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Sample records for 2d particle arrays

  1. Multienzyme Inkjet Printed 2D Arrays.

    PubMed

    Gdor, Efrat; Shemesh, Shay; Magdassi, Shlomo; Mandler, Daniel

    2015-08-19

    The use of printing to produce 2D arrays is well established, and should be relatively facile to adapt for the purpose of printing biomaterials; however, very few studies have been published using enzyme solutions as inks. Among the printing technologies, inkjet printing is highly suitable for printing biomaterials and specifically enzymes, as it offers many advantages. Formulation of the inkjet inks is relatively simple and can be adjusted to a variety of biomaterials, while providing nonharmful environment to the enzymes. Here we demonstrate the applicability of inkjet printing for patterning multiple enzymes in a predefined array in a very straightforward, noncontact method. Specifically, various arrays of the enzymes glucose oxidase (GOx), invertase (INV) and horseradish peroxidase (HP) were printed on aminated glass surfaces, followed by immobilization using glutardialdehyde after printing. Scanning electrochemical microscopy (SECM) was used for imaging the printed patterns and to ascertain the enzyme activity. The successful formation of 2D arrays consisting of enzymes was explored as a means of developing the first surface confined enzyme based logic gates. Principally, XOR and AND gates, each consisting of two enzymes as the Boolean operators, were assembled, and their operation was studied by SECM. PMID:26214072

  2. 2D Electrostatic Actuation of Microshutter Arrays

    NASA Technical Reports Server (NTRS)

    Burns, Devin E.; Oh, Lance H.; Li, Mary J.; Jones, Justin S.; Kelly, Daniel P.; Zheng, Yun; Kutyrev, Alexander S.; Moseley, Samuel H.

    2015-01-01

    An electrostatically actuated microshutter array consisting of rotational microshutters (shutters that rotate about a torsion bar) were designed and fabricated through the use of models and experiments. Design iterations focused on minimizing the torsional stiffness of the microshutters, while maintaining their structural integrity. Mechanical and electromechanical test systems were constructed to measure the static and dynamic behavior of the microshutters. The torsional stiffness was reduced by a factor of four over initial designs without sacrificing durability. Analysis of the resonant behavior of the microshutter arrays demonstrates that the first resonant mode is a torsional mode occurring around 3000 Hz. At low vacuum pressures, this resonant mode can be used to significantly reduce the drive voltage necessary for actuation requiring as little as 25V. 2D electrostatic latching and addressing was demonstrated using both a resonant and pulsed addressing scheme.

  3. 2D Electrostatic Actuation of Microshutter Arrays

    NASA Technical Reports Server (NTRS)

    Burns, Devin E.; Oh, Lance H.; Li, Mary J.; Kelly, Daniel P.; Kutyrev, Alexander S.; Moseley, Samuel H.

    2015-01-01

    Electrostatically actuated microshutter arrays consisting of rotational microshutters (shutters that rotate about a torsion bar) were designed and fabricated through the use of models and experiments. Design iterations focused on minimizing the torsional stiffness of the microshutters, while maintaining their structural integrity. Mechanical and electromechanical test systems were constructed to measure the static and dynamic behavior of the microshutters. The torsional stiffness was reduced by a factor of four over initial designs without sacrificing durability. Analysis of the resonant behavior of the microshutters demonstrates that the first resonant mode is a torsional mode occurring around 3000 Hz. At low vacuum pressures, this resonant mode can be used to significantly reduce the drive voltage necessary for actuation requiring as little as 25V. 2D electrostatic latching and addressing was demonstrated using both a resonant and pulsed addressing scheme.

  4. Focusing surface wave imaging with flexible 2D array

    NASA Astrophysics Data System (ADS)

    Zhou, Shiyuan; Fu, Junqiang; Li, Zhe; Xu, Chunguang; Xiao, Dingguo; Wang, Shaohan

    2016-04-01

    Curved surface is widely exist in key parts of energy and power equipment, such as, turbine blade cylinder block and so on. Cycling loading and harsh working condition of enable fatigue cracks appear on the surface. The crack should be found in time to avoid catastrophic damage to the equipment. A flexible 2D array transducer was developed. 2D Phased Array focusing method (2DPA), Mode-Spatial Double Phased focusing method (MSDPF) and the imaging method using the flexible 2D array probe are studied. Experiments using these focusing and imaging method are carried out. Surface crack image is obtained with both 2DPA and MSDPF focusing method. It have been proved that MSDPF can be more adaptable for curved surface and more calculate efficient than 2DPA.

  5. 2-D scalable optical controlled phased-array antenna system

    NASA Astrophysics Data System (ADS)

    Chen, Maggie Yihong; Howley, Brie; Wang, Xiaolong; Basile, Panoutsopoulos; Chen, Ray T.

    2006-02-01

    A novel optoelectronically-controlled wideband 2-D phased-array antenna system is demonstrated. The inclusion of WDM devices makes a highly scalable system structure. Only (M+N) delay lines are required to control a M×N array. The optical true-time delay lines are combination of polymer waveguides and optical switches, using a single polymeric platform and are monolithically integrated on a single substrate. The 16 time delays generated by the device are measured to range from 0 to 175 ps in 11.6 ps. Far-field patterns at different steering angles in X-band are measured.

  6. Antiferromagnetism in 2D arrays of superconducting rings

    NASA Astrophysics Data System (ADS)

    Davidović, D.; Kumar, S.; Reich, D. H.; Siegel, J.; Field, S. B.; Tiberio, R. C.; Hey, R.; Ploog, K.

    1996-03-01

    An array of isolated superconducting rings at Φ_0/2 applied flux is equivalent to a 2D random field Ising antiferromagnet. The quantized magnetic moments of the rings play the role of Ising spins, and small variations in the rings' areas lead to a Gaussian random field. Using SQUID magnetometry and scanning Hall probe microscopy, we studied the dynamics and antiferromagnetic correlations of arrays of micron-size Al rings, arranged on square, honeycomb, triangular, and kagomé lattices. All the arrays exhibit short range antiferromagnetic order. Spin freezing at low temperatures and the random field prevent the development of long range correlations on bipartite lattices. Effects of geometrical frustration on the triangular and kagomé lattices were also observed.

  7. 2-D soft x-ray arrays in the EAST

    NASA Astrophysics Data System (ADS)

    Chen, Kaiyun; Xu, Liqing; Hu, Liqun; Duan, Yanmin; Li, Xueqin; Yuan, Yi; Mao, Songtao; Sheng, Xiuli; Zhao, Jinlong

    2016-06-01

    A high spatial and temporal resolution soft x-ray (SXR) imaging diagnostic has been installed in EAST for the study of magnetohydrodynamics activities and core high-Z impurity transport. Up to 122 lines of sight view the poloidal plasma from three directions (two up-down symmetrical horizontal arrays and one vertical array), which renders the diagnostic able to provide detailed tomographic reconstructions under various conditions. Fourier-Bessel method based on flux coordinates was employed for 2-D SXR tomographic reconstruction. Examples of several events measured by SXR diagnostic in EAST are shown, namely the crash patterns of sawtooth, periodical burst of edge localized modes, and the transport of high-Z intrinsic impurities.

  8. Controlling cell growth with tailorable 2D nanoholes arrays.

    PubMed

    Fragal, Vanessa H; Cellet, Thelma Sley P; Fragal, Elizângela H; Pereira, Guilherme M; Garcia, Francielle P; Nakamura, Celso V; Asefa, Tewodros; Rubira, Adley F; Silva, Rafael

    2016-03-15

    A facile and reproducible route that can lead to two-dimensional arrays of nanopores in thin polymer films is demonstrated. The formation of the pores in the polymer films involves breath figure phenomenon and occurs during the film deposition by spin coating. The formation of nanoporous thin films takes only few seconds, and the method does not require complex equipment or expensive chemicals. This method also constitutes a straightforward approach to control the size of the pores formed in thin films. Besides allowing control over the average pore size of the porous films, the use of dynamic deposition with the breath figure phenomenon causes the reduction in the pore size to nanometer scale. The nanoporous arrays obtained by the breath figure are applied as substrates for cell growth, and the effect of their nanopore size on cell growth was evaluated. Notably, it is found that cell viability is related to pore size, where 2D nanoporous structure is more beneficial for cell culture than 2D microporous structures. The change in the average pore size of the polymer films from 1.22 μm to 346 nm results in a threefold increase in cell viability. PMID:26722796

  9. 2D optoacoustic array for high resolution imaging

    NASA Astrophysics Data System (ADS)

    Ashkenazi, S.; Witte, R. S.; Kim, K.; Huang, S.-W.; Hou, Y.; O'Donnell, M.

    2006-02-01

    An optoacoustic detector denotes the detection of acoustic signals by optical devices. Recent advances in fabrication techniques and the availability of high power tunable laser sources have greatly accelerated the development of efficient optoacoustic detectors. The unique advantages of optoacoustic technology are of special interest in applications that require high resolution imaging. For these applications optoacoustic technology enables high frequency transducer arrays with element size on the order of 10 μm. Laser generated ultrasound (photoacoustic effect) has been studied since the early observations of A.G. Bell (1880) of audible sound generated by light absorption . Modern studies have demonstrated the use of the photoacoustic effect to form a versatile imaging modality for medical and biological applications. A short laser pulse illuminates a tissue creating rapid thermal expansion and acoustic emission. Detection of the resulting acoustic field by an array enables the imaging of the tissue optical absorption using ultrasonic imaging methods. We present an integrated imaging system that employs photoacoustic sound generation and 2D optoacoustic reception. The optoacoustic receiver consists of a thin polymer Fabry-Perot etalon. The etalon is an optical resonator of a high quality factor (Q = 750). The relatively low elasticity modulus of the polymer and the high Q-factor of the resonator combine to yield high ultrasound sensitivity. The etalon thickness (10 μm) was optimized for wide bandwidth (typically above 50 MHz). An optical scanning and focusing system is used to create a large aperture and high density 2D ultrasonic receiver array. High resolution 3D images of phantom targets and biological tissue samples were obtained.

  10. Antenna coupled detectors for 2D staring focal plane arrays

    NASA Astrophysics Data System (ADS)

    Gritz, Michael A.; Kolasa, Borys; Lail, Brian; Burkholder, Robert; Chen, Leonard

    2013-06-01

    Millimeter-wave (mmW)/sub-mmW/THz region of the electro-magnetic spectrum enables imaging thru clothing and other obscurants such as fog, clouds, smoke, sand, and dust. Therefore considerable interest exists in developing low cost millimeter-wave imaging (MMWI) systems. Previous MMWI systems have evolved from crude mechanically scanned, single element receiver systems into very complex multiple receiver camera systems. Initial systems required many expensive mmW integrated-circuit low-noise amplifiers. In order to reduce the cost and complexity of the existing systems, attempts have been made to develop new mmW imaging sensors employing direct detection arrays. In this paper, we report on Raytheon's recent development of a unique focal plane array technology, which operates broadly from the mmW through the sub-mmW/THz region. Raytheon's innovative nano-antenna based detector enables low cost production of 2D staring mmW focal plane arrays (mmW FPA), which not only have equivalent sensitivity and performance to existing MMWI systems, but require no mechanical scanning.

  11. Mirror effects and optical meta-surfaces in 2d atomic arrays

    NASA Astrophysics Data System (ADS)

    Shahmoon, Ephraim; Wild, Dominik; Lukin, Mikhail; Yelin, Susanne

    2016-05-01

    Strong optical response of natural and artificial (meta-) materials typically relies on the fact that the lattice constant that separates their constituent particles (atoms or electromagnetic resonators, respectively) is much smaller than the optical wavelength. Here we consider a single layer of a 2d atom array with a lattice constant on the order of an optical wavelength, which can be thought of as a highly dilute 2d metamaterial (meta-surface). Our theoretical analysis shows how strong scattering of resonant incoming light off the array can be controlled by choosing its lattice constant, e.g. allowing the array to operate as a perfect mirror or a retro-reflector for most incident angles of the incoming light. We discuss the prospects for quantum metasurfaces, i.e. the ability to shape the output quantum state of light by controlling the atomic states, and the possible generality of our results as a universal wave phenomena.

  12. Self-leveling 2D DPN probe arrays

    NASA Astrophysics Data System (ADS)

    Haaheim, Jason R.; Val, Vadim; Solheim, Ed; Bussan, John; Fragala, J.; Nelson, Mike

    2010-02-01

    Dip Pen Nanolithography® (DPN®) is a direct write scanning probe-based technique which operates under ambient conditions, making it suitable to deposit a wide range of biological and inorganic materials. Precision nanoscale deposition is a fundamental requirement to advance nanoscale technology in commercial applications, and tailoring chemical composition and surface structure on the sub-100 nm scale benefits researchers in areas ranging from cell adhesion to cell-signaling and biomimetic membranes. These capabilities naturally suggest a "Desktop Nanofab" concept - a turnkey system that allows a non-expert user to rapidly create high resolution, scalable nanostructures drawing upon well-characterized ink and substrate pairings. In turn, this system is fundamentally supported by a portfolio of MEMS devices tailored for microfluidic ink delivery, directed placement of nanoscale materials, and cm2 tip arrays for high-throughput nanofabrication. Massively parallel two-dimensional nanopatterning is now commercially available via NanoInk's 2D nano PrintArray™, making DPN a high-throughput (>3×107 μm2 per hour), flexible and versatile method for precision nanoscale pattern formation. However, cm2 arrays of nanoscopic tips introduce the nontrivial problem of getting them all evenly touching the surface to ensure homogeneous deposition; this requires extremely precise leveling of the array. Herein, we describe how we have made the process simple by way of a selfleveling gimbal attachment, coupled with semi-automated software leveling routines which bring the cm^2 chip to within 0.002 degrees of co-planarity. This excellent co-planarity yields highly homogeneous features across a square centimeter, with <6% feature size standard deviation. We have engineered the devices to be easy to use, wire-free, and fully integrated with both of our patterning tools: the DPN 5000, and the NLP 2000.

  13. Quantum Simulation with 2D Arrays of Trapped Ions

    NASA Astrophysics Data System (ADS)

    Richerme, Philip

    2016-05-01

    The computational difficulty of solving fully quantum many-body spin problems is a significant obstacle to understanding the behavior of strongly correlated quantum matter. This work proposes the design and construction of a 2D quantum spin simulator to investigate the physics of frustrated materials, highly entangled states, mechanisms potentially underpinning high-temperature superconductivity, and other topics inaccessible to current 1D systems. The effective quantum spins will be encoded within the well-isolated electronic levels of trapped ions, confined in a two-dimensional planar geometry, and made to interact using phonon-mediated optical dipole forces. The system will be scalable to 100+ quantum particles, far beyond the realm of classical intractability, while maintaining individual-ion control, long quantum coherence times, and site-resolved projective spin measurements. Once constructed, the two-dimensional quantum simulator will implement a broad range of spin models on a variety of reconfigurable lattices and characterize their behavior through measurements of spin-spin correlations and entanglement. This versatile tool will serve as an important experimental resource for exploring difficult quantum many-body problems in a regime where classical methods fail.

  14. Particle sensor array

    NASA Technical Reports Server (NTRS)

    Buehler, Martin G. (Inventor); Blaes, Brent R. (Inventor); Lieneweg, Udo (Inventor)

    1994-01-01

    A particle sensor array which in a preferred embodiment comprises a static random access memory having a plurality of ion-sensitive memory cells, each such cell comprising at least one pull-down field effect transistor having a sensitive drain surface area (such as by bloating) and at least one pull-up field effect transistor having a source connected to an offset voltage. The sensitive drain surface area and the offset voltage are selected for memory cell upset by incident ions such as alpha-particles. The static random access memory of the present invention provides a means for selectively biasing the memory cells into the same state in which each of the sensitive drain surface areas is reverse biased and then selectively reducing the reversed bias on these sensitive drain surface areas for increasing the upset sensitivity of the cells to ions. The resulting selectively sensitive memory cells can be used in a number of applications. By way of example, the present invention can be used for measuring the linear energy transfer of ion particles, as well as a device for assessing the resistance of CMOS latches to Cosmic Ray induced single event upsets. The sensor of the present invention can also be used to determine the uniformity of an ion beam.

  15. Electric field enhancement in a self-assembled 2D array of silver nanospheres

    SciTech Connect

    El-Khoury, Patrick Z. E-mail: wayne.hess@pnnl.gov; Gong, Yu; Joly, Alan G.; Abellan, Patricia; Browning, Nigel D.; Hess, Wayne P. E-mail: wayne.hess@pnnl.gov; Khon, Elena; Hu, Dehong; Zamkov, Mikhail; Evans, James E.

    2014-12-07

    We investigate the plasmonic properties of a self-assembled 2D array of Ag nanospheres (average particle diameter/inter-particle separation distance of 9/3.7 nm). The structures of the individual particles and their assemblies are characterized using high-resolution transmission electron microscopy (HR-TEM). The plasmonic response of the nanoparticle network is probed using two-photon photoemission electron microscopy (TP-PEEM). HR-TEM and TP-PEEM statistics reveal the structure and plasmonic response of the network to be homogeneous on average. This translates into a relatively uniform surface-enhanced Raman scattering (SERS) response from biphenyl,4-4{sup ′}-dithiol (BPDT) molecules adsorbed onto different sites of the network. Reproducible, bright, and low-background SERS spectra are recorded and assigned on the basis of density functional theory calculations in which BPDT is chemisorbed onto the vertex of a finite tetrahedral Ag cluster consisting of 20 Ag atoms. A notable agreement between experiment and theory allows us to rigorously account for the observable vibrational states of BPDT in the ∼200–2200 cm{sup −1} region of the spectrum. Finite difference time domain simulations further reveal that physical enhancement factors on the order of 10{sup 6} are attainable at the nanogaps formed between the silver nanospheres in the 2D array. Combined with modest chemical enhancement factors, this study paves the way for reproducible single molecule signals from an easily self-assembled SERS substrate.

  16. Electric Field Enhancement in a Self-Assembled 2D Array of Silver Nanospheres

    SciTech Connect

    El-Khoury, Patrick Z.; Khon, Elena; Gong, Yu; Joly, Alan G.; Abellan, Patricia; Evans, James E.; Browning, Nigel D.; Hu, Dehong; Zamkov, Mikhail; Hess, Wayne P.

    2014-12-07

    We investigate the plasmonic properties of a self-assembled 2D array of Ag nanospheres (average particle diameter/inter-particle separation distance of ~9/~4 nm). The structures of the individual particles and their assemblies are characterized using high-resolution transmission electron microscopy (HR-TEM). The plasmonic response of the nanoparticle network is probed using two-photon photoemission electron microscopy (TP-PEEM). HR-TEM and TP-PEEM statistics reveal the structure and plasmonic response of the network to be homogeneous on average. This translates into a relatively uniform surface-enhanced Raman scattering (SERS) response from biphenyl,4-4’-dithiol (BPDT) molecules adsorbed onto different sites of the network. Bright and background free SERS spectra are recorded, assigned on the basis of density 2 functional theory calculations in which BPDT is chemisorbed onto the vertex of a finitie tetrahedral Ag cluster consisting of 20 Ag atoms. A remarkable agreement between experiment and theory allows us to rigorously account for the observable vibrational states of BPDT in the ~200-2200 cm-1 region of the spectrum. Finite difference time domain simulations further reveal that physical enhancement factors on the order of 106 are attainable at the nanogaps formed between the silver nanospheres in the 2D array. Combined with modest chemical enhancement factors, this study paves the way for reproducible single molecule signals from an easily self-assembled SERS substrate.

  17. Improved beamforming using curved sparse 2D arrays in ultrasound.

    PubMed

    Kirkebø, Jan Egil; Austeng, Andreas

    2007-05-01

    In this work we have investigated the effect of curving phase-steered sparse periodic two-dimensional arrays in one direction, and relate this effect to the geometry of the arrays. We have shown that curving is equivalent to removing some of the element periodicity, thus adding some "randomness" to the layout. Compared to flat phase-steered periodically sparse two-dimensional arrays, curving offers an even greater suppression of grating lobes located at directions along the curvature. The class of arrays yielding improved performance due to this suppression of grating lobes has been characterized. The point spread functions of some previously proposed array layouts, shown to be promising for ultrasonic imaging, have been simulated. The arrays have been simulated with various number of elements as well as various focal points, with array and field parameters typical to those in volumetric cardiac imaging. On a 48 x 48 element grid with a transducer center frequency of 3 MHz and the target at 40 mm, reductions in the peak sidelobe level of up to 12dB were recorded for some critical steering directions, without significant differences in the beamwidth. The integrated sidelobe ratio was also examined, showing an almost equivalent performance as the flat array. This study shows that, without adding any complexity to the system, the overall image quality of a volumetric imaging system can be improved significantly by curving the array in one direction. PMID:17313966

  18. Fast 2D DOA Estimation Algorithm by an Array Manifold Matching Method with Parallel Linear Arrays

    PubMed Central

    Yang, Lisheng; Liu, Sheng; Li, Dong; Jiang, Qingping; Cao, Hailin

    2016-01-01

    In this paper, the problem of two-dimensional (2D) direction-of-arrival (DOA) estimation with parallel linear arrays is addressed. Two array manifold matching (AMM) approaches, in this work, are developed for the incoherent and coherent signals, respectively. The proposed AMM methods estimate the azimuth angle only with the assumption that the elevation angles are known or estimated. The proposed methods are time efficient since they do not require eigenvalue decomposition (EVD) or peak searching. In addition, the complexity analysis shows the proposed AMM approaches have lower computational complexity than many current state-of-the-art algorithms. The estimated azimuth angles produced by the AMM approaches are automatically paired with the elevation angles. More importantly, for estimating the azimuth angles of coherent signals, the aperture loss issue is avoided since a decorrelation procedure is not required for the proposed AMM method. Numerical studies demonstrate the effectiveness of the proposed approaches. PMID:26907301

  19. Fast 2D DOA Estimation Algorithm by an Array Manifold Matching Method with Parallel Linear Arrays.

    PubMed

    Yang, Lisheng; Liu, Sheng; Li, Dong; Jiang, Qingping; Cao, Hailin

    2016-01-01

    In this paper, the problem of two-dimensional (2D) direction-of-arrival (DOA) estimation with parallel linear arrays is addressed. Two array manifold matching (AMM) approaches, in this work, are developed for the incoherent and coherent signals, respectively. The proposed AMM methods estimate the azimuth angle only with the assumption that the elevation angles are known or estimated. The proposed methods are time efficient since they do not require eigenvalue decomposition (EVD) or peak searching. In addition, the complexity analysis shows the proposed AMM approaches have lower computational complexity than many current state-of-the-art algorithms. The estimated azimuth angles produced by the AMM approaches are automatically paired with the elevation angles. More importantly, for estimating the azimuth angles of coherent signals, the aperture loss issue is avoided since a decorrelation procedure is not required for the proposed AMM method. Numerical studies demonstrate the effectiveness of the proposed approaches. PMID:26907301

  20. Controlling avalanche criticality in 2D nano arrays.

    PubMed

    Zohar, Y C; Yochelis, S; Dahmen, K A; Jung, G; Paltiel, Y

    2013-01-01

    Many physical systems respond to slowly changing external force through avalanches spanning broad range of sizes. Some systems crackle even without apparent external force, such as bursts of neuronal activity or charge transfer avalanches in 2D molecular layers. Advanced development of theoretical models describing disorder-induced critical phenomena calls for experiments probing the dynamics upon tuneable disorder. Here we show that isomeric structural transitions in 2D organic self-assembled monolayer (SAM) exhibit critical dynamics with experimentally tuneable disorder. The system consists of field effect transistor coupled through SAM to illuminated semiconducting nanocrystals (NCs). Charges photoinduced in NCs are transferred through SAM to the transistor surface and modulate its conductivity. Avalanches of isomeric structural transitions are revealed by measuring the current noise I(t) of the transistor. Accumulated surface traps charges reduce dipole moments of the molecules, decrease their coupling, and thus decrease the critical disorder of the SAM enabling its tuning during experiments.

  1. Synchronization of semiconductor laser arrays with 2D Bragg structures

    NASA Astrophysics Data System (ADS)

    Baryshev, V. R.; Ginzburg, N. S.

    2016-08-01

    A model of a planar semiconductor multi-channel laser is developed. In this model two-dimensional (2D) Bragg mirror structures are used for synchronizing radiation of multiple laser channels. Coupling of longitudinal and transverse waves can be mentioned as the distinguishing feature of these structures. Synchronization of 20 laser channels is demonstrated with a semi-classical approach based on Maxwell-Bloch equations.

  2. Spot Weld Analysis With 2D Ultrasonic Arrays

    PubMed Central

    Denisov, A. A.; Shakarji, C. M.; Lawford, B. B.; Maev, R. Gr.; Paille, J. M.

    2004-01-01

    This paper describes a threefold method of testing the performance of an array-based ultrasonic tool for nondestructive testing of spot welds. The tool is described in its capabilities, use, and advantages over existing counterparts. Performance testing for and the results from carrying out the testing are described. The three performance testing methods include 1) the use of calibrated samples, 2) comparisons with actual spot-welds, and 3) a performance evaluation of the embedded fitting software. The test of the fitting software was carried out by a comparison of results with reference fits supplied by the National Institute of Standards and Technology. PMID:27366607

  3. 3D/2D convertible projection-type integral imaging using concave half mirror array.

    PubMed

    Hong, Jisoo; Kim, Youngmin; Park, Soon-gi; Hong, Jong-Ho; Min, Sung-Wook; Lee, Sin-Doo; Lee, Byoungho

    2010-09-27

    We propose a new method for implementing 3D/2D convertible feature in the projection-type integral imaging by using concave half mirror array. The concave half mirror array has the partially reflective characteristic to the incident light. And the reflected term is modulated by the concave mirror array structure, while the transmitted term is unaffected. With such unique characteristic, 3D/2D conversion or even the simultaneous display of 3D and 2D images is also possible. The prototype was fabricated by the aluminum coating and the polydimethylsiloxane molding process. We could experimentally verify the 3D/2D conversion and the display of 3D image on 2D background with the fabricated prototype.

  4. Designing 2D arrays for SHM of planar structures: a review

    NASA Astrophysics Data System (ADS)

    Stepinski, Tadeusz; Ambrozinski, Lukasz; Uhl, Tadeusz

    2013-04-01

    Monitoring structural integrity of large planar structures that aims at detecting and localizing impact or damage at any point of the structure requires normally a relatively dense network of uniformly distributed ultrasonic sensors. 2-D ultrasonic phased arrays, due to their beam-steering capability and all azimuth angle coverage are a very promising tool for structural health monitoring (SHM) of plate-like structures using Lamb waves (LW). Linear phased arrays that have been proposed for that purpose, produce mirrored image characterized by azimuth dependent resolution, which prevents unequivocal damage localization. 2D arrays do not have this drawback and they are even capable of mode selectivity when generating and receiving LWs. Performance of 2D arrays depends on their topology as well as the number of elements (transducers) used and their spacing in terms of wavelength. In this paper we propose a consistent methodology for three-step: theoretical, numerical and experimental investigation of a diversity of 2D array topologies in SHM applications. In the first step, the theoretical evaluation is performed using frequency-dependent structure transfer function (STF). STF that defines linear propagation of different LWs modes through the dispersive medium enables theoretical investigation of the particular array performance for a predefined tone-burst excitation signal. A dedicated software tool has been developed for the numerical evaluation of 2D array directional characteristics (beampattern) in a specific structure. The simulations are performed using local interaction simulation approach (LISA), implemented using NVIDIA CUDA graphical computation unit (GPU), which enables time-efficient 3D simulations of LWs propagation. Beampatterns of a 2D array can be to some extend evaluated analytically and using numerical simulations; in most cases, however, they require experimental verification. Using scanning laser vibrometer is proposed for that purpose, in a setup

  5. Inspection design using 2D phased array, TFM and cueMAP software

    SciTech Connect

    McGilp, Ailidh; Dziewierz, Jerzy; Lardner, Tim; Mackersie, John; Gachagan, Anthony

    2014-02-18

    A simulation suite, cueMAP, has been developed to facilitate the design of inspection processes and sparse 2D array configurations. At the core of cueMAP is a Total Focusing Method (TFM) imaging algorithm that enables computer assisted design of ultrasonic inspection scenarios, including the design of bespoke array configurations to match the inspection criteria. This in-house developed TFM code allows for interactive evaluation of image quality indicators of ultrasonic imaging performance when utilizing a 2D phased array working in FMC/TFM mode. The cueMAP software uses a series of TFM images to build a map of resolution, contrast and sensitivity of imaging performance of a simulated reflector, swept across the inspection volume. The software takes into account probe properties, wedge or water standoff, and effects of specimen curvature. In the validation process of this new software package, two 2D arrays have been evaluated on 304n stainless steel samples, typical of the primary circuit in nuclear plants. Thick section samples have been inspected using a 1MHz 2D matrix array. Due to the processing efficiency of the software, the data collected from these array configurations has been used to investigate the influence sub-aperture operation on inspection performance.

  6. Designing of sparse 2D arrays for Lamb wave imaging using coarray concept

    NASA Astrophysics Data System (ADS)

    Ambroziński, Łukasz; Stepinski, Tadeusz; Uhl, Tadeusz

    2015-03-01

    2D ultrasonic arrays have considerable application potential in Lamb wave based SHM systems, since they enable equivocal damage imaging and even in some cases wave-mode selection. Recently, it has been shown that the 2D arrays can be used in SHM applications in a synthetic focusing (SF) mode, which is much more effective than the classical phase array mode commonly used in NDT. The SF mode assumes a single element excitation of subsequent transmitters and off-line processing the acquired data. In the simplest implementation of the technique, only single multiplexed input and output channels are required, which results in significant hardware simplification. Application of the SF mode for 2D arrays creates additional degrees of freedom during the design of the array topology, which complicates the array design process, however, it enables sparse array designs with performance similar to that of the fully populated dense arrays. In this paper we present the coarray concept to facilitate synthesis process of an array's aperture used in the multistatic synthetic focusing approach in Lamb waves-based imaging systems. In the coherent imaging, performed in the transmit/receive mode, the sum coarray is a morphological convolution of the transmit/receive sub-arrays. It can be calculated as the set of sums of the individual sub-arrays' elements locations. The coarray framework will be presented here using a an example of a star-shaped array. The approach will be discussed in terms of beampatterns of the resulting imaging systems. Both simulated and experimental results will be included.

  7. Laser fabrication of 2D and 3D metal nanoparticle structures and arrays.

    PubMed

    Kuznetsov, A I; Kiyan, R; Chichkov, B N

    2010-09-27

    A novel method for fabrication of 2D and 3D metal nanoparticle structures and arrays is proposed. This technique is based on laser-induced transfer of molten metal nanodroplets from thin metal films. Metal nanoparticles are produced by solidification of these nanodroplets. The size of the transferred nanoparticles can be controllably changed in the range from 180 nm to 1500 nm. Several examples of complex 2D and 3D microstructures generated form gold nanoparticles are demonstrated. PMID:20941016

  8. 2D aperture synthesis for Lamb wave imaging using co-arrays

    NASA Astrophysics Data System (ADS)

    Ambrozinski, Lukasz; Stepinski, Tadeusz; Uhl, Tadeusz

    2014-03-01

    2D ultrasonic arrays in Lamb wave based SHM systems can operate in the phased array (PA) or synthetic focusing (SF) mode. In the real-time PA approach, multiple electronically delayed signals excite transmitting elements to form the desired wave-front, whereas receiving elements are used to sense scattered waves. Due to that, the PA mode requires multi channeled hardware and multiple excitations at numerous azimuths to scan the inspected region of interest. To the contrary, the SF mode, assumes a single element excitation of subsequent transmitters and off-line processing of the acquired data. In the simplest implementation of the SF technique, a single multiplexed input and output channels are required, which results in significant hardware simplification. Performance of a 2D imaging array depends on many parameters, such as, its topology, number of its transducers and their spacing in terms of wavelength as well as the type of weighting function (apodization). Moreover, it is possible to use sparse arrays, which means that not all array elements are used for transmitting and/ or receiving. In this paper the co-array concept is applied to facilitate the synthesis process of an array's aperture used in the multistatic synthetic focusing approach in Lamb waves-based imaging systems. In the coherent imaging, performed in the transmit/receive mode, the sum co-array is a morphological convolution of the transmit/receive sub-arrays. It can be calculated as the set of sums of the individual elements' locations in the sub-arrays used for imaging. The coarray framework will be presented here using two different array topologies, aID uniform linear array and a cross-shaped array that will result in a square coarray. The approach will be discussed in terms of array patterns and beam patterns of the resulting imaging systems. Both, theoretical and experimental results will be given.

  9. Dynamic photorefractive self-amplified angular-multiplex 2-D optical beam-array generation

    NASA Technical Reports Server (NTRS)

    Zhou, Shaomin; Yeh, Pochi; Liu, Hua-Kuang

    1993-01-01

    A real-time 2-D angular-multiplex beam-array holographic storage and reconstruction technique using electrically-addressed spatial light modulators(E-SLM's) and photorefractive crystals is described. Using a liquid crystal television (LCTV) spatial light modulator (SLM) for beam steering and lithium niobate photorefractive crystal for holographic recording, experimental results of generating large and complicated arrays of laser beams with high diffraction efficiency and good uniformity are presented.

  10. 2D Traveling Wave Array Employing a Trapezoidal Dielectric Wedge for Beam Steering

    NASA Technical Reports Server (NTRS)

    Host, Nicholas K.; Chen, Chi-Chih; Volakis, John L.; Miranada, Felix A.

    2014-01-01

    This presentation addresses the progress made so far in the development of an antenna array with reconfigurable transmission line feeds connecting each element in series. In particular, 2D traveling wave array employing trapezoidal Dielectric Wedge for Beam Steering will be discussed. The presentation includes current status of the effort and suggested future work. The work is being done as part of the NASA Office of the Chief Technologist's Space Technology Research Fellowship (NSTRF).

  11. 2D Array of Far-infrared Thermal Detectors: Noise Measurements and Processing Issues

    NASA Technical Reports Server (NTRS)

    Lakew, B.; Aslam, S.; Stevenson, T.

    2008-01-01

    A magnesium diboride (MgB2) detector 2D array for use in future space-based spectrometers is being developed at GSFC. Expected pixel sensitivities and comparison to current state-of-the-art infrared (IR) detectors will be discussed.

  12. High power, high efficiency, 2D laser diode arrays for pumping solid state lasers

    SciTech Connect

    Rosenberg, A.; McShea, J.C.; Bogdan, A.R.; Petheram, J.C.; Rosen, A.

    1987-11-01

    This document reports the current performance of 2D laser diode arrays operating at 770 nm and 808 nm for pumping promethium and neodymium solid state lasers, respectively. Typical power densities are in excess of 2kw/cm/sup 2/ with overall efficiencies greater than 30%.

  13. 2D biological representations with reduced speckle obtained from two perpendicular ultrasonic arrays.

    PubMed

    Rodriguez-Hernandez, Miguel A; Gomez-Sacristan, Angel; Sempere-Payá, Víctor M

    2016-04-29

    Ultrasound diagnosis is a widely used medical tool. Among the various ultrasound techniques, ultrasonic imaging is particularly relevant. This paper presents an improvement to a two-dimensional (2D) ultrasonic system using measurements taken from perpendicular planes, where digital signal processing techniques are used to combine one-dimensional (1D) A-scans were acquired by individual transducers in arrays located in perpendicular planes. An algorithm used to combine measurements is improved based on the wavelet transform, which includes a denoising step during the 2D representation generation process. The inclusion of this new denoising stage generates higher quality 2D representations with a reduced level of speckling. The paper includes different 2D representations obtained from noisy A-scans and compares the improvements obtained by including the denoising stage.

  14. 2D biological representations with reduced speckle obtained from two perpendicular ultrasonic arrays.

    PubMed

    Rodriguez-Hernandez, Miguel A; Gomez-Sacristan, Angel; Sempere-Payá, Víctor M

    2016-04-29

    Ultrasound diagnosis is a widely used medical tool. Among the various ultrasound techniques, ultrasonic imaging is particularly relevant. This paper presents an improvement to a two-dimensional (2D) ultrasonic system using measurements taken from perpendicular planes, where digital signal processing techniques are used to combine one-dimensional (1D) A-scans were acquired by individual transducers in arrays located in perpendicular planes. An algorithm used to combine measurements is improved based on the wavelet transform, which includes a denoising step during the 2D representation generation process. The inclusion of this new denoising stage generates higher quality 2D representations with a reduced level of speckling. The paper includes different 2D representations obtained from noisy A-scans and compares the improvements obtained by including the denoising stage. PMID:27163318

  15. Preliminary work of real-time ultrasound imaging system for 2-D array transducer.

    PubMed

    Li, Xu; Yang, Jiali; Ding, Mingyue; Yuchi, Ming

    2015-01-01

    Ultrasound (US) has emerged as a non-invasive imaging modality that can provide anatomical structure information in real time. To enable the experimental analysis of new 2-D array ultrasound beamforming methods, a pre-beamformed parallel raw data acquisition system was developed for 3-D data capture of 2D array transducer. The transducer interconnection adopted the row-column addressing (RCA) scheme, where the columns and rows were active in sequential for transmit and receive events, respectively. The DAQ system captured the raw data in parallel and the digitized data were fed through the field programmable gate array (FPGA) to implement the pre-beamforming. Finally, 3-D images were reconstructed through the devised platform in real-time. PMID:26405923

  16. The inspection of anisotropic single-crystal components using a 2-D ultrasonic array.

    PubMed

    Lane, Christopher J L; Dunhill, A K; Drinkwater, Bruce W; Wilcox, Paul D

    2010-12-01

    Single-crystal metal alloys are used extensively in the manufacture of jet engine components for their excellent mechanical properties at elevated temperatures. The inspection of these components using 2-D ultrasonic arrays potentially allows the detection of subsurface defects in threedimensions from one inspection location. Such methods are not currently suitable for the inspection of single-crystal components because the high elastic anisotropy of single-crystal materials causes directional variation in ultrasonic waves. In this paper, a model of wave propagation in anisotropic material is used to correct an ultrasonic imaging algorithm and is applied to a single-crystal test specimen. For this correctedalgorithm, the orientation of the crystal in a specimen must be known before the inspection. Using the same ultrasonic array to measure the orientation and perform the defect inspection offers the most practical solution. Therefore, potential crystallographic orientation methods using 2-D ultrasonic arrays are also developed and evaluated. PMID:21156370

  17. Tracking errors in 2D multiple particle tracking microrheology

    NASA Astrophysics Data System (ADS)

    Kowalczyk, Anne; Oelschlaeger, Claude; Willenbacher, Norbert

    2015-01-01

    Tracking errors due to particles moving in and out of the focal plane are a fundamental problem of multiple particle tracking microrheology. Here, we present a new approach to treat these errors so that a statistically significant number of particle trajectories with reasonable length are received, which is important for an unbiased analysis of multiple particle tracking data from inhomogeneous fluids. Starting from Crocker and Grier’s tracking algorithm, we identify particle displacements between subsequent images as artificial jumps; if this displacement deviates more than four standard deviations from the mean value, trajectories are terminated at such positions. In a further processing step, trajectories separated by a time gap Δ {τ\\text{max}} are merged based on an adaptive search radius criterion accounting for individual particle mobility. For a series of Newtonian fluids covering the viscosity range 6-1300 mPa s, this approach yields the correct viscosity but also results in a viscosity-independent number of trajectories equal to the average number of particles in an image with a minimum length covering at least two orders of magnitude in time. This allows for an unbiased characterization of heterogeneous fluids. For a Carbopol ETD 2050 solution we recover the expected broad variation of particle mobility. Consistent with the widely accepted structural model of highly swollen microgel particles suspended in a polymer solution, we find about 2/3 of the tracers are elastically trapped.

  18. Time multiplexing super resolution using a 2D Barker-based array

    NASA Astrophysics Data System (ADS)

    Ilovitsh, Asaf; Ilovitsh, Tali; Preter, Eyal; Levanon, Nadav; Zalevsky, Zeev

    2016-03-01

    We propose the use of a two dimensional Barker-based array in order to improve the performance of the standard time multiplexing super resolution system. The Barker-based array is a 2D generalization of the standard 1D Barker code. It enables achieving a two dimensional super resolution image using only one dimensional scan, by exploiting its unique auto correlation property. A sequence of low resolution images are captured at different lateral positions of the array, and are decoded properly using the same array. In addition, we present the use of a mismatched array for the decoding process. The cross correlation between the Barker-based array and the mismatched array has a perfect peak to sidelobes ratio, making it ideal for the super resolution process. Also, we propose the projection of this array onto the object using a phase-only spatial light modulator. Projecting the array eliminates the need for printing it, mechanically shifting it, and having a direct contact with the object, which is not feasible in many imaging applications. The proposed method is presented analytically, demonstrated via numerical simulation, and validated by laboratory experiments.

  19. 2D to 3D crossover of the magnetic properties in ordered arrays of iron oxide nanocrystals.

    PubMed

    Faure, Bertrand; Wetterskog, Erik; Gunnarsson, Klas; Josten, Elisabeth; Hermann, Raphaël P; Brückel, Thomas; Andreasen, Jens Wenzel; Meneau, Florian; Meyer, Mathias; Lyubartsev, Alexander; Bergström, Lennart; Salazar-Alvarez, German; Svedlindh, Peter

    2013-02-01

    The magnetic 2D to 3D crossover behavior of well-ordered arrays of monodomain γ-Fe(2)O(3) spherical nanoparticles with different thicknesses has been investigated by magnetometry and Monte Carlo (MC) simulations. Using the structural information of the arrays obtained from grazing incidence small-angle X-ray scattering and scanning electron microscopy together with the experimentally determined values for the saturation magnetization and magnetic anisotropy of the nanoparticles, we show that MC simulations can reproduce the thickness-dependent magnetic behavior. The magnetic dipolar particle interactions induce a ferromagnetic coupling that increases in strength with decreasing thickness of the array. The 2D to 3D transition in the magnetic properties is mainly driven by a change in the orientation of the magnetic vortex states with increasing thickness, becoming more isotropic as the thickness of the array increases. Magnetic anisotropy prevents long-range ferromagnetic order from being established at low temperature and the nanoparticle magnetic moments instead freeze along directions defined by the distribution of easy magnetization directions.

  20. Reconfigurable 2D cMUT-ASIC arrays for 3D ultrasound image

    NASA Astrophysics Data System (ADS)

    Song, Jongkeun; Jung, Sungjin; Kim, Youngil; Cho, Kyungil; Kim, Baehyung; Lee, Seunghun; Na, Junseok; Yang, Ikseok; Kwon, Oh-kyong; Kim, Dongwook

    2012-03-01

    This paper describes the design and implementations of the complete 2D capacitive micromachined ultrasound transducer electronics and its analog front-end module for transmitting high voltage ultrasound pulses and receiving its echo signals to realize 3D ultrasound image. In order to minimize parasitic capacitances and ultimately improve signal-to- noise ratio (SNR), cMUT has to be integrate with Tx/Rx electronics. Additionally, in order to integrate 2D cMUT array module, significant optimized high voltage pulser circuitry, low voltage analog/digital circuit design and packaging challenges are required due to high density of elements and small pitch of each element. We designed 256(16x16)- element cMUT and reconfigurable driving ASIC composed of 120V high voltage pulser, T/R switch, low noise preamplifier and digital control block to set Tx frequency of ultrasound and pulse train in each element. Designed high voltage analog ASIC was successfully bonded with 2D cMUT array by flip-chip bonding process and it connected with analog front-end board to transmit pulse-echo signals. This implementation of reconfigurable cMUT-ASIC-AFE board enables us to produce large aperture 2D transducer array and acquire high quality of 3D ultrasound image.

  1. Chemiresistive Sensor Arrays from Conductive 2D Metal-Organic Frameworks.

    PubMed

    Campbell, Michael G; Liu, Sophie F; Swager, Timothy M; Dincă, Mircea

    2015-11-01

    Applications of porous metal-organic frameworks (MOFs) in electronic devices are rare, owing in large part to a lack of MOFs that display electrical conductivity. Here, we describe the use of conductive two-dimensional (2D) MOFs as a new class of materials for chemiresistive sensing of volatile organic compounds (VOCs). We demonstrate that a family of structurally analogous 2D MOFs can be used to construct a cross-reactive sensor array that allows for clear discrimination between different categories of VOCs. Experimental data show that multiple sensing mechanisms are operative with high degrees of orthogonality, establishing that the 2D MOFs used here are mechanistically unique and offer advantages relative to other known chemiresistor materials.

  2. Improved 2-D resistivity imaging of features in covered karst terrain with arrays of implanted electrodes

    NASA Astrophysics Data System (ADS)

    Kiflu, H. G.; Kruse, S. E.; Harro, D.; Loke, M. H.; Wilkinson, P. B.

    2013-12-01

    Electrical resistivity tomography is commonly used to identify geologic features associated with sinkhole formation. In covered karst terrain, however, it can be difficult to resolve the depth to top of limestone with this method. This is due to the fact that array lengths, and hence depth of resolution, are often limited by residential or commercial lot dimensions in urban environments. Furthermore, the sediments mantling the limestone are often clay-rich and highly conductive. The resistivity method has limited sensitivity to resistive zones beneath conductive zones. This sensitivity can be improved significantly with electrodes implanted at depth in the cover sediments near the top of limestone. An array of deep electrodes is installed with direct push technology in the karst cover. When combined with a surface array in which each surface electrode is underlain by a deep electrode, the array geometry is similar to a borehole array turned on its side. This method, called the Multi-Electrode Resistivity Implant Technique (MERIT), offers the promise of significantly improved resolution of epikarst and cover collapse development zones in the overlying sediment, the limestone or at the sediment-bedrock interface in heterogeneous karst environments. With a non-traditional array design, the question of optimal array geometries arises. Optimizing array geometries is complicated by the fact that many plausible 4-electrode readings will produce negative apparent resistivity values, even in homogeneous terrain. Negative apparent resistivities cannot be used in inversions based on the logarithm of the apparent resistivity. New algorithms for seeking optimal array geometries have been developed by modifying the 'Compare R' method of Wilkinson and Loke. The optimized arrays show significantly improved resolution over basic arrays adapted from traditional 2D surface geometries. Several MERIT case study surveys have been conducted in covered karst in west-central Florida, with

  3. Optimized arrays for 2-D resistivity survey lines with a large number of electrodes

    NASA Astrophysics Data System (ADS)

    Loke, M. H.; Wilkinson, P. B.; Chambers, J. E.; Uhlemann, S. S.; Sorensen, J. P. R.

    2015-01-01

    Previous studies show that optimized arrays generated using the 'Compare R' method have significantly better resolution than conventional arrays. This method determines the optimum set of arrays by selecting those that give the maximum model resolution. The number of possible arrays (the comprehensive data set) increases with the fourth power of the number of electrodes. The optimization method faces practical limitations for 2-D survey lines with more than 60 electrodes where the number of possible arrays exceeds a million. Several techniques are proposed to reduce the calculation time for such survey lines. A single-precision version of the 'Compare R' algorithm using a new ranking function reduces the calculation time by two to eight times while providing results similar to the double-precision version. Recent improvements in computer GPU technology can reduce the calculation time by about seven times. The calculation time is reduced by half by using the fact that arrays that are symmetrical about the center of the line produce identical changes in the model resolution values. It is further reduced by more than thirty times by calculating the Sherman-Morrison update for all the possible two-electrode combinations, which are then used to calculate the model resolution values for the four-electrode arrays. The calculation time is reduced by more then ten times by using a subset of the comprehensive data set consisting of only symmetrical arrays. Tests with a synthetic model and field data set show that optimized arrays derived from this subset produce inversion models with differences of less than 10% from those derived using the full comprehensive data set. The optimized data sets produced models that are more accurate than the Wenner-Schlumberger array data sets in all the tests.

  4. 2D and 3D ordered arrays of Co magnetic nanowires

    NASA Astrophysics Data System (ADS)

    Garcia, J.; Prida, V. M.; Vega, V.; Rosa, W. O.; Caballero-Flores, R.; Iglesias, L.; Hernando, B.

    2015-06-01

    Cobalt nanowire arrays spatially distributed in 2D and 3D arrangements have been performed by pulsed electrodeposition into the pores of planar and cylindrical nanoporous anodic alumina membranes, respectively. Morphological characterization points out the good filling factor reached by electroplated Co nanowires in both kinds of alumina membranes exhibiting hexagonally self-ordered porous structures. Co nanowires grown in both kinds of alumina templates exhibit the same crystalline phases. DC magnetometry and First Order Reversal Curve (FORC) analysis were carried out in order to determine the overall magnetic behavior for both nanowire array geometries. It is found that when the Co nanowires of two kinds of arrays are perpendicularly magnetized, both hysteresis loops are identical, suggesting that neither the intrinsic magnetic behavior of the nanowires nor the collective one depend on the arrays geometry. FORC analysis performed along the radial direction of the Co nanowire arrays embedded in the cylindrical alumina template reveals that the contribution of each nanowire to the magnetization reversal process involves its specific orientation with respect to the applied field direction. Furthermore, the comparison between the magnetic properties for both kinds of Co nanowire arrays allows discussing about the effect of the cylindrical geometry of the template on the magnetostatic interaction among nanowires.

  5. Nanohole-array-based device for 2D snapshot multispectral imaging

    PubMed Central

    Najiminaini, Mohamadreza; Vasefi, Fartash; Kaminska, Bozena; Carson, Jeffrey J. L.

    2013-01-01

    We present a two-dimensional (2D) snapshot multispectral imager that utilizes the optical transmission characteristics of nanohole arrays (NHAs) in a gold film to resolve a mixture of input colors into multiple spectral bands. The multispectral device consists of blocks of NHAs, wherein each NHA has a unique periodicity that results in transmission resonances and minima in the visible and near-infrared regions. The multispectral device was illuminated over a wide spectral range, and the transmission was spectrally unmixed using a least-squares estimation algorithm. A NHA-based multispectral imaging system was built and tested in both reflection and transmission modes. The NHA-based multispectral imager was capable of extracting 2D multispectral images representative of four independent bands within the spectral range of 662 nm to 832 nm for a variety of targets. The multispectral device can potentially be integrated into a variety of imaging sensor systems. PMID:24005065

  6. Spatially Resolved Synthetic Spectra from 2D Simulations of Stainless Steel Wire Array Implosions

    SciTech Connect

    Clark, R. W.; Giuliani, J. L.; Thornhill, J. W.; Chong, Y. K.; Dasgupta, A.; Davis, J.

    2009-01-21

    A 2D radiation MHD model has been developed to investigate stainless steel wire array implosion experiments on the Z and refurbished Z machines. This model incorporates within the Mach2 MHD code a self-consistent calculation of the non-LTE kinetics and ray trace based radiation transport. Such a method is necessary in order to account for opacity effects in conjunction with ionization kinetics of K-shell emitting plasmas. Here the model is used to investigate multi-dimensional effects of stainless steel wire implosions. In particular, we are developing techniques to produce non-LTE, axially and/or radially resolved synthetic spectra based upon snapshots of our 2D simulations. Comparisons between experimental spectra and these synthetic spectra will allow us to better determine the state of the experimental pinches.

  7. Fast Confocal Raman Imaging Using a 2-D Multifocal Array for Parallel Hyperspectral Detection.

    PubMed

    Kong, Lingbo; Navas-Moreno, Maria; Chan, James W

    2016-01-19

    We present the development of a novel confocal hyperspectral Raman microscope capable of imaging at speeds up to 100 times faster than conventional point-scan Raman microscopy under high noise conditions. The microscope utilizes scanning galvomirrors to generate a two-dimensional (2-D) multifocal array at the sample plane, generating Raman signals simultaneously at each focus of the array pattern. The signals are combined into a single beam and delivered through a confocal pinhole before being focused through the slit of a spectrometer. To separate the signals from each row of the array, a synchronized scan mirror placed in front of the spectrometer slit positions the Raman signals onto different pixel rows of the detector. We devised an approach to deconvolve the superimposed signals and retrieve the individual spectra at each focal position within a given row. The galvomirrors were programmed to scan different focal arrays following Hadamard encoding patterns. A key feature of the Hadamard detection is the reconstruction of individual spectra with improved signal-to-noise ratio. Using polystyrene beads as test samples, we demonstrated not only that our system images faster than a conventional point-scan method but that it is especially advantageous under noisy conditions, such as when the CCD detector operates at fast read-out rates and high temperatures. This is the first demonstration of multifocal confocal Raman imaging in which parallel spectral detection is implemented along both axes of the CCD detector chip. We envision this novel 2-D multifocal spectral detection technique can be used to develop faster imaging spontaneous Raman microscopes with lower cost detectors. PMID:26654100

  8. Low-voltage coded excitation utilizing a miniaturized integrated ultrasound system employing piezoelectric 2-D arrays.

    PubMed

    Triger, Simon; Saillant, Jean-Francois; Demore, Christine E M; Cochran, Sandy; Cumming, David R S

    2010-01-01

    We describe the development of an integrated, miniaturized ultrasound system designed for use with low-voltage piezoelectric transducer arrays. The technology targets low-frequency NDT and medium- to high-frequency sonar applications, at 1.2 MHz frequency. We have constructed a flexible, reconfigurable, low cost building block capable of 3-D beam forming. The tessellation of multiple building blocks permits formation of scalable 2-D macro-arrays of increased size and varying shape. This differs from conventional ultrasound solutions by integrating the entire system in a single module. No long RF cables are required to link the array elements to the electronics. The close coupling of the array and electronics assists in achieving adequate receive signal amplitudes with differential transmission voltages as low as +/- 3.3 V, although the system can be used at higher voltages. The system has been characterized by identifying flat-bottomed holes as small as 1 mm in diameter located at depths up to 190 mm in aluminum, and holes as small as 3 mm in diameter at a depth of 160 mm in cast iron. The results confirm the ability of the highly integrated system to obtain reflections from the targets despite the +/- 3.3 V excitation voltage by exploiting coding in low-voltage ultrasound.

  9. 2D array of cold-electron nanobolometers with double polarised cross-dipole antennas

    PubMed Central

    2012-01-01

    A novel concept of the two-dimensional (2D) array of cold-electron nanobolometers (CEB) with double polarised cross-dipole antennas is proposed for ultrasensitive multimode measurements. This concept provides a unique opportunity to simultaneously measure both components of an RF signal and to avoid complicated combinations of two schemes for each polarisation. The optimal concept of the CEB includes a superconductor-insulator-normal tunnel junction and an SN Andreev contact, which provides better performance. This concept allows for better matching with the junction gate field-effect transistor (JFET) readout, suppresses charging noise related to the Coulomb blockade due to the small area of tunnel junctions and decreases the volume of a normal absorber for further improvement of the noise performance. The reliability of a 2D array is considerably increased due to the parallel and series connections of many CEBs. Estimations of the CEB noise with JFET readout give an opportunity to realise a noise equivalent power (NEP) that is less than photon noise, specifically, NEP = 4 10−19 W/Hz1/2 at 7 THz for an optical power load of 0.02 fW. PMID:22512950

  10. Large 2D-arrays of size-controllable silver nanoparticles prepared by hybrid deposition

    NASA Astrophysics Data System (ADS)

    Dieu Thuy Ung, Thi; Hoa Nguyen, Thi; Liem Nguyen, Quang

    2016-09-01

    Two main results are presented in this paper. (i) Silver nanoparticles (AgNPs) with uniform size-distribution and controllability in the range of 20-50 nm were synthesized by seeding and growing at ambient conditions. The single-crystal Ag nano-seeds were created by reduction of AgNO3 in presence of citrate surfactant at 70 °C. Then, importantly, the fresh AgCl precursor was used in the presence of polyvinylpyrrolidone to adjust the reaction rate with ascorbic acid to generate Ag for growing on the surface of single-crystal Ag nano-seeds. The AgNPs size could be well-controlled by varying the amount of Ag nano-seeds while keeping the AgCl precursor concentration to be constant. (ii) The large 2D-arrays with homogeneous and dense monolayers of AgNPs were prepared on ITO substrates by hybrid method, in which the key technological point is the surface functionalization of AgNPs using mixed alkanethiols (dodecanethiol:octadecanethiol = 6:1). We have used the fabricated 2D-arrays from the 50 nm AgNPs as a surface enhanced Raman scattering substrate to take the Raman scattering spectra of rhodamine B (RhB), glucose and viral pathogen (H5N1) at very low concentrations of 10-10 M, 10-12 M and 4 ng μl-1, respectively.

  11. 2D array of cold-electron nanobolometers with double polarised cross-dipole antennas

    NASA Astrophysics Data System (ADS)

    Kuzmin, Leonid S.

    2012-04-01

    A novel concept of the two-dimensional (2D) array of cold-electron nanobolometers (CEB) with double polarised cross-dipole antennas is proposed for ultrasensitive multimode measurements. This concept provides a unique opportunity to simultaneously measure both components of an RF signal and to avoid complicated combinations of two schemes for each polarisation. The optimal concept of the CEB includes a superconductor-insulator-normal tunnel junction and an SN Andreev contact, which provides better performance. This concept allows for better matching with the junction gate field-effect transistor (JFET) readout, suppresses charging noise related to the Coulomb blockade due to the small area of tunnel junctions and decreases the volume of a normal absorber for further improvement of the noise performance. The reliability of a 2D array is considerably increased due to the parallel and series connections of many CEBs. Estimations of the CEB noise with JFET readout give an opportunity to realise a noise equivalent power (NEP) that is less than photon noise, specifically, NEP = 4 10-19 W/Hz1/2 at 7 THz for an optical power load of 0.02 fW.

  12. 2-D array for 3-D Ultrasound Imaging Using Synthetic Aperture Techniques

    PubMed Central

    Daher, Nadim M.; Yen, Jesse T.

    2010-01-01

    A 2-D array of 256 × 256 = 65,536 elements, with total area 4 × 4 = 16 cm2, serves as a flexible platform for developing acquisition schemes for 3-D rectilinear ultrasound imaging at 10 MHz using synthetic aperture techniques. This innovative system combines a simplified interconnect scheme and synthetic aperture techniques with a 2-D array for 3-D imaging. A row-column addressing scheme is used to access different elements for different transmit events. This addressing scheme is achieved through a simple interconnect, consisting of one top, one bottom single layer flex circuits, which, compared to multi-layer flex circuits, are simpler to design, cheaper to manufacture and thinner so their effect on the acoustic response is minimized. We present three designs that prioritize different design objectives: volume acquisiton time, resolution, and sensitivity, while maintaining acceptable figures for the other design objectives. For example, one design overlooks time acquisition requirements, assumes good noise conditions, and optimizes for resolution, achieving −6 dB and −20 dB beamwidths of less than 0.2 and 0.5 millimeters, respectively, for an F/2 aperture. Another design can acquire an entire volume in 256 transmit events, with −6dB and −20 dB beamwidths in the order of 0.4 and 0.8 millimeters, respectively. PMID:16764446

  13. Large 2D-arrays of size-controllable silver nanoparticles prepared by hybrid deposition

    NASA Astrophysics Data System (ADS)

    Dieu Thuy Ung, Thi; Hoa Nguyen, Thi; Liem Nguyen, Quang

    2016-09-01

    Two main results are presented in this paper. (i) Silver nanoparticles (AgNPs) with uniform size-distribution and controllability in the range of 20–50 nm were synthesized by seeding and growing at ambient conditions. The single-crystal Ag nano-seeds were created by reduction of AgNO3 in presence of citrate surfactant at 70 °C. Then, importantly, the fresh AgCl precursor was used in the presence of polyvinylpyrrolidone to adjust the reaction rate with ascorbic acid to generate Ag for growing on the surface of single-crystal Ag nano-seeds. The AgNPs size could be well-controlled by varying the amount of Ag nano-seeds while keeping the AgCl precursor concentration to be constant. (ii) The large 2D-arrays with homogeneous and dense monolayers of AgNPs were prepared on ITO substrates by hybrid method, in which the key technological point is the surface functionalization of AgNPs using mixed alkanethiols (dodecanethiol:octadecanethiol = 6:1). We have used the fabricated 2D-arrays from the 50 nm AgNPs as a surface enhanced Raman scattering substrate to take the Raman scattering spectra of rhodamine B (RhB), glucose and viral pathogen (H5N1) at very low concentrations of 10‑10 M, 10‑12 M and 4 ng μl‑1, respectively.

  14. Photoacoustic imaging for deep targets in the breast using a multichannel 2D array transducer

    NASA Astrophysics Data System (ADS)

    Xie, Zhixing; Wang, Xueding; Morris, Richard F.; Padilla, Frederic R.; Lecarpentier, Gerald L.; Carson, Paul L.

    2011-03-01

    A photoacoustic (PA) imaging system was developed to achieve high sensitivity for the detection and characterization of vascular anomalies in the breast in the mammographic geometry. Signal detection from deep in the breast was achieved by a broadband 2D PVDF planar array that has a round shape with one side trimmed straight to improve fit near the chest wall. This array has 572 active elements and a -6dB bandwidth of 0.6-1.7 MHz. The low frequency enhances imaging depth and increases the size of vascular collections displayed without edge enhancement. The PA signals from all the elements go through low noise preamplifiers in the probe that are very close to the array elements for optimized noise control. Driven by 20 independent on-probe signal processing channels, imaging with both high sensitivity and good speed was achieved. To evaluate the imaging depth and the spatial resolution of this system,2.38mm I.D. artificial vessels embedded deeply in ex vivo breasts harvested from fresh cadavers and a 3mm I.D. tube in breast mimicking phantoms made of pork loin and fat tissues were imaged. Using near-infrared laser light with incident energy density within the ANSI safety limit, imaging depths of up to 49 mm in human breasts and 52 mm in phantoms were achieved. With a high power tunable laser working on multiple wavelengths, this system might contribute to 3D noninvasive imaging of morphological and physiological tissue features throughout the breast.

  15. Conductance based characterization of structure and hopping site density in 2D molecule-nanoparticle arrays.

    PubMed

    McCold, Cliff E; Fu, Qiang; Howe, Jane Y; Hihath, Joshua

    2015-09-28

    Composite molecule-nanoparticle hybrid systems have recently emerged as important materials for applications ranging from chemical sensing to nanoscale electronics. However, creating reproducible and repeatable composite materials with precise properties has remained one of the primary challenges to the implementation of these technologies. Understanding the sources of variation that dominate the assembly and transport behavior is essential for the advancement of nanoparticle-array based devices. In this work, we use a combination of charge-transport measurements, electron microscopy, and optical characterization techniques to determine the role of morphology and structure on the charge transport properties of 2-dimensional monolayer arrays of molecularly-interlinked Au nanoparticles. Using these techniques we are able to determine the role of both assembly-dependent and particle-dependent defects on the conductivities of the films. These results demonstrate that assembly processes dominate the dispersion of conductance values, while nanoparticle and ligand features dictate the mean value of the conductance. By performing a systematic study of the conductance of these arrays as a function of nanoparticle size we are able to extract the carrier mobility for specific molecular ligands. We show that nanoparticle polydispersity correlates with the void density in the array, and that because of this correlation it is possible to accurately determine the void density within the array directly from conductance measurements. These results demonstrate that conductance-based measurements can be used to accurately and non-destructively determine the morphological and structural properties of these hybrid arrays, and thus provide a characterization platform that helps move 2-dimensional nanoparticle arrays toward robust and reproducible electronic systems.

  16. 2D MHD test-particle simulations in modeling geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Li, Z.; Elkington, S. R.; Hudson, M. K.; Murphy, J. J.; Schmitt, P.; Wiltberger, M. J.

    2012-12-01

    The effects of magnetic storms on the evolution of the electron radiation belts are studied using MHD test-particle simulations. The 2D guiding center code developed by Elkington et al. (2002) has been used to simulate particle motion in the Solar Magnetic equatorial plane in the MHD fields calculated from the Lyon-Fedder-Mobarry global MHD code. However, our study shows that the B-minimum plane is well off the SM equatorial plane during solstice events. Since 3D test-particle simulation is computationally expensive, we improve the 2D model by pushing particles in the B-minimum surface instead of the SM equatorial plane. Paraview software is used to visualize the LFM data file and to find the B-minimum surface. Magnetic and electric fields on B-minimum surface are projected to the equatorial plane for particle pushing.

  17. Holographic method for site-resolved detection of a 2D array of ultracold atoms

    NASA Astrophysics Data System (ADS)

    Hoffmann, Daniel Kai; Deissler, Benjamin; Limmer, Wolfgang; Hecker Denschlag, Johannes

    2016-08-01

    We propose a novel approach to site-resolved detection of a 2D gas of ultracold atoms in an optical lattice. A near-resonant laser beam is coherently scattered by the atomic array, and after passing a lens its interference pattern is holographically recorded by superimposing it with a reference laser beam on a CCD chip. Fourier transformation of the recorded intensity pattern reconstructs the atomic distribution in the lattice with single-site resolution. The holographic detection method requires only about two hundred scattered photons per atom in order to achieve a high reconstruction fidelity of 99.9 %. Therefore, additional cooling during detection might not be necessary even for light atomic elements such as lithium. Furthermore, first investigations suggest that small aberrations of the lens can be post-corrected in imaging processing.

  18. Quantum simulation of 2D topological physics in a 1D array of optical cavities.

    PubMed

    Luo, Xi-Wang; Zhou, Xingxiang; Li, Chuan-Feng; Xu, Jin-Shi; Guo, Guang-Can; Zhou, Zheng-Wei

    2015-07-06

    Orbital angular momentum of light is a fundamental optical degree of freedom characterized by unlimited number of available angular momentum states. Although this unique property has proved invaluable in diverse recent studies ranging from optical communication to quantum information, it has not been considered useful or even relevant for simulating nontrivial physics problems such as topological phenomena. Contrary to this misconception, we demonstrate the incredible value of orbital angular momentum of light for quantum simulation by showing theoretically how it allows to study a variety of important 2D topological physics in a 1D array of optical cavities. This application for orbital angular momentum of light not only reduces required physical resources but also increases feasible scale of simulation, and thus makes it possible to investigate important topics such as edge-state transport and topological phase transition in a small simulator ready for immediate experimental exploration.

  19. 2D electrostatic micromirror array with high field factor for high-power application

    NASA Astrophysics Data System (ADS)

    Lani, S.; Bayat, D.; Pétremand, Y.

    2013-03-01

    This paper reports the fabrication of a 20×20 micro mirror array (MMA) designed for high optical power application (5- 8kW/m2). Each pixel can attain a 2D mechanical tilt angle of +/- 4° in any arbitrary axis with an applied voltage of 150V. A novel packaging architecture is proposed to increase the ratio of mirror surface to packaging surface based on fully vertically integration process of the actuation (vertical electrodes), electrical interconnections (TSV) and signal processing (electronic). All components have a pitch smaller than the mirror surface. A detailed assessment of the fabrication process - including 3D wafer level assembly, through silicon via (TSV), electronic integration, and characterization methodology is presented with experimental results.

  20. Single particle 3D reconstruction for 2D crystal images of membrane proteins.

    PubMed

    Scherer, Sebastian; Arheit, Marcel; Kowal, Julia; Zeng, Xiangyan; Stahlberg, Henning

    2014-03-01

    In cases where ultra-flat cryo-preparations of well-ordered two-dimensional (2D) crystals are available, electron crystallography is a powerful method for the determination of the high-resolution structures of membrane and soluble proteins. However, crystal unbending and Fourier-filtering methods in electron crystallography three-dimensional (3D) image processing are generally limited in their performance for 2D crystals that are badly ordered or non-flat. Here we present a single particle image processing approach, which is implemented as an extension of the 2D crystallographic pipeline realized in the 2dx software package, for the determination of high-resolution 3D structures of membrane proteins. The algorithm presented, addresses the low single-to-noise ratio (SNR) of 2D crystal images by exploiting neighborhood correlation between adjacent proteins in the 2D crystal. Compared with conventional single particle processing for randomly oriented particles, the computational costs are greatly reduced due to the crystal-induced limited search space, which allows a much finer search space compared to classical single particle processing. To reduce the considerable computational costs, our software features a hybrid parallelization scheme for multi-CPU clusters and computer with high-end graphic processing units (GPUs). We successfully apply the new refinement method to the structure of the potassium channel MloK1. The calculated 3D reconstruction shows more structural details and contains less noise than the map obtained by conventional Fourier-filtering based processing of the same 2D crystal images.

  1. A 2-D Array of Superconducting Magnesium Diboride (MgB2) Far-IR Thermal Detectors for Planetary Exploration

    NASA Technical Reports Server (NTRS)

    Lakew, Brook

    2009-01-01

    A 2-D array of superconducting Magnesium Diboride(MgB2) far IR thermal detectors has been fabricated. Such an array is intended to be at the focal plane of future generation thermal imaging far-IR instruments that will investigate the outer planets and their icy moons. Fabrication and processing of the pixels of the array as well as noise characterization of architectured MgB2 thin films will be presented. Challenges and solutions for improving the performance of the array will be discussed.

  2. 2D-DOA estimation of noncircular signals for uniform rectangular array via NC-PARAFAC method

    NASA Astrophysics Data System (ADS)

    Zhang, Licen; Lv, Weihua; Zhang, Xiaofei; Li, Shu

    2016-11-01

    In this paper, we propose a two-dimensional direction of arrival (2D-DOA) estimation algorithm for uniform rectangular array via noncircular-parallel factor (NC-PARAFAC) method. Compared to the conventional parallel factor (PARAFAC) algorithm, the proposed algorithm exploits the property of noncircular signals to double the array aperture. Therefore, the angle estimation performance of the proposed algorithm is better than the conventional PARAFAC method. The proposed algorithm achieves automatically paired two-dimensional angle estimates, and has better 2D-DOA estimation performance than some conventional algorithms, which include estimation of signal parameters via rotational invariance technique (ESPRIT), propagator method (PM), PARAFAC algorithm, noncircular-ESPRIT (NC-ESPRIT) and noncircular-PM (NC-PM). We also derive the Cramér-Rao bound for the 2D-DOA estimation of noncircular signals with uniform rectangular array. Simulation results verify the effectiveness and improvement of the proposed algorithm.

  3. Quality assurance of asymmetric jaw alignment using 2D diode array

    SciTech Connect

    Kim, Sun Mo; Yeung, Ivan W. T.; Moseley, Douglas J.

    2013-12-15

    Purpose: A method using a 2D diode array is proposed to measure the junction gap (or overlap) and dose with high precision for routine quality assurance of the asymmetric jaw alignment.Methods: The central axis (CAX) of the radiation field was determined with a 15 × 15 cm{sup 2} photon field at four cardinal collimator angles so that the junction gap (or overlap) can be measured with respect to the CAX. Two abutting fields having a field size of 15 cm (length along the axis parallel to the junction) × 7.5 cm (width along the axis perpendicular to the junction) were used to irradiate the 2D diode array (MapCHECK2) with 100 MU delivered at the photon energy of 6 MV. The collimator was slightly rotated at 15° with respect to the beam central axis to increase the number of diodes effective on the measurement of junction gap. The junction gap and dose measured in high spatial resolution were compared to the conventional methods using an electronic portal imaging device (EPID) and radiochromic film, respectively. In addition, the reproducibility and sensitivity of the proposed method to the measurements of junction gap and dose were investigated.Results: The junction gap (or overlap) and dose measured by MapCHECK2 agreed well to those measured by the conventional methods of EPID and film (the differences ranged from −0.01 to 0 cm and from −1.34% to 0.6% for the gap and dose, respectively). No variation in the repeat measurements of the junction gap was found whereas the measurements of junction dose were found to vary in quite a small range over the days of measurement (0.21%–0.35%). While the sensitivity of the measured junction gap to the actual junction gap applied was the ideal value of 1 cm/cm as expected, the sensitivity of the junction dose to the actual junction gap increased as the junction gap (or overlap) decreased (maximum sensitivity: 201.7%/cm).Conclusions: The initial results suggest that the method is applicable for a comprehensive quality

  4. Quantum-Carnot engine for particle confined to 2D symmetric potential well

    NASA Astrophysics Data System (ADS)

    Belfaqih, Idrus Husin; Sutantyo, Trengginas Eka Putra; Prayitno, T. B.; Sulaksono, Anto

    2015-09-01

    Carnot model of heat engine is the most efficient cycle consisting of isothermal and adiabatic processes which are reversible. Although ideal gas usually used as a working fluid in the Carnot engine, Bender used quantum particle confined in 1D potential well as a working fluid. In this paper, by following Bender we generalize the situation to 2D symmetric potential well. The efficiency is express as the ratio of the initial length of the system to the final length of the compressed system. The result then is shown that for the same ratio, 2D potential well is more efficient than 1D potential well.

  5. Quantum-Carnot engine for particle confined to 2D symmetric potential well

    SciTech Connect

    Belfaqih, Idrus Husin Sutantyo, Trengginas Eka Putra Prayitno, T. B.; Sulaksono, Anto

    2015-09-30

    Carnot model of heat engine is the most efficient cycle consisting of isothermal and adiabatic processes which are reversible. Although ideal gas usually used as a working fluid in the Carnot engine, Bender used quantum particle confined in 1D potential well as a working fluid. In this paper, by following Bender we generalize the situation to 2D symmetric potential well. The efficiency is express as the ratio of the initial length of the system to the final length of the compressed system. The result then is shown that for the same ratio, 2D potential well is more efficient than 1D potential well.

  6. Towards Simulating the Transverse Ising Model in a 2D Array of Trapped Ions

    NASA Astrophysics Data System (ADS)

    Sawyer, Brian

    2013-05-01

    Two-dimensional Coulomb crystals provide a useful platform for large-scale quantum simulation. Penning traps enable confinement of large numbers of ions (>100) and allow for the tunable-range spin-spin interactions demonstrated in linear ion strings, facilitating simulation of quantum magnetism at a scale that is currently intractable on classical computers. We readily confine hundreds of Doppler laser-cooled 9Be+ within a Penning trap, producing a planar array of ions with self-assembled triangular order. The transverse ``drumhead'' modes of our 2D crystal along with the valence electron spin of Be+ serve as a resource for generating spin-motion and spin-spin entanglement. Applying a spin-dependent optical dipole force (ODF) to the ion array, we perform spectroscopy and thermometry of individual drumhead modes. This ODF also allows us to engineer long-range Ising spin couplings of either ferromagnetic or anti-ferromagnetic character whose approximate power-law scaling with inter-ion distance, d, may be varied continuously from 1 /d0 to 1 /d3. An effective transverse magnetic field is applied via microwave radiation at the ~124-GHz spin-flip frequency, and ground states of the effective Ising Hamiltonian may in principle be prepared adiabatically by slowly decreasing this transverse field in the presence of the induced Ising coupling. Long-range anti-ferromagnetic interactions are of particular interest due to their inherent spin frustration and resulting large, near-degenerate manifold of ground states. We acknowledge support from NIST and the DARPA-OLE program.

