Science.gov

Sample records for dual electrostatic switch

  1. Electrostatic Switching in Vertically Oriented Nanotubes for Nonvolatile Memory Applications

    NASA Technical Reports Server (NTRS)

    Kaul, Anupama B.; Khan, Paul; Jennings, Andrew T.; Greer, Julia R.; Megerian, Krikor G.; Allmen, Paul von

    2009-01-01

    We have demonstrated electrostatic switching in vertically oriented nanotubes or nanofibers, where a nanoprobe was used as the actuating electrode inside an SEM. When the nanoprobe was manipulated to be in close proximity to a single tube, switching voltages between 10 V - 40 V were observed, depending on the geometrical parameters. The turn-on transitions appeared to be much sharper than the turn-off transitions which were limited by the tube-to-probe contact resistances. In many cases, stiction forces at these dimensions were dominant, since the tube appeared stuck to the probe even after the voltage returned to 0 V, suggesting that such structures are promising for nonvolatile memory applications. The stiction effects, to some extent, can be adjusted by engineering the switch geometry appropriately. Nanoscale mechanical measurements were also conducted on the tubes using a custom-built anoindentor inside an SEM, from which preliminary material parameters, such as the elastic modulus, were extracted. The mechanical measurements also revealed that the tubes appear to be well adhered to the substrate. The material parameters gathered from the mechanical measurements were then used in developing an electrostatic model of the switch using a commercially available finite-element simulator. The calculated pull-in voltages appeared to be in agreement to the experimentally obtained switching voltages to first order.

  2. Electrostatic Switching in Vertically Oriented Nanotubes for Nonvolatile Memory Applications

    NASA Technical Reports Server (NTRS)

    Kaul, Anupama B.; Khan, Paul; Jennings, Andrew T.; Greer, Julia R.; Megerian, Krikor G.; Allmen, Paul von

    2009-01-01

    We have demonstrated electrostatic switching in vertically oriented nanotubes or nanofibers, where a nanoprobe was used as the actuating electrode inside an SEM. When the nanoprobe was manipulated to be in close proximity to a single tube, switching voltages between 10 V - 40 V were observed, depending on the geometrical parameters. The turn-on transitions appeared to be much sharper than the turn-off transitions which were limited by the tube-to-probe contact resistances. In many cases, stiction forces at these dimensions were dominant, since the tube appeared stuck to the probe even after the voltage returned to 0 V, suggesting that such structures are promising for nonvolatile memory applications. The stiction effects, to some extent, can be adjusted by engineering the switch geometry appropriately. Nanoscale mechanical measurements were also conducted on the tubes using a custom-built anoindentor inside an SEM, from which preliminary material parameters, such as the elastic modulus, were extracted. The mechanical measurements also revealed that the tubes appear to be well adhered to the substrate. The material parameters gathered from the mechanical measurements were then used in developing an electrostatic model of the switch using a commercially available finite-element simulator. The calculated pull-in voltages appeared to be in agreement to the experimentally obtained switching voltages to first order.

  3. Parallel-Plate Electrostatic Dual Mass Oscillator

    SciTech Connect

    Allen, James J.; Dyck, Christopher W.; Huber, Robert J.

    1999-07-22

    A surface-micromachined two-degree-of-freedom system that was driven by parallel-plate actuation at antiresonance was demonstrated. The system consisted of an absorbing mass connected by folded springs to a drive mass. The system demonstrated substantial motion amplification at antiresonance. The absorber mass amplitudes were 0.8-0.85 pm at atmospheric pressure while the drive mass amplitudes were below 0.1 pm. Larger absorber mass amplitudes were not possible because of spring softening in the drive mass springs. Simple theory of the dual-mass oscillator has indicated that the absorber mass may be insensitive to limited variations in strain and damping. This needs experimental verification. Resonant and antiresonant frequencies were measured and compared to the designed values. Resonant frequency measurements were difficult to compare to the design calculations because of time-varying spring softening terms that were caused by the drive configuration. Antiresonant frequency measurements were close to the design value of 5.1 kHz. The antiresonant frequency was not dependent on spring softening. The measured absorber mass displacement at antiresonance was compared to computer simulated results. The measured value was significantly greater, possibly due to neglecting fringe fields in the force expression used in the simulation.

  4. Dual wavelength Q-switched cascade laser.

    PubMed

    Li, Jianfeng; Hu, Tomonori; Jackson, Stuart D

    2012-06-15

    A diode-cladding-pumped dual wavelength Q-switched Ho3+-doped fluoride cascade fiber laser operating in the mid-infrared is demonstrated. Stable pulse trains from the (5)I6 → (5)I7 and (5)I7 → (5)I8 laser transitions were produced, and the μs-level time delay between the pulses from each transition was dependent on the pump power. At maximum pump power and at an acousto-optic modulator repetition rate of 25 kHz, the (5)I6 → (5)I7 transition pulse operated at 3.005 μm, a pulse energy of 29 μJ, and a pulse width of 380 ns; the (5)I7 → (5)I8 transition pulse correspondingly produced 7 μJ pulse energy and 260 ns pulse width at 2.074 μm. To the best of our knowledge, this is the first demonstration of a Q-switched fiber laser operating beyond 3 μm.

  5. Sub-hundred nanosecond electrostatic actuated RF MEMS switched capacitors

    NASA Astrophysics Data System (ADS)

    Verger, A.; Pothier, A.; Guines, C.; Crunteanu, A.; Blondy, P.; Orlianges, J.-C.; Dhennin, J.; Broue, A.; Courtade, F.; Vendier, O.

    2010-06-01

    This paper presents a new mechanical architecture for RF MEMS components that are able to achieve reconfiguration faster than conventional MEMS switches. For most MEMS switches, the electrical switching speed is generally limited to a few microseconds, inherently restricted by the delay required to mechanically move their mobile membrane up and down. By using a proper mechanical design and the structural material fabrication process, this paper will show miniature bridges that are able to exhibit mechanical resonance frequencies over 10 MHz range to be compared to the few tens of kHz for conventional RF MEMS switches. As a result, the switching speed of these miniature components is greatly improved and reaches 50 to 100 ns. Such performance has been achieved using composite micro-beams based on the multilayer material assembly of alumina/aluminum/alumina. To our knowledge, this is the fastest switching speed reported for RF MEMS components so far.

  6. Development of Electrostatic Actuator for Ohmic-Contact RF MEMS Switch/Relay

    NASA Astrophysics Data System (ADS)

    Seki, Tomonori; Masuda, Takahiro; Uno, Yutaka; Sato, Fumihiko; Imanaka, Koichi; Sugiyama, Susumu

    A compact switch/relay with excellent high frequency performance at around 2GHz is developed by adopting a novel non-linear spring structure and high frequency signal line structure. The non-linear spring system applied to an electrostatic actuator of RF MEMS switch/relay increases restoration force for switching reliability. The maximum restoration force can be three times higher than that of a linear spring system actuator. No failure due to restoration force shortage is observed during switching test up to 100 million cycles. The present RF MEMS switch/relay has been shown competitive RF performance over conventional RF switches such as PIN diodes and GaAs MMIC both by the experimental results.

  7. Simulation, fabrication, and dynamics characteristics of electrostatically actuated switches

    NASA Astrophysics Data System (ADS)

    Postnikov, A. V.; Amirov, Ildar I.; Naumov, V. V.; Kalnov, V. A.

    2008-03-01

    A MEMS capacitive-type sensor is basically an electrostatic transducer that depends on electrical energy in terms of constant voltage (voltage drive) or constant charge storage (current drive) to facilitate monitoring of capacitance change due to an external mechanical excitation, such as force, acoustical pressure or acceleration. Microfabricated cantilever beams are widely used in MEMS capacitive-type sensors as the sensing element1. One such representative of movable microdevices are the surface micromachined mechanical resonators that come in many geometrical configurations, such as laterally movable comb resonators, laterally and vertically movable beam resonators, and torsional resonators. The successful design and fabrication of these devices requires computer-aided design _CAD_ simulation tools capable of accurately simulating the electromechanical performance of MEMS devices. Accurate simulations are critical for the expeditious development of commercial products at reasonable cost. All CAD simulation tools require accurate measurements to verify models and to provide the values of the constants used in the models. In particular, in the case of micromechanical resonators, it is challenging to determine the mechanical properties of both static and dynamic behaviors of such micromechanical resonators2,3. The testing of these movable structures is usually performed using electrostatic excitation and detection by capacitive, piezoresistive, and optical methods4. This paper presents the design, fabrication and testing of capacitive aluminum resonator with various movable membrane geometries, fabricated with surface micromachining.

  8. Variable dual-frequency electrostatic wave launcher for plasma applications

    NASA Astrophysics Data System (ADS)

    Jorns, Benjamin; Sorenson, Robert; Choueiri, Edgar

    2011-12-01

    A variable tuning system is presented for launching two electrostatic waves concurrently in a magnetized plasma. The purpose of this system is to satisfy the wave launching requirements for plasma applications where maximal power must be coupled into two carefully tuned electrostatic waves while minimizing erosion to the launching antenna. Two parallel LC traps with fixed inductors and variable capacitors are used to provide an impedance match between a two-wave source and a loop antenna placed outside the plasma. Equivalent circuit analysis is then employed to derive an analytical expression for the normalized, average magnetic flux density produced by the antenna in this system as a function of capacitance and frequency. It is found with this metric that the wave launcher can couple to electrostatic modes at two variable frequencies concurrently while attenuating noise from the source signal at undesired frequencies. An example based on an experiment for plasma heating with two electrostatic waves is used to demonstrate a procedure for tailoring the wave launcher to accommodate the frequency range and flux densities of a specific two-wave application. This example is also used to illustrate a method based on averaging over wave frequencies for evaluating the overall efficacy of the system. The wave launcher is shown to be particularly effective for the illustrative example—generating magnetic flux densities in excess of 50% of the ideal case at two variable frequencies concurrently—with a high adaptability to a number of plasma dynamics and heating applications.

  9. Variable dual-frequency electrostatic wave launcher for plasma applications.

    PubMed

    Jorns, Benjamin; Sorenson, Robert; Choueiri, Edgar

    2011-12-01

    A variable tuning system is presented for launching two electrostatic waves concurrently in a magnetized plasma. The purpose of this system is to satisfy the wave launching requirements for plasma applications where maximal power must be coupled into two carefully tuned electrostatic waves while minimizing erosion to the launching antenna. Two parallel LC traps with fixed inductors and variable capacitors are used to provide an impedance match between a two-wave source and a loop antenna placed outside the plasma. Equivalent circuit analysis is then employed to derive an analytical expression for the normalized, average magnetic flux density produced by the antenna in this system as a function of capacitance and frequency. It is found with this metric that the wave launcher can couple to electrostatic modes at two variable frequencies concurrently while attenuating noise from the source signal at undesired frequencies. An example based on an experiment for plasma heating with two electrostatic waves is used to demonstrate a procedure for tailoring the wave launcher to accommodate the frequency range and flux densities of a specific two-wave application. This example is also used to illustrate a method based on averaging over wave frequencies for evaluating the overall efficacy of the system. The wave launcher is shown to be particularly effective for the illustrative example--generating magnetic flux densities in excess of 50% of the ideal case at two variable frequencies concurrently--with a high adaptability to a number of plasma dynamics and heating applications.

  10. Dual combination combination multi switching synchronization of eight chaotic systems

    NASA Astrophysics Data System (ADS)

    Khan, Ayub; Khattar, Dinesh; Prajapati, Nitish

    2017-08-01

    In this paper, a novel scheme for synchronizing four drive and four response systems is proposed by the authors. The idea of multi switching and dual combination synchronization is extended to dual combination-combination multi switching synchronization involving eight chaotic systems and is a first of its kind. Due to the multiple combination of chaotic systems and multi switching the resultant dynamic behaviour is so complex that, in communication theory, transmission and security of the resultant signal is more effective. Using Lyapunov stability theory, sufficient conditions are achieved and suitable controllers are designed to realise the desired synchronization. Corresponding theoretical analysis is presented and numerical simulations performed to demonstrate the effectiveness of the proposed scheme.

  11. Switch isotropic/anisotropic wettability via dual-scale rods

    NASA Astrophysics Data System (ADS)

    He, Yang; Jiang, Chengyu; Wang, Shengkun; Ma, Zhibo; Yuan, Weizheng

    2014-10-01

    It is the first time to demonstrate the comparison of isotropic/anisotropic wettability between dual-scale micro-nano-rods and single-scale micro-rods. Inspired by the natural structures of rice leaf, a series of micro-nano-rods and micro-rods with different geometric parameters were fabricated using micro-fabrication technology. Experimental measured apparent contact angles and advancing and receding contact angles from orthogonal orientations were characterized. The difference of contact angles from orthogonal orientation on dual-scale rods was much smaller than those on single-scale rods in both static and dynamic situation. It indicated that the dual-scale micro-nano-rods showed isotropic wettability, while single-scale micro-rods showed anisotropic wettability. The switch of isotropic/anisotropic wettability could be illustrated by different wetting state and contact line moving. It offers a facial way to switch isotropic/anisotropic wettability of the surface via dual-scale or single-scale structure.

  12. Electrostatic actuation and electromechanical switching behavior of one-dimensional nanostructures.

    PubMed

    Subramanian, Arunkumar; Alt, Andreas R; Dong, Lixin; Kratochvil, Bradley E; Bolognesi, Colombo R; Nelson, Bradley J

    2009-10-27

    We report on the electromechanical actuation and switching performance of nanoconstructs involving doubly clamped, individual multiwalled carbon nanotubes. Batch-fabricated, three-state switches with low ON-state voltages (6.7 V average) are demonstrated. A nanoassembly architecture that permits individual probing of one device at a time without crosstalk from other nanotubes, which are originally assembled in parallel, is presented. Experimental investigations into device performance metrics such as hysteresis, repeatability and failure modes are presented. Furthermore, current-driven shell etching is demonstrated as a tool to tune the nanomechanical clamping configuration, stiffness, and actuation voltage of fabricated devices. Computational models, which take into account the nonlinearities induced by stress-stiffening of 1-D nanowires at large deformations, are presented. Apart from providing accurate estimates of device performance, these models provide new insights into the extension of stable travel range in electrostatically actuated nanowire-based constructs as compared to their microscale counterparts.

  13. Regime-Switching Bivariate Dual Change Score Model.

    PubMed

    Chow, Sy-Miin; Grimm, Kevin J; Filteau, Guillaume; Dolan, Conor V; McArdle, John J

    2013-07-01

    Mixture structural equation model with regime switching (MSEM-RS) provides one possible way of representing over-time heterogeneities in dynamic processes by allowing a system to manifest qualitatively or quantitatively distinct change processes conditional on the latent "regime" the system is in at a particular time point. Unlike standard mixture structural equation models such as growth mixture models, MSEM-RS allows individuals to transition between latent classes over time. This class of models, often referred to as regime-switching models in the time series and econometric applications, can be specified as regime-switching mixture structural equation models when the number of repeated measures involved is not large. We illustrate the empirical utility of such models using one special case-a regime-switching bivariate dual change score model in which two growth processes are allowed to manifest regime-dependent coupling relations with one another. The proposed model is illustrated using a set of longitudinal reading and arithmetic performance data from the Early Childhood Longitudinal Study, Kindergarten Class of 1998-99 study (ECLS-K; U.S. Department of Education, National Center for Education Statistics, 2010).

  14. Electrostatics

    SciTech Connect

    Wallace, John P.; Wallace, Michael J.

    2015-12-04

    Quantum mechanics should be able to generate the basic properties of a particle. One of the most basic properties are charge and the associated electrostatic electric field. Electrostatic force is a fundamental characteristics of a charged fermion and should have its nature described by the fermion’s structure. To produce the particle properties require two spaces that define both their dynamics and their base structure. Relativity and the conservation of energy dictate how these two separate spaces are connected and the differential equations that describe behavior within these two spaces. The main static characteristic of an elementary fermion are mass and charge. Mass represents a scale measure of the fermion and it appears that charge results from the detailed structure of the fermion, which must merge into the electric field description of Maxwell. Coulomb’s law is a good approximation for large distances, but it is a poor approximation at dimension on the order of a particle’s Compton wavelength. The relativistic description of the fermion in its own frame of reference contains the information required for producing the electrostatic field over all space without a singularity as a source. With this description it is possible to understand the first order correction to the ionization energy of hydrogen. The role of nuclear effects on ionization energies can now be better defined for nuclei heavier than hydrogen.

  15. A dual-stimuli-responsive fluorescent switch ultrathin film

    NASA Astrophysics Data System (ADS)

    Li, Zhixiong; Liang, Ruizheng; Liu, Wendi; Yan, Dongpeng; Wei, Min

    2015-10-01

    Stimuli-responsive fluorescent switches have shown broad applications in optical devices, biological materials and intelligent responses. Herein, we describe the design and fabrication of a dual-stimuli-responsive fluorescent switch ultrathin film (UTF) via a three-step layer-by-layer (LBL) technique: (i) encapsulation of spiropyran (SP) within an amphiphilic block copolymer (PTBEM) to give the (SP@PTBEM) micelle; (ii) the mixture of riboflavin (Rf) and poly(styrene 4-sulfonate) (PSS) to enhance the adhesion ability of small molecules; (iii) assembly of negatively charged SP@PTBEM and Rf-PSS with cationic layered double hydroxide (LDH) nanoplatelets to obtain the (Rf-PSS/LDH/SP@PTBEM)n UTFs (n: bilayer number). The assembly process of the UTFs and their luminescence properties, as monitored by fluorescence spectroscopy and scanning electron microscopy (SEM), present a uniform and ordered layered structure with stepwise growth. The resulting Rf-PSS/LDH/SP@PTBEM UTF serves as a three-state switchable multicolor (green, yellow, and red) luminescent system based on stimulation from UV/Vis light and pH, with an acceptable reversibility. Therefore, this work provides a facile way to fabricate stimuli-responsive solid-state film switches with tunable-color luminescence, which have potential applications in the areas of displays, sensors, and rewritable optical memory and fluorescent logic devices.Stimuli-responsive fluorescent switches have shown broad applications in optical devices, biological materials and intelligent responses. Herein, we describe the design and fabrication of a dual-stimuli-responsive fluorescent switch ultrathin film (UTF) via a three-step layer-by-layer (LBL) technique: (i) encapsulation of spiropyran (SP) within an amphiphilic block copolymer (PTBEM) to give the (SP@PTBEM) micelle; (ii) the mixture of riboflavin (Rf) and poly(styrene 4-sulfonate) (PSS) to enhance the adhesion ability of small molecules; (iii) assembly of negatively charged SP

  16. Electrostatic energy harvesting device with dual resonant structure for wideband random vibration sources at low frequency.

    PubMed

    Zhang, Yulong; Wang, Tianyang; Zhang, Ai; Peng, Zhuoteng; Luo, Dan; Chen, Rui; Wang, Fei

    2016-12-01

    In this paper, we present design and test of a broadband electrostatic energy harvester with a dual resonant structure, which consists of two cantilever-mass subsystems each with a mass attached at the free edge of a cantilever. Comparing to traditional devices with single resonant frequency, the proposed device with dual resonant structure can resonate at two frequencies. Furthermore, when one of the cantilever-masses is oscillating at resonance, the vibration amplitude is large enough to make it collide with the other mass, which provides strong mechanical coupling between the two subsystems. Therefore, this device can harvest a decent power output from vibration sources at a broad frequency range. During the measurement, continuous power output up to 6.2-9.8 μW can be achieved under external vibration amplitude of 9.3 m/s(2) at a frequency range from 36.3 Hz to 48.3 Hz, which means the bandwidth of the device is about 30% of the central frequency. The broad bandwidth of the device provides a promising application for energy harvesting from the scenarios with random vibration sources. The experimental results indicate that with the dual resonant structure, the vibration-to-electricity energy conversion efficiency can be improved by 97% when an external random vibration with a low frequency filter is applied.

  17. Electrostatic stiffness correction for quadrature error in decoupled dual-mass MEMS gyroscope

    NASA Astrophysics Data System (ADS)

    Li, Hongsheng; Cao, Huiliang; Ni, Yunfang

    2014-07-01

    This paper proposes an electrostatic stiffness correction method for the quadrature error (QUER) in a decoupled dual-mass gyroscope structure. The QUER is caused by the imperfections during the structure manufacturing process, and the two masses usually have different QUERs. The harm contribution to the Coriolis signal is analyzed and quantified. The generating forms of QUER motion in both masses are analyzed, the correction electrodes' working principle is introduced, and a single mass individual correction method is proposed. The QUER stiffness correction system is designed based on a PI controller, and the experiments are arranged to verify the theoretical analysis. The bias stability decreases from 2.06 to 0.64 deg/h after the QUER correction, and the parameters of scale factor such as nonlinearly, asymmetry, and repeatability, reduce from 143, 557, and 210 ppm to 84, 242, and 175 ppm, respectively.

  18. Magnetoluminescent light switches--dual modality in DNA detection.

    PubMed

    Smolensky, Eric D; Peterson, Katie L; Weitz, Evan A; Lewandowski, Cutler; Pierre, Valérie C

    2013-06-19

    The synthesis and properties of two responsive magnetoluminescent iron oxide nanoparticles for dual detection of DNA by MRI and luminescence spectroscopy are presented. These magnetoluminescent agents consist of iron oxide nanoparticles conjugated with metallointercalators via a polyethylene glycol linker. Two metallointercalators were investigated: Ru(bpy')(phen)(dppz), which turns on upon DNA intercalation, and Eu-DOTA-Phen, which turns off. The characteristic light-switch responses of the metallointercalators are not affected by the iron oxide nanoparticles; upon binding to DNA the luminescence of the ruthenium complexes increases by ca. 20-fold, whereas that of the europium complex is >95% quenched. Additionally, the 17-20 nm magnetite cores, having permeable PEG coatings and stable dopamide anchors, render the two constructs efficient responsive contrast agents for MRI with unbound longitudinal and transverse relaxivities of 12.4-9.2 and 135-128 mM(-1)(Fe)s(-1), respectively. Intercalation of the metal complexes in DNA results in the formation of large clusters of nanoparticles with a resultant decrease of both r1 and r2 by 32-63% and 24-38%, respectively. The potential application of these responsive magnetoluminescent assemblies and their reversible catch-and-release properties for the purification of DNA is presented.

  19. A fast switching electrostatic deflector system for actinide isotopic ratio measurements

    NASA Astrophysics Data System (ADS)

    Zorko, Benjamin; Child, D. P.; Hotchkis, M. A. C.

    2010-04-01

    We have implemented a fast switching electrostatic system on the actinides beamline on the ANTARES accelerator at ANSTO, to improve the precision of analyses by accelerator mass spectrometry. This high-energy bouncing system is based on a pair of deflector plates, deflecting in the orbit plane, set at the entrance and exit of the analysing magnet. The design of deflector plates is unique, and it was modelled by SIMION in order to minimize field inhomogenity and fringe field effects. The pair of deflector plates are supplied by a high-voltage amplifier driven by an EPICS-enabled control unit, with two 4 W power supplies providing up to ±10 kV modulation. The high-energy bouncing system is synchronized with the existing low-energy bouncing system. To measure the isotopic ratio with the new system, the magnetic fields of the injector and analysing magnets are set to transmit selected isotopes along the beam line with zero voltage applied. The other isotopes of interest are transmitted by keeping the magnetic fields constant and modulating the voltages on the injector magnet chamber and on the high-energy deflector plates.

  20. Two-step switching in dual-frequency nematic liquid crystal mixtures

    NASA Astrophysics Data System (ADS)

    Mrukiewicz, M.; Perkowski, P.; Piecek, W.; Mazur, R.; Chojnowska, O.; Garbat, K.

    2015-11-01

    The so-called dual-frequency nematic mixtures are very promising components for applications in fast operating devices. Compared with classical nematics, they exhibit positive or negative anisotropy of the electric permittivity depending on the applied frequencies of an external electric field. Owing to this property, an overall switching process from planar to homeotropic orientations, and vice versa, can be shortened by using the electric field with two different frequencies. Electro-optical switching characteristics of transmission versus time as a function of applied voltage were obtained for two different dual-frequency mixtures in twisted nematic cells. For one of the investigated mixtures, unusual decrease in the light transmission at switching from the homeotropic to planar orientation at threshold voltage was observed. The switching process apparently occurs in two steps. The mechanism of the two-step switching at twisted dual-frequency nematic structures was discussed. The explanation of the switching mechanism takes into account the influence of the electric field with different frequencies on molecules with transverse and longitudinal dipole moments. Moreover, molecular structure of compounds constituting the mixtures was analyzed. Additionally, response times of the switching driven with low and high frequency pulses were shown. This work helps to understand the molecular interaction and electro-optical switching in the dual-frequency nematic liquid crystals.

  1. The HgF2 Ionic Switch: A Triumph of Electrostatics against Relativistic Odds.

    PubMed

    Donald, Kelling J; Kretz, William J; Omorodion, Oluwarotimi

    2015-11-16

    A remarkable transition in the chemical bonding in (HgF2)n clusters as a function of n is identified and characterized. HgF2 is a fascinating material. Certain significant consequences of relativistic effects on the structure of the HgF2 molecule, dimer, and trimer disappear in the extended solid. Relativistic effects in Hg ensure that HgX2 molecules (X≡F, Cl, Br, and I) are linear, rigid, and form weakly bound dimers and trimers held together by weak electrostatic and van der Waals-type forces (unlike ZnX2 and CdX2 systems in which the intermonomer contacts are strong polar covalent bonds). For HgF2, the location and nature of an apparent transition from weak interactions in the smallest (HgF2)n clusters to ionic bonding in the (fluorite) HgF2 extended solid has remained a mystery. Computational evidence obtained at the M06-2X, B97D3, and MP2 levels of theory and reported herein indicate that polar covalent bonding in (HgF2)n begins as early as n=5. For n=2 through to n=13, the transition or switch from weak (primarily dipole-dipole-type) intermonomer interactions to a preference for polar covalent bonding occurs within the range 5

  2. Switchable dual-wavelength CNT-based Q-switched using arrayed waveguide gratings (AWG)

    NASA Astrophysics Data System (ADS)

    Ahmad, H.; Hamdan, K. Z.; Muhammad, F. D.; Harun, S. W.; Zulkifli, M. Z.

    2015-02-01

    In this paper, a dual-wavelength synchronously pulsed fiber laser Q-switched by carbon nanotube-based saturable absorber with switchable wavelength spacing enabled using arrayed waveguide grating (AWG) is proposed and demonstrated. By just switching the channels of the AWG, discrete tuning in wavelength spacing of the dual-wavelength Q-switched laser operation can be attained over several nanometers, ranging from 1.6 to 4.0 nm in a stable dual-wavelength regime without employing any modulation technique or intracavity spectral filters. Our experimental results show that the fiber laser can generate Q-switched microsecond pulses with a wide repetition rate range, starting from 12.0 kHz to a maximum value of 54.9 kHz. This proposed system is also reasonably simple to realize at low cost.

  3. Electrostatically driven second-sphere ligand switch between high and low reorganization energy forms of native cytochrome c.

    PubMed

    Alvarez-Paggi, Damián; Castro, María A; Tórtora, Verónica; Castro, Laura; Radi, Rafael; Murgida, Daniel H

    2013-03-20

    We have employed a combination of protein film voltammetry, time-resolved vibrational spectroelectrochemistry and molecular dynamics simulations to evaluate the electron-transfer reorganization free energy (λ) of cytochrome c (Cyt) in electrostatic complexes that mimic some basic features of protein-protein and protein-lipid interactions. The results reveal the existence of two native-like conformations of Cyt that present significantly different λ values. Conversion from the high to the low λ forms is triggered by electrostatic interactions, and involves the rupture of a weak H-bond between first- (M80) and second-sphere (Y67) ligands of the heme iron, as a distinctive feature of the conformational switch. The two flexible Ω loops operate as transducers of the electrostatic signal. This fine-tuning effect is abolished in the Y67F Cyt mutant, which presents a λ value similar to the WT protein in electrostatic complexes. We propose that interactions of Cyt with the natural redox partner proteins activate a similar mechanism to minimize the reorganization energy of interprotein electron transfer.

  4. Dual field effects in spinel ferrite field effect devices: electrostatic carrier doping and redox reactions

    NASA Astrophysics Data System (ADS)

    Tanaka, Hidekazu

    2015-03-01

    Spinel ferrite is a good candidate as a tunable magnetic semiconductor with high TC. Here, we report the gate-induced conductance modulation of (Fe3-xZnx) O4 solid solution to demonstrate the dual contributions of volatile and non-volatile field effects arising from electronic carrier doping and redox reactions using field effect device structure with a ferroelectric Pb(Zr,Ti)O3 and an ionic liquid DEME-TFSI. In the Pb(Zr,Ti)O3/(Fe2.5Zn0.5) O4 FET, the gate voltage dependence of channel conductance on the (Fe,Zn)3O4 layer shows the typical hysteresis behavior reflecting the ferroelectric polarization, indicating the static carrier modulation . In contrast, in the DEME-TFSI/(Fe2.5Zn0.5) O4 FET, a large hysteresis observed in the drain current vs gate voltage characteristics is not accounted for solely by electrostatic doping, strongly suggesting the presence of chemical reactions. In more details, the characteristic hysteresis virtually disappears for the heavily Zn substituted system,(Fe2.2Zn0.8) O4 with less carrier concentration. These observations revealed the coexistence of two types of field effects in the Fe3-xZnxO4 devices, and the tuning of field-effect characteristics via composition engineering should be extremely useful for fabricating high-performance oxide field-effect devices.

  5. Electrostatic Switch Function in the Mechanism of Protein Kinase A Iα Activation: Results of the Molecular Dynamics Simulation

    PubMed Central

    Rogacheva, Olga N.; Shchegolev, Boris F.

    2017-01-01

    We used molecular dynamics to find the average path of the A-domain H → B conformational transition in protein kinase A Iα. We obtained thirteen productive trajectories and processed them sequentially using factor and cross-correlation analyses. The conformational transition is presented as partly deterministic sequence of six events. Event B represents H → B transition of the phosphate binding cassette. Main participants of this event form electrostatic switch cAMP(O6)–A202(N-H)–G199(C=O). Through this switch, cAMP transmits information about its binding to hydrophobic switch L203–Y229 and thus triggers conformational transition of A-domain. Events C and D consist in N3A-motif displacement towards phosphate binding cassette and B/C-helix rotation. Event E involves an increase in interaction energy between Y229 and β-subdomain. Taken together, events B, E, and D correspond to the hinge movement towards β-barrel. Transition of B/C-helix turn (a.a. 229–234) from α-form to π-form accounts for event F. Event G implies that π-helical turn is replaced by kink. Emerging in the resulting conformation, electrostatic interaction R241–E200 facilitates kink formation. The obtained data on the mechanism of cAMP-dependent activation of PKA Iα may contribute to new approaches to designing pharmaceuticals based on cAMP analogs. PMID:28367443

  6. Electrostatic Radio Frequency (RF) Microelectromechanical Systems (MEMS) Switches With Metal Alloy Electric Contacts

    DTIC Science & Technology

    2004-09-01

    III. Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 3.1 Micro-Switch Physical Description . . . . . . . . . . . 17 3.2 MEMS...Contact Force Equations . . . . . . . . . . . 41 3.8 Macro-Switch Contact Resistance . . . . . . . . . . . . 46 3.9 Electron Transport Theory and...presentation of pertinent theory . Chapter four summarizes the methodology used to select alloy contact materials. Chapter five presents an analysis of micro

  7. A Dual-Range Strain Gage Weighing Transducer Employing Automatic Switching

    Treesearch

    Rodger A. Arola

    1968-01-01

    Describes a dual-range strain gage transducer which has proven to be an excellent weight-sensing device for weighing trees and tree-length logs; discusses basic principals of the design and operation; and shows that a single transducer having two sensitivity ranges with automatic internal switching can sense weight with good repeatability and that one calibration curve...

  8. Dual-kind Q-switching of erbium fiber laser

    SciTech Connect

    Barmenkov, Yuri O. Kir'yanov, Alexander V.; Cruz, Jose L.; Andres, Miguel V.

    2014-03-03

    Two different regimes of Q-switching in the same implementation of an actively Q-switched erbium-doped fiber laser are demonstrated. Depending on the active fiber length and repetition rate of an intracavity Q-cell (acousto-optic modulator), the laser operates either in the regime of common, rather long and low-power, pulses composed of several sub-pulses or in the one of very short and powerful stimulated Brillouin scattering-induced pulses. The basic physical reason of the laser system to oscillate in one of these two regimes is the existence or absence of CW narrow-line “bad-cavity” lasing in the intervals when the Q-cell is blocked.

  9. Doppler phase shifting using dual, switched phase shifting devices

    NASA Technical Reports Server (NTRS)

    Gutierrez, Roman C. (Inventor)

    2002-01-01

    A system of inducing a phase shift using moving reflector elements. The moving reflectors can be moving mirrors or an acousto-optical filter. The moving reflectors oscillate i.e. the move first in a first direction and then in a second direction. Two different reflectors are used so that the light can be switched between the reflectors. During a first portion of the cycle the light is coupled to the first modulator which moves the reflector in the first direction. The second modulator is out of phase with the first modulator, and the light is switched to that second modulator during a second portion of the cycle. The second modulator is also moving in the first direction when the light is applied thereto. In this way, the light obtains a constant direction Doppler shift.

  10. Dual energy with dual source CT and kVp switching with single source CT: a comparison of dual energy performance

    NASA Astrophysics Data System (ADS)

    Grasruck, M.; Kappler, S.; Reinwand, M.; Stierstorfer, K.

    2009-02-01

    Stimulated by the introduction of clinical dual source CT, the interest in dual energy methods has been increasing in the past years. Whereas the potential of material decomposition by dual energy methods is known since the early 1980ies, the realization of dual energy methods is a wide field of today's research. Energy separation can be achieved with energy selective detectors or by varying X-ray source spectra. This paper focuses on dual energy techniques with varying X-ray spectra. These can be provided by dual source CT devices, operated with different kVp settings on each tube. Excellent spectral separation is the key property for use in clinical routine. The drawback of higher cost for two tubes and two detectors leads to an alternative realization, where a single source CT yields different spectra by fast kVp switching from reading to reading. This provides access to dual-energy methods in single source CT. However, this technique comes with some intrinsic limitations. The maximum X-ray flux is reduced in comparison to the dual source system. The kVp rise and fall time between each reading reduces the spectral separation. In comparison to dual source CT, for a constant number of projections per energy spectrum the temporal resolution is reduced; a reasonable trade of between reduced numbers of projection and limited temporal resolution has to be found. The overall dual energy performance is the guiding line for our investigations. We present simulations and measurements which benchmark both solutions in terms of spectral behavior, especially of spectral separation.

  11. A dual VCDL DLL based gate driver for zero-voltage-switching DC-DC converter

    NASA Astrophysics Data System (ADS)

    Xin, Tian; Xiangxin, Liu; Wenhong, Li

    2010-07-01

    This paper presents a dual voltage-controlled-delay-line (VCDL) delay-lock-loop (DLL) based gate driver for a zero-voltage-switching (ZVS) DC-DC converter. Using the delay difference of two VCDLs for the dead time control, the dual VCDL DLL is able to implement ZVS control with high accuracy while keeping good linearity performance of the DLL and low power consumption. The design is implemented in the CSM 2P4M 0.35 μm CMOS process. The measurement results indicate that an efficiency improvement of 2%-4% is achieved over the load current range from 100 to 600 mA at 4 MHz switching frequency with 3.3 V input and 1.3 V output voltage.

  12. Nonlinear ultrafast switching based on soliton self-trapping in dual-core photonic crystal fibre

    NASA Astrophysics Data System (ADS)

    Stajanca, P.; Bugar, I.

    2016-11-01

    In this paper, we present a systematic numerical study of a novel ultrafast nonlinear switching concept based on soliton self-trapping in dual-core (DC) photonic crystal fibre (PCF). The geometrical parameters of highly-nonlinear (HN) DC microstructure are optimized with regard to desired linear and nonlinear propagation characteristics. The comparable magnitude of fibre coupling length and soliton period is identified as a key condition for presented switching concept. The optimized DC PCF design is subjected to detailed nonlinear numerical study. Complex temporal-spectral-spatial transformations of 100 fs hyperbolic secant pulse at 1550 nm in the DC PCF are studied numerically employing a model based on coupled generalized nonlinear Schrödinger equations solved by a split-step Fourier method. For the optimized DC structure, mutual interplay of solitonic and coupling processes gives rise to nonlinear switching of self-trapped soliton. The output channel (fibre core) for the generated soliton can be controlled via the input pulse energy. For vertical polarization, the optimal soliton switching with extinction ratio contrast of 32.4 dB at 10.75 mm propagation distance is achieved. Even better switching contrast of 34.8 dB can be achieved for horizontal polarization at optimal propagation distance of 10.25 mm. Besides energy-controlled soliton self-trapping switching, the fibre supports also nonlinear polarization switching with soliton switching contrast as high as 37.4 dB. The proposed fibre holds a high application potential allowing efficient ultrafast switching of sub-nanojoule pulses at over-Tb/s data rates requiring only about 1 cm fibre length.

  13. Synchronized dual tunable wavelength Q-switched Nd:Glass laser.

    PubMed

    Men, Shaojie; Liu, Zhaojun; Cong, Zhenhua; Liu, Yang; Zhang, Sasa; Li, Yongfu; Lu, Qingming; Zhang, Xingyu

    2014-12-15

    A flash-lamp pumped electro-optically Q-switched dual tunable wavelength Nd:Glass laser is demonstrated. An Nd:Glass rod was selected as the laser medium and a DKDP crystal was employed as the Q-switch. A cubic polarizer was placed in the cavity to divide the randomly polarized radiation into two orthogonally polarized beams. The two beams were tuned by two Littman-gratings and output independently. For Q-switched operation, the tuning range was 1050.1 - 1061.6 nm and 1050.5 - 1060.2 nm for the horizontal and vertical polarizations, respectively. When the horizontally polarized output was fixed at 1059.1 nm, the synchronized vertically polarized one can be tuned from 1051.5 to 1057.5 nm.

  14. The association between media multitasking, task-switching, and dual-task performance.

    PubMed

    Alzahabi, Reem; Becker, Mark W

    2013-10-01

    The recent rise in media use has prompted researchers to investigate its influence on users' basic cognitive processes, such as attention and cognitive control. However, most of these investigations have failed to consider that the rise in media use has been accompanied by an even more dramatic rise in media multitasking (engaging with multiple forms of media simultaneously). Here we investigate how one's ability to switch between 2 tasks and to perform 2 tasks simultaneously is associated with media multitasking experience. Participants saw displays comprised of a number-letter pair and classified the number as odd or even and/or the letter as a consonant or vowel. In task-switching blocks, a cue indicated which classification to perform on each trial. In dual-task blocks, participants performed both classifications. Heavy and light media multitaskers showed comparable performance in the dual-task. Across 2 experiments, heavy media multitaskers were better able to switch between tasks in the task-switching paradigm. Thus, while media multitasking was not associated with increased ability to process 2 tasks in parallel, it was associated with an increased ability to shift between discrete tasks. PsycINFO Database Record (c) 2013 APA, all rights reserved.

  15. Graphene-based passively Q-switched dual-wavelength erbium-doped fiber laser.

    PubMed

    Luo, Zhengqian; Zhou, Min; Weng, Jian; Huang, Guoming; Xu, Huiying; Ye, Chenchun; Cai, Zhiping

    2010-11-01

    We demonstrate a compact Q-switched dual-wavelength erbium-doped fiber (EDF) laser based on graphene as a saturable absorber (SA). By optically driven deposition of graphene on a fiber core, the SA is constructed and inserted into a diode-pumped EDF laser cavity. Also benefiting from the strong third-order optical nonlinearity of graphene to suppress the mode competition of EDF, a stable dual-wavelength Q-switching operation has been achieved using a two-reflection peak fiber Bragg grating as the external cavity mirror. The Q-switched EDF laser has a low pump threshold of 6.5 mW at 974 nm and a wide range of pulse-repetition rate from 3.3 to 65.9 kHz. The pulse duration and the pulse energy have been characterized. This is, to the best of our knowledge, the first demonstration of a graphene-based Q-switched laser.

  16. Initial use of fast switched dual energy CT for coronary artery disease

    NASA Astrophysics Data System (ADS)

    Pavlicek, William; Panse, Prasad; Hara, Amy; Boltz, Thomas; Paden, Robert; Yamak, Didem; Licato, Paul; Chandra, Naveen; Okerlund, Darin; Dutta, Sandeep; Bhotika, Rahul; Langan, David

    2010-04-01

    Coronary CT Angiography (CTA) is limited in patients with calcified plaque and stents. CTA is unable to confidently differentiate fibrous from lipid plaque. Fast switched dual energy CTA offers certain advantages. Dual energy CTA removes calcium thereby improving visualization of the lumen and potentially providing a more accurate measure of stenosis. Dual energy CTA directly measures calcium burden (calcium hydroxyapatite) thereby eliminating a separate non-contrast series for Agatston Scoring. Using material basis pairs, the differentiation of fibrous and lipid plaques is also possible. Patency of a previously stented coronary artery is difficult to visualize with CTA due to resolution constraints and localized beam hardening artifacts. Monochromatic 70 keV or Iodine images coupled with Virtual Non-stent images lessen beam hardening artifact and blooming. Virtual removal of stainless steel stents improves assessment of in-stent re-stenosis. A beating heart phantom with 'cholesterol' and 'fibrous' phantom coronary plaques were imaged with dual energy CTA. Statistical classification methods (SVM, kNN, and LDA) distinguished 'cholesterol' from 'fibrous' phantom plaque tissue. Applying this classification method to 16 human soft plaques, a lipid 'burden' may be useful for characterizing risk of coronary disease. We also found that dual energy CTA is more sensitive to iodine contrast than conventional CTA which could improve the differentiation of myocardial infarct and ischemia on delayed acquisitions. These phantom and patient acquisitions show advantages with using fast switched dual energy CTA for coronary imaging and potentially extends the use of CT for addressing problem areas of non-invasive evaluation of coronary artery disease.

  17. Pyrene-based dual-mode fluorescence switches and logic gates that function in solution and film.

    PubMed

    Zhou, Weidong; Li, Yongjun; Li, Yuliang; Liu, Huibiao; Wang, Shu; Li, Cuihong; Yuan, Mingjian; Liu, Xiaofeng; Zhu, Daoben

    2006-07-17

    A dual-mode fluorescence switch controlled by external inputs such as protons and metal ions is described, and each state corresponds to a specific fluorescent emission peak. Based on the reversible changes of the fluorescence emission of the switch responding to different external stimuli, the corresponding integrated logic gates and communication networks have been constructed in solid film or in solution.

  18. Doxorubicin Delivery Using pH and Redox Dual-Responsive Hollow Nanocapsules with a Cationic Electrostatic Barrier

    PubMed Central

    Teranishi, Ryoma; Matsuki, Ryota; Yuba, Eiji; Harada, Atsushi; Kono, Kenji

    2016-01-01

    For the delivery of doxorubicin (DOX), pH and redox dual responsive hollow nanocapsules were prepared through the stabilization of polymer vesicles, which spontaneously formed from polyamidoamine dendron-poly(l-lysine) (PAMAM dendron-PLL), by the introduction of disulfide (SS) bonds between PLLs. The SS-bonded nanocapsules exhibited a very slow release of DOX under an extracellular environment because the cationic PLL membrane acted as an electrostatic barrier against the protonated DOX molecules. However, increasing the glutathione concentration to the intracellular level facilitated the immediate release of DOX through the collapse of nanocapsules by the spontaneous cleavage of SS bonds. SS-bonded nanocapsules also escaped from the endosome by the buffering effect of PAMAM dendrons, and DOX delivery into the cytoplasm was achieved. Furthermore, DOX molecules delivered by SS-bonded nanocapsules exhibited an effective in vitro anticancer effect to HeLa cells. PMID:28042818

  19. Dual-loss-modulated Q-switched Tm:LuAG laser with AOM and monolayer graphene.

    PubMed

    Luan, Chao; Yang, Ke Jian; Zhao, Jia; Zhao, Sheng Zhi; Qiao, Wen Chao; Li, Tao; Feng, Tian Li; Liu, Cheng; Qiao, Jun Peng; Zheng, Li He; Xu, Jun; Wang, Qing Guo; Su, Liang Bi

    2015-09-20

    A laser-diode-pumped dual-loss-modulated Q-switching Tm:LuAG laser with an acousto-optic modulator (AOM) and monolayer graphene saturable absorber (SA) around 2 μm is presented for the first time to the best of our knowledge. The average output power and the pulse widths for different repetition rates have been measured. In comparison with the singly Q-switching laser with AOM or with monolayer graphene SA, the dual-loss-modulated Q-switching laser could generate shorter pulse width and higher peak power. The maximum pulse width compression ratio was found to be 3.11, and the highest peak power was enhanced 97.4 times. The experimental results show that the dual-loss-modulated technology is an efficient method for compressing the pulse width, improving the peak power, and enhancing the pulse stability for the Q-switched lasers at 2 μm.

  20. Design improvement of permanent magnet flux switching motor with dual rotor structure

    NASA Astrophysics Data System (ADS)

    Soomro, H. A.; Sulaiman, E.; Kumar, R.; Rahim, N. S.

    2017-08-01

    This paper presents design enhancement to reduce permanent magnet (PM) volume for 7S-6P-7S dual rotor permanent magnet flux-switching machines (DRPMFSM) for electric vehicle application. In recent years, Permanent magnet flux switching (PMFS) motor and a new member of brushless permanent magnet machine are prominently used for the electric vehicle. Though, more volume of Rare-Earth Permanent Magnet (REPM) is used to increase the cost and weight of these motors. Thus, to overcome the issue, new configuration of 7S-6P- 7S dual rotor permanent magnet flux-switching machine (DRPMFSM) has been proposed and investigated in this paper. Initially proposed 7S-6P-7S DRPMFSM has been optimized using “deterministic optimization” to reduce the volume of PM and to attain optimum performances. In addition, the performances of initial and optimized DRPMFSM have been compared such that back-emf, cogging torque, average torque, torque and power vs speed performances, losses and efficiency have been analysed by 2D-finite element analysis (FEA) using the JMAG- Designer software ver. 14.1. Consequently, the final design 7S-6P-7S DRPMFSM has achieved the efficiency of 83.91% at reduced PM volume than initial design to confirm the better efficient motor for HEVs applications.

  1. Dual-wavelength passively Q-switched Nd:GYSGG laser by tungsten disulfide saturable absorber.

    PubMed

    Gao, Y J; Zhang, B Y; Song, Q; Wang, G J; Wang, W J; Hong, M H; Dou, R Q; Sun, D L; Zhang, Q L

    2016-06-20

    A dual-wavelength passively Q-switched Nd:GYSGG laser using vacuum evaporating tungsten disulfide (WS2) as a saturable absorber was demonstrated for the first time to the best of our knowledge. The WS2 saturable absorber was prepared simply by evaporating nanometer WS2 powders onto a quartz substrate in a vacuum. By inserting the WS2 saturable absorber into the laser cavity, stable Q-switched laser operation was achieved with a maximum average output power of 367 mW, a pulse repetition rate of 70.7 kHz, the shortest pulse width of 591 ns, and pulse energy of about 1.05 μJ. By vacuum evaporation method, a high-quality WS2 saturable absorber can be produced, and it seems to be a suitable method for fabrication of 2D transition metal dichalcogenides.

  2. Switching between Anion-Binding Catalysis and Aminocatalysis with a Rotaxane Dual-Function Catalyst.

    PubMed

    Eichstaedt, Katarzyna; Jaramillo-Garcia, Javier; Leigh, David A; Marcos, Vanesa; Pisano, Simone; Singleton, Thomas A

    2017-07-12

    The "off" state for aminocatalysis by a switchable [2]rotaxane is shown to correspond to an "on" state for anion-binding catalysis. Conversely, the aminocatalysis "on" state of the dual-function rotaxane is inactive in anion-binding catalysis. Switching between the different states is achieved through the stimuli-induced change of position of the macrocycle on the rotaxane thread. The anion-binding catalysis results from a pair of triazolium groups that act together to CH-hydrogen-bond to halide anions when the macrocycle is located on an alternative (ammonium) binding site, stabilizing the in situ generation of benzhydryl cation and oxonium ion intermediates from activated alkyl halides. The aminocatalysis and anion-binding catalysis sites of the dual-function rotaxane catalyst can be sequentially concealed or revealed, enabling catalysis of both steps of a tandem reaction process.

  3. Collaborative Tracking Control of Dual Linear Switched Reluctance Machines Over Communication Network With Time Delays.

    PubMed

    Qiu, Li; Shi, Yang; Pan, Jianfei; Zhang, Bo; Xu, Gang

    2016-10-11

    This paper investigates the collaborative tracking control for dual linear switched reluctance machines (LSRMs) over a communication network with random time delays. Considering the spatio-temporal constraint relationship of the dual LSRMs in complex industrial processes, the collaborative tracking control scheme is proposed based on the networked motion control method. The stability conditions and the controller design method for the networked dual LSRMs are obtained from the two motors relative position error by using Lyapunov theory and delay systems approach. Four different allocation schemes combined with two kinds of external control signals are applied onto the collaborative tracking control experiment platform of the dual LSRMs to validate the effectiveness of the proposed method. The maximum steady-state relative position error within 0.104 mm can be achieved under the constant absolute position reference input signal of 3 mm, and the maximum absolute relative position error within ±0.46 mm can be achieved under the sinusoidal reference of 8 mm amplitude and 0.2 Hz.

  4. Electrostatic control of polarity of α-MoTe2 transistors with dual top gates

    NASA Astrophysics Data System (ADS)

    Nakaharai, Shu; Yamamoto, Mahito; Ueno, Keiji; Lin, Yen-Fu; Li, Song-Lin; Tsukagoshi, Kazuhito

    2015-03-01

    Transition metal dichalcogenides have been expected for future applications in nanoelectronics due to their unique features of the atomically-thin structure. Using semiconducting α-molybdenum ditelluride (α-MoTe2) , we realized field effect transistors (FETs) in which the polarity (n- or p-type) can be electrostatically controlled without impurity doping. The fabricated device had a pair of top gates (aluminum electrode on silicon dioxide) attached in series with a gap length of 100 nm in between. We experimentally performed transistor operations in both n-FET and p-FET modes in a single device by changing the voltage applied to one of the two top gates, which determined the transistor polarity, and sweeping the bias of the other gate. The demonstrated reversibility of the transistor polarity will contribute to the renovated architecture of logic circuits with lower numbers of transistors and hence the lower power consumption than the conventional technology.

  5. Real-Time DC-dynamic Biasing Method for Switching Time Improvement in Severely Underdamped Fringing-field Electrostatic MEMS Actuators

    PubMed Central

    Small, Joshua; Fruehling, Adam; Garg, Anurag; Liu, Xiaoguang; Peroulis, Dimitrios

    2014-01-01

    Mechanically underdamped electrostatic fringing-field MEMS actuators are well known for their fast switching operation in response to a unit step input bias voltage. However, the tradeoff for the improved switching performance is a relatively long settling time to reach each gap height in response to various applied voltages. Transient applied bias waveforms are employed to facilitate reduced switching times for electrostatic fringing-field MEMS actuators with high mechanical quality factors. Removing the underlying substrate of the fringing-field actuator creates the low mechanical damping environment necessary to effectively test the concept. The removal of the underlying substrate also a has substantial improvement on the reliability performance of the device in regards to failure due to stiction. Although DC-dynamic biasing is useful in improving settling time, the required slew rates for typical MEMS devices may place aggressive requirements on the charge pumps for fully-integrated on-chip designs. Additionally, there may be challenges integrating the substrate removal step into the back-end-of-line commercial CMOS processing steps. Experimental validation of fabricated actuators demonstrates an improvement of 50x in switching time when compared to conventional step biasing results. Compared to theoretical calculations, the experimental results are in good agreement. PMID:25145811

  6. Real-time DC-dynamic biasing method for switching time improvement in severely underdamped fringing-field electrostatic MEMS actuators.

    PubMed

    Small, Joshua; Fruehling, Adam; Garg, Anurag; Liu, Xiaoguang; Peroulis, Dimitrios

    2014-08-15

    Mechanically underdamped electrostatic fringing-field MEMS actuators are well known for their fast switching operation in response to a unit step input bias voltage. However, the tradeoff for the improved switching performance is a relatively long settling time to reach each gap height in response to various applied voltages. Transient applied bias waveforms are employed to facilitate reduced switching times for electrostatic fringing-field MEMS actuators with high mechanical quality factors. Removing the underlying substrate of the fringing-field actuator creates the low mechanical damping environment necessary to effectively test the concept. The removal of the underlying substrate also a has substantial improvement on the reliability performance of the device in regards to failure due to stiction. Although DC-dynamic biasing is useful in improving settling time, the required slew rates for typical MEMS devices may place aggressive requirements on the charge pumps for fully-integrated on-chip designs. Additionally, there may be challenges integrating the substrate removal step into the back-end-of-line commercial CMOS processing steps. Experimental validation of fabricated actuators demonstrates an improvement of 50x in switching time when compared to conventional step biasing results. Compared to theoretical calculations, the experimental results are in good agreement.

  7. 888 nm pumped dual Nd:YVO4 crystals acousto-optic Q-switched laser

    NASA Astrophysics Data System (ADS)

    Zhang, Wenqi; Shen, Yijie; Meng, Yuan; Gong, Mali

    2017-10-01

    888 nm pumped acousto-optic (AO) Q-switched laser with high output power and high efficiency under dual Nd:YVO4 crystals configuration is firstly demonstrated and rate equations for dual-crystal lasers are further ameliorated and investigated. In continuous wave (CW) operation, we experimentally achieve a maximum output power exceeding 50 W. The global optical efficiency reaches 49.5% and the slope efficiency attains 55.5% via using a 1.5 at.% crystal with a 0.5 at.% crystal. In Q-switch operation, by utilizing double 0.5 at.% crystals, the global optical efficiency rises from 25.6% to 45.6% and the pulse duration varies from 26.2 to 42.4 ns when pulse repetition frequency (PRF) increases from 10 to 100 kHz. The measured beam quality factors M2 at 100 kHz are 1.012 and 1.041 with 52.8 W output power in the two orthogonal directions respectively.

  8. Efficacy of fixed filtration for rapid kVp-switching dual energy x-ray systems

    SciTech Connect

    Yao, Yuan; Wang, Adam S.; Pelc, Norbert J.

    2014-03-15

    Purpose: Dose efficiency of dual kVp imaging can be improved if the two beams are filtered to remove photons in the common part of their spectra, thereby increasing spectral separation. While there are a number of advantages to rapid kVp-switching for dual energy, it may not be feasible to have two different filters for the two spectra. Therefore, the authors are interested in whether a fixed added filter can improve the dose efficiency of kVp-switching dual energy x-ray systems. Methods: The authors hypothesized that a K-edge filter would provide the energy selectivity needed to remove overlap of the spectra and hence increase the precision of material separation at constant dose. Preliminary simulations were done using calcium and water basis materials and 80 and 140 kVp x-ray spectra. Precision of the decomposition was evaluated based on the propagation of the Poisson noise through the decomposition function. Considering availability and cost, the authors chose a commercial Gd{sub 2}O{sub 2}S screen as the filter for their experimental validation. Experiments were conducted on a table-top system using a phantom with various thicknesses of acrylic and copper and 70 and 125 kVp x-ray spectra. The authors kept the phantom exposure roughly constant with and without filtration by adjusting the tube current. The filtered and unfiltered raw data of both low and high energy were decomposed into basis material and the variance of the decomposition for each thickness pair was calculated. To evaluate the filtration performance, the authors measured the ratio of material decomposition variance with and without filtration. Results: Simulation results show that the ideal filter material depends on the object composition and thickness, and ranges across the lanthanide series, with higher atomic number filters being preferred for more attenuating objects. Variance reduction increases with filter thickness, and substantial reductions (40%) can be achieved with a 2× loss in

  9. High contrast ratio and fast-switching dual polymer electrochromic devices

    SciTech Connect

    Sapp, S.A.; Sotzing, G.A.; Reynolds, J.R.

    1998-08-01

    A series of dual polymer electrochromic devices (ECDs) based on 12 complementary pairs of conducting polymer films have been constructed using 3,4-ethylenedioxythiophene-containing conducting polymers. Poly[3,6-bis(2-(3,4-ethylenedioxythiophene))-N-methylcarbazole] (PBEDOT-NCH{sub 3}Cz), poly[3,6-bis(2-(3,4-ethylenedioxythiophene))-N-eicosylcarbazole] (PBEDOT-NC{sub 20}H{sub 41}Cz), and poly[4,4{prime}-bis(2-(3,4-ethylenedioxythiophene))biphenyl] (PBEDOT-BP) were utilized as anodically coloring polymers that electrochemically switch between an oxidized deep blue absorptive state and a transmissive (orange or yellow) reduced state. Poly(3,4-ethylenedioxythiophene)(PEDOT) and its alkyl derivatives (PEDOT-C{sub 14}H{sub 29} and PEDOT-C{sub 16}H{sub 33}) have been used as high-contrast cathodically coloring polymers that switch between a deep blue absorptive state in the reduced form and a sky blue, highly transmissive state in the oxidized form. The dual polymer ECDs were constructed by separating complementary pairs of EC polymer films, deposited on ITO glass, with a gel electrolyte composed of a lithium salt and plasticized poly(methyl methacrylate) (PMMA). Device contrast ratios, measured as {Delta}%T, ranged from 27% to 63%, and subsecond switching times for full color change were achieved. These devices were found to exhibit extremely high coloration efficiencies of up to 1400 cm{sup 2}/C over narrow (ca. 100 nm) wavelength ranges and to retain up to 60% of their optical response after 10,000 deep, double potential steps, rendering them useful for EC applications.

  10. Dual field effects in electrolyte-gated spinel ferrite: electrostatic carrier doping and redox reactions

    PubMed Central

    Ichimura, Takashi; Fujiwara, Kohei; Tanaka, Hidekazu

    2014-01-01

    Controlling the electronic properties of functional oxide materials via external electric fields has attracted increasing attention as a key technology for next-generation electronics. For transition-metal oxides with metallic carrier densities, the electric-field effect with ionic liquid electrolytes has been widely used because of the enormous carrier doping capabilities. The gate-induced redox reactions revealed by recent investigations have, however, highlighted the complex nature of the electric-field effect. Here, we use the gate-induced conductance modulation of spinel ZnxFe3−xO4 to demonstrate the dual contributions of volatile and non-volatile field effects arising from electronic carrier doping and redox reactions. These two contributions are found to change in opposite senses depending on the Zn content x; virtual electronic and chemical field effects are observed at appropriate Zn compositions. The tuning of field-effect characteristics via composition engineering should be extremely useful for fabricating high-performance oxide field-effect devices. PMID:25056718

  11. Clinical efficacy of the dual-pulsed Q-switched neodymium:yttrium-aluminum-garnet laser: Comparison with conservative mode.

    PubMed

    Kim, Byung Wook; Lee, Mi Hye; Chang, Sung Eun; Yun, Woo Jin; Won, Chong Hyun; Lee, Mi Woo; Choi, Jee Ho; Moon, Kee Chan

    2013-12-01

    The quality (Q)-switched neodymium:yttrium-aluminum-garnet (Nd:YAG) laser is one of the first non-ablative lasers to be used for facial resurfacing and photorejuvenation. Recently, the method of low-fluence Q-switched Nd:YAG lasers known as 'laser toning' has been used for non-ablative skin rejuvenation and for the treatment of melasma in Asian countries. We report our experience of using a novel Q-switched Nd:YAG laser that was operated as a dual pulse at half fluence and 140-μs intervals compared with conservative mode laser.

  12. Video game practice optimizes executive control skills in dual-task and task switching situations.

    PubMed

    Strobach, Tilo; Frensch, Peter A; Schubert, Torsten

    2012-05-01

    We examined the relation of action video game practice and the optimization of executive control skills that are needed to coordinate two different tasks. As action video games are similar to real life situations and complex in nature, and include numerous concurrent actions, they may generate an ideal environment for practicing these skills (Green & Bavelier, 2008). For two types of experimental paradigms, dual-task and task switching respectively; we obtained performance advantages for experienced video gamers compared to non-gamers in situations in which two different tasks were processed simultaneously or sequentially. This advantage was absent in single-task situations. These findings indicate optimized executive control skills in video gamers. Similar findings in non-gamers after 15 h of action video game practice when compared to non-gamers with practice on a puzzle game clarified the causal relation between video game practice and the optimization of executive control skills.

  13. Dual origin of defect magnetism in graphene and its reversible switching by molecular doping.

    PubMed

    Nair, R R; Tsai, I-L; Sepioni, M; Lehtinen, O; Keinonen, J; Krasheninnikov, A V; Castro Neto, A H; Katsnelson, M I; Geim, A K; Grigorieva, I V

    2013-01-01

    Control of magnetism by applied voltage is desirable for spintronics applications. Finding a suitable material remains an elusive goal, with only a few candidates found so far. Graphene is one of them and attracts interest because of its weak spin-orbit interaction, the ability to control electronic properties by the electric field effect and the possibility to introduce paramagnetic centres such as vacancies and adatoms. Here we show that the magnetism of adatoms in graphene is itinerant and can be controlled by doping, so that magnetic moments are switched on and off. The much-discussed vacancy magnetism is found to have a dual origin, with two approximately equal contributions; one from itinerant magnetism and the other from dangling bonds. Our work suggests that graphene's spin transport can be controlled by the field effect, similar to its electronic and optical properties, and that spin diffusion can be significantly enhanced above a certain carrier density.

  14. A single-inductor dual-output switching converter with average current mode control

    NASA Astrophysics Data System (ADS)

    Weiwei, Xu; Xiaoting, Zhu; Zhiliang, Hong; D, Killat

    2009-09-01

    An integrated single-inductor dual-output (SIDO) switching DC-DC converter is presented. The outputs are specified with 1.2 V/400 mA and 1.8 V/200 mA. A decoupling small signal model is proposed to analyze the multi-loop system and to design the on-chip compensators. An average current control mode is introduced with lossless, continuous current detection. The converter has been fabricated in a 0.25 μm 2P4M CMOS process. The power efficiency is 86% at a total output power of 840 mW while the output ripples are about 40 mV at an oscillator frequency of 600 kHz.

  15. Calcium binding by synaptotagmin's C2A domain is an essential element of the electrostatic switch that triggers synchronous synaptic transmission.

