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Shiva Abbaszadeh, Garry Chinn, Craig S Levin
The kinematics of Compton scatter can be used to estimate the interaction sequence of inter-crystal scatter interactions in 3-D position-sensitive cadmium zinc telluride (CZT) detectors. However, in the case of intra-crystal scatter in a "cross-strip" CZT detector slab, multiple anode and cathode strips may be triggered, creating position ambiguity due to uncertainty in possible combinations of anode-cathode pairings. As a consequence, methods such as energy-weighted centroid are not applicable to position the interactions...
November 13, 2017: Physics in Medicine and Biology
Luca Cocchi, Salvatore Passaro, Fabio Caratori Tontini, Guido Ventura
Subduction-transform edge propagators are lithospheric tears bounding slabs and back-arc basins. The volcanism at these edges is enigmatic because it is lacking comprehensive geological and geophysical data. Here we present bathymetric, potential-field data, and direct observations of the seafloor on the 90 km long Palinuro volcanic chain overlapping the E-W striking tear of the roll-backing Ionian slab in Southern Tyrrhenian Sea. The volcanic chain includes arc-type central volcanoes and fissural, spreading-type centers emplaced along second-order shears...
November 13, 2017: Nature Communications
Cesare Corrado, Nejib Zemzemi
Computational models of heart electrophysiology achieved a considerable interest in the medical community as they represent a novel framework for the study of the mechanisms underpinning heart pathologies. The high demand of computational resources and the long computational time required to evaluate the model solution hamper the use of detailed computational models in clinical applications. In this paper, we present a multi-front eikonal algorithm that adapts the conduction velocity (CV) to the activation frequency of the tissue substrate...
November 3, 2017: Medical Image Analysis
Lifang Gao, Xu Yang, Yang Shu, Xuwei Chen, Jianhua Wang
HYPOTHESIS: A novel slab optical waveguide sensor exploiting an ionic liquid (trihexyl(tetradecyl)phosphonium chloride)-based film can be used to detect gaseous ammonia. Bromothymol blue (BTB) incorporated into the ethyl cellulose-supported ionic liquid film can absorb the evanescent wave generated in the sensor and act as an indicator. The diffusion of gaseous ammonia across the sensing film is thus expected to change the absorbance of bromothymol blue, providing the basis for sensitive ammonia detection...
October 31, 2017: Journal of Colloid and Interface Science
G Sakr, C Sartel, V Sallet, A Lusson, G Patriarche, P Galtier, J Barjon
The diffusion of excitons injected in ZnO/Zn0.92Mg0.08O quantum well heterostructures grown by metal-organic-vapor-phase-epitaxy on non-polar ZnO substrates is investigated at room temperature. Cathodoluminescence linescans in a field-emission-gun scanning-electron-microscope are performed across cleaved cross-sections. A 55 nm diffusion length is assessed for excitons in bulk ZnMgO. When prepared as small angle bevels using focused ion beam (FIB), the effective diffusion length of excitons is shown to decrease down to 8 nm in the thinner part of the slab...
November 9, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Konstantin O Nagornov, Anton N Kozhinov, Yury O Tsybin
Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) at the cyclotron frequency instead of the reduced cyclotron frequency has been experimentally demonstrated using narrow aperture detection electrode (NADEL) ICR cells. Here, based on the results of SIMION simulations, we provide the initial mechanistic insights into the cyclotron frequency regime generation in FT-ICR MS. The reason for cyclotron frequency regime is found to be a new type of a collective motion of ions with a certain dispersion in the initial characteristics, such as pre-excitation ion velocities, in a highly non-quadratic trapping potential as realized in NADEL ICR cells...
November 8, 2017: Journal of the American Society for Mass Spectrometry
R Ghahraman Asl, H A Nedaie, N Banaee
The aim of this study is to evaluate the application and accuracy of polymer gels for determining electron dose distributions in the presence of small heterogeneities made of bone and air. Different cylindrical phantoms containing MAGIC (Methacrylic and Ascorbic acid in Gelatin Initiated by Copper) normoxic polymer gel were used under the slab phantoms during irradiation. MR images of the irradiated gel phantoms were obtained to determine their R2 (spin-spin) relaxation maps for conversion to absorbed dose...