  7. Quantitative Verification of Dynamic Wedge Dose Distribution Using a 2D Ionization Chamber Array.

    PubMed

    Sahnoun, Tarek; Farhat, Leila; Mtibaa, Anis; Besbes, Mounir; Daoud, Jamel

    2015-10-01

    The accuracy of two calculation algorithms of the Eclipse 8.9 treatment planning system (TPS)--the anisotropic analytic algorithm (AAA) and pencil-beam convolution (PBC)--in modeling the enhanced dynamic wedge (EDW) was investigated. Measurements were carried out for 6 and 18 MV photon beams using a 2D ionization chamber array. Accuracy of the TPS was evaluated using a gamma index analysis with the following acceptance criteria for dose differences (DD) and distance to agreement (DTA): 3%/3 mm and 2%/2 mm. The TPS models the dose distribution accurately except for 20×20 cm(2) field size, 60 (°) and 45 (°) wedge angles using PBC at 6 MV photon energy. For these latter fields, the pass rate and the mean value of gamma were less than 90% and more than 0.5, respectively at the (3%/3 mm) acceptance criteria. In addition, an accuracy level of (2%/2 mm) was achieved using AAA with better agreement for 18 MV photon energy.

  8. A preliminary evaluation work on a 3D ultrasound imaging system for 2D array transducer

    NASA Astrophysics Data System (ADS)

    Zhong, Xiaoli; Li, Xu; Yang, Jiali; Li, Chunyu; Song, Junjie; Ding, Mingyue; Yuchi, Ming

    2016-04-01

    This paper presents a preliminary evaluation work on a pre-designed 3-D ultrasound imaging system. The system mainly consists of four parts, a 7.5MHz, 24×24 2-D array transducer, the transmit/receive circuit, power supply, data acquisition and real-time imaging module. The row-column addressing scheme is adopted for the transducer fabrication, which greatly reduces the number of active channels . The element area of the transducer is 4.6mm by 4.6mm. Four kinds of tests were carried out to evaluate the imaging performance, including the penetration depth range, axial and lateral resolution, positioning accuracy and 3-D imaging frame rate. Several strong reflection metal objects , fixed in a water tank, were selected for the purpose of imaging due to a low signal-to-noise ratio of the transducer. The distance between the transducer and the tested objects , the thickness of aluminum, and the seam width of the aluminum sheet were measured by a calibrated micrometer to evaluate the penetration depth, the axial and lateral resolution, respectively. The experiment al results showed that the imaging penetration depth range was from 1.0cm to 6.2cm, the axial and lateral resolution were 0.32mm and 1.37mm respectively, the imaging speed was up to 27 frames per second and the positioning accuracy was 9.2%.

  9. Self-alignment of silver nanoparticles in highly ordered 2D arrays.

    PubMed

    Rodríguez-León, Ericka; Íñiguez-Palomares, Ramón; Urrutia-Bañuelos, Efraín; Herrera-Urbina, Ronaldo; Tánori, Judith; Maldonado, Amir

    2015-01-01

    We have synthesized silver nanoparticles in the non-polar phase of non-aqueous microemulsions. The nanocrystals have been grown by reducing silver ions in the microemulsion cylindrical micelles formed by the reducing agent (ethylene glycol). By a careful deposit of the microemulsion phase on a substrate, the micelles align in a hexagonal geometry, thus forming a 2D array of parallel strings of individual silver nanoparticles on the substrate. The microemulsions are the ternary system of anionic surfactant, non-polar solvent (isooctane), and solvent polar (ethylene glycol); the size of synthesized nanoparticles is about 7 nm and they are monodisperse. The study of the microstructure was realized by transmission electron microscopy, high-resolution technique transmission electron microscopy (HR-TEM), and Fourier processing using the software Digital Micrograph for the determination of the crystalline structure of the HR-TEM images of the nanocrystals; chemical composition was determined using the energy-dispersive X-ray spectroscopy. Addition technique polarizing light microscopy allowed the observation of the hexagonal phase of the system. This method of synthesis and self-alignment could be useful for the preparation of patterned materials at the nanometer scale.

  10. Quantum information experiments with 2D arrays of hundreds of trapped ions

    NASA Astrophysics Data System (ADS)

    Gilmore, Kevin; Bohnet, Justin; Sawyer, Brian; Britton, Joseph; Wall, Michael; Foss-Feig, Michael; Rey, Ana Maria; Bollinger, John

    2016-05-01

    We summarize recent experimental work with 2D arrays of hundreds of trapped 9 Be+ ions stored in a Penning trap. Penning traps utilize static magnetic and electric fields to confine ions, and enable the trapping and laser cooling of ion crystals larger than typically possible in RF ion traps. We work with single-plane ion crystals where the ions form a triangular lattice through minimization of their Coulomb potential energy. The crystals rotate, and we present numerical studies that determine optimal operating parameters for producing low temperature, stable 2-dimensional crystals with Doppler laser cooling and a rotating wall potential. Our qubit is the electron spin-flip transition in the ground state of 9 Be+ and is sensitive to magnetic field fluctuations. Through mitigation of part-per-billion, vibration-induced magnetic field fluctuations we demonstrate T2 coherence times longer than 50 ms. We engineer long-range Ising interactions with spin-dependent optical dipole forces, and summarize recent measurements that characterize the entanglement generated through single-axis twisting. Supported by: JILA-NSF-PFC-1125844, NSF-PHY-1521080, ARO, AFOSR, AFOSR-MURI.

  11. Dosimetric verification of gated delivery of electron beams using a 2D ion chamber array

    PubMed Central

    Yoganathan, S. A.; Das, K. J. Maria; Raj, D. Gowtham; Kumar, Shaleen

    2015-01-01

    The purpose of this study was to compare the dosimetric characteristics; such as beam output, symmetry and flatness between gated and non-gated electron beams. Dosimetric verification of gated delivery was carried for all electron beams available on Varian CL 2100CD medical linear accelerator. Measurements were conducted for three dose rates (100 MU/min, 300 MU/min and 600 MU/min) and two respiratory motions (breathing period of 4s and 8s). Real-time position management (RPM) system was used for the gated deliveries. Flatness and symmetry values were measured using Imatrixx 2D ion chamber array device and the beam output was measured using plane parallel ion chamber. These detector systems were placed over QUASAR motion platform which was programmed to simulate the respiratory motion of target. The dosimetric characteristics of gated deliveries were compared with non-gated deliveries. The flatness and symmetry of all the evaluated electron energies did not differ by more than 0.7 % with respect to corresponding non-gated deliveries. The beam output variation of gated electron beam was less than 0.6 % for all electron energies except for 16 MeV (1.4 %). Based on the results of this study, it can be concluded that Varian CL2100 CD is well suitable for gated delivery of non-dynamic electron beams. PMID:26170552

  12. Dosimetric verification of gated delivery of electron beams using a 2D ion chamber array.

    PubMed

    Yoganathan, S A; Das, K J Maria; Raj, D Gowtham; Kumar, Shaleen

    2015-01-01

    The purpose of this study was to compare the dosimetric characteristics; such as beam output, symmetry and flatness between gated and non-gated electron beams. Dosimetric verification of gated delivery was carried for all electron beams available on Varian CL 2100CD medical linear accelerator. Measurements were conducted for three dose rates (100 MU/min, 300 MU/min and 600 MU/min) and two respiratory motions (breathing period of 4s and 8s). Real-time position management (RPM) system was used for the gated deliveries. Flatness and symmetry values were measured using Imatrixx 2D ion chamber array device and the beam output was measured using plane parallel ion chamber. These detector systems were placed over QUASAR motion platform which was programmed to simulate the respiratory motion of target. The dosimetric characteristics of gated deliveries were compared with non-gated deliveries. The flatness and symmetry of all the evaluated electron energies did not differ by more than 0.7 % with respect to corresponding non-gated deliveries. The beam output variation of gated electron beam was less than 0.6 % for all electron energies except for 16 MeV (1.4 %). Based on the results of this study, it can be concluded that Varian CL2100 CD is well suitable for gated delivery of non-dynamic electron beams.

  13. Self-alignment of silver nanoparticles in highly ordered 2D arrays

    NASA Astrophysics Data System (ADS)

    Rodríguez-León, Ericka; Íñiguez-Palomares, Ramón; Urrutia-Bañuelos, Efraín; Herrera-Urbina, Ronaldo; Tánori, Judith; Maldonado, Amir

    2015-03-01

    We have synthesized silver nanoparticles in the non-polar phase of non-aqueous microemulsions. The nanocrystals have been grown by reducing silver ions in the microemulsion cylindrical micelles formed by the reducing agent (ethylene glycol). By a careful deposit of the microemulsion phase on a substrate, the micelles align in a hexagonal geometry, thus forming a 2D array of parallel strings of individual silver nanoparticles on the substrate. The microemulsions are the ternary system of anionic surfactant, non-polar solvent (isooctane), and solvent polar (ethylene glycol); the size of synthesized nanoparticles is about 7 nm and they are monodisperse. The study of the microstructure was realized by transmission electron microscopy, high-resolution technique transmission electron microscopy (HR-TEM), and Fourier processing using the software Digital Micrograph for the determination of the crystalline structure of the HR-TEM images of the nanocrystals; chemical composition was determined using the energy-dispersive X-ray spectroscopy. Addition technique polarizing light microscopy allowed the observation of the hexagonal phase of the system. This method of synthesis and self-alignment could be useful for the preparation of patterned materials at the nanometer scale.

  14. Coherent beam combining using a 2D internally sensed optical phased array.

    PubMed

    Roberts, Lyle E; Ward, Robert L; Sutton, Andrew J; Fleddermann, Roland; de Vine, Glenn; Malikides, Emmanuel A; Wuchenich, Danielle M R; McClelland, David E; Shaddock, Daniel A

    2014-08-01

    Coherent combination of multiple lasers using an optical phased array (OPA) is an effective way to scale optical intensity in the far field beyond the capabilities of single fiber lasers. Using an actively phase locked, internally sensed, 2D OPA we demonstrate over 95% fringe visibility of the interfered beam, λ/120 RMS output phase stability over a 5 Hz bandwidth, and quadratic scaling of intensity in the far field using three emitters. This paper presents a new internally sensed OPA architecture that employs a modified version of digitally enhanced heterodyne interferometry (DEHI) based on code division multiplexing to measure and control the phase of each emitter. This internally sensed architecture can be implemented with no freespace components, offering improved robustness to shock and vibration exhibited by all-fiber devices. To demonstrate the concept, a single laser is split into three channels/emitters, each independently controlled using separate electro-optic modulators. The output phase of each channel is measured using DEHI to sense the small fraction of light that is reflected back into the fiber at the OPA's glass-air interface. The relative phase between emitters is used to derive the control signals needed to stabilize their relative path lengths and maintain coherent combination in the far field.

  15. Feasibility of MatriXX 2D detector array for HDR brachytherapy planning system assessment

    NASA Astrophysics Data System (ADS)

    Zeman, Jozef; Valenta, Jiri; Gabris, Frantisek; Grezdo, Jozef; Stastna, Simona

    2012-10-01

    IBA Dosimetry GmbH participated in the Joint Research Project ‘Increasing cancer treatment efficacy using 3D brachytherapy’ as a non-funded partner in the work package which was mostly dedicated to the determination of dose-to-water distribution from a high-dose-rate (HDR) brachytherapy source. The dose distribution was measured with a MatriXX (MXX) 2D detector array and compared with Dose Cube Data, calculated by treatment planning systems (TPS). All measurements and calculations were performed in cooperation with OUSA, Bratislava and FNB, Prague. The comparison has been carried out for three irradiation geometries: single source position, single line and four line motions of the source, and with the effective point of measurement in a plane at 6 mm, 10 mm and 20 mm distance from the source position. The comparison of the MXX measurements and the TPS calculations was evaluated by the commercial IBA Dosimetry software OmniPro I'mRT (1) as the difference between maximum of measured and calculated values and (2) as the maximum difference between the two-dimensional distributions of measured and calculated values. The dose distribution was evaluated by the gamma method with parameters 3 mm and 3%. All differences of comparison of the MXX measurements and TPS calculations were within the range ±10% and the γ-index was less than 1 for 96% (or 97%, respectively) of the dose distribution in the plane at 10 mm distance from the source position.

  16. Self-alignment of silver nanoparticles in highly ordered 2D arrays.

    PubMed

    Rodríguez-León, Ericka; Íñiguez-Palomares, Ramón; Urrutia-Bañuelos, Efraín; Herrera-Urbina, Ronaldo; Tánori, Judith; Maldonado, Amir

    2015-01-01

    We have synthesized silver nanoparticles in the non-polar phase of non-aqueous microemulsions. The nanocrystals have been grown by reducing silver ions in the microemulsion cylindrical micelles formed by the reducing agent (ethylene glycol). By a careful deposit of the microemulsion phase on a substrate, the micelles align in a hexagonal geometry, thus forming a 2D array of parallel strings of individual silver nanoparticles on the substrate. The microemulsions are the ternary system of anionic surfactant, non-polar solvent (isooctane), and solvent polar (ethylene glycol); the size of synthesized nanoparticles is about 7 nm and they are monodisperse. The study of the microstructure was realized by transmission electron microscopy, high-resolution technique transmission electron microscopy (HR-TEM), and Fourier processing using the software Digital Micrograph for the determination of the crystalline structure of the HR-TEM images of the nanocrystals; chemical composition was determined using the energy-dispersive X-ray spectroscopy. Addition technique polarizing light microscopy allowed the observation of the hexagonal phase of the system. This method of synthesis and self-alignment could be useful for the preparation of patterned materials at the nanometer scale. PMID:25883540

  17. Verification measurements of an eMC algorithm using a 2D ion chamber array.

    PubMed

    Wanklyn, Mark D; Kidane, Ghirmay; Crees, Liz

    2016-01-01

    The aim of this study was to assess the suitability of the Im'RT MatriXX 2D ion chamber array for performing verification measurements on the Varian Eclipse electron Monte Carlo (eMC) algorithm for a range of clinical energies (6, 12, and 20 MeV) on a Varian 2100iX linear accelerator. Firstly, the suitability of the MatriXX for measuring percentage depth doses (PDD) in water was assessed, including characterization of the inherent buildup found in the MatriXX. Secondly the suitability of the MatriXX for measuring dose distributions in homogeneous and heterogeneous phantoms was assessed using gamma analysis at 3%/3 mm. It was found that after adjusting the PDD curves for the inherent buildup, that the position of R50,D measured using the MatriXX agreed to within 1 mm to the PDDs generated using the eMC algorithm for all energies used in this study. Gamma analysis at 3%/3mm showed very good agreement (> 95%) for all cases in both homogeneous and heterogeneous phantoms. It was concluded that the Im'RT MatriXX is a suitable device for performing eMC verification and could potentially be used for routine energy checks of electron beams. PMID:27685111

  18. A 2-D Implicit, Energy and Charge Conserving Particle In Cell Method

    SciTech Connect

    McPherson, Allen L.; Knoll, Dana A.; Cieren, Emmanuel B.; Feltman, Nicolas; Leibs, Christopher A.; McCarthy, Colleen; Murthy, Karthik S.; Wang, Yijie

    2012-09-10

    Recently, a fully implicit electrostatic 1D charge- and energy-conserving particle-in-cell algorithm was proposed and implemented by Chen et al ([2],[3]). Central to the algorithm is an advanced particle pusher. Particles are moved using an energy conserving scheme and are forced to stop at cell faces to conserve charge. Moreover, a time estimator is used to control errors in momentum. Here we implement and extend this advanced particle pusher to include 2D and electromagnetic fields. Derivations of all modifications made are presented in full. Special consideration is taken to ensure easy coupling into the implicit moment based method proposed by Taitano et al [19]. Focus is then given to optimizing the presented particle pusher on emerging architectures. Two multicore implementations, and one GPU (Graphics Processing Unit) implementation are discussed and analyzed.

  19. Packaging and modular assembly of large-area and fine-pitch 2-D ultrasonic transducer arrays.

    PubMed

    Lin, Der-Song; Wodnicki, Robert; Zhuang, Xuefeng; Woychik, Charles; Thomenius, Kai E; Fisher, Rayette A; Mills, David M; Byun, Albert J; Burdick, William; Khuri-Yakub, Pierre; Bonitz, Barry; Davies, Todd; Thomas, Glen; Otto, Bernd; Töpper, Michael; Fritzsch, Thomas; Ehrmann, Oswin

    2013-07-01

    A promising transducer architecture for largearea arrays employs 2-D capacitive micromachined ultrasound transducer (CMUT) devices with backside trench-frame pillar interconnects. Reconfigurable array (RA) application-specified integrated circuits (ASICs) can provide efficient interfacing between these high-element-count transducer arrays and standard ultrasound systems. Standard electronic assembly techniques such as flip-chip and ball grid array (BGA) attachment, along with organic laminate substrate carriers, can be leveraged to create large-area arrays composed of tiled modules of CMUT chips and interface ASICs. A large-scale, fully populated and integrated 2-D CMUT array with 32 by 192 elements was developed and demonstrates the feasibility of these techniques to yield future large-area arrays. This study demonstrates a flexible and reliable integration approach by successfully combining a simple under-bump metallization (UBM) process and a stacked CMUT/interposer/ASIC module architecture. The results show high shear strength of the UBM (26.5 g for 70-μm balls), high interconnect yield, and excellent CMUT resonance uniformity (s = 0.02 MHz). A multi-row linear array was constructed using the new CMUT/interposer/ASIC process using acoustically active trench-frame CMUT devices and mechanical/ nonfunctional Si backside ASICs. Imaging results with the completed probe assembly demonstrate a functioning device based on the modular assembly architecture. PMID:25004504

  20. Simulations of two-particle interactions with 2D quantum walks in time

    SciTech Connect

    Schreiber, A.; Laiho, K.; Silberhorn, C.; Rohde, P. P.; Štefaňak, M.; Potoček, V.; Hamilton, C.; Jex, I.

    2014-12-04

    We present the experimental implementation of a quantum walk on a two-dimensional lattice and show how to employ the optical system to simulate the quantum propagation of two interacting particles. Our quantum walk in time transfers the spatial spread of a quantum walk into the time domain, which guarantees a high stability and scalability of the setup. We present with our device quantum walks over 12 steps on a 2D lattice. By changing the properties of the driving quantum coin, we investigate different kinds of two-particle interactions and reveal their impact on the occurring quantum propagation.

  1. Joint Estimation of 2D-DOA and Frequency Based on Space-Time Matrix and Conformal Array

    PubMed Central

    Wan, Liang-Tian; Liu, Lu-Tao; Si, Wei-Jian; Tian, Zuo-Xi

    2013-01-01

    Each element in the conformal array has a different pattern, which leads to the performance deterioration of the conventional high resolution direction-of-arrival (DOA) algorithms. In this paper, a joint frequency and two-dimension DOA (2D-DOA) estimation algorithm for conformal array are proposed. The delay correlation function is used to suppress noise. Both spatial and time sampling are utilized to construct the spatial-time matrix. The frequency and 2D-DOA estimation are accomplished based on parallel factor (PARAFAC) analysis without spectral peak searching and parameter pairing. The proposed algorithm needs only four guiding elements with precise positions to estimate frequency and 2D-DOA. Other instrumental elements can be arranged flexibly on the surface of the carrier. Simulation results demonstrate the effectiveness of the proposed algorithm. PMID:24453856

  2. Compact optical true time delay beamformer for a 2D phased array antenna using tunable dispersive elements.

    PubMed

    Ye, Xingwei; Zhang, Fangzheng; Pan, Shilong

    2016-09-01

    A hardware-compressive optical true time delay architecture for 2D beam steering in a planar phased array antenna is proposed using fiber-Bragg-grating-based tunable dispersive elements (TDEs). For an M×N array, the proposed system utilizes N TDEs and M wavelength-fixed optical carriers to control the time delays. Both azimuth and elevation beam steering are realized by programming the settings of the TDEs. An experiment is carried out to demonstrate the delay controlling in a 2×2 array, which is fed by a wideband pulsed signal. Radiation patterns calculated from the experimentally measured waveforms at the four antennas match well with the theoretical results.

  3. Hydrates in the California Borderlands: 2D CSEM inversion results from towed and seafloor arrays

    NASA Astrophysics Data System (ADS)

    Kannberg, P. K.; Constable, S.; Key, K.

    2013-12-01

    Methane hydrate, an ice-like solid clathrate of methane and water, forms in shallow continental slope sediments, and is both a potential energy source and geologic hazard. Traditionally, methane hydrate presence is inferred from a seismically detected bathymetry tracking velocity inversion, known as the bottom-simulating reflector (BSR). However the BSR is an indicator of free gas at the base of the hydrate stability zone, and not an indicator of hydrate. As such, seismic methods are limited in their capacity to identify and quantify hydrate presence and concentration. Controlled source electromagnetic (CSEM) methods are sensitive to, and are able to directly detect, the presence of electrically resistive methane hydrate and free gas. Additionally, because shallow resistors can mimic deeper resistors in seafloor instruments, understanding the shallow sediment structure can inform deeper crustal modeling. We conducted two CSEM surveys in the San Nicolas Basin, located 150km west of San Diego where a BSR was identified from legacy seismics. Both surveys were conducted using a deep-towed EM transmitter followed by 4 towed 3-axis electric field receivers spaced every 200 m from 400-1000 m behind the transmitter. Either a half-hertz or quarter-hertz modified square wave was transmitted on a 200 ampere, 100 m dipole that was flown between 50 and 100m above the seafloor. The short transmitter-receiver offset allows resolution of shallow structure (less than 1km below seafloor), while the longer transmitter-seafloor receiver resolves deeper structure. Between the two surveys, 27 seafloor receivers were deployed and ~150km of lines were towed, including 5 transects of the basin coincident with legacy seismic lines, and a short-offset repeatability study. Initial 1D modeling showed the presence of a resistor coincident with the BSR. Further 2D inversions using the MARE2DEM inversion program were run for the towed array. These inversions show a 4 ohm-m resistor in the central

  4. Variable FOV optical illumination system with constant aspect ratio for 2-D array lasers diodes

    NASA Astrophysics Data System (ADS)

    Arasa, J.; de la Fuente, M. C.; Ibañez, C.

    2008-09-01

    In this contribution we present a compact system to create an illumination distribution with a constant aspect ratio 3:4 and FOV from 0.4 to 1 degree. Besides, the system must delivery 40 W from 170 individual laser diodes placed in a regular 2-D array distribution of 10 x 20 mm. The main problem that must be solved is the high asymmetry of the individual sources; emission divergence's ratio 3:73 (0.3 vs. 7.4 degree) combined with the flux holes due to the laser's heat drain. In one axis (divergence of 0.3º) the best design strategy approach is a Galileo telescope but in the other axis a collimator configuration is the best solution. To manage both solutions at the same time is the aim of this contribution. Unfortunately for the Galileo strategy, source dimensions are too large so aspheric surfaces are needed, and the collimator configuration requires an EFL that must change from 573 to 1432 mm. The presented solution uses a set of three fixed anamorphic lenses, two of them pure cylinders, combined with a wheel of anamorphic lenses that have the function to change the FOV of the system. The most important contribution of the design is to obtain a constant final ratio 3:4 from an initial ratio of 3:73 with no losses of energy. The proposed solution produces an illumination pattern with peaks and valleys lower than 40%. This pattern distribution might be unacceptable for a standard illumination solution. However, the actual FOV is used to illuminate far away targets thus air turbulence is enough to homogenize the distribution on the target.

  5. Single-element based ultra-wideband antenna array concepts for wireless high-precision 2-D local positioning

    NASA Astrophysics Data System (ADS)

    Gardill, M.; Fischer, G.; Weigel, R.; Koelpin, A.

    2013-07-01

    We generally categorize the approaches for ultra-wideband antenna array design, and consequently propose simplified concepts for antenna arrays for a high-precision, ultra-wideband FMCW radar 2-D local positioning system to obtain robustness against multi path interference, perform angle of arrival analysis, as well as instantaneous heading estimation. We focus on low-cost and mechanical robust, industrial-application ready antennas. The antenna arrays are optimized for operation in the 5 GHz to 8 GHz frequency range and are designed towards supporting full omnidirectional 360° as well as partial half-plane direction of arrival estimation. Two different concepts for vehicle- as well as wall-mounted antenna array systems are proposed and discussed. We propose a wideband unidirectional bow-tie antenna array element having 97% impedance and 37% pattern bandwidth and a robust vehicle mounted omnidirectional antenna element having more than 85% impedance and pattern bandwidth.

  6. Construction of inorganic-organic 2D/2D WO₃/g-C₃N₄ nanosheet arrays toward efficient photoelectrochemical splitting of natural seawater.

    PubMed

    Li, Yuangang; Wei, Xiaoliang; Yan, Xiangyang; Cai, Jiangtao; Zhou, Anning; Yang, Mengru; Liu, Kaiqiang

    2016-04-21

    Hydrogen production from seawater and solar energy based on photoelectrochemical cells is extremely attractive due to earth-abundance of seawater and solar radiation. Herein, we report the successful fabrication of novel inorganic-organic 2D/2D WO3/g-C3N4 nanosheet arrays (WO3/g-C3N4 NSAs) grown on a FTO substrate via a facile hydrothermal growth and deposition-annealing process, and their application in natural seawater splitting. The results indicate that the WO3/g-C3N4 NSAs exhibit a photocurrent density of 0.73 mA cm(-2) at 1.23 V versus RHE under AM 1.5G (100 mW cm(-2)) illumination, which is 2-fold higher than that of WO3 NSAs. More importantly, the WO3/g-C3N4 NSA photoanode is quite stable during seawater splitting and the photocurrent density does not substantially decrease after continuous illumination for 3600 s. The remarkably enhanced performance originates primarily from the formation of the WO3/g-C3N4 heterojunction between WO3 and g-C3N4 nanosheets, which accelerates charge transfer and separation, and prolongs the lifetime of electrons as demonstrated by EIS and Mott-Schottky analyses. Finally, a possible mechanism for the improved performance was proposed and discussed. PMID:27022001

  7. Application of X-Y Separable 2-D Array Beamforming for Increased Frame Rate and Energy Efficiency in Handheld Devices

    PubMed Central

    Owen, Kevin; Fuller, Michael I.; Hossack, John A.

    2015-01-01

    Two-dimensional arrays present significant beamforming computational challenges because of their high channel count and data rate. These challenges are even more stringent when incorporating a 2-D transducer array into a battery-powered hand-held device, placing significant demands on power efficiency. Previous work in sonar and ultrasound indicates that 2-D array beamforming can be decomposed into two separable line-array beamforming operations. This has been used in conjunction with frequency-domain phase-based focusing to achieve fast volume imaging. In this paper, we analyze the imaging and computational performance of approximate near-field separable beamforming for high-quality delay-and-sum (DAS) beamforming and for a low-cost, phaserotation-only beamforming method known as direct-sampled in-phase quadrature (DSIQ) beamforming. We show that when high-quality time-delay interpolation is used, separable DAS focusing introduces no noticeable imaging degradation under practical conditions. Similar results for DSIQ focusing are observed. In addition, a slight modification to the DSIQ focusing method greatly increases imaging contrast, making it comparable to that of DAS, despite having a wider main lobe and higher side lobes resulting from the limitations of phase-only time-delay interpolation. Compared with non-separable 2-D imaging, up to a 20-fold increase in frame rate is possible with the separable method. When implemented on a smart-phone-oriented processor to focus data from a 60 × 60 channel array using a 40 × 40 aperture, the frame rate per C-mode volume slice increases from 16 to 255 Hz for DAS, and from 11 to 193 Hz for DSIQ. Energy usage per frame is similarly reduced from 75 to 4.8 mJ/ frame for DAS, and from 107 to 6.3 mJ/frame for DSIQ. We also show that the separable method outperforms 2-D FFT-based focusing by a factor of 1.64 at these data sizes. This data indicates that with the optimal design choices, separable 2-D beamforming can

  8. Application of X-Y separable 2-D array beamforming for increased frame rate and energy efficiency in handheld devices.

    PubMed

    Owen, Kevin; Fuller, Michael; Hossack, John

    2012-07-01

    Two-dimensional arrays present significant beamforming computational challenges because of their high channel count and data rate. These challenges are even more stringent when incorporating a 2-D transducer array into a battery-powered hand-held device, placing significant demands on power efficiency. Previous work in sonar and ultrasound indicates that 2-D array beamforming can be decomposed into two separable line-array beamforming operations. This has been used in conjunction with frequency-domain phase-based focusing to achieve fast volume imaging. In this paper, we analyze the imaging and computational performance of approximate near-field separable beamforming for high-quality delay-and-sum (DAS) beamforming and for a low-cost, phase-rotation-only beamforming method known as direct-sampled in-phase quadrature (DSIQ) beamforming. We show that when high-quality time-delay interpolation is used, separable DAS focusing introduces no noticeable imaging degradation under practical conditions. Similar results for DSIQ focusing are observed. In addition, a slight modification to the DSIQ focusing method greatly increases imaging contrast, making it comparable to that of DAS, despite having a wider main lobe and higher side lobes resulting from the limitations of phase-only time-delay interpolation. Compared with non-separable 2-D imaging, up to a 20-fold increase in frame rate is possible with the separable method. When implemented on a smart-phone-oriented processor to focus data from a 60 x 60 channel array using a 40 x 40 aperture, the frame rate per C-mode volume slice increases from 16 to 255 Hz for DAS, and from 11 to 193 Hz for DSIQ. Energy usage per frame is similarly reduced from 75 to 4.8 mJ/ frame for DAS, and from 107 to 6.3 mJ/frame for DSIQ. We also show that the separable method outperforms 2-D FFT-based focusing by a factor of 1.64 at these data sizes. This data indicates that with the optimal design choices, separable 2-D beamforming can

  9. Multi-particle FEM modeling on microscopic behavior of 2D particle compaction

    NASA Astrophysics Data System (ADS)

    Zhang, Y. X.; An, X. Z.; Zhang, Y. L.

    2015-03-01

    In this paper, the discrete random packing and various ordered packings such as tetragonal and hexagonal close packed structures generated by discrete element method and honeycomb, which is manually generated were input as the initial packing structures into the multi-particle finite element model (FEM) to study their densification during compaction, where each particle is discretized as a FEM mesh. The macro-property such as relative density and micro-properties such as local morphology, stress, coordination number and densification mechanism obtained from various initial packings are characterized and analyzed. The results show that the coupling of discrete feature in particle scale with the continuous FEM in macro-scale can effectively conquer the difficulties in traditional FEM modeling, which provides a reasonable way to reproduce the compaction process and identify the densification mechanism more accurately and realistically.

  10. Guided Lamb wave based 2-D spiral phased array for structural health monitoring of thin panel structures

    NASA Astrophysics Data System (ADS)

    Yoo, Byungseok

    2011-12-01

    In almost all industries of mechanical, aerospace, and civil engineering fields, structural health monitoring (SHM) technology is essentially required for providing the reliable information of structural integrity of safety-critical structures, which can help reduce the risk of unexpected and sometimes catastrophic failures, and also offer cost-effective inspection and maintenance of the structures. State of the art SHM research on structural damage diagnosis is focused on developing global and real-time technologies to identify the existence, location, extent, and type of damage. In order to detect and monitor the structural damage in plate-like structures, SHM technology based on guided Lamb wave (GLW) interrogation is becoming more attractive due to its potential benefits such as large inspection area coverage in short time, simple inspection mechanism, and sensitivity to small damage. However, the GLW method has a few critical issues such as dispersion nature, mode conversion and separation, and multiple-mode existence. Phased array technique widely used in all aspects of civil, military, science, and medical industry fields may be employed to resolve the drawbacks of the GLW method. The GLW-based phased array approach is able to effectively examine and analyze complicated structural vibration responses in thin plate structures. Because the phased sensor array operates as a spatial filter for the GLW signals, the array signal processing method can enhance a desired signal component at a specific direction while eliminating other signal components from other directions. This dissertation presents the development, the experimental validation, and the damage detection applications of an innovative signal processing algorithm based on two-dimensional (2-D) spiral phased array in conjunction with the GLW interrogation technique. It starts with general backgrounds of SHM and the associated technology including the GLW interrogation method. Then, it is focused on the

  11. 2D SQIF arrays using 20 000 YBCO high R n Josephson junctions

    NASA Astrophysics Data System (ADS)

    Mitchell, E. E.; Hannam, K. E.; Lazar, J.; Leslie, K. E.; Lewis, C. J.; Grancea, A.; Keenan, S. T.; Lam, S. K. H.; Foley, C. P.

    2016-06-01

    Superconducting quantum interference filters (SQIFs) have been created using two dimensional arrays of YBCO step-edge Josephson junctions connected together in series and parallel configurations via superconducting loops with a range of loop areas and loop inductances. A SQIF response, as evidenced by a single large anti-peak at zero applied flux, is reported at 77 K for step-edge junction arrays with the junction number N = 1 000 up to 20 000. The SQIF sensitivity (slope of peak) increased linearly with N up to a maximum of 1530 V T-1. Array parameters related to geometry and average junction characteristics are investigated in order to understand and improve the SQIF performance in high temperature superconducting arrays. Initial investigations also focus on the effect of the SQUID inductance factor on the SQIF sensitivity by varying both the mean critical current and the mean inductance of the loops in the array. The RF response to a 30 MHz signal is demonstrated.

  12. 2D SQIF arrays using 20 000 YBCO high R n Josephson junctions

    NASA Astrophysics Data System (ADS)

    Mitchell, E. E.; Hannam, K. E.; Lazar, J.; Leslie, K. E.; Lewis, C. J.; Grancea, A.; Keenan, S. T.; Lam, S. K. H.; Foley, C. P.

    2016-06-01

    Superconducting quantum interference filters (SQIFs) have been created using two dimensional arrays of YBCO step-edge Josephson junctions connected together in series and parallel configurations via superconducting loops with a range of loop areas and loop inductances. A SQIF response, as evidenced by a single large anti-peak at zero applied flux, is reported at 77 K for step-edge junction arrays with the junction number N = 1 000 up to 20 000. The SQIF sensitivity (slope of peak) increased linearly with N up to a maximum of 1530 V T‑1. Array parameters related to geometry and average junction characteristics are investigated in order to understand and improve the SQIF performance in high temperature superconducting arrays. Initial investigations also focus on the effect of the SQUID inductance factor on the SQIF sensitivity by varying both the mean critical current and the mean inductance of the loops in the array. The RF response to a 30 MHz signal is demonstrated.

  13. Fabrication of large-sized two-dimensional ordered surface array with well-controlled structure via colloidal particle lithography.

    PubMed

    Meng, Xiaohui; Zhang, Xinping; Ye, Lei; Qiu, Dong

    2014-06-17

    Epoxy resin coated glass slides were used for colloidal particle lithography, in order to prepare well-defined 2D surface arrays. Upon the assistance of a large-sized 2D colloidal single crystal as template, centimeter-sized ordered surface arrays of bowl-like units were obtained. Systematic studies revealed that the parameters of obtained surface arrays could be readily controlled by some operational factors, such as temperature, epoxy resin layer thickness, and template particle size. With epoxy resin substituting for normal linear polymer, the height/diameter ratio of bowls in the formed surface arrays can be largely increased. With further reactive plasma etching, the parameters of ordered surface arrays could be finely tuned through controlling etching time. This study provides a facile way to prepare large-sized 2D surface arrays with tunable parameters.

  14. Compact optical true time delay beamformer for a 2D phased array antenna using tunable dispersive elements.

    PubMed

    Ye, Xingwei; Zhang, Fangzheng; Pan, Shilong

    2016-09-01

    A hardware-compressive optical true time delay architecture for 2D beam steering in a planar phased array antenna is proposed using fiber-Bragg-grating-based tunable dispersive elements (TDEs). For an M×N array, the proposed system utilizes N TDEs and M wavelength-fixed optical carriers to control the time delays. Both azimuth and elevation beam steering are realized by programming the settings of the TDEs. An experiment is carried out to demonstrate the delay controlling in a 2×2 array, which is fed by a wideband pulsed signal. Radiation patterns calculated from the experimentally measured waveforms at the four antennas match well with the theoretical results. PMID:27607946

  15. The Use of Geometric Properties of 2D Arrays across Development

    ERIC Educational Resources Information Center

    Gibson, Brett M.; Leichtman, Michelle D.; Costa, Rachel; Bemis, Rhyannon

    2009-01-01

    Four- to 10-year-old children (n = 50) participated in a 2D search task that included geometry (with- and without lines) and feature conditions. During each of 27 trials, participants watched as a cartoon character hid behind one of three landmarks arranged in a triangle on a computer screen. During feature condition trials, participants could use…

  16. 2D Radiation MHD K-shell Modeling of Single Wire Array Stainless Steel Experiments on the Z Machine

    SciTech Connect

    Thornhill, J. W.; Giuliani, J. L.; Apruzese, J. P.; Chong, Y. K.; Davis, J.; Dasgupta, A.; Whitney, K. G.; Clark, R. W.; Jones, B.; Coverdale, C. A.; Ampleford, D. J.; Cuneo, M. E.; Deeney, C.

    2009-01-21

    Many physical effects can produce unstable plasma behavior that affect K-shell emission from arrays. Such effects include: asymmetry in the initial density profile, asymmetry in power flow, thermal conduction at the boundaries, and non-uniform wire ablation. Here we consider how asymmetry in the radiation field also contributes to the generation of multidimensional plasma behavior that affects K-shell power and yield. To model this radiation asymmetry, we have incorporated into the MACH2 r-z MHD code a self-consistent calculation of the non-LTE population kinetics based on radiation transport using multi-dimensional ray tracing. Such methodology is necessary for modeling the enhanced radiative cooling that occurs at the anode and cathode ends of the pinch during the run-in phase of the implosion. This enhanced radiative cooling is due to reduced optical depth at these locations producing an asymmetric flow of radiative energy that leads to substantial disruption of large initial diameter (>5 cm) pinches and drives 1D into 2D fluid (i.e., Rayleigh-Taylor like) flows. The impact of this 2D behavior on K-shell power and yield is investigated by comparing 1D and 2D model results with data obtained from a series of single wire array stainless steel experiments performed on the Z generator.

  17. 2D XANES-XEOL mapping: observation of enhanced band gap emission from ZnO nanowire arrays

    NASA Astrophysics Data System (ADS)

    Wang, Zhiqiang; Guo, Xiaoxuan; Sham, Tsun-Kong

    2014-05-01

    Using 2D XANES-XEOL spectroscopy, it is found that the band gap emission of ZnO nanowire arrays is substantially enhanced i.e. that the intensity ratio between the band gap and defect emissions increases by more than an order of magnitude when the excitation energy is scanned across the O K-edge. Possible mechanisms are discussed.Using 2D XANES-XEOL spectroscopy, it is found that the band gap emission of ZnO nanowire arrays is substantially enhanced i.e. that the intensity ratio between the band gap and defect emissions increases by more than an order of magnitude when the excitation energy is scanned across the O K-edge. Possible mechanisms are discussed. Electronic supplementary information (ESI) available: XEOL spectra with different excitation energies. X-ray attenuation length vs. photon energy. Details of surface defects in ZnO NWs. The second O K-edge and Zn L-edge 2D XANES-XEOL maps. Comparison of the first and second TEY at O K-edge and Zn L-edge scans, respectively. Raman spectra of the ZnO NWs with different IBGE/IDE ratios. See DOI: 10.1039/c4nr01049c

  18. Characterization of responses of 2d array seven29 detector and its combined use with octavius phantom for the patient-specific quality assurance in rapidarc treatment delivery

    SciTech Connect

    Syamkumar, S.A.; Padmanabhan, Sriram; Sukumar, Prabakar; Nagarajan, Vivekanandan

    2012-04-01

    A commercial 2D array seven29 detector has been characterized and its performance has been evaluated. 2D array ionization chamber equipped with 729 ionization chambers uniformly arranged in a 27 Multiplication-Sign 27 matrix with an active area of 27 Multiplication-Sign 27 cm{sup 2} was used for the study. An octagon-shaped phantom (Octavius Phantom) with a central cavity is used to insert the 2D ion chamber array. All measurements were done with a linear accelerator. The detector dose linearity, reproducibility, output factors, dose rate, source to surface distance (SSD), and directional dependency has been studied. The performance of the 2D array, when measuring clinical dose maps, was also investigated. For pretreatment quality assurance, 10 different RapidArc plans conforming to the clinical standards were selected. The 2D array demonstrates an excellent short-term output reproducibility. The long-term reproducibility was found to be within {+-}1% over a period of 5 months. Output factor measurements for the central chamber of the array showed no considerable deviation from ion chamber measurements. We found that the 2D array exhibits directional dependency for static fields. Measurement of beam profiles and wedge-modulated fields with the 2D array matched very well with the ion chamber measurements in the water phantom. The study shows that 2D array seven29 is a reliable and accurate dosimeter and a useful tool for quality assurance. The combination of the 2D array with the Octavius phantom proved to be a fast and reliable method for pretreatment verification of rotational treatments.

  19. Dosimetric characteristics of the novel 2D ionization chamber array OCTAVIUS Detector 1500

    SciTech Connect

    Stelljes, T. S. Looe, H. K.; Chofor, N.; Poppe, B.; Harmeyer, A.; Reuter, J.; Harder, D.

    2015-04-15

    Purpose: The dosimetric properties of the OCTAVIUS Detector 1500 (OD1500) ionization chamber array (PTW-Freiburg, Freiburg, Germany) have been investigated. A comparative study was carried out with the OCTAVIUS Detector 729 and OCTAVIUS Detector 1000 SRS arrays. Methods: The OD1500 array is an air vented ionization chamber array with 1405 detectors in a 27 × 27 cm{sup 2} measurement area arranged in a checkerboard pattern with a chamber-to-chamber distance of 10 mm in each row. A sampling step width of 5 mm can be achieved by merging two measurements shifted by 5 mm, thus fulfilling the Nyquist theorem for intensity modulated dose distributions. The stability, linearity, and dose per pulse dependence were investigated using a Semiflex 31013 chamber (PTW-Freiburg, Freiburg, Germany) as a reference detector. The effective depth of measurement was determined by measuring TPR curves with the array and a Roos chamber type 31004 (PTW-Freiburg, Freiburg, Germany). Comparative output factor measurements were performed with the array, the Semiflex 31010 ionization chamber and the Diode 60012 (both PTW-Freiburg, Freiburg, Germany). The energy dependence of the OD1500 was measured by comparing the array’s readings to those of a Semiflex 31010 ionization chamber for varying mean photon energies at the depth of measurement, applying to the Semiflex chamber readings the correction factor k{sub NR} for nonreference conditions. The Gaussian lateral dose response function of a single array detector was determined by searching the convolution kernel suitable to convert the slit beam profiles measured with a Diode 60012 into those measured with the array’s central chamber. An intensity modulated dose distribution measured with the array was verified by comparing a OD1500 measurement to TPS calculations and film measurements. Results: The stability and interchamber sensitivity variation of the OD1500 array were within ±0.2% and ±0.58%, respectively. Dose linearity was within 1

  20. A Novel 2-D Coherent DOA Estimation Method Based on Dimension Reduction Sparse Reconstruction for Orthogonal Arrays

    PubMed Central

    Wang, Xiuhong; Mao, Xingpeng; Wang, Yiming; Zhang, Naitong; Li, Bo

    2016-01-01

    Based on sparse representations, the problem of two-dimensional (2-D) direction of arrival (DOA) estimation is addressed in this paper. A novel sparse 2-D DOA estimation method, called Dimension Reduction Sparse Reconstruction (DRSR), is proposed with pairing by Spatial Spectrum Reconstruction of Sub-Dictionary (SSRSD). By utilizing the angle decoupling method, which transforms a 2-D estimation into two independent one-dimensional (1-D) estimations, the high computational complexity induced by a large 2-D redundant dictionary is greatly reduced. Furthermore, a new angle matching scheme, SSRSD, which is less sensitive to the sparse reconstruction error with higher pair-matching probability, is introduced. The proposed method can be applied to any type of orthogonal array without requirement of a large number of snapshots and a priori knowledge of the number of signals. The theoretical analyses and simulation results show that the DRSR-SSRSD method performs well for coherent signals, which performance approaches Cramer–Rao bound (CRB), even under a single snapshot and low signal-to-noise ratio (SNR) condition. PMID:27649191

  1. A Novel 2-D Coherent DOA Estimation Method Based on Dimension Reduction Sparse Reconstruction for Orthogonal Arrays.

    PubMed

    Wang, Xiuhong; Mao, Xingpeng; Wang, Yiming; Zhang, Naitong; Li, Bo

    2016-01-01

    Based on sparse representations, the problem of two-dimensional (2-D) direction of arrival (DOA) estimation is addressed in this paper. A novel sparse 2-D DOA estimation method, called Dimension Reduction Sparse Reconstruction (DRSR), is proposed with pairing by Spatial Spectrum Reconstruction of Sub-Dictionary (SSRSD). By utilizing the angle decoupling method, which transforms a 2-D estimation into two independent one-dimensional (1-D) estimations, the high computational complexity induced by a large 2-D redundant dictionary is greatly reduced. Furthermore, a new angle matching scheme, SSRSD, which is less sensitive to the sparse reconstruction error with higher pair-matching probability, is introduced. The proposed method can be applied to any type of orthogonal array without requirement of a large number of snapshots and a priori knowledge of the number of signals. The theoretical analyses and simulation results show that the DRSR-SSRSD method performs well for coherent signals, which performance approaches Cramer-Rao bound (CRB), even under a single snapshot and low signal-to-noise ratio (SNR) condition. PMID:27649191

  2. Graphene/carbon nanotube hybrid-based transparent 2D optical array.

    PubMed

    Kim, Un Jeong; Lee, Il Ha; Bae, Jung Jun; Lee, Sangjin; Han, Gang Hee; Chae, Seung Jin; Güneş, Fethullah; Choi, Jun Hee; Baik, Chan Wook; Kim, Sun Il; Kim, Jong Min; Lee, Young Hee

    2011-09-01

    Graphene/carbon nanotube (CNT) hybrid structures are fabricated for use as optical arrays. Vertically aligned CNTs are directly synthesized on a graphene/quartz substrate using plasma-enhanced chemical vapor deposition (PECVD). Graphene preserves the transparency and resistance during CNT growth. Highly aligned single-walled CNTs show a better performance for the diffraction intensity. PMID:21769950

  3. The Octavius1500 2D ion chamber array and its associated phantoms: Dosimetric characterization of a new prototype

    SciTech Connect

    Van Esch, Ann Huyskens, Dominique P.; Basta, Katarzyna; Evrard, Marie; Ghislain, Michel; Sergent, Francois

    2014-09-15

    Purpose: The purpose of the study is to characterize the prototype of the new Octavius1500 (PTW, Freiburg, Germany) 2D ion chamber array, covering its use in different phantom setups, from the most basic solid water sandwich setup to the more complex cylindrical Octavius{sup ®} 4D (Oct4D) (PTW) phantom/detector combination. The new detector houses nearly twice the amount of ion chambers as its predecessors (Seven29 and Octavius729), thereby tackling one of the most important limitations of ion chamber (or diode) arrays, namely the limited detector density. The 0.06 cm{sup 3} cubic ion chambers are now arranged in a checkerboard pattern, leaving no lines (neither longitudinally nor laterally) without detectors. Methods: All measurements were performed on a dual energy (6 MV and 18 MV) iX Clinac (Varian Medical Systems, Palo Alto, CA) and all calculations were done in the Eclipse treatment planning system (Varian) with the Anisotropic Analytical Algorithm. First, the basic characteristics of the 2D array, such as measurement stability, dose rate dependence and dose linearity were investigated in the solid water sandwich setup. Second, the directional dependence was assessed to allow the evaluation of the new Octavius2D phantom (Oct2D{sup 1500}) for planar verification measurements of composite plans. Third, measurements were performed in the Oct4D phantom to evaluate the impact of the increased detector density on the accuracy of the volumetric dose reconstruction. Results: While showing equally good dose linearity and dose rate independence, the Octavius1500 outperforms the previous models because of its instantaneous measurement stability and its twofold active area coverage. Orthogonal field-by-field measurements immediately benefit from the increased detector density. The 3.9 cm wide compensation cavity in the new Oct2D{sup 1500} phantom prototype adequately corrects for directional dependence from the rear, resulting in good agreement within the target dose

  4. Persistent current in a 2D Josephson junction array wrapped around a cylinder

    NASA Astrophysics Data System (ADS)

    Garanin, D. A.; Chudnovsky, E. M.

    2016-07-01

    We study persistent currents in a Josephson junction array wrapped around a cylinder. The T = 0 quantum statistical mechanics of the array is equivalent to the statistical mechanics of a classical xy spin system in 2+1 dimensions at the effective temperature T*=\\sqrt{2JU} , with J being the Josephson energy of the junction and U being the charging energy of the superconducting island. It is investigated analytically and numerically on lattices containing over one million sites. For weak disorder and T*\\ll J the dependence of the persistent current on disorder and T* computed numerically agrees quantitatively with the analytical result derived within the spin-wave approximation. The high-T* and/or strong-disorder behavior is dominated by instantons corresponding to the vortex loops in 2 + 1 dimensions. The current becomes destroyed completely at the quantum phase transition into the Cooper-pair insulating phase.

  5. Enhanced Optical Cross Section via Collective Coupling of Atomic Dipoles in a 2D Array

    NASA Astrophysics Data System (ADS)

    Bettles, Robert J.; Gardiner, Simon A.; Adams, Charles S.

    2016-03-01

    Enhancing the optical cross section is an enticing goal in light-matter interactions, due to its fundamental role in quantum and nonlinear optics. Here, we show how dipolar interactions can suppress off-axis scattering in a two-dimensional atomic array, leading to a subradiant collective mode where the optical cross section is enhanced by almost an order of magnitude. As a consequence, it is possible to attain an optical depth which implies high-fidelity extinction, from a monolayer. Using realistic experimental parameters, we also model how lattice vacancies and the atomic trapping depth affect the transmission, concluding that such high extinction should be possible, using current experimental techniques.

  6. A fast and conformal heating scheme for producing large thermal lesions using a 2D ultrasound phased array.

    PubMed

    Liu, Hao-Li; Lin, Win-Li; Chen, Yung-Yaw

    2007-02-01

    The treatment conformability and the total treatment time of large tumors are both important issues in ultrasound thermal therapy. Previous heating strategies all show their restrictions in achieving these two issues to satisfactory levels simultaneously. This work theoretically presents a new heating strategy which is capable of both increasing the treatment conformability and shortening the treatment time, when using a 2D ultrasound phased array transducer. To perform this, a set of the multiple-foci patterns (considered the basic heating units) were temporally switched to steer the beam at different focal planes with the lesion length being well-controlled. Then, to conformally cover an irregular target volume, the 2D phased array was laterally shifted by a positioning system to deposit a suitable heating unit to cover a subvolume part. Results demonstrated that the totally treatment time can be largely reduced. The heating rate can be increased up to 0.96 cm3/min compared to the previously reported 0.26 cm3/min. Also, the proposed scheme showed that the tumor regions can be completely treated with the normal tissue damage at satisfactory level. The feasibility of the proposed strategy for irregular tumor treatment was also demonstrated. This study offers useful information in large tumor treatment in ultrasound thermal therapy.

  7. Arrayed van der Waals Vertical Heterostructures Based on 2D GaSe Grown by Molecular Beam Epitaxy.

    PubMed

    Yuan, Xiang; Tang, Lei; Liu, Shanshan; Wang, Peng; Chen, Zhigang; Zhang, Cheng; Liu, Yanwen; Wang, Weiyi; Zou, Yichao; Liu, Cong; Guo, Nan; Zou, Jin; Zhou, Peng; Hu, Weida; Xiu, Faxian

    2015-05-13

    Vertically stacking two-dimensional (2D) materials can enable the design of novel electronic and optoelectronic devices and realize complex functionality. However, the fabrication of such artificial heterostructures on a wafer scale with an atomically sharp interface poses an unprecedented challenge. Here, we demonstrate a convenient and controllable approach for the production of wafer-scale 2D GaSe thin films by molecular beam epitaxy. In situ reflection high-energy electron diffraction oscillations and Raman spectroscopy reveal a layer-by-layer van der Waals epitaxial growth mode. Highly efficient photodetector arrays were fabricated, based on few-layer GaSe on Si. These photodiodes show steady rectifying characteristics and a high external quantum efficiency of 23.6%. The resultant photoresponse is super-fast and robust, with a response time of 60 μs. Importantly, the device shows no sign of degradation after 1 million cycles of operation. We also carried out numerical simulations to understand the underlying device working principles. Our study establishes a new approach to produce controllable, robust, and large-area 2D heterostructures and presents a crucial step for further practical applications.

  8. Color generation and refractive index sensing using diffraction from 2D silicon nanowire arrays.

    PubMed

    Walia, Jaspreet; Dhindsa, Navneet; Khorasaninejad, Mohammadreza; Saini, Simarjeet Singh

    2014-01-15

    Tunable structural color generation from vertical silicon nanowires arranged in different square lattices is demonstrated. The generated colors are adjustable using well-defined Bragg diffraction theory, and only depend on the lattice spacing and angles of incidence. Vivid colors spanning from bright red to blue are easily achieved. In keeping with this, a single square lattice of silicon nanowires is also able to produce different colors spanning the entire visible range. It is also shown that the 2D gratings also have a third grating direction when rotated 45 degrees. These simple and elegant solutions to color generation from silicon are used to demonstrate a cost-effective refractive index sensor. The sensor works by measuring color changes resulting from changes in the refractive index of the medium surrounding the nanowires using a trichromatic RGB decomposition. Moreover, the sensor produces linear responses in the trichromatic decomposition values versus the surrounding medium index. An index resolution of 10(-4) is achieved by performing basic image processing on the collected images, without the need for a laser or a spectrometer. Spectral analysis enables an increase in the index resolution of the sensor to a value of 10(-6) , with a sensitivity of 400 nm/RIU. PMID:23784866

  9. 2D array transducers for real-time 3D ultrasound guidance of interventional devices

    NASA Astrophysics Data System (ADS)

    Light, Edward D.; Smith, Stephen W.

    2009-02-01

    We describe catheter ring arrays for real-time 3D ultrasound guidance of devices such as vascular grafts, heart valves and vena cava filters. We have constructed several prototypes operating at 5 MHz and consisting of 54 elements using the W.L. Gore & Associates, Inc. micro-miniature ribbon cables. We have recently constructed a new transducer using a braided wiring technology from Precision Interconnect. This transducer consists of 54 elements at 4.8 MHz with pitch of 0.20 mm and typical -6 dB bandwidth of 22%. In all cases, the transducer and wiring assembly were integrated with an 11 French catheter of a Cook Medical deployment device for vena cava filters. Preliminary in vivo and in vitro testing is ongoing including simultaneous 3D ultrasound and x-ray fluoroscopy.

  10. Enhanced Optical Cross Section via Collective Coupling of Atomic Dipoles in a 2D Array.

    PubMed

    Bettles, Robert J; Gardiner, Simon A; Adams, Charles S

    2016-03-11

    Enhancing the optical cross section is an enticing goal in light-matter interactions, due to its fundamental role in quantum and nonlinear optics. Here, we show how dipolar interactions can suppress off-axis scattering in a two-dimensional atomic array, leading to a subradiant collective mode where the optical cross section is enhanced by almost an order of magnitude. As a consequence, it is possible to attain an optical depth which implies high-fidelity extinction, from a monolayer. Using realistic experimental parameters, we also model how lattice vacancies and the atomic trapping depth affect the transmission, concluding that such high extinction should be possible, using current experimental techniques. PMID:27015480

  11. Nanobump arrays fabricated by laser irradiation of polystyrene particle layers on silicon

    SciTech Connect

    Huang, S.M.; Sun, Z.; Luk'yanchuk, B.S.; Hong, M.H.; Shi, L.P.

    2005-04-18

    Two-dimensional (2D) nanobump arrays were fabricated by laser irradiation of a regular lattice of absorptive polystyrene (PS) microspheres on an undoped (100) Si wafer. The experiments were performed with single-pulse 248 nm KrF laser radiation. The structure of the arrays fabricated by this method was characterized by field emission scanning electron microscope and atomic force microscope. The near-field effects under the absorptive particle are studied. The ablation and thermal processes induced by the optical near-field around the particles are investigated. The formation mechanism of nanobumps is discussed.

  12. Continuous catchment-scale monitoring of geomorphic processes with a 2-D seismological array

    NASA Astrophysics Data System (ADS)

    Burtin, A.; Hovius, N.; Milodowski, D.; Chen, Y.-G.; Wu, Y.-M.; Lin, C.-W.; Chen, H.

    2012-04-01

    The monitoring of geomorphic processes during extreme climatic events is of a primary interest to estimate their impact on the landscape dynamics. However, available techniques to survey the surface activity do not provide a relevant time and/or space resolution. Furthermore, these methods hardly investigate the dynamics of the events since their detection are made a posteriori. To increase our knowledge of the landscape evolution and the influence of extreme climatic events on a catchment dynamics, we need to develop new tools and procedures. In many past works, it has been shown that seismic signals are relevant to detect and locate surface processes (landslides, debris flows). During the 2010 typhoon season, we deployed a network of 12 seismometers dedicated to monitor the surface processes of the Chenyoulan catchment in Taiwan. We test the ability of a two dimensional array and small inter-stations distances (~ 11 km) to map in continuous and at a catchment-scale the geomorphic activity. The spectral analysis of continuous records shows a high-frequency (> 1 Hz) seismic energy that is coherent with the occurrence of hillslope and river processes. Using a basic detection algorithm and a location approach running on the analysis of seismic amplitudes, we manage to locate the catchment activity. We mainly observe short-time events (> 300 occurrences) associated with debris falls and bank collapses during daily convective storms, where 69% of occurrences are coherent with the time distribution of precipitations. We also identify a couple of debris flows during a large tropical storm. In contrast, the FORMOSAT imagery does not detect any activity, which somehow reflects the lack of extreme climatic conditions during the experiment. However, high resolution pictures confirm the existence of links between most of geomorphic events and existing structures (landslide scars, gullies...). We thus conclude to an activity that is dominated by reactivation processes. It

  13. Parallel acquisition of Raman spectra from a 2D multifocal array using a modulated multifocal detection scheme

    NASA Astrophysics Data System (ADS)

    Kong, Lingbo; Chan, James W.

    2015-03-01

    A major limitation of spontaneous Raman scattering is its intrinsically weak signals, which makes Raman analysis or imaging of biological specimens slow and impractical for many applications. To address this, we report the development of a novel modulated multifocal detection scheme for simultaneous acquisition of full Raman spectra from a 2-D m × n multifocal array. A spatial light modulator (SLM), or a pair of galvo-mirrors, is used to generate m × n laser foci. Raman signals generated within each focus are projected simultaneously into a spectrometer and detected by a CCD camera. The system can resolve the Raman spectra with no crosstalk along the vertical pixels of the CCD camera, e.g., along the entrance slit of the spectrometer. However, there is significant overlap of the spectra in the horizontal pixel direction, e.g., along the dispersion direction. By modulating the excitation multifocal array (illumination modulation) or the emitted Raman signal array (detection modulation), the superimposed Raman spectra of different multifocal patterns are collected. The individual Raman spectrum from each focus is then retrieved from the superimposed spectra using a postacquisition data processing algorithm. This development leads to a significant improvement in the speed of acquiring Raman spectra. We discuss the application of this detection scheme for parallel analysis of individual cells with multifocus laser tweezers Raman spectroscopy (M-LTRS) and for rapid confocal hyperspectral Raman imaging.

  14. Mid-infrared extraordinary transmission through Ga-doped ZnO films with 2D hole arrays

    NASA Astrophysics Data System (ADS)

    Cleary, Justin W.; Nader Esfahani, Nima; Vangala, Shiva; Guo, Junpeng; Hendrickson, Joshua R.; Leedy, Kevin D.; Look, David C.

    2014-03-01

    Extraordinary optical transmission (EOT), through highly conductive ZnO films with sub-wavelength hole arrays is investigated in the long-wavelength infrared regime. EOT is facilitated by the excitation of surface plasmon polaritons (SPPs) on Ga-Doped ZnO films and can be tuned utilizing the physical parameters such as film thickness, period, hole size, and hole shape, as well as doping of the film. Analytical and finite-difference time-domain calculations are completed for 1 micron thick films with square, circular, and triangular hole arrays demonstrating SPP coupling and EOT. The fundamental plasmonic modes are observed in each of these hole shapes at wavelengths that correspond to strong EOT peaks. Doping tunability for these structures is also observed. Ga-doped ZnO films are grown via pulsed laser deposition (PLD) on silicon with plasma frequencies in the near-infrared. The sub-wavelength 2D hole arrays are fabricated in the Ga-doped ZnO films via standard lithography and etching processes. This highly conductive ZnO EOT structure may prove useful in novel integrated components such as tunable biosensors or surface plasmon coupling mechanisms.

  15. A MEMS probe card with 2D dense-arrayed 'hoe'-shaped metal tips

    NASA Astrophysics Data System (ADS)

    Wang, Fei; Li, Xinxin; Feng, Songlin

    2008-05-01

    In this paper, we present a novel MEMS probe card with densely area-arrayed microprobes for the wafer-level test of advanced ICs. In a 4 inch silicon wafer, a total of about 110 000 probe tips can be simultaneously fabricated, with a two-dimensional tip pitch of 240 µm × 160 µm. The 'hoe-shaped' microprobe structure is composed of one or two planar arms and an up-tilted tip, both of which are high-yield fabricated with metal micromachining techniques including low-stress nickel electroplating. With micromachined cavities, the silicon wafer serves as moulds for the up-tilted metal probes. Then, the microprobes are finally flip-chip packaged to a ceramic board for further connection to automatic testing equipment (ATE). After the probe structures are formed, the silicon wafer is removed completely by using TMAH wet etching, while the probes are freed by silicon laterally etching. The measured spring constants for all the three types of probes agree well with the designed values. As both mechanical anchors and electrical interconnections, the Sn-Ag solder-bumps feature satisfactory properties. The tested contact resistance values for three different thin-film pads on dies under test are always below 0.8 Ω, while the current leakage between two adjacent probes is only about 150 pA under 3.3 V.

  16. Tumor-tracking radiotherapy of moving targets; verification using 3D polymer gel, 2D ion-chamber array and biplanar diode array

    NASA Astrophysics Data System (ADS)

    Ceberg, Sofie; Falk, Marianne; Rosenschöld, Per Munck Af; Cattell, Herbert; Gustafsson, Helen; Keall, Paul; Korreman, Stine S.; Medin, Joakim; Nordström, Fredrik; Persson, Gitte; Sawant, Amit; Svatos, Michelle; Zimmerman, Jens; Bäck, Sven ÅJ

    2010-11-01

    The aim of this study was to carry out a dosimetric verification of a dynamic multileaf collimator (DMLC)-based tumor-tracking delivery during respiratory-like motion. The advantage of tumor-tracking radiation delivery is the ability to allow a tighter margin around the target by continuously following and adapting the dose delivery to its motion. However, there are geometric and dosimetric uncertainties associated with beam delivery system constraints and output variations, and several investigations have to be accomplished before a clinical integration of this tracking technique. Two types of delivery were investigated in this study I) a single beam perpendicular to a target with a one dimensional motion parallel to the MLC moving direction, and II) an intensity modulated arc delivery (RapidArc®) with a target motion diagonal to the MLC moving direction. The feasibility study (I) was made using an 2D ionisation chamber array and a true 3D polymer gel. The arc delivery (II) was verified using polymer gel and a biplanar diode array. Good agreement in absorbed dose was found between delivery to a static target and to a moving target with DMLC tracking using all three detector systems. However, due to the limited spatial resolution of the 2D array a detailed comparison was not possible. The RapidArc® plan delivery was successfully verified using the biplanar diode array and true 3D polymer gel, and both detector systems could verify that the DMLC-based tumor-tracking delivery system has a very good ability to account for respiratory target motion.

  17. Beam perturbation characteristics of a 2D transmission silicon diode array, Magic Plate.

    PubMed

    Alrowaili, Ziyad A; Lerch, Michael L F; Petasecca, Marco; Carolan, Martin G; Metcalfe, Peter E; Rosenfeld, Anatoly B

    2016-01-01

    The main objective of this study is to demonstrate the performance characteristics of the Magic Plate (MP) system when operated upstream of the patient in trans-mission mode (MPTM). The MPTM is an essential component of a real-time QA system designed for operation during radiotherapy treatment. Of particular interest is a quantitative study into the influence of the MP on the radiation beam quality at several field sizes and linear accelerator potential differences. The impact is measured through beam perturbation effects such as changes in the skin dose and/or percentage depth dose (PDD) (both in and out of field). The MP was placed in the block tray of a Varian linac head operated at 6, 10 and 18 MV beam energy. To optimize the MPTM operational setup, two conditions were investigated and each setup was compared to the case where no MP is positioned in place (i.e., open field): (i) MPTM alone and (ii) MPTM with a thin passive contamination electron filter. The in-field and out-of-field surface doses of a solid water phantom were investigated for both setups using a Markus plane parallel (Model N23343) and Attix parallel-plate, MRI model 449 ionization chambers. In addition, the effect on the 2D dose distribution measured by the Delta4 QA system was also investi-gated. The transmission factor for both of these MPTM setups in the central axis was also investigated using a Farmer ionization chamber (Model 2571A) and an Attix ionization chamber. Measurements were performed for different irradiation field sizes of 5 × 5 cm2 and 10 × 10 cm2. The change in the surface dose relative to dmax was measured to be less than 0.5% for the 6 MV, 10 MV, and 18 MV energy beams. Transmission factors measured for both set ups (i & ii above) with 6 MV, 10 MV, and 18 MV at a depth of dmax and a depth of 10 cm were all within 1.6% of open field. The impact of both the bare MPTM and the MPTM with 1 mm buildup on 3D dose distribution in comparison to the open field investigated using

  18. A 2D ion chamber array audit of wedged and asymmetric fields in an inhomogeneous lung phantom

    SciTech Connect

    Lye, Jessica; Dunn, Leon Alves, Andrew; Kenny, John; Lehmann, Joerg; Williams, Ivan; Kron, Tomas; Cole, Andrew

    2014-10-15

    Purpose: The Australian Clinical Dosimetry Service (ACDS) has implemented a new method of a nonreference condition Level II type dosimetric audit of radiotherapy services to increase measurement accuracy and patient safety within Australia. The aim of this work is to describe the methodology, tolerances, and outcomes from the new audit. Methods: The ACDS Level II audit measures the dose delivered in 2D planes using an ionization chamber based array positioned at multiple depths. Measurements are made in rectilinear homogeneous and inhomogeneous phantoms composed of slabs of solid water and lung. Computer generated computed tomography data sets of the rectilinear phantoms are supplied to the facility prior to audit for planning of a range of cases including reference fields, asymmetric fields, and wedged fields. The audit assesses 3D planning with 6 MV photons with a static (zero degree) gantry. Scoring is performed using local dose differences between the planned and measured dose within 80% of the field width. The overall audit result is determined by the maximum dose difference over all scoring points, cases, and planes. Pass (Optimal Level) is defined as maximum dose difference ≤3.3%, Pass (Action Level) is ≤5.0%, and Fail (Out of Tolerance) is >5.0%. Results: At close of 2013, the ACDS had performed 24 Level II audits. 63% of the audits passed, 33% failed, and the remaining audit was not assessable. Of the 15 audits that passed, 3 were at Pass (Action Level). The high fail rate is largely due to a systemic issue with modeling asymmetric 60° wedges which caused a delivered overdose of 5%–8%. Conclusions: The ACDS has implemented a nonreference condition Level II type audit, based on ion chamber 2D array measurements in an inhomogeneous slab phantom. The powerful diagnostic ability of this audit has allowed the ACDS to rigorously test the treatment planning systems implemented in Australian radiotherapy facilities. Recommendations from audits have led to

  19. Constraining Polarized Foregrounds for EoR Experiments I: 2D Power Spectra from the PAPER-32 Imaging Array

    NASA Astrophysics Data System (ADS)

    Kohn, S. A.; Aguirre, J. E.; Nunhokee, C. D.; Bernardi, G.; Pober, J. C.; Ali, Z. S.; Bradley, R. F.; Carilli, C. L.; DeBoer, D. R.; Gugliucci, N. E.; Jacobs, D. C.; Klima, P.; MacMahon, D. H. E.; Manley, J. R.; Moore, D. F.; Parsons, A. R.; Stefan, I. I.; Walbrugh, W. P.

    2016-06-01

    Current generation low-frequency interferometers constructed with the objective of detecting the high-redshift 21 cm background aim to generate power spectra of the brightness temperature contrast of neutral hydrogen in primordial intergalactic medium. Two-dimensional (2D) power spectra (power in Fourier modes parallel and perpendicular to the line of sight) that formed from interferometric visibilities have been shown to delineate a boundary between spectrally smooth foregrounds (known as the wedge) and spectrally structured 21 cm background emission (the EoR window). However, polarized foregrounds are known to possess spectral structure due to Faraday rotation, which can leak into the EoR window. In this work we create and analyze 2D power spectra from the PAPER-32 imaging array in Stokes I, Q, U, and V. These allow us to observe and diagnose systematic effects in our calibration at high signal-to-noise within the Fourier space most relevant to EoR experiments. We observe well-defined windows in the Stokes visibilities, with Stokes Q, U, and V power spectra sharing a similar wedge shape to that seen in Stokes I. With modest polarization calibration, we see no evidence that polarization calibration errors move power outside the wedge in any Stokes visibility to the noise levels attained. Deeper integrations will be required to confirm that this behavior persists to the depth required for EoR detection.

  20. Combining the switched-beam and beam-steering capabilities in a 2-D phased array antenna system

    NASA Astrophysics Data System (ADS)

    Tsai, Yi-Che; Chen, Yin-Bing; Hwang, Ruey-Bing

    2016-01-01

    This paper presents the development, fabrication, and measurement of a novel beam-forming system consisting of 16 subarray antennas, each containing four aperture-coupled patch antennas, and the application of this system in smart wireless communication systems. The beam patterns of each of the subarray antennas can be switched toward one of nine zones over a half space by adjusting the specific phase delay angles among the four antenna elements. Furthermore, when all subarrays are pointed at the same zone, slightly continuous beam steering in around 1° increments can be achieved by dynamically altering the progressive phase delay angle among the subarrays. Phase angle calibration was implemented by coupling each transmitter output and down converter into the in-phase/quadrature baseband to calculate the correction factor to the weight. In addition, to validate the proposed concepts and the fabricated 2-D phased array antenna system, this study measured the far-field radiation patterns of the aperture-coupled patch array integrated with feeding networks and a phase-calibration system to carefully verify its spatially switched-beam and beam-steering characteristics at a center frequency of 2.4 GHz which can cover the industrial, scientific, and medical band and some long-term evolution applications. In addition, measured results were compared with calculated results, and agreement between them was observed.

  1. A Novel Acousto-Electric Levitator for Studies of Drop and Particle Clusters and Arrays

    NASA Technical Reports Server (NTRS)

    Tian, Yuren; Apfel, Robert E.; Zheng, Yibing

    1999-01-01

    A novel and compact instrumentation for studying the behavior of drop sprays and of clusters of drops now permits fundamental research into the behavior of reacting and non-reacting fluid and solid species. The new capability is made possible by simultaneous acousto-electric levitation and charging of "seed" droplets (10-30 microns in diameter) which come together in 2-D clusters (with up to 300 droplets). These clusters are interesting in their own right because of their crystalline and quasi-crystalline forms, which depend on the acoustic and electric field parameters. By varying the electric and acoustic field intensities, one can cause a cluster of droplets to condense into larger drops (e.g. 50-300 microns) which, because of their charge, form uniformly spaced 2-D arrays of monodispersed drops (e.g. 30-40 array drops in preliminary experiments). One or more layers of these 2-D arrays can form in the acoustic standing wave. Such a configuration permits a wide range of fundamental studies of drop evaporation, combustion, and nucleation. The drops can be single or multicomponent. Therefore, fundamental materials studies can also be performed. Using this same Cluster and Array Generation (CAG) instrumentation, it has been also possible in preliminary experiments to demonstrate the clustering and arraying of solid particles, both coated with an electrically conducting layer and uncoated, and both charged and uncharged.

  2. In vivo liver tracking with a high volume rate 4D ultrasound scanner and a 2D matrix array probe

    NASA Astrophysics Data System (ADS)

    Lediju Bell, Muyinatu A.; Byram, Brett C.; Harris, Emma J.; Evans, Philip M.; Bamber, Jeffrey C.

    2012-03-01

    The effectiveness of intensity-modulated radiation therapy (IMRT) is compromised by involuntary motion (e.g. respiration, cardiac activity). The feasibility of processing ultrasound echo data to automatically estimate 3D liver motion for real-time IMRT guidance was previously demonstrated, but performance was limited by an acquisition speed of 2 volumes per second due to hardware restrictions of a mechanical linear array probe. Utilizing a 2D matrix array probe with parallel receive beamforming offered increased acquisition speeds and an opportunity to investigate the benefits of higher volume rates. In vivo livers of three volunteers were scanned with and without respiratory motion at volume rates of 24 and 48 Hz, respectively. Respiration was suspended via voluntary breath hold. Correlation-based, phase-sensitive 3D speckle tracking was applied to consecutively acquired volumes of echo data. Volumes were omitted at fixed intervals and 3D speckle tracking was re-applied to study the effect of lower scan rates. Results revealed periodic motion that corresponded with the heart rate or breathing cycle in the absence or presence of respiration, respectively. For cardiac-induced motion, volume rates for adequate tracking ranged from 8 to 12 Hz and was limited by frequency discrepancies between tracking estimates from higher and lower frequency scan rates. Thus, the scan rate of volume data acquired without respiration was limited by the need to sample the frequency induced by the beating heart. In respiratory-dominated motion, volume rate limits ranged from 4 to 12 Hz, interpretable from the root-mean-squared deviation (RMSD) from tracking estimates at 24 Hz. While higher volume rates yielded RMSD values less than 1 mm in most cases, lower volume rates yielded RMSD values of 2-6 mm.

  3. Optimal design of a generalized compound eye particle detector array

    NASA Astrophysics Data System (ADS)

    Nehorai, Arye; Liu, Zhi; Paldi, Eytan

    2006-05-01

    We analyze the performance of a novel detector array for detecting and localizing particle emitting sources. The array is spherically shaped and consists of multiple "eyelets," each having a conical shape with a lens on top and a particle detectors subarray inside. The array's configuration is inspired by and generalizes the biological compound eye: it has a global spherical shape and allows a large number of detectors in each eyelet. The array can be used to detect particles including photons (e.g. visible light, X or γ rays), electrons, protons, neutrons, or α particles. We analyze the performance of the array by computing statistical Cramer-Rao bounds on the errors in estimating the direction of arrival (DOA) of the incident particles. In numerical examples, we first show the influence of the array parameters on its performance bound on the mean-square angular error (MSAE). Then we optimize the array's configuration according to a min-max criterion, i.e. minimize the worst case lower bound of the MSAE. Finally we introduce two estimators of the source direction using the proposed array and analyze their performance, thereby showing that the performance bound is attainable in practice. Potential applications include artificial vision, astronomy, and security.

