4,693 research outputs found
The entangling side of the Unruh-Hawking effect
We show that the Unruh effect can create net quantum entanglement between
inertial and accelerated observers depending on the choice of the inertial
state. This striking result banishes the extended belief that the Unruh effect
can only destroy entanglement and furthermore provides a new and unexpected
source for finding experimental evidence of the Unruh and Hawking effects.Comment: 4 pages, 4 figures. Added Journal referenc
Impact of Gamma Radiation on Dynamic RDSON Characteristics in AlGaN/GaN Power HEMTs
GaN high-electron-mobility transistors (HEMTs) are promising next-generation devices in the power electronics field which can coexist with silicon semiconductors, mainly in some radiation-intensive environments, such as power space converters, where high frequencies and voltages are also needed. Its wide band gap (WBG), large breakdown electric field, and thermal stability improve actual silicon performances. However, at the moment, GaN HEMT technology suffers from some reliability issues, one of the more relevant of which is the dynamic on-state resistance (RON_dyn) regarding power switching converter applications. In this study, we focused on the drain-to-source on-resistance (RDSON) characteristics under 60Co gamma radiation of two different commercial power GaN HEMT structures. Different bias conditions were applied to both structures during irradiation and some static measurements, such as threshold voltage and leakage currents, were performed. Additionally, dynamic resistance was measured to obtain practical information about device trapping under radiation during switching mode, and how trapping in the device is affected by gamma radiation. The experimental results showed a high dependence on the HEMT structure and the bias condition applied during irradiation. Specifically, a free current collapse structure showed great stability until 3.7 Mrad(Si), unlike the other structure tested, which showed high degradation of the parameters measured. The changes were demonstrated to be due to trapping effects generated or enhanced by gamma radiation. These new results obtained about RON_dyn will help elucidate trap behaviors in switching transistors
Political allegation and literary speech in "¡Vámonos con Pancho Villa! y Se llevaron el cañón para Bachimba" by Rafael F. Muñoz
El presente artÃculo muestra el valor literario e ideológico de la narrativa de Rafael F. Muñoz y, más particularmente de sus dos novelas. A lo largo de él se analizan ¡Vámonos con Pancho Villa! y Se llevaron el cañón para Bachimba como ejemplos de obras que responden a las polémicas literarias y polÃticas de su tiempo sirviéndose de la figura de Pancho Villa.The present article shows the literary and ideological value of the narrative of Rafael F. Muñoz and, more particularly of his two novels. Along him they are analyzed ¡Vámonos con Pancho Villa! and Se llevaron el cañón para Bachimba as examples of works that answer to the literary and political polemics of his time being served Pancho Villa's figure
Mechanical systems subjected to generalized nonholonomic constraints
We study mechanical systems subject to constraint functions that can be
dependent at some points and independent at the rest. Such systems are modelled
by means of generalized codistributions. We discuss how the constraint force
can transmit an impulse to the motion at the points of dependence and derive an
explicit formula to obtain the ``post-impact'' momentum in terms of the
``pre-impact'' momentum.Comment: 24 pages, no figure
Physical qubits from charged particles: IR divergences in quantum information
We consider soft photons effects (IR structure of QED) on the construction of
physical qubits. Soft-photons appear when we build charged qubits from the
asymptotic states of QED. This construction is necessary in order to include
the effect of soft photons on entanglement measures. The nonexistence of free
charged particles (due to the long range of QED interactions) lead us to
question the sense of the very concept of free charged qubit. In this letter,
using the "dressing" formalism, we build physical charged qubits from dressed
fields which have the correct asymptotic behavior, are gauge invariant, their
propagators have a particle pole structure and are free from infrared
divergences. Finally, we discuss the impact of the soft corrections on the
entanglement measures.Comment: 4 pages, 2 figures, RevTeX. Version 2: Some references update
Global controllability tests for geometric hybrid control systems
Hybrid systems are characterized by having an interaction between continuous
dynamics and discrete events. The contribution of this paper is to provide
hybrid systems with a novel geometric formulation so that controls can be
added. Using this framework we describe some new global controllability tests
for hybrid control systems exploiting the geometry and the topology of the set
of jump points, where the instantaneous change of dynamics take place.
