bluuebunny/crossref_metadata_2025 huggingface dataset:
GEANT4-MT : bringing multi-threading into GEANT4 production
Authors: Ahn Sunil , Apostolakis John , Asai Makoto , Brandt Daniel , Cooperman Gene , Cosmo Gabriele , Dotti Andrea , Dong Xin , Yung Jun Soon , Nowak Andrzej
Published: June 2014

GEANT4-MT is the multi-threaded version of the GEANT4 particle transport code.(1, 2) The key goals for the design of GEANT4-MT have been a) the need to reduce the memory footprint of the multi-threaded application compared to the use of separate jobs and processes; b) to create an easy migration of the existing applications; and c) to use efficiently many threads or cores, by scaling up to tens and potentially hundreds of workers. The first public release of a GEANT4-MT prototype was made in 2011. We report on the revision of GEANT4-MT for inclusion in the production-level release scheduled for end of 2013. This has involved significant re-engineering of the prototype in order to incorporate it into the main GEANT4 development line, and the porting of GEANT4-MT threading code to additional platforms. In order to make the porting of applications as simple as possible, refinements addressed the needs of standalone applications. Further adaptations were created to improve the fit with the frameworks of High Energy Physics (HEP) experiments. We report on performances measurements on Intel Xeon™, AMD Opteron™ the first trials of GEANT4-MT on the Intel Many Integrated Cores (MIC) architecture, in the form of the Xeon Phi™ co-processor.(3) These indicate near-linear scaling through about 200 threads on 60 cores, when holding fixed the number of events per thread.
On the use of tally servers in Monte Carlo simulations of light-water reactors
Authors: Romano Paul K. , Forget Benoit , Smith Kord , Siegel Andrew
Published: June 2014

An algorithm for decomposing tally data in Monte Carlo simulations using servers has recently been proposed and analyzed. In the present work, we make a number of refinements to a theoretical performance model of the tally server algorithm to better predict the performance of a realistic reactor simulation using Monte Carlo. The impact of subdividing fuel into annular segments on parameters of the performance model is evaluated and shown to result in a predicted overhead of less than 20% for a PWR benchmark on the Mira Blue Gene/Q supercomputer. Additionally, a parameter space study is performed comparing tally server implementations using blocking and non-blocking communication. Non-blocking communication is shown to reduce the communication overhead relative to blocking communication, in some cases resulting in negative overhead.
High performances simulation of ultrasonic fields for Non Destructive Testing
Authors: Lambert Jason , Lacassagne Lionel , Rougeron Gilles , Le Berre Stéphane , Chatillon Sylvain
Published: June 2014

Ultrasonic imaging is a commonly used method to detect and identify defects in a mechanical part in nuclear applications. Nowadays massively parallel architectures enable the simulation of ultrasonic field emitted by a phased array transducer inspecting a part across a coupling medium. In this paper, regular field computation model will be discussed along its implementations on General Purpose Processors (GPP) and Graphic Processing Units (GPU).
Parametric study of spallation targets for the MYRRHA reactor using MCNPX simulations
Authors: Rebello A. L. P. , Martinez A. S. , Gonçalves A. C.
Published: June 2014

The present work aims to evaluate the behavior of neutron multiplicity in a spallation target using MCNPX simulations, focusing on its application in the MYRRHA reactor. It was studied the two types of spallation target proposed for the MYRRHA project, windowless and windows target, in order to compare them and find saturation boundaries. Some saturation boundaries were found and the windowless target proved to be as viable as the windows one. Each one produced nearly the same number of neutrons per incident proton. Using the concept of neutron cost, it was also observed that the optimum conditions on neutron production occur at about 1GeV, for both target designs.
TRIPOLI-4® - MCNP5 ITER A-lite neutronic model benchmarking
Authors: Jaboulay J.-C. , Cayla P.-Y. , Fausser C. , Lee Y.-K. , Trama J.-C. , Li-Puma A.
Published: June 2014

The aim of this paper is to present the capability of TRIPOLI-4®, the CEA Monte Carlo code, to model a large-scale fusion reactor with complex neutron source and geometry. In the past, numerous benchmarks were conducted for TRIPOLI-4® assessment on fusion applications. Experiments (KANT, OKTAVIAN, FNG) analysis and numerical benchmarks (between TRIPOLI-4® and MCNP5) on the HCLL DEMO2007 and ITER models were carried out successively. In this previous ITER benchmark, nevertheless, only the neutron wall loading was analyzed, its main purpose was to present MCAM (the FDS Team CAD import tool) extension for TRIPOLI-4®. Starting from this work a more extended benchmark has been performed about the estimation of neutron flux, nuclear heating in the shielding blankets and tritium production rate in the European TBMs (HCLL and HCPB) and it is presented in this paper. The methodology to build the TRIPOLI-4® A-lite model is based on MCAM and the MCNP A-lite model (version 4.1). Simplified TBMs (from KIT) have been integrated in the equatorial-port. Comparisons of neutron wall loading, flux, nuclear heating and tritium production rate show a good agreement between the two codes. Discrepancies are mainly included in the Monte Carlo codes statistical error.
Implementation and verification of nuclear interactions in a Monte-Carlo code for the Procom-ProGam proton therapy planning system
Authors: Kostyuchenko V.I. , Makarova A.S. , Ryazantsev O.B. , Samarin S.I. , Uglov A.S.
Published: June 2014