  4. A Comparative Analysis for Verification of IMRT and VMAT Treatment Plans using a 2-D and 3-D Diode Array

    NASA Astrophysics Data System (ADS)

    Dance, Michael J.

    With the added complexity of current radiation treatment dose delivery modalities such as IMRT (Intensity Modulated Radiation Therapy) and VMAT (Volumetric Modulated Arc Therapy), quality assurance (QA) of these plans become multifaceted and labor intensive. To simplify the patient specific quality assurance process, 2D or 3D diode arrays are used to measure the radiation fluence for IMRT and VMAT treatments which can then be quickly and easily compared against the planned dose distribution. Because the arrays that can be used for IMRT and VMAT patient-specific quality assurance are of different geometry (planar vs. cylindrical), the same IMRT or VMAT treatment plan measured by two different arrays could lead to different measured radiation fluences, regardless of the output and performance of linear accelerator. Thus, the purpose of this study is to compare patient specific QA results as measured by the MapCHECK 2 and ArcCHECK diode arrays for the same IMRT and VMAT treatment plans to see if one diode array consistently provides a closer comparison to reference data. Six prostate and three thoracic spine IMRT treatment plans as well as three prostate and three thoracic spine VMAT treatment plans were produced. Radiotherapy plans for this study were generated using the Pinnacle TPS v9.6 (Philips Radiation Oncology Systems, Fitchburg, WI) using 6 MV, 6 MV FFF, and 10 MV x-ray beams from a Varian TrueBeam linear accelerator (Varian Medical Systems, Palo Alto, CA) with a 120-millenium multi-leaf collimator (MLC). Each IMRT and VMAT therapy plan was measured on Sun Nuclear's MapCHECK 2 and ArcCHECK diode arrays. IMRT measured data was compared with planned dose distribution using Sun Nuclear's 3DVH quality assurance software program using gamma analysis and dose-volume histograms for target volumes and critical structures comparison. VMAT arc plans measured on the MapCHECK 2 and ArcCHECK were compared using beam-by-beam analysis with the gamma evaluation method with

  5. MagicPlate-512: A 2D silicon detector array for quality assurance of stereotactic motion adaptive radiotherapy

    SciTech Connect

    Petasecca, M. Newall, M. K.; Aldosari, A. H.; Fuduli, I.; Espinoza, A. A.; Porumb, C. S.; Guatelli, S.; Metcalfe, P.; Lerch, M. L. F.; Rosenfeld, A. B.; Booth, J. T.; Colvill, E.; Duncan, M.; Cammarano, D.; Carolan, M.; Oborn, B.; Perevertaylo, V.; Keall, P. J.

    2015-06-15

    Purpose: Spatial and temporal resolutions are two of the most important features for quality assurance instrumentation of motion adaptive radiotherapy modalities. The goal of this work is to characterize the performance of the 2D high spatial resolution monolithic silicon diode array named “MagicPlate-512” for quality assurance of stereotactic body radiation therapy (SBRT) and stereotactic radiosurgery (SRS) combined with a dynamic multileaf collimator (MLC) tracking technique for motion compensation. Methods: MagicPlate-512 is used in combination with the movable platform HexaMotion and a research version of radiofrequency tracking system Calypso driving MLC tracking software. The authors reconstruct 2D dose distributions of small field square beams in three modalities: in static conditions, mimicking the temporal movement pattern of a lung tumor and tracking the moving target while the MLC compensates almost instantaneously for the tumor displacement. Use of Calypso in combination with MagicPlate-512 requires a proper radiofrequency interference shielding. Impact of the shielding on dosimetry has been simulated by GEANT4 and verified experimentally. Temporal and spatial resolutions of the dosimetry system allow also for accurate verification of segments of complex stereotactic radiotherapy plans with identification of the instant and location where a certain dose is delivered. This feature allows for retrospective temporal reconstruction of the delivery process and easy identification of error in the tracking or the multileaf collimator driving systems. A sliding MLC wedge combined with the lung motion pattern has been measured. The ability of the MagicPlate-512 (MP512) in 2D dose mapping in all three modes of operation was benchmarked by EBT3 film. Results: Full width at half maximum and penumbra of the moving and stationary dose profiles measured by EBT3 film and MagicPlate-512 confirm that motion has a significant impact on the dose distribution. Motion

  6. Characterization of a novel 2D array dosimeter for patient-specific quality assurance with volumetric arc therapy

    SciTech Connect

    Stathakis, Sotirios; Myers, Pamela; Esquivel, Carlos; Mavroidis, Panayiotis; Papanikolaou, Nikos

    2013-07-15

    Purpose: In this study, the authors are evaluating a new, commercially available 2D array that offers 3D dose reconstruction for patient specific intensity modulated radiation therapy quality assurance (IMRT QA).Methods: The OCTAVIUS 4D system and its accompanying software (VERISOFT) by PTW were evaluated for the accuracy of the dose reconstruction for patient specific pretreatment IMRT QA. OCTAVIUS 4D measures the dose plane at the linac isocenter as the phantom rotates synchronously with the gantry, maintaining perpendicularity with the beam, by means of an inclinometer and a motor. The measurements collected during a volumetric modulated arc therapy delivery (VMAT) are reconstructed into a 3D dose volume. The VERISOFT application is used to perform the analysis, by comparing the reconstructed dose against the 3D dose matrix from the treatment planning system (TPS) that is computed for the same geometry and beam arrangement as that of the measurement. In this study, the authors evaluated the 3D dose reconstruction algorithm of this new system using a series of tests. Using the Octavius 4D phantom as the patient, dose distributions for various field sizes, beam orientations, shapes, and combination of fields were calculated using the Pinnacle3, TPS, and the respective DICOMRT dose was exported to the VERISOFT analysis software. Measurements were obtained by delivering the test treatment plans and comparisons were made based on gamma index, dose profiles, and isodose distribution analysis. In addition, output factors were measured and the dose linearity of the array was assessed. Those measurements were compared against measurements in water using a single, calibrated ionization chamber as well as calculations from Pinnacle for the same delivery geometries.Results: The number of voxels that met the 3%/3 mm criteria for the volumetric 3D gamma index analysis ranged from 92.3% to 98.9% for all the patient plans that the authors evaluated. 2D gamma analysis in the

  7. Delocalization of two interacting particles in the 2D Harper model

    NASA Astrophysics Data System (ADS)

    Frahm, Klaus M.; Shepelyansky, Dima L.

    2016-01-01

    We study the problem of two interacting particles in a two-dimensional quasiperiodic potential of the Harper model. We consider an amplitude of the quasiperiodic potential such that in absence of interactions all eigenstates are exponentially localized while the two interacting particles are delocalized showing anomalous subdiffusive spreading over the lattice with the spreading exponent b ≈ 0.5 instead of a usual diffusion with b = 1. This spreading is stronger than in the case of a correlated disorder potential with a one particle localization length as for the quasiperiodic potential. At the same time we do not find signatures of ballistic pairs existing for two interacting particles in the localized phase of the one-dimensional Harper model.

  8. Trapped Particles by Large-Amplitude Waves in 2D Yukawa Liquids

    SciTech Connect

    Hou Lujing; Piel, Alexander

    2008-09-07

    In an ordinary plasma, trapping of a particle of velocity {nu} occurs when its kinetic energy in the wave frame is smaller than the wave potential, i.e., when q{phi}{sub pp}>(1/2)m({nu}-{nu}{sub {phi}}){sup 2}. However, simulation with Brownian Dynamics method shows that the situation is quite different in a strongly-coupled complex plasma (SCCP), where trapping of a particle requires additional energy to overcome the potential barrier formed by all the other particles (the ''cage''), and the trapping condition then reads: q{phi}{sub pp}>(1/2)m({nu}-{nu}{sub {phi}}){sup 2}+{phi}{sub c}. It is found that, because of strong-coupling effect, the particle trapping has no direct connection with so-called ''resonant'' particles. Meanwhile, detrapping process becomes significant in SCCP, and all trapped particles have a finite trapping lifetime decaying exponentially with a rate related to its mean free path.

  9. SU-E-T-65: Characterization of a 2D Array for QA and Pretreatment Plan Verification

    SciTech Connect

    Anvari, A; Aghamiri, S; Mahdavi, S; Alaei, P

    2014-06-01

    Purpose: The OCTAVIUS detector729 is a 2D array of 729 air vented cubic plane parallel ion chambers used for pretreatment verification and QA. In this study we investigated dosimetric characteristics of this system for clinical photon beam dosimetry. Methods: Detector performance evaluation included determination of the location of the effective point of measurement (EPM), sensitivity, linearity, and reproducibility of detector response, as well as output factor, dose rate, and source to surface distance (SSD) dependence. Finally, assessment of wedge modulated fields was carried out. All the evaluations were performed five times for low and high photon energies. For reference measurements, a 0.6 cc ionization chamber was used. Data analysis and comparison of the OCTAVIUS detector with reference ion chamber data was performed using the VeriSoft patient plan verification software. Results: The reproducibility and stability of the measurements are excellent, the detector showed same signal with a maximum deviation of less than 0.5% in short and long term. Results of sensitivity test showed same signal with a maximum deviation of approximately 0.1%. As the detector 729 response is linear with dose and dose rate, it can be used for the measurement at regions of high dose gradient effectively. The detector agrees with the ionization chamber measurement to within 1% for SSD range of 75 to 125 cm. Also, its measured wedge modulated profiles matched very well with ion chamber dose profiles acquired in a water tank. Conclusions: As the response of the detector 729 is linear with dose and dose rate, it can be used for the measurements in the areas of dose gradients effectively. Based on the measurements and comparisons performed, this system is a reliable and accurate dosimeter for QA and pretreatment plan verification in radiotherapy.

  10. Micro-patterning of ionic reservoirs within a double bilayer lipid membrane to fabricate a 2D array of ion-channel switch based electrochemical biosensors

    SciTech Connect

    Sansinena, J. M.; Yee, C. K.; Sapuri, A.; Swanson, Basil I.; Redondo, A.; Parikh, A. N.

    2004-01-01

    We present a simple approach for the design of ionic reservoir arrays within a double phospholipid bilayer to ultimately develop a 2D array of ion-channel switch based electrochemical biosensors. As a first step, a primary bilayer lipid membrane is deposited onto an array of electrodes patterned onto a substrate surface. Subsequently, an array of microvoids is created within the bilayer by a wet photolithographic patterning of phospholipid bilayers using a deep UV light source and a quartz/chrome photomask. To ensure registry, the photomask used to pattern bilayers is designed to match up the microvoids within the primary bilayer with the array of electrodes on the substrate surface. The deposition of a secondary bilayer lipid membrane onto the primary bilayer that spans across the patterned microvoids leads to the formation of the array of ionic reservoirs within the double phospholipid bilayer. This is accomplished using giant unilamellar vesicles and by exploiting membrane electrostatics. The use of ion-channels incorporated into the secondary bilayer that covers the individual ionic reservoirs allows the construction of a 2D array of ion-channel switch based electrochemical biosensors that are able to recognize different target-agents simultaneously.

  11. A 2D Particle in Cell model for ion extraction and focusing in electrostatic accelerators.

    PubMed

    Veltri, P; Cavenago, M; Serianni, G

    2014-02-01

    Negative ions are fundamental to produce intense and high energy neutral beams used to heat the plasma in fusion devices. The processes regulating the ion extraction involve the formation of a sheath on a scale comparable to the Debye length of the plasma. On the other hand, the ion acceleration as a beam is obtained on distances greater than λD. The paper presents a model for both the phases of ion extraction and acceleration of the ions and its implementation in a numerical code. The space charge of particles is deposited following usual Particle in Cell codes technique, while the field is solved with finite element methods. Some hypotheses on the beam plasma transition are described, allowing to model both regions at the same time. The code was tested with the geometry of the NIO1 negative ions source, and the results are compared with existing ray tracing codes and discussed.

  12. A 2D Particle in Cell model for ion extraction and focusing in electrostatic accelerators

    SciTech Connect

    Veltri, P. Serianni, G.; Cavenago, M.

    2014-02-15

    Negative ions are fundamental to produce intense and high energy neutral beams used to heat the plasma in fusion devices. The processes regulating the ion extraction involve the formation of a sheath on a scale comparable to the Debye length of the plasma. On the other hand, the ion acceleration as a beam is obtained on distances greater than λ{sub D}. The paper presents a model for both the phases of ion extraction and acceleration of the ions and its implementation in a numerical code. The space charge of particles is deposited following usual Particle in Cell codes technique, while the field is solved with finite element methods. Some hypotheses on the beam plasma transition are described, allowing to model both regions at the same time. The code was tested with the geometry of the NIO1 negative ions source, and the results are compared with existing ray tracing codes and discussed.

  13. A 2D Particle in Cell model for ion extraction and focusing in electrostatic accelerators

    NASA Astrophysics Data System (ADS)

    Veltri, P.; Cavenago, M.; Serianni, G.

    2014-02-01

    Negative ions are fundamental to produce intense and high energy neutral beams used to heat the plasma in fusion devices. The processes regulating the ion extraction involve the formation of a sheath on a scale comparable to the Debye length of the plasma. On the other hand, the ion acceleration as a beam is obtained on distances greater than λD. The paper presents a model for both the phases of ion extraction and acceleration of the ions and its implementation in a numerical code. The space charge of particles is deposited following usual Particle in Cell codes technique, while the field is solved with finite element methods. Some hypotheses on the beam plasma transition are described, allowing to model both regions at the same time. The code was tested with the geometry of the NIO1 negative ions source, and the results are compared with existing ray tracing codes and discussed.

  14. SU-E-P-35: Real-Time Patient Transit Dose Verification of Volumetric Modulated Arc Radiotherapy by a 2D Ionization Chamber Array

    SciTech Connect

    Liu, X

    2015-06-15

    Purpose: To explore the real-time dose verification method in volumetric modulated arc radiotherapy (VMAT) with a 2D array ion chamber array. Methods: The 2D ion chamber array was fixed on the panel of electronic portal imaging device (EPID). Source-detector distance (SDD)was 140cm. 8mm RW3 solid water was added to the detector panel to achieve maximum readings.The patient plans for esophageal, prostate and liver cancers were selected to deliver on the cylindrical Cheese phantom 5 times in order to validate the reproducibility of doses. Real-time patient transit dose measurements were performed at each fraction. Dose distributions wereevaluated using gamma index criteria of 3mm DTA and 3% dose difference referred to the firsttime Result. Results: The gamma index pass rate in the Cheese phantom were about 98%; The gamma index pass rate for esophageal, liver and prostate cancer patient were about 92%,94%, and 92%, respectively; Gamma pass rate for all single fraction were more than 90%. Conclusion: The 2D array is capable of monitoring the real time transit doses during VMAT delivery. It is helpful to improve the treatment accuracy.

  15. SU-D-BRE-04: Evaluating the Dose Accuracy of a 2D Ion Chamber Array in High Dose Rate Pencil Beam Scanning Proton Beam

    SciTech Connect

    Perles, L; Mascia, A; Piskulich, F; Lepage, R; Zhang, Y; Giebeler, A; Dong, L

    2014-06-01

    Purpose: To evaluate the absolute dose accuracy of the PTW Octavius 729 XDR 2D ion chamber array at a high dose rate pencil beam scanning proton therapy facility. Methods: A set of 18 plans were created in our treatment planning system, each of which comprising a unique combination of field sizes (FS), length of spread out of Bragg peaks (SOBP) and depths. The parameters used were: FS of 5×5cm{sup 2}, 10×10cm{sup 2} and 15×15cm{sup 2}; flat SOBP of 5cm and 10cm; and isocenter depths of 10cm, 15cm and 20cm, which coincides with the center of the SOBP. The 2D array detector was positioned at the machine isocenter and the appropriate amount of solid water was used to match the planned depths of 10, 15 and 20 cm water equivalent depth. Subsequently, we measured the absolute dose at isocenter using a CC04 ion chamber in a 1D water tank. Both 2D array and CC04 were previously cross calibrated. We also collected the MU rates used by our proton machine from the log files. Results: The relative differences between the CC04 and the 2D array can be summarized into two groups, one with 5 cm SOBP and another with 10 cm SOBP. Plotting these datasets against FS shows that the 2D array response for high dose rate fields (FS of 5×5cm{sup 2} and 5cm SOBP) can be up to 2% lower. Similarly, plotting them against isocenter depths reveals the detector's response can be up to 2% lower for higher energy beams (about 200MeV nominal). The MU rate found in the machine log files for 5cm SOBP's were as high as twice the MU rate for the 10cm SOBP. Conclusion: The 2D array dose response showed a dose rate effect in scanning pencil beam delivery, which needs to be corrected to achieve a better dose accuracy.

  16. Robust and highly performant ring detection algorithm for 3d particle tracking using 2d microscope imaging

    PubMed Central

    Afik, Eldad

    2015-01-01

    Three-dimensional particle tracking is an essential tool in studying dynamics under the microscope, namely, fluid dynamics in microfluidic devices, bacteria taxis, cellular trafficking. The 3d position can be determined using 2d imaging alone by measuring the diffraction rings generated by an out-of-focus fluorescent particle, imaged on a single camera. Here I present a ring detection algorithm exhibiting a high detection rate, which is robust to the challenges arising from ring occlusion, inclusions and overlaps, and allows resolving particles even when near to each other. It is capable of real time analysis thanks to its high performance and low memory footprint. The proposed algorithm, an offspring of the circle Hough transform, addresses the need to efficiently trace the trajectories of many particles concurrently, when their number in not necessarily fixed, by solving a classification problem, and overcomes the challenges of finding local maxima in the complex parameter space which results from ring clusters and noise. Several algorithmic concepts introduced here can be advantageous in other cases, particularly when dealing with noisy and sparse data. The implementation is based on open-source and cross-platform software packages only, making it easy to distribute and modify. It is implemented in a microfluidic experiment allowing real-time multi-particle tracking at 70 Hz, achieving a detection rate which exceeds 94% and only 1% false-detection. PMID:26329642

  17. Particle Identification in the NIMROD-ISiS Detector Array

    SciTech Connect

    Wuenschel, S.; Hagel, K.; May, L. W.; Wada, R.; Yennello, S. J.

    2009-03-10

    Interest in the influence of the neutron-to-proton (N/Z) ratio on multifragmenting nuclei has demanded an improvement in the capabilities of multi-detector arrays as well as the companion analysis methods. The particle identification method used in the NIMROD-ISiS 4{pi} array is described. Performance of the detectors and the analysis method are presented for the reaction of {sup 86}Kr+{sup 64}Ni at 35 MeV/u.

  18. Facile synthesis of core-shell and Janus particles via 2-D dendritic growth of gold film.

    PubMed

    Jang, Se Gyu; Kim, Se-Heon; Lee, Su Yeon; Jeong, Woong Chan; Yang, Seung-Man

    2010-10-15

    We report a facile method for the electroless deposition (ELD) of gold film via two-dimensional (2-D) dendritic growth. Our scheme employs protonated amine groups, which electrostatically attract both the negatively charged reducing agent and gold-precursor. This electrostatic interaction increases the local concentrations of gold-precursor and reducing agent near the silica surface to levels high enough for gold films with a 2-D fractal morphology to form directly on the surfaces of the amine-functionalized silica nanospheres by diffusion-limited aggregation. Our one-pot reaction avoids the need for seed attachment, which is typically employed for the growth of metallic shells on nanospheres. Therefore, the proposed method significantly reduces the number of processing steps required for the production of core-shell nanospheres. The gold morphologies were systematically investigated in terms of various synthesis variables, including solution pH, reducing agent concentration, and gold precursor injection speed. In addition, we synthesized gold-capped silica nanospheres via ELD of gold on a patterned array of silica nanospheres embedded in polystyrene (PS) film followed by dissolution of the PS matrix, thus demonstrating the potential utility of the proposed method in emerging fields of materials science such as patterning of noble metals and studies of nanometer-scale optics. PMID:20678776

  19. Particle visualization in high-power impulse magnetron sputtering. I. 2D density mapping

    SciTech Connect

    Britun, Nikolay Palmucci, Maria; Konstantinidis, Stephanos; Snyders, Rony

    2015-04-28

    Time-resolved characterization of an Ar-Ti high-power impulse magnetron sputtering discharge has been performed. This paper deals with two-dimensional density mapping in the discharge volume obtained by laser-induced fluorescence imaging. The time-resolved density evolution of Ti neutrals, singly ionized Ti atoms (Ti{sup +}), and Ar metastable atoms (Ar{sup met}) in the area above the sputtered cathode is mapped for the first time in this type of discharges. The energetic characteristics of the discharge species are additionally studied by Doppler-shift laser-induced fluorescence imaging. The questions related to the propagation of both the neutral and ionized discharge particles, as well as to their spatial density distributions, are discussed.

  20. Update on the Fabrication and Performance of 2-D Arrays of Superconducting Magnesium Diboride (MgB2) Thermal Detectors for Outer-Planets Exploration

    NASA Technical Reports Server (NTRS)

    Lakew, Brook; Aslam, S.

    2011-01-01

    Detectors with better performance than the current thermopile detectors that operate at room temperature will be needed at the focal plane of far-infrared instruments on future planetary exploration missions. We will present an update on recent results from the 2-D array of MgB2 thermal detectors being currently developed at NASA Goddard. Noise and sensitivity results will be presented and compared to thermal detectors currently in use on planetary missions.

  1. On-line quality assurance of rotational radiotherapy treatment delivery by means of a 2D ion chamber array and the Octavius phantom

    SciTech Connect

    Esch, Ann van; Clermont, Christian; Devillers, Magali; Iori, Mauro; Huyskens, Dominique P.

    2007-10-15

    For routine pretreatment verification of innovative treatment techniques such as (intensity modulated) dynamic arc therapy and helical TomoTherapy, an on-line and reliable method would be highly desirable. The present solution proposed by TomoTherapy, Inc. (Madison, WI) relies on film dosimetry in combination with up to two simultaneous ion chamber point dose measurements. A new method is proposed using a 2D ion chamber array (Seven29, PTW, Freiburg, Germany) inserted in a dedicated octagonal phantom, called Octavius. The octagonal shape allows easy positioning for measurements in multiple planes. The directional dependence of the response of the detector was primarily investigated on a dual energy (6 and 18 MV) Clinac 21EX (Varian Medical Systems, Palo Alto, CA) as no fixed angle incidences can be calculated in the Hi-Art TPS of TomoTherapy. The array was irradiated from different gantry angles and with different arc deliveries, and the dose distributions at the level of the detector were calculated with the AAA (Analytical Anisotropic Algorithm) photon dose calculation algorithm implemented in Eclipse (Varian). For validation on the 6 MV TomoTherapy unit, rotational treatments were generated, and dose distributions were calculated with the Hi-Art TPS. Multiple cylindrical ion chamber measurements were used to cross-check the dose calculation and dose delivery in Octavius in the absence of the 2D array. To compensate for the directional dependence of the 2D array, additional prototypes of Octavius were manufactured with built-in cylindrically symmetric compensation cavities. When using the Octavius phantom with a 2 cm compensation cavity, measurements with an accuracy comparable to that of single ion chambers can be achieved. The complete Octavius solution for quality assurance of rotational treatments consists of: The 2D array, two octagonal phantoms (with and without compensation layer), an insert for nine cylindrical ion chambers, and a set of inserts of

  2. Origin of energetic ions observed in the terrestrial ion foreshock : 2D full-particle simulations

    NASA Astrophysics Data System (ADS)

    Savoini, Philippe; Lembege, bertrand

    2016-04-01

    Collisionless shocks are well-known structures in astrophysical environments which dissipate bulk flow kinetic energy and accelerate large fraction of particle. Spacecrafts have firmly established the existence of the so-called terrestrial foreshock region magnetically connected to the shock and filled by two distinct populations in the quasi-perpendicular shock region (i.e. for 45r{ } ≤ quad θ Bn quad ≤ 90r{ }, where θ Bn is the angle between the shock normal and the upstream magnetic field) : (i) the field-aligned ion beams or `` FAB '' characterized by a gyrotropic distributionsout{,} and (ii) the gyro-phase bunched ions or `` GPB '' characterized by a NON gyrotropic distribution. The present work is based on the use of two dimensional PIC simulation of a curved shock and associated foreshock region where full curvature effects, time of flight effects and both electrons and ions dynamics are fully described by a self consistent approach. Our previous analysis (Savoini et Lembège, 2015) has evidenced that these two types of backstreaming populations can originate from the shock front itself without invoking any local diffusion by ion beam instabilities. Present results are focussed on individual ion trajectories and evidence that "FAB" population is injected into the foreshock mainly along the shock front whereas the "GPB" population penetrates more deeply the shock front. Such differences explain why the "FAB" population loses their gyro-phase coherency and become gyrotropic which is not the case for the "GPB". The impact of these different injection features on the energy gain for each ion population will be presented in détails. Savoini, P. and B. Lembège (2015), `` Production of nongyrotropic and gyrotropic backstreaming ion distributions in the quasi-perpendicular ion foreshock région '', J. Geophys. Res., 120, pp 7154-7171, doi = 10.1002/2015JA021018.

  3. Dirac equation in 2-dimensional curved spacetime, particle creation, and coupled waveguide arrays

    NASA Astrophysics Data System (ADS)

    Koke, Christian; Noh, Changsuk; Angelakis, Dimitris G.

    2016-11-01

    When quantum fields are coupled to gravitational fields, spontaneous particle creation may occur similarly to when they are coupled to external electromagnetic fields. A gravitational field can be incorporated as a background spacetime if the back-action of matter on the field can be neglected, resulting in modifications of the Dirac or Klein-Gordon equations for elementary fermions and bosons respectively. The semi-classical description predicts particle creation in many situations, including the expanding-universe scenario, near the event horizon of a black hole (the Hawking effect), and an accelerating observer in flat spacetime (the Unruh effect). In this work, we give a pedagogical introduction to the Dirac equation in a general 2D spacetime and show examples of spinor wave packet dynamics in flat and curved background spacetimes. In particular, we cover the phenomenon of particle creation in a time-dependent metric. Photonic analogs of these effects are then proposed, where classical light propagating in an array of coupled waveguides provides a visualisation of the Dirac spinor propagating in a curved 2D spacetime background. The extent to which such a single-particle description can be said to mimic particle creation is discussed.

  4. Kondo effect at low electron density and high particle-hole asymmetry in 1D, 2D, and 3D

    NASA Astrophysics Data System (ADS)

    Žitko, Rok; Horvat, Alen

    2016-09-01

    Using the perturbative scaling equations and the numerical renormalization group, we study the characteristic energy scales in the Kondo impurity problem as a function of the exchange coupling constant J and the conduction-band electron density. We discuss the relation between the energy gain (impurity binding energy) Δ E and the Kondo temperature TK. We find that the two are proportional only for large values of J , whereas in the weak-coupling limit the energy gain is quadratic in J , while the Kondo temperature is exponentially small. The exact relation between the two quantities depends on the detailed form of the density of states of the band. In the limit of low electron density the Kondo screening is affected by the strong particle-hole asymmetry due to the presence of the band-edge van Hove singularities. We consider the cases of one- (1D), two- (2D), and three-dimensional (3D) tight-binding lattices (linear chain, square lattice, cubic lattice) with inverse-square-root, step-function, and square-root onsets of the density of states that are characteristic of the respective dimensionalities. We always find two different regimes depending on whether TK is higher or lower than μ , the chemical potential measured from the bottom of the band. For 2D and 3D, we find a sigmoidal crossover between the large-J and small-J asymptotics in Δ E and a clear separation between Δ E and TK for TK<μ . For 1D, there is, in addition, a sizable intermediate-J regime where the Kondo temperature is quadratic in J due to the diverging density of states at the band edge. Furthermore, we find that in 1D the particle-hole asymmetry leads to a large decrease of TK compared to the standard result obtained by approximating the density of states to be constant (flat-band approximation), while in 3D the opposite is the case; this is due to the nontrivial interplay of the exchange and potential scattering renormalization in the presence of particle-hole asymmetry. The 2D square

  5. Conductive polymer-mediated 2D and 3D arrays of Mn3O4 nanoblocks and mesoporous conductive polymers as their replicas

    NASA Astrophysics Data System (ADS)

    Nakagawa, Yoshitaka; Kageyama, Hiroyuki; Matsumoto, Riho; Oaki, Yuya; Imai, Hiroaki

    2015-11-01

    Orientation-controlled 2D and 3D microarrays of Mn3O4 nanocuboids that were mediated by a conductive polymer were fabricated by evaporation-induced self-assembly of the oxide nanoblocks and subsequent polymerization of pyrrole in the interparticle spaces. Free-standing mesoporous polypyrroles (PPy) having chain- and square-grid-like nanovoid arrays were obtained as replicas of the composite assemblies by dissolving the oxide nanoblocks. The PPy-mediated manganese oxide arrays exhibited stable electrochemical performance as an ultrathin anode of a lithium-ion secondary battery.Orientation-controlled 2D and 3D microarrays of Mn3O4 nanocuboids that were mediated by a conductive polymer were fabricated by evaporation-induced self-assembly of the oxide nanoblocks and subsequent polymerization of pyrrole in the interparticle spaces. Free-standing mesoporous polypyrroles (PPy) having chain- and square-grid-like nanovoid arrays were obtained as replicas of the composite assemblies by dissolving the oxide nanoblocks. The PPy-mediated manganese oxide arrays exhibited stable electrochemical performance as an ultrathin anode of a lithium-ion secondary battery. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr05912g

  6. Silicon PIN diode array hybrids for charged particle detection

    SciTech Connect

    Shapiro, S.L.; Dunwoodie, W.M.; Arens, J.F.; Jernigan, J.G.; Gaalema, S.

    1988-09-01

    We report on the design of silicon PIN diode array hybrids for use as charged particle detectors. A brief summary of the need for vertex detectors is presented. Circuitry, block diagrams and device specifications are included. 8 refs., 7 figs., 1 tab.

  7. Particle-gamma studies with the new Hyperion array

    NASA Astrophysics Data System (ADS)

    Hughes, R. O.; Burke, J. T.; Fisher, S.; Parker, J.; Ota, S.; Ting, A.; Casperson, R. J.; McCleskey, E.; McIntosh, A. B.; Beausang, C. W.; Wilson, E.; Humby, P.

    2015-10-01

    Hyperion is a charged-particle and γ-ray spectroscopy array for low energy nuclear physics studies consisting of a highly segmented silicon telescope for charged particle detection surrounded by up to 14 HPGe ``clover'' γ-ray detectors. Hyperion was designed and built between March 2014 and May 2015 as a significant upgrade to the existing STARLiTeR array currently at Texas A&M University Cyclotron Institute. The array was installed in May 2015 in preparation for its commissioning runs scheduled for September 2015. Hyperion will offer high particle-gamma and particle-gamma-gamma detection efficiencies and is intended to be used both for low energy structure studies and indirect measurements of neutron cross sections via the surrogate method. Details of the new array and the commissioning experiment focusing on 167 , 168 , 169Tm studies will be presented. This work was performed under the auspices of the US Department of Energy by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344. Supported by DoE grant numbers DE-FG52-09NA29467 (TAMU), DE-NA0001801, DE-FG02-05ER41379 (UofR).

  8. Manipulation of Magnetic Particles for Use in Photonic Biosensor Arrays

    NASA Astrophysics Data System (ADS)

    Siebe, Craig

    Trapping magnetic nanoparticles in wells in a photonic crystal biosensor array using magnetophoresis is desirable because it would allow for covalent bonding of antibodies onto the particles which would lead to an increase in sensitivity of the sensor. It was hypothesized that this could be achieved by engineering a magnetic field at each well by placing a, "magnetic tip," under each well and exposing the array to a uniform magnetic field which would create a magnetic gradient at each well in order to trap magnetic particles. A computational COMSOL model was created to determine the ideal shapes for the magnetic tips, but fabrication factors and the COMSOL model led to the tips being the same shape as the wells. Dip coating, centrifuging, and electrophoresis of iron oxide particles were tried as methods to fabricate magnetic tips. Electroplating the particles was determined to be the best method. Microscale arrays were fabricated and tested with micron scale beads in 3 different well sizes. Then smaller grooves were created by drop casting PMMA groves using PDMS imprints of CDs. Electron beam lithography and stamping into spin coated PMMA were also tried briefly. Trapping of 350 nm magnetic beads was attempted but was unsuccessful. Probably this occurred because the gradient produced by the magnetic tips was not strong enough to overcome the hydrodynamic forces of water that was swept over the array with Couette flows to clean the surface.

  9. Super-radiant plasmon mode is more efficient for SERS than the sub-radiant mode in highly packed 2D gold nanocube arrays

    SciTech Connect

    Mahmoud, Mahmoud A.

    2015-08-21

    The field coupling in highly packed plasmonic nanoparticle arrays is not localized due to the energy transport via the sub-radiant plasmon modes, which is formed in addition to the regular super-radiant plasmon mode. Unlike the sub-radiant mode, the plasmon field of the super-radiant mode cannot extend over long distances since it decays radiatively with a shorter lifetime. The coupling of the plasmon fields of gold nanocubes (AuNCs) when organized into highly packed 2D arrays was examined experimentally. Multiple plasmon resonance optical peaks are observed for the AuNC arrays and are compared to those calculated using the discrete dipole approximation. The calculated electromagnetic plasmon fields of the arrays displayed high field intensity for the nanocubes located in the center of the arrays for the lower energy super-radiant mode, while the higher energy sub-radiant plasmon mode displayed high field intensity at the edges of the arrays. The Raman signal enhancement by the super-radiant plasmon mode was found to be one hundred fold greater than that by sub-radiant plasmon mode because the super-radiant mode has higher scattering and stronger plasmon field intensity relative to the sub-radiant mode.

  10. Super-radiant plasmon mode is more efficient for SERS than the sub-radiant mode in highly packed 2D gold nanocube arrays.

    PubMed

    Mahmoud, Mahmoud A

    2015-08-21

    The field coupling in highly packed plasmonic nanoparticle arrays is not localized due to the energy transport via the sub-radiant plasmon modes, which is formed in addition to the regular super-radiant plasmon mode. Unlike the sub-radiant mode, the plasmon field of the super-radiant mode cannot extend over long distances since it decays radiatively with a shorter lifetime. The coupling of the plasmon fields of gold nanocubes (AuNCs) when organized into highly packed 2D arrays was examined experimentally. Multiple plasmon resonance optical peaks are observed for the AuNC arrays and are compared to those calculated using the discrete dipole approximation. The calculated electromagnetic plasmon fields of the arrays displayed high field intensity for the nanocubes located in the center of the arrays for the lower energy super-radiant mode, while the higher energy sub-radiant plasmon mode displayed high field intensity at the edges of the arrays. The Raman signal enhancement by the super-radiant plasmon mode was found to be one hundred fold greater than that by sub-radiant plasmon mode because the super-radiant mode has higher scattering and stronger plasmon field intensity relative to the sub-radiant mode.

  11. 3D rotating wall vessel and 2D cell culture of four veterinary virus pathogens: A comparison of virus yields, portions of infectious particles and virus growth curves.

    PubMed

    Malenovská, Hana

    2016-02-01

    Only very few comparative studies have been performed that evaluate general trends of virus growth under 3D in comparison with 2D cell culture conditions. The aim of this study was to investigate differences when four animal viruses are cultured in 2D and 3D. Suid herpesvirus 1 (SuHV-1), Vesicular stomatitis virus (VSIV), Bovine adenovirus (BAdV) and Bovine parainfluenza 3 virus (BPIV-3) were cultivated in 3D rotating wall vessels (RWVs) and conventional 2D cultures. The production of virus particles, the portion of infectious particles, and the infectious growth curves were compared. For all viruses, the production of virus particles (related to cell density), including the non-infectious ones, was lower in 3D than in 2D culture. The production of only infectious particles was significantly lower in BAdV and BPIV-3 in 3D cultures in relation to cell density. The two cultivation approaches resulted in significantly different virus particle-to-TCID50 ratios in three of the four viruses: lower in SuHV-1 and BPIV-3 and higher in BAdV in 3D culture. The infectious virus growth rates were not significantly different in all viruses. Although 3D RWV culture resulted in lower production of virus particles compared to 2D systems, the portion of infectious particles was higher for some viruses.

  12. Proteome analysis of the large and the small rubber particles of Hevea brasiliensis using 2D-DIGE.

    PubMed

    Xiang, Qiulan; Xia, Kecan; Dai, Longjun; Kang, Guijuan; Li, Yu; Nie, Zhiyi; Duan, Cuifang; Zeng, Rizhong

    2012-11-01

    The rubber particle is a specialized organelle in which natural rubber is synthesised and stored in the laticifers of Hevea brasiliensis (para rubber tree). It has been demonstrated that the small rubber particles (SRPs) has higher rubber biosynthesis ratio than the large rubber particles (LRPs), but the underlying molecular mechanism still remains unknown. In this study, LRPs and SRPs were firstly separated from the fresh latex using differential centrifugation, and two-dimensional difference in-gel electrophoresis (2D-DIGE) combined with MALDI-TOF/TOF was then applied to investigate the proteomic alterations associated with the changed rubber biosynthesis capacity between LRPs and SRPs. A total of 53 spots corresponding to 22 gene products, were significantly altered with the |ratio|≥2.0 and T value ≤0.05, among which 15 proteins were up-regulated and 7 were down-regulated in the SRPs compared with the LRPs. The 15 up-regulated proteins in the SRPs included small rubber particle protein (SRPP), 3-hydroxy-3-methylglutaryl-CoA synthase (HMGCS), phospholipase D alpha (PLD α), ethylene response factor 2, eukaryotic translation initiation factor 5A isoform IV (eIF 5A-4), 70-kDa heat shock cognate protein (HSC 70), several unknown proteins, etc., whereas the 7 up-regulated proteins in the LRPs were rubber elongation factor (REF, 19.6kDa), ASR-like protein 1, REF-like stress-related protein 1, a putative phosphoglyceride transfer family protein, β-1,3-glucanase, a putative retroelement, and a hypothetical protein. Since several proteins related to rubber biosynthesis were differentially expressed between LRPs and SRPs, the comparative proteome data may provide useful insights into understanding the mechanism involved in rubber biosynthesis and latex coagulation in H. brasiliensis.

  13. SU-E-T-644: Evaluation of Angular Dependence Correction for 2D Array Detector Using for Quality Assurance of Volumetric Modulated Arc Therapy

    SciTech Connect

    Karthikeyan, N; Ganesh, K M; Vikraman, S; Shariff, MH

    2014-06-15

    Purpose: To evaluate the angular dependence correction for Matrix Evolution 2D array detector in quality assurance of volumetric modulated arc therapy(VMAT). Methods: Total ten patients comprising of different sites were planned for VMAT and taken for the study. Each plan was exposed on Matrix Evolution 2D array detector with Omnipro IMRT software based on the following three different methods using 6MV photon beams from Elekta Synergy linear accelerator. First method, VMAT plan was delivered on Matrix Evolution detector as it gantry mounted with dedicated holder with build-up of 2.3cm. Second, the VMAT plan was delivered with the static gantry angle on to the table mounted setup. Third, the VMAT plan was delivered with actual gantry angle on Matrix Evolution detector fixed in Multicube phantom with gantry angle sensor and angular dependence correction were applied to quantify the plan quality. For all these methods, the corresponding QA plans were generated in TPS and the dose verification was done for both point and 2D fluence analysis with pass criteria of 3% dose difference and 3mm distance to agreement. Results: The measured point dose variation for the first method was observed as 1.58±0.6% of mean and SD with TPS calculated. For second and third method, the mean and standard deviation(SD) was observed as 1.67±0.7% and 1.85±0.8% respectively. The 2D fluence analysis of measured and TPS calculated has the mean and SD of 97.9±1.1%, 97.88±1.2% and 97.55±1.3% for first, second and third methods respectively. The calculated two-tailed Pvalue for point dose and 2D fluence analysis shows the insignificance with values of 0.9316 and 0.9015 respectively, among the different methods of QA. Conclusion: The qualitative evaluation of angular dependence correction for Matrix Evolution 2D array detector shows its competency in accuracy of quality assurance measurement of composite dose distribution of volumetric modulated arc therapy.

  14. Realization of thermally durable close-packed 2D gold nanoparticle arrays using self-assembly and plasma etching

    NASA Astrophysics Data System (ADS)

    Sivaraman, Sankar K.; Santhanam, Venugopal

    2012-06-01

    Realization of thermally and chemically durable, ordered gold nanostructures using bottom-up self-assembly techniques are essential for applications in a wide range of areas including catalysis, energy generation, and sensing. Herein, we describe a modular process for realizing uniform arrays of gold nanoparticles, with interparticle spacings of 2 nm and above, by using RF plasma etching to remove ligands from self-assembled arrays of ligand-coated gold nanoparticles. Both nanoscale imaging and macroscale spectroscopic characterization techniques were used to determine the optimal conditions for plasma etching, namely RF power, operating pressure, duration of treatment, and type of gas. We then studied the effect of nanoparticle size, interparticle spacing, and type of substrate on the thermal durability of plasma-treated and untreated nanoparticle arrays. Plasma-treated arrays showed enhanced chemical and thermal durability, on account of the removal of ligands. To illustrate the application potential of the developed process, robust SERS (surface-enhanced Raman scattering) substrates were formed using plasma-treated arrays of silver-coated gold nanoparticles that had a silicon wafer or photopaper as the underlying support. The measured value of the average SERS enhancement factor (2 × 105) was quantitatively reproducible on both silicon and paper substrates. The silicon substrates gave quantitatively reproducible results even after thermal annealing. The paper-based SERS substrate was also used to swab and detect probe molecules deposited on a solid surface.

  15. Slow magnetic relaxation in a hydrogen-bonded 2D array of mononuclear dysprosium(III) oxamates.

    PubMed

    Fortea-Pérez, Francisco R; Vallejo, Julia; Julve, Miguel; Lloret, Francesc; De Munno, Giovanni; Armentano, Donatella; Pardo, Emilio

    2013-05-01

    The reaction of N-(2,6-dimethylphenyl)oxamic acid with dysprosium(III) ions in a controlled basic media afforded the first example of a mononuclear lanthanide oxamate complex exhibiting a field-induced slow magnetic relaxation behavior typical of single-ion magnets (SIMs). The hydrogen-bond-mediated self-assembly of this new bifunctional dysprosium(III) SIM in the solid state provides a unique example of 2D hydrogen-bonded polymer with a herringbone net topology.

  16. Large-area 2D periodic crystalline silicon nanodome arrays on nanoimprinted glass exhibiting photonic band structure effects.

    PubMed

    Becker, C; Lockau, D; Sontheimer, T; Schubert-Bischoff, P; Rudigier-Voigt, E; Bockmeyer, M; Schmidt, F; Rech, B

    2012-04-01

    Two-dimensional silicon nanodome arrays are prepared on large areas up to 50 cm² exhibiting photonic band structure effects in the near-infrared and visible wavelength region by downscaling a recently developed fabrication method based on nanoimprint-patterned glass, high-rate electron-beam evaporation of silicon, self-organized solid phase crystallization and wet-chemical etching. The silicon nanodomes, arranged in square lattice geometry with 300 nm lattice constant, are optically characterized by angular resolved reflection measurements, allowing the partial determination of the photonic band structure. This experimentally determined band structure agrees well with the outcome of three-dimensional optical finite-element simulations. A 16% photonic bandgap is predicted for an optimized geometry of the silicon nanodome arrays. By variation of the duration of the selective etching step, the geometry as well as the optical properties of the periodic silicon nanodome arrays can be controlled systematically.

  17. Ceria-Zirconia Particles Wrapped in a 2D Carbon Envelope: Improved Low-Temperature Oxygen Transfer and Oxidation Activity.

    PubMed

    Aneggi, Eleonora; Rico-Perez, Veronica; de Leitenburg, Carla; Maschio, Stefano; Soler, Lluís; Llorca, Jordi; Trovarelli, Alessandro

    2015-11-16

    Engineering the interface between different components of heterogeneous catalysts at nanometer level can radically alter their performances. This is particularly true for ceria-based catalysts where the interactions are critical for obtaining materials with enhanced properties. Here we show that mechanical contact achieved by high-energy milling of CeO2-ZrO2 powders and carbon soot results in the formation of a core of oxide particles wrapped in a thin carbon envelope. This 2D nanoscale carbon arrangement greatly increases the number and quality of contact points between the oxide and carbon. Consequently, the temperatures of activation and transfer of the oxygen in ceria are shifted to exceptionally low temperatures and the soot combustion rate is boosted. The study confirms the importance of the redox behavior of ceria-zirconia particles in the mechanism of soot oxidation and shows that the organization of contact points at the nanoscale can significantly modify the reactivity resulting in unexpected properties and functionalities. PMID:26448053

  18. Ceria–Zirconia Particles Wrapped in a 2D Carbon Envelope: Improved Low-Temperature Oxygen Transfer and Oxidation Activity

    PubMed Central

    Aneggi, Eleonora; Rico-Perez, Veronica; de Leitenburg, Carla; Maschio, Stefano; Soler, Lluís; Llorca, Jordi; Trovarelli, Alessandro

    2015-01-01

    Engineering the interface between different components of heterogeneous catalysts at nanometer level can radically alter their performances. This is particularly true for ceria-based catalysts where the interactions are critical for obtaining materials with enhanced properties. Here we show that mechanical contact achieved by high-energy milling of CeO2–ZrO2 powders and carbon soot results in the formation of a core of oxide particles wrapped in a thin carbon envelope. This 2D nanoscale carbon arrangement greatly increases the number and quality of contact points between the oxide and carbon. Consequently, the temperatures of activation and transfer of the oxygen in ceria are shifted to exceptionally low temperatures and the soot combustion rate is boosted. The study confirms the importance of the redox behavior of ceria-zirconia particles in the mechanism of soot oxidation and shows that the organization of contact points at the nanoscale can significantly modify the reactivity resulting in unexpected properties and functionalities. PMID:26448053

  19. Ceria-Zirconia Particles Wrapped in a 2D Carbon Envelope: Improved Low-Temperature Oxygen Transfer and Oxidation Activity.

    PubMed

    Aneggi, Eleonora; Rico-Perez, Veronica; de Leitenburg, Carla; Maschio, Stefano; Soler, Lluís; Llorca, Jordi; Trovarelli, Alessandro

    2015-11-16

    Engineering the interface between different components of heterogeneous catalysts at nanometer level can radically alter their performances. This is particularly true for ceria-based catalysts where the interactions are critical for obtaining materials with enhanced properties. Here we show that mechanical contact achieved by high-energy milling of CeO2-ZrO2 powders and carbon soot results in the formation of a core of oxide particles wrapped in a thin carbon envelope. This 2D nanoscale carbon arrangement greatly increases the number and quality of contact points between the oxide and carbon. Consequently, the temperatures of activation and transfer of the oxygen in ceria are shifted to exceptionally low temperatures and the soot combustion rate is boosted. The study confirms the importance of the redox behavior of ceria-zirconia particles in the mechanism of soot oxidation and shows that the organization of contact points at the nanoscale can significantly modify the reactivity resulting in unexpected properties and functionalities.

  20. New aQTL SNPs for the CYP2D6 Identified by a Novel Mediation Analysis of Genome-Wide SNP Arrays, Gene Expression Arrays, and CYP2D6 Activity

    PubMed Central

    Wang, Zhiping; Boustani, Malaz; Liu, Yunlong; Skaar, Todd; Li, Lang

    2013-01-01

    Background. The genome-wide association studies (GWAS) have been successful during the last few years. A key challenge is that the interpretation of the results is not straightforward, especially for transacting SNPs. Integration of transcriptome data into GWAS may provide clues elucidating the mechanisms by which a genetic variant leads to a disease. Methods. Here, we developed a novel mediation analysis approach to identify new expression quantitative trait loci (eQTL) driving CYP2D6 activity by combining genotype, gene expression, and enzyme activity data. Results. 389,573 and 1,214,416 SNP-transcript-CYP2D6 activity trios are found strongly associated (P < 10−5, FDR = 16.6% and 11.7%) for two different genotype platforms, namely, Affymetrix and Illumina, respectively. The majority of eQTLs are trans-SNPs. A single polymorphism leads to widespread downstream changes in the expression of distant genes by affecting major regulators or transcription factors (TFs), which would be visible as an eQTL hotspot and can lead to large and consistent biological effects. Overlapped eQTL hotspots with the mediators lead to the discovery of 64 TFs. Conclusions. Our mediation analysis is a powerful approach in identifying the trans-QTL-phenotype associations. It improves our understanding of the functional genetic variations for the liver metabolism mechanisms. PMID:24232670

  1. Phase-rotation based receive-beamformer for miniaturized volumetric ultrasound imaging scanners using 2-D CMUT-on-ASIC arrays

    NASA Astrophysics Data System (ADS)

    Kim, Bae-Hyung; Lee, Seunghun; Song, Jongkeun; Kim, Youngil; Jeon, Taeho; Cho, Kyungil

    2013-03-01

    Up-to-date capacitive micromachined ultrasonic transducer (CMUT) technologies provide us unique opportunities to minimize the size and cost of ultrasound scanners by integrating front-end circuits into CMUT arrays. We describe a design prototype of a portable ultrasound scan-head probe using 2-D phased CMUT-on-ASIC arrays of 3-MHz 250 micrometer-pitch by fabricating and integrating front-end electronics with 2-D CMUT array elements. One of the objectives of our work is to design a receive beamformer architecture for the smart probe with compact size and comparable performance. In this work, a phase-rotation based receive beamformer using the sampling frequency of 4 times the center frequency and a hybrid beamforming to reduce the channel counts of the system-side are introduced. Parallel beamforming is considered for the purpose of saving power consumption of battery (by firing fewer times per image frame). This architecture has the advantage of directly obtaining I and Q components. By using the architecture, the interleaved I/Q data from the storage is acquired and I/Q demodulation for baseband processing is directly achieved without demodulators including sin and cosine lookup tables and mixers. Currently, we are extending the presented architecture to develop a true smart probe by including lower power devices and cooling systems, and bringing wireless data transmission into consideration.

  2. Plasmonic spectrum on 1D and 2D periodic arrays of rod-shape metal nanoparticle pairs with different core patterns for biosensor and solar cell applications

    NASA Astrophysics Data System (ADS)

    Kumara, N. T. R. N.; Chou Chau, Yuan-Fong; Huang, Jin-Wei; Huang, Hung Ji; Lin, Chun-Ting; Chiang, Hai-Pang

    2016-11-01

    Simulations of surface plasmon resonance (SPR) on the near field intensity and absorption spectra of one-dimensional (1D) and two-dimensional (2D) periodic arrays of rod-shape metal nanoparticle (MNP) pairs using the finite element method (FEM) and taking into account the different core patterns for biosensor and solar cell applications are investigated. A tunable optical spectrum corresponding to the transverse SPR modes is observed. The peak resonance wavelength (λ res) can be shifted to red as the core patterns in rod-shape MNPs have been changed. We find that the 2D periodic array of core–shell MNP pairs (case 2) exhibit a red shifted SPR that can be tuned the gap enhancement and absorption efficiency simultaneously over an extended wavelength range. The tunable optical performances give us a qualitative idea of the geometrical properties of the periodic array of rod-shape MNP pairs on SPRs that can be as a promising candidate for plasmonic biosensor and solar cell applications.

  3. 2D and 3D spatially addressed arrays for high-throughput automated synthesis of combinatorial libraries.

    PubMed

    Patek, Marcel; Safar, Pavel; Smrcina, Martin; Wegrzyniak, Eric; Bjergarde, Kirsten; Weichsel, Aleksandra; Strop, Peter

    2004-01-01

    One of the key elements in the drug discovery process is the use of automation to synthesize libraries of compounds for biological screening. The "split-and-mix" approaches in combinatorial chemistry have been recognized as extremely powerful techniques to access large numbers of compounds, while requiring only few reaction steps. However, the need for effective encoding/deconvolution strategies and demands for larger amounts of compounds have somewhat limited the use of these techniques in the pharmaceutical industry. In this paper, we describe a concept of directed sort and combine synthesis with spatially arranged arrays of macroscopic supports. Such a concept attempts to balance the number of reaction steps, the confidence in compound identity, and the quantity of synthesized compounds. Using three-dimensional arrays of frames each containing a two-dimensional array of macroscopic solid supports, we have conceptualized and developed a modular semiautomated system with a capacity of up to 100 000 compounds per batch. Modularity of this system enables flexibility either to produce large diverse combinatorial libraries or to synthesize more focused smaller libraries, both as single compounds in 12-15 micromol quantities. This method using sortable and spatially addressed arrays is exemplified by the synthesis of a 15 360 compound library.

  4. Monte Carlo simulation of the dose response of a novel 2D silicon diode array for use in hybrid MRI–LINAC systems

    SciTech Connect

    Gargett, Maegan Rosenfeld, Anatoly; Oborn, Brad; Metcalfe, Peter

    2015-02-15

    Purpose: MRI-guided radiation therapy systems (MRIgRT) are being developed to improve online imaging during treatment delivery. At present, the operation of single point dosimeters and an ionization chamber array have been characterized in such systems. This work investigates a novel 2D diode array, named “magic plate,” for both single point calibration and 2D positional performance, the latter being a key element of modern radiotherapy techniques that will be delivered by these systems. Methods: GEANT4 Monte Carlo methods have been employed to study the dose response of a silicon diode array to 6 MV photon beams, in the presence of in-line and perpendicularly aligned uniform magnetic fields. The array consists of 121 silicon diodes (dimensions 1.5 × 1.5 × 0.38 mm{sup 3}) embedded in kapton substrate with 1 cm pitch, spanning a 10 × 10 cm{sup 2} area in total. A geometrically identical, water equivalent volume was simulated concurrently for comparison. The dose response of the silicon diode array was assessed for various photon beam field shapes and sizes, including an IMRT field, at 1 T. The dose response was further investigated at larger magnetic field strengths (1.5 and 3 T) for a 4 × 4 cm{sup 2} photon field size. Results: The magic plate diode array shows excellent correspondence (< ± 1%) to water dose in the in-line orientation, for all beam arrangements and magnetic field strengths investigated. The perpendicular orientation, however, exhibits a dose shift with respect to water at the high-dose-gradient beam edge of jaw-defined fields [maximum (4.3 ± 0.8)% over-response, maximum (1.8 ± 0.8)% under-response on opposing side for 1 T, uncertainty 1σ]. The trend is not evident in areas with in-field dose gradients typical of IMRT dose maps. Conclusions: A novel 121 pixel silicon diode array detector has been characterized by Monte Carlo simulation for its performance inside magnetic fields representative of current prototype and proposed MRI

  5. Scattering of electromagnetic radiation by three-dimensional periodic arrays of identical particles.

    PubMed

    Xu, Yu-Lin

    2014-02-01

    The generalized multiparticle Mie-solution (GMM), a Lorenz-Mie-type rigorous theory for the scattering of a monochromatic plane wave by an arbitrary configuration of nonintersecting scattering bodies, has lately been revisited and further developed. A recent progress is the initiation of a special version applied to one- and two-dimensional (1D and 2D) periodic arrays (PAs) of identical particles [J. Opt. Soc. Am. A30, 1053 (2013)]. As a continuous advance, the present work extends the initiative PA-type solution from 1D and 2D to the more involved three-dimensional (3D) regular arrays. Analytical formulations applicable to the 3D PAs are derived, including the special PA-type explicit expressions for cross sections of extinction, scattering, backscattering, and radiation pressure. The specific PA-version is a complement to the general formulation and solution process of the standard GMM. In either 1D and 2D or 3D cases, the newly devised PA-approach is capable of providing expeditiously theoretical predictions of radiative scattering characteristics for periodic structures consisting of a huge number of identical unit cells, which the general approach of the GMM is unable to handle in practical calculations, owing to excessive computing time and/or computer memory requirements. To illustrate practical applications, sample numerical solutions obtained via the PA-approach are shown for 3D PAs of finite lengths that have ∼5×10(7) component particles, including structures having a rectangular opening. Also discussed is potential future work on the theory and its tests.

  6. Gravity driven deterministic lateral displacement for suspended particles in a 3D obstacle array

    NASA Astrophysics Data System (ADS)

    Du, Siqi; Drazer, German

    2016-08-01

    We present a simple modification to enhance the separation ability of deterministic lateral displacement (DLD) systems by expanding the two-dimensional nature of these devices and driving the particles into size-dependent, fully three-dimensional trajectories. Specifically, we drive the particles through an array of long cylindrical posts, such that they not only move parallel to the basal plane of the posts as in traditional two-dimensional DLD systems (in-plane motion), but also along the axial direction of the solid posts (out-of-plane motion). We show that the (projected) in-plane motion of the particles is completely analogous to that observed in 2D-DLD systems. In fact, a theoretical model originally developed for force-driven, two-dimensional DLD systems accurately describes the experimental results. More importantly, we analyze the particles out-of-plane motion and observe, for certain orientations of the driving force, significant differences in the out-of-plane displacement depending on particle size. Therefore, taking advantage of both the in-plane and out-of-plane motion of the particles, it is possible to achieve the simultaneous fractionation of a polydisperse suspension into multiple streams.

  7. Gravity driven deterministic lateral displacement for suspended particles in a 3D obstacle array.

    PubMed

    Du, Siqi; Drazer, German

    2016-01-01

    We present a simple modification to enhance the separation ability of deterministic lateral displacement (DLD) systems by expanding the two-dimensional nature of these devices and driving the particles into size-dependent, fully three-dimensional trajectories. Specifically, we drive the particles through an array of long cylindrical posts, such that they not only move parallel to the basal plane of the posts as in traditional two-dimensional DLD systems (in-plane motion), but also along the axial direction of the solid posts (out-of-plane motion). We show that the (projected) in-plane motion of the particles is completely analogous to that observed in 2D-DLD systems. In fact, a theoretical model originally developed for force-driven, two-dimensional DLD systems accurately describes the experimental results. More importantly, we analyze the particles out-of-plane motion and observe, for certain orientations of the driving force, significant differences in the out-of-plane displacement depending on particle size. Therefore, taking advantage of both the in-plane and out-of-plane motion of the particles, it is possible to achieve the simultaneous fractionation of a polydisperse suspension into multiple streams. PMID:27526935

  8. Gravity driven deterministic lateral displacement for suspended particles in a 3D obstacle array.

    PubMed

    Du, Siqi; Drazer, German

    2016-08-16

    We present a simple modification to enhance the separation ability of deterministic lateral displacement (DLD) systems by expanding the two-dimensional nature of these devices and driving the particles into size-dependent, fully three-dimensional trajectories. Specifically, we drive the particles through an array of long cylindrical posts, such that they not only move parallel to the basal plane of the posts as in traditional two-dimensional DLD systems (in-plane motion), but also along the axial direction of the solid posts (out-of-plane motion). We show that the (projected) in-plane motion of the particles is completely analogous to that observed in 2D-DLD systems. In fact, a theoretical model originally developed for force-driven, two-dimensional DLD systems accurately describes the experimental results. More importantly, we analyze the particles out-of-plane motion and observe, for certain orientations of the driving force, significant differences in the out-of-plane displacement depending on particle size. Therefore, taking advantage of both the in-plane and out-of-plane motion of the particles, it is possible to achieve the simultaneous fractionation of a polydisperse suspension into multiple streams.

  9. Gravity driven deterministic lateral displacement for suspended particles in a 3D obstacle array

    PubMed Central

    Du, Siqi; Drazer, German

    2016-01-01

    We present a simple modification to enhance the separation ability of deterministic lateral displacement (DLD) systems by expanding the two-dimensional nature of these devices and driving the particles into size-dependent, fully three-dimensional trajectories. Specifically, we drive the particles through an array of long cylindrical posts, such that they not only move parallel to the basal plane of the posts as in traditional two-dimensional DLD systems (in-plane motion), but also along the axial direction of the solid posts (out-of-plane motion). We show that the (projected) in-plane motion of the particles is completely analogous to that observed in 2D-DLD systems. In fact, a theoretical model originally developed for force-driven, two-dimensional DLD systems accurately describes the experimental results. More importantly, we analyze the particles out-of-plane motion and observe, for certain orientations of the driving force, significant differences in the out-of-plane displacement depending on particle size. Therefore, taking advantage of both the in-plane and out-of-plane motion of the particles, it is possible to achieve the simultaneous fractionation of a polydisperse suspension into multiple streams. PMID:27526935

  10. Simulating Dynamic Stall in a 2D VAWT: Modeling strategy, verification and validation with Particle Image Velocimetry data

    NASA Astrophysics Data System (ADS)

    Simão Ferreira, C. J.; Bijl, H.; van Bussel, G.; van Kuik, G.

    2007-07-01

    The implementation of wind energy conversion systems in the built environment renewed the interest and the research on Vertical Axis Wind Turbines (VAWT), which in this application present several advantages over Horizontal Axis Wind Turbines (HAWT). The VAWT has an inherent unsteady aerodynamic behavior due to the variation of angle of attack with the angle of rotation, perceived velocity and consequentially Reynolds number. The phenomenon of dynamic stall is then an intrinsic effect of the operation of a Vertical Axis Wind Turbine at low tip speed ratios, having a significant impact in both loads and power. The complexity of the unsteady aerodynamics of the VAWT makes it extremely attractive to be analyzed using Computational Fluid Dynamics (CFD) models, where an approximation of the continuity and momentum equations of the Navier-Stokes equations set is solved. The complexity of the problem and the need for new design approaches for VAWT for the built environment has driven the authors of this work to focus the research of CFD modeling of VAWT on: •comparing the results between commonly used turbulence models: URANS (Spalart-Allmaras and k-epsilon) and large eddy models (Large Eddy Simulation and Detached Eddy Simulation) •verifying the sensitivity of the model to its grid refinement (space and time), •evaluating the suitability of using Particle Image Velocimetry (PIV) experimental data for model validation. The 2D model created represents the middle section of a single bladed VAWT with infinite aspect ratio. The model simulates the experimental work of flow field measurement using Particle Image Velocimetry by Simão Ferreira et al for a single bladed VAWT. The results show the suitability of the PIV data for the validation of the model, the need for accurate simulation of the large eddies and the sensitivity of the model to grid refinement.

  11. Real-time texture analysis for identifying optimum microbubble concentration in 2-D ultrasonic particle image velocimetry.

    PubMed

    Niu, Lili; Qian, Ming; Yan, Liang; Yu, Wentao; Jiang, Bo; Jin, Qiaofeng; Wang, Yanping; Shandas, Robin; Liu, Xin; Zheng, Hairong

    2011-08-01

    Many recent studies on ultrasonic particle image velocimetry (Echo PIV) showed that the accuracy of two-dimensional (2-D) flow velocity measured depends largely on the concentration of ultrasound contrast agents (UCAs) during imaging. This article presents a texture-based method for identifying the optimum microbubble concentration for Echo PIV measurements in real-time. The texture features, standard deviation of gray level, and contrast, energy and homogeneity of gray level co-occurrence matrix were extracted from ultrasound contrast images of rotational and pulsatile flow (10 MHz) in vitro and in vivo mouse common carotid arterial flow (40 MHz) with UCAs at various concentrations. The results showed that, at concentration of 0.8∼2 × 10³ bubbles/mL in vitro and 1∼5 × 10⁵ bubbles/mL in vivo, image texture features had a peak value or trough value, and velocity vectors with high accuracy can be obtained. Otherwise, poor quality velocity vectors were obtained. When the texture features were used as a feature set, the accuracy of K-nearest neighbor classifier can reach 86.4% in vitro and 87.5% in vivo, respectively. The texture-based method is shown to be able to quickly identify the optimum microbubble concentration and improve the accuracy for Echo PIV imaging.

  12. Dielectrophoresis-based particle sensor using nanoelectrode arrays

    NASA Technical Reports Server (NTRS)

    Li, Jun (Inventor); Cassell, Alan M. (Inventor); Arumugam, Prabhu U. (Inventor)

    2009-01-01

    A method for concentrating or partly separating particles of a selected species from a liquid or fluid containing these particles and flowing in a channel, and for determining if the selected species particle is present in the liquid or fluid. A time varying electrical field E, having a root-mean-square intensity E.sup.2.sub.rms with a non-zero gradient in a direction transverse to the liquid or fluid flow direction, is produced by a nanostructure electrode array, with a very high magnitude gradient near exposed electrode tips. A dielectrophoresis force causes the selected particles to accumulate near the electrode tips, if the medium and selected particles have substantially different dielectric constants. An insulating material surrounds most of each of the nanostructure electrodes, and a region of the insulating material surface is functionalized to promote attachment of the selected species particles to the surface. An electrical property value Z(meas) is measured at the functionalized surface and is compared with a reference value Z(ref) to determine if the selected species particles are attached to the functionalized surface.

  13. Accelerated short-TE 3D proton echo-planar spectroscopic imaging using 2D-SENSE with a 32-channel array coil.

    PubMed

    Otazo, Ricardo; Tsai, Shang-Yueh; Lin, Fa-Hsuan; Posse, Stefan

    2007-12-01

    MR spectroscopic imaging (MRSI) with whole brain coverage in clinically feasible acquisition times still remains a major challenge. A combination of MRSI with parallel imaging has shown promise to reduce the long encoding times and 2D acceleration with a large array coil is expected to provide high acceleration capability. In this work a very high-speed method for 3D-MRSI based on the combination of proton echo planar spectroscopic imaging (PEPSI) with regularized 2D-SENSE reconstruction is developed. Regularization was performed by constraining the singular value decomposition of the encoding matrix to reduce the effect of low-value and overlapped coil sensitivities. The effects of spectral heterogeneity and discontinuities in coil sensitivity across the spectroscopic voxels were minimized by unaliasing the point spread function. As a result the contamination from extracranial lipids was reduced 1.6-fold on average compared to standard SENSE. We show that the acquisition of short-TE (15 ms) 3D-PEPSI at 3 T with a 32 x 32 x 8 spatial matrix using a 32-channel array coil can be accelerated 8-fold (R = 4 x 2) along y-z to achieve a minimum acquisition time of 1 min. Maps of the concentrations of N-acetyl-aspartate, creatine, choline, and glutamate were obtained with moderate reduction in spatial-spectral quality. The short acquisition time makes the method suitable for volumetric metabolite mapping in clinical studies.

  14. Graphene Paper Decorated with a 2D Array of Dendritic Platinum Nanoparticles for Ultrasensitive Electrochemical Detection of Dopamine Secreted by Live Cells.

    PubMed

    Zan, Xiaoli; Bai, Hongwei; Wang, Chenxu; Zhao, Faqiong; Duan, Hongwei

    2016-04-01

    To circumvent the bottlenecks of non-flexibility, low sensitivity, and narrow workable detection range of conventional biosensors for biological molecule detection (e.g., dopamine (DA) secreted by living cells), a new hybrid flexible electrochemical biosensor has been created by decorating closely packed dendritic Pt nanoparticles (NPs) on freestanding graphene paper. This innovative structural integration of ultrathin graphene paper and uniform 2D arrays of dendritic NPs by tailored wet chemical synthesis has been achieved by a modular strategy through a facile and delicately controlled oil-water interfacial assembly method, whereby the uniform distribution of catalytic dendritic NPs on the graphene paper is maximized. In this way, the performance is improved by several orders of magnitude. The developed hybrid electrode shows a high sensitivity of 2 μA cm(-2) μM(-1), up to about 33 times higher than those of conventional sensors, a low detection limit of 5 nM, and a wide linear range of 87 nM to 100 μM. These combined features enable the ultrasensitive detection of DA released from pheochromocytoma (PC 12) cells. The unique features of this flexible sensor can be attributed to the well-tailored uniform 2D array of dendritic Pt NPs and the modular electrode assembly at the oil-water interface. Its excellent performance holds much promise for the future development of optimized flexible electrochemical sensors for a diverse range of electroactive molecules to better serve society. PMID:26918612

  15. Graphene Paper Decorated with a 2D Array of Dendritic Platinum Nanoparticles for Ultrasensitive Electrochemical Detection of Dopamine Secreted by Live Cells.

    PubMed

    Zan, Xiaoli; Bai, Hongwei; Wang, Chenxu; Zhao, Faqiong; Duan, Hongwei

    2016-04-01

    To circumvent the bottlenecks of non-flexibility, low sensitivity, and narrow workable detection range of conventional biosensors for biological molecule detection (e.g., dopamine (DA) secreted by living cells), a new hybrid flexible electrochemical biosensor has been created by decorating closely packed dendritic Pt nanoparticles (NPs) on freestanding graphene paper. This innovative structural integration of ultrathin graphene paper and uniform 2D arrays of dendritic NPs by tailored wet chemical synthesis has been achieved by a modular strategy through a facile and delicately controlled oil-water interfacial assembly method, whereby the uniform distribution of catalytic dendritic NPs on the graphene paper is maximized. In this way, the performance is improved by several orders of magnitude. The developed hybrid electrode shows a high sensitivity of 2 μA cm(-2) μM(-1), up to about 33 times higher than those of conventional sensors, a low detection limit of 5 nM, and a wide linear range of 87 nM to 100 μM. These combined features enable the ultrasensitive detection of DA released from pheochromocytoma (PC 12) cells. The unique features of this flexible sensor can be attributed to the well-tailored uniform 2D array of dendritic Pt NPs and the modular electrode assembly at the oil-water interface. Its excellent performance holds much promise for the future development of optimized flexible electrochemical sensors for a diverse range of electroactive molecules to better serve society.

  16. Long-wavelength infrared surface plasmons on Ga-doped ZnO films excited via 2D hole arrays for extraordinary optical transmission

    NASA Astrophysics Data System (ADS)

    Cleary, Justin W.; Esfahani, Nima Nader; Vangala, Shivashankar; Guo, Junpeng; Hendrickson, Joshua R.; Leedy, Kevin D.; Thomson, Darren; Look, David C.

    2013-09-01

    Extraordinary optical transmission (EOT) through highly conductive ZnO films with sub-wavelength hole arrays is investigated in the long-wavelength infrared regime. EOT is facilitated by the excitation of surface plasmon polaritons (SPPs) and can be tuned utilizing the physical structure size such as period. Pulse laser deposited Ga-doped ZnO has been shown to have fluctuations in optical and electrical parameters based on fabrication techniques, providing a complimentary tuning means. The sub-wavelength 2D hole arrays are fabricated in the Ga-doped ZnO films via standard lithography and etching processes. Optical reflection measurements completed with a microscope coupled FTIR system contain absorption resonances that are in agreement with analytical theories for excitation of SPPs on 2D structures. EOT through Ga-doped ZnO is numerically demonstrated at wavelengths where SPPs are excited. This highly conductive ZnO EOT structure may prove useful in novel integrated components such as tunable biosensors or surface plasmon coupling mechanisms.

  17. Accelerated short-TE 3D proton echo-planar spectroscopic imaging using 2D-SENSE with a 32-channel array coil.

    PubMed

    Otazo, Ricardo; Tsai, Shang-Yueh; Lin, Fa-Hsuan; Posse, Stefan

    2007-12-01

    MR spectroscopic imaging (MRSI) with whole brain coverage in clinically feasible acquisition times still remains a major challenge. A combination of MRSI with parallel imaging has shown promise to reduce the long encoding times and 2D acceleration with a large array coil is expected to provide high acceleration capability. In this work a very high-speed method for 3D-MRSI based on the combination of proton echo planar spectroscopic imaging (PEPSI) with regularized 2D-SENSE reconstruction is developed. Regularization was performed by constraining the singular value decomposition of the encoding matrix to reduce the effect of low-value and overlapped coil sensitivities. The effects of spectral heterogeneity and discontinuities in coil sensitivity across the spectroscopic voxels were minimized by unaliasing the point spread function. As a result the contamination from extracranial lipids was reduced 1.6-fold on average compared to standard SENSE. We show that the acquisition of short-TE (15 ms) 3D-PEPSI at 3 T with a 32 x 32 x 8 spatial matrix using a 32-channel array coil can be accelerated 8-fold (R = 4 x 2) along y-z to achieve a minimum acquisition time of 1 min. Maps of the concentrations of N-acetyl-aspartate, creatine, choline, and glutamate were obtained with moderate reduction in spatial-spectral quality. The short acquisition time makes the method suitable for volumetric metabolite mapping in clinical studies. PMID:17968995

  18. Graphene Paper Decorated with a 2D Array of Dendritic Platinum Nanoparticles for Ultrasensitive Electrochemical Detection of Dopamine Secreted by Live Cells

    PubMed Central

    Zan, Xiaoli; Wang, Chenxu

    2016-01-01

    Abstract To circumvent the bottlenecks of non‐flexibility, low sensitivity, and narrow workable detection range of conventional biosensors for biological molecule detection (e.g., dopamine (DA) secreted by living cells), a new hybrid flexible electrochemical biosensor has been created by decorating closely packed dendritic Pt nanoparticles (NPs) on freestanding graphene paper. This innovative structural integration of ultrathin graphene paper and uniform 2D arrays of dendritic NPs by tailored wet chemical synthesis has been achieved by a modular strategy through a facile and delicately controlled oil–water interfacial assembly method, whereby the uniform distribution of catalytic dendritic NPs on the graphene paper is maximized. In this way, the performance is improved by several orders of magnitude. The developed hybrid electrode shows a high sensitivity of 2 μA cm−2 μm −1, up to about 33 times higher than those of conventional sensors, a low detection limit of 5 nm, and a wide linear range of 87 nm to 100 μm. These combined features enable the ultrasensitive detection of DA released from pheochromocytoma (PC 12) cells. The unique features of this flexible sensor can be attributed to the well‐tailored uniform 2D array of dendritic Pt NPs and the modular electrode assembly at the oil–water interface. Its excellent performance holds much promise for the future development of optimized flexible electrochemical sensors for a diverse range of electroactive molecules to better serve society. PMID:26918612

  19. VFLOW2D - A Vorte-Based Code for Computing Flow Over Elastically Supported Tubes and Tube Arrays

    SciTech Connect

    WOLFE,WALTER P.; STRICKLAND,JAMES H.; HOMICZ,GREGORY F.; GOSSLER,ALBERT A.

    2000-10-11

    A numerical flow model is developed to simulate two-dimensional fluid flow past immersed, elastically supported tube arrays. This work is motivated by the objective of predicting forces and motion associated with both deep-water drilling and production risers in the oil industry. This work has other engineering applications including simulation of flow past tubular heat exchangers or submarine-towed sensor arrays and the flow about parachute ribbons. In the present work, a vortex method is used for solving the unsteady flow field. This method demonstrates inherent advantages over more conventional grid-based computational fluid dynamics. The vortex method is non-iterative, does not require artificial viscosity for stability, displays minimal numerical diffusion, can easily treat moving boundaries, and allows a greatly reduced computational domain since vorticity occupies only a small fraction of the fluid volume. A gridless approach is used in the flow sufficiently distant from surfaces. A Lagrangian remap scheme is used near surfaces to calculate diffusion and convection of vorticity. A fast multipole technique is utilized for efficient calculation of velocity from the vorticity field. The ability of the method to correctly predict lift and drag forces on simple stationary geometries over a broad range of Reynolds numbers is presented.