Controllability is understood as the existence of a feasible trajectory for the
system joining any two given points. As a result we describe examples where
none of the continuous control systems are controllable, but the associated
hybrid system is controllable because of the characteristics of the jump set.Comment: 27 pages, 5 figure
Unveiling quantum entanglement degradation near a Schwarzschild black hole
We analyze the entanglement degradation provoked by the Hawking effect in a
bipartite system Alice-Rob when Rob is in the proximities of a Schwarzschild
black hole while Alice is free falling into it. We will obtain the limit in
which the tools imported from the Unruh entanglement degradation phenomenon can
be used properly, keeping control on the approximation. As a result, we will be
able to determine the degree of entanglement as a function of the distance of
Rob to the event horizon, the mass of the black hole, and the frequency of
Rob's entangled modes. By means of this analysis we will show that all the
interesting phenomena occur in the vicinity of the event horizon and that the
presence of event horizons do not effectively degrade the entanglement when Rob
is far off the black hole. The universality of the phenomenon is presented:
There are not fundamental differences for different masses when working in the
natural unit system adapted to each black hole. We also discuss some aspects of
the localization of Alice and Rob states. All this study is done without using
the single mode approximation.Comment: 16 pages, 10 figures, revtex4. Added Journal referenc
Biorefineries: Achievements and challenges for a bio-based economy
Funding
This work was supported by a project (FQM-176) financed
by the Junta de AndalucÃa. FM-M, acknowledges the support
from the Global Challenges Research Fund from Swansea
University, and from the Royal Society of Chemistry
Enablement Grant (E21-7051491439).Climate change, socioeconomical pressures, and new policy and legislation are
driving a decarbonization process across industries, with a critical shift from a
fossil-based economy toward a biomass-based one. This new paradigm implies
not only a gradual phasing out of fossil fuels as a source of energy but also a
move away from crude oil as a source of platform chemicals, polymers, drugs,
solvents and many other critical materials, and consumer goods that are
ubiquitous in our everyday life. If we are to achieve the United Nations’
Sustainable Development Goals, crude oil must be substituted by renewable
sources, and in this evolution, biorefineries arise as the critical alternative to
traditional refineries for producing fuels, chemical building blocks, and materials
out of non-edible biomass and biomass waste. State-of-the-art biorefineries
already produce cost-competitive chemicals and materials, but other products
remain challenging from the economic point of view, or their scaled-up
production processes are still not sufficiently developed. In particular, lignin’s
depolymerization is a required milestone for the success of integrated
biorefineries, and better catalysts and processes must be improved to
prepare bio-based aromatic simple molecules. This review summarizes
current challenges in biorefinery systems, while it suggests possible
directions and goals for sustainable development in the years to come.Project (FQM-176) financed by the Junta de AndalucÃaGlobal Challenges Research Fund from Swansea UniversityRoyal Society of Chemistry Enablement Grant (E21-7051491439
Understanding the impact of line-of-sight in the ergodic spectral efficiency of cellular networks
In this paper we investigate the impact of lineof-sight (LoS) condition in the ergodic spectral efficiency of cellular networks. To achieve this goal, we have considered the kappa-mu shadowed model, which is a general model that provides an excellent fit to a wide set of propagation conditions. To overcome the mathematical complexity of the analysis, we have split the analysis between large and small-scale effects. Building on the proposed framework, we study a number of scenarios that range from heavily-fluctuating LoS to deterministic-LoS. Finally, we shed light on the interplay between fading severity and spectral efficiency by means of the amount of fading.Universidad de Málaga. Campus de Excelencia Internacional AndalucÃa Tech
Complicaciones en el uso de aloinjertos intercalares tras resección de tumores óseos
La reconstrucción ósea mediante aloinjertos intercalares es una técnica de uso frecuente tras resecciones tumorales, que presenta -a largo plazo- mejores resultados que las endoprótesis diafisarias o los autoinjertos vascularizados. Sin embargo, entre las complicaciones más frecuentes destacan las infecciones y las fracturas del aloinjero asociadas a roturas o aflojamientos de la osteosÃntesis. Se presentan dos casos tratados con reconstrucciones de este tipo en los que el sistema de osteosÃntesis utilizado fracasó, en uno de ellos de forma repetida.The reconstruction of skeletal defects using bone allografts is a frequent procedure after tumoral resections associated to good long-term results, usually better than diaphyseal endoprostheses or autologous grafts. Nevertheless, there are some complications: infection and allograft fracture associated with failure or broken fixation. We report two cases of bone reconstruction in who the fixation failed, twice in one of them
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