title: Invariants of free turbulent decay

abstract:
  In practically all turbulent flows, turbulent energy decay is present and
competes with numerous other phenomena. In Kolmogorov's theory, decay proceeds
by transfer from large energy-containing scales towards small viscous scales
through the "inertial cascade." Yet, this description cannot predict an actual
decay rate, even in the simplest case of homogeneous isotropic turbulence
(HIT). As empirically observed over 50 years, the steepness of the "infrared"
spectrum - at scales larger than energy-containing eddies - determines decay,
but theoretical understanding is still missing. Here, HIT decay laws are
derived from angular momentum invariance at large scales - an approach first
mentioned by Landau in 1944, but unduly dismissed later. This invariance also
predicts the so-far unexplored turbulence decay in layer, tube, and spot zones
in a fluid at rest. Beyond expanded and simplified theoretical descriptions,
these findings suggest new practical modeling strategies for turbulent
dissipation, often deficient in applied simulations.


title:
Characterizing and modeling cyclic behavior in non-stationary time
  series through multi-resolution analysis

abstract:
  A method based on wavelet transform and genetic programming is proposed for
characterizing and modeling variations at multiple scales in non-stationary
time series. The cyclic variations, extracted by wavelets and smoothened by
cubic splines, are well captured by genetic programming in the form of
dynamical equations. For the purpose of illustration, we analyze two different
non-stationary financial time series, S&P CNX Nifty closing index of the
National Stock Exchange (India) and Dow Jones industrial average closing values
through Haar, Daubechies-4 and continuous Morlet wavelets for studying the
character of fluctuations at different scales, before modeling the cyclic
behavior through GP. Cyclic variations emerge at intermediate time scales and
the corresponding dynamical equations reveal characteristic behavior at
different scales.


title:
Does the Danube exist? Versions of reality given by various regional
  climate models and climatological datasets

abstract:
  We present an intercomparison and verification analysis of several regional
climate models (RCMs) nested into the same run of the same Atmospheric Global
Circulation Model (AGCM) regarding their representation of the statistical
properties of the hydrological balance of the Danube river basin for 1961-1990.
We also consider the datasets produced by the driving AGCM, from the ECMWF and
NCEP-NCAR reanalyses. The hydrological balance is computed by integrating the
precipitation and evaporation fields over the area of interest. Large
discrepancies exist among RCMs for the monthly climatology as well as for the
mean and variability of the annual balances, and only few datasets are
consistent with the observed discharge values of the Danube at its Delta, even
if the driving AGCM provides itself an excellent estimate. Since the considered
approach relies on the mass conservation principle and bypasses the details of
the air-land interface modeling, we propose that the atmospheric components of
RCMs still face difficulties in representing the water balance even on a
relatively large scale. Their reliability on smaller river basins may be even
more problematic. Moreover, since for some models the hydrological balance
estimates obtained with the runoff fields do not agree with those obtained via
precipitation and evaporation, some deficiencies of the land models are also
apparent. NCEP-NCAR and ERA-40 reanalyses result to be largely inadequate for
representing the hydrology of the Danube river basin, both for the
reconstruction of the long-term averages and of the seasonal cycle, and cannot
in any sense be used as verification. We suggest that these results should be
carefully considered in the perspective of auditing climate models and
assessing their ability to simulate future climate changes.

categories: physics.ao-ph physics.data-an physics.geo-ph physics.soc-ph


title: Hawks and Doves on Small-World Networks

abstract:
  We explore the Hawk-Dove game on networks with topologies ranging from
regular lattices to random graphs with small-world networks in between. This is
done by means of computer simulations using several update rules for the
population evolutionary dynamics. We find the overall result that cooperation
is sometimes inhibited and sometimes enhanced in those network structures, with
respect to the mixing population case. The differences are due to different
update rules and depend on the gain-to-cost ratio. We analyse and qualitatively
explain this behavior by using local topological arguments.


title: Bubbles and denaturation in DNA

abstract:
  The local opening of DNA is an intriguing phenomenon from a statistical
physics point of view, but is also essential for its biological function. For
instance, the transcription and replication of our genetic code can not take
place without the unwinding of the DNA double helix. Although these biological
processes are driven by proteins, there might well be a relation between these
biological openings and the spontaneous bubble formation due to thermal
fluctuations. Mesoscopic models, like the Peyrard-Bishop-Dauxois model, have
fairly accurately reproduced some experimental denaturation curves and the
sharp phase transition in the thermodynamic limit. It is, hence, tempting to
see whether these models could be used to predict the biological activity of
DNA. In a previous study, we introduced a method that allows to obtain very
accurate results on this subject, which showed that some previous claims in
this direction, based on molecular dynamics studies, were premature. This could
either imply that the present PBD should be improved or that biological
activity can only be predicted in a more complex frame work that involves
interactions with proteins and super helical stresses. In this article, we give
detailed description of the statistical method introduced before. Moreover, for
several DNA sequences, we give a thorough analysis of the bubble-statistics as
function of position and bubble size and the so-called $l$-denaturation curves
that can be measured experimentally. These show that some important
experimental observations are missing in the present model. We discuss how the
present model could be improved.


title: Social Dilemmas and Cooperation in Complex Networks

abstract:
  In this paper we extend the investigation of cooperation in some classical
evolutionary games on populations were the network of interactions among
individuals is of the scale-free type. We show that the update rule, the payoff
computation and, to some extent the timing of the operations, have a marked
influence on the transient dynamics and on the amount of cooperation that can
be established at equilibrium. We also study the dynamical behavior of the
populations and their evolutionary stability.


title:
Effect of an original gear mesh modelling on the modal behaviour of gear
  transmission

abstract:
  Prediction of the vibroacoustic behaviour of geared transmissions is
generally based on determining the excitation sources, the overall modelling of
the transmission, the modal analysis and the solving of the parametric
equations of the motion generated by these models. On the building process of
such large degrees of freedom models, the elastic coupling induced by the gear
mesh is generally described by the meshing stiffness. Nevertheless, when the
contact is established along the tooth width, the resulting moment can
constrain the rotational angles associated to wheel tilting and flexural
deformation of shafts. The scope of this study is to introduce the coupling
terms between wheels associated to this phenomenum. One shows also on the basis
of some examples in what manner they can influence the modal behaviour and the
vibroacoustic response of the transmission.


title:
Generating multi-GeV electron bunches using single stage laser wakefield
  acceleration in a 3D nonlinear regime

abstract:
  The extraordinary ability of space-charge waves in plasmas to accelerate
charged particles at gradients that are orders of magnitude greater than in
current accelerators has been well documented. We develop a phenomenological
framework for Laser WakeField Acceleration (LWFA) in the 3D nonlinear regime,
in which the plasma electrons are expelled by the radiation pressure of a short
pulse laser, leading to nearly complete blowout. Our theory provides a recipe
for designing a LWFA for given laser and plasma parameters and estimates the
number and the energy of the accelerated electrons whether self-injected or
externally injected. These formulas apply for self-guided as well as externally
guided pulses (e.g. by plasma channels). We demonstrate our results by
presenting a sample Particle-In-Cell (PIC) simulation of a 30f sec, 200T W
laser interacting with a 0.75cm long plasma with density 1.5*10^18 cm^-3 to
produce an ultra-short (10f s) mono-energetic bunch of self-injected electrons
at 1.5 GeV with 0.3nC of charge. For future higher-energy accelerator
applications we propose a parameter space, that is distinct from that described
by Gordienko and Pukhov [Physics of Plasmas 12, 043109 (2005)] in that it
involves lower densities and wider spot sizes while keeping the intensity
relatively constant. We find that this helps increase the output electron beam
energy while keeping the efficiency high.


title:
Probability Distributions of Random Electromagnetic Fields in the
  Presence of a Semi-Infinite Isotropic Medium

abstract:
  Using a TE/TM decomposition for an angular plane-wave spectrum of free random
electromagnetic waves and matched boundary conditions, we derive the
probability density function for the energy density of the vector electric
field in the presence of a semi-infinite isotropic medium. The theoretical
analysis is illustrated with calculations and results for good electric
conductors and for a lossless dielectric half-space. The influence of the
permittivity and conductivity on the intensity, random polarization,
statistical distribution and standard deviation of the field is investigated,
both for incident plus reflected fields and for refracted fields. External
refraction is found to result in compression of the fluctuations of the random
field.


title: The Nanotechnology R(evolution)

abstract:
  Nanotechnology as a social concept and investment focal point has drawn much
attention. Here we consider the place of nanotechnology in the second great
technological revolution of mankind that began some 200 years ago. The
so-called nanotechnology revolution represents both a continuation of prior
science and technology trends and a re-awakening to the benefits of significant
investment in fundamental research. We consider the role the military might
play in the development of nanotechnology innovations, nanotechnology's context
in the history of technology, and the global competition to lead the next
technological revolution.


title: Fluctuating hydrodynamic modelling of fluids at the nanoscale

abstract:
  A good representation of mesoscopic fluids is required to combine with
molecular simulations at larger length and time scales (De Fabritiis {\it et.
al}, Phys. Rev. Lett. 97, 134501 (2006)). However, accurate computational
models of the hydrodynamics of nanoscale molecular assemblies are lacking, at
least in part because of the stochastic character of the underlying fluctuating
hydrodynamic equations. Here we derive a finite volume discretization of the
compressible isothermal fluctuating hydrodynamic equations over a regular grid
in the Eulerian reference system. We apply it to fluids such as argon at
arbitrary densities and water under ambient conditions. To that end, molecular
dynamics simulations are used to derive the required fluid properties. The
equilibrium state of the model is shown to be thermodynamically consistent and
correctly reproduces linear hydrodynamics including relaxation of sound and
shear modes. We also consider non-equilibrium states involving diffusion and
convection in cavities with no-slip boundary conditions.


title:
A mechanism to derive multi-power law functions: an application in the
  econophysics framework

abstract:
  It is generally recognized that economical systems, and more in general
complex systems, are characterized by power law distributions. Sometime, these
distributions show a changing of the slope in the tail so that, more
appropriately, they show a multi-power law behavior. We present a method to
derive analytically a two-power law distribution starting from a single power
law function recently obtained, in the frameworks of the generalized
statistical mechanics based on the Sharma-Taneja-Mittal information measure. In
order to test the method, we fit the cumulative distribution of personal income
and gross domestic production of several countries, obtaining a good agreement
for a wide range of data.


