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Sample records for silicon controlled rectifier

  1. A series-resonant silicon-controlled-rectifier power processor for ion thrusters

    NASA Technical Reports Server (NTRS)

    Shumaker, H. A.; Biess, J. J.; Goldin, D. S.

    1973-01-01

    A program to develop a power processing system for ion thrusters is presented. Basic operation of the silicon controlled rectifier series inverter circuitry is examined. The approach for synthesizing such circuits into a system which limits the electrical stress levels on the power source, semiconductor switching elements, and the ion thruster load is described. Experimental results are presented for a 2.5-kW breadboard system designed to operate a 20-cm ion thruster.

  2. Understanding of self-terminating pulse generation using silicon controlled rectifier and RC load

    NASA Astrophysics Data System (ADS)

    Chang, Chris; Alves, Fabio; Karunasiri, Gamani

    2016-01-01

    Recently a silicon controlled rectifier (SCR)-based circuit that generates self-terminating voltage pulses was employed for the detection of light and ionizing radiation in pulse mode. The circuit consisted of a SCR connected in series with a RC load and DC bias. In this paper, we report the investigation of the physics underlying the pulsing mechanism of the SCR-based. It was found that during the switching of SCR, the voltage across the capacitor increased beyond that of the DC bias, thus generating a reverse current in the circuit, which helped to turn the SCR off. The pulsing was found to be sustainable only for a specific range of RC values depending on the SCR's intrinsic turn-on/off times. The findings of this work will help to design optimum SCR based circuits for pulse mode detection of light and ionizing radiation without external amplification circuitry.

  3. Road load simulator tests of the Gould phase 1 functional model silicon controlled rectifier ac motor controller for electric vehicles

    NASA Technical Reports Server (NTRS)

    Gourash, F.

    1984-01-01

    The test results for a functional model ac motor controller for electric vehicles and a three-phase induction motor which were dynamically tested on the Lewis Research Center road load simulator are presented. Results show that the controller has the capability to meet the SAE-J227a D cycle test schedule and to accelerate a 1576-kg (3456-lb) simulated vehicle to a cruise speed of 88.5 km/hr (55 mph). Combined motor controller efficiency is 72 percent and the power inverter efficiency alone is 89 percent for the cruise region of the D cycle. Steady state test results for motoring, regeneration, and thermal data obtained by operating the simulator as a conventional dynamometer are in agreement with the contractor's previously reported data. The regeneration test results indicate that a reduction in energy requirements for urban driving cycles is attainable with regenerative braking. Test results and data in this report serve as a data base for further development of ac motor controllers and propulsion systems for electric vehicles. The controller uses state-of-the-art silicon controlled rectifier (SCR) power semiconductors and microprocessor-based logic and control circuitry. The controller was developed by Gould Laboratories under a Lewis contract for the Department of Energy's Electric and Hybrid Vehicle program.

  4. Road load simulator tests of the Gould Phase I functional model silicon controlled rectifier ac motor controller for electric vehicles

    SciTech Connect

    Gourash, F.

    1984-02-01

    This report presents the test results for a functional model ac motor controller for electric vehicles and a three-phase induction motor which were dynamically tested on the Lewis Research Center road load simulator. Results show that the controller has the capability to meet the SAE-J227a D cycle test schedule and to accelerate a 1576-kg (3456-lb) simulated vehicle to a cruise speed of 88.5 km/hr (55 mph). Combined motor controller efficiency is 72 percent and the power inverter efficiency alone is 89 percent for the cruise region of the D cycle. Steady state test results for motoring, regeneration, and thermal data obtained by operating the simulator as a conventional dynamometer are in agreement with the contractor's previously reported data. The regeneration test results indicate that a reduction in energy requirements for urban driving cycles is attainable with regenerative braking. Test results and data in this report serve as a data base for further development of ac motor controllers and propulsion systems for electric vehicles. The controller uses state-of-the-art silicon controlled rectifier (SCR) power semiconductors and microprocessor-based logic and control circuitry. The controller was developed by Gould Laboratories under a Lewis contract for the Department of Energy's Electric and Hybrid Vehicle program.

  5. Road load simulator tests of the Gould phase 1 functional model silicon controlled rectifier ac motor controller for electric vehicles

    NASA Astrophysics Data System (ADS)

    Gourash, F.

    1984-02-01

    The test results for a functional model ac motor controller for electric vehicles and a three-phase induction motor which were dynamically tested on the Lewis Research Center road load simulator are presented. Results show that the controller has the capability to meet the SAE-J227a D cycle test schedule and to accelerate a 1576-kg (3456-lb) simulated vehicle to a cruise speed of 88.5 km/hr (55 mph). Combined motor controller efficiency is 72 percent and the power inverter efficiency alone is 89 percent for the cruise region of the D cycle. Steady state test results for motoring, regeneration, and thermal data obtained by operating the simulator as a conventional dynamometer are in agreement with the contractor's previously reported data. The regeneration test results indicate that a reduction in energy requirements for urban driving cycles is attainable with regenerative braking. Test results and data in this report serve as a data base for further development of ac motor controllers and propulsion systems for electric vehicles. The controller uses state-of-the-art silicon controlled rectifier (SCR) power semiconductors and microprocessor-based logic and control circuitry. The controller was developed by Gould Laboratories under a Lewis contract for the Department of Energy's Electric and Hybrid Vehicle program.

  6. High holding voltage segmentation stacking silicon-controlled-rectifier structure with field implant as body ties blocking layer

    NASA Astrophysics Data System (ADS)

    Yen, Shiang-Shiou; Cheng, Chun-Hu; Lan, Yu-Pin; Chiu, Yu-Chien; Fan, Chia-Chi; Hsu, Hsiao-Hsuan; Chang, Shao-Chin; Jiang, Zhe-Wei; Hung, Li-Yue; Tsai, Chi-Chung; Chang, Chun-Yen

    2016-04-01

    High electrostatic discharge (ESD) protection robustness and good transient-induced latchup immunity are two important issues for high voltage integrate circuit application. In this study, we report a high-voltage-n-type-field (HVNF) implantation to act as the body ties blocking layer in segmented topology silicon-controlled-rectifier (SCR) structure in 0.11 µm 32 V high voltage process. This body ties blocking layer eliminate the elevated triggered voltage in segmented technique. Using a large resistance as shunt resistor in resistor assisted triggered SCRs stacking structure, the double snapback phenomenon is eliminate. The series SCR could be decoupled a sufficient voltage drop to turned-on when a very low current flow through the shunt resistor. The holding voltage and the failure current of 22 V and 3.4 A are achieved in the best condition of segmented topology SCR stacking structure, respectively. It improves the latchup immunity at high voltage ICs application. On the other hand, the triggered voltage almost keep the same value which is identical to SCR single cell without using segmented topology.

  7. Road load simulator tests of the Gould phase 1 functional model silicon controlled rectifier ac motor controller for electric vehicles. Final Report

    SciTech Connect

    Gourash, F.

    1984-02-01

    The test results for a functional model ac motor controller for electric vehicles and a three-phase induction motor which were dynamically tested on the Lewis Research Center road load simulator are presented. Results show that the controller has the capability to meet the SAE-J227a D cycle test schedule and to accelerate a 1576-kg (3456-lb) simulated vehicle to a cruise speed of 88.5 km/hr (55 mph). Combined motor controller efficiency is 72 percent and the power inverter efficiency alone is 89 percent for the cruise region of the D cycle. Steady state test results for motoring, regeneration, and thermal data obtained by operating the simulator as a conventional dynamometer are in agreement with the contractor's previously reported data. The regeneration test results indicate that a reduction in energy requirements for urban driving cycles is attainable with regenerative braking. Test results and data in this report serve as a data base for further development of ac motor controllers and propulsion systems for electric vehicles. The controller uses state-of-the-art silicon controlled rectifier (SCR) power semiconductors and microprocessor-based logic and control circuitry. The controller was developed by Gould Laboratories under a Lewis contract for the Department of Energy's Electric and Hybrid Vehicle program.

  8. Apparatus for controlling the firing of rectifiers in polyphase rectifying circuits

    DOEpatents

    Yarema, R.J.

    1979-09-18

    A polyphase rectifier is controlled with precision by a circuit that filters and shifts a reference signal associated with each phase and that starts a ramp signal at a zero crossing of the shifted reference signal. The difference between the ramp signal and an external trigger signal is used to generate a pulse that switches power rectifiers into conduction. The circuit reduces effects of variations that introduce subharmonics into a rectified signal and it can be used for constant or time-varying external trigger signals.

  9. An Inductorless Self-Controlled Rectifier for Piezoelectric Energy Harvesting

    PubMed Central

    Lu, Shaohua; Boussaid, Farid

    2015-01-01

    This paper presents a high-efficiency inductorless self-controlled rectifier for piezoelectric energy harvesting. High efficiency is achieved by discharging the piezoelectric device (PD) capacitance each time the current produced by the PD changes polarity. This is achieved automatically without the use of delay lines, thereby making the proposed circuit compatible with any type of PD. In addition, the proposed rectifier alleviates the need for an inductor, making it suitable for on-chip integration. Reported experimental results show that the proposed rectifier can harvest up to 3.9 times more energy than a full wave bridge rectifier. PMID:26610492

  10. An Inductorless Self-Controlled Rectifier for Piezoelectric Energy Harvesting.

    PubMed

    Lu, Shaohua; Boussaid, Farid

    2015-01-01

    This paper presents a high-efficiency inductorless self-controlled rectifier for piezoelectric energy harvesting. High efficiency is achieved by discharging the piezoelectric device (PD) capacitance each time the current produced by the PD changes polarity. This is achieved automatically without the use of delay lines, thereby making the proposed circuit compatible with any type of PD. In addition, the proposed rectifier alleviates the need for an inductor, making it suitable for on-chip integration. Reported experimental results show that the proposed rectifier can harvest up to 3.9 times more energy than a full wave bridge rectifier. PMID:26610492

  11. Analysis of junction-barrier-controlled Schottky (JBS) rectifier characteristics

    NASA Astrophysics Data System (ADS)

    Baliga, B. Jayant

    1985-11-01

    This paper provides analytical solutions for the forward conduction and reverse leakage characteristics of junction-barrier-controlled Schottky (JBS) rectifiers. Good agreement between the calculated output characteristics using these solutions and experimental measurements on devices fabricated with different junction depths and Schottky barrier heights is observed. These equations are valuable for the analysis and design of JBS power rectifiers.

  12. Fast controller for a unity-power-factor PWM rectifier

    SciTech Connect

    Eissa, M.O.; Leeb, S.B.; Verghese, G.C.; Stankovic, A.M.

    1996-01-01

    This paper presents an analog implementation of a fast controller for a unity-power-factor (UPF) PWM rectifier. The best settling times of many popular controllers for this type of converter are on the order of a few line cycles, corresponding to bandwidths under 20 Hz. The fast controller demonstrated in this paper can exercise control action at a rate comparable to the switching frequency rather than the line frequency. In order to accomplish this while maintaining unity power factor during steady-state operation, the fast controller employs a ripple-feedback cancellation scheme.

  13. Temperature-gated thermal rectifier for active heat flow control.

    PubMed

    Zhu, Jia; Hippalgaonkar, Kedar; Shen, Sheng; Wang, Kevin; Abate, Yohannes; Lee, Sangwook; Wu, Junqiao; Yin, Xiaobo; Majumdar, Arun; Zhang, Xiang

    2014-08-13

    Active heat flow control is essential for broad applications of heating, cooling, and energy conversion. Like electronic devices developed for the control of electric power, it is very desirable to develop advanced all-thermal solid-state devices that actively control heat flow without consuming other forms of energy. Here we demonstrate temperature-gated thermal rectification using vanadium dioxide beams in which the environmental temperature actively modulates asymmetric heat flow. In this three terminal device, there are two switchable states, which can be regulated by global heating. In the "Rectifier" state, we observe up to 28% thermal rectification. In the "Resistor" state, the thermal rectification is significantly suppressed (<1%). To the best of our knowledge, this is the first demonstration of solid-state active-thermal devices with a large rectification in the Rectifier state. This temperature-gated rectifier can have substantial implications ranging from autonomous thermal management of heating and cooling systems to efficient thermal energy conversion and storage. PMID:25010206

  14. Design, fabrication, and characterization of 4H-silicon carbide rectifiers for power switching applications

    NASA Astrophysics Data System (ADS)

    Sheridan, David Charles

    Silicon Carbide has received a substantial increase in research interest over the past few years as a base material system for high-frequency and high-power semiconductor devices. Of the over 1200 polytypes, 4H-SiC is the most attractive polytype for power devices due to its wide band gap (3.2eV), excellent thermal conductivity (4.9 W/cm·K), and high critical field strength (˜2 x 106 V/cm). Important for power devices, the 10x increase in critical field strength of SiC allows high voltage blocking layers to be fabricated significantly thinner than for comparable Si devices. For power rectifiers, this reduces device on-resistance, while maintaining the same high voltage blocking capability. In this work, 4H-SiC Schottky, pn, and junction barrier Schottky (JBS) rectifiers for use in high voltage switching applications have been designed, fabricated, and extensively characterized. First, a detailed review of 4H-SiC material parameters was performed and SiC models were implemented into a standard Si drift-diffusion numerical simulator. Using these models, a SiC simulation methodology was developed in order to enable predictive SiC device design. A wide variety of rectifier and edge termination designs were investigated and optimized with respect to breakdown efficiency, area consumption, resistance to interface charge, and fabrication practicality. Simulated termination methods include: field plates, floating guard rings, and a variety of junction termination extensions (JTE). Using the device simulation results, both Schottky and JBS rectifiers were fabricated with a novel self-aligned edge termination design, and fabricated with process elements developed at the Alabama Microelectronics Science and Technology Center facility. These rectifiers exhibited near-ideal forward characteristics and had blocking voltages in excess of 2.5kV. The SiC diodes were subjected to inductive switching tests, and were found to have superior reverse recovery characteristics compared to a similar Si diode. Finally, the performance of these SiC rectifiers were tested in inductive switching circuits and in high dose gamma radiation environments. In both cases, these devices were shown to be superior to their silicon counterparts. The details of this work was presented and published in the proceedings of the 45th International Meeting of the American Vacuum Society [1], the 1999 International Conference on Silicon Carbide and Related Materials [2, 3] and the 2000 European Conference on Silicon Carbide and Related Materials [4]. The expanded conference papers were published in the international journal. Solid-State Electronics [5, 6].

  15. Modelling a single phase voltage controlled rectifier using Laplace transforms

    NASA Technical Reports Server (NTRS)

    Kraft, L. Alan; Kankam, M. David

    1992-01-01

    The development of a 20 kHz, AC power system by NASA for large space projects has spurred a need to develop models for the equipment which will be used on these single phase systems. To date, models for the AC source (i.e., inverters) have been developed. It is the intent of this paper to develop a method to model the single phase voltage controlled rectifiers which will be attached to the AC power grid as an interface for connected loads. A modified version of EPRI's HARMFLO program is used as the shell for these models. The results obtained from the model developed in this paper are quite adequate for the analysis of problems such as voltage resonance. The unique technique presented in this paper uses the Laplace transforms to determine the harmonic content of the load current of the rectifier rather than a curve fitting technique. Laplace transforms yield the coefficient of the differential equations which model the line current to the rectifier directly.

  16. Low-Loss Schottky Rectifier Utilizing Trench Sidewall as Junction-Barrier-Controlled Schottky Contact

    NASA Astrophysics Data System (ADS)

    Kim, Han-Soo; Kim, Seong-Dong; Han, Min-Koo; Choi, Yearn-Ik

    1995-02-01

    A novel junction barrier contolled Schottky (JBS) rectifier structure, which has increased the Schottky contact area by utilizing the trench sidewall, has been proposed. The proposed device consists of a JBS rectifier positioned vertically along the trench sidewall as well as laterally along the surface. The additional sidewall Schottky contact reduces the forward voltage drop by enlarging the Schottky active area. The new trench structure shifts the peak electric field from Schottky contact surface to the silicon bulk and the leakage current by the barrier height lowering effect is decreased. An intensive 2-dimensional numerical simulation by MEDICI shows that the leakage current of the trenched JBS rectifier is less than 60% of that of the conventional Schottky rectifier, while the forward voltage drop of the trenched JBS rectifier is almost the same as that of the conventional Schottky rectifier.

  17. Auxiliary Supply Assisted Harmonic Suppression for 12-Pulse Phase-Controlled Rectifiers

    NASA Astrophysics Data System (ADS)

    Ueda, Shigeta; Fukuda, Shoji

    A 12-pulse phase-controlled rectifier consists of two sets of 6-pulse rectifiers. It is found that harmonic distortion of the input current is minimized if dc currents of the two rectifiers are in a boundary between continuous and discontinuous conduction modes. In order to realize the boundary mode operation under any load conditions an auxiliary voltage supply (AVS) is introduced. The AVS is required a bi-directional power flow but its handled net power is quite small. Capacity of AVS is less than 10% of rated rectifier output. A simple AVS arrangement is proposed and the usefulness is verified by simulation and experimental results.

  18. Advanced Control Strategy for Single-Phase Voltage-Source Active Rectifier with Low Harmonic Emission

    NASA Astrophysics Data System (ADS)

    Blahnk, Vojt?ch; Peroutka, Zden?k; Talla, Jakub

    2014-03-01

    This paper introduces the advanced control of single-phase voltage-source active rectifier. This control provide direct control of trolley-wire current and active damping of low-frequency disturbances at the converter ac side. Our proposed control strategy combines PR controller with feed-forward model and low-frequency harmonic compensator based on resonant controllers. Achieved experimental results show excellent converter behavior, where converter is fed by strongly distorted supply voltage.

  19. WASTE MINIMIZATION ASSESSMENT FOR A MANUFACTURER OF SILICON-CONTROLLED RECTIFIERS AND SCHOTTKY RECTIFIERS

    EPA Science Inventory

    The U.S. Environmental Protection Agency (EPA) has funded a pilot project to assist small- and medium-size manufacturers who want to minimize their generation of waste but who lack the expertise to do so. In an effort to assist these manufacturers Waste Minimization Assessment Ce...

  20. An Integrated Power-Efficient Active Rectifier With Offset-Controlled High Speed Comparators for Inductively Powered Applications

    PubMed Central

    Lee, Hyung-Min; Ghovanloo, Maysam

    2011-01-01

    We present an active full-wave rectifier with offset-controlled high speed comparators in standard CMOS that provides high power conversion efficiency (PCE) in high frequency (HF) range for inductively powered devices. This rectifier provides much lower dropout voltage and far better PCE compared to the passive on-chip or off-chip rectifiers. The built-in offset-control functions in the comparators compensate for both turn-on and turn-off delays in the main rectifying switches, thus maximizing the forward current delivered to the load and minimizing the back current to improve the PCE. We have fabricated this active rectifier in a 0.5-μm 3M2P standard CMOS process, occupying 0.18 mm2 of chip area. With 3.8 V peak ac input at 13.56 MHz, the rectifier provides 3.12 V dc output to a 500 Ω load, resulting in the PCE of 80.2%, which is the highest measured at this frequency. In addition, overvoltage protection (OVP) as safety measure and built-in back telemetry capabilities have been incorporated in our design using detuning and load shift keying (LSK) techniques, respectively, and tested. PMID:22174666

  1. Nanoscale Spin Seebeck Rectifier: Controlling Thermal Spin Transport across Insulating Magnetic Junctions with Localized Spin

    NASA Astrophysics Data System (ADS)

    Ren, Jie; Fransson, Jonas; Zhu, Jian-Xin

    2014-06-01

    The spin Seebeck effect is studied across a charge insulating magnetic junction, in which thermal-spin conjugate transport is assisted by the exchange interactions between the localized spin in the center and electrons in metallic leads. We show that, in contrast with bulk spin Seebeck effect, the figure of merit of such nanoscale thermal-spin conversion can be infinite, leading to the ideal Carnot efficiency in the linear response regime. We also find that in the nonlinear spin Seebeck transport regime the device possesses the asymmetric and negative differential spin Seebeck effects. In the last, the situations with leaking electron tunneling are also discussed. This nanoscale thermal spin rectifier, by tuning the junction parameters, can act as a spin Seebeck diode, spin Seebeck transistor, and spin Seebeck switch, which could have substantial implications for flexible thermal and information control in molecular spin caloritronics.

  2. Combinational logic for generating gate drive signals for phase control rectifiers

    NASA Technical Reports Server (NTRS)

    Dolland, C. R.; Trimble, D. W. (Inventor)

    1982-01-01

    Control signals for phase-delay rectifiers, which require a variable firing angle that ranges from 0 deg to 180 deg, are derived from line-to-line 3-phase signals and both positive and negative firing angle control signals which are generated by comparing current command and actual current. Line-to-line phases are transformed into line-to-neutral phases and integrated to produce 90 deg phase delayed signals that are inverted to produce three cosine signals, such that for each its maximum occurs at the intersection of positive half cycles of the other two phases which are inputs to other inverters. At the same time, both positive and negative (inverted) phase sync signals are generated for each phase by comparing each with the next and producing a square wave when it is greater. Ramp, sync and firing angle controls signals are than used in combinational logic to generate the gate firing control signals SCR gate drives which fire SCR devices in a bridge circuit.

  3. Controllable step motors and rectifiers of magnetic flux quanta using periodic arrays of asymmetric pinning defects

    NASA Astrophysics Data System (ADS)

    Zhu, B. Y.; Marchesoni, F.; Moshchalkov, V. V.; Nori, Franco

    2003-07-01

    We study the transport of vortices in superconductors with regular arrays of asymmetric pinning wells when applying an alternating electrical current. The asymmetric traps are modelled by the superposition of two interpenetrating square lattices of weak and strong pinning centers with separation smaller than the lattice constant. We show that this system can induce a net rectifying or diode effect for the vortex motion, including collective step-motor-type dynamics, where many vortices move forward a controlled and exact number of pin-lattice spacings at each cycle of the ac driving force. This system exhibits a remarkable net dc response with striking sawtooth-type oscillations. The net dc voltage response Vdc of the ac-driven vortices versus both the half period P and the amplitude FL of the “square wave” ac drive has been detailed in the present work. The influence of the equilibrium thermal noise, the shift between the two pinning sublattices, the degree of translational and orientational disorder, and the size of the simulation system on the Vdc response of the vortex motion at ac drive has also been addressed. Devil staircase and Arnold’s tongue structures are revealed. We also analytically derive all the key features of our numerical results. This system provides a very controllable stepmotor for the control of collective motion. Our results apply mutatis mutandis to arrays of Josephson junctions, colloidal systems with optical traps, Wigner crystals, and any system with repelling movable objects that can be pinned by a lattice of traps.

  4. Real-time multi-DSP control of three-phase current-source unity power factor PWM rectifier

    SciTech Connect

    Xiao Wang; Boon-Teck Ooi . Dept. of Electrical Engineering)

    1993-07-01

    The design of a real-time multi-DSP controller for a high-quality six-valve three-phase current-source unity power factor PWM rectifier is discussed in this paper. With the decoupler preprocessor and the dynamic trilogic PWM trigger scheme, each of the three input currents can be controlled independently. Based on the a-b-c frame system model and the fast parallel computer control, the pole-placement control method is implemented successfully to achieve fast response in the ac currents. The low-frequency resonance in the ac filter L-C networks has been damped effectively. The experimental results are obtained from a 1-kVA bipolar transistor current-source PWM rectifier with a real-time controller using three TMS320C25 DSP's.

  5. Transformer-rectifier flux pump using inductive current transfer and thermally controlled Nb(3)Sn cryotrons.

    PubMed

    Atherton, D L; Davies, R

    1979-10-01

    Transformer-rectifier flux pumps using thermally switched Nb(3)Sn cryotrons are being investigated as a loss make-up device for the proposed isochorically operated (sealed) superconducting magnets for the Canadian Maglev vehicle. High currents (1000 A) were obtained in an experimental flux pump using inductive current transfer and operating at 2 Hz. PMID:18699368

  6. Co-Design Method and Wafer-Level Packaging Technique of Thin-Film Flexible Antenna and Silicon CMOS Rectifier Chips for Wireless-Powered Neural Interface Systems.

    PubMed

    Okabe, Kenji; Jeewan, Horagodage Prabhath; Yamagiwa, Shota; Kawano, Takeshi; Ishida, Makoto; Akita, Ippei

    2015-01-01

    In this paper, a co-design method and a wafer-level packaging technique of a flexible antenna and a CMOS rectifier chip for use in a small-sized implantable system on the brain surface are proposed. The proposed co-design method optimizes the system architecture, and can help avoid the use of external matching components, resulting in the realization of a small-size system. In addition, the technique employed to assemble a silicon large-scale integration (LSI) chip on the very thin parylene film (5 μm) enables the integration of the rectifier circuits and the flexible antenna (rectenna). In the demonstration of wireless power transmission (WPT), the fabricated flexible rectenna achieved a maximum efficiency of 0.497% with a distance of 3 cm between antennas. In addition, WPT with radio waves allows a misalignment of 185% against antenna size, implying that the misalignment has a less effect on the WPT characteristics compared with electromagnetic induction. PMID:26694407

  7. Co-Design Method and Wafer-Level Packaging Technique of Thin-Film Flexible Antenna and Silicon CMOS Rectifier Chips for Wireless-Powered Neural Interface Systems

    PubMed Central

    Okabe, Kenji; Jeewan, Horagodage Prabhath; Yamagiwa, Shota; Kawano, Takeshi; Ishida, Makoto; Akita, Ippei

    2015-01-01

    In this paper, a co-design method and a wafer-level packaging technique of a flexible antenna and a CMOS rectifier chip for use in a small-sized implantable system on the brain surface are proposed. The proposed co-design method optimizes the system architecture, and can help avoid the use of external matching components, resulting in the realization of a small-size system. In addition, the technique employed to assemble a silicon large-scale integration (LSI) chip on the very thin parylene film (5 μm) enables the integration of the rectifier circuits and the flexible antenna (rectenna). In the demonstration of wireless power transmission (WPT), the fabricated flexible rectenna achieved a maximum efficiency of 0.497% with a distance of 3 cm between antennas. In addition, WPT with radio waves allows a misalignment of 185% against antenna size, implying that the misalignment has a less effect on the WPT characteristics compared with electromagnetic induction. PMID:26694407

  8. Rectifier cabinet static breaker

    DOEpatents

    Costantino, Jr, Roger A.; Gliebe, Ronald J.

    1992-09-01

    A rectifier cabinet static breaker replaces a blocking diode pair with an SCR and the installation of a power transistor in parallel with the latch contactor to commutate the SCR to the off state. The SCR serves as a static breaker with fast turnoff capability providing an alternative way of achieving reactor scram in addition to performing the function of the replaced blocking diodes. The control circuitry for the rectifier cabinet static breaker includes on-line test capability and an LED indicator light to denote successful test completion. Current limit circuitry provides high-speed protection in the event of overload.

  9. Improved power regenerative controls by using thyristor rectifier bridge of voltage source inverter and a switching transistor

    SciTech Connect

    Matsui, K. ); Mizuno, U.; Murai, Y. )

    1992-10-01

    In this paper, a few improved techniques of regenerative control for the voltage source inverter are described. In the proposed equipment, the thyristor rectifier bridge can be also utilized for regeneration through a dc reactor or capacitor. For the firs t converter mentioned, a novel PWM strategy is proposed in which the polarity of the sawtooth carrier waveforms is reversed alternately at every 60[degrees] interval of the fundamental frequency to reduce the harmonics in quantity. For the next proposed type, a modified Cuk converter method is described for regeneration, whose output current becomes a perfectly zero ripple. The third purpose is to propose a novel frequency analysis method using the switching function. The validity of its theory is confirmed experimentally.

  10. A Novel Controllable Hybrid-Anode AlGaN/GaN Field-Effect Rectifier with Low Operation Voltage

    NASA Astrophysics Data System (ADS)

    Wang, Zhi-Gang; Chen, Wan-Jun; Zhang, Bo; Li, Zhao-Ji

    2012-10-01

    A novel controllable hybrid-anode AlGaN/GaN field-effect rectifier (HA-FER) with low operation voltage (LOV) is proposed. Its mechanism can be explained by the field-controlled energy band model. This model reveals that the electric field in the AlGaN layer alters the energy band to result in a variation of the two-dimensional electron gas (2DEG) at AlGaN/GaN interface; the field can be changed by the thickness d of the AlGaN layer and the applied bias. As the d reduces below the critical thickness, the 2DEG vanishes and then the channel is pinched of. Therefore, the threshold voltage of HA-FER can be designed as low as 0 V leading to LOV (< 1 V). The analytical characteristic of the HA-FER is calculated and validated by the simulated results. These results also demonstrate that the forward properties of HA-FER are superior to the conventional SBD due to the high Schottky barrier.

  11. Fault Detection of Rectifier based on Residuals

    NASA Astrophysics Data System (ADS)

    Qingfeng, Liu; Zhaoxia, Leng; Jinkun, Sun; Huamin, Wang

    For diagnosing failure and sick rectifying elements, a fault detection and prediction method of rectifier was presented in this paper. The output voltage of rectifier was contrasted with normal simulation signal in phase to obtain the difference signal. After it was processed according to the set threshold, the coding of the difference signal was achieved. The signal coding was adopted to diagnose failure elements or sick elements. In simulation test, the fault code tables of rectifier with different control angle were given. The simulation results show the validity of the fault detection method presented in this paper.

  12. Silicon controlled rectifier polyphase bridge inverter commutated with gate-turn-off thyristor

    NASA Technical Reports Server (NTRS)

    Edwards, Dean B. (Inventor); Rippel, Wally E. (Inventor)

    1986-01-01

    A polyphase SCR inverter (10) having N switching poles, each comprised of two SCR switches (1A, 1B; 2A, 2B . . . NA, NB) and two diodes (D1B; D1B; D2A, D2B . . . DNA, DNB) in series opposition with saturable reactors (L1A, L1B; L2A, L2B . . . LNA, LNB) connecting the junctions between the SCR switches and diodes to an output terminal (1, 2 . . . 3) is commutated with only one GTO thyristor (16) connected between the common negative terminal of a dc source and a tap of a series inductor (14) connected to the positive terminal of the dc source. A clamp winding (22) and diode (24) are provided, as is a snubber (18) which may have its capacitance (c) sized for maximum load current divided into a plurality of capacitors (C.sub.1, C.sub.2 . . . C.sub.N), each in series with an SCR switch S.sub.1, S.sub.2 . . . S.sub.N). The total capacitance may be selected by activating selected switches as a function of load current. A resistor 28 and SCR switch 26 shunt reverse current when the load acts as a generator, such as a motor while braking.

  13. The inwardly rectifying K+ channel KIR7.1 controls uterine excitability throughout pregnancy

    PubMed Central

    McCloskey, Conor; Rada, Cara; Bailey, Elizabeth; McCavera, Samantha; van den Berg, Hugo A; Atia, Jolene; Rand, David A; Shmygol, Anatoly; Chan, Yi-Wah; Quenby, Siobhan; Brosens, Jan J; Vatish, Manu; Zhang, Jie; Denton, Jerod S; Taggart, Michael J; Kettleborough, Catherine; Tickle, David; Jerman, Jeff; Wright, Paul; Dale, Timothy; Kanumilli, Srinivasan; Trezise, Derek J; Thornton, Steve; Brown, Pamela; Catalano, Roberto; Lin, Nan; England, Sarah K; Blanks, Andrew M

    2014-01-01

    Abnormal uterine activity in pregnancy causes a range of important clinical disorders, including preterm birth, dysfunctional labour and post-partum haemorrhage. Uterine contractile patterns are controlled by the generation of complex electrical signals at the myometrial smooth muscle plasma membrane. To identify novel targets to treat conditions associated with uterine dysfunction, we undertook a genome-wide screen of potassium channels that are enriched in myometrial smooth muscle. Computational modelling identified Kir7.1 as potentially important in regulating uterine excitability during pregnancy. We demonstrate Kir7.1 current hyper-polarizes uterine myocytes and promotes quiescence during gestation. Labour is associated with a decline, but not loss, of Kir7.1 expression. Knockdown of Kir7.1 by lentiviral expression of miRNA was sufficient to increase uterine contractile force and duration significantly. Conversely, overexpression of Kir7.1 inhibited uterine contractility. Finally, we demonstrate that the Kir7.1 inhibitor VU590 as well as novel derivative compounds induces profound, long-lasting contractions in mouse and human myometrium; the activity of these inhibitors exceeds that of other uterotonic drugs. We conclude Kir7.1 regulates the transition from quiescence to contractions in the pregnant uterus and may be a target for therapies to control uterine contractility. PMID:25056913

  14. Analysis of single phase rectifier circuits

    NASA Astrophysics Data System (ADS)

    Lazar, James Frederick

    1997-11-01

    The preponderant application of rectifier circuits is the powering of dc loads from the ac utility line. Ordinary rectifier circuits present a nonlinear load impedance to the utility line, thereby generating harmonic currents, and contributing to the harmonic current problem. There are many active and passive rectifier circuits offering reduced harmonic currents, and in this work a methodology is developed by which these circuits may be analyzed and compared. Rectifier circuits can be classified as either active or passive. A passive rectifier circuit contains passive components (inductors, capacitors, saturable reactors, etc.), and passive switches (rectifier diodes) only. Active rectifier circuits use at least one controllable active switch (power transistor), in addition to passive switches and passive components. The performance characteristics of these circuits can be assessed with respect to a fictional device called the ideal rectifier. This assessment allows direct comparison of various approaches, passive or active, using the ideal rectifier as the common reference. Rectifier circuit performance may also be compared against specified requirements. The next topic considered is the analysis of active rectifier circuits employing a pwm (pulse width modulation) converter as a means to control power flow within the rectifier circuit. The pwm converter is modeled using the pwm switch method. A large-signal nonlinear pwm switch model is used for modeling large-signal rectifier circuit behavior, and models are developed for operation in either the continuous or discontinuous conduction mode. Similarly, a small-signal model is developed for small-signal considerations. In addition, for pwm converters operating in the continuous conduction mode, the effect of lossy resistive elements inside the converter are accounted for in the pwm switch model, and this modeling technique is shown to give results identical to those obtained via the state-space averaging method. The methods developed are then applied to the analysis of the boost rectifier operating in the discontinuous conduction mode. Three control schemes are compared, each offering a different compromise between circuit complexity and performance. Finally, a design example is given, and experimental results are provided.

  15. An acoustic rectifier.

    PubMed

    Liang, B; Guo, X S; Tu, J; Zhang, D; Cheng, J C

    2010-12-01

    The detection of acoustic signals is of relevance for a range of practical applications, for example in medical diagnostics. However, whereas rectification of electric current and other energy forms such as thermal flux has been demonstrated, acoustic rectification has not yet been achieved. Here, on the basis of the earlier theoretical proposal of an 'acoustic diode', we present the first experimental demonstration of a rectified energy flux of acoustic waves. A one-dimensional acoustic rectifier is fabricated by coupling a superlattice with a layer of ultrasound contrast agent microbubble suspension. A significant rectifying effect is observed within two frequency bands at locations that agree well with theoretical predictions. Following optimization of the concentration of the microbubble suspension, rectifying ratios can be as high as ~10(4). This realization of an acoustic rectifier should have substantial practical significance, for example in the focusing of ultrasound in medical applications. PMID:20972430

  16. Noise Properties of Rectifying Nanopores

    SciTech Connect

    Powell, M R; Sa, N; Davenport, M; Healy, K; Vlassiouk, I; Letant, S E; Baker, L A; Siwy, Z S

    2011-02-18

    Ion currents through three types of rectifying nanoporous structures are studied and compared for the first time: conically shaped polymer nanopores, glass nanopipettes, and silicon nitride nanopores. Time signals of ion currents are analyzed by power spectrum. We focus on the low-frequency range where the power spectrum magnitude scales with frequency, f, as 1/f. Glass nanopipettes and polymer nanopores exhibit non-equilibrium 1/f noise, thus the normalized power spectrum depends on the voltage polarity and magnitude. In contrast, 1/f noise in rectifying silicon nitride nanopores is of equilibrium character. Various mechanisms underlying the voltage-dependent 1/f noise are explored and discussed, including intrinsic pore wall dynamics, and formation of vortices and non-linear flow patterns in the pore. Experimental data are supported by modeling of ion currents based on the coupled Poisson-Nernst-Planck and Navier Stokes equations. We conclude that the voltage-dependent 1/f noise observed in polymer and glass asymmetric nanopores might result from high and asymmetric electric fields inducing secondary effects in the pore such as enhanced water dissociation.

  17. Silicon Sheet Quality is Improved By Meniscus Control

    NASA Technical Reports Server (NTRS)

    Yates, D. A.; Hatch, A. E.; Goldsmith, J. M.

    1983-01-01

    Better quality silicon crystals for solar cells are possible with instrument that monitors position of meniscus as sheet of solid silicon is drawn from melt. Using information on meniscus height, instrument generates feedback signal to control melt temperature. Automatic control ensures more uniform silicon sheets.

  18. Control of silicon nanoparticle size embedded in silicon oxynitride dielectric matrix

    SciTech Connect

    Ehrhardt, F.; Ferblantier, G.; Muller, D.; Slaoui, A.; Ulhaq-Bouillet, C.; Rinnert, H.

    2013-07-21

    In this study, silicon rich silicon oxynitride layers containing more than 15% nitrogen were deposited by electron cyclotron resonance assisted plasma enhanced vapor deposition in order to form silicon nanoparticles after a high temperature thermal annealing. The effect of the flows of the precursor gases on the composition and the structural properties of the layers was assessed by Rutherford backscattering spectroscopy, elastic recoil detection analysis, and infrared spectroscopic measurements. The morphological and crystallinity properties were investigated by energy filtered transmission electron microscopy and Raman spectroscopy. We show that the excess of silicon in the silicon oxynitride layer controls the silicon nanoparticles size. On the other hand, the crystalline fraction of particles is found to be strongly correlated to the nanoparticle size. Finally, the photoluminescence measurements show that it is also possible to tune the photoluminescence peak position between 400 and 800 nm and its intensity by changing the silicon excess in the silicon rich silicon oxynitride matrix.

  19. Curvature Control of Silicon Microlens for THz Dielectric Antenna

    NASA Technical Reports Server (NTRS)

    Lee, Choonsup; Chattopadhyay, Goutam; Cooper, Ken; Mehdi, Imran

    2012-01-01

    We have controlled the curvature of silicon microlens by changing the amount of photoresist in order to microfabricate hemispherical silicon microlens which can improve the directivity and reduce substrate mode losses.

  20. Optically controlled quadrature coupler on silicon substrate

    NASA Astrophysics Data System (ADS)

    Bhadauria, Avanish; Sharma, Sonia; Sonania, Shikha; Akhtar, Jamil

    2016-03-01

    In this paper, we have proposed and studied an optically controlled quadrature coupler fabricated on silicon substrate. The optically controlled quadrature coupler can be realized by terminating its coupled or through ports by optically induced load. Simulation and experimental results show that by varying optical intensity, we can control the phase and amplitude of output RF signal and can realize optically controlled reflection type attenuator, reflection type phase-shifter and ultrafast switches. The new kind of proposed device can be useful for ultra-fast signal processing and modulation schemes in high speed communication especially in QPSK modulation. The optical control has several advantages over conventional techniques such as MEMS and other semiconductor switching, which have several inherent disadvantages and limitations like low response time, low power handling capacity, device parasitic and non-linearity.

  1. Artificial neural networks for control of a grid-connected rectifier/inverter under disturbance, dynamic and power converter switching conditions.

    PubMed

    Li, Shuhui; Fairbank, Michael; Johnson, Cameron; Wunsch, Donald C; Alonso, Eduardo; Proaño, Julio L

    2014-04-01

    Three-phase grid-connected converters are widely used in renewable and electric power system applications. Traditionally, grid-connected converters are controlled with standard decoupled d-q vector control mechanisms. However, recent studies indicate that such mechanisms show limitations in their applicability to dynamic systems. This paper investigates how to mitigate such restrictions using a neural network to control a grid-connected rectifier/inverter. The neural network implements a dynamic programming algorithm and is trained by using back-propagation through time. To enhance performance and stability under disturbance, additional strategies are adopted, including the use of integrals of error signals to the network inputs and the introduction of grid disturbance voltage to the outputs of a well-trained network. The performance of the neural-network controller is studied under typical vector control conditions and compared against conventional vector control methods, which demonstrates that the neural vector control strategy proposed in this paper is effective. Even in dynamic and power converter switching environments, the neural vector controller shows strong ability to trace rapidly changing reference commands, tolerate system disturbances, and satisfy control requirements for a faulted power system. PMID:24807951

  2. Reversible fluctuation rectifier

    NASA Astrophysics Data System (ADS)

    Sokolov, I. M.

    1999-10-01

    The analysis of a Feynman's ratchet system [J. M. R. Parrondo and P. Español, Am. J. Phys. 64, 1125 (1996)] and of its electrical counterpart, a diode engine [I. M. Sokolov, Europhys. Lett. 44, 278 (1998)] has shown that ``fluctuation rectifiers'' consisting of a nonlinear element (ratchet, diode) and a linear element (vane, resistor) kept at different temperatures always show efficiency smaller than the Carnot value, thus indicating the irreversible mode of operation. We show that this irreversibility is not intrinsic for a system in simultaneous contact with two heat baths at different temperatures and that a fluctuation rectifier can work reversibly. This is illustrated by a model with two diodes switched in opposite directions, where the Carnot efficiency is achieved when backward resistivity of the diodes tends to infinity.

  3. What controls silicon isotope fractionation during dissolution of diatom opal?

    NASA Astrophysics Data System (ADS)

    Wetzel, F.; de Souza, G. F.; Reynolds, B. C.

    2014-04-01

    The silicon isotope composition of opal frustules from photosynthesising diatoms is a promising tool for studying past changes in the marine silicon cycle, and indirectly that of carbon. Dissolution of this opal may be accompanied by silicon isotope fractionation that could disturb the pristine silicon isotope composition of diatom opal acquired in the surface ocean. It has previously been shown that dissolution of fresh and sediment trap diatom opal in seawater does fractionate silicon isotopes. However, as the mechanism of silicon isotope fractionation remained elusive, it is uncertain whether opal dissolution in general is associated with silicon isotope fractionation considering that opal chemistry and surface properties are spatially and temporally (i.e. opal of different age) diverse. In this study we dissolved sediment core diatom opal in 5 mM NaOH and found that this process is not associated with significant silicon isotope fractionation. Since no variability of the isotope effect was observed over a wide range of dissolution rates, we can rule out the suggestion that back-reactions had a significant influence on the net isotope effect. Similarly, we did not observe an impact of temperature, specific surface area, or degree of undersaturation on silicon isotope partitioning during dissolution, such that these can most likely also be ruled out as controlling factors. We discuss the potential impacts of the chemical composition of the dissolution medium and age of diatom opal on silicon isotope fractionation during dissolution. It appears most likely that the controlling mechanism of silicon isotope fractionation during dissolution is related to the reactivity, or potentially, aluminium content of the opal. Such a dependency would imply that silicon isotope fractionation during dissolution of diatom opal is spatially and temporally variable. However, since the isotope effects during dissolution are small, the silicon isotope composition of diatom opal appears to be robust against dissolution in the deep sea sedimentary environment.

  4. Method of controlling defect orientation in silicon crystal ribbon growth

    NASA Technical Reports Server (NTRS)

    Leipold, M. H. (Inventor)

    1978-01-01

    The orientation of twinning and other effects in silicon crystal ribbon growth is controlled by use of a starting seed crystal having a specific (110) crystallographic plane and (112) crystallographic growth direction.

  5. Features of Controlled Laser Thermal Cleavage of Crystalline Silicon

    SciTech Connect

    Serdyukov, A. N. Shalupaev, S. V.; Nikityuk, Yu. V.

    2010-11-15

    Controlled laser thermal cleavage of crystalline silicon has been numerically simulated. A 3D analysis of the thermoelastic fields formed in a single-crystal silicon wafer as a result of successive laser heating and exposure to a coolant was performed for three different versions of anisotropy. The simulation was performed for laser irradiation with different wavelengths: 1.06 and 0.808 {mu}m. The calculation results have been experimentally verified using a YAG laser. The results can be used in the electronics industry to optimize the precise separation of silicon wafers into crystals.

  6. High-current, low-forward-drop JBS power rectifiers

    NASA Astrophysics Data System (ADS)

    Chang, H.-R.; Baliga, B. J.

    1986-03-01

    The junction- barrier-controlled Schottky (JBS) rectifier is a Schottky rectifier with a p- n junction grid structure integrated into the device structure to improve its reverse blocking characteristics. This paper reports the development of large area (0.5 cm 2), 30 V, JBS rectifiers capable of handling over 25 A of forward current while operating at up to 125°C with good reverse blocking characteristics. Trade-off curves between forward voltage drop and reverse leakage current are introduced to allow optimization of these devices.

  7. A simple method to control nanotribology behaviors of monocrystalline silicon

    NASA Astrophysics Data System (ADS)

    Wang, X. D.; Guo, J.; Chen, C.; Chen, L.; Qian, L. M.

    2016-01-01

    A simple method was proposed to control the nanotribology behaviors of monocrystalline silicon against SiO2 microsphere by adjusting relative humidity (RH). Experimental results indicated that adhesion work, friction coefficient, and nanowear of silicon against SiO2 microsphere significantly varied between 60% and 90% RH. Under 60% RH, adhesion work was 119 mN/m, and friction coefficient was about 0.53. However, adhesion work and friction coefficient decreased to ˜70 mN/m and ˜0.3 under 90% RH, respectively. An apparent wear track ˜13 nm deep formed on the silicon surface under 60% RH, whereas no obvious wear scar was observed on the silicon surface under 90% RH. Analysis indicated that such tribological behaviors were due to different water condensations on the silicon surface under 60% and 90% RH. Under 60% RH, the water that condensed on the surfaces of the silicon sample and SiO2 tip mainly consisted of ice-like water. As a result, adhesion work was enlarged by the breaking force of the ice-like water bridge in the contact area. Given that a ≡Si-O-Si≡ bonding bridge easily formed between the silicon surface and the SiO2 tip with the help of water condensation under 60% RH instead of 90% RH, the friction coefficient was large and the nanowear of the silicon sample was severe under 60% RH. These results may help elucidate the nanotribology behaviors of silicon and facilitate the tribological design of dynamic microelectromechanical systems working under humid conditions.

  8. Controlling cellular activity by manipulating silicone surface roughness.

    PubMed

    Prasad, Babu R; Brook, Michael A; Smith, Terry; Zhao, Shigui; Chen, Yang; Sheardown, Heather; D'souza, Renita; Rochev, Yuri

    2010-07-01

    Silicone elastomers exhibit a broad range of beneficial properties that are exploited in biomaterials. In some cases, however, problems can arise at silicone elastomer interfaces. With breast implants, for example, the fibrous capsule that forms at the silicone interface can undergo contracture, which can lead to the need for revision surgery. The relationship between surface topography and wound healing--which could impact on the degree of contracture--has not been examined in detail. To address this, we prepared silicone elastomer samples with rms surface roughnesses varying from 88 to 650 nm and examined the growth of 3T3 fibroblasts on these surfaces. The PicoGreen assay demonstrated that fibroblast growth decreased with increases in surface roughness. Relatively smooth (approximately 88 nm) PDMS samples had ca. twice as much fibroblast DNA per unit area than the 'bumpy' (approximately 378 nm) and very rough (approximately 604 and approximately 650 nm) PDMS samples. While the PDMS sample with roughness of approximately 650 nm had significantly fewer fibroblasts at 24h than the TCP control, fibroblasts on the smooth silicone surprisingly reached confluence much more rapidly than on TCP, the gold standard for cell culture. Thus, increasing the surface roughness at the sub-micron scale could be a strategy worthy of consideration to help mitigate fibroblast growth and control fibrous capsule formation on silicone elastomer implants. PMID:20363600

  9. Controlled growth of nanocrystalline silicon within amorphous silicon carbide thin films

    NASA Astrophysics Data System (ADS)

    Kole, Arindam; Chaudhuri, Partha

    2014-04-01

    Controlled formation of nanocrystalline silicon (nc-Si) within hydrogenated amorphous silicon carbide (a-SiC:H) thin films has been demonstrated by a rf (13.56 MHz) plasma chemical vapour deposition (PECVD) method at a low deposition temperature of 200°C by regulating the deposition pressure (Pr) between 26.7 Pa and 133.3 Pa. Evolution of the size and the crystalline silicon volume fraction within the a-SiC:H matrix has been studied by XRD, Raman and HRTEM. The study reveals that at Pr of 26.7 Pa there are mostly isolated grains of nc-Si within the a-SiC:H matrix with average size of 4.5 nm. With increase of Pr the isolated nc-Si grains coalesce more and more giving rise to larger size connected nc-Si islands which appear as microcrystalline silicon in the Raman spectra. As a result net isolated nc-Si volume fraction decreases while the total crystalline silicon volume fraction increases.

  10. Automated system to control the polarization voltage of silicon detectors

    NASA Astrophysics Data System (ADS)

    Altieri, S.; Fossati, F.; Lanza, A.; Pinelli, T.

    1995-04-01

    A remote controlled system to maintain polarization voltage across a silicon detector within a user defined window is described. The system regulates silicon bias voltage, caused by increased leakage current due to radiation damage, by switching external resistors to maintain a constant voltage drop across the bias load resistor, independent of leakage current. This Z80 microprocessor based system links with the host computer by a RS-232 serial port. The voltage resolution of the system is less than 0.2 V in the worst case.

  11. Treatment to Control Adhesion of Silicone-Based Elastomers

    NASA Technical Reports Server (NTRS)

    deGroh, Henry C., III; Puleo, Bernadette J.; Waters, Deborah L.

