title: Force transmission in a packing of pentagonal particles

abstract:
  We perform a detailed analysis of the contact force network in a dense
confined packing of pentagonal particles simulated by means of the contact
dynamics method. The effect of particle shape is evidenced by comparing the
data from pentagon packing and from a packing with identical characteristics
except for the circular shape of the particles. A counterintuitive finding of
this work is that, under steady shearing, the pentagon packing develops a lower
structural anisotropy than the disk packing. We show that this weakness is
compensated by a higher force anisotropy, leading to enhanced shear strength of
the pentagon packing. We revisit "strong" and "weak" force networks in the
pentagon packing, but our simulation data provide also evidence for a large
class of "very weak" forces carried mainly by vertex-to-edge contacts. The
strong force chains are mostly composed of edge-to-edge contacts with a marked
zig-zag aspect and a decreasing exponential probability distribution as in a
disk packing.


title:
Rediscovering the Co-occurrence Principles of Vowel Inventories: A
  Complex Network Approach

abstract:
  In this work, we attempt to capture patterns of co-occurrence across vowel
systems and at the same time figure out the nature of the force leading to the
emergence of such patterns. For this purpose we define a weighted network where
the vowels are the nodes and an edge between two nodes (read vowels) signify
their co-occurrence likelihood over the vowel inventories. Through this network
we identify communities of vowels, which essentially reflect their patterns of
co-occurrence across languages. We observe that in the assortative vowel
communities the constituent nodes (read vowels) are largely uncorrelated in
terms of their features and show that they are formed based on the principle of
maximal perceptual contrast. However, in the rest of the communities, strong
correlations are reflected among the constituent vowels with respect to their
features indicating that it is the principle of feature economy that binds them
together. We validate the above observations by proposing a quantitative
measure of perceptual contrast as well as feature economy and subsequently
comparing the results obtained due to these quantifications with those where we
assume that the vowel inventories had evolved just by chance.


title:
Long-term variations in the correlation between NAO and solar activity:
  the importance of North-South solar activity asymmetry for atmospheric
  circulation

abstract:
  General atmospheric circulation is the system of atmospheric motions over the
Earth on the scale of the whole globe. Two main types of circulation have been
identified: zonal - characterized by low amplitude waves in the troposphere
moving quickly from west to east, and meridional with stationary high amplitude
waves when the meridional transfer is intensified. The prevailing type of
circulation is related to global climate. Based on many years of observations,
certain circulation epochs have been defined when the same type of circulation
prevails for years or decades. Here we study the relation between long-term
changes in solar activity and prevailing type of atmospheric circulation, using
NAO index reconstructed for the last four centuries as a proxy for large-scale
atmospheric circulation. We find that when the southern solar hemisphere is
more active, increasing solar activity in the secular solar cycle results in
increasing zonality of the circulation, while when the northern solar
hemisphere is more active, increasing solar activity increases meridional
circulation. In an attempt to explain the observations, we compare the
short-term reaction of NAO and NAM indices to different solar drivers: powerful
solar flares, high speed solar wind streams, and magnetic clouds


title:
Demonstration of the spin-statistics connection in elementary quantum
  mechanics

abstract:
  A simple demonstration of the spin-statistics connection is presented. The
effect of exchange and space inversion operators on two-particle states is
reviewed. The connection follows directly from successive application of these
operations to the two-particle wave function for identical particles in an
s-state, evaluated at spatial coordinates $\pm x$, but at equal time,
\emph{i.e.}, at spacelike interval.


title: Optical frequency standard with $Sr^+$: A theoretical many-body approach

abstract:
  Demands from several areas of science and technology have lead to a worldwide
search for accurate optical clocks with an uncertainty of 1 part in $10^{18}$,
which is $10^{3}$ times more accurate than the present day cesium atomic clocks
based on microwave frequency regime. In this article we discuss the electric
quadrupole and the hyperfine shifts in the $5s ^{2}S_{1/2}\longrightarrow4d
^{2}D_{5/2}$ clock transition in $\mathrm{Sr^{+}}$, one of the most promising
candidates for next generation optical clocks. We have applied relativistic
coupled cluster theory for determining the electric quadrupole moment of the
$4d ^{2}D_{5/2}$ state of $\mathrm{^{88}Sr^{+}}$ and the magnetic dipole ($A$)
and electric quadrupole ($B$) hyperfine constants for the $5s ^{2}S_{1/2}$ and
$4d ^{2}D_{5/2}$ states which are important in the study of frequency standards
with $\mathrm{Sr^{+}}$. The effects of electron correlation which are very
crucial for the accurate determination of these quantities have been discussed.


title:
Quantization, Doppler shift and the invariance of the speed of light via
  the invariance of the counted numbers of photons: An interesting pedagogical
  problem

abstract:
  We show that when the observers are located in a plane electromagnetic wave
it is not compulsory for them to take into account the time dilation and length
contraction effects when the wave is detected from two inertial reference
frames in relative motion. We also illustrate the difference between the
approach that uses Einstein type of observers confronted with time dilation and
length contraction effects and an unconventional approach that uses observers
detecting information from the energy that arrives at their location.


title: Introductory Quantum Physics Courses using a LabVIEW multimedia module

abstract:
  We present the development of a LabVIEW multimedia module for introductory
Quantum Physics courses and our experience in the use of this application as an
educational tool in learning methodologies. The program solves the Time
Dependent Schrodinger Equation for arbitrary potentials. We describe the
numerical method used for solving this equation, as well as some mathematical
tools employed to reduce the calculation time and to obtain more accurate
results. As an illustration, we present the evolution of a wave packet for
three different potentials: the repulsive barrier potential, the repulsive step
potential, and the harmonic oscillator. This application has been successfully
integrated in the learning strategies of the course Quantum Physics for
Engineering at the Polytechnic University of Valencia, Spain.


title: Testing theoretical models of magnetic damping using an air track

abstract:
  Magnetic braking is a long-established application of Lenz's law. A rigorous
analysis of the laws governing this problem involves solving Maxwell's
equations in a time-dependent situation. Approximate models have been developed
to describe different experiences related to this phenomenon. In this paper we
present a new method for the analysis of the magnetic braking using a magnet
fixed to the glider of an air track. The forces acting on the glider, a result
of the eddy currents, can be easily observed and measured. As a consequence of
the air track inclination, the glider accelerates at the beginning, although it
asymptotically tends towards a uniform rectilinear movement characterized by a
terminal speed. This speed depends on the interaction between the magnetic
field and the conductivity properties of the air track. Compared with previous
related approaches, in our experimental setup the magnet fixed to the glider
produces a magnetic braking force which acts continuously, rather than over a
short period of time. The experimental results satisfactorily concur with the
theoretical models adapted to this configuration.


title:
Observation of the Faraday effect via beam deflection in a longitudinal
  magnetic field

abstract:
  We report the observation of the magnetic field induced circular differential
deflection of light at the interface of a Faraday medium. The difference in the
angles of refraction or reflection between the two circular polarization
components is a function of the magnetic field strength and the Verdet
constant. The reported phenomena permit the observation of the Faraday effect
not via polarization rotation in transmission, but via changes in the
propagation direction in refraction or in reflection. An unpolarized light beam
is predicted to split into its two circular polarization components. The light
deflection arises within a few wavelengths at the interface and is therefore
independent of pathlength.


title:
Hilbert Space Becomes Ultrametric in the High Dimensional Limit:
  Application to Very High Frequency Data Analysis

abstract:
  An ultrametric topology formalizes the notion of hierarchical structure. An
ultrametric embedding, referred to here as ultrametricity, is implied by a
natural hierarchical embedding. Such hierarchical structure can be global in
the data set, or local. By quantifying extent or degree of ultrametricity in a
data set, we show that ultrametricity becomes pervasive as dimensionality
and/or spatial sparsity increases. This leads us to assert that very high
dimensional data are of simple structure. We exemplify this finding through a
range of simulated data cases. We discuss also application to very high
frequency time series segmentation and modeling.


title:
Modeling the selective partitioning of cations into negatively charged
  nanopores in water

abstract:
  Partitioning and transport of water and small solutes into and through
nanopores is important to a variety of chemical and biological processes and
applications. Here we study the partitioning of positive ions of increasing
size into the pore interior using extensive molecular dynamics simulations.
Despite the simplicity of the simulation system, the results provide new and
useful insights on both the pore hydration and ion partitioning. For low
negative charge densities on the pore, the driving force for partitioning of
positive ions into the pore is weak, and no partitioning is observed.
Increasing the pore charge gradually leads to partitioning of positive ions
into the pore. Interestingly, over a range of intermediate negative charge
densities, nanopores display both thermodynamic as well as kinetic selectivity
toward partitioning of the larger K+ and Cs+ ions into their interior over the
smaller Na+ ions. The variation of thermodynamic driving force and the average
partitioning time with the pore charge density together suggest the presence of
free energy barriers in the partitioning process. We discuss the role of ion
hydration in the bulk and in the pore interior as well as of the pore hydration
in determining the barrier heights for ion partitioning and the observed
thermodynamic and kinetic selectivity.


title:
Accurate estimations of circumstellar and interstellar lines of
  quadruply ionized vanadium using the coupled cluster approach

abstract:
  Accurate {\it ab initio} calculations have been carried out to study the
valence electron removal energies and oscillator strengths of astrophysically
important electromagnetic transitions of quadruply ionized vanadium, $V^{4+}$.
Many important electron correlations are considered to all-orders using the
relativistic coupled-cluster theory. Calculated ionization potentials and fine
structure splittings are compared with the experimental values, wherever
available. To our knowledge, oscillator strengths of electric dipole
transitions are predicted for the first time for most of the transitions. The
transitions span in the range of ultraviolet, visible and near infrared regions
and are important for astrophysical observations.