title:
Derivation of the potential, field, and locally-conserved charge-current
  density of an arbitrarily moving point-charge

abstract:
  The complete charge-current density and field strength of an arbitrarily
accelerated relativistic point-charge are explicitly calculated. The current
density includes, apart from the well-established three-dimensional
delta-function which is sufficient for its global conservation, additional
delta-contributions depending on the second and third proper-time derivatives
of the position, which are necessary for its local conservation as required by
the internal consistency of classical electrodynamics which implies that local
charge-conservation is an {identity}. Similarly, the field strength includes an
additional delta-contribution which is necessary for obtaining this result. The
Lienard-Wiechert field and charge-current density must therefore be interpreted
as nonlinear generalized functions, i.e., not just as distributions, even
though only linear operations are necessary to verify charge-current
conservation. The four-potential from which this field and the conserved
charge-current density derive is found to be unique in the sense that it is the
only one reducing to an invariant scalar function in the instantaneous rest
frame of the point-charge that leads to a point-like locally-conserved
charge-current density.


title: Enhancement of Rydberg atom interactions using ac Stark shifts

abstract:
  The ac Stark effect was used to induce resonant energy transfer between
translationally cold Rydberg atoms. The Rb Rydberg atoms were obtained by laser
excitation of cold atoms from a magneto-optical trap. Using two-photon
microwave spectroscopy of the 49s_{1/2}-50s_{1/2} transition, the field
strength of a 28.5 GHz dressing field was calibrated. When this dressing field
was set at specific field strengths, the two-atom dipole-dipole process
43d_{5/2} + 43d_{5/2} -> 45p_{3/2} + 41f was dramatically enhanced, due to
induced degeneracy of the initial and final states. A series of observed
resonant field strengths correspond to different magnetic sublevel
possibilities for the initial and final states. These agree well with
calculated resonance fields based on a perturbative ac Stark shift formula.
This method for enhancing interactions is complementary to dc
electric-field-induced resonant energy transfer, but has more flexibility due
to the possibility of varying the applied frequency.


title: Quantum Game Theory and Open Access Publishing

abstract:
  The digital revolution of the information age and in particular the sweeping
changes of scientific communication brought about by computing and novel
communication technology, potentiate global, high grade scientific information
for free. The arXiv for example is the leading scientific communication
platform, mainly for mathematics and physics, where everyone in the world has
free access on. While in some scientific disciplines the open access way is
successfully realized, other disciplines (e.g. humanities and social sciences)
dwell on the traditional path, even though many scientists belonging to these
communities approve the open access principle. In this paper we try to explain
these different publication patterns by using a game theoretical approach.
Based on the assumption, that the main goal of scientists is the maximization
of their reputation, we model different possible game settings, namely a zero
sum game, the prisoners' dilemma case and a version of the stag hunt game, that
show the dilemma of scientists belonging to ''non-open access communities''.
  From an individual perspective, they have no incentive to deviate from the
Nash Equilibrium of traditional publishing. By extending the model using the
quantum game theory approach it can be shown, that if the strength of
entanglement exceeds a certain value, the scientists will overcome the dilemma
and terminate to publish only traditionally in all three settings.


title: Rubidium lifetime in a dark magneto-optical trap

abstract:
  Measurements of rubidium lifetime in a dark magneto-optical trap (DMOT) was
performed at various populations of the bright and dark hyperfine states of the
trapped atoms. The rubidium lifetime in the trap appeared to be shorter if the
atom spent more time in the bright state. A simple explanation of this effect
is based on the increase of the cross-section of rubidium collisions with the
surrounding warm atoms upon rubidium electronic excitation.


title:
Wakefields Generated by Electron Beams Passing Through a Waveguide
  Loaded With an Active Medium

abstract:
  The wakefields of a relativistic electron beam passing through a waveguide
loaded with an active medium with weak resonant dispersion have been
considered. For the calculations in this paper the parameters of the medium are
those of a solution of fullerene (C60) in a nematic liquid crystal that
exhibits activity in the X-band. It was shown that several of the TM
accelerating modes can be amplified for the geometries under consideration;
structures in which higher order modes are amplified exhibit essential
advantages as PASERs. In particular, the amplification of the highest mode
occurs in a structure loaded with a rather thick active medium layer that
maximizes the energy stored by the active medium.


title: Spatial dispersion and energy in strong chiral medium

abstract:
  Since the discovery of backward-wave materials, people have tried to realize
strong chiral medium, which is traditionally thought impossible mainly for the
reason of energy and spatial dispersion. We compare the two most popular
descriptions of chiral medium. After analyzing several possible reasons for the
traditional restriction, we show that strong chirality parameter leads to
positive energy without any frequency-band limitation in the weak spatial
dispersion. Moreover, strong chirality does not result in a strong spatial
dispersion, which occurs only around the traditional limit point. For strong
spatial dispersion where higher-order terms of spatial dispersion need to be
considered, the energy conversation is also valid. Finally, we show that strong
chirality need to be realized from the conjugated type of spatial dispersion.


title:
Transient Hollow Cathode Effects and Z pinch Formation in a High Current
  Capillary Discharge with a Metal Plasma

abstract:
  The results from a series of experiments are presented whose purpose is to
explore different schemes which may lead to the formation of pure metal plasmas
in a capillary discharge with parameters appropriate for X ray lasing. The
experiments were performed in ceramic wall capillary discharges at currents of
up to 120 kA, with an available ID of between 3 and 8 mm and with lengths from
60 to 100 mm. Initial plasma conditions in the capillary exploit transient
hollow cathode effects in a preionizing discharge. A laser focussed onto the
back surface of the cathode initiates both beam activity in the capillary
volume and plasma injection. To promote metal ablation into the pinch channel
of elements other than the ceramic wall material, a number of graded ring
schemes have been tried. The plasma is observed axially using both time and
energy resolved soft X-ray pin hole images as well as from time resolved soft
X-ray spectra. By varying the rate of rise of the current of the main
discharge, and the preionizing conditions the diameter and the stability of the
Z-pinch column are seen to be affected. The ratio of the species from the
ablated wall material to the plasma formed from the graded ring structure is
found to depend both on the capillary dimensions as well as the other operating
conditions.


title: New evidence for triton and helion clustering in nuclei

abstract:
  Normally one plots separation energies $S_{1n}$ and $S_{2n}$ as a function of
neutron number $N$ for a particular proton number $Z$ or plot $S_{1p}$ and
$S_{2p}$ as a function of $Z$ for a particular $N$. Here we plot the separation
energies a little differently: $S_{1n}$ and $S_{2n}$ as a function of $Z$ for a
particular $N$. The same with $S_{1p}$ and $S_{2p}$ as a function of N for a
particular Z. A systematic study of these new plots brings out certain very
interesting generic features which clearly indicate presence of triton ("t")
${^{3}_{1} H_{2}}$ and helion ("h") ${^{3}_{2} He_{1}}$ clustering in nuclei.


title: Fast Switching Ferroelectric Materials for Accelerator Applications

abstract:
  Fast switching (< 10 nsec) measurement results on the recently developed
BST(M) (barium strontium titanium oxide composition with magnesium-based
additions) ferroelectric materials are presented. These materials can be used
as the basis for new advanced technology components suitable for high-gradient
accelerators. A ferroelectric ceramic has an electric field-dependent
dielectric permittivity that can be altered by applying a bias voltage.
Ferroelectric materials offer significant benefits for linear collider
applications, in particular, for switching and control elements where a very
short response time of <10 nsec is required. The measurement results presented
here show that the new BST(M) ceramic exhibits a high tunability factor: a bias
field of 40-50 kV/cm reduces the permittivity by a factor of 1.3-1.5. The
recently developed technology of gold biasing contact deposition on large
diameter (110 cm) thin wall ferroelectric rings allowed ~few nsec switching
times in witness sample experiments. The ferroelectric rings can be used at
high pulsed power (tens of megawatts) for X-band components as well as at high
average power in the range of a few kilowatts for the L-band phase-shifter,
under development for optimization of the ILC rf coupling. Accelerator
applications include fast active X-band and Ka-band high-power ferroelectric
switches, high-power X-band and L-band phase shifters, and tunable
dielectric-loaded accelerating structures.


title: Studies of Particle Acceleration by an Active Microwave Medium

abstract:
  The PASER is potentially a very attractive method for particle acceleration,
in which energy from an active medium is transferred to a charged particle
beam. The effect is similar to the action of a maser or laser with the
stimulated emission of radiation being produced by the virtual photons in the
electromagnetic field of the beam. We have been investigating the possibility
of developing a demonstration PASER operating at X-band. The less restrictive
beam transport and device dimensional tolerances required for working at X-band
rather than optical frequencies as well as the widespread application of X-band
hardware in accelerator technology all contribute to the attractiveness of
performing a PASER demonstration experiment in this frequency range. Key to
this approach is the availability of a new class of active materials that
exhibit photoinduced electron spin polarization. We will report on the status
of active material development and measurements, numerical simulations, and
progress towards a planned microwave PASER acceleration experiment at the
Argonne Wakefield Accelerator facility.


title:
Calculation of three-body resonances using slow-variable discretization
  coupled with complex absorbing potential

abstract:
  We developed a method to calculate positions and widths of three-body
resonances. The method combines the hyperspherical adiabatic approach, slow
variable discretization method (Tolstikhin et al., J. Phys. B: At. Mol. Opt.
Phys. 29, L389 (1996)), and a complex absorbing potential. The method can be
used to obtain resonances having short-range or long-range wave functions. In
particular, we applied the method to obtain very shallow three-body Efimov
resonances for a model system (Nielsen et al., Phys. Rev. A 66, 012705 (2002)).