    2013-01-01

    Seals are used to facilitate the joining of two items, usually temporarily. At some point in the future, it is expected that the items will need to be separated. This innovation enables control of the adhesive properties of silicone-based elastomers. The innovation may also be effective on elastomers other than the silicone-based ones. A technique has been discovered that decreases the level of adhesion of silicone- based elastomers to negligible levels. The new technique causes less damage to the material compared to alternative adhesion mitigation techniques. Silicone-based elastomers are the only class of rubber-like materials that currently meet NASA s needs for various seal applications. However, silicone-based elastomers have natural inherent adhesive properties. This stickiness can be helpful, but it can frequently cause problems as well, such as when trying to get items apart. In the past, seal adhesion was not always adequately addressed, and has caused in-flight failures where seals were actually pulled from their grooves, preventing subsequent spacecraft docking until the seal was physically removed from the flange via an extravehicular activity (EVA). The primary method used in the past to lower elastomer seal adhesion has been the application of some type of lubricant or grease to the surface of the seal. A newer method uses ultraviolet (UV) radiation a mixture of UV wavelengths in the range of near ultraviolet (NUV) and vacuum ultraviolet (VUV) wavelengths.

  12. Polarization-independent silicon metadevices for efficient optical wavefront control

    SciTech Connect

    Chong, Katie E.; Staude, Isabelle; James, Anthony Randolph; Dominguez, Jason James; Liu, Sheng; Campione, Salvatore; Subramania, Ganapathi Subramanian; Luk, Ting S.; Decker, Manuel; Neshev, Dragomir N.; Brener, Igal; Kivshar, Yuri S.

    2015-07-20

    In this study, we experimentally demonstrate a functional silicon metadevice at telecom wavelengths that can efficiently control the wavefront of optical beams by imprinting a spatially varying transmittance phase independent of the polarization of the incident beam. Near-unity transmittance efficiency and close to 0–2π phase coverage are enabled by utilizing the localized electric and magnetic Mie-type resonances of low-loss silicon nanoparticles tailored to behave as electromagnetically dual-symmetric scatterers. We apply this concept to realize a metadevice that converts a Gaussian beam into a vortex beam. The required spatial distribution of transmittance phases is achieved by a variation of the lattice spacing as a single geometric control parameter.

  13. Polarization-independent silicon metadevices for efficient optical wavefront control

    DOE PAGESBeta

    Chong, Katie E.; Staude, Isabelle; James, Anthony Randolph; Dominguez, Jason James; Liu, Sheng; Campione, Salvatore; Subramania, Ganapathi Subramanian; Luk, Ting S.; Decker, Manuel; Neshev, Dragomir N.; et al

    2015-07-20

    In this study, we experimentally demonstrate a functional silicon metadevice at telecom wavelengths that can efficiently control the wavefront of optical beams by imprinting a spatially varying transmittance phase independent of the polarization of the incident beam. Near-unity transmittance efficiency and close to 0–2π phase coverage are enabled by utilizing the localized electric and magnetic Mie-type resonances of low-loss silicon nanoparticles tailored to behave as electromagnetically dual-symmetric scatterers. We apply this concept to realize a metadevice that converts a Gaussian beam into a vortex beam. The required spatial distribution of transmittance phases is achieved by a variation of the latticemore » spacing as a single geometric control parameter.« less

  14. Controllable nonlinear refraction characteristics in hydrogenated nanocrystalline silicon

    SciTech Connect

    Zheng, D. Q.; Ye, Q. H.; Shen, W. Z.; Su, W. A.

    2014-02-07

    Nonlinear refraction (NLR) of hydrogenated nanocrystalline silicon (nc-Si:H) has been investigated through the close aperture Z-scan method. We demonstrate a significant NLR and a unique feature of controllable NLR characteristics between saturable and Kerr NLR with the incident photon energy. We numerically evaluate the proportion of these two mechanisms in different wavelengths by a modified NLR equation. The band tail of nc-Si:H appears to play a crucial role in such NLR responses.

  15. Controlling diffusion of lithium in silicon nanostructures

    NASA Astrophysics Data System (ADS)

    Chelikowsky, James R.; Chan, Tzu-Liang

    2010-03-01

    The ability to control the diffusion of dopants or impurities is a controlling factor in the functionalization of materials used in nano-devices. Here we examine Li in Si nanostructures as atoms with low atomic mass such as Li can be used as a carrier for energy storage with high specific energy capacity. Using real space pseudopotential calculations, we determine how the factors of size and dimensionality can be used to achieve an optimal diffusion of Li atoms in Si nanostructures. We find that Li has a strong tendency to stay inside the core of Si nanostructures because it is energetically more stable inside, and the energy barrier to diffuse towards the core is in general lower than diffusing towards the surface. This situation will lead to a faster charging of Li atoms into Si nanostructures compared to the discharging process. In addition, we find that the diffusion barrier is significantly reduced with decreasing nanocrystal size, which implies the kinetics of impurities inside nanostructures can be accelerated by manipulating the nanostructure's size.

  16. An Auxiliary Supply Assisted Input Current Harmonic Reduction for 12-pulse Diode Rectifiers

    NASA Astrophysics Data System (ADS)

    Fukuda, Shoji; Ohta, Masaaki

    Diode rectifiers have been widely used for an ac-to-dc converter. One of their problems is that they include large lower-order harmonics in the input current. A 12-pulse diode rectifier is useful for reducing them but it still includes the (12m ± 1)th (m: integer) harmonics. In order to further reduce the input current harmonics a single-phase square wave auxiliary voltage supply is inserted in the middle dc bus of a 12-pulse diode rectifier. The purpose is to obtain a 12-pulse diode rectifier whose harmonic contents are equivalent to those of a 24-pulse diode rectifier. Theoretical analysis of the auxiliary supply assisted 12-pulse diode rectifier is presented and a control method of the auxiliary supply in relation to the dc load current is proposed. Effectiveness of an auxiliary supply is verified by simulation and experimental results.

  17. Realistic-contact-induced enhancement of rectifying in carbon-nanotube/graphene-nanoribbon junctions

    SciTech Connect

    Zhang, Xiang-Hua; Li, Xiao-Fei; Wang, Ling-Ling Xu, Liang; Luo, Kai-Wu

    2014-03-10

    Carbon-nanotube/graphene-nanoribbon junctions were recently fabricated by the controllable etching of single-walled carbon-nanotubes [Wei et al., Nat. Commun. 4, 1374 (2013)] and their electronic transport properties were studied here. First principles results reveal that the transmission function of the junctions show a heavy dependence on the shape of contacts, but rectifying is an inherent property which is insensitive to the details of contacts. Interestingly, the rectifying ratio is largely enhanced in the junction with a realistic contact and the enhancement is insensitive to the details of contact structures. The stability of rectifying suggests a significant feasibility to manufacture realistic all-carbon rectifiers in nanoelectronics.

  18. Single-switch 3{phi} PWM low harmonic rectifiers

    SciTech Connect

    Ismail, E.H.; Erickson, R.

    1996-03-01

    Existing 3{phi} ac-dc low-harmonic rectifiers are costly and require complex control schemes to minimize input current harmonics. Introduced here are two new classes of low cost 3{phi} ac-dc high power factor/low harmonic controlled rectifiers. These are derived from parent dc-dc converter topologies containing boost-type inputs and buck-type inputs. With a single active switch in addition to the diode bridge rectifier, the converters are capable of drawing a high-quality input current waveform naturally at nearly unit power factor. Thus, a simple 3{phi} ac-dc high power factor rectifier is obtained. Two algorithms are introduced in this paper for constructing a 3{phi} ac-dc high-quality rectifier. These algorithms depend on the simple switched-mode boost-type input converter and buck-type input converter modified by an input filter. For most known dc-dc converters which belong to these classes, there are corresponding 3{phi} ac-dc high power factor topologies, which use the same number of transistors and use six additional fast diodes. Analytical and simulation results are supplied to demonstrate the validity of the concept.

  19. Controlled thinning and surface smoothening of silicon nanopillars.

    PubMed

    Kalem, S; Werner, P; Nilsson, B; Talalaev, V G; Hagberg, M; Arthursson, O; Södervall, U

    2009-11-01

    A convenient method has been developed to thin electron beam fabricated silicon nanopillars under controlled surface manipulation by transforming the surface of the pillars to an oxide shell layer followed by the growth of sacrificial ammonium silicon fluoride coating. The results show the formation of an oxide shell and a silicon core without significantly changing the original length and shape of the pillars. The oxide shell layer thickness can be controlled from a few nanometers up to a few hundred nanometers. While downsizing in diameter, smooth Si pillar surfaces of less than 10 nm roughness within 2 microm were produced after exposure to vapors of HF and HNO3 mixture as evidenced by transmission electron microscopy (TEM) analysis. The attempt to expose for long durations leads to the growth of a thick oxide whose strain effect on pillars can be assessed by coupled LO-TO vibrational modes of Si-O bonds. Photoluminescence (PL) of the pillar structures which have been downsized exhibits visible and infrared emissions, which are attributable to microscopic pillars and to the confinement of excited carriers in the Si core, respectively. The formation of smooth core-shell structures while reducing the diameter of the Si pillars has a potential in fabricating nanoscale electronic devices and functional components. PMID:19801781

  20. Nanostructured silicon membranes for control of molecular transport.

    PubMed

    Srijanto, Bernadeta R; Retterer, Scott T; Fowlkes, Jason D; Doktycz, Mitchel J

    2010-11-01

    A membrane that allows selective transport of molecular species requires precise engineering on the nanoscale. Membrane permeability can be tuned by controlling the physical structure and surface chemistry of the pores. Here, a combination of electron beam and optical lithography, along with cryogenic deep reactive ion etching, has been used to fabricate silicon membranes that are physically robust, have uniform pore sizes, and are directly integrated into a microfluidic network. Additional reductions in pore size were achieved using plasma enhanced chemical vapor deposition and atomic layer deposition of silicon dioxide to coat membrane surfaces. Cross sectioning of the membranes using focused ion beam milling was used to determine the physical shape of the membrane pores before and after coating. Functional characterization of the membranes was performed by using quantitative fluorescence microscopy to document the transport of molecular species across the membrane. PMID:24932436

  1. Nanostructured Silicon Membranes for Control of Molecular Transport

    SciTech Connect

    Srijanto, Bernadeta R; Retterer, Scott T; Fowlkes, Jason Davidson; Doktycz, Mitchel John

    2010-01-01

    A membrane that allows selective transport of molecular species requires precise engineering on the nanoscale. Membrane permeability can be tuned by controlling the physical structure of the pores. Here, a combination of electron-beam and optical lithography, along with cryogenic deep reactive ion etching, has been used to fabricate silicon membranes that are physically robust, have uniform pore-sizes, and are directly integrated into a microfluidic network. Additional reductions in pore size were achieved using plasma enhanced chemical vapor deposition of silicon dioxide to coat membrane surfaces. Cross sectioning of the membranes using focused ion beam milling was used to determine the physical shape of the membrane pores before and after coating.

  2. Single phase switch mode rectifiers

    SciTech Connect

    Dawande, M.S.; Dubey, G.K.

    1995-12-31

    AC to DC power conversion received a considerable boost with the introduction of self commutated devices such as power transistors, MOSFETs, IGBTs and GTOs. Not only the availability of these devices led to the development of several converter configurations and active waveshaping techniques but allowed the power conversion to be realized economically and efficiently. The advantages associated with these devices include near sinusoidal input current, smaller sizes of input/output filters and efficient power conversion. The first switch mode rectifier circuit consisted of front end diode rectifier, a boost inductor and an active switch as shown in a figure. The converter is of boost type (output dc voltage greater than the rms value of input voltage) and is capable of only unidirectional power flow (source to load). Few configurations of SMRs which use diode rectifier and MOSFET switch have been reported recently. These can be used in low to medium power applications. In this paper six new single phase SMR circuits are presented. Comparative study of these circuits has been carried out and experimental results for unity power factor operation are given for three of these to verify feasibility of these SMR circuits.

  3. Experimental investigation of radiative thermal rectifier using vanadium dioxide

    NASA Astrophysics Data System (ADS)

    Ito, Kota; Nishikawa, Kazutaka; Iizuka, Hideo; Toshiyoshi, Hiroshi

    2014-12-01

    Vanadium dioxide (VO2) exhibits a phase-change behavior from the insulating state to the metallic state around 340 K. By using this effect, we experimentally demonstrate a radiative thermal rectifier in the far-field regime with a thin film VO2 deposited on the silicon wafer. A rectification contrast ratio as large as two is accurately obtained by utilizing a one-dimensional steady-state heat flux measurement system. We develop a theoretical model of the thermal rectifier with optical responses of the materials retrieved from the measured mid-infrared reflection spectra, which is cross-checked with experimentally measured heat flux. Furthermore, we tune the operating temperatures by doping the VO2 film with tungsten (W). These results open up prospects in the fields of thermal management and thermal information processing.

  4. Experimental investigation of radiative thermal rectifier using vanadium dioxide

    SciTech Connect

    Ito, Kota; Nishikawa, Kazutaka; Iizuka, Hideo; Toshiyoshi, Hiroshi

    2014-12-22

    Vanadium dioxide (VO{sub 2}) exhibits a phase-change behavior from the insulating state to the metallic state around 340 K. By using this effect, we experimentally demonstrate a radiative thermal rectifier in the far-field regime with a thin film VO{sub 2} deposited on the silicon wafer. A rectification contrast ratio as large as two is accurately obtained by utilizing a one-dimensional steady-state heat flux measurement system. We develop a theoretical model of the thermal rectifier with optical responses of the materials retrieved from the measured mid-infrared reflection spectra, which is cross-checked with experimentally measured heat flux. Furthermore, we tune the operating temperatures by doping the VO{sub 2} film with tungsten (W). These results open up prospects in the fields of thermal management and thermal information processing.

  5. Initial rectified attractors for perfect synchronization of chaotic systems

    NASA Astrophysics Data System (ADS)

    Sun, Mingxuan; He, Xiongxiong; Yu, Li

    2005-12-01

    The controlled attractor with initial rectifying action, referred to as initial rectified attractor (IRA) in this Letter, is introduced for the purpose of chaos synchronization. An IRA-based design is presented to make the states of the drive system and the response system synchronized within finite time. The reaching time is shown independent of initial conditions and dynamics of the chaotic systems, and can be pre-specified. With numerical experiments we demonstrate that such perfect synchronization can be achieved for modified Chua's circuit systems and Genesio chaotic systems.

  6. Control and data acquisition electronics for the CDF Silicon Vertex Detector

    SciTech Connect

    Turner, K.J.; Nelson, C.A.; Shaw, T.M.; Wesson, T.R.

    1991-11-01

    A control and data acquisition system has been designed for the CDF Silicon Vertex Detector (SVX) at Fermilab. The system controls the operation of the SVX Rev D integrated circuit (SVX IC) that is used to instrument a 46,000 microstrip silicon detector. The system consists of a Fastbus Sequencer, a Crate Controller and Digitizer modules. 11 refs., 6 figs., 3 tabs.

  7. Recruitment of Gβγ controls the basal activity of G-protein coupled inwardly rectifying potassium (GIRK) channels: crucial role of distal C terminus of GIRK1

    PubMed Central

    Kahanovitch, Uri; Tsemakhovich, Vladimir; Berlin, Shai; Rubinstein, Moran; Styr, Boaz; Castel, Ruth; Peleg, Sagit; Tabak, Galit; Dessauer, Carmen W; Ivanina, Tatiana; Dascal, Nathan

    2014-01-01

    The G-protein coupled inwardly rectifying potassium (GIRK, or Kir3) channels are important mediators of inhibitory neurotransmission via activation of G-protein coupled receptors (GPCRs). GIRK channels are tetramers comprising combinations of subunits (GIRK1–4), activated by direct binding of the Gβγ subunit of Gi/o proteins. Heterologously expressed GIRK1/2 exhibit high, Gβγ-dependent basal currents (Ibasal) and a modest activation by GPCR or coexpressed Gβγ. Inversely, the GIRK2 homotetramers exhibit low Ibasal and strong activation by Gβγ. The high Ibasal of GIRK1 seems to be associated with its unique distal C terminus (G1-dCT), which is not present in the other subunits. We investigated the role of G1-dCT using electrophysiological and fluorescence assays in Xenopus laevis oocytes and protein interaction assays. We show that expression of GIRK1/2 increases the plasma membrane level of coexpressed Gβγ (a phenomenon we term ‘Gβγ recruitment’) but not of coexpressed Gαi3. All GIRK1-containing channels, but not GIRK2 homomers, recruited Gβγ to the plasma membrane. In biochemical assays, truncation of G1-dCT reduces the binding between the cytosolic parts of GIRK1 and Gβγ, but not Gαi3. Nevertheless, the truncation of G1-dCT does not impair activation by Gβγ. In fluorescently labelled homotetrameric GIRK1 channels and in the heterotetrameric GIRK1/2 channel, the truncation of G1-dCT abolishes Gβγ recruitment and decreases Ibasal. Thus, we conclude that G1-dCT carries an essential role in Gβγ recruitment by GIRK1 and, consequently, in determining its high basal activity. Our results indicate that G1-dCT is a crucial part of a Gβγ anchoring site of GIRK1-containing channels, spatially and functionally distinct from the site of channel activation by Gβγ. PMID:25384780

  8. Reliable 3-phase PWM boost rectifiers employing a stacked dual boost converter subtopology

    SciTech Connect

    Salmon, J.C.

    1996-05-01

    This paper describes circuit topologies for 3-phase pulse-width modulation (PWM) boost rectifiers that operate with a unity fundamental power factor and a low-distortion ac line current. Overlap delays between the switching of the upper and lower devices in a PWM rectifier leg are not critical and diodes eliminates the possibility of the dc-link capacitor discharging into short circuits and shoot-through fault conditions. The rectifiers are controlled using a stacked dual boost converter cell subtopology model that can be used in two current control modes. The dual current-control mode shapes two line currents and can achieve current distortion levels below 5%. The single current-control mode shapes one line current and can achieve current distortion levels close to 5% with the rectifier output dc voltage at the standard level associated with a rectified mains voltage. The per-unit current ratings for the switches in the 3-phase PWM switch networks are around 15--20% of the input rms line current as compared to 71% for a standard 3-phase PWM rectifier. Circuit simulations and experimental results are used to demonstrate the performance and feasibility of the rectifiers described.

  9. Method for rapid, controllable growth and thickness, of epitaxial silicon films

    DOEpatents

    Wang, Qi; Stradins, Paul; Teplin, Charles; Branz, Howard M.

    2009-10-13

    A method of producing epitaxial silicon films on a c-Si wafer substrate using hot wire chemical vapor deposition by controlling the rate of silicon deposition in a temperature range that spans the transition from a monohydride to a hydrogen free silicon surface in a vacuum, to obtain phase-pure epitaxial silicon film of increased thickness is disclosed. The method includes placing a c-Si substrate in a HWCVD reactor chamber. The method also includes supplying a gas containing silicon at a sufficient rate into the reaction chamber to interact with the substrate to deposit a layer containing silicon thereon at a predefined growth rate to obtain phase-pure epitaxial silicon film of increased thickness.

  10. Controlled delivery of acyclovir from porous silicon micro- and nanoparticles

    NASA Astrophysics Data System (ADS)

    Maniya, Nalin H.; Patel, Sanjaykumar R.; Murthy, Z. V. P.

    2015-03-01

    In this work, micro- and nanoparticles of porous silicon (PSi) are demonstrated to act as effective carrier for the controlled delivery of acyclovir (ACV). PSi films prepared by electrochemical etching were fractured by ultrasonication to prepare micro- and nanoparticles. PSi native particles were thermally oxidized (TOPSi) and thermally hydrosilylated using undecylenic acid (UnPSi). PSi particles with three different surface chemistries were then loaded with ACV by physical adsorption and covalent attachment. Such particles were characterized by scanning electron microscopy, dynamic light scattering, and Fourier transform infrared spectroscopy. In vitro ACV release experiments in phosphate buffered saline showed sustained release behaviour from both micro- and nanoparticles and order of release was found to be native PSi > TOPSi > UnPSi. Drug release kinetics study using Korsmeyer-Peppas model suggested a combination of both drug diffusion and Si scaffold erosion based drug release mechanisms.

  11. Ordered silicon nanorod arrays with controllable geometry and robust hydrophobicity

    NASA Astrophysics Data System (ADS)

    Zi-Wen, Wang; Jia-Qi, Cai; Yi-Zhi, Wu; Hui-Jie, Wang; Xiao-Liang, Xu

    2015-01-01

    Highly ordered silicon nanorod (SiNR) arrays with controllable geometry are fabricated via nanosphere lithography and metal-assisted chemical etching. It is demonstrated that the key to achieving a high-quality metal mask is to construct a non-close-packed template that can be removed with negligible damage to the mask. Hydrophobicity of SiNR arrays of different geometries is also studied. It is shown that the nanorod structures are effectively quasi-hydrophobic with a contact angle as high as 142°, which would be useful in self-cleaning nanorod-based device applications. Project supported by the National Natural Science Foundation of China (Grant No. 51272246) and the Scientific and Technological Research Foundation of Anhui Province, China (Grant No. 12010202035).

  12. Controlled Thin-Film Growth Of Silicon Carbide Polytypes

    NASA Technical Reports Server (NTRS)

    Powell, J. Anthony; Larkin, David J.

    1995-01-01

    Improved deposition process to grows thin layers of silicon carbide having chosen crystalline structures. Process incorporated into sequences of deposition and etching steps used to fabricate silicon-carbide-based semiconductor devices. Important advance because silicon carbide emerging as superior semiconductor for devices operating under conditions of high power, high temperature, and/or high frequency. Furthermore, various crystalline structures of SiC have different electronic properties, each suited to specific application.

  13. Steric stabilization of nonaqueous silicon slips. I - Control of particle agglomeration and packing. II - Pressure casting of powder compacts

    NASA Technical Reports Server (NTRS)

    Kerkar, Awdhoot V.; Henderson, Robert J. M.; Feke, Donald L.

    1990-01-01

    The application of steric stabilization to control particle agglomeration and packing of silicon powder in benzene and trichloroethylene is reported. The results provide useful guidelines for controlling unfavorable particle-particle interactions during nonaqueous processing of silicon-based ceramic materials. The application of steric stabilization to the control and improvement of green processing of nonaqueous silicon slips in pressure consolidation is also demonstrated.

  14. Controlled 3D buckling of silicon nanowires for stretchable electronics.

    PubMed

    Xu, Feng; Lu, Wei; Zhu, Yong

    2011-01-25

    Silicon (Si) nanowire (NW) coils were fabricated on elastomeric substrates by a controlled buckling process. Si NWs were first transferred onto prestrained and ultraviolet/ozone (UVO)-treated poly(dimethylsiloxane) (PDMS) substrates and buckled upon release of the prestrain. Two buckling modes (the in-plane wavy mode and the three-dimensional coiled mode) were found; a transition between them was achieved by controlling the UVO treatment of PDMS. Structural characterization revealed that the NW coils were oval-shaped. The oval-shaped NW coils exhibited very large stretchability up to the failure strain of PDMS (∼104% in our study). Such a large stretchability relies on the effectiveness of the coil shape in mitigating the maximum local strain, with a mechanics that is similar to the motion of a coil spring. Single NW devices based on coiled NWs were demonstrated with a nearly constant electrical response in a large strain range. In addition to the wavy shape, the coil shape represents an effective architecture in accommodating large tension, compression, bending, and twist, which may find important applications for stretchable electronics and other stretchable technologies. PMID:21189041

  15. High current JBS rectifiers and their impact on switching power supplies

    NASA Astrophysics Data System (ADS)

    Baliga, B. J.; Chang, H.-R.; Steigerwald, R. L.

    The junction barrier controlled Schottky (JBS) rectifier is a Schottky rectifier with a p-n junction grid structure integrated into the device structure to improve its reverse blocking characteristics. This paper reports the development of large area (0.5 sq cm), 30 V, JBS rectifiers capable of handling over 25 A of forward current while operating at up to 125 C with good reverse blocking characteristics. Trade-off curves between forward voltage drop and reverse leakage current are introduced to allow optimization of these devices. Evaluation of their impact on low voltage switching power supplies is presented.

  16. Approaching the downsizing limit of silicon for surface-controlled lithium storage.

    PubMed

    Wang, Bin; Li, Xianglong; Luo, Bin; Hao, Long; Zhou, Min; Zhang, Xinghao; Fan, Zhuangjun; Zhi, Linjie

    2015-03-01

    Graphene-sheet-supported uniform ultrasmall (≈3 nm) silicon quantum dots have been successfully synthesized by a simple and effective self-assembly strategy, exhibiting unprecedented fast, surface-controlled lithium-storage behavior and outstanding lithium-storage properties including extraordinary rate capability and remarkable cycling stability, attributable to the intrinsic role of approaching the downsizing limit of silicon. PMID:25581500

  17. ISGV Self-rectifying Turbine Design For Thermoacoustic Application

    NASA Astrophysics Data System (ADS)

    Sammak, Shervin; Asghary, Maryam; Ghorbanian, Kaveh

    2014-11-01

    Thermoacoustic engines produce the acoustic power from wasted heat and then electricity can be generated from acoustic power. Utilizing self-rectifying turbine after a thermoacoustic engine allows for deploying standard generators with high enough rotational speed that remarkably reduce abrasion, size and cost and significantly increase efficiency and controllability in comparison with linear alternators. In this paper, by evaluating all different type of self-rectifying turbine, impulse turbine with self-piched controlled (ISGV) is chosen as the most appropriate type for this application. This kind of turbine is designed in detail for a popular engine, thermoacoustic stirling heat engine (TASHE). In order to validate the design, a full scale size of designed turbine is modeled in ANSYS CFX. As a result, optimum power and efficiency gained based on numerical data.

  18. A boron nitride nanotube peapod thermal rectifier

    NASA Astrophysics Data System (ADS)

    Loh, G. C.; Baillargeat, D.

    2014-06-01

    The precise guidance of heat from one specific location to another is paramount in many industrial and commercial applications, including thermal management and thermoelectric generation. One of the cardinal requirements is a preferential conduction of thermal energy, also known as thermal rectification, in the materials. This study introduces a novel nanomaterial for rectifying heat—the boron nitride nanotube peapod thermal rectifier. Classical non-equilibrium molecular dynamics simulations are performed on this nanomaterial, and interestingly, the strength of the rectification phenomenon is dissimilar at different operating temperatures. This is due to the contingence of the thermal flux on the conductance at the localized region around the scatterer, which varies with temperature. The rectification performance of the peapod rectifier is inherently dependent on its asymmetry. Last but not least, the favourable rectifying direction in the nanomaterial is established.

  19. A boron nitride nanotube peapod thermal rectifier

    SciTech Connect

    Loh, G. C.; Baillargeat, D.

    2014-06-28

    The precise guidance of heat from one specific location to another is paramount in many industrial and commercial applications, including thermal management and thermoelectric generation. One of the cardinal requirements is a preferential conduction of thermal energy, also known as thermal rectification, in the materials. This study introduces a novel nanomaterial for rectifying heat—the boron nitride nanotube peapod thermal rectifier. Classical non-equilibrium molecular dynamics simulations are performed on this nanomaterial, and interestingly, the strength of the rectification phenomenon is dissimilar at different operating temperatures. This is due to the contingence of the thermal flux on the conductance at the localized region around the scatterer, which varies with temperature. The rectification performance of the peapod rectifier is inherently dependent on its asymmetry. Last but not least, the favourable rectifying direction in the nanomaterial is established.

  20. Controlled silica synthesis inspired by diatom silicon biomineralization.

    PubMed

    Vrieling, Engel G; Sun, Qianyao; Beelen, Theo P M; Hazelaar, Sandra; Gieskes, Winfried W C; van Santen, Rutger A; Sommerdijk, Nico A J M

    2005-01-01

    Silica becomes increasingly used in chemical, pharmaceutical, and (nano)technological processes, resulting in an increased demand for well-defined silicas and silica-based materials. The production of highly structured silica from cheap starting materials and under ambient conditions, which is a target for many researchers, is already realized in the formation of diatom biosilica, producing highly hierarchical ordered meso- and macropores silica structures. This notion formed the starting point in our integrative biomolecular and biomimetic study on diatom silicon biomineralization in which we have analyzed silica transformations and structure-direction in polymer-mediated silica syntheses using a combination of (ultra)small-angle X-ray scattering and (cryo)electron microscopy. Using bio-analogous reaction conditions and reagents, such as waterglass and (combinations of) polyethylene oxide (PEO) based polymers, we demonstrate in this review the synthesis of tailor-made mesoporous silicas in which we can, as in biosilica synthesis, control the morphological features of the resulting materials on the nanometer level as well as on the micrometer level. PMID:15762163

  1. Control of carbon balance in a silicon smelting furnace

    DOEpatents

    Dosaj, Vishu D.; Haines, Cathryn M.; May, James B.; Oleson, John D.

    1992-12-29

    The present invention is a process for the carbothermic reduction of silicon dioxide to form elemental silicon. Carbon balance of the process is assessed by measuring the amount of carbon monoxide evolved in offgas exiting the furnace. A ratio of the amount of carbon monoxide evolved and the amount of silicon dioxide added to the furnace is determined. Based on this ratio, the carbon balance of the furnace can be determined and carbon feed can be adjusted to maintain the furnace in carbon balance.

  2. Making silicon hydrophobic: wettability control by two-lengthscale simultaneous patterning with femtosecond laser irradiation

    NASA Astrophysics Data System (ADS)

    Zorba, V.; Persano, L.; Pisignano, D.; Athanassiou, A.; Stratakis, E.; Cingolani, R.; Tzanetakis, P.; Fotakis, C.

    2006-07-01

    We report on the wettability properties of silicon surfaces, simultaneously structured on the micrometre-scale and the nanometre-scale by femtosecond (fs) laser irradiation to render silicon hydrophobic. By varying the laser fluence, it was possible to control the wetting properties of a silicon surface through a systematic and reproducible variation of the surface roughness. In particular, the silicon-water contact angle could be increased from 66° to more than 130°. Such behaviour is described by incomplete liquid penetration within the silicon features, still leaving partially trapped air inside. We also show how controllable design and tailoring of the surface microstructures by wettability gradients can drive the motion of the drop's centre of mass towards a desired direction (even upwards).

  3. All-optical control of light on a silicon chip.

    PubMed

    Almeida, Vilson R; Barrios, Carlos A; Panepucci, Roberto R; Lipson, Michal

    2004-10-28

    Photonic circuits, in which beams of light redirect the flow of other beams of light, are a long-standing goal for developing highly integrated optical communication components. Furthermore, it is highly desirable to use silicon--the dominant material in the microelectronic industry--as the platform for such circuits. Photonic structures that bend, split, couple and filter light have recently been demonstrated in silicon, but the flow of light in these structures is predetermined and cannot be readily modulated during operation. All-optical switches and modulators have been demonstrated with III-V compound semiconductors, but achieving the same in silicon is challenging owing to its relatively weak nonlinear optical properties. Indeed, all-optical switching in silicon has only been achieved by using extremely high powers in large or non-planar structures, where the modulated light is propagating out-of-plane. Such high powers, large dimensions and non-planar geometries are inappropriate for effective on-chip integration. Here we present the experimental demonstration of fast all-optical switching on silicon using highly light-confining structures to enhance the sensitivity of light to small changes in refractive index. The transmission of the structure can be modulated by up to 94% in less than 500 ps using light pulses with energies as low as 25 pJ. These results confirm the recent theoretical prediction of efficient optical switching in silicon using resonant structures. PMID:15510144

  4. Polyamines as gating molecules of inward-rectifier K+ channels.

    PubMed

    Oliver, D; Baukrowitz, T; Fakler, B

    2000-10-01

    Inward-rectifier potassium (Kir) channels comprise a superfamily of potassium (K+) channels with unique structural and functional properties. Expressed in virtually all types of cells they are responsible for setting the resting membrane potential, controlling the excitation threshold and secreting K+ ions. All Kir channels present an inwardly rectifying current-voltage relation, meaning that at any given driving force the inward flow of K+ ions exceeds the outward flow for the opposite driving force. This inward-rectification is due to a voltage-dependent block of the channel pore by intracellular polyamines and magnesium. The present molecular-biophysical understanding of inward-rectification and its physiological consequences is the topic of this review. In addition to polyamines, Kir channels are gated by intracellular protons, G-proteins, ATP and phospholipids depending on the respective Kir subfamily as detailed in the following review articles. PMID:10998040

  5. Sized controlled synthesis, purification, and cell studies with silicon quantum dots.

    PubMed

    Shiohara, Amane; Prabakar, Sujay; Faramus, Angelique; Hsu, Chia-Yen; Lai, Ping-Shan; Northcote, Peter T; Tilley, Richard D

    2011-08-01

    This article describes the size control synthesis of silicon quantum dots with simple microemulsion techniques. The silicon nanocrystals are small enough to be in the strong confinement regime and photoluminesce in the blue region of the visible spectrum and the emission can be tuned by changing the nanocrystal size. The silicon quantum dots were capped with allylamine either a platinum catalyst or UV-radiation. An extensive purification protocol is reported and assessed using (1)H NMR to produce ultra pure silicon quantum dots suitable for biological studies. The highly pure quantum dots were used in cellular uptake experiments and monitored using confocal microscopy. The results showed that the amine terminated silicon nanocrystals accumulated in lysosome but not in nuclei and could be used as bio-markers to monitor cancer cells over long timescales. PMID:21727983

  6. Sized controlled synthesis, purification, and cell studies with silicon quantum dots

    NASA Astrophysics Data System (ADS)

    Shiohara, Amane; Prabakar, Sujay; Faramus, Angelique; Hsu, Chia-Yen; Lai, Ping-Shan; Northcote, Peter T.; Tilley, Richard D.

    2011-08-01

    This article describes the size control synthesis of silicon quantum dots with simple microemulsion techniques. The silicon nanocrystals are small enough to be in the strong confinement regime and photoluminesce in the blue region of the visible spectrum and the emission can be tuned by changing the nanocrystal size. The silicon quantum dots were capped with allylamine either a platinum catalyst or UV-radiation. An extensive purification protocol is reported and assessed using 1H NMR to produce ultra pure silicon quantum dots suitable for biological studies. The highly pure quantum dots were used in cellular uptake experiments and monitored using confocal microscopy. The results showed that the amine terminated silicon nanocrystals accumulated in lysosome but not in nuclei and could be used as bio-markers to monitor cancer cells over long timescales.This article describes the size control synthesis of silicon quantum dots with simple microemulsion techniques. The silicon nanocrystals are small enough to be in the strong confinement regime and photoluminesce in the blue region of the visible spectrum and the emission can be tuned by changing the nanocrystal size. The silicon quantum dots were capped with allylamine either a platinum catalyst or UV-radiation. An extensive purification protocol is reported and assessed using 1H NMR to produce ultra pure silicon quantum dots suitable for biological studies. The highly pure quantum dots were used in cellular uptake experiments and monitored using confocal microscopy. The results showed that the amine terminated silicon nanocrystals accumulated in lysosome but not in nuclei and could be used as bio-markers to monitor cancer cells over long timescales. Electronic supplementary information (ESI) available. See DOI: 10.1039/c1nr10458f

  7. Distributed rectifier loads in electric power systems

    SciTech Connect

    Heydt, G.T.; Grady, W.M.

    1984-09-01

    The level of rectifier and flourescent loads in electric power systems is often significant in localized areas. Typically, the nonlinear loads are distributed over many distribution and subtransmission busses. In this paper, the harmonic signal levels resulting from distributed rectifier loads are examined using a recently reported harmonic power flow study algorithm. Because the algorithm does not rely on superposition or sinusoidal bus voltage assumptions, it may be applied in cases of high harmonic content such as nearresonant conditions. A case history is presented and examination of alternative methods of harmonic attenuation is presented. Also, for six pulse, line commutated rectifiers, the effect of dc circuit load variation and dc circuit inductance on harmonic signal levels is examined.

  8. Modelling and engineering of stress based controlled oxidation effects for silicon nanostructure patterning

    NASA Astrophysics Data System (ADS)

    Han, Xiang-Lei; Larrieu, Guilhem; Krzeminski, Christophe

    2013-12-01

    Silicon nanostructure patterning with tight geometry control is an important challenge at the bottom level. In that context, stress based controlled oxidation appears to be an efficient tool for precise nanofabrication. Here, we investigate the stress-retarded oxidation phenomenon in various silicon nanostructures (nanobeams, nanorings and nanowires) at both the experimental and the theoretical levels. Different silicon nanostructures have been fabricated by a top-down approach. Complex dependence of the stress build-up on the nano-objects dimension, shape and size has been demonstrated experimentally and physically explained by modelling. For the oxidation of a two-dimensional nanostructure (nanobeam), relative independence to size effects has been observed. On the other hand, radial stress increase with geometry downscaling of a one-dimensional nanostructure (nanowire) has been carefully emphasized. The study of shape engineering by retarded oxidation effects for vertical silicon nanowires is finally discussed.

  9. Controls on silicon cycling in Southeast Asian rice production systems

    NASA Astrophysics Data System (ADS)

    Klotzbcher, Thimo; Marxen, Anika; Vetterlein, Doris; Jahn, Reinhold

    2013-04-01

    Recent research suggests that silicon (Si) is beneficial for rice plants, i.e., a sufficient Si supply improves their resistance against pests and pathogens and increases the uptake of essential nutrients. Despite its potential importance for rice yields, cycling of Si in rice production systems is poorly studied. We assess plant-available Si (Sipa; determined using acetate extraction) in topsoils (Ap+Arp horizons) and Si uptake by plants at 70 paddy fields managed by local farmers in contrasting regions of Vietnam and the Philippines. First results show that Sipa contents are considerably larger in Philippine (217 100 mg Sipa kg-1 ) than in Vietnamese (32 19 mg Sipa kg-1) paddy soils. Rice straw from the Philippines contains 8.6 0.9 % Si, straw from Vietnam 5.0 1.2 % Si. Laboratory experiments showed that Si is limiting the growth of rice plants in some of the Vietnamese soils. We assume that differences in geo-/ pedologic conditions between Vietnam and the Philippines explain the data. Large Sipa contents in the Philippine soils are due to recent rock formation by active volcanism, hence, by a large Sipa input due to mineral weathering in recent geologic history. In contrast, parent materials of the Vietnamese paddy soils derive from old and highly weathered land surfaces. Hence, our data suggest that geo-/pedologic conditions are the main control for the availability of Si in paddy soils. Currently, we examine the relevance of agricultural practices for small-scale differences in the availability of Si within regions. Inadequate practices, such as removal of rice straw from the fields, might deplete Sipa in paddy soils causing a decrease in rice yields in some regions of Vietnam. We investigate the role of phytoliths (amorphous Si bodies contained in rice straw) as source of Sipa in paddy soils. Our methods include laboratory experiments and the assessment of turnover times of phytoliths in paddy soils; first results will be presented and discussed at the EGU conference.

  10. Analysis of parametric transformer with rectifier load

    SciTech Connect

    Ichinokura, O.; Jinzenji, T. ); Tajima, K. )

    1993-03-01

    This paper describes a push-pull parametric transformer constructed using a pair of orthogonal-cores. The operating characteristics of the parametric transformer with a rectifier load were analyzed based on SPICE simulations. The analysis results show good agreement with experiment. It was found that the input surge current of the full-wave rectifier circuit with a smoothing capacitor can be compensated by the parametric transformer. Use of the parametric transformer as a power stabilizer is anticipated owing to its various functions such as for voltage regulation and overload protection.

  11. Process to produce silicon carbide fibers using a controlled concentration of boron oxide vapor

    NASA Technical Reports Server (NTRS)

    Barnard, Thomas Duncan (Inventor); Lipowitz, Jonathan (Inventor); Nguyen, Kimmai Thi (Inventor)

    2001-01-01

    A process for producing polycrystalline silicon carbide by heating an amorphous ceramic fiber that contains silicon and carbon in an environment containing boron oxide vapor. The boron oxide vapor is produced in situ by the reaction of a boron containing material such as boron carbide and an oxidizing agent such as carbon dioxide, and the amount of boron oxide vapor can be controlled by varying the amount and rate of addition of the oxidizing agent.

  12. Process to produce silicon carbide fibers using a controlled concentration of boron oxide vapor

    NASA Technical Reports Server (NTRS)

    Barnard, Thomas Duncan (Inventor); Lipowitz, Jonathan (Inventor); Nguyen, Kimmai Thi (Inventor)

    2000-01-01

    A process for producing polycrystalline silicon carbide includes heating an amorphous ceramic fiber that contains silicon and carbon in an environment containing boron oxide vapor. The boron oxide vapor is produced in situ by the reaction of a boron containing material such as boron carbide and an oxidizing agent such as carbon dioxide, and the amount of boron oxide vapor can be controlled by varying the amount and rate of addition of the oxidizing agent.

  13. PWM rectifier with low dc voltage ripple for magnet supply

    SciTech Connect

    Ciscato, D. ); Malesani, L.; Rosetto, L.; Tenti, P. ); Basile, G.L.; Pasti, M. ); Voelker, F. )

    1992-04-01

    PWM bridge rectifiers with GTO switches are considered for application to particle accelerator magnet power supplies, where two-quadrant operation and extremely low dc current ripple are required. Different control strategies, with both preprogrammed and variable switching patterns, are examined and compared in view of optimization of the system performance. In particular, optimum digital PWM, multilevel delta modulation, and hybrid PWM/delta techniques are analyzed. In this paper the validity of the control methods is verified by simulation and experimental tests on a 60-kW prototype.

  14. Novel plasma control method in PECVD for preparing microcrystalline silicon

    SciTech Connect

    Nishimiya, T.; Kondo, M.; Matsuda, A.

    1997-07-01

    A novel plasma enhanced vapor deposition (PECVD) technique employing biased wall (BW) method has been developed for the enhanced growth rate of the hydrogenated microcrystalline silicon ({micro}c-Si:H) films. Using this method, the authors have achieved a growth rate of more than 6{angstrom}/sec for the formation of {micro}c-Si:H having an average grain size of 200{angstrom} at 350 C.

  15. Engineered Asymmetric Composite Membranes with Rectifying Properties.

    PubMed

    Wen, Liping; Xiao, Kai; Sainath, Annadanam V Sesha; Komura, Motonori; Kong, Xiang-Yu; Xie, Ganhua; Zhang, Zhen; Tian, Ye; Iyoda, Tomokazu; Jiang, Lei

    2016-01-01

    Asymmetric composite membranes with rectifying properties are developed by grafting pH-stimulus-responsive materials onto the top layer of the composite structure, which is prepared by two novel block copolymers using a phase-separation technique. This engineered asymmetric composite membrane shows potential applications in sensors, filtration, and nanofluidic devices. PMID:26630640

  16. RF sputtering for controlling dihydride and monohydride bond densities in amorphous silicon hydride

    DOEpatents

    Jeffery, F.R.; Shanks, H.R.

    1980-08-26

    A process is described for controlling the dihydride and monohydride bond densities in hydrogenated amorphous silicone produced by reactive rf sputtering of an amorphous silicon target. There is provided a chamber with an amorphous silicon target and a substrate therein with the substrate and the target positioned such that when rf power is applied to the target the substrate is in contact with the sputtering plasma produced thereby. Hydrogen and argon are fed to the chamber and the pressure is reduced in the chamber to a value sufficient to maintain a sputtering plasma therein, and then rf power is applied to the silicon target to provide a power density in the range of from about 7 watts per square inch to about 22 watts per square inch to sputter an amorphous solicone hydride onto the substrate, the dihydride bond density decreasing with an increase in the rf power density. Substantially pure monohydride films may be produced.

  17. Amorphous silicon Schottky barrier solar cells incorporating a thin insulating layer and a thin doped layer

    DOEpatents

    Carlson, David E.

    1980-01-01

    Amorphous silicon Schottky barrier solar cells which incorporate a thin insulating layer and a thin doped layer adjacent to the junction forming metal layer exhibit increased open circuit voltages compared to standard rectifying junction metal devices, i.e., Schottky barrier devices, and rectifying junction metal insulating silicon devices, i.e., MIS devices.

  18. Thermal system design and modeling of meniscus controlled silicon growth process for solar applications

    NASA Astrophysics Data System (ADS)

    Wang, Chenlei

    The direct conversion of solar radiation to electricity by photovoltaics has a number of significant advantages as an electricity generator. That is, solar photovoltaic conversion systems tap an inexhaustible resource which is free of charge and available anywhere in the world. Roofing tile photovoltaic generation, for example, saves excess thermal heat and preserves the local heat balance. This means that a considerable reduction of thermal pollution in densely populated city areas can be attained. A semiconductor can only convert photons with the energy of the band gap with good efficiency. It is known that silicon is not at the maximum efficiency but relatively close to it. There are several main parts for the photovoltaic materials, which include, single- and poly-crystalline silicon, ribbon silicon, crystalline thin-film silicon, amorphous silicon, copper indium diselenide and related compounds, cadmium telluride, et al. In this dissertation, we focus on melt growth of the single- and poly-crystalline silicon manufactured by Czochralski (Cz) crystal growth process, and ribbon silicon produced by the edge-defined film-fed growth (EFG) process. These two methods are the most commonly used techniques for growing photovoltaic semiconductors. For each crystal growth process, we introduce the growth mechanism, growth system design, general application, and progress in the numerical simulation. Simulation results are shown for both Czochralski and EFG systems including temperature distribution of the growth system, velocity field inside the silicon melt and electromagnetic field for the EFG growth system. Magnetic field is applied on Cz system to reduce the melt convection inside crucible and this has been simulated in our numerical model. Parametric studies are performed through numerical and analytical models to investigate the relationship between heater power levels and solidification interface movement and shape. An inverse problem control scheme is developed to control the solidification interface of Cz system by adjusting heater powers. For the EFG system, parametric studies are performed to discuss the effect of several growth parameters including window opening size, argon gas flow rate and growth thermal environment on the temperature distribution, silicon tube thickness and pulling rate. Two local models are developed and integrated with the global model to investigate the detailed transport phenomena in a small region around the solidification interface including silicon crystal, silicon melt, free surface, liquid-solid interface and graphite die design. Different convection forms are taken into consideration.

  19. Advanced process control and novel test methods for PVD silicon and elastomeric silicone coatings utilized on ion implant disks, heatsinks and selected platens

    SciTech Connect

    Springer, J.; Allen, B.; Wriggins, W.; Kuzbyt, R.; Sinclair, R.

    2012-11-06

    Coatings play multiple key roles in the proper functioning of mature and current ion implanters. Batch and serial implanters require strategic control of elemental and particulate contamination which often includes scrutiny of the silicon surface coatings encountering direct beam contact. Elastomeric Silicone Coatings must accommodate wafer loading and unloading as well as direct backside contact during implant plus must maintain rigid elemental and particulate specifications. The semiconductor industry has had a significant and continuous effort to obtain ultra-pure silicon coatings with sustained process performance and long life. Low particles and reduced elemental levels for silicon coatings are a major requirement for process engineers, OEM manufacturers, and second source suppliers. Relevant data will be presented. Some emphasis and detail will be placed on the structure and characteristics of a relatively new PVD Silicon Coating process that is very dense and homogeneous. Wear rate under typical ion beam test conditions will be discussed. The PVD Silicon Coating that will be presented here is used on disk shields, wafer handling fingers/fences, exclusion zones of heat sinks, beam dumps and other beamline components. Older, legacy implanters can now provide extended process capability using this new generation PVD silicon - even on implanter systems that were shipped long before the advent of silicon coating for contamination control. Low particles and reduced elemental levels are critical performance criteria for the silicone elastomers used on disk heatsinks and serial implanter platens. Novel evaluation techniques and custom engineered tools are used to investigate the surface interaction characteristics of multiple Elastomeric Silicone Coatings currently in use by the industry - specifically, friction and perpendicular stiction. These parameters are presented as methods to investigate the critical wafer load and unload function. Unique tools and test methods have been developed that deliver accurate and repeatable data, which will be described.

  20. An evaluation system for experimental silicon and silicon carbide super gate turn off thyristors.

    PubMed

    Bayne, Stephen; Lacouture, Shelby; Lawson, Kevin; Giesselmann, Michael; Scozzie, Charles J; O'Brien, Heather; Ogunniyi, Aderinto A

    2014-07-01

    This paper describes the design and implementation of a small-scale pulsed power system specifically intended to evaluate the suitability of experimental silicon and silicon carbide high power Super Gate Turn Off thyristors for high action (500 A(2) s and above) pulsed power applications where energy is extracted from a storage element in a rapid and controlled manner. To this end, six of each type of device was placed in a controlled three phase rectifier circuit which was in turn connected to an aircraft ground power motor-generator set and subjected to testing protocols with varying power levels, while parameters such as offset firing angle were varied. PMID:25085173

  1. Etching anisotropy mechanisms lead to morphology-controlled silicon nanoporous structures by metal assisted chemical etching.

    PubMed

    Jiang, Bing; Li, Meicheng; Liang, Yu; Bai, Yang; Song, Dandan; Li, Yingfeng; Luo, Jian

    2016-01-28

    The etching anisotropy induced by the morphology and rotation of silver particles controls the morphology of silicon nanoporous structures, through various underlying complex etching mechanisms. The level of etching anisotropy can be modulated by controlling the morphology of the silver catalyst to obtain silicon nanoporous structures with straight pores, cone-shaped pores and pyramid-shaped pores. In addition, the structures with helical pores are obtained by taking advantage of the special anisotropic etching, which is induced by the rotation and revolution of silver particles during the etching process. An investigation of the etching anisotropy during metal assisted chemical etching will promote a deep understanding of the chemical etching mechanism of silicon, and provide a feasible approach to fabricate Si nanoporous structures with special morphologies. PMID:26785718

  2. Flow restrictor silicon membrane microvalve actuated by optically controlled paraffin phase transition

    NASA Astrophysics Data System (ADS)

    Kolari, K.; Havia, T.; Stuns, I.; Hjort, K.

