WorldWideScience

Sample records for resonance spatial modulation

  1. Spatial Terahertz Modulator

    Science.gov (United States)

    Xie, Zhenwei; Wang, Xinke; Ye, Jiasheng; Feng, Shengfei; Sun, Wenfeng; Akalin, Tahsin; Zhang, Yan

    2013-11-01

    Terahertz (THz) technology is a developing and promising candidate for biological imaging, security inspection and communications, due to the low photon energy, the high transparency and the broad band properties of the THz radiation. However, a major encountered bottleneck is lack of efficient devices to manipulate the THz wave, especially to modulate the THz wave front. A wave front modulator should allow the optical or electrical control of the spatial transmission (or reflection) of an input THz wave and hence the ability to encode the information in a wave front. Here we propose a spatial THz modulator (STM) to dynamically control the THz wave front with photo-generated carriers. A computer generated THz hologram is projected onto a silicon wafer by a conventional spatial light modulator (SLM). The corresponding photo-generated carrier spatial distribution will be induced, which forms an amplitude hologram to modulate the wave front of the input THz beam. Some special intensity patterns and vortex beams are generated by using this method. This all-optical controllable STM is structure free, high resolution and broadband. It is expected to be widely used in future THz imaging and communication systems.

  2. Integrated unaligned resonant modulator tuning

    Energy Technology Data Exchange (ETDEWEB)

    Zortman, William A.; Lentine, Anthony L.

    2017-10-03

    Methods and systems for tuning a resonant modulator are disclosed. One method includes receiving a carrier signal modulated by the resonant modulator with a stream of data having an approximately equal number of high and low bits, determining an average power of the modulated carrier signal, comparing the average power to a predetermined threshold, and operating a tuning device coupled to the resonant modulator based on the comparison of the average power and the predetermined threshold. One system includes an input structure, a plurality of processing elements, and a digital control element. The input structure is configured to receive, from the resonant modulator, a modulated carrier signal. The plurality of processing elements are configured to determine an average power of the modulated carrier signal. The digital control element is configured to operate a tuning device coupled to the resonant modulator based on the average power of the modulated carrier signal.

  3. Spatially modulated imaging system

    International Nuclear Information System (INIS)

    Barrett, H.H.

    1975-01-01

    Noncoherent radiation, such as x-rays, is spatially coded, directed through an object and spatially detected to form a spatially coded pattern, from which an image of the object may be reconstructed. The x-ray source may be formed by x-ray fluorescence and substration of the holographic images formed by two sources having energy levels predominantly above and below the maximum absorption range of an agent in the object may be used to enhance contrast in the reproduced image. (Patent Office Record)

  4. Enhancing molecular logic through modulation of temporal and spatial constraints with quantum dot-based systems that use fluorescent (Förster) resonance energy transfer

    Science.gov (United States)

    Claussen, Jonathan C.; Algar, W. Russ; Hildebrandt, Niko; Susumu, Kimihiro; Ancona, Mario G.; Medintz, Igor L.

    2013-10-01

    Luminescent semiconductor nanocrystals or quantum dots (QDs) contain favorable photonic properties (e.g., resistance to photobleaching, size-tunable PL, and large effective Stokes shifts) that make them well-suited for fluorescence (Förster) resonance energy transfer (FRET) based applications including monitoring proteolytic activity, elucidating the effects of nanoparticles-mediated drug delivery, and analyzing the spatial and temporal dynamics of cellular biochemical processes. Herein, we demonstrate how unique considerations of temporal and spatial constraints can be used in conjunction with QD-FRET systems to open up new avenues of scientific discovery in information processing and molecular logic circuitry. For example, by conjugating both long lifetime luminescent terbium(III) complexes (Tb) and fluorescent dyes (A647) to a single QD, we can create multiple FRET lanes that change temporally as the QD acts as both an acceptor and donor at distinct time intervals. Such temporal FRET modulation creates multi-step FRET cascades that produce a wealth of unique photoluminescence (PL) spectra that are well-suited for the construction of a photonic alphabet and photonic logic circuits. These research advances in bio-based molecular logic open the door to future applications including multiplexed biosensing and drug delivery for disease diagnostics and treatment.

  5. Regional left ventricular myocardial contraction abnormalities and asynchrony in patients with hypertrophic cardiomyopathy evaluated by magnetic resonance spatial modulation of magnetization myocardial tagging

    International Nuclear Information System (INIS)

    Mishiro, Yuichiro; Oki, Takashi; Iuchi, Arata

    1999-01-01

    Global left ventricular (LV) pump function is generally preserved in patients with hypertrophic cardiomyopathy (HCM). However, it is unknown whether regional myocardial contractility is impaired, especially in nonhypertrophied regions. The purpose of this study was to evaluate regional LV myocardial contraction in patients with HCM using magnetic resonance (MR) spatial modulation of magnetization (SPAMM) myocardial tagging. The study group comprised 20 patients with asymmetric septal hypertrophy (HCM group) and 16 age-matched normal patients (control group), and data were collected using transthoracic M-mode and 2-dimensional echocardiography, and MR SPAMM myocardial tagging. The systolic strain ratio, maximum systolic strain velocity, and time from end-diastole to maximum systolic strain (ΔT) in the anterior, ventricular septal, inferior and lateral regions for 2 LV short-axis sections at the levels of the chordae tendineae and papillary muscles were measured at 50-ms intervals by MR myocardial tagging. The end-diastolic anterior and ventricular septal wall thicknesses and LV mass index were significantly different between the HCM and control groups. The systolic strain ratio for all 4 walls, particularly the anterior and ventricular septal regions, was significantly lower in the HCM group. In the HCM group, the maximum systolic strain velocity was significantly lower and ΔT was significantly shorter for all 4 walls, particularly the anterior and ventricular septal regions. The standard deviation for the ΔT, calculated from the ΔT for the 8 regions of the 2 LV short-axis sections, was significantly greater in the HCM group. In conclusion, regional LV myocardial contraction is impaired in both hypertrophied and nonhypertrophied regions, and systolic LV wall asynchrony occurs in patients with HCM. (author)

  6. Liquid crystal television spatial light modulators

    Science.gov (United States)

    Liu, Hua-Kuang; Chao, Tien-Hsin

    1989-01-01

    The spatial light modulation characteristics and capabilities of the liquid crystal television (LCTV) spatial light modulators (SLMs) are discussed. A comparison of Radio Shack, Epson, and Citizen LCTV SLMs is made.

  7. Pulse shaping using a spatial light modulator

    CSIR Research Space (South Africa)

    Botha, N

    2009-07-01

    Full Text Available Femtosecond pulse shaping can be done by different kinds of pulse shapers, such as liquid crystal spatial light modulators (LC SLM), acousto optic modulators (AOM) and deformable and movable mirrors. A few applications where pulse shaping...

  8. Electrothermal Frequency Modulated Resonator for Mechanical Memory

    KAUST Repository

    Hafiz, Md Abdullah Al; Kosuru, Lakshmoji; Younis, Mohammad I.

    2016-01-01

    In this paper, we experimentally demonstrate a mechanical memory device based on the nonlinear dynamics of an electrostatically actuated microelectromechanical resonator utilizing an electrothermal frequency modulation scheme. The microstructure

  9. Modulation of Intracellular Quantum Dot to Fluorescent Protein Förster Resonance Energy Transfer via Customized Ligands and Spatial Control of Donor–Acceptor Assembly

    Directory of Open Access Journals (Sweden)

    Lauren D. Field

    2015-12-01

    Full Text Available Understanding how to controllably modulate the efficiency of energy transfer in Förster resonance energy transfer (FRET-based assemblies is critical to their implementation as sensing modalities. This is particularly true for sensing assemblies that are to be used as the basis for real time intracellular sensing of intracellular processes and events. We use a quantum dot (QD donor -mCherry acceptor platform that is engineered to self-assemble in situ wherein the protein acceptor is expressed via transient transfection and the QD donor is microinjected into the cell. QD-protein assembly is driven by metal-affinity interactions where a terminal polyhistidine tag on the protein binds to the QD surface. Using this system, we show the ability to modulate the efficiency of the donor–acceptor energy transfer process by controllably altering either the ligand coating on the QD surface or the precise location where the QD-protein assembly process occurs. Intracellularly, a short, zwitterionic ligand mediates more efficient FRET relative to longer ligand species that are based on the solubilizing polymer, poly(ethylene glycol. We further show that a greater FRET efficiency is achieved when the QD-protein assembly occurs free in the cytosol compared to when the mCherry acceptor is expressed tethered to the inner leaflet of the plasma membrane. In the latter case, the lower FRET efficiency is likely attributable to a lower expression level of the mCherry acceptor at the membrane combined with steric hindrance. Our work points to some of the design considerations that one must be mindful of when developing FRET-based sensing schemes for use in intracellular sensing.

  10. GCCS Spatial Data Base Module

    National Research Council Canada - National Science Library

    Bell, Paul

    1998-01-01

    .... JMTK is divided into three primary areas: (1) Visual, (2) Analysis (non-visual), and (3) Spatial Data Base (SDBM). The primary objective of the SDBM effort is to define, design, develop and test mapping, charting and geodesy...

  11. Electron paramagnetic resonance field-modulation eddy-current analysis of silver-plated graphite resonators

    Science.gov (United States)

    Mett, Richard R.; Anderson, James R.; Sidabras, Jason W.; Hyde, James S.

    2005-09-01

    Magnetic field modulation is often introduced into a cylindrical TE011 electron paramagnetic resonance (EPR) cavity through silver plating over a nonconductive substrate. The plating thickness must be many times the skin depth of the rf and smaller than the skin depth of the modulation. We derive a parameter that quantifies the modulation field penetration and find that it also depends on resonator dimensions. Design criteria based on this parameter are presented graphically. This parameter is then used to predict the behavior of eddy currents in substrates of moderate conductivity, such as graphite. The conductivity of the graphite permits improved plating uniformity and permits use of electric discharge machining (EDM) techniques to make the resonator. EDM offers precision tolerances of 0.005 mm and is suitable for small, complicated shapes that are difficult to machine by other methods. Analytic predictions of the modulation penetration are compared with the results of finite-element simulations. Simulated magnetic field modulation uniformity and penetration are shown for several elemental coils and structures including the plated graphite TE011 cavity. Fabrication and experimental testing of the structure are discussed. Spatial inhomogeneity of the modulation phase is also investigated by computer simulation. We find that the modulation phase is uniform to within 1% over the TE011 cavity. Structures of lower symmetry have increased phase nonuniformity.

  12. Spatial neutron kinetic module of ROSA code

    International Nuclear Information System (INIS)

    Cherezov, A.L.; Shchukin, N.V.

    2009-01-01

    A spatial neutron kinetic module was developed for computer code ROSA. The paper describes a numerical scheme used in the module for resolving neutron kinetic equations. Analytical integration for delayed neutrons emitters method and direct numerical integration method (Gear's method) were analyzed. The two methods were compared on their efficiency and accuracy. Both methods were verified with test problems. The results obtained in the verification studies were presented [ru

  13. Spatial light modulation for mode conditioning

    DEFF Research Database (Denmark)

    Glückstad, Jesper; Palima, Darwin

    We demonstrate patented techniques for generating tuneable complex field distributions for controllable coupling to high-order guided modes of micro-structured fibres. The optical Fourier transform of binary phase-only patterns which are encoded on a computer-controlled spatial light modulator......, generates complex field distributions for selective launching of a desired mode. Both the amplitude and the phase of the programmable fields are modulated by straightforward and fast adjustments of simple pre-defined binary phase-only diffractive patterns. Experiments demonstrate tuneable coupling...

  14. Spatial Modulation in the Underwater Acoustic Communication Channel

    National Research Council Canada - National Science Library

    Kilfoyle, Daniel

    2000-01-01

    .... The technique, termed spatial modulation, seeks to control the spatial distribution of signal energy such that multiple parallel communication channels are supported by the single, physical ocean channel...

  15. Enhanced Interferometry with Programmable Spatial Light Modulator

    Science.gov (United States)

    2010-06-07

    Interferometry, Spatial Light Modulator, Surface Accuracy, Optics, Mirror, Zernike , Freeform Optics, Null Testing, Hartman, Wavefront 16. SECURITY...S L M P ix e l- c a m Tilted Flat Mirror L a s e r PV. ± 3.4 λ -Tilt by the flat mirror, ~7 waves ~ 14 fringes Interferogram 3D view (Various...Interferogram ( 3D view) x- profile y- profile (Various waveplates and telescopes not shown) SLM can compensate tilted wavefronts with an accuracy of

  16. Optical encryption using pseudorandom complex spatial modulation.

    Science.gov (United States)

    Sarkadi, Tamás; Koppa, Pál

    2012-12-01

    In this paper we propose a new (to our knowledge) complex spatial modulation method to encode data pages applicable in double random phase encryption (DRPE) to make the system more resistant to brute-force attack. The proposed modulation method uses data page pixels with random phase and amplitude values with the condition that the intensity of the interference of light from two adjacent pixels should correspond to the encoded information. A differential phase contrast technique is applied to recover the data page at the output of the system. We show that the proposed modulation method can enhance the robustness of the DRPE technique using point spread function analysis. Key space expansion is determined by numeric model calculations.

  17. All-dielectric metamaterial frequency selective surface based on spatial arrangement ceramic resonators

    Science.gov (United States)

    Li, Liyang; Wang, Jun; Feng, Mingde; Ma, Hua; Wang, Jiafu; Du, Hongliang; Qu, Shaobo

    In this paper, we demonstrate a method of designing all-dielectric metamaterial frequency selective surface (FSS) with ceramic resonators in spatial arrangement. Compared with the traditional way, spatial arrangement provides a flexible way to handle the permutation and combination of different ceramic resonators. With this method, the resonance response can be adjusted easily to achieve pass/stop band effects. As an example, a stop band spatial arrangement all-dielectric metamaterial FSS is designed. Its working band is in 11.65-12.23GHz. By adjusting permittivity and geometrical parameters of ceramic resonators, we can easily modulate the resonances, band pass or band stop characteristic, as well as the working band.

  18. Electrothermal Frequency Modulated Resonator for Mechanical Memory

    KAUST Repository

    Hafiz, Md Abdullah Al

    2016-08-18

    In this paper, we experimentally demonstrate a mechanical memory device based on the nonlinear dynamics of an electrostatically actuated microelectromechanical resonator utilizing an electrothermal frequency modulation scheme. The microstructure is deliberately fabricated as an in-plane shallow arch to achieve geometric quadratic nonlinearity. We exploit this inherent nonlinearity of the arch and drive it at resonance with minimal actuation voltage into the nonlinear regime, thereby creating softening behavior, hysteresis, and coexistence of states. The hysteretic frequency band is controlled by the electrothermal actuation voltage. Binary values are assigned to the two allowed dynamical states on the hysteretic response curve of the arch resonator with respect to the electrothermal actuation voltage. Set-and-reset operations of the memory states are performed by applying controlled dc pulses provided through the electrothermal actuation scheme, while the read-out operation is performed simultaneously by measuring the motional current through a capacitive detection technique. This novel memory device has the advantages of operating at low voltages and under room temperature. [2016-0043

  19. Axially modulated arch resonator for logic and memory applications

    KAUST Repository

    Hafiz, Md Abdullah Al; Tella, Sherif Adekunle; Alcheikh, Nouha; Fariborzi, Hossein; Younis, Mohammad I.

    2018-01-01

    We demonstrate reconfigurable logic and random access memory devices based on an axially modulated clamped-guided arch resonator. The device is electrostatically actuated and the motional signal is capacitively sensed, while the resonance frequency

  20. Spatial Modulation Improves Performance in CTIS

    Science.gov (United States)

    Bearman, Gregory H.; Wilson, Daniel W.; Johnson, William R.

    2009-01-01

    Suitably formulated spatial modulation of a scene imaged by a computed-tomography imaging spectrometer (CTIS) has been found to be useful as a means of improving the imaging performance of the CTIS. As used here, "spatial modulation" signifies the imposition of additional, artificial structure on a scene from within the CTIS optics. The basic principles of a CTIS were described in "Improvements in Computed- Tomography Imaging Spectrometry" (NPO-20561) NASA Tech Briefs, Vol. 24, No. 12 (December 2000), page 38 and "All-Reflective Computed-Tomography Imaging Spectrometers" (NPO-20836), NASA Tech Briefs, Vol. 26, No. 11 (November 2002), page 7a. To recapitulate: A CTIS offers capabilities for imaging a scene with spatial, spectral, and temporal resolution. The spectral disperser in a CTIS is a two-dimensional diffraction grating. It is positioned between two relay lenses (or on one of two relay mirrors) in a video imaging system. If the disperser were removed, the system would produce ordinary images of the scene in its field of view. In the presence of the grating, the image on the focal plane of the system contains both spectral and spatial information because the multiple diffraction orders of the grating give rise to multiple, spectrally dispersed images of the scene. By use of algorithms adapted from computed tomography, the image on the focal plane can be processed into an image cube a three-dimensional collection of data on the image intensity as a function of the two spatial dimensions (x and y) in the scene and of wavelength (lambda). Thus, both spectrally and spatially resolved information on the scene at a given instant of time can be obtained, without scanning, from a single snapshot; this is what makes the CTIS such a potentially powerful tool for spatially, spectrally, and temporally resolved imaging. A CTIS performs poorly in imaging some types of scenes in particular, scenes that contain little spatial or spectral variation. The computed spectra of

  1. Wave propagation in spatially modulated tubes

    Energy Technology Data Exchange (ETDEWEB)

    Ziepke, A., E-mail: ziepke@itp.tu-berlin.de; Martens, S.; Engel, H. [Institut für Theoretische Physik, Hardenbergstraße 36, EW 7-1, Technische Universität Berlin, 10623 Berlin (Germany)

    2016-09-07

    We investigate wave propagation in rotationally symmetric tubes with a periodic spatial modulation of cross section. Using an asymptotic perturbation analysis, the governing quasi-two-dimensional reaction-diffusion equation can be reduced into a one-dimensional reaction-diffusion-advection equation. Assuming a weak perturbation by the advection term and using projection method, in a second step, an equation of motion for traveling waves within such tubes can be derived. Both methods predict properly the nonlinear dependence of the propagation velocity on the ratio of the modulation period of the geometry to the intrinsic width of the front, or pulse. As a main feature, we observe finite intervals of propagation failure of waves induced by the tube’s modulation and derive an analytically tractable condition for their occurrence. For the highly diffusive limit, using the Fick-Jacobs approach, we show that wave velocities within modulated tubes are governed by an effective diffusion coefficient. Furthermore, we discuss the effects of a single bottleneck on the period of pulse trains. We observe period changes by integer fractions dependent on the bottleneck width and the period of the entering pulse train.

  2. Evolution of dense spatially modulated electron bunches

    Science.gov (United States)

    Balal, N.; Bratman, V. L.; Friedman, A.

    2018-03-01

    An analytical theory describing the dynamics of relativistic moving 1D electron pulses (layers) with the density modulation affected by a space charge has been revised and generalized for its application to the formation of dense picosecond bunches from linear accelerators with laser-driven photo injectors, and its good agreement with General Particle Tracer simulations has been demonstrated. Evolution of quasi-one-dimensional bunches (disks), for which the derived formulas predict longitudinal expansion, is compared with that for thin and long electron cylinders (threads), for which the excitation of non-linear waves with density spikes was found earlier by Musumeci et al. [Phys. Rev. Lett. 106(18), 184801 (2011)] and Musumeci et al. [Phys. Rev. Spec. Top. -Accel. Beams 16(10), 100701 (2013)]. Both types of bunches can be used for efficiency enhancement of THz sources based on the Doppler frequency up-shifted coherent spontaneous radiation of electrons. Despite the strong Coulomb repulsion, the periodicity of a preliminary modulation in dense 1D layers persists during their expansion in the most interesting case of a relatively small change in particle energy. However, the period of modulation increases and its amplitude decreases in time. In the case of a large change in electron energy, the uniformity of periodicity is broken due to different relativistic changes in longitudinal scales along the bunch: the "period" of modulation decreases and its amplitude increases from the rear to the front boundary. Nevertheless, the use of relatively long electron bunches with a proper preliminary spatial modulation of density can provide a significantly higher power and a narrower spectrum of coherent spontaneous radiation of dense bunches than in the case of initially short single bunches with the same charge.

  3. Method and apparatus for resonant frequency waveform modulation

    Science.gov (United States)

    Taubman, Matthew S [Richland, WA

    2011-06-07

    A resonant modulator device and process are described that provide enhanced resonant frequency waveforms to electrical devices including, e.g., laser devices. Faster, larger, and more complex modulation waveforms are obtained than can be obtained by use of conventional current controllers alone.

  4. Nonlinear Resonance Islands and Modulational Effects in a Proton Synchrotron

    Energy Technology Data Exchange (ETDEWEB)

    Satogata, Todd Jeffrey [Northwestern Univ., Evanston, IL (United States)

    1993-01-01

    We examine both one-dimensional and two-dimensional nonlinear resonance islands created in the transverse phase space of a proton synchrotron by nonlinear magnets. We also examine application of the theoretical framework constructed to the phenomenon of modulational diffusion in a collider model of the Fermilab Tevatron. For the one-dimensional resonance island system, we examine the effects of two types of modulational perturbations on the stability of these resonance islands: tune modulation and beta function modulation. Hamiltonian models are presented which predict stability boundaries that depend on only three paramders: the strength and frequency of the modulation and the frequency of small oscillations inside the resonance island. These. models are compared to particle tracking with excellent agreement. The tune modulation model is also successfully tested in experiment, where frequency domain analysis coupled with tune modulation is demonstrated to be useful in measuring the strength of a nonlinear resonance. Nonlinear resonance islands are also examined in two transverse dimensions in the presence of coupling and linearly independent crossing resonances. We present a first-order Hamiltonian model which predicts fixed point locations, but does not reproduce small oscillation frequencies seen in tracking; therefore in this circumstance such a model is inadequate. Particle tracking is presented which shows evidence of two-dimensional persistent signals, and we make suggestions on methods for observing such signals in future experiment.

  5. Competing Turing and Faraday Instabilities in Longitudinally Modulated Passive Resonators.

    Science.gov (United States)

    Copie, François; Conforti, Matteo; Kudlinski, Alexandre; Mussot, Arnaud; Trillo, Stefano

    2016-04-08

    We experimentally investigate the interplay of Turing (modulational) and Faraday (parametric) instabilities in a bistable passive nonlinear resonator. The Faraday branch is induced via parametric resonance owing to a periodic modulation of the resonator dispersion. We show that the bistable switching dynamics is dramatically affected by the competition between the two instability mechanisms, which dictates two completely novel scenarios. At low detunings from resonance, switching occurs between the stable stationary lower branch and the Faraday-unstable upper branch, whereas at high detunings we observe the crossover between the Turing and Faraday periodic structures. The results are well explained in terms of the universal Lugiato-Lefever model.

  6. The time course of attention modulation elicited by spatial uncertainty.

    Science.gov (United States)

    Huang, Dan; Liang, Huilou; Xue, Linyan; Wang, Meijian; Hu, Qiyi; Chen, Yao

    2017-09-01

    Uncertainty regarding the target location is an influential factor for spatial attention. Modulation in spatial uncertainty can lead to adjustments in attention scope and variations in attention effects. Hence, investigating spatial uncertainty modulation is important for understanding the underlying mechanism of spatial attention. However, the temporal dynamics of this modulation remains unclear. To evaluate the time course of spatial uncertainty modulation, we adopted a Posner-like attention orienting paradigm with central or peripheral cues. Different numbers of cues were used to indicate the potential locations of the target and thereby manipulate the spatial uncertainty level. The time interval between the onsets of the cue and the target (stimulus onset asynchrony, SOA) varied from 50 to 2000ms. We found that under central cueing, the effect of spatial uncertainty modulation could be detected from 200 to 2000ms after the presence of the cues. Under peripheral cueing, the effect of spatial uncertainty modulation was observed from 50 to 2000ms after cueing. Our results demonstrate that spatial uncertainty modulation produces robust and sustained effects on target detection speed. The time course of this modulation is influenced by the cueing method, which suggests that discrepant processing procedures are involved under different cueing conditions. Copyright © 2017 Elsevier Ltd. All rights reserved.

  7. Multiple Spatial Coherence Resonances and Spatial Patterns in a Noise-Driven Heterogeneous Neuronal Network

    Science.gov (United States)

    Li, Yu-Ye; Ding, Xue-Li

    2014-12-01

    Heterogeneity of the neurons and noise are inevitable in the real neuronal network. In this paper, Gaussian white noise induced spatial patterns including spiral waves and multiple spatial coherence resonances are studied in a network composed of Morris—Lecar neurons with heterogeneity characterized by parameter diversity. The relationship between the resonances and the transitions between ordered spiral waves and disordered spatial patterns are achieved. When parameter diversity is introduced, the maxima of multiple resonances increases first, and then decreases as diversity strength increases, which implies that the coherence degrees induced by noise are enhanced at an intermediate diversity strength. The synchronization degree of spatial patterns including ordered spiral waves and disordered patterns is identified to be a very low level. The results suggest that the nervous system can profit from both heterogeneity and noise, and the multiple spatial coherence resonances are achieved via the emergency of spiral waves instead of synchronization patterns.

  8. Multiple Spatial Coherence Resonances and Spatial Patterns in a Noise-Driven Heterogeneous Neuronal Network

    International Nuclear Information System (INIS)

    Li Yu-Ye; Ding Xue-Li

    2014-01-01

    Heterogeneity of the neurons and noise are inevitable in the real neuronal network. In this paper, Gaussian white noise induced spatial patterns including spiral waves and multiple spatial coherence resonances are studied in a network composed of Morris—Lecar neurons with heterogeneity characterized by parameter diversity. The relationship between the resonances and the transitions between ordered spiral waves and disordered spatial patterns are achieved. When parameter diversity is introduced, the maxima of multiple resonances increases first, and then decreases as diversity strength increases, which implies that the coherence degrees induced by noise are enhanced at an intermediate diversity strength. The synchronization degree of spatial patterns including ordered spiral waves and disordered patterns is identified to be a very low level. The results suggest that the nervous system can profit from both heterogeneity and noise, and the multiple spatial coherence resonances are achieved via the emergency of spiral waves instead of synchronization patterns. (interdisciplinary physics and related areas of science and technology)

  9. Nonlinear resonance islands and modulational effects in a proton synchrotron

    International Nuclear Information System (INIS)

    Satogata, T.J.

    1993-01-01

    The authors examine one-dimensional and two-dimensional nonlinear resonance islands created in the transverse phase space of a proton synchrotron by nonlinear magnets. The authors examine application of the theoretical framework constructed to the phenomenon of modulational diffusion in a collider model of the Fermilab Tevatron. For the one-dimensional resonance island system, the authors examine the effects of two types of modulational perturbations on the stability of these resonance islands: Tune modulation and beta function modulation. Hamiltonian models are presented which predict stability boundaries that depend on only three parameters: The strength and frequency of the modulation and the frequency of small oscillations inside the resonance island. The tune modulation model is successfully tested in experiment, where frequency domain analysis coupled with tune modulation is demonstrated to be useful in measuring the strength of a nonlinear resonance. Nonlinear resonance islands are examined in two transverse dimensions in the presence of coupling and linearly independent crossing resonances. The authors present a first-order Hamiltonian model which predicts fixed point locations, but does not reproduce small oscillation frequencies seen in tracking. Particle tracking is presented which shows evidence of two-dimensional persistent signals, and the authors make suggestions on methods for observing such signals in future experiment. The authors apply the tune modulation stability diagram to the explicitly two-dimensional phenomenon of modulational diffusion in the Fermilab Tevatron with beam-beam kicks as the source of nonlinearity. The amplitude growth created by this mechanism in simulation is exponential rather than root-time as predicted by modulational diffusion models. The authors comment upon the luminosity and lifetime limitations such a mechanism implies in a proton storage ring

  10. Axially modulated arch resonator for logic and memory applications

    KAUST Repository

    Hafiz, Md Abdullah Al

    2018-01-17

    We demonstrate reconfigurable logic and random access memory devices based on an axially modulated clamped-guided arch resonator. The device is electrostatically actuated and the motional signal is capacitively sensed, while the resonance frequency is modulated through an axial electrostatic force from the guided side of the microbeam. A multi-physics finite element model is used to verify the effectiveness of the axial modulation. We present two case studies: first, a reconfigurable two-input logic gate based on the linear resonance frequency modulation, and second, a memory element based on the hysteretic frequency response of the resonator working in the nonlinear regime. The energy consumptions of the device for both logic and memory operations are in the range of picojoules, promising for energy efficient alternative computing paradigm.

  11. Resonant transducers for solid-state plasma density modulation

    Energy Technology Data Exchange (ETDEWEB)

    Hallock, Gary A., E-mail: hallock@ece.utexas.edu [The University of Texas at Austin, Austin, Texas 78701 (United States); Meier, Mark A., E-mail: mark.a.meier@exxonmobil.com [ExxonMobil Upstream Research Company, Houston, Texas 77389 (United States)

    2016-04-15

    We have developed transducers capable of modulating the plasma density and plasma density gradients in indium antimonide. These transducers make use of piezoelectric drivers to excite acoustic pressure resonance at 3λ/2, generating large amplitude standing waves and plasma density modulations. The plasma density has been directly measured using a laser diagnostic. A layered media model shows good agreement with the experimental measurements.

  12. Spatial localization in nuclear magnetic resonance spectroscopy

    International Nuclear Information System (INIS)

    Keevil, Stephen F

    2006-01-01

    The ability to select a discrete region within the body for signal acquisition is a fundamental requirement of in vivo NMR spectroscopy. Ideally, it should be possible to tailor the selected volume to coincide exactly with the lesion or tissue of interest, without loss of signal from within this volume or contamination with extraneous signals. Many techniques have been developed over the past 25 years employing a combination of RF coil properties, static magnetic field gradients and pulse sequence design in an attempt to meet these goals. This review presents a comprehensive survey of these techniques, their various advantages and disadvantages, and implications for clinical applications. Particular emphasis is placed on the reliability of the techniques in terms of signal loss, contamination and the effect of nuclear relaxation and J-coupling. The survey includes techniques based on RF coil and pulse design alone, those using static magnetic field gradients, and magnetic resonance spectroscopic imaging. Although there is an emphasis on techniques currently in widespread use (PRESS, STEAM, ISIS and MRSI), the review also includes earlier techniques, in order to provide historical context, and techniques that are promising for future use in clinical and biomedical applications. (topical review)

  13. Magnetic Resonance Microscopy Spatially Resolved NMR Techniques and Applications

    CERN Document Server

    Codd, Sarah

    2008-01-01

    This handbook and ready reference covers materials science applications as well as microfluidic, biomedical and dental applications and the monitoring of physicochemical processes. It includes the latest in hardware, methodology and applications of spatially resolved magnetic resonance, such as portable imaging and single-sided spectroscopy. For materials scientists, spectroscopists, chemists, physicists, and medicinal chemists.

  14. Electrical Modulation of Fano Resonance in Plasmonic Nanostructures Using Graphene

    DEFF Research Database (Denmark)

    Emani, Naresh K.; Chung, Ting-Fung; Kildishev, Alexander V.

    2014-01-01

    Pauli blocking of interband transistions gives rise to tunable optical properties in single layer graphene (SLG). This effect is exploited in a graphene-nanoantenna hybrid device where Fano resonant plasmonic nanostructures are fabricated on top of a graphene sheet. The use of Fano resonant eleme......-element simulations. Our approach can be used for development of next generation of tunable plasmonic and hybrid nanophotonic devices.......Pauli blocking of interband transistions gives rise to tunable optical properties in single layer graphene (SLG). This effect is exploited in a graphene-nanoantenna hybrid device where Fano resonant plasmonic nanostructures are fabricated on top of a graphene sheet. The use of Fano resonant...... elements enhances the interaction of incident radiation with the graphene sheet and enables efficient electrical modulation of the plasmonic resonance. We observe electrically controlled damping in the Fano resonances occurring at approximately 2 μm, and the results are verified by full-wave 3D finite...

  15. Spatially resolved remote measurement of temperature by neutron resonance absorption

    Energy Technology Data Exchange (ETDEWEB)

    Tremsin, A.S., E-mail: ast@ssl.berkeley.edu [Space Sciences Laboratory, University of California at Berkeley, 7 Gauss Way, Berkeley, CA 94720 (United States); Kockelmann, W.; Pooley, D.E. [STFC, Rutherford Appleton Laboratory, ISIS Facility, Didcot OX11 0QX (United Kingdom); Feller, W.B. [NOVA Scientific, Inc., 10 Picker Road, Sturbridge, MA 01566 (United States)

    2015-12-11

    Deep penetration of neutrons into most engineering materials enables non-destructive studies of their bulk properties. The existence of sharp resonances in neutron absorption spectra enables isotopically-resolved imaging of elements present in a sample, as demonstrated by previous studies. At the same time the Doppler broadening of resonance peaks provides a method of remote measurement of temperature distributions within the same sample. This technique can be implemented at a pulsed neutron source with a short initial pulse allowing for the measurement of the energy of each registered neutron by the time of flight technique. A neutron counting detector with relatively high timing and spatial resolution is used to demonstrate the possibility to obtain temperature distributions across a 100 µm Ta foil with ~millimeter spatial resolution. Moreover, a neutron transmission measurement over a wide energy range can provide spatially resolved sample information such as temperature, elemental composition and microstructure properties simultaneously.

  16. GCCS Spatial Data Base Module Extensions

    National Research Council Canada - National Science Library

    Bell, Paul

    1998-01-01

    .... JMTK is divided into three primary areas: (1) Visual, (2) Analysis (nonvisual), and (3) Spatial Data Base (SDBM). The primary objective of the SDBM effort is to define, design, develop and test mapping, charting and geodesy...

  17. Spatial Resolution of a Wedge Shaped MSGC Module

    CERN Document Server

    Bachmann, Sebastian

    1997-01-01

    A banana shaped closed design MSGC detector module was tested together with silicon detectors and other MSGCs in a 100 GeV muon beam. Despite of an undesirable geometry of the test setup, a spatial resolution below 40 micron m was reached. The efficiency of the module, defined by track reconstruction, shows to be 95,6 percent

  18. Giant magnetic modulation of a planar, hybrid metamolecule resonance

    International Nuclear Information System (INIS)

    Gregory, Simon A; Stenning, Gavin B G; Bowden, Graham J; De Groot, Peter A J; Zheludev, Nikolay I

    2014-01-01

    Coupling magnetic elements to metamaterial structures creates hybrid metamolecules with new opportunities. Here we report on the magnetic control of a metamolecule resonance, by utilizing the interaction between a single split ring resonator (SRR) and a magnetic thin film of permalloy. To suppress eddy current shielding, the permalloy films are patterned into arrays of 30–500 μm diameter discs. Strong hybridized resonances were observed at the anticrossing between the split ring resonance and the ferromagnetic resonance (FMR) of the permalloy. In particular, it is possible to achieve 40 dB modulation of the electric (symmetric) mode of the SRR on sweeping the applied magnetic field through the SRR/FMR anticrossing. The results open the way to the design of planar metamaterials, with potential applications in nonlinear metamaterials, tunable metamaterials and spintronics. (papers)

  19. A low-voltage high-speed terahertz spatial light modulator using active metamaterial

    Directory of Open Access Journals (Sweden)

    Saroj Rout

    2016-11-01

    Full Text Available An all solid-state metamaterial based terahertz (THz spatial light modulator (SLM is presented which uses high mobility 2DEG to manipulate the metamaterial resonant frequency (0.45 THz leading to terahertz wave modulation. The 2DEG is created by embedding pseudomorphic high-electron mobility transistors in the capacitive gap of each electrical-LC resonator, allowing the charge density to be controlled with very low voltage (1 V and modulating speeds up to 10 MHz while consuming sub-milliwatt power. We have demonstrated our SLM as a 2 × 2 pixel array operating around 0.45 THz by raster scanning a 6 × 6 image of an occluded metal object behind a thick polystyrene screen using a single-pixel THz imaging setup.

  20. Neutron detection in the frame of spatial magnetic spin resonance

    Energy Technology Data Exchange (ETDEWEB)

    Jericha, Erwin, E-mail: jericha@ati.ac.at [TU Wien, Atominstitut, Stadionallee 2, 1020 Wien (Austria); Bosina, Joachim [TU Wien, Atominstitut, Stadionallee 2, 1020 Wien (Austria); Austrian Academy of Sciences, Stefan Meyer Institute, Boltzmanngasse 3, 1090 Wien (Austria); Institut Laue–Langevin, 71 Avenue des Martyrs, 38042 Grenoble (France); Geltenbort, Peter [Institut Laue–Langevin, 71 Avenue des Martyrs, 38042 Grenoble (France); Hino, Masahiro [Kyoto University, Research Reactor Institute, Kumatori, Osaka 590-0494 (Japan); Mach, Wilfried [TU Wien, Atominstitut, Stadionallee 2, 1020 Wien (Austria); Oda, Tatsuro [Kyoto University, Department of Nuclear Engineering, Kyoto 615-8540 (Japan); Badurek, Gerald [TU Wien, Atominstitut, Stadionallee 2, 1020 Wien (Austria)

    2017-02-11

    This work is related to neutron detection in the context of the polarised neutron optics technique of spatial magnetic spin resonance. By this technique neutron beams may be tailored in their spectral distribution and temporal structure. We have performed experiments with very cold neutrons (VCN) at the high-flux research reactor of the Institut Laue Langevin (ILL) in Grenoble to demonstrate the potential of this method. A combination of spatially and temporally resolving neutron detection allowed us to characterize a prototype neutron resonator. With this detector we were able to record neutron time-of-flight spectra, assess and minimise neutron background and provide for normalisation of the spectra owing to variations in reactor power and ambient conditions at the same time.

  1. The effect of compressibility on the Alfven spatial resonance heating

    International Nuclear Information System (INIS)

    Azevedo, C.A.

    1984-01-01

    The effect of compressibility of magnetic field line on the damping rate of Alfven spatial resonance heating for a high beta plasma (Kinetic pressure/magnetic pressure) was analysed, using the ideal MHD (Magnetohydrodynamic) model in cylindrical geometry for a diffuse θ-pinch with conducting wall. The dispersion relation was obtained solving the equation of motion in the plasma and vacuum regions together with boundary conditions. (Author) [pt

  2. Modulated Acquisition of Spatial Distortion Maps

    Directory of Open Access Journals (Sweden)

    Aleš Švigelj

    2013-08-01

    Full Text Available This work discusses a novel approach to image acquisition which improves the robustness of captured data required for 3D range measurements. By applying a pseudo-random code modulation to sequential acquisition of projected patterns the impact of environmental factors such as ambient light and mutual interference is significantly reduced. The proposed concept has been proven with an experimental range sensor based on the laser triangulation principle. The proposed design can potentially enhance the use of this principle to a variety of outdoor applications, such as autonomous vehicles, pedestrians’ safety, collision avoidance, and many other tasks, where robust real-time distance detection in real world environment is crucial.

  3. Modulated acquisition of spatial distortion maps.

    Science.gov (United States)

    Volkov, Alexey; Gros, Jerneja Zganec; Zganec, Mario; Javornik, Tomaž; Svigelj, Aleš

    2013-08-21

    This work discusses a novel approach to image acquisition which improves the robustness of captured data required for 3D range measurements. By applying a pseudo-random code modulation to sequential acquisition of projected patterns the impact of environmental factors such as ambient light and mutual interference is significantly reduced. The proposed concept has been proven with an experimental range sensor based on the laser triangulation principle. The proposed design can potentially enhance the use of this principle to a variety of outdoor applications, such as autonomous vehicles, pedestrians' safety, collision avoidance, and many other tasks, where robust real-time distance detection in real world environment is crucial.

  4. Fourier optical cryptosystem using complex spatial modulation

    International Nuclear Information System (INIS)

    Sarkadi, T; Koppa, P

    2014-01-01

    Our goal is to enhance the security level of a Fourier optical encryption system. Therefore we propose a Mach–Zehnder interferometer based encryption setup. The input data is organized in a binary array, and it is encoded in the two wave fronts propagated in the arms of the interferometer. Both input wave fronts are independently encrypted by Fourier systems, hence the proposed method has two encryption keys. During decryption, the encrypted wave fronts are propagated through the interferometer setup. The interference pattern of the output shows the reconstructed data in cases where the correct decryption Fourier keys are used. We propose a novel input image modulation method with a user defined phase parameter. We show that the security level of the proposed cryptosystem can be enhanced by an optimally chosen phase parameter. (paper)

  5. Modulation of the Object/Background Interaction by Spatial Frequency

    Directory of Open Access Journals (Sweden)

    Yanju Ren

    2011-05-01

    Full Text Available With regard to the relationship between object and background perception in the natural scene images, functional isolation hypothesis and interactive hypothesis were proposed. Based on previous studies, the present study investigated the role of spatial frequency in the relationship between object and background perception in the natural scene images. In three experiments, participants reported the object, background, or both after seeing each picture for 500 ms followed by a mask. The authors found that (a backgrounds were identified more accurately when they contained a consistent rather than an inconsistent object, independently of spatial frequency; (b objects were identified more accurately in a consistent than an inconsistent background under the condition of low spatial frequencies but not high spatial frequencies; (c spatial frequency modulation remained when both objects and backgrounds were reported simultaneously. The authors conclude that object/background interaction is partially dependent on spatial frequency.

  6. Stochastic resonance based on modulation instability in spatiotemporal chaos.

    Science.gov (United States)

    Han, Jing; Liu, Hongjun; Huang, Nan; Wang, Zhaolu

    2017-04-03

    A novel dynamic of stochastic resonance in spatiotemporal chaos is presented, which is based on modulation instability of perturbed partially coherent wave. The noise immunity of chaos can be reinforced through this effect and used to restore the coherent signal information buried in chaotic perturbation. A theoretical model with fluctuations term is derived from the complex Ginzburg-Landau equation via Wigner transform. It shows that through weakening the nonlinear threshold and triggering energy redistribution, the coherent component dominates the instability damped by incoherent component. The spatiotemporal output showing the properties of stochastic resonance may provide a potential application of signal encryption and restoration.

  7. Spatially modulated structural colour in bird feathers

    Science.gov (United States)

    Parnell, Andrew J.; Washington, Adam L.; Mykhaylyk, Oleksandr O.; Hill, Christopher J.; Bianco, Antonino; Burg, Stephanie L.; Dennison, Andrew J. C.; Snape, Mary; Cadby, Ashley J.; Smith, Andrew; Prevost, Sylvain; Whittaker, David M.; Jones, Richard A. L.; Fairclough, J. Patrick. A.; Parker, Andrew R.

    2015-12-01

    Eurasian Jay (Garrulus glandarius) feathers display periodic variations in the reflected colour from white through light blue, dark blue and black. We find the structures responsible for the colour are continuous in their size and spatially controlled by the degree of spinodal phase separation in the corresponding region of the feather barb. Blue structures have a well-defined broadband ultra-violet (UV) to blue wavelength distribution; the corresponding nanostructure has characteristic spinodal morphology with a lengthscale of order 150 nm. White regions have a larger 200 nm nanostructure, consistent with a spinodal process that has coarsened further, yielding broader wavelength white reflectance. Our analysis shows that nanostructure in single bird feather barbs can be varied continuously by controlling the time the keratin network is allowed to phase separate before mobility in the system is arrested. Dynamic scaling analysis of the single barb scattering data implies that the phase separation arrest mechanism is rapid and also distinct from the spinodal phase separation mechanism i.e. it is not gelation or intermolecular re-association. Any growing lengthscale using this spinodal phase separation approach must first traverse the UV and blue wavelength regions, growing the structure by coarsening, resulting in a broad distribution of domain sizes.

  8. Spatially modulated structural colour in bird feathers.

    Science.gov (United States)

    Parnell, Andrew J; Washington, Adam L; Mykhaylyk, Oleksandr O; Hill, Christopher J; Bianco, Antonino; Burg, Stephanie L; Dennison, Andrew J C; Snape, Mary; Cadby, Ashley J; Smith, Andrew; Prevost, Sylvain; Whittaker, David M; Jones, Richard A L; Fairclough, J Patrick A; Parker, Andrew R

    2015-12-21

    Eurasian Jay (Garrulus glandarius) feathers display periodic variations in the reflected colour from white through light blue, dark blue and black. We find the structures responsible for the colour are continuous in their size and spatially controlled by the degree of spinodal phase separation in the corresponding region of the feather barb. Blue structures have a well-defined broadband ultra-violet (UV) to blue wavelength distribution; the corresponding nanostructure has characteristic spinodal morphology with a lengthscale of order 150 nm. White regions have a larger 200 nm nanostructure, consistent with a spinodal process that has coarsened further, yielding broader wavelength white reflectance. Our analysis shows that nanostructure in single bird feather barbs can be varied continuously by controlling the time the keratin network is allowed to phase separate before mobility in the system is arrested. Dynamic scaling analysis of the single barb scattering data implies that the phase separation arrest mechanism is rapid and also distinct from the spinodal phase separation mechanism i.e. it is not gelation or intermolecular re-association. Any growing lengthscale using this spinodal phase separation approach must first traverse the UV and blue wavelength regions, growing the structure by coarsening, resulting in a broad distribution of domain sizes.

  9. Spatially correlated disorder in striped precursor magnetic modulations

    International Nuclear Information System (INIS)

    Porta, Marcel; Castan, Teresa; LLoveras, Pol; Planes, Antoni; Saxena, Avadh

    2007-01-01

    We use a Ginzburg-Landau model that includes long-range dipolar interactions and spatially correlated quenched-in disorder coupled to the local magnetization to study the properties of the precursor magnetic modulations as a function of the characteristics of the disorder. We find that although the modulation pattern is very robust and does not depend on details of the pair correlation function G(r), the scaling behaviour of the characteristic length of the striped magnetic modulations depends on the behaviour of G(r) for small values of r

  10. Electronic modulation of infrared radiation in graphene plasmonic resonators.

    Science.gov (United States)

    Brar, Victor W; Sherrott, Michelle C; Jang, Min Seok; Kim, Seyoon; Kim, Laura; Choi, Mansoo; Sweatlock, Luke A; Atwater, Harry A

    2015-05-07

    All matter at finite temperatures emits electromagnetic radiation due to the thermally induced motion of particles and quasiparticles. Dynamic control of this radiation could enable the design of novel infrared sources; however, the spectral characteristics of the radiated power are dictated by the electromagnetic energy density and emissivity, which are ordinarily fixed properties of the material and temperature. Here we experimentally demonstrate tunable electronic control of blackbody emission from graphene plasmonic resonators on a silicon nitride substrate. It is shown that the graphene resonators produce antenna-coupled blackbody radiation, which manifests as narrow spectral emission peaks in the mid-infrared. By continuously varying the nanoresonator carrier density, the frequency and intensity of these spectral features can be modulated via an electrostatic gate. This work opens the door for future devices that may control blackbody radiation at timescales beyond the limits of conventional thermo-optic modulation.

  11. Optimal Fisher Discriminant Ratio for an Arbitrary Spatial Light Modulator

    Science.gov (United States)

    Juday, Richard D.

    1999-01-01

    Optimizing the Fisher ratio is well established in statistical pattern recognition as a means of discriminating between classes. I show how to optimize that ratio for optical correlation intensity by choice of filter on an arbitrary spatial light modulator (SLM). I include the case of additive noise of known power spectral density.

  12. Creation and detection of optical modes with spatial light modulators

    CSIR Research Space (South Africa)

    Forbes, A

    2016-06-01

    Full Text Available (1979). 24. J. A. Davis, K. O. Valade´z, and D. M. Cottrell, “Encoding amplitude and phase information onto a binary phase-only spatial light modulator,” Appl. Opt. 42, 2003–2008 (2003). 25. E. Bolduc, N. Bent, E. Santamato, E. Karimi, and R. W. Boyd...

  13. Beam-quality measurements using a spatial light modulator

    CSIR Research Space (South Africa)

    Schulze, C

    2012-11-01

    Full Text Available We present a fast and easy technique for measuring the beam propagation ratio, M2, of laser beams using a spatial light modulator. Our technique is based on digitally simulating the free-space propagation of light, thus eliminating the need...

  14. Temporal Modulation Detection Depends on Sharpness of Spatial Tuning.

    Science.gov (United States)

    Zhou, Ning; Cadmus, Matthew; Dong, Lixue; Mathews, Juliana

    2018-04-25

    Prior research has shown that in electrical hearing, cochlear implant (CI) users' speech recognition performance is related in part to their ability to detect temporal modulation (i.e., modulation sensitivity). Previous studies have also shown better speech recognition when selectively stimulating sites with good modulation sensitivity rather than all stimulation sites. Site selection based on channel interaction measures, such as those using imaging or psychophysical estimates of spread of neural excitation, has also been shown to improve speech recognition. This led to the question of whether temporal modulation sensitivity and spatial selectivity of neural excitation are two related variables. In the present study, CI users' modulation sensitivity was compared for sites with relatively broad or narrow neural excitation patterns. This was achieved by measuring temporal modulation detection thresholds (MDTs) at stimulation sites that were significantly different in their sharpness of the psychophysical spatial tuning curves (PTCs) and measuring MDTs at the same sites in monopolar (MP) and bipolar (BP) stimulation modes. Nine postlingually deafened subjects implanted with Cochlear Nucleus® device took part in the study. Results showed a significant correlation between the sharpness of PTCs and MDTs, indicating that modulation detection benefits from a more spatially restricted neural activation pattern. There was a significant interaction between stimulation site and mode. That is, using BP stimulation only improved MDTs at stimulation sites with broad PTCs but had no effect or sometimes a detrimental effect on MDTs at stimulation sites with sharp PTCs. This interaction could suggest that a criterion number of nerve fibers is needed to achieve optimal temporal resolution, and, to achieve optimized speech recognition outcomes, individualized selection of site-specific current focusing strategies may be necessary. These results also suggest that the removal of

  15. Spatially tuned normalization explains attention modulation variance within neurons.

    Science.gov (United States)

    Ni, Amy M; Maunsell, John H R

    2017-09-01

    Spatial attention improves perception of attended parts of a scene, a behavioral enhancement accompanied by modulations of neuronal firing rates. These modulations vary in size across neurons in the same brain area. Models of normalization explain much of this variance in attention modulation with differences in tuned normalization across neurons (Lee J, Maunsell JHR. PLoS One 4: e4651, 2009; Ni AM, Ray S, Maunsell JHR. Neuron 73: 803-813, 2012). However, recent studies suggest that normalization tuning varies with spatial location both across and within neurons (Ruff DA, Alberts JJ, Cohen MR. J Neurophysiol 116: 1375-1386, 2016; Verhoef BE, Maunsell JHR. eLife 5: e17256, 2016). Here we show directly that attention modulation and normalization tuning do in fact covary within individual neurons, in addition to across neurons as previously demonstrated. We recorded the activity of isolated neurons in the middle temporal area of two rhesus monkeys as they performed a change-detection task that controlled the focus of spatial attention. Using the same two drifting Gabor stimuli and the same two receptive field locations for each neuron, we found that switching which stimulus was presented at which location affected both attention modulation and normalization in a correlated way within neurons. We present an equal-maximum-suppression spatially tuned normalization model that explains this covariance both across and within neurons: each stimulus generates equally strong suppression of its own excitatory drive, but its suppression of distant stimuli is typically less. This new model specifies how the tuned normalization associated with each stimulus location varies across space both within and across neurons, changing our understanding of the normalization mechanism and how attention modulations depend on this mechanism. NEW & NOTEWORTHY Tuned normalization studies have demonstrated that the variance in attention modulation size seen across neurons from the same cortical

  16. Diffuse optical imaging using spatially and temporally modulated light

    Science.gov (United States)

    O'Sullivan, Thomas D.; Cerussi, Albert E.; Cuccia, David J.; Tromberg, Bruce J.

    2012-07-01

    The authors describe the development of diffuse optical imaging (DOI) technologies, specifically the use of spatial and temporal modulation to control near infrared light propagation in thick tissues. We present theory and methods of DOI focusing on model-based techniques for quantitative, in vivo measurements of endogenous tissue absorption and scattering properties. We specifically emphasize the common conceptual framework of the scalar photon density wave for both temporal and spatial frequency-domain approaches. After presenting the history, theoretical foundation, and instrumentation related to these methods, we provide a brief review of clinical and preclinical applications from our research as well as our outlook on the future of DOI technology.

  17. Sensitivity and spatial resolution for electron-spin-resonance detection by magnetic resonance force microscopy

    International Nuclear Information System (INIS)

    Zhang, Z.; Roukes, M.L.; Hammel, P.C.

    1996-01-01

    The signal intensity of electron spin resonance in magnetic resonance force microscopy (MRFM) experiments employing periodic saturation of the electron spin magnetization is determined by four parameters: the rf field H 1 , the modulation level of the bias field H m , the spin relaxation time τ 1 , and the magnetic size R(∂H/∂z) of the sample. Calculations of the MRFM spectra obtained from a 2,2-diphenyl-1-picrylhydrazyl particle have been performed for various conditions. The results are compared with experimental data and excellent agreement is found. The systematic variation of the signal intensity as a function of H 1 and H m provides a powerful tool to characterize the MRFM apparatus. copyright 1996 American Institute of Physics

  18. Double resonance modulation characteristics of optically injection-locked Fabry–Perot lasers

    International Nuclear Information System (INIS)

    Dorogush, E S; Afonenko, A A

    2015-01-01

    The distributed resonator model is used to show the presence of several resonance responses on the modulation characteristic of optically injection-locked Fabry–Perot lasers. The positions of the resonance peaks on the modulation characteristic are determined by the resonator length and frequency detuning of optical injection. It is shown that an appropriate choice of the resonator length and injection locking conditions allows one to obtain efficient modulation in two ranges near 40 – 60 GHz or to increase the direct modulation bandwidth up to 50 GHz. (control of laser radiation parameters)

  19. Double resonance modulation characteristics of optically injection-locked Fabry–Perot lasers

    Energy Technology Data Exchange (ETDEWEB)

    Dorogush, E S; Afonenko, A A [Belarusian State University, Minsk (Belarus)

    2015-12-31

    The distributed resonator model is used to show the presence of several resonance responses on the modulation characteristic of optically injection-locked Fabry–Perot lasers. The positions of the resonance peaks on the modulation characteristic are determined by the resonator length and frequency detuning of optical injection. It is shown that an appropriate choice of the resonator length and injection locking conditions allows one to obtain efficient modulation in two ranges near 40 – 60 GHz or to increase the direct modulation bandwidth up to 50 GHz. (control of laser radiation parameters)

  20. Thermal effects in microfluidics with thermal conductivity spatially modulated

    Science.gov (United States)

    Vargas Toro, Agustín.

    2014-05-01

    A heat transfer model on a microfluidic is resolved analytically. The model describes a fluid at rest between two parallel plates where each plate is maintained at a differentially specified temperature and the thermal conductivity of the microfluidic is spatially modulated. The heat transfer model in such micro-hydrostatic configuration is analytically resolved using the technique of the Laplace transform applying the Bromwich Integral and the Residue theorem. The temperature outline in the microfluidic is presented as an infinite series of Bessel functions. It is shown that the result for the thermal conductivity spatially modulated has as a particular case the solution when the thermal conductivity is spatially constant. All computations were performed using the computer algebra software Maple. It is claimed that the analytical obtained results are important for the design of nanoscale devices with applications in biotechnology. Furthermore, it is suggested some future research lines such as the study of the heat transfer model in a microfluidic resting between coaxial cylinders with radially modulated thermal conductivity in order to achieve future developments in this area.

  1. Flicker in a twisted nematic spatial light modulator

    Science.gov (United States)

    Calderón-Hermosillo, Yuliana; García-Márquez, Jorge; Espinosa-Luna, Rafael; Ochoa, Noé Alcalá; López, Víctor; Aguilar, Alberto; Noé-Arias, Enrique; Alayli, Yasser

    2013-06-01

    Liquid Crystal on Silicon (LCoS) Spatial Light Modulators (SLM) are widely used for their capability to control beams howbeit fluctuations in phase and amplitude. It is then necessary to understand the negative effects of these fluctuations, also known as flicker, and the means to mitigate them. The flicker is observed either as high frequency variations of polarization, attenuation or high phase fluctuations on the wave front modulated by the LCoS device. Here, we compare the flicker behavior in a twisted nematic (TN) LCoS-SLM for different polarization schemes and temperatures. The quantitative evaluation shows that flicker is effectively reduced only by chilling the LCoS panel to temperatures just below 0 °C but, the LCoS modulation capability is also affected.

  2. Spatial distribution measured by the modulation transfer function

    International Nuclear Information System (INIS)

    Rossi, P.; Brice, D.K.; Doyle, B.L.

    2003-01-01

    Spatial distributions in ion micro-beam and IBA experimental practice are regularly characterized through the parameters of FWHM and tail area percentage (TF, tail fraction). Linear and stationary transducer theory allows these distributions to be described in the Fourier-dual frequency space, and provides an indirect method to evaluate them through measurement of the modulation transfer function (MTF). We suggest direct measurement of MTF by employing bar pattern grids, similar to those used for calibration of radiological equipment. Assuming spatial distributions of the form exp(-(|αx|) η ), we are able to relate the MTF measurements to the more popular FWHM and TF. This new approach to determine spatial resolution can become a standard for use by the micro-beam community

  3. Topologically determined optimal stochastic resonance responses of spatially embedded networks

    International Nuclear Information System (INIS)

    Gosak, Marko; Marhl, Marko; Korosak, Dean

    2011-01-01

    We have analyzed the stochastic resonance phenomenon on spatial networks of bistable and excitable oscillators, which are connected according to their location and the amplitude of external forcing. By smoothly altering the network topology from a scale-free (SF) network with dominating long-range connections to a network where principally only adjacent oscillators are connected, we reveal that besides an optimal noise intensity, there is also a most favorable interaction topology at which the best correlation between the response of the network and the imposed weak external forcing is achieved. For various distributions of the amplitudes of external forcing, the optimal topology is always found in the intermediate regime between the highly heterogeneous SF network and the strong geometric regime. Our findings thus indicate that a suitable number of hubs and with that an optimal ratio between short- and long-range connections is necessary in order to obtain the best global response of a spatial network. Furthermore, we link the existence of the optimal interaction topology to a critical point indicating the transition from a long-range interactions-dominated network to a more lattice-like network structure.

  4. Optical particle trapping and dynamic manipulation using spatial light modulation

    DEFF Research Database (Denmark)

    Eriksen, René Lynge

    suitable for optical trapping. A phaseonly spatial light modulator (SLM) is used for the phase encoding of the laser beam. The SLM is controlled directly from a standard computer where phase information is represented as gray-scale image information. Experimentally, both linear and angular movements......This thesis deals with the spatial phase-control of light and its application for optical trapping and manipulation of micron-scale objects. Utilizing the radiation pressure, light exerts on dielectric micron-scale particles, functionality of optical tweezers can be obtained. Multiple intensity...... compression factors of two, which is not achievable with binary phase encoding, have been successfully demonstrated. In addition, the GPC method has been miniaturized and implemented in a planar optical platform and shown to work acceptably, with relatively high visibility. Furthermore, the GPC method has...

  5. Optical trapping and tweezing using a spatial light modulator

    CSIR Research Space (South Africa)

    Ismail, Y

    2009-07-01

    Full Text Available using a spatial light modulator Y.Ismail1,2, M. G. Mclaren1,3, A. Forbes1,2,4 1 CSIR National Laser Centre 2 School of Physics, University of KwaZulu-Natal 3 School of Physics, University of the Witwatersrand 4 School of Physics, University... of Stellenbosch Presented at the 2009 South African Institute of Physics Annual Conference University of KwaZulu-Natal Durban, South Africa 6-10 July 2009 Optical tweezing is based on the manipulation of micron sized particles in 3 dimensions 100X...

  6. A transfer-matrix method for spatially modulated structures

    International Nuclear Information System (INIS)

    Surda, A.

    1991-03-01

    A cluster transfer-matrix method convenient for calculation of spatially modulated structures of a wide class of lattice-gas models is developed. The method formulates the problem of calculation of the partition function in terms of non-linear mapping of effective multi-site fields. It is applied to a lattice-gas model qualitatively describing the system of oxygen atoms in the basal planes of high-temperature superconductors. The properties of an incommensurate structure occurring at intermediate temperatures are discussed in detail. (author). 21 refs, 15 figs

  7. Aberration compensation using a spatial light modulator LCD

    International Nuclear Information System (INIS)

    Amezquita, R; Rincon, O; Torres, Y M

    2011-01-01

    The dynamic correction of aberrations introduced in optical systems have been a widely discussed topic in the past 10 years. Adaptive optics is the most important developed field where the Shack-Hartmann sensors and deformable mirrors are used for the measurement and correction of wavefronts. In this paper, an interferometric set-up which uses a Spatial Light Modulator (SLM) as an active element is proposed. Using this SLM a procedure for the compensation of all phase aberrations present in the experimental setup is shown.

  8. Optimum condition for spatial ion cyclotron resonance in a multiple magnetic mirror field

    International Nuclear Information System (INIS)

    Mieno, Tetsu; Hatakeyama, Rikizo; Sato, Noriyoshi

    1988-01-01

    A Spatial cyclotron resonance of ion beams passing through a multiple magnetic mirror field is investigated experimentally by varying parameters of the multiple mirror field. The optimum resonance condition is realized with a decrease in the cell length of the multiple mirror along the beams to satisfy the local condition of the spatial ion cyclotron resonance. The results show a remarkable increase of nonadiabatic transfer of the beam energy into the transverse direction to the magnetic field. (author)

  9. Demonstration of spatial-light-modulation-based four-wave mixing in cold atoms

    Science.gov (United States)

    Juo, Jz-Yuan; Lin, Jia-Kang; Cheng, Chin-Yao; Liu, Zi-Yu; Yu, Ite A.; Chen, Yong-Fan

    2018-05-01

    Long-distance quantum optical communications usually require efficient wave-mixing processes to convert the wavelengths of single photons. Many quantum applications based on electromagnetically induced transparency (EIT) have been proposed and demonstrated at the single-photon level, such as quantum memories, all-optical transistors, and cross-phase modulations. However, EIT-based four-wave mixing (FWM) in a resonant double-Λ configuration has a maximum conversion efficiency (CE) of 25% because of absorptive loss due to spontaneous emission. An improved scheme using spatially modulated intensities of two control fields has been theoretically proposed to overcome this conversion limit. In this study, we first demonstrate wavelength conversion from 780 to 795 nm with a 43% CE by using this scheme at an optical density (OD) of 19 in cold 87Rb atoms. According to the theoretical model, the CE in the proposed scheme can further increase to 96% at an OD of 240 under ideal conditions, thereby attaining an identical CE to that of the previous nonresonant double-Λ scheme at half the OD. This spatial-light-modulation-based FWM scheme can achieve a near-unity CE, thus providing an easy method of implementing an efficient quantum wavelength converter for all-optical quantum information processing.

  10. Drug diffusion across skin with diffusivity spatially modulated

    Science.gov (United States)

    Montoya Arroyave, Isabel

    2014-05-01

    A diffusion and delivery model of a drug across the skin with diffusivity spatially modulated is formulated and solved analytically using computer algebra. The model is developed using one-dimensional diffusion equation with a diffusivity which is a function of position in the skin; with an initial condition which is describing that the drug is initially contained inside a therapeutic patch; with a boundary condition according to which the change in concentration in the patch is minimal, such that assumption of zero flux at the patch-skin interface is valid; and with other boundary condition according to which the microcirculation in the capillaries just below the dermis carries the drug molecules away from the site at a very fast rate, maintaining the inner concentration at 0. The model is solved analytically by the method of the Laplace transform, with Bromwich integral and residue theorem. The concentration profile of the drug in the skin is expressed as an infinite series of Bessel functions. The corresponding total amount of delivered drug is expressed as an infinite series of decreasing exponentials. Also, the corresponding effective time for the therapeutic patch is determined. All computations were performed using computer algebra software, specifically Maple. The analytical results obtained are important for understanding and improving currentapplications of therapeutic patches. For future research it is interesting to consider more general models of spatial modulation of the diffusivity and the possible application of other computer algebra software such as Mathematica and Maxima.

  11. Recent advances in IR liquid crystal spatial light modulators

    Science.gov (United States)

    Peng, Fenglin; Twieg, Robert J.; Wu, Shin-Tson

    2015-09-01

    Liquid crystal (LC) is an amazing class of electro-optic media; its applications span from visible to infrared, millimeter wave, and terahertz regions. In the visible and short-wavelength infrared (SWIR) regions, most LCs are highly transparent. However, to extend the electro-optic application of LCs into MWIR and LWIR, several key technical challenges have to be overcome: (1) low absorption loss, (2) high birefringence, (3) low operation voltage, and (4) fast response time. In the MWIR and LWIR regions, several fundamental molecular vibration bands and overtones exist, which contribute to high absorption loss. The absorbed light turns to heat and then alters the birefringence locally, which in turns causes spatially non-uniform phase modulation. To suppress the optical loss, several approaches have been investigated: (1) Employing thin cell gap by choosing a high birefringence LC mixture; (2) Shifting the absorption bands outside the spectral region of interest by deuteration, fluorination, or chlorination; (3) Reducing the overtone absorption by using a short alkyl chain. In this paper, we report some recently developed chlorinated LC compounds and mixtures with low absorption loss in the SWIR and MWIR regions. To achieve fast response time, we demonstrated a polymer network liquid crystal with 2π phase change at MWIR and response time less than 5 ms. Approaches to extend such a liquid crystal spatial light modulator to long-wavelength infrared will be discussed.

  12. Modulation of microsaccades by spatial frequency during object categorization.

    Science.gov (United States)

    Craddock, Matt; Oppermann, Frank; Müller, Matthias M; Martinovic, Jasna

    2017-01-01

    The organization of visual processing into a coarse-to-fine information processing based on the spatial frequency properties of the input forms an important facet of the object recognition process. During visual object categorization tasks, microsaccades occur frequently. One potential functional role of these eye movements is to resolve high spatial frequency information. To assess this hypothesis, we examined the rate, amplitude and speed of microsaccades in an object categorization task in which participants viewed object and non-object images and classified them as showing either natural objects, man-made objects or non-objects. Images were presented unfiltered (broadband; BB) or filtered to contain only low (LSF) or high spatial frequency (HSF) information. This allowed us to examine whether microsaccades were modulated independently by the presence of a high-level feature - the presence of an object - and by low-level stimulus characteristics - spatial frequency. We found a bimodal distribution of saccades based on their amplitude, with a split between smaller and larger microsaccades at 0.4° of visual angle. The rate of larger saccades (⩾0.4°) was higher for objects than non-objects, and higher for objects with high spatial frequency content (HSF and BB objects) than for LSF objects. No effects were observed for smaller microsaccades (<0.4°). This is consistent with a role for larger microsaccades in resolving HSF information for object identification, and previous evidence that more microsaccades are directed towards informative image regions. Copyright © 2016 Elsevier Ltd. All rights reserved.

  13. Experimental and numerical investigations of temporally and spatially periodic modulated wave trains

    Science.gov (United States)

    Houtani, H.; Waseda, T.; Tanizawa, K.

    2018-03-01

    A number of studies on steep nonlinear waves were conducted experimentally with the temporally periodic and spatially evolving (TPSE) wave trains and numerically with the spatially periodic and temporally evolving (SPTE) ones. The present study revealed that, in the vicinity of their maximum crest height, the wave profiles of TPSE and SPTE modulated wave trains resemble each other. From the investigation of the Akhmediev-breather solution of the nonlinear Schrödinger equation (NLSE), it is revealed that the dispersion relation deviated from the quadratic dependence of frequency on wavenumber and became linearly dependent instead. Accordingly, the wave profiles of TPSE and SPTE breathers agree. The range of this agreement is within the order of one wave group of the maximum crest height and persists during the long-term evolution. The findings extend well beyond the NLSE regime and can be applied to modulated wave trains that are highly nonlinear and broad-banded. This was demonstrated from the numerical wave tank simulations with a fully nonlinear potential flow solver based on the boundary element method, in combination with the nonlinear wave generation method based on the prior simulation with the higher-order spectral model. The numerical wave tank results were confirmed experimentally in a physical wave tank. The findings of this study unravel the fundamental nature of the nonlinear wave evolution. The deviation of the dispersion relation of the modulated wave trains occurs because of the nonlinear phase variation due to quasi-resonant interaction, and consequently, the wave geometry of temporally and spatially periodic modulated wave trains coincides.

  14. Speckless head-up display on two spatial light modulators

    Science.gov (United States)

    Siemion, Andrzej; Ducin, Izabela; Kakarenko, Karol; Makowski, Michał; Siemion, Agnieszka; Suszek, Jarosław; Sypek, Maciej; Wojnowski, Dariusz; Jaroszewicz, Zbigniew; Kołodziejczyk, Andrzej

    2010-12-01

    There is a continuous demand for the computer generated holograms to give an almost perfect reconstruction with a reasonable cost of manufacturing. One method of improving the image quality is to illuminate a Fourier hologram with a quasi-random, but well known, light field phase distribution. It can be achieved with a lithographically produced phase mask. Up to date, the implementation of the lithographic technique is relatively complex and time and money consuming, which is why we have decided to use two Spatial Light Modulators (SLM). For the correctly adjusted light polarization a SLM acts as a pure phase modulator with 256 adjustable phase levels between 0 and 2π. The two modulators give us an opportunity to use the whole surface of the device and to reduce the size of the experimental system. The optical system with one SLM can also be used but it requires dividing the active surface into halves (one for the Fourier hologram and the second for the quasi-random diffuser), which implies a more complicated optical setup. A larger surface allows to display three Fourier holograms, each for one primary colour: red, green and blue. This allows to reconstruct almost noiseless colourful dynamic images. In this work we present the results of numerical simulations of image reconstructions with the use of two SLM displays.

