Path Length Variations Research Articles

Enhanced direct position determination using dynamic sensor array response

An improvement in localisation of co-channel transmitters using direct position determination (DPD) is addressed. DPD techniques estimate the locations of signal emitters by finding the peaks of a spatial pseudo-spectral-function (PSF) within a definite area. Actually, different algorithms/beamformers such as Bartlett, minimum variance distortionless response (MVDR), and multiple signal classification (MUSIC) are distinguished by their PSFs. Mathematically, a PSF is a function of location through the array steering/pointing vector whose elements are the channel responses between any arbitrary point in the search area and each sensor antenna for a narrowband system model. Clearly, the amplitude and phase of each complex element of the pointing vector characterise the attenuation and delay of paths between search points and sensors, respectively. Classical DPD methods do not consider the dependency of attenuation on channel path length variation during area scanning, which consequently generates PSFs full of spurious peaks. The authors propose a more realistic channel model that remarks the free-space-path-loss as a deterministic, path-length-dependent factor beside the stochastic ones such as fading; therefore, they call it dynamic sensor array response (DSAR). Simulations show that range dependency of DSAR can effectively enhance the performance of the DPD algorithm for MVDR and MUSIC beamformers.

A spatially resolved transmittance spectroscopy system for detecting internal rots in onions

Abstract This study presents the development of a spatially resolved transmittance system for detecting internal rots in onions, particularly small and localised rots. A two-wavelength classifier was chosen by considering sensitivities to rots and path-length variations. Near-infrared spectroscopy transmittance measurements were carried out on rot-affected onions, to determine wavelength sensitivities to the presence and severity of rots. Finite Element simulations of light transport in onions were run to determine wavelength sensitivities to source-detector separation. A spatially resolved transmittance system was then developed, using two laser diodes as sources (728 and 805 nm wavelengths) and a single photodiode as detector. The system was experimentally verified, with the measured spatial profiles of the transmittance ratios of the two source wavelengths being sensitive to variation in position and size of internal rots in onions.

Dispersion scanning beam medium infra-red interferometry for divertor plasma density measurement in DTT

Dispersion Interferometers (DI) present the fundamental advantage over conventional ones to be insensitive to mechanical vibrations without requiring a second wavelength interferometer to measure path length variations. On the other hand, their optical setup requires duplication of nearly all optical components for any measuring chord. This makes the realization of a multi-channel interferometer that is needed to obtain density profiles via Abel inversion of line integral measurements more complicated. To overcome such drawback of the DI, in this work we propose to join the dispersion technique to the beam scanning one, which has been already successfully implemented in the conventional mid-infrared two-colour interferometer. In particular, we present a preliminary design of a DI scanning interferometer for the new Divertor Test Tokamak (DTT) facility, presently in construction. DTT is designed to study a large suite of alternative divertor magnetic configurations in order to ensure acceptable conditions at the walls while maintaining sufficient core performance. In this contest, measuring plasma parameters in the divertor region is very important though it often presents various difficulties. To improve divertor measurements the proposed interferometer will measure the density along the divertor legs from the strike points up the X-point. The interferometer will use a CO2 laser (λ =10.6 μm) and a double pass optical scheme. Phase modulation method will be used to improve the resolution of the measurement and to extend the measuring range above the 1020 m−2 line integral limitation of the standard homodyne implementation. Both improvements are important in this application, considering the wide density range expected in the DTT divertor region. Comparing to shorter wavelengths, more commonly used in the DI interferometers, the CO2 wavelength improves density resolution while providing good immunity to the diffraction effect due to the expected high density gradient.

