1,394 research outputs found
Strain induced coherent dynamics of coupled carriers and Mn spins in a quantum dot
We report on the coherent dynamics of the spin of an individual magnetic atom
coupled to carriers in a semiconductor quantum dot which has been investigated
by resonant photoluminescence of the positively charged exciton (X+). We
demonstrate that a positively charged CdTe/ZnTe quantum dot doped with a single
Mn atom forms an ensemble of optical Lambda systems which can be addressed
independently. We show that the spin dynamics of the X+Mn complex is dominated
by the electron-Mn exchange interaction and report on the coherent dynamics of
the electron-Mn spin system that is directly observed in the time domain.
Quantum beats reflecting the coherent transfer of population between
electron-Mn spin states, which are mixed by an anisotropic strain in the plane
of the quantum dot, are clearly observed. We finally highlight that this strain
induced coherent coupling is tunable with an external magnetic field
Resonant photoluminescence and dynamics of a hybrid Mn-hole spin in a positively charged magnetic quantum dot
We analyze, through resonant photoluminescence, the spin dynamics of an
individual magnetic atom (Mn) coupled to a hole in a semiconductor quantum dot.
The hybrid Mn-hole spin and the positively charged exciton in a CdTe/ZnTe
quantum dot forms an ensemble of systems which can be addressed
optically. Auto-correlation of the resonant photoluminescence and resonant
optical pumping experiments are used to study the spin relaxation channels in
this multilevel spin system. We identified for the hybrid Mn-hole spin an
efficient relaxation channel driven by the interplay of the Mn-hole exchange
interaction and the coupling to acoustic phonons. We also show that the optical
systems are connected through inefficient spin-flips than can be
enhanced under weak transverse magnetic field. The dynamics of the resonant
photoluminescence in a p-doped magnetic quantum dot is well described by a
complete rate equation model. Our results suggest that long lived hybrid
Mn-hole spin could be obtained in quantum dot systems with large
heavy-hole/light-hole splitting
Cluster density functional theory for lattice models based on the theory of Mobius functions
Rosenfeld's fundamental measure theory for lattice models is given a rigorous
formulation in terms of the theory of Mobius functions of partially ordered
sets. The free-energy density functional is expressed as an expansion in a
finite set of lattice clusters. This set is endowed a partial order, so that
the coefficients of the cluster expansion are connected to its Mobius function.
Because of this, it is rigorously proven that a unique such expansion exists
for any lattice model. The low-density analysis of the free-energy functional
motivates a redefinition of the basic clusters (zero-dimensional cavities)
which guarantees a correct zero-density limit of the pair and triplet direct
correlation functions. This new definition extends Rosenfeld's theory to
lattice model with any kind of short-range interaction (repulsive or
attractive, hard or soft, one- or multi-component...). Finally, a proof is
given that these functionals have a consistent dimensional reduction, i.e. the
functional for dimension d' can be obtained from that for dimension d (d'<d) if
the latter is evaluated at a density profile confined to a d'-dimensional
subset.Comment: 21 pages, 2 figures, uses iopart.cls, as well as diagrams.sty
(included
Effectiveness of slow motion video compared to real time video in improving the accuracy and consistency of subjective gait analysis in dogs
Objective measures of canine gait quality via force plates, pressure mats or kinematic analysis are considered superior to subjective gait assessment (SGA). Despite research demonstrating that SGA does not accurately detect subtle lameness, it remains the most commonly performed diagnostic test for detecting lameness in dogs. This is largely because the financial, temporal and spatial requirements for existing objective gait analysis equipment makes this technology impractical for
use in general practice. The utility of slow motion video as a potential tool to augment SGA is currently untested. To evaluate a more accessible way to overcome the limitations of SGA, a slow motion video study was undertaken. Three experienced veterinarians reviewed video footage of 30 dogs, 15 with a diagnosis of primary limb lameness based on history and physical examination, and 15 with no indication of limb lameness based on history and physical examination. Four different videos were made for each dog, demonstrating each dog walking and trotting in real time, and then again walking and trotting in 50% slow motion. For each video, the veterinary raters assessed both the degree of lameness, and which limb(s) they felt represented the source of the lameness. Spearman’s rho, Cramer’s V, and t-tests were performed to determine if slow motion video increased either the accuracy or consistency of raters’ SGA relative to real time video. Raters demonstrated no significant increase in consistency or accuracy in their SGA of slow motion video relative to real time video. Based on these findings, slow motion video does not increase the consistency or accuracy of SGA values. Further research is required to determine if slow motion video will benefit SGA in other ways