  20. MCT-Based LWIR and VLWIR 2D Focal Plane Detector Arrays for Low Dark Current Applications at AIM

    NASA Astrophysics Data System (ADS)

    Hanna, S.; Eich, D.; Mahlein, K.-M.; Fick, W.; Schirmacher, W.; Thöt, R.; Wendler, J.; Figgemeier, H.

    2016-09-01

    We present our latest results on n-on- p as well as on p-on- n low dark current planar mercury cadmium telluride (MCT) photodiode technology long wavelength infrared (LWIR) and very long wavelength infrared (VLWIR) two-dimensional focal plane arrays (FPAs) with quantum efficiency (QE) cut-off wavelength >11 μm at 80 K and a 512 × 640 pixel format FPA at 20 μm pitch stitched from two 512 × 320 pixel photodiode arrays. Significantly reduced dark currents as compared with Tennant's "Rule 07" are demonstrated in both polarities while retaining good detection efficiency ≥60% for operating temperatures between 30 K and 100 K. This allows for the same dark current performance at 20 K higher operating temperature than with previous AIM INFRAROT-MODULE GmbH (AIM) technology. For p-on- n LWIR MCT FPAs, broadband photoresponse nonuniformity of only about 1.2% is achieved at 55 K with low defective pixel numbers. For an n-on- p VLWIR MCT FPA with 13.6 μm cut-off at 55 K, excellent photoresponse nonuniformity of about 3.1% is achieved at moderate defective pixel numbers. This advancement in detector technology paves the way for outstanding signal-to-noise ratio performance infrared detection, enabling cutting-edge next-generation LWIR/VLWIR detectors for space instruments and devices with higher operating temperature and low size, weight, and power for field applications.

  1. Feasibility of vibro-acoustography with a quasi-2D ultrasound array transducer for detection and localizing of permanent prostate brachytherapy seeds: A pilot ex vivo study

    SciTech Connect

    Mehrmohammadi, Mohammad; Kinnick, Randall R.; Fatemi, Mostafa; Alizad, Azra; Davis, Brian J.

    2014-09-15

    Purpose: Effective permanent prostate brachytherapy (PPB) requires precise placement of radioactive seeds in and around the prostate. The impetus for this research is to examine a new ultrasound-based imaging modality, vibro-acoustography (VA), which may serve to provide a high rate of PPB seed detection while also effecting enhanced prostate imaging. The authors investigate the ability of VA, implemented on a clinical ultrasound (US) scanner and equipped with a quasi-2D (Q2D) array US transducer, to detect and localize PPB seeds in excised prostate specimens. Methods: Nonradioactive brachytherapy seeds were implanted into four excised cadaver prostates. A clinical US scanner equipped with a Q2D array US transducer was customized to acquire both US and C-scan VA images at various depths. The VA images were then used to detect and localize the implanted seeds in prostate tissue. To validate the VA results, computed tomography (CT) images of the same tissue samples were obtained to serve as the reference by which to evaluate the performance of VA in PPB seed detection. Results: The results indicate that VA is capable of accurately identifying the presence and distribution of PPB seeds with a high imaging contrast. Moreover, a large ratio of the PPB seeds implanted into prostate tissue samples could be detected through acquired VA images. Using CT-based seed identification as the standard, VA was capable of detecting 74%–92% of the implanted seeds. Additionally, the angular independency of VA in detecting PPB seeds was demonstrated through a well-controlled phantom experiment. Conclusions: Q2DVA detected a substantial portion of the seeds by using a 2D array US transducer in excised prostate tissue specimens. While VA has inherent advantages associated with conventional US imaging, it has the additional advantage of permitting detection of PPB seeds independent of their orientation. These results suggest the potential of VA as a method for PPB imaging that

  2. Dielectrophoresis-Based Particle Sensor Using Nanoelectrode Arrays

    NASA Technical Reports Server (NTRS)

    Li, Jun; Cassell, Alan M.; Arumugam, Prabhu U.

    2013-01-01

    A method has been developed for concentrating, or partly separating, particles of a selected species from a liquid or gas containing these particles, and flowing in a channel. An example of this is to promote an accumulation (and thus concentration) of the selected particle (e.g., biological species such as E. coli, salmonella, anthrax, tobacco mosaic virus or herpes simplex, and non-biological materials such as nano- and microparticles, quantum dots, nanowires, nano - tubes, and other inorganic particles) adjacent to the first surface. Additionally, this method can also determine if the particle species is present in the liquid. This is accomplished by providing an insulating material in an interstitial volume between two or more adjacent nanostructure electrodes. It can also be accomplished by providing a functionalizing substance, located on a selected region of the insulating material surface, which promotes attachment of the selected species particles to the functionalized surface, and measuring a selected electrical property such as electrical impedance, conductance, or capacitance. A time-varying electrical field E, having a root-mean-square intensity of E(sup 2) rms, with a non-zero gradient in a direction transverse to the liquid or fluid flow direction, is produced by a nanostructure electrode array with a very high-magnitude gradient near exposed electrode tips. A dielectrophoretic force causes the selected particles to accumulate near the electrode tips, if the medium and selected particles have substantially different dielectric constants. An insulating material surrounds most of the nanostructure electrodes, and a region of the insulating material surface is functionalized to promote attachment of the selected particle species to the surface. An electrical property value Z(meas) is measured at the functionalized surface, and is compared with a reference value Z(ref) to determine if the selected species particles are attached to the functionalized

  3. Progress in the development and demonstration of a 2D-matrix phased array ultrasonic probe for under-sodium viewing

    NASA Astrophysics Data System (ADS)

    Larche, M. R.; Baldwin, D. L.; Edwards, M. K.; Mathews, R. A.; Prowant, M. S.; Diaz, A. A.

    2016-02-01

    Optically opaque liquid sodium used in liquid metal fast reactors poses a unique set of challenges for nondestructive evaluation. The opaque nature of the sodium prevents visual examinations of components within this medium, but ultrasonic waves are able to propagate through sodium so an ultrasonic testing (UT) technique can be applied for imaging objects in sodium. A UT sensor used in liquid sodium during a refueling outage must be capable of withstanding the 260°C corrosive environment and must also be able to wet (couple the ultrasonic waves) so that sound can propagate into the sodium. A multi-year iterative design effort, based on earlier work in the 1970s, has set out to improve the design and fabrication processes needed for a UT sensor technology capable of overcoming the temperature and wetting issues associated with this environment. Robust materials and improved fabrication processes have resulted in single-element sensors and two different linear-array sensors that have functioned in liquid sodium. More recent efforts have been focused on improving signal-to-noise ratio and image resolution in the highly attenuating liquid sodium. In order to accomplish this, modeling and simulation tools were used to design a 60-element 2D phased-array sensor operating at 2 MHz that features a separate transmitter and receiver. This design consists of 30 transmit elements and another 30 receive elements, each arranged in a rectangular matrix pattern that is 10 rows tall and 3 wide. The fabrication of this 2D array is currently underway and will be followed by a series of performance tests in water, hot oil, and finally in liquid sodium at 260°C. The performance testing cycle will evaluate multiple characteristics of the sensor that are crucial to performance including: transmit-uniformity, element sensitivity variations, element-to-element energy leakage, sound field dimensions, and spatial resolution. This paper will present a summary of results from the previous UT

  4. 2D silicon-based surface-normal vertical cavity photonic crystal waveguide array for high-density optical interconnects

    NASA Astrophysics Data System (ADS)

    Ahn, JaeHyun; Subbaraman, Harish; Zhu, Liang; Chakravarty, Swapnajit; Tutuc, Emanuel; Chen, Ray T.

    2013-02-01

    In this paper, we present the design guidelines, fabrication challenges and device evaluation results of a surface-normal photonic crystal waveguide array for high-density optical interconnects. We utilize the slow light effect of photonic crystals to increase the effective interaction length between photons and medium, which in turn can be used to decrease the physical length and make compact devices. The effect of the structural parameters variations on the guided mode are studied in order to provide a guideline for fabrication. Photonic crystal waveguides are vertically implemented in a silicon-on insulator substrate. Our structure possesses advantages such as universal design, CMOS compatibility, and simple fabrication process, suitable for high dense on-chip applications. Transmission results show increase of power near 1.67 μm wavelength, which agrees with our simulation results.

  5. State of the art of AIM LWIR and VLWIR MCT 2D focal plane detector arrays for higher operating temperatures

    NASA Astrophysics Data System (ADS)

    Figgemeier, H.; Hanna, S.; Eich, D.; Mahlein, K.-M.; Fick, W.; Schirmacher, W.; Thöt, R.

    2016-05-01

    In this paper AIM presents its latest results on both n-on-p and p-on-n low dark current planar MCT photodiode technology LWIR and VLWIR two-dimensional focal plane detector arrays with a cut-off wavelength >11μm at 80K and a 640x512 pixel format at a 20μm pitch. Thermal dark currents significantly reduced as compared to `Tennant's Rule 07' at a yet good detection efficiency >60% as well as results from NETD and photo response performance characterization are presented. The demonstrated detector performance paces the way for a new generation of higher operating temperature LWIR MCT FPAs with a <30mK NETD up to a 110K detector operating temperature and with good operability.

  6. Array of neutral particle analyzers at DIII-D

    SciTech Connect

    Carolipio, E.M.; Heidbrink, W.W.

    1996-12-01

    Local measurements of the fast-ion distribution in auxiliary-heated plasmas are key to understanding the behavior of energetic particles under a variety of conditions, such as beam-ion transport during Alfven instabilities and the acceleration of beam ions by fast waves. For the first time at DIII-D, line-averaged and local measurements of the energetic-particle density (for E = 5--75 keV) are possible using an array of four compact charge-exchange analyzers. The installation consists of three vertically-viewing analyzers with fixed sightlines, measuring particles with {chi} = 90{degree} (where {chi} is the angle between the particle`s velocity and the toroidal direction) and one horizontally-viewing analyzer with a variable sightline, measuring particles with 2{degree}{grave U} {chi} {acute U} 60{degree}. All the analyzers can make passive measurements while three detectors, with sightlines that intersect deuterium heating beams, can make active charge-exchange measurements.

  7. Solid State Neutral Particle Analyzer Array on NSTX

    SciTech Connect

    K. Shinohara; D.S. Darrow; A.L. Roquemore; S.S. Medley; F.E. Cecil

    2004-05-13

    A Solid State Neutral Particle Analyzer (SSNPA) array has been installed on the National Spherical Torus Experiment (NSTX). The array consists of four chords viewing through a common vacuum flange. The tangency radii of the viewing chords are 60, 90, 100, and 120 cm. They view across the three co-injection neutral beam lines (deuterium, 80 keV (typ.) with tangency radii 48.7, 59.2, and 69.4 cm) on NSTX and detect co-going energetic ions. A silicon photodiode used was calibrated by using a mono-energetic deuteron beam source. Deuterons with energy above 40 keV can be detected with the present setup. The degradation of the performance was also investigated. Lead shots and epoxy are used for neutron shielding to reduce handling any hazardous heavy metal. This method also enables us to make an arbitrary shape to be fit into the complex flight tube.

  8. Array of neutral particle analyzers at DIII-D

    SciTech Connect

    Carolipio, E.M.; Heidbrink, W.W.

    1997-01-01

    Local measurements of the fast-ion distribution in auxiliary-heated plasmas are key to understanding the behavior of energetic particles under a variety of conditions, such as beam{endash}ion transport during Alfv{acute e}n instabilities and the acceleration of beam ions by fast waves. For the first time at DIII-D, line-averaged and local measurements of the energetic-particle density (for E=5{endash}75 keV) are possible using an array of four compact charge{endash}exchange analyzers [P. Beiersdorfer {ital et al.}, Rev. Sci. Instrum. {bold 58}, 2092 (1987)]. The installation consists of three vertically viewing analyzers with fixed sightlines, measuring particles with {chi}=90{degree} (where {chi} is the angle between the particle{close_quote}s velocity and the toroidal direction), and one horizontally viewing analyzer with a variable sightline, measuring particles with 2{degree}{approx_lt}{chi}{approx_lt}60{degree}. All the analyzers can make passive measurements while three detectors, with sightlines that intersect deuterium heating beams, can make active charge{endash}exchange measurements. {copyright} {ital 1997 American Institute of Physics.}

  9. Self-Assembly of Two- and Three-Dimensional Particle Arrays by Manipulating the Hydrophobicity of Silica Nanospheres

    SciTech Connect

    Wang, Wei; Gu, Baohua

    2005-11-01

    The surface hydrophobicity of colloidal silica (SiO2) nanopheres is manipulated by a chemical graft of alkyl chains with silane coupling agents or by physical adsorption of a cationic surfactant. The surface-modified SiO2 spheres can be transferred from the aqueous phase to organic solvents and readily self-assemble at the water-air interface to form two-dimensional (2D) particle arrays. Closely packed particle monolayers are obtained by adjusting the hydrophilic/hydrophobic balance of the synthesized SiO2 spheres and may further be transferred onto solid substrates layer by layer to form three-dimensional (3D) ordered particle arrays with a hexagonal close-packed (hcp) crystalline structure. The 2D monolayer and 3D multilayer SiO2 films exhibit photonic crystal properties, which were determined by the UV-visible spectroscopic analysis in transmission mode. In the multilayer films, the Bragg diffraction maxima increased with an increase in thickness of the particle layers. The experimentally observed diffraction positions are in good agreement with those that were theoretically calculated.

  10. Time-resolved dosimetric verification of respiratory-gated radiotherapy exposures using a high-resolution 2D ionisation chamber array.

    PubMed

    King, R B; Agnew, C E; O'Connell, B F; Prise, K M; Hounsell, A R; McGarry, C K

    2016-08-01

    The aim of this work was to track and verify the delivery of respiratory-gated irradiations, performed with three versions of TrueBeam linac, using a novel phantom arrangement that combined the OCTAVIUS(®) SRS 1000 array with a moving platform. The platform was programmed to generate sinusoidal motion of the array. This motion was tracked using the real-time position management (RPM) system and four amplitude gating options were employed to interrupt MV beam delivery when the platform was not located within set limits. Time-resolved spatial information extracted from analysis of x-ray fluences measured by the array was compared to the programmed motion of the platform and to the trace recorded by the RPM system during the delivery of the x-ray field. Temporal data recorded by the phantom and the RPM system were validated against trajectory log files, recorded by the linac during the irradiation, as well as oscilloscope waveforms recorded from the linac target signal. Gamma analysis was employed to compare time-integrated 2D x-ray dose fluences with theoretical fluences derived from the probability density function for each of the gating settings applied, where gamma criteria of 2%/2 mm, 1%/1 mm and 0.5%/0.5 mm were used to evaluate the limitations of the RPM system. Excellent agreement was observed in the analysis of spatial information extracted from the SRS 1000 array measurements. Comparisons of the average platform position with the expected position indicated absolute deviations of  <0.5 mm for all four gating settings. Differences were observed when comparing time-resolved beam-on data stored in the RPM files and trajectory logs to the true target signal waveforms. Trajectory log files underestimated the cycle time between consecutive beam-on windows by 10.0  ±  0.8 ms. All measured fluences achieved 100% pass-rates using gamma criteria of 2%/2 mm and 50% of the fluences achieved pass-rates  >90% when criteria of 0.5%/0.5

  11. Time-resolved dosimetric verification of respiratory-gated radiotherapy exposures using a high-resolution 2D ionisation chamber array.

    PubMed

    King, R B; Agnew, C E; O'Connell, B F; Prise, K M; Hounsell, A R; McGarry, C K

    2016-08-01

    The aim of this work was to track and verify the delivery of respiratory-gated irradiations, performed with three versions of TrueBeam linac, using a novel phantom arrangement that combined the OCTAVIUS(®) SRS 1000 array with a moving platform. The platform was programmed to generate sinusoidal motion of the array. This motion was tracked using the real-time position management (RPM) system and four amplitude gating options were employed to interrupt MV beam delivery when the platform was not located within set limits. Time-resolved spatial information extracted from analysis of x-ray fluences measured by the array was compared to the programmed motion of the platform and to the trace recorded by the RPM system during the delivery of the x-ray field. Temporal data recorded by the phantom and the RPM system were validated against trajectory log files, recorded by the linac during the irradiation, as well as oscilloscope waveforms recorded from the linac target signal. Gamma analysis was employed to compare time-integrated 2D x-ray dose fluences with theoretical fluences derived from the probability density function for each of the gating settings applied, where gamma criteria of 2%/2 mm, 1%/1 mm and 0.5%/0.5 mm were used to evaluate the limitations of the RPM system. Excellent agreement was observed in the analysis of spatial information extracted from the SRS 1000 array measurements. Comparisons of the average platform position with the expected position indicated absolute deviations of  <0.5 mm for all four gating settings. Differences were observed when comparing time-resolved beam-on data stored in the RPM files and trajectory logs to the true target signal waveforms. Trajectory log files underestimated the cycle time between consecutive beam-on windows by 10.0  ±  0.8 ms. All measured fluences achieved 100% pass-rates using gamma criteria of 2%/2 mm and 50% of the fluences achieved pass-rates  >90% when criteria of 0.5%/0.5

  12. Time-resolved dosimetric verification of respiratory-gated radiotherapy exposures using a high-resolution 2D ionisation chamber array

    NASA Astrophysics Data System (ADS)

    King, R. B.; Agnew, C. E.; O'Connell, B. F.; Prise, K. M.; Hounsell, A. R.; McGarry, C. K.

    2016-08-01

    The aim of this work was to track and verify the delivery of respiratory-gated irradiations, performed with three versions of TrueBeam linac, using a novel phantom arrangement that combined the OCTAVIUS® SRS 1000 array with a moving platform. The platform was programmed to generate sinusoidal motion of the array. This motion was tracked using the real-time position management (RPM) system and four amplitude gating options were employed to interrupt MV beam delivery when the platform was not located within set limits. Time-resolved spatial information extracted from analysis of x-ray fluences measured by the array was compared to the programmed motion of the platform and to the trace recorded by the RPM system during the delivery of the x-ray field. Temporal data recorded by the phantom and the RPM system were validated against trajectory log files, recorded by the linac during the irradiation, as well as oscilloscope waveforms recorded from the linac target signal. Gamma analysis was employed to compare time-integrated 2D x-ray dose fluences with theoretical fluences derived from the probability density function for each of the gating settings applied, where gamma criteria of 2%/2 mm, 1%/1 mm and 0.5%/0.5 mm were used to evaluate the limitations of the RPM system. Excellent agreement was observed in the analysis of spatial information extracted from the SRS 1000 array measurements. Comparisons of the average platform position with the expected position indicated absolute deviations of  <0.5 mm for all four gating settings. Differences were observed when comparing time-resolved beam-on data stored in the RPM files and trajectory logs to the true target signal waveforms. Trajectory log files underestimated the cycle time between consecutive beam-on windows by 10.0  ±  0.8 ms. All measured fluences achieved 100% pass-rates using gamma criteria of 2%/2 mm and 50% of the fluences achieved pass-rates  >90% when criteria of 0.5%/0.5 mm were

  13. Hybrid plan verification for intensity-modulated radiation therapy (IMRT) using the 2D ionization chamber array I'mRT MatriXX--a feasibility study.

    PubMed

    Dobler, Barbara; Streck, Natalia; Klein, Elisabeth; Loeschel, Rainer; Haertl, Petra; Koelbl, Oliver

    2010-01-21

    The 2D ionization chamber array I'mRT MatriXX (IBA, Schwarzenbruck, Germany) has been developed for absolute 2D dosimetry and verification of intensity-modulated radiation therapy (IMRT) for perpendicular beam incidence. The aim of this study is to evaluate the applicability of I'mRT MatriXX for oblique beam incidence and hybrid plan verification of IMRT with original gantry angles. For the assessment of angular dependence, open fields with gantry angles in steps of 10 degrees were calculated on a CT scan of I'mRT MatriXX. For hybrid plan verification, 17 clinical IMRT plans and one rotational plan were used. Calculations were performed with pencil beam (PB), collapsed cone (CC) and Monte Carlo (MC) methods, which had been previously validated. Measurements were conducted on an Elekta SynergyS linear accelerator. To assess the potential and limitations of the system, gamma evaluation was performed with different dose tolerances and distances to agreement. Hybrid plan verification passed the gamma test with 4% dose tolerance and 3 mm distance to agreement in all cases, in 82-88% of the cases for tolerances of 3%/3 mm, and in 59-76% of the cases if 3%/2 mm were used. Separate evaluation of the low dose and high dose regions showed that I'mRT MatriXX can be used for hybrid plan verification of IMRT plans within 3% dose tolerance and 3 mm distance to agreement with a relaxed dose tolerance of 4% in the low dose region outside the multileaf collimator (MLC).

  14. A novel silicon array designed for intraoperative charged particle imaging.

    PubMed

    Tornai, Martin P; Patt, Bradley E; Iwanczyk, Jan S; Tull, Carolyn R; MacDonald, Lawrence R; Hoffman, Edward J

    2002-11-01

    A novel Si-PIN imaging array is under investigation for a charged particle (beta, positron, or alpha) sensitive intraoperative camera to be used for (residual) tumor identification during surgery. This class of collimator-less nuclear imaging device has a higher signal response for direct interactions than its scintillator-optical detector-based counterparts. Monte Carlo simulations with 635 keV betas were performed, yielding maximum and projected ranges of 1.64 and 0.55 mm in Si. Up to 90% of these betas were completely absorbed in the first 0.30 mm. Based on these results, 300 microm thick prototype Si detector arrays were designed in a 16 x 16 crossed-grid arrangement with 0.8 mm wide orthogonal strips on 1.0 mm pitch. A NIM- and CAMAC-based high-density data acquisition and processing system was used to collect the list mode data. The system was calibrated by comparisons of measured spectra to energy deposition simulations or by direct measurement of various >100 keV conversion electron or beta emitters. Mean electronic noise per strip was <3.6 keV FWHM at room temperature. When detecting positrons, which have an accompanying 511 keV annihilation background, the flood irradiated beta/gamma ratio was approximately 40, indicating that beta images could be made without the use of background rejection techniques. The intrinsic spatial resolution corresponds to the 1 x 1 mm2 pixel size, and measurements of beta emitting point and line sources yielded FWHM resolutions of 1.5 (lateral) and 2.5 mm (diagonal), respectively, with the larger widths due to particle range blurting effects. Deconvolution of the finite source size yielded intrinsic resolutions that corresponded to the image pixel size. Transmission images of circle and line phantoms with various hole sizes and pitch were resolved with either pure beta or positron irradiation without a background correction. This novel semiconductor imaging device facilitates high charged particle and low gamma sensitivity

  15. An analog-digital hybrid RX beamformer chip with non-uniform sampling for ultrasound medical imaging with 2D CMUT array.

    PubMed

    Um, Ji-Yong; Kim, Yoon-Jee; Cho, Seong-Eun; Chae, Min-Kyun; Song, Jongkeun; Kim, Baehyung; Lee, Seunghun; Bang, Jihoon; Kim, Youngil; Cho, Kyungil; Kim, Byungsub; Sim, Jae-Yoon; Park, Hong-June

    2014-12-01

    To reduce the memory area, a two-stage RX beamformer (BF) chip with 64 channels is proposed for the ultrasound medical imaging with a 2D CMUT array. The chip retrieved successfully two B-mode phantom images with a steering angle from -45 (°) to +45 (°), the maximum delay range of 8 μs, and the delay resolution of 6.25 ns. An analog-digital hybrid BF (HBF) is chosen for the proposed chip to utilize the easy beamforming operation in the digital domain and also to reduce chip area by minimizing the number of ADCs. The chip consists of eight analog beamformers (ABF) for the 1st-stage and a digital beamformer (DBF) for the 2nd-stage. The two-stage architecture reduces the memory area of both ABF and DBF by around four times. The DBF circuit is divided into three steps to further reduce the digital FIFO memory area by around twice. Coupled with the non-uniform sampling scheme, the proposed two-stage HBF chip reduces the total memory area by around 40 times compared to the uniform-sampling single-stage BF chip. The chip fabricated in a 0.13- μm CMOS process occupies the area of 19.4 mm(2), and dissipates 1.14 W with the analog supply of 3.3 V and the digital supply of 1.2 V.

  16. Full-particle 2-D Simulations of the Ion Foreshock associated to a Supercritical Quasi-perpendicular Curved Collisionless Shock : Origin of Backstreaming Energetic Particles

    NASA Astrophysics Data System (ADS)

    Savoini, P.; Lembege, B.

    2014-12-01

    The ion foreshock located upstream of the Earth's bow shock is populated with ions reflected back by the shock front. In-situ spacecraft measurements have clearly established the existence of two distinct populations in the upstream of the quasi-perpendicular shock region (i.e. for 45o ≤ ΘBn≤ 90o, where ΘBn is the angle between the shock normal and the upstream magnetostatic field): (i) field-aligned ion beams (or 'FAB') characterized by a gyrotropic distribution, and (ii) gyro-phase bunched ions (or 'GPB') characterized by a NON gyrotropic distribution, which exhibits a non-vanishing perpendicular bulk velocity. The use of 2D PIC simulations where full curvature effects, time of flight effects and both electrons and ions dynamics are fully described, has evidenced that the shock front itself can be the possible source of these two characteristic populations. A recent analysis has evidenced that both populations can be discriminated in terms of interaction time (Δtinter) with the shock front. 'GPB' and 'FAB' populations are characterized by a short (Δtinter ~ 1 τci) and much larger (Δtinter ≥ 2 τci) interaction time respectively, where τci is the ion upstream gyroperiod. In addition, present statistical results evidence that: (i) backstreaming ions are splitted into 'FAB' and 'GPB' populations depending on their injection angle when hitting the shock front (defined between the local normal to the shock front and the gyration velocity vector). (ii) As a consequence, ion trajectories strongly differ between the 'FAB' and 'GPB' populations at the shock front. In particular, 'FAB' ions suffer multi-bounces along the curved front whereas 'GPB' ions make only one bounce. Such differences may explain why the 'FAB' population loses their gyro-phase coherency and become gyrotropic which is not the case for the 'GPB'. Then, the differences observed between 'FAB' and 'GPB' populations do not involve some distinct reflection processes as often claimed in the

  17. Towards 2D nanocomposites

    NASA Astrophysics Data System (ADS)

    Jang, Hyun-Sook; Yu, Changqian; Hayes, Robert; Granick, Steve

    2015-03-01

    Polymer vesicles (``polymersomes'') are an intriguing class of soft materials, commonly used to encapsulate small molecules or particles. Here we reveal they can also effectively incorporate nanoparticles inside their polymer membrane, leading to novel ``2D nanocomposites.'' The embedded nanoparticles alter the capacity of the polymersomes to bend and to stretch upon external stimuli.

  18. Stochastic Multi-Scale Reconstruction of 3D Microstructure Consisting of Polycrystalline Grains and Second-Phase Particles from 2D Micrographs

    NASA Astrophysics Data System (ADS)

    Chen, Shaohua; Kirubanandham, Antony; Chawla, Nikhilesh; Jiao, Yang

    2016-03-01

    An accurate knowledge of the 3D polycrystalline microstructure of a material is crucial to its property prediction, performance optimization, and design. Here, we present a multi-scale computational scheme that allows one to stochastically reconstruct the 3D microstructure of a highly heterogeneous polycrystalline material with large variation in grain size, morphology, and spatial distribution, as well as the distribution of second-phase particles, from single-2D electron back-scattered diffraction (EBSD) micrograph. Specifically, the two-point correlation functions S 2 are employed to statistically characterize grain morphology, orientation, and spatial distribution and are incorporated into the simulated annealing procedure for microstructure reconstruction. During the reconstruction, the original polycrystalline microstructure is coarsened such that the large grains are reconstructed first and the smaller ones are generated later. The second-phase particles are then inserted into the reconstructed polycrystalline material based on the pair-correlation function g 2 sampled from the 2D back-scattered electron micrograph. The utility of our multi-scale scheme is demonstrated by successfully reconstructing a highly heterogeneous polycrystalline Sn-rich solder joint with Cu6Sn5 intermetallic particles. The accuracy of our reconstruction is ascertained by comparing the virtual microstructure with the actual 3D structure of the joint obtained via serial sectioning techniques.

  19. The evaluation of a 2D diode array in “magic phantom” for use in high dose rate brachytherapy pretreatment quality assurance

    SciTech Connect

    Espinoza, A.; Petasecca, M.; Fuduli, I.; Lerch, M. L. F.; Rosenfeld, A. B.; Howie, A.; Bucci, J.; Corde, S.; Jackson, M.

    2015-02-15

    Purpose: High dose rate (HDR) brachytherapy is a treatment method that is used increasingly worldwide. The development of a sound quality assurance program for the verification of treatment deliveries can be challenging due to the high source activity utilized and the need for precise measurements of dwell positions and times. This paper describes the application of a novel phantom, based on a 2D 11 × 11 diode array detection system, named “magic phantom” (MPh), to accurately measure plan dwell positions and times, compare them directly to the treatment plan, determine errors in treatment delivery, and calculate absorbed dose. Methods: The magic phantom system was CT scanned and a 20 catheter plan was generated to simulate a nonspecific treatment scenario. This plan was delivered to the MPh and, using a custom developed software suite, the dwell positions and times were measured and compared to the plan. The original plan was also modified, with changes not disclosed to the primary authors, and measured again using the device and software to determine the modifications. A new metric, the “position–time gamma index,” was developed to quantify the quality of a treatment delivery when compared to the treatment plan. The MPh was evaluated to determine the minimum measurable dwell time and step size. The incorporation of the TG-43U1 formalism directly into the software allows for dose calculations to be made based on the measured plan. The estimated dose distributions calculated by the software were compared to the treatment plan and to calibrated EBT3 film, using the 2D gamma analysis method. Results: For the original plan, the magic phantom system was capable of measuring all dwell points and dwell times and the majority were found to be within 0.93 mm and 0.25 s, respectively, from the plan. By measuring the altered plan and comparing it to the unmodified treatment plan, the use of the position–time gamma index showed that all modifications made could be

  20. Long-term decoding stability of local field potentials from silicon arrays in primate motor cortex during a 2D center out task

    NASA Astrophysics Data System (ADS)

    Wang, Dong; Zhang, Qiaosheng; Li, Yue; Wang, Yiwen; Zhu, Junming; Zhang, Shaomin; Zheng, Xiaoxiang

    2014-06-01

    Objective. Many serious concerns exist in the long-term stability of brain-machine interfaces (BMIs) based on spike signals (single unit activity, SUA; multi unit activity, MUA). Some studies showed local field potentials (LFPs) could offer a stable decoding performance. However, the decoding stability of LFPs was examined only when high quality spike signals were recorded. Here we aim to examine the long-term decoding stability of LFPs over a larger time scale when the quality of spike signals was from good to poor or even no spike was recorded. Approach. Neural signals were collected from motor cortex of three monkeys via silicon arrays over 230, 290 and 690 days post-implantation when they performed 2D center out task. To compare long-term stability between LFPs and spike signals, we examined them in neural signals characteristics, directional tuning properties and offline decoding performance, respectively. Main results. We observed slow decreasing trends in the number of LFP channels recorded and mean LFP power in different frequency bands when spike signals quality decayed over time. The number of significantly directional tuning LFP channels decreased more slowly than that of tuning SUA and MUA. The variable preferred directions for the same signal features across sessions indicated non-stationarity of neural activity. We also found that LFPs achieved better decoding performance than SUA and MUA in retrained decoder when the quality of spike signals seriously decayed. Especially, when no spike was recorded in one monkey after 671 days post-implantation, LFPs still provided some kinematic information. In addition, LFPs outperformed MUA in long-term decoding stability in a static decoder. Significance. Our results suggested that LFPs were more durable and could provide better decoding performance when spike signals quality seriously decayed. It might be due to their resistance to recording degradation and their high redundancy among channels.

  1. Imaging transverse isotropic properties of muscle by monitoring acoustic radiation force induced shear waves using a 2-D matrix ultrasound array.

    PubMed

    Wang, Michael; Byram, Brett; Palmeri, Mark; Rouze, Ned; Nightingale, Kathryn

    2013-09-01

    A 2-D matrix ultrasound array is used to monitor acoustic radiation force impulse (ARFI) induced shear wave propagation in 3-D in excised canine muscle. From a single acquisition, both the shear wave phase and group velocity can be calculated to estimate the shear wave speed (SWS) along and across the fibers, as well as the fiber orientation in 3-D. The true fiber orientation found using the 3-D radon transform on B-mode volumes of the muscle was used to verify the fiber direction estimated from shear wave data. For the simplified imaging case when the ARFI push can be oriented perpendicular to the fibers, the error in estimating the fiber orientation using phase and group velocity measurements was 3.5 ± 2.6° and 3.4 ± 1.4° (mean ± standard deviation), respectively, over six acquisitions in different muscle samples. For the more general case when the push is oblique to the fibers, the angle between the push and the fibers is found using the dominant orientation of the shear wave displacement magnitude. In 30 acquisitions on six different muscle samples with oblique push angles up to 40°, the error in the estimated fiber orientation using phase and group velocity measurements was 5.4 ± 2.9° and 5.3 ± 3.2°, respectively, after estimating and accounting for the additional unknown push angle. Either the phase or group velocity measurements can be used to estimate fiber orientation and SWS along and across the fibers. Although it is possible to perform these measurements when the push is not perpendicular to the fibers, highly oblique push angles induce lower shear wave amplitudes which can cause inaccurate SWS measurements.

  2. Investigation of the Triggering Mechanism of Magnetospheric Substorm via 2-1/2 D Full-Particle Simulation

    NASA Astrophysics Data System (ADS)

    Uchino, H.; Machida, S.

    2012-12-01

    A physical process of the substorm triggering in the Earth's Magnetotail is thought to be closely related to the magnetic reconnection and the tearing instability. Recently we proposed a new scheme of the substorm onset called "Catapult Current Sheet Relaxation (CCSR) Model " to physically understand the results from GEOTAIL and THEMIS data. The CCSR Model has characters that are the decrease of the total pressure and thinning of the current sheet at the distance about -12Re in the magnetotail a few minutes before the substorm onset, and the simultaneous occurrence of the dipolarization at X~-10Re and the magnetic reconnection at X~-20Re at the time of the onset. In this study, we investigate a stability of the current sheet and the particle acceleration via particle simulation in order to assess the validity of the CCSR model and to clarify the mechanism of substorm onset. We give an initial magnetic field structure which is akin to the Earth's dipole magnetic field together with a stretched magnetic field by thin current sheet, and further add a weak northward magnetic field at the place where Near-Earth Neutral Line is expected to be formed. The results of simulation contain similar features that characterize the CCSR Model. A physically interpretation of the simulation result with the linear instability theory as well as comparison with observations will be given.

  3. Particle Size Distributions Obtained Through Unfolding 2D Sections: Towards Accurate Distributions of Nebular Solids in the Allende Meteorite

    NASA Technical Reports Server (NTRS)

    Christoffersen, P. A.; Simon, Justin I.; Ross, D. K.; Friedrich, J. M.; Cuzzi, J. N.

    2012-01-01

    Size distributions of nebular solids in chondrites suggest an efficient sorting of these early forming objects within the protoplanetary disk. The effect of this sorting has been documented by investigations of modal abundances of CAIs (e.g., [1-4]) and chondrules (e.g., [5-8]). Evidence for aerodynamic sorting in the disk is largely qualitative, and needs to be carefully assessed. It may be a way of concentrating these materials into planetesimal-mass clumps, perhaps 100 fs of ka after they formed. A key parameter is size/density distributions of particles (i.e., chondrules, CAIs, and metal grains), and in particular, whether the radius-density product (rxp) is a better metric for defining the distribution than r alone [9]. There is no consensus between r versus rxp based models. Here we report our initial tests and preliminary results, which when expanded will be used to test the accuracy of current dynamical disk models.

  4. SU-E-T-35: An Investigation of the Accuracy of Cervical IMRT Dose Distribution Using 2D/3D Ionization Chamber Arrays System and Monte Carlo Simulation

    SciTech Connect

    Zhang, Y; Yang, J; Liu, H; Liu, D

    2014-06-01

    Purpose: The purpose of this work is to compare the verification results of three solutions (2D/3D ionization chamber arrays measurement and Monte Carlo simulation), the results will help make a clinical decision as how to do our cervical IMRT verification. Methods: Seven cervical cases were planned with Pinnacle 8.0m to meet the clinical acceptance criteria. The plans were recalculated in the Matrixx and Delta4 phantom with the accurate plans parameters. The plans were also recalculated by Monte Carlo using leaf sequences and MUs for individual plans of every patient, Matrixx and Delta4 phantom. All plans of Matrixx and Delta4 phantom were delivered and measured. The dose distribution of iso slice, dose profiles, gamma maps of every beam were used to evaluate the agreement. Dose-volume histograms were also compared. Results: The dose distribution of iso slice and dose profiles from Pinnacle calculation were in agreement with the Monte Carlo simulation, Matrixx and Delta4 measurement. A 95.2%/91.3% gamma pass ratio was obtained between the Matrixx/Delta4 measurement and Pinnacle distributions within 3mm/3% gamma criteria. A 96.4%/95.6% gamma pass ratio was obtained between the Matrixx/Delta4 measurement and Monte Carlo simulation within 2mm/2% gamma criteria, almost 100% gamma pass ratio within 3mm/3% gamma criteria. The DVH plot have slightly differences between Pinnacle and Delta4 measurement as well as Pinnacle and Monte Carlo simulation, but have excellent agreement between Delta4 measurement and Monte Carlo simulation. Conclusion: It was shown that Matrixx/Delta4 and Monte Carlo simulation can be used very efficiently to verify cervical IMRT delivery. In terms of Gamma value the pass ratio of Matrixx was little higher, however, Delta4 showed more problem fields. The primary advantage of Delta4 is the fact it can measure true 3D dosimetry while Monte Carlo can simulate in patients CT images but not in phantom.

  5. Shock interaction with three-dimensional face centered cubic array of particles

    NASA Astrophysics Data System (ADS)

    Mehta, Y.; Neal, C.; Jackson, T. L.; Balachandar, S.; Thakur, S.

    2016-09-01

    In this paper we present three-dimensional fully resolved numerical simulations of shock propagation in air over a face centered cubic (fcc) array of particles. It is well know that shock interaction with a single particle results in nonmonotonic drag on the particle and that the peak force is an order of magnitude greater than the steady-state force. However, there is currently a substantial lack of numerical results for shock propagation over multiple particles. We therefore compute the unsteady inviscid drag coefficient as a function of time for the fcc array of particles and investigate the effect of varying the shock Mach number and the volume fraction. We compare the unsteady drag for the fcc array against the unsteady drag for a single spherical particle and against the unsteady drag for a structured one-dimensional array of spherical particles and make relevant observations. We also plot the local Mach number contours to explain the various observed complex physical mechanisms occurring during shock-particle interaction. Finally, since shock interaction with particles lead to transmitted and reflected waves, we compute the average pressure in the computational domain to characterize the strength of the transmitted shock wave to study pressure attenuation behind the particle barrier. By analyzing the pressure field we can determine the effect of particles on the flow.

  6. Transport and deposition of polymer-modified Fe0 nanoparticles in 2-D heterogeneous porous media: effects of particle concentration, Fe0 content, and coatings.

    PubMed

    Phenrat, Tanapon; Cihan, Abdullah; Kim, Hye-Jin; Mital, Menka; Illangasekare, Tissa; Lowry, Gregory V

    2010-12-01

    Concentrated suspensions of polymer-modified Fe(0) nanoparticles (NZVI) are injected into heterogeneous porous media for groundwater remediation. This study evaluated the effect of porous media heterogeneity and the dispersion properties including particle concentration, Fe(0) content, and adsorbed polymer mass and layer thickness which are expected to affect the delivery and emplacement of NZVI in heterogeneous porous media in a two-dimensional (2-D) cell. Heterogeneity in hydraulic conductivity had a significant impact on the deposition of NZVI. Polymer modified NZVI followed preferential flow paths and deposited in the regions where fluid shear is insufficient to prevent NZVI agglomeration and deposition. NZVI transported in heterogeneous porous media better at low particle concentration (0.3 g/L) than at high particle concentrations (3 and 6 g/L) due to greater particle agglomeration at high concentration. High Fe(0) content decreased transport during injection due to agglomeration promoted by magnetic attraction. NZVI with a flat adsorbed polymeric layer (thickness ∼30 nm) could not be transported effectively due to pore clogging and deposition near the inlet, while NZVI with a more extended adsorbed layer thickness (i.e., ∼70 nm) were mobile in porous media. This study indicates the importance of characterizing porous media heterogeneity and NZVI dispersion properties as part of the design of a robust delivery strategy for NZVI in the subsurface. PMID:21058703

  7. Transport and deposition of polymer-modified Fe0 nanoparticles in 2-D heterogeneous porous media: effects of particle concentration, Fe0 content, and coatings.

    PubMed

    Phenrat, Tanapon; Cihan, Abdullah; Kim, Hye-Jin; Mital, Menka; Illangasekare, Tissa; Lowry, Gregory V

    2010-12-01

    Concentrated suspensions of polymer-modified Fe(0) nanoparticles (NZVI) are injected into heterogeneous porous media for groundwater remediation. This study evaluated the effect of porous media heterogeneity and the dispersion properties including particle concentration, Fe(0) content, and adsorbed polymer mass and layer thickness which are expected to affect the delivery and emplacement of NZVI in heterogeneous porous media in a two-dimensional (2-D) cell. Heterogeneity in hydraulic conductivity had a significant impact on the deposition of NZVI. Polymer modified NZVI followed preferential flow paths and deposited in the regions where fluid shear is insufficient to prevent NZVI agglomeration and deposition. NZVI transported in heterogeneous porous media better at low particle concentration (0.3 g/L) than at high particle concentrations (3 and 6 g/L) due to greater particle agglomeration at high concentration. High Fe(0) content decreased transport during injection due to agglomeration promoted by magnetic attraction. NZVI with a flat adsorbed polymeric layer (thickness ∼30 nm) could not be transported effectively due to pore clogging and deposition near the inlet, while NZVI with a more extended adsorbed layer thickness (i.e., ∼70 nm) were mobile in porous media. This study indicates the importance of characterizing porous media heterogeneity and NZVI dispersion properties as part of the design of a robust delivery strategy for NZVI in the subsurface.

  8. Electrostatic quadrupole array for focusing parallel beams of charged particles

    DOEpatents

    Brodowski, John

    1982-11-23

    An array of electrostatic quadrupoles, capable of providing strong electrostatic focusing simultaneously on multiple beams, is easily fabricated from a single array element comprising a support rod and multiple electrodes spaced at intervals along the rod. The rods are secured to four terminals which are isolated by only four insulators. This structure requires bias voltage to be supplied to only two terminals and eliminates the need for individual electrode bias and insulators, as well as increases life by eliminating beam plating of insulators.

  9. Asymmetrical Polyhedral Configuration of Giant Vesicles Induced by Orderly Array of Encapsulated Colloidal Particles.

    PubMed

    Natsume, Yuno; Toyota, Taro

    2016-01-01

    Giant vesicles (GVs) encapsulating colloidal particles by a specific volume fraction show a characteristic configuration under a hypertonic condition. Several flat faces were formed in GV membrane with orderly array of inner particles. GV shape changed from the spherical to the asymmetrical polyhedral configuration. This shape deformation was derived by entropic interaction between inner particles and GV membrane. Because a part of inner particles became to form an ordered phase in the region neighboring the GV membrane, free volume for the other part of particles increased. Giant vesicles encapsulating colloidal particles were useful for the model of "crowding effect" which is the entropic interaction in the cell.

  10. Asymmetrical Polyhedral Configuration of Giant Vesicles Induced by Orderly Array of Encapsulated Colloidal Particles

    PubMed Central

    Natsume, Yuno; Toyota, Taro

    2016-01-01

    Giant vesicles (GVs) encapsulating colloidal particles by a specific volume fraction show a characteristic configuration under a hypertonic condition. Several flat faces were formed in GV membrane with orderly array of inner particles. GV shape changed from the spherical to the asymmetrical polyhedral configuration. This shape deformation was derived by entropic interaction between inner particles and GV membrane. Because a part of inner particles became to form an ordered phase in the region neighboring the GV membrane, free volume for the other part of particles increased. Giant vesicles encapsulating colloidal particles were useful for the model of “crowding effect” which is the entropic interaction in the cell. PMID:26752650

  11. Fractal and fractional calculus to model hydrological processes with application to particle-based 2D and 3D landslide simulation

    NASA Astrophysics Data System (ADS)

    Martelloni, Gianluca; Bagnoli, Franco; Di Cintio, Pierfrancesco

    2015-04-01

    We integrate existing soil infiltration modeling with particle based methods in order to simulate two and three-dimensional setups of triggered landslides. Commonly, the infiltration models are based on continuum schemes (e.g. Eulerian approach) by means of which it is possible to define the field of the pore pressure within a soil. By contrast, the particle based methods follow a Lagrangian scheme that allows one to identify the particle trajectories and their dynamical properties. In this work, in order to simulate the triggering mechanism, we apply the classical, fractal and fractional Richards equations and the Mohr-Coulomb failure criterion, adapted to the molecular dynamics technique. In our scheme the (local) positive pore pressure is simply implemented as a perturbation of the rest state of each grain. Therefore, the pore pressure function can be interpreted as a time-space dependent scalar field acting on each particle. To initialize the system we generate, using a molecular dynamics based algorithm, a mechanically stable disk (2D) or sphere (3D) packing simulating the consolidated soil. In this way, we can built the micro and macro pore structure related to different infiltration time scales. The inter-particle interactions are modeled with a Lennard-Jones like potential. The particle positions are updated in time, after and during a rainfall, with standard molecular dynamics. We analyze the sensitivity of the model with respect to the variation of some parameters such as hydraulic conductivity, cohesion, slope and friction angle, soil depth and fractional order of the generalized infiltration model. In addition, we consider both regular and random particle configurations. The results of our simulations are found to be in agreement with real landslides. In particular, the mean velocity patterns of the simulated landslides appear extremely similar to the observed ones. Moreover, it is possible to apply the method of the inverse surface displacement

  12. Array of amorphous calcium phosphate particles improves cellular activity on a hydrophobic surface.

    PubMed

    Kim, InAe; Kim, Hyun Jung; Kim, Hyun-Man

    2010-04-01

    Poor interaction between cells and surfaces, especially hydrophobic surfaces, results in delayed proliferation and increased apoptosis due to low cell adhesion signaling. To improve cell adhesion, hydrophilic array of amorphous calcium phosphate (ACP) was fabricated on a surface. A phosphate-buffered solution containing calcium ions was prepared at low temperature to prevent spontaneous precipitation. Then, the ion solution was heated to generate nuclei of ACP nanoparticles. The ACP nanoparticles adhered to the hydrophobic polystyrene surface forming an array composed of ACP particles. Multiple treatments of these nuclei with fresh CaP ion solutions increased the diameter and decreased the solubility of ACP particles enough to mediate cellular adhesion. The particle density in the array was dependent on the ion concentration of the CaP ion solutions. The ACP array improved a wide variety of activities when osteoblastic MC3T3-E1 cells were cultured on the ACP array fabricated on a hydrophobic bacteriological dish surface, compared to those cultured without the ACP array in vitro. The use of ACP array resulted in a lower apoptosis and also increased the spreading of cells to form stress fibers and focal contacts. Cells cultured on the ACP array proliferated more than cells cultured on a hydrophobic surface without the ACP array. The ACP array increased the expression of markers of differentiation in osteoblast. These results indicate that an array of ACP can be used as a coating material for enhancing biocompatibility in tissue engineering or biomaterials rather than modifying the surface with organic molecules. PMID:20119940

  13. Proof of principle study of ultrasonic particle manipulation by a circular array device

    PubMed Central

    Grinenko, Alon; Wilcox, Paul D.; Courtney, Charles R. P.; Drinkwater, Bruce W.

    2012-01-01

    A feasibility study of a circular ultrasonic array device for acoustic particle manipulation is presented. A general approach based on Green's function is developed to analyse the underlying properties of a circular acoustic array. It allows the size of a controllable device area as a function of the number of array elements to be established and the array excitation required to produce a desired field distribution to be determined. A set of quantitative parameters characterizing the complexity of the pressure landscape is suggested, and relation to the number of array elements is found. Next, a finite-element model of a physically realizable circular piezo-acoustic array device is employed to demonstrate that the trapping capability can be achieved in practice. PMID:23197936

  14. Multi-particle trapping and manipulation by a high-frequency array transducer

    SciTech Connect

    Yoon, Changhan; Kang, Bong Jin; Lee, Changyang; Kim, Hyung Ham Shung, K. Kirk

    2014-11-24

    We report the multiple micro-particle trapping and manipulation by a single-beam acoustic tweezer using a high-frequency array transducer. A single acoustic beam generated by a 30 MHz ultrasonic linear array transducer can entrap and transport multiple micro-particles located at the main lobe and the grating lobes. The distance between trapped particles can be adjusted by changing the transmit arrangement of array-based acoustic tweezers and subsequently the location of grating lobes. The experiment results showed that the proposed method can trap and manipulate multiple particles within a range of hundreds of micrometers. Due to its simplicity and low acoustic power, which is critical to protect cells from any thermal and mechanical damages, the technique may be used for transportation of cells in cell biology, biosensors, and tissue engineering.

  15. Transport of inertial particles by viscous streaming in arrays of oscillating probes

    NASA Astrophysics Data System (ADS)

    Chong, Kwitae; Kelly, Scott D.; Smith, Stuart T.; Eldredge, Jeff D.

    2016-01-01

    A mechanism for the transport of microscale particles in viscous fluids is demonstrated. The mechanism exploits the trapping of such particles by rotational streaming cells established in the vicinity of an oscillating cylinder, recently analyzed in previous work. The present work explores a strategy of transporting particles between the trapping points established by multiple cylinders undergoing oscillations in sequential intervals. It is demonstrated that, by controlling the sequence of oscillation intervals, an inertial particle is effectively and predictably transported between the stable trapping points. Arrays of cylinders in various arrangements are investigated, revealing a technique for constructing arbitrary particle trajectories. It is found that the domain from which particles can be transported and trapped by an oscillator is extended, even to regions in which particles are shielded, by the presence of other stationary cylinders. The timescales for transport are examined, as are the mechanisms by which particles are drawn away from an obstacle toward the trapping point of an oscillator.

  16. Self-propelled particle transport in regular arrays of rigid asymmetric obstacles.

    PubMed

    Potiguar, Fabricio Q; Farias, G A; Ferreira, W P

    2014-07-01

    We report numerical results which show the achievement of net transport of self-propelled particles (SPPs) in the presence of a two-dimensional regular array of convex, either symmetric or asymmetric, rigid obstacles. The repulsive interparticle (soft disks) and particle-obstacle interactions present no alignment rule. We find that SPPs present a vortex-type motion around convex symmetric obstacles even in the absence of hydrodynamic effects. Such a motion is not observed for a single SPP, but is a consequence of the collective motion of SPPs around the obstacles. A steady particle current is spontaneously established in an array of nonsymmetric convex obstacles (which presents no cavity in which particles may be trapped), and in the absence of an external field. Our results are mainly a consequence of the tendency of the self-propelled particles to attach to solid surfaces.

  17. Brownian simulation of many-particle binding to a reversible receptor array

    SciTech Connect

    Edelstein, A.L.; Agmon, N.

    1997-04-01

    The principles and practice of a many-body Brownian dynamics algorithm of reversible binding to a static three-dimensional receptor array are presented. The mixed boundary conditions at the array are compared with single-particle direct propagation using a novel operator discretization. The many-body aspects are checked against previous one-dimensional Brownian simulations. The long-time behavior agrees with expected analytic solutions. 39 refs., 9 figs., 1 tab.

  18. Force variation within arrays of monodisperse spherical particles

    NASA Astrophysics Data System (ADS)

    Akiki, G.; Jackson, T. L.; Balachandar, S.

    2016-08-01

    This study presents a direct numerical simulation analysis of the force distribution within a cluster of monodisperse spherical particles. A direct forcing immersed boundary method is used to calculate the forces on individual particles for a volume fraction range of 0.11 ≤ϕ ≤0 .44 and a Reynolds number range of 1 .47 ≤Re ≤636 . The hydrodynamic streamwise force is shown to have a normal distribution with a standard deviation ratio to the mean drag that decreases with increasing volume fraction and ranges between 17% and 26%. The lift forces also follow a normal distribution that has a significant standard deviation to mean drag ratio of around 14.5%, which does not vary significantly with the Reynolds number and volume fraction. A model is introduced that adds the identified normal distribution of the forces to the quasisteady force used in point-particle models. A nonisotropic method of defining spatial parameters is presented. It highlights the contribution of each parameter to the variation of the forces on each particle. The results show that the drag is influenced by the closest four to eight neighboring spheres. The drag force is highly dependent on the streamwise distances of the spheres located upstream. For low volume fractions and Reynolds number, the lateral distances of the spheres located downstream also have a significant contribution to those variations. The results also show that the lateral force variation is mostly dictated by the lateral distance of one to two spheres located upstream of each sphere.

  19. Magnetofluidic concentration and separation of non-magnetic particles using two magnet arrays.

    PubMed

    Hejazian, Majid; Nguyen, Nam-Trung

    2016-07-01

    The present paper reports the use of diluted ferrofluid and two arrays of permanent magnets for the size-selective concentration of non-magnetic particles. The micro magnetofluidic device consists of a straight channels sandwiched between two arrays of permanent magnets. The permanent magnets create multiple capture zones with minimum magnetic field strength along the channel. The complex interaction between magnetic forces and hydrodynamic force allows the device to operate in different regimes suitable for concentration of non-magnetic particles with small difference in size. Our experimental results show that non-magnetic particles with diameters of 3.1 μm and 4.8 μm can be discriminated and separated with this method. The results from this study could be used as a guide for the design of size-sensitive separation devices for particle and cell based on negative magnetophoresis. PMID:27478527

  20. Magnetofluidic concentration and separation of non-magnetic particles using two magnet arrays.

    PubMed

    Hejazian, Majid; Nguyen, Nam-Trung

    2016-07-01

    The present paper reports the use of diluted ferrofluid and two arrays of permanent magnets for the size-selective concentration of non-magnetic particles. The micro magnetofluidic device consists of a straight channels sandwiched between two arrays of permanent magnets. The permanent magnets create multiple capture zones with minimum magnetic field strength along the channel. The complex interaction between magnetic forces and hydrodynamic force allows the device to operate in different regimes suitable for concentration of non-magnetic particles with small difference in size. Our experimental results show that non-magnetic particles with diameters of 3.1 μm and 4.8 μm can be discriminated and separated with this method. The results from this study could be used as a guide for the design of size-sensitive separation devices for particle and cell based on negative magnetophoresis.

  1. Statics and dynamics of colloidal particles on optical tray arrays

    SciTech Connect

    Reichardt, Charles; Reichhardt, Cynthia J

    2009-01-01

    We examine the statics and dynamics of charged colloids interacting with periodic optical trap arrays. In particular we study the regime where more than one colloid is confined in each trap, creating effective dimer, trimer, and higher order states called colloidal molecular crystals. The n-mer states have all effective orientational degree of freedom which can be controlled with an external driving field. In general, the external field causes a polarization effect where the orientation of the n-mers aligns with the external field, similar to liquid crystal systems. Additionally, under a rotating external drive the n-mers can rotate with the drive. In some cases a series of structural transitions in the colloidal crystal states occur in the rotating field due to a competition between the ordering of the colloidal molecular crystals and the polarization effect which orients the n-mers in the direction of the drive. We also show that for some parameters, the n-mers continuously rotate with the drive without witching, that depinning transitions can occur where the colloids jump from well to well, and that there are a number of distinct dynamical transitions between the phases. Finally, we illustrate colloidal orderings at fillings of more than four colloids per trap, indicating that it is possible to create higher order colloidal crystal cluster phases.

  2. Hygroscopic particle behavior studied by interdigitated array microelectrode impedance sensors.

    PubMed

    Schindelholz, Eric; Tsui, Lok-kun; Kelly, Robert G

    2014-01-01

    The hygroscopic behavior of soluble salts bears importance in many research fields including atmospheric sciences, corrosion, porous building materials, and pharmaceuticals. Several methods have been used to study deliquescence (solid to liquid) and efflorescence (liquid to solid) phase transitions of these salts. In this study, we measured the deliquescence and efflorescence RH values of single salt microparticles deposited on an interdigitated microelectrode sensor via electrical impedance. The salts examined were NaCl, LiCl, NaBr, KCl, and MgCl2. Measured values were in agreement with in situ optical microscopic observations and, with the exception of MgCl2, literature values. In the case of MgCl2, deliquescence occurred at 33% RH and 12-15% RH, with the latter range being previously unreported. The depressed deliquescence RH was hypothesized to be a result of the formation of a metastable MgCl2 hydrate. Incomplete efflorescence of MgCl2 was also observed after exposure to <1.5% RH for up to 22 h due to formation of solid shells which trapped fluid. The phenomena elucidated by these results provide an explanation for the anomalous water retention and uptake behavior of MgCl2 below 33% RH reported elsewhere in the literature. The results presented in this study validate the use of this method as an alternative or complementary method for study of bulk-phase transitions of substrate-deposited particles across a broad RH range. These findings also demonstrate the utility of this method for detection of fluid trapping which cannot be directly ascertained by gravimetric and line-of-sight techniques commonly used in the study of hygroscopic particles.

  3. Reconstruction of 2D seismic wavefield from Long-Period Seismogram and Short-Period Seismogram Envelope by Seismic Gradiometry applied to the Hi-net Array

    NASA Astrophysics Data System (ADS)

    Maeda, Takuto; Nishida, Kiwamu; Takagi, Ryota; Obara, Kazushige

    2016-04-01

    The high-sensitive seismograph network (Hi-net) operated by National Research Institute for Earth Science and Disaster Prevention (NIED) has about 800 stations with average separation of 20 km all over the Japanese archipelago. Although it is equipped with short-period seismometers, we also can observe long-period seismic wave up to 100 s in periods for significantly large earthquakes. In this case, we may treat long-period seismic waves as a 2D wavefield with station separations shorter than wavelength rather than individual traces at stations. In this study, we attempt to reconstruct 2D wavefield and obtain its propagation properties from seismic gradiometry (SG) method. The SG estimates the wave amplitude and its spatial derivative coefficients from discrete station record by the Taylor series approximation with an inverse problem. By using spatial derivatives in horizontal directions, we can obtain properties of propagating wave packet such as the arrival direction, slowness, geometrical spreading and radiation pattern. In addition, by using spatial derivatives together with free-surface boundary condition, we may decompose the vector elastic 2D wavefield estimated by the SG into divergence and rotation components. First, we applied the seismic gradiometry to a synthetic long-period (20-50 s) seismogram dataset computed by numerical simulation in realistic 3D medium at the Hi-net station layout as a feasibility test. We confirmed that the wave amplitude and its spatial derivatives are very well reproduced with average correlation coefficients higher than 0.99 in this period range. Applications to a real large earthquakes show that the amplitude and phase of the wavefield are well reconstructed with additional information of arrival direction and its slowness. The reconstructed wavefield contained a clear contrast in slowness between body and surface waves, regional non-great-circle-path wave propagation which may be attributed to scattering. Slowness

  4. Evaluation of the ability of a 2D ionisation chamber array and an EPID to detect systematic delivery errors in IMRT plans

    NASA Astrophysics Data System (ADS)

    Bawazeer, Omemh; Gray, Alison; Arumugam, Sankar; Vial, Philip; Thwaites, David; Descallar, Joseph; Holloway, Lois

    2014-03-01

    Two clinical intensity modulated radiotherapy plans were selected. Eleven plan variations were created with systematic errors introduced: Multi-Leaf Collimator (MLC) positional errors with all leaf pairs shifted in the same or the opposite direction, and collimator rotation offsets. Plans were measured using an Electronic Portal Imaging Device (EPID) and an ionisation chamber array. The plans were evaluated using gamma analysis with different criteria. The gamma pass rates remained around 95% or higher for most cases with MLC positional errors of 1 mm and 2 mm with 3%/3mm criteria. The ability of both devices to detect delivery errors was similar.

  5. Polycrystalline CVD diamond pixel array detector for nuclear particles monitoring

    NASA Astrophysics Data System (ADS)

    Pacilli, M.; Allegrini, P.; Girolami, M.; Conte, G.; Spiriti, E.; Ralchenko, V. G.; Komlenok, M. S.; Khomic, A. A.; Konov, V. I.

    2013-02-01

    We report the 90Sr beta response of a polycrystalline diamond pixel detector fabricated using metal-less graphitic ohmic contacts. Laser induced graphitization was used to realize multiple squared conductive contacts with 1mm × 1mm area, 0.2 mm apart, on one detector side while on the other side, for biasing, a 9mm × 9mm large graphite contact was realized. A proximity board was used to wire bonding nine pixels at a time and evaluate the charge collection homogeneity among the 36 detector pixels. Different configurations of biasing were experimented to test the charge collection and noise performance: connecting the pixel at the ground potential of the charge amplifier led to best results and minimum noise pedestal. The expected exponential trend typical of beta particles has been observed. Reversing the bias polarity the pulse height distribution (PHD) does not changes and signal saturation of any pixel was observed around ±200V (0.4 V/μm). Reasonable pixels response uniformity has been evidenced even if smaller pitch 50÷100 μm structures need to be tested.

  6. FePt films on self-assembled SiO2 particle arrays

    NASA Astrophysics Data System (ADS)

    Makarov, D.; Brombacher, C.; Liscio, F.; Maret, M.; Parlinska, M.; Meier, S.; Kappenberger, P.; Albrecht, M.

    2008-03-01

    Chemically L10 ordered (001) textured FePt thin films with perpendicular magnetic anisotropy can be grown on amorphous planar SiO2 substrate with an underlayer stack of [Pt (3nm )/Cr (50nm)] adopting a [002] orientation when deposited at 350°C. This knowledge of optimum layer stack was transferred to self-assembled SiO2 particle arrays. While 330nm SiO2 particle arrays reveal perpendicular magnetic anisotropy with a remanence of almost one and a coercivity of 370mT, on 160nm particles, the FePt caps show a (111) texturing, leading to the random orientation of the easy axis of the magnetization.

  7. Detection and localization of particle-emitting sources with compound-eye inspired detector arrays

    NASA Astrophysics Data System (ADS)

    Liu, Zhi

    2007-08-01

    We develop methods to detect and localize particle-emitting sources using detector arrays that are inspired by biological compound eyes. The sources of interest may be optical, nuclear, or cosmic; they emit particles such as visible photons, neutrons, protons, or charged particles. Our results may have wide applications to artificial vision, which can be important in robotics (robot vision) or medicine (e.g., artificial eyes for the blind); security, where the detection of nuclear materials is needed; or astronomy. This dissertation consists of three parts. First, we detect a far-field particle source using two directional detector arrays: cubic and spherical. We propose a mean-difference test (MDT) detector, analyze its statistical performance, and show that the MDT has a number of advantages over the generalized likelihood- ratio test (GLRT). Second, we localize the source by proposing a novel biologically inspired detector array, whose configuration generalizes the compound eye of insects. This array combines the advantages of compound eyes (e.g., large field-of-view) and human eyes (e.g., high angular resolution). Based on a statistical model of the array measurements, we analyze the array performance by computing the Cramérao bound (CRB) on the error in estimating the source direction. We also derive lower bounds on the mean-square angular error (MSAE) of the source localization and investigate the MSAE of two source- direction estimators. Numerical examples, including the optimal array design, are presented to further illustrate the array performance. Third, we derive a statistical angular resolution limit (ARL) on resolving two closely spaced point sources in a three-dimensional frame, which is applicable to various measurement models (e.g., radar, sonar, or astronomy). Using the asymptotic analysis of the GLRT, we derive the ARL with constraints on the probabilities of false alarm and detection. Our results give explicit analytical expression for the ARL

  8. Sub-grid drag models for horizontal cylinder arrays immersed in gas-particle multiphase flows

    SciTech Connect

    Sarkar, Avik; Sun, Xin; Sundaresan, Sankaran

    2013-09-08

    Immersed cylindrical tube arrays often are used as heat exchangers in gas-particle fluidized beds. In multiphase computational fluid dynamics (CFD) simulations of large fluidized beds, explicit resolution of small cylinders is computationally infeasible. Instead, the cylinder array may be viewed as an effective porous medium in coarse-grid simulations. The cylinders' influence on the suspension as a whole, manifested as an effective drag force, and on the relative motion between gas and particles, manifested as a correction to the gas-particle drag, must be modeled via suitable sub-grid constitutive relationships. In this work, highly resolved unit-cell simulations of flow around an array of horizontal cylinders, arranged in a staggered configuration, are filtered to construct sub-grid, or `filtered', drag models, which can be implemented in coarse-grid simulations. The force on the suspension exerted by the cylinders is comprised of, as expected, a buoyancy contribution, and a kinetic component analogous to fluid drag on a single cylinder. Furthermore, the introduction of tubes also is found to enhance segregation at the scale of the cylinder size, which, in turn, leads to a reduction in the filtered gas-particle drag.

  9. A fully automated in vitro diagnostic system based on magnetic tunnel junction arrays and superparamagnetic particles

    NASA Astrophysics Data System (ADS)

    Lian, Jie; Chen, Si; Qiu, Yuqin; Zhang, Suohui; Shi, Stone; Gao, Yunhua

    2012-04-01

    A fully automated in vitro diagnostic (IVD) system for diagnosing acute myocardial infarction was developed using high sensitivity MTJ array as sensors and nano-magnetic particles as tags. On the chip is an array of 12 × 106 MTJ devices integrated onto a 3 metal layer CMOS circuit. The array is divided into 48 detection areas, therefore 48 different types of bio targets can be analyzed simultaneously if needed. The chip is assembled with a micro-fluidic cartridge which contains all the reagents necessary for completing the assaying process. Integrated with electrical, mechanical and micro-fluidic pumping devices and with the reaction protocol programed in a microprocessor, the system only requires a simple one-step analyte application procedure to operate and yields results of the three major AMI bio-markers (cTnI, MYO, CK-MB) in 15 mins.

  10. Cleaning Surface Particle Contamination with Ultrapure Water (UPW) Megasonic Flow on Genesis Array Collectors

    NASA Technical Reports Server (NTRS)

    Allton, J. H.; Calaway, Michael J.; Hittle, J. D.; Rodriquez, M. C.; Stansbery, E. K.; McNamara, K. M.

    2006-01-01

    The hard landing experienced by the Genesis sample return capsule breached the science canister containing the solar wind collectors. This impact into the damp lakebed contaminated collector surfaces with pulverized collector and spacecraft materials and Utah sediment and brine residue. The gold foil, polished aluminum, and bulk metallic glass remained intact, but the solar wind bulk and regime-specific array collectors were jarred loose from their frames and fractured into greater than 10,000 specimens. After a year of investigation and cleaning experimentation, the Genesis Science Team determined that array collectors had 4 classes of contaminants: particles, molecular film, submicron inorganic particulate ("aerosol"), and pre-launch surface contamination. We discuss here use of megasonically energized ultrapure water (UPW) for removing particulate debris from array collector fragments.

  11. Cu-PDC-bpa solid coordination frameworks (PDC=2,5-pyrindinedicarboxylate; bpa=1,2-DI(4-pyridil)ethane)): 2D and 3D structural flexibility producing a 3-c herringbone array next to ideal

    SciTech Connect

    Llano-Tomé, Francisco; Bazán, Begoña; Urtiaga, Miren-Karmele; Barandika, Gotzone; Antonia Señarís-Rodríguez, M.; and others

    2015-10-15

    Combination of polycarboxylate anions and dipyridyl ligands is an effective strategy to produce solid coordination frameworks (SCF) which are crystalline materials based on connections between metal ions through organic ligands. In this context, this work is focused on two novel Cu{sup II}-based SCFs exhibiting PDC (2,5-pyridinedicarboxylate) and bpa (1,2-di(4-pyridyl)ethane), being the first structures reported in literature containing both ligands. Chemical formula are [Cu{sub 2}[(PDC){sub 2}(bpa)(H{sub 2}O){sub 2}]·3H{sub 2}O·DMF (1), and [Cu{sub 2}(PDC){sub 2}(bpa)(H{sub 2}O){sub 2}]·7H{sub 2}O (2), where DMF is dimethylformamide. Compounds 1 and 2 have been characterized by means of X-ray diffraction (XRD), infrared spectroscopy (IR), thermogravimetric (TG) analysis, differential thermal analysis (DTA) and dielectric measurements. The crystallographic analysis revealed that compounds 1 and 2 can be described as herringbone-type layers formed by helicoidal Cu-PDC-Cu chains connected through bpa ligands. Solvent molecules are crystallized between the layers, providing the inter-layer connections through hydrogen bonds. Differences between both compounds are attributable to the flexibility of bpa (in 2D) as well as to the 3D packing of the layers which is solvent dependent. This fact results in the fact that compound 2 is the most regular 3-c herringbone array reported so far. The structural dynamism of these networks is responsible for the crystalline to-amorphous to-crystalline (CAC) transformation from compound 1 to compound 2. Crystallochemical features for both compounds have also been studied and compared to similar 3-connected herringbone-arrays. - Graphical abstract: Cu-PDC-bpa 3-c herringbone arrays. - Highlights: • The most ideal herringbone array reported so far is a Cu-PDC-bpa SCF. • Conformational freedom of bpa results in 2D and 3D flexibility of the SCFs. • The flexibility of the SCFs is related to a phase transformation. • Dielectric

  12. Two dimensional, electronic particle tracking in liquids with a graphene-based magnetic sensor array

    NASA Astrophysics Data System (ADS)

    Neumann, Rodrigo F.; Engel, Michael; Steiner, Mathias

    2016-07-01

    The investigation and control of liquid flow at the nanometer scale is a key area of applied research with high relevance to physics, chemistry, and biology. We introduce a method and a device that allows the spatial resolution of liquid flow by integrating an array of graphene-based magnetic (Hall) sensors that is used for tracking the movement of magnetic nanoparticles immersed in a liquid under investigation. With a novel device concept based on standard integration processes and experimentally verified material parameters, we numerically simulate the performance of a single sensor pixel, as well as the whole sensor array, for tracking magnetic nanoparticles having typical properties. The results demonstrate that the device enables (a) the detection of individual nanoparticles in the liquid with high accuracy and (b) the reconstruction of a particle's flow-driven trajectory across the integrated sensor array with sub-pixel precision as a function of time, in what we call the ``Magnetic nanoparticle velocimetry'' technique. Since the method does not rely on optical detection, potential lab-on-chip applications include particle tracking and flow analysis in opaque media at the sub-micron scale.The investigation and control of liquid flow at the nanometer scale is a key area of applied research with high relevance to physics, chemistry, and biology. We introduce a method and a device that allows the spatial resolution of liquid flow by integrating an array of graphene-based magnetic (Hall) sensors that is used for tracking the movement of magnetic nanoparticles immersed in a liquid under investigation. With a novel device concept based on standard integration processes and experimentally verified material parameters, we numerically simulate the performance of a single sensor pixel, as well as the whole sensor array, for tracking magnetic nanoparticles having typical properties. The results demonstrate that the device enables (a) the detection of individual

  13. Versatile Particle-Based Route to Engineer Vertically Aligned Silicon Nanowire Arrays and Nanoscale Pores.

    PubMed

    Elnathan, Roey; Isa, Lucio; Brodoceanu, Daniel; Nelson, Adrienne; Harding, Frances J; Delalat, Bahman; Kraus, Tobias; Voelcker, Nicolas H

    2015-10-28

    Control over particle self-assembly is a prerequisite for the colloidal templating of lithographical etching masks to define nanostructures. This work integrates and combines for the first time bottom-up and top-down approaches, namely, particle self-assembly at liquid-liquid interfaces and metal-assisted chemical etching, to generate vertically aligned silicon nanowire (VA-SiNW) arrays and, alternatively, arrays of nanoscale pores in a silicon wafer. Of particular importance, and in contrast to current techniques, including conventional colloidal lithography, this approach provides excellent control over the nanowire or pore etching site locations and decouples nanowire or pore diameter and spacing. The spacing between pores or nanowires is tuned by adjusting the specific area of the particles at the liquid-liquid interface before deposition. Hence, the process enables fast and low-cost fabrication of ordered nanostructures in silicon and can be easily scaled up. We demonstrate that the fabricated VA-SiNW arrays can be used as in vitro transfection platforms for transfecting human primary cells.

  14. Application of a Halbach magnetic array for long-range cell and particle separations in biological samples

    NASA Astrophysics Data System (ADS)

    Kang, Joo H.; Driscoll, Harry; Super, Michael; Ingber, Donald E.

    2016-05-01

    Here, we describe a versatile application of a planar Halbach permanent magnet array for an efficient long-range magnetic separation of living cells and microparticles over distances up to 30 mm. A Halbach array was constructed from rectangular bar magnets using 3D-printed holders and compared to a conventional alternating array of identical magnets. We theoretically predicted the superiority of the Halbach array for a long-range magnetic separation and then experimentally validated that the Halbach configuration outperforms the alternating array for isolating magnetic microparticles or microparticle-bound bacterial cells at longer distances. Magnetophoretic velocities (ymag) of magnetic particles (7.9 μm diameter) induced by the Halbach array in a microfluidic device were significantly higher and extended over a larger area than those induced by the alternating magnet array (ymag = 178 versus 0 μm/s at 10 mm, respectively). When applied to 50 ml tubes (˜30 mm diameter), the Halbach array removed >95% of Staphylococcus aureus bacterial cells bound with 1 μm magnetic particles compared to ˜70% removed using the alternating array. In addition, the Halbach array enabled manipulation of 1 μm magnetic beads in a deep 96-well plate for ELISA applications, which was not possible with the conventional magnet arrays. Our analysis demonstrates the utility of the Halbach array for the future design of devices for high-throughput magnetic separations of cells, molecules, and toxins.