    PubMed

    Striegel, Amelia R; Biela, Laurie M; Evans, Chantell S; Wang, Zhao; Delehoy, Jillian B; Sutton, R Bryan; Chapman, Edwin R; Reist, Noreen E

    2012-01-25

    Synaptotagmin is the major calcium sensor for fast synaptic transmission that requires the synchronous fusion of synaptic vesicles. Synaptotagmin contains two calcium-binding domains: C2A and C2B. Mutation of a positively charged residue (R233Q in rat) showed that Ca2+-dependent interactions between the C2A domain and membranes play a role in the electrostatic switch that initiates fusion. Surprisingly, aspartate-to-asparagine mutations in C2A that inhibit Ca2+ binding support efficient synaptic transmission, suggesting that Ca2+ binding by C2A is not required for triggering synchronous fusion. Based on a structural analysis, we generated a novel mutation of a single Ca2+-binding residue in C2A (D229E in Drosophila) that inhibited Ca2+ binding but maintained the negative charge of the pocket. This C2A aspartate-to-glutamate mutation resulted in ∼80% decrease in synchronous transmitter release and a decrease in the apparent Ca2+ affinity of release. Previous aspartate-to-asparagine mutations in C2A partially mimicked Ca2+ binding by decreasing the negative charge of the pocket. We now show that the major function of Ca2+ binding to C2A is to neutralize the negative charge of the pocket, thereby unleashing the fusion-stimulating activity of synaptotagmin. Our results demonstrate that Ca2+ binding by C2A is a critical component of the electrostatic switch that triggers synchronous fusion. Thus, Ca2+ binding by C2B is necessary and sufficient to regulate the precise timing required for coupling vesicle fusion to Ca2+ influx, but Ca2+ binding by both C2 domains is required to flip the electrostatic switch that triggers efficient synchronous synaptic transmission.

  16. Musical training, bilingualism, and executive function: a closer look at task switching and dual-task performance.

    PubMed

    Moradzadeh, Linda; Blumenthal, Galit; Wiseheart, Melody

    2015-07-01

    This study investigated whether musical training and bilingualism are associated with enhancements in specific components of executive function, namely, task switching and dual-task performance. Participants (n = 153) belonging to one of four groups (monolingual musician, bilingual musician, bilingual non-musician, or monolingual non-musician) were matched on age and socioeconomic status and administered task switching and dual-task paradigms. Results demonstrated reduced global and local switch costs in musicians compared with non-musicians, suggesting that musical training can contribute to increased efficiency in the ability to shift flexibly between mental sets. On dual-task performance, musicians also outperformed non-musicians. There was neither a cognitive advantage for bilinguals relative to monolinguals, nor an interaction between music and language to suggest additive effects of both types of experience. These findings demonstrate that long-term musical training is associated with improvements in task switching and dual-task performance. Copyright © 2014 Cognitive Science Society, Inc.

  17. Musical Training, Bilingualism, and Executive Function: A Closer Look at Task Switching and Dual-Task Performance

    ERIC Educational Resources Information Center

    Moradzadeh, Linda; Blumenthal, Galit; Wiseheart, Melody

    2015-01-01

    This study investigated whether musical training and bilingualism are associated with enhancements in specific components of executive function, namely, task switching and dual-task performance. Participants (n = 153) belonging to one of four groups (monolingual musician, bilingual musician, bilingual non-musician, or monolingual non-musician)…

  18. Musical Training, Bilingualism, and Executive Function: A Closer Look at Task Switching and Dual-Task Performance

    ERIC Educational Resources Information Center

    Moradzadeh, Linda; Blumenthal, Galit; Wiseheart, Melody

    2015-01-01

    This study investigated whether musical training and bilingualism are associated with enhancements in specific components of executive function, namely, task switching and dual-task performance. Participants (n = 153) belonging to one of four groups (monolingual musician, bilingual musician, bilingual non-musician, or monolingual non-musician)…

  19. Antagonistic control of a dual-input mammalian gene switch by food additives.

    PubMed

    Xie, Mingqi; Ye, Haifeng; Hamri, Ghislaine Charpin-El; Fussenegger, Martin

    2014-08-01

    Synthetic biology has significantly advanced the design of mammalian trigger-inducible transgene-control devices that are able to programme complex cellular behaviour. Fruit-based benzoate derivatives licensed as food additives, such as flavours (e.g. vanillate) and preservatives (e.g. benzoate), are a particularly attractive class of trigger compounds for orthogonal mammalian transgene control devices because of their innocuousness, physiological compatibility and simple oral administration. Capitalizing on the genetic componentry of the soil bacterium Comamonas testosteroni, which has evolved to catabolize a variety of aromatic compounds, we have designed different mammalian gene expression systems that could be induced and repressed by the food additives benzoate and vanillate. When implanting designer cells engineered for gene switch-driven expression of the human placental secreted alkaline phosphatase (SEAP) into mice, blood SEAP levels of treated animals directly correlated with a benzoate-enriched drinking programme. Additionally, the benzoate-/vanillate-responsive device was compatible with other transgene control systems and could be assembled into higher-order control networks providing expression dynamics reminiscent of a lap-timing stopwatch. Designer gene switches using licensed food additives as trigger compounds to achieve antagonistic dual-input expression profiles and provide novel control topologies and regulation dynamics may advance future gene- and cell-based therapies. © The Author(s) 2014. Published by Oxford University Press on behalf of Nucleic Acids Research.

  20. Dual energy CT via fast kVp switching spectrum estimation

    NASA Astrophysics Data System (ADS)

    Xu, Dan; Langan, David A.; Wu, Xiaoye; Pack, Jed D.; Benson, Thomas M.; Tkaczky, J. Eric; Schmitz, Andrea M.

    2009-02-01

    Recently there has been significant interest in dual energy CT imaging with several acquisition methods being actively pursued. Here we investigate fast kVp switching where the kVp alternates between low and high kVp every view. Fast kVp switching enables fine temporal registration, helical and axial acquisitions, and full field of view. It also presents several processing challenges. The rise and fall of the kVp, which occurs during the view integration period, is not instantaneous and complicates the measurement of the effective spectrum for low and high kVp views. Further, if the detector digital acquisition system (DAS) and generator clocks are not fully synchronous, jitter is introduced in the kVp waveform relative to the view period. In this paper we develop a method for estimation of the resulting spectrum for low and high kVp views. The method utilizes static kVp acquisitions of air with a small bowtie filter as a basis set. A fast kVp acquisition of air with a small bowtie filter is performed and the effective kVp is estimated as a linear combination of the basis vectors. The effectiveness of this method is demonstrated through the reconstruction of a water phantom acquired with a fast kVp acquisition. The impact of jitter due to the generator and detector DAS clocks is explored via simulation. The error is measured relative to spectrum variation and material decomposition accuracy.

  1. Antagonistic control of a dual-input mammalian gene switch by food additives

    PubMed Central

    Xie, Mingqi; Ye, Haifeng; Hamri, Ghislaine Charpin-El; Fussenegger, Martin

    2014-01-01

    Synthetic biology has significantly advanced the design of mammalian trigger-inducible transgene-control devices that are able to programme complex cellular behaviour. Fruit-based benzoate derivatives licensed as food additives, such as flavours (e.g. vanillate) and preservatives (e.g. benzoate), are a particularly attractive class of trigger compounds for orthogonal mammalian transgene control devices because of their innocuousness, physiological compatibility and simple oral administration. Capitalizing on the genetic componentry of the soil bacterium Comamonas testosteroni, which has evolved to catabolize a variety of aromatic compounds, we have designed different mammalian gene expression systems that could be induced and repressed by the food additives benzoate and vanillate. When implanting designer cells engineered for gene switch-driven expression of the human placental secreted alkaline phosphatase (SEAP) into mice, blood SEAP levels of treated animals directly correlated with a benzoate-enriched drinking programme. Additionally, the benzoate-/vanillate-responsive device was compatible with other transgene control systems and could be assembled into higher-order control networks providing expression dynamics reminiscent of a lap-timing stopwatch. Designer gene switches using licensed food additives as trigger compounds to achieve antagonistic dual-input expression profiles and provide novel control topologies and regulation dynamics may advance future gene- and cell-based therapies. PMID:25030908

  2. Dual-wavelength synchronously Q-switched solid-state laser with multi-layered graphene as saturable absorber.

    PubMed

    Zhao, Yongguang; Li, Xianlei; Xu, Miaomiao; Yu, Haohai; Wu, Yongzhong; Wang, Zhengping; Hao, Xiaopeng; Xu, Xinguang

    2013-02-11

    Using multilayered graphene as the saturable absorber (SA), Nd:LYSO crystal as the laser material, we demonstrated a laser-diode (LD) pumped, dual-wavelength passively Q-switched solid-state laser. The maximum average output power is 1.8 W, the largest pulse energy and highest peak power is 11.3 μJ, 118 W, respectively. As we have known, they are the best results for passively Q-switched operation of graphene. The pulse laser is strong enough to realize extra-cavity frequency conversions. With a KTP crystal as the sum-frequency generator, the dual wavelengths are proved to be well time overlapped, which manifests the synchronous modulation to the dual-wavelength with multi-layered graphene.

  3. Dual conical conducting filament model in resistance switching TiO2 thin films.

    PubMed

    Kim, Kyung Min; Park, Tae Hyung; Hwang, Cheol Seong

    2015-01-19

    The resetting behaviors of Pt/TiO2/Pt resistive switching (RS) cell in unipolar RS operations were studied in detail through an experiment and by modeling. The experiment showed that the apparently highly arbitrary resetting current-voltage (I-V) curves could be grouped into three types: normal, delayed, and abnormal behaviors. A dual conical conducting filament (CF) model was conceived, and their electrothermal behaviors were analytically described from the heat-balance and charge-transport equations. The almost spontaneous resetting behavior of the normal reset could be easily understood from the mutually constructive interference effect between the Joule heating and temperature-dependent resistance effect along the CF. The delayed reset could be explained by the time-dependent increase in the reset voltage during the rest process, which was most probably induced in the more conical-shaped CF. The abnormal reset could be understood from the temporal transfer of oxygen ions near the kink positions of the two different-diameter portions of the more cylindrical CFs, which temporally decreases the overall resistance immediately prior for the actual reset to occur. The accuracy of the dual conical CF model was further confirmed by adopting a more thorough electrothermal simulation package, COMSOL.

  4. Dual Conical Conducting Filament Model in Resistance Switching TiO2 Thin Films

    PubMed Central

    Kim, Kyung Min; Park, Tae Hyung; Hwang, Cheol Seong

    2015-01-01

    The resetting behaviors of Pt/TiO2/Pt resistive switching (RS) cell in unipolar RS operations were studied in detail through an experiment and by modeling. The experiment showed that the apparently highly arbitrary resetting current-voltage (I–V) curves could be grouped into three types: normal, delayed, and abnormal behaviors. A dual conical conducting filament (CF) model was conceived, and their electrothermal behaviors were analytically described from the heat-balance and charge-transport equations. The almost spontaneous resetting behavior of the normal reset could be easily understood from the mutually constructive interference effect between the Joule heating and temperature-dependent resistance effect along the CF. The delayed reset could be explained by the time-dependent increase in the reset voltage during the rest process, which was most probably induced in the more conical-shaped CF. The abnormal reset could be understood from the temporal transfer of oxygen ions near the kink positions of the two different-diameter portions of the more cylindrical CFs, which temporally decreases the overall resistance immediately prior for the actual reset to occur. The accuracy of the dual conical CF model was further confirmed by adopting a more thorough electrothermal simulation package, COMSOL. PMID:25598439

  5. Dual Conical Conducting Filament Model in Resistance Switching TiO2 Thin Films

    NASA Astrophysics Data System (ADS)

    Kim, Kyung Min; Park, Tae Hyung; Hwang, Cheol Seong

    2015-01-01

    The resetting behaviors of Pt/TiO2/Pt resistive switching (RS) cell in unipolar RS operations were studied in detail through an experiment and by modeling. The experiment showed that the apparently highly arbitrary resetting current-voltage (I-V) curves could be grouped into three types: normal, delayed, and abnormal behaviors. A dual conical conducting filament (CF) model was conceived, and their electrothermal behaviors were analytically described from the heat-balance and charge-transport equations. The almost spontaneous resetting behavior of the normal reset could be easily understood from the mutually constructive interference effect between the Joule heating and temperature-dependent resistance effect along the CF. The delayed reset could be explained by the time-dependent increase in the reset voltage during the rest process, which was most probably induced in the more conical-shaped CF. The abnormal reset could be understood from the temporal transfer of oxygen ions near the kink positions of the two different-diameter portions of the more cylindrical CFs, which temporally decreases the overall resistance immediately prior for the actual reset to occur. The accuracy of the dual conical CF model was further confirmed by adopting a more thorough electrothermal simulation package, COMSOL.

  6. MTL–Independent Phenotypic Switching in Candida tropicalis and a Dual Role for Wor1 in Regulating Switching and Filamentation

    PubMed Central

    Porman, Allison M.; Wang, Na; Bennett, Richard J.

    2013-01-01

    Phenotypic switching allows for rapid transitions between alternative cell states and is important in pathogenic fungi for colonization and infection of different host niches. In Candida albicans, the white-opaque phenotypic switch plays a central role in regulating the program of sexual mating as well as interactions with the mammalian host. White-opaque switching is controlled by genes encoded at the MTL (mating-type-like) locus that ensures that only a or α cells can switch from the white state to the mating-competent opaque state, while a/α cells are refractory to switching. Here, we show that the related pathogen C. tropicalis undergoes white-opaque switching in all three cell types (a, α, and a/α), and thus switching is independent of MTL control. We also demonstrate that C. tropicalis white cells are themselves mating-competent, albeit at a lower efficiency than opaque cells. Transcriptional profiling of C. tropicalis white and opaque cells reveals significant overlap between switch-regulated genes in MTL homozygous and MTL heterozygous cells, although twice as many genes are white-opaque regulated in a/α cells as in a cells. In C. albicans, the transcription factor Wor1 is the master regulator of the white-opaque switch, and we show that Wor1 also regulates switching in C. tropicalis; deletion of WOR1 locks a, α, and a/α cells in the white state, while WOR1 overexpression induces these cells to adopt the opaque state. Furthermore, we show that WOR1 overexpression promotes both filamentous growth and biofilm formation in C. tropicalis, independent of the white-opaque switch. These results demonstrate an expanded role for C. tropicalis Wor1, including the regulation of processes necessary for infection of the mammalian host. We discuss these findings in light of the ancestral role of Wor1 as a transcriptional regulator of the transition between yeast form and filamentous growth. PMID:23555286

  7. The role of dual-task and task-switch in prospective memory: behavioural data and neural correlates.

    PubMed

    Bisiacchi, Patrizia S; Schiff, Sami; Ciccola, Alessia; Kliegel, Matthias

    2009-04-01

    Event-based prospective memory (PM) requires remembering the delayed execution of an intended action in response to a pre-specified PM cue while being actively engaged in an ongoing task in which the cue is embedded. To date, experimental paradigms vary as to whether or not they require participants immediately to stop working on the ongoing task whenever they encounter a PM event (cue) and directly switch to the prospective action (task-switch approach). Alternatively, several other paradigms used in the literature encourage participants to continue working on the ongoing task item after the cue, and only then, perform the prospective action (dual-task approach). The present study explores the possible behavioural and electrophysiological effects that both approaches may have on PM performance. Seventeen young adults performed both versions of a standard PM task in a counterbalanced order during which behavioural data and electroencephalogram (EEG) were recorded. Behavioural data showed a decrement in PM performance in the task-switch compared to the dual-task condition. In addition, EEG data revealed differences between the dual-task and task-switch approach in event-related potential (ERP) components associated with response inhibition and with post-retrieval monitoring (i.e. late positive complex). No differences between the two tasks were found with regard to the PM event detection processes (i.e. N300) and the retrieval of the intended action from long-term memory. In sum, findings demonstrate that it does make a difference which task approach is applied and suggest that dual-task and task-switch paradigms may result in different processing and neurophysiological dynamics particularly concerning attentional resources and cognitive control.

  8. Bipolar switching polarity reversal by electrolyte layer sequence in electrochemical metallization cells with dual-layer solid electrolytes.

    PubMed

    Soni, Rohit; Meuffels, Paul; Petraru, Adrian; Hansen, Mirko; Ziegler, Martin; Vavra, Ondrej; Kohlstedt, Hermann; Jeong, Doo Seok

    2013-12-21

    Bipolar switching behaviours of electrochemical metallization (ECM) cells with dual-layer solid electrolytes (SiOx-Ge0.3Se0.7) were analyzed. Type 1 ECM cell, Pt (bottom electrode)/SiOx/Ge0.3Se0.7/Cu (top electrode), exhibited typical eightwise current-voltage (I-V) hysteresis of ECM cells whereas Type 2 ECM cell, Pt (bottom electrode)/Ge0.3Se0.7/SiOx/Cu(top electrode), showed counter-eightwise hysteresis. In addition, absolute off-switching voltage in Type 2 cell is lower than that in Type 1 cell while on-switching voltage in both cells is almost the same. An attempt to understand this electrolyte-stack-sequence-depending switching polarity reversal was made in terms of the ECM cell potential change upon the electrolyte stack sequence and the consequent change in Cu filament growth direction. Relevant experimental evidence for the hypothesis was obtained regarding the switching behaviours. Furthermore, given the switching polarity reversal, feasibility of serial complementary resistive switches was also demonstrated.

  9. Percutaneous Dual-Switching Monopolar Radiofrequency Ablation Using a Separable Clustered Electrode: A Preliminary Study

    PubMed Central

    Choi, Tae Won; Lee, Dong Ho; Lee, Jeong-Hoon; Yu, Su Jong; Kim, Yoon Jun; Yoon, Jung-Hwan; Han, Joon Koo

    2017-01-01

    Objective To prospectively evaluate the safety and therapeutic effectiveness of dual-switching monopolar (DSM) radiofrequency ablation (RFA) for the treatment of hepatocellular carcinoma (HCC), and to retrospectively compare the results with those of single-switching monopolar (SSM) RFA in a historical control group. Materials and Methods This study was approved by the Institutional Review Board, with informed consent obtained from all patients. Fifty-two HCC patients who underwent DSM-RFA using a separable clustered electrode and dual-generators were prospectively enrolled. Technical parameters, complications, technical success, technical effectiveness, and local tumor progression (LTP) rates were evaluated by means of post-procedural and follow-up imaging. Thereafter, the outcome of DSM-RFA was compared with those of 249 retrospectively included HCC patients treated with SSM-RFA. Results There were two major complications (3.8%, 2/52) including pleural and pericardial effusion in the DSM-RFA group. The DSM-RFA yielded a 100% technical success rate, a 98.1% technical effectiveness rate, and a 4.3% 2-year LTP rate. In a retrospective comparison between the two groups, DSM-RFA created significantly larger ablation volume (4.20 ± 2.07 cm3/min vs. 3.03 ± 1.99 cm3/min, p < 0.01), and delivered higher energy (1.43 ± 0.37 kcal/min vs. 1.25 ± 0.50 kcal/min, p < 0.01) per given time, than SSM-RFA. There was no significant difference in major procedure-related complications (3.8% vs. 4.4%) and technical effectiveness rate (98.1% vs. 96.4%) between the two groups (p = 1.00). In addition, the 2-year LTP rate of DSM-RFA and SSM-RFA were 4.3% and 10.1%, respectively (p = 0.15). Conclusion DSM-RFA using a separable clustered electrode is safe and provides high local tumor control and good preliminary clinical outcome for small HCCs, which are at least comparable to those of SSM-RFA. PMID:28860897

  10. Multipath-switching device utilizing a GaAs-based multiterminal nanowire junction with size-controlled dual Schottky wrap gates

    NASA Astrophysics Data System (ADS)

    Kasai, Seiya; Nakamura, Tatsuya; Shiratori, Yuta

    2007-05-01

    A multipath-switching device using a multiterminal nanowire junction with size-controlled dual gates is proposed and demonstrated experimentally. The device switches a number of output terminals according to multiple-valued input voltages for electrons entering from a root terminal. The switching function is implemented by dual gating on multiple nanowires with different threshold voltages Vth. Systematic Vth shift is made by changing gate lengths in nanometer scale. A triple-path-switching device is fabricated using AlGaAs /GaAs etched nanowires and nanometer-scale Schottky wrap gates. Its correct operation is confirmed at room temperature. Obtained results are explained by a simple analytical model.

  11. Electrostatic Linear Actuator

    NASA Technical Reports Server (NTRS)

    Collins, Earl R., Jr.; Curry, Kenneth C.

    1990-01-01

    Electrically charged helices attract or repel each other. Proposed electrostatic linear actuator made with intertwined dual helices, which holds charge-bearing surfaces. Dual-helix configuration provides relatively large unbroken facing charged surfaces (relatively large electrostatic force) within small volume. Inner helix slides axially in outer helix in response to voltages applied to conductors. Spiral form also makes components more rigid. Actuator conceived to have few moving parts and to be operable after long intervals of inactivity.

  12. Multiple-stimulus-responsive supramolecular gels of two components and dual chiroptical switches.

    PubMed

    Miao, Wangen; Qin, Long; Yang, Dong; Jin, Xue; Liu, Minghua

    2015-01-12

    A new class of L-glutamic gelators, LG12(CH2)nCOOH, containing different lengths of methylene spacer were synthesized. It was found that the gelation ability of these compounds themselves was very weak. However, when another compound, p-xylylenediamine (XEA), was introduced, the gelation ability was improved greatly. In particular, LG12(CH2)10COOH showed super-gelation ability in the presence of XEA, which could immobilize almost all of the solvents except methanol. Moreover, the formed supramolecular gels even could be molded. Interestingly, some supramolecular gels of LG12(CH2)nCOOH and XEA could respond to multiple stimuli, such as heating, shaking, sonication, and acid/base. The studies of CD spectra suggested that the supramolecular chirality induced by self-assembled chiral gelator molecules in gels could be tuned by the length of methylene spacer. In addition, the supramolecular chirality could be regulated as on/off by heating-cooling or external NH3/HCl. This would facilitate the development of dual chiroptical switches by temperature and acid/base. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. A dual-channel flux-switching permanent magnet motor for hybrid electric vehicles

    NASA Astrophysics Data System (ADS)

    Hua, Wei; Wu, Zhongze; Cheng, Ming; Wang, Baoan; Zhang, Jianzhong; Zhou, Shigui

    2012-04-01

    The flux-switching permanent magnet (FSPM) motor is a relatively novel brushless machine having both magnets and concentrated windings in the stator, which exhibits inherently sinusoidal PM flux-linkage, back-EMF waveforms, and high torque capability. However, in the application of hybrid electric vehicles, it is essential to prevent magnets and armature windings moving in radial direction due to the possible vibration during operation, and to ensure fault-tolerant capability. Hence, in this paper based on an original FSPM motor, a dual-channel FSPM (DC-FSPM) motor with modified structure to fix both armature windings and magnets and improved reliability is proposed for a practical 10 kW integral starter/generator (ISG) in hybrid electric vehicles. The influences of different solutions and the end-effect on the static characteristics, are evaluated based on the 2D and 3D finite element analysis, respectively. Finally, both the predicted and experimental results, compared with a prototype DC-FSPM motor and an interior PM motor used in Honda Civic, confirm that the more sinusoidal back-EMF waveform and lower torque ripple can be achieved in the DC-FSPM motor, whereas the torque is smaller under the same coil current.

  14. Dual-mode ion switching conducting polymer films as high energy supercapacitor materials

    SciTech Connect

    Naoi, Katsuhiko; Oura, Yasushi

    1995-12-31

    The electropolymerized polypyrrole films formed from micellar solution of anionic surfactants, viz., Dodecylbenzene sulfonate (DBS), showed potential-dependent anion and cation ion switching behavior and the peculiar columnar structure. The formation process and the redox of the polypyrrole was studied with the in situ atomic force microscopy (AFM) and electrochemical quartz crystal microbalance (EQCM) methods. In-situ AFM observation clearly indicated that such a columnar structure started to form around critical charge densities of 60--100 mC cm{sup {minus}2}. The cyclic voltammogram for the PPy doped with DBS{sup {minus}} film showed two redox couples, each of which corresponds to a cation and an anion exchange process. Thus, the film behaves as a dual-mode ion doping/undoping exchanger. As the PPy film was prepared in higher concentration of the surfactant dopant, where the micelles are formed in solution, the resulting film showed a considerably higher (ca. three orders of magnitude) diffusion coefficient compared to ordinary PPy films so far reported. Such an enhanced diffusivity of ions could be attributed to a peculiar structure of the polymer formed. The feasibility of such polypyrrole in use of supercapacitor material was discussed.

  15. Simultaneous dual-wavelength Q-switched Nd:YAG laser at 1052 and 1073  nm.

    PubMed

    Lin, Haifeng; Zhu, Wenzhang; Xiong, Feibing; Ruan, Jianjian

    2017-02-01

    We report a continuous-wave dual-wavelength Nd:YAG laser at 1052 and 1073 nm, for the first time to the best of our knowledge, in free-running mode. The maximum output power reaches 6.64 W with slope efficiency of about 42.1% with respect to the absorbed power. Inserting a Cr:YAG saturable absorber, the dual-wavelength laser can operate in the Q-switching regime with maximum average output power of 880 mW. The minimum pulse width and the highest pulse repetition rate are 28 ns and 17.12 kHz, respectively. The dual-wavelength laser has potential to generate a 5.7 THz wave via the difference-frequency method.

  16. Dual delta tunnel FET: An energy efficient switch with improved current switching ratio and steeper subthreshold slope

    NASA Astrophysics Data System (ADS)

    Gaurav, Vivek; Dash, Sidhartha; Mishra, Guru Prasad

    2017-07-01

    In this paper, a single gate tunnel FET has been designed with two delta layers in both the source and channel regions. The width, position and doping concentration of both the delta regions are optimized to maximize the current switching ratio. The simulation work of the present DD-TFET device has been carried out by 2-D TCAD device simulator from Synopsys and the results are compared with the results of source delta doped TFET (SD-TFET), channel delta doped TFET (CD-TFET) and conventional TFET. The proposed device exhibits its superiority over other designs in terms of ON-state current, current switching ratio and subthreshold swing. Thus DD-TFET can be used as an energy efficient switch and has the potential to replace MOSFETs in high-speed and low-power applications.

  17. Liver fat quantification using fast kVp-switching dual energy CT

    NASA Astrophysics Data System (ADS)

    Kriston, Andras; Mendonça, Paulo; Silva, Alvin; Paden, Robert G.; Pavlicek, William; Sahani, Dushyant; Janos Kis, Benedek; Rusko, Laszlo; Okerlund, Darin; Bhotika, Rahul

    2011-03-01

    Nonalcoholic steatohepatitis (NASH) is a liver disease that occurs in patients that lack a history of the well-proven association of alcohol use. A major symptom of NASH is increased fat deposition in the liver. Gemstone Spectral Imaging (GSI) with fast kVp-switching enables projection-based material decomposition, offering the opportunity to accurately characterize tissue types, e.g., fat and healthy liver tissue, based on their energy-sensitive material attenuation and density. We describe our pilot efforts to apply GSI to locate and quantify the amount of fat deposition in the liver. Two approaches are presented, one that computes percentage fat from the difference in HU values at high and low energies and the second based on directly computing fat volume fraction at each voxel using multi-material decomposition. Simulation software was used to create a phantom with a set of concentric rings, each composed of fat and soft tissue in different relative amounts with attenuation values obtained from the National Institute of Standards and Technology. Monte Carlo 80 and 140 kVp X-ray projections were acquired and CT images of the phantom were reconstructed. Results demonstrated the sensitivity of dual energy CT to the presence of fat and its ability to distinguish fat from soft tissue. Additionally, actual patient (liver) datasets were acquired using GSI and monochromatic images at 70 and 140 keV were reconstructed. Preliminary results demonstrate a tissue sensitivity that appears sufficient to quantify fat content with a degree of accuracy as may be needed for non-invasive clinical assessment of NASH.

  18. LD end-pumped acousto-optic Q-switched 1319 nm/1338 nm dual-wavelength Nd:YAG laser

    NASA Astrophysics Data System (ADS)

    Wu, C. T.; Yu, M.; Wang, C.; Yu, K.; Yu, Y. J.; Chen, X. Y.; Jin, G. Y.

    2016-10-01

    Laser characteristics of acousto-optic Q-switched operation of 1319 nm/1338 nm dual-wavelength composite Nd:YAG laser were studied. Maximum output power of 5.77 W was achieved in CW operation. Under Q-switched operation, the maximum peak power of 3.96 kW and minimum pulse width of 65.6 ns was obtained at repetition frequency of 20 kHz with the duty ratio of 96%. The influence of the duration of the ultrasonic field acted on the Q-switch to the output characteristics of dual-wavelength composite Nd:YAG laser had been reported first time.

  19. Dual-energy technique for digital flat-panel detectors without x-ray tube voltage switching

    NASA Astrophysics Data System (ADS)

    Coello, Christopher S.; Dinten, Jean-Marc; Arques, Marc; Rohr, Pierre; Odet, Christophe

    2007-03-01

    Dual-energy imaging increases the possibility of pulmonary nodule detection by reducing the bone structure noise. The major problem of the dual-energy acquisition process with digital flat-panel detectors is the interval of time between low-energy (LE) exposure and high-energy (HE) exposure. Due to misregistration between LE and HE images, motion artifacts pollute the subtracted image. This paper presents a new acquisition approach for dual-energy imaging developed in order to reduce this inter-exposure time. The idea is to keep the tube voltage constant and to just switch a filter in front of the imaged object and thus to modulate the outgoing x-ray spectrum. The first part of this study presents how to optimize system parameters for the new acquisition protocol: source voltage, dynamic filtration before the patient, exposure time for LE and HE acquisition. The tube load is kept constant to focus the optimization study on the dose and the exposure time. A noise quality factor (NQF) and a spectral quality factor (SQF) are used as criteria for optimization. The new approach system is then compared to the state-of-the-art system with voltage switching between low and high energy. A filtering algorithm of dual energy acquisitions enabling a significant noise reduction is presented. Performance between its combination with the new acquisition protocol and the reference one are compared. For a limited noise quality factor, three times faster acquisition time is obtained using the new system. Noise reduction techniques improve the image SNR by 61% in the new system and only 32% in the reference system, without taking into account the impact of better registration on the dual-energy image quality.

  20. Using a black phosphorus saturable absorber to generate dual wavelengths in a Q-switched ytterbium-doped fiber laser

    NASA Astrophysics Data System (ADS)

    Rashid, F. A. A.; Azzuhri, Saaidal R.; Salim, M. A. M.; Shaharuddin, R. A.; Ismail, M. A.; Ismail, M. F.; Razak, M. Z. A.; Ahmad, H.

    2016-08-01

    Using a few-layer black phosphorus (BP) thin film that acts as a saturable absorber (SA) in an ytterbium-doped fiber laser setup, we experimentally demonstrated a passively dual-wavelength Q-switching laser operation. The setup also incorporated a D-shaped polished fiber as a wavelength selective filter. As the SA was used in the ring cavity, a dual-wavelength Q-switch produced consistent outputs at 1038.68 and 1042.05 nm. A maximum pulse energy of 2.09 nJ with a shortest pulse width of 1.16 µs was measured for the achieved pulses. In addition, the repetition rate increased from 52.52 to 58.73 kHz with the increment of the pump level. Throughout the measurement process, the results were obtained consistently and this demonstrates that the BP film is a very good candidate to produce Q-switching pulses for the 1 micron region.

  1. Switch to Dolutegravir plus Rilpivirine Dual Therapy in cART-Experienced Subjects: An Observational Cohort.

    PubMed

    Capetti, Amedeo F; Sterrantino, Gaetana; Cossu, Maria Vittoria; Orofino, GianCarlo; Barbarini, Giorgio; De Socio, Giuseppe V; Di Giambenedetto, Simona; Di Biagio, Antonio; Celesia, Benedetto M; Argenteri, Barbara; Rizzardini, Giuliano

    2016-01-01

    Little information is available on the efficacy and safety of the dual combination of ripivirine plus dolutegravir. This work aims at beginning to fill this gap. All HIV-1 infected subjects treated with ripivirine plus dolutegravir between October 2014 and September 2015 in eight Italian centres were included in an observational cohort. Data were collected at baseline and at weeks 4, 12, 24 and 48. One hundred and thirty-two subjects were followed for a median of 24 months, mean 33 months. One subject discontinued the study drug at week 24 for headache, one for drug interaction and one died after week 24 of illicit drug abuse. The mean age was 51.8, females 31.7% and non-caucasians 10%. Fifty-seven (43.2%) had at least one failure in their treatment history. Reasons for switching were simplification (53.0%), toxicity (34.8%), drug interactions (n = 7), persistent low-level viremia (n = 4), non-adherence (n = 3) and viral failure (n = 2). Sixty patients (45.5%) had reverse transcriptase (RT) mutations and 69 (44,7%) had protease (PR) mutations. Sixteen had baseline viral replication, 27 had < 50 HIV-1 RNA copies/mL and in 89 (67.4%) no virus was detected (NVD, 0 copies/mL). At w4, 114 (86.4%) had NVD, 15 had 1 to 49 HIV-1 RNA copies/mL and 3 had 50 to 57 copies/mL. At week 24 one subject had viral rebound without mutations due to missed drug refill, 19 had 1 to 49 copies/mL, and 112 had NVD. All 132 subjects were tested at weeks 4 and 24. Of the 50 subjects who had a 48-week follow-up, one had a treatment interruption, four had 1 to 49 copies/mL and 45 had NVD. Among the entire population, one subject had low-level, one intermediate and 4 high-level resistance to rilpivirine: none failed by week 48. Mean serum creatinine increased by +0.1 mg/dL. During the follow-up one patient reported headache and insomnia. Ripivirine plus dolutegravir proved safe and effective in this cohort of non-naïve HIV-1 infected subjects.

  2. Switch to Dolutegravir plus Rilpivirine Dual Therapy in cART-Experienced Subjects: An Observational Cohort

    PubMed Central

    Capetti, Amedeo F.; Sterrantino, Gaetana; Cossu, Maria Vittoria; Orofino, GianCarlo; Barbarini, Giorgio; De Socio, Giuseppe V.; Di Giambenedetto, Simona; Di Biagio, Antonio; Celesia, Benedetto M.; Argenteri, Barbara; Rizzardini, Giuliano

    2016-01-01

    Introduction Little information is available on the efficacy and safety of the dual combination of ripivirine plus dolutegravir. This work aims at beginning to fill this gap. Methods All HIV-1 infected subjects treated with ripivirine plus dolutegravir between October 2014 and September 2015 in eight Italian centres were included in an observational cohort. Data were collected at baseline and at weeks 4, 12, 24 and 48. Results One hundred and thirty-two subjects were followed for a median of 24 months, mean 33 months. One subject discontinued the study drug at week 24 for headache, one for drug interaction and one died after week 24 of illicit drug abuse. The mean age was 51.8, females 31.7% and non-caucasians 10%. Fifty-seven (43.2%) had at least one failure in their treatment history. Reasons for switching were simplification (53.0%), toxicity (34.8%), drug interactions (n = 7), persistent low-level viremia (n = 4), non-adherence (n = 3) and viral failure (n = 2). Sixty patients (45.5%) had reverse transcriptase (RT) mutations and 69 (44,7%) had protease (PR) mutations. Sixteen had baseline viral replication, 27 had < 50 HIV-1 RNA copies/mL and in 89 (67.4%) no virus was detected (NVD, 0 copies/mL). At w4, 114 (86.4%) had NVD, 15 had 1 to 49 HIV-1 RNA copies/mL and 3 had 50 to 57 copies/mL. At week 24 one subject had viral rebound without mutations due to missed drug refill, 19 had 1 to 49 copies/mL, and 112 had NVD. All 132 subjects were tested at weeks 4 and 24. Of the 50 subjects who had a 48-week follow-up, one had a treatment interruption, four had 1 to 49 copies/mL and 45 had NVD. Among the entire population, one subject had low-level, one intermediate and 4 high-level resistance to rilpivirine: none failed by week 48. Mean serum creatinine increased by +0.1 mg/dL. During the follow-up one patient reported headache and insomnia. Conclusions Ripivirine plus dolutegravir proved safe and effective in this cohort of non-naïve HIV-1 infected subjects. PMID

  3. Dual referenced composite free layer design optimization for improving switching efficiency of spin-transfer torque RAM

    NASA Astrophysics Data System (ADS)

    Bell, Roy; Hu, Jiaxi; Victora, R. H.

    2017-05-01

    We present a detailed numerical analysis of switching efficiency for the recently proposed dual referenced composite free layer structure with respect to Gilbert damping. Low anisotropy assistive layers enable reduction of Gilbert damping and an increase of partial spin polarization within those low anisotropy layers—not feasible with single layer structures that require high anisotropy for thermal stability. When the damping of the soft layers is ultra-low, an efficiency (kBT /μ A ) of 8.1 is achieved for the composite structure with perpendicular anisotropy. This represents an improvement of 286% and 913% relative to the state-of-the-art dual-referenced and conventional STT-RAM cells, respectively. Results for structures with longitudinal anisotropy are also presented. A linear calculation of the STT polarization pre-factor is also described that captures all reflections.

  4. Electro-optically Q-switched dual-wavelength Nd:YLF laser emitting at 1047 nm and 1053 nm

    NASA Astrophysics Data System (ADS)

    Men, Shaojie; Liu, Zhaojun; Cong, Zhenhua; Li, Yongfu; Zhang, Xingyu

    2015-05-01

    A flash-lamp pumped electro-optically Q-switched dual-wavelength Nd:YLF laser is demonstrated. Two Nd:YLF crystals placed in two cavities are employed to generate orthogonally polarized 1047 nm and 1053 nm radiations, respectively. The two cavities are jointed together by a polarizer and share the same electro-optical Q-switch. Two narrow-band pass filters are used to block unexpected oscillations at the hold-off state of the electro-optical Q-switch. In this case, electro-optical Q-switching is able to operate successfully. With pulse synchronization realized, the maximum output energy of 66.2 mJ and 83.9 mJ are obtained for 1047 nm and 1053 nm lasers, respectively. Correspondingly, the minimum pulse width is both 17 ns for 1047 nm and 1053 nm lasers. Sum frequency generation is realized. This demonstrates the potential of this laser in difference-frequency generations to obtain terahertz wave.

  5. Dual-wavelength continuous-wave and passively Q-switched Nd,Y:SrF2 ceramic laser

    NASA Astrophysics Data System (ADS)

    Zhang, Feng; Liu, Jie; Li, Weiwei; Mei, Bingchu; Jiang, Dapeng; Qian, Xiaobo; Su, Liangbi

    2016-10-01

    A polycrystalline ceramic based on an Nd,Y:SrF2 single crystal was successfully fabricated and its laser performance was experimentally investigated. We obtained dual-wavelength continuous-wave operation at the wavelengths of 1050.5 and 1058.0 nm. The maximum output power and slope efficiency were 750 mW and 31.5%, respectively. In the passively Q-switched operation, the shortest pulse with a 169-ns duration was also obtained, and the corresponding maximum repetition rate and single pulse energy were 7.3 kHz and 19.2 μJ, respectively.

  6. Dual Emissive-Reflective Display Materials with Large Emission Switching Using Highly Luminescent Lanthanide(III) Complex and Electrochromic Material

    NASA Astrophysics Data System (ADS)

    Kanazawa, Kenji; Nakamura, Kazuki; Kobayashi, Norihisa

    2013-05-01

    Electroswitching of emission and coloration was achieved by a combination of a luminescent Eu(III) complex and an electrochromic molecule of diheptyl viologen (HV2+), in order to utilize them as novel display devices with dual emissive-reflective modes. The coloration was associated with the HV2+ electrochromism. Emission control was also achieved by the HV2+ electrochromism via intermolecular energy transfer from the excited state of the Eu(III) ion to the HV+. In order to improve ON-OFF contrast in emission, the emission quantum yield of Eu(III) complex were considerably improved using low vibrational phosphine oxide ligands, resulting in the large control of emission switching.

  7. Stable passively Q-switched and gain-switched Yb-doped all-fiber laser based on a dual-cavity with fiber Bragg gratings.

    PubMed

    Jin, Dongchen; Sun, Ruoyu; Shi, Hongxing; Liu, Jiang; Wang, Pu

    2013-11-04

    We demonstrate a stable passively Q-switched and gain-switched Yb-doped all-fiber laser cladding-pumped by a continuous fiber-coupled 976 nm laser diode. By use of an all-fiber dual-cavity, the efficient elements of the laser mainly include the fiber Bragg gratings and rare-earth doped fiber, allowing the oscillator to be integrated in a compact size with reliable and stable output. In this scheme, an efficient laser output with 45 ns pulse width, 62 μJ pulse energy, and 1.4 kW peak power operating at 1081 nm was obtained. To the best of our knowledge, this is the minimum pulse width in this similar kind of all-fiber configuration at present. Sequential nanosecond pulses were obtained at the repetition rate of several to tens of kHz with the variation of the diode pumping power. Effects of laser parameters such as pump power, cavity length, external-cavity wavelength, and FBG reflectivity on laser performance were also presented and discussed.

  8. Investigation of a tubular dual-stator flux-switching permanent-magnet linear generator for free-piston energy converter

    NASA Astrophysics Data System (ADS)

    Sui, Yi; Zheng, Ping; Tong, Chengde; Yu, Bin; Zhu, Shaohong; Zhu, Jianguo

    2015-05-01

    This paper describes a tubular dual-stator flux-switching permanent-magnet (PM) linear generator for free-piston energy converter. The operating principle, topology, and design considerations of the machine are investigated. Combining the motion characteristic of free-piston Stirling engine, a tubular dual-stator PM linear generator is designed by finite element method. Some major structural parameters, such as the outer and inner radii of the mover, PM thickness, mover tooth width, tooth width of the outer and inner stators, etc., are optimized to improve the machine performances like thrust capability and power density. In comparison with conventional single-stator PM machines like moving-magnet linear machine and flux-switching linear machine, the proposed dual-stator flux-switching PM machine shows advantages in higher mass power density, higher volume power density, and lighter mover.

  9. Exciter switch

    NASA Technical Reports Server (NTRS)

    Mcpeak, W. L.

    1975-01-01

    A new exciter switch assembly has been installed at the three DSN 64-m deep space stations. This assembly provides for switching Block III and Block IV exciters to either the high-power or 20-kW transmitters in either dual-carrier or single-carrier mode. In the dual-carrier mode, it provides for balancing the two drive signals from a single control panel located in the transmitter local control and remote control consoles. In addition to the improved switching capabilities, extensive monitoring of both the exciter switch assembly and Transmitter Subsystem is provided by the exciter switch monitor and display assemblies.

  10. Task switching: the effect of task recency with dual- and single-affordance stimuli.

    PubMed

    Sumner, Petroc; Ahmed, Lubna

    2006-07-01

    When we switch to a new task, performance is transiently relatively poor, but improves dramatically after one trial. Such a "switch cost" may result from the preceding task being highly primed while the new task is not yet primed. This predicts that it should become more difficult to switch back to Task A when more trials of Task B have intervened. Such a lag effect has been found in some but not in most previous experiments, and to resolve this discrepancy we examined the effects of task lag with different stimuli. We found that when stimuli uniquely and clearly cued the task--minimizing the need for control--switch reaction time increased with task lag. However, when the need for control was increased by using similar or identical stimuli in the two tasks, this lag effect was abolished or reversed. Thus only when control processes are minimized can priming explain the difficulty of switching back from Task B to Task A. Second, we asked how the impact of control is mediated in conditions where it is not minimized. If it is mediated through altering the relative activation states of competing tasks, then as it becomes easier to do one task--the relative task-set activation state is tipped in that task's favour--it should always become harder to do the other task. On the other hand, if control bias affects switch performance directly, this relationship need not hold. We found that as it becomes easier to perform one task it can become easier, not harder, to switch to the competing task. Thus control bias must act directly on switch performance, rather than only through its influence on relative task-set activation.

  11. Stable Q-switched and mode-locked Nd:GdVO4/KTP green laser with dual-loss-modulation.

    PubMed

    Zhang, Gang; Zhao, Shengzhi; Li, Guiqiu; Li, Dechun; Yang, Kejian; Cheng, Kang; Zhang, Yan

    2010-08-20

    A diode-pumped dual-loss-modulated Q-switched and mode-locked (QML) Nd:GdVO(4)/KTP green laser with an acousto-optic modulator (AOM) and GaAs saturable absorber is presented. The experimental results show that the stability and the peak power of the dual-loss-modulated QML Nd:GdVO(4)/KTP green laser are significantly improved. The pulse width of the Q-switched pulse envelope in the dual-loss-modulation QML green laser has a compression of 50% compared with that in the singly passively QML green laser with GaAs. By using a hyperbolic secant square function and considering the Gaussian distribution of the intracavity photon density, the coupled equations for diode-pumped dual-loss-modulated QML Nd:GdVO(4) green laser are given, and the numerical solutions of the equations are in good agreement with the experimental results.

  12. Design of a constant-voltage and constant-current controller with dual-loop and adaptive switching frequency control

    NASA Astrophysics Data System (ADS)

    Yingping, Chen; Zhiqian, Li

    2015-05-01

    A 5.0-V 2.0-A flyback power supply controller providing constant-voltage (CV) and constant-current (CC) output regulation without the use of an optical coupler is presented. Dual-close-loop control is proposed here due to its better regulation performance of tolerance over process and temperature compared with open loop control used in common. At the same time, the two modes, CC and CV, could switch to each other automatically and smoothly according to the output voltage level not sacrificing the regulation accuracy at the switching phase, which overcomes the drawback of the digital control scheme depending on a hysteresis comparator to change the mode. On-chip compensation using active capacitor multiplier technique is applied to stabilize the voltage loop, eliminate an additional package pin, and save on the die area. The system consumes as little as 100 mW at no-load condition without degrading the transient response performance by utilizing the adaptive switching frequency control mode. The proposed controller has been implemented in a commercial 0.35-μm 40-V BCD process, and the active chip area is 1.5 × 1.0 mm2. The total error of the output voltage due to line and load variations is less than ±1.7%.

  13. High repetition rate dual-rod acousto-optics Q-switched composite Nd:YVO4 laser.

    PubMed

    Yan, Xingpeng; Liu, Qiang; Fu, Xing; Chen, Hailong; Gong, Mali; Wang, Dongsheng

    2009-11-23

    We demonstrate the high-repetition rate acousto-optic Q-switching of a dual-rod Nd:YVO4 laser. Two thermally bonded composite YVO4-Nd:YVO4-YVO4 rod crystals were used as the gain medium to reduce the serious thermal effect. The pump mode and its influence on the laser mode were analyzed, and the effective pump radius was controlled by tuning the spectrum of laser diodes with adjustment on the temperature of laser diodes. Three different configurations of cavity optics were designed and the output performance using these cavities was investigated. In Q-switching operation, 73.2 W TEM00 mode average power at 650 kHz was obtained. The stable Q-switching range was from 80 kHz to 650 kHz with the pulse duration increasing from 17.5 ns to 80 ns. In CW operation, 78 W TEM00 mode and 93 W multi-mode output power was achieved with different cavity designs, corresponding to the optical-optical efficiency of 46.5% and 52.2% respectively.

  14. Passively Q-switched and mode-locked dual-wavelength Nd:GGG laser with Cr4+:YAG as a saturable absorber

    NASA Astrophysics Data System (ADS)

    Chu, Hongwei; Zhao, Shengzhi; Li, Yufei; Yang, Kejian; Li, Guiqiu; Li, Dechun; Zhao, Jia; Qiao, Wenchao; Li, Tao; Feng, Chuansheng; Zhang, Haijuan

    2014-03-01

    By using neodymium-doped gadolinium gallium garnet (Nd:GGG) as a laser medium, a simultaneously passively Q-switched and mode-locked (QML) dual-wavelength laser with Cr4+:YAG as a saturable absorber is presented. The laser simultaneously oscillated at 1061 nm and 1063 nm, corresponding to a frequency difference of 0.53 THz. QML pulses with nearly 100% modulation depth were observed. The mode-locked pulse duration underneath the Q-switched envelope was estimated to be about 908 ps. The experimental results indicated that the dual-wavelength QML Nd:GGG laser can be an excellent candidate for the generation of THz waves.

  15. Dual Gate Black Phosphorus Field Effect Transistors on Glass for NOR Logic and Organic Light Emitting Diode Switching.

    PubMed

    Kim, Jin Sung; Jeon, Pyo Jin; Lee, Junyeong; Choi, Kyunghee; Lee, Hee Sung; Cho, Youngsuk; Lee, Young Tack; Hwang, Do Kyung; Im, Seongil

    2015-09-09

    We have fabricated dual gate field effect transistors (FETs) with 12 nm-thin black phosphorus (BP) channel on glass substrate, where our BP FETs have a patterned-gate architecture with 30 nm-thick Al2O3 dielectrics on top and bottom of a BP channel. Top gate dielectric has simultaneously been used as device encapsulation layer, controlling the threshold voltage of FETs as well when FETs mainly operate under bottom gate bias. Bottom, top, and dual gate-controlling mobilities were estimated to be 277, 92, and 213 cm(2)/V s, respectively. Maximum ON-current was measured to be ∼5 μA at a drain voltage of -0.1 V but to be as high as ∼50 μA at -1 V, while ON/OFF current ratio appeared to be 3.6 × 10(3) V. As a result, our dual gate BP FETs demonstrate organic light emitting diode (OLED) switching for green and blue OLEDs, also demonstrating NOR logic functions by separately using top- and bottom-input.

  16. Electrostatic actuation of nanomechanical optical fibers with integrated electrodes

    NASA Astrophysics Data System (ADS)

    Podoliak, Nina; Lian, Zhenggang; Segura, Martha; Loh, Wei H.; Horak, Peter

    2014-05-01

    We investigate theoretically and experimentally the possibility of electrostatic actuation of nanomechanical optical fibers with integrated electrodes. The fiber has two optically guiding cores suspended in air by thin flexible membranes. This fiber structure allows for control of the optical properties via nanometer-range mechanical core movements. The electrostatic actuation of the fiber is generated by electrically charged electrodes embedded in the fiber cladding. Fiber designs with one to four electrodes are analyzed and, in particular, a quadrupole geometry is shown to allow for all-fiber optical switching in a 10cm fiber with an operating voltage of 25 - 30V. A multi-material fiber draw technique is demonstrated to fabricate a fiber with well-defined dual core structure in the middle and four continuous metal electrodes in the cladding. The fabricated fiber is analyzed and compared with the modeled requirements for electrostatic actuation.

  17. CD163 Binding to Haptoglobin-Hemoglobin Complexes Involves a Dual-point Electrostatic Receptor-Ligand Pairing*

    PubMed Central

    Nielsen, Marianne Jensby; Andersen, Christian Brix Folsted; Moestrup, Søren Kragh

    2013-01-01

    Formation of the haptoglobin (Hp)-hemoglobin (Hb) complex in human plasma leads to a high affinity recognition by the endocytic macrophage receptor CD163. A fast segregation of Hp-Hb from CD163 occurs at endosomal conditions (pH <6.5). The ligand binding site of CD163 has previously been shown to involve the scavenger receptor cysteine-rich (SRCR) domain 3. This domain and the adjacent SRCR domain 2 of CD163 contain a consensus motif for a calcium-coordinated acidic amino acid triad cluster as originally identified in the SRCR domain of the scavenger receptor MARCO. Here we show that site-directed mutagenesis in each of these acidic triads of SRCR domains 2 and 3 abrogates the high affinity binding of recombinant CD163 to Hp-Hb. In the ligand, Hp Arg-252 and Lys-262, both present in a previously identified CD163 binding loop of Hp, were revealed as essential residues for the high affinity receptor binding. These findings are in accordance with pairing of the calcium-coordinated acidic clusters in SRCR domains 2 and 3 with the two basic Arg/Lys residues in the Hp loop. Such a two-point electrostatic pairing is mechanistically similar to the pH-sensitive pairings disclosed in crystal structures of ligands in complex with tandem LDL receptor repeats or tandem CUB domains in other endocytic receptors. PMID:23671278

  18. Passively Q-switched dual-wavelength Yb:LSO laser based on tungsten disulphide saturable absorber

    NASA Astrophysics Data System (ADS)

    Jing-Hui, Liu; Jin-Rong, Tian; He-Yang, Guoyu; Run-Qin, Xu; Ke-Xuan, Li; Yan-Rong, Song; Xin-Ping, Zhang; Liang-Bi, Su; Jun, Xu

    2016-03-01

    We demonstrate a passively Q-switched Yb:LSO laser based on tungsten disulphide (WS2) saturable absorber operating at 1034 nm and 1056 nm simultaneously. The saturable absorbers were fabricated by spin coating method. With low speed, the WS2 nanoplatelets embedded in polyvinyl alcohol could be coated on a BK7 glass substrate coated with high-refractive-index thin polymer. The shortest pulse width of 1.6 μs with a repetition rate of 76.9 kHz is obtained. As the pump power increases to 9 W, the maximum output power is measured to be 250 mW, corresponding to a single pulse energy of 3.25 μJ. To the best of our knowledge, this is the first time to obtain dual-wavelength Q-switched solid-state laser using few-layer WS2 nanoplatelets. Project supported by the National Scientific Research Project of China (Grant No. 61177047), Beijing Municipal Natural Science Foundation, China (Grant No. 1102005), and the Basic Research Foundation of Beijing University of Technology, China (Grant No. X3006111201501).

  19. Hypersensitive dual-function luminescence switching of a silver-chalcogenolate cluster-based metal-organic framework

    NASA Astrophysics Data System (ADS)

    Huang, Ren-Wu; Wei, Yong-Sheng; Dong, Xi-Yan; Wu, Xiao-Hui; Du, Chen-Xia; Zang, Shuang-Quan; Mak, Thomas C. W.

    2017-07-01

    Silver(I) chalcogenide/chalcogenolate clusters are promising photofunctional materials for sensing, optoelectronics and solar energy harvesting applications. However, their instability and poor room-temperature luminescent quantum yields have hampered more extensive study. Here, we graft such clusters to adaptable bridging ligands, enabling their interconnection and the formation of rigid metal-organic frameworks. By controlling the spatial separation and orientation of the clusters, they then exhibit enhanced stability (over one year) and quantum yield (12.1%). Ultrafast dual-function fluorescence switching (<1 s) is also achieved, with turn-off triggered by O2 and multicoloured turn-on by volatile organic compounds. Single-crystal X-ray diffraction of the inclusion materials, obtained by single-crystal-to-single-crystal transformation, enables precise determination of the position of the small molecules within the framework, elucidating the switching mechanism. The work enriches the cluster-based metal-organic framework portfolio, bridges the gap between silver chalcogenide/chalcogenolate clusters and metal-organic frameworks, and provides a foundation for further development of functional silver-cluster-based materials.

  20. Hypersensitive dual-function luminescence switching of a silver-chalcogenolate cluster-based metal-organic framework.

    PubMed

    Huang, Ren-Wu; Wei, Yong-Sheng; Dong, Xi-Yan; Wu, Xiao-Hui; Du, Chen-Xia; Zang, Shuang-Quan; Mak, Thomas C W

    2017-07-01

    Silver(i) chalcogenide/chalcogenolate clusters are promising photofunctional materials for sensing, optoelectronics and solar energy harvesting applications. However, their instability and poor room-temperature luminescent quantum yields have hampered more extensive study. Here, we graft such clusters to adaptable bridging ligands, enabling their interconnection and the formation of rigid metal-organic frameworks. By controlling the spatial separation and orientation of the clusters, they then exhibit enhanced stability (over one year) and quantum yield (12.1%). Ultrafast dual-function fluorescence switching (<1 s) is also achieved, with turn-off triggered by O2 and multicoloured turn-on by volatile organic compounds. Single-crystal X-ray diffraction of the inclusion materials, obtained by single-crystal-to-single-crystal transformation, enables precise determination of the position of the small molecules within the framework, elucidating the switching mechanism. The work enriches the cluster-based metal-organic framework portfolio, bridges the gap between silver chalcogenide/chalcogenolate clusters and metal-organic frameworks, and provides a foundation for further development of functional silver-cluster-based materials.

  1. Switchable dual-wavelength Q-switched and mode-locked fiber lasers using a large-angle tilted fiber grating.

    PubMed

    Zhang, Zuxing; Mou, Chengbo; Yan, Zhijun; Wang, Yongjin; Zhou, Kaiming; Zhang, Lin

    2015-01-26

    We proposed and demonstrated pulsed fiber lasers Q-switched and mode-locked by using a large-angle tilted fiber grating, for the first time to our best knowledge. Owing to the unique polarization properties of the large-angle tilted fiber grating (LA-TFG), i.e. polarization-dependent loss and polarization-mode splitting, switchable dual-wavelength Q-switched and mode-locked pulses have been achieved with short and long cavities, respectively. For the mode-locking case, the laser was under the operation of nanosecond rectangular pulses, due to the peak-power clamping effect. With the increasing pump power, the durations of both single- and dual-wavelength rectangular pulses increase. It was also found that each filtered wavelength of the dual-wavelength rectangular pulse corresponds to an individual nanosecond rectangular pulse by employing a tunable bandpass filter.

  2. Photonic crystal fiber based dual-wavelength Q-switched fiber laser using graphene oxide as a saturable absorber.

    PubMed

    Ahmad, H; Soltanian, M R K; Pua, C H; Alimadad, M; Harun, S W

    2014-06-01

    A Q-switched dual-wavelength fiber laser with narrow channel spacing is proposed and demonstrated. The fiber laser is built around a 3 m long erbium doped fiber as the gain medium and a 10 cm long photonic crystal fiber (PCF) as the element used to generate the dual-wavelength output. The PCF has a solid core approximately 4.37 μm in diameter and is surrounded by microscopic air-holes with a diameter of about 5.06 μm each as well as a zero-dispersion wavelength of about 980 nm. A graphene oxide based saturable absorber is used to generate the desired pulsed output. At the maximum pump power of 72 mW the laser is capable of generating pulses with a repetition rate and pulse-width of 31.0 kHz and 7.0 μs, respectively, as well as an average output power and pulse energy of 0.086 mW and 2.8 nJ, respectively. The proposed fiber laser has substantial potential for use in applications that require longer duration pulsed outputs such as in range finding and terahertz radiation generation.

  3. Switching to boosted protease inhibitor plus a second antiretroviral drug (dual therapy) for treatment simplification: a multicenter observational study.

    PubMed

    Latini, Alessandra; Fabbiani, Massimiliano; Borghi, Vanni; Sterrantino, Gaetana; Giannetti, Alberto; Lorenzini, Patrizia; Loiacono, Laura; Ammassari, Adriana; Bellagamba, Rita; Colafigli, Manuela; D'Ettorre, Gabriella; Di Giambenedetto, Simona; Antinori, Andrea; Zaccarelli, Mauro

    2016-08-11

    Aim of the study was to assess predictors of discontinuation/toxicity of boosted PI-based (PI/r) dual therapy (DT). Observational, retrospective switch study in patients successfully treated with triple drugs regimen. Patients switched to PI/r based DT [darunavir (DRV/r), lopinavir (LPV/r) or atazanavir (ATV/r)] plus a second drug: [raltegravir (RAL), maraviroc (MVC) etravirine (ETR), lamivudine (3TC) or tenofovir (TDF)] between 2009 and 2014 were included. The effect of each drug as well as other clinical and virological cofactors over treatment discontinuation (TD) was assessed using survival analysis. Overall, 376 patients were included with mean follow-up of 73 weeks. The most commonly used drugs in DT were DRV/r (63.0 %) and RAL (53.7 %). TD was observed in 77 (20,4 %) patients: 38 (10,1 %) virological failure, 35 (9,3 %) toxicity/intolerance (4 deaths) and 4 (1 %) interruptions for patients decision. At Cox Model, adjusted by demographic and laboratory variables, DRV/r and ATV/r significantly reduced the likelihood of TD and longer treatment was associated with lower risk, while low CD4 count at baseline and number of previous regimens with a higher risk. Moreover, RAL and 3TC use were significantly associated with lower TD by toxicity. In our clinical practice experience, switching virologically suppressed patients to PI/r based DT showed adequate safety and efficacy, so that it may be used in selected patients with specific medical needs.

  4. Electrostatic Precipitator

    NASA Image and Video Library

    2017-06-09

    New Electrostatic Precipitator in a flow-through system. The precipitator system is being developed to remove dust from the atmospheric intakes of the MARS ISRU chambers. It uses electrostatic forces for the dust removal.

  5. Dual-period tunable phase grating based on a single in-plane switching.

    PubMed

    Gao, Liang; Zheng, Zhe-Zhe; Zhu, Ji-Liang; Han, Wen-Ming; Sun, Yu-Bao

    2016-08-15

    We proposed a dual-period phase grating using a polymer-stabilized blue phase liquid crystal (PS-BPLC). High efficiencies of 38% for the short-period phase grating and 30% for the long-period phase grating have been achieved because of the electric-field-induced rectangular-like phase profile of a PS-BPLC, which agrees quite well with the simulation results. The diffraction angle and the diffraction efficiency can be alternatively tuned by a bias voltage and intensity of applied voltage. The diffracted light of each diffraction order is elliptically polarized, and its ellipticity is larger than that induced by using the conventional nematic LCs. Such a device also shows sub-millisecond response time and holds great potential for photonics applications.

  6. Passively synchronized Q-switched and mode-locked dual-band Tm3+:ZBLAN fiber lasers using a common graphene saturable absorber

    PubMed Central

    Jia, Chenglai; Shastri, Bhavin J.; Abdukerim, Nurmemet; Rochette, Martin; Prucnal, Paul R.; Saad, Mohammed; Chen, Lawrence R.

    2016-01-01

    Dual-band fiber lasers are emerging as a promising technology to penetrate new industrial and medical applications from their dual-band properties, in addition to providing compactness and environmental robustness from the waveguide structure. Here, we demonstrate the use of a common graphene saturable absorber and a single gain medium (Tm3+:ZBLAN fiber) to implement (1) a dual-band fiber ring laser with synchronized Q-switched pulses at wavelengths of 1480 nm and 1840 nm, and (2) a dual-band fiber linear laser with synchronized mode-locked pulses at wavelengths of 1480 nm and 1845 nm. Q-switched operation at 1480 nm and 1840 nm is achieved with a synchronized repetition rate from 20 kHz to 40.5 kHz. For synchronous mode-locked operation, pulses with full-width at half maximum durations of 610 fs and 1.68 ps at wavelengths of 1480 nm and 1845 nm, respectively, are obtained at a repetition rate of 12.3 MHz. These dual-band pulsed sources with an ultra-broadband wavelength separation of ~360 nm will add new capabilities in applications including optical sensing, spectroscopy, and communications. PMID:27804993

  7. Passively synchronized Q-switched and mode-locked dual-band Tm(3+):ZBLAN fiber lasers using a common graphene saturable absorber.

    PubMed

    Jia, Chenglai; Shastri, Bhavin J; Abdukerim, Nurmemet; Rochette, Martin; Prucnal, Paul R; Saad, Mohammed; Chen, Lawrence R

    2016-11-02

    Dual-band fiber lasers are emerging as a promising technology to penetrate new industrial and medical applications from their dual-band properties, in addition to providing compactness and environmental robustness from the waveguide structure. Here, we demonstrate the use of a common graphene saturable absorber and a single gain medium (Tm(3+):ZBLAN fiber) to implement (1) a dual-band fiber ring laser with synchronized Q-switched pulses at wavelengths of 1480 nm and 1840 nm, and (2) a dual-band fiber linear laser with synchronized mode-locked pulses at wavelengths of 1480 nm and 1845 nm. Q-switched operation at 1480 nm and 1840 nm is achieved with a synchronized repetition rate from 20 kHz to 40.5 kHz. For synchronous mode-locked operation, pulses with full-width at half maximum durations of 610 fs and 1.68 ps at wavelengths of 1480 nm and 1845 nm, respectively, are obtained at a repetition rate of 12.3 MHz. These dual-band pulsed sources with an ultra-broadband wavelength separation of ~360 nm will add new capabilities in applications including optical sensing, spectroscopy, and communications.

