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Kosmos
Astronomia Astrofizyka
Inne

Kultura
Sztuka dawna i współczesna, muzea i kolekcje

Metoda
Metodologia nauk, Matematyka, Filozofia, Miary i wagi, Pomiary

Materia
Substancje, reakcje, energia
Fizyka, chemia i inżynieria materiałowa

Człowiek
Antropologia kulturowa Socjologia Psychologia Zdrowie i medycyna

Wizje
Przewidywania Kosmologia Religie Ideologia Polityka

Ziemia
Geologia, geofizyka, geochemia, środowisko przyrodnicze

Życie
Biologia, biologia molekularna i genetyka

Cyberprzestrzeń
Technologia cyberprzestrzeni, cyberkultura, media i komunikacja

Działalność
Wiadomości | Gospodarka, biznes, zarządzanie, ekonomia

Technologie
Budownictwo, energetyka, transport, wytwarzanie, technologie informacyjne

# Kolekcje IOP - FEATURED

Featured

## Anomalous Higgs Yukawa couplings

In the standard model, the Higgs boson h couples to the quarks and charged leptons according to the
well-known formula ##IMG## [http://ej.iop.org/images/0295-5075/108/1/11002/epl16591ieqn1.gif]
{$(m_\psi/v) h \bar{\psi}\psi$} , where ##IMG##
[http://ej.iop.org/images/0295-5075/108/1/11002/epl16591ieqn2.gif] {$\psi =\text{quark }(q)$} or
lepton ##IMG## [http://ej.iop.org/images/0295-5075/108/1/11002/epl16591ieqn3.gif] {$(l)$} and
##IMG## [http://ej.iop.org/images/0295-5075/108/1/11002/epl16591ieqn4.gif] {$v = 246\ \text{GeV}$}
is its vacuum expectation value. Suppose ##IMG##
[http://ej.iop.org/images/0295-5075/108/1/11002/epl16591ieqn5.gif] {$m_\psi$} is of radiative origin
instead, then the effective ##IMG##
[http://ej.iop.org/images/0295-5075/108/1/11002/epl16591ieqn6.gif] {$h \bar{\psi} \psi$} Yukawa
coupling will not be exactly ##IMG##

2014/10/04 - 20:02

## Effective description of the interaction between anisotropic viscous fingers

We study patterns formed by viscous fingering in a rectangular network of microfluidic channels. Due
to the strong anisotropy of such a system, the emerging patterns have a form of thin needle-like
fingers, which interact with each other, competing for an available flow. We develop an upscaled
description of this system in which only the fingers are tracked and the effective interactions
between them are introduced, mediated through the evolving pressure field. Due to the quasi-2d
geometry of the system, this is conveniently accomplished using conformal mapping techniques. A
complex two-phase flow problem is thus reduced to a much simpler task of tracking evolving shapes in
a 2d complex plane. This description, although simplified, turns out to capture all the key features
of the system's dynamics and allows for the effective prediction of the resulting growth patterns.

2014/10/02 - 11:33

## Optical transmittance of multilayer graphene

We study the optical transmittance of multilayer graphene films up to 65 layers thick. By combing
large-scale tight-binding simulation and optical measurement on CVD multilayer graphene, the optical
transmission through graphene films in the visible region is found to be solely determined by the
number of graphene layers. We argue that the optical transmittance measurement is more reliable in
the determination of the number of layers than the commonly used the Raman spectroscopy. Moreover,
the optical transmittance measurement can be applied also to other 2D materials with weak van der
Waals interlayer interaction.

2014/10/02 - 11:33

## A novel time dependent gamma evaluation function for dynamic 2D and 3D dose distributions

Modern external beam radiotherapy requires detailed verification and quality assurance so that
confidence can be placed on both the delivery of a single treatment fraction and on the consistency
of delivery throughout the treatment course. To verify dose distributions, a comparison between
prediction and measurement must be made. Comparisons between two dose distributions are commonly
performed using a Gamma evaluation which is a calculation of two quantities on a pixel by pixel
basis; the dose difference, and the distance to agreement. By providing acceptance criteria (e.g.
3%, 3 mm), the function will find the most appropriate match within its two degrees of freedom. For
complex dynamic treatments such as IMRT or VMAT it is important to verify the dose delivery in a
time dependent manner and so a gamma evaluation that includes a degree of freedom in the time domain
via a third parameter, time to agreement, is presented here. A C++ (mex) based gamma function was
created th...