  15. Superhydrophobic Surface Enhanced Raman Scattering Sensing using Janus Particle Arrays Realized by Site-Specific Electrochemical Growth

    PubMed Central

    Hricko, Patrick John; Huang, Po-Hsun; Li, Sixing; Zhao, Yanhui; Xie, Yuliang; Guo, Feng; Wang, Lin

    2014-01-01

    Site-specific electrochemical deposition is used to prepare polystyrene (PS)-Ag Janus particle arrays with superhydrophobic properties. The analyte molecules can be significantly enriched using the superhydrophobic property of the PS-Ag Janus particle array before SERS detections, enabling an extremely sensitive detection of molecules in a highly diluted solution (e.g., femtomolar level). This superhydrophobic surface enhanced Raman scattering sensing concept described here is of critical significance in biosensing and bioanalysis. Most importantly, the site-specific electrochemical growth method we developed here is a versatile approach that can be used to prepare Janus particle arrays with different properties for various applications. PMID:24748991

  16. The Fluctuation-Dissipation Theorem of Colloidal Particle's energy on 2D Periodic Substrates: A Monte Carlo Study of thermal noise-like fluctuation and diffusion like Brownian motion

    NASA Astrophysics Data System (ADS)

    Najafi, Amin

    2014-05-01

    Using the Monte Carlo simulations, we have calculated mean-square fluctuations in statistical mechanics, such as those for colloids energy configuration are set on square 2D periodic substrates interacting via a long range screened Coulomb potential on any specific and fixed substrate. Random fluctuations with small deviations from the state of thermodynamic equilibrium arise from the granular structure of them and appear as thermal diffusion with Gaussian distribution structure as well. The variations are showing linear form of the Fluctuation-Dissipation Theorem on the energy of particles constitutive a canonical ensemble with continuous diffusion process of colloidal particle systems. The noise-like variation of the energy per particle and the order parameter versus the Brownian displacement of sum of large number of random steps of particles at low temperatures phase are presenting a markovian process on colloidal particles configuration, too.

  17. Nanosphere lithography based technique for fabrication of large area well ordered metal particle arrays

    NASA Astrophysics Data System (ADS)

    Barcelo, Steven J.; Lam, Si-Ty; Gibson, Gary A.; Sheng, Xia; Henze, Dick

    2012-03-01

    Nanosphere lithography is an effective technique for high throughput fabrication of well-ordered patterns, but expanding the method to large area coverage of nanoparticles less than 300 nm in diameter while maintaining good order has proven challenging. Here we demonstrate a nanosphere lithography based technique for fabricating large area, wellordered arrays of hemispherical metal particles which pushes the limits of these size constraints. First, large area monolayers of polystyrene (PS) nanospheres are assembled at an air-water interface and then transferred to a submerged substrate. The submerged substrate is supported at a 10° angle so that the water draining speed can be used to control the transfer rate, which is essential for hydrophobic substrates such as the polymer-coated glass used in our work. A double liftoff procedure was used to transfer the PS pattern to a silver particle array on an arbitrary substrate, achieving tunable control over the final metal particle diameter and spacing in the range of 50-150 nm and 100-200 nm, respectively. Additional control over particle shape and diameter can be obtained by modifying the substrate surface energy. For example, depositing silver on ITO-coated glass rather than a more hydrophilic clean glass substrate leads to a more hemispherical particle shape and a diameter reduction of 20%. Peak wavelength-selective reflection greater than 70% and total extinction greater than 90% were measured. The intensity, position and bandwidth of the main plasmon resonance of the arrays were shown to have minimal angle dependence up to at least 30° off normal.

  18. Analysis of the Dynamic Sensitivity of Hemisphere-Shaped Electrostatic Sensors’ Circular Array for Charged Particle Monitoring

    PubMed Central

    Tang, Xin; Chen, Zhong-Sheng; Li, Yue; Hu, Zheng; Yang, Yong-Min

    2016-01-01

    Electrostatic sensor arrays (ESAs) are promising in industrial applications related to charged particle monitoring. Sensitivity is a fundamental and commonly-used sensing characteristic of an ESA. However, the usually used spatial sensitivity, which is called static sensitivity here, is not proper for moving particles or capable of reflecting array signal processing algorithms integrated in an ESA. Besides, reports on ESAs for intermittent particles are scarce yet, especially lacking suitable array signal processing algorithms. To solve the problems, the dynamic sensitivity of ESA is proposed, and a hemisphere-shaped electrostatic sensors’ circular array (HSESCA) along with its application in intermittent particle monitoring are taken as an example. In detail, a sensing model of the HSESCA is built. On this basis, its array signals are analyzed; the dynamic sensitivity is thereupon defined by analyzing the processing of the array signals. Besides, a component extraction-based array signal processing algorithm for intermittent particles is proposed, and the corresponding dynamic sensitivity is analyzed quantitatively. Moreover, simulated and experimental results are discussed, which validate the accuracy of the models and the effectiveness of the relevant approaches. The proposed dynamic sensitivity of ESA, as well as the array signal processing algorithm are expected to provide references in modeling, designing and using ESAs. PMID:27589767

  19. Analysis of the Dynamic Sensitivity of Hemisphere-Shaped Electrostatic Sensors' Circular Array for Charged Particle Monitoring.

    PubMed

    Tang, Xin; Chen, Zhong-Sheng; Li, Yue; Hu, Zheng; Yang, Yong-Min

    2016-01-01

    Electrostatic sensor arrays (ESAs) are promising in industrial applications related to charged particle monitoring. Sensitivity is a fundamental and commonly-used sensing characteristic of an ESA. However, the usually used spatial sensitivity, which is called static sensitivity here, is not proper for moving particles or capable of reflecting array signal processing algorithms integrated in an ESA. Besides, reports on ESAs for intermittent particles are scarce yet, especially lacking suitable array signal processing algorithms. To solve the problems, the dynamic sensitivity of ESA is proposed, and a hemisphere-shaped electrostatic sensors' circular array (HSESCA) along with its application in intermittent particle monitoring are taken as an example. In detail, a sensing model of the HSESCA is built. On this basis, its array signals are analyzed; the dynamic sensitivity is thereupon defined by analyzing the processing of the array signals. Besides, a component extraction-based array signal processing algorithm for intermittent particles is proposed, and the corresponding dynamic sensitivity is analyzed quantitatively. Moreover, simulated and experimental results are discussed, which validate the accuracy of the models and the effectiveness of the relevant approaches. The proposed dynamic sensitivity of ESA, as well as the array signal processing algorithm are expected to provide references in modeling, designing and using ESAs. PMID:27589767

  20. Two dimensional, electronic particle tracking in liquids with a graphene-based magnetic sensor array.

    PubMed

    Neumann, Rodrigo F; Engel, Michael; Steiner, Mathias

    2016-07-14

    The investigation and control of liquid flow at the nanometer scale is a key area of applied research with high relevance to physics, chemistry, and biology. We introduce a method and a device that allows the spatial resolution of liquid flow by integrating an array of graphene-based magnetic (Hall) sensors that is used for tracking the movement of magnetic nanoparticles immersed in a liquid under investigation. With a novel device concept based on standard integration processes and experimentally verified material parameters, we numerically simulate the performance of a single sensor pixel, as well as the whole sensor array, for tracking magnetic nanoparticles having typical properties. The results demonstrate that the device enables (a) the detection of individual nanoparticles in the liquid with high accuracy and (b) the reconstruction of a particle's flow-driven trajectory across the integrated sensor array with sub-pixel precision as a function of time, in what we call the "Magnetic nanoparticle velocimetry" technique. Since the method does not rely on optical detection, potential lab-on-chip applications include particle tracking and flow analysis in opaque media at the sub-micron scale.

  1. Glucose sensing through Fano resonances in mesoscale silica core-gold shell particles arrays

    NASA Astrophysics Data System (ADS)

    Pincella, Francesca; Huang, Zhiwei

    2016-03-01

    We report the development of a versatile, cheap and reusable plasmonic sensor able to detect glucose in the physiological concentration range by means of a simple label-free optical detection scheme. In order to achieve the aforementioned goal we applied a self-assembly deposition technique for the large-scale arraying of mesoscale gold nanoshell particles. Different from metallic nanospheres arrays, the localized surface plasmon resonances of gold nanoshells arrays extend in both the visible and near-infrared range, making them extremely promising for their use in biological media. Furthermore, the optical response of mesoscale gold nanoshells arrays showed another remarkable characteristic, which is the presence of various Fano resonances that have the advantage of enhancing the sensitivity of the plasmonic substrate to the external media thanks to their sharp features and increased spectral contrast. The plasmonic sensor was shown to have an extended working range with a good linear response for large refractive index shifts, where a bulk refractive index sensitivity of 0.93 RIU-1 (RIU, refractive index units) was achieved experimentally. In addition, the plasmonic sensor could detect aqueous glucose solutions in the blood concentration range (0-25 mM), with a sensitivity of 0.24 M-1.

  2. Dean-flow-coupled elasto-inertial three-dimensional particle focusing under viscoelastic flow in a straight channel with asymmetrical expansion-contraction cavity arrays.

    PubMed

    Yuan, D; Zhang, J; Yan, S; Pan, C; Alici, G; Nguyen, N T; Li, W H

    2015-07-01

    In this paper, 3D particle focusing in a straight channel with asymmetrical expansion-contraction cavity arrays (ECCA channel) is achieved by exploiting the dean-flow-coupled elasto-inertial effects. First, the mechanism of particle focusing in both Newtonian and non-Newtonian fluids was introduced. Then particle focusing was demonstrated experimentally in this channel with Newtonian and non-Newtonian fluids using three different sized particles (3.2 μm, 4.8 μm, and 13 μm), respectively. Also, the effects of dean flow (or secondary flow) induced by expansion-contraction cavity arrays were highlighted by comparing the particle distributions in a single straight rectangular channel with that in the ECCA channel. Finally, the influences of flow rates and distances from the inlet on focusing performance in the ECCA channel were studied. The results show that in the ECCA channel particles are focused on the cavity side in Newtonian fluid due to the synthesis effects of inertial and dean-drag force, whereas the particles are focused on the opposite cavity side in non-Newtonian fluid due to the addition of viscoelastic force. Compared with the focusing performance in Newtonian fluid, the particles are more easily and better focused in non-Newtonian fluid. Besides, the Dean flow in visco-elastic fluid in the ECCA channel improves the particle focusing performance compared with that in a straight channel. A further advantage is three-dimensional (3D) particle focusing that in non-Newtonian fluid is realized according to the lateral side view of the channel while only two-dimensional (2D) particle focusing can be achieved in Newtonian fluid. Conclusively, this novel Dean-flow-coupled elasto-inertial microfluidic device could offer a continuous, sheathless, and high throughput (>10 000 s(-1)) 3D focusing performance, which may be valuable in various applications from high speed flow cytometry to cell counting, sorting, and analysis.

  3. Dean-flow-coupled elasto-inertial three-dimensional particle focusing under viscoelastic flow in a straight channel with asymmetrical expansion–contraction cavity arrays

    PubMed Central

    Yuan, D.; Zhang, J.; Yan, S.; Pan, C.; Alici, G.; Nguyen, N. T.; Li, W. H.

    2015-01-01

    In this paper, 3D particle focusing in a straight channel with asymmetrical expansion–contraction cavity arrays (ECCA channel) is achieved by exploiting the dean-flow-coupled elasto-inertial effects. First, the mechanism of particle focusing in both Newtonian and non-Newtonian fluids was introduced. Then particle focusing was demonstrated experimentally in this channel with Newtonian and non-Newtonian fluids using three different sized particles (3.2 μm, 4.8 μm, and 13 μm), respectively. Also, the effects of dean flow (or secondary flow) induced by expansion–contraction cavity arrays were highlighted by comparing the particle distributions in a single straight rectangular channel with that in the ECCA channel. Finally, the influences of flow rates and distances from the inlet on focusing performance in the ECCA channel were studied. The results show that in the ECCA channel particles are focused on the cavity side in Newtonian fluid due to the synthesis effects of inertial and dean-drag force, whereas the particles are focused on the opposite cavity side in non-Newtonian fluid due to the addition of viscoelastic force. Compared with the focusing performance in Newtonian fluid, the particles are more easily and better focused in non-Newtonian fluid. Besides, the Dean flow in visco-elastic fluid in the ECCA channel improves the particle focusing performance compared with that in a straight channel. A further advantage is three-dimensional (3D) particle focusing that in non-Newtonian fluid is realized according to the lateral side view of the channel while only two-dimensional (2D) particle focusing can be achieved in Newtonian fluid. Conclusively, this novel Dean-flow-coupled elasto-inertial microfluidic device could offer a continuous, sheathless, and high throughput (>10 000 s−1) 3D focusing performance, which may be valuable in various applications from high speed flow cytometry to cell counting, sorting, and analysis. PMID:26339309

  4. Dean-flow-coupled elasto-inertial three-dimensional particle focusing under viscoelastic flow in a straight channel with asymmetrical expansion-contraction cavity arrays.

    PubMed

    Yuan, D; Zhang, J; Yan, S; Pan, C; Alici, G; Nguyen, N T; Li, W H

    2015-07-01

    In this paper, 3D particle focusing in a straight channel with asymmetrical expansion-contraction cavity arrays (ECCA channel) is achieved by exploiting the dean-flow-coupled elasto-inertial effects. First, the mechanism of particle focusing in both Newtonian and non-Newtonian fluids was introduced. Then particle focusing was demonstrated experimentally in this channel with Newtonian and non-Newtonian fluids using three different sized particles (3.2 μm, 4.8 μm, and 13 μm), respectively. Also, the effects of dean flow (or secondary flow) induced by expansion-contraction cavity arrays were highlighted by comparing the particle distributions in a single straight rectangular channel with that in the ECCA channel. Finally, the influences of flow rates and distances from the inlet on focusing performance in the ECCA channel were studied. The results show that in the ECCA channel particles are focused on the cavity side in Newtonian fluid due to the synthesis effects of inertial and dean-drag force, whereas the particles are focused on the opposite cavity side in non-Newtonian fluid due to the addition of viscoelastic force. Compared with the focusing performance in Newtonian fluid, the particles are more easily and better focused in non-Newtonian fluid. Besides, the Dean flow in visco-elastic fluid in the ECCA channel improves the particle focusing performance compared with that in a straight channel. A further advantage is three-dimensional (3D) particle focusing that in non-Newtonian fluid is realized according to the lateral side view of the channel while only two-dimensional (2D) particle focusing can be achieved in Newtonian fluid. Conclusively, this novel Dean-flow-coupled elasto-inertial microfluidic device could offer a continuous, sheathless, and high throughput (>10 000 s(-1)) 3D focusing performance, which may be valuable in various applications from high speed flow cytometry to cell counting, sorting, and analysis. PMID:26339309

  5. Heavy Higgs boson with a light sneutrino next-to-lightest supersymmetric particle in the MSSM with enhanced SU(2) D-terms.

    SciTech Connect

    Medina, A. D.; Shah, N. R.; Wagner, C. E. M.; High Energy Physics; Univ. of California at Davis; Univ. of Chicago

    2009-01-01

    The minimal supersymmetric extension of the standard model provides a solution to the hierarchy problem and leads to the presence of a light Higgs. A Higgs boson with mass above the present experimental bound may only be obtained for relatively heavy third generation squarks, requiring a precise, somewhat unnatural balance between different contributions to the effective Higgs mass parameter. It was recently noticed that somewhat heavier Higgs bosons, which are naturally beyond the CERN LEP bound, may be obtained by enhanced weak SU(2) D-terms. Such contributions appear in models with an enhanced electroweak gauge symmetry, provided the supersymmetry breaking masses associated with the scalars responsible for the breakdown of the enhanced gauge symmetry group to the standard model one are larger than the enhanced symmetry breaking scale. In this article we emphasize that the enhanced SU(2) D-terms will not only raise the Higgs boson mass but also affect the spectrum of the nonstandard Higgs bosons, sleptons, and squarks, which therefore provide a natural contribution to the T parameter, compensating for the negative one coming from the heavy Higgs boson. The sleptons and nonstandard Higgs bosons of these models, in particular, may act in a way similar to the so-called inert Higgs doublet. The phenomenological properties of these models are emphasized, and possible cosmological implications as well as collider signatures are described.

  6. Cu-PDC-bpa solid coordination frameworks (PDC=2,5-pyrindinedicarboxylate; bpa=1,2-DI(4-pyridil)ethane)): 2D and 3D structural flexibility producing a 3-c herringbone array next to ideal

    NASA Astrophysics Data System (ADS)

    Llano-Tomé, Francisco; Bazán, Begoña; Urtiaga, Miren-Karmele; Barandika, Gotzone; Antonia Señarís-Rodríguez, M.; Sánchez-Andújar, Manuel; Arriortua, María-Isabel

    2015-10-01

    Combination of polycarboxylate anions and dipyridyl ligands is an effective strategy to produce solid coordination frameworks (SCF) which are crystalline materials based on connections between metal ions through organic ligands. In this context, this work is focused on two novel CuII-based SCFs exhibiting PDC (2,5-pyridinedicarboxylate) and bpa (1,2-di(4-pyridyl)ethane), being the first structures reported in literature containing both ligands. Chemical formula are [Cu2[(PDC)2(bpa)(H2O)2]·3H2O·DMF (1), and [Cu2(PDC)2(bpa)(H2O)2]·7H2O (2), where DMF is dimethylformamide. Compounds 1 and 2 have been characterized by means of X-ray diffraction (XRD), infrared spectroscopy (IR), thermogravimetric (TG) analysis, differential thermal analysis (DTA) and dielectric measurements. The crystallographic analysis revealed that compounds 1 and 2 can be described as herringbone-type layers formed by helicoidal Cu-PDC-Cu chains connected through bpa ligands. Solvent molecules are crystallized between the layers, providing the inter-layer connections through hydrogen bonds. Differences between both compounds are attributable to the flexibility of bpa (in 2D) as well as to the 3D packing of the layers which is solvent dependent. This fact results in the fact that compound 2 is the most regular 3-c herringbone array reported so far. The structural dynamism of these networks is responsible for the crystalline to-amorphous to-crystalline (CAC) transformation from compound 1 to compound 2. Crystallochemical features for both compounds have also been studied and compared to similar 3-connected herringbone-arrays.

  7. Design of solid state neutral particle analyzer array for National Spherical Torus Experiment-Upgrade

    SciTech Connect

    Liu, D. Heidbrink, W. W.; Zhu, Y. B.; Tritz, K.; Roquemore, A. L.; Medley, S. S.

    2014-11-15

    A new compact, multi-channel Solid State Neutral Particle Analyzer (SSNPA) diagnostic based on silicon photodiode array has been designed and is being fabricated for the National Spherical Torus Experiment-Upgrade (NSTX-U). The SSNPA system utilizes a set of vertically stacked photodiode arrays in current mode viewing the same plasma region with different filter thickness to obtain fast temporal resolution (∼120 kHz bandwidth) and coarse energy information in three bands of >25 keV, >45 keV, and >65 keV. The SSNPA system consists of 15 radial sightlines that intersect existing on-axis neutral beams at major radii between 90 and 130 cm, 15 tangential sightlines that intersect new off-axis neutral beams at major radii between 120 and 145 cm. These two subsystems aim at separating the response of passing and trapped fast ions. In addition, one photodiode array whose viewing area does not intersect any neutral beams is used to monitor passive signals produced by fast ions that charge exchange with background neutrals.

  8. Discharges on a negatively biased solar array in a charged particle environment

    NASA Technical Reports Server (NTRS)

    Snyder, D. B.

    1983-01-01

    The charging behavior of a negatively biased solar cell array when subjected to a charged particle environment is studied in the ion density range from 200 to 12 000 ions/sq cm with the applied bias range of -500 to -1400 V. The profile of the surface potentials across the array is related to the presence of discharges. At the low end of the ion density range the solar cell cover slides charge to from 0 to +5 volts independent of the applied voltage. No discharges are seen at bias voltages as large as -1400 V. At the higher ion densities the cover slide potential begins to fluctuate, and becomes significantly negative. Under these conditions discharges can occur. The threshold bias voltage for discharges decreases with increasing ion density. A condition for discharges emerging from the experimental observations is that the average coverslide potential must be more negative than -4 V. The observations presented suggest that the plasma potential near the array becomes negative before a discharge occurs. This suggests that discharges are driven by an instability in the plasma.

  9. Design of solid state neutral particle analyzer array for National Spherical Torus Experiment-Upgrade

    NASA Astrophysics Data System (ADS)

    Liu, D.; Heidbrink, W. W.; Tritz, K.; Zhu, Y. B.; Roquemore, A. L.; Medley, S. S.

    2014-11-01

    A new compact, multi-channel Solid State Neutral Particle Analyzer (SSNPA) diagnostic based on silicon photodiode array has been designed and is being fabricated for the National Spherical Torus Experiment-Upgrade (NSTX-U). The SSNPA system utilizes a set of vertically stacked photodiode arrays in current mode viewing the same plasma region with different filter thickness to obtain fast temporal resolution (˜120 kHz bandwidth) and coarse energy information in three bands of >25 keV, >45 keV, and >65 keV. The SSNPA system consists of 15 radial sightlines that intersect existing on-axis neutral beams at major radii between 90 and 130 cm, 15 tangential sightlines that intersect new off-axis neutral beams at major radii between 120 and 145 cm. These two subsystems aim at separating the response of passing and trapped fast ions. In addition, one photodiode array whose viewing area does not intersect any neutral beams is used to monitor passive signals produced by fast ions that charge exchange with background neutrals.

  10. Design of solid state neutral particle analyzer array for National Spherical Torus Experiment-Upgrade.

    PubMed

    Liu, D; Heidbrink, W W; Tritz, K; Zhu, Y B; Roquemore, A L; Medley, S S

    2014-11-01

    A new compact, multi-channel Solid State Neutral Particle Analyzer (SSNPA) diagnostic based on silicon photodiode array has been designed and is being fabricated for the National Spherical Torus Experiment-Upgrade (NSTX-U). The SSNPA system utilizes a set of vertically stacked photodiode arrays in current mode viewing the same plasma region with different filter thickness to obtain fast temporal resolution (∼120 kHz bandwidth) and coarse energy information in three bands of >25 keV, >45 keV, and >65 keV. The SSNPA system consists of 15 radial sightlines that intersect existing on-axis neutral beams at major radii between 90 and 130 cm, 15 tangential sightlines that intersect new off-axis neutral beams at major radii between 120 and 145 cm. These two subsystems aim at separating the response of passing and trapped fast ions. In addition, one photodiode array whose viewing area does not intersect any neutral beams is used to monitor passive signals produced by fast ions that charge exchange with background neutrals.

  11. Two-color beam improvement of the colloidal particle lens array assisted surface nanostructuring

    SciTech Connect

    Afanasiev, Andrei; Bredikhin, Vladimir; Pikulin, Alexander; Ilyakov, Igor; Shishkin, Boris; Akhmedzhanov, Rinat; Bityurin, Nikita

    2015-05-04

    We consider laser nanostructuring of the material surface by means of a colloidal particle lens array. Here, the monolayer of dielectric micro- or nanospheres placed on the surface acts as an array of near-field lenses that focus the laser radiation into the multitude of distinct spots, allowing the formation of many structures in a single stage. We show that conversion of a small part of the energy of the femtosecond beam into the second harmonic (SH) is an efficient way to increase the surface density of obtained nanostructures. By combining the fundamental frequency and the SH, one benefits both from the power of the former and from the focusing ability of the latter. This combination provides an efficient nanostructuring with sphere diameter close to the wavelength of the second harmonic. The possibility to create arrays of nanostructures with surface density above 5×10{sup 8} cm{sup −2} with femtosecond Ti:sapphire laser operating at 800 nm was demonstrated by employing 0.45 μm spheres.

  12. A tapered aluminium microelectrode array for improvement of dielectrophoresis-based particle manipulation.

    PubMed

    Buyong, Muhamad Ramdzan; Larki, Farhad; Faiz, Mohd Syafiq; Hamzah, Azrul Azlan; Yunas, Jumrail; Majlis, Burhanuddin Yeop

    2015-01-01

    In this work, the dielectrophoretic force (F(DEP)) response of Aluminium Microelectrode Arrays with tapered profile is investigated through experimental measurements and numerical simulations. A standard CMOS processing technique with a step for the formation of a tapered profile resist is implemented in the fabrication of Tapered Aluminium Microelectrode Arrays (TAMA). The F(DEP) is investigated through analysis of the Clausius-Mossotti factor (CMF) and cross-over frequency (f(xo)). The performance of TAMA with various side wall angles is compared to that of microelectrodes with a straight cut sidewall profile over a wide range of frequencies through FEM numerical simulations. Additionally, electric field measurement (EFM) is performed through scanning probe microscopy (SPM) in order to obtain the region of force focus in both platforms. Results showed that the tapered profile microelectrodes with angles between 60° and 70° produce the highest electric field gradient on the particles. Also, the region of the strongest electric field in TAMA is located at the bottom and top edge of microelectrode while the strongest electric field in microelectrodes with straight cut profile is found at the top corner of the microelectrode. The latter property of microelectrodes improves the probability of capturing/repelling the particles at the microelectrode's side wall. PMID:25970255

  13. A Tapered Aluminium Microelectrode Array for Improvement of Dielectrophoresis-Based Particle Manipulation

    PubMed Central

    Buyong, Muhamad Ramdzan; Larki, Farhad; Faiz, Mohd Syafiq; Hamzah, Azrul Azlan; Yunas, Jumrail; Majlis, Burhanuddin Yeop

    2015-01-01

    In this work, the dielectrophoretic force (FDEP) response of Aluminium Microelectrode Arrays with tapered profile is investigated through experimental measurements and numerical simulations. A standard CMOS processing technique with a step for the formation of a tapered profile resist is implemented in the fabrication of Tapered Aluminium Microelectrode Arrays (TAMA). The FDEP is investigated through analysis of the Clausius-Mossotti factor (CMF) and cross-over frequency (fxo). The performance of TAMA with various side wall angles is compared to that of microelectrodes with a straight cut sidewall profile over a wide range of frequencies through FEM numerical simulations. Additionally, electric field measurement (EFM) is performed through scanning probe microscopy (SPM) in order to obtain the region of force focus in both platforms. Results showed that the tapered profile microelectrodes with angles between 60° and 70° produce the highest electric field gradient on the particles. Also, the region of the strongest electric field in TAMA is located at the bottom and top edge of microelectrode while the strongest electric field in microelectrodes with straight cut profile is found at the top corner of the microelectrode. The latter property of microelectrodes improves the probability of capturing/repelling the particles at the microelectrode’s side wall. PMID:25970255

  14. Finite element simulations of hydrodynamic trapping in microfluidic particle-trap array systems

    PubMed Central

    Xu, Xiaoxiao; Li, Zhenyu; Nehorai, Arye

    2013-01-01

    Computational fluid dynamic (CFD) simulation is a powerful tool in the design and implementation of microfluidic systems, especially for systems that involve hydrodynamic behavior of objects such as functionalized microspheres, biological cells, or biopolymers in complex structures. In this work, we investigate hydrodynamic trapping of microspheres in a novel microfluidic particle-trap array device by finite element simulations. The accuracy of the time-dependent simulation of a microsphere's motion towards the traps is validated by our experimental results. Based on the simulation, we study the fluid velocity field, pressure field, and force and stress on the microsphere in the device. We further explore the trap array's geometric parameters and critical fluid velocity, which affect the microsphere's hydrodynamic trapping. The information is valuable for designing microfluidic devices and guiding experimental operation. Besides, we provide guidelines on the simulation set-up and release an openly available implementation of our simulation in one of the popular FEM softwares, COMSOL Multiphysics. Researchers may tailor the model to simulate similar microfluidic systems that may accommodate a variety of structured particles. Therefore, the simulation will be of particular interest to biomedical research involving cell or bead transport and migration, blood flow within microvessels, and drug delivery. PMID:24404071

  15. Simulation on a novel micron-array inertial impactor for submicron and ultrafine particle separation

    NASA Astrophysics Data System (ADS)

    Liu, Rui-Tao; Tao, Lu-Qi; Yang, Yi; Ren, Tian-Ling

    2016-08-01

    The particulate matter (PM), which was put forward in 1997 by US, had taken more and more attention due to the influence on human health. Although the mass concentration, number concentration and chemical composition of PM were still major research directions, how to collect these PMs more efficiently becomes critical. Inertial impactor is an effective separation device, however, due to different motion states of PM2.5 and PM0.3 in the flow field, the inertial impactor which can separate PM0.3 from other PMs has not been fabricated. In this work, the motion states for both submicron and ultrafine particles were studied by using classical theory of channel aerodynamic, and a novel micron-array inertial impactor was designed and simulated for the first time. Besides, the influence of some characteristic parameters (W, T, S, Dc, etc.) on particle collection efficiency were researched and discussed through simulation results. This novel structure can be easily fabricated by MEMS technology or laser direct writing and also can be widely used in particle separation or flexible sensor fields.

  16. Performance of the solid state neutral particle analyzer array on the national spherical torus experiment

    SciTech Connect

    Liu, D.; Heidbrink, W. W.; Darrow, D. S.; Roquemore, A. L.; Medley, S. S.; Shinohara, K.

    2006-10-15

    The solid state neutral particle analyzer (SSNPA) array on the national spherical torus experiment (NSTX) consists of four chords with tangency radii of 60, 90, 100, and 120 cm that view across the three coinjection neutral beam lines. Each chord utilizes a silicon photodiode that is coupled to fast digitizers to measure the energy distribution of charge exchange fast neutral particles (30-100 keV). By the end of the NSTX 2005 experimental campaign, the electromagnetic noise in the SSNPA was reduced by half and reasonable signals were obtained with good electromagnetic shielding, fast digitization of raw signals, software-based pulse height analysis, and pulse shape discrimination. Energy resolution of {approx}10 keV and time resolution of 2 ms have been achieved. Temporal evolutions of energetic neutral flux obtained with the SSNPA are in good agreement with those obtained with the E(parallel sign)B-type neutral particle analyzer. With these improvements, the SSNPA can be used to study magnetohydrodynamic instabilities and fast ion redistribution. Example data from plasma discharges are presented along with the noise reduction techniques and postshot pulse height analysis methods.

  17. Development of the Plastic Scintillator Detector Array for the Prototype of the Dark Matter Particle Explorer

    NASA Astrophysics Data System (ADS)

    Zhang, Yongjie; Sun, Zhiyu; Yu, Yuhong; Zhou, Yong; Fang, Fang; Chen, Junling

    2016-07-01

    The scientific object of Dark Matter Particles Explorer(DAMPE) is the measurement of electrons and photons in the range of 5GeV~10TeV and the flux of nuclei up to 500TeV with excellent resolution , and the realization of measurements will identify possible Dark Matter(DM) signature and help deepen our understanding of the origin and propagation of high energy cosmic ray respectively. Plastic Scintillator Detector Array (PSD), which adopts perpendicular structure with two layers and each layer consists of 15 scintillator strips, is one sub-detector of DAMPE for detecting heavy ions and distinguishing photons and electrons. In this paper, the design and some test results of PSD are to be described.

  18. Aniso2D

    2005-07-01

    Aniso2d is a two-dimensional seismic forward modeling code. The earth is parameterized by an X-Z plane in which the seismic properties Can have monoclinic with x-z plane symmetry. The program uses a user define time-domain wavelet to produce synthetic seismograms anrwhere within the two-dimensional media.

  19. Self-Assembly and Electrostriction of Arrays and Chains of Hopfion Particles in Chiral Liquid Crystals

    SciTech Connect

    Ackerman, P. J.; van de Lagemaat, J.; Smalyukh, I. I.

    2015-01-21

    Some of the most exotic condensed matter phases, such as twist grain boundary and blue phases in liquid crystals and Abrikosov phases in superconductors, contain arrays of topological defects in their ground state. Comprised of a triangular lattice of double-twist tubes of magnetization, the so-called ‘A-phase’ in chiral magnets is an example of a thermodynamically stable phase with topologically nontrivial solitonic field configurations referred to as two-dimensional skyrmions, or baby-skyrmions. Here we report that three-dimensional skyrmions in the form of double-twist tori called ‘hopfions’, or ‘torons’ when accompanied by additional self-compensating defects, self-assemble into periodic arrays and linear chains that exhibit electrostriction. In confined chiral nematic liquid crystals, this self-assembly is similar to that of liquid crystal colloids and originates from long-range elastic interactions between particle-like skyrmionic torus knots of molecular alignment field, which can be tuned from isotropic repulsive to weakly or highly anisotropic attractive by low-voltage electric fields.

  20. Self-Assembly and Electrostriction of Arrays and Chains of Hopfion Particles in Chiral Liquid Crystals

    DOE PAGES

    Ackerman, P. J.; van de Lagemaat, J.; Smalyukh, I. I.

    2015-01-21

    Some of the most exotic condensed matter phases, such as twist grain boundary and blue phases in liquid crystals and Abrikosov phases in superconductors, contain arrays of topological defects in their ground state. Comprised of a triangular lattice of double-twist tubes of magnetization, the so-called ‘A-phase’ in chiral magnets is an example of a thermodynamically stable phase with topologically nontrivial solitonic field configurations referred to as two-dimensional skyrmions, or baby-skyrmions. Here we report that three-dimensional skyrmions in the form of double-twist tori called ‘hopfions’, or ‘torons’ when accompanied by additional self-compensating defects, self-assemble into periodic arrays and linear chains thatmore » exhibit electrostriction. In confined chiral nematic liquid crystals, this self-assembly is similar to that of liquid crystal colloids and originates from long-range elastic interactions between particle-like skyrmionic torus knots of molecular alignment field, which can be tuned from isotropic repulsive to weakly or highly anisotropic attractive by low-voltage electric fields.« less

  1. Self-assembly and electrostriction of arrays and chains of hopfion particles in chiral liquid crystals

    PubMed Central

    Ackerman, Paul J.; van de Lagemaat, Jao; Smalyukh, Ivan I.

    2015-01-01

    Some of the most exotic condensed matter phases, such as twist grain boundary and blue phases in liquid crystals and Abrikosov phases in superconductors, contain arrays of topological defects in their ground state. Comprised of a triangular lattice of double-twist tubes of magnetization, the so-called ‘A-phase’ in chiral magnets is an example of a thermodynamically stable phase with topologically nontrivial solitonic field configurations referred to as two-dimensional skyrmions, or baby-skyrmions. Here we report that three-dimensional skyrmions in the form of double-twist tori called ‘hopfions’, or ‘torons’ when accompanied by additional self-compensating defects, self-assemble into periodic arrays and linear chains that exhibit electrostriction. In confined chiral nematic liquid crystals, this self-assembly is similar to that of liquid crystal colloids and originates from long-range elastic interactions between particle-like skyrmionic torus knots of molecular alignment field, which can be tuned from isotropic repulsive to weakly or highly anisotropic attractive by low-voltage electric fields. PMID:25607778

  2. Self-assembly and electrostriction of arrays and chains of hopfion particles in chiral liquid crystals

    NASA Astrophysics Data System (ADS)

    Ackerman, Paul J.; van de Lagemaat, Jao; Smalyukh, Ivan I.

    2015-01-01

    Some of the most exotic condensed matter phases, such as twist grain boundary and blue phases in liquid crystals and Abrikosov phases in superconductors, contain arrays of topological defects in their ground state. Comprised of a triangular lattice of double-twist tubes of magnetization, the so-called ‘A-phase’ in chiral magnets is an example of a thermodynamically stable phase with topologically nontrivial solitonic field configurations referred to as two-dimensional skyrmions, or baby-skyrmions. Here we report that three-dimensional skyrmions in the form of double-twist tori called ‘hopfions’, or ‘torons’ when accompanied by additional self-compensating defects, self-assemble into periodic arrays and linear chains that exhibit electrostriction. In confined chiral nematic liquid crystals, this self-assembly is similar to that of liquid crystal colloids and originates from long-range elastic interactions between particle-like skyrmionic torus knots of molecular alignment field, which can be tuned from isotropic repulsive to weakly or highly anisotropic attractive by low-voltage electric fields.

  3. Origin of the Ion Foreshock in a Quasi-perpendicular Curved Collisionless Shock: Particles Trajectory Analysis in 2D PIC Simulations

    NASA Astrophysics Data System (ADS)

    Savoini, P.; Lembege, B.

    2015-12-01

    The ion foreshock located upstream of the Earth's shock wave is populated with ions having interacted with the shock, and then, reflected back with an high energy gain. Spacecrafts have clearly established the existence of two distinct populations in the quasi-perpendicular shock region (i.e. for 45° ≤ ΘBn ≤ 90°, where ΘBn is the angle between the shock normal and the upstream magnetic field) : (i) field-aligned ion beams or « FAB » characterized by a gyrotropic distribution, and (ii) gyro-phase bunched ions or « GPB » characterized by a NON gyrotropic distribution. One of the important unresolved problem is the exact origin of the particles contributing to these two populations. To our knowledge, it was the first time that full-particle simulations have been performed including self-consistently the shock front curvature and nonstationarity, and the time-of-flight effects. Our analysis evidences that these two backstreaming populations may be reflected by the front itself and can be differentiated both in terms of interaction time and trajectory within the shock front. In particular, simulations evidence that "GPB" population is characterized by a short interaction time (ΔTinter = 1 to 2 τci) while the "FAB" population corresponds to a much larger time range (from 1 τci to 10 τci), where tci is the upstream ion gyroperiod. Present individual ion trajectories evidence that "FAB" population shows a strong perpendicular drift at the shock front (i.e. strong dependence of the pitch angle to the perpendicular velocity) whereas the "GPB" population shows no perpendicular drift (i.e. its pitch angle is mainly driven by the parallel velocity). Such differences explain why the "FAB" population loses their gyro-phase coherency and become gyrotropic which is not the case for the "GPB". This important result was not expected and greatly simplifies the question of their origin.

  4. Unparticle example in 2D.

    PubMed

    Georgi, Howard; Kats, Yevgeny

    2008-09-26

    We discuss what can be learned about unparticle physics by studying simple quantum field theories in one space and one time dimension. We argue that the exactly soluble 2D theory of a massless fermion coupled to a massive vector boson, the Sommerfield model, is an interesting analog of a Banks-Zaks model, approaching a free theory at high energies and a scale-invariant theory with nontrivial anomalous dimensions at low energies. We construct a toy standard model coupling to the fermions in the Sommerfield model and study how the transition from unparticle behavior at low energies to free particle behavior at high energies manifests itself in interactions with the toy standard model particles.

  5. Multi-scale analysis of collective behavior in 2D self-propelled particle models of swarms: An Advection-Diffusion with Memory Approach

    NASA Astrophysics Data System (ADS)

    Raghib, Michael; Levin, Simon; Kevrekidis, Ioannis

    2010-05-01

    Self-propelled particle models (SPP's) are a class of agent-based simulations that have been successfully used to explore questions related to various flavors of collective motion, including flocking, swarming, and milling. These models typically consist of particle configurations, where each particle moves with constant speed, but changes its orientation in response to local averages of the positions and orientations of its neighbors found within some interaction region. These local averages are based on `social interactions', which include avoidance of collisions, attraction, and polarization, that are designed to generate configurations that move as a single object. Errors made by the individuals in the estimates of the state of the local configuration are modeled as a random rotation of the updated orientation resulting from the social rules. More recently, SPP's have been introduced in the context of collective decision-making, where the main innovation consists of dividing the population into naïve and `informed' individuals. Whereas naïve individuals follow the classical collective motion rules, members of the informed sub-population update their orientations according to a weighted average of the social rules and a fixed `preferred' direction, shared by all the informed individuals. Collective decision-making is then understood in terms of the ability of the informed sub-population to steer the whole group along the preferred direction. Summary statistics of collective decision-making are defined in terms of the stochastic properties of the random walk followed by the centroid of the configuration as the particles move about, in particular the scaling behavior of the mean squared displacement (msd). For the region of parameters where the group remains coherent , we note that there are two characteristic time scales, first there is an anomalous transient shared by both purely naïve and informed configurations, i.e. the scaling exponent lies between 1 and

  6. Design Study of a Multi-channel Array Particle Spectrometer for Space Missions

    NASA Astrophysics Data System (ADS)

    Trindade, Andreia; Assis, P.; Brogueira, P.; Gonçalves, P.; Keating, A.; Pimenta, M.; Rodrigues, P.; Trindade, A.

    In this work, a novel particle spectrometer is proposed to fulfil the need to map the space radiation environment for future space missions and to provide more accurate scientific data. The concept of the instrument brings together new radiation-hard technologies, for the photo-sensors and scintillating materials that will improve the quality of the data, while taking into account the limited resources such as mass, power and accommodation, allocated for space radiation monitors. The Multi-channel Array Particle Spectrometer (MAPS), can measure fluxes and energy dis-tributions of protons, ions, electrons and gammas in a wide energy range based on the 3D reconstruction of the particle track through the detector and its deposited energy in the active volume. It consists on a 8 x 8 segmented scintillator block built from 3.2 x 3.2 x 20 mm3 indi-vidual LYSO:Ce rods that are readout at both ends by two 64 pixel Silicon Photo-Multipliers (SiPMs) matrices, a new generation of high gain (105-106) avalanche photodiodes working in controlled Geiger mode, that collect the scintillating light produced by the interactions of the charged particles in the crystals. Each SiPM matrix is readout by a 64 channel mixed sig-nal analog-digital ASIC, offering both particle identification and particle counting capabilities. Power cycling design of the ASIC allows to activate the particle identification block only during a pre-determined time slice, keeping the total power budget of less than 1 mW/channel. An on-board FPGA sorts the serialized data from the two ASICs and computes the trigger primitives in real-time and in an event-by-event basis. Whenever a charged particle crosses the segmented volume of the detector, the XY coordinates, given by the pixelized crystal positions, and the deposited energy in each crystal is recorded. The double readout scheme allows to compute the light collection asymmetry between both ends of the crystal and to use that information to record the

  7. Mesh2d

    2011-12-31

    Mesh2d is a Fortran90 program designed to generate two-dimensional structured grids of the form [x(i),y(i,j)] where [x,y] are grid coordinates identified by indices (i,j). The x(i) coordinates alone can be used to specify a one-dimensional grid. Because the x-coordinates vary only with the i index, a two-dimensional grid is composed in part of straight vertical lines. However, the nominally horizontal y(i,j0) coordinates along index i are permitted to undulate or otherwise vary. Mesh2d also assignsmore » an integer material type to each grid cell, mtyp(i,j), in a user-specified manner. The complete grid is specified through three separate input files defining the x(i), y(i,j), and mtyp(i,j) variations.« less

  8. Silicon PIN diode hybrid arrays for charged particle detection: Building blocks for vertex detectors at the SSC

    SciTech Connect

    Kramer, G.; Gaalema, S.; Shapiro, S.L.; Dunwoodie, W.M.; Arens, J.F.; Jernigan, J.G.

    1989-05-01

    Two-dimensional arrays of solid state detectors have long been used in visible and infrared systems. Hybrid arrays with separately optimized detector and readout substrates have been extensively developed for infrared sensors. The characteristics and use of these infrared readout chips with silicon PIN diode arrays produced by MICRON SEMICONDUCTOR for detecting high-energy particles are reported. Some of these arrays have been produced in formats as large as 512 /times/ 512 pixels; others have been radiation hardened to total dose levels beyond 1 Mrad. Data generation rates of 380 megasamples/second have been achieved. Analog and digital signal transmission and processing techniques have also been developed to accept and reduce these high data rates. 9 refs., 15 figs., 2 tabs.

  9. Responsive ionic liquid-polymer 2D photonic crystal gas sensors.

    PubMed

    Smith, Natasha L; Hong, Zhenmin; Asher, Sanford A

    2014-12-21

    We developed novel air-stable 2D polymerized photonic crystal (2DPC) sensing materials for visual detection of gas phase analytes such as water and ammonia by utilizing a new ionic liquid, ethylguanidine perchlorate (EGP) as the mobile phase. Because of the negligible ionic liquid vapor pressure these 2DPC sensors are indefinitely air stable and, therefore, can be used to sense atmospheric analytes. 2D arrays of ~640 nm polystyrene nanospheres were attached to the surface of crosslinked poly(hydroxyethyl methacrylate) (pHEMA)-based polymer networks dispersed in EGP. The wavelength of the bright 2D photonic crystal diffraction depends sensitively on the 2D array particle spacing. The volume phase transition response of the EGP-pHEMA system to water vapor or gaseous ammonia changes the 2DPC particle spacing, enabling the visual determination of the analyte concentration. Water absorbed by EGP increases the Flory-Huggins interaction parameter, which shrinks the polymer network and causes a blue shift in the diffracted light. Ammonia absorbed by the EGP deprotonates the pHEMA-co-acrylic acid carboxyl groups, swelling the polymer which red shifts the diffracted light.

  10. Comparative Study on Synthesizing Reconfigurable Time- Modulated Linear Arrays using Differential Evolution, Artificial Bee Colony and Particle Swarm Optimization

    NASA Astrophysics Data System (ADS)

    Mandal, S. K.; Singh, Harshavardhan; Mahanti, G. K.; Ghatak, Rowdra

    2014-10-01

    This paper presents a new technique based on optimization tools to design phase only, digitally controlled, reconfigurable antenna arrays through time modulation. In the proposed approach, the on-time durations of the time-modulated elements and the static amplitudes of the array elements are perturbed in such a way that the same on-time sequence and discrete values of static amplitudes for four bit digital attenuators produces either a pencil or a flat-top beam pattern, depending on the suitable discrete phase distributions of five bit digital phase shifters. In order to illustrate the technique, three optimization tools: differential evolution (DE), artificial bee colony (ABC), and particle swarm optimization (PSO) are employed and their performances are compared. The numerical results for a 20-element linear array are presented.

  11. Front-end electronics for CsI based charged particle array for the study of reaction dynamics

    NASA Astrophysics Data System (ADS)

    Jhingan, Akhil; Sugathan, P.; Kaur, Gurpreet; Kapoor, K.; Saneesh, N.; Banerjee, T.; Singh, Hardev; Kumar, A.; Behera, B. R.; Nayak, B. K.

    2015-06-01

    The characteristics and performance of a new detector system based on CsI(TI) scintillators, and its front-end electronics are presented. The detector system has been developed for the detection of light charged particles to investigate fusion-fission dynamics, and will also serve as ancillary detector for an array of neutron detectors. CsI scintillators are read by photo-diodes. The main feature of the array is its compact and simple high density front-end electronics which includes custom developed low noise charge sensitive preamplifiers (with very low power consumption for operation inside vacuum), NIM differential drivers, and commercially available Mesytec amplifiers with two different time constants for particle identification using a ballistic deficit technique.

  12. Compact and multi-view solid state neutral particle analyzer arrays on National Spherical Torus Experiment-Upgrade

    NASA Astrophysics Data System (ADS)

    Liu, D.; Heidbrink, W. W.; Tritz, K.; Fredrickson, E. D.; Hao, G. Z.; Zhu, Y. B.

    2016-11-01

    A compact and multi-view solid state neutral particle analyzer (SSNPA) diagnostic based on silicon photodiode arrays has been successfully tested on the National Spherical Torus Experiment-Upgrade. The SSNPA diagnostic provides spatially, temporally, and pitch-angle resolved measurements of fast-ion distribution by detecting fast neutral flux resulting from the charge exchange (CX) reactions. The system consists of three 16-channel subsystems: t-SSNPA viewing the plasma mid-radius and neutral beam (NB) line #2 tangentially, r-SSNPA viewing the plasma core and NB line #1 radially, and p-SSNPA with no intersection with any NB lines. Due to the setup geometry, the active CX signals of t-SSNPA and r-SSNPA are mainly sensitive to passing and trapped particles, respectively. In addition, both t-SSNPA and r-SSNPA utilize three vertically stacked arrays with different filter thicknesses to obtain coarse energy information. The experimental data show that all channels are operational. The signal to noise ratio is typically larger than 10, and the main noise is x-ray induced signal. The active and passive CX signals are clearly observed on t-SSNPA and r-SSNPA during NB modulation. The SSNPA data also indicate significant losses of passing particles during sawteeth, while trapped particles are weakly affected. Fluctuations up to 120 kHz have been observed on SSNPA, and they are strongly correlated with magnetohydrodynamics instabilities.

  13. Measuring Displacement and Contact Forces Among the Particles in Unloading of Slope by PFC2D (Particle Flow Code) / Pomiary przemieszczeń i sił kontaktu pomiędzy cząstkami materialnymi w trakcie wybierania wyrobiska pochyłego przy pomocy programu PFC2D

    NASA Astrophysics Data System (ADS)

    Behbahani, Seyed Saleh; Moarefvand, Parviz; Ahangari, Kaveh; Goshtasbi, Kamran

    2013-06-01

    When instability is observed in the walls of open pit mining, at this time, engineers are faced with a moving mass which is a combination of materials that move on each other and on the main slip surface. Modeling of this movement can have an effective assistance to mining engineers to predict the movement behavior, displacement estimate, and the moving volumes. One of the suitable software which is capable of modeling of sliding behavior is PFC (Particle Flow Code). It is based on Discrete Element Method and released by the Itasca Company. In this paper, the modeling of sliding mass and unloading it in seven stages have been done. During the seven stages of unloading the maximum displacement and maximum contact forces among the particles are obtained. Maximum displacement happened in the fifth stage of the unloading and it is equal to 134.8 meters. Maximum contact forces occurred in the first stage of the unloading after initial equilibrium stage and it is equal to 1917 kN. The model for unloading of sliding mass presented in this paper is just an example and it is not a definite model for unloading of each sliding mass. Unloading of sliding mass depends on the situation of sliding mass and its volume and also mining limitations. W przypadku wystąpienia niestabilności ścian pochyłego wyrobiska odkrywkowego, inżynierowie mają do czynienia z przemieszczającą się masa - będącą kombinacją materiałów przesuwających się względem siebie a także zsuwających się w dół po powierzchni spadu. Modelowanie tego ruchu może znacznie pomóc inżynierom-górnikom w prognozowaniu zachowań terenu w trakcie tego ruchu, do szacowania wielkości przemieszczeń i objętości przemieszczających się mas materiału. Jednym z programów wspomagających modelowanie przemieszczeń tego typu jest oprogramowanie Particle Flow Code PFC, rozprowadzane przez firmę Itasca, wykorzystujące metodę elementów dyskretnych. W pracy tej przeprowadzono modelowanie ruchu

  14. Geometric phases generated by the non-trivial spatial topology of static vector fields linearly coupled to a neutral spin-endowed particle: application to 171Yb atoms trapped in a 2D optical lattice

    NASA Astrophysics Data System (ADS)

    Bouchiat, Marie-Anne; Bouchiat, Claude

    2012-10-01

    We have constructed the geometric phases emerging from the non-trivial topology of a space-dependent magnetic field B(r), interacting with the spin magnetic moment of a neutral particle. Our basic tool, adapted from a previous work on Berry’s phases, is the space-dependent unitary transformation {U}({\\mathbf {r}}), which leads to the identity, {U}({\\mathbf {r}})^{\\dag }\\, {\\mathbf {S}}\\,{\\bm \\cdot}\\, {\\mathbf {B}}({\\mathbf {r}}) \\, {U}({\\mathbf {r}}) = \\vert {\\mathbf {B}}({\\mathbf {r}}) \\vert \\, S_z, at each point r. In the ‘rotated’ Hamiltonian \\widehat{ H}, \\frac{ \\partial }{\\partial {\\mathbf {r}}} is replaced by the non-Abelian covariant derivative \\frac{ \\partial }{\\partial {\\mathbf {r}}}- \\frac{i}{\\hbar } {A}({\\mathbf {r}}) where {A}({\\mathbf {r}}) = i \\hbar \\, {U}^{\\dag }\\,{\\bm\\cdot}\\, \\frac{ \\partial }{\\partial {\\mathbf {r}}} {U} can be written as A1(r)Sx + A2(r)Sy + A3(r)Sz. The Abelian differentials Ak(r)·dr are given in terms of the Euler angles defining the orientation of B(r). The non-Abelian field {A}({\\mathbf {r}}) transforms as a Yang-Mills field; however, its vanishing ‘curvature’ reveals its purely geometric character. We have defined a perturbation scheme based upon the assumption that in \\widehat{ H} the longitudinal field A3(r) dominates the transverse field A1, 2(r) contributions, evaluated to second order. The geometry embedded in both the vector field A3(r) and the geometric magnetic field \\mathbf { B}_3 ({\\mathbf {r}}) = \\frac{ \\partial }{\\partial {\\mathbf {r}}}\\wedge {{\\mathbf {A}}}_3({\\mathbf {r}}) is described by their associated Aharonov-Bohm phase. As an illustration we study the physics of cold 171Yb atoms dressed by overlaying two circularly polarized stationary waves with orthogonal directions, which form a 2D square optical lattice. The frequency is tuned midway between the two hyperfine levels of the (6s6p)3P1 states to protect the optical B(r) field generated by the

  15. "Phoswich Wall": A charged-particle detector array for inverse-kinematic reactions with the Gretina/GRETA γ-ray arrays

    NASA Astrophysics Data System (ADS)

    Sarantites, D. G.; Reviol, W.; Elson, J. M.; Kinnison, J. E.; Izzo, C. J.; Manfredi, J.; Liu, J.; Jung, H. S.; Goerres, J.

    2015-08-01

    A high-efficiency, forward-hemisphere detector system for light charged particles and low-Z heavy ions, as obtained in an accelerator experiment, is described. It consists of four 8×8 pixel multianode photomultiplier tubes with 2.2-mm thick CsI(Tl) and 12 -μm thick fast-plastic scintillation detectors. Its phoswich structure allows individual Z resolution for 1H, 4He, 7Li, 4He+4He, 9Be, 11B, 12C, and 14N ions, which are target-like fragments detected in strongly inverse kinematics. The device design has been optimized for use with a 4π γ-ray array, and the main applications are transfer reactions and Coulomb excitation. A high-angular resolution for the detection of the target-like fragments is achieved which permits angular distributions to be measured in the rest frame of the projectile-like fragment with a resolution of ~ 2 °.

  16. High divergent 2D grating

    NASA Astrophysics Data System (ADS)

    Wang, Jin; Ma, Jianyong; Zhou, Changhe

    2014-11-01

    A 3×3 high divergent 2D-grating with period of 3.842μm at wavelength of 850nm under normal incidence is designed and fabricated in this paper. This high divergent 2D-grating is designed by the vector theory. The Rigorous Coupled Wave Analysis (RCWA) in association with the simulated annealing (SA) is adopted to calculate and optimize this 2D-grating.The properties of this grating are also investigated by the RCWA. The diffraction angles are more than 10 degrees in the whole wavelength band, which are bigger than the traditional 2D-grating. In addition, the small period of grating increases the difficulties of fabrication. So we fabricate the 2D-gratings by direct laser writing (DLW) instead of traditional manufacturing method. Then the method of ICP etching is used to obtain the high divergent 2D-grating.

  17. Understanding the interaction between energetic ions and freestanding graphene towards practical 2D perforation

    NASA Astrophysics Data System (ADS)

    Buchheim, Jakob; Wyss, Roman M.; Shorubalko, Ivan; Park, Hyung Gyu

    2016-04-01

    We report experimentally and theoretically the behavior of freestanding graphene subjected to bombardment of energetic ions, investigating the capability of large-scale patterning of freestanding graphene with nanometer sized features by focused ion beam technology. A precise control over the He+ and Ga+ irradiation offered by focused ion beam techniques enables investigating the interaction of the energetic particles and graphene suspended with no support and allows determining sputter yields of the 2D lattice. We found a strong dependency of the 2D sputter yield on the species and kinetic energy of the incident ion beams. Freestanding graphene shows material semi-transparency to He+ at high energies (10-30 keV) allowing the passage of >97% He+ particles without creating destructive lattice vacancy. Large Ga+ ions (5-30 keV), in contrast, collide far more often with the graphene lattice to impart a significantly higher sputter yield of ~50%. Binary collision theory applied to monolayer and few-layer graphene can successfully elucidate this collision mechanism, in great agreement with experiments. Raman spectroscopy analysis corroborates the passage of a large fraction of He+ ions across graphene without much damaging the lattice whereas several colliding ions create single vacancy defects. Physical understanding of the interaction between energetic particles and suspended graphene can practically lead to reproducible and efficient pattern generation of unprecedentedly small features on 2D materials by design, manifested by our perforation of sub-5 nm pore arrays. This capability of nanometer-scale precision patterning of freestanding 2D lattices shows the practical applicability of focused ion beam technology to 2D material processing for device fabrication and integration.We report experimentally and theoretically the behavior of freestanding graphene subjected to bombardment of energetic ions, investigating the capability of large-scale patterning of

  18. Understanding the interaction between energetic ions and freestanding graphene towards practical 2D perforation.

    PubMed

    Buchheim, Jakob; Wyss, Roman M; Shorubalko, Ivan; Park, Hyung Gyu

    2016-04-21

    We report experimentally and theoretically the behavior of freestanding graphene subjected to bombardment of energetic ions, investigating the capability of large-scale patterning of freestanding graphene with nanometer sized features by focused ion beam technology. A precise control over the He(+) and Ga(+) irradiation offered by focused ion beam techniques enables investigating the interaction of the energetic particles and graphene suspended with no support and allows determining sputter yields of the 2D lattice. We found a strong dependency of the 2D sputter yield on the species and kinetic energy of the incident ion beams. Freestanding graphene shows material semi-transparency to He(+) at high energies (10-30 keV) allowing the passage of >97% He(+) particles without creating destructive lattice vacancy. Large Ga(+) ions (5-30 keV), in contrast, collide far more often with the graphene lattice to impart a significantly higher sputter yield of ∼50%. Binary collision theory applied to monolayer and few-layer graphene can successfully elucidate this collision mechanism, in great agreement with experiments. Raman spectroscopy analysis corroborates the passage of a large fraction of He(+) ions across graphene without much damaging the lattice whereas several colliding ions create single vacancy defects. Physical understanding of the interaction between energetic particles and suspended graphene can practically lead to reproducible and efficient pattern generation of unprecedentedly small features on 2D materials by design, manifested by our perforation of sub-5 nm pore arrays. This capability of nanometer-scale precision patterning of freestanding 2D lattices shows the practical applicability of focused ion beam technology to 2D material processing for device fabrication and integration.

  19. CYP2D7 Sequence Variation Interferes with TaqMan CYP2D6*15 and *35 Genotyping

    PubMed Central

    Riffel, Amanda K.; Dehghani, Mehdi; Hartshorne, Toinette; Floyd, Kristen C.; Leeder, J. Steven; Rosenblatt, Kevin P.; Gaedigk, Andrea

    2016-01-01

    TaqMan™ genotyping assays are widely used to genotype CYP2D6, which encodes a major drug metabolizing enzyme. Assay design for CYP2D6 can be challenging owing to the presence of two pseudogenes, CYP2D7 and CYP2D8, structural and copy number variation and numerous single nucleotide polymorphisms (SNPs) some of which reflect the wild-type sequence of the CYP2D7 pseudogene. The aim of this study was to identify the mechanism causing false-positive CYP2D6*15 calls and remediate those by redesigning and validating alternative TaqMan genotype assays. Among 13,866 DNA samples genotyped by the CompanionDx® lab on the OpenArray platform, 70 samples were identified as heterozygotes for 137Tins, the key SNP of CYP2D6*15. However, only 15 samples were confirmed when tested with the Luminex xTAG CYP2D6 Kit and sequencing of CYP2D6-specific long range (XL)-PCR products. Genotype and gene resequencing of CYP2D6 and CYP2D7-specific XL-PCR products revealed a CC>GT dinucleotide SNP in exon 1 of CYP2D7 that reverts the sequence to CYP2D6 and allows a TaqMan assay PCR primer to bind. Because CYP2D7 also carries a Tins, a false-positive mutation signal is generated. This CYP2D7 SNP was also responsible for generating false-positive signals for rs769258 (CYP2D6*35) which is also located in exon 1. Although alternative CYP2D6*15 and *35 assays resolved the issue, we discovered a novel CYP2D6*15 subvariant in one sample that carries additional SNPs preventing detection with the alternate assay. The frequency of CYP2D6*15 was 0.1% in this ethnically diverse U.S. population sample. In addition, we also discovered linkage between the CYP2D7 CC>GT dinucleotide SNP and the 77G>A (rs28371696) SNP of CYP2D6*43. The frequency of this tentatively functional allele was 0.2%. Taken together, these findings emphasize that regardless of how careful genotyping assays are designed and evaluated before being commercially marketed, rare or unknown SNPs underneath primer and/or probe regions can impact

  20. CYP2D7 Sequence Variation Interferes with TaqMan CYP2D6 (*) 15 and (*) 35 Genotyping.

    PubMed

    Riffel, Amanda K; Dehghani, Mehdi; Hartshorne, Toinette; Floyd, Kristen C; Leeder, J Steven; Rosenblatt, Kevin P; Gaedigk, Andrea

    2015-01-01

    TaqMan™ genotyping assays are widely used to genotype CYP2D6, which encodes a major drug metabolizing enzyme. Assay design for CYP2D6 can be challenging owing to the presence of two pseudogenes, CYP2D7 and CYP2D8, structural and copy number variation and numerous single nucleotide polymorphisms (SNPs) some of which reflect the wild-type sequence of the CYP2D7 pseudogene. The aim of this study was to identify the mechanism causing false-positive CYP2D6 (*) 15 calls and remediate those by redesigning and validating alternative TaqMan genotype assays. Among 13,866 DNA samples genotyped by the CompanionDx® lab on the OpenArray platform, 70 samples were identified as heterozygotes for 137Tins, the key SNP of CYP2D6 (*) 15. However, only 15 samples were confirmed when tested with the Luminex xTAG CYP2D6 Kit and sequencing of CYP2D6-specific long range (XL)-PCR products. Genotype and gene resequencing of CYP2D6 and CYP2D7-specific XL-PCR products revealed a CC>GT dinucleotide SNP in exon 1 of CYP2D7 that reverts the sequence to CYP2D6 and allows a TaqMan assay PCR primer to bind. Because CYP2D7 also carries a Tins, a false-positive mutation signal is generated. This CYP2D7 SNP was also responsible for generating false-positive signals for rs769258 (CYP2D6 (*) 35) which is also located in exon 1. Although alternative CYP2D6 (*) 15 and (*) 35 assays resolved the issue, we discovered a novel CYP2D6 (*) 15 subvariant in one sample that carries additional SNPs preventing detection with the alternate assay. The frequency of CYP2D6 (*) 15 was 0.1% in this ethnically diverse U.S. population sample. In addition, we also discovered linkage between the CYP2D7 CC>GT dinucleotide SNP and the 77G>A (rs28371696) SNP of CYP2D6 (*) 43. The frequency of this tentatively functional allele was 0.2%. Taken together, these findings emphasize that regardless of how careful genotyping assays are designed and evaluated before being commercially marketed, rare or unknown SNPs underneath primer

  1. Fabrication of hexagonally patterned flower-like silver particle arrays as surface-enhanced Raman scattering substrates

    NASA Astrophysics Data System (ADS)

    Tang, Haibin; Zheng, Peng; Meng, Guowen; Li, Zhongbo; Zhu, Chuhong; Han, Fangming; Ke, Yan; Wang, Zhaoming; Zhou, Fei; Wu, Nianqiang

    2016-08-01

    Hierarchical assembly of plasmonic nanostructures can induce high surface-enhanced Raman scattering (SERS) activity. However, it is a challenge to uniformly disperse the hierarchical nanostructures onto a planar substrate to achieve SERS signal reproducibility. This report presents a facile route to fabricate a hexagonally patterned flower-like silver particle array as the SERS substrate. First, hexagonally ordered silver hemisphere arrays with smooth surface are molded in the pores of an anodic aluminum oxide template. Ag-nanosheets are then electrodeposited onto the surface of individual silver hemispheres. The numerous nano-edges and nano-gaps between adjacent nanosheets render a large number of hot spots, leading to high SERS activity over a larger area of chip. The silver flower-like array is employed as the SERS substrate, which is able to detect 0.1 nM rhodamine 6 G and 1 μM 3,3’,4,4’-tetrachlorobiphenyl (PCB-77, a persistent organic pollutant).

  2. Fabrication of hexagonally patterned flower-like silver particle arrays as surface-enhanced Raman scattering substrates.

    PubMed

    Tang, Haibin; Zheng, Peng; Meng, Guowen; Li, Zhongbo; Zhu, Chuhong; Han, Fangming; Ke, Yan; Wang, Zhaoming; Zhou, Fei; Wu, Nianqiang

    2016-08-12

    Hierarchical assembly of plasmonic nanostructures can induce high surface-enhanced Raman scattering (SERS) activity. However, it is a challenge to uniformly disperse the hierarchical nanostructures onto a planar substrate to achieve SERS signal reproducibility. This report presents a facile route to fabricate a hexagonally patterned flower-like silver particle array as the SERS substrate. First, hexagonally ordered silver hemisphere arrays with smooth surface are molded in the pores of an anodic aluminum oxide template. Ag-nanosheets are then electrodeposited onto the surface of individual silver hemispheres. The numerous nano-edges and nano-gaps between adjacent nanosheets render a large number of hot spots, leading to high SERS activity over a larger area of chip. The silver flower-like array is employed as the SERS substrate, which is able to detect 0.1 nM rhodamine 6 G and 1 μM 3,3',4,4'-tetrachlorobiphenyl (PCB-77, a persistent organic pollutant). PMID:27363662

  3. Guided self-assembly of microgels: from particle arrays to anisotropic nanostructures

    SciTech Connect

    Hiltl, Stephanie; Schürings, Marco-Philipp; Balaceanu, Andreea; Mayorga, Veronika; Liedel, Clemens; Pich, Andrij; Böker, Alexander

    2012-01-06

    We investigate the guided large scale self-assembly of microgels consisting of N-vinylcaprolactam (VCL), N-isopropylacrylamide (NiPAAm) and acetoacetoxyethyl methacrylate (AAEM) using nanostructured substrates fabricated via controlled wrinkling. Depending on the type of microgel, the arrangement in the grooves of the substrates influences the particle shape and the overall pattern formation. Thus we obtain straight lines composed of single particles as well as zigzag-structures. In an additional processing step, we use the nanostructured substrates as stamps to transfer the formed microgel patterns onto a planar support. Subsequent UV-crosslinking of the microgel strings yields anisotropic particles.

  4. Comparative particle recoveries by the retracting rotorod, rotoslide and Burkard spore trap sampling in a compact array

    NASA Astrophysics Data System (ADS)

    Solomon, W. R.; Burge, H. A.; Boise, J. R.; Becker, M.

    1980-06-01

    An array comprising 4 intermittent (retracting) rotorods, 3 (“swingshield”) rotoslides and one Burkard (Hirst) automatic volumetric spore trap was operated on an urban rooftop during 70 periods of 9, 15 or 24 hours in late summer. Standard sampling procedures were utilized and recoveries of pollens as well as spores of Alternaria, Epicoccum, Pithomyces and Ganoderma species compared. Differences between paired counts from each sampler type showed variances increasing with levels of particle prevalence (and deposition). In addition, minimal, non-random, side-to-side and intersampler differences were noted for both impactor types. Exclusion of particles between operating intervals by rotoslides and rotorods was virtually complete. Spore trap recoveries for all particle categories, per m3, exceeded those by both impactors. The greatest (7-fold) difference was noted for the smallest type examined ( Ganoderma). For ragweed pollen, an overall spore trap/impactor ratio approached 1.5. Rain effects were difficult to discern but seemed to influence rotoslides least. Overall differences between impactors were quite small but generally favored the rotoslide in this comparison. Our data confirm the relative advantages of suction traps for small particles. Both impactors and spore traps are suited to pollen and large spore collection, and, with some qualification, data from both may be compared.

  5. Efficient design, accurate fabrication and effective characterization of plasmonic quasicrystalline arrays of nano-spherical particles

    PubMed Central

    Namin, Farhad A.; Yuwen, Yu A.; Liu, Liu; Panaretos, Anastasios H.; Werner, Douglas H.; Mayer, Theresa S.

    2016-01-01

    In this paper, the scattering properties of two-dimensional quasicrystalline plasmonic lattices are investigated. We combine a newly developed synthesis technique, which allows for accurate fabrication of spherical nanoparticles, with a recently published variation of generalized multiparticle Mie theory to develop the first quantitative model for plasmonic nano-spherical arrays based on quasicrystalline morphologies. In particular, we study the scattering properties of Penrose and Ammann- Beenker gold spherical nanoparticle array lattices. We demonstrate that by using quasicrystalline lattices, one can obtain multi-band or broadband plasmonic resonances which are not possible in periodic structures. Unlike previously published works, our technique provides quantitative results which show excellent agreement with experimental measurements. PMID:26911709

  6. Ultrafast 2D IR microscopy

    PubMed Central

    Baiz, Carlos R.; Schach, Denise; Tokmakoff, Andrei

    2014-01-01

    We describe a microscope for measuring two-dimensional infrared (2D IR) spectra of heterogeneous samples with μm-scale spatial resolution, sub-picosecond time resolution, and the molecular structure information of 2D IR, enabling the measurement of vibrational dynamics through correlations in frequency, time, and space. The setup is based on a fully collinear “one beam” geometry in which all pulses propagate along the same optics. Polarization, chopping, and phase cycling are used to isolate the 2D IR signals of interest. In addition, we demonstrate the use of vibrational lifetime as a contrast agent for imaging microscopic variations in molecular environments. PMID:25089490

  7. Dynamics of self-driven and flocking particles on periodic arrays

    NASA Astrophysics Data System (ADS)

    Drocco, J.; Lopatina, L. M.; Reichhardt, C.; Olson Reichhardt, C. J.

    2012-10-01

    Recently there has been growing interest in what is called active matter, or collections of particles that are self driven rather than driven with an external field. Examples of such systems include swimming bacteria, flocks of birds or fish, and pedestrian flow. There have also been recent experimental realizations of self-driven systems using colloidal particles undergoing self-catalytic interactions. One example of this is light-induced catalysis where the colloids become self-driven in the presence of light. Almost all of these studies have been performed in the absence of a substrate. Here we examine how a substrate can be used to direct the motion of the particles. We demonstrate a self-induced ratchet effect that occurs in the presence of disorder as well as the direction of the particle along symmetry directions of the substrate. The type of substrate we consider may be created using various optical techniques, and studies of this system could lead to insights into the nonequilibrium behavior of active matter as well as to applications such as sorting of different active particle species or of active and non-active particles.

  8. AnisWave 2D

    2004-08-01

    AnisWave2D is a 2D finite-difference code for a simulating seismic wave propagation in fully anisotropic materials. The code is implemented to run in parallel over multiple processors and is fully portable. A mesh refinement algorithm has been utilized to allow the grid-spacing to be tailored to the velocity model, avoiding the over-sampling of high-velocity materials that usually occurs in fixed-grid schemes.

  9. Measurement of Temperature, Density, and Particle Transport with Localized Dopants in Wire-Array Z Pinches

    SciTech Connect

    Jones, B.; Deeney, C.; McKenney, J. L.; Ampleford, D. J.; Coverdale, C. A.; LePell, P. D.; Shelton, K. P.; Safronova, A. S.; Kantsyrev, V. L.; Osborne, G.; Sotnikov, V. I.; Ivanov, V. V.; Fedin, D.; Nalajala, V.; Yilmaz, F.; Shrestha, I.

    2008-03-14

    Axially localized NaF dopants are coated onto Al cylindrical wire arrays in order to act as spectroscopic tracers in the stagnated z-pinch plasma. Non-local-thermodynamic-equilibrium kinetic models fit to Na K-shell lines provide an independent measurement of the density and temperature that is consistent with spectroscopic analysis of K-shell emissions from Al and an alloyed Mg dopant. Axial transport of the Na dopant is observed, enabling quantitative study of instabilities in dense z-pinch plasmas.

  10. Rectification of swimming bacteria and self-driven particle systems by arrays of asymmetric barriers.

    PubMed

    Wan, M B; Olson Reichhardt, C J; Nussinov, Z; Reichhardt, C

    2008-07-01

    We show that the recent experimental observation of the rectification of swimming bacteria in a system with an array of asymmetric barriers occurs due to the ballistic component of the bacteria trajectories introduced by the bacterial "motor." Each bacterium selects a random direction for motion and then moves in this direction for a fixed period of time before randomly changing its orientation and moving in a new direction. In the limit where the bacteria undergo only Brownian motion on the size scale of the barriers, rectification does not occur. We examine the effects of steric interactions between the bacteria and observe a clogging effect upon increasing the bacteria density. PMID:18764155

  11. Plasmon-enhanced enzyme-linked immunosorbent assay on large arrays of individual particles made by electron beam lithography.

    PubMed

    Chen, Si; Svedendahl, Mikael; Antosiewicz, Tomasz J; Käll, Mikael

    2013-10-22

    Ultrasensitive biosensing is one of the main driving forces behind the dynamic research field of plasmonics. We have previously demonstrated that the sensitivity of single nanoparticle plasmon spectroscopy can be greatly enhanced by enzymatic amplification of the refractive index footprint of individual protein molecules, so-called plasmon-enhanced enzyme-linked immunosorbent assay (ELISA). The technique, which is based on generation of an optically dense precipitate catalyzed by horseradish peroxidase at the metal surface, allowed for colorimetric analysis of ultralow molecular surface coverages with a limit of detection approaching the single molecule limit. However, the plasmonic response induced by a single enzyme can be expected to vary for a number of reasons, including inhomogeneous broadening of the sensing properties of individual particles, variation in electric field enhancement over the surface of a single particle and variation in size and morphology of the enzymatic precipitate. In this report, we discuss how such inhomogeneities affect the possibility to quantify the number of molecules bound to a single nanoparticle. The discussion is based on simulations and measurements of large arrays of well-separated gold nanoparticles fabricated by electron beam lithography (EBL). The new data confirms the intrinsic single-molecule sensitivity of the technique but we were not able to clearly resolve the exact number of adsorbed molecules per single particle. The results indicate that the main sources of uncertainty come from variations in sensitivity across the surface of individual particles and between different particles. There is also a considerable uncertainty in the actual precipitate morphology produced by individual enzyme molecules. Possible routes toward further improvements of the methodology are discussed.

  12. Optimization of the particle density to maximize the SERS enhancement factor of periodic plasmonic nanostructure array.

    PubMed

    Wei, Shuhua; Zheng, Mengjie; Xiang, Quan; Hu, Hailong; Duan, Huigao

    2016-09-01

    Low-cost surface-enhanced Raman scattering (SERS) substrate with the largest possible enhancement factor is highly desirable for SERS-based sensing applications. In this work, we systematically investigated how the density of plasmonic nanostructures affects the intensity of SERS signal. By directly depositing of metallic layer on electron-beam-lithography defined dielectric nanoposts, plasmonic structures array with different densities were reliably fabricated for SERS measurements. Two main experimental phenomena were obtained: (1) the SERS intensity did not increase monotonically when increasing the density of plasmonic structures, and (2) these ultra-dense plasmonic structures resulted in the maximal SERS intensity. These results could be well explained based on finite-difference time domain (FDTD) simulations and provide robust experimental evidences to guide the design of the best possible SERS substrate. PMID:27607665

  13. Polystyrene Core-Silica Shell Particles with Defined Nanoarchitectures as a Versatile Platform for Suspension Array Technology.

