2,780 research outputs found
Analytical Studies on a Modified Nagel-Schreckenberg Model with the Fukui-Ishibashi Acceleration Rule
We propose and study a one-dimensional traffic flow cellular automaton model
of high-speed vehicles with the Fukui-Ishibashi-type (FI) acceleration rule for
all cars, and the Nagel-Schreckenberg-type (NS) stochastic delay mechanism. By
using the car-oriented mean field theory, we obtain analytically the
fundamental diagrams of the average speed and vehicle flux depending on the
vehicle density and stochastic delay probability. Our theoretical results,
which may contribute to the exact analytical theory of the NS model, are in
excellent agreement with numerical simulations.Comment: 3 pages previous; now 4 pages 2 eps figure
Oscillatory fracture path in thin elastic sheet
We report a novel mode of oscillatory crack propagation when a cutting tip is
driven through a thin brittle polymer film. The phenomenon is so robust that it
can easily be reproduced at hand (using CD packaging material for example).
Careful experiments show that the amplitude and wavelength of the oscillatory
crack path scale lineraly with the width of the cutting tip over a wide range
of lenghtscales but are independant of the width of thje sheet and the cutting
speed. A simple geometric model is presented, which provides a simple but
thorough interpretation of the oscillations.Comment: 6 pages, submitted to Comptes Rendus Academie des Sciences. Movies
available at http://www.lmm.jussieu.fr/platefractur
Inverse Scattering Problem for Vector Fields and the Cauchy Problem for the Heavenly Equation
We solve the inverse scattering problem for multidimensional vector fields
and we use this result to construct the formal solution of the Cauchy problem
for the second heavenly equation of Plebanski, a scalar nonlinear partial
differential equation in four dimensions relevant in General Relativity, which
arises from the commutation of multidimensional Hamiltonian vector fields.Comment: 15 pages, submitted to Phisics Letters A. This paper replaces
nlin.SI/051204
Effects of etchants in the transfer of chemical vapor deposited graphene
The quality of graphene can be strongly modified during the transfer process following chemical vapor deposition (CVD) growth. Here, we transferred CVD-grown graphene from a copper foil to a SiO2/Si substrate using wet etching with four different etchants: HNO3, FeCl3, (NH4)2S2O8, and a commercial copper etchant. We then compared the quality of graphene after the transfer process in terms of surface modifications, pollutions (residues and contaminations), and electrical properties (mobility and density). Our tests and analyses showed that the commercial copper etchant provides the best structural integrity, the least amount of residues, and the smallest doping carrier concentration
Unravelling mechanisms of protein and lipid oxidation in mayonnaise at multiple length scales
Raw dat
On (non-Hermitian) Lagrangeans in (particle) physics and their dynamical generation
On the basis of a new method to derive the effective action the
nonperturbative concept of "dynamical generation" is explained. A non-trivial,
non-Hermitian and PT-symmetric solution for Wightman's scalar field theory in
four dimensions is dynamically generated, rehabilitating Symanzik's precarious
phi**4-theory with a negative quartic coupling constant as a candidate for an
asymptotically free theory of strong interactions. Finally it is shown making
use of dynamically generation that a Symanzik-like field theory with scalar
confinement for the theory of strong interactions can be even suggested by
experiment.Comment: 12 pages, no figures, accepted for publication in Czech.J.Phys.,
revised with respect to obvious typo
Monte Carlo Simulation of Sinusoidally Modulated Superlattice Growth
The fabrication of ZnSe/ZnTe superlattices grown by the process of rotating
the substrate in the presence of an inhomogeneous flux distribution instead of
successively closing and opening of source shutters is studied via Monte Carlo
simulations. It is found that the concentration of each compound is
sinusoidally modulated along the growth direction, caused by the uneven arrival
of Se and Te atoms at a given point of the sample, and by the variation of the
Te/Se ratio at that point due to the rotation of the substrate. In this way we
obtain a ZnSeTe alloy in which the composition varies
sinusoidally along the growth direction. The period of the modulation is
directly controlled by the rate of the substrate rotation. The amplitude of the
compositional modulation is monotonous for small angular velocities of the
substrate rotation, but is itself modulated for large angular velocities. The
average amplitude of the modulation pattern decreases as the angular velocity
of substrate rotation increases and the measurement position approaches the
center of rotation. The simulation results are in good agreement with
previously published experimental measurements on superlattices fabricated in
this manner
Image resonance in the many-body density of states at a metal surface
The electronic properties of a semi-infinite metal surface without a bulk gap are studied by a formalism that is able to account for the continuous spectrum of the system. The density of states at the surface is calculated within the GW approximation of many-body perturbation theory. We demonstrate the presence of an unoccupied surface resonance peaked at the position of the first image state. The resonance encompasses the whole Rydberg series of image states and cannot be resolved into individual peaks. Its origin is the shift in spectral weight when many-body correlation effects are taken into account
A dedicated haem lyase is required for the maturation of a novel bacterial cytochrome c with unconventional covalent haem binding
In bacterial c-type cytochromes, the haem cofactor is covalently attached via two cysteine residues organized in a haem c-binding motif. Here, a novel octa-haem c protein, MccA, is described that contains only seven conventional haem c-binding motifs (CXXCH), in addition to several single cysteine residues and a conserved CH signature. Mass spectrometric analysis of purified MccA from Wolinella succinogenes suggests that two of the single cysteine residues are actually part of an unprecedented CX15CH sequence involved in haem c binding. Spectroscopic characterization of MccA identified an unusual high-potential haem c with a red-shifted absorption maximum, not unlike that of certain eukaryotic cytochromes c that exceptionally bind haem via only one thioether bridge. A haem lyase gene was found to be specifically required for the maturation of MccA in W. succinogenes. Equivalent haem lyase-encoding genes belonging to either the bacterial cytochrome c biogenesis system I or II are present in the vicinity of every known mccA gene suggesting a dedicated cytochrome c maturation pathway. The results necessitate reconsideration of computer-based prediction of putative haem c-binding motifs in bacterial proteomes
Orbit spaces of free involutions on the product of two projective spaces
Let be a finitistic space having the mod 2 cohomology algebra of the
product of two projective spaces. We study free involutions on and
determine the possible mod 2 cohomology algebra of orbit space of any free
involution, using the Leray spectral sequence associated to the Borel fibration
. We also
give an application of our result to show that if has the mod 2 cohomology
algebra of the product of two real projective spaces (respectively complex
projective spaces), then there does not exist any -equivariant
map from for (respectively ), where
is equipped with the antipodal involution.Comment: 14 pages, to appear in Results in Mathematic
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