A great breakthrough in proton therapy has happened in the new century: several tens of dedicated centers are now operated throughout the world and their number increases every year. An important component of proton therapy is a treatment planning system. To make calculations faster, these systems usually use analytical methods whose reliability and accuracy do not allow the advantages of this method of treatment to implement to the full extent. Predictions by the Monte Carlo (MC) method are a “gold” standard for the verification of calculations with these systems. At the Institute of Experimental and Theoretical Physics (ITEP) which is one of the eldest proton therapy centers in the world, an MC code is an integral part of their treatment planning system. This code which is called IThMC was developed by scientists from RFNC-VNIITF (Snezhinsk) under ISTC Project 3563.
Optimising the nuclear data energy group structure used for fusion systems
Authors: Morgan L. W. G. , Sublet J-C. , Haeck W.
Published: June 2014

The generation of reaction rates within Monte-Carlo (MC) transport codes can be accomplished via 1) the standard point-wise estimator approach of tallying the pointwise flux and pointwise partial cross sections and/or 2) the multigroup approach which convolves a pointwise neutron flux with pre-defined binned partial cross-sections. Even fine multigroup sampling is more efficient when compared to pointwise Monte-Carlo sampling due to the removal of the cross-section interpolation from the calculation. This paper describes the four stage optimization procedure used to find an energy binning format which enables an accurate enough and computationally efficient calculation of any reaction rate when applied to MC modeling of fusion devices. This optimum format, named FOMG (Fusion Optimised Multi-Group), was evaluated using a SINBAD (Shielding Integral Benchmark Archive Database) benchmark. Despite the number of multi-group bins exceeding the number of data elements for a significant number of the ENDF files the MCNP simulation took more than one hundred times longer to calculate reaction rates using the pointwise approach when compared to the multi-group method with FOMG structure.
Verification of Three Dimensional Triangular Prismatic Discrete Ordinates Transport Code ENSEMBLE-TRIZ by Comparison with Monte Carlo Code GMVP
Authors: Homma Yuto , Moriwaki Hiroyuki , Ohki Shigeo , Ikeda Kazumi
Published: June 2014

This paper deals with verification of three dimensional triangular prismatic discrete ordinates transport calculation code ENSEMBLE-TRIZ by comparison with multi-group Monte Carlo calculation code GMVP in a large fast breeder reactor. The reactor is a 750 MWe electric power sodium cooled reactor. Nuclear characteristics are calculated at beginning of cycle of an initial core and at beginning and end of cycle of equilibrium core. According to the calculations, the differences between the two methodologies are smaller than 0.0002 Δk in the multi-plication factor, relatively about 1% in the control rod reactivity, and 1% in the sodium void reactivity.
Secondary neutron source modelling using MCNPX and ALEPH codes
Authors: Trakas Christos , Kerkar Nordine
Published: June 2014

Monitoring the subcritical state and divergence of reactors requires the presence of neutron sources. But mainly secondary neutrons from these sources feed the ex-core detectors (SRD, Source Range Detector) whose counting rate is correlated with the level of the subcriticality of reactor.

In cycle 1, primary neutrons are provided by sources activated outside of the reactor (e.g. Cf252); part of this source can be used for the divergence of cycle 2 (not systematic). A second family of neutron sources is used for the second cycle: the spontaneous neutrons of actinides produced after irradiation of fuel in the first cycle. Both families of sources are not sufficient to efficiently monitor the divergence of the second cycles and following ones, in most reactors. Secondary sources cluster (SSC) fulfil this role. In the present case, the SSC [Sb, Be], after activation in the first cycle (production of Sb124, unstable), produces in subsequent cycles a photo-neutron source by gamma (from Sb124)-neutron (on Be9) reaction.

This paper presents the model of the process between irradiation in cycle 1 and cycle 2 results for SRD counting rate at the beginning of cycle 2, using the MCNPX code and the depletion chain ALEPH-V1 (coupling of MCNPX and ORIGEN codes). The results of this simulation are compared with two experimental results of the PWR 1450 MWe-N4 reactors. A good agreement is observed between these results and the simulations. The subcriticality of the reactors is about at -15,000 pcm. Discrepancies on the SRD counting rate between calculations and measurements are in the order of 10%, lower than the combined uncertainty of measurements and code simulation.

This comparison validates the AREVA methodology, which allows having an SRD counting rate best-estimate for cycles 2 and next ones and optimizing the position of the SSC, depending on the geographic location of sources, main parameter for optimal monitoring of subcritical states.
Generalisation of opacity formulas for neutron transport
Authors: de Mulatier Clélia , Zoia Andrea , Rosso Alberto , Diop Cheikh M.
Published: June 2014

In the context of reactor physics, one is often called to relate the physical properties of a medium to the statistics of the random trajectories of the neutrons flowing through it. For instance, Cauchy’s formula establishes a link between the average length of the neutron paths (which is proportional to the medium opacity) and the volume-to-surface ratio of the traversed medium. In this work, we consider some extensions of such results for neutrons undergoing scattering, absorption and branching. A validation of the proposed formulas via Monte Carlo simulations is discussed.
PENSSART, a new Monte Carlo system for quality control in radiotherapy
Authors: Le Loirec C. , Garcia-Hernandez J. C. , Bonniaud G. , Guérin L. , Batalla A. , Poumarède B. , Lazaro D.
Published: June 2014