title: Spin magnetohydrodynamics

abstract:
  Starting from the non-relativistic Pauli description of spin-1/2 particles, a
set of fluid equations, governing the dynamics of such particles interacting
with external fields and other particles, is derived. The equations describe
electrons, positrons, holes, and similar conglomerates. In the case of
electrons, the magnetohydrodynamic limit of an electron-ion plasma is
investigated. The results should be of interest and relevance both to
laboratory and astrophysical plasmas.


title: Three-Loop Radiative Corrections to Lamb Shift and Hyperfine Splitting

abstract:
  We consider three-loop radiative corrections to the Lamb shift and hyperfine
splitting. Corrections of order $\alpha^3(Z\alpha)^5m$ are the largest still
unknown contributions to the Lamb shift in hydrogen. We calculated radiative
corrections to the Lamb shift and hyperfine splitting generated by the diagrams
with insertions of one radiative photon and electron polarization loops in the
graphs with two external photons. We also obtained corrections generated by the
gauge invariant sets of diagrams with two reducible radiative photon insertions
in the electron line and polarization operator insertion in one of the
radiative photons, and diagrams with two reducible radiative photon insertions
in the electron line and polarization operator insertion in one the external
photons. Corrections to the Lamb shift and hyperfine splitting generated by the
diagrams with insertions of the three-loop one-particle reducible diagrams with
radiative photons in the electron line are calculated in the Yennie gauge.


title: "Antiferromagnetism" in social relations and Bonabeau model

abstract:
  We here present a fixed agents version of an original model of the emergence
of hierarchies among social agents first introduced by Bonabeau \textit{et al}.
Having interactions occurring on a social network rather than among 'walkers'
doesn't drastically alter the dynamics. But it makes social structures more
stable and give a clearer picture of the social organisation in a `mixed'
regime.


title:
Direct observation of free excitons in luminescence spectra of xenon
  clusters

abstract:
  Luminescence of surface and free bulk excitons is detected in xenon for the
first time for substrate-free rare-gas clusters. Xenon clusters were produced
by the method of gas condensation in a supersonic jet emitted into vacuum.
Optical study was accompanied by electron diffraction measurements to determine
the structure of clusters.


title:
Dual-Band Negative Index Metamaterial: Double-Negative at 813 nm and
  Single-Negative at 772 nm

abstract:
  This work is concerned with the experimental demonstration of a dual-band
negative index metamaterial. The sample is double-negative (showing both a
negative effective permeability and a negative effective permittivity) for
wavelengths between 799 and 818 nm of linearly polarized light with a real part
of refractive index of about -1.0 at 813 nm; the ratio -Re(n)/Im(n) is close to
1.3 at that wavelength. For an orthogonal polarization, the same sample also
exhibits a negative refractive index in the visible (at 772 nm). The
spectroscopic measurements of the material are in good agreement with the
results obtained from a finite element electromagnetic solver for the actual
geometry of the fabricated sample at both polarizations.


title:
Helicity fluctuation, generation of linking number and effect on
  resistivity

abstract:
  The energy of the stochastic magnetic field is bounded from below by a
topological quantity expressing the degree of linkage of the field lines. When
the bound is saturated one can assume that the storage of a certain magnetic
energy requires a minimal degree of topological complexity. It is then possible
to infer a connection between the helicity content and the average curvature of
the magnetic field lines. The random curvature induce random drifts leading to
an additional dissipation and modified resistivity.


title: Objective quantum theory based on the CP(N-1) affine gauge fields

abstract:
  The ordinary linear quantum theory predicts the quantum correlations at any
distance (the universal superposition principle). It creates the decoherence
problem since quantum interactions entangle states into non-separable
combination. On the other hand the linear quantum theory prevents the existence
of the localizable solutions, and after all, leads to the divergences problem
in the quantum field theory. In order to overcome these difficulties the
non-perturbative nonlinearity originated by the curvature of the compact
quantum phase space has been used.


title: The falling chain of Hopkins, Tait, Steele and Cayley

abstract:
  A uniform, flexible and frictionless chain falling link by link from a heap
by the edge of a table falls with an acceleration $g/3$ if the motion is
nonconservative, but $g/2$ if the motion is conservative, $g$ being the
acceleration due to gravity. Unable to construct such a falling chain, we use
instead higher-dimensional versions of it. A home camcorder is used to measure
the fall of a three-dimensional version called an $xyz$-slider. After
frictional effects are corrected for, its vertical falling acceleration is
found to be $a_x/g = 0.328 \pm 0.004$. This result agrees with the theoretical
value of $a_x/g = 1/3$ for an ideal energy-conserving $xyz$-slider.


title: Two-Loop Bethe Logarithms for non-S Levels

abstract:
  Two-loop Bethe logarithms are calculated for excited P and D states in
hydrogenlike systems, and estimates are presented for all states with higher
angular momenta. These results complete our knowledge of the P and D energy
levels in hydrogen at the order of alpha^8 m_e c^2, where m_e is the electron
mass and c is the speed of light, and scale as Z^6, where Z is the nuclear
charge number. Our analytic and numerical calculations are consistent with the
complete absence of logarithmic terms of order (alpha/pi)^2 (Z alpha)^6 ln[(Z
alpha)^(-2)] m_e c^2 for D states and all states with higher angular momenta.
For higher excited P and D states, a number of poles from lower-lying levels
have to subtracted in the numerical evaluation. We find that, surprisingly, the
corrections of the "squared decay-rate type" are the numerically dominant
contributions in the order (alpha/pi)^2 (Z alpha)^6 m_e c^2 for states with
large angular momenta, and provide an estimate of the entire B_60-coefficient
for Rydberg states with high angular momentum quantum numbers. Our results
reach the predictive limits of the quantum electrodynamic theory of the Lamb
shift.


title: Towards absolute calibration of optical tweezers

abstract:
  Aiming at absolute force calibration of optical tweezers, following a
critical review of proposed theoretical models, we present and test the results
of MDSA (Mie-Debye-Spherical Aberration) theory, an extension of a previous
(MD) model, taking account of spherical aberration at the glass/water
interface. This first-principles theory is formulated entirely in terms of
experimentally accessible parameters (none adjustable). Careful experimental
tests of the MDSA theory, undertaken at two laboratories, with very different
setups, are described. A detailed description is given of the procedures
employed to measure laser beam waist, local beam power at the transparent
microspheres trapped by the tweezers, microsphere radius and the trap
transverse stiffness, as a function of radius and height in the (inverted
microscope) sample chamber. We find generally very good agreement with MDSA
theory predictions, for a wide size range, from the Rayleigh domain to large
radii, including the values most often employed in practice, and at different
chamber heights, both with objective overfilling and underfilling. The results
asymptotically approach geometrical optics in the mean over size intervals, as
they should, and this already happens for size parameters not much larger than
unity. MDSA predictions for the trapping threshold, position of stiffness peak,
stiffness variation with height, multiple equilibrium points and `hopping'
effects among them are verified. Remaining discrepancies are ascribed to focus
degradation, possibly arising from objective aberrations in the infrared, not
yet included in MDSA theory.


title: Goedel and Physics

abstract:
  We introduce some early considerations of physical and mathematical
impossibility as preludes to the Goedel incompleteness theorems. We consider
some informal aspects of these theorems and their underlying assumptions and
discuss some the responses to these theorems by those seeking to draw
conclusions from them about the completability of theories of physics. We argue
that there is no reason to expect Goedel incompleteness to handicap the search
for a description of the laws of Nature, but we do expect it to limit what we
can predict about the outcomes of those laws, and examples are given. We
discuss the Goedel universe and the role it played in exposing the full
spectrum of possibilities that a global understanding of space-time would
reveal. Finally,we show how recent studies of supertasks have shown how global
space-time structure determines the ultimate capability of computational
devices within them.

categories: physics.hist-ph astro-ph gr-qc physics.pop-ph


title: Observation of intermittency in wave turbulence

abstract:
  We report the observation of intermittency in gravity-capillary wave
turbulence on the surface of mercury. We measure the temporal fluctuations of
surface wave amplitude at a given location. We show that the shape of the
probability density function of the local slope increments of the surface waves
strongly changes across the time scales. The related structure functions and
the flatness are found to be power laws of the time scale on more than one
decade. The exponents of these power laws increase nonlinearly with the order
of the structure function. All these observations show the intermittent nature
of the increments of the local slope in wave turbulence. We discuss the
possible origin of this intermittency.

categories: physics.flu-dyn cond-mat.other nlin.CD physics.class-ph


title:
The Effect Of On-Ramp And Off-Ramp On The One Dimensional Road With Open
  Boundaries

abstract:
  The effect of one on-ramp (entry) and one off-ramp (exit) is investigated
numerically in one dimensional-cellular automaton traffic flow model, with open
boundary conditions, using parallel dynamics. Our aim in this paper is to study
how the injecting rates $\alpha$ and $\alpha_{0}$ and the extracting rates
$\beta$ and $\beta_{0}$ acts on the density and flux of cars in one dimensional
road. The priority of occupation at entry site $i_{1}$ (moving at exit site
$i_{2}$) is attributed to the particle which entered (absorbed) in the chain.
Phase diagrams in ($\beta_{0},\alpha_{0}$), and ($\beta,\alpha_{0}$) plans are
established. For $\alpha=0.1$, they show three different topologies in the flow
behaviour. The first one correspond to the presence of four regions, by varying
$\alpha_{0}$; namely low density phase (LDP), intermediate density phase (IDP),
plateau current phase (PCP) and high density phase (HDP). In the second
topology the interdmediate density phase disappears. The third topology
presents only two regions; i.e. low and high density phases. For small values
of $\alpha$, the (IDP) and (PCP) disappears, respectively, by increasing
$\beta$. When increasing $\alpha$, the forth topology, corresponding to one
phase (HDP), appears for low values of $\beta$ and $\beta_{0}$


title:
LArGe: Background suppression using liquid argon (LAr) scintillation for
  0$\nu\beta\beta$ decay search with enriched germanium (Ge) detectors

abstract:
  Measurements with a bare p-type high purity germanium diode (HPGe) submerged
in a 19 kg liquid argon (LAr) scintillation detector at MPIK Heidelberg are
reported. The liquid argon--germanium system (LArGe) is operated as a 4$\pi$
anti-Compton spectrometer to suppress backgrounds in the HPGe. This R&D is
carried out in the framework of the GERDA experiment which searches for
0$\nu\beta\beta$ decays with HPGe detectors enriched in $^{76}$Ge. The goal of
this work is to develop a novel method to discriminate backgrounds in
0$\nu\beta\beta$ search which would ultimately allow to investigate the
effective neutrino mass free of background events down to the inverse mass
hierarchy scale. Other applications in low-background counting are expected.