  15. Estimation and Compensation of aberrations in Spatial Light Modulators

    International Nuclear Information System (INIS)

    Arias, Augusto; Castaneda, Roman

    2011-01-01

    The spatial light modulator (SLM) Holoeye LC-R720 is based on LCoS (Liquid Crystal on Silicon) technology. Due to the induced curvatures on the silicon plate by the production process, there are static aberrations in the wave-fronts modified by the SLM. In order to calculate the aberrated wave-front we used phase-shifting interferometry, an optimization algorithm for far field propagation, and the geometric characterization of the focal spot along the caustic. Zernike polynomials were used for expanding and comparing the wave-fronts. The aberration compensation was carried out by displaying the conjugated transmittance on the SLM. The complexity of the experimental setup and the requirements of the digital processing of each estimation method were comparatively analyzed.

  16. The tempo-spatially modulated polarization atmosphere Michelson interferometer.

    Science.gov (United States)

    Zhang, ChunMin; Zhu, HuaChun; Zhao, Baochang

    2011-05-09

    A space-based tempo-spatially modulated polarization atmosphere Michelson interferometer (TSMPAMI) is described. It uses the relative movement between the TSMPAMI and the measured target to change optical path difference. The acquisition method of interferogram is presented. The atmospheric temperatures and horizontal winds can be derived from the optical observations. The measurement errors of the winds and temperatures are discussed through simulations. In the presence of small-scale structures of the atmospheric fields, the errors are found to be significantly influenced by the mismatch of the scenes observed by the adjacent CCD sub-areas aligned along the orbiter's track during successive measurements due to the orbital velocity and the exposure time. For most realistic conditions of the orbit and atmosphere, however, the instrument is proven suitable for measuring the atmospheric parameters. © 2011 Optical Society of America

  17. Spiral Waves and Multiple Spatial Coherence Resonances Induced by Colored Noise in Neuronal Network

    International Nuclear Information System (INIS)

    Tang Zhao; Li Yuye; Xi Lei; Jia Bing; Gu Huaguang

    2012-01-01

    Gaussian colored noise induced spatial patterns and spatial coherence resonances in a square lattice neuronal network composed of Morris-Lecar neurons are studied. Each neuron is at resting state near a saddle-node bifurcation on invariant circle, coupled to its nearest neighbors by electronic coupling. Spiral waves with different structures and disordered spatial structures can be alternately induced within a large range of noise intensity. By calculating spatial structure function and signal-to-noise ratio (SNR), it is found that SNR values are higher when the spiral structures are simple and are lower when the spatial patterns are complex or disordered, respectively. SNR manifest multiple local maximal peaks, indicating that the colored noise can induce multiple spatial coherence resonances. The maximal SNR values decrease as the correlation time of the noise increases. These results not only provide an example of multiple resonances, but also show that Gaussian colored noise play constructive roles in neuronal network. (general)

  18. Stochastic resonance in a single-mode laser driven by frequency modulated signal and coloured noises

    Institute of Scientific and Technical Information of China (English)

    Jin Guo-Xiang; Zhang Liang-Ying; Cao Li

    2009-01-01

    By adding frequency modulated signals to the intensity equation of gain-noise model of the single-mode laser driven by two coloured noises which are correlated, this paper uses the linear approximation method to calculate the power spectrum and signal-to-noise ratio (SNR) of the laser intensity. The results show that the SNR appears typical stochastic resonance with the variation of intensity of the pump noise and quantum noise. As the amplitude of a modulated signal has effects on the SNR, it shows suppression, monotone increasing, stochastic resonance, and multiple stochastic resonance with the variation of the frequency of a carrier signal and modulated signal.

  19. Spatial confinement of ferromagnetic resonances in honeycomb antidot lattices

    International Nuclear Information System (INIS)

    Krivoruchko, V.N.; Marchenko, A.I.

    2012-01-01

    We report on a theoretical investigation of the magnetic static and dynamic properties of a thin ferromagnetic film with honeycomb lattice of circular antidots using micromagnetic simulations and analytical calculations. The theoretical model is based on the Landau–Lifshitz equations and directly accounts for the effects of the magnetic state nonuniformity. A direct calculation of local dynamic susceptibility tensor yields that the resonance spectra consist of four different quasi-uniform modes of the magnetization precession related to the confinement of magnetic domains by the hole mesh. Three of four resonant modes follow a two-fold variation with respect to the in-plane orientation of the applied magnetic field. The easy axes of these modes are mutually rotated by 60° and combine to yield the apparent six-fold configurational anisotropy. Additionally, a mode with intrinsic six-fold symmetry behavior exists, as well. Micromagnetic calculations of the local dynamic susceptibility tensor allow identifying the magnetic unit cell areas/domains responsible for each resonance mode. - Highlights: ► We study the magnetic static and dynamic properties of honeycomb antidot lattices. ► Micromagnetic simulation and analytical calculation were used. ► Four quasi-uniform precession modes exist in resonance spectra. ► The antidot unit cell areas responsible for each resonance mode were identified.

  20. Non-monotonic resonance in a spatially forced Lengyel-Epstein model

    Energy Technology Data Exchange (ETDEWEB)

    Haim, Lev [Physics Department, Ben-Gurion University of the Negev, Beer-Sheva 84105 (Israel); Department of Oncology, Soroka University Medical Center, Beer-Sheva 84101 (Israel); Hagberg, Aric [Center for Nonlinear Studies, Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Meron, Ehud [Physics Department, Ben-Gurion University of the Negev, Beer-Sheva 84105 (Israel); Department of Solar Energy and Environmental Physics, BIDR, Ben-Gurion University of the Negev, Sede Boqer Campus, Midreshet Ben-Gurion 84990 (Israel)

    2015-06-15

    We study resonant spatially periodic solutions of the Lengyel-Epstein model modified to describe the chlorine dioxide-iodine-malonic acid reaction under spatially periodic illumination. Using multiple-scale analysis and numerical simulations, we obtain the stability ranges of 2:1 resonant solutions, i.e., solutions with wavenumbers that are exactly half of the forcing wavenumber. We show that the width of resonant wavenumber response is a non-monotonic function of the forcing strength, and diminishes to zero at sufficiently strong forcing. We further show that strong forcing may result in a π/2 phase shift of the resonant solutions, and argue that the nonequilibrium Ising-Bloch front bifurcation can be reversed. We attribute these behaviors to an inherent property of forcing by periodic illumination, namely, the increase of the mean spatial illumination as the forcing amplitude is increased.

  1. Graphene metamaterial spatial light modulator for infrared single pixel imaging.

    Science.gov (United States)

    Fan, Kebin; Suen, Jonathan Y; Padilla, Willie J

    2017-10-16

    High-resolution and hyperspectral imaging has long been a goal for multi-dimensional data fusion sensing applications - of interest for autonomous vehicles and environmental monitoring. In the long wave infrared regime this quest has been impeded by size, weight, power, and cost issues, especially as focal-plane array detector sizes increase. Here we propose and experimentally demonstrated a new approach based on a metamaterial graphene spatial light modulator (GSLM) for infrared single pixel imaging. A frequency-division multiplexing (FDM) imaging technique is designed and implemented, and relies entirely on the electronic reconfigurability of the GSLM. We compare our approach to the more common raster-scan method and directly show FDM image frame rates can be 64 times faster with no degradation of image quality. Our device and related imaging architecture are not restricted to the infrared regime, and may be scaled to other bands of the electromagnetic spectrum. The study presented here opens a new approach for fast and efficient single pixel imaging utilizing graphene metamaterials with novel acquisition strategies.

  2. Remote distractor effects and saccadic inhibition: spatial and temporal modulation.

    Science.gov (United States)

    Walker, Robin; Benson, Valerie

    2013-09-12

    The onset of a visual distractor remote from a saccade target is known to increase saccade latency (the remote distractor effect [RDE]). In addition, distractors may also selectively inhibit saccades that would be initiated about 90 ms after distractor onset (termed saccadic inhibition [SI]). Recently, it has been proposed that the transitory inhibition of saccades (SI) may underlie the increase in mean latency (RDE). In a first experiment, the distractor eccentricity was manipulated, and a robust RDE that was strongly modulated by distractor eccentricity was observed. However, the underlying latency distributions did not reveal clear evidence of SI. A second experiment manipulated distractor spatial location and the timing of the distractor onset in relation to the target. An RDE was again observed with remote distractors away from the target axis and under conditions with early-onset distractors that would be unlikely to produce SI, whereas later distractor onsets produced an RDE along with some evidence of an SI effect. A third experiment using a mixed block of target-distractor stimulus-onset asynchronies (SOAs) revealed an RDE that varied with both distractor eccentricity and SOA and changes to latency distributions consistent with the timing of SI. We argue that the notion that SI underpins the RDE is similar to the earlier argument that express saccades underlie the fixation offset (gap) effect and that changes in mean latency and to the shape of the underlying latency distributions following a visual onset may involve more than one inhibitory process.

  3. Measurement of elastic modules of structural ceramic by acoustic resonance

    International Nuclear Information System (INIS)

    Ahn, Bong Young; Lee Seong Suck; Kim, Young Gil

    1993-01-01

    Elastic moduli of structural ceramic materials, Al 2 O 3 , SiC, Si 3 N 4 , were measured by acoustic resonance method. Young's modulus, shear modulus, and Poisson's ratio were calculated from the torsional and flexural resonant frequencies, densities, and the dimensions of the specimen. The results by acoustic resonance method were compared with the results by ultrasonic method and the differences were less than 4%.

  4. Modulation and rehabilitation of spatial neglect by sensory stimulation.

    Science.gov (United States)

    Kerkhoff, Georg

    2003-01-01

    After unilateral cortical or subcortical, often parieto-temporal lesions, patients exhibit a marked neglect of their contralateral space and/or body side. These patients are severely disabled in all daily activities, have a poor rehabilitation outcome and therefore require professional treatment. Unfortunately, effective treatments for neglect are just in the process of development. The present chapter reviews three aspects related to the rehabilitation of neglect. The first part summarizes findings about spontaneous recovery in patients and experimental animals with neglect. The second part deals with techniques and studies evaluating short-term sensory modulation effects in neglect. In contrast to many other neurological syndromes spatial neglect may be modulated transiently but dramatically in its severity by sensory (optokinetic, neck proprioceptive, vestibular, attentional, somatosensory-magnetic) stimulation. In part three, current treatment approaches are summarized, with a focus on three novel techniques: repetitive optokinetic stimulation, neck vibration training and peripheral somatosensory-magnetic stimulation. Recent studies of repetitive optokinetic as well as neck vibratory treatment both indicate significantly greater as well as multimodal improvements in neglect symptomatology as compared to the standard treatment of neglect. This clear superiority might result from the partial (re)activation of a distributed, multisensory vestibular network in the lesioned hemisphere. Somatosensory-magnetic stimulation of the neglected or extinguishing hand provides another feasible, non-invasive stimulation technique. It may be particularly suited for the rehabilitation of somatosensory extinction and unawareness of the contralesional body side. Finally, pharmacological approaches for the treatment of neglect are shortly addressed. Isolated drug treatment of neglect is currently no successful rehabilitation strategy due to inconsistent results as well as possible

  5. Transmission Property of Directly Modulated Signals Enhanced by a Micro-ring Resonator

    DEFF Research Database (Denmark)

    An, Yi; Lorences Riesgo, Abel; Seoane, Jorge

    2012-01-01

    A silicon micro-ring resonator is used to enhance the modulation speed of a 10-Gbit/s directly modulated laser to 40 Gbit/s. The generated signal is transmitted error free over 4.5 km SSMF. Dispersion tolerance is also studied....

  6. Internal resonances in periodically modulated long Josephson junctions

    DEFF Research Database (Denmark)

    Larsen, Britt Hvolbæk; Mygind, Jesper; Ustinov, Alexey V.

    1995-01-01

    Current-voltage (I-V) characteristics of long Josephson junctions with a periodic lattice of localized inhomogeneities are studied. The interaction between the moving fluxons and the inhomogeneities causes resonant steps in the IV-curve. Some of these steps are due to a synchronization to resonant...... Fiske modes in the sub-junctions formed between the inhomogeneities. The voltage positions of the resonant steps oscillate as function of the applied magnetic field with a period corresponding to the inclusion of one magnetic flux quantum, Φ0=h/2e, per sub-junction. A qualitative explanation that takes...

  7. Axially Modulated Clamped-Guided Arch Resonator for Memory and Logic Applications

    KAUST Repository

    Hafiz, Md Abdullah Al; Tella, Sherif Adekunle; Alcheikh, Nouha; Fariborzi, Hossein; Younis, Mohammad I.

    2017-01-01

    We experimentally demonstrate memory and logic devices based on an axially modulated clamped-guided arch resonator. The device are electrostatically actuated and capacitively sensed, while the resonance frequency modulation is achieved through an axial electrostatic force from the guided side of the clamped-guided arch microbeam. We present two case studies: first, a dynamic memory based on the nonlinear frequency response of the resonator, and second, a reprogrammable two-input logic gate based on the linear frequency modulation of the resonator. These devices show energy cost per memory/logic operation in pJ, are fully compatible with CMOS fabrication processes, have the potential for on-chip system integration, and operate at room temperature.

  8. Axially Modulated Clamped-Guided Arch Resonator for Memory and Logic Applications

    KAUST Repository

    Hafiz, Md Abdullah Al

    2017-11-03

    We experimentally demonstrate memory and logic devices based on an axially modulated clamped-guided arch resonator. The device are electrostatically actuated and capacitively sensed, while the resonance frequency modulation is achieved through an axial electrostatic force from the guided side of the clamped-guided arch microbeam. We present two case studies: first, a dynamic memory based on the nonlinear frequency response of the resonator, and second, a reprogrammable two-input logic gate based on the linear frequency modulation of the resonator. These devices show energy cost per memory/logic operation in pJ, are fully compatible with CMOS fabrication processes, have the potential for on-chip system integration, and operate at room temperature.

  9. AUS module MIRANDA - a data preparation code based on multiregion resonance theory

    International Nuclear Information System (INIS)

    Robinson, G.S.

    1977-07-01

    MIRANDA is a data preparation module of the AUS reactor neutronics scheme and is used to prepare multigroup cross-section data which are pertinent to a particular reactor system from a general purpose multigroup library of cross sections. The cross-section library has been prepared from ENDF/B and includes temperature dependent data and resonance cross sections represented by subgroup parameters. The MIRANDA module includes a multiregion resonance calculation in slab, cylinder or cluster geometry, a homogeneous Bsub(L) flux solution, and a group condensation facility. Interaction with other AUS modules, particularly for burnup calculations, is provided. (Author)

  10. Spatial effects of Fano resonance in local tunneling conductivity in vicinity of impurity on semiconductor surface

    OpenAIRE

    Mantsevich, V. N.; Maslova, N. S.

    2009-01-01

    We present the results of local tunneling conductivity spatial distribution detailed theoretical investigations in vicinity of impurity atom for a wide range of applied bias voltage. We observed Fano resonance in tunneling conductivity resulting from interference between resonant tunneling channel through impurity energy level and direct tunneling channel between the tunneling contact leads. We have found that interference between tunneling channels strongly modifies form of tunneling conduct...

  11. Spatial coherence resonance and spatial pattern transition induced by the decrease of inhibitory effect in a neuronal network

    Science.gov (United States)

    Tao, Ye; Gu, Huaguang; Ding, Xueli

    2017-10-01

    Spiral waves were observed in the biological experiment on rat brain cortex with the application of carbachol and bicuculline which can block inhibitory coupling from interneurons to pyramidal neurons. To simulate the experimental spiral waves, a two-dimensional neuronal network composed of pyramidal neurons and inhibitory interneurons was built. By decreasing the percentage of active inhibitory interneurons, the random-like spatial patterns change to spiral waves and to random-like spatial patterns or nearly synchronous behaviors. The spiral waves appear at a low percentage of inhibitory interneurons, which matches the experimental condition that inhibitory couplings of the interneurons were blocked. The spiral waves exhibit a higher order or signal-to-noise ratio (SNR) characterized by spatial structure function than both random-like spatial patterns and nearly synchronous behaviors, which shows that changes of the percentage of active inhibitory interneurons can induce spatial coherence resonance-like behaviors. In addition, the relationship between the coherence degree and the spatial structures of the spiral waves is identified. The results not only present a possible and reasonable interpretation to the spiral waves observed in the biological experiment on the brain cortex with disinhibition, but also reveal that the spiral waves exhibit more ordered degree in spatial patterns.

  12. Composite modulation of Fano resonance in plasmonic microstructures by electric-field and microcavity

    International Nuclear Information System (INIS)

    Zhang, Fan; Wu, Chenyun; Yang, Hong; Hu, Xiaoyong; Gong, Qihuang

    2014-01-01

    Composite modulation of Fano resonance by using electric-field and microcavity simultaneously is realized in a plasmonic microstructure, which consists of a gold nanowire grating inserted into a Fabry-Perot microcavity composited of a liquid crystal layer sandwiched between two indium tin oxide layers. The Fano resonance wavelength varies with the applied voltage and the microcavity resonance. A large shift of 48 nm in the Fano resonance wavelength is achieved when the applied voltage is 20 V. This may provide a new way for the study of multi-functional integrated photonic circuits and chips based on plasmonic microstructures

  13. Composite modulation of Fano resonance in plasmonic microstructures by electric-field and microcavity

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Fan; Wu, Chenyun; Yang, Hong [State Key Laboratory for Mesoscopic Physics and Department of Physics, Peking University, Beijing 100871 (China); Hu, Xiaoyong, E-mail: xiaoyonghu@pku.edu.cn; Gong, Qihuang [State Key Laboratory for Mesoscopic Physics and Department of Physics, Peking University, Beijing 100871 (China); Collaborative Innovation Center of Quantum Matter, Beijing 100871 (China)

    2014-11-03

    Composite modulation of Fano resonance by using electric-field and microcavity simultaneously is realized in a plasmonic microstructure, which consists of a gold nanowire grating inserted into a Fabry-Perot microcavity composited of a liquid crystal layer sandwiched between two indium tin oxide layers. The Fano resonance wavelength varies with the applied voltage and the microcavity resonance. A large shift of 48 nm in the Fano resonance wavelength is achieved when the applied voltage is 20 V. This may provide a new way for the study of multi-functional integrated photonic circuits and chips based on plasmonic microstructures.

  14. Array-Enhanced Coherence Resonance: Nontrivial Effects of Heterogeneity and Spatial Independence of Noise

    International Nuclear Information System (INIS)

    Zhou, Changsong; Kurths, Juergen; Hu, Bambi

    2001-01-01

    We demonstrate the effect of coherence resonance in a heterogeneous array of coupled Fitz Hugh--Nagumo neurons. It is shown that coupling of such elements leads to a significantly stronger coherence compared to that of a single element. We report nontrivial effects of parameter heterogeneity and spatial independence of noise on array-enhanced coherence resonance; especially, we find that (i) the coherence increases as spatial correlation of the noise decreases, and (ii) inhomogeneity in the parameters of the array enhances the coherence. Our results have the implication that generic heterogeneity and background noise can play a constructive role to enhance the time precision of firing in neural systems

  15. Developing a training module on Gender & spatial justice

    NARCIS (Netherlands)

    Tummers, L.C.

    2015-01-01

    Justice is more than a legal matter: it has spatial and environmental implications and is related to engineering. The concept of ‘spatial justice’ was introduced in 2010 in planning by Eduard Soja. It indicates the accessibility of urban resources such as education and healthcare. Under democratic

  16. Ring resonator-based on-chip modulation transformer for high-performance phase-modulated microwave photonic links.

    Science.gov (United States)

    Zhuang, Leimeng; Taddei, Caterina; Hoekman, Marcel; Leinse, Arne; Heideman, René; van Dijk, Paulus; Roeloffzen, Chris

    2013-11-04

    In this paper, we propose and experimentally demonstrate a novel wideband on-chip photonic modulation transformer for phase-modulated microwave photonic links. The proposed device is able to transform phase-modulated optical signals into intensity-modulated versions (or vice versa) with nearly zero conversion of laser phase noise to intensity noise. It is constructed using waveguide-based ring resonators, which features simple architecture, stable operation, and easy reconfigurability. Beyond the stand-alone functionality, the proposed device can also be integrated with other functional building blocks of photonic integrated circuits (PICs) to create on-chip complex microwave photonic signal processors. As an application example, a PIC consisting of two such modulation transformers and a notch filter has been designed and realized in TriPleX(TM) waveguide technology. The realized device uses a 2 × 2 splitting circuit and 3 ring resonators with a free spectral range of 25 GHz, which are all equipped with continuous tuning elements. The device can perform phase-to-intensity modulation transform and carrier suppression simultaneously, which enables high-performance phase-modulated microwave photonics links (PM-MPLs). Associated with the bias-free and low-complexity advantages of the phase modulators, a single-fiber-span PM-MPL with a RF bandwidth of 12 GHz (3 dB-suppression band 6 to 18 GHz) has been demonstrated comprising the proposed PIC, where the achieved spurious-free dynamic range performance is comparable to that of Class-AB MPLs using low-biased Mach-Zehnder modulators.

  17. Modulation Spectroscopy and Opto Mechanics of Micro Toroidal Resonators

    Science.gov (United States)

    2017-08-01

    collaboration between UTRGV and Rice University. We planned 1) to acquire research instrumentation for experimental studies of micro-ring resonators on...reflected   from   the   ring   ( black   trace)   and   the   corresponding   I   and   Q   demodulation   outputs.  The

  18. Ultracompact electro-optic phase modulator based on III-V-on-silicon microdisk resonator.

    Science.gov (United States)

    Lloret, J; Kumar, R; Sales, S; Ramos, F; Morthier, G; Mechet, P; Spuesens, T; Van Thourhout, D; Olivier, N; Fédéli, J-M; Capmany, J

    2012-06-15

    A novel ultracompact electro-optic phase modulator based on a single 9 μm-diameter III-V microdisk resonator heterogeneously integrated on and coupled to a nanophotonic waveguide is presented. Modulation is enabled by effective index modification through carrier injection. Proof-of-concept implementation involving binary phase shift keying modulation format is assembled. A power imbalance of ∼0.6  dB between both symbols and a modulation rate up to 1.8 Gbps are demonstrated without using any special driving technique.

  19. Identify Dynamic Network Modules with Temporal and Spatial Constraints

    Energy Technology Data Exchange (ETDEWEB)

    Jin, R; McCallen, S; Liu, C; Almaas, E; Zhou, X J

    2007-09-24

    Despite the rapid accumulation of systems-level biological data, understanding the dynamic nature of cellular activity remains a difficult task. The reason is that most biological data are static, or only correspond to snapshots of cellular activity. In this study, we explicitly attempt to detangle the temporal complexity of biological networks by using compilations of time-series gene expression profiling data.We define a dynamic network module to be a set of proteins satisfying two conditions: (1) they form a connected component in the protein-protein interaction (PPI) network; and (2) their expression profiles form certain structures in the temporal domain. We develop the first efficient mining algorithm to discover dynamic modules in a temporal network, as well as frequently occurring dynamic modules across many temporal networks. Using yeast as a model system, we demonstrate that the majority of the identified dynamic modules are functionally homogeneous. Additionally, many of them provide insight into the sequential ordering of molecular events in cellular systems. We further demonstrate that identifying frequent dynamic network modules can significantly increase the signal to noise separation, despite the fact that most dynamic network modules are highly condition-specific. Finally, we note that the applicability of our algorithm is not limited to the study of PPI systems, instead it is generally applicable to the combination of any type of network and time-series data.

  20. Sensitivity Analysis and Requirements for Temporally and Spatially Resolved Thermometry Using Neutron Resonance Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez, Juan Carlos [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Barnes, Cris William [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Mocko, Michael Jeffrey [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Zavorka, Lukas [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2018-01-31

    This report is intended to examine the use of neutron resonance spectroscopy (NRS) to make time- dependent and spatially-resolved temperature measurements of materials in extreme conditions. Specifically, the sensitivities of the temperature estimate on neutron-beam and diagnostic parameters is examined. Based on that examination, requirements are set on a pulsed neutron-source and diagnostics to make a meaningful measurement.

  1. Spatial confinement of acoustic and optical waves in stubbed slab structure as optomechanical resonator

    Energy Technology Data Exchange (ETDEWEB)

    Li, Changsheng, E-mail: lcs135@163.com; Huang, Dan; Guo, Jierong

    2015-02-20

    We theoretically demonstrate that acoustic waves and optical waves can be spatially confined in the same micro-cavity by specially designed stubbed slab structure. The proposed structure presents both phononic and photonic band gaps from finite element calculation. The creation of cavity mode inside the band gap region provides strong localization of phonon and photon in the defect region. The practical parameters to inject cavity and work experimentally at telecommunication range are discussed. This structure can be precisely fabricated, hold promises to enhance acousto-optical interactions and design new applications as optomechanical resonator. - Highlights: • A resonator simultaneously supports acoustic and optical modes. • Strong spatial confinement and slow group velocity. • Potential to work as active optomechanical resonator.

  2. Method for spatially modulating X-ray pulses using MEMS-based X-ray optics

    Science.gov (United States)

    Lopez, Daniel; Shenoy, Gopal; Wang, Jin; Walko, Donald A.; Jung, Il-Woong; Mukhopadhyay, Deepkishore

    2015-03-10

    A method and apparatus are provided for spatially modulating X-rays or X-ray pulses using microelectromechanical systems (MEMS) based X-ray optics. A torsionally-oscillating MEMS micromirror and a method of leveraging the grazing-angle reflection property are provided to modulate X-ray pulses with a high-degree of controllability.

  3. Shaping and detecting mid-IR light with a spatial light modulator

    CSIR Research Space (South Africa)

    Maweza, Elijah L

    2016-10-01

    Full Text Available modulator Maweza, Elijah L Gailele, Lucas M Strauss, Hencharl J Litvin, Ihar Forbes, Andrew Dudley, Angela L ABSTRACT: We demonstrate the operation and calibration of a spatial light modulator in the mid-IR region by creating and measuring...

  4. Ferromagnetic resonance in a topographically modulated permalloy film

    Science.gov (United States)

    Sklenar, J.; Tucciarone, P.; Lee, R. J.; Tice, D.; Chang, R. P. H.; Lee, S. J.; Nevirkovets, I. P.; Heinonen, O.; Ketterson, J. B.

    2015-04-01

    A major focus within the field of magnonics involves the manipulation and control of spin-wave modes. This is usually done by patterning continuous soft magnetic films. Here, we report on work in which we use topographic modifications of a continuous magnetic thin film, rather than lithographic patterning techniques, to modify the ferromagnetic resonance spectrum. To demonstrate this technique we have performed in-plane, broadband, ferromagnetic resonance studies on a 100-nm-thick permalloy film sputtered onto a colloidal crystal with individual sphere diameters of 200 nm. Effects resulting from the, ideally, sixfold-symmetric underlying colloidal crystal were studied as a function of the in-plane field angle through experiment and micromagnetic modeling. Experimentally, we find two primary modes; the ratio of the intensities of these two modes exhibits a sixfold dependence. Detailed micromagnetic modeling shows that both modes are quasiuniform and nodeless in the unit cell but that they reside in different demagnetized regions of the unit cell. Our results demonstrate that topographic modification of magnetic thin films opens additional directions for manipulating ferromagnetic resonant excitations.

  5. "Chess-board pattern" spatial modulation of magnetization. Assessment of myocardial function

    DEFF Research Database (Denmark)

    Thomsen, C

    1992-01-01

    . Through spatial modulation of the magnetization the entire image can be labeled in different patterns. Two new pulse sequences are presented, giving a chess-board like spatial modulation. These pulse sequences have several advantages compared with the previously published methods, as the modulation time...... is half that required to obtain a 2-dimensional grid, the area in the image with high signal intensity was significantly larger, and the radiofrequency power deposition was substantially decreased. By labeling the heart at diastole the chess-board pattern tagging of the heart wall could be followed...

  6. Rewards modulate saccade latency but not exogenous spatial attention.

    Directory of Open Access Journals (Sweden)

    Stephen eDunne

    2015-07-01

    Full Text Available The eye movement system is sensitive to reward. However, whilst the eye movement system is extremely flexible, the extent to which changes to oculomotor behaviour induced by reward paradigms persist beyond the training period or transfer to other oculomotor tasks is unclear. To address these issues we examined the effects of presenting feedback that represented small monetary rewards to spatial locations on the latency of saccadic eye movements, the time-course of learning and extinction of the effects of rewarding saccades on exogenous spatial attention and oculomotor IOR. Reward feedback produced a relative facilitation of saccadic latency in a stimulus driven saccade task which persisted for 3 blocks of extinction trials. However this hemifield-specific effect failed to transfer to peripheral cueing tasks. We conclude that rewarding specific spatial locations is unlikely to induce long-term, systemic changes to the human oculomotor or attention systems.

  7. Rewards modulate saccade latency but not exogenous spatial attention.

    Science.gov (United States)

    Dunne, Stephen; Ellison, Amanda; Smith, Daniel T

    2015-01-01

    The eye movement system is sensitive to reward. However, whilst the eye movement system is extremely flexible, the extent to which changes to oculomotor behavior induced by reward paradigms persist beyond the training period or transfer to other oculomotor tasks is unclear. To address these issues we examined the effects of presenting feedback that represented small monetary rewards to spatial locations on the latency of saccadic eye movements, the time-course of learning and extinction of the effects of rewarding saccades on exogenous spatial attention and oculomotor inhibition of return. Reward feedback produced a relative facilitation of saccadic latency in a stimulus driven saccade task which persisted for three blocks of extinction trials. However, this hemifield-specific effect failed to transfer to peripheral cueing tasks. We conclude that rewarding specific spatial locations is unlikely to induce long-term, systemic changes to the human oculomotor or attention systems.

  8. Resonators for magnetohydrodynamic waves in the solar corona: The effect of modulation of radio emission

    International Nuclear Information System (INIS)

    Zaitsev, V.V.; Stepanov, A.V.

    1982-01-01

    It is shown that the existence of a minimum of the Alfven speed in the corona at a height of approx.1R/sub sun/ follows from the characteristics of type II radio bursts. The region of a reduced Alfven speed is a resonator for a fast magnetosonic (FMS) waves. The eigenmodes of the resonator are determined. The period of the fundamental mode has the order of several minutes. In the resonator FMS waves can be excited at the Cherenkov resonance by streams of energetic ions. Modulations of metal solar radio emission with a period of several minutes is explained by the effect of the propagation of radio waves through an oscillating magnetohydrodynamic (MHD) resonator

  9. Resonators for magnetohydrodynamic waves in the solar corona: radioemission modulation effect

    International Nuclear Information System (INIS)

    Zajtsev, V.V.; Stepanov, A.V.

    1982-01-01

    Data on type 2 solar radio bursts are analyzed in the framework of a model of radio emission production by shock waves. Type 2 solar radio bursts data are shown to suggest the existence of Alfven velocity minimum at a height of the one solar radius in the corona. The domain of a low Alfven velocity is a resonator for the fast magnetosonic waves. The eigenmodes of the resonator are determined. The main mode period is about a few minutes. Fast modes in the resonator can be amplified by energetic ion beams at the Cherenkov resonance. The modulation of meter solar radio emission with a period of about a few minutes can be explained by radiowave propagation through the MHD-resonator

  10. Transmitted spectral modulation of double-ring resonator using liquid crystals in terahertz range

    Science.gov (United States)

    Sun, Huijuan; Zhou, Qingli; Wang, Xiumin; Li, Chenyu; Wu, Ani; Zhang, Cunlin

    2013-12-01

    Metamaterials with subwavelength structural features show unique electromagnetic responses that are unattainable with natural materials. Recent research on these artificial materials has been pushed forward to the terahertz region because of potential applications in biological fingerprinting, security imaging, remote sensing, and high frequency magnetic and electric resonant devices. Active control of their properties could further facilitate and open up new applications in terms of modulation and switching. Liquid crystals, which have been the subject of research for more than a century, have the unique properties for the development of many other optical components such as light valves, tunable filters and tunable lenses. In this paper, we investigated the transmitted spectral modulation in terahertz range by using liquid crystals (5CB and TEB300) covering on the fabricated double-ring resonators to realize the shift of the resonance frequency. Our obtained results indicate the low frequency resonance shows the obvious blue-shift, while the location of high frequency resonance is nearly unchanged. We believe this phenomenon is related to not only the refractive index of the covering liquid crystals but also the resonant mechanism of both resonances.

  11. Role of density modulation in the spatially resolved dynamics of strongly confined liquids.

    Science.gov (United States)

    Saw, Shibu; Dasgupta, Chandan

    2016-08-07

    Confinement by walls usually produces a strong modulation in the density of dense liquids near the walls. Using molecular dynamics simulations, we examine the effects of the density modulation on the spatially resolved dynamics of a liquid confined between two parallel walls, using a resolution of a fraction of the interparticle distance in the liquid. The local dynamics is quantified by the relaxation time associated with the temporal autocorrelation function of the local density. We find that this local relaxation time varies in phase with the density modulation. The amplitude of the spatial modulation of the relaxation time can be quite large, depending on the characteristics of the wall and thermodynamic parameters of the liquid. To disentangle the effects of confinement and density modulation on the spatially resolved dynamics, we compare the dynamics of a confined liquid with that of an unconfined one in which a similar density modulation is induced by an external potential. We find several differences indicating that density modulation alone cannot account for all the features seen in the spatially resolved dynamics of confined liquids. We also examine how the dynamics near a wall depends on the separation between the two walls and show that the features seen in our simulations persist in the limit of large wall separation.

  12. Modulation equations for spatially periodic systems: derivation and solutions

    NARCIS (Netherlands)

    Schielen, R.; Doelman, A.

    1996-01-01

    We study a class of partial dierential equations in one spatial dimension, which can be seen as model equations for the analysis of pattern formation in physical systems dened on unbounded, weakly oscillating domains. We perform a linear and weakly nonlinear stability analysis for solutions that

  13. Acousto-plasmofluidics: Acoustic modulation of surface plasmon resonance in microfluidic systems

    Directory of Open Access Journals (Sweden)

    Daniel Ahmed

    2015-09-01

    Full Text Available We acoustically modulated the localized surface plasmon resonances (LSPRs of metal nanostructures integrated within microfluidic systems. An acoustically driven micromixing device based on bubble microstreaming quickly and homogeneously mixes multiple laminar flows of different refractive indices. The altered refractive index of the mixed fluids enables rapid modulation of the LSPRs of gold nanodisk arrays embedded within the microfluidic channel. The device features fast response for dynamic operation, and the refractive index within the channel is tailorable. With these unique features, our “acousto-plasmofluidic” device can be useful in applications such as optical switches, modulators, filters, biosensors, and lab-on-a-chip systems.

  14. Laterally vibrating resonator based elasto-optic modulation in aluminum nitride

    Directory of Open Access Journals (Sweden)

    Siddhartha Ghosh

    2016-06-01

    Full Text Available An integrated strain-based optical modulator driven by a piezoelectric laterally vibrating resonator is demonstrated. The composite structure consists of an acoustic Lamb wave resonator, in which a photonic racetrack resonator is internally embedded to enable overlap of the guided optical mode with the induced strain field. Both types of resonators are defined in an aluminum nitride (AlN thin film, which rests upon a layer of silicon dioxide in order to simultaneously define optical waveguides, and the structure is released from a silicon substrate. Lateral vibrations produced by the acoustic resonator are transferred through a partially etched layer of AlN, producing a change in the effective index of the guided wave through the interaction of the strain components with the AlN elasto-optic (p coefficients. Optical modulation through the elasto-optic effect is demonstrated at electromechanically actuated frequencies of 173 MHz and 843 MHz. This device geometry further enables the development of MEMS-based optical modulators in addition to studying elasto-optic interactions in suspended piezoelectric thin films.

  15. Pulse width modulation based pneumatic frequency tuner of the superconducting resonators at IUAC

    International Nuclear Information System (INIS)

    Pandey, A.; Suman, S.K.; Mathuria, D.S.

    2015-01-01

    The existing phase locking scheme of the quarter wave resonators (QWR) used in superconducting linear accelerator (LINAC) of IUAC consists of a fast time (electronic) and a slow time (pneumatic) control. Presently, piezo based mechanical tuners are being used to phase lock the resonators installed in the second and third accelerating modules of LINAC. However, due to space constraint, the piezo tuner can't be implemented on the resonators of the first accelerating module. Therefore, helium gas operated mechanical tuners are being used to phase lock the resonators against the master oscillator (MO) frequency. The present pneumatic frequency tuner has limitations of non-linearity, hysteresis and slow response time. To overcome these problems and to improve the dynamics of the existing tuner, a new pulse width modulation (PWM) based pneumatic frequency tuning system was adopted and successfully tested. After successful test, the PWM based pneumatic frequency tuner was installed in four QWR of the first accelerating module of LINAC. During beam run the PWM based frequency tuner performed well and the cavities could be phase locked at comparatively higher accelerating fields. A comparison of the existing tuning mechanism and the PWM based tuning system along with the test results will be presented in the paper. (author)

  16. Spatial and verbal working memory: A functional magnetic resonance imaging study

    Directory of Open Access Journals (Sweden)

    Blaž Koritnik

    2004-08-01

    Full Text Available According to numerous studies, working memory is not a unitary system. Baddeley's model of working memory includes besides central executive also two separate systems for verbal and visuo-spatial information processing. A modality- and process-specific specialization presumably exists in working memory system of the frontal lobes. In our preliminary study, we have used functional magnetic resonance imaging to study the pattern of cortical activation during spatial and verbal n-back task in six healthy subjects. A bilateral fronto-parietal cortical network was activated in both tasks. There was larger activation of right parietal and bilateral occipital areas in spatial than in vebal task. Activation of left sensorimotor area was larger in verbal compared to spatial task. No task-specific differences were found in the prefrontal cortex. Our results support the assumption that modality-specific processes exist within the working-memory system.

  17. Prefrontal Cortical GABA Modulation of Spatial Reference and Working Memory

    OpenAIRE

    Auger, Meagan L.; Floresco, Stan B.

    2014-01-01

    Background: Dysfunction in prefrontal cortex (PFC) GABA transmission has been proposed to contribute to cognitive dysfunction in schizophrenia, yet how this system regulates different cognitive and mnemonic functions remains unclear. Methods: We assessed the effects of pharmacological reduction of GABAA signaling in the medial PFC of rats on spatial reference/working memory using different versions of the radial-arm maze task. We used a massed-trials procedure to probe how PFC GABA regulates ...

  18. Spatial auditory attention is modulated by tactile priming.

    Science.gov (United States)

    Menning, Hans; Ackermann, Hermann; Hertrich, Ingo; Mathiak, Klaus

    2005-07-01

    Previous studies have shown that cross-modal processing affects perception at a variety of neuronal levels. In this study, event-related brain responses were recorded via whole-head magnetoencephalography (MEG). Spatial auditory attention was directed via tactile pre-cues (primes) to one of four locations in the peripersonal space (left and right hand versus face). Auditory stimuli were white noise bursts, convoluted with head-related transfer functions, which ensured spatial perception of the four locations. Tactile primes (200-300 ms prior to acoustic onset) were applied randomly to one of these locations. Attentional load was controlled by three different visual distraction tasks. The auditory P50m (about 50 ms after stimulus onset) showed a significant "proximity" effect (larger responses to face stimulation as well as a "contralaterality" effect between side of stimulation and hemisphere). The tactile primes essentially reduced both the P50m and N100m components. However, facial tactile pre-stimulation yielded an enhanced ipsilateral N100m. These results show that earlier responses are mainly governed by exogenous stimulus properties whereas cross-sensory interaction is spatially selective at a later (endogenous) processing stage.

  19. Factors modulating social influence on spatial choice in rats.

    Science.gov (United States)

    Bisbing, Teagan A; Saxon, Marie; Sayde, Justin M; Brown, Michael F

    2015-07-01

    Three experiments examined the conditions under which the spatial choices of rats searching for food are influenced by the choices made by other rats. Model rats learned a consistent set of baited locations in a 5 × 5 matrix of locations, some of which contained food. In Experiment 1, subject rats could determine the baited locations after choosing 1 location because all of the baited locations were on the same side of the matrix during each trial (the baited side varied over trials). Under these conditions, the social cues provided by the model rats had little or no effect on the choices made by the subject rats. The lack of social influence on choices occurred despite a simultaneous social influence on rats' location in the testing arena (Experiment 2). When the outcome of the subject rats' own choices provided no information about the positions of other baited locations, on the other hand, social cues strongly controlled spatial choices (Experiment 3). These results indicate that social information about the location of food influences spatial choices only when those cues provide valid information that is not redundant with the information provided by other cues. This suggests that social information is learned about, processed, and controls behavior via the same mechanisms as other kinds of stimuli. (c) 2015 APA, all rights reserved).

  20. Optimised frequency modulation for continuous-wave optical magnetic resonance sensing using nitrogen-vacancy ensembles.

    Science.gov (United States)

    El-Ella, Haitham A R; Ahmadi, Sepehr; Wojciechowski, Adam M; Huck, Alexander; Andersen, Ulrik L

    2017-06-26

    Magnetometers based on ensembles of nitrogen-vacancy centres are a promising platform for continuously sensing static and low-frequency magnetic fields. Their combination with phase-sensitive (lock-in) detection creates a highly versatile sensor with a sensitivity that is proportional to the derivative of the optical magnetic resonance lock-in spectrum, which is in turn dependant on the lock-in modulation parameters. Here we study the dependence of the lock-in spectral slope on the modulation of the spin-driving microwave field. Given the presence of the intrinsic nitrogen hyperfine spin transitions, we experimentally show that when the ratio between the hyperfine linewidth and their separation is ≳ 1/4, square-wave based frequency modulation generates the steepest slope at modulation depths exceeding the separation of the hyperfine lines, compared to sine-wave based modulation. We formulate a model for calculating lock-in spectra which shows excellent agreement with our experiments, and which shows that an optimum slope is achieved when the linewidth/separation ratio is ≲ 1/4 and the modulation depth is less then the resonance linewidth, irrespective of the modulation function used.

  1. Observation of resonant symmetry lifting by an effective bias field in a parametrically modulated atomic trap

    International Nuclear Information System (INIS)

    Kim, Yonghee; Heo, Myoung-Sun; Moon, Geol; Kim, Ji-Hyoun; Jhe, Wonho; Noh, Heung-Ryoul

    2010-01-01

    We experimentally demonstrate resonant symmetry lifting in a parametrically modulated magneto-optical trap of cold 85 Rb atoms. This is achieved by applying a weak additional modulation at half the frequency of the strong parametric modulation, which acts as an effective static bias field to the system. We measure the system response by varying the amplitude of the additional fictitious bias as well as the relative phase between the bias and the parametric drive, and the results are in good agreement with theory. The additional modulation provides an additional degree of freedom to control the system, which is useful for investigating system properties such as susceptibility, dynamic response, and related critical phenomena. We also have measured the amplitude of the response to higher harmonics of the additional modulation frequency, which allows more precise understanding of the system dynamics.

  2. Optimised frequency modulation for continuous-wave optical magnetic resonance sensing using nitrogen-vacancy ensembles

    DEFF Research Database (Denmark)

    El-Ella, Haitham; Ahmadi, Sepehr; Wojciechowski, Adam

    2017-01-01

    transitions, we experimentally show that when the ratio between the hyperfine linewidth and their separation is ≥ 1=4, square-wave based frequency modulation generates the steepest slope at modulation depths exceeding the separation of the hyperfine lines, compared to sine-wave based modulation. We formulate......Magnetometers based on ensembles of nitrogen-vacancy centres are a promising platform for continuously sensing static and low-frequency magnetic fields. Their combination with phase-sensitive (lock-in) detection creates a highly versatile sensor with a sensitivity that is proportional...... to the derivative of the optical magnetic resonance lock-in spectrum, which is in turn dependant on the lock-in modulation parameters. Here we study the dependence of the lock-in spectral slope on the modulation of the spin-driving microwave field. Given the presence of the intrinsic nitrogen hyperfine spin...

  3. POLIDENT: A Module for Generating Continuous-Energy Cross Sections from ENDF Resonance Data

    Energy Technology Data Exchange (ETDEWEB)

    Dunn, M.E.; Greene, N.M.

    2000-12-01

    POLIDENT (Point Libraries of Data from ENDF/B Tapes) is an AMPX module that accesses the resonance parameters from File 2 of an ENDF/B library and constructs the continuous-energy cross sections in the resonance energy region. The cross sections in the resonance range are subsequently combined with the File 3 background data to construct the cross-section representation over the complete energy range. POLIDENT has the capability to process all resonance reactions that are identified in File 2 of the ENDF/B library. In addition, the code has the capability to process the single- and multi-level Breit-Wigner, Reich-Moore and Adler-Adler resonance formalisms that are identified in File 2. POLIDENT uses a robust energy-mesh-generation scheme that determines the minimum, maximum and points of inflection in the cross-section function in the resolved-resonance region. Furthermore, POLIDENT processes all continuous-energy cross-section reactions that are identified in File 3 of the ENDF/B library and outputs all reactions in an ENDF/B TAB1 format that can be accessed by other AMPX modules.

  4. Effect of spatially correlated noise on coherence resonance in a network of excitable cells

    International Nuclear Information System (INIS)

    Kwon, Okyu; Jo, Hang-Hyun; Moon, Hie-Tae

    2005-01-01

    We study the effect of spatially correlated noise on coherence resonance (CR) in a Watts-Strogatz small-world network of Fitz Hugh-Nagumo neurons, where the noise correlation decays exponentially with distance between neurons. It is found that CR is considerably improved just by a small fraction of long-range connections for an intermediate coupling strength. For other coupling strengths, an abrupt change in CR occurs following the drastic fracture of the clustered structures in the network. Our study shows that spatially correlated noise plays a significant role in the phenomenon of CR reinforcing the role of the clustered structure of the system

  5. Spatial attention related SEP amplitude modulations covary with BOLD signal in S1--a simultaneous EEG--fMRI study.

    Science.gov (United States)

    Schubert, Ruth; Ritter, Petra; Wüstenberg, Torsten; Preuschhof, Claudia; Curio, Gabriel; Sommer, Werner; Villringer, Arno

    2008-11-01

    Recent studies investigating the influence of spatial-selective attention on primary somatosensory processing have produced inconsistent results. The aim of this study was to explore the influence of tactile spatial-selective attention on spatiotemporal aspects of evoked neuronal activity in the primary somatosensory cortex (S1). We employed simultaneous electroencephalography (EEG)-functional magnetic resonance imaging (fMRI) in 14 right-handed subjects during bilateral index finger Braille stimulation to investigate the relationship between attentional effects on somatosensory evoked potential (SEP) components and the blood oxygenation level-dependent (BOLD) signal. The 1st reliable EEG response following left tactile stimulation (P50) was significantly enhanced by spatial-selective attention, which has not been reported before. FMRI analysis revealed increased activity in contralateral S1. Remarkably, the effect of attention on the P50 component as well as long-latency SEP components starting at 190 ms for left stimuli correlated with attentional effects on the BOLD signal in contralateral S1. The implications are 2-fold: First, the correlation between early and long-latency SEP components and the BOLD effect suggest that spatial-selective attention enhances processing in S1 at 2 time points: During an early passage of the signal and during a later passage, probably via re-entrant feedback from higher cortical areas. Second, attentional modulations of the fast electrophysiological signals and the slow hemodynamic response are linearly related in S1.

  6. Prefrontal cortical GABA modulation of spatial reference and working memory.

    Science.gov (United States)

    Auger, Meagan L; Floresco, Stan B

    2014-10-31

    Dysfunction in prefrontal cortex (PFC) GABA transmission has been proposed to contribute to cognitive dysfunction in schizophrenia, yet how this system regulates different cognitive and mnemonic functions remains unclear. We assessed the effects of pharmacological reduction of GABAA signaling in the medial PFC of rats on spatial reference/working memory using different versions of the radial-arm maze task. We used a massed-trials procedure to probe how PFC GABA regulates susceptibility to proactive interference. Male rats were well-trained to retrieve food from the same 4 arms of an 8-arm maze, receiving 5 trials/day (1-2 min intervals). Infusions of the GABAA receptor antagonist bicuculline (12.5-50 ng) markedly increased working and reference memory errors and response latencies. Similar treatments also impaired short-term memory on an 8-baited arm task. These effects did not appear to be due to increased susceptibility to proactive interference. In contrast, PFC inactivation via infusion of GABA agonists baclofen/muscimol did not affect reference/working memory. In comparison to the pronounced effects on the 8-arm maze tasks, PFC GABAA antagonism only causes a slight and transient decrease in accuracy on a 2-arm spatial discrimination. These findings demonstrate that prefrontal GABA hypofunction severely disrupts spatial reference and short-term memory and that disinhibition of the PFC can, in some instances, perturb memory processes not normally dependent on the frontal lobes. Moreover, these impairments closely resemble those observed in schizophrenic patients, suggesting that perturbation in PFC GABA signaling may contribute to these types of cognitive deficits associated with the disorder. © The Author 2014. Published by Oxford University Press on behalf of CINP.

  7. Bi-Frequency Modulated Quasi-Resonant Converters: Theory and Applications

    Science.gov (United States)

    Zhang, Yuefeng

    1995-01-01

    To avoid the variable frequency operation of quasi -resonant converters, many soft-switching PWM converters have been proposed, all of them require an auxiliary switch, which will increase the cost and complexity of the power supply system. In this thesis, a new kind of technique for quasi -resonant converters has been proposed, which is called the bi-frequency modulation technique. By operating the quasi-resonant converters at two switching frequencies, this technique enables quasi-resonant converters to achieve the soft-switching, at fixed switching frequencies, without an auxiliary switch. The steady-state analysis of four commonly used quasi-resonant converters, namely, ZVS buck, ZCS buck, ZVS boost, and ZCS boost converter has been presented. Using the concepts of equivalent sources, equivalent sinks, and resonant tank, the large signal models of these four quasi -resonant converters were developed. Based on these models, the steady-state control characteristics of BFM ZVS buck, BFM ZCS buck, BFM ZVS boost, and BFM ZCS boost converter have been derived. The functional block and design consideration of the bi-frequency controller were presented, and one of the implementations of the bi-frequency controller was given. A complete design example has been presented. Both computer simulations and experimental results have verified that the bi-frequency modulated quasi-resonant converters can achieve soft-switching, at fixed switching frequencies, without an auxiliary switch. One of the application of bi-frequency modulation technique is for EMI reduction. The basic principle of using BFM technique for EMI reduction was introduced. Based on the spectral analysis, the EMI performances of the PWM, variable-frequency, and bi-frequency modulated control signals was evaluated, and the BFM control signals show the lowest EMI emission. The bi-frequency modulated technique has also been applied to the power factor correction. A BFM zero -current switching boost converter has

  8. Self focusing in a spatially modulated electrostatic field particle accelerator

    Science.gov (United States)

    Russman, F.; Marini, S.; Peter, E.; de Oliveira, G. I.; Rizzato, F. B.

    2018-02-01

    In the present analysis, we study the action of a three-dimensional (3D) modulated electrostatic wave over a charged particle. Meanwhile, the particle's velocity is smaller than the phase-velocity of the carrier, and the particle could be reflected by the potential or could pass through the potential with no significant change in the longitudinal velocity—and its dynamics could be described by a ponderomotive approximation. Otherwise, the particle is trapped by the potential and it is accelerated towards the speed of light, independently of the initial particle's phase—in this case, the ponderomotive approximation is no longer valid. During the acceleration process, numerical simulations show the particle is focused, simultaneously. These results suggest the accelerator proposed here is promising.

  9. Terahertz modulation based on surface plasmon resonance by self-gated graphene

    Science.gov (United States)

    Qian, Zhenhai; Yang, Dongxiao; Wang, Wei

    2018-05-01

    We theoretically and numerically investigate the extraordinary optical transmission through a terahertz metamaterial composed of metallic ring aperture arrays. The physical mechanism of different transmission peaks is elucidated to be magnetic polaritons or propagation surface plasmons with the help of surface current and electromagnetic field distributions at respective resonance frequencies. Then, we propose a high performance terahertz modulator based on the unique PSP resonance and combined with the metallic ring aperture arrays and a self-gated parallel-plate graphene capacitor. Because, to date, few researches have exhibited gate-controlled graphene modulation in terahertz region with low insertion losses, high modulation depth and low control voltage at room temperature. Here, we propose a 96% amplitude modulation with 0.7 dB insertion losses and ∼5.5 V gate voltage. Besides, we further study the absorption spectra of the modulator. When the transmission of modulator is very low, a 91% absorption can be achieved for avoiding damaging the source devices.

  10. Electrically and spatially controllable PDLC phase gratings for diffraction and modulation of laser beams

    Energy Technology Data Exchange (ETDEWEB)

    Hadjichristov, Georgi B., E-mail: georgibh@issp.bas.bg [Laboratory of Optics and Spectroscopy, Georgi Nadjakov Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee Blvd., BG-1784 Sofia (Bulgaria); Marinov, Yordan G.; Petrov, Alexander G. [Laboratory of Biomolecular Layers, Georgi Nadjakov Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee Blvd., BG-1784 Sofia, Bulgaria (Bulgaria)

    2016-03-25

    We present a study on electrically- and spatially-controllable laser beam diffraction, electrooptic (EO) phase modulation, as well as amplitude-frequency EO modulation by single-layer microscale polymer-dispersed liquid crystal (PDLC) phase gratings (PDLC SLPGs) of interest for device applications. PDLC SLPGs were produced from nematic liquid crystal (LC) E7 in photo-curable NOA65 polymer. The wedge-formed PDLC SLPGs have a continuously variable thickness (2–25 µm). They contain LC droplets of diameters twice as the layer thickness, with a linear-gradient size distribution along the wedge. By applying alternating-current (AC) electric field, the PDLC SLPGs produce efficient: (i) diffraction splitting of transmitted laser beams; (ii) spatial redistribution of diffracted light intensity; (iii) optical phase modulation; (iv) amplitude-frequency modulation, all controllable by the driven AC field and the droplet size gradient.

  11. Expectancy modulates pupil size during endogenous orienting of spatial attention.

    Science.gov (United States)

    Dragone, Alessio; Lasaponara, Stefano; Pinto, Mario; Rotondaro, Francesca; De Luca, Maria; Doricchi, Fabrizio

    2018-05-01

    fMRI investigations in healthy humans have documented phasic changes in the level of activation of the right temporal-parietal junction (TPJ) during cued voluntary orienting of spatial attention. Cues that correctly predict the position of upcoming targets in the majority of trials, i.e., predictive cues, produce higher deactivation of the right TPJ as compared with non-predictive cues. Since the right TPJ is the recipient of noradrenergic (NE) innervation, it has been hypothesised that changes in the level of TPJ activity are matched with changes in the level of NE activity. Based on aforementioned fMRI findings, this might imply that orienting with predictive cues is matched with different levels of NE activity as compared with non-predictive cues. To test this hypothesis, we measured changes in pupil dilation, an indirect index of NE activity, during voluntary orienting of attention with highly predictive (80% validity) or non-predictive (50% validity) cues. In agreement with current interpretations of the tonic/phasic activity of the Locus Coeruleus-Norepinephrinic system (LC-NE), we found that the steady level of cue predictiveness that characterised both the predictive and non-predictive conditions caused, across consecutive blocks of trials, a progressive decrement in pupil dilation during the baseline-fixation period that anticipated the cue period. With predictive cues we observed increased pupil dilation as compared with non-predictive cues. In addition, the relative reduction in pupil size observed with non-predictive cues increased as a function of cue-duration. These results show that changes in the predictiveness of cues that guide voluntary orienting of spatial attention are matched with changes in pupil dilation and, putatively, with corresponding changes in LC-NE activity. Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. Modulating Spatial Processes and Navigation via Transcranial Electrical Stimulation: A Mini Review

    Directory of Open Access Journals (Sweden)

    Tad T. Brunyé

    2018-01-01

    Full Text Available Transcranial electrical stimulation (tES uses low intensity current to alter neuronal activity in superficial cortical regions, and has gained popularity as a tool for modulating several aspects of perception and cognition. This mini-review article provides an overview of tES and its potential for modulating spatial processes underlying successful navigation, including spatial attention, spatial perception, mental rotation and visualization. Also considered are recent advances in empirical research and computational modeling elucidating several stable cortical-subcortical networks with dynamic involvement in spatial processing and navigation. Leveraging these advances may prove valuable for using tES, particularly transcranial direct and alternating current stimulation (tDCS/tACS, to indirectly target subcortical brain regions by altering neuronal activity in distant yet functionally connected cortical areas. We propose future research directions to leverage these advances in human neuroscience.

  13. Selective spatial attention modulates bottom-up informational masking of speech

    OpenAIRE

    Carlile, Simon; Corkhill, Caitlin

    2015-01-01

    To hear out a conversation against other talkers listeners overcome energetic and informational masking. Largely attributed to top-down processes, information masking has also been demonstrated using unintelligible speech and amplitude-modulated maskers suggesting bottom-up processes. We examined the role of speech-like amplitude modulations in information masking using a spatial masking release paradigm. Separating a target talker from two masker talkers produced a 20?dB improvement in speec...

  14. An electro-optic spatial light modulator for thermoelastic generation of programmably focused ultrasound

    Science.gov (United States)

    1984-12-01

    The concept proposed is an electro-optic technique that would make it possible to spatially modulate a high power pulsed laser beam to thermoelastically induce focused ultrasound in a test material. Being a purely electro-optic device, the modulator, and therefore the depth at which the acoustic focus occurs, can be programmed electronically at electronic speeds. If successful, it would become possible to scan ultrasound continuously in three dimensions within the component or structure under test.

  15. Spatial modulation of the Fermi level by coherent illumination of undoped GaAs

    Science.gov (United States)

    Nolte, D. D.; Olson, D. H.; Glass, A. M.

    1989-11-01

    The Fermi level in undoped GaAs has been modulated spatially by optically quenching EL2 defects. The spatial gradient of the Fermi level produces internal electric fields that are much larger than fields generated by thermal diffusion alone. The resulting band structure is equivalent to a periodic modulation-doped p-i-p structure of alternating insulating and p-type layers. The internal fields are detected via the electro-optic effect by the diffraction of a probe laser in a four-wave mixing geometry. The direct control of the Fermi level distinguishes this phenomenon from normal photorefractive behavior and introduces a novel nonlinear optical process.

  16. Generating shaped femtosecond pulses in the far infrared using a spatial light modulator and difference frequency generation

    CSIR Research Space (South Africa)

    Botha, N

    2010-08-31

    Full Text Available Femtosecond pulse shaping can be done by different kinds of pulse shapers, such as liquid crystal spatial light modulators (LC SLM), acousto optic modulators (AOM) and deformable and movable mirrors. A few applications where pulse shaping...

  17. Resonance modulation, annihilation and generation of anti-resonance and anti-phasonance in 3D neuronal systems: interplay of resonant and amplifying currents with slow dynamics.

    Science.gov (United States)

    Rotstein, Horacio G

    2017-08-01

    Subthreshold (membrane potential) resonance and phasonance (preferred amplitude and zero-phase responses to oscillatory inputs) in single neurons arise from the interaction between positive and negative feedback effects provided by relatively fast amplifying currents and slower resonant currents. In 2D neuronal systems, amplifying currents are required to be slave to voltage (instantaneously fast) for these phenomena to occur. In higher dimensional systems, additional currents operating at various effective time scales may modulate and annihilate existing resonances and generate antiresonance (minimum amplitude response) and antiphasonance (zero-phase response with phase monotonic properties opposite to phasonance). We use mathematical modeling, numerical simulations and dynamical systems tools to investigate the mechanisms underlying these phenomena in 3D linear models, which are obtained as the linearization of biophysical (conductance-based) models. We characterize the parameter regimes for which the system exhibits the various types of behavior mentioned above in the rather general case in which the underlying 2D system exhibits resonance. We consider two cases: (i) the interplay of two resonant gating variables, and (ii) the interplay of one resonant and one amplifying gating variables. Increasing levels of an amplifying current cause (i) a response amplification if the amplifying current is faster than the resonant current, (ii) resonance and phasonance attenuation and annihilation if the amplifying and resonant currents have identical dynamics, and (iii) antiresonance and antiphasonance if the amplifying current is slower than the resonant current. We investigate the underlying mechanisms by extending the envelope-plane diagram approach developed in previous work (for 2D systems) to three dimensions to include the additional gating variable, and constructing the corresponding envelope curves in these envelope-space diagrams. We find that antiresonance and

  18. Investigation of the Spatial Resolution of MR-Based Polymer Gel Dosimetry versus Film Densitometry using Dose Modulation Transfer Function

    Directory of Open Access Journals (Sweden)

    Reza Moghadam-Drodkhani

    2011-03-01

    Full Text Available Introduction: The conventional methods of dosimetry are not capable of dosimetry in such a small volume of less than one cubic millimeter. Although the polymer gel dosimetry method based on magnetic resonance imaging (MRI could achieve three dimensional dosimetry with high resolution, a spatial resolution evaluation based on gel dose modulation transfer function has not been investigated yet. Therefore, in this study, the spatial resolution of two systems of film densitometry and polymer gel dosimetry based on MRI has been evaluated by using the dose modulation transfer function (DMTF.   Material and Methods: Kodak therapy verification films and MAGICA polymer gel samples were positioned below a brass absorption grid with different periodic slices (a/2= 280, 525, 1125 μm, which was placed in a water bath container to avoid regions of dose build-up just below the absorption grid and then irradiated with Cobalt-60 photons on a Theratron external-beam treatment unit. Dose variation under the brass grid was determined using a calibration curve, while transverse relaxation time (T2 as the selective parameter in a dose image based on multiple echo MRI with 1.5 Tesla GE Signa Echo Speed system (FOV=10 cm, matrix size=512 ×512, pixel size =0.199×0.199 mm2, TE = 20, 40, 60, 80 ms, TR=4200 ms, NEX = 4, slice thickness=2 mm, gap=1 mm was calculated. DMTF from the modulation depths of T2 and variation in film optical density after calibration would be achieved. The results of polymer gel were compared with film. Results: After deriving the dose distribution profile under the absorption grid, minima and maxima at the smallest period of a = 560 μm could scarcely be resolved, but the modulations due to a=2250 μm and a = 1050 μm grids could be discerned. The modulation depth for a=2250 μm grid was set to 100% and the other modulations were subsequently referred to this maximum modulation. For film densitometry at a = 1050 μm, the modulation depth was

  19. Selective spatial attention modulates bottom-up informational masking of speech.

    Science.gov (United States)

    Carlile, Simon; Corkhill, Caitlin

    2015-03-02

    To hear out a conversation against other talkers listeners overcome energetic and informational masking. Largely attributed to top-down processes, information masking has also been demonstrated using unintelligible speech and amplitude-modulated maskers suggesting bottom-up processes. We examined the role of speech-like amplitude modulations in information masking using a spatial masking release paradigm. Separating a target talker from two masker talkers produced a 20 dB improvement in speech reception threshold; 40% of which was attributed to a release from informational masking. When across frequency temporal modulations in the masker talkers are decorrelated the speech is unintelligible, although the within frequency modulation characteristics remains identical. Used as a masker as above, the information masking accounted for 37% of the spatial unmasking seen with this masker. This unintelligible and highly differentiable masker is unlikely to involve top-down processes. These data provides strong evidence of bottom-up masking involving speech-like, within-frequency modulations and that this, presumably low level process, can be modulated by selective spatial attention.

  20. Selective attention modulates human auditory brainstem responses: relative contributions of frequency and spatial cues.

    Directory of Open Access Journals (Sweden)

    Alexandre Lehmann

    Full Text Available Selective attention is the mechanism that allows focusing one's attention on a particular stimulus while filtering out a range of other stimuli, for instance, on a single conversation in a noisy room. Attending to one sound source rather than another changes activity in the human auditory cortex, but it is unclear whether attention to different acoustic features, such as voice pitch and speaker location, modulates subcortical activity. Studies using a dichotic listening paradigm indicated that auditory brainstem processing may be modulated by the direction of attention. We investigated whether endogenous selective attention to one of two speech signals affects amplitude and phase locking in auditory brainstem responses when the signals were either discriminable by frequency content alone, or by frequency content and spatial location. Frequency-following responses to the speech sounds were significantly modulated in both conditions. The modulation was specific to the task-relevant frequency band. The effect was stronger when both frequency and spatial information were available. Patterns of response were variable between participants, and were correlated with psychophysical discriminability of the stimuli, suggesting that the modulation was biologically relevant. Our results demonstrate that auditory brainstem responses are susceptible to efferent modulation related to behavioral goals. Furthermore they suggest that mechanisms of selective attention actively shape activity at early subcortical processing stages according to task relevance and based on frequency and spatial cues.

  1. Oral contraceptive therapy modulates hemispheric asymmetry in spatial attention.

    Science.gov (United States)

    Cicinelli, Ettore; De Tommaso, Marina; Cianci, Antonio; Colacurci, Nicola; Rella, Leonarda; Loiudice, Luisa; Cicinelli, Maria Vittoria; Livrea, Paolo

    2011-12-01

    Functional cerebral asymmetries (FCAs) are known to fluctuate across the menstrual cycle. The visual line-bisection task administered to normally cycling women showed different patterns of the interhemispheric interactions during menses and the midluteal cycle phase. However, the contribution of estrogens and progestins hormones to this phenomenon is still unclear. The aim of our study was to show a variation of FCAs in women administered oral contraceptives (OCs) using the visual line-bisection task. Visual line-bisection task with three horizontal lines was administered to 36 healthy women taking a 21-day OC. Twenty-nine patients were right handed. The task was administered during OC intake (day 10) and at the end of the pill-free period. The right-handed women showed a significant leftward bias of veridical center on the first and third lines during OC intake compared with an opposite rightward bias during the pill-free period. The same phenomenon of contralateral deviation was observed in left-handed women on day 10 of OC intake. The results of this study confirm a hormonal modulation on interhemispheric interaction and suggest that OCs may improve the interhemispheric interaction reducing FCAs compared with the low hormone level period. This opens new insights in OC prescription and choice of administration schedule in order to improve cognitive performances. Copyright © 2011 Elsevier Inc. All rights reserved.

  2. The effect of spatial light modulator (SLM) dependent dispersion on spatial beam shaping

    CSIR Research Space (South Africa)

    Spangenberg, D-M

    2013-08-01

    Full Text Available on the pixels between zero and two pi for a specific wavelength. It is therefore unavoidable when using the same SLM, to do beam shaping of a source which emits multiple wavelengths or a wide bandwidth, that the device will not modulate all wavelengths between...

  3. Three-Wave Resonance Modulation and Fine Structures in the Solar Short Centimeter Wave Bursts

    Institute of Scientific and Technical Information of China (English)

    王德焴; 吴洪敖; 秦至海

    1994-01-01

    A theoretical model is presented. We propose that when the radiation of solar radio bursts propagates outward as a pump wave through the conora, the three-wave resonance interaction would occur if the radio emission interacts with the MHD wave and scattering wave in the conora. This process induces a nonlinear modulation in the emission flux S. The statistical relations between the repetition rates R and S and between the modulation amplitude △S and S, observed from 1.36cm, 2cm and 3.2cm solar radio bursts could be well interpreted by this model under the conditions of imperfect matching and k2≠0. The appreciable difference in the modulation periods among the 2cm, 3.2cm and 1.36cm waves might be caused by the differences in the MHD waves joining in the modulation. Several theoretical expectations have been made from this model, which may be inspected in further observation.

  4. Field and frequency modulated sub-THz electron spin resonance spectrometer

    Directory of Open Access Journals (Sweden)

    Christian Caspers

    2016-05-01

    Full Text Available 260-GHz radiation is used for a quasi-optical electron spin resonance (ESR spectrometer which features both field and frequency modulation. Free space propagation is used to implement Martin-Puplett interferometry with quasi-optical isolation, mirror beam focusing, and electronic polarization control. Computer-aided design and polarization pathway simulation lead to the design of a compact interferometer, featuring lateral dimensions less than a foot and high mechanical stability, with all components rated for power levels of several Watts suitable for gyrotron radiation. Benchmark results were obtained with ESR standards (BDPA, DPPH using field modulation. Original high-field ESR of 4f electrons in Sm3+-doped Ceria was detected using frequency modulation. Distinct combinations of field and modulation frequency reach a signal-to-noise ratio of 35 dB in spectra of BDPA, corresponding to a detection limit of about 1014 spins.

  5. Information transfer with rate-modulated Poisson processes: a simple model for nonstationary stochastic resonance.

    Science.gov (United States)

    Goychuk, I

    2001-08-01

    Stochastic resonance in a simple model of information transfer is studied for sensory neurons and ensembles of ion channels. An exact expression for the information gain is obtained for the Poisson process with the signal-modulated spiking rate. This result allows one to generalize the conventional stochastic resonance (SR) problem (with periodic input signal) to the arbitrary signals of finite duration (nonstationary SR). Moreover, in the case of a periodic signal, the rate of information gain is compared with the conventional signal-to-noise ratio. The paper establishes the general nonequivalence between both measures notwithstanding their apparent similarity in the limit of weak signals.

  6. Time dependence of resonance γ-radiation modulated by acoustic excitations

    International Nuclear Information System (INIS)

    Mkrtchyan, A.R.; Arakelyan, A.R.; Gabrielyan, R.G.; Kocharyan, L.A.; Grigoryan, G.R.; Slavinskii, M.M.

    1984-01-01

    Experimental investigations of the time dependence of the γ-resonance absorption line intensity in case of modulation by acoustic waves are presented. 57 Co was used as source and a stainless steel foil was chosen as an absorber. The time dependences of the counting rate of the resonant γ-quanta corresponding to excitations with 3400 Hz and with 1.5 or 7 V at the vibrosystem transducer are plotted. The measurements show that the method has principal advantages over the conventional Moessbauer spectroscopy

  7. Microring resonator based modulator made by direct photodefinition of an electro-optic polymer

    Science.gov (United States)

    Balakrishnan, M.; Faccini, M.; Diemeer, M. B. J.; Klein, E. J.; Sengo, G.; Driessen, A.; Verboom, W.; Reinhoudt, D. N.

    2008-04-01

    A laterally coupled microring resonator was fabricated by direct photodefinition of negative photoresist SU8, containing tricyanovinylidenediphenylaminobenzene chromophore, by exploiting the low ultraviolet absorption window of this chromophore. The ring resonator was first photodefined by slight cross-linking. Thereafter, poling (to align the chromophores) and further cross-linking (to increase the glass transition temperature) were simultaneously carried out. The material showed excellent photostability and the electro-optic modulation with an r33 of 11pm/V was demonstrated at 10MHz.

