title: Electron Mobility in Dense Argon Gas at Several Temperatures

abstract:
  The mobility $\mu$ of excess electrons in dense Argon gas has been measured
as a function of the applied electric field $E$ and of the gas density N at
several temperatures in the range $142.6<T<200$ K, encompassing the critical
temperature Tc=150.86 K. We report here measurements at densities up to N?7
nm$^{-3}$, close to the critical density, $N_c \approx$ 8.1 nm$^{-3}$, reached
for the isotherm closest to the critical one. At all temperatures, below as
well as above Tc, and up to moderately high densities, the density-normalized
mobility $\mu N$ shows the usual electric field dependence present in a gas
with a Ramsauer-Townsend minimum due to the mainly attractive electron-atom
interaction. mN is constant and field independent for small values of $E,$
shows a maximum for a reduced field $E/N \approx$ 4 mTd, and then decreases
rapidly with the field, approximately proportional to $(E/N)^{-1/2}.$ The
zero-field density-normalized mobility $\mu_0 N, $for all T>$T_c,$ shows the
well known anomalous positive density effect, i.e., m0N increases with
increasing N, confirming previous results obtained for T=300 K and 162.7 K.
Below Tc, however, $\mu_0 N$ does not show the expected anomalous positive
density effect, but it rather features a broad maximum. This appears to be a
crossover behavior between the positive density effect shown for T>Tc and the
small negative effect previously observed for T$\approx$ 90 K. In any case, the
data at all temperatures confirm the interpretation of the anomalous density
effect as being essentially due by the density-dependent quantum shift of the
electron ground state kinetic energy in a disordered medium as a result of
multiple scattering (MS) processes, although other MS processes do influence
the outcome of the experiment.


title:
Heterogeneous nucleation - current transients under chemical reaction
  control

abstract:
  Heterogeneous nucleation on catalytic surfaces plunged into a fluid is
described through a stochastic model. To generate this non-equilibrium process
we assume that the turn on of a electrostatic potential triggers a complex
dynamics that includes a free Brownian motion, a reaction kinetic and a
stimulated migration before the final adhesion of ions on the surface
(electrode). At, when the potential is switched on, the spatial symmetry is
broken and a two-stage process is developed. First the ion undergoes a change
in its electrochemical character (at some region of the space) and then reacts
at some specific points to stick together on the surface. The continuous
addition of ions develops a material deposit connected to the current transient
signals measured in electrochemical deposition processes. Unlike current models
found in the literature, this procedure avoids the computation of the area
covered by the diffusion zones, allowing a formalism skill to describe equally
well the absorption of ions by channels on electrified surfaces. The theory is
applied to the electrodeposition of nickel on n-silicon and explains the
failure of standard three-dimensional nucleation models to reproduce situations
where interfacial relations control the dynamics. It is shown that, processes
dominated by chemical reactions on the electrode can not be classified as
possessing an exclusively instantaneous or progressive character, rather, they
mix together these two limiting forms of nuclei activation to defines the
current transients in its beginning.


title: Angular momenta creation in relativistic electron-positron plasma

abstract:
  Creation of angular momentum in a relativistic electron-positron plasma is
explored. It is shown that a chain of angular momentum carrying vortices is a
robust asymptotic state sustained by the generalized nonlinear Schrodinger
equation characteristic to the system. The results may suggest a possible
electromagnetic origin of angular momenta when it is applied to the MeV epoch
of the early Universe.


title: Nonlinear Magneto-Optical Rotation of Elliptically Polarized Light

abstract:
  We predict theoretically and demonstrate experimentally an
ellipticity-dependent nonlinear magneto-optic rotation of
elliptically-polarized light propagating in a coherent atomic medium. We show
that this effect results from a hexadecapole and higher order momenta of atomic
coherence, and is associated with an enhancement of Kerr and higher orders
nonlinearities accompanied by suppression of the other linear and nonlinear
susceptibility terms of the medium. These nonlinearities might be useful for
quantum signal processing. In particular, we report an observation of an
enhancement the polarization rotation of elliptically polarized light resonant
with the 5S_{1/2} F=2 -> 5P_{1/2} F=1 transition of Rb87.


title: Parameter identification using the Hilbert transform

abstract:
  Many physical systems can be adequately modelled using a second order
approximation. The problem of plant identification reduces to the problem of
estimating the position of a single pair of complex conjugate poles. One
approach to the problem is to apply the method of least squares to the time
domain data. This type of computation is best carried out in "batch" mode and
applies to an entire data set. Another approach would be to design an adaptive
filter and to use autoregressive, AR, techniques. This would be well suited to
continuous real-time data and could track slow changes on the underlying plant.
I this paper we present a very fast but approximate technique for the
estimation of the position of a single pair of complex conjugate poles, using
the Hilbert transform to reconstruct the analytic signal.


title:
Temperature dependence of optical rotation study on parity-violating
  phase transition of D-, L-, and DL-alanine

abstract:
  Chiral molecules are characterized by a specific optical rotation angle. An
experimental method was presented to dissect the temperature dependence of the
optical rotation angle with the molecular chirality of D-alanine, L-alanine and
DL-alanine crystals. Salam hypothesis predicted that quantum mechanical
cooperative and condensation phenomena may give rise to a second order phase
transition below a critical temperature linking the transformation of D-amino
acids to L-amino acids due to parity-violating energy difference. The
temperature- dependent measurement of the optical rotation angle of D-, L- and
DL-alanine crystals provided the direct evidence of the phase transition, but
denied the configuration change from D-alanine to L-alanine. New views on Salam
hypothesis are presented to demonstrate its importance in the application of
low temperature enantiomeric separation and the origin of biochirality.


title:
Polarization independent hot electron production from modulated solid
  surfaces

abstract:
  We present measurements of hard x-rays in the 50-300 keV range from copper
plasmas produced by 100 fs, 806 nm laser pulses at a peak intensity ~ 1016 W
cm-2. Surface roughness, even at the tens of nanometer level, is shown to
influence the emission characteristics. The enhanced emission from rough
targets is attributed to depolarization of light as well as extra absorption
facilitated by the surface irregularities.


title:
Low Temperature Dependence in 1H CRAMPS & 13C CP/MAS ssNMR Spectra of
  Alanine Enantiomers

abstract:
  1H RAMPS solid state NMR and 13C CP/MAS spectra of D- and L- alanine crystals
were measured at temperature ranging from 220K to 295K. Some major points are
as follows: (1)alpha-H and protons in the methyl group showed a spin-spin
coupling effect as temperature went down in the 1H- MAS spectra of D-alanine.
(2) In the 1H CRAMPS spectra, peak widths of alpha-H and beta-H showed a
different trend between alanine enantiomers when temperature varied.(3) The
dynamic behavior of 13C spectra showed an obvious change around 250K, which was
supposed as a phase transition in alanine crystal. In the discussion section,
we give these experimental phenomena a possible explanation related to
chirality.


title:
Retarded Electromagnetic Interaction and the Origin of Non-linear
  Phenomena in Optics

abstract:
  The non-linear relation between electric polarization and electric field
strength is achieved through introducing the retarded electromagnetic
interactions between classical charge particles. The result agrees with the
phenomenological theory in current non-linear optics, means that the non-linear
phenomena in optics come from the retarded electromagnetic interaction between
charged particles. The result slao shows that that most of non-linear
phenomenon in optics violate symmetry of time reversal.


title: The Biosynthetic Order of Amino Acid Addition to the Genetic Code

abstract:
  The previously formulated model for the evolution of the genetic code was
shown to clarify why base triplets of some precursor amino acids differ by a
single base from product amino acid codons, while others show less homology.
First, the model indicated that the direction of code evolution changed on
expansion from the N-fixers code (stage 2). Growth of the code from 16 codons
in the NAN column (N, any standard nucleotide) proceeded by assignment of
codons in the GNN, ANN, CNN and UNN rows. Expansion phase (stage 4 to 7)
precursor/product pairs that spanned this shift included aspartate/threonine,
aspartate/methionine and glutamate/proline. Both 5' and mid-base differ in the
codons of each of these pairs. Second, post-expansion additions (stage 9 to 14)
required codon reassignment, eliminating initial correlations. Codons for the
post-expansion pair, aspartate (glutamate)/arginine, also differ at both 5' and
mid-base sites. Third, the distribution of core structure groups among
acceptors indicated that variant tRNA specific for a sibling, rather than
precursor, commonly participated as cofactors in early amino acid synthesis.
Sibling pairs, rather than precursor/product pairs, then exhibit codon
correlations. On removing these sources of variation, highly significant
correlations emerged between codons assigned to biosynthetically related amino
acids.


title:
Effect of Electron Energy Distribution Function on Power Deposition and
  Plasma Density in an Inductively Coupled Discharge at Very Low Pressures

abstract:
  A self-consistent 1-D model was developed to study the effect of the electron
energy distribution function (EEDF) on power deposition and plasma density
profiles in a planar inductively coupled plasma (ICP) in the non-local regime
(pressure < 10 mTorr). The model consisted of three modules: (1) an electron
energy distribution function (EEDF) module to compute the non-Maxwellian EEDF,
(2) a non-local electron kinetics module to predict the non-local electron
conductivity, RF current, electric field and power deposition profiles in the
non-uniform plasma, and (3) a heavy species transport module to solve for the
ion density and velocity profiles as well as the metastable density. Results
using the non-Maxwellian EEDF model were compared with predictions using a
Maxwellian EEDF, under otherwise identical conditions. The RF electric field,
current, and power deposition profiles were different, especially at 1mTorr,
for which the electron effective mean free path was larger than the skin depth.
The plasma density predicted by the Maxwellian EEDF was up to 93% larger for
the conditions examined. Thus, the non-Maxwellian EEDF must be accounted for in
modeling ICPs at very low pressures.