title: A Vertex Trigger based on Cylindrical Multiwire Proportional Chambers

abstract:
  The article describes the technical implementation and the performance of the
z-vertex trigger (CIP2k), which is part of the H1-experiment at HERA.


title: Coherent Slowing of a Supersonic Beam with an Atomic Paddle

abstract:
  We report the slowing of a supersonic beam by elastic reflection from a
receding atomic mirror. We use a pulsed supersonic nozzle to generate a 511 +/-
9 m/s beam of helium that we slow by reflection from a Si(111)-H(1x1) crystal
placed on the tip of a spinning rotor. We were able to reduce the velocity of
helium by 246 m/s and show that the temperature of the slowed beam is lower
than 250 mK in the co-moving frame.


title: Growing networks under geographical constraints

abstract:
  Inspired by the structure of technological networks, we discuss network
evolution mechanisms which give rise to topological properties found in real
spatial networks. Thus, the peculiar structure of transport and distribution
networks is fundamentally determined by two factors. These are the dependence
of the spatial interaction range of vertices on the vertex attractiveness (or
importance within the network) and on the inhomogeneous distribution of
vertices in space. We propose and analyse numerically a simple model based on
these generating mechanisms which seems, for instance, to be able to reproduce
known structural features of the Internet.


title:
Preacceleration without radiation: the non-existence of preradiation
  phenomenon

abstract:
  An unexpected prediction of classical electrodynamics is that a charge can
accelerate before a force is applied. We would expect that a preaccelerated
charge would radiate so that there would be spontaneous preradiation, an
acausal phenomenon. We reexamine the subtle relation between the Larmor formula
for the power radiated by a point charge and the Abraham-Lorentz equation and
find that for well-behaved external forces acting for finite times, the charge
does not radiate in time intervals where there is preacceleration. That is, for
these forces preradiation does not exist even though the charge is
preaccelerated. The radiative energy is emitted only in time intervals when the
external force acts on the charge.


title:
Comment on 'A generalized Helmholtz theorem for time-varying vector
  fields by A. M. Davis, [Am. J. Phys. 74, 72-76 (2006)]'

abstract:
  In a recent paper Davis formulated a generalized Helmholtz theorem for a
time-varying vector field in terms of the Lorenz gauge retarded potentials. The
purposes of this comment are to point out that Davis's generalization of the
theorem is a version of the extension of the Helmholtz theorem formulated some
years ago by McQuistan and also by Jefimenko and more recently by the present
author and to show that Davis's expression for the time-dependent vector field
is also valid for potentials in gauges other than the Lorenz gaug


title: Instantaneous fields in classical electrodynamics

abstract:
  In this paper we express the retarded fields of Maxwell's theory in terms of
the instantaneous fields of a Galilei-invariant electromagnetic and we find the
vector function whose spatial and temporal derivatives transform the
instantaneous fields into the retarded ones. We conclude that the instantaneous
fields can formally be introduced as unphysical objects into classical
electrodynamics which can be used to find the physical retarded fields.


title:
Fluctuations in time intervals of financial data from the view point of
  the Gini index

abstract:
  We propose an approach to explain fluctuations in time intervals of financial
markets data from the view point of the Gini index. We show the explicit form
of the Gini index for a Weibull distribution which is a good candidate to
describe the first passage time of foreign exchange rate. The analytical
expression of the Gini index gives a very close value with that of empirical
data analysis.


title: Comment on Wavelet Analysis and scaling properties of time series

abstract:
  In a recent work Manimaran et al. [Manimaran et al., Phys. Rev. E 72, 046120
(2005)] propose to use multiresolution Daubechies (DB) wavelets to (detrend)
remove the low frequency trends and subsequently to quantify the multifractal
structure in a given time series. In this comment, by applying DB wavelets to
the long range correlated data we show that in the presence of linear trends,
the wavelets could not able to distinguish the correlations from trends. As the
DB wavelets based detrending will not be able to quantify the correlations
masked by trends, its multifractal extension can not always yield a correct
estimate of the multifractal spectrum of the given data.


title:
High-sensitivity time-resolved intracavity laser Fourier transform
  spectroscopy with vertical cavity surface emitting multiple quantum well
  lasers

abstract:
  Spectra comprised of hundreds of time-components for absorption path lengths
up to 130 km have been recorded around 1050 nm by combining two recent
techniques, intracavity laser spectroscopy with vertical external cavity
surface emitting multiple-quantum-well lasers and time-resolved Fourier
transform spectroscopy. A sensitivity of 1 10^{-10} cm^{-1}.Hz^{-1/2} is
achieved, for simultaneously acquired 10^4 spectral elements, three orders of
magnitude better than the sensitivity obtained in previous similar experiments.
Specific advantages of the method, especially for frequency and intensity
metrology of weak absorption transitions, are discussed.


title: Harris sheet solution for magnetized quantum plasmas

abstract:
  We construct an infinite family of one-dimensional equilibrium solutions for
purely magnetized quantum plasmas described by the quantum hydrodynamic model.
The equilibria depends on the solution of a third-order ordinary differential
equation, which is written in terms of two free functions. One of these free
functions is associated to the magnetic field configuration, while the other is
specified by an equation of state. The case of a Harris sheet type magnetic
field, together with an isothermal distribution, is treated in detail. In
contrast to the classical Harris sheet solution, the quantum case exhibits an
oscillatory pattern for the density.


title: The Rise and Rise of Citation Analysis

abstract:
  With the vast majority of scientific papers now available online, this paper
describes how the Web is allowing physicists and information providers to
measure more accurately the impact of these papers and their authors. Provides
a historical background of citation analysis, impact factor, new citation data
sources (e.g., Google Scholar, Scopus, NASA's Astrophysics Data System Abstract
Service, MathSciNet, ScienceDirect, SciFinder Scholar, Scitation/SPIN, and
SPIRES-HEP), as well as h-index, g-index, and a-index.


title: The effect of electric fields on lipid membranes

abstract:
  Contrary to existing theoretical models, experimental evidence points out
that electroporation (membrane defect formation under external electric fields)
starts to occur within the range of transmembrane voltages that cells may
routinely experience, curiously, just above the range of transmembrane voltages
involved in neural signal transmission. Understanding the underlying principles
of electric fields-lipid membrane interactions seems to carry a great
biological importance.
  An argument is presented toward understanding the theoretical aspects of
electroporation by using the DLVO theory, which has not been recognized
previously in the context of electroporation. Further, the dispersion
interactions (with its quantum nature), of the double layer counterions and
membrane lipid molecules over the Stern layer are emphasized. The sign of these
forces is such that they compress the membrane. A parallel is drawn to the
theory of thin films. The argument is that the external electric field breaks
the symmetry of the disjoining pressures on both sides of a lipid membrane,
resulting in a protrusion of only few lipid molecules. That compromises the
membrane stability on a nanoscale and makes it traversable to ions. The
presented estimate based on these arguments is consistent to electroporation
experiments and existing numerical simulations.


title: Gas Analysis and Monitoring Systems for the RPC Detector of CMS at LHC

abstract:
  The Resistive Plate Chambers (RPC) detector of the CMS experiment at the LHC
proton collider (CERN, Switzerland) will employ an online gas analysis and
monitoring system of the freon-based gas mixture used. We give an overview of
the CMS RPC gas system, describe the project parameters and first results on
gas-chromatograph analysis. Finally, we report on preliminary results for a set
of monitor RPC.


title: Educational cosmic ray experiments with Geiger counters

abstract:
  Experiments concerning the physics of cosmic rays offer to high-school
teachers and students a relatively easy approach to the field of research in
high energy physics. The detection of cosmic rays does not necessarily require
the use of sophisticated equipment, and various properties of the cosmic
radiation can be observed and analysed even by the use of a single Geiger
counter. Nevertheless, the variety of such kind of experiments and the results
obtained are limited because of the inclusive nature of these measurements. A
significant improvement may be obtained when two or more Geiger counters are
operated in coincidence. In this paper we discuss the potential of performing
educational cosmic ray experiments with Geiger counters. In order to show also
the educational value of coincidence techniques, preliminary results of cosmic
ray experiments carried out by the use of a simple coincidence circuit are
briefly discussed.


title:
Interfusion, labeling and stream lines in flow of inviscid barotropic
  fluid

abstract:
  It is shown that the Euler system of hydrodynamic equations for inviscid
barotropic fluid for density and velocity is not a complete system of dynamic
equations for the inviscicd barotropic fluid. It is only a closed subsystem of
four dynamic equation. The complete system of dynamic equation consists of
seven dynamic equations for seven dependent variables: density, velocity and
labeling (Lagrangian coordinates, considered as dependent variables). Solution
of the Cauchy problem for the Euler subsystem is unique. Solution of the Cauchy
problem for the complete hydrodynamic system, containing seven equations, is
unique only for irrotational flows. For vortical flows solution of the Cauchy
problem is not unique. The reason of the nonuniqueness is an interfusion, which
cannot be taken into account properly in the framework of hydrodynamics. There
are some arguments in favour of connection between interfusion and turbulence.


title:
Quantifying bid-ask spreads in the Chinese stock market using
  limit-order book data: Intraday pattern, probability distribution, long
  memory, and multifractal nature

abstract:
  The statistical properties of the bid-ask spread of a frequently traded
Chinese stock listed on the Shenzhen Stock Exchange are investigated using the
limit-order book data. Three different definitions of spread are considered
based on the time right before transactions, the time whenever the highest
buying price or the lowest selling price changes, and a fixed time interval.
The results are qualitatively similar no matter linear prices or logarithmic
prices are used. The average spread exhibits evident intraday patterns
consisting of a big L-shape in morning transactions and a small L-shape in the
afternoon. The distributions of the spread with different definitions decay as
power laws. The tail exponents of spreads at transaction level are well within
the interval $(2,3)$ and that of average spreads are well in line with the
inverse cubic law for different time intervals. Based on the detrended
fluctuation analysis, we found the evidence of long memory in the bid-ask
spread time series for all three definitions, even after the removal of the
intraday pattern. Using the classical box-counting approach for multifractal
analysis, we show that the time series of bid-ask spread does not possess
multifractal nature.