    PubMed

    Sarma, Dominik; Gawlitza, Kornelia; Rurack, Knut

    2016-04-19

    The need for rapid and high-throughput screening in analytical laboratories has led to significant growth in interest in suspension array technologies (SATs), especially with regard to cytometric assays targeting a low to medium number of analytes. Such SAT or bead-based assays rely on spherical objects that constitute the analytical platform. Usually, functionalized polymer or silica (SiO2) microbeads are used which each have distinct advantages and drawbacks. In this paper, we present a straightforward synthetic route to highly monodisperse SiO2-coated polystyrene core-shell (CS) beads for SAT with controllable architectures from smooth to raspberry- and multilayer-like shells by varying the molecular weight of poly(vinylpyrrolidone) (PVP), which was used as the stabilizer of the cores. The combination of both organic polymer core and a structurally controlled inorganic SiO2 shell in one hybrid particle holds great promises for flexible next-generation design of the spherical platform. The particles were characterized by electron microscopy (SEM, T-SEM, and TEM), thermogravimetry, flow cytometry, and nitrogen adsorption/desorption, offering comprehensive information on the composition, size, structure, and surface area. All particles show ideal cytometric detection patterns and facile handling due to the hybrid structure. The beads are endowed with straightforward modification possibilities through the defined SiO2 shells. We successfully implemented the particles in fluorometric SAT model assays, illustrating the benefits of tailored surface area which is readily available for small-molecule anchoring. Very promising assay performance was shown for DNA hybridization assays with quantification limits down to 8 fmol. PMID:27018430

  14. Spectral properties of a charged particle in antidot array: A limiting case of quantum billiard

    SciTech Connect

    Geyler, V.A.; Pavlov, B.S.; Popov, I.Y.

    1996-10-01

    A model of the periodic array of quantum antidots in the presence of a uniform magnetic field is suggested. The model can be conceived as a periodic lattice of resonators (curvilinear triangles) connected through {open_quote}{open_quote}infinitely small{close_quote}{close_quote} openings at the vertices of the triangles. The model Hamiltonian is obtained by means of operator extension theory in indefinite metric spaces. In the case of rational magnetic flux through an elementary cell of the lattice, the dispersion equation is found in an explicit form with the help of harmonic analysis on the magnetic translation group. It is proved, at least in the case of integer flux, that the spectrum of the model Hamiltonian consists of three parts: (1) Landau levels (they correspond to the classical orbits lying between antidots); (2) extended states that correspond to the classical propagation trajectories; and (3) bound states satisfying the dispersion equation; they correspond to the classical chaotic orbits rotating around single antidots. Among other things, methods of finding the Green{close_quote}s function for some planar domains with curvilinear boundaries are derived. {copyright} {ital 1996 American Institute of Physics.}

  15. Functionalized Polymer Microgel Particles Enable Customizable Production of Label-Free Sensor Arrays

    PubMed Central

    Lifson, Mark A.; Carter, Jared A.; Miller, Benjamin L.

    2015-01-01

    Probe molecule immobilization onto surfaces is a critical step in the production of many analytical devices, including labeled and label-free microarrays. New methods to increase the density and uniformity of probe deposition have the potential to significantly enhance the ultimate limits of detection and reproducibility. Hydrogel-based materials have been employed in the past to provide a 3D protein-friendly surface for deposition of antibodies and nucleic acids. However, these methods are susceptible to variation during polymerization of the hydrogel scaffold, and provide limited opportunities for tuning deposition parameters on an antibody-by-antibody basis. In this work, a versatile hydrogel nanoparticle deposition method was developed for the production of label-free microarrays, and tested in the context of antibody-antigen binding. Poly (N-isopropylacrylamide) nanoparticles (PNIPAM) were conjugated to antibodies using an avidin/biotin system and deposited onto surfaces using a noncontact printing system. After drying, these gel spots formed uniform and thin layers < 10 nm in height. The conjugates were characterized with dynamic light scattering, scanning electron microscopy, and atomic force microscopy. We tested this format in the context of tumor necrosis factor-alpha (TNF-α) detection via Arrayed Imaging Reflectometry (AIR), a label-free protein microarray method. This method of probe molecule deposition should be generally useful in the production of microarrays for label-free detection. PMID:26140413

  16. Sensitivity of the Cherenkov Telescope Array to the detection of axion-like particles at high gamma-ray opacities

    SciTech Connect

    Meyer, Manuel; Conrad, Jan E-mail: conrad@fysik.su.se

    2014-12-01

    Extensions of the Standard Model of particles commonly predict the existence of axion(-like) particles (ALPs) that could be detected through their coupling to photons in external magnetic fields. This coupling could lead to modifications of γ-ray spectra from extragalactic sources. Above a certain energy, the γ-ray flux should be exponentially damped due to the interaction with photons of background radiations fields. ALPs, on the other hand, propagate unimpeded over cosmological distances and a reconversion into γ-rays could lead to an additional component in the spectra. Here, we present the sensitivity of the proposed Cherenkov Telescope Array (CTA) to detect this spectral hardening. Using the full instrumental response functions of CTA, a combined likelihood analysis of four γ-ray sources shows that a significant detection of the ALP signal is possible for couplings g{sub aγ} ≳ 2 × 10{sup −11} GeV{sup −1} and ALP masses m{sub a} ∼< 100 neV. We discuss the dependency of these values on different model assumptions and magnetic-field scenarios and identify the best observation strategy to search for an ALP induced boost of the γ-ray flux.

  17. DYNA2D96. Explicit 2-D Hydrodynamic FEM Program

    SciTech Connect

    Whirley, R.G.

    1992-04-01

    DYNA2D is a vectorized, explicit, two-dimensional, axisymmetric and plane strain finite element program for analyzing the large deformation dynamic and hydrodynamic response of inelastic solids. DYNA2D contains 13 material models and 9 equations of state (EOS) to cover a wide range of material behavior. The material models implemented in all machine versions are: elastic, orthotropic elastic, kinematic/isotropic elastic plasticity, thermoelastoplastic, soil and crushable foam, linear viscoelastic, rubber, high explosive burn, isotropic elastic-plastic, temperature-dependent elastic-plastic. The isotropic and temperature-dependent elastic-plastic models determine only the deviatoric stresses. Pressure is determined by one of 9 equations of state including linear polynomial, JWL high explosive, Sack Tuesday high explosive, Gruneisen, ratio of polynomials, linear polynomial with energy deposition, ignition and growth of reaction in HE, tabulated compaction, and tabulated.

  18. Graphene suspensions for 2D printing

    NASA Astrophysics Data System (ADS)

    Soots, R. A.; Yakimchuk, E. A.; Nebogatikova, N. A.; Kotin, I. A.; Antonova, I. V.

    2016-04-01

    It is shown that, by processing a graphite suspension in ethanol or water by ultrasound and centrifuging, it is possible to obtain particles with thicknesses within 1-6 nm and, in the most interesting cases, 1-1.5 nm. Analogous treatment of a graphite suspension in organic solvent yields eventually thicker particles (up to 6-10 nm thick) even upon long-term treatment. Using the proposed ink based on graphene and aqueous ethanol with ethylcellulose and terpineol additives for 2D printing, thin (~5 nm thick) films with sheet resistance upon annealing ~30 MΩ/□ were obtained. With the ink based on aqueous graphene suspension, the sheet resistance was ~5-12 kΩ/□ for 6- to 15-nm-thick layers with a carrier mobility of ~30-50 cm2/(V s).

  19. Gold nanoparticle-protein arrays improve resolution for cryo-electron microscopy.

    PubMed

    Hu, Minghui; Qian, Luping; Briñas, Raymond P; Lymar, Elena S; Kuznetsova, Larisa; Hainfeld, James F

    2008-01-01

    Cryo-electron microscopy single particle analysis shows limited resolution due to poor alignment precision of noisy images taken under low electron exposure. Certain advantages can be obtained by assembling proteins into two-dimensional (2D) arrays since protein particles are locked into repetitive orientation, thus improving alignment precision. We present a labeling method to prepare protein 2D arrays using gold nanoparticles (NPs) interconnecting genetic tag sites on proteins. As an example, mycobacterium tuberculosis 20S proteasomes tagged with 6x-histidine were assembled into 2D arrays using 3.9-nm Au NPs functionalized with nickel-nitrilotriacetic acid. The averaged top-view images from the array particles showed higher resolution (by 6-8A) compared to analysis of single particles. The correct 7-fold symmetry was also evident by using array particles whereas it was not clear by analysis of a comparable number of single particles. The applicability of this labeling method for three-dimensional reconstruction of biological macromolecules is discussed.

  20. MOSS2D V1

    2001-01-31

    This software reduces the data from two-dimensional kSA MOS program, k-Space Associates, Ann Arbor, MI. Initial MOS data is recorded without headers in 38 columns, with one row of data per acquisition per lase beam tracked. The final MOSS 2d data file is reduced, graphed, and saved in a tab-delimited column format with headers that can be plotted in any graphing software.

  1. Tuning the Friction Characteristics of Gecko-Inspired Polydimethylsiloxane Micropillar Arrays by Embedding Fe₃O₄ and SiO₂ Particles.

    PubMed

    Tian, Ye; Zhao, Zizhou; Zaghi, Gina; Kim, Yongkwan; Zhang, Dongxing; Maboudian, Roya

    2015-06-24

    In order to improve stiffness of polydimethylsiloxane (PDMS) pillars while maintaining high friction, the effects of embedding Fe3O4 and SiO2 particles on the friction behavior of PDMS micropillars are studied. Both types of added particles increase the stiffness of the PDMS composite, but affect the friction behavior differently. The frictional force of the fibrillar array fabricated with Fe3O4/PDMS composite decreases initially, then increases as the particle content increases. For silica/PDMS composite pillars, the frictional force is independent of the particle density. Characterization by scanning electron microscopy shows that Fe3O4 particles are distributed uniformly in the PDMS matrix at low concentration, but heterogeneous distribution is observed at high particle loading, with particles being hindered from penetrating into the pillars. For silica/PDMS composite pillars, the particles distribute homogeneously inside the pillars, which is attributed to the formation of hydrogen bonding between silica particles and PDMS. The difference in particle distribution behavior is used to explain the observed difference in the friction response of these two composite systems.

  2. Tuning the Friction Characteristics of Gecko-Inspired Polydimethylsiloxane Micropillar Arrays by Embedding Fe₃O₄ and SiO₂ Particles.

    PubMed

    Tian, Ye; Zhao, Zizhou; Zaghi, Gina; Kim, Yongkwan; Zhang, Dongxing; Maboudian, Roya

    2015-06-24

    In order to improve stiffness of polydimethylsiloxane (PDMS) pillars while maintaining high friction, the effects of embedding Fe3O4 and SiO2 particles on the friction behavior of PDMS micropillars are studied. Both types of added particles increase the stiffness of the PDMS composite, but affect the friction behavior differently. The frictional force of the fibrillar array fabricated with Fe3O4/PDMS composite decreases initially, then increases as the particle content increases. For silica/PDMS composite pillars, the frictional force is independent of the particle density. Characterization by scanning electron microscopy shows that Fe3O4 particles are distributed uniformly in the PDMS matrix at low concentration, but heterogeneous distribution is observed at high particle loading, with particles being hindered from penetrating into the pillars. For silica/PDMS composite pillars, the particles distribute homogeneously inside the pillars, which is attributed to the formation of hydrogen bonding between silica particles and PDMS. The difference in particle distribution behavior is used to explain the observed difference in the friction response of these two composite systems. PMID:26042962

  3. Cross-correlation focus method with an electrostatic sensor array for local particle velocity measurement in dilute gas-solid two-phase flow

    NASA Astrophysics Data System (ADS)

    Wang, Chao; Zhang, Jingyu; Gao, Wenbin; Ding, Hongbing; Wu, Weiping

    2015-11-01

    The gas-solid two-phase flow has been widely applied in the power, chemical and metallurgical industries. It is of great significance in the research of gas-solid two-phase flow to measure particle velocity at different locations in the pipeline. Thus, an electrostatic sensor array comprising eight arc-shaped electrodes was designed. The relationship between the cross-correlation (CC) velocity and the distribution of particle velocity, charge density and electrode spatial sensitivity was analysed. Then the CC sensitivity and its calculation method were proposed. According to the distribution of CC sensitivity, it was found that, between different electrode pairs, it had different focus areas. The CC focus method was proposed for particle velocity measurement at different locations and validated by a belt-style electrostatic induction experiment facility. Finally, the particle velocities at different locations with different flow conditions were measured to research the particle velocity distribution in a dilute horizontal pneumatic conveying pipeline.

  4. Estimation of Acoustic Particle Motion and Source Bearing Using a Drifting Hydrophone Array Near a River Current Turbine to Assess Disturbances to Fish

    NASA Astrophysics Data System (ADS)

    Murphy, Paul G.

    River hydrokinetic turbines may be an economical alternative to traditional energy sources for small communities on Alaskan rivers. However, there is concern that sound from these turbines could affect sockeye salmon (Oncorhynchus nerka), an important resource for small, subsistence based communities, commercial fisherman, and recreational anglers. The hearing sensitivity of sockeye salmon has not been quantified, but behavioral responses to sounds at frequencies less than a few hundred Hertz have been documented for Atlantic salmon (Salmo salar), and particle motion is thought to be the primary mode of stimulation. Methods of measuring acoustic particle motion are well-established, but have rarely been necessary in energetic areas, such as river and tidal current environments. In this study, the acoustic pressure in the vicinity of an operating river current turbine is measured using a freely drifting hydrophone array. Analysis of turbine sound reveals tones that vary in frequency and magnitude with turbine rotation rate, and that may sockeye salmon may sense. In addition to pressure, the vertical components of particle acceleration and velocity are estimated by calculating the finite difference of the pressure signals from the hydrophone array. A method of determining source bearing using an array of hydrophones is explored. The benefits and challenges of deploying drifting hydrophone arrays for marine renewable energy converter monitoring are discussed.

  5. Fano-like resonance emerging from magnetic and electric plasmon mode coupling in small arrays of gold particles

    NASA Astrophysics Data System (ADS)

    Bakhti, Saïd; Tishchenko, Alexandre V.; Zambrana-Puyalto, Xavier; Bonod, Nicolas; Dhuey, Scott D.; Schuck, P. James; Cabrini, Stefano; Alayoglu, Selim; Destouches, Nathalie

    2016-09-01

    In this work we theoretically and experimentally analyze the resonant behavior of individual 3 × 3 gold particle oligomers illuminated under normal and oblique incidence. While this structure hosts both dipolar and quadrupolar electric and magnetic delocalized modes, only dipolar electric and quadrupolar magnetic modes remain at normal incidence. These modes couple into a strongly asymmetric spectral response typical of a Fano-like resonance. In the basis of the coupled mode theory, an analytical representation of the optical extinction in terms of singular functions is used to identify the hybrid modes emerging from the electric and magnetic mode coupling and to interpret the asymmetric line profiles. Especially, we demonstrate that the characteristic Fano line shape results from the spectral interference of a broad hybrid mode with a sharp one. This structure presents a special feature in which the electric field intensity is confined on different lines of the oligomer depending on the illumination wavelength relative to the Fano dip. This Fano-type resonance is experimentally observed performing extinction cross section measurements on arrays of gold nano-disks. The vanishing of the Fano dip when increasing the incidence angle is also experimentally observed in accordance with numerical simulations.

  6. Fabrication of a gel particle array in a microfluidic device for bioassays of protein and glucose in human urine samples.

    PubMed

    Lin, Ling; Gao, Zhaoxin; Wei, Huibin; Li, Haifang; Wang, Feng; Lin, Jin-Ming

    2011-09-01

    This paper describes a simple method for fabricating a series of poly(ethylene glycol) diacrylate (PEG-DA) hydrogel microstructures inside microfluidic channels as probe for proteins and glucose. In order to demonstrate the feasibility of this newly developed system, bovine serum albumin (BSA) was chosen as a model protein. PEG microcolumns were used for the parallel detection of multiple components. Using tetrabromophenol blue (TBPB) and the horseradish peroxidase/glucose oxidase reaction system, bovine serum albumin (BSA) and glucose in human urine were detected by color changes. The color changes for BSA within a concentration range of 1-150 μM, and glucose within a range of 50 mM-2 M could be directly distinguished by eyes or precisely identified by optical microscope. To show the practicability of the gel particle array, protein and glucose concentrations of real human urine samples were determined, resulting in a good correlation with hospital analysis. Notably, only a 5 µL sample was needed for a parallel measurement of both analytes. Conveniently, no special readout equipment or power source was required during the diagnosis process, which is promising for an application in rapid point-of-care diagnosis. PMID:22662039

  7. Particle gamma correlations in 12C measured with the CsI(Tl) based detector array CHIMERA

    NASA Astrophysics Data System (ADS)

    Cardella, G.; Acosta, L.; Amorini, F.; Auditore, L.; Berceanu, I.; Castoldi, A.; De Filippo, E.; Dell`Aquila, D.; Francalanza, L.; Gnoffo, B.; Guazzoni, C.; Lanzalone, G.; Lombardo, I.; Minniti, T.; Morgana, E.; Norella, S.; Pagano, A.; Pagano, E. V.; Papa, M.; Pirrone, S.; Politi, G.; Pop, A.; Quattrocchi, L.; Rizzo, F.; Rosato, E.; Russotto, P.; Trifirò, A.; Trimarchi, M.; Verde, G.; Vigilante, M.

    2015-11-01

    The gamma decay of the first excited 4.44 MeV 2+level of 12C, populated by inelastic scattering of proton and 16O beams at various energies was studied in order to test γ-ray detection efficiency and the quality of angular distribution information given by the CsI(Tl) detectors of the 4π CHIMERA array. The γ-decay was measured in coincidence with ejectile scattered particles in an approximately 4π geometry allowing to extract the angular distribution in the reference frame of recoiling 12C target. The typical sin2 (2θ) behavior of angular distribution was observed in the case of 16O beam. Besides that, for the proton beam, in order to explain the observed distribution, the addition of an incoherent flat contribution was required. This latter is the effect of proton spin flip events allowing the population of M=±1 magnetic substates, that is not possible in reactions induced by 16O beam. A comparison with previously collected data, obtained measuring only in and out of plane proton-γ-ray coincidences, confirms the good quality of the angular distribution information given by the apparatus. Possible applications with radioactive beams are outlined.

  8. Fano-like resonance emerging from magnetic and electric plasmon mode coupling in small arrays of gold particles.

    PubMed

    Bakhti, Saïd; Tishchenko, Alexandre V; Zambrana-Puyalto, Xavier; Bonod, Nicolas; Dhuey, Scott D; Schuck, P James; Cabrini, Stefano; Alayoglu, Selim; Destouches, Nathalie

    2016-01-01

    In this work we theoretically and experimentally analyze the resonant behavior of individual 3 × 3 gold particle oligomers illuminated under normal and oblique incidence. While this structure hosts both dipolar and quadrupolar electric and magnetic delocalized modes, only dipolar electric and quadrupolar magnetic modes remain at normal incidence. These modes couple into a strongly asymmetric spectral response typical of a Fano-like resonance. In the basis of the coupled mode theory, an analytical representation of the optical extinction in terms of singular functions is used to identify the hybrid modes emerging from the electric and magnetic mode coupling and to interpret the asymmetric line profiles. Especially, we demonstrate that the characteristic Fano line shape results from the spectral interference of a broad hybrid mode with a sharp one. This structure presents a special feature in which the electric field intensity is confined on different lines of the oligomer depending on the illumination wavelength relative to the Fano dip. This Fano-type resonance is experimentally observed performing extinction cross section measurements on arrays of gold nano-disks. The vanishing of the Fano dip when increasing the incidence angle is also experimentally observed in accordance with numerical simulations.

  9. A Northern Sky Survey for Point-like Sources of EeV Neutral Particles with the Telescope Array Experiment

    NASA Astrophysics Data System (ADS)

    Abbasi, R. U.; Abe, M.; Abu-Zayyad, T.; Allen, M.; Anderson, R.; Azuma, R.; Barcikowski, E.; Belz, J. W.; Bergman, D. R.; Blake, S. A.; Cady, R.; Chae, M. J.; Cheon, B. G.; Chiba, J.; Chikawa, M.; Cho, W. R.; Fujii, T.; Fukushima, M.; Goto, T.; Hanlon, W.; Hayashi, Y.; Hayashida, N.; Hibino, K.; Honda, K.; Ikeda, D.; Inoue, N.; Ishii, T.; Ishimori, R.; Ito, H.; Ivanov, D.; Jui, C. C. H.; Kadota, K.; Kakimoto, F.; Kalashev, O.; Kasahara, K.; Kawai, H.; Kawakami, S.; Kawana, S.; Kawata, K.; Kido, E.; Kim, H. B.; Kim, J. H.; Kim, J. H.; Kitamura, S.; Kitamura, Y.; Kuzmin, V.; Kwon, Y. J.; Lan, J.; Lim, S. I.; Lundquist, J. P.; Machida, K.; Martens, K.; Matsuda, T.; Matsuyama, T.; Matthews, J. N.; Minamino, M.; Mukai, K.; Myers, I.; Nagasawa, K.; Nagataki, S.; Nakamura, T.; Nonaka, T.; Nozato, A.; Ogio, S.; Ogura, J.; Ohnishi, M.; Ohoka, H.; Oki, K.; Okuda, T.; Ono, M.; Oshima, A.; Ozawa, S.; Park, I. H.; Pshirkov, M. S.; Rodriguez, D. C.; Rubtsov, G.; Ryu, D.; Sagawa, H.; Sakurai, N.; Sampson, A. L.; Scott, L. M.; Shah, P. D.; Shibata, F.; Shibata, T.; Shimodaira, H.; Shin, B. K.; Smith, J. D.; Sokolsky, P.; Springer, R. W.; Stokes, B. T.; Stratton, S. R.; Stroman, T. A.; Suzawa, T.; Takamura, M.; Takeda, M.; Takeishi, R.; Taketa, A.; Takita, M.; Tameda, Y.; Tanaka, H.; Tanaka, K.; Tanaka, M.; Thomas, S. B.; Thomson, G. B.; Tinyakov, P.; Tkachev, I.; Tokuno, H.; Tomida, T.; Troitsky, S.; Tsunesada, Y.; Tsutsumi, K.; Uchihori, Y.; Udo, S.; Urban, F.; Vasiloff, G.; Wong, T.; Yamane, R.; Yamaoka, H.; Yamazaki, K.; Yang, J.; Yashiro, K.; Yoneda, Y.; Yoshida, S.; Yoshii, H.; Zollinger, R.; Zundel, Z.

    2015-05-01

    We report on the search for steady point-like sources of neutral particles around 1018 eV between 2008 and 2013 May with the scintillator SD of the Telescope Array experiment. We found overall no significant point-like excess above 0.5 EeV in the northern sky. Subsequently, we also searched for coincidence with the Fermi bright Galactic sources. No significant coincidence was found within the statistical uncertainty. Hence, we set an upper limit on the neutron flux that corresponds to an averaged flux of 0.07 km-2 yr-1 for E\\gt 1 EeV in the northern sky at the 95% confidence level. This is the most stringent flux upper limit in a northern sky survey assuming point-like sources. The upper limit at the 95% confidence level on the neutron flux from Cygnus X-3 is also set to 0.2 km-2 yr-1 for E\\gt 0.5 EeV. This is an order of magnitude lower than previous flux measurements.

  10. Is Upregulation of Aquaporin 4-M1 Isoform Responsible for the Loss of Typical Orthogonal Arrays of Particles in Astrocytomas?

    PubMed Central

    Fallier-Becker, Petra; Nieser, Maike; Wenzel, Ulrike; Ritz, Rainer; Noell, Susan

    2016-01-01

    The astrocytic endfoot membranes of the healthy blood-brain barrier—contacting the capillary—are covered with a large number of the water channel aquaporin 4 (AQP4). They form orthogonal arrays of particles (OAPs), which consist of AQP4 isoform M1 and M23. Under pathologic conditions, AQP4 is distributed over the whole cell and no or only small OAPs are found. From cell culture experiments, it is known that cells transfected only with AQP4-M1 do not form OAPs or only small ones. We hypothesized that in astrocytomas the situation may be comparable to the in vitro experiments expecting an upregulation of AQP4-M1. Quantitative Real-time PCR (qRT-PCR) of different graded astrocytomas revealed an upregulation of both isoforms AQP4 M1 and M23 in all astrocytomas investigated. In freeze fracture replicas of low-grade malignancy astrocytomas, more OAPs than in high-grade malignancy astrocytomas were found. In vitro, cultured glioma cells did not express AQP4, whereas healthy astrocytes revealed a slight upregulation of both isoforms and only a few OAPs in freeze fracture analysis. Taken together, we found a correlation between the decrease of OAPs and increasing grade of malignancy of astrocytomas but this was not consistent with an upregulation of AQP4-M1 in relation to AQP4 M23. PMID:27483250

  11. Anisotropy test of the axion-like particle Universe opacity effect: a case for the Cherenkov Telescope Array

    SciTech Connect

    Wouters, Denis; Brun, Pierre E-mail: pierre.brun@cea.fr

    2014-01-01

    The opacity of the Universe to gamma rays is still poorly measured, in particular anomalies may have been observed. Assuming that such anomalies find their origin in conventional physics like intrinsic source spectra or the density of the extragalactic background light, they would be evenly distributed over the sky. If they exist, axion-like particles (ALPs) would have a potential effect on the opacity of the Universe to gamma rays, possibly related to the anomalies in the spectral indices of distant gamma-ray sources. Under the assumption that distant sources offer suitable environments for their production, ALPs convert back to photons in the Galactic magnetic field and their effect on the opacity is expected to depend on the position of the sources. In that case the anomaly is expected to exhibit peculiar correlations on the sky. We propose a method to test the origin of the opacity anomaly, based on angular correlations of spectral softening anomalies. Such a diagnosis requires a wide-field survey of high-energy gamma-ray sources over a broad range of energy. The future Cherenkov Telescope Array (CTA) is perfectly suited to perform such a study. It is shown that while the current sample of sources is not large enough to base conclusions on, with this method CTA will be sensitive to ALP couplings to gamma rays of the order of 3 × 10{sup −11}GeV{sup −1} for ALP masses below 10{sup −8} eV.

  12. Fano-like resonance emerging from magnetic and electric plasmon mode coupling in small arrays of gold particles

    PubMed Central

    Bakhti, Saïd; Tishchenko, Alexandre V.; Zambrana-Puyalto, Xavier; Bonod, Nicolas; Dhuey, Scott D.; Schuck, P. James; Cabrini, Stefano; Alayoglu, Selim; Destouches, Nathalie

    2016-01-01

    In this work we theoretically and experimentally analyze the resonant behavior of individual 3 × 3 gold particle oligomers illuminated under normal and oblique incidence. While this structure hosts both dipolar and quadrupolar electric and magnetic delocalized modes, only dipolar electric and quadrupolar magnetic modes remain at normal incidence. These modes couple into a strongly asymmetric spectral response typical of a Fano-like resonance. In the basis of the coupled mode theory, an analytical representation of the optical extinction in terms of singular functions is used to identify the hybrid modes emerging from the electric and magnetic mode coupling and to interpret the asymmetric line profiles. Especially, we demonstrate that the characteristic Fano line shape results from the spectral interference of a broad hybrid mode with a sharp one. This structure presents a special feature in which the electric field intensity is confined on different lines of the oligomer depending on the illumination wavelength relative to the Fano dip. This Fano-type resonance is experimentally observed performing extinction cross section measurements on arrays of gold nano-disks. The vanishing of the Fano dip when increasing the incidence angle is also experimentally observed in accordance with numerical simulations. PMID:27580515

  13. Fano-like resonance emerging from magnetic and electric plasmon mode coupling in small arrays of gold particles.

    PubMed

    Bakhti, Saïd; Tishchenko, Alexandre V; Zambrana-Puyalto, Xavier; Bonod, Nicolas; Dhuey, Scott D; Schuck, P James; Cabrini, Stefano; Alayoglu, Selim; Destouches, Nathalie

    2016-01-01

    In this work we theoretically and experimentally analyze the resonant behavior of individual 3 × 3 gold particle oligomers illuminated under normal and oblique incidence. While this structure hosts both dipolar and quadrupolar electric and magnetic delocalized modes, only dipolar electric and quadrupolar magnetic modes remain at normal incidence. These modes couple into a strongly asymmetric spectral response typical of a Fano-like resonance. In the basis of the coupled mode theory, an analytical representation of the optical extinction in terms of singular functions is used to identify the hybrid modes emerging from the electric and magnetic mode coupling and to interpret the asymmetric line profiles. Especially, we demonstrate that the characteristic Fano line shape results from the spectral interference of a broad hybrid mode with a sharp one. This structure presents a special feature in which the electric field intensity is confined on different lines of the oligomer depending on the illumination wavelength relative to the Fano dip. This Fano-type resonance is experimentally observed performing extinction cross section measurements on arrays of gold nano-disks. The vanishing of the Fano dip when increasing the incidence angle is also experimentally observed in accordance with numerical simulations. PMID:27580515

  14. The red-shift of surface plasmon absorption of 2D nanogold arrangement from disordered to ordered.

    PubMed

    Tang, Junke; Li, Jinru; Rong, Huiling; Zou, Bingsuo; Jiang, Long

    2008-01-01

    In this article, the changing of surface plasmon resonance (SPR) absorption of 2D arrangement of Au (3 nm) nanoparticles coated with 1-dodecanethiol (C12H25SH), obtained at different desolvation extents, had been investigated. It has been found that an obvious red-shifted happened when these arrays changed from loose, disordered to close-packed and ordered. Both transmission electron microscopy pictures and variation of SPR absorption of these arrays showed that the formation of long range two-dimension (2D) arrangement of nanoparticles coated with C12H25SH might be involved in two stages: At the first stage the particles can move freely and random patterns from loose to close package was driven by the Brownian Movement of solvated particles and as a result the voids were eliminated. The red shift of SPR absorption with the coverage (d lamda/d theta) is relative low. At the second stage, where the particles cannot move freely because of lack of solvent and a long-range two-dimension crystal was formed, the SPR shift to a longer wavelength with a larger d lamda/d theta. It is mainly attributed to the strong increase of the orientation and dipolar moment of the absorbed C12H25SH molecule on nanoparticles.

  15. Practical Algorithm For Computing The 2-D Arithmetic Fourier Transform

    NASA Astrophysics Data System (ADS)

    Reed, Irving S.; Choi, Y. Y.; Yu, Xiaoli

    1989-05-01

    Recently, Tufts and Sadasiv [10] exposed a method for computing the coefficients of a Fourier series of a periodic function using the Mobius inversion of series. They called this method of analysis the Arithmetic Fourier Transform(AFT). The advantage of the AFT over the FN 1' is that this method of Fourier analysis needs only addition operations except for multiplications by scale factors at one stage of the computation. The disadvantage of the AFT as they expressed it originally is that it could be used effectively only to compute finite Fourier coefficients of a real even function. To remedy this the AFT developed in [10] is extended in [11] to compute the Fourier coefficients of both the even and odd components of a periodic function. In this paper, the improved AFT [11] is extended to a two-dimensional(2-D) Arithmetic Fourier Transform for calculating the Fourier Transform of two-dimensional discrete signals. This new algorithm is based on both the number-theoretic method of Mobius inversion of double series and the complex conjugate property of Fourier coefficients. The advantage of this algorithm over the conventional 2-D FFT is that the corner-turning problem needed in a conventional 2-D Discrete Fourier Transform(DFT) can be avoided. Therefore, this new 2-D algorithm is readily suitable for VLSI implementation as a parallel architecture. Comparing the operations of 2-D AFT of a MxM 2-D data array with the conventional 2-D FFT, the number of multiplications is significantly reduced from (2log2M)M2 to (9/4)M2. Hence, this new algorithm is faster than the FFT algorithm. Finally, two simulation results of this new 2-D AFT algorithm for 2-D artificial and real images are given in this paper.

  16. Development of a particle nanoimprinting technique by core-shell particles.

    PubMed

    Watanabe, H; Nishimura, M; Fukui, Y; Fujimoto, K

    2014-02-18

    We developed a particle nanoimprinting technique assisted by the array of core-shell particles. Core-shell particles composed of a solid core of polystyrene and a soft shell were prepared by soap-free emulsion polymerization and subsequently seeded polymerization. By the Langmuir-Blodgett method, particles were arranged into a closely packed 2D array over the water surface and transferred onto a polystyrene (PS) substrate at a regular interval. The PS substrate was heated up above its glass transition temperature (Tg) by either UV irradiation using a high-pressure Hg lamp or heat treatment in a temperature-controlled incubator. It could be observed that a nanopatterned indented surface was formed through the denting of particles into the PS substrate (particle nanoindenting). By the detachment of particles from the substrate by ultrasonication in ethanol, nanoholes were produced over the surface (particle nanoimprinting). The depth and the wall of nanoholes and their interval were tunable by the shell thickness and the 2D packing ratio of core-shell particle monolayers. The contact angle decreased from 70 degrees of the pristine particle monolayer to 13 degrees by the particle nanoindenting, and again increased to 50 degrees by detaching the particles from the substrate to create the nanoholes. The use of nanoholes as zepto-litter volume vessels enabled us to produce and arrange nanocrystals, such as NaCl and CaCO3 (zepto-reactor).

  17. Development of a particle nanoimprinting technique by core-shell particles.

    PubMed

    Watanabe, H; Nishimura, M; Fukui, Y; Fujimoto, K

    2014-02-18

    We developed a particle nanoimprinting technique assisted by the array of core-shell particles. Core-shell particles composed of a solid core of polystyrene and a soft shell were prepared by soap-free emulsion polymerization and subsequently seeded polymerization. By the Langmuir-Blodgett method, particles were arranged into a closely packed 2D array over the water surface and transferred onto a polystyrene (PS) substrate at a regular interval. The PS substrate was heated up above its glass transition temperature (Tg) by either UV irradiation using a high-pressure Hg lamp or heat treatment in a temperature-controlled incubator. It could be observed that a nanopatterned indented surface was formed through the denting of particles into the PS substrate (particle nanoindenting). By the detachment of particles from the substrate by ultrasonication in ethanol, nanoholes were produced over the surface (particle nanoimprinting). The depth and the wall of nanoholes and their interval were tunable by the shell thickness and the 2D packing ratio of core-shell particle monolayers. The contact angle decreased from 70 degrees of the pristine particle monolayer to 13 degrees by the particle nanoindenting, and again increased to 50 degrees by detaching the particles from the substrate to create the nanoholes. The use of nanoholes as zepto-litter volume vessels enabled us to produce and arrange nanocrystals, such as NaCl and CaCO3 (zepto-reactor). PMID:24446687

  18. Development of an Aquaporin-4 Orthogonal Array of Particle-Based ELISA for Neuromyelitis Optica Autoantibodies Detection

    PubMed Central

    Pisani, Francesco; Settanni, Paolo; Rosito, Stefania; Mola, Maria Grazia; Iorio, Raffaele; Tortorella, Carla; Ruggieri, Maddalena; Trojano, Maria; Svelto, Maria; Frigeri, Antonio; Nicchia, Grazia Paola

    2015-01-01

    Serological markers of Nuromyelitis Optica (NMO), an autoimmune disorder of the central nervous system, are autoantibodies targeting the astrocytic water channel aquaporin-4 (AQP4). We have previously demonstrated that the main epitopes for these autoantibodies (AQP4-IgG) are generated by the supramolecular arrangement of AQP4 tetramers into an Orthogonal Array of Particles (OAPs). Many tests have been developed to detect AQP4-IgG in patient sera but several procedural issues affect OAP assembly and consequently test sensitivity. To date, the protein based ELISA test shows the lowest sensitivity while representing a valid alternative to the more sensitive cell based assay (CBA), which, however, shows economic, technical and interpretation problems. Here we have developed a high perfomance ELISA in which native OAPs are used as the molecular target. To this aim a native size exclusion chromatography method has been developed to isolate integral, highly pure and AQP4-IgG-recognized OAPs from rat brain. These OAPs were immobilized and oriented on a plastic plate by a sandwich approach and 139 human sera were tested, including 67 sera from NMO patients. The OAP-ELISA showed a 99% specificity and a higher sensitivity (91%) compared to the CBA test. A comparative analysis revealed an end-point titer three orders of magnitude higher than the commercial ELISA and six times higher than our in-house CBA test. We show that CNS-extracted OAPs are crucial elements in order to perform an efficient AQP4-IgG test and the OAP-ELISA developed represents a valid alternative to the CBA currently used. PMID:26599905

  19. Interconnection of nanoparticles within 2D superlattices of PbS/oleic acid thin films.

    PubMed

    Simon, Paul; Bahrig, Lydia; Baburin, Igor A; Formanek, Petr; Röder, Falk; Sickmann, Jan; Hickey, Stephen G; Eychmüller, Alexander; Lichte, Hannes; Kniep, Rüdiger; Rosseeva, Elena

    2014-05-21

    Make it connected! 2D close-packed layers of inorganic nanoparticles are interconnected by organic fibrils of oleic acid as clearly visualized by electron holography. These fibrils can be mineralised by PbS to transform an organic-inorganic framework to a completely interconnected inorganic semiconducting 2D array.

  20. A 2-D ECE Imaging Diagnostic for TEXTOR

    NASA Astrophysics Data System (ADS)

    Wang, J.; Deng, B. H.; Domier, C. W.; Luhmann, H. Lu, Jr.

    2002-11-01

    A true 2-D extension to the UC Davis ECE Imaging (ECEI) concept is under development for installation on the TEXTOR tokamak in 2003. This combines the use of linear arrays with multichannel conventional wideband heterodyne ECE radiometers to provide a true 2-D imaging system. This is in contrast to current 1-D ECEI systems in which 2-D images are obtained through the use of multiple plasma discharges (varying the scanned emission frequency each discharge). Here, each array element of the 20 channel mixer array measures plasma emission at 16 simultaneous frequencies to form a 16x20 image of the plasma electron temperature Te. Correlation techniques can then be applied to any pair of the 320 image elements to study both radial and poloidal characteristics of turbulent Te fluctuations. The system relies strongly on the development of low cost, wideband (2-18 GHz) IF detection electronics for use in both ECE Imaging as well as conventional heterodyne ECE radiometry. System details, with a strong focus on the wideband IF electronics development, will be presented. *Supported by U.S. DoE Contracts DE-FG03-95ER54295 and DE-FG03-99ER54531.

  1. 3D Finite Element Analysis of Particle-Reinforced Aluminum

    NASA Technical Reports Server (NTRS)

    Shen, H.; Lissenden, C. J.

    2002-01-01

    Deformation in particle-reinforced aluminum has been simulated using three distinct types of finite element model: a three-dimensional repeating unit cell, a three-dimensional multi-particle model, and two-dimensional multi-particle models. The repeating unit cell model represents a fictitious periodic cubic array of particles. The 3D multi-particle (3D-MP) model represents randomly placed and oriented particles. The 2D generalized plane strain multi-particle models were obtained from planar sections through the 3D-MP model. These models were used to study the tensile macroscopic stress-strain response and the associated stress and strain distributions in an elastoplastic matrix. The results indicate that the 2D model having a particle area fraction equal to the particle representative volume fraction of the 3D models predicted the same macroscopic stress-strain response as the 3D models. However, there are fluctuations in the particle area fraction in a representative volume element. As expected, predictions from 2D models having different particle area fractions do not agree with predictions from 3D models. More importantly, it was found that the microscopic stress and strain distributions from the 2D models do not agree with those from the 3D-MP model. Specifically, the plastic strain distribution predicted by the 2D model is banded along lines inclined at 45 deg from the loading axis while the 3D model prediction is not. Additionally, the triaxial stress and maximum principal stress distributions predicted by 2D and 3D models do not agree. Thus, it appears necessary to use a multi-particle 3D model to accurately predict material responses that depend on local effects, such as strain-to-failure, fracture toughness, and fatigue life.

  2. On the current drive capability of low dimensional semiconductors: 1D versus 2D

    DOE PAGES

    Zhu, Y.; Appenzeller, J.

    2015-10-29

    Low-dimensional electronic systems are at the heart of many scaling approaches currently pursuit for electronic applications. Here, we present a comparative study between an array of one-dimensional (1D) channels and its two-dimensional (2D) counterpart in terms of current drive capability. Lastly, our findings from analytical expressions derived in this article reveal that under certain conditions an array of 1D channels can outperform a 2D field-effect transistor because of the added degree of freedom to adjust the threshold voltage in an array of 1D devices.

  3. On the Current Drive Capability of Low Dimensional Semiconductors: 1D versus 2D.

    PubMed

    Zhu, Y; Appenzeller, J

    2015-12-01

    Low-dimensional electronic systems are at the heart of many scaling approaches currently pursuit for electronic applications. Here, we present a comparative study between an array of one-dimensional (1D) channels and its two-dimensional (2D) counterpart in terms of current drive capability. Our findings from analytical expressions derived in this article reveal that under certain conditions an array of 1D channels can outperform a 2D field-effect transistor because of the added degree of freedom to adjust the threshold voltage in an array of 1D devices.

  4. Radar chart array analysis to visualize effects of formulation variables on IgG1 particle formation as measured by multiple analytical techniques.

    PubMed

    Kalonia, Cavan; Kumru, Ozan S; Kim, Jae Hyun; Middaugh, C Russell; Volkin, David B

    2013-12-01

    This study presents a novel method to visualize protein aggregate and particle formation data to rapidly evaluate the effect of solution and stress conditions on the physical stability of an immunoglobulin G (IgG) 1 monoclonal antibody (mAb). Radar chart arrays were designed so that hundreds of microflow digital imaging (MFI) solution measurements, evaluating different mAb formulations under varying stresses, could be presented in a single figure with minimal loss of data resolution. These MFI radar charts show measured changes in subvisible particle number, size, and morphology distribution as a change in the shape of polygons. Radar charts were also created to visualize mAb aggregate and particle formation across a wide size range by combining data sets from size-exclusion chromatography, Archimedes resonant mass measurements, and MFI. We found that the environmental/mechanical stress condition (e.g., heat vs. agitation) was the most important factor in influencing the particle size and morphology distribution with this IgG1 mAb. Additionally, the presence of NaCl exhibited a pH and stress-dependent behavior resulting in promotion or inhibition mAb particle formation. This data visualization technique provides a comprehensive analysis of the aggregation tendencies of this IgG1 mAb in different formulations with varying stresses as measured by different analytical techniques. PMID:24122556

  5. Radar chart array analysis to visualize effects of formulation variables on IgG1 particle formation as measured by multiple analytical techniques.

    PubMed

    Kalonia, Cavan; Kumru, Ozan S; Kim, Jae Hyun; Middaugh, C Russell; Volkin, David B

    2013-12-01

    This study presents a novel method to visualize protein aggregate and particle formation data to rapidly evaluate the effect of solution and stress conditions on the physical stability of an immunoglobulin G (IgG) 1 monoclonal antibody (mAb). Radar chart arrays were designed so that hundreds of microflow digital imaging (MFI) solution measurements, evaluating different mAb formulations under varying stresses, could be presented in a single figure with minimal loss of data resolution. These MFI radar charts show measured changes in subvisible particle number, size, and morphology distribution as a change in the shape of polygons. Radar charts were also created to visualize mAb aggregate and particle formation across a wide size range by combining data sets from size-exclusion chromatography, Archimedes resonant mass measurements, and MFI. We found that the environmental/mechanical stress condition (e.g., heat vs. agitation) was the most important factor in influencing the particle size and morphology distribution with this IgG1 mAb. Additionally, the presence of NaCl exhibited a pH and stress-dependent behavior resulting in promotion or inhibition mAb particle formation. This data visualization technique provides a comprehensive analysis of the aggregation tendencies of this IgG1 mAb in different formulations with varying stresses as measured by different analytical techniques.

  6. Application of radar chart array analysis to visualize effects of formulation variables on IgG1 particle formation as measured by multiple analytical techniques

    PubMed Central

    Kalonia, Cavan; Kumru, Ozan S.; Kim, Jae Hyun; Middaugh, C. Russell; Volkin, David B.

    2013-01-01

    This study presents a novel method to visualize protein aggregate and particle formation data to rapidly evaluate the effect of solution and stress conditions on the physical stability of an IgG1 monoclonal antibody (mAb). Radar chart arrays were designed so that hundreds of Microflow Digital Imaging (MFI) solution measurements, evaluating different mAb formulations under varying stresses, could be presented in a single figure with minimal loss of data resolution. These MFI radar charts show measured changes in subvisible particle number, size and morphology distribution as a change in the shape of polygons. Radar charts were also created to visualize mAb aggregate and particle formation across a wide size range by combining data sets from size exclusion chromatography (SEC), Archimedes resonant mass measurements, and MFI. We found that the environmental/mechanical stress condition (e.g., heat vs. agitation) was the most important factor in influencing the particle size and morphology distribution with this IgG1 mAb. Additionally, the presence of NaCl exhibited a pH and stress dependent behavior resulting in promotion or inhibition mAb particle formation. This data visualization technique provides a comprehensive analysis of the aggregation tendencies of this IgG1 mAb in different formulations with varying stresses as measured by different analytical techniques. PMID:24122556

  7. Perspectives for spintronics in 2D materials

    NASA Astrophysics Data System (ADS)

    Han, Wei

    2016-03-01

    The past decade has been especially creative for spintronics since the (re)discovery of various two dimensional (2D) materials. Due to the unusual physical characteristics, 2D materials have provided new platforms to probe the spin interaction with other degrees of freedom for electrons, as well as to be used for novel spintronics applications. This review briefly presents the most important recent and ongoing research for spintronics in 2D materials.

  8. Quantitative 2D liquid-state NMR.

    PubMed

    Giraudeau, Patrick

    2014-06-01

    Two-dimensional (2D) liquid-state NMR has a very high potential to simultaneously determine the absolute concentration of small molecules in complex mixtures, thanks to its capacity to separate overlapping resonances. However, it suffers from two main drawbacks that probably explain its relatively late development. First, the 2D NMR signal is strongly molecule-dependent and site-dependent; second, the long duration of 2D NMR experiments prevents its general use for high-throughput quantitative applications and affects its quantitative performance. Fortunately, the last 10 years has witnessed an increasing number of contributions where quantitative approaches based on 2D NMR were developed and applied to solve real analytical issues. This review aims at presenting these recent efforts to reach a high trueness and precision in quantitative measurements by 2D NMR. After highlighting the interest of 2D NMR for quantitative analysis, the different strategies to determine the absolute concentrations from 2D NMR spectra are described and illustrated by recent applications. The last part of the manuscript concerns the recent development of fast quantitative 2D NMR approaches, aiming at reducing the experiment duration while preserving - or even increasing - the analytical performance. We hope that this comprehensive review will help readers to apprehend the current landscape of quantitative 2D NMR, as well as the perspectives that may arise from it.

  9. ELLIPT2D: A Flexible Finite Element Code Written Python

    SciTech Connect

    Pletzer, A.; Mollis, J.C.

    2001-03-22

    The use of the Python scripting language for scientific applications and in particular to solve partial differential equations is explored. It is shown that Python's rich data structure and object-oriented features can be exploited to write programs that are not only significantly more concise than their counter parts written in Fortran, C or C++, but are also numerically efficient. To illustrate this, a two-dimensional finite element code (ELLIPT2D) has been written. ELLIPT2D provides a flexible and easy-to-use framework for solving a large class of second-order elliptic problems. The program allows for structured or unstructured meshes. All functions defining the elliptic operator are user supplied and so are the boundary conditions, which can be of Dirichlet, Neumann or Robbins type. ELLIPT2D makes extensive use of dictionaries (hash tables) as a way to represent sparse matrices.Other key features of the Python language that have been widely used include: operator over loading, error handling, array slicing, and the Tkinter module for building graphical use interfaces. As an example of the utility of ELLIPT2D, a nonlinear solution of the Grad-Shafranov equation is computed using a Newton iterative scheme. A second application focuses on a solution of the toroidal Laplace equation coupled to a magnetohydrodynamic stability code, a problem arising in the context of magnetic fusion research.

  10. Integrated X-ray and charged particle active pixel CMOS sensor arrays using an epitaxial silicon sensitive region

    SciTech Connect

    Kleinfelder, Stuart; Bichsel, Hans; Bieser, Fred; Matis, Howard S.; Rai, Gulshan; Retiere, Fabrice; Weiman, Howard; Yamamoto, Eugene

    2002-07-01

    Integrated CMOS Active Pixel Sensor (APS) arrays have been fabricated and tested using X-ray and electron sources. The 128 by 128 pixel arrays, designed in a standard 0.25 micron process, use a {approx}10 micron epitaxial silicon layer as a deep detection region. The epitaxial layer has a much greater thickness than the surface features used by standard CMOS APS, leading to stronger signals and potentially better signal-to-noise ratio (SNR). On the other hand, minority carriers confined within the epitaxial region may diffuse to neighboring pixels, blur images and reduce peak signal intensity. But for low-rate, sparse-event images, centroid analysis of this diffusion may be used to increase position resolution. Careful trade-offs involving pixel size and sense-node area verses capacitance must be made to optimize overall performance. The prototype sensor arrays, therefore, include a range of different pixel designs, including different APS circuits and a range of different epitaxial layer contact structures. The fabricated arrays were tested with 1.5 GeV electrons and Fe-55 X-ray sources, yielding a measured noise of 13 electrons RMS and an SNR for single Fe-55 X-rays of greater than 38.

  11. Staring 2-D hadamard transform spectral imager

    DOEpatents

    Gentry, Stephen M.; Wehlburg, Christine M.; Wehlburg, Joseph C.; Smith, Mark W.; Smith, Jody L.

    2006-02-07

    A staring imaging system inputs a 2D spatial image containing multi-frequency spectral information. This image is encoded in one dimension of the image with a cyclic Hadamarid S-matrix. The resulting image is detecting with a spatial 2D detector; and a computer applies a Hadamard transform to recover the encoded image.

  12. 2D materials for nanophotonic devices

    NASA Astrophysics Data System (ADS)

    Xu, Renjing; Yang, Jiong; Zhang, Shuang; Pei, Jiajie; Lu, Yuerui

    2015-12-01

    Two-dimensional (2D) materials have become very important building blocks for electronic, photonic, and phononic devices. The 2D material family has four key members, including the metallic graphene, transition metal dichalcogenide (TMD) layered semiconductors, semiconducting black phosphorous, and the insulating h-BN. Owing to the strong quantum confinements and defect-free surfaces, these atomically thin layers have offered us perfect platforms to investigate the interactions among photons, electrons and phonons. The unique interactions in these 2D materials are very important for both scientific research and application engineering. In this talk, I would like to briefly summarize and highlight the key findings, opportunities and challenges in this field. Next, I will introduce/highlight our recent achievements. We demonstrated atomically thin micro-lens and gratings using 2D MoS2, which is the thinnest optical component around the world. These devices are based on our discovery that the elastic light-matter interactions in highindex 2D materials is very strong. Also, I would like to introduce a new two-dimensional material phosphorene. Phosphorene has strongly anisotropic optical response, which creates 1D excitons in a 2D system. The strong confinement in phosphorene also enables the ultra-high trion (charged exciton) binding energies, which have been successfully measured in our experiments. Finally, I will briefly talk about the potential applications of 2D materials in energy harvesting.

  13. Internal Photoemission Spectroscopy of 2-D Materials

    NASA Astrophysics Data System (ADS)

    Nguyen, Nhan; Li, Mingda; Vishwanath, Suresh; Yan, Rusen; Xiao, Shudong; Xing, Huili; Cheng, Guangjun; Hight Walker, Angela; Zhang, Qin

    Recent research has shown the great benefits of using 2-D materials in the tunnel field-effect transistor (TFET), which is considered a promising candidate for the beyond-CMOS technology. The on-state current of TFET can be enhanced by engineering the band alignment of different 2D-2D or 2D-3D heterostructures. Here we present the internal photoemission spectroscopy (IPE) approach to determine the band alignments of various 2-D materials, in particular SnSe2 and WSe2, which have been proposed for new TFET designs. The metal-oxide-2-D semiconductor test structures are fabricated and characterized by IPE, where the band offsets from the 2-D semiconductor to the oxide conduction band minimum are determined by the threshold of the cube root of IPE yields as a function of photon energy. In particular, we find that SnSe2 has a larger electron affinity than most semiconductors and can be combined with other semiconductors to form near broken-gap heterojunctions with low barrier heights which can produce a higher on-state current. The details of data analysis of IPE and the results from Raman spectroscopy and spectroscopic ellipsometry measurements will also be presented and discussed.

  14. 2D materials: to graphene and beyond.

    PubMed

    Mas-Ballesté, Rubén; Gómez-Navarro, Cristina; Gómez-Herrero, Julio; Zamora, Félix

    2011-01-01

    This review is an attempt to illustrate the different alternatives in the field of 2D materials. Graphene seems to be just the tip of the iceberg and we show how the discovery of alternative 2D materials is starting to show the rest of this iceberg. The review comprises the current state-of-the-art of the vast literature in concepts and methods already known for isolation and characterization of graphene, and rationalizes the quite disperse literature in other 2D materials such as metal oxides, hydroxides and chalcogenides, and metal-organic frameworks.

  15. Rheological Properties of Quasi-2D Fluids in Microgravity

    NASA Technical Reports Server (NTRS)

    Stannarius, Ralf; Trittel, Torsten; Eremin, Alexey; Harth, Kirsten; Clark, Noel; Maclennan, Joseph; Glaser, Matthew; Park, Cheol; Hall, Nancy; Tin, Padetha

    2015-01-01

    In recent years, research on complex fluids and fluids in restricted geometries has attracted much attention in the scientific community. This can be attributed not only to the development of novel materials based on complex fluids but also to a variety of important physical phenomena which have barely been explored. One example is the behavior of membranes and thin fluid films, which can be described by two-dimensional (2D) rheology behavior that is quite different from 3D fluids. In this study, we have investigated the rheological properties of freely suspended films of a thermotropic liquid crystal in microgravity experiments. This model system mimics isotropic and anisotropic quasi 2D fluids [46]. We use inkjet printing technology to dispense small droplets (inclusions) onto the film surface. The motion of these inclusions provides information on the rheological properties of the films and allows the study of a variety of flow instabilities. Flat films have been investigated on a sub-orbital rocket flight and curved films (bubbles) have been studied in the ISS project OASIS. Microgravity is essential when the films are curved in order to avoid sedimentation. The experiments yield the mobility of the droplets in the films as well as the mutual mobility of pairs of particles. Experimental results will be presented for 2D-isotropic (smectic-A) and 2D-nematic (smectic-C) phases.

  16. 2-d Finite Element Code Postprocessor

    1996-07-15

    ORION is an interactive program that serves as a postprocessor for the analysis programs NIKE2D, DYNA2D, TOPAZ2D, and CHEMICAL TOPAZ2D. ORION reads binary plot files generated by the two-dimensional finite element codes currently used by the Methods Development Group at LLNL. Contour and color fringe plots of a large number of quantities may be displayed on meshes consisting of triangular and quadrilateral elements. ORION can compute strain measures, interface pressures along slide lines, reaction forcesmore » along constrained boundaries, and momentum. ORION has been applied to study the response of two-dimensional solids and structures undergoing finite deformations under a wide variety of large deformation transient dynamic and static problems and heat transfer analyses.« less

  17. Matrix models of 2d gravity

    SciTech Connect

    Ginsparg, P.

    1991-01-01

    These are introductory lectures for a general audience that give an overview of the subject of matrix models and their application to random surfaces, 2d gravity, and string theory. They are intentionally 1.5 years out of date.

  18. Matrix models of 2d gravity

    SciTech Connect

    Ginsparg, P.

    1991-12-31

    These are introductory lectures for a general audience that give an overview of the subject of matrix models and their application to random surfaces, 2d gravity, and string theory. They are intentionally 1.5 years out of date.

  19. Brittle damage models in DYNA2D

    SciTech Connect

    Faux, D.R.

    1997-09-01

    DYNA2D is an explicit Lagrangian finite element code used to model dynamic events where stress wave interactions influence the overall response of the system. DYNA2D is often used to model penetration problems involving ductile-to-ductile impacts; however, with the advent of the use of ceramics in the armor-anti-armor community and the need to model damage to laser optics components, good brittle damage models are now needed in DYNA2D. This report will detail the implementation of four brittle damage models in DYNA2D, three scalar damage models and one tensor damage model. These new brittle damage models are then used to predict experimental results from three distinctly different glass damage problems.

  20. Laboratory Experiments On Continually Forced 2d Turbulence

    NASA Astrophysics Data System (ADS)

    Wells, M. G.; Clercx, H. J. H.; Van Heijst, G. J. F.

    There has been much recent interest in the advection of tracers by 2D turbulence in geophysical flows. While there is a large body of literature on decaying 2D turbulence or forced 2D turbulence in unbounded domains, there have been very few studies of forced turbulence in bounded domains. In this study we present new experimental results from a continuously forced quasi 2D turbulent field. The experiments are performed in a square Perspex tank filled with water. The flow is made quasi 2D by a steady background rotation. The rotation rate of the tank has a small (<8 %) sinusoidal perturbation which leads to the periodic formation of eddies in the corners of the tank. When the oscillation period of the perturbation is greater than an eddy roll-up time-scale, dipole structures are observed to form. The dipoles can migrate away from the walls, and the interior of the tank is continually filled with vortexs. From experimental visualizations the length scale of the vortexs appears to be largely controlled by the initial formation mechanism and large scale structures are not observed to form at large times. Thus the experiments provide a simple way of cre- ating a continuously forced 2D turbulent field. The resulting structures are in contrast with most previous laboratory experiments on 2D turbulence which have investigated decaying turbulence and have observed the formations of large scale structure. In these experiments, decaying turbulence had been produced by a variety of methods such as the decaying turbulence in the wake of a comb of rods (Massen et al 1999), organiza- tion of vortices in thin conducting liquids (Cardoso et al 1994) or in rotating systems where there are sudden changes in angular rotation rate (Konijnenberg et al 1998). Results of dye visualizations, particle tracking experiments and a direct numerical simulation will be presented and discussed in terms of their oceanographic application. Bibliography Cardoso,O. Marteau, D. &Tabeling, P

  1. Chemical Approaches to 2D Materials.

    PubMed

    Samorì, Paolo; Palermo, Vincenzo; Feng, Xinliang

    2016-08-01

    Chemistry plays an ever-increasing role in the production, functionalization, processing and applications of graphene and other 2D materials. This special issue highlights a selection of enlightening chemical approaches to 2D materials, which nicely reflect the breadth of the field and convey the excitement of the individuals involved in it, who are trying to translate graphene and related materials from the laboratory into a real, high-impact technology. PMID:27478083

  2. Chemical Approaches to 2D Materials.

    PubMed

    Samorì, Paolo; Palermo, Vincenzo; Feng, Xinliang

    2016-08-01

    Chemistry plays an ever-increasing role in the production, functionalization, processing and applications of graphene and other 2D materials. This special issue highlights a selection of enlightening chemical approaches to 2D materials, which nicely reflect the breadth of the field and convey the excitement of the individuals involved in it, who are trying to translate graphene and related materials from the laboratory into a real, high-impact technology.

  3. Wide-Field H2D+ Observations of Starless Cores

    NASA Astrophysics Data System (ADS)

    Di Francesco, James; Friesen, R.; Caselli, P.; Myers, P. C.; van der Tak, F. F. S.; Ceccarelli, C.

    2009-01-01

    In recent years, isolated starless cores have been revealed to have significant chemical differentiation with very low abundances of carbon-bearing molecules (such as CO and its isotopologues) in their cold, dense interiors. The inner regions of such cores, however, may be quite interesting, e.g., if contraction or collapse begins there. To explore these regions, we present detections of six isolated starless cores in the 110-111 line of H2D+ at 372 GHz using the new HARP instrument at the James Clerk Maxwell Telescope. Since the detection of this line requires very dry conditions on Mauna Kea (i.e., κ(225 GHz) < 0.05), only a multi-beam receiver system like the 4 X 4 HARP array can locate H2D+ emission across such cores in a practical amount of observing time. In all cases, the brightest line emission is coincident with the local peak of submillimeter continuum emission, but significant H2D+ emission is detected offset from the continuum peak in some. In addition, we describe the thermal and turbulent velocity fields in these cores revealed by these lines.

  4. Glitter in a 2D monolayer.

    PubMed

    Yang, Li-Ming; Dornfeld, Matthew; Frauenheim, Thomas; Ganz, Eric

    2015-10-21

    We predict a highly stable and robust atomically thin gold monolayer with a hexagonal close packed lattice stabilized by metallic bonding with contributions from strong relativistic effects and aurophilic interactions. We have shown that the framework of the Au monolayer can survive 10 ps MD annealing simulations up to 1400 K. The framework is also able to survive large motions out of the plane. Due to the smaller number of bonds per atom in the 2D layer compared to the 3D bulk we observe significantly enhanced energy per bond (0.94 vs. 0.52 eV per bond). This is similar to the increase in bond strength going from 3D diamond to 2D graphene. It is a non-magnetic metal, and was found to be the global minima in the 2D space. Phonon dispersion calculations demonstrate high kinetic stability with no negative modes. This 2D gold monolayer corresponds to the top monolayer of the bulk Au(111) face-centered cubic lattice. The close-packed lattice maximizes the aurophilic interactions. We find that the electrons are completely delocalized in the plane and behave as 2D nearly free electron gas. We hope that the present work can inspire the experimental fabrication of novel free standing 2D metal systems.

  5. 2d index and surface operators

    NASA Astrophysics Data System (ADS)

    Gadde, Abhijit; Gukov, Sergei

    2014-03-01

    In this paper we compute the superconformal index of 2d (2, 2) supersymmetric gauge theories. The 2d superconformal index, a.k.a. flavored elliptic genus, is computed by a unitary matrix integral much like the matrix integral that computes the 4d superconformal index. We compute the 2d index explicitly for a number of examples. In the case of abelian gauge theories we see that the index is invariant under flop transition and under CY-LG correspondence. The index also provides a powerful check of the Seiberg-type duality for non-abelian gauge theories discovered by Hori and Tong. In the later half of the paper, we study half-BPS surface operators in = 2 super-conformal gauge theories. They are engineered by coupling the 2d (2, 2) supersymmetric gauge theory living on the support of the surface operator to the 4d = 2 theory, so that different realizations of the same surface operator with a given Levi type are related by a 2d analogue of the Seiberg duality. The index of this coupled system is computed by using the tools developed in the first half of the paper. The superconformal index in the presence of surface defect is expected to be invariant under generalized S-duality. We demonstrate that it is indeed the case. In doing so the Seiberg-type duality of the 2d theory plays an important role.

  6. Verification of sub-grid filtered drag models for gas-particle fluidized beds with immersed cylinder arrays

    SciTech Connect

    Sarkar, Avik; Sun, Xin; Sundaresan, Sankaran

    2014-04-23

    The accuracy of coarse-grid multiphase CFD simulations of fluidized beds may be improved via the inclusion of filtered constitutive models. In our previous study (Sarkar et al., Chem. Eng. Sci., 104, 399-412), we developed such a set of filtered drag relationships for beds with immersed arrays of cooling tubes. Verification of these filtered drag models is addressed in this work. Predictions from coarse-grid simulations with the sub-grid filtered corrections are compared against accurate, highly-resolved simulations of full-scale turbulent and bubbling fluidized beds. The filtered drag models offer a computationally efficient yet accurate alternative for obtaining macroscopic predictions, but the spatial resolution of meso-scale clustering heterogeneities is sacrificed.

  7. Effects of Ytterbium Oxide Nanopowder Particle Size on the Acoustic Properties of Silicone Rubber Lens for Medical Echo Array Probe

    NASA Astrophysics Data System (ADS)

    Yohachi; Yamashita; Hosono, Yasuharu; Yamamoto, Noriko; Itsumi, Kazuhiro

    2008-05-01

    The effects of Yb2O3 powder particle size, namely, 2000, 16, and 8 nm, on the physical and acoustic properties of a high-temperature-vulcanization (HTV) silicone (Q) rubber have been investigated in order to develop an acoustic lens material with a low sound velocity (c) and acoustic attenuation coefficient (α). The Yb2O3-doped HTV Q rubber with the large particle size of 2000 nm showed a density (ρ) of 1.6×103 kg/m3, with c = 828 m/s, characteristic acoustic impedance (Z) = 1.32×106 kg·m-2·s-1, α= 1.32 dB·mm-1·MHz-1, and an α-figure of merit (FOM) (α×c) of 1090 at 5 MHz at 37 °C. For the Yb2O3-doped Q rubber with the small particle size of 8 nm, ρ= 1.57×103 kg/m3, c = 864 m/s, Z = 1.36×106 kg·m-2·s-1, α= 0.68 dB·mm-1·MHz-1, and α-FOM = 590. The 16 nm Yb2O3-doped Q rubber had intermediate values of α= 0.88 dB·mm-1·MHz-1 and α-FOM = 760. These results show that there is a clear dopant particle size dependence on the acoustic properties of Yb2O3-doped HTV Q rubbers. The 8-nm-doped HTV Q rubber also showed an excellent mechanical properties for practical application. Microstructure observation revealed that the low-α rubber shows a uniform Yb2O3 nanopowder distribution in the HTV Q rubber matrix.

  8. Novel electrodeless-dielectrophoresis device for nanoparticle trapping using three-dimensional inverted-pyramid arrays

    NASA Astrophysics Data System (ADS)

    Chiou, Chi-Han; Chien-Lung Lin, Liang-Ju, Jr.; Kuo, Ju-Nan

    2016-05-01

    A novel electrodeless-dielectrophoresis (EDEP) device incorporating three-dimensional (3D) inverted-pyramid arrays is proposed for the trapping and separation of nanoparticles. The electrokinetic phenomena in the proposed device are investigated both numerically and experimentally. The results reveal that the pyramid structures induce a 3D squeezed electric field, which allows particle trapping with a lower driving voltage than that required in traditional two-dimensional (2D) EDEP devices. Overall, the proposed EDEP device provides a mass-producible solution for nanoparticle-trapping applications and overcomes the Poisson statistical limit inherent in 2D nanogap-based EDEP devices with smaller (pL) sample volumes.

  9. Thermal Modeling of the Main Rings of Saturn through random distribution particle arrays and ray-tracing simulations

    NASA Astrophysics Data System (ADS)

    Flandes, Alberto; Spilker, Linda; Déau, Estelle

    2016-10-01

    Saturn's rings are a complex collection of icy particles with diameters from 1 m to few meters. Their natural window of study is the infrared because its temperatures are between 40K and 120K. The main driver of the temperature of these rings is the direct solar radiation as well as the solar radiation reflected off Saturn's atmosphere. The second most important energy source is the infrared radiation coming from Saturn itself. The study of the variations of temperatures of the rings, or, in general, their thermal behavior, may provide important information on their composition, their structure and their dynamics. Models that consider these and other energy sources are able to explain, to a first approximation, the observed temperature variations of the rings. The challenge for these models is to accurately describe the variation of illumination on the rings, i. e., how the illuminated and non-illuminated regions of the ring particles change at the different observation geometries. This shadowing mainly depends on the optical depth, as well as the general structure of the rings.In this work, We show a semi-analytical model that considers the main energy sources of the rings and their average properties (e.g., optical depth, particle size range and vertical distribution). In order to deal with the shadowing at specific geometries, the model uses the ray-tracing technique. The goal is to describe the ring temperatures observed by the Composite Infrared Spectrometer, CIRS, onboard the Cassini spacecraft, which is in orbit around Saturn since 2004. So far, the model is able to reproduce some of the general features of specific regions of the A, B and C rings.

  10. Orthotropic Piezoelectricity in 2D Nanocellulose

    NASA Astrophysics Data System (ADS)

    García, Y.; Ruiz-Blanco, Yasser B.; Marrero-Ponce, Yovani; Sotomayor-Torres, C. M.

    2016-10-01

    The control of electromechanical responses within bonding regions is essential to face frontier challenges in nanotechnologies, such as molecular electronics and biotechnology. Here, we present Iβ-nanocellulose as a potentially new orthotropic 2D piezoelectric crystal. The predicted in-layer piezoelectricity is originated on a sui-generis hydrogen bonds pattern. Upon this fact and by using a combination of ab-initio and ad-hoc models, we introduce a description of electrical profiles along chemical bonds. Such developments lead to obtain a rationale for modelling the extended piezoelectric effect originated within bond scales. The order of magnitude estimated for the 2D Iβ-nanocellulose piezoelectric response, ~pm V‑1, ranks this material at the level of currently used piezoelectric energy generators and new artificial 2D designs. Such finding would be crucial for developing alternative materials to drive emerging nanotechnologies.

  11. Orthotropic Piezoelectricity in 2D Nanocellulose

    PubMed Central

    García, Y.; Ruiz-Blanco, Yasser B.; Marrero-Ponce, Yovani; Sotomayor-Torres, C. M.

    2016-01-01

    The control of electromechanical responses within bonding regions is essential to face frontier challenges in nanotechnologies, such as molecular electronics and biotechnology. Here, we present Iβ-nanocellulose as a potentially new orthotropic 2D piezoelectric crystal. The predicted in-layer piezoelectricity is originated on a sui-generis hydrogen bonds pattern. Upon this fact and by using a combination of ab-initio and ad-hoc models, we introduce a description of electrical profiles along chemical bonds. Such developments lead to obtain a rationale for modelling the extended piezoelectric effect originated within bond scales. The order of magnitude estimated for the 2D Iβ-nanocellulose piezoelectric response, ~pm V−1, ranks this material at the level of currently used piezoelectric energy generators and new artificial 2D designs. Such finding would be crucial for developing alternative materials to drive emerging nanotechnologies. PMID:27708364

  12. 2D microwave imaging reflectometer electronics

    SciTech Connect

    Spear, A. G.; Domier, C. W. Hu, X.; Muscatello, C. M.; Ren, X.; Luhmann, N. C.; Tobias, B. J.

    2014-11-15

    A 2D microwave imaging reflectometer system has been developed to visualize electron density fluctuations on the DIII-D tokamak. Simultaneously illuminated at four probe frequencies, large aperture optics image reflections from four density-dependent cutoff surfaces in the plasma over an extended region of the DIII-D plasma. Localized density fluctuations in the vicinity of the plasma cutoff surfaces modulate the plasma reflections, yielding a 2D image of electron density fluctuations. Details are presented of the receiver down conversion electronics that generate the in-phase (I) and quadrature (Q) reflectometer signals from which 2D density fluctuation data are obtained. Also presented are details on the control system and backplane used to manage the electronics as well as an introduction to the computer based control program.

  13. Optical modulators with 2D layered materials

    NASA Astrophysics Data System (ADS)

    Sun, Zhipei; Martinez, Amos; Wang, Feng

    2016-04-01

    Light modulation is an essential operation in photonics and optoelectronics. With existing and emerging technologies increasingly demanding compact, efficient, fast and broadband optical modulators, high-performance light modulation solutions are becoming indispensable. The recent realization that 2D layered materials could modulate light with superior performance has prompted intense research and significant advances, paving the way for realistic applications. In this Review, we cover the state of the art of optical modulators based on 2D materials, including graphene, transition metal dichalcogenides and black phosphorus. We discuss recent advances employing hybrid structures, such as 2D heterostructures, plasmonic structures, and silicon and fibre integrated structures. We also take a look at the future perspectives and discuss the potential of yet relatively unexplored mechanisms, such as magneto-optic and acousto-optic modulation.

  14. High density pixel array

    NASA Technical Reports Server (NTRS)

    Wiener-Avnear, Eliezer (Inventor); McFall, James Earl (Inventor)

    2004-01-01

    A pixel array device is fabricated by a laser micro-milling method under strict process control conditions. The device has an array of pixels bonded together with an adhesive filling the grooves between adjacent pixels. The array is fabricated by moving a substrate relative to a laser beam of predetermined intensity at a controlled, constant velocity along a predetermined path defining a set of grooves between adjacent pixels so that a predetermined laser flux per unit area is applied to the material, and repeating the movement for a plurality of passes of the laser beam until the grooves are ablated to a desired depth. The substrate is of an ultrasonic transducer material in one example for fabrication of a 2D ultrasonic phase array transducer. A substrate of phosphor material is used to fabricate an X-ray focal plane array detector.

  15. Inkjet printing of 2D layered materials.

    PubMed

    Li, Jiantong; Lemme, Max C; Östling, Mikael

    2014-11-10

    Inkjet printing of 2D layered materials, such as graphene and MoS2, has attracted great interests for emerging electronics. However, incompatible rheology, low concentration, severe aggregation and toxicity of solvents constitute critical challenges which hamper the manufacturing efficiency and product quality. Here, we introduce a simple and general technology concept (distillation-assisted solvent exchange) to efficiently overcome these challenges. By implementing the concept, we have demonstrated excellent jetting performance, ideal printing patterns and a variety of promising applications for inkjet printing of 2D layered materials. PMID:25169938

  16. Inkjet printing of 2D layered materials.

    PubMed

    Li, Jiantong; Lemme, Max C; Östling, Mikael

    2014-11-10

    Inkjet printing of 2D layered materials, such as graphene and MoS2, has attracted great interests for emerging electronics. However, incompatible rheology, low concentration, severe aggregation and toxicity of solvents constitute critical challenges which hamper the manufacturing efficiency and product quality. Here, we introduce a simple and general technology concept (distillation-assisted solvent exchange) to efficiently overcome these challenges. By implementing the concept, we have demonstrated excellent jetting performance, ideal printing patterns and a variety of promising applications for inkjet printing of 2D layered materials.

  17. Effects of fine metal oxide particle dopant on the acoustic properties of silicone rubber lens for medical array probe.

    PubMed

    Hosono, Yasuharu; Yamashita, Yohachi; Itsumi, Kazuhiro

    2007-08-01

    The effects of fine metal oxide particles, particularly those of high-density elements (7.7 to 9.7 x 10(3) kg/m3), on the acoustic properties of silicone rubber have been investigated in order to develop an acoustic lens with a low acoustic attenuation. Silicone rubber doped with Yb2O3 powder having nanoparticle size of 16 nm showed a lower acoustic attenuation than silicone rubber doped with powders of CeO2, Bi2O3, Lu2O3 and HfO2. The silicone rubber doped with Yb2O3 powder showed a sound speed of 0.88 km/s, an acoustic impedance of 1.35 x 10(6) kg/m2s, an acoustic attenuation of 0.93 dB/mmMHz, and a Shore A hardness of 55 at 37 degrees C. Although typical silicone rubber doped with SiO2 (2.6 x 10(3) kg/m3) shows a sound speed of about 1.00 km/s, heavy metal oxide particles decreased the sound velocities to lower than 0.93 km/s. Therefore, an acoustic lens of silicone rubber doped with Yb2O3 powder provides increased sensitivity because it realizes a thinner acoustic lens than is conventionally used due to its low sound speed. Moreover, it has an advantage in that a focus point is not changed when the acoustic lens is pressed to a human body due to its reasonable hardness.