title:
Information Transfer Time: The Role of Holomorphism, Stationary Phase,
  and Noise

abstract:
  In this paper we present an analysis of information transfer time based on
holomorphism, causality and the classical principle of stationary phase. We
also make a preliminary study of the effect of noise on information transfer
time, and find that noise tends to increase transfer times. Noise and
information signals are both essentially acausal, such that analytic
continuation (i.e. prediction) is impossible, which also implies that their
frequency spectra cannot be holomorphic. This leads to the paradox of a
non-holomorphic information-bearing light signal, yet whose underlying Maxwell
equations governing the propagation of the EM wave describe a holomorphic
function in spacetime. We find that application of stationary phase and entropy
arguments circumvents this difficulty, with stationary phase only suggesting
the most likely transfer times of an information signal in the presence of
noise. Faster transit times are not excluded, but are highly improbable.
Stationary phase solutions, by definition, do not include signal forerunners,
whose detection in the presence of noise is also unreliable. Hence a finite
information capacity ensues, as expected from Shannon's law, and information
cannot be transferred faster than c. We also find that the method of stationary
phase implies complex transfer times. However, by considering spacetime to be
isomorphic with the complex temporal plane, we find that an imaginary time is
equivalent to a real distance, and can be interpreted as the uncertainty in the
spatial position of the information pulse. Finally, we apply our theory to a
photonic band gap crystal, and find that information transfer speed and
tunneling is always subluminal.


title:
A new ab initio method of calculating $Z_{eff}$ and positron
  annihilation rates using coupled-channel T-matrix amplitudes

abstract:
  A new {\it ab initio} theoretical formulation to calculate $Z_{eff}$ and
hence the positron annihilation rates is presented using the on-shell and
half-offshell T-matrix scattering amplitudes without any explicit use of the
scattering wave function. The formulation is exact and universal, as long as
the dynamics of the system can be described by a Lippmann-Schwinger type
equation. It could serve as an effective tool as all the $T-$, $K-$, and
$S-$matrix formulations, yield directly the scattering amplitudes; not the wave
function. We also present a basic numerical test of the formulation.


title: Jacobi Identity for Poisson Brackets: A Concise Proof

abstract:
  In view of the recent interest in a short proof of the Jacobi identity for
the Poisson-brackets, we provide an alternative simple proof for the same. Our
derivation is based on the validity of the Leibnitz rule in the context of
dynamical evolution.


title: Resonant helical deformations in nonhomogeneous Kirchhoff filaments

abstract:
  We study the three-dimensional static configurations of nonhomogeneous
Kirchhoff filaments with periodically varying Young's modulus. This type of
variation may occur in long tandemly repeated sequences of DNA. We analyse the
effects of the Young's modulus frequence and amplitude of oscillation in the
stroboscopic maps, and in the regular (non chaotic) spatial configurations of
the filaments. Our analysis shows that the tridimensional conformations of long
filaments may depend critically on the Young's modulus frequence in case of
resonance with other natural frequencies of the filament. As expected, far from
resonance the shape of the solutions remain very close to that of the
homogeneous case. In the case of biomolecules, it is well known that various
other elements, besides sequence-dependent effects, combine to determine their
conformation, like self-contact, salt concentration, thermal fluctuations,
anisotropy and interaction with proteins. Our results show that
sequence-dependent effects alone may have a significant influence on the shape
of these molecules, including DNA. This could, therefore, be a possible
mechanical function of the ``junk'' sequences.


title: Magnetic Trapping of Metastable Calcium Atoms

abstract:
  Metastable calcium atoms, produced in a magneto-optic trap (MOT) operating
within the singlet system, are continuously loaded into a magnetic trap formed
by the magnetic quadrupole field of the MOT. At MOT temperatures of 3 mK and
240 ms loading time we observe 1.1 x 10^8 magnetically trapped 3P2 atoms at
densities of 2.4 x 10^8 cm^-3 and temperatures of 0.61 mK. In a modified scheme
we first load a MOT for metastable atoms at a temperature of 0.18 mK and
subsequently release these atoms into the magnetic trap. In this case 240 ms of
loading yields 2.4 x 10^8 trapped 3P2 atoms at a peak density of 8.7 x 10^10
cm^-3 and a temperature of 0.13 mK. The temperature decrease observed in the
magnetic trap for both loading schemes can be explained only in part by trap
size effects.


title:
Brownian motion, ionic flux, catalytic reaction and heterogeneous
  nucleation in biological systems

abstract:
  A model to describe the arising of new structures in an initial homogeneous
biological system is proposed. The essay is motivated by the intention to work
on a non-equilibrium situation grouping together several mechanisms and
processes as: catalytic reactions on a surface, diffusion, stimulated migration
and selective heterogeneous reaction. A model for morphogenesis in early
embryos is developed on two basic assumptions; (i) the existence of an
electrified surface that defines the shape (form) of the growing structure and
(ii) a mechanism to select morphogens (ions or free radicals) from an initially
homogeneous medium. The homogeneity is broke when an electric potential arise
between different parcels of the system, triggering a complex dynamic that
drive the development of material deposits into localized regions of the space.
The evolution of the deposits is described by a stochastic formalism allowing
for analytical expressions relating macroscopic.


title: Model of Internal Friction Damping in Solids

abstract:
  A model for harmonic oscillator damping due to the internal friction of
solids has been developed, based on considerations of a long period pendulum.
The assumption of a complex elastic modulus to describe stress-strain
hysteresis in the support structure of the pendulum yields an expression for
the figure of merit Q that agrees with many experiments involving material
damping. As such, the approximations of this linear model stand in contrast
with common theory.


title: Infinitely-fast diffusion in Single-File Systems

abstract:
  We have used Dynamic Monte Carlo (DMC) methods and analytical techniques to
analyze Single-File Systems for which diffusion is infinitely-fast. We have
simplified the Master Equation removing the fast reactions and we have
introduced a DMC algorithm for infinitely-fast diffusion. The DMC method for
fast diffusion give similar results as the standard DMC with high diffusion
rates. We have investigated the influence of characteristic parameters, such as
pipe length, adsorption, desorption and conversion rate constants on the
steady-state properties of Single-File Systems with a reaction, looking at
cases when all the sites are reactive and when only some of them are reactive.
We find that the effect of fast diffusion on single-file properties of the
system is absent even when diffusion is infinitely-fast. Diffusion is not
important in these systems. Smaller systems are less reactive and the occupancy
profiles for infinitely-long systems show an exponential behavior.


title: Ab initio molecular dynamics study of liquid methanol

abstract:
  We present a density-functional theory based molecular-dynamics study of the
structural, dynamical, and electronic properties of liquid methanol under
ambient conditions. The calculated radial distribution functions involving the
oxygen and hydroxyl hydrogen show a pronounced hydrogen bonding and compare
well with recent neutron diffraction data, except for an underestimate of the
oxygen-oxygen correlation. We observe that, in line with infrared spectroscopic
data, the hydroxyl stretching mode is significantly red-shifted in the liquid.
A substantial enhancement of the dipole moment is accompanied by significant
fluctuations due to thermal motion. Our results provide valuable data for
improvement of empirical potentials.


title: Analise Termodinamica de um circuito RLC

abstract:
  We analyse a RLC circuit taking the Second Law of Thermodynamics into
consideration.


title: Ownership and Trade from Evolutionary Games

abstract:
  Ownership and trade emerge from anarchy as evolutionary stable strategies. In
these evolutionary game models, ownership status provides an endogenous
asymmetrizing criterion enabling cheaper resolution of property conflicts.

categories: physics.bio-ph cs.GT nlin.AO nlin.CG physics.soc-ph q-bio.PE


title:
Hyperspherical partial wave theory applied to electron hydrogen-atom
  ionization calculation for equal energy sharing kinematics

abstract:
  Hyperspherical partial wave theory has been applied here in a new way in the
calculation of the triple differential cross sections for the ionization of
hydrogen atoms by electron impact at low energies for various
equal-energy-sharing kinematic conditions. The agreement of the cross section
results with the recent absolute measurements of R\"oder \textit {et al} [51]
and with the latest theoretical results of the ECS and CCC calculations [29]
for different kinematic conditions at 17.6 eV is very encouraging. The other
calculated results, for relatively higher energies, are also generally
satisfactory, particularly for large $\Theta_{ab}$ geometries. In view of the
present results, together with the fact that it is capable of describing
unequal-energy-sharing kinematics [35], it may be said that the hyperspherical
partial wave theory is quite appropriate for the description of ionization
events of electron-hydrogen type systems. It is also clear that the present
approach in the implementation of the hyperspherical partial wave theory is
very appropriate.


title: SINGINT: Automatic numerical integration of singular integrands

abstract:
  We explore the combination of deterministic and Monte Carlo methods to
facilitate efficient automatic numerical computation of multidimensional
integrals with singular integrands. Two adaptive algorithms are presented that
employ recursion and are runtime and memory optimised, respectively. SINGINT, a
C implementation of the algorithms, is introduced and its utilisation in the
calculation of particle scattering amplitudes is exemplified.


title:
Thermodynamics of the Harmonic Oscillator: Wien's Displacement Law and
  the Planck Spectrum

abstract:
  A thermodynamic analysis of the harmonic oscillator is presented. Motivation
for the study is provided by the blackbody radiation spectrum; when blackbody
radiation is regarded as a system of noninteracting harmonic oscillator modes,
the thermodynamics follows from that of the harmonic oscillators. Using the
behavior of a harmonic oscillator thermodynamic system under a quasi-static
change of oscillator frequency w, we show that the thermodynamic functions can
all be derived from a single function of w/T, analogous to Wien's displacement
theorem. The high- and low-frequency energy limits allow asymptotic energy
forms involving T alone or w alone, corresponding to energy equipartition and
zero-point energy. It is noted that the Planck spectrum with zero-point
radiation corresponds to the function satisfying the Wien displacement result
which provides the smoothest possible interpolation between energy
equipartition at low frequency and zero-point energy at high frequency.


title:
Derivation of the Blackbody Radiation Spectrum from a Natural
  Maximum-Entropy Principle Involving Casimir Energies and Zero-Point Radiation

abstract:
  By numerical calculation, the Planck spectrum with zero-point radiation is
shown to satisfy a natural maximum-entropy principle whereas alternative
choices of spectra do not. Specifically, if we consider a set of
conducting-walled boxes, each with a partition placed at a different location
in the box, so that across the collection of boxes the partitions are uniformly
spaced across the volume, then the Planck spectrum correspond to that spectrum
of random radiation (having constant energy kT per normal mode at low
frequencies and zero-point energy (1/2)hw per normal mode at high frequencies)
which gives maximum uniformity across the collection of boxes for the radiation
energy per box. The analysis involves Casimir energies and zero-point radiation
which do not usually appear in thermodynamic analyses. For simplicity, the
analysis is presented for waves in one space dimension.