  8. Passively synchronized Q-switched and mode-locked dual-band Tm3+:ZBLAN fiber lasers using a common graphene saturable absorber

    NASA Astrophysics Data System (ADS)

    Jia, Chenglai; Shastri, Bhavin J.; Abdukerim, Nurmemet; Rochette, Martin; Prucnal, Paul R.; Saad, Mohammed; Chen, Lawrence R.

    2016-11-01

    Dual-band fiber lasers are emerging as a promising technology to penetrate new industrial and medical applications from their dual-band properties, in addition to providing compactness and environmental robustness from the waveguide structure. Here, we demonstrate the use of a common graphene saturable absorber and a single gain medium (Tm3+:ZBLAN fiber) to implement (1) a dual-band fiber ring laser with synchronized Q-switched pulses at wavelengths of 1480 nm and 1840 nm, and (2) a dual-band fiber linear laser with synchronized mode-locked pulses at wavelengths of 1480 nm and 1845 nm. Q-switched operation at 1480 nm and 1840 nm is achieved with a synchronized repetition rate from 20 kHz to 40.5 kHz. For synchronous mode-locked operation, pulses with full-width at half maximum durations of 610 fs and 1.68 ps at wavelengths of 1480 nm and 1845 nm, respectively, are obtained at a repetition rate of 12.3 MHz. These dual-band pulsed sources with an ultra-broadband wavelength separation of ~360 nm will add new capabilities in applications including optical sensing, spectroscopy, and communications.

  9. Head and body CTDIw of dual-energy x-ray CT with fast-kVp switching

    NASA Astrophysics Data System (ADS)

    Li, Baojun; Yadava, Girijesh; Hsieh, Jiang; Chandra, Naveen; Kulpins, Mary Sue

    2010-04-01

    Dual-energy CT has attracted much attention in recent years. Most recently, a fast-kVp switching (FKS) dual-energy method has been presented with clinical and phantom results to demonstrate its efficacy. The purpose of our study was to quantitatively compare the CTDIW of FKS and routine CT exams under the body and head conditions. For a fair comparison, the low contrast detectability (LCD) was matched before measuring dose. In FKS protocols, an x-ray generator switch rapidly between 140kVp and 80kVp in adjacent views, and the effective tube current is around 600mA. In addition to the tube voltage and current, the flux ratio between high and low kVp is optimized by asymmetric sampling of 35%-65%. The head and body protocols further differ by the gantry speed (0.9sec/1.0sec) and type of bowtie filter (head/body). For baseline single-energy, we followed the IEC standard head and body protocols (120kV, 1sec, 5mm) but iteratively adjusted the tube current (mA) in order to match the LCD. CTDIW was measured using either a 16 cm (for head scanning) or a 32 cm (for body scanning) PMMA phantom of at least 14 cm in length. The LCD was measured using the water section of Catphan 600. To make the study repeatable, the automated statistical LCD measurement tool available on GE Discovery CT750 scanner was used in this work. The mean CTDIW for the head and body single-energy acquisitions were 57.5mGy and 29.2mGy, respectively. The LCD was measured at 0.45% and 0.42% (slice thickness=5mm, object size=3mm, central 4 images), respectively. The average CTDIW for FKS head and body scans was 70.4mGy and 33.4mGy, respectively, at the optimal monochromatic energy of 65 keV. The corresponding LCD was measured at 0.45% and 0.43%, respectively. This demonstrates that, with matching LCD, CTDIW of FKS is comparable to that of routine CT exams under head and body conditions.

  10. All-fiber dual wavelength passive Q-switched fiber laser using a dispersion-decreasing taper fiber in a nonlinear loop mirror.

    PubMed

    Ahmad, Harith; Dernaika, Mohamad; Harun, Sulaiman Wadi

    2014-09-22

    This paper describes a proposal and successful demonstration of a dual wavelength all-fiber passively Q-switched erbium-doped fiber ring laser. The Q-switch operation was realized by using a nonlinear loop mirror that incorporated an unbalanced dispersion-decreasing taper fiber to act as a saturable absorber without additional elements. This setup enabled a fiber ring laser to achieve a performance of 48.7 kHz repetition rate with pulse duration of around 3.2 μs and approximate pulse energy of 20 nJ.

  11. Continuous-wave and actively Q-switched resonantly dual-end-pumped Er : YAG ceramic laser emitting at 1.6 μm

    SciTech Connect

    Dai, T Y; Deng, Yu; Ju, Y-L; Yao, B Q; Duan, X M; Wang, Y Z

    2015-12-31

    We demonstrate a continuous-wave (cw) and actively Q-switched Er : YAG ceramic laser resonantly dual-end-pumped by a 1532 nm fibre-coupled laser diode. A maximum cw output power of 1.48 W at 1645.3 nm is obtained at an absorbed pump power of 12.72 W, corresponding to a slope efficiency of 19.2%. In the Q-switched regime the maximum pulse energy of 0.84 mJ is reached at a pulse repetition rate of 100 Hz, pulse duration of 48.03 ns and absorbed pump power of 10.51 W. (lasers)

  12. Continuous-wave and actively Q-switched resonantly dual-end-pumped Er : YAG ceramic laser emitting at 1.6 μm

    NASA Astrophysics Data System (ADS)

    Dai, T. Y.; Deng, Yu; Ju, Y.-L.; Yao, B. Q.; Duan, X. M.; Wang, Y. Z.

    2015-12-01

    We demonstrate a continuous-wave (cw) and actively Q-switched Er : YAG ceramic laser resonantly dual-end-pumped by a 1532 nm fibre-coupled laser diode. A maximum cw output power of 1.48 W at 1645.3 nm is obtained at an absorbed pump power of 12.72 W, corresponding to a slope efficiency of 19.2%. In the Q-switched regime the maximum pulse energy of 0.84 mJ is reached at a pulse repetition rate of 100 Hz, pulse duration of 48.03 ns and absorbed pump power of 10.51 W.

  13. Diode-pumped passively dual-wavelength Q-switched Nd:GYSGG laser using graphene oxide as the saturable absorber.

    PubMed

    Song, Qi; Wang, Guoju; Zhang, Bingyuan; Wang, Wenjun; Wang, Minghong; Zhang, Qingli; Sun, Guihua; Bo, Yong; Peng, Qinjun

    2015-04-01

    The performance of a diode end-pumped passively Q-switched dual-wavelength Nd:GYSGG laser operating at 1057.28 and 1060.65 nm with graphene oxide as the saturable absorber was demonstrated. The maximum dual-wavelength average output power of 521 mW was achieved under the absorbed pump power of 5.4 W, corresponding to the optical-to-optical conversion and slope efficiency of 9.8% and 21%, respectively. The minimum pulse width was 115 ns with a pulse repetition rate of 338 kHz.

  14. Numerical simulation of dual-loss-modulated Q-switched and mode-locked laser with an acousto-optic and Cr4+:YAG saturable absorber.

    PubMed

    Zhao, Shengzhi; Li, Guiqiu; Li, Dechun; Yang, Kejian; Li, Yufei; Li, Ming; Li, Tao; Zhang, Gang; Cheng, Kang

    2010-04-01

    By considering the influence of the turn-off time and the modulation frequency of the acousto-optic (AO) modulator as well as the Gaussian spatial distribution of the photon density, we give a developed rate equation model for a diode-pumped dual-loss-modulated Q-switched and mode-locked (QML) Nd:GdVO(4) laser with AO modulator and Cr(4+):YAG saturable absorber. With this developed model, the dual-loss-modulated QML laser characteristics, such as pulse width and pulse energy, can be numerically simulated, and the theoretical evaluations are in good agreement with the experimental results.

  15. 808-nm diode-pumped dual-wavelength passively Q-switched Nd:LuLiF4 laser with Bi-doped GaAs

    NASA Astrophysics Data System (ADS)

    Li, S. X.; Li, T.; Li, D. C.; Zhao, S. Z.; Li, G. Q.; Hang, Y.; Zhang, P. X.; Li, X. Y.; Qiao, H.

    2015-09-01

    Diode-pumped CW and passively Q-switched Nd:LuLiF4 lasers with stable, synchronous dual-wavelength operations near 1047 and 1053 nm were demonstrated for the first time. The maximal CW output power of 821 mW was obtained at an incident pump power of 6.52 W. Employing high quality Bi-doped GaAs as saturable absorber, stable dual-wavelength Q-switched operation was realized. Under 6.52 W incident pump power, the minimal pulse duration of 1.5 ns, the largest single pulse energy of 11.32 μJ, and the highest peak power of 7.25 kW were achieved.

  16. Dual-wavelength Q-switched Er:SrF2 laser with a black phosphorus absorber in the mid-infrared region.

    PubMed

    Liu, Jingjing; Liu, Jie; Guo, Zhinan; Zhang, Han; Ma, Weiwei; Wang, Jingya; Su, Liangbi

    2016-12-26

    An efficient Er:SrF2 crystal, lightly Er-doped to a concentration of 4at.%, was successfully grown by the traditional Bridgman method and displayed excellent spectral properties. A diode-end-pumped passively Q-switched dual-wavelength laser, operating at 2.79 μm wavelength, was demonstrated with this crystal by using black phosphorus as the saturable absorber (BP-SA). In the compact passively Q-switched Er:SrF2 laser, the maximum average output power of 180 mW was achieved at an absorbed pump power of 2.47 W, with a pulse duration of 702 ns and a repetition rate of 77.03 kHz. To the best of our knowledge, this is the first reported application of BP-SA to dual-wavelength pulse laser operation in the mid-infrared region.

  17. A 0.9-V switched-opamp-based delta—sigma ADC with dual cycle shift DWA

    NASA Astrophysics Data System (ADS)

    Jinchen, Zhao; Menglian, Zhao; Xiaobo, Wu; Hanqing, Wang

    2013-06-01

    This paper presents a low-power high-precision switched-opamp(SO)-based delta—sigma (ΔΣ) analog-to-digital converter (ADC). The proposed SO design allows circuit operation at sub-1 V supply voltage, only needs to work in half of a clock cycle, and thus is suitable for low power applications. In addition, an opamp-sharing technique is applied to save on hardware overheads. Due to the use of a dual cycle shift data weighted averaging (DCS-DWA) technique, mismatch errors caused in the feedback DAC have been eliminated without introducing signal-dependent tones. The proposed ADC has been implemented in a standard 0.18 μm process and measured to have a 92.2 dB peak SNDR and 94.1 dB dynamic range with 25 kHz signal bandwidth. The power consumption is 58 μW for the modulator at 0.9 V supply voltage and 96 μW for the decimation filter, which translate to the figure-of-merit (FOM) of 35.4 fJ/step for the solo modulator, and 94 fJ/step for the whole system.

  18. Temperature controlled water/oil wettability of a surface fabricated by a block copolymer: application as a dual water/oil on-off switch.

    PubMed

    Xue, Baolong; Gao, Longcheng; Hou, Yongping; Liu, Zhiwen; Jiang, Lei

    2013-01-11

    A temperature controlled dual water/oil on-off switch is achieved by using a PMMA-b-PNIPAAm block-copolymer coated mesh, determined by the conformational change of the PNIPAAm chain around the lower critical solution temperature (LCST) and also the cooperation between PNIPAAm and PMMA. Water can permeate through the BCP-coated mesh, and oil cannot below the LCST, whereas oil can and water cannot above the LCST.

  19. Electrostatics 1979,

    DTIC Science & Technology

    1979-11-28

    UK also perform consulting work on elec- trostatic problems. Two of these are the Wolfson Electrostatics Unit of the Department of Electrical...Cross (Wolfson Electrostatics Advisory Unit , Univ. of Southampton, UK ) reported that the application of high electro- static fields does indeed aid heat...062 917 OFFICE OF NAVAL RESEARCH LONDON ( ENGLAND ) F/0 20/3 ELECTROSTATICS 1979. (U) NOV 79 1 KAUFMAN UNCLASSIFIE’ ONLC-1 7 N JJ32 L136 I L. - ’III

  20. Electrostatic precipitation

    SciTech Connect

    Albanese, V.

    1980-07-22

    A method is described of improving the conductivity of particles entrained in a stream of particle-laden gas formed by the burning of coal. The particles are collected by an electrostatic precipitator which comprises treating said gas containing particles prior to contact with the electrostatic precipitator at a temperature not greater than about 800/sup 0/F with a resistivitydecreasing amount of hexamethylene tetramine or its water-soluble salts and thereafter passing the gas to the electrostatic precipitator.

  1. All-fiber dual-wavelength Q-switched and mode-locked EDFL by SMF-THDF-SMF structure as a saturable absorber

    NASA Astrophysics Data System (ADS)

    Latiff, A. A.; Kadir, N. A.; Ismail, E. I.; Shamsuddin, H.; Ahmad, H.; Harun, S. W.

    2017-04-01

    We demonstrate all-fiber dual-wavelength Q-switched and mode-locked erbium-doped fiber laser (EDFL) by utilizing the thulium-holmium-doped fiber (THDF) as a fiber saturable absorber (SA) and also a Mach-Zehnder interferometer (MZI) element. The 19 cm long THDF has a core diameter of 11.5 μm, refractive index difference of 0.005, and cutoff wavelength of 1810 nm. Stable dual-wavelength Q-switching operation was generated at 1555.14 nm and 1557.64 nm with free spectral range (FSR) of 2.5 nm. The repetition rate of 14.45-78.49 kHz was obtained between 12 and 100 mW pump power. At maximum pump power, the maximum output power and pulse energy were 2.58 mW and 32.87 nJ, respectively. By adding 195 cm long SMF in the same cavity, the stable dual-wavelength mode-locking operation was started at 166 mW and continue stable to 201 mW pump power. This mode-locking operation produced stable dual-wavelength pulses at 1530.34 nm and 1532.84 nm with a repetition rate of 1 MHz with a pulse duration of 128 ns and signal-to-noise ratio (SNR) of 62 dB. It shares the same value of FSR in Q-switching operation. The highest output power of 1.57 nJ corresponds to the maximum output power of 1.57 mW was obtained. Our results validate the linear absorption characteristic at C-band region and multimode fiber effect of THDF can be utilized as SA to generate stable all-fiber dual-wavelength pulsed lasers. Remarkably, these findings expand a fiber gain medium application in short pulse generation.

  2. Interdomain Contacts Control Native State Switching of RfaH on a Dual-Funneled Landscape

    PubMed Central

    Ramírez-Sarmiento, César A.; Noel, Jeffrey K.; Valenzuela, Sandro L.; Artsimovitch, Irina

    2015-01-01

    RfaH is a virulence factor from Escherichia coli whose C-terminal domain (CTD) undergoes a dramatic α-to-β conformational transformation. The CTD in its α-helical fold is stabilized by interactions with the N-terminal domain (NTD), masking an RNA polymerase binding site until a specific recruitment site is encountered. Domain dissociation is triggered upon binding to DNA, allowing the NTD to interact with RNA polymerase to facilitate transcription while the CTD refolds into the β-barrel conformation that interacts with the ribosome to activate translation. However, structural details of this transformation process in the context of the full protein remain to be elucidated. Here, we explore the mechanism of the α-to-β conformational transition of RfaH in the full-length protein using a dual-basin structure-based model. Our simulations capture several features described experimentally, such as the requirement of disruption of interdomain contacts to trigger the α-to-β transformation, confirms the roles of previously indicated residues E48 and R138, and suggests a new important role for F130, in the stability of the interdomain interaction. These native basins are connected through an intermediate state that builds up upon binding to the NTD and shares features from both folds, in agreement with previous in silico studies of the isolated CTD. We also examine the effect of RNA polymerase binding on the stabilization of the β fold. Our study shows that native-biased models are appropriate for interrogating the detailed mechanisms of structural rearrangements during the dramatic transformation process of RfaH. PMID:26230837

  3. Device and circuit modeling for a 3.5- to 6.5-GHz GaAs monolithic dual-gate FET switch module

    NASA Astrophysics Data System (ADS)

    Fu, Michael C.; Gupta, Ramesh K.

    The design approach and measured performance of a broadband (3.5- to 6.5-GHz), dual-gate field-effect transistor (DGFET) switch module with an on-chip, TTL-compatible switch control circuit are presented. This MMIC switch module is a key element in the development of a highly reliable and lightweight microwave switch matrix. A computer program was developed for modeling the equivalent circuit element values for the DGFET from physical device parameters. The program is used to predict the small-signal, three-port, S-parameters for DGFET devices. These modeled parameters are then used to design a self-biased monolithic DGFET switch module with chip dimensions of 1.5 x 2.5 mm. Measurements show that the switch module has an ON-state gain of approximately 11 dB over the 3.5- to 6.5-GHz range, with better than 50-dB ON- to-OFF isolation. The measured gain in the ON state is within 1 dB of the modeled performance over the 3.5- to 6.5-GHz band.

  4. Consumption patterns and biomarkers of exposure in cigarette smokers switched to Snus, various dissolvable tobacco products, Dual use, or tobacco abstinence.

    PubMed

    Krautter, George R; Chen, Peter X; Borgerding, Michael F

    2015-03-01

    The objectives of this clinical study were to evaluate changes in tobacco product use behavior and levels of selected biomarkers of exposure (BOEs) for smokers who switched to one of six conditions during clinical confinement: exclusive use of; Camel Snus, Sticks, Strips or Orbs, controlled Dual use of cigarettes and Camel Snus, or tobacco abstinence. The controlled Dual use (DU) condition mandated a 60% reduction in cigarettes smoked per day (CPD). 167 healthy U.S. male and female smokers were randomized to the six groups (n=25-30/group). Subjects smoked their usual brand of cigarette for 1 day prior to switching to their designated intervention condition. Levels of thirty-two BOEs in plasma, whole blood, urine and feces were determined before and after switching. Questionnaires that scored nicotine dependence and withdrawal discomfort were also administered. After 5 days, exclusive Snus, Sticks, Strips, or Orbs use averaged 6.1, 5.9, 13.5, and 8.5 units/day, respectively. DU subjects smoked 7.6 CPD and used 3.2 Snus pouches/day, on average. After 5 days, substantial reductions of most biomarkers, including nicotine, were observed in all groups. Toxicant exposures were similar to being tobacco abstinent after switching exclusively to Camel Snus, Sticks, Strips or Orbs. DU reductions were more modest.

  5. High peak power, 28 ns Q-switched Tm:LuAG laser at a 2 μm wavelength by dual-loss-modulation

    NASA Astrophysics Data System (ADS)

    Luan, Chao; Yang, Kejian; Zhao, Jia; Zhao, Shengzhi; Qiao, Wenchao; Li, Tao; Liu, Cheng; Chu, Hongwei; Qiao, Junpeng; Zheng, Lihe; Xu, Xiaodong; Xu, Jun

    2016-02-01

    By employing output couplers (OCs) with different transmissions T and GaAs saturable absorbers (SAs) with different modulation depth ΔR in a passively Q-switched Tm:LuAG laser at 2 μm, the optimal parameters of OCs and SAs for obtaining short pulse width and high peak power were investigated. By inserting an electro-optical modulator (EOM) into the optimized passively Q-switched Tm:LuAG laser (T  =  2%/ΔR  =  19%), a dual-loss-modulated Q-switched Tm:LuAG laser with an EOM and GaAs was realized. The experimental results show that the dual-loss-modulated Q-switched laser can generate a shorter pulse width and higher peak power than the single-loss-modulated case. At an incident pump power of 8.4 W, the shortest pulse width achieved was 28 ns and the highest peak power reached 74 kW.

  6. Structural basis of the mercury(II)-mediated conformational switching of the dual-function transcriptional regulator MerR

    PubMed Central

    Chang, Chih-Chiang; Lin, Li-Ying; Zou, Xiao-Wei; Huang, Chieh-Chen; Chan, Nei-Li

    2015-01-01

    The mer operon confers bacterial resistance to inorganic mercury (Hg2+) and organomercurials by encoding proteins involved in sensing, transport and detoxification of these cytotoxic agents. Expression of the mer operon is under tight control by the dual-function transcriptional regulator MerR. The metal-free, apo MerR binds to the mer operator/promoter region as a repressor to block transcription initiation, but is converted into an activator upon Hg2+-binding. To understand how MerR interacts with Hg2+ and how Hg2+-binding modulates MerR function, we report here the crystal structures of apo and Hg2+-bound MerR from Bacillus megaterium, corresponding respectively to the repressor and activator conformation of MerR. To our knowledge, the apo-MerR structure represents the first visualization of a MerR family member in its intact and inducer-free form. And the Hg2+-MerR structure offers the first view of a triligated Hg2+-thiolate center in a metalloprotein, confirming that MerR binds Hg2+ via trigonal planar coordination geometry. Structural comparison revealed the conformational transition of MerR is coupled to the assembly/disassembly of a buried Hg2+ binding site, thereby providing a structural basis for the Hg2+-mediated functional switching of MerR. The pronounced Hg2+-induced repositioning of the MerR DNA-binding domains suggests a plausible mechanism for the transcriptional regulation of the mer operon. PMID:26150423

  7. Proposed ultralow-energy dual photonic-crystal nanobeam devices for on-chip N x N switching, logic, and wavelength multiplexing.

    PubMed

    Soref, Richard; Hendrickson, Joshua

    2015-12-14

    Silicon-on-insulator Mach-Zehnder interferometer structures that utilize a photonic crystal nanobeam waveguide in each of two connecting arms are proposed here as efficient 2 × 2 resonant, wavelength-selective electro-optical routing switches that are readily cascaded into on-chip N × N switching networks. A localized lateral PN junction of length ~2 μm within each of two identical nanobeams is proposed as a means of shifting the transmission resonance by 400 pm within the 1550 nm band. Using a bias swing ΔV = 2.7 V, the 474 attojoules-per-bit switching mechanism is free-carrier sweepout due to PN depletion layer widening. Simulations of the 2 × 2 outputs versus voltage are presented. Dual-nanobeam designs are given for N × N data-routing matrix switches, electrooptical logic unit cells, N × M wavelength selective switches, and vector matrix multipliers. Performance penalties are analyzed for possible fabrication induced errors such as non-ideal 3-dB couplers, differences in optical path lengths, and variations in photonic crystal cavity resonances.

  8. Aluminum electrode modulated bipolar resistive switching of Al/fuel-assisted NiOx/ITO memory devices modeled with a dual-oxygen-reservoir structure.

    PubMed

    Chiang, Kun-Keng; Chen, Jen-Sue; Wu, Jih-Jen

    2012-08-01

    Bipolar resistive switching in Al/fuel-assisted NiO(x) (40 nm)/ITO devices is demonstrated in this work. XPS analysis reveals the simultaneous presence of metallic Ni, Ni(2)O(3), and NiO components in the fuel-assisted NiO(x). The concentration, as well as spreading of the metallic Ni and accompanying oxygen vacancies, are related to the Al/NiO(x) interfacial reaction, which is enhanced by the increasing thickness of the Al top electrode. Correspondingly, the preswitching-on voltage decreases while the preswitching-off voltage increases with increasing thickness (from 15 to 60 nm) of Al. However, in regular switching operation, set and reset voltages are considerably lowered for devices with an increased thickness of the Al top electrode. The bipolar resistive switching behaviors of Al/fuel-assisted NiO(x)/ITO devices are therefore discussed based on the formation of conductive paths and their correlation with the Al-electrode modulated composition in the fuel-assisted NiO(x). The Al/NiO(x) interfacial reaction region pairs with ITO to form a dual-oxygen-reservoir structure. Mechanisms of construction/destruction of conducting paths originating from the electrochemical redox reactions at the interface between NiO(x), and the dual oxygen reservoirs will also be explicated.

  9. Dual-wavelength Q-switched thulium-fluoride fiber laser for S+/S band using molybdenum disulfide (MoS2) as a saturable absorber

    NASA Astrophysics Data System (ADS)

    Ahmad, H.; Reduan, S. A.; Safaei, R.

    2017-06-01

    In this work a Q-switched, dual-wavelength fiber laser is proposed and demonstrated for S+/S band operation. The proposed laser combines a 14.5 m long thulium-fluoride fiber with an absorption rate of 0.15 dB m-1 at a wavelength of 1400 nm with a 0.5 cm-long photonics crystal fiber to generate the desired dual-wavelength output in the S  +  /S band region. The generated output is then Q-switched using a compact MoS2-based saturable absorber. A dual-wavelength output with lasing wavelengths at 1473.6 and 1479.3 nm is obtained. The pulses have a repetition rate and pulse width of approximately 15.9 kHz and 4.1 µs at a maximum pump power of 126.4 mW, as well as a maximum average output power and pulse energy of 1.3 mW and 83.7 nJ at the same pump power. The generated pulses have a 3 dB bandwidth of 4.7 µs, along with a signal-to-noise ratio of 32.0 dB. The proposed laser is able to transmit within the S-band transmission region or shorter, thus making it highly viable for a multitude of photonics applications.

  10. Retrospective analysis of melasma treatment using a dual mode of low-fluence Q-switched and long-pulse Nd:YAG laser vs. low-fluence Q-switched Nd:YAG laser monotherapy.

    PubMed

    Choi, Chun Pil; Yim, Seon Mi; Seo, Soo Hong; Ahn, Hyo Hyun; Kye, Young Chul; Choi, Jae Eun

    2015-02-01

    Despite the effectiveness of low-fluence Q-switched Nd:YAG laser (QSNY) treatment in melasma, adverse events, including mottled hypopigmentation (MH) and rebound hyperpigmentation (RH) have been reported. To compare the effectiveness and safety of combination therapy using low-fluence QSNY and long-pulse Nd:YAG laser (LPNY) (Dual toning), with low-fluence QSNY monotherapy (QS toning), in Asian melasma patients. Patients were treated for 10 sessions at 1-week intervals with QSNY (6 mm spot); 2.5-3.0 J/cm(2) for QS toning (n = 177) or 2.1-2.5 J/cm(2) for dual toning (n = 183). The dual toning group was immediately treated with LPNY (7 mm spot, 15-17 J/cm(2)). The results were evaluated using the modified Melasma Area and Severity Index (mMASI) score and the physician's global assessment. MH or RH were significantly lower (1.1% vs. 14.1%) and the treatment efficacy was improved (median decrease of mMASI, 3.6 vs. 3.0) in the dual toning group compared with the QS toning group. Periorbital melasma showed distinctively high rates of adverse events in the QS toning group (23.9% vs. 5.7%), which were significantly reduced in the dual toning group (2.9%). Dual toning could represent a safe and effective treatment for Asian melasma patients, as it is associated with minimal adverse events and improved treatment efficacy compared with QS toning monotherapy.

  11. Dual-functional Memory and Threshold Resistive Switching Based on the Push-Pull Mechanism of Oxygen Ions

    PubMed Central

    Huang, Yi-Jen; Chao, Shih-Chun; Lien, Der-Hsien; Wen, Cheng-Yen; He, Jr-Hau; Lee, Si-Chen

    2016-01-01

    The combination of nonvolatile memory switching and volatile threshold switching functions of transition metal oxides in crossbar memory arrays is of great potential for replacing charge-based flash memory in very-large-scale integration. Here, we show that the resistive switching material structure, (amorphous TiOx)/(Ag nanoparticles)/(polycrystalline TiOx), fabricated on the textured-FTO substrate with ITO as the top electrode exhibits both the memory switching and threshold switching functions. When the device is used for resistive switching, it is forming-free for resistive memory applications with low operation voltage (<±1 V) and self-compliance to current up to 50 μA. When it is used for threshold switching, the low threshold current is beneficial for improving the device selectivity. The variation of oxygen distribution measured by energy dispersive X-ray spectroscopy and scanning transmission electron microscopy indicates the formation or rupture of conducting filaments in the device at different resistance states. It is therefore suggested that the push and pull actions of oxygen ions in the amorphous TiOx and polycrystalline TiOx films during the voltage sweep account for the memory switching and threshold switching properties in the device. PMID:27052322

  12. Dual-functional Memory and Threshold Resistive Switching Based on the Push-Pull Mechanism of Oxygen Ions.

    PubMed

    Huang, Yi-Jen; Chao, Shih-Chun; Lien, Der-Hsien; Wen, Cheng-Yen; He, Jr-Hau; Lee, Si-Chen

    2016-04-07

    The combination of nonvolatile memory switching and volatile threshold switching functions of transition metal oxides in crossbar memory arrays is of great potential for replacing charge-based flash memory in very-large-scale integration. Here, we show that the resistive switching material structure, (amorphous TiOx)/(Ag nanoparticles)/(polycrystalline TiOx), fabricated on the textured-FTO substrate with ITO as the top electrode exhibits both the memory switching and threshold switching functions. When the device is used for resistive switching, it is forming-free for resistive memory applications with low operation voltage (<± 1 V) and self-compliance to current up to 50 μA. When it is used for threshold switching, the low threshold current is beneficial for improving the device selectivity. The variation of oxygen distribution measured by energy dispersive X-ray spectroscopy and scanning transmission electron microscopy indicates the formation or rupture of conducting filaments in the device at different resistance states. It is therefore suggested that the push and pull actions of oxygen ions in the amorphous TiOx and polycrystalline TiOx films during the voltage sweep account for the memory switching and threshold switching properties in the device.

  13. A non-critically phase matched KTA optical parametric oscillator intracavity pumped by an actively Q-switched Nd:GYSGG laser with dual signal wavelengths

    NASA Astrophysics Data System (ADS)

    Zhong, Kai; Guo, Shibei; Wang, Maorong; Mei, Jialin; Xu, Degang; Yao, Jianquan

    2015-06-01

    A non-critically phase matched eye-safe KTA optical parametric oscillator intracavity pumped by a dual-wavelength acousto-optically Q-switched Nd:GYSGG laser is demonstrated. Simultaneous dual signal wavelength at 1525.1 nm/1531.2 nm can be realized using only one laser crystal and one nonlinear crystal. When the absorbed diode pump power at 808 nm is 7.48 W, the maximum output power, single pulse energy and peak power are 296 mW, 2.96 μJ and 6.4 kW, respectively. As the signal wavelengths exactly locates at the absorption band of C2H2, such an Nd:GYSGG/KTA eye-safe laser has good application prospects in differential absorption lidar (DIAL) for C2H2 detection and difference frequency generation for terahertz waves at 0.77 THz.

  14. Switch to Ritonavir-Boosted versus Unboosted Atazanavir plus Raltegravir Dual-Drug Therapy Leads to Similar Efficacy and Safety Outcomes in Clinical Practice

    PubMed Central

    Gantner, Pierre; Bani-Sadr, Firouze; Garraffo, Rodolphe; Roger, Pierre-Marie; Treger, Michèle; Jovelin, Thomas; Pugliese, Pascal; Rey, David

    2016-01-01

    Objectives To assess immunovirological response, safety and pharmacokinetic of NRTI-sparing regimen dual therapy of atazanavir (ATV) and raltegravir (RAL) in maintenance strategy. Methods A retrospective analysis was conducted on a cohort of HIV-infected adults followed in French centers (Dat’AIDS cohort), comparing the proportions of virological and therapeutic failures between ATV + RAL and ATV/ritonavir + RAL dual therapy regimens. Results 283 patients were assessed: 185 switched for ATV + RAL and 98 for ATV/ritonavir + RAL dual therapy. Virological failure rate at week 96 was 13.8% (95% CI, 9.8–17.8), without difference between the two groups (Log-rank Test, p = 0.87). The cumulative percentages of patients remaining free of therapeutic failure at week 24, 48 and 96 of dual therapy were 74.9% (95% CI, 69.9–80.0), 65.4% (95% CI, 59.8–70.9) and 53.4% (95% CI, 47.5–59.2), respectively. Four out of 39 confirmed virological failures developed RAL resistance. By multivariate analysis, virological failure was associated with high HIV-1 RNA zenith (p = 0.02), low CD4+ T-cell count at baseline (p<0.001) and short duration on antiretroviral therapy (p<0.001). Before week 96, dual therapy was discontinued in 44 patients (16%) because of various adverse events, with no difference between the two groups. Minimal plasma levels were targeted in 84% and 87% of patients for ATV and RAL, respectively, and both were significantly higher in ritonavir-boosted regimen. Conclusions Emerging RAL-resistance and discontinuations for adverse events resulted in moderate efficacy rates of ATV and RAL dual therapy in heavily pretreated patients. PMID:27798641

  15. Optically controllable dual-mode switching in single-mode Fabry-Pérot laser diode subject to one side-mode feedback and external single mode injection

    NASA Astrophysics Data System (ADS)

    Wu, Jian-Wei; Won, Yong Hyub

    2017-06-01

    In this paper, broadly tunable dual-mode lasing system is presented and demonstrated based on single-mode Fabry-Pérot laser diode subject to the feedback of one side mode amplified by an erbium-doped fiber amplifier in the external feedback cavity. The spacing between two resonance modes in output lasing spectrum is broadly tuned by introducing differently amplified side mode into the single-mode laser via the external cavity consisted of amplifier, filter, and polarization controller so that two difference frequencies of 1 THz and 0.6 THz are given to display the tunable behavior of dual-mode emission in this work. Therefore, under an external injection mode into the laser condition, the power dependent injection locking and optical bistability of generated dual-mode emission are discussed in detail. At different wavelength detunings, the emitted two resonance modes including the dominant and feedback modes are switched to on- or off-state by selecting proper high-low power level of the external injection mode. As a consequence, the maximum value of achieved dual-mode on-off ratio is as high as up to 45 dB.

  16. Multimaterial Decomposition Algorithm for the Quantification of Liver Fat Content by Using Fast-Kilovolt-Peak Switching Dual-Energy CT: Experimental Validation.

    PubMed

    Hyodo, Tomoko; Hori, Masatoshi; Lamb, Peter; Sasaki, Kosuke; Wakayama, Tetsuya; Chiba, Yasutaka; Mochizuki, Teruhito; Murakami, Takamichi

    2017-02-01

    Purpose To assess the ability of fast-kilovolt-peak switching dual-energy computed tomography (CT) by using the multimaterial decomposition (MMD) algorithm to quantify liver fat. Materials and Methods Fifteen syringes that contained various proportions of swine liver obtained from an abattoir, lard in food products, and iron (saccharated ferric oxide) were prepared. Approval of this study by the animal care and use committee was not required. Solid cylindrical phantoms that consisted of a polyurethane epoxy resin 20 and 30 cm in diameter that held the syringes were scanned with dual- and single-energy 64-section multidetector CT. CT attenuation on single-energy CT images (in Hounsfield units) and MMD-derived fat volume fraction (FVF; dual-energy CT FVF) were obtained for each syringe, as were magnetic resonance (MR) spectroscopy measurements by using a 1.5-T imager (fat fraction [FF] of MR spectroscopy). Reference values of FVF (FVFref) were determined by using the Soxhlet method. Iron concentrations were determined by inductively coupled plasma optical emission spectroscopy and divided into three ranges (0 mg per 100 g, 48.1-55.9 mg per 100 g, and 92.6-103.0 mg per 100 g). Statistical analysis included Spearman rank correlation and analysis of covariance. Results Both dual-energy CT FVF (ρ = 0.97; P < .001) and CT attenuation on single-energy CT images (ρ = -0.97; P < .001) correlated significantly with FVFref for phantoms without iron. Phantom size had a significant effect on dual-energy CT FVF after controlling for FVFref (P < .001). The regression slopes for CT attenuation on single-energy CT images in 20- and 30-cm-diameter phantoms differed significantly (P = .015). In sections with higher iron concentrations, the linear coefficients of dual-energy CT FVF decreased and those of MR spectroscopy FF increased (P < .001). Conclusion Dual-energy CT FVF allows for direct quantification of fat content in units of volume percent. Dual-energy CT FVF was larger in 30

  17. Electrostatic Precipitator

    NASA Image and Video Library

    2017-06-09

    Dr. Carlos Calle, lead scientist in the Kennedy Space Center's Electrostatics and Surface Physics Laboratory, left, and Jay Phillips, a research physicist, are modifying an electrostatic precipitator to help remove dust from simulated Martian atmosphere. NASA's Journey to Mars requires cutting-edge technologies to solve the problems explorers will face on the Red Planet. Scientists are developing some of the needed solutions by adapting a device to remove the ever-present dust from valuable elements in the Martian atmosphere. Those commodities include oxygen, water and methane.

  18. Electrostatic Precipitator

    NASA Image and Video Library

    2017-06-09

    Dr. Carlos Calle, lead scientist in the Kennedy Space Center's Electrostatics and Surface Physics Laboratory, left, and Jay Phillips, a research physicist, are modifying an electrostatic precipitator to help remove dust from a simulated Martian atmosphere. NASA's Journey to Mars requires cutting-edge technologies to solve the problems explorers will face on the Red Planet. Scientists are developing some of the needed solutions by adapting a device to remove the ever-present dust from valuable elements in the Martian atmosphere. Those commodities include oxygen, water and methane.

  19. Electrostatic Precipitator

    NASA Image and Video Library

    2017-06-09

    In their Swamp Works laboratory at NASA's Kennedy Space Center, Dr. Carlos Calle and Jay Phillips are testing an electrostatic precipitator using dust that closely approximates the make-up of that on Mars. They upgraded their electrostatic precipitator to fully simulate Martian atmosphere by designing and constructing a dust aerosolization pre-chamber. The agency's Journey to Mars requires cutting-edge technologies to solve the problems explorers will face on the Red Planet. Scientists are developing some of the needed solutions by adapting a device to remove the ever-present dust from valuable elements in the Martian atmosphere. Those commodities include oxygen, water and methane.

  20. Electrostatic Precipitator

    NASA Image and Video Library

    2017-06-09

    Jay Phillips, a research physicist in the Kennedy Space Center's Electrostatics and Surface Physics Laboratory, left, and Dr. Carlos Calle, lead scientist in the lab, are modifying an electrostatic precipitator to help remove dust from simulated Martian atmosphere. NASA's Journey to Mars requires cutting-edge technologies to solve the problems explorers will face on the Red Planet. Scientists are developing some of the needed solutions by adapting a device to remove the ever-present dust from valuable elements in the Martian atmosphere. Those commodities include oxygen, water and methane.

  1. Initial evaluation of virtual un-enhanced imaging derived from fast kVp-switching dual energy contrast enhanced CT for the abdomen

    NASA Astrophysics Data System (ADS)

    Joshi, M.; Mendonca, P.; Okerlund, D.; Lamb, P.; Kulkarni, N.; Pinho, D.; Sahani, D.; Bhotika, R.

    2011-03-01

    The feasibility and utility of creating virtual un-enhanced images from contrast enhanced data acquired using a fast switching dual energy CT acquisition, is explored. Utilizing projection based material decomposition data, monochromatic images are generated and a Multi-material decomposition technique is applied. Quantitative and qualitative evaluation is performed to assess the equivalence of Virtual Un-Enhanced (VUE) and True Un-enhanced (TUE) for multiple tissue types and different organs in the abdomen. Ten patient cases were analyzed where a TUE and a subsequent Contrast Enhanced (CE) acquisition were obtained using fast kVp-switching dual energy CT utilizing Gemstone Spectral Imaging. Quantitative measurements were made by placing multiple Regions of Interest on the different tissues and organs in both the TUE and the VUE images. The absolute Hounsfield Unit (HU) differences in the mean values between TUE & VUE were calculated as well as the differences of the standard deviations. Qualitative analysis was done by two radiologists for overall image quality, presence of residual contrast, appearance of pathology, appearance and contrast of normal tissues and organs in comparison to the TUE. There is a very strong correlation between the TUE and VUE images.

  2. Electrostatic Toys.

    ERIC Educational Resources Information Center

    Greenslade, Thomas B., Jr.

    1982-01-01

    Describes typical electrostatic toys which may be used to show students phenomena associated with sparks, sudden drops in potential, induction, and forces between bodies of like and opposite charges. Many of these demonstrations are suitable for student projects. (Author/JN)

  3. Multipolar electrostatics.

    PubMed

    Cardamone, Salvatore; Hughes, Timothy J; Popelier, Paul L A

    2014-06-14

    Atomistic simulation of chemical systems is currently limited by the elementary description of electrostatics that atomic point-charges offer. Unfortunately, a model of one point-charge for each atom fails to capture the anisotropic nature of electronic features such as lone pairs or π-systems. Higher order electrostatic terms, such as those offered by a multipole moment expansion, naturally recover these important electronic features. The question remains as to why such a description has not yet been widely adopted by popular molecular mechanics force fields. There are two widely-held misconceptions about the more rigorous formalism of multipolar electrostatics: (1) Accuracy: the implementation of multipole moments, compared to point-charges, offers little to no advantage in terms of an accurate representation of a system's energetics, structure and dynamics. (2) Efficiency: atomistic simulation using multipole moments is computationally prohibitive compared to simulation using point-charges. Whilst the second of these may have found some basis when computational power was a limiting factor, the first has no theoretical grounding. In the current work, we disprove the two statements above and systematically demonstrate that multipole moments are not discredited by either. We hope that this perspective will help in catalysing the transition to more realistic electrostatic modelling, to be adopted by popular molecular simulation software.

  4. MEMS electrostatic influence machines

    NASA Astrophysics Data System (ADS)

    Phu Le, Cuong; Halvorsen, Einar

    2016-11-01

    This paper analyses the possibility of MEMS electrostatic influence machines using electromechanical switches like the historical predecessors did two centuries ago. We find that a generator design relying entirely on standard silicon-on-insulator(SOI) micromachining is conceivable and analyze its performance by simulations. The concept appears preferable over comparable diode circuits due to its higher maximum energy, faster charging and low precharging voltage. A full electromechanical lumped-model including parasitic capacitances of the switches is built to capture the dynamic of the generator. Simulation results show that the output voltage can be exponentially bootstrapped from a very low precharging voltage so that otherwise inadequately small voltage differences or charge imbalances can be made useful.

  5. Mid-infrared passively switched pulsed dual wavelength Ho3+-doped fluoride fiber laser at 3 μm and 2 μm

    PubMed Central

    Li, Jianfeng; Luo, Hongyu; Wang, Lele; Liu, Yong; Yan, Zhijun; Zhou, Kaiming; Zhang, Lin; Turistsyn, Sergei K.

    2015-01-01

    Cascade transitions of rare earth ions involved in infrared host fiber provide the potential to generate dual or multiple wavelength lasing at mid-infrared region. In addition, the fast development of saturable absorber (SA) towards the long wavelengths motivates the realization of passively switched mid-infrared pulsed lasers. In this work, by combing the above two techniques, a new phenomenon of passively Q-switched ~3 μm and gain-switched ~2 μm pulses in a shared cavity was demonstrated with a Ho3+-doped fluoride fiber and a specifically designed semiconductor saturable absorber (SESAM) as the SA. The repetition rate of ~2 μm pulses can be tuned between half and same as that of ~3 μm pulses by changing the pump power. The proposed method here will add new capabilities and more flexibility for generating mid-infrared multiple wavelength pulses simultaneously that has important potential applications for laser surgery, material processing, laser radar, and free-space communications, and other areas. PMID:26041105

  6. Mid-infrared passively switched pulsed dual wavelength Ho(3+)-doped fluoride fiber laser at 3 μm and 2 μm.

    PubMed

    Li, Jianfeng; Luo, Hongyu; Wang, Lele; Liu, Yong; Yan, Zhijun; Zhou, Kaiming; Zhang, Lin; Turistsyn, Sergei K

    2015-06-04

    Cascade transitions of rare earth ions involved in infrared host fiber provide the potential to generate dual or multiple wavelength lasing at mid-infrared region. In addition, the fast development of saturable absorber (SA) towards the long wavelengths motivates the realization of passively switched mid-infrared pulsed lasers. In this work, by combing the above two techniques, a new phenomenon of passively Q-switched ~3 μm and gain-switched ~2 μm pulses in a shared cavity was demonstrated with a Ho(3+)-doped fluoride fiber and a specifically designed semiconductor saturable absorber (SESAM) as the SA. The repetition rate of ~2 μm pulses can be tuned between half and same as that of ~3 μm pulses by changing the pump power. The proposed method here will add new capabilities and more flexibility for generating mid-infrared multiple wavelength pulses simultaneously that has important potential applications for laser surgery, material processing, laser radar, and free-space communications, and other areas.

  7. Retreatment using a dual mode of low-fluence Q-switched and long-pulse Nd:YAG laser in patients with melasma aggravation after previous therapy.

    PubMed

    Choi, Chun Pil; Yim, Seon Mi; Seo, Soo Hong; Ahn, Hyo Hyun; Kye, Young Chul; Choi, Jae Eun

    2015-06-01

    Aggravated melasma after treatment is vulnerable to stimulation, can easily deteriorate, and may be distressing without proper management. To retrospectively assess the effectiveness and safety of combination therapy using low-fluence Q-switched neodymium-doped yttrium aluminum garnet (Nd:YAG) laser (QSNY) and long-pulse Nd:YAG laser (LPNY) (dual toning) in patients with rebound melasma. A total of 30 patients with aggravated melasma after previous therapy who were treated with dual toning were enrolled. A total of 10 sessions were conducted at 1-week intervals, followed by maintenance treatment. The results were evaluated using the modified Melasma Area and Severity Index (mMASI) and the physician's global assessment (PGA) before and 2 months after completing the 10 treatment sessions. The baseline mMASI was 10.48 ± 3.64, which significantly decreased to 3.22 ± 1.45 2 months after completing the 10 treatment sessions (p < 0.001). Twenty-four patients (80%) had PGA grade 4 (76-100% improvement) and 6 patients (20%) had PGA grade 3 (51-75% improvement). Dual toning may be a safe and effective salvage treatment for patients with aggravated melasma after previous treatment. LPNY may stabilize melasma activity to prevent rebound hyperpigmentation via dermal remodeling.

  8. Serial or overlapping processing in multitasking as individual preference: Effects of stimulus preview on task switching and concurrent dual-task performance.

    PubMed

    Reissland, Jessika; Manzey, Dietrich

    2016-07-01

    Understanding the mechanisms and performance consequences of multitasking has long been in focus of scientific interest, but has been investigated by three research lines more or less isolated from each other. Studies in the fields of the psychological refractory period, task switching, and interruptions have scored with a high experimental control, but usually do not give participants many degrees of freedom to self-organize the processing of two concurrent tasks. Individual strategies as well as their impact on efficiency have mainly been neglected. Self-organized multitasking has been investigated in the field of human factors, but primarily with respect to overall performance without detailed investigation of how the tasks are processed. The current work attempts to link aspects of these research lines. All of them, explicitly or implicitly, provide hints about an individually preferred type of task organization, either more cautious trying to work strictly serially on only one task at a time or more daring with a focus on task interleaving and, if possible, also partially overlapping (parallel) processing. In two experiments we investigated different strategies of task organization and their impact on efficiency using a new measure of overall multitasking efficiency. Experiment 1 was based on a classical task switching paradigm with two classification tasks, but provided one group of participants with a stimulus preview of the task to switch to next, enabling at least partial overlapping processing. Indeed, this preview led to a reduction of switch costs and to an increase of dual-task efficiency, but only for a subgroup of participants. They obviously exploited the possibility of overlapping processing, while the others worked mainly serially. While task-sequence was externally guided in the first experiment, Experiment 2 extended the approach by giving the participants full freedom of task organization in concurrent performance of the same tasks. Fine

  9. Power distribution of a co-axial dual-mechanical-port flux-switching permanent magnet machine for fuel-based extended range electric vehicles

    NASA Astrophysics Data System (ADS)

    Zhou, Lingkang; Hua, Wei; Zhang, Gan

    2017-05-01

    In this paper, power distribution between the inner and outer machines of a co-axial dual-mechanical-port flux-switching permanent magnet (CADMP-FSPM) machine is investigated for fuel-based extended range electric vehicle (ER-EV). Firstly, the topology and operation principle of the CADMP-FSPM machine are introduced, which consist of an inner FSPM machine used for high-speed, an outer FSPM machine for low-speed, and a magnetic isolation ring between them. Then, the magnetic field coupling of the inner and outer FSPM machines is analyzed with more attention paid to the optimization of the isolation ring thickness. Thirdly, the power-dimension (PD) equations of the inner and outer FSPM machines are derived, respectively, and thereafter, the PD equation of the whole CADMP-FSPM machine can be given. Finally, the PD equations are validated by finite element analysis, which supplies the guidance on the design of this type of machines.

  10. OCDMA PON supporting ONU inter-networking based on gain-switched Fabry-Pérot lasers with external dual-wavelength injection.

    PubMed

    Liu, Jie; Zeng, Duoduo; Guo, Changjian; Xu, Lei; He, Sailing

    2010-10-25

    We propose and demonstrate an OCDMA-PON scheme with optical network unit (ONU) internetworking capability, which utilizes low-cost gain-switched Fabry-Pérot (GS-FP) lasers with external dual-wavelength injection as the pulse sources on the ONU side. The injection-generated optical pulses in two wavelengths from the same GS-FP laser are used separately for the PON uplink transmission and ONU internetworking. Experimental results based on a two-user OCDMA system confirm the feasibility of the proposed scheme. With OCDMA technologies, separate ONU-internetworking groups can be established using different optical codes. We also give experiment results to analyze the performance of the ONU-ONU transmission at different power of interference signals when two ONU-internetworking groups are present in the OCDMA-PON.

  11. Multiparametric Evaluation of Head and Neck Squamous Cell Carcinoma Using a Single-Source Dual-Energy CT with Fast kVp Switching: State of the Art.

    PubMed

    Lam, Stephanie; Gupta, Rajiv; Kelly, Hillary; Curtin, Hugh D; Forghani, Reza

    2015-11-06

    There is an increasing body of evidence establishing the advantages of dual-energy CT (DECT) for evaluation of head and neck squamous cell carcinoma (HNSCC). Focusing on a single-source DECT system with fast kVp switching, we will review the principles behind DECT and associated post-processing steps that make this technology especially suitable for HNSCC evaluation and staging. The article will review current applications of DECT for evaluation of HNSCC including use of different reconstructions to improve tumor conspicuity, tumor-normal soft tissue interface, accuracy of invasion of critical structures such as thyroid cartilage, and reduce dental artifact. We will provide a practical approach for DECT implementation into routine clinical use and a multi-parametric approach for scan interpretation based on the experience at our institution. The article will conclude with a brief overview of potential future applications of the technique.

  12. Q-switched dual-wavelength fiber laser using a graphene oxide saturable absorber and singlemode-multimode-singlemode fiber structure

    NASA Astrophysics Data System (ADS)

    Ahmad, H.; Zulkifli, A. Z.; Yasin, M.; Thambiratnam, K.

    2016-10-01

    A Q-switched dual-wavelength fiber laser using a graphene oxide-based saturable absorber to generate the desired output pulses is proposed and demonstrated. The system utilizes a singlemode-multimode-singlemode fiber structure to control the net losses in the cavity so that only two dominant wavelengths are allowed to oscillate. The proposed system is capable of generating an output with a high repetition rate of 27.1 kHz and a narrow pulse width of 4.03 µs. The output pulses also have average output power and pulse energy of up to 0.5 mW and 18.5 nJ, respectively. The 1st harmonic obtained has a high signal-to-noise ratio of 33.2 dB, indicating a highly stable pulse output with minimum mode hopping.

  13. Electrostatic monitoring

    DOEpatents

    Orr, Christopher Henry; Luff, Craig Janson; Dockray, Thomas; Macarthur, Duncan Whittemore

    2001-01-01

    The apparatus and method provide a technique for more simply measuring alpha and/or beta emissions arising from items or locations. The technique uses indirect monitoring of the emissions by detecting ions generated by the emissions, the ions being attracted electrostatically to electrodes for discharge of collection. The apparatus and method employ a chamber which is sealed around the item or location during monitoring with no air being drawn into or expelled from the chamber during the monitoring process. A simplified structure and operations arises as a result, but without impairing the efficiency and accuracy of the detection technique.

  14. Experimental and theoretical study on an intracavity KTiOPO4 optical parametric oscillator pumped by a dual loss modulated Q-switched and mode-locked laser

    NASA Astrophysics Data System (ADS)

    Qiao, Junpeng; Zhao, Shengzhi; Yang, Kejian; Zhao, Jia; Li, Guiqiu; Li, Dechun; Li, Tao; Qiao, Wenchao; Chu, Hongwei; Luan, Chao

    2017-07-01

    In this paper, a sub-nanosecond KTiOPO4 (KTP)-based intracavity optical parametric oscillator (IOPO) pumped by a dual-loss modulated Q-switched and mode-locked (QML) laser with an acousto-optic modulator (AOM) and a Cr4+:YAG saturable absorber (Cr4+:YAG-SA) has been demonstrated. By changing the initial transmission of Cr4+:YAG-SA and the transmission of the output coupler at the signal wavelength, the signal pulse width compression can be realized. At an incident pump power of 8.3 W and an AOM repetition rate of 15 kHz, a single signal pulse underneath Q-switched envelope with the shortest pulse width of 220 ps was obtained. The experimental results reveal that this is a simple and effective way to obtain the sub-nanosecond OPO signal pulses. In addition, the related coupled rate equations have been set up and the simulation results agreed with the experimental results well.

  15. Numerical solutions of diode-pumped dual-loss-modulated Q-switched and mode-locked green laser with acousto-optic modulator and Cr 4+: YAG saturable absorber

    NASA Astrophysics Data System (ADS)

    Zhang, Gang; Zhao, Shengzhi; Li, Dechun; Yang, Kejian; Li, Guiqiu; Cheng, Kang; Zhang, Yan

    2011-04-01

    By considering the influence of the acousto-optic (AO) modulator and the nonlinear loss due to harmonic conversion in the intra-cavity frequency-doubling laser, a developed rate equation model for diode-pumped dual-loss-modulated Q-switched and mode-locked (QML) Nd:LuVO4/KTP green laser with acousto-optic (AO) modulator and Cr4+:YAG saturable absorber is presented. With this developed model, the pulse width, single-pulse energy and the other dual-loss-modulated QML green laser characteristics are numerically simulated. The simulation results show that the turnoff time is of great importance for the pulse energy and pulse width of the Q-switched pulse. A diode-pumped dual-loss-modulated QML Nd:LuVO4/KTP laser is constructed to successfully demonstrate the numerical simulation application.

  16. A novel strategy for dual-channel detection of metallothioneins and mercury based on the conformational switching of functional chimera aptamer.

    PubMed

    Tang, Xian; Wang, Yong-Sheng; Xue, Jin-Hua; Zhou, Bin; Cao, Jin-Xiu; Chen, Si-Han; Li, Ming-Hui; Wang, Xiao-Feng; Zhu, Yu-Feng; Huang, Yan-Qin

    2015-03-25

    A novel strategy for dual-channel detection of metallothioneins (MTs) and Hg(2+) has been proposed. In the absence of Hg(2+), the functional chimera aptamer (FCA) designed can form an intact G-quadruplex with flexibility, which was demonstrated to have peroxidase-like activities upon hemin binding. In the presence of Hg(2+), the formation of T-Hg(2+)-T complex results in the conformational switching of FCA, which lost the peroxidase-like activities and cannot catalyze the oxidation of ABTS by H2O2. Upon addition of MTs in this solution, MTs could interact with Hg(2+) to form a MTs-Hg(2+) complex, leading to the recovery of the G-quadruplex DNAzyme. The color and absorbance of the sensing system were also changed accordingly. In the optimizing condition, ΔA was directly proportional to the concentration ranging from 8.84 nM to 1.0 μM for Hg(2+), and 7.82 nM to 0.462 μM for MTs with the detection limits of 2.65 nM and 2.34 nM, respectively. The proposed dual-channel method avoids the label steps in common methods, and allows direct analysis of the samples without costly instruments, and is reliable, inexpensive and sensitive. Copyright © 2015 Elsevier B.V. All rights reserved.

  17. Dual-loss-modulated Q-switched mode-locked laser intracavity pumped temperature-tuned subnanosecond KTiOPO4 optical parametric oscillator.

    PubMed

    Chu, Hongwei; Zhao, Jia; Yang, Kejian; Zhao, Shengzhi; Li, Dechun; Li, Tao; Li, Guiqiu; Qiao, Wenchao

    2015-12-10

    Using an acousto-optic modulator (AOM) and Cr4+:YAG as the dual-loss modulation, an intracavity KTiOPO4 optical parametric oscillator (OPO) pumped by a simultaneously Q-switched and mode-locked (QML) YVO4/Nd:YVO4 laser was realized. The shortest mode-locking pulse duration of the signal wave at 1573 nm was directly measured as 450 ps at an AOM frequency of 2 kHz and a diode pump power of 10.5 W, corresponding to a peak power of 35.5 kW. The temperature tuning of the output signal wavelength was realized in the range from 1571.99 to 1572.61 nm with a blueshift ratio of 0.027  nm/°C. A set of coupled rate equations for the dual-loss-modulated QML laser pumping intracavity OPO was built for the first time to our knowledge. The numerical solutions were fitted with the experimental results.

  18. Non-mechanical optical path switching and its application to dual beam spectroscopy including gas filter correlation radiometry

    NASA Technical Reports Server (NTRS)

    Sachse, Glen W. (Inventor); Wang, Liang-Guo (Inventor)

    1992-01-01

    A non-mechanical optical switch is developed for alternately switching a monochromatic or quasi-monochromatic light beam along two optical paths. A polarizer polarizes light into a single, e.g., vertical component which is then rapidly modulated into vertical and horizontal components by a polarization modulator. A polarization beam splitter then reflects one of these components along one path and transmits the other along the second path. In the specific application of gas filter correlation radiometry, one path is directed through a vacuum cell and one path is directed through a gas correlation cell containing a desired gas. Reflecting mirrors cause these two paths to intersect at a second polarization beam splitter which reflects one component and transmits the other to recombine them into a polarization modulated beam which can be detected by an appropriate single sensor.

  19. Idler-resonant intracavity KTA-based OPO pumped by a dual-loss modulated-Q-switched-laser with AOM and Cr4+:YAG

    NASA Astrophysics Data System (ADS)

    Qiao, Junpeng; Zhao, Shengzhi; Yang, Kejian; Zhao, Jia; Li, Guiqiu; Li, Dechun; Li, Tao; Qiao, Wenchao

    2017-06-01

    An idler-resonant KTiOAsO4 (KTA)-based intracavity optical parametric oscillator (IOPO) pumped by a dual-loss-modulated Q-switched laser with an acousto-optic modulator (AOM) and a Cr4+:YAG saturable absorber (Cr4+:YAG-SA) has been presented. By utilizing a type-II non-critically phase-matched KTA crystal, signal wave at 1535 nm and idler wave at 3467 nm have been generated. Under an incident pump power of 18.3 W, maximum output powers of 615 mW for signal wave and 228 mW for idler wave were obtained at an AOM modulation rate of 10 kHz, corresponding to a whole optical-to-optical conversion efficiency of 4.6%. The shortest pulse widths of signal and idler wave were measured to be 898 ps and 2.9 ns, corresponding to the highest peak powers of 68.4 and 7.9 kW, respectively. In comparison with IOPO pumped by a singly Q-switched laser with an AOM, the IOPO pumped by a doubly Q-switched laser (DIOPO) with an AOM and a Cr4+:YAG-SA can generate signal wave and idler wave with shorter pulse width and higher peak power. By considering the spatial Gaussian distribution of intracavity photon density, a set of coupled rate equations for the idler-resonant DIOPO were built for the first time to the best of our knowledge. The simulation results agreed well with the experimental results.

  20. Appearance and Frequency of Gas Interface Artifacts Involving Small Bowel on Rapid-Voltage-Switching Dual-Energy CT Iodine-Density Images.

    PubMed

    Wu, En-Haw; Kim, So Yeon; Wang, Z Jane; Chang, Wei-Chou; Zhao, Li-Qin; Yeh, Benjamin M

    2016-02-01

    The purpose of this study is to describe the appearance and frequency of gas interface artifacts in the jejunum that may mimic severe bowel disease on iodine-density images generated from rapid-voltage-switching dual-energy CT (DECT) scans. Two readers retrospectively reviewed 108 consecutive abdominal rapid-voltage-switching DECT scans to record the presence of image artifacts in jejunal segments with different degrees of gaseous luminal filling, classified as full, partial, or absent. Readers viewed iodine-density images and corresponding 140-kVp and 65-keV virtual monochromatic images and classified the jejunal artifacts on iodine-density images as pseudostratified appearance of the bowel wall, pseudopneumatosis, pseudohyperenhancement, or pseudohypoenhancement. We correlated the presence of the artifacts with clinical features suggesting bowel disease. Image artifacts were found in 91 of 108 scans (84.3%), appeared in 148 of 265 jejunal segments (55.8%), and included each type except for pseudohypoenhancement. Artifacts occurred exclusively when gas was present in the bowel lumen and were seen in 59 of 59 (100%) fully gas-distended segments, 89 of 98 (90.8%) partially gas-distended segments, and none of 108 gas-absent segments (p < 0.0001). In fully and partially gas-distended jejunal segments (n = 157), 148 (94.3%) segments had two or more artifacts. None of the patients was found to have clinical bowel-related injury on follow-up of medical records. Pseudostratified appearance, pseudopneumatosis, and pseudohyperenhancement, but not pseudohypoenhancement, artifacts are common in gas-filled jejunal segments on iodine-density images generated from rapid-voltage-switching DECT scans and are not seen in the corresponding 140-kVp or 65-keV images. Knowledge of the appearance of such iodine-density image artifacts will avoid potential examination interpretation pitfalls.

  1. Appearance and Frequency of Gas Interface Artifacts Involving Small Bowel on Rapid-Voltage-Switching Dual-Energy CT Iodine-Density Images

    PubMed Central

    Wu, En-Haw; Kim, So Yeon; Wang, Z. Jane; Chang, Wei-Chou; Zhao, Li-Qin; Yeh, Benjamin M.

    2016-01-01

    OBJECTIVE The purpose of this study is to describe the appearance and frequency of gas interface artifacts in the jejunum that may mimic severe bowel disease on iodine-density images generated from rapid-voltage-switching dual-energy CT (DECT) scans. MATERIALS AND METHODS Two readers retrospectively reviewed 108 consecutive abdominal rapid-voltage-switching DECT scans to record the presence of image artifacts in jejunal segments with different degrees of gaseous luminal filling, classified as full, partial, or absent. Readers viewed iodine-density images and corresponding 140-kVp and 65-keV virtual monochromatic images and classified the jejunal artifacts on iodine-density images as pseudostratified appearance of the bowel wall, pseudopneumatosis, pseudohyperenhancement, or pseudohypoenhancement. We correlated the presence of the artifacts with clinical features suggesting bowel disease. RESULTS Image artifacts were found in 91 of 108 scans (84.3%), appeared in 148 of 265 jejunal segments (55.8%), and included each type except for pseudohypoenhancement. Artifacts occurred exclusively when gas was present in the bowel lumen and were seen in 59 of 59 (100%) fully gas-distended segments, 89 of 98 (90.8%) partially gas-distended segments, and none of 108 gas-absent segments (p < 0.0001). In fully and partially gas-distended jejunal segments (n = 157), 148 (94.3%) segments had two or more artifacts. None of the patients was found to have clinical bowel-related injury on follow-up of medical records. CONCLUSION Pseudostratified appearance, pseudopneumatosis, and pseudohyperenhancement, but not pseudohypoenhancement, artifacts are common in gas-filled jejunal segments on iodine-density images generated from rapid-voltage-switching DECT scans and are not seen in the corresponding 140-kVp or 65-keV images. Knowledge of the appearance of such iodine-density image artifacts will avoid potential examination interpretation pitfalls. PMID:26797356

  2. Effectiveness, Safety, and Costs of a Treatment Switch to Dolutegravir Plus Rilpivirine Dual Therapy in Treatment-Experienced HIV Patients.

