598 research outputs found
Instanton-like Excitations in 2D Fermionic Field Theory
New non-perturbatives excitations in the massless Thirring and Schwinger
models are discussed.Comment: Revtex, 9pp, to be published in New Trends in Theoretical Physic
On the determination of constitutive parametersin a hyperelastic model for a soft tissue
The aim of this paper is to study a model of hyperelastic materials and itsapplications into soft tissue mechanics. In particular, we first determine an unbounded domain of the constitutive parameters of the model making our smoothstrain energy function to be polyconvex and hence satisfying the Legendre–Hadamard condition. Thus, physically reasonable material behaviour are described by our model with these parameters and a plently of tissues can betreated. Furthermore, we localize bounded subsets of constitutive parameters in fixed physical and very general bounds and then introduce a family of descrete stress–strain curves. Whence, various classes of tissues are characterized. Ourgeneral approach is based on a detailed analytical study of the first Piola–Kirchhoff stress tensor through its dependence on the invariants and on the constitutive parameters. The uniqueness of parameters for one tissue is discussed by introducing the notion of manifold of constitutive parameters, whichis locally represented by possibly different physical quantities. The advantage of our study is that we show a possible way to improve of the usual approachesshown in the literature which are mainly based on the minimization of a costfunction as the difference between experimental and model results
A weak KAM approach to the periodic stationary Hartree equation
AbstractWe present, through weak KAM theory, an investigation of the stationary Hartree equation in the periodic setting. More in details, we study the Mean Field asymptotics of quantum many body operators thanks to various integral identities providing the energy of the ground state and the minimum value of the Hartree functional. Finally, the ground state of the multiple-well case is studied in the semiclassical asymptotics thanks to the Agmon metric
Inflation and late-time accelerated expansion driven by -essence degenerate dynamics
We consider a k-essence model in which a single scalar field can be
responsible for both primordial inflation and the present observed acceleration
of the cosmological background geometry, while also admitting a nonsingular de
Sitter beginning of the Universe (it arises from de Sitter and ends in de
Sitter). The early one is driven by a slow-roll potential, and the late one is
driven by a dynamical dimensional reduction process which freezes the scalar
field in a degenerate surface, turning it into a cosmological constant. This is
done by proposing a realizable stable cosmic time crystal, although giving a
different interpretation to the ''moving ground stat'', in which there is no
motion because the system loses degrees of freedom. Furthermore, the model is
free of pathologies such as propagating superluminal perturbations, negative
energies, and perturbation instabilities.Comment: 11 pages, 2 figures. Replaced to match published versio
Analysis of Deterioration in a Plasma Focus Device
Indexación: Scopus.The Plasma Focus (PF) is a kind of dense transient plasmas in with high-pulsed voltage. To produce devices for eld application it is necessary to obtain PF equipment able to operate for a long period of time. Thus, a reliability analysis is indispensable. In this work a reliability analysis program for plasma focus devices is presented. The program considers a criticality analysis using Failure Modes and Effects Criticality Analysis (FMECA) to identify the most important failure modes of the system. Said failure modes are studied operating the Plasma Focus for many cycles, obtaining from them the characteristic curves of V(t) and İ(t). Feature Extraction (FE) techniques are applied to obtain a list of parameters that correlate to the degrading process. Furthermore, Machine Learning tools are used to learn from the obtained data, linking the changes in these parameters during its life cycle to the decay of the system in hope for future implementation of a predictive maintenance system and a reference for data analysis and prediction in PFs. The study was applied to a portable plasma focus device operated at 2 joules of stored energy. © Published under licence by IOP Publishing Ltd.The work is supported by IAEA CRP contract 20370 and by grant ACT-1115, CONICYT, Chile.https://iopscience.iop.org/article/10.1088/1742-6596/1043/1/01204
Numerical investigation of 48 V electrification potential in terms of fuel economy and vehicle performance for a lambda-1 gasoline passenger car
Real Driving Emissions (RDE) regulations require the adoption of stoichiometric operation across the entire engine map for downsized turbocharged gasoline engines, which have been so far generally exploiting spark timing retard and mixture enrichment for knock mitigation. However, stoichiometric operation has a detrimental effect on engine and vehicle performances if no countermeasures are taken, such as alternative approaches for knock mitigation, as the exploitation of Miller cycle and/or powertrain electrification to improve vehicle acceleration performance. This research activity aims, therefore, to assess the potential of 48 V electrification and of the adoption of Miller cycle for a downsized and stoichiometric turbocharged gasoline engine. An integrated vehicle and powertrain model was developed for a reference passenger car, equipped with a EU5 gasoline turbocharged engine. Afterwards, two different 48 V electrified powertrain concepts, one featuring a Belt Starter Generator (BSG) mild-hybrid architecture, the other featuring, in addition to the BSG, a Miller cycle engine combined with an e-supercharger were developed and investigated. Vehicle performances were evaluated both in terms of elasticity maneuvers and of CO2 emissions for type approval and RDE driving cycles. Numerical simulations highlighted potential improvements up to 16% CO2 reduction on RDE driving cycle of a 48 V electrified vehicle featuring a high efficiency powertrain with respect to a EU5 engine and more than 10% of transient performance improvement
Optical Properties of a \theta-Vacuum
Chern-Simons (CS) forms generalize the minimal coupling between gauge
potentials and point charges, to sources represented by charged extended
objects (branes). The simplest example of such a CS-brane coupling is a domain
wall coupled to the electromagnetic CS three-form. This describes a
topologically charged interface where the CS form AdA is supported, separating
two three-dimensional spatial regions in 3+1 spacetime. Electrodynamics at
either side of the brane is described by the same Maxwell's equations, but
those two regions have different vacua, characterized by a different value of
the \theta-parameter multiplying the Pontryagin form F ^ F. The \theta-term is
the abelian version of the concept introduced by 't Hooft for the resolution of
the U(1) problem in QCD. We point out that CS-generalized classical
electrodynamics shows new phenomena when two neighboring regions with different
\theta-vacua are present. These topological effects result from surface effects
induced by the boundary and we explore the consequences of such boundary
effects for the propagation of the electromagnetic field in Maxwell theory.