A new Monte Carlo system called PENSSART for PENELOPE Simulation for the Safety in Radiotherapy has been developed for quality control of the treatment plans. PENSSART is based on the 2006 release of PENELOPE that we have adapted to allow for the transport of particles in voxelized geometries. The new platform is built upon three main modules that help the user in the definition of the different control procedure steps. The purpose of this study was twofold. In a first part we have validated the beam implementation and the patient/phantom description in PENSSART. In a second part we have compared dose distributions obtained experimentally, with PENSSART and also with an algorithm usually used in clinical practice for treatment planning. The results demonstrate the usefulness of the developed system.
Benchmarking MCNP and TRIPOLI with PGNAA measurements
Authors: Carasco C. , Perot B. , Sikora A. , Mauerhofer E. , Havenith A. , Payan E. , Kettler J. , Kring T. , Ma J.L.
Published: June 2014

The French Alternative Energies and Atomic Energy Commission (CEA Cadarache), the Forschungszentrum Jülich GmbH (FZJ), and the RWTH Aachen University (RWTH) are involved in a cooperation aiming at characterizing toxic and reactive elements in radioactive waste packages by means of Prompt Gamma Neutron Activation Analysis (PGNAA). The design of an optimized measurement system and the assessment of its performances for realistic scenarios can be conveniently studied by numerical Monte Carlo simulation, provided the model and nuclear data offer a sufficient precision.

Previous studies performed with MCNP have shown that when the nuclear data libraries lack of precision, relevant results can still be obtained by performing calculations in multiple steps (by first determining the radiative capture rate, and transporting the induced gamma toward the detector) and by injecting valid gamma-ray production data in-between [1]. In such cases, it is interesting to compare the results obtained with different codes. In the present paper, we propose to compare the MCNP and TRIPOLI codes with measurements obtained in MEDINA (Multi Element Detection based on Instrumental Neutron Activation), which is the new FZJ PGNAA facility [2]. The aim of the measurement campaign is to assess capture gamma rays of toxic elements that can be found in 200 L waste drums which are expected for geological repository.
Fast Monte Carlo Electron-Photon Transport Method and Application in Accurate Radiotherapy
Authors: Hao Lijuan , Sun Guangyao , Zheng Huaqing , Song Jing , Chen Zhenping , Li Gui ,   FDS Team
Published: June 2014

Monte Carlo (MC) method is the most accurate computational method for dose calculation, but its wide application on clinical accurate radiotherapy is hindered due to its poor speed of converging and long computation time. In the MC dose calculation research, the main task is to speed up computation while high precision is maintained.

The purpose of this paper is to enhance the calculation speed of MC method for electron-photon transport with high precision and ultimately to reduce the accurate radiotherapy dose calculation time based on normal computer to the level of several hours, which meets the requirement of clinical dose verification.

Based on the existing Super Monte Carlo Simulation Program (SuperMC), developed by FDS Team, a fast MC method for electron-photon coupled transport was presented with focus on two aspects: firstly, through simplifying and optimizing the physical model of the electron-photon transport, the calculation speed was increased with slightly reduction of calculation accuracy; secondly, using a variety of MC calculation acceleration methods, for example, taking use of obtained information in previous calculations to avoid repeat simulation of particles with identical history; applying proper variance reduction techniques to accelerate MC method convergence rate, etc.

The fast MC method was tested by a lot of simple physical models and clinical cases included nasopharyngeal carcinoma, peripheral lung tumor, cervical carcinoma, etc. The result shows that the fast MC method for electron-photon transport was fast enough to meet the requirement of clinical accurate radiotherapy dose verification. Later, the method will be applied to the Accurate/Advanced Radiation Therapy System ARTS as a MC dose verification module.
Radiation transport in random disperse media implemented in the Monte Carlo code PRIZMA
Authors: Kashayeva Elena A. , Malyshkin Gennady N. , Mukhamadiev Rim F.
Published: June 2014

The paper describes PRIZMA capabilities for modeling radiation transport in random disperse media by the Monte Carlo method. It proposes a method for simulating radiation transport in binary media with variable volume fractions.
Parallelization of TWOPORFLOW, a Cartesian Grid based Two-phase Porous Media Code for Transient Thermo-hydraulic Simulations
Authors: Trost Nico , Jiménez Javier , Imke Uwe , Sanchez Victor
Published: June 2014

TWOPORFLOW is a thermo-hydraulic code based on a porous media approach to simulate single- and two-phase flow including boiling. It is under development at the Institute for Neutron Physics and Reactor Technology (INR) at KIT. The code features a 3D transient solution of the mass, momentum and energy conservation equations for two inter-penetrating fluids with a semi-implicit continuous Eulerian type solver. The application domain of TWOPORFLOW includes the flow in standard porous media and in structured porous media such as micro-channels and cores of nuclear power plants. In the latter case, the fluid domain is coupled to a fuel rod model, describing the heat flow inside the solid structure. In this work, detailed profiling tools have been utilized to determine the optimization potential of TWOPORFLOW. As a result, bottle-necks were identified and reduced in the most feasible way, leading for instance to an optimization of the water-steam property computation. Furthermore, an OpenMP implementation addressing the routines in charge of inter-phase momentum-, energy- and mass-coupling delivered good performance together with a high scalability on shared memory architectures. In contrast to that, the approach for distributed memory systems was to solve sub-problems resulting by the decomposition of the initial Cartesian geometry. Thread communication for the sub-problem boundary updates was accomplished by the Message Passing Interface (MPI) standard.
Comparison of some parallelisation strategies of thermalhydraulics codes on GPUs
Authors: Jendoubi T. , Bergeaud V. , Geay A.
Published: June 2014