2014/09/21 - 05:29

## Modeling localized delivery of Doxorubicin to the brain following focused ultrasound enhanced blood-brain barrier permeability

Doxorubicin (Dox) is a well-established chemotherapeutic agent, however it has limited efficacy in
treating brain malignancies due to the presence of the blood-brain barrier (BBB). Recent preclinical
studies have demonstrated that focused ultrasound induced BBB disruption (BBBD) enables efficient
delivery of Dox to the brain. For future treatment planning of BBBD-based drug delivery, it is
crucial to establish a mathematical framework to predict the effect of transient BBB permeability
enhancement on the spatiotemporal distribution of Dox at the targeted area. The constructed model
considers Dox concentrations within three compartments (plasma, extracellular, intracellular) that
are governed by various transport processes (e.g. diffusion in interstitial space, exchange across
vessel wall, clearance by cerebral spinal fluid, uptake by brain cells). By examining several
clinical treatment aspects (e.g. sonication scheme, permeability enhancement, injection mode), our
simulation res...

2014/09/21 - 05:29

## Review on the characteristics of radiation detectors for dosimetry and imaging

The enormous advances in the understanding of human anatomy, physiology and pathology in recent
decades have led to ever-improving methods of disease prevention, diagnosis and treatment. Many of
these achievements have been enabled, at least in part, by advances in ionizing radiation detectors.
Radiology has been transformed by the implementation of multi-slice CT and digital x-ray imaging
systems, with silver halide films now largely obsolete for many applications. Nuclear medicine has
benefited from more sensitive, faster and higher-resolution detectors delivering ever-higher SPECT
and PET image quality. PET/MR systems have been enabled by the development of gamma ray detectors
that can operate in high magnetic fields. These huge advances in imaging have enabled equally
impressive steps forward in radiotherapy delivery accuracy, with 4DCT, PET and MRI routinely used in
treatment planning and online image guidance provided by cone-beam CT. The challenge of ensuring
safe, a...

2014/09/21 - 05:29

## A quantum informed continuum model for ferroelectric materials

Quantum mechanical stress relations are studied to guide the development of a continuum scale
electromechanical constitutive model for ferroelectric materials. Stresses at the quantum scale are
determined through the use of the Hellmann–Feynman theorem to obtain an electrostatic stress that
depends on the electric quadrupole density as opposed to polarization dependent electrostriction.
The result is integrated into a continuum model using a generalized set of electronic coordinate
vector order parameters contained within a Lagrangian density formulation. The new constitutive
model is shown to be consistent with both quantum based stress and classical phenomenological
electrostriction. This conclusion is verified through a numerical study of lead titanate where
calculations of energy, stress and polarization from density functional theory (DFT) are fit to
continuum stored energy and electrostatic stresses. The numerical analysis includes uncertainty
quantification using Bayesian ...

2014/09/21 - 05:29

## Flexible piezoelectric energy harvesting from jaw movements

Piezoelectric fiber composites (PFC) represent an interesting subset of smart materials that can
function as sensor, actuator and energy converter. Despite their excellent potential for energy
harvesting, very few PFC mechanisms have been developed to capture the human body power and convert
it into an electric current to power wearable electronic devices. This paper provides a proof of
concept for a head-mounted device with a PFC chin strap capable of harvesting energy from jaw
movements. An electromechanical model based on the bond graph method is developed to predict the
power output of the energy harvesting system. The optimum resistance value of the load and the best
stretch ratio in the strap are also determined. A prototype was developed and tested and its
performances were compared to the analytical model predictions. The proposed piezoelectric strap
mechanism can be added to all types of head-mounted devices to power small-scale electronic devices
such as hearing aids, e...

2014/09/21 - 05:29

## Impact damage detection in light composite sandwich panels using piezo-based nonlinear vibro-acoustic modulations

The nonlinear vibro-acoustic modulation technique is used for impact damage detection in light
composite sandwich panels. The method utilizes piezo-based low-frequency vibration and
high-frequency ultrasonic excitations. The work presented focuses on the analysis of modulation
intensity. The results show that the method can be used for impact damage detection reliably
separating damage-related from vibro-acoustic modulations from other intrinsic nonlinear
modulations.