title: Foreshocks Explained by Cascades of Triggered Seismicity

abstract:
  The observation of foreshocks preceding large earthquakes and the suggestion
that foreshocks have specific properties that may be used to distinguish them
from other earthquakes have raised the hope that large earthquakes may be
predictable. Among proposed anomalous properties are the larger proportion than
normal of large versus small foreshocks, the power law acceleration of
seismicity rate as a function of time to the mainshock and the spatial
migration of foreshocks toward the mainshock, when averaging over many
sequences. Using Southern California seismicity, we show that these properties
and others arise naturally from the simple model that any earthquake may
trigger other earthquakes, without arbitrary distinction between foreshocks,
aftershocks and mainshocks. We find that foreshocks precursory properties are
independent of the mainshock size. This implies that earthquakes (large or
small) are predictable to the same degree as seismicity rate is predictable
from past seismicity by taking into account cascades of triggering. The
cascades of triggering give rise naturally to long-range and long-time
interactions, which can explain the observations of correlations in seismicity
over surprisingly large length scales.


title: Rapid Adiabatic Passage from an Atomic to a Molecular Condensate

abstract:
  We examine collective magnetoassociation of a Bose-Einstein condensate (BEC),
focusing on rapid adiabatic passage from atoms to molecules induced by a sweep
of the magnetic field across a wide (>~ 10 G) Feshbach resonance in 85Rb. This
problem raises an interest because strong magnetoassociation is expected to
favor the creation of molecular-dissociated atom pairs over the formation of
molecular BEC [Javanainen and Mackie, Phys. Rev. Lett. 88, 090403 (2002)].
Nevertheless, the conversion to atom pairs is found to depend on the direction
of the sweep, so that a system initially above threshold (open dissociation
channel) may in fact give near-complete conversion to molecules.

categories: physics.atom-ph cond-mat.soft cond-mat.stat-mech physics.chem-ph quant-ph


title: Force on an Asymmetric Capacitor

abstract:
  When a high voltage (~30 kV) is applied to a capacitor whose electrodes have
different physical dimensions, the capacitor experiences a net force toward the
smaller electrode (Biefeld-Brown effect). We have verified this effect by
building four capacitors of different shapes. The effect may have applications
to vehicle propulsion and dielectric pumps. We review the history of this
effect briefly through the history of patents by Thomas Townsend Brown. At
present, the physical basis for the Biefeld-Brown effect is not understood. The
order of magnitude of the net force on the asymmetric capacitor is estimated
assuming two different mechanisms of charge conduction between its electrodes:
ballistic ionic wind and ionic drift. The calculations indicate that ionic wind
is at least three orders of magnitude too small to explain the magnitude of the
observed force on the capacitor. The ionic drift transport assumption leads to
the correct order of magnitude for the force, however, it is difficult to see
how ionic drift enters into the theory. Finally, we present a detailed
thermodynamic treatment of the net force on an asymmetric capacitor. In the
future, to understand this effect, a detailed theoretical model must be
constructed that takes into account plasma effects: ionization of gas (or air)
in the high electric field region, charge transport, and resulting dynamic
forces on the electrodes. The next series of experiments should determine
whether the effect occurs in vacuum, and a careful study should be carried out
to determine the dependence of the observed force on gas pressure, gas species
and applied voltage.


title:
Tree-body loss of of trapped ultracold $^{87}$Rb atoms due to a Feshbach
  resonance

abstract:
  The loss of ultracold trapped atoms in the vicinity of a Feshbach resonance
is treated as a two-stage reaction, using the Breit-Wigner theory. The first
stage is the formation of a resonant diatomic molecule, and the second one is
its deactivation by inelastic collisions with other atoms. This model is
applied to the analysis of recent experiments on $^{87}$Rb, leading to an
estimated value of $7\times 10^{-11}$ cm$^{3}/$s for the deactivation rate
coefficient.


title: Transformation Properties of the Lagrangian and Eulerian Strain Tensors

abstract:
  A coordinate independent derivation of the Eulerian and Lagrangian strain
tensors of finite deformation theory is given based on the parallel propagator,
the world function, and the displacement vector field as a three-point tensor.
The derivation explicitly shows that the Eulerian and Lagrangian strain tensors
are two-point tensors, each a function of both the spatial and material
coordinates. The Eulerian strain is a two-point tensor that transforms as a
second rank tensor under transformation of spatial coordinates and transforms
as a scalar under transformation of the material coordinates. The Lagrangian
strain is a two-point tensor that transforms as scalar under transformation of
spatial coordinates and transforms as a second rank tensor under transformation
of the material coordinates. These transformation properties are needed when
transforming the strain tensors from one frame of reference to another moving
frame.


title: Stress in Rotating Disks and Cylinders

abstract:
  The solution of the classic problem of stress in a rotating elastic disk or
cylinder, as solved in standard texts on elasticity theory, has two features:
dynamical equations are used that are valid only in an inertial frame of
reference, and quadratic terms are dropped in displacement gradient in the
definition of the strain. I show that, in an inertial frame of reference where
the dynamical equations are valid, it is incorrect to drop the quadratic terms
because they are as large as the linear terms that are kept. I provide an
alternate formulation of the problem by transforming the dynamical equations to
a corotating frame of reference of the disk/cylinder, where dropping the
quadratic terms in displacement gradient is justified. The analysis shows that
the classic textbook derivation of stress and strain must be interpreted as
being carried out in the corotating frame of the medium.


title:
Enhanced Kerr nonlinearity for self-action via atomic coherence in a
  four-level atomic system

abstract:
  Enhancement of optical Kerr nonlinearity for self-action by
electro-magnetically induced transparency in a four-level atomic system
including dephasing between the ground states is studied in detail by solving
the density matrix equations for the atomic levels. We discern three major
contributions, from energy shifts of the ground states induced by the probe
light, to the third-order susceptibility in the four-level system. In this
four-level system with the frequency-degenerate probes, quantum interference
amongst the three contributions can, not only enhance the third-order
susceptibility more effectively than in the three-level system with the same
characteristic parameters, but also make the ratio between its real and
imaginary part controllable. Due to dephasing between the two ground states and
constructive quantum interference, the most effective enhancement generally
occurs at an offset that is determined by the atomic transition frequency
difference and the coupling Rabi frequency.


title:
Stability of charge inversion, Thomson problem and application to
  electrophoresis

abstract:
  We analyse charge inversion in colloidal systems at zero temperature using
stability concepts, and connect this to the classical Thomson problem of
arranging electrons on sphere. We show that for a finite microion charge, the
globally stable, lowest energy state of the complex formed by the colloid and
the oppositely charged microions is always overcharged. This effect disappears
in the continuous limit. Additionally, a layer of at least twice as many
microions as required for charge neutrality is always locally stable. In an
applied external electric field the stability of the microion cloud is reduced.
Finally, this approach is applied to a system of two colloids at low but finite
temperature.


title:
On unusual narrow transmission bands for a multi-layered periodic
  structure containing left-handed materials

abstract:
  A multi-layered structure consisting of alternate right-handed material (RHM)
and left-handed material (LHM)is considered and the unusual narrow transmission
bands are explained as the competitive results of the Bragg condition and the
transparent condition. These unusual narrow transmission bands may exist
regardless whether the optical length of the LHM layer cancels the optical
length of the RHM layer or not. This unusual transmission property may
disappear when the reflection coefficient for each interface is small and the
optical length of the LHM layer does not cancel the optical length of the RHM
layer. An non-ideal model when the LHM is dispersive and lossy is also employed
to confirm the unusual transmission phenomenon.


title: The SLAC Polarized Electron Source

abstract:
  The SLAC PES, developed in the early 1990s for the SLC, has been in
continuous use since 1992, during which time it has undergone numerous
upgrades. The upgrades include improved cathodes with their matching laser
systems, modified activation techniques and better diagnostics. The source
itself and its performance with these upgrades will be described with special
attention given to recent high-intensity long-pulse operation for the E-158
fixed-target parity-violating experiment.


title:
Self-consistent system of equations for a kinetic description of the
  low-pressure discharges accounting for the nonlocal and collisionless
  electron dynamics

abstract:
  For low-pressure discharges, when the electron mean free path is larger or
comparable with the discharge length, the electron dynamics is essentially
nonlocal. Moreover, the electron energy distribution function (EEDF) deviates
considerably from a Maxwellian. Therefore, an accurate kinetic description of
the low-pressure discharges requires knowledge of the nonlocal conductivity
operator and calculation of the nonMaxwellian EEDF. The previous treatments
made use of simplifying assumptions: a uniform density profile and a Maxwellian
EEDF. In the present study a self-consistent system of equations for the
kinetic description of nonlocal, nonuniform, nearly collisionless plasmas of
low-pressure discharges is derived. It consists of the nonlocal conductivity
operator and the averaged kinetic equation for calculation of the nonMaxwellian
EEDF. The importance of accounting for the nonuniform plasma density profile on
both the current density profile and the EEDF is demonstrated.


title: Citation Networks in High Energy Physics

abstract:
  The citation network constituted by the SPIRES data base is investigated
empirically. The probability that a given paper in the SPIRES data base has $k$
citations is well described by simple power laws, $P(k) \propto k^{-\alpha}$,
with $\alpha \approx 1.2$ for $k$ less than 50 citations and $\alpha \approx
2.3$ for 50 or more citations. Two models are presented that both represent the
data well, one which generates power laws and one which generates a stretched
exponential. It is not possible to discriminate between these models on the
present empirical basis. A consideration of citation distribution by subfield
shows that the citation patterns of high energy physics form a remarkably
homogeneous network. Further, we utilize the knowledge of the citation
distributions to demonstrate the extreme improbability that the citation
records of selected individuals and institutions have been obtained by a random
draw on the resulting distribution.