  8. Phase modulation spectroscopy of space-charge wave resonances in Bi12SiO20

    DEFF Research Database (Denmark)

    Vasnetsov, M.; Buchhave, Preben; Lyuksyutov, S.

    1997-01-01

    A new experimental method for the study of resonance effects and space-charge wave excitation in photorefractive Bi12SiO20 crystals by using a combination of frequency detuning and phase modulation technique has been developed. The accuracy of the method allows a detection of resonance peaks...... of diffraction efficiency within 0.5 Hz. Numerical simulations of the nonlinear differential equations describing the behaviour of the space-charge waves in photorefractive crystals have been performed and found to be in a good agreement with experiment. We have measured the photocurrent through the crystal...

  9. Wavelength modulated surface enhanced (resonance) Raman scattering for background-free detection.

    Science.gov (United States)

    Praveen, Bavishna B; Steuwe, Christian; Mazilu, Michael; Dholakia, Kishan; Mahajan, Sumeet

    2013-05-21

    Spectra in surface-enhanced Raman scattering (SERS) are always accompanied by a continuum emission called the 'background' which complicates analysis and is especially problematic for quantification and automation. Here, we implement a wavelength modulation technique to eliminate the background in SERS and its resonant version, surface-enhanced resonance Raman scattering (SERRS). This is demonstrated on various nanostructured substrates used for SER(R)S. An enhancement in the signal to noise ratio for the Raman bands of the probe molecules is also observed. This technique helps to improve the analytical ability of SERS by alleviating the problem due to the accompanying background and thus making observations substrate independent.

  10. Attention Modulates Visual-Tactile Interaction in Spatial Pattern Matching

    Science.gov (United States)

    Göschl, Florian; Engel, Andreas K.; Friese, Uwe

    2014-01-01

    Factors influencing crossmodal interactions are manifold and operate in a stimulus-driven, bottom-up fashion, as well as via top-down control. Here, we evaluate the interplay of stimulus congruence and attention in a visual-tactile task. To this end, we used a matching paradigm requiring the identification of spatial patterns that were concurrently presented visually on a computer screen and haptically to the fingertips by means of a Braille stimulator. Stimulation in our paradigm was always bimodal with only the allocation of attention being manipulated between conditions. In separate blocks of the experiment, participants were instructed to (a) focus on a single modality to detect a specific target pattern, (b) pay attention to both modalities to detect a specific target pattern, or (c) to explicitly evaluate if the patterns in both modalities were congruent or not. For visual as well as tactile targets, congruent stimulus pairs led to quicker and more accurate detection compared to incongruent stimulation. This congruence facilitation effect was more prominent under divided attention. Incongruent stimulation led to behavioral decrements under divided attention as compared to selectively attending a single sensory channel. Additionally, when participants were asked to evaluate congruence explicitly, congruent stimulation was associated with better performance than incongruent stimulation. Our results extend previous findings from audiovisual studies, showing that stimulus congruence also resulted in behavioral improvements in visuotactile pattern matching. The interplay of stimulus processing and attentional control seems to be organized in a highly flexible fashion, with the integration of signals depending on both bottom-up and top-down factors, rather than occurring in an ‘all-or-nothing’ manner. PMID:25203102

  11. Attention modulates visual-tactile interaction in spatial pattern matching.

    Directory of Open Access Journals (Sweden)

    Florian Göschl

    Full Text Available Factors influencing crossmodal interactions are manifold and operate in a stimulus-driven, bottom-up fashion, as well as via top-down control. Here, we evaluate the interplay of stimulus congruence and attention in a visual-tactile task. To this end, we used a matching paradigm requiring the identification of spatial patterns that were concurrently presented visually on a computer screen and haptically to the fingertips by means of a Braille stimulator. Stimulation in our paradigm was always bimodal with only the allocation of attention being manipulated between conditions. In separate blocks of the experiment, participants were instructed to (a focus on a single modality to detect a specific target pattern, (b pay attention to both modalities to detect a specific target pattern, or (c to explicitly evaluate if the patterns in both modalities were congruent or not. For visual as well as tactile targets, congruent stimulus pairs led to quicker and more accurate detection compared to incongruent stimulation. This congruence facilitation effect was more prominent under divided attention. Incongruent stimulation led to behavioral decrements under divided attention as compared to selectively attending a single sensory channel. Additionally, when participants were asked to evaluate congruence explicitly, congruent stimulation was associated with better performance than incongruent stimulation. Our results extend previous findings from audiovisual studies, showing that stimulus congruence also resulted in behavioral improvements in visuotactile pattern matching. The interplay of stimulus processing and attentional control seems to be organized in a highly flexible fashion, with the integration of signals depending on both bottom-up and top-down factors, rather than occurring in an 'all-or-nothing' manner.

  12. Parametric Amplification Protocol for Frequency-Modulated Magnetic Resonance Force Microscopy Signals

    Science.gov (United States)

    Harrell, Lee; Moore, Eric; Lee, Sanggap; Hickman, Steven; Marohn, John

    2011-03-01

    We present data and theoretical signal and noise calculations for a protocol using parametric amplification to evade the inherent tradeoff between signal and detector frequency noise in force-gradient magnetic resonance force microscopy signals, which are manifested as a modulated frequency shift of a high- Q microcantilever. Substrate-induced frequency noise has a 1 / f frequency dependence, while detector noise exhibits an f2 dependence on modulation frequency f . Modulation of sample spins at a frequency that minimizes these two contributions typically results in a surface frequency noise power an order of magnitude or more above the thermal limit and may prove incompatible with sample spin relaxation times as well. We show that the frequency modulated force-gradient signal can be used to excite the fundamental resonant mode of the cantilever, resulting in an audio frequency amplitude signal that is readily detected with a low-noise fiber optic interferometer. This technique allows us to modulate the force-gradient signal at a sufficiently high frequency so that substrate-induced frequency noise is evaded without subjecting the signal to the normal f2 detector noise of conventional demodulation.

  13. Graded Neuronal Modulations Related to Visual Spatial Attention

    Science.gov (United States)

    Maunsell, John H. R.

    2016-01-01

    Studies of visual attention in monkeys typically measure neuronal activity when the stimulus event to be detected occurs at a cued location versus when it occurs at an uncued location. But this approach does not address how neuronal activity changes relative to conditions where attention is unconstrained by cueing. Human psychophysical studies have used neutral cueing conditions and found that neutrally cued behavioral performance is generally intermediate to that of cued and uncued conditions (Posner et al., 1978; Mangun and Hillyard, 1990; Montagna et al., 2009). To determine whether the neuronal correlates of visual attention during neutral cueing are similarly intermediate, we trained macaque monkeys to detect changes in stimulus orientation that were more likely to occur at one location (cued) than another (uncued), or were equally likely to occur at either stimulus location (neutral). Consistent with human studies, performance was best when the location was cued, intermediate when both locations were neutrally cued, and worst when the location was uncued. Neuronal modulations in visual area V4 were also graded as a function of cue validity and behavioral performance. By recording from both hemispheres simultaneously, we investigated the possibility of switching attention between stimulus locations during neutral cueing. The results failed to support a unitary “spotlight” of attention. Overall, our findings indicate that attention-related changes in V4 are graded to accommodate task demands. SIGNIFICANCE STATEMENT Studies of the neuronal correlates of attention in monkeys typically use visual cues to manipulate where attention is focused (“cued” vs “uncued”). Human psychophysical studies often also include neutrally cued trials to study how attention naturally varies between points of interest. But the neuronal correlates of this neutral condition are unclear. We measured behavioral performance and neuronal activity in cued, uncued, and neutrally

  14. Graded Neuronal Modulations Related to Visual Spatial Attention.

    Science.gov (United States)

    Mayo, J Patrick; Maunsell, John H R

    2016-05-11

    Studies of visual attention in monkeys typically measure neuronal activity when the stimulus event to be detected occurs at a cued location versus when it occurs at an uncued location. But this approach does not address how neuronal activity changes relative to conditions where attention is unconstrained by cueing. Human psychophysical studies have used neutral cueing conditions and found that neutrally cued behavioral performance is generally intermediate to that of cued and uncued conditions (Posner et al., 1978; Mangun and Hillyard, 1990; Montagna et al., 2009). To determine whether the neuronal correlates of visual attention during neutral cueing are similarly intermediate, we trained macaque monkeys to detect changes in stimulus orientation that were more likely to occur at one location (cued) than another (uncued), or were equally likely to occur at either stimulus location (neutral). Consistent with human studies, performance was best when the location was cued, intermediate when both locations were neutrally cued, and worst when the location was uncued. Neuronal modulations in visual area V4 were also graded as a function of cue validity and behavioral performance. By recording from both hemispheres simultaneously, we investigated the possibility of switching attention between stimulus locations during neutral cueing. The results failed to support a unitary "spotlight" of attention. Overall, our findings indicate that attention-related changes in V4 are graded to accommodate task demands. Studies of the neuronal correlates of attention in monkeys typically use visual cues to manipulate where attention is focused ("cued" vs "uncued"). Human psychophysical studies often also include neutrally cued trials to study how attention naturally varies between points of interest. But the neuronal correlates of this neutral condition are unclear. We measured behavioral performance and neuronal activity in cued, uncued, and neutrally cued blocks of trials. Behavioral

  15. Complementary theta resonance filtering by two spatially segregated mechanisms in CA1 hippocampal pyramidal neurons.

    Science.gov (United States)

    Hu, Hua; Vervaeke, Koen; Graham, Lyle J; Storm, Johan F

    2009-11-18

    Synaptic input to a neuron may undergo various filtering steps, both locally and during transmission to the soma. Using simultaneous whole-cell recordings from soma and apical dendrites from rat CA1 hippocampal pyramidal cells, and biophysically detailed modeling, we found two complementary resonance (bandpass) filters of subthreshold voltage signals. Both filters favor signals in the theta (3-12 Hz) frequency range, but have opposite location, direction, and voltage dependencies: (1) dendritic H-resonance, caused by h/HCN-channels, filters signals propagating from soma to dendrite when the membrane potential is close to rest; and (2) somatic M-resonance, caused by M/Kv7/KCNQ and persistent Na(+) (NaP) channels, filters signals propagating from dendrite to soma when the membrane potential approaches spike threshold. Hippocampal pyramidal cells participate in theta network oscillations during behavior, and we suggest that that these dual, polarized theta resonance mechanisms may convey voltage-dependent tuning of theta-mediated neural coding in the entorhinal/hippocampal system during locomotion, spatial navigation, memory, and sleep.

  16. Super-resolution with an optically-addressable liquid crystal spatial light modulator

    International Nuclear Information System (INIS)

    McOrist, J.; Sharma, M.D.; Sheppard, C.J.R.

    2002-01-01

    Full text: An optically-addressable liquid crystal spatial light modulator has been used to generate super-resolving masks. This approach avoids problems of low efficiency and coupling between amplitude and phase modulation, that occur when using conventional liquid crystal modulators. When addressed by a programmed light intensity distribution, it allows filters to be changed rapidly to modify the response of a system or permit the investigation of different filter designs. The device used is not pixellated, with a spatial resolution of 30 line pairs/mm over an area 18mm X 18mm, and can achieve continuously-variable phase modulation up to 1.5 wavelengths. The system consists of a write-beam that is collimated from a white-light source. An input mask was used in our experiments determines the modulation pattern of the read-beam. The read-beam from a HeNe laser reflects from the modulator and is focused by a microscope objective. The value of the phase change induced by the transparent regions of the mask can be altered continuously by adjusting the brightness of the write-beam. We have used this system to attain super-resolution by simple Toraldo filters, consisting of arrays of rings. Copyright (2002) Australian Society for Electron Microscopy Inc

  17. Phase-sensitive detection of optical resonances by using an acousto-optic modulator in the Raman - Nath diffraction mode

    International Nuclear Information System (INIS)

    Baryshev, V N; Domnin, Yu S; Kopylov, L N

    2007-01-01

    A new method for frequency control of an external cavity diode laser without direct modulation of the injection current is proposed. The Pound - Drever optical heterodyne technique or the method of frequency control by frequency-modulated sidebands, in which an acousto-optic modulator operating in the Raman - Nath diffraction mode is used as an external phase modulator, can be employed to obtain error signals upon automatic frequency locking of the diode laser to the saturated absorption resonances within the D 2 line of cesium atoms or to the optical cavity resonances. (control of laser radiation parameters)

  18. A digital receiver module with direct data acquisition for magnetic resonance imaging systems.

    Science.gov (United States)

    Tang, Weinan; Sun, Hongyu; Wang, Weimin

    2012-10-01

    A digital receiver module for magnetic resonance imaging (MRI) with detailed hardware implementations is presented. The module is based on a direct sampling scheme using the latest mixed-signal circuit design techniques. A single field-programmable gate array chip is employed to perform software-based digital down conversion for radio frequency signals. The modular architecture of the receiver allows multiple acquisition channels to be implemented on a highly integrated printed circuit board. To maintain the phase coherence of the receiver and the exciter in the context of direct sampling, an effective phase synchronization method was proposed to achieve a phase deviation as small as 0.09°. The performance of the described receiver module was verified in the experiments for both low- and high-field (0.5 T and 1.5 T) MRI scanners and was compared to a modern commercial MRI receiver system.

  19. Linearity optimizations of analog ring resonator modulators through bias voltage adjustments

    Science.gov (United States)

    Hosseinzadeh, Arash; Middlebrook, Christopher T.

    2018-03-01

    The linearity of ring resonator modulator (RRM) in microwave photonic links is studied in terms of instantaneous bandwidth, fabrication tolerances, and operational bandwidth. A proposed bias voltage adjustment method is shown to maximize spur-free dynamic range (SFDR) at instantaneous bandwidths required by microwave photonic link (MPL) applications while also mitigating RRM fabrication tolerances effects. The proposed bias voltage adjustment method shows RRM SFDR improvement of ∼5.8 dB versus common Mach-Zehnder modulators at 500 MHz instantaneous bandwidth. Analyzing operational bandwidth effects on SFDR shows RRMs can be promising electro-optic modulators for MPL applications which require high operational frequencies while in a limited bandwidth such as radio-over-fiber 60 GHz wireless network access.

  20. Electro-optical modulator in a polymerinfiltrated silicon slotted photonic crystal waveguide heterostructure resonator.

    Science.gov (United States)

    Wülbern, Jan Hendrik; Petrov, Alexander; Eich, Manfred

    2009-01-05

    We present a novel concept of a compact, ultra fast electro-optic modulator, based on photonic crystal resonator structures that can be realized in two dimensional photonic crystal slabs of silicon as core material employing a nonlinear optical polymer as infiltration and cladding material. The novel concept is to combine a photonic crystal heterostructure cavity with a slotted defect waveguide. The photonic crystal lattice can be used as a distributed electrode for the application of a modulation signal. An electrical contact is hence provided while the optical wave is kept isolated from the lossy metal electrodes. Thereby, well known disadvantages of segmented electrode designs such as excessive scattering are avoided. The optical field enhancement in the slotted region increases the nonlinear interaction with an external electric field resulting in an envisaged switching voltage of approximately 1 V at modulation speeds up to 100 GHz.

  1. Resonator-Based Silicon Electro-Optic Modulator with Low Power Consumption

    Science.gov (United States)

    Xin, Maoqing; Danner, Aaron J.; Eng Png, Ching; Thor Lim, Soon

    2009-04-01

    This paper demonstrates, via simulation, an electro-optic modulator based on a subwavelength Fabry-Perot resonator cavity with low power consumption of 86 µW/µm. This is, to the best of our knowledge, the lowest power reported for silicon photonic bandgap modulators. The device is modulated at a doped p-i-n junction overlapping the cavity in a silicon waveguide perforated with etched holes, with the doping area optimized for minimum power consumption. The surface area of the entire device is only 2.1 µm2, which compares favorably to other silicon-based modulators. A modulation speed of at least 300 MHz is detected from the electrical simulator after sidewall doping is introduced which is suitable for sensing or fiber to the home (FTTH) technologies, where speed can be traded for low cost and power consumption. The device does not rely on ultra-high Q, and could serve as a sensor, modulator, or passive filter with built-in calibration.

  2. Strategy modulates spatial perspective-taking: evidence for dissociable disembodied and embodied routes

    Science.gov (United States)

    Gardner, Mark R.; Brazier, Mark; Edmonds, Caroline J.; Gronholm, Petra C.

    2013-01-01

    Previous research provides evidence for a dissociable embodied route to spatial perspective-taking that is under strategic control. The present experiment investigated further the influence of strategy on spatial perspective-taking by assessing whether participants may also elect to employ a separable “disembodied” route loading on inhibitory control mechanisms. Participants (N = 92) undertook both the “own body transformation” (OBT) perspective-taking task, requiring speeded spatial judgments made from the perspective of an observed figure, and a control task measuring ability to inhibit spatially compatible responses in the absence of a figure. Perspective-taking performance was found to be related to performance on the response inhibition control task, in that participants who tended to take longer to adopt a new perspective also tended to show a greater elevation in response times when inhibiting spatially compatible responses. This relationship was restricted to those participants reporting that they adopted the perspective of another by reversing left and right whenever confronted with a front-view figure; it was absent in those participants who reported perspective-taking by mentally transforming their spatial orientation to align with that of the figure. Combined with previously published results, these findings complete a double dissociation between embodied and disembodied routes to spatial perspective-taking, implying that spatial perspective-taking is subject to modulation by strategy, and suggesting that embodied routes to perspective-taking may place minimal demands on domain general executive functions. PMID:23964229

  3. The modulation of simple reaction time by the spatial probability of a visual stimulus

    Directory of Open Access Journals (Sweden)

    Carreiro L.R.R.

    2003-01-01

    Full Text Available Simple reaction time (SRT in response to visual stimuli can be influenced by many stimulus features. The speed and accuracy with which observers respond to a visual stimulus may be improved by prior knowledge about the stimulus location, which can be obtained by manipulating the spatial probability of the stimulus. However, when higher spatial probability is achieved by holding constant the stimulus location throughout successive trials, the resulting improvement in performance can also be due to local sensory facilitation caused by the recurrent spatial location of a visual target (position priming. The main objective of the present investigation was to quantitatively evaluate the modulation of SRT by the spatial probability structure of a visual stimulus. In two experiments the volunteers had to respond as quickly as possible to the visual target presented on a computer screen by pressing an optic key with the index finger of the dominant hand. Experiment 1 (N = 14 investigated how SRT changed as a function of both the different levels of spatial probability and the subject's explicit knowledge about the precise probability structure of visual stimulation. We found a gradual decrease in SRT with increasing spatial probability of a visual target regardless of the observer's previous knowledge concerning the spatial probability of the stimulus. Error rates, below 2%, were independent of the spatial probability structure of the visual stimulus, suggesting the absence of a speed-accuracy trade-off. Experiment 2 (N = 12 examined whether changes in SRT in response to a spatially recurrent visual target might be accounted for simply by sensory and temporally local facilitation. The findings indicated that the decrease in SRT brought about by a spatially recurrent target was associated with its spatial predictability, and could not be accounted for solely in terms of sensory priming.

  4. Design, status and first operations of the spallation neutron source polyphase resonant converter modulator system

    Energy Technology Data Exchange (ETDEWEB)

    Reass, W. A. (William A.); Apgar, S. E. (Sean E.); Baca, D. M. (David M.); Doss, James D.; Gonzales, J. (Jacqueline); Gribble, R. F. (Robert F.); Hardek, T. W. (Thomas W.); Lynch, M. T. (Michael T.); Rees, D. E. (Daniel E.); Tallerico, P. J. (Paul J.); Trujillo, P. B. (Pete B.); Anderson, D. E. (David E.); Heidenreich, D. A. (Dale A.); Hicks, J. D. (Jim D.); Leontiev, V. N.

    2003-01-01

    The Spallation Neutron Source (SNS) is a new 1.4 MW average power beam, 1 GeV accelerator being built at Oak Ridge National Laboratory. The accelerator requires 15 converter-modulator stations each providing between 9 and 11 MW pulses with up to a 1 .I MW average power. The converter-modulator can be described as a resonant 20 kHz polyphase boost inverter. Each converter modulator derives its buss voltage from a standard substation cast-core transformer. Each substation is followed by an SCR pre-regulator to accommodate voltage changes from no load to full load, in addition to providing a soft-start function. Energy storage is provided by self-clearing metallized hazy polypropylene traction capacitors. These capacitors do not fail short, but clear any internal anomaly. Three 'H-Bridge' IGBT transistor networks are used to generate the polyphase 20 kHz transformer primary drive waveforms. The 20 kHz drive waveforms are time-gated to generate the desired klystron pulse width. Pulse width modulation of the individual 20 lcHz pulses is utilized to provide regulated output waveforms with DSP based adaptive feedforward and feedback techniques. The boost transformer design utilizes nanocrystalline alloy that provides low core loss at design flux levels and switching frequencies. Capacitors are used on the transformer secondary networks to resonate the leakage inductance. The transformers are wound for a specific leakage inductance, not turns ratio. This design technique generates multiple secondary volts per turn as compared to the primary. With the appropriate tuning conditions, switching losses are minimized. The resonant topology has the added benefit of being deQed in a klystron fault condition, with little energy deposited in the arc. This obviates the need of crowbars or other related networks. A review of these design parameters, operational performance, production status, and OWL installation and performance to date will be presented.

  5. Design, status and first operations of the spallation neutron source polyphase resonant converter modulator system

    International Nuclear Information System (INIS)

    Reass, W.A.; Apgar, S.E.; Baca, D.M.; Doss, James D.; Gonzales, J.; Gribble, R.F.; Hardek, T.W.; Lynch, M.T.; Rees, D.E.; Tallerico, P.J.; Trujillo, P.B.; Anderson, D.E.; Heidenreich, D.A.; Hicks, J.D.; Leontiev, V.N.

    2003-01-01

    The Spallation Neutron Source (SNS) is a new 1.4 MW average power beam, 1 GeV accelerator being built at Oak Ridge National Laboratory. The accelerator requires 15 converter-modulator stations each providing between 9 and 11 MW pulses with up to a 1 .I MW average power. The converter-modulator can be described as a resonant 20 kHz polyphase boost inverter. Each converter modulator derives its buss voltage from a standard substation cast-core transformer. Each substation is followed by an SCR pre-regulator to accommodate voltage changes from no load to full load, in addition to providing a soft-start function. Energy storage is provided by self-clearing metallized hazy polypropylene traction capacitors. These capacitors do not fail short, but clear any internal anomaly. Three 'H-Bridge' IGBT transistor networks are used to generate the polyphase 20 kHz transformer primary drive waveforms. The 20 kHz drive waveforms are time-gated to generate the desired klystron pulse width. Pulse width modulation of the individual 20 lcHz pulses is utilized to provide regulated output waveforms with DSP based adaptive feedforward and feedback techniques. The boost transformer design utilizes nanocrystalline alloy that provides low core loss at design flux levels and switching frequencies. Capacitors are used on the transformer secondary networks to resonate the leakage inductance. The transformers are wound for a specific leakage inductance, not turns ratio. This design technique generates multiple secondary volts per turn as compared to the primary. With the appropriate tuning conditions, switching losses are minimized. The resonant topology has the added benefit of being deQed in a klystron fault condition, with little energy deposited in the arc. This obviates the need of crowbars or other related networks. A review of these design parameters, operational performance, production status, and OWL installation and performance to date will be presented.

  6. Vortex formation in Taylor-Couette flow with weakly spatial modulation

    International Nuclear Information System (INIS)

    Li, Z.; Khayat, R.E.

    2002-01-01

    The onset of the vortex structure in axisymmetric Taylor-Couette flow with spatially modulated cylinders is examined. The modulation amplitude is assumed to be small for a regular perturbation solution to be sought at small to moderate Taylor numbers. It is found that the presence of a weak modulation of the outer or inner cylinders leads unavoidably to the emergence of steady vortex flow even for a vanishingly small Taylor number. This situation is reminiscent of the onset of an imperfect bifurcation. The vortex structure of the forced TVF is found to have same periodicity when only one cylinder is modulated or the two modulations are commensurate for the Taylor number measured. The vortex structure is quasi-periodic when the two modulations are incommensurate. For a certain Taylor number, there exists a critical wavelength for the presence of the strongest vortex flow when the modulation is in the form of sinusoidal. This critical wavelength tends to the critical value predicted by the linear stability analysis when Ta approaches the supercritical value. (author)

  7. High throughput diffractive multi-beam femtosecond laser processing using a spatial light modulator

    Energy Technology Data Exchange (ETDEWEB)

    Kuang Zheng [Laser Group, Department of Engineering, University of Liverpool Brownlow Street, Liverpool L69 3GQ (United Kingdom)], E-mail: z.kuang@liv.ac.uk; Perrie, Walter [Laser Group, Department of Engineering, University of Liverpool Brownlow Street, Liverpool L69 3GQ (United Kingdom); Leach, Jonathan [Department of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ (United Kingdom); Sharp, Martin; Edwardson, Stuart P. [Laser Group, Department of Engineering, University of Liverpool Brownlow Street, Liverpool L69 3GQ (United Kingdom); Padgett, Miles [Department of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ (United Kingdom); Dearden, Geoff; Watkins, Ken G. [Laser Group, Department of Engineering, University of Liverpool Brownlow Street, Liverpool L69 3GQ (United Kingdom)

    2008-12-30

    High throughput femtosecond laser processing is demonstrated by creating multiple beams using a spatial light modulator (SLM). The diffractive multi-beam patterns are modulated in real time by computer generated holograms (CGHs), which can be calculated by appropriate algorithms. An interactive LabVIEW program is adopted to generate the relevant CGHs. Optical efficiency at this stage is shown to be {approx}50% into first order beams and real time processing has been carried out at 50 Hz refresh rate. Results obtained demonstrate high precision surface micro-structuring on silicon and Ti6Al4V with throughput gain >1 order of magnitude.

  8. Design and implementation of a risk assessment module in a spatial decision support system

    Science.gov (United States)

    Zhang, Kaixi; van Westen, Cees; Bakker, Wim

    2014-05-01

    The spatial decision support system named 'Changes SDSS' is currently under development. The goal of this system is to analyze changing hydro-meteorological hazards and the effect of risk reduction alternatives to support decision makers in choosing the best alternatives. The risk assessment module within the system is to assess the current risk, analyze the risk after implementations of risk reduction alternatives, and analyze the risk in different future years when considering scenarios such as climate change, land use change and population growth. The objective of this work is to present the detailed design and implementation plan of the risk assessment module. The main challenges faced consist of how to shift the risk assessment from traditional desktop software to an open source web-based platform, the availability of input data and the inclusion of uncertainties in the risk analysis. The risk assessment module is developed using Ext JS library for the implementation of user interface on the client side, using Python for scripting, as well as PostGIS spatial functions for complex computations on the server side. The comprehensive consideration of the underlying uncertainties in input data can lead to a better quantification of risk assessment and a more reliable Changes SDSS, since the outputs of risk assessment module are the basis for decision making module within the system. The implementation of this module will contribute to the development of open source web-based modules for multi-hazard risk assessment in the future. This work is part of the "CHANGES SDSS" project, funded by the European Community's 7th Framework Program.

  9. Parametric resonances in the amplitude-modulated probe-field absorption spectrum of a two-level atom driven by a resonance amplitude- and phase-modulated pumping field

    International Nuclear Information System (INIS)

    Sushilov, N.V.; Kholodkevich, E.D.

    1995-01-01

    An analytical expression is derived for the polarization induced by a weak probe field with periodically modulated amplitude in a two-level medium saturated by a strong amplitude-and phase-modulated resonance field. It is shown that the absorption spectrum of the probe field includes parametric resonances, the maxima corresponding to the condition δ= 2nΓ-Ω w and the minima to that of δ= (2n + 1)Γ- w , where δ is the probe-field detuning front the resonance frequency, Ω w is the modulation frequency of the probe-field amplitude, and Γ is the transition line width, n = 1, 2, 3, hor-ellipsis. At the specific modulation parameters, a substantial region of negative values (i.e., the region of amplification without the population inversion) exists in the absorption spectrum of the probe field

  10. Two spatial light modulator system for laboratory simulation of random beam propagation in random media.

    Science.gov (United States)

    Wang, Fei; Toselli, Italo; Korotkova, Olga

    2016-02-10

    An optical system consisting of a laser source and two independent consecutive phase-only spatial light modulators (SLMs) is shown to accurately simulate a generated random beam (first SLM) after interaction with a stationary random medium (second SLM). To illustrate the range of possibilities, a recently introduced class of random optical frames is examined on propagation in free space and several weak turbulent channels with Kolmogorov and non-Kolmogorov statistics.

  11. Evaluation Method for Fieldlike-Torque Efficiency by Modulation of the Resonance Field

    Science.gov (United States)

    Kim, Changsoo; Kim, Dongseuk; Chun, Byong Sun; Moon, Kyoung-Woong; Hwang, Chanyong

    2018-05-01

    The spin Hall effect has attracted a lot of interest in spintronics because it offers the possibility of a faster switching route with an electric current than with a spin-transfer-torque device. Recently, fieldlike spin-orbit torque has been shown to play an important role in the magnetization switching mechanism. However, there is no simple method for observing the fieldlike spin-orbit torque efficiency. We suggest a method for measuring fieldlike spin-orbit torque using a linear change in the resonance field in spectra of direct-current (dc)-tuned spin-torque ferromagnetic resonance. The fieldlike spin-orbit torque efficiency can be obtained in both a macrospin simulation and in experiments by simply subtracting the Oersted field from the shifted amount of resonance field. This method analyzes the effect of fieldlike torque using dc in a normal metal; therefore, only the dc resistivity and the dimensions of each layer are considered in estimating the fieldlike spin-torque efficiency. The evaluation of fieldlike-torque efficiency of a newly emerging material by modulation of the resonance field provides a shortcut in the development of an alternative magnetization switching device.

  12. Synchronisation of self-oscillations in a solid-state ring laser with pump modulation in the region of parametric resonance between self-modulation and relaxation oscillations

    International Nuclear Information System (INIS)

    Dudetskiy, V Yu; Lariontsev, E G; Chekina, S N

    2014-01-01

    The synchronisation of the self-modulation oscillation frequency in a Nd : YAG ring laser by an external periodic signal modulating the pump power in the region of parametric resonance between self-modulation and relaxation oscillations is studied theoretically and experimentally. The characteristic features of synchronisation processes in lasers operating in the self-modulation regime of the first kind and in the regime with a doubled self-modulation period are considered. Two bistable branches of synchronisation of self-modulation oscillations are found by numerical calculation. The experimental data agree well with the numerical simulation results for one of these branches, but the other branch of bistable self-modulation oscillations was not observed experimentally. (control of laser radiation parameters)

  13. Modulation of the pupil function of microscope objective lens for multifocal multi-photon microscopy using a spatial light modulator

    Science.gov (United States)

    Matsumoto, Naoya; Okazaki, Shigetoshi; Takamoto, Hisayoshi; Inoue, Takashi; Terakawa, Susumu

    2014-02-01

    We propose a method for high precision modulation of the pupil function of a microscope objective lens to improve the performance of multifocal multi-photon microscopy (MMM). To modulate the pupil function, we adopt a spatial light modulator (SLM) and place it at the conjugate position of the objective lens. The SLM can generate an arbitrary number of spots to excite the multiple fluorescence spots (MFS) at the desired positions and intensities by applying an appropriate computer-generated hologram (CGH). This flexibility allows us to control the MFS according to the photobleaching level of a fluorescent protein and phototoxicity of a specimen. However, when a large number of excitation spots are generated, the intensity distribution of the MFS is significantly different from the one originally designed due to misalignment of the optical setup and characteristics of the SLM. As a result, the image of a specimen obtained using laser scanning for the MFS has block noise segments because the SLM could not generate a uniform MFS. To improve the intensity distribution of the MFS, we adaptively redesigned the CGH based on the observed MFS. We experimentally demonstrate an improvement in the uniformity of a 10 × 10 MFS grid using a dye solution. The simplicity of the proposed method will allow it to be applied for calibration of MMM before observing living tissue. After the MMM calibration, we performed laser scanning with two-photon excitation to observe a real specimen without detecting block noise segments.

  14. In Vivo Assessment of Neurotransmitters and Modulators with Magnetic Resonance Spectroscopy: Application to Schizophrenia

    Science.gov (United States)

    Wijtenburg, S. Andrea; Yang, Shaolin; Fischer, Bernard A.; Rowland, Laura M.

    2015-01-01

    In vivo measurement of neurotransmitters and modulators is now feasible with advanced proton magnetic resonance spectroscopy (1H-MRS) techniques. This review provides a basic tutorial of MRS, describes the methods available to measure brain glutamate, glutamine, γ-aminobutyric acid, glutathione, N-acetylaspartylglutamate, glycine, and serine at magnetic field strengths of 3Tesla or higher, and summarizes the neurochemical findings in schizophrenia. Overall, 1H-MRS holds great promise for producing biomarkers that can serve as treatment targets, prediction of disease onset, or illness exacerbation in schizophrenia and other brain diseases. PMID:25614132

  15. Hyperfine interaction mediated electric-dipole spin resonance: the role of frequency modulation

    International Nuclear Information System (INIS)

    Li, Rui

    2016-01-01

    The electron spin in a semiconductor quantum dot can be coherently controlled by an external electric field, an effect called electric-dipole spin resonance (EDSR). Several mechanisms can give rise to the EDSR effect, among which there is a hyperfine mechanism, where the spin-electric coupling is mediated by the electron–nucleus hyperfine interaction. Here, we investigate the influence of frequency modulation (FM) on the spin-flip efficiency. Our results reveal that FM plays an important role in the hyperfine mechanism. Without FM, the electric field almost cannot flip the electron spin; the spin-flip probability is only about 20%. While under FM, the spin-flip probability can be improved to approximately 70%. In particular, we find that the modulation amplitude has a lower bound, which is related to the width of the fluctuated hyperfine field. (paper)

  16. Basis for calculating cross sections for nuclear magnetic resonance spin-modulated polarized neutron scattering.

    Science.gov (United States)

    Kotlarchyk, Michael; Thurston, George M

    2016-12-28

    In this work we study the potential for utilizing the scattering of polarized neutrons from nuclei whose spin has been modulated using nuclear magnetic resonance (NMR). From first principles, we present an in-depth development of the differential scattering cross sections that would arise in such measurements from a hypothetical target system containing nuclei with non-zero spins. In particular, we investigate the modulation of the polarized scattering cross sections following the application of radio frequency pulses that impart initial transverse rotations to selected sets of spin-1/2 nuclei. The long-term aim is to provide a foundational treatment of the scattering cross section associated with enhancing scattering signals from selected nuclei using NMR techniques, thus employing minimal chemical or isotopic alterations, so as to advance the knowledge of macromolecular or liquid structure.

  17. Temporal focusing-based widefield multiphoton microscopy with spatially modulated illumination for biotissue imaging.

    Science.gov (United States)

    Chang, Chia-Yuan; Lin, Cheng-Han; Lin, Chun-Yu; Sie, Yong-Da; Hu, Yvonne Yuling; Tsai, Sheng-Feng; Chen, Shean-Jen

    2018-01-01

    A developed temporal focusing-based multiphoton excitation microscope (TFMPEM) has a digital micromirror device (DMD) which is adopted not only as a blazed grating for light spatial dispersion but also for patterned illumination simultaneously. Herein, the TFMPEM has been extended to implement spatially modulated illumination at structured frequency and orientation to increase the beam coverage at the back-focal aperture of the objective lens. The axial excitation confinement (AEC) of TFMPEM can be condensed from 3.0 μm to 1.5 μm for a 50 % improvement. By using the TFMPEM with HiLo technique as two structured illuminations at the same spatial frequency but different orientation, reconstructed biotissue images according to the condensed AEC structured illumination are shown obviously superior in contrast and better scattering suppression. Picture: TPEF images of the eosin-stained mouse cerebellar cortex by conventional TFMPEM (left), and the TFMPEM with HiLo technique as 1.09 μm -1 spatially modulated illumination at 90° (center) and 0° (right) orientations. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Ultrawide Band Gap β-Ga2O3 Nanomechanical Resonators with Spatially Visualized Multimode Motion.

    Science.gov (United States)

    Zheng, Xu-Qian; Lee, Jaesung; Rafique, Subrina; Han, Lu; Zorman, Christian A; Zhao, Hongping; Feng, Philip X-L

    2017-12-13

    Beta gallium oxide (β-Ga 2 O 3 ) is an emerging ultrawide band gap (4.5 eV-4.9 eV) semiconductor with attractive properties for future power electronics, optoelectronics, and sensors for detecting gases and ultraviolet radiation. β-Ga 2 O 3 thin films made by various methods are being actively studied toward such devices. Here, we report on the experimental demonstration of single-crystal β-Ga 2 O 3 nanomechanical resonators using β-Ga 2 O 3 nanoflakes grown via low-pressure chemical vapor deposition (LPCVD). By investigating β-Ga 2 O 3 circular drumhead structures, we demonstrate multimode nanoresonators up to the sixth mode in high and very high frequency (HF/VHF) bands, and also realize spatial mapping and visualization of the multimode motion. These measurements reveal a Young's modulus of E Y = 261 GPa and anisotropic biaxial built-in tension of 37.5 MPa and 107.5 MPa. We find that thermal annealing can considerably improve the resonance characteristics, including ∼40% upshift in frequency and ∼90% enhancement in quality (Q) factor. This study lays a foundation for future exploration and development of mechanically coupled and tunable β-Ga 2 O 3 electronic, optoelectronic, and physical sensing devices.

  19. Double-Slot Hybrid Plasmonic Ring Resonator Used for Optical Sensors and Modulators

    Directory of Open Access Journals (Sweden)

    Xu Sun

    2015-11-01

    Full Text Available An ultra-high sensitivity double-slot hybrid plasmonic (DSHP ring resonator, used for optical sensors and modulators, is developed. Due to high index contrast, as well as plasmonic enhancement, a considerable part of the optical energy is concentrated in the narrow slots between Si and plasmonic materials (silver is used in this paper, which leads to high sensitivity to the infiltrating materials. By partial opening of the outer plasmonic circular sheet of the DSHP ring, a conventional side-coupled silicon on insulator (SOI bus waveguide can be used. Experimental results demonstrate ultra-high sensitivity (687.5 nm/RIU of the developed DSHP ring resonator, which is about five-times higher than for the conventional Si ring with the same geometry. Further discussions show that a very low detection limit (5.37 × 10−6 RIU can be achieved after loaded Q factor modifications. In addition, the plasmonic metal structures offer also the way to process optical and electronic signals along the same hybrid plasmonic circuits with small capacitance (~0.275 fF and large electric field, which leads to possible applications in compact high-efficiency electro-optic modulators, where no extra electrodes for electronic signals are required.

  20. Double closed-loop resonant micro optic gyro using hybrid digital phase modulation.

    Science.gov (United States)

    Ma, Huilian; Zhang, Jianjie; Wang, Linglan; Jin, Zhonghe

    2015-06-15

    It is well-known that the closed-loop operation in optical gyros offers wider dynamic range and better linearity. By adding a stair-like digital serrodyne wave to a phase modulator can be used as a frequency shifter. The width of one stair in this stair-like digital serrodyne wave should be set equal to the optical transmission time in the resonator, which is relaxed in the hybrid digital phase modulation (HDPM) scheme. The physical mechanism for this relaxation is firstly indicated in this paper. Detailed theoretical and experimental investigations are presented for the HDPM. Simulation and experimental results show that the width of one stair is not restricted by the optical transmission time, however, it should be optimized according to the rise time of the output of the digital-to-analogue converter. Based on the optimum parameters of the HDPM, a bias stability of 0.05°/s for the integration time of 400 seconds in 1 h has been carried out in an RMOG with a waveguide ring resonator with a length of 7.9 cm and a diameter of 2.5 cm.

  1. Single-photon three-qubit quantum logic using spatial light modulators.

    Science.gov (United States)

    Kagalwala, Kumel H; Di Giuseppe, Giovanni; Abouraddy, Ayman F; Saleh, Bahaa E A

    2017-09-29

    The information-carrying capacity of a single photon can be vastly expanded by exploiting its multiple degrees of freedom: spatial, temporal, and polarization. Although multiple qubits can be encoded per photon, to date only two-qubit single-photon quantum operations have been realized. Here, we report an experimental demonstration of three-qubit single-photon, linear, deterministic quantum gates that exploit photon polarization and the two-dimensional spatial-parity-symmetry of the transverse single-photon field. These gates are implemented using a polarization-sensitive spatial light modulator that provides a robust, non-interferometric, versatile platform for implementing controlled unitary gates. Polarization here represents the control qubit for either separable or entangling unitary operations on the two spatial-parity target qubits. Such gates help generate maximally entangled three-qubit Greenberger-Horne-Zeilinger and W states, which is confirmed by tomographical reconstruction of single-photon density matrices. This strategy provides access to a wide range of three-qubit states and operations for use in few-qubit quantum information processing protocols.Photons are essential for quantum information processing, but to date only two-qubit single-photon operations have been realized. Here the authors demonstrate experimentally a three-qubit single-photon linear deterministic quantum gate by exploiting polarization along with spatial-parity symmetry.

  2. Modal resonant dynamics of cables with a flexible support: A modulated diffraction problem

    Science.gov (United States)

    Guo, Tieding; Kang, Houjun; Wang, Lianhua; Liu, Qijian; Zhao, Yueyu

    2018-06-01

    Modal resonant dynamics of cables with a flexible support is defined as a modulated (wave) diffraction problem, and investigated by asymptotic expansions of the cable-support coupled system. The support-cable mass ratio, which is usually very large, turns out to be the key parameter for characterizing cable-support dynamic interactions. By treating the mass ratio's inverse as a small perturbation parameter and scaling the cable tension properly, both cable's modal resonant dynamics and the flexible support dynamics are asymptotically reduced by using multiple scale expansions, leading finally to a reduced cable-support coupled model (i.e., on a slow time scale). After numerical validations of the reduced coupled model, cable-support coupled responses and the flexible support induced coupling effects on the cable, are both fully investigated, based upon the reduced model. More explicitly, the dynamic effects on the cable's nonlinear frequency and force responses, caused by the support-cable mass ratio, the resonant detuning parameter and the support damping, are carefully evaluated.

  3. Impaired early visual response modulations to spatial information in chronic schizophrenia

    Science.gov (United States)

    Knebel, Jean-François; Javitt, Daniel C.; Murray, Micah M.

    2011-01-01

    Early visual processing stages have been demonstrated to be impaired in schizophrenia patients and their first-degree relatives. The amplitude and topography of the P1 component of the visual evoked potential (VEP) are both affected; the latter of which indicates alterations in active brain networks between populations. At least two issues remain unresolved. First, the specificity of this deficit (and suitability as an endophenotype) has yet to be established, with evidence for impaired P1 responses in other clinical populations. Second, it remains unknown whether schizophrenia patients exhibit intact functional modulation of the P1 VEP component; an aspect that may assist in distinguishing effects specific to schizophrenia. We applied electrical neuroimaging analyses to VEPs from chronic schizophrenia patients and healthy controls in response to variation in the parafoveal spatial extent of stimuli. Healthy controls demonstrated robust modulation of the VEP strength and topography as a function of the spatial extent of stimuli during the P1 component. By contrast, no such modulations were evident at early latencies in the responses from patients with schizophrenia. Source estimations localized these deficits to the left precuneus and medial inferior parietal cortex. These findings provide insights on potential underlying low-level impairments in schizophrenia. PMID:21764264

  4. Directed transport in a periodic tube driven by asymmetric unbiased forces coexisting with spatially modulated noises

    International Nuclear Information System (INIS)

    Li Fengguo; Ai Baoquan

    2011-01-01

    Graphical abstract: The current J as a function of the phase shift φ and ε at a = 1/2π, b = 0.5/2π, k B T = 0.5, α = 0.1, and F 0 = 0.5. Highlights: → Unbiased forces and spatially modulated white noises affect the current. → In the adiabatic limit, the analytical expression of directed current is obtained. → Their competition will induce current reversals. → For negative asymmetric parameters of the force, there exists an optimum parameter. → The current increases monotonously for positive asymmetric parameters. - Abstract: Transport of Brownian particles in a symmetrically periodic tube is investigated in the presence of asymmetric unbiased external forces and spatially modulated Gaussian white noises. In the adiabatic limit, we obtain the analytical expression of the directed current. It is found that the temporal asymmetry can break thermodynamic equilibrium and induce a net current. Their competition between the temporal asymmetry force and the phase shift between the noise modulation and the tube shape will induce some peculiar phenomena, for example, current reversals. The current changes with the phase shift in the form of the sine function. For negative asymmetric parameters of the force, there exists an optimum parameter at which the current takes its maximum value. However, the current increases monotonously for positive asymmetric parameters.

  5. Sleep modulates the neural substrates of both spatial and contextual memory consolidation.

    Directory of Open Access Journals (Sweden)

    Géraldine Rauchs

    -training sleep modulates the neural substrates of the consolidation of both the spatial and contextual memories acquired during virtual navigation.

  6. Multi Criteria Evaluation Module for RiskChanges Spatial Decision Support System

    Science.gov (United States)

    Olyazadeh, Roya; Jaboyedoff, Michel; van Westen, Cees; Bakker, Wim

    2015-04-01

    Multi-Criteria Evaluation (MCE) module is one of the five modules of RiskChanges spatial decision support system. RiskChanges web-based platform aims to analyze changes in hydro-meteorological risk and provides tools for selecting the best risk reduction alternative. It is developed under CHANGES framework (changes-itn.eu) and INCREO project (increo-fp7.eu). MCE tool helps decision makers and spatial planners to evaluate, sort and rank the decision alternatives. The users can choose among different indicators that are defined within the system using Risk and Cost Benefit analysis results besides they can add their own indicators. Subsequently the system standardizes and prioritizes them. Finally, the best decision alternative is selected by using the weighted sum model (WSM). The Application of this work is to facilitate the effect of MCE for analyzing changing risk over the time under different scenarios and future years by adopting a group decision making into practice and comparing the results by numeric and graphical view within the system. We believe that this study helps decision-makers to achieve the best solution by expressing their preferences for strategies under future scenarios. Keywords: Multi-Criteria Evaluation, Spatial Decision Support System, Weighted Sum Model, Natural Hazard Risk Management

  7. Hemispheric asymmetry: Looking for a novel signature of the modulation of spatial attention in multisensory processing.

    Science.gov (United States)

    Chen, Yi-Chuan; Spence, Charles

    2017-06-01

    The extent to which attention modulates multisensory processing in a top-down fashion is still a subject of debate among researchers. Typically, cognitive psychologists interested in this question have manipulated the participants' attention in terms of single/dual tasking or focal/divided attention between sensory modalities. We suggest an alternative approach, one that builds on the extensive older literature highlighting hemispheric asymmetries in the distribution of spatial attention. Specifically, spatial attention in vision, audition, and touch is typically biased preferentially toward the right hemispace, especially under conditions of high perceptual load. We review the evidence demonstrating such an attentional bias toward the right in extinction patients and healthy adults, along with the evidence of such rightward-biased attention in multisensory experimental settings. We then evaluate those studies that have demonstrated either a more pronounced multisensory effect in right than in left hemispace, or else similar effects in the two hemispaces. The results suggest that the influence of rightward-biased attention is more likely to be observed when the crossmodal signals interact at later stages of information processing and under conditions of higher perceptual load-that is, conditions under which attention is perhaps a compulsory enhancer of information processing. We therefore suggest that the spatial asymmetry in attention may provide a useful signature of top-down attentional modulation in multisensory processing.

  8. Spatial Variations of Poloidal and Toroidal Mode Field Line Resonances Observed by MMS

    Science.gov (United States)

    Le, G.; Chi, P. J.; Strangeway, R. J.; Russell, C. T.; Slavin, J. A.; Anderson, B. J.; Kepko, L.; Nakamura, R.; Plaschke, F.; Torbert, R. B.

    2017-12-01

    Field line resonances (FLRs) are magnetosphere's responses to solar wind forcing and internal instabilities generated by solar wind-magnetospheric interactions. They are standing waves along the Earth's magnetic field lines oscillating in either poloidal or toroidal modes. The two types of waves have their unique frequency characteristics. The eigenfrequency of FLRs is determined by the length of the field line and the plasma density, and thus gradually changes with L. For toroidal mode oscillations with magnetic field perturbations in the azimuthal direction, ideal MHD predicts that each field line oscillates independently with its own eigenfrequency. For poloidal mode waves with field lines oscillating radially, their frequency cannot change with L easily as L shells need to oscillate in sync to avoid efficient damping due to phase mixing. Observations, mainly during quiet times, indeed show that poloidal mode waves often exhibit nearly constant frequency across L shells. Our recent observations, on the other hand, reveal a clear L-dependent frequency trend for a long lasting storm-time poloidal wave event, indicating the wave can maintain its power with changing frequencies for an extended period [Le et al., 2017]. The spatial variation of the frequency shows discrete spatial structures. The frequency remains constant within each discrete structure that spans about 1 REalong L, and changes discretely. We present a follow-up study to investigate spatial variations of wave frequencies using the Wigner-Ville distribution. We examine both poloidal and toroidal waves under different geomagnetic conditions using multipoint observations from MMS, and compare their frequency and occurrence characteristics for insights into their generation mechanisms. Reference: Le, G., et al. (2017), Global observations of magnetospheric high-m poloidal waves during the 22 June 2015 magnetic storm, Geophys. Res. Lett., 44, 3456-3464, doi:10.1002/2017GL073048.

  9. Underwater wireless optical MIMO system with spatial modulation and adaptive power allocation

    Science.gov (United States)

    Huang, Aiping; Tao, Linwei; Niu, Yilong

    2018-04-01

    In this paper, we investigate the performance of underwater wireless optical multiple-input multiple-output communication system combining spatial modulation (SM-UOMIMO) with flag dual amplitude pulse position modulation (FDAPPM). Channel impulse response for coastal and harbor ocean water links are obtained by Monte Carlo (MC) simulation. Moreover, we obtain the closed-form and upper bound average bit error rate (BER) expressions for receiver diversity including optical combining, equal gain combining and selected combining. And a novel adaptive power allocation algorithm (PAA) is proposed to minimize the average BER of SM-UOMIMO system. Our numeric results indicate an excellent match between the analytical results and numerical simulations, which confirms the accuracy of our derived expressions. Furthermore, the results show that adaptive PAA outperforms conventional fixed factor PAA and equal PAA obviously. Multiple-input single-output system with adaptive PAA obtains even better BER performance than MIMO one, at the same time reducing receiver complexity effectively.

  10. Gray Scale Operation Of A Multichannel Optical Convolver Using The Semetex Magnetooptic Spatial Light Modulator

    Science.gov (United States)

    Davis, Jeffrey A.; Day, Timothy; Lilly, Roger A.; Taber, Donald B.; Liu, Hua-Kuang; Davis, J. A.; Day, T.; Lilly, R. A.; Taber, D. B.; Liu, H.-K.

    1988-02-01

    We present a new multichannel optical correlator/convolver architecture which uses an acoustooptic light modulator (AOLM) for the input channel and a Semetex magnetooptic spatial light modulator (MOSLM) for the set of parallel reference channels. Details of the anamorphic optical system are discussed. Experimental results illustrate use of the system as a convolver for performing digital multiplication by analog convolution (DMAC). A limited gray scale capability for data stored by the MOSLM is demonstrated by implementing this DMAC algorithm with trinary logic. Use of the MOSLM allows the number of parallel channels for the convolver to be increased significantly compared with previously reported techniques while retaining the capability for updating both channels at high speeds.

  11. A generalized interface module for the coupling of spatial kinetics and thermal-hydraulics codes

    Energy Technology Data Exchange (ETDEWEB)

    Barber, D.A.; Miller, R.M.; Joo, H.G.; Downar, T.J. [Purdue Univ., West Lafayette, IN (United States). Dept. of Nuclear Engineering; Wang, W. [SCIENTECH, Inc., Rockville, MD (United States); Mousseau, V.A.; Ebert, D.D. [Nuclear Regulatory Commission, Washington, DC (United States). Office of Nuclear Regulatory Research

    1999-03-01

    A generalized interface module has been developed for the coupling of any thermal-hydraulics code to any spatial kinetics code. The coupling scheme was designed and implemented with emphasis placed on maximizing flexibility while minimizing modifications to the respective codes. In this design, the thermal-hydraulics, general interface, and spatial kinetics codes function independently and utilize the Parallel Virtual Machine software to manage cross-process communication. Using this interface, the USNRC version of the 3D neutron kinetics code, PARCX, has been coupled to the USNRC system analysis codes RELAP5 and TRAC-M. RELAP5/PARCS assessment results are presented for two NEACRP rod ejection benchmark problems and an NEA/OECD main steam line break benchmark problem. The assessment of TRAC-M/PARCS has only recently been initiated, nonetheless, the capabilities of the coupled code are presented for a typical PWR system/core model.

  12. A generalized interface module for the coupling of spatial kinetics and thermal-hydraulics codes

    International Nuclear Information System (INIS)

    Barber, D.A.; Miller, R.M.; Joo, H.G.; Downar, T.J.; Mousseau, V.A.; Ebert, D.D.

    1999-01-01

    A generalized interface module has been developed for the coupling of any thermal-hydraulics code to any spatial kinetics code. The coupling scheme was designed and implemented with emphasis placed on maximizing flexibility while minimizing modifications to the respective codes. In this design, the thermal-hydraulics, general interface, and spatial kinetics codes function independently and utilize the Parallel Virtual Machine software to manage cross-process communication. Using this interface, the USNRC version of the 3D neutron kinetics code, PARCX, has been coupled to the USNRC system analysis codes RELAP5 and TRAC-M. RELAP5/PARCS assessment results are presented for two NEACRP rod ejection benchmark problems and an NEA/OECD main steam line break benchmark problem. The assessment of TRAC-M/PARCS has only recently been initiated, nonetheless, the capabilities of the coupled code are presented for a typical PWR system/core model

  13. Spatial modulation of above-the-gap cathodoluminescence in InP nanowires

    International Nuclear Information System (INIS)

    Tizei, L H G; Zagonel, L F; Ugarte, D; Cotta, M A; Tencé, M; Stéphan, O; Kociak, M; Chiaramonte, T

    2013-01-01

    We report the observation of light emission on wurtzite InP nanowires excited by fast electrons. The experiments were performed in a scanning transmission electron microscope using an in-house-built cathodoluminescence detector. Besides the exciton emission, at 850 nm, emission above the band gap from 400 to 800 nm was observed. In particular, this broad emission presented systematic periodic modulations indicating variations in the local excitation probability. The physical origin of the detected emission is not clear. Measurements of the spatial variation of the above-the-gap emission points to the formation of leaky cavity modes of a plasmonic nature along the nanowire length, indicating the wave nature of the excitation. We propose a phenomenological model, which fits closely the observed spatial variations. (paper)

  14. Spatial modulation of above-the-gap cathodoluminescence in InP nanowires

    Science.gov (United States)

    Tizei, L. H. G.; Zagonel, L. F.; Tencé, M.; Stéphan, O.; Kociak, M.; Chiaramonte, T.; Ugarte, D.; Cotta, M. A.

    2013-12-01

    We report the observation of light emission on wurtzite InP nanowires excited by fast electrons. The experiments were performed in a scanning transmission electron microscope using an in-house-built cathodoluminescence detector. Besides the exciton emission, at 850 nm, emission above the band gap from 400 to 800 nm was observed. In particular, this broad emission presented systematic periodic modulations indicating variations in the local excitation probability. The physical origin of the detected emission is not clear. Measurements of the spatial variation of the above-the-gap emission points to the formation of leaky cavity modes of a plasmonic nature along the nanowire length, indicating the wave nature of the excitation. We propose a phenomenological model, which fits closely the observed spatial variations.

  15. Index mismatch aberration correction over long working distances using spatial light modulation.

    Science.gov (United States)

    Gjonaj, Bergin; Johnson, Patrick; Bonn, Mischa; Domke, Katrin F

    2012-11-20

    For many microscopy applications, millimeters-long free working distances (LWD) are required. However, the high resolution and contrast of LWD objectives operated in air are lost when introducing glass and/or liquid with the sample. We propose to use spatial light modulation to correct for such beam aberrations caused by refractive index mismatches. Focusing a monochromatic laser beam with a 10 mm working distance air objective (50×, 0.5 NA) through air, glass, and water, we manage to restore a sharp, intense focus (FWHMLWD air objectives, extending their usage beyond applications in air.

  16. Trinary Encoder, Decoder, Multiplexer and Demultiplexer Using Savart Plate and Spatial Light Modulator

    Science.gov (United States)

    Ghosh, Amal K.; Singha Roy, Souradip; Mandal, Sudipta; Basuray, Amitabha

    Optoelectronic processors have already been developed with the strong potentiality of optics in information and data processing. Encoder, Decoder, Multiplexers and Demultiplexers are the most important components in modern system designs and in communications. We have implemented the same using trinary logic gates with signed magnitude defined as Modified Trinary Number (MTN). The Spatial Light Modulator (SLM) based optoelectronic circuit is suitable for high speed data processing and communications using photon as carrier. We also presented here a possible method of implementing the same using light with photon as carrier of information. The importance of the method is that all the basic gates needed may be fabricated based on basic building block.

  17. Theory of coherent quantum phase slips in Josephson junction chains with periodic spatial modulations

    Science.gov (United States)

    Svetogorov, Aleksandr E.; Taguchi, Masahiko; Tokura, Yasuhiro; Basko, Denis M.; Hekking, Frank W. J.

    2018-03-01

    We study coherent quantum phase slips which lift the ground state degeneracy in a Josephson junction ring, pierced by a magnetic flux of the magnitude equal to half of a flux quantum. The quantum phase-slip amplitude is sensitive to the normal mode structure of superconducting phase oscillations in the ring (Mooij-Schön modes). These, in turn, are affected by spatial inhomogeneities in the ring. We analyze the case of weak periodic modulations of the system parameters and calculate the corresponding modification of the quantum phase-slip amplitude.

  18. Orthogonal decomposition of a optical random field using a spatial modulator of light of liquid crystal

    International Nuclear Information System (INIS)

    Velez Juarez, Esteban; Rodriguez Garciapinna, Jorge L.; Ostrovsky, Andrey S.

    2016-01-01

    A technique for experimental determining the coherent-mode structure of electromagnetic field is proposed. This technique is based on the coherence measurements of the field in some reference basis and represents a nontrivial vector generalization of the dual-mode field correlation method recently reported by F. Ferreira and M. Belsley. The justifiability and efficiency of the proposed technique is illustrated by an example of determining the coherent-mode structure of some specially generated and experimentally characterized secondary electromagnetic source using a spatial modulator of light of liquid crystal (SLM-LC). (Author)

  19. Development of two U.H.F. band resonators for application to CO2 laser electro-optical modulation

    International Nuclear Information System (INIS)

    Egan, M.G.; Blanc, P.; Sexton, M.C.

    1980-01-01

    The purpose of this report is to describe the design and testing of two U.H.F. band resonators destined for use in the linear electro-optical modulator of the CO 2 Laser Rapid Interferometer diagnostic at present under development for the WEGA Tokamak. The resonators take the form of a re-entrant coaxial line cavity and an interdigital line filter, both of which possess the regions of high electric field necessary to activate the linear electro-optical effect

  20. A metamaterial terahertz modulator based on complementary planar double-split-ring resonator

    Science.gov (United States)

    Wang, Chang-hui; Kuang, Deng-feng; Chang, Sheng-jiang; Lin, Lie

    2013-07-01

    A metamaterial based on complementary planar double-split-ring resonator (DSRR) structure is presented and demonstrated, which can optically tune the transmission of the terahertz (THz) wave. Unlike the traditional DSRR metamaterials, the DSRR discussed in this paper consists of two split rings connected by two bridges. Numerical simulations with the finite-difference time-domain (FDTD) method reveal that the transmission spectra of the original and the complementary metamaterials are both in good agreement with Babinet's principle. Then by increasing the carrier density of the intrinsic GaAs substrate, the magnetic response of the complementary special DSRR metamaterial can be weakened or even turned off. This metamaterial structure is promised to be a narrow-band THz modulator with response time of several nanoseconds.

  1. Development of a hemispherical rotational modulation collimator system for imaging spatial distribution of radiation sources

    Science.gov (United States)

    Na, M.; Lee, S.; Kim, G.; Kim, H. S.; Rho, J.; Ok, J. G.

    2017-12-01

    Detecting and mapping the spatial distribution of radioactive materials is of great importance for environmental and security issues. We design and present a novel hemispherical rotational modulation collimator (H-RMC) system which can visualize the location of the radiation source by collecting signals from incident rays that go through collimator masks. The H-RMC system comprises a servo motor-controlled rotating module and a hollow heavy-metallic hemisphere with slits/slats equally spaced with the same angle subtended from the main axis. In addition, we also designed an auxiliary instrument to test the imaging performance of the H-RMC system, comprising a high-precision x- and y-axis staging station on which one can mount radiation sources of various shapes. We fabricated the H-RMC system which can be operated in a fully-automated fashion through the computer-based controller, and verify the accuracy and reproducibility of the system by measuring the rotational and linear positions with respect to the programmed values. Our H-RMC system may provide a pivotal tool for spatial radiation imaging with high reliability and accuracy.

  2. Spatial light modulators for full cross-connections in optical networks

    Science.gov (United States)

    Juday, Richard D. (Inventor)

    2004-01-01

    A polarization-independent optical switch is disclosed for switching at least one incoming beam from at least one input source to at least one output drain. The switch includes a polarizing beam splitter to split each of the at least one incoming beam into a first input beam and a second input beam, wherein the first input beam and the second input beams are independently polarized; a wave plate optically coupled to the second input beam for converting the polarization of the second input beam to an appropriately polarized second input beam; a beam combiner optically coupled to the first input beam and the modified second input beam, wherein the beam combiner accepts the first input beam and the modified second input beam to produce a combined beam; the combined beam is invariant to the polarization state of the input source's polarization; and a controllable spatial light modulator optically coupled to the combined beam, wherein the combined beam is diffracted by the controllable spatial light modulator to place light at a plurality of output locations.

  3. Excitation of large-amplitude parametric resonance by the mechanical stiffness modulation of a microstructure

    International Nuclear Information System (INIS)

    Krylov, Slava; Gerson, Yuval; Nachmias, Tali; Keren, Uri

    2010-01-01

    In this work we report on an approach allowing efficient parametric excitation of large-amplitude stable oscillations of a microstructure operated by a parallel-plate electrode, and present results of a theoretical and experimental investigation of the device. The frame-type structure, fabricated from a silicon on insulator (SOI) substrate using deep reactive ion etching (DRIE), consists a pair of cantilever-type suspensions connected at their ends by a link. The time-varying electrostatic force applied to the link by a parallel-plate electrode is transformed into a periodic tension of the beams, resulting in the modulation of their flexural stiffness and consequently the mechanical parametric excitation of the structure. The lateral compliance of the beams allows for large-amplitude in-plane oscillations in the direction parallel to the electrode while high axial stiffness prevents undesirable instabilities. The lumped model of the device, considered as an assembly of geometrically nonlinear massless flexures and a rigid massive link and built using the Rayleigh–Ritz method, predicted the feasibility of the excitation approach. The fabricated devices were operated in ambient air conditions by a combination of a steady (dc) and time-dependent (ac) components of voltage and the large-amplitude responses, up to 75 µm, in the vicinity of the principal parametric and primary resonances were registered by means of video acquisition and image processing. The shapes of the experimental resonant curves were consistent with those predicted by the model. The location and size of the instability regions on the frequency–voltage plane (parametric tongues) were quantitatively in good agrement with the model results. Theoretical and experimental results indicate that the suggested approach can be efficiently used for excitation of various types of microdevices where stable resonant operation combined with robustness and large vibrational amplitudes are desirable

  4. Spatial profiling of ion and neutral excitation in noble gas electron cyclotron resonance plasmas

    International Nuclear Information System (INIS)

    Rhoades, R.L.; Gorbatkin, S.M.

    1994-01-01

    Optical emission from neutrals and ions of several noble gases has been profiled in an electron cyclotron resonance plasma system. In argon plasmas with a net microwave power of 750 W, the neutral (696.5-nm) and ion (488-nm) emission profiles are slightly center peaked at 0.32 mTorr and gradually shift to a hollow appearance at 2.5 mTorr. Neon profiles show a similar trend from 2.5 to 10.0 mTorr. For the noble gases, transition pressure scales with the ionization potential of the gas, which is consistent with neutral depletion. Studies of noble gas mixtures, however, indicate that neutral depletion is not always dominant in the formation of hollow profiles. For Kr/Ar, Ar/Ne, and Ne/He plasmas, the majority gas tends to set the overall shape of the profile at any given pressure. For the conditions of the current system, plasma density appears to be more dominant than electron temperature in the formation of hollow profiles. The general method described is also a straightforward, inexpensive technique for measuring the spatial distribution of power deposited in plasmas, particularly where absolute scale can be calibrated by some other means

  5. Two-component vector solitons in defocusing Kerr-type media with spatially modulated nonlinearity

    Energy Technology Data Exchange (ETDEWEB)

    Zhong, Wei-Ping, E-mail: zhongwp6@126.com [Department of Electronic and Information Engineering, Shunde Polytechnic, Guangdong Province, Shunde 528300 (China); Texas A and M University at Qatar, P.O. Box 23874 Doha (Qatar); Belić, Milivoj [Texas A and M University at Qatar, P.O. Box 23874 Doha (Qatar); Institute of Physics, University of Belgrade, P.O. Box 57, 11001 Belgrade (Serbia)

    2014-12-15

    We present a class of exact solutions to the coupled (2+1)-dimensional nonlinear Schrödinger equation with spatially modulated nonlinearity and a special external potential, which describe the evolution of two-component vector solitons in defocusing Kerr-type media. We find a robust soliton solution, constructed with the help of Whittaker functions. For specific choices of the topological charge, the radial mode number and the modulation depth, the solitons may exist in various forms, such as the half-moon, necklace-ring, and sawtooth vortex-ring patterns. Our results show that the profile of such solitons can be effectively controlled by the topological charge, the radial mode number, and the modulation depth. - Highlights: • Two-component vector soliton clusters in defocusing Kerr-type media are reported. • These soliton clusters are constructed with the help of Whittaker functions. • The half-moon, necklace-ring and vortex-ring patterns are found. • The profile of these solitons can be effectively controlled by three soliton parameters.

  6. High spatial resolution distributed fiber system for multi-parameter sensing based on modulated pulses.

    Science.gov (United States)

    Zhang, Jingdong; Zhu, Tao; Zhou, Huan; Huang, Shihong; Liu, Min; Huang, Wei

    2016-11-28

    We demonstrate a cost-effective distributed fiber sensing system for the multi-parameter detection of the vibration, the temperature, and the strain by integrating phase-sensitive optical time domain reflectometry (φ-OTDR) and Brillouin optical time domain reflectometry (B-OTDR). Taking advantage of the fast changing property of the vibration and the static properties of the temperature and the strain, both the width and intensity of the laser pulses are modulated and injected into the single-mode sensing fiber proportionally, so that three concerned parameters can be extracted simultaneously by only one photo-detector and one data acquisition channel. A data processing method based on Gaussian window short time Fourier transform (G-STFT) is capable of achieving high spatial resolution in B-OTDR. The experimental results show that up to 4.8kHz vibration sensing with 3m spatial resolution at 10km standard single-mode fiber can be realized, as well as the distributed temperature and stress profiles along the same fiber with 80cm spatial resolution.

  7. How does experience modulate auditory spatial processing in individuals with blindness?

    Science.gov (United States)

    Tao, Qian; Chan, Chetwyn C H; Luo, Yue-jia; Li, Jian-jun; Ting, Kin-hung; Wang, Jun; Lee, Tatia M C

    2015-05-01

    Comparing early- and late-onset blindness in individuals offers a unique model for studying the influence of visual experience on neural processing. This study investigated how prior visual experience would modulate auditory spatial processing among blind individuals. BOLD responses of early- and late-onset blind participants were captured while performing a sound localization task. The task required participants to listen to novel "Bat-ears" sounds, analyze the spatial information embedded in the sounds, and specify out of 15 locations where the sound would have been emitted. In addition to sound localization, participants were assessed on visuospatial working memory and general intellectual abilities. The results revealed common increases in BOLD responses in the middle occipital gyrus, superior frontal gyrus, precuneus, and precentral gyrus during sound localization for both groups. Between-group dissociations, however, were found in the right middle occipital gyrus and left superior frontal gyrus. The BOLD responses in the left superior frontal gyrus were significantly correlated with accuracy on sound localization and visuospatial working memory abilities among the late-onset blind participants. In contrast, the accuracy on sound localization only correlated with BOLD responses in the right middle occipital gyrus among the early-onset counterpart. The findings support the notion that early-onset blind individuals rely more on the occipital areas as a result of cross-modal plasticity for auditory spatial processing, while late-onset blind individuals rely more on the prefrontal areas which subserve visuospatial working memory.

  8. Direct current modulation of spin-Hall-induced spin torque ferromagnetic resonance in platinum/permalloy bilayer thin films

    Science.gov (United States)

    Hirayama, Shigeyuki; Mitani, Seiji; Otani, YoshiChika; Kasai, Shinya

    2018-06-01

    We examined the spin-Hall-induced spin torque ferromagnetic resonance (ST-FMR) in platinum/permalloy bilayer thin films under bias direct current (DC). The bias DC modulated the symmetric components of the ST-FMR spectra, while no dominant modulation was found in the antisymmetric components. A detailed analysis in combination with simple model calculations clarified that the major origin of the modulation can be attributed to the DC resistance change under the precessional motion of magnetization. This effect is the second order contribution for the precession angle, even though the contribution can be comparable to the rectification voltage under some specific conditions.