Modern supercomputers architecture is now often based on hybrid concepts combining parallelism to distributed memory, parallelism to shared memory and also to GPUs. In this work, we propose a new approach to take advantage of these graphic cards in TH algorithms.
Monte Carlo simulation on Graphical Processor Unit of the scattered beam in radiography non-destructive testing context
Authors: Tisseur David , Andrieux Alexan , Costin Marius , Vabre Alexandre
Published: June 2014

CEA-LIST develops CIVA software for non-destructive testing simulation. Radiography Monte Carlo simulation for the scattered beam can be quite long (several hours) even on a multi-thread CPU implementation. In order to reduce this computation time, we have modified and adapted for CIVA a GPU open source code named MCGPU. This paper presents our work and the results of cross comparison between CIVA and the modified MCGPU code in a NDT context.
Regional Scale HPC Reactive Transport Simulation of Nuclear Spent Fuel Repository in Forsmark, Sweden
Authors: de Vries L.M. , Molinero J. , Ebrahimi H. , Svensson U. , Lichtner P. , Abarca E.
Published: June 2014

The future nuclear spent fuel repository in the Forsmark area in Sweden, constructed at a depth of 500 meters, is designed to be isolated from people and nature for at least 100.000 years. As part of the safety assessment of the repository, it is necessary to simulate the interaction of the repository compounds with the surrounding groundwater and rock. To evaluate the geochemical evolution in the region under sealed repository conditions, a HPC framework, which couples a groundwater flow simulator (DarcyTools) optimized for fractured rock hydrology and a high performance reactive transport code (PFlotran) was developed. The migration of a hyper-alkaline plume (high pH plume) over 10.000 years is simulated in a large scale 3D model (100 Million cells). The results show the control of the rock fractures in the movement of the reactive plume.
DIANE multiparticle transport code
Authors: Caillaud M. , Lemaire S. , Ménard S. , Rathouit P. , Ribes J.C. , Riz D.
Published: June 2014

DIANE is the general Monte Carlo code developed at CEA-DAM. DIANE is a 3D multiparticle multigroup code. DIANE includes automated biasing techniques and is optimized for massive parallel calculations.
Capabilities overview of the MORET 5 Monte Carlo code
Authors: Cochet B. , Jinaphanh A. , Heulers L. , Jacquet O.
Published: June 2014

The MORET code is a simulation tool that solves the transport equation for neutrons using the Monte Carlo method. It allows users to model complex three-dimensional geometrical configurations, describe the materials, define their own tallies in order to analyse the results. The MORET code has been initially designed to perform calculations for criticality safety assessments. New features has been introduced in the MORET 5 code to expand its use for reactor applications. This paper presents an overview of the MORET 5 code capabilities, going through the description of materials, the geometry modelling, the transport simulation and the definition of the outputs.
Multi-scale study of condensation in water jets using ellipsoidal-statistical Bhatnagar-Gross-Krook and molecular dynamics modeling
Authors: Li Zheng , Borner Arnaud , Levin Deborah A.
Published: June 2014

Homogeneous water condensation and ice formation in supersonic expansions to vacuum for stagnation pressures from 12 to 1000 mbar are studied using the particle-based Ellipsoidal-Statistical Bhatnagar-Gross-Krook (ES-BGK) method. We find that when condensation starts to occur, at a stagnation pressure of 96 mbar, the increase in the degree of condensation causes an increase in the rotational temperature due to the latent heat of vaporization. The simulated rotational temperature profiles along the plume expansion agree well with measurements confirming the kinetic homogeneous condensation models and the method of simulation. Comparisons of the simulated gas and cluster number densities, cluster size for different stagnation pressures along the plume centerline were made and it is found that the cluster size increase linearly with respect to stagnation pressure, consistent with classical nucleation theory. The sensitivity of our results to cluster nucleation model and latent heat values based on bulk water, specific cluster size, or bulk ice are examined. In particular, the ES-BGK simulations are found to be too coarse-grained to provide information on the phase or structure of the clusters formed. For this reason, molecular dynamics simulations of water condensation in a one-dimensional free expansion to simulate the conditions in the core of a plume are performed. We find that the internal structure of the clusters formed depends on the stagnation temperature. A larger cluster of average size 21 was tracked down the expansion, and a calculation of its average internal temperature as well as a comparison of its radial distribution functions (RDFs) with values measured for solid amorphous ice clusters lead us to conclude that this cluster is in a solid-like rather than liquid form. In another molecular-dynamics simulation at a much lower stagnation temperature, a larger cluster of size 324 and internal temperature 200 K was extracted from an expansion plume and equilibrated to determine its RDF and self-diffusion coefficient. The value of the latter shows that this cluster is formed in a supercooled liquid state rather than in an amorphous solid state.
Communication: He-tagged vibrational spectra of the SarGlyH+ and H+(H2O)2,3 ions: Quantifying tag effects in cryogenic ion vibrational predissociation (CIVP) spectroscopy
Authors: Johnson Christopher J. , Wolk Arron B. , Fournier Joseph A. , Sullivan Erin N. , Weddle Gary H. , Johnson Mark A.
Published: June 2014