title:
Monitoring of the Membrane Potential in Proteoliposomes with
  Incorporated Cytochrome-c Oxidase Using the Fluorescent Dye Indocyanine

abstract:
  A method has been developed to monitor changes of the membrane potential
across vesicle membranes in real time. Using the potential-sensitive
fluorescent dye indocyanine and on the basis of water/lipid redistribution
model, a calculation procedure has been introduced to estimate the membrane
potential in vesicles with incorporated cytochrome-c oxidase. Physical
parameters, such as vesicle size distribution and density of the lipid bilayer
were estimated and used as calculation parameters. By extrapolation of
transient potential change to zero time, the initial rate of the potential
change (dU/dt) has been calculated. It is also shown, that the initial
potential change (dU/dt) may be used to study the proton/electron stoichiometry
of cytochrome-c oxidase incorporated in the vesicles.


title: Geometry and Quantum Mechanics

abstract:
  Attempts for a geometrical interpretation of Quantum Theory were made,
notably the deBroglie-Bohm formulation. This was further refined by Santamato
who invoked Weyl's geometry. However these attempts left a number of unanswered
questions. In the present paper we return to these two formulations, in the
context of recent studies invoking fuzzy spacetime and noncommutative geometry.
We argue that it is now possible to explain the earlier shortcomings. At the
same time we get an insight into the geometric origin of the deBroglie
wavelength itself as also the Wilson-Sommerfeld Quantization rule.


title: Brownian Motion of Grains and Negative Friction in Dusty Plasmas

abstract:
  Within the approximation of dominant charging collisions the explicit
microscopic calculations of the Fokker-Planck kinetic coefficients for
highly-charged grains moving in plasma are performed. It is shown that due to
ion absorption by grain the friction coefficient can be negative and the
appropriate threshold value of the grain charge is found. The stationary
solutions of the Fokker-Planck equation with the velocity dependent kinetic
coefficient are obtained and the considerable deviation of such solutions from
the Maxwellian distribution is established.


title: Resolved diffraction patterns from a reflection grating for atoms

abstract:
  We have studied atomic diffraction at normal incidence from an evanescent
standing wave with a high resolution using velocity selective Raman
transitions. We have observed up to 3 resolved orders of diffraction, which are
well accounted for by a scalar diffraction theory. In our experiment the
transverse coherence length of the source is greater than the period of the
diffraction grating.


title: Degradation of GPS performance in geomagnetically disturbed conditions

abstract:
  The GPS performance is impaired in conditions of geomagnetic distrubances.
The rms error of positioning accuracy increases in the case where two-frequency
GPS receivers of three main types (ASHTECH, TRIMBLE, and AOA) are in operation.
For ASHTECH receivers (unlike AOA and TRIMBLE) there is also a clear
correlation between the slip density of the one- and two-frequency modes of
positioning and the level of geomagnetic disturbance.


title:
Hydration of Krypton and Consideration of Clathrate Models of
  Hydrophobic Effects from the Perspective of Quasi-Chemical Theory

abstract:
  AIMD results on a liquid krypton-water system are compared to recent XAFS
results for the radial hydration structure for a Kr atom in liquid water
solution. The comparisons with the liquid solution results are satisfactory and
significantly different from the radial distributions extracted from the data
on the solid clathrate hydrate phase. The calculations also produce the
coordination number distribution that can be examined for metastable
coordination structures suggesting possibilities for clathrate-like
organization; none are seen in these results. Clathrate pictures of hydrophobic
hydration are discussed, as is the quasi-chemical theory that should provide a
basis for clathrate pictures. Outer shell contributions are discussed and
accurately estimated; they are positive and larger than the positive
experimental hydration free energy of Kr(aq), implying that inner shell
contributions must be negative. Clathrate-like inner shell coordination
structures extracted from the simulation of the liquid, and then subjected to
quantum chemical optimization, always decomposed. Interactions with the outer
shell material are decisive in stabilizing coordination structures observed in
liquid solution and in clathrate phases. The ``what are we to tell students''
question about hydrophobic hydration, often answered with structural models
such as clathrate pictures, is then considered; we propose an alternative
answer that is consistent with successful molecular theories of hydrophobic
effects and based upon distinctive observable properties of liquid water.
Considerations of parsimony, for instance Ockham's razor, then suggest that
additional structural hypotheses in response to ``what are we to tell
students'' aren't required at this stage


title: Progress in Muon Cooling Research and Development

abstract:
  The MuCool R&D program is described. The aim of MuCool is to develop all key
pieces of hardware required for ionization cooling of a muon beam. This effort
will lead to a more detailed understanding of the construction and operating
costs of such hardware, as well as to optimized designs that can be used to
build a Neutrino Factory or Muon Collider. This work is being undertaken by a
broad collaboration including physicists and engineers from many national
laboratories and universities in the U.S. and abroad. The intended schedule of
work will lead to ionization cooling being well enough established that a
construction decision for a Neutrino Factory could be taken before the end of
this decade based on a solid technical foundation.


title: Effect of Cooling Water on Stability of NLC Linac Components

abstract:
  Vertical vibration of linac components (accelerating structures, girders and
quadrupoles) in the NLC has been studied experimentally and analytically.
Effects such as structural resonances and vibration caused by cooling water
both in accelerating structures and quadrupoles have been considered.
Experimental data has been compared with analytical predictions and simulations
using ANSYS. A design, incorporating the proper decoupling of structure
vibrations from the linac quadrupoles, is being pursued.


title:
Modifications of the Lorentz Force Law Complying with Galilean
  Transformations and the Local-Ether Propagation Model

abstract:
  It is generally expected from intuition that the electromagnetic force
exerted on a charged particle should remain unchanged when observed in
different reference frames in uniform translational motion. In the special
relativity, this invariance is achieved by invoking the Lorentz transformation
of space and time. In this investigation an entirely different interpretation
of the invariance of force is presented. We propose a new model of the
electromagnetic force given in terms of the augmented potentials, which are
derived from the electric scalar potential by incorporating a velocity
difference between involved particles. The propagation of the potentials is
supposed to follow the local-ether model. All of the position vectors, time
derivatives, and velocities involved in the proposed potentials and force law
are referred specifically to their respective frames. By virtue of this
feature, the electromagnetic force is independent of reference frame simply
based on Galilean transformations. The proposed model looks quite different
from the Lorentz force law, except the electrostatic force. However, under the
common low-speed condition where the mobile charged particles forming the
current drift very slowly in a neutralizing matrix, it is shown that the
proposed model reduces to the Lorentz force law, if the latter is observed in
the matrix frame as done tacitly in common practice.


title:
Three Dimensional Photothermal Deflection of Solids Using Modulated CW
  Lasers : Theoretical Development

abstract:
  In this paper, a detailed theoretical treatment of the three dimensional
photothermal deflection, under modulated cw excitation, is presented for a
three layer system (backing-solid sample- fluid).By using a technique based on
Green's function and integral transformations we find the explicit expressions
for laser induced temperature distribution function and the photothermal
deflection of the probe beam. Numerical analysis of those expressions for
certain solid samples leads to some interesting results.


title: Analise Termodinamica da aceleracao de uma massa

abstract:
  We analyse the acceleration of a mass with a simple structure taking into
account Thermodynamics. Two situations are analysed. The first one for the
application of a localized force to a point of the mass. The second one for the
application of a force to the entire mass. The two situations are not
equivalent. For the first situation we have an increase of temperature of the
mass, resulting from an internal damping, during a transient.


title:
Generic composition of boosts: an elementary derivation of the Wigner
  rotation

abstract:
  Because of its apparent complexity, the discussion of Wigner rotation is
usually reduced to the study of Thomas precession, which is too specific a case
to allow a deep understanding of boost composition. However, by simple
arguments and linear algebra, the result for the Wigner rotation is obtained
straightforwardly, leading to a formula written in a manageable form, The
result is exemplified in the context of the aberration of light.


title: Polarized Electrons Using the PWT RF Gun

abstract:
  Future colliders that require low-emittance highly-polarized electron beams
are the main motivation for developing a polarized rf gun. However there are
both technical and physics issues in generating highly polarized electron beams
using rf guns that remain to be resolved. The PWT design offers promising
features that may facilitate solutions to technical problems such as field
emission and poor vacuum. Physics issues such as emission time now seem to be
satisfactorily resolved. Other issues, such as the effect of magnetic fields at
the cathode-both those associated with the rf field and those imposed by
schemes to produce flat beams-are still open questions. Potential solution of
remaining problems will be discussed in the context of the PWT design.


title:
Alternative statistical-mechanical descriptions of decaying
  two-dimensional turbulence in terms of "patches" and "points"

abstract:
  Numerical and analytical studies of decaying, two-dimensional (2D)
Navier-Stokes (NS) turbulence at high Reynolds numbers are reported. The effort
is to determine computable distinctions between two different formulations of
maximum entropy predictions for the decayed, late-time state. Both formulations
define an entropy through a somewhat ad hoc discretization of vorticity to the
"particles" of which statistical mechanical methods are employed to define an
entropy, before passing to a mean-field limit. In one case, the particles are
delta-function parallel "line" vortices ("points" in two dimensions), and in
the other, they are finite-area, mutually-exclusive convected "patches" of
vorticity which in the limit of zero area become "points." We use
time-dependent, spectral-method direct numerical simulation of the
Navier-Stokes equations to see if initial conditions which should relax to
different late-time states under the two formulations actually do so.


title: Guided Modes in Negative Refractive Index Waveguides

abstract:
  We study linear guided waves propagating in a slab waveguide made of a
negative-refraction- index material, the so-called left-handed waveguide. We
reveal that the guided waves in left-handed waveguides possess a number of
peculiar properties, such as the absence of the fundamental modes, mode double
degeneracy, and sign-varying energy ux. In particular, we predict the existence
of novel types of guided waves with a dipole-vortex structure of the Pointing
vector.


title: The Nobel Prize in Physics 2002 for the observation of cosmic neutrinos

abstract:
  A brief description of the work for which the first half of the Nobel prize
for physics for the year 2002 is presented.


