions with DABCO as a catalyst, affording the corresponding adducts in good yields. Furthermore, compounds resulting from the addition with 2-mercaptobenzyl alcohol were used as starting materials for the synthesis of chiral 3-nitro-2H-thiochromenes. For some of the compounds synthesized herein, the antioxidant and antiproliferative activities against a panel of human solid tumor cell lines were assayed and compared with those of carbohydrate-nitroalkene substrates.Junta de Extremadura GR15022Unión Europea FP7-REGPOT-2012-CT2012-31637-IMBRAI

Effects of in vivo treatment with the dopamine antagonist pimozide and gonadotropin-releasing hormone agonist (GnRHa) on the reproductive axis of Senegalese sole (Solea senegalensis)

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Estudio preliminar sobre una posible inhibición dopaminérgia en la reproducción del lenguado senegalés (Solea senegalensis)

El objetivo del presente estudio fue evaluar el efecto del sistema dopaminérgico sobre la reproducción del lenguado senegalés (Solea senegalensis). Para ello, reproductores de lenguado senegalés nacidos y criados en cautividad (generación F1) fueron tratados con 1) GnRHa, 2) inhibidor dopaminérgico (pimozide) o 3) un tratamiento combinado (GnRHa + pimozide). El efecto de los tratamientos se evaluó a nivel de producción de huevos y esperma (cantidad y calidad); además se estudió el efecto sobre niveles plasmáticos de esteroides sexuales y desarrollo gonadal (histología). Las hembras no mostraron una estimulación en la ocurrencia de puestas por el tratamiento combinado GnRHa + pimozide respecto a aquellas tratadas solo con GnRHa. Sin embargo, los machos que recibieron el tratamiento combinado mostraron una mayor estimulación en la producción de esperma y en el grado de maduración testicular respecto a aquellos que recibieron solo GnRHa o pimozide. Los resultados indican que el sistema dopaminérgico no parece ejercer una acción fuerte sobre la ocurrencia de puestas en hembras, aunque podría estimular la espermiación en machos de lenguado senegalés.Preliminary study on dopaminergic inhibition in Senegalese sole reproduction (Solea senegalensis) The aim of the present study was to evaluate the effect of the dopaminergic system on Senegalese sole (Solea senegalensis) reproduction. For this purpose, Senegalese sole breeders hatched and raised in captivity (F1 generation) were treated with 1) GnRHa, 2) a well-known dopaminergic inhibitor (pimozide) or 3) a combined treatment (GnRHa + pimozide). The effect of each treatment was determined by studying spawning occurrence and sperm (quantity and quality); in addition, effects on sex steroids levels and on gonadal development (histology) were also considered. Females did not show any improvement of spawning occurrence by combining GnRHa and pimozide respect to those females treated only with GnRHa. However, males which received the combined treatment showed a greater stimulation of sperm production and testicular maturity than those males treated with a single GnRHa or pimozide treatment. Our results indicate that dopaminergic system do not seem to play a strong action on eggs spawning in females, but may stimulate spermiation in Senegalese sole males

Type-II GaAsSb/GaAsN superlattice solar cells

Dilute nitride GaAsSbN is an ideal candidate to form the 1-1.15 eV lattice-matched sub-cell that would significantly enhance the performance of 3- and 4-junction solar cells. However, growth problems inherent to this quaternary alloy lead typically to a poor crystal quality that limits its applicability. Better compositional control and crystal quality have been recently reported by growing the material as a GaAsSb/GaAsN superlattice, because of the spatial separation of Sb and N that avoid miscibility problems. Moreover, these structures provide bandgap tunability trough period thickness. Here we study the performance of lattice-matched 1.15 eV GaAsSb/GaAsN type-II perlattice p-i-n junction solar cells with different period thickness and compare them with the bulk and GaAsSbN/GaAs type-I superlattice counterparts. We demonstrate carrier lifetime tunability through the period thickness in the type-II structures. However, the long carrier lifetimes achievable with periods thicker than 12 nm are incompatible with a high carrier extraction efficiency under short-circuit conditions. Only superlattices with thinner periods and short carrier lifetimes show good solar cell performance. Quantum kinetic calculations based on the non-equilibrium Green's function (NEGF) formalism predict a change in transport regime from direct tunneling extraction to sequential tunneling with sizable thermionic emission components when passing from 6 nm to 12 nm period length, which for low carrier lifetime results in a decrease of extraction efficiency by more than 30%

Strain-balanced type-II superlattices for efficient multi-junction solar cells

Multi-junction solar cells made by assembling semiconductor materials with different bandgap energies have hold the record conversion efficiencies for many years and are currently approaching 50%. Theoretical efficiency limits make use of optimum designs with the right lattice constant-bandgap energy combination, which requires a 1.0–1.15eV material lattice-matched to GaAs/Ge. Nevertheless, the lack of suitable semiconductor materials is hindering the achievement of the predicted efficiencies, since the only candidates were up to now complex quaternary and quinary alloys with inherent epitaxial growth problems that degrade carrier dynamics. Here we show how the use of strain-balanced GaAsSb/GaAsN superlattices might solve this problem. We demonstrate that the spatial separation of Sb and N atoms avoids the ubiquitous growth problems and improves crystal quality. Moreover, these new structures allow for additional control of the effective bandgap through the period thickness and provide a type-II band alignment with long carrier lifetimes. All this leads to a strong enhancement of the external quantum efficiency under photovoltaic conditions with respect to bulk layers of equivalent thickness. Our results show that GaAsSb/GaAsN superlattices with short periods are the ideal (pseudo) material to be integrated in new GaAs/Ge-based multi-junction solar cells that could approach the theoretical efficiency limit