2014/09/21 - 05:29

## Status of eye lens radiation dose monitoring in European hospitals

A questionnaire was developed by the members of WG12 of EURADOS in order to establish an overview of
the current status of eye lens radiation dose monitoring in hospitals. The questionnaire was sent to
medical physicists and radiation protection officers in hospitals across Europe. Specific topics
were addressed in the questionnaire such as: knowledge of the proposed eye lens dose limit;
monitoring and dosimetry issues; training and radiation protection measures. The results of the
survey highlighted that the new eye lens dose limit can be exceeded in interventional radiology
procedures and that eye lens protection is crucial. Personnel should be properly trained in how to
use protective equipment in order to keep eye lens doses as low as reasonably achievable. Finally,
the results also highlighted the need to improve the design of eye dosemeters in order to ensure
satisfactory use by workers.

2014/09/16 - 00:49

## Motor protein traffic regulation by supply–demand balance of resources

In cells and in in vitro assays the number of motor proteins involved in biological transport
processes is far from being unlimited. The cytoskeletal binding sites are in contact with the same
finite reservoir of motors (either the cytosol or the flow chamber) and hence compete for recruiting
the available motors, potentially depleting the reservoir and affecting cytoskeletal transport. In
this work we provide a theoretical framework in which to study, analytically and numerically, how
motor density profiles and crowding along cytoskeletal filaments depend on the competition of motors
for their binding sites. We propose two models in which finite processive motor proteins actively
advance along cytoskeletal filaments and are continuously exchanged with the motor pool. We first
look at homogeneous reservoirs and then examine the effects of free motor diffusion in the
surrounding medium. We consider as a reference situation recent in vitro experimental setups of
kines...

2014/09/11 - 19:56

## Energy harvester for rotating environments using offset pendulum and nonlinear dynamics

We present an energy harvester for environments that rotate through the Earth’s gravitational field.
Example applications include shafts connected to motors, axles, propellers, fans, and wheels or
tires. Our approach uses the unique dynamics of an offset pendulum along with a nonlinear bistable
restoring spring to improve the operational bandwidth of the system. Depending on the speed of the
rotating environment, the system can act as a bistable oscillator, monostable stiffening oscillator,
or linear oscillator. We apply our approach to a tire pressure monitoring system mounted on a car
rim. Simulation and experimental test results show that the prototype generator is capable of
directly powering an RF transmission every 60 s or less over a speed range of 10 to 155 kph.

2014/09/11 - 19:56

## The role of muscle synergies in myoelectric control: trends and challenges for simultaneous multifunction control

Myoelectric control is filled with potential to significantly change human–robot interaction due to
the ability to non-invasively measure human motion intent. However, current control schemes have
struggled to achieve the robust performance that is necessary for use in commercial applications. As
demands in myoelectric control trend toward simultaneous multifunctional control, multi-muscle
coordinations, or synergies, play larger roles in the success of the control scheme. Detecting and
refining patterns in muscle activations robust to the high variance and transient changes associated
with surface electromyography is essential for efficient, user-friendly control. This article
reviews the role of muscle synergies in myoelectric control schemes by dissecting each component of
the scheme with respect to associated challenges for achieving robust simultaneous control of
myoelectric interfaces. Electromyography recording details, signal feature extraction, pattern
recognition and m...

2014/09/11 - 19:56

## A dedicated high-resolution PET imager for plant sciences

PET provides an in vivo molecular and functional imaging capability that could be valuable for
studying the interaction of plants in changing environments at the whole-plant level. We have
developed a dedicated plant PET imager housed in a plant growth chamber (PGC), which provides a
fully controlled environment. The system currently contains two types of scintillation detector
modules from commercial small animal PET scanners: 84 microPET® detectors, which are made with
scintillation crystal arrays of 2.2 mm 3 × 2.2 mm 3 × 10 mm 3 crystals to provide a large detection
area; and 32 Inveon™ detectors, which are made with scintillation crystal arrays of 1.5 mm 3
× 1.5 mm 3 × 10 mm 3 crystals to provide higher spatial resolution. The detector modules are
configured to form two half-rings, which provide a 15 cm-diameter trans-axial field of view (FOV)
for dynamic tomographic imaging of small plants. Alternatively, the...