title:
Evolution of electronic and ionic structure of Mg-clusters with the
  growth cluster size

abstract:
  The optimized structure and electronic properties of neutral and singly
charged magnesium clusters have been investigated using ab initio theoretical
methods based on density-functional theory and systematic post-Hartree-Fock
many-body perturbation theory accounting for all electrons in the system. We
have systematically calculated the optimized geometries of neutral and singly
charged magnesium clusters consisting of up to 21 atoms, electronic shell
closures, binding energies per atom, ionization potentials and the gap between
the highest occupied and the lowest unoccupied molecular orbitals. We have
investigated the transition to the hcp structure and metallic evolution of the
magnesium clusters, as well as the stability of linear chains and rings of
magnesium atoms. The results obtained are compared with the available
experimental data and the results of other theoretical works.


title: Teaching with Physlets: Examples from Optics

abstract:
  Physlets are scriptable Java applets that can be used for physics
instruction. In this article we discuss the pedagogical foundations of Physlet
use and provide a sample of Physlet-based exercises that could be used to teach
optics.


title: Transfer Potentials shape and equilibrate Monetary Systems

abstract:
  We analyze a monetary system of random money transfer on the basis of double
entry bookkeeping. Without boundary conditions, we do not reach a price
equilibrium and violate text-book formulas of economists quantity theory
(MV=PQ). To match the resulting quantity of money with the model assumption of
a constant price, we have to impose boundary conditions. They either restrict
specific transfers globally or impose transfers locally. Both connect through a
general framework of transfer potentials. We show that either restricted or
imposed transfers can shape gaussian, tent-shape exponential,
boltzmann-exponential, pareto or periodic equilibrium distributions. We derive
the master equation and find its general time dependent approximate solution.
An equivalent of quantity theory for random money transfer under the boundary
conditions of transfer potentials is given.


title:
Electrospray techniques for the study of liquid energetics by
  hyperquenched glass calorimetry

abstract:
  We describe an electrospray technique for in situ preparation, for
differential scanning calorimetry study, of samples of molecular liquids
quenched into the glassy state on extremely short time scales (hyperquenched).
We study the case of propylene glycol PG in some detail. Using a fictive
temperature method of obtaining the temperature dependence of enthalpy
relaxation, we show that the electrospray method yields quenching rates of ~105
K/s, while the more common method, dropping a sealed pan of sample into liquid
nitrogen, yields only 120 K/s. Hyperquenched samples start to relax
exothermically far below the glass temperature, at a temperature where the
thermal energy permits escape from the shallow traps in which the system
becomes localized during hyperquenching. This permits estimation of the trap
depths, which are then compared with the activation energy estimated from the
fictive temperature of the glass and the relaxation time at the fictive
temperature. The trap depth in molar energy units is compared with the "height
of the landscape" for PG, the quasi-lattice energy of the liquid based on the
enthalpy of vaporization, and the single molecule activation energy for
diffusion in hydrogen bonded crystals. The implications for the topography of
the energy landscape and the mechanism of its exploration, are considered.


title:
Simplified amino acid alphabets based on deviation of conditional
  probability from random background

abstract:
  The primitive data for deducing the Miyazawa-Jernigan contact energy or
BLOSUM score matrix consists of pair frequency counts. Each amino acid
corresponds to a conditional probability distribution. Based on the deviation
of such conditional probability from random background, a scheme for reduction
of amino acid alphabet is proposed. It is observed that evident discrepancy
exists between reduced alphabets obtained from raw data of the
Miyazawa-Jernigan's and BLOSUM's residue pair counts. Taking homologous
sequence database SCOP40 as a test set, we detect homology with the obtained
coarse-grained substitution matrices. It is verified that the reduced alphabets
obtained well preserve information contained in the original 20-letter
alphabet.


title:
Advanced configuration of gravitational-wave interferometer on the base
  of "sensitive mode" in "white-light cavity"

abstract:
  A novel conception of "sensitive mode" (SM) is proposed to apply in
gravitational-wave advanced interferometer configuration. The SM is resonant
oscillation of electromagnetic field in "white-light cavity", where the
resonance line is broadened without decreasing cavity quality. The frequency of
the SM is greatly susceptible to the change of cavity length, and the SM is
established in a cavity with time constant smaller than a conventional mode.
Due to these advantages the sensitivity and bandwidth of AIC can be increased.


title:
Distances and classification of amino acids for different protein
  secondary structures

abstract:
  Window profiles of amino acids in protein sequences are taken as a
description of the amino acid environment. The relative entropy or
Kullback-Leibler distance derived from profiles is used as a measure of
dissimilarity for comparison of amino acids and secondary structure
conformations. Distance matrices of amino acid pairs at different conformations
are obtained, which display a non-negligible dependence of amino acid
similarity on conformations. Based on the conformation specific distances
clustering analysis for amino acids is conducted.


title: Laser Stripping via a Broad Stark State for a High-Intensity Proton Ring

abstract:
  A new type of charge-exchange injection scheme for high-intensity proton
rings that use a laser beam and an undulator magnet is proposed. The elementary
stripping process is resonant photoionization via a broad Stark state formed by
the Stark effect at an energy level near the peak of the potential barrier. The
method used to estimate the parameters of the necessary laser beam and magnetic
field is described. As an application to an actual accelerator, a laser
stripping system using a high-finesse Fabry-Perot resonator and an undulator is
proposed. An estimation of the photon loss due to the pumping-up of H$^0$
atoms, tunability of the system and the emittance growth due to stripping in
the undulator magnet is also given.


title: A Short Range Force

abstract:
  Gravitomagnetic and gravitoelectric forces have been studied for sometime and
tests for detecting such forces arising from the earth, are under way. We apply
similar considerations at the level of elementary particles in a formulation
using General Relativity, and deduce the presence of short range forces. A
possible candidate could be the somewhat recently detected but otherwise
mysterious short range $B_{(3)}$ force, mediated by massive "photons".


title: GUI Tools for an Enhanced User Experience

abstract:
  For instruments with many occasional users, it is important to have easy to
use software. To support the frequent users it is important to be flexible.
Using a scripting language to design a GUI and exposing it to the user allows
us to do both. We present our work on a GUI for reflectometry data analysis and
reduction written in Tcl/Tk and Octave, with underlying C code for the
numerically intensive portions. As well as being easier to train new users, the
new software allows existing users to do in minutes what used to take hours.


title: The right tool for the job

abstract:
  Tcl/tk provides for fast and flexible interface design but slow and
cumbersome vector processing. Octave provides fast and flexible vector
processing but slow and cumbersome interface design. Calling octave from tcl
gives you the flexibility to do a broad range of fast numerical manipulations
as part of an embedded GUI. We present a way to communicate between them.


title: Dense Atom Clouds in a Holographic Atom Trap

abstract:
  We demonstrate the production of high density cold atom samples (2e14
atoms/cc) in a simple optical lattice formed with YAG light that is diffracted
from a holographic phase plate. A loading protocol is described that results in
10,000 atoms per lattice site. Rapid free evaporation leads to phase space
densities of 1/150 within 50 msec. The resulting small, high density atomic
clouds are very attractive for a number of experiments, including ultracold
Rydberg atom physics.


title:
Improving efficiency of supercontinuum generation in photonic crystal
  fibers by direct degenerate four-wave-mixing

abstract:
  We numerically study supercontinuum (SC) generation in photonic crystal
fibers pumped with low-power 30-ps pulses close to the zero dispersion
wavelength 647nm. We show how the efficiency is significantly improved by
designing the dispersion to allow widely separated spectral lines generated by
degenerate four-wave-mixing (FWM) directly from the pump to broaden and merge.
By proper modification of the dispersion profile the generation of additional
FWM Stokes and anti-Stokes lines results in efficient generation of an 800nm
wide SC. Simulations show that the predicted efficient SC generation is more
robust and can survive fiber imperfections modelled as random fluctuations of
the dispersion coefficients along the fiber length.


title: Aerosol contents at an altitude of ~2 km in central Himalayas

abstract:
  Aerosols, both natural and anthropogenic, play an important role in the
atmospheric science, by imparting radiative forcing and perturbing the
radiative balance of the Earth atmosphere system as well as by degrading the
environment. To understand the effect of aerosols on our geo/biosphere system,
it is essential to characterize their physical and chemical properties
regionally because of the regional nature of their properties and the short
lifetime. As most of the aerosol sources are of terrestrial origin the
variability of their properties will be very large close to the surface. At
higher altitudes, above the mixing region, and in the free troposphere, the
aerosol characteristics have a more synoptic perspective; would be indicative
of the background level and are useful to understand long-term impacts. Such
systematic measurements of aerosols at high altitudes are practically
non-existing in India. Realising the potential and need for such studies, an
activity has been initiated at Manora Peak, Nainital in the Shivalik Hills of
Central Himalayas at an altitude of $\sim$2 km. The present paper provides the
preliminary results of these aerosol measurements. These daytime measurements
are compared with the existing earlier nighttime measurements.


title: Modeling Copper Cables and Connectors

abstract:
  High-speed data busses constructed from copper components are both difficult
to model and important to accurately simulate. Using analytic signal theory and
an extension of the skin effect for non-uniform conductivity, experimental data
taken from IEEE 1394-1995 cables and connectors is used to predict the transfer
function of a 4.5 meter cable with two connectors. With these techniques any
length of cable between two connectors can be simulated with high accuracy,
including all the cable and connector losses and the infinitely summed standing
waves that occur between the connectors.


title: Flux Correlation Approach to Thermal Reactions and Recombination Rate

abstract:
  The rate constants for recombination and exchange processes are studied in
terms of two different flux correlation approaches: one is the Yamamoto
approach, which is based on the linear response theory, and the other is the
Miller one. Using those approaches we consider two exactly solvable cases,
i.e., the free particle and the parabolic potential models. Since the rate
constants for recombination and exchange processes are calculated by Laplace
transforms of the flux correlation functions, the two approaches give different
results. In the present calculation, we find that the rate constant in the
Yamamoto approach is larger than that in the Miller approach by about 40% at
low temperature ($\sim 100$ K) and high pressure ($\sim 1$ GPa). The difference
is considerable in the region where quantum effects dominate.


title: Boundary processing for Monte Carlo Simulations in the Gap-Tooth Scheme

abstract:
  This note reports on a scheme for interpolating the boundary conditions be-
tween non-adjacent modeling regions when the model is based on Monte-Carlo
computations of a collection of particles. The scheme conserves particles in a
natural way, and thereby can be made to conserve other quantities.