  9. Plasmon-modulated photoluminescence from gold nanostructures and its dependence on plasmon resonance, excitation energy, and band structure

    NARCIS (Netherlands)

    Le Thi Ngoc, Loan; Wiedemair, Justyna; van den Berg, Albert; Carlen, Edwin

    2015-01-01

    Two distinct single-photon plasmon-modulated photoluminescence processes are generated from nanostructured gold surfaces by tuning the spectral overlap of the incident laser source, localized surface plasmon resonance band, and the interband transitions between the d and sp bands, near the X-and

  10. Two-Dimensional Nuclear Magnetic Resonance Structure Determination Module for Introductory Biochemistry: Synthesis and Structural Characterization of Lyso-Glycerophospholipids

    Science.gov (United States)

    Garrett, Teresa A.; Rose, Rebecca L.; Bell, Sidney M.

    2013-01-01

    In this laboratory module, introductory biochemistry students are exposed to two-dimensional [superscript 1]H-nuclear magnetic resonance of glycerophospholipids (GPLs). Working in groups of three, students enzymatically synthesized and purified a variety of 2-acyl lyso GPLs. The structure of the 2-acyl lyso GPL was verified using [superscript…

  11. Parameter Diversity Induced Multiple Spatial Coherence Resonances and Spiral Waves in Neuronal Network with and Without Noise

    International Nuclear Information System (INIS)

    Li Yuye; Jia Bing; Gu Huaguang; An Shucheng

    2012-01-01

    Diversity in the neurons and noise are inevitable in the real neuronal network. In this paper, parameter diversity induced spiral waves and multiple spatial coherence resonances in a two-dimensional neuronal network without or with noise are simulated. The relationship between the multiple resonances and the multiple transitions between patterns of spiral waves are identified. The coherence degrees induced by the diversity are suppressed when noise is introduced and noise density is increased. The results suggest that natural nervous system might profit from both parameter diversity and noise, provided a possible approach to control formation and transition of spiral wave by the cooperation between the diversity and noise. (general)

  12. Task and spatial frequency modulations of object processing: an EEG study.

    Directory of Open Access Journals (Sweden)

    Matt Craddock

    Full Text Available Visual object processing may follow a coarse-to-fine sequence imposed by fast processing of low spatial frequencies (LSF and slow processing of high spatial frequencies (HSF. Objects can be categorized at varying levels of specificity: the superordinate (e.g. animal, the basic (e.g. dog, or the subordinate (e.g. Border Collie. We tested whether superordinate and more specific categorization depend on different spatial frequency ranges, and whether any such dependencies might be revealed by or influence signals recorded using EEG. We used event-related potentials (ERPs and time-frequency (TF analysis to examine the time course of object processing while participants performed either a grammatical gender-classification task (which generally forces basic-level categorization or a living/non-living judgement (superordinate categorization on everyday, real-life objects. Objects were filtered to contain only HSF or LSF. We found a greater positivity and greater negativity for HSF than for LSF pictures in the P1 and N1 respectively, but no effects of task on either component. A later, fronto-central negativity (N350 was more negative in the gender-classification task than the superordinate categorization task, which may indicate that this component relates to semantic or syntactic processing. We found no significant effects of task or spatial frequency on evoked or total gamma band responses. Our results demonstrate early differences in processing of HSF and LSF content that were not modulated by categorization task, with later responses reflecting such higher-level cognitive factors.

  13. Task and spatial frequency modulations of object processing: an EEG study.

    Science.gov (United States)

    Craddock, Matt; Martinovic, Jasna; Müller, Matthias M

    2013-01-01

    Visual object processing may follow a coarse-to-fine sequence imposed by fast processing of low spatial frequencies (LSF) and slow processing of high spatial frequencies (HSF). Objects can be categorized at varying levels of specificity: the superordinate (e.g. animal), the basic (e.g. dog), or the subordinate (e.g. Border Collie). We tested whether superordinate and more specific categorization depend on different spatial frequency ranges, and whether any such dependencies might be revealed by or influence signals recorded using EEG. We used event-related potentials (ERPs) and time-frequency (TF) analysis to examine the time course of object processing while participants performed either a grammatical gender-classification task (which generally forces basic-level categorization) or a living/non-living judgement (superordinate categorization) on everyday, real-life objects. Objects were filtered to contain only HSF or LSF. We found a greater positivity and greater negativity for HSF than for LSF pictures in the P1 and N1 respectively, but no effects of task on either component. A later, fronto-central negativity (N350) was more negative in the gender-classification task than the superordinate categorization task, which may indicate that this component relates to semantic or syntactic processing. We found no significant effects of task or spatial frequency on evoked or total gamma band responses. Our results demonstrate early differences in processing of HSF and LSF content that were not modulated by categorization task, with later responses reflecting such higher-level cognitive factors.

  14. Enhancement of epidemic spread by noise and stochastic resonance in spatial network models with viral dynamics.

    Science.gov (United States)

    Tuckwell, H C; Toubiana, L; Vibert, J F

    2000-05-01

    We extend a previous dynamical viral network model to include stochastic effects. The dynamical equations for the viral and immune effector densities within a host population of size n are bilinear, and the noise is white, additive, and Gaussian. The individuals are connected with an n x n transmission matrix, with terms which decay exponentially with distance. In a single individual, for the range of noise parameters considered, it is found that increasing the amplitude of the noise tends to decrease the maximum mean virion level, and slightly accelerate its attainment. Two different spatial dynamical models are employed to ascertain the effects of environmental stochasticity on viral spread. In the first model transmission is unrestricted and there is no threshold within individuals. This model has the advantage that it can be analyzed using a Fokker-Planck approach. The noise is found both to synchronize and uniformize the trajectories of the viral levels across the population of infected individuals, and thus to promote the epidemic spread of the virus. Quantitative measures of the speed of spread and overall amplitude of the epidemic are obtained as functions of the noise and virulence parameters. The mean amplitude increases steadily without threshold effects for a fixed value of the virulence as the noise amplitude sigma is increased, and there is no evidence of a stochastic resonance. However, the speed of transmission, both with respect to its mean and variance, undergoes rapid increases as sigma changes by relatively small amounts. In the second, more realistic, model, there is a threshold for infection and an upper limit to the transmission rate. There may be no spread of infection at all in the absence of noise. With increasing noise level and a low threshold, the mean maximum virion level grows quickly and shows a broad-based stochastic resonance effect. When the threshold within individuals is increased, the mean population virion level increases only

  15. A multi-modal stereo microscope based on a spatial light modulator.

    Science.gov (United States)

    Lee, M P; Gibson, G M; Bowman, R; Bernet, S; Ritsch-Marte, M; Phillips, D B; Padgett, M J

    2013-07-15

    Spatial Light Modulators (SLMs) can emulate the classic microscopy techniques, including differential interference (DIC) contrast and (spiral) phase contrast. Their programmability entails the benefit of flexibility or the option to multiplex images, for single-shot quantitative imaging or for simultaneous multi-plane imaging (depth-of-field multiplexing). We report the development of a microscope sharing many of the previously demonstrated capabilities, within a holographic implementation of a stereo microscope. Furthermore, we use the SLM to combine stereo microscopy with a refocusing filter and with a darkfield filter. The instrument is built around a custom inverted microscope and equipped with an SLM which gives various imaging modes laterally displaced on the same camera chip. In addition, there is a wide angle camera for visualisation of a larger region of the sample.

  16. Efficient illumination of spatial light modulators for optical trapping and manipulation

    DEFF Research Database (Denmark)

    Bañas, Andrew Rafael; Kopylov, Oleksii; Raaby, Peter

    Energy efficiency is always desirable. This is particularly true with lasers that find many applications in research and industry. Combined with spatial light modulators (SLMs) lasers are used for optical trapping and manipulation, sorting, microscopy or biological stimulation1. Besides efficiency....... We have also shown dynamic SLM-generated patterns for materials processing and biological research. To efficiently illuminate an SLM, we used a compact pen-sized GPC-LS in place of an iris. For the same input power, hologram reconstructions are ~3x brighter or alternatively ~3x more focal spots can...... be addressed. This allows better response or increased parallel addressing for e.g. optical manipulation and sorting. Simple yet effective, a GPC-LS could save substantial power in applications that truncate lasers to a specific shape....

  17. Optical Implementation Of The Hopfield Model Using A Spatial Light Modulator Discussion Of Properties And Performance

    Science.gov (United States)

    Torzynski, Marc

    1989-01-01

    In this paper we propose an optical design for implementation of neuronic Hopfield network. We describe the algorithm and its potential possibilities as associative (or content addressable) memory. We then describe the optical set (using a magneto-optic spatial light modulator) and explaning its operating mode: the binary transparency of the SLM does not allow a direct and accurate experimental realisation of the theoretical algorithm. However, there is a particular setup that can implemented it powerfully but with a reduction of the effective number of neurons. The operating speed is then evaluated from the characteristics of the SLM "Sight-Mod" manufactured by SEMETEX corp.: the maximun operating frequency seems limited by the speed of the optical valve.

  18. Efficient and accurate laser shaping with liquid crystal spatial light modulators

    Energy Technology Data Exchange (ETDEWEB)

    Maxson, Jared M.; Bartnik, Adam C.; Bazarov, Ivan V. [Cornell Laboratory for Accelerator-Based Sciences and Education, Cornell University, Ithaca, New York 14853 (United States)

    2014-10-27

    A phase-only spatial light modulator (SLM) is capable of precise transverse laser shaping by either functioning as a variable phase grating or by serving as a variable mask via polarization rotation. As a phase grating, the highest accuracy algorithms, based on computer generated holograms (CGHs), have been shown to yield extended laser shapes with <10% rms error, but conversely little is known about the experimental efficiency of the method in general. In this work, we compare the experimental tradeoff between error and efficiency for both the best known CGH method and polarization rotation-based intensity masking when generating hard-edged flat top beams. We find that the masking method performs comparably with CGHs, both having rms error < 10% with efficiency > 15%. Informed by best practices for high efficiency from a SLM phase grating, we introduce an adaptive refractive algorithm which has high efficiency (92%) but also higher error (16%), for nearly cylindrically symmetric cases.

  19. Adaptive electron beam shaping using a photoemission gun and spatial light modulator

    Science.gov (United States)

    Maxson, Jared; Lee, Hyeri; Bartnik, Adam C.; Kiefer, Jacob; Bazarov, Ivan

    2015-02-01

    The need for precisely defined beam shapes in photoelectron sources has been well established. In this paper, we use a spatial light modulator and simple shaping algorithm to create arbitrary, detailed transverse laser shapes with high fidelity. We transmit this shaped laser to the photocathode of a high voltage dc gun. Using beam currents where space charge is negligible, and using an imaging solenoid and fluorescent viewscreen, we show that the resultant beam shape preserves these detailed features with similar fidelity. Next, instead of transmitting a shaped laser profile, we use an active feedback on the unshaped electron beam image to create equally accurate and detailed shapes. We demonstrate that this electron beam feedback has the added advantage of correcting for electron optical aberrations, yielding shapes without skew. The method may serve to provide precisely defined electron beams for low current target experiments, space-charge dominated beam commissioning, as well as for online adaptive correction of photocathode quantum efficiency degradation.

  20. Stochastic resonance driven by time-modulated correlated coloured noise sources in a single-mode laser

    International Nuclear Information System (INIS)

    De-Yi, Chen; Li, Zhang

    2009-01-01

    This paper investigates the phenomenon of stochastic resonance in a single-mode laser driven by time-modulated correlated coloured noise sources. The power spectrum and signal-to-noise ratio R of the laser intensity are calculated by the linear approximation. The effects caused by noise self-correlation time τ 1 , τ 2 and cross-correlated time τ 3 for stochastic resonance are analysed in two ways: τ 1 , τ 2 and τ 3 are taken to be the independent variables and the parameters respectively. The effects of the gain coefficient Γ and loss coefficient K on the stochastic resonance are also discussed. It is found that besides the presence of the standard form and the broad sense of stochastic resonance, the number of extrema in the curve of R versus K is reduced with the increase of the gain coefficient Γ

  1. Neutron resonance transmission spectroscopy with high spatial and energy resolution at the J-PARC pulsed neutron source

    Energy Technology Data Exchange (ETDEWEB)

    Tremsin, A.S., E-mail: ast@ssl.berkeley.edu [University of California at Berkeley, 7 Gauss Way, Berkeley, CA 94720 (United States); Shinohara, T.; Kai, T.; Ooi, M. [Japan Atomic Energy Agency, 2–4 Shirakata-shirane, Tokai-mura, Naka-gun, Ibaraki 319-1195 (Japan); Kamiyama, T.; Kiyanagi, Y.; Shiota, Y. [Hokkaido University, Kita 13 Nishi 8 Kita-ku, Sapporo-shi, Hokkaido 060-8628 (Japan); McPhate, J.B.; Vallerga, J.V.; Siegmund, O.H.W. [University of California at Berkeley, 7 Gauss Way, Berkeley, CA 94720 (United States); Feller, W.B. [NOVA Scientific, Inc., 10 Picker Rd., Sturbridge, MA 01566 (United States)

    2014-05-11

    The sharp variation of neutron attenuation at certain energies specific to particular nuclides (the lower range being from ∼1 eV up to ∼1 keV), can be exploited for the remote mapping of element and/or isotope distributions, as well as temperature probing, within relatively thick samples. Intense pulsed neutron beam-lines at spallation sources combined with a high spatial, high-timing resolution neutron counting detector, provide a unique opportunity to measure neutron transmission spectra through the time-of-flight technique. We present the results of experiments where spatially resolved neutron resonances were measured, at energies up to 50 keV. These experiments were performed with the intense flux low background NOBORU neutron beamline at the J-PARC neutron source and the high timing resolution (∼20 ns at epithermal neutron energies) and spatial resolution (∼55 µm) neutron counting detector using microchannel plates coupled to a Timepix electronic readout. Simultaneous element-specific imaging was carried out for several materials, at a spatial resolution of ∼150 µm. The high timing resolution of our detector combined with the low background beamline, also enabled characterization of the neutron pulse itself – specifically its pulse width, which varies with neutron energy. The results of our measurements are in good agreement with the predicted results for the double pulse structure of the J-PARC facility, which provides two 100 ns-wide proton pulses separated by 600 ns, broadened by the neutron energy moderation process. Thermal neutron radiography can be conducted simultaneously with resonance transmission spectroscopy, and can reveal the internal structure of the samples. The transmission spectra measured in our experiments demonstrate the feasibility of mapping elemental distributions using this non-destructive technique, for those elements (and in certain cases, specific isotopes), which have resonance energies below a few keV, and with lower

  2. Three-Dimensional Dosimetric Validation of a Magnetic Resonance Guided Intensity Modulated Radiation Therapy System

    Energy Technology Data Exchange (ETDEWEB)

    Rankine, Leith J., E-mail: Leith_Rankine@med.unc.edu [Department of Radiation Oncology, Washington University School of Medicine, St Louis, Missouri (United States); Department of Radiation Oncology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina (United States); Mein, Stewart [Medical Physics Graduate Program, Duke University, Durham, North Carolina (United States); Cai, Bin; Curcuru, Austen [Department of Radiation Oncology, Washington University School of Medicine, St Louis, Missouri (United States); Juang, Titania; Miles, Devin [Medical Physics Graduate Program, Duke University, Durham, North Carolina (United States); Mutic, Sasa; Wang, Yuhe [Department of Radiation Oncology, Washington University School of Medicine, St Louis, Missouri (United States); Oldham, Mark [Medical Physics Graduate Program, Duke University, Durham, North Carolina (United States); Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina (United States); Li, H. Harold, E-mail: hli@radonc.wustl.edu [Department of Radiation Oncology, Washington University School of Medicine, St Louis, Missouri (United States)

    2017-04-01

    Purpose: To validate the dosimetric accuracy of a commercially available magnetic resonance guided intensity modulated radiation therapy (MRgIMRT) system using a hybrid approach: 3-dimensional (3D) measurements and Monte Carlo calculations. Methods and Materials: We used PRESAGE radiochromic plastic dosimeters with remote optical computed tomography readout to perform 3D high-resolution measurements, following a novel remote dosimetry protocol. We followed the intensity modulated radiation therapy commissioning recommendations of American Association of Physicists in Medicine Task Group 119, adapted to incorporate 3D data. Preliminary tests (“AP” and “3D-Bands”) were delivered to 9.5-cm usable diameter cylindrical PRESAGE dosimeters to validate the treatment planning system (TPS) for nonmodulated deliveries; assess the sensitivity, uniformity, and rotational symmetry of the PRESAGE dosimeters; and test the robustness of the remote dosimetry protocol. Following this, 4 clinical MRgIMRT plans (“MultiTarget,” “Prostate,” “Head/Neck,” and “C-Shape”) were measured using 13-cm usable diameter PRESAGE dosimeters. For all plans, 3D-γ (3% or 3 mm global, 10% threshold) passing rates were calculated and 3D-γ maps were examined. Point doses were measured with an IBA-CC01 ionization chamber for validation of absolute dose. Finally, by use of an in-house-developed, GPU-accelerated Monte Carlo algorithm (gPENELOPE), we independently calculated dose for all 6 Task Group 119 plans and compared against the TPS. Results: For PRESAGE measurements, 3D-γ analysis yielded passing rates of 98.7%, 99.2%, 98.5%, 98.0%, 99.2%, and 90.7% for AP, 3D-Bands, MultiTarget, Prostate, Head/Neck, and C-Shape, respectively. Ion chamber measurements were within an average of 0.5% (±1.1%) from the TPS dose. Monte Carlo calculations demonstrated good agreement with the TPS, with a mean 3D-γ passing rate of 98.5% ± 1.9% using a stricter 2%/2-mm criterion. Conclusions: We

  3. Three-Dimensional Dosimetric Validation of a Magnetic Resonance Guided Intensity Modulated Radiation Therapy System

    International Nuclear Information System (INIS)

    Rankine, Leith J.; Mein, Stewart; Cai, Bin; Curcuru, Austen; Juang, Titania; Miles, Devin; Mutic, Sasa; Wang, Yuhe; Oldham, Mark; Li, H. Harold

    2017-01-01

    Purpose: To validate the dosimetric accuracy of a commercially available magnetic resonance guided intensity modulated radiation therapy (MRgIMRT) system using a hybrid approach: 3-dimensional (3D) measurements and Monte Carlo calculations. Methods and Materials: We used PRESAGE radiochromic plastic dosimeters with remote optical computed tomography readout to perform 3D high-resolution measurements, following a novel remote dosimetry protocol. We followed the intensity modulated radiation therapy commissioning recommendations of American Association of Physicists in Medicine Task Group 119, adapted to incorporate 3D data. Preliminary tests (“AP” and “3D-Bands”) were delivered to 9.5-cm usable diameter cylindrical PRESAGE dosimeters to validate the treatment planning system (TPS) for nonmodulated deliveries; assess the sensitivity, uniformity, and rotational symmetry of the PRESAGE dosimeters; and test the robustness of the remote dosimetry protocol. Following this, 4 clinical MRgIMRT plans (“MultiTarget,” “Prostate,” “Head/Neck,” and “C-Shape”) were measured using 13-cm usable diameter PRESAGE dosimeters. For all plans, 3D-γ (3% or 3 mm global, 10% threshold) passing rates were calculated and 3D-γ maps were examined. Point doses were measured with an IBA-CC01 ionization chamber for validation of absolute dose. Finally, by use of an in-house-developed, GPU-accelerated Monte Carlo algorithm (gPENELOPE), we independently calculated dose for all 6 Task Group 119 plans and compared against the TPS. Results: For PRESAGE measurements, 3D-γ analysis yielded passing rates of 98.7%, 99.2%, 98.5%, 98.0%, 99.2%, and 90.7% for AP, 3D-Bands, MultiTarget, Prostate, Head/Neck, and C-Shape, respectively. Ion chamber measurements were within an average of 0.5% (±1.1%) from the TPS dose. Monte Carlo calculations demonstrated good agreement with the TPS, with a mean 3D-γ passing rate of 98.5% ± 1.9% using a stricter 2%/2-mm criterion. Conclusions: We

  4. Improved QRD-M Detection Algorithm for Generalized Spatial Modulation Scheme

    Directory of Open Access Journals (Sweden)

    Xiaorong Jing

    2017-01-01

    Full Text Available Generalized spatial modulation (GSM is a spectral and energy efficient multiple-input multiple-output (MIMO transmission scheme. It will lead to imperfect detection performance with relatively high computational complexity by directly applying the original QR-decomposition with M algorithm (QRD-M to the GSM scheme. In this paper an improved QRD-M algorithm is proposed for GSM signal detection, which achieves near-optimal performance but with relatively low complexity. Based on the QRD, the improved algorithm firstly transforms the maximum likelihood (ML detection of the GSM signals into searching an inverted tree structure. Then, in the searching process of the M branches, the branches corresponding to the illegitimate transmit antenna combinations (TACs and related to invalid number of active antennas are cut in order to improve the validity of the resultant branches at each level by taking advantage of characteristics of GSM signals. Simulation results show that the improved QRD-M detection algorithm provides similar performance to maximum likelihood (ML with the reduced computational complexity compared to the original QRD-M algorithm, and the optimal value of parameter M of the improved QRD-M algorithm for detection of the GSM scheme is equal to modulation order plus one.

  5. Spatial light modulator array with heat minimization and image enhancement features

    Science.gov (United States)

    Jain, Kanti [Briarcliff Manor, NY; Sweatt, William C [Albuquerque, NM; Zemel, Marc [New Rochelle, NY

    2007-01-30

    An enhanced spatial light modulator (ESLM) array, a microelectronics patterning system and a projection display system using such an ESLM for heat-minimization and resolution enhancement during imaging, and the method for fabricating such an ESLM array. The ESLM array includes, in each individual pixel element, a small pixel mirror (reflective region) and a much larger pixel surround. Each pixel surround includes diffraction-grating regions and resolution-enhancement regions. During imaging, a selected pixel mirror reflects a selected-pixel beamlet into the capture angle of a projection lens, while the diffraction grating of the pixel surround redirects heat-producing unused radiation away from the projection lens. The resolution-enhancement regions of selected pixels provide phase shifts that increase effective modulation-transfer function in imaging. All of the non-selected pixel surrounds redirect all radiation energy away from the projection lens. All elements of the ESLM are fabricated by deposition, patterning, etching and other microelectronic process technologies.

  6. Non-Contact Surface Roughness Measurement by Implementation of a Spatial Light Modulator

    Directory of Open Access Journals (Sweden)

    Laura Aulbach

    2017-03-01

    Full Text Available The surface structure, especially the roughness, has a significant influence on numerous parameters, such as friction and wear, and therefore estimates the quality of technical systems. In the last decades, a broad variety of surface roughness measurement methods were developed. A destructive measurement procedure or the lack of feasibility of online monitoring are the crucial drawbacks of most of these methods. This article proposes a new non-contact method for measuring the surface roughness that is straightforward to implement and easy to extend to online monitoring processes. The key element is a liquid-crystal-based spatial light modulator, integrated in an interferometric setup. By varying the imprinted phase of the modulator, a correlation between the imprinted phase and the fringe visibility of an interferogram is measured, and the surface roughness can be derived. This paper presents the theoretical approach of the method and first simulation and experimental results for a set of surface roughnesses. The experimental results are compared with values obtained by an atomic force microscope and a stylus profiler.

  7. Spatial Location in Brief, Free-Viewing Face Encoding Modulates Contextual Face Recognition

    Directory of Open Access Journals (Sweden)

    Fatima M. Felisberti

    2013-08-01

    Full Text Available The effect of the spatial location of faces in the visual field during brief, free-viewing encoding in subsequent face recognition is not known. This study addressed this question by tagging three groups of faces with cheating, cooperating or neutral behaviours and presenting them for encoding in two visual hemifields (upper vs. lower or left vs. right. Participants then had to indicate if a centrally presented face had been seen before or not. Head and eye movements were free in all phases. Findings showed that the overall recognition of cooperators was significantly better than cheaters, and it was better for faces encoded in the upper hemifield than in the lower hemifield, both in terms of a higher d' and faster reaction time (RT. The d' for any given behaviour in the left and right hemifields was similar. The RT in the left hemifield did not vary with tagged behaviour, whereas the RT in the right hemifield was longer for cheaters than for cooperators. The results showed that memory biases in contextual face recognition were modulated by the spatial location of briefly encoded faces and are discussed in terms of scanning reading habits, top-left bias in lighting preference and peripersonal space.

  8. Seeing music: The perception of melodic 'ups and downs' modulates the spatial processing of visual stimuli.

    Science.gov (United States)

    Romero-Rivas, Carlos; Vera-Constán, Fátima; Rodríguez-Cuadrado, Sara; Puigcerver, Laura; Fernández-Prieto, Irune; Navarra, Jordi

    2018-05-10

    Musical melodies have "peaks" and "valleys". Although the vertical component of pitch and music is well-known, the mechanisms underlying its mental representation still remain elusive. We show evidence regarding the importance of previous experience with melodies for crossmodal interactions to emerge. The impact of these crossmodal interactions on other perceptual and attentional processes was also studied. Melodies including two tones with different frequency (e.g., E4 and D3) were repeatedly presented during the study. These melodies could either generate strong predictions (e.g., E4-D3-E4-D3-E4-[D3]) or not (e.g., E4-D3-E4-E4-D3-[?]). After the presentation of each melody, the participants had to judge the colour of a visual stimulus that appeared in a position that was, according to the traditional vertical connotations of pitch, either congruent (e.g., high-low-high-low-[up]), incongruent (high-low-high-low-[down]) or unpredicted with respect to the melody. Behavioural and electroencephalographic responses to the visual stimuli were obtained. Congruent visual stimuli elicited faster responses at the end of the experiment than at the beginning. Additionally, incongruent visual stimuli that broke the spatial prediction generated by the melody elicited larger P3b amplitudes (reflecting 'surprise' responses). Our results suggest that the passive (but repeated) exposure to melodies elicits spatial predictions that modulate the processing of other sensory events. Copyright © 2018 Elsevier Ltd. All rights reserved.

  9. Resonance

    DEFF Research Database (Denmark)

    Petersen, Nils Holger

    2014-01-01

    A chapter in a book about terminology within the field of medievalism: the chapter discusses the resonance of medieval music and ritual in modern (classical) music culture and liturgical practice.......A chapter in a book about terminology within the field of medievalism: the chapter discusses the resonance of medieval music and ritual in modern (classical) music culture and liturgical practice....

  10. Off-resonant vibrational excitation: Orientational dependence and spatial control of photofragments

    DEFF Research Database (Denmark)

    Machholm, Mette; Henriksen, Niels Engholm

    2000-01-01

    Off-resonant and resonant vibrational excitation with short intense infrared (IR) laser pulses creates localized oscillating wave packets, but differs by the efficiency of the excitation and surprisingly by the orientational dependence. Orientational selectivity of the vibrational excitation...... of randomly oriented heteronuclear diatomic molecules can be obtained under simultaneous irradiation by a resonant and an off-resonant intense IR laser pulse: Molecules with one initial orientation will be vibrationally excited, while those with the opposite orientation will be at rest. The orientation-dependent...... distribution. (C) 2000 American Institute of Physics....

  11. Electrical noise modulates perception of electrical pulses in humans: sensation enhancement via stochastic resonance.

    Science.gov (United States)

    Iliopoulos, Fivos; Nierhaus, Till; Villringer, Arno

    2014-03-01

    Although noise is usually considered to be harmful for signal detection and information transmission, stochastic resonance (SR) describes the counterintuitive phenomenon of noise enhancing the detection and transmission of weak input signals. In mammalian sensory systems, SR-related phenomena may arise both in the peripheral and the central nervous system. Here, we investigate behavioral SR effects of subliminal electrical noise stimulation on the perception of somatosensory stimuli in humans. We compare the likelihood to detect near-threshold pulses of different intensities applied on the left index finger during presence vs. absence of subliminal noise on the same or an adjacent finger. We show that (low-pass) noise can enhance signal detection when applied on the same finger. This enhancement is strong for near-threshold pulses below the 50% detection threshold and becomes stronger when near-threshold pulses are applied as brief trains. The effect reverses at pulse intensities above threshold, especially when noise is replaced by subliminal sinusoidal stimulation, arguing for a peripheral direct current addition. Unfiltered noise applied on longer pulses enhances detection of all pulse intensities. Noise applied to an adjacent finger has two opposing effects: an inhibiting effect (presumably due to lateral inhibition) and an enhancing effect (most likely due to SR in the central nervous system). In summary, we demonstrate that subliminal noise can significantly modulate detection performance of near-threshold stimuli. Our results indicate SR effects in the peripheral and central nervous system.

  12. Suggestion-Induced Modulation of Semantic Priming during Functional Magnetic Resonance Imaging

    Science.gov (United States)

    Ulrich, Martin; Kiefer, Markus; Bongartz, Walter; Grön, Georg; Hoenig, Klaus

    2015-01-01

    Using functional magnetic resonance imaging during a primed visual lexical decision task, we investigated the neural and functional mechanisms underlying modulations of semantic word processing through hypnotic suggestions aimed at altering lexical processing of primes. The priming task was to discriminate between target words and pseudowords presented 200 ms after the prime word which was semantically related or unrelated to the target. In a counterbalanced study design, each participant performed the task once at normal wakefulness and once after the administration of hypnotic suggestions to perceive the prime as a meaningless symbol of a foreign language. Neural correlates of priming were defined as significantly lower activations upon semantically related compared to unrelated trials. We found significant suggestive treatment-induced reductions in neural priming, albeit irrespective of the degree of suggestibility. Neural priming was attenuated upon suggestive treatment compared with normal wakefulness in brain regions supporting automatic (fusiform gyrus) and controlled semantic processing (superior and middle temporal gyri, pre- and postcentral gyri, and supplementary motor area). Hence, suggestions reduced semantic word processing by conjointly dampening both automatic and strategic semantic processes. PMID:25923740

  13. Suggestion-Induced Modulation of Semantic Priming during Functional Magnetic Resonance Imaging.

    Directory of Open Access Journals (Sweden)

    Martin Ulrich

    Full Text Available Using functional magnetic resonance imaging during a primed visual lexical decision task, we investigated the neural and functional mechanisms underlying modulations of semantic word processing through hypnotic suggestions aimed at altering lexical processing of primes. The priming task was to discriminate between target words and pseudowords presented 200 ms after the prime word which was semantically related or unrelated to the target. In a counterbalanced study design, each participant performed the task once at normal wakefulness and once after the administration of hypnotic suggestions to perceive the prime as a meaningless symbol of a foreign language. Neural correlates of priming were defined as significantly lower activations upon semantically related compared to unrelated trials. We found significant suggestive treatment-induced reductions in neural priming, albeit irrespective of the degree of suggestibility. Neural priming was attenuated upon suggestive treatment compared with normal wakefulness in brain regions supporting automatic (fusiform gyrus and controlled semantic processing (superior and middle temporal gyri, pre- and postcentral gyri, and supplementary motor area. Hence, suggestions reduced semantic word processing by conjointly dampening both automatic and strategic semantic processes.

  14. Magnetic resonance assessment of prostate localization variability in intensity-modulated radiotherapy for prostate cancer

    International Nuclear Information System (INIS)

    Villeirs, Geert M.; Meerleer, Gert O. de; Verstraete, Koenraad L.; Neve, Wilfried J. de

    2004-01-01

    Purpose: To measure prostate motion with magnetic resonance imaging (MRI) during a course of intensity-modulated radiotherapy. Methods and materials: Seven patients with prostate carcinoma were scanned supine on a 1.5-Tesla MRI system with weekly pretreatment and on-treatment HASTE T2-weighted images in 3 orthogonal planes. The bladder and rectal volumes and position of the prostatic midpoint (PMP) and margins relative to the bony pelvis were measured. Results: All pretreatment positions were at the mean position as computed from the on-treatment scans in each patient. The PMP variability (given as 1 SD) in the anterior-posterior (AP), superior-inferior (SI), and right-left (RL) directions was 2.6, 2.4, and 1.0 mm, respectively. The largest variabilities occurred at the posterior (3.2 mm), superior (2.6 mm), and inferior (2.6 mm) margins. A strong correlation was found between large rectal volume (>95th percentile) and anterior PMP displacement. A weak correlation was found between bladder volume and superior PMP displacement. Conclusions: All pretreatment positions were representative of the subsequent on-treatment positions. A clinical target volume (CTV) expansion of 5.3 mm in any direction was sufficient to ascertain a 95% coverage of the CTV within the planning target volume (PTV), provided that a rectal suppository is administered to avoid rectal overdistension and that the patient has a comfortably filled bladder (<300 mL)

  15. Length-extension resonator as a force sensor for high-resolution frequency-modulation atomic force microscopy in air.

    Science.gov (United States)

    Beyer, Hannes; Wagner, Tino; Stemmer, Andreas

    2016-01-01

    Frequency-modulation atomic force microscopy has turned into a well-established method to obtain atomic resolution on flat surfaces, but is often limited to ultra-high vacuum conditions and cryogenic temperatures. Measurements under ambient conditions are influenced by variations of the dew point and thin water layers present on practically every surface, complicating stable imaging with high resolution. We demonstrate high-resolution imaging in air using a length-extension resonator operating at small amplitudes. An additional slow feedback compensates for changes in the free resonance frequency, allowing stable imaging over a long period of time with changing environmental conditions.

  16. The spatial resolution in dosimetry with normoxic polymer-gels investigated with the dose modulation transfer approach

    International Nuclear Information System (INIS)

    Bayreder, Christian; Schoen, Robert; Wieland, M.; Georg, Dietmar; Moser, Ewald; Berg, Andreas

    2008-01-01

    The verification of dose distributions with high dose gradients as appearing in brachytherapy or stereotactic radiotherapy for example, calls for dosimetric methods with sufficiently high spatial resolution. Polymer gels in combination with a MR or optical scanner as a readout device have the potential of performing the verification of a three-dimensional dose distribution within a single measurement. The purpose of this work is to investigate the spatial resolution achievable in MR-based polymer gel dosimetry. The authors show that dosimetry on a very small spatial scale (voxel size: 94x94x1000 μm 3 ) can be performed with normoxic polymer gels using parameter selective T2 imaging. In order to prove the spatial resolution obtained we are relying on the dose-modulation transfer function (DMTF) concept based on very fine dose modulations at half periods of 200 μm. Very fine periodic dose modulations of a 60 Co photon field were achieved by means of an absorption grid made of tungsten-carbide, specifically designed for quality control. The dose modulation in the polymer gel is compared with that of film dosimetry in one plane via the DMTF concept for general access to the spatial resolution of a dose imaging system. Additionally Monte Carlo simulations were performed and used for the calculation of the DMTF of both, the polymer gel and film dosimetry. The results obtained by film dosimetry agree well with those of Monte Carlo simulations, whereas polymer gel dosimetry overestimates the amplitude value of the fine dose modulations. The authors discuss possible reasons. The in-plane resolution achieved in this work competes with the spatial resolution of standard clinical film-scanner systems

  17. Influence of Spatial Resolution in Three-dimensional Cine Phase Contrast Magnetic Resonance Imaging on the Accuracy of Hemodynamic Analysis.

    Science.gov (United States)

    Fukuyama, Atsushi; Isoda, Haruo; Morita, Kento; Mori, Marika; Watanabe, Tomoya; Ishiguro, Kenta; Komori, Yoshiaki; Kosugi, Takafumi

    2017-10-10

    We aim to elucidate the effect of spatial resolution of three-dimensional cine phase contrast magnetic resonance (3D cine PC MR) imaging on the accuracy of the blood flow analysis, and examine the optimal setting for spatial resolution using flow phantoms. The flow phantom has five types of acrylic pipes that represent human blood vessels (inner diameters: 15, 12, 9, 6, and 3 mm). The pipes were fixed with 1% agarose containing 0.025 mol/L gadolinium contrast agent. A blood-mimicking fluid with human blood property values was circulated through the pipes at a steady flow. Magnetic resonance (MR) images (three-directional phase images with speed information and magnitude images for information of shape) were acquired using the 3-Tesla MR system and receiving coil. Temporal changes in spatially-averaged velocity and maximum velocity were calculated using hemodynamic analysis software. We calculated the error rates of the flow velocities based on the volume flow rates measured with a flowmeter and examined measurement accuracy. When the acrylic pipe was the size of the thoracicoabdominal or cervical artery and the ratio of pixel size for the pipe was set at 30% or lower, spatially-averaged velocity measurements were highly accurate. When the pixel size ratio was set at 10% or lower, maximum velocity could be measured with high accuracy. It was difficult to accurately measure maximum velocity of the 3-mm pipe, which was the size of an intracranial major artery, but the error for spatially-averaged velocity was 20% or less. Flow velocity measurement accuracy of 3D cine PC MR imaging for pipes with inner sizes equivalent to vessels in the cervical and thoracicoabdominal arteries is good. The flow velocity accuracy for the pipe with a 3-mm-diameter that is equivalent to major intracranial arteries is poor for maximum velocity, but it is relatively good for spatially-averaged velocity.

  18. Microring resonator based modulator made by direct photodefinition of an electro-optic polymer

    NARCIS (Netherlands)

    Lam, Nghi Q.; Balakrishnan, M.; Faccini, M.; Diemeer, Mart; Klein, E.J.; Sengo, G.; Sengo, G.; Driessen, A.; Verboom, Willem; Reinhoudt, David

    2008-01-01

    A laterally coupled microring resonator was fabricated by direct photodefinition of negative photoresist SU8, containing tricyanovinylidenediphenylaminobenzene chromophore, by exploiting the low ultraviolet absorption window of this chromophore. The ring resonator was first photodefined by slight

  19. Differential modulation of lateral septal vasopressin receptor blockade in spatial learning, social recognition, and anxiety-related behaviors in rats

    NARCIS (Netherlands)

    Everts, HGJ; Koolhaas, JM

    1999-01-01

    The role of lateral septal vasopressin (VP) in the modulation of spatial memory, social memory, and anxiety-related behavior was studied in adult, male Wistar rats. Animals were equipped with osmotic minipumps delivering the VP-antagonist d(CH2)5-D-Tyr(Et)VAVP (1 ng/0.5 mu l per h) bilaterally into

  20. Utilization of a liquid crystal spatial light modulator in a gray scale detour phase method for Fourier holograms.

    Science.gov (United States)

    Makey, Ghaith; El-Daher, Moustafa Sayem; Al-Shufi, Kanj

    2012-11-10

    This paper introduces a new modification for the well-known binary detour phase method, which is largely used to represent Fourier holograms; the modification utilizes gray scale level control provided by a liquid crystal spatial light modulator to improve the traditional binary detour phase. Results are shown by both simulation and experiment.

  1. MIRANDA - a module based on multiregion resonance theory for generating cross sections within the AUS neutronics code system

    International Nuclear Information System (INIS)

    Robinson, G.S.

    1985-12-01

    MIRANDA is the cross-section generation module of the AUS neutronics code system used to prepare multigroup cross-section data which are pertinent to a particular study from a general purpose multigroup library of cross sections. Libraries have been prepared from ENDF/B which are suitable for thermal and fast fission reactors and for fusion blanket studies. The libraries include temperature dependent data, resonance cross sections represented by subgroup parameters and may contain photon as well as neutron data. The MIRANDA module includes a multiregion resonance calculation in slab, cylinder or cluster geometry, a homogeneous B L flux solution, and a group condensation facility. This report documents the modifications to an earlier version of MIRANDA and provides a complete user's manual

  2. Polarization study of non-resonant X-ray magnetic scattering from spin-density-wave modulation in chromium

    International Nuclear Information System (INIS)

    Ohsumi, Hiroyuki; Takata, Masaki

    2007-01-01

    We present a polarization study of non-resonant X-ray magnetic scattering in pure chromium. Satellite reflections are observed at +/-Q and +/-2Q, where Q is the modulation wave vector of an itinerant spin-density-wave. The first and second harmonics are confirmed to have magnetic and charge origin, respectively, by means of polarimetry without using an analyzer crystal. This alternative technique eliminates intolerable intensity loss at an analyzer by utilizing the sample crystal also as an analyzer crystal

  3. Reconstruction of high temporal resolution Thomson scattering data during a modulated electron cyclotron resonance heating using conditional averaging

    International Nuclear Information System (INIS)

    Kobayashi, T.; Yoshinuma, M.; Ohdachi, S.; Ida, K.; Itoh, K.; Moon, C.; Yamada, I.; Funaba, H.; Yasuhara, R.; Tsuchiya, H.; Yoshimura, Y.; Igami, H.; Shimozuma, T.; Kubo, S.; Tsujimura, T. I.; Inagaki, S.

    2016-01-01

    This paper provides a software application of the sampling scope concept for fusion research. The time evolution of Thomson scattering data is reconstructed with a high temporal resolution during a modulated electron cyclotron resonance heating (MECH) phase. The amplitude profile and the delay time profile of the heat pulse propagation are obtained from the reconstructed signal for discharges having on-axis and off-axis MECH depositions. The results are found to be consistent with the MECH deposition.

  4. Reconstruction of high temporal resolution Thomson scattering data during a modulated electron cyclotron resonance heating using conditional averaging

    Energy Technology Data Exchange (ETDEWEB)

    Kobayashi, T., E-mail: kobayashi.tatsuya@LHD.nifs.ac.jp; Yoshinuma, M.; Ohdachi, S. [National Institute for Fusion Science, Toki 509-5292 (Japan); SOKENDAI (The Graduate University for Advanced Studies), Toki 509-5292 (Japan); Ida, K. [National Institute for Fusion Science, Toki 509-5292 (Japan); SOKENDAI (The Graduate University for Advanced Studies), Toki 509-5292 (Japan); Research Center for Plasma Turbulence, Kyushu University, Kasuga 816-8580 (Japan); Itoh, K. [National Institute for Fusion Science, Toki 509-5292 (Japan); Research Center for Plasma Turbulence, Kyushu University, Kasuga 816-8580 (Japan); Moon, C.; Yamada, I.; Funaba, H.; Yasuhara, R.; Tsuchiya, H.; Yoshimura, Y.; Igami, H.; Shimozuma, T.; Kubo, S.; Tsujimura, T. I. [National Institute for Fusion Science, Toki 509-5292 (Japan); Inagaki, S. [Research Center for Plasma Turbulence, Kyushu University, Kasuga 816-8580 (Japan); Research Institute for Applied Mechanics, Kyushu University, Kasuga 816-8580 (Japan)

    2016-04-15

    This paper provides a software application of the sampling scope concept for fusion research. The time evolution of Thomson scattering data is reconstructed with a high temporal resolution during a modulated electron cyclotron resonance heating (MECH) phase. The amplitude profile and the delay time profile of the heat pulse propagation are obtained from the reconstructed signal for discharges having on-axis and off-axis MECH depositions. The results are found to be consistent with the MECH deposition.

  5. Serotonergic modulation of spatial working memory: predictions from a computational network model

    Directory of Open Access Journals (Sweden)

    Maria eCano-Colino

    2013-09-01

    Full Text Available Serotonin (5-HT receptors of types 1A and 2A are massively expressed in prefrontal cortex (PFC neurons, an area associated with cognitive function. Hence, 5-HT could be effective in modulating prefrontal-dependent cognitive functions, such as spatial working memory (SWM. However, a direct association between 5-HT and SWM has proved elusive in psycho-pharmacological studies. Recently, a computational network model of the PFC microcircuit was used to explore the relationship between 5‑HT and SWM (Cano-Colino et al. 2013. This study found that both excessive and insufficient 5-HT levels lead to impaired SWM performance in the network, and it concluded that analyzing behavioral responses based on confidence reports could facilitate the experimental identification of SWM behavioral effects of 5‑HT neuromodulation. Such analyses may have confounds based on our limited understanding of metacognitive processes. Here, we extend these results by deriving three additional predictions from the model that do not rely on confidence reports. Firstly, only excessive levels of 5-HT should result in SWM deficits that increase with delay duration. Secondly, excessive 5-HT baseline concentration makes the network vulnerable to distractors at distances that were robust to distraction in control conditions, while the network still ignores distractors efficiently for low 5‑HT levels that impair SWM. Finally, 5-HT modulates neuronal memory fields in neurophysiological experiments: Neurons should be better tuned to the cued stimulus than to the behavioral report for excessive 5-HT levels, while the reverse should happen for low 5-HT concentrations. In all our simulations agonists of 5-HT1A receptors and antagonists of 5-HT2A receptors produced behavioral and physiological effects in line with global 5-HT level increases. Our model makes specific predictions to be tested experimentally and advance our understanding of the neural basis of SWM and its neuromodulation

  6. Tilt-effect of holograms and images displayed on a spatial light modulator.

    Science.gov (United States)

    Harm, Walter; Roider, Clemens; Bernet, Stefan; Ritsch-Marte, Monika

    2015-11-16

    We show that a liquid crystal spatial light modulator (LCOS-SLM) can be used to display amplitude images, or phase holograms, which change in a pre-determined way when the display is tilted, i.e. observed under different angles. This is similar to the tilt-effect (also called "latent image effect") known from various security elements ("kinegrams") on credit cards or bank notes. The effect is achieved without any specialized optical components, simply by using the large phase shifting capability of a "thick" SLM, which extends over several multiples of 2π, in combination with the angular dependence of the phase shift. For hologram projection one can use the fact that the phase of a monochromatic wave is only defined modulo 2π. Thus one can design a phase pattern extending over several multiples of 2π, which transforms at different readout angles into different 2π-wrapped phase structures, due to the angular dependence of the modulo 2π operation. These different beams then project different holograms at the respective readout angles. In amplitude modulation mode (with inserted polarizer) the intensity of each SLM pixel oscillates over several periods when tuning its control voltage. Since the oscillation period depends on the readout angle, it is possible to find a certain control voltage which produces two (or more) selectable gray levels at a corresponding number of pre-determined readout angles. This is done with all SLM pixels individually, thus constructing different images for the selected angles. We experimentally demonstrate the reconstruction of multiple (Fourier- and Fresnel-) holograms, and of different amplitude images, by readout of static diffractive patterns in a variable angular range between 0° and 60°.

  7. Correcting the wavefront aberration of membrane mirror based on liquid crystal spatial light modulator

    Science.gov (United States)

    Yang, Bin; Wei, Yin; Chen, Xinhua; Tang, Minxue

    2014-11-01

    Membrane mirror with flexible polymer film substrate is a new-concept ultra lightweight mirror for space applications. Compared with traditional mirrors, membrane mirror has the advantages of lightweight, folding and deployable, low cost and etc. Due to the surface shape of flexible membrane mirror is easy to deviate from the design surface shape, it will bring wavefront aberration to the optical system. In order to solve this problem, a method of membrane mirror wavefront aberration correction based on the liquid crystal spatial light modulator (LCSLM) will be studied in this paper. The wavefront aberration correction principle of LCSLM is described and the phase modulation property of a LCSLM is measured and analyzed firstly. Then the membrane mirror wavefront aberration correction system is designed and established according to the optical properties of a membrane mirror. The LCSLM and a Hartmann-Shack sensor are used as a wavefront corrector and a wavefront detector, respectively. The detected wavefront aberration is calculated and converted into voltage value on LCSLM for the mirror wavefront aberration correction by programming in Matlab. When in experiment, the wavefront aberration of a glass plane mirror with a diameter of 70 mm is measured and corrected for verifying the feasibility of the experiment system and the correctness of the program. The PV value and RMS value of distorted wavefront are reduced and near diffraction limited optical performance is achieved. On this basis, the wavefront aberration of the aperture center Φ25 mm in a membrane mirror with a diameter of 200 mm is corrected and the errors are analyzed. It provides a means of correcting the wavefront aberration of membrane mirror.

  8. Magnetic resonance sialography for investigating major salivary gland duct system after intensity-modulated radiotherapy of nasopharyngeal carcinoma

    International Nuclear Information System (INIS)

    Ou Dan; He Xiayun; Zhang Yunyan

    2013-01-01

    We investigated the value of magnetic resonance sialography for evaluating xerostomia induced by intensity-modulated radiotherapy for nasopharyngeal carcinoma. Fourteen patients with nasopharyngeal carcinoma were treated with intensity-modulated radiotherapy. Salivary function was assessed by magnetic resonance sialography and subjective evaluation criteria pre-treatment, 1 week and 1 year post-radiotherapy. A magnetic resonance sialography categorical scoring system was used to compare the visibility of salivary ducts. The average mean dose was 38.93 Gy to the parotid glands and 59.34 Gy to the submandibular glands. Before radiotherapy, the visibility scores of both the parotid and submandibular ducts increased after secretion stimulation. The scores decreased and the response to stimulation was attenuated 1 week post-radiotherapy. For most of the parotid ducts, the visibility score improved at 1 year post-radiotherapy both at rest and under stimulation, but not for the submandibular ducts. With a median follow-up of 12.3 months, 8/12 patients had grade 1 xerostomia and 4/12 had grade 2 xerostomia. Magnetic resonance sialography allows non-invasive evaluation of radiation-induced ductal changes in the major salivary glands and enables reliable prediction of radiation-induced xerostomia. (author)

  9. Detection and quantification of creep strain using process compensated resonance testing (PCRT) sorting modules trained with modeled resonance spectra

    Science.gov (United States)

    Heffernan, Julieanne; Biedermann, Eric; Mayes, Alexander; Livings, Richard; Jauriqui, Leanne; Goodlet, Brent; Aldrin, John C.; Mazdiyasni, Siamack

    2018-04-01

    Process Compensated Resonant Testing (PCRT) is a full-body nondestructive testing (NDT) method that measures the resonance frequencies of a part and correlates them to the part's material and/or damage state. PCRT testing is used in the automotive, aerospace, and power generation industries via automated PASS/FAIL inspections to distinguish parts with nominal process variation from those with the defect(s) of interest. Traditional PCRT tests are created through the statistical analysis of populations of "good" and "bad" parts. However, gathering a statistically significant number of parts can be costly and time-consuming, and the availability of defective parts may be limited. This work uses virtual databases of good and bad parts to create two targeted PCRT inspections for single crystal (SX) nickel-based superalloy turbine blades. Using finite element (FE) models, populations were modeled to include variations in geometric dimensions, material properties, crystallographic orientation, and creep damage. Model results were verified by comparing the frequency variation in the modeled populations with the measured frequency variations of several physical blade populations. Additionally, creep modeling results were verified through the experimental evaluation of coupon geometries. A virtual database of resonance spectra was created from the model data. The virtual database was used to create PCRT inspections to detect crystallographic defects and creep strain. Quantification of creep strain values using the PCRT inspection results was also demonstrated.

  10. Double parametric resonance for matter-wave solitons in a time-modulated trap

    International Nuclear Information System (INIS)

    Baizakov, Bakhtiyor; Salerno, Mario; Filatrella, Giovanni; Malomed, Boris

    2005-01-01

    We analyze the motion of solitons in a self-attractive Bose-Einstein condensate, loaded into a quasi-one-dimensional parabolic potential trap, which is subjected to time-periodic modulation with an amplitude ε and frequency Ω. First, we apply the variational approximation, which gives rise to decoupled equations of motion for the center-of-mass coordinate of the soliton, ξ(t), and its width a(t). The equation for ξ(t) is the ordinary Mathieu equation (ME) (it is an exact equation that does not depend on the adopted ansatz), the equation for a(t) being a nonlinear generalization of the ME. Both equations give rise to the same map of instability zones in the (ε,Ω) plane, generated by the parametric resonances (PRs), if the instability is defined as the onset of growth of the amplitude of the parametrically driven oscillations. In this sense, the double PR is predicted. Direct simulations of the underlying Gross-Pitaevskii equation give rise to a qualitatively similar but quantitatively different stability map for oscillations of the soliton's width a(t). In the direct simulations, we identify the soliton dynamics as unstable if the instability (again, realized as indefinite growth of the amplitude of oscillations) can be detected during a time comparable with, or smaller than, the lifetime of the condensate (therefore accessible to experimental detection). Two-soliton configurations are also investigated. It is concluded that multiple collisions between solitons are elastic, and they do not affect the instability borders

  11. Input-dependent frequency modulation of cortical gamma oscillations shapes spatial synchronization and enables phase coding.

    Science.gov (United States)

    Lowet, Eric; Roberts, Mark; Hadjipapas, Avgis; Peter, Alina; van der Eerden, Jan; De Weerd, Peter

    2015-02-01

    Fine-scale temporal organization of cortical activity in the gamma range (∼25-80Hz) may play a significant role in information processing, for example by neural grouping ('binding') and phase coding. Recent experimental studies have shown that the precise frequency of gamma oscillations varies with input drive (e.g. visual contrast) and that it can differ among nearby cortical locations. This has challenged theories assuming widespread gamma synchronization at a fixed common frequency. In the present study, we investigated which principles govern gamma synchronization in the presence of input-dependent frequency modulations and whether they are detrimental for meaningful input-dependent gamma-mediated temporal organization. To this aim, we constructed a biophysically realistic excitatory-inhibitory network able to express different oscillation frequencies at nearby spatial locations. Similarly to cortical networks, the model was topographically organized with spatially local connectivity and spatially-varying input drive. We analyzed gamma synchronization with respect to phase-locking, phase-relations and frequency differences, and quantified the stimulus-related information represented by gamma phase and frequency. By stepwise simplification of our models, we found that the gamma-mediated temporal organization could be reduced to basic synchronization principles of weakly coupled oscillators, where input drive determines the intrinsic (natural) frequency of oscillators. The gamma phase-locking, the precise phase relation and the emergent (measurable) frequencies were determined by two principal factors: the detuning (intrinsic frequency difference, i.e. local input difference) and the coupling strength. In addition to frequency coding, gamma phase contained complementary stimulus information. Crucially, the phase code reflected input differences, but not the absolute input level. This property of relative input-to-phase conversion, contrasting with latency codes

  12. Psychophysical testing of spatial and temporal dimensions of endogenous analgesia: conditioned pain modulation and offset analgesia.

    Science.gov (United States)

    Honigman, Liat; Yarnitsky, David; Sprecher, Elliot; Weissman-Fogel, Irit

    2013-08-01

    The endogenous analgesia (EA) system is psychophysically evaluated using various paradigms, including conditioned pain modulation (CPM) and offset analgesia (OA) testing, respectively, the spatial and temporal filtering processes of noxious information. Though both paradigms assess the function of the EA system, it is still unknown whether they reflect the same aspects of EA and consequently whether they provide additive or equivalent data. Twenty-nine healthy volunteers (15 males) underwent 5 trials of different stimulation conditions in random order including: (1) the classic OA three-temperature stimulus train ('OA'); (2) a three-temperature stimulus train as control for the OA ('OAcon'); (3) a constant temperature stimulus ('constant'); (4) the classic parallel CPM ('CPM'); and (5) a combination of OA and CPM ('OA + CPM'). We found that in males, the pain reduction during the OA + CPM condition was greater than during the OA (P = 0.003) and CPM (P = 0.07) conditions. Furthermore, a correlation was found between OA and CPM (r = 0.62, P = 0.01) at the time of maximum OA effect. The additive effect found suggests that the two paradigms represent at least partially different aspects of EA. The moderate association between the CPM and OA magnitudes indicates, on the other hand, some commonality of their underlying mechanisms.

  13. Holographic Fabrication of Designed Functional Defect Lines in Photonic Crystal Lattice Using a Spatial Light Modulator

    Directory of Open Access Journals (Sweden)

    Jeffrey Lutkenhaus

    2016-04-01

    Full Text Available We report the holographic fabrication of designed defect lines in photonic crystal lattices through phase engineering using a spatial light modulator (SLM. The diffracted beams from the SLM not only carry the defect’s content but also the defect related phase-shifting information. The phase-shifting induced lattice shifting in photonic lattices around the defects in three-beam interference is less than the one produced by five-beam interference due to the alternating shifting in lattice in three beam interference. By designing the defect line at a 45 degree orientation and using three-beam interference, the defect orientation can be aligned with the background photonic lattice, and the shifting is only in one side of the defect line, in agreement with the theory. Finally, a new design for the integration of functional defect lines in a background phase pattern reduces the relative phase shift of the defect and utilizes the different diffraction efficiency between the defect line and background phase pattern. We demonstrate that the desired and functional defect lattice can be registered into the background lattice through the direct imaging of designed phase patterns.

  14. PHASE QUANTIZATION STUDY OF SPATIAL LIGHT MODULATOR FOR EXTREME HIGH-CONTRAST IMAGING

    Energy Technology Data Exchange (ETDEWEB)

    Dou, Jiangpei; Ren, Deqing, E-mail: jpdou@niaot.ac.cn, E-mail: jiangpeidou@gmail.com [Physics and Astronomy Department, California State University Northridge, 18111 Nordhoff Street, Northridge, CA 91330 (United States)

    2016-11-20

    Direct imaging of exoplanets by reflected starlight is extremely challenging due to the large luminosity ratio to the primary star. Wave-front control is a critical technique to attenuate the speckle noise in order to achieve an extremely high contrast. We present a phase quantization study of a spatial light modulator (SLM) for wave-front control to meet the contrast requirement of detection of a terrestrial planet in the habitable zone of a solar-type star. We perform the numerical simulation by employing the SLM with different phase accuracy and actuator numbers, which are related to the achievable contrast. We use an optimization algorithm to solve the quantization problems that is matched to the controllable phase step of the SLM. Two optical configurations are discussed with the SLM located before and after the coronagraph focal plane mask. The simulation result has constrained the specification for SLM phase accuracy in the above two optical configurations, which gives us a phase accuracy of 0.4/1000 and 1/1000 waves to achieve a contrast of 10{sup -10}. Finally, we have demonstrated that an SLM with more actuators can deliver a competitive contrast performance on the order of 10{sup -10} in comparison to that by using a deformable mirror.

  15. Adaptive electron beam shaping using a photoemission gun and spatial light modulator

    Directory of Open Access Journals (Sweden)

    Jared Maxson

    2015-02-01

    Full Text Available The need for precisely defined beam shapes in photoelectron sources has been well established. In this paper, we use a spatial light modulator and simple shaping algorithm to create arbitrary, detailed transverse laser shapes with high fidelity. We transmit this shaped laser to the photocathode of a high voltage dc gun. Using beam currents where space charge is negligible, and using an imaging solenoid and fluorescent viewscreen, we show that the resultant beam shape preserves these detailed features with similar fidelity. Next, instead of transmitting a shaped laser profile, we use an active feedback on the unshaped electron beam image to create equally accurate and detailed shapes. We demonstrate that this electron beam feedback has the added advantage of correcting for electron optical aberrations, yielding shapes without skew. The method may serve to provide precisely defined electron beams for low current target experiments, space-charge dominated beam commissioning, as well as for online adaptive correction of photocathode quantum efficiency degradation.

  16. Dynamic wavefront sensing and correction with low-cost twisted nematic spatial light modulators

    International Nuclear Information System (INIS)

    Duran, Vicente; Climent, Vicent; Lancis, Jesus; Tajahuerce, Enrique; Bara, Salvador; Arines, Justo; Ares, Jorge; Andres, Pedro; Jaroszewicz, Zbigniew

    2010-01-01

    Off-the-shelf twisted nematic liquid crystal displays (TNLCDs) show some interesting features such as high spatial resolution, easy handling, wide availability, and low cost. We describe a compact adaptive optical system using just one TNLCD to measure and compensate optical aberrations. The current system operates at a frame rate of the order of 10 Hz with a four level codification scheme. Wavefront estimation is performed through conventional Hartmann-Shack sensing architecture. The system has proved to work properly with a maximum rms aberration of 0.76 microns and wavefront gradient of 50 rad/mm at a wavelength of 514 nm. These values correspond to typical aberrations found in human eyes. The key of our approach is careful characterization and optimization of the TNLCD for phase-only modulation. For this purpose, we exploit the so-called retarder-rotator approach for twisted nematic liquid crystal cells. The optimization process has been successfully applied to SLMs working either in transmissive or in reflective mode, even when light depolarization effects are observed.

  17. Through tissue imaging of a live breast cancer tumour model using handheld surface enhanced spatially offset resonance Raman spectroscopy (SESORRS).

    Science.gov (United States)

    Nicolson, Fay; Jamieson, Lauren E; Mabbott, Samuel; Plakas, Konstantinos; Shand, Neil C; Detty, Michael R; Graham, Duncan; Faulds, Karen

    2018-04-21

    In order to improve patient survival and reduce the amount of unnecessary and traumatic biopsies, non-invasive detection of cancerous tumours is of imperative and urgent need. Multicellular tumour spheroids (MTS) can be used as an ex vivo cancer tumour model, to model in vivo nanoparticle (NP) uptake by the enhanced permeability and retention (EPR) effect. Surface enhanced spatially offset Raman spectroscopy (SESORS) combines both surface enhanced Raman spectroscopy (SERS) and spatially offset Raman spectroscopy (SORS) to yield enhanced Raman signals at much greater sub-surface levels. By utilizing a reporter that has an electronic transition in resonance with the laser frequency, surface enhanced resonance Raman scattering (SERRS) yields even greater enhancement in Raman signal. Using a handheld SORS spectrometer with back scattering optics, we demonstrate the detection of live breast cancer 3D MTS containing SERRS active NPs through 15 mm of porcine tissue. False color 2D heat intensity maps were used to determine tumour model location. In addition, we demonstrate the tracking of SERRS-active NPs through porcine tissue to depths of up to 25 mm. This unprecedented performance is due to the use of red-shifted chalcogenpyrylium-based Raman reporters to demonstrate the novel technique of surface enhanced spatially offset resonance Raman spectroscopy (SESORRS) for the first time. Our results demonstrate a significant step forward in the ability to detect vibrational fingerprints from a tumour model at depth through tissue. Such an approach offers significant promise for the translation of NPs into clinical applications for non-invasive disease diagnostics based on this new chemical principle of measurement.

  18. Toward Bayesian inference of the spatial distribution of proteins from three-cube Förster resonance energy transfer data

    DEFF Research Database (Denmark)

    Hooghoudt, Jan Otto; Barroso, Margarida; Waagepetersen, Rasmus Plenge

    2017-01-01

    Főrster resonance energy transfer (FRET) is a quantum-physical phenomenon where energy may be transferred from one molecule to a neighbour molecule if the molecules are close enough. Using fluorophore molecule marking of proteins in a cell it is possible to measure in microscopic images to what....... In this paper we propose a new likelihood-based approach to statistical inference for FRET microscopic data. The likelihood function is obtained from a detailed modeling of the FRET data generating mechanism conditional on a protein configuration. We next follow a Bayesian approach and introduce a spatial point...

  19. Emphasis of spatial cues in the temporal fine structure during the rising segments of amplitude-modulated sounds

    Science.gov (United States)

    Dietz, Mathias; Marquardt, Torsten; Salminen, Nelli H.; McAlpine, David

    2013-01-01

    The ability to locate the direction of a target sound in a background of competing sources is critical to the survival of many species and important for human communication. Nevertheless, brain mechanisms that provide for such accurate localization abilities remain poorly understood. In particular, it remains unclear how the auditory brain is able to extract reliable spatial information directly from the source when competing sounds and reflections dominate all but the earliest moments of the sound wave reaching each ear. We developed a stimulus mimicking the mutual relationship of sound amplitude and binaural cues, characteristic to reverberant speech. This stimulus, named amplitude modulated binaural beat, allows for a parametric and isolated change of modulation frequency and phase relations. Employing magnetoencephalography and psychoacoustics it is demonstrated that the auditory brain uses binaural information in the stimulus fine structure only during the rising portion of each modulation cycle, rendering spatial information recoverable in an otherwise unlocalizable sound. The data suggest that amplitude modulation provides a means of “glimpsing” low-frequency spatial cues in a manner that benefits listening in noisy or reverberant environments. PMID:23980161

  20. Resonances

    DEFF Research Database (Denmark)

    an impetus or drive to that account: change, innovation, rupture, or discontinuity. Resonances: Historical Essays on Continuity and Change explores the historiographical question of the modes of interrelation between these motifs in historical narratives. The essays in the collection attempt to realize...

  1. Study the effects of varying interference upon the optical properties of turbid samples using NIR spatial light modulation

    Science.gov (United States)

    Shaul, Oren; Fanrazi-Kahana, Michal; Meitav, Omri; Pinhasi, Gad A.; Abookasis, David

    2018-03-01

    Optical properties of biological tissues are valuable diagnostic parameters which can provide necessary information regarding tissue state during disease pathogenesis and therapy. However, different sources of interference, such as temperature changes may modify these properties, introducing confounding factors and artifacts to data, consequently skewing their interpretation and misinforming clinical decision-making. In the current study, we apply spatial light modulation, a type of diffuse reflectance hyperspectral imaging technique, to monitor the variation in optical properties of highly scattering turbid media in the presence varying levels of the following sources of interference: scattering concentration, temperature, and pressure. Spatial near-infrared (NIR) light modulation is a wide-field, non-contact emerging optical imaging platform capable of separating the effects of tissue scattering from those of absorption, thereby accurately estimating both parameters. With this technique, periodic NIR illumination patterns at alternately low and high spatial frequencies, at six discrete wavelengths between 690 to 970 nm, were sequentially projected upon the medium while a CCD camera collects the diffusely reflected light. Data analysis based assumptions is then performed off-line to recover the medium's optical properties. We conducted a series of experiments demonstrating the changes in absorption and reduced scattering coefficients of commercially available fresh milk and chicken breast tissue under different interference conditions. In addition, information on the refractive index was study under increased pressure. This work demonstrates the utility of NIR spatial light modulation to detect varying sources of interference upon the optical properties of biological samples.

  2. Compensation for the phase-type spatial periodic modulation of the near-field beam at 1053 nm

    Science.gov (United States)

    Gao, Yaru; Liu, Dean; Yang, Aihua; Tang, Ruyu; Zhu, Jianqiang

    2017-10-01

    A phase-only spatial light modulator is used to provide and compensate for the spatial periodic modulation (SPM) of the near-field beam at the near infrared at 1053nm wavelength with an improved iterative weight-based method. The transmission characteristics of the incident beam has been changed by a spatial light modulator (SLM) to shape the spatial intensity of the output beam. The propagation and reverse propagation of the light in free space are two important processes in the iterative process. The based theory is the beam angular spectrum transmit formula (ASTF) and the principle of the iterative weight-based method. We have made two improvements to the originally proposed iterative weight-based method. We select the appropriate parameter by choosing the minimum value of the output beam contrast degree and use the MATLAB built-in angle function to acquire the corresponding phase of the light wave function. The required phase that compensates for the intensity distribution of the incident SPM beam is iterated by this algorithm, which can decrease the magnitude of the SPM of the intensity on the observation plane. The experimental results show that the phase-type SPM of the near-field beam is subject to a certain restriction. We have also analyzed some factors that make the results imperfect. The experiment results verifies the possible applicability of this iterative weight-based method to compensate for the SPM of the near-field beam.

  3. Analysis of a PWM Resonant Buck Chopper for Use as a Ship Service Converter Module

    National Research Council Canada - National Science Library

    Ciezki, John

    1999-01-01

    .... This study provides a background analysis into resonant converters which utilize zero-voltage-switching and zero-current-switching techniques to mitigate the aforementioned concerns and facilitate...

  4. Nonlinear convective flows in a two-layer system under the action of spatial temperature modulation of heat release/consumption at the interface

    Science.gov (United States)

    Simanovskii, Ilya B.; Viviani, Antonio; Dubois, Frank

    2018-06-01

    An influence of a spatial temperature modulation of the interfacial heat release/consumption on nonlinear convective flows in the 47v2 silicone oil - water system, is studied. Rigid heat-insulated lateral walls, corresponding to the case of closed cavities, have been considered. Transitions between the flows with different spatial structures, have been investigated. It is shown that the spatial modulation can change the sequence of bifurcations and lead to the appearance of specific steady and oscillatory flows in the system.

  5. Spatial and object-based attention modulates broadband high-frequency responses across the human visual cortical hierarchy.

    Science.gov (United States)

    Davidesco, Ido; Harel, Michal; Ramot, Michal; Kramer, Uri; Kipervasser, Svetlana; Andelman, Fani; Neufeld, Miri Y; Goelman, Gadi; Fried, Itzhak; Malach, Rafael

    2013-01-16

    One of the puzzling aspects in the visual attention literature is the discrepancy between electrophysiological and fMRI findings: whereas fMRI studies reveal strong attentional modulation in the earliest visual areas, single-unit and local field potential studies yielded mixed results. In addition, it is not clear to what extent spatial attention effects extend from early to high-order visual areas. Here we addressed these issues using electrocorticography recordings in epileptic patients. The patients performed a task that allowed simultaneous manipulation of both spatial and object-based attention. They were presented with composite stimuli, consisting of a small object (face or house) superimposed on a large one, and in separate blocks, were instructed to attend one of the objects. We found a consistent increase in broadband high-frequency (30-90 Hz) power, but not in visual evoked potentials, associated with spatial attention starting with V1/V2 and continuing throughout the visual hierarchy. The magnitude of the attentional modulation was correlated with the spatial selectivity of each electrode and its distance from the occipital pole. Interestingly, the latency of the attentional modulation showed a significant decrease along the visual hierarchy. In addition, electrodes placed over high-order visual areas (e.g., fusiform gyrus) showed both effects of spatial and object-based attention. Overall, our results help to reconcile previous observations of discrepancy between fMRI and electrophysiology. They also imply that spatial attention effects can be found both in early and high-order visual cortical areas, in parallel with their stimulus tuning properties.

  6. Peculiarities of the fundamental mode structure in stable-resonator lasers upon spatially inhomogeneous amplification

    International Nuclear Information System (INIS)

    Gorbunkov, Mikhail V; Kostryukov, P V; Telegin, L S; Tunkin, V G; Yakovlev, D V

    2007-01-01

    The structure of the fundamental mode of a laser is calculated by the iteration Fox-Li method in the case of inhomogeneous unsaturated amplification produced by axially symmetric longitudinal pumping. The calculation is performed for different parameters g 1 and g 2 of the resonator within the entire stability region. It is shown that in the case of inhomogeneous amplification, the fundamental mode considerably deviates from the Gaussian mode of an empty resonator only in the so-called critical configurations of the resonator, when the quantity [arccos(g 1 g 2 ) 1/2 ]/π is zero or takes a number of values expressed by irreducible fractions m/n. For the Fresnel number N F = 9, configurations with m/n = 1/2, 2/5, 3/8, 1/3, 3/10, 1/4, 1/5, 1/6, 1/8, and 1/10 are pronounced. As N F increases, the number of critical configurations increases. The expansion in a system of Laguerre-Gaussian beams shows that the fundamental mode in critical configurations is formed by a set of beams with certain radial indices p phased in the active medium. (resonators. modes)

  7. The generation of flat-top beams by complex amplitude modulation with a phase-only spatial light modulator

    CSIR Research Space (South Africa)

    Hendriks, A

    2012-08-01

    Full Text Available amplitude modulation of the light, i.e., in amplitude and phase. We outline the theoretical concept, and then illustrate its use with the example of the laser beam shaping of Gaussian beams into flat-top beams. We quantify the performance of this approach...

