927 research outputs found
Alternative resonance energy transfer mechanisms in polymer light harvesting
Dendrimeric polymers are a subject of considerable interest, particularly for their applications in energy harvesting devices, but also in organic light-emitting diodes, photosensitizers, quantum logic devices and low-threshold lasers. The distinctive light harvesting characteristics of these materials owe their origin to the speed, efficiency and highly directed nature of the multi-step processes that deliver captured light energy to the core. Recently it has been shown how iterative calculations, based on a matrix representation of the connectivity and propensity for energy transfer between different chromophores, effectively model the time-dependent flux of energy within dendrimer materials. This paper reports the formulation and results of an extended approach, accommodating additional mechanisms by means of which excitations of energy higher than the incoming photons can be generated and propagated towards a trap. It is also shown how the structure of the dendrimer and the operation of a spectroscopic gradient affect this energy flow. These mechanisms explain experimental observations in which energy coupling of four photons or more is observed in large aryl ether azodendrimers, at relatively low levels of irradiance
Effect of the Gribov horizon on the Polyakov loop and vice versa
We consider finite temperature SU(2) gauge theory in the continuum
formulation, which necessitates the choice of a gauge fixing. Choosing the
Landau gauge, the existing gauge copies are taken into account by means of the
Gribov-Zwanziger (GZ) quantization scheme, which entails the introduction of a
dynamical mass scale (Gribov mass) directly influencing the Green functions of
the theory. Here, we determine simultaneously the Polyakov loop (vacuum
expectation value) and Gribov mass in terms of temperature, by minimizing the
vacuum energy w.r.t. the Polyakov loop parameter and solving the Gribov gap
equation. Inspired by the Casimir energy-style of computation, we illustrate
the usage of Zeta function regularization in finite temperature calculations.
Our main result is that the Gribov mass directly feels the deconfinement
transition, visible from a cusp occurring at the same temperature where the
Polyakov loop becomes nonzero. In this exploratory work we mainly restrict
ourselves to the original Gribov-Zwanziger quantization procedure in order to
illustrate the approach and the potential direct link between the vacuum
structure of the theory (dynamical mass scales) and (de)confinement. We also
present a first look at the critical temperature obtained from the Refined
Gribov-Zwanziger approach. Finally, a particular problem for the pressure at
low temperatures is reported.Comment: 19 pages, 8 .pdf figures. v2: extended section 3 + extra references;
version accepted for publication in EPJ
Penicillin Allergy Assessment and Skin Testing in the Outpatient Setting
Penicillin allergies are among of the most commonly reported allergies, yet only 10% of these patients are truly allergic. This leads to potential inadvertent negative consequences for patients and makes treatment decisions challenging for clinicians. Thus, allergy assessment and penicillin skin testing (PST) are important management strategies to reconcile and clarify labeled penicillin allergies. While PST is more common in the inpatient setting where the results will immediately impact antibiotic management, this process is becoming of increasing importance in the outpatient setting. PST in the outpatient setting allows clinicians to proactively de-label and educate patients accordingly so beta-lactam antibiotics may be appropriately prescribed when necessary for future infections. While allergists have primarily been responsible for PST in the outpatient setting, there is an increasing role for pharmacist involvement in the process. This review highlights the importance of penicillin allergy assessments, considerations for PST in the outpatient setting, education and advocacy for patients and clinicians, and the pharmacist’s role in outpatient PST
SU(2) x U(1) Yang-Mills theories in 3d with Higgs field and Gribov ambiguity
We study the structure of the gauge propagators of a 3d version of the electroweak interaction in terms of the Higgs vacuum expectation value., of the non-Abelian gauge coupling g, and of the Abelian gauge coupling g', when nonperturbative effects related to the non-Abelian gauge fixing are introduced by means of an adapted path integral measure. In the perturbative regime of small nonAbelian coupling g and sufficiently large, nu the well-known standard Z and W propagators are recovered, together with a massless photon. In general, depending on the relative magnitudes of g, g' and., we uncover a quite different propagator structure. In a later stage of research, the results here derived can be used to study the associated phase diagram in more depth
A modified Brazilian test for the generalized-fracturetoughness determination in multimaterial corners. Numerical and experimental results
IX CONGRESO NACIONAL DE
MATERIALES COMPUESTOS. Celebrado en
Girona, 5, 6, 7 y 8 de julio de 2011In the present work, a general procedure for the experimental evaluation of the
generalized fracture toughness in multimaterial corners is defined. The proposed
method is suitable for closed corners (all material wedges being bonded) having two
singular terms in the asymptotic stress representation at the corner tip. For a particular
corner configuration, the method finds the load configuration at which one of the
singular terms vanishes, thus the main stress contribution being controlled by the other
non-vanishing singular term. The experimental test, until failure, using the previously
defined load configuration allows the generalized fracture toughness associated to each
singular term to be evaluated. The whole procedure has been applied to a bimaterial
CFRP-Adhesive bimaterial corner and the generalized fracture toughness values have
been obtained. The testing of mixed modes has permitted a failure envelope based on
the generalized fracture toughness values at the corner tip to be defined. Previously
published results, with different geometries, but involving the same corner, have shown
that the failure envelope can predict accurately the failure initiation at these corners.Junta de Andalucía y Fondo Social Europeo P08-TEP-4071Junta de Andalucía y Fondo Social Europeo P08-TEP-4051Ministerio de Ciencia e Innovación MAT2009-14022CAPES Ministerio de Educación de Brasi
U(1) Noncommutative Gauge Fields and Magnetogenesis
The connection between the Lorentz invariance violation in the lagrangean
context and the quantum theory of noncommutative fields is established for the
U(1) gauge field. The modified Maxwell equations coincide with other
derivations obtained using different procedures. These modified equations are
interpreted as describing macroscopic ones in a polarized and magnetized
medium. A tiny magnetic field (seed) emerges as particular static solution that
gradually increases once the modified Maxwell equations are solved as a
self-consistent equations system.Comment: 4 page
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