2014/09/06 - 17:32

## Optimizing 4DCBCT projection allocation to respiratory bins

4D cone beam computed tomography (4DCBCT) is an emerging image guidance strategy used in
radiotherapy where projections acquired during a scan are sorted into respiratory bins based on the
respiratory phase or displacement. 4DCBCT reduces the motion blur caused by respiratory motion but
increases streaking artefacts due to projection under-sampling as a result of the irregular nature
of patient breathing and the binning algorithms used. For displacement binning the streak artefacts
are so severe that displacement binning is rarely used clinically. The purpose of this study is to
investigate if sharing projections between respiratory bins and adjusting the location of
respiratory bins in an optimal manner can reduce or eliminate streak artefacts in 4DCBCT images. We
introduce a mathematical optimization framework and a heuristic solution method, which we will call
the optimized projection allocation algorithm, to determine where to position the respiratory bins
and which projectio...

2014/09/06 - 17:32

## GSE statistics without spin

Energy level statistics following the Gaussian Symplectic Ensemble (GSE) of Random Matrix Theory
have been predicted theoretically and observed numerically in numerous quantum chaotic systems.
However, in all these systems there has been one unifying feature: the combination of half-integer
spin and time-reversal invariance. Here we provide an alternative mechanism for obtaining GSE
statistics that is derived from geometric symmetries of a quantum system which alleviates the need
for spin. As an example, we construct a quantum graph with a discrete symmetry given by the
quaternion group Q 8 and observe GSE statistics within one of its subspectra. We then show how to
isolate this subspectrum and construct a quantum graph with a scalar valued wave function and a pure
GSE spectrum.

2014/08/30 - 04:04

## Interaction corrections to the minimal conductivity of graphene via dimensional regularization

We compute the two-loop interaction correction to the minimal conductivity of disorder-free
intrinsic graphene with the help of dimensional regularization. The calculation is done in two
different ways: via density-density and via current-current correlation functions. Upon properly
renormalizing the perturbation theory, in both cases, we find that ##IMG##
[http://ej.iop.org/images/0295-5075/107/5/57001/epl16495ieqn1.gif] {$\sigma = \sigma_0\,( 1 + \alpha\,(19-6\pi)/12) \approx \sigma_0 \,(1 + 0.01\, \alpha)$} , where ##IMG##
[http://ej.iop.org/images/0295-5075/107/5/57001/epl16495ieqn2.gif] {$\alpha = e^2 / (4 \pi \hbar v)$} is the renormalized fine structure constant and ##IMG##
[http://ej.iop.org/images/0295-5075/107/5/57001/epl16495ieqn3.gif] {$\sigma_0 = e^2 / (4 \hbar)$} .
Our results are consistent with experimental uncertainties and resolve a theoretical dispute.

2014/08/30 - 04:04

## Dose heterogeneity correction for low-energy brachytherapy sources using dual-energy CT images

Permanent seed implant brachytherapy is currently used for adjuvant radiotherapy of early stage
prostate and breast cancer patients. The current standard for calculation of dose around
brachytherapy sources is based on the AAPM TG-43 formalism, which generates the dose in a
homogeneous water medium. Recently, AAPM TG-186 emphasized the importance of accounting for tissue
heterogeneities. We have previously reported on a methodology where the absorbed dose in tissue can
be obtained by multiplying the dose, calculated by the TG-43 formalism, by an inhomogeneity
correction factor (ICF). In this work we make use of dual energy CT (DECT) images to extract ICF
parameters. The advantage of DECT over conventional CT is that it eliminates the need for tissue
segmentation as well as assignment of population based atomic compositions. DECT images of a
heterogeneous phantom were acquired and the dose was calculated using both TG-43 and TG-43 ##IMG##
{$\times \text{ICF}$}

2014/08/22 - 22:50

## Evaluation of low-dose limits in 3D-2D rigid registration for surgical guidance

An algorithm for intensity-based 3D-2D registration of CT and C-arm fluoroscopy is evaluated for use
in surgical guidance, specifically considering the low-dose limits of the fluoroscopic x-ray
projections. The registration method is based on a framework using the covariance matrix adaptation
evolution strategy (CMA-ES) to identify the 3D patient pose that maximizes the gradient information
similarity metric. Registration performance was evaluated in an anthropomorphic head phantom
emulating intracranial neurosurgery, using target registration error (TRE) to characterize accuracy
and robustness in terms of 95% confidence upper bound in comparison to that of an infrared surgical
tracking system. Three clinical scenarios were considered: (1) single-view image + guidance, wherein
a single x-ray projection is used for visualization and 3D-2D guidance; (2) dual-view image +
guidance, wherein one projection is acquired for visualization, combined with a second (lower-dose)
projection a...