To assess the degree to which more perturbative, but widely used “tag” species (Ar, H2, Ne) affect the intrinsic band patterns of the isolated ions, we describe the extension of mass-selective, cryogenic ion vibrational spectroscopy to the very weakly interacting helium complexes of three archetypal ions: the dipeptide SarGlyH+ and the small protonated water clusters: H+(H2O)2,3, including the H5O2+ “Zundel” ion. He adducts were generated in a 4.5 K octopole ion trap interfaced to a double-focusing, tandem time-of-flight photofragmentation mass spectrometer to record mass-selected vibrational predissociation spectra. The H2 tag-induced shift (relative to that by He) on the tag-bound NH stretch of the SarGlyH+ spectrum is quite small (12 cm−1), while the effect on the floppy H5O2+ ion is more dramatic (125 cm−1) in going from Ar (or H2) to Ne. The shifts from Ne to He, on the other hand, while quantitatively significant (maximum of 10 cm−1), display the same basic H5O2+ band structure, indicating that the He-tagged H5O2+ spectrum accurately represents the delocalized nature of the vibrational zero-point level. Interestingly, the He-tagged spectrum of H+(H2O)3 reveals the location of the non-bonded OH group on the central H3O+ ion to fall between the collective non-bonded OH stretches on the flanking water molecules in a position typically associated with a neutral OH group.
Ultra-sharp plasmonic resonances from monopole optical nanoantenna phased arrays
Authors: Li Shi-Qiang , Zhou Wei , Bruce Buchholz D. , Ketterson John B. , Ocola Leonidas E. , Sakoda Kazuaki , Chang Robert P. H.
Published: June 2014

Diffractively coupled plasmonic resonances possess both ultra-sharp linewidths and giant electric field enhancement around plasmonic nanostructures. They can be applied to create a new generation of sensors, detectors, and nano-optical devices. However, all current designs require stringent index-matching at the resonance condition that limits their applicability. Here, we propose and demonstrate that it is possible to relieve the index-matching requirement and to induce ultra-sharp plasmon resonances in an ordered vertically aligned optical nano-antenna phased array by transforming a dipole resonance to a monopole resonance with a mirror plane. Due to the mirror image effect, the monopole resonance not only retained the dipole features but also enhanced them. The engineered resonances strongly suppressed the radiative decay channel, resulting in a four-order of magnitude enhancement in local electric field and a Q-factor greater than 200.
In situ magnetic compensation for potassium spin-exchange relaxation-free magnetometer considering probe beam pumping effect
Authors: Fang Jiancheng , Wang Tao , Quan Wei , Yuan Heng , Zhang Hong , Li Yang , Zou Sheng
Published: June 2014

A novel method to compensate the residual magnetic field for an atomic magnetometer consisting of two perpendicular beams of polarizations was demonstrated in this paper. The method can realize magnetic compensation in the case where the pumping rate of the probe beam cannot be ignored. In the experiment, the probe beam is always linearly polarized, whereas, the probe beam contains a residual circular component due to the imperfection of the polarizer, which leads to the pumping effect of the probe beam. A simulation of the probe beam's optical rotation and pumping rate was demonstrated. At the optimized points, the wavelength of the probe beam was optimized to achieve the largest optical rotation. Although, there is a small circular component in the linearly polarized probe beam, the pumping rate of the probe beam was non-negligible at the optimized wavelength which if ignored would lead to inaccuracies in the magnetic field compensation. Therefore, the dynamic equation of spin evolution was solved by considering the pumping effect of the probe beam. Based on the quasi-static solution, a novel magnetic compensation method was proposed, which contains two main steps: (1) the non-pumping compensation and (2) the sequence compensation with a very specific sequence. After these two main steps, a three-axis in situ magnetic compensation was achieved. The compensation method was suitable to design closed-loop spin-exchange relaxation-free magnetometer. By a combination of the magnetic compensation and the optimization, the magnetic field sensitivity was approximately 4 fT/Hz1/2, which was mainly dominated by the noise of the magnetic shield.
Self-generation and management of spin-electromagnetic wave solitons and chaos
Authors: Ustinov Alexey B. , Kondrashov Alexandr V. , Nikitin Andrey A. , Kalinikos Boris A.
Published: June 2014

Self-generation of microwave spin-electromagnetic wave envelope solitons and chaos has been observed and studied. For the investigation, we used a feedback active ring oscillator based on artificial multiferroic, which served as a nonlinear waveguide. We show that by increasing the wave amplification in the feedback ring circuit, a transition from monochromatic auto-generation to soliton train waveform and then to dynamical chaos occurs in accordance with the Ruelle-Takens scenario. Management of spin-electromagnetic-wave solitons and chaos parameters by both dielectric permittivity and magnetic permeability of the multiferroic waveguiding structure is demonstrated.
Exchange interaction between the triplet exciton and the localized spin in copper-phthalocyanine
Authors: Wu Wei
Published: June 2014

