4,999 research outputs found
Macroscopic polarization and band offsets at nitride heterojunctions
Ab initio electronic structure studies of prototypical polar interfaces of
wurtzite III-V nitrides show that large uniform electric fields exist in
epitaxial nitride overlayers, due to the discontinuity across the interface of
the macroscopic polarization of the constituent materials. Polarization fields
forbid a standard evaluation of band offsets and formation energies: using new
techniques, we find a large forward-backward asymmetry of the offset (0.2 eV
for AlN/GaN (0001), 0.85 eV for GaN/AlN (0001)), and tiny interface formation
energies.Comment: RevTeX 4 pages, 2 figure
Cervical syringomyelia secondary to single space-occupying intracranial lesions in dogs: magnetic resonance imaging findings and risk factors
This study has identified risk factors for the development of SCSM in dogs with a single space-occupying intracranial lesion. When one or more of these risk factors are identified, it is advisable to extend the MRI study to the cervical spine, to investigate the presence of SCSM. Conversely, in dogs with SCSM and no concurrent cervical or congenital caudal fossa disease, the MRI study should be extended to the brain to investigate for a potential mass lesion
The construction of Dirac wave packets for a fermionic particle non-minimally coupling with an external magnetic field
We shall proceed with the construction of normalizable Dirac wave packets for
{\em fermionic} particles (neutrinos) with dynamics governed by a ``modified''
Dirac equation with a non-minimal coupling with an external magnetic field. We
are not only interested on the analytic solutions of the ``modified'' Dirac
wave equation but also on the construction of Dirac wave packets which can be
used for describing the dynamics of some observable physical quantities which
are relevant in the context of the quantum oscillation phenomena. To conclude,
we discuss qualitatively the applicability of this formal construction in the
treatment of chiral (and flavor) oscillations in the theoretical context of
neutrino physics.Comment: 10 page
Second-order corrections to neutrino two-flavor oscillation parameters in the wave packet approach
We report about an analytic study involving the {\em intermediate} wave
packet formalism for quantifying the physically relevant information which
appear in the neutrino two-flavor conversion formula and help us to obtain more
precise limits and ranges for neutrino flavor oscillation. By following the
sequence of analytic approximations where we assume a strictly peaked momentum
distribution and consider the second-order corrections in a power series
expansion of the energy, we point out a {\em residual} time-dependent phase
which, coupled with the {\em spreading/slippage} effects, can subtly modify the
neutrino oscillation parameters and limits. Such second-order effects are
usually ignored in the relativistic wave packet treatment, but they present an
evident dependence on the propagation regime so that some small modifications
to the oscillation pattern, even in the ultra-relativistic limit, can be
quantified. These modifications are implemented in the confront with the
neutrino oscillation parameter range (mass-squared difference \Delta m^{\2}
and the mixing-angle ) where we assume the same wave packet parameters
previously noticed in the literature in a kind of {\em toy model} for some
reactor experiments. Generically speaking, our analysis parallels the recent
experimental purposes which concern with higher precision parameter
measurements. To summarize, we show that the effectiveness of a more accurate
determination of \Delta m^{\2} and depends on the wave packet width
and on the averaged propagating energy flux which still
correspond to open variables for some classes of experiments. \Comment: 25 pages, 5 figure
Use of biological drugs in patients with psoriasis and psoriatic arthritis in italy: Results from the PSONG survey
This Italian multicenter retrospective study compared the drug survival and efficacy of differentanti-TNF agents in psoriasis (PsO) and psoriatic arthritis (PsA) patients. A database of PsO/PsApatients treated with adalimumab, etanercept, and infliximab from May 2013 to May 2014 wasanalyzed. PASI 75, 90, and 100 was calculated at each time point to evaluate efficacy. Drug sur-vival rate and probability of maintaining PASI response were evaluated. The impact of dependentvariables on probability of PASI 75 loss was evaluated by logistic regression. 1,235 patients wereincluded, 577 with PsO and 658 with PsA. Highest survival rates were observed with adalimumabfollowed by etanercept and infliximab in PsO and PsA patients. The probability of maintainingPASI response was significantly higher for adalimumab followed by infliximab. For PsO patients,the odds of losing PASI 75 was higher in etanercept-treated patients (OR: 8.1; 95% CI: 4.2–15.6,p<.001) or infliximab (OR: 6.6; 95% CI: 2.6–16.3,p<.001) vs. adalimumab. Likewise, for PsApatients the odds of losing PASI 75 was higher in etanercept-treated patients (OR: 2.3; 95% CI:1.4–3.8,p5.01) or infliximab (OR: 2.2; 95% CI: 1.1–4.1,p5.018) vs. adalimumab. Adalimumabcould be the best therapeutic option over other anti-TNF agents for the treatment of PsO and PsApatients
The charmonium and bottomonium mass spectroscopy with a simple approximaton of the kinetic term
In this paper we propose a particular description of meson spectroscopy, with
emphasis in heavy bound states like charmonia and bottomonia, after working on
the main aspects of the construction of an effective potential model. We use
the prerogatives from ``soft QCD'' to determine the effective potential terms,
establishing the asymptotic Coulomb term from one gluon exchange approximation.