title:
Atom interferometry using wavepackets with constant spatial
  displacements

abstract:
  We demonstrate a standing wave light pulse sequence that places atoms into a
superposition of displaced wavepackets with precisely controlled displacements
that remain constant for times as long as 1 s. The separated wavepackets are
subsequently recombined resulting in atom interference patterns that probe
energy differences of approximately 10^-34 J, and can provide acceleration
measurements that are insensitive to platform vibrations.


title: The hypernuclear physics heritage of Dick Dalitz (1925-2006)

abstract:
  The major contributions of Richard H. Dalitz to hypernuclear physics, since
his first paper in 1955 to his last one in 2005 covering a span of 50 years
during which he founded and led the theoretical study of hypernuclei, are
reviewed from a personal perspective. Topical remarks on the search for
quasi-bound antikaon-nuclear states are made.


title: Optical Magnetism: from Red to Blue

abstract:
  A family of coupled nano-strips with varying dimensions is fabricated to
obtain optical magnetic responses across the whole visible spectrum, from red
to blue. The proposed approach provides one with a universal building block and
a general recipe for producing controllable optical magnetism for various
practical implementations.


title: Multipole structure and coordinate systems

abstract:
  Multipole expansions depend on the coordinate system, so that coefficients of
multipole moments can be set equal to zero by an appropriate choice of
coordinates. Therefore, it is meaningless to say that a physical system has a
nonvanishing quadrupole moment, say, without specifying which coordinate system
is used. (Except if this moment is the lowest non-vanishing one.) This result
is demonstrated for the case of two equal like electric charges. Specifically,
an adapted coordinate system in which the potential is given by a monopole term
only is explicitly found, the coefficients of all higher multipoles vanish
identically. It is suggested that this result can be generalized to other
potential problems, by making equal coordinate surfaces coincide with the
potential problem's equipotential surfaces.


title:
Humidity contribution to C_n^2 over a 600m pathlength in a tropical
  marine environment

abstract:
  We present new optical turbulence structure parameter measurements, C_n^2,
over sea water between La Parguera and Magueyes Island (17.6N 67W) on the
southwest coast of Puerto Rico. The 600 meter horizontal paths were located
approximately 1.5 m and 10 m above sea level. No data of this type has ever
been made available in the literature. Based on the data, we show that the
C_n^2 measurements are about 7 times less compared to equivalent land data.
This strong evidence reinforces our previous argument that humidity must be
accounted for to better ascertain the near surface atmospheric turbulence
effects, which current visible / near infrared C_n^2 bulk models fail to do. We
also explore the generalised fractal dimension of this littoral data and
compare it to our reference land data. We find cases that exhibit monofractal
characteristics, that is to say, the effect of rising temperatures during the
daylight hours upon turbulence are counterbalanced by humidity, leading to a
single characteristic scale for the measurements. In other words, significant
moisture changes in the measurement volume cancels optical turbulence increases
due to temperature rises. Figures available as JPG only.


title:
Influence of lasers propagation delay on the sensitivity of atom
  interferometers

abstract:
  In atom interferometers based on two photon transitions, the delay induced by
the difference of the laser beams paths makes the interferometer sensitive to
the fluctuations of the frequency of the lasers. We first study, in the general
case, how the laser frequency noise affects the performance of the
interferometer measurement. Our calculations are compared with the measurements
performed on our cold atom gravimeter based on stimulated Raman transitions. We
finally extend this study to the case of cold atom gradiometers.


title:
Octupole Contributions to the Generalized Oscillator Strengths of
  Discrete Dipole Transitions in Noble Gases

abstract:
  The generalized oscillator strengths (GOS) of discrete excitations np-nd,
both dipole (L=1) and octupole (L=3) are studied, the latter for the first
time. We demonstrate that although the relevant transitions in the same atom
are closely located in energy, the dependence of their GOS on the momentum
transfer q squared, is remarkably different, so that the GOS corresponding to
L=3 have at least one extra maximum as a function of q squared and dominate
over those of the L=1, starting from about q=1.25$ atomic unit (a.u.). The
calculations were performed in the one particle Hartree-Fock approximation and
with account of many-electron correlations via the Random Phase Approximation
with Exchange. The GOS are studied for values of q squared up to 30 a.u.


title:
Random, but not so much: A parameterization for the returns and
  correlation matrix of financial time series

abstract:
  A parameterization that is a modified version of a previous work is proposed
for the returns and correlation matrix of financial time series and its
properties are studied. This parameterization allows easy introduction of
non-stationarity and it shows several of the characteristics of the true,
observed realizations, such as fat tails, volatility clustering, and a spectrum
of eigenvalues of the correlation matrix that can be understood as an extension
of Random Matrix Theory results. The predicted behavior of this
parameterization for the eigenvalues is compared with the eigenvalues of
Brazilian assets and it is shown that those predictions fit the data better
than Random Matrix Theory.


title: Reversals in nature and the nature of reversals

abstract:
  The asymmetric shape of reversals of the Earth's magnetic field indicates a
possible connection with relaxation oscillations as they were early discussed
by van der Pol. A simple mean-field dynamo model with a spherically symmetric
$\alpha$ coefficient is analysed with view on this similarity, and a comparison
of the time series and the phase space trajectories with those of paleomagnetic
measurements is carried out. For highly supercritical dynamos a very good
agreement with the data is achieved. Deviations of numerical reversal sequences
from Poisson statistics are analysed and compared with paleomagnetic data. The
role of the inner core is discussed in a spectral theoretical context and
arguments and numerical evidence is compiled that the growth of the inner core
might be important for the long term changes of the reversal rate and the
occurrence of superchrons.


title: On Vlasov approach to tokamaks near magnetic axis

abstract:
  A previous proof of non existence of tokamak equilibria with purely poloidal
flow within macroscopic theory [Throumoulopoulos, Weitzner, Tasso, Physics of
Plasmas Vol. 13, 122501 (2006)] motivated this microscopic analysis near
magnetic axis for toroidal and "straight" tokamak plasmas. Despite the new
exact solutions of Vlasov's equation found here, the structure of macroscopic
flows remains elusive.


title: Systematics of spin-polarized small Na clusters

abstract:
  Inspired by recent experiments on fully spin polarized Na clusters, we
perform a systematic survey of neutral Na clusters at all conceivable spin
polarizations. We study the impact of spin state on ionic configuration, on
global shape, and on optical response. For small clusters, the magic electronic
shell at 4 spin-up electrons is a dominating feature leading to preferred
binding for all clusters having four spin-up electrons (combined with 1 to 4
spin-down electrons). Such a preference fades away for larger systems where the
unpolarized state is generally preferred.


title:
Multiscale coupling of molecular dynamics and hydrodynamics: application
  to DNA translocation through a nanopore

abstract:
  We present a multiscale approach to the modeling of polymer dynamics in the
presence of a fluid solvent. The approach combines Langevin Molecular Dynamics
(MD) techniques with a mesoscopic Lattice-Boltzmann (LB) method for the solvent
dynamics. A unique feature of the present approach is that hydrodynamic
interactions between the solute macromolecule and the aqueous solvent are
handled explicitly, and yet in a computationally tractable way due to the dual
particle-field nature of the LB solver. The suitability of the present LB-MD
multiscale approach is demonstrated for the problem of polymer fast
translocation through a nanopore. We also provide an interpretation of our
results in the context of DNA translocation through a nanopore, a problem that
has attracted much theoretical and experimental attention recently.


title: Interplay between topology and dynamics in the World Trade Web

abstract:
  We present an empirical analysis of the network formed by the trade
relationships between all world countries, or World Trade Web (WTW). Each
(directed) link is weighted by the amount of wealth flowing between two
countries, and each country is characterized by the value of its Gross Domestic
Product (GDP). By analysing a set of year-by-year data covering the time
interval 1950-2000, we show that the dynamics of all GDP values and the
evolution of the WTW (trade flow and topology) are tightly coupled. The
probability that two countries are connected depends on their GDP values,
supporting recent theoretical models relating network topology to the presence
of a `hidden' variable (or fitness). On the other hand, the topology is shown
to determine the GDP values due to the exchange between countries. This leads
us to a new framework where the fitness value is a dynamical variable
determining, and at the same time depending on, network topology in a
continuous feedback.


title:
Coarse-grained analysis of a lattice Boltzmann model for planar streamer
  fronts

abstract:
  We study the traveling wave solutions of a lattice Boltzmann model for the
planar streamer fronts that appear in the transport of electrons through a gas
in a strong electrical field. To mimic the physical properties of the impact
ionization reaction, we introduce a reaction matrix containing reaction rates
that depend on the electron velocities. Via a Chapman--Enskog expansion, one is
able to find only a rough approximation for a macroscopic evolution law that
describes the traveling wave solution. We propose to compute these solutions
with the help of a coarse-grained time-stepper, which is an effective evolution
law for the macroscopic fields that only uses appropriately initialized
simulations of the lattice Boltzmann model over short time intervals. The
traveling wave solution is found as a fixed point of the sequential application
of the coarse-grained time-stepper and a shift-back operator. The fixed point
is then computed with a Newton-Krylov Solver. We compare the resulting
solutions with those of the approximate PDE model, and propose a method to find
the minimal physical wave speed.