title:
Explicit wave-averaged primitive equations using a Generalized
  Lagrangian Mean

abstract:
  The generalized Langrangian mean theory provides exact equations for general
wave-turbulence-mean flow interactions in three dimensions. For practical
applications, these equations must be closed by specifying the wave forcing
terms. Here an approximate closure is obtained under the hypotheses of small
surface slope, weak horizontal gradients of the water depth and mean current,
and weak curvature of the mean current profile. These assumptions yield
analytical expressions for the mean momentum and pressure forcing terms that
can be expressed in terms of the wave spectrum. A vertical change of coordinate
is then applied to obtain glm2z-RANS equations (55) and (57) with non-divergent
mass transport in cartesian coordinates. To lowest order, agreement is found
with Eulerian-mean theories, and the present approximation provides an explicit
extension of known wave-averaged equations to short-scale variations of the
wave field, and vertically varying currents only limited to weak or localized
profile curvatures. Further, the underlying exact equations provide a natural
framework for extensions to finite wave amplitudes and any realistic situation.
The accuracy of the approximations is discussed using comparisons with exact
numerical solutions for linear waves over arbitrary bottom slopes, for which
the equations are still exact when properly accounting for partial standing
waves. For finite amplitude waves it is found that the approximate solutions
are probably accurate for ocean mixed layer modelling and shoaling waves,
provided that an adequate turbulent closure is designed. However, for surf zone
applications the approximations are expected to give only qualitative results
due to the large influence of wave nonlinearity on the vertical profiles of
wave forcing terms.


title: Turbulent Diamagnetism in Flowing Liquid Sodium

abstract:
  The nature of Ohm's law is examined in a turbulent flow of liquid sodium. A
magnetic field is applied to the flowing sodium, and the resulting magnetic
field is measured. The mean velocity field of the sodium is also measured in an
identical-scale water model of the experiment. These two fields are used to
determine the terms in Ohm's law, indicating the presence of currents driven by
a turbulent electromotive force. These currents result in a diamagnetic effect,
generating magnetic field in opposition to the dominant fields of the
experiment. The magnitude of the fluctuation-driven magnetic field is
comparable to that of the field induced by the sodium's mean flow.


title: Would Bohr be born if Bohm were born before Born?

abstract:
  I discuss a hypothetical historical context in which a Bohm-like
deterministic interpretation of the Schrodinger equation could have been
proposed before the Born probabilistic interpretation and argue that in such a
context the Copenhagen (Bohr) interpretation would probably have never achieved
great popularity among physicists.

categories: physics.soc-ph hep-th physics.hist-ph quant-ph


title: The BiPo detector for ultralow radioactivity measurements

abstract:
  The BiPo project is dedicated to the measurement of extremely low
radioactivity contamination of SuperNEMO source foils (^{208}Tl < 2 \muBq/kg
and ^{214}Bi < 10 \muBq/kg). The R&D phase is started: a modular BiPo prototype
with its shielding test facility is under construction. The goal of this
prototype is to study the background and particularly the surface contamination
of scintillators. The first capsule has been installed in the Canfranc
Underground Laboratory in October, 17th and is now taking data. After 10.7 days
of measurements, a preliminary upper limit on the surface radiopurity of the
scintillators of A(^{208}Tl) < 60 \muBq/m^2 (90% C. L.) has been obtained.


title: Magnetic trapping and Zeeman relaxation of imidogen (NH X-triplet-Sigma)

abstract:
  Imidogen (NH) radicals are magnetically trapped and their Zeeman relaxation
and energy transport collision cross sections with helium are measured.
Continuous buffer-gas loading of the trap is direct from a room-temperature
molecular beam. The Zeeman relaxation (inelastic) cross section of magnetically
trapped electronic, vibrational and rotational ground state imidogen in
collisions with He-3 is measured to be 3.8 +/- 1.1 E-19 cm^2 at 710 mK. The
NH-He energy transport cross section is also measured, indicating a ratio of
diffusive to inelastic cross sections of gamma = 7 E4 in agreement with the
recent theory of Krems et al. (PRA 68 051401(R) (2003))


title: Hempel's dilemma and the physics of computation

abstract:
  Carl Gustav Hempel (1905-1997) formulated the dilemma that carries his name
in an attempt to determine the boundaries of physics. Where does physics go
over into metaphysics? The purpose of this contribution is to indicate how a
recently developed field of research, the physics of computation, might offer a
new answer to that old question: The boundary between physics and metaphysics
is the boundary between what can and what cannot be computed in the age of the
universe.


title:
Analysis of a Symmetry leading to an Inertial Range Similarity Theory
  for Isotropic Turbulence

abstract:
  We present a theoretical attack on the classical problem of intermittency and
anomalous scaling in turbulence. Our focus is on an ideal situation: high
Reynolds number isotropic turbulence driven by steady large scale forcing.
Moreover, the fluid is incompressible and no confining boundaries are present.
We start from a good set of basis functions for the velocity field. These are
real and divergence-free. To each wave-vector k in Fourier space there is one
pair of basis functions with respectively left and right-handed polarity.
Isotropy makes all k on the shell of constant |k| statistically equivalent.
Consequently, the coefficients, X+ and X-, to the basis functions in that shell
become two random variables whose joint pdf describes the statistics at scale L
=2*pi/|k|. Moreover, (X+)**2+(X-)**2 becomes a random variable for the energy.
Switching to polar coordinates, the joint pdf expands in azimuthal modes. We
focus on the axisymmetric mode which is itself a pdf and characterized by it
radial profile P(r;L). Observations from both shell model and DNS data indicate
that (1) the moments of P(r;L) scale as power laws in L, and (2) the profile
obeys an affine symmetry P(r;L)=C(L)*f((lnr-mu(L))/sigma(L)). We raise the
question: What statistics agree with both observation? The answer is pleasing.
We find the functions f, mu, sigma C analytically in terms of a few constants.
Moreover, we obtain closed form expressions for both scaling exponents and
coefficients in the power laws. A virtual origin also emerges as an intrinsic
length scale L0 for the inertial range.


title: A Zeeman Slower based on magnetic dipoles

abstract:
  A transverse Zeeman slower composed of an array of compact discrete neodymium
magnets is considered. A simple and precise model of such a slower based on
magnetic dipoles is developed. The theory of a general Zeeman slower is
modified to include spatial nonuniformity of the slowing laser beam intensity
due to its convergence and absorption by slowed atoms. The slower needs no high
currents or water cooling and the spatial distribution of its magnetic field
can be adjusted. In addition the slower provides a possibility to cool the
slowed atoms transversally along the whole length of the slower. Such a slower
would be ideal for transportable optical atomic clocks and their future
applications in space physics.


title: Explaining the pearl necklace of SNR 1987A by coherent optics

abstract:
  A lot of beautiful observations of Supernova remnant 1987A give a precise
idea of its structure and its evolution. The regular interpretations of the
observations set that the large energy needed to explain the brightness of the
pearl necklaces is provided by shock waves involving remnants of a first
explosion and a wave produced by the observed explosion although the existence
of this wave is discussed. We develop the alternative explanation of the
necklaces by photoionization. Our main hypothesis is that the explosion of the
blue supergiant progenitor produces two neutron stars and a central brilliant
object, a linear system similar to those which were observed by Halton Arp. We
suppose that these stars remains bright in extreme UV, to maintain the strong
ionization of a bubble of hot hydrogen nearly transparent in far UV (defined as
the range of Lyman frequencies of atomic hydrogen). Outside the bubbles, three
shells containing atomic hydrogen generate resonant, superradiant scatterings
at Lyman frequencies, in tangential competing modes. The superradiance cools
the gas and absorbs strongly the radial far UV light, hiding the stars. The
shells may be identified with the inner active shells found from light echoes.


title: Phase transitions in social sciences: two-populations mean field theory

abstract:
  A new mean field statistical mechanics model of two interacting groups of
spins is introduced and the phase transition studied in terms of their relative
size. A jump of the average magnetization is found for large values of the
mutual interaction when the relative percentage of the two populations crosses
a critical threshold. It is shown how the critical percentage depends on
internal interactions and on the initial magnetizations. The model is
interpreted as a prototype of resident-immigrant cultural interaction and
conclusions from the social sciences perspectives are drawn.

categories: physics.soc-ph cond-mat.stat-mech math-ph math.MP


title: How does degree heterogeneity affect an order-disorder transition?

abstract:
  We focus on the role played by the node degree distribution on the way
collective phenomena emerge on complex networks. To address this question, we
focus analytically on a typical model for cooperative behaviour, the Majority
Rule, applied to dichotomous networks. The latter are composed of two kinds of
nodes, each kind $i$ being characterized by a degree $k_i$. Dichotomous
networks are therefore a simple instance of heterogeneous networks, especially
adapted in order to reveal the effect of degree heterogeneity. Our main result
are that degree heterogeneity affects the location of the order-disorder
transition and that the system exhibits non-equipartition of the average
opinion between the two kinds of nodes. This effect is observed in the ordered
phase and in the disordered phase.


title:
A Study of the LXeGRIT Detection Efficiency for MeV Gamma-Rays during
  the 2000 Balloon Flight Campaign

abstract:
  LXeGRIT - Liquid Xenon Gamma-Ray Imaging Telescope - is the first prototype
of a Compton telescope for \MeV \g-ray astrophysics based on a LXe time
projection chamber. One of the most relevant figures of merit for a Compton
telescope is the detection efficiency for \g-rays, which depends on diverse
contributions such as detector geometry and passive materials, trigger
efficiency, dead time, etc. A detailed study of the efficiency of the LXeGRIT
instrument, based both on laboratory measurements and Monte Carlo simulations,
is presented in this paper.


title:
An optical fiber-taper probe for wafer-scale microphotonic device
  characterization

abstract:
  A small depression is created in a straight optical fiber taper to form a
local probe suitable for studying closely spaced, planar microphotonic devices.
The tension of the "dimpled" taper controls the probe-sample interaction length
and the level of noise present during coupling measurements. Practical
demonstrations with high-Q silicon microcavities include testing a dense array
of undercut microdisks (maximum Q = 3.3x10^6) and a planar microring (Q =
4.8x10^6).