2014/08/22 - 22:50

## An exponential growth of computational phantom research in radiation protection, imaging, and radiotherapy: a review of the fifty-year history

Radiation dose calculation using models of the human anatomy has been a subject of great interest to
radiation protection, medical imaging, and radiotherapy. However, early pioneers of this field did
not foresee the exponential growth of research activity as observed today. This review article walks
the reader through the history of the research and development in this field of study which started
some 50 years ago. This review identifies a clear progression of computational phantom complexity
which can be denoted by three distinct generations. The first generation of stylized phantoms,
representing a grouping of less than dozen models, was initially developed in the 1960s at Oak Ridge
National Laboratory to calculate internal doses from nuclear medicine procedures. Despite their
anatomical simplicity, these computational phantoms were the best tools available at the time for
internal/external dosimetry, image evaluation, and treatment dose evaluations. A second generation
of a l...

2014/08/22 - 22:50

## Real-time interactive treatment planning

The goal of this work is to develop an interactive treatment planning platform that permits
real-time manipulation of dose distributions including DVHs and other dose metrics. The hypothesis
underlying the approach proposed here is that the process of evaluating potential dose distribution
options and deciding on the best clinical trade-offs may be separated from the derivation of the
actual delivery parameters used for the patient’s treatment. For this purpose a novel algorithm for
deriving an Achievable Dose Estimate (ADE) was developed. The ADE algorithm is computationally
efficient so as to update dose distributions in effectively real-time while accurately incorporating
the limits of what can be achieved in practice. The resulting system is a software environment for
interactive real-time manipulation of dose that permits the clinician to rapidly develop a fully
customized 3D dose distribution. Graphical navigation of dose distributions is achieved by a
sophisticated method ...

2014/08/22 - 22:50

## A new determination of the 209 Po half-life

A substantial 25% error in the then-known and accepted (102 ± 5) year half-life of 209 Po was
reported on in 2007. This error was detected from decay data from two separate primary
standardizations of a 209 Po solution standard, which were performed approximately 12 years apart.
Despite author claims that this observation was not a new half-life determination, it was
nevertheless included in subsequent nuclear data evaluations and compilations to obtain a currently
tabulated value of (115 ± 13) a, computed from the median and range of the two half-life reports. A
third primary standardization on the identical 209 Po solution has since been performed to derive a
new half-life value of (125.2 ± 3.3) a. This half-life determination was obtained from 30 distinct
data sets over a period of 20.7 years, encompassing over 700 liquid scintillation measurements with
nearly 50 counting sources all prepared from the same solution, and as obtained over a very bro...

2014/08/19 - 16:53

## Origami interleaved tube cellular materials

A novel origami cellular material based on a deployable cellular origami structure is described. The
structure is bi-directionally flat-foldable in two orthogonal ( x and y ) directions and is
relatively stiff in the third orthogonal ( z ) direction. While such mechanical orthotropicity is
well known in cellular materials with extruded two dimensional geometry, the interleaved tube
geometry presented here consists of two orthogonal axes of interleaved tubes with high interfacial
surface area and relative volume that changes with fold-state. In addition, the foldability still
allows for fabrication by a flat lamination process, similar to methods used for conventional
expanded two dimensional cellular materials. This article presents the geometric characteristics of
the structure together with corresponding kinematic and mechanical modeling, explaining the
orthotropic elastic behavior of the structure with classical dimensional scaling analysis.

2014/08/19 - 16:53

## Material selection for elastic energy absorption in origami-inspired compliant corrugations

Elastic absorption of kinetic energy and distribution of impact forces are required in many
applications. Recent attention to the potential for using origami in engineering may provide new
methods for energy absorption and force distribution. A three-stage strategy is presented for
selecting materials for such origami-inspired designs that can deform to achieve a desired motion
without yielding, absorb elastic strain energy, and be lightweight or cost effective. Two material
indices are derived to meet these requirements based on compliant mechanism theory. Finite element
analysis is used to investigate the effects of the material stiffness in the Miura-ori tessellation
on its energy absorption and force distribution characteristics compared with a triangular wave
corrugation. An example is presented of how the method can be used to select a material for a
general energy absorption application of the Miura-ori. Whereas the focus of this study is the
Miura-ori tessellation, the me...

