Orbital and spin relaxation in single and coupled quantum dots

Phonon-induced orbital and spin relaxation rates of single electron states in lateral single and double quantum dots are obtained numerically for realistic materials parameters. The rates are calculated as a function of magnetic field and interdot coupling, at various field and quantum dot orientations. It is found that orbital relaxation is due to deformation potential phonons at low magnetic fields, while piezoelectric phonons dominate the relaxation at high fields. Spin relaxation, which is dominated by piezoelectric phonons, in single quantum dots is highly anisotropic due to the interplay of the Bychkov-Rashba and Dresselhaus spin-orbit couplings. Orbital relaxation in double dots varies strongly with the interdot coupling due to the cyclotron effects on the tunneling energy. Spin relaxation in double dots has an additional anisotropy due to anisotropic spin hot spots which otherwise cause giant enhancement of the rate at useful magnetic fields and interdot couplings. Conditions for the absence of the spin hot spots in in-plane magnetic fields (easy passages) and perpendicular magnetic fields (weak passages) are formulated analytically for different growth directions of the underlying heterostructure. It is shown that easy passages disappear (spin hot spots reappear) if the double dot system loses symmetry by an xy-like perturbation.Comment: 13 pages, 9 figure

Using quantum state protection via dissipation in a quantum-dot molecule to solve the Deutsch problem

The wide set of control parameters and reduced size scale make semiconductor quantum dots attractive candidates to implement solid-state quantum computation. Considering an asymmetric double quantum dot coupled by tunneling, we combine the action of a laser field and the spontaneous emission of the excitonic state to protect an arbitrary superposition state of the indirect exciton and ground state. As a by-product we show how to use the protected state to solve the Deutsch problem.Comment: 8 pages, 1 figure, 2 table

Spin relaxation in quantum dots with random spin-orbit coupling

We investigate the longitudinal spin relaxation arising due to spin-flip transitions accompanied by phonon emission in quantum dots where the strength of the Rashba spin-orbit coupling is a random function of the lateral (in-plane) coordinate on the spatial nanoscale. In this case the Rashba contribution to the spin-orbit coupling cannot be completely removed by applying a uniform external bias across the quantum dot plane. Due to the remnant random contribution, the spin relaxation rate cannot be decreased by more than two orders of magnitude even when the external bias fully compensates the regular part of the spin-orbit coupling.Comment: 13 pages, 4 figure

14C dating of the last Croscat volcano eruption (Garrotxa Region, NE Iberian Peninsula)

In this shortnote, we present the results of a geochronological study of the last eruption in the volcanic region of the Garrotxa (NE Iberian Peninsula). Four 14C analysis of organic matter contained in palaeosols located under volcanic pyroclastic fall deposits of the Croscat volcano were made. The samples gave ages between 13160 and 15710 years cal BP, and are in accord with our palynological analysis and climate reconstruction at that time. The ages that we report are the youngest obtained for volcanic activity in the Iberian Peninsula

Percepciones del consumidor sobre la carne de caprino en España

Se ha realizado una encuesta a consumidores (n=119) con el fin de conocer la percepción que tenían de la carne de caprino frente a la carne de ovino en función de diversos aspectos relacionados con la intención de compra y la percepción de su calidad. El cuestionario constó de 11 enunciados afirmativos, respondidos hedónicamente mediante una escala categórica de 7 puntos (1: “totalmente en desacuerdo”, 7: “totalmente de acuerdo”). El análisis de las respuestas se realizó mediante frecuencias. Los resultados obtenidos han demostrado, globalmente, una sensibilidad positiva hacia la carne de caprino tanto en parámetros decisivos a la hora de la intención de compra como en parámetros de calidad sensorial de la carne. Esto ha sucedido en contra de lo que podría pensarse dado, en nuestro país, el alto consumo y consideración de calidad que tiene la especie ovina.Comisión Interministerial de Ciencia y Tecnología AGL2005-05777- C02-01/GA

NOD1 downregulates intestinal serotonin transporter and interacts with other pattern recognition receptors

Serotonin (5-HT) is an essential gastrointestinal modulator whose effects regulate the intestinal physiology. 5-HT effects depend on extracellular 5-HT bioavailability, which is controlled by the serotonin transporter (SERT) expressed in both the apical and basolateral membranes of enterocytes. SERT is a critical target for regulating 5-HT levels and consequently, modulating the intestinal physiology. The deregulation of innate immune receptors has been extensively studied in inflammatory bowel diseases (IBD), where an exacerbated defense response to commensal microbiota is observed. Interestingly, many innate immune receptors seem to affect the serotonergic system, demonstrating a new way in which microbiota could modulate the intestinal physiology. Therefore, our aim was to analyze the effects of NOD1 activation on SERT function, as well as NOD1's interaction with other immune receptors such as TLR2 and TLR4. Our results showed that NOD1 activation inhibits SERT activity and expression in Caco-2/TC7 cells through the extracellular signal-regulated kinase (ERK) signaling pathway. A negative feedback between 5-HT and NOD1 expression was also described. The results showed that TLR2 and TLR4 activation seems to regulate NOD1 expression in Caco-2/TC7 cells. To assess the extend of cross-talk between NOD1 and TLRs, NOD1 expression was measured in the intestinal tract (ileum and colon) of wild type mice and mice with individual knockouts of TLR2, and TLR4 as well as double knockout TLR2/TLR4 mice. Hence, we demonstrate that NOD1 acts on the serotonergic system decreasing SERT activity and molecular expression. Additionally, NOD1 expression seems to be modulated by 5-HT and other immune receptors as TLR2 and TLR4. This study could clarify the relation between both the intestinal serotonergic system and innate immune system, and their implications in intestinal inflammation