title: Liquid drop splashing on smooth, rough and textured surfaces

abstract:
  Splashing occurs when a liquid drop hits a dry solid surface at high
velocity. This paper reports experimental studies of how the splash depends on
the roughness and the texture of the surfaces as well as the viscosity of the
liquid. For smooth surfaces, there is a "corona" splash caused by the presence
of air surrounding the drop. There are several regimes that occur as the
velocity and liquid viscosity are varied. There is also a "prompt" splash that
depends on the roughness and texture of the surfaces. A measurement of the size
distribution of the ejected droplets is sensitive to the surface roughness. For
a textured surface in which pillars are arranged in a square lattice,
experiment shows that the splashing has a four-fold symmetry. The splash occurs
predominantly along the diagonal directions. In this geometry, two factors
affect splashing the most: the pillar height and spacing between pillars.


title: Universality of the rainfall phenomenon

abstract:
  We show that the universal properties of the rainfall phenomenon are the
scaling properties of the probability density function of inter-drop intervals
during quiescent periods, time intervals of sparse precipitation, and the
universal shape of the probability density function of drop diameters during
non-quiescent periods, time intervals of active precipitation. Our results
indicate that the continuous flux-like vision of rainfall based on quantities
such as the rain duration, rain intensity and drought duration is ineffective
in detecting the universality of the phenomenon. A comprehensive understanding
of rainfall behavior must rest on the acknowledgment of its discrete drop-like
nature.


title:
Hydrodynamic and magnetohydrodynamic computations inside a rotating
  sphere

abstract:
  Numerical solutions of the incompressible magnetohydrodynamic (MHD) equations
are reported for the interior of a rotating, perfectly-conducting, rigid
spherical shell that is insulator-coated on the inside. A previously-reported
spectral method is used which relies on a Galerkin expansion in
Chandrasekhar-Kendall vector eigenfunctions of the curl. The new ingredient in
this set of computations is the rigid rotation of the sphere. After a few
purely hydrodynamic examples are sampled (spin down, Ekman pumping, inertial
waves), attention is focused on selective decay and the MHD dynamo problem. In
dynamo runs, prescribed mechanical forcing excites a persistent velocity field,
usually turbulent at modest Reynolds numbers, which in turn amplifies a small
seed magnetic field that is introduced. A wide variety of dynamo activity is
observed, all at unit magnetic Prandtl number. The code lacks the resolution to
probe high Reynolds numbers, but nevertheless interesting dynamo regimes turn
out to be plentiful in those parts of parameter space in which the code is
accurate. The key control parameters seem to be mechanical and magnetic
Reynolds numbers, the Rossby and Ekman numbers (which in our computations are
varied mostly by varying the rate of rotation of the sphere) and the amount of
mechanical helicity injected. Magnetic energy levels and magnetic dipole
behavior are exhibited which fluctuate strongly on a time scale of a few eddy
turnover times. These seem to stabilize as the rotation rate is increased until
the limit of the code resolution is reached.


title:
The sensitivity and stability of the ocean's thermohaline circulation to
  finite amplitude perturbations

abstract:
  Within a simple model context, the sensitivity and stability of the
thermohaline circulation to finite amplitude perturbations is studied. A new
approach is used to tackle this nonlinear problem. The method is based on the
computation of the so-called Conditional Nonlinear Optimal Perturbation (CNOP)
which is a nonlinear generalization of the linear singular vector approach
(LSV). It is shown that linearly stable thermohaline circulation states can
become nonlinearly unstable and the properties of the perturbations with
optimal nonlinear growth are determined. An asymmetric nonlinear response to
perturbations exists with respect to the sign of finite amplitude freshwater
perturbations, on both thermally dominated and salinity dominated thermohaline
flows. This asymmetry is due to the nonlinear interaction of the perturbations
through advective processes.


title:
Confined space and effective interactions of multiple self-avoiding
  chains

abstract:
  We study the link between three seeming-disparate cases of self-avoiding
polymers: strongly overlapping multiple chains in dilute solution, chains under
spherical confinement, and the onset of semi-dilute solutions. Our main result
is that the free energy for overlapping $n$ chains is \emph{independent} of
chain length and scales as $n^{9/4}$, slowly crossing over to $n^3$, as $n$
increases. For strongly confined polymers inside a spherical cavity, we show
that rearranging the chains does not cost an additional free energy. Our
results imply that, during cell cycle, \emph{global} reorganization of
eukaryotic chromosomes in a large cell nucleus could be readily achieved.


title:
A Multiwire Proportional Chamber for Precision Studies of Neutron Beta
  Decay Angular Correlations

abstract:
  A new multiwire proportional chamber (MWPC) was designed and constructed for
precision studies of neutron beta decay angular correlations. Its design has
several novel features, including the use of low pressure neopentane as the
MWPC gas and an entrance window made of thin Mylar sheet reinforced with Kevlar
fibers. In the initial off-line performance tests, the gas gain of neopentane
and the position resolution were studied.


title:
Octonionic Hyper-strong and Hyper-weak Fields and Their Quantum
  Equations

abstract:
  Based on Maxwellian quaternionic electromagnetic theory, the octonionic
hyper-strong field, hyper-weak field and the quantum interplays can be
presented by analogy with octonionic electromagnetic, gravitational, strong and
weak interactions. In the hyper-weak field, the study deduces some conclusions
of field source particles and intermediate particles which are consistent with
Dirac equation, Yang-Mills equation, Schrodinger equation and Klein-Gordon
equation. It predicts some new intermediate particles and observed abnormal
phenomena about galaxy clusters which may be caused by the hyper-weak field. In
the hyper-strong field, the paper draws some conclusions of the field source
particles and intermediate particles which are coincident with Dirac-like
equations. It predicts some new intermediate particles, three kinds of colors,
and some observed abnormal phenomena which may be caused by the sub-quarks in
hyper-strong field. The researches results show that there may exist the some
new field source particles in the hyper-strong and hyper-weak fields.


title: Comment on Universal Reduced Potential Function for Diatomic Systems

abstract:
  First principles prove why a recent claim by R.H. Xie and P.S. Hsu (Phys.
Rev. Lett. 96, 243201 (2006)) on the scaling power of a covalent Sutherland
parameter to expose a universal function cannot be validated.


title:
Elastoplastic equations with exact consistency of strains for the
  elastic strain frame and the velocities of points

abstract:
  We obtain an exact strain consistency equation for full, elastic, and plastic
strain characteristics that have a clear physical meaning and are naturally
related to stresses. The dynamic equations are represented in a form that does
not use the objective stress rate. This obviates a number of essential
difficulties in theory of finite elastoplastic strains.


title: Better Physics Teaching Can Increase Physics Enrollment

abstract:
  Our main goal is to develop plans to increase physics enrollment. Once again
we thoroughly analyze the problem from the beginning and reach the conclusion
that the most appropriate starting point in this direction should be to look
into K-12 teaching. We give a few recommendations to improve science/physics
teaching at K-12 level. It is proposed that the quickest way to make some
advancement is to start teacher training or refresher courses for school
teachers to fill up their gaps in knowledge. We suggest a comparison of the
affectivity of different methods of teaching to decide which one of them works
better under what type of circumstances. We also propose a few steps to improve
physics teaching standards at the higher levels.


title:
Relativistic coupled-cluster single-double method applied to
  alkali-metal atoms

abstract:
  A relativistic version of the coupled-cluster single-double (CCSD) method is
developed for atoms with a single valence electron. In earlier work, a
linearized version of the CCSD method (with extensions to include a dominant
class of triple excitations) led to accurate predictions for energies,
transition amplitudes, hyperfine constants, and other properties of monovalent
atoms. Further progress in high-precision atomic structure calculations for
heavy atoms calls for improvement of the linearized coupled-cluster
methodology. In the present work, equations for the single and double
excitation coefficients of the Dirac-Fock wave function, including all
non-linear coupled-cluster terms that contribute at the single-double level are
worked out. Contributions of the non-linear terms to energies, electric-dipole
matrix elements, and hyperfine constants of low-lying states in alkali-metal
atoms from Li to Cs are evaluated and the results are compared with other
calculations and with precise experiments.


title:
Threshold power reduction for forming bright solitons guided in nonlocal
  nonlinear media

abstract:
  We study the formation of dark-bright vector soliton pairs in nonlocal
Kerr-type nonlinear medium. We show, by analytical analysis and direct
numerical calculation, that in addition to stabilize vector soliton pairs
nonlocal nonlinearity also helps to reduce the threshold power for forming a
guided bright soliton. With help of the nonlocality, it is expected that the
observation of dark-bright vector soliton pairs in experiments becomes more
workable.


title:
Design and performance of the silicon sensors for the CMS barrel pixel
  detector

abstract:
  The CMS experiment at the LHC includes a hybrid silicon pixel detector for
the reconstruction of charged tracks and of the interaction vertices. The
barrel region consists of n-in-n sensors with 100X150 um^2 cell size processed
on diffusion oxygenated float zone silicon. A biasing grid is implemented and
pixel isolation is achieved with the moderated p-spray technique. An extensive
test program was carried out on the H2 beam line of the CERN SPS. In this paper
we describe the sensor layout, the beam test setup and the results obtained
with both irradiated and non-irradiated prototype devices. Measurements of
charge collection, hit detection efficiency, Lorentz angle and spatial
resolution are presented.


title:
Intra-operative quantification of the surgical gesture in orbital
  surgery: Application to the proptosis reduction

abstract:
  Proptosis is characterized by a protrusion of the eyeball due to an increase
of the orbital tissue volume. To recover a normal eyeball positioning, the most
frequent surgical technique (BROD technique) consists in the osteotomy of
orbital walls combined with a loading on the eyeball to initiate tissue
decompression. This paper proposed an experimental method to quantify the
intra-operative clinical gesture in proptosis reduction, and the pilot study
concerned one clinical case. The eyeball's backward displacement was measured
by an optical 3D localizer and the load applied by the surgeon was
simultaneously measured by a custom-made force gauge. Quasi-static stiffness of
the intra-orbital content was evaluated. The average values for the whole
experiment was 16 N (SD: 3 N) for the force exerted by the surgeon and 9 mm
(SD: 4 mm) for the eyeball backward displacement. The averaged quasi-static
stiffness of the orbital content was evaluated to 2.4 N/mm (SD: 1.2) and showed
a global decrease of 45% post-operatively.


