1,001 research outputs found
P-Type Impurities in 4H-SiC Calculated Using Density Functional Theory
We have investigated the p-dopant potential of 14 different impurities (Be, B, F, Mg, Al, Ca, Sc, Cu, Zn, Ga, In, Ba, Pt, and Tl) within 4H-SiC via Density Functional Theory (DFT) calculations using a hybrid density functional. We analyse the incorporation energies of impurity atoms on Si and C sites as well as the character of lattice distortion induced by impurities. The calculated thermal ionization energies confirm that Al and Ga on the Si site are the best candidates for p-doping of 4H-SiC. Although we find some correlation of incorporation energies with atomic radii of impurities, the difference in chemical interaction with neighbouring atoms and strong lattice distortions play important roles in determining the impurity incorporation energies and charge transition levels. We find Al to still be the best and most industrially viable p-dopant for 4H-SiC
«Белая дача» А.П. Чехова – как часть культурного ландшафта Крыма
Данная работа написана в рамках научного проекта кафедры культурологии «Культурные ландшафты Крыма» и посвящена рассмотрению «Белой дачи» А.П. Чехова (ныне Дом-музей А.П. Чехова в Ялте) как культурному ландшафту – результату сотворчества человека и природы
Critical disorder effects in Josephson-coupled quasi-one-dimensional superconductors
Effects of non-magnetic randomness on the critical temperature T_c and
diamagnetism are studied in a class of quasi-one dimensional superconductors.
The energy of Josephson-coupling between wires is considered to be random,
which is typical for dirty organic superconductors. We show that this
randomness destroys phase coherence between the wires and T_c vanishes
discontinuously when the randomness reaches a critical value. The parallel and
transverse components of the penetration depth are found to diverge at
different critical temperatures T_c^{(1)} and T_c, which correspond to
pair-breaking and phase-coherence breaking. The interplay between disorder and
quantum phase fluctuations results in quantum critical behavior at T=0,
manifesting itself as a superconducting-normal metal phase transition of
first-order at a critical disorder strength.Comment: 4 pages, 2 figure
Arithmetic properties of blocks of consecutive integers
This paper provides a survey of results on the greatest prime factor, the
number of distinct prime factors, the greatest squarefree factor and the
greatest m-th powerfree part of a block of consecutive integers, both without
any assumption and under assumption of the abc-conjecture. Finally we prove
that the explicit abc-conjecture implies the Erd\H{o}s-Woods conjecture for
each k>2.Comment: A slightly corrected and extended version of a paper which will
appear in January 2017 in the book From Arithmetic to Zeta-functions
published by Springe
Quantum Mechanics of Multi-Prong Potentials
We describe the bound state and scattering properties of a quantum mechanical
particle in a scalar -prong potential. Such a study is of special interest
since these situations are intermediate between one and two dimensions. The
energy levels for the special case of identical prongs exhibit an
alternating pattern of non-degeneracy and fold degeneracy. It is shown
that the techniques of supersymmetric quantum mechanics can be used to generate
new solutions. Solutions for prongs of arbitrary lengths are developed.
Discussions of tunneling in -well potentials and of scattering for piecewise
constant potentials are given. Since our treatment is for general values of
, the results can be studied in the large limit. A somewhat surprising
result is that a free particle incident on an -prong vertex undergoes
continuously increased backscattering as the number of prongs is increased.Comment: 17 pages. LATEX. On request, TOP_DRAW files or hard copies available
for 7 figure
The optical conductivity of the quasi one-dimensional conductors: the role of forward scattering by impurities
We calculate the average conductivity sigma (omega) of interacting electrons
in one dimension in the presence of a long-range random potential (forward
scattering disorder). Taking the curvature of the energy dispersion into
account, we show that weak disorder leads to a transport scattering rate that
vanishes as omega^2 for small frequency omega. This implies that the real part
of the conductivity remains finite for omega -> 0, while the imaginary part
diverges. These effects are lost within the usual bosonization approach, which
relies on the linearization of the energy dispersion. We discuss our result in
the light of a recent experiment.Comment: 5 RevTex pages; more careful comparison with experiments and
discussion of interchain hopping added; some references added; to appear in
Phys. Rev.