Triplet excitonic state in the organic molecule may arise from a singlet excitation and the following inter-system crossing. Especially for a spin-bearing molecule, an exchange interaction between the triplet exciton and the original spin on the molecule can be expected. In this paper, such exchange interaction in copper-phthalocyanine (CuPc, spin-\documentclass[12pt]{minimal}\begin{document}$\frac{1}{2}$\end{document}12) was investigated from first-principles by using density-functional theory within a variety of approximations to the exchange correlation, ranging from local-density approximation to long-range corrected hybrid-exchange functional. The magnitude of the computed exchange interaction is in the order of meV with the minimum value (1.5 meV, ferromagnetic) given by the long-range corrected hybrid-exchange functional CAM-B3LYP. This exchange interaction can therefore give rise to a spin coherence with an oscillation period in the order of picoseconds, which is much shorter than the triplet lifetime in CuPc (typically tens of nanoseconds). This implies that it might be possible to manipulate the localized spin on Cu experimentally using optical excitation and inter-system crossing well before the triplet state disappears.
Adiabatically implementing quantum gates
Authors: Sun Jie , Lu Songfeng , Liu Fang
Published: June 2014

We show that, through the approach of quantum adiabatic evolution, all of the usual quantum gates can be implemented efficiently, yielding running time of order O(1). This may be considered as a useful alternative to the standard quantum computing approach, which involves quantum gates transforming quantum states during the computing process.
In-well pumped mid-infrared PbTe/CdTe quantum well vertical external cavity surface emitting lasers
Authors: Khiar A. , Volobuev V. , Witzan M. , Hochreiner A. , Eibelhuber M. , Springholz G.
Published: June 2014

Optical in-well pumped mid-infrared vertical external cavity surface emitting lasers based on PbTe quantum wells embedded in CdTe barriers are realized. In contrast to the usual ternary barrier materials of lead salt lasers such as PbEuTe of PbSrTe, the combination of narrow-gap PbTe with wide-gap CdTe offers an extremely large carrier confinement, preventing charge carrier leakage from the quantum wells. In addition, optical in-well pumping can be achieved with cost effective and readily available near infrared lasers. Free carrier absorption, which is a strong loss mechanism in the mid-infrared, is strongly reduced due to the insulating property of CdTe. Lasing is observed from 85 K to 300 K covering a wavelength range of 3.3–4.2 μm. The best laser performance is achieved for quantum well thicknesses of 20 nm. At low temperature, the threshold power is around 100 mWP and the output power more than 700 mWP. The significance of various charge carrier loss mechanisms are analyzed by modeling the device performance. Although Auger losses are quite low in IV–VI semiconductors, an Auger coefficient of CA = 3.5 × 10−27 cm6 s−1 was estimated for the laser structure, which is attributed to the large conduction band offset.
Temperature dependent dielectric and magnetic properties of GdFe1−xNixO3 (0.0 ≤ x ≤ 0.3) orthoferrites
Authors: Kaur Pawanpreet , Sharma K. K. , Pandit Rabia , Kumar Ravi , Kotnala R. K. , Shah Jyoti
Published: June 2014

The polycrystalline samples of GdFe1−xNixO3 (x = 0.0, 0.1, 0.2, 0.3) orthoferrites are synthesized via solid state reaction route. The Rietveld fitted X-ray diffraction patterns confirm the formation of orthorhombic phase with Pbnm space group for all the samples. The dielectric measurements reveal an enhancement in dielectric constant and tangent loss with increase in both temperature as well as Nickel (Ni) substitution. Dielectric studies are also in support with the induction of delocalized charge carriers in the GdFeO3 matrix with increasing Ni doping. Magnetization versus applied field study shows the non-saturating hysteresis curves suggesting the canted type antiferromagnetic behavior in the considered orthoferrites. Moreover, the observed magnetic behavior is complex and the doping affects the magnitude of magnetization differently at 300 K and 80 K. It has further been noticed that the incorporated Ni3+ ions enhances the symmetry of the magnetization curves. The as-prepared samples may find their applications in the decoupling capacitors.
Conductance with stochastic resonance in Mn12 redox network without tuning
Authors: Hirano Yoshiaki , Segawa Yuji , Kuroda-Sowa Takayoshi , Kawai Tomoji , Matsumoto Takuya
Published: June 2014

Artificial neuron-based information processing is one of the attractive approaches of molecular-scale electronics, which can exploit the ability of molecular system for self-assembling or self-organization. The self-organized Mn12/DNA redox network shows nonlinear current-voltage characteristics that can be described by the Coulomb blockade network model. As a demonstration of the nonlinear network system, we have observed stochastic resonance without tuning for weak periodic input signals and thermal noise, which suggests a route to neural network composed of molecular materials.
Control of collective network chaos
Authors: Wagemakers Alexandre , Barreto Ernest , Sanjuán Miguel A. F. , So Paul
Published: June 2014