title: Dynamical hysteresis in multisite protein modification

abstract:
  Multisite protein modification is a ubiquitous mechanism utilized by cells to
control protein functions. We have recently proposed a dynamical description of
multisite protein modification which embodies all the essential features of the
process (E. Milotti, A. Del Fabbro, C. Dalla Pellegrina, and R. Chignola,
Physica A, in press), and we have used this model to analyze the stability and
the time-scales of this mechanism. The same model can be used to understand how
the system responds to stimuli: here we show that it displays
frequency-dependent dynamical hysteresis. This behavior closely parallels --
with the due differences -- what is observed in magnetic systems. By selecting
model parameters that span the known biological ranges, we find that the
frequency-dependent features cover the band of the observed oscillations of
molecular intracellular signals, and this suggests that this mechanism may have
an important role in cellular information processing.


title: On the Electrodynamics of Moving Particles in Gravitational Fields

abstract:
  The present work aims to search for an implementation of new symmetries in
the space-time in order to enable us to find a connection between
electrodynamics and gravitation, from where quantum principles naturally
emerge. To do that, first of all we build a heuristic model of the
electromagnetic nature of the electron so that the influence of the
gravitational field on the electrodynamics of such moving particle leads us
essentially to an elimination of the classical idea of rest by introducing the
idea of a universal minimum limit of speed ($V$). Such a lowest limit $V$,
being unattainable by the particles, represents a fundamental and preferred
reference frame connected to a universal background field (a vacuum energy)
that breaks Lorentz symmetry. So there emerges a new principle of symmetry in
the space-time at the subatomic level for very low energies close to the
background frame ($v\approx V$), providing a fundamental understanding for the
uncertainty principle.


title: Structural constraints in complex networks

abstract:
  We present a link rewiring mechanism to produce surrogates of a network where
both the degree distribution and the rich--club connectivity are preserved. We
consider three real networks, the AS--Internet, the protein interaction and the
scientific collaboration. We show that for a given degree distribution, the
rich--club connectivity is sensitive to the degree--degree correlation, and on
the other hand the degree--degree correlation is constrained by the rich--club
connectivity. In particular, in the case of the Internet, the assortative
coefficient is always negative and a minor change in its value can reverse the
network's rich--club structure completely; while fixing the degree distribution
and the rich--club connectivity restricts the assortative coefficient to such a
narrow range, that a reasonable model of the Internet can be produced by
considering mainly the degree distribution and the rich--club connectivity. We
also comment on the suitability of using the maximal random network as a null
model to assess the rich--club connectivity in real networks.


title: Multi-directed Eulerian growing networks

abstract:
  We introduce and analyze a model of a multi-directed Eulerian network, that
is a directed and weighted network where a path exists that passes through all
the edges of the network once and only once. Networks of this type can be used
to describe information networks such as human language or DNA chains. We are
able to calculate the strength and degree distribution in this network and find
that they both exhibit a power law with an exponent between 2 and 3. We then
analyze the behavior of the accelerated version of the model and find that the
strength distribution has a double slope power law behavior. Finally we
introduce a non-Eulerian version of the model and find that the statistical
topological properties remain unchanged. Our analytical results are compared
with numerical simulations.


title: Controlling the direction and amount of a splash with textured surface

abstract:
  Because splashing is such a violent process, one might naively expect that
neither the direction of droplet emission nor the amount of ejected material
can be controlled with any precision. Even though it is observed countless
times in the course of a day, drop splashing is highly non-intuitive: for
example, it is surprising that the surrounding air pressure determines whether
a drop will splash when hitting a smooth surface. Here we describe a discovery
with significant practical ramifications: the direction, as well as the number,
of the ejected droplets can be controlled by the texture of a surface.


title: Sivashinsky equation in a rectangular domain

abstract:
  The (Michelson) Sivashinsky equation of premixed flames is studied in a
rectangular domain in two dimensions. A huge number of 2D stationary solutions
are trivially obtained by addition of two 1D solutions. With Neumann boundary
conditions, it is shown numerically that adding two stable 1D solutions leads
to a 2D stable solution. This type of solution is shown to play an important
role in the dynamics of the equation with additive noise.


title:
Fermat's principle of least time in the presence of uniformly moving
  boundaries and media

abstract:
  The refraction of a light ray by a homogeneous, isotropic and non-dispersive
transparent material half-space in uniform rectilinear motion is investigated
theoretically. The approach is an amalgamation of the original Fermat's
principle and the fact that an isotropic optical medium at rest becomes
optically anisotropic in a frame where the medium is moving at a constant
velocity. Two cases of motion are considered: a) the material half-space is
moving parallel to the interface; b) the material half-space is moving
perpendicular to the interface. In each case, a detailed analysis of the
obtained refraction formula is provided, and in the latter case, an intriguing
backward refraction of light is noticed and thoroughly discussed. The results
confirm the validity of Fermat's principle when the optical media and the
boundaries between them are moving at relativistic speeds.


title: Verification of the Rayleigh Scattering Cross Section

abstract:
  A simple experiment is described for the direct determination of the
wavelength dependence of the Rayleigh scattering cross section using the
classical example of the blue sky.


title: Seeking for Simplicity in Complex Networks

abstract:
  Complex networks can be understood as graphs whose connectivity deviates from
those of regular or near-regular graphs, which are understood as being
`simple'. While a great deal of the attention so far dedicated to complex
networks has been duly driven by the `complex' nature of these structures, in
this work we address the identification of simplicity, in the sense of
regularity, in complex networks. The basic idea is to seek for subgraphs
exhibiting small dispersion (e.g. standard deviation or entropy) of local
measurements such as the node degree and clustering coefficient. This approach
paves the way for the identification of subgraphs (patches) with nearly uniform
connectivity, therefore complementing the characterization of the complexity of
networks. We also performed analysis of cascade failures, revealing that the
removal of vertices in `simple' regions results in smaller damage to the
network structure than the removal of vertices in the heterogeneous regions. We
illustrate the potential of the proposed methodology with respect to four
theoretical models as well as protein-protein interaction networks of three
different species. Our results suggest that the simplicity of protein
interaction grows as the result of natural selection. This increase in
simplicity makes these networks more robust to cascade failures.


title: LHCb Level-0 Trigger Detectors

abstract:
  The calorimeter and muon systems are essential components to provide a
trigger for the LHCb experiment. The calorimeter system comprises a
scintillating pad detector and pre-shower, followed by electromagnetic and
hadronic calorimeters. The calorimeter system allows photons, electrons and
hadrons to be identified, and their energy to be measured. The muon system
consists of five measuring stations equipped with Multi-Wire Proportional
Chambers (MWPCs) and triple-Gas Electron Multiplier (GEM) detectors, separated
by iron filters. It allows the muons identification and transverse momentum
measurement. The status of the two systems and their expected performance is
presented.


title:
Infrared emission spectrum and potentials of $0_u^+$ and $0_g^+$ states
  of Xe$_2$ excimers produced by electron impact

abstract:
  We present an investigation of the Xe$_{2}$ excimer emission spectrum
observed in the near infrared range about 7800 cm$^{-1}$ in pure Xe gas and in
an Ar (90%) --Xe (10%) mixture and obtained by exciting the gas with energetic
electrons. The Franck--Condon simulation of the spectrum shape suggests that
emission stems from a bound--free molecular transition never studied before.
The states involved are assigned as the bound $(3)0_{u}^{+} $ state with $6p
[1/2]_{0}$ atomic limit and the dissociative $(1)0_{g}^{+}$ state with $6s
[3/2]_{1}$ limit. Comparison with the spectrum simulated by using theoretical
potentials shows that the dissociative one does not reproduce correctly the
spectrum features.


title: A three-dimensional degree of polarization based on Rayleigh scattering

abstract:
  A measure of the degree of polarization for the three-dimensional
polarization matrix (coherence matrix) of an electromagnetic field is proposed,
based on Rayleigh scattering. The degree of polarization, due to dipole
scattering of the three-dimensional state of polarization, is averaged over all
scattering directions. This gives a well-defined purity measure, which, unlike
other proposed measures of the three-dimensional degree of polarization, is not
a unitary invariant of the matrix. This is demonstrated and discussed for
several examples, including a partially polarized transverse beam.


title:
Emergence of time-horizon invariant correlation structure in financial
  returns by subtraction of the market mode

abstract:
  We investigate the emergence of a structure in the correlation matrix of
assets' returns as the time-horizon over which returns are computed increases
from the minutes to the daily scale. We analyze data from different stock
markets (New York, Paris, London, Milano) and with different methods. Result
crucially depends on whether the data is restricted to the ``internal''
dynamics of the market, where the ``center of mass'' motion (the market mode)
is removed or not. If the market mode is not removed, we find that the
structure emerges, as the time-horizon increases, from splitting a single large
cluster. In NYSE we find that when the market mode is removed, the structure of
correlation at the daily scale is already well defined at the 5 minutes
time-horizon, and this structure accounts for 80 % of the classification of
stocks in economic sectors. Similar results, though less sharp, are found for
the other markets. We also find that the structure of correlations in the
overnight returns is markedly different from that of intraday activity.


title: A method for testing handgun bullets in deer

abstract:
  Using service handguns to test bullets in deer is problematic because of
velocity loss with range and accuracy giving sub-optimal shot placement. An
alternate method is presented using a scoped muzzleloader shooting saboted
handgun bullets to allow precise (within 2" in many cases) shot placement for
studying terminal ballistics in a living target. Deer are baited to a known
range and path obstructions are used to place the deer broadside to the
shooter. Muzzleloading powder charges provide a combination of muzzle velocity
and velocity loss due to air resistance for a given ballistic coefficient that
produce impact velocities corresponding to typical pistol velocities. With
readily available sabots, this approach allows for testing of terminal
ballistics of .355, .357, .40, .429, .45, and .458 caliber bullets with two
muzzleloaders (.45 and .50 caliber). Examples are described demonstrating the
usefulness of testing handgun bullets in deer for acoustic shooting event
reconstruction, understanding tissue damage effects, and comparing relative
incapacitation of different loads.