  8. Matter-wave solitons and finite-amplitude Bloch waves in optical lattices with a spatially modulated nonlinearity

    OpenAIRE

    Zhang, Jie-Fang; Li, Yi-Shen; Meng, Jianping; Wu, Lei; Malomed, Boris A.

    2010-01-01

    We investigate solitons and nonlinear Bloch waves in Bose-Einstein condensates trapped in optical lattices. By introducing specially designed localized profiles of the spatial modulation of the attractive nonlinearity, we construct an infinite number of exact soliton solutions in terms of the Mathieu and elliptic functions, with the chemical potential belonging to the semi-infinite bandgap of the optical-lattice-induced spectrum. Starting from the exact solutions, we employ the relaxation met...

  9. Spatial power distribution in the SR-0 experimental module of the SPHINX nuclear transmutation system - 2006 and 2007 variants

    International Nuclear Information System (INIS)

    Rypar, Vojtech; Svadlenkova, Marie; Novak, Evzen; Viererbl, Ladislav; Lahodova, Zdena; Bily, Tomas

    2007-11-01

    Experiments were performed with various assemblies modelling the SPHINX transmutation system with the aim to investigate the effect of materials in the SR-0 modules, i.e. LiF, NaF, graphite, on the spatial power distribution of the reaction rates of the activation detectors, axial and radial distribution of the fission products of the fuel pins located in some points of the reactor core, and photon dose distribution by using thermoluminescent dosemeters

  10. Parity generator and parity checker in the modified trinary number system using savart plate and spatial light modulator

    Science.gov (United States)

    Ghosh, Amal K.

    2010-09-01

    The parity generators and the checkers are the most important circuits in communication systems. With the development of multi-valued logic (MVL), the proposed system with parity generators and checkers is the most required using the recently developed optoelectronic technology in the modified trinary number (MTN) system. This system also meets up the tremendous needs of speeds by exploiting the savart plates and spatial light modulators (SLM) in the optical tree architecture (OTA).

  11. Imaging nanoscale spatial modulation of a relativistic electron beam with a MeV ultrafast electron microscope

    Science.gov (United States)

    Lu, Chao; Jiang, Tao; Liu, Shengguang; Wang, Rui; Zhao, Lingrong; Zhu, Pengfei; Liu, Yaqi; Xu, Jun; Yu, Dapeng; Wan, Weishi; Zhu, Yimei; Xiang, Dao; Zhang, Jie

    2018-03-01

    An accelerator-based MeV ultrafast electron microscope (MUEM) has been proposed as a promising tool to the study structural dynamics at the nanometer spatial scale and the picosecond temporal scale. Here, we report experimental tests of a prototype MUEM where high quality images with nanoscale fine structures were recorded with a pulsed ˜3 MeV picosecond electron beam. The temporal and spatial resolutions of the MUEM operating in the single-shot mode are about 4 ps (FWHM) and 100 nm (FWHM), corresponding to a temporal-spatial resolution of 4 × 10-19 s m, about 2 orders of magnitude higher than that achieved with state-of-the-art single-shot keV UEM. Using this instrument, we offer the demonstration of visualizing the nanoscale periodic spatial modulation of an electron beam, which may be converted into longitudinal density modulation through emittance exchange to enable production of high-power coherent radiation at short wavelengths. Our results mark a great step towards single-shot nanometer-resolution MUEMs and compact intense x-ray sources that may have widespread applications in many areas of science.

  12. High power operation of the polyphase resonant converter modulator system for the spallation neutron source linear accelerator

    CERN Document Server

    Reass, W A; Baca, D M; Doss, J D; Gonzáles, J M; Gribble, R F; Trujillo, P G

    2003-01-01

    The spallation neutron source (SNS) is a new 1.4 MW average power beam, 1 GeV accelerator being built at Oak Ridge national laboratory. The accelerator requires 15 "long-pulse" converter-modulator stations each providing a maximum of 11 MW pulses with a 1.1 MW average power. Two variants of the converter-modulator are utilized, an 80 kV and a 140 kV design, the voltage dependant on the type of klystron load. The converter-modulator can be described as a resonant zero-voltage- switching polyphase boost inverter. As noted in Figure 1, each converter modulator derives its buss voltage from a standard 13.8 kV to 2100 Y (1.5 MVA) substation cast-core transformer. The substation also contains harmonic traps and filters to accommodate IEEE 519 and 141 regulations. Each substation is followed by an SCR preregulator to accommodate system voltage changes from no load to full load, in addition to providing a soft-start function. Energy storage and filtering is provided by special low inductance self-clearing metallized ...

  13. Spatial configuration of a plasma bunch formed under gyromagnetic resonance in a magnetic mirror trap

    Energy Technology Data Exchange (ETDEWEB)

    Andreev, V. V.; Novitskii, A. A.; Umnov, A. M.; Chuprov, D. V., E-mail: chu-d@mail.ru [Peoples’ Friendship University of Russia (Russian Federation)

    2016-06-15

    The spatial configuration of a relativistic plasma bunch generated under the gyromagnetic autoresonance and confined in a magnetic mirror trap has been studied experimentally and numerically. The characteristics of bremsstrahlung generated by the plasma bunch from the gas and chamber walls were investigated using X-ray spectroscopy and radiometry, which made it possible to determine the localization of the bunch and analyze the dynamics of its confinement.

  14. Size modulated transition in the fluid–structure interaction losses in nano mechanical beam resonators

    Energy Technology Data Exchange (ETDEWEB)

    Vishwakarma, S. D.; Pratap, R., E-mail: pratap@mecheng.iisc.ernet.in [Center for Nano Science and Engineering, Indian Institute of Science, Bengaluru 560012 (India); Pandey, A. K., E-mail: ashok@iith.ac.in [Department of Mechanical and Aerospace Engineering, Indian Institute of Technology, Hyderabad, Kandi, Sangareddy - 502285 (India); Parpia, J. M.; Craighead, H. G. [Center for Materials Research, Cornell University, Ithaca, New York 14853 (United States); Verbridge, S. S. [Biomedical Engineering and Mechanics, Virginia Tech, Blacksburg, Virginia 24061 (United States)

    2016-05-21

    An understanding of the dominant dissipative mechanisms is crucial for the design of a high-Q doubly clamped nanobeam resonator to be operated in air. We focus on quantifying analytically the viscous losses—the squeeze film damping and drag force damping—that limit the net quality factor of a beam resonator, vibrating in its flexural fundamental mode with the surrounding fluid as air at atmospheric pressure. Specifically, drag force damping dominates at smaller beam widths and squeeze film losses dominate at larger beam widths, with no significant contribution from structural losses and acoustic radiation losses. The combined viscous losses agree well with the experimentally measured Q of the resonator over a large range of beam widths, within the limits of thin beam theory. We propose an empirical relation between the maximum quality factor and the ratio of maximum beam width to the squeeze film air gap thickness.

  15. Magnetic Resonance-Based Treatment Planning for Prostate Intensity-Modulated Radiotherapy: Creation of Digitally Reconstructed Radiographs

    International Nuclear Information System (INIS)

    Chen, Lili; Nguyen, Thai-Binh; Jones, Elan; Chen Zuoqun; Luo Wei; Wang Lu; Price, Robert A.; Pollack, Alan; Ma, C.-M. Charlie

    2007-01-01

    Purpose: To develop a technique to create magnetic resonance (MR)-based digitally reconstructed radiographs (DRR) for initial patient setup for routine clinical applications of MR-based treatment planning for prostate intensity-modulated radiotherapy. Methods and Materials: Twenty prostate cancer patients' computed tomography (CT) and MR images were used for the study. Computed tomography and MR images were fused. The pelvic bony structures, including femoral heads, pubic rami, ischium, and ischial tuberosity, that are relevant for routine clinical patient setup were manually contoured on axial MR images. The contoured bony structures were then assigned a bulk density of 2.0 g/cm 3 . The MR-based DRRs were generated. The accuracy of the MR-based DDRs was quantitatively evaluated by comparing MR-based DRRs with CT-based DRRs for these patients. For each patient, eight measuring points on both coronal and sagittal DRRs were used for quantitative evaluation. Results: The maximum difference in the mean values of these measurement points was 1.3 ± 1.6 mm, and the maximum difference in absolute positions was within 3 mm for the 20 patients investigated. Conclusions: Magnetic resonance-based DRRs are comparable to CT-based DRRs for prostate intensity-modulated radiotherapy and can be used for patient treatment setup when MR-based treatment planning is applied clinically

  16. Spatial distribution of charged particles along the ion-optical axis in electron cyclotron resonance ion sources. Experimental results

    International Nuclear Information System (INIS)

    Panitzsch, Lauri

    2013-01-01

    The experimental determination of the spatial distribution of charged particles along the ion-optical axis in electron cyclotron resonance ion sources (ECRIS) defines the focus of this thesis. The spatial distributions of different ion species were obtained in the object plane of the bending magnet (∼45 cm downstream from the plasma electrode) and in the plane of the plasma electrode itself, both in high spatial resolution. The results show that each of the different ion species forms a bloated, triangular structure in the aperture of the plasma electrode. The geometry and the orientation of these structures are defined by the superposition of the radial and axial magnetic fields. The radial extent of each structure is defined by the charge of the ion. Higher charge states occupy smaller, more concentrated structures. The total current density increases towards the center of the plasma electrode. The circular and star-like structures that can be observed in the beam profiles of strongly focused, extracted ion beams are each dominated by ions of a single charge state. In addition, the spatially resolved current density distribution of charged particles in the plasma chamber that impinge on the plasma electrode was determined, differentiating between ions and electrons. The experimental results of this work show that the electrons of the plasma are strongly connected to the magnetic field lines in the source and thus spatially well confined in a triangular-like structure. The intensity of the electrons increases towards the center of the plasma electrode and the plasma chamber, as well. These electrons are surrounded by a spatially far less confined and less intense ion population. All the findings mentioned above were already predicted in parts by simulations of different groups. However, the results presented within this thesis represent the first (and by now only) direct experimental verification of those predictions and are qualitatively transferable to other

  17. Spatial distribution of charged particles along the ion-optical axis in electron cyclotron resonance ion sources. Experimental results

    Energy Technology Data Exchange (ETDEWEB)

    Panitzsch, Lauri

    2013-02-08

    The experimental determination of the spatial distribution of charged particles along the ion-optical axis in electron cyclotron resonance ion sources (ECRIS) defines the focus of this thesis. The spatial distributions of different ion species were obtained in the object plane of the bending magnet ({approx}45 cm downstream from the plasma electrode) and in the plane of the plasma electrode itself, both in high spatial resolution. The results show that each of the different ion species forms a bloated, triangular structure in the aperture of the plasma electrode. The geometry and the orientation of these structures are defined by the superposition of the radial and axial magnetic fields. The radial extent of each structure is defined by the charge of the ion. Higher charge states occupy smaller, more concentrated structures. The total current density increases towards the center of the plasma electrode. The circular and star-like structures that can be observed in the beam profiles of strongly focused, extracted ion beams are each dominated by ions of a single charge state. In addition, the spatially resolved current density distribution of charged particles in the plasma chamber that impinge on the plasma electrode was determined, differentiating between ions and electrons. The experimental results of this work show that the electrons of the plasma are strongly connected to the magnetic field lines in the source and thus spatially well confined in a triangular-like structure. The intensity of the electrons increases towards the center of the plasma electrode and the plasma chamber, as well. These electrons are surrounded by a spatially far less confined and less intense ion population. All the findings mentioned above were already predicted in parts by simulations of different groups. However, the results presented within this thesis represent the first (and by now only) direct experimental verification of those predictions and are qualitatively transferable to

  18. Spatial image modulation to improve performance of computed tomography imaging spectrometer

    Science.gov (United States)

    Bearman, Gregory H. (Inventor); Wilson, Daniel W. (Inventor); Johnson, William R. (Inventor)

    2010-01-01

    Computed tomography imaging spectrometers ("CTIS"s) having patterns for imposing spatial structure are provided. The pattern may be imposed either directly on the object scene being imaged or at the field stop aperture. The use of the pattern improves the accuracy of the captured spatial and spectral information.

  19. Acousto-optic resonant coupling of three spatial modes in an optical fiber.

    Science.gov (United States)

    Park, Hee Su; Song, Kwang Yong

    2014-01-27

    A fiber-optic analogue to an externally driven three-level quantum state is demonstrated by acousto-optic coupling of the spatial modes in a few-mode fiber. Under the condition analogous to electromagnetically induced transparency, a narrow-bandwidth transmission within an absorption band for the fundamental mode is demonstrated. The presented structure is an efficient converter between the fundamental mode and the higher-order modes that cannot be easily addressed by previous techniques, therefore can play a significant role in the next-generation space-division multiplexing communications as an arbitrarily mode-selectable router.

  20. OMERACT Rheumatoid Arthritis Magnetic Resonance Imaging Studies. Summary of OMERACT 6 MR Imaging Module

    DEFF Research Database (Denmark)

    McQueen, F; Lassere, M; Edmonds, J

    2003-01-01

    Magnetic resonance image (MRI) scanning is a new method for imaging and quantifying joint inflammation and damage in rheumatoid arthritis (RA). Over the past 4 years, the OMERACT MR Imaging Group has been developing and testing the RA-MRI scoring system (RAMRIS) for use in RA. The OMERACT filter...

  1. Pseudoneglect in line bisection judgement is associated with a modulation of right hemispheric spatial attention dominance in right-handers.

    Science.gov (United States)

    Zago, Laure; Petit, Laurent; Jobard, Gael; Hay, Julien; Mazoyer, Bernard; Tzourio-Mazoyer, Nathalie; Karnath, Hans-Otto; Mellet, Emmanuel

    2017-01-08

    The objective of this study was to validate a line bisection judgement (LBJ) task for use in investigating the lateralized cerebral bases of spatial attention in a sample of 51 right-handed healthy participants. Using functional magnetic resonance imaging (fMRI), the participants performed a LBJ task that was compared to a visuomotor control task during which the participants made similar saccadic and motoric responses. Cerebral lateralization was determined using a voxel-based functional asymmetry analysis and a hemispheric functional lateralization index (HFLI) computed from fMRI contrast images. Behavioural attentional deviation biases were assessed during the LBJ task and a "paper and pencil" symbol cancellation task (SCT). Individual visuospatial skills were also evaluated. The results showed that both the LBJ and SCT tasks elicited leftward spatial biases in healthy subjects, although the biases were not correlated, which indicated their independence. Neuroimaging results showed that the LBJ task elicited a right hemispheric lateralization, with rightward asymmetries found in a large posterior occipito-parietal area, the posterior calcarine sulcus (V1p) and the temporo-occipital junction (TOJ) and in the inferior frontal gyrus, the anterior insula and the superior medial frontal gyrus. The comparison of the LBJ asymmetry map to the lesion map of neglect patients who suffer line bisection deviation demonstrated maximum overlap in a network that included the middle occipital gyrus (MOG), the TOJ, the anterior insula and the inferior frontal region, likely subtending spatial LBJ bias. Finally, the LBJ task-related cerebral lateralization was specifically correlated with the LBJ spatial bias but not with the SCT bias or with the visuospatial skills of the participants. Taken together, these results demonstrated that the LBJ task is adequate for investigating spatial lateralization in healthy subjects and is suitable for determining the factors underlying the

  2. Electron paramagnetic resonance imaging of tumor hypoxia: enhanced spatial and temporal resolution for in vivo pO2 determination.

    Science.gov (United States)

    Matsumoto, Ken-ichiro; Subramanian, Sankaran; Devasahayam, Nallathamby; Aravalluvan, Thirumaran; Murugesan, Ramachandran; Cook, John A; Mitchell, James B; Krishna, Murali C

    2006-05-01

    The time-domain (TD) mode of electron paramagnetic resonance (EPR) data collection offers a means of estimating the concentration of a paramagnetic probe and the oxygen-dependent linewidth (LW) to generate pO2 maps with minimal errors. A methodology for noninvasive pO2 imaging based on the application of TD-EPR using oxygen-induced LW broadening of a triarylmethyl (TAM)-based radical is presented. The decay of pixel intensities in an image is used to estimate T2*, which is inversely proportional to pO2. Factors affecting T2* in each pixel are critically analyzed to extract the contribution of dissolved oxygen to EPR line-broadening. Suitable experimental and image-processing parameters were obtained to produce pO2 maps with minimal artifacts. Image artifacts were also minimized with the use of a novel data collection strategy using multiple gradients. Results from a phantom and in vivo imaging of tumor-bearing mice validated this novel method of noninvasive oximetry. The current imaging protocols achieve a spatial resolution of approximately 1.0 mm and a temporal resolution of approximately 9 s for 2D pO2 mapping, with a reliable oxygen resolution of approximately 1 mmHg (0.12% oxygen in gas phase). This work demonstrates that in vivo oximetry can be performed with good sensitivity, accuracy, and high spatial and temporal resolution.

  3. Design and Analysis of Enhanced Modulation Response in Integrated Coupled Cavities DBR Lasers Using Photon-Photon Resonance

    Directory of Open Access Journals (Sweden)

    Paolo Bardella

    2016-01-01

    Full Text Available In the last few decades, various solutions have been proposed to increase the modulation bandwidth and, consequently, the transmission bit-rate of semiconductor lasers. In this manuscript, we discuss a design procedure for a recently proposed laser cavity realized with the monolithic integration of two distributed Bragg reflector (DBR lasers allowing one to extend the modulation bandwidth. Such an extension is obtained introducing in the dynamic response a photon-photon resonance (PPR at a frequency higher than the modulation bandwidth of the corresponding single-section laser. Design guidelines will be proposed, and dynamic small and large signal simulations results, calculated using a finite difference traveling wave (FDTW numerical simulator, will be discussed to confirm the design results. The effectiveness of the design procedure is verified in a structure with PPR frequency at 35 GHz allowing one to obtain an open eye diagram for a non-return-to-zero (NRZ digital signal up to 80 GHz . Furthermore, the investigation of the rich dynamics of this structure shows that with proper bias conditions, it is possible to obtain also a tunable self-pulsating signal in a frequency range related to the PPR design.

  4. Control of alpha particle transport by spatially inhomogeneous ion cyclotron resonance heating

    International Nuclear Information System (INIS)

    Chang, C.S.; Imre, K.; Weitzner, H.; Colestock, P.

    1990-02-01

    Control of the radial alpha particle transport by using Ion Cyclotron Range of Frequency waves is investigated in a large-aspect-ratio tokamak geometry. It is shown that spatially inhomogeneous ICRF-wave energy with properly selected frequencies and wave numbers can induce fast convective transport of alpha particles at the speed of order υ alpha ∼ (P RF /n α ε 0 ) ρ p , where P RF is the ICRF-wave power density, n α is the alpha density, ε 0 is the alpha birth energy, and ρ p is the poloidal gyroradius of alpha particles at the birth energy. Application to ITER plasmas is studied and possible antenna designs to control alpha particle flux are discussed. 8 refs., 3 figs

  5. Spatial Precision in Magnetic Resonance Imaging–Guided Radiation Therapy: The Role of Geometric Distortion

    Energy Technology Data Exchange (ETDEWEB)

    Weygand, Joseph, E-mail: jw2899@columbia.edu [Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas (United States); The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, Texas (United States); Fuller, Clifton David [The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, Texas (United States); Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas (United States); Ibbott, Geoffrey S. [Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas (United States); The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, Texas (United States); Mohamed, Abdallah S.R. [Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas (United States); Department of Clinical Oncology and Nuclear Medicine, Alexandria University, Alexandria (Egypt); Ding, Yao [Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas (United States); Yang, Jinzhong [Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas (United States); The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, Texas (United States); Hwang, Ken-Pin [Department of Imaging Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas (United States); Wang, Jihong [Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas (United States); The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, Texas (United States)

    2016-07-15

    Because magnetic resonance imaging–guided radiation therapy (MRIgRT) offers exquisite soft tissue contrast and the ability to image tissues in arbitrary planes, the interest in this technology has increased dramatically in recent years. However, intrinsic geometric distortion stemming from both the system hardware and the magnetic properties of the patient affects MR images and compromises the spatial integrity of MRI-based radiation treatment planning, given that for real-time MRIgRT, precision within 2 mm is desired. In this article, we discuss the causes of geometric distortion, describe some well-known distortion correction algorithms, and review geometric distortion measurements from 12 studies, while taking into account relevant imaging parameters. Eleven of the studies reported phantom measurements quantifying system-dependent geometric distortion, while 2 studies reported simulation data quantifying magnetic susceptibility–induced geometric distortion. Of the 11 studies investigating system-dependent geometric distortion, 5 reported maximum measurements less than 2 mm. The simulation studies demonstrated that magnetic susceptibility–induced distortion is typically smaller than system-dependent distortion but still nonnegligible, with maximum distortion ranging from 2.1 to 2.6 mm at a field strength of 1.5 T. As expected, anatomic landmarks containing interfaces between air and soft tissue had the largest distortions. The evidence indicates that geometric distortion reduces the spatial integrity of MRI-based radiation treatment planning and likely diminishes the efficacy of MRIgRT. Better phantom measurement techniques and more effective distortion correction algorithms are needed to achieve the desired spatial precision.

  6. Spatial Precision in Magnetic Resonance Imaging–Guided Radiation Therapy: The Role of Geometric Distortion

    International Nuclear Information System (INIS)

    Weygand, Joseph; Fuller, Clifton David; Ibbott, Geoffrey S.; Mohamed, Abdallah S.R.; Ding, Yao; Yang, Jinzhong; Hwang, Ken-Pin; Wang, Jihong

    2016-01-01

    Because magnetic resonance imaging–guided radiation therapy (MRIgRT) offers exquisite soft tissue contrast and the ability to image tissues in arbitrary planes, the interest in this technology has increased dramatically in recent years. However, intrinsic geometric distortion stemming from both the system hardware and the magnetic properties of the patient affects MR images and compromises the spatial integrity of MRI-based radiation treatment planning, given that for real-time MRIgRT, precision within 2 mm is desired. In this article, we discuss the causes of geometric distortion, describe some well-known distortion correction algorithms, and review geometric distortion measurements from 12 studies, while taking into account relevant imaging parameters. Eleven of the studies reported phantom measurements quantifying system-dependent geometric distortion, while 2 studies reported simulation data quantifying magnetic susceptibility–induced geometric distortion. Of the 11 studies investigating system-dependent geometric distortion, 5 reported maximum measurements less than 2 mm. The simulation studies demonstrated that magnetic susceptibility–induced distortion is typically smaller than system-dependent distortion but still nonnegligible, with maximum distortion ranging from 2.1 to 2.6 mm at a field strength of 1.5 T. As expected, anatomic landmarks containing interfaces between air and soft tissue had the largest distortions. The evidence indicates that geometric distortion reduces the spatial integrity of MRI-based radiation treatment planning and likely diminishes the efficacy of MRIgRT. Better phantom measurement techniques and more effective distortion correction algorithms are needed to achieve the desired spatial precision.

  7. Computational hologram synthesis and representation on spatial light modulators for real-time 3D holographic imaging

    International Nuclear Information System (INIS)

    Reichelt, Stephan; Leister, Norbert

    2013-01-01

    In dynamic computer-generated holography that utilizes spatial light modulators, both hologram synthesis and hologram representation are essential in terms of fast computation and high reconstruction quality. For hologram synthesis, i.e. the computation step, Fresnel transform based or point-source based raytracing methods can be applied. In the encoding step, the complex wave-field has to be optimally represented by the SLM with its given modulation capability. For proper hologram reconstruction that implies a simultaneous and independent amplitude and phase modulation of the input wave-field by the SLM. In this paper, we discuss full complex hologram representation methods on SLMs by considering inherent SLM parameter such as modulation type and bit depth on their reconstruction performance such as diffraction efficiency and SNR. We review the three implementation schemes of Burckhardt amplitude-only representation, phase-only macro-pixel representation, and two-phase interference representation. Besides the optical performance we address their hardware complexity and required computational load. Finally, we experimentally demonstrate holographic reconstructions of different representation schemes as obtained by functional prototypes utilizing SeeReal's viewing-window holographic display technology. The proposed hardware implementations enable a fast encoding of complex-valued hologram data and thus will pave the way for commercial real-time holographic 3D imaging in the near future.

  8. Spatial Steering of Cyclotron-Resonance Maser Array Antenna by Magnetic Fields

    International Nuclear Information System (INIS)

    Kesar, A.; Jerby, E.

    2001-01-01

    The novel concept of radiation lobe generation and steering by cyclotron-resonance maser (CRM) array is presented. In this scheme the gain and phase of each CRM-element in the array are tuned by magnetic fields which control the cyclotron synchronism condition and the pitch-ratio of each CRM-element. These operating parameters are controlled by the magnetic fields of the solenoid and the kicker, respectively. A numerical example of a CRM-array operating in a gyro-TWT mode is presented. The radiation pattern of a 10-element CRM phased array (15 kV, 1A each) is calculated. The radiation lobe steering by the magnetic field controls is demonstrated in this analysis. A 40 lobe steering range is shown for the 10-element CRM-array at 7.3 GHz. An experimental device is built in our laboratory to demonstrate the active CRM-array antenna concept. Preliminary experimental results of gain and phase-delay of a single CRM-element, as function of electron-beam parameters are presented. These results are compared to the numerical model

  9. Wave power balance in resonant dissipative media with spatial and temporal dispersion

    International Nuclear Information System (INIS)

    Tokman, M.D.; Gavrilova, M.A.; Westerhof, E. . www.rijnh.nl

    2003-01-01

    A power balance for waves in resonant dissipative media is formulated, which generalizes well-known expressions for dielectric wave energy density, wave energy flux, and dissipated power density. The identification of the different terms with wave energy density and flux remains only phenomenological. The result is better viewed as an equation for the evolution of wave intensity. In that form, its consequences are discussed in particular in relation to anomalous dispersion. A discrimination is made between boundary and initial value problems. For boundary value problems, anomalous dispersion is shown not to lead to unphysical results. In contrast, for initial value problems the solution for the evolution of wave intensity is shown to be at fault in the case of anomalous dispersion. Further illustration is provided by consideration of wave dispersion in a medium of charged harmonic oscillators and of ordinary-mode dispersion in plasma. Both are characterized by anomalous dispersion and show marked differences in the solutions of the dispersion relation solved either for complex wave vector at real frequency, k(ω) (applicable to boundary value problems), or for complex frequency at real wave vector ω(k) (applicable to initial value problems). (author)

  10. SU-F-J-214: Dose Reduction by Spatially Optimized Image Quality Via Fluence Modulated Proton CT (FMpCT)

    International Nuclear Information System (INIS)

    De Angelis, L; Landry, G; Dedes, G; Parodi, K; Hansen, D; Rit, S; Belka, C

    2016-01-01

    Purpose: Proton CT (pCT) is a promising imaging modality for reducing range uncertainty in image-guided proton therapy. Range uncertainties partially originate from X-ray CT number conversion to stopping power ratio (SPR) and are limiting the exploitation of the full potential of proton therapy. In this study we explore the concept of spatially dependent fluence modulated proton CT (FMpCT), for achieving optimal image quality in a clinical region of interest (ROI), while reducing significantly the imaging dose to the patient. Methods: The study was based on simulated ideal pCT using pencil beam (PB) scanning. A set of 250 MeV protons PBs was used to create 360 projections of a cylindrical water phantom and a head and neck cancer patient. The tomographic images were reconstructed using a filtered backprojection (FBP) as well as an iterative algorithm (ITR). Different fluence modulation levels were investigated and their impact on the image was quantified in terms of SPR accuracy as well as noise within and outside selected ROIs, as a function of imaging dose. The unmodulated image served as reference. Results: Both FBP reconstruction and ITR without total variation (TV) yielded image quality in the ROIs similar to the reference images, for modulation down to 0.1 of the full proton fluence. The average dose was reduced by 75% for the water phantom and by 40% for the patient. FMpCT does not improve the noise for ITR with TV and modulation 0.1. Conclusion: This is the first work proposing and investigating FMpCT for producing optimal image quality for treatment planning and image guidance, while simultaneously reducing imaging dose. Future work will address spatial resolution effects and the impact of FMpCT on the quality of proton treatment plans for a prototype pCT scanner capable of list mode data acquisition. Acknowledgement: DFG-MAP DFG - Munich-Centre for Advanced Photonics (MAP)

  11. SU-F-J-214: Dose Reduction by Spatially Optimized Image Quality Via Fluence Modulated Proton CT (FMpCT)

    Energy Technology Data Exchange (ETDEWEB)

    De Angelis, L; Landry, G; Dedes, G; Parodi, K [Ludwig-Maximilians-Universitaet Muenchen (LMU Munich), Garching b. Muenchen (Germany); Hansen, D [Aarhus University Hospital, Aarhus, Jutland (Denmark); Rit, S [University Lyon, Lyon, Auvergne-Rhone-Alpes (France); Belka, C [LMU Munich, Munich (Germany)

    2016-06-15

    Purpose: Proton CT (pCT) is a promising imaging modality for reducing range uncertainty in image-guided proton therapy. Range uncertainties partially originate from X-ray CT number conversion to stopping power ratio (SPR) and are limiting the exploitation of the full potential of proton therapy. In this study we explore the concept of spatially dependent fluence modulated proton CT (FMpCT), for achieving optimal image quality in a clinical region of interest (ROI), while reducing significantly the imaging dose to the patient. Methods: The study was based on simulated ideal pCT using pencil beam (PB) scanning. A set of 250 MeV protons PBs was used to create 360 projections of a cylindrical water phantom and a head and neck cancer patient. The tomographic images were reconstructed using a filtered backprojection (FBP) as well as an iterative algorithm (ITR). Different fluence modulation levels were investigated and their impact on the image was quantified in terms of SPR accuracy as well as noise within and outside selected ROIs, as a function of imaging dose. The unmodulated image served as reference. Results: Both FBP reconstruction and ITR without total variation (TV) yielded image quality in the ROIs similar to the reference images, for modulation down to 0.1 of the full proton fluence. The average dose was reduced by 75% for the water phantom and by 40% for the patient. FMpCT does not improve the noise for ITR with TV and modulation 0.1. Conclusion: This is the first work proposing and investigating FMpCT for producing optimal image quality for treatment planning and image guidance, while simultaneously reducing imaging dose. Future work will address spatial resolution effects and the impact of FMpCT on the quality of proton treatment plans for a prototype pCT scanner capable of list mode data acquisition. Acknowledgement: DFG-MAP DFG - Munich-Centre for Advanced Photonics (MAP)

  12. Spatial light modulators and applications III; Proceedings of the Meeting, San Diego, CA, Aug. 7, 8, 1989

    Science.gov (United States)

    Efron, Uzi (Editor)

    1990-01-01

    Recent advances in the technology and applications of spatial light modulators (SLMs) are discussed in review essays by leading experts. Topics addressed include materials for SLMs, SLM devices and device technology, applications to optical data processing, and applications to artificial neural networks. Particular attention is given to nonlinear optical polymers, liquid crystals, magnetooptic SLMs, multiple-quantum-well SLMs, deformable-mirror SLMs, three-dimensional optical memories, applications of photorefractive devices to optical computing, photonic neurocomputers and learning machines, holographic associative memories, SLMs as parallel memories for optoelectronic neural networks, and coherent-optics implementations of neural-network models.

  13. Trinary flip-flops using Savart plate and spatial light modulator for optical computation in multivalued logic

    Science.gov (United States)

    Ghosh, Amal K.; Basuray, Amitabha

    2008-11-01

    The memory devices in multi-valued logic are of most significance in modern research. This paper deals with the implementation of basic memory devices in multi-valued logic using Savart plate and spatial light modulator (SLM) based optoelectronic circuits. Photons are used here as the carrier to speed up the operations. Optical tree architecture (OTA) has been also utilized in the optical interconnection network. We have exploited the advantages of Savart plates, SLMs and OTA and proposed the SLM based high speed JK, D-type and T-type flip-flops in a trinary system.

  14. Resonant transmission and mode modulation of acoustic waves in H-shaped metallic gratings

    International Nuclear Information System (INIS)

    Deng, Yu-Qiang; Fan, Ren-Hao; Zhang, Kun; Peng, Ru-Wen; Qi, Dong-Xiang

    2015-01-01

    In this work, we demonstrate that resonant full transmission of acoustic waves exists in subwavelength H-shaped metallic gratings, and transmission peaks can be efficiently tuned by adjusting the grating geometry. We investigate this phenomenon through both numerical simulations and theoretical calculations based on rigorous-coupled wave analysis. The transmission peaks are originated from Fabry-Perot resonances together with the couplings between the diffractive wave on the surface and the multiple guided modes in the slits. Moreover, the transmission modes can be efficiently tuned by adjusting the cavity geometry, without changing the grating thickness. The mechanism is analyzed based on an equivalent circuit model and verified by both the theoretical calculations and the numerical simulations. This research has potential application in acoustic-device miniaturization over a wide range of wavelengths

  15. Pulse width modulated push-pull driven parallel resonant converter with active free-wheel

    Science.gov (United States)

    Reass, William A.; Schrank, Louis

    2004-06-22

    An apparatus and method for high frequency alternating power generation to control kilowatts of supplied power in microseconds. The present invention includes a means for energy storage, push-pull switching means, control electronics, transformer means, resonant circuitry and means for excess energy recovery, all in electrical communication. A push-pull circuit works synchronously with a force commutated free-wheel transistor to provide current pulses to a transformer. A change in the conduction angle of the push-pull circuit changes the amount of energy coupled into the transformer's secondary oscillating circuit, thereby altering the induced secondary resonating voltage. At the end of each pulse, the force commutated free-wheel transistor causes residual excess energy in the primary circuit to be transmitted back to the storage capacitor for later use.

  16. Spatial Distribution of Lactococcus lactis Colonies Modulates the Production of Major Metabolites during the Ripening of a Model Cheese.

    Science.gov (United States)

    Le Boucher, Clémentine; Gagnaire, Valérie; Briard-Bion, Valérie; Jardin, Julien; Maillard, Marie-Bernadette; Dervilly-Pinel, Gaud; Le Bizec, Bruno; Lortal, Sylvie; Jeanson, Sophie; Thierry, Anne

    2016-01-01

    In cheese, lactic acid bacteria are immobilized at the coagulation step and grow as colonies. The spatial distribution of bacterial colonies is characterized by the size and number of colonies for a given bacterial population within cheese. Our objective was to demonstrate that different spatial distributions, which lead to differences in the exchange surface between the colonies and the cheese matrix, can influence the ripening process. The strategy was to generate cheeses with the same growth and acidification of a Lactococcus lactis strain with two different spatial distributions, big and small colonies, to monitor the production of the major ripening metabolites, including sugars, organic acids, peptides, free amino acids, and volatile metabolites, over 1 month of ripening. The monitored metabolites were qualitatively the same for both cheeses, but many of them were more abundant in the small-colony cheeses than in the big-colony cheeses over 1 month of ripening. Therefore, the results obtained showed that two different spatial distributions of L. lactis modulated the ripening time course by generating moderate but significant differences in the rates of production or consumption for many of the metabolites commonly monitored throughout ripening. The present work further explores the immobilization of bacteria as colonies within cheese and highlights the consequences of this immobilization on cheese ripening. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

  17. Cognitive Modules Utilized for Narrative Comprehension in Children: A Functional Magnetic Resonance Imaging Study

    OpenAIRE

    Schmithorst, Vincent J.; Holland, Scott K.; Plante, Elena

    2005-01-01

    The ability to comprehend narratives constitutes an important component of human development and experience. The neural correlates of auditory narrative comprehension in children were investigated in a large-scale functional magnetic resonance imaging (fMRI) study involving 313 subjects ages 5–18. Using group Independent Component Analysis (ICA), bilateral task-related components were found comprising the primary auditory cortex, the mid-superior temporal gyrus, the hippocampus, the angular g...

  18. Models of the Dynamics of Spatially Separated Broadband Electromagnetic Fields Interacting with Resonant Atoms

    Science.gov (United States)

    Basharov, A. M.

    2018-03-01

    The Markov model of spontaneous emission of an atom localized in a spatial region with a broadband electromagnetic field with zero photon density is considered in the conditions of coupling of the electromagnetic field with the broadband field of a neighboring space. The evolution operator of the system and the kinetic equation for the atom are obtained. It is shown that the field coupling constant affects the rate of spontaneous emission of the atom, but is not manifested in the atomic frequency shift. The analytic expression for the radiative decay constant for the atom is found to be analogous in a certain sense to the expression for the decay constant for a singly excited localized ensemble of identical atoms in the conditions when the effect of stabilization of its excited state by the Stark interaction with the vacuum broadband electromagnetic field is manifested. The model is formulated based on quantum stochastic differential equations of the non- Wiener type and the generalized algebra of the Ito differential of quantum random processes.

  19. Ergodic channel capacity of spatial correlated multiple-input multiple-output free space optical links using multipulse pulse-position modulation

    Science.gov (United States)

    Wang, Huiqin; Wang, Xue; Cao, Minghua

    2017-02-01

    The spatial correlation extensively exists in the multiple-input multiple-output (MIMO) free space optical (FSO) communication systems due to the channel fading and the antenna space limitation. Wilkinson's method was utilized to investigate the impact of spatial correlation on the MIMO FSO communication system employing multipulse pulse-position modulation. Simulation results show that the existence of spatial correlation reduces the ergodic channel capacity, and the reception diversity is more competent to resist this kind of performance degradation.

  20. Modulation of spatial attention by goals, statistical learning, and monetary reward.

    Science.gov (United States)

    Jiang, Yuhong V; Sha, Li Z; Remington, Roger W

    2015-10-01

    This study documented the relative strength of task goals, visual statistical learning, and monetary reward in guiding spatial attention. Using a difficult T-among-L search task, we cued spatial attention to one visual quadrant by (i) instructing people to prioritize it (goal-driven attention), (ii) placing the target frequently there (location probability learning), or (iii) associating that quadrant with greater monetary gain (reward-based attention). Results showed that successful goal-driven attention exerted the strongest influence on search RT. Incidental location probability learning yielded a smaller though still robust effect. Incidental reward learning produced negligible guidance for spatial attention. The 95 % confidence intervals of the three effects were largely nonoverlapping. To understand these results, we simulated the role of location repetition priming in probability cuing and reward learning. Repetition priming underestimated the strength of location probability cuing, suggesting that probability cuing involved long-term statistical learning of how to shift attention. Repetition priming provided a reasonable account for the negligible effect of reward on spatial attention. We propose a multiple-systems view of spatial attention that includes task goals, search habit, and priming as primary drivers of top-down attention.

  1. Spatial mapping of mineralization with manganese-enhanced magnetic resonance imaging

    Science.gov (United States)

    Chesnick, I.E.; Centeno, J.A.; Todorov, T.I.; Koenig, A.E.; Potter, K.

    2011-01-01

    Paramagnetic manganese can be employed as a calcium surrogate to sensitize the magnetic resonance imaging (MRI) technique to the processing of calcium during the bone formation process. At low doses, after just 48h of exposure, osteoblasts take up sufficient quantities of manganese to cause marked reductions in the water proton T1 values compared with untreated cells. After just 24h of exposure, 25??M MnCl2 had no significant effect on cell viability. However, for mineralization studies 100??M MnCl2 was used to avoid issues of manganese depletion in calvarial organ cultures and a post-treatment delay of 48h was implemented to ensure that manganese ions taken up by osteoblasts is deposited as mineral. All specimens were identified by their days in vitro (DIV). Using inductively coupled plasma optical emission spectroscopy (ICP-OES), we confirmed that Mn-treated calvariae continued to deposit mineral in culture and that the mineral composition was similar to that of age-matched controls. Notably there was a significant decrease in the manganese content of DIV18 compared with DIV11 specimens, possibly relating to less manganese sequestration as a result of mineral maturation. More importantly, quantitative T1 maps of Mn-treated calvariae showed localized reductions in T1 values over the calvarial surface, indicative of local variations in the surface manganese content. This result was verified with laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). We also found that ??R1 values, calculated by subtracting the relaxation rate of Mn-treated specimens from the relaxation rate of age-matched controls, were proportional to the surface manganese content and thus mineralizing activity. From this analysis, we established that mineralization of DIV4 and DIV11 specimens occurred in all tissue zones, but was reduced for DIV18 specimens because of mineral maturation with less manganese sequestration. In DIV25 specimens, active mineralization was observed for

  2. Spatial frequency information modulates response inhibition and decision-making processes.

    Directory of Open Access Journals (Sweden)

    Sara Jahfari

    Full Text Available We interact with the world through the assessment of available, but sometimes imperfect, sensory information. However, little is known about how variance in the quality of sensory information affects the regulation of controlled actions. In a series of three experiments, comprising a total of seven behavioral studies, we examined how different types of spatial frequency information affect underlying processes of response inhibition and selection. Participants underwent a stop-signal task, a two choice speed/accuracy balance experiment, and a variant of both these tasks where prior information was given about the nature of stimuli. In all experiments, stimuli were either intact, or contained only high-, or low- spatial frequencies. Overall, drift diffusion model analysis showed a decreased rate of information processing when spatial frequencies were removed, whereas the criterion for information accumulation was lowered. When spatial frequency information was intact, the cost of response inhibition increased (longer SSRT, while a correct response was produced faster (shorter reaction times and with more certainty (decreased errors. When we manipulated the motivation to respond with a deadline (i.e., be fast or accurate, removal of spatial frequency information slowed response times only when instructions emphasized accuracy. However, the slowing of response times did not improve error rates, when compared to fast instruction trials. These behavioral studies suggest that the removal of spatial frequency information differentially affects the speed of response initiation, inhibition, and the efficiency to balance fast or accurate responses. More generally, the present results indicate a task-independent influence of basic sensory information on strategic adjustments in action control.

  3. Flux penetration in a superconducting alloy with spatial by modulated concentration

    International Nuclear Information System (INIS)

    Dobrosavljevic, L.; Centre National de la Recherche Scientifique, 38 - Grenoble

    1976-01-01

    The flux penetration in inhomogeneous superconductors with periodic structure is studied. Superconducting alloys with the impurity concentration varying periodically in one direction are considered. In a London model the magnetic structure of a single vortex, the change of its self-energy and of the interaction between two vortices due to the concentration modulation are studied. The matching between the vortex lattice and the periodic modulation of the concentration are also studied: at some definite values of the external field, H=Hsub(n1,n2), the vortices are arranged in a triangular lattice in such a way that all the vortices lie in the high concentration regions. The projection of the sides of the triangles on the modulation direction is then a multiple of the modulation period L 0 . At H=Hsub(n1,n2) the Gibbs' free energy of the system is lowered and a pinning vortices takes place. The possibility of such a matching effect in the low field region (H> approximately Hsub(1)) and in the intermediate field region (Hsub(c1) [fr

  4. Nonlocality, Correlations, and Magnetotransport in a Spatially Modulated Two-Dimensional Electron Gas

    Science.gov (United States)

    Raichev, O. E.

    2018-04-01

    It is shown that the classical commensurability phenomena in weakly modulated two-dimensional electron systems is a manifestation of the intrinsic properties of the correlation functions describing a homogeneous electron gas in a magnetic field. The theory demonstrates the importance for consideration of nonlocal response and removes the gap between classical and quantum approaches to magnetotransport in such systems.

  5. Stress Modulates the Use of Spatial versus Stimulus-Response Learning Strategies in Humans

    Science.gov (United States)

    Philippsen, Christine; Richter, Steffen; Bohringer, Andreas; Wippich, Werner; Schachinger, Hartmut; Schwabe, Lars; Oitzl, Melly S.

    2007-01-01

    Animal studies provided evidence that stress modulates multiple memory systems, favoring caudate nucleus-based "habit" memory over hippocampus-based "cognitive" memory. However, effects of stress on learning strategy and memory consolidation were not differentiated. We specifically address the effects of psychosocial stress on the applied learning…

  6. Modulation of Hippocampal Theta Oscillations and Spatial Memory by Relaxin-3 Neurons of the Nucleus Incertus

    Science.gov (United States)

    Ma, Sherie; Olucha-Bordonau, Francisco E.; Hossain, M. Akhter; Lin, Feng; Kuei, Chester; Liu, Changlu; Wade, John D.; Sutton, Steven W.; Nunez, Angel; Gundlach, Andrew L.

    2009-01-01

    Hippocampal theta rhythm is thought to underlie learning and memory, and it is well established that "pacemaker" neurons in medial septum (MS) modulate theta activity. Recent studies in the rat demonstrated that brainstem-generated theta rhythm occurs through a multisynaptic pathway via the nucleus incertus (NI), which is the primary source of the…

  7. Correlation between near-infrared spectroscopy and magnetic resonance imaging of rat brain oxygenation modulation

    International Nuclear Information System (INIS)

    Chen Yu; Tailor, Dharmesh R; Intes, Xavier; Chance, Britton

    2003-01-01

    We measure the tissue oxygen and haemoglobin concentrations in the rat brain during modulation of inhaled oxygen concentration (FiO 2 ), using non-invasive frequency domain near-infrared oximetry. The rise in oxygenated haemoglobin concentration and the decline in deoxygenated haemoglobin concentration are demonstrated in correspondence with the modulation of FiO 2 , which is changed from 20% to 100% in increments of 20%. Furthermore, the tissue oxygenation saturation also shows the corresponding trend and changes ranging from approximately 70% to 90%. The relative changes in deoxygenated haemoglobin concentration are compared to the blood-oxygenation-level-dependent (BOLD) MRI signal recorded during a similar FiO 2 protocol. A linear relationship with high correlation coefficient between the relative changes in the BOLD MRI signal and the NIRS signal is observed

  8. Correlation between near-infrared spectroscopy and magnetic resonance imaging of rat brain oxygenation modulation

    Energy Technology Data Exchange (ETDEWEB)

    Chen Yu [Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA (United States); Tailor, Dharmesh R [Department of Bioengineering, University of Pennsylvania, Philadelphia, PA (United States); Intes, Xavier [Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA (United States); Chance, Britton [Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA (United States)

    2003-02-21

    We measure the tissue oxygen and haemoglobin concentrations in the rat brain during modulation of inhaled oxygen concentration (FiO{sub 2}), using non-invasive frequency domain near-infrared oximetry. The rise in oxygenated haemoglobin concentration and the decline in deoxygenated haemoglobin concentration are demonstrated in correspondence with the modulation of FiO{sub 2}, which is changed from 20% to 100% in increments of 20%. Furthermore, the tissue oxygenation saturation also shows the corresponding trend and changes ranging from approximately 70% to 90%. The relative changes in deoxygenated haemoglobin concentration are compared to the blood-oxygenation-level-dependent (BOLD) MRI signal recorded during a similar FiO{sub 2} protocol. A linear relationship with high correlation coefficient between the relative changes in the BOLD MRI signal and the NIRS signal is observed.

  9. Performance analysis of decode-and-forward dual-hop optical spatial modulation with diversity combiner over atmospheric turbulence

    Science.gov (United States)

    Odeyemi, Kehinde O.; Owolawi, Pius A.; Srivastava, Viranjay M.

    2017-11-01

    Dual-hops transmission is a growing interest technique that can be used to mitigate against atmospheric turbulence along the Free Space Optical (FSO) communication links. This paper analyzes the performance of Decode-and-Forward (DF) dual-hops FSO systems in-conjunction with spatial modulation and diversity combiners over a Gamma-Gamma atmospheric turbulence channel using heterodyne detection. Maximum Ratio Combiner (MRC), Equal Gain Combiner (EGC) and Selection Combiner (SC) are considered at the relay and destination as mitigation tools to improve the system error performance. Power series expansion of modified Bessel function is used to derive the closed form expression for the end-to-end Average Pairwise Error Probability (APEP) expressions for each of the combiners under study and a tight upper bound on the Average Bit Error Rate (ABER) per hop is given. Thus, the overall end-to-end ABER for the dual-hops FSO system is then evaluated. The numerical results depicted that dual-hops transmission systems outperformed the direct link systems. Moreover, the impact of having the same and different combiners at the relay and destination are also presented. The results also confirm that the combination of dual hops transmission with spatial modulation and diversity combiner significantly improves the systems error rate with the MRC combiner offering an optimal performance with respect to variation in atmospheric turbulence, change in links average received SNR and link range of the system.

  10. Multi-point laser spark generation for internal combustion engines using a spatial light modulator

    International Nuclear Information System (INIS)

    Lyon, Elliott; Kuang, Zheng; Dearden, Geoff; Cheng, Hua; Page, Vincent; Shenton, Tom

    2014-01-01

    This paper reports on a technique demonstrating for the first time successful multi-point laser-induced spark generation, which is variable in three dimensions and derived from a single laser beam. Previous work on laser ignition of internal combustion engines found that simultaneously igniting in more than one location resulted in more stable and faster combustion – a key potential advantage over conventional spark ignition. However, previous approaches could only generate secondary foci at fixed locations. The work reported here is an experimental technique for multi-point laser ignition, in which several sparks with arbitrary spatial location in three dimensions are created by variable diffraction of a pulsed single laser beam source and transmission through an optical plug. The diffractive multi-beam arrays and patterns are generated using a spatial light modulator on which computer generated holograms are displayed. A gratings and lenses algorithm is used to accurately modulate the phase of the input laser beam and create multi-beam output. The underpinning theory, experimental arrangement and results obtained are presented and discussed. (paper)

  11. Tools for Multimode Quantum Information: Modulation, Detection, and Spatial Quantum Correlations

    DEFF Research Database (Denmark)

    Lassen, Mikael Østergaard; Delaubert, Vincent; Janousek, Jirí

    2007-01-01

    We present here all the tools required for continuous variable parallel quantum information protocols based on spatial multi-mode quantum correlations and entanglement. We describe techniques for encoding and detecting this quantum information with high efficiency in the individual modes. We use ...

  12. Spatial Attention-Related Modulation of the N170 by Backward Masked Fearful Faces

    Science.gov (United States)

    Carlson, Joshua M.; Reinke, Karen S.

    2010-01-01

    Facial expressions are a basic form of non-verbal communication that convey important social information to others. The relevancy of this information is highlighted by findings that backward masked facial expressions facilitate spatial attention. This attention effect appears to be mediated through a neural network consisting of the amygdala,…

  13. In situ targeting TEM8 via immune response and polypeptide recognition by wavelength-modulated surface plasmon resonance biosensor

    Science.gov (United States)

    Wang, Yimin; Luo, Zewei; Liu, Kunping; Wang, Jie; Duan, Yixiang

    2016-01-01

    There is an increasing interest in real-time and in situ monitoring of living cell activities in life science and medicine. This paper reports a whole cell sensing protocol over the interface of Au film coupled in a wavelength-modulated surface plasmon resonance (WMSPR) biosensor. With dual parabolic mirrors integrated in the sensor, the compact and miniaturized instrument shows satisfactory refractive index sensitivity (2220 nm/RIU) and a high resolution of resonance wavelength shift of 0.3 nm to liquid samples. The affinity interactions between the biomarker of human tumor endothelial marker 8 (TEM8) and antibody (Ab) or specific polypeptide (PEP) were firstly introduced to WMSPR biosensor analysis. Both the interaction events of Ab-cell and PEP-cell over the Au film interface can be recognized by the sensor and the balance time of interactions is about 20 min. The concentration range of Ab for quantitative monitoring of the TEM8 expression on human colon carcinoma SW620 cells was investigated. The present low-cost and time-saving method provides a time resolution of binding specificity between Ab/PEP and TEM8 for real-time analysis of antigen on living tumor cell surface. PMID:26822761

  14. Weight dependent modulation of motor resonance induced by weight estimation during observation of partially occluded lifting actions.

    Science.gov (United States)

    Valchev, Nikola; Zijdewind, Inge; Keysers, Christian; Gazzola, Valeria; Avenanti, Alessio; Maurits, Natasha M

    2015-01-01

    Seeing others performing an action induces the observers' motor cortex to "resonate" with the observed action. Transcranial magnetic stimulation (TMS) studies suggest that such motor resonance reflects the encoding of various motor features of the observed action, including the apparent motor effort. However, it is unclear whether such encoding requires direct observation or whether force requirements can be inferred when the moving body part is partially occluded. To address this issue, we presented participants with videos of a right hand lifting a box of three different weights and asked them to estimate its weight. During each trial we delivered one transcranial magnetic stimulation (TMS) pulse over the left primary motor cortex of the observer and recorded the motor evoked potentials (MEPs) from three muscles of the right hand (first dorsal interosseous, FDI, abductor digiti minimi, ADM, and brachioradialis, BR). Importantly, because the hand shown in the videos was hidden behind a screen, only the contractions in the actor's BR muscle under the bare skin were observable during the entire videos, while the contractions in the actor's FDI and ADM muscles were hidden during the grasp and actual lift. The amplitudes of the MEPs recorded from the BR (observable) and FDI (hidden) muscle increased with the weight of the box. These findings indicate that the modulation of motor excitability induced by action observation extends to the cortical representation of muscles with contractions that could not be observed. Thus, motor resonance appears to reflect force requirements of observed lifting actions even when the moving body part is occluded from view. Copyright © 2014 Elsevier Ltd. All rights reserved.

  15. Analysis of spatial diffusion of ferric ions in PVA-GTA gel dosimeters through magnetic resonance imaging

    Energy Technology Data Exchange (ETDEWEB)

    Marrale, Maurizio [Dipartimento di Fisica e Chimica, Universitá di Palermo, Viale delle Scienze, Edificio 18, 90128 Palermo (Italy); Istituto Nazionale di Fisica Nucleare (INFN) – Gruppo V Sezione di Catania, Via Santa Sofia, 64, 95123 Catania (Italy); ATeN Center, Università di Palermo, Viale delle Scienze, Edificio 18, 90128 Palermo (Italy); Collura, Giorgio [Dipartimento di Fisica e Chimica, Universitá di Palermo, Viale delle Scienze, Edificio 18, 90128 Palermo (Italy); Istituto Nazionale di Fisica Nucleare (INFN) – Gruppo V Sezione di Catania, Via Santa Sofia, 64, 95123 Catania (Italy); Gallo, Salvatore, E-mail: salvatore.gallo05@unipa.it [Dipartimento di Fisica e Chimica, Universitá di Palermo, Viale delle Scienze, Edificio 18, 90128 Palermo (Italy); Istituto Nazionale di Fisica Nucleare (INFN) – Gruppo V Sezione di Catania, Via Santa Sofia, 64, 95123 Catania (Italy); Dipartimento di Fisica, Universitá di Milano, Via Giovanni Celoria 16, 20133 Milano (Italy); Nici, Stefania [Dipartimento di Fisica e Chimica, Universitá di Palermo, Viale delle Scienze, Edificio 18, 90128 Palermo (Italy); Tranchina, Luigi [ATeN Center, Università di Palermo, Viale delle Scienze, Edificio 18, 90128 Palermo (Italy); Abbate, Boris Federico [U.O.C. Fisica Sanitaria, A.R.N.A.S., Ospedale Civico Palermo, Piazza Nicola Leotta 4, 90127 Palermo (Italy); Marineo, Sandra; Caracappa, Santo [Istituto Zooprofilattico Sperimentale della Sicilia (IZS), Via Gino Marinuzzi, 3, 90129 Palermo (Italy); and others

    2017-04-01

    Highlights: • Analysis of ferric ions diffusion throughout the gel matrix in PVA-GTA samples. • Measurements with preclinical 7T MRI scanner with spatial resolution of 200 μm. • Diffusion process is much slower for PVA-GTA gels than for agarose ones. - Abstract: This work focused on the analysis of the temporal diffusion of ferric ions through PVA-GTA gel dosimeters. PVA-GTA gel samples, partly exposed with 6 MV X-rays in order to create an initial steep gradient, were mapped using magnetic resonance imaging on a 7T MRI scanner for small animals. Multiple images of the gels were acquired over several hours after irradiation and were analyzed to quantitatively extract the signal profile. The spatial resolution achieved is 200 μm and this makes this technique particularly suitable for the analysis of steep gradients of ferric ion concentration. The results obtained with PVA-GTA gels were compared with those achieved with agarose gels, which is a standard dosimetric gel formulation. The analysis showed that the diffusion process is much slower (more than five times) for PVA-GTA gels than for agarose ones. Furthermore, it is noteworthy that the diffusion coefficient value obtained through MRI analysis is significantly consistent with that obtained in separate study Marini et al. (Submitted for publication) using a totally independent method such as spectrophotometry. This is a valuable result highlighting that the good dosimetric features of this gel matrix not only can be reproduced but also can be measured through independent experimental techniques based on different physical principles.

  16. On-chip transduction of nucleic acid hybridization using spatial profiles of immobilized quantum dots and fluorescence resonance energy transfer.

    Science.gov (United States)

    Tavares, Anthony J; Noor, M Omair; Vannoy, Charles H; Algar, W Russ; Krull, Ulrich J

    2012-01-03

    The glass surface of a glass-polydimethylsiloxane (PDMS) microfluidic channel was modified to develop a solid-phase assay for quantitative determination of nucleic acids. Electroosmotic flow (EOF) within channels was used to deliver and immobilize semiconductor quantum dots (QDs), and electrophoresis was used to decorate the QDs with oligonucleotide probe sequences. These processes took only minutes to complete. The QDs served as energy donors in fluorescence resonance energy transfer (FRET) for transduction of nucleic acid hybridization. Electrokinetic injection of fluorescent dye (Cy3) labeled oligonucleotide target into a microfluidic channel and subsequent hybridization (within minutes) provided the proximity for FRET, with emission from Cy3 being the analytical signal. The quantification of target concentration was achieved by measurement of the spatial length of coverage by target along a channel. Detection of femtomole quantities of target was possible with a dynamic range spanning an order of magnitude. The assay provided excellent resistance to nonspecific interactions of DNA. Further selectivity of the assay was achieved using 20% formamide, which allowed discrimination between a fully complementary target and a 3 base pair mismatch target at a contrast ratio of 4:1. © 2011 American Chemical Society

  17. OMERACT Rheumatoid Arthritis Magnetic Resonance Imaging Studies. Summary of OMERACT 6 MR Imaging Module

    DEFF Research Database (Denmark)

    McQueen, F; Lassere, M; Edmonds, J

    2003-01-01

    correlates closely with histological evidence and work continues on validating MR erosions with reference to radiographic techniques. The RAMRIS has demonstrated good reliability for bone erosion and synovitis at the wrists and metacarpophalangeal joints subject to reader training, with slightly lower levels......Magnetic resonance image (MRI) scanning is a new method for imaging and quantifying joint inflammation and damage in rheumatoid arthritis (RA). Over the past 4 years, the OMERACT MR Imaging Group has been developing and testing the RA-MRI scoring system (RAMRIS) for use in RA. The OMERACT filter...... and scoring, as well as cost and safety issues. The OMERACT RAMRIS provides a framework for scoring inflammation and damage in RA upon which further modifications can be built. It has been endorsed by the MRI working group and OMERACT 6 participants as useful for inclusion as an outcome measure in clinical...

  18. Acoustically modulated magnetic resonance imaging of gas-filled protein nanostructures

    Science.gov (United States)

    Lu, George J.; Farhadi, Arash; Szablowski, Jerzy O.; Lee-Gosselin, Audrey; Barnes, Samuel R.; Lakshmanan, Anupama; Bourdeau, Raymond W.; Shapiro, Mikhail G.

    2018-05-01

    Non-invasive biological imaging requires materials capable of interacting with deeply penetrant forms of energy such as magnetic fields and sound waves. Here, we show that gas vesicles (GVs), a unique class of gas-filled protein nanostructures with differential magnetic susceptibility relative to water, can produce robust contrast in magnetic resonance imaging (MRI) at sub-nanomolar concentrations, and that this contrast can be inactivated with ultrasound in situ to enable background-free imaging. We demonstrate this capability in vitro, in cells expressing these nanostructures as genetically encoded reporters, and in three model in vivo scenarios. Genetic variants of GVs, differing in their magnetic or mechanical phenotypes, allow multiplexed imaging using parametric MRI and differential acoustic sensitivity. Additionally, clustering-induced changes in MRI contrast enable the design of dynamic molecular sensors. By coupling the complementary physics of MRI and ultrasound, this nanomaterial gives rise to a distinct modality for molecular imaging with unique advantages and capabilities.

  19. Stochastic resonance for signal-modulated pump noise in a single-mode laser

    Institute of Scientific and Technical Information of China (English)

    Liangying Zhang; Li Cao; Fahui Zhu

    2006-01-01

    By adopting the gain-noise model of the single-mode laser in which with bias and periodical signals serve as inputs, combining with the effect of coloured pump noise, we use the linear approximation method to calculate the power spectrum and signal-to-noise ratio (SNR) of the laser intensity under the condition of pump noise and quantum noise cross-related in the form of δ function. It is found that with the change of pump noise correlation time, both SNR and the output power will occur stochastic resonance (SR). If the bias signal α is very small, changing the intensities of pump noise and quantum noise respectively does not lead to the appearance of SR in the SNR; while α increases to a certain number, SR appears.

  20. Combined resonant tank capacitance and pulse frequency modulation control for ZCS-SR inverter-fed high voltage DC power supply

    International Nuclear Information System (INIS)

    Lee, S S; Iqbal, S; Kamarol, M

    2011-01-01

    Conventional pulse frequency modulated (PFM) zero current switching (ZCS) series resonant (SR) inverter fed high voltage dc power supplies have nearly zero switching loss. However, they have limitations of poor controllability at light loads and large output voltage ripple at low switching frequencies. To address these problems, this paper proposes a combined resonant tank capacitance and pulse frequency modulation based control approach. For the realization of the proposed control approach, the tank circuit of the resonant inverter is made up of several resonant capacitors that are switched into or out of the tank circuit by electromechanical switches. The output voltage of the converter is regulated by digitally modulating the resonant tank capacitance and narrowly varying the switching frequency. The proposed control scheme has several features, namely a wide range of controllability even at light loads, less output voltage ripple, and less current stress on the inverter's power switches at light loads. Therefore, the proposed control approach alleviates most of the problems associated with conventional PFM. Experimental results obtained from a scaled down laboratory prototype are presented to verify the effectiveness of the proposed system.

  1. Sunlight Modulates Fruit Metabolic Profile and Shapes the Spatial Pattern of Compound Accumulation within the Grape Cluster.

    Science.gov (United States)

    Reshef, Noam; Walbaum, Natasha; Agam, Nurit; Fait, Aaron

    2017-01-01

    Vineyards are characterized by their large spatial variability of solar irradiance (SI) and temperature, known to effectively modulate grape metabolism. To explore the role of sunlight in shaping fruit composition and cluster uniformity, we studied the spatial pattern of incoming irradiance, fruit temperature and metabolic profile within individual grape clusters under three levels of sunlight exposure. The experiment was conducted in a vineyard of Cabernet Sauvignon cv. located in the Negev Highlands, Israel, where excess SI and midday temperatures are known to degrade grape quality. Filtering SI lowered the surface temperature of exposed fruits and increased the uniformity of irradiance and temperature in the cluster zone. SI affected the overall levels and patterns of accumulation of sugars, organic acids, amino acids and phenylpropanoids, across the grape cluster. Increased exposure to sunlight was associated with lower accumulation levels of malate, aspartate, and maleate but with higher levels of valine, leucine, and serine, in addition to the stress-related proline and GABA. Flavan-3-ols metabolites showed a negative response to SI, whereas flavonols were highly induced. The overall levels of anthocyanins decreased with increased sunlight exposure; however, a hierarchical cluster analysis revealed that the members of this family were grouped into three distinct accumulation patterns, with malvidin anthocyanins and cyanidin-glucoside showing contrasting trends. The flavonol-glucosides, quercetin and kaempferol, exhibited a logarithmic response to SI, leading to improved cluster uniformity under high-light conditions. Comparing the within-cluster variability of metabolite accumulation highlighted the stability of sugars, flavan-3-ols, and cinnamic acid metabolites to SI, in contrast to the plasticity of flavonols. A correlation-based network analysis revealed that extended exposure to SI modified metabolic coordination, increasing the number of negative

  2. Development of Instrumentation for Spin-Echo Induced Spatial Beam Modulations

    DEFF Research Database (Denmark)

    Sales, Morten

    Spin-Echo Modulated Small Angle Neutron Scattering in Time-of-Flight mode (ToF SEMSANS) is an emerging technique extending the measurable phase space covered by neutron scattering. Using inclined magnetic field surfaces, (very) small angle scattering from a sample can be mapped into the spin...... orientation of the neutron as it has been shown in Spin-Echo Small Angle Neutron Scattering (SESANS). Taking this technique further we have shown that it is possible to perform quantitative Dark-Field Imaging, where the small angle scattering signal of individual areas in a neutron image can be obtained...

  3. Simulating atmospheric turbulence using a phase-only spatial light modulator

    CSIR Research Space (South Africa)

    Burger, L

    2008-04-01

    Full Text Available is zero and the outer scale is infinity. These assumptions lead to a well-defined distribution for the randomness in the refractive index of the atmosphere, which can be applied in the laboratory, giving a good approximation for a real atmosphere.1.... There are two basic aims: first, to expound on the steps required to actually simulate atmospheric turbulence in the laboratory, and second, to point out some of the limitations in using spatial light modula- Research Articles South African Journal of Science...

  4. Matter-wave solitons and finite-amplitude Bloch waves in optical lattices with spatially modulated nonlinearity

    Science.gov (United States)

    Zhang, Jie-Fang; Li, Yi-Shen; Meng, Jianping; Wu, Lei; Malomed, Boris A.

    2010-09-01

    We investigate solitons and nonlinear Bloch waves in Bose-Einstein condensates trapped in optical lattices (OLs). By introducing specially designed localized profiles of the spatial modulation of the attractive nonlinearity, we construct an infinite set of exact soliton solutions in terms of Mathieu and elliptic functions, with the chemical potential belonging to the semi-infinite gap of the OL-induced spectrum. Starting from the particular exact solutions, we employ the relaxation method to construct generic families of soliton solutions in a numerical form. The stability of the solitons is investigated through the computation of the eigenvalues for small perturbations, and also by direct simulations. Finally, we demonstrate a virtually exact (in the numerical sense) composition relation between nonlinear Bloch waves and solitons.

  5. Matter-wave solitons and finite-amplitude Bloch waves in optical lattices with spatially modulated nonlinearity

    International Nuclear Information System (INIS)

    Zhang Jiefang; Meng Jianping; Wu Lei; Li Yishen; Malomed, Boris A.

    2010-01-01

    We investigate solitons and nonlinear Bloch waves in Bose-Einstein condensates trapped in optical lattices (OLs). By introducing specially designed localized profiles of the spatial modulation of the attractive nonlinearity, we construct an infinite set of exact soliton solutions in terms of Mathieu and elliptic functions, with the chemical potential belonging to the semi-infinite gap of the OL-induced spectrum. Starting from the particular exact solutions, we employ the relaxation method to construct generic families of soliton solutions in a numerical form. The stability of the solitons is investigated through the computation of the eigenvalues for small perturbations, and also by direct simulations. Finally, we demonstrate a virtually exact (in the numerical sense) composition relation between nonlinear Bloch waves and solitons.

  6. The nanosizing of fluorescent objects by 458 nm spatially modulated illumination microscopy using a simplified size evaluation algorithm

    Energy Technology Data Exchange (ETDEWEB)

    Schweitzer, Andreas; Wagner, Christian; Cremer, Christoph [Kirchhoff-Institute for Physics of the University, Im Neuenheimer Feld 227, 69120 Heidelberg (Germany)

    2004-07-07

    In fluorescent light microscopy, structured illumination approaches have emerged as a novel tool to analyse subwavelength sized objects in thick transparent specimens. In this report, new size measurements ('nanosizing') of small subwavelength sized fluorescent objects applying spatially modulated illumination (SMI) microscopy with an excitation wavelength of {lambda}{sub ex} 458 nm are presented. These measurements were made using fluorescent particles with a given diameter. From the SMI data achieved, the size (diameter) was determined using special calibration curves derived from analytical considerations assuming a Gaussian dye distribution within the object. The results showed that with SMI microscopy combined with suitable calibration, size measurements of objects considerably smaller than the epifluorescent optical resolution at {lambda}{sub ex} = 458 nm are feasible.

  7. High-efficiency and flexible generation of vector vortex optical fields by a reflective phase-only spatial light modulator.

    Science.gov (United States)

    Cai, Meng-Qiang; Wang, Zhou-Xiang; Liang, Juan; Wang, Yan-Kun; Gao, Xu-Zhen; Li, Yongnan; Tu, Chenghou; Wang, Hui-Tian

    2017-08-01

    The scheme for generating vector optical fields should have not only high efficiency but also flexibility for satisfying the requirements of various applications. However, in general, high efficiency and flexibility are not compatible. Here we present and experimentally demonstrate a solution to directly, flexibly, and efficiently generate vector vortex optical fields (VVOFs) with a reflective phase-only liquid crystal spatial light modulator (LC-SLM) based on optical birefringence of liquid crystal molecules. To generate the VVOFs, this approach needs in principle only a half-wave plate, an LC-SLM, and a quarter-wave plate. This approach has some advantages, including a simple experimental setup, good flexibility, and high efficiency, making the approach very promising in some applications when higher power is need. This approach has a generation efficiency of 44.0%, which is much higher than the 1.1% of the common path interferometric approach.

  8. Electronic origin of spatial self-phase modulation: Evidenced by comparing graphite with C{sub 60} and graphene

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Y. L.; Zhu, L. L. [College of Electronic Information and Optical Engineering, Nankai University, Tianjin 300071 (China); Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Wu, Q.; Sun, F.; Wei, J. K.; Tian, Y. C.; Wang, W. L.; Bai, X. D.; Zhao, Jimin, E-mail: jmzhao@iphy.ac.cn, E-mail: xzuonku@outlook.com [Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Zuo, Xu, E-mail: jmzhao@iphy.ac.cn, E-mail: xzuonku@outlook.com [College of Electronic Information and Optical Engineering, Nankai University, Tianjin 300071 (China)

    2016-06-13

    We report unambiguous observation of spatial self-phase modulation (SSPM) in a dispersive suspension of graphite flakes. This coherent nonlinear optical effect in bulk graphite is found to be broadband and large, with a third-order nonlinear susceptibility χ{sup (3)} of 2.2 × 10{sup −9} esu (i.e., 3.1 × 10{sup −17} m{sup 2}/V{sup 2} in SI units) at 532 nm excitation. Comparison with other carbon allotropes shows that this value is 5 × 10{sup 7} times higher than that of C{sub 60} but ∼50 times lower than that of graphene, fully exhibiting the electronic origin of SSPM.

