229 research outputs found
Quantum calculations of the carrier mobility in thin films: Methodology, Matthiessen's rule and comparison with semi-classical approaches
We discuss the calculation of the carrier mobility in silicon films within
the quantum Non-Equilibrium Green's Functions (NEGF) framework. We introduce a
new method for the extraction of the carrier mobility that is free from contact
resistance contamination, and provides accurate mobilities at a reasonable
cost, with minimal needs for ensemble averages. We then introduce a new
paradigm for the definition of the partial mobility associated with a
given elastic scattering mechanism "M", taking phonons (PH) as a reference
(). We argue that this definition
makes better sense in a quantum transport framework as it is free from long
range interference effects that can appear in purely ballistic calculations. As
a matter of fact, these mobilities satisfy Matthiessen's rule for three
mechanisms [surface roughness (SR), remote Coulomb scattering (RCS) and
phonons] much better than the usual, single mechanism calculations. We also
discuss the problems raised by the long range spatial correlations in the RCS
disorder. Finally, we compare semi-classical Kubo-Greenwood (KG) and quantum
NEGF calculations. We show that KG and NEGF are in reasonable agreement for
phonon and RCS, yet not for SR. We point to possible deficiencies in the
treatment of SR scattering in KG, opening the way for further improvements.Comment: Submitted to Journal of Applied Physic
Model for the on-site matrix elements of the tight-binding hamiltonian of a strained crystal: Application to silicon, germanium and their alloys
We discuss a model for the on-site matrix elements of the sp3d5s*
tight-binding hamiltonian of a strained diamond or zinc-blende crystal or
nanostructure. This model features on-site, off-diagonal couplings between the
s, p and d orbitals, and is able to reproduce the effects of arbitrary strains
on the band energies and effective masses in the full Brillouin zone. It
introduces only a few additional parameters and is free from any ambiguities
that might arise from the definition of the macroscopic strains as a function
of the atomic positions. We apply this model to silicon, germanium and their
alloys as an illustration. In particular, we make a detailed comparison of
tight-binding and ab initio data on strained Si, Ge and SiGe.Comment: Submitted to Phys. Rev.
Generalized q-Oscillators and their Hopf Structures
We study the relationships among the various forms of the oscillator
algebra and consider the conditions under which it supports a Hopf structure.
We also present a generalization of this algebra together with its
corresponding Hopf structure. Its multimode extensions are also considered.Comment: 14 page
Localized Endomorphisms of the Chiral Ising Model
Based on the treatment of the chiral Ising model by Mack and Schomerus, we
present examples of localized endomorphisms and
. It is shown that they lead to the same
superselection sectors as the global ones in the sense that unitary equivalence
and holds. Araki's formalism of the selfdual CAR algebra is
used for the proof. We prove local normality and extend representations and
localized endomorphisms to a global algebra of observables which is generated
by local von Neumann algebras on the punctured circle. In this framework, we
manifestly prove fusion rules and derive statistics operators.Comment: 41 pages, latex2
I-21 Current therapeutic guidelines in Duchenne Muscular Dystrophy to prolong life
Duchenne's myopathy is an X-linked disease with well defined evolutionary phases, characterized by degradation of the walking function, development of evolutive scoliosis and progressive decline of the respiratory function leading patients to premature death.
In 1985 Y. Rideau in France carried out a new global therapeutic strategy for treatment of lower limb deformities, scoliosis deformity and progressive restrictive syndrome.
The indication for surgery at the lower limbs is made very early, at the onset of the first signs of disease. The procedures are carried out at the same time and always bilaterally; they include: (i) hip section of superficial flexors; (ii) iliotibial band resection; (iii) subcutaneous tenotomy of semitendineous and gracilis; (iv) subcutaneous lengthening of Achilles tendons.
In the post-operative period, the patient begins exercises of active and passive mobility in few days and after three weeks recovers his performances; ambulation will remain almost normal for several years. A comparison of two groups of patients, the first precociously operated on the lower limbs, the other one not operated, shows better performances in the operated group.
The indications for surgical treatment of Duchenne scoliosis must be made after the loss of ambulation and not too late, to avoid the concurrent respiratory restrictive syndrome makes the patient inoperable. Over ten years ago, in Poitiers, a specific instrumentation for Duchenne scoliosis was created, providing for cylindrical rods fixed by peduncular screws at the sacro-lumbar level. On the dorso-lumbar level, the rod becomes flat to allow more flexibility of the trunk. The complications observed in a group of 55 patients operated for scoliosis, consisted in 2 cases of breaking of rods and 1 superficial infection. The surgery approach in DMD has the double aim to prolong the time of the autonomous ambulation and to avoid the evolution of scoliosis, limiting the harmful effects of the scoliosis on the respiratory function.
However, the surgery alone is unable to prolong the life expectancy in these patients, without treating the restrictive respiratory syndrome, first by nasal ventilation and then by elective tracheotomy, essential for the survival of the patient
Some remarks on the Gauss decomposition for quantum group GL_q(n)
In this letter some properties of the Gauss decomposition of quantum group
with application to q-bosonization are considered.Comment: 11 page
Classification of the quantum deformation of the superalgebra
We present a classification of the possible quantum deformations of the
supergroup and its Lie superalgebra . In each case, the
(super)commutation relations and the Hopf structures are explicitly computed.
For each matrix, one finds two inequivalent coproducts whether one chooses
an unbraided or a braided framework while the corresponding structures are
isomorphic as algebras. In the braided case, one recovers the classical algebra
for suitable limits of the deformation parameters but this is no
longer true in the unbraided case.Comment: 23p LaTeX2e Document - packages amsfonts,subeqn - misprints and
errors corrected, one section adde
Analysis of defect capture cross sections using non-radiative multiphonon-assisted trapping model
A multiphonon-assisted model included in a Poisson-Schroedinger solver has been applied to the calculation of the capture/emission trapping rates of CMOS oxide interface defects. The dependencies of trap capture cross-sections with trap energy, depth, applied bias and temperature have been extracted, with the purpose of evaluating the accuracy of constant cross-section models adopted in compact and empirical approaches. The model has been applied to the extraction of interface trap concentrations and to the accurate AC analysis of the trap frequency response
AC analysis of defect cross sections using non-radiative MPA quantum model
A multiphonon-assisted model included in a Poisson-Schroedinger solver has been applied for the calculation of the capture/emission trapping rates of Si/SiO2 interface defects and their dependence with respect to the trap energy and depth in the oxide. The accurate trap cross-sections extracted with this approach permit compact modeling engineers to evaluate the accuracy of constant cross-section models. The model has been applied to extract the trap concentration and frequency response, comparing AC simulations with measurements. © 2011 IEEE
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