title: Dynamics of clustered opinions in complex networks

abstract:
  A simple model for simulating tug of war game as varying the player number in
a team is discussed to identify the slow pace of fast change. This model shows
that a large number of information sources leads slow change for the system.
Also, we introduce an opinion diffusion model including the effect of a high
degree of clustering. This model shows that the de facto standard and lock-in
effect, well-known phenomena in economics and business management, can be
explained by the network clusters.


title: Inverse cascades and alpha-effect at low magnetic Prandtl number

abstract:
  Dynamo action in a fully helical Beltrami (ABC) flow is studied using both
direct numerical simulations and subgrid modeling. Sufficient scale separation
is given in order to allow for large-scale magnetic energy build-up. Growth of
magnetic energy obtains down to a magnetic Prandtl number PM=RM/RV close to
0.005, where RV and RM are the kinetic and magnetic Reynolds numbers. The
critical magnetic Reynolds number for dynamo action RMc seems to saturate at
values close to 20. Detailed studies of the dependence of the amplitude of the
saturated magnetic energy with PM are presented. In order to decrease PM,
numerical experiments are conducted with either RV or RM kept constant. In the
former case, the ratio of magnetic to kinetic energy saturates to a value
slightly below unity as PM decreases. Examination of energy spectra and
structures in real space both reveal that quenching of the velocity by the
large-scale magnetic field takes place, with an inverse cascade of magnetic
helicity and a force-free field at large scale in the saturated regime.


title: Critical transient in the Barab\'asi model of human dynamics

abstract:
  We introduce an exact probabilistic description for L=2 of the Barab\'asi
model for the dynamics of a list of L tasks. This permits to study the problem
out of stationarity, and to solve explicitly the extremal limit case where a
critical behavior for the waiting time distribution is observed. This behavior
deviates at any finite time from that of the stationary state. We study also
the characteristic relaxation time for finite time deviations from stationarity
in all cases showing that it diverges in the extremal limit confirming that
this deviations are important at all time.


title:
Measuring and modeling physics students' conceptual knowledge structures
  through term association times

abstract:
  Traditional problem-based exams are not efficient instruments for assessing
the "structure" of physics students' conceptual knowledge or for providing
diagnostically detailed feedback to students and teachers. We present the Free
Term Entry task, a candidate assessment instrument for exploring the
connections between concepts in a student's understanding of a subject. In this
task, a student is given a general topic area and asked to respond with as many
terms from the topic area as possible in a given time; the "thinking time"
between each term-entry event is recorded along with the response terms. The
task was given to students from two different introductory physics classes.
Response term thinking times were found to correlate with the strength of the
association between two concepts. In addition, sets of thinking times from the
task show distinct, characteristic patterns which might prove valuable for
student assessment. We propose a quantitative dynamical model named the Matrix
Walk Model which is able to match many aspects of the observed data. One
particular feature of the data -- a distinct "spike" superimposed on the
otherwise log-normal distribution of most thinking time sets -- has not been
fit. The spike, other patterns observed in the data, and the proposed
phenomenological model could all benefit from a grounding in cognitive theory.


title: An easy reading of modern ether-drift experiments

abstract:
  Modern ether-drift experiments look for a preferred reference frame searching
for modulations of the beat note of two optical resonators that might be
induced by the Earth's rotation. We present a compact formalism to evaluate the
signal for most experiments where two arbitrary gaseous media fill the
resonating cavities. Our predictions can provide useful hints to optimize the
experimental set up and the data taking.


title: A cyclic universe with colour fields

abstract:
  The topology of the universe is discussed in relation to the singularity
problem. We explore the possibility that the initial state of the universe
might have had a structure with 3-Klein bottle topology, which would lead to a
model of a nonsingular oscillating (cyclic) universe with a well-defined
boundary condition. The same topology is assumed to be intrinsic to the nature
of the hypothetical primitive constituents of matter (usually called preons)
giving rise to the observed variety of elementary particles. Some
phenomenological implications of this approach are also discussed.


title: Detecting and localizing the foci in human epileptic seizures

abstract:
  We consider the electrical signals recorded from a subdural array of
electrodes placed on the pial surface of the brain for chronic evaluation of
epileptic patients before surgical resection. A simple and computationally fast
method to analyze the interictal phase synchrony between such electrodes is
introduced and developed with the aim of detecting and localizing the foci of
the epileptic seizures. We evaluate the method by comparing the results of
surgery to the localization predicted here. We find an indication of good
correspondence between the success or failure in the surgery and the agreement
between our identification and the regions actually operated on.


title: Lagrangian Statistics of Navier-Stokes- and MHD-Turbulence

abstract:
  We report on a comparison of high-resolution numerical simulations of
Lagrangian particles advected by incompressible turbulent hydro- and
magnetohydrodynamic (MHD) flows. Numerical simulations were performed with up
to $1024^3$ collocation points and 10 million particles in the Navier-Stokes
case and $512^3$ collocation points and 1 million particles in the MHD case. In
the hydrodynamics case our findings compare with recent experiments from
Mordant et al. [1] and Xu et al. [2]. They differ from the simulations of
Biferale et al. [3] due to differences of the ranges choosen for evaluating the
structure functions. In Navier-Stokes turbulence intermittency is stronger than
predicted by a multifractal approach of [3] whereas in MHD turbulence the
predictions from the multifractal approach are more intermittent than observed
in our simulations. In addition, our simulations reveal that Lagrangian
Navier-Stokes turbulence is more intermittent than MHD turbulence, whereas the
situation is reversed in the Eulerian case. Those findings can not consistently
be described by the multifractal modeling. The crucial point is that the
geometry of the dissipative structures have different implications for
Lagrangian and Eulerian intermittency. Application of the multifractal approach
for the modeling of the acceleration PDFs works well for the Navier-Stokes case
but in the MHD case just the tails are well described.


title:
Quasi-phasematching of harmonic generation via multimode beating in
  waveguides

abstract:
  A new scheme for quasi-phasematching high harmonic generation (HHG) in gases
is proposed. In this, the rapid variation of the axial intensity resulting from
excitation of more than one mode of a waveguide is used to achieve quasi
phasematching. Numerical modeling demonstrates enhancement of the harmonic
signal over that achieved for a single coherence length by factors >10^4.


title: Bright quasi-phasematched soft x-ray harmonic radiation from Argon ions

abstract:
  Selective enhancement (>10^3) of harmonics extending to the water window
(~4nm) generated in an argon gas filled straight bore capillary waveguide is
demonstrated. This enhancement is in good agreement with modeling which
indicates that multimode quasi-phasematching (MMQPM) is achieved by rapid axial
intensity modulations caused by beating between the fundamental and higher
order capillary modes. Substantial pulse-energies (>10nJ per pulse per harmonic
order) at wavelengths beyond the carbon K-edge (~4.37nm, ~284eV) up to ~360eV
are observed from argon ions for the first time.


title:
Science Citation Index data: Two additional reasons against its use for
  administrative purposes

abstract:
  First, for decades the use of anonymity in reviews for science funding
proposals and for evaluating manuscripts for publication has been gradually
corrupting American science, encouraging and rewarding the dark elements of
human nature. Unethical reviewers, secure and unaccountable through anonymity,
all too often make untrue and/or pejorative statements to eliminate their
professional competitors. Survival in this corrupt environment has led to a
consensus-only mentality. Consequently, important scientific contradictions, if
they can be published at all, are selectively ignored in many instances out of
fear of anonymous retaliation. Science Citation Index data in such a corrupt
environment may be of little administrative value, except for possible use in
documenting scientific fraud. Second, as knowledge of the administrative use of
Science Citation Index data spreads, scientists will adapt and will shift to
research on popular subjects to elicit greater numbers of citations, rather
than to take the paths less trodden where important scientific discoveries may
lay waiting.


title: Trapping of Rb atoms by ac electric fields

abstract:
  We demonstrate trapping of an ultracold gas of neutral atoms in a macroscopic
ac electric trap. Three-dimensional confinement is obtained by switching
between two saddle-point configurations of the electric field. Stable trapping
is observed in a narrow range of switching frequencies around 60 Hz. The
dynamic confinement of the atoms is directly visualized at different phases of
the ac switching cycle. We observe about 10^5 Rb atoms in the 1 mm^3 large and
several microkelvins deep trap with a lifetime of approximately 5 s.


title: Failure in Complex Social Networks

abstract:
  Tolerance against failures and errors is an important feature of many complex
networked systems [1,2]. It has been shown that a class of inhomogeneously
wired networks called scale-free[1,3] networks can be surprisingly robust to
failures, suggesting that socially self-organized systems such as the
World-Wide Web, the Internet, and other kinds of social networks [4] may have
significant tolerance against failures by virtue of their scale-free degree
distribution. I show that this finding only holds on the assumption that the
diffusion process supported by the network is a simple one, requiring only a
single contact in order for transmission to be successful.


title:
Comment on "Preacceleration without radiation: The nonexistence of
  preradiation phenomenon," by J.A. Heras [Am. J. Phys. 74, 1025 (2006)]

abstract:
  It is argued that a recent claim that there is no radiation in the
preacceleration part of a non-runaway solution of the Abraham--Lorentz equation
is incorrect.


title: Observation of single collisionally cooled trapped ions in a buffer gas

abstract:
  Individual Ba ions are trapped in a gas-filled linear ion trap and observed
with a high signal-to-noise ratio by resonance fluorescence. Single-ion storage
times of ~5 min (~1 min) are achieved using He (Ar) as a buffer gas at
pressures in the range 8e-5 - 4e-3 torr. Trap dynamics in buffer gases are
experimentally studied in the simple case of single ions. In particular, the
cooling effects of light gases such as He and Ar and the destabilizing
properties of heavier gases such as Xe are studied. A simple model is offered
to explain the observed phenomenology.


title:
Self-similar signature of the active solar corona within the inertial
  range of solar wind turbulence

abstract:
  We quantify the scaling of magnetic energy density in the inertial range of
solar wind turbulence seen in-situ at 1AU with respect to solar activity. At
solar maximum, when the coronal magnetic field is dynamic and topologically
complex, we find self-similar scaling in the solar wind, whereas at solar
mimimum, when the coronal fields are more ordered, we find multifractality.
This quantifies the solar wind signature that is of direct coronal origin, and
distinguishes it from that of local MHD turbulence, with quantitative
implications for our understanding of coronal heating of the solar wind.