A Path Planning Method Based on Multi- Objective Cauchy Mutation Cat Swarm Optimization Algorithm for Navigation System of Intelligent Patrol Car

The intelligent patrol car with environmental sensing and autonomous navigation is a special robot, which is mostly used for equipment defect detection in industrial areas such as the power distribution room or data center room. A path planning algorithm for the navigation system of intelligent patrol car is proposed to ensure efficient and secure navigation in the complex indoor environment, and its effect is verified by simulation and experiment. First, a patrol car platform integrated with several intelligent devices is built to achieve global localization, mapping and path planning. Then a new co-optimization on multi-objective Cauchy mutation cat swarm optimization (MOCMCSO) and artificial potential field method (APFM) is proposed to solve the multi-objective optimization problem on shortest global path length and minimum total turning-angle variation. The optimal path is written into the navigation module to drive the patrol car to move and navigate. The simulations are carried out to confirm that the method can achieve a balance between the shortest path and good path smoothness, which has less optimization time and lower fitness value compared with multi-objective cat swarm optimization (MOCSO) and multi-objective particle swarm optimization (MOPSO), and is more suitable for global path planning in indoor environment. Finally, the experiments have been carried out in the data center equipment room to verify the effectiveness and superiority over the path planning algorithm on MOCMCSO.

Online Trajectory Optimization Using Inexact Gradient Feedback for Time-Varying Environments

This article considers the problem of online trajectory design under time-varying environments. We formulate the general trajectory optimization problem within the framework of time-varying constrained convex optimization and propose a novel version of online gradient ascent algorithm (OGA) for such problems. Respecting the online nature, we carefully select the step size of OGA at each iteration so that the iterates stay feasible. Importantly, the proposed algorithm allows noisy gradients, expanding the range of practical applicability. In contrast to the most available literature, we present the offline sublinear regret of OGA up to the path length variations of the offline optimal solution, the cumulative gradient, and the error in the gradient variations. Furthermore, we establish a lower-bound on the offline dynamic regret, which defines the optimality of any trajectory. To show the efficacy of the proposed algorithm, we consider two practical problems of interest. First, a device to device (D2D) communications setting, where the goal is to design a user trajectory while maximizing its connectivity to the internet. Second, planning energy-efficient trajectories for unmanned surface vehicles (USV) under strong disturbances in ocean environments. Different from the state-of-the-art trajectory planning algorithms that entail planning and re-planning the full trajectory using the forecast data at each time instant, the proposed algorithm is entirely online and relies mostly on the ocean velocity measurements at the vehicle location. The detailed simulation results demonstrate the significance of the proposed algorithm on both synthetic and real data sets. Video result is available at https://tinyurl.com/y3ahmhsf .

Multiwavelength holography: height measurements despite axial motion of several wavelengths during exposure.

Interferometric measurements of rotating objects face an axial motion component if the optical axis of the measurement system is not pointing towards the axis of rotation. In a typical interferometer, axial motion of half a wavelength reduces the interference contrast to zero. Our setup compensates for this axial component by an adapted variation of the reference path length during exposure utilizing a piezoelectric actuator. We present off-center measurements on a cylinder, rotating with different angular velocities. The repeatability of these measurements is dominated by motion blur, which demonstrates that the compensation of the axial motion works accurately.

Genetic cooperativity in multi-layer networks implicates cell survival and senescence in the striatum of Huntington's disease mice synchronous to symptoms.

MotivationHuntington’s disease (HD) may evolve through gene deregulation. However, the impact of gene deregulation on the dynamics of genetic cooperativity in HD remains poorly understood. Here, we built a multi-layer network model of temporal dynamics of genetic cooperativity in the brain of HD knock-in mice (allelic series of Hdh mice). To enhance biological precision and gene prioritization, we integrated three complementary families of source networks, all inferred from the same RNA-seq time series data in Hdh mice, into weighted-edge networks where an edge recapitulates path-length variation across source-networks and age-points.ResultsWeighted edge networks identify two consecutive waves of tight genetic cooperativity enriched in deregulated genes (critical phases), pre-symptomatically in the cortex, implicating neurotransmission, and symptomatically in the striatum, implicating cell survival (e.g. Hipk4) intertwined with cell proliferation (e.g. Scn4b) and cellular senescence (e.g. Cdkn2a products) responses. Top striatal weighted edges are enriched in modulators of defective behavior in invertebrate models of HD pathogenesis, validating their relevance to neuronal dysfunction in vivo. Collectively, these findings reveal highly dynamic temporal features of genetic cooperativity in the brain of Hdh mice where a 2-step logic highlights the importance of cellular maintenance and senescence in the striatum of symptomatic mice, providing highly prioritized targets.Availability and implementationWeighted edge network analysis (WENA) data and source codes for performing spectral decomposition of the signal (SDS) and WENA analysis, both written using Python, are available at http://www.broca.inserm.fr/HD-WENA/.Supplementary information Supplementary data are available at Bioinformatics online.