title:
Vortex tubes in velocity fields of laboratory isotropic turbulence:
  dependence on the Reynolds number

abstract:
  The streamwise and transverse velocities are measured simultaneously in
isotropic grid turbulence at relatively high Reynolds numbers, Re(lambda) =
110-330. Using a conditional averaging technique, we extract typical
intermittency patterns, which are consistent with velocity profiles of a model
for a vortex tube, i.e., Burgers vortex. The radii of the vortex tubes are
several of the Kolmogorov length regardless of the Reynolds number. Using the
distribution of an interval between successive enhancements of a small-scale
velocity increment, we study the spatial distribution of vortex tubes. The
vortex tubes tend to cluster together. This tendency is increasingly
significant with the Reynolds number. Using statistics of velocity increments,
we also study the energetical importance of vortex tubes as a function of the
scale. The vortex tubes are important over the background flow at small scales
especially below the Taylor microscale. At a fixed scale, the importance is
increasingly significant with the Reynolds number.


title:
A study on transmitted intensity of disturbance for air-spaced Glan-type
  polarizing prisms

abstract:
  We study theoretically and experimentally the transmission intensity of
polarized light through the air-spaced Glan-type polarizing prsims. It is found
that the variation of the transmitted intensity with the rotation angle
deviates from Malus Law, exhibiting a cyclic fluctuation with the rotation
angle. The occurrence of the disturbance is explained by the use of an argument
based on the interference effect produced from the air-gap in the prisms. The
theoretcal results are well agreed with the experimental ones. By selecting the
proper cut angle of prism and reducing the thickness of air-gap in prism, the
disturbance may be minimized.


title:
Traveling wave packets of total electron content disturbances as deduced
  from global GPS network data

abstract:
  We identified a new class of mid-latitude medium-scale traveling ionospheric
disturbances (MS TIDs), viz. traveling wave packets (TWPs) of total electron
content (TEC) disturbances. For the first time, the morphology of TWPs is
presented for 105 days. Using the technique of GPS interferometry of TIDs we
carried out a detailed analysis of the spatial-temporal properties of TWPs by
considering an example of the most conspicuous manifestation of TWPs on October
18, 2001 over California, USA. The velocity and direction of TWPs correspond to
those of mid-latitude MS TIDs obtained previously from analyzing the phase
characteristics of HF radio signals as well as signals from geostationary
satellites and discrete cosmic radio sources.


title: The Driven Pendulum at Arbitrary Drive Angle

abstract:
  We discuss the equation of motion of the driven pendulum and generalize it to
arbitrary driving angle. The pendulum will oscillate about a stable angle other
than straight down if the drive amplitude and frequency are large enough for a
given drive angle. The emphasis is on the parameters associated with a simply
made demonstration apparatus.


title:
Longitudinal phase space manipulation in energy recovering linac-driven
  free-electron lasers

abstract:
  Energy recovering an electron beam after it has participated in a
free-electron laser (FEL) interaction can be quite challenging because of the
substantial FEL-induced energy spread and the energy anti-damping that occurs
during deceleration. In the Jefferson Lab infrared FEL driver-accelerator, such
an energy recovery scheme was implemented by properly matching the longitudinal
phase space throughout the recirculation transport by employing the so-called
energy compression scheme. In the present paper,after presenting a
single-particle dynamics approach of the method used to energy-recover the
electron beam, we report on experimental validation of the method obtained by
measurements of the so-called "compression efficiency" and "momentum
compaction" lattice transfer maps at different locations in the recirculation
transport line. We also compare these measurements with numerical tracking
simulations.


title: Yet Another Analysis of Dice Problems

abstract:
  During the MaxEnt 2002 workshop in Moscow, Idaho, Tony Vignaux asked again a
few simple questions about using Maximum Entropy or Bayesian approaches for the
famous Dice problems which have been analyzed many times through this workshop
and also in other places. Here, there is another analysis of these problems. I
hope that, this paper will answer a few questions of Tony and other
participants of the workshop on the situations where we can use Maximum Entropy
or Bayesian approaches or even the cases where we can actually use both of
them.
  Keywords: Dice problems and probability theory, Maximum Likelihood, Bayesian
inference, Maximum A Posteriori, Entropy, Maximum entropy, Maximum entropy in
the mean.


title: Improved large-mode area endlessly single-mode photonic crystal fibers

abstract:
  We numerically study the possibilities for improved large-mode area endlessly
single mode photonic crystal fibers for use in high-power delivery
applications. By carefully choosing the optimal hole diameter we find that a
triangular core formed by three missing neighboring air holes considerably
improves the mode area and loss properties compared to the case with a core
formed by one missing air hole. In a realized fiber we demonstrate an
enhancement of the mode area by ~30 % without a corresponding increase in the
attenuation.


title: MCMC joint separation and segmentation of hidden Markov fields

abstract:
  In this contribution, we consider the problem of the blind separation of
noisy instantaneously mixed images. The images are modelized by hidden Markov
fields with unknown parameters. Given the observed images, we give a Bayesian
formulation and we propose to solve the resulting data augmentation problem by
implementing a Monte Carlo Markov Chain (MCMC) procedure. We separate the
unknown variables into two categories:
  1. The parameters of interest which are the mixing matrix, the noise
covariance and the parameters of the sources distributions. 2. The hidden
variables which are the unobserved sources and the unobserved pixels
classification labels.
  The proposed algorithm provides in the stationary regime samples drawn from
the posterior distributions of all the variables involved in the problem
leading to a flexibility in the cost function choice.
  We discuss and characterize some problems of non identifiability and
degeneracies of the parameters likelihood and the behavior of the MCMC
algorithm in this case.
  Finally, we show the results for both synthetic and real data to illustrate
the feasibility of the proposed solution. keywords: MCMC, blind source
separation, hidden Markov fields, segmentation, Bayesian approach


title: Wavelet Domain Image Separation

abstract:
  In this paper, we consider the problem of blind signal and image separation
using a sparse representation of the images in the wavelet domain. We consider
the problem in a Bayesian estimation framework using the fact that the
distribution of the wavelet coefficients of real world images can naturally be
modeled by an exponential power probability density function. The Bayesian
approach which has been used with success in blind source separation gives also
the possibility of including any prior information we may have on the mixing
matrix elements as well as on the hyperparameters (parameters of the prior laws
of the noise and the sources). We consider two cases: first the case where the
wavelet coefficients are assumed to be i.i.d. and second the case where we
model the correlation between the coefficients of two adjacent scales by a
first order Markov chain. This paper only reports on the first case, the second
case results will be reported in a near future. The estimation computations are
done via a Monte Carlo Markov Chain (MCMC) procedure. Some simulations show the
performances of the proposed method. Keywords: Blind source separation,
wavelets, Bayesian estimation, MCMC Hasting-Metropolis algorithm.


title:
Binary N-Step Markov Chain as an Exactly Solvable Model of Long-Range
  Correlated Systems

abstract:
  A theory of systems with long-range correlations based on the consideration
of binary N-step Markov chains is developed. In our model, the conditional
probability that the i-th symbol in the chain equals zero (or unity) is a
linear function of the number of unities among the preceding N symbols. The
model allows exact analytical treatment. The correlation and distribution
functions as well as the variance of number of symbols in the words of
arbitrary length L are obtained analytically and numerically. A self-similarity
of the studied stochastic process is revealed and the similarity transformation
of the chain parameters is presented. The diffusion equation governing the
distribution function of the L-words is explored. If the persistent
correlations are not extremely strong, the distribution function is shown to be
the Gaussian with the variance being nonlinearly dependent on L. The
applicability of the developed theory to the coarse-grained written and DNA
texts is discussed.


title: A Stationary Universe and the Basics of Relativity Theory

abstract:
  A stationary line element of general relativity seems to be compatible to
essential cosmological facts (though only as far as one can expect solving the
nonlinear Einstein equations neglecting local cosmic evolution and all spatial
inhomogeneities as well).
  There is a preferred spatially Euclidean cosmic reference frame where the
extra-galactic speed of light is constant c* = c, and the galaxies are
statistically at rest. Spectral rods and atomic clocks, however, do not
indicate this cosmic space and this cosmic time.
  The solutions put up here for discussion are suitable to avoid serious
difficulties in physics such as a beginning of the universe as a whole or the
necessity of continuous creation of matter or an empty universe with a
cosmological constant but no matter at all.
  Especially from the stationary line element, it follows a negative cosmic
gravitational pressure of one third the critical energy density. In addition,
there is an average baryonic radiation density equivalent to a black body
radiation of approximately 3 K.
  The resulting increase of the time rate of natural clocks in comparison with
cosmic time is a simple explanation for the redshift of starlight. This
redshift turns out to be independent of time, thus indicating a stationary
universe.


title: Dielectrophoresis of charged colloidal suspensions

abstract:
  We present a theoretical study of dielectrophoretic (DEP) crossover spectrum
of two polarizable particles under the action of a nonuniform AC electric
field. For two approaching particles, the mutual polarization interaction
yields a change in their respective dipole moments, and hence, in the DEP
crossover spectrum. The induced polarization effects are captured by the
multiple image method. Using spectral representation theory, an analytic
expression for the DEP force is derived. We find that the mutual polarization
effects can change the crossover frequency at which the DEP force changes sign.
The results are found to be in agreement with recent experimental observation
and as they go beyond the standard theory, they help to clarify the important
question of the underlying polarization mechanisms.


title: Unification of classic and quantum mechanics

abstract:
  This paper is a serious attempt at reconciling quantum and classical
mechanics through the concept of dynamic space and the acceptance of non-zero
Ricci tensor for vacuum. Starting with scalar particles, the paper shows that
with those two points allow predictions of General Relativity to be made with
an equation which includes Klein-Gordon as a special case; this equation is
designated the \emph{source equation}. The paper then moves on to show that
Dirac equation is compatible with the source equation written in a more general
form. 4-dimensional optics is introduced as an alternative to space-time, which
is shown to allow similar predictions except in extreme situations, but has the
great advantage of ascribing both gravity and electro dynamics to space
curvature.