    PubMed

    Revuelta-Herrero, José Luis; Chamorro-de-Vega, Esther; Rodríguez-González, Carmen Guadalupe; Alonso, Roberto; Herranz-Alonso, Ana; Sanjurjo-Sáez, María

    2017-08-01

    Evidence about the use of dolutegravir (DTG) and rilpivirine (RPV) as an antiretroviral therapy (ART) in treatment-experienced patients is scarce. To explore the effectiveness, safety, and costs of switching to a DTG plus RPV regimen in this population. This observational, prospective study included all treatment-experienced patients who switched to DTG plus RPV between November 2014 and July 2016. Patients were excluded if resistance mutations to integrase inhibitors or RPV were found. The effectiveness endpoint was the proportion of patients who achieved virological suppression (viral load [VL] <50 copies/mL) at week 48 (W48). Safety (incidence of adverse events leading to discontinuation and laboratory abnormalities), adherence, and costs were analyzed. A total of 35 patients were included, and 91.4% were virologically suppressed at baseline. Patients were treated with ART for a median of 14 years (interquartile range = 7-20). At W48, 91.4% of patients were virologically suppressed (95% CI = 77.0-98.2). Two of the 3 patients not suppressed at baseline achieved undetectable VL at W48, and 2 patients discontinued DTG plus RPV (intolerance and a drug-drug interaction). None of the virologically suppressed patients at baseline showed virological rebound through W48. There were no significant changes in lipid, liver, and renal profiles. The proportion of patients with an ART adherence >90% increased from 65.6% to 93.8% ( P = 0.004). The annual per-patient ART costs dropped by €665 ( P = 0.265). Switching to DTG plus RPV seems to be an effective and safe strategy. Significant improvements in patients' adherence and costs were achieved.

  3. Smectic A Filled Birefringent Elements and Fast Switching Twisted Dual Frequency Nematic Cells Used for Digital Light Deflection

    NASA Technical Reports Server (NTRS)

    Pishnyak, Oleg; Golovin, Andrii; Kreminskia, Liubov; Pouch, John J.; Miranda, Felix A.; Winker, Bruce K.; Lavrentovich, Oleg D.

    2006-01-01

    We describe the application of smectic A (SmA) liquid crystals for beam deflection. SmA materials can be used in digital beam deflectors (DBDs) as fillers for passive birefringent prisms. SmA prisms have high birefringence and can be constructed in a variety of shapes, including single prisms and prismatic blazed gratings of different angles and profiles. We address the challenges of uniform alignment of SmA, such as elimination of focal conic domains. Fast rotation of the incident light polarization in DBDs is achieved by an electrically switched 90 twisted nematic (TN) cell.

  4. Comparative study of dual-pulsed 1064 nm Q-switched Nd:YAG laser and single-pulsed 1064 nm Q-switched Nd:YAG laser by using zebrafish model and prospective split-face analysis of facial melasma.

    PubMed

    Jang, Hee Won; Chun, Seung Hyun; Park, Hae Chul; Ryu, Hwa Jung; Kim, Il-Hwan

    2017-04-01

    Recently dual-pulsed low-fluence 1064-nm Q-switched Nd:YAG (QSNY) laser has been developed for reducing complication during melasma treatment. Comparison of the efficacy and safety between dual-pulsed mode and single-pulsed mode for the treatment of melasma. In preclinical study, adult zebrafish were irradiated with dual-pulsed and single-pulsed mode. Changes of melanophore and cell death were assessed. In split-face clinical study, dual-pulsed and single-pulsed mode were irradiated on the left and right side of the face, respectively. L* value, clinical digital photos, modified Melasma Area and Severity Index (MASI) scores, and side effects were measured. As compared to single-pulsed mode and dual-pulsed mode with longer intervals, zebrafish melanophore was cleared quickly at dual-pulsed mode with 80-μsec interval and 0.3 J/cm(2) fluence. Dual-pulsed mode showed the least regeneration of melanophore at 4 weeks after irradiation and no cell death was observed with 80-μsec interval. Both pulse modes improved melasma significantly but modified MASI score and L* value were not significantly different between each other. Lesser pain and shorter duration of post-laser erythema were observed with dual-pulsed mode. Dual-pulsed mode was as effective as single-pulsed mode for the treatment of melasma and revealed less side effects.

  5. Stable narrow spacing dual-wavelength Q-switched graphene oxide embedded in a photonic crystal fiber

    NASA Astrophysics Data System (ADS)

    Ahmad, H.; Soltanian, M. R. K.; Alimadad, M.; Harun, S. W.

    2014-10-01

    An ultra-stable dual-wavelength saturable absorber based on a cladding-embedded commercial graphene oxide (GO) solution by capillary action in a solid core photonic crystal fiber (PCF) is demonstrated for the first time. The saturation absorption property is achieved through evanescent coupling between the guided light and the cladding-filled graphene layers. Stable spacing dual-wavelength fiber lasing is attained by controlling the polarization state of a simple 0.9 m long ring of highly doped Leikki Er80-8/125 erbium-doped fiber as the primary gain medium with PCF, polarization controller and tunable bandpass filter. Embedded GO is used to generate the desired pulsed output, and the laser is capable of generating pulses having a repetition rate of 24 kHz with an average output power and pulse energy of 0.167 mW and 8.98 nJ, respectively, at the maximum pump power of 220 mW.

  6. Dual therapy with darunavir/r plus etravirine is safe and effective as switching therapy in antiretroviral experienced HIV-patients. The BITER Study.

    PubMed

    Portilla, Joaquín; Arazo, Piedad; Crusells, Josefa; Pérez-Martínez, Laura; Martínez-Madrid, Onofre; Boix, Vicente; Moreno, Javier; Navarro, Vicente; Rubio, Teresa; Reus, Sergio; Galera, Carlos; Bernal, Enrique; Jover, Francisco; Amador, Concepcion; Baño, David; Merino, Esperanza; Saiz-de-la-Hoya, Pablo

    2014-01-01

    between baseline and week 24. Estimated glomerular filtrate rate increased from 83.4±24.7 to 88.5±56.8 mL/min, p=NS. Regarding reason to switching, it improved in 42 cases, no changes: 20 cases; worsened: 4 cases, and non-applicable or unknown: 24 cases. Switching to dual therapy with DRV/r+ETR is an effective strategy in selected heavily experienced ART patients, even in those with LLV (<1000 cop/mL). This cART is safe and well tolerated, can reduce number of pills and improve adherence.

  7. Dual therapy with darunavir/r plus etravirine is safe and effective as switching therapy in antiretroviral experienced HIV-patients. The BITER Study

    PubMed Central

    Portilla, Joaquín; Arazo, Piedad; Crusells, Josefa; Pérez-Martínez, Laura; Martínez-Madrid, Onofre; Boix, Vicente; Moreno, Javier; Navarro, Vicente; Rubio, Teresa; Reus, Sergio; Galera, Carlos; Bernal, Enrique; Jover, Francisco; Amador, Concepcion; Baño, David; Merino, Esperanza; Saiz-de-la-Hoya, Pablo

    2014-01-01

    any significant difference in lab parameters between baseline and week 24. Estimated glomerular filtrate rate increased from 83.4±24.7 to 88.5±56.8 mL/min, p=NS. Regarding reason to switching, it improved in 42 cases, no changes: 20 cases; worsened: 4 cases, and non-applicable or unknown: 24 cases. Conclusions Switching to dual therapy with DRV/r+ETR is an effective strategy in selected heavily experienced ART patients, even in those with LLV (<1000 cop/mL). This cART is safe and well tolerated, can reduce number of pills and improve adherence. PMID:25397547

  8. Evaluation of image quality of coronary artery plaque with rapid kVp-switching dual-energy CT.

    PubMed

    Ohta, Yasutoshi; Kitao, Shinichiro; Watanabe, Tomomi; Kishimoto, Junichi; Yamamoto, Kazuhiro; Ogawa, Toshihide

    2017-02-01

    We evaluated the virtual monochromatic imaging (VMI) energy levels that maximize image quality of each coronary plaque component in dual-energy computed tomography angiography in 495 coronary segments (45 for each energy level). Maximal signal-to-noise ratios were different for plaque, lumen, fat, and surrounding tissue (p<0.05). Maximal contrast-to-noise ratios were observed at 70keV for calcified plaque (CP), non-calcified plaque (NCP), and fat in comparison with the lumen (p<0.05), and 70keV and 120keV for NCP in comparison with fat (p=0.144). VMI demonstrated maximal image quality at different energy levels for each component of coronary artery plaque.

  9. Electric-field control of tri-state phase transformation with a selective dual-ion switch.

    PubMed

    Lu, Nianpeng; Zhang, Pengfei; Zhang, Qinghua; Qiao, Ruimin; He, Qing; Li, Hao-Bo; Wang, Yujia; Guo, Jingwen; Zhang, Ding; Duan, Zheng; Li, Zhuolu; Wang, Meng; Yang, Shuzhen; Yan, Mingzhe; Arenholz, Elke; Zhou, Shuyun; Yang, Wanli; Gu, Lin; Nan, Ce-Wen; Wu, Jian; Tokura, Yoshinori; Yu, Pu

    2017-06-01

    Materials can be transformed from one crystalline phase to another by using an electric field to control ion transfer, in a process that can be harnessed in applications such as batteries, smart windows and fuel cells. Increasing the number of transferrable ion species and of accessible crystalline phases could in principle greatly enrich material functionality. However, studies have so far focused mainly on the evolution and control of single ionic species (for example, oxygen, hydrogen or lithium ions). Here we describe the reversible and non-volatile electric-field control of dual-ion (oxygen and hydrogen) phase transformations, with associated electrochromic and magnetoelectric effects. We show that controlling the insertion and extraction of oxygen and hydrogen ions independently of each other can direct reversible phase transformations among three different material phases: the perovskite SrCoO3-δ (ref. 12), the brownmillerite SrCoO2.5 (ref. 13), and a hitherto-unexplored phase, HSrCoO2.5. By analysing the distinct optical absorption properties of these phases, we demonstrate selective manipulation of spectral transparency in the visible-light and infrared regions, revealing a dual-band electrochromic effect that could see application in smart windows. Moreover, the starkly different magnetic and electric properties of the three phases-HSrCoO2.5 is a weakly ferromagnetic insulator, SrCoO3-δ is a ferromagnetic metal, and SrCoO2.5 is an antiferromagnetic insulator-enable an unusual form of magnetoelectric coupling, allowing electric-field control of three different magnetic ground states. These findings open up opportunities for the electric-field control of multistate phase transformations with rich functionalities.

  10. Qualitative Comparison of Noncontrast Head Dual-Energy Computed Tomography Using Rapid Voltage Switching Technique and Conventional Computed Tomography.

    PubMed

    Hwang, William D; Mossa-Basha, Mahmud; Andre, Jalal B; Hippe, Daniel S; Culbertson, Scott; Anzai, Yoshimi

    2016-01-01

    Dual-energy computed tomography (DECT) allows image reconstruction along a spectrum of virtual monochromatic energy levels. We sought to determine the optimal energy level(s) for viewing supratentorial brain and posterior fossa and compare those to polychromatic conventional CT (CCT). Furthermore, we compared 2 groups scanned with separate DECT imaging protocols. In addition, we quantify the radiation dose of DECT versus CCT. Forty-four nonacute patients underwent noncontrast DECT and recent CCT on the same scanner. Dual-energy CT images of the head were reconstructed at 5 keV intervals from 50 to 100 keV and randomized with CCT for blinded reader analysis. Evaluation of gray-white matter differentiation, posterior fossa artifact, and overall image noise was performed in consensus using a 5-point scale. In addition, the CTDIvol was compared with CCT examinations. Optimal monochromatic viewing levels in evaluating gray-white matter differentiation were 50 to 55 keV and 50 to 60 keV, using regular-dose DECT (R-DECT) and low-dose DECT (L-DECT), respectively. The optimal levels for mitigating posterior fossa artifacts were 80 to 100 keV utilizing both R-DECT and L-DECT, whereas the optimal viewing levels for improved overall image noise were 60 to 65 keV and 65 to 70 keV for R-DECT and L-DECT, respectively. Readers favored both DECT techniques over CCT. The CTDIvol for DECT was 10% and 37% lower than CCT without a statistically significant reduction in image quality. Optimized noncontrast DECT compared favorably to CCT, with a significant dose reduction benefit.

  11. Electric-field control of tri-state phase transformation with a selective dual-ion switch

    NASA Astrophysics Data System (ADS)

    Lu, Nianpeng; Zhang, Pengfei; Zhang, Qinghua; Qiao, Ruimin; He, Qing; Li, Hao-Bo; Wang, Yujia; Guo, Jingwen; Zhang, Ding; Duan, Zheng; Li, Zhuolu; Wang, Meng; Yang, Shuzhen; Yan, Mingzhe; Arenholz, Elke; Zhou, Shuyun; Yang, Wanli; Gu, Lin; Nan, Ce-Wen; Wu, Jian; Tokura, Yoshinori; Yu, Pu

    2017-06-01

    Materials can be transformed from one crystalline phase to another by using an electric field to control ion transfer, in a process that can be harnessed in applications such as batteries, smart windows and fuel cells. Increasing the number of transferrable ion species and of accessible crystalline phases could in principle greatly enrich material functionality. However, studies have so far focused mainly on the evolution and control of single ionic species (for example, oxygen, hydrogen or lithium ions). Here we describe the reversible and non-volatile electric-field control of dual-ion (oxygen and hydrogen) phase transformations, with associated electrochromic and magnetoelectric effects. We show that controlling the insertion and extraction of oxygen and hydrogen ions independently of each other can direct reversible phase transformations among three different material phases: the perovskite SrCoO3-δ (ref. 12), the brownmillerite SrCoO2.5 (ref. 13), and a hitherto-unexplored phase, HSrCoO2.5. By analysing the distinct optical absorption properties of these phases, we demonstrate selective manipulation of spectral transparency in the visible-light and infrared regions, revealing a dual-band electrochromic effect that could see application in smart windows. Moreover, the starkly different magnetic and electric properties of the three phases—HSrCoO2.5 is a weakly ferromagnetic insulator, SrCoO3-δ is a ferromagnetic metal, and SrCoO2.5 is an antiferromagnetic insulator—enable an unusual form of magnetoelectric coupling, allowing electric-field control of three different magnetic ground states. These findings open up opportunities for the electric-field control of multistate phase transformations with rich functionalities.

  12. The conserved dual phosphorylation sites of the Candida albicans Hog1 protein are crucial for white-opaque switching, mating, and pheromone-stimulated cell adhesion.

    PubMed

    Chang, Wen-Han; Liang, Shen-Huan; Deng, Fu-Sheng; Lin, Ching-Hsuan

    2016-08-01

    Candida albicans is an opportunistic human pathogen capable of causing life-threatening infections in immunocompromised patients. C. albicans has a unique morphological transition between white and opaque phases. These two cells differ in virulence, mating capability, biofilm formation, and host-cell interaction. Previous studies revealed that deletion of the SSK2, PBS2, or HOG1 gene resulted in 100% opaque cell formation and suppressed the mating response. Thr-174 and Tyr-176 of the Hog1 protein are important phosphoacceptors and can be activated in response to stimuli. In this study, we first demonstrated the importance of two conserved phosphorylation sites in white-opaque switching, mating, and pheromone-stimulated cell adhesion. Six Hog1 point-mutated strains were generated, including nonphosphorylated strains (Hog1(T174A), Hog1(Y176F), and Hog1(T174A,Y176F)) and negatively charged phosphorylated strains (Hog1(T174D), Hog1(Y176D), and Hog1(T174D,Y176D)). Point mutation on Thr-174, Tyr-176 or in combination with the Hog1 protein in C. albicans MTL homozygous strains stimulated opaque cell formation at a frequency of 100%. Furthermore, mating projections of point-mutated strains were significantly shorter and their mating efficiencies and pheromone-stimulated cell adhesive numbers were lower than those of the wild-type. By investigating the effects of Hog1 phosphorylation in ssk1Δ and sln1Δ, we also demonstrate that the phosphorylation intensity of Hog1p is directly involved in the white-opaque switching. Taken together, the results of our study demonstrate that dual phosphorylation sites of C. albicans are crucial for white-opaque transition, sexual mating, and pheromone-induced cell adhesion.

  13. Relative dose in dual energy fast-kVp switching and conventional kVp imaging: spatial frequency dependent noise characteristics and low contrast imaging

    NASA Astrophysics Data System (ADS)

    Yadava, Girijesh K.; Chandra, Naveen; Hsieh, Jiang

    2011-03-01

    Dual energy computed tomography offers unique diagnostic value by enabling access to material density, effective atomic number, and energy specific spectral characteristics, which remained indeterminate with conventional kVp imaging. Gemstone Spectral Imaging (GSI) is one of the dual energy methods based on fast kVp switching between two x-ray spectra, 80 kVp and 140 kVp nominal, in adjacent projections. The purpose of this study was to compare relative dose between GSI monochromatic and conventional kVp imaging for equivalent image noise characteristics. A spatialfrequency domain noise power spectrum (NPS) was used as a more complete noise descriptor for the comparison of the two image types. Uniform 20cm water phantom images from GSI and conventional 120 kVp scans were used for NPS calculation. In addition, a low contrast imaging study of the two image types with equivalent noise characteristics was conducted for contrast-to-noise-ratio (CNR) and low contrast detectability (LCD) in the Catphan600® phantom. From three GSI presets ranging from medium to low dose, we observed that conventional 120kVp scan requires ~ 7% - 18% increase in dose to match the noise characteristics in optimal noise GSI monochromatic image; and that the 65 keV monochromatic image CNR for a 0.5% contrast object is 22% higher compared to corresponding 120 kVp scan. Optimal use of the two energy spectra within GSI results in reduced noise and improved CNR in the monochromatic images, indicating the potential for use of this image type in routine clinical applications.

  14. Performance Evaluation of Material Decomposition With Rapid-Kilovoltage-Switching Dual-Energy CT and Implications for Assessing Bone Mineral Density.

    PubMed

    Wait, John M S; Cody, Dianna; Jones, Aaron K; Rong, John; Baladandayuthapani, Veerabhadran; Kappadath, S Cheenu

    2015-06-01

    The purpose of this article is to quantitatively investigate the accuracy and performance of dual-energy CT (DECT) material density images and to calculate the areal bone mineral density (aBMD) for comparison with dual-energy x-ray absorptiometry (DEXA). A rapid-kilovoltage-switching DECT scanner was used to create material density images of various two-material phantoms of known concentrations under different experimental conditions. They were subsequently also scanned by single-energy CT and DEXA. The total uncertainty and accuracy of the DECT concentration measurements was quantified by the root-mean-square (RMS) error, and linear regression was performed to evaluate measurement changes under varying scanning conditions. Alterations to accuracy with concentric (anthropomorphic) phantom geometry were explored. The sensitivity of DECT and DEXA to changes in material density was evaluated. Correlations between DEXA and DECT-derived aBMD values were assessed. The RMS error of DECT concentration measurements in air ranged from 9% to 244% depending on the materials. Concentration measurements made off-isocenter or with a different DECT protocol were slightly lower (≈ 5%), whereas measurement in scattering conditions resulted in a reduction of 8-27%. In concentric phantoms, higher-attenuating material in the outer chamber increased measured values of the inner material for all methods. DECT was more sensitive than DEXA to changes in BMD at 2 mg/mL K2HPO4. Measurements of aBMD using DECT and DEXA were highly correlated (R(2) = 0.98). DECT material density images were linear in response but prone to poor accuracy and biases. DECT-based aBMD could be used to monitor relative change in bone density.

  15. Dual Labeling Biotin Switch Assay to Reduce Bias Derived from Different Cysteine Subpopulations: A Method to Maximize S-Nitrosylation Detection

    PubMed Central

    Chung, Heaseung Sophia; Murray, Christopher I.; Venkatraman, Vidya; Crowgey, Erin L.; Rainer, Peter P.; Cole, Robert N.; Bomgarden, Ryan D.; Rogers, John C.; Balkan, Wayne; Hare, Joshua M.; Kass, David A.; Van Eyk, Jennifer E.

    2016-01-01

    Rationale S-nitrosylation (SNO), an oxidative post-translational modification of cysteine residues, responds to changes in the cardiac redox-environment. Classic biotin switch assay and its derivatives are the most common methods used for detecting SNO. In this approach, the labile SNO group is selectively replaced with a single stable tag. To date, a variety of thiol-reactive tags have been introduced. However, these methods have not produced a consistent dataset which suggests an incomplete capture by a single tag and potentially the presence of different cysteine subpopulations. Objective To investigate potential labeling bias in the existing methods with a single tag to detect SNO, explore if there are distinct cysteine subpopulations, and then, develop a strategy to maximize the coverage of SNO proteome. Methods and Results We obtained SNO-modified cysteine datasets for wild-type and S-nitrosoglutathione reductase (GSNOR) knock-out mouse hearts (GSNOR is a negative regulator of GSNO production) and NO-induced human embryonic kidney cell using two labeling reagents; the cysteine-reactive pyridyldithiol and iodoacetyl based tandem mass tags. Comparison revealed that <30% of the SNO-modified residues were detected by both tags, while the remaining SNO sites were only labeled by one reagent. Characterization of the two distinct subpopulations of SNO residues indicated that pyridyldithiol reagent preferentially labels cysteine residues that are more basic and hydrophobic. Based on this observation, we proposed a parallel dual labeling strategy followed by an optimized proteomics workflow. This enabled the profiling of 493 SNO-sites in GSNOR knock-out hearts. Conclusions Using a protocol comprising two tags for dual labeling maximizes overall detection of SNO by reducing the previously unrecognized labeling bias derived from different cysteine subpopulations. PMID:26338901

  16. A dual-loss-modulated Q-switched and mode-locked Nd:GdVO4 laser with AOM and V3 + :YAG saturable absorber at 1.34 µm

    NASA Astrophysics Data System (ADS)

    Zhang, Gang; Zhao, Shengzhi; Li, Yufei; Li, Guiqiu; Li, Dechun; Yang, Kejian; Cheng, Kang

    2011-03-01

    Stable and robust pulses can be generated in a diode-pumped Q-switched and mode-locked (QML) c-cut Nd:GdVO4/V3 + :YAG laser at 1.34 µm by inserting an acousto-optic modulator (AOM) into the laser cavity. In this kind of dual-loss-modulation QML laser, the pulse width of the Q-switched pulse envelope has a compression of 68% and the pulse energy has an improvement of seven times compared with that in the solely passively QML laser with V3 + :YAG. By considering the influence of the turnoff time and the modulation frequency of the AOM as well as the thermal lens effect, a developed rate equation model for dual-loss-modulation QML lasers is given and the numerical solutions of the rate equations are in good agreement with the experimental results.

  17. Dual regulatory switch through interactions of Tcf7l2/Tcf4 with stage-specific partners propels oligodendroglial maturation

    PubMed Central

    Zhao, Chuntao; Deng, Yaqi; Liu, Lei; Yu, Kun; Zhang, Liguo; Wang, Haibo; He, Xuelian; Wang, Jincheng; Lu, Changqing; Wu, Laiman N; Weng, Qinjie; Mao, Meng; Li, Jianrong; van Es, Johan H; Xin, Mei; Parry, Lee; Goldman, Steven A; Clevers, Hans; Lu, Q. Richard

    2016-01-01

    Constitutive activation of Wnt/β-catenin inhibits oligodendrocyte myelination. Tcf7l2/Tcf4, a β-catenin transcriptional partner, is required for oligodendrocyte differentiation. How Tcf7l2 modifies β-catenin signalling and controls myelination remains elusive. Here we define a stage-specific Tcf7l2-regulated transcriptional circuitry in initiating and sustaining oligodendrocyte differentiation. Multistage genome occupancy analyses reveal that Tcf7l2 serially cooperates with distinct co-regulators to control oligodendrocyte lineage progression. At the differentiation onset, Tcf7l2 interacts with a transcriptional co-repressor Kaiso/Zbtb33 to block β-catenin signalling. During oligodendrocyte maturation, Tcf7l2 recruits and cooperates with Sox10 to promote myelination. In that context, Tcf7l2 directly activates cholesterol biosynthesis genes and cholesterol supplementation partially rescues oligodendrocyte differentiation defects in Tcf712 mutants. Together, we identify stage-specific co-regulators Kaiso and Sox10 that sequentially interact with Tcf7l2 to coordinate the switch at the transitions of differentiation initiation and maturation during oligodendrocyte development, and point to a previously unrecognized role of Tcf7l2 in control of cholesterol biosynthesis for CNS myelinogenesis. PMID:26955760

  18. Fast kVp-switching dual energy contrast-enhanced thorax and cardiac CT: A phantom study on the accuracy of iodine concentration and effective atomic number measurement.

    PubMed

    Papadakis, Antonios E; Damilakis, John

    2017-09-01

    To assess the effect of vessel diameter and exposure parameters on the estimation accuracy of concentration and effective atomic number (Zeff ) of iodine (I) in contrast-enhanced thorax and cardiac dual-energy CT using a modern fast kVp-switching CT scanner. A standard semi-anthropomorphic cardiac CT phantom devised to simulate the human chest at three different body habitus i.e., medium-sized, large-sized, and obese, was scanned using a fast kVp-switching Revolution-GSI GE CT scanner. Five cylindrical, 10 mm diameter, vials were filled with solutions prepared by diluting I contrast at five concentrations (2.5, 5, 10, 15, and 20 mg I/ml). To simulate small vessels, pipette tips with a diameter ranging from 5 mm to 0.5 mm were employed. The vials and pipette tips were accommodated within the semi-anthropomorphic phantom. CT acquisitions were performed in the fast kVp-switching dual-energy mode at six different CTDIw values. Acquisitions were also performed at 80, 100, 120, and 140 kVp. Images were acquired at 64 × 0.625 mm beam collimation and reconstructed at 2.5 mm using all available reconstruction filter kernels. Virtual monochromatic spectral (VMS) images, iodine concentration (IMeas ), and Zeff maps were reconstructed. Hounsfield unit as a function of energy (HUkeV ) in VMS and single-kVp (HUkVp ), IMeas and Zeff were measured at each CTDIw . The effect of vessel diameter on IMeas and Zeff was investigated. Measured HUkeV and Zeff were compared to theoretically estimated values and IMeas were compared to nominal (INom ) values. In 10 mm diameter vessels, HUkeV values were accurate to 18% for the medium-sized, 22% for the large-sized and 39% for the obese phantoms. IMeas was underestimated by up to 10% for the medium-sized, 26% for the large-sized and 33% for the obese phantom. IMeas error decreased with increasing CTDIw from ±0.799 mg/ml at 8.61 mGy to ±0.082 mg/ml at 32.01 mGy. The percentage difference between measured and theoretically estimated Zeff

  19. Dual Circuitry for Odor–Shock Conditioning during Infancy: Corticosterone Switches between Fear and Attraction via Amygdala

    PubMed Central

    Moriceau, Stephanie; Wilson, Donald A.; Levine, Seymour; Sullivan, Regina M.

    2006-01-01

    Rat pups must learn maternal odor to support attachment behaviors, including nursing and orientation toward the mother. Neonates have a sensitive period for rapid, robust odor learning characterized by increased ability to learn odor preferences and decreased ability to learn odor aversions. Specifically, odor–0.5 mA shock association paradoxically causes an odor preference and coincident failure of amygdala activation in pups until postnatal day 10 (P10). Because sensitive-period termination coincides with a declining “stress hyporesponsive period” when corticosterone release is attenuated, we explored the role of corticosterone in sensitive-period termination. Odor was paired with 0.5 mA shock in either sensitive-period (P8) or postsensitive-period (P12) pups while manipulating corticosterone. We then assessed preference/aversion learning and the olfactory neural circuitry underlying its acquisition. Although sensitive-period control paired odor–shock pups learned an odor preference without amygdala participation, systemic (3 mg/kg, i.p.; 24 h and 30 min before training) or intra-amygdala corticosterone (50 or 100 ng; during training) permitted precocious odor-aversion learning and evoked amygdala neural activity similar to that expressed by older pups. In postsensitive-period (P12) pups, control paired odor–shock pups showed an odor aversion and amygdala activation, whereas corticosterone-depleted (adrenalectomized) paired odor–shock pups showed odor-preference learning and activation of an odor learning circuit characteristic of the sensitive period. Intra-amygdala corticosterone receptor antagonist (0.3 ng; during training) infused into postsensitive-period (P12) paired odor–shock pups also showed odor-preference learning. These results suggest corticosterone is important in sensitive-period termination and developmental emergence of olfactory fear conditioning, acting via the amygdala as a switch between fear and attraction. Because maternal

  20. Compound semiconductor optical waveguide switch

    DOEpatents

    Spahn, Olga B.; Sullivan, Charles T.; Garcia, Ernest J.

    2003-06-10

    An optical waveguide switch is disclosed which is formed from III-V compound semiconductors and which has a moveable optical waveguide with a cantilevered portion that can be bent laterally by an integral electrostatic actuator to route an optical signal (i.e. light) between the moveable optical waveguide and one of a plurality of fixed optical waveguides. A plurality of optical waveguide switches can be formed on a common substrate and interconnected to form an optical switching network.

  1. Electrostatically screened, voltage-controlled electrostatic chuck

    DOEpatents

    Klebanoff, Leonard Elliott

    2001-01-01

    Employing an electrostatically screened, voltage-controlled electrostatic chuck particularly suited for holding wafers and masks in sub-atmospheric operations will significantly reduce the likelihood of contaminant deposition on the substrates. The electrostatic chuck includes (1) an insulator block having a outer perimeter and a planar surface adapted to support the substrate and comprising at least one electrode (typically a pair of electrodes that are embedded in the insulator block), (2) a source of voltage that is connected to the at least one electrode, (3) a support base to which the insulator block is attached, and (4) a primary electrostatic shield ring member that is positioned around the outer perimeter of the insulator block. The electrostatic chuck permits control of the voltage of the lithographic substrate; in addition, it provides electrostatic shielding of the stray electric fields issuing from the sides of the electrostatic chuck. The shielding effectively prevents electric fields from wrapping around to the upper or front surface of the substrate, thereby eliminating electrostatic particle deposition.

  2. Non-linear switching based on dual-core non-linear optical fiber couplers with XPM and Raman intrapulse applied to femtosecond pulse propagation

    NASA Astrophysics Data System (ADS)

    Gonçalves Correia, Dayse; Viana Ávila, Kilvia Maria; Cavalcante, Daniel do Nascimento e. Sá; Ferreira Pinto, Paulo Victor; Tadeu de Carvalho Belchior Magalhães, Francisco; Pinheiro de Moura, Lucas; da Conceição Ferreira, Alisson; Mendonça Menezes, Jose Wally; de Freitas Guimarães, Glendo

    2016-03-01

    In this work, we investigated the optical switching process for three shapes of femtosecond pulses (soliton, Gaussian and super-Gaussian) propagating inside a symmetrical dual-core non-linear directional coupler by simulating their propagation via the coupled non-linear Schrödinger equations. In all simulations, we considered the dispersive effects of second and third order, besides the self-phase modulation and self-steepening non-linear effects. We studied three scenarios for each of the three pulse shapes under investigation. In the first scenario, we added only cross-phase modulation (XPM); in the second approach, we added only Raman scattering; in the third one, we combined both. The study was performed for distinct polarization modes and for different values of the Raman factor, with power range varying from 1 to 300 W. We noted that the XPM non-linear effect results in a decrease in the critical power threshold, whereas the Raman scattering causes an increase. For the first scenario (only XPM effect), the critical power threshold reduced from 113.72 to 104.69 W for the soliton pulse, from 111.49 to 100.77 W for the Gaussian and from 92.79 to 80.47 W for the Super-Gaussian pulse shape. For the second scenario (only Raman scattering), the critical power increased for a Raman factor varying from 1 to 10 fs, and the three pulse shapes reached thresholds above 150 W from a 5 fs factor, reaching more than 200 W for the super-Gaussian pulse as the Raman factor increased. For the third scenario (with both effects combined), we highlight that for a fixed XPM factor of 2, the critical power remained unchanged with the variation of the Raman factor. Hence, we observed that the Super-Gaussian pulse reached lower values for critical power when compared to the other pulse shapes.

  3. Erected mirror optical switch

    DOEpatents

    Allen, James J.

    2005-06-07

    A microelectromechanical (MEM) optical switching apparatus is disclosed that is based on an erectable mirror which is formed on a rotatable stage using surface micromachining. An electrostatic actuator is also formed on the substrate to rotate the stage and mirror with a high angular precision. The mirror can be erected manually after fabrication of the device and used to redirect an incident light beam at an arbitrary angel and to maintain this state in the absence of any applied electrical power. A 1.times.N optical switch can be formed using a single rotatable mirror. In some embodiments of the present invention, a plurality of rotatable mirrors can be configured so that the stages and mirrors rotate in unison when driven by a single micromotor thereby forming a 2.times.2 optical switch which can be used to switch a pair of incident light beams, or as a building block to form a higher-order optical switch.

  4. Compact electrostatic comb actuator

    DOEpatents

    Rodgers, M. Steven; Burg, Michael S.; Jensen, Brian D.; Miller, Samuel L.; Barnes, Stephen M.

    2000-01-01

    A compact electrostatic comb actuator is disclosed for microelectromechanical (MEM) applications. The actuator is based upon a plurality of meshed electrostatic combs, some of which are stationary and others of which are moveable. One or more restoring springs are fabricated within an outline of the electrostatic combs (i.e. superposed with the moveable electrostatic combs) to considerably reduce the space required for the actuator. Additionally, a truss structure is provided to support the moveable electrostatic combs and prevent bending or distortion of these combs due to unbalanced electrostatic forces or external loading. The truss structure formed about the moveable electrostatic combs allows the spacing between the interdigitated fingers of the combs to be reduced to about one micron or less, thereby substantially increasing the number of active fingers which can be provided in a given area. Finally, electrostatic shields can be used in the actuator to substantially reduce unwanted electrostatic fields to further improve performance of the device. As a result, the compact electrostatic comb actuator of the present invention occupies only a fraction of the space required for conventional electrostatic comb actuators, while providing a substantial increase in the available drive force (up to one-hundred times).

  5. Kelvin transformation and inverse multipoles in electrostatics

    NASA Astrophysics Data System (ADS)

    Amaral, R. L. P. G.; Ventura, O. S.; Lemos, N. A.

    2017-03-01

    The inversion in the sphere or Kelvin transformation, which exchanges the radial coordinate for its inverse, is used as a guide to relate distinct electrostatic problems with dual features. The exact solution of some nontrivial problems are obtained through the mapping from simple highly symmetric systems. In particular, the concept of multipole expansion is revisited from a point of view opposed to the usual one: the sources are distributed in a region far from the origin while the electrostatic potential is described at points close to it.

  6. Intra-cavity frequency doubled Nd:YAG laser with dual-stability-range cavity emitting high power near-diffraction-limited radiation in CW and Q-switched mode

    NASA Astrophysics Data System (ADS)

    Woll, Dirk; Gregg, Jeffrey; Lefort, James; Morehead, James J.; Lindahl, Jennifer

    2010-02-01

    A diode-pumped frequency-doubled Nd:YAG laser has been demonstrated which emits 7.2 W of 532-nm radiation in the CW mode as well as 23 ns, 2.7 mJ pulses at a repetition rate of 10 kHz in the Q-switched mode. The high power in both modes was achieved by intra-cavity second harmonic generation in lithium triborate. The nonlinear output coupling through SHG in this laser causes a factor of 5.7 change of intra-cavity power between the CW and the Q-switched mode. The resulting variation of the thermal lens in the laser rod makes it challenging to maintain a geometrically stable cavity in both operation regimes, which is essential for diffraction limited beam quality. Diffraction limited beam quality with M2 values of less than 1.1 in the CW and less than 1.2 in the Q-switched regime was achieved by a novel dual-stabilityrange cavity-design. This design provides geometrically stable cavity configurations in both operation regimes, which are separated by an unstable region. This cavity makes it possible to switch between the two operation regimes without any moving components.

  7. A new type of DNA "light-switch": a dual photochemical sensor and metalating agent for duplex and G-quadruplex DNA.

    PubMed

    Wachter, Erin; Howerton, Brock S; Hall, Emily C; Parkin, Sean; Glazer, Edith C

    2014-01-11

    Ru(bpy)2dppz, a well studied "light-switch" metal complex, transforms into a photochemical "light-switch" and DNA damaging agent by incorporating structural strain. This distorted compound is photoreactive and ejects a ligand upon binding duplex and G-quadruplex DNA, producing a reactive metal center that metalates the DNA.

  8. DEPPDB - DNA electrostatic potential properties database. Electrostatic properties of genome DNA elements.

    PubMed

    Osypov, Alexander A; Krutinin, Gleb G; Krutinina, Eugenia A; Kamzolova, Svetlana G

    2012-04-01

    Electrostatic properties of genome DNA are important to its interactions with different proteins, in particular, related to transcription. DEPPDB - DNA Electrostatic Potential (and other Physical) Properties Database - provides information on the electrostatic and other physical properties of genome DNA combined with its sequence and annotation of biological and structural properties of genomes and their elements. Genomes are organized on taxonomical basis, supporting comparative and evolutionary studies. Currently, DEPPDB contains all completely sequenced bacterial, viral, mitochondrial, and plastids genomes according to the NCBI RefSeq, and some model eukaryotic genomes. Data for promoters, regulation sites, binding proteins, etc., are incorporated from established DBs and literature. The database is complemented by analytical tools. User sequences calculations are available. Case studies discovered electrostatics complementing DNA bending in E.coli plasmid BNT2 promoter functioning, possibly affecting host-environment metabolic switch. Transcription factors binding sites gravitate to high potential regions, confirming the electrostatics universal importance in protein-DNA interactions beyond the classical promoter-RNA polymerase recognition and regulation. Other genome elements, such as terminators, also show electrostatic peculiarities. Most intriguing are gene starts, exhibiting taxonomic correlations. The necessity of the genome electrostatic properties studies is discussed.

  9. Electrostatic Levitator Electrodes

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Electrostatic levitation system inside Electrostatic Levitator (ESL) vacuum chamber. The ESL uses static electricity to suspend an object (about 2-3 mm in diameter) inside a vacuum chamber while a laser heats the sample until it melts. This lets scientists record a wide range of physical properties without the sample contacting the container or any instruments, conditions that would alter the readings. The Electrostatic Levitator is one of several tools used in NASA's microgravity materials science program.

  10. Electrostatic Levitator Electrodes

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Electrostatic levitation system inside Electrostatic Levitator (ESL) vacuum chamber. The ESL uses static electricity to suspend an object (about 2-3 mm in diameter) inside a vacuum chamber while a laser heats the sample until it melts. This lets scientists record a wide range of physical properties without the sample contacting the container or any instruments, conditions that would alter the readings. The Electrostatic Levitator is one of several tools used in NASA's microgravity materials science program.

  11. ELECTROSTATIC POWER GENERATOR.

    DTIC Science & Technology

    ELECTROSTATIC GENERATORS , POWER EQUIPMENT, ELECTRIC GOVERNORS, CIRCUITS, VACUUM SEALS, ELECTRICAL INSULATION, VACUUM, ELECTRODES, FINISHES, SURFACE...FINISHING, SURFACE PROPERTIES, HARDNESS, PULSE GENERATORS , TRANSFORMERS, FIELD EMISSION.

  12. ELECTROSTATIC POWER GENERATOR.

    DTIC Science & Technology

    ELECTROSTATIC GENERATORS , POWER EQUIPMENT, ELECTRICAL INSULATION, FIELD EMISSION, ELECTRODES, VACUUM, SURFACE PROPERTIES, ANODES, CATHODES, POLISHES...DIELECTRICS, COATINGS, PRESSURE, HARDNESS, PULSE GENERATORS , TRANSFORMERS, VACUUM SEALS, EQUATIONS.

  13. Edutainment Science: Electrostatics

    ERIC Educational Resources Information Center

    Ahlers, Carl

    2009-01-01

    Electrostatics should find a special place in all primary school science curricula. It is a great learning area that reinforces the basics that underpin electricity and atomic structure. Furthermore, it has many well documented hands-on activities. Unfortunately, the "traditional" electrostatics equipment such as PVC rods, woollen cloths, rabbit…

  14. Electrostatic Levitator (ESL)

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Dr. Rulison of Space System LORAl working with the Electrostatic Levitation (ESL) prior to the donation. Space System/LORAL donated the electrostatic containerless processing system to NASA's Marshall Space Flight Center (MSFC). The official hand over took place in July 1998.

  15. Edutainment Science: Electrostatics

    ERIC Educational Resources Information Center

    Ahlers, Carl

    2009-01-01

    Electrostatics should find a special place in all primary school science curricula. It is a great learning area that reinforces the basics that underpin electricity and atomic structure. Furthermore, it has many well documented hands-on activities. Unfortunately, the "traditional" electrostatics equipment such as PVC rods, woollen cloths, rabbit…

  16. Thermal management and performance evaluation of a dual bi-directional, soft-switched IGBT-based inverter for the 1st autonomous microgrid power system in Taiwan under various operating conditions

    NASA Astrophysics Data System (ADS)

    Chang, Tien-Chan; Fuh, Yiin-Kuen; Lu, Hong-Yi; Tu, Sheng-Xun

    2016-06-01

    The thermal management of the inverter system is of great importance since very high voltage/current will be switched intermittently and/or continuously and high temperature is excruciably detrimental to the service life of electronics, especially for the switching devices such as insulated gate bipolar transistor (IGBT). In this study, a newly developed dual bi-directional IGBT-based inverter in conjunction with autonomous microgrid system is investigated with particular focus on the thermal management and performance evaluation under various operation conditions. Locally enhanced heat transfer approach such as oblique orientation and heat dissipating materials are experimentally investigated. The studied inverter system is initially packaged by a galvanized steel plate (size 62 × 48 × 18 cm) and the switching power is set in the range of 0.5-3 kW. The module is operated at the switching and pulse frequencies of 60 Hz and 20 kHz, respectively. The adoption of heat dissipating material in either paste or film form had experimentally shown to possess the flexibility tailoring heat transfer performance locally. Experimental studies of heat dissipating film with various hotspot scenarios showed that the temperature difference can be appreciably reduced as much as 13.1 and 15.4 °C, respectively with facilitation of one- and two-layers of heat dissipating film. From the measurement results, the measured peak temperature is highly dominated by the thickness of heat dissipating film, showing the dominance of thickness-dependent thermal resistance and resultant heat accumulation phenomena.

  17. Electrostatic Field Invisibility Cloak

    PubMed Central

    Lan, Chuwen; Yang, Yuping; Geng, Zhaoxin; Li, Bo; Zhou, Ji

    2015-01-01

    The invisibility cloak has been drawing much attention due to its new concept for manipulating many physical fields, from oscillating wave fields (electromagnetic, acoustic and elastic) to static magnetic fields, dc electric fields, and diffusive fields. Here, an electrostatic field invisibility cloak has been theoretically investigated and experimentally demonstrated to perfectly hide two dimensional objects without disturbing their external electrostatic fields. The desired cloaking effect has been achieved via both cancelling technology and transformation optics (TO). This study demonstrates a novel way for manipulating electrostatic fields, which shows promise for a wide range of potential applications. PMID:26552343

  18. Electrostatic Field Invisibility Cloak.

    PubMed

    Lan, Chuwen; Yang, Yuping; Geng, Zhaoxin; Li, Bo; Zhou, Ji

    2015-11-10

    The invisibility cloak has been drawing much attention due to its new concept for manipulating many physical fields, from oscillating wave fields (electromagnetic, acoustic and elastic) to static magnetic fields, dc electric fields, and diffusive fields. Here, an electrostatic field invisibility cloak has been theoretically investigated and experimentally demonstrated to perfectly hide two dimensional objects without disturbing their external electrostatic fields. The desired cloaking effect has been achieved via both cancelling technology and transformation optics (TO). This study demonstrates a novel way for manipulating electrostatic fields, which shows promise for a wide range of potential applications.

  19. The electrostatic storage tube

    NASA Technical Reports Server (NTRS)

    Rutherford, R. E., Jr.

    1973-01-01

    An electrostatic camera system is discussed which is based on the electrostatic storage tube. The development of the system was begun following a series of experiments which indicated that the device offers signficantly improved performance over currently available devices. The approach used in developing the high performance camera involves: converting the input image to an electron image at low loss, applying a low noise gain process, and storing the resulting charge pattern in a low-loss target. The basic processes and elements of the electrostatic storage tube are illustrated and discussed. Graphs that depict the camera performance characteristics are included.

  20. InGaAs/GaAs saturable absorber for diode-pumped passively Q-switched dual-wavelength Tm:YAP lasers.

    PubMed

    Yao, Baoquan; Tian, Yi; Li, Gang; Wang, Yuezhu

    2010-06-21

    We demonstrate the first use of InGaAs/GaAs as a saturable absorber in the Q-switching of a diode pumped Tm(3+) doped laser operating at the wavelengths of 1940 nm and 1986 nm. The influence of the semiconductor saturable absorber's (SESA) position and thermal lens effect on the Q-switch characteristics was investigated. With a pump power of 35 W, the maximum pulse energy of 28.1 microJ with a pulse width of 447 ns at the pulse repetition frequency (PRF) of 43.7 kHz was obtained by selecting the appropriate position of the SESA.

  1. Multimaterial Decomposition Algorithm for the Quantification of Liver Fat Content by Using Fast-Kilovolt-Peak Switching Dual-Energy CT: Clinical Evaluation.

    PubMed

    Hyodo, Tomoko; Yada, Norihisa; Hori, Masatoshi; Maenishi, Osamu; Lamb, Peter; Sasaki, Kosuke; Onoda, Minori; Kudo, Masatoshi; Mochizuki, Teruhito; Murakami, Takamichi

    2017-04-01

    Purpose To assess the clinical accuracy and reproducibility of liver fat quantification with the multimaterial decomposition (MMD) algorithm, comparing the performance of MMD with that of magnetic resonance (MR) spectroscopy by using liver biopsy as the reference standard. Materials and Methods This prospective study was approved by the institutional ethics committee, and patients provided written informed consent. Thirty-three patients suspected of having hepatic steatosis underwent non-contrast material-enhanced and triple-phase dynamic contrast-enhanced dual-energy computed tomography (CT) (80 and 140 kVp) and single-voxel proton MR spectroscopy within 30 days before liver biopsy. Percentage fat volume fraction (FVF) images were generated by using the MMD algorithm on dual-energy CT data to measure hepatic fat content. FVFs determined by using dual-energy CT and percentage fat fractions (FFs) determined by using MR spectroscopy were compared with histologic steatosis grade (0-3, as defined by the nonalcoholic fatty liver disease activity score system) by using Jonckheere-Terpstra trend tests and were compared with each other by using Bland-Altman analysis. Real non-contrast-enhanced FVFs were compared with triple-phase contrast-enhanced FVFs to determine the reproducibility of MMD by using Bland-Altman analyses. Results Both dual-energy CT FVF and MR spectroscopy FF increased with increasing histologic steatosis grade (trend test, P < .001 for each). The Bland-Altman plot of dual-energy CT FVF and MR spectroscopy FF revealed a proportional bias, as indicated by the significant positive slope of the line regressing the difference on the average (P < .001). The 95% limits of agreement for the differences between real non-contrast-enhanced and contrast-enhanced FVFs were not greater than about 2%. Conclusion The MMD algorithm quantifying hepatic fat in dual-energy CT images is accurate and reproducible across imaging phases. (©) RSNA, 2017 Online supplemental

  2. Micromachined electrostatic vertical actuator

    SciTech Connect

    Lee, A.P.; Sommargren, G.E.; McConaghy, C.F.; Krulevitch, P.A.

    1999-10-19

    A micromachined vertical actuator utilizing a levitational force, such as in electrostatic comb drives, provides vertical actuation that is relatively linear in actuation for control, and can be readily combined with parallel plate capacitive position sensing for position control. The micromachined electrostatic vertical actuator provides accurate movement in the sub-micron to micron ranges which is desirable in the phase modulation instrument, such as optical phase shifting. For example, compact, inexpensive, and position controllable micromirrors utilizing an electrostatic vertical actuator can replace the large, expensive, and difficult-to-maintain piezoelectric actuators. A thirty pound piezoelectric actuator with corner cube reflectors, as utilized in a phase shifting diffraction interferometer can be replaced with a micromirror and a lens. For any very precise and small amplitudes of motion, micromachined electrostatic actuation may be used because it is the most compact in size, with low power consumption and has more straightforward sensing and control options.

  3. More Electrostatic Explorations.

    ERIC Educational Resources Information Center

    Stewart, Gay; Gallai, Ditta

    1998-01-01

    Presents worksheet activities that enable students to explore the concept of electrostatic induction and learn the meaning of grounding. Students build two classic devices, the electrophorus and the leaf electroscope. (DDR)

  4. More Electrostatic Explorations.

    ERIC Educational Resources Information Center

    Stewart, Gay; Gallai, Ditta

    1998-01-01

    Presents worksheet activities that enable students to explore the concept of electrostatic induction and learn the meaning of grounding. Students build two classic devices, the electrophorus and the leaf electroscope. (DDR)

  5. Micromachined electrostatic vertical actuator

    DOEpatents

    Lee, Abraham P.; Sommargren, Gary E.; McConaghy, Charles F.; Krulevitch, Peter A.

    1999-10-19

    A micromachined vertical actuator utilizing a levitational force, such as in electrostatic comb drives, provides vertical actuation that is relatively linear in actuation for control, and can be readily combined with parallel plate capacitive position sensing for position control. The micromachined electrostatic vertical actuator provides accurate movement in the sub-micron to micron ranges which is desirable in the phase modulation instrument, such as optical phase shifting. For example, compact, inexpensive, and position controllable micromirrors utilizing an electrostatic vertical actuator can replace the large, expensive, and difficult-to-maintain piezoelectric actuators. A thirty pound piezoelectric actuator with corner cube reflectors, as utilized in a phase shifting diffraction interferometer can be replaced with a micromirror and a lens. For any very precise and small amplitudes of motion` micromachined electrostatic actuation may be used because it is the most compact in size, with low power consumption and has more straightforward sensing and control options.

  6. Electrostatic discharge test apparatus

    NASA Technical Reports Server (NTRS)

    Smith, William C. (Inventor)

    1989-01-01

    Electrostatic discharge properties of materials are quantitatively measured and ranked. Samples (20) are rotated on a turntable (15) beneath selectable, co-available electrostatic chargers (30/40), one being a corona charging element (30) and the other a sample-engaging triboelectric charging element (40). They then pass under a voltage meter (25) to measure the amount of residual charge on the samples (20). After charging is discontinued, measurements are continued to record the charge decay history over time.

  7. Electrostatic discharge test apparatus

    NASA Technical Reports Server (NTRS)

    Smith, William Conrad (Inventor)

    1988-01-01

    Electrostatic discharge properties of materials are quantitatively measured and ranked. Samples are rotated on a turntable beneath selectable, co-available electrostatic chargers, one being a corona charging element and the other a sample-engaging triboelectric charging element. Samples then pass under a voltage meter to measure the amount of residual charge on the samples. After charging is discontinued, measurements are continued to record the charge decay history over time.

  8. Electrostatic Levitator Electrode Layout

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Schematic of Electrostatic Levitator (ESL) electrodes and controls system. The ESL uses static electricity to suspend an object (about 2-3 mm in diameter) inside a vacuum chamber while a laser heats the sample until it melts. This lets scientists record a wide range of physical properties without the sample contacting the container or any instruments, conditions that would alter the readings. The Electrostatic Levitator is one of several tools used in NASA's microgravity materials science program.

  9. Graphene Electrostatic Microphone

    NASA Astrophysics Data System (ADS)

    Zhou, Qin; Onishi, Seita; Zettl, A.

    2015-03-01

    We demonstrate a wideband electrostatic graphene microphone displaying flat frequency response over the entire human audible region as well as into the ultrasonic regime. Using the microphone, low-level ultrasonic bat calls are successfully recorded. The microphone can be paired with a similarly constructed electrostatic graphene loudspeaker to create a wideband ultrasonic radio. Materials Sciences Division, Lawrence Berkeley National Laboratory Kavli Energy NanoSciences Institute at the University of California - Berkeley.

  10. Electrostatic Levitator in Use

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Metal droplet levitated inside the Electrostatic Levitator (ESL). The ESL uses static electricity to suspend an object (about 2-3 mm in diameter) inside a vacuum chamber while a laser heats the sample until it melts. This lets scientists record a wide range of physical properties without the sample contacting the container or any instruments, conditions that would alter the readings. The Electrostatic Levitator is one of several tools used in NASA's microgravity materials science program.

  11. Electrostatic Levitator Electrode Layout

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Schematic of Electrostatic Levitator (ESL) electrodes and controls system. The ESL uses static electricity to suspend an object (about 2-3 mm in diameter) inside a vacuum chamber while a laser heats the sample until it melts. This lets scientists record a wide range of physical properties without the sample contacting the container or any instruments, conditions that would alter the readings. The Electrostatic Levitator is one of several tools used in NASA's microgravity materials science program.

  12. Electrostatic Levitator Layout

    NASA Technical Reports Server (NTRS)

    1998-01-01

    General oayout of Electrostatic Levitator (ESL). The ESL uses static electricity to suspend an object (about 2-3 mm in diameter) inside a vacuum chamber while a laser heats the sample until it melts. This lets scientists record a wide range of physical properties without the sample contacting the container or any instruments, conditions that would alter the readings. The Electrostatic Levitator is one of several tools used in NASA's microgravity materials science program.

  13. Dynamics of electrostatic microelectromechanical systems actuators

    NASA Astrophysics Data System (ADS)

    Yang, Yisong; Zhang, Ruifeng; Zhao, Le

    2012-02-01

    Electrostatic actuators are simple but important switching devices for microelectromechanical systems applications. Due to the difficulties associated with the electrostatic nonlinearity, precise mathematical description is often hard to obtain for the dynamics of these actuators. Here we present two sharp theorems concerning the dynamics of an undamped electrostatic actuator with one-degree of freedom, subject to linear and nonlinear elastic forces, respectively. We prove that both situations are characterized by the onset of one-stagnation-point periodic response below a well-defined pull-in voltage and a finite-time touch-down or collapse of the actuator above this pull-in voltage. In the linear-force situation, the stagnation level, pull-in voltage, and pull-in coordinate of the movable electrode may all be determined explicitly, following the recent work of Leus and Elata based on numerics. Furthermore, in the nonlinear-force situation, the stagnation level, pull-in voltage, and pull-in coordinate may be described completely in terms of the electrostatic and mechanical parameters of the model so that they approach those in the linear-force situation monotonically in the zero nonlinear-force limit.

  14. Efficient optimization of electrostatic interactions between biomolecules.

    SciTech Connect

    Bardhan, J. P.; Altman, M. D.; White, J. K.; Tidor, B.; Mathematics and Computer Science; MIT

    2007-01-01

    We present a PDE-constrained approach to optimizing the electrostatic interactions between two biomolecules. These interactions play important roles in the determination of binding affinity and specificity, and are therefore of significant interest when designing a ligand molecule to bind tightly to a receptor. Using a popular continuum model and physically reasonable assumptions, the electrostatic component of the binding free energy is a convex, quadratic function of the ligand charge distribution. Traditional optimization methods require exhaustive pre-computation, and the expense has precluded a full exploration of the promise of electrostatic optimization in biomolecule analysis and design. In this paper we describe an approach in which the electrostatic simulations and optimization problem are solved simultaneously; unlike many PDE- constrained optimization frameworks, the proposed method does not incorporate the PDE as a set of equality constraints. This co-optimization approach can be used by itself to solve unconstrained problems or those with linear equality constraints, or in conjunction with primal-dual interior point methods to solve problems with inequality constraints. Model problems demonstrate that the co-optimization method is computationally efficient and can be used to solve realistic problems.

  15. Fluorescent "on-off-on" switching sensor based on CdTe quantum dots coupled with multiwalled carbon nanotubes@graphene oxide nanoribbons for simultaneous monitoring of dual foreign DNAs in transgenic soybean.

    PubMed

    Li, Yaqi; Sun, Li; Qian, Jing; Long, Lingliang; Li, Henan; Liu, Qian; Cai, Jianrong; Wang, Kun

    2017-06-15

    With the increasing concern of potential health and environmental risk, it is essential to develop reliable methods for transgenic soybean detection. Herein, a simple, sensitive and selective assay was constructed based on homogeneous fluorescence resonance energy transfer (FRET) between CdTe quantum dots (QDs) and multiwalled carbon nanotubes@graphene oxide nanoribbons (MWCNTs@GONRs) to form the fluorescent "on-off-on" switching for simultaneous monitoring dual target DNAs of promoter cauliflower mosaic virus 35s (P35s) and terminator nopaline synthase (TNOS) from transgenic soybean. The capture DNAs were immobilized with corresponding QDs to obtain strong fluorescent signals (turning on). The strong π-π stacking interaction between single-stranded DNA (ssDNA) probes and MWCNTs@GONRs led to minimal background fluorescence due to the FRET process (turning off). The targets of P35s and TNOS were recognized by dual fluorescent probes to form double-stranded DNA (dsDNA) through the specific hybridization between target DNAs and ssDNA probes. And the dsDNA were released from the surface of MWCNTs@GONRs, which leaded the dual fluorescent probes to generate the strong fluorescent emissions (turning on). Therefore, this proposed homogeneous assay can be achieved to detect P35s and TNOS simultaneously by monitoring the relevant fluorescent emissions. Moreover, this assay can distinguish complementary and mismatched nucleic acid sequences with high sensitivity. The constructed approach has the potential to be a tool for daily detection of genetically modified organism with the merits of feasibility and reliability. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. Electrostatic analysis of nanoelectromechanical systems

    NASA Astrophysics Data System (ADS)

    Xu, Yang

    We present a multiscale method, seamlessly combining semiclassical, effective-mass Schrodinger (EMS), and tight-binding (TB) theories proposed for electrostatic analysis of silicon nanoelectromechanical systems (NEMS). By using appropriate criteria, we identify the physical models that are accurate in each local region. If the local physical model is semiclassical, the charge density is directly computed by the semiclassical theory. If the local physical model is quantum-mechanical (EMS or TB model), the charge density is calculated by using the theory of local density of states (LDOS). The LDOS is efficiently calculated from Green's function by using Haydock's recursion method where the Green's function is expressed as a continued fraction based on the local Hamiltonian. Once the charge density is determined, a Poisson equation is solved self-consistently to determine the electronic properties. The accuracy and efficiency of the multiscale method are demonstrated by considering several NEMS examples. The multiscale method can be used to compute the effect of surface and interior defects such as vacancies and broken bonds on the performance of microelectromechanical systems (MEMS). By combining multiscale electrostatic analysis with mechanical analysis, we compute the capacitance-voltage and pull-in/pull-out voltages of MEMS switches in the presence of defects in the dielectric oxide layer. Our results indicate that both surface and interior defects can change the pull-in/pull-out voltages significantly. These voltage offsets can lead to an eventual failure of the MEMS switches. The self-consistent TB method is used to investigate carbon nanotube (CNT)-based sensors. We compute the screening effects of semiconducting and metallic single-wall carbon nanotubes (SWNTs) when water molecules and various ions pass through the nanotubes. The trajectories of ions and water molecules are obtained from molecular dynamics (MD) simulations. It is shown that metallic SWNTs have

  17. Large electrostatic accelerators

    SciTech Connect

    Jones, C.M.

    1984-01-01

    The increasing importance of energetic heavy ion beams in the study of atomic physics, nuclear physics, and materials science has partially or wholly motivated the construction of a new generation of large electrostatic accelerators designed to operate at terminal potentials of 20 MV or above. In this paper, the author briefly discusses the status of these new accelerators and also discusses several recent technological advances which may be expected to further improve their performance. The paper is divided into four parts: (1) a discussion of the motivation for the construction of large electrostatic accelerators, (2) a description and discussion of several large electrostatic accelerators which have been recently completed or are under construction, (3) a description of several recent innovations which may be expected to improve the performance of large electrostatic accelerators in the future, and (4) a description of an innovative new large electrostatic accelerator whose construction is scheduled to begin next year. Due to time and space constraints, discussion is restricted to consideration of only tandem accelerators.

  18. Electrostatics at the nanoscale

    SciTech Connect

    Walker, David A.; Kowalczyk, Bartlomiej; Olvera de la Cruz, Monica; Grzybowski, Bartosz A.

    2011-01-01

    Electrostatic forces are amongst the most versatile interactions to mediate the assembly of nanostructured materials. Depending on experimental conditions, these forces can be long- or short-ranged, can be either attractive or repulsive, and their directionality can be controlled by the shapes of the charged nano-objects. This Review is intended to serve as a primer for experimentalists curious about the fundamentals of nanoscale electrostatics and for theorists wishing to learn about recent experimental advances in the field. Accordingly, the first portion introduces the theoretical models of electrostatic double layers and derives electrostatic interaction potentials applicable to particles of different sizes and/or shapes and under different experimental conditions. This discussion is followed by the review of the key experimental systems in which electrostatic interactions are operative. Examples include electroactive and “switchable” nanoparticles, mixtures of charged nanoparticles, nanoparticle chains, sheets, coatings, crystals, and crystals-within-crystals. Applications of these and other structures in chemical sensing and amplification are also illustrated.

  19. Electrostatics at the nanoscale.

    PubMed

    Walker, David A; Kowalczyk, Bartlomiej; de la Cruz, Monica Olvera; Grzybowski, Bartosz A

    2011-04-01

    Electrostatic forces are amongst the most versatile interactions to mediate the assembly of nanostructured materials. Depending on experimental conditions, these forces can be long- or short-ranged, can be either attractive or repulsive, and their directionality can be controlled by the shapes of the charged nano-objects. This Review is intended to serve as a primer for experimentalists curious about the fundamentals of nanoscale electrostatics and for theorists wishing to learn about recent experimental advances in the field. Accordingly, the first portion introduces the theoretical models of electrostatic double layers and derives electrostatic interaction potentials applicable to particles of different sizes and/or shapes and under different experimental conditions. This discussion is followed by the review of the key experimental systems in which electrostatic interactions are operative. Examples include electroactive and "switchable" nanoparticles, mixtures of charged nanoparticles, nanoparticle chains, sheets, coatings, crystals, and crystals-within-crystals. Applications of these and other structures in chemical sensing and amplification are also illustrated.

  20. Electrostatic beneficiation of coal

    SciTech Connect

    Mazumder, M.K.; Tennal, K.B.; Lindquist, D.

    1994-10-01

    Dry physical beneficiation of coal has many advantages over wet cleaning methods and post combustion flue gas cleanup processes. The dry beneficiation process is economically competitive and environmentally safe and has the potential of making vast amounts of US coal reserves available for energy generation. While the potential of the electrostatic beneficiation has been studied for many years in laboratories and in pilot plants, a successful full scale electrostatic coal cleaning plant has not been commercially realized yet. In this paper the authors review some of the technical problems that are encountered in this method and suggest possible solutions that may lead toward its full utilization in cleaning coal.

  1. Electrostatic graphene loudspeaker

    NASA Astrophysics Data System (ADS)

    Zhou, Qin; Zettl, A.

    2013-06-01

    Graphene has extremely low mass density and high mechanical strength, and key qualities for efficient wide-frequency-response electrostatic audio speaker design. Low mass ensures good high frequency response, while high strength allows for relatively large free-standing diaphragms necessary for effective low frequency response. Here, we report on construction and testing of a miniaturized graphene-based electrostatic audio transducer. The speaker/earphone is straightforward in design and operation and has excellent frequency response across the entire audio frequency range (20 Hz-20 kHz), with performance matching or surpassing commercially available audio earphones.

  2. Electrostatic Levitator Vacuum Chamber

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Optical ports ring the Electrostatic Levitator (ESL) vacuum chamber to admit light from the heating laser (beam passes through the window at left), positioning lasers (one port is at center), and lamps to allow diagnostic instruments to view the sample. The ESL uses static electricity to suspend an object (about 2-3 mm in diameter) inside a vacuum chamber while a laser heats the sample until it melts. This lets scientists record a wide range of physical properties without the sample contacting the container or any instruments, conditions that would alter the readings. The Electrostatic Levitator is one of several tools used in NASA's microgravity materials science program.

  3. Electrostatic Levitator Inspected

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Larry Savage, Dr. Jan Rogers, Dr. Michael Robinson (All NASA) and Doug Huie (Mevatec) inspect the Electrostatic Levitator (ESL) at NASA's Marshall Space Flight Center (MSFC). The ESL uses static electricity to suspend an object (about 2-3 mm in diameter) inside a vacuum chamber while a laser heats the sample until it melts. This lets scientists record a wide range of physical properties without the sample contacting the container or any instruments, conditions that would alter the readings. The Electrostatic Levitator is one of several tools used in NASA's microgravity materials science program.

  4. Electrostatic Levitator (ESL) Undercooling

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Graph depicting Electrostatic Levitator (ESL) heating and cooling cycle to achieve undercooling of liquid metals. The ESL uses static electricity to suspend an object (about 3-4 mm in diameter) inside a vacuum chamber while a laser heats the sample until it melts. This lets scientists record a wide range of physical properties without the sample contracting the container or any instruments, conditions that would alter the readings. The electrostatic Levitator is one of several tools used in NASA's microgravity matierials sciences program.

  5. Electrostatic Levitator at Work

    NASA Technical Reports Server (NTRS)

    2000-01-01

    A 3 mm drop of nickel-zirconium, heated to incandescence, hovers between electrically charged plates inside the Electrostatic Levitator (ESL). The ESL uses static electricity to suspend an object (about 2-3 mm in diameter) inside a vacuum chamber while a laser heats the sample until it melts. This lets scientists record a wide range of physical properties without the sample contacting the container or any instruments, conditions that would alter the readings. The Electrostatic Levitator is one of several tools used in NASA's microgravity materials science program.

  6. Effect of particle distribution on electrostatic tomography system

    NASA Astrophysics Data System (ADS)

    Gao, Heming; Xu, Chuanlong; Fu, Feifei; Wang, Shimin

    2012-03-01

    Particle is charged due to frictional contact and collisions between particles and pipe wall. Electrostatic tomography technology (EST) is used to monitor the traveling particle charge. However the electric field distribution in the electrostatic sensor arrays is simultaneously affected by both the particle permittivity distribution and particle charge. In the paper, the effect of the different particle flow regimes on EST is investigated numerically and experimentally. Results indicated the particle distribution affected the induced charge on the electrostatic sensor array. But the effect relates to the relationship between the charge distribution and the particle distribution. Furthermore, a fusion of dual modality tomography system consisting of a capacitance sensor and electrostatic sensor arrays is used to investigate the relationship between the particle distribution and charge distribution in a gravity conveying rig. Results showed that the higher particle concentration has higher charge distribution in the gravity conveying rig. Additionally, the measurement of the mass flow rate by EST was investigated.

  7. Magnetosheath electrostatic turbulence

    NASA Technical Reports Server (NTRS)

    Rodriquez, P.

    1977-01-01

    The spectrum of electrostatic plasma waves in the terrestrial magnetosheath was studied using the plasma wave experiment on the IMP-6 satellite. Electrostatic plasma wave turbulence is almost continuously present throughout the magnetosheath with broadband (20 Hz- 70 kHz) r.m.s. field intensities typically 0.01 - 1.0 millivolts/m. Peak intensities of about 1.0 millivolts/m near the electron plasma frequency (30 - 60 kHz) were detected occasionally. The components usually identified in the spectrum of magnetosheath electrostatic turbulence include a high frequency ( or = 30 kHz) component peaking at the electron plasma frequency f sub pe, a low frequency component with a broad intensity maximum below the nominal ion plasma frequency f sub pi (approximately f sub pe/43), and a less well defined intermediate component in the range f sub pi f f sub pe. The intensity distribution of magnetosheath electrostatic turbulence clearly shows that the low frequency component is associated with the bow shock, suggesting that the ion heating begun at the shock continues into the downstream magnetosheath.

  8. Electrostatic space radiation shielding

    NASA Astrophysics Data System (ADS)

    Tripathi, R.; Wilson, J. W.; Youngquist, R. C.

    For the success of NASA s new vision for space exploration to Moon Mars and beyond exposures from the hazards of severe space radiation in deep space long duration missions is a must solve problem The payload penalty demands a very stringent requirement on the design of the spacecrafts for human deep space missions The exploration beyond low Earth orbit LEO to enable routine access of space will require protection from the hazards of the accumulated exposures of space radiation Galactic Cosmic Rays GCR and Solar Particle Events SPE and minimizing the production of secondary radiation is a great advantage There is a need to look to new horizons for newer technologies The present investigation revisits electrostatic active radiation shielding and explores the feasibility of using the electrostatic shielding in concert with the state-of-the-art materials shielding and protection technologies The full space radiation environment has been used for the first time to explore the feasibility of electrostatic shielding The goal is to repel enough positive charge ions so that they miss the spacecraft without attracting thermal electrons Conclusions will be drawn should the electrostatic shielding be successful for the future directions of space radiation protection

  9. Nanoscale Electrostatics in Mitosis

    NASA Astrophysics Data System (ADS)

    Gagliardi, L. John; West, Patrick Michael

    2001-04-01

    Primitive biological cells had to divide with very little biology. This work simulates a physicochemical mechanism, based upon nanoscale electrostatics, which explains the anaphase A poleward motion of chromosomes. In the cytoplasmic medium that exists in biological cells, electrostatic fields are subject to strong attenuation by Debye screening, and therefore decrease rapidly over a distance equal to several Debye lengths. However, the existence of microtubules within cells changes the situation completely. Microtubule dimer subunits are electric dipolar structures, and can act as intermediaries that extend the reach of the electrostatic interaction over cellular distances. Experimental studies have shown that intracellular pH rises to a peak at mitosis, and decreases through cytokinesis. This result, in conjunction with the electric dipole nature of microtubule subunits and the Debye screened electrostatic force is sufficient to explain and unify the basic events during mitosis and cytokinesis: (1) assembly of asters, (2) motion of the asters to poles, (3) poleward motion of chromosomes (anaphase A), (4) cell elongation, and (5) cytokinesis. This paper will focus on a simulation of the dynamics if anaphase A motion based on this comprehensive model. The physicochemical mechanisms utilized by primitive cells could provide important clues regarding our understanding of cell division in modern eukaryotic cells.

  10. Electrostatics of Rigid Polyelectrolytes

    SciTech Connect

    Wong, G.C.L.

    2009-06-04

    The organization of rigid biological polyelectrolytes by multivalent ions and macroions are important for many fundamental problems in biology and biomedicine, such as cytoskeletal regulation and antimicrobial sequestration in cystic fibrosis. These polyelectrolytes have been used as model systems for understanding electrostatics in complex fluids. Here, we review some recent results in theory, simulations, and experiments.

  11. Electrostatically Enhanced Vortex Separator

    NASA Technical Reports Server (NTRS)

    Collins, Earl R.

    1993-01-01

    Proposed device removes fine particles from high-pressure exhaust gas of chemical reactor. Negatively charged sectors on rotating disks in vortex generator attracts positively charged particles from main stream of exhaust gas. Electrostatic charge enhances particle-separating action of vortex. Gas without particles released to atmosphere.

  12. An asymmetry in electrostatics

    NASA Astrophysics Data System (ADS)

    Ganci, Salvatore

    2013-11-01

    This paper outlines a misuse of the electrostatic induction concept. A non-symmetrical behaviour was observed in a charge by the induction of an insulated hollow metallic conductor (the Faraday ice pail experiment). The major consequence of this experiment is a quick demonstration that the Earth must have a net negative charge.

  13. Electrostatic trapping of ammonia molecules

    PubMed

    Bethlem; Berden; Crompvoets; Jongma; van Roij AJ; Meijer

    2000-08-03

    The ability to cool and slow atoms with light for subsequent trapping allows investigations of the properties and interactions of the trapped atoms in unprecedented detail. By contrast, the complex structure of molecules prohibits this type of manipulation, but magnetic trapping of calcium hydride molecules thermalized in ultra-cold buffer gas and optical trapping of caesium dimers generated from ultra-cold caesium atoms have been reported. However, these methods depend on the target molecules being paramagnetic or able to form through the association of atoms amenable to laser cooling, respectively, thus restricting the range of species that can be studied. Here we describe the slowing of an adiabatically cooled beam of deuterated ammonia molecules by time-varying inhomogeneous electric fields and subsequent loading into an electrostatic trap. We are able to trap state-selected ammonia molecules with a density of 10(6) cm(-3) in a volume of 0.25 cm3 at temperatures below 0.35 K. We observe pronounced density oscillations caused by the rapid switching of the electric fields during loading of the trap. Our findings illustrate that polar molecules can be efficiently cooled and trapped, thus providing an opportunity to study collisions and collective quantum effects in a wide range of ultra-cold molecular systems.

  14. Prospective randomized controlled clinical and histopathological study of acne vulgaris treated with dual mode of quasi-long pulse and Q-switched 1064-nm Nd:YAG laser assisted with a topically applied carbon suspension.

    PubMed

    Jung, Jae Yoon; Hong, Jong Soo; Ahn, Chang Ho; Yoon, Ji Young; Kwon, Hyuck Hoon; Suh, Dae Hun

    2012-04-01

    Acne treatments using laser and light devices have been reported to have varying degrees of efficacy. However, there has been no study of treatment of acne using a dual mode (quasi-long pulse and Q-switched mode) 1064-nm Nd:YAG laser assisted with a topically applied carbon suspension. To evaluate the clinical efficacy, safety, and histological changes of new laser treatment method for acne vulgaris. Twenty-two patients received 3 sessions of quasi-long pulse and Q-switched Nd:YAG laser treatment assisted with a topically applied carbon suspension at 2-week intervals in a randomized split face manner. At the final visit, the inflammatory acne lesions were reduced on the laser-treated side by 58.6% (P < .001), but increased on the untreated side by 5%. The noninflammatory acne lesions were reduced on the laser-treated side by 52.4% (P < .001). Sebum output reduction, inflammatory cell and cytokine reductions, a decrease of the thickness of a perifollicular stratum corneum and a full epithelium, and skin rejuvenation effect were found. The histopathologic examination of the acne lesions showed decreased inflammation and immunostaining intensity for interleukin 8, matrix metalloproteinase-9, toll-like receptor-2, and nuclear factor kappa B, and tumor necrosis factor alpha was reduced significantly. No severe adverse reactions were reported. All patients reported mild transient erythema that disappeared in a few hours. The number of subjects studied was small. This laser treatment was rapid and effective for treating not only the inflammatory but also the noninflammatory acne lesions when compared with the control side. The histopathologic findings correlated well with the clinical acne grade and treatment response. This novel laser treatment appears to be safe and effective for acne treatment. Copyright © 2012 American Academy of Dermatology, Inc. Published by Mosby, Inc. All rights reserved.

  15. Cygnus PFL Switch Jitter

    SciTech Connect

    C. Mitton, G. Corrow, M. Hansen, D. Henderson, et al.

    2007-07-21

    The Cygnus Dual Beam Radiographic Facility consists of two identical radiographic sources: Cygnus 1 and Cygnus 2. Each source has the following X-ray output: 1-mm diameter spot size, 4 rads at 1 m, 50-ns full-widthhalf-maximum. The diode pulse has the following electrical specifications: 2.25 MV, 60 kA, 60 ns. This Radiographic Facility is located in an underground tunnel test area at the Nevada Test Site (NTS). The sources were developed to produce high-resolution images on subcritical tests performed at NTS. Subcritical tests are single-shot, high-value events. For this application, it is desirable to maintain a high level of reproducibility in source output. The major components of the Cygnus machines are Marx generator, water-filled pulse forming line (PFL), water-filled coaxial transmission line, threecell inductive voltage adder, and rod-pinch diode. A primary source of fluctuation in Cygnus shot-to-shot performance may be jitter in breakdown of the main PFL switch, which is a “self-break” switch. The PFL switch breakdown time determines the peak PFL charging voltage, which ultimately affects the source X-ray spectrum and dose. Therefore, PFL switch jitter may contribute to shot-to-shot variation in these parameters, which are crucial to radiographic quality. In this paper we will present PFL switch jitter analysis for both Cygnus machines and present the correlation with dose. For this analysis, the PFL switch on each machine was maintained at a single gap setting, which has been used for the majority of shots at NTS. In addition the PFL switch performance for one larger switch gap setting will be examined.

  16. Cygnus Water Switch Jitter

    SciTech Connect

    Charles V. Mitton, George D. Corrow, Mark D. Hansen, David J. Henderson, et al.

    2008-03-01

    The Cygnus Dual Beam Radiographic Facility consists of two identical radiographic sources - Cygnus 1 and Cygnus 2. Each source has the following x-ray output: 1-mm diameter spot size, 4 rad at 1 m, 50-ns Full Width Half Max. The diode pulse has the following electrical specifications: 2.25 MV, 60 kA, 60 ns. This Radiographic Facility is located in an underground tunnel test area at the Nevada Test Site (NTS). The sources were developed to produce high-resolution images on subcritical tests which are performed at NTS. Subcritical tests are single-shot, high-value events. For this application, it is desirable to maintain a high level of reproducibility in source output. The major components of the Cygnus machines are: Marx generator, water-filled pulse–forming line (PFL), water-filled coaxial transmission line, three-cell inductive voltage adder, and rod-pinch diode. A primary source of fluctuation in Cygnus shot-to-shot performance is jitter in breakdown of the main PFL switch, which is a “self-break” switch. The PFL switch breakdown time determines the peak PFL charging voltage, which ultimately affects the diode pulse. Therefore, PFL switch jitter contributes to shot-to-shot variation in source endpoint energy and dose. In this paper we will present PFL switch jitter analysis for both Cygnus machines and give the correlation with diode performance. For this analysis the PFL switch on each machine was maintained at a single gap setting which has been used for the majority of shots at NTS. In addition to this analysis, PFL switch performance for different switch gap settings taken recently will be examined. Lastly, implications of source jitter for radiographic diagnosis of subcritical shots will be discussed.

  17. Automated Electrostatics Environmental Chamber

    NASA Technical Reports Server (NTRS)

    Calle, Carlos; Lewis, Dean C.; Buchanan, Randy K.; Buchanan, Aubri

    2005-01-01

    The Mars Electrostatics Chamber (MEC) is an environmental chamber designed primarily to create atmospheric conditions like those at the surface of Mars to support experiments on electrostatic effects in the Martian environment. The chamber is equipped with a vacuum system, a cryogenic cooling system, an atmospheric-gas replenishing and analysis system, and a computerized control system that can be programmed by the user and that provides both automation and options for manual control. The control system can be set to maintain steady Mars-like conditions or to impose temperature and pressure variations of a Mars diurnal cycle at any given season and latitude. In addition, the MEC can be used in other areas of research because it can create steady or varying atmospheric conditions anywhere within the wide temperature, pressure, and composition ranges between the extremes of Mars-like and Earth-like conditions.

  18. Electrostatically clean solar array

    NASA Technical Reports Server (NTRS)

    Stern, Theodore Garry (Inventor); Krumweide, Duane Eric (Inventor)

    2004-01-01

    Provided are methods of manufacturing an electrostatically clean solar array panel and the products resulting from the practice of these methods. The preferred method uses an array of solar cells, each with a coverglass where the method includes machining apertures into a flat, electrically conductive sheet so that each aperture is aligned with and undersized with respect to its matched coverglass sheet and thereby fashion a front side shield with apertures (FSA). The undersized portion about each aperture of the bottom side of the FSA shield is bonded to the topside portions nearest the edges of each aperture's matched coverglass. Edge clips are attached to the front side aperture shield edges with the edge clips electrically and mechanically connecting the tops of the coverglasses to the solar panel substrate. The FSA shield, edge clips and substrate edges are bonded so as to produce a conductively grounded electrostatically clean solar array panel.

  19. Biobriefcase electrostatic aerosol collector

    DOEpatents

    Bell, Perry M.; Christian, Allen T.; Bailey, Christopher G.; Willis, Ladona; Masquelier, Donald A.; Nasarabadi, Shanavaz L.

    2009-03-17

    A system for sampling air and collecting particles entrained in the air comprising a receiving surface, a liquid input that directs liquid to the receiving surface and produces a liquid surface, an air input that directs the air so that the air with particles entrained in the air impact the liquid surface, and an electrostatic contact connected to the liquid that imparts an electric charge to the liquid. The particles potentially including bioagents become captured in the liquid by the air with particles entrained in the air impacting the liquid surface. Collection efficiency is improved by the electrostatic contact electrically charging the liquid. The effects of impaction and adhesion due to electrically charging the liquid allows a unique combination in a particle capture medium that has a low fluid consumption rate while maintaining high efficiency.

  20. Electrostatic Levitator Vacuum Chambers

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Optical prots ring the Electrostatic Levitator (ESL) vacuum chamber to admit light from the heating laser (the beam passes through the window at left), poisitioning lasers (one port is at center), and lamps (such as the deuterium arc lamp at right), and to allow diagnostic instruments to view the sample. The ESL uses static electricity to suspend an object (about 2-3 mm in diameter) inside a vacuum chamber while a laser heats the sample until it melts. This lets scientists record a wide range of physical properties without the sample contacting the container or any instruments, conditions that would alter the readings. The Electrostatic Levitator is one of several tools used in NASA's microgravity materials science program.

  1. Electrostatic separation of brass from industrial wastes

    SciTech Connect

    Iuga, A.; Morar, R.; Samuila, A.; Mihailescu, M.; Cuglesan, I.; Dascalescu, L.

    1999-05-01

    Previous studies have demonstrated that electrostatic separation can be successfully employed for the recycling of nonferrous metals from chopped electric wire and cable scrap. The aim of this paper was to investigate the possibility of using the electric field forces for the selective sorting of other granular mixtures, such as brass dross. Laboratory tests of electrostatic separation were carried out on three samples: 0.08--1 mm, 0.08--0.2 mm, and 0.2--1 mm, containing more than 66% of brass. Sample 1 was separated in a corona-electrostatic field, generated by a standard electrode arrangement: a grounded rotating roll electrode (diameter 150 mm) and two high-voltage electrodes (wire-type dual corona electrode + tubular electrode). Processing of the other two samples was carried out in a custom-designed separator comprising an extended corona field generated between a matrix-type multineedle corona electrode and a roll electrode of large diameter (250 mm). Chemical analysis of the products showed that more than 90% of the brass can be recovered with a purity higher than 95%. The extended corona field electrode arrangement proposed in this paper seems to be a promising solution for the effective recycling of other granular wastes containing copper, aluminum, and their alloys.

  2. Micromachined silicon electrostatic chuck

    SciTech Connect

    Anderson, R.A.; Seager, C.H.

    1994-12-31

    In the field of microelectronics, and in particular the fabrication of microelectronics during plasma etching processes, electrostatic chucks have been used to hold silicon wafers during the plasma etching process. Current electrostatic chucks that operate by the {open_quotes}Johnson-Rahbek Effect{close_quotes} consist of a metallic base plate that is typically coated with a thick layer of slightly conductive dielectric material. A silicon wafer of approximately the same size as the chuck is placed on top of the chuck and a potential difference of several hundred volts is applied between the silicon and the base plate of the electrostatic chuck. This causes an electrostatic attraction proportional to the square of the electric field in the gap between the silicon wafer and the chuck face. When the chuck is used in a plasma filled chamber the electric potential of the wafer tends to be fixed by the effective potential of the plasma. The purpose of the dielectric layer on the chuck is to prevent the silicon wafer from coming into direct electrical contact with the metallic part of the chuck and shorting out the potential difference. On the other hand, a small amount of conductivity appears to be desirable in the dielectric coating so that much of its free surface between points of contact with the silicon wafer is maintained near the potential of the metallic base plate; otherwise, a much larger potential difference would be needed to produce a sufficiently large electric field in the vacuum gap between the wafer and chuck. Typically, the face of the chuck has a pattern of grooves in which about 10 torr pressure of helium gas is maintained. This gas provides cooling (thermal contact) between the wafer and the chuck. A pressure of 10 torr is equivalent to about 0.2 psi.

  3. Electrostatic curtain studies

    SciTech Connect

    Meyer, L C

    1992-05-01

    This report presents the results of experiments using electrostatic curtains (ESCS) as a transuranic (TRU) contamination control technique. The TRU contaminants included small (micrometer to sub micrometer) particles of plutonium and americium compounds associated with defense-related waste. Three series of experiments were conducted. The first was with uncontaminated Idaho National Engineering Laboratory (INEL) soil, the second used contaminated soil containing plutonium-239 (from a mixture of Rocky Flats Plant contaminated soil and INEL uncontaminated soil), and the third was uncontaminated INEL soil spiked with plutonium-239. All experiments with contaminated soil were conducted inside a glove box containing a dust generator, low volume cascade impactor (LVCI), electrostatic separator, and electrostatic materials. The data for these experiments consisted of the mass of dust collected on the various material coupons, plates, and filters; radiochemical analysis of selected samples; and photographs, as well as computer printouts giving particle size distributions and dimensions from the scanning electron microscope (SEM). The following results were found: (a) plutonium content (pCi/g) was found to increase with smaller soil particle sizes and (b) the electrostatic field had a stronger influence on smaller particle sizes compared to larger particle sizes. The SEM analysis indicated that the particle size of the tracer Pu239 used in the spiked soil experiments was below the detectable size limit (0.5 {mu}m) of the SEM and, thus, may not be representative of plutonium particles found in defense-related waste. The use of radiochemical analysis indicated that plutonium could be found on separator plates of both polarities, as well as passing through the electric field and collecting on LVCI filters.

  4. Electrostatic Levitator Operations

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Dr. Jan Rogers (left) and Larry Savage (foreground) of the Science Directorate at NASA's Marshall Space Flight Center are joined by Dr. Richard Weber (Center) and April Hixon of Containerless Research Inc. of Evanston, Ill., in conducting an experiment run of the Electrostatic Levitator (ESL) using insulating materials. Materials researchers use unique capability of the facility to levitate and study the properties of various materials important in manufacturing processes.

  5. Abdominal rapid-kVp-switching dual-energy MDCT with reduced IV contrast compared to conventional MDCT with standard weight-based IV contrast: an intra-patient comparison.

    PubMed

    Clark, Zachary E; Bolus, David N; Little, Mark D; Morgan, Desiree E

    2015-04-01

    Perform intra-patient comparison of attenuation values on lower keV dual-energy abdominal CT images using reduced IV contrast dose compared to conventional single energy polychromatic beam abdominal MDCT images using standard IV contrast dose. IRB approved retrospective evaluation of consecutive adults who had both standard IV contrast dosage conventional multiphasic MDCT (SECT) and reduced IV contrast dosage rapid kV-switching dual-energy multiphasic MDCT (rsDECT) of the abdomen. Arterial phase dual-energy 52, 70 and 78 keV simulated monoenergetic HU were compared (t test) to arterial phase SECT HU for: aorta, liver, pancreas, psoas, and hepatic/pancreatic tumors. Contrast to noise ratios (CNR), IV contrast dose reduction and dose-length product (DLP) were recorded. Two blinded independent readers evaluated the CT datasets for subjective image quality based on a five point scale. Twenty-nine scan pairs in 24 subjects (13 M, mean age 64, weight 76.7 kg) were evaluated. Mean reduction in IV contrast dose was 37 %. Mean ± SD HU on 52 keV rsDECT vs. SECT were: aorta 534 ± 138 vs. 271 ± 69; liver 88 ± 24 vs. 67 ± 16; pancreas 140 ± 60 vs. 89 ± 40; psoas 63 ± 15 vs. 50 ± 12 (all p < 0.001). Noise was higher for 52 keV compared to SECT (p < 0.001); CNRs were not significantly different. Mean ± SD DLP for rsDECT was 1421 ± 563 and SECT 1335 ± 562 mGy·cm (p = 0.640). For tumor vs. nontumoral parenchyma, mean absolute contrast difference was 58.4 HU on 52 keV, and 29.0 HU on SECT. Nearly all images were rated as good or excellent and there were no statistically significant differences in image quality between the DECT and SECT images. Statistically significant gains in vascular and parenchymal enhancement without adverse effect on CNR or lesion contrast were observed in this intra-patient comparison using reduced IV contrast dose rsDECT compared to standard weight-based IV dose conventional SECT.

  6. Electrostatics of Granular Materials

    NASA Technical Reports Server (NTRS)

    Marshall, John

    2004-01-01

    The purpose of the research was to continue developing an understanding of electrostatic phenomena in preparation for any future flight opportunities of the EGM experiment, originally slated for a 2004 Space Station deployment. Work would be based on theoretical assessments, ground-based lab experiments, and reduced-gravity experiments. The ability to examine dipoles in the lab proved to be elusive, and thus, effort was concentrated on monopoles -how materials become charged, the fate of the charge, the role of material type, and so forth. Several significant milestones were achieved in this regard. In regard of the dipoles, experiments were designed in collaboration with the University of Chicago school district who had access to reduced gravity on the KC-135 aircraft. Two experiments were slated to fly last year but were cancelled after the Columbia accident. One of the experiments has been given a second life and will fly sometime in 2005 if the Shuttle flights resume. There remains active interest in the question of electrostatic dipoles within the educational community, and experiments using magnetic dipoles as a substitute are to be examined. The KC-135 experiments will also examine dispersion methods for particles as a verification of possible future techniques in microgravity. Both laboratory and theoretical work established a number of breakthroughs in our understanding of electrostatic phenomena. These breakthroughs are listed in this paper.

  7. Electrostatic Plasma Accelerator (EPA)

    NASA Technical Reports Server (NTRS)

    Brophy, John R.; Aston, Graeme

    1989-01-01

    The Electrostatic Plasma Accelerator (EPA) is a thruster concept which promises specific impulse levels between low power arcjets and those of the ion engine while retaining the relative simplicity of the arcjet. The EPA thruster produces thrust through the electrostatic acceleration of a moderately dense plasma. No accelerating electrodes are used and the specific impulse is a direct function of the applied discharge voltage and the propellant atomic mass. The goal of the present program is to demonstrate feasibility of the EPA thruster concept through experimental and theoretical investigations of the EPA acceleration mechanism and discharge chamber performance. Experimental investigations will include operating the test bed ion (TBI) engine as an EPA thruster and parametrically varying the thruster geometry and operating conditions to quantify the electrostatic plasma acceleration effect. The theoretical investigations will include the development of a discharge chamber model which describes the relationships between the engine size, plasma properties, and overall performance. For the EPA thruster to be a viable propulsion concept, overall thruster efficiencies approaching 30% with specific impulses approaching 1000 s must be achieved.

  8. Electrostatic space radiation shielding

    NASA Astrophysics Data System (ADS)

    Tripathi, Ram K.; Wilson, John W.; Youngquist, Robert C.

    2008-09-01

    For the success of NASA’s new vision for space exploration to Moon, Mars and beyond, exposures from the hazards of severe space radiation in deep space long duration missions is ‘a must solve’ problem. The payload penalty demands a very stringent requirement on the design of the spacecrafts for human deep space missions. The exploration beyond low Earth orbit (LEO) to enable routine access of space will require protection from the hazards of the accumulated exposures of space radiation, Galactic Cosmic Rays (GCR) and Solar Particle Events (SPE), and minimizing the production of secondary radiation is a great advantage. There is a need to look to new horizons for newer technologies. The present investigation revisits electrostatic active radiation shielding and explores the feasibility of using the electrostatic shielding in concert with the state-of-the-art materials shielding and protection technologies. The full space radiation environment has been used, for the first time, to explore the feasibility of electrostatic shielding. The goal is to repel enough positive charge ions so that they miss the spacecraft without attracting thermal electrons. Conclusions are drawn for the future directions of space radiation protection.

  9. Switch wear leveling

    DOEpatents

    Wu, Hunter; Sealy, Kylee; Gilchrist, Aaron

    2015-09-01

    An apparatus for switch wear leveling includes a switching module that controls switching for two or more pairs of switches in a switching power converter. The switching module controls switches based on a duty cycle control technique and closes and opens each switch in a switching sequence. The pairs of switches connect to a positive and negative terminal of a DC voltage source. For a first switching sequence a first switch of a pair of switches has a higher switching power loss than a second switch of the pair of switches. The apparatus includes a switch rotation module that changes the switching sequence of the two or more pairs of switches from the first switching sequence to a second switching sequence. The second switch of a pair of switches has a higher switching power loss than the first switch of the pair of switches during the second switching sequence.

  10. Innovative Electrostatic Adhesion Technologies

    NASA Astrophysics Data System (ADS)

    Gagliano, L.; Bryan, T.; Williams, S.; McCoy, B.; MacLeod, T.

    Developing specialized Electro-Static grippers (commercially used in Semiconductor Manufacturing and in package handling) will allow gentle and secure Capture, Soft Docking, and Handling of a wide variety of materials and shapes (such as upper-stages, satellites, arrays, and possibly asteroids) without requiring physical features or cavities for a pincher or probe or using harpoons or nets. Combined with new rigid boom mechanisms or small agile chaser vehicles, flexible, high speed Electro-Static Grippers can enable compliant capture of spinning objects starting from a safe stand-off distance. Electroadhesion (EA) can enable lightweight, ultra-low-power, compliant attachment in space by using an electrostatic force to adhere similar and dissimilar surfaces. A typical EA enabled device is composed of compliant space-rated materials, such as copper-clad polyimide encapsulated by polymers. Attachment is induced by strong electrostatic forces between any substrate material, such as an exterior satellite panel and a compliant EA surface. When alternate positive and negative charges are induced in adjacent planar electrodes in an EA surface, the electric fields set up opposite charges on the substrate and cause an electrostatic adhesion between the electrodes and the induced charges on the substrate. Since the electrodes and the polymer are compliant and can conform to uneven or rough surfaces, the electrodes can remain intimately close to the entire surface, enabling high clamping pressures. Clamping pressures of more than 3 N/cm2 in shear can be achieved on a variety of substrates with ultra-low holding power consumption (measured values are less than 20 microW/Newton weight held). A single EA surface geometry can be used to clamp both dielectric and conductive substrates, with slightly different physical mechanisms. Furthermore EA clamping requires no normal force be placed on the substrate, as conventional docking requires. Internally funded research and development

  11. Innovative Electrostatic Adhesion Technologies

    NASA Technical Reports Server (NTRS)

    Bryan, Tom; Macleod, Todd; Gagliano, Larry; Williams, Scott; McCoy, Brian

    2015-01-01

    Developing specialized Electro-Static grippers (commercially used in Semiconductor Manufacturing and in package handling) will allow gentle and secure Capture, Soft Docking, and Handling of a wide variety of materials and shapes (such as upper-stages, satellites, arrays, and possibly asteroids) without requiring physical features or cavities for a pincher or probe or using harpoons or nets. Combined with new rigid boom mechanisms or small agile chaser vehicles, flexible, high speed Electro-Static Grippers can enable compliant capture of spinning objects starting from a safe stand-off distance. Electroadhesion (EA) can enable lightweight, ultra-low-power, compliant attachment in space by using an electrostatic force to adhere similar and dissimilar surfaces. A typical EA enabled device is composed of compliant space-rated materials, such as copper-clad polyimide encapsulated by polymers. Attachment is induced by strong electrostatic forces between any substrate material, such as an exterior satellite panel and a compliant EA gripper pad surface. When alternate positive and negative charges are induced in adjacent planar electrodes in an EA surface, the electric fields set up opposite charges on the substrate and cause an electrostatic adhesion between the electrodes and the induced charges on the substrate. Since the electrodes and the polymer are compliant and can conform to uneven or rough surfaces, the electrodes can remain intimately close to the entire surface, enabling high clamping pressures. Clamping pressures of more than 3 N/cm2 in shear can be achieved on a variety of substrates with ultra-low holding power consumption (measured values are less than 20 microW/Newton weight held). A single EA surface geometry can be used to clamp both dielectric and conductive substrates, with slightly different physical mechanisms. Furthermore EA clamping requires no normal force be placed on the substrate, as conventional docking requires. Internally funded research and

  12. Switching subtype-selectivity: Fragment replacement strategy affords novel class of peroxisome proliferator-activated receptor α/δ (PPARα/δ) dual agonists.

    PubMed

    Shioi, Ryuta; Okazaki, Shogo; Noguchi-Yachide, Tomomi; Ishikawa, Minoru; Makishima, Makoto; Hashimoto, Yuichi; Yamaguchi, Takao

    2017-07-15

    Peroxisome proliferator-activated receptors (PPARs) are important drug targets for treatment of dyslipidemia, type 2 diabetes, cardiovascular disease, nonalcoholic fatty liver disease and nonalcoholic steatohepatitis, and great efforts have been made to develop novel PPAR ligands. However, most existing PPAR ligands contain a carboxylic acid (CA) or thiazolidinedione (TZD) structure (acidic head group) that is essential for activity. We recently discovered non-CA/TZD class PPARα/δ partial agonists, which contain an acetamide moiety and adjacent methyl group, linked to a 1,2,4-oxadiazole ring ("fragment a"). We hypothesized that the acetamide structure might interact with the CA/TZD-binding pocket. To test this idea, we firstly replaced fragment a in one of our compounds with the α-alkoxy-CA structure often found in PPAR agonists. Secondly, we replaced the α-alkoxy-CA head group of several reported PPAR agonists with our acetamide-based fragment a. The agonistic activities of the synthesized hybrid compounds toward PPARs (PPARα, PPARγ and PPARδ) were evaluated by means of cell-based reporter gene assays. All the hybrid molecules showed PPAR-agonistic activities, but replacement of the α-alkoxy-CA head group altered the maximum efficacy and the subtype-specificity. The acetamide-based hybrid molecules showed partial agonism toward PPARα and PPARδ, whereas the α-alkoxy-CA-based molecules were generally selective for PPARα and PPARγ, with relatively high activation efficacies. Thus, the fragment replacement strategy appears promising for the development of novel acetamide-based PPARα/δ dual agonists. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. Spacecraft Electrostatic Radiation Shielding

    NASA Technical Reports Server (NTRS)

    2008-01-01

    This project analyzed the feasibility of placing an electrostatic field around a spacecraft to provide a shield against radiation. The concept was originally proposed in the 1960s and tested on a spacecraft by the Soviet Union in the 1970s. Such tests and analyses showed that this concept is not only feasible but operational. The problem though is that most of this work was aimed at protection from 10- to 100-MeV radiation. We now appreciate that the real problem is 1- to 2-GeV radiation. So, the question is one of scaling, in both energy and size. Can electrostatic shielding be made to work at these high energy levels and can it protect an entire vehicle? After significant analysis and consideration, an electrostatic shield configuration was proposed. The selected architecture was a torus, charged to a high negative voltage, surrounding the vehicle, and a set of positively charged spheres. Van de Graaff generators were proposed as the mechanism to move charge from the vehicle to the torus to generate the fields necessary to protect the spacecraft. This design minimized complexity, residual charge, and structural forces and resolved several concerns raised during the internal critical review. But, it still is not clear if such a system is costeffective or feasible, even though several studies have indicated usefulness for radiation protection at energies lower than that of the galactic cosmic rays. Constructing such a system will require power supplies that can generate voltages 10 times that of the state of the art. Of more concern is the difficulty of maintaining the proper net charge on the entire structure and ensuring that its interaction with solar wind will not cause rapid discharge. Yet, if these concerns can be resolved, such a scheme may provide significant radiation shielding to future vehicles, without the excessive weight or complexity of other active shielding techniques.

  14. Micromachined, Electrostatically Deformable Reflectors

    NASA Technical Reports Server (NTRS)

    Bartman, Randall K.; Wang, Paul K. C.; Miller, Linda M.; Kenny, Thomas W.; Kaiser, William J.; Hadaegh, Fred Y.; Agronin, Michael L.

    1995-01-01

    Micromachined, closed-loop, electrostatically actuated reflectors (microCLEARs) provide relatively simple and inexpensive alternatives to large, complex, expensive adaptive optics used to control wavefronts of beams of light in astronomy and in experimental laser weapons. Micromachining used to make deformable mirror, supporting structure, and actuation circuitry. Development of microCLEARs may not only overcome some of disadvantages and limitations of older adaptive optics but may also satisfy demands of potential market for small, inexpensive deformable mirrors in electronically controlled film cameras, video cameras, and other commercial optoelectronic instruments.

  15. Electrostatically Driven Nanoballoon Actuator.

    PubMed

    Barzegar, Hamid Reza; Yan, Aiming; Coh, Sinisa; Gracia-Espino, Eduardo; Dunn, Gabriel; Wågberg, Thomas; Louie, Steven G; Cohen, Marvin L; Zettl, Alex

    2016-11-09

    We demonstrate an inflatable nanoballoon actuator based on geometrical transitions between the inflated (cylindrical) and collapsed (flattened) forms of a carbon nanotube. In situ transmission electron microscopy experiments employing a nanoelectromechanical manipulator show that a collapsed carbon nanotube can be reinflated by electrically charging the nanotube, thus realizing an electrostatically driven nanoballoon actuator. We find that the tube actuator can be reliably cycled with only modest control voltages (few volts) with no apparent wear or fatigue. A complementary theoretical analysis identifies critical parameters for nanotube nanoballoon actuation.

  16. Electrostatic Return of Contaminants

    NASA Technical Reports Server (NTRS)

    Rantanen, R.; Gordon, T.

    2003-01-01

    A Model has been developed capable of calculating the electrostatic return of spacecraft-emitted molecules that are ionized and attracted back to the spacecraft by the spacecraft electric potential on its surfaces. The return of ionized contaminant molecules to charged spacecraft surfaces is very important to all altitudes. It is especially important at geosynchronous and interplanetary environments, since it may be the only mechanism by which contaminants can degrade a surface. This model is applicable to all altitudes and spacecraft geometries. In addition to results of the model will be completed to cover a wide range of potential space systems.

  17. PREFACE: Electrostatics 2015

    NASA Astrophysics Data System (ADS)

    Matthews, James

    2015-10-01

    Electrostatics 2015, supported by the Institute of Physics, was held in the Sir James Matthews building at Southampton Solent University, UK between 12th and 16th April 2015. Southampton is a historic city on the South Coast of England with a strong military and maritime history. Southampton is home to two Universities: Solent University, which hosted the conference, and the University of Southampton, where much work is undertaken related to electrostatics. 37 oral and 44 poster presentations were accepted for the conference, and 60 papers were submitted and accepted for the proceedings. The Bill Bright Memorial Lecture was delivered this year by Professor Mark Horenstein from Boston University who was, until recently, Editor-in-Chief of the Journal of Electrostatics. He spoke on The contribution of surface potential to diverse problems in electrostatics and his thorough knowledge of the subject of electrostatics was evident in the presentation. The first session was chaired by the Conference Chair, Dr Keith Davies, whose experience in the field showed through his frequent contributions to the discussions throughout the conference. Hazards and Electrostatic Discharge have formed a strong core to Electrostatics conferences for many years, and this conference contained sessions on both Hazards and on ESD, including an invited talk from Dr Jeremy Smallwood on ESD in Industry - Present and Future. Another strong theme to emerge from this year's programme was Non-Thermal Plasmas, which was covered in two sessions. There were two invited talks on this subject: Professor Masaaki Okubo gave a talk on Development of super-clean diesel engine and combustor using nonthermal plasma hybrid after treatment and Dr David Go presented a talk on Atmospheric-pressure ionization processes: New approaches and applications for plasmas in contact with liquids. A new innovation to the conference this year was the opportunity for conference sponsors to present to the delegates a technical

  18. Coaxial Switch

    DTIC Science & Technology

    2014-04-23

    08-2015 Publication Coaxial Switch David J. Bamford et al Naval Undersea Warfare Center Division, Newport 1176 Howell Street, Bldg 102T, Code 00L...Distribution A A coaxial switch having a housing and a shaft extending through and rotatably mounted to the housing. The shaft extends from opposite...conductor members are electrically connected together. When the coaxial switch is engaged, the conductor members are inserted into the connector body

  19. Task switching: effects of practice on switch and mixing costs.

    PubMed

    Strobach, Tilo; Liepelt, Roman; Schubert, Torsten; Kiesel, Andrea

    2012-01-01

    In the task-switching paradigm, mixing costs indicate the performance costs to mix two different tasks, while switch costs indicate the performance costs to switch between two sequentially presented tasks. Applying tasks with bivalent stimuli and responses, many studies demonstrated substantial mixing and switch costs and a reduction of these costs as a result of practice. The present study investigates whether extensive practice of a task-switching situation including tasks with univalent stimuli eliminates these costs. Participants practiced switching between a visual and an auditory task. These tasks were chosen because they had shown eliminated performance costs in a comparable dual-task practice study (Schumacher et al. Psychol Sci 12:101-108, 2001). Participants either performed the tasks with univalent responses (i.e., visual-manual and auditory-verbal stimulus-response mappings) or bivalent responses (i.e., visual-manual and auditory-manual stimulus-response mappings). Both valence conditions revealed substantial mixing and switch costs at the beginning of practice, yet, mixing costs were largely eliminated after eight practice sessions while switch costs were still existent.

  20. Hazard of electrostatic generation in a pneumatic conveying system: electrostatic effects on the accuracy of electrical capacitance tomography measurements and generation of spark

    NASA Astrophysics Data System (ADS)

    Zhang, Yan; Chii Liang, Yung; Wang, Chi-Hwa

    2008-01-01

    The study of the hazard of electrostatic generation in pneumatic conveying systems was attempted by examining the sensitivity of electrical capacitance tomography (ECT) and the phenomena of spark generation due to strong electrostatics. The influence on ECT measurement accuracy of an electrostatic charge was analysed with reference to a switch capacitor configuration model. Consequently, it was found that the electrostatic charge introduced at the bend with sharp angles influenced the ECT results most significantly in pneumatic conveying systems, especially for the cases where a spark was generated. The investigation of spark generation indicated that a strong electrostatic charge can cause major discharges inside or outside the pipeline to damage the experimental instrument in severe cases.

  1. Electrostatic Beneficiation of Coal

    SciTech Connect

    D. Lindquist; K. B. Tennal; M. K. Mazumder

    1998-10-29

    It was suggested in the proposal that small particles, due to low inertia, may not impact on the surfaces of the tribocharger. They would, thus, not receive charge and would not be beneficiated in the electrostatic separation. A milling process was proposed in which the small particles are stirred together with larger carrier beads producing the desired contact charge exchange. A force is necessary for removing the coal particles from the carrier beads. In copying machines electrostatic force is used to pull toner particles away horn iron carrier particles which are held back by magnetic force. Aerodynamic force is used in test instruments for measuring the charge to mass ratio on toners. A similar system of milling and removal is desired for use with the small coal particles. The carrier beads need to be made of copper rather than iron. This complicates the separation process since copper is non-magnetic. We are working on coating of iron beads with a layer of copper. Dr. Robert Engleken of Arkansas State University has supplied us with several test batches of copper-coated iron in the size range of -40 +70 mesh. ` We are currently testing whether the milling process used with the copper coated iron beads produces the desired charge on the coal particles.

  2. Undamped electrostatic plasma waves

    SciTech Connect

    Valentini, F.; Perrone, D.; Veltri, P.; Califano, F.; Pegoraro, F.; Morrison, P. J.; O'Neil, T. M.

    2012-09-15

    Electrostatic waves in a collision-free unmagnetized plasma of electrons with fixed ions are investigated for electron equilibrium velocity distribution functions that deviate slightly from Maxwellian. Of interest are undamped waves that are the small amplitude limit of nonlinear excitations, such as electron acoustic waves (EAWs). A deviation consisting of a small plateau, a region with zero velocity derivative over a width that is a very small fraction of the electron thermal speed, is shown to give rise to new undamped modes, which here are named corner modes. The presence of the plateau turns off Landau damping and allows oscillations with phase speeds within the plateau. These undamped waves are obtained in a wide region of the (k,{omega}{sub R}) plane ({omega}{sub R} being the real part of the wave frequency and k the wavenumber), away from the well-known 'thumb curve' for Langmuir waves and EAWs based on the Maxwellian. Results of nonlinear Vlasov-Poisson simulations that corroborate the existence of these modes are described. It is also shown that deviations caused by fattening the tail of the distribution shift roots off of the thumb curve toward lower k-values and chopping the tail shifts them toward higher k-values. In addition, a rule of thumb is obtained for assessing how the existence of a plateau shifts roots off of the thumb curve. Suggestions are made for interpreting experimental observations of electrostatic waves, such as recent ones in nonneutral plasmas.

  3. Electrostatic Plasma Accelerator (EPA)

    NASA Technical Reports Server (NTRS)

    Brophy, John R.; Aston, Graeme

    1995-01-01

    The application of electric propulsion to communications satellites, however, has been limited to the use of hydrazine thrusters with electric heaters for thrust and specific impulse augmentation. These electrothermal thrusters operate at specific impulse levels of approximately 300 s with heater powers of about 500 W. Low power arcjets (1-3 kW) are currently being investigated as a way to increase specific impulse levels to approximately 500 s. Ion propulsion systems can easily produce specific impulses of 3000 s or greater, but have yet to be applied to communications satellites. The reasons most often given for not using ion propulsion systems are their high level of overall complexity, low thrust with long burn times, and the difficulty of integrating the propulsion system into existing commercial spacecraft busses. The Electrostatic Plasma Accelerator (EPA) is a thruster concept which promises specific impulse levels between low power arcjets and those of the ion engine while retaining the relative simplicity of the arcjet. The EPA thruster produces thrust through the electrostatic acceleration of a moderately dense plasma. No accelerating electrodes are used and the specific impulse is a direct function of the applied discharge voltage and the propellant atomic mass.

  4. Electrostatic Plasma Accelerator (EPA)

    NASA Technical Reports Server (NTRS)

    Brophy, John R.; Aston, Graeme

    1995-01-01

    The application of electric propulsion to communications satellites, however, has been limited to the use of hydrazine thrusters with electric heaters for thrust and specific impulse augmentation. These electrothermal thrusters operate at specific impulse levels of approximately 300 s with heater powers of about 500 W. Low power arcjets (1-3 kW) are currently being investigated as a way to increase specific impulse levels to approximately 500 s. Ion propulsion systems can easily produce specific impulses of 3000 s or greater, but have yet to be applied to communications satellites. The reasons most often given for not using ion propulsion systems are their high level of overall complexity, low thrust with long burn times, and the difficulty of integrating the propulsion system into existing commercial spacecraft busses. The Electrostatic Plasma Accelerator (EPA) is a thruster concept which promises specific impulse levels between low power arcjets and those of the ion engine while retaining the relative simplicity of the arcjet. The EPA thruster produces thrust through the electrostatic acceleration of a moderately dense plasma. No accelerating electrodes are used and the specific impulse is a direct function of the applied discharge voltage and the propellant atomic mass.

  5. Accuracies of the synthesized monochromatic CT numbers and effective atomic numbers obtained with a rapid kVp switching dual energy CT scanner

    SciTech Connect

    Goodsitt, Mitchell M.; Christodoulou, Emmanuel G.; Larson, Sandra C.

    2011-04-15

    Purpose: This study was performed to investigate the accuracies of the synthesized monochromatic images and effective atomic number maps obtained with the new GE Discovery CT750 HD CT scanner. Methods: A Gammex-RMI model 467 tissue characterization phantom and the CT number linearity section of a Phantom Laboratory Catphan 600 phantom were scanned using the dual energy (DE) feature on the GE CT750 HD scanner. Synthesized monochromatic images at various energies between 40 and 120 keV and effective atomic number (Z{sub eff}) maps were generated. Regions of interest were placed within these images/maps to measure the average monochromatic CT numbers and average Z{sub eff} of the materials within these phantoms. The true Z{sub eff} values were either supplied by the phantom manufacturer or computed using Mayneord's equation. The linear attenuation coefficients for the true CT numbers were computed using the NIST XCOM program with the input of manufacturer supplied elemental compositions and densities. The effects of small variations in the assumed true densities of the materials were also investigated. Finally, the effect of body size on the accuracies of the synthesized monochromatic CT numbers was investigated using a custom lumbar section phantom with and without an external fat-mimicking ring. Results: Other than the Z{sub eff} of the simulated lung inserts in the tissue characterization phantom, which could not be measured by DECT, the Z{sub eff} values of all of the other materials in the tissue characterization and Catphan phantoms were accurate to 15%. The accuracies of the synthesized monochromatic CT numbers of the materials in both phantoms varied with energy and material. For the 40-120 keV range, RMS errors between the measured and true CT numbers in the Catphan are 8-25 HU when the true CT numbers were computed using the nominal plastic densities. These RMS errors improve to 3-12 HU for assumed true densities within the nominal density {+-}0.02 g

  6. Low voltage nanoelectromechanical switches based on silicon carbide nanowires.

    PubMed

    Feng, X L; Matheny, M H; Zorman, C A; Mehregany, M; Roukes, M L

    2010-08-11

    We report experimental demonstrations of electrostatically actuated, contact-mode nanoelectromechanical switches based on very thin silicon carbide (SiC) nanowires (NWs). These NWs are lithographically patterned from a 50 nm thick SiC layer heteroepitaxially grown on single-crystal silicon (Si). Several generic designs of in-plane electrostatic SiC NW switches have been realized, with NW widths as small as approximately 20 nm and lateral switching gaps as narrow as approximately 10 nm. Very low switch-on voltages are obtained, from a few volts down to approximately 1 V level. Two-terminal, contact-mode "hot" switching with high on/off ratios (>10(2) or 10(3)) has been demonstrated repeatedly for many devices. We find enhanced switching performance in bare SiC NWs, with lifetimes exceeding those based on metallized SiC NWs.

  7. Dual current readout for precision plating

    NASA Technical Reports Server (NTRS)

    Iceland, W. F.

    1970-01-01

    Bistable amplifier prevents damage in the low range circuitry of a dual scale ammeter. It senses the current and switches automatically to the high range circuitry as the current rises above a preset level.

  8. Dual photochemical replenisher system reduces chemical losses

    NASA Technical Reports Server (NTRS)

    Kolber, J. M.

    1967-01-01

    Dual replenisher system reduces chemical losses and maintains optimum solution concentration during long nonprocessing cycles of photo processing machines. Using a single 3-position switch and solenoid control valves, the system provides instantaneous flow control to each processing tank.

  9. Optical switches and switching methods

    DOEpatents

    Doty, Michael

    2008-03-04

    A device and method for collecting subject responses, particularly during magnetic imaging experiments and testing using a method such as functional MRI. The device comprises a non-metallic input device which is coupled via fiber optic cables to a computer or other data collection device. One or more optical switches transmit the subject's responses. The input device keeps the subject's fingers comfortably aligned with the switches by partially immobilizing the forearm, wrist, and/or hand of the subject. Also a robust nonmetallic switch, particularly for use with the input device and methods for optical switching.

  10. Surface-micromachined miniature rf switch

    NASA Astrophysics Data System (ADS)

    Guo, Fangmin; Lai, Zongsheng; Zhu, Ziqiang; Fan, Zhong; Long, Yongfu; Yang, Gen Q.; Ge, Xiaohong; Chen, Siqin; Xie, Jianfang

    2001-09-01

    A surface micromachined miniature switch has been made on silicon substrate using an electroplated gold micro-beam as the cantilevered arm, a chromium-to-gold electrical contact, and electrostatic actuation as the switching mechanism. The switch has an electrical isolation of -30dB in the 'off' state and an insertion loss of 4-7dB form 1 to 10 Ghz with a return loss of -15dB in the 'on' state. The high insertion loss has attributed to generation of parasitic current in low resistivity of the silicon substrate.

  11. Evidence of the direct involvement of the substrate TCP radical in functional switching from oxyferrous O2 carrier to ferric peroxidase in the dual-function hemoglobin/dehaloperoxidase from Amphitrite ornata.

    PubMed

    Sun, Shengfang; Sono, Masanori; Du, Jing; Dawson, John H

    2014-08-05

    The coelomic O2-binding hemoglobin dehaloperoxidase (DHP) from the sea worm Amphitrite ornata is a dual-function heme protein that also possesses a peroxidase activity. Two different starting oxidation states are required for reversible O2 binding (ferrous) and peroxidase (ferric) activity, bringing into question how DHP manages the two functions. In our previous study, the copresence of substrate 2,4,6-trichlorophenol (TCP) and H2O2 was found to be essential for the conversion of oxy-DHP to enzymatically active ferric DHP. On the basis of that study, a functional switching mechanism involving substrate radicals (TCP(•)) was proposed. To further support this mechanism, herein we report details of our investigations into the H2O2-mediated conversion of oxy-DHP to the ferric or ferryl ([TCP] < [H2O2]) state triggered by both biologically relevant [TCP and 4-bromophenol (4-BP)] and nonrelevant (ferrocyanide) compounds. At <50 μM H2O2, all of these conversion reactions are completely inhibited by ferric heme ligands (KCN and imidazole), indicating the involvement of ferric DHP. Furthermore, the spin-trapping reagent 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) effectively inhibits the TCP/4-BP (but not ferrocyanide)-triggered conversion of oxy-DHP to ferric DHP. These results and O2 concentration-dependent conversion rates observed in this study demonstrate that substrate TCP triggers the conversion of oxy-DHP to a peroxidase by TCP(•) oxidation of the deoxyferrous state. TCP(•) is progressively generated, by increasingly produced amounts of ferric DHP, upon H2O2 oxidation of TCP catalyzed initially by trace amounts of ferric enzyme present in the oxy-DHP sample. The data presented herein further address the mechanism of how the halophenolic substrate triggers the conversion of hemoglobin DHP into a peroxidase.

  12. Micromechanical Switches on GaAs for Microwave Applications

    NASA Technical Reports Server (NTRS)

    Randall, John N.; Goldsmith, Chuck; Denniston, David; Lin, Tsen-Hwang

    1995-01-01

    In this presentation, we describe the fabrication of micro-electro-mechanical system (MEMS) devices, in particular, of low-frequency multi-element electrical switches using SiO2 cantilevers. The switches discussed are related to micromechanical membrane structures used to perform switching of optical signals on silicon substrates. These switches use a thin metal membrane which is actuated by an electrostatic potential, causing the switch to make or break contact. The advantages include: superior isolation, high power handling capabilities, high radiation hardening, very low power operations, and the ability to integrate onto GaAs monolithic microwave integrated circuit (MMIC) chips.

  13. ELECTROSTATIC MEMORY SYSTEM

    DOEpatents

    Chu, J.C.

    1958-09-23

    An improved electrostatic memory system is de scribed fer a digital computer wherein a plarality of storage tubes are adapted to operate in either of two possible modes. According to the present irvention, duplicate storage tubes are provided fur each denominational order of the several binary digits. A single discriminator system is provided between corresponding duplicate tubes to determine the character of the infurmation stored in each. If either tube produces the selected type signal, corresponding to binazy "1" in the preferred embodiment, a "1" is regenerated in both tubes. In one mode of operation each bit of information is stored in two corresponding tubes, while in the other mode of operation each bit is stored in only one tube in the conventional manner.

  14. Versatile electrostatic trap

    SciTech Connect

    Veldhoven, Jacqueline van; Bethlem, Hendrick L.; Schnell, Melanie; Meijer, Gerard

    2006-06-15

    A four electrode electrostatic trap geometry is demonstrated that can be used to combine a dipole, quadrupole, and hexapole field. A cold packet of {sup 15}ND{sub 3} molecules is confined in both a purely quadrupolar and hexapolar trapping field and additionally, a dipole field is added to a hexapole field to create either a double-well or a donut-shaped trapping field. The profile of the {sup 15}ND{sub 3} packet in each of these four trapping potentials is measured, and the dependence of the well-separation and barrier height of the double-well and donut potential on the hexapole and dipole term are discussed.

  15. Teaching Electrostatics in University Courses

    ERIC Educational Resources Information Center

    Hughes, J. F.

    1974-01-01

    Describes an optional course on applied electrostatics that was offered to electrical engineers in their final year. Topics included the determination of electric fields, nature of the charging process, static electricity in liquids, solid state processes, charged particle applications, and electrostatic ignition. (GS)

  16. Teaching Electrostatics in University Courses

    ERIC Educational Resources Information Center

    Hughes, J. F.

    1974-01-01

    Describes an optional course on applied electrostatics that was offered to electrical engineers in their final year. Topics included the determination of electric fields, nature of the charging process, static electricity in liquids, solid state processes, charged particle applications, and electrostatic ignition. (GS)

  17. ION SWITCH

    DOEpatents

    Cook, B.

    1959-02-10

    An ion switch capable of transferring large magnitudes of power is described. An ion switch constructed in accordance with the invention includes a pair of spaced control electrodes disposed in a highly evacuated region for connection in a conventional circuit to control the passing of power therethrough. A controllable ionic conduction path is provided directiy between the control electrodes by a source unit to close the ion switch. Conventional power supply means are provided to trigger the source unit and control the magnitude, durations and pulse repetition rate of the aforementioned ionic conduction path.

  18. Designing and operating electrostatically driven microengines

    SciTech Connect

    Rodgers, M.S.; Sniegowski, J.J.; Miller, S.L.; LaVigne, G.F.

    1998-02-01

    Microelectromechanical engines that convert the linear outputs from dual orthogonal electrostatic actuators to rotary motion were first developed in 1993. Referred to as microengines, these early devices demonstrated the potential of microelectromechanical technology, but, as expected from any first-of-its-kind device, were not yet optimized. Yield was relatively low, and the 10 micronewtons of force generated by the actuators was not always enough to ensure reliable operation. Since initial development, these engines have undergone a continuous series of significant improvements on three separate fronts: design, fabrication, and electrical activation. Although all three areas will be discussed, emphasis will be on aspects related to mechanical design and generation of the electrical waveforms used to drive these devices. Microtransmissions that dramatically increase torque will also be discussed. Electrostatically driven microengines can be operated at hundreds of thousands of revolutions per minute making large gear reduction ratios feasible; overall ratios of 3,000,000:1 have been successfully demonstrated. Today`s microengines have evolved into high endurance (one test device has seen over 7,000,000,000 revolutions), high yield, robust devices that have become the primary actuation source for MicroElectroMechanical Systems (MEMS) at Sandia National Laboratories.

  19. Development of Electrostatic Actuator, which enables the Stable Contact Resistance, Driven at Low Voltage

    NASA Astrophysics Data System (ADS)

    Masuda, Takahiro; Seki, Tomonori; Miyaji, Takaaki; Sato, Fumihiko

    The switches play an important role in making the multifunctional radio communication circuit and therefore, the high-performance microminiaturized high-frequency switches are urgently expected. RF-MEMS switch with mechanical switching structure is hoped to improve both high-frequency signal loss and isolation quality simultaneously and to provide better linearity on the performance and compatibility to silicon-based circuit elements. But considering the applications, such as cellular phone and wireless-LAN, lower driving voltage and smaller switch dimensions are required. In order to solve these requirements, a novel electrostatic actuator with a unique structure of movable electrodes which enables the stable contact resistance is developed for RF-MEMS switches. This actuator has slits between the movable electrodes and the restoring spring. The electrostatic actuator with a movable electrode area of 0.5mm2 was driven at low voltage of 9-11V. And no defect due to restoration shortage is observed during switching test up to 400million cycles. In this paper, the results of mechanical design of the electrostatic actuator, the simulation, the experiments, and the reliability test are described

  20. Arterial switch.

    PubMed

    Planche, C; Lacour-Gayet, F; Serraf, A

    1998-01-01

    A relatively large spectra of anatomic variations are found within the unifying features of discordant ventriculoarterial connections. Variants that lend themselves to anatomic repair by the arterial switch operation are discussed, these include transposition of the great arteries with intact ventricular septum (TGA IVS), TGA associated with a ventricular septal defect (TGA VSD), double-outlet right ventricle with subpulmonary VSD (DORV VSD), and TGA or DORV with VSD associated with coarctation. Double discordance with VSD, which is currently treated by double switch or Rastelli and atrial switch and which probably represents, in our department, the only remaining indication for atrial switch, is not discussed. Also, we exclude TGA associated with pulmonary stenosis, which is treated by Rastelli or REV operation.

  1. Magnetic switching

    NASA Astrophysics Data System (ADS)

    Kirbie, H. C.

    1989-04-01

    Magnetic switching is a pulse compression technique that uses a saturable inductor (reactor) to pass pulses of energy between two capacitors. A high degree of pulse compression can be achieved in a network when several of these simple, magnetically switched circuits are connected in series. Individual inductors are designed to saturate in cascade as a pulse moves along the network. The technique is particularly useful when a single-pulse network must be very reliable or when a multi-pulse network must operate at a high pulse repetition frequency (PRF). Today, magnetic switches trigger spark gaps, sharpen the risetimes of high energy pulses, power large lasers, and drive high PRF linear induction accelerators. This paper will describe the technique of magnetic pulse compression using simple networks and design equations. A brief review of modern magnetic materials and of their role in magnetic switch design will be presented.

  2. Acceleration switch

    DOEpatents

    Abbin, J.P. Jr.; Devaney, H.F.; Hake, L.W.

    1979-08-29

    The disclosure relates to an improved integrating acceleration switch of the type having a mass suspended within a fluid filled chamber, with the motion of the mass initially opposed by a spring and subsequently not so opposed.

  3. Acceleration switch

    DOEpatents

    Abbin, Jr., Joseph P.; Devaney, Howard F.; Hake, Lewis W.

    1982-08-17

    The disclosure relates to an improved integrating acceleration switch of the type having a mass suspended within a fluid filled chamber, with the motion of the mass initially opposed by a spring and subsequently not so opposed.

  4. Nucleosome Switches

    NASA Astrophysics Data System (ADS)

    Schwab, David J.; Bruinsma, Robijn F.; Rudnick, Joseph; Widom, Jonathan

    2008-06-01

    We present a statistical-mechanical model for the positioning of nucleosomes along genomic DNA molecules as a function of the strength of the binding potential and the chemical potential of the nucleosomes. We show that a significant section of the DNA is composed of two-level nucleosome switching regions where the nucleosome distribution undergoes a localized, first-order transition. The location of the nucleosome switches shows a strong correlation with the location of gene-regulation regions.

  5. Nucleosome switches.

    PubMed

    Schwab, David J; Bruinsma, Robijn F; Rudnick, Joseph; Widom, Jonathan

    2008-06-06

    We present a statistical-mechanical model for the positioning of nucleosomes along genomic DNA molecules as a function of the strength of the binding potential and the chemical potential of the nucleosomes. We show that a significant section of the DNA is composed of two-level nucleosome switching regions where the nucleosome distribution undergoes a localized, first-order transition. The location of the nucleosome switches shows a strong correlation with the location of gene-regulation regions.

  6. Micromachined silicon electrostatic chuck

    DOEpatents

    Anderson, R.A.; Seager, C.H.

    1996-12-10

    An electrostatic chuck is faced with a patterned silicon plate, created by micromachining a silicon wafer, which is attached to a metallic base plate. Direct electrical contact between the chuck face (patterned silicon plate`s surface) and the silicon wafer it is intended to hold is prevented by a pattern of flat-topped silicon dioxide islands that protrude less than 5 micrometers from the otherwise flat surface of the chuck face. The islands may be formed in any shape. Islands may be about 10 micrometers in diameter or width and spaced about 100 micrometers apart. One or more concentric rings formed around the periphery of the area between the chuck face and wafer contain a low-pressure helium thermal-contact gas used to assist heat removal during plasma etching of a silicon wafer held by the chuck. The islands are tall enough and close enough together to prevent silicon-to-silicon electrical contact in the space between the islands, and the islands occupy only a small fraction of the total area of the chuck face, typically 0.5 to 5 percent. The pattern of the islands, together with at least one hole bored through the silicon veneer into the base plate, will provide sufficient gas-flow space to allow the distribution of the helium thermal-contact gas. 6 figs.

  7. Micromachined silicon electrostatic chuck

    DOEpatents

    Anderson, Robert A.; Seager, Carleton H.

    1996-01-01

    An electrostatic chuck is faced with a patterned silicon plate 11, created y micromachining a silicon wafer, which is attached to a metallic base plate 13. Direct electrical contact between the chuck face 15 (patterned silicon plate's surface) and the silicon wafer 17 it is intended to hold is prevented by a pattern of flat-topped silicon dioxide islands 19 that protrude less than 5 micrometers from the otherwise flat surface of the chuck face 15. The islands 19 may be formed in any shape. Islands may be about 10 micrometers in diameter or width and spaced about 100 micrometers apart. One or more concentric rings formed around the periphery of the area between the chuck face 15 and wafer 17 contain a low-pressure helium thermal-contact gas used to assist heat removal during plasma etching of a silicon wafer held by the chuck. The islands 19 are tall enough and close enough together to prevent silicon-to-silicon electrical contact in the space between the islands, and the islands occupy only a small fraction of the total area of the chuck face 15, typically 0.5 to 5 percent. The pattern of the islands 19, together with at least one hole 12 bored through the silicon veneer into the base plate, will provide sufficient gas-flow space to allow the distribution of the helium thermal-contact gas.

  8. Electrostatic drops in orbit

    NASA Astrophysics Data System (ADS)

    Rodriguez, Isabel J.; Schmidt, Erin; Weislogel, Mark M.; Pettit, Donald

    2016-11-01

    We present what we think are the first intentional electrostatic orbits in the near-weightless environment of a drop tower. Classical physics problems involving Coulombic forces in orbital mechanics have traditionally been confined to thought experiments due to practical terrestrial experimental limitations, namely, the preponderance of gravity. However, the use of a drop tower as an experimental platform can overcome this challenge for brief periods. We demonstrate methanol-water droplets in orbit around a variety of charged objects- some of which can be used to validate special cases of N-body systems. Footage collected via a high-speed camera is analyzed and orbital trajectories are compared with existing theoretical predictions. Droplets of diameters 0.5 to 2mm in a variety of obits are observed. Due to the repeatability of drop tower initial conditions and effective low-g environment, such experiments may be used to construct empirical analogues and confirm analyses toward the benefit of other fields including space and planetary science. NASA Cooperative Agreement NNX12A047A, Portland State LSAMP, Robert E. McNair Scholars Program.

  9. A spherical electrostatic orrery

    NASA Astrophysics Data System (ADS)

    Smetana, Carole; Alexander, David; Robertson, Scott; Vilkaitis, Kim; Walch, Bob

    1996-11-01

    An electrostatic orrery for studying Keplerian orbits has been constructed in which one or more negatively charged hollow glass microparticles orbit a 9.5-mm-diam metal sphere at +8-kV potential in a vacuum. The device is similar to an earlier cylindrical orrery in which particles orbit a rod [Biewer et al., Am. J. Phys. 62(9), 821-827 (1994)]. Electrically biased cylinders covering the rod supporting the sphere give nearly spherical potential surfaces inside the trap. Additional electrodes at the boundary are used to reduce the perturbation of gravity and to prevent motion resulting in collisions with the supporting rod. Orbits last approximately 10 min or about 104 revolutions. The orbiters are illuminated with a slide projector and can be seen with the naked eye as well as videotaped. The trap has been used to observe orbital precession, interparticle collisions, and the effects of time-independent perturbations. This apparatus provides an opportunity for the study and demonstration of orbital motion in a laboratory.

  10. The Electrostatic Bell

    NASA Astrophysics Data System (ADS)

    Martrou, Guillaume; Leonetti, Marc

    2016-11-01

    An initially static fluid-fluid interface is known to become unstable under a strong electric field leading to jet instability, surface pattern and spout formation. Applying an electric field to an initial dripping mode accelerates the dripping rate and leads to a continuous jet mode. We show that those two different configurations, when applied to dielectric liquids, can lead to the same instability, the formation of an unexpected macroscopic fluid bell-shape of typical size few times the capillary length even if the needle is as small as 200 μm . The instability results from the competition between the dielectric and the gravity forces, reminiscent of the Taylor-Melcher mechanism. The study is performed on several fluids of various densities, permittivity and surface tension on a large range of electric field. We show that the transition is an imperfect subcritical bifurcation with its characteristic bottleneck effect (lag time). Finally, in the case of flow rate, we established a shape diagram with four domains corresponding to dripping, jetting, bridge and electrostatic bell.

  11. Dual redundant core memory systems

    NASA Technical Reports Server (NTRS)

    Hull, F. E.

    1972-01-01

    Electronic memory system consisting of series redundant drive switch circuits, triple redundant majority voted memory timing functions, and two data registers to provide functional dual redundancy is described. Signal flow through the circuits is illustrated and equence of events which occur within the memory system is explained.

  12. Cygnus Diverter Switch Analysis

    SciTech Connect

    G. Corrow, M. Hansen, D. Henderson, C. Mitton et al.

    2008-02-01

    The Cygnus Dual Beam Radiographic Facility consists of two 2.25-MV, 60-kA, 50-ns x-ray sources fielded in an underground laboratory at the Nevada Test Site. The tests performed in this laboratory involve study of the dynamic properties of plutonium and are called subcritical experiments. From end-to-end, the Cygnus machines utilize the following components: Marx generator, water-filled pulse-forming line (PFL), waterfilled coaxial transmission line (WTL), 3-cell inductive voltage adder (IVA), and rod-pinch diode. The upstream WTL interface to the PFL is via a radial insulator with coaxial geometry. The downstream WTL terminates in a manifold where the center conductor splits into three lines which individually connect to each of the IVA cell inputs. There is an impedance mismatch at this juncture. It is a concern that a reflected pulse due to anomalous behavior in the IVA or diode might initiate breakdown upon arrival at the upstream PFL/WTL insulator. Therefore near the beginning of the WTL a radial diverter switch is installed to protect the insulator from over voltage and breakdown. The diverter has adjustable gap spacing, and an in-line aqueous-solution (sodium thiosulfate) resistor array for energy dissipation. There are capacitive voltage probes at both ends of the WTL and on the diverter switch. These voltage signals will be analyzed to determine diverter performance. Using this analysis the usefulness of the diverter switch will be evaluated.

  13. Explosion safety in industrial electrostatics

    NASA Astrophysics Data System (ADS)

    Szabó, S. V.; Kiss, I.; Berta, I.

    2011-01-01

    Complicated industrial systems are often endangered by electrostatic hazards, both from atmospheric (lightning phenomenon, primary and secondary lightning protection) and industrial (technological problems caused by static charging and fire and explosion hazards.) According to the classical approach protective methods have to be used in order to remove electrostatic charging and to avoid damages, however no attempt to compute the risk before and after applying the protective method is made, relying instead on well-educated and practiced expertise. The Budapest School of Electrostatics - in close cooperation with industrial partners - develops new suitable solutions for probability based decision support (Static Control Up-to-date Technology, SCOUT) using soft computing methods. This new approach can be used to assess and audit existing systems and - using the predictive power of the models - to design and plan activities in industrial electrostatics.

  14. Computational Methods for Biomolecular Electrostatics

    PubMed Central

    Dong, Feng; Olsen, Brett; Baker, Nathan A.

    2008-01-01

    An understanding of intermolecular interactions is essential for insight into how cells develop, operate, communicate and control their activities. Such interactions include several components: contributions from linear, angular, and torsional forces in covalent bonds, van der Waals forces, as well as electrostatics. Among the various components of molecular interactions, electrostatics are of special importance because of their long range and their influence on polar or charged molecules, including water, aqueous ions, and amino or nucleic acids, which are some of the primary components of living systems. Electrostatics, therefore, play important roles in determining the structure, motion and function of a wide range of biological molecules. This chapter presents a brief overview of electrostatic interactions in cellular systems with a particular focus on how computational tools can be used to investigate these types of interactions. PMID:17964951

  15. Electrostatic prepregging of thermoplastic matrices

    NASA Technical Reports Server (NTRS)

    Muzzy, John D.; Varughese, Babu; Thammongkol, Vivan; Tincher, Wayne

    1989-01-01

    Thermoplastic towpregs of PEEK/AS-4, PEEK/S-2 glass and LaRC-TPI/AS-4, produced by electrostatic deposition of charged and fluidized polymer powders on spread continuous fiber tows, are described. Processing parameters for combining PEEK 150 powder with unsized 3k AS-4 carbon fiber are presented. The experimental results for PEEK 150/AS-4 reveal that electrostatic fluidized bed coating may be an economically attractive process for producing towpreg.

  16. Optical switch

    DOEpatents

    Reedy, Robert P.

    1987-01-01

    An optical switching device (10) is provided whereby light from a first glass fiber (16) or a second glass fiber (14) may be selectively transmitted into a third glass fiber (18). Each glass fiber is provided with a focusing and collimating lens system (26, 28, 30). In one mode of operation, light from the first glass fiber (16) is reflected by a planar mirror (36) into the third glass fiber (18). In another mode of operation, light from the second glass fiber (14) passes directly into the third glass fiber (18). The planar mirror (36) is attached to a rotatable table (32) which is rotated to provide the optical switching.

  17. Optical switch

    DOEpatents

    Reedy, R.P.

    1987-11-10

    An optical switching device is provided whereby light from a first glass fiber or a second glass fiber may be selectively transmitted into a third glass fiber. Each glass fiber is provided with a focusing and collimating lens system. In one mode of operation, light from the first glass fiber is reflected by a planar mirror into the third glass fiber. In another mode of operation, light from the second glass fiber passes directly into the third glass fiber. The planar mirror is attached to a rotatable table which is rotated to provide the optical switching. 3 figs.

  18. Optical switch

    DOEpatents

    Reedy, R.P.

    1985-01-18

    An optical switching device is provided whereby light from a first glass fiber or a second glass fiber may be selectively transmitted into a third glass fiber. Each glass fiber is provided with a focusing and collimating lens system. In one mode of operation, light from the first glass fiber is reflected by a planar mirror into the third glass fiber. In another mode of operation, light from the second glass fiber passes directly into the third glass fiber. The planar mirror is attached to a rotatable table which is rotated to provide the optical switching.

  19. Voltage-Boosting Driver For Switching Regulator

    NASA Technical Reports Server (NTRS)

    Trump, Ronald C.

    1990-01-01

    Driver circuit assures availability of 10- to 15-V gate-to-source voltage needed to turn on n-channel metal oxide/semiconductor field-effect transistor (MOSFET) acting as switch in switching voltage regulator. Includes voltage-boosting circuit efficiently providing gate voltage 10 to 15 V above supply voltage. Contains no exotic parts and does not require additional power supply. Consists of NAND gate and dual voltage booster operating in conjunction with pulse-width modulator part of regulator.

  20. Voltage-Boosting Driver For Switching Regulator

    NASA Technical Reports Server (NTRS)

    Trump, Ronald C.

    1990-01-01

    Driver circuit assures availability of 10- to 15-V gate-to-source voltage needed to turn on n-channel metal oxide/semiconductor field-effect transistor (MOSFET) acting as switch in switching voltage regulator. Includes voltage-boosting circuit efficiently providing gate voltage 10 to 15 V above supply voltage. Contains no exotic parts and does not require additional power supply. Consists of NAND gate and dual voltage booster operating in conjunction with pulse-width modulator part of regulator.

  1. A physically based model for dielectric charging in an integrated optical MEMS wavelength selective switch.

    SciTech Connect

    Nielson, Gregory N.; Barbastathis, George

    2005-07-01

    A physical parameter based model for dielectric charge accumulation is proposed and used to predict the displacement versus applied voltage and pull-in response of an electrostatic MEMS wavelength selective integrated optical switch.

  2. Electrostatically driven complexation

    NASA Astrophysics Data System (ADS)

    Netz, Roland

    2004-03-01

    Many biological and synthetic systems are electrically charged, which makes them soluble in aqueous environments. Often, electrostatic interactions are dominant, and lead to complexation (i.e. tight aggregation) of oppositely charged objects. As an example, charged polymers such as DNA exhibit a number of different complexation modes when mixed with other charged objects such as spheres or cylinders. A simple model for the complexation of semiflexible polyelectrolytes with oppositely charged spheres is considered, which can exhibit tightly wrapped polymer structures. Using the appropriate parameters for DNA-histone complexes, one finds complete wrapping for intermediate salt concentrations only, in agreement with experiments. The forces needed to pull the DNA off from histones show a plateau at 10-40 pN (depending on salt concentration). We also consider the interaction between such complexes, which have been measured using osmometry, and found to be attractive for intermediate salt concentration (suggesting precipitation) and repulsive elsewhere. Chain fluctuations can be treated within a normal-mode analysis and distinguish associated-unwrapped from dissociated structures. Since some time it is known that also similarly charged objects attract each other for sufficiently large surface-charge densities and/or in the presence of multivalent ions, a phenomenon not explicable within standard (Poisson-Boltzmann) approaches. The so-called strong-coupling theory, valid in the limit of large surface charge densities and for multi-valent ions, yields attraction between similarly charged walls, cylinders, and spheres in quantitative agreement with Monte-Carlo simulations. Charged complexes can be destroyed by applying an electric field, which is an important factor in understanding their electrophoresis. By performing dynamic simulations, the relation between the electrophoretic mobility and the non-equilibrium perturbation of the complex structure is investigated. 1

  3. Designing pH induced fold switch in proteins

    NASA Astrophysics Data System (ADS)

    Baruah, Anupaul; Biswas, Parbati

    2015-05-01

    This work investigates the computational design of a pH induced protein fold switch based on a self-consistent mean-field approach by identifying the ensemble averaged characteristics of sequences that encode a fold switch. The primary challenge to balance the alternative sets of interactions present in both target structures is overcome by simultaneously optimizing two foldability criteria corresponding to two target structures. The change in pH is modeled by altering the residual charge on the amino acids. The energy landscape of the fold switch protein is found to be double funneled. The fold switch sequences stabilize the interactions of the sites with similar relative surface accessibility in both target structures. Fold switch sequences have low sequence complexity and hence lower sequence entropy. The pH induced fold switch is mediated by attractive electrostatic interactions rather than hydrophobic-hydrophobic contacts. This study may provide valuable insights to the design of fold switch proteins.

  4. Designing pH induced fold switch in proteins.

    PubMed

    Baruah, Anupaul; Biswas, Parbati

    2015-05-14

    This work investigates the computational design of a pH induced protein fold switch based on a self-consistent mean-field approach by identifying the ensemble averaged characteristics of sequences that encode a fold switch. The primary challenge to balance the alternative sets of interactions present in both target structures is overcome by simultaneously optimizing two foldability criteria corresponding to two target structures. The change in pH is modeled by altering the residual charge on the amino acids. The energy landscape of the fold switch protein is found to be double funneled. The fold switch sequences stabilize the interactions of the sites with similar relative surface accessibility in both target structures. Fold switch sequences have low sequence complexity and hence lower sequence entropy. The pH induced fold switch is mediated by attractive electrostatic interactions rather than hydrophobic-hydrophobic contacts. This study may provide valuable insights to the design of fold switch proteins.

  5. Optimization of electrostatic dual-grid beam-deflection system

    NASA Technical Reports Server (NTRS)

    Hudson, W. R.; Lathem, W. C.; Power, J. L.; Banks, B. A.

    1972-01-01

    Tests were performed to minimize accelerator grid erosion of a 5-cm diameter Kaufman ion thruster due to direct beam impingement. Several different screen hole diameters, pillow-shape-square screen holes, and dished screen grids were tried. The optimization was accomplished by copper plating the accelerator grid before testing each grid configuration on a thruster for a 2-hour run. The thruster beam sputtered copper and molybdenum from the accelerator grid where the beam impinged. The observed erosion patterns and measured accelerator currents were used to determine how to modify the accelerator system. The lowest erosion was obtained for a 50-percent open area pillow-shape-square-aperture screen grid, dished 0.043 centimeter convex toward the accelerator grid, which was positioned with the center of the screen grid 0.084 centimeter from the accelerator grid. During this investigation the accelerator current was reduced from 120 to 55 microamperes and was also more uniformly distributed over the area of the accelerator grid.

  6. Switching Transistor

    NASA Technical Reports Server (NTRS)

    1981-01-01

    Westinghouse Electric Corporation's D60T transistors are used primarily as switching devices for controlling high power in electrical circuits. It enables reduction in the number and size of circuit components and promotes more efficient use of energy. Wide range of application from a popcorn popper to a radio frequency generator for solar cell production.

  7. EPRICON: Agentless flue gas conditioning for electrostatic precipitators

    SciTech Connect

    Bibbo, P.P.

    1995-09-01

    Achieving efficient particulate control in coal burning electric utility plants is becoming an increasingly difficult proposition, giver, the variety of regulatory, technical, operating and environmental pressures that exist in the US. For most powerplants, particulate control is achieved by an electrostatic precipitator (ESP). Under optimal conditions, modern ESPs are capable of achieving particulate removal efficiencies of 99.7 %. Unfortunately, optimal conditions are not always present. ESP`s are sensitive to flue gas conditions, and those conditions may change dramatically after a fuel switch or the installation of some types of emissions control technology upstream of the ESP. Gas conditioning has been shown to be an effective means of returning flue gas to the ``optimal`` conditions required for efficient ESP operation following a fuel switch to a low, or at least, lower sulfur coal. Borrowing technology common in conventional soap-making plants around the turn of the century, sulfur-burning SO3 gas conditioning has been the solution to may difficult fuels in electrostatic precipitators. Although it has contributed most to improved ESP performance after a fuel switch, conventional gas conditioning has significant drawbacks. In an effort to develop an alternative to conventional SO{sub 3} gas conditioning, the Electric Power Research Institute (EPRI) initiated a research and development project that has produced an alternative and modem technology for flue gas conditioning, now called EPRICON, and licensed it to Research-Cottrell. This article describes the EPRICON process and its performance in pilot and demonstration plants.

  8. Switched power workshop. [Switched power electron guns

    SciTech Connect

    Palmer, R.B.

    1988-01-01

    This paper discusses the design of a switched power electron gun. Particular topics discussed are: vacuum photodiode switch; laser switched solid state diodes; gun performance; charging supply; and laser requirements. (LSP)

  9. Engineering scale electrostatic enclosure demonstration

    SciTech Connect

    Meyer, L.C.

    1993-09-01

    This report presents results from an engineering scale electrostatic enclosure demonstration test. The electrostatic enclosure is part of an overall in-depth contamination control strategy for transuranic (TRU) waste recovery operations. TRU contaminants include small particles of plutonium compounds associated with defense-related waste recovery operations. Demonstration test items consisted of an outer Perma-con enclosure, an inner tent enclosure, and a ventilation system test section for testing electrostatic curtain devices. Three interchangeable test fixtures that could remove plutonium from the contaminated dust were tested in the test section. These were an electret filter, a CRT as an electrostatic field source, and an electrically charged parallel plate separator. Enclosure materials tested included polyethylene, anti-static construction fabric, and stainless steel. The soil size distribution was determined using an eight stage cascade impactor. Photographs of particles containing plutonium were obtained with a scanning electron microscope (SEM). The SEM also provided a second method of getting the size distribution. The amount of plutonium removed from the aerosol by the electrostatic devices was determined by radiochemistry from input and output aerosol samplers. The inner and outer enclosures performed adequately for plutonium handling operations and could be used for full scale operations.

  10. Finite element based electrostatic-structural coupled analysis with automated mesh morphing

    SciTech Connect

    OWEN,STEVEN J.; ZHULIN,V.I.; OSTERGAARD,D.F.

    2000-02-29

    A co-simulation tool based on finite element principles has been developed to solve coupled electrostatic-structural problems. An automated mesh morphing algorithm has been employed to update the field mesh after structural deformation. The co-simulation tool has been successfully applied to the hysteric behavior of a MEMS switch.

  11. Figuring on energy: fuel-switch mirage

    SciTech Connect

    Schaffer, P.

    1984-06-25

    DOE's Petroleum Supply Annual: 1983 does not support the idea that the 1981-83 drop in natural gas consumption was due to industrial users switching to oil. A consumption breakdown shows a pattern of reduced oil use during the same period. The American Gas Association estimates that gas utilities lost 0.325 quads in 1982 because of dual-fuel switching, but gas consumption continued to decline even after the fuel-switching trend reversed. The author traces the problem to state rate regulators whose policies subsidize residential users at the expense of industry rather than to interfuel competition.

  12. Surface electrostatics: theory and computations

    PubMed Central

    Chatzigeorgiou, G.; Javili, A.; Steinmann, P.

    2014-01-01

    The objective of this work is to study the electrostatic response of materials accounting for boundary surfaces with their own (electrostatic) constitutive behaviour. The electric response of materials with (electrostatic) energetic boundary surfaces (surfaces that possess material properties and constitutive structures different from those of the bulk) is formulated in a consistent manner using a variational framework. The forces and moments that appear due to bulk and surface electric fields are also expressed in a consistent manner. The theory is accompanied by numerical examples on porous materials using the finite-element method, where the influence of the surface electric permittivity on the electric displacement, the polarization stress and the Maxwell stress is examined. PMID:24711720

  13. Synthesis of electrostatic multielectrode deflectors

    SciTech Connect

    Cho, H.; Szilagyi, M.

    1995-09-01

    Synthesis of electrostatic deflectors with given source parameters, first-order properties, and minimum aberrations can be realized by using the cubic spline method or the {ital a} {ital priori} given multielectrode approach. Synthesis of electrostatic deflectors was successfully achieved previously by using the cubic spline method. In this paper we present synthesis of electrostatic deflectors based on the {ital a} {ital priori} given multielectrode approach for the purpose of obtaining the minimum beam spot size through a sequential optimization technique. Our calculations show that the third-order geometrical deflection aberrations can be reduced by about two to three orders of magnitude using a multielectrode deflector with three units or five units, each having short cylindrical segments with geometrically octupole symmetry. {copyright} {ital 1995} {ital American} {ital Vacuum} {ital Society}

  14. Polarizable multipolar electrostatics for cholesterol

    NASA Astrophysics Data System (ADS)

    Fletcher, Timothy L.; Popelier, Paul L. A.

    2016-08-01

    FFLUX is a novel force field under development for biomolecular modelling, and is based on topological atoms and the machine learning method kriging. Successful kriging models have been obtained for realistic electrostatics of amino acids, small peptides, and some carbohydrates but here, for the first time, we construct kriging models for a sizeable ligand of great importance, which is cholesterol. Cholesterol's mean total (internal) electrostatic energy prediction error amounts to 3.9 kJ mol-1, which pleasingly falls below the threshold of 1 kcal mol-1 often cited for accurate biomolecular modelling. We present a detailed analysis of the error distributions.

  15. Electrostatic Unbalances of Transmission Lines.

    DTIC Science & Technology

    1985-08-01

    RD-A±68 742 ELECTROSTATIC UMBALANCES OF TEMNISSION LINES(U) AIR 1V2 FORCE INST OF TECH WRIGHNT-PATTERSON AFD OH J NOUIKOWSKI AUG 85 AFIT/CI/ NR -BS...CONTROLLING OFFICE NAME AND ADORESS 12. REPORT DATE AFIT/ NR 1985 WPAFB OH 45433 - 6583 1i. NUMBER OF PAGES ___102 14. MONITORING AGENCY NAME & ADDRESS...return it to: AF IT/ NR Wright-Patterson AFB OH 45433 RESEARCH TITLE: Electrostatic Unbalances oJCTransmission Lines *AUTHOR: Jioseph Nowikowski

  16. Electrostatically actuatable light modulating device

    DOEpatents

    Koehler, Dale R.

    1991-01-01

    The electrostatically actuatable light modulator utilizes an opaque substrate plate patterned with an array of aperture cells, the cells comprised of physically positionable dielectric shutters and electrostatic actuators. With incorporation of a light source and a viewing screen, a projection display system is effected. Inclusion of a color filter array aligned with the aperture cells accomplishes a color display. The system is realized in terms of a silicon based manufacturing technology allowing fabrication of a high resolution capability in a physically small device which with the utilization of included magnification optics allows both large and small projection displays.

  17. Electrostatic disturbances aboard LISA Pathfinder

    NASA Astrophysics Data System (ADS)

    Ferroni, Valerio

    Test mass charging and stray electrostatic fields are a potentially important source of force noise for the LISA Pathfinder mission. During the flight we plan to measure the relevant stray electrostatic fields on the surfaces of both the test mass and the electrode housing and compensate them with DC electrode bias voltages. In addition we monitor the charge and reduce it to near zero by UV illumination. We describe the analysis techniques used during the mission and explain the importance of periodic charging/discharging and of long-term charge measurements to limit the force noise at low frequency, which is particularly relevant for the eLISA mission.

  18. Fabrication of nanoscale electrostatic lenses

    NASA Astrophysics Data System (ADS)

    Sinno, I.; Sanz-Velasco, A.; Kang, S.; Jansen, H.; Olsson, E.; Enoksson, P.; Svensson, K.

    2010-09-01

    The fabrication of cylindrical multi-element electrostatic lenses at the nanoscale presents a challenge; they are high-aspect-ratio structures that should be rotationally symmetric, well aligned and freestanding, with smooth edges and flat, clean surfaces. In this paper, we present the fabrication results of a non-conventional process, which uses a combination of focused gallium ion-beam milling and hydrofluoric acid vapor etching. This process makes it possible to fabricate nanoscale electrostatic lenses down to 140 nm in aperture diameter and 4.2 µm in column length, with a superior control of the geometry as compared to conventional lithography-based techniques.

  19. Electrostatics at the molecular level

    NASA Astrophysics Data System (ADS)

    Zürcher, Ulrich

    2017-01-01

    In molecular systems, positive and negative charges are separated, making them ideal systems to examine electrostatic interactions. The attractive force between positive and negative charges is balanced by repulsive ‘forces’ that are quantum-mechanical in origin. We introduce an ‘effective’ potential energy that captures the repulsion; it allows us to obtain fairly accurate estimates of the bonding properties of molecular systems. We use units (e.g., kcal mol-1 for energy) that emphasize the relevance of electrostatics to macroscopic behavior.

  20. Charge sniffer for electrostatics demonstrations

    NASA Astrophysics Data System (ADS)

    Dinca, Mihai P.

    2011-02-01

    An electronic electroscope with a special design for demonstrations and experiments on static electricity is described. It operates as an electric charge sniffer by detecting slightly charged objects when they are brought to the front of its sensing electrode. The sniffer has the advantage of combining high directional sensitivity with a logarithmic bar display. It allows for the identification of electric charge polarity during charge separation by friction, peeling, electrostatic induction, batteries, or secondary coils of power transformers. Other experiments in electrostatics, such as observing the electric field of an oscillating dipole and the distance dependence of the electric field generated by simple charge configurations, are also described.

  1. Switch-less operation of a TEA CO2 laser.

    PubMed

    Biswas, Dhruba; Nilaya, J; Sai Prasad, M; Raote, Pallavi

    2005-11-14

    We report here the operation of a UV pre-ionised mini-TEA CO2 laser where the use of an external switch has been dispensed with. This was rendered possible by making the preioniser spark array play a dual role- that of a switch as well as of a source of UV photons that pre-conditioned the inter-electrode volume.

  2. Resistivity Problems in Electrostatic Precipitation

    ERIC Educational Resources Information Center

    White, Harry J.

    1974-01-01

    The process of electrostatic precipitation has ever-increasing application in more efficient collection of fine particles from industrial air emissions. This article details a large number of new developments in the field. The emphasis is on high resistivity particles which are a common cause of poor precipitator performance. (LS)

  3. Electrostatic Precipitator (ESP) TRAINING MANUAL

    EPA Science Inventory

    The manual assists engineers in using a computer program, the ESPVI 4.0W, that models all elements of an electrostatic precipitator (ESP). The program is a product of the Electric Power Research Institute and runs in the Windows environment. Once an ESP is accurately modeled, the...

  4. Defining protein electrostatic recognition processes

    NASA Astrophysics Data System (ADS)

    Getzoff, Elizabeth D.; Roberts, Victoria A.

    The objective is to elucidate the nature of electrostatic forces controlling protein recognition processes by using a tightly coupled computational and interactive computer graphics approach. The TURNIP program was developed to determine the most favorable precollision orientations for two molecules by systematic search of all orientations and evaluation of the resulting electrostatic interactions. TURNIP was applied to the transient interaction between two electron transfer metalloproteins, plastocyanin and cytochrome c. The results suggest that the productive electron-transfer complex involves interaction of the positive region of cytochrome c with the negative patch of plastocyanin, consistent with experimental data. Application of TURNIP to the formation of the stable complex between the HyHEL-5 antibody and its protein antigen lysozyme showed that long-distance electrostatic forces guide lysozyme toward the HyHEL-5 binding site, but do not fine tune its orientation. Determination of docked antigen/antibody complexes requires including steric as well as electrostatic interactions, as was done for the U10 mutant of the anti-phosphorylcholine antibody S107. The graphics program Flex, a convenient desktop workstation program for visualizing molecular dynamics and normal mode motions, was enhanced. Flex now has a user interface and was rewritten to use standard graphics libraries, so as to run on most desktop workstations.

  5. Electrostatic Precipitator (ESP) TRAINING MANUAL

    EPA Science Inventory

    The manual assists engineers in using a computer program, the ESPVI 4.0W, that models all elements of an electrostatic precipitator (ESP). The program is a product of the Electric Power Research Institute and runs in the Windows environment. Once an ESP is accurately modeled, the...

  6. Electrostatic spin crossover effect in polar magnetic molecules

    NASA Astrophysics Data System (ADS)

    Baadji, Nadjib; Piacenza, Manuel; Tugsuz, Tugba; Sala, Fabio Della; Maruccio, Giuseppe; Sanvito, Stefano

    2009-10-01

    The magnetic configuration of a nanostructure can be altered by an external magnetic field, by spin-transfer torque or by its magnetoelastic response. Here, we explore an alternative route, namely the possibility of switching the sign of the exchange coupling between two magnetic centres by means of an electric potential. This general effect, which we name electrostatic spin crossover, occurs in insulating molecules with super-exchange magnetic interaction and inversion symmetry breaking. As an example we present the case of a family of di-cobaltocene-based molecules. The critical fields for switching, calculated from first principles, are of the order of 1Vnm-1 and can be achieved in two-terminal devices. More crucially, such critical fields can be engineered with an appropriate choice of substituents to add to the basic di-cobaltocene unit. This suggests that an easy chemical strategy for achieving the synthesis of suitable molecules is possible.

  7. A Simple Apparatus for Electrostatic Force Measurement.

    ERIC Educational Resources Information Center

    Hale, D. P.

    1981-01-01

    Describes the construction of an apparatus that demonstrates that electrostatic forces can be large and also gives some idea of dependence of electrostatic forces between charged parallel discs on potential differences and separation. (CS)

  8. Fast 1 kV metal-oxide-semiconductor field-effect transistor switch

    NASA Astrophysics Data System (ADS)

    Dedman, C. J.; Roberts, E. H.; Gibson, S. T.; Lewis, B. R.

    2001-09-01

    A fast, high-voltage switch based on cheap and readily available components is described. This simple circuit can switch 1 kV to ground with a fall time of ˜2.5 ns, and has proved a cost-effective means of driving electrostatic gating and rereferencing devices in pulsed ion-beam experiments.

  9. Air-bridge and Vertical CNT Switches for High Performance Switching Applications

    NASA Technical Reports Server (NTRS)

    Kaul, Anupama B.; Wong, Eric W.; Epp, Larry; Bronikowski, Michael J.; Hunt, BBrian D.

    2006-01-01

    Carbon nanotubes are attractive for switching applications since electrostatically-actuated CNT switches have low actuation voltages and power requirements, while allowing GHz switching speeds that stem from the inherently high elastic modulus and low mass of the CNT.Our first NEM structure, the air-bridge switch, consists of suspended single-walled nanotubes (SWNTs) that lie above a sputtered Nb base electrode, where contact to the CNTs is made using evaporated Au/Ti. Electrical measurements of these air-bridge devices show well-defined ON and OFF states as a dc bias of a few volts is applied between the CNT and the Nb-base electrode. The CNT air-bridge switches were measured to have switching times down to a few nanoseconds. Our second NEM structure, the vertical CNT switch, consists of nanotubes grown perpendicular to the substrate. Vertical multi-walled nanotubes (MWNTs) are grown directly on a heavily doped Si substrate, from 200 - 300 nm wide, approximately 1 micrometer deep nano-pockets, with Nb metal electrodes to result in the formation of a vertical single-pole-double-throw switch architecture.

  10. Quantitative nanoscale electrostatics of viruses

    NASA Astrophysics Data System (ADS)

    Hernando-Pérez, M.; Cartagena-Rivera, A. X.; Lošdorfer Božič, A.; Carrillo, P. J. P.; San Martín, C.; Mateu, M. G.; Raman, A.; Podgornik, R.; de Pablo, P. J.

    2015-10-01

    Electrostatics is one of the fundamental driving forces of the interaction between biomolecules in solution. In particular, the recognition events between viruses and host cells are dominated by both specific and non-specific interactions and the electric charge of viral particles determines the electrostatic force component of the latter. Here we probe the charge of individual viruses in liquid milieu by measuring the electrostatic force between a viral particle and the Atomic Force Microscope tip. The force spectroscopy data of co-adsorbed φ29 bacteriophage proheads and mature virions, adenovirus and minute virus of mice capsids is utilized for obtaining the corresponding density of charge for each virus. The systematic differences of the density of charge between the viral particles are consistent with the theoretical predictions obtained from X-ray structural data. Our results show that the density of charge is a distinguishing characteristic of each virus, depending crucially on the nature of the viral capsid and the presence/absence of the genetic material.Electrostatics is one of the fundamental driving forces of the interaction between biomolecules in solution. In particular, the recognition events between viruses and host cells are dominated by both specific and non-specific interactions and the electric charge of viral particles determines the electrostatic force component of the latter. Here we probe the charge of individual viruses in liquid milieu by measuring the electrostatic force between a viral particle and the Atomic Force Microscope tip. The force spectroscopy data of co-adsorbed φ29 bacteriophage proheads and mature virions, adenovirus and minute virus of mice capsids is utilized for obtaining the corresponding density of charge for each virus. The systematic differences of the density of charge between the viral particles are consistent with the theoretical predictions obtained from X-ray structural data. Our results show that the density of

  11. Quantum coherent switch utilizing commensurate nanoelectrode and charge density periodicities

    DOEpatents

    Harrison, Neil; Singleton, John; Migliori, Albert

    2008-08-05

    A quantum coherent switch having a substrate formed from a density wave (DW) material capable of having a periodic electron density modulation or spin density modulation, a dielectric layer formed onto a surface of the substrate that is orthogonal to an intrinsic wave vector of the DW material; and structure for applying an external spatially periodic electrostatic potential over the dielectric layer.

  12. Enhanced performance of electrostatic precipitators through chemical modification of particle resistivity and cohesion

    SciTech Connect

    Durham, M.D.; Baldrey, K.E.; Bustard, C.J.

    1995-11-01

    Control of fine particles, including particulate air toxics, from utility boilers is required near-term by state and federal air regulations. Electrostatic precipitators (ESP) serve as the primary air pollution control device for the majority of coal-fired utility boilers in the Eastern and Midwestern united States. Cost-effective retrofit technologies for fine particle control, including flue gas conditioning, are needed for the large base of existing ESPs. Flue has conditioning is an attractive option because it requires minimal structural changes and lower capital costs. For flue gas conditioning to be effective for fine particle control, cohesive and particle agglomerating agents are needed to reduce reentrainment losses, since a large percentage of particulate emissions from well-performing ESPs are due to erosion, rapping, and non-rapping reentrainment. A related and somewhat ironic development is that emissions reductions of SO{sub 2} from utility boilers, as required by the Title IV acid rain program of the 1990 Clean Air Act amendments, has the potential to substantially increase particulate air toxics from existing ESPs. The switch to low-sulfur coals as an SO{sub 2} control strategy by many utilities has exacerbated ESP performance problems associated with high resistivity flyash. The use of flue gas conditioning has increased in the past several years to maintain adequate performance in ESPs which were not designed for high resistivity ash. However, commercially available flue gas conditioning systems, including NH{sub 3}/SO{sub 3} dual gas conditioning systems, have problems and inherent drawbacks which create a need for alternative conditioning agents. in particular, NH{sub 3}/SO{sub 3} systems can create odor and ash disposal problems due to ammonia outgassing. In addition, there are concerns over chemical handling safety and the potential for accidental releases.

  13. On electrostatically actuated NEMS/MEMS circular plates

    NASA Astrophysics Data System (ADS)

    Caruntu, Dumitru I.; Alvarado, Iris

    2011-04-01

    This paper deals with electrostatically actuated micro and nano-electromechanical (MEMS/NEMS) circular plates. The system under investigation consists of two bodies, a deformable and conductive circular plate placed above a fixed, rigid and conductive ground plate. The deformable circular plate is electrostatically actuated by applying an AC voltage between the two plates. Nonlinear parametric resonance and pull-in occur at certain frequencies and relatively large AC voltage, respectively. Such phenomena are useful for applications such as sensors, actuators, switches, micro-pumps, micro-tweezers, chemical and mass sensing, and micro-mirrors. A mathematical model of clamped circular MEMS/NEMS electrostatically actuated plates has been developed. Since the model is in the micro- and nano-scale, surface forces, van der Waals and/or Casimir, acting on the plate are included. A perturbation method, the Method of Multiple Scales (MMS), is used for investigating the case of weakly nonlinear MEMS/NEMS circular plates. Two time scales, fast and slow, are considered in this work. The amplitude-frequency and phase-frequency response of the plate in the case of primary resonance are obtained and discussed.

  14. Electrostatic Spraying With Conductive Liquids

    NASA Technical Reports Server (NTRS)

    Kosmo, Joseph J.; Dawn, Frederic S.; Erlandson, Robert E.; Atkins, Loren E.

    1989-01-01

    Thin, uniform polymer coatings applied in water base normally impossible to charge. Electrostatic sprayer modified so applies coatings suspended or dissolved in electrically conductive liquids. Nozzle and gun constructed of nonconductive molded plastic. Liquid passageway made long enough electrical leakage through it low. Coaxial hose for liquid built of polytetrafluoroethylene tube, insulating sleeve, and polyurethane jacket. Sprayer provided with insulated seal at gun-to-hose connection, nonconductive airhose, pressure tank electrically isolated from ground, and special nozzle electrode. Supply of atomizing air reduced so particle momentum controlled by electrostatic field more effectively. Developed to apply water-base polyurethane coating to woven, shaped polyester fabric. Coating provides pressure seal for fabric, which is part of spacesuit. Also useful for applying waterproof, decorative, or protective coatings to fabrics for use on Earth.

  15. Electrostatic interactions in molecular materials

    NASA Astrophysics Data System (ADS)

    Painelli, Anna; Terenziani, Francesca

    2004-03-01

    Non-additive collective behavior appears in molecular materials as a result of intermolecular interactions. We present a model for interacting polar and polarizable molecules that applies to different supramolecular architectures of donor-π-acceptor molecules. We follow a bottom-up modeling strategy: the detailed analysis of spectroscopic data of solvated molecules leads to the definition of a simple two-state model for the molecular units. Classical electrostatic interactions are then introduced to model molecular clusters. The molecular properties are strickingly affected by supramolecular interactions, as demonstrated by spectroscopic studies. Brand new phenomena, like phase transitions and multielectron transfer, with no counterpart at the molecular level are observed as direct consequences of electrostatic intermolecular interactions.

  16. Closed loop electrostatic levitation system

    NASA Technical Reports Server (NTRS)

    Rhim, W. K.; Saffren, M. M.; Elleman, D. D. (Inventor)

    1985-01-01

    An electrostatic levitation system is described, which can closely control the position of objects of appreciable size. A plurality of electrodes surround the desired position of an electrostatically charged object, the position of the objects is monitored, and the voltages applied to the electrodes are varied to hold the object at a desired position. In one system, the object is suspended above a plate-like electrode which has a concave upper face to urge the object toward the vertical axis of the curved plate. An upper electrode that is also curved can be positioned above the object, to assure curvature of the field at any height above the lower plate. In another system, four spherical electrodes are positioned at the points of a tetrahedron, and the voltages applied to the electrodes are varied in accordance with the object position as detected by two sensors.

  17. Asteroid electrostatic instrumentation and modelling

    NASA Astrophysics Data System (ADS)

    Aplin, K. L.; Bowles, N. E.; Urbak, E.; Keane, D.; Sawyer, E. C.

    2011-06-01

    Asteroid surface material is expected to become photoelectrically charged, and is likely to be transported through electrostatic levitation. Understanding any movement of the surface material is relevant to proposed space missions to return samples to Earth for detailed isotopic analysis. Motivated by preparations for the Marco Polo sample return mission, we present electrostatic modelling for a real asteroid, Itokawa, for which detailed shape information is available, and verify that charging effects are likely to be significant at the terminator and at the edges of shadow regions for the Marco Polo baseline asteroid, 1999JU3. We also describe the Asteroid Charge Experiment electric field instrumentation intended for Marco Polo. Finally, we find that the differing asteroid and spacecraft potentials on landing could perturb sample collection for the short landing time of 20min that is currently planned.

  18. Electrostatic Gating of Ultrathin Films

    NASA Astrophysics Data System (ADS)

    Goldman, A. M.

    2014-07-01

    Electrostatic gating of ultrathin films can be used to modify electronic and magnetic properties of materials by effecting controlled alterations of carrier concentration while, in principle, not changing the level of disorder. As such, electrostatic gating can facilitate the development of novel devices and can serve as a means of exploring the fundamental properties of materials in a manner far simpler than is possible with the conventional approach of chemical doping. The entire phase diagram of a compound can be traversed by changing the gate voltage. In this review, we survey results involving conventional field effect devices as well as more recent progress, which has involved structures that rely on electrochemical configurations such as electric double-layer transistors. We emphasize progress involving thin films of oxide materials such as high-temperature superconductors, magnetic oxides, and oxides that undergo metal-insulator transitions.

  19. Electrostatic Spraying With Conductive Liquids

    NASA Technical Reports Server (NTRS)

    Kosmo, Joseph J.; Dawn, Frederic S.; Erlandson, Robert E.; Atkins, Loren E.

    1989-01-01

    Thin, uniform polymer coatings applied in water base normally impossible to charge. Electrostatic sprayer modified so applies coatings suspended or dissolved in electrically conductive liquids. Nozzle and gun constructed of nonconductive molded plastic. Liquid passageway made long enough electrical leakage through it low. Coaxial hose for liquid built of polytetrafluoroethylene tube, insulating sleeve, and polyurethane jacket. Sprayer provided with insulated seal at gun-to-hose connection, nonconductive airhose, pressure tank electrically isolated from ground, and special nozzle electrode. Supply of atomizing air reduced so particle momentum controlled by electrostatic field more effectively. Developed to apply water-base polyurethane coating to woven, shaped polyester fabric. Coating provides pressure seal for fabric, which is part of spacesuit. Also useful for applying waterproof, decorative, or protective coatings to fabrics for use on Earth.

  20. The Electrostatic Levitation Facility at NASA's Marshall Space Flight Center

    NASA Technical Reports Server (NTRS)

    Rogers, Jan R.; Hyers, Robert W.; Savage, Larry; Robinson, Michael B.; Rathz, Thomas J.; Rose, M. Franklin (Technical Monitor)

    2000-01-01

    Containerless processing is an important area of research in materials science. Electrostatic levitation (ESL) represents an emerging technology which permits containerless processing in a vacuum environment. NASA's Marshall Space Flight Center (MSFC) established a levitation facility to provide a critical resource to the microgravity materials science research community to continue and enhance ground-based research in the support of the development of flight experiments during the transition to Space Station. During ESL processing, charged specimens are levitated in the electrostatic field produced by the system's electrodes. Three sets of positioning electrodes represent the heart of the MSFC system. Two dual-axis position sensitive detectors provide input for the PID control-loop computer. Sample position is maintained by adjusting the control voltages for the power supplies of the positioning electrodes. A UV source refreshes the charge on specimens during processing via the photoelectric effect. Lasers permit sample heating independent of positioning. The processing chamber typically operates under vacuum condition approximately = 10(exp -7) Torr. Electrostatic levitation provides a materials science research tool for investigations of refractory solids and melts. Topics of investigation include thermophysical properties, phase equilibria, metastable phase formation, undercooling and nucleation, time-temperature-transformation diagrams and other aspects of materials processing. Current capabilities and recent results of processing studies for metals, alloys and oxides will be reviewed.

  1. Electrostatic forces for personnel restraints

    NASA Technical Reports Server (NTRS)

    Ashby, N.; Ciciora, J.; Gardner, R.; Porter, K.

    1977-01-01

    The feasibility of utilizing electrostatic forces for personnel retention devices on exterior spacecraft surfaces was analyzed. The investigation covered: (1) determination of the state of the art; (2) analysis of potential adhesion surfaces; (3) safety considerations for personnel; (4) electromagnetic force field determination and its effect on spacecraft instrumentation; and (5) proposed advances to current technology based on documentation review, analyses, and experimental test data.

  2. Defining Protein Electrostatic Recognition Processes

    DTIC Science & Technology

    1989-11-30

    making and aligning expanded molecular dot surfaces for each molecule and checking these surfaces for interpenetration. The program TURNIP used these...year of this contract, we have developed and optimized the TURNIP program, which consists of two parts. First, the electrostatic pctcntia! due to mo...supercomputer where the rotation and translation of molecule 2 occurs. The program TURNIP is written in the programming language C, and has been optimized

  3. Defining Protein Electrostatic Recognition Processes

    DTIC Science & Technology

    1992-01-01

    approach. We developed the TURNIP program to determine the most favorable precollision orientations for two molecules by systematic search of all...orientations and evaluation of the resulting electrostatic interactions. TURNIP was applied to the transient interaction between two electron transfer...region of cytochrome c with the negative patch of plastocyanin, consistent with experimental data. Application of TURNIP to the formation of the stable

  4. Electrostatic generator/motor configurations

    DOEpatents

    Post, Richard F

    2014-02-04

    Electrostatic generators/motors designs are provided that generally may include a first cylindrical stator centered about a longitudinal axis; a second cylindrical stator centered about the axis, a first cylindrical rotor centered about the axis and located between the first cylindrical stator and the second cylindrical stator. The first cylindrical stator, the second cylindrical stator and the first cylindrical rotor may be concentrically aligned. A magnetic field having field lines about parallel with the longitudinal axis is provided.

  5. High power ferrite microwave switch

    NASA Technical Reports Server (NTRS)

    Bardash, I.; Roschak, N. K.

    1975-01-01

    A high power ferrite microwave switch was developed along with associated electronic driver circuits for operation in a spaceborne high power microwave transmitter in geostationary orbit. Three units were built and tested in a space environment to demonstrate conformance to the required performance characteristics. Each unit consisted of an input magic-tee hybrid, two non-reciprocal latching ferrite phase shifters, an out short-slot 3 db quadrature coupler, a dual driver electronic circuit, and input logic interface circuitry. The basic mode of operation of the high power ferrite microwave switch is identical to that of a four-port, differential phase shift, switchable circulator. By appropriately designing the phase shifters and electronic driver circuits to operate in the flux-transfer magnetization mode, power and temperature insensitive operation was achieved. A list of the realized characteristics of the developed units is given.

  6. KSC Electrostatic Discharge (ESD) Issues

    NASA Technical Reports Server (NTRS)

    Buhler, Charles

    2008-01-01

    Discussion of key electrostatic issues that have arisen during the past few years at KSC that the Electrostatics Laboratory has studied. The lab has studied in depth the Space Shuttle's Thermal Control System Blankets, the International Space Station Thermal Blanket, the Pan/Tilt Camera Blankets, the Kapton Purge Barrier Curtain, the Aclar Purge Barrier Curtain, the Thrust Vector Controller Blankets, the Tyvek Reaction Control System covers, the AID-PAK and FLU-9 pyro inflatable devices, the Velostat Solid Rocket Booster mats, and the SCAPE suits. In many cases these materials are insulating meaning that they might be a source of unsafe levels of electrostatic discharge (ESD). For each, the lab provided in-depth testing of each material within its current configuration to ensure that it does not cause an ESD concern that may violate the safety of the astronauts, the workers and equipment for NASA. For example the lab provides unique solutions and testing such as Spark Incendivity Testing that checks whether a material is capable of generating a spark strong enough to ignite a flammable gas. The lab makes recommendations to changes in specifications, procedures, and material if necessary. The lab also consults with a variety of non-safety related ESD issues for the agency.

  7. Voltage limitations of electrostatic accelerators

    SciTech Connect

    Hyder, H.R. )

    1999-04-01

    The history of electrostatic accelerators has been punctuated by a series of projects in which innovative designs have failed to meet the expectations of their designers. From the early, air-insulated Van de Graaffs at Round Hill to certain of the large pressurized heavy ion accelerators of the 1970s and 1980s, increases in size or changes in design and materials have not always led to the maximum voltages expected or extrapolated. Since these failures have continued beyond childhood into a mature technology, it is reasonable to assume that the causes of voltage limitation are varied and complex. They have remained poorly understood for a number of reasons: resources for an extended program of research into breakdown and failure of electrostatic generators have always been meager, especially for large machines devoted to nuclear research; the inaccessibility of pressurized generators makes instrumentation difficult and testing slow; the calculation of transient and dynamic effects is laborious and the results difficult to verify; voltage test experiments on operating accelerators are inhibited by the significant risk of damage due to energy release on breakdown: and the total voltages (though not the local fields) achieved in many electrostatic accelerators exceed those produced in any other man-made environment. In this review, the behavior of several generators of different designs is examined in order to assess the importance of the various design features and operating conditions that control the maximum voltage achievable in a working machine. [copyright] [ital 1999 American Institute of Physics.

  8. Electrostatic effects in DNA stretching

    NASA Astrophysics Data System (ADS)

    Tkachenko, Alexei V.

    2006-10-01

    The response of a semiflexible polyelectrolyte chain to stretching in the regimes of moderate and weak screening is studied theoretically, with a special focus on DNA experiments. By using the nonlinear Poisson-Boltzmann description of electrostatic self-interactions of the chain, we explicitly demonstrate the applicability of the concept of effective charge to certain aspects of the problem. This charge can be extracted from the far-field asymptotic behavior of the electrostatic potential of the fully aligned chain. Surprisingly, in terms of the effective charge, the electrostatically renormalized persistence length can be formally described by the classical Odijk-Skolnick-Fixman formula, whose domain of applicability is normally limited to the linearized Debye-Hückel (DH) approximation. However, the short-scale behavior of the chain in the nonlinear regime deviates from the of DH-based result, even upon charge renormalization. This difference is revealed in the calculated stretching curves for strongly charged DNA. These results are in good agreement with recent experiments. In the limit of weak screening we predict the elastic response to have a distinctive two-stage character, with a peculiar intermediate “unstretchable” regime.

  9. Monitoring Mars for Electrostatic Disturbances

    NASA Technical Reports Server (NTRS)

    Compton, D.

    2011-01-01

    The DSN radio telescope DSS-13 was used to monitor Mars for electrostatic discharges from 17 February to 11 April, 2010, and from 19 April to 4 May, 2011, over a total of 72 sessions. Of these sessions, few showed noteworthy results and no outstanding electrostatic disturbances were observed on Mars from analyzing the kurtosis of radio emission from Mars. Electrostatic discharges on mars were originally detected in June of 2006 by Ruf et al. using DSS-13. he kurtosis (normalized fourth moment of the electrical field strength) is sensitive to non-thermal radiation. Two frequencies bands, either 2.4 and 8.4 GHz or 8.4 and 32 GHz were used. The non-thermal radiation spectrum should have peaks at the lowest three modes of the theoretical Schumann Resonances of Mars. The telescope was pointed away from Mars every 5 minutes for 45 seconds to confirm if Mars was indeed the sources of any events. It was shown that by including a down-link signal in one channel and by observing when the kurtosis changed as the telescope was pointed away from the source that the procedure can monitor Mars without the need of extra equipment monitoring a control source.

  10. Quantitative nanoscale electrostatics of viruses.

    PubMed

    Hernando-Pérez, M; Cartagena-Rivera, A X; Lošdorfer Božič, A; Carrillo, P J P; San Martín, C; Mateu, M G; Raman, A; Podgornik, R; de Pablo, P J

    2015-11-07

    Electrostatics is one of the fundamental driving forces of the interaction between biomolecules in solution. In particular, the recognition events between viruses and host cells are dominated by both specific and non-specific interactions and the electric charge of viral particles determines the electrostatic force component of the latter. Here we probe the charge of individual viruses in liquid milieu by measuring the electrostatic force between a viral particle and the Atomic Force Microscope tip. The force spectroscopy data of co-adsorbed ϕ29 bacteriophage proheads and mature virions, adenovirus and minute virus of mice capsids is utilized for obtaining the corresponding density of charge for each virus. The systematic differences of the density of charge between the viral particles are consistent with the theoretical predictions obtained from X-ray structural data. Our results show that the density of charge is a distinguishing characteristic of each virus, depending crucially on the nature of the viral capsid and the presence/absence of the genetic material.

  11. Magnetic switching

    SciTech Connect

    Birx, D.; Cook, E.; Hawkins, S.; Poor, S.; Reginato, L.; Schmidt, J.; Smith, M.

    1983-06-01

    The paper discusses the development program in magnetic switching which was aimed at solving the rep-rate and reliability limitations of the ATA spark gaps. The end result has been a prototype physically very similar to the present Advanced Test Accelerator (ATA) pulse power unit but vastly superior in performance. This prototype, which is easily adaptable to the existing systems, has achieved a burst rep-rate of 20 kHz and an output voltage of 500 kV. A one-on-one substitution of the existing pulse power module would result in a 100 MeV accelerator. Furthermore, the high efficiency of the magnetic pulse compression stages has allowed CW operation of the prototype at one kilohertz opening up other applications for the pulse power. Performance and design details will be described.

  12. Plasma Switch Development.

    DTIC Science & Technology

    1984-06-08

    switch :9 (1) the low-pressure gas switch 17 (2) the surface flashover switch ,18 (3) the thyrtron,’ŕ (4) the high pressure...spark gap, (5) the magnetic switch .’ 9 20 and (6) the ECS. The ongoing research for both the low pressure gas and surface flashover closing- switches has... investigations into optimizing gas mixtures for opening switch applications 1 ’"’"’’’a𔃻 ; and a preliminary study of the discharge stabili-

  13. Engineering Photonic Switches for Quantum Information Processing

    NASA Astrophysics Data System (ADS)

    Oza, Neal N.

    In this dissertation, we describe, characterize, and demonstrate the operation of a dual-in, dual-out, all-optical, fiber-based quantum switch. This "cross-bar" switch is particularly useful for applications in quantum information processing because of its low-loss, high-speed, low-noise, and quantum-state-retention properties. Building upon on our lab's prior development of an ultrafast demultiplexer [1-3] , the new cross-bar switch can be used as a tunable multiplexer and demultiplexer. In addition to this more functional geometry, we present results demonstrating faster performance with a switching window of ≈45 ps, corresponding to >20-GHz switching rates. We show a switching fidelity of >98%, i. e., switched polarization-encoded photonic qubits are virtually identical to unswitched photonic qubits. We also demonstrate the ability to select one channel from a two-channel quantum data stream with the state of the measured (recovered) quantum channel having >96% relative fidelity with the state of that channel transmitted alone. We separate the two channels of the quantum data stream by 155 ps, corresponding to a 6.5-GHz datastream. Finally, we describe, develop, and demonstrate an application that utilizes the switch's higher-speed, lower-loss, and spatio-temporal-encoding features to perform quantum state tomographies on entangled states in higher-dimensional Hilbert spaces. Since many previous demonstrations show bipartite entanglement of two-level systems, we define "higher" as d > 2 where d represents the dimensionality of a photon. We show that we can generate and measure time-bin-entangled, two-photon, qutrit (d = 3) and ququat (d = 4) states with >85% and >64% fidelity to an ideal maximally entangled state, respectively. Such higher-dimensional states have applications in dense coding [4] , loophole-free tests of nonlocality [5] , simplifying quantum logic gates [6] , and increasing tolerance to noise and loss for quantum information processing [7] .

  14. Fast Electromechanical Switches Based on Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    Kaul, Anupama; Wong, Eric; Epp, Larry

    2008-01-01

    Electrostatically actuated nanoelectromechanical switches based on carbon nanotubes have been fabricated and tested in a continuing effort to develop high-speed switches for a variety of stationary and portable electronic equipment. As explained below, these devices offer advantages over electrostatically actuated microelectromechanical switches, which, heretofore, have represented the state of the art of rapid, highly miniaturized electromechanical switches. Potential applications for these devices include computer memories, cellular telephones, communication networks, scientific instrumentation, and general radiation-hard electronic equipment. A representative device of the present type includes a single-wall carbon nanotube suspended over a trench about 130 nm wide and 20 nm deep in an electrically insulating material. The ends of the carbon nanotube are connected to metal electrodes, denoted the source and drain electrodes. At bottom of the trench is another metal electrode, denoted the pull electrode (see figure). In the off or open switch state, no voltage is applied, and the nanotube remains out of contact with the pull electrode. When a sufficiently large electric potential (switching potential) is applied between the pull electrode and either or both of the source and drain electrodes, the resulting electrostatic attraction bends and stretches the nanotube into contact with the pull electrode, thereby putting the switch into the "on" or "closed" state, in which substantial current (typically as much as hundreds of nanoamperes) is conducted. Devices of this type for use in initial experiments were fabricated on a thermally oxidized Si wafer, onto which Nb was sputter-deposited for use as the pull-electrode layer. Nb was chosen because its refractory nature would enable it to withstand the chemical and thermal conditions to be subsequently imposed for growing carbon nanotubes. A 200- nm-thick layer of SiO2 was formed on top of the Nb layer by plasma

  15. Electrostatic particle collection in vacuum

    NASA Astrophysics Data System (ADS)

    Afshar-Mohajer, Nima; Damit, Brian; Wu, Chang-Yu; Sorloaica-Hickman, Nicoleta

    2011-09-01

    Lunar grains accumulate charges due to solar-based ionizing radiations, and the repelling action of like-charged particles causes the levitation of lunar dust. The lunar dust deposit on sensitive and costly surfaces of investigative equipment is a serious concern in lunar explorations. Inspired by electrostatic precipitators (ESPs), the Electrostatic Lunar Dust Collector (ELDC) was proposed for collecting already charged lunar dust particles to prevent the lunar dust threat. As the conditions for terrestrial counterparts are not valid in the lunar environment, equations developed for terrestrial devices yield incorrect predictions in lunar application. Hence, a mathematical model was developed for the ELDC operating in vacuum to determine its collection efficiency. The ratios of electrical energy over potential energy, kinetic energy over potential energy and the ratio of ELDC dimensions were identified to be the key dimensionless parameters. Sensitivity analyses of the relevant parameters showed that depending on ELDC orientation, smaller particles would be collected more easily at vertical orientation, whereas larger particles were easier to collect in a horizontal ELDC configuration. In the worst case scenario, the electrostatic field needed to be 10 times stronger in the vertical mode in order to adequately collect larger particles. The collection efficiency was very sensitive to surface potential of lunar dust and it reached the maximum when surface potential was between 30 and 120 V. Except for regions of the lunar day side with surface potential close to zero, providing 1 kV ( E = 20 kV m -1) with the ELDC was more than enough for collecting all the particles in the most critical orientation. The needed field strength was about 4000 times less than that for repelling 1-μm size particles already settled on the surfaces. The analysis shows that the ELDC offers a viable solution for lunar dust control due to its effectiveness, ease of cleaning and low voltage

  16. Electrostatic Plugging of Multidipole Cusps.

    DTIC Science & Technology

    1982-05-01

    IN, rtid’( rio~ s I REORTNUMER 2 GOVT ACCESSION No 3 RECIPtE%T’. CATALOG, # MtSF.P 4. TTLE wd Sbt,( ) TYPE OF REPDRT & PER,00 COvERED jElectrostatic...corresponding loss widths are W = 9 mm and W = 3 mm. This L ~ L2 analysis was performed for many ’PE, and a linear relationship was found between n and...VE)/Te (18)e t o reP Now V/rp = A the surface area of the plasma: A = SL , (19)c with S the distance between cusps ( 8 cm) and L the magnetic cuspc

  17. Electrostatic effects in collagen fibrillization

    NASA Astrophysics Data System (ADS)

    Morozova, Svetlana; Muthukumar, Murugappan

    2014-03-01

    Using light scattering and AFM techniques, we have measured the kinetics of fibrillization of collagen (pertinent to the vitreous of human eye) as a function of pH and ionic strength. At higher and lower pH, collagen triple-peptides remain stable in solution without fibrillization. At neutral pH, the fibrillization occurs and its growth kinetics is slowed upon either an increase in ionic strength or a decrease in temperature. We present a model, based on polymer crystallization theory, to describe the observed electrostatic nature of collagen assembly.

  18. Switch Transcripts in Immunoglobulin Class Switching

    NASA Astrophysics Data System (ADS)

    Lorenz, Matthias; Jung, Steffen; Radbruch, Andreas

    1995-03-01

    B cells can exchange gene segments for the constant region of the immunoglobulin heavy chain, altering the class and effector function of the antibodies that they produce. Class switching is directed to distinct classes by cytokines, which induce transcription of the targeted DNA sequences. These transcripts are processed, resulting in spliced "switch" transcripts. Switch recombination can be directed to immunoglobulin G1 (IgG1) by the heterologous human metallothionein II_A promoter in mutant mice. Induction of the structurally conserved, spliced switch transcripts is sufficient to target switch recombination to IgG1, whereas transcription alone is not.

  19. Dual antiretroviral therapy for HIV infection.

    PubMed

    Soriano, Vicente; Fernandez-Montero, Jose Vicente; Benitez-Gutierrez, Laura; Mendoza, Carmen de; Arias, Ana; Barreiro, Pablo; Peña, José M; Labarga, Pablo

    2017-08-01

    For two decades, triple combinations of antiretrovirals have been the standard treatment for HIV infection. The challenges of such lifelong therapy include long-term side effects, high costs and reduced drug adherence. The recent advent of more potent and safer antiretrovirals has renewed the interest for simpler HIV regimens. Areas covered: We discuss the pros and cons of dual antiretroviral therapies in both drug-naïve and in treatment-experienced patients with viral suppression (switch strategy). Expert opinion: Some dual antiretroviral regimens are safe and efficacious, particularly as maintenance therapy. At this time, combinations of dolutegravir plus rilpivirine represent the best dual regimen. Longer follow-up and larger study populations are needed before supporting dolutegravir plus lamivudine. In contrast, dual therapy based on maraviroc is less effective. Although dual regimens with boosted protease inhibitors plus either lamivudine or raltegravir may be effective, they are penalized by metabolic side effects and risk for drug interactions. The newest dual regimens could save money, reduce toxicity and spare drug options for the future. For the first time in HIV therapeutics, less can be more. Dual therapy switching has set up a new paradigm in HIV treatment that uses induction-maintenance.

  20. Electrostatic potential map modelling with COSY Infinity

    NASA Astrophysics Data System (ADS)

    Maloney, J. A.; Baartman, R.; Planche, T.; Saminathan, S.

    2016-06-01

    COSY Infinity (Makino and Berz, 2005) is a differential-algebra based simulation code which allows accurate calculation of transfer maps to arbitrary order. COSY's existing internal procedures were modified to allow electrostatic elements to be specified using an array of field potential data from the midplane. Additionally, a new procedure was created allowing electrostatic elements and their fringe fields to be specified by an analytic function. This allows greater flexibility in accurately modelling electrostatic elements and their fringe fields. Applied examples of these new procedures are presented including the modelling of a shunted electrostatic multipole designed with OPERA, a spherical electrostatic bender, and the effects of different shaped apertures in an electrostatic beam line.

  1. Multi-output Q-switched solid-state laser using an intra-cavity MEMS micromirror array

    NASA Astrophysics Data System (ADS)

    Bauer, Ralf; Lubeigt, Walter; Clark, Caspar; McBrearty, Euan; Uttamchandani, Deepak

    2013-03-01

    Multiple individually-controllable Q-switched laser outputs from a single diode-pumped Nd:YAG module are presented by using an electrostatic MEMS scanning micromirror array as cavity end-mirror. The gold coated, 700 μm diameter and 25 μm thick, single-crystal silicon micromirrors possess resonant tilt frequencies of ~8 kHz with optical scan angles of up to 78°. Dual laser output resulting from the actuation of two neighboring mirrors was observed resulting in a combined average output power of 125 mW and pulse durations of 30 ns with resulting pulse energies of 7.9 μJ and 7.1 μJ. The output power was limited by thermal effects on the gold-coated mirror surface. Dielectric coatings with increased reflectivity and therefore lower thermal stresses are required to power-scale this technique. An initial SiO2/Nb2O5 test coating was applied to a multi-mirror array with individual optical scan angles of 14° at a resonant tilt frequency of 10.4 kHz. The use of this dielectric coated array inside a 3-mirror Nd:YAG laser cavity led to a single mirror output with average Q-switched output power of 750 mW and pulse durations of 295 ns resulting in pulse energies of 36 μJ.

  2. Molecular electrostatic potential as a graph.

    PubMed

    Daza, Edgar E; Maza, Julio; Torres, Raul

    2013-06-01

    We present several procedures to represent molecular electrostatic potential as a graph, based on the pattern of critical points and their neighborhood relations. This representation is used for the molecular electrostatic comparison, which is reduced to a comparison of tree-type graphs. Several methods to compare trees are also presented. The applications of this algorithm to compare and classify molecules through their electrostatic potential are illustrated.

  3. Electrostatics in pharmaceutical aerosols for inhalation.

    PubMed

    Wong, Jennifer; Chan, Hak-Kim; Kwok, Philip Chi Lip

    2013-08-01

    Electrostatics continues to play an important role in pharmaceutical aerosols for inhalation. Despite its ubiquitous nature, the charging process is complex and not well understood. Nonetheless, significant advances in the past few years continue to improve understanding and lead to better control of electrostatics. The purpose of this critical review is to present an overview of the literature, with an emphasis on how electrostatic charge can be useful in improving pulmonary drug delivery.

  4. Microencapsulation and Electrostatic Processing Device

    NASA Technical Reports Server (NTRS)

    Morrison, Dennis R. (Inventor); Mosier, Benjamin (Inventor); Cassanto, John M. (Inventor)

    2001-01-01

    A microencapsulation and electrostatic processing (MEP) device is provided for forming microcapsules. In one embodiment, the device comprises a chamber having a filter which separates a first region in the chamber from a second region in the chamber. An aqueous solution is introduced into the first region through an inlet port, and a hydrocarbon/ polymer solution is introduced into the second region through another inlet port. The filter acts to stabilize the interface and suppress mixing between the two immiscible solutions as they are being introduced into their respective regions. After the solutions have been introduced and have become quiescent, the interface is gently separated from the filter. At this point, spontaneous formation of microcapsules at the interface may begin to occur, or some fluid motion may be provided to induce microcapsule formation. In any case, the fluid shear force at the interface is limited to less than 100 dynes/sq cm. This low-shear approach to microcapsule formation yields microcapsules with good sphericity and desirable size distribution. The MEP device is also capable of downstream processing of microcapsules, including rinsing, re-suspension in tertiary fluids, electrostatic deposition of ancillary coatings, and free-fluid electrophoretic separation of charged microcapsules.

  5. Electrostatic charging of lunar dust

    SciTech Connect

    Walch, Bob; Horanyi, Mihaly; Robertson, Scott

    1998-10-21

    Transient dust clouds suspended above the lunar surface were indicated by the horizon glow observed by the Surveyor spacecrafts and the Lunar Ejecta and Meteorite Experiment (Apollo 17), for example. The theoretical models cannot fully explain these observations, but they all suggest that electrostatic charging of the lunar surface due to exposure to the solar wind plasma and UV radiation could result in levitation, transport and ejection of small grains. We report on our experimental studies of the electrostatic charging properties of an Apollo-17 soil sample and two lunar simulants MLS-1 and JSC-1. We have measured their charge after exposing individual grains to a beam of fast electrons with energies in the range of 20{<=}E{<=}90 eV. Our measurements indicate that the secondary electron emission yield of the Apollo-17 sample is intermediate between MLS-1 and JSC-1, closer to that of MLS-1. We will also discuss our plans to develop a laboratory lunar surface model, where time dependent illumination and plasma bombardment will closely emulate the conditions on the surface of the Moon.

  6. Breakdown mechanisms in electrostatic deflector

    NASA Astrophysics Data System (ADS)

    Re, M.; Cuttone, G.; Zappalà, E.; Passarello, S.

    2001-12-01

    The Electrostatic Beam Deflectors for the K800 Superconducting Cyclotron are the most critical elements of the beam extraction system. It has been carried out an accurate investigation from the microscopic point of view, leading to a better comprehension of the complex phenomena taking part in the breakdown process. The environmental conditions are high electric field (up to 130 kV/cm), high magnetic field (up to 5 T) in addition with high energy (70 MeV/u) and high power ion beam. It has been found that all the materials constituent the electrostatic deflector, and not only the electrodes, give an important contribute to the mechanism of breakdown that occurs in two main ways: insulator metalization and enhanced electrodes electron emission. These two effects are involved in a positive feedback process which amplifies the effects leading to a fast breakdown. These phenomena are here shown and some possible solutions are at the moment under test using several bulk (Mo, Ti, Cu) and coating materials (TiN, Diamond Like Carbon).

  7. Electrostatic Tuning of Cellular Excitability

    PubMed Central

    Börjesson, Sara I.; Parkkari, Teija; Hammarström, Sven; Elinder, Fredrik

    2010-01-01

    Abstract Voltage-gated ion channels regulate the electric activity of excitable tissues, such as the heart and brain. Therefore, treatment for conditions of disturbed excitability is often based on drugs that target ion channels. In this study of a voltage-gated K channel, we propose what we believe to be a novel pharmacological mechanism for how to regulate channel activity. Charged lipophilic substances can tune channel opening, and consequently excitability, by an electrostatic interaction with the channel's voltage sensors. The direction of the effect depends on the charge of the substance. This was shown by three compounds sharing an arachidonyl backbone but bearing different charge: arachidonic acid, methyl arachidonate, and arachidonyl amine. Computer simulations of membrane excitability showed that small changes in the voltage dependence of Na and K channels have prominent impact on excitability and the tendency for repetitive firing. For instance, a shift in the voltage dependence of a K channel with −5 or +5 mV corresponds to a threefold increase or decrease in K channel density, respectively. We suggest that electrostatic tuning of ion channel activity constitutes a novel and powerful pharmacological approach with which to affect cellular excitability. PMID:20141752

  8. Electrostatic discharge concepts and definitions

    SciTech Connect

    Borovina, Dan L

    2008-01-01

    Many objects -like a human body, plastic wrap, or a rolling cart -that are electrically neutral, overall, can gain a net electrostatic charge by means of one of three methods: induction, physical transfer, or triboelectric charging (separation of conductive surfaces). The result is a voltage difference between the charged object and other objects, creating a situation where current flow is likely if two objects come into contact or close proximity. This current flow is known as electrostatic discharge, or ESD. The energy and voltage of the discharge can be influenced by factors such as the temperature and humidity in the room, the types of materials or flooring involved, or the clothing and footwear a person uses. Given the possible ranges of the current and voltage characteristic of an ESD pulse, it is important to consider the safety risks associated with detonator handling, assembly and disassembly, transportation and maintenance. For main charge detonators, these safety risks include high explosive violent reactions (HEVR) as well as inadvertent nuclear detonations (lND).

  9. Electrostatic properties of graphitic nanostructures

    NASA Astrophysics Data System (ADS)

    Erbahar, Dogan

    2014-03-01

    Carbon nanostructures are considered to be one of the most important candidates of circuit elements for future nanoelectronics. However, being one of the main issues of conventional circuitry used today, charge accumulation on circuit elements can also be expected to have important effects on the performance of the nanoscale devices. In this work we investigated charge accumulation on various graphitic systems by simulated charge doping. We report ab initio density functional theory (DFT) calculations of electrostatically charged multilayered carbon nano structures. We investigate the effect of total and background charge on charge distribution profiles on the systems under consideration varying from multilayered graphene to multiwalled carbon nanotubes. We show that the charge distribution profile on the inner layers are mainly induced from the background charge which is imposed by the code on periodic systems. Our population anaylsis indicates that the outermost two layers effectively shields the inner layers electrostatically. Illuminating the typical skin depth of those systems our results could give important insights for designing the nanocircuit elements.

  10. Electrostatics of Deformable Lipid Membranes

    PubMed Central

    Vorobyov, Igor; Bekker, Borislava; Allen, Toby W.

    2010-01-01

    Abstract It was recently demonstrated that significant local deformations of biological membranes take place due to the fields of charged peptides and ions, challenging the standard model of membrane electrostatics. The ability of ions to retain their immediate hydration environment, combined with the lack of sensitivity of permeability to ion type or even ion pairs, led us to question the extent to which hydration energetics and electrostatics control membrane ion permeation. Using the arginine analog methyl-guanidinium as a test case, we find that although hydrocarbon electronic polarizability causes dramatic changes in ion solvation free energy, as well as a significant change (∼0.4 V) in the membrane dipole potential, little change in membrane permeation energetics occurs. We attribute this to compensation of solvation terms from polar and polarizable nonpolar components within the membrane, and explain why the dipole potential is not fully sensed in terms of the locally deformed bilayer interface. Our descriptions provide a deeper understanding of the translocation process and allow predictions for poly-ions, ion pairs, charged lipids, and lipid flip-flop. We also report simulations of large hydrophobic-ion-like membrane defects and the ionophore valinomycin, which exhibit little membrane deformation, as well as hydrophilic defects and the ion channel gramicidin A, to provide parallels to membranes deformed by unassisted ion permeation. PMID:20550903

  11. Latching relay switch assembly

    DOEpatents

    Duimstra, Frederick A.

    1991-01-01

    A latching relay switch assembly which includes a coil section and a switch or contact section. The coil section includes at least one permanent magnet and at least one electromagnet. The respective sections are, generally, arranged in separate locations or cavities in the assembly. The switch is latched by a permanent magnet assembly and selectively switched by an overriding electromagnetic assembly.

  12. Preconceptual design for the electrostatic enclosure

    SciTech Connect

    Meyer, L.C.

    1992-09-01

    This report presents a preconceptual design (design criteria and assumptions) for electrostatic enclosures to be used during buried transuranic waste recovery operations. These electrostatic enclosures (along with the application of dust control products) will provide an in-depth contamination control strategy. As part of this preconceptual design, options for electrostatic curtain design are given including both hardwall and fabric enclosures. Ventilation systems, doors, air locks, electrostatic curtains, and supporting systems also are discussed. In addition to the conceptual design, engineering scale tests are proposed to be run at the Test Reactor Area. The planned engineering scale tests will give final material specifications for full-scale retrieval demonstrations.

  13. Limiting assumptions in molecular modeling: electrostatics.

    PubMed

    Marshall, Garland R

    2013-02-01

    Molecular mechanics attempts to represent intermolecular interactions in terms of classical physics. Initial efforts assumed a point charge located at the atom center and coulombic interactions. It is been recognized over multiple decades that simply representing electrostatics with a charge on each atom failed to reproduce the electrostatic potential surrounding a molecule as estimated by quantum mechanics. Molecular orbitals are not spherically symmetrical, an implicit assumption of monopole electrostatics. This perspective reviews recent evidence that requires use of multipole electrostatics and polarizability in molecular modeling.

  14. Identifying Student Use of Ball-and-Stick Images versus Electrostatic Potential Map Images via Eye Tracking

    ERIC Educational Resources Information Center

    Williamson, Vickie M.; Hegarty, Mary; Deslongchamps, Ghislain; Williamson, Kenneth C., III

    2013-01-01

    This pilot study examined students' use of ball-and-stick images versus electrostatic potential maps when asked questions about electron density, positive charge, proton attack, and hydroxide attack with six different molecules (two alcohols, two carboxylic acids, and two hydroxycarboxylic acids). Students' viewing of these dual images…

  15. Identifying Student Use of Ball-and-Stick Images versus Electrostatic Potential Map Images via Eye Tracking

    ERIC Educational Resources Information Center

    Williamson, Vickie M.; Hegarty, Mary; Deslongchamps, Ghislain; Williamson, Kenneth C., III

    2013-01-01

    This pilot study examined students' use of ball-and-stick images versus electrostatic potential maps when asked questions about electron density, positive charge, proton attack, and hydroxide attack with six different molecules (two alcohols, two carboxylic acids, and two hydroxycarboxylic acids). Students' viewing of these dual images…

  16. Electrostatic atomization: Effect of electrode materials on electrostatic atomizer performance

    NASA Astrophysics Data System (ADS)

    Sankaran, Abhilash; Staszel, Christopher; Kashir, Babak; Perri, Anthony; Mashayek, Farzad; Yarin, Alexander

    2016-11-01

    Electrostatic atomization was studied experimentally with a pointed electrode in a converging nozzle. Experiments were carried out on poorly conductive canola oil where it was observed that electrode material may affect charge transfer. This points at the possible faradaic reactions that can occur at the surfaces of the electrodes. The supply voltage is applied to the sharp electrode and the grounded nozzle body constitutes the counter-electrode. The charge transfer is controlled by the electrochemical reactions on both the electrodes. The electrical performance study of the atomizer issuing a charged oil jet was conducted using three different nozzle body materials - brass, copper and stainless steel. Also, two sharp electrode materials - brass and stainless steel - were tested. The experimental results revealed that both the nozzle body material, as well as the sharp electrode material affected the spray and leak currents. Moreover, the effect of the sharp electrode material is quite significant. This research is supported by NSF Grant 1505276.

  17. Radiation hard vacuum switch

    DOEpatents

    Boettcher, Gordon E.

    1990-03-06

    A vacuum switch with an isolated trigger probe which is not directly connected to the switching electrodes. The vacuum switch within the plasmatron is triggered by plasma expansion initiated by the trigger probe which travels through an opening to reach the vacuum switch elements. The plasma arc created is directed by the opening to the space between the anode and cathode of the vacuum switch to cause conduction.

  18. Radiation hard vacuum switch

    DOEpatents

    Boettcher, Gordon E.

    1990-01-01

    A vacuum switch with an isolated trigger probe which is not directly connected to the switching electrodes. The vacuum switch within the plasmatron is triggered by plasma expansion initiated by the trigger probe which travels through an opening to reach the vacuum switch elements. The plasma arc created is directed by the opening to the space between the anode and cathode of the vacuum switch to cause conduction.

  19. Temporal switching jitter in photoconductive switches

    SciTech Connect

    GAUDET,JOHN A.; SKIPPER,MICHAEL C.; ABDALLA,MICHAEL D.; AHERN,SEAN M.; MAR,ALAN; LOUBRIEL,GUILLERMO M.; ZUTAVERN,FRED J.; O'MALLEY,MARTIN W.; HELGESON,WESLEY D.; ROMERO,SAMUEL P.

    2000-04-13

    This paper reports on a recent comparison made between the Air Force Research Laboratory (AFRL) gallium arsenide, optically-triggered switch test configuration and the Sandia National Laboratories (SNL) gallium arsenide, optically-triggered switch test configuration. The purpose of these measurements was to compare the temporal switch jitter times. It is found that the optical trigger laser characteristics are dominant in determining the PCSS jitter.

  20. Portable liquid collection electrostatic precipitator

    DOEpatents

    Carlson, Duane C.; DeGange, John J.; Halverson, Justin E.

    2005-10-18

    A portable liquid collection electrostatic collection precipitator for analyzing air is provided which is a relatively small, self-contained device. The device has a tubular collection electrode, a reservoir for a liquid, and a pump. The pump pumps the liquid into the collection electrode such that the liquid flows down the exterior of the collection electrode and is recirculated to the reservoir. An air intake is provided such that air to be analyzed flows through an ionization section to ionize analytes in the air, and then flows near the collection electrode where ionized analytes are collected. A portable power source is connected to the air intake and the collection electrode. Ionizable constituents in the air are ionized, attracted to the collection electrode, and precipitated in the liquid. The precipitator may also have an analyzer for the liquid and may have a transceiver allowing remote operation and data collection.

  1. Microencapsulation and Electrostatic Processing Method

    NASA Technical Reports Server (NTRS)

    Morrison, Dennis R. (Inventor); Mosier, Benjamin (Inventor)

    2000-01-01

    Methods are provided for forming spherical multilamellar microcapsules having alternating hydrophilic and hydrophobic liquid layers, surrounded by flexible, semi-permeable hydrophobic or hydrophilic outer membranes which can be tailored specifically to control the diffusion rate. The methods of the invention rely on low shear mixing and liquid-liquid diffusion process and are particularly well suited for forming microcapsules containing both hydrophilic and hydrophobic drugs. These methods can be carried out in the absence of gravity and do not rely on density-driven phase separation, mechanical mixing or solvent evaporation phases. The methods include the process of forming, washing and filtering microcapsules. In addition, the methods contemplate coating microcapsules with ancillary coatings using an electrostatic field and free fluid electrophoresis of the microcapsules. The microcapsules produced by such methods are particularly useful in the delivery of pharmaceutical compositions.

  2. Electrostatic interactions between Janus particles

    NASA Astrophysics Data System (ADS)

    de Graaf, Joost; Boon, Niels; Dijkstra, Marjolein; van Roij, René

    2012-09-01

    In this paper we study the electrostatic properties of "Janus" spheres with unequal charge densities on both hemispheres. We introduce a method to compare primitive-model Monte Carlo simulations of the ionic double layer with predictions of (mean-field) nonlinear Poisson-Boltzmann theory. We also derive practical Derjaguin Landau Verwey Overbeek (DLVO)-like expressions that describe the Janus-particle pair interactions by mean-field theory. Using a large set of parameters, we are able to probe the range of validity of the Poisson-Boltzmann approximation, and thus of DLVO-like theories, for such particles. For homogeneously charged spheres this range corresponds well to the range that was predicted by field-theoretical studies of homogeneously charged flat surfaces. Moreover, we find similar ranges for colloids with a Janus-type charge distribution. The techniques and parameters we introduce show promise for future studies of an even wider class of charged-patterned particles.

  3. Electrostatic generator/motor configurations

    DOEpatents

    Post, Richard Freeman

    2012-09-11

    Electrostatic generators/motors designs are provided that include a stator fixedly connected to a first central support centered about a central axis. The stator elements are attached to the first central support. Similarly, a second stator is connected to a central support centered about the central axis, and the second stator has stator elements attached to the second central support. A rotor is located between the first stator and the second stator and includes an outer support, where the rotor is rotatably centered about the central axis, the rotor having elements in contact with the outer support, each rotor element having an extending rotor portion that extends radially from the outer support toward the axis of rotation.

  4. Large Aperture Electrostatic Dust Detector

    SciTech Connect

    C.H. Skinner, R. Hensley, and A.L Roquemore

    2007-10-09

    Diagnosis and management of dust inventories generated in next-step magnetic fusion devices is necessary for their safe operation. A novel electrostatic dust detector, based on a fine grid of interlocking circuit traces biased to 30 or 50 ν has been developed for the detection of dust particles on remote surfaces in air and vacuum environments. Impinging dust particles create a temporary short circuit and the resulting current pulse is recorded by counting electronics. Up to 90% of the particles are ejected from the grid or vaporized suggesting the device may be useful for controlling dust inventories. We report measurements of the sensitivity of a large area (5x5 cm) detector to microgram quantities of dust particles and review its applications to contemporary tokamaks and ITER.

  5. Efficacy and tolerability of switching to a dual therapy with darunavir/ritonavir plus raltegravir in HIV-infected patients with HIV-1 RNA ≤50 cp/mL.

    PubMed

    Madeddu, Giordano; Rusconi, Stefano; Cozzi-Lepri, Alessandro; Di Giambenedetto, Simona; Bonora, Stefano; Carbone, Alessia; De Luca, Andrea; Gianotti, Nicola; Di Biagio, Antonio; Antinori, Andrea

    2017-08-01

    Nucleos(t)ide reverse transcriptase inhibitors (NRTI) toxicity may represent a threat for long-term success of combined antiretroviral therapy. Some studies have suggested a possible improvement of NRTI-related toxicity after switching to NRTI-sparing regimens. We aimed to explore the efficacy and tolerability of switching to darunavir/ritonavir (DRV/r) plus raltegravir (RAL) while having a viral load (VL) ≤50 copies/mL in the clinical setting. Treatment-experienced HIV 1-infected patients enrolled in the ICONA Foundation Study cohort were included if they switched their current regimen to DRV/r + RAL with a HIV-RNA ≤50 copies/mL. Different definitions of virological failure (VF) and treatment failure (TF) were employed. Kaplan-Meier curves and Cox regression models were performed to estimate time to event probability. We included 72 HIV-infected patients, 22 (31%) of these were female, 31 (43%) men who have sex with men (MSM) amd 15 (21%) had hepatitis co-infections. Median age was 44 (IQR: 35-50) years amd CD4 count was 389 (IQR 283-606) cells/mmc. Median follow-up time for TF was 24 (IQR 9-31) months. Twenty-five discontinuations occurred (60% simplifications); only 2 (8%) were toxicity-driven (lipid elevations). The probability of VF (confirmed VL >50 copies/mL) was estimated at 7% [95% confidence interval (CI) 1-13%] by 12 and 9% (95% CI 2-16%) by 24 months. When considering TF, we found a probability of stop/intensification/single VL > 200 copies/mL of 13% (95% CI 1-17%) and 22% (95% CI 11-33%) by 12 and 24 months. Female gender (adjusted relative hazard, ARH = 0.10; 95% CI 0.01-0.74; p = 0.024) and older age (AHR = 0.50 per 10 years older; 95% CI 0.25-0.99; p = 0.045) were associated with a lower risk of TF. A previous PI failure was strongly associated with TF (AHR = 52.6, 95% CI 3.6-779; p = 0.004). DRV/r + RAL is a valuable NRTI-sparing option, especially in female and older patients, with a relatively low risk of VF and good

  6. Isolated Fast High-Voltage Switching Circuit

    NASA Technical Reports Server (NTRS)

    Rizzi, Anthony

    1992-01-01

    Electrically isolated switching circuit supplies pulses at potentials up to 6.5 kV and currents up to 6.5 A, lasting as long as few microseconds. Turn-on time about 40 ns; turn-off time about 3 microseconds. Electrically isolated from control circuitry by means of fiber-optic signal coupling and isolated power supply. Electrical isolation protects both technician and equipment. This and similar circuits useful in such industrial and scientific applications as high-voltage, high-frequency test equipment; electrostatic-discharge test equipment; plasma-laboratory instrumentation; spark chambers; and electromagnetic-interference test equipment.

  7. Lifetime characteristics of ohmic MEMS switches

    NASA Astrophysics Data System (ADS)

    Maciel, John; Majumder, Sumit; Morrison, Richard; Lampen, James

    2003-12-01

    In the future, MEMS switches will be important building blocks for designing phase shifters, smart antennas, cell phones and switched filters for military and commercial markets, to name a few. Low power consumption, large ratio of off-impedance to on-impedance and the ability to be integrated with other electronics makes MEMS switches an attractive alternative to other mechanical and solid-state switches. Radant MEMS has developed an electrostatically actuated broadband ohmic microswitch that has applications from DC through the microwave region. The microswitch is a 3-terminal device based on a cantilever beam and is fabricated using an all-metal, surface micromachining process. It operates in a hermetic environment obtained through a wafer-bonding process. We have developed PC-based test stations to cycle switches and measure lifetime under DC and RF loads. Best-case lifetimes of 1011 cycles have been achieved in T0-8 cans (a precursor to our wafer level cap) while greater than 1010 cycles have been achieved in the wafer level package. Several switches from different lots have been operated to 1010 cycles. Current typical lifetime exceeds 2 billion cycles and is limited by contact stiction resulting in stuck-closed failures. Stuck-closed failures can be intermittent with a large number of switches continuing to operate with occasional sticks beyond several billion cycles. To eliminate contact stiction, we need to better control the ambient gas composition in the die cavity. We expect lifetime to improve as we continue to develop and optimize the wafer capping process. We present DC and RF lifetime data under varying conditions.

  8. Electrostatics with Computer-Interfaced Charge Sensors

    ERIC Educational Resources Information Center

    Morse, Robert A.

    2006-01-01

    Computer interfaced electrostatic charge sensors allow both qualitative and quantitative measurements of electrostatic charge but are quite sensitive to charges accumulating on modern synthetic materials. They need to be used with care so that students can correctly interpret their measurements. This paper describes the operation of the sensors,…

  9. Ionic electrostatic excitations along biological membranes

    NASA Astrophysics Data System (ADS)

    Moradi, Afshin

    2011-02-01

    A theoretical analysis of ionic electrostatic excitations of a charged biological membrane is presented within the framework of the fluid theory for surface ions inside and outside the cell, in conjunction with the Poisson's equation. General expressions of dispersion relations are obtained for electrostatic oscillations of intrinsic cellular with different shapes and symmetries.

  10. Electrostatics experiments with sharp metal points

    NASA Astrophysics Data System (ADS)

    Ivanov, Dragia; Nikolov, Stefan

    2016-11-01

    In this paper we examine the phenomena that arise around an electrically charged sharp metal spike and present numerous experiments that can be used in the teaching of electrostatics. The experiments are quite spectacular and attention-grabbing while being relatively simple and easy to perform in any decently supplied physics education laboratory that is equipped with an electrostatic machine (like a Wimshurst machine).

  11. Preliminary tests of the electrostatic plasma accelerator

    NASA Technical Reports Server (NTRS)

    Aston, G.; Acker, T.

    1990-01-01

    This report describes the results of a program to verify an electrostatic plasma acceleration concept and to identify those parameters most important in optimizing an Electrostatic Plasma Accelerator (EPA) thruster based upon this thrust mechanism. Preliminary performance measurements of thrust, specific impulse and efficiency were obtained using a unique plasma exhaust momentum probe. Reliable EPA thruster operation was achieved using one power supply.

  12. Review on the Modeling of Electrostatic MEMS

    PubMed Central

    Chuang, Wan-Chun; Lee, Hsin-Li; Chang, Pei-Zen; Hu, Yuh-Chung

    2010-01-01

    Electrostatic-driven microelectromechanical systems devices, in most cases, consist of couplings of such energy domains as electromechanics, optical electricity, thermoelectricity, and electromagnetism. Their nonlinear working state makes their analysis complex and complicated. This article introduces the physical model of pull-in voltage, dynamic characteristic analysis, air damping effect, reliability, numerical modeling method, and application of electrostatic-driven MEMS devices. PMID:22219707

  13. Electrostatics with Computer-Interfaced Charge Sensors

    ERIC Educational Resources Information Center

    Morse, Robert A.

    2006-01-01

    Computer interfaced electrostatic charge sensors allow both qualitative and quantitative measurements of electrostatic charge but are quite sensitive to charges accumulating on modern synthetic materials. They need to be used with care so that students can correctly interpret their measurements. This paper describes the operation of the sensors,…

  14. Review on the modeling of electrostatic MEMS.

    PubMed

    Chuang, Wan-Chun; Lee, Hsin-Li; Chang, Pei-Zen; Hu, Yuh-Chung

    2010-01-01

    Electrostatic-driven microelectromechanical systems devices, in most cases, consist of couplings of such energy domains as electromechanics, optical electricity, thermoelectricity, and electromagnetism. Their nonlinear working state makes their analysis complex and complicated. This article introduces the physical model of pull-in voltage, dynamic characteristic analysis, air damping effect, reliability, numerical modeling method, and application of electrostatic-driven MEMS devices.

  15. Using Programmable Calculators to Solve Electrostatics Problems.

    ERIC Educational Resources Information Center

    Yerian, Stephen C.; Denker, Dennis A.

    1985-01-01

    Provides a simple routine which allows first-year physics students to use programmable calculators to solve otherwise complex electrostatic problems. These problems involve finding electrostatic potential and electric field on the axis of a uniformly charged ring. Modest programing skills are required of students. (DH)

  16. Control of electrostatic damage to electronic circuits

    SciTech Connect

    Kirk, W.J. Jr.

    1980-03-01

    Static is caused by the flow of materials and people within an environment. The static voltages generated by these movements can degrade or destroy many solid state devices currently being used in sophisticated electronic equipment. Discharge of static voltages through these sensitive devices during assembly operations can lead to a nonfunctional assembly fabricated from parts which previously were acceptable or to later failure of an assembly which was functional after fabrication. Sources of electrostatic charges, equipment and methods for minimizing the generation of electrostatic voltages during the production, assembly and packaging of solid state electronic equipment, and the sensitivity of solid state devices to electrostatic damage are discussed. It is concluded that static awareness is the key to an effective electrostatic damage (ESD) control program, and that production facilities must incorporate electrostatic protection facilities, materials, and processes so that workers can concentrate on producing a high-quality product without having to be overly concerned about ESD procedures. (LCL)

  17. Electrostatic thin film chemical and biological sensor

    DOEpatents

    Prelas, Mark A.; Ghosh, Tushar K.; Tompson, Jr., Robert V.; Viswanath, Dabir; Loyalka, Sudarshan K.

    2010-01-19

    A chemical and biological agent sensor includes an electrostatic thin film supported by a substrate. The film includes an electrostatic charged surface to attract predetermined biological and chemical agents of interest. A charge collector associated with said electrostatic thin film collects charge associated with surface defects in the electrostatic film induced by the predetermined biological and chemical agents of interest. A preferred sensing system includes a charge based deep level transient spectroscopy system to read out charges from the film and match responses to data sets regarding the agents of interest. A method for sensing biological and chemical agents includes providing a thin sensing film having a predetermined electrostatic charge. The film is exposed to an environment suspected of containing the biological and chemical agents. Quantum surface effects on the film are measured. Biological and/or chemical agents can be detected, identified and quantified based on the measured quantum surface effects.

  18. Electrostatic interaction in atomic force microscopy

    PubMed Central

    Butt, Hans-Jüurgen

    1991-01-01

    In atomic force microscopy, the stylus experiences an electrostatic force when imaging in aqueous medium above a charged surface. This force has been calculated numerically with continuum theory for a silicon nitrite or silicon oxide stylus. For comparison, the Van der Waals force was also calculated. In contrast to the Van der Waals attraction, the electrostatic force is repulsive. At a distance of 0.5 nm the electrostatic force is typically 10-12-10-10 N and thus comparable in strength to the Van der Waals force. The electrostatic force increases with increasing surface charge density and decreases roughly exponentially with distance. It can be reduced by imaging in high salt concentrations. Below surface potentials of ≈50 mV, a simple analytical approximation of the electrostatic force is described. PMID:19431803

  19. Latching micro optical switch

    DOEpatents

    Garcia, Ernest J; Polosky, Marc A

    2013-05-21

    An optical switch reliably maintains its on or off state even when subjected to environments where the switch is bumped or otherwise moved. In addition, the optical switch maintains its on or off state indefinitely without requiring external power. External power is used only to transition the switch from one state to the other. The optical switch is configured with a fixed optical fiber and a movable optical fiber. The movable optical fiber is guided by various actuators in conjunction with a latching mechanism that configure the switch in one position that corresponds to the on state and in another position that corresponds to the off state.

  20. The role of electrostatics in the B to A transition of DNA: from solution to assembly.

    PubMed

    Rudd, Laura; Lee, Dominic J; Kornyshev, Alexei A

    2007-10-17

    On the basis of a wealth of published experimental data and computer simulations, we build a simple physical model that allows us to rationalize the A to B transition of DNA in solution and in aggregates. In both cases we find that the electrostatic interactions are strong enough, alone, to induce the transition independently of other energetic contributions, e.g. those related to hydration. On the basis of this analysis we conclude that in ethanol/water mixtures, the effect responsible for the transition is the reduction of dielectric constant in the mixture. This is manifested in electrostatic self-energy terms that include the interaction of phosphate charges with condensed counterions. But in dense aggregates, electrostatics plays a dual role, giving rise to two competing effects. In the absence of groove localized counterions the electrostatic self-energy favours the B form, and the electrostatic interaction energy between neighbouring DNA favours the A form. However, the addition of enough counterions localized in the narrow groove reverses this. In dry aggregates of DNA both terms, in most cases, conspire to keep DNA in the A form. The analysis gives a broad picture of the B to A transition and sets a number of new research goals, particularly concerning simulations that may test our simple model for aggregates.

  1. Uncertainty quantification in capacitive RF MEMS switches

    NASA Astrophysics Data System (ADS)

    Pax, Benjamin J.

    Development of radio frequency micro electrical-mechanical systems (RF MEMS) has led to novel approaches to implement electrical circuitry. The introduction of capacitive MEMS switches, in particular, has shown promise in low-loss, low-power devices. However, the promise of MEMS switches has not yet been completely realized. RF-MEMS switches are known to fail after only a few months of operation, and nominally similar designs show wide variability in lifetime. Modeling switch operation using nominal or as-designed parameters cannot predict the statistical spread in the number of cycles to failure, and probabilistic methods are necessary. A Bayesian framework for calibration, validation and prediction offers an integrated approach to quantifying the uncertainty in predictions of MEMS switch performance. The objective of this thesis is to use the Bayesian framework to predict the creep-related deflection of the PRISM RF-MEMS switch over several thousand hours of operation. The PRISM switch used in this thesis is the focus of research at Purdue's PRISM center, and is a capacitive contacting RF-MEMS switch. It employs a fixed-fixed nickel membrane which is electrostatically actuated by applying voltage between the membrane and a pull-down electrode. Creep plays a central role in the reliability of this switch. The focus of this thesis is on the creep model, which is calibrated against experimental data measured for a frog-leg varactor fabricated and characterized at Purdue University. Creep plasticity is modeled using plate element theory with electrostatic forces being generated using either parallel plate approximations where appropriate, or solving for the full 3D potential field. For the latter, structure-electrostatics interaction is determined through immersed boundary method. A probabilistic framework using generalized polynomial chaos (gPC) is used to create surrogate models to mitigate the costly full physics simulations, and Bayesian calibration and forward

  2. Disparate bilingual experiences modulate task-switching advantages: A diffusion-model analysis of the effects of interactional context on switch costs.

    PubMed

    Hartanto, Andree; Yang, Hwajin

    2016-05-01

    Drawing on the adaptive control hypothesis (Green & Abutalebi, 2013), we investigated whether bilinguals' disparate interactional contexts modulate task-switching performance. Fifty-eight bilinguals within the single-language context (SLC) and 75 bilinguals within the dual-language context (DLC) were compared in a typical task-switching paradigm. Given that DLC bilinguals switch between languages within the same context, while SLC bilinguals speak only one language in one environment and therefore rarely switch languages, we hypothesized that the two groups' stark difference in their interactional contexts of conversational exchanges would lead to differences in switch costs. As predicted, DLC bilinguals showed smaller switch costs than SLC bilinguals. Our diffusion-model analyses suggest that DLC bilinguals' benefits in switch costs are more likely driven by task-set reconfiguration than by proactive interference. Our findings underscore the modulating role of the interactional context of conversational exchanges in task switching. Copyright © 2016 Elsevier B.V. All rights reserved.

  3. Assessment and control of electrostatic charges. [hazards to space missions

    NASA Technical Reports Server (NTRS)

    Barrett, M.

    1974-01-01

    The experience is described of NASA and DOD with electrostatic problems, generation mechanisms, and type of electrostatic hazards. Guidelines for judging possible effects of electrostatic charges on space missions are presented along with mathematical formulas and definitions.

  4. Independently tunable dual-band plasmonically induced transparency based on hybrid metal-graphene metamaterials at mid-infrared frequencies.

    PubMed

    Sun, Chen; Dong, Zhewei; Si, Jiangnan; Deng, Xiaoxu

    2017-01-23

    A tunable dual-band plasmonically induced transparency (PIT) device based on hybrid metal-graphene nanostructures is proposed theoretically and numerically at mid-infrared frequencies, which is composed of two kinds of gold dolmen-like structures with different sizes placed on separate graphene interdigitated finger sets respectively. The coupled Lorentz oscillator model is used to explain the physical mechanism of the PIT effect at multiple frequency domains. The finite-difference time-domain (FDTD) solutions are employed to simulate the characteristics of the hybrid metal-graphene dual-band PIT device. The simulated spectral locations of multiple transparency peaks are separately and dynamically modulated by varying the Fermi energy of corresponding graphene finger set, which is in good accordance with the theoretical analysis. Distinguished from the conventional metallic PIT devices, multiple PIT resonances in the hybrid metal-graphene PIT device are independently modulated by electrostatically changing bias voltages applied on corresponding graphene fingers, which can be widely applied in optical information processing as tunable sensors, switches, and filters.

  5. A tunable dual frequency dye laser - dual frequency oscillator design

    NASA Technical Reports Server (NTRS)

    Abury, Y.

    1983-01-01

    The pulsed dye laser offers a tunable oscillator, followed by three amplifiers. It is pumped by a dual frequency Nd:YAG laser. Tuning and spectral width are controlled by a holographic network connected to a high power telescope. The modified two wavelength dye laser allows for absorption lidar techniques for remote sensing of the atmosphere. Line switching is achieved by electrooptical commutation. A feasibility experiment was performed with the original oscillator. A model was then built, and tested with different dyes. After a few modifications were made to improve the conversion efficiency, this oscillator was inserted in the laser to check whether the amplifier stages were correctly adjusted.

  6. ELECTROSTATICALLY ENHANCED BARRIER FILTER COLLECTION

    SciTech Connect

    John Erjavec; Michael D. Mann; Ryan Z. Knutson; Michael L. Swanson; Michael E. Collings

    2003-06-01

    This work was performed through the University of North Dakota (UND) Chemical Engineering Department with assistance from UND's Energy & Environmental Research Center. This research was undertaken in response to the U.S. Department of Energy Federal Technology Center Program Solicitation No. DE-PS26-99FT40479, Support of Advanced Coal Research at U.S. Universities and Colleges. Specifically, this research was in support of the UCR Core Program and addressees Topic 1, Improved Hot-Gas Contaminant and Particulate Removal Techniques, introducing an advanced design for particulate removal. Integrated gasification combined cycle (IGCC) offers the potential for very high efficiency and clean electric generation. In IGCC, the product gas from the gasifier needs to be cleaned of particulate matter to avoid erosion and high-temperature corrosion difficulties arising with the turbine blades. Current methods involve cooling the gases to {approx}100 C to condense alkalis and remove sulfur and particulates using conventional scrubber technology. This ''cool'' gas is then directed to a turbine for electric generation. While IGCC has the potential to reach efficiencies of over 50%, the current need to cool the product gas for cleaning prior to firing it in a turbine is keeping IGCC from reaching its full potential. The objective of the current project was to develop a highly reliable particulate collector system that can meet the most stringent turbine requirements and emission standards, can operate at temperatures above 1500 F, is applicable for use with all U.S. coals, is compatible with various sorbent injection schemes for sulfur and alkali control, can be integrated into a variety of configurations for both pressurized gasification and combustion, increases allowable face velocity to reduce filter system capital cost, and is cost-competitive with existing technologies. The collector being developed is a new concept in particulate control called electrostatically enhanced

  7. Electrostatic-free piezoresponse force microscopy

    PubMed Central

    Kim, Sungho; Seol, Daehee; Lu, Xiaoli; Alexe, Marin; Kim, Yunseok

    2017-01-01

    Contact and non-contact based atomic force microscopy (AFM) approaches have been extensively utilized to explore various nanoscale surface properties. In most AFM-based measurements, a concurrent electrostatic effect between the AFM tip/cantilever and sample surface can occur. This electrostatic effect often hinders accurate measurements. Thus, it is very important to quantify as well as remove the impact of the electrostatic effect on AFM-based measurements. In this study, we examine the impact of the electrostatic effect on the electromechanical (EM) response in piezoresponse force microscopy as a model AFM mode. We quantitatively studied the effects of increasing the external electric field and reducing the spring constant of a cantilever. Further, we explored ways to minimize the electrostatic effect. The results provide broad guidelines for quantitatively analyzing the EM response as well as, eventually, for obtaining the electrostatic-free EM response. The conclusions can be applied to other AFM-based measurements that are subject to a strong electrostatic effect between the AFM tip/cantilever and sample surface, regardless of contact and non-contact modes. PMID:28139715

  8. Electrostatic-free piezoresponse force microscopy

    NASA Astrophysics Data System (ADS)

    Kim, Sungho; Seol, Daehee; Lu, Xiaoli; Alexe, Marin; Kim, Yunseok

    2017-01-01

    Contact and non-contact based atomic force microscopy (AFM) approaches have been extensively utilized to explore various nanoscale surface properties. In most AFM-based measurements, a concurrent electrostatic effect between the AFM tip/cantilever and sample surface can occur. This electrostatic effect often hinders accurate measurements. Thus, it is very important to quantify as well as remove the impact of the electrostatic effect on AFM-based measurements. In this study, we examine the impact of the electrostatic effect on the electromechanical (EM) response in piezoresponse force microscopy as a model AFM mode. We quantitatively studied the effects of increasing the external electric field and reducing the spring constant of a cantilever. Further, we explored ways to minimize the electrostatic effect. The results provide broad guidelines for quantitatively analyzing the EM response as well as, eventually, for obtaining the electrostatic-free EM response. The conclusions can be applied to other AFM-based measurements that are subject to a strong electrostatic effect between the AFM tip/cantilever and sample surface, regardless of contact and non-contact modes.

  9. Intrinsic electrostatic effects in nanostructured ceramics

    SciTech Connect

    Uberuaga, Blas Pedro; Stanek, Chris R; Nerikar, Pankaj V

    2009-01-01

    Using empirical potentials, we have found that electrostatic dipoles can be created at grain boundaries formed from non-polar surfaces of fluorite-structured materials. In particular, the {Sigma}5(310)/[001] symmetric tilt grain boundary reconstructs to break the symmetry in the atomic structure at the boundary, forming the dipole. This dipole results in an abrupt change in electrostatic potential across the boundary. In multilayered ceramics composed of stacks of grain boundaries, the change in electrostatic potential at the boundary results in profound electrostatic effects within the crystalline layers, the nature of which depends on the electrostatic boundary conditions. For open-circuit boundary conditions, layers with either high or low electrostatic potential are formed. By contrast, for short-circuit boundary conditions, electric fields can be created within each layer, the strength of which then depends on the thickness of the layers. These electrostatic effects may have important consequences for the behavior of defects and dopants within these materials and offer the possibility of interesting technological applications.

  10. Heat Switches for ADRs

    NASA Technical Reports Server (NTRS)

    DiPirro, M. J.; Shirron, P. J.

    2014-01-01

    Heat switches are key elements in the cyclic operation of Adiabatic Demagnetization Refrigerators (ADRs). Several of the types of heat switches that have been used for ADRs are described in this paper. Key elements in selection and design of these switches include not only ON/OFF switching ratio, but also method of actuation, size, weight, and structural soundness. Some of the trade-off are detailed in this paper.

  11. Heat switches for ADRs

    NASA Astrophysics Data System (ADS)

    DiPirro, M. J.; Shirron, P. J.

    2014-07-01

    Heat switches are key elements in the cyclic operation of Adiabatic Demagnetization Refrigerators (ADRs). Several of the types of heat switches that have been used for ADRs are described in this paper. Key elements in selection and design of these switches include not only ON/OFF switching ratio, but also method of actuation, size, weight, and structural soundness. Some of the trade-off are detailed in this paper.

  12. Remote switch actuator

    DOEpatents

    Haas, Edwin Gerard; Beauman, Ronald; Palo, Jr., Stefan

    2013-01-29

    The invention provides a device and method for actuating electrical switches remotely. The device is removably attached to the switch and is actuated through the transfer of a user's force. The user is able to remain physically removed from the switch site obviating need for protective equipment. The device and method allow rapid, safe actuation of high-voltage or high-current carrying electrical switches or circuit breakers.

  13. Aptamer induced multicoloured Au NCs-MoS2 "switch on" fluorescence resonance energy transfer biosensor for dual color simultaneous detection of multiple tumor markers by single wavelength excitation.

    PubMed

    Xu, Shenghao; Feng, Xiuying; Gao, Teng; Liu, Gufan; Mao, Yaning; Lin, Jiehua; Yu, Xijuan; Luo, Xiliang

    2017-08-29

    An aptamer induced "switch on" fluorescence resonance energy transfer (FRET) biosensor for the simultaneous detection of multiple tumor markers (e.g., AFP and CEA) combining molybdenum disulfide (MoS2) nanosheets with multicolored Au NCs by a single excitation was developed for the first time. Here, AFP aptamer functionalized green colored Au NCs (510 nm) and CEA aptamer functionalized red colored Au NCs (650 nm) are used as energy donors, while MoS2 is used as energy receptor. On the basis of recording the change of the recovered fluorescence intensity at 510 nm and 650 nm upon the addition of targets CEA and AFP, these two tumor markers can be simultaneously quantitatively detected, with detection limits of 0.16 and 0.21 ng mL(-1) (3σ) for AFP and CEA, respectively. In addition, it is noteworthy that the developed biosensor can not only realize accurate quantitative determination of multiple tumor markers by fluorescent intensity, but also be applied in semi-quantitative determination through photo visualization. More importantly, confocal microscope experiments prove that serums from normal and hepatoma patients can also be visually and qualitatively discriminated by this FRET-based biosensor with a single excitation wavelength, indicating promising potential of this assay for clinical diagnosis. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. DNA/chitosan electrostatic complex.

    PubMed

    Bravo-Anaya, Lourdes Mónica; Soltero, J F Armando; Rinaudo, Marguerite

    2016-07-01

    Up to now, chitosan and DNA have been investigated for gene delivery due to chitosan advantages. It is recognized that chitosan is a biocompatible and biodegradable non-viral vector that does not produce immunological reactions, contrary to viral vectors. Chitosan has also been used and studied for its ability to protect DNA against nuclease degradation and to transfect DNA into several kinds of cells. In this work, high molecular weight DNA is compacted with chitosan. DNA-chitosan complex stoichiometry, net charge, dimensions, conformation and thermal stability are determined and discussed. The influence of external salt and chitosan molecular weight on the stoichiometry is also discussed. The isoelectric point of the complexes was found to be directly related to the protonation degree of chitosan. It is clearly demonstrated that the net charge of DNA-chitosan complex can be expressed in terms of the ratio [NH3(+)]/[P(-)], showing that the electrostatic interactions between DNA and chitosan are the main phenomena taking place in the solution. Compaction of DNA long chain complexed with low molar mass chitosan gives nanoparticles with an average radius around 150nm. Stable nanoparticles are obtained for a partial neutralization of phosphate ionic sites (i.e.: [NH3(+)]/[P(-)] fraction between 0.35 and 0.80).

  15. Internal Electrostatic Discharge Monitor - IESDM

    NASA Technical Reports Server (NTRS)

    Kim, Wousik; Goebel, Dan M.; Jun, Insoo; Garrett, Henry B.

    2011-01-01

    A document discusses an innovation designed to effectively monitor dielectric charging in spacecraft components to measure the potential for discharge in order to prevent damage from internal electrostatic discharge (IESD). High-energy electrons penetrate the structural materials and shielding of a spacecraft and then stop inside dielectrics and keep accumulating. Those deposited charges generate an electric field. If the electric field becomes higher than the breakdown threshold (approx. =2 x 10(exp 5) V/cm), discharge occurs. This monitor measures potentials as a function of dielectric depth. Differentiation of potential with respect to the depth yields electric field. Direct measurement of the depth profile of the potential in a dielectric makes real-time electronic field evaluation possible without simulations. The IESDM has been designed to emulate a multi-layer circuit board, to insert very thin metallic layers between the dielectric layers. The conductors serve as diagnostic monitoring locations to measure the deposited electron-charge and the charge dynamics. Measurement of the time-dependent potential of the metal layers provides information on the amount of charge deposited in the dielectrics and the movement of that charge with time (dynamics).

  16. Apollo Ring Optical Switch

    SciTech Connect

    Maestas, J.H.

    1987-03-01

    An optical switch was designed, built, and installed at Sandia National Laboratories in Albuquerque, New Mexico, to facilitate the integration of two Apollo computer networks into a single network. This report presents an overview of the optical switch as well as its layout, switch testing procedure and test data, and installation.

  17. Triggered plasma opening switch

    DOEpatents

    Mendel, Clifford W.

    1988-01-01

    A triggerable opening switch for a very high voltage and current pulse includes a transmission line extending from a source to a load and having an intermediate switch section including a plasma for conducting electrons between transmission line conductors and a magnetic field for breaking the plasma conduction path and magnetically insulating the electrons when it is desired to open the switch.

  18. Electrostatic Stabilization Of Growing Protein Crystals

    NASA Technical Reports Server (NTRS)

    Shlichta, Paul J.

    1991-01-01

    Proposed technique produces large crystals in compact, economical apparatus. Report presents concept for supporting protein crystals during growth in microgravity. Yields crystals larger and more-nearly perfect than those grown on Earth. Combines best features of sandwich-drop and electrostatic-levitation methods of support. Drop of protein solution inserted between pair of glass or plastic plates, as in sandwich-drop-support method. Electrostatically charged ring confines drop laterally and shapes it, as in electrostatic technique. Apparatus also made to accommodate several drops simultaneously between same pair of supporting plates. Drops can be inserted and crystals removed through ducts in plates.

  19. Antimicrobial peptide coatings for hydroxyapatite: electrostatic and covalent attachment of antimicrobial peptides to surfaces.

    PubMed

    Townsend, Leigh; Williams, Richard L; Anuforom, Olachi; Berwick, Matthew R; Halstead, Fenella; Hughes, Erik; Stamboulis, Artemis; Oppenheim, Beryl; Gough, Julie; Grover, Liam; Scott, Robert A H; Webber, Mark; Peacock, Anna F A; Belli, Antonio; Logan, Ann; de Cogan, Felicity

    2017-01-01

    The interface between implanted devices and their host tissue is complex and is often optimized for maximal integration and cell adhesion. However, this also gives a surface suitable for bacterial colonization. We have developed a novel method of modifying the surface at the material-tissue interface with an antimicrobial peptide (AMP) coating to allow cell attachment while inhibiting bacterial colonization. The technology reported here is a dual AMP coating. The dual coating consists of AMPs covalently bonded to the hydroxyapatite surface, followed by deposition of electrostatically bound AMPs. The dual approach gives an efficacious coating which is stable for over 12 months and can prevent colonization of the surface by both Gram-positive and Gram-negative bacteria.

  20. Part D Plan Switching Among Medicare Beneficiaries With Schizophrenia.

    PubMed

    Zhang, Yuting; Talisa, Victor; Baik, Seo Hyon

    2015-10-01

    Most Medicare schizophrenia patients were randomly assigned in 2006 to one of 409 benchmark plans. This study examined plan switching and factors affecting switching among beneficiaries with schizophrenia. The data were 2006 Medicare pharmacy data for three groups of schizophrenia patients: those with Medicaid coverage ("dual eligibles"; N=93,705), Medicare beneficiaries with a low-income subsidy (N=56,148), and Medicare beneficiaries without the subsidy (N=36,107). Switching frequency and how patient and plan characteristics affected switching were examined. Beneficiaries who switched their Part D plan at least once included 10.7% of the dual eligibles, 9.8% of those with a subsidy, and 5.5% of those without. Several factors affected likelihood of switching, including age, geographic region, and proportion of prescriptions filled by beneficiaries who were covered or whose prescriptions required utilization review in the original plan. Plan switching among Medicare beneficiaries with schizophrenia was relatively infrequent but may be driven by the need for better drug coverage and less restrictive utilization policies.

  1. Multi-residue analytical method for the determination of endocrine disruptors and related compounds in river and waste water using dual column liquid chromatography switching system coupled to mass spectrometry.

    PubMed

    Gorga, Marina; Petrovic, Mira; Barceló, Damià

    2013-06-21

    The present study describes a novel, fully automated method, based on column switching using EQuan™ columns for an integrated sample preconcentration and liquid chromatography coupled to tandem mass spectrometry (LC-LC-MS/MS). The method allows the unequivocal identification and quantification of the most relevant environmental endocrine disruptors compounds (EDCs) and compounds suspected to be EDCs, such as natural and synthetic estrogens and their conjugates, antimicrobials, parabens, bisphenol A, alkylphenolic compounds, benzotriazoles, and organophosphorus flame retardants, in surface river water and wastewater samples. Applying this technique, water samples were directly injected into the chromatographic system and the target compounds were concentrated into the loading column. Thereafter, the analytes were transferred into the analytical column for subsequent detection by MS-MS (QqQ). A comparative study employing three types of columns, with different chemical modifications, was performed in order to determine the optimal column that allowed maximum retention and subsequent elution of the analytes. Using this new optimized methodology a fast and easy online methodology for the analysis of EDCs in surface river water and wastewater with low limits of quantification (LOQ) was obtained. LOQs ranged from 0.008 to 1.54 ng/L for surface river water and from 0.178/0.364 to 12.5/25.0 ng/L (except for alkylphenol monoethoxylates) for effluent/influent waste water. Moreover, employing approximately 1h, a complete analysis was performed which was significant improvement in comparison to other methods reported previously. This method was used to track the presence and fate of target compounds in the Ebro River which is the most important river in Spain whose intensive agricultural and industrial activities concentrate mainly close to the main cities in the basin, deteriorating soil and water quality. Copyright © 2013 Elsevier B.V. All rights reserved.

  2. REMOTE CONTROLLED SWITCHING DEVICE

    DOEpatents

    Hobbs, J.C.

    1959-02-01

    An electrical switching device which can be remotely controlled and in which one or more switches may be accurately operated at predetermined times or with predetermined intervening time intervals is described. The switching device consists essentially of a deck, a post projecting from the deck at right angles thereto, cam means mounted for rotation around said posts and a switch connected to said deck and actuated by said cam means. Means is provided for rotating the cam means at a constant speed and the switching apparatus is enclosed in a sealed container with external adjusting means and electrical connection elements.

  3. Electrostatic correlations near charged planar surfaces

    PubMed Central

    Deng, Mingge; Em Karniadakis, George

    2014-01-01

    Electrostatic correlation effects near charged planar surfaces immersed in a symmetric electrolytes solution are systematically studied by numerically solving the nonlinear six-dimensional electrostatic self-consistent equations. We compare our numerical results with widely accepted mean-field (MF) theory results, and find that the MF theory remains quantitatively accurate only in weakly charged regimes, whereas in strongly charged regimes, the MF predictions deviate drastically due to the electrostatic correlation effects. We also observe a first-order like phase-transition corresponding to the counterion condensation phenomenon in strongly charged regimes, and compute the phase diagram numerically within a wide parameter range. Finally, we investigate the interactions between two likely-charged planar surfaces, which repulse each other as MF theory predicts in weakly charged regimes. However, our results show that they attract each other above a certain distance in strongly charged regimes due to significant electrostatic correlations. PMID:25194382

  4. Electrostatic Liquid-Drop-Levitation System

    NASA Technical Reports Server (NTRS)

    Rhim, Won Kyu; Chung, San Kun; Hyson, Michael T.; Elleman, Daniel D.

    1988-01-01

    Electrostatic levitator has levitated drops of liquid up to 4 mm in diameter while maintaining spherical drop shapes. Stable levitation of spherical drops valuable in experiments involving super-cooling, solidification, and crystal growth.

  5. Electrostatic discharge control for STDN stations

    NASA Technical Reports Server (NTRS)

    Mckiernan, J.

    1983-01-01

    This manual defines the requirements and control methods necessary to control the effect of electrostatic discharges that damage or destroy electronic equipment components. Test procedures for measuring the effectiveness of the control are included.

  6. NEW APPROACHES: A novel Kelvin Electrostatic Generator

    NASA Astrophysics Data System (ADS)

    Hill, M.; Jacobs, D. J.

    1997-01-01

    A form of the Kelvin Electrostatic Generator, made from readily available components, is described and an explanation given of how it works. The device described can generate 10 - 12 mm long sparks in air.

  7. The Electrocardiogram as an Example of Electrostatics

    ERIC Educational Resources Information Center

    Hobbie, Russell K.

    1973-01-01

    Develops a simplified electrostatic model of the heart with conduction within the torso neglected to relate electrocardiogram patterns to the charge distribution within the myocardium. Suggests its application to explanation of Coulomb's law in general physics. (CC)

  8. Nonlinear electrostatic drift Kelvin-Helmholtz instability

    NASA Technical Reports Server (NTRS)

    Sharma, Avadhesh C.; Srivastava, Krishna M.

    1993-01-01

    Nonlinear analysis of electrostatic drift Kelvin-Helmholtz instability is performed. It is shown that the analysis leads to the propagation of the weakly nonlinear dispersive waves, and the nonlinear behavior is governed by the nonlinear Burger's equation.

  9. Electrostatic processing of polymers and polymer composites

    NASA Astrophysics Data System (ADS)

    Sanders, Elliot Howard

    2005-11-01

    Polymers are a broad class of molecules whose use in modern life is undeniable ranging from automobile parts to pharmaceuticals. One method applicable to polymer material production is known as electrostatic processing which includes electrospraying, used to produce films or microparticles, and electrospinning, which can be used to produce fibers or non-woven materials. Electrostatic processing typically results in products with droplet or fiber diameters on the micron or nanometer scale. We have sought to develop novel polymeric materials and composites using electrostatic processing. The end uses of these materials were diverse, and included controlled release of drugs, microencapsulation of proteins and enzymes, provision of molecular cues for directed cell growth, hydronium ion transport, and electrically conductive polymer and catalytically active composites. We have successfully demonstrated that electrostatic processing can be used to produce a wide variety of functionally active polymer based materials with significant commercial, medical, and scientific potential.

  10. Stochastic ion acceleration by beating electrostatic waves.

    PubMed

    Jorns, B; Choueiri, E Y

    2013-01-01

    A study is presented of the stochasticity in the orbit of a single, magnetized ion produced by the particle's interaction with two beating electrostatic waves whose frequencies differ by the ion cyclotron frequency. A second-order Lie transform perturbation theory is employed in conjunction with a numerical analysis of the maximum Lyapunov exponent to determine the velocity conditions under which stochasticity occurs in this dynamical system. Upper and lower bounds in ion velocity are found for stochastic orbits with the lower bound approximately equal to the phase velocity of the slower wave. A threshold condition for the onset of stochasticity that is linear with respect to the wave amplitudes is also derived. It is shown that the onset of stochasticity occurs for beating electrostatic waves at lower total wave energy densities than for the case of a single electrostatic wave or two nonbeating electrostatic waves.

  11. Monitoring by Control Technique - Electrostatic Precipitators

    EPA Pesticide Factsheets

    Stationary source emissions monitoring is required to demonstrate that a source is meeting the requirements in Federal or state rules. This page is about electrostatic precipitator control techniques used to reduce pollutant emissions.

  12. On the Switching Control

    NASA Astrophysics Data System (ADS)

    Balas, Valentina E.; Balas, Marius M.

    2009-04-01

    The paper is discussing the measures able to reject the instability that may unexpectedly appear in particular conditions, in switching controllers applications. The switching controllers' effect is explained by the combined effects of the unsuitable choice of the switching moments (in the first or third quadrants of the phase trajectory of the switching error) and of the temporal aliasing that can distort the digital control systems when the sampling rate is close to the frequency of the oscillations that are produced by the commutation. The correct switching moments are located into the second and fourth quadrants of the phase trajectory of the switching error, but an active preparation of the commutation may be simply achieved by using a tracking controller, that is driving the output of open loop controller to follow the output of the close loop controller, permanently minimizing the switching error. Simulations issued from a dc driver speed controller and from an aircraft are provided.

  13. Miniature Bipolar Electrostatic Ion Thruster

    NASA Technical Reports Server (NTRS)

    Hartley, Frank T.

    2006-01-01

    The figure presents a concept of a bipolar miniature electrostatic ion thruster for maneuvering a small spacecraft. The ionization device in the proposed thruster would be a 0.1-micron-thick dielectric membrane with metal electrodes on both sides. Small conical holes would be micromachined through the membrane and electrodes. An electric potential of the order of a volt applied between the membrane electrodes would give rise to an electric field of the order of several mega-volts per meter in the submicron gap between the electrodes. An electric field of this magnitude would be sufficient to ionize all the molecules that enter the holes. In a thruster-based on this concept, one or more propellant gases would be introduced into such a membrane ionizer. Unlike in larger prior ion thrusters, all of the propellant molecules would be ionized. This thruster would be capable of bipolar operation. There would be two accelerator grids - one located forward and one located aft of the membrane ionizer. In one mode of operation, which one could denote the forward mode, positive ions leaving the ionizer on the backside would be accelerated to high momentum by an electric field between the ionizer and an accelerator grid. Electrons leaving the ionizer on the front side would be ejected into free space by a smaller accelerating field. The equality of the ion and electron currents would eliminate the need for an additional electron- or ion-emitting device to keep the spacecraft charge-neutral. In another mode of operation, which could denote the reverse mode, the polarities of the voltages applied to the accelerator grids and to the electrodes of the membrane ionizer would be the reverse of those of the forward mode. The reversal of electric fields would cause the ion and electrons to be ejected in the reverse of their forward mode directions, thereby giving rise to thrust in the direction opposite that of the forward mode.

  14. Electrostatic Beneficiation of Lunar Simulant

    NASA Technical Reports Server (NTRS)

    Trigwell, Steve; Captain, James; Captain, Janine; Arens, Ellen; Quinn, Jacqueline; Calle, Carlos

    2006-01-01

    Electrostatic beneficiation of lunar regolith is a method allowing refinement of specific minerals in the material for processing on the moon. The use of tribocharging the regolith prior to separation was investigated on the lunar simulant MLS-I by passing the dust through static mixers constructed from different materials; aluminum, copper, stainless steel, and polytetrafluoroethylene (PTFE). The amount of charge acquired by the simulant was dependent upon the difference in the work function of the dust and the charging material. XPS and SEM were used to characterize the simulant after it was sieved into five size fractions (> 100 pm, 75-100 pm, 50- 75 pm, 50-25 pm, and < 25 pm), where very little difference in surface composition was observed between the sizes. Samples of the smallest (< 25 pm) and largest (> 100 pm) size fractions were beneficiated through a charge separator using the aluminum (charged the simulant negatively) and PTFE (charged positively) mixers. The mass fractions of the separated simulant revealed that for the larger particle size, significant unipolar charging was observed for both mixers, whereas for the smaller particle sizes, more bipolar charging was observed, probably due to the finer simulant adhering to the inside of the mixers shielding the dust from the charging material. Subsequent XPS analysis of the beneficiated fractions showed the larger particle size fraction having some species differentiation, but very little difference for the smaller.size. Although MLS-1 was made to have similar chemistry to actual lunar dust, its mineralogy is quite different. On-going experiments are using NASA JSC-1 lunar simulant. A vacuum chamber has been constructed, and future experiments are planned in a simulated lunar environment.

  15. Electrostatic Levitation Furnace for the ISS

    NASA Technical Reports Server (NTRS)

    Murakami, Keiji; Koshikawa, Naokiyo; Shibasaki, Kohichi; Ishikawa, Takehiko; Okada, Junpei; Takada, Tetsuya; Arai, Tatsuya; Fujino, Naoki; Yamaura, Yukiko

    2012-01-01

    JAXA (Japan Aerospace Exploration Agency) has just started the development of Electrostatic Levitation Furnace to be launched in 2014 for the ISS. This furnace can control the sample position with electrostatic force and heat it above 2000 degree Celsius using semiconductor laser from four different directions. The announcement of Opportunity will be issued soon for this furnace. In this paper, we will show the specifications of this furnace and also the development schedule

  16. High-energy capacitance electrostatic micromotors

    NASA Astrophysics Data System (ADS)

    Baginsky, I. L.; Kostsov, E. G.

    2003-03-01

    The design and parameters of a new electrostatic micromotor with high energy output are described. The motor is created by means of microelectronic technology. Its operation is based on the electromechanic energy conversion during the electrostatic rolling of the metallic films (petals) on the ferroelectric film surface. The mathematical simulation of the main characteristics of the rolling process is carried out. The experimentally measured parameters of the petal step micromotors are shown. The motor operation and its efficiency are investigated.

  17. Miniature Electrostatic Ion Thruster With Magnet

    NASA Technical Reports Server (NTRS)

    Hartley, Frank T.

    2006-01-01

    A miniature electrostatic ion thruster is proposed that, with one exception, would be based on the same principles as those of the device described in the previous article, "Miniature Bipolar Electrostatic Ion Thruster". The exceptional feature of this thruster would be that, in addition to using electric fields for linear acceleration of ions and electrons, it would use a magnetic field to rotationally accelerate slow electrons into the ion stream to neutralize the ions.

  18. Electrostatic camera system functional design study

    NASA Technical Reports Server (NTRS)

    Botticelli, R. A.; Cook, F. J.; Moore, R. F.

    1972-01-01

    A functional design study for an electrostatic camera system for application to planetary missions is presented. The electrostatic camera can produce and store a large number of pictures and provide for transmission of the stored information at arbitrary times after exposure. Preliminary configuration drawings and circuit diagrams for the system are illustrated. The camera system's size, weight, power consumption, and performance are characterized. Tradeoffs between system weight, power, and storage capacity are identified.

  19. Low power interface IC's for electrostatic energy harvesting applications

    NASA Astrophysics Data System (ADS)

    Kempitiya, Asantha

    interest where the storage capacitor can be optimized to produce almost 70% of the ideal power taken as the power harvested with synchronous converters when neglecting the power consumption associated with synchronizing control circuitry. Theoretical predictions are confirmed by measurements on an asynchronous EHC implemented with a macro-scale electrostatic converter prototype. Based on the preceding analysis, the design of a novel ultra low power electrostatic integrated energy harvesting circuit is proposed for efficient harvesting of mechanical energy. The fundamental challenges of designing reliable low power sensing circuits for charge constrained electrostatic energy harvesters with capacity to self power its controller and driver stages are addressed. Experimental results are presented for a controller design implemented in AMI 0.7muM high voltage CMOS process using a macro-scale electrostatic converter prototype. The EHC produces 1.126muW for a power investment of 417nW with combined conduction and controller losses of 450nW which is a 20-30% improvement compared to prior art on electrostatic EHCs operating under charge constrain. Inherently dual plate variable capacitors harvest energy only during half of the mechanical cycle with the other half unutilized for energy conversion. To harvest mechanical energy over the complete mechanical vibration cycle, a low power energy harvesting circuit (EHC) that performs charge constrained synchronous energy conversion on a tri-plate variable capacitor for maximizing energy conversion is proposed. The tri-plate macro electrostatic generator with capacitor variation of 405pF to 1.15nF and 405pF to 1.07nF on two complementary adjacent capacitors is fabricated and used in the characterization of the designed EHC. The integrated circuit fabricated in AMI 0.7muM high voltage CMOS process, produces a total output power of 497nW to a 10muF reservoir capacitor from a 98Hz vibration signal. In summary, the thesis lays out the

  20. An improved proximity force approximation for electrostatics

    SciTech Connect

    Fosco, Cesar D.; Lombardo, Fernando C.; Mazzitelli, Francisco D.

    2012-08-15

    A quite straightforward approximation for the electrostatic interaction between two perfectly conducting surfaces suggests itself when the distance between them is much smaller than the characteristic lengths associated with their shapes. Indeed, in the so called 'proximity force approximation' the electrostatic force is evaluated by first dividing each surface into a set of small flat patches, and then adding up the forces due two opposite pairs, the contributions of which are approximated as due to pairs of parallel planes. This approximation has been widely and successfully applied in different contexts, ranging from nuclear physics to Casimir effect calculations. We present here an improvement on this approximation, based on a derivative expansion for the electrostatic energy contained between the surfaces. The results obtained could be useful for discussing the geometric dependence of the electrostatic force, and also as a convenient benchmark for numerical analyses of the tip-sample electrostatic interaction in atomic force microscopes. - Highlights: Black-Right-Pointing-Pointer The proximity force approximation (PFA) has been widely used in different areas. Black-Right-Pointing-Pointer The PFA can be improved using a derivative expansion in the shape of the surfaces. Black-Right-Pointing-Pointer We use the improved PFA to compute electrostatic forces between conductors. Black-Right-Pointing-Pointer The results can be used as an analytic benchmark for numerical calculations in AFM. Black-Right-Pointing-Pointer Insight is provided for people who use the PFA to compute nuclear and Casimir forces.

  1. Failure mechanisms of DC and capacitive RF MEMS switches

    NASA Astrophysics Data System (ADS)

    Patton, Steven T.; Zabinski, Jeffrey S.

    2006-01-01

    Microelectromechanical systems (MEMS) radio frequency (RF) switches hold great promise in a myriad of commercial, aerospace, and military applications including cellular phones and phased array antennas. However, there is limited understanding of the factors determining the performance and reliability of these devices. Fundamental studies of hot-switched DC (gold versus gold) and capacitive (gold versus silicon nitride) MEMS RF switch contacts were conducted in a controlled air environment at MEMS-scale forces using a micro/nanoadhesion apparatus as a switch simulator. This paper reviews key experimental results from the switch simulator and how they relate to failure mechanisms of MEMS switches. For DC switch contacts, electric current had a profound effect on deformation mechanisms, adhesion, contact resistance (R), and reliability/durability. At low current (1-10 μA), junction growth/force relaxation, slightly higher R, and switching induced adhesion growth were prominent. At high current (1-10 mA), asperity melting, slightly lower R, and shorting were present. Adhesion increased during cycling at low current and was linked to the creation of smooth contact surfaces, increased van der Waals interaction, and chemical bonding. Surface roughening by nanowire formation (which also caused shorting) prevented adhesion at high current. Aging of the contacts in air led to hydrocarbon adsorption and less adhesion. Studies of capacitive switches demonstrated that excessive adhesion was the primary failure mechanism and that both mechanical and electrical effects were contributing factors. The mechanical effect is adhesion growth with cycling due to surface smoothening, which allows increased van der Waals interaction and chemical bonding. The electrical effect on adhesion is due to electrostatic force associated with trapped parasitic charge in the dielectric, and was only observed after operating the switch at 40 V bias and above. The two effects are additive; however

  2. Optics Elements for Modeling Electrostatic Lenses and Accelerator Components: III. Electrostatic Deflectors

    SciTech Connect

    Brown, T.A.; Gillespie, G.H.

    1999-10-21

    Ion-beam optics models for simulating electrostatic prisms (deflectors) of different geometries have been developed for the computer code TRACE 3-D. TRACE 3-D is an envelope (matrix) code, which includes a linear space charge model, that was originally developed to model bunched beams in magnetic transport systems and radiofrequency (RF) accelerators. Several new optical models for a number of electrostatic lenses and accelerator columns have been developed recently that allow the code to be used for modeling beamlines and accelerators with electrostatic components. The new models include a number of options for: (1) Einzel lenses, (2) accelerator columns, (3) electrostatic prisms, and (4) electrostatic quadrupoles. A prescription for setting up the initial beam appropriate to modeling 2-D (continuous) beams has also been developed. The models for electrostatic prisms are described in this paper. The electrostatic prism model options allow the modeling of cylindrical, spherical, and toroidal electrostatic deflectors. The application of these models in the development of ion-beam transport systems is illustrated through the modeling of a spherical electrostatic analyzer as a component of the new low energy beamline at CAMS.

  3. Superconducting switch permits measurement of small voltages at cryogenic temperatures

    NASA Technical Reports Server (NTRS)

    Govednik, R. E.; Huebener, R. P.

    1968-01-01

    Dual-coil, superconducting, on-off switch measures small, thermoelectrically generated voltages produced by thermocouples in a liquid helium bath. Placed in a shunt configuration between the thermocouple and the measuring device, the measuring device sees the sum of the voltage to be measured and the spurious thermoelectric voltages.

  4. Nonlinear Compensation of Solar Array Simulators with Dual Power Regulation

    NASA Astrophysics Data System (ADS)

    Mizrah, E. A.; Tkachev, S. B.; Poymanov, D. N.; Fedchenko, A. S.

    2016-11-01

    During the tests of the spacecraft electrical systems there is a need for simulators of individual parts of the spacecrafts, in particular, solar array simulators (SAS). One of the topologies of medium and high power SAS simulators has dual control of consumed power and contains series or parallel connected linear and switching regulators. This topology allows to provide wide bandwidth and high efficiency, but the range of the resistance change of periodically switched SAS load is limited to the value of the stabilized attribute. Nonlinear compensator (NC) allows to reduce the average feedback voltage of the switching regulator in case of periodic load switching, which, in turn, allows to increase the average value of the stabilized attribute. The describing function method provides a mathematical description of the NC electrical circuit, which allows to select parameters of NC that eliminate the excitation of self-oscillation based on the SAS load switching frequency range and to study the switching regulator stability.

  5. Development of micromachined RF switches with piezofilm actuation

    NASA Astrophysics Data System (ADS)

    Fox, Colin H.; Chen, Xuesheng; Jiang, Hong Wen; Kirby, Paul B.; McWilliam, Stewart

    2002-07-01

    Current developments in RF systems require high-performance switches for applications including signal routing, impedance matching and adjustable gain amplifiers. The use of micro-switches to replace traditional semiconductor components is increasingly common, because of their advantages in terms of electrical isolation and power loss. This paper reports on a research program relating to the development of a silicon micro-machined RF micro-switch that uses thin-film piezoelectric material for actuation. Piezoelectric actuation has potential advantages over electrostatic actuation in terms of achievable forces and simplicity of structural design. This paper gives an overview of the design and analysis of a prototype switch. The design concept, based on a cantilevered silicon beam or plate, is described. A low order mathematical model, incorporating the mechanical and electrical characteristics of the switch and the interaction between the silicon structure and the piezo-drive is summarized. This allows the basic behavior of the switch to be quantified, and provides a useful tool for design and optimization purposes. The outline design and manufacture/processing of a prototype switch is discussed.

  6. Gamma-ray irradiation of ohmic MEMS switches

    NASA Astrophysics Data System (ADS)

    Maciel, John J.; Lampen, James L.; Taylor, Edward W.

    2012-10-01

    Radio Frequency (RF) Microelectromechanical System (MEMS) switches are becoming important building blocks for a variety of military and commercial applications including switch matrices, phase shifters, electronically scanned antennas, switched filters, Automatic Test Equipment, instrumentation, cell phones and smart antennas. Low power consumption, large ratio of off-impedance to on-impedance, extreme linearity, low mass, small volume and the ability to be integrated with other electronics makes MEMS switches an attractive alternative to other mechanical and solid-state switches for a variety of space applications. Radant MEMS, Inc. has developed an electrostatically actuated broadband ohmic microswitch that has applications from DC through the microwave region. Despite the extensive earth based testing, little is known about the performance and reliability of these devices in space environments. To help fill this void, we have irradiated our commercial-off-the-shelf SPST, DC to 40 GHz MEMS switches with gamma-rays as an initial step to assessing static impact on RF performance. Results of Co-60 gamma-ray irradiation of the MEMS switches at photon energies ≥ 1.0 MeV to a total dose of ~ 118 krad(Si) did not show a statistically significant post-irradiation change in measured broadband, RF insertion loss, insertion phase, return loss and isolation.

  7. Optoelectronic techniques for broadband switching

    NASA Astrophysics Data System (ADS)

    Su, S. F.; Jou, L.; Lenart, J.

    1988-01-01

    Optoelectronic switching employs a hybrid optical/electronic principle to perform the switching function and is applicable for either analog broadband or high-bit rate digital switching. The major advantages of optoelectronic switching include high isolation, low crosstalk, small physical size, light weight, and low power consumption. These advantages make optoelectronic switching an excellent candidate for on-board satellite switching. This paper describes a number of optoelectronic switching architectures. System components required for implementing these switching architectures are discussed. Performance of these architectures are evaluated by calculating their crosstalk, isolation, insertion loss, matrix size, drive power, throughput, and switching speed. Technologies needed for monolithic optoelectronic switching are also identified.

  8. Characterization for the performance of capacitive switches activated by mechanical shock

    PubMed Central

    Younis, Mohammad I.; Alsaleem, Fadi M; Miles, Ronald; Su, Quang

    2009-01-01

    This paper presents experimental and theoretical investigation of a new concept of switches (triggers) that are actuated at or beyond a specific level of mechanical shock or acceleration. The principle of operation of the switches is based on dynamic pull-in instability induced by the combined interaction between electrostatic and mechanical shock forces. These switches can be tuned to be activated at various shock and acceleration thresholds by adjusting the DC voltage bias. Two commercial off-the-shelf capacitive accelerometers operating in air are tested under mechanical shock and electrostatic loading. A single-degree-of-freedom model accounting for squeeze-film damping, electrostatic forces, and mechanical shock is utilized for the theoretical investigation. Good agreement is found between simulation results and experimental data. Our results indicate that designing these new switches to respond quasi-statically to mechanical shock makes them robust against variations in shock shape and duration. More importantly, quasi-static operation makes the switches insensitive to variations in damping conditions. This can be promising to lower the cost of packaging for these switches since they can operate in atmospheric pressure with no hermetic sealing or costly package required. PMID:21720493

  9. Correlated polarization-switching kinetics in bulk polycrystalline ferroelectrics: A self-consistent mesoscopic switching model

    NASA Astrophysics Data System (ADS)

    Khachaturyan, Ruben; Wehner, Jens; Genenko, Yuri A.

    2017-08-01

    Analysis of statistical distributions and auto- and cross correlations of polarization and electric field during the field-driven polarization reversal in a bulk polycrystalline ferroelectric is performed. A mesoscopic switching model is used which accounts self-consistently for the development of depolarization fields. Correlations mediated by electrostatic fields are shown to be mostly isotropic and short range at the typical scale of the grain size which is explained by an effective screening via adapting bound charges. The short-range screening clarifies the paradoxical ability of common statistical concepts neglecting the feedback effect of depolarization fields to adequately describe the polarization switching kinetics. The statistical distribution of the local electric field magnitudes is continuously spreading in the course of the global polarization reversal due to mismatching of both dielectric tensor and spontaneous polarization at grain boundaries. The increasing field dispersion substantially contributes to the well-known deceleration of the polarization reversal at long times.

  10. PCE: web tools to compute protein continuum electrostatics

    PubMed Central

    Miteva, Maria A.; Tufféry, Pierre; Villoutreix, Bruno O.

    2005-01-01

    PCE (protein continuum electrostatics) is an online service for protein electrostatic computations presently based on the MEAD (macroscopic electrostatics with atomic detail) package initially developed by D. Bashford [(2004) Front Biosci., 9, 1082–1099]. This computer method uses a macroscopic electrostatic model for the calculation of protein electrostatic properties, such as pKa values of titratable groups and electrostatic potentials. The MEAD package generates electrostatic energies via finite difference solution to the Poisson–Boltzmann equation. Users submit a PDB file and PCE returns potentials and pKa values as well as color (static or animated) figures displaying electrostatic potentials mapped on the molecular surface. This service is intended to facilitate electrostatics analyses of proteins and thereby broaden the accessibility to continuum electrostatics to the biological community. PCE can be accessed at . PMID:15980492

  11. PCE: web tools to compute protein continuum electrostatics.

    PubMed

    Miteva, Maria A; Tufféry, Pierre; Villoutreix, Bruno O

    2005-07-01

    PCE (protein continuum electrostatics) is an online service for protein electrostatic computations presently based on the MEAD (macroscopic electrostatics with atomic detail) package initially developed by D. Bashford [(2004) Front Biosci., 9, 1082-1099]. This computer method uses a macroscopic electrostatic model for the calculation of protein electrostatic properties, such as pK(a) values of titratable groups and electrostatic potentials. The MEAD package generates electrostatic energies via finite difference solution to the Poisson-Boltzmann equation. Users submit a PDB file and PCE returns potentials and pK(a) values as well as color (static or animated) figures displaying electrostatic potentials mapped on the molecular surface. This service is intended to facilitate electrostatics analyses of proteins and thereby broaden the accessibility to continuum electrostatics to the biological community. PCE can be accessed at http://bioserv.rpbs.jussieu.fr/PCE.

  12. Electrostatic force microscopy studies of nanoscale systems

    NASA Astrophysics Data System (ADS)

    Howell, Stephen Wayne

    Electrostatic force microscopy has been used to study the electrostatic force on a nanometer length scale. The experimental techniques, implemented to measure electrostatic force, were based on established methods reported in the literature. These measurements were acquired using an electrostatic force microscope (EFM). The EFM consisted of a commercially available atomic force microscope (AFM) that was modified to measure the electrostatic interaction between an AFM tip and a sample substrate. In addition to modifying the commercial AFM, a homebuilt AFM/EFM was constructed at Purdue capable of making electrostatic measurements in an ultra high vacuum environment. After performing several experiments designed to test both the operation and the sensitivity of the EFM, extensive studies of several nanoscale systems were conducted. In particular, the EFM was used to measure the electrostatic potentials of a single nanometer-sized gold cluster and self-assembled arrays of encapsulated gold clusters. The surface potential of the array was found to be at a higher positive potential than the underlying gold substrate, indicating that the encapsulated clusters have a lower work function than bulk gold. In addition, the EFM was used to measure surface potential as a function of time for various LTG:GaAs substrates after the removal of the oxide layer. The behavior of the surface potential with respect to time was found to be dependent on the agent used for the oxide removal. Finally, the EFM was used to measure the surface potential of self-assembled monolayers chemisorb onto Au(111). The monolayers' surface potentials were found to depend on the molecular structure of the molecules forming the monolayer.

  13. Electrostatic energy barriers from dielectric membranes upon approach of translocating DNA molecules.

    PubMed

    Buyukdagli, Sahin; Ala-Nissila, T

    2016-02-28

    We probe the electrostatic cost associated with the approach phase of DNA translocation events. Within an analytical theory at the Debye-Hückel level, we calculate the electrostatic energy of a rigid DNA molecule interacting with a dielectric membrane. For carbon or silicon based low permittivity neutral membranes, the DNA molecule experiences a repulsive energy barrier between 10 k(B)T and 100 k(B)T. In the case of engineered membranes with high dielectric permittivities, the membrane surface attracts the DNA with an energy of the same magnitude. Both the repulsive and attractive interactions result from image-charge effects and their magnitude survive even for the thinnest graphene-based membranes of size d ≈ 6 Å. For weakly charged membranes, the electrostatic energy is always attractive at large separation distances but switches to repulsive close to the membrane surface. We also characterise the polymer length dependence of the interaction energy. For specific values of the membrane charge density, low permittivity membranes repel short polymers but attract long polymers. Our results can be used to control the strong electrostatic energy of DNA-membrane interactions prior to translocation events by chemical engineering of the relevant system parameters.

  14. The Two Sides of Complement C3d: Evolution of Electrostatics in a Link between Innate and Adaptive Immunity

    PubMed Central

    Kieslich, Chris A.; Morikis, Dimitrios

    2012-01-01

    The interaction between complement fragment C3d and complement receptor 2 (CR2) is a key aspect of complement immune system activation, and is a component in a link between innate and adaptive immunities. The complement immune system is an ancient mechanism for defense, and can be found in species that have been on Earth for the last 600 million years. However, the link between the complement system and adaptive immunity, which is formed through the association of the B-cell co-receptor complex, including the C3d-CR2 interaction, is a much more recent adaptation. Human C3d and CR2 have net charges of −1 and +7 respectively, and are believed to have evolved favoring the role of electrostatics in their functions. To investigate the role of electrostatics in the function and evolution of human C3d and CR2, we have applied electrostatic similarity methods to identify regions of evolutionarily conserved electrostatic potential based on 24 homologues of complement C3d and 4 homologues of CR2. We also examine the effects of structural perturbation, as introduced through molecular dynamics and mutations, on spatial distributions of electrostatic potential to identify perturbation resistant regions, generated by so-called electrostatic “hot-spots”. Distributions of electrostatic similarity based on families of perturbed structures illustrate the presence of electrostatic “hot-spots” at the two functional sites of C3d, while the surface of CR2 lacks electrostatic “hot-spots” despite its excessively positive nature. We propose that the electrostatic “hot-spots” of C3d have evolved to optimize its dual-functionality (covalently attaching to pathogen surfaces and interaction with CR2), which are both necessary for the formation B-cell co-receptor complexes. Comparison of the perturbation resistance of the electrostatic character of the homologues of C3d suggests that there was an emergence of a new role of electrostatics, and a transition in the function of C3

  15. The two sides of complement C3d: evolution of electrostatics in a link between innate and adaptive immunity.

    PubMed

    Kieslich, Chris A; Morikis, Dimitrios

    2012-01-01

    The interaction between complement fragment C3d and complement receptor 2 (CR2) is a key aspect of complement immune system activation, and is a component in a link between innate and adaptive immunities. The complement immune system is an ancient mechanism for defense, and can be found in species that have been on Earth for the last 600 million years. However, the link between the complement system and adaptive immunity, which is formed through the association of the B-cell co-receptor complex, including the C3d-CR2 interaction, is a much more recent adaptation. Human C3d and CR2 have net charges of -1 and +7 respectively, and are believed to have evolved favoring the role of electrostatics in their functions. To investigate the role of electrostatics in the function and evolution of human C3d and CR2, we have applied electrostatic similarity methods to identify regions of evolutionarily conserved electrostatic potential based on 24 homologues of complement C3d and 4 homologues of CR2. We also examine the effects of structural perturbation, as introduced through molecular dynamics and mutations, on spatial distributions of electrostatic potential to identify perturbation resistant regions, generated by so-called electrostatic "hot-spots". Distributions of electrostatic similarity based on families of perturbed structures illustrate the presence of electrostatic "hot-spots" at the two functional sites of C3d, while the surface of CR2 lacks electrostatic "hot-spots" despite its excessively positive nature. We propose that the electrostatic "hot-spots" of C3d have evolved to optimize its dual-functionality (covalently attaching to pathogen surfaces and interaction with CR2), which are both necessary for the formation B-cell co-receptor complexes. Comparison of the perturbation resistance of the electrostatic character of the homologues of C3d suggests that there was an emergence of a new role of electrostatics, and a transition in the function of C3d, after the

  16. Monolithic Microwave Switching Matrix

    NASA Technical Reports Server (NTRS)

    Fujikawa, Gene; Ch'en, Daniel R.; Petersen, Wendell C.

    1989-01-01

    Gallium arsenide integrated-circuit chip switches any of three microwave input signals to any of three output ports. Measuring 4.9 mm on side, chip contains nine field-effect transistor (FET) crosspoint switches. Housed in custom-designed package with standard connectors for easy integration into system. FET's on chip operated as passive switches and consume no static power and insignificant amounts of switching power. Chip module cascades with similar modules into large arrays handling as many as 100 inputs and 100 outputs. Applications include switching and routing vast amounts of data between computers at extremely high speed. On communications satellite, chip switches microwave signals to and from Earth stations and other satellites.

  17. Effective switching frequency multiplier inverter

    DOEpatents

    Su, Gui-Jia; Peng, Fang Z.

    2007-08-07

    A switching frequency multiplier inverter for low inductance machines that uses parallel connection of switches and each switch is independently controlled according to a pulse width modulation scheme. The effective switching frequency is multiplied by the number of switches connected in parallel while each individual switch operates within its limit of switching frequency. This technique can also be used for other power converters such as DC/DC, AC/DC converters.

  18. Double-Bounce Switching

    DTIC Science & Technology

    1983-06-01

    module. Adjustments provided to investigate double- bounce switching are noted. limitation is at a higher level and occurs in the conventionally...To be presented at the 4th IEEE PUlsed Power Conference, June 6-8, 1983, Albuquerque, NM. DOUBLE- BOUNCE SWITCHING* George B. Frazier and Steven R...Ashby Physics International Company 2700 Merced Street San Leandro, California 94577 Abstract Double- bounce switching is a technique for

  19. Avalanche Photoconductive Switching

    DTIC Science & Technology

    1989-06-01

    held off across the switch. In our case this corresponds to 70 kV/cm and is limited by surface flashover . The pulse length is determined by the...off across the gap of the switch, which in turn appears to be limited by surface flashover . There appears to be a threshold electric field of 20-60...and understand this mode of operation. Introduction Laser activated photoconductive switching in semiconductors is a promising technology for high

  20. Thermally actuated thermionic switch

    DOEpatents

    Barrus, Donald M.; Shires, Charles D.

    1988-01-01

    A thermally actuated thermionic switch which responds to an increase of temperature by changing from a high impedance to a low impedance at a predictable temperature set point. The switch has a bistable operation mode switching only on temperature increases. The thermionic material may be a metal which is liquid at the desired operation temperature and held in matrix in a graphite block reservoir, and which changes state (ionizes, for example) so as to be electrically conductive at a desired temperature.

  1. Thermally actuated thermionic switch

    DOEpatents

    Barrus, D.M.; Shires, C.D.

    1982-09-30

    A thermally actuated thermionic switch which responds to an increase of temperature by changing from a high impedance to a low impedance at a predictable temperature set point. The switch has a bistable operation mode switching only on temperature increases. The thermionic material may be a metal which is liquid at the desired operation temperature and held in matrix in a graphite block reservoir, and which changes state (ionizes, for example) so as to be electrically conductive at a desired temperature.

  2. Solid state switch

    DOEpatents

    Merritt, Bernard T.; Dreifuerst, Gary R.

    1994-01-01

    A solid state switch, with reverse conducting thyristors, is designed to operate at 20 kV hold-off voltage, 1500 A peak, 1.0 .mu.s pulsewidth, and 4500 pps, to replace thyratrons. The solid state switch is more reliable, more economical, and more easily repaired. The switch includes a stack of circuit card assemblies, a magnetic assist and a trigger chassis. Each circuit card assembly contains a reverse conducting thyristor, a resistor capacitor network, and triggering circuitry.

  3. AC magnetohydrodynamic microfluidic switch

    SciTech Connect

    Lemoff, A V; Lee, A P

    2000-03-02

    A microfluidic switch has been demonstrated using an AC Magnetohydrodynamic (MHD) pumping mechanism in which the Lorentz force is used to pump an electrolytic solution. By integrating two AC MHD pumps into different arms of a Y-shaped fluidic circuit, flow can be switched between the two arms. This type of switch can be used to produce complex fluidic routing, which may have multiple applications in {micro}TAS.

  4. High response piezoelectric and piezoresistive materials for fast, low voltage switching: simulation and theory of transduction physics at the nanometer-scale.

    PubMed

    Newns, Dennis M; Elmegreen, Bruce G; Liu, Xiao-Hu; Martyna, Glenn J

    2012-07-17

    Field effect transistors are reaching the limits imposed by the scaling of materials and the electrostatic gating physics underlying the device. In this Communication, a new type of switch based on different physics, which combines known piezoelectric and piezoresistive materials, is described and is shown by theory and simulation to achieve gigahertz digital switching at low voltage (0.1 V).

  5. Dual-beam mastering for advanced formats

    NASA Astrophysics Data System (ADS)

    Verhaart, Gerarous J.; Stockx, Harry; Wijn, Josephus M.; Yoon, Du-Seop

    1996-09-01

    A dual beam recorder for high density format has been developed. The recorder features remote control of size and mutual distance of both recording spots, a special beam pointing control system, and a high accuracy, laser interferometer controlled, radial drive. The recorder can switch between very dissimilar formats without intermediate alignment. The performance of the recorder has been shown for DVD, MO, and even higher density formats. Track pitches down to 0.7 micrometers have been realized.

  6. Alarm toe switch

    DOEpatents

    Ganyard, Floyd P.

    1982-01-01

    An alarm toe switch inserted within a shoe for energizing an alarm circuit n a covert manner includes an insole mounting pad into which a miniature reed switch is fixedly molded. An elongated slot perpendicular to the reed switch is formed in the bottom surface of the mounting pad. A permanent cylindrical magnet positioned in the forward portion of the slot with a diameter greater than the pad thickness causes a bump above the pad. A foam rubber block is also positioned in the slot rearwardly of the magnet and holds the magnet in normal inoperative relation. A non-magnetic support plate covers the slot and holds the magnet and foam rubber in the slot. The plate minimizes bending and frictional forces to improve movement of the magnet for reliable switch activation. The bump occupies the knuckle space beneath the big toe. When the big toe is scrunched rearwardly the magnet is moved within the slot relative to the reed switch, thus magnetically activating the switch. When toe pressure is released the foam rubber block forces the magnet back into normal inoperative position to deactivate the reed switch. The reed switch is hermetically sealed with the magnet acting through the wall so the switch assembly S is capable of reliable operation even in wet and corrosive environments.

  7. Reusable fast opening switch

    DOEpatents

    Van Devender, J.P.; Emin, D.

    1983-12-21

    A reusable fast opening switch for transferring energy, in the form of a high power pulse, from an electromagnetic storage device such as an inductor into a load. The switch is efficient, compact, fast and reusable. The switch comprises a ferromagnetic semiconductor which undergoes a fast transition between conductive and metallic states at a critical temperature and which undergoes the transition without a phase change in its crystal structure. A semiconductor such as europium rich europhous oxide, which undergoes a conductor to insulator transition when it is joule heated from its conductor state, can be used to form the switch.

  8. Reusable fast opening switch

    DOEpatents

    Van Devender, John P.; Emin, David

    1986-01-01

    A reusable fast opening switch for transferring energy, in the form of a high power pulse, from an electromagnetic storage device such as an inductor into a load. The switch is efficient, compact, fast and reusable. The switch comprises a ferromagnetic semiconductor which undergoes a fast transition between conductive and insulating states at a critical temperature and which undergoes the transition without a phase change in its crystal structure. A semiconductor such as europium rich europhous oxide, which undergoes a conductor to insulator transition when it is joule heated from its conductor state, can be used to form the switch.

  9. Platform switching and bone platform switching.

    PubMed

    Carinci, Francesco; Brunelli, Giorgio; Danza, Matteo

    2009-01-01

    Bone platform switching involves an inward bone ring in the coronal part of the implant that is in continuity with the alveolar bone crest. Bone platform switching is obtained by using a dental fixture with a reverse conical neck. A retrospective study was performed to evaluate the effectiveness of conventional vs reverse conical neck implants. In the period between May 2004 and November 2007, 86 patients (55 females and 31 males; median age, 53 years) were operated and 234 implants were inserted: 40 and 194 were conventional vs reverse conical neck implants, respectively. Kaplan-Meier algorithm and Cox regression were used to detect those variables associated with the clinical outcome. No differences in survival and success rates were detected between conventional vs reverse conical neck implants alone or in combination with any of the studied variables. Although bone platform switching leads to several advantages, no statistical difference in alveolar crest resorption is detected in comparison with reverse conical neck implants. We suppose that the proximity of the implant abutment junction to the alveolar crestal bone gives no protection against the microflora contained in the micrograph. Additional studies on larger series and a combination of platform switching and bone platform switching could lead to improved clinical outcomes.

  10. High speed packet switching

    NASA Technical Reports Server (NTRS)

    1991-01-01

    This document constitutes the final report prepared by Proteon, Inc. of Westborough, Massachusetts under contract NAS 5-30629 entitled High-Speed Packet Switching (SBIR 87-1, Phase 2) prepared for NASA-Greenbelt, Maryland. The primary goal of this research project is to use the results of the SBIR Phase 1 effort to develop a sound, expandable hardware and software router architecture capable of forwarding 25,000 packets per second through the router and passing 300 megabits per second on the router's internal busses. The work being delivered under this contract received its funding from three different sources: the SNIPE/RIG contract (Contract Number F30602-89-C-0014, CDRL Sequence Number A002), the SBIR contract, and Proteon. The SNIPE/RIG and SBIR contracts had many overlapping requirements, which allowed the research done under SNIPE/RIG to be applied to SBIR. Proteon funded all of the work to develop new router interfaces other than FDDI, in addition to funding the productization of the router itself. The router being delivered under SBIR will be a fully product-quality machine. The work done during this contract produced many significant findings and results, summarized here and explained in detail in later sections of this report. The SNIPE/RIG contract was completed. That contract had many overlapping requirements with the SBIR contract, and resulted in the successful demonstration and delivery of a high speed router. The development that took place during the SNIPE/RIG contract produced findings that included the choice of processor and an understanding of the issues surrounding inter processor communications in a multiprocessor environment. Many significant speed enhancements to the router software were made during that time. Under the SBIR contract (and with help from Proteon-funded work), it was found that a single processor router achieved a throughput significantly higher than originally anticipated. For this reason, a single processor router was

  11. Electrostatics of DNA complexes with cationic lipids

    NASA Astrophysics Data System (ADS)

    Cherstvy, Andrey

    2007-03-01

    We present the exact solutions of the linear Poisson-Boltzmann theory for several problems relevant to electrostatics of DNA complexes with cationic lipids. We calculate the electrostatic potential and energy for lamellar and inverted hexagonal phases, concentrating on the effects of water-membrane dielectric boundaries. Our results for the complex energy agree qualitatively well with the known numerical solutions of the nonlinear Poisson-Boltzmann equation. Using the solution for the lamellar phase, we calculate its compressibility modulus and compare our findings with experimental data available suggesting a new scaling dependence on DNA-DNA separations in the complex. Also, we treat analytically charge-charge electrostatic interactions across, along, and in between two low-dielectric membranes. We obtain an estimate for the strength of electrostatic interactions of 1D DNA smectic layers across a lipid membrane. We discuss also some aspects of 2D DNA condensation and DNA-DNA attraction in DNA-lipid lamellar phase in the presence of di- and tri-valent cations and analyze the equilibrium intermolecular separations using the recently developed theory of electrostatic interactions of DNA helical charge motifs.

  12. Electrostatic effects on hyaluronic acid configuration

    NASA Astrophysics Data System (ADS)

    Berezney, John; Saleh, Omar

    2015-03-01

    In systems of polyelectrolytes, such as solutions of charged biopolymers, the electrostatic repulsion between charged monomers plays a dominant role in determining the molecular conformation. Altering the ionic strength of the solvent thus affects the structure of such a polymer. Capturing this electrostatically-driven structural dependence is important for understanding many biological systems. Here, we use single molecule manipulation experiments to collect force-extension behavior on hyaluronic acid (HA), a polyanion which is a major component of the extracellular matrix in all vertebrates. By measuring HA elasticity in a variety of salt conditions, we are able to directly assess the contribution of electrostatics to the chain's self-avoidance and local stiffness. Similar to recent results from our group on single-stranded nucleic acids, our data indicate that HA behaves as a swollen chain of electrostatic blobs, with blob size proportional to the solution Debye length. Our data indicate that the chain structure within the blob is not worm-like, likely due to long-range electrostatic interactions. We discuss potential models of this effect.

  13. Model of a SNS Electrostatic LEBT with a Near-Ground Beam Chopper

    NASA Astrophysics Data System (ADS)

    Han, B. X.; Stockli, M. P.

    2009-03-01

    The low energy beam transport (LEBT) of the Spallation Neutron Source (SNS) accelerator consists of two electrostatic lenses, of which the second is split into four electrically-isolated segments. Adding fast pulsed voltages to the lens high voltage creates the transverse fields required for beam chopping. Electric sparks, however, create transients that enter the fast high-voltage switches, which are occasionally damaged and cause machine downtime. This work models a new configuration of the electrostatic LEBT, which chops the beam with four shielded, near-ground electrodes between the two lenses. The model shows that the new configuration can match the RFQ injection requirements and sufficiently deflect the beam in the phase-space using the same chopping voltages as in the baseline LEBT.

  14. Decoupling Control of Micromachined Spinning-Rotor Gyroscope with Electrostatic Suspension

    PubMed Central

    Sun, Boqian; Wang, Shunyue; Li, Haixia; He, Xiaoxia

    2016-01-01

    A micromachined gyroscope in which a high-speed spinning rotor is suspended electrostatically in a vacuum cavity usually functions as a dual-axis angular rate sensor. An inherent coupling error between the two sensing axes exists owing to the angular motion of the spinning rotor being controlled by a torque-rebalance loop. In this paper, a decoupling compensation method is proposed and investigated experimentally based on an electrostatically suspended micromachined gyroscope. In order to eliminate the negative spring effect inherent in the gyroscope dynamics, a stiffness compensation scheme was utilized in design of the decoupled rebalance loop to ensure loop stability and increase suspension stiffness. The experimental results show an overall stiffness increase of 30.3% after compensation. A decoupling method comprised of inner- and outer-loop decoupling compensators is proposed to minimize the cross-axis coupling error. The inner-loop decoupling compensator aims to attenuate the angular position coupling. The experimental frequency response shows a position coupling attenuation by 14.36 dB at 1 Hz. Moreover, the cross-axis coupling between the two angular rate output signals can be attenuated theoretically from −56.2 dB down to −102 dB by further appending the outer-loop decoupling compensator. The proposed dual-loop decoupling compensation algorithm could be applied to other dual-axis spinning-rotor gyroscopes with various suspension solutions. PMID:27775624

  15. Decoupling Control of Micromachined Spinning-Rotor Gyroscope with Electrostatic Suspension.

    PubMed

    Sun, Boqian; Wang, Shunyue; Li, Haixia; He, Xiaoxia

    2016-10-20

    A micromachined gyroscope in which a high-speed spinning rotor is suspended electrostatically in a vacuum cavity usually functions as a dual-axis angular rate sensor. An inherent coupling error between the two sensing axes exists owing to the angular motion of the spinning rotor being controlled by a torque-rebalance loop. In this paper, a decoupling compensation method is proposed and investigated experimentally based on an electrostatically suspended micromachined gyroscope. In order to eliminate the negative spring effect inherent in the gyroscope dynamics, a stiffness compensation scheme was utilized in design of the decoupled rebalance loop to ensure loop stability and increase suspension stiffness. The experimental results show an overall stiffness increase of 30.3% after compensation. A decoupling method comprised of inner- and outer-loop decoupling compensators is proposed to minimize the cross-axis coupling error. The inner-loop decoupling compensator aims to attenuate the angular position coupling. The experimental frequency response shows a position coupling attenuation by 14.36 dB at 1 Hz. Moreover, the cross-axis coupling between the two angular rate output signals can be attenuated theoretically from -56.2 dB down to -102 dB by further appending the outer-loop decoupling compensator. The proposed dual-loop decoupling compensation algorithm could be applied to other dual-axis spinning-rotor gyroscopes with various suspension solutions.

  16. A study of local electrostatic filtration and main pre-filtration on airborne and surface dust levels in air-conditioned office premises.

    PubMed

    Croxford, B; Tham, K W; Young, A; Oreszczyn, T; Wyon, D

    2000-09-01

    The impact of electrostatic precipitation as a useful form of particulate filtration in the breathing zone is investigated in an intervention study in an air-conditioned commercial office in central London. Surface dust deposition and airborne dust levels are measured in the open plan zones of two floors--a control floor and a floor where the intervention is effected. The intervention consists of a sequence of weekly scenarios where the main pre-filters of the air-handling unit are switched between new and old filters, and where the electrostatic filters, located as uniformly as practicable on the open plan areas, are switched on or off. This 2 x 2 set of interventions is repeated over 4 cycles. It was found that the breathing zone filtration (BZF) by electrostatic precipitators reduces airborne dust significantly and appears to be more efficient in reducing smaller sized particles. No significant effect of BZF filters in reducing surface dust deposition was detected.

  17. Flexible Electrostatic Technologies for Capture and Handling, Phase 1

    NASA Technical Reports Server (NTRS)

    Bryan, Thomas

    2015-01-01

    Fundamental to many of NASA's in-space transportation missions is the capture and handling of various objects and vehicles in various orbits for servicing, debris disposal, sample retrieval, and assembly without the benefit of sufficient grapple fixtures and docking ports. To perform similar material handling tasks on Earth, pincher grippers, suction grippers, or magnetic chucks are used, but are unable to reliably grip aluminum and composite spacecraft, insulation, radiators, solar arrays, or extra-terrestrial objects in the vacuum of outer space without dedicated handles in the right places. The electronic Flexible Electrostatic Technologies for space Capture and Handling (FETCH) will enable reliable and compliant gripping (soft dock) of practically any object in various orbits or surfaces without dedicated mechanical features, very low impact capture, and built-in proximity sensing without any conventional actuators. Originally developed to handle semiconductor and glass wafers during vacuum chamber processing without contamination, the normal rigid wafer handling chucks are replaced with thin metal foil segments laminated in flexible insulation driven by commercial off-the-shelf solid state, high-voltage power supplies. Preliminary testing in NASA Marshall Space Flight Center's (MSFC's) Flat Floor Robotics Lab demonstrated compliant alignment and gripping with a full-sized, 150-lb microsat mockup and translation before a clean release with a flip of a switch. The flexible electrostatic gripper pads can be adapted to various space applications with different sizes, shapes, and foil electrode layouts even with openings through the gripper pads for addition of guidance sensors or injection of permanent adhesives. With gripping forces estimated between 0.5 and 2.5 lb/in2 or 70-300 lb/ft2 of surface contact, the FETCH can turn on and off rapidly and repeatedly to enable sample handling, soft docking, in-space assembly, precision relocation, and surface translation

  18. Characterization and modeling of electrostatically actuated polysilicon micromechanical devices

    NASA Astrophysics Data System (ADS)

    Chan, Edward Keat Leem

    Sensors, actuators, transducers, microsystems and MEMS (MicroElertroMechanical Systems) are some of the terms describing technologies that interface information processing systems with the physical world. Electrostatically actuated micromechanical devices are important building blocks in many of these technologies. Arrays of these devices are used in video projection displays, fluid pumping systems, optical communications systems, tunable lasers and microwave circuits. Well-calibrated simulation tools are essential for propelling ideas from the drawing board into production. This work characterizes a fabrication process---the widely-used polysilicon MUMPs process---to facilitate the design of electrostatically actuated micromechanical devices. The operating principles of a representative device---a capacitive microwave switch---are characterized using a wide range of electrical and optical measurements of test structures along with detailed electromechanical simulations. Consistency in the extraction of material properties from measurements of both pull-in voltage and buckling amplitude is demonstrated. Gold is identified as an area-dependent source of nonuniformity in polysilicon thicknesses and stress. Effects of stress gradients, substrate curvature, and film coverage are examined quantitatively. Using well-characterized beams as in-situ surface probes, capacitance-voltage and surface profile measurements reveal that compressible surface residue modifies the effective electrical gap when the movable electrode contacts an underlying silicon nitride layer. A compressible contact surface model used in simulations improves the fit to measurements. In addition, the electric field across the nitride causes charge to build up in the nitride, increasing the measured capacitance over time. The rate of charging corresponds to charge injection through direct tunneling. A novel actuator that can travel stably beyond one-third of the initial gap (a trademark limitation of

  19. Asymmetrical Switch Costs in Children

    ERIC Educational Resources Information Center

    Ellefson, Michelle R.; Shapiron, Laura R.; Chater, Nick

    2006-01-01

    Switching between tasks produces decreases in performance as compared to repeating the same task. Asymmetrical switch costs occur when switching between two tasks of unequal difficulty. This asymmetry occurs because the cost is greater when switching to the less difficult task than when switching to the more difficult task. Various theories about…

  20. Biomolecular electrostatics and solvation: a computational perspective

    SciTech Connect

    Ren, Pengyu; Chun, Jaehun; Thomas, Dennis G.; Schnieders, Michael; Marucho, Marcelo; Zhang, Jiajing; Baker, Nathan A.

    2012-11-01

    An understanding of molecular interactions is essential for insight into biological systems at the molecular scale. Among the various components of molecular interactions, electrostatics are of special importance because of their long-range nature and their influence on polar or charged molecules, including water, aqueous ions, proteins, nucleic acids, carbohydrates, and membrane lipids. In particular, robust models of electrostatic interactions are essential for understanding the solvation properties of biomolecules and the effects of solvation upon biomolecular folding, binding, enzyme catalysis and dynamics. Electrostatics, therefore, are of central importance to understanding biomolecular structure and modeling interactions within and among biological molecules. This review discusses the solvation of biomolecules with a computational biophysics view towards describing the phenomenon. While our main focus lies on the computational aspect of the models, we summarize the common characteristics of biomolecular solvation (e.g., solvent structure, polarization, ion binding, and nonpolar behavior) in order to provide reasonable backgrounds to understand the solvation models.

  1. Arbitrary order permanent Cartesian multipolar electrostatic interactions

    NASA Astrophysics Data System (ADS)

    Boateng, H. A.; Todorov, I. T.

    2015-01-01

    Recently, there has been a concerted effort to implement advanced classical potential energy surfaces by adding higher order multipoles to fixed point charge electrostatics in a bid to increase the accuracy of simulations of condensed phase systems. One major hurdle is the unwieldy nature of the expressions which in part has limited developers mostly to including only dipoles and quadrupoles. In this paper, we present a generalization of the Cartesian formulation of electrostatic multipolar interactions that enables the specification of an arbitrary order of multipoles. Specifically, we derive formulas for arbitrary order implementation of the particle mesh Ewald method and give a closed form formula for the stress tensor in the reciprocal space. In addition, we provide recurrence relations for common electrostatic potentials employed in molecular simulations, which allows for the generalization to arbitrary order and guarantees a computational cost that scales as O(p3) for Cartesian multipole interactions of order p.

  2. Electrostatic coating technologies for food processing.

    PubMed

    Barringer, Sheryl A; Sumonsiri, Nutsuda

    2015-01-01

    The application of electrostatics in both powder and liquid coating can improve the quality of food, such as its appearance, aroma, taste, and shelf life. Coatings can be found most commonly in the snack food industry, as well as in confectionery, bakery, meat and cheese processing. In electrostatic powder coating, the most important factors influencing coating quality are powder particle size, density, flowability, charge, and resistivity, as well as the surface properties and characteristics of the target. The most important factors during electrostatic liquid coating, also known as electrohydrodynamic coating, include applied voltage and electrical resistivity and viscosity of the liquid. A good understanding of these factors is needed for the design of optimal coating systems for food processing.

  3. Using electrostatic modelling to study cone discharges

    NASA Astrophysics Data System (ADS)

    Azizi, W.

    2015-10-01

    Cone discharges, also known as bulking brush discharges, can arise when charged insulating powder accumulates in a heap in silos. They can be an effective ignition source to relatively ignition sensitive powders and therefore represent a possible electrostatic hazard. The current international guidance on control of electrostatic hazards (IEC/TS 60079-32-1 [1]), endorses the usage of electrostatic modelling to estimate the electric field above the powder heap. “Such model calculations should be based on the charge to mass ratio, bulk density and filling rate of the powder, the relative permittivity and resistivity of the bulked powder as well as the silo geometry.” This study shows a practical demonstration of this modelling technique. It also examines whether the shape of the heap affects the strength of the electric field above the powder heap, and thus the likelihood of cone discharges from occurring.

  4. Local Electrostatic Moments and Periodic Boundary Conditition

    SciTech Connect

    Schultz, P.A.

    1998-12-04

    Electronic structure calculations frequently invoke periodic boundary conditions to solve for electrostatic potentials. For systems that are electronically charged, or contain dipole (or higher) moments, this artifice introduces spurious potentials due to the interactions between the system and multipole moments of its periodic images in aperiodic directions. I describe a method to properly handle the multipole moments of the electron density in electronic structure calculations using periodic boundary conditions. The density for which an electrostatic potential is to be evaluated is divided into two pieces. A local density is constructed that matches the desired moments of the full density, and its potential computed treating this density as isolated. With the density of this local moment countercharge removed from the full density, the remainder density lacks the troublesome moments and its electrostatic potential can be evaluated accurately using periodic boundary conditions.

  5. Ferroelectric Switching by the Grounded Scanning Probe Microscopy Tip

    SciTech Connect

    Ievlev, Anton V.; Morozovska, A. N.; Shur, Vladimir Ya.; Kalinin, Sergei V.

    2015-06-19

    The process of polarization reversal by the tip of scanning probe microscope was intensively studied for last two decades. Number of the abnormal switching phenomena was reported by the scientific groups worldwide. In particularly it was experimentally and theoretically shown that slow dynamics of the surface screening controls kinetics of the ferroelectric switching, backswitching and relaxation and presence of the charges carriers on the sample surface and in the sample bulk significantly change polarization reversal dynamics. Here we experimentally demonstrated practical possibility of the history dependent polarization reversal by the grounded SPM tip. This phenomenon was attributed to induction of the slowly dissipating charges into the surface of the grounded tip that enables polarization reversal under the action of the produced electric field. Analytical and numerical electrostatic calculations allow additional insight into nontrivial abnormal switching phenomena reported earlier.

  6. Ferroelectric Switching by the Grounded Scanning Probe Microscopy Tip

    DOE PAGES

    Ievlev, Anton V.; Morozovska, A. N.; Shur, Vladimir Ya.; ...

    2015-06-19

    The process of polarization reversal by the tip of scanning probe microscope was intensively studied for last two decades. Number of the abnormal switching phenomena was reported by the scientific groups worldwide. In particularly it was experimentally and theoretically shown that slow dynamics of the surface screening controls kinetics of the ferroelectric switching, backswitching and relaxation and presence of the charges carriers on the sample surface and in the sample bulk significantly change polarization reversal dynamics. Here we experimentally demonstrated practical possibility of the history dependent polarization reversal by the grounded SPM tip. This phenomenon was attributed to induction ofmore » the slowly dissipating charges into the surface of the grounded tip that enables polarization reversal under the action of the produced electric field. Analytical and numerical electrostatic calculations allow additional insight into nontrivial abnormal switching phenomena reported earlier.« less

  7. Graphene-based plasmonic switches at near infrared frequencies

    NASA Astrophysics Data System (ADS)

    Gómez-Díaz, J. S.; Perruisseau-Carrier, J.

    2013-07-01

    The concept, analysis, and design of series switches for graphene-strip plasmonic waveguides at near infrared frequencies are presented. Switching is achieved by using graphene's field effect to selectively enable or forbid propagation on a section of the graphene strip waveguide, thereby allowing good transmission or high isolation, respectively. The electromagnetic modeling of the proposed structure is performed using full-wave simulations and a transmission line model combined with a matrix-transfer approach, which takes into account the characteristics of the plasmons supported by the different graphene-strip waveguide sections of the device. The performance of the switch is evaluated versus different parameters of the structure, including surrounding dielectric media, electrostatic gating and waveguide dimensions.

  8. Graphene-based plasmonic switches at near infrared frequencies.

    PubMed

    Gómez-Díaz, J S; Perruisseau-Carrier, J

    2013-07-01

    The concept, analysis, and design of series switches for graphene-strip plasmonic waveguides at near infrared frequencies are presented. Switching is achieved by using graphene's field effect to selectively enable or forbid propagation on a section of the graphene strip waveguide, thereby allowing good transmission or high isolation, respectively. The electromagnetic modeling of the proposed structure is performed using full-wave simulations and a transmission line model combined with a matrix-transfer approach, which takes into account the characteristics of the plasmons supported by the different graphene-strip waveguide sections of the device. The performance of the switch is evaluated versus different parameters of the structure, including surrounding dielectric media, electrostatic gating and waveguide dimensions.

  9. Dual-Energy CT: New Horizon in Medical Imaging.

    PubMed

    Goo, Hyun Woo; Goo, Jin Mo

    2017-01-01

    Dual-energy CT has remained underutilized over the past decade probably due to a cumbersome workflow issue and current technical limitations. Clinical radiologists should be made aware of the potential clinical benefits of dual-energy CT over single-energy CT. To accomplish this aim, the basic principle, current acquisition methods with advantages and disadvantages, and various material-specific imaging methods as clinical applications of dual-energy CT should be addressed in detail. Current dual-energy CT acquisition methods include dual tubes with or without beam filtration, rapid voltage switching, dual-layer detector, split filter technique, and sequential scanning. Dual-energy material-specific imaging methods include virtual monoenergetic or monochromatic imaging, effective atomic number map, virtual non-contrast or unenhanced imaging, virtual non-calcium imaging, iodine map, inhaled xenon map, uric acid imaging, automatic bone removal, and lung vessels analysis. In this review, we focus on dual-energy CT imaging including related issues of radiation exposure to patients, scanning and post-processing options, and potential clinical benefits mainly to improve the understanding of clinical radiologists and thus, expand the clinical use of dual-energy CT; in addition, we briefly describe the current technical limitations of dual-energy CT and the current developments of photon-counting detector.

  10. Dual-Energy CT: New Horizon in Medical Imaging

    PubMed Central

    Goo, Jin Mo

    2017-01-01

    Dual-energy CT has remained underutilized over the past decade probably due to a cumbersome workflow issue and current technical limitations. Clinical radiologists should be made aware of the potential clinical benefits of dual-energy CT over single-energy CT. To accomplish this aim, the basic principle, current acquisition methods with advantages and disadvantages, and various material-specific imaging methods as clinical applications of dual-energy CT should be addressed in detail. Current dual-energy CT acquisition methods include dual tubes with or without beam filtration, rapid voltage switching, dual-layer detector, split filter technique, and sequential scanning. Dual-energy material-specific imaging methods include virtual monoenergetic or monochromatic imaging, effective atomic number map, virtual non-contrast or unenhanced imaging, virtual non-calcium imaging, iodine map, inhaled xenon map, uric acid imaging, automatic bone removal, and lung vessels analysis. In this review, we focus on dual-energy CT imaging including related issues of radiation exposure to patients, scanning and post-processing options, and potential clinical benefits mainly to improve the understanding of clinical radiologists and thus, expand the clinical use of dual-energy CT; in addition, we briefly describe the current technical limitations of dual-energy CT and the current developments of photon-counting detector. PMID:28670151

  11. Dual LED/incandescent security fixture

    DOEpatents

    Gauna, Kevin Wayne

    2005-06-21

    A dual LED and incandescent security lighting system uses a hybrid approach to LED illumination. It combines an ambient LED illuminator with a standard incandescent lamp on a motion control sensor. The LED illuminator will activate with the onset of darkness (daylight control) and typically remain on during the course of the night ("always on"). The LED illumination, typically amber, is sufficient to provide low to moderate level lighting coverage to the wall and ground area adjacent to and under the fixture. The incandescent lamp is integrated with a motion control circuit and sensor. When movement in the field of view is detected (after darkness), the incandescent lamp is switched on, providing an increased level of illumination to the area. Instead of an "always on" LED illuminator, the LEDs may also be switched off when the incandescent lamp is switched on.

  12. Quantum cryptography without switching.

    PubMed

    Weedbrook, Christian; Lance, Andrew M; Bowen, Warwick P; Symul, Thomas; Ralph, Timothy C; Lam, Ping Koy

    2004-10-22

    We propose a new coherent state quantum key distribution protocol that eliminates the need to randomly switch between measurement bases. This protocol provides significantly higher secret key rates with increased bandwidths than previous schemes that only make single quadrature measurements. It also offers the further advantage of simplicity compared to all previous protocols which, to date, have relied on switching.

  13. Power-Switching Circuit

    NASA Technical Reports Server (NTRS)

    Praver, Gerald A.; Theisinger, Peter C.; Genofsky, John

    1987-01-01

    Functions of circuit breakers, meters, and switches combined. Circuit that includes power field-effect transistors (PFET's) provides on/off switching, soft starting, current monitoring, current tripping, and protection against overcurrent for 30-Vdc power supply at normal load currents up to 2 A. Has no moving parts.

  14. Reflective HTS switch

    DOEpatents

    Martens, J.S.; Hietala, V.M.; Hohenwarter, G.K.G.

    1994-09-27

    A HTS (High Temperature Superconductor) switch includes a HTS conductor for providing a superconducting path for an electrical signal and an serpentine wire actuator for controllably heating a portion of the conductor sufficiently to cause that portion to have normal, and not superconducting, resistivity. Mass of the portion is reduced to decrease switching time. 6 figs.

  15. Reflective HTS switch

    SciTech Connect

    Martens, Jon S.; Hietala, Vincent M.; Hohenwarter, Gert K. G.

    1994-01-01

    A HTS switch includes a HTS conductor for providing a superconducting path for an electrical signal and an serpentine wire actuator for controllably heating a portion of the conductor sufficiently to cause that portion to have normal, and not superconducting, resistivity. Mass of the portion is reduced to decrease switching time.

  16. Manually operated coded switch

    DOEpatents

    Barnette, Jon H.

    1978-01-01

    The disclosure relates to a manually operated recodable coded switch in which a code may be inserted, tried and used to actuate a lever controlling an external device. After attempting a code, the switch's code wheels must be returned to their zero positions before another try is made.

  17. Electrostatic Precipitation in Nearly Pure Gaseous Nitrogen

    NASA Technical Reports Server (NTRS)

    Buhler, Charles; Calle, Carlos; Clements, Sid; Cox, Bobby; Ritz, Mindy

    2008-01-01

    Electrostatic precipitation was performed in a nearly pure gaseous nitrogen system as a possible remedy for black dust contaminant from high pressure 6000 psi lines at the NASA Kennedy Space Center. The results of a prototype electrostatic precipitator that was built and tested using nitrogen gas at standard atmospheric pressures is presented. High voltage pulsed waveforms are generated using a rotating spark gap system at 30 Hz. A unique dust delivery system utilizing the Venturi effect was devised that supplies a given amount of dust per unit time for testing purposes.

  18. Fabrication of Electrostatically Actuated Microshutters Arrays

    NASA Technical Reports Server (NTRS)

    Oh, L.; Li, M.; Kelly, D.; Kutyrev, A.; Moseley, S.

    2016-01-01

    A new fabrication process has been developed to actuate microshutter arrays (MSA) electrostatically at NASA Goddard Space Flight Center. The microshutters, made with silicon nitride membranes with a pixel size of 100 x 200 sq microns, rotate on torsion bars. The microshutters are actuated, latched, and addressed electrostatically by applying voltages on the electrodes the front and back sides of the microshutters. The atomic layer deposition (ALD) of aluminum oxide was used to insulate electrodes on the back side of walls; the insulation can withstand over 100 V. The ALD aluminum oxide is dry etched, and then the microshutters are released in vapor HF.

  19. Electrostatic supersolitons in three-species plasmas

    SciTech Connect

    Verheest, Frank; Hellberg, Manfred A.; Kourakis, Ioannis

    2013-01-15

    Superficially, electrostatic potential profiles of supersolitons look like those of traditional solitons. However, their electric field profiles are markedly different, having additional extrema on the wings of the standard bipolar structure. This new concept was recently pointed out in the literature for a plasma model with five species. Here, it is shown that electrostatic supersolitons are not an artefact of exotic, complicated plasma models, but can exist even in three-species plasmas and are likely to occur in space plasmas. Further, a methodology is given to delineate their existence domains in a systematic fashion by determining the specific limiting factors.

  20. Electrostatic Evaluation of the Propellant Handlers Ensemble

    NASA Technical Reports Server (NTRS)

    Hogue, Michael D.; Calle, Carlos I.; Buhler, Charles

    2006-01-01

    The Self-Contained Atmospheric Protective Ensemble (SCAPE) used in propellant handling at NASA's Kennedy Space Center (KSC) has recently completed a series of tests to determine its electrostatic properties of the coverall fabric used in the Propellant Handlers Ensemble (PHE). Understanding these electrostatic properties are fundamental to ensuring safe operations when working with flammable rocket propellants such as hydrazine, methyl hydrazine, and unsymmetrical dimethyl hydrazine. These tests include surface resistivity, charge decay, triboelectric charging, and flame incendivity. In this presentation, we will discuss the results of these tests on the current PHE as well as new fabrics and materials being evaluated for the next generation of PHE.