The reactive transport of Li as a monitor of weathering processes in kinetically limited weathering regimes

Analytical solutions to reactive-transport equations describing the evolution of Li concentrations and isotopic ratios are presented for one-dimensional flow paths where reaction stoichiometry is constant along the flow path. These solutions are considered appropriate for chemical weathering in rapidly eroding catchments. The solutions may be described by two dimensionless numbers; 1) a Damköhler number describing the product of reaction rate and fluid residence time, and 2) a net partition coefficient which describes the fraction of Li re-precipitated in secondary minerals as the product of a fluid-secondary mineral partition coefficient and the mass fraction of secondary mineral precipitates. In settings where water entering flow paths is dilute, Li concentrations will increase along the flow path until they reach a limiting value determined by the net partition coefficient. Simultaneously, 7Li/6Li isotopic ratios will increase to a limiting value of the source rock ratio minus the secondary mineral–fluid Li-isotopic fractionation factor. Waters with Li-isotopic ratios in excess of this limiting value must have evolved with a change of reaction stoichiometry and/or partition coefficient along the flow path such that at some point net removal of Li to secondary minerals exceeds that supplied by dissolution of primary minerals. The modelling shows that the multiple controls on chemical weathering rates (temperature, rainfall, erosion rate, hydrology) cannot be inferred from Li concentration and isotopic ratio data alone, which only provide two independent constraints. Caution should be exercised in interpretation of oceanic Li records in terms of potential climatic variables. The model is illustrated by a set of Li concentration and isotopic ratio measurements on river waters and bed sands in the Alaknanda river basin which forms the headwaters of the Ganges. This illustrates how values of the Damköhler number and net partition coefficient can be used to trace weathering processes. Water samples from catchments with similar lithologies and climates scatter along contours of approximately constant net partition coefficient, reflecting similar reaction stoichiometries, but with more variable Damköhler numbers reflecting variations in flow path length, fluid flux and/or reaction rate. Samples from the lower, warmer and less rapidly eroding catchments have high 7Li/6Li isotopic ratios with lower Li concentrations and must reflect at least a two-stage weathering process where reaction stoichiometry and/or Li fluid–mineral partition coefficients change along the flow path so that net Li is removed in the later stages.

Effect of plume motion path on heat transfer characteristics in two-dimensional turbulent thermal convection

The Grossman and Lohse (GL) theory is an important theory for studying the heat transfer characteristics of the turbulent convection. Previous computational studies have found that when the Ra number is higher than a certain value, the change of the heat transfer Nu number with Ra number in two-dimensional turbulent thermal convection is different from that in the three-dimensional thermal convection, deviating from the multiples line of the GL theory prediction. Therefore, the value of studying the two-dimensional numerical calculation of turbulent thermal convection with high Ra number is questioned. The numerical calculations of a series of two-dimensional turbulent thermal convection events with high and very high Ra number(specifically, maximum Ra = 10<sup>13</sup> with Pr = 0.7 and 4.3) are carried out in this paper. The results show that there exists a good correlation between the heat transfer Nu number and the variation of large scale circulation path length(that reflects the plume motion) with Ra number in the two-dimensional turbulent convection, and they have two Ra number transition points. The first transition point appears in the large scale circulation from the ellipse to the circle, when its circumference C<sub>LSC</sub> of the large scale circulation suddenly decreases with Ra number increasing. The second transition point appears at the minimum circumference C<sub>LSC</sub>, and then the plume rheology becomes vortex group and the circumference C<sub>LSC</sub> increases with Ra number increasing. The Ra number at transition point for a smaller Pr number is lower. The variation of the heat transfer Nu number after Ra<sup>0.3</sup> compensation shows that the local scale law of Nu number decreases as the circumference C<sub>LSC</sub> of the large scale circulation becomes small, and a phenomenon of deviating from the multiples line of GL theory prediction appears. When Ra number is higher than the second transition point, the local scale law of the Nu number varying with Ra number is in good agreement with the multiples line of GL theory prediction again in 2D turbulent thermal convection. It means that the numerical results of two-dimensional turbulent thermal convection can correctly reflect the heat transfer characteristics of turbulent thermal convection under the condition of very high Ra number.