title: Hydration and mobility of HO-(aq)

abstract:
  The hydroxide anion plays an essential role in many chemical and biochemical
reactions. But a molecular-scale description of its hydration state, and hence
also its transport, in water is currently controversial. The statistical
mechanical quasi-chemical theory of solutions suggests that HO[H2O]3- is the
predominant species in the aqueous phase under standard conditions. This result
is in close agreement with recent spectroscopic studies on hydroxide water
clusters, and with the available thermodynamic hydration free energies. In
contrast, a recent ab initio molecular dynamics simulation has suggested that
HO[H_2O]4- is the only dominant aqueous solution species. We apply adiabatic ab
initio molecular dynamics simulations, and find good agreement with both the
quasi-chemical theoretical predictions and experimental results. The present
results suggest a picture that is simpler, more traditional, but with
additional subtlety. These coordination structures are labile but the
tri-coordinate species is the prominent case. This conclusion is unaltered with
changes in the electronic density functional. No evidence is found for
rate-determining activated inter-conversion of a HO[H2O]4- trap structure to
HO[H2O]3-, mediating hydroxide transport. The view of HO- diffusion as the
hopping of a proton hole has substantial validity, the rate depending largely
on the dynamic disorder of the water hydrogen-bond network.


title: Red herrings and rotten fish

abstract:
  A longstanding problem in biology has been the origin of pervasive
quarter-power allometric scaling laws that relate many characteristics of
organisms to body mass (M) across the entire spectrum of life from molecules
and microbes to ecosystems and mammals. In particular, whole-organism metabolic
rate, B=aM^b, where a is a taxon-dependent normalisation constant and b is
approximately equal to 3/4 for both animals and plants. Recently Darveau et al.
(hereafter referred to as DSAH) proposed a "multiple-causes model" for B as
"the sum of multiple contributors to metabolism", B_i, which were assumed to
scale as M^(b_i). They obtained for average values of b: 0.78 for the basal
rate and 0.86 for the maximally active rate. In this note we show that DSAH
contains serious technical, theoretical and conceptual errors, including
misrepresentations of published data and of our previous work. We also show
that, within experimental error, there is no empirical evidence for an increase
in b during aerobic activity as suggested by DSAH. Moreover, since DSAH
consider only metabolic rates of mammals and make no attempt to explain why
metabolic rates for other taxa and many other attributes in diverse organisms
also scale with quarter-powers (including most of their input data), their
formulation is hardly the "unifying principle" they claim. These problems were
not addressed in commentaries by Weibel and Burness.


title:
Systematic comparison of force fields for microscopic simulations of
  NaCl in aqueous solutions: Diffusion, free energy of hydration and structural
  properties

abstract:
  In this paper we compare different force fields that are widely used
(Gromacs, Charmm-22/x-Plor, Charmm-27, Amber-1999, OPLS-AA) in biophysical
simulations containing aqueous NaCl. We show that the uncertainties of the
microscopic parameters of, in particular, sodium and, to a lesser extent,
chloride translate into large differences in the computed radial-distribution
functions. This uncertainty reflects the incomplete experimental knowledge of
the structural properties of ionic aqueous solutions at finite molarity.We
discuss possible implications on the computation of potential of mean force and
effective potentials.


title:
Earthquake behaviour and large-event predictability in a sheared
  granular stick-slip system

abstract:
  We present results from a physical experiment which demonstrates that a
sheared granular medium behaves in a manner analogous to earthquake activity.
The device consists of an annular plate rotating over a granular medium in a
stick-slip fashion. Previous observations by us include a bounded critical
state with a power law distribution of event energy consistent with the
Gutenberg-Richter law, here we also reveal stair-case seismicity, clustering,
foreshocks, aftershocks and seismic quiescence. Subcritical and supercritical
regimes have also been observed by us depending on the system configuration. We
investigate the predictability of large events. Using the quiescence between
`shock' events as an alarm condition, it is found that large events are
respectively unpredictable, marginally predictable and highly predictable in
the subcritical, critical and supercritical states.


title: Gauge Poisson representations for birth/death master equations

abstract:
  Poisson representation techniques provide a powerful method for mapping
master equations for birth/death processes -- found in many fields of physics,
chemistry and biology -- into more tractable stochastic differential equations.
However, the usual expansion is not exact in the presence of boundary terms,
which commonly occur when the differential equations are nonlinear. In this
paper, a gauge Poisson technique is introduced that eliminates boundary terms,
to give an exact representation as a weighted rate equation with stochastic
terms. These methods provide novel techniques for calculating and understanding
the effects of number correlations in systems that have a master equation
description. As examples, correlations induced by strong mutations in genetics,
and the astrophysical problem of molecule formation on microscopic grain
surfaces are analyzed. Exact analytic results are obtained that can be compared
with numerical simulations, demonstrating that stochastic gauge techniques can
give exact results where standard Poisson expansions are not able to.

categories: physics.bio-ph astro-ph physics.gen-ph q-bio.PE q-bio.QM


title:
Failure of geometric electromagnetism in the adiabatic vector Kepler
  problem

abstract:
  The magnetic moment of a particle orbiting a straight current-carrying wire
may precess rapidly enough in the wire's magnetic field to justify an adiabatic
approximation, eliminating the rapid time dependence of the magnetic moment and
leaving only the particle position as a slow degree of freedom. To zeroth order
in the adiabatic expansion, the orbits of the particle in the plane
perpendicular to the wire are Keplerian ellipses. Higher order post-adiabatic
corrections make the orbits precess, but recent analysis of this `vector Kepler
problem' has shown that the effective Hamiltonian incorporating a
post-adiabatic scalar potential (`geometric electromagnetism') fails to predict
the precession correctly, while a heuristic alternative succeeds. In this paper
we resolve the apparent failure of the post-adiabatic approximation, by
pointing out that the correct second-order analysis produces a third
Hamiltonian, in which geometric electromagnetism is supplemented by a tensor
potential. The heuristic Hamiltonian of Schmiedmayer and Scrinzi is then shown
to be a canonical transformation of the correct adiabatic Hamiltonian, to
second order. The transformation has the important advantage of removing a
$1/r^3$ singularity which is an artifact of the adiabatic approximation.


title: Pair dynamics in a glass forming binary mixture: Simulations and theory

abstract:
  We have carried out molecular dynamics simulations to understand the dynamics
of a tagged pair of atoms in a strongly non-ideal glass-forming binary
Lennard-Jones mixture (commonly known as Kob-Andersen model). The generalized
time-dependent pair distribution function is calculated separately for the
three pairs (AA, BB and AB). The three pairs are found to behave differently.
The relative diffusion constants are found to vary in the order $D_R^{BB} >
D_R^{AB} > D_R^{AA}$, with $D_R^{BB} \simeq 2D_R^{AA}$, showing the importance
of the hopping process (B hops much more than A). We introduce a non-Gaussian
parameter ($\alpha_2^P (t)$) to monitor the relative motion of a pair of atoms,
and evaluate it for all the three pairs, with initial separations chosen to be
at the first peak of the corresponding partial radial distribution functions.
At intermediate times, significant deviation from the Gaussian behavior of the
pair distribution functions is observed, with different degree for the three
pairs. A simple mean-field (MF) model, proposed originally by Haan [Phys. Rev.
A ${\bf 20}$, 2516 (1979)] for one component liquid, is applied to the case of
binary mixture, and compared with the simulation results. While the MF model
successfully describe the dynamics of the AA and AB pair, the agreement for the
BB pair is less satisfactory. This is attributed to the large scale anharmonic
motions of the B particles in a weak effective potential. Dynamics of next
nearest neighbor pairs are also investigated.


title:
Non-linear quantization for arbitrary distributions and applications to
  Medical Image Processing

abstract:
  We report the development of a scalar quantization approach that helps build
tables of decision and reconstruction levels for any probability density
function (pdf). Several example pdf's are used for illustration:
  Uniform, Gaussian, Laplace, one-sided Rayleigh, and Gamma (One sided and
double-sided symmetrical). The main applications of the methodology are
principally aimed at Multiresolution Image compression where generally the
Stretched Exponential pdf is encountered. Specialising to this important case,
we perform quantization and information entropy calculations from selected
medical MRI (Magnetic Resonance Imaging) pictures of the human brain. The image
histograms are fitted to a Stretched exponential model and the corresponding
entropies are compared.


title: Broad distribution effects in sums of lognormal random variables

abstract:
  The lognormal distribution describing, e.g., exponentials of Gaussian random
variables is one of the most common statistical distributions in physics. It
can exhibit features of broad distributions that imply qualitative departure
from the usual statistical scaling associated to narrow distributions.
Approximate formulae are derived for the typical sums of lognormal random
variables. The validity of these formulae is numerically checked and the
physical consequences, e.g., for the current flowing through small tunnel
junctions, are pointed out.


title:
Quantumlike chaos in the frequency distributions of bases A, C, G, T in
  human chromosome1 DNA

abstract:
  Recent studies of DNA sequence of letters A, C, G and T exhibit the inverse
power law form. Inverse power-law form of the power spectra of fractal
space-time fluctuations is generic to the dynamical systems in nature and is
identified as self-organized criticality. In this study it is shown that the
power spectra of the frequency distributions of bases A, C, G, T in the Human
chromosome 1 DNA exhibit self-organized criticality. DNA is a quasicrystal
possessing maximum packing efficiency in a hierarchy of spirals or loops.
Self-organized criticality implies that non-coding introns may not be
redundant, but serve to organize the effective functioning of the coding exons
in the DNA molecule as a complete unit.


title:
On the physical nature of the electromagnetic induced transparency
  effect

abstract:
  The origin of the electromagnetic induced transparency (EIT) effect is
explained not as the vanish of atom-field interaction, but as the growing of
stimulated emission process due to the efficient four- photon mixing, which
allows the atom to return in the initial state. We point out the importance of
creation the new mathematical model for description the dynamics of optical
transitions, which should be based on the concept of the time invariance
violation in electromagnetic interactions.


title: Developing Mathematics for Insight into Sensorimotor Neurobiology

abstract:
  This paper summarizes a research program to express the organization of
sensorimotor control by specifying physiological states and the conditions for
transitions among them. By a slight change in standard notation, conditional
dynamics provides a moving spotlight, focussing on salient subspaces within a
high-dimensional space. This mathematical approach serves as a window on the
organization of sensorimotor neurobiology. The intertwined efforts to express
the intrinsic organization of neurobiology and to clarify it mathematically are
yielding a mathematical structure that is growing on fertile empirical ground.