  9. Superresolution size determination in fluorescence microscopy: A comparison between spatially modulated illumination and confocal laser scanning microscopy

    International Nuclear Information System (INIS)

    Spoeri, Udo; Failla, Antonio Virgilio; Cremer, Christoph

    2004-01-01

    Recently developed far field light optical methods are a powerful tool to analyze biological nanostructures and their dynamics, in particular including the interior of three-dimensionally conserved cells. In this article, the recently described method of spatially modulated illumination (SMI) microscopy has been further extended to the online determination of the extension of small, subwavelength sized, fluorescent objects (nanosizing). Using fluorescence excitation with 488 nm, the determination of fluorescent labeled object diameters down to 40 nm corresponding to about 1/12th of the wavelength used for one-photon excitation could be shown. The results of the SMI nanosizing procedure for a detailed, systematic variation of the object diameter are presented together with a fast algorithm for online size evaluation. In addition, we show a direct comparison of the diameter of 'colocalization volumes' between SMI nanosizing and conventional confocal laser scanning microscopy

  10. The spatial module as environmental conditioning element: the Spanish pavilion by Corrales and Molezun

    Directory of Open Access Journals (Sweden)

    R. Suárez

    2017-06-01

    Full Text Available In the 50s a review of Modern Movement, which assimilates modular serialization and a connection with the environmental context, although with remote premises of the contemporary paradigms of sustainability arise. In this context, within national stage, stands out the Spanish pavilion at the Brussels International Exhibition in 1958 by Corrales and Molezún. This work seeks a quantitatively reveal of the environmental performance of the pavilion in its two locations and settings, in Brussels and Madrid, through simulation and analysis of energy and lighting models which reproduces the characteristic of the pavilion with the purpose of contributing to give a new critical point of view, valuing the module efficiency to adapt to different environmental conditions. The completed analysis reveals the influence of the climate, compactness and orientation, as in the difficulties associated with thermal comfort and natural light when glazing percentage are important and there are high solar radiation settings.

  11. Context-dependent modulation of hippocampal and cortical recruitment during remote spatial memory retrieval.

    Science.gov (United States)

    Lopez, Joëlle; Herbeaux, Karin; Cosquer, Brigitte; Engeln, Michel; Muller, Christophe; Lazarus, Christine; Kelche, Christian; Bontempi, Bruno; Cassel, Jean-Christophe; de Vasconcelos, Anne Pereira

    2012-04-01

    According to systems consolidation, as hippocampal-dependent memories mature over time, they become additionally (or exclusively) dependent on extra-hippocampal structures. We assessed the recruitment of hippocampal and cortical structures on remote memory retrieval in a performance-degradation resistant (PDR; no performance degradation with time) versus performance-degradation prone (PDP; performance degraded with time) context. Using a water-maze task in two contexts with a hidden platform and three control conditions (home cage, visible platform with or without access to distal cues), we compared neuronal activation (c-Fos imaging) patterns in the dorsal hippocampus and the medial prefrontal cortex (mPFC) after the retrieval of recent (5 days) versus remote (25 days) spatial memory. In the PDR context, the hippocampus exhibited greater c-Fos protein expression on remote than recent memory retrieval, be it in the visible or hidden platform group. In the PDP context, hippocampal activation increased at the remote time point and only in the hidden platform group. In the anterior cingulate cortex, c-Fos expression was greater for remote than for recent memory retrieval and only in the PDR context. The necessity of the mPFC for remote memory retrieval in the PDR context was confirmed using region-specific lidocaine inactivation, which had no impact on recent memory. Conversely, inactivation of the dorsal hippocampus impaired both recent and remote memory in the PDR context, and only recent memory in the PDP context, in which remote memory performance was degraded. While confirming that neuronal circuits supporting spatial memory consolidation are reorganized in a time-dependent manner, our findings further indicate that mPFC and hippocampus recruitment (i) depends on the content and perhaps the strength of the memory and (ii) may be influenced by the environmental conditions (e.g., cue saliency, complexity) in which memories are initially formed and subsequently

  12. Kinesthetic and vestibular information modulate alpha activity during spatial navigation: a mobile EEG study.

    Science.gov (United States)

    Ehinger, Benedikt V; Fischer, Petra; Gert, Anna L; Kaufhold, Lilli; Weber, Felix; Pipa, Gordon; König, Peter

    2014-01-01

    In everyday life, spatial navigation involving locomotion provides congruent visual, vestibular, and kinesthetic information that need to be integrated. Yet, previous studies on human brain activity during navigation focus on stationary setups, neglecting vestibular and kinesthetic feedback. The aim of our work is to uncover the influence of those sensory modalities on cortical processing. We developed a fully immersive virtual reality setup combined with high-density mobile electroencephalography (EEG). Participants traversed one leg of a triangle, turned on the spot, continued along the second leg, and finally indicated the location of their starting position. Vestibular and kinesthetic information was provided either in combination, as isolated sources of information, or not at all within a 2 × 2 full factorial intra-subjects design. EEG data were processed by clustering independent components, and time-frequency spectrograms were calculated. In parietal, occipital, and temporal clusters, we detected alpha suppression during the turning movement, which is associated with a heightened demand of visuo-attentional processing and closely resembles results reported in previous stationary studies. This decrease is present in all conditions and therefore seems to generalize to more natural settings. Yet, in incongruent conditions, when different sensory modalities did not match, the decrease is significantly stronger. Additionally, in more anterior areas we found that providing only vestibular but no kinesthetic information results in alpha increase. These observations demonstrate that stationary experiments omit important aspects of sensory feedback. Therefore, it is important to develop more natural experimental settings in order to capture a more complete picture of neural correlates of spatial navigation.

  13. Kinesthetic and Vestibular Information Modulate Alpha Activity during Spatial Navigation: A Mobile EEG Study

    Directory of Open Access Journals (Sweden)

    Benedikt Valerian Ehinger

    2014-02-01

    Full Text Available In everyday life, spatial navigation involving locomotion provides congruent visual, vestibular and kinesthetic information that need to be integrated. Yet, previous studies on human brain activity during navigation focus on stationary setups, neglecting vestibular and kinesthetic feedback. The aim of our work is to uncover the influence of those sensory modalities on cortical processing. We developed a fully immersive virtual reality setup combined with high-density mobile electroencephalography (EEG. Participants traversed one leg of a triangle, turned on the spot, continued along the second leg and finally indicated the location of their starting position. Vestibular and kinesthetic information was provided either in combination, as isolated sources of information or not at all within a 2x2 full factorial intra-subjects design. EEG data were processed by clustering independent components, and time-frequency spectrograms were calculated. In parietal, occipital and temporal clusters, we detected alpha suppression during the turning movement, which is associated with a heightened demand of visuo-attentional processing, and closely resembles results reported in previous stationary studies. This decrease is present in all conditions and therefore seems to generalize to more natural settings. Yet, in incongruent conditions, when different sensory modalities did not match, the decrease is significantly stronger. Additionally, in more anterior areas, we found that providing only vestibular but no kinesthetic information results in alpha increase. These observations demonstrate that stationary experiments omit important aspects of sensory feedback. Therefore, it is important to develop more natural experimental settings in order to capture a more complete picture of neural correlates of spatial navigation.

  14. Spatial representation and cognitive modulation of response variability in the lateral intraparietal area priority map.

    Science.gov (United States)

    Falkner, Annegret L; Goldberg, Michael E; Krishna, B Suresh

    2013-10-09

    The lateral intraparietal area (LIP) in the macaque contains a priority-based representation of the visual scene. We previously showed that the mean spike rate of LIP neurons is strongly influenced by spatially wide-ranging surround suppression in a manner that effectively sharpens the priority map. Reducing response variability can also improve the precision of LIP's priority map. We show that when a monkey plans a visually guided delayed saccade with an intervening distractor, variability (measured by the Fano factor) decreases both for neurons representing the saccade goal and for neurons representing the broad spatial surround. The reduction in Fano factor is maximal for neurons representing the saccade goal and steadily decreases for neurons representing more distant locations. LIP Fano factor changes are behaviorally significant: increasing expected reward leads to lower variability for the LIP representation of both the target and distractor locations, and trials with shorter latency saccades are associated with lower Fano factors in neurons representing the surround. Thus, the LIP Fano factor reflects both stimulus and behavioral engagement. Quantitative modeling shows that the interaction between mean spike count and target-receptive field (RF) distance in the surround during the predistractor epoch is multiplicative: the Fano factor increases more steeply with mean spike count further away from the RF. A negative-binomial model for LIP spike counts captures these findings quantitatively, suggests underlying mechanisms based on trial-by-trial variations in mean spike rate or burst-firing patterns, and potentially provides a principled framework to account simultaneously for the previously observed unsystematic relationships between spike rate and variability in different brain areas.

  15. Novel Application of Time-Spatial Labeling Inversion Pulse Magnetic Resonance Imaging for Diagnosis of External Hydrocephalus.

    Science.gov (United States)

    Nakae, Shunsuke; Murayama, Kazuhiro; Adachi, Kazuhide; Kumai, Tadashi; Abe, Masato; Hirose, Yuichi

    2018-01-01

    Although a subdural fluid collection frequently is observed, diagnostic methods that differentiate between the subdural collection caused by external hydrocephalus and that caused by subdural hygroma have not been established. Here, we report a case of external hydrocephalus caused by Gliadel-induced eosinophilic meningitis that has been previously reported in only 1 case and can be diagnosed by time-spatial labeling inversion pulse magnetic resonance imaging (time-SLIP MRI). A tumor located in the left temporal was detected incidentally in an 81-year-old man by examination of a head injury. The tumor was surgically resected and diagnosed as a high-grade glioma during the surgery; Gliadel wafers subsequently were implanted. Three weeks after the resection, the patient showed disturbed consciousness, and computed tomography revealed a subdural fluid collection. The out-flow of cerebrospinal through the resection cavity was detected by time-SLIP MRI. Cerebrospinal tests indicated high white blood cell counts and high protein levels, with more than 90% of the white blood cell count comprising eosinophils. Therefore, we suspected that the subdural fluid collection was caused by external hydrocephalus because of Gliadel-induced eosinophilic meningitis. We surgically removed the Gliadel wafers and subsequently performed a surgery to insert a ventriculoperitoneal shunt. Histologic examination indicated eosinophilic accumulation around the Gliadel wafers. The patient's symptoms improved after the insertion of a ventriculoperitoneal shunt. In the present case, time-SLIP MRI was a useful and noninvasive method for diagnosing external hydrocephalus which was caused by eosinophilic meningitis because of Gliadel-induced eosinophilic meningitis. Copyright © 2017 Elsevier Inc. All rights reserved.

  16. Opposite monosynaptic scaling of BLP-vCA1 inputs governs hopefulness- and helplessness-modulated spatial learning and memory.

    Science.gov (United States)

    Yang, Ying; Wang, Zhi-Hao; Jin, Sen; Gao, Di; Liu, Nan; Chen, Shan-Ping; Zhang, Sinan; Liu, Qing; Liu, Enjie; Wang, Xin; Liang, Xiao; Wei, Pengfei; Li, Xiaoguang; Li, Yin; Yue, Chenyu; Li, Hong-Lian; Wang, Ya-Li; Wang, Qun; Ke, Dan; Xie, Qingguo; Xu, Fuqiang; Wang, Liping; Wang, Jian-Zhi

    2016-07-14

    Different emotional states lead to distinct behavioural consequences even when faced with the same challenging events. Emotions affect learning and memory capacities, but the underlying neurobiological mechanisms remain elusive. Here we establish models of learned helplessness (LHL) and learned hopefulness (LHF) by exposing animals to inescapable foot shocks or with anticipated avoidance trainings. The LHF animals show spatial memory potentiation with excitatory monosynaptic upscaling between posterior basolateral amygdale (BLP) and ventral hippocampal CA1 (vCA1), whereas the LHL show memory deficits with an attenuated BLP-vCA1 connection. Optogenetic disruption of BLP-vCA1 inputs abolishes the effects of LHF and impairs synaptic plasticity. By contrast, targeted BLP-vCA1 stimulation rescues the LHL-induced memory deficits and mimics the effects of LHF. BLP-vCA1 stimulation increases synaptic transmission and dendritic plasticity with the upregulation of CREB and intrasynaptic AMPA receptors in CA1. These findings indicate that opposite excitatory monosynaptic scaling of BLP-vCA1 controls LHF- and LHL-modulated spatial memory, revealing circuit-specific mechanisms linking emotions to memory.

  17. Opposite monosynaptic scaling of BLP–vCA1 inputs governs hopefulness- and helplessness-modulated spatial learning and memory

    Science.gov (United States)

    Yang, Ying; Wang, Zhi-Hao; Jin, Sen; Gao, Di; Liu, Nan; Chen, Shan-Ping; Zhang, Sinan; Liu, Qing; Liu, Enjie; Wang, Xin; Liang, Xiao; Wei, Pengfei; Li, Xiaoguang; Li, Yin; Yue, Chenyu; Li, Hong-lian; Wang, Ya-Li; Wang, Qun; Ke, Dan; Xie, Qingguo; Xu, Fuqiang; Wang, Liping; Wang, Jian-Zhi

    2016-01-01

    Different emotional states lead to distinct behavioural consequences even when faced with the same challenging events. Emotions affect learning and memory capacities, but the underlying neurobiological mechanisms remain elusive. Here we establish models of learned helplessness (LHL) and learned hopefulness (LHF) by exposing animals to inescapable foot shocks or with anticipated avoidance trainings. The LHF animals show spatial memory potentiation with excitatory monosynaptic upscaling between posterior basolateral amygdale (BLP) and ventral hippocampal CA1 (vCA1), whereas the LHL show memory deficits with an attenuated BLP–vCA1 connection. Optogenetic disruption of BLP–vCA1 inputs abolishes the effects of LHF and impairs synaptic plasticity. By contrast, targeted BLP–vCA1 stimulation rescues the LHL-induced memory deficits and mimics the effects of LHF. BLP–vCA1 stimulation increases synaptic transmission and dendritic plasticity with the upregulation of CREB and intrasynaptic AMPA receptors in CA1. These findings indicate that opposite excitatory monosynaptic scaling of BLP–vCA1 controls LHF- and LHL-modulated spatial memory, revealing circuit-specific mechanisms linking emotions to memory. PMID:27411738

  18. Generation of sinusoidal fringes with a holographic phase grating and a phase-only spatial light modulator

    International Nuclear Information System (INIS)

    Berberova, Natalia; Stoykova, Elena; Sainov, Ventseslav

    2012-01-01

    A variety of pattern projection methods for the three-dimensional capture of objects is based on the generation of purely sinusoidal fringes. This is not an easy task, especially when a portable non-interferometric system for outdoor usage is required. The use of phase gratings with coherent illumination as a possible solution has the advantage of providing good stability and a large measurement volume. In this work, we analyze the quality of fringes projected with two sinusoidal phase gratings. The first grating is recorded on a silver-halide holographic plate by means of a Michelson interferometer. The spatial resolution of the silver-halide material used is greater than 6000 lines per millimeter, and the recorded grating is practically analogous to a smooth variation of the phase profile. The second grating is formed as a sinusoidal phase variation on a liquid crystal-on-silicon phase-only reflective display with a resolution of 1920×1080 pixels, a pixel pitch of 8 μm and 256 phase levels. The frequency content of the fringes projected with both gratings is analyzed and compared on the basis of the calculated Fresnel diffraction pattern, taking into account that the sinusoidal phase distribution in the case of a spatial light modulator is both sampled and quantized. Experimental fringe patterns projected using both gratings are also provided.

  19. Short-term sleep deprivation impairs spatial working memory and modulates expression levels of ionotropic glutamate receptor subunits in hippocampus.

    Science.gov (United States)

    Xie, Meilan; Yan, Jie; He, Chao; Yang, Li; Tan, Gang; Li, Chao; Hu, Zhian; Wang, Jiali

    2015-06-01

    Hippocampus-dependent learning memory is sensitive to sleep deprivation (SD). Although the ionotropic glutamate receptors play a vital role in synaptic plasticity and learning and memory, however, whether the expression of these receptor subunits is modulated by sleep loss remains unclear. In the present study, western blotting was performed by probing with specific antibodies against the ionotropic α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor subunits GluA1, GluA2, GluA3, and against the N-methyl-d-aspartate (NMDA) glutamate receptor subunits GluN1, GluN2A, GluN2B. In hippocampus, down regulation of surface GluA1 and GluN2A surface expression were observed in both SD groups. However, surface expression level of GluA2, GluA3, GluN1 and GluN2B was significantly up-regulated in 8h-SD rats when compared to the 4h-SD rats. In parallel with the complex changes in AMPA and NMDA receptor subunit expressions, we found the 8h-SD impaired rat spatial working memory in 30-s-delay T-maze task, whereas no impairment of spatial learning was observed in 4h-SD rats. These results indicate that sleep loss alters the relative expression levels of the AMPA and NMDA receptors, thus affects the synaptic strength and capacity for plasticity and partially contributes to spatial memory impairment. Copyright © 2015. Published by Elsevier B.V.

  20. Spatial Attention and Temporal Expectation Under Timed Uncertainty Predictably Modulate Neuronal Responses in Monkey V1

    Science.gov (United States)

    Sharma, Jitendra; Sugihara, Hiroki; Katz, Yarden; Schummers, James; Tenenbaum, Joshua; Sur, Mriganka

    2015-01-01

    The brain uses attention and expectation as flexible devices for optimizing behavioral responses associated with expected but unpredictably timed events. The neural bases of attention and expectation are thought to engage higher cognitive loci; however, their influence at the level of primary visual cortex (V1) remains unknown. Here, we asked whether single-neuron responses in monkey V1 were influenced by an attention task of unpredictable duration. Monkeys covertly attended to a spot that remained unchanged for a fixed period and then abruptly disappeared at variable times, prompting a lever release for reward. We show that monkeys responded progressively faster and performed better as the trial duration increased. Neural responses also followed monkey's task engagement—there was an early, but short duration, response facilitation, followed by a late but sustained increase during the time monkeys expected the attention spot to disappear. This late attentional modulation was significantly and negatively correlated with the reaction time and was well explained by a modified hazard function. Such bimodal, time-dependent changes were, however, absent in a task that did not require explicit attentional engagement. Thus, V1 neurons carry reliable signals of attention and temporal expectation that correlate with predictable influences on monkeys' behavioral responses. PMID:24836689

  1. Using Pitch, Amplitude Modulation, and Spatial Cues for Separation of Harmonic Instruments from Stereo Music Recordings

    Directory of Open Access Journals (Sweden)

    Bryan Pardo

    2007-01-01

    Full Text Available Recent work in blind source separation applied to anechoic mixtures of speech allows for improved reconstruction of sources that rarely overlap in a time-frequency representation. While the assumption that speech mixtures do not overlap significantly in time-frequency is reasonable, music mixtures rarely meet this constraint, requiring new approaches. We introduce a method that uses spatial cues from anechoic, stereo music recordings and assumptions regarding the structure of musical source signals to effectively separate mixtures of tonal music. We discuss existing techniques to create partial source signal estimates from regions of the mixture where source signals do not overlap significantly. We use these partial signals within a new demixing framework, in which we estimate harmonic masks for each source, allowing the determination of the number of active sources in important time-frequency frames of the mixture. We then propose a method for distributing energy from time-frequency frames of the mixture to multiple source signals. This allows dealing with mixtures that contain time-frequency frames in which multiple harmonic sources are active without requiring knowledge of source characteristics.

  2. Phase modulation and structural effects in a D-shaped all-solid photonic crystal fiber surface plasmon resonance sensor.

    Science.gov (United States)

    Tan, Zhixin; Hao, Xin; Shao, Yonghong; Chen, Yuzhi; Li, Xuejin; Fan, Ping

    2014-06-16

    We numerically investigate a D-shaped fiber surface plasmon resonance sensor based on all-solid photonic crystal fiber (PCF) with finite element method. In the side-polished PCF sensor, field leakage is guided to penetrate through the gap between the rods, causing a pronounced phase modulation in the deep polishing case. Taking advantage of these amplified phase shifts, a high-performance fiber sensor design is proposed. The significant enhancements arising from this new sensor design should lift the performance of the fiber SPR sensor into the range capable of detecting a wide range of biochemical interactions, which makes it especially attractive for many in vivo and in situ bioanalysis applications. Several parameters which influence the field leakage, such as the polishing position, the pitch of the PCF, and the rod diameter, are inspected to evaluate their impacts. Furthermore, we develop a mathematical model to describe the effects of varying the structural parameters of a D-shaped PCF sensor on the evanescent field and the sensor performance.

  3. Insulin modulates hippocampally-mediated spatial working memory via glucose transporter-4.

    Science.gov (United States)

    Pearson-Leary, J; Jahagirdar, V; Sage, J; McNay, E C

    2018-02-15

    The insulin-regulated glucose transporter, GluT4, is a key molecule in peripheral insulin signaling. Although GluT4 is abundantly expressed in neurons of specific brain regions such as the hippocampus, the functional role of neuronal GluT4 is unclear. Here, we used pharmacological inhibition of GluT4-mediated glucose uptake to determine whether GluT4 mediates insulin-mediated glucose uptake in the hippocampus. Consistent with previous reports, we found that glucose utilization increased in the dorsal hippocampus of male rats during spontaneous alternation (SA), a hippocampally-mediated spatial working memory task. We previously showed that insulin signaling within the hippocampus is required for processing this task, and that administration of exogenous insulin enhances performance. At baseline levels of hippocampal insulin, inhibition of GluT4-mediated glucose uptake did not affect SA performance. However, inhibition of an upstream regulator of GluT4, Akt, did impair SA performance. Conversely, when a memory-enhancing dose of insulin was delivered to the hippocampus prior to SA-testing, inhibition of GluT4-mediated glucose transport prevented cognitive enhancement. These data suggest that baseline hippocampal cognitive processing does not require functional hippocampal GluT4, but that cognitive enhancement by supra-baseline insulin does. Consistent with these findings, we found that in neuronal cell culture, insulin increases glucose utilization in a GluT4-dependent manner. Collectively, these data demonstrate a key role for GluT4 in transducing the procognitive effects of elevated hippocampal insulin. Copyright © 2017 Elsevier B.V. All rights reserved.

  4. Fluorescence resonance energy transfer measured by spatial photon migration in CdSe-ZnS quantum dots colloidal systems as a function of concentration

    Energy Technology Data Exchange (ETDEWEB)

    Azevedo, G.; Monte, A. F. G.; Reis, A. F.; Messias, D. N. [Laboratório de Espectroscopia Óptica, Instituto de Física, Universidade Federal de Uberlândia, Uberlândia, MG 38400-902 (Brazil)

    2014-11-17

    The study of the spatial photon migration as a function of the concentration brings into attention the problem of the energy transfer in quantum dot embedded systems. By measuring the photon propagation and its spatial dependence, it is possible to understand the whole dynamics in a quantum dot system, and also improve their concentration dependence to maximize energy propagation due to radiative and non-radiative processes. In this work, a confocal microscope was adapted to scan the spatial distribution of photoluminescence from CdSe-ZnS core-shell quantum dots in colloidal solutions. The energy migration between the quantum dots was monitored by the direct measurement of the photon diffusion length, according to the diffusion theory. We observed that the photon migration length decreases by increasing the quantum dot concentration, this kind of behavior has been regarded as a signature of Förster resonance energy transfer in the system.

  5. Deep brain stimulation modulates synchrony within spatially and spectrally distinct resting state networks in Parkinson's disease.

    Science.gov (United States)

    Oswal, Ashwini; Beudel, Martijn; Zrinzo, Ludvic; Limousin, Patricia; Hariz, Marwan; Foltynie, Tom; Litvak, Vladimir; Brown, Peter

    2016-05-01

    Chronic dopamine depletion in Parkinson's disease leads to progressive motor and cognitive impairment, which is associated with the emergence of characteristic patterns of synchronous oscillatory activity within cortico-basal-ganglia circuits. Deep brain stimulation of the subthalamic nucleus is an effective treatment for Parkinson's disease, but its influence on synchronous activity in cortico-basal-ganglia loops remains to be fully characterized. Here, we demonstrate that deep brain stimulation selectively suppresses certain spatially and spectrally segregated resting state subthalamic nucleus-cortical networks. To this end we used a validated and novel approach for performing simultaneous recordings of the subthalamic nucleus and cortex using magnetoencephalography (during concurrent subthalamic nucleus deep brain stimulation). Our results highlight that clinically effective subthalamic nucleus deep brain stimulation suppresses synchrony locally within the subthalamic nucleus in the low beta oscillatory range and furthermore that the degree of this suppression correlates with clinical motor improvement. Moreover, deep brain stimulation relatively selectively suppressed synchronization of activity between the subthalamic nucleus and mesial premotor regions, including the supplementary motor areas. These mesial premotor regions were predominantly coupled to the subthalamic nucleus in the high beta frequency range, but the degree of deep brain stimulation-associated suppression in their coupling to the subthalamic nucleus was not found to correlate with motor improvement. Beta band coupling between the subthalamic nucleus and lateral motor areas was not influenced by deep brain stimulation. Motor cortical coupling with subthalamic nucleus predominantly involved driving of the subthalamic nucleus, with those drives in the higher beta frequency band having much shorter net delays to subthalamic nucleus than those in the lower beta band. These observations raise the

  6. A fully-integrated 12.5-Gb/s 850-nm CMOS optical receiver based on a spatially-modulated avalanche photodetector

    NARCIS (Netherlands)

    Lee, M.J.; Youn, J.S.; Park, K.Y.; Choi, W.Y.

    2014-01-01

    We present a fully integrated 12.5-Gb/s optical receiver fabricated with standard 0.13-µm complementary metal-oxide-semiconductor (CMOS) technology for 850-nm optical interconnect applications. Our integrated optical receiver includes a newly proposed CMOS-compatible spatially-modulated avalanche

  7. Reference-free determination of tissue absorption coefficient by modulation transfer function characterization in spatial frequency domain.

    Science.gov (United States)

    Chen, Weiting; Zhao, Huijuan; Li, Tongxin; Yan, Panpan; Zhao, Kuanxin; Qi, Caixia; Gao, Feng

    2017-08-08

    Spatial frequency domain (SFD) measurement allows rapid and non-contact wide-field imaging of the tissue optical properties, thus has become a potential tool for assessing physiological parameters and therapeutic responses during photodynamic therapy of skin diseases. The conventional SFD measurement requires a reference measurement within the same experimental scenario as that for a test one to calibrate mismatch between the real measurements and the model predictions. Due to the individual physical and geometrical differences among different tissues, organs and patients, an ideal reference measurement might be unavailable in clinical trials. To address this problem, we present a reference-free SFD determination of absorption coefficient that is based on the modulation transfer function (MTF) characterization. Instead of the absolute amplitude that is used in the conventional SFD approaches, we herein employ the MTF to characterize the propagation of the modulated lights in tissues. With such a dimensionless relative quantity, the measurements can be naturally corresponded to the model predictions without calibrating the illumination intensity. By constructing a three-dimensional database that portrays the MTF as a function of the optical properties (both the absorption coefficient μ a and the reduced scattering coefficient [Formula: see text]) and the spatial frequency, a look-up table approach or a least-square curve-fitting method is readily applied to recover the absorption coefficient from a single frequency or multiple frequencies, respectively. Simulation studies have verified the feasibility of the proposed reference-free method and evaluated its accuracy in the absorption recovery. Experimental validations have been performed on homogeneous tissue-mimicking phantoms with μ a ranging from 0.01 to 0.07 mm -1 and [Formula: see text] = 1.0 or 2.0 mm -1 . The results have shown maximum errors of 4.86 and 7% for [Formula: see text] = 1.0 mm -1 and

  8. Quality of Intensity Modulated Radiation Therapy Treatment Plans Using a 60Co Magnetic Resonance Image Guidance Radiation Therapy System

    International Nuclear Information System (INIS)

    Wooten, H. Omar; Green, Olga; Yang, Min; DeWees, Todd; Kashani, Rojano; Olsen, Jeff; Michalski, Jeff; Yang, Deshan; Tanderup, Kari; Hu, Yanle; Li, H. Harold; Mutic, Sasa

    2015-01-01

    Purpose: This work describes a commercial treatment planning system, its technical features, and its capabilities for creating 60 Co intensity modulated radiation therapy (IMRT) treatment plans for a magnetic resonance image guidance radiation therapy (MR-IGRT) system. Methods and Materials: The ViewRay treatment planning system (Oakwood Village, OH) was used to create 60 Co IMRT treatment plans for 33 cancer patients with disease in the abdominal, pelvic, thorax, and head and neck regions using physician-specified patient-specific target coverage and organ at risk (OAR) objectives. Backup plans using a third-party linear accelerator (linac)-based planning system were also created. Plans were evaluated by attending physicians and approved for treatment. The 60 Co and linac plans were compared by evaluating conformity numbers (CN) with 100% and 95% of prescription reference doses and heterogeneity indices (HI) for planning target volumes (PTVs) and maximum, mean, and dose-volume histogram (DVH) values for OARs. Results: All 60 Co IMRT plans achieved PTV coverage and OAR sparing that were similar to linac plans. PTV conformity for 60 Co was within <1% and 3% of linac plans for 100% and 95% prescription reference isodoses, respectively, and heterogeneity was on average 4% greater. Comparisons of OAR mean dose showed generally better sparing with linac plans in the low-dose range <20 Gy, but comparable sparing for organs with mean doses >20 Gy. The mean doses for all 60 Co plan OARs were within clinical tolerances. Conclusions: A commercial 60 Co MR-IGRT device can produce highly conformal IMRT treatment plans similar in quality to linac IMRT for a variety of disease sites. Additional work is in progress to evaluate the clinical benefit of other novel features of this MR-IGRT system

  9. Polycrystalline magnetic garnet films comprising weakly coupled crystallites for piezoelectrically-driven magneto-optic spatial light modulators

    Energy Technology Data Exchange (ETDEWEB)

    Mito, S.; Sakurai, H.; Takagi, H.; Inoue, M. [Toyohashi University of Technology, Toyohashi, Aichi 441-8580 (Japan); Baryshev, A. V. [Electronics-Inspired Interdisciplinary Research Institute Toyohashi, Aichi 441-8580 (Japan); Ioffe Physical-Technical Institute, St. Petersburg 194021 (Russian Federation)

    2012-04-01

    We have investigated the magnetization process of the polycrystalline magnetic garnet films in order to determine the most suitable composition of garnet films for piezoelectrically-driven magneto-optic spatial light modulators (MOSLMs). For experiment, the bismuth-dysprosium-aluminum-substituted yttrium iron (Bi{sub 1.3}Dy{sub 0.7}Y{sub 1.0}Fe{sub 3.1}Al{sub 1.9}O{sub 12}) garnet films were deposited by an RF magnetron sputter and annealed at 700 deg. C in air. The annealing time was varied in a range of several minutes to control the grain size. The saturation magnetization, the remanent magnetization and the composition of the fabricated garnet films slightly changed versus the annealing time. Experiments showed that the coercivity and the grain size increased at longer annealing; the coercivity was larger for films with bigger grains. This work shows that garnet films with smaller coercivity are most suitable for controlling the magnetization of garnet and, correspondingly, the magneto-optical rotation of MOSLM pixels driven by piezoelectrics.

  10. Local electrophoresis deposition assisted by laser trapping coupled with a spatial light modulator for three-dimensional microfabrication

    Science.gov (United States)

    Matsuura, Toshiki; Takai, Takanari; Iwata, Futoshi

    2017-10-01

    We describe a novel three-dimensional fabrication technique using local electrophoresis deposition assisted by laser trapping coupled with a spatial light modulator (SLM). In a solution containing nanometer-scale colloidal Au particles, multiple laser spots formed on a conductive substrate by the SLM gathered the nanoparticles together, and then the nanoparticles were electrophoretically deposited onto the substrate by an applied electrical field. However, undesirable sub-spots often appeared due to optical interference from the multiple laser spots, which deteriorated the accuracy of the deposition. To avoid the appearance of undesirable sub-spots, we proposed a method using quasi-multiple spots, which we realized by switching the position of a single spot briefly using the SLM. The method allowed us to deposit multiple dots on the substrate without undesirable sub-dot deposition. By moving the substrate downward during deposition, multiple micro-pillar structures could be fabricated. As a fabrication property, the dependence of the pillar diameter on laser intensity was investigated by changing the number of laser spots. The smallest diameter of the four pillars fabricated in this study was 920 nm at the laser intensity of 2.5 mW. To demonstrate the effectiveness of the method, multiple spiral structures were fabricated. Quadruple spirals of 46 µm in height were successfully fabricated with a growth rate of 0.21 µm/s using 2200 frames of the CGH patterns displayed in the SLM at a frame rate of 10 fps.

  11. Autostereoscopic three-dimensional display by combining a single spatial light modulator and a zero-order nulled grating

    Science.gov (United States)

    Su, Yanfeng; Cai, Zhijian; Liu, Quan; Lu, Yifan; Guo, Peiliang; Shi, Lingyan; Wu, Jianhong

    2018-04-01

    In this paper, an autostereoscopic three-dimensional (3D) display system based on synthetic hologram reconstruction is proposed and implemented. The system uses a single phase-only spatial light modulator to load the synthetic hologram of the left and right stereo images, and the parallax angle between two reconstructed stereo images is enlarged by a grating to meet the split angle requirement of normal stereoscopic vision. To realize the crosstalk-free autostereoscopic 3D display with high light utilization efficiency, the groove parameters of the grating are specifically designed by the rigorous coupled-wave theory for suppressing the zero-order diffraction, and then the zero-order nulled grating is fabricated by the holographic lithography and the ion beam etching. Furthermore, the diffraction efficiency of the fabricated grating is measured under the illumination of a laser beam with a wavelength of 532 nm. Finally, the experimental verification system for the proposed autostereoscopic 3D display is presented. The experimental results prove that the proposed system is able to generate stereoscopic 3D images with good performances.

  12. Improvement of diffraction efficiency of three-dimensional magneto-optic spatial light modulator with magnetophotonic crystal

    Energy Technology Data Exchange (ETDEWEB)

    Nakamura, K.; Takagi, H., E-mail: takagi@ee.tut.ac.jp; Lim, P. B.; Inoue, M., E-mail: inoue@tut.ac.jp [Department of Electrical and Electronic Information Engineering, Toyohashi University of Technology, Toyohashi, Aichi 441 8580 (Japan); Goto, Taichi [Department of Electrical and Electronic Information Engineering, Toyohashi University of Technology, Toyohashi, Aichi 441 8580 (Japan); JST, PRESTO, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012 (Japan); Horimai, H. [HolyMine Corporation, Atsugi, Kanagawa 243 0813 (Japan); Yoshikawa, H. [Department of Computer Engineering, College of Science and Technology, Nihon University, Funabashi, Chiba 274 8501 (Japan); Bove, V. M. [MIT Media Lab, Cambridge, Massachusetts 02139 (United States)

    2016-01-11

    We have developed three-dimensional magneto-optic spatial light modulators (3D-MOSLMs) that use magnetic domains as submicron scale pixels to represent holograms. Our display system uses a submicron-scale magnetic pixel array on an amorphous TbFe film to create a wide viewing angle hologram. However, in previous work the reconstructed images had a low intensity and a low optical contrast; brightness of the reconstructed image was 4.4 × 10{sup −2 }cd/m{sup 2} with 532 nm illumination light at 10.8 mW/cm{sup 2}, while display standard ISO13406 recommends 100 cd/m{sup 2} or more. In this paper, we describe our development of a 3D-MOSLM composed of an artificial magnetic lattice structure of magnetophotonic crystals (MPCs). The MPCs enhance the diffraction efficiency of reconstructed 3D images and reduce the power consumption for controlling the magnetic pixels by a light localization effect. We demonstrate reconstructed 3D images using the MPC and show significant brightness improvement.

  13. Adaptive optics scanning laser ophthalmoscope using liquid crystal on silicon spatial light modulator: Performance study with involuntary eye movement

    Science.gov (United States)

    Huang, Hongxin; Toyoda, Haruyoshi; Inoue, Takashi

    2017-09-01

    The performance of an adaptive optics scanning laser ophthalmoscope (AO-SLO) using a liquid crystal on silicon spatial light modulator and Shack-Hartmann wavefront sensor was investigated. The system achieved high-resolution and high-contrast images of human retinas by dynamic compensation for the aberrations in the eyes. Retinal structures such as photoreceptor cells, blood vessels, and nerve fiber bundles, as well as blood flow, could be observed in vivo. We also investigated involuntary eye movements and ascertained microsaccades and drifts using both the retinal images and the aberrations recorded simultaneously. Furthermore, we measured the interframe displacement of retinal images and found that during eye drift, the displacement has a linear relationship with the residual low-order aberration. The estimated duration and cumulative displacement of the drift were within the ranges estimated by a video tracking technique. The AO-SLO would not only be used for the early detection of eye diseases, but would also offer a new approach for involuntary eye movement research.

  14. High spatial and temporal resolution retrospective cine cardiovascular magnetic resonance from shortened free breathing real-time acquisitions.

    Science.gov (United States)

    Xue, Hui; Kellman, Peter; Larocca, Gina; Arai, Andrew E; Hansen, Michael S

    2013-11-14

    Cine cardiovascular magnetic resonance (CMR) is challenging in patients who cannot perform repeated breath holds. Real-time, free-breathing acquisition is an alternative, but image quality is typically inferior. There is a clinical need for techniques that achieve similar image quality to the segmented cine using a free breathing acquisition. Previously, high quality retrospectively gated cine images have been reconstructed from real-time acquisitions using parallel imaging and motion correction. These methods had limited clinical applicability due to lengthy acquisitions and volumetric measurements obtained with such methods have not previously been evaluated systematically. This study introduces a new retrospective reconstruction scheme for real-time cine imaging which aims to shorten the required acquisition. A real-time acquisition of 16-20s per acquired slice was inputted into a retrospective cine reconstruction algorithm, which employed non-rigid registration to remove respiratory motion and SPIRiT non-linear reconstruction with temporal regularization to fill in missing data. The algorithm was used to reconstruct cine loops with high spatial (1.3-1.8 × 1.8-2.1 mm²) and temporal resolution (retrospectively gated, 30 cardiac phases, temporal resolution 34.3 ± 9.1 ms). Validation was performed in 15 healthy volunteers using two different acquisition resolutions (256 × 144/192 × 128 matrix sizes). For each subject, 9 to 12 short axis and 3 long axis slices were imaged with both segmented and real-time acquisitions. The retrospectively reconstructed real-time cine images were compared to a traditional segmented breath-held acquisition in terms of image quality scores. Image quality scoring was performed by two experts using a scale between 1 and 5 (poor to good). For every subject, LAX and three SAX slices were selected and reviewed in the random order. The reviewers were blinded to the reconstruction approach and acquisition protocols and

  15. 120W, NA_0.15 fiber coupled LD module with 125-μm clad/NA 0.22 fiber by spatial coupling method

    Science.gov (United States)

    Ishige, Yuta; Kaji, Eisaku; Katayama, Etsuji; Ohki, Yutaka; Gajdátsy, Gábor; Cserteg, András.

    2018-02-01

    We have fabricated a fiber coupled semiconductor laser diode module by means of spatial beam combining of single emitter broad area semiconductor laser diode chips in the 9xx nm band. In the spatial beam multiplexing method, the numerical aperture of the output light from the optical fiber increases by increasing the number of laser diodes coupled into the fiber. To reduce it, we have tried the approach to improving assembly process technology. As a result, we could fabricate laser diode modules having a light output power of 120W or more and 95% power within NA of 0.15 or less from a single optical fiber with 125-μm cladding diameter. Furthermore, we have obtained that the laser diode module maintaining high coupling efficiency can be realized even around the fill factor of 0.95. This has been achieved by improving the optical alignment method regarding the fast axis stack pitch of the laser diodes in the laser diode module. Therefore, without using techniques such as polarization combining and wavelength combining, high output power was realized while keeping small numerical aperture. This contributes to a reduction in unit price per light output power of the pumping laser diode module.

  16. Analysis of the unmodulated diffraction beam of the phase-only liquid crystal spatial light modulator and a method for reducing its influence

    International Nuclear Information System (INIS)

    Qi, Yue; Li, Dayu; Hu, Lifa; Xuan, Li; Xia, Mingliang

    2012-01-01

    As a wavefront corrector, the phase-only liquid crystal spatial light modulator has been widely using in adaptive optics systems. However, the unmodulated diffracted beam of the modulator will affect the light spot centroid detection accuracy of a Shack–Hartmann wavefront sensor and decrease the image quality after correction. In this paper, we have diminished the effect by introducing a modified weight algorithm in our closed-loop adaptive optics system. The Strehl ratio of the image is higher than 0.8 after correction, even when the wavefront aberration is larger than 3 μm. The correction precision and image quality are both improved significantly. (paper)

  17. Weight dependent modulation of motor resonance induced by weight estimation during observation of partially occluded lifting actions

    NARCIS (Netherlands)

    Valchev, Nikola; Zijdewind, Inge; Keysers, Christian; Gazzola, Valeria; Avenanti, Alessio; Maurits, Natasha M.

    Seeing others performing an action induces the observers' motor cortex to "resonate" with the observed action. Transcranial magnetic stimulation (TMS) studies suggest that such motor resonance reflects the encoding of various motor features of the observed action, including the apparent motor

  18. Weight dependent modulation of motor resonance induced by weight estimation during observation of partially occluded lifting actions

    NARCIS (Netherlands)

    Valchev, N.; Zijdewind, I.; Keysers, C.; Gazzola, V.; Avenanti, A.; Maurits, N.M.

    2015-01-01

    Seeing others performing an action induces the observers' motor cortex to "resonate" with the observed action. Transcranial magnetic stimulation (TMS) studies suggest that such motor resonance reflects the encoding of various motor features of the observed action, including the apparent motor

  19. The development of a colour liquid crystal display spatial light modulator and applications in polychromatic optical data processing

    Science.gov (United States)

    Aiken, John Charles

    The development of a colour Spatial Light Modulator (SLM) and its application to optical information processing is described. Whilst monochrome technology has been established for many years, this is not the case for colour where commercial systems are unavailable. A main aspect of this study is therefore, how the use of colour can add an additional dimension to optical information processing. A well established route to monochrome system development has been the use of (black and white) liquid crystal televisions (LCTV) as SLM, providing useful performance at a low-cost. This study is based on the unique use of a colour display removed from a LCTV and operated as a colour SLM. A significant development has been the replacement of the original TV electronics operating the display with enhanced drive electronics specially developed for this application. Through a computer interface colour images from a drawing package or video camera can now be readily displayed on the LCD as input to an optical system. A detailed evaluation of the colour LCD optical properties, indicates that the new drive electronics have considerably improved the operation of the display for use as a colour SLM. Applications are described employing the use of colour in Fourier plane filtering, image correlation and speckle metrology. The SLM (and optical system) developed demonstrates, how the addition of colour has greatly enhanced its capabilities to implement principles of optical data processing, conventionally performed monochromatically. The hybrid combination employed, combining colour optical data processing with electronic techniques has resulted in a capable development system. Further development of the system using current colour LCDs and the move towards a portable system, is considered in the study conclusion.

  20. Near-field observation of spatial phase shifts associated with Goos-Hänschen and surface plasmon resonance effects

    NARCIS (Netherlands)

    Jose, J.; Segerink, Franciscus B.; Korterik, Jeroen P.; Offerhaus, Herman L.

    2008-01-01

    We report the near-field observation of the phase shifts associated with total internal reflection on a glass-air interface and surface plasmon resonance on a glass-gold-air system. The phase of the evanescent waves on glass and gold surfaces, as a function of incident angle, is measured using a

  1. Spatial profiling of degradation processes in hindered-amine-stabilized polymers by electron spin resonance imaging of nitroxides

    Czech Academy of Sciences Publication Activity Database

    Marek, Antonín; Kaprálková, Ludmila; Pfleger, Jiří; Pospíšil, Jan; Pilař, Jan

    2005-01-01

    Roč. 99, S (2005), s. 195-198 ISSN 0009-2770. [Meeting on Chemistry and Life /3./. Brno, 20.9.2005-22.9.2005] Institutional research plan: CEZ:AV0Z40500505 Keywords : polymer degradation * nitroxides * electron spin resonance imaging Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 0.445, year: 2005

  2. Spatial structure of standing wave electromagnetic fields at the lower harmonics of the ionospheric Alfvén resonator

    Czech Academy of Sciences Publication Activity Database

    Prikner, Karel; Feygin, F. Z.; Raita, T.

    2014-01-01

    Roč. 58, č. 2 (2014), s. 326-337 ISSN 0039-3169 Grant - others:European Commission(XE) HPRI 200100132 Institutional research plan: CEZ:AV0Z30120515 Keywords : ionospheric Alfvén resonator * full-wave numerical simulation * EISCAT measurements * standing wave oscillations Subject RIV: DE - Earth Magnetism, Geodesy, Geography Impact factor: 0.806, year: 2014

  3. H-1 and N-15 resonance assignment of the second fibronectin type III module of the neural cell adhesion molecule

    DEFF Research Database (Denmark)

    Kiselyov, Vladislav V; Berezin, Vladimir; Bock, Elisabeth

    2008-01-01

    We report here the NMR assignment of the second fibronectin type III module of the neural cell adhesion molecule (NCAM). This module has previously been shown to interact with the fibroblast growth factor receptor (FGFR), and the FGFR-binding site was mapped by NMR to the FG-loop region of the mo......We report here the NMR assignment of the second fibronectin type III module of the neural cell adhesion molecule (NCAM). This module has previously been shown to interact with the fibroblast growth factor receptor (FGFR), and the FGFR-binding site was mapped by NMR to the FG-loop region...... of the module. The FG-loop region also contains a putative nucleotide-binding motif, which was shown by NMR to interact with ATP. Furthermore, ATP was demonstrated to inhibit binding of the second F3 module of NCAM to FGFR....

  4. Phenolic acid intake, delivered via moderate champagne wine consumption, improves spatial working memory via the modulation of hippocampal and cortical protein expression/activation.

    Science.gov (United States)

    Corona, Giulia; Vauzour, David; Hercelin, Justine; Williams, Claire M; Spencer, Jeremy P E

    2013-11-10

    While much data exist for the effects of flavonoid-rich foods on spatial memory in rodents, there are no such data for foods/beverages predominantly containing hydroxycinnamates and phenolic acids. To address this, we investigated the effects of moderate Champagne wine intake, which is rich in these components, on spatial memory and related mechanisms relative to the alcohol- and energy-matched controls. In contrast to the isocaloric and alcohol-matched controls, supplementation with Champagne wine (1.78 ml/kg BW, alcohol 12.5% vol.) for 6 weeks led to an improvement in spatial working memory in aged rodents. Targeted protein arrays indicated that these behavioral effects were paralleled by the differential expression of a number of hippocampal and cortical proteins (relative to the isocaloric control group), including those involved in signal transduction, neuroplasticity, apoptosis, and cell cycle regulation. Western immunoblotting confirmed the differential modulation of brain-derived neurotrophic factor, cAMP response-element-binding protein (CREB), p38, dystrophin, 2',3'-cyclic-nucleotide 3'-phosphodiesterase, mammalian target of rapamycin (mTOR), and Bcl-xL in response to Champagne supplementation compared to the control drink, and the modulation of mTOR, Bcl-xL, and CREB in response to alcohol supplementation. Our data suggest that smaller phenolics such as gallic acid, protocatechuic acid, tyrosol, caftaric acid, and caffeic acid, in addition to flavonoids, are capable of exerting improvements in spatial memory via the modulation in hippocampal signaling and protein expression. Changes in spatial working memory induced by the Champagne supplementation are linked to the effects of absorbed phenolics on cytoskeletal proteins, neurotrophin expression, and the effects of alcohol on the regulation of apoptotic events in the hippocampus and cortex.

  5. Infrared to visible image up-conversion using optically addressed spatial light modulator utilizing liquid crystal and InGaAs photodiodes

    Energy Technology Data Exchange (ETDEWEB)

    Solodar, A., E-mail: asisolodar@gmail.com; Arun Kumar, T.; Sarusi, G.; Abdulhalim, I. [Department of Electro-Optics Engineering and The Ilse Katz Institute for Nanoscale Science and Technology, Ben Gurion University of the Negev, Beer Sheva 84105 (Israel)

    2016-01-11

    Combination of InGaAs/InP heterojunction photodetector with nematic liquid crystal (LC) as the electro-optic modulating material for optically addressed spatial light modulator for short wavelength infra-red (SWIR) to visible light image conversion was designed, fabricated, and tested. The photodetector layer is composed of 640 × 512 photodiodes array based on heterojunction InP/InGaAs having 15 μm pitch on InP substrate and with backside illumination architecture. The photodiodes exhibit extremely low, dark current at room temperature, with optimum photo-response in the SWIR region. The photocurrent generated in the heterojunction, due to the SWIR photons absorption, is drifted to the surface of the InP, thus modulating the electric field distribution which modifies the orientation of the LC molecules. This device can be attractive for SWIR to visible image upconversion, such as for uncooled night vision goggles under low ambient light conditions.

  6. Electron spin resonance and electron spin echo modulation spectroscopic studies on the structure and reactivity of Pd(I) species in SAPO-11 molecular sieves

    International Nuclear Information System (INIS)

    Chul Wee Lee; Jong-Sung Yu; Kevan, L.

    1992-01-01

    This paper explores the possibility of using Pd ions in SAPO-11 by adding [Pd(NH 3 ) 4 ] 2+ during the synthesis of SAPO-11 to form PdSAPO-11, which is compared with solid-state ion exchange PdSAPO-11 and impregnation PdH-SAPO-11 in which palladium is in an extraframework position. Electron spin resonance and electron spin echo modulation spectroscopies are used to determine if the palladium position in PdSAPO-11 is located in a framework or extraframework

  7. High-resolution resonant magnetic x-ray scattering on TbNi2B2C: Determination of the modulation wave vector in the orthorhombic phase

    International Nuclear Information System (INIS)

    Song, C.; Wermeille, D.; Goldman, A. I.; Canfield, P. C.; Rhee, J. Y.; Harmon, B. N.

    2001-01-01

    Resonant magnetic x-ray scattering measurements have been performed on a single crystal of TbNi 2 B 2 C to uniquely determine the modulation wave vector in the low-temperature orthorhombic phase. Below the transition temperature of 14.4(±0.1)K, two magnetic satellite peaks develop, centered on (h00) orth charge reflections. Our study shows that the longitudinal modulation of the magnetic moment is along the longer basal plane axes of the orthorhombic phase. Power law fits to the temperature dependence of the structural distortion, a/b-1, and the magnetic scattering intensity result in the same exponent, β, and transition temperature evidencing explicitly that the structural phase transition is magneto-elastic in origin

  8. Manipulating femtosecond laser interactions in bulk glass and thin-film with spatial light modulation (Conference Presentation)

    Science.gov (United States)

    Alimohammadian, Ehsan; Ho, Stephen; Ertorer, Erden; Gherghe, Sebastian; Li, Jianzhao; Herman, Peter R.

    2017-03-01

    Spatial Light Modulators (SLM) are emerging as a power tool for laser beam shaping whereby digitally addressed phase shifts can impose computer-generated hologram patterns on incoming laser light. SLM provide several additional advantages with ultrashort-pulsed lasers in controlling the shape of both surface and internal interactions with materials. Inside transparent materials, nonlinear optical effects can confine strong absorption only to the focal volume, extend dissipation over long filament tracks, or reach below diffraction-limited spot sizes. Hence, SLM beam shaping has been widely adopted for laser material processing applications that include parallel structuring, filamentation, fiber Bragg grating formation and optical aberration correction. This paper reports on a range of SLM applications we have studied in femtosecond processing of transparent glasses and thin films. Laser phase-fronts were tailored by the SLM to compensate for spherical surface aberration, and to further address the nonlinear interactions that interplay between Kerr-lens self-focusing and plasma defocusing effects over shallow and deep focusing inside the glass. Limits of strong and weak focusing were examined around the respective formation of low-loss optical waveguides and long uniform filament tracks. Further, we have employed the SLM for beam patterning inside thin film, exploring the limits of phase noise, resolution and fringe contrast during interferometric intra-film structuring. Femtosecond laser pulses of 200 fs pulse duration and 515 nm wavelength were shaped by a phase-only LCOS-SLM (Hamamatsu X10468-04). By imposing radial phase profiles, axicon, grating and beam splitting gratings, volume shape control of filament diameter, length, and uniformity as well as simultaneous formation of multiple filaments has been demonstrated. Similarly, competing effects of spherical surface aberration, self-focusing, and plasma de-focusing were studied and delineated to enable formation

  9. Validation of Lectora based interactive module to improve the ability of junior high school students spatial in learning Geometry

    Directory of Open Access Journals (Sweden)

    Tika Septia

    2017-12-01

    Full Text Available Rapid technological developments provide opportunities for educators to develop learning media through interactive modules integrated into lectora software. The development of an interactive module based on lectora can motivate students to learn independently, to be creative, and to enjoy what they are doing. Research into the development of an interactive module based on lectora geometry flat side material aimed to develop an interactive module based on lectora geometry flat side material, with the research design consisting of analysis, design, development, implementation, and evaluation of the module. The result obtained from the use of an interactive module based on lectora geometry flat side material that had been designed and validated and later revised showed an average value of the feasibility of content to be 3.75, the average value of the aspects of presentation was 2.94, the average value aspects of language was 3.06, and the average value of the aspects of graph was 2.86. This research enabled us to conclude that an interactive module based on lectora geometry flat side material could be categorized as valid.

  10. Periodic modulation-based stochastic resonance algorithm applied to quantitative analysis for weak liquid chromatography-mass spectrometry signal of granisetron in plasma

    Science.gov (United States)

    Xiang, Suyun; Wang, Wei; Xiang, Bingren; Deng, Haishan; Xie, Shaofei

    2007-05-01

    The periodic modulation-based stochastic resonance algorithm (PSRA) was used to amplify and detect the weak liquid chromatography-mass spectrometry (LC-MS) signal of granisetron in plasma. In the algorithm, the stochastic resonance (SR) was achieved by introducing an external periodic force to the nonlinear system. The optimization of parameters was carried out in two steps to give attention to both the signal-to-noise ratio (S/N) and the peak shape of output signal. By applying PSRA with the optimized parameters, the signal-to-noise ratio of LC-MS peak was enhanced significantly and distorted peak shape that often appeared in the traditional stochastic resonance algorithm was corrected by the added periodic force. Using the signals enhanced by PSRA, this method extended the limit of detection (LOD) and limit of quantification (LOQ) of granisetron in plasma from 0.05 and 0.2 ng/mL, respectively, to 0.01 and 0.02 ng/mL, and exhibited good linearity, accuracy and precision, which ensure accurate determination of the target analyte.

  11. Transient nutation electron spin resonance spectroscopy on spin-correlated radical pairs: A theoretical analysis on hyperfine-induced nuclear modulations

    Science.gov (United States)

    Weber, Stefan; Kothe, Gerd; Norris, James R.

    1997-04-01

    The influence of anisotropic hyperfine interaction on transient nutation electron paramagnetic resonance (EPR) of light-induced spin-correlated radical pairs is studied theoretically using the density operator formalism. Analytical expressions for the time evolution of the transient EPR signal during selective microwave excitation of single transitions are derived for a model system comprised of a weakly coupled radical pair and one hyperfine-coupled nucleus with I=1/2. Zero-quantum electron coherence and single-quantum nuclear coherence are created as a result of the sudden light-induced generation of the radical pair state from a singlet-state precursor. Depending on the relative sizes of the nuclear Zeeman frequency and the secular and pseudo-secular parts of the hyperfine coupling, transitions between levels with different nuclear spin orientations are predicted to modulate the time-dependent EPR signal. These modulations are in addition to the well-known transient nutations and electron zero-quantum precessions. Our calculations provide insight into the mechanism of recent experimental observations of coherent nuclear modulations in the time-resolved EPR signals of doublets and radical pairs. Two distinct mechanisms of the modulations are presented for various microwave magnetic field strengths. The first modulation scheme arises from electron and nuclear coherences initiated by the laser excitation pulse and is "read out" by the weak microwave magnetic field. While the relative modulation depth of these oscillations with respect to the signal intensity is independent of the Rabi frequency, ω1, the frequencies of this coherence phenomenon are modulated by the effective microwave amplitude and determined by the nuclear Zeeman interaction and hyperfine coupling constants as well as the electron-electron spin exchange and dipolar interactions between the two radical pair halves. In a second mechanism the modulations are both created and detected by the microwave

  12. A Novel high-speed polymeric EO modulator based on a combination of a microring resonator and an MZI

    NARCIS (Netherlands)

    Leinse, Arne; Diemeer, Mart; Rousseau, A.; Driessen, A.

    2005-01-01

    A Mach-Zehnder interferometer with an electrooptic polymer microring resonator adjacent to one of its branches is realized in a polymer layer stack. The microresonator is defined by reactive ion etching in the nonlinear PMMA-DR1 polymer and waveguide definition is done without etching, by using a

  13. High spatial resolution magnetic resonance imaging of experimental cerebral venous thrombosis with a blood pool contrast agent

    International Nuclear Information System (INIS)

    Spuentrup, E.; Wiethoff, A.J.; Parsons, E.C.; Spangenberg, P.; Stracke, C.P.

    2010-01-01

    Purpose: The purpose of this study was to investigate the feasibility of clot visualization in small sinus and cortical veins with contrast enhanced MRA in a cerebral venous thrombosis animal model using a blood pool contrast agent, Gadofosveset, and high spatial resolution imaging. Material and methods: For induction of cerebral venous thrombosis a recently developed combined interventional and microsurgical model was used. Cerebral sinus and cortical vein thrombosis was induced in six pigs. Two further pigs died during the procedure. Standard structural, time-of-flight- and phase contrast-angiograms were followed by fast time resolved high resolution 3D MRA (4D MRA) and subsequent high spatial resolution 3D MRA in the equilibrium phase with and without addition of parallel imaging. Visualization of the clots using the different sequences was subjectively compared and contrast-to-noise ratio (CNR) was assessed. Results: In the remaining six animals the procedure and MR-imaging protocol including administration of Gadofosveset was successfully completed. The 3D high resolution MRA in the equilibrium phase without the addition of parallel imaging was superior to all the other applied MR measurement techniques in terms of visualization of the clots. Only applying this sequence bridging vein thromboses were also seen as a small filling defect with a high CNR of >18. Conclusion: Only the non-accelerated high spatial resolution 3D MRA in the equilibrium in conjunction with the blood pool agent Gadofosveset allows for high-contrast visualization of very small clots in the cerebral sinus and cortical veins. Statement clinical impact: Detection of cortical vein thrombosis is of high clinical impact. Conventional MRI sequences often fail to visualize the clot. We could demonstrate that, in contrast to conventional sequences, with high spatial resolution 3D MRA in the equilibrium in conjunction with the blood pool agent Gadofosveset very small clots in the cerebral sinus and

  14. Gene Network Construction from Microarray Data Identifies a Key Network Module and Several Candidate Hub Genes in Age-Associated Spatial Learning Impairment.

    Science.gov (United States)

    Uddin, Raihan; Singh, Shiva M

    2017-01-01

    As humans age many suffer from a decrease in normal brain functions including spatial learning impairments. This study aimed to better understand the molecular mechanisms in age-associated spatial learning impairment (ASLI). We used a mathematical modeling approach implemented in Weighted Gene Co-expression Network Analysis (WGCNA) to create and compare gene network models of young (learning unimpaired) and aged (predominantly learning impaired) brains from a set of exploratory datasets in rats in the context of ASLI. The major goal was to overcome some of the limitations previously observed in the traditional meta- and pathway analysis using these data, and identify novel ASLI related genes and their networks based on co-expression relationship of genes. This analysis identified a set of network modules in the young, each of which is highly enriched with genes functioning in broad but distinct GO functional categories or biological pathways. Interestingly, the analysis pointed to a single module that was highly enriched with genes functioning in "learning and memory" related functions and pathways. Subsequent differential network analysis of this "learning and memory" module in the aged (predominantly learning impaired) rats compared to the young learning unimpaired rats allowed us to identify a set of novel ASLI candidate hub genes. Some of these genes show significant repeatability in networks generated from independent young and aged validation datasets. These hub genes are highly co-expressed with other genes in the network, which not only show differential expression but also differential co-expression and differential connectivity across age and learning impairment. The known function of these hub genes indicate that they play key roles in critical pathways, including kinase and phosphatase signaling, in functions related to various ion channels, and in maintaining neuronal integrity relating to synaptic plasticity and memory formation. Taken together, they

  15. One- and two-dimensional gap solitons and dynamics in the PT-symmetric lattice potential and spatially-periodic momentum modulation

    Science.gov (United States)

    Chen, Yong; Yan, Zhenya; Li, Xin

    2018-02-01

    The influence of spatially-periodic momentum modulation on beam dynamics in parity-time (PT) symmetric optical lattice is systematically investigated in the one- and two-dimensional nonlinear Schrödinger equations. In the linear regime, we demonstrate that the momentum modulation can alter the first and second PT thresholds of the classical lattice, periodically or regularly change the shapes of the band structure, rotate and split the diffraction patterns of beams leading to multiple refraction and emissions. In the Kerr-nonlinear regime for one-dimension (1D) case, a large family of fundamental solitons within the semi-infinite gap can be found to be stable, even beyond the second PT threshold; it is shown that the momentum modulation can shrink the existing range of fundamental solitons and not change their stability. For two-dimension (2D) case, most solitons with higher intensities are relatively unstable in their existing regions which are narrower than those in 1D case, but we also find stable fundamental solitons corroborated by linear stability analysis and direct beam propagation. More importantly, the momentum modulation can also utterly change the direction of the transverse power flow and control the energy exchange among gain or loss regions.

  16. Memory modulation across neural systems: intra-amygdala glucose reverses deficits caused by intraseptal morphine on a spatial task but not on an aversive task.

    Science.gov (United States)

    McNay, E C; Gold, P E

    1998-05-15

    Based largely on dissociations of the effects of different lesions on learning and memory, memories for different attributes appear to be organized in independent neural systems. Results obtained with direct injections of drugs into one brain region at a time support a similar conclusion. The present experiments investigated the effects of simultaneous pharmacological manipulation of two neural systems, the amygdala and the septohippocampal system, to examine possible interactions of memory modulation across systems. Morphine injected into the medial septum impaired memory both for avoidance training and during spontaneous alternation. When glucose was concomitantly administered to the amygdala, glucose reversed the morphine-induced deficits in memory during alternation but not for avoidance training. These results suggest that the amygdala is involved in modulation of spatial memory processes and that direct injections of memory-modulating drugs into the amygdala do not always modulate memory for aversive events. These findings are contrary to predictions from the findings of lesion studies and of studies using direct injections of drugs into single brain areas. Thus, the independence of neural systems responsible for processing different classes of memory is less clear than implied by studies using lesions or injections of drugs into single brain areas.

  17. Deconstruction of spatial integrity in visual stimulus detected by modulation of synchronized activity in cat visual cortex.

    Science.gov (United States)

    Zhou, Zhiyi; Bernard, Melanie R; Bonds, A B

    2008-04-02

    Spatiotemporal relationships among contour segments can influence synchronization of neural responses in the primary visual cortex. We performed a systematic study to dissociate the impact of spatial and temporal factors in the signaling of contour integration via synchrony. In addition, we characterized the temporal evolution of this process to clarify potential underlying mechanisms. With a 10 x 10 microelectrode array, we recorded the simultaneous activity of multiple cells in the cat primary visual cortex while stimulating with drifting sine-wave gratings. We preserved temporal integrity and systematically degraded spatial integrity of the sine-wave gratings by adding spatial noise. Neural synchronization was analyzed in the time and frequency domains by conducting cross-correlation and coherence analyses. The general association between neural spike trains depends strongly on spatial integrity, with coherence in the gamma band (35-70 Hz) showing greater sensitivity to the change of spatial structure than other frequency bands. Analysis of the temporal dynamics of synchronization in both time and frequency domains suggests that spike timing synchronization is triggered nearly instantaneously by coherent structure in the stimuli, whereas frequency-specific oscillatory components develop more slowly, presumably through network interactions. Our results suggest that, whereas temporal integrity is required for the generation of synchrony, spatial integrity is critical in triggering subsequent gamma band synchronization.

  18. Clinical application of bilateral high temporal and spatial resolution dynamic contrast-enhanced magnetic resonance imaging of the breast at 7 T

    Energy Technology Data Exchange (ETDEWEB)

    Pinker, K.; Baltzer, P.; Bernathova, M.; Weber, M.; Leithner, D.; Helbich, T.H. [Medical University Vienna, Department of Biomedical Imaging and Image-guided Therapy, Division of Molecular and Gender Imaging, Waehringer Guertel 18-20, 1090, Vienna (Austria); Bogner, W.; Trattnig, S.; Gruber, S.; Zaric, O. [Medical University Vienna, Department of Biomedical Imaging and Image-guided Therapy, MR Centre of Excellence, Vienna (Austria); Abeyakoon, O. [King' s College, Department of Radiology, London (United Kingdom); Dubsky, P. [Medical University Vienna, Department of Surgery, Vienna (Austria); Bago-Horvath, Z. [Medical University Vienna, Department of Pathology, Vienna (Austria)

    2014-04-15

    The objective of our study was to evaluate the clinical application of bilateral high spatial and temporal resolution dynamic contrast-enhanced magnetic resonance imaging (HR DCE-MRI) of the breast at 7 T. Following institutional review board approval 23 patients with a breast lesion (BIRADS 0, 4-5) were included in our prospective study. All patients underwent bilateral HR DCE-MRI of the breast at 7 T (spatial resolution of 0.7 mm{sup 3} voxel size, temporal resolution of 14 s). Two experienced readers (r1, r2) and one less experienced reader (r3) independently assessed lesions according to BI-RADS registered. Image quality, lesion conspicuity and artefacts were graded from 1 to 5. Sensitivity, specificity and diagnostic accuracy were assessed using histopathology as the standard of reference. HR DCE-MRI at 7 T revealed 29 lesions in 23 patients (sensitivity 100 % (19/19); specificity of 90 % (9/10)) resulting in a diagnostic accuracy of 96.6 % (28/29) with an AUC of 0.95. Overall image quality was excellent in the majority of cases (27/29) and examinations were not hampered by artefacts. There was excellent inter-reader agreement for diagnosis and image quality parameters (κ = 0.89-1). Bilateral HR DCE-MRI of the breast at 7 T is feasible with excellent image quality in clinical practice and allows accurate breast cancer diagnosis. (orig.)

  19. Trinary arithmetic and logic unit (TALU) using savart plate and spatial light modulator (SLM) suitable for optical computation in multivalued logic

    Science.gov (United States)

    Ghosh, Amal K.; Bhattacharya, Animesh; Raul, Moumita; Basuray, Amitabha

    2012-07-01

    Arithmetic logic unit (ALU) is the most important unit in any computing system. Optical computing is becoming popular day-by-day because of its ultrahigh processing speed and huge data handling capability. Obviously for the fast processing we need the optical TALU compatible with the multivalued logic. In this regard we are communicating the trinary arithmetic and logic unit (TALU) in modified trinary number (MTN) system, which is suitable for the optical computation and other applications in multivalued logic system. Here the savart plate and spatial light modulator (SLM) based optoelectronic circuits have been used to exploit the optical tree architecture (OTA) in optical interconnection network.

  20. Cellulose-Pectin Spatial Contacts Are Inherent to Never-Dried Arabidopsis Primary Cell Walls: Evidence from Solid-State Nuclear Magnetic Resonance1[OPEN

    Science.gov (United States)

    Wang, Tuo; Park, Yong Bum; Hong, Mei

    2015-01-01

    The structural role of pectins in plant primary cell walls is not yet well understood because of the complex and disordered nature of the cell wall polymers. We recently introduced multidimensional solid-state nuclear magnetic resonance spectroscopy to characterize the spatial proximities of wall polysaccharides. The data showed extensive cross peaks between pectins and cellulose in the primary wall of Arabidopsis (Arabidopsis thaliana), indicating subnanometer contacts between the two polysaccharides. This result was unexpected because stable pectin-cellulose interactions are not predicted by in vitro binding assays and prevailing cell wall models. To investigate whether the spatial contacts that give rise to the cross peaks are artifacts of sample preparation, we now compare never-dried Arabidopsis primary walls with dehydrated and rehydrated samples. One-dimensional 13C spectra, two-dimensional 13C-13C correlation spectra, water-polysaccharide correlation spectra, and dynamics data all indicate that the structure, mobility, and intermolecular contacts of the polysaccharides are indistinguishable between never-dried and rehydrated walls. Moreover, a partially depectinated cell wall in which 40% of homogalacturonan is extracted retains cellulose-pectin cross peaks, indicating that the cellulose-pectin contacts are not due to molecular crowding. The cross peaks are observed both at −20°C and at ambient temperature, thus ruling out freezing as a cause of spatial contacts. These results indicate that rhamnogalacturonan I and a portion of homogalacturonan have significant interactions with cellulose microfibrils in the native primary wall. This pectin-cellulose association may be formed during wall biosynthesis and may involve pectin entrapment in or between cellulose microfibrils, which cannot be mimicked by in vitro binding assays. PMID:26036615

  1. Temporal and spatial characteristics of the area at risk investigated using computed tomography and T1-weighted magnetic resonance imaging

    DEFF Research Database (Denmark)

    van der Pals, Jesper; Hammer-Hansen, Sophia; Nielles-Vallespin, Sonia

    2015-01-01

    AIMS: Cardiovascular magnetic resonance (CMR) imaging can measure the myocardial area at risk (AAR), but the technique has received criticism for inadequate validation. CMR commonly depicts an AAR that is wider than the infarct, which in turn would require a lateral perfusion gradient within...... and fluorescent microparticle pathology were used to investigate the AAR in a canine model (n = 10) of ischaemia and reperfusion. AAR size by CMR correlated well with CT (R(2) = 0.80), microsphere blood flow (R(2) = 0.80), and pathology (R(2) = 0.74) with good limits of agreement [-0.79 ± 4.02% of the left.......05 ± 0.02 mL/g/min, lateral vs. core, P = 0.001). The transmural extent of MI was lower in the lateral portion of the AAR than the core (28.2 ± 10.2 vs. 17.4 ± 8.4% of the wall, P = 0.001). CONCLUSION: T1-weighted CMR accurately quantifies size of the AAR with excellent agreement compared with three...