    2014-08-01

    Restrictor valves allow proportional control of fluid flow but are rarely integrated in microfluidic systems. In this study, an optically actuated silicon membrane restrictor microvalve is demonstrated. Its actuation is based on the phase transition of paraffin, using a paraffin wax mixed with a suitable concentration of optically absorbing nanographite particles. Backing up the membrane with oil (the melted paraffin) allows for a compliant yet strong contact to the valve seat, which enables handling of high pressures. At flow rates up to 30?L min-1 and at a pressure of 2 bars, the valve can successfully be closed and control the flow level by restriction. The use of this paraffin composite as an adhesive layer sandwiched between the silicon valve and glass eases fabrication. This type of restrictor valve is best suited for high pressure, low volume flow silicon-based nanofluidic systems.

  3. Etching anisotropy mechanisms lead to morphology-controlled silicon nanoporous structures by metal assisted chemical etching

    NASA Astrophysics Data System (ADS)

    Jiang, Bing; Li, Meicheng; Liang, Yu; Bai, Yang; Song, Dandan; Li, Yingfeng; Luo, Jian

    2016-01-01

    The etching anisotropy induced by the morphology and rotation of silver particles controls the morphology of silicon nanoporous structures, through various underlying complex etching mechanisms. The level of etching anisotropy can be modulated by controlling the morphology of the silver catalyst to obtain silicon nanoporous structures with straight pores, cone-shaped pores and pyramid-shaped pores. In addition, the structures with helical pores are obtained by taking advantage of the special anisotropic etching, which is induced by the rotation and revolution of silver particles during the etching process. An investigation of the etching anisotropy during metal assisted chemical etching will promote a deep understanding of the chemical etching mechanism of silicon, and provide a feasible approach to fabricate Si nanoporous structures with special morphologies.

  4. An optical leaky wave antenna with silicon perturbations for electronic control

    NASA Astrophysics Data System (ADS)

    Campione, Salvatore; Song, Qi; Boyraz, Ozdal; Capolino, Filippo

    2011-10-01

    An optical leaky wave antenna (OLWA) is a device that radiates a light wave into the surrounding space from a leaky wave (LW) guided mode or receives optical power from the surrounding space into a guided optical mode. In this work, we propose and provide a 3D analysis of a novel CMOS compatible OLWA made of a silicon nitride (Si3N4) waveguide comprising periodic silicon perturbations which allow electronic tuning capability. The analysis presented here includes the effect of the number of semiconductor perturbations, the antenna radiation pattern and directivity. We show that the number of the silicon perturbations has to be large to provide a long radiating section required to achieve radiation with high directivity. In other words, the proposed structure allows for a very narrow-beam radiation. Preliminary results are confirmed by exploiting leaky wave and antenna array factor theory, as well as verified by means of two full-wave simulators (HFSS and COMSOL). Our purpose is to ultimately use PIN junctions as building blocks for each silicon implantation for the electronic control of the radiation. In particular, the electronic tunability of the optical parameters of silicon (such as refractive index and absorption coefficient) via current injection renders itself the ideal platform for optical antennas that can facilitate electronic beam control, and boost the efficiency of optoelectronic devices such as light-emitting diodes, lasers and solar cells, and bio-chemical sensors.

  5. Controlling Dopant Profiles in Hyperdoped Silicon by Modifying Dopant Evaporation Rates During Pulsed Laser Melting

    SciTech Connect

    Recht, D.; Sullivan, J. T.; Reedy, R.; Buonassisi, T.; Aziz, M. J.

    2012-03-12

    We describe a method to control the sub-surface dopant profile in 'hyperdoped' silicon fabricated by ion implantation and pulsed laser melting. Dipping silicon ion implanted with sulfur into hydrofluoric acid prior to nanosecond pulsed laser melting leads to a tenfold increase in the rate of sulfur evaporation from the surface of the melt. This results in an 80% reduction of the near-surface dopant concentration, effectively embedding the hyperdoped region in a layer up to 180 nm beneath the surface. This method should facilitate the development of blocked impurity band devices.

  6. Identification and control of the origin of photoluminescence from silicon quantum dots.

    PubMed

    Hao, H L; Shen, W Z

    2008-11-12

    We present a detailed investigation into the origin of photoluminescence (PL) from silicon quantum dots in hydrogenated amorphous silicon nitride annealed in oxygen ambient. On the basis of structural characterization, temperature-dependent PL, time-resolved PL, and PL excitation spectra, we identify that the luminescence of the oxidized samples originates from the localized exciton radiative recombination via the surface states related to Si-N or Si-O-Si bonds. In combination with the results due to annealing in argon and hydrogen environments, we have further shown that control of the origin of the PL can be realized by modifying the radiative defect density through annealing treatment. PMID:21832793

  7. Controlled release from a composite silicone/hydrogel membrane.

    PubMed

    Hu, Z; Wang, C; Nelson, K D; Eberhart, R C

    2000-01-01

    To enhance the drug uptake and release capacity of silicone rubber (SR), N-isopropylacrylamide (NIPA) hydrogel particles have been incorporated into a SR membrane. The NIPA particles were thoroughly blended with uncured SR with a certain ratio at room temperature. The mixture was then cast in a Petri dish to 1 mm thickness and cured 10 hours at 90 degrees C. The SR/NIPA composite gel can absorb water approximately equal to its dry weight. Brilliant blue, used as a mock drug, was loaded into the composite gel. Drug release increased exponentially to a final value that is temperature dependent: low at T> =34 degrees C, and high at T< 34 degrees C. This finding is because the hydrophobicity of NIPA changes with temperature. Pulsed release in response to temperature switching between 20 and 39 degrees C has been achieved. Drug uptake and release capability strongly depends upon the structure of the composite gel. The optimal range of NIPA composition is between 75 and 87% by volume. In the cited range, the NIPA particles form an interconnected network that provides a channel for diffusion of drug solution. The SR/NIPA composite gel has promising attributes as a wound dressing and other uses. PMID:10926140

  8. Multi-crystalline silicon solidification under controlled forced convection

    NASA Astrophysics Data System (ADS)

    Cablea, M.; Zaidat, K.; Gagnoud, A.; Nouri, A.; Chichignoud, G.; Delannoy, Y.

    2015-05-01

    Multi-crystalline silicon wafers have a lower production cost compared to mono-crystalline wafers. This comes at the price of reduced quality in terms of electrical properties and as a result the solar cells made from such materials have a reduced efficiency. The presence of different impurities in the bulk material plays an important role during the solidification process. The impurities are related to different defects (dislocations, grain boundaries) encountered in multi-crystalline wafers. Applying an alternative magnetic field during the solidification process has various benefits. Impurities concentration in the final ingot could be reduced, especially metallic species, due to a convective term added in the liquid that reduces the concentration of impurities in the solute boundary layer. Another aspect is the solidification interface shape that is influenced by the electromagnetic stirring. A vertical Bridgman type furnace was used in order to study the solidification process of Si under the influence of a travelling magnetic field able to induce a convective flow in the liquid. The furnace was equipped with a Bitter type three-phase electromagnet that provides the required magnetic field. A numerical model of the furnace was developed in ANSYS Fluent commercial software. This paper presents experimental and numerical results of this approach, where interface markings were performed.

  9. Coherent control of single spins in silicon carbide at room temperature

    NASA Astrophysics Data System (ADS)

    Widmann, Matthias; Lee, Sang-Yun; Rendler, Torsten; Son, Nguyen Tien; Fedder, Helmut; Paik, Seoyoung; Yang, Li-Ping; Zhao, Nan; Yang, Sen; Booker, Ian; Denisenko, Andrej; Jamali, Mohammad; Momenzadeh, S. Ali; Gerhardt, Ilja; Ohshima, Takeshi; Gali, Adam; Janzén, Erik; Wrachtrup, Jörg

    2015-02-01

    Spins in solids are cornerstone elements of quantum spintronics. Leading contenders such as defects in diamond or individual phosphorus dopants in silicon have shown spectacular progress, but either lack established nanotechnology or an efficient spin/photon interface. Silicon carbide (SiC) combines the strength of both systems: it has a large bandgap with deep defects and benefits from mature fabrication techniques. Here, we report the characterization of photoluminescence and optical spin polarization from single silicon vacancies in SiC, and demonstrate that single spins can be addressed at room temperature. We show coherent control of a single defect spin and find long spin coherence times under ambient conditions. Our study provides evidence that SiC is a promising system for atomic-scale spintronics and quantum technology.

  10. Coherent control of single spins in silicon carbide at room temperature.

    PubMed

    Widmann, Matthias; Lee, Sang-Yun; Rendler, Torsten; Son, Nguyen Tien; Fedder, Helmut; Paik, Seoyoung; Yang, Li-Ping; Zhao, Nan; Yang, Sen; Booker, Ian; Denisenko, Andrej; Jamali, Mohammad; Momenzadeh, S Ali; Gerhardt, Ilja; Ohshima, Takeshi; Gali, Adam; Janzén, Erik; Wrachtrup, Jörg

    2015-02-01

    Spins in solids are cornerstone elements of quantum spintronics. Leading contenders such as defects in diamond or individual phosphorus dopants in silicon have shown spectacular progress, but either lack established nanotechnology or an efficient spin/photon interface. Silicon carbide (SiC) combines the strength of both systems: it has a large bandgap with deep defects and benefits from mature fabrication techniques. Here, we report the characterization of photoluminescence and optical spin polarization from single silicon vacancies in SiC, and demonstrate that single spins can be addressed at room temperature. We show coherent control of a single defect spin and find long spin coherence times under ambient conditions. Our study provides evidence that SiC is a promising system for atomic-scale spintronics and quantum technology. PMID:25437256

  11. Controlled shallow single-ion implantation in silicon using an active substrate for sub-20-keV ions

    NASA Astrophysics Data System (ADS)

    Jamieson, D. N.; Yang, C.; Hopf, T.; Hearne, S. M.; Pakes, C. I.; Prawer, S.; Mitic, M.; Gauja, E.; Andresen, S. E.; Hudson, F. E.; Dzurak, A. S.; Clark, R. G.

    2005-05-01

    We demonstrate a method for the controlled implantation of single ions into a silicon substrate with energy of sub-20-keV. The method is based on the collection of electron-hole pairs generated in the substrate by the impact of a single ion. We have used the method to implant single 14-keV P31 ions through nanoscale masks into silicon as a route to the fabrication of devices based on single donors in silicon.

  12. Three phase six-switch PWM buck rectifier with power factor improvement

    NASA Astrophysics Data System (ADS)

    Zafarullah Khan, M.; Mohsin Naveed, M.; Akbar Hussain, D. M.

    2013-06-01

    Conventional Phase Controlled Rectifier injects low order current harmonics into the AC mains. Large size filtering components are required to attenuate these harmonics. In this paper, three phase six-switch PWM buck rectifier is presented which operates at nearly unity power factor and provides variable output voltage. Small size energy storing components are required depending upon switching frequency. MATLAB simulation is performed and modified Sinusoidal Pulse Width Modulation (SPWM) switching technique is used in 3kW prototype converter to demonstrate low input current THD, nearly unity displacement factor, well regulated output voltage and reduced switching losses compared to conventional SPWM.

  13. Energy-harvesting shock absorber with a mechanical motion rectifier

    NASA Astrophysics Data System (ADS)

    Li, Zhongjie; Zuo, Lei; Kuang, Jian; Luhrs, George

    2013-02-01

    Energy-harvesting shock absorbers are able to recover the energy otherwise dissipated in the suspension vibration while simultaneously suppressing the vibration induced by road roughness. They can work as a controllable damper as well as an energy generator. An innovative design of regenerative shock absorbers is proposed in this paper, with the advantage of significantly improving the energy harvesting efficiency and reducing the impact forces caused by oscillation. The key component is a unique motion mechanism, which we called ‘mechanical motion rectifier (MMR)’, to convert the oscillatory vibration into unidirectional rotation of the generator. An implementation of a MMR-based harvester with high compactness is introduced and prototyped. A dynamic model is created to analyze the general properties of the motion rectifier by making an analogy between mechanical systems and electrical circuits. The model is capable of analyzing electrical and mechanical components at the same time. Both simulation and experiments are carried out to verify the modeling and the advantages. The prototype achieved over 60% efficiency at high frequency, much better than conventional regenerative shock absorbers in oscillatory motion. Furthermore, road tests are done to demonstrate the feasibility of the MMR shock absorber, in which more than 15 Watts of electricity is harvested while driving at 15 mph on a smooth paved road. The MMR-based design can also be used for other applications of vibration energy harvesting, such as from tall buildings or long bridges.

  14. Silicon-Germanium Voltage-Controlled Oscillator at 105 GHz

    NASA Technical Reports Server (NTRS)

    Wong, Alden; Larocca, Tim; Chang, M. Frank; Samoska, Lorene A.

    2011-01-01

    A group at UCLA, in collaboration with the Jet Propulsion Laboratory, has designed a voltage-controlled oscillator (VCO) created specifically for a compact, integrated, electronically tunable frequency generator useable for submillimeter- wave science instruments operating in extreme cold environments.

  15. Controlled Fluxes of Silicon Nanoparticles By Extraction from a Pulsed RF Plasma

    NASA Astrophysics Data System (ADS)

    Girshick, Steven; Larriba-Andaluz, Carlos

    2015-09-01

    Deposition of silicon nanoparticles onto substrates may be a means of growing monocrystalline silicon films at low substrate temperature if the nanoparticles' impact energy and size can be controlled to provide melting or amorphization of the nanoparticle without damaging the underlying film. In order to explore conditions that could produce such controlled fluxes of nanoparticles we numerically model a pulsed RF argon-silane plasma, with a positive DC bias applied during the afterglow phase of each pulse so as to extract and accelerate negatively charged silicon particles. Operating parameters studied include pulse on time, pulse off time, DC bias voltage, RF voltage and pressure. This set of parameters is tested to find conditions under which one can achieve a periodic steady state with repeatable pulse-to-pulse conditions that maximize silicon film growth rates while maintaining nanoparticle impact energies in the range 0.5-2.0 eV/atom. We utilize a previously developed 1-D dusty plasma numerical model, modified to consider pulsing and applied substrate bias. This model self-consistently solves for the coupled behavior of plasma, chemistry, and aerosol. Results show that it is possible by this method to produce nanoparticle fluxes that are tailored with respect to their distribution of impact energies and mass deposition rates. Partially supported by US Dept. of Energy Office of Fusion Energy Science (DE-SC0001939), US National Science Foundation (CHE-124752), and Minnesota Supercomputing Institute.

  16. Development of high temperature gallium phosphide rectifiers

    NASA Technical Reports Server (NTRS)

    Craford, M. G.; Keune, D. L.

    1972-01-01

    Large area high performance, GaP rectifiers were fabricated by means of Zn diffusion into vapor phase epitaxial GaP. Devices with an active area of 0.01 sq cm typically exhibit forward voltages of 3 volts for a bias current of 1 ampere and have reverse breakdown voltages of 300 volts for temperatures from 27 C to 400 C. Typical device reverse saturation current at a reverse bias of 150 volts is less than 10 to the minus 9th power amp at 27 C and less than 0.000050 amp at 400 C.

  17. High Voltage GaN Schottky Rectifiers

    SciTech Connect

    CAO,X.A.; CHO,H.; CHU,S.N.G.; CHUO,C.-C.; CHYI,J.-I.; DANG,G.T.; HAN,JUNG; LEE,C.-M.; PEARTON,S.J.; REN,F.; WILSON,R.G.; ZHANG,A.P.

    1999-10-25

    Mesa and planar GaN Schottky diode rectifiers with reverse breakdown voltages (V{sub RB}) up to 550V and >2000V, respectively, have been fabricated. The on-state resistance, R{sub ON}, was 6m{Omega}{center_dot} cm{sup 2} and 0.8{Omega}cm{sup 2}, respectively, producing figure-of-merit values for (V{sub RB}){sup 2}/R{sub ON} in the range 5-48 MW{center_dot}cm{sup -2}. At low biases the reverse leakage current was proportional to the size of the rectifying contact perimeter, while at high biases the current was proportional to the area of this contact. These results suggest that at low reverse biases, the leakage is dominated by the surface component, while at higher biases the bulk component dominates. On-state voltages were 3.5V for the 550V diodes and {ge}15 for the 2kV diodes. Reverse recovery times were <0.2{micro}sec for devices switched from a forward current density of {approx}500A{center_dot}cm{sup -2} to a reverse bias of 100V.

  18. Controlling magnetic and electric dipole modes in hollow silicon nanocylinders.

    PubMed

    van de Haar, Marie Anne; van de Groep, Jorik; Brenny, Benjamin J M; Polman, Albert

    2016-02-01

    We propose a dielectric nanoresonator geometry consisting of hollow dielectric nanocylinders which support geometrical resonances. We fabricate such hollow Si particles with an outer diameter of 108-251 nm on a Si substrate, and determine their resonant modes with cathodo-luminescence (CL) spectroscopy and optical dark-field (DF) scattering measurements. The scattering behavior is numerically investigated in a systematic fashion as a function of wavelength and particle geometry. We find that the additional design parameter as a result of the introduction of a center gap can be used to control the relative spectral spacing of the resonant modes, which will enable additional control over the angular radiation pattern of the scatterers. Furthermore, the gap offers direct access to the enhanced magnetic dipole modal field in the center of the particle. PMID:26906780

  19. Control of silicon oxynitrides refractive index by reactive-assisted ion beam sputter deposition

    NASA Astrophysics Data System (ADS)

    Ida, Michel; Chaton, Patrick; Rafin, B.

    1994-11-01

    This paper presents the properties of silicon oxynitrides obtained by reactive ion beam sputter deposition: Dual Ion Beam System. Control of refractive index was achieved by adjusting the process parameters as ion beam current, ion beam energy and reactive gas partial pressure of oxygen and nitrogen. The main difficulty was to achieve stoichiometric nitride, it has been shown that energetic ionized nitrogen was needed to obtain silicon nitride. The major parameter, to obtain variable compositions between silica and silicon nitride, was the oxygen partial pressure with a fixed nitrogen partial pressure. Optical constants in the visible range, refractive index and extinction coefficient, have been measured by spectrophotometry and spectroscopic ellipsometry. Stoichiometry, contamination and packing density have been measured by Rutherford Backscattering and Nuclear Reaction Analysis. The correlation between the film composition and optical constants is shown. Various test results indicate that silicon oxynitrides obtained by reactive assisted ion beam sputtering are high quality optical materials. These films are homogeneous isotropic, with a high packing density. The extinction coefficient is in the order of 10-4 after 300 degree(s)C annealing. All values of refractive index between 1.49 and 2.1 can be chosen.

  20. Quantum entanglement and spin control in silicon nanocrystal.

    PubMed

    Berec, Vesna

    2012-01-01

    Selective coherence control and electrically mediated exchange coupling of single electron spin between triplet and singlet states using numerically derived optimal control of proton pulses is demonstrated. We obtained spatial confinement below size of the Bohr radius for proton spin chain FWHM. Precise manipulation of individual spins and polarization of electron spin states are analyzed via proton induced emission and controlled population of energy shells in pure (29)Si nanocrystal. Entangled quantum states of channeled proton trajectories are mapped in transverse and angular phase space of (29)Si <100> axial channel alignment in order to avoid transversal excitations. Proton density and proton energy as impact parameter functions are characterized in single particle density matrix via discretization of diagonal and nearest off-diagonal elements. We combined high field and low densities (1 MeV/92 nm) to create inseparable quantum state by superimposing the hyperpolarizationed proton spin chain with electron spin of (29)Si. Quantum discretization of density of states (DOS) was performed by the Monte Carlo simulation method using numerical solutions of proton equations of motion. Distribution of gaussian coherent states is obtained by continuous modulation of individual spin phase and amplitude. Obtained results allow precise engineering and faithful mapping of spin states. This would provide the effective quantum key distribution (QKD) and transmission of quantum information over remote distances between quantum memory centers for scalable quantum communication network. Furthermore, obtained results give insights in application of channeled protons subatomic microscopy as a complete versatile scanning-probe system capable of both quantum engineering of charged particle states and characterization of quantum states below diffraction limit linear and in-depth resolution.PACS NUMBERS: 03.65.Ud, 03.67.Bg, 61.85.+p, 67.30.hj. PMID:23028884

  1. Quantum Entanglement and Spin Control in Silicon Nanocrystal

    PubMed Central

    Berec, Vesna

    2012-01-01

    Selective coherence control and electrically mediated exchange coupling of single electron spin between triplet and singlet states using numerically derived optimal control of proton pulses is demonstrated. We obtained spatial confinement below size of the Bohr radius for proton spin chain FWHM. Precise manipulation of individual spins and polarization of electron spin states are analyzed via proton induced emission and controlled population of energy shells in pure 29Si nanocrystal. Entangled quantum states of channeled proton trajectories are mapped in transverse and angular phase space of 29Si axial channel alignment in order to avoid transversal excitations. Proton density and proton energy as impact parameter functions are characterized in single particle density matrix via discretization of diagonal and nearest off-diagonal elements. We combined high field and low densities (1 MeV/92 nm) to create inseparable quantum state by superimposing the hyperpolarizationed proton spin chain with electron spin of 29Si. Quantum discretization of density of states (DOS) was performed by the Monte Carlo simulation method using numerical solutions of proton equations of motion. Distribution of gaussian coherent states is obtained by continuous modulation of individual spin phase and amplitude. Obtained results allow precise engineering and faithful mapping of spin states. This would provide the effective quantum key distribution (QKD) and transmission of quantum information over remote distances between quantum memory centers for scalable quantum communication network. Furthermore, obtained results give insights in application of channeled protons subatomic microscopy as a complete versatile scanning-probe system capable of both quantum engineering of charged particle states and characterization of quantum states below diffraction limit linear and in-depth resolution. PACS numbers: 03.65.Ud, 03.67.Bg, 61.85.+p, 67.30.hj PMID:23028884

  2. Coherent control of single spins in a silicon carbide pn junction device at room temperature

    NASA Astrophysics Data System (ADS)

    Lee, Sang-Yun; Widmann, Matthias; Booker, Ian; Niethammer, Matthias; Ohshima, Takeshi; Gali, Adam; Son, Nguyen T.; Janzén, Erik; Wrachtrup, Joerg

    Spins in single defects have been studied for quantum information science and quantum metrology. It has been proven that spins of the single nitrogen-vacancy (NV) centers in diamond can be used as a quantum bit, and a single spin sensor operating at ambient conditions. Recently, there has been a growing interest in a new material in which color centers similar to NV centers can be created and whose electrical properties can also be well controlled, thus existing electronic devices can easily be adapted as a platform for quantum applications. We recently reported that single spins of negatively charged silicon vacancies in SiC can be coherently controlled and long-lived at room temperature. As a next step, we isolated single silicon vacancies in a SiC pn junction device and investigated how the change in Fermi level, induced by applying bias, alters the charge state of silicon vacancies, thus affects the spin state control. This study will allow us to envision quantum applications based on single defects incorporated in modern electronic devices.

  3. A function of delayed rectifier potassium channels in glial cells: maintenance of an auxiliary membrane potential under pathological conditions.

    PubMed

    Pannicke, T; Faude, F; Reichenbach, A; Reichelt, W

    2000-04-17

    Müller glial cells from human and guinea-pig retinae were investigated using the whole-cell patch-clamp technique. Human Müller cells from eyes with different diseases were characterized by diminished inwardly-rectifying K(+) currents. A comparable reduction of these currents was achieved in guinea pig Müller cells by treatment with iodoacetate to generate ischemia-like conditions. Consequently, the membrane potentials were reduced significantly in both diseased human and iodoacetate-treated guinea-pig Müller cells as compared to normal controls. However, the potentials were still clearly negative. Delayed rectifier currents could still be recorded under these conditions. Application of quinine blocked the delayed rectifier K(+) channels, and resulted in a total breakdown of the membrane potentials. Thus, it becomes apparent that the glial delayed rectifier K(+) channels are necessary to maintain an 'auxiliary' membrane potential under certain pathological conditions that are characterized by an almost total loss of inward rectifier conductance. Therefore, the delayed rectifier K(+) channels of glial cells may become crucial for the support of basic glial functions. PMID:10799684

  4. Formation of size controlled silicon nanocrystals in nitrogen free silicon dioxide matrix prepared by plasma enhanced chemical vapor deposition

    SciTech Connect

    Laube, J. Gutsch, S.; Hiller, D.; Zacharias, M.; Bruns, M.; Kübel, C.; Weiss, C.

    2014-12-14

    This paper reports the growth of silicon nanocrystals (SiNCs) from SiH4–O{sub 2} plasma chemistry. The formation of an oxynitride was avoided by using O{sub 2} instead of the widely used N{sub 2}O as precursor. X-ray photoelectron spectroscopy is used to prove the absence of nitrogen in the layers and determine the film stoichiometry. It is shown that the Si rich film growth is achieved via non-equilibrium deposition that resembles a interphase clusters mixture model. Photoluminescence and Fourier transformed infrared spectroscopy are used to monitor the formation process of the SiNCs, to reveal that the phase separation is completed at lower temperatures as for SiNCs based on oxynitrides. Additionally, transmission electron microscopy proves that the SiNC sizes are well controllable by superlattice configuration, and as a result, the optical emission band of the Si nanocrystal can be tuned over a wide range.

  5. A molecular half-wave rectifier.

    PubMed

    Nijhuis, Christian A; Reus, William F; Siegel, Adam C; Whitesides, George M

    2011-10-01

    This paper describes the performance of junctions based on self-assembled monolayers (SAMs) as the functional element of a half-wave rectifier (a simple circuit that converts, or rectifies, an alternating current (AC) signal to a direct current (DC) signal). Junctions with SAMs of 11-(ferrocenyl)-1-undecanethiol or 11-(biferrocenyl)-1-undecanethiol on ultraflat, template-stripped Ag (Ag(TS)) bottom electrodes, and contacted by top electrodes of eutectic indium-gallium (EGaIn), rectified AC signals, while similar junctions based on SAMs of 1-undecanethiol-SAMs lacking the ferrocenyl terminal group-did not. SAMs in these AC circuits (operating at 50 Hz) remain stable over a larger window of applied bias than in DC circuits. AC measurements, therefore, can investigate charge transport in SAM-based junctions at magnitudes of bias inaccessible to DC measurements. For junctions with SAMs of alkanethiols, combining the results from AC and DC measurements identifies two regimes of bias with different mechanisms of charge transport: (i) low bias (|V| < 1.3 V), at which direct tunneling dominates, and (ii) high bias (|V| > 1.3 V), at which Fowler-Nordheim (FN) tunneling dominates. For junctions with SAMs terminated by Fc moieties, the transition to FN tunneling occurs at |V| ≈ 2.0 V. Furthermore, at sufficient forward bias (V > 0.5 V), hopping makes a significant contribution to charge transport and occurs in series with direct tunneling (V ≲ 2.0 V) until FN tunneling activates (V ≳ 2.0 V). Thus, for Fc-terminated SAMs at forward bias, three regimes are apparent: (i) direct tunneling (V = 0-0.5 V), (ii) hopping plus direct tunneling (V ≈ 0.5-2.0 V), and (iii) FN tunneling (V ≳ 2.0 V). Since hopping does not occur at reverse bias, only two regimes are present over the measured range of reverse bias. This difference in the mechanisms of charge transport at forward and reverse bias for junctions with Fc moieties resulted in large rectification ratios (R > 100) and enabled half-wave rectification. PMID:21842878

  6. Inward rectifier current noise in frog skeletal muscle.

    PubMed Central

    DeCoursey, T E; Dempster, J; Hutter, O F

    1984-01-01

    Inwardly rectifying K+ currents were studied in cut muscle fibres from frogs using the Vaseline-gap voltage-clamp method. Both faces of the membrane were exposed to 120 mM-K+ methylsulphate solution. At small negative potentials, -10 and -21 mV, the current noise spectrum, after subtraction of a control spectrum at the zero current potential, could be fitted by a Lorentzian spectral component, usually with an additional 1/f component, where f is the frequency. At more negative potentials the 1/f component predominated. The zero frequency amplitude of the Lorentzian averaged 2.6 X 10(-24) A2 Hz-1 at -10 mV and 4.6 X 10(-24) A2 Hz-1 at -21 mV, with a mean half-power frequency, fc, of 34 Hz and 45 Hz, respectively. The time constant of the K+ current activation upon hyperpolarization agrees with that calculated from fc, and the Lorentzian disappears upon replacement of external K+ by tetraethylammonium (TEA+) or Rb+. Thus, the Lorentzian component appears to be ascribable to fluctuations originating in the inwardly rectifying mechanism. The noise spectra and macroscopic currents were interpreted by assuming that the inwardly rectifying K+ conductance is proportional to the product of two parameters: ps representing the state of the mechanism that gives rise to the observable macroscopic current relaxations and to the current fluctuations resulting in the observed Lorentzian spectra, and pf describing the instantaneous rectification of the single-channel conductance. Alternatively, pf may represent another mechanism in series with ps, but which fluctuates too rapidly to measure. Using this model the limiting single-channel conductance, gamma, was found to be approximately 9 pS. The corresponding specific density of channels is about 1 micron-2, assuming uniform distribution over all regions of the membrane. A preliminary value for gamma ( DeCoursey & Hutter , 1982) was derived without consideration of instantaneous rectification. Systematic errors in these results due to voltage decrement in the T-tubules are evaluated in an Appendix, and are found to be tolerably small in the voltage range studied. PMID:6330346

  7. 46 CFR 120.360 - Semiconductor rectifier systems.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 4 2014-10-01 2014-10-01 false Semiconductor rectifier systems. 120.360 Section 120.360 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) SMALL PASSENGER VESSELS CARRYING MORE... INSTALLATION Power Sources and Distribution Systems § 120.360 Semiconductor rectifier systems. (a)...

  8. 46 CFR 129.360 - Semiconductor-rectifier systems.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 4 2014-10-01 2014-10-01 false Semiconductor-rectifier systems. 129.360 Section 129.360 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) OFFSHORE SUPPLY VESSELS ELECTRICAL INSTALLATIONS Power Sources and Distribution Systems § 129.360 Semiconductor-rectifier systems. (a)...

  9. High-Efficiency Harmonically Terminated Diode and Transistor Rectifiers

    SciTech Connect

    Roberg, M; Reveyrand, T; Ramos, I; Falkenstein, EA; Popovic, Z

    2012-12-01

    This paper presents a theoretical analysis of harmonically terminated high-efficiency power rectifiers and experimental validation on a class-C single Schottky-diode rectifier and a class-F-1 GaN transistor rectifier. The theory is based on a Fourier analysis of current and voltage waveforms, which arise across the rectifying element when different harmonic terminations are presented at its terminals. An analogy to harmonically terminated power amplifier (PA) theory is discussed. From the analysis, one can obtain an optimal value for the dc load given the RF circuit design. An upper limit on rectifier efficiency is derived for each case as a function of the device on-resistance. Measured results from fundamental frequency source-pull measurement of a Schottky diode rectifier with short-circuit terminations at the second and third harmonics are presented. A maximal device rectification efficiency of 72.8% at 2.45 GHz matches the theoretical prediction. A 2.14-GHz GaN HEMT rectifier is designed based on a class-F-1 PA. The gate of the transistor is terminated in an optimal impedance for self-synchronous rectification. Measurements of conversion efficiency and output dc voltage for varying gate RF impedance, dc load, and gate bias are shown with varying input RF power at the drain. The rectifier demonstrates an efficiency of 85% for a 10-W input RF power at the transistor drain with a dc voltage of 30 V across a 98-Omega resistor.

  10. The effects of DC ripple from cathodic protection rectifiers

    SciTech Connect

    Pellet, L.A.; Koenig, R.

    1998-12-31

    The phenomenon of ripple in Direct Current Cathodic Protection (CP) circuits, resulting from the use of single phase Alternating Current (AC) rectifiers, is not well understood by most cathodic protection personnel. This paper discusses studies conducted in an attempt to verify the existence and magnitude of this ripple and differences in corrosion rates, if any, between filtered and unfiltered rectified DC current.

  11. 46 CFR 129.360 - Semiconductor-rectifier systems.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 4 2011-10-01 2011-10-01 false Semiconductor-rectifier systems. 129.360 Section 129.360 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) OFFSHORE SUPPLY VESSELS ELECTRICAL INSTALLATIONS Power Sources and Distribution Systems § 129.360 Semiconductor-rectifier systems. (a)...

  12. 46 CFR 120.360 - Semiconductor rectifier systems.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 4 2011-10-01 2011-10-01 false Semiconductor rectifier systems. 120.360 Section 120.360 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) SMALL PASSENGER VESSELS CARRYING MORE... INSTALLATION Power Sources and Distribution Systems § 120.360 Semiconductor rectifier systems. (a)...

  13. 46 CFR 129.360 - Semiconductor-rectifier systems.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Semiconductor-rectifier systems. 129.360 Section 129.360 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) OFFSHORE SUPPLY VESSELS ELECTRICAL INSTALLATIONS Power Sources and Distribution Systems § 129.360 Semiconductor-rectifier systems. (a)...

  14. 46 CFR 120.360 - Semiconductor rectifier systems.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Semiconductor rectifier systems. 120.360 Section 120.360 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) SMALL PASSENGER VESSELS CARRYING MORE... INSTALLATION Power Sources and Distribution Systems § 120.360 Semiconductor rectifier systems. (a)...

  15. Candidate locations for SPS rectifying antennas

    NASA Technical Reports Server (NTRS)

    Eberhardt, A. W.

    1977-01-01

    The feasibility of placing 120 Satellite Power System (SPS) rectifying antenna (rectenna) sites across the U.S. was studied. An initial attempt is made to put two land sites in each state using several land site selection criteria. When only 69 land sites are located, it is decided to put the remaining sites in the sea and sea site selection criteria are identified. An estimated projection of electrical demand distribution for the year 2000 is then used to determine the distribution of these sites along the Pacific, Atlantic, and Gulf Coasts. A methodology for distributing rectenna sites across the country and for fine-tuning exact locations is developed, and recommendations on rectenna design and operations are made.

  16. Neural induction suppresses early expression of the inward-rectifier K+ channel in the ascidian blastomere.

    PubMed Central

    Okamura, Y; Takahashi, K

    1993-01-01

    1. Early expression of ion channels following neural induction was examined in isolated, cleavage-arrested blastomeres from the ascidian embryo using a two-electrode voltage clamp. Currents were recorded from the isolated, cleavage-arrested blastomere, a4-2, after treatment with serine protease, subtilisin, which induces neural differentiation as consistently as cell contact. 2. The inward-rectifier K+ current increased at the late gastrula stage shortly after the sensitive period for neural induction both in the induced (protease-treated) and uninduced cells. Ca2+ channels, characteristic of epidermal-type differentiation, and delayed-rectifier K+ channels and differentiated-type Na+ channels, characteristic of neural-type differentiation appeared much later than the inward-rectifier K+ channels, at a time corresponding to the tail bud stage of the intact embryo. 3. When cells were treated with subtilisin during the critical period for neural induction, the increase in the inward-rectifier K+ current from the late gastrula stage to the neurula stage was about three times smaller (3.67 +/- 1.74 nA, mean +/- S.D., n = 14) than in untreated cells (11.25 +/- 3.10 nA, n = 26). The same changes in the inward-rectifier K+ channel were also observed in a4 2 blastomeres which were induced by cell contact with an A4-1 blastomere. However, when cells were treated with subtilisin after the critical period for neural induction, the amplitude of the inward-rectifier K+ current was the same as in untreated cells. Thus the expressed level of the inward-rectifier K+ channel was linked to the determination of neural or epidermal cell types. 4. There was no significant difference in the input capacitance of induced and uninduced cells, indicating that the difference in the amplitude of the inward-rectifier K+ currents derived from a difference in the channel density rather than a difference in cell surface area. 5. The expression of the inward-rectifier K+ channel at the late gastrula stage was sensitive to alpha-amanitin, a highly specific transcription inhibitor. In both induced and uninduced cells, injection of alpha-amanitin at the 32-cell stage reduced the current density of the inward-rectifier K+ channel to about 2 nA/nF, corresponding to 13% of that recorded from uninjected cells. By contrast, the expression of the fast-inactivating-type Na+ current, which transiently increased along with the inward-rectifier K+ channel, was resistant to alpha-amanitin injection. 6. The dose of alpha-amanitin injected was controlled by monitoring co-injected fluorescent dye, fura-2.(ABSTRACT TRUNCATED AT 400 WORDS) Images Fig. 6 Fig. 8 Fig. 11 PMID:8246182

  17. Gate-controlled-diodes in silicon-on-sapphire: A computer simulation

    NASA Technical Reports Server (NTRS)

    Gassaway, J. D.

    1974-01-01

    The computer simulation of the electrical behavior of a Gate-Controlled Diode (GCD) fabricated in Silicon-On-Sapphire (SOS) was described. A procedure for determining lifetime profiles from capacitance and reverse current measurements on the GCD was established. Chapter 1 discusses the SOS structure and points out the need of lifetime profiles to assist in device design for GCD's and bipolar transistors. Chapter 2 presents the one-dimensional analytical formula for electrostatic analysis of the SOS-GCD which are useful for data interpretation and setting boundary conditions on a simplified two-dimensional analysis. Chapter 3 gives the results of a two-dimensional analysis which treats the field as one-dimensional until the silicon film is depleted and the field penetrates the sapphire substrate. Chapter 4 describes a more complete two-dimensional model and gives results of programs implementing the model.

  18. Surface photovoltage method for the quality control of silicon epitaxial layers on sapphire

    SciTech Connect

    Yaremchuk, A. F.; Starkov, A. V.; Zaikin, A. V.; Alekseev, A. V.; Sokolov, E. M.

    2014-12-15

    The surface photovoltage method is used to study “silicon-on-sapphire” epitaxial layers with a thickness of 0.3–0.6 μm, which are used to fabricate p-channel MOS (metal—oxide-semiconductor) transistors with improved radiation hardness. It is shown that the manner in which the photoconductivity of the epitaxial layer decays after the end of a light pulse generated by a light-emitting diode (wavelength ∼400 nm) strongly depends on the density of structural defects in the bulk of the structure. This enables control over how a “silicon-on-sapphire” structure is formed to provide the manufacturing of MOS structures with optimal operating characteristics.

  19. Controlling the Er content of porous silicon using the doping current intensity

    PubMed Central

    2014-01-01

    The results of an investigation on the Er doping of porous silicon are presented. Electrochemical impedance spectroscopy, optical reflectivity, and spatially resolved energy dispersive spectroscopy (EDS) coupled to scanning electron microscopy measurements were used to investigate on the transient during the first stages of constant current Er doping. Depending on the applied current intensity, the voltage transient displays two very different behaviors, signature of two different chemical processes. The measurements show that, for equal transferred charge and identical porous silicon (PSi) layers, the applied current intensity also influences the final Er content. An interpretative model is proposed in order to describe the two distinct chemical processes. The results can be useful for a better control over the doping process. PACS 81.05.Rm; 82.45.Rr PMID:25024691

  20. Fabrication of ultrathin and highly uniform silicon on insulator by numerically controlled plasma chemical vaporization machining.

    PubMed

    Sano, Yasuhisa; Yamamura, Kazuya; Mimura, Hidekazu; Yamauchi, Kazuto; Mori, Yuzo

    2007-08-01

    Metal-oxide semiconductor field-effect transistors fabricated on a silicon-on-insulator (SOI) wafer operate faster and at a lower power than those fabricated on a bulk silicon wafer. Scaling down, which improves their performances, demands thinner SOI wafers. In this article, improvement on the thinning of SOI wafers by numerically controlled plasma chemical vaporization machining (PCVM) is described. PCVM is a gas-phase chemical etching method in which reactive species generated in atmospheric-pressure plasma are used. Some factors affecting uniformity are investigated and methods for improvements are presented. As a result of thinning a commercial 8 in. SOI wafer, the initial SOI layer thickness of 97.5+/-4.7 nm was successfully thinned and made uniform at 7.5+/-1.5 nm. PMID:17764362

  1. Water/glycol temperature control circuit failed in the automatic mode: Apollo 16

    NASA Technical Reports Server (NTRS)

    1972-01-01

    An anomaly report concerning failure of the water/glycol temperature control circuit during the Apollo 16 flight is presented. The anomaly is described and diagrams of the system are presented. The malfunction was caused by cracked semiconductor chips in the output silicon-controlled rectifier. Surface contamination in the crack allowed the device to self-gate on and remain on, resulting in a secondary failure of the feedback capacitor.

  2. Silicon oxide nanowires: facile and controlled large area fabrication of vertically oriented silicon oxide nanowires for photoluminescence and sensor applications.

    PubMed

    Alabi, Taiwo R; Yuan, Dajun; Bucknall, David; Das, Suman

    2013-09-25

    We describe a technique for the fabrication of dense and patterned arrays of aligned silicon oxide nanowires for applications in surface modification, optoelectronic, and electromechanical based devices. Conventional techniques for the fabrication of silicon oxide nanowires based on the vapor-liquid-solid (VLS) chemical vapor deposition (CVD) processes involve the use of high temperatures and catalysts. We demonstrate a technique that extends the use of a plasma thermal reactive ion etching for the fabrication of aligned silicon oxide nanowires with aspect ratios extending up to 20 and lengths exceeding 1 μm. The process incorporates phase separated PS-b-P4VP block copolymer loaded with an iron salt. The iron salt preferentially segregates into the P4VP layer and during an O2 etch is not removed but forms a hexagonally packed array on the silicon oxide substrate. Further etching with CHF3/O2 gas mixture over time can generate nanodots, to nanopillars, and then nanowires of silicon oxide. The photoluminescence property of the as-fabricated nanowire arrays as well as the parasitic ferromagnetic effect from the iron oxide-tipped section of the wires resulting in coalescence under an scanning electron microscope (SEM) are demonstrated. This technique is simpler compared to existing VLS fabrication approaches and can be used for the direct fabrication of patterned arrays of nanowires when a laser interference ablation step is incorporated into the fabrication procedure. PMID:23915216

  3. Self- and dopant diffusion in extrinsic boron doped isotopically controlled silicon multilayer structures

    SciTech Connect

    Sharp, Ian D.; Bracht, Hartmut A.; Silvestri, Hughes H.; Nicols, Samuel P.; Beeman, Jeffrey W.; Hansen, John L.; Nylandsted Larsen, Arne; Haller, Eugene E.

    2002-04-01

    Isotopically controlled silicon multilayer structures were used to measure the enhancement of self- and dopant diffusion in extrinsic boron doped silicon. {sup 30}Si was used as a tracer through a multilayer structure of alternating natural Si and enriched {sup 28}Si layers. Low energy, high resolution secondary ion mass spectrometry (SIMS) allowed for simultaneous measurement of self- and dopant diffusion profiles of samples annealed at temperatures between 850 C and 1100 C. A specially designed ion- implanted amorphous Si surface layer was used as a dopant source to suppress excess defects in the multilayer structure, thereby eliminating transient enhanced diffusion (TED) behavior. Self- and dopant diffusion coefficients, diffusion mechanisms, and native defect charge states were determined from computer-aided modeling, based on differential equations describing the diffusion processes. We present a quantitative description of B diffusion enhanced self-diffusion in silicon and conclude that the diffusion of both B and Si is mainly mediated by neutral and singly positively charged self-interstitials under p-type doping. No significant contribution of vacancies to either B or Si diffusion is observed.

  4. A CMOS microdisplay with integrated controller utilizing improved silicon hot carrier luminescent light sources

    NASA Astrophysics Data System (ADS)

    Venter, Petrus J.; Alberts, Antonie C.; du Plessis, Monuko; Joubert, Trudi-Heleen; Goosen, Marius E.; Janse van Rensburg, Christo; Rademeyer, Pieter; Fauré, Nicolaas M.

    2013-03-01

    Microdisplay technology, the miniaturization and integration of small displays for various applications, is predominantly based on OLED and LCoS technologies. Silicon light emission from hot carrier electroluminescence has been shown to emit light visibly perceptible without the aid of any additional intensification, although the electrical to optical conversion efficiency is not as high as the technologies mentioned above. For some applications, this drawback may be traded off against the major cost advantage and superior integration opportunities offered by CMOS microdisplays using integrated silicon light sources. This work introduces an improved version of our previously published microdisplay by making use of new efficiency enhanced CMOS light emitting structures and an increased display resolution. Silicon hot carrier luminescence is often created when reverse biased pn-junctions enter the breakdown regime where impact ionization results in carrier transport across the junction. Avalanche breakdown is typically unwanted in modern CMOS processes. Design rules and process design are generally tailored to prevent breakdown, while the voltages associated with breakdown are too high to directly interact with the rest of the CMOS standard library. This work shows that it is possible to lower the operating voltage of CMOS light sources without compromising the optical output power. This results in more efficient light sources with improved interaction with other standard library components. This work proves that it is possible to create a reasonably high resolution microdisplay while integrating the active matrix controller and drivers on the same integrated circuit die without additional modifications, in a standard CMOS process.

  5. Large area and structured epitaxial graphene produced by confinement controlled sublimation of silicon carbide

    PubMed Central

    de Heer, Walt A.; Berger, Claire; Ruan, Ming; Sprinkle, Mike; Li, Xuebin; Hu, Yike; Zhang, Baiqian; Hankinson, John; Conrad, Edward

    2011-01-01

    After the pioneering investigations into graphene-based electronics at Georgia Tech, great strides have been made developing epitaxial graphene on silicon carbide (EG) as a new electronic material. EG has not only demonstrated its potential for large scale applications, it also has become an important material for fundamental two-dimensional electron gas physics. It was long known that graphene mono and multilayers grow on SiC crystals at high temperatures in ultrahigh vacuum. At these temperatures, silicon sublimes from the surface and the carbon rich surface layer transforms to graphene. However the quality of the graphene produced in ultrahigh vacuum is poor due to the high sublimation rates at relatively low temperatures. The Georgia Tech team developed growth methods involving encapsulating the SiC crystals in graphite enclosures, thereby sequestering the evaporated silicon and bringing growth process closer to equilibrium. In this confinement controlled sublimation (CCS) process, very high-quality graphene is grown on both polar faces of the SiC crystals. Since 2003, over 50 publications used CCS grown graphene, where it is known as the “furnace grown” graphene. Graphene multilayers grown on the carbon-terminated face of SiC, using the CCS method, were shown to consist of decoupled high mobility graphene layers. The CCS method is now applied on structured silicon carbide surfaces to produce high mobility nano-patterned graphene structures thereby demonstrating that EG is a viable contender for next-generation electronics. Here we present for the first time the CCS method that outperforms other epitaxial graphene production methods. PMID:21960446

  6. Improved quality control of silicon wafers using novel off-line air pocket image analysis

    NASA Astrophysics Data System (ADS)

    Valley, John F.; Sanna, M. Cristina

    2014-08-01

    Air pockets (APK) occur randomly in Czochralski (Cz) grown silicon (Si) crystals and may become included in wafers after slicing and polishing. Previously the only APK of interest were those that intersected the front surface of the wafer and therefore directly impacted device yield. However mobile and other electronics have placed new demands on wafers to be internally APK-free for reasons of thermal management and packaging yield. We present a novel, recently patented, APK image processing technique and demonstrate the use of that technique, off-line, to improve quality control during wafer manufacturing.

  7. Electrically conductive, black thermal control coatings for space craft application. II - Silicone matrix formulation

    NASA Technical Reports Server (NTRS)

    Hribar, V. F.; Bauer, J. L.; O'Donnell, T. P.

    1986-01-01

    Five black electrically conductive thermal-control coatings have been formulated and tested for application on the Galileo spacecraft. The coatings consisted of organic and inorganic systems applied on titanium and aluminum surfaces. The coatings were tested under simulated space environment conditions. Coated specimens were subjected to thermal radiation and convective and conductive heating from -196 to 538 C. Mechanical, physical, thermal, electrical, and optical characteristics, formulation, mixing, application, surface preparation of substrates, and a method of determining electrical resistance are presented for the silicone matrix formulation designated as GF-580.

  8. Strong visible magnetic resonance of size-controlled silicon-nanoblock metasurfaces

    NASA Astrophysics Data System (ADS)

    Yi, Yoonsik; Yoo, SeokJae; Choe, Jong-Ho; Park, Sang-Gil; Jeong, Ki-Hun; Park, Q.-Han; Choi, Choon-Gi

    2016-04-01

    To extend the operating window of all-dielectric metamaterials into the visible regime, obtaining controllable magnetic resonance is essential. We experimentally demonstrated strong magnetic resonance at 595 nm using an array of amorphous silicon (a-Si) nanoblocks. The results of both theoretical calculations and experiments show that magnetic resonance can be tuned continuously by appropriately varying the size and thickness of a-Si nanoblocks. We also experimentally achieved a magnetic resonance Q-factor of ∼10, which is a higher value than that yielded by a metallic split-ring resonator in the visible regime.

  9. Pore Size Control of Ultra-thin Silicon Membranes by Rapid Thermal Carbonization

    PubMed Central

    Fang, David Z.; Striemer, Christopher C.; Gaborski, Thomas R.; McGrath, James L.; Fauchet, Philippe M.