A free-standing wire scattering technique to monitor calibration variations of the DIII-D density profile reflectometer.

Real-time phase calibration of the ITER profile reflectometer is essential due to the long plasma duration and expected waveguide path length changes during a discharge. Progress has been recently made in addressing this issue by employing a phase calibration technique on DIII-D that monitors calibration variations that occur during each plasma discharge. By installing a thin free-standing metallic wire (1 mm diameter) near the end of the overmoded waveguide transmission system (oriented perpendicular to the waveguide axis), the round-trip phase shift from the wire is detected simultaneously with the plasma phase shifts. Variations in the reflectometer round trip path length (∼26 m) are then calculated after each DIII-D plasma discharge, allowing the calibration phase to be accurately monitored and updated. The round-trip reflectometer path length is observed to vary by ∼3 mm (root mean square value) during a typical DIII-D discharge. Using the variations in calibration phase, the density profile measurement accuracy can be improved. Since the wire retro-reflected power is ∼0.01 of the plasma signal, minimal effect is observed on the reflected signal from the plasma. Importantly, through a suitable choice in wire diameter, the calibration signal can be made approximately independent of the V-band reflectometer launch polarization. This is particularly important on DIII-D since orthogonal X- and O-mode polarized beams are coupled into the same transmission waveguide and launch antenna.

A gravitational telescope deformation model for geodetic VLBI

We have measured the geometric deformations of the Onsala 20 m VLBI telescope utilizing a combination of laser scanner, laser tracker, and electronic distance meters. The data put geometric constraints on the electromagnetic raypath variations inside the telescope. The results show that the propagated distance of the electromagnetic signal inside the telescope differs from the telescope’s focal length variation, and that the deformations alias as a vertical or tropospheric component. We find that for geodetic purposes, structural deformations of the telescope are more important than optic properties, and that for geodetic modelling the variations in raypath centroid rather than focal length should be used. All variations that have been identified as significant in previous studies can be quantified. We derived coefficients to model the gravitational deformation effect on the path length and provide uncertainty intervals for this model. The path length variation due to gravitational deformation of the Onsala 20 m telescope is in the range of 7–11 mm, comparing elevation 0 $$^{\circ }$$ and 90 $$^{\circ }$$ , and can be modelled with an uncertainty of 0.3 mm.

All-fiber, thermo-optic liquid level sensor.

This paper proposes an all-optical-fiber sensor for continuous measurements of liquid levels. The proposed sensor utilizes an optically absorbing vanadium doped optical fiber, which is configured as a long-gauge, optically-heated, fiber-optic, Fabry-Perot interferometer that is immersed into the measured liquid. The sensor is excited cyclically by a medium-power 980 nm optical source, which induces periodic temperature variation and, consequently, optical path length modulation within the vanadium doped fiber. The amplitude of this path length variation depends on the liquid level and is measured by an interferometric approach. The relation between the liquid level and the amplitude of optical path length modulation caused by the fiber's temperature variation were investigated analytically, and the theoretical model proved to be in good agreement with the experimental results. Two versions of level sensors are demonstrated experimentally, the first with single-side optical heating power delivery and 0.45 m measurement range, and the second with dual-side power delivery and 1 m of operational measurement span. Experimental measurement level resolutions achieved for 0.45 m and 1m operational measurement span were approximately 2 and 3 mm, respectively. The simple and efficient design of sensor and signal interrogation system, the latter is based solely on a few widely available telecom components, provides straightforward opportunities for use of the proposed system in a variety of industrial applications.

