523 research outputs found
Entanglement and the Lower Bounds on the Speed of Quantum Evolution
The concept of quantum speed limit-time (QSL) was initially introduced as a
lower bound to the time interval that a given initial state may need
so as to evolve into a state orthogonal to itself. Recently [V. Giovannetti, S.
Lloyd, and L. Maccone, Phys. Rev. A {\bf 67}, 052109 (2003)] this bound has
been generalized to the case where does not necessarily evolve into an
orthogonal state, but into any other . It was pointed out that, for
certain classes of states, quantum entanglement enhances the evolution "speed"
of composite quantum systems. In this work we provide an exhaustive and
systematic QSL study for pure and mixed states belonging to the whole
15-dimensional space of two qubits, with a not necessarily orthogonal
state to . We display convincing evidence for a clear correlation
between concurrence, on the one hand, and the speed of quantum evolution
determined by the action of a rather general local Hamiltonian, on the other
one.Comment: 19 pages, 5 figure
Double quantum dot with tunable coupling in an enhancement-mode silicon metal-oxide semiconductor device with lateral geometry
We present transport measurements of a tunable silicon
metal-oxide-semiconductor double quantum dot device with lateral geometry.
Experimentally extracted gate-to-dot capacitances show that the device is
largely symmetric under the gate voltages applied. Intriguingly, these gate
voltages themselves are not symmetric. Comparison with numerical simulations
indicates that the applied gate voltages serve to offset an intrinsic asymmetry
in the physical device. We also show a transition from a large single dot to
two well isolated coupled dots, where the central gate of the device is used to
controllably tune the interdot coupling.Comment: 4 pages, 3 figures, to be published in Applied Physics Letter
Adaptación transcultural de un cuestionario para medir la calidad de vida de los pacientes con anticoagulación oral
ObjetivoAdaptar a la cultura y el idioma españoles un cuestionario desarrollado para evaluar la calidad de vida de los pacientes con tratamiento anticoagulante oral (TAO) y medir su validezDiseñoEstudio observacional, descriptivo, de validación de un instrumento de medida de calidad de vida relacionada con la salud. Emplazamiento. Atención primaria y atención especializadaParticipantesUn total de 225 pacientes que incluía a todos los pacientes de nuestro centro que utilizan TAO y una muestra consecutiva de pacientes con TAO del servicio de hematología del hospital de referenciaMediciones principalesTraducción directa,traducción inversa y prueba de validez. Análisis factorial y agrupación por dimensiones de los ítems, análisis de la consistencia interna y análisis de correlación ítem-total de la versión definitiva del cuestionario en españolResultadosLa edad media de los pacientes fue de 65 ± 13 años, el 51,1% era mujer y el 45,8% era controlado en atención primaria. En el estudio de validez se realizó un análisis factorial con la extracción de 5 factores que explican el 41,62% del valor total de la varianza y la obtención de una agrupación diferente de la original, con unvalor de alfa de Cronbach global de 0,82 y de 0,56–0,74 en las diferentes dimensiones y análisis de correlación ítem-total con valores estadísticamente significativos, excepto en la pregunta número 29ConclusionesTras realizar la adaptación a la cultura y el idioma españoles de un cuestionario desarrollado para evaluar la calidad de vida de los pacientes con TAO, se ha obtenido un instrumento útil y válido para nuestro entornoObjectiveTo adapt to Spanish culture and language a questionnaire developed to evaluate the quality of life of patients taking oral anticoagulation treatment (OAT) and to measure its validityDesignA descriptive observation study to validate an instrument to measure health-related quality of lifeSettingPrimary and specialist careParticipants225 patients, all the patients at our centre who were on OAT and a consecutive sample of patients on OAT from the referral hospital's haemotology serviceMain measurementsDirect translation, back- translation, and pilot study. Factor analysis and item-dimension grouping, internal consistency analysis and analysis of the item- total correlation of the definitive version of the questionnaire in SpanishResultsMean age was 65 (SD=13 years); 51% were women; 45.8% were monitored in PC. Validity study: factor analysis extracted 5 factors that explained 41.62% of total variance value and obtained a grouping different from the original; Cronbach's alpha was .82 overall and ran from .56 to .74 in the various dimensions; and item-total correlation analysis had statistically significant values,except for question 29ConclusionsAfter adaptation to Spanish culture and language of a questionnaire developed to evaluate the quality of life of patients taking OAT, it was found to be a useful instrument, valid for use in our milie
Photoelectrochemical water splitting with ITO/WO3/BiVO4/CoPi multishell nanotubes fabricated by soft-templating in vacuum
A well-established procedure for the photoelectrochemical (PEC) splitting of
water relies on using porous electrodes of WO3 sensitized with BiVO4 as a