Several features, including optical and electrostatic/magnetostatic responses,
which may be observable in condensed matter systems, like topological
insulators, are discussed.Comment: 11 pages, no figure
Investigation on virucidal activity of chlorine dioxide. Experimental data on Feline calicivirus, HAV and Coxsackie B5
Introduction. The aim of this study was to evaluate the efficacy
of ClO2 with regard to viruses which show a particular resistance
to oxidizing agent such as HAV and Norwalk and Norwalk-like
viruses, and which play an important role in the epidemiology of
viral foodborne diseases.
In the food industry, disinfection of processing systems and equipment
is a very important instrument to prevent secondary contamination
and to guarantee food safety. Among disinfectants,
chlorine dioxide (ClO2) presents a good efficacy at wide range
of pH values, its action is rapid and generates few reaction byproducts
if compared to hypoclorite. Experimental studies have
highlighted that ClO2 shows a good bactericidal activity and it is
also active towards viruses. Furthermore, the low concentrations
and low contact times required to obtain microbial load reduction
are favourable elements for the application of this compound in
the industrial sanitizing practices.
Methods. As it is impossible to cultivate the Norwalk virus in vitro,
we tested the resistance of Feline calicivirus (F9 strain) vs. ClO2, in
comparison with HAV (strain HM-175) and CoxsackieB5. Chlorine
dioxide was used at concentrations ranging from 0.2 to 0.8 mg/l in
water solution, at pH 7 and at +20 °C. Viral suspensions were added
to disinfecting solution and, at pre-set times, were sampled to undergo
to titration after blocking the disinfectant action with thiosulphate 0.05
M. On the basis of the data obtained, for each virus and in relation
to different concentrations, mean reduction times were calculated for
99%, 99.9% and 99.99% using the regression analysis model.
Results. As regards Feline calicivirus, at a concentration of 0.8
mg/l of ClO2, we obtained the complete elimination of the viral
titre in 2 min while 30 min were required at concentrations of 0.2
mg/l. Coxackie B5 showed a similar behaviour, being completely
inactivated in 4 min with 0.4 mg/l of ClO2 and after 30 min at a
concentration of 0.2 mg/l. Inactivation was quicker for HAV, which
was eliminated after only 30 sec at a concentration of 0.8 mg/l and
after 5 min at 0.4 mg/l.
Conclusion. Our data show that for complete inactivation of HAV
and Feline calicivirus, concentrations ? 0.6 mg/l are required.
This observation is true for Coxsackie B5 too, but this virus has
shown a good sensitivity at all concentration tested according to
regression analysis results. For Feline calicivirus and HAV, at
low concentrations of disinfectant, prolonged contact times were
needed to obtain a 99.99% reduction of viral titres (about 16 and
20 minutes respectively)
Myocarditis Mimicking an Acute Coronary Syndrome: A Case Related to Salmonella enteritis
Infective myocarditis is most commonly due to a viral infection; occasionally it has been related to bacteria. Gastrointestinal infections associated with myocarditis have only rarely been described in young people, and the pathogenesis is unclear. We report a case of myocarditis mimicking an acute coronary syndrome (ACS) in a patient hospitalized for fever and diarrhoea. Salmonella enteritidis was isolated from stool, and no other pathogens were found. The coronary angiography was normal, and there were not other coronary artery risk factors, other than hypertension. The patient was treated with ciprofloxacin, acetylsalicylate acid, and ramipril with rapid clinical improvement and normalization of cardiac abnormalities. Final diagnosis of Salmonella enteritis and related myocarditis was made based on clinical, laboratory, ECG and echocardiographical findings
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