2,277 research outputs found
Optical implementability of the two-dimensional Quantum Walk
We propose an optical cavity implementation of the two-dimensional coined
quantum walk on the line. The implementation makes use of only classical
resources, and is tunable in the sense that a large number of different unitary
transformations can be implemented by tuning some parameters of the device.Comment: 9 pages, 3 figure
Collisionless Hydrodynamics of Doped Graphene in a Magnetic Field
The electrodynamics of a two-dimensional gas of massless fermions in graphene
is studied by a collisionless hydrodynamic approach. A low-energy dispersion
relation for the collective modes (plasmons) is derived both in the absence and
in the presence of a perpendicular magnetic field. The results for graphene are
compared to those for a standard two-dimensional gas of massive electrons. We
further compare the results within the classical hydrodynamic approach to the
full quantum mechanical calculation in the random phase approximation. The
low-energy dispersion relation is shown to be a good approximation at small
wave vectors. The limitations of this approach at higher order is also
discussed.Comment: 7 pages, 1 figur
La diagnosi de les habilitats cientÃfiques. Un instrument per a orientar l’e/a de les ciències en aules multiculturals
La recerca s'inicia el curs escolar 2007-08 i sorgeix de la necessitat de reflexionar respecte a la incorporació de l’alumnat nouvingut a les classes de Ciències que fem als instituts de secundà ria de Catalunya, principalment a les à rees on el percentatge d’alumnes amb diferents bagatges culturals supera el 20 % del total. Els factors que influeixen en la incorporació a les classes són diversos i difÃcilment abastables en una recerca com aquesta; aixà que ens hem centrat en l’avaluació de les habilitats cientÃfiques com a pas previ per a l’orientació de l’E/A de les Ciències en aules multiculturals. Suposà vem que la diagnosi era una eina molt interessant per optimitzar els E/A de les Ciències però, hem descobert que també ho és per fer aflorar les diferències culturals que haurÃem de tenir en compte a l’hora d’enfrontar unes classes multiculturals en un món globalitzat i canviant
Sex and Age-Related Differences in Neuroticism and Allostatic Load Index in Urban Patients with General Anxiety Disorder Treated with Alprazolam
Introduction: Allostatic Load (AL) index proposes indicators for the functioningof the main potentially stress-affected systems. Sex differences instress response and stress-related diseases susceptibility have been describedfor the general population. In this observational study we describe the effectsof sex and age on allostatic load variables, in a cohort of patients with generalanxiety disorders and neuroticism treated with alprazolam during 12 weeks,before and after treatment. Methods: Patients with general (DSM IV) anxietydisorders with >6 in Hamilton scale, Allostatic load (>1 Crimmins and SeemanAL modified criteria) and neuroticism >18 (NEO-FFI inventory), wereincluded. All patients completed psychiatric assessment, allostatic load indexdetermination before (−1 week) and after 12 weeks of treatment with alprazolam(0.25 - 1 mg/t.i.d). Allostatic load parameters comprised cardiovascular,metabolic and inflammatory variables. Univariate analysis (two-wayANOVA), Student?s t-test (related variables) and Pearson correlations weredetermined. Results: Fifty-four patients, 35 females (48.6 ± 11.7 years) and 19males (44.2 ± 12.8 years) with general anxiety disorder were included; 28 patientswith <50 years (60.7% females), and 26 with ≥50 years (69.2% females).Younger patients (<50 years) (two-way ANOVA, p = 0.02) were significantlyassociated with lower allostatic load index after treatment. However, womenshowed higher anxiety levels in both, before (Two-way ANOVA, p = 0.059)and after treatment (two-way ANOVA, p = 0.005), with a significantly betterprofile than men in many individual AL variables, particularly cardiovascular(systolic blood pressure), obesity (body mass index), and lipids (higher HDLlevels). After treatment a higher reduction of fibrinogen levels was found inmen (two-way ANOVA, p = 0.02). Conclusions: In this preliminary analysiswe described sex and age differences in psychiatry aspects and allostatic loadindexes in patients with general anxiety disorders in the short-term treatmentwith alprazolam. These considerations remark the need of pondering sex andage differences during the use of drugs for protracted periods.Fil: D`Alessio, Luciana. Universidad Nacional Arturo Jauretche. Unidad Ejecutora de Estudios en Neurociencias y Sistemas Complejos. Provincia de Buenos Aires. Ministerio de Salud. Hospital Alta Complejidad en Red El Cruce Dr. Néstor Carlos Kirchner Samic. Unidad Ejecutora de Estudios en Neurociencias y Sistemas Complejos. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - La Plata. Unidad Ejecutora de Estudios en Neurociencias y Sistemas Complejos; Argentina. Consejo Nacional de Investigaciones CientÃficas y Técnicas; ArgentinaFil: Soria, Carlos A.. Henri Laborit Institute Of Biosciences; ArgentinaFil: Remedi, Carolina. Henri Laborit Institute Of Biosciences; Argentina; ArgentinaFil: Roldán, Emilio J. A.. Instituto de NeurobiologÃa IDNEU; Argentin
Spin-wave amplification and lasing driven by inhomogeneous spin transfer torques
We show that an inhomogeneity in the spin-transfer torques in a metallic
ferromagnet under suitable conditions strongly amplifies incoming spin waves.
Moreover, at nonzero temperatures the incoming thermally occupied spin waves
will be amplified such that the region with inhomogeneous spin transfer torques
emits spin waves spontaneously, thus constituting a spin-wave laser. We
determine the spin-wave scattering amplitudes for a simplified model and
set-up, and show under which conditions the amplification and lasing occurs.
Our results are interpreted in terms of a so-called black-hole laser, and could
facilitate the field of magnonics, that aims to utilize spin waves in logic and
data-processing devices.Comment: 5 pages, 4 figure
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