Under certain conditions, the collective behavior of a large globally-coupled heterogeneous network of coupled oscillators, as quantified by the macroscopic mean field or order parameter, can exhibit low-dimensional chaotic behavior. Recent advances describe how a small set of “reduced” ordinary differential equations can be derived that captures this mean field behavior. Here, we show that chaos control algorithms designed using the reduced equations can be successfully applied to imperfect realizations of the full network. To systematically study the effectiveness of this technique, we measure the quality of control as we relax conditions that are required for the strict accuracy of the reduced equations, and hence, the controller. Although the effects are network-dependent, we show that the method is effective for surprisingly small networks, for modest departures from global coupling, and even with mild inaccuracy in the estimate of network heterogeneity.
Electron dynamics of the buffer layer and bilayer graphene on SiC
Authors: Shearer Alex J. , Johns James E. , Caplins Benjamin W. , Suich David E. , Hersam Mark C. , Harris Charles B.
Published: June 2014

Angle- and time-resolved two-photon photoemission (TPPE) was used to investigate electronic states in the buffer layer of 4H-SiC(0001). An image potential state (IPS) series was observed on this strongly surface-bound buffer layer, and dispersion measurements indicated free-electron-like behavior for all states in this series. These results were compared with TPPE taken on bilayer graphene, which also show the existence of a free-electron-like IPS series. Lifetimes for the n = 2, and n = 3 states were obtained from time-resolved TPPE; slightly increased lifetimes were observed in the bilayer graphene sample for the n = 2 the n = 3 states. Despite the large band gap of graphene at the center of the Brillouin zone, the lifetime results demonstrate that the graphene layers do not behave as a simple tunneling barrier, suggesting that the buffer layer and graphene overlayers play a direct role in the decay of IPS electrons.
Influence of the substrate on the diffusion coefficient and the momentum relaxation in graphene: The role of surface polar phonons
Authors: Rengel R. , Pascual E. , Martín M. J.
Published: June 2014

Knowing the influence of the substrate type on the diffusion coefficient and the momentum relaxation in graphene is of great importance for the development of new device models specifically adapted to the peculiarities of this material. In this work, the influence of surface polar phonons at low and high electric fields is evaluated by means of ensemble Monte Carlo simulations for several types of substrates. The results show that at low fields, surface polar phonons have a major role on reducing the scattering time, breaking the correlation of velocity fluctuations, and degrading the diffusion coefficient. At high fields, the differences with regard to suspended samples in terms of diffusivity and momentum relaxation tend to reduce, providing at the same time larger saturation velocities, particularly for h-BN.
Note: High-efficiency broadband acoustic energy harvesting using Helmholtz resonator and dual piezoelectric cantilever beams
Authors: Yang Aichao , Li Ping , Wen Yumei , Lu Caijiang , Peng Xiao , He Wei , Zhang Jitao , Wang Decai , Yang Feng
Published: June 2014

A high-efficiency broadband acoustic energy harvester consisting of a compliant-top-plate Helmholtz resonator (HR) and dual piezoelectric cantilever beams is proposed. Due to the high mechanical quality factor of beams and the strong multimode coupling of HR cavity, top plate and beams, the high efficiency in a broad bandwidth is obtained. Experiment exhibits that the proposed harvester at 170–206 Hz has 28–188 times higher efficiency than the conventional harvester using a HR with a piezoelectric composite diaphragm. For input acoustic pressure of 2.0 Pa, the proposed harvester exhibits 0.137–1.43 mW output power corresponding to 0.035–0.36 μW cm−3 volume power density at 170–206 Hz.
Absolute dual-comb spectroscopy at 1.55 μm by free-running Er:fiber lasers
Authors: Cassinerio Marco , Gambetta Alessio , Coluccelli Nicola , Laporta Paolo , Galzerano Gianluca
Published: June 2014

We report on a compact scheme for absolute referencing and coherent averaging for dual-comb based spectrometers, exploiting a single continuous-wave (CW) laser in a transfer oscillator configuration. The same CW laser is used for both absolute calibration of the optical frequency axis and the generation of a correction signal which is used for a real-time jitter compensation in a fully electrical feed-forward scheme. The technique is applied to a near-infrared spectrometer based on a pair of free-running mode-locked Er:fiber lasers, allowing to perform real-time absolute-frequency measurements over an optical bandwidth of more than 25 nm, with coherent interferogram averaging over 1-s acquisition time, leading to a signal-to-noise ratio improvement of 29 dB over the 50 μs single shot acquisition. Using 10-cm single pass cell, a value of 1.9 × 10−4 cm−1 Hz−0.5 noise-equivalent-absorption over 1 s integration time is obtained, which can be further scaled down with a multi-pass or resonant cavity. The adoption of a single CW laser, together with the absence of optical locks, and the full-fiber design makes this spectrometer a robust and compact system to be employed in gas-sensing applications.
Changes in velocity profile according to blood viscosity in a microchannel
Authors: Yeom Eunseop , Kang Yang Jun , Lee Sang-Joon
Published: June 2014