title:
Experiments and numerical results on nonlinear vibrations of an
  impacting hertzian contact. Part 1: harmonic excitation

abstract:
  The purpose of this paper is to investigate experimental and numerical
dynamic responses of a preloaded vibro-impacting Hertzian contact under
sinusoidal excitation. Dynamic response under random excitation is analysed in
the second part of this paper. A test rig is built corresponding to a double
sphere-plane contact preloaded by the weight of a moving cylinder. Typical
response curves are obtained for several input levels. Time traces and spectral
contents are explored. Both amplitude and phase of harmonics of the dynamic
response are investigated. Linearised resonance frequency and damping ratio are
identified from the almost linear behaviour under very small input amplitude.
Increasing the external input amplitude, the softening behaviour induced by
Hertzian nonlinear stiffness is clearly demonstrated. Resonance peak is
confined in a narrow frequency range. Jump discontinuities are identified for
both amplitude and phase responses. Forced response spectrum exhibits several
harmonics because of nonlinear Hertzian restoring force. Numerical simulations
show a very good agreement with experimental results. For higher input
amplitude, system exhibits vibro-impacts. Loss of contact non-linearity clearly
dominates the dynamic behaviour of the vibroimpacting contact and leads to a
wide frequency range softening resonance. Spectral content of the response is
dominated by both the first and the second harmonics. Evolution of the
experimental downward jump frequency versus input amplitude allows the
identification of the nonlinear damping law during intermittent contact.
Simulations of the vibroimpacting Hertzian contact are performed using a
shooting method and show a very good agreement with experimental results.


title:
Experiments and numerical results on nonlinear vibrations of an
  impacting hertzian contact. Part 2: random excitation

abstract:
  Non linear dynamic behaviour of a normally excited preloaded Hertzian contact
(including possible contact losses) is investigated using an experimental test
rig. It consists on a double sphere plane contact loaded by the weight of a
rigid moving mass. Contact vibrations are generated by a external Gaussian
white noise and exhibit vibroimpact responses when the input level is
sufficiently high. Spectral contents and statistics of the stationary
transmitted normal force are analysed. A single-degree-of-freedom non linear
oscillator including loss of contact and Hertzian non linearities is built for
modelling the experimental system. Theoretical responses are obtained by using
the stationary Fokker-Planck equation and also Monte Carlo simulations. When
contact loss occurrence is very occasional, numerical results shown a very good
agreement with experimental ones. When vibroimpacts occur, results remain in
reasonable agreement with experimental ones, that justify the modelling and the
numerical methods described in this paper. The contact loss non linearity
appears to be rather strong compared to the Hertzian non linearity. It actually
induces a large broadening of the spectral contents of the response. This
result is of great importance in noise generation for a lot of systems such as
mechanisms using contacts to transform motions and forces (gears,
ball-bearings, cam systems, to name a few). It is also of great importance for
tribologists preoccupied to prevent surface dammage.


title: The optical near-field of an aperture tip

abstract:
  We use fluorescent nanospheres as scalar detectors for the electric-field
intensity in order to probe the near-field of an optical tip used in
aperture-type near-field scanning optical microscopy (NSOM). Surprisingly, the
recorded fluorescence images show two intensity lobes if the sphere diameter is
smaller that the aperture diameter, as expected only in the case of vector
detectors like single molecules. We present a simple but realistic, analytical
model for the electric field created by light emitted by a NSOM tip which is
quantitative agreement with the experimental data.


title:
Modeling and Analysis of Composite Antenna Superstrates Consisting on
  Grids of Loaded Wires

abstract:
  We study the characteristics and radiation mechanism of antenna superstrates
based on closely located periodical grids of loaded wires. An explicit
analytical method based on the local field approach is used to study the
reflection and transmission properties of such superstrates. It is shown that
as a result of proper impedance loading there exists a rather wide frequency
band over which currents induced to the grids cancel each other, leading to a
wide transmission maximum. In this regime radiation is produced by the magnetic
dipole moments created by circulating out-of-phase currents flowing in the
grids. An impedance matrix representation is derived for the superstrates, and
the analytical results are validated using full-wave simulations. As a
practical application example we study numerically the radiation
characteristics of dipole antennas illuminating finite-size superstrates.


title: Electrophoresis of positioned nucleosomes

abstract:
  We present in this paper an original approach to compute the electrophoretic
mobility of rigid nucleo-protein complexes like nucleosomes. This model allows
to address theoretically the influence of complex position along DNA, as well
as wrapped length of DNA on the electrophoretic mobility of the complex. The
predictions of the model are in qualitative agreement with experimental results
on mononucleosomes assembled on short DNA fragments (<400bp). Influence of
additional experimental parameters like gel concentration, ionic strength,
effective charges is also discussed in the framework of the model, and is found
to be qualitatively consistent with experiments when available. Based on the
present model, we propose a simple semi-empirical formula describing
positioning of nucleosomes as seen through electrophoresis.


title: Design strategies for optimizing holographic optical tweezers setups

abstract:
  We provide a detailed account of the construction of a system of holographic
optical tweezers. While much information is available on the design, alignment
and calibration of other optical trapping configurations, those based on
holography are relatively poorly described. Inclusion of a spatial light
modulator in the setup gives rise to particular design trade-offs and
constraints, and the system benefits from specific optimization strategies,
which we discuss.


title:
Effect of Elasticity of Shafts, Bearings, Casing and Couplings on the
  Critical Rotational Speeds of a Gearbox

abstract:
  The aim of this study is to analyse the influence of the mechanical
characteristics of the set of components on the critical rotational speeds of a
gearbox. The case of a gearbox fitted out with a helical gear pair was
considered. The shafts and the casing were discretised using the finite element
method. The elastic coupling between the toothed wheels was characterised by a
12 x12 stiffness matrix. The bearings were modelled using radial, axial and
rotational stiffness elements. The calculation of the vibration response
induced by the static transmission error showed that the highest dynamic mesh
forces correspond to a resonant excitation of modes which have a high potential
energy associated with the mesh stiffness. The numerical simulations performed
showed that a realistic prediction of the critical rotational speeds should
take account of all the components of the gearbox.


title:
Optimization of quantum Monte Carlo wave functions by energy
  minimization

abstract:
  We study three wave function optimization methods based on energy
minimization in a variational Monte Carlo framework: the Newton, linear and
perturbative methods. In the Newton method, the parameter variations are
calculated from the energy gradient and Hessian, using a reduced variance
statistical estimator for the latter. In the linear method, the parameter
variations are found by diagonalizing a non-symmetric estimator of the
Hamiltonian matrix in the space spanned by the wave function and its
derivatives with respect to the parameters, making use of a strong
zero-variance principle. In the less computationally expensive perturbative
method, the parameter variations are calculated by approximately solving the
generalized eigenvalue equation of the linear method by a nonorthogonal
perturbation theory. These general methods are illustrated here by the
optimization of wave functions consisting of a Jastrow factor multiplied by an
expansion in configuration state functions (CSFs) for the C$_2$ molecule,
including both valence and core electrons in the calculation. The Newton and
linear methods are very efficient for the optimization of the Jastrow, CSF and
orbital parameters. The perturbative method is a good alternative for the
optimization of just the CSF and orbital parameters. Although the optimization
is performed at the variational Monte Carlo level, we observe for the C$_2$
molecule studied here, and for other systems we have studied, that as more
parameters in the trial wave functions are optimized, the diffusion Monte Carlo
total energy improves monotonically, implying that the nodal hypersurface also
improves monotonically.

categories: physics.chem-ph cond-mat.mtrl-sci cond-mat.other physics.comp-ph


title:
On the angular distribution and spin polarization of the photoelectrons
  from semi-filled shell atoms

abstract:
  We present here the results of calculations of photoelectrons' angular
anisotropy and spin-polarization parameters for a number of semi-filled shell
atoms. We consider ionization of outer or in some cases next to the outer
electrons in a number of elements from I, V, and VI groups of the Periodic
Table. All calculations are performed with account of multi-electron
correlations in the frame of the Spin Polarized version of the Random Phase
Approximation with Exchange - SP RPAE. We consider the dipole angular
distribution and spin polarization of photoelectrons from semi-filled subshells
and from closed shells that are neighbors to the semi-filled shells. We have
considered also angular anisotropy and spin-polarization of photoelectrons from
some excited atoms that are formed by spin-flip of one of the outer electrons.
To check the accuracy and consistency of the applied SP RPAE approach and to
see the role of the nuclear charge variation only, we have calculated the
dipole angular anisotropy and spin-polarization parameters of 3p - electrons in
K and compare them to Ar and K+ that have the same configuration. Entirely, we
have calculated the angular anisotropy and spin-polarization parameters for
following subshells of atoms N (2p), P (3p), Ar (3p), K+(3p), K(3p), Cr(3p,
3d), Cr*(3d), Mn(3p, 3d), As(3d, 4p), Mo(4p, 4d), Mo*(4d), Tc(4p, 4d), Sb(4d,
5p), Eu(4f). The peculiarities of obtained parameters as function of photon
frequencies are discussed, as well as some specific features of considered
semi-filled shell objects.


title:
Two-photon fluorescence measurements of reversible photodegradation in a
  dye-doped polymer

abstract:
  We report on the dynamics of photodegradation and subsequent recovery of
two-photon fluorescence in a dye-doped polymer. The energy dependence suggests
that photo-degradation is a linear process while recovery is entropic. Such
recovery could be useful to high-intensity devices such as two-photon
absorbers, which can be used in many applications.


title:
Influence de l'\'{e}lasticit\'{e} des lignes d'arbres, des roulements et
  du carter sur les vitesses critiques de rotation d'une transmission par
  engrenages

abstract:
  The dynamic behaviour of a gearbox fitted out with a helical gear pair is
studied. Shafts, bearings and housing are discretised using the finite element
method. The elastic coupling between the toothed wheels is characterised by a
12x12 stiffness matrix. The calculation of the vibration response induced by
the static transmission error shows that the highest dynamic mesh forces
correspond to a resonant excitation of modes which have a high mesh stiffness
energy. The numerical simulations show that a realistic prediction of the
critical rotational speeds should take account of all the components of the
gearbox.


