11,049 research outputs found
Gauged Thirring Model in the Heisenberg Picture
We consider the (2+1)-dimensional gauged Thirring model in the Heisenberg
picture. In this context we evaluate the vacuum polarization tensor as well as
the corrected gauge boson propagator and address the issues of generation of
mass and dynamics for the gauge boson (in the limits of QED and Thirring
model as a gauge theory, respectively) due to the radiative corrections.Comment: 14 pages, LaTex, no figure
Causal Theory for the Gauged Thirring Model
We consider the (2+1)-dimensional massive Thirring model as a gauge theory,
with one fermion flavor, in the framework of the causal perturbation theory and
address the problem of dynamical mass generation for the gauge boson. In this
context we get an unambiguous expression for the coefficient of the induced
Chern-Simons term.Comment: LaTex, 21 pages, no figure
Radiative Corrections for the Gauged Thirring Model in Causal Perturbation Theory
We evaluate the one-loop fermion self-energy for the gauged Thirring model in
(2+1) dimensions, with one massive fermion flavor, in the framework of the
causal perturbation theory. In contrast to QED, the corresponding two-point
function turns out to be infrared finite on the mass shell. Then, by means of a
Ward identity, we derive the on-shell vertex correction and discuss the role
played by causality for nonrenormalizable theories.Comment: LaTex, 09 pages, no figures. Title changed and introduction enlarged.
To be published in Eur. Phys. J.
Axial Anomaly through Analytic Regularization
In this work we consider the 2-point Green's functions in (1+1) dimensional
quantum electrodynamics and show that the correct implementation of analytic
regularization gives a gauge invariant result for the vaccum polarization
amplitude and the correct coefficient for the axial anomaly.Comment: 8 pages, LaTeX, no figure
Glutathione release in extracellular form by S. cerevisiae strains
Glutathione (GSH, L-\uf067-glutamyl-L-cysteinyl-glycine) is the most abundant non-protein thiol compound widely present in living organisms, from prokaryotes to eukaryotes (Anderson 1998). It is synthesised intracellularly by the consecutive actions of \uf067-glutamylcysteine synthetase, feedback inhibited by GSH, and GSH synthetase. This tripeptide\u2019s very low redox potential gives it the properties of a cellular redox buffer (Udeh and Achremowicz 1997). In living tissues, GSH plays a pivotal role in bioreduction, protection against oxidative stress, xenobiotic and endogenous toxic metabolite detoxification, enzyme activity and sulphur and nitrogen metabolism (Penninckx 2002). These characteristics make this active tripeptide an important aid and/or support for the treatment of numerous diseases, such as HIV infections, liver cirrhosis, pancreatic inflammations and aging (Wu et al., 2004). In addition, GSH is of interest in the food additive industry and sports nutrition (Lomaestro and Malone 1995).
Yeasts, in particular belonging to the genus Saccharomyces, are the most commonly used microorganisms on an industrial scale for GSH fermentative production; however GSH contents of the wild-type strains are usually variable (0.1 \u2013 1% dw) and always in intracellular form (Rollini and Manzoni 2006).
The present research was aimed at obtaining GSH in extracellular form, released from cells, at high levels. Samples of S. cerevisiae (baker\u2019s yeast) from different suppliers were tested, together with reference strains belonging to international collections. Cells were comparatively treated employing physical and chemical procedures. The best result (2.9 g/l, 90% of produced GSH in extracellular form) was achieved at 24 h reaction, employing lyophilised cells from compressed baker\u2019s yeast. The possibility of obtaining GSH directly in extracellular form, skipping the downstream cell extraction step, represents an interesting opportunity of reducing GSH production cost and furthering the range of application and utilization of this molecule
Messiah: An ITS drive safety application
This article describes a novel safety application based on the open source navigation software OsmAnd,
which runs on the Android platform. The application offers vehicles with "smart navigation", and maintains a network
of the vehicles that use our application. The process of network creation and maintenance is important as
our application enables vehicles to communicate with one another to exchange useful information. The main
function of the application is to inform vehicles of relevant vehicles approaching, termed as "administrative
vehicles" in this article, and include ambulances, police cars and fire brigades. Based on the received
information, our application notifies the driver, who can now take navigation decisions based on it. While developing
the application, problems were found when attempting to create an Ad-hoc network. A solution to the problem of managing the Ad-hoc network has been proposed and is under development
A novel on-board Unit to accelerate the penetration of ITS services
In-vehicle connectivity has experienced a big expansion in recent years. Car manufacturers have mainly proposed OBU-based solutions, but these solutions do not take full advantage of the opportunities of inter-vehicle peer-to-peer communications. In this paper we introduce GRCBox, a novel architecture that allows OEM user-devices to directly communicate when located in neighboring vehicles. In this paper we also describe EYES, an application we developed to illustrate the type of novel applications that can be implemented on top of the GRCBox. EYES is an ITS overtaking assistance system that provides the driver with real-time video fed from the vehicle located in front. Finally, we evaluated the GRCbox and the EYES application and showed that, for device-to-device communication, the performance of the GRCBox architecture is comparable to an infrastructure network, introducing a negligible impact
Optimization of photon storage fidelity in ordered atomic arrays
A major application for atomic ensembles consists of a quantum memory for
light, in which an optical state can be reversibly converted to a collective
atomic excitation on demand. There exists a well-known fundamental bound on the
storage error, when the ensemble is describable by a continuous medium governed
by the Maxwell-Bloch equations. The validity of this model can break down,
however, in systems such as dense, ordered atomic arrays, where strong
interference in emission can give rise to phenomena such as subradiance and
"selective" radiance. Here, we develop a general formalism that finds the
maximum storage efficiency for a collection of atoms with discrete, known
positions, and a given spatial mode in which an optical field is sent. As an
example, we apply this technique to study a finite two-dimensional square array
of atoms. We show that such a system enables a storage error that scales with
atom number like ,
and that, remarkably, an array of just atoms in principle allows
for an efficiency comparable to a disordered ensemble with optical depth of
around 600.Comment: paper is now identical to published versio
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