visible scavenger photoanode semiconductor. In this work, we propose an evolved
photoelectrode fabricated by a soft-template approach consisting of supported
multishell nanotubes (NTs). These NTs are formed by a concentric layered
structure of indium tin oxide (ITO), WO3, and BiVO4, together with a final film
of cobalt phosphate (CoPi) co-catalyst. Photoelectrode manufacturing is easily
implemented at large scale and combines thermal evaporation of single
crystalline organic nanowires (ONWs), magnetron sputtering (for ITO and WO3),
solution dripping, and electrochemical deposition processes (for BiVO4 and
CoPi, respectively) plus annealing under mild conditions. The obtained NT
electrodes depict a large electrochemically active surface and outperform by
more than one order of magnitude the efficiency of equivalent planar-layered
electrodes. A thorough electrochemical analysis of the electrodes under blue
and solar light illumination demonstrates the critical role of the WO3/BiVO4
Schottky barrier heterojunction in the control of the NT electrode efficiency
and its dependence on the BiVO4 outer layer thickness. Oxygen evolution
reaction (OER) performance was maximized with the CoPi electrocatalyst,
rendering high photocurrents under one sun illumination. The reported results
demonstrate the potential of the soft-template methodology for the large area
fabrication of highly efficient multishell ITO/WO3/BiVO4/CoPi NT electrodes, or
other alternative combinations, for the photoelectrochemical splitting of
water.Comment: Manuscript: 39 pages, 8 figures and 1 table. SI: 15 pages, 9 figures
and 1 tabl
Harnessing a Vibroacoustic Mode for Enabling Smart Functions on Surface Acoustic Wave Devices -- Application to Icing Monitoring and Deicing
Microacoustic wave devices are essential components in the RF electronics and
MEMS industry with increasing impact in various sensing and actuation
applications. Reliable and smart operation of acoustic wave devices at low
costs would cause a crucial advancement. Herein, we present the enablement of
temperature and mechanical sensing capabilities in a Rayleigh-mode standing
surface acoustic wave (sSAW) chip device by harnessing an acoustic shear plate
wave mode using the same set of electrodes. Most importantly, this mode is
excited by switching the polarity of the sSAW transducer electrodes by simple
electronics, allowing for direct and inexpensive compatibility with an existing
setup. We validated the method in the emergent topic of surface de-icing by
continuously monitoring temperature and water liquid-solid phase changes using
the plate wave mode, and on-demand Rayleigh-wave deicing with a negligible
energy cost. The flexibility for adapting the system to different scenarios,
loads and scalability opens the path to impact in lab-on-a-chip, IoT
technology, and sectors requiring autonomous acoustic wave actuators.Comment: 8 pages, 3 figure
Development of a gas chromatography - mass spectrometry method for the determination of carbon disulfide in the atmosphere
[EN] Carbon disulfide (CS2), a relevant reduced sulfur compound in air, is well-known for its malodor and its significant effect on global atmospheric chemistry. Therefore, a reliable method for determining CS2 in atmospheric samples has been developed based on solid-phase sampling and gas chromatography-mass spectrometry (GC-MS). Two types of solid-phase sampling supports (Orbo-32 and SKC) and the elution with organic solvents - hexane and toluene - were evaluated for low-volume outdoor sampling. Recovery studies and the standard addition method were carried out to demonstrate the proper determination of CS2 in the absence of the influence of interferences such as ozone, hydrogen sulfide or water - important atmospheric pollutants. The proposed methodology was validated by performing experiments in a high-volume smog chamber and by comparison with two reference optical methods, Fourier Transform Infrared (FTIR) and Differential Optical Absorption Spectroscopy (DOAS) installed in these facilities. Satisfactory analytical parameters were reported: fast analysis, a correct repeatability of 6±1% and reproducibility of 14±3%, and low detection limits of 0.3-0.9pgm-3. Finally, the method was successfully applied to industrial samples near a pulp factory area, where a high correlation between industrial emissions and reported carbon disulfide concentrations were observed. © 2011 Elsevier B.V.The research leading to these results received funding from the Centro de Investigacion del Medio Ambiente (CIMA), Consejeria de Medio Ambiente, Gobierno de Cantabria. The Instituto Universitario CEAM-UMH is partly supported by Generalitat Valenciana, Fundacion Bancaja, and the projects GRACCIE (Consolider-Ingenio 2010) and FEEDBACKS (Prometeo - Generalitat Valenciana). We also acknowledged the European Community's Seventh Framework Program under the grant agreement no. 228335 (Eurochamp2), the Spanish Ministry of Science and Innovation, through INNPLANTA project: PCT-440000-2010-003 and the EUPHORE staff for their support in the chamber experiments. The authors also thank J.T.B. for his contribution.Borrás García, EM.; Ródenas, M.; Dieguez, J.; Pérez-García, M.; Lomba, R.; Lavin, J.; Tortajada-Genaro, LA. (2012). Development of a gas chromatography - mass spectrometry method for the determination of carbon disulfide in the atmosphere. Microchemical Journal. 101:37-42. https://doi.org/10.1016/j.microc.2011.10.002S374210
Laser induced enhancement of dichroism in supported silver nanoparticles deposited by evaporation at glancing angles
were deposited on flat substrates by physical vapor deposition in a glancing angle
configuration. The particles were characterized by scanning electron microscopy and atomic
force microscopy and their optical properties examined by UV–vis absorption spectroscopy
using linearly polarized light. It was found that, depending on the amount of deposited silver
and the evaporation angle, part of the ‘as-prepared’ samples present NPs characterized by an
anisotropic shape and a polarization dependent SPR absorption and different colors when
using polarized white light at 0 and 90 . Low-power irradiation of these materials with an
infrared Nd-YAG nanosecond laser in ambient conditions produced an enhancement in such
dichroism. At higher powers, the dichroism was lost and the SPR bands shifted to lower
wavelengths as a result of the reshaping of the silver NPs in the form of spheres. The possible
factors contributing to the observed changes in dichroism are discussed
Study of idfferential protein expression in healthy human skeletal muscles using electrophoresis bidimentional
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Rhodamine 6G and 800 intermolecular heteroaggregates embedded in PMMA for near-infrared wavelength shifting
The opto-electronic properties of small-molecules and functional dyes usually differ when incorporated into solid matrices with respect to their isolated form due to an aggregation phenomenon that alters their optical and fluorescent properties. These spectroscopic modifications are studied in the framework of the exciton theory of aggregates, which has been extensively applied in the literature for the study of molecular aggregates of the same type of molecules (homoaggregation). Despite the demonstrated potential of the control of the heteroaggregation process (aggregation of different types of molecules), most of the reported works are devoted to intramolecular aggregates, complex molecules formed by several chromophores attached by organic linkers. The intramolecular aggregates are specifically designed to hold a certain molecular structure that, on the basis of the exciton theory, modifies their optical and fluorescent properties with respect to the isolated chromophores that form the molecule. The present article describes in detail the incorporation of Rhodamine 6G (Rh6G) and 800 (Rh800) into polymeric matrices of poly-(methyl methacrylate), PMMA. The simultaneous incorporation of both dyes results in an enhanced fluorescent emission in the near-infrared (NIR), originating from the formation of ground-state Rh6G–Rh800 intermolecular heteroaggregates. The systematic control of the concentration of both rhodamines provides a model system for the elucidation of the heteroaggregate formation. The efficient energy transfer between Rh6G and Rh800 molecules can be used as wavelength shifters to convert effectively the light from visible to NIR, a very convenient wavelength range for many practical applications which make use of inexpensive commercial detectors and systems
Wetting Angles on Illuminated Ta2O5 Thin Films with Controlled Nanostructure
Ta2O5 thin films with different nanostructure and surface roughness have been prepared by electron evaporation
at different angles between the evaporation source and the substrates. Large variation of refraction indexes
(n) from 1.40 to 1.80 were obtained by changing the geometry of evaporation and/or by annealing the evaporated
films at increasing temperatures up to 1000 °C to make them crystalline. Very flat and compact thin films (n
) 2.02) were also obtained by assisting the growth by bombardment with O2
+ ions of 800 eV kinetic energy.
A similar correlation has been found between the wetting contact angle of water and the roughness of the
films for the evaporated and evaporated + annealed samples, irrespective of their procedure of preparation
and other microstructural characteristics. When the films were illuminated with UV light of h > Eg ) 4.2 eV
(Eg, band gap energy of Ta2O5), their surface became superhydrophilic (contact angle < 10°) in a way quite
similar to those reported for illuminated TiO2 thin films. The rate of transformation into the superhydrophilic
state was smaller for the crystalline than for the amorphous films, suggesting that in Ta2O5 the size of crystal
domains at the surface is an important parameter for the control of this kinetics. Changes in the water contact
angle on films illuminated with visible light were also found when they were subjected to implantation with
N2
+ ions of 800 eV kinetic energy. The origin of this photoactivity is discussed in terms of the electronic
band gap states associated with the nitrogen-implanted atoms. The possibility of preparing antireflective and
self-cleaning coatings of Ta2O5 is discussed
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