Training children aged 5-10years in compliance control: tracing smaller figures yields better learning not specific to the scale of drawn figures.

Previously we developed a method that supports active movement generation to allow practice with improvement of good compliance control in tracing and drawing. We showed that the method allowed children with motor impairments to improve at a 3D tracing task to become as proficient as typically developing children and that the training improved 2D figure copying. In this study, we expanded the training protocol to include a wider variety of ages (5-10-year-olds) and we made the figures traced in training the same as in figure copying, but varied the scale of training and copying figures to assess the generality of learning. Forty-eight children were assigned to groups trained using large or small figures. All were tested before training with a tracing task and a copying task. Then, the children trained over five sessions in the tracing task with either small or large figures. Finally, the tracing and copying tasks were tested again following training. A mean speed measure was used to control for path length variations in the timed task. Performance on both tasks at both baseline and posttest varied as a function of the size of the figure and age. In addition, tracing performance also varied with the level of support. In particular, speeds were higher with more support, larger figures and older children. After training, performance improved. Speeds increased. In tracing, performance improved more for large figures traced by children who trained on large figures. In copying, however, performance only improved significantly for children who had trained on small figures and it improved equally for large and small figures. In conclusion, training by tracing smaller figures yielded better learning that was not, however, specific to the scale of drawn figures. Small figures exhibit greater mean curvature. We infer that it yielded better general improvement.

Characterization of spectral and intensity changes with measurement geometry in various light guides used in scintillation dosimetry.

To characterize response changes of various light guides used in megavoltage (MV) photon beam scintillation dosimetry as a function of irradiation conditions. Particular emphasis was placed on quantifying the impact of response changes on the Čerenkov light ratio (CLR). Intensity and spectral response measurements as a function of dose, depth, and fiber-beam angle were performed with a commercial scintillation detector stripped of its scintillation material and five different custom-made light guides. The core materials of the light guides investigated consisted of polymethyl methacrylate (PMMA), low- and high-hydroxyl content silica, and polystyrene. Dose levels ranging from 50monitor units (MU) to 1000MU, depths ranging from 1 to 20cm, and fiber-beam angles ranging from 10° to 90° were investigated. All measurements were performed at a photon beam energy of 6MV. The CLR was calculated by taking the ratio of the responses in the blue to green spectral regions. There was no significant change in the CLR measured with the modified commercial scintillation detector as a function of delivered dose. In addition, increases in the CLR as functions of depth and fiber-beam angle were observed where the maximum changes were 4.2% and 3.6%, respectively. The spectrum measurements showed no observable changes in spectral shape with depth except for the low-hydroxyl content silica fiber. Variations in the measured spectral shape with fiber-beam angle were observed for all fibers investigated. The magnitude of the changes in the spectral shape varied with fiber type, where the silica fibers exhibited the largest changes and the plastic fibers exhibited the smallest changes. Increases in the CLR were observed for the silica fibers with depth and for all fibers with fiber-beam angle. The plastic fibers showed no significant change in the CLR as a function of depth. Increases of 3.1% and 9.5% in the CLR were observed for the high- and low-hydroxyl content silica fibers, respectively, over the range of depths investigated. Variations of 2.3%, 6.1%, 5.1% and 11.9% were observed for the PMMA, polystyrene, high-hydroxyl, and low-hydroxyl content silica fiber CLR values as a function of fiber-beam angle, respectively. The insignificant change in the CLR with delivered dose indicates that a single CLR value over the investigated dose range is sufficient for accurate Čerenkov subtraction. Variations in the stem-effect spectrum shape can occur with changes in irradiation geometry. The magnitude of the changes are governed by the fiber construction and the optical properties of the fiber. The observed spectral shape changes can be explained by a combination of variations in optical path length through the fiber and the fiber fluorescent signal contribution to the stem-effect. These spectral shape variations directly influence the calculated CLR values. This work confirms that careful characterization of scintillation detectors is important as changes in the stem-effect spectrum can cause changes in the CLR. If the CLR changes between the reference and measurement conditions, this could result in an incorrect stem-effect subtraction and reduced measurement accuracy.