title: Probability as a physical motive

abstract:
  Recent theoretical progress in nonequilibrium thermodynamics, linking the
physical principle of Maximum Entropy Production ("MEP") to the
information-theoretical "MaxEnt" principle of scientific inference, together
with conjectures from theoretical physics that there may be no fundamental
causal laws but only probabilities for physical processes, and from
evolutionary theory that biological systems expand "the adjacent possible" as
rapidly as possible, all lend credence to the proposition that probability
should be recognized as a fundamental physical motive. It is further proposed
that spatial order and temporal order are two aspects of the same thing, and
that this is the essence of the second law of thermodynamics.


title: Clustering of Aerosols in Atmospheric Turbulent Flow

abstract:
  A mechanism of formation of small-scale inhomogeneities in spatial
distributions of aerosols and droplets associated with clustering instability
in the atmospheric turbulent flow is discussed. The particle clustering is a
consequence of a spontaneous breakdown of their homogeneous space distribution
due to the clustering instability, and is caused by a combined effect of the
particle inertia and a finite correlation time of the turbulent velocity field.
In this paper a theoretical approach proposed in Phys. Rev. E 66, 036302 (2002)
is further developed and applied to investigate the mechanisms of formation of
small-scale aerosol inhomogeneities in the atmospheric turbulent flow. The
theory of the particle clustering instability is extended to the case when the
particle Stokes time is larger than the Kolmogorov time scale, but is much
smaller than the correlation time at the integral scale of turbulence. We
determined the criterion of the clustering instability for the Stokes number
larger than 1. We discussed applications of the analyzed effects to the
dynamics of aerosols and droplets in the atmospheric turbulent flow.


title: Classical light dispersion theory in a regular lattice

abstract:
  We study the dynamics of an infinite regular lattice of classical charged
oscillators. Each individual oscillator is described as a point particle
subject to a harmonic restoring potential, to the retarded electromagnetic
field generated by all the other particles, and to the radiation reaction
expressed according to the Lorentz--Dirac equation. Exact normal mode
solutions, describing the propagation of plane electromagnetic waves through
the lattice, are obtained for the complete linearized system of infinitely many
oscillators. At variance with all the available results, our method is valid
for any values of the frequency, or of the ratio between wavelength and lattice
parameter. A remarkable feature is that the proper inclusion of radiation
reaction in the dynamics of the individual oscillators does not give rise to
any extinction coefficient for the global normal modes of the lattice. The
dispersion relations resulting from our solution are numerically studied for
the case of a simple cubic lattice. New predictions are obtained in this way
about the behavior of the crystal at frequencies near the proper oscillation
frequency of the dipoles.

categories: physics.optics cond-mat.str-el math-ph math.MP physics.class-ph


title:
A class of vector identities relevant to the representation of the
  electric current density

abstract:
  A rigorous mathematical proof is given of a class of vector identities that
provide a way to separate an arbitrary vector field (over a linear space) into
the sum of a radial (i.e., pointing toward the radial unit vector) vector
field, minus the divergence of a tensor plus the curl of an axial vector. Such
a separation is applied to the representation of electric current densities
yielding a specific form of the effective polarization and magnetization fields
which is also discussed in some details.


title:
Goal Oriented Adaptive Finite Element Method for the Precise Simulation
  of Optical Components

abstract:
  Adaptive finite elements are the method of choice for accurate simulations of
optical components. However as shown recently by Bienstman et al. many finite
element mode solvers fail to compute the propagation constant's imaginary part
of a leaky waveguide with sufficient accuracy. In this paper we show that with
a special goal oriented error estimator for capturing radiation losses this
problem is overcome.


title: Deviations from the local field approximation in negative streamer heads

abstract:
  Negative streamer ionization fronts in nitrogen under normal conditions are
investigated both in a particle model and in a fluid model in local field
approximation. The parameter functions for the fluid model are derived from
swarm experiments in the particle model. The front structure on the inner scale
is investigated in a 1D setting, allowing reasonable run-time and memory
consumption and high numerical accuracy without introducing super-particles. If
the reduced electric field immediately before the front is >= 50kV/(cm bar),
solutions of fluid and particle model agree very well. If the field increases
up to 200kV/(cm bar), the solutions of particle and fluid model deviate, in
particular, the ionization level behind the front becomes up to 60% higher in
the particle model while the velocity is rather insensitive. Particle and fluid
model deviate because electrons with high energies do not yet fully run away
from the front, but are somewhat ahead. This leads to increasing ionization
rates in the particle model at the very tip of the front. The energy overshoot
of electrons in the leading edge of the front actually agrees quantitatively
with the energy overshoot in the leading edge of an electron swarm or avalanche
in the same electric field.


title:
Characterization of large area avalanche photodiodes in X-ray and
  VUV-light detection

abstract:
  The present manuscript summarizes novel studies on the application of large
area avalanche photodiodes (LAAPDs) to the detection of X-rays and vacuum
ultraviolet (VUV) light. The operational characteristics of four different
LAAPDs manufactured by Advanced Photonix Inc., with active areas of 80 and 200
mm^2 were investigated for X-ray detection at room temperature. The best energy
resolution was found to be in the 10-18% range for 5.9 keV X-rays. The LAAPD,
being compact, simple to operate and with high counting rate capability (up to
about 10^5/s), proved to be useful in several applications, such as low-energy
X-ray detection, where they can reach better performance than proportional
counters. Since X-rays are used as reference in light measurements, the gain
non-linearity between 5.9 keV X-rays and light pulses was investigated. The
gain ratio between X-rays and VUV light decreases with gain, reaching 10 and 6%
variations for VUV light produced in argon (~128 nm) and xenon (~172 nm),
respectively, for a gain 200, while for visible light (~635 nm) the variation
is lower than 1%. The effect of temperature on the LAAPD performance was
investigated. Relative gain variations of about -5% per Celsius degree were
observed for the highest gains. The excess noise factor was found to be
independent on temperature, being between 1.8 and 2.3 for gains from 50 to 300.
The energy resolution is better for decreasing temperatures due mainly to the
dark current. LAAPDs were tested under intense magnetic fields up to 5 T, being
insensitive when used in X-ray and visible-light detection, while for VUV light
a significant amplitude reduction was observed at 5 T.


title: Changes in number and intensity of world-wide tropical cyclones

abstract:
  Bayesian statistical models were developed for the number of tropical
cyclones and the rate at which these cyclones became hurricanes in the North
Atlantic, North and South Indian, and East and West Pacific Oceans. We find
that there is small probability that the number of cyclones has increased in
the past thirty years. The rate at which these storms become hurricanes appears
to be constant. The rate at which hurricanes evolve into category 4 and higher
major storms does appear to have increased. We also investigate storm intensity
by measuring the distribution of individual storm lifetime in days, storm track
length, and Emanuel's power dissiptation index. We find little evidence that,
overall, the mean of the distribution of individual storm intensity is changing
through time, but the variability of the distribution has increased. The cold
tongue index and the North Atlantic oscillation index were found to be strongly
associated with storm quality in the Western, and to a smaller extent, the
Eastern Pacific oceans. The North Atlantic oscillation index was strongly
associated with the increase in the rate of strong storms evolving.


title:
A Relativistic-Proton Dark Matter Would Be Evidence The Big Bang
  Probably Satisfied The Second Law Of Thermodynamics

abstract:
  A new research hypothesis has been developed by the author based upon finding
astronomically based `cosmic constituents` of the Universe that may be created
or influenced by or have a special relationship with possible dark matter
candidates. He then developed a list of 14 relevant and plausible `cosmic
constituents` of the Universe, which then was used to establish a list of
constraints regarding the nature and characteristics of the long-sought dark
matter particles. A dark matter candidate was then found that best conformed to
the 14 constraints established by the `cosmic constituents.` The author then
used this same dark matter candidate to provide evidence that the Big Bang was
relativistic, had a low entropy, and therefore probably satisfied the Second
Law of Thermodynamics.


title:
A Comparison of Two Shallow Water Models with Non-Conforming Adaptive
  Grids: classical tests

abstract:
  In an effort to study the applicability of adaptive mesh refinement (AMR)
techniques to atmospheric models an interpolation-based spectral element
shallow water model on a cubed-sphere grid is compared to a block-structured
finite volume method in latitude-longitude geometry. Both models utilize a
non-conforming adaptation approach which doubles the resolution at fine-coarse
mesh interfaces. The underlying AMR libraries are quad-tree based and ensure
that neighboring regions can only differ by one refinement level.
  The models are compared via selected test cases from a standard test suite
for the shallow water equations. They include the advection of a cosine bell, a
steady-state geostrophic flow, a flow over an idealized mountain and a
Rossby-Haurwitz wave. Both static and dynamics adaptations are evaluated which
reveal the strengths and weaknesses of the AMR techniques. Overall, the AMR
simulations show that both models successfully place static and dynamic
adaptations in local regions without requiring a fine grid in the global
domain. The adaptive grids reliably track features of interests without visible
distortions or noise at mesh interfaces. Simple threshold adaptation criteria
for the geopotential height and the relative vorticity are assessed.


title:
A basic problem in the correlations between statistics and
  thermodynamics

abstract:
  By using a fonctionelle of probability distributions, several different
statistical physics including extensive and nonextensive statistics are unified
in a general method. The essential equivalence between the MaxEnt process of
the most probable probility distribution in these statistics and the famous
thermodynamical relation dU=TdS is strictly proved without any additional
assumption. Moreover, it is expounded that all the conclusions of these
different statistics can be directly derived from the equivalent relation.


title: Super-relativity in the quantum theory

abstract:
  The relativity to the measuring device in quantum theory, i.e. the covariance
of local dynamical variables relative transformations to moving quantum
reference frame in Hilbert space, may be achieved only by the rejection of
super-selection rule. In order to avoid the subjective nuance, I emphasis that
the notion of "measurement" here, is nothing but the covariant differentiation
procedure in the functional quantum phase space $CP(N-1)$, having pure
objective sense of evolution. Transition to the local moving quantum reference
frame leads to some particle-like solutions of quasi-linear field PDE in the
dynamical space-time. Thereby, the functionally covariant quantum dynamics
gives the perspective to unify the Einstein relativity and quantum principles
which are obviously contradictable under the standard approaches.