  18. 2D to 3D transition of polymeric carbon nitride nanosheets

    SciTech Connect

    Chamorro-Posada, Pedro; Vázquez-Cabo, José; Martín-Ramos, Pablo; Martín-Gil, Jesús; Navas-Gracia, Luis M.; Dante, Roberto C.

    2014-11-15

    The transition from a prevalent turbostratic arrangement with low planar interactions (2D) to an array of polymeric carbon nitride nanosheets with stronger interplanar interactions (3D), occurring for samples treated above 650 °C, was detected by terahertz-time domain spectroscopy (THz-TDS). The simulated 3D material made of stacks of shifted quasi planar sheets composed of zigzagged polymer ribbons, delivered a XRD simulated pattern in relatively good agreement with the experimental one. The 2D to 3D transition was also supported by the simulation of THz-TDS spectra obtained from quantum chemistry calculations, in which the same broad bands around 2 THz and 1.5 THz were found for 2D and 3D arrays, respectively. This transition was also in accordance with the tightening of the interplanar distance probably due to an interplanar π bond contribution, as evidenced also by a broad absorption around 2.6 eV in the UV–vis spectrum, which appeared in the sample treated at 650 °C, and increased in the sample treated at 700 °C. The band gap was calculated for 1D and 2D cases. The value of 3.374 eV for the 2D case is, within the model accuracy and precision, in a relative good agreement with the value of 3.055 eV obtained from the experimental results. - Graphical abstract: 2D lattice mode vibrations and structural changes correlated with the so called “2D to 3D transition”. - Highlights: • A 2D to 3D transition has been detected for polymeric carbon nitride. • THz-TDS allowed us to discover and detect the 2D to 3D transition of polymeric carbon nitride. • We propose a structure for polymeric carbon nitride confirming it with THz-TDS.

  19. Parallel stitching of 2D materials

    DOE PAGES

    Ling, Xi; Wu, Lijun; Lin, Yuxuan; Ma, Qiong; Wang, Ziqiang; Song, Yi; Yu, Lili; Huang, Shengxi; Fang, Wenjing; Zhang, Xu; et al

    2016-01-27

    Diverse parallel stitched 2D heterostructures, including metal–semiconductor, semiconductor–semiconductor, and insulator–semiconductor, are synthesized directly through selective “sowing” of aromatic molecules as the seeds in the chemical vapor deposition (CVD) method. Lastly, the methodology enables the large-scale fabrication of lateral heterostructures, which offers tremendous potential for its application in integrated circuits.

  20. Parallel Stitching of 2D Materials.

    PubMed

    Ling, Xi; Lin, Yuxuan; Ma, Qiong; Wang, Ziqiang; Song, Yi; Yu, Lili; Huang, Shengxi; Fang, Wenjing; Zhang, Xu; Hsu, Allen L; Bie, Yaqing; Lee, Yi-Hsien; Zhu, Yimei; Wu, Lijun; Li, Ju; Jarillo-Herrero, Pablo; Dresselhaus, Mildred; Palacios, Tomás; Kong, Jing

    2016-03-23

    Diverse parallel stitched 2D heterostructures, including metal-semiconductor, semiconductor-semiconductor, and insulator-semiconductor, are synthesized directly through selective "sowing" of aromatic molecules as the seeds in the chemical vapor deposition (CVD) method. The methodology enables the large-scale fabrication of lateral heterostructures, which offers tremendous potential for its application in integrated circuits.

  1. Interaction of large, high power systems with operational orbit charged particle environments. [large solar arrays in space

    NASA Technical Reports Server (NTRS)

    Purvis, C. K.; Stevens, N. J.; Berkopec, F. D.

    1978-01-01

    Concepts are presently being advanced for space systems to be used for such activities as manufacturing, earth observations, scientific exploration, power generation and human habitation, in locations ranging from low earth orbit (300-500 km) to geosynchronous orbit and beyond. Many of these systems concepts envision large structures and high power levels, and consequently higher operating voltages than have been used in space to date. The potential impact of interactions of space systems with their operational orbit charged particle environments on the systems' performance must be accounted for in the design process. A potentially hazardous spacecraft-environment interaction is discussed, namely the interaction of large high voltage systems with low energy (less than 50 eV) plasmas which can result in loss of power, and/or arcing. The impact of this class of interactions on system operation is most severe at low orbits where the ambient plasmas are densest. Results of experimental work and predictions of simple analytical models are presented and their implications for design of space systems are discussed.

  2. Direct writing of micro/nano-scale patterns by means of particle lens arrays scanned by a focused diode pumped Nd:YVO4 laser

    NASA Astrophysics Data System (ADS)

    Pena, Ana; Wang, Zengbo; Whitehead, David; Li, Lin

    2010-11-01

    A practical approach to a well-known technique of laser micro/nano-patterning by optical near fields is presented. It is based on surface patterning by scanning a Gaussian laser beam through a self-assembled monolayer of silica micro-spheres on a single-crystalline silicon (Si) substrate. So far, the outcome of this kind of near-field patterning has been related to the simultaneous, parallel surface-structuring of large areas either by top hat or Gaussian laser intensity distributions. We attempt to explore the possibility of using the same technique in order to produce single, direct writing of features. This could be of advantage for applications in which only some areas need to be patterned (i.e. local area selective patterning) or single lines are required (e.g. a particular micro/nano-fluidic channel). A diode pumped Nd:YVO4 laser system (wavelength of 532 nm, pulse duration of 8 ns, repetition rate of 30 kHz) with a computer-controlled 3 axis galvanometer beam scanner was employed to write user-defined patterns through the particle lens array on the Si substrate. After laser irradiation, the obtained patterns which are in the micro-scale were composed of sub-micro/micro-holes or bumps. The micro-pattern resolution depends on the dimension of both the micro-sphere’s diameter and the beam’s spot size. The developed technique could potentially be employed to fabricate photonic crystal structures mimicking nature’s butterfly wings and anti-reflective “moth eye” arrays for photovoltaic cells.

  3. Enhancement of biomixing by swimming cells in 2D films

    NASA Astrophysics Data System (ADS)

    Gollub, Jerry; Kurtuldu, Huseyin; Guasto, Jeffrey; Johnson, Karl

    2011-11-01

    Fluid mixing in active suspensions of microorganisms is important to ecological phenomena and shows surprising statistical behavior. We investigate the mixing produced by swimming unicellular algal cells (Chlamydomonas) in quasi-2D films by tracking the motions of cells and of microscopic passive tracer particles advected by the fluid. The reduced spatial dimension of the system leads to long-range flows and a surprisingly strong dependence of tracer transport on the swimmer concentration. The mean square displacements are well described by a stochastic Langevin model, with an effective diffusion coefficient D growing as the 3/2 power of the swimmer concentration, due to the interaction of tracer particles with multiple swimmers. We also discuss the anomalous probability distributions of tracer displacements, which become Gaussian at high concentration, but show strong power-law tails at low concentration. Supported by NSF Grant DMR-0803153.

  4. areaDetector: Software for 2-D Detectors in EPICS

    SciTech Connect

    Rivers, M.

    2011-09-23

    areaDetector is a new EPICS module designed to support 2-D detectors. It is modular C++ code that greatly simplifies the task of writing support for a new detector. It also supports plugins, which receive detector data from the driver and process it in some way. Existing plugins perform Region-Of-Interest extraction and analysis, file saving (in netCDF, HDF, TIFF and JPEG formats), color conversion, and export to EPICS records for image display in clients like ImageJ and IDL. Drivers have now been written for many of the detectors commonly used at synchrotron beamlines, including CCDs, pixel array and amorphous silicon detectors, and online image plates.

  5. areaDetector: Software for 2-D Detectors in EPICS

    SciTech Connect

    Rivers, Mark L.

    2010-06-23

    areaDetector is a new EPICS module designed to support 2-D detectors. It is modular C++ code that greatly simplifies the task of writing support for a new detector. It also supports plugins, which receive detector data from the driver and process it in some way. Existing plugins perform Region-Of-Interest extraction and analysis, file saving (in netCDF, HDF, TIFF and JPEG formats), color conversion, and export to EPICS records for image display in clients like ImageJ and IDL. Drivers have now been written for many of the detectors commonly used at synchrotron beamlines, including CCDs, pixel array and amorphous silicon detectors, and online image plates.

  6. Application of 2D Non-Graphene Materials and 2D Oxide Nanostructures for Biosensing Technology

    PubMed Central

    Shavanova, Kateryna; Bakakina, Yulia; Burkova, Inna; Shtepliuk, Ivan; Viter, Roman; Ubelis, Arnolds; Beni, Valerio; Starodub, Nickolaj; Yakimova, Rositsa; Khranovskyy, Volodymyr

    2016-01-01

    The discovery of graphene and its unique properties has inspired researchers to try to invent other two-dimensional (2D) materials. After considerable research effort, a distinct “beyond graphene” domain has been established, comprising the library of non-graphene 2D materials. It is significant that some 2D non-graphene materials possess solid advantages over their predecessor, such as having a direct band gap, and therefore are highly promising for a number of applications. These applications are not limited to nano- and opto-electronics, but have a strong potential in biosensing technologies, as one example. However, since most of the 2D non-graphene materials have been newly discovered, most of the research efforts are concentrated on material synthesis and the investigation of the properties of the material. Applications of 2D non-graphene materials are still at the embryonic stage, and the integration of 2D non-graphene materials into devices is scarcely reported. However, in recent years, numerous reports have blossomed about 2D material-based biosensors, evidencing the growing potential of 2D non-graphene materials for biosensing applications. This review highlights the recent progress in research on the potential of using 2D non-graphene materials and similar oxide nanostructures for different types of biosensors (optical and electrochemical). A wide range of biological targets, such as glucose, dopamine, cortisol, DNA, IgG, bisphenol, ascorbic acid, cytochrome and estradiol, has been reported to be successfully detected by biosensors with transducers made of 2D non-graphene materials. PMID:26861346

  7. Application of 2D Non-Graphene Materials and 2D Oxide Nanostructures for Biosensing Technology.

    PubMed

    Shavanova, Kateryna; Bakakina, Yulia; Burkova, Inna; Shtepliuk, Ivan; Viter, Roman; Ubelis, Arnolds; Beni, Valerio; Starodub, Nickolaj; Yakimova, Rositsa; Khranovskyy, Volodymyr

    2016-01-01

    The discovery of graphene and its unique properties has inspired researchers to try to invent other two-dimensional (2D) materials. After considerable research effort, a distinct "beyond graphene" domain has been established, comprising the library of non-graphene 2D materials. It is significant that some 2D non-graphene materials possess solid advantages over their predecessor, such as having a direct band gap, and therefore are highly promising for a number of applications. These applications are not limited to nano- and opto-electronics, but have a strong potential in biosensing technologies, as one example. However, since most of the 2D non-graphene materials have been newly discovered, most of the research efforts are concentrated on material synthesis and the investigation of the properties of the material. Applications of 2D non-graphene materials are still at the embryonic stage, and the integration of 2D non-graphene materials into devices is scarcely reported. However, in recent years, numerous reports have blossomed about 2D material-based biosensors, evidencing the growing potential of 2D non-graphene materials for biosensing applications. This review highlights the recent progress in research on the potential of using 2D non-graphene materials and similar oxide nanostructures for different types of biosensors (optical and electrochemical). A wide range of biological targets, such as glucose, dopamine, cortisol, DNA, IgG, bisphenol, ascorbic acid, cytochrome and estradiol, has been reported to be successfully detected by biosensors with transducers made of 2D non-graphene materials.

  8. Detailed temporally resolved 2-D Velocity Measurements in a Novel Heat Exchanger Surface

    NASA Astrophysics Data System (ADS)

    Guezennec, Yann G.; Ko, Jang-Hyok; Choi, Woong-Chul

    1998-11-01

    Using flow visualization as a primary tool, a novel, high-performance heat transfer surface for compact heat exchangers was designed, specifically for low Reynolds number applications. This geometry was specifically created to enhance or generate strong three-dimensional transport even at low Reynolds number. It consists of a staggered array of "pin" mounted normal to the fins. A 15:1 model of this heat exchanger surface core was built out of Plexiglas to provide optical access and this model was placed in a 1'x1' water channel. The flow speed was adjusted to match the Reynolds based on the hydraulic diameter based on the fin pitch. The flow was seeded with small polystyrene particles and illuminated by a laser sheet from an Argon Ion laser. The fluid motion was recorded using a CCD camera and an S-VHS video recorder. In post-processing, the video records were automatically digitized and processed using a cinematographic PIV technique. The temporal evolution of the 2-D flow field (side view) clearly shows the presence of unsteady, shed vortical regions behind the pins, modulated by the spatially-periodic acceleration/deceleration and meandering of the mean flow between the periodic array of staggered pins. In the perpendicular view (top view), the results show the presence of two strong cross-stream transport mechanisms, mainly the horse-shoe vortex near the pin-fin junctions and the very strong spanwise transport in the separated wake region of the pins. This transport is most likely associated with the strong interaction of the longitudinal vortices (emanating form the horseshoe) and the spanwise vortices from the pin wake. This vortex interaction sets up a strong spanwise pressure gradient inducing large cross-stream transport from the fin to the core flow. Animation of the results illustrating these effects will be presented.

  9. Using dispersive medium to control excitons in 2D materials

    NASA Astrophysics Data System (ADS)

    Klots, Andrey; Bolotin, Kirill I.

    Excitons in 2D materials (2DMs) are known to be sensitive to the surrounding environment. This makes it possible to modify 2D excitons by depositing materials with controlled dielectric constant on top of 2DMs. This possibility becomes especially interesting if we consider materials with dielectric permittivity ɛ that depends both on wavevector k (this happens if the medium is spatially non-uniform) and frequency ω. Here, we develop platforms to control ɛ (k , ω) and explore resulting changes in light-matter interactions of 2DMs. To examine the effect of wavevector-dependent permittivity of the medium, we study absorption/photoluminescence of graphene and MoS2 in the vicinity of highly non-uniform medium - an array of metal nanoparticles, 3-5 nm in diameter. In this case absorption of light can lead to creation of excitons with non-zero momentum. These dark states are not accessible via regular absorption spectroscopy. We study the case of frequency-dependent permittivity by surrounding MoS2 by a highly-dispersive media (e.g. dielectric liquids, graphene and VO2) . We demonstrate non-trivial frequency-dependent renormalization of the quasiparticle bandgap and exciton binding energies.

  10. Stochastic Inversion of 2D Magnetotelluric Data

    SciTech Connect

    Chen, Jinsong

    2010-07-01

    The algorithm is developed to invert 2D magnetotelluric (MT) data based on sharp boundary parametrization using a Bayesian framework. Within the algorithm, we consider the locations and the resistivity of regions formed by the interfaces are as unknowns. We use a parallel, adaptive finite-element algorithm to forward simulate frequency-domain MT responses of 2D conductivity structure. Those unknown parameters are spatially correlated and are described by a geostatistical model. The joint posterior probability distribution function is explored by Markov Chain Monte Carlo (MCMC) sampling methods. The developed stochastic model is effective for estimating the interface locations and resistivity. Most importantly, it provides details uncertainty information on each unknown parameter. Hardware requirements: PC, Supercomputer, Multi-platform, Workstation; Software requirements C and Fortan; Operation Systems/version is Linux/Unix or Windows

  11. Explicit 2-D Hydrodynamic FEM Program

    1996-08-07

    DYNA2D* is a vectorized, explicit, two-dimensional, axisymmetric and plane strain finite element program for analyzing the large deformation dynamic and hydrodynamic response of inelastic solids. DYNA2D* contains 13 material models and 9 equations of state (EOS) to cover a wide range of material behavior. The material models implemented in all machine versions are: elastic, orthotropic elastic, kinematic/isotropic elastic plasticity, thermoelastoplastic, soil and crushable foam, linear viscoelastic, rubber, high explosive burn, isotropic elastic-plastic, temperature-dependent elastic-plastic. Themore » isotropic and temperature-dependent elastic-plastic models determine only the deviatoric stresses. Pressure is determined by one of 9 equations of state including linear polynomial, JWL high explosive, Sack Tuesday high explosive, Gruneisen, ratio of polynomials, linear polynomial with energy deposition, ignition and growth of reaction in HE, tabulated compaction, and tabulated.« less

  12. Stochastic Inversion of 2D Magnetotelluric Data

    2010-07-01

    The algorithm is developed to invert 2D magnetotelluric (MT) data based on sharp boundary parametrization using a Bayesian framework. Within the algorithm, we consider the locations and the resistivity of regions formed by the interfaces are as unknowns. We use a parallel, adaptive finite-element algorithm to forward simulate frequency-domain MT responses of 2D conductivity structure. Those unknown parameters are spatially correlated and are described by a geostatistical model. The joint posterior probability distribution function ismore » explored by Markov Chain Monte Carlo (MCMC) sampling methods. The developed stochastic model is effective for estimating the interface locations and resistivity. Most importantly, it provides details uncertainty information on each unknown parameter. Hardware requirements: PC, Supercomputer, Multi-platform, Workstation; Software requirements C and Fortan; Operation Systems/version is Linux/Unix or Windows« less

  13. Static & Dynamic Response of 2D Solids

    1996-07-15

    NIKE2D is an implicit finite-element code for analyzing the finite deformation, static and dynamic response of two-dimensional, axisymmetric, plane strain, and plane stress solids. The code is fully vectorized and available on several computing platforms. A number of material models are incorporated to simulate a wide range of material behavior including elasto-placicity, anisotropy, creep, thermal effects, and rate dependence. Slideline algorithms model gaps and sliding along material interfaces, including interface friction, penetration and single surfacemore » contact. Interactive-graphics and rezoning is included for analyses with large mesh distortions. In addition to quasi-Newton and arc-length procedures, adaptive algorithms can be defined to solve the implicit equations using the solution language ISLAND. Each of these capabilities and more make NIKE2D a robust analysis tool.« less

  14. Static & Dynamic Response of 2D Solids

    SciTech Connect

    Lin, Jerry

    1996-07-15

    NIKE2D is an implicit finite-element code for analyzing the finite deformation, static and dynamic response of two-dimensional, axisymmetric, plane strain, and plane stress solids. The code is fully vectorized and available on several computing platforms. A number of material models are incorporated to simulate a wide range of material behavior including elasto-placicity, anisotropy, creep, thermal effects, and rate dependence. Slideline algorithms model gaps and sliding along material interfaces, including interface friction, penetration and single surface contact. Interactive-graphics and rezoning is included for analyses with large mesh distortions. In addition to quasi-Newton and arc-length procedures, adaptive algorithms can be defined to solve the implicit equations using the solution language ISLAND. Each of these capabilities and more make NIKE2D a robust analysis tool.

  15. Explicit 2-D Hydrodynamic FEM Program

    SciTech Connect

    Lin, Jerry

    1996-08-07

    DYNA2D* is a vectorized, explicit, two-dimensional, axisymmetric and plane strain finite element program for analyzing the large deformation dynamic and hydrodynamic response of inelastic solids. DYNA2D* contains 13 material models and 9 equations of state (EOS) to cover a wide range of material behavior. The material models implemented in all machine versions are: elastic, orthotropic elastic, kinematic/isotropic elastic plasticity, thermoelastoplastic, soil and crushable foam, linear viscoelastic, rubber, high explosive burn, isotropic elastic-plastic, temperature-dependent elastic-plastic. The isotropic and temperature-dependent elastic-plastic models determine only the deviatoric stresses. Pressure is determined by one of 9 equations of state including linear polynomial, JWL high explosive, Sack Tuesday high explosive, Gruneisen, ratio of polynomials, linear polynomial with energy deposition, ignition and growth of reaction in HE, tabulated compaction, and tabulated.

  16. 2D photonic-crystal optomechanical nanoresonator.

    PubMed

    Makles, K; Antoni, T; Kuhn, A G; Deléglise, S; Briant, T; Cohadon, P-F; Braive, R; Beaudoin, G; Pinard, L; Michel, C; Dolique, V; Flaminio, R; Cagnoli, G; Robert-Philip, I; Heidmann, A

    2015-01-15

    We present the optical optimization of an optomechanical device based on a suspended InP membrane patterned with a 2D near-wavelength grating (NWG) based on a 2D photonic-crystal geometry. We first identify by numerical simulation a set of geometrical parameters providing a reflectivity higher than 99.8% over a 50-nm span. We then study the limitations induced by the finite value of the optical waist and lateral size of the NWG pattern using different numerical approaches. The NWG grating, pierced in a suspended InP 265-nm thick membrane, is used to form a compact microcavity involving the suspended nanomembrane as an end mirror. The resulting cavity has a waist size smaller than 10 μm and a finesse in the 200 range. It is used to probe the Brownian motion of the mechanical modes of the nanomembrane. PMID:25679837

  17. Compact 2-D graphical representation of DNA

    NASA Astrophysics Data System (ADS)

    Randić, Milan; Vračko, Marjan; Zupan, Jure; Novič, Marjana

    2003-05-01

    We present a novel 2-D graphical representation for DNA sequences which has an important advantage over the existing graphical representations of DNA in being very compact. It is based on: (1) use of binary labels for the four nucleic acid bases, and (2) use of the 'worm' curve as template on which binary codes are placed. The approach is illustrated on DNA sequences of the first exon of human β-globin and gorilla β-globin.

  18. 2D materials: Graphene and others

    NASA Astrophysics Data System (ADS)

    Bansal, Suneev Anil; Singh, Amrinder Pal; Kumar, Suresh

    2016-05-01

    Present report reviews the recent advancements in new atomically thick 2D materials. Materials covered in this review are Graphene, Silicene, Germanene, Boron Nitride (BN) and Transition metal chalcogenides (TMC). These materials show extraordinary mechanical, electronic and optical properties which make them suitable candidates for future applications. Apart from unique properties, tune-ability of highly desirable properties of these materials is also an important area to be emphasized on.

  19. Layer Engineering of 2D Semiconductor Junctions.

    PubMed

    He, Yongmin; Sobhani, Ali; Lei, Sidong; Zhang, Zhuhua; Gong, Yongji; Jin, Zehua; Zhou, Wu; Yang, Yingchao; Zhang, Yuan; Wang, Xifan; Yakobson, Boris; Vajtai, Robert; Halas, Naomi J; Li, Bo; Xie, Erqing; Ajayan, Pulickel

    2016-07-01

    A new concept for junction fabrication by connecting multiple regions with varying layer thicknesses, based on the thickness dependence, is demonstrated. This type of junction is only possible in super-thin-layered 2D materials, and exhibits similar characteristics as p-n junctions. Rectification and photovoltaic effects are observed in chemically homogeneous MoSe2 junctions between domains of different thicknesses. PMID:27136275

  20. Realistic and efficient 2D crack simulation

    NASA Astrophysics Data System (ADS)

    Yadegar, Jacob; Liu, Xiaoqing; Singh, Abhishek

    2010-04-01

    Although numerical algorithms for 2D crack simulation have been studied in Modeling and Simulation (M&S) and computer graphics for decades, realism and computational efficiency are still major challenges. In this paper, we introduce a high-fidelity, scalable, adaptive and efficient/runtime 2D crack/fracture simulation system by applying the mathematically elegant Peano-Cesaro triangular meshing/remeshing technique to model the generation of shards/fragments. The recursive fractal sweep associated with the Peano-Cesaro triangulation provides efficient local multi-resolution refinement to any level-of-detail. The generated binary decomposition tree also provides efficient neighbor retrieval mechanism used for mesh element splitting and merging with minimal memory requirements essential for realistic 2D fragment formation. Upon load impact/contact/penetration, a number of factors including impact angle, impact energy, and material properties are all taken into account to produce the criteria of crack initialization, propagation, and termination leading to realistic fractal-like rubble/fragments formation. The aforementioned parameters are used as variables of probabilistic models of cracks/shards formation, making the proposed solution highly adaptive by allowing machine learning mechanisms learn the optimal values for the variables/parameters based on prior benchmark data generated by off-line physics based simulation solutions that produce accurate fractures/shards though at highly non-real time paste. Crack/fracture simulation has been conducted on various load impacts with different initial locations at various impulse scales. The simulation results demonstrate that the proposed system has the capability to realistically and efficiently simulate 2D crack phenomena (such as window shattering and shards generation) with diverse potentials in military and civil M&S applications such as training and mission planning.

  1. 2D Spinodal Decomposition in Forced Turbulence

    NASA Astrophysics Data System (ADS)

    Fan, Xiang; Diamond, Patrick; Chacon, Luis; Li, Hui

    2015-11-01

    Spinodal decomposition is a second order phase transition for binary fluid mixture, from one thermodynamic phase to form two coexisting phases. The governing equation for this coarsening process below critical temperature, Cahn-Hilliard Equation, is very similar to 2D MHD Equation, especially the conserved quantities have a close correspondence between each other, so theories for MHD turbulence are used to study spinodal decomposition in forced turbulence. Domain size is increased with time along with the inverse cascade, and the length scale can be arrested by a forced turbulence with direct cascade. The two competing mechanisms lead to a stabilized domain size length scale, which can be characterized by Hinze Scale. The 2D spinodal decomposition in forced turbulence is studied by both theory and simulation with ``pixie2d.'' This work focuses on the relation between Hinze scale and spectra and cascades. Similarities and differences between spinodal decomposition and MHD are investigated. Also some transport properties are studied following MHD theories. This work is supported by the Department of Energy under Award Number DE-FG02-04ER54738.

  2. MAGNUM-2D computer code: user's guide

    SciTech Connect

    England, R.L.; Kline, N.W.; Ekblad, K.J.; Baca, R.G.

    1985-01-01

    Information relevant to the general use of the MAGNUM-2D computer code is presented. This computer code was developed for the purpose of modeling (i.e., simulating) the thermal and hydraulic conditions in the vicinity of a waste package emplaced in a deep geologic repository. The MAGNUM-2D computer computes (1) the temperature field surrounding the waste package as a function of the heat generation rate of the nuclear waste and thermal properties of the basalt and (2) the hydraulic head distribution and associated groundwater flow fields as a function of the temperature gradients and hydraulic properties of the basalt. MAGNUM-2D is a two-dimensional numerical model for transient or steady-state analysis of coupled heat transfer and groundwater flow in a fractured porous medium. The governing equations consist of a set of coupled, quasi-linear partial differential equations that are solved using a Galerkin finite-element technique. A Newton-Raphson algorithm is embedded in the Galerkin functional to formulate the problem in terms of the incremental changes in the dependent variables. Both triangular and quadrilateral finite elements are used to represent the continuum portions of the spatial domain. Line elements may be used to represent discrete conduits. 18 refs., 4 figs., 1 tab.

  3. Engineering light outcoupling in 2D materials.

    PubMed

    Lien, Der-Hsien; Kang, Jeong Seuk; Amani, Matin; Chen, Kevin; Tosun, Mahmut; Wang, Hsin-Ping; Roy, Tania; Eggleston, Michael S; Wu, Ming C; Dubey, Madan; Lee, Si-Chen; He, Jr-Hau; Javey, Ali

    2015-02-11

    When light is incident on 2D transition metal dichalcogenides (TMDCs), it engages in multiple reflections within underlying substrates, producing interferences that lead to enhancement or attenuation of the incoming and outgoing strength of light. Here, we report a simple method to engineer the light outcoupling in semiconducting TMDCs by modulating their dielectric surroundings. We show that by modulating the thicknesses of underlying substrates and capping layers, the interference caused by substrate can significantly enhance the light absorption and emission of WSe2, resulting in a ∼11 times increase in Raman signal and a ∼30 times increase in the photoluminescence (PL) intensity of WSe2. On the basis of the interference model, we also propose a strategy to control the photonic and optoelectronic properties of thin-layer WSe2. This work demonstrates the utilization of outcoupling engineering in 2D materials and offers a new route toward the realization of novel optoelectronic devices, such as 2D LEDs and solar cells.

  4. ISS Solar Array Management

    NASA Technical Reports Server (NTRS)

    Williams, James P.; Martin, Keith D.; Thomas, Justin R.; Caro, Samuel

    2010-01-01

    The International Space Station (ISS) Solar Array Management (SAM) software toolset provides the capabilities necessary to operate a spacecraft with complex solar array constraints. It monitors spacecraft telemetry and provides interpretations of solar array constraint data in an intuitive manner. The toolset provides extensive situational awareness to ensure mission success by analyzing power generation needs, array motion constraints, and structural loading situations. The software suite consists of several components including samCS (constraint set selector), samShadyTimers (array shadowing timers), samWin (visualization GUI), samLock (array motion constraint computation), and samJet (attitude control system configuration selector). It provides high availability and uptime for extended and continuous mission support. It is able to support two-degrees-of-freedom (DOF) array positioning and supports up to ten simultaneous constraints with intuitive 1D and 2D decision support visualizations of constraint data. Display synchronization is enabled across a networked control center and multiple methods for constraint data interpolation are supported. Use of this software toolset increases flight safety, reduces mission support effort, optimizes solar array operation for achieving mission goals, and has run for weeks at a time without issues. The SAM toolset is currently used in ISS real-time mission operations.

  5. Defect formation and coarsening in hexagonal 2D curved crystals.

    PubMed

    García, Nicolás A; Pezzutti, Aldo D; Register, Richard A; Vega, Daniel A; Gómez, Leopoldo R

    2015-02-01

    In this work we study the processes of defect formation and coarsening of two-dimensional (2D) curved crystal structures. These processes are found to strongly deviate from their counterparts in flat systems. In curved backgrounds the process of defect formation is deeply affected by the curvature, and at the onset of a phase transition the early density of defects becomes highly inhomogeneous. We observe that even a single growing crystal can produce varying densities of defects depending on its initial position and local orientation with regard to the substrate. This process is completely different from flat space, where grain boundaries are formed due to the impingement of different propagating crystals. Quenching the liquid into the crystal phase leads to the formation of a curved polycrystalline structure, characterized by complex arrays of defects. During annealing, mechanisms of geodesic curvature-driven grain boundary motion and defect annihilation lead to increasing crystalline order. Linear arrays of defects diffuse to regions of high curvature, where they are absorbed by disclinations. At the early stage of coarsening the density of dislocations is insensitive to the geometry while the population of isolated disclinations is deeply affected by curvature. The regions with high curvature act as traps for the diffusion of different structures of defects, including disclinations and domain walls.

  6. 2D Doppler backscattering using synthetic aperture microwave imaging of MAST edge plasmas

    NASA Astrophysics Data System (ADS)

    Thomas, D. A.; Brunner, K. J.; Freethy, S. J.; Huang, B. K.; Shevchenko, V. F.; Vann, R. G. L.

    2016-02-01

    Doppler backscattering (DBS) is already established as a powerful diagnostic; its extension to 2D enables imaging of turbulence characteristics from an extended region of the cut-off surface. The Synthetic Aperture Microwave Imaging (SAMI) diagnostic has conducted proof-of-principle 2D DBS experiments of MAST edge plasma. SAMI actively probes the plasma edge using a wide (±40° vertical and horizontal) and tuneable (10-34.5 GHz) beam. The Doppler backscattered signal is digitised in vector form using an array of eight Vivaldi PCB antennas. This allows the receiving array to be focused in any direction within the field of view simultaneously to an angular range of 6-24° FWHM at 10-34.5 GHz. This capability is unique to SAMI and is a novel way of conducting DBS experiments. In this paper the feasibility of conducting 2D DBS experiments is explored. Initial observations of phenomena previously measured by conventional DBS experiments are presented; such as momentum injection from neutral beams and an abrupt change in power and turbulence velocity coinciding with the onset of H-mode. In addition, being able to carry out 2D DBS imaging allows a measurement of magnetic pitch angle to be made; preliminary results are presented. Capabilities gained through steering a beam using a phased array and the limitations of this technique are discussed.

  7. GBL-2D Version 1.0: a 2D geometry boolean library.

    SciTech Connect

    McBride, Cory L. (Elemental Technologies, American Fort, UT); Schmidt, Rodney Cannon; Yarberry, Victor R.; Meyers, Ray J.

    2006-11-01

    This report describes version 1.0 of GBL-2D, a geometric Boolean library for 2D objects. The library is written in C++ and consists of a set of classes and routines. The classes primarily represent geometric data and relationships. Classes are provided for 2D points, lines, arcs, edge uses, loops, surfaces and mask sets. The routines contain algorithms for geometric Boolean operations and utility functions. Routines are provided that incorporate the Boolean operations: Union(OR), XOR, Intersection and Difference. A variety of additional analytical geometry routines and routines for importing and exporting the data in various file formats are also provided. The GBL-2D library was originally developed as a geometric modeling engine for use with a separate software tool, called SummitView [1], that manipulates the 2D mask sets created by designers of Micro-Electro-Mechanical Systems (MEMS). However, many other practical applications for this type of software can be envisioned because the need to perform 2D Boolean operations can arise in many contexts.

  8. Periodically sheared 2D Yukawa systems

    SciTech Connect

    Kovács, Anikó Zsuzsa; Hartmann, Peter; Donkó, Zoltán

    2015-10-15

    We present non-equilibrium molecular dynamics simulation studies on the dynamic (complex) shear viscosity of a 2D Yukawa system. We have identified a non-monotonic frequency dependence of the viscosity at high frequencies and shear rates, an energy absorption maximum (local resonance) at the Einstein frequency of the system at medium shear rates, an enhanced collective wave activity, when the excitation is near the plateau frequency of the longitudinal wave dispersion, and the emergence of significant configurational anisotropy at small frequencies and high shear rates.

  9. ENERGY LANDSCAPE OF 2D FLUID FORMS

    SciTech Connect

    Y. JIANG; ET AL

    2000-04-01

    The equilibrium states of 2D non-coarsening fluid foams, which consist of bubbles with fixed areas, correspond to local minima of the total perimeter. (1) The authors find an approximate value of the global minimum, and determine directly from an image how far a foam is from its ground state. (2) For (small) area disorder, small bubbles tend to sort inwards and large bubbles outwards. (3) Topological charges of the same sign repel while charges of opposite sign attract. (4) They discuss boundary conditions and the uniqueness of the pattern for fixed topology.

  10. Structure, Density and Velocity Fluctuations in Quasi-2D non-Brownian Suspensions of Spheres

    NASA Astrophysics Data System (ADS)

    Rouyer, Florence; Lhuillier, Daniel; Martin, Jérôme; Salin, Dominique

    1999-11-01

    Non-brownian sedimenting suspensions exhibit density and velocity fluctuations. We have performed experiments on a quasi-2D counter-flow stabilized suspension of 2000 spherical particles, namely a liquid-solid fluidized bed in a Hele-Shaw cell. This 2D suspension displays a uniform concentration but the particle radial distribution function and the fluctuations of the particle number in a sub-volume of the suspension suggest that the micostructure is homogeneous but not random. We have also measured the velocity fluctuations of a test-particle and the fluctuation of the mean particle velocity in a sub-volume. It happens that the relation between velocity and concentration fluctuation in a sub-volume can be deduced from a balance between buoyancy and parietal friction forces.

  11. A Cartesian grid finite-difference method for 2D incompressible viscous flows in irregular geometries

    NASA Astrophysics Data System (ADS)

    Sanmiguel-Rojas, Enrique; Ortega-Casanova, Joaquin; del Pino, Carlos; Fernandez-Feria, Ramon

    2004-11-01

    A method for generating a non-uniform cartesian grid for irregular two-dimensional (2D) geometries such that all the boundary points are regular mesh points is given. The resulting non-uniform grid is used to discretize the Navier-Stokes equations for 2D incompressible viscous flows using finite difference approximations. To that end, finite-difference approximations of the derivatives on a non-uniform mesh are given. We test the method with two different examples: the shallow water flow on a lake with irregular contour, and the pressure driven flow through an irregular array of circular cylinders.

  12. WFR-2D: an analytical model for PWAS-generated 2D ultrasonic guided wave propagation

    NASA Astrophysics Data System (ADS)

    Shen, Yanfeng; Giurgiutiu, Victor

    2014-03-01

    This paper presents WaveFormRevealer 2-D (WFR-2D), an analytical predictive tool for the simulation of 2-D ultrasonic guided wave propagation and interaction with damage. The design of structural health monitoring (SHM) systems and self-aware smart structures requires the exploration of a wide range of parameters to achieve best detection and quantification of certain types of damage. Such need for parameter exploration on sensor dimension, location, guided wave characteristics (mode type, frequency, wavelength, etc.) can be best satisfied with analytical models which are fast and efficient. The analytical model was constructed based on the exact 2-D Lamb wave solution using Bessel and Hankel functions. Damage effects were inserted in the model by considering the damage as a secondary wave source with complex-valued directivity scattering coefficients containing both amplitude and phase information from wave-damage interaction. The analytical procedure was coded with MATLAB, and a predictive simulation tool called WaveFormRevealer 2-D was developed. The wave-damage interaction coefficients (WDICs) were extracted from harmonic analysis of local finite element model (FEM) with artificial non-reflective boundaries (NRB). The WFR-2D analytical simulation results were compared and verified with full scale multiphysics finite element models and experiments with scanning laser vibrometer. First, Lamb wave propagation in a pristine aluminum plate was simulated with WFR-2D, compared with finite element results, and verified by experiments. Then, an inhomogeneity was machined into the plate to represent damage. Analytical modeling was carried out, and verified by finite element simulation and experiments. This paper finishes with conclusions and suggestions for future work.

  13. Microwave Assisted 2D Materials Exfoliation

    NASA Astrophysics Data System (ADS)

    Wang, Yanbin

    Two-dimensional materials have emerged as extremely important materials with applications ranging from energy and environmental science to electronics and biology. Here we report our discovery of a universal, ultrafast, green, solvo-thermal technology for producing excellent-quality, few-layered nanosheets in liquid phase from well-known 2D materials such as such hexagonal boron nitride (h-BN), graphite, and MoS2. We start by mixing the uniform bulk-layered material with a common organic solvent that matches its surface energy to reduce the van der Waals attractive interactions between the layers; next, the solutions are heated in a commercial microwave oven to overcome the energy barrier between bulk and few-layers states. We discovered the minutes-long rapid exfoliation process is highly temperature dependent, which requires precise thermal management to obtain high-quality inks. We hypothesize a possible mechanism of this proposed solvo-thermal process; our theory confirms the basis of this novel technique for exfoliation of high-quality, layered 2D materials by using an as yet unknown role of the solvent.

  14. Determining ice water content from 2D crystal images in convective cloud systems

    NASA Astrophysics Data System (ADS)

    Leroy, Delphine; Coutris, Pierre; Fontaine, Emmanuel; Schwarzenboeck, Alfons; Strapp, J. Walter

    2016-04-01

    Cloud microphysical in-situ instrumentation measures bulk parameters like total water content (TWC) and/or derives particle size distributions (PSD) (utilizing optical spectrometers and optical array probes (OAP)). The goal of this work is to introduce a comprehensive methodology to compute TWC from OAP measurements, based on the dataset collected during recent HAIC (High Altitude Ice Crystals)/HIWC (High Ice Water Content) field campaigns. Indeed, the HAIC/HIWC field campaigns in Darwin (2014) and Cayenne (2015) provide a unique opportunity to explore the complex relationship between cloud particle mass and size in ice crystal environments. Numerous mesoscale convective systems (MCSs) were sampled with the French Falcon 20 research aircraft at different temperature levels from -10°C up to 50°C. The aircraft instrumentation included an IKP-2 (isokinetic probe) to get reliable measurements of TWC and the optical array probes 2D-S and PIP recording images over the entire ice crystal size range. Based on the known principle relating crystal mass and size with a power law (m=α•Dβ), Fontaine et al. (2014) performed extended 3D crystal simulations and thereby demonstrated that it is possible to estimate the value of the exponent β from OAP data, by analyzing the surface-size relationship for the 2D images as a function of time. Leroy et al. (2015) proposed an extended version of this method that produces estimates of β from the analysis of both the surface-size and perimeter-size relationships. Knowing the value of β, α then is deduced from the simultaneous IKP-2 TWC measurements for the entire HAIC/HIWC dataset. The statistical analysis of α and β values for the HAIC/HIWC dataset firstly shows that α is closely linked to β and that this link changes with temperature. From these trends, a generalized parameterization for α is proposed. Finally, the comparison with the initial IKP-2 measurements demonstrates that the method is able to predict TWC values

  15. Three-bosons in 2D with a magnetic field

    NASA Astrophysics Data System (ADS)

    Rittenhouse, Seth; Johnson, Brad; Wray, Andrew; D'Incao, Jose

    2016-05-01

    Systems of interacting particles in reduced dimensions in the presence of external fields can exhibit a number of surprising behaviors, for instance the emergence of the fractional quantum Hall effect. Examining few-body interactions and effects can lead to significant insights within these systems. In this talk we examine a system of three bosons confined to two dimensions in the presence of a perpendicular magnetic field within the framework of the adiabatic hyperspherical method. For the case of zero-range, regularized pseudo-potential interactions, we find that the system is nearly separable in hyperspherical coordinates and that, away from a set of narrow avoided crossings, the full energy eigenspectrum as a function of the 2D s-wave scattering length is well described by ignoring coupling between adiabatic hyperradial potentials. In the case of weak attractive or repulsive interactions, we find the lowest three-body energy states exhibit even/odd parity oscillations as a function of total internal 2D angular momentum and that for weak repulsive interactions, the universal lowest energy interacting state has an internal angular momentum of M=3. We also discuss the effect of including finite range and higher partial-wave interactions.

  16. New Approach for 2D Readout of GEM Detectors

    SciTech Connect

    Hasell, Douglas K

    2011-10-29

    Detectors based on Gas Electron Multiplication (GEM) technology are becoming more and more widely used in nuclear and high energy physics and are being applied in astronomy, medical physics, industry, and homeland security. GEM detectors are thin, low mass, insensitive to magnetic fields, and can currently provide position resolutions down to {approx}50 microns. However, the designs for reconstructing the position, in two dimensions (2D), of the charged particles striking a GEM detector are often complicated to fabricate and expensive. The objective of this proposal is to investigate a simpler procedure for producing the two dimensional readout layer of GEM detectors using readily available printed circuit board technology which can be tailored to the detector requirements. We will use the established GEM laboratory and facilities at M.I.T. currently employed in developing GEM detectors for the STAR forward tracking upgrade to simplify the testing and evaluation of the new 2D readout designs. If this new design proves successful it will benefit future nuclear and high energy physics experiments already being planned and will similarly extend and simplify the application of GEM technology to other branches of science, medicine, and industry. These benefits would be not only in lower costs for fabrication but also it increased flexibility for design and application.

  17. 2-D or not 2-D, that is the question: A Northern California test

    SciTech Connect

    Mayeda, K; Malagnini, L; Phillips, W S; Walter, W R; Dreger, D

    2005-06-06

    Reliable estimates of the seismic source spectrum are necessary for accurate magnitude, yield, and energy estimation. In particular, how seismic radiated energy scales with increasing earthquake size has been the focus of recent debate within the community and has direct implications on earthquake source physics studies as well as hazard mitigation. The 1-D coda methodology of Mayeda et al. has provided the lowest variance estimate of the source spectrum when compared against traditional approaches that use direct S-waves, thus making it ideal for networks that have sparse station distribution. The 1-D coda methodology has been mostly confined to regions of approximately uniform complexity. For larger, more geophysically complicated regions, 2-D path corrections may be required. The complicated tectonics of the northern California region coupled with high quality broadband seismic data provides for an ideal ''apples-to-apples'' test of 1-D and 2-D path assumptions on direct waves and their coda. Using the same station and event distribution, we compared 1-D and 2-D path corrections and observed the following results: (1) 1-D coda results reduced the amplitude variance relative to direct S-waves by roughly a factor of 8 (800%); (2) Applying a 2-D correction to the coda resulted in up to 40% variance reduction from the 1-D coda results; (3) 2-D direct S-wave results, though better than 1-D direct waves, were significantly worse than the 1-D coda. We found that coda-based moment-rate source spectra derived from the 2-D approach were essentially identical to those from the 1-D approach for frequencies less than {approx}0.7-Hz, however for the high frequencies (0.7{le} f {le} 8.0-Hz), the 2-D approach resulted in inter-station scatter that was generally 10-30% smaller. For complex regions where data are plentiful, a 2-D approach can significantly improve upon the simple 1-D assumption. In regions where only 1-D coda correction is available it is still preferable over 2

  18. The impact of agrin on the formation of orthogonal arrays of particles in cultured astrocytes from wild-type and agrin-null mice.

    PubMed

    Fallier-Becker, Petra; Sperveslage, Jan; Wolburg, Hartwig; Noell, Susan

    2011-01-01

    Astrocytic endfeet membranes are studded with aquaporin-4 (AQP4) containing orthogonal arrays of particles (OAP) which can be visualized exclusively by the freeze-fracturing method. They are predominantly expressed where the astroglial membrane is in contact with the superficial and perivascular basal lamina. This polarity seems to be essential for the integrity of the blood-brain barrier (BBB). The basal lamina containing many extracellular matrix (ECM) components such as collagen, laminin and heparansulfate proteoglycans like agrin is thought to influence this OAP-related polarity of astrocytes. Recently, we have shown that agrin, in particular the neuronal isoform A4B8, is capable of influencing the formation of OAPs in astrocytes when cultured in the presence of agrin-conditioned media. In this paper we wanted to investigate whether coating with exogenous agrin compared to coating with other ECM components would induce OAP formation in astrocytes of the agrin-null mouse. For this purpose, we cultured astrocytes from agrin-null and wild-type mice on agrin- or ECM-coated surfaces. Immunofluorescent cytochemical staining of AQP4 indicated a higher AQP4 expression level in cultures with agrin- or ECM-coated than in cultures with uncoated surfaces, whereas western blot analyses and PCR showed no differences. α-Dystroglycan is thought to be a potential receptor of agrin and was immunostained in wild-type as well as in agrin-null astrocytes. In freeze-fracture replicas, we observed an increase in OAP density in astrocytes when growing on agrin- and ECM-coatings. These results concurred with other experiments in which changes in volume were measured following hypotonic stress, which supported the positive influence of exogenous agrin on AQP4 insertion into the membrane, on OAP formation and on water transport. PMID:20920487

  19. Models Ion Trajectories in 2D and 3D Electrostatic and Magnetic Fields

    2000-02-21

    SIMION3D7.0REV is a C based ion optics simulation program that can model complex problems using Laplace equation solutions for potential fields. The program uses an ion optics workbench that can hold up to 200 2D and/or 3D electrostatic/magnetic potential arrays. Arrays can have up to 50,000,000 points. SIMION3D7.0''s 32 bit virtual Graphics User Interface provides a highly interactive advanced user environment. All potential arrays are visualized as 3D objects that the user can cut awaymore » to inspect ion trajectories and potential energy surfaces. User programs allow the user to customize the program for specific simulations. A geometry file option supports the definition of highly complex array geometry. Algorithm modifications have improved this version''s computational speed and accuracy.« less

  20. Canard configured aircraft with 2-D nozzle

    NASA Technical Reports Server (NTRS)

    Child, R. D.; Henderson, W. P.

    1978-01-01

    A closely-coupled canard fighter with vectorable two-dimensional nozzle was designed for enhanced transonic maneuvering. The HiMAT maneuver goal of a sustained 8g turn at a free-stream Mach number of 0.9 and 30,000 feet was the primary design consideration. The aerodynamic design process was initiated with a linear theory optimization minimizing the zero percent suction drag including jet effects and refined with three-dimensional nonlinear potential flow techniques. Allowances were made for mutual interference and viscous effects. The design process to arrive at the resultant configuration is described, and the design of a powered 2-D nozzle model to be tested in the LRC 16-foot Propulsion Wind Tunnel is shown.

  1. 2D quantum gravity from quantum entanglement.

    PubMed

    Gliozzi, F

    2011-01-21

    In quantum systems with many degrees of freedom the replica method is a useful tool to study the entanglement of arbitrary spatial regions. We apply it in a way that allows them to backreact. As a consequence, they become dynamical subsystems whose position, form, and extension are determined by their interaction with the whole system. We analyze, in particular, quantum spin chains described at criticality by a conformal field theory. Its coupling to the Gibbs' ensemble of all possible subsystems is relevant and drives the system into a new fixed point which is argued to be that of the 2D quantum gravity coupled to this system. Numerical experiments on the critical Ising model show that the new critical exponents agree with those predicted by the formula of Knizhnik, Polyakov, and Zamolodchikov.

  2. Metrology for graphene and 2D materials

    NASA Astrophysics Data System (ADS)

    Pollard, Andrew J.

    2016-09-01

    The application of graphene, a one atom-thick honeycomb lattice of carbon atoms with superlative properties, such as electrical conductivity, thermal conductivity and strength, has already shown that it can be used to benefit metrology itself as a new quantum standard for resistance. However, there are many application areas where graphene and other 2D materials, such as molybdenum disulphide (MoS2) and hexagonal boron nitride (h-BN), may be disruptive, areas such as flexible electronics, nanocomposites, sensing and energy storage. Applying metrology to the area of graphene is now critical to enable the new, emerging global graphene commercial world and bridge the gap between academia and industry. Measurement capabilities and expertise in a wide range of scientific areas are required to address this challenge. The combined and complementary approach of varied characterisation methods for structural, chemical, electrical and other properties, will allow the real-world issues of commercialising graphene and other 2D materials to be addressed. Here, examples of metrology challenges that have been overcome through a multi-technique or new approach are discussed. Firstly, the structural characterisation of defects in both graphene and MoS2 via Raman spectroscopy is described, and how nanoscale mapping of vacancy defects in graphene is also possible using tip-enhanced Raman spectroscopy (TERS). Furthermore, the chemical characterisation and removal of polymer residue on chemical vapour deposition (CVD) grown graphene via secondary ion mass spectrometry (SIMS) is detailed, as well as the chemical characterisation of iron films used to grow large domain single-layer h-BN through CVD growth, revealing how contamination of the substrate itself plays a role in the resulting h-BN layer. In addition, the role of international standardisation in this area is described, outlining the current work ongoing in both the International Organization of Standardization (ISO) and the

  3. Multiple-plane particle image velocimetry using a light-field camera.

    PubMed

    Skupsch, Christoph; Brücker, Christoph

    2013-01-28

    Planar velocity fields in flows are determined simultaneously on parallel measurement planes by means of an in-house manufactured light-field camera. The planes are defined by illuminating light sheets with constant spacing. Particle positions are reconstructed from a single 2D recording taken by a CMOS-camera equipped with a high-quality doublet lens array. The fast refocusing algorithm is based on synthetic-aperture particle image velocimetry (SAPIV). The reconstruction quality is tested via ray-tracing of synthetically generated particle fields. The introduced single-camera SAPIV is applied to a convective flow within a measurement volume of 30 x 30 x 50 mm³.

  4. Comparison of 1D and 2D CSR Models with Application to the FERMI@ELETTRA Bunch Compressors

    SciTech Connect

    Bassi, G.; Ellison, J.A.; Heinemann, K.

    2011-03-28

    We compare our 2D mean field (Vlasov-Maxwell) treatment of coherent synchrotron radiation (CSR) effects with 1D approximations of the CSR force which are commonly implemented in CSR codes. In our model we track particles in 4D phase space and calculate 2D forces [1]. The major cost in our calculation is the computation of the 2D force. To speed up the computation and improve 1D models we also investigate approximations to our exact 2D force. As an application, we present numerical results for the Fermi{at}Elettra first bunch compressor with the configuration described in [1].

  5. CYP2D6*36 gene arrangements within the cyp2d6 locus: association of CYP2D6*36 with poor metabolizer status.

    PubMed

    Gaedigk, Andrea; Bradford, L Dianne; Alander, Sarah W; Leeder, J Steven

    2006-04-01

    Unexplained cases of CYP2D6 genotype/phenotype discordance continue to be discovered. In previous studies, several African Americans with a poor metabolizer phenotype carried the reduced function CYP2D6*10 allele in combination with a nonfunctional allele. We pursued the possibility that these alleles harbor either a known sequence variation (i.e., CYP2D6*36 carrying a gene conversion in exon 9 along the CYP2D6*10-defining 100C>T single-nucleotide polymorphism) or novel sequences variation(s). Discordant cases were evaluated by long-range polymerase chain reaction (PCR) to test for gene rearrangement events, and a 6.6-kilobase pair PCR product encompassing the CYP2D6 gene was cloned and entirely sequenced. Thereafter, allele frequencies were determined in different study populations comprising whites, African Americans, and Asians. Analyses covering the CYP2D7 to 2D6 gene region established that CYP2D6*36 did not only exist as a gene duplication (CYP2D6*36x2) or in tandem with *10 (CYP2D6*36+*10), as previously reported, but also by itself. This "single" CYP2D6*36 allele was found in nine African Americans and one Asian, but was absent in the whites tested. Ultimately, the presence of CYP2D6*36 resolved genotype/phenotype discordance in three cases. We also discovered an exon 9 conversion-positive CYP2D6*4 gene in a duplication arrangement (CYP2D6*4Nx2) and a CYP2D6*4 allele lacking 100C>T (CYP2D6*4M) in two white subjects. The discovery of an allele that carries only one CYP2D6*36 gene copy provides unequivocal evidence that both CYP2D6*36 and *36x2 are associated with a poor metabolizer phenotype. Given a combined frequency of between 0.5 and 3% in African Americans and Asians, genotyping for CYP2D6*36 should improve the accuracy of genotype-based phenotype prediction in these populations.

  6. Addressable, large-field second harmonic generation microscopy based on 2D acousto-optical deflector and spatial light modulator

    PubMed Central

    Shao, Yonghong; Liu, Honghai; Qin, Wan; Qu, Junle; Peng, Xiang; Niu, Hanben

    2013-01-01

    We present an addressable, large-field second harmonic generation microscope by combining a 2D acousto-optical deflector with a spatial light modulator. The SLM shapes an incoming mode-locked, near-infrared Ti:Sapphire laser beam into a multifocus array, which can be rapidly scanned by changing the incident angle of the laser beam using a 2D acousto-optical deflector. Compared to the single-beam-scan technique, the multifocus array scan can increase the scanning rate and the field-of-view size with the multi-region imaging ability. PMID:24307756

  7. A new inversion method for (T2, D) 2D NMR logging and fluid typing

    NASA Astrophysics Data System (ADS)

    Tan, Maojin; Zou, Youlong; Zhou, Cancan

    2013-02-01

    One-dimensional nuclear magnetic resonance (1D NMR) logging technology has some significant limitations in fluid typing. However, not only can two-dimensional nuclear magnetic resonance (2D NMR) provide some accurate porosity parameters, but it can also identify fluids more accurately than 1D NMR. In this paper, based on the relaxation mechanism of (T2, D) 2D NMR in a gradient magnetic field, a hybrid inversion method that combines least-squares-based QR decomposition (LSQR) and truncated singular value decomposition (TSVD) is examined in the 2D NMR inversion of various fluid models. The forward modeling and inversion tests are performed in detail with different acquisition parameters, such as magnetic field gradients (G) and echo spacing (TE) groups. The simulated results are discussed and described in detail, the influence of the above-mentioned observation parameters on the inversion accuracy is investigated and analyzed, and the observation parameters in multi-TE activation are optimized. Furthermore, the hybrid inversion can be applied to quantitatively determine the fluid saturation. To study the effects of noise level on the hybrid method and inversion results, the numerical simulation experiments are performed using different signal-to-noise-ratios (SNRs), and the effect of different SNRs on fluid typing using three fluid models are discussed and analyzed in detail.

  8. 2-D Reflectometer Modeling for Optimizing the ITER Low-field Side Reflectometer System

    SciTech Connect

    Kramer, G.J.; Nazikian, R.; Valeo, E.J.; Budny, R.V.; Kessel, C.; Johnson, D.

    2005-09-02

    The response of a low-field side reflectometer system for ITER is simulated with a 2?D reflectometer code using a realistic plasma equilibrium. It is found that the reflected beam will often miss its launch point by as much as 40 cm and that a vertical array of receiving antennas is essential in order to observe a reflection on the low-field side of ITER.

  9. Seeded growth of robust SERS-active 2D Au@Ag nanoparticulate films

    SciTech Connect

    Baker, Gary A; Dai, Sheng; Hagaman, Edward {Ed} W; Mahurin, Shannon Mark; Zhu, Haoguo; Bao, Lili

    2008-01-01

    We demonstrate herein a novel and versatile solution-based methodology for fabricating self-organized two-dimensional (2D) Au nanoparticle arrays on glass using in situ nucleation at an aminosilane monolayer followed by seeded, electroless growth; subsequent deposition of Ag produced Au{at}Ag core-shell nanoparticulate films which proved highly promising as surface-enhanced Raman scattering (SERS) platforms.

  10. Magnetic arrays

    DOEpatents

    Trumper, David L.; Kim, Won-jong; Williams, Mark E.

    1997-05-20

    Electromagnet arrays which can provide selected field patterns in either two or three dimensions, and in particular, which can provide single-sided field patterns in two or three dimensions. These features are achieved by providing arrays which have current densities that vary in the windings both parallel to the array and in the direction of array thickness.

  11. Magnetic arrays

    DOEpatents

    Trumper, D.L.; Kim, W.; Williams, M.E.

    1997-05-20

    Electromagnet arrays are disclosed which can provide selected field patterns in either two or three dimensions, and in particular, which can provide single-sided field patterns in two or three dimensions. These features are achieved by providing arrays which have current densities that vary in the windings both parallel to the array and in the direction of array thickness. 12 figs.

  12. Radiofrequency Spectroscopy and Thermodynamics of Fermi Gases in the 2D to Quasi-2D Dimensional Crossover

    NASA Astrophysics Data System (ADS)

    Cheng, Chingyun; Kangara, Jayampathi; Arakelyan, Ilya; Thomas, John

    2016-05-01

    We tune the dimensionality of a strongly interacting degenerate 6 Li Fermi gas from 2D to quasi-2D, by adjusting the radial confinement of pancake-shaped clouds to control the radial chemical potential. In the 2D regime with weak radial confinement, the measured pair binding energies are in agreement with 2D-BCS mean field theory, which predicts dimer pairing energies in the many-body regime. In the qausi-2D regime obtained with increased radial confinement, the measured pairing energy deviates significantly from 2D-BCS theory. In contrast to the pairing energy, the measured radii of the cloud profiles are not fit by 2D-BCS theory in either the 2D or quasi-2D regimes, but are fit in both regimes by a beyond mean field polaron-model of the free energy. Supported by DOE, ARO, NSF, and AFOSR.

  13. Competing coexisting phases in 2D water

    PubMed Central

    Zanotti, Jean-Marc; Judeinstein, Patrick; Dalla-Bernardina, Simona; Creff, Gaëlle; Brubach, Jean-Blaise; Roy, Pascale; Bonetti, Marco; Ollivier, Jacques; Sakellariou, Dimitrios; Bellissent-Funel, Marie-Claire

    2016-01-01

    The properties of bulk water come from a delicate balance of interactions on length scales encompassing several orders of magnitudes: i) the Hydrogen Bond (HBond) at the molecular scale and ii) the extension of this HBond network up to the macroscopic level. Here, we address the physics of water when the three dimensional extension of the HBond network is frustrated, so that the water molecules are forced to organize in only two dimensions. We account for the large scale fluctuating HBond network by an analytical mean-field percolation model. This approach provides a coherent interpretation of the different events experimentally (calorimetry, neutron, NMR, near and far infra-red spectroscopies) detected in interfacial water at 160, 220 and 250 K. Starting from an amorphous state of water at low temperature, these transitions are respectively interpreted as the onset of creation of transient low density patches of 4-HBonded molecules at 160 K, the percolation of these domains at 220 K and finally the total invasion of the surface by them at 250 K. The source of this surprising behaviour in 2D is the frustration of the natural bulk tetrahedral local geometry and the underlying very significant increase in entropy of the interfacial water molecules. PMID:27185018

  14. Phase Engineering of 2D Tin Sulfides.

    PubMed

    Mutlu, Zafer; Wu, Ryan J; Wickramaratne, Darshana; Shahrezaei, Sina; Liu, Chueh; Temiz, Selcuk; Patalano, Andrew; Ozkan, Mihrimah; Lake, Roger K; Mkhoyan, K A; Ozkan, Cengiz S

    2016-06-01

    Tin sulfides can exist in a variety of phases and polytypes due to the different oxidation states of Sn. A subset of these phases and polytypes take the form of layered 2D structures that give rise to a wide host of electronic and optical properties. Hence, achieving control over the phase, polytype, and thickness of tin sulfides is necessary to utilize this wide range of properties exhibited by the compound. This study reports on phase-selective growth of both hexagonal tin (IV) sulfide SnS2 and orthorhombic tin (II) sulfide SnS crystals with diameters of over tens of microns on SiO2 substrates through atmospheric pressure vapor-phase method in a conventional horizontal quartz tube furnace with SnO2 and S powders as the source materials. Detailed characterization of each phase of tin sulfide crystals is performed using various microscopy and spectroscopy methods, and the results are corroborated by ab initio density functional theory calculations. PMID:27099950

  15. Phase Engineering of 2D Tin Sulfides.

    PubMed

    Mutlu, Zafer; Wu, Ryan J; Wickramaratne, Darshana; Shahrezaei, Sina; Liu, Chueh; Temiz, Selcuk; Patalano, Andrew; Ozkan, Mihrimah; Lake, Roger K; Mkhoyan, K A; Ozkan, Cengiz S

    2016-06-01

    Tin sulfides can exist in a variety of phases and polytypes due to the different oxidation states of Sn. A subset of these phases and polytypes take the form of layered 2D structures that give rise to a wide host of electronic and optical properties. Hence, achieving control over the phase, polytype, and thickness of tin sulfides is necessary to utilize this wide range of properties exhibited by the compound. This study reports on phase-selective growth of both hexagonal tin (IV) sulfide SnS2 and orthorhombic tin (II) sulfide SnS crystals with diameters of over tens of microns on SiO2 substrates through atmospheric pressure vapor-phase method in a conventional horizontal quartz tube furnace with SnO2 and S powders as the source materials. Detailed characterization of each phase of tin sulfide crystals is performed using various microscopy and spectroscopy methods, and the results are corroborated by ab initio density functional theory calculations.

  16. Competing coexisting phases in 2D water

    NASA Astrophysics Data System (ADS)

    Zanotti, Jean-Marc; Judeinstein, Patrick; Dalla-Bernardina, Simona; Creff, Gaëlle; Brubach, Jean-Blaise; Roy, Pascale; Bonetti, Marco; Ollivier, Jacques; Sakellariou, Dimitrios; Bellissent-Funel, Marie-Claire

    2016-05-01

    The properties of bulk water come from a delicate balance of interactions on length scales encompassing several orders of magnitudes: i) the Hydrogen Bond (HBond) at the molecular scale and ii) the extension of this HBond network up to the macroscopic level. Here, we address the physics of water when the three dimensional extension of the HBond network is frustrated, so that the water molecules are forced to organize in only two dimensions. We account for the large scale fluctuating HBond network by an analytical mean-field percolation model. This approach provides a coherent interpretation of the different events experimentally (calorimetry, neutron, NMR, near and far infra-red spectroscopies) detected in interfacial water at 160, 220 and 250 K. Starting from an amorphous state of water at low temperature, these transitions are respectively interpreted as the onset of creation of transient low density patches of 4-HBonded molecules at 160 K, the percolation of these domains at 220 K and finally the total invasion of the surface by them at 250 K. The source of this surprising behaviour in 2D is the frustration of the natural bulk tetrahedral local geometry and the underlying very significant increase in entropy of the interfacial water molecules.

  17. 2-D Inhomogeneous Modeling of the Solar CO Bands

    NASA Astrophysics Data System (ADS)

    Ayres, T. R.

    1996-05-01

    The recent discovery of off-limb emissions in the mid-IR ( ~ 5 mu m) vibration-rotation bands of solar carbon monoxide (CO) has sparked new interest in the formation of the molecular lines, and their ability to diagnose thermal conditions at high altitudes. The off-limb extensions of the strong CO lines indicate the penetration of cool material (T ~ 3500 K) several hundred kilometers into the otherwise hot (T ~ 6000 K) chromosphere. The origin of the cool gas, and its role in the thermal energy balance, remain controversial. The interpretation of the CO observations must rely heavily upon numerical modeling, in particular highly-inhomogeneous thermal structures arrayed in a 2-D scheme that can properly treat the geometry of the grazing rays at the solar limb. The radiation transport, itself, is especially simple for the CO off-limb emissions, because the fundamental bands form quite close to LTE (high collision rates; low spontaneous decay rates) and the background continuum is purely thermal as well (f--f transitions in H(-) and H). Thus, the geometrical aspects of the problem can be treated in considerably more detail than would be practical for typical NLTE scattering lines. I describe the recent modeling efforts, and the diagnostic potential of the CO bands for future observational studies of inhomogeneous surface structure on the Sun, and on other stars of late spectral type. This work was supported by NSF grant AST-9218063 to the University of Colorado.

  18. Application specific serial arithmetic arrays

    NASA Technical Reports Server (NTRS)

    Winters, K.; Mathews, D.; Thompson, T.

    1990-01-01

    High performance systolic arrays of serial-parallel multiplier elements may be rapidly constructed for specific applications by applying hardware description language techniques to a library of full-custom CMOS building blocks. Single clock pre-charged circuits have been implemented for these arrays at clock rates in excess of 100 Mhz using economical 2-micron (minimum feature size) CMOS processes, which may be quickly configured for a variety of applications. A number of application-specific arrays are presented, including a 2-D convolver for image processing, an integer polynomial solver, and a finite-field polynomial solver.

  19. VizieR Online Data Catalog: c2d Spitzer final data release (DR4) (Evans+, 2003)

    NASA Astrophysics Data System (ADS)

    Evans, N. J., II; Allen, L. E.; Blake, G. A.; Boogert, A. C. A.; Bourke, T.; Harvey, P. M.; Kessler, J. E.; Koerner, D. W.; Lee, C. W.; Mundy, L. G.; Myers, P. C.; Padgett, D. L.; Pontoppidan, K.; Sargent, A. I.; Stapelfeldt, K. R.; van Dishoeck, E. F.; Young, C. H.; Young, K. E.

    2014-05-01

    This is the final delivery (DR4, Fall 2006 and Fall 2007) of the Spitzer Space Telescope "From Molecular Cores to Planet-Forming Disks" (c2d) Legacy Project. The data are also available as Enhanced Products from the Spitzer Science Center (SSC). c2d has delivered 867 catalogs. IRSA has merged these delivered catalogs into four groups - Clouds, Off-Cloud, Cores, Stars - and serves them through the general catalog search engine Gator. Many of the delivered catalogs, images and spectra are accessible through IRSA's general search service, Atlas. As a service to its users, the CDS has downloaded a dataset containing most of the c2d data (but not all columns) from the IRSA archive. The individual catalogs are listed below: C2D Fall '07 Full CLOUDS Catalog (CHA_II, LUP, OPH, PER, SER) C2D Fall '07 High Reliability (HREL) CLOUDS Catalog (CHA_II, LUP, OPH, PER, SER) C2D Fall '07 candidate Young Stellar Objects (YSO) CLOUDS Catalog (CHA_II, LUP, OPH, PER, SER) C2D Fall '07 Full OFF-CLOUD Catalog (CHA_II, LUP, OPH, PER, SER) C2D Fall '07 candidate Young Stellar Objects (YSO) OFF-CLOUD Catalog (CHA_II, LUP, OPH, PER, SER) C2D Fall '07 Full CORES Catalog C2D Fall '07 candidate Young Stellar Objects (YSO) CORES Catalog C2D Fall '07 Full STARS Catalog C2D Fall '07 candidate Young Stellar Objects (YSO) STARS Catalog These tables have been merged into a single table at CDS. All three SIRTF instruments (Infrared Array Camera [IRAC], Multiband Imaging Photometer for SIRTF [MIPS], and Infrared Spectrograph [IRS]) were used to observe sources that span the evolutionary sequence from molecular cores to protoplanetary disks, encompassing a wide range of cloud masses, stellar masses, and star-forming environments. (1 data file).

  20. 2-D Animation's Not Just for Mickey Mouse.

    ERIC Educational Resources Information Center

    Weinman, Lynda

    1995-01-01

    Discusses characteristics of two-dimensional (2-D) animation; highlights include character animation, painting issues, and motion graphics. Sidebars present Silicon Graphics animations tools and 2-D animation programs for the desktop computer. (DGM)

  1. Generates 2D Input for DYNA NIKE & TOPAZ

    SciTech Connect

    Hallquist, J. O.; Sanford, Larry

    1996-07-15

    MAZE is an interactive program that serves as an input and two-dimensional mesh generator for DYNA2D, NIKE2D, TOPAZ2D, and CHEMICAL TOPAZ2D. MAZE also generates a basic template for ISLAND input. MAZE has been applied to the generation of input data to study the response of two-dimensional solids and structures undergoing finite deformations under a wide variety of large deformation transient dynamic and static problems and heat transfer analyses.

  2. MAZE96. Generates 2D Input for DYNA NIKE & TOPAZ

    SciTech Connect

    Sanford, L.; Hallquist, J.O.

    1992-02-24

    MAZE is an interactive program that serves as an input and two-dimensional mesh generator for DYNA2D, NIKE2D, TOPAZ2D, and CHEMICAL TOPAZ2D. MAZE also generates a basic template for ISLAND input. MAZE has been applied to the generation of input data to study the response of two-dimensional solids and structures undergoing finite deformations under a wide variety of large deformation transient dynamic and static problems and heat transfer analyses.

  3. Design of easily testable and reconfigurable systolic arrays

    SciTech Connect

    Kim, J.H.

    1987-01-01

    Systolic arrays are considered to be preferred architectures for executing linear algebraic operations. In this thesis, easily testable and reconfigurable (ETAR) systolic arrays are studied to achieve the yield enhancement. New 2-D systolic arrays that lend themselves to easy reconfiguration as well as efficient implementations of algorithms are proposed. The 2-D bidirectional and unidirectional systolic arrays proposed are often better architectures than the rectangular and hexagonal systolic arrays proposed earlier, if one considers area, time and reconfigurability. Methods to design linear and 2-D ETAR systolic arrays are proposed. Procedures to design linear and 2-D unidirectional and bidirectional systolic arrays are given. The main feature of the proposed designs is that the COMUs of the PEs in the linear array can all be tested simultaneously. Another feature is that the throughputs of the reconfigured linear unidirectional as well as bidirectional arrays can remain to be equal to those of the fault-free linear arrays. A reconfiguration algorithm for 2-D systolic arrays is also proposed.

  4. Offering an Array of Improvements

    NASA Technical Reports Server (NTRS)

    2001-01-01

    Sensors Unlimited, Inc., with SBIR funding from NASA's Langley Research Center, Goddard Space Flight Center, Marshall Space Flight Center, and the Jet Propulsion Laboratory, developed a monolithic focal plane array for near-infrared imaging. The company developed one- (1- D) and two-dimensional (2-D) imaging arrays consisting of a highly reliable InGaAs p-I-n diode as a photodetector for monitoring a variety of applications, including single element device applications in receivers. The InGaAs 1-D and 2-D arrays have many applications. For example, they monitor the performance of dense wavelength division multiplexing (DWDM) systems- the process of packaging many channels into a single fiber-optic cable. Sensors Unlimited commercially offers its LXTM and LYTM Series InGaAs linear arrays for reliable DWDM performance monitoring. The LX and LY arrays enable instrument module designs with no moving parts, which provides for superior uniformity, and fast, linear outputs that remain stable over a wide temperature range. Innovative technologies derived from the monolithic focal plane array have enabled telecommunication companies to optimize existing bandwidth in their fiber-optic networks in order to support a high volume of network traffic. At the same time, the technologies obtained from the array have the potential for reducing costs, while increasing performance from Sensors Unlimited's current product lines.

  5. 2d PDE Linear Symmetric Matrix Solver

    1983-10-01

    ICCG2 (Incomplete Cholesky factorized Conjugate Gradient algorithm for 2d symmetric problems) was developed to solve a linear symmetric matrix system arising from a 9-point discretization of two-dimensional elliptic and parabolic partial differential equations found in plasma physics applications, such as resistive MHD, spatial diffusive transport, and phase space transport (Fokker-Planck equation) problems. These problems share the common feature of being stiff and requiring implicit solution techniques. When these parabolic or elliptic PDE''s are discretized withmore » finite-difference or finite-element methods,the resulting matrix system is frequently of block-tridiagonal form. To use ICCG2, the discretization of the two-dimensional partial differential equation and its boundary conditions must result in a block-tridiagonal supermatrix composed of elementary tridiagonal matrices. The incomplete Cholesky conjugate gradient algorithm is used to solve the linear symmetric matrix equation. Loops are arranged to vectorize on the Cray1 with the CFT compiler, wherever possible. Recursive loops, which cannot be vectorized, are written for optimum scalar speed. For matrices lacking symmetry, ILUCG2 should be used. Similar methods in three dimensions are available in ICCG3 and ILUCG3. A general source containing extensions and macros, which must be processed by a pre-compiler to obtain the standard FORTRAN source, is provided along with the standard FORTRAN source because it is believed to be more readable. The pre-compiler is not included, but pre-compilation may be performed by a text editor as described in the UCRL-88746 Preprint.« less

  6. 2d PDE Linear Asymmetric Matrix Solver

    1983-10-01

    ILUCG2 (Incomplete LU factorized Conjugate Gradient algorithm for 2d problems) was developed to solve a linear asymmetric matrix system arising from a 9-point discretization of two-dimensional elliptic and parabolic partial differential equations found in plasma physics applications, such as plasma diffusion, equilibria, and phase space transport (Fokker-Planck equation) problems. These equations share the common feature of being stiff and requiring implicit solution techniques. When these parabolic or elliptic PDE''s are discretized with finite-difference or finite-elementmore » methods, the resulting matrix system is frequently of block-tridiagonal form. To use ILUCG2, the discretization of the two-dimensional partial differential equation and its boundary conditions must result in a block-tridiagonal supermatrix composed of elementary tridiagonal matrices. A generalization of the incomplete Cholesky conjugate gradient algorithm is used to solve the matrix equation. Loops are arranged to vectorize on the Cray1 with the CFT compiler, wherever possible. Recursive loops, which cannot be vectorized, are written for optimum scalar speed. For problems having a symmetric matrix ICCG2 should be used since it runs up to four times faster and uses approximately 30% less storage. Similar methods in three dimensions are available in ICCG3 and ILUCG3. A general source, containing extensions and macros, which must be processed by a pre-compiler to obtain the standard FORTRAN source, is provided along with the standard FORTRAN source because it is believed to be more readable. The pre-compiler is not included, but pre-compilation may be performed by a text editor as described in the UCRL-88746 Preprint.« less

  7. Position control using 2D-to-2D feature correspondences in vision guided cell micromanipulation.

    PubMed

    Zhang, Yanliang; Han, Mingli; Shee, Cheng Yap; Ang, Wei Tech

    2007-01-01

    Conventional camera calibration that utilizes the extrinsic and intrinsic parameters of the camera and the objects has certain limitations for micro-level cell operations due to the presence of hardware deviations and external disturbances during the experimental process, thereby invalidating the extrinsic parameters. This invalidation is often neglected in macro-world visual servoing and affects the visual image processing quality, causing deviation from the desired position in micro-level cell operations. To increase the success rate of vision guided biological micromanipulations, a novel algorithm monitoring the changing image pattern of the manipulators including the injection micropipette and cell holder is designed and implemented based on 2 dimensional (2D)-to 2D feature correspondences and can adjust the manipulator and perform position control simultaneously. When any deviation is found, the manipulator is retracted to the initial focusing plane before continuing the operation.