Ground-Based Differential Interferometric Radar Monitoring of Unstable Mountain Blocks in a Coastal Environment

In this paper, we present the results of eight years of continuous monitoring with a ground-based, interferometric, real-aperture radar of two unstable mountain blocks at Tafjord on the western coast of Norway. A real-time, interferometric, ground-based radar has the capability to provide high accuracy range measurements by using the phase of the transmitted signal, thus achieving sub-millimeter accuracy when a sufficient signal-to-noise level is present. The main challenge with long term monitoring is the variations in radio refractivity caused by changes in the atmosphere. The range variations caused by refractive changes in the atmosphere are corrected using meteorological data. We use triangular corner reflectors as references to improve the signal-to-clutter ratio and improve the accuracy of the measurements. We have also shown that by using differential interferometry, a significant part of the variation caused by radio refractivity variations is removed. The overall reduction in path length variation when using differential interferometry varies from 27 to 164 times depending on the radar-to-reflector path length. The measurements reveal cyclic seasonal variations, which are coherent with air temperature. The results show that radar measurements are as accurate as data from in situ instruments like extensometers and crack meters, making it possible to monitor inaccessible areas. The total measured displacement is between 1.2 mm and 4.7 mm for the two monitored mountain blocks.

Wideband multi-stage CROW filters with relaxed fabrication tolerances.

We present wideband and large free spectral range optical filters with steep passband edges for the selection of adjacent WDM communication channels that can be reliably fabricated with mainstream silicon photonics technology. The devices are based on three cascaded stages of coupled resonator optical waveguides loaded on a common bus waveguide. These stages differ in the number of resonators but are implemented with exactly identical unit cells, comprised of a matched racetrack resonator layout and a uniform spacing between cells. The different number of resonators in each stage allows a high rejection in the through port response enabled by the interleaved distribution of zeros. Furthermore, the exact replication of a unique cell avoids the passband ripple and high lobes in the stopband that typically arise in apodized coupled resonator optical waveguide based filters due to fabrication and coupling induced variations in the effective path length of each resonator. Silicon photonics filters designed for the selection of 9 adjacent optical carriers generated by a 100 GHz free spectral range comb laser have been successfully fabricated with 248 nm DUV lithography, achieving an out-of-band rejection above 11 dB and an insertion loss of less than 0.5 dB for the worst channels.

A Permutation Disalignment Index-Based Complex Network Approach to Evaluate Longitudinal Changes in Brain-Electrical Connectivity

In the study of neurological disorders, Electroencephalographic (EEG) signal processing can provide valuable information because abnormalities in the interaction between neuron circuits may reflect on macroscopic abnormalities in the electrical potentials that can be detected on the scalp. A Mild Cognitive Impairment (MCI) condition, when caused by a disorder degenerating into dementia, affects the brain connectivity. Motivated by the promising results achieved through the recently developed descriptor of coupling strength between EEG signals, the Permutation Disalignment Index (PDI), the present paper introduces a novel PDI-based complex network model to evaluate the longitudinal variations in brain-electrical connectivity. A group of 33 amnestic MCI subjects was enrolled and followed-up with over four months. The results were compared to MoCA (Montreal Cognitive Assessment) tests, which scores the cognitive abilities of the patient. A significant negative correlation could be observed between MoCA variation and the characteristic path length ( λ ) variation ( r = - 0 . 56 , p = 0 . 0006 ), whereas a significant positive correlation could be observed between MoCA variation and the variation of clustering coefficient (CC, r = 0 . 58 , p = 0 . 0004 ), global efficiency (GE, r = 0 . 57 , p = 0 . 0005 ) and small worldness (SW, r = 0 . 57 , p = 0 . 0005 ). Cognitive decline thus seems to reflect an underlying cortical “disconnection” phenomenon: worsened subjects indeed showed an increased λ and decreased CC, GE and SW. The PDI-based connectivity model, proposed in the present work, could be a novel tool for the objective quantification of longitudinal brain-electrical connectivity changes in MCI subjects.