title:
On the opportunity of spectroscopic determination of absolute atomic
  densities in non-equilibrium plasmas from measured relative intensities
  within resonance multiplets distorted by self-absorption

abstract:
  The opportunities of the application of the recently proposed approach in
optical emission spectroscopy of non-equilibrium plasmas have been studied. The
approach consists of several methods of the determination of {\em absolute}
particle densities of atoms from measured {\em relative} intensities within
resonance multiplets distorted by self-absorption. All available spectroscopic
data concerning resonance spectral lines of atoms having multiplet ground
states from boron up to gallium were analyzed. It is found that in the case of
C, O, F, S and Cl atoms an application of the methods needs VUV technique,
while densities of B, Al, Si, Sc, Ti, V, Co, Ni, Ga atoms may be obtained by
means of the intensity measurements in UV and visible parts of emission spectra
suitable for ordinary spectrometers used for optical diagnostics and monitoring
of non-equilibrium plasmas including industrial plasma technologies.


title: Mathematics and explanation in astronomy and astrophysics

abstract:
  The purpose of this paper is to expound and clarify the mathematics and
explanations commonly employed in certain notable areas of astronomy and
astrophysics. The first section concentrates upon the mathematics employed to
represent and understand stellar structure and evolution. The second section
analyses two different explanations for the structure of spiral galaxies.


title:
Reflectivity and Exact Asymptotic Forms of the Dielectric Function of
  Non-Ideal Plasmas

abstract:
  The problem of calculation of the reflectivity of non-ideal shock-compressed
plasmas is revisited. The dielectric formalism based on the method of moments
incorporating exact asymptotic forms and sum rules is applied to the new
experimental data. The approach is based on the Ansatz of reflection of laser
radiation from a thin shock-front and possesses one adjustable parameter which
depends only on the thermodynamic conditions of the experiment. A
self-consistent agreement with all available experimental data is achieved.


title:
Optical bistability in Er-Yb co-doped phosphate glass microspheres at
  room temperature

abstract:
  We experimentally demonstrate optical bistability in Er3+-Yb3+ phosphate
glass microspheres at 295 K. Bistability is associated with both Er3+
fluorescence and lasing behavior, and chromatic switching. The chromatic
switching results from an intrinsic mechanism exploiting the thermal coupling
of closely-spaced energy levels, and occurs simultaneously with the intensity
switching. A contrast ratio of 3.2 has been obtained for chromatic switching,
and the intensity switching shows ratios of 2.4 for 550 nm and, 1.8 for the 660
nm fluorescence emissions, and 11 for the IR lasing at 1.5 um. Concurrent with
these observations, we investigate a temperature dependent absorption of pump
power which exhibits bistable behavior. The influences of the host matrix on
lasing and fluorescence mechanisms are highlighted.


title:
Comparison of two models of a Double Inlet Miniature Pulse Tube
  Refrigerator - Part B : Electrical Analogy

abstract:
  The design of a Double Inlet Pulse Tube Refrigerator is investigated by means
of an analogy with an electric circuit. The results obtained with the electric
scheme are compared with both those of the thermodynamic model (Part A) and
experiments. The basic formulation of equivalent electronic components is
discussed and a few improvements are proposed to adjust the theoretical
expressions of the electrical impedances of capillaries and regenerator in
order to consider additional effects such pressure drops due to geometrical
singularities at different internal flow regimes. A simplified formulation for
the regenerator inefficiency is deduced from considerations on its harmonic
functioning. The main purpose of this analysis considers especially the design
of miniature cryocoolers dedicated to electronic applications. These models are
applied to a commercial miniature refrigerator. A discussion of their relevance
is achieved and a few suggestions on the refrigerator design are proposed to
improve the cooling production.


title:
Micro Drift Chamber as a high resolution vertex detector for the DIRAC
  experiment

abstract:
  A possible implementation of the Micro Drift Chamber (MDC) technique as a
high resolution vertex detector in the upstream part of the DIRAC spectrometer
was investigated in this paper. Simulations of different MDC layout were
performed with the help of GARFIELD package. Based on the results of simulation
the optimal chamber geometry and the gas mixture were selected.
  One cell prototype was produced and its characteristics were measured at
different particle fluxes, various gas pressures and thresholds of electronics.
  Data observed together with expected coordinate resolution of MDC allow to
employ such detector in different field of application including the DIRAC
experiment.


title: Secondary Scintillation Yield in Pure Xenon

abstract:
  The xenon secondary scintillation yield was studied as a function of the
electric field in the scintillation region, in a gas proportional scintillation
counter operated at room temperature. A large area avalanche photodiode was
used for the readout of the VUV secondary scintillation produced in the gas,
together with the 5.9 keV x-rays directly absorbed in the photodiode. The
latter was used as a reference for the determination of the number of charge
carriers produced by the scintillation pulse and, thus, the number of VUV
photons impinging the photodiode. A value of 140 photons/kV was obtained for
the scintillation amplification parameter. The attained results are in good
agreement with those predicted, for room temperature, by Monte Carlo simulation
and Boltzmann calculations, as well as with those obtained for saturated xenon
vapour, at cryogenic temperatures, and are about a factor of two higher than
former results measured at room temperature.


title: Testing Gravity with Muonium

abstract:
  Recently a new technique for the production of muon ($\mu^+$) and muonium
($\mu^+e^-$) beams of unprecedented brightness has been proposed. As one
consequence and using a highly stable Mach-Zehnder type interferometer, a
measurement of the gravitational acceleration $\bar{g}$ of muonium atoms at the
few percent level of precision appears feasible within 100 days of running
time. The inertial mass of muonium is dominated by the mass of the positively
charged - antimatter - muon. The measurement of $\bar{g}$ would be the first
test of the gravitational interaction of antimatter, of a purely leptonic
system, and of particles of the second generation.


title:
Title Excited state dynamics of liquid water: Insight from the
  dissociation reaction following two-photon excitation

abstract:
  We use transient absorption spectroscopy to monitor the ionization and
dissociation products following two-photon excitation of pure liquid water. The
two decay mechanisms occur with similar yield for an excitation energy of 9.3
eV, whereas the major channel at 8.3 eV is dissociation. The geminate
recombination kinetics of the H and OH fragments, which can be followed in the
transient absorption probed at 267 nm, provide a window on the dissociation
dynamics at the lower excitation energy. Modeling the OH geminate recombination
indicates that the dissociating H atoms have enough kinetic energy to escape
the solvent cage and one or two additional solvent shells. The average initial
separation of H and OH fragments is 0.7+-0.2 nm. Our observation suggests that
the hydrogen bonding environment does not prevent direct dissociation of an O-H
bond in the excited state. We discuss the implications of our measurement for
the excited state dynamics of liquid water and explore the role of those
dynamics in the ionization mechanism at low excitation energies.


title: Numerical Verification of the Weak Turbulent Model for Swell Evolution

abstract:
  The purpose of this article is numerical verification of the theory of weak
turbulence. We performed numerical simulation of an ensemble of nonlinearly
interacting free gravity waves (swell) by two different methods: solution of
primordial dynamical equations describing potential flow of the ideal fluid
with a free surface and, solution of the kinetic Hasselmann equation,
describing the wave ensemble in the framework of the theory of weak turbulence.
  In both cases we observed effects predicted by this theory: frequency
downshift, angular spreading and formation of Zakharov-Filonenko spectrum
$I_{\omega} \sim \omega^{-4}$. To achieve quantitative coincidence of the
results obtained by different methods, one has to supply the Hasselmann kinetic
equation by an empirical dissipation term $S_{diss}$ modeling the coherent
effects of white-capping. Using of the standard dissipation terms from
operational wave predicting model ({\it WAM}) leads to significant improvement
on short times, but not resolve the discrepancy completely, leaving the
question about optimal choice of $S_{diss}$ open. In a long run {\it WAM}
dissipative terms overestimate dissipation essentially.

categories: physics.flu-dyn physics.ao-ph physics.comp-ph physics.geo-ph


title: Magneto-electrostatic trapping of ground state OH molecules

abstract:
  We report the magnetic confinement of neutral, ground state hydroxyl radicals
(OH) at a density of $\sim3\times10^{3}$ cm$^{-3}$ and temperature of $\sim$30
mK. An adjustable electric field of sufficient magnitude to polarize the OH is
superimposed on the trap in either a quadrupole or homogenous field geometry.
The OH is confined by an overall potential established via molecular state
mixing induced by the combined electric and magnetic fields acting on the
molecule's electric dipole and magnetic dipole moments, respectively. An
effective molecular Hamiltonian including Stark and Zeeman terms has been
constructed to describe single molecule dynamics inside the trap. Monte Carlo
simulation using this Hamiltonian accurately models the observed trap dynamics
in various trap configurations. Confinement of cold polar molecules in a
magnetic trap, leaving large, adjustable electric fields for control, is an
important step towards the study of low energy dipole-dipole collisions.


title: Rayleigh's collapsing time of a spherical cavity: the $\Delta$-factor

abstract:
  New corrections to the equation of motion and total collapsing time of an
empty spherical cavity immersed in an infinite incompressible medium are
proposed on the assumption of a non-uniform density. The dimensionless number
quantifying the corrections with respect to the standard Rayleigh results
(coined the $\Delta$-factor) is fully independent of other possible
contributions like surface tension and viscous terms. The $\Delta$-factor
effect advocated here can be seen as a direct consequence of a mass-shell
non-trivial solution to the continuity equation. The consistency of the
corrections with respect to the Bernoulli theorem and some physical
consequences in the framework of the Rayleigh-Plesset equation are also
discussed.


