Spin-orbit interaction and spin relaxation in a two-dimensional electron gas

Using time-resolved Faraday rotation, the drift-induced spin-orbit Field of a two-dimensional electron gas in an InGaAs quantum well is measured. Including measurements of the electron mobility, the Dresselhaus and Rashba coefficients are determined as a function of temperature between 10 and 80 K. By comparing the relative size of these terms with a measured in-plane anisotropy of the spin dephasing rate, the D'yakonv-Perel' contribution to spin dephasing is estimated. The measured dephasing rate is significantly larger than this, which can only partially be explained by an inhomogeneous g-factor.Comment: 6 pages, 5 figure

Photocurrent in nanostructures with asymmetric antidots

The steady current induced by electromagnetic field in a 2D system with asymmetric scatterers is studied. The scatterers are assumed to be oriented cuts with one diffusive and another specular sides. Besides, the existence of isotropic impurity scatterers is assumed. This simple model simulates the lattice of half-disk which have been studied numerically recently. The model allows the exact solution in the framework of the kinetic equation. The static current response in the second order of electric field is obtained. The photogalvanic tensor contains both responses to linear and circular polarization of electromagnetic field. The model possesses non-analyticity with regards to the rate of impurity scattering.Comment: 9 pages, 6 figure

Colgajos libres en cirugía de la mano: nuestra experiencia en 49 casos

ResumenObjetivoRevisar los colgajos libres utilizados más frecuentemente en la reconstrucción de la mano y evaluar sus resultados, ventajas y complicaciones.Material y métodoEntre el 2011 y el 2014, 49 pacientes fueron intervenidos mediante diferentes transferencias microquirúrgicas, con una edad media de 41 años (25-57). En función de la localización del defecto, se han realizado: a) 29 colgajos libres para los dedos; b) 11 transferencias libres para cobertura de la mano, diferenciando entre zona dorsal de la mano y primera comisura: 5 pacientes; zona volar: 2 pacientes, y cobertura de ambas simultáneamente: 4 pacientes, y c) 9 transferencias óseas vascularizadas para seudoartosis (7 casos) y reconstrucción de articulaciones (2 casos) en la mano y los dedos.Los resultados fueron evaluados en términos de supervivencia del colgajo, complicaciones, reintervenciones y satisfacción del paciente. Además, en los casos de afectación de los pulpejos de los dedos, también se valoró el índice de discriminación de 2 puntos.ResultadosEl porcentaje de supervivencia del colgajo fue del 100%. En 5 casos fue necesaria una tenoartrólisis secundaria y en otro caso (lateral de brazo para cobertura volar de 4 dedos) se intervino al paciente en 2 ocasiones más para la separación completa de los dedos. Se obtuvieron buenos resultados estéticos y funcionales en todos los pacientes, con alto grado de satisfacción. Los pacientes con afectación del pulpejo obtuvieron una media en el índice de discriminación de 2 puntos de 9,1mm (8-11).ConclusionesEn nuestra opinión, el uso de colgajos libres en cirugía de la mano proporciona un mejor resultado, sin sacrificar —a diferencia de los colgajos locales—, otras zonas sanas de la mano, consiguiéndose una mínima morbilidad de la zona donante y muy buenos resultados estéticos y funcionales.AbstractObjectiveTo review the free flaps most frequently used in hand reconstruction and evaluate their results, advantages and complications.Material and methodsA total of 49 patients, with a mean age of 41 years old (25-57), underwent different microsurgical transfers for hand reconstruction between 2011 and 2014. The type of transfer performed depended on the location of the defects: a) 29 free flaps for finger reconstruction, b) 11 free transfers for hand coverage (dorsal coverage and first web space: 5 patients; volar hand defects: 2 patients; coverage of both regions of the hand at the same time: 4 patients, and c) 9 free vascularised bone transfers for non-unions (7 cases) and joint reconstructions (2 cases) in hand and fingers.The results were evaluated in terms of flap survival, complications, secondary procedures, and patient satisfaction. In addition, when fingertip reconstruction was involved, the two-point discrimination test was also assessed.ResultsThe survival rate was 100%. A secondary tenolysis was necessary in 5 cases, and another patient underwent two more surgeries to split the fingers (lateral arm used for volar coverage of the fingers). Good aesthetic and functional results and a high level of satisfaction were obtained. The means 2-PD in fingertip reconstruction was 9.1mm (8-11).ConclusionsIn our opinion, the use of free flaps for hand surgery reconstruction provides better outcomes, without sacrificing, in contrast to local flaps, other areas of the hand, with good aesthetic and functional results, as well as low donor site morbidity

Ofd1 Controls Dorso-Ventral Patterning and Axoneme Elongation during Embryonic Brain Development.