At the same time, a linear confinement term is introduced in agreement with QCD
and phenomenological prescription. The main aspect of this work is the
simplification in the calculation, consequence of a precise and simplified
description of the kinetic term of the Hamiltonian. With this proposition we
perform the calculations of mass spectroscopy for charmonium and bottomonium
mesons and we discuss the real physical possibilities of developing a
generalized potential model, its possible advantages relative to experimental
parameterization and complexity in numerical calculations
The canonical GRB scenario
The canonical GRB scenario implied by the fireshell model is briefly summarized
Enzyme activation by alternating magnetic field: Importance of the bioconjugation methodology
Iron oxide nanoparticles (NPs) are attractive materials for enzyme immobilization and, thanks to their superparamagnetism, can be accessed by remote stimuli. This can be exploited to activate molecules that are not remotely actuable. Here, we demonstrate that thermophilic enzymes chemically linked to NPs can be activated in a \u201cwireless\u201d fashion by an external alternate magnetic field (AMF). To this aim, we have conjugated, with different binding strategies, the thermophilic enzymes \u3b1-amylase and L-aspartate oxidase to iron oxide NPs obtaining NP-enzyme systems with activities depending on the different orientations and stretching of the enzymes. Since enzyme activation occurs without a significant rise of the \u201coverall\u201d temperature of the systems, we have speculated a local NP-enzyme heating that does not immediately interest the rest of the solution that remains at relatively low temperature, low enough to allow non-thermophilic enzymes to work together with the NP-conjugated thermophilic enzymes. Nanoactuation of thermophilic enzymes by AMF has potential applications in different fields. Indeed, multi-enzymatic processes with enzymes with different temperature optima could be carried out in the same reaction pot and thermolabile products could be efficiently produced by thermophilic enzymes without suffering for the high temperatures. Moreover, our findings represent a proof of concept of the possibility to achieve a fine-tuning of the enzyme-NP system with the aim to intervene in cell metabolism
Qualitative modelling and analysis of regulations in multi-cellular systems using Petri nets and topological collections
In this paper, we aim at modelling and analyzing the regulation processes in
multi-cellular biological systems, in particular tissues.
The modelling framework is based on interconnected logical regulatory
networks a la Rene Thomas equipped with information about their spatial
relationships. The semantics of such models is expressed through colored Petri
nets to implement regulation rules, combined with topological collections to
implement the spatial information.
Some constraints are put on the the representation of spatial information in
order to preserve the possibility of an enumerative and exhaustive state space
exploration.
This paper presents the modelling framework, its semantics, as well as a
prototype implementation that allowed preliminary experimentation on some
applications.Comment: In Proceedings MeCBIC 2010, arXiv:1011.005
The sieve-element endoplasmic reticulum: A focal point of phytoplasma-host plant interaction?
The rough endoplasmic reticulum (r-ER) is of paramount importance for adaptive responses to biotic stresses due to an increased demand for de novo synthesis of immunity-related proteins and signaling components. In nucleate cells, disturbance of r-ER integrity and functionality leads to the “unfolded protein response” (UPR), which is an important component of innate plant immune signalling. In contrast to an abundance of reports on r-ER responses to biotic challenges, sieve-element endoplasmic reticulum (SE-ER) responses to phytoplasma infection have not been investigated. We found that morphological SE-ER changes, associated with phytoplasma infection, are accompanied by differential expression of genes encoding proteins involved in shaping and anchoring the reticulum. Phytoplasma infection also triggers an increased release of bZIP signals from the (SE-ER)/r-ER and consequent differential expression of UPR-related genes. The modified expression patterns seem to reflect a trade-off between survival of host cells, needed for the phytoplasmic biotrophic lifestyle, and phytoplasmas. Specialized plasmodesmata between sieve element and companion cell may provide a corridor for transfer of phytoplasma effectors inducing UPR-related gene expression in companion cells
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