Influencia de la raza sobre la aceptabilidad en el hogar de la carne de cabrito y comparación con la especie ovina

Las razas autóctonas caprinas españolas de aptitud cárnica, aunque cuentan con un censo relativamente escaso (22.000 cabezas en pureza), cumplen una importante misión como agentes valorizadores de zonas y recursos marginales y suponen una importante reserva de nuestro patrimonio genético. Desgraciadamente, en muchos casos, ni el potencial productivo ni la calidad de sus productos están medianamente estudiados. De todas las especies de rumiantes que existen en España, la única que no posee ninguna marca de calidad es la especie caprina. La consecución de alguna distinción de este tipo podría ayudar a mejorar las rentas de los productores, a la propia subsistencia de las distintas agrupaciones y a la revalorización de la carne de esta especie. Por otra parte, existe la creencia de que los resultados de investigación que se pueden obtener con otras especies (bovino y ovino fundamentalmente) pueden ser fácilmente aplicables a las cabras, lo cual es definitivamente incierto debido a las múltiples especificidades de la especie caprina, incluyendo su carne (Sierra y Sañudo, 1987; Morand- Fehr y Lebbie, 2004). Por todo ello, se plantea el siguiente objetivo: Estudio de la apreciación global, por parte del consumidor en condiciones reales de cocinado en el hogar, de la calidad de la carne del cabrito de diversas razas caprinas en comparación con ovinos lechales, que podrían ser considerados como un producto de calidad de referencia.Comisión Interministerial de Ciencia y Tecnología (CICYT) AGL2005-05777-C02-01/GA

Advances in the modeling of the Iberian thermal lithosphere and perspectives on deep geothermal studies

Renewable energy sources are key to achieve the transition toward clean energy system. Among them, the geothermal energy has a production whose effectiveness requires sufficient understanding of the temperature distribution and fluid circulation at depth, as well as of the lithological and petrophysical properties of the crust. The focus of this paper is twofold: first, we summarize the main advances in the development of new methodologies and numerical codes to characterize the properties of the thermal lithosphere in terms of its, temperature, density and composition; second, based on the compilation of available thermal modelling results, we present the depth of the thermal Lithosphere-Asthenosphere Boundary (LAB) of the Iberian Peninsula and the temperature distribution at crustal depths of 5, 10, and 20 km, in addition to at Moho level. At 5 km depth, the temperature is above 110 °C with local anomalies (> 130 °C) located in the Iberian Massif and Cenozoic volcanic provinces. A similar pattern is observed at 10 and 20 km depth, where temperatures are above 190 °C and 350 °C, respectively. At 20 km depth, anomalies above > 500 °C, delineate the SE and NE Cenozoic volcanic provinces. At Moho depths, temperature ranges from 450 to 800 °C with hot regions mainly located along the Iberian Massif and the SE and NE volcanic provinces. The compiled results do not show any lithospheric anomaly that could give rise to high temperatures at shallow depths, but they do show an acceptable exploitation potential at intermediate depths. With regard to the direct use of district and greenhouse heating and for industrial processes, the potential is great throughout the Peninsula, the main challenges being the availability of groundwater and drilling costs

Non-alcoholic fatty liver in hereditary fructose intolerance

Background: Non-alcoholic fatty liver disease (NAFLD) is characterized by fat accumulation affecting >5% of the liver volume that is not explained by alcohol abuse. It is known that fructose gives rise to NAFLD and it has been recently described that the ingestion of fructose in low amounts in aldolase B deficient mice is associated with the development of fatty liver. Therefore, it is reasonable that patients with HFI (Hereditary Fructose Intolerance) present fatty liver at diagnosis, but its prevalence in patients treated and with adequate follow-up is not well documented in the literature. The aim of this study is to analyze the association between HFI and NAFLD in treated patients. Methods: A cross-sectional observational study was conducted. The population comprised 16 genetically diagnosed HFI patients aged from 3 years to 48 and in dietary treatment of fructose, sorbitol and sacarose exclusion at least for two years. Blood samples were obtained for analytical studies and anthropometric measurements of each patient were performed. Results: Patients presented a Body Mass Index (BMI) of 17.9 ± 2.9 kg/m 2 . The HOMA index and Quick index were in normal range for our population. The S-adenosyl-methionine (SAM)/S-adenosyl-L-homocysteine (SAH) ratio was increased in the patients in whom this analysis was performed. By imaging techniques it was observed that 9 of the 16 patients presented fatty liver (7 by hepatic MRI). Of these 9 patients, only 3 presented hepatomegaly. 7 of 9 patients affected by the c.448G > C mutation had fatty infiltration, of which three of them presented in addition hepatomegaly. Conclusions: There is a high prevalence of fatty liver in HFI patients and it is not related to obesity and insulin resistance. The diagnosis of fatty liver in HFI patients and, above all, the identification of new therapeutic approaches, can positively impact the quality of life of these patients