2014/08/19 - 16:53

## Repair-dependent cell radiation survival and transformation: an integrated theory

The repair-dependent model of cell radiation survival is extended to include radiation-induced
transformations. The probability of transformation is presumed to scale with the number of
potentially lethal damages that are repaired in a surviving cell or the interactions of such
damages. The theory predicts that at doses corresponding to high survival, the transformation
frequency is the sum of simple polynomial functions of dose; linear, quadratic, etc, essentially as
described in widely used linear-quadratic expressions. At high doses, corresponding to low survival,
the ratio of transformed to surviving cells asymptotically approaches an upper limit. The low dose
fundamental- and high dose plateau domains are separated by a downwardly concave transition region.
Published transformation data for mammalian cells show the high-dose plateaus predicted by the
repair-dependent model for both ultraviolet and ionizing radiation. For the neoplastic
transformation experiments that were an...

2014/08/15 - 11:29

## Non-invasive whole-body plethysmograph for assessment and prediction of radiation-induced lung injury using simultaneously acquired nitric oxide and lung volume measurements

Radiation-induced lung injury (RILI) is a prevalent side effect in patients who undergo thoracic
irradiation as part of their cancer treatment. Preclinical studies play a major role in
understanding disease onset under controlled experimental conditions. The aim of this work is to
develop a single-chambered optimized, non-invasive, whole-body plethysmograph prototype for
unrestrained small animal lung volume measurements for preclinical RILI studies. The system is also
designed to simultaneously obtain nitric oxide (NO) measurements of the expired breath. The device
prototype was tested using computer simulations, phantom studies and in vivo measurements in
experimental animal models of RILI. The system was found to improve resemblance to true breathing
signal characteristics as measured by improved skewness (21.83%) and kurtosis (51.94%) in addition
to increased overall signal sensitivity (3.61%) of the acquired breath signal, when compared to
matching control data. NO co...

2014/08/15 - 11:29

## A new approach for dose calculation in targeted radionuclide therapy (TRT) based on collapsed cone superposition: validation with 90 Y

To speed-up the absorbed dose (AD) computation while accounting for tissue heterogeneities, a
Collapsed Cone (CC) superposition algorithm was developed and validated for 90 Y. The superposition
was implemented with an Energy Deposition Kernel scaled with the radiological distance, along with
CC acceleration. The validation relative to Monte Carlo simulations was performed on 6 phantoms
involving soft tissue, lung and bone, a radioembolisation treatment and a simulated bone metastasis
treatment. As a figure of merit, the relative AD difference ( Δ AD) in low gradient regions (LGR),
distance to agreement (DTA) in high gradient regions and the γ (1%,1 mm) criterion were used for the
phantoms. Mean organ doses and γ (3%,3 mm) were used for the patient data. For the semi-infinite
sources, Δ AD in LGR was below 1%. DTA was below 0.6 mm. All profiles verified the γ (1%,1 mm)
criterion. For both clinical cases, mean doses differed by less than 1% fo...

2014/08/07 - 16:56

## Estimation of optoacoustic contrast agent concentration with self-calibration blind logarithmic unmixing

Chromophore quantification in optoacoustic tomography is challenging due to signal contributions
from strongly absorbing background tissue chromophores and the depth-dependent light attenuation.
Herein we present a procedure capable of correcting for wavelength-dependent light fluence
variations using a logarithmic representation of the images taken at different wavelengths assisted
with a blind unmixing approach. It is shown that the serial expansion of the logarithm of an
optoacoustic image contains a term representing the ratio between absorption of the probe of
interest and other background components. Under assumptions of tissue-like background absorption
variations, this term can be readily isolated with an unmixing algorithm, attaining quantitative
maps of photo-absorbing agent distribution.

2014/08/07 - 16:56

## The KdV equation under periodic boundary conditions and its perturbations

In this paper we discuss properties of the Korteweg–de Vries (KdV) equation under periodic boundary
conditions, especially those which are important for studying perturbations of the equation. We then
review what is known about the long-time behaviour of solutions for perturbed KdV equations.