  2. Device for imaging an object by means of masks of spatially modulable electromagnetic radiation or corpuscular radiation of high energy

    International Nuclear Information System (INIS)

    Barrett, H.H.

    1979-01-01

    The radiogram of the thyroid is produced by means of a detector device operating similar to a scintillation camera. Between thyroid and detector device there is placed a mask having modulating areas, permeable and impermeable to radiation succeeding each other with decreasing extension. The scanning signal has got the shape of a radar signal with chirp modulation. The filtering unit used for it is a pulse compression filter. The image of the radiation energy distribution on the recording surface of the detector device is thus decoded and compressed to a number of image points giving the picture of the thyroid. (RW) [de

  3. Diffusion-weighted magnetic resonance imaging of the normal endometrium: temporal and spatial variations of the apparent diffusion coefficient

    International Nuclear Information System (INIS)

    Fornasa, Francesca; Montemezzi, Stefania

    2012-01-01

    Background: Diffusion-weighted magnetic resonance imaging (DWI) is increasingly used in the diagnosis of endometrial disease. No complete knowledge, however, exists yet of the influence of physiology on the endometrial apparent diffusion coefficient (ADC) values on which DWI is based. Purpose: To establish whether the ADC values measured with DWI in the endometrium of healthy reproductive-aged women significantly vary from the early proliferative to the periovulatory phase of the menstrual cycle and between the fundus and the isthmus of the uterus. Material and Methods: In 17 women the endometrial ADC values measured on the fifth menstrual day, both at the fundus and at the isthmus of the uterus, were compared to the values obtained on the 14th day before the subsequent cycle. In 81 women (menstrual day: fifth through 21st) the endometrial ADC values measured at the fundus were compared to the values obtained at the isthmus of the uterus. All examinations were performed with a 1.5 T magnet (b values: 0 and 800 mm/s 2 ). The results were analyzed by means of Student's t-test per paired data. Results: The endometrial ADC values measured on the fifth day of the menstrual cycle were lower than those obtained in the periovulatory phase both at the fundus (mean 0.923 vs. 1.256 x 10 - 3 mm 2 /s) and at the isthmus (mean 1.297 vs. 1.529 x 10 - 3 mm 2 /s) of the uterus. The endometrial ADC values measured at the fundus of the uterus were lower than those obtained at the isthmus (mean 1.132 vs. 1.420 x 10 - 3 mm 2 /s) through the menstrual cycle. All these differences were highly significant (P < 0.001) at statistical analysis. Conclusion: Physiological variations occurring in endometrial ADC values of healthy women should be considered by the radiologists when interpreting DWI examinations in patients with endometrial disease

  4. Analysis of spatial and temporal dynamics of xylem refilling in Acer rubrum L. using magnetic resonance imaging (MRI.

    Directory of Open Access Journals (Sweden)

    Maciej Andrzej Zwieniecki

    2013-07-01

    Full Text Available We report results of an analysis of embolism formation and subsequent refilling observed in stems of Acer rubrum L. using magnetic resonance imaging (MRI. MRI is one of the very few techniques that can provide direct non-destructive observations of the water content within opaque biological materials at a micrometer resolution. Thus, it has been used to determine temporal dynamics and water distributions within xylem tissue. In this study, we found good agreement between MRI measures of pixel brightness to assess xylem liquid water content and the percent loss in hydraulic conductivity (PLC in response to water stress (P50 values of 2.51 and 2.70 for MRI and PLC, respectively. These data provide strong support that pixel brightness is well correlated to PLC and can be used as a proxy of PLC even when single vessels cannot be resolved on the image. Pressure induced embolism in moderately stressed plants resulted in initial drop of pixel brightness. This drop was followed by brightness gain over 100 minutes following pressure application suggesting that plants can restore water content in stem after induced embolism. This recovery was limited only to current year wood ring; older wood did not show signs of recovery within the length of experiment (16 hours. In vivo MRI observations of the xylem of moderately stressed (~-0.5 MPa A. rubrum stems revealed evidence of a spontaneous embolism formation followed by rapid refilling (~30 minutes. Spontaneous (not induced embolism formation was observed only once, despite over 60 hours of continuous MRI observations made on several plants. Thus this observation provide evidence for presence of naturally occurring embolism-refilling cycle in A. rubrum, but it is impossible to infer any conclusions in relation to its frequency in nature.

  5. Analysis of spatial and temporal dynamics of xylem refilling in Acer rubrum L. using magnetic resonance imaging.

    Science.gov (United States)

    Zwieniecki, Maciej A; Melcher, Peter J; Ahrens, Eric T

    2013-01-01

    We report results of an analysis of embolism formation and subsequent refilling observed in stems of Acer rubrum L. using magnetic resonance imaging (MRI). MRI is one of the very few techniques that can provide direct non-destructive observations of the water content within opaque biological materials at a micrometer resolution. Thus, it has been used to determine temporal dynamics and water distributions within xylem tissue. In this study, we found good agreement between MRI measures of pixel brightness to assess xylem liquid water content and the percent loss in hydraulic conductivity (PLC) in response to water stress (P50 values of 2.51 and 2.70 for MRI and PLC, respectively). These data provide strong support that pixel brightness is well correlated to PLC and can be used as a proxy of PLC even when single vessels cannot be resolved on the image. Pressure induced embolism in moderately stressed plants resulted in initial drop of pixel brightness. This drop was followed by brightness gain over 100 min following pressure application suggesting that plants can restore water content in stem after induced embolism. This recovery was limited only to current-year wood ring; older wood did not show signs of recovery within the length of experiment (16 h). In vivo MRI observations of the xylem of moderately stressed (~-0.5 MPa) A. rubrum stems revealed evidence of a spontaneous embolism formation followed by rapid refilling (~30 min). Spontaneous (not induced) embolism formation was observed only once, despite over 60 h of continuous MRI observations made on several plants. Thus this observation provide evidence for the presence of naturally occurring embolism-refilling cycle in A. rubrum, but it is impossible to infer any conclusions in relation to its frequency in nature.

  6. Modulation of Posterior Alpha Activity by Spatial Attention Allows for Controlling A Continuous Brain-Computer Interface

    NARCIS (Netherlands)

    Horschig, J.M.; Oosterheert, W.; Oostenveld, R.; Jensen, O.

    2015-01-01

    Here we report that the modulation of alpha activity by covert attention can be used as a control signal in an online brain-computer interface, that it is reliable, and that it is robust. Subjects were instructed to orient covert visual attention to the left or right hemifield. We decoded the

  7. Do not resonate with actions: sentence polarity modulates cortico-spinal excitability during action-related sentence reading.

    Directory of Open Access Journals (Sweden)

    Marco Tullio Liuzza

    Full Text Available BACKGROUND: Theories of embodied language suggest that the motor system is differentially called into action when processing motor-related versus abstract content words or sentences. It has been recently shown that processing negative polarity action-related sentences modulates neural activity of premotor and motor cortices. METHODS AND FINDINGS: We sought to determine whether reading negative polarity sentences brought about differential modulation of cortico-spinal motor excitability depending on processing hand-action related or abstract sentences. Facilitatory paired-pulses Transcranial Magnetic Stimulation (pp-TMS was applied to the primary motor representation of the right-hand and the recorded amplitude of induced motor-evoked potentials (MEP was used to index M1 activity during passive reading of either hand-action related or abstract content sentences presented in both negative and affirmative polarity. Results showed that the cortico-spinal excitability was affected by sentence polarity only in the hand-action related condition. Indeed, in keeping with previous TMS studies, reading positive polarity, hand action-related sentences suppressed cortico-spinal reactivity. This effect was absent when reading hand action-related negative polarity sentences. Moreover, no modulation of cortico-spinal reactivity was associated with either negative or positive polarity abstract sentences. CONCLUSIONS: Our results indicate that grammatical cues prompting motor negation reduce the cortico-spinal suppression associated with affirmative action sentences reading and thus suggest that motor simulative processes underlying the embodiment may involve even syntactic features of language.

  8. An emotion-based facial expression word activates laughter module in the human brain: a functional magnetic resonance imaging study.

    Science.gov (United States)

    Osaka, Naoyuki; Osaka, Mariko; Kondo, Hirohito; Morishita, Masanao; Fukuyama, Hidenao; Shibasaki, Hiroshi

    2003-04-10

    We report an fMRI experiment demonstrating that visualization of onomatopoeia, an emotion-based facial expression word, highly suggestive of laughter, heard by the ear, significantly activates both the extrastriate visual cortex near the inferior occipital gyrus and the premotor (PM)/supplementary motor area (SMA) in the superior frontal gyrus while non-onomatopoeic words under the same task that did not imply laughter do not activate these areas in humans. We tested the specific hypothesis that an activation in extrastriate visual cortex and PM/SMA would be modulated by image formation of onomatopoeia implying laughter and found the hypothesis to be true. Copyright 2003 Elsevier Science Ireland Ltd.

  9. On-chip multiplexed solid-phase nucleic acid hybridization assay using spatial profiles of immobilized quantum dots and fluorescence resonance energy transfer.

    Science.gov (United States)

    Noor, M Omair; Tavares, Anthony J; Krull, Ulrich J

    2013-07-25

    A microfluidic based solid-phase assay for the multiplexed detection of nucleic acid hybridization using quantum dot (QD) mediated fluorescence resonance energy transfer (FRET) is described herein. The glass surface of hybrid glass-polydimethylsiloxane (PDMS) microfluidic channels was chemically modified to assemble the biorecognition interface. Multiplexing was demonstrated using a detection system that was comprised of two colors of immobilized semi-conductor QDs and two different oligonucleotide probe sequences. Green-emitting and red-emitting QDs were paired with Cy3 and Alexa Fluor 647 (A647) labeled oligonucleotides, respectively. The QDs served as energy donors for the transduction of dye labeled oligonucleotide targets. The in-channel assembly of the biorecognition interface and the subsequent introduction of oligonucleotide targets was accomplished within minutes using a combination of electroosmotic flow and electrophoretic force. The concurrent quantification of femtomole quantities of two target sequences was possible by measuring the spatial coverage of FRET sensitized emission along the length of the channel. In previous reports, multiplexed QD-FRET hybridization assays that employed a ratiometric method for quantification had challenges associated with lower analytical sensitivity arising from both donor and acceptor dilution that resulted in reduced energy transfer pathways as compared to single-color hybridization assays. Herein, a spatial method for quantification that is based on in-channel QD-FRET profiles provided higher analytical sensitivity in the multiplexed assay format as compared to single-color hybridization assays. The selectivity of the multiplexed hybridization assays was demonstrated by discrimination between a fully-complementary sequence and a 3 base pair sequence at a contrast ratio of 8 to 1. Copyright © 2013 Elsevier B.V. All rights reserved.

  10. High quality broadband spatial reflections of slow Rayleigh surface acoustic waves modulated by a graded grooved surface

    KAUST Repository

    Xu, Yanlong

    2015-01-21

    We report high quality broadband spatial reflections of Rayleigh surface acoustic waves (SAWs) through a graded grooved surface. High quality means that no wave is allowed to transmit and the incident wave is nearly all reflected to the input side. The graded grooved surface is structured by drilling one dimensional array of graded grooves with increased depths on a flat surface. We investigate SAW dispersion relations, wave field distribution at several typical SAW wavelengths, and time evolution of a Gaussian pulse through the graded grooved surface. Results show that the input broadband Rayleigh SAWs can be slowed, spatially enhanced and stopped, and finally reflected to the input side. The study suggests that engraving the flat surface can be used as an efficient and economical way to manipulate Rayleigh SAWs, which has potential application in novel SAW devices such as filters, reflectors, sensors, energy harvesters, and diodes.

  11. Localized and periodic exact solutions to the nonlinear Schroedinger equation with spatially modulated parameters: Linear and nonlinear lattices

    International Nuclear Information System (INIS)

    Belmonte-Beitia, Juan; Konotop, Vladimir V.; Perez-Garcia, Victor M.; Vekslerchik, Vadym E.

    2009-01-01

    Using similarity transformations we construct explicit solutions of the nonlinear Schroedinger equation with linear and nonlinear periodic potentials. We present explicit forms of spatially localized and periodic solutions, and study their properties. We put our results in the framework of the exploited perturbation techniques and discuss their implications on the properties of associated linear periodic potentials and on the possibilities of stabilization of gap solitons using polychromatic lattices.

  12. Determination of the complex refractive index segments of turbid sample with multispectral spatially modulated structured light and models approximation

    Science.gov (United States)

    Meitav, Omri; Shaul, Oren; Abookasis, David

    2017-09-01

    Spectral data enabling the derivation of a biological tissue sample's complex refractive index (CRI) can provide a range of valuable information in the clinical and research contexts. Specifically, changes in the CRI reflect alterations in tissue morphology and chemical composition, enabling its use as an optical marker during diagnosis and treatment. In the present work, we report a method for estimating the real and imaginary parts of the CRI of a biological sample using Kramers-Kronig (KK) relations in the spatial frequency domain. In this method, phase-shifted sinusoidal patterns at single high spatial frequency are serially projected onto the sample surface at different near-infrared wavelengths while a camera mounted normal to the sample surface acquires the reflected diffuse light. In the offline analysis pipeline, recorded images at each wavelength are converted to spatial phase maps using KK analysis and are then calibrated against phase-models derived from diffusion approximation. The amplitude of the reflected light, together with phase data, is then introduced into Fresnel equations to resolve both real and imaginary segments of the CRI at each wavelength. The technique was validated in tissue-mimicking phantoms with known optical parameters and in mouse models of ischemic injury and heat stress. Experimental data obtained indicate variations in the CRI among brain tissue suffering from injury. CRI fluctuations correlated with alterations in the scattering and absorption coefficients of the injured tissue are demonstrated. This technique for deriving dynamic changes in the CRI of tissue may be further developed as a clinical diagnostic tool and for biomedical research applications. To the best of our knowledge, this is the first report of the estimation of the spectral CRI of a mouse head following injury obtained in the spatial frequency domain.

  13. Rapid 3D µ-printing of polymer optical whispering-gallery mode resonators.

    Science.gov (United States)

    Wu, Jushuai; Guo, Xin; Zhang, A Ping; Tam, Hwa-Yaw

    2015-11-16

    A novel microfabrication method for rapid printing of polymer optical whispering-gallery mode (WGM) resonators is presented. A 3D micro-printing technology based on high-speed optical spatial modulator (SLM) and high-power UV light source is developed to fabricate suspended-disk WGM resonator array using SU-8 photoresist. The optical spectral responses of the fabricated polymer WGM resonators were measured with a biconically tapered optical fiber. Experimental results reveal that the demonstrated method is very flexible and time-saving for rapid fabrication of complex polymer WGM resonators.

  14. High Spatial Resolution Cardiovascular Magnetic Resonance at 7.0 Tesla in Patients with Hypertrophic Cardiomyopathy – First Experiences: Lesson Learned from 7.0 Tesla

    Science.gov (United States)

    Prothmann, Marcel; von Knobelsdorff-Brenkenhoff, Florian; Töpper, Agnieszka; Dieringer, Matthias A.; Shahid, Etham; Graessl, Andreas; Rieger, Jan; Lysiak, Darius; Thalhammer, C.; Huelnhagen, Till; Kellman, Peter; Niendorf, Thoralf; Schulz-Menger, Jeanette

    2016-01-01

    Background Cardiovascular Magnetic Resonance (CMR) provides valuable information in patients with hypertrophic cardiomyopathy (HCM) based on myocardial tissue differentiation and the detection of small morphological details. CMR at 7.0T improves spatial resolution versus today’s clinical protocols. This capability is as yet untapped in HCM patients. We aimed to examine the feasibility of CMR at 7.0T in HCM patients and to demonstrate its capability for the visualization of subtle morphological details. Methods We screened 131 patients with HCM. 13 patients (9 males, 56 ±31 years) and 13 healthy age- and gender-matched subjects (9 males, 55 ±31years) underwent CMR at 7.0T and 3.0T (Siemens, Erlangen, Germany). For the assessment of cardiac function and morphology, 2D CINE imaging was performed (voxel size at 7.0T: (1.4x1.4x2.5) mm3 and (1.4x1.4x4.0) mm3; at 3.0T: (1.8x1.8x6.0) mm3). Late gadolinium enhancement (LGE) was performed at 3.0T for detection of fibrosis. Results All scans were successful and evaluable. At 3.0T, quantification of the left ventricle (LV) showed similar results in short axis view vs. the biplane approach (LVEDV, LVESV, LVMASS, LVEF) (p = 0.286; p = 0.534; p = 0.155; p = 0.131). The LV-parameters obtained at 7.0T where in accordance with the 3.0T data (pLVEDV = 0.110; pLVESV = 0.091; pLVMASS = 0.131; pLVEF = 0.182). LGE was detectable in 12/13 (92%) of the HCM patients. High spatial resolution CINE imaging at 7.0T revealed hyperintense regions, identifying myocardial crypts in 7/13 (54%) of the HCM patients. All crypts were located in the LGE-positive regions. The crypts were not detectable at 3.0T using a clinical protocol. Conclusions CMR at 7.0T is feasible in patients with HCM. High spatial resolution gradient echo 2D CINE imaging at 7.0T allowed the detection of subtle morphological details in regions of extended hypertrophy and LGE. PMID:26863618

  15. Laser beam shaping limitations for laboratory simulation of turbulence using a phase-only spatial light modulator

    CSIR Research Space (South Africa)

    Litvin, IA

    2007-09-01

    Full Text Available ) where ],[ 10∈ρ and ],[ πθ 20∈ , in an infinite series of these polynomials will be complete. The circle polynomials of Zernike have the form of complex angular function modulated by a real radial polynomial: θρθρ immnmn eRnZ )()1....0 − ⎥⎥⎦ ⎤ ⎢⎢⎣ ⎡ = ∫ h h n dhhCkr , (8) where h is the height from some reference level, usually ground or sea level. The key parameter in the turbulence model is the refractive index structure constant, 2nC , which in general...

  16. Advances in magnetic resonance 10

    CERN Document Server

    Waugh, John S

    2013-01-01

    Advances in Magnetic Resonance, Volume 10, presents a variety of contributions to the theory and practice of magnetic resonance. The book contains three chapters that examine superoperators in magnetic resonance; ultrasonically modulated paramagnetic resonance; and the utility of electron paramagnetic resonance (EPR) and electron-nuclear double-resonance (ENDOR) techniques for studying low-frequency modes of atomic fluctuations and their significance for understanding the mechanism of structural phase transitions in solids.

  17. Modulation of Posterior Alpha Activity by Spatial Attention Allows for Controlling A Continuous Brain-Computer Interface.

    Science.gov (United States)

    Horschig, Jörn M; Oosterheert, Wouter; Oostenveld, Robert; Jensen, Ole

    2015-11-01

    Here we report that the modulation of alpha activity by covert attention can be used as a control signal in an online brain-computer interface, that it is reliable, and that it is robust. Subjects were instructed to orient covert visual attention to the left or right hemifield. We decoded the direction of attention from the magnetoencephalogram by a template matching classifier and provided the classification outcome to the subject in real-time using a novel graphical user interface. Training data for the templates were obtained from a Posner-cueing task conducted just before the BCI task. Eleven subjects participated in four sessions each. Eight of the subjects achieved classification rates significantly above chance level. Subjects were able to significantly increase their performance from the first to the second session. Individual patterns of posterior alpha power remained stable throughout the four sessions and did not change with increased performance. We conclude that posterior alpha power can successfully be used as a control signal in brain-computer interfaces. We also discuss several ideas for further improving the setup and propose future research based on solid hypotheses about behavioral consequences of modulating neuronal oscillations by brain computer interfacing.

  18. Collective excitations in semiconductor superlattices and plasma modes of a two-dimensional electron gas with spatially modulated charge density

    International Nuclear Information System (INIS)

    Eliasson, G.L.

    1987-01-01

    The theory of collective excitations in semiconductor superlattices is formulated by using linear response theory. Different kinds of collective excitations in type I (GaAs-GaAlAs) and type II (GaSb-InAs) superlattices are surveyed. Special attention is paid to the presence of surface and finite-size effects. In calculating the dielectric matrix, the effect of different approximations of the system is discussed. The theory for inelastic length scattering (Raman scattering), and for Electron Energy Loss (EEL) due to collective excitations, is formulated. Calculations for several model systems are presented and the main features of the spectra are discussed. In part II the theory of collective excitations of a two-dimensional electron gas with a spatially periodic equilibrium density is formulated. As a first example a periodic array of two-dimensional electron gas strips with constant equilibrium density is studied. The integral equation that describes the charge fluctuations on the strips is derived and solved numerically. The spatial dependence of the density fluctuation across a single strip can be in the form of either propagating or evanescent waves

  19. A fully-integrated 12.5-Gb/s 850-nm CMOS optical receiver based on a spatially-modulated avalanche photodetector.

    Science.gov (United States)

    Lee, Myung-Jae; Youn, Jin-Sung; Park, Kang-Yeob; Choi, Woo-Young

    2014-02-10

    We present a fully integrated 12.5-Gb/s optical receiver fabricated with standard 0.13-µm complementary metal-oxide-semiconductor (CMOS) technology for 850-nm optical interconnect applications. Our integrated optical receiver includes a newly proposed CMOS-compatible spatially-modulated avalanche photodetector, which provides larger photodetection bandwidth than previously reported CMOS-compatible photodetectors. The receiver also has high-speed CMOS circuits including transimpedance amplifier, DC-balanced buffer, equalizer, and limiting amplifier. With the fabricated optical receiver, detection of 12.5-Gb/s optical data is successfully achieved at 5.8 pJ/bit. Our receiver achieves the highest data rate ever reported for 850-nm integrated CMOS optical receivers.

  20. Slow light enhanced optical nonlinearity in a silicon photonic crystal coupled-resonator optical waveguide.

    Science.gov (United States)

    Matsuda, Nobuyuki; Kato, Takumi; Harada, Ken-Ichi; Takesue, Hiroki; Kuramochi, Eiichi; Taniyama, Hideaki; Notomi, Masaya

    2011-10-10

    We demonstrate highly enhanced optical nonlinearity in a coupled-resonator optical waveguide (CROW) in a four-wave mixing experiment. Using a CROW consisting of 200 coupled resonators based on width-modulated photonic crystal nanocavities in a line defect, we obtained an effective nonlinear constant exceeding 10,000 /W/m, thanks to slow light propagation combined with a strong spatial confinement of light achieved by the wavelength-sized cavities.

  1. Development and validation of a novel large field of view phantom and a software module for the quality assurance of geometric distortion in magnetic resonance imaging.

    Science.gov (United States)

    Torfeh, Tarraf; Hammoud, Rabih; McGarry, Maeve; Al-Hammadi, Noora; Perkins, Gregory

    2015-09-01

    To develop and validate a large field of view phantom and quality assurance software tool for the assessment and characterization of geometric distortion in MRI scanners commissioned for radiation therapy planning. A purpose built phantom was developed consisting of 357 rods (6mm in diameter) of polymethyl-methacrylat separated by 20mm intervals, providing a three dimensional array of control points at known spatial locations covering a large field of view up to a diameter of 420mm. An in-house software module was developed to allow automatic geometric distortion assessment. This software module was validated against a virtual dataset of the phantom that reproduced the exact geometry of the physical phantom, but with known translational and rotational displacements and warping. For validation experiments, clinical MRI sequences were acquired with and without the application of a commercial 3D distortion correction algorithm (Gradwarp™). The software module was used to characterize and assess system-related geometric distortion in the sequences relative to a benchmark CT dataset, and the efficacy of the vendor geometric distortion correction algorithms (GDC) was also assessed. Results issued from the validation of the software against virtual images demonstrate the algorithm's ability to accurately calculate geometric distortion with sub-pixel precision by the extraction of rods and quantization of displacements. Geometric distortion was assessed for the typical sequences used in radiotherapy applications and over a clinically relevant 420mm field of view (FOV). As expected and towards the edges of the field of view (FOV), distortion increased with increasing FOV. For all assessed sequences, the vendor GDC was able to reduce the mean distortion to below 1mm over a field of view of 5, 10, 15 and 20cm radius respectively. Results issued from the application of the developed phantoms and algorithms demonstrate a high level of precision. The results indicate that this

  2. Performance evaluation of a sub-millimeter spatial resolution PET detector module using a digital silicon photomultiplier coupled LGSO array

    Energy Technology Data Exchange (ETDEWEB)

    Leem, Hyun Tae [Molecular Imaging Research & Education (MiRe) Laboratory, Department of Electronic Engineering, Sogang University, Seoul (Korea, Republic of); Choi, Yong, E-mail: ychoi@sogang.ac.kr [Molecular Imaging Research & Education (MiRe) Laboratory, Department of Electronic Engineering, Sogang University, Seoul (Korea, Republic of); Kim, Kyu Bom; Lee, Sangwon [Molecular Imaging Research & Education (MiRe) Laboratory, Department of Electronic Engineering, Sogang University, Seoul (Korea, Republic of); Yamamoto, Seiichi [Department of Medical Technology, Nagoya University Graduate School of Medicine, Nagoya (Japan); Yeom, Jung-Yeol, E-mail: jungyeol@korea.ac.kr [School of Biomedical Engineering, Korea University, Seoul (Korea, Republic of)

    2017-02-21

    In positron emission tomography (PET) for breast, brain and small animal imaging, the spatial resolution of a PET detector is crucial to obtain high quality PET images. In this study, a PET detector for sub-millimeter spatial resolution imaging purpose was assembled using 4×4 pixels of a digital silicon photomultiplier (dSiPM, DPC-3200-22-44, Philips) coupled with a 15×15 LGSO array with BaSO{sub 4} reflector, and a 1 mm thick acrylic light guide for light distribution between the dSiPM pixels. The active area of each dSiPM pixel was 3.2×3.9 mm{sup 2} and the size of each LGSO scintillator element was 0.7×0.7×6 mm{sup 3}. In this paper, we experimentally demonstrated the performance of the PET detector by measuring the energy resolution, 2D flood map, peak to valley (P/V) ratio, and coincidence resolving time (CRT). All measurements were performed at a temperature of 10±1 ℃. The average energy resolution was 15.6% (without correcting for saturation effects) at 511 keV and the best CRT was 242±5 ps. The 2D flood map obtained with an energy window of 400–600 keV demonstrated clear identification of all pixels, and the average P/V ratio of the X- and Y-directions were 7.31 and 7.81, respectively. This study demonstrated that the PET detector could be suitable for application in high resolution PET while achieving good timing resolution.

  3. A Novel Heterocyclic Compound CE-104 Enhances Spatial Working Memory in the Radial Arm Maze in Rats and Modulates the Dopaminergic System.

    Science.gov (United States)

    Aher, Yogesh D; Subramaniyan, Saraswathi; Shanmugasundaram, Bharanidharan; Sase, Ajinkya; Saroja, Sivaprakasam R; Holy, Marion; Höger, Harald; Beryozkina, Tetyana; Sitte, Harald H; Leban, Johann J; Lubec, Gert

    2016-01-01

    Various psychostimulants targeting monoamine neurotransmitter transporters (MATs) have been shown to rescue cognition in patients with neurological disorders and improve cognitive abilities in healthy subjects at low doses. Here, we examined the effects upon cognition of a chemically synthesized novel MAT inhibiting compound 2-(benzhydrylsulfinylmethyl)-4-methylthiazole (named as CE-104). The efficacy of CE-104 in blocking MAT [dopamine transporter (DAT), serotonin transporter (SERT), and norepinephrine transporter] was determined using in vitro neurotransmitter uptake assay. The effect of the drug at low doses (1 and 10 mg/kg) on spatial memory was studied in male rats in the radial arm maze (RAM). Furthermore, the dopamine receptor and transporter complex levels of frontal cortex (FC) tissue of trained and untrained animals treated either with the drug or vehicle were quantified on blue native PAGE (BN-PAGE). The drug inhibited dopamine (IC50: 27.88 μM) and norepinephrine uptake (IC50: 160.40 μM), but had a negligible effect on SERT. In the RAM, both drug-dose groups improved spatial working memory during the performance phase of RAM as compared to vehicle. BN-PAGE Western blot quantification of dopamine receptor and transporter complexes revealed that D1, D2, D3, and DAT complexes were modulated due to training and by drug effects. The drug's ability to block DAT and its influence on DAT and receptor complex levels in the FC is proposed as a possible mechanism for the observed learning and memory enhancement in the RAM.

  4. Heavy nucleus resonant absorption in heterogeneous lattices. I- Apollo 2 self-shielding formalism; Absorption resonnante des noyaux lourds dans les reseaux heterogenes. I -Formalisme du module d`autoprotection d`Apollo 2

    Energy Technology Data Exchange (ETDEWEB)

    Coste, M.

    1994-01-01

    This note gives in detailed way the self-shielding formalism which is used in the multigroup transport code APOLLO2. The self-shielded cross-sections are performed with the same scheme as in APOLLO1. We use two equivalencies, first an heterogeneous/homogeneous equivalence which gives the reaction rates and then a multigroup equivalence in order to obtain the cross-sections which preserve these reaction rates. However, numerous improvements were implemented, specially in the homogenization step. Homogenization can be performed group per group with different modelizations of the heavy slowing-down operator (statistical, intermediary and ``wide resonance`` models), which allows us to fit correctly the resonance shapes. Moreover, we can take exactly into account the spatial interferences between resonant isotopes with the background matrix model. Consequently, we are now able to perform, for instance, the radial distribution of the resonant absorption inside a fuel pin. (author). 7 refs., 3 figs.

  5. High spatial resolution and temporally resolved T2* mapping of normal human myocardium at 7.0 Tesla: an ultrahigh field magnetic resonance feasibility study.

    Directory of Open Access Journals (Sweden)

    Fabian Hezel

    Full Text Available Myocardial tissue characterization using T(2(* relaxation mapping techniques is an emerging application of (preclinical cardiovascular magnetic resonance imaging. The increase in microscopic susceptibility at higher magnetic field strengths renders myocardial T(2(* mapping at ultrahigh magnetic fields conceptually appealing. This work demonstrates the feasibility of myocardial T(2(* imaging at 7.0 T and examines the applicability of temporally-resolved and high spatial resolution myocardial T(2(* mapping. In phantom experiments single cardiac phase and dynamic (CINE gradient echo imaging techniques provided similar T(2(* maps. In vivo studies showed that the peak-to-peak B(0 difference following volume selective shimming was reduced to approximately 80 Hz for the four chamber view and mid-ventricular short axis view of the heart and to 65 Hz for the left ventricle. No severe susceptibility artifacts were detected in the septum and in the lateral wall for T(2(* weighting ranging from TE = 2.04 ms to TE = 10.2 ms. For TE >7 ms, a susceptibility weighting induced signal void was observed within the anterior and inferior myocardial segments. The longest T(2(* values were found for anterior (T(2(* = 14.0 ms, anteroseptal (T(2(* = 17.2 ms and inferoseptal (T(2(* = 16.5 ms myocardial segments. Shorter T(2(* values were observed for inferior (T(2(* = 10.6 ms and inferolateral (T(2(* = 11.4 ms segments. A significant difference (p = 0.002 in T(2(* values was observed between end-diastole and end-systole with T(2(* changes of up to approximately 27% over the cardiac cycle which were pronounced in the septum. To conclude, these results underscore the challenges of myocardial T(2(* mapping at 7.0 T but demonstrate that these issues can be offset by using tailored shimming techniques and dedicated acquisition schemes.

  6. Estradiol treatment in preadolescent females enhances adolescent spatial memory and differentially modulates hippocampal region-specific phosphorylated ERK labeling.

    Science.gov (United States)

    Wartman, Brianne C; Keeley, Robin J; Holahan, Matthew R

    2012-10-24

    Estrogen levels in rats are positively correlated with enhanced memory function and hippocampal dendritic spine density. There is much less work on the long-term effects of estradiol manipulation in preadolescent rats. The present work examined how injections of estradiol during postnatal days 19-22 (p19-22; preadolescence) affected water maze performance and hippocampal phosphorylated ERK labeling. To investigate this, half of the estradiol- and vehicle-treated female rats were trained on a water maze task 24h after the end of estradiol treatment (p23-27) while the other half was not trained. All female rats were tested on the water maze from p40 to p44 (adolescence) and hippocampal pERK1/2 labeling was assessed as a putative marker of neuronal plasticity. During adolescence, preadolescent-trained groups showed lower latencies than groups without preadolescent training. Retention data revealed lower latencies in both estradiol groups, whether preadolescent trained or not. Immunohistochemical detection of hippocampal pERK1/2 revealed elevations in granule cell labeling associated with the preadolescent trained groups and reductions in CA1 labeling associated with estradiol treatment. These results show a latent beneficial effect of preadolescent estradiol treatment on adolescent spatial performance and suggest an organizational effect of prepubescent exogenously applied estradiol. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

  7. Functional Alterations of Postcentral Gyrus Modulated by Angry Facial Expressions during Intraoral Tactile Stimuli in Patients with Burning Mouth Syndrome: A Functional Magnetic Resonance Imaging Study

    Science.gov (United States)

    Yoshino, Atsuo; Okamoto, Yasumasa; Doi, Mitsuru; Okada, Go; Takamura, Masahiro; Ichikawa, Naho; Yamawaki, Shigeto

    2017-01-01

    Previous findings suggest that negative emotions could influence abnormal sensory perception in burning mouth syndrome (BMS). However, few studies have investigated the underlying neural mechanisms associated with BMS. We examined activation of brain regions in response to intraoral tactile stimuli when modulated by angry facial expressions. We performed functional magnetic resonance imaging on a group of 27 BMS patients and 21 age-matched healthy controls. Tactile stimuli were presented during different emotional contexts, which were induced via the continuous presentation of angry or neutral pictures of human faces. BMS patients exhibited higher tactile ratings and greater activation in the postcentral gyrus during the presentation of tactile stimuli involving angry faces relative to controls. Significant positive correlations between changes in brain activation elicited by angry facial images in the postcentral gyrus and changes in tactile rating scores by angry facial images were found for both groups. For BMS patients, there was a significant positive correlation between changes in tactile-related activation of the postcentral gyrus elicited by angry facial expressions and pain intensity in daily life. Findings suggest that neural responses in the postcentral gyrus are more strongly affected by angry facial expressions in BMS patients, which may reflect one possible mechanism underlying impaired somatosensory system function in this disorder. PMID:29163243

  8. Functional Alterations of Postcentral Gyrus Modulated by Angry Facial Expressions during Intraoral Tactile Stimuli in Patients with Burning Mouth Syndrome: A Functional Magnetic Resonance Imaging Study

    Directory of Open Access Journals (Sweden)

    Atsuo Yoshino

    2017-11-01

    Full Text Available Previous findings suggest that negative emotions could influence abnormal sensory perception in burning mouth syndrome (BMS. However, few studies have investigated the underlying neural mechanisms associated with BMS. We examined activation of brain regions in response to intraoral tactile stimuli when modulated by angry facial expressions. We performed functional magnetic resonance imaging on a group of 27 BMS patients and 21 age-matched healthy controls. Tactile stimuli were presented during different emotional contexts, which were induced via the continuous presentation of angry or neutral pictures of human faces. BMS patients exhibited higher tactile ratings and greater activation in the postcentral gyrus during the presentation of tactile stimuli involving angry faces relative to controls. Significant positive correlations between changes in brain activation elicited by angry facial images in the postcentral gyrus and changes in tactile rating scores by angry facial images were found for both groups. For BMS patients, there was a significant positive correlation between changes in tactile-related activation of the postcentral gyrus elicited by angry facial expressions and pain intensity in daily life. Findings suggest that neural responses in the postcentral gyrus are more strongly affected by angry facial expressions in BMS patients, which may reflect one possible mechanism underlying impaired somatosensory system function in this disorder.

  9. Urinary 1H Nuclear Magnetic Resonance Metabolomic Fingerprinting Reveals Biomarkers of Pulse Consumption Related to Energy-Metabolism Modulation in a Subcohort from the PREDIMED study.

    Science.gov (United States)

    Madrid-Gambin, Francisco; Llorach, Rafael; Vázquez-Fresno, Rosa; Urpi-Sarda, Mireia; Almanza-Aguilera, Enrique; Garcia-Aloy, Mar; Estruch, Ramon; Corella, Dolores; Andres-Lacueva, Cristina

    2017-04-07

    Little is known about the metabolome fingerprint of pulse consumption. The study of robust and accurate biomarkers for pulse dietary assessment has great value for nutritional epidemiology regarding health benefits and their mechanisms. To characterize the fingerprinting of dietary pulses (chickpeas, lentils, and beans), spot urine samples from a subcohort from the PREDIMED study were stratified using a validated food frequency questionnaire. Urine samples of nonpulse consumers (≤4 g/day of pulse intake) and habitual pulse consumers (≥25 g/day of pulse intake) were analyzed using a 1 H nuclear magnetic resonance (NMR) metabolomics approach combined with multi- and univariate data analysis. Pulse consumption showed differences through 16 metabolites coming from (i) choline metabolism, (ii) protein-related compounds, and (iii) energy metabolism (including lower urinary glucose). Stepwise logistic regression analysis was applied to design a combined model of pulse exposure, which resulted in glutamine, dimethylamine, and 3-methylhistidine. This model was evaluated by a receiver operating characteristic curve (AUC > 90% in both training and validation sets). The application of NMR-based metabolomics to reported pulse exposure highlighted new candidates for biomarkers of pulse consumption and the impact on energy metabolism, generating new hypotheses on energy modulation. Further intervention studies will confirm these findings.

  10. Predicting the severity and prognosis of trismus after intensity-modulated radiation therapy for oral cancer patients by magnetic resonance imaging.

    Directory of Open Access Journals (Sweden)

    Li-Chun Hsieh

    Full Text Available To develop magnetic resonance imaging (MRI indicators to predict trismus outcome for post-operative oral cavity cancer patients who received adjuvant intensity-modulated radiation therapy (IMRT, 22 patients with oral cancer treated with IMRT were studied over a two-year period. Signal abnormality scores (SA scores were computed from Likert-type ratings of the abnormalities of nine masticator structures and compared with the Mann-Whitney U-test and Kruskal-Wallis one-way ANOVA test between groups. Seventeen patients (77.3% experienced different degrees of trismus during the two-year follow-up period. The SA score correlated with the trismus grade (r = 0.52, p<0.005. Patients having progressive trismus had higher mean doses of radiation to multiple structures, including the masticator and lateral pterygoid muscles, and the parotid gland (p<0.05. In addition, this group also had higher SA-masticator muscle dose product at 6 months and SA scores at 12 months (p<0.05. At the optimum cut-off points of 0.38 for the propensity score, the sensitivity was 100% and the specificity was 93% for predicting the prognosis of the trismus patients. The SA score, as determined using MRI, can reflect the radiation injury and correlate to trismus severity. Together with the radiation dose, it could serve as a useful biomarker to predict the outcome and guide the management of trismus following radiation therapy.

  11. Quality of Intensity Modulated Radiation Therapy Treatment Plans Using a ⁶⁰Co Magnetic Resonance Image Guidance Radiation Therapy System.

    Science.gov (United States)

    Wooten, H Omar; Green, Olga; Yang, Min; DeWees, Todd; Kashani, Rojano; Olsen, Jeff; Michalski, Jeff; Yang, Deshan; Tanderup, Kari; Hu, Yanle; Li, H Harold; Mutic, Sasa

    2015-07-15

    This work describes a commercial treatment planning system, its technical features, and its capabilities for creating (60)Co intensity modulated radiation therapy (IMRT) treatment plans for a magnetic resonance image guidance radiation therapy (MR-IGRT) system. The ViewRay treatment planning system (Oakwood Village, OH) was used to create (60)Co IMRT treatment plans for 33 cancer patients with disease in the abdominal, pelvic, thorax, and head and neck regions using physician-specified patient-specific target coverage and organ at risk (OAR) objectives. Backup plans using a third-party linear accelerator (linac)-based planning system were also created. Plans were evaluated by attending physicians and approved for treatment. The (60)Co and linac plans were compared by evaluating conformity numbers (CN) with 100% and 95% of prescription reference doses and heterogeneity indices (HI) for planning target volumes (PTVs) and maximum, mean, and dose-volume histogram (DVH) values for OARs. All (60)Co IMRT plans achieved PTV coverage and OAR sparing that were similar to linac plans. PTV conformity for (60)Co was within 20 Gy. The mean doses for all (60)Co plan OARs were within clinical tolerances. A commercial (60)Co MR-IGRT device can produce highly conformal IMRT treatment plans similar in quality to linac IMRT for a variety of disease sites. Additional work is in progress to evaluate the clinical benefit of other novel features of this MR-IGRT system. Copyright © 2015 Elsevier Inc. All rights reserved.

  12. Physics of Gate Modulated Resonant Tunneling (RT)-FETs: Multi-barrier MOSFET for steep slope and high on-current

    Science.gov (United States)

    Afzalian, Aryan; Colinge, Jean-Pierre; Flandre, Denis

    2011-05-01

    A new concept of nanoscale MOSFET, the Gate Modulated Resonant Tunneling Transistor (RT-FET), is presented and modeled using 3D Non-Equilibrium Green's Function simulations enlightening the main physical mechanisms. Owing to the additional tunnel barriers and the related longitudinal confinement present in the device, the density of state is reduced in its off-state, while remaining comparable in its on-state, to that of a MOS transistor without barriers. The RT-FET thus features both a lower RT-limited off-current and a faster increase of the current with V G, i.e. an improved slope characteristic, and hence an improved Ion/ Ioff ratio. Such improvement of the slope can happen in subthreshold regime, and therefore lead to subthreshold slope below the kT/q limit. In addition, faster increase of current and improved slope occur above threshold and lead to high thermionic on-current and significant Ion/ Ioff ratio improvement, even with threshold voltage below 0.2 V and supply voltage V dd of a few hundreds of mV as critically needed for future technology nodes. Finally RT-FETs are intrinsically immune to source-drain tunneling and are therefore promising candidate for extending the roadmap below 10 nm.

  13. Aerobic endurance capacity affects spatial memory and SIRT1 is a potent modulator of 8-oxoguanine repair.

    Science.gov (United States)

    Sarga, L; Hart, N; Koch, L G; Britton, S L; Hajas, G; Boldogh, I; Ba, X; Radak, Z

    2013-11-12

    Regular exercise promotes brain function via a wide range of adaptive responses, including the increased expression of antioxidant and oxidative DNA damage-repairing systems. Accumulation of oxidized DNA base lesions and strand breaks is etiologically linked to for example aging processes and age-associated diseases. Here we tested whether exercise training has an impact on brain function, extent of neurogenesis, and expression of 8-oxoguanine DNA glycosylase-1 (Ogg1) and SIRT1 (silent mating-type information regulation 2 homolog). To do so, we utilized strains of rats with low- and high-running capacity (LCR and HCR) and examined learning and memory, DNA synthesis, expression, and post-translational modification of Ogg1 hippocampal cells. Our results showed that rats with higher aerobic/running capacity had better spatial memory, and expressed less Ogg1, when compared to LCR rats. Furthermore, exercise increased SIRT1 expression and decreased acetylated Ogg1 (AcOgg1) levels, a post-translational modification important for efficient repair of 8-oxo-7,8-dihydroguanine (8-oxoG). Our data on cell cultures revealed that nicotinamide, a SIRT1-specific inhibitor, caused the greatest increase in the acetylation of Ogg1, a finding further supported by our other observations that silencing SIRT1 also markedly increased the levels of AcOgg1. These findings imply that high-running capacity is associated with increased hippocampal function, and SIRT1 level/activity and inversely correlates with AcOgg1 levels and thereby the repair of genomic 8-oxoG. Copyright © 2013 IBRO. Published by Elsevier Ltd. All rights reserved.

  14. Modulational effects in accelerators

    International Nuclear Information System (INIS)

    Satogata, T.

    1997-01-01

    We discuss effects of field modulations in accelerators, specifically those that can be used for operational beam diagnostics and beam halo control. In transverse beam dynamics, combined effects of nonlinear resonances and tune modulations influence diffusion rates with applied tune modulation has been demonstrated. In the longitudinal domain, applied RF phase and voltage modulations provide mechanisms for parasitic halo transport, useful in slow crystal extraction. Experimental experiences with transverse tune and RF modulations are also discussed

  15. Magnetic resonance signal moment determination using the Earth's magnetic field

    KAUST Repository

    Fridjonsson, Einar Orn; Creber, Sarah A.; Vrouwenvelder, Johannes S.; Johns, Michael L.

    2015-01-01

    We demonstrate a method to manipulate magnetic resonance data such that the moments of the signal spatial distribution are readily accessible. Usually, magnetic resonance imaging relies on data acquired in so-called k-space which is subsequently Fourier transformed to render an image. Here, via analysis of the complex signal in the vicinity of the centre of k-space we are able to access the first three moments of the signal spatial distribution, ultimately in multiple directions. This is demonstrated for biofouling of a reverse osmosis (RO) membrane module, rendering unique information and an early warning of the onset of fouling. The analysis is particularly applicable for the use of mobile magnetic resonance spectrometers; here we demonstrate it using an Earth's magnetic field system.

  16. Magnetic resonance signal moment determination using the Earth's magnetic field

    KAUST Repository

    Fridjonsson, Einar Orn

    2015-03-01

    We demonstrate a method to manipulate magnetic resonance data such that the moments of the signal spatial distribution are readily accessible. Usually, magnetic resonance imaging relies on data acquired in so-called k-space which is subsequently Fourier transformed to render an image. Here, via analysis of the complex signal in the vicinity of the centre of k-space we are able to access the first three moments of the signal spatial distribution, ultimately in multiple directions. This is demonstrated for biofouling of a reverse osmosis (RO) membrane module, rendering unique information and an early warning of the onset of fouling. The analysis is particularly applicable for the use of mobile magnetic resonance spectrometers; here we demonstrate it using an Earth\\'s magnetic field system.

  17. Attending to global versus local stimulus features modulates neural processing of low versus high spatial frequencies: An analysis with event-related brain potentials.

    Directory of Open Access Journals (Sweden)

    Anastasia V Flevaris

    2014-04-01

    Full Text Available Spatial frequency (SF selection has long been recognized to play a role in global and local processing, though the nature of the relationship between SF processing and global/local perception is debated. Previous studies have shown that attention to relatively lower SFs facilitates global perception, and that attention to relatively higher SFs facilitates local perception. Here we recorded event-related brain potentials (ERPs to investigate whether processing of low versus high SFs is modulated automatically during global and local perception, and to examine the time course of any such effects. Participants compared bilaterally presented hierarchical letter stimuli and attended to either the global or local levels. Irrelevant SF grating probes flashed at the center of the display 200 ms after the onset of the hierarchical letter stimuli could either be low or high in SF. It was found that ERPs elicited by the SF grating probes differed as a function of attended level (global vs. local. ERPs elicited by low SF grating probes were more positive in the interval 196-236 ms during global than local attention, and this difference was greater over the right occipital scalp. In contrast, ERPs elicited by the high SF gratings were more positive in the interval 250-290 ms during local than global attention, and this difference was bilaterally distributed over the occipital scalp. These results indicate that directing attention to global versus local levels of a hierarchical display facilitates automatic perceptual processing of low versus high SFs, respectively, and this facilitation is not limited to the locations occupied by the hierarchical display. The relatively long latency of these attention-related ERP modulations suggests that initial (early SF processing is not affected by attention to hierarchical level, lending support to theories positing a higher level mechanism to underlie the relationship between SF processing and global versus local

  18. Investigation of the thermal and optical performance of a spatial light modulator with high average power picosecond laser exposure for materials processing applications

    Science.gov (United States)

    Zhu, G.; Whitehead, D.; Perrie, W.; Allegre, O. J.; Olle, V.; Li, Q.; Tang, Y.; Dawson, K.; Jin, Y.; Edwardson, S. P.; Li, L.; Dearden, G.

    2018-03-01

    Spatial light modulators (SLMs) addressed with computer generated holograms (CGHs) can create structured light fields on demand when an incident laser beam is diffracted by a phase CGH. The power handling limitations of these devices based on a liquid crystal layer has always been of some concern. With careful engineering of chip thermal management, we report the detailed optical phase and temperature response of a liquid cooled SLM exposed to picosecond laser powers up to 〈P〉  =  220 W at 1064 nm. This information is critical for determining device performance at high laser powers. SLM chip temperature rose linearly with incident laser exposure, increasing by only 5 °C at 〈P〉  =  220 W incident power, measured with a thermal imaging camera. Thermal response time with continuous exposure was 1-2 s. The optical phase response with incident power approaches 2π radians with average power up to 〈P〉  =  130 W, hence the operational limit, while above this power, liquid crystal thickness variations limit phase response to just over π radians. Modelling of the thermal and phase response with exposure is also presented, supporting experimental observations well. These remarkable performance characteristics show that liquid crystal based SLM technology is highly robust when efficiently cooled. High speed, multi-beam plasmonic surface micro-structuring at a rate R  =  8 cm2 s-1 is achieved on polished metal surfaces at 〈P〉  =  25 W exposure while diffractive, multi-beam surface ablation with average power 〈P〉  =100 W on stainless steel is demonstrated with ablation rate of ~4 mm3 min-1. However, above 130 W, first order diffraction efficiency drops significantly in accord with the observed operational limit. Continuous exposure for a period of 45 min at a laser power of 〈P〉  =  160 W did not result in any detectable drop in diffraction efficiency, confirmed afterwards by the efficient

  19. A novel heterocyclic compound CE-104 enhances spatial working memory in the radial arm maze in rats and modulates the dopaminergic system

    Directory of Open Access Journals (Sweden)

    Yogesh D Aher

    2016-02-01

    Full Text Available Various psychostimulants targeting monoamine neurotransmitter transporters (MAT have been shown to rescue cognition in patients with neurological disorders and improve cognitive abilities in healthy subjects at low doses. Here, we examined the effects upon cognition of a chemically synthetized novel MAT inhibiting compound 2-(benzhydrylsulfinylmethyl-4-methylthiazole (named as CE-104. The efficacy of CE-104 in blocking MAT (DAT – dopamine transporter, SERT – serotonin transporter and NET – norepinephrine transporter was determined using in vitro neurotransmitter uptake assay. The effect of the drug at low doses (1 and 10mg/kg on spatial memory was studied in male rats in the radial arm maze (RAM. Furthermore, the dopamine receptor and transporter complex levels of frontal cortex (FC tissue of trained and untrained animals treated either with the drug or vehicle were quantified on blue native PAGE (BN-PAGE. The drug inhibited dopamine (IC50: 27.88µM and norepinephrine uptake (IC50: 160.40µM, but had a negligible effect on SERT. In the RAM, both drug-dose groups improved spatial working memory during the performance phase of RAM as compared to vehicle. BN-PAGE western blot quantification of dopamine receptor and transporter complexes revealed that D1, D2, D3 and DAT complexes were modulated due to training and by drug effects. The drug’s ability to block DAT and its influence on dopamine transporter and receptor complex levels in the FC is proposed as a possible mechanism for the observed learning and memory enhancement in the RAM.

  20. Comparison of spatial working memory in children with prenatal alcohol exposure and those diagnosed with ADHD; A functional magnetic resonance imaging study

    Directory of Open Access Journals (Sweden)

    Malisza Krisztina L

    2012-05-01

    Full Text Available Abstract Background Alcohol related neurodevelopmental disorder (ARND falls under the umbrella of fetal alcohol spectrum disorder (FASD, but individuals do not demonstrate the facial characteristics associated with fetal alcohol syndrome (FAS, making diagnosis difficult. While attentional problems in ARND are similar to those found in attention-deficit/hyperactivity disorder (ADHD, the underlying impairment in attention pathways may be different. Methods Functional magnetic resonance imaging (fMRI of a working memory (1-back task of 63 children, 10 to 14 years old, diagnosed with ARND and ADHD, as well as typically developing (TD controls, was conducted at 3 T. Diffusion tensor imaging (DTI data were also acquired. Results Activations were observed in posterior parietal and occipital regions in the TD group and in dorsolateral prefrontal and posterior parietal regions in the ARND group, whereas the ADHD group activated only dorsolateral prefrontal regions, during the working memory component of the task (1-back minus 0-back contrast. The increases in frontal and parietal activity were significantly greater in the ARND group compared to the other groups. This increased activity was associated with reduced accuracy and increased response time variability, suggesting that ARND subjects exert greater effort to manage short-term memory load. Significantly greater intra-subject variability, demonstrated by fMRI region-of-interest analysis, in the ADHD and ARND groups compared to the TD group suggests that moment-to-moment lapses in attention contributed to their poorer task performance. Differences in functional activity in ARND subjects with and without a diagnosis of ADHD resulted primarily from reduced activation by the ARND/ADHD + group during the 0-back task. In contrast, children with ADHD alone clearly showed reduced activations during the 1-back task. DTI analysis revealed that the TD group had significantly higher total tract volume

  1. Planning magnetic resonance imaging for prostate cancer intensity-modulated radiation therapy: Impact on target volumes, radiotherapy dose and androgen deprivation administration.

    Science.gov (United States)

    Horsley, Patrick J; Aherne, Noel J; Edwards, Grace V; Benjamin, Linus C; Wilcox, Shea W; McLachlan, Craig S; Assareh, Hassan; Welshman, Richard; McKay, Michael J; Shakespeare, Thomas P

    2015-03-01

    Magnetic resonance imaging (MRI) scans are increasingly utilized for radiotherapy planning to contour the primary tumors of patients undergoing intensity-modulated radiation therapy (IMRT). These scans may also demonstrate cancer extent and may affect the treatment plan. We assessed the impact of planning MRI detection of extracapsular extension, seminal vesicle invasion, or adjacent organ invasion on the staging, target volume delineation, doses, and hormonal therapy of patients with prostate cancer undergoing IMRT. The records of 509 consecutive patients with planning MRI scans being treated with IMRT for prostate cancer between January 2010 and July 2012 were retrospectively reviewed. Tumor staging and treatment plans before and after MRI were compared. Of the 509 patients, 103 (20%) were upstaged and 44 (9%) were migrated to a higher risk category as a result of findings at MRI. In 94 of 509 patients (18%), the MRI findings altered management. Ninety-four of 509 patients (18%) had a change to their clinical target volume (CTV) or treatment technique, and in 41 of 509 patients (8%) the duration of hormone therapy was changed because of MRI findings. The use of radiotherapy planning MRI altered CTV design, dose and/or duration of androgen deprivation in 18% of patients in this large, single institution series of men planned for dose-escalated prostate IMRT. This has substantial implications for radiotherapy target volumes and doses, as well as duration of androgen deprivation. Further research is required to investigate whether newer MRI techniques can simultaneously fulfill staging and radiotherapy contouring roles. © 2014 Wiley Publishing Asia Pty Ltd.

  2. Dosimetric feasibility of magnetic resonance imaging-guided tri-cobalt 60 preoperative intensity modulated radiation therapy for soft tissue sarcomas of the extremity.

    Science.gov (United States)

    Kishan, Amar U; Cao, Minsong; Mikaeilian, Argin G; Low, Daniel A; Kupelian, Patrick A; Steinberg, Michael L; Kamrava, Mitchell

    2015-01-01

    The purpose of this study was to investigate the dosimetric differences of delivering preoperative intensity modulated radiation therapy (IMRT) to patients with soft tissue sarcomas of the extremity (ESTS) with a teletherapy system equipped with 3 rotating (60)Co sources and a built-in magnetic resonance imaging and with standard linear accelerator (LINAC)-based IMRT. The primary study population consisted of 9 patients treated with preoperative radiation for ESTS between 2008 and 2014 with LINAC-based static field IMRT. LINAC plans were designed to deliver 50 Gy in 25 fractions to 95% of the planning target volume (PTV). Tri-(60)Co system IMRT plans were designed with ViewRay system software. Tri-(60)Co-based IMRT plans achieved equivalent target coverage and dosimetry for organs at risk (long bone, skin, and skin corridor) compared with LINAC-based IMRT plans. The maximum and minimum PTV doses, heterogeneity indices, and ratio of the dose to 50% of the volume were equivalent for both planning systems. One LINAC plan violated the maximum bone dose constraint, whereas none of the tri-(60)Co plans did. Using a tri-(60)Co system, we were able to achieve equivalent dosimetry to the PTV and organs at risk for patients with ESTS compared with LINAC-based IMRT plans. The tri-(60)Co system may be advantageous over current treatment platforms by allowing PTV reduction and by elimination of the additional radiation dose associated with daily image guidance, but this needs to be evaluated prospectively. Copyright © 2015 American Society for Radiation Oncology. Published by Elsevier Inc. All rights reserved.

  3. Resting-state functional connectivity modulation and sustained changes after real-time functional magnetic resonance imaging neurofeedback training in depression.

    Science.gov (United States)

    Yuan, Han; Young, Kymberly D; Phillips, Raquel; Zotev, Vadim; Misaki, Masaya; Bodurka, Jerzy

    2014-11-01

    Amygdala hemodynamic responses to positive stimuli are attenuated in major depressive disorder (MDD) and normalize with remission. Real-time functional magnetic resonance imaging neurofeedback (rtfMRI-nf) training with the goal of upregulating amygdala activity during recall of happy autobiographical memories (AMs) has been suggested, and recently explored, as a novel therapeutic approach that resulted in improvement in self-reported mood in depressed subjects. In this study, we assessed the possibility of sustained brain changes as well as the neuromodulatory effects of rtfMRI-nf training of the amygdala during recall of positive AMs in MDD and matched healthy subjects. MDD and healthy subjects went through one visit of rtfMRI-nf training. Subjects were assigned to receive active neurofeedback from the left amygdale (LA) or from a control region putatively not modulated by AM recall or emotion regulation, that is, the left horizontal segment of the intraparietal sulcus. To assess lasting effects of neurofeedback in MDD, the resting-state functional connectivity before and after rtfMRI-nf in 27 depressed subjects, as well as in 27 matched healthy subjects before rtfMRI-nf was measured. Results show that abnormal hypo-connectivity with LA in MDD is reversed after rtfMRI-nf training by recalling positive AMs. Although such neuromodulatory changes are observed in both MDD groups receiving feedback from respective active and control brain regions, only in the active group are larger decreases of depression severity associated with larger increases of amygdala connectivity and a significant, positive correlation is found between the connectivity changes and the days after neurofeedback. In addition, active neurofeedback training of the amygdala enhances connectivity with temporal cortical regions, including the hippocampus. These results demonstrate lasting brain changes induced by amygdala rtfMRI-nf training and suggest the importance of reinforcement learning in

  4. Spatially resolved ozone densities and gas temperatures in a time modulated RF driven atmospheric pressure plasma jet: an analysis of the production and destruction mechanisms

    International Nuclear Information System (INIS)

    Zhang Shiqiang; Van Gessel, Bram; Hofmann, Sven; Van Veldhuizen, Eddie; Bruggeman, Peter; Van Gaens, Wouter; Bogaerts, Annemie

    2013-01-01

    In this work, a time modulated RF driven DBD-like atmospheric pressure plasma jet in Ar + 2%O 2 , operating at a time averaged power of 6.5 W is investigated. Spatially resolved ozone densities and gas temperatures are obtained by UV absorption and Rayleigh scattering, respectively. Significant gas heating in the core of the plasma up to 700 K is found and at the position of this increased gas temperature a depletion of the ozone density is found. The production and destruction reactions of O 3 in the jet effluent as a function of the distance from the nozzle are obtained from a zero-dimensional chemical kinetics model in plug flow mode which considers relevant air chemistry due to air entrainment in the jet fluent. A comparison of the measurements and the models show that the depletion of O 3 in the core of the plasma is mainly caused by an enhanced destruction of O 3 due to a large atomic oxygen density. (paper)

  5. Quantum-mechanical elaboration for the description of low- and high-order harmonics generated by extended gas media: prospects to the efficiency enhancement in spatially modulated media

    Science.gov (United States)

    Stremoukhov, Sergey Yu; Andreev, Anatoly V.

    2018-03-01

    A simple model fully matching the description of the low- and high-order harmonic generation in extended media interacting with multicolor laser fields is proposed. The extended atomic media is modeled by a 1D chain of atoms, the number of atoms and the distance between them depend on the pressure of the gas and the length of the gas cell. The response of the individual atoms is calculated accurately in the frame of the non-perturbative theory where the driving field for each atom is calculated with account of dispersion properties of any multicolor field component. In spite of the simplicity of the proposed model it provides the detailed description of behaviour of harmonic spectra under variation of the gas pressure and medium length, it also predicts a scaling law for harmonic generation (an invariant). To demonstrate the wide range of applications of the model we have simulated the results of recent experiments dealing with spatially modulated media and obtained good coincidence between the numerical results and the experimental ones.

  6. Coherent control through near-resonant Raman transitions

    International Nuclear Information System (INIS)

    Dai Xingcan; Lerch, Eliza-Beth W.; Leone, Stephen R.

    2006-01-01

    The phase of an electronic wave function is shown to play an important role in coherent control experiments. By using a pulse shaping system with a femtosecond laser, we explore the phase relationships among resonant and off-resonant Raman transitions in Li 2 by measuring the phases of the resulting wave packets, or quantum beats. Specific pixels in a liquid-crystal spatial light modulator are used to isolate the resonant and off-resonant portions of the Raman transitions in Li 2 . The off-resonant Raman transitions have an approximately 90 degree sign phase shift with respect to the resonant Raman transition, and there is an approximately 180 degree sign phase shift between the blue-detuned and the red-detuned off-resonant Raman transitions. Calculations using second-order time-dependent perturbation theory for the electronic transitions agree with the experimental results for the laser pulse intensities used here. Interferences between the off-resonant Raman transitions as a function of detuning are used to demonstrate coherent control of the Raman quantum wave packet

  7. Molecular and applied modulation effects in electron-electron double resonance. 7. Modulation frequency effects for the CH/sub 2/COO/sup -/ radical in irradiated zinc acetate

    Energy Technology Data Exchange (ETDEWEB)

    Perkins, Jr, R C; Dalton, L R [Vanderbilt Univ., Nashville, Tenn. (USA). Dept. of Chemistry; Kispert, L D

    1977-04-01

    Frequency-swept absorption ELDOR signals for the CH/sub 2/COO/sup -/radical in zinc acetate depend upon Zeeman modulation frequency, the signals going from a positive to a negative sense as the Zeeman modulation frequency is varied from 100 to 1 kHz. A mathematical formulation derived explicitly considering applied electromagnetic radiation and Zeeman modulation fields is employed to computer-simulate the experimentally observed effects.

  8. 1H, 15N and 13C backbone and side-chain resonance assignments of a family 32 carbohydrate-binding module from the Clostridium perfringens NagH.

    Science.gov (United States)

    Grondin, Julie M; Chitayat, Seth; Ficko-Blean, Elizabeth; Boraston, Alisdair B; Smith, Steven P

    2012-10-01

    The Gram-positive anaerobe Clostridium perfringens is an opportunistic bacterial pathogen that secretes a battery of enzymes involved in glycan degradation. These glycoside hydrolases are thought to be involved in turnover of mucosal layer glycans, and in the spread of major toxins commonly associated with the development of gastrointestinal diseases and gas gangrene in humans. These enzymes employ multi-modularity and carbohydrate-binding function to degrade extracellular eukaryotic host sugars. Here, we report the full (1)H, (15)N and (13)C chemical shift resonance assignments of the first family 32 carbohydrate-binding module from NagH, a secreted family 84 glycoside hydrolase.

  9. Mapping of the Underlying Neural Mechanisms of Maintenance and Manipulation in Visuo-Spatial Working Memory Using An n-back Mental Rotation Task: A Functional Magnetic Resonance Imaging Study.

    Science.gov (United States)

    Lamp, Gemma; Alexander, Bonnie; Laycock, Robin; Crewther, David P; Crewther, Sheila G

    2016-01-01

    Mapping of the underlying neural mechanisms of visuo-spatial working memory (WM) has been shown to consistently elicit activity in right hemisphere dominant fronto-parietal networks. However to date, the bulk of neuroimaging literature has focused largely on the maintenance aspect of visuo-spatial WM, with a scarcity of research into the aspects of WM involving manipulation of information. Thus, this study aimed to compare maintenance-only with maintenance and manipulation of visuo-spatial stimuli (3D cube shapes) utilizing a 1-back task while functional magnetic resonance imaging (fMRI) scans were acquired. Sixteen healthy participants (9 women, M = 23.94 years, SD = 2.49) were required to perform the 1-back task with or without mentally rotating the shapes 90° on a vertical axis. When no rotation was required (maintenance-only condition), a right hemispheric lateralization was revealed across fronto-parietal areas. However, when the task involved maintaining and manipulating the same stimuli through 90° rotation, activation was primarily seen in the bilateral parietal lobe and left fusiform gyrus. The findings confirm that the well-established right lateralized fronto-parietal networks are likely to underlie simple maintenance of visuo-spatial stimuli. The results also suggest that the added demand of manipulation of information maintained online appears to require further neural recruitment of functionally related areas. In particular mental rotation of visuospatial stimuli required bilateral parietal areas, and the left fusiform gyrus potentially to maintain a categorical or object representation. It can be concluded that WM is a complex neural process involving the interaction of an increasingly large network.

  10. The Value of Neurosurgical and Intraoperative Magnetic Resonance Imaging and Diffusion Tensor Imaging Tractography in Clinically Integrated Neuroanatomy Modules: A Cross-Sectional Study

    Science.gov (United States)

    Familiari, Giuseppe; Relucenti, Michela; Heyn, Rosemarie; Baldini, Rossella; D'Andrea, Giancarlo; Familiari, Pietro; Bozzao, Alessandro; Raco, Antonino

    2013-01-01

    Neuroanatomy is considered to be one of the most difficult anatomical subjects for students. To provide motivation and improve learning outcomes in this area, clinical cases and neurosurgical images from diffusion tensor imaging (DTI) tractographies produced using an intraoperative magnetic resonance imaging apparatus (MRI/DTI) were presented and…

  11. Emphasis of spatial cues in the temporal fine structure during the rising segments of amplitude-modulated sounds II: single-neuron recordings

    Science.gov (United States)

    Marquardt, Torsten; Stange, Annette; Pecka, Michael; Grothe, Benedikt; McAlpine, David

    2014-01-01

    Recently, with the use of an amplitude-modulated binaural beat (AMBB), in which sound amplitude and interaural-phase difference (IPD) were modulated with a fixed mutual relationship (Dietz et al. 2013b), we demonstrated that the human auditory system uses interaural timing differences in the temporal fine structure of modulated sounds only during the rising portion of each modulation cycle. However, the degree to which peripheral or central mechanisms contribute to the observed strong dominance of the rising slope remains to be determined. Here, by recording responses of single neurons in the medial superior olive (MSO) of anesthetized gerbils and in the inferior colliculus (IC) of anesthetized guinea pigs to AMBBs, we report a correlation between the position within the amplitude-modulation (AM) cycle generating the maximum response rate and the position at which the instantaneous IPD dominates the total neural response. The IPD during the rising segment dominates the total response in 78% of MSO neurons and 69% of IC neurons, with responses of the remaining neurons predominantly coding the IPD around the modulation maximum. The observed diversity of dominance regions within the AM cycle, especially in the IC, and its comparison with the human behavioral data suggest that only the subpopulation of neurons with rising slope dominance codes the sound-source location in complex listening conditions. A comparison of two models to account for the data suggests that emphasis on IPDs during the rising slope of the AM cycle depends on adaptation processes occurring before binaural interaction. PMID:24554782

  12. Evaluation of white matter integrity in systemic lupus erythematosus by diffusion tensor magnetic resonance imaging: a study using tract-based spatial statistics

    International Nuclear Information System (INIS)

    Goulart Correa, Diogo; Ventura, Nina; Gasparetto, Emerson Leandro; Zimmermann, Nicolle; Paz Fonseca, Rochele; Batista Pereira, Denis; Netto, Tania Maria; Doring, Thomas M.

    2016-01-01

    The aim of this study was to evaluate the white matter integrity in brains of patients with systemic lupus erythematosus (SLE) using a voxel-based analyses of diffusion tensor imaging (DTI) data. Fifty-seven patients with SLE were compared to 36 control patients who were matched by gender, age, education, and Mini Mental State Examination score. DTI was performed along 30 noncollinear directions in a 1.5 Tesla scanner. For tract-based spatial statistics (TBSS), a white matter skeleton was created, and a permutation-based inference with 5000 permutations and a threshold of p < 0.05 was used to identify abnormalities in fractional anisotropy (FA). The mean (MD), radial (RD), and axial diffusivities (AD) were also projected onto the mean FA skeleton. We found a significant decrease of global FA in SLE patients compared to controls. The areas of reduced FA included the right superior corona radiata, the right superior longitudinal fasciculus, the body of the corpus callosum, the right inferior fronto-occipital fasciculus, the right thalamic radiation, and the right uncinate fasciculus. Patients with SLE also had increased AD and RD in several areas. Substantial overlap of areas with increased AD and RD occurred and were spatially much more extensive than the areas of reduced FA. Significant increases of AD values were concordant to those of RD and MD and more extensive than FA changes. Analyzing all diffusivity parameters, using TBSS, can detect more white matter microstructural changes in patients with SLE than analyzing FA alone. (orig.)