Oral-facial-digital type I syndrome (OFDI) is a human X-linked dominant-male-lethal developmental disorder caused by mutations in the OFD1 gene. Similar to other inherited disorders associated to ciliary dysfunction OFD type I patients display neurological abnormalities. We characterized the neuronal phenotype that results from Ofd1 inactivation in early phases of mouse embryonic development and at post-natal stages. We determined that Ofd1 plays a crucial role in forebrain development, and in particular, in the control of dorso-ventral patterning and early corticogenesis. We observed abnormal activation of Sonic hedgehog (Shh), a major pathway modulating brain development. Ultrastructural studies demonstrated that early Ofd1 inactivation results in the absence of ciliary axonemes despite the presence of mature basal bodies that are correctly orientated and docked. Ofd1 inducible-mediated inactivation at birth does not affect ciliogenesis in the cortex, suggesting a developmental stage-dependent role for a basal body protein in ciliogenesis. Moreover, we showed defects in cytoskeletal organization and apical-basal polarity in Ofd1 mutant embryos, most likely due to lack of ciliary axonemes. Thus, the present study identifies Ofd1 as a developmental disease gene that is critical for forebrain development and ciliogenesis in embryonic life, and indicates that Ofd1 functions after docking and before elaboration of the axoneme in vivo

Target Motion Variability and On-Line Positioning Accuracy during External-Beam Radiation Therapy of Prostate Cancer with an Endorectal Balloon Device

Purpose:: To prospectively define the setup error and the interfraction prostate localization accuracy of the planning target volume (PTV) in the presence of an endorectal balloon (ERB) device. Patients and Methods:: Weekly portal images (PIs) of 15 patients undergoing external-beam radiotherapy were analyzed. Displacements of the isocenter and the center of the ERB were measured. The setup and target motion variability were assessed with regard to the position variability of the ERB. Results:: The setup error was random and target motion variability was largest in the craniocaudal direction. The mean displacement of the isocenter was 2.1 mm (± 1.2 mm SD [standard deviation]), 2.4 mm (± 2.2 mm SD), and 3.8 mm (± 4.0 mm SD) in the left-right, craniocaudal, and anteroposterior directions, respectively (p = 0.1). The mean displacement of the ERB was 2.0 mm (± 1.4 mm SD), 4.1 mm (± 2.0 mm SD), and 3.8 mm (± 3.3 mm SD; p = 0.03). Setup margin and internal margin contributed equally to the PTV margin. Cumulative placement insecurity of the field and the ERB together was 4.0 mm (± 2.1 mm SD) laterally, 6.4 mm (± 2.5 mm SD) craniocaudally, and 7.7 mm (± 7.0 mm SD) anteroposteriorly. The 95% CIs (confidence intervals) were 2.9-5.2 mm, 5.1-7.8 mm, and 3.8-11.5 mm. In 35% of cases, the estimation of the dorsal margin exceeded 1 cm. Conclusion:: Margin estimate dorsally may exceed 1 cm and on-line position verification with an ERB cannot be recommended for dose escalation > 70 G

Photogalvanic current in artificial asymmetric nanostructures

We develop a theoretic description of the photogalvanic current induced by a high frequency radiation in asymmetric nanostructures and show that it describes well the results of numerical simulations. Our studies allow to understand the origin of the electronic ratchet transport in such systems and show that they can be used for creation of new types of detectors operating at room temperature in a terahertz radiation range.Comment: 11 pages, 9 figs, EPJ latex styl

Gate-controlled spin-orbit interaction in a parabolic GaAs/AlGaAs quantum well

We study the tunability of the spin-orbit interaction in a two-dimensional electron gas with a front and a back gate electrode by monitoring the spin precession frequency of drifting electrons using time-resolved Kerr rotation. The Rashba spin splitting can be tuned by the gate biases, while we find a small Dresselhaus splitting that depends only weakly on the gating. We determine the absolute values and signs of the two components and show that for zero Rashba spin splitting the anisotropy of the spin-dephasing rate vanishes.Comment: 5 pages, 3 figure

First results on proton radiography with nuclear emulsion detectors

We propose an innovative method for proton radiography based on nuclear emulsion film detectors, a technique in which images are obtained by measuring the position and the residual range of protons passing through the patient's body. For this purpose, nuclear emulsion films interleaved with tissue equivalent absorbers can be used to reconstruct proton tracks with very high accuracy. This is performed through a fully automated scanning procedure employing optical microscopy, routinely used in neutrino physics experiments. Proton radiography can be used in proton therapy to obtain direct information on the average tissue density for treatment planning optimization and to perform imaging with very low dose to the patient. The first prototype of a nuclear emulsion based detector has been conceived, constructed and tested with a therapeutic proton beam. The first promising experimental results have been obtained by imaging simple phantoms.Comment: Submitted to Journal of Instrumentation (JINST