2014/08/07 - 16:56

## There is only one KAM curve

We consider the standard family of area-preserving twist maps of the annulus and the corresponding
KAM curves. Addressing a question raised by Kolmogorov, we show that, instead of viewing these
invariant curves as separate objects, each of which having its own Diophantine frequency, one can
encode them in a single function of the frequency, which is naturally defined in a complex domain
containing the real Diophantine frequencies and which is monogenic in the sense of Borel; this
implies a remarkable property of quasianalyticity, a form of uniqueness of the monogenic
continuation, although real frequencies constitute a natural boundary for the analytic continuation
from the Weierstraß point of view because of the density of the resonances.

2014/07/30 - 01:49

## Minimizing the 1/ r 2 perturbation for ideal fluence detectors in small source ? -irradiation fields

A technique for analyzing the effect of the geometrical shape of a source or a detector, using a
quadrupole expansion, is described herein. It is shown that this method may be exploited to predict,
optimize the geometry of a source, or a measurement device, and nearly eliminate, the departure from
the 1/ r 2 fall-off characteristic due to irradiation from small sources. We have investigated
several simple shapes that have a vanishing Q 2 quadrupole moment: a right circular cylinder with a
diameter to depth ratio of ##IMG##
[http://ej.iop.org/images/0031-9155/59/16/4465/pmb497320ieqn001.gif] {$\sqrt{2}$} , a cone with a
radius to height ratio of unity, and an oblate ellipsoid with a diameter to depth ratio of ##IMG##
[http://ej.iop.org/images/0031-9155/59/16/4465/pmb497320ieqn002.gif] {$\sqrt{3/2}$} . These ideal
shapes produce optimally small departures in a 1/ r 2 field, nearly mimicking...

2014/07/26 - 16:49

## 3D reconstruction of scintillation light emission from proton pencil beams using limited viewing angles?a simulation study

An accurate and high-resolution quality assurance (QA) method for proton radiotherapy beams is
necessary to ensure correct dose delivery to the target. Detectors based on a large volume of liquid
scintillator have shown great promise in providing fast and high-resolution measurements of proton
treatment fields. However, previous work with these detectors has been limited to two-dimensional
measurements, and the quantitative measurement of dose distributions was lacking. The purpose of the
current study is to assess the feasibility of reconstructing three-dimensional (3D) scintillation
light distributions of spot scanning proton beams using a scintillation system. The proposed system
consists of a tank of liquid scintillator imaged by charge-coupled device cameras at three
orthogonal viewing angles. Because of the limited number of viewing angles, we developed a
profile-based technique to obtain an initial estimate that can improve the quality of the 3D
reconstruction. We found th...

2014/07/26 - 16:49

## Universal properties of branching random walks in confined geometries

Characterizing the occupation statistics of random walks through confined geometries amounts to
assessing the distribution of the travelled length ℓ and the number of collisions n performed by the
stochastic process in a given region, for which remarkably simple Cauchy-like formulas were
established in the case of branching Pearson random walks with exponentially distributed jumps. In
this letter, we derive two key results: first, we show that such formulas strikingly carry over to
the much broader class of branching processes with arbitrary jumps, and have thus a universal
character; second, we obtain a stronger version of these formulas relating the travelled length
density and the collision density at any point of the phase space. Our results are key to such
technological issues as the analysis of radiation flow for nuclear reactor design and medical
diagnosis and apply more broadly to physical and biological systems with diffusion, reproduction and
death.

2014/07/25 - 08:46

## Multi-fingered haptic palpation utilizing granular jamming stiffness feedback actuators

This paper describes a multi-fingered haptic palpation method using stiffness feedback actuators for
simulating tissue palpation procedures in traditional and in robot-assisted minimally invasive
surgery. Soft tissue stiffness is simulated by changing the stiffness property of the actuator
during palpation. For the first time, granular jamming and pneumatic air actuation are combined to
realize stiffness modulation. The stiffness feedback actuator is validated by stiffness measurements
in indentation tests and through stiffness discrimination based on a user study. According to the
indentation test results, the introduction of a pneumatic chamber to granular jamming can amplify
the stiffness variation range and reduce hysteresis of the actuator. The advantage of multi-fingered
palpation using the proposed actuators is proven by the comparison of the results of the stiffness
discrimination performance using two-fingered (sensitivity: 82.2%, specificity: 88.9%, positive
predicative...