title:
Mod\'{e}lisation et analyse de l'erreur statique de transmission d'un
  engrenage. Influence des d\'{e}formations des roues et interactions entre les
  couples de dents en prise

abstract:
  We have developped a numerical tool in order to predict vibratory excitation
of a gearbox induced by the meshing process. We propose a method based on a 3D
Finite Element modelling of each toothed wheel. A non linear algorithm computes
the fluctuations of static transmission error and mesh stiffness. Numerical
simulations show the effect of wheel body deformation and the interactions
between adjacent loaded teeth. The method developped allows to analyse the
effect of different tooth modification types an manufacturing errors on the
static transmission error.


title:
A hybrid method for calorimetry with subnanolitre samples using Schottky
  junctions

abstract:
  A micrometer scale calorimeter realized by using Schottky junctions as a
thermometer is presented. Combined with a hybrid experimental method, it
enables simultaneous time-resolved measurements of variations in both the
energy and the heat capacity of subnanolitre samples.


title: Generating green to red light with semiconductor lasers

abstract:
  Diode lasers enable one to continuously cover the 730 to 1100 nm range as
well as the 370 to 550 nm range by frequency doubling, but a large part of the
electro-magnetic spectrum spanning from green to red remains accessible only
through expensive and unpractical optically pumped dye lasers. Here we devise a
method to multiply the frequency of optical waves by a factor 3/2 with a
conversion that is phase-coherent and highly efficient. Together with harmonic
generation, it will enable one to cover the visible spectrum with semiconductor
lasers, opening new avenues in important fields such as laser spectroscopy and
optical metrology.


title:
A scalable Computer-Aided Detection system for microcalcification
  cluster identification in a pan-European distributed database of mammograms

abstract:
  A computer-aided detection (CADe) system for microcalcification cluster
identification in mammograms has been developed in the framework of the
EU-founded MammoGrid project. The CADe software is mainly based on wavelet
transforms and artificial neural networks. It is able to identify
microcalcifications in different kinds of mammograms (i.e. acquired with
different machines and settings, digitized with different pitch and bit depth
or direct digital ones). The CADe can be remotely run from GRID-connected
acquisition and annotation stations, supporting clinicians from geographically
distant locations in the interpretation of mammographic data. We report the
FROC analyses of the CADe system performances on three different dataset of
mammograms, i.e. images of the CALMA INFN-founded database collected in the
Italian National screening program, the MIAS database and the so-far collected
MammoGrid images. The sensitivity values of 88% at a rate of 2.15 false
positive findings per image (FP/im), 88% with 2.18 FP/im and 87% with 5.7 FP/im
have been obtained on the CALMA, MIAS and MammoGrid database respectively.


title:
R\'{e}sonance 2-surharmonique d'un contact unilat\'{e}ral hertzien :
  approches th\'{e}orique et exp\'{e}rimentale

abstract:
  For a preloaded impact oscillator under superharmonic excitation of order 2,
the Hertzian non linearity constitutes the precursor of vibroimpacts
established over a wide frequency range. The theoretical study is performed by
using the shooting method with an arc length continuation. Experimental results
obtained from a devoted test rig agree with theoretical ones. Particularly, the
threeshold level of the excitation necessary to induce vibroimpacts is
confirmed.


title:
Dispersion of critical rotational speeds of gearbox: effect of bearings
  stiffnesses

abstract:
  Noise measurement on a population of a gearbox manufactured in large number
reveals a high variability principally due to tolerances on each design
parameter of the gear. Gearbox noise results mainly from vibration of its
housing excited by the transmission error. High dynamic mesh load, high
vibratory response of housing and high acoustic level of the gearbox can be
observed for some critical rotational speeds. These ones correspond to
excitation in a resonant manner of some particular modes which store a high
potential energy at the meshing stiffness. Variability of the associated
critical modes depend on tolerances affected to gear design parameters. It also
depends on bearings stiffnesses dispersion. The physical origins of the
bearings stiffnesses variability are preloads. Bearings stiffnesses and
tolerances affect the characteristics of the meshing stiffness and the dynamic
transfer from dynamic meshing force to the housing vibratory response. The
purpose of this paper is to study effect of the bearings stiffnesses
variability by estimating the first two moments of statistical distribution of
critical modes.


title: Vacuum Predictions and Measurements for an Internal Pellet Target

abstract:
  Measurements with low Z targets at internal experiments typically imply a gas
load which deteriorates the ring vacuum. Future experiments need reliable
estimates for the expected vacuum conditions in order to design 4-pi detectors
closely surrounding the interaction area.
  We present a method for the calculation of the resulting vacuum of such a
complex system using a Pellet Target. In order to test the method, a vacuum
system with diagnostic tools has been set up and a Pellet Target was operated
under realistic conditions. The results for the absolute vacuum agree within
factors of two with the expected pressures.


title:
Coupled computation of meshing and bearings stiffnesses : effect on
  radiated gearbox noise

abstract:
  This study focus on the acoustical behavior of gearbox induced by the static
transmission error under load (STE). An original method is developed allowing
to compute simultaneously STE, meshing and bearings stiffnesses. These
characteristics mainly govern the vibrational and the acoustical behaviors of
the geared system. The proposed procedure is based on two computational methods
allowing to calculate the STE and the bearing equilibrium which are integrated
in a coupled computational procedure. The technique has been implemented to
treat an illustrating example and compared to standard uncoupled approach.
Comparative results concern the STE, meshing stiffness, bearings stiffnesses,
shafts misalignments, critical eigenmodes and associated critical running
speeds, housing vibratory response and radiated noise.


title: Ising, Schelling and Self-Organising Segregation

abstract:
  The similarities between phase separation in physics and residential
segregation by preference in the Schelling model of 1971 are reviewed. Also,
new computer simulations of asymmetric interactions different from the usual
Ising model are presented, showing spontaneous magnetisation (= self-organising
segregation) and in one case a sharp phase transition.


title:
On the third order structure function for rotating 3D homogeneous
  turbulent flow

abstract:
  A form for the two-point third order structure function has been calculated
for three dimensional homogeneous incompressible slowly rotating turbulent
fluid. It has been argued that it may possibly hint at the initiation of the
phenomenon of two-dimensionalisation of the 3D incompressible turbulence owing
to rotation.


title:
An Automatic System to Discriminate Malignant from Benign Massive
  Lesions on Mammograms

abstract:
  Mammography is widely recognized as the most reliable technique for early
detection of breast cancers. Automated or semi-automated computerized
classification schemes can be very useful in assisting radiologists with a
second opinion about the visual diagnosis of breast lesions, thus leading to a
reduction in the number of unnecessary biopsies. We present a computer-aided
diagnosis (CADi) system for the characterization of massive lesions in
mammograms, whose aim is to distinguish malignant from benign masses. The CADi
system we realized is based on a three-stage algorithm: a) a segmentation
technique extracts the contours of the massive lesion from the image; b)
sixteen features based on size and shape of the lesion are computed; c) a
neural classifier merges the features into an estimated likelihood of
malignancy. A dataset of 226 massive lesions (109 malignant and 117 benign) has
been used in this study. The system performances have been evaluated terms of
the receiver-operating characteristic (ROC) analysis, obtaining A_z =
0.80+-0.04 as the estimated area under the ROC curve.


title: Spectral transitions in networks

abstract:
  We study the level spacing distribution p(s) in the spectrum of random
networks. According to our numerical results, the shape of p(s) in the
Erdos-Renyi (E-R) random graph is determined by the average degree <k>, and
p(s) undergoes a dramatic change when <k> is varied around the critical point
of the percolation transition, <k>=1. When <k> > 1, the p(s) is described by
the statistics of the Gaussian Orthogonal Ensemble (GOE), one of the major
statistical ensembles in Random Matrix Theory, whereas at <k>=1 it follows the
Poisson level spacing distribution. Closely above the critical point, p(s) can
be described in terms of an intermediate distribution between Poisson and the
GOE, the Brody-distribution. Furthermore, below the critical point p(s) can be
given with the help of the regularised Gamma-function. Motivated by these
results, we analyse the behaviour of p(s) in real networks such as the
Internet, a word association network and a protein protein interaction network
as well. When the giant component of these networks is destroyed in a node
deletion process simulating the networks subjected to intentional attack, their
level spacing distribution undergoes a similar transition to that of the E-R
graph.


title: Antarctica: A Southern Hemisphere Windpower Station?

abstract:
  The International Polar Year commences in 2007. We offer a macroproject plan
to generate a large amount of electricity on the continent of Antarctica by
using sail-like wind dams incorporating air turbines. Electricity can be used
to make exploration and exploitation efforts on Antarctica easier. We offer the
technical specifications for the Fabric Aerial Dam and indicate some of the
geographical facts underpinning our macro-engineering proposal.


title: Precision Spectroscopy at Heavy Ion Ring Accelerator SIS300

abstract:
  Unique spectroscopic possibilities open up if a laser beam interacts with
relativistic lithium-like ions stored in the heavy ion ring accelerator SIS300
at the future Facility for Antiproton and Ion Research FAIR in Darmstadt,
Germany. At a relativistic factor gamma = 36 the 2P 1/2 level can be excited
from the 2S 1/2 ground state for any element with frequency doubled dye-lasers
in collinear geometry. Precise transition energy measurements can be performed
if the fluorescence photons, boosted in forward direction into the X-ray
region, are energetically analyzed with a single crystal monochromator. The
hyperfine structure can be investigated at the 2P 1/2 - 2S 1/2 transition for
all elements and at the 2P 3/2 - 2S 1/2 transition for elements with Z < 50.
Isotope shifts and nuclear moments can be measured with unprecedented
precision, in principle even for only a few stored radioactive species with
known nuclear spin. A superior relative line width in the order of 5E-7 may be
feasible after laser cooling, and even polarized external beams may be prepared
by optical pumping.


title: Beam Space Propulsion

abstract:
  Author offers a revolutionary method non-rocket transfer of energy and thrust
into Space with distance of millions kilometers. The author has developed
theory and made the computations. The method is more efficient than
transmission of energy by high-frequency waves. The method may be used for
space launch and for acceleration the spaceship and probes for very high
speeds, up to relativistic speed by current technology. Research also contains
prospective projects which illustrate the possibilities of the suggested
method.