  13. Evaluation of white matter integrity in systemic lupus erythematosus by diffusion tensor magnetic resonance imaging: a study using tract-based spatial statistics

    Energy Technology Data Exchange (ETDEWEB)

    Goulart Correa, Diogo; Ventura, Nina; Gasparetto, Emerson Leandro [Federal University of Rio de Janeiro, Department of Radiology, Hospital Universitario Clementino Fraga Filho, Rio de Janeiro, RJ (Brazil); Clinica de Diagnostico por Imagem (CDPI), Rio de Janeiro, RJ (Brazil); Zimmermann, Nicolle; Paz Fonseca, Rochele [Federal University of Rio de Janeiro, Department of Radiology, Hospital Universitario Clementino Fraga Filho, Rio de Janeiro, RJ (Brazil); Pontifical Catholic University of Rio Grande do Sul, Department of Psychology, Porto Alegre, RS (Brazil); Batista Pereira, Denis; Netto, Tania Maria [Federal University of Rio de Janeiro, Department of Radiology, Hospital Universitario Clementino Fraga Filho, Rio de Janeiro, RJ (Brazil); Doring, Thomas M. [Clinica de Diagnostico por Imagem (CDPI), Rio de Janeiro, RJ (Brazil)

    2016-08-15

    The aim of this study was to evaluate the white matter integrity in brains of patients with systemic lupus erythematosus (SLE) using a voxel-based analyses of diffusion tensor imaging (DTI) data. Fifty-seven patients with SLE were compared to 36 control patients who were matched by gender, age, education, and Mini Mental State Examination score. DTI was performed along 30 noncollinear directions in a 1.5 Tesla scanner. For tract-based spatial statistics (TBSS), a white matter skeleton was created, and a permutation-based inference with 5000 permutations and a threshold of p < 0.05 was used to identify abnormalities in fractional anisotropy (FA). The mean (MD), radial (RD), and axial diffusivities (AD) were also projected onto the mean FA skeleton. We found a significant decrease of global FA in SLE patients compared to controls. The areas of reduced FA included the right superior corona radiata, the right superior longitudinal fasciculus, the body of the corpus callosum, the right inferior fronto-occipital fasciculus, the right thalamic radiation, and the right uncinate fasciculus. Patients with SLE also had increased AD and RD in several areas. Substantial overlap of areas with increased AD and RD occurred and were spatially much more extensive than the areas of reduced FA. Significant increases of AD values were concordant to those of RD and MD and more extensive than FA changes. Analyzing all diffusivity parameters, using TBSS, can detect more white matter microstructural changes in patients with SLE than analyzing FA alone. (orig.)

  14. Extended abstract: ergodic magnetic limiter experiments on TEXT with a 7/3 resonance

    International Nuclear Information System (INIS)

    deGrassie, J.S.; Ohyabu, N.; Brooks, N.H.

    1984-05-01

    The ergodic magnetic limiter coils on TEXT have been reconfigured to produce the primary helical perturbation resonance at m = 7 / n = 3. The experiments continue to demonstrate that the weak resonant perturbations modify the edge conditions in keeping with model predictions. We observe a reduction in the intrinsic impurity levels accompanying the helical current pulse, presumably the result of a reduction in the electron temperature in the edge. Heat follows the perturbed field lines to the limiter, generating heat load patterns which reflect the geometry of a magnetic island - limiter intersection. A strong spatial modulation of the electron density in the scrape-off-layer also reflects the helical mode structure

  15. Identifying differences in brain activities and an accurate detection of autism spectrum disorder using resting state functional-magnetic resonance imaging : A spatial filtering approach.

    Science.gov (United States)

    Subbaraju, Vigneshwaran; Suresh, Mahanand Belathur; Sundaram, Suresh; Narasimhan, Sundararajan

    2017-01-01

    This paper presents a new approach for detecting major differences in brain activities between Autism Spectrum Disorder (ASD) patients and neurotypical subjects using the resting state fMRI. Further the method also extracts discriminative features for an accurate diagnosis of ASD. The proposed approach determines a spatial filter that projects the covariance matrices of the Blood Oxygen Level Dependent (BOLD) time-series signals from both the ASD patients and neurotypical subjects in orthogonal directions such that they are highly separable. The inverse of this filter also provides a spatial pattern map within the brain that highlights those regions responsible for the distinguishable activities between the ASD patients and neurotypical subjects. For a better classification, highly discriminative log-variance features providing the maximum separation between the two classes are extracted from the projected BOLD time-series data. A detailed study has been carried out using the publicly available data from the Autism Brain Imaging Data Exchange (ABIDE) consortium for the different gender and age-groups. The study results indicate that for all the above categories, the regional differences in resting state activities are more commonly found in the right hemisphere compared to the left hemisphere of the brain. Among males, a clear shift in activities to the prefrontal cortex is observed for ASD patients while other parts of the brain show diminished activities compared to neurotypical subjects. Among females, such a clear shift is not evident; however, several regions, especially in the posterior and medial portions of the brain show diminished activities due to ASD. Finally, the classification performance obtained using the log-variance features is found to be better when compared to earlier studies in the literature. Copyright © 2016 Elsevier B.V. All rights reserved.

  16. Functional Magnetic Resonance Imaging

    Science.gov (United States)

    Voos, Avery; Pelphrey, Kevin

    2013-01-01

    Functional magnetic resonance imaging (fMRI), with its excellent spatial resolution and ability to visualize networks of neuroanatomical structures involved in complex information processing, has become the dominant technique for the study of brain function and its development. The accessibility of in-vivo pediatric brain-imaging techniques…

  17. Stochastic resonance in a gain-noise model of a single-mode laser driven by pump noise and quantum noise with cross-correlation between real and imaginary parts under direct signal modulation

    Institute of Scientific and Technical Information of China (English)

    Chen Li-Mei; Cao Li; Wu Da-Jin

    2007-01-01

    Stochastic resonance (SR) is studied in a gain-noise model of a single-mode laser driven by a coloured pump noise and a quantum noise with cross-correlation between real and imaginary parts under a direct signal modulation. By using a linear approximation method, we find that the SR appears during the variation of signal-to-noise ratio (SNR)separately with the pump noise self-correlation time τ, the noise correlation coefficient between the real part and the imaginary part of the quantum noise λq, the attenuation coefficient γ and the deterministic steady-state intensity I0.In addition, it is found that the SR can be characterized not only by the dependence of SNR on the noise variables of τand λq, but also by the dependence of SNR on the laser system variables of γ and I0. Thus our investigation extends the characteristic quantity of SR proposed before.

  18. The modulation of the motor resonance triggered by reach-to-grasp movements: No role of human physical similarity as conveyed by age.

    Science.gov (United States)

    Marino, Barbara F M; Ricciardelli, Paola

    2017-07-01

    The activation of the mirror-neuron circuit during the observation of motor acts is thought to be the basis of human capacity to read the intentions behind the behavior of others. Growing empirical evidence shows a different activation of the mirror-neuron resonance mechanism depending on how much the observer and the observed agent share their motor repertoires. Here, the possible modulatory effect of physical similarity between the observer and the agent was investigated in three studies. We used a visuo-motor priming task in which participants were asked to categorize manipulable and non-manipulable objects into natural or man-made kinds after having watched precision and power reach-to-grasp movements. Physical similarity was manipulated by presenting reach-to-grasp movements performed by the hands of actors of three different age ranges that are adults of the same age as the participants, children, and elderly. Faster responses were observed in trials where power grip movements were performed by the adults and precision grip movements were performed by the elderly (Main Study). This finding is not in keeping with the idea that physical similarity shapes the mirror-neuron resonance. Instead, it suggests an effect of the kinematic organization of the reach-to-grasp movements, which systematically changed with the actor age as revealed by a kinematic analysis. The differential effect played by adult and elderly actor primes was lost when static grasping hands (Control Study 1) and reach-to-grasp movements with uniform kinematic profiles (Control Study 2) were used. Therefore, we found preliminary evidence that mirror-neuron resonance is not shaped by physical similarity but by the kinematics of the observed action. This finding is novel as it suggests that human ability to read the intentions behind the behavior of others may benefit from a mere visual processing of spatiotemporal patterns.

  19. High-spatial-resolution isotropic three-dimensional fast-recovery fast spin-echo magnetic resonance dacryocystography combined with topical administration of sterile saline solution

    International Nuclear Information System (INIS)

    Jing, Zhang; Lang, Chen; Qiu-Xia, Wang; Rong, Liu; Xin, Luo; Wen-Zhen, Zhu; Li-Ming, Xia; Jian-Pin, Qi; He, Wang

    2013-01-01

    Objective: This study aims to investigate the clinical performance of three-dimensional (3D) fast-recovery fast spin-echo (FRFSE) magnetic resonance dacryocystography (MRD) with topical administration of sterile saline solution for the assessment of the lacrimal drainage system (LDS). Methods: A total of 13 healthy volunteers underwent both 3D-FRFSE MRD and two-dimensional (2D)-impulse recovery (IR)-single-shot fast spin-echo (SSFSE) MRD after topical administration of sterile saline solution, and 31 patients affected by primary LDS outflow impairment or postsurgical recurrent epiphora underwent 3D-FRFSE MRD and conventional T1- and T2-weighted sequences. All patients underwent lacrimal endoscopy or surgery, which served as a standard of reference for confirming the MRD findings. Results: 3D-FRFSE MRD detected more visualized superior and inferior canaliculi and nasolacrimal duct than 2D-IR-SSFSE MRD. Compared with 2D-IR-SSFSE MRD, 3D-FRFSE MRD showed more visualized segments per LDS, although the difference was not statistically significant. Significant improvements in the inferior canaliculus and nasolacrimal duct visibility grades were achieved using 3D-FRFSE MRD. 3D-FRFSE MRD had 100% sensitivity and 63.6% specificity for detecting LDS obstruction. In 51 out of the 62 LDSs that were assessed, a 90% agreement was noted between the findings of 3D-FRFSE MRD and lacrimal endoscopy in detecting the obstruction level. Conclusion: 3D-FRFSE MRD combined with topical administration of sterile saline solution is a simple and noninvasive method of obtaining detailed morphological and functional information on the LDS. Overall, 3D-FRFSE MRD could be used as a reliable diagnostic method in many patients with epiphora prior to surgery

  20. Value of high spatial and high temporal resolution magnetic resonance angiography for differentiation between idiopathic and thromboembolic pulmonary hypertension: initial results

    Energy Technology Data Exchange (ETDEWEB)

    Ley, Sebastian; Eichinger, Monika [DKFZ, Department of Radiology (E010), Heidelberg (Germany); Johannes Gutenberg-University, Department of Radiology, University Hospital Mainz, Mainz (Germany); Fink, Christian; Zaporozhan, Julia; Puderbach, Michael; Plathow, Christian; Kauczor, Hans-Ulrich [DKFZ, Department of Radiology (E010), Heidelberg (Germany); Borst, Mathias M.; Meyer, F. Joachim; Gruenig, Ekkehard [University Heidelberg, Department of Internal Medicine, Heidelberg (Germany); Kreitner, Karl-Friedrich [Johannes Gutenberg-University, Department of Radiology, University Hospital Mainz, Mainz (Germany)

    2005-11-01

    Differentiation between different forms of pulmonary hypertension (PH) is essential for correct disease management. The goal of this study was to elucidate the clinical impact of high spatial resolution MR angiography (SR-MRA) and time-resolved MRA (TR-MRA) to differentiate between patients with chronic thromboembolic PH (CTEPH) and idiopathic pulmonary arterial hypertension (IPAH). Ten PH patients and five volunteers were examined. Twenty TR-MRA data sets (TA 1.5 s) and SR-MRA (TA 23 s) were acquired. TR-MRA data sets were subtracted as angiography and perfusion images. Evaluation comprised analysis of vascular pathologies on a segmental basis, detection of perfusion defects, and bronchial arteries by two readers in consensus. Technical evaluation comprised evaluation of image quality, signal-to-noise ratio (SNR) measurements, and contrast-media passage time. Visualization of the pulmonary arteries was possible down to a subsegmental (SR-MRA) and to a segmental (TR-MRA) level. SR-MRA outperformed TR-MRA in direct visualization of intravascular changes. Patients with IPAH predominantly showed tortuous pulmonary arteries while in CTEPH wall irregularities and abnormal proximal-to-distal tapering was found. Perfusion images showed a diffuse pattern in IPAH and focal defects in CTEPH. TR-MRA and SR-MRA resulted in the same final diagnosis. Both MRA techniques allowed for differentiation between IPAH and CTEPH. Therefore, TR-MRA can be used in the clinical setting, especially in dyspneic patients. (orig.)

  1. Observation of pulsed neutron Ramsey resonance

    Energy Technology Data Exchange (ETDEWEB)

    Masuda, Y. [High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba Ibaraki 305-0801 (Japan)]. E-mail: yasuhiro.masuda@kek.jp; Skoy, V. [Joint Institute for Nuclear Reasearch, 141980 Dubna, Moscow Region (Russian Federation); Ino, T. [High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba Ibaraki 305-0801 (Japan); Jeong, S.C. [High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba Ibaraki 305-0801 (Japan); Watanabe, Y. [High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba Ibaraki 305-0801 (Japan)

    2007-07-15

    A Ramsey resonance for pulsed neutrons was observed. The separated oscillatory fields for nuclear magnetic resonance were synchronized with a neutron pulse, and then the Ramsey resonance was observed as a function of the neutron velocity. The phase of one of the oscillatory fields was modulated as a function of the neutron time of flight for a neutron velocity measurement.

  2. Modulation of auditory spatial attention by visual emotional cues: differential effects of attentional engagement and disengagement for pleasant and unpleasant cues.

    Science.gov (United States)

    Harrison, Neil R; Woodhouse, Rob

    2016-05-01

    Previous research has demonstrated that threatening, compared to neutral pictures, can bias attention towards non-emotional auditory targets. Here we investigated which subcomponents of attention contributed to the influence of emotional visual stimuli on auditory spatial attention. Participants indicated the location of an auditory target, after brief (250 ms) presentation of a spatially non-predictive peripheral visual cue. Responses to targets were faster at the location of the preceding visual cue, compared to at the opposite location (cue validity effect). The cue validity effect was larger for targets following pleasant and unpleasant cues compared to neutral cues, for right-sided targets. For unpleasant cues, the crossmodal cue validity effect was driven by delayed attentional disengagement, and for pleasant cues, it was driven by enhanced engagement. We conclude that both pleasant and unpleasant visual cues influence the distribution of attention across modalities and that the associated attentional mechanisms depend on the valence of the visual cue.

  3. Spatial frequency-dependent feedback of visual cortical area 21a modulating functional orientation column maps in areas 17 and 18 of the cat.

    Science.gov (United States)

    Huang, Luoxiu; Chen, Xin; Shou, Tiande

    2004-02-20

    The feedback effect of activity of area 21a on orientation maps of areas 17 and 18 was investigated in cats using intrinsic signal optical imaging. A spatial frequency-dependent decrease in response amplitude of orientation maps to grating stimuli was observed in areas 17 and 18 when area 21a was inactivated by local injection of GABA, or by a lesion induced by liquid nitrogen freezing. The decrease in response amplitude of orientation maps of areas 17 and 18 after the area 21a inactivation paralleled the normal response without the inactivation. Application in area 21a of bicuculline, a GABAa receptor antagonist caused an increase in response amplitude of orientation maps of area 17. The results indicate a positive feedback from high-order visual cortical area 21a to lower-order areas underlying a spatial frequency-dependent mechanism.

  4. Improving the spatial accuracy in functional magnetic resonance imaging (fMRI) based on the blood oxygenation level dependent (BOLD) effect: benefits from parallel imaging and a 32-channel head array coil at 1.5 Tesla.

    Science.gov (United States)

    Fellner, C; Doenitz, C; Finkenzeller, T; Jung, E M; Rennert, J; Schlaier, J

    2009-01-01

    Geometric distortions and low spatial resolution are current limitations in functional magnetic resonance imaging (fMRI). The aim of this study was to evaluate if application of parallel imaging or significant reduction of voxel size in combination with a new 32-channel head array coil can reduce those drawbacks at 1.5 T for a simple hand motor task. Therefore, maximum t-values (tmax) in different regions of activation, time-dependent signal-to-noise ratios (SNR(t)) as well as distortions within the precentral gyrus were evaluated. Comparing fMRI with and without parallel imaging in 17 healthy subjects revealed significantly reduced geometric distortions in anterior-posterior direction. Using parallel imaging, tmax only showed a mild reduction (7-11%) although SNR(t) was significantly diminished (25%). In 7 healthy subjects high-resolution (2 x 2 x 2 mm3) fMRI was compared with standard fMRI (3 x 3 x 3 mm3) in a 32-channel coil and with high-resolution fMRI in a 12-channel coil. The new coil yielded a clear improvement for tmax (21-32%) and SNR(t) (51%) in comparison with the 12-channel coil. Geometric distortions were smaller due to the smaller voxel size. Therefore, the reduction in tmax (8-16%) and SNR(t) (52%) in the high-resolution experiment seems to be tolerable with this coil. In conclusion, parallel imaging is an alternative to reduce geometric distortions in fMRI at 1.5 T. Using a 32-channel coil, reduction of the voxel size might be the preferable way to improve spatial accuracy.

  5. Nanoantenna using mechanical resonance

    KAUST Repository

    Chang Hwa Lee,

    2010-11-01

    Nanoantenna using mechanical resonance vibration is made from an indium tin oxide (ITO) coated vertically aligned nanorod array. Only this structure works as a radio with demodulator without any electrical circuit using field emission phenomenon. A top-down fabrication method of an ITO coated nanorod array is proposed using a modified UV lithography. The received radio frequency and the resonance frequency of nanoantenna can be controlled by the fabrication condition through the height of a nanorod array. The modulated signals are received successfully with the transmission carrier wave frequency (248MHz) and the proposed nanoantenna is expected to be used in communication system for ultra small scale sensor. ©2010 IEEE.

  6. Accounting for Non-Gaussian Sources of Spatial Correlation in Parametric Functional Magnetic Resonance Imaging Paradigms II: A Method to Obtain First-Level Analysis Residuals with Uniform and Gaussian Spatial Autocorrelation Function and Independent and Identically Distributed Time-Series.

    Science.gov (United States)

    Gopinath, Kaundinya; Krishnamurthy, Venkatagiri; Lacey, Simon; Sathian, K

    2018-02-01

    In a recent study Eklund et al. have shown that cluster-wise family-wise error (FWE) rate-corrected inferences made in parametric statistical method-based functional magnetic resonance imaging (fMRI) studies over the past couple of decades may have been invalid, particularly for cluster defining thresholds less stringent than p functions (sACFs) of fMRI data had been modeled incorrectly to follow a Gaussian form, whereas empirical data suggest otherwise. Hence, the residuals from general linear model (GLM)-based fMRI activation estimates in these studies may not have possessed a homogenously Gaussian sACF. Here we propose a method based on the assumption that heterogeneity and non-Gaussianity of the sACF of the first-level GLM analysis residuals, as well as temporal autocorrelations in the first-level voxel residual time-series, are caused by unmodeled MRI signal from neuronal and physiological processes as well as motion and other artifacts, which can be approximated by appropriate decompositions of the first-level residuals with principal component analysis (PCA), and removed. We show that application of this method yields GLM residuals with significantly reduced spatial correlation, nearly Gaussian sACF and uniform spatial smoothness across the brain, thereby allowing valid cluster-based FWE-corrected inferences based on assumption of Gaussian spatial noise. We further show that application of this method renders the voxel time-series of first-level GLM residuals independent, and identically distributed across time (which is a necessary condition for appropriate voxel-level GLM inference), without having to fit ad hoc stochastic colored noise models. Furthermore, the detection power of individual subject brain activation analysis is enhanced. This method will be especially useful for case studies, which rely on first-level GLM analysis inferences.

  7. Left Gastric Vein Visualization with Hepatopetal Flow Information in Healthy Subjects Using Non-Contrast-Enhanced Magnetic Resonance Angiography with Balanced Steady-State Free-Precession Sequence and Time-Spatial Labeling Inversion Pulse.

    Science.gov (United States)

    Furuta, Akihiro; Isoda, Hiroyoshi; Ohno, Tsuyoshi; Ono, Ayako; Yamashita, Rikiya; Arizono, Shigeki; Kido, Aki; Sakashita, Naotaka; Togashi, Kaori

    2018-01-01

    To selectively visualize the left gastric vein (LGV) with hepatopetal flow information by non-contrast-enhanced magnetic resonance angiography under a hypothesis that change in the LGV flow direction can predict the development of esophageal varices; and to optimize the acquisition protocol in healthy subjects. Respiratory-gated three-dimensional balanced steady-state free-precession scans were conducted on 31 healthy subjects using two methods (A and B) for visualizing the LGV with hepatopetal flow. In method A, two time-spatial labeling inversion pulses (Time-SLIP) were placed on the whole abdomen and the area from the gastric fornix to the upper body, excluding the LGV area. In method B, nonselective inversion recovery pulse was used and one Time-SLIP was placed on the esophagogastric junction. The detectability and consistency of LGV were evaluated using the two methods and ultrasonography (US). Left gastric veins by method A, B, and US were detected in 30 (97%), 24 (77%), and 23 (74%) subjects, respectively. LGV flow by US was hepatopetal in 22 subjects and stagnant in one subject. All hepatopetal LGVs by US coincided with the visualized vessels in both methods. One subject with non-visualized LGV in method A showed stagnant LGV by US. Hepatopetal LGV could be selectively visualized by method A in healthy subjects.

  8. 3.0 Tesla high spatial resolution contrast-enhanced magnetic resonance angiography (CE-MRA) of the pulmonary circulation: initial experience with a 32-channel phased array coil using a high relaxivity contrast agent.

    Science.gov (United States)

    Nael, Kambiz; Fenchel, Michael; Krishnam, Mayil; Finn, J Paul; Laub, Gerhard; Ruehm, Stefan G

    2007-06-01

    To evaluate the technical feasibility of high spatial resolution contrast-enhanced magnetic resonance angiography (CE-MRA) with highly accelerated parallel acquisition at 3.0 T using a 32-channel phased array coil, and a high relaxivity contrast agent. Ten adult healthy volunteers (5 men, 5 women, aged 21-66 years) underwent high spatial resolution CE-MRA of the pulmonary circulation. Imaging was performed at 3 T using a 32-channel phase array coil. After intravenous injection of 1 mL of gadobenate dimeglumine (Gd-BOPTA) at 1.5 mL/s, a timing bolus was used to measure the transit time from the arm vein to the main pulmonary artery. Subsequently following intravenous injection of 0.1 mmol/kg of Gd-BOPTA at the same rate, isotropic high spatial resolution data sets (1 x 1 x 1 mm3) CE-MRA of the entire pulmonary circulation were acquired using a fast gradient-recalled echo sequence (TR/TE 3/1.2 milliseconds, FA 18 degrees) and highly accelerated parallel acquisition (GRAPPA x 6) during a 20-second breath hold. The presence of artifact, noise, and image quality of the pulmonary arterial segments were evaluated independently by 2 radiologists. Phantom measurements were performed to assess the signal-to-noise ratio (SNR). Statistical analysis of data was performed by using Wilcoxon rank sum test and 2-sample Student t test. The interobserver variability was tested by kappa coefficient. All studies were of diagnostic quality as determined by both observers. The pulmonary arteries were routinely identified up to fifth-order branches, with definition in the diagnostic range and excellent interobserver agreement (kappa = 0.84, 95% confidence interval 0.77-0.90). Phantom measurements showed significantly lower SNR (P < 0.01) using GRAPPA (17.3 +/- 18.8) compared with measurements without parallel acquisition (58 +/- 49.4). The described 3 T CE-MRA protocol in addition to high T1 relaxivity of Gd-BOPTA provides sufficient SNR to support highly accelerated parallel acquisition

  9. Multiphoton resonances

    International Nuclear Information System (INIS)

    Shore, B.W.

    1977-01-01

    The long-time average of level populations in a coherently-excited anharmonic sequence of energy levels (e.g., an anharmonic oscillator) exhibits sharp resonances as a function of laser frequency. For simple linearly-increasing anharmonicity, each resonance is a superposition of various multiphoton resonances (e.g., a superposition of 3, 5, 7, . . . photon resonances), each having its own characteristic width predictable from perturbation theory

  10. Index modulation for 5G wireless communications

    CERN Document Server

    Wen, Miaowen; Yang, Liuqing

    2017-01-01

    This book presents a thorough examination of index modulation, an emerging 5G modulation technique. It includes representative transmitter and receiver design, optimization, and performance analysis of index modulation in various domains. First, the basic spatial modulation system for the spatial domain is introduced. Then, the development of a generalized pre-coding aided quadrature spatial modulation system as well as a virtual spatial modulation system are presented. For the space-time domain, a range of differential spatial modulation systems are examined, along with the pre-coding design. Both basic and enhanced index modulated OFDM systems for the frequency domain are discussed, focusing on the verification of their strong capabilities in inter-carrier interference mitigation. Finally, key open problems are highlighted and future research directions are considered. Designed for researchers and professionals, this book is essential for anyone working in communications networking, 5G, and system design. A...

  11. Resonant freak microwaves

    International Nuclear Information System (INIS)

    Aguiar, F.M. de

    2011-01-01

    The Helmholtz equation describing transverse magnetic modes in a closed flat microwave resonator with 60 randomly distributed discs is numerically solved. At lower frequencies, the calculated wave intensity spatially distributed obeys the universal Porter-Thomas form if localized modes are excluded. A superposition of resonant modes is shown to lead to rare events of extreme intensities (freak waves) at localized 'hot spots'. The temporally distributed intensity of such a superposition at the center of a hot spot also follows the Porter-Thomas form. Branched modes are found at higher frequencies. The results bear resemblance to recent experiments reported in an open cavity.

  12. Modulation of sphingosine 1-phosphate (S1P) attenuates spatial learning and memory impairments in the valproic acid rat model of autism.

    Science.gov (United States)

    Wu, Hongmei; Zhang, Quanzhi; Gao, Jingquan; Sun, Caihong; Wang, Jia; Xia, Wei; Cao, Yonggang; Hao, Yanqiu; Wu, Lijie

    2018-03-01

    Autism spectrum disorders (ASD) are a set of pervasive neurodevelopmental disorders that manifest in early childhood, and it is growing up to be a major cause of disability in children. However, the etiology and treatment of ASD are not well understood. In our previous study, we found that serum levels of sphingosine 1-phosphate (S1P) were increased significantly in children with autism, indicating that S1P levels may be involved in ASD. The objective of this study was to identify a link between increased levels of S1P and neurobehavioral changes in autism. We utilized a valproic acid (VPA) -induced rat model of autism to evaluate the levels of S1P and the expression of sphingosine kinase (SphK), a key enzyme for S1P production, in serum and hippocampal tissue. Furthermore, we assessed cognitive functional changes and histopathological and neurochemical alterations in VPA-exposed rats after SphK blockade to explore the possible link between increased levels of S1P and neurobehavioral changes in autism. We found that SphK2 and S1P are upregulated in hippocampal tissue from VPA-exposed rats, while pharmacological inhibition of SphK reduced S1P levels, attenuated spatial learning and memory impairments, increased the expression of phosphorylated CaMKII and CREB and autophagy-related proteins, inhibited cytochrome c release, decreased the expression of apoptosis related proteins, and protected against neuronal loss in the hippocampus. We have demonstrated that an increased level of SphK2/S1P is involved in the spatial learning and memory impairments of autism, and this signaling pathway represents a novel therapeutic target and direction for future studies.

  13. Modulations of eye movement patterns by spatial filtering during the learning and testing phases of an old/new face recognition task.

    Science.gov (United States)

    Lemieux, Chantal L; Collin, Charles A; Nelson, Elizabeth A

    2015-02-01

    In two experiments, we examined the effects of varying the spatial frequency (SF) content of face images on eye movements during the learning and testing phases of an old/new recognition task. At both learning and testing, participants were presented with face stimuli band-pass filtered to 11 different SF bands, as well as an unfiltered baseline condition. We found that eye movements varied significantly as a function of SF. Specifically, the frequency of transitions between facial features showed a band-pass pattern, with more transitions for middle-band faces (≈5-20 cycles/face) than for low-band (≈20 cpf) ones. These findings were similar for the learning and testing phases. The distributions of transitions across facial features were similar for the middle-band, high-band, and unfiltered faces, showing a concentration on the eyes and mouth; conversely, low-band faces elicited mostly transitions involving the nose and nasion. The eye movement patterns elicited by low, middle, and high bands are similar to those previous researchers have suggested reflect holistic, configural, and featural processing, respectively. More generally, our results are compatible with the hypotheses that eye movements are functional, and that the visual system makes flexible use of visuospatial information in face processing. Finally, our finding that only middle spatial frequencies yielded the same number and distribution of fixations as unfiltered faces adds more evidence to the idea that these frequencies are especially important for face recognition, and reveals a possible mediator for the superior performance that they elicit.

  14. Readout from iconic memory and selective spatial attention involve similar neural processes.

    Science.gov (United States)

    Ruff, Christian C; Kristjánsson, Arni; Driver, Jon

    2007-10-01

    Iconic memory and spatial attention are often considered separately, but they may have functional similarities. Here we provide functional magnetic resonance imaging evidence for some common underlying neural effects. Subjects judged three visual stimuli in one hemifield of a bilateral array comprising six stimuli. The relevant hemifield for partial report was indicated by an auditory cue, administered either before the visual array (precue, spatial attention) or shortly after the array (postcue, iconic memory). Pre- and postcues led to similar activity modulations in lateral occipital cortex contralateral to the cued side. This finding indicates that readout from iconic memory can have some neural effects similar to those of spatial attention. We also found common bilateral activation of a fronto-parietal network for postcue and precue trials. These neuroimaging data suggest that some common neural mechanisms underlie selective spatial attention and readout from iconic memory. Some differences were also found; compared with precues, postcues led to higher activity in the right middle frontal gyrus.

  15. Optically Modulated Multiband Terahertz Perfect Absorber

    DEFF Research Database (Denmark)

    Seren, Huseyin R.; Keiser, George R.; Cao, Lingyue

    2014-01-01

    response of resonant metamaterials continues to be a challengingendeavor. Resonant perfect absorbers have flourished as one of the mostpromising metamaterial devices with applications ranging from power har-vesting to terahertz imaging. Here, an optically modulated resonant perfectabsorber is presented....... Utilizing photo-excited free carriers in silicon padsplaced in the capacitive gaps of split ring resonators, a dynamically modu-lated perfect absorber is designed and fabricated to operate in reflection.Large modulation depth (38% and 91%) in two absorption bands (with 97%and 92% peak absorption...

  16. Feasibility of magnetic resonance imaging-guided liver stereotactic body radiation therapy: A comparison between modulated tri-cobalt-60 teletherapy and linear accelerator-based intensity modulated radiation therapy.

    Science.gov (United States)

    Kishan, Amar U; Cao, Minsong; Wang, Pin-Chieh; Mikaeilian, Argin G; Tenn, Stephen; Rwigema, Jean-Claude M; Sheng, Ke; Low, Daniel A; Kupelian, Patrick A; Steinberg, Michael L; Lee, Percy

    2015-01-01

    The purpose of this study was to investigate the dosimetric feasibility of liver stereotactic body radiation therapy (SBRT) using a teletherapy system equipped with 3 rotating (60)Co sources (tri-(60)Co system) and a built-in magnetic resonance imager (MRI). We hypothesized tumor size and location would be predictive of favorable dosimetry with tri-(60)Co SBRT. The primary study population consisted of 11 patients treated with SBRT for malignant hepatic lesions whose linear accelerator (LINAC)-based SBRT plans met all mandatory Radiation Therapy Oncology Group (RTOG) 1112 organ-at-risk (OAR) constraints. The secondary study population included 5 additional patients whose plans did not meet the mandatory constraints. Patients received 36 to 60 Gy in 3 to 5 fractions. Tri-(60)Co system SBRT plans were planned with ViewRay system software. All patients in the primary study population had tri-(60)Co SBRT plans that passed all RTOG constraints, with similar planning target volume coverage and OAR doses to LINAC plans. Mean liver doses and V10Gy to the liver, although easily meeting RTOG 1112 guidelines, were significantly higher with tri-(60)Co plans. When the 5 additional patients were included in a univariate analysis, the tri-(60)Co SBRT plans were still equally able to pass RTOG constraints, although they did have inferior ability to pass more stringent liver and kidney constraints (P < .05). A multivariate analysis found the ability of a tri-(60)Co SBRT plan to meet these constraints depended on lesion location and size. Patients with smaller or more peripheral lesions (as defined by distance from the aorta, chest wall, liver dome, and relative lesion volume) were significantly more likely to have tri-(60)Co plans that spared the liver and kidney as well as LINAC plans did (P < .05). It is dosimetrically feasible to perform liver SBRT with a tri-(60)Co system with a built-in MRI. Patients with smaller or more peripheral lesions are more likely to have optimal liver

  17. Ion cyclotron wave excitation by double resonance coupling

    International Nuclear Information System (INIS)

    Fasoli, A.; Good, T.N.; Paris, P.J.; Skiff, F.; Tran, M.Q.

    1990-07-01

    A modulated high frequency wave is used to remotely excite low frequency oscillations in a linear, strongly magnetized plasma column. An electromagnetic wave is launched as an extraordinary mode across the plasma by an external waveguide in the Upper Hybrid frequency regime f=f UH =f ce =8 GHz, with P≤2 W. By frequency modulating (at f FM =1-60 kHz, with f ci ≅30 kHz) the pump wave, the resonant layer is swept radially across the profile and perpendicularly to the field lines at f=f FM . The resulting radial oscillation of the electron linear and non linear pressure can be considered to act as a source term for the ion wave. A localized virtual antenna is thereby created inside the plasma. Measurements of the ion dielectric response (interferograms and perturbed distribution functions) via laser induced fluorescence identify the two branches (forward, or ion-acoustic-like, and backward, or Bernstein, modes) of the electrostatic dispersion relation in the ion cyclotron frequency range. By changing the modulation bandwidth, and thus the spatial excursion of the oscillating resonant layer, a control on the perpendicular wavelength of the excited mode can be exerted. In particular, the possibility of selective excitation of the ion Bernstein wave is demonstrated experimentally. (author) 38 refs., 13 figs

  18. Electrical field excitation in non-uniform plasma by a modulated electron beam

    International Nuclear Information System (INIS)

    Anisimov, I.O.; Borisov, O.A.

    2000-01-01

    Excitation of electric fields due to a modulated electron beam in a warm non-uniform plasma is treated for weak beams in warm plasma. It is shown that the maximum electric field magnitude that is reached near the local plasma resonance point depends significantly on the direction of the electron stream motion. In collisional plasma the magnitude of the Langmuir wave that propagates to the subcritical plasma also depends on the direction of the electron stream motion. The motion of the modulated electron stream front results in beatings between oscillations on the modulation frequency and on the local electron plasma frequencies at the initial moment. Later these beatings damp in the supercritical plasma, whereas in the subcritical plasma they are transformed into spatial beatings between the field of the modulated electron stream and the excited Langmuir wave. (orig.)

  19. Synchrobetatron resonances

    International Nuclear Information System (INIS)

    1977-03-01

    At the 1975 Particle Accelerator Conference it was reported that a class of resonances were observed in SPEAR II that had not appeared before in SPEAR I. While the existence of sideband resonances of the main betatron oscillation frequencies has been previously observed and analyzed, the resonances observed in SPEAR do not appear to be of the same variety. Experiments were performed at SPEAR to identify the mechanism believed to be the most likely explanation. Some of the current experimental knowledge and theoretical views on the source of these resonances are presented

  20. Snake resonances

    International Nuclear Information System (INIS)

    Tepikian, S.

    1988-01-01

    Siberian Snakes provide a practical means of obtaining polarized proton beams in large accelerators. The effect of snakes can be understood by studying the dynamics of spin precession in an accelerator with snakes and a single spin resonance. This leads to a new class of energy independent spin depolarizing resonances, called snake resonances. In designing a large accelerator with snakes to preserve the spin polarization, there is an added constraint on the choice of the vertical betatron tune due to the snake resonances. 11 refs., 4 figs

  1. Linear signal processing using silicon micro-ring resonators

    DEFF Research Database (Denmark)

    Peucheret, Christophe; Ding, Yunhong; Ou, Haiyan

    2012-01-01

    We review our recent achievements on the use of silicon micro-ring resonators for linear optical signal processing applications, including modulation format conversion, phase-to-intensity modulation conversion and waveform shaping.......We review our recent achievements on the use of silicon micro-ring resonators for linear optical signal processing applications, including modulation format conversion, phase-to-intensity modulation conversion and waveform shaping....

  2. Pattern formation in optical resonators

    International Nuclear Information System (INIS)

    Weiss, C O; Larionova, Ye

    2007-01-01

    We review pattern formation in optical resonators. The emphasis is on 'particle-like' structures such as vortices or spatial solitons. On the one hand, similarities impose themselves with other fields of physics (condensed matter, phase transitions, particle physics, fluds/super fluids). On the other hand the feedback is led by the resonator mirrors to bi- and multi-stability of the spatial field structure, which is the basic ingredient for optical information processing. The spatial dimension or the 'parallelism' is the strength of optics compared to electronics (and will have to be employed to fully use the advantages optics offers in information processing). But even in the 'serial' processing tasks of telecoms (e.g. information buffering) spatial resonator solitons can do better than the schemes proposed so far-including 'slow light'. Pattern formation in optical resonators will likely be the key to brain-like information processing like cognition, learning and association; to complement the precise but limited algorithmic capabilities of electronic processing. But even in the short term it will be useful for solving serial optical processing problems. The prospects for technical uses of pattern formation in resonators are one motivation for this research. The fundamental similarities with other fields of physics, on the other hand, inspire transfer of concepts between fields; something that has always proven fruitful for gaining deeper insights or for solving technical problems

  3. Nonlinear resonances

    CERN Document Server

    Rajasekar, Shanmuganathan

    2016-01-01

    This introductory text presents the basic aspects and most important features of various types of resonances and anti-resonances in dynamical systems. In particular, for each resonance, it covers the theoretical concepts, illustrates them with case studies, and reviews the available information on mechanisms, characterization, numerical simulations, experimental realizations, possible quantum analogues, applications and significant advances made over the years. Resonances are one of the most fundamental phenomena exhibited by nonlinear systems and refer to specific realizations of maximum response of a system due to the ability of that system to store and transfer energy received from an external forcing source. Resonances are of particular importance in physical, engineering and biological systems - they can prove to be advantageous in many applications, while leading to instability and even disasters in others. The book is self-contained, providing the details of mathematical derivations and techniques invo...

  4. Superresolution Imaging Using Resonant Multiples

    KAUST Repository

    Guo, Bowen

    2017-12-22

    A resonant multiple is defined as a multiple reflection that revisits the same subsurface location along coincident reflection raypaths. We show that resonant first-order multiples can be migrated with either Kirchhoff or wave-equation migration methods to give images with approximately twice the spatial resolution compared to post-stack primary-reflection images. A moveout-correction stacking method is proposed to enhance the signal-to-noise ratios (SNRs) of the resonant multiples before superresolution migration. The effectiveness of this procedure is validated by synthetic and field data tests.

  5. Superresolution Imaging Using Resonant Multiples

    KAUST Repository

    Guo, Bowen; Schuster, Gerard T.

    2017-01-01

    A resonant multiple is defined as a multiple reflection that revisits the same subsurface location along coincident reflection raypaths. We show that resonant first-order multiples can be migrated with either Kirchhoff or wave-equation migration methods to give images with approximately twice the spatial resolution compared to post-stack primary-reflection images. A moveout-correction stacking method is proposed to enhance the signal-to-noise ratios (SNRs) of the resonant multiples before superresolution migration. The effectiveness of this procedure is validated by synthetic and field data tests.

  6. Parametric effect of a spatially periodic voltage depression on operation of Cerenkov sources of electromagnetic radiation

    International Nuclear Information System (INIS)

    Nusinovich, G.S.; Vlasov, A.N.

    1994-01-01

    In microwave sources of coherent Cerenkov radiation the electrons usually propagate near the rippled wall of a slow-wave structure. These ripples cause the periodic modulation of electron potential depression, and therefore, lead to periodic modulation of electron axial velocities. Since the period of this electrostatic pumping is the period of the slow-wave structure the parametric coupling of electrons to originally nonsynchronous spatial harmonics of the microwave field may occur. This effect can be especially important for backward-wave oscillators (BWO's) driven by high current, relativistic electron beams. In the paper both linear and nonlinear theories of the relativistic resonant BWO with periodic modulation of electron axial velocities are developed and results illustrating the evolution of the linear gain function and the efficiency of operation in the large-signal regime are presented

  7. Discontinuous conduction mode analysis of phase-modulated series ...

    Indian Academy of Sciences (India)

    modulated dc–dc series resonant converter (SRC) operating in discontinuous conduction mode (DCM). The conventional fundamental harmonic approximation technique is extended for a non-ideal series resonant tank to clarify the limitations of ...

  8. Electron spin resonance and electron spin echo modulation studies of Cu(II) ions in the aluminosilicate chabazite: A comparison of Cu(II) cation location and adsorbate interaction with isostructural silicoaluminophosphate-34

    International Nuclear Information System (INIS)

    Zamadics, M.; Kevan, L.

    1992-01-01

    This study focuses on Cu(II) ions exchanged in the aluminosilicate zeolite chabazite. The various Cu(II) species formed after dehydration, rehydration, and exposure to adsorbates are characterized by electron spin resonance and electron spin echo modulation spectroscopies. These results are interpreted in terms of Cu(II) ion location and adsorbate interaction. The results of this study are compared to the results found earlier for SAPO-34, chabazite's structural analog from the silicoaluminophosphate group. In a hydrated sample of chabazite the Cu(II) ions are found to be in a near octahedral environment coordinated to three nonequivalent water molecules and three framework oxygens. The most probable location of the Cu(II) ion in a hydrated sample is above the plane of the six-membered ring slightly displaced into the ellipsoidal cavity. A somewhat similar location and coordination is found for Cu(II) ions in H-SAPO-34. A feature common to both CuH-chabazite and CuH-SAPO-34 is the generation of two distinct Cu(II) species upon dehydration. It is found that Cu(II) cations in chabazite interact with the various adsorbate molecules in a similar manner as Cu(II) cation in H-chabazite and three molecules of ethanol and three propanol molecules. Only the Cu(II) ions located in the hexagonal rings after dehydration were found to complex with ethylene. The differences observed in the interaction of the Cu(II) in with water, propanol, and ehtylene between SAPO-34 and chabazite can be related to the differing cation densities of these two materials. 32 refs., 7 figs., 21 tabs

  9. Measurement of large nonlinear refractive index of natural pigment extracted from Hibiscus rosa-sinensis leaves with a low power CW laser and by spatial self-phase modulation technique

    Science.gov (United States)

    Biswas, S.; Kumbhakar, P.

    2017-02-01

    We have reported here, for the first time, to the best of our knowledge, a high nonlinear refractive index (n2e) of a natural pigment extracted from Hibiscus rosa-sinensis leaves by using spatial self-phase modulation technique (SSPM) with a low power CW He-Ne laser radiation at 632.8 nm. It is found by UV-Vis absorption spectroscopic analysis that chlrophyll-a, chlrophyll-b and carotenoid are present in the pigment extract with 56%, 25% and 19%, respectively. The photoluminescence (PL) emission characteristics of the extracted samples have also been measured at room temperature as well as in the temperature range of 283-333 K to investigate the effect of temperature on luminescent properties of the sample. By analyzing the SSPM experimental data, the nonlinear refractive index value of pigment extract has been determined to be 3.5 × 10- 5 cm2/W. The large nonlinear refractive index has been assigned due to asymmetrical structure, molecular reorientation and thermally induced nonlinearity in the sample. The presented results might open new avenues for the green and economical technique of syntheses of organic dyes with such a large nonlinear optical property.

  10. Tuning Fano Resonances with Graphene

    DEFF Research Database (Denmark)

    Emani, Naresh K.; Chung, Ting-Fung; Prokopeva, Ludmila

    2013-01-01

    We demonstrate strong electrical control of plasmonic Fano resonances in dolmen structures using tunable interband transitions in graphene. Such graphene-plasmonic hybrid devices can have applications in light modulation and sensing. OCIS codes: (250.5403) Plasmonics; (160.4670) Optical materials...

  11. Switching management in couplers with biharmonic longitudinal modulation of refractive index

    OpenAIRE

    Kartashov, Yaroslav V.; Vysloukh, Victor A.

    2009-01-01

    We address light propagation in couplers with longitudinal biharmonic modulation of refractive index in neighboring channels. While simplest single-frequency out-of-phase modulation allows suppression of coupling for strictly defined set of resonant frequencies, the addition of modulation on multiple frequency dramatically modifies the structure of resonances. Thus, additional modulation on double frequency may suppress primary resonance, while modulation on triple frequency causes fusion of ...

  12. Efficient primary and parametric resonance excitation of bistable resonators

    KAUST Repository

    Ramini, Abdallah

    2016-09-12

    We experimentally demonstrate an efficient approach to excite primary and parametric (up to the 4th) resonance of Microelectromechanical system MEMS arch resonators with large vibrational amplitudes. A single crystal silicon in-plane arch microbeam is fabricated such that it can be excited axially from one of its ends by a parallel-plate electrode. Its micro/nano scale vibrations are transduced using a high speed camera. Through the parallel-plate electrode, a time varying electrostatic force is applied, which is converted into a time varying axial force that modulates dynamically the stiffness of the arch resonator. Due to the initial curvature of the structure, not only parametric excitation is induced, but also primary resonance. Experimental investigation is conducted comparing the response of the arch near primary resonance using the axial excitation to that of a classical parallel-plate actuation where the arch itself forms an electrode. The results show that the axial excitation can be more efficient and requires less power for primary resonance excitation. Moreover, unlike the classical method where the structure is vulnerable to the dynamic pull-in instability, the axial excitation technique can provide large amplitude motion while protecting the structure from pull-in. In addition to primary resonance, parametrical resonances are demonstrated at twice, one-half, and two-thirds the primary resonance frequency. The ability to actuate primary and/or parametric resonances can serve various applications, such as for resonator based logic and memory devices. (C) 2016 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license

  13. DIELECTRIC WAKE FIELD RESONATOR ACCELERATOR MODULE

    Energy Technology Data Exchange (ETDEWEB)

    Hirshfield, Jay L.

    2013-11-06

    Results are presented from experiments, and numerical analysis of wake fields set up by electron bunches passing through a cylindrical or rectangular dielectric-lined structure. These bunches excite many TM-modes, with Ez components of the wake fields sharply localized on the axis of the structure periodically behind the bunches. The experiment with the cylindrical structure, carried out at ATF Brookhaven National Laboratory, used up to three 50 MeV bunches spaced by one wake field period (21 cm) to study the superposition of wake fields by measuring the energy loss of each bunch after it passed through the 53-cm long dielectric element. The millimeter-wave spectrum of radiation excited by the passage of bunches is also studied. Numerical analysis was aimed not only to simulate the behavior of our device, but in general to predict dielectric wake field accelerator performance. It is shown that one needs to match the radius of the cylindrical dielectric channel with the bunch longitudinal rms-length to achieve optimal performance.

  14. Cross-Modulation Interference with Lateralization of Mixed-Modulated Waveforms

    Science.gov (United States)

    Hsieh, I-Hui; Petrosyan, Agavni; Goncalves, Oscar F.; Hickok, Gregory; Saberi, Kourosh

    2010-01-01

    Purpose: This study investigated the ability to use spatial information in mixed-modulated (MM) sounds containing concurrent frequency-modulated (FM) and amplitude-modulated (AM) sounds by exploring patterns of interference when different modulation types originated from different loci as may occur in a multisource acoustic field. Method:…

  15. Low field magnetic resonance imaging

    Science.gov (United States)

    Pines, Alexander; Sakellariou, Dimitrios; Meriles, Carlos A.; Trabesinger, Andreas H.

    2010-07-13

    A method and system of magnetic resonance imaging does not need a large homogenous field to truncate a gradient field. Spatial information is encoded into the spin magnetization by allowing the magnetization to evolve in a non-truncated gradient field and inducing a set of 180 degree rotations prior to signal acquisition.

  16. Nanotube resonator devices

    Science.gov (United States)

    Jensen, Kenneth J; Zettl, Alexander K; Weldon, Jeffrey A

    2014-05-06

    A fully-functional radio receiver fabricated from a single nanotube is being disclosed. Simultaneously, a single nanotube can perform the functions of all major components of a radio: antenna, tunable band-pass filter, amplifier, and demodulator. A DC voltage source, as supplied by a battery, can power the radio. Using carrier waves in the commercially relevant 40-400 MHz range and both frequency and amplitude modulation techniques, successful music and voice reception has been demonstrated. Also disclosed are a radio transmitter and a mass sensor using a nanotube resonator device.

  17. Accelerating two-dimensional nuclear magnetic resonance correlation spectroscopy via selective coherence transfer

    Science.gov (United States)

    Ye, Qimiao; Chen, Lin; Qiu, Wenqi; Lin, Liangjie; Sun, Huijun; Cai, Shuhui; Wei, Zhiliang; Chen, Zhong

    2017-01-01

    Nuclear magnetic resonance (NMR) spectroscopy serves as an important tool for both qualitative and quantitative analyses of various systems in chemistry, biology, and medicine. However, applications of one-dimensional 1H NMR are often restrained by the presence of severe overlap among different resonances. The advent of two-dimensional (2D) 1H NMR constitutes a promising alternative by extending the crowded resonances into a plane and thereby alleviating the spectral congestions. However, the enhanced ability in discriminating resonances is achieved at the cost of extended experimental duration due to necessity of various scans with progressive delays to construct the indirect dimension. Therefore, in this study, we propose a selective coherence transfer (SECOT) method to accelerate acquisitions of 2D correlation spectroscopy by converting chemical shifts into spatial positions within the effective sample length and then performing an echo planar spectroscopic imaging module to record the spatial and spectral information, which generates 2D correlation spectrum after 2D Fourier transformation. The feasibility and effectiveness of SECOT have been verified by a set of experiments under both homogeneous and inhomogeneous magnetic fields. Moreover, evaluations of SECOT for quantitative analyses are carried out on samples with a series of different concentrations. Based on these experimental results, the SECOT may open important perspectives for fast, accurate, and stable investigations of various chemical systems both qualitatively and quantitatively.

  18. Laser trapping and spatial light modulators

    DEFF Research Database (Denmark)

    Glückstad, Jesper

    2012-01-01

    INVITED: Robotics at the macro-scale typically uses light for carrying information in machine vision for monitoring and feedback in intelligent robotic guidance systems. With light’s miniscule momentum, shrinking robots down to the micro-scale regime creates opportunities for exploiting optical f...

  19. Resonance detection of Moessbauer radiation

    International Nuclear Information System (INIS)

    Morozov, V.V.

    1985-01-01

    The resonance detection method as compared with the usual method of registering Moessbauer spectra has a number of advantages, one of which is the increase of resolution of the Moessbauer spectrum. The method is based on the modulation of a secondary radiation of a converter tuned in the resonance with the Moessbauer gamma-quantum source. The resonance detection method with account of supression, secondary radiation outgoing from the converter is investigated. The converter represents a substrate enriched by the Moessbauer isotope placed either inside the gas counter, or coupled with any other detecting device. Analytical expressions for Moessbauer spectrum parameters: effect, area and width of the spectral line are derived. It is shown that the joint application of usual and resonance detection methods for registering the Moessbauer spectrum allows one to determine parameters of the source, converter and the investigated absorber

  20. Resonances for coupled Bose-Einstein condensates

    International Nuclear Information System (INIS)

    Haroutyunyan, H.L.; Nienhuis, G.

    2004-01-01

    The properties of a Bose-Einstein condensate in a two-well potential can be manipulated by periodic modulation of the potential parameters. We study the effects arising from modulating the barrier height and the difference in well depth. At certain modulation frequencies the system exhibits resonances, which may show up in an enhancement of the tunneling rate between the wells. Resonances can be used to control the particle distribution over the wells. Some of the effects occurring in the two-well system also arise for a Bose-Einstein condensate in an optical lattice

  1. Cortical and Subcortical Coordination of Visual Spatial Attention Revealed by Simultaneous EEG-fMRI Recording.

    Science.gov (United States)

    Green, Jessica J; Boehler, Carsten N; Roberts, Kenneth C; Chen, Ling-Chia; Krebs, Ruth M; Song, Allen W; Woldorff, Marty G

    2017-08-16

    Visual spatial attention has been studied in humans with both electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) individually. However, due to the intrinsic limitations of each of these methods used alone, our understanding of the systems-level mechanisms underlying attentional control remains limited. Here, we examined trial-to-trial covariations of concurrently recorded EEG and fMRI in a cued visual spatial attention task in humans, which allowed delineation of both the generators and modulators of the cue-triggered event-related oscillatory brain activity underlying attentional control function. The fMRI activity in visual cortical regions contralateral to the cued direction of attention covaried positively with occipital gamma-band EEG, consistent with activation of cortical regions representing attended locations in space. In contrast, fMRI activity in ipsilateral visual cortical regions covaried inversely with occipital alpha-band oscillations, consistent with attention-related suppression of the irrelevant hemispace. Moreover, the pulvinar nucleus of the thalamus covaried with both of these spatially specific, attention-related, oscillatory EEG modulations. Because the pulvinar's neuroanatomical geometry makes it unlikely to be a direct generator of the scalp-recorded EEG, these covariational patterns appear to reflect the pulvinar's role as a regulatory control structure, sending spatially specific signals to modulate visual cortex excitability proactively. Together, these combined EEG/fMRI results illuminate the dynamically interacting cortical and subcortical processes underlying spatial attention, providing important insight not realizable using either method alone. SIGNIFICANCE STATEMENT Noninvasive recordings of changes in the brain's blood flow using functional magnetic resonance imaging and electrical activity using electroencephalography in humans have individually shown that shifting attention to a location in space

  2. Multiquark Resonances

    CERN Document Server

    Esposito, A.; Polosa, A.D.

    2016-01-01

    Multiquark resonances are undoubtedly experimentally observed. The number of states and the amount of details on their properties has been growing over the years. It is very recent the discovery of two pentaquarks and the confirmation of four tetraquarks, two of which had not been observed before. We mainly review the theoretical understanding of this sector of particle physics phenomenology and present some considerations attempting a coherent description of the so called X and Z resonances. The prominent problems plaguing theoretical models, like the absence of selection rules limiting the number of states predicted, motivate new directions in model building. Data are reviewed going through all of the observed resonances with particular attention to their common features and the purpose of providing a starting point to further research.

  3. Neuroaesthetic Resonance

    DEFF Research Database (Denmark)

    Brooks, Anthony Lewis

    2013-01-01

    Neuroaesthetic Resonance emerged from a mature body of patient- centered gesture-control research investigating non-formal rehabilitation via ICT-enhanced-Art to question ‘Aesthetic Resonance’. Motivating participation, ludic engagement, and augmenting physical motion in non-formal (fun) treatment...... sessions are achieved via adaptive action-analyzed activities. These interactive virtual environments are designed to empower patients’ creative and/or playful expressions via digital feedback stimuli. Unconscious self- pushing of limits result from innate distractive mechanisms offered by the alternative...... the unencumbered motion-to-computer-generated activities - ‘Music Making’, ‘Painting’, ‘Robotic’ and ‘Video Game’ control. A focus of this position paper is to highlight how Aesthetic Resonance, in this context, relates to the growing body of research on Neuroaesthetics to evolve Neuroaesthetic Resonance....

  4. Cervical Gross Tumor Volume Dose Predicts Local Control Using Magnetic Resonance Imaging/Diffusion-Weighted Imaging—Guided High-Dose-Rate and Positron Emission Tomography/Computed Tomography—Guided Intensity Modulated Radiation Therapy

    Energy Technology Data Exchange (ETDEWEB)

    Dyk, Pawel; Jiang, Naomi; Sun, Baozhou; DeWees, Todd A. [Department of Radiation Oncology, Washington University School of Medicine, St Louis, Missouri (United States); Fowler, Kathryn J.; Narra, Vamsi [Department of Diagnostic Radiology, Mallinckrodt Institute of Radiology, Washington University School of Medicine, St Louis, Missouri (United States); Garcia-Ramirez, Jose L.; Schwarz, Julie K. [Department of Radiation Oncology, Washington University School of Medicine, St Louis, Missouri (United States); Grigsby, Perry W., E-mail: pgrigsby@wustl.edu [Department of Radiation Oncology, Washington University School of Medicine, St Louis, Missouri (United States); Division of Nuclear Medicine, Mallinckrodt Institute of Radiology, Washington University School of Medicine, St Louis, Missouri (United States); Division of Gynecologic Oncology, Mallinckrodt Institute of Radiology, Washington University School of Medicine, St Louis, Missouri (United States); Alvin J. Siteman Cancer Center, Washington University School of Medicine, St Louis, Missouri (United States)

    2014-11-15

    Purpose: Magnetic resonance imaging/diffusion weighted-imaging (MRI/DWI)-guided high-dose-rate (HDR) brachytherapy and {sup 18}F-fluorodeoxyglucose (FDG) — positron emission tomography/computed tomography (PET/CT)-guided intensity modulated radiation therapy (IMRT) for the definitive treatment of cervical cancer is a novel treatment technique. The purpose of this study was to report our analysis of dose-volume parameters predicting gross tumor volume (GTV) control. Methods and Materials: We analyzed the records of 134 patients with International Federation of Gynecology and Obstetrics stages IB1-IVB cervical cancer treated with combined MRI-guided HDR and IMRT from July 2009 to July 2011. IMRT was targeted to the metabolic tumor volume and lymph nodes by use of FDG-PET/CT simulation. The GTV for each HDR fraction was delineated by use of T2-weighted or apparent diffusion coefficient maps from diffusion-weighted sequences. The D100, D90, and Dmean delivered to the GTV from HDR and IMRT were summed to EQD2. Results: One hundred twenty-five patients received all irradiation treatment as planned, and 9 did not complete treatment. All 134 patients are included in this analysis. Treatment failure in the cervix occurred in 24 patients (18.0%). Patients with cervix failures had a lower D100, D90, and Dmean than those who did not experience failure in the cervix. The respective doses to the GTV were 41, 58, and 136 Gy for failures compared with 67, 99, and 236 Gy for those who did not experience failure (P<.001). Probit analysis estimated the minimum D100, D90, and Dmean doses required for ≥90% local control to be 69, 98, and 260 Gy (P<.001). Conclusions: Total dose delivered to the GTV from combined MRI-guided HDR and PET/CT-guided IMRT is highly correlated with local tumor control. The findings can be directly applied in the clinic for dose adaptation to maximize local control.

  5. Baryon Resonances

    International Nuclear Information System (INIS)

    Oset, E.; Sarkar, S.; Sun Baoxi; Vicente Vacas, M.J.; Ramos, A.; Gonzalez, P.; Vijande, J.; Martinez Torres, A.; Khemchandani, K.

    2010-01-01

    In this talk I show recent results on how many excited baryon resonances appear as systems of one meson and one baryon, or two mesons and one baryon, with the mesons being either pseudoscalar or vectors. Connection with experiment is made including a discussion on old predictions and recent results for the photoproduction of the Λ(1405) resonance, as well as the prediction of one 1/2 + baryon state around 1920 MeV which might have been seen in the γp→K + Λ reaction.

  6. Spatial Operations

    Directory of Open Access Journals (Sweden)

    Anda VELICANU

    2010-09-01

    Full Text Available This paper contains a brief description of the most important operations that can be performed on spatial data such as spatial queries, create, update, insert, delete operations, conversions, operations on the map or analysis on grid cells. Each operation has a graphical example and some of them have code examples in Oracle and PostgreSQL.

  7. Spatializing Time

    DEFF Research Database (Denmark)

    Thomsen, Bodil Marie Stavning

    2011-01-01

    The article analyses some of artist Søren Lose's photographic installations in which time, history and narration is reflected in the creation of allegoric, spatial relations.......The article analyses some of artist Søren Lose's photographic installations in which time, history and narration is reflected in the creation of allegoric, spatial relations....

  8. Spatial Computation

    Science.gov (United States)

    2003-12-01

    Computation and today’s microprocessors with the approach to operating system architecture, and the controversy between microkernels and monolithic kernels...Both Spatial Computation and microkernels break away a relatively monolithic architecture into in- dividual lightweight pieces, well specialized...for their particular functionality. Spatial Computation removes global signals and control, in the same way microkernels remove the global address

  9. 996 RESONANCE November 2013

    Indian Academy of Sciences (India)

    IAS Admin

    996. RESONANCE. November 2013. Page 2. 997. RESONANCE. November 2013. Page 3. 998. RESONANCE. November 2013. Page 4. 999. RESONANCE. November 2013. Page 5. 1000. RESONANCE. November 2013. Page 6. 1001. RESONANCE. November 2013. Page 7. 1002. RESONANCE. November 2013 ...

  10. 817 RESONANCE September 2013

    Indian Academy of Sciences (India)

    IAS Admin

    817. RESONANCE ⎜ September 2013. Page 2. 818. RESONANCE ⎜ September 2013. Page 3. 819. RESONANCE ⎜ September 2013. Page 4. 820. RESONANCE ⎜ September 2013. Page 5. 821. RESONANCE ⎜ September 2013. Page 6. 822. RESONANCE ⎜ September 2013. Page 7. 823. RESONANCE ⎜ September ...

  11. 369 RESONANCE April 2016

    Indian Academy of Sciences (India)

    IAS Admin

    369. RESONANCE ⎜ April 2016. Page 2. 370. RESONANCE ⎜ April 2016. Page 3. 371. RESONANCE ⎜ April 2016. Page 4. 372. RESONANCE ⎜ April 2016. Page 5. 373. RESONANCE ⎜ April 2016. Page 6. 374. RESONANCE ⎜ April 2016. Page 7. 375. RESONANCE ⎜ April 2016.

  12. Off-resonance artifacts correction with convolution in k-space (ORACLE).

    Science.gov (United States)

    Lin, Wei; Huang, Feng; Simonotto, Enrico; Duensing, George R; Reykowski, Arne

    2012-06-01

    Off-resonance artifacts hinder the wider applicability of echo-planar imaging and non-Cartesian MRI methods such as radial and spiral. In this work, a general and rapid method is proposed for off-resonance artifacts correction based on data convolution in k-space. The acquired k-space is divided into multiple segments based on their acquisition times. Off-resonance-induced artifact within each segment is removed by applying a convolution kernel, which is the Fourier transform of an off-resonance correcting spatial phase modulation term. The field map is determined from the inverse Fourier transform of a basis kernel, which is calibrated from data fitting in k-space. The technique was demonstrated in phantom and in vivo studies for radial, spiral and echo-planar imaging datasets. For radial acquisitions, the proposed method allows the self-calibration of the field map from the imaging data, when an alternating view-angle ordering scheme is used. An additional advantage for off-resonance artifacts correction based on data convolution in k-space is the reusability of convolution kernels to images acquired with the same sequence but different contrasts. Copyright © 2011 Wiley-Liss, Inc.

  13. Force detection of nuclear magnetic resonance

    International Nuclear Information System (INIS)

    Rugar, D.; Zueger, O.; Hoen, S.; Yannoni, C.S.; Vieth, H.M.; Kendrick, R.D.

    1994-01-01

    Micromechanical sensing of magnetic force was used to detect nuclear magnetic resonance with exceptional sensitivity and spatial resolution. With a 900 angstrom thick silicon nitride cantilever capable of detecting subfemtonewton forces, a single shot sensitivity of 1.6 x 10 13 protons was achieved for an ammonium nitrate sample mounted on the cantilever. A nearby millimeter-size iron particle produced a 600 tesla per meter magnetic field gradient, resulting in a spatial resolution of 2.6 micrometers in one dimension. These results suggest that magnetic force sensing is a viable approach for enhancing the sensitivity and spatial resolution of nuclear magnetic resonance microimaging

  14. Synchrobetatron resonances

    International Nuclear Information System (INIS)

    Anon.

    1977-01-01

    At the 1975 Particle Accelerator Conference it was reported that a class of resonances were observed in SPEAR II that had not appeared before in SPEAR I. These resonances occur when the betatron oscillation wave numbers ν/sub x/ or ν/sub y/ and the synchrotron wave number ν/sub s/ satisfy the relation (ν/sub x,y/ - mν/sub s/) = 5, with m an integer denoting the m/sup th/ satellite. The main difference between SPEAR II and SPEAR I is the value of ν/sub s/, which in SPEAR II is approximately 0.04, an order of magnitude larger than in SPEAR I. An ad hoc meeting was held at the 1975 Particle Accelerator Conference, where details of the SPEAR II results were presented and various possible mechanisms for producing these resonances were discussed. Later, experiments were performed at SPEAR to identify the mechanism believed to be the most likely explanation. Some of the current experimental knowledge and theoretical views on the source of these resonances are presented

  15. Autostereogram resonators

    Science.gov (United States)

    Leavey, Sean; Rae, Katherine; Murray, Adam; Courtial, Johannes

    2012-09-01

    Autostereograms, or "Magic Eye" pictures, are repeating patterns designed to give the illusion of depth. Here we discuss optical resonators that create light patterns which, when viewed from a suitable position by a monocular observer, are autostereograms of the three-dimensional shape of one of the mirror surfaces.

  16. Profile inversion of principal diffusivities through the use of a spatially modulated heating and a Fourier analysis; Inversion des profils des diffusivites principales par l'application d'un chauffage spatialement module et une analyse dans le domaine de Fourier

    Energy Technology Data Exchange (ETDEWEB)

    Krapez, J.C.; Spagnolo, L. [Politechnique di Bari (Italy); Friess, M. [Deutsches Luft- und Raumfahrtzentrum eV (DLR), Stuttgart (Germany); Maier, H.P. [Stuttgart Univ., MPA (Germany); Neuer, G. [Institut fur Kernenergetik und Energiesysteme, Universitat Stuttgart (Germany)

    2003-07-01

    The through-thickness thermal diffusivity can be evaluated by the classical flash method. If an homogeneous and extended source is used to irradiate the surface and a thermographic camera is used to monitor the temperature evolution of the opposite side, a map of the through-thickness thermal diffusivity can be obtained in a single experiment and without any contact with the sample under inspection. In order to measure the in-plane thermal diffusivity of a plate-like sample or in one of the principal directions of its plane, a thermal gradient across the plane of the material has to be settled. The ratio of the Fourier transform of temperature at two different spatial frequencies is an exponential function of time multiplied by the diffusivity in the considered principal direction. This can be used to evaluate the diffusivity in an homogenous material. In order to maximize the signal-to-noise ratio, it is better if heat is absorbed over a series of periodic parallel strips (grid flash method). When the material presents a transverse gradient of conductivity, we propose, as a first approach, to perform the Fourier analysis over a sliding window corresponding to one period of the grid pattern. This method allowed us to quantify in situ the diffusivity decrease in a tensile composite sample due to the stress-induced density increase of transverse microcracks. We finally analysed a more rigorous method for transverse conductivity profile inversion. It is based on a perturbation method. The analytical expression of the 'transfer function' between the Fourier transform of the temperature contrast and the Fourier transform of conductivity was established. We validated the proposed inverse technique on simulated and noise-corrupted thermograms. The approach is robust and the simulated profiles are very well resolved. (authors)

  17. Parametric resonance and cooling on an atom chip

    International Nuclear Information System (INIS)

    Yan Bo; Li Xiaolin; Ke Min; Wang Yuzhu

    2008-01-01

    This paper observes the parametric excitation on atom chip by measuring the trap loss when applying a parametric modulation. By modulating the current in chip wires, it modulates not only the trap frequency but also the trap position. It shows that the strongest resonance occurs when the modulation frequency equals to the trap frequency. The resonance amplitude increases exponentially with modulation depth. Because the Z-trap is an anharmonic trap, there exists energy selective excitation which would cause parametric cooling. We confirm this effect by observing the temperature of atom cloud dropping

  18. What's Behind a "+" Sign? Perceiving an Arithmetic Operator Recruits Brain Circuits for Spatial Orienting.

    Science.gov (United States)

    Mathieu, Romain; Epinat-Duclos, Justine; Sigovan, Monica; Breton, Audrey; Cheylus, Anne; Fayol, Michel; Thevenot, Catherine; Prado, Jérôme

    2018-05-01

    Do mathematical symbols evoke spatial representations? Although behavioral studies have long demonstrated interactions between space and the processing of Arabic digits, how to interpret these results remains controversial. Here, we tested whether activity in regions supporting spatial processing contributes to the processing of symbols conveying fundamental arithmetic concepts-such as operation signs-even in the absence of associated digits. Using functional magnetic resonance imaging, we show that merely perceiving a "+" sign triggers activity in brain regions that support the orienting of spatial attention in adults. Activity in these regions was greater for "+" than for "×" signs, indicating that it is modulated by whether an operator reflects an operation that evokes numerical manipulation (rather than rote memorization). Finally, the degree to which subjects activated a spatial region in response to a "+" sign was correlated with the degree to which subjects benefited from being briefly presented with that sign before having to calculate a single-digit addition problem, an effect termed operator-priming. Therefore, not only are some arithmetic operators linked to spatial intuitions, but such intuitions might also have an important role during arithmetic calculation. More generally, our findings support the view that mathematical symbols inherently evoke spatial representations.

  19. Spatial Theography

    OpenAIRE

    van Noppen, Jean Pierre

    1995-01-01

    Descriptive theology («theography») frequently resorts to metaphorical modes of meaning. Among these metaphors, the spatial language of localization and orientation plays an important role to delineate tentative insights into the relationship between the human and the divine. These spatial metaphors are presumably based on the universal human experience of interaction between the body and its environment. It is dangerous, however, to postulate universal agreement on meanings associated with s...

  20. Resonating Statements

    DEFF Research Database (Denmark)

    Hjelholt, Morten; Jensen, Tina Blegind

    2015-01-01

    IT projects are often complex arrangements of technological components, social actions, and organizational transformation that are difficult to manage in practice. This paper takes an analytical discourse perspective to explore the process of legitimizing IT projects. We introduce the concept...... of resonating statements to highlight how central actors navigate in various discourses over time. Particularly, the statements and actions of an IT project manager are portrayed to show how individuals can legitimize actions by connecting statements to historically produced discourses. The case study...... as part of a feedback loop to re-attach the localized IT project to the broader national discourse. The paper concludes with reflections on how to actively build on resonating statements as a strategic resource for legitimizing IT projects...