Red blood cells (RBCs) are important to dictate hemorheological properties of blood. The shear-thinning effect of blood is mainly attributed to the characteristics of the RBCs. Variations in hemorheological properties alter flow resistance and wall shear stress in blood vessels. Therefore, detailed understanding of the relationship between the hemorheological and hemodynamic properties is of great importance. In this study, blood viscosity and blood flow were simultaneously measured in the same microfluidic device by monitoring the flow-switching phenomenon. To investigate blood flows according to hemorheological variations, the flow rate of blood samples (RBCs suspended in autologous plasma, dextran-treated plasma, and in phosphate buffered saline solution) was precisely controlled with a syringe pump. Velocity profiles of blood flows were measured by using a micro-particle image velocimetry technique. The shape of velocity profiles was quantified by using a curve-fitting equation. It is found that the shape of the velocity profiles is highly correlated with blood viscosity. To demonstrate the relationship under ex vivo conditions, biophysical properties and velocity profiles were measured in an extracorporeal rat bypass loop. Experimental results show that increased blood viscosity seems to induce blunt velocity profile with high velocity component at the wall of the microchannel. Simultaneous measurement of blood viscosity and velocity profile would be useful for understanding the effects of hemorheological features on the hemodynamic characteristics in capillary blood vessels.
Rapid decline in detections of the Tasmanian bettong (Bettongia gaimardi) following local incursion of feral cats (Felis catus)
Authors: Fancourt Bronwyn A.
Published: June 2014

An abrupt decline in the number of Tasmanian bettongs (Bettongia gaimardi) was observed as part of a study investigating population declines in the eastern quoll (Dasyurus viverrinus). Seven remote camera surveys were undertaken at a monitoring site between February 2012 and October 2013. An 11% reduction in bettong detections was observed immediately following the first appearance of feral cats (Felis catus) (at least three individuals) at the site. Within four months, bettong detections had fallen by 58% and by 100% within six months. No bettongs were detected in subsequent surveys undertaken 10, 12 and 16 months after cats were first observed. Cat predation and toxoplasmosis are discussed as mechanisms possibly responsible for the local disappearance of bettongs from this site, together with implications for the future management and conservation of the species.
Assessment of temporal genetic variability of two epibenthic amphipod species in an eastern Australian estuarine environment and their suitability as biological monitors
Authors: Chung Pann Pann , Chu Ida , Ballard J. William O.
Published: June 2014

Population studies often assume temporally stable and consistent patterns of genetic variability. Violations of this assumption can lead to misrepresentation of the amount and patterns of genetic variability in natural populations, which can be problematic in basic research and environmental monitoring studies that are designed to detect environmental perturbation. We collected two endemic species of amphipods, Melita plumulosa and Melita matilda, in a major eastern Australian waterway between November 2009 and October 2011, and assessed genetic variation at the mitochondrial cytochromec oxidase subunitI locus. Overall, M. plumulosa was found to be more genetically variable than M. matilda. No distinct temporal trends in levels and patterns of genetic variation were identified in either species. These findings, combined with the published results demonstrating that M. plumulosa has greater sensitivity to a range of sediment-bound metals and organic contaminants, suggests it to be an informative species for environmental monitoring purposes.
Maritime route of colonization of Europe
Authors: Paschou Peristera , Drineas Petros , Yannaki Evangelia , Razou Anna , Kanaki Katerina , Tsetsos Fotis , Padmanabhuni Shanmukha Sampath , Michalodimitrakis Manolis , Renda Maria C. , Pavlovic Sonja , Anagnostopoulos Achilles , Stamatoyannopoulos John A. , Kidd Kenneth K. , Stamatoyannopoulos George
Published: June 2014

Significance

The question of colonization of Europe by Neolithic people of the Near East and their contribution to the farming economy of Europe has been addressed with extensive archaeological studies and many genetic investigations of extant European and Near Eastern populations. Here, we use DNA polymorphisms of extant populations to investigate the patterns of gene flow from the Near East to Europe. Our data support the hypothesis that Near Eastern migrants reached Europe from Anatolia. A maritime route and island hopping was mainly used by these Near Eastern migrants to reach Southern Europe.
Anthropogenic changes in sodium affect neural and muscle development in butterflies
Authors: Snell-Rood Emilie C. , Espeset Anne , Boser Christopher J. , White William A. , Smykalski Rhea
Published: June 2014

Significance

Sodium is an essential micronutrient that is often limited in animal diets. It is important in the development of neural tissue and thought to have driven the evolution of specific foraging behavior. Human activity is drastically altering patterns of sodium availability, particularly through road salt application, but we know little about the consequences of such anthropogenic change on the development and evolution of wild animals. Here, we show that road salt runoff affects sodium concentrations of roadside plants, which in turn, have significant, (sometimes positive) effects on neural and muscular development of herbivores. These results suggest that anthropogenic changes in sodium can have major consequences for both behavioral development and selection on foraging behavior.
Plant roots use a patterning mechanism to position lateral root branches toward available water
Authors: Bao Yun , Aggarwal Pooja , Robbins Neil E. , Sturrock Craig J. , Thompson Mark C. , Tan Han Qi , Tham Cliff , Duan Lina , Rodriguez Pedro L. , Vernoux Teva , Mooney Sacha J. , Bennett Malcolm J. , Dinneny José R.
Published: June 2014

Significance

Few studies have asked at what spatial scale environmental stimuli regulate plant development and when during the patterning process these signals act. We have discovered that plant roots can sense microscale heterogeneity in water availability across their circumference, which causes dramatic differences in the patterning of tissues along this axis. Root branching is a target of such hydropatterning; lateral roots only form on the side of the main root contacting water in soil or agar. We show that hydropatterning is a conserved process in
Arabidopsis
, maize, and rice and reveal the importance of auxin biosynthesis and transport in regulating this process.