title: Reliability of rank order in sampled networks

abstract:
  In complex scale-free networks, ranking the individual nodes based upon their
importance has useful applications, such as the identification of hubs for
epidemic control, or bottlenecks for controlling traffic congestion. However,
in most real situations, only limited sub-structures of entire networks are
available, and therefore the reliability of the order relationships in sampled
networks requires investigation. With a set of randomly sampled nodes from the
underlying original networks, we rank individual nodes by three centrality
measures: degree, betweenness, and closeness. The higher-ranking nodes from the
sampled networks provide a relatively better characterisation of their ranks in
the original networks than the lower-ranking nodes. A closeness-based order
relationship is more reliable than any other quantity, due to the global nature
of the closeness measure. In addition, we show that if access to hubs is
limited during the sampling process, an increase in the sampling fraction can
in fact decrease the sampling accuracy. Finally, an estimation method for
assessing sampling accuracy is suggested.

categories: physics.soc-ph cond-mat.stat-mech physics.data-an stat.AP


title: Modeling protein synthesis from a physicist's perspective: a toy model

abstract:
  Proteins are polymers of amino acids. These macromolecules are synthesized by
intracellular machines called ribosomes. Although the experimental
investigation of protein synthesis has been a traditional area of research in
molecular cell biology, important quantitative models of protein synthesis have
been reported in research journals devoted to statistical physics and related
interdisciplinary topics. From the perspective of a physicist, protein
synthesis is the classical transport of interacting ribosomes on a messenger
RNA (mRNA) template that dictates the sequence of the amino acids on the
protein. We discuss appropriate simplification of the models and methods. In
particular, we develop and analyze a simple toy model using some elementary
techniques of non-equilibrium statistical mechanics and predict the average
rate of protein synthesis and the spatial organization of the ribosomes in the
steady state.

categories: physics.bio-ph cond-mat.stat-mech q-bio.BM q-bio.SC


title: Has the second law of thermodynamics really been violated ?

abstract:
  Some works have appeared in recent accredited literature considering the
possibility of macroscopic violations of the second law in simulated as well as
really executed experiments. We argue the inexistence of such violations in
experiments based on the so-called nonbias diode, demonstrating that the
interpretation of the authors is flawed by a confusion between the concepts of
thermal equilibrium and thermodynamic equilibrium. We also discuss an
isomorphic experimental set up based on the evaporation-condensation of a
liquid in a closed atmosphere. Some critical observations are then made
concerning recent attempts to reformulate classical equilibrium thermodynamics.


title: Slow dynamics in a turbulent von K\'arm\'an swirling flow

abstract:
  We present an experimental study of a turbulent von K\'arm\'an flow produced
in a cylindrical container using two propellers. The mean flow is stationary up
to $Re = 10^4$, where a bifurcation takes place. The new regime breaks some
symmetries of the problem, and is time-dependent. The axisymmetry is broken by
the presence of equatorial vortices with a precession movement, being the
velocity of the vortices proportional to the Reynolds number. The reflection
symmetry through the equatorial plane is broken, and the shear layer of the
mean flow appears displaced from the equator. These two facts appear
simultaneously. In the exact counterrotating case, a bistable regime appears
between both mirrored solutions and spontaneous reversals of the azimuthal
velocity are registered. This evolution can be explained using a three-well
potential model with additive noise. A regime of forced periodic response is
observed when a very weak input signal is applied.


title: Parameters of the Free Core Nutation from VLBI Data

abstract:
  Several VLBI EOP series were investigated with goal of determination of
parameters of the Free Core Nutation (FCN). Both the amplitude and period of
the FCN were studied using spectral and wavelet analysis. Our analysis reveals
a variability of both the amplitude (known also from other investigations) and
the period (or phase) of the FCN nutation. The FCN amplitude varies in the
range about 0.1--0.3 mas, and the FCN period -- in the range about 415--490
solar days. The latter may be also explained by changes in the FCN phase.
Comparison of time variations of the FCN period and amplitude obtained by
different authors and methods shows substantial discrepancies at the edges of
the period of observations.


title:
Two-Particle Models, Diagrams and Graphs as Aids to Understanding
  Internal Energy

abstract:
  Single particle models are sufficient for many topics in introductory physics
courses, but become misleading when applied to situations involving changes in
internal energy. This paper merges two parallel attempts to reform the teaching
of energy in the introductory physics curriculum, resulting in an approach to
internal energy that is conceptually correct, mathematically rigorous, and yet
simple enough for the introductory student to understand. It uses diagrams and
graphs to provide concrete and visual means to track energy storage and
transfer, and takes the smallest possible step in mathematical complexity -
from one-particle to two-particle models - necessary to achieve consistency
with a sound conceptual approach. The mathematical development is guided by the
idea that the term "work" should receive a clear conceptual definition as
energy that is transferred through the boundary of a system; mathematical
expressions are identified as work - of any sort - only when they correspond to
this definition.


title: Planar Atom Trap and Magnetic Resonance 'Lens' Designs

abstract:
  We present various planar magnetic designs that create points above the plane
where the magnitude of the static magnetic field is a local minimum. Structures
with these properties are of interest in the disciplines of neutral atom
confinement, magnetic levitation, and magnetic resonance imaging. Each planar
permanent magnet design is accompanied by the equivalent planar single
non-crossing conductor design. Presented designs fall into three categories
producing: a) zero value magnetic field magnitude point minima, b) non-zero
magnetic field magnitude point minima requiring external bias magnetic field,
and c) self-biased non-zero magnetic field magnitude point minima. We also
introduce the Principle of Amperean Current Doubling in planar perpendicularly
magnetized thin films that can be used to improve the performance of each
permanent magnet design we present. Single conductor current-carrying designs
are suitable for single layer lithographic fabrication, as we experimentally
demonstrate. Finally, we present the case that nanometer scale recording of
perpendicular anisotropy thin magnetic films using presently available data
storage technology can provide the ultimate miniaturization of the presented
designs.


title: Falling Bodies: the Obvious,the Subtle, and the Wrong

abstract:
  An important scientific debate took place regarding falling bodies hundreds
of years ago, and it still warrants introspection. Galileo argued that in a
vacuum all bodies fall at the same rate relative to the earth, independent of
their mass. Aristotle seemed to consider all media to be viscous, and argued
that heavier bodies fall faster. Aristotle was challenged by Philoponus, who
argued that light and heavy weights fall about equally fast in air, eleven
hundred years before Galileo. As we shall see, the problem is more subtle than
meets the eye -- even in a frictionless medium. Philoponus and Galileo are
right part of the time, and Aristotle is partly right some of the time. In fact
they are all wrong the rest of the time, with the lightest body falling fastest
when two bodies fall toward the earth. In principle the results of a free fall
experiment depend on whether falling masses originate on earth, are
extraterrestrial, are sequential or concurrent, or are simultaneous for
coincident or separated bodies, etc. When single falling bodies originate from
the earth, all bodies (light and heavy) fall at the same rate relative to the
earth in agreement with Galileo's view. Einstein's General Relativity (EGR), in
which gravity is due to space-time curvature, was motivated by the Galilean
notion that free-fall is independent of the mass and properties of a falling
body, and is just due to the properties of the milieu it finds itself in.
Quantum mechanics is found to violate the Equivalence Principle of EGR.


title:
Evaluation of three methods for calculating statistical significance
  when incorporating a systematic uncertainty into a test of the
  background-only hypothesis for a Poisson process

abstract:
  Hypothesis tests for the presence of new sources of Poisson counts amidst
background processes are frequently performed in high energy physics (HEP),
gamma ray astronomy (GRA), and other branches of science. While there are
conceptual issues already when the mean rate of background is precisely known,
the issues are even more difficult when the mean background rate has
non-negligible uncertainty. After describing a variety of methods to be found
in the HEP and GRA literature, we consider in detail three classes of
algorithms and evaluate them over a wide range of parameter space, by the
criterion of how close the ensemble-average Type I error rate (rejection of the
background-only hypothesis when it is true) compares with the nominal
significance level given by the algorithm. We recommend wider use of an
algorithm firmly grounded in frequentist tests of the ratio of Poisson means,
although for very low counts the over-coverage can be severe due to the effect
of discreteness. We extend the studies of Cranmer, who found that a popular
Bayesian-frequentist hybrid can undercover severely when taken to high Z
values. We also examine the profile likelihood method, which has long been used
in GRA and HEP; it provides an excellent approximation in much of the parameter
space, as previously studied by Rolke and collaborators.


title: Lorentz transformations: Einstein's derivation simplified

abstract:
  We show that the Lorentz transformations for the space-time coordinates of
the same event are a direct consequence of the principle of relativity and of
Einstein's distant clocks synchronization procedure. In our approach, imposing
the linear character of the Lorentz transformations we guess that the
transformation equation for the space coordinate has the form x=ax'+cbt'.
Imposing the condition that it accounts for the time dilation relativistic
effect and taking into account the fact that due to the clock synchronization a
la Einstein the space-time coordinates of the same event in the two frames are
related by x=ct and x'=ct', we find out expressions for a and b. Dividing the
transformation equation for the space coordinate by c we obtain the
transformation equation for the time coordinate t=at'+b/cx'. Combining the two
transformation equations we obtain directly the inverse Lorentz
transformations.


title:
Analysis of a large-scale weighted network of one-to-one human
  communication

abstract:
  We construct a connected network of 3.9 million nodes from mobile phone call
records, which can be regarded as a proxy for the underlying human
communication network at the societal level. We assign two weights on each edge
to reflect the strength of social interaction, which are the aggregate call
duration and the cumulative number of calls placed between the individuals over
a period of 18 weeks. We present a detailed analysis of this weighted network
by examining its degree, strength, and weight distributions, as well as its
topological assortativity and weighted assortativity, clustering and weighted
clustering, together with correlations between these quantities. We give an
account of motif intensity and coherence distributions and compare them to a
randomized reference system. We also use the concept of link overlap to measure
the number of common neighbors any two adjacent nodes have, which serves as a
useful local measure for identifying the interconnectedness of communities. We
report a positive correlation between the overlap and weight of a link, thus
providing strong quantitative evidence for the weak ties hypothesis, a central
concept in social network analysis. The percolation properties of the network
are found to depend on the type and order of removed links, and they can help
understand how the local structure of the network manifests itself at the
global level. We hope that our results will contribute to modeling weighted
large-scale social networks, and believe that the systematic approach followed
here can be adopted to study other weighted networks.