289 research outputs found
Variational approach to the scattering of charged particles by a many-electron system
We report a variational approach to the nonlinearly screened interaction of
charged particles with a many-electron system. This approach has been developed
by introducing a modification of the Schwinger variational principle of
scattering theory, which allows to obtain nonperturbative scattering
cross-sections of moving projectiles from the knowledge of the linear and
quadratic density-response functions of the target. Our theory is illustrated
with a calculation of the energy loss per unit path length of slow antiprotons
moving in a uniform electron gas, which shows good agreement with a fully
nonlinear self-consistent Hartree calculation. Since available self-consistent
calculations are restricted to low heavy-projectile velocities, we expect our
theory to have novel applications to a variety of processes where nonlinear
screening plays an important role.Comment: 10 pages, 2 figures; Accepted to Physical Review
Randomized Controlled Trial of the Effectiveness of Genetic Counseling and a Distance, Computer-Based, Lifestyle Intervention Program for Adult Offspring of Patients with Type 2 Diabetes: Background, Study Protocol, and Baseline Patient Characteristics
Relatives of type 2 diabetic patients are at a high risk of developing type 2 diabetes and should be regarded as target of intervention for diabetes prevention. However, it is usually hard to motivate them to implement preventive lifestyle changes, because of lack of opportunity to take advises from medical professionals, inadequate risk perception, and low priority for preventive behavior. Prevention strategy for them therefore should be highly acceptable and suited for them. The parallel, three-group trial is now being conducted to investigate the effects of genetic counseling and/or a computerized behavioral program on the prevention of type 2 diabetes in that population. The preventive strategies used in this study could provide a novel solution to the numbers of genetically high-risk individuals, if found to be effective. The objective of this paper is to describe the background, protocol, and baseline patient characteristics of the trial
Critical statistics in a power-law random banded matrix ensemble
We investigate the statistical properties of the eigenvalues and eigenvectors
in a random matrix ensemble with . It is known that
this model shows a localization-delocalization transition (LDT) as a function
of the parameter . The model is critical at and the eigenstates
are multifractals. Based on numerical simulations we demonstrate that the
spectral statistics at criticality differs from semi-Poisson statistics which
is expected to be a general feature of systems exhibiting a LDT or `weak
chaos'.Comment: 4 pages in PS including 5 figure
Level spacings at the metal-insulator transition in the Anderson Hamiltonians and multifractal random matrix ensembles
We consider orthogonal, unitary, and symplectic ensembles of random matrices
with (1/a)(ln x)^2 potentials, which obey spectral statistics different from
the Wigner-Dyson and are argued to have multifractal eigenstates. If the
coefficient is small, spectral correlations in the bulk are universally
governed by a translationally invariant, one-parameter generalization of the
sine kernel. We provide analytic expressions for the level spacing distribution
functions of this kernel, which are hybrids of the Wigner-Dyson and Poisson
distributions. By tuning the single parameter, our results can be excellently
fitted to the numerical data for three symmetry classes of the
three-dimensional Anderson Hamiltonians at the metal-insulator transition,
previously measured by several groups using exact diagonalization.Comment: 12 pages, 8 figures, REVTeX. Additional figure and text on the level
number variance, to appear in Phys.Rev.
An Efficient Ligation Method in the Making of an in vitro Virus for in vitro Protein Evolution
The “in vitro virus” is a molecular construct to perform evolutionary protein engineering. The “virion (=viral particle)” (mRNA-peptide fusion), is made by bonding a nascent protein with its coding mRNA via puromycin in a test tube for in vitro translation. In this work, the puromycin-linker was attached to mRNA using the Y-ligation, which was a method of two single-strands ligation at the end of a double-stranded stem to make a stem-loop structure. This reaction gave a yield of about 95%. We compared the Y-ligation with two other ligation reactions and showed that the Y-ligation gave the best productivity. An efficient amplification of the in vitro virus with this “viral genome” was demonstrated
Off-diagonal correlations in one-dimensional anyonic models: A replica approach
We propose a generalization of the replica trick that allows to calculate the
large distance asymptotic of off-diagonal correlation functions in anyonic
models with a proper factorizable ground-state wave-function. We apply this new
method to the exact determination of all the harmonic terms of the correlations
of a gas of impenetrable anyons and to the Calogero Sutherland model. Our
findings are checked against available analytic and numerical results.Comment: 19 pages, 5 figures, typos correcte
Correlation functions of the BC Calogero-Sutherland model
The BC-type Calogero-Sutherland model (CSM) is an integrable extension of the
ordinary A-type CSM that possesses a reflection symmetry point. The BC-CSM is
related to the chiral classes of random matrix ensembles (RMEs) in exactly the
same way as the A-CSM is related to the Dyson classes. We first develop the
fermionic replica sigma-model formalism suitable to treat all chiral RMEs. By
exploiting ''generalized color-flavor transformation'' we then extend the
method to find the exact asymptotics of the BC-CSM density profile. Consistency
of our result with the c=1 Gaussian conformal field theory description is
verified. The emerging Friedel oscillations structure and sum rules are
discussed in details. We also compute the distribution of the particle nearest
to the reflection point.Comment: 12 pages, no figure, REVTeX4. sect.V updated, references added (v3
Energy level statistics of a critical random matrix ensemble
We study level statistics of a critical random matrix ensemble of a power-law
banded complex Hermitean matrices. We compute numerically the level
compressibility via the level number variance and compare it with the
analytical formula for the exactly solvable model of Moshe, Neuberger and
Shapiro.Comment: 8 pages, 3 figure
Time-dependent density-functional theory approach to nonlinear particle-solid interactions in comparison with scattering theory
An explicit expression for the quadratic density-response function of a
many-electron system is obtained in the framework of the time-dependent
density-functional theory, in terms of the linear and quadratic
density-response functions of noninteracting Kohn-Sham electrons and functional
derivatives of the time-dependent exchange-correlation potential. This is used
to evaluate the quadratic stopping power of a homogeneous electron gas for slow
ions, which is demonstrated to be equivalent to that obtained up to second
order in the ion charge in the framework of a fully nonlinear scattering
approach. Numerical calculations are reported, thereby exploring the range of
validity of quadratic-response theory.Comment: 14 pages, 3 figures. To appear in Journal of Physics: Condensed
Matte
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