    2010-01-01

    Rapid thermal carbonization in a dilute acetylene (C2H2) atmosphere has been used to chemically modify and precisely tune the pore size of ultrathin porous nanocrystalline silicon (pnc-Si). The magnitude of size reduction was controlled by varying the process temperature and time. Under certain conditions, the carbon coating displayed atomic ordering indicative of graphene layer formation conformal to the pore walls. Initial experiments show that carbonized membranes follow theoretical predictions for hydraulic permeability and retain the precise separation capabilities of untreated membranes. PMID:20839831

  10. Controlling the spectrum of photons generated on a silicon nanophotonic chip.

    PubMed

    Kumar, Ranjeet; Ong, Jun Rong; Savanier, Marc; Mookherjea, Shayan

    2014-01-01

    Directly modulated semiconductor lasers are widely used, compact light sources in optical communications. Semiconductors can also be used to generate nonclassical light; in fact, CMOS-compatible silicon chips can be used to generate pairs of single photons at room temperature. Unlike the classical laser, the photon-pair source requires control over a two-dimensional joint spectral intensity (JSI) and it is not possible to process the photons separately, as this could destroy the entanglement. Here we design a photon-pair source, consisting of planar lightwave components fabricated using CMOS-compatible lithography in silicon, which has the capability to vary the JSI. By controlling either the optical pump wavelength, or the temperature of the chip, we demonstrate the ability to select different JSIs, with a large variation in the Schmidt number. Such control can benefit high-dimensional communications where detector-timing constraints can be relaxed by realizing a large Schmidt number in a small frequency range. PMID:25410792

  11. Controlling the spectrum of photons generated on a silicon nanophotonic chip

    PubMed Central

    Kumar, Ranjeet; Ong, Jun Rong; Savanier, Marc; Mookherjea, Shayan

    2014-01-01

    Directly modulated semiconductor lasers are widely used, compact light sources in optical communications. Semiconductors can also be used to generate nonclassical light; in fact, CMOS-compatible silicon chips can be used to generate pairs of single photons at room temperature. Unlike the classical laser, the photon-pair source requires control over a two-dimensional joint spectral intensity (JSI) and it is not possible to process the photons separately, as this could destroy the entanglement. Here we design a photon-pair source, consisting of planar lightwave components fabricated using CMOS-compatible lithography in silicon, which has the capability to vary the JSI. By controlling either the optical pump wavelength, or the temperature of the chip, we demonstrate the ability to select different JSIs, with a large variation in the Schmidt number. Such control can benefit high-dimensional communications where detector-timing constraints can be relaxed by realizing a large Schmidt number in a small frequency range. PMID:25410792

  12. Open Air Silicon Deposition by Atmospheric Pressure Plasma under Local Ambient Gas Control

    NASA Astrophysics Data System (ADS)

    Naito, Teruki; Konno, Nobuaki; Yoshida, Yukihisa

    2015-09-01

    In this paper, we report open air silicon (Si) deposition by combining a silane free Si deposition technology and a newly developed local ambient gas control technology. Recently, material processing in open air has been investigated intensively. While a variety of materials have been deposited, there were only few reports on Si deposition due to the susceptibility to contamination and the hazardous nature of source materials. Since Si deposition is one of the most important processes in device fabrication, we have developed open air silicon deposition technologies in BEANS project. For a clean and safe process, a local ambient gas control head was designed. Process gas leakage was prevented by local evacuation, and air contamination was shut out by inert curtain gas. By numerical and experimental investigations, a safe and clean process condition with air contamination less than 10 ppm was achieved. Si film was deposited in open air by atmospheric pressure plasma enhanced chemical transport under the local ambient gas control. The film was microcrystalline Si with the crystallite size of 17 nm, and the Hall mobility was 2.3 cm2/V .s. These properties were comparable to those of Si films deposited in a vacuum chamber. This research has been conducted as one of the research items of New Energy and Industrial Technology Development Organization ``BEANS'' project.

  13. Precision envelope detector and linear rectifier circuitry

    DOEpatents

    Davis, Thomas J.

    1980-01-01

    Disclosed is a method and apparatus for the precise linear rectification and envelope detection of oscillatory signals. The signal is applied to a voltage-to-current converter which supplies current to a constant current sink. The connection between the converter and the sink is also applied through a diode and an output load resistor to a ground connection. The connection is also connected to ground through a second diode of opposite polarity from the diode in series with the load resistor. Very small amplitude voltage signals applied to the converter will cause a small change in the output current of the converter, and the difference between the output current and the constant current sink will be applied either directly to ground through the single diode, or across the output load resistor, dependent upon the polarity. Disclosed also is a full-wave rectifier utilizing constant current sinks and voltage-to-current converters. Additionally, disclosed is a combination of the voltage-to-current converters with differential integrated circuit preamplifiers to boost the initial signal amplitude, and with low pass filtering applied so as to obtain a video or signal envelope output.

  14. Nitrate-Dependent Control of Shoot K Homeostasis by the Nitrate Transporter1/Peptide Transporter Family Member NPF7.3/NRT1.5 and the Stelar K+ Outward Rectifier SKOR in Arabidopsis.

    PubMed

    Drechsler, Navina; Zheng, Yue; Bohner, Anne; Nobmann, Barbara; von Wirén, Nicolaus; Kunze, Reinhard; Rausch, Christine

    2015-12-01

    Root-to-shoot translocation and shoot homeostasis of potassium (K) determine nutrient balance, growth, and stress tolerance of vascular plants. To maintain the cation-anion balance, xylem loading of K(+) in the roots relies on the concomitant loading of counteranions, like nitrate (NO3 (-)). However, the coregulation of these loading steps is unclear. Here, we show that the bidirectional, low-affinity Nitrate Transporter1 (NRT1)/Peptide Transporter (PTR) family member NPF7.3/NRT1.5 is important for the NO3 (-)-dependent K(+) translocation in Arabidopsis (Arabidopsis thaliana). Lack of NPF7.3/NRT1.5 resulted in K deficiency in shoots under low NO3 (-) nutrition, whereas the root elemental composition was unchanged. Gene expression data corroborated K deficiency in the nrt1.5-5 shoot, whereas the root responded with a differential expression of genes involved in cation-anion balance. A grafting experiment confirmed that the presence of NPF7.3/NRT1.5 in the root is a prerequisite for proper root-to-shoot translocation of K(+) under low NO3 (-) supply. Because the depolarization-activated Stelar K(+) Outward Rectifier (SKOR) has previously been described as a major contributor for root-to-shoot translocation of K(+) in Arabidopsis, we addressed the hypothesis that NPF7.3/NRT1.5-mediated NO3 (-) translocation might affect xylem loading and root-to-shoot K(+) translocation through SKOR. Indeed, growth of nrt1.5-5 and skor-2 single and double mutants under different K/NO3 (-) regimes revealed that both proteins contribute to K(+) translocation from root to shoot. SKOR activity dominates under high NO3 (-) and low K(+) supply, whereas NPF7.3/NRT1.5 is required under low NO3 (-) availability. This study unravels nutritional conditions as a critical factor for the joint activity of SKOR and NPF7.3/NRT1.5 for shoot K homeostasis. PMID:26508776

  15. Nitrate-Dependent Control of Shoot K Homeostasis by the Nitrate Transporter1/Peptide Transporter Family Member NPF7.3/NRT1.5 and the Stelar K+ Outward Rectifier SKOR in Arabidopsis1[OPEN

    PubMed Central

    Drechsler, Navina; Zheng, Yue; Nobmann, Barbara; Rausch, Christine

    2015-01-01

    Root-to-shoot translocation and shoot homeostasis of potassium (K) determine nutrient balance, growth, and stress tolerance of vascular plants. To maintain the cation-anion balance, xylem loading of K+ in the roots relies on the concomitant loading of counteranions, like nitrate (NO3−). However, the coregulation of these loading steps is unclear. Here, we show that the bidirectional, low-affinity Nitrate Transporter1 (NRT1)/Peptide Transporter (PTR) family member NPF7.3/NRT1.5 is important for the NO3−-dependent K+ translocation in Arabidopsis (Arabidopsis thaliana). Lack of NPF7.3/NRT1.5 resulted in K deficiency in shoots under low NO3− nutrition, whereas the root elemental composition was unchanged. Gene expression data corroborated K deficiency in the nrt1.5-5 shoot, whereas the root responded with a differential expression of genes involved in cation-anion balance. A grafting experiment confirmed that the presence of NPF7.3/NRT1.5 in the root is a prerequisite for proper root-to-shoot translocation of K+ under low NO3− supply. Because the depolarization-activated Stelar K+ Outward Rectifier (SKOR) has previously been described as a major contributor for root-to-shoot translocation of K+ in Arabidopsis, we addressed the hypothesis that NPF7.3/NRT1.5-mediated NO3− translocation might affect xylem loading and root-to-shoot K+ translocation through SKOR. Indeed, growth of nrt1.5-5 and skor-2 single and double mutants under different K/NO3− regimes revealed that both proteins contribute to K+ translocation from root to shoot. SKOR activity dominates under high NO3− and low K+ supply, whereas NPF7.3/NRT1.5 is required under low NO3− availability. This study unravels nutritional conditions as a critical factor for the joint activity of SKOR and NPF7.3/NRT1.5 for shoot K homeostasis. PMID:26508776

  16. Controllable electrical and physical breakdown of poly-crystalline silicon nanowires by thermally assisted electromigration

    PubMed Central

    Park, Jun-Young; Moon, Dong-Il; Seol, Myeong-Lok; Jeon, Chang-Hoon; Jeon, Gwang-Jae; Han, Jin-Woo; Kim, Choong-Ki; Park, Sang-Jae; Lee, Hee Chul; Choi, Yang-Kyu

    2016-01-01

    The importance of poly-crystalline silicon (poly-Si) in semiconductor manufacturing is rapidly increasing due to its highly controllable conductivity and excellent, uniform deposition quality. With the continuing miniaturization of electronic components, low dimensional structures such as 1-dimensional nanowires (NWs) have attracted a great deal of attention. But such components have a much higher current density than 2- or 3- dimensional films, and high current can degrade device lifetime and lead to breakdown problems. Here, we report on the electrical and thermal characteristics of poly-Si NWs, which can also be used to control electrical and physical breakdown under high current density. This work reports a controllable catastrophic change of poly-Si NWs by thermally-assisted electromigration and underlying mechanisms. It also reports the direct and real time observation of these catastrophic changes of poly-Si nanowires for the first time, using scanning electron microscopy. PMID:26782708

  17. Controllable electrical and physical breakdown of poly-crystalline silicon nanowires by thermally assisted electromigration.

    PubMed

    Park, Jun-Young; Moon, Dong-Il; Seol, Myeong-Lok; Jeon, Chang-Hoon; Jeon, Gwang-Jae; Han, Jin-Woo; Kim, Choong-Ki; Park, Sang-Jae; Lee, Hee Chul; Choi, Yang-Kyu

    2016-01-01

    The importance of poly-crystalline silicon (poly-Si) in semiconductor manufacturing is rapidly increasing due to its highly controllable conductivity and excellent, uniform deposition quality. With the continuing miniaturization of electronic components, low dimensional structures such as 1-dimensional nanowires (NWs) have attracted a great deal of attention. But such components have a much higher current density than 2- or 3-dimensional films, and high current can degrade device lifetime and lead to breakdown problems. Here, we report on the electrical and thermal characteristics of poly-Si NWs, which can also be used to control electrical and physical breakdown under high current density. This work reports a controllable catastrophic change of poly-Si NWs by thermally-assisted electromigration and underlying mechanisms. It also reports the direct and real time observation of these catastrophic changes of poly-Si nanowires for the first time, using scanning electron microscopy. PMID:26782708

  18. Controllable electrical and physical breakdown of poly-crystalline silicon nanowires by thermally assisted electromigration

    NASA Astrophysics Data System (ADS)

    Park, Jun-Young; Moon, Dong-Il; Seol, Myeong-Lok; Jeon, Chang-Hoon; Jeon, Gwang-Jae; Han, Jin-Woo; Kim, Choong-Ki; Park, Sang-Jae; Lee, Hee Chul; Choi, Yang-Kyu

    2016-01-01

    The importance of poly-crystalline silicon (poly-Si) in semiconductor manufacturing is rapidly increasing due to its highly controllable conductivity and excellent, uniform deposition quality. With the continuing miniaturization of electronic components, low dimensional structures such as 1-dimensional nanowires (NWs) have attracted a great deal of attention. But such components have a much higher current density than 2- or 3- dimensional films, and high current can degrade device lifetime and lead to breakdown problems. Here, we report on the electrical and thermal characteristics of poly-Si NWs, which can also be used to control electrical and physical breakdown under high current density. This work reports a controllable catastrophic change of poly-Si NWs by thermally-assisted electromigration and underlying mechanisms. It also reports the direct and real time observation of these catastrophic changes of poly-Si nanowires for the first time, using scanning electron microscopy.

  19. Maximal rectification ratios for idealized bi-segment thermal rectifiers

    PubMed Central

    Shih, Tien-Mo; Gao, Zhaojing; Guo, Ziquan; Merlitz, Holger; Pagni, Patrick J.; Chen, Zhong

    2015-01-01

    Thermal rectifiers whose forward heat fluxes are greater than reverse counterparts have been extensively studied. Here we have discovered, idealized, and derived the ultimate limit of such rectification ratios, which are partially validated by numerical simulations, experiments, and micro-scale Hamiltonian-oscillator analyses. For rectifiers whose thermal conductivities (κ) are linear with the temperature, this limit is simply a numerical value of 3. For those whose conductivities are nonlinear with temperatures, the maxima equal κmax/κmin, where two extremes denote values of the solid segment materials that can be possibly found or fabricated within a reasonable temperature range. Recommendations for manufacturing high-ratio rectifiers are also given with examples. Under idealized assumptions, these proposed rectification limits cannot be defied by any bi-segment thermal rectifiers. PMID:26238970

  20. Electrical detection of dengue virus (DENV) DNA oligomer using silicon nanowire biosensor with novel molecular gate control.

    PubMed

    Nuzaihan M N, M; Hashim, U; Md Arshad, M K; Kasjoo, S R; Rahman, S F A; Ruslinda, A R; Fathil, M F M; Adzhri, R; Shahimin, M M

    2016-09-15

    In this paper, a silicon nanowire biosensor with novel molecular gate control has been demonstrated for Deoxyribonucleic acid (DNA) detection related to dengue virus (DENV). The silicon nanowire was fabricated using the top-down nanolithography approach, through nanostructuring of silicon-on-insulator (SOI) layers achieved by combination of the electron-beam lithography (EBL), plasma dry etching and size reduction processes. The surface of the fabricated silicon nanowire was functionalized by means of a three-step procedure involving surface modification, DNA immobilization and hybridization. This procedure acts as a molecular gate control to establish the electrical detection for 27-mers base targets DENV DNA oligomer. The electrical detection is based on the changes in current, resistance and conductance of the sensor due to accumulation of negative charges added by the immobilized probe DNA and hybridized target DNA. The sensitivity of the silicon nanowire biosensors attained was 45.0µAM(-1), which shows a wide-range detection capability of the sensor with respect to DNA. The limit of detection (LOD) achieved was approximately 2.0fM. The demonstrated results show that the silicon nanowire has excellent properties for detection of DENV with outstanding repeatability and reproducibility performances. PMID:27107147

  1. Robust Two-Qubit Gates for Donors in Silicon Controlled by Hyperfine Interactions

    NASA Astrophysics Data System (ADS)

    Kalra, Rachpon; Laucht, Arne; Hill, Charles D.; Morello, Andrea; CentreQuantum Computation; Communication Technology, Australia Team

    2015-03-01

    The electron spin of a single atom in silicon is an excellent candidate for the building-block of a quantum computer. Recent breakthrough experiments have shown an individual phosphorus impurity atom can be used to store and elaborate one bit of quantum information. To continue along this exciting path, it is necessary to couple multiple phosphorus atoms in a controllable way and demonstrate quantum logic operations between pairs of qubits. This was thought to require exquisite control of their mutual interaction, and atomically-precise placement of the spins. Our work shows that the nuclei, to which the electrons are bound, can be exploited to enable a logic operation based on selective resonant excitation. This operation has the enormous advantage that the inter-qubit interaction does not require any modification. Our calculations show that high-fidelity operations can be performed while tolerating a rather wide range of distances between atoms. This drastically reduces the demands posed on device fabrication, paving the way forward for large-scale quantum-information processing in silicon. Funded by the Australian Research Council (CE11E000127) and the U.S. Army Research Office (W911NF-13-1-0024).

  2. Precision Control of Thermal Transport in Cryogenic Single-Crystal Silicon Devices

    NASA Technical Reports Server (NTRS)

    Rostem, K.; Chuss, D. T.; Colazo, F. A.; Crowe, E. J.; Denis, K. L.; Lourie, N. P.; Moseley, S. H.; Stevenson, T. R.; Wollack, E. J.

    2014-01-01

    We report on the diffusive-ballistic thermal conductance of multi-moded single-crystal silicon beams measured below 1 K. It is shown that the phonon mean-free-path is a strong function of the surface roughness characteristics of the beams. This effect is enhanced in diffuse beams with lengths much larger than, even when the surface is fairly smooth, 510 nm rms, and the peak thermal wavelength is 0.6 microns. Resonant phonon scattering has been observed in beams with a pitted surface morphology and characteristic pit depth of 30 nm. Hence, if the surface roughness is not adequately controlled, the thermal conductance can vary significantly for diffuse beams fabricated across a wafer. In contrast, when the beam length is of order, the conductance is dominated by ballistic transport and is effectively set by the beam cross-sectional area. We have demonstrated a uniformity of +/-8% in fractional deviation for ballistic beams, and this deviation is largely set by the thermal conductance of diffuse beams that support the micro-electro-mechanical device and electrical leads. In addition, we have found no evidence for excess specific heat in single-crystal silicon membranes. This allows for the precise control of the device heat capacity with normal metal films. We discuss the results in the context of the design and fabrication of large-format arrays of far-infrared and millimeter wavelength cryogenic detectors.

  3. Precision control of thermal transport in cryogenic single-crystal silicon devices

    SciTech Connect

    Rostem, K.; Chuss, D. T.; Colazo, F. A.; Crowe, E. J.; Denis, K. L.; Lourie, N. P.; Moseley, S. H.; Stevenson, T. R.; Wollack, E. J.

    2014-03-28

    We report on the diffusive-ballistic thermal conductance of multi-moded single-crystal silicon beams measured below 1 K. It is shown that the phonon mean-free-path ℓ is a strong function of the surface roughness characteristics of the beams. This effect is enhanced in diffuse beams with lengths much larger than ℓ, even when the surface is fairly smooth, 5–10 nm rms, and the peak thermal wavelength is 0.6 μm. Resonant phonon scattering has been observed in beams with a pitted surface morphology and characteristic pit depth of 30 nm. Hence, if the surface roughness is not adequately controlled, the thermal conductance can vary significantly for diffuse beams fabricated across a wafer. In contrast, when the beam length is of order ℓ, the conductance is dominated by ballistic transport and is effectively set by the beam cross-sectional area. We have demonstrated a uniformity of ±8% in fractional deviation for ballistic beams, and this deviation is largely set by the thermal conductance of diffuse beams that support the micro-electro-mechanical device and electrical leads. In addition, we have found no evidence for excess specific heat in single-crystal silicon membranes. This allows for the precise control of the device heat capacity with normal metal films. We discuss the results in the context of the design and fabrication of large-format arrays of far-infrared and millimeter wavelength cryogenic detectors.

  4. Silicon-based current-controlled reconfigurable magnetoresistance logic combined with non-volatile memory

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaozhong; Luo, Zhaochu

    2015-03-01

    Silicon-based complementary metal-oxide-semiconductor (CMOS) transistors have achieved great success. However, the traditional development pathway is approaching its fundamental limits. Magnetoelectronics logic, especially magnetic-field-based logic, shows promise for surpassing the development limits of CMOS logic. Existing proposals of magnetic-field-based logic are based on exotic semiconductors and difficult for further technological implementation. We proposed a kind of diode-assisted geometry-enhanced low-magnetic-field magnetoresistance (MR) mechanism. It couples p-n junction's nonlinear transport characteristic and Lorentz force by geometry, and shows extremely large low-magnetic-field MR (>120% at 0.15 T) Further, it is applied to experimentally demonstrate current-controlled reconfigurable MR logic on the silicon platform at room temperature. This logic device could perform Boolean logic AND, OR, NAND and NOR in one device. Combined with non-volatile magnetic memory, this logic architecture has the advantages of current-controlled reconfiguration, zero refresh consumption, instant-on performance and would bridge the processor-memory gap.

  5. Noise rectifier based on the two-dimensional electron gas

    SciTech Connect

    Cheremisin, M. V.

    2012-09-15

    The dc voltage observed at low temperatures in a 2D electron sample in the absence of noticeable external excitations [1] is accounted by the Schottky contact rectification of the noise generated in the measuring circuit. The rectified voltage is shown to depend on the asymmetry of the contact pair. The dependence of the rectified voltage on the noise amplitude first follows the trivial quadratic law, then exhibits a nearly linear behavior, and finally, levels off.

  6. Fabrication of Size-Controlled Gold Nanoparticles on Silicone Oil Surface and Mechanism for Size-Controllability

    NASA Astrophysics Data System (ADS)

    Zhang, Chuhang; Feng, Yuanxin

    2015-07-01

    By thermal evaporation method, size-controlled gold (Au) nanoparticles were fabricated on silicone oil surface and the growth mechanism was investigated. Atomic force microscopy (AFM) study showed that quasi-circular granules with height of 10.0 nm and diameter of 60.0 nm were formed on the oil surface, which was independent with substrate temperature Ts. Transmission electron microscopy (TEM) observation revealed that the granules were further composed of Au nanoparticles. By changing Ts from 285 to 343 K, the mean diameter of nanoparticles can be well manipulated from 7.2 0.7 to 10.1 1.0 nm. The one dimensional power spectra density analysis and high resolution TEM study demonstrated that the origin of the size-controllability of the Au nanoparticles were dominated by the simple aggregation of small nanoparticles. Subsequently, a sequential growth model for Au nanoparticle was presented.

  7. Accurate control of oxygen level in cells during culture on silicone rubber membranes with application to stem cell differentiation.

    PubMed

    Powers, Daryl E; Millman, Jeffrey R; Bonner-Weir, Susan; Rappel, Michael J; Colton, Clark K

    2010-01-01

    Oxygen level in mammalian cell culture is often controlled by placing culture vessels in humidified incubators with a defined gas phase partial pressure of oxygen (pO(2gas)). Because the cells are consuming oxygen supplied by diffusion, a difference between pO(2gas) and that experienced by the cells (pO(2cell)) arises, which is maximal when cells are cultured in vessels with little or no oxygen permeability. Here, we demonstrate theoretically that highly oxygen-permeable silicone rubber membranes can be used to control pO(2cell) during culture of cells in monolayers and aggregates much more accurately and can achieve more rapid transient response following a disturbance than on polystyrene and fluorinated ethylene-propylene copolymer membranes. Cell attachment on silicone rubber was achieved by physical adsorption of fibronectin or Matrigel. We use these membranes for the differentiation of mouse embryonic stem cells to cardiomyocytes and compare the results with culture on polystyrene or on silicone rubber on top of polystyrene. The fraction of cells that are cardiomyocyte-like increases with decreasing pO(2) only when using oxygen-permeable silicone membrane-based dishs, which contract on silicone rubber but not polystyrene. The high permeability of silicone rubber results in pO(2cell) being equal to pO(2gas) at the tissue-membrane interface. This, together with geometric information from histological sections, facilitates development of a model from which the pO(2) distribution within the resulting aggregates is computed. Silicone rubber membranes have significant advantages over polystyrene in controlling pO(2cell), and these results suggest they are a valuable tool for investigating pO(2) effects in many applications, such as stem cell differentiation. PMID:20039374

  8. Beds of reconfigurable angled hairs rectify Stokes flows

    NASA Astrophysics Data System (ADS)

    Alvarado, Jose; Comtet, Jean; Hosoi, Anette Peko

    2015-11-01

    Biological tissues such as intestines, blood vessels, kidneys, and tongues are coated with beds of passive, elongated, hair-like protrusions such as microvilli, hyaluronans, primary cilia, and papillae. Stresses from fluid flows can bend deformable hairs, but this reconfiguration can in turn affect confined fluid flows. We investigate this elastoviscous coupling by developing a biomimetic model system of elastomer hair beds subject to shear-driven Stokes flows in a Taylor-Couette geometry. We characterize this system with a theoretical model which shows that reconfiguration of hair beds is controlled by a single elastoviscous number. Hair bending results in an apparent shear thinning because the hair tip lowers toward the base and thus widens the gap through which fluid flows. When hairs are cantilevered at an angle subnormal to the surface, flow against the grain bends hairs away from the base and thus narrows the gap. Beds of reconfigurable angled hairs can thus give rise to an asymmetric flow impedance at arbitrarily low Reynolds number and could therefore function as a microfluidic rectifier.

  9. Electrical control of interfacial trapping for magnetic tunnel transistor on silicon

    SciTech Connect

    Lu, Y. Lacour, D.; Lengaigne, G.; Le Gall, S.; Suire, S.; Montaigne, F.; Hehn, M.; Wu, M. W.

    2014-01-27

    We demonstrate an electrical control of an interfacial trapping effect for hot electrons injected in silicon by studying a magnetic tunnel transistor on wafer bonded Si substrate. Below 25 K, hot electrons are trapped at the Cu/Si interface, resulting in collector current suppression through scattering in both parallel and antiparallel magnetic configurations. Consequently, the magneto-current ratio strongly decreases from 300% at 27 K to 30% at 22 K. The application of a relatively small electric field (∼333 V/cm) across the Cu/Si interface is enough to strip the trapped electrons and restore the magneto-current ratio at low temperature. We also present a model taking into account the effects of both electric field and temperature that closely reproduces the experimental results and allows extraction of the trapping binding energy (∼1.6 meV)

  10. Controllable surface-plasmon resonance in engineered nanometer epitaxial silicide particles embedded in silicon

    NASA Technical Reports Server (NTRS)

    Fathauer, R. W.; Ksendzov, A.; Iannelli, J. M.; George, T.

    1991-01-01

    Epitaxial CoSi2 particles in a single-crystal silicon matrix are grown by molecular-beam epitaxy using a technique that allows nanometer control over particle size in three dimensions. These composite layers exhibit resonant absorption predicted by effective-medium theory. Selection of the height and diameter of disklike particles through a choice of growth conditions allows tailoring of the depolarization factor and hence of the surface-plasmon resonance energy. Resonant absorption from 0.49 to 1.04 eV (2.5 to 1.2 micron) is demonstrated and shown to agree well with values predicted by the Garnett (1904, 1906) theory using the bulk dielectric constants for CoSi2 and Si.

  11. Doping strategies to control A-centres in silicon: insights from hybrid density functional theory.

    PubMed

    Wang, H; Chroneos, A; Londos, C A; Sgourou, E N; Schwingenschlgl, U

    2014-05-14

    Hybrid density functional theory is used to gain insights into the interaction of intrinsic vacancies (V) and oxygen-vacancy pairs (VO, known as A-centres) with the dopants (D) germanium (Ge), tin (Sn), and lead (Pb) in silicon (Si). We determine the structures as well as binding and formation energies of the DVO and DV complexes. The results are discussed in terms of the density of states and in view of the potential of isovalent doping to control A-centres in Si. We argue that doping with Sn is the most efficient isovalent doping strategy to suppress A-centres by the formation of SnVO complexes, as these are charge neutral and strongly bound. PMID:24667874

  12. "Thunderstruck": Plasma-Polymer-Coated Porous Silicon Microparticles As a Controlled Drug Delivery System.

    PubMed

    McInnes, Steven J P; Michl, Thomas D; Delalat, Bahman; Al-Bataineh, Sameer A; Coad, Bryan R; Vasilev, Krasimir; Griesser, Hans J; Voelcker, Nicolas H

    2016-02-24

    Controlling the release kinetics from a drug carrier is crucial to maintain a drug's therapeutic window. We report the use of biodegradable porous silicon microparticles (pSi MPs) loaded with the anticancer drug camphothecin, followed by a plasma polymer overcoating using a loudspeaker plasma reactor. Homogenous "Teflon-like" coatings were achieved by tumbling the particles by playing AC/DC's song "Thunderstruck". The overcoating resulted in a markedly slower release of the cytotoxic drug, and this effect correlated positively with the plasma polymer coating times, ranging from 2-fold up to more than 100-fold. Ultimately, upon characterizing and verifying pSi MP production, loading, and coating with analytical methods such as time-of-flight secondary ion mass spectrometry, scanning electron microscopy, thermal gravimetry, water contact angle measurements, and fluorescence microscopy, human neuroblastoma cells were challenged with pSi MPs in an in vitro assay, revealing a significant time delay in cell death onset. PMID:26836366

  13. Silicon microgyroscope temperature prediction and control system based on BP neural network and Fuzzy-PID control method

    NASA Astrophysics Data System (ADS)

    Xia, Dunzhu; Kong, Lun; Hu, Yiwei; Ni, Peizhen

    2015-02-01

    We present a novel silicon microgyroscope (SMG) temperature prediction and control system in a narrow space. As the temperature of SMG is closely related to its drive mode frequency and driving voltage, a temperature prediction model can be established based on the BP neural network. The simulation results demonstrate that the established temperature prediction model can estimate the temperature in the range of -40 to 60 °C with an error of less than ±0.05 °C. Then, a temperature control system based on the combination of fuzzy logic controller and the increment PID control method is proposed. The simulation results prove that the Fuzzy-PID controller has a smaller steady state error, less rise time and better robustness than the PID controller. This is validated by experimental results that show the Fuzzy-PID control method can achieve high precision in keeping the SMG temperature stable at 55 °C with an error of less than 0.2 °C. The scale factor can be stabilized at 8.7 mV/°/s with a temperature coefficient of 33 ppm °C-1. ZRO (zero rate output) instability is decreased from 1.10°/s (9.5 mV) to 0.08°/s (0.7 mV) when the temperature control system is implemented over an ambient temperature range of -40 to 60 °C.

  14. An ultra-low-voltage rectifier for PE energy harvesting applications

    NASA Astrophysics Data System (ADS)

    Jingmin, Wang; Zheng, Yang; Zhangming, Zhu; Yintang, Yang

    2016-02-01

    An ultra low voltage rectifier with high power conversion efficiency (PCE) for PE energy harvesting applications is presented in this paper. This is achieved by utilizing the DTMOS which the body terminal is connected to the gate terminal in a diode connected transistor. This implementation facilitates the rectifier with dynamic control over the threshold voltage. Moreover, we use input powered to take the place of output powered to reduce the power loss and thereby increasing the power conversion efficiency. Based on standard SMIC 0.18 μm CMOS technology, the simulation results show that the voltage conversion efficiency and the power conversion efficiency can reach up to 90.5% and 95.5% respectively, when the input voltage equals to 0.2 V @ 100 Hz with load resistance 50 kω. Input voltages with frequencies in the range of 10 Hz-1 kHz can be rectified. Project supported by the National Natural Science Foundation of China (Nos. 61234002, 61322405, 61306044, 61376033) and the National High-Tech Program of China (No. 2013AA014103).

  15. Input-output harmonic elimination of the PWM Boost Type Rectifier under unbalanced operating conditions

    NASA Astrophysics Data System (ADS)

    Stankovic, Ana Vladan

    1998-12-01

    It is the purpose of this research to propose a new control strategy to improve the performance of the PWM Boost Type Rectifier under unbalanced operating conditions. A complete analysis for the input-output harmonic elimination of the Boost Type Rectifier is presented. An analytical solution for harmonic elimination under unbalanced input voltages and balanced input impedances is obtained. Based on the analysis of the open loop configuration, a closed loop solution is proposed. The proposed technique maintains a high quality of input and output waveforms under unbalanced input voltages and balanced input impedances when this method is applied. The theoretical and experimental results show excellent agreement. The proposed method is useful particularly in applications with PWM inverters for variable speed drives, where the huge second harmonic at the dc link can cause significant torque pulsations in electrical machines. This research also extends to a more general case. In general, both input voltages and input impedances can be unbalanced. As in the previous case, the proposed solution is analyzed in the closed loop configuration. Again, the high quality of the input and output waveforms is maintained under a completely unbalanced system. The range of imbalance in both input voltages and input impedances, for which the proposed method would still be valid, is analyzed in detail. It has been shown that the PWM Boost Type Rectifier can operate from the single-phase power supply (the special case of imbalance) when the proposed method is applied. This is an extremely important contribution, since it means that the PWM Boost Type Rectifier can operate from the center-tapped transformer and still maintain high quality input and output characteristics. This generalized method for input-output harmonic elimination under unbalanced input voltages and unbalanced input impedances also allows power factor correction. This general case is very useful under severe fault conditions in the power system.

  16. Characterization of a proton-activated, outwardly rectifying anion channel

    PubMed Central

    Lambert, Sachar; Oberwinkler, Johannes

    2005-01-01

    Anion channels are present in every mammalian cell and serve many different functions, including cell volume regulation, ion transport across epithelia, regulation of membrane potential and vesicular acidification. Here we characterize a proton-activated, outwardly rectifying current endogenously expressed in HEK293 cells. Binding of three to four protons activated the anion permeable channels at external pH below 5.5 (50% activation at pH 5.1). The proton-activated current is strongly outwardly rectifying, due to an outwardly rectifying single channel conductance and an additional voltage dependent facilitation at depolarized membrane potentials. The anion channel blocker 4,4′-diisothiocyanostilbene-2,2′-disulphonic acid (DIDS) rapidly and potently inhibited the channel (IC50: 2.9 μm). Flufenamic acid blocked this channel only slowly, while mibefradil and amiloride at high concentrations had no effect. As determined from reversal potential measurements under bi-ionic conditions, the relative permeability sequence of this channel was SCN−> I−> NO3−> Br−> Cl−. None of the previously characterized anion channel matches the properties of the proton-activated, outwardly rectifying channel. Specifically, the proton-activated and the volume-regulated anion channels are two distinct and separable populations of ion channels, each having its own set of biophysical and pharmacological properties. We also demonstrate endogenous proton-activated currents in primary cultured hippocampal astrocytes. The proton-activated current in astrocytes is also carried by anions, strongly outwardly rectifying, voltage dependent and inhibited by DIDS. Proton-activated, outwardly rectifying anion channels therefore may be a broadly expressed part of the anionic channel repertoire of mammalian cells. PMID:15961423

  17. Voltage-clamp analysis of a crayfish rectifying synapse.

    PubMed Central

    Giaume, C; Kado, R T; Korn, H

    1987-01-01

    1. The rectifying crayfish giant motor synapse has been studied in the second abdominal ganglion, using the double-voltage-clamp technique which allowed direct measurements of junctional current at various fixed transjunctional potentials. 2. The transjunctional potential (Vj), defined as the difference between the voltages recorded in the lateral giant axon and the giant motor fibre, was varied from -70 to +50 mV, the minimum and maximum junctional chord conductances (gmin and gmax, respectively) were found to be 1.2 +/- 1.3 microS (n = 10) and 22.9 +/- 6.3 microS (n = 10), respectively. 3. For a given Vj, changes in the lateral giant axon or giant motor fibre membrane potential over a range of +/- 30 mV around their resting levels did not influence the junctional permeability (gj), indicating that the inside-outside potential of the junctional channel does not control gj. 4. Therefore, the steady-state junctional chord conductances were dependent only upon Vj. 5. The voltage dependence of the chord conductance was well fitted by a modified Boltzmann relation given by the equation (Formula: see text) with the constants: A = 0.15 +/- 0.03 mV-1 (n = 10) and V0 = 28 +/- 4 mV (n = 10); the latter two parameters were also found to be independent of both transmembrane potentials. 6. The junctional currents were already constant 1 ms after step changes in the junctional voltage; this was three orders of magnitude faster than the other known examples of voltage-controlled gap junctions between embryonic cells. 7. Our results may be interpreted by a highly voltage-dependent probability of opening of the junctional channels. They also suggest that the gap-junction channels forming the giant motor synapse respond very rapidly to potential and that the hemi-channels which constitute them may not be symmetric. PMID:2824761

  18. Single-Phase Boost Rectifier Adding a Capacitor for Pumping Action in DC Circuit

    NASA Astrophysics Data System (ADS)

    Oishi, Hayato; Neba, Yasuhiko; Ishizaka, Kouichi; Itoh, Ryozo

    To obtain higher DC output voltage, a single-phase boost rectifier adding a capacitor for pumping action in DC circuit is studied. This gives two-stage boost operation by means of inductive and capacitive energy storage/transfer mechanisms under the high-frequency switching. The experimental prototype, employing an insulated-gate bipolar transistor as an active power switching device and a PI controller for output voltage regulation, is implemented to investigate the operation. The experimental results confirm that the input current can almost be waveshaped sinusoidally with a near-unity power factor by the current-mode control.

  19. Through-Silicon-Via Design with Clustering Structure and Adaptive Through-Silicon-Via Control for Three-Dimentional Solid-State-Drive Boost Converter System

    NASA Astrophysics Data System (ADS)

    Johguchi, Koh; Hatanaka, Teruyoshi; Takeuchi, Ken

    2012-02-01

    This paper presents a through-silicon-via (TSV) design methodology for three-dimentional solid-state-drive (3D-SSD) system with the 20 V boost converter. Although TSV technologies give compact packaging and high performance compared to the conventional wire-bonding technology, the parasitic resistors and capacitors of TSVs may cause the performance degradation. Additionally, since the number of the activated NAND chip is dynamically changed as access patterns from real processor, the optimum design point for the boost converter is also moved according to the situation. Then, the clustering method with two different sizes of Cu-TSVs and the adaptive TSV number controlling technique for polycrystalline silicon TSVs are proposed to reduce the parasitic resistors and capacitors. With the cluster structure and Cu-TSVs, the performance of the proposed 3D-SSD is improved by ˜10%. Furthermore, the adaptive TSV number controller enhances the performance up to 2 times higher for poly-Si TSV case by reducing the parasitic elements due to TSVs.

  20. Implementation of Statistical Process Control: Evaluating the Mechanical Performance of a Candidate Silicone Elastomer Docking Seal

    NASA Technical Reports Server (NTRS)

    Oravec, Heather Ann; Daniels, Christopher C.

    2014-01-01

    The National Aeronautics and Space Administration has been developing a novel docking system to meet the requirements of future exploration missions to low-Earth orbit and beyond. A dynamic gas pressure seal is located at the main interface between the active and passive mating components of the new docking system. This seal is designed to operate in the harsh space environment, but is also to perform within strict loading requirements while maintaining an acceptable level of leak rate. In this study, a candidate silicone elastomer seal was designed, and multiple subscale test articles were manufactured for evaluation purposes. The force required to fully compress each test article at room temperature was quantified and found to be below the maximum allowable load for the docking system. However, a significant amount of scatter was observed in the test results. Due to the stochastic nature of the mechanical performance of this candidate docking seal, a statistical process control technique was implemented to isolate unusual compression behavior from typical mechanical performance. The results of this statistical analysis indicated a lack of process control, suggesting a variation in the manufacturing phase of the process. Further investigation revealed that changes in the manufacturing molding process had occurred which may have influenced the mechanical performance of the seal. This knowledge improves the chance of this and future space seals to satisfy or exceed design specifications.

  1. Observation of DNA dynamics near silicon nanopores by controlling the ultraviolet light spot

    NASA Astrophysics Data System (ADS)

    Yamazaki, Hirohito; Ito, Shintaro; Esashika, Keiko; Saiki, Toshiharu

    2015-03-01

    Biopolymer translocation through a nanopore is an attractive phenomenon in the field of biophysics. When the voltage is applied through a nanopore, DNA coils thread into a nanopore by deforming its coil structure and recoil after translocation through a nanopore. Because DNA coil structure is relative with DNA translocation, DNA dynamics near a nanopore have a correlation with DNA translocation. To investigate DNA dynamics, we developed the optical nanopore detection system, which has a capability to observe DNA dynamics near nanopore at sub-100-nm and sub-millisecond resolutions. Here, we report our experimental results of DNA dynamics near nanopores by controlling position of light spots. Because silicon have high refractive index and extinction coefficient at ultraviolet light, the ultraviolet light creates z- and x-polarized light spot, which locate on nanopores and 50 nm apart from nanopores, respectively. By controlling light polarization, we observed different fluorescence intensity traces between z- and x-polarized light spot. The experimental results showed that fluorescence intensity trance of z-polarized light spot decayed faster than that of x-polarized light spot, which explain DNA dynamics near nanopores change by position from nanopores.

  2. Controlling damping and quality factors of silicon microcantilevers by selective metallization

    NASA Astrophysics Data System (ADS)

    Sosale, Guruprasad; Das, Kaushik; Fréchette, Luc; Vengallatore, Srikar

    2011-10-01

    Ceramic microresonators coated with relatively thin metallic films are widely used for sensing, scanning probe microscopy, signal processing and vibration energy harvesting. The metallization improves optical reflectivity and electrical conductivity, but invariably degrades the quality factor (Q) of resonance by increasing the amount of energy dissipated during vibration. Developing strategies for controlling damping due to metallization is vital for the design of high-performance microresonators. This paper presents a strategy based on the insight that dissipation is a function of the deformation experienced by the thin film during oscillation. Therefore, damping can be controlled by patterning the metal in regions of low strain. A simple analytical model is developed to quantify the change in damping as a function of selective metallization along the length of a microcantilever. The predictions of this model are in good agreement with measurements of damping in single-crystal silicon microcantilevers that are partially coated on one surface with 100 nm thick aluminum films. Crucially, damping due to clamping, support and viscous losses is minimized in these structures to enable a careful comparison of theory with experiments. Coating 20% of the length of the beam starting from the tip has no significant impact on damping in either the first or the second mode of vibration. In contrast, placing the same size of metallization at the root leads to considerable dissipation; in the first mode, the damping due to this patch is ~60% of that caused by a full coat.

  3. Vertically aligned crystalline silicon nanowires with controlled diameters for energy conversion applications: Experimental and theoretical insights

    NASA Astrophysics Data System (ADS)

    Razek, Sara Abdel; Swillam, Mohamed A.; Allam, Nageh K.

    2014-05-01

    Vertically orientated single crystalline silicon nanowire (SiNW) arrays with controlled diameters are fabricated via a metal-assisted chemical etching method. The diameter of the fabricated nanowires is controlled by simply varying the etching time in HF/H2O2 electrolytes. The fabricated SiNWs have diameters ranging from 117 to 650 nm and lengths from 8 to 18 ?m. The optical measurements showed a significant difference in the reflectance/absorption of the SiNWs with different diameters, where the reflectance increases with increasing the diameter of the SiNWs. The SiNWs showed significant photoluminescence (PL) emission spectra with peaks lying between 380 and 670 nm. The PL intensity increases as the diameter increases and shows red shift for peaks at 670 nm. The increase or decrease of reflectivity is coincident with PL intensity at wavelength 660 nm. The x-ray diffraction patterns confirm the high crystallinity of the fabricated SiNWs. In addition, the Raman spectra showed a shift in the first order transverse band toward lower frequencies compared to that usually seen for c-Si. Finite difference time domain simulations have been performed to confirm the effect of change of diameter on the optical properties of the nanowires. The simulation results showed good agreement with the experimental results for the SiNWs of different diameters.

  4. Vertically aligned crystalline silicon nanowires with controlled diameters for energy conversion applications: Experimental and theoretical insights

    SciTech Connect

    Razek, Sara Abdel; Swillam, Mohamed A.; Allam, Nageh K.

    2014-05-21

    Vertically orientated single crystalline silicon nanowire (SiNW) arrays with controlled diameters are fabricated via a metal-assisted chemical etching method. The diameter of the fabricated nanowires is controlled by simply varying the etching time in HF/H{sub 2}O{sub 2} electrolytes. The fabricated SiNWs have diameters ranging from 117 to 650 nm and lengths from 8 to 18 μm. The optical measurements showed a significant difference in the reflectance/absorption of the SiNWs with different diameters, where the reflectance increases with increasing the diameter of the SiNWs. The SiNWs showed significant photoluminescence (PL) emission spectra with peaks lying between 380 and 670 nm. The PL intensity increases as the diameter increases and shows red shift for peaks at ∼670 nm. The increase or decrease of reflectivity is coincident with PL intensity at wavelength ∼660 nm. The x-ray diffraction patterns confirm the high crystallinity of the fabricated SiNWs. In addition, the Raman spectra showed a shift in the first order transverse band toward lower frequencies compared to that usually seen for c-Si. Finite difference time domain simulations have been performed to confirm the effect of change of diameter on the optical properties of the nanowires. The simulation results showed good agreement with the experimental results for the SiNWs of different diameters.

  5. Application of artificial intelligence control to the vapor-liquid-solid silicon carbide whisker process

    SciTech Connect

    Shalek, P.D.; Parkinson, W.J.

    1989-01-01

    Silicon carbide whiskers have excellent mechanical and chemical properties, making them very desirable as a reinforcement for structural ceramic and other composite materials. Los Alamos has developed a laboratory-scale batch process for producing very high quality SiC whiskers by the vapor-liquid-solid (VLS) method which is an active candidate for technology transfer involving significant scale-up. The process, however, involves quite complex chemical/physical and parametric relationships and has not as yet lent itself successfully to modeling. An expert computer system was therefore developed to facilitate the transfer of this technology to industry. Optimum conditions were determined by relating the many process parameters to product results to establish a set of rules for running the process. These are incorporated in a two-phase expert system designed to guide inexperienced users. In Phase 1, an expert consultant program provides the user with information that enables him to set up the run. This information is incorporated into the rule base that makes up Phase 2 --- the control system. At present, the operator functions as the controller by responding to the decisions of the expert system; automation can be added later. 13 refs., 16 figs.

  6. Strain and electric field control of hyperfine interactions for donor spin qubits in silicon

    NASA Astrophysics Data System (ADS)

    Usman, M.; Hill, C. D.; Rahman, R.; Klimeck, G.; Simmons, M. Y.; Rogge, S.; Hollenberg, L. C. L.

    2015-06-01

    Control of hyperfine interactions is a fundamental requirement for quantum computing architecture schemes based on shallow donors in silicon. However, at present, there is lacking an atomistic approach including critical effects of central-cell corrections and nonstatic screening of the donor potential capable of describing the hyperfine interaction in the presence of both strain and electric fields in realistically sized devices. We establish and apply a theoretical framework, based on atomistic tight-binding theory, to quantitatively determine the strain and electric-field-dependent hyperfine couplings of donors. Our method is scalable to millions of atoms, and yet captures the strain effects with an accuracy level of DFT method. Excellent agreement with the available experimental data sets allow reliable investigation of the design space of multiqubit architectures, based on both strain only as well as hybrid (strain + field) control of qubits. The benefits of strain are uncovered by demonstrating that a hybrid control of qubits based on (001) compressive strain and in-plane (100 or 010) fields results in higher gate fidelities and or faster gate operations, for all of the four donor species considered (P, As, Sb, and Bi). The comparison between different donor species in strained environments further highlights the trends of hyperfine shifts, providing predictions where no experimental data exists. While faster gate operations are realizable with in-plane fields for P, As, and Sb donors, only for the Bi donor, our calculations predict faster gate response in the presence of both in-plane and out-of-plane fields, truly benefiting from the proposed planar field control mechanism of the hyperfine interactions.

  7. 35 GHz integrated circuit rectifying antenna with 33 percent efficiency

    NASA Technical Reports Server (NTRS)

    Yoo, T.-W.; Chang, K.

    1991-01-01

    A 35 GHz integrated circuit rectifying antenna (rectenna) has been developed using a microstrip dipole antenna and beam-lead mixer diode. Greater than 33 percent conversion efficiency has been achieved. The circuit should have applications in microwave/millimeter-wave power transmission and detection.

  8. 46 CFR 183.360 - Semiconductor rectifier systems.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...) Meet Sections 35.84.2 and 35.84.4 of the ABS Steel Vessel Rules (incorporated by reference; see 46 CFR... 46 Shipping 7 2012-10-01 2012-10-01 false Semiconductor rectifier systems. 183.360 Section 183.360... TONS) ELECTRICAL INSTALLATION Power Sources and Distribution Systems § 183.360 Semiconductor...

  9. 46 CFR 183.360 - Semiconductor rectifier systems.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...) Meet Sections 35.84.2 and 35.84.4 of the ABS Steel Vessel Rules (incorporated by reference; see 46 CFR... 46 Shipping 7 2013-10-01 2013-10-01 false Semiconductor rectifier systems. 183.360 Section 183.360... TONS) ELECTRICAL INSTALLATION Power Sources and Distribution Systems § 183.360 Semiconductor...

  10. 35 GHz integrated circuit rectifying antenna with 33 percent efficiency

    NASA Astrophysics Data System (ADS)

    Yoo, T.-W.; Chang, K.

    1991-11-01

    A 35 GHz integrated circuit rectifying antenna (rectenna) has been developed using a microstrip dipole antenna and beam-lead mixer diode. Greater than 33 percent conversion efficiency has been achieved. The circuit should have applications in microwave/millimeter-wave power transmission and detection.

  11. Comparison of Rectified and Unrectified Sockets for Transtibial Amputees

    PubMed Central

    Engsberg, Jack R.; Sprouse, S. Wayne; Uhrich, Mary L.; Ziegler, Barbara R.; Luitjohan, F. Daniel

    2008-01-01

    The current method for fabricating prosthetic sockets is to modify a positive mold to account for the non-homogeneity of the residual limb to tolerate load (i.e., rectified socket). We tested unrectified sockets by retaining the shape of the residual limb, except for a distal end pad, using an alginate gel process instead of casting. This investigation compared rectified and unrectified sockets. Forty-three adults with unilateral transtibial amputations were tested after randomly wearing both rectified and unrectified sockets for at least 4 weeks. Testing included a gait analysis, energy expenditure and Prosthesis Evaluation Questionnaire (PEQ). Results indicated no differences between sockets for gait speed and timing, gait kinematics and kinetics, and gait energy expenditure. There were also no differences in the Prosthetic Evaluation Questionnaire and 16 subjects selected the rectified socket, 25 selected the unrectified socket, and 2 subjects selected to use both sockets as their exit socket. Results seemed to indicate that more than one paradigm exists for shaping prosthetic sockets, and this paradigm may be helpful in understanding the mechanisms of socket fit. The alginate gel fabrication method was simpler than the traditional method. The method could be helpful in other countries where prosthetic care is lacking, may be helpful with new amputees, and may be helpful in typical clinics to reduce costs and free the prosthetist to focus more time on patient needs. PMID:18776945

  12. 125. JOB NO. LINE 5044, INTERNATIONAL RECTIFIER CORP., RACHELLE LABORATORIES, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    125. JOB NO. LINE 5044, INTERNATIONAL RECTIFIER CORP., RACHELLE LABORATORIES, INC., LONG BEACH, CA, BY J.C. FULTON, SEPTEMBER 1982, LINE 5044, CLIFTON AND CO., ON FILE ENGINEERS DEPARTMENT, PORT OF LONG BEACH - Ford Motor Company Long Beach Assembly Plant, Assembly Building, 700 Henry Ford Avenue, Long Beach, Los Angeles County, CA

  13. 37. VIEW OF SIX GAP ROTARY RECTIFIER FOR MAINTAINING CORONA ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    37. VIEW OF SIX GAP ROTARY RECTIFIER FOR MAINTAINING CORONA DISCHARGE IN THE COTTRELL ELECTROSTATIC GENERATORS. THE SYSTEM WAS CAPABLE OF PROVIDING 88,000 VOLTS TO THE ELECTRODES WITHIN THE PRECIPITATOR CHAMBER THE UNIT WAS LOCATED TO THE REAR OF BOILER 904 IN AN ENCLOSED ROOM. - New York, New Haven & Hartford Railroad, Cos Cob Power Plant, Sound Shore Drive, Greenwich, Fairfield County, CT

  14. 46 CFR 183.360 - Semiconductor rectifier systems.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...) Meet Sections 35.84.2 and 35.84.4 of the ABS Steel Vessel Rules (incorporated by reference; see 46 CFR... 46 Shipping 7 2010-10-01 2010-10-01 false Semiconductor rectifier systems. 183.360 Section 183.360... TONS) ELECTRICAL INSTALLATION Power Sources and Distribution Systems § 183.360 Semiconductor...