  8. INVITED ARTICLE: Towards dense, realistic granular media in 2D

    NASA Astrophysics Data System (ADS)

    Luding, Stefan

    2009-12-01

    The development of an applicable theory for granular matter—with both qualitative and quantitative value—is a challenging prospect, given the multitude of states, phases and (industrial) situations it has to cover. Given the general balance equations for mass, momentum and energy, the limiting case of dilute and almost elastic granular gases, where kinetic theory works perfectly well, is the starting point. In most systems, low density co-exists with very high density, where the latter is an open problem for kinetic theory. Furthermore, many additional nonlinear phenomena and material properties are important in realistic granular media, involving, e.g.: (i) multi-particle interactions and elasticity (ii) strong dissipation, (iii) friction, (iv) long-range forces and wet contacts, (v) wide particle size distributions and (vi) various particle shapes. Note that, while some of these issues are more relevant for high density, others are important for both low and high densities; some of them can be dealt with by means of kinetic theory, some cannot. This paper is a review of recent progress towards more realistic models for dense granular media in 2D, even though most of the observations, conclusions and corrections given are qualitatively true also in 3D. Starting from an elastic, frictionless and monodisperse hard sphere gas, the (continuum) balance equations of mass, momentum and energy are given. The equation of state, the (Navier-Stokes level) transport coefficients and the energy-density dissipation rate are considered. Several corrections are applied to those constitutive material laws—one by one—in order to account for the realistic physical effects and properties listed above.

  9. Elastic behavior of Bi2Se3 2D nanosheets grown by van der Waals epitaxy

    NASA Astrophysics Data System (ADS)

    Yan, Haoming; Vajner, Cooper; Kuhlman, Michael; Guo, Lingling; Li, Lin; Araujo, Paulo T.; Wang, Hung-Ta

    2016-07-01

    Elastic properties of bismuth selenite (Bi2Se3) two-dimensional (2D) nanosheets were investigated using atomic force microscope (AFM) nanoindentations. Bi2Se3 2D nanosheets were synthesized by van der Waals epitaxy and subsequently transferred on SiO2/Si substrates containing pre-fabricated hole arrays. The suspension of 2D nanosheets was confirmed via the distinct optical contrast characteristics and AFM. In nanoindentations, the correlation between a point force load and the elastic response in the deformation depth was found being thickness-dependent, between 7 and 12 quintuple layers. The Young's modulus, E = 17.86-25.45 GPa (fitted value = 20.67 GPa), and the pretension, T = 0.0218-0.0417 N/m, acquired according to the bending plate regime are consistent with ones from the stretching membrane regime. Furthermore, these Bi2Se3 2D nanosheets could elastically endure a 4.0%-8.3% strain before being ruptured with AFM tips. Compliant and robust elastic properties of Bi2Se3 2D nanosheets, as observed, provide a feasible way for exploring the topological phase transition.

  10. Network models for 2D disordered superconductors

    NASA Astrophysics Data System (ADS)

    Kagalovsky, Victor; Horovitz, Baruch; Avishai, Yshai

    2004-04-01

    We study new random matrix symmetry classes which arise in models of non-interacting quasi-particles in disordered superconductors. Within the Altland-Zirnbauer classification scheme these are class C (with time-reversal symmetry broken and spin-rotaion invariance intact), and class D where both symmetries are broken. Preliminary studies of the two remaining symmetry classes CI and DIII are briefly mentioned. New results are presented pertaining to the 3d realization of class C, which, physically, corresponds to a layered superconductor.

  11. A Planar Quantum Transistor Based on 2D-2D Tunneling in Double Quantum Well Heterostructures

    SciTech Connect

    Baca, W.E.; Blount, M.A.; Hafich, M.J.; Lyo, S.K.; Moon, J.S.; Reno, J.L.; Simmons, J.A.; Wendt, J.R.

    1998-12-14

    We report on our work on the double electron layer tunneling transistor (DELTT), based on the gate-control of two-dimensional -- two-dimensional (2D-2D) tunneling in a double quantum well heterostructure. While previous quantum transistors have typically required tiny laterally-defined features, by contrast the DELTT is entirely planar and can be reliably fabricated in large numbers. We use a novel epoxy-bond-and-stop-etch (EBASE) flip-chip process, whereby submicron gating on opposite sides of semiconductor epitaxial layers as thin as 0.24 microns can be achieved. Because both electron layers in the DELTT are 2D, the resonant tunneling features are unusually sharp, and can be easily modulated with one or more surface gates. We demonstrate DELTTs with peak-to-valley ratios in the source-drain I-V curve of order 20:1 below 1 K. Both the height and position of the resonant current peak can be controlled by gate voltage over a wide range. DELTTs with larger subband energy offsets ({approximately} 21 meV) exhibit characteristics that are nearly as good at 77 K, in good agreement with our theoretical calculations. Using these devices, we also demonstrate bistable memories operating at 77 K. Finally, we briefly discuss the prospects for room temperature operation, increases in gain, and high-speed.

  12. 'Brukin2D': a 2D visualization and comparison tool for LC-MS data

    PubMed Central

    Tsagkrasoulis, Dimosthenis; Zerefos, Panagiotis; Loudos, George; Vlahou, Antonia; Baumann, Marc; Kossida, Sophia

    2009-01-01

    Background Liquid Chromatography-Mass Spectrometry (LC-MS) is a commonly used technique to resolve complex protein mixtures. Visualization of large data sets produced from LC-MS, namely the chromatogram and the mass spectra that correspond to its compounds is the focus of this work. Results The in-house developed 'Brukin2D' software, built in Matlab 7.4, which is presented here, uses the compound data that are exported from the Bruker 'DataAnalysis' program, and depicts the mean mass spectra of all the chromatogram compounds from one LC-MS run, in one 2D contour/density plot. Two contour plots from different chromatograph runs can then be viewed in the same window and automatically compared, in order to find their similarities and differences. The results of the comparison can be examined through detailed mass quantification tables, while chromatogram compound statistics are also calculated during the procedure. Conclusion 'Brukin2D' provides a user-friendly platform for quick, easy and integrated view of complex LC-MS data. The software is available at . PMID:19534737

  13. Inhibition of human cytochrome P450 2D6 (CYP2D6) by methadone.

    PubMed Central

    Wu, D; Otton, S V; Sproule, B A; Busto, U; Inaba, T; Kalow, W; Sellers, E M

    1993-01-01

    1. In microsomes prepared from three human livers, methadone competitively inhibited the O-demethylation of dextromethorphan, a marker substrate for CYP2D6. The apparent Ki value of methadone ranged from 2.5 to 5 microM. 2. Two hundred and fifty-two (252) white Caucasians, including 210 unrelated healthy volunteers and 42 opiate abusers undergoing treatment with methadone were phenotyped using dextromethorphan as the marker drug. Although the frequency of poor metabolizers was similar in both groups, the extensive metabolizers among the opiate abusers tended to have higher O-demethylation metabolic ratios and to excrete less of the dose as dextromethorphan metabolites than control extensive metabolizer subjects. These data suggest inhibition of CYP2D6 by methadone in vivo as well. 3. Because methadone is widely used in the treatment of opiate abuse, inhibition of CYP2D6 activity in these patients might contribute to exaggerated response or unexpected toxicity from drugs that are substrates of this enzyme. PMID:8448065

  14. Mean and turbulent flow development through an array of rotating elements

    NASA Astrophysics Data System (ADS)

    Craig, Anna; Dabiri, John; Koseff, Jeffrey

    2014-11-01

    The adjustment of an incoming boundary layer profile as it impacts and interacts with an array of elements has received significant attention in the context of terrestrial and aquatic canopies and more recently in the context of horizontal axis wind farms. The distance required for the mean flow profile to stabilize, the energy transport through the array, and the structure of the turbulence within the array are directly dependent upon such factors as the element height, density, rigidity/flexibility, frontal area distribution, element homogeneity, and underlying topography. In the present study, the mean and turbulent development of the flow through an array of rotating elements was examined experimentally. Element rotation has been shown to drastically alter wake dynamics of single and paired elements, but the possible extension of such rotation-driven dynamics had not previously been examined on larger groups of elements. Practically, such an array of rotating elements may provide insight into the flow dynamics of an array of vertical axis wind turbines. 2D particle image velocimetry was used along the length of the array in order to examine the effects of an increasing ratio of cylinder rotation speed to streamwise freestream velocity on flow development and structure. Work supported by a NSF Graduate Research Fellowship & Stanford Graduate Fellowship to A.E.C, by funding to J.O.D. from ONR N000141211047 and the Gordon and Betty Moore Foundation through Grant GBMF2645, and by funding from the EFML.

  15. The horizontal planar structure of kinetic energy in a model vertical-axis wind turbine array

    NASA Astrophysics Data System (ADS)

    Craig, Anna; Zeller, Robert; Zarama, Francisco; Weitzman, Joel; Dabiri, John; Koseff, Jeffrey

    2013-11-01

    Recent studies have indicated that arrays of vertical axis wind turbines (VAWTs) could potentially harvest significantly more power per unit land area than arrays composed of conventional horizontal axis wind turbines. However, to design VAWT arrays for optimal power conversion, a more comprehensive understanding of inter-turbine energy transfer is needed. In the presented study, a geometrically scaled array of rotating circular cylinders is used to model a VAWT array. The horizontal inter-cylinder mean fluid velocities and Reynolds stresses are measured on several cross-sections using 2D particle image velocimetry in a flume. Two orientations of the array relative to the incoming flow are tested. The results indicate that cylinder rotation drives asymmetric mean flow patterns within and above the array, resulting in non-uniform distributions of turbulent kinetic energy. The variability is observed to be directly related to the ratio of the cylinder rotation speed to the streamwise water velocity. Emphasis is placed on the implications of the asymmetries for power production. Work supported by a Stanford Graduate Fellowship to A.E.C, by funding to J.O.D. from ONR N000141211047 and the Gordon and Betty Moore Foundation through Grant GBMF2645, and by funding from the Environmental Fluid Mechanics Laboratory, Stanford University.

  16. Cooperative dynamics in ultrasoft 2D crystals

    NASA Astrophysics Data System (ADS)

    Sprakel, Joris; van der Meer, Berend; Dijkstra, Marjolein; van der Gucht, Jasper

    2015-03-01

    The creation, annihilation, and diffusion of defects in crystal lattices play an important role during crystal melting and deformation. Although it is well understood how defects form and react when crystals are subjected to external stresses, it remains unclear how crystals cope with internal stresses. We report a study in which we create a highly localized internal stress, by means of optical tweezing, in a crystal formed from micrometer-sized colloidal spheres and directly observe how the solid reacts using microscopy. We find that, even though the excitation is highly localized, a collective dance of colloidal particles results; these collective modes take the form of closed rings or open-ended strings, depending on the sequence of events which nucleate the rearrangements. Surprisingly, we find from Brownian Dynamics simulations that these cooperative dynamics are thermally-activated modes inherent to the crystal, and can even occur through a single, sufficiently large thermal fluctuation, resulting in the irreversible displacement of 100s of particles from their lattice sites.

  17. Advances in fast 2D camera data handling and analysis on NSTX

    SciTech Connect

    Davis, W. M.; Patel, R. I.; Boeglin, W. U.; Roquemore, A. L.; Maqueda, R. J.; Zweben, S. J.

    2010-07-01

    The use of fast 2D cameras on NSTX continues to grow. There are 6 cameras with the capability of taking up to 1–2 gigabytes (GBs) of data apiece during each plasma shot on the National Spherical Torus Experiment (NSTX). Efficient storage and retrieval of this data remains a challenge. Performance comparisons are presented for reading data stored in MDSplus, using both compressed data and segmented records, and direct access I/O with different read sizes. Encouragingly, fast 2D camera data provides considerable insight into plasma complexities, such as small-scale turbulence and particle transport. The last part of this paper is an example of more recent uses: dual cameras looking at the same region of the plasma from different angles, which can provide trajectories of incandescent particles in 3D. A laboratory simulation of the 3D trajectories is presented, as well as corresponding data from NSTX plasma where glowing dust particles can be followed.

  18. Electrostatic 2D assembly of bionanoparticles on a cationic lipid monolayer.

    NASA Astrophysics Data System (ADS)

    Kewalramani, Sumit; Wang, Suntao; Fukuto, Masafumi; Yang, Lin; Niu, Zhongwei; Nguyen, Giang; Wang, Qian

    2010-03-01

    We present a grazing-incidence small-angle X-ray scattering (GISAXS) study on 2D assembly of cowpea mosaic virus (CPMV) under a mixed cationic-zwitterionic (DMTAP^+-DMPC) lipid monolayer at the air-water interface. The inter-particle and particle-lipid electrostatic interactions were varied by controlling the subphase pH and the membrane charge density. GISAXS data show that 2D crystals of CPMV are formed above a threshold membrane charge density and only in a narrow pH range just above CPMV's isoelectric point, where the charge on CPMV is expected to be weakly negative. The particle density for the 2D crystals is similar to that for the densest lattice plane in the 3D crystals of CPMV. The results show that the 2D crystallization is achieved in the part of the phase space where the electrostatic interactions are expected to maximize the adsorption of CPMV onto the lipid membrane. This electrostatics-based strategy for controlling interfacial nanoscale assembly should be generally applicable to other nanoparticles.

  19. Correlated Electron Phenomena in 2D Materials

    NASA Astrophysics Data System (ADS)

    Lambert, Joseph G.

    In this thesis, I present experimental results on coherent electron phenomena in layered two-dimensional materials: single layer graphene and van der Waals coupled 2D TiSe2. Graphene is a two-dimensional single-atom thick sheet of carbon atoms first derived from bulk graphite by the mechanical exfoliation technique in 2004. Low-energy charge carriers in graphene behave like massless Dirac fermions, and their density can be easily tuned between electron-rich and hole-rich quasiparticles with electrostatic gating techniques. The sharp interfaces between regions of different carrier densities form barriers with selective transmission, making them behave as partially reflecting mirrors. When two of these interfaces are set at a separation distance within the phase coherence length of the carriers, they form an electronic version of a Fabry-Perot cavity. I present measurements and analysis of multiple Fabry-Perot modes in graphene with parallel electrodes spaced a few hundred nanometers apart. Transition metal dichalcogenide (TMD) TiSe2 is part of the family of materials that coined the term "materials beyond graphene". It contains van der Waals coupled trilayer stacks of Se-Ti-Se. Many TMD materials exhibit a host of interesting correlated electronic phases. In particular, TiSe2 exhibits chiral charge density waves (CDW) below TCDW ˜ 200 K. Upon doping with copper, the CDW state gets suppressed with Cu concentration, and CuxTiSe2 becomes superconducting with critical temperature of T c = 4.15 K. There is still much debate over the mechanisms governing the coexistence of the two correlated electronic phases---CDW and superconductivity. I will present some of the first conductance spectroscopy measurements of proximity coupled superconductor-CDW systems. Measurements reveal a proximity-induced critical current at the Nb-TiSe2 interfaces, suggesting pair correlations in the pure TiSe2. The results indicate that superconducting order is present concurrently with CDW in

  20. Magnetically actuated microshutter arrays

    NASA Astrophysics Data System (ADS)

    Mott, David B.; Aslam, Shahid; Blumenstock, Kenneth A.; Fettig, Rainer K.; Franz, David E.; Kutyrev, Alexander S.; Li, Mary J.; Monroy, Carlos J.; Moseley, S. Harvey; Schwinger, David S.

    2001-10-01

    Two-dimensional microshutter arrays are being developed at NASA Goddard Space Flight Center (GSFC) for the Next Generation Space Telescope (NGST) for use in the near-infrared region. Functioning as focal plane object selection devices, the microshutter arrays are 2-D programmable masks with high efficiency and high contrast. The NGST environment requires cryogenic operation at 45 K. Arrays are close-packed silicon nitride membranes with a unit cell size of 100x100 micrometer. Individual shutters are patterned with a torsion flexure permitting shutters to open 90 degrees with minimized mechanical stress concentration. The mechanical shutter arrays are fabricated with MEMS technologies. The processing includes a RIE front-etch to form shutters out of the nitride membrane, an anisotropic back-etch for wafer thinning, and a deep RIE (DRIE) back-etch down to the nitride shutter membrane to form frames and to relieve the shutters from the silicon substrate. A layer of magnetic material is deposited onto each shutter. Onto the side-wall of the support structure a metal layer is deposited that acts as a vertical hold electrode. Shutters are rotated into the support structure by means of an external magnet that is swept across the shutter array for opening. Addressing is performed through a scheme using row and column address lines on each chip and external addressing electronics.

  1. Kokkos Array

    SciTech Connect

    Edwards Daniel Sunderland, Harold Carter

    2012-09-12

    The Kokkos Array library implements shared-memory array data structures and parallel task dispatch interfaces for data-parallel computational kernels that are performance-portable to multicore-CPU and manycore-accelerator (e.g., GPGPU) devices.

  2. Differential Analysis of 2D NMR Spectra: New Natural Products from a Pilot-Scale Fungal Extract Library

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Using a newly developed protocol for the differential analysis of arrays of 2D NMR spectra, we were able to rapidly identify two previously unreported indole alkaloids from a library of unfractionated fungal extracts. Differential analyses of NMR spectra thus constitute an effective tool for the non...

  3. Systolic arrays

    SciTech Connect

    Moore, W.R.; McCabe, A.P.H.; Vrquhart, R.B.

    1987-01-01

    Selected Contents of this book are: Efficient Systolic Arrays for the Solution of Toeplitz Systems, The Derivation and Utilization of Bit Level Systolic Array Architectures, an Efficient Systolic Array for Distance Computation Required in a Video-Codec Based Motion-Detection, On Realizations of Least-Squares Estimation and Kalman Filtering by Systolic Arrays, and Comparison of Systolic and SIMD Architectures for Computer Vision Computations.

  4. Nanocylinder arrays

    DOEpatents

    Tuominen, Mark; Schotter, Joerg; Thurn-Albrecht, Thomas; Russell, Thomas P.

    2009-08-11

    Pathways to rapid and reliable fabrication of nanocylinder arrays are provided. Simple methods are described for the production of well-ordered arrays of nanopores, nanowires, and other materials. This is accomplished by orienting copolymer films and removing a component from the film to produce nanopores, that in turn, can be filled with materials to produce the arrays. The resulting arrays can be used to produce nanoscale media, devices, and systems.

  5. Nanocylinder arrays

    DOEpatents

    Tuominen, Mark; Schotter, Joerg; Thurn-Albrecht, Thomas; Russell, Thomas P.

    2007-03-13

    Pathways to rapid and reliable fabrication of nanocylinder arrays are provided. Simple methods are described for the production of well-ordered arrays of nanopores, nanowires, and other materials. This is accomplished by orienting copolymer films and removing a component from the film to produce nanopores, that in turn, can be filled with materials to produce the arrays. The resulting arrays can be used to produce nanoscale media, devices, and systems.

  6. 2D DEM model of sand transport with wind interaction

    NASA Astrophysics Data System (ADS)

    Oger, L.; Valance, A.

    2013-06-01

    The advance of the dunes in the desert is a threat to the life of the local people. The dunes invade houses, agricultural land and perturb the circulation on the roads. It is therefore very important to understand the mechanism of sand transport in order to fight against desertification. Saltation in which sand grains are propelled by the wind along the surface in short hops, is the primary mode of blown sand movement [1]. The saltating grains are very energetic and when impact a sand surface, they rebound and consequently eject other particles from the sand bed. The ejected grains, called reptating grains, contribute to the augmentation of the sand flux. Some of them can be promoted to the saltation motion. We use a mechanical model based on the Discrete Element Method to study successive collisions of incident energetic beads with granular packing in the context of Aeolian saltation transport. We investigate the collision process for the case where the incident bead and those from the packing have identical mechanical properties. We analyze the features of the consecutive collision processes made by the transport of the saltating disks by a wind in which its profile is obtained from the counter-interaction between air flow and grain flows. We used a molecular dynamics method known as DEM (soft Discrete Element Method) with a initial static packing of 20000 2D particles. The dilation of the upper surface due to the consecutive collisions is responsible for maintaining the flow at a given energy input due to the wind.

  7. Nonlinear force dependence on optically bound micro-particle arrays in the evanescent fields of fundamental and higher order microfibre modes

    PubMed Central

    Maimaiti, Aili; Holzmann, Daniela; Truong, Viet Giang; Ritsch, Helmut; Nic Chormaic, Síle

    2016-01-01

    Particles trapped in the evanescent field of an ultrathin optical fibre interact over very long distances via multiple scattering of the fibre-guided fields. In ultrathin fibres that support higher order modes, these interactions are stronger and exhibit qualitatively new behaviour due to the coupling of different fibre modes, which have different propagation wave-vectors, by the particles. Here, we study one dimensional longitudinal optical binding interactions of chains of 3 μm polystyrene spheres under the influence of the evanescent fields of a two-mode microfibre. The observation of long-range interactions, self-ordering and speed variation of particle chains reveals strong optical binding effects between the particles that can be modelled well by a tritter scattering-matrix approach. The optical forces, optical binding interactions and the velocity of bounded particle chains are calculated using this method. Results show good agreement with finite element numerical simulations. Experimental data and theoretical analysis show that higher order modes in a microfibre offer a promising method to not only obtain stable, multiple particle trapping or faster particle propulsion speeds, but that they also allow for better control over each individual trapped object in particle ensembles near the microfibre surface. PMID:27451935

  8. Nonlinear force dependence on optically bound micro-particle arrays in the evanescent fields of fundamental and higher order microfibre modes

    NASA Astrophysics Data System (ADS)

    Maimaiti, Aili; Holzmann, Daniela; Truong, Viet Giang; Ritsch, Helmut; Nic Chormaic, Síle

    2016-07-01

    Particles trapped in the evanescent field of an ultrathin optical fibre interact over very long distances via multiple scattering of the fibre-guided fields. In ultrathin fibres that support higher order modes, these interactions are stronger and exhibit qualitatively new behaviour due to the coupling of different fibre modes, which have different propagation wave-vectors, by the particles. Here, we study one dimensional longitudinal optical binding interactions of chains of 3 μm polystyrene spheres under the influence of the evanescent fields of a two-mode microfibre. The observation of long-range interactions, self-ordering and speed variation of particle chains reveals strong optical binding effects between the particles that can be modelled well by a tritter scattering-matrix approach. The optical forces, optical binding interactions and the velocity of bounded particle chains are calculated using this method. Results show good agreement with finite element numerical simulations. Experimental data and theoretical analysis show that higher order modes in a microfibre offer a promising method to not only obtain stable, multiple particle trapping or faster particle propulsion speeds, but that they also allow for better control over each individual trapped object in particle ensembles near the microfibre surface.

  9. Nonlinear force dependence on optically bound micro-particle arrays in the evanescent fields of fundamental and higher order microfibre modes.

    PubMed

    Maimaiti, Aili; Holzmann, Daniela; Truong, Viet Giang; Ritsch, Helmut; Nic Chormaic, Síle

    2016-01-01

    Particles trapped in the evanescent field of an ultrathin optical fibre interact over very long distances via multiple scattering of the fibre-guided fields. In ultrathin fibres that support higher order modes, these interactions are stronger and exhibit qualitatively new behaviour due to the coupling of different fibre modes, which have different propagation wave-vectors, by the particles. Here, we study one dimensional longitudinal optical binding interactions of chains of 3 μm polystyrene spheres under the influence of the evanescent fields of a two-mode microfibre. The observation of long-range interactions, self-ordering and speed variation of particle chains reveals strong optical binding effects between the particles that can be modelled well by a tritter scattering-matrix approach. The optical forces, optical binding interactions and the velocity of bounded particle chains are calculated using this method. Results show good agreement with finite element numerical simulations. Experimental data and theoretical analysis show that higher order modes in a microfibre offer a promising method to not only obtain stable, multiple particle trapping or faster particle propulsion speeds, but that they also allow for better control over each individual trapped object in particle ensembles near the microfibre surface. PMID:27451935

  10. Nonlinear force dependence on optically bound micro-particle arrays in the evanescent fields of fundamental and higher order microfibre modes.

    PubMed

    Maimaiti, Aili; Holzmann, Daniela; Truong, Viet Giang; Ritsch, Helmut; Nic Chormaic, Síle

    2016-01-01

    Particles trapped in the evanescent field of an ultrathin optical fibre interact over very long distances via multiple scattering of the fibre-guided fields. In ultrathin fibres that support higher order modes, these interactions are stronger and exhibit qualitatively new behaviour due to the coupling of different fibre modes, which have different propagation wave-vectors, by the particles. Here, we study one dimensional longitudinal optical binding interactions of chains of 3 μm polystyrene spheres under the influence of the evanescent fields of a two-mode microfibre. The observation of long-range interactions, self-ordering and speed variation of particle chains reveals strong optical binding effects between the particles that can be modelled well by a tritter scattering-matrix approach. The optical forces, optical binding interactions and the velocity of bounded particle chains are calculated using this method. Results show good agreement with finite element numerical simulations. Experimental data and theoretical analysis show that higher order modes in a microfibre offer a promising method to not only obtain stable, multiple particle trapping or faster particle propulsion speeds, but that they also allow for better control over each individual trapped object in particle ensembles near the microfibre surface.

  11. Quantum Diffusion on Molecular Tubes: Universal Scaling of the 1D to 2D Transition

    NASA Astrophysics Data System (ADS)

    Chuang, Chern; Lee, Chee Kong; Moix, Jeremy M.; Knoester, Jasper; Cao, Jianshu

    2016-05-01

    The transport properties of disordered systems are known to depend critically on dimensionality. We study the diffusion coefficient of a quantum particle confined to a lattice on the surface of a tube, where it scales between the 1D and 2D limits. It is found that the scaling relation is universal and independent of the temperature, disorder, and noise parameters, and the essential order parameter is the ratio between the localization length in 2D and the circumference of the tube. Phenomenological and quantitative expressions for transport properties as functions of disorder and noise are obtained and applied to real systems: In the natural chlorosomes found in light-harvesting bacteria the exciton transfer dynamics is predicted to be in the 2D limit, whereas a family of synthetic molecular aggregates is found to be in the homogeneous limit and is independent of dimensionality.

  12. Quantum Diffusion on Molecular Tubes: Universal Scaling of the 1D to 2D Transition.

    PubMed

    Chuang, Chern; Lee, Chee Kong; Moix, Jeremy M; Knoester, Jasper; Cao, Jianshu

    2016-05-13

    The transport properties of disordered systems are known to depend critically on dimensionality. We study the diffusion coefficient of a quantum particle confined to a lattice on the surface of a tube, where it scales between the 1D and 2D limits. It is found that the scaling relation is universal and independent of the temperature, disorder, and noise parameters, and the essential order parameter is the ratio between the localization length in 2D and the circumference of the tube. Phenomenological and quantitative expressions for transport properties as functions of disorder and noise are obtained and applied to real systems: In the natural chlorosomes found in light-harvesting bacteria the exciton transfer dynamics is predicted to be in the 2D limit, whereas a family of synthetic molecular aggregates is found to be in the homogeneous limit and is independent of dimensionality. PMID:27232033

  13. 2D modeling of electromagnetic waves in cold plasmas

    SciTech Connect

    Crombé, K.; Van Eester, D.; Koch, R.; Kyrytsya, V.

    2014-02-12

    The consequences of sheath (rectified) electric fields, resulting from the different mobility of electrons and ions as a response to radio frequency (RF) fields, are a concern for RF antenna design as it can cause damage to antenna parts, limiters and other in-vessel components. As a first step to a more complete description, the usual cold plasma dielectric description has been adopted, and the density profile was assumed to be known as input. Ultimately, the relevant equations describing the wave-particle interaction both on the fast and slow timescale will need to be tackled but prior to doing so was felt as a necessity to get a feeling of the wave dynamics involved. Maxwell's equations are solved for a cold plasma in a 2D antenna box with strongly varying density profiles crossing also lower hybrid and ion-ion hybrid resonance layers. Numerical modelling quickly becomes demanding on computer power, since a fine grid spacing is required to capture the small wavelengths effects of strongly evanescent modes.

  14. Electron dynamics and valley relaxation in 2D semiconductors

    NASA Astrophysics Data System (ADS)

    Gundogdu, Kenan

    2015-03-01

    Single layer transition metal dichalcogenides are 2D semiconducting systems with unique electronic band structure. Two-valley energy bands along with strong spin-orbital coupling lead to valley dependent career spin polarization, which is the basis for recently proposed valleytronic applications. Since the durations of valley population provide the time window in which valley specific processes take place, it is an essential parameter for developing valleytronic devices. These systems also exhibit unusually strong many body affects, such as strong exciton and trion binding, due to reduced dielectric screening of Coulomb interactions. But there is not much known about the impact of strong many particle correlations on spin and valley polarization dynamics. Here we report direct measurements of ultrafast valley specific relaxation dynamics in single layer MoS2 and WS2. We found that excitonic many body interactions significantly contribute to the relaxation process. Biexciton formation reveals hole valley spin relaxation time. Our results also suggest initial fast intervalley electron scattering and electron spin relaxation leads to loss of electron valley polarization, which then facilitates hole valley relaxation via excitonic spin exchange interaction.

  15. 2D Fluidization of Nanomaterials by Biomimetic Membranes

    NASA Astrophysics Data System (ADS)

    Kelly, Kathleen; Forstner, Martin

    2012-02-01

    The last decade has seen much progress in the synthesis and manufacturing of a large variety of nanometer sized particles of different materials, geometries and properties. If they can be assembled into larger structures, these manmade nano-objects are posed to be the ``atoms'' and ``molecules'' of new materials. In order to facilitate their dynamic rearrangements we have developed a method that uses material specific binding peptides to anchor nano-objects to lipids in supported bilayers (SLB). In this study we use single walled carbon nanotubes (CNT) with a mean length of 1 micrometer as model of a potential nano-building block. By fluorescently labeling CNTs we are able to use video-microscopy to investigate the dynamic behavior of membrane anchored CNTs. We show that the 2D fluidity of the lipid membrane can be successfully templated on the CNTs and that they stay laterally mobile while being confined to a plane. Furthermore, the dependence of CNT mobility on specific binding stoichiometries is discussed.

  16. Velocity distributions for 2D inelastic granular gases

    NASA Astrophysics Data System (ADS)

    Miracle, Dylan J.; Goldman, Daniel I.; Moon, Sung Joon; Rericha, Erin; Swift, J. B.; Swinney, Harry L.

    2002-11-01

    A previous study of a vertically vibrated 2D granular gas found a time-averaged horizontal velocity distribution function of the form P(v) exp(-C|v|^3/2) for the entire velocity range(F. Rouyer and N. Menon, Phys. Rev. Lett. 85), 3676 (2000).. We examine the dependence of the velocity distribution function on phase in the cycle, height above the plate and air pressure in the container. We use 1.6 mm stainless steel balls confined to a vertical plane by a container 32σ tall, 48σ wide, and 1.15σ thick, where σ is the particle diameter. The container oscillates with peak acceleration 20g and frequency 50 Hz. We observe that a shock forms at collision of the plate with the layer and propagates through the layer, heating the grains. The shock rapidly decays over a distance of approximately 8σ above the plate; above this height the granular temperature and density are essentially independent of phase in the cycle. In this steady-state region, we compare the observed functional form of the velocity distribution to molecular dynamics simulations.

  17. Phase Behavior of 2D Charged Hydrophobic Colloids in Flat and Curved Space

    NASA Astrophysics Data System (ADS)

    Kelleher, Colm; Guerra, Rodrigo; Chaikin, Paul

    Charged hydrophobic colloids, when dispersed in oil with a relatively high dielectric constant, can become highly charged. In the presence of an interface with a conducting aqueous phase, particles bind strongly to the interface via image-charge attraction. At sufficiently high density, these charged interfacial particles self-organize into a 2D repulsive (Wigner) crystalline solid phase, while at lower densities, the particles form a 2D fluid. By observing samples prepared at different densities, we can probe various points in the phase diagram of this soft 2D material, and compare our results with applicable theory and simulations. In this talk, we present two sets of experiments we have performed on this system: first, we show how we can use gravity as an external force to create a controlled density gradient, and thereby directly measure the equation of state and other quantities of interest. Second, we discuss how, by observing particles which are bound to the surface of spherical droplets, we can explore how the presence of finite background curvature affects the phase behavior of the system.

  18. Mechanical characterization of 2D, 2D stitched, and 3D braided/RTM materials

    NASA Technical Reports Server (NTRS)

    Deaton, Jerry W.; Kullerd, Susan M.; Portanova, Marc A.

    1993-01-01

    Braided composite materials have potential for application in aircraft structures. Fuselage frames, floor beams, wing spars, and stiffeners are examples where braided composites could find application if cost effective processing and damage tolerance requirements are met. Another important consideration for braided composites relates to their mechanical properties and how they compare to the properties of composites produced by other textile composite processes being proposed for these applications. Unfortunately, mechanical property data for braided composites do not appear extensively in the literature. Data are presented in this paper on the mechanical characterization of 2D triaxial braid, 2D triaxial braid plus stitching, and 3D (through-the-thickness) braid composite materials. The braided preforms all had the same graphite tow size and the same nominal braid architectures, (+/- 30 deg/0 deg), and were resin transfer molded (RTM) using the same mold for each of two different resin systems. Static data are presented for notched and unnotched tension, notched and unnotched compression, and compression after impact strengths at room temperature. In addition, some static results, after environmental conditioning, are included. Baseline tension and compression fatigue results are also presented, but only for the 3D braided composite material with one of the resin systems.

  19. A 2D electrostatic PIC code for the Mark III Hypercube

    SciTech Connect

    Ferraro, R.D.; Liewer, P.C.; Decyk, V.K.

    1990-12-31

    We have implemented a 2D electrostastic plasma particle in cell (PIC) simulation code on the Caltech/JPL Mark IIIfp Hypercube. The code simulates plasma effects by evolving in time the trajectories of thousands to millions of charged particles subject to their self-consistent fields. Each particle`s position and velocity is advanced in time using a leap frog method for integrating Newton`s equations of motion in electric and magnetic fields. The electric field due to these moving charged particles is calculated on a spatial grid at each time by solving Poisson`s equation in Fourier space. These two tasks represent the largest part of the computation. To obtain efficient operation on a distributed memory parallel computer, we are using the General Concurrent PIC (GCPIC) algorithm previously developed for a 1D parallel PIC code.

  20. Computational Screening of 2D Materials for Photocatalysis.

    PubMed

    Singh, Arunima K; Mathew, Kiran; Zhuang, Houlong L; Hennig, Richard G

    2015-03-19

    Two-dimensional (2D) materials exhibit a range of extraordinary electronic, optical, and mechanical properties different from their bulk counterparts with potential applications for 2D materials emerging in energy storage and conversion technologies. In this Perspective, we summarize the recent developments in the field of solar water splitting using 2D materials and review a computational screening approach to rapidly and efficiently discover more 2D materials that possess properties suitable for solar water splitting. Computational tools based on density-functional theory can predict the intrinsic properties of potential photocatalyst such as their electronic properties, optical absorbance, and solubility in aqueous solutions. Computational tools enable the exploration of possible routes to enhance the photocatalytic activity of 2D materials by use of mechanical strain, bias potential, doping, and pH. We discuss future research directions and needed method developments for the computational design and optimization of 2D materials for photocatalysis.

  1. Synthetic Covalent and Non-Covalent 2D Materials.

    PubMed

    Boott, Charlotte E; Nazemi, Ali; Manners, Ian

    2015-11-16

    The creation of synthetic 2D materials represents an attractive challenge that is ultimately driven by their prospective uses in, for example, electronics, biomedicine, catalysis, sensing, and as membranes for separation and filtration. This Review illustrates some recent advances in this diverse field with a focus on covalent and non-covalent 2D polymers and frameworks, and self-assembled 2D materials derived from nanoparticles, homopolymers, and block copolymers.

  2. A Geometric Boolean Library for 2D Objects

    2006-01-05

    The 2D Boolean Library is a collection of C++ classes -- which primarily represent 2D geometric data and relationships, and routines -- which contain algorithms for 2D geometric Boolean operations and utility functions. Classes are provided for 2D points, lines, arcs, edgeuses, loops, surfaces and mask sets. Routines are provided that incorporate the Boolean operations Union(OR), XOR, Intersection and Difference. Various analytical geometry routines and routines for importing and exporting the data in various filemore » formats, are also provided in the library.« less

  3. Protein structure validation and identification from unassigned residual dipolar coupling data using 2D-PDPA.

    PubMed

    Fahim, Arjang; Mukhopadhyay, Rishi; Yandle, Ryan; Prestegard, James H; Valafar, Homayoun

    2013-08-22

    More than 90% of protein structures submitted to the PDB each year are homologous to some previously characterized protein structure. The extensive resources that are required for structural characterization of proteins can be justified for the 10% of the novel structures, but not for the remaining 90%. This report presents the 2D-PDPA method, which utilizes unassigned residual dipolar coupling in order to address the economics of structure determination of routine proteins by reducing the data acquisition and processing time. 2D-PDPA has been demonstrated to successfully identify the correct structure of an array of proteins that range from 46 to 445 residues in size from a library of 619 decoy structures by using unassigned simulated RDC data. When using experimental data, 2D-PDPA successfully identified the correct NMR structures from the same library of decoy structures. In addition, the most homologous X-ray structure was also identified as the second best structural candidate. Finally, success of 2D-PDPA in identifying and evaluating the most appropriate structure from a set of computationally predicted structures in the case of a previously uncharacterized protein Pf2048.1 has been demonstrated. This protein exhibits less than 20% sequence identity to any protein with known structure and therefore presents a compelling and practical application of our proposed work.

  4. Protein structure validation and identification from unassigned residual dipolar coupling data using 2D-PDPA.

    PubMed

    Fahim, Arjang; Mukhopadhyay, Rishi; Yandle, Ryan; Prestegard, James H; Valafar, Homayoun

    2013-01-01

    More than 90% of protein structures submitted to the PDB each year are homologous to some previously characterized protein structure. The extensive resources that are required for structural characterization of proteins can be justified for the 10% of the novel structures, but not for the remaining 90%. This report presents the 2D-PDPA method, which utilizes unassigned residual dipolar coupling in order to address the economics of structure determination of routine proteins by reducing the data acquisition and processing time. 2D-PDPA has been demonstrated to successfully identify the correct structure of an array of proteins that range from 46 to 445 residues in size from a library of 619 decoy structures by using unassigned simulated RDC data. When using experimental data, 2D-PDPA successfully identified the correct NMR structures from the same library of decoy structures. In addition, the most homologous X-ray structure was also identified as the second best structural candidate. Finally, success of 2D-PDPA in identifying and evaluating the most appropriate structure from a set of computationally predicted structures in the case of a previously uncharacterized protein Pf2048.1 has been demonstrated. This protein exhibits less than 20% sequence identity to any protein with known structure and therefore presents a compelling and practical application of our proposed work. PMID:23973992

  5. Protein Structure Validation and Identification from Unassigned Residual Dipolar Coupling Data Using 2D-PDPA

    PubMed Central

    Fahim, Arjang; Mukhopadhyay, Rishi; Yandle, Ryan; Prestegard, James H.; Valafar, Homayoun

    2014-01-01

    More than 90% of protein structures submitted to the PDB each year are homologous to some previously characterized protein structure. The extensive resources that are required for structural characterization of proteins can be justified for the 10% of the novel structures, but not for the remaining 90%. This report presents the 2D-PDPA method, which utilizes unassigned residual dipolar coupling in order to address the economics of structure determination of routine proteins by reducing the data acquisition and processing time. 2D-PDPA has been demonstrated to successfully identify the correct structure of an array of proteins that range from 46 to 445 residues in size from a library of 619 decoy structures by using unassigned simulated RDC data. When using experimental data, 2D-PDPA successfully identified the correct NMR structures from the same library of decoy structures. In addition, the most homologous X-ray structure was also identified as the second best structural candidate. Finally, success of 2D-PDPA in identifying and evaluating the most appropriate structure from a set of computationally predicted structures in the case of a previously uncharacterized protein Pf2048.1 has been demonstrated. This protein exhibits less than 20% sequence identity to any protein with known structure and therefore presents a compelling and practical application of our proposed work. PMID:23973992

  6. DETECTION OF N{sub 2}D{sup +} IN A PROTOPLANETARY DISK

    SciTech Connect

    Huang, Jane; Öberg, Karin I.

    2015-08-20

    Observations of deuterium fractionation in the solar system, and in interstellar and circumstellar material, are commonly used to constrain the formation environment of volatiles. Toward protoplanetary disks, this approach has been limited by the small number of detected deuterated molecules, i.e., DCO{sup +} and DCN. Based on ALMA Cycle 2 observations toward the disk around the T Tauri star AS 209, we report the first detection of N{sub 2}D{sup +} (J = 3–2) in a protoplanetary disk. These data are used together with previous Submillimeter Array observations of N{sub 2}H{sup +} (J = 3–2) to estimate a disk-averaged D/H ratio of 0.3–0.5, an order of magnitude higher than disk-averaged ratios previously derived for DCN/HCN and DCO{sup +}/HCO{sup +} around other young stars. The high fractionation in N{sub 2}H{sup +} is consistent with model predictions. The presence of abundant N{sub 2}D{sup +} toward AS 209 also suggests that N{sub 2}D{sup +} and the N{sub 2}D{sup +}/N{sub 2}H{sup +} ratio can be developed into effective probes of deuterium chemistry, kinematics, and ionization processes outside the CO snow line of disks.

  7. VizieR Online Data Catalog: The 2dF Galaxy Redshift Survey (2dFGRS) (2dFGRS Team, 1998-2003)

    NASA Astrophysics Data System (ADS)

    Colless, M.; Dalton, G.; Maddox, S.; Sutherland, W.; Norberg, P.; Cole, S.; Bland-Hawthorn, J.; Bridges, T.; Cannon, R.; Collins, C.; Couch, W.; Cross, N.; Deeley, K.; de Propris, R.; Driver, S. P.; Efstathiou, G.; Ellis, R. S.; Frenk, C. S.; Glazebrook, K.; Jackson, C.; Lahav, O.; Lewis, I.; Lumsden, S.; Madgwick, D.; Peacock, J. A.; Peterson, B. A.; Price, I.; Seaborne, M.; Taylor, K.

    2007-11-01

    The 2dF Galaxy Redshift Survey (2dFGRS) is a major spectroscopic survey taking full advantage of the unique capabilities of the 2dF facility built by the Anglo-Australian Observatory. The 2dFGRS is integrated with the 2dF QSO survey (2QZ, Cat. VII/241). The 2dFGRS obtained spectra for 245591 objects, mainly galaxies, brighter than a nominal extinction-corrected magnitude limit of bJ=19.45. Reliable (quality>=3) redshifts were obtained for 221414 galaxies. The galaxies cover an area of approximately 1500 square degrees selected from the extended APM Galaxy Survey in three regions: a North Galactic Pole (NGP) strip, a South Galactic Pole (SGP) strip, and random fields scattered around the SGP strip. Redshifts are measured from spectra covering 3600-8000 Angstroms at a two-pixel resolution of 9.0 Angstrom and a median S/N of 13 per pixel. All redshift identifications are visually checked and assigned a quality parameter Q in the range 1-5; Q>=3 redshifts are 98.4% reliable and have an rms uncertainty of 85 km/s. The overall redshift completeness for Q>=3 redshifts is 91.8% but this varies with magnitude from 99% for the brightest galaxies to 90% for objects at the survey limit. The 2dFGRS data base is available on the World Wide Web at http://www.mso.anu.edu.au/2dFGRS/. (6 data files).

  8. Pareto joint inversion of 2D magnetotelluric and gravity data

    NASA Astrophysics Data System (ADS)

    Miernik, Katarzyna; Bogacz, Adrian; Kozubal, Adam; Danek, Tomasz; Wojdyła, Marek

    2015-04-01

    In this contribution, the first results of the "Innovative technology of petrophysical parameters estimation of geological media using joint inversion algorithms" project were described. At this stage of the development, Pareto joint inversion scheme for 2D MT and gravity data was used. Additionally, seismic data were provided to set some constrains for the inversion. Sharp Boundary Interface(SBI) approach and description model with set of polygons were used to limit the dimensionality of the solution space. The main engine was based on modified Particle Swarm Optimization(PSO). This algorithm was properly adapted to handle two or more target function at once. Additional algorithm was used to eliminate non- realistic solution proposals. Because PSO is a method of stochastic global optimization, it requires a lot of proposals to be evaluated to find a single Pareto solution and then compose a Pareto front. To optimize this stage parallel computing was used for both inversion engine and 2D MT forward solver. There are many advantages of proposed solution of joint inversion problems. First of all, Pareto scheme eliminates cumbersome rescaling of the target functions, that can highly affect the final solution. Secondly, the whole set of solution is created in one optimization run, providing a choice of the final solution. This choice can be based off qualitative data, that are usually very hard to be incorporated into the regular inversion schema. SBI parameterisation not only limits the problem of dimensionality, but also makes constraining of the solution easier. At this stage of work, decision to test the approach using MT and gravity data was made, because this combination is often used in practice. It is important to mention, that the general solution is not limited to this two methods and it is flexible enough to be used with more than two sources of data. Presented results were obtained for synthetic models, imitating real geological conditions, where

  9. Klassifikation von Standardebenen in der 2D-Echokardiographie mittels 2D-3D-Bildregistrierung

    NASA Astrophysics Data System (ADS)

    Bergmeir, Christoph; Subramanian, Navneeth

    Zum Zweck der Entwicklung eines Systems, das einen unerfahrenen Anwender von Ultraschall (US) zur Aufnahme relevanter anatomischer Strukturen leitet, untersuchen wir die Machbarkeit von 2D-US zu 3D-CT Registrierung. Wir verwenden US-Aufnahmen von Standardebenen des Herzens, welche zu einem 3D-CT-Modell registriert werden. Unser Algorithmus unterzieht sowohl die US-Bilder als auch den CT-Datensatz Vorverarbeitungsschritten, welche die Daten durch Segmentierung auf wesentliche Informationen in Form von Labein für Muskel und Blut reduzieren. Anschließend werden diese Label zur Registrierung mittels der Match-Cardinality-Metrik genutzt. Durch mehrmaliges Registrieren mit verschiedenen Initialisierungen ermitteln wir die im US-Bild sichtbare Standardebene. Wir evaluierten die Methode auf sieben US-Bildern von Standardebenen. Fünf davon wurden korrekt zugeordnet.

  10. Epitaxial 2D SnSe2/ 2D WSe2 van der Waals Heterostructures.

    PubMed

    Aretouli, Kleopatra Emmanouil; Tsoutsou, Dimitra; Tsipas, Polychronis; Marquez-Velasco, Jose; Aminalragia Giamini, Sigiava; Kelaidis, Nicolaos; Psycharis, Vassilis; Dimoulas, Athanasios

    2016-09-01

    van der Waals heterostructures of 2D semiconductor materials can be used to realize a number of (opto)electronic devices including tunneling field effect devices (TFETs). It is shown in this work that high quality SnSe2/WSe2 vdW heterostructure can be grown by molecular beam epitaxy on AlN(0001)/Si(111) substrates using a Bi2Se3 buffer layer. A valence band offset of 0.8 eV matches the energy gap of SnSe2 in such a way that the VB edge of WSe2 and the CB edge of SnSe2 are lined up, making this materials combination suitable for (nearly) broken gap TFETs. PMID:27537619

  11. CVMAC 2D Program: A method of converting 3D to 2D

    SciTech Connect

    Lown, J.

    1990-06-20

    This paper presents the user with a method of converting a three- dimensional wire frame model into a technical illustration, detail, or assembly drawing. By using the 2D Program, entities can be mapped from three-dimensional model space into two-dimensional model space, as if they are being traced. Selected entities to be mapped can include circles, arcs, lines, and points. This program prompts the user to digitize the view to be mapped, specify the layers in which the new two-dimensional entities will reside, and select the entities, either by digitizing or windowing. The new two-dimensional entities are displayed in a small view which the program creates in the lower left corner of the drawing. 9 figs.

  12. Tissue matrix arrays for high throughput screening and systems analysis of cell function

    PubMed Central

    Beachley, Vince Z.; Wolf, Matthew T.; Sadtler, Kaitlyn; Manda, Srikanth S.; Jacobs, Heather; Blatchley, Michael; Bader, Joel S.; Pandey, Akhilesh; Pardoll, Drew; Elisseeff, Jennifer H.

    2015-01-01

    Cell and protein arrays have demonstrated remarkable utility in the high-throughput evaluation of biological responses; however, they lack the complexity of native tissue and organs. Here, we describe tissue extracellular matrix (ECM) arrays for screening biological outputs and systems analysis. We spotted processed tissue ECM particles as two-dimensional arrays or incorporated them with cells to generate three-dimensional cell-matrix microtissue arrays. We then investigated the response of human stem, cancer, and immune cells to tissue ECM arrays originating from 11 different tissues, and validated the 2D and 3D arrays as representative of the in vivo microenvironment through quantitative analysis of tissue-specific cellular responses, including matrix production, adhesion and proliferation, and morphological changes following culture. The biological outputs correlated with tissue proteomics, and network analysis identified several proteins linked to cell function. Our methodology enables broad screening of ECMs to connect tissue-specific composition with biological activity, providing a new resource for biomaterials research and translation. PMID:26480475

  13. 2D Four-Channel Perfect Reconstruction Filter Bank Realized with the 2D Lattice Filter Structure

    NASA Astrophysics Data System (ADS)

    Sezen, S.; Ertüzün, A.

    2006-12-01

    A novel orthogonal 2D lattice structure is incorporated into the design of a nonseparable 2D four-channel perfect reconstruction filter bank. The proposed filter bank is obtained by using the polyphase decomposition technique which requires the design of an orthogonal 2D lattice filter. Due to constraint of perfect reconstruction, each stage of this lattice filter bank is simply parameterized by two coefficients. The perfect reconstruction property is satisfied regardless of the actual values of these parameters and of the number of the lattice stages. It is also shown that a separable 2D four-channel perfect reconstruction lattice filter bank can be constructed from the 1D lattice filter and that this is a special case of the proposed 2D lattice filter bank under certain conditions. The perfect reconstruction property of the proposed 2D lattice filter approach is verified by computer simulations.

  14. Electrochemical fabrication of 2D and 3D nickel nanowires using porous anodic alumina templates

    NASA Astrophysics Data System (ADS)

    Mebed, A. M.; Abd-Elnaiem, Alaa M.; Al-Hosiny, Najm M.

    2016-06-01

    Mechanically stable nickel (Ni) nanowires array and nanowires network were synthesized by pulse electrochemical deposition using 2D and 3D porous anodic alumina (PAA) templates. The structures and morphologies of as-prepared films were characterized by X-ray diffraction and scanning electron microscopy, respectively. The grown Ni nanowire using 3D PAA revealed more strength and larger surface area than has grown Ni use 2D PAA template. The prepared nanowires have a face-centered cubic crystal structure with average grain size 15 nm, and the preferred orientation of the nucleation of the nanowires is (111). The diameter of the nanowires is about 50-70 nm with length 3 µm. The resulting 3D Ni nanowire lattice, which provides enhanced mechanical stability and an increased surface area, benefits energy storage and many other applications which utilize the large surface area.

  15. Functional characterization of CYP2D6 enhancer polymorphisms

    PubMed Central

    Wang, Danxin; Papp, Audrey C.; Sun, Xiaochun

    2015-01-01

    CYP2D6 metabolizes nearly 25% of clinically used drugs. Genetic polymorphisms cause large inter-individual variability in CYP2D6 enzyme activity and are currently used as biomarker to predict CYP2D6 metabolizer phenotype. Previously, we had identified a region 115 kb downstream of CYP2D6 as enhancer for CYP2D6, containing two completely linked single nucleotide polymorphisms (SNPs), rs133333 and rs5758550, associated with enhanced transcription. However, the enhancer effect on CYP2D6 expression, and the causative variant, remained to be ascertained. To characterize the CYP2D6 enhancer element, we applied chromatin conformation capture combined with the next-generation sequencing (4C assays) and chromatin immunoprecipitation with P300 antibody, in HepG2 and human primary culture hepatocytes. The results confirmed the role of the previously identified enhancer region in CYP2D6 expression, expanding the number of candidate variants to three highly linked SNPs (rs133333, rs5758550 and rs4822082). Among these, only rs5758550 demonstrated regulating enhancer activity in a reporter gene assay. Use of clustered regularly interspaced short palindromic repeats mediated genome editing in HepG2 cells targeting suspected enhancer regions decreased CYP2D6 mRNA expression by 70%, only upon deletion of the rs5758550 region. These results demonstrate robust effects of both the enhancer element and SNP rs5758550 on CYP2D6 expression, supporting consideration of rs5758550 for CYP2D6 genotyping panels to yield more accurate phenotype prediction. PMID:25381333

  16. An Incompressible 2D Didactic Model with Singularity and Explicit Solutions of the 2D Boussinesq Equations

    NASA Astrophysics Data System (ADS)

    Chae, Dongho; Constantin, Peter; Wu, Jiahong

    2014-09-01

    We give an example of a well posed, finite energy, 2D incompressible active scalar equation with the same scaling as the surface quasi-geostrophic equation and prove that it can produce finite time singularities. In spite of its simplicity, this seems to be the first such example. Further, we construct explicit solutions of the 2D Boussinesq equations whose gradients grow exponentially in time for all time. In addition, we introduce a variant of the 2D Boussinesq equations which is perhaps a more faithful companion of the 3D axisymmetric Euler equations than the usual 2D Boussinesq equations.

  17. Adaptation algorithms for 2-D feedforward neural networks.

    PubMed

    Kaczorek, T

    1995-01-01

    The generalized weight adaptation algorithms presented by J.G. Kuschewski et al. (1993) and by S.H. Zak and H.J. Sira-Ramirez (1990) are extended for 2-D madaline and 2-D two-layer feedforward neural nets (FNNs).

  18. Integrating Mobile Multimedia into Textbooks: 2D Barcodes

    ERIC Educational Resources Information Center

    Uluyol, Celebi; Agca, R. Kagan

    2012-01-01

    The major goal of this study was to empirically compare text-plus-mobile phone learning using an integrated 2D barcode tag in a printed text with three other conditions described in multimedia learning theory. The method examined in the study involved modifications of the instructional material such that: a 2D barcode was used near the text, the…

  19. Efficient Visible Quasi-2D Perovskite Light-Emitting Diodes.

    PubMed

    Byun, Jinwoo; Cho, Himchan; Wolf, Christoph; Jang, Mi; Sadhanala, Aditya; Friend, Richard H; Yang, Hoichang; Lee, Tae-Woo

    2016-09-01

    Efficient quasi-2D-structure perovskite light-emitting diodes (4.90 cd A(-1) ) are demonstrated by mixing a 3D-structured perovskite material (methyl ammonium lead bromide) and a 2D-structured perovskite material (phenylethyl ammonium lead bromide), which can be ascribed to better film uniformity, enhanced exciton confinement, and reduced trap density. PMID:27334788

  20. CYP2D6: novel genomic structures and alleles

    PubMed Central

    Kramer, Whitney E.; Walker, Denise L.; O’Kane, Dennis J.; Mrazek, David A.; Fisher, Pamela K.; Dukek, Brian A.; Bruflat, Jamie K.; Black, John L.

    2010-01-01

    Objective CYP2D6 is a polymorphic gene. It has been observed to be deleted, to be duplicated and to undergo recombination events involving the CYP2D7 pseudogene and surrounding sequences. The objective of this study was to discover the genomic structure of CYP2D6 recombinants that interfere with clinical genotyping platforms that are available today. Methods Clinical samples containing rare homozygous CYP2D6 alleles, ambiguous readouts, and those with duplication signals and two different alleles were analyzed by long-range PCR amplification of individual genes, PCR fragment analysis, allele-specific primer extension assay, and DNA sequencing to characterize alleles and genomic structure. Results Novel alleles, genomic structures, and the DNA sequence of these structures are described. Interestingly, in 49 of 50 DNA samples that had CYP2D6 gene duplications or multiplications where two alleles were detected, the chromosome containing the duplication or multiplication had identical tandem alleles. Conclusion Several new CYP2D6 alleles and genomic structures are described which will be useful for CYP2D6 genotyping. The findings suggest that the recombination events responsible for CYP2D6 duplications and multiplications are because of mechanisms other than interchromosomal crossover during meiosis. PMID:19741566

  1. Efficient Visible Quasi-2D Perovskite Light-Emitting Diodes.

    PubMed

    Byun, Jinwoo; Cho, Himchan; Wolf, Christoph; Jang, Mi; Sadhanala, Aditya; Friend, Richard H; Yang, Hoichang; Lee, Tae-Woo

    2016-09-01

    Efficient quasi-2D-structure perovskite light-emitting diodes (4.90 cd A(-1) ) are demonstrated by mixing a 3D-structured perovskite material (methyl ammonium lead bromide) and a 2D-structured perovskite material (phenylethyl ammonium lead bromide), which can be ascribed to better film uniformity, enhanced exciton confinement, and reduced trap density.

  2. Systematic Approach to Electrostatically Induced 2D Crystallization of Nanoparticles at Liquid Interfaces

    SciTech Connect

    Fukuto, M.; Kewalramani, S.; Wang, S.; Lin, Y.; Nguyen, G.; Wang, Q.; Yang, L.

    2011-02-07

    We report an experimental demonstration of a strategy for inducing two-dimensional (2D) crystallization of charged nanoparticles on oppositely charged fluid interfaces. This strategy aims to maximize the interfacial adsorption of nanoparticles, and hence their lateral packing density, by utilizing a combination of weakly charged particles and a high surface charge density on the planar interface. In order to test this approach, we investigated the assembly of cowpea mosaic virus (CPMV) on positively charged lipid monolayers at the aqueous solution surface, by means of in situ X-ray scattering measurements at the liquid-vapor interface. The assembly was studied as a function of the solution pH, which was used to vary the charge on CPMV, and of the mole fraction of the cationic lipid in the binary lipid monolayer, which set the interface charge density. The 2D crystallization of CPMV occurred in a narrow pH range just above the particle's isoelectric point, where the particle charge was weakly negative, and only when the cationic-lipid fraction in the monolayer exceeded a threshold. The observed 2D crystals exhibited nearly the same packing density as the densest lattice plane within the known 3D crystals of CPMV. The above electrostatic approach of maximizing interfacial adsorption may provide an efficient route to the crystallization of nanoparticles at aqueous interfaces.

  3. Numerical studies of the melting transition in 2D Yukawa systems

    SciTech Connect

    Hartmann, P.; Donko, Z.; Kalman, G. J.

    2008-09-07

    We present the latest results of our systematic studies of the solid--liquid phase transition in 2D classical many-particle systems interacting with the Yukawa potential. Our previous work is extended by applying the molecular dynamic simulations to systems with up to 1.6 million particles in the computational box (for {kappa} = 2 case). Equilibrium simulations are performed for different coupling parameters in the vicinity of the expected melting transition ({gamma}{sub m}{sup {kappa}}{sup ={sup 2}}{approx_equal}415) and a wide range of observables are averaged over uncorrelated samples of the micro-canonical ensemble generated by the simulations.

  4. 2D materials and van der Waals heterostructures.

    PubMed

    Novoselov, K S; Mishchenko, A; Carvalho, A; Castro Neto, A H

    2016-07-29

    The physics of two-dimensional (2D) materials and heterostructures based on such crystals has been developing extremely fast. With these new materials, truly 2D physics has begun to appear (for instance, the absence of long-range order, 2D excitons, commensurate-incommensurate transition, etc.). Novel heterostructure devices--such as tunneling transistors, resonant tunneling diodes, and light-emitting diodes--are also starting to emerge. Composed from individual 2D crystals, such devices use the properties of those materials to create functionalities that are not accessible in other heterostructures. Here we review the properties of novel 2D crystals and examine how their properties are used in new heterostructure devices.

  5. Van der Waals stacked 2D layered materials for optoelectronics

    NASA Astrophysics Data System (ADS)

    Zhang, Wenjing; Wang, Qixing; Chen, Yu; Wang, Zhuo; Wee, Andrew T. S.

    2016-06-01

    The band gaps of many atomically thin 2D layered materials such as graphene, black phosphorus, monolayer semiconducting transition metal dichalcogenides and hBN range from 0 to 6 eV. These isolated atomic planes can be reassembled into hybrid heterostructures made layer by layer in a precisely chosen sequence. Thus, the electronic properties of 2D materials can be engineered by van der Waals stacking, and the interlayer coupling can be tuned, which opens up avenues for creating new material systems with rich functionalities and novel physical properties. Early studies suggest that van der Waals stacked 2D materials work exceptionally well, dramatically enriching the optoelectronics applications of 2D materials. Here we review recent progress in van der Waals stacked 2D materials, and discuss their potential applications in optoelectronics.

  6. Monte Carlo simulations of a novel Micromegas 2D array for proton dosimetry.

    PubMed

    Dolney, D; Ainsley, C; Hollebeek, R; Maughan, R

    2016-02-21

    Modern proton therapy affords control of the delivery of radiotherapeutic dose on fine length and temporal scales. The authors have developed a novel detector technology based on Micromesh Gaseous Structure (Micromegas) that is uniquely tailored for applications using therapeutic proton beams. An implementation of a prototype Micromegas detector for Monte Carlo using Geant4 is presented here. Comparison of simulation results with measurements demonstrates agreement in relative dose along the proton longitudinal dose profile to be 1%. The effect of a radioactive calibration source embedded in the chamber gas is demonstrated by measurements and reproduced by simulations, also at the 1% level. Our Monte Carlo simulations are shown to reproduce the time structure of ionization pulses produced by a double-scattering delivery system.

  7. Monte Carlo simulations of a novel Micromegas 2D array for proton dosimetry

    NASA Astrophysics Data System (ADS)

    Dolney, D.; Ainsley, C.; Hollebeek, R.; Maughan, R.

    2016-02-01

    Modern proton therapy affords control of the delivery of radiotherapeutic dose on fine length and temporal scales. The authors have developed a novel detector technology based on Micromesh Gaseous Structure (Micromegas) that is uniquely tailored for applications using therapeutic proton beams. An implementation of a prototype Micromegas detector for Monte Carlo using Geant4 is presented here. Comparison of simulation results with measurements demonstrates agreement in relative dose along the proton longitudinal dose profile to be 1%. The effect of a radioactive calibration source embedded in the chamber gas is demonstrated by measurements and reproduced by simulations, also at the 1% level. Our Monte Carlo simulations are shown to reproduce the time structure of ionization pulses produced by a double-scattering delivery system.

  8. MEAN FLOW AND TURBULENCE MEASUREMENTS AROUND A 2-D ARRAY OF BUILDINGS IN A WIND TUNNEL

    EPA Science Inventory

    In order to predict the dispersion of harmful materials released in or near an urban environment, it is important to first understand the complex flow patterns which result from the interaction of the wind with buildings and, more commonly, clusters of buildings. Recent advanc...

  9. Optimized 2D array of thin silicon pillars for efficient antireflective coatings in the visible spectrum.

    PubMed

    Proust, Julien; Fehrembach, Anne-Laure; Bedu, Frédéric; Ozerov, Igor; Bonod, Nicolas

    2016-04-25

    Light reflection occuring at the surface of silicon wafers is drastically diminished by etching square pillars of height 110 nm and width 140 nm separated by a 100 nm gap distance in a square lattice. The design of the nanostructure is optimized to widen the spectral tolerance of the antireflective coatings over the visible spectrum for both fundamental polarizations. Angle and polarized resolved optical measurements report a light reflection remaining under 5% when averaged in the visible spectrum for both polarizations in a wide angular range. Light reflection remains almost insensitive to the light polarization even in oblique incidence.

  10. Optimized 2D array of thin silicon pillars for efficient antireflective coatings in the visible spectrum

    PubMed Central

    Proust, Julien; Fehrembach, Anne-Laure; Bedu, Frédéric; Ozerov, Igor; Bonod, Nicolas

    2016-01-01

    Light reflection occuring at the surface of silicon wafers is drastically diminished by etching square pillars of height 110 nm and width 140 nm separated by a 100 nm gap distance in a square lattice. The design of the nanostructure is optimized to widen the spectral tolerance of the antireflective coatings over the visible spectrum for both fundamental polarizations. Angle and polarized resolved optical measurements report a light reflection remaining under 5% when averaged in the visible spectrum for both polarizations in a wide angular range. Light reflection remains almost insensitive to the light polarization even in oblique incidence. PMID:27109643

  11. Estrogen-Induced Cholestasis Leads to Repressed CYP2D6 Expression in CYP2D6-Humanized Mice

    PubMed Central

    Pan, Xian

    2015-01-01

    Cholestasis activates bile acid receptor farnesoid X receptor (FXR) and subsequently enhances hepatic expression of small heterodimer partner (SHP). We previously demonstrated that SHP represses the transactivation of cytochrome P450 2D6 (CYP2D6) promoter by hepatocyte nuclear factor (HNF) 4α. In this study, we investigated the effects of estrogen-induced cholestasis on CYP2D6 expression. Estrogen-induced cholestasis occurs in subjects receiving estrogen for contraception or hormone replacement, or in susceptible women during pregnancy. In CYP2D6-humanized transgenic (Tg-CYP2D6) mice, cholestasis triggered by administration of 17α-ethinylestradiol (EE2) at a high dose led to 2- to 3-fold decreases in CYP2D6 expression. This was accompanied by increased hepatic SHP expression and subsequent decreases in the recruitment of HNF4α to CYP2D6 promoter. Interestingly, estrogen-induced cholestasis also led to increased recruitment of estrogen receptor (ER) α, but not that of FXR, to Shp promoter, suggesting a predominant role of ERα in transcriptional regulation of SHP in estrogen-induced cholestasis. EE2 at a low dose (that does not cause cholestasis) also increased SHP (by ∼50%) and decreased CYP2D6 expression (by 1.5-fold) in Tg-CYP2D6 mice, the magnitude of differences being much smaller than that shown in EE2-induced cholestasis. Taken together, our data indicate that EE2-induced cholestasis increases SHP and represses CYP2D6 expression in Tg-CYP2D6 mice in part through ERα transactivation of Shp promoter. PMID:25943116

  12. Partial clustering prevents global crystallization in a binary 2D colloidal glass former.

    PubMed

    Ebert, F; Maret, G; Keim, P

    2009-07-01

    A mixture of two types of super-paramagnetic colloidal particles with long-range dipolar interaction is confined by gravity to the flat interface of a hanging water droplet. The particles are observed by video microscopy and the dipolar interaction strength is controlled via an external magnetic field. The system is a model system to study the glass transition in 2D, and it exhibits partial clustering of the small particles (N. Hoffmann et al., Phys. Rev. Lett. 97, 078301 (2006)). This clustering is strongly dependent on the relative concentration [Formula: see text] of big and small particles. However, changing the interaction strength [Formula: see text] reveals that the clustering does not depend on the interaction strength. The partial clustering scenario is quantified using Minkowski functionals and partial structure factors. Evidence that partial clustering prevents global crystallization is discussed.

  13. Spectroscopy and Thermometry of Drumhead Modes in a Mesoscopic 2D Coulomb Crystal of ^9Be^+

    NASA Astrophysics Data System (ADS)

    Sawyer, Brian; Britton, Joseph; Teale, Carson; Keith, Adam; Wang, Joseph; Freericks, James; Bollinger, John

    2013-04-01

    We demonstrate spectroscopy and thermometry of individual motional modes in a mesoscopic 2D ion array using entanglement between ion valence electron spins and collective motion. Our system is a ˜400 μm-diameter planar crystal of several hundred ^9Be^+ ions exhibiting complex drumhead modes in the confining potential of a Penning trap. Exploiting precise control over the ^9Be^+ valence electron spins, we apply a homogeneous spin-dependent optical dipole force to excite arbitrary transverse modes with wavelengths ranging from the array diameter to the interparticle spacing of ˜20 μm. In addition to temperature measurements, this spin-motion entanglement induced by the spin-dependent optical dipole force allows for extremely sensitive detection of external forces (˜100 yN) acting on the ion crystal. Characterization of mode frequencies and temperatures is critical for quantum simulation experiments that make use of the ion spins.

  14. Ultra-slim 2D- and depth-imaging camera modules for mobile imaging

    NASA Astrophysics Data System (ADS)

    Brückner, Andreas; Oberdörster, Alexander; Dunkel, Jens; Reimann, Andreas; Wippermann, Frank

    2016-03-01

    In this contribution, a microoptical imaging system is demonstrated that is inspired by the insect compound eye. The array camera module achieves HD resolution with a z-height of 2.0 mm, which is about 50% compared to traditional cameras with comparable parameters. The FOV is segmented by multiple optical channels imaging in parallel. The partial images are stitched together to form a final image of the whole FOV by image processing software. The system is able to acquire depth maps along with the 2D video and it includes light field imaging features such as software refocusing. The microlens arrays are realized by microoptical technologies on wafer-level which are suitable for a potential fabrication in high volume.

  15. Influence of lattice defects on the ferromagnetic resonance behaviour of 2D magnonic crystals

    PubMed Central

    Manzin, Alessandra; Barrera, Gabriele; Celegato, Federica; Coïsson, Marco; Tiberto, Paola

    2016-01-01

    This paper studies, from a modelling point of view, the influence of randomly distributed lattice defects (non-patterned areas and variable hole size) on the ferromagnetic resonance behaviour and spin wave mode profiles of 2D magnonic crystals based on Ni80Fe20 antidot arrays with hexagonal lattice. A reference sample is first defined via the comparison of experimental and simulated hysteresis loops and magnetoresistive curves of patterned films, prepared by self-assembly of polystyrene nanospheres. Second, a parametric analysis of the dynamic response is performed, investigating how edge, quasi-uniform and localized modes are affected by alterations of the lattice geometry and bias field amplitude. Finally, some results about the possible use of magnetic antidot arrays in frequency-based sensors for magnetic bead detection are presented, highlighting the need for an accurate control of microstructural features. PMID:26911336

  16. Simplified and economical 2D IR spectrometer design using a dual acousto-optic modulator.

    PubMed

    Skoff, David R; Laaser, Jennifer E; Mukherjee, Sudipta S; Middleton, Chris T; Zanni, Martin T

    2013-08-30

    Over the last decade two-dimensional infrared (2D IR) spectroscopy has proven to be a very useful extension of infrared spectroscopy, yet the technique remains restricted to a small group of specialized researchers because of its experimental complexity and high equipment cost. We report on a spectrometer that is compact, mechanically robust, and is much less expensive than previous designs because it uses a single pixel MCT detector rather than an array detector. Moreover, each axis of the spectrum can be collected in either the time or frequency domain via computer programming. We discuss pulse sequences for scanning the probe axis, which were not previously possible. We present spectra on metal carbonyl compounds at 5 µm and a model peptide at 6 µm. Data collection with a single pixel MCT takes longer than using an array detector, but publishable quality data are still achieved with only a few minutes of averaging.

  17. Simplified and economical 2D IR spectrometer design using a dual acousto-optic modulator

    NASA Astrophysics Data System (ADS)

    Skoff, David R.; Laaser, Jennifer E.; Mukherjee, Sudipta S.; Middleton, Chris T.; Zanni, Martin T.

    2013-08-01

    Over the last decade two-dimensional infrared (2D IR) spectroscopy has proven to be a very useful extension of infrared spectroscopy, yet the technique remains restricted to a small group of specialized researchers because of its experimental complexity and high equipment cost. We report on a spectrometer that is compact, mechanically robust, and is much less expensive than previous designs because it uses a single pixel MCT detector rather than an array detector. Moreover, each axis of the spectrum can be collected in either the time or frequency domain via computer programming. We discuss pulse sequences for scanning the probe axis, which were not previously possible. We present spectra on metal carbonyl compounds at 5 μm and a model peptide at 6 μm. Data collection with a single pixel MCT takes longer than using an array detector, but publishable quality data are still achieved with only a few minutes of averaging.

  18. Inelastic electron transport in granular arrays

    SciTech Connect

    Altland, A.; Glazman, L.I.; Kamenev, A.; Meyer, J.S. . E-mail: jmeyer@mps.ohio-state.edu

    2006-11-15

    Transport properties of granular systems are governed by Coulomb blockade effects caused by the discreteness of the electron charge. We show that, in the limit of vanishing mean level spacing on the grains, the low-temperature behavior of 1d and 2d arrays is insulating at any inter-grain coupling (characterized by a dimensionless conductance g). In 2d and g >> 1, there is a sharp Berezinskii-Kosterlitz-Thouless crossover to the conducting phase at a certain temperature, T {sub BKT}. These results are obtained by applying an instanton analysis to map the conventional 'phase' description of granular arrays onto the dual 'charge' representation.

  19. Inelastic electron transport in granular arrays.

    SciTech Connect

    Altland, A.; Glazman, L. I.; Kamenev, A.; Meyer, J. S.; Materials Science Division; Univ. zu Koln; Univ. Minnesota; Ohio State Univ.

    2006-01-01

    Transport properties of granular systems are governed by Coulomb blockade effects caused by the discreteness of the electron charge. We show that, in the limit of vanishing mean level spacing on the grains, the low-temperature behavior of 1d and 2d arrays is insulating at any inter-grain coupling (characterized by a dimensionless conductance g). In 2d and g 1, there is a sharp Berezinskii-Kosterlitz-Thouless crossover to the conducting phase at a certain temperature, T{sub BKT}. These results are obtained by applying an instanton analysis to map the conventional 'phase' description of granular arrays onto the dual 'charge' representation.

  20. Synthesis of zeolite as ordered multicrystal arrays.

    PubMed

    Lee, Jin Seok; Lee, Yun-Jo; Tae, Eunju Lee; Park, Yong Soo; Yoon, Kyung Byung

    2003-08-01

    Zeolites are crystalline nanoporous aluminosilicates widely used in industry. In order for zeolites to find applications as innovative materials, they need to be organized into large two- and three-dimensional (2D and 3D) arrays. We report that uniformly aligned polyurethane films can serve as templates for the synthesis of uniformly aligned 2D and possibly 3D arrays of silicalite-1 crystals, in which the orientations of the crystals are controlled by the nature of the polymers. We propose that the supramolecularly organized organic-inorganic composites that consist of the hydrolyzed organic products and the seed crystals are responsible for this phenomenon.