title: An Fe-Si-Ni solidification model of the Earth's layering

abstract:
  The physical process creating layered structure in planetary rocky bodies is
considered here to be multicomponent solidification. This is a unified
alternative approach to the present interpretations where each layer is
reasoned and matched individually. The Earth's solidification is modelled using
the ternary phase diagram Fe-Si-Ni. The four cotectic concentrations and the
four corresponding seismic discontinuity radii have been used to show that the
silicon concentration as a function of the distance R from the centre of the
Earth can be modelled by C(Si) = G(R/Re)(R/Re) where G = 0.583, Re is the
Earth's radius and the Ni/Fe ratio is 0.072. Earth would have up to 13
chemically different layers. This model predicts that there are three to four
chemically slightly different sublayers in the D" layer and two boundaries in
the inner core at radii 870 km and 1050 km. The observed hemispheric asymmetry
in the inner core could follow if the Ni-concentration slightly varies locally.
Although this model can account for all the layers using only three elements it
can not, of course, match the full chemistry of the real Earth.


title:
Temperature, precipitation and extreme events during the last century in
  Italy

abstract:
  Around the mid 1990s, the authors set up a broad-based research program with
the aim of better understanding the evolution of Italian climate in the last
100/150 years. The program was developed both within European (UE IMPROVE and
ALPCLIM projects) and National projects (National Research Council (CNR)
project "Reconstruction of the Past Climate in the Mediterranean area"). At
present it is in progress within the "Progetto Finalizzato CLIMAGRI", a project
of the Italian "Ministero per le Politiche Agricole e Forestali". Moreover, in
the next two years, further activities will be performed within the research
program "Local climate variability in relation to global climatic change
phenomena" funded by the Italian "Ministero per l'Istruzione, l'Universita' e
la Ricerca" and by Genoa, Milan, Trieste, Turin and Udine Universities. The
studies so far carried out have improved the availability and the quality of
Italian data and have produced interesting information on the evolution of
temperature, precipitation and some other parameters in the last 100/150 years.
The paper summarises the main results obtained within the research program.


title: Complex Dynamics of Real Quantum, Classical and Hybrid Micro-Machines

abstract:
  Any real interaction process produces many incompatible system versions, or
realisations, giving rise to omnipresent dynamic randomness and universally
defined complexity (arXiv:physics/9806002). Since quantum behaviour dynamically
emerges as the lowest complexity level (arXiv:quant-ph/9902016), quantum
interaction randomness can only be relatively strong, which reveals the causal
origin of quantum indeterminacy (arXiv:quant-ph/9511037) and true quantum chaos
(arXiv:quant-ph/9511035), but rigorously excludes the possibility of unitary
quantum computation, even in an "ideal", noiseless system. Any real computation
is an internally chaotic (multivalued) process of system complexity development
occurring in different regimes. Unitary quantum machines, including their
postulated "magic", cannot be realised as such because their dynamically
single-valued scheme is incompatible with the irreducibly high dynamic
randomness at quantum complexity levels and should be replaced by explicitly
chaotic, intrinsically creative machines already realised in living organisms
and providing their quite different, realistic kind of magic. The related
concepts of reality-based, complex-dynamical nanotechnology, biotechnology and
intelligence are outlined, together with the ensuing change in research
strategy. The unreduced, dynamically multivalued solution to the many-body
problem reveals the true, complex-dynamical basis of solid-state dynamics,
including the origin and internal dynamics of macroscopic quantum states. The
critical, "end-of-science" state of unitary knowledge and the way to positive
change are causally specified within the same, universal concept of complexity.


title: Sub-picosecond compression by velocity bunching in a photo-injector

abstract:
  We present an experimental evidence of a bunch compression scheme that uses a
traveling wave accelerating structure as a compressor. The bunch length issued
from a laser-driven radio-frequency electron source was compressed by a factor
>3 using an S-band traveling wave structure located immediately downstream from
the electron source. Experimental data are found to be in good agreement with
particle tracking simulations.


title: Model Flames in the Boussinesq Limit: The Effects of Feedback

abstract:
  We have studied the fully nonlinear behavior of pre-mixed flames in a
gravitationally stratified medium, subject to the Boussinesq approximation. Key
results include the establishment of criterion for when such flames propagate
as simple planar flames; elucidation of scaling laws for the effective flame
speed; and a study of the stability properties of these flames. The simplicity
of some of our scalings results suggests that analytical work may further
advance our understandings of buoyant flames.


title:
Noether symmetries for charged particle motion under a magnetic monopole
  and general electric fields

abstract:
  The search for Noether point symmetries for non-relativistic charged particle
motion is reduced to the solution for a set of two coupled, linear partial
differential equations for the electromagnetic field. These equations are
completely solved when the magnetic field is produced by a fixed magnetic
monopole. The result is applied to central electric field cases, in particular
to the time-dependent monopole-oscillator problem. As an additional example of
the theory, we found all Noether point symmetries and invariants for a constant
magnetic field and a time-dependent harmonic electric field with a forcing
term.


title: Mass redistribution in variable mass systems

abstract:
  We have developed an alternative formulation based on ${\bf F} = M {\bf a}$
rather than ${\bf F} = d{\bf P}/dt$ for studying variable mass systems. It is
shown that ${\bf F} = M {\bf a}$ can be particularly useful in this context, as
illustrated by various examples involving chains and ropes. The method implies
the division of the whole system into two parts, which are considered
separately, allowing to explore certain aspects as constraint forces.


title: Nyquist method for Wigner-Poisson quantum plasmas

abstract:
  By means of the Nyquist method, we investigate the linear stability of
electrostatic waves in homogeneous equilibria of quantum plasmas described by
the Wigner-Poisson system. We show that, unlike the classical Vlasov-Poisson
system, the Wigner-Poisson case does not necessarily possess a Penrose
functional determining its linear stability properties. The Nyquist method is
then applied to a two-stream distribution, for which we obtain an exact,
necessary and sufficient condition for linear stability, as well as to a
bump-in-tail equilibrium.


title:
A modified Least Squares Lattice filter to identify non stationary
  process

abstract:
  In this paper the author proposes to use the Least Squares Lattice filter
with forgetting factor to estimate time-varying parameters of the model for
noise processes. We simulated an Auto-Regressive (AR) noise process in which we
let the parameters of the AR vary in time. We investigate a new way of
implementation of Least Squares Lattice filter in following the non stationary
time series for stochastic process. Moreover we introduce a modified Least
Squares Lattice filter to whiten the time-series and to remove the non
stationarity. We apply this algorithm to the identification of real times
series data produced by recorded voice.


title: Mixed perturbative expansion: the validity of a model for the cascading

abstract:
  A new type of perturbative expansion is built in order to give a rigorous
derivation and to clarify the range of validity of some commonly used model
equations.
  This model describes the evolution of the modulation of two short and
localized pulses, fundamental and second harmonic, propagating together in a
bulk uniaxial crystal with non-vanishing second order susceptibility $\chi^(2)$
and interacting through the nonlinear effect known as ``cascading'' in
nonlinear optics.
  The perturbative method mixes a multi-scale expansion with a power series
expansion of the susceptibility, and must be carefully adapted to the physical
situation. It allows the determination of the physical conditions under which
the model is valid: the order of magnitude of the walk-off, phase-mismatch,and
anisotropy must have determined values.


title: Supercritical bifurcation of a hula hoop

abstract:
  The motion of a hoop hung on a spinning wire provides an illustrative and
pedagogical example of a supercritical bifurcation. Above a certain angular
velocity threshold Omega_c, the hoop rises, making an angle theta =
(Omega-Omega_c)^(1/2) with the vertical. The equation of motion is derived in
the limit of a long massless wire, and the calculated steady states are
compared to experimental measurements. This simple experiment is suitable for
classroom demonstration, and provides an interesting alternative to the
classical experiment of the bead sliding on a rotation hoop.


title:
Intermittency, scaling and the Fokker-Planck approach to fluctuations of
  the solar wind bulk plasma parameters as seen by the WIND spacecraft

abstract:
  The solar wind provides a natural laboratory for observations of MHD
turbulence over extended temporal scales. Here, we apply a model independent
method of differencing and rescaling to identify self-similarity in the
Probability Density Functions (PDF) of fluctuations in solar wind bulk plasma
parameters as seen by the WIND spacecraft. Whereas the fluctuations of speed v
and IMF magnitude B are multi-fractal, we find that the fluctuations in the ion
density rho, energy densities B^2 and rho v^2 as well as MHD-approximated
Poynting flux vB^2 are mono-scaling on the timescales up to ~26 hours. The
single curve, which we find to describe the fluctuations PDF of all these
quantities up to this timescale, is non-Gaussian. We model this PDF with two
approaches-- Fokker-Planck, for which we derive the transport coefficients and
associated Langevin equation, and the Castaing distribution that arises from a
model for the intermittent turbulent cascade.


title: Nondispersive two-electron wave packets in driven helium

abstract:
  We provide a detailed quantum treatment of the spectral characteristics and
of the dynamics of nondispersive two-electron wave packets along the
periodically driven, collinear frozen planet configuration of helium. These
highly correlated, long-lived wave packets arise as a quantum manifestation of
regular islands in a mixed classical phase space, which are induced by
nonlinear resonances between the external driving and the unperturbed dynamics
of the frozen-planet configuration. Particular emphasis is given to the
dependence of the ionization rates of the wave packet states on the driving
field parameters and on the quantum mechanical phase space resolution, preceded
by a comparison of 1D and 3D life times of the unperturbed frozen planet.
Furthermore, we study the effect of a superimposed static electric field
component, which, on the grounds of classical considerations, is expected to
stabilize the real 3D dynamics against large (and possibly ionizing) deviations
from collinearity.


title:
Ab initio oscillator strengths for transitions between J=1 odd and J=1,2
  even excited states of Ne I

abstract:
  Ab initio theory is developed for radiative transitions between excited
states of neon. Calculations of energies for even excited states J=1, J=2
supplement our previous calculations for J=1 odd excited states. Line strengths
for transitions between J=1 odd and J=1,2 even states of Ne I are evaluated. A
comparison with experiments and semiempirical calculations is given.