December 2017: Health Physics
Anna S Pavlova, Evgeniya S Dyudeeva, Maxim S Kupryushkin, Nariman V Amirkhanov, Dmitrii V Pyshnyi, Inna A Pyshnaya
SDS-PAGE is considered to be a universal method for size-based separation and analysis of proteins. In this study, we applied the principle of SDS-PAGE to the analysis of new entirely uncharged nucleic acid (NA) analogues, - phosphoryl guanidine oligonucleotides (PGOs). The procedure was also shown to be suitable for morpholino oligonucleotides (PMOs) and peptide nucleic acids (PNAs). It was demonstrated that SDS can establish hydrophobic interactions with these types of synthetic NAs, giving them a net negative charge and thus making these molecules mobile in polyacrylamide slab gels under the influence of an electric field...
November 7, 2017: Electrophoresis
A Asambe, A K B Sackey, L B Tekdek
This study investigated the prevalence of African swine fever virus (ASFV) and classical swine fever virus (CSFV) antibodies in pigs in Benue State, Nigeria. Serum samples were collected from a total of 460 pigs, including 416 from 74 piggeries and 44 from Makurdi slaughter slab. The samples were analysed using indirect enzyme-linked immunosorbent assay (ELISA) test kit to detect the presence of ASFV antibodies, while competitive ELISA test kit was used to detect antibodies to CSFV. Our findings showed a total ASF prevalence of 13 (2...
November 6, 2017: Tropical Animal Health and Production
Yu Guo, Meng Xiao, Shanhui Fan
We consider the process of conversion between linear polarizations as light is reflected from a photonic crystal slab. We observe that, over a wide range of frequencies, complete polarization conversion can be found at isolated wave vectors. Moreover, such an effect is topological: the complex reflection coefficients have a nonzero winding number in the wave vector space. We also show that bound states in continuum in this system have their wave vectors lying on the critical coupling curve that defines the condition for complete polarization conversion...
October 20, 2017: Physical Review Letters
Fabio Daniel Barazza, Christophe Murith, Martha Palacios, Walther Gfeller, Emanuel Christen
We present and discuss the results of a national survey on radon remediation. The main purpose of the survey was the evaluation of the rate of radon remediation in Switzerland and to identify the main reasons for not taking action in cases of high radon levels. Switzerland is strongly affected by the radon problem and extensive efforts have been made to map the radon potential and to investigate the most effective methods to reduce radon levels in different buildings. However, since the radon remediation of buildings has been given over to experts in the private sector and since there is no obligation to report a finished remediation to the authorities, it is difficult for the Federal Office for Public Health (FOPH) to track the activities in this field...
November 2, 2017: Journal of Radiological Protection: Official Journal of the Society for Radiological Protection
U C Hasar, G Buldu, M Bute, A Muratoglu
A calibration-free method for extraction of electromagnetic properties of magnetically coupled anisotropic biaxial metamaterial (MM) slabs from waveguide measurements is proposed. It relies on three measurement steps (thru, empty line, and the same line arbitrarily loaded by the MM slab) to extract electromagnetic properties. It is evaluated against another calibration-dependent method for retrieval of electromagnetic properties of a MM slab constructed by C-shaped resonators. From evaluation analysis, we note that our method, as compared to the calibration-dependent method, not only accurately extracts electromagnetic properties without requiring the use of expensive calibration standards but also is reference-invariant...
October 2017: Review of Scientific Instruments
Bo-Dong Peng, Yan Song, Dong-Wei Hei, Jun Zhao
For the quantitative investigation of MeV-photon-induced changes in the refractive indices of bulk semiconductors, a model was established to describe the evolution of the excess carrier density, including the generation and recombination processes. The two key parameters of the evolution model, namely, the summed injection intensity and the gamma intensity curve, were obtained via dose measurements and gamma pulse monitoring, respectively. An interferometric method of measuring instantaneous changes in the refractive index and obtaining real-time measurements of the excess carrier density in bulk materials was successfully implemented...
October 2017: Review of Scientific Instruments
Kuang Cheng Chen, Jiun Wen Yang, Yueh-Chieh Yang, Chang Fu Khin, M Ng Mou Kehn
The metasurface lens composing of 2D periodic metallic patches on a grounded dielectric slab possesses several advantages such as being light, low-profile, compact, and also cheap to manufacture. In this paper, a Luneburg lens synthesized by a metasurface and designated for use as a surface wave antenna is proposed. Two types of unit cell will be compared, one whose surface wave modal dispersion varies significantly with the grazing direction and another that does not. In the context of being applied as surface wave antennas, it will be shown that the Luneburg lens synthesized by the latter kind of unit cell provides improved performance as compared to the former...