title: Wireless Transfer of Electricity in Outer Space

abstract:
  Author offers conclusions from his research of a revolutionary new idea -
transferring electric energy in the hard vacuum of outer space wirelessly,
using a plasma power cord as an electric cable (wire). He shows that a certain
minimal electric currency creates a compressed force that supports the plasma
cable in the compacted form. A large energy can be transferred hundreds of
millions of kilometers by this method. The required mass of the plasma cable is
only hundreds of grams. He computed the macroprojects: transference of hundreds
kilowatts of energy to Earth Space Station, transferring energy to the Moon or
back, transferring energy to a spaceship at distance 100 million of kilometers,
the transfer energy to Mars when one is located at opposed side of the distant
Sun, transfer colossal energy from one of Earth's continents to another
continent (for example, between Europe-USA) wirelessly-using Earth ionosphere
as cable, using Earth as gigantic storage of electric energy, using the plasma
ring as huge MagSail for moving of spaceships. He also demonstrates that
electric currency in a plasma cord can accelerate or brake spacecraft and space
apparatus.


title:
Cheap Textile Dam Protection of Seaport Cities against Hurricane Storm
  Surge Waves, Tsunamis, and Other Weather-Related Floods

abstract:
  Author offers to complete research on a new method and cheap applicatory
design for land and sea textile dams. The offered method for the protection of
the USA's major seaport cities against hurricane storm surge waves, tsunamis,
and other weather-related inundations is the cheapest (to build and maintain of
all extant anti-flood barriers) and it, therefore, has excellent prospective
applications for defending coastal cities from natural weather-caused
disasters. It may also be a very cheap method for producing a big amount of
cyclical renewable hydropower, land reclamation from the ocean, lakes,
riverbanks, as well as land transportation connection of islands, and islands
to mainland, instead of very costly over-water bridges and underwater tunnels.


title:
Theory of Space Magnetic Sail Some Common Mistakes and Electrostatic
  MagSail

abstract:
  The first reports on the "Space Magnetic Sail" concept appeared more 30 years
ago. During the period since some hundreds of research and scientific works
have been published, including hundreds of research report by professors at
major famous universities. The author herein shows that all these works related
to Space Magnetic Sail concept are technically incorrect because their authors
did not take into consideration that solar wind impinging a MagSail magnetic
field creates a particle magnetic field opposed to the MagSail field. In the
incorrect works, the particle magnetic field is hundreds times stronger than a
MagSail magnetic field That means all the laborious and costly computations in
revealed in such technology discussions are useless: the impractical findings
on sail thrust (drag), time of flight within the Solar System and speed of
interstellar trips are essentially worthless working data! The author reveals
the correct equations for any estimated performance of a Magnetic Sail as well
as a new type of Magnetic Sail (without a matter ring).


title: A Low-Cost Natural Gas/Freshwater Aerial Pipeline

abstract:
  Offered is a new type of low-cost aerial pipeline for delivery of natural
gas, an important industrial and residential fuel, and freshwater as well as
other payloads over long distances. The offered pipeline dramatically decreases
the construction and operation costs and the time necessary for pipeline
construction. A dual-use type of freight pipeline can improve an arid rural
environment landscape and provide a reliable energy supply for cities. Our
aerial pipeline is a large, self-lofting flexible tube disposed at high
altitude. Presently, the term "natural gas" lacks a precise technical
definition, but the main components of natural gas are methane, which has a
specific weight less than air. A lift force of one cubic meter of methane
equals approximately 0.5 kg. The lightweight film flexible pipeline can be
located in the Earth-atmosphere at high altitude and poses no threat to
airplanes or the local environment. The authors also suggest using lift force
of this pipeline in tandem with wing devices for cheap shipment of a various
payloads (oil, coal and water) over long distances. The article contains a
computed macroproject in northwest China for delivery of 24 billion cubic meter
of gas and 23 millions tonnes of water annually.


title: Long Term Economic Relationships From Cointegration Maps

abstract:
  We employ the Bayesian framework to define a cointegration measure aimed to
represent long term relationships between time series. For visualization of
these relationships we introduce a dissimilarity matrix and a map based on the
Sorting Points Into Neighborhoods (SPIN) technique, which has been previously
used to analyze large data sets from DNA arrays. We exemplify the technique in
three data sets: US interest rates, monthly inflation rates and gross domestic
product growth rates.


title: Symptoms of complexity in a tourism system

abstract:
  Tourism destinations behave as dynamic evolving complex systems, encompassing
numerous factors and activities which are interdependent and whose
relationships might be highly nonlinear. Traditional research in this field has
looked after a linear approach: variables and relationships are monitored in
order to forecast future outcomes with simplified models and to derive
implications for management organisations. The limitations of this approach
have become apparent in many cases, and several authors claim for a new and
different attitude.
  While complex systems ideas are amongst the most promising interdisciplinary
research themes emerged in the last few decades, very little has been done so
far in the field of tourism. This paper presents a brief overview of the
complexity framework as a means to understand structures, characteristics,
relationships, and explores the implications and contributions of the
complexity literature on tourism systems. The objective is to allow the reader
to gain a deeper appreciation of this point of view.


title:
Variability of Critical Rotational Speeds of Gearbox by Misalignement
  and Manufacturing Errors

abstract:
  Noise measurement on a population of gearbox manufactured in large number
often reveals high variability due to tolerances on each gear design parameter
(manufacturing errors). Gearbox noise results mainly from housing vibration
induced by the gear meshing process. High acoustic levels correspond to
excitation in a resonant manner of some critical modes. All gearbox modes and
especially these critical modes depend on tolerances related to gear design
parameters through the meshing stiffness. Tolerances are considered on shaft
misalignment errors, teeth profile errors and teeth longitudinal errors. We
introduce these tolerances as geometric random gaussian parameters. The
critical modes are extracted using an efficient procedure. The retained
"statistical" method to treat tolerances is the Taguchi's method. We illustrate
this methodology considering two different gearbox dynamic models fitted out
with a single spur gear. Obtained dispersion results are validated by
comparison with Monte-Carlo simulations.


title:
Gearboxes: indirect identification of dynamic forces transmitted to
  housing through bearings

abstract:
  In order to determine indirectly the generalized forces applied on the
gearbox, two approaches are tested, one is a numerical method, the other is
experimental. For the numerical method, the vibration response of the gearbox
can be evaluated with use of a finite element analysis and a spectral and
iterative method. It's confirmed that applying the generalized forces
transmitted through the bearings on the empty housing allows to rebuild the
housing response (reciprocity principle). The simulation on the time- and
space-averaged mean square vibration velocity shows the vibration response of
the housing is induced principally by the axial exciting forces, and
secondarily by the moments Mx and My. transmitted on the free side (the 6 mm
thick face). Realistic estimation of these excitation forces needs a modelling
of the whole gearbox taking into account the mechanical properties of the
housing. For the experimental approach, an inverse method based upon the FRF
measurement and characterisation of gearbox vibration response is developed.
Beginning from the equivalent forces obtained by this inverse method, a
resulting force and a moment are derived for representing the distributed force
acting on each bearing. The comparison between the results obtained by these
two methods shows the effectiveness of this indirect force determination
methodology.


title:
Response of an impacting hertzian contact to an order-2 subharmonic
  excitation : theory and experiments

abstract:
  Response of a normally excited preloaded Hertzian contact is investigated in
order to analyze the subharmonic resonance of order 2. The nonlinearity
associated with contact losses is included. The method of multiple scales is
used to obtain the non-trivial steady state solutions, their stability, and the
frequency-response curves. To this end, a third order Taylor series of the
elastic Hertzian contact force is introduced over the displacement interval
where the system remains in contact. A classical time integration method is
also used in conjunction with a shooting method to take into account losses of
contact. The theoretical results show that the subharmonic resonance
constitutes a precursor of dynamic responses characterised by loss of contact,
and consequently, the resonance establishes over a wide frequency range.
Finally, experimental validations are also presented in this paper. To this
end, a specific test rig is used. It corresponds to a double sphere-plane
contact preloaded by the weight of a moving mass. Experimental results show
good agreements with theoretical ones.


title:
Operations structure for the management, control and support of the
  INFN-GRID/Grid.It production infrastructure

abstract:
  Moving from a National Grid Testbed to a Production quality Grid service for
the HEP applications requires an effective operations structure and
organization, proper user and operations support, flexible and efficient
management and monitoring tools. Moreover the middleware releases should be
easily deployable using flexible configuration tools, suitable for various and
different local computing farms. The organizational model, the available tools
and the agreed procedures for operating the national/regional grid
infrastructures that are part of the world-wide EGEE grid as well as the
interconnection of the regional operations structures with the global
management, control and support structure play a key role for the success of a
real production grid. In this paper we describe the operations structure that
we are currently using at the Italian Grid Operation and Support Center. The
activities described cover monitoring, management and support for the
INFN-GRID/Grid.It production grid (spread over more than 30 sites) and its
interconnection with the EGEE/LCG structure as well as the roadmap to improve
the global support quality, stability and reliability of the Grid service.


title:
Investigation of Whispering Gallery Modes in Circular Arrays of
  Dielectric Spherical Particles using multisphere Mie Scattering formalism

abstract:
  quality factor depending on the material used. If these arrays consist of
metal particles, then they cannot have a high quality factor because their
light absorption restricts performance. In this paper we address the following
question: can bound modes be formed in dielectric systems where the absorption
of light is negligible? Our investigation of circular arrays of spherical
particles within the framework of the multisphere Mie scattering theory using
the simplest dipolarlike approach shows that (1) high quality modes in an array
of 10 or more particles can be attained at least for a refractive index n > 2,
so optical materials like TiO2 or GaAs can be used; (2) the most bound modes
have nearly transverse polarization perpendicular to the circular plane; (3) in
a particularly interesting case of TiO2 particles (rutile phase, n = 2.7), the
quality factor of the most bound mode increases almost by an order of magnitude
with the addition of 10 extra particles, while for particles made of GaAs the
quality factor increases by almost two orders of magnitude with the addition of
ten extra particles. The consideration of higher multipole contributions has
demonstrated that the error of the dipolar approach does not exceed one percent
if the refractive index nr is greater than 2. Minimum acceptable disordering
not affecting the quality factor is studied.