  15. 46 CFR 183.360 - Semiconductor rectifier systems.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...) Meet Sections 35.84.2 and 35.84.4 of the ABS Steel Vessel Rules (incorporated by reference; see 46 CFR... 46 Shipping 7 2011-10-01 2011-10-01 false Semiconductor rectifier systems. 183.360 Section 183.360... TONS) ELECTRICAL INSTALLATION Power Sources and Distribution Systems § 183.360 Semiconductor...

  16. Deconvolving the controls on the deep ocean's silicon stable isotope distribution

    NASA Astrophysics Data System (ADS)

    de Souza, Gregory F.; Slater, Richard D.; Dunne, John P.; Sarmiento, Jorge L.

    2014-07-01

    We trace the marine biogeochemical silicon (Si) cycle using the stable isotope composition of Si dissolved in seawater (expressed as δ30Si). Open ocean δ30Si observations indicate a surprisingly strong influence of the physical circulation on the large-scale marine Si distribution. Here, we present an ocean general circulation model simulation that deconvolves the physical and biogeochemical controls on the δ30Si distribution in the deep oceanic interior. By parsing dissolved Si into its preformed and regenerated components, we separate the influence of deep water formation and circulation from the effects of biogeochemical cycling related to opal dissolution at depth. We show that the systematic meridional δ30Si gradient observed in the deep Atlantic Ocean is primarily determined by the preformed component of Si, whose distribution in the interior is controlled solely by the circulation. We also demonstrate that the δ30Si value of the regenerated component of Si in the global deep ocean is dominantly set by oceanic regions where opal export fluxes to the deep ocean are large, i.e. primarily in the Southern Ocean's opal belt. The global importance of this regionally dynamic Si cycling helps explain the observed strong physical control on the oceanic δ30Si distribution, since most of the regenerated Si present within the deep Atlantic and Indo-Pacific Oceans is in fact transported into these basins by deep waters flowing northward from the Southern Ocean. Our results thus provide a mechanistic explanation for the observed δ30Si distribution that emphasizes the dominant importance of the Southern Ocean in the marine Si cycle.

  17. Controllable growth of silicon nanowire arrays fabricated by two-step silver catalyzed chemical etching

    NASA Astrophysics Data System (ADS)

    Tian, Ji-Li; Zhang, Hua-Yu

    2015-12-01

    Silicon nanowire arrays (SiNWs) were prepared by the two-step silver catalyzed chemical etching process. The influence of various factors such as deposition time of silver nanoparticles, etching process and post-treatment conditions on the morphology and structure of SiNWs were systematically investigated. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Ultraviolet-Visible spectroscopy (UV-Vis) and Fourier-transform infrared spectroscopy (FTIR) were used to characterize the SiNWs. The results revealed the existence of a positive linear relationship between length and etching time, which could be used to control the length of the SiNWs. The length and diameter of the nanowires both gradually decreased as the duration of the post-treatment process increased. SiNWs can be obtained with better uniformity by optimizing the post-treatment duration. In addition, four different lengths of SiNWs with regular and uniform morphology were fabricated using the above controllable growth process. The results showed that the silver catalyst was completely removed after the as-obtained SiNWs were immersed into HNO3. All the as-prepared SiNWs showed a good light reflection performance, which was enhanced with increasing lengths of the arrays. The reflectance of the as-obtained SiNWs was found to be less than 1% within the range of the visible spectrum (300-800 nm). These results confirm that this simple fabrication method can help achieve controllable growth of SiNWs of desired sizes.

  18. PLGA-Mesoporous Silicon Microspheres for the in Vivo Controlled Temporospatial Delivery of Proteins.

    PubMed

    Minardi, Silvia; Pandolfi, Laura; Taraballi, Francesca; De Rosa, Enrica; Yazdi, Iman K; Liu, Xeuwu; Ferrari, Mauro; Tasciotti, Ennio

    2015-08-01

    In regenerative medicine, the temporospatially controlled delivery of growth factors (GFs) is crucial to trigger the desired healing mechanisms in the target tissues. The uncontrolled release of GFs has been demonstrated to cause severe side effects in the surrounding tissues. The aim of this study was to optimize a translational approach for the fine temporal and spatial control over the release of proteins, in vivo. Hence, we proposed a newly developed multiscale composite microsphere based on a core consisting of the nanostructured silicon multistage vector (MSV) and a poly(dl-lactide-co-glycolide) acid (PLGA) outer shell. Both of the two components of the resulting composite microspheres (PLGA-MSV) can be independently tailored to achieve multiple release kinetics contributing to the control of the release profile of a reporter protein in vitro. The influence of MSV shape (hemispherical or discoidal) and size (1, 3, or 7 μm) on PLGA-MSV's morphology and size distribution was investigated. Second, the copolymer ratio of the PLGA used to fabricate the outer shell of PLGA-MSV was varied. The composites were fully characterized by optical microscopy, scanning electron microscopy, ζ potential, Fourier transform infrared spectroscopy, and thermogravimetric analysis-differential scanning calorimetry, and their release kinetics over 30 days. PLGA-MSV's biocompatibility was assessed in vitro with J774 macrophages. Finally, the formulation of PLGA-MSV was selected, which concurrently provided the most consistent microsphere size and allowed for a zero-order release kinetic. The selected PLGA-MSVs were injected in a subcutaneous model in mice, and the in vivo release of the reporter protein was followed over 2 weeks by intravital microscopy, to assess if the zero-order release was preserved. PLGA-MSV was able to retain the payload over 2 weeks, avoiding the initial burst release typical of most drug delivery systems. Finally, histological evaluation assessed the biocompatibility of the platform in vivo. PMID:26108253

  19. Controllable light-induced conic structures in silicon nanowire arrays by metal-assisted chemical etching

    NASA Astrophysics Data System (ADS)

    Zhang, Shenli; Wang, Xinwei; Liu, Hong; Shen, Wenzhong

    2014-01-01

    Silicon nanowires (SiNWs) have long been considered a promising material due to their extraordinary electrical and optical properties. As a simple, highly efficient fabrication method for SiNWs, metal-assisted chemical etching (MACE) has been intensively studied over recent years. However, effective control by modulation of simple parameters is still a challenging topic and some key questions still remain in the mechanistic processes. In this work, a novel method to manipulate SiNWs with a light-modulated MACE process has been systematically investigated. Conic structures consisting of inclined and clustered SiNWs can be generated and effectively modified by the incident light while new patterns such as ‘bamboo shoot’ arrays can also be formed under certain conditions. More importantly, detailed study has revealed a new top-down ‘diverting etching’ model of the conic structures in this process, different from the previously proposed ‘bending’ model. As a consequence of this mechanism, preferential lateral mass transport of silver particles occurs. Evidence suggests a relationship of this phenomenon to the inhomogeneous distribution of the light-induced electron-hole pairs beneath the etching front. Study on the morphological change and related mechanism will hopefully open new routes to understand and modulate the formation of SiNWs and other nanostructures.

  20. Silicon as Reducing Agent for Controlled Production of Plasmonic Copper Nanocomposite Glasses: A Spectroscopic Study

    NASA Astrophysics Data System (ADS)

    Jiménez, José A.

    2015-11-01

    The use of silicon to produce metal nanocomposite phosphate glasses with plasmonic properties is proposed. It is demonstrated how the reducing properties of Si powder allow for producing Cu nanocomposite glasses in a controlled manner during heat treatment (HT). Cu/Si-codoped glasses were prepared in a 50BaO-50P2O5 matrix by a simple melt-quench method in ambient atmosphere. The worst-case scenario is considered by having the noble metal introduced in its higher oxidation state as copper(II) oxide, i.e., instead of using monovalent copper. Optical absorption and photoluminescence (PL) spectroscopy, including emission decay dynamics, were employed for characterization of the melt-quenched glass, and for investigating the influence of HT on material optical properties. Remarkably, increasing amounts of Si powder were observed to suppress and ultimately remove the Cu2+ visible absorption band in the CuO-containing glasses. Moreover, subsequent HT of the glass with the highest Si content resulted in progressive development of the surface plasmon resonance of Cu nanoparticles with increasing holding time. PL spectroscopy analysis is further employed towards elucidating the Cu2+ → Cu+ → Cu0 valence state changes likely occurring during the melting and subsequent thermal processing.

  1. Controllable light-induced conic structures in silicon nanowire arrays by metal-assisted chemical etching.

    PubMed

    Zhang, Shenli; Wang, Xinwei; Liu, Hong; Shen, Wenzhong

    2014-01-17

    Silicon nanowires (SiNWs) have long been considered a promising material due to their extraordinary electrical and optical properties. As a simple, highly efficient fabrication method for SiNWs, metal-assisted chemical etching (MACE) has been intensively studied over recent years. However, effective control by modulation of simple parameters is still a challenging topic and some key questions still remain in the mechanistic processes. In this work, a novel method to manipulate SiNWs with a light-modulated MACE process has been systematically investigated. Conic structures consisting of inclined and clustered SiNWs can be generated and effectively modified by the incident light while new patterns such as 'bamboo shoot' arrays can also be formed under certain conditions. More importantly, detailed study has revealed a new top-down 'diverting etching' model of the conic structures in this process, different from the previously proposed 'bending' model. As a consequence of this mechanism, preferential lateral mass transport of silver particles occurs. Evidence suggests a relationship of this phenomenon to the inhomogeneous distribution of the light-induced electron-hole pairs beneath the etching front. Study on the morphological change and related mechanism will hopefully open new routes to understand and modulate the formation of SiNWs and other nanostructures. PMID:24334462

  2. Interface control and mechanical property improvements in silicon carbide/titanium composites

    NASA Technical Reports Server (NTRS)

    Brewer, W. D.; Unnam, J.

    1982-01-01

    Several composite systems made of titanium matrix reinforced with silicon carbide fiber were investigated to obtain a better understanding of composite-degradation mechanisms and to develop techniques to minimize loss of mechanical properties during fabrication and in service. Emphasis was on interface control by fiber or matrix coatings. X-ray diffraction studies on planar samples showed that the formation of titanium silicides was greatly inhibited by the presence of aluminum or Ti3A1 layers at the fiber-matrix interface, with the Ti3A1 being more effective in reducing the reactions. Fiber studies showed that coating the fiber with a 1-micron-thick layer of aluminum improved the as-fabricated strength of a stoichiometric SiC fiber and reduced the fiber degradation during exposure to composite-fabrication conditions. Applying an interfacial barrier by coating the matrix foils instead of the fibers was found to be an effective method for improving composite strength. Reducing the fabrication temperature also resulted in significant improvements in composite strengths. Good-quality, well-consolidated composites were fabricated at temperatures well below those currently used for SiC-Ti composite fabrication.

  3. Erbium-doped slot waveguides containing size-controlled silicon nanocrystals

    SciTech Connect

    Hoffmann, R.; Beyer, J. Heitmann, J.; Klemm, V.; Rafaja, D.; Johnson, B. C.; McCallum, J. C.

    2015-04-28

    Silicon based slot waveguides with a slot containing Si nanocrystals (Si-nc) and Erbium ions (Er{sup 3+}) inside a silica matrix were prepared using sputter deposition and low-energy ion implantation. This sequence enabled independent optimization of nanocrystal formation and Er{sup 3+} incorporation parameters. Using a superlattice approach, the size of the Si-nc inside the slot could be controlled and optimized for maximum Er{sup 3+} luminescence yield at 1.54 μm. Er{sup 3+} is found to be efficiently pumped by Si-nc of sizes around 3 to 4 nm. Increasing Er{sup 3+} photoluminescence at 1.54 μm with increasing post-implantation annealing temperatures up to 1000 °C is attributed to annealing of matrix or Si-nc interface defects mainly. Additionally, a dependence of the Er{sup 3+} luminescence intensity on both the excitation and emission linear polarization orientation is shown, which demonstrates efficient field enhancement in sputtered slot waveguide structures.

  4. Junction barrier Schottky rectifier with an improved P-well region

    NASA Astrophysics Data System (ADS)

    Wang, Ying; Li, Ting; Cao, Fei; Shao, Lei; Chen, Yu-Xian

    2012-12-01

    A junction barrier Schottky (JBS) rectifier with an improved P-well on 4H—SiC is proposed to improve the VF—IR trade-off and the breakdown voltage. The reverse current density of the proposed JBS rectifier at 300 K and 800 V is about 3.3×10-8 times that of the common JBS rectifier at no expense of the forward voltage drop. This is because the depletion layer thickness in the P-well region at the same reverse voltage is larger than in the P+ grid, resulting in a lower spreading current and tunneling current. As a result, the breakdown voltage of the proposed JBS rectifier is over 1.6 kV, that is about 0.8 times more than that of the common JBS rectifier due to the uniform electric field. Although the series resistance of the proposed JBS rectifier is a little larger than that of the common JBS rectifier, the figure of merit (FOM) of the proposed JBS rectifier is about 2.9 times that of the common JBS rectifier. Based on simulating the values of susceptibility of the two JBS rectifiers to electrostatic discharge (ESD) in the human body model (HBM) circuits, the failure energy of the proposed JBS rectifier increases 17% compared with that of the common JBS rectifier.

  5. Parameter Plane Synthesis and Performance Investigation of a Three-Phase Three-Level Bidirectional Rectifier

    NASA Astrophysics Data System (ADS)

    Bhat, Abdul Hamid; Langer, Nitin

    2014-12-01

    In this paper, parameter plane synthesis of a three-phase neutral-point clamped bidirectional rectifier has been performed. The converter involves one outer-loop PI voltage controller and two inner-loop PI current controllers for the closed-loop control. D-partition technique has been employed for the precise design of the voltage controller. An experimental prototype of the converter has been developed, and the experimental investigation of the converter performance in closed loop has been carried out. DSP DS1104 of dSPACE has been used for real-time implementation of the designed controller. The converter gives a very good performance in steady state and dynamic state (for rectification as well as inversion modes of operation) using the designed controller parameters.

  6. Method of purifying metallurgical grade silicon employing reduced pressure atmospheric control

    NASA Technical Reports Server (NTRS)

    Ingle, W. M.; Thompson, S. W.; Chaney, R. E. (Inventor)

    1979-01-01

    A method in which a quartz tube is charged with chunks of metallurgical grade silicon and/or a mixture of such chunks and high purity quartz sand, and impurities from a class including aluminum, boron, as well as certain transition metals including nickel, iron, and manganese is described. The tube is then evacuated and heated to a temperature within a range of 800 C to 1400 C. A stream of gas comprising a reactant, such as silicon tetrafluoride, is continuously delivered at low pressures through the charge for causing a metathetical reaction of impurities of the silicon and the reactant to occur for forming a volatile halide and leaving a residue of silicon of an improved purity. The reactant which included carbon monoxide gas and impurities such as iron and nickel react to form volatile carbonyls.

  7. Control of silicon solidification and the impurities from an Al-Si melt

    NASA Astrophysics Data System (ADS)

    Wang, Panpan; Lu, Huimin; Lai, Yuanshi

    2014-03-01

    The investigation on purification of metallurgical grade silicon by solidification of hypereutectic Al-Si melt under the temperature gradient as an intensified separation way was carried out. Based on the available thermodynamic parameters and experimental data, the thermodynamic behavior and chemical composition of metallic impurities was studied in the solidification process. The principle for the silicon growth in the Al-Si melts was investigated. The results indicated that the refined silicon grains were successfully enriched at the top of the Al-Si alloy. Then the top part refined silicon was collected by aqua regia leaching. Electrorefining of the bottom part (Al-22%Si) was investigated effectively in view of recovering pure Si and Al. Additionally, according to previous investigation, the optimized technical process for SOG-Si production was proposed.

  8. Process for the controlled growth of single-crystal films of silicon carbide polytypes on silicon carbide wafers

    NASA Technical Reports Server (NTRS)

    Powell, J. Anthony (Inventor)

    1991-01-01

    This invention is a method for the controlled growth of single-crystal semiconductor device quality films of SiC polytypes on vicinal (0001) SiC wafers with low tilt angles. Both homoepitaxial and heteroepitaxial SiC films can be produced on the same wafer. In particular, 3C-SiC and 6H-SiC films can be produced within selected areas of the same 6H-SiC wafer.

  9. Process for the controlled growth of single-crystal films of silicon carbide polytypes on silicon carbide wafers

    NASA Technical Reports Server (NTRS)

    Larkin, David J. (Inventor); Powell, J. Anthony (Inventor)

    1992-01-01

    A method for the controlled growth of single-crystal semiconductor-device-quality films of SiC polytypes on vicinal (0001) SiC wafers with low tilt angles is presented. Both homoepitaxial and heteroepitaxial SiC films can be produced on the same wafer. In particular, 3C-SiC and 6H-SiC films can be produced within selected areas of the same 6H-SiC wafer.

  10. A 13.56 MHz CMOS Active Rectifier With Switched-Offset and Compensated Biasing for Biomedical Wireless Power Transfer Systems.

    PubMed

    Lu, Yan; Ki, Wing-Hung

    2013-07-01

    A full-wave active rectifier switching at 13.56 MHz with compensated bias current for a wide input range for wirelessly powered high-current biomedical implants is presented. The four diodes of a conventional passive rectifier are replaced by two cross-coupled PMOS transistors and two comparator- controlled NMOS switches to eliminate diode voltage drops such that high voltage conversion ratio and power conversion efficiency could be achieved even at low AC input amplitude |VAC|. The comparators are implemented with switched-offset biasing to compensate for the delays of active diodes and to eliminate multiple pulsing and reverse current. The proposed rectifier uses a modified CMOS peaking current source with bias current that is quasi-inversely proportional to the supply voltage to better control the reverse current over a wide AC input range (1.5 to 4 V). The rectifier was fabricated in a standard 0.35 μm CMOS N-well process with active area of 0.0651 mm(2). For the proposed rectifier measured at |VAC| = 3.0 V, the voltage conversion ratios are 0.89 and 0.93 for RL=500 Ω and 5 kΩ, respectively, and the measured power conversion efficiencies are 82.2% to 90.1% with |VAC| ranges from 1.5 to 4 V for RL=500 Ω. PMID:23846494

  11. Development of a Thermal Rectifier Usable at High Temperature

    NASA Astrophysics Data System (ADS)

    Takeuchi, Tsunehiro; Goto, Hiroki; Toyama, Yasuhiro; Itoh, Takashi; Mikami, Masashi

    2011-05-01

    By using Al-based metallic alloys characterized by a disordered structure and a narrow pseudogap of a few hundred meV in energy width persisting at the Fermi level, we succeeded in preparing materials possessing a large increase of thermal conductivity with increasing temperature. This unusual increase of thermal conductivity is caused by the electronic structure effect known as the bipolar diffusion effect (BDE) in the context of the two-band model. A thermal rectifier was constructed using materials exhibiting the BDE. By showing the thermal rectification of the bulk sample prepared in this study, we demonstrate that our newly proposed idea of a thermal rectifier using the BDE is applicable for practical use.

  12. A Microfluidic Rectifier: Anisotropic Flow Resistance at Low Reynolds Numbers

    NASA Astrophysics Data System (ADS)

    Groisman, Alex; Quake, Stephen R.

    2004-03-01

    It is one of the basic concepts of Newtonian fluid dynamics that at low Reynolds number (Re) the Navier-Stokes equation is linear and flows are reversible. In microfluidic devices, where Re is essentially always low, this implies that flow resistance in microchannels is isotropic. Here we present a microfluidic rectifier: a microscopic channel of a special shape whose flow resistance is strongly anisotropic, differing by up to a factor of 2 for opposite flow directions. Its nonlinear operation at arbitrary small Re is due to non-Newtonian elastic properties of the working fluid, which is a 0.01% aqueous solution of a high molecular weight polymer. The rectifier works as a dynamic valve and may find applications in microfluidic pumps and other integrated devices.

  13. Rectifying behaviour of spin coated pn hetero-junction

    NASA Astrophysics Data System (ADS)

    Yogamalar, N. Rajeswari; Bose, A. Chandra

    2015-06-01

    Rectifying pn hetero- junction is fabricated with an acceptor p-type organic semiconductor namely tetra- chloro dihydroxy tetra-iodo fluorescein (Rose Bengal (RB)) followed by an inorganic n-type ZnO semiconductor on indium tin oxide (ITO) substrate. The n-type ZnO films are formed by unintentional doping and doping with aluminium (Al) and yttrium (Y) donors. The surface morphology and the distribution of grains are observed from scanning electron microscopy (SEM) and atomic force microscopy (AFM). The current-voltage (I-V) characteristic of the rectifying diode is measured to characterize the junction properties. The I-V plots obtained from the hetero- junction with electric contact shows a diode characteristic different from that of an ideal behavior. The overall efficiency of the diode exhibits a greater dependency on the film crystallinity, carrier concentration, and reverse saturation current.

  14. Doping controlled roughness and defined mesoporosity in chemically etched silicon nanowires with tunable conductivity

    NASA Astrophysics Data System (ADS)

    McSweeney, W.; Lotty, O.; Mogili, N. V. V.; Glynn, C.; Geaney, H.; Tanner, D.; Holmes, J. D.; O'Dwyer, C.

    2013-07-01

    By using Si(100) with different dopant type (n++-type (As) or p-type (B)), we show how metal-assisted chemically etched (MACE) nanowires (NWs) can form with rough outer surfaces around a solid NW core for p-type NWs, and a unique, defined mesoporous structure for highly doped n-type NWs. We used high resolution electron microscopy techniques to define the characteristic roughening and mesoporous structure within the NWs and how such structures can form due to a judicious choice of carrier concentration and dopant type. The n-type NWs have a mesoporosity that is defined by equidistant pores in all directions, and the inter-pore distance is correlated to the effective depletion region width at the reduction potential of the catalyst at the silicon surface in a HF electrolyte. Clumping in n-type MACE Si NWs is also shown to be characteristic of mesoporous NWs when etched as high density NW layers, due to low rigidity (high porosity). Electrical transport investigations show that the etched nanowires exhibit tunable conductance changes, where the largest resistance increase is found for highly mesoporous n-type Si NWs, in spite of their very high electronic carrier concentration. This understanding can be adapted to any low-dimensional semiconducting system capable of selective etching through electroless, and possibly electrochemical, means. The process points to a method of multiscale nanostructuring NWs, from surface roughening of NWs with controllable lengths to defined mesoporosity formation, and may be applicable to applications where high surface area, electrical connectivity, tunable surface structure, and internal porosity are required.

  15. Factors controlling the silicon isotope composition of dissolved silicate and biogenic silica in the Peruvian Upwelling

    NASA Astrophysics Data System (ADS)

    Grasse, P.; Haynert, K.; Brzezinski, M. A.; Frank, M.

    2014-12-01

    The stable silicon (Si) isotope composition (δ30Si) of dissolved silicic acid (Si(OH)4) and of biogenic silica (bSiO2) reflects changes in nutrient utilization and biogeochemical cycling in the present and past ocean. Here we present dissolved and biogenic Si isotope signatures at 9 shelf stations in the upwelling area off Peru obtained during RV Meteor cruise M93 in February 2013 in the frame of the German SFB 754 project to better understand the processes influencing the Si isotope distributions. Primary productivity in the upwelling area of Peru is dominated by diatoms, which preferentially incorporate the lighter 28Si when building their frustules thus leaving seawater enriched in 30Si. Previous studies have suggested that the fractionation factors accompanying this process are species dependent ranging from -0.5‰ to -2.1‰ and that the dissolved Si isotope signature off Peru is strongly influenced by water mass mixing resulting in less fractionated surface water signatures during strong upwelling. To disentangle these processes, information on the Si isotope composition of dissolved and particulate Si is compared with that of the corresponding diatom assemblages. Si isotope signatures of particulate samples are consistently lower than the surrounding seawater ranging from 1‰ to 2‰ (±0.2 2sd). The highest fractionation factors between bSiO2 and Si(OH)4 (ΔbSiO2-SI(OH)4) in surface waters are found at the lowest Si(OH)4 concentrations with an average fractionation factor of -0.9‰, which agrees well with previously reported values. Diatom species effects do not seem to exert a major influence on the isotope signature of the biogenic silica, which instead appears to be mainly controlled by fractionation during biological uptake and water mass mixing.

  16. SiC MOSFET Based Single Phase Active Boost Rectifier with Power Factor Correction for Wireless Power Transfer Applications

    SciTech Connect

    Onar, Omer C; Tang, Lixin; Chinthavali, Madhu Sudhan; Campbell, Steven L; Miller , John M.

    2014-01-01

    Wireless Power Transfer (WPT) technology is a novel research area in the charging technology that bridges the utility and the automotive industries. There are various solutions that are currently being evaluated by several research teams to find the most efficient way to manage the power flow from the grid to the vehicle energy storage system. There are different control parameters that can be utilized to compensate for the change in the impedance due to variable parameters such as battery state-of-charge, coupling factor, and coil misalignment. This paper presents the implementation of an active front-end rectifier on the grid side for power factor control and voltage boost capability for load power regulation. The proposed SiC MOSFET based single phase active front end rectifier with PFC resulted in >97% efficiency at 137mm air-gap and >95% efficiency at 160mm air-gap.

  17. Receptor stimulation causes slow inhibition of IRK1 inwardly rectifying K+ channels by direct protein kinase A-mediated phosphorylation.

    PubMed Central

    Wischmeyer, E; Karschin, A

    1996-01-01

    Strongly rectifying IRK-type inwardly rectifying K+ channels are involved in the control of neuronal excitability in the mammalian brain. Whole-cell patch-clamp experiments show that cloned rat IRK1 (Kir 2.1) channels, when heterologously expressed in mammalian COS-7 cells, are inhibited following the activation of coexpressed serotonin (5-hydroxytryptamine) type 1A receptors by receptor agonists. Inhibition is mimicked by internal perfusion with GTP[gamma-S] and elevation of internal cAMP concentrations. Addition of the catalytic subunits of protein kinase A (PKA) to the internal recording solution causes complete inhibition of wild-type IRK1 channels, but not of mutant IRK1(S425N) channels in which a C-terminal PKA phosphorylation site has been removed. Our data suggest that in the nervous system serotonin may negatively control IRK1 channel activity by direct PKA-mediated phosphorylation. Images Fig. 3 PMID:8650176

  18. An Integrated Amorphous Silicon Gate Driver Circuit Using Voltage-Controlled Capacitance Modeling for High Definition Television

    NASA Astrophysics Data System (ADS)

    Han, Sang-Kug; Choi, Hoon; Moon, Kyo-Ho; Choi, Young-Seok; Jeong, Kyung-Deuk; Park, Kwang-Mook; Choi, Sie-Young

    2012-04-01

    We have developed the integrated amorphous silicon gate driver circuit using the model extraction technique of the inverted staggered and nonsymmetric amorphous silicon (a-Si) thin film transistor. The relation between capacitance characteristics of hydrogenated a-Si (a-Si:H) integrated transistors and the output signal of the gate driver circuit is analyzed using UTMOST IV ver. 1.6.4.R and SMARTSPICE ver. 3.19.15.C. The accuracy of the simulated gate output signal using voltage-controlled capacitance modeling is verified with measured data. The a-Si gate driver circuit using the proposed (TFT) model increased the accuracy of rising (95.3%) and falling (92%) time, compared to the conventional model. The suggested model extraction technique can be used for bottom gate and asymmetric TFT structures.

  19. Enhanced photocurrent in thin-film amorphous silicon solar cells via shape controlled three-dimensional nanostructures

    NASA Astrophysics Data System (ADS)

    Hilali, Mohamed M.; Yang, Shuqiang; Miller, Mike; Xu, Frank; Banerjee, Sanjay; Sreenivasan, S. V.

    2012-10-01

    In this paper, we have explored manufacturable approaches to sub-wavelength controlled three-dimensional (3D) nano-patterns with the goal of significantly enhancing the photocurrent in amorphous silicon solar cells. Here we demonstrate efficiency enhancement of about 50% over typical flat a-Si thin-film solar cells, and report an enhancement of 20% in optical absorption over Asahi textured glass by fabricating sub-wavelength nano-patterned a-Si on glass substrates. External quantum efficiency showed superior results for the 3D nano-patterned thin-film solar cells due to enhancement of broadband optical absorption. The results further indicate that this enhanced light trapping is achieved with minimal parasitic absorption losses in the deposited transparent conductive oxide for the nano-patterned substrate thin-film amorphous silicon solar cell configuration. Optical simulations are in good agreement with experimental results, and also show a significant enhancement in optical absorption, quantum efficiency and photocurrent.

  20. Size Control of Porous Silicon-Based Nanoparticles via Pore-Wall Thinning.

    PubMed

    Secret, Emilie; Leonard, Camille; Kelly, Stefan J; Uhl, Amanda; Cozzan, Clayton; Andrew, Jennifer S

    2016-02-01

    Photoluminescent silicon nanocrystals are very attractive for biomedical and electronic applications. Here a new process is presented to synthesize photoluminescent silicon nanocrystals with diameters smaller than 6 nm from a porous silicon template. These nanoparticles are formed using a pore-wall thinning approach, where the as-etched porous silicon layer is partially oxidized to silica, which is dissolved by a hydrofluoric acid solution, decreasing the pore-wall thickness. This decrease in pore-wall thickness leads to a corresponding decrease in the size of the nanocrystals that make up the pore walls, resulting in the formation of smaller nanoparticles during sonication of the porous silicon. Particle diameters were measured using dynamic light scattering, and these values were compared with the nanocrystallite size within the pore wall as determined from X-ray diffraction. Additionally, an increase in the quantum confinement effect is observed for these particles through an increase in the photoluminescence intensity of the nanoparticles compared with the as-etched nanoparticles, without the need for a further activation step by oxidation after synthesis. PMID:26796986

  1. Electrical Control of g-Factor in a Few-Hole Silicon Nanowire MOSFET.

    PubMed

    Voisin, B; Maurand, R; Barraud, S; Vinet, M; Jehl, X; Sanquer, M; Renard, J; De Franceschi, S

    2016-01-13

    Hole spins in silicon represent a promising yet barely explored direction for solid-state quantum computation, possibly combining long spin coherence, resulting from a reduced hyperfine interaction, and fast electrically driven qubit manipulation. Here we show that a silicon-nanowire field-effect transistor based on state-of-the-art silicon-on-insulator technology can be operated as a few-hole quantum dot. A detailed magnetotransport study of the first accessible hole reveals a g-factor with unexpectedly strong anisotropy and gate dependence. We infer that these two characteristics could enable an electrically driven g-tensor-modulation spin resonance with Rabi frequencies exceeding several hundred mega-Hertz. PMID:26599868

  2. The properties of polycrystalline silicon solar cells with controlled titanium additions

    NASA Technical Reports Server (NTRS)

    Rohatgi, A.; Hopkins, R. H.; Davis, J. R., Jr.

    1981-01-01

    By coupling the results of electrical measurements, such as spectral response, lighted and dark I-V determinations, and deep-level-transient spectroscopy with optical and laser scan photomicroscopy, the effects of grain boundaries and impurities on silicon solar cells were evaluated. Titanium, which produces two deep levels in silicon, degrades cell performance by reducing bulk lifetime and thus cell short-circuit current. Electrically active grain boundaries induce carrier recombination in the bulk and depletion regions of the solar cell. Experimental data imply a small but measurable segregation of titanium into some grain boundaries of the polycrystalline silicon containing high Ti concentration. However, for the titanium-contaminated polycrystalline material used in this study, solar cell performance is dominated by the electrically active titanium concentration in the grains. Microstructural impacts on the devices are of secondary importance

  3. Ultrafast optical control using the Kerr nonlinearity in hydrogenated amorphous silicon microcylindrical resonators

    PubMed Central

    Vukovic, N.; Healy, N.; Suhailin, F. H.; Mehta, P.; Day, T. D.; Badding, J. V.; Peacock, A. C.

    2013-01-01

    Microresonators are ideal systems for probing nonlinear phenomena at low thresholds due to their small mode volumes and high quality (Q) factors. As such, they have found use both for fundamental studies of light-matter interactions as well as for applications in areas ranging from telecommunications to medicine. In particular, semiconductor-based resonators with large Kerr nonlinearities have great potential for high speed, low power all-optical processing. Here we present experiments to characterize the size of the Kerr induced resonance wavelength shifting in a hydrogenated amorphous silicon resonator and demonstrate its potential for ultrafast all-optical modulation and switching. Large wavelength shifts are observed for low pump powers due to the high nonlinearity of the amorphous silicon material and the strong mode confinement in the microcylindrical resonator. The threshold energy for switching is less than a picojoule, representing a significant step towards advantageous low power silicon-based photonic technologies. PMID:24097126

  4. High reliability megawatt transformer/rectifier

    NASA Technical Reports Server (NTRS)

    Zwass, Samuel; Ashe, Harry; Peters, John W.

    1991-01-01

    The goal of the two phase program is to develop the technology and design and fabricate ultralightweight high reliability DC to DC converters for space power applications. The converters will operate from a 5000 V dc source and deliver 1 MW of power at 100 kV dc. The power weight density goal is 0.1 kg/kW. The cycle to cycle voltage stability goals was + or - 1 percent RMS. The converter is to operate at an ambient temperature of -40 C with 16 minute power pulses and one hour off time. The uniqueness of the design in Phase 1 resided in the dc switching array which operates the converter at 20 kHz using Hollotron plasma switches along with a specially designed low loss, low leakage inductance and a light weight high voltage transformer. This approach reduced considerably the number of components in the converter thereby increasing the system reliability. To achieve an optimum transformer for this application, the design uses four 25 kV secondary windings to produce the 100 kV dc output, thus reducing the transformer leakage inductance, and the ac voltage stresses. A specially designed insulation system improves the high voltage dielectric withstanding ability and reduces the insulation path thickness thereby reducing the component weight. Tradeoff studies and tests conducted on scaled-down model circuits and using representative coil insulation paths have verified the calculated transformer wave shape parameters and the insulation system safety. In Phase 1 of the program a converter design approach was developed and a preliminary transformer design was completed. A fault control circuit was designed and a thermal profile of the converter was also developed.

  5. High reliability megawatt transformer/rectifier

    NASA Astrophysics Data System (ADS)

    Zwass, Samuel; Ashe, Harry; Peters, John W.

    1991-03-01

    The goal of the two phase program is to develop the technology and design and fabricate ultralightweight high reliability DC to DC converters for space power applications. The converters will operate from a 5000 V dc source and deliver 1 MW of power at 100 kV dc. The power weight density goal is 0.1 kg/kW. The cycle to cycle voltage stability goals was + or - 1 percent RMS. The converter is to operate at an ambient temperature of -40 C with 16 minute power pulses and one hour off time. The uniqueness of the design in Phase 1 resided in the dc switching array which operates the converter at 20 kHz using Hollotron plasma switches along with a specially designed low loss, low leakage inductance and a light weight high voltage transformer. This approach reduced considerably the number of components in the converter thereby increasing the system reliability. To achieve an optimum transformer for this application, the design uses four 25 kV secondary windings to produce the 100 kV dc output, thus reducing the transformer leakage inductance, and the ac voltage stresses. A specially designed insulation system improves the high voltage dielectric withstanding ability and reduces the insulation path thickness thereby reducing the component weight. Tradeoff studies and tests conducted on scaled-down model circuits and using representative coil insulation paths have verified the calculated transformer wave shape parameters and the insulation system safety. In Phase 1 of the program a converter design approach was developed and a preliminary transformer design was completed. A fault control circuit was designed and a thermal profile of the converter was also developed.

  6. New unimolecular rectifiers and through-bond electron tunneling probed by IETs

    NASA Astrophysics Data System (ADS)

    Honciuc, Andrei

    Rectification of electrical current by a monolayer of organic molecules, sandwiched between two macroscopic metal electrodes, can be viewed as rectification in parallel by many individual rectifiers, or unimolecular rectification. A new class of such rectifiers, namely [6]-[6] fullerene monoadducts show current rectification in monolayers sandwiched between Au electrodes at room temperature. They form very sturdy monolayers at the air-water interface, and can be easily transferred onto Au solid substrates by the Langmuir-Schaefer technique. The current-voltage measurements show that these molecules rectify current in a mechanism opposite to the one predicted by Aviram-Ratner model. Indirect spectroscopic techniques were used to determine the placement of relevant molecular orbitals, relative to the Fermi level of the Au electrodes. The results strongly indicate that the dominant enhanced electron transport takes place through a relevant unoccupied molecular orbital, which is placed asymmetrically in the gap. Hexadecylquinolinium-gamma-tricyanoquinodimethanide and its tetrafluoro analog exhibit a strongly polarized charge transfer (CT) band in solid Langmuir-Blodgett (LB) monolayers. Both compounds rectify in a LB monolayer sandwiched between Au electrodes at room temperature. The direction of polarization of the CT band can be controlled during monolayer deposition: the CT band transition dipole is either perpendicular or parallel to the substrate, depending on film transfer pressure. This CT band was thought to play an important role in the mechanism of rectification. Inelastic electron tunneling spectroscopy (IETS) can elucidate the electron transport mechanism in metal | organic | metal tunneling junctions. An inelastic tunneling spectrometer was built in our laboratory, and the principles are presented in detail. The spectra acquired at intermediate biases (0--0.5 V) at the temperature of 4.2 K are due to known molecular vibrational modes. For higher bias ranges, broad bands are observed at 4.2 K: these bands are probably due to the onset of resonance between the Fermi level of the metal electrodes and an available molecular orbital. These bands, together with the corresponding current enhancement observed in the current-voltage scans of the same junctions appear to be both manifestations of unimolecular rectification.

  7. Single-Phase Active Boost Rectifier with Power Factor Correction for Wireless Power Transfer Applications

    SciTech Connect

    Chinthavali, Madhu Sudhan; Onar, Omer C; Miller, John M; Tang, Lixin

    2013-01-01

    Wireless Power Transfer (WPT) technology is a novel research area in the charging technology that bridges utility and the automotive industries. There are various solutions that are currently being evaluated by several research teams to find the most efficient way to manage the power flow from the grid to the vehicle energy storage system. There are different control parameters that can be utilized to compensate for the change in the impedance. To understand the power flow through the system this paper presents a novel approach to the system model and the impact of different control parameters on the load power. The implementation of an active front-end rectifier on the grid side for power factor control and voltage boost capability for load power regulation is also discussed.

  8. RF rectifiers for EM power harvesting in a Deep Brain Stimulating device.

    PubMed

    Hosain, Md Kamal; Kouzani, Abbas Z; Tye, Susannah; Kaynak, Akif; Berk, Michael

    2015-03-01

    A passive deep brain stimulation (DBS) device can be equipped with a rectenna, consisting of an antenna and a rectifier, to harvest energy from electromagnetic fields for its operation. This paper presents optimization of radio frequency rectifier circuits for wireless energy harvesting in a passive head-mountable DBS device. The aim is to achieve a compact size, high conversion efficiency, and high output voltage rectifier. Four different rectifiers based on the Delon doubler, Greinacher voltage tripler, Delon voltage quadrupler, and 2-stage charge pumped architectures are designed, simulated, fabricated, and evaluated. The design and simulation are conducted using Agilent Genesys at operating frequency of 915 MHz. A dielectric substrate of FR-4 with thickness of 1.6 mm, and surface mount devices (SMD) components are used to fabricate the designed rectifiers. The performance of the fabricated rectifiers is evaluated using a 915 MHz radio frequency (RF) energy source. The maximum measured conversion efficiency of the Delon doubler, Greinacher tripler, Delon quadrupler, and 2-stage charge pumped rectifiers are 78, 75, 73, and 76 % at -5 dBm input power and for load resistances of 5-15 kΩ. The conversion efficiency of the rectifiers decreases significantly with the increase in the input power level. The Delon doubler rectifier provides the highest efficiency at both -5 and 5 dBm input power levels, whereas the Delon quadrupler rectifier gives the lowest efficiency for the same inputs. By considering both efficiency and DC output voltage, the charge pump rectifier outperforms the other three rectifiers. Accordingly, the optimised 2-stage charge pumped rectifier is used together with an antenna to harvest energy in our DBS device. PMID:25600671

  9. Power Factor Improvement of Single-Phase Diode Rectifier Circuit By Field-Weakening of Inverter Driven IPM Motor

    NASA Astrophysics Data System (ADS)

    Takahashi, Isao; Haga, Hitoshi

    This paper proposes a novel inverter drive system to improve input power factor of the single-phase diode rectifier. Conventional rectifier needs a high frequency switching devices and a reactor to improve input power factor. However, the proposed power converter doesn’t need the switching device, the electrolytic capacitor and the reactor. By making many ripples across the dc-bus voltage and then, the input power factor can be improved. The proposed system consists of an only single-phase diode rectifier, small film capacitor, three-phase inverter and motor. The proposed system adopts an interior permanent magnet (IPM) synchronous motor. The IPM motor is well known as a high efficiency motor and can get field weakening. The basic ideas of the inverter control method are based on two following operations. First, the inverter’s controlled synchronous with the dc-bus ripple voltage by field-weakening method.The other is direct active power feeding from the source side to the motor without smoothing the dc-bus voltage. This paper describes that the proposed method can obtain the input power factor 97.3% by experimental tests, and realize the small size and the long life of the system.

  10. Novel synthetic methodology for controlling the orientation of zinc oxide nanowires grown on silicon oxide substrates

    NASA Astrophysics Data System (ADS)

    Cho, Jinhyun; Salleh, Najah; Blanco, Carlos; Yang, Sungwoo; Lee, Chul-Jin; Kim, Young-Woo; Kim, Jungsang; Liu, Jie

    2014-03-01

    This study presents a simple method to reproducibly obtain well-aligned vertical ZnO nanowire arrays on silicon oxide (SiOx) substrates using seed crystals made from a mixture of ammonium hydroxide (NH4OH) and zinc acetate (Zn(O2CCH3)2) solution. In comparison, high levels of OH- concentration obtained using NaOH or KOH solutions lead to incorporation of Na or K atoms into the seed crystals, destroying the c-axis alignment of the seeds and resulting in the growth of misaligned nanowires. The use of NH4OH eliminates the metallic impurities and ensures aligned nanowire growth in a wide range of OH- concentrations in the seed solution. The difference of crystalline orientations between NH4OH- and NaOH-based seeds is directly observed by lattice-resolved images and electron diffraction patterns using a transmission electron microscope (TEM). This study obviously suggests that metallic impurities incorporated into the ZnO nanocrystal seeds are one of the factors that generates the misaligned ZnO nanowires. This method also enables the use of silicon oxide substrates for the growth of vertically aligned nanowires, making ZnO nanostructures compatible with widely used silicon fabrication technology.This study presents a simple method to reproducibly obtain well-aligned vertical ZnO nanowire arrays on silicon oxide (SiOx) substrates using seed crystals made from a mixture of ammonium hydroxide (NH4OH) and zinc acetate (Zn(O2CCH3)2) solution. In comparison, high levels of OH- concentration obtained using NaOH or KOH solutions lead to incorporation of Na or K atoms into the seed crystals, destroying the c-axis alignment of the seeds and resulting in the growth of misaligned nanowires. The use of NH4OH eliminates the metallic impurities and ensures aligned nanowire growth in a wide range of OH- concentrations in the seed solution. The difference of crystalline orientations between NH4OH- and NaOH-based seeds is directly observed by lattice-resolved images and electron diffraction patterns using a transmission electron microscope (TEM). This study obviously suggests that metallic impurities incorporated into the ZnO nanocrystal seeds are one of the factors that generates the misaligned ZnO nanowires. This method also enables the use of silicon oxide substrates for the growth of vertically aligned nanowires, making ZnO nanostructures compatible with widely used silicon fabrication technology. Electronic supplementary information (ESI) available: Additional SEM images, photographs of seed solution and XRD peaks and XPS. See DOI: 10.1039/c3nr03694d

  11. Design of a nanomechanical fluid control valve based on functionalized silicon cantilevers: coupling molecular mechanics with classical engineering design

    NASA Astrophysics Data System (ADS)

    Solares, Santiago D.; Blanco, Mario; Goddard, William A., III

    2004-11-01

    Process engineering design relies on a host of mechanical devices that enable transport phenomena to take place under controlled conditions. These devices include pipes, valves, pumps, chemical reactors, heat exchangers, packed columns, etc. Mass, energy, and momentum transfer will also be essential phenomena in nanoprocess engineering, particularly at the interface between micro- and nanodevices. Control valves are one of the most fundamental components. In this paper we explore the design of a silicon cantilever valve for fluid transport control at the molecular level (34.5-70 nm in length). We utilize design elements that can be synthesized with existing or emerging chemical and solid state fabrication methods. Thus, the valve is constructed with functionalized silicon surfaces, single-wall carbon nanotubes, and organic monolayers. While molecular mechanics design limitations were overcome with help from classical engineering approximations, nonlinear effects, such as nanotube crimping (for an in-line valve design), are accounted for through full-physics atomistic simulations. Optimal design geometries and operating deflection ranges have been estimated for a device containing over 75 000 atoms.

  12. Optically-controlled extinction ratio and Q-factor tunable silicon microring resonators based on optical forces

    PubMed Central

    Long, Yun; Wang, Jian

    2014-01-01

    Tunability is a desirable property of microring resonators to facilitate superior performance. Using light to control light, we present an alternative simple approach to tuning the extinction ratio (ER) and Q-factor of silicon microring resonators based on optical forces. We design an opto-mechanical tunable silicon microring resonator consisting of an add-drop microring resonator and a control-light-carrying waveguide (“controlling” waveguide). One of the two bus waveguides of the microring resonator is a deformable nanostring put in parallel with the “controlling” waveguide. The tuning mechanism relies on the optical force induced deflection of suspended nanostring, leading to the change of coupling coefficient of microring and resultant tuning of ER and Q-factor. Two possible geometries, i.e. double-clamped nanostring and cantilever nanostring, are studied in detail for comparison. The obtained results imply a favorable structure with the microring positioned at the end of the cantilever nanostring. It features a wide tuning range of ER from 5.6 to 39.9 dB and Q-factor from 309 to 639 as changing the control power from 0 to 1.4 mW. PMID:24958225

  13. Electronic transport properties of silicon clusters

    NASA Astrophysics Data System (ADS)

    Matsuura, Yukihito

    2016-02-01

    The electronic transport properties of silicon clusters were examined via theoretical calculations using the first-principles method. Additionally, p-type doping and n-type doping were analyzed by calculating conductance and current of boron- and phosphorus-doped silicon clusters. The p-type doping and n-type doping provided a new transmission peak at an energy level around the Fermi level to increase conductance. Furthermore, simultaneous boron and phosphorus doping resulted in noticeable rectifying characteristics, with the current drive in forward bias being three times higher than that in the reverse bias. A p-n junction was achieved even on a molecular scale.

  14. Process for fabricating device structures for real-time process control of silicon doping

    DOEpatents

    Weiner, Kurt H.

    2001-01-01

    Silicon device structures designed to allow measurement of important doping process parameters immediately after the doping step has occurred. The test structures are processed through contact formation using standard semiconductor fabrication techniques. After the contacts have been formed, the structures are covered by an oxide layer and an aluminum layer. The aluminum layer is then patterned to expose the contact pads and selected regions of the silicon to be doped. Doping is then performed, and the whole structure is annealed with a pulsed excimer laser. But laser annealing, unlike standard annealing techniques, does not effect the aluminum contacts because the laser light is reflected by the aluminum. Once the annealing process is complete, the structures can be probed, using standard techniques, to ascertain data about the doping step. Analysis of the data can be used to determine probable yield reductions due to improper execution of the doping step and thus provide real-time feedback during integrated circuit fabrication.

  15. Controlled release of theophylline from poly(vinyl alcohol) hydrogels/porous silicon nanostructured systems

    NASA Astrophysics Data System (ADS)

    Cervantes-Rincón, N.; Medellín-Rodríguez, F. J.; Escobar-Barrios, V. A.; Palestino, G.

    2013-03-01

    In this research, hybrid hydrogels of poly (vinyl alcohol)/ porous silicon (PSi)/theophylline were synthesized by the freezing and thawing method. We evaluated the influence of the synthesis parameters of the poly (vinyl alcohol) (PVA) hydrogels in relation to their ability to swell and drug released. The parameters studied (using an experimental design developed in Minitab 16) were the polymer concentration, the freezing temperature and the number of freezing/thawing (f/t) cycles. Nanostructured porous silicon particles (NsPSi) and theophylline were added within the polymer matrix to increase the drug charge and the polymer mechanical strength. The hybrid hydrogels were characterized by Infrared Spectroscopy Fourier Transform (FTIR), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Differential Scanning Calorimetry (DSC), drug delivery kinetics were engineered according to the desired drug release schedule.

  16. Controlled release of indomethacin from alginate-poloxamer-silicon carbide composites decrease in-vitro inflammation.