Lattice density-functional theory of surface melting: the effect of a square-gradient correction
I use the method of classical density-functional theory in the
weighted-density approximation of Tarazona to investigate the phase diagram and
the interface structure of a two-dimensional lattice-gas model with three
phases -- vapour, liquid, and triangular solid. While a straightforward
mean-field treatment of the interparticle attraction is unable to give a stable
liquid phase, the correct phase diagram is obtained when including a suitably
chosen square-gradient term in the system grand potential. Taken this theory
for granted, I further examine the structure of the solid-vapour interface as
the triple point is approached from low temperature. Surprisingly, a novel
phase (rather than the liquid) is found to grow at the interface, exhibiting an
unusually long modulation along the interface normal. The conventional
surface-melting behaviour is recovered only by artificially restricting the
symmetries being available to the density field.Comment: 16 pages, 6 figure
SoK: Lending Pools in Decentralized Finance
Lending pools are decentralized applications which allow mutually untrusted users to lend and borrow crypto-assets. These applications feature complex, highly parametric incentive mechanisms to equilibrate the loan market. This complexity makes the behaviour of lending pools difficult to understand and to predict: indeed, ineffective incentives and attacks could potentially lead to emergent unwanted behaviours. Reasoning about lending pools is made even harder by the lack of executable models of their behaviour: to precisely understand how users interact with lending pools, eventually one has to inspect their implementations, where the incentive mechanisms are intertwined with low-level implementation details. Further, the variety of existing implementations makes it difficult to distill the common aspects of lending pools. We systematize the existing knowledge about lending pools, leveraging a new formal model of interactions with users, which reflects the archetypal features of mainstream implementations. This enables us to prove some general properties of lending pools, and to precisely describe vulnerabilities and attacks. We also discuss the role of lending pools in the broader context of decentralized finance and identify relevant research challenges
Density functional theory for nearest-neighbor exclusion lattice gasses in two and three dimensions
To speak about fundamental measure theory obliges to mention dimensional
crossover. This feature, inherent to the systems themselves, was incorporated
in the theory almost from the beginning. Although at first it was thought to be
a consistency check for the theory, it rapidly became its fundamental pillar,
thus becoming the only density functional theory which possesses such a
property. It is straightforward that dimensional crossover connects, for
instance, the parallel hard cube system (three-dimensional) with that of
squares (two-dimensional) and rods (one-dimensional). We show here that there
are many more connections which can be established in this way. Through them we
deduce from the functional for parallel hard (hyper)cubes in the simple
(hyper)cubic lattice the corresponding functionals for the nearest-neighbor
exclusion lattice gases in the square, triangular, simple cubic, face-centered
cubic, and body-centered cubic lattices. As an application, the bulk phase
diagram for all these systems is obtained.Comment: 13 pages, 13 figures; needs revtex
The NADES glyceline as a potential Green Solvent: A comprehensive study of its thermophysical properties and effect of water inclusion
In this paper, two Natural Deep Eutectic Solvents, glyceline (Gly) and glyceline-water (GlyW), containing choline chloride as acceptor H-bond compound and glycerol as donor H-bond group are studied. For glyceline the mole relation is 1 (choline chloride): 2 (glycerol) and for glyceline-water the mole relation is 1 (choline chloride): 1.99 (glycerol): 1.02 water. The ternary NADES has been synthetized and characterized chemically by NMR techniques for this work. Several thermophysical properties in a wide range of temperature (278.15–338.15)¿K and at atmospheric pressure (0.1¿MPa) have been measured for both compounds: density, , speed of sound, , refractive index, , surface tension,, isobaric molar heat capacity, , kinematic viscosity, , and electric conductivity,. Furthermore, some related properties have been also calculated: isobaric expansibility, , isentropic compressibility, , molar refraction, , entropy and enthalpy of surface formationper unit surface area ( and ), and dynamic viscosity, , and viscous flow and electrical conductivity activation energies. The results have been discussed in terms of the effect of temperature and the inclusion of water. We conclude that the compound containing water into the structure has a higher molar volume and a higher fluidity. The binary NADES (Gly) is a more structured liquid than ternary one (GlyW)
Nuevas modalidades de participación ciudadana en ciencia: hibridación, satelización y despatrimonialización
I La emergencia de los tecnocidanos
1. Legos, amateurs, nerds y tecnoácratas.
1.1 La construcción social de los públicos de la ciencia
1.2 La demanda social de participación en ciencia
1.3 Tecnoacracia: de los amateurs a los hackers
2. CriptopolÃticas: activismo y tecnologÃas de despliegue
2.1 La ciencia como gestión de datos
2.2 La GPL como motor de Internet
2.3 Bien común y open access
II La movilización de los tecnocidanos
3. Movilización de hÃbridos: nuevos actores y nuevos consensos
3.1 La irrupción de los hÃbridos
3.2 La polÃtica de los casos: tablas y comentarios
4. Satelización de e-sujetos: cálculo distribuido y popular power
4.1. Grid computing y wifi networks: la próxima revolución
4.2 La polÃtica de los casos: tablas y comentarios
5. Despatrimonialización de prácticas: open source y open access
5.1 La cultura hacker y el procomún
5.2 La polÃtica de los casos: tablas y comentarios
III La promesa de los tecnocidanos
6. Las nuevas encrucijadas de la tecnociencia: ciudadanÃa y participación
6.1 Resumen
6.2 Recomendaciones
6.3 BibliografÃa (resumen)La participación ciudadana en ciencia conoce en nuestra época una verdadera edad dorada. Hace apenas unas décadas era inimaginable la
creciente influencia que la ciudadanÃa iba a tener en la marcha de la ciencia. Y, aunque algunos movimientos de activistas contra las nucleares lograron en los 80 situar en la agenda polÃtica de muchos gobiernos la resistencia popular al desarrollo de esta fuente de energÃa, lo cierto es que la presencia hoy de las ONG en la toma de decisiones comienza a ser algo habitual y, en algunos casos, alcanza la condición de estructural.
Las sociedades modernas han necesitado explorar formas muy innovadoras de organización social que les permitan afrontar las nuevas encrucijadas a las que nos aboca la llamada sociedad del riesgo. Nadie
discute que estamos hablando de asuntos de extrema gravedad, como lo manifiesta la experiencia adquirida durante las anteriores crisis del SIDA, de los alimentos y cultivos transgénicos y de las vacas locas. En su conjunto, los tres casos señalados (entre los muchos que podrÃamos mencionar) comparten
algunos aspectos que aquà queremos subrayar. Quienes desde responsabilidades de gobierno o empresariales lamentaron el desbordamiento del tradicional sistema de expertos por los movimientos de agitación ciudadana, aprendieron que la gestión de estos conflictos tiene que ser menos vertical y más dialogante. Descubrieron también que no es fácil hacer frente a organizaciones que saben aprovechar muy bien las múltiples oportunidades que ofrecen las nuevas tecnologÃas de la información y de la comunicación (TIC).Fundación Española de Ciencia y TecnologÃa, FECYT (2004
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