Implementing population health managemen
Purpose The purpose of this paper is to gain insight into how population health management (PHM) strategies can successfully integrate and reorganize public health, health care, social care and community services to improve population health and quality of care while reducing costs growth, this study compared four large-scale transformation programs: Greater Manchester Devolution, Vancouver Healthy City Strategy, Gen-H Cincinnati and Gesundes Kinzigtal. Design/methodology/approach Following the realist methodology, this explorative comparative case-study investigated PHM initiatives' key features and participants' experiences of developing such initiatives. A semi-structured interview guideline based on a theoretical framework for PHM guided the interviews with stakeholders (20) from different sectors. Findings Five initial program theories important to the development of PHM were formulated: (1) create trust in a shared vision and understanding of the PHM rationale to establish stakeholders' commitment to the partnership; (2) create shared ownership for achieving the initiative's goals; (3) create shared financial interest that reduces perceived financial risks to provide financial sustainability; (4) create a learning environment to secure initiative's credibility and (5) create citizens' and professionals' awareness of the required attitudes and behaviours. Originality/value The study highlights initial program theories for the implementation of PHM including different strategies and structures underpinning the initiatives. These insights provide a deeper understanding of how large-scale transformation could be developed
Stripes, Non-Fermi-Liquid Behavior, and High-Tc Superconductivity
The electronic structure of the high-Tc cuprates is studied in terms of
"large-U" and "small-U" orbitals. A striped structure and three types of
quasiparticles are obtained, polaron-like "stripons" carrying charge, "svivons"
carrying spin, and "quasielectrons" carrying both. The anomalous properties are
explained, and specifically the behavior of the resistivity, Hall constant, and
thermoelectric power. High-temperature superconductivity results from
transitions between pair states of quasielectrons and stripons.Comment: 4 page
Theory of Coexistence of Superconductivity and Ferroelectricity : A Dynamical Symmetry Model
We propose and investigate a model for the coexistence of Superconductivity
(SC) and Ferroelectricity (FE) based on the dynamical symmetries for
the pseudo-spin SC sector, for the displaced oscillator FE sector, and
for the composite system. We assume a minimal
symmetry-allowed coupling, and simplify the hamiltonian using a double mean
field approximation (DMFA). A variational coherent state (VCS) trial
wave-function is used for the ground state: the energy, and the relevant order
parameters for SC and FE are obtained. For positive sign of the SC-FE coupling
coefficient, a non-zero value of either order parameter can suppress the other
(FE polarization suppresses SC and vice versa). This gives some support to
"Matthias' Conjecture" [1964], that SC and FE tend to be mutually exclusive.
For such a Ferroelectric Superconductor we predict: a) the SC gap
(and ) will increase with increasing applied pressure when pressure
quenches FE as in many ferroelectrics, and b) the FE polarization will increase
with increaesing magnetic field up to . The last result is equivalent to
the prediction of a new type of Magneto-Electric Effect in a coexistent SC-FE
material. Some discussion will be given of the relation of these results to the
cuprate superconductors.Comment: 46 page
Epidermal growth factor receptor expression in pancreatic lesions induced in the rat by azaserine.
In the present study, the expression of the epidermal growth factor receptor (EGFR) was investigated in putative preneoplastic and neoplastic acinar cell lesions induced in the rat pancreas by azaserine, using Northern blotting, in situ hybridisation (ISH) and immunohistochemistry. EGFR protein levels were decreased in putative preneoplastic eosinophilic acinar cell lesions (atypical acinar cell nodules, AACN) in comparison with normal acinar cells of the pancreas. However, EGFR mRNA expression correlated positively with the volume of AACN in pancreatic homogenates and ISH showed equal or stronger EGFR mRNA expression in AACN than in the surrounding normal acinar cells. Neither EGFR protein nor EGFR mRNA was detected in more advanced lesions such as acinar adenocarcinomas (in situ). Moreover, EGFR protein expression showed an inverse relationship with the mitotic rate of the acinar cells. These findings suggest that down-regulation of EGFR at the protein level may abrogate negative constraints on cell growth, which may stimulate the development of putative preneoplastic AACN to more advanced lesions and, ultimately, acinar adenocarcinomas
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