October 30, 2017: Optics Express
Dmitry A Bykov, Evgeni A Bezus, Leonid L Doskolovich
We present an iterative method for calculating complex-frequency eigenmodes of photonic crystal slabs with 1D periodicity based on the aperiodic Fourier modal method. By comparison with the known methods, we show that the proposed method is efficient for studying resonant properties of long-period photonic crystal slabs and diffraction gratings. We demonstrate that the method can be used to calculate the eigenmodes of the structures with periods up to at least 500λ. We discuss different aspects of the mode calculation, including convergence of the method, mode field and dispersion analysis...
October 30, 2017: Optics Express
Olivier Parriaux
The numerical modeling of a directional coupler composed of four identical slab waveguides reveals that the ratio of the field extrema of the four propagating modes is close to the golden ratio ϕ. This is confirmed by an analytical derivation leading to the exact dispersion equation of the eigenmodes of the four-waveguide coupler and to the expression of the ratio between field extrema. A coupled wave analysis gives the analytical expression of the propagation constants of the coupler eigenmodes and of the ratio between extrema in terms of the coupling coefficients between waveguides; it shows that this ratio is strictly equal to ϕ in weakly coupled structures where the coupling coefficient between next-nearest neighboring waveguides is negligible...
November 1, 2017: Journal of the Optical Society of America. A, Optics, Image Science, and Vision
Dibbyan Mazumder, Gurudas Kar, Ram Mohan Vasu, Debasish Roy, Rajan Kanhirodan
We obtain vibro-acoustic (VA) spectral signatures of a remotely palpated region in tissue or tissue-like objects through diffusing-wave spectroscopy (DWS) measurements. Remote application of force is through focused ultrasound, and the spectral signatures correspond to vibrational modes of the focal volume (also called the ROI) excited through ultrasound forcing. In DWS, one recovers the time evolution of mean-square displacement (MSD) of Brownian particles from the measured decay of intensity autocorrelation of light, adapted also to local particles pertaining only to the ROI...
November 1, 2017: Journal of the Optical Society of America. A, Optics, Image Science, and Vision
Zhaoyang Li, Takashi Kurita, Noriaki Miyanaga
Zigzag and non-zigzag beam waist shifts in a multiple-pass zigzag slab amplifier are investigated based on the propagation of a Gaussian beam. Different incident angles in the zigzag and non-zigzag planes would introduce a direction-dependent waist-shift-difference, which distorts the beam quality in both the near- and far-fields. The theoretical model and analytical expressions of this phenomenon are presented, and intensity distributions in the two orthogonal planes are simulated and compared. A geometrical optics compensation method by a beam with 90° rotation is proposed, which not only could correct the direction-dependent waist-shift-difference but also possibly average the traditional thermally induced wavefront-distortion-difference between the horizontal and vertical beam directions...
October 20, 2017: Applied Optics
Meilin Lv, Xiaoqin Sun, Shunhang Wei, Cai Shen, Yongli Mi, Xiaoxiang Xu
Ultrathin nitrogen-doped perovskite nanosheets LaTa2O6.77N0.15(-) have been fabricated by exfoliating Dion-Jacobson-type layered perovskite RbLaTa2O6.77N0.15. These nanosheets demonstrate superior photocatalytic activities for water splitting into hydrogen and oxygen and remain active with photon wavelengths as far as 600 nm. Their apparent quantum efficiency under visible-light illumination (λ ≥ 420 nm) approaches 1.29% and 3.27% for photocatalytic hydrogen and oxygen production, being almost 4-fold and 8-fold higher than bulk RbLaTa2O6...
November 7, 2017: ACS Nano
Xinyu Liu, Kathy Beaudette, Xianghong Wang, Linbo Liu, Brett E Bouma, Martin Villiger
Birefringence imaging, including polarization sensitive optical coherence tomography (PS-OCT), can provide valuable insight into the microscopic structure and organization of many biological tissues. In this paper, we report on a method to fabricate tissue-like birefringence phantoms for such imaging modalities. We utilize the photo-elastic effect, wherein birefringence is induced by stretching a polymer sample after heating it above its glass-transition temperature. The cooled samples stably exhibit homogeneous birefringence, and were assembled into phantoms containing multiple well-defined regions of distinct birefringence...
October 1, 2017: Biomedical Optics Express
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