2014/07/22 - 20:56

## Open problems in nuclear reaction theory

Description unavailable

2014/07/16 - 22:56

## Black-hole entropy from complex Ashtekar variables

In loop quantum gravity, the number ##IMG##
[http://ej.iop.org/images/0295-5075/107/1/10005/epl16379ieqn1.gif] {$N_\Gamma(A,\gamma)$} of
microstates of a black hole for a given discrete geometry Γ depends on the so-called Barbero-Immirzi
parameter γ . Using a suitable analytic continuation of γ to complex values, we show that the number
##IMG## [http://ej.iop.org/images/0295-5075/107/1/10005/epl16379ieqn2.gif] {$N_\Gamma(A,\pm i)$} of
microstates behaves as ##IMG## [http://ej.iop.org/images/0295-5075/107/1/10005/epl16379ieqn3.gif]
{$\exp(A/(4\ell_\text{Pl}^2))$} for a large area A in the large spin semiclassical limit. Such a
correspondence with the semiclassical Bekenstein-Hawking entropy law points towards an unanticipated
and remarkable feature of the original complex Ashtekar variables for quantum gravity.

2014/07/11 - 07:59

## Subharmonic oscillations of collective molecular motors

We study a generic two-state model for an assembly of molecular motors which is described by means
of a pair of integro-partial differential equations and leads to oscillatory motion in the presence
of an elastic coupling to its environment. We discuss a reduction of the system to a minimal set of
three ordinary differential equations that successfully capture the complex nonlinear dynamics of
the full system. In the limit of high mobility and large elastic modulus, we report on the emergence
of subharmonics in the power spectrum of the oscillations. This provides a rationale for the
unexplained observation of secondary peaks in a minimal actomyosin system in vitro ( PlaçaisP.-Y.
et al. , Phys. Rev. Lett. 103 , (2009) 158102), showing that the phenomenon is robust and genuine.

2014/07/09 - 03:43

## Site-specific range uncertainties caused by dose calculation algorithms for proton therapy

The purpose of this study was to assess the possibility of introducing site-specific range margins
to replace current generic margins in proton therapy. Further, the goal was to study the potential
of reducing margins with current analytical dose calculations methods. For this purpose we
investigate the impact of complex patient geometries on the capability of analytical dose
calculation algorithms to accurately predict the range of proton fields. Dose distributions
predicted by an analytical pencil-beam algorithm were compared with those obtained using Monte Carlo
(MC) simulations (TOPAS). A total of 508 passively scattered treatment fields were analyzed for
seven disease sites (liver, prostate, breast, medulloblastoma–spine, medulloblastoma–whole brain,
lung and head and neck). Voxel-by-voxel comparisons were performed on two-dimensional distal dose
surfaces calculated by pencil-beam and MC algorithms to obtain the average range differences and
root mean square deviation for ea...

2014/07/05 - 17:56

## From data to dynamical systems

This article is part of a series commemorating the 50th anniversary of Ed Lorenz's seminal paper
‘Deterministic nonperiodic flow’. The system he studied has become the object of extensive
mathematical investigations and serves as a paradigm of a low-dimensional chaotic dynamical system.
Nonetheless, Lorenz maintained his focus on the relationship between dynamical models and empirical
data. This paper reviews some of the difficulties encountered in fitting chaotic models to data and
then pursues fits of models with stable periodic orbits to data in the presence of noise. Starting
with Lorenz's model in a regime with a stable periodic orbit, it investigates how well properties of
the deterministic system can be recovered from trajectories of stochastic perturbations. A numerical
study suggests, surprisingly, that the stability properties of the periodic orbit cannot be fully
recovered from a finite length trajectory as the magnitude of the stochastic perturbation converges
to zero...

2014/06/28 - 16:29

## Decay of correlation for random intermittent maps

We study a class of random transformations built over finitely many intermittent maps sharing a
common indifferent fixed point. Using a Young-tower technique, we show that the map with the fastest
relaxation rate dominates the asymptotics. In particular, we prove that the rate of correlation
decay for the annealed dynamics of the random map is the same as the sharp rate of correlation decay
for the map with the fastest relaxation rate.

2014/06/24 - 17:24