Quantitative analysis based on spectral shape deformation: A review of the theory and its applications

Most of the commonly used calibration methods in quantitative spectroscopic analysis are established or derived from the assumption of a linear relationship between the concentrations of the analytes of interest and corresponding absolute spectral intensities. They are not applicable for heterogeneous samples where the potential uncontrolled variations in optical path length due to the changes in samples' physical properties undermine the basic assumption behind them. About a decade ago, a unique calibration strategy was proposed to extract chemical information from spectral data contaminated with multiplicative light scattering effects. From then on, this calibration strategy has been attentively examined, modified, and used by its developers. After more than 10 years of development, some important features of the calibration strategy have been identified. It has been proved that the calibration strategy can solve many complex problems in quantitative spectroscopic analysis. But, because of the relatively low awareness of the calibration strategy among chemometrics society, its potential has not been fully exploited yet. This paper reviews the theory of the calibration strategy and its applications with a view to introducing the unique and powerful calibration strategy to a wider audience.

Ultrametricity of optimal transport substates for multiple interacting paths over a square lattice network.

We model a set of point-to-point transports on a network as a system of polydisperse interacting self-avoiding walks (SAWs) over a finite square lattice. The ends of each SAW may be located both at random, uniformly distributed, positions or with one end fixed at a lattice corner. The total energy of the system is computed as the sum over all SAWs, which may represent either the time needed to complete the transport over the network, or the resources needed to build the networking infrastructure. We focus especially on the second aspect by assigning a concave cost function to each site to encourage path overlap. A simulated annealing optimization, based on a modified Berg-Foerster-Aragao de Carvalho-Caracciolo-Froehlich (BFACF) algorithm developed for polymers, is used to probe the complex conformational substate structure at zero temperature. We characterize the average cost gains (and path-length variations) for increasing polymer density with respect to a Dijkstra routing and find a nonmonotonic behavior as recently found for random networks. We observe the emergence of ergodicity breaking and of nontrivial overlap distributions among replicas when switching from a convex to a concave cost function (e.g., x^{γ}, where x represents the node overlap). Finally, we show that the space of ground states for γ<1 is compatible with an ultrametric structure, as seen in many complex systems such as some spin glasses.

Internal target volume margins for liver tumours treated with gated scanned carbon-ion radiotherapy

A promising approach to treating liver cancer with radiotherapy, is using a combination of a conformal technique, such as carbon ion-beam therapy, and beam gating. This study aims to assess the dosimetric implications, in a dose planning and verification study, of the use of gated internal target volume (ITVgate) when beam gating is used. Patients were immobilised with abdominal compression and a subset of these patients were treated using beam gating. The delivered dose was reconstructed. Significant dose degradation in the clinical target volume (CTV) due to the patient’s motion was identified. In addition, new plan optimisations were performed for the PTVgate, obtained from the geometric union of the phase-CTVs in the gating window. Finally, the concept of CTV expansion, including water equivalent path length variations (PTVgWEPL), was evaluated. When breathing was regular in amplitude, dose planning to the PTVgate resulted in a reduction in the dose delivered to healthy liver tissue without compromising the target coverage. In contrast, the use of PTVgWEPL concept resulted in a delivered plan with minor deviations from the planned treatment. The planned dose for the two concepts was verified in a 3D-motion water phantom. The mean relative deviations between measurements and the reconstructed dose were below 5% and were therefore within the clinically acceptable range for treatment.