    PubMed

    Díaz-Rodríguez, P; Landin, M

    2015-03-01

    Composites of biomorphic silicon carbides (bioSiCs) and hydrogels are proposed in order to obtain materials able to load and release poor soluble drugs with application in bone pathologies therapy. Hydrogels composed by alginate and poloxamer were loaded with indomethacin, incorporated into the ceramics and crosslinked. The indomethacin release profile is dependent on the microstructure of the bioSiC selected. The loaded oak and sapelli bioSiCs composites have adequate release profiles to promote the decreasing of the secretion of pro-inflammatory cytokines in LPS stimulated macrophages, showing stronger anti-inflammatory effects than pine bioSiC composites. The released indomethacin is able to modulate the degradation of chondrocytes extracellular matrix and promote the formation of new collagen by osteoarthritic chondrocytes. Particles derived from mechanical wear of biomorphic silicon carbides do not show high toxicity, being similar to the zirconia particles. PMID:25596416

  17. Programmable scan controller for fast access to individual elements in a self-scanned silicon photodiode array

    NASA Astrophysics Data System (ADS)

    Ricci, D.; Lampugnani, L.; Papoff, P.; Rotunno, T.

    1986-08-01

    A programmable scan controller to implement a fast access readout of individual photodiodes in a self-scanned silicon photodiode array (SPDA) was assembled using transistor-transistor logic (TTL) presettable counters handled by a single-chip microcontroller. This controller makes it possible to skip groups of unwanted diodes at fast scan rate, whereas the others are read and digitized at normal scan rate. The skipping scan rate (Fs) and the reading scan rate (Fr) are switch selectable, the former in the 4 MHz-250 kHz range, the latter in the Fs/2-Fs/4095 range. Any scan pattern is software programmable. Up to 29 groups of contiguous diodes can be skipped. Integration time and number of scans are also software programmable. Programming is accomplished by the host computer issuing the scan parameters through a strobed 8-bit parallel port to the microcontroller, which provides for the controls necessary for the scan pattern generation required.

  18. Novel synthetic methodology for controlling the orientation of zinc oxide nanowires grown on silicon oxide substrates.

    PubMed

    Cho, Jinhyun; Salleh, Najah; Blanco, Carlos; Yang, Sungwoo; Lee, Chul-Jin; Kim, Young-Woo; Kim, Jungsang; Liu, Jie

    2014-04-01

    This study presents a simple method to reproducibly obtain well-aligned vertical ZnO nanowire arrays on silicon oxide (SiOx) substrates using seed crystals made from a mixture of ammonium hydroxide (NH4OH) and zinc acetate (Zn(O2CCH3)2) solution. In comparison, high levels of OH(-) concentration obtained using NaOH or KOH solutions lead to incorporation of Na or K atoms into the seed crystals, destroying the c-axis alignment of the seeds and resulting in the growth of misaligned nanowires. The use of NH4OH eliminates the metallic impurities and ensures aligned nanowire growth in a wide range of OH(-) concentrations in the seed solution. The difference of crystalline orientations between NH4OH- and NaOH-based seeds is directly observed by lattice-resolved images and electron diffraction patterns using a transmission electron microscope (TEM). This study obviously suggests that metallic impurities incorporated into the ZnO nanocrystal seeds are one of the factors that generates the misaligned ZnO nanowires. This method also enables the use of silicon oxide substrates for the growth of vertically aligned nanowires, making ZnO nanostructures compatible with widely used silicon fabrication technology. PMID:24584438

  19. Controlled Prelithiation of Silicon Monoxide for High Performance Lithium-Ion Rechargeable Full Cells.

    PubMed

    Kim, Hye Jin; Choi, Sunghun; Lee, Seung Jong; Seo, Myung Won; Lee, Jae Goo; Deniz, Erhan; Lee, Yong Ju; Kim, Eun Kyung; Choi, Jang Wook

    2016-01-13

    Despite the recent considerable progress, the reversibility and cycle life of silicon anodes in lithium-ion batteries are yet to be improved further to meet the commercial standards. The current major industry, instead, adopts silicon monoxide (SiOx, x ≈ 1), as this phase can accommodate the volume change of embedded Si nanodomains via the silicon oxide matrix. However, the poor Coulombic efficiencies (CEs) in the early period of cycling limit the content of SiOx, usually below 10 wt % in a composite electrode with graphite. Here, we introduce a scalable but delicate prelithiation scheme based on electrical shorting with lithium metal foil. The accurate shorting time and voltage monitoring allow a fine-tuning on the degree of prelithiation without lithium plating, to a level that the CEs in the first three cycles reach 94.9%, 95.7%, and 97.2%. The excellent reversibility enables robust full-cell operations in pairing with an emerging nickel-rich layered cathode, Li[Ni0.8Co0.15Al0.05]O2, even at a commercial level of initial areal capacity of 2.4 mAh cm(-2), leading to a full cell energy density 1.5-times as high as that of graphite-LiCoO2 counterpart in terms of the active material weight. PMID:26694703

  20. Rapid thermal processing of high-efficiency silicon solar cells with controlled in-situ annealing

    SciTech Connect

    Doshi, P.; Rohatgi, A.; Ropp, M.; Chen, Z.; Ruby, D.; Meier, D.L.

    1995-01-01

    Silicon solar cell efficiencies of 17.1%, 16.4%, 14.8%, and 14.9% have been achieved on FZ, Cz, multicrystalline (mc-Si), and dendritic web (DW) silicon, respectively, using simplified, cost-effective rapid thermal processing (RTP). These represent the highest reported efficiencies for solar cells processed with simultaneous front and back diffusion with no conventional high-temperature furnace steps. Appropriate diffusion temperature coupled with the added in-situ anneal resulted in suitable minority-carrier lifetime and diffusion profiles for high-efficiency cells. The cooling rate associated with the in-situ anneal can improve the lifetime and lower the reverse saturation current density (J{sub 0}), however, this effect is material and base resistivity specific. PECVD antireflection (AR) coatings provided low reflectance and efficient front surface and bulk defect passivation. Conventional cells fabricated on FZ silicon by furnace diffusions and oxidations gave an efficiency of 18.8% due to greater short wavelength response and lower J{sub 0}.

  1. Primary structure and characterization of a small-conductance inwardly rectifying potassium channel from human hippocampus.

    PubMed Central

    Périer, F; Radeke, C M; Vandenberg, C A

    1994-01-01

    We have isolated a human hippocampus cDNA that encodes an inwardly rectifying potassium channel, termed HIR (hippocampal inward rectifier), with strong rectification characteristics. Single-channel recordings indicate that the HIR channel has an unusually small conductance (13 pS), distinguishing HIR from other cloned inward rectifiers. RNA blot analyses show that HIR transcripts are present in heart, skeletal muscle, and several different brain regions, including the hippocampus. Images PMID:8016146

  2. Self-Vth-Cancellation High-Efficiency CMOS Rectifier Circuit for UHF RFIDs

    NASA Astrophysics Data System (ADS)

    Kotani, Koji; Ito, Takashi

    A high-efficiency CMOS rectifier circuit for UHF RFID applications was developed. The rectifier utilizes a self-Vth-cancellation (SVC) scheme in which the threshold voltage of MOSFETs is cancelled by applying gate bias voltage generated from the output voltage of the rectifier itself. A very simple circuit configuration and zero power dissipation characteristics in biasing enable excellent power conversion efficiency (PCE), especially under small RF input power conditions. At higher RF input power conditions, the PCE of the rectifier automatically decreases. This is the built-in self-power-regulation function. The proposed SVC CMOS rectifier was fabricated with a 0.35-m CMOS process and the measured performance was compared with those of conventional nMOS, pMOS, and CMOS rectifiers and other types of Vth cancellation rectifiers as well. The SVC CMOS rectifier achieves 32% of PCE at the -10dBm RF input power condition. This PCE is larger than rectifiers reported to date under this condition.

  3. Development of design model for a rectifier in GAX absorption heat pump systems

    SciTech Connect

    Kang, Y.T.; Chen, W.; Christensen, R.N.

    1996-11-01

    This paper develops a model for design of a rectifier in generator-absorber heat exchanger (GAX) heat pump systems with an ammonia-water solution pair. The objectives of this paper are to provide further understanding of the rectification process in ammonia-water systems and serve as a design tool for the rectifier using a stable computation method. Simultaneous heat and mass transfer analysis is performed for the rectification process. Three different geometric configurations of the rectifier, namely, vertical fluted tube, confined cross flow with fluted tube, and coiled smooth tube, are considered in this paper. The effects of the temperature difference between interface and bulk vapor and heat transfer coefficients in each region on the rectifier size are investigated. The importance of the composition of rectifying vapor, z, is studied. The results show that the temperature difference between the interface and the bulk vapor region should be minimized to obtain a rectifier of small size and a high coefficient of performance (COP). During the rectification process, the composition of rectifying vapor should be lower than the liquid concentration, i.e., z < x{sub l}. The heat transfer coefficient in the vapor region has a much more dominant effect on the rectifier size than that in the liquid and the coolant regions. Mass transfer has a more significant effect on the rectifier size than heat transfer.

  4. Physiological and molecular characterization of an IRK-type inward rectifier K+ channel in a tumour mast cell line.

    PubMed

    Wischmeyer, E; Lentes, K U; Karschin, A

    1995-04-01

    The basophilic leucaemia cell line RBL-2H3 exhibits a robust inwardly rectifying potassium current, IKIR, which is likely to be modulated by G proteins. We examined the physiological and molecular properties of this KIR conductance to define the nature of the underlying channel species. The macroscopic conductance revealed characteristics typical of classical K+ inward rectifiers of the IRK type. Channel gating was rapid, first order (tau approximately 1 ms at -100 mV) and steeply voltage dependent. Both activation potential and slope conductance were dependent on extracellular K+ concentration ([K+]o) and inward rectification persisted in the absence of internal Mg2+. The current was susceptible to a concentration- and voltage-dependent block by extracellular Na+, Cs+ and Ba2+. Initial IKIR whole-cell amplitudes as well as current rundown were dependent on the presence of 1 mM internal ATP. Perfusion of intracellular guanosine 5'-Q-(3-thiotriphosphate) (GTP[gamma S]) suppressed IKIR with an average half-time of decline of approximately 400 s. It was demonstrated that the dominant IRK-type 25 pS conductance channel was indeed suppressed by 100 microM preloaded GTP[gamma S]. Reverse transcriptase-polymerase chain reactions (RT-PCR) with RBL cell poly(A)+ RNA identified a full length K+ inward rectifier with 94% base pair homology to the recently cloned mouse IRK1 channel. It is concluded that RBL cells express a classical voltage-dependent IRK-type K+ inward rectifier RBL-IRK1 which is negatively controlled by G proteins. PMID:7603835

  5. Silicon nanocrystals in SiN{sub x}/SiO{sub 2} hetero-superlattices: The loss of size control after thermal annealing

    SciTech Connect

    Zelenina, A. Zacharias, M.; Sarikov, A.; Zhigunov, D. M.; Weiss, C.; Zakharov, N.; Werner, P.; López-Conesa, L.; Peiró, F.

    2014-06-28

    Superlattices containing 3 nm thick silicon rich silicon nitride sublayers and 3 nm and 10 nm thick SiO{sub 2} barriers were prepared by plasma enhanced chemical vapor deposition. Despite the as-prepared samples represented a well-kept multilayer structure with smooth interfaces, the high temperature annealing resulted in the total destruction of multilayer structure in the samples containing 3 nm SiO{sub 2} barriers. Energy-filtered transmission electron microscopy images of these samples indicated a silicon nanoclusters formation with sizes of 2.5–12.5 nm, which were randomly distributed within the structure. Although in the sample with 10 nm SiO{sub 2} barriers some fragments of the multilayer structure could be still observed after thermal annealing, nevertheless, the formation of large nanocrystals with diameters up to 10 nm was confirmed by dark field transmission electron microscopy. Thus, in contrast to the previously published results, the expected size control of silicon nanocrystals was lost. According to the FTIR results, the thermal annealing of SiN{sub x}/SiO{sub 2} superlattices led to the formation of silicon nanocrystals in mostly oxynitride matrix. Annealed samples demonstrated a photoluminescence peak at 885 nm related to the luminescence of silicon nanocrystals, as confirmed by time-resolved photoluminescence measurements. The loss of nanocrystals size control is discussed in terms of the migration of oxygen atoms from the SiO{sub 2} barriers into the silicon rich silicon nitride sublayers. A thermodynamic mechanism responsible for this process is proposed. According to this mechanism, the driving force for the oxygen migration is the gain in the configuration entropy related to the relative arrangements of oxygen and nitrogen atoms.

  6. Inward rectifier potassium currents in mammalian skeletal muscle fibres

    PubMed Central

    DiFranco, Marino; Yu, Carl; Quiñonez, Marbella; Vergara, Julio L

    2015-01-01

    Inward rectifying potassium (Kir) channels play a central role in maintaining the resting membrane potential of skeletal muscle fibres. Nevertheless their role has been poorly studied in mammalian muscles. Immunohistochemical and transgenic expression were used to assess the molecular identity and subcellular localization of Kir channel isoforms. We found that Kir2.1 and Kir2.2 channels were targeted to both the surface andthe transverse tubular system membrane (TTS) compartments and that both isoforms can be overexpressed up to 3-fold 2 weeks after transfection. Inward rectifying currents (IKir) had the canonical features of quasi-instantaneous activation, strong inward rectification, depended on the external [K+], and could be blocked by Ba2+ or Rb+. In addition, IKir records show notable decays during large 100 ms hyperpolarizing pulses. Most of these properties were recapitulated by model simulations of the electrical properties of the muscle fibre as long as Kir channels were assumed to be present in the TTS. The model also simultaneously predicted the characteristics of membrane potential changes of the TTS, as reported optically by a fluorescent potentiometric dye. The activation of IKir by large hyperpolarizations resulted in significant attenuation of the optical signals with respect to the expectation for equal magnitude depolarizations; blocking IKir with Ba2+ (or Rb+) eliminated this attenuation. The experimental data, including the kinetic properties of IKir and TTS voltage records, and the voltage dependence of peak IKir, while measured at widely dissimilar bulk [K+] (96 and 24 mm), were closely predicted by assuming Kir permeability (PKir) values of ∼5.5 × 10−6 cm s−1 and equal distribution of Kir channels at the surface and TTS membranes. The decay of IKir records and the simultaneous increase in TTS voltage changes were mostly explained by K+ depletion from the TTS lumen. Most importantly, aside from allowing an accurate estimation of most of the properties of IKir in skeletal muscle fibres, the model demonstrates that a substantial proportion of IKir (>70%) arises from the TTS. Overall, our work emphasizes that measured intrinsic properties (inward rectification and external [K] dependence) and localization of Kir channels in the TTS membranes are ideally suited for re-capturing potassium ions from the TTS lumen during, and immediately after, repetitive stimulation under physiological conditions. Key points This paper provides a comprehensive electrophysiological characterization of the external [K+] dependence and inward rectifying properties of Kir channels in fast skeletal muscle fibres of adult mice. Two isoforms of inward rectifier K channels (IKir2.1 and IKir2.2) are expressed in both the surface and the transverse tubular system (TTS) membranes of these fibres. Optical measurements demonstrate that Kir currents (IKir) affect the membrane potential changes in the TTS membranes, and result in a reduction in luminal [K+]. A model of the muscle fibre assuming that functional Kir channels are equally distributed between the surface and TTS membranes accounts for both the electrophysiological and the optical data. Model simulations demonstrate that the more than 70% of IKir arises from the TTS membranes. [K+] increases in the lumen of the TTS resulting from the activation of K delayed rectifier channels (Kv) lead to drastic enhancements of IKir, and to right-shifts in their reversal potential. These changes are predicted by the model. PMID:25545278

  7. Chemical control over the formation and reactivity of ultra-thin films and amino-terminated layers on silicon

    NASA Astrophysics Data System (ADS)

    Rodriguez-Reyes, Juan Carlos F.

    The physical-chemical properties of several interfacial systems of technological relevance are investigated, having as a common goal the elucidation of strategies towards their atomic- and molecular-level control. Such systems can be classified in three groups: (i) ultra-thin films deposited using metalorganic precursors, (ii) metalorganic monolayers on silicon, and (iii) amine-functionalized silicon surfaces. Experimental, theoretical and chemometric methods are conveniently combined to gain a solid understanding of these systems. The ultra-thin films under investigation are titanium carbonitride (TiNC) and hafnium oxide (HfO2). Since these films may serve as substrates for deposition of other materials in circuit components, their surface chemistry needs to be understood and controlled in order to facilitate further deposition steps. The surface of a TiCN film is transformed to titanium nitride (TiN) through nitridation with ammonia; this compositional change can be reversed by the partial decomposition of ethylene molecules on the surface. The surface reactivity is observed to depend on the film composition, and therefore the method described above serves to reversibly tune the reactivity of Ti-based films. As for HfO2 films, it is found that the deposition temperature affects the degree of crystallinity of the films, which in turn affects their surface chemistry. Thus, together with a control of the composition, it is found that the reactivity of a film can be controlled precisely by controlling the crystallinity. The investigation of metalorganic monolayers on silicon surfaces was motivated by the need for understanding the first steps of metalorganic-based deposition of films, which is usually characterized by a heavy presence of contaminants that degrade the film properties. Through a combination of vibrational (infrared) spectroscopy and theoretical methods, a feasible pathway for the adsorption and decomposition of Ti[N(CH3)2]4 is found. This pathway starts with the ligand-mediated attachment of the precursor (through a N atom), followed by dissociation of a metal-ligand bond. In addition, the C-H bond is broken, possibly forming Si-C bonds and causing carbon incorporation. This model is found to be rather robust and to adequately describe other types of metalorganic precursors. It allows establishing a generalized model able to explain the success or failure of a metalorganic precursor chemistry for film deposition. Finally, amine-functionalized silicon surfaces are considered as prototypical systems where the spatial distribution of adsorbates and the control over the reactivity of surface sites can be investigated. The spatial distribution of molecules is investigated at the atomic level by considering the saturation of a Si(100) surface with NH3. It is found that the distribution of (Si)NH2 species can be controlled thermally and, more importantly, that during thermal decomposition N inserts into the substrate in manners that minimize the arising strain. When the surface is covered with NH 3 or with organic amines, its chemical behavior is determined by the basicity of the molecule functionalizing the surface. The precise tuning of the reactivity (basicity) of surface sites opens the doors for highly controllable, selective reactions. Although these results are obtained from rather fundamental grounds, their interpretation is often translated into manners in which technological applications can be improved. Further directions worth exploring emanated from this work are outlined and discussed. Ultimately, this work intends to highlight the current importance of surface physical chemistry in the continuous development of modern society through the improvement of its technology.

  8. Fabrication of periodic silicon nanopillars in a two-dimensional hexagonal array with enhanced control on structural dimension and period.

    PubMed

    Choi, Jea-Young; Alford, T L; Honsberg, Christiana B

    2015-04-01

    We present a method to fabricate well-controlled periodic silicon nanopillars (Si NPs) in hexagonal arrays using silica nanosphere (SNS) lithography (SNL) combined with metal-assisted chemical etching (MaCE). The period of the Si NPs is easily changed by using our silica nanosphere (SNS) spin-coating process, which provides excellent monolayer uniformity and coverage (>95%) over large surface areas. The size of the deposited SNS is adjusted by reactive ion etching (RIE) to produce a target diameter at a fixed period for control of the surface pattern size after a gold metal mask layer deposition. The Si NPs are etched with the MaCE technique following introduction of a Ni interfacial layer between the Si and Au catalyst layer for adhesion and improved lithographical accuracy. The result is a fast, convenient, and large-area applicable Si surface nanolithography technique for accurate and reproducible Si NP fabrication. PMID:25781034

  9. Silicone metalization

    DOEpatents

    Maghribi, Mariam N.; Krulevitch, Peter; Hamilton, Julie

    2008-12-09

    A system for providing metal features on silicone comprising providing a silicone layer on a matrix and providing a metal layer on the silicone layer. An electronic apparatus can be produced by the system. The electronic apparatus comprises a silicone body and metal features on the silicone body that provide an electronic device.

  10. Silicone metalization

    DOEpatents

    Maghribi, Mariam N.; Krulevitch, Peter; Hamilton, Julie

    2006-12-05

    A system for providing metal features on silicone comprising providing a silicone layer on a matrix and providing a metal layer on the silicone layer. An electronic apparatus can be produced by the system. The electronic apparatus comprises a silicone body and metal features on the silicone body that provide an electronic device.

  11. Control of interface fracture in silicon nitride ceramics: influence of different rare earth elements

    SciTech Connect

    Sun, E.Y.; Becher, P.F.; Waters, S.B.; Hsueh, Chun-Hway; Plucknett, K.P.; Hoffmann, M.J.

    1996-10-01

    The toughness of self-reinforced silicon nitride ceramics is improved by enhancing crack deflection and crack bridging mechanisms. Both mechanisms rely on the interfacial debonding process between the elongated {Beta}-Si{sub 3}N{sub 4} grains and the intergranular amorphous phases. The various sintering additives used for densification may influence the interfacial debonding process by modifying the thermal and mechanical properties of the intergranular glasses, which will result in different residual thermal expansion mismatch stresses; and the atomic bonding structure across the {Beta}-Si{sub 3}N{sub 4} glass interface. Earlier studies indicated that self-reinforced silicon nitrides sintered with different rare earth additives and/or different Y{sub 2}O{sub 3}:AI{sub 2}0{sub 3} ratios could exhibit different fracture behavior that varied from intergranular to transgranular fracture. No studies have been conducted to investigate the influence of sintering additives on the interfacial fracture in silicon nitride ceramics. Because of the complexity of the material system and the extremely small scale, it is difficult to conduct quantitative analyses on the chemistry and stress states of the intergranular glass phases and to relate the results to the bulk properties. The influence of different sintering additives on the interfacial fracture behavior is assessed using model systems in which {Beta}-Si{sub 3}N{sub 4}whiskers are embedded in SIAIRE (RE: rare-earth) oxynitride glasses. By systematically varying the glass composition, the role of various rare-earth additives on interfacial fracture has been examined. Specifically, four different additives were investigated: Al{sub 2}0{sub 3}, Y{sub 2}0{sub 3}, La{sub 2}O{sub 3}, and Yb{sub 2}O{sub 3}. In addition, applying the results from the model systems, the R- curve behavior of self-reinforced silicon nitride ceramics sintered with different Y{sub 2}0{sub 3}:AI{sub 2}0{sub 3} ratios was characterized.

  12. Photoelectrochemical diffusion length measurements on p-type multicrystalline silicon for industrial quality control

    SciTech Connect

    Sarti, D.; Chareyron, B.; Le, Q.N.; Bastide, S.; Lincot, D.

    1994-12-31

    The authors report on a method based on photoelectrochemistry which allows the measurement of diffusion lengths of multicrystalline silicon before fabricating the photovoltaic device. The results obtained with this method after two years experience on a production line, by the photovoltaic manufacturer Photowatt Int. are presented. It concerns the variation of the diffusion length within the ingots and its correlation with the short-circuit current of the final cells, and the effect of industrial gettering. The authors also present diffusion length maps on a 10 x 10 cm{sup 2} cell.

  13. Microcomputer controlled soft start of motor

    NASA Astrophysics Data System (ADS)

    Gao, Miao; Wang, Yanpeng; Li, Shian

    2005-12-01

    Improving the starting characteristics of a motor is an important part of the motor control. An intelligent soft starting technique was adopted in the starter and used in the present study because of its many advantages compared with conventional starting processes. The core of the soft starter was a single chip (Atmel 8098), its soul was the software and its control object was a Silicon Controlled Rectifier (SCR). The starter achieved not only current-limit starting, but also closed-loop control with a stator current detection circuit. In conclusion, as a result of digital control, starting characteristic can be conveniently chosen according to the load. In addition the starter is of small size, and starting is smooth and reliable due to current feedback.

  14. Directed drop transport rectified from orthogonal vibrations via a flat wetting barrier ratchet.

    PubMed

    Duncombe, Todd A; Parsons, James F; Böhringer, Karl F

    2012-09-25

    We introduce the wetting barrier ratchet, a digital microfluidic technology for directed drop transport in an open air environment. Cyclic drop footprint oscillations initiated by orthogonal vibrations as low as 37 μm in amplitude at 82 Hz are rectified into fast (mm/s) and controlled transport along a fabricated ratchet design. The ratchet is made from a simple wettability pattern atop a microscopically flat surface consisting of periodic semi-circular hydrophilic features on a hydrophobic background. The microfluidic ratchet capitalizes on the asymmetric contact angle hysteresis induced by the curved features to drive transport. In comparison to the previously reported texture ratchets, wetting barrier ratchets require 3-fold lower actuation amplitudes for a 10 μL drop, have a simplified fabrication, and can be made optically flat for applications where transparency is paramount. PMID:22934529

  15. A novel solid-state thermal rectifier based on reduced graphene oxide.

    PubMed

    Tian, He; Xie, Dan; Yang, Yi; Ren, Tian-Ling; Zhang, Gang; Wang, Yu-Feng; Zhou, Chang-Jian; Peng, Ping-Gang; Wang, Li-Gang; Liu, Li-Tian

    2012-01-01

    Recently, manipulating heat transport by phononic devices has received significant attention, in which phonon--a heat pulse through lattice, is used to carry energy. In addition to heat control, the thermal devices might also have broad applications in the renewable energy engineering, such as thermoelectric energy harvesting. Elementary phononic devices such as diode, transistor and logic devices have been theoretically proposed. In this work, we experimentally create a macroscopic scale thermal rectifier based on reduced graphene oxide. Obvious thermal rectification ratio up to 1.21 under 12 K temperature bias has been observed. Moreover, this ratio can be enhanced further by increasing the asymmetric ratio. Collectively, our results raise the exciting prospect that the realization of macroscopic phononic device with large-area graphene based materials is technologically feasible, which may open up important applications in thermal circuits and thermal management. PMID:22826801

  16. Etched profile control in anisotropic etching of silicon by TMAH+Triton

    NASA Astrophysics Data System (ADS)

    Pal, Prem; Gosálvez, M. A.; Sato, K.

    2012-06-01

    The adverse effect of mechanical agitation (magnetic bead stirring) as well as galvanic interaction between the evolving facets of the etch front on the amount of undercutting during anisotropic etching of Si{1 0 0} wafers in surfactant-added tetramethylammonium hydroxide (TMAH) is studied by etching different mask patterns in magnetically stirred and nonstirred solutions. Triton X-100, with formula C14H22O(C2H4O)n, where n = 9-10, is used as the surfactant. The stirring results conclude that the adsorption of the surfactant on the etched silicon surfaces is predominantly physical in nature rather than chemical (physisorption versus chemisorption). The proposed model to account for the galvanic interaction between the evolving facets indicates that the underlying chemical etching process can be significantly surpassed by the onset of an electrochemical etching contribution when the relative area of the exposed {1 0 0} surface becomes relatively small in comparison to that of the developed {1 1 1} sidewalls. This study is useful for engineering applications where surfactant-added TMAH is used for the fabrication of silicon MEMS structures that should contain negligible undercutting.

  17. Highly sensitive silicon nanowire biosensor with novel liquid gate control for detection of specific single-stranded DNA molecules.

    PubMed

    Adam, Tijjani; Hashim, U

    2015-05-15

    The study demonstrates the development of a liquid-based gate-control silicon nanowire biosensor for detection of specific single-stranded DNA (ssDNA) molecules. The sensor was fabricated using conventional photolithography coupled with an inductively coupled plasma dry etching process. Prior to the application of DNA to the device, its linear response to pH was confirmed by serial dilution from pH 2 to pH 14. Then, the sensor surface was silanized and directly aminated with (3-aminopropyl) triethoxysilane to create a molecular binding chemistry for biofunctionalization. The resulting Si‒O‒Si‒ components were functionalized with receptor ssDNA, which interacted with the targeted ssDNA to create a field across the silicon nanowire and increase the current. The sensor shows selectivity for the target ssDNA in a linear range from target ssDNA concentrations of 100 pM to 25 nM. With its excellent detection capabilities, this sensor platform is promising for detection of specific biomarkers and other targeted proteins. PMID:25453738

  18. Controlling the shape and gap width of silicon electrodes using local anodic oxidation and anisotropic TMAH wet etching

    NASA Astrophysics Data System (ADS)

    Rouhi, Jalal; Mahmud, Shahrom; Derita Hutagalung, Sabar; Naderi, Nima; Kakooei, Saeid; Johar Abdullah, Mat

    2012-06-01

    A simple method for fabricating silicon electrodes with various shapes and gap widths was designed using the special properties of anisotropic tetramethylammonium hydroxide (TMAH) wet etching and local anodic oxidation (LAO). A statistical system was used for the optimization of the parameters of the LAO process to facilitate a better understanding and precise analysis of the process. Analyses of the interaction effects among the significant factors of LAO showed that the relative humidity and applied voltage were interdependent. They had the strongest interaction effect on the dimensions of the oxide mask. TMAH with a concentration of 25% was used as an etchant solution in (1 0 0) silicon with a rectangular oxide mask. The observed undercutting at convex corners, tip shape of emitters and gap widths of electrodes were exactly consistent with theoretical studies. Combination of the LAO method and anisotropic TMAH wet etching was successfully used to fabricate Si nano-gap electrodes. This fabrication method of sharp and round tip emitters was simple, controllable and faster than common techniques. These results indicate that the method can be a new approach for studying the electrical properties of nano-gap electrodes.

  19. High-stroke silicon-on-insulator MEMS nanopositioner: Control design for non-raster scan atomic force microscopy

    SciTech Connect

    Maroufi, Mohammad Fowler, Anthony G. Bazaei, Ali Moheimani, S. O. Reza

    2015-02-15

    A 2-degree of freedom microelectromechanical systems nanopositioner designed for on-chip atomic force microscopy (AFM) is presented. The device is fabricated using a silicon-on-insulator-based process and is designed as a parallel kinematic mechanism. It contains a central scan table and two sets of electrostatic comb actuators along each orthogonal axis, which provides displacement ranges greater than ±10 μm. The first in-plane resonance modes are located at 1274 Hz and 1286 Hz for the X and Y axes, respectively. To measure lateral displacements of the stage, electrothermal position sensors are incorporated in the design. To facilitate high-speed scans, the highly resonant dynamics of the system are controlled using damping loops in conjunction with internal model controllers that enable accurate tracking of fast sinusoidal set-points. To cancel the effect of sensor drift on controlled displacements, washout controllers are used in the damping loops. The feedback controlled nanopositioner is successfully used to perform several AFM scans in contact mode via a Lissajous scan method with a large scan area of 20 μm × 20 μm. The maximum scan rate demonstrated is 1 kHz.

  20. High-stroke silicon-on-insulator MEMS nanopositioner: control design for non-raster scan atomic force microscopy.

    PubMed

    Maroufi, Mohammad; Fowler, Anthony G; Bazaei, Ali; Moheimani, S O Reza

    2015-02-01

    A 2-degree of freedom microelectromechanical systems nanopositioner designed for on-chip atomic force microscopy (AFM) is presented. The device is fabricated using a silicon-on-insulator-based process and is designed as a parallel kinematic mechanism. It contains a central scan table and two sets of electrostatic comb actuators along each orthogonal axis, which provides displacement ranges greater than ±10 μm. The first in-plane resonance modes are located at 1274 Hz and 1286 Hz for the X and Y axes, respectively. To measure lateral displacements of the stage, electrothermal position sensors are incorporated in the design. To facilitate high-speed scans, the highly resonant dynamics of the system are controlled using damping loops in conjunction with internal model controllers that enable accurate tracking of fast sinusoidal set-points. To cancel the effect of sensor drift on controlled displacements, washout controllers are used in the damping loops. The feedback controlled nanopositioner is successfully used to perform several AFM scans in contact mode via a Lissajous scan method with a large scan area of 20 μm × 20 μm. The maximum scan rate demonstrated is 1 kHz. PMID:25725850

  1. High-stroke silicon-on-insulator MEMS nanopositioner: Control design for non-raster scan atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Maroufi, Mohammad; Fowler, Anthony G.; Bazaei, Ali; Moheimani, S. O. Reza

    2015-02-01

    A 2-degree of freedom microelectromechanical systems nanopositioner designed for on-chip atomic force microscopy (AFM) is presented. The device is fabricated using a silicon-on-insulator-based process and is designed as a parallel kinematic mechanism. It contains a central scan table and two sets of electrostatic comb actuators along each orthogonal axis, which provides displacement ranges greater than 10 ?m. The first in-plane resonance modes are located at 1274 Hz and 1286 Hz for the X and Y axes, respectively. To measure lateral displacements of the stage, electrothermal position sensors are incorporated in the design. To facilitate high-speed scans, the highly resonant dynamics of the system are controlled using damping loops in conjunction with internal model controllers that enable accurate tracking of fast sinusoidal set-points. To cancel the effect of sensor drift on controlled displacements, washout controllers are used in the damping loops. The feedback controlled nanopositioner is successfully used to perform several AFM scans in contact mode via a Lissajous scan method with a large scan area of 20 ?m 20 ?m. The maximum scan rate demonstrated is 1 kHz.

  2. Thermally controlled coupling of a rolled-up microtube integrated with a waveguide on a silicon electronic-photonic integrated circuit.

    PubMed

    Zhong, Qiuhang; Tian, Zhaobing; Veerasubramanian, Venkat; Dastjerdi, M Hadi Tavakoli; Mi, Zetian; Plant, David V

    2014-05-01

    We report on the first experimental demonstration of the thermal control of coupling strength between a rolled-up microtube and a waveguide on a silicon electronic-photonic integrated circuit. The microtubes are fabricated by selectively releasing a coherently strained GaAs/InGaAs heterostructure bilayer. The fabricated microtubes are then integrated with silicon waveguides using an abruptly tapered fiber probe. By tuning the gap between the microtube and the waveguide using localized heaters, the microtube-waveguide evanescent coupling is effectively controlled. With heating, the extinction ratio of a microtube whispering-gallery mode changes over an 18 dB range, while the resonant wavelength remains approximately unchanged. Utilizing this dynamic thermal tuning effect, we realize coupling modulation of the microtube integrated with the silicon waveguide at 2 kHz with a heater voltage swing of 0-6 V. PMID:24784081

  3. Quantum rectifier in a one-dimensional photonic channel

    NASA Astrophysics Data System (ADS)

    Mascarenhas, E.; Santos, M. F.; Auffèves, A.; Gerace, D.

    2016-04-01

    By using a fully quantum approach based on an input-output formulation of the stochastic Schrödinger equation, we show rectification of radiation fields in a one-dimensional waveguide doped with a pair of ideal two-level systems for three topical cases: classical driving, under the action of noise, and single-photon pulsed excitation. We show that even under the constant action of unwanted noise the device still operates effectively as an optical isolator, which is of critical importance for noise resistance. Finally, harnessing stimulated emission allows for nonreciprocal behavior for single-photon inputs, thus showing purely quantum rectification at the single-photon level. The latter is a considerable step towards the ultimate goal of devising an unconditional quantum rectifier for arbitrary quantum states.

  4. A passive UHF RFID tag with a dynamic-Vth-cancellation rectifier

    NASA Astrophysics Data System (ADS)

    Jinpeng, Shen; Bo, Wang; Shan, Liu; Xin'an, Wang; Zhengkun, Ruan; Shoucheng, Li

    2013-09-01

    This paper presents a passive UHF RFID tag with a dynamic-Vth-cancellation (DVC) rectifier. In the rectifier, the threshold voltages of MOSFETs are cancelled by applying gate bias voltages, which are dynamically changed according to the states of the MOSFETs. The DVC rectifier enables both low ON-resistance and small reverse leakage of the MOSFETs, resulting in high power conversion efficiency (PCE). An area-efficient demodulator with a novel average detector is also designed, which takes advantage of the rectifier's first stage as the envelope detector. The whole tag chip is implemented in a 0.18 μm CMOS process with a die size of 880 × 950 μm2. Measurement results show that the rectifier achieves a maximum PCE of 53.7% with 80 kΩ resistor load.

  5. Input Power Quality Improvement in Switched Reluctance Motor Drive using Minnesota Rectifier

    NASA Astrophysics Data System (ADS)

    Singh, B.; Rajesh, M.

    2013-09-01

    This paper deals with an input power quality improvement in a midpoint converter based switched reluctance motor (SRM) drive at ac mains using Minnesota rectifier. Normally a midpoint converter is used as a power converter for SRM drive. Conventionally three phase ac mains fed bridge rectifier is used as a dc source to feed this power converter which produces high content of harmonics at ac mains with a very low power factor. The proposed Minnesota rectifier with a midpoint converter fed SRM drive improves the power factor at ac mains with low current harmonics. This method provides constant dc link voltage and balanced capacitor voltages of the midpoint converter. The Minnesota rectifier fed SRM drive is modelled and its performance is simulated in Matlab/Simulink environment. The performance of Minnesota rectifier is compared with a conventional bridge topology for SRM drive to demonstrate improved power quality at ac mains.

  6. Single-molecule designs for electric switches and rectifiers.

    PubMed

    Kornilovitch, Pavel; Bratkovsky, Alexander; Williams, Stanley

    2003-12-01

    A design for molecular rectifiers is proposed. Current rectification is based on the spatial asymmetry of a molecule and requires only one resonant conducting molecular orbital. Rectification is caused by asymmetric coupling of the orbital to the electrodes, which results in asymmetric movement of the two Fermi levels with respect to the orbital under external bias. Results from numerical studies of the family of suggested molecular rectifiers, HS-(CH(2))(n)-C(6)H(4)(CH(2))(m)SH, are presented. Current rectification ratios in excess of 100 are achievable for n = 2 and m > 6. A class of bistable stator-rotor molecules is proposed. The stationary part connects the two electrodes and facilitates electron transport between them. The rotary part, which has a large dipole moment, is attached to an atom of the stator via a single sigma bond. Electrostatic bonds formed between the oxygen atom of the rotor and hydrogen atoms of the stator make the symmetric orientation of the dipole unstable. The rotor has two potential minima with equal energy for rotation about the sigma bond. The dipole can be flipped between the two states by an external electric field. Both rotor-orientation states have asymmetric current-voltage characteristics that are the reverse of each other, so they are distinguishable electrically. Theoretical results on conformation, energy barriers, retention times, switching voltages, and current-voltage characteristics are presented for a particular stator-rotor molecule. Such molecules could be the base for single-molecule switches, reversible diodes, and other molecular electronic devices. PMID:14976019

  7. Hot electron pump: a plasmonic rectifying antenna (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Yanik, Ahmet A.; Hossain, Golam I.

    2015-09-01

    Plasmonic nanostructures have been widely explored to improve absorption efficiency of conventional solar cells, either by employing them as a light scatterer, or as a source of local field enhancement. Unavoidable ohmic loss associated with the plasmonic metal nanostructures in visible spectrum, limits the efficiency improvement of photovoltaic devices by employing this local photon density of states (LDOS) engineering approach. Instead of using plasmonic structures as efficiency improving layer, recently, there has been a growing interest in exploring plasmoinc nanoparticle as the active medium for photovoltaic device. By extracting hot electrons that are created in metallic nanoparticles in a non-radiative Landau decay of surface plasmons, many novel plasmonic photovoltaic devices have been proposed. Moreover, these hot electrons in metal nanoparticles promises high efficiency with a spectral response that is not limited by the band gap of the semiconductors (active material of conventional solar cell). In this work, we will show a novel photovoltaic configuration of plasmonic nanoparticle that acts as an antenna by capturing free space ultrahigh frequency electromagnetic wave and rectify them through an ultrafast hot electron pump and eventually inject DC current in the contact of the device. We will introduce a bottom-up quantum mechanical approach model to explain fundamental physical processes involved in this hot electron pump rectifying antenna and it's ultrafast dynamics. Our model is based on non-equilibrium Green's function formalism, a robust theoretical framework to investigate transport and design nanoscale electronic devices. We will demonstrate some fundamental limitations that go the very foundations of quantum mechanics.

  8. Voltage controlling mechanisms in low resistivity silicon solar cells: A unified approach

    NASA Technical Reports Server (NTRS)

    Weizer, V. G.; Swartz, C. K.; Hart, R. E.; Godlewski, M. P.

    1984-01-01

    An experimental technique capable of resolving the dark saturation current into its base and emitter components is used as the basis of an analysis in which the voltage limiting mechanisms were determined for a variety of high voltage, low resistivity silicon solar cells. The cells studied include the University of Florida hi-low emitter cell, the NASA and the COMSAT multi-step diffused cells, the Spire Corporation ion-implanted emitter cell, and the University of New South Wales MINMIS and MINP cells. The results proved to be, in general, at variance with prior expectations. Most surprising was the finding that the MINP and the MINMIS voltage improvements are due, to a considerable extent, to a previously unrecognized optimization of the base component of the saturation current. This result is substantiated by an independent analysis of the material used to fabricate these devices.

  9. A study of the factors which control the efficiency of ion-implanted silicon solar cells

    NASA Technical Reports Server (NTRS)

    Douglas, E. C.; Daiello, R. V.

    1980-01-01

    The objective of this work was to determine experimentally the ion-implantation parameters and furnace annealing conditions required to produce high-efficiency solar cells. A comprehensive experimental study was conducted in which the optimum ion-implantation parameters were found by a systematic variation of the implant parameters followed by detailed studies of solar-cell devices. Two furnace heat-treatment techniques were found which effectively anneal the implanted layers and at the same time preserve or improve the diffusion length in the bulk silicon. Detailed characteristics of both the junction and bulk properties of solar cells fabricated over the spectrum of implant parameters are discussed. Optimized implant parameters and annealing conditions were found which allow for the fabrication of 14-15-percent (AM1) efficient solar cells.

  10. Kinetics and fracture resistance of lithiated silicon nanostructure pairs controlled by their mechanical interaction

    PubMed Central

    Lee, Seok Woo; Lee, Hyun-Wook; Ryu, Ill; Nix, William D.; Gao, Huajian; Cui, Yi

    2015-01-01

    Following an explosion of studies of silicon as a negative electrode for Li-ion batteries, the anomalous volumetric changes and fracture of lithiated single Si particles have attracted significant attention in various fields, including mechanics. However, in real batteries, lithiation occurs simultaneously in clusters of Si in a confined medium. Hence, understanding how the individual Si structures interact during lithiation in a closed space is necessary. Here, we demonstrate physical and mechanical interactions of swelling Si structures during lithiation using well-defined Si nanopillar pairs. Ex situ SEM and in situ TEM studies reveal that compressive stresses change the reaction kinetics so that preferential lithiation occurs at free surfaces when the pillars are mechanically clamped. Such mechanical interactions enhance the fracture resistance of lithiated Si by lessening the tensile stress concentrations in Si structures. This study will contribute to improved design of Si structures at the electrode level for high-performance Li-ion batteries. PMID:26112834

  11. Surface polarity control to reinforce dopant adhesion in laser doping of textured silicon

    NASA Astrophysics Data System (ADS)

    Nishimura, Hideki; Okamura, Takanori; Yamamoto, Yuki; Fuyuki, Takashi

    2014-05-01

    Increasing energy conversion efficiency without any extra cost is required for crystalline silicon (c-Si) solar cells. Laser doping (LD) can meet these requirements because it can be performed in an ambient atmosphere at room temperature. In this study, spin-coated phosphorus silicate glass (PSG) was formed on textured c-Si as a precursor for LD. We found that after LD, the reinforcement of the interface between PSG and the Si surface improved the photovoltaic characteristics Voc and Jsc. The interface was reinforced by changing the c-Si surface from hydrophobic to hydrophilic before spin coating. The reinforced interface led to a reduction in the number of surface voids and an enhancement of the transfer of dopant atoms.

  12. Characterization of a controlled electroless deposition of copper thin film on germanium and silicon surfaces

    NASA Astrophysics Data System (ADS)

    Scudiero, Louis; Fasasi, Ayuba; Griffiths, Peter R.

    2011-02-01

    Nanofilms of copper were deposited on silicon and, for the first time, on polycrystalline germanium substrates by electroless deposition. Germanium or silicon disks were immersed in a 10 mM copper sulfate solution containing dilute hydrofluoric acid at room temperature. This simple one-step deposition does not require the use of laborious operations or expensive equipment, that the reaction medium be degassed, or that the film be annealed. The copper film grows in a few minutes, producing a film on both Ge and Si that covers a very large area of the substrate in contrast to other metals such as Au, Ag, Pt and Pd for which deposition on Ge and Si produces islands or dendrites. Atomic force microscopy, X-ray photoelectron spectroscopy (XPS) and powder X-ray diffraction (PXRD) were used to characterize the microstructure and confirmed the formation of elemental copper nanofilms. The AFM micrographs reveal a Stranski-Krastanov type of film growth (layers + islands) that varies with the length of time the Ge or Si substrate is immersed in the CuSO4 solution. Thicker films were observed on the Ge than on the Si substrate resulting in larger particles and rougher surface than on Si. XPS analysis shows that the elemental copper is deposited on both Ge and Si substrates and that the films oxidize over a period of weeks with air exposure at room temperature. Finally, PXRD data reveal two preferential orientations (1 1 1) and (2 0 0) for the copper crystallites grown on both Ge and Si. The same intensity of the (1 1 1)-texture was measured on both Ge and Si substrate which is an important result because it has been shown that the (1 1 1) texture reduces stress-induced voiding and increases resistance to electromigration in metal interconnects.

  13. Evaluation of the SCR controller noise problem

    SciTech Connect

    Bassett, R R; Barnaby, B E

    1981-12-01

    Several types of solid state controllers are available for application to electric vehicles. The silicon controlled rectifier (SCR) type provides a current waveform of fixed pulse height and variable ratio on to off time. The controller provides step-free operation through a four-speed manual transmission. However, because the current is chopped, the circuits produce loud hums of varying frequency, which in some mounting situations may be amplified. This noise disappoints those who expect an electric vehicle to boast relatively silent operation. To evaluate the problem, components of a test bed, consisting of a battery bank, dc motor, SCR controller, charger, and appropriate cabling, were fitted with accelerometers, and the noises were evaluated for amplitude and spectral characteristics. Transient currents and voltages were also measured and analyzed to identify the source of the noise and the frequencies involved.

  14. Gated photoluminescence study of oxide-free InP MIS structure having an ultrathin silicon interface control layer

    NASA Astrophysics Data System (ADS)

    Fu, Zhengwen; Kasai, Seiya; Hasegawa, Hideki

    2002-05-01

    In order to investigate the effectiveness of a novel oxide-free surface passivation approach for InP, using an ultrathin silicon interface control layer (Si ICL), gated photoluminescence characteristics of the Si 3N 4/Si ICL/n-InP metal-semiconductor-insulator (MIS) structure were studied at room temperature. As compared with gated PL spectra of Si 3N 4/n-InP MIS without Si ICL, PL intensities of the sample with Si ICL were much more strongly modulated by the gate voltage. The interface state density distribution was estimated by an optical analog of the Terman's C- V analysis and a good agreement with the C- V analysis was obtained. The result indicates complete removal of Fermi level pinning over the entire bandgap in the novel oxide-free MIS structure.

  15. Semiconductor-metal phase transition of vanadium dioxide nanostructures on silicon substrate: Applications for thermal control of spacecraft

    SciTech Connect

    Leahu, G. L. Li Voti, R. Larciprete, M. C. Belardini, A. Mura, F. Sibilia, C.; Bertolotti, M.; Fratoddi, I.

    2014-06-19

    We present a detailed infrared study of the semiconductor-to-metal transition (SMT) in a vanadium dioxide (VO2) film deposited on silicon wafer. The VO2 phase transition is studied in the mid-infrared (MIR) region by analyzing the transmittance and the reflectance measurements, and the calculated emissivity. The temperature behaviour of the emissivity during the SMT put into evidence the phenomenon of the anomalous absorption in VO2 which has been explained by applying the Maxwell Garnett effective medium approximation theory, together with a strong hysteresis phenomenon, both useful to design tunable thermal devices to be applied for the thermal control of spacecraft. We have also applied the photothermal radiometry in order to study the changes in the modulated emissivity induced by laser. Experimental results show how the use of these techniques represent a good tool for a quantitative measurement of the optothermal properties of vanadium dioxide based structures.

  16. Cell technology: Advanced silicon sheet

    NASA Technical Reports Server (NTRS)

    Morrison, Andrew D.

    1986-01-01

    The Flat-plate Solar Array (FSA)-sponsored Fourth Silicon Stress/Strain Workshop reviewed, coordinated, and assessed the progress in understanding and controlling stress and strain during the crystal growth of silicon ribbons. dislocation electrical activity and limits on solar cell efficiency, and on studying the effects of dopants on EFG characteristics. Work on silicon for high-efficiency solar cells, stress-strain relationships in silicon ribbon, and high temperature deformation of dendritic web ribbon was also discussed.

  17. 75 FR 24747 - SCI, LLC/Zener-Rectifier Operations Division A Wholly Owned Subsidiary of SCI, LLC/ON...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-05-05

    ... Employment and Training Administration SCI, LLC/Zener-Rectifier Operations Division A Wholly Owned Subsidiary..., 2009, applicable to workers of SCI LLC/Zener-Rectifier, Operations Division, a wholly owned subsidiary... issued as follows: All workers of SCI LLC/Zener-Rectifier, Operations Division, a wholly owned...

  18. Novel silicone compatible cross-linkers for controlled functionalization of PDMS networks

    NASA Astrophysics Data System (ADS)

    Madsen, Frederikke B.; Egede Daugaard, Anders; Hvilsted, Sren; Skov, Anne Ladegaard

    2013-04-01

    Polydimethylsiloxane (PDMS) elastomers are excellent materials for dielectric electroactive polymers (DEAPs) due to their high efficiency and fast response. PDMS suffers, however, from low dielectric permittivity and high voltages are therefore required when the material is used for DEAP actuators. In order to improve the dielectric properties of PDMS a novel system is developed where push-pull dipoles are grafted to a new silicone compatible cross-linker. The grafted cross-linkers are prepared by reaction of two different push-pull dipole alkynes as well as a fluorescent alkyne with the new azide-functional cross-linker by click chemistry. The dipole cross-linkers are used to prepare PDMS elastomers of various chains lengths providing different network densities. The functionalized cross-linkers are incorporated successfully into the networks and are well distributed as determined by the fluorescent functional cross-linker and fluorescence microscopy. The thermal, mechanical and electro-mechanical properties of PDMS elastomers of 0 wt% to 3.6 wt% of push-pull dipole cross-linker are investigated. An increase in the dielectric permittivity of 19 % at only 0.46 wt% of pure push-pull dipole is observed. Furthermore, the dielectric losses are found to be very low while the electrical breakdown strengths are high and adequate for DEAP applications.

  19. Hierarchical porous silicon carbide with controlled micropores and mesopores for electric double layer capacitors

    NASA Astrophysics Data System (ADS)

    Kim, Myeongjin; Oh, Ilgeun; Kim, Jooheon

    2015-05-01

    Three-dimensional hierarchical micro and mesoporous silicon carbide spheres (MMPSiC) are prepared by the template method and carbonization reaction via the aerosol spray drying method. The mesopores are generated by the self-assembly of the structure-directing agents, whereas the micropores are derived from the partial evaporation of Si atoms during carbonization. To investigate the effect of mesopore size on electrochemical performance, three types of MMPSiC with different mesopore size were fabricated by using three different structure directing agents (cetyltriethylammonium bromide (CTAB), Polyethylene glycol hexadecyl ether (Brij56), and Poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (P123)). The MMPSiC electrode prepared with Brij56 exhibits the highest charge storage capacity with a specific capacitance of 253.7 F g-1 at a scan rate of 5 mV s-1 and 87.9% rate performance from 5 to 500 mV s-1 in 1 M Na2SO4 aqueous electrolyte. The outstanding electrochemical performance might be because of the ideal mesopore size, which effectively reduces the resistant pathways for ion diffusion in the pores and provides a large accessible surface area for ion transport/charge storage. These encouraging results demonstrate that the MMPSiC prepared with Brij56 is a promising candidate for high performance electrode materials for supercapacitors.

  20. Wave-aberration control with a liquid crystal on silicon (LCOS) spatial phase modulator.

    PubMed

    Fernández, Enrique J; Prieto, Pedro M; Artal, Pablo

    2009-06-22

    Liquid crystal on Silicon (LCOS) spatial phase modulators offer enhanced possibilities for adaptive optics applications in terms of response velocity and fidelity. Unlike deformable mirrors, they present a capability for reproducing discontinuous phase profiles. This ability also allows an increase in the effective stroke of the device by means of phase wrapping. The latter is only limited by the diffraction related effects that become noticeable as the number of phase cycles increase. In this work we estimated the ranges of generation of the Zernike polynomials as a means for characterizing the performance of the device. Sets of images systematically degraded with the different Zernike polynomials generated using a LCOS phase modulator have been recorded and compared with their theoretical digital counterparts. For each Zernike mode, we have found that image degradation reaches a limit for a certain coefficient value; further increase in the aberration amount has no additional effect in image quality. This behavior is attributed to the intensification of the 0-order diffraction. These results have allowed determining the usable limits of the phase modulator virtually free from diffraction artifacts. The results are particularly important for visual simulation and ophthalmic testing applications, although they are equally interesting for any adaptive optics application with liquid crystal based devices. PMID:19550501

  1. Kinetics and fracture resistance of lithiated silicon nanostructure pairs controlled by their mechanical interaction

    SciTech Connect

    Lee, Seok Woo; Lee, Hyun-Wook; Ryu, Ill; Nix, William D.; Gao, Huajian; Cui, Yi; /Stanford U., Materials Sci. Dept. /SLAC

    2015-06-01

    Following an explosion of studies of silicon as a negative electrode for Li-ion batteries, the anomalous volumetric changes and fracture of lithiated single Si particles have attracted significant attention in various fields, including mechanics. However, in real batteries, lithiation occurs simultaneously in clusters of Si in a confined medium. Hence, understanding how the individual Si structures interact during lithiation in a closed space is necessary. Herein, we demonstrate physical/mechanical interactions of swelling Si structures during lithiation using well-defined Si nanopillar pairs. Ex situ SEM and in situ TEM studies reveal that compressive stresses change the reaction kinetics so that preferential lithiation occurs at free surfaces when the pillars are mechanically clamped. Such mechanical interactions enhance the fracture resistance of This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering, under Contract No. DE-AC02-76SF00515. SLAC-PUB-16300 2 lithiated Si by lessening the tensile stress concentrations in Si structures. This study will contribute to improved design of Si structures at the electrode level for high performance Li-ion batteries.

  2. Glass frit bonding with controlled width and height using a two-step wet silicon etching procedure

    NASA Astrophysics Data System (ADS)

    Yifang, Liu; Daner, Chen; Liwei, Lin; Gaofeng, Zheng; Jianyi, Zheng; Lingyun, Wang; Daoheng, Sun

    2016-03-01

    A simple and versatile two-step silicon wet etching technique for the control of the width and height of the glass frit bonding layer has been developed to improve bonding strength and reliability in wafer-level microelectromechanical systems (MEMS) packaging processes. The height of the glass frit bonding layer is set by the design of a vertical reference wall which regulates the distance between the silicon wafer and the encapsulation capping substrate. On the other hand, the width of the bonding layer is constrained between two micro grooves which are used to accommodate the spillages of extra glass frit during the bonding process. An optimized thermal bonding process, including the formation of glass liquid, removal of gas bubbles under vacuum and the filling of voids under normal atmospheric condition has been developed to suppress the formation of the bubbles/voids. The stencil printing and pre-sintering processes for the glass frit have been characterized before the thermal bonding process under different magnitudes of bonding pressure. The bonding gap thickness is found to be equal to the height of the reference wall of 10 μm in the prototype design. The bubbles/voids are found to be suppressed effectively and the bonding strength increases from 10.2 to 19.1 MPa as compared with a conventional thermal annealing process in air. Experimentally, prototype samples are measured to have passed the high hermetic sealing leakage tests of 5  ×  10-8 atm cc s-1.

  3. Optimum system design of a three-phase rectifier-inverter type of frequency changer

    SciTech Connect

    Ziogas, P.D.; Kang, Y-G.; Stefanovic, V.R.

    1985-09-01

    Steadily decreasing prices and improved performance of semiconductor devices have raised expectations towards the development and large-scale application of motor-mounted static converters. In view of this, the design of a rectifier-inverter type of frequency changer which requires very small reactive components is considered. Accordingly, rectifier and inverter PWM schemes which generate the minimum possible harmonic distortion are first discussed. By using a suitable analysis method, ''optimum'' design data are obtained for every major system component. Resulting reactive component values are shown to be considerably smaller than the ones required by typical rectifier-inverter structures. Predicted key results are verified by computer simulation.

  4. Controlled Synthesis of Millimeter-Long Silicon Nanowires with Uniform Electronic Properties

    PubMed Central

    Park, Won Il; Zheng, Gengfeng; Jiang, Xiaocheng; Tian, Bozhi; Lieber, Charles M.

    2009-01-01

    We report the nanocluster-catalyzed growth of ultra-long and highly-uniform single-crystalline silicon nanowires (SiNWs) with millimeter-scale lengths and aspect ratios up to ca. 100,000. The average SiNW growth rate using disilane (Si2H6) at 400 °C was 31 µm/min, while the growth rate determined for silane (SiH4) reactant under similar growth conditions was 130 times lower. Transmission electron microscopy studies of millimeter-long SiNWs with diameters of 20–80 nm show that the nanowires grow preferentially along the <110> direction independent of diameter. In addition, ultra-long SiNWs were used as building blocks to fabricate one-dimensional arrays of field-effect transistors (FETs) consisting of ca. 100 independent devices per nanowire. Significantly, electrical transport measurements demonstrated that the millimeter-long SiNWs had uniform electrical properties along the entire length of wires, and each device can behave as a reliable FET with an on-state current, threshold voltage, and transconductance values (average ± 1 standard deviation) of 1.8 ± 0.3 µA, 6.0 ± 1.1 V, 210 ± 60 nS, respectively. Electronically-uniform millimeter-long SiNWs were also functionalized with monoclonal antibody receptors, and used to demonstrate multiplexed detection of cancer marker proteins with a single nanowire. The synthesis of structurally- and electronically-uniform ultra-long SiNWs may open up new opportunities for integrated nanoelectronics, and could serve as unique building blocks linking integrated structures from the nanometer through millimeter length scales. PMID:18710294

  5. Controlled synthesis of millimeter-long silicon nanowires with uniform electronic properties.

    PubMed

    Park, Won Il; Zheng, Gengfeng; Jiang, Xiaocheng; Tian, Bozhi; Lieber, Charles M

    2008-09-01

    We report the nanocluster-catalyzed growth of ultralong and highly uniform single-crystalline silicon nanowires (SiNWs) with millimeter-scale lengths and aspect ratios up to approximately 100,000. The average SiNW growth rate using disilane (Si 2H 6) at 400 degrees C was 31 microm/min, while the growth rate determined for silane (SiH 4) reactant under similar growth conditions was 130 times lower. Transmission electron microscopy studies of millimeter-long SiNWs with diameters of 20-80 nm show that the nanowires grow preferentially along the 110 direction independent of diameter. In addition, ultralong SiNWs were used as building blocks to fabricate one-dimensional arrays of field-effect transistors (FETs) consisting of approximately 100 independent devices per nanowire. Significantly, electrical transport measurements demonstrated that the millimeter-long SiNWs had uniform electrical properties along the entire length of wires, and each device can behave as a reliable FET with an on-state current, threshold voltage, and transconductance values (average +/-1 standard deviation) of 1.8 +/- 0.3 microA, 6.0 +/- 1.1 V, 210 +/- 60 nS, respectively. Electronically uniform millimeter-long SiNWs were also functionalized with monoclonal antibody receptors and used to demonstrate multiplexed detection of cancer marker proteins with a single nanowire. The synthesis of structurally and electronically uniform ultralong SiNWs may open up new opportunities for integrated nanoelectronics and could serve as unique building blocks linking integrated structures from the nanometer through millimeter length scales. PMID:18710294

  6. D0 Silicon Strip Detector Upgrade Project SVX Sequencer Controller Board

    SciTech Connect

    Utes, M.; /Fermilab

    2001-05-29

    The Sequencer Controller boards are 9U by 340mm circuit boards that will reside in slot 1 of each of eight Sequencer crates in the D0 detector platform. The primary purpose is to control the Sequencers during data acquisition based on trigger information from the D0 Trigger Framework. Functions and features are as follows: (1) Receives the Serial Command Link (SCL) from the D0 Trigger System and controls the operation of the Sequencers by forming a custom serial control link (NRZ/Clock) which is distributed individually to each Sequencer via the 11 Backplane; (2) Controllable delays adjust NRZ control link phasing to compensate for the various cable-length delays between the Sequencers and SVX chips, delay control is common for slots 2-11, and for slots 12-21 of the crate; (3) Each NRZ control link is phase controlled so that commands reach each Sequencer in a given half-crate simultaneously, i.e., the link is compensated for backplane propagation delays; (4) External communication via MIL-STD-1553; (5) Stand-alone operation via 1553 trigger commands in absence of an SCL link; (6) 1553-writeable register for triggering a laser, etc. followed by an acquisition cycle; (7) TTL front panel input to trigger an acquisition cycle, e.g. from a scintillator; (8) Synch Trig, Veto, Busy and Preamp Reset TTL outputs on front panel LEMOs; (9) On-board 53.104 MHz oscillator for stand-alone operation; (10) 1553 or SCL-triggerable Cal-inject cycle; (11) Front-panel inputs to accept NRZ/Clock link from the VRB Controller; (12) Front panel displays and LEDs show the board status at a glance; and (13) In-system programmable EPLDs are programmed via Altera's 'Byteblaster'.

  7. Analysis of three-phase rectifiers with AC-side switches and interleaved three-phase voltage-source converters

    NASA Astrophysics Data System (ADS)

    Miller, Stephanie Katherine Teixeira

    Of all the alternative and renewable energy sources, wind power is the fastest growing alternative energy source with a total worldwide capacity of over 93 GW as of the end of 2007. However, making wind energy a sustainable and reliable source of electricity doesn't come without its set of challenges. As the wind turbines increase in size and turbine technology moves towards off-shore wind farms and direct drive transmission, the need for a reliable and efficient power electronics interface to convert the variable-frequency variable-magnitude output of the wind turbine's generator into the fixed-frequency fixed-magnitude voltage of the utility grid is critical. This dissertation investigates a power electronics interface envisioned to operate with an induction generator-based variable-speed wind turbine. The research conclusions and the interface itself are applicable to a variety of applications, including uninterruptible power supplies, industrial drives, and power quality applications, among others. The three-phase PWM rectifiers with ac-side bidirectional switches are proposed as the rectification stage of the power electronics interface. Modulation strategies are proposed for the rectifiers and the operation of the rectifiers in conjunction with an induction generator is demonstrated. The viability of using these rectifiers in place of the standard three-phase voltage-source converter is analyzed by comparing losses and common-mode voltage generation of the two topologies. Parallel three-phase voltage-source converter modules operated in an interleaved fashion are proposed for the inversion stage of the power electronics interface. The interleaved three-phase voltage-source converters are analyzed by deriving analytical models for the common-mode voltage, ac phase current, and dc-link current to reveal their spectra and the harmonic cancellation effects of interleaving. The practical problem of low frequency circulating current in parallel voltage-source converters is also analyzed. The low frequency circulating current characteristics of abc, dq, and nonlinear average current control are determined and experimental results for the nonlinear average current control are presented.

  8. Mitigating impact of rectified RF sheath potential on the ELMs

    NASA Astrophysics Data System (ADS)

    Gui, Bin; Xu, Xueqiao; Xia, Tianyang

    2014-10-01

    Here we report on the BOUT++ simulation results for the mitigating impact of rectified RF sheath potential on the peeling-ballooning modes. The limiter and the RF wave antenna are placed at the outer middle plane in the scrape-off-layer (SOL) in shift-circle geometry. The external shear flow is induced by the limiter and the RF wave. Besides this, the sheath boundary conditions are imposed on the perturbed potential and parallel current. From the three-field simulations, it is found that the energy loss is suppressed by the external shear flow in the nonlinear phase. The external shear flow due to the RF wave leads to a broad turbulence spectrum. The wider spectrum leads to a weaker turbulence transport and results in a smaller energy loss. The perturbed electric potential and the parallel current near the sheath region are also suppressed locally due to the sheath boundary condition. Based on this work, this effect of limiter will also be applied in six-field which includes more physics effects. The effect of sheath boundary conditions on the thermal conductivities and heat flux will be studied. This work was performed for USDOE by LLNL under DE-AC52-07NA27344, LLNL LDRD project 12-ERD-022 and the China Natural Science Foundation under Contract No. 10721505. LLNL-ABS-657008.

  9. Finite element modeling of electrically rectified piezoelectric energy harvesters

    NASA Astrophysics Data System (ADS)

    Wu, P. H.; Shu, Y. C.

    2015-09-01

    Finite element models are developed for designing electrically rectified piezoelectric energy harvesters. They account for the consideration of common interface circuits such as the standard and parallel-/series-SSHI (synchronized switch harvesting on inductor) circuits, as well as complicated structural configurations such as arrays of piezoelectric oscillators. The idea is to replace the energy harvesting circuit by the proposed equivalent load impedance together with the capacitance of negative value. As a result, the proposed framework is capable of being implemented into conventional finite element solvers for direct system-level design without resorting to circuit simulators. The validation based on COMSOL simulations carried out for various interface circuits by the comparison with the standard modal analysis model. The framework is then applied to the investigation on how harvested power is reduced due to fabrication deviations in geometric and material properties of oscillators in an array system. Remarkably, it is found that for a standard array system with strong electromechanical coupling, the drop in peak power turns out to be insignificant if the optimal load is carefully chosen. The second application is to design broadband energy harvesting by developing array systems with suitable interface circuits. The result shows that significant broadband is observed for the parallel (series) connection of oscillators endowed with the parallel-SSHI (series-SSHI) circuit technique.

  10. Remote Electrical Stimulation by Means of Implanted Rectifiers

    PubMed Central

    Ivorra, Antoni

    2011-01-01

    Miniaturization of active implantable medical devices is currently compromised by the available means for electrically powering them. Most common energy supply techniques for implants – batteries and inductive couplers – comprise bulky parts which, in most cases, are significantly larger than the circuitry they feed. Here, for overcoming such miniaturization bottleneck in the case of implants for electrical stimulation, it is proposed to make those implants act as rectifiers of high frequency bursts supplied by remote electrodes. In this way, low frequency currents will be generated locally around the implant and these low frequency currents will perform stimulation of excitable tissues whereas the high frequency currents will cause only innocuous heating. The present study numerically demonstrates that low frequency currents capable of stimulation can be produced by a miniature device behaving as a diode when high frequency currents, neither capable of thermal damage nor of stimulation, flow through the tissue where the device is implanted. Moreover, experimental evidence is provided by an in vivo proof of concept model consisting of an anesthetized earthworm in which a commercial diode was implanted. With currently available microelectronic techniques, very thin stimulation capsules (diameter <500 µm) deliverable by injection are easily conceivable. PMID:21850274

  11. Remote electrical stimulation by means of implanted rectifiers.

    PubMed

    Ivorra, Antoni

    2011-01-01

    Miniaturization of active implantable medical devices is currently compromised by the available means for electrically powering them. Most common energy supply techniques for implants--batteries and inductive couplers--comprise bulky parts which, in most cases, are significantly larger than the circuitry they feed. Here, for overcoming such miniaturization bottleneck in the case of implants for electrical stimulation, it is proposed to make those implants act as rectifiers of high frequency bursts supplied by remote electrodes. In this way, low frequency currents will be generated locally around the implant and these low frequency currents will perform stimulation of excitable tissues whereas the high frequency currents will cause only innocuous heating. The present study numerically demonstrates that low frequency currents capable of stimulation can be produced by a miniature device behaving as a diode when high frequency currents, neither capable of thermal damage nor of stimulation, flow through the tissue where the device is implanted. Moreover, experimental evidence is provided by an in vivo proof of concept model consisting of an anesthetized earthworm in which a commercial diode was implanted. With currently available microelectronic techniques, very thin stimulation capsules (diameter <500 µm) deliverable by injection are easily conceivable. PMID:21850274

  12. Intravitreal Controlled Release of Dexamethasone from Engineered Microparticles of Porous Silicon Dioxide

    PubMed Central

    Wang, Chengyun; Hou, Huiyuan; Nan, Kaihui; Sailor, Michael J; Freeman, William R.; Cheng, Lingyun

    2014-01-01

    Dexamethasone is a glucocorticoid that is widely used in the ophthalmic arena. The recent FDA approved dexamethasone implant can provide a three month efficacy but with high rate of drug related cataract and high intraocular pressure (IOP). It seems that higher steroid in aqueous humor and around lens may be associated with these complications based on clinical fact that higher IOP was observed with intravitreal triamcinolone acetonide (TA) than with subtenon TA. We hypothesize that placing a sustained dexamethasone release system near back of the eye through a fine needle can maximize efficacy while mitigate higher rate of IOP rise and cataract. To develop a sustained intravitreal dexamethasone delivery system, porous silicon dioxide (pSiO2) microparticles were fabricated and functionalized with amines as well as carboxyl groups. Dexamethasone was conjugated to pSiO2 through the Steglich Esterificaion Reaction between hydroxyl of dexamethasone and carboxyl groups on the pSiO2. The drug loading was confirmed by Fourier transform infrared spectroscopy (FTIR) and loading efficiency was quantitated using thermogravimetric analysis (TGA). In vitro release was conducted for three months and dexamethasone was confirmed in the released samples using liquid chromatography-tandem mass spectrometry (LC/MS/MS). A pilot ocular safety and determination of vitreous drug level was performed in rabbit eyes. The drug loading study demonstrated that loading efficiency was from 5.96% to 10.77% depending on the loading reaction time, being higher with longer loading reaction time before reaching saturation around 7 days. In vitro drug release study revealed that dexamethasone release from pSiO2 particles was sustainable for over 90 days and was 80 days longer than free dexamethasone or infiltration-loaded pSiO2 particle formulation in the same setting. Pilot in vivo study demonstrated no sign of ocular adverse reaction in rabbit eyes following a single 3 mg intravitreal injection and free drug level at 2-week was 107.23+/−10.54 ng/mL that is well above the therapeutic level but only around 20% level of dexamethasone released from OZURDEX ® (dexamethasone intravitreal implant) in a rabbit eye model. In conclusion, dexamethasone is able to covalently load to the pSiO2 particles and provide sustained drug release for at least 3 months in vitro. Intravitreal injection of these particles were well tolerated in rabbit eyes and free drug level in vitreous at 2-week was well above the therapeutic level. PMID:25446320

  13. Design and test of a 2.25-MW transformer rectifier assembly

    NASA Technical Reports Server (NTRS)

    Cormier, R.; Daeges, J.

    1989-01-01

    A new 2.25-MW transformer rectifier assembly was fabricated for DSS-13 at Goldstone, California. The transformer rectifier will provide constant output power of 2.25 MW at any voltage from 31 kV to 125 kV. This will give a new capability of 1 MW of RF power at X-band, provided appropriate microwave tubes are in the power amplifier. A description of the design and test results is presented.

  14. On the Control of the Fixed Charge Densities in Al2O3-Based Silicon Surface Passivation Schemes.

    PubMed

    Simon, Daniel K; Jordan, Paul M; Mikolajick, Thomas; Dirnstorfer, Ingo

    2015-12-30

    A controlled field-effect passivation by a well-defined density of fixed charges is crucial for modern solar cell surface passivation schemes. Al2O3 nanolayers grown by atomic layer deposition contain negative fixed charges. Electrical measurements on slant-etched layers reveal that these charges are located within a 1 nm distance to the interface with the Si substrate. When inserting additional interface layers, the fixed charge density can be continuously adjusted from 3.5 10(12) cm(-2) (negative polarity) to 0.0 and up to 4.0 10(12) cm(-2) (positive polarity). A HfO2 interface layer of one or more monolayers reduces the negative fixed charges in Al2O3 to zero. The role of HfO2 is described as an inert spacer controlling the distance between Al2O3 and the Si substrate. It is suggested that this spacer alters the nonstoichiometric initial Al2O3 growth regime, which is responsible for the charge formation. On the basis of this charge-free HfO2/Al2O3 stack, negative or positive fixed charges can be formed by introducing additional thin Al2O3 or SiO2 layers between the Si substrate and this HfO2/Al2O3 capping layer. All stacks provide very good passivation of the silicon surface. The measured effective carrier lifetimes are between 1 and 30 ms. This charge control in Al2O3 nanolayers allows the construction of zero-fixed-charge passivation layers as well as layers with tailored fixed charge densities for future solar cell concepts and other field-effect based devices. PMID:26618751

  15. D0 Silicon Upgrade: Cryolab Control Valve Modification Information for D0-EVMF-H

    SciTech Connect

    Rucincki, Russ; /Fermilab

    1995-10-26

    This engineering note documents some information regarding the solenoid magnet flow valve, EVMF. See also EN-437 'Control Dewar valve sizing' also for further information on this valve. This note documents the modification done to the valve to change it to a Cv = 0.32.

  16. Innovative Switching Sequences for Sensorless Capacitor Voltage Balancing of Three-Phase NPC Rectifier

    NASA Astrophysics Data System (ADS)

    Langer, Nitin; Bhat, Abdul Hamid; Agarwal, Pramod

    2014-01-01

    This paper presents a modulation strategy for self-balancing of capacitor voltages of three-phase neutral-point clamped bi-directional rectifier (without feedback controller and sensors). It is identified that regions within a sector are divided into two categories: (a) One small vector among three selected vectors and (b) Two small vectors among three selected vectors. For category (a) positive and negative commutation state of small vector is implemented for equal duty cycle but for category (b) positive and negative commutation state of small vectors is implemented for unequal duty cycle. Based on this observation, an innovative idea is executed to remove these discrepancies. The innovative optimized space vector switching sequences negative and positive commutation state of both the small vectors are implemented for equal duty cycle during each sampling period resulting in self-balancing of DC-bus capacitors with much reduced ripples under steady-state and dynamic load conditions for both rectification and inversion mode of operation. The converter exhibits excellent performance in terms of other critical parameters like unity input power factor, low input current THD, minimum possible switching losses, reduced-rippled and well-regulated DC voltage. The proposed control algorithm is tested through exhaustive simulation of converter using MATLAB Simulink software.

  17. Operational research on a high-T c rectifier-type superconducting flux pump

    NASA Astrophysics Data System (ADS)

    Geng, Jianzhao; Matsuda, K.; Fu, Lin; Shen, Boyang; Zhang, Xiuchang; Coombs, T. A.

    2016-03-01

    High-T c superconducting (HTS) flux pumps are capable of injecting flux into a superconducting circuit, which can achieve persistent current operation for HTS magnets. In this paper, we studied the operation of a rectifier-type HTS flux pump. The flux pump employs a transformer to generate high alternating current in its secondary winding, which is connected to an HTS load shorted by an HTS bridge. A high frequency ac field is intermittently applied perpendicular to the bridge, thus, generating flux flow. The dynamic resistance caused by the flux flow ‘rectifies’ the secondary current, resulting in a direct current in the load. We have found that the final load current can easily be controlled by changing the phase difference between the secondary current and the bridge field. The bridge field of frequency ranging from 10 to 40 Hz and magnitude ranging from 0 to 0.66 T was tested. Flux pumping was observed for field magnitudes of 50 mT or above. We have found that both higher field magnitude and higher field frequency result in a faster pumping speed and a higher final load current. This can be attributed to the influence of dynamic resistance. The dynamic resistance measured in the flux pump is comparable with the theoretical calculation. The experimental results fully support a first order circuit model. The flux pump is much more controllable than the traveling wave flux pumps based on permanent magnets, which makes it promising for practical use.

  18. Single delayed rectifier channels in frog atrial cells. Effects of beta-adrenergic stimulation.

    PubMed Central

    Duchatelle-Gourdon, I; Hartzell, H C

    1990-01-01

    The patch-clamp technique with two pipettes was used to record single delayed K+ channels (cell-attached electrode) and to control the potential and the composition of the intracellular compartment (whole-cell electrode). With 30 microM cAMP in the cell and physiological potassium concentrations inside and outside the patch, a channel carrying an outward current was characterized. Its open probability was very low and the channel was recorded in only 5% of patches under control conditions. Increasing intracellular cAMP increased the probability of finding a channel in a patch 10-fold. The channel had the characteristics expected of a delayed rectifier channel. The time-course of its ensemble average resembled the whole-cell current in the same cell. The current-voltage relationship exhibited inward rectification, with a slope conductance of 20 pS in the linear portion and a reversal potential close to EK. Both the open- and the closed-time distributions were described by the sum of two exponentials, suggesting a complicated gating scheme involving two closed states and two open states. The beta-adrenergic stimulation did not change the conductance of the channel, but increased its probability of opening. Images FIGURE 1 FIGURE 2 FIGURE 4 PMID:2160847

  19. DNA Physical Mapping via the Controlled Translocation of Single Molecules through a 5-10nm Silicon Nitride Nanopore

    NASA Astrophysics Data System (ADS)

    Stein, Derek; Reisner, Walter; Jiang, Zhijun; Hagerty, Nick; Wood, Charles; Chan, Jason

    2009-03-01

    The ability to map the binding position of sequence-specific markers, including transcription-factors, protein-nucleic acids (PNAs) or deactivated restriction enzymes, along a single DNA molecule in a nanofluidic device would be of key importance for the life-sciences. Such markers could give an indication of the active genes at particular stage in a cell's transcriptional cycle, pinpoint the location of mutations or even provide a DNA barcode that could aid in genomics applications. We have developed a setup consisting of a 5-10 nm nanopore in a 20nm thick silicon nitride film coupled to an optical tweezer setup. The translocation of DNA across the nanopore can be detected via blockades in the electrical current through the pore. By anchoring one end of the translocating DNA to an optically trapped microsphere, we hope to stretch out the molecule in the nanopore and control the translocation speed, enabling us to slowly scan across the genome and detect changes in the baseline current due to the presence of bound markers.

  20. Controlled aluminum-induced crystallization of an amorphous silicon thin film by using an oxide-layer diffusion barrier

    NASA Astrophysics Data System (ADS)

    Hwang, Ji-Hyun; Kwak, Hyunmin; Kwon, Myeung Hoi

    2014-03-01

    Aluminum-induced crystallization (AIC) of amorphous silicon with an Al2O3 diffusion barrier was investigated for controlling Si crystallization and preventing layer exchange during the annealing process. An Al2O3 layer was deposited between the a-Si and the Al films (a-Si/Al2O3/Al/Glass) and was blasted with an air spray gun with alumina beads to form diffusion channels between the Si and the Al layers. During the annealing process, small grain Si x Al seeds were formed at the channels. Then, the Al2O3 diffusion barrier was restructured to close the channels and prevent further diffusion of Al atoms into the a-Si layer. A polycrystalline Si film with (111), (220) and (311) crystallization peaks in the X-ray diffraction pattern was formed by annealing at 560 °C in a conventional furnace. That film showed a p-type semiconducting behavior with good crystallinity and a large grain size of up to 14.8 µm. No layer conversion occurred between the Si and the Al layers, which had been the fundamental obstacle to the applications in the crystallization of a-Si films by using the AIC method.

  1. Operation and test of hybridized silicon p-i-n arrays using open-source array control hardware and software

    NASA Astrophysics Data System (ADS)

    Moore, Andrew C.; Ninkov, Zoran; Burley, Gregory S.; Forrest, William J.; McMurtry, Craig W.; Avery, Lars E.

    2003-05-01

    A system for controlling and testing high-resolution non-destructive astronomical imagers was constructed using open-source components, both hardware and software. The open-source electronics design, originated by Carnegie Observatories (OCIW) for CCD cameras, was modified, assembled, and augmented with new circuitry which facilitates monitoring of voltages and currents. The electronics was run from Python user interface software based on a design from the University of Rochester. This new software utilized the Numarray and pyFITS modules developed at the Space Telescope Science Institute (STScI). Interfacing to the "dv" FITS image analysis package from the NASA IRTF was also implemented. Python (the STScI language of choice) was used as the primary language for systems integration, scripts for data acquisition, and scripts for data analysis. The DSP clocking software was a mixture of C and Motorola 56303 assembly. An interrupt-driven kernel-mode PCI device driver for Red Hat Linux was written in C, and used the PC processor and memory for image processing and acquisition. Two 1Κ × 1Κ Raytheon SB226-based hybridized silicon p-i-n arrays were operated and tested with the new system at temperatures as low as 10K. Signal path gain, node capacitance, well depth, dark current, and MTF measurements were made and are presented here.

  2. BOREAS TE-18, 60-m, Radiometrically Rectified Landsat TM Imagery

    NASA Technical Reports Server (NTRS)

    Hall, Forrest G. (Editor); Knapp, David

    2000-01-01

    The BOREAS TE-18 team used a radiometric rectification process to produce standardized DN values for a series of Landsat TM images of the BOREAS SSA and NSA in order to compare images that were collected under different atmospheric conditions. The images for each study area were referenced to an image that had very clear atmospheric qualities. The reference image for the SSA was collected on 02-Sep-1994, while the reference image for the NSA was collected on 2 1 Jun-1995. The 23 rectified images cover the period of 07-Jul-1985 to 18-Sep-1994 in the SSA and 22-Jun-1984 to 09-Jun-1994 in the NSA. Each of the reference scenes had coincident atmospheric optical thickness measurements made by RSS-11. The radiometric rectification process is described in more detail by Hall et al. (1991). The original Landsat TM data were received from CCRS for use in the BOREAS project. Due to the nature of the radiometric rectification process and copyright issues, the full-resolution (30-m) images may not be publicly distributed. However, this spatially degraded 60-m resolution version of the images may be openly distributed and is available on the BOREAS CD-ROM series. After the radiometric rectification processing, the original data were degraded to a 60-m pixel size from the original 30-m pixel size by averaging the data over a 2- by 2-pixel window. The data are stored in binary image-format files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Activity Archive Center (DAAC).

  3. BOREAS TE-18, 30-m, Radiometrically Rectified Landsat TM Imagery

    NASA Technical Reports Server (NTRS)

    Hall, Forrest G. (Editor); Knapp, David

    2000-01-01

    The BOREAS TE-18 team used a radiometric rectification process to produce standardized DN values for a series of Landsat TM images of the BOREAS SSA and NSA in order to compare images that were collected under different atmospheric conditions. The images for each study area were referenced to an image that had very clear atmospheric qualities. The reference image for the SSA was collected on 02-Sep-1994, while the reference image for the NSA was collected on 21-Jun-1995. the 23 rectified images cover the period of 07-Jul-1985 to 18 Sep-1994 in the SSA and from 22-Jun-1984 to 09-Jun-1994 in the NSA. Each of the reference scenes had coincident atmospheric optical thickness measurements made by RSS-11. The radiometric rectification process is described in more detail by Hall et al. (199 1). The original Landsat TM data were received from CCRS for use in the BOREAS project. The data are stored in binary image-format files. Due to the nature of the radiometric rectification process and copyright issues, these full-resolution images may not be publicly distributed. However, a spatially degraded 60-m resolution version of the images is available on the BOREAS CD-ROM series. See Sections 15 and 16 for information about how to possibly acquire the full resolution data. Information about the full-resolution images is provided in an inventory listing on the CD-ROMs. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Activity Archive Center (DAAC).

  4. Damping of a parallel ac-dc power system using PID power system stabilizers and rectifier current regulators

    SciTech Connect

    Hsu, Y.Y.; Wang, L. )

    1988-09-01

    A novel approach is presented to improve the dynamic stability of a parallel AC-DC power system. The developed scheme employs a proportional-integral-derivative (PID) power system stabilizer (PSS) and a PID rectifier current regulator (RCR) to enhance the damping for the electromagnetical mode of the system. The parameters of the proposed PID controllers are determined using a unified approach based on modal control theory. Eigenvalue analyses are performed for the system under various operating conditions in order to compare the damping effects provided by the two different control schemes. To demonstrate the effectiveness of the proposed damping schemes under disturbance conditions simulated dynamic response tests based on a nonlinear system model are also performed.

  5. Characteristics of degenerately doped silicon for spectral control in thermophotovoltaic systems

    SciTech Connect

    Ehsani, H.; Bhat, I.; Borrego, J.; Gutmann, R.; Brown, E.; Dzeindziel, R.; Freeman, M.; Choudhury, N.

    1995-07-01

    Heavily doped Si was investigated for use as spectral control filter in thermal photovoltaic (TPV) system. These filters should reflect radiation at 4 {micro}m and above and transmit radiation at 2 {micro}m and below. Two approaches have been used for introducing impurities into Si to achieve high doping concentration. One was the diffusion technique, using spin-on dopants. The plasma wavelength ({lambda}{sub p}) of these filters could be adjusted by controlling the diffusion conditions. The minimum plasma wavelength achieved was 4.8 {micro}m. In addition, a significant amount of absorption was observed for the wavelength 2 {micro}m and below. The second approach was doping by ion implantation followed by thermal annealing with a capped layer of doped glass. Implantation with high dosage of B and As followed by high temperature annealing (> 1,000 C) resulted in a plasma wavelength that could be controlled between 3.5 and 6 {micro}m. The high temperature annealing (> 1,000 C) that was necessary to activate the dopant atoms and to heal the implantation damage, also caused significant absorption at 2 {micro}m. For phosphorus implanted Si, a moderate temperature (800--900 C) was sufficient to activate most of the phosphorus and to heal the implantation damage. The position of the plasma turn-on wavelength for an implantation dose of 2 {times} 10{sup 16} cm{sup {minus}2} of P was at 2.9 {micro}m. The absorption at 2 {micro}m was less than 20% and the reflection at 5 {micro}m was about 70%.

  6. Commissioning of the control and data acquisition electronics for the CDF Silicon Vertex Detector

    SciTech Connect

    Tkaczyk, S.M.; Turner, K.J.; Nelson, C.A.; Shaw, T.M.; Wesson, T.R. ); Bailey, M.W.; Kruse, M.C. ); Castro, A. )

    1991-11-01

    The SVX data acquisition system includes three components: a Fastbus Sequencer, an SVX Rabbit Crate Controller and a Digitizer. These modules are integrated into the CDF DAQ system and operate the readout chips. The results of the extensive functional tests of the SVX modules are reported. We discuss the stability of the Sequencers, systematic differences between them and methods of synchronization with the Tevatron beam crossings. The Digitizer ADC calibration procedure run on the microsequencer is described. The microsequencer code used for data taking and SVX chip calibration modes is described. Measurements of the SVX data scan time are discussed.

  7. An 18.2%-efficient black-silicon solar cell achieved through control of carrier recombination in nanostructures.

    PubMed

    Oh, Jihun; Yuan, Hao-Chih; Branz, Howard M

    2012-11-01

    Silicon nanowire and nanopore arrays promise to reduce manufacturing costs and increase the power conversion efficiency of photovoltaic devices. So far, however, photovoltaic cells based on nanostructured silicon exhibit lower power conversion efficiencies than conventional cells due to the enhanced photocarrier recombination associated with the nanostructures. Here, we identify and separately measure surface recombination and Auger recombination in wafer-based nanostructured silicon solar cells. By identifying the regimes of junction doping concentration in which each mechanism dominates, we were able to design and fabricate an independently confirmed 18.2%-efficient nanostructured 'black-silicon' cell that does not need the antireflection coating layer(s) normally required to reach a comparable performance level. Our results suggest design rules for efficient high-surface-area solar cells with nano- and microstructured semiconductor absorbers. PMID:23023643

  8. Formation mechanism and control of MgO·Al2O3 inclusions in non-oriented silicon steel

    NASA Astrophysics Data System (ADS)

    Sun, Yan-hui; Zeng, Ya-nan; Xu, Rui; Cai, Kai-ke

    2014-11-01

    On the basis of the practical production of non-oriented silicon steel, the formation of MgO·Al2O3 inclusions was analyzed in the process of "basic oxygen furnace (BOF) → RH → compact strip production (CSP)". The thermodynamic and kinetic conditions of the formation of MgO·Al2O3 inclusions were discussed, and the behavior of slag entrapment in molten steel during RH refining was simulated by computational fluid dynamics (CFD) software. The results showed that the MgO/Al2O3 mass ratio was in the range from 0.005 to 0.017 and that MgO·Al2O3 inclusions were not observed before the RH refining process. In contrast, the MgO/Al2O3 mass ratio was in the range from 0.30 to 0.50, and the percentage of MgO·Al2O3 spinel inclusions reached 58.4% of the total inclusions after the RH refining process. The compositions of the slag were similar to those of the inclusions; furthermore, the critical velocity of slag entrapment was calculated to be 0.45 m·s-1 at an argon flow rate of 698 L·min-1, as simulated using CFD software. When the test steel was in equilibrium with the slag, [Mg] was 0.00024wt%-0.00028wt% and [Al]s was 0.31wt%-0.37wt%; these concentrations were theoretically calculated to fall within the MgO·Al2O3 formation zone, thereby leading to the formation of MgO·Al2O3 inclusions in the steel. Thus, the formation of MgO·Al2O3 inclusions would be inhibited by reducing the quantity of slag entrapment, controlling the roughing slag during casting, and controlling the composition of the slag and the MgO content in the ladle refractory.

  9. 3D spirals with controlled chirality fabricated using metal-assisted chemical etching of silicon.

    PubMed

    Hildreth, Owen J; Fedorov, Andrei G; Wong, Ching Ping

    2012-11-27

    The ability to fabricate 3D spiraling structures using metal-assisted chemical etching (MaCE) is one of the unique advantages of MaCE over traditional etching methods. However, control over the chirality of the spiraling structures has not been established. In this work, a systematic parametric study was undertaken for MaCE of star-shaped catalysts, examining the influence of arm shape, arm length, number of arms, center core diameter, and catalyst thickness on the rotation direction. This data was used to identify a set of geometric parameters that reliably induce rotation in a predefined direction such that large arrays of 3D spiraling structures can be fabricated with the same chirality. Electroless deposition into the MaCE template was used to examine the full etch path of the catalyst and an experimental fit was established to control rotation angle by adjusting the catalyst's center core diameter. The ability to fabricate large arrays of 3D spiraling structures with predefined chirality could have important applications in photonics and optoelectronics. PMID:23039816

  10. A High-Throughput Electrophysiology Assay Identifies Inhibitors of the Inwardly Rectifying Potassium Channel Kir7.1.

    PubMed

    Wright, Paul D; Kanumilli, Srinivasan; Tickle, David; Cartland, Jamie; Bouloc, Nathalie; Dale, Timothy; Tresize, Derek J; McCloskey, Conor; McCavera, Samantha; Blanks, Andrew M; Kettleborough, Catherine; Jerman, Jeffrey C

    2015-07-01

    Kir7.1 is an inwardly rectifying potassium channel that has been implicated in controlling the resting membrane potential of the myometrium. Abnormal uterine activity in pregnancy plays an important role in postpartum hemorrhage, and novel therapies for this condition may lie in manipulation of membrane potential. This work presents an assay development and screening strategy for identifying novel inhibitors of Kir7.1. A cell-based automated patch-clamp electrophysiology assay was developed using the IonWorks Quattro (Molecular Devices, Sunnyvale, CA) system, and the iterative optimization is described. In total, 7087 compounds were tested, with a hit rate (>40% inhibition) of 3.09%. During screening, average Z' values of 0.63 ± 0.09 were observed. After chemistry triage, lead compounds were resynthesized and activity confirmed by IC50 determinations. The most potent compound identified (MRT00200769) gave rise to an IC50 of 1.3 µM at Kir7.1. Compounds were assessed for selectivity using the inwardly rectifying potassium channel Kir1.1 (ROMK) and hERG (human Ether-à-go-go Related Gene). Pharmacological characterization of known Kir7.1 inhibitors was also carried out and analogues of VU590 tested to assess selectivity at Kir7.1. PMID:25656238

  11. A superconducting/magnetic hybrid rectifier based on Fe single-crystal nanocentres: role of magnetic and geometric asymmetries

    NASA Astrophysics Data System (ADS)

    Gomez, A.; Gonzalez, E. M.; Iglesias, M.; Sanchez, N.; Palomares, F. J.; Cebollada, F.; Gonzalez, J. M.; Vicent, J. L.

    2013-03-01

    Vortex lattice motion driven by alternating forces on asymmetric pinning potentials generates a net flow of vortices. This rectifier (ratchet) effect is studied in hybrid samples fabricated with arrays of Fe single-crystal nanotriangles embedded in Nb films. In these samples two different asymmetric potentials generate the ratchet effect: (i) potentials with geometric asymmetry and (ii) potentials with magnetic asymmetry. The asymmetry of the geometric potential cannot be manipulated, but the asymmetry of the magnetic potential can be tailored. In geometric ratchet interstitial vortices play a crucial role and they permit tuning the output voltage polarity. In magnetic ratchet the output voltage amplitude can be controlled by tailoring the magnetic stray field configurations due to different magnetic remanent states of the Fe single-crystal nanostructures. These configurations are modified by changing the direction of the saturating applied field and also by using different orientations of the Fe magnetocrystalline easy axes within the triangles. When both mechanisms coexist, the geometric potential governs the rectifier effect behaviour.

  12. Silicon Control of Strontium and Cesium Partitioning in Hydroxide-Weathered Sediments

    SciTech Connect

    Chorover, Jon; Choi, Sunkyung; Rotenberg, P.; Serne, R. Jeffrey; Rivera, Nelson; Strepka, Caleb R.; Thompson, Aaron; Mueller, Karl T.; O'Day, Peggy A.

    2008-04-15

    Cation partitioning in an aqueous soil suspension depends on the coupling of reaction time, sorbate amount and mineral weathering reactions. These factors were varied in sediment suspension experiments to identify geochemical processes that affect migration of Sr2+ and Cs+ introduced to the subsurface by caustic high level radioactive waste (HLRW). Three glacio-fluvial and lacustrine sediments from the Hanford Site were subjected to hyperalkaline (pH > 13), Na–Al–NO3–OH solution conditions within a gradient field of (i) sorptive concentration (10-5–10-3 M) and (ii) reaction time (0–365 d). Strontium uptake (qSr) exceeded that of cesium at nearly all reaction times. Sorbent affinity for both Cs+ and Sr2+ increased with clay plus silt content at early times, but a prolonged slow uptake process was observed over the course of sediment weathering that erased the texture effect for Sr2+; all sediments showed similar mass normalized uptake after several months of reaction time. Strontium became progressively recalcitrant to desorption after 92 d, with accumulation and aging of neoformed aluminosilicates. Formation of Cs+ and Sr2+-containing cancrinite and sodalite was observed after 183 d by SEM and synchrotron u-XRF and u-XRD. EXAFS data showed ncorporation of Sr2+ into both feldspathoid and SrCO3(s) coordination environments after one year. Adsorption was predominant at early times and low sorbate amount, whereas recipitation, controlled largely by sediment Si release, became increasingly important at longer times and higher sorbate amount. Kinetics of contaminant desorption at pH 8 from one year-weathered sediments showed significant dependence on background cation (Ca2+ versus K+) composition. Results of this study indicate that co-precipitation and ion exchange in neoformed aluminosilicates may be an important mechanism controlling Sr2+ and Cs+ mobility in siliceous sediments impacted by hyperalkaline HLRW.

  13. Iodine 125 Brachytherapy With Vitrectomy and Silicone Oil in the Treatment of Uveal Melanoma: 1-to-1 Matched Case-Control Series

    SciTech Connect

    McCannel, Tara A. McCannel, Colin A.

    2014-06-01

    Purpose: We initially reported the radiation-attenuating effect of silicone oil 1000 centistokes for iodine 125. The purpose of this report was to compare the clinical outcomes in case patients who had iodine 125 brachytherapy with vitrectomy and silicone oil 1000 centistokes with the outcomes in matched control patients who underwent brachytherapy alone. Methods and Materials: Consecutive patients with uveal melanoma who were treated with iodine 125 plaque brachytherapy and vitrectomy with silicone oil with minimum 1-year follow-up were included. Control patients who underwent brachytherapy alone were matched for tumor size, location, and sex. Baseline patient and tumor characteristics and tumor response to radiation, final visual acuity, macular status, central macular thickness by ocular coherence tomography (OCT), cataract progression, and metastasis at last follow-up visit were compared. Surgical complications were also determined. Results: Twenty case patients met the inclusion criteria. The average follow-up time was 22.1 months in case patients and 19.4 months in control patients. The final logMAR vision was 0.81 in case patients and 1.1 in control patients (P=.071); 8 case patients and 16 control patients had abnormal macular findings (P=.011); and the average central macular thickness by OCT was 293.2 μm in case patients and 408.5 μm in control patients (P=.016). Eleven case patients (55%) and 1 control patient (5%) had required cataract surgery at last follow-up (P=.002). Four patients in the case group and 1 patient in the control group experienced metastasis (P=.18). Among the cases, intraoperative retinal tear occurred in 3 patients; total serous retinal detachment and macular hole developed in 1 case patient each. There was no case of rhegmatogenous retinal detachment, treatment failure, or local tumor dissemination in case patients or control patients. Conclusions: With up to 3 years of clinical follow-up, silicone oil during brachytherapy for the treatment of uveal melanoma resulted in fewer abnormal maculas, lower central macular thickness on OCT, and a trend toward better final visual acuity in comparison with matched control patients who underwent brachytherapy alone.

  14. Locale and chemistry of spermine binding in the archetypal inward rectifier Kir2.1

    PubMed Central

    Zhu, Emily A.; Nichols, Colin G.

    2010-01-01

    Polyamine block of inwardly rectifying potassium (Kir) channels underlies their steep voltage dependence observed in vivo. We have examined the potency, voltage dependence, and kinetics of spermine block in dimeric Kir2.1 constructs containing one nonreactive subunit and one cysteine-substituted subunit before and after modification by methanethiosulfonate (MTS) reagents. At position 169C (between the D172 “rectification controller” and the selectivity filter), modification by either 2-aminoethyl MTS (MTSEA) or 2-(trimethylammonium)ethyl MTS (MTSET) reduced the potency and voltage dependence of spermine block, consistent with this position overlapping the spermine binding site. At position 176C (between D172 and the M2 helix bundle crossing), modification by MTSEA also weakened spermine block. In contrast, MTSET modification of 176C dramatically slowed the kinetics of spermine unblock, with almost no effect on potency or voltage dependence. The data are consistent with MTSET modification of 176C introducing a localized barrier in the inner cavity, resulting in slower spermine entry into and exit from a “deep” binding site (likely between the D172 rectification controller and the selectivity filter), but leaving the spermine binding site mostly unaffected. These findings constrain the location of deep spermine binding that underlies steeply voltage-dependent block, and further suggest important chemical details of high affinity binding of spermine in Kir2.1 channels—the archetypal model of strong inward rectification. PMID:20421374

  15. Surprise signals in the supplementary eye field: rectified prediction errors drive exploration-exploitation transitions.

    PubMed

    Kawaguchi, Norihiko; Sakamoto, Kazuhiro; Saito, Naohiro; Furusawa, Yoshito; Tanji, Jun; Aoki, Masashi; Mushiake, Hajime

    2015-02-01

    Visual search is coordinated adaptively by monitoring and predicting the environment. The supplementary eye field (SEF) plays a role in oculomotor control and outcome evaluation. However, it is not clear whether the SEF is involved in adjusting behavioral modes based on preceding feedback. We hypothesized that the SEF drives exploration-exploitation transitions by generating "surprise signals" or rectified prediction errors, which reflect differences between predicted and actual outcomes. To test this hypothesis, we introduced an oculomotor two-target search task in which monkeys were required to find two valid targets among four identical stimuli. After they detected the valid targets, they exploited their knowledge of target locations to obtain a reward by choosing the two valid targets alternately. Behavioral analysis revealed two distinct types of oculomotor search patterns: exploration and exploitation. We found that two types of SEF neurons represented the surprise signals. The error-surprise neurons showed enhanced activity when the monkey received the first error feedback after the target pair change, and this activity was followed by an exploratory oculomotor search pattern. The correct-surprise neurons showed enhanced activity when the monkey received the first correct feedback after an error trial, and this increased activity was followed by an exploitative, fixed-type search pattern. Our findings suggest that error-surprise neurons are involved in the transition from exploitation to exploration and that correct-surprise neurons are involved in the transition from exploration to exploitation. PMID:25411455

  16. Control of inhibitor precipitation for producing grain-oriented silicon steel

    SciTech Connect

    Obara, T.; Takeuchi, H.; Takamiya, T.; Kan, T. )

    1993-04-01

    Grain-oriented electrical steels have been widely used for various products, and hence, improving their properties is greatly desired to thus save electricity. Magnetic properties of grain-oriented 3% Si steels have been steadily improved since Goss invented this steel. The authors are convinced that the possibility of further improvement still exists. An important metallurgical basis for producing grain-oriented Si steel is controlling the primary recrystallization texture and the dispersion of inhibitors. Mechanisms of secondary recrystallization and the influence of primary texture on it have been discussed by Harase et al. It is well known that the inhibitor plays its role at the secondary recrystallization stage. Three important metallurgical factors related to the inhibitor exist in the process: dissolution, precipitation, and Ostwald ripening. The most important of these processes is precipitation, which is achieved primarily during hot rolling and comprises a cooling process and a deformation process. The purpose of this article is to clarify the metallurgical sequence of precipitation during hot rolling and then to improve the process by the application of this information to obtain improved magnetic properties.

  17. D0 Silicon Upgrade: Control Dewar Venturi Calibration Explanation for Toshiba

    SciTech Connect

    Kuwazaki, Andrew; /Fermilab

    1997-01-24

    This document is intended to explain the calibration data for the venturi, FE-3253H, which is installed in the control dewar. Further, this document will help explain how to use the venturi to make mass flow measurements during typical operating conditions. The purpose of the calibration data enclosed from the Colorado Engineering Experiment Station Inc. is to experimentally show that the venturi follows the flow equation which is enclosed as Eq. 7-36 on page 155, from the Applied Fluid Dynamics Handbook. The calibration data serves to show that the Subsonic Venturi, Serial Number 611980-18, produces results predicted by the compressible subsonic flow mass flow rate equation above and to experimentally determine the discharge coefficient C. Colorado Engineering Experiment Station Inc. ran tests at 15 independent differential pressures to conclude that use of this venturi will perform according to the mass flow rate equation. In order to verify the results from the Colorado Engineering Experiment Station Inc. we have provided you with a step-by-step procedure using the values they have chosen.

  18. Characterization and properties of controlled nucleation thermochemical deposited (CNTD) silicon carbide

    NASA Technical Reports Server (NTRS)

    Dutta, S.; Rice, R. W.; Graham, H. C.; Mendiratta, M. C.

    1978-01-01

    The microstructure of controlled nucleation thermochemical deposition (CNTD) - SiC material was studied and the room temperature and high temperature bend strength and oxidation resistance was evaluated. Utilizing the CNTD process, ultrafine grained (0.01-0.1 mm) SiC was deposited on W - wires (0.5 mm diameter by 20 cm long) as substrates. The deposited SiC rods had superior surface smoothness and were without any macrocolumnar growth commonly found in conventional CVD material. At both room and high temperature (1200 - 1380 C), the CNTD - SiC exhibited bend strength approximately 200,000 psi (1380 MPa), several times higher than that of hot pressed, sintered, or CVD SiC. The excellent retention of strength at high temperature was attributed to the high purity and fine grain size of the SiC deposit and the apparent absence of grain growth at elevated temperatures. The rates of weight change for CNTD - SiC during oxidation were lower than for NC-203 (hot pressed SiC), higher than for GE's CVD - SiC, and considerably below those for HS-130 (hot pressed Si3N4). The high purity, fully dense, and stable grain size CNTD - SiC material shows potential for high temperature structural applications; however problem areas might include: scaling the process to make larger parts, deposition on removable substrates, and the possible residual tensile stress.

  19. Surface trimming of silicon photonics devices using controlled reactive ion etching chemistry

    NASA Astrophysics Data System (ADS)

    Chandran, S.; Das, B. K.

    2015-06-01

    Surface trimming of rib waveguides fabricated in 5-μm SOI substrate has been carried out successfully without any significant increase of propagation losses. A reactive ion etching chemistry has been optimized for trimming and an empirical model has been developed to obtain the resulting waveguide geometries. This technique has been used to demonstrate smaller footprint devices like multimode interference based power splitters and ring resonators after defining them photolithographically with relatively large cross-section rib waveguides. We have been also successful to fabricate 2D tapered spot-size converter useful for monolithic integration of waveguides with varying heights and widths. The taper length is again precisely controlled by photolithographic definition. Minimum insertion loss of such a spot-size converter integrated between waveguides with 3-μm height difference has been recorded to be ∼2 dB. It has been also shown that the overall fiber-to-chip coupling loss can be reduced by >3 dB by using such spot-size converters at the input/output side of the waveguides.

  20. Controlled Release of Antibiotics From Vitamin E-Loaded Silicone-Hydrogel Contact Lenses.

    PubMed

    Paradiso, Patrizia; Serro, Ana Paula; Saramago, Benilde; Colaço, Rogério; Chauhan, Anuj

    2016-03-01

    Symptoms of bacterial and fungal keratitis are typically treated through the frequent application of antibiotic and antifungal eye drops. The high frequency of half hourly or hourly eye drop administration required to treat these indications is tedious and could reduce compliance. Here, we combine in vitro experiments with a mathematical model to develop therapeutic soft contact lenses to cure keratitis by extended release of suitable drugs. We specifically focus on increasing the release duration of levofloxacin and chlorhexidine from 1-DAY ACUVUE(®) TrueEye™ and ACUVUE OASYS(®) contact lenses by incorporating vitamin E diffusion barriers. Results show that 20% of vitamin E loading in the contact lens increases the release duration of levofloxacin to 100 h and 50 h from 1-DAY ACUVUE(®) TrueEye™ and ACUVUE OASYS(®), respectively, which is a 3- and 6-fold increase, respectively, for the 2 lenses. For chlorhexidine, the increase is 2.5- and 10-fold, for the TrueEye™ and OASYS(®), respectively, to 130 h and 170 h. The mass of drug loaded in the lenses can be controlled to achieve a daily release comparable to the commonly prescribed eye drop therapy. The vitamin E-loaded lenses retain all critical properties for in vivo use. PMID:26886333

  1. A high switching frequency IGBT PWM rectifier/inverter system for ac motor drives operating from single phase supply

    NASA Astrophysics Data System (ADS)

    Thiyagarajah, K.; Ranganathan, V. T.; Ramakrishna Iyengar, B. S.

    1991-10-01

    A pulse-width-modulated (PWM) rectifier/inverter system using insulated-gate-bipolar-transistors (IGBTs), capable of switching at 20 kHz is reported. The base drive circuit for the IGBT, incorporating short-circuit protection, is presented. The inverter uses an Undeland snubber together with a simple energy recovery circuit, which ensures reliable and efficient operation even for 20 kHz switching. The front end for the system is a regenerative single phase full-bridge IGBT inverter along with an ac reactor. Steady-state design considerations are explained, and control techniques for unity power factor operation and fast current control of the front end converter, in a rotating as well as a stationary reference frame, are discussed and compared. Results from computer simulations and experimental results for a 1.5-kW prototype system are presented.

  2. A Novel Approach of Daunorubicin Application on Formation of Proliferative Retinopathy Using a Porous Silicon Controlled Delivery System: Pharmacodynamics

    PubMed Central

    Hou, Huiyuan; Huffman, Kristyn; Rios, Sandy; Freeman, William R.; Sailor, Michael J.; Cheng, Lingyun

    2015-01-01

    Purpose. Proliferative vitreoretinopathy (PVR) is the most common cause of poor visual outcomes in association with retinal detachment surgeries and ocular trauma. Daunorubicin (DNR) has shown the strongest efficacy in proliferation inhibition in vitro. However, clinical studies have shown only mild effect owing to limitations of narrow therapeutic window and short vitreous half-life. Methods. Three milligrams of DNR-loaded particles were intravitreally injected into 18 pigmented rabbits, and vitreous samples were collected up to 84 days for analysis. Thirty-seven rabbits were used for a dose-escalation (1, 3, 6 mg) safety and efficacy study in a rabbit PVR model using a pretreatment design. Results. Loading efficiency of DNR was 108.55 ± 12 μg per 1 mg particles. Eighty-four days of follow-up did not reveal any adverse reaction. Pharmacokinetic analysis demonstrated a vitreous half-life of 29 days with a maximum DNR concentration of 178 ng/mL and a minimum concentration of 29 ng/mL at day 84. Daunorubicin-loaded porous silicon (pSi) particles were dosed 8 to 9 weeks before PVR induction, and PVR severity score was dose dependent (Spearman ρ = −0.25, P = 0.0005). Proliferative vitreoretinopathy with tractional retinal detachment was 88% in the control group, 63% in the low-dose group, 14% in the medium-dose group, and 0% in the high-dose group (Cochran-Armitage Trend Test, Z = 8.99, ρ = −0.67, P < 0.0001). Conclusions. Daunorubicin-loaded pSi particles can safely reside in the vitreous for at least 3 months. The pSi-based delivery expanded the therapeutic window of DNR by a factor of 862 and drove down the minimum effective concentration by a factor of 175. PMID:25829415

  3. A Benchtop Closed-loop System Controlled by a Bio-Inspired Silicon Implementation of the Pancreatic β Cell

    PubMed Central

    Oliver, Nick; Georgiou, Pantelis; Johnston, Desmond; Toumazou, Christofer

    2009-01-01

    The normal pancreatic β-cell membrane depolarizes in response to increasing concentrations of glucose in a bursting pattern. At <7 mM (126 mg/dl), the cell is electrically silent. The bursting pulse width increases as glucose rises >7 mM (126 mg/dl) until a continuous train of bursting is seen at >25 mM (450 mg/dl). A bio-inspired silicon device has been developed using analogue electronics to implement membrane depolarization of the β cell. The device is ultralow powered, miniaturized (5 × 5 mm), and produces a bursting output identical to that characterized in electrophysiological studies. Objective The goal of this study was to demonstrate the ability of silicon implementation of β-cell electrophysiology to respond to a simulated glucose input and to drive an infusion pump in vitro. Method The silicon device response to a current source was recorded at varying simulated glucose concentrations. Subsequently, the bursting response to a changing analyte concentration measured by an amperometric enzyme electrode was converted to a voltage, driving a syringe pump loaded with a 50-ml syringe containing water. Results Bursting responses are comparable to those recorded in electrophysiology. Silicon β-cell implementation bursts with a pulse width proportional to concentration and is able to drive an infusion pump. Conclusion This is the first in vitro demonstration of closed loop insulin delivery utilizing miniaturized silicon implementation of β-cell physiology in analogue electronics. PMID:20144397

  4. Periodic silicon nanocone arrays with controllable dimensions prepared by two-step etching using nanosphere lithography and NH4OH/H2O2 solution

    NASA Astrophysics Data System (ADS)

    Yang, Mingfei; Yu, HongYu; Sun, Xiaowei; Li, Junshuai; Li, Xiaocheng; Ke, Lin; Hu, Junhui; Wang, Fei; Jiao, Zhihui

    2011-01-01

    An electroless chemical etching technique using polystyrene nanospheres as a self-assembled mask is developed to fabricate size-controllable, periodic silicon nanopillars (NPs) and subsequent nanocone (NC) arrays. The Si NCs are obtained based on the NPs structure using cost-effective ammonia-related etching chemistry. The diameter, height, and periodicity of the NCs can be systematically controlled. Optical measurement shows a good improvement in the reduction of reflectance properties with Si NCs structures. This method is potentially beneficial to many device applications including super-capacitors, batteries, solar cells, etc.

  5. High-performance AlGaN /GaN lateral field-effect rectifiers compatible with high electron mobility transistors

    NASA Astrophysics Data System (ADS)

    Chen, Wanjun; Wong, King-Yuen; Huang, Wei; Chen, Kevin J.

    2008-06-01

    A high electron mobility transistor (HEMT)-compatible power lateral field-effect rectifier (L-FER) with low turn-on voltage is demonstrated using the same fabrication process as that for normally off AlGaN /GaN HEMT, providing a low-cost solution for GaN power integrated circuits. The power rectifier features a Schottky-gate-controlled two-dimensional electron gas channel between the cathode and anode. By tying up the Schottky gate and anode together, the forward turn-on voltage of the rectifier is determined by the threshold voltage of the channel instead of the Schottky barrier. The L-FER with a drift length of 10μm features a forward turn-on voltage of 0.63V at a current density of 100A/cm2. This device also exhibits a reverse breakdown voltage (BV) of 390V at a current level of 1mA/mm and a specific on resistance (RON,sp) of 1.4mΩcm2, yielding a figure of merit (BV2/RON,sp) of 108MW/cm2. The excellent device performance, coupled with the lateral device structure and process compatibility with AlGaN /GaN HEMT, make the proposed L-FER a promising candidate for GaN power integrated circuits.

  6. Crystal Structure of the Eukaryotic Strong Inward-Rectifier K[superscript +] Channel Kir2.2 at 3.1 Å Resolution

    SciTech Connect

    Tao, Xiao; Avalos, Jose L.; Chen, Jiayun; MacKinnon, Roderick

    2010-03-29

    Inward-rectifier potassium (K{sup +}) channels conduct K{sup +} ions most efficiently in one direction, into the cell. Kir2 channels control the resting membrane voltage in many electrically excitable cells, and heritable mutations cause periodic paralysis and cardiac arrhythmia. We present the crystal structure of Kir2.2 from chicken, which, excluding the unstructured amino and carboxyl termini, is 90% identical to human Kir2.2. Crystals containing rubidium (Rb{sup +}), strontium (Sr{sup 2+}), and europium (Eu{sup 3+}) reveal binding sites along the ion conduction pathway that are both conductive and inhibitory. The sites correlate with extensive electrophysiological data and provide a structural basis for understanding rectification. The channel's extracellular surface, with large structured turrets and an unusual selectivity filter entryway, might explain the relative insensitivity of eukaryotic inward rectifiers to toxins. These same surface features also suggest a possible approach to the development of inhibitory agents specific to each member of the inward-rectifier K{sup +} channel family.

  7. Reconfigurable Resonant Regulating Rectifier With Primary Equalization for Extended Coupling- and Loading-Range in Bio-Implant Wireless Power Transfer.

    PubMed

    Li, Xing; Meng, Xiaodong; Tsui, Chi-Ying; Ki, Wing-Hung

    2015-12-01

    Wireless power transfer using reconfigurable resonant regulating ( R(3) ) rectification suffers from limited range in accommodating varying coupling and loading conditions. A primary-assisted regulation principle is proposed to mitigate these limitations, of which the amplitude of the rectifier input voltage on the secondary side is regulated by accordingly adjusting the voltage amplitude Veq on the primary side. A novel current-sensing method and calibration scheme track Veq on the primary side. A ramp generator simultaneously provides three clock signals for different modules. Both the primary equalizer and the R(3) rectifier are implemented as custom integrated circuits fabricated in a 0.35 μm CMOS process, with the global control implemented in FPGA. Measurements show that with the primary equalizer, the workable coupling and loading ranges are extended by 250% at 120 mW load and 300% at 1.2 cm coil distance compared to the same system without the primary equalizer. A maximum rectifier efficiency of 92.5% and a total system efficiency of 62.4% are demonstrated. PMID:26742141

  8. Temperature-dependent rectifying and photovoltaic characteristics of an oxygen-deficient Bi2Sr2Co2Oy/Si heterojunction

    NASA Astrophysics Data System (ADS)

    Yan, Guo-Ying; Bai, Zi-Long; Li, Hui-Ling; Fu, Guang-Sheng; Liu, Fu-Qiang; Yu, Wei; Wang, Jiang-Long; Wang, Shu-Fang

    2013-10-01

    A Bi2Sr2Co2Oy/Si heterojunction is obtained by growing a layer of p-type oxygen-deficient Bi2Sr2Co2Oy film on a commercial n-type silicon wafer by pulsed laser deposition. Its rectifying and photovoltaic properties are studied in a wide temperature range from 20 K to 300 K. The transport mechanism under the forward bias can be attributed to a trap-filled space-charge-limited current conduction mechanism. Under the irradiation of a 532-nm continuous wave laser, a clear photovoltaic effect is observed and the magnitude of photovoltage increases as the temperature decreases. The results demonstrate the potential application of a Bi2Sr2Co2Oy-based heterojunction in the photoelectronic devices.

  9. Polycrystalline silicon availability for photovoltaic and semiconductor industries

    NASA Technical Reports Server (NTRS)

    Ferber, R. R.; Costogue, E. N.; Pellin, R.

    1982-01-01

    Markets, applications, and production techniques for Siemens process-produced polycrystalline silicon are surveyed. It is noted that as of 1982 a total of six Si materials suppliers were servicing a worldwide total of over 1000 manufacturers of Si-based devices. Besides solar cells, the Si wafers are employed for thyristors, rectifiers, bipolar power transistors, and discrete components for control systems. An estimated 3890 metric tons of semiconductor-grade polycrystalline Si will be used in 1982, and 6200 metric tons by 1985. Although the amount is expected to nearly triple between 1982-89, research is being carried out on the formation of thin films and ribbons for solar cells, thereby eliminating the waste produced in slicing Czolchralski-grown crystals. The free-world Si production in 1982 is estimated to be 3050 metric tons. Various new technologies for the formation of polycrystalline Si at lower costs and with less waste are considered. New entries into the industrial Si formation field are projected to produce a 2000 metric ton excess by 1988.

  10. Size control, quantum confinement, and oxidation kinetics of silicon nanocrystals synthesized at a high rate by expanding thermal plasma

    SciTech Connect

    Han, Lihao E-mail: A.H.M.Smets@tudelft.nl; Zeman, Miro; Smets, Arno H. M. E-mail: A.H.M.Smets@tudelft.nl

    2015-05-25

    The growth mechanism of silicon nanocrystals (Si NCs) synthesized at a high rate by means of expanding thermal plasma chemical vapor deposition technique are studied in this letter. A bimodal Gaussian size distribution is revealed from the high-resolution transmission electron microscopy images, and routes to reduce the unwanted large Si NCs are discussed. Photoluminescence and Raman spectroscopies are employed to study the size-dependent quantum confinement effect, from which the average diameters of the small Si NCs are determined. The surface oxidation kinetics of Si NCs are studied using Fourier transform infrared spectroscopy and the importance of post-deposition passivation treatments of hydrogenated crystalline silicon surfaces are demonstrated.

  11. Composition Comprising Silicon Carbide

    NASA Technical Reports Server (NTRS)

    Mehregany, Mehran (Inventor); Zorman, Christian A. (Inventor); Fu, Xiao-An (Inventor); Dunning, Jeremy L. (Inventor)

    2012-01-01

    A method of depositing a ceramic film, particularly a silicon carbide film, on a substrate is disclosed in which the residual stress, residual stress gradient, and resistivity are controlled. Also disclosed are substrates having a deposited film with these controlled properties and devices, particularly MEMS and NEMS devices, having substrates with films having these properties.

  12. Microrectenna: A Terahertz Antenna and Rectifier on a Chip

    NASA Technical Reports Server (NTRS)

    Siegel, Peter

    2007-01-01

    A microrectenna that would operate at a frequency of 2.5 THz has been designed and partially fabricated. The circuit is intended to be a prototype of an extremely compact device that could be used to convert radio-beamed power to DC to drive microdevices (see Figure 1). The microrectenna (see Figure 2) circuit consists of an antenna, a diode rectifier and a DC output port. The antenna consists of a twin slot array in a conducting ground plane (denoted the antenna ground plane) over an enclosed quarter-wavelength-thick resonant cavity (denoted the reflecting ground plane). The circuit also contains a planar high-frequency low-parasitic Schottky-barrier diode, a low-impedance microstrip transmission line, capacitors, and contact beam leads. The entire 3-D circuit is fabricated monolithically from a single GaAs wafer. The resonant cavity renders the slot radiation pattern unidirectional with a half-power beam width of about 65. A unique metal mesh on the rear of the wafer forms the backplate for the cavity but allows the GaAs to be wet etched from the rear surface of the twin slot antennas and ground plane. The beam leads protrude past the edge of the chip and are used both to mount the microrectenna and to make the DC electrical connection with external circuitry. The antenna ground plane and the components on top of it are formed on a 2- m thick GaAs membrane that is grown in the initial wafer MBE (molecular beam epitaxy) process. The side walls of the antenna cavity are not metal coated and, hence, would cause some loss of power; however, the relatively high permittivity (epsilon=13) of the GaAs keeps the cavity modes well confined, without the usual surface-wave losses associated with thick dielectric substrates. The Schottky-barrier diode has the usual submicron dimensions associated with THz operation and is formed in a mesa process above the antenna ground plane. The diode is connected at the midpoint of a microstrip transmission line, which is formed on 1- m-thick SiO (permittivity of 5) laid down on top of the GaAs membrane. The twin slots are fed in phase by this structure. To prevent radio-frequency (RF) leakage past the slot antennas, low-loss capacitors are integrated into the microstrip transmission line at the edges of the slots. The DC current- carrying lines extend from the outer edges of the capacitors, widen approaching the edges of the chip, and continue past the edges of the chip to become the beam leads used in tacking down the devices. The structure provides a self-contained RF to DC converter that works in the THz range.

  13. Theoretical study on the rectifying performance of organoimido derivatives of hexamolybdates.

    PubMed

    Wen, Shizheng; Yang, Guochun; Yan, Likai; Li, Haibin; Su, Zhongmin

    2013-02-25

    We design a new type of molecular diode, based on the organoimido derivatives of hexamolybdates, by exploring the rectifying performances using density functional theory combined with the non-equilibrium Green's function. Asymmetric current-voltage characteristics were obtained for the models with an unexpected large rectification ratio. The rectifying behavior can be understood by the asymmetrical shift of the transmission peak observed under different polarities. It is interesting to find that the preferred electron-transport direction in our studied system is different from that of the organic D-bridge-A system. The results show that the studied organic-inorganic hybrid systems have an intrinsically robust rectifying ratio, which should be taken into consideration in the design of the molecular diodes. PMID:23303530

  14. Recovery Act: High-Efficiency, Wideband Three-Phase Rectifiers and Adaptive Rectifier Management for Telecomm Central Office and Large Data Center Applications

    SciTech Connect

    Mark A. Johnson

    2012-06-29

    Lineage Power and Verizon teamed up to address a DOE funding opportunity focused on improving the power conversion chain in telecommunications facilities and data centers. The project had three significant elements: the design and development of high efficiency and high power three-phase rectifiers by Lineage Power, design and development of software to optimize overall plant energy efficiency by Lineage Power, and a field trial in active Verizon telecommunications facilities where energy consumption was measured before and after efficiency upgrades.

  15. Patterned porous silicon photonic crystals with modular surface chemistry for spatial control of neural stem cell differentiation.

    PubMed

    Huang, Tiffany H; Pei, Yi; Zhang, Douglas; Li, Yanfen; Kilian, Kristopher A

    2016-06-01

    We present a strategy to spatially define regions of gold and nanostructured silicon photonics, each with materials-specific surface chemistry, for azide-alkyne cycloaddition of different bioactive peptides. Neural stem cells are spatially directed to undergo neurogenesis and astrogenesis as a function of both surface properties and peptide identity. PMID:27173986

  16. The first-principles study of oscillating rectifying performance in nanoribbon-chain-carbon nanotube junctions

    NASA Astrophysics Data System (ADS)

    Qiu, Ming; Liew, K. M.

    2013-05-01

    Electronic transport properties of armchair graphene nanoribbon and capped carbon nanotube junctions, covalently bridged by carbon atomic chains with different numbers of carbon atoms, are investigated. The first-principles calculations based on non-equilibrium Green's functions with the density-functional theory show that their I-V characteristics display odd-even effects and rectifying behaviors show obvious oscillations, namely, different bond patterns for even- and odd-numbered carbon chains affect the contact bonds, charge transfer, density of states, evolutions of molecular orbitals, and rectifying performance.

  17. Silicones as nonocclusive topical agents.

    TOXLINE Toxicology Bibliographic Information

    De Paepe K; Sieg A; Le Meur M; Rogiers V

    2014-01-01

    BACKGROUND/AIMS: Silicone excipients are commonly used ingredients because of their emollient and skin-conditioning effects, and their ability to form uniform, water-resistant, yet permeable films. Based on comparisons with organic materials and conflicting knowledge from silicones used in scar treatment, the misconception still exists that silicone topical excipients are occlusive substances that may block the passive loss of water through the upper skin layers. Therefore, 3 types of common silicone excipients and 3 water-in-(oil-plus-silicone) or W/(O + Si) creams, containing 10% (w/w) of the respective silicones, were investigated as a function of time and compared to petrolatum.METHODS: Transepidermal water loss (TEWL) and skin hydration measurements were carried out after a single topical application on forearm skin of 26 healthy young female volunteers.RESULTS: Both petrolatum and silicones significantly decreased TEWL 15 min after application, but the measurements for the silicones were not significantly different from the untreated control values. The tested silicones did not moisturize the skin. Petrolatum formed an occlusive layer, creating an increase in skin hydration for more than 4 h. The results measured for the W/(O + Si) creams indicated that they moisturized the skin, without any effect on TEWL.CONCLUSION: A clear difference was shown between the skin occlusive properties of petrolatum and the water vapor permeability of the common silicone excipient materials.

  18. Enantioselective Protein-Sterol Interactions Mediate Regulation of Both Prokaryotic and Eukaryotic Inward Rectifier K+ Channels by Cholesterol

    PubMed Central

    D'Avanzo, Nazzareno; Hyrc, Krzysztof; Enkvetchakul, Decha; Covey, Douglas F.; Nichols, Colin G.

    2011-01-01

    Cholesterol is the major sterol component of all mammalian cell plasma membranes and plays a critical role in cell function and growth. Previous studies have shown that cholesterol inhibits inward rectifier K+ (Kir) channels, but have not distinguished whether this is due directly to protein-sterol interactions or indirectly to changes in the physical properties of the lipid bilayer. Using purified bacterial and eukaryotic Kir channels reconstituted into liposomes of controlled lipid composition, we demonstrate by 86Rb+ influx assays that bacterial Kir channels (KirBac1.1 and KirBac3.1) and human Kir2.1 are all inhibited by cholesterol, most likely by locking the channels into prolonged closed states, whereas the enantiomer, ent-cholesterol, does not inhibit these channels. These data indicate that cholesterol regulates Kir channels through direct protein-sterol interactions likely taking advantage of an evolutionarily conserved binding pocket. PMID:21559361

  19. Direct Production of Silicones From Sand

    SciTech Connect

    Larry N. Lewis; F.J. Schattenmann: J.P. Lemmon

    2001-09-30

    Silicon, in the form of silica and silicates, is the second most abundant element in the earth's crust. However the synthesis of silicones (scheme 1) and almost all organosilicon chemistry is only accessible through elemental silicon. Silicon dioxide (sand or quartz) is converted to chemical-grade elemental silicon in an energy intensive reduction process, a result of the exceptional thermodynamic stability of silica. Then, the silicon is reacted with methyl chloride to give a mixture of methylchlorosilanes catalyzed by cooper containing a variety of tract metals such as tin, zinc etc. The so-called direct process was first discovered at GE in 1940. The methylchlorosilanes are distilled to purify and separate the major reaction components, the most important of which is dimethyldichlorosilane. Polymerization of dimethyldichlorosilane by controlled hydrolysis results in the formation of silicone polymers. Worldwide, the silicones industry produces about 1.3 billion pounds of the basic silicon polymer, polydimethylsiloxane.

  20. Investigation of device geometry- and temperature-dependent characteristics of AlGaN/GaN lateral field-effect rectifier

    NASA Astrophysics Data System (ADS)

    Chen, Wanjun; Zhang, Jing; Wang, Zhigang; Wei, Jin; Zhang, Bo; Chen, Kevin J.

    2013-01-01

    The temperature-dependent characteristics of AlGaN/GaN lateral field-effect rectifiers (L-FER) are studied in detail by investigating the dependence of forward and reverse characteristics on the device geometry (Schottky-gate-controlled channel) and temperature. The forward current increased with the decrease of channel length, while the specific on-resistance showed a positive temperature coefficient. Moreover, different temperature-dependent reverse characteristics were observed for the L-FERs with different device geometries. A combination of impact ionization in the Schottky-gate-controlled channel and the Schottky reverse leakage current is applied to understand the reverse breakdown of L-FER.

  1. Gravity-Feed Growth of Silicon Ribbon

    NASA Technical Reports Server (NTRS)

    Cullen, G. W.

    1982-01-01

    In inverted Stepanov apparatus, silicon is melted in vee-shaped crucible that has long narrow slot at bottom of vee. Molten silicon flows from slot at a rate controlled by fluid pressure. As it emerges, it cools and solidifies to form a continuous ribbon. To eliminate surface-tension effects, crucible walls are made of a material that liquid silicon does not wet.

  2. Local controlled release of 1-hydroxyethylidene diphosphonate using silicone-rubber matrices. Effects of sterilization on in vitro release and in vivo efficacy.

    PubMed

    Johnston, T P; Bove, E L; Bolling, S F; Schoen, F J; Boyd, J A; Golomb, G; Levy, R J

    1988-01-01

    Calcification (CALC) is the most frequent cause of the clinical failure of bioprosthetic heart valves (BHVs). Controlled release of disodium ethanehydroxydiphosphonate (EHDP) has been demonstrated to inhibit subdermal BHV calcification at effective low local doses, avoiding adverse effects. However, the eventual circulatory use of controlled release EHDP necessitates addressing several critical issues that may affect efficacy. These include the effects of sterilization on EHDP release and the efficacy of sustained release matrices containing CaEHDP, which is less soluble than NaEHDP. The effects of CaEHDP-NaEHDP incorporation and steam sterilization on controlled release of EHDP from silicone-rubber matrices was studied both in vitro and in vivo using a rat subdermal model and sheep tricuspid valve replacements. Autoclaved EHDP matrices (20% wt/wt) released 88.9% +/- 7.84 of contained drug after 140 days in vitro, compared with control (87.6% +/- 10.3 cumulative release). Autoclaved EHDP matrices completely inhibited BHV CALC in 60 day rat subdermal implants (8.84 +/- 3.68 micrograms Ca++/mg tissue), comparable to nonsterilized EHDP-loaded matrices (7.06 +/- 2.00 micrograms Ca++/mg tissue). Nontreated CALC levels were 183 +/- 7.60 micrograms Ca++/mg tissue. Na-CaEHDP co-incorporation into silicone rubber matrices markedly prolonged controlled release with the 1:1 Na-CaEHDP mixture demonstrating an extrapolated release duration of approximately 20 years, assuming the total amount of dispersed drug was released. Data from tricuspid valve replacements in sheep demonstrate erratic control calcification (41.3 +/- 14.9 micrograms Ca++/mg tissue), but complete suppression of BHV calcification with Na2EHDP controlled release (5.74 +/- 1.35 micrograms Ca++/mg tissue) after 150 days. PMID:3143390

  3. IPM Motor Drive Method Using a New Inverter Having the Operation of High Power Factor Single-phase Diode Rectifier without Electrolytic Capacitor

    NASA Astrophysics Data System (ADS)

    Haga, Hitoshi; Takahashi, Isao; Ohishi, Kiyoshi

    This paper proposes a new inverter drive system for an interior permanent magnet (IPM) synchronous motor and an inverter control strategy to obtain the unity power factor operation of the single-phase diode rectifier. The motor drive system for home appliances requires improving the input power factor without a reactor, an electrolytic capacitor and a switching device. This paper can achieve to improve the input power factor without a reactor, a current control-switching converter and an electrolytic capacitor. The proposed system consists of only single-phase diode rectifier, small film capacitor (10uF/kW) across the dc-bus, three-phase inverter and IPM motor. Source side energy provides directly to the motor without smoothing the dc-bus voltage. There are many ripple voltages across the dc-bus. A principle of unity-power-factor operation is that the inverter makes the waveform of input current sinusoidal. The unity power factor operation is achieved by dither effect. For IPM motor, the inverter control scheme in this paper is based on direct torque control (DTC). The proposed system is constructed by the input current controller based on DTC. The additional current controller improves its input current waveform. This paper describes that the proposed method achieves the power factor 98.8% by experimental tests.

  4. Improving point registration in dental cephalograms by two-stage rectified point translation transform

    NASA Astrophysics Data System (ADS)

    Tam, W. K.; Lee, H. J.

    2012-02-01

    Cephalometric analysis requires to detect landmarks on cephalograms. Current registration techniques, such as that use scale-invariant feature descriptor (SIFT), perform poorly on cephalograms. We proposed to improve the registration technique for detecting the landmarks on cephalograms. The results were compared with the landmark identified by dental professionals. Twenty digital cephalograms were collected from a dental clinic. Twenty orthodontic landmarks were identified by dental professionals on each image; one of them was used as a template image. We automatically locate the landmarks using a two stages approach, the global registration of the interest points between two images and a local registration of the landmarks. In the first stage, SIFT was employed to establish point-to-point matching pairs. The matched points on the input image were treated as a set of translation transforms from the original template image. The consistence of the translation was controlled by applying a rectification factor defined in this study. In the second stage, we localized the search within the suspected regions around the landmarks derived by the translations in the first stage. Local registrations were rectified and fine-tuned until the translations close to the identified landmarks were obtained. Our method could detect all the landmarks with error distances less than the 2mm standard set forth by previous researcher. By improving the consistence of the translations, the performance of registration between two images was greatly improved. This method can be used as an initial step to locate the regions around the landmarks for improving detection in the future work.

  5. Corticotropin releasing hormone inhibits an inwardly rectifying potassium current in rat corticotropes.

    PubMed Central

    Kuryshev, Y A; Haak, L; Childs, G V; Ritchie, A K

    1997-01-01

    1. The perforated-patch-clamp technique was used to identify an inwardly rectifying K+ current (IK(IR)) in cultured rat anterior pituitary cells highly enriched in corticotropes. IK(IR) was rapidly activating and highly selective for K+. The K+ conductance was approximately proportional to the square root of the extracellular K+ concentration. 2. IK(IR) was blocked in a voltage-dependent manner by external Ba2+ and Cs+, slightly attenuated by 5 mM 4-aminopyridine (15% inhibition) and insensitive to 10 mM tetraethylammonium, 2 mM Ca2+, 1 mM Cd2+ and 50 microM La3+. 3. In physiological saline, 100 microM Ba2+, which inhibits 86% of IK(IR) at the cell resting potential, depolarized cells by 6.1 +/- 0.7 mV from a mean resting potential of -59.6 +/- 0.8 mV. 4. Corticotropin releasing hormone (CRH), which activates adenylyl cyclase and stimulates adrenocorticotropic hormone (ACTH) secretion from corticotropes, inhibited IK(IR) by 25% and depolarized the cells by 10.2 +/- 1.0 mV. Dibutyryl cAMP ((Bu)2cAMP) mimicked these effects. 5. The membrane depolarization evoked by Ba2+ or CRH increased the cell firing frequency. Comparison of cells exhibiting a membrane potential of approximately -50 mV revealed that spike frequency in the presence of CRH (109 +/- 7 spikes (5 min)-1) was greater than in control (60 +/- 5 spikes (5 min)-1) or Ba(2+)-treated (77 +/- 15 spikes (5 min)-1) corticotropes. 6. The data suggest that IK(IR) contributes to maintenance of the resting membrane potential of rat corticotropes. Inhibition of IK(IR) plays a role in, but does not account for all of, the membrane depolarization and enhancement of firing frequency evoked by CRH. PMID:9263909

  6. Design and Modelling of a Silicon Optical MEMS Switch Controlled by Magnetic Field Generated by a Plain Coil

    NASA Astrophysics Data System (ADS)

    Golebiowski, J.; Milcarz, Sz

    2014-04-01

    Optical switches can be made as a silicon cantilever with a magnetic layer. Such a structure is placed in a magnetic field of a planar coil. There is a torque deflecting the silicon beam with NiFe layer depending on a flux density of the magnetic field. The study shows an analysis of ferromagnetic layer parameters, beam's dimensions on optical switch characteristics. Different constructions of the beams were simulated for a range of values of magnetic field strength from 100 to 1000 A/m. An influence of the actuators parameters on characteristics was analysed. The loss of stiffness of the beam caused by specific constructions effected in displacements reaching 85 nm. Comsol Multiphysics 4.3b was used for the simulations.

  7. A Robust Silicon-on-Insulator Static-Random-Access-Memory Architecture by using Advanced Actively Body-Bias Controlled Technology

    NASA Astrophysics Data System (ADS)

    Hirano, Yuuichi; Tsujiuchi, Mikio; Ishikawa, Kozo; Shinohara, Hirofumi; Terada, Takashi; Maki, Yukio; Iwamatsu, Toshiaki; Eikyu, Katsumi; Uchida, Tetsuya; Obayashi, Shigeki; Nii, Koji; Tsukamoto, Yasumasa; Yabuuchi, Makoto; Ipposhi, Takashi; Oda, Hidekazu; Inoue, Yasuo

    2008-04-01

    This paper presents that advanced actively body-bias controlled (Advanced ABC) technology contributes to enhancing operation margins of static random access memory (SRAM). For the first time, significant enhancement of static noise margin (SNM) is successfully realized by using a body bias of load, access, and driver transistors while suppressing threshold-voltage variations. In this technology, well taps control the body potential of the load transistor and word lines also control the body potential of the access and driver transistors. It is demonstrated that the write and read margins of 65-nm-node silicon-on-insulator (SOI) SRAMs are improved by the Advanced ABC technology. Furthermore, it is found that the SNM is enhanced by 27% for 32 nm and 49% for 22 nm node. It is summarized that this technology is one of countermeasures for emerging generations.

  8. Controllability of self-aligned four-terminal planar embedded metal double-gate low-temperature polycrystalline-silicon thin-film transistors on a glass substrate

    NASA Astrophysics Data System (ADS)

    Ohsawa, Hiroki; Sasaki, Shun; Hara, Akito

    2016-03-01

    Self-aligned four-terminal n-channel (n-ch) and p-channel (p-ch) planar embedded metal double-gate polycrystalline-silicon (poly-Si) thin-film transistors (TFTs) were fabricated on a glass substrate at a low temperature of 550 °C. This device includes a metal top gate (TG) and a metal bottom gate (BG), which are used as the drive and control gates or vice versa. The BG was embedded in a glass substrate, and a poly-Si channel with large lateral grains was fabricated by continuous-wave laser lateral crystallization. The threshold voltage modulation factors under various control gate voltages (γ = ΔVth/ΔVCG) were nearly equal to the theoretical predictions in both the n- and p-ch TFTs. By exploiting this high controllability, an enhancement depletion (ED) inverter was fabricated, and successful operation at 2.0 V was confirmed.

  9. CMOS-Compatible Room-Temperature Rectifier Toward Terahertz Radiation Detection

    NASA Astrophysics Data System (ADS)

    Varlamava, Volha; De Amicis, Giovanni; Del Monte, Andrea; Perticaroli, Stefano; Rao, Rosario; Palma, Fabrizio

    2016-03-01

    In this paper, we present a new rectifying device, compatible with the technology of CMOS image sensors, suitable for implementing a direct-conversion detector operating at room temperature for operation at up to terahertz frequencies. The rectifying device can be obtained by introducing some simple modifications of the charge-storage well in conventional CMOS integrated circuits, making the proposed solution easy to integrate with the existing imaging systems. The rectifying device is combined with the different elements of the detector, composed of a 3D high-performance antenna and a charge-storage well. In particular, its position just below the edge of the 3D antenna takes maximum advantage of the high electric field concentrated by the antenna itself. In addition, the proposed structure ensures the integrity of the charge-storage well of the detector. In the structure, it is not necessary to use very scaled and costly technological nodes, since the CMOS transistor only provides the necessary integrated readout electronics. On-wafer measurements of RF characteristics of the designed junction are reported and discussed. The overall performances of the entire detector in terms of noise equivalent power (NEP) are evaluated by combining low-frequency measurements of the rectifier with numerical simulations of the 3D antenna and the semiconductor structure at 1 THz, allowing prediction of the achievable NEP.

  10. Commutation Characteristics of Snubber Circuits of PWM Rectifier for Converter without DC Link Components

    NASA Astrophysics Data System (ADS)

    Iimori, Kenichi; Shinohara, Katsuji; Yamamoto, Kichiro; Ikeda, Motonobu

    This paper describes commutation characteristics of snubber circuits of the PWM rectifier for the converter without DC link components. The DC link part of this converter has no smoothing circuit such as electrolytic capacitors and reactors. Therefore, one of the switches in the upper arms and one of the switches in the lower arms of the rectifier must be on-state in order to assure the path of the load current. The rectifier section of this converter requires the LC filter to improve the AC source current waveforms. Consequently, dead time should be applied to each of the commutation switches to prevent short circuit through the filter capacitors. The currents of the load are kept through the snubber circuit during the dead-time period. In this paper, we discuss an analytical method of the converter with the snubber circuit of the rectifier, and the experimental results are used to verify the analytical method. Next, the optimal snubber parameters are determined by calculation for 0.75kW induction motor driven by this converter. Finally, suitable snubber circuits for bidirectional switches are discussed.

  11. 27 CFR 1.21 - Domestic producers, rectifiers, blenders, and warehousemen.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... spirits or wine, or bottling, or warehousing and bottling, distilled spirits; or (b) While so engaged... FEDERAL ALCOHOL ADMINISTRATION ACT, NONINDUSTRIAL USE OF DISTILLED SPIRITS AND WINE, BULK SALES AND BOTTLING OF DISTILLED SPIRITS Basic Permits When Required § 1.21 Domestic producers, rectifiers,...

  12. Fluorescence of silicon nanoparticles suspended in water: reactive co-deposition for the control of surface properties of clusters

    NASA Astrophysics Data System (ADS)

    von Haeften, K.; Akraiam, A.; Torricelli, G.; Brewer, A.

    2010-10-01

    Fluorescent silicon nanoparticles have been produced in a two-step process in ultra high vacuum. First, silicon clusters were produced in the gas phase in a molecular beam. At the end of the cluster beam machine the cluster were co-deposited with water onto a cold target. Melting of the ice yields a suspension that fluoresces at 420 nm when excited with ultraviolet light. The fluorescence intensity remains constant over a period of more than a year. Photo-absorption and photo-luminescence spectra provide evidence of a Si/SiO2 core-shell structure having a silicon core size of at least 1.4 nm in diameter and oxygen deficient O-Si-O defects as the origin of the deep-blue fluorescence. Furthermore, the fluorescent suspension was deposited on freshly cleaved highly oriented pyrolytic graphite (HOPG). AFM images recorded in UHV showed networks of agglomerated clusters, their smallest units having a diameter of typically 0.7 nm.

  13. Simple evaporation controller for thin-film deposition from a resistively heated boat

    NASA Technical Reports Server (NTRS)

    Scofield, John H.; Bajuk, Lou; Mohler, William

    1990-01-01

    A simple, inexpensive circuit is described for switching the current through a resistively heated evaporation boat during thin-film deposition. The circuit uses a silicon-controlled rectifier (SCR) to switch the 0-15-A current in the primary of a 2-kV A step-down transformer that supplies the 0-200-A current to an evaporation boat. The circuit is controlled by a 0-10 V-dc signal similar to that furnished by an Inficon XTC deposition-rate controller. This circuit may be assembled from a handful of parts for a cost of about $400, nearly one-tenth the cost of similar commercial units. Minimum construction is required, since the circuit is built around an off-the-shelf, self-contained SCR unit.

  14. Silicon nitride/silicon carbide composite powders

    DOEpatents

    Dunmead, Stephen D.; Weimer, Alan W.; Carroll, Daniel F.; Eisman, Glenn A.; Cochran, Gene A.; Susnitzky, David W.; Beaman, Donald R.; Nilsen, Kevin J.

    1996-06-11

    Prepare silicon nitride-silicon carbide composite powders by carbothermal reduction of crystalline silica powder, carbon powder and, optionally, crystalline silicon nitride powder. The crystalline silicon carbide portion of the composite powders has a mean number diameter less than about 700 nanometers and contains nitrogen. The composite powders may be used to prepare sintered ceramic bodies and self-reinforced silicon nitride ceramic bodies.

  15. An RF Energy Harvester System Using UHF Micropower CMOS Rectifier Based on a Diode Connected CMOS Transistor

    PubMed Central

    Shokrani, Mohammad Reza; Hamidon, Mohd Nizar B.; Rokhani, Fakhrul Zaman; Shafie, Suhaidi Bin

    2014-01-01

    This paper presents a new type diode connected MOS transistor to improve CMOS conventional rectifier's performance in RF energy harvester systems for wireless sensor networks in which the circuits are designed in 0.18 μm TSMC CMOS technology. The proposed diode connected MOS transistor uses a new bulk connection which leads to reduction in the threshold voltage and leakage current; therefore, it contributes to increment of the rectifier's output voltage, output current, and efficiency when it is well important in the conventional CMOS rectifiers. The design technique for the rectifiers is explained and a matching network has been proposed to increase the sensitivity of the proposed rectifier. Five-stage rectifier with a matching network is proposed based on the optimization. The simulation results shows 18.2% improvement in the efficiency of the rectifier circuit and increase in sensitivity of RF energy harvester circuit. All circuits are designed in 0.18 μm TSMC CMOS technology. PMID:24782680

  16. An RF energy harvester system using UHF micropower CMOS rectifier based on a diode connected CMOS transistor.

    PubMed

    Shokrani, Mohammad Reza; Khoddam, Mojtaba; Hamidon, Mohd Nizar B; Kamsani, Noor Ain; Rokhani, Fakhrul Zaman; Shafie, Suhaidi Bin

    2014-01-01

    This paper presents a new type diode connected MOS transistor to improve CMOS conventional rectifier's performance in RF energy harvester systems for wireless sensor networks in which the circuits are designed in 0.18  μm TSMC CMOS technology. The proposed diode connected MOS transistor uses a new bulk connection which leads to reduction in the threshold voltage and leakage current; therefore, it contributes to increment of the rectifier's output voltage, output current, and efficiency when it is well important in the conventional CMOS rectifiers. The design technique for the rectifiers is explained and a matching network has been proposed to increase the sensitivity of the proposed rectifier. Five-stage rectifier with a matching network is proposed based on the optimization. The simulation results shows 18.2% improvement in the efficiency of the rectifier circuit and increase in sensitivity of RF energy harvester circuit. All circuits are designed in 0.18 μm TSMC CMOS technology. PMID:24782680

  17. Lithographic wavelength control of an external cavity laser with a silicon photonic crystal cavity-based resonant reflector.

    PubMed

    Liles, Alexandros A; Debnath, Kapil; O'Faolain, Liam

    2016-03-01

    We report the experimental demonstration of a new design for external cavity hybrid lasers consisting of a III-V semiconductor optical amplifier (SOA) with fiber reflector and a photonic crystal (PhC)-based resonant reflector on SOI. The silicon reflector is composed of an SU8 polymer bus waveguide vertically coupled to a PhC cavity and provides a wavelength-selective optical feedback to the laser cavity. This device exhibits milliwatt-level output power and side-mode suppression ratios of more than 25 dB. PMID:26974073

  18. Increase of delayed rectifier potassium currents in large aspiny neurons in the neostriatum following transient forebrain ischemia.

    PubMed

    Deng, P; Pang, Z-P; Zhang, Y; Xu, Z C

    2005-01-01

    Large aspiny (LA) neurons in the neostriatum are resistant to cerebral ischemia whereas spiny neurons are highly vulnerable to the same insult. Excitotoxicity has been implicated as the major cause of neuronal damage after ischemia. Voltage-dependent potassium currents play important roles in controlling neuronal excitability and therefore influence the ischemic outcome. To reveal the ionic mechanisms underlying the ischemia-resistance, the delayed rectifier potassium currents (Ik) in LA neurons were studied before and at different intervals after transient forebrain ischemia using brain slices and acute dissociation preparations. The current density of Ik increased significantly 24 h after ischemia and returned to control levels 72 h following reperfusion. Among currents contributing to Ik, the margatoxin-sensitive currents increased 24 h after ischemia while the KCNQ/M current remained unchanged after ischemia. Activation of protein kinase A (PKA) down-regulated Ik in both control and ischemic LA neurons, whereas inhibition of PKA only up-regulated Ik and margatoxin-sensitive currents 72 h after ischemia, indicating an active PKA regulation on Ik at this time. Protein tyrosine kinases had a tonic inhibition on Ik to a similar extent before and after ischemia. Compared with that of control neurons, the spike width was significantly shortened 24 h after ischemia due to facilitated repolarization, which could be reversed by blocking margatoxin-sensitive currents. The increase of Ik in LA neurons might be one of the protective mechanisms against ischemic insult. PMID:15680698

  19. Silicone-Acyclovir Controlled Release Devices Suppress Primary Herpes Simplex Virus-2 and Varicella Zoster Virus Infections In Vitro

    PubMed Central

    Berkower, Carol L.; Johnson, Nicole M.; Longdo, Stephen B.; McGusty-Robinson, Shenika O.; Semenkow, Samantha L.; Margulies, Barry J.

    2013-01-01

    Following initial infection, herpesviruses retreat into a permanent latent state with periodic reactivation resulting in an enhanced likelihood of transmission and clinical disease. The nucleoside analogue acyclovir reduces clinical symptoms of the three human alpha herpesviruses, HSV-1, HSV-2, and VZV. Long-term administration of acyclovir (ACV) can reduce the frequency and severity of reactivation, but its low bioavailability and short half-life require a daily drug regimen. Our lab is working to develop a subcutaneous delivery system to provide long-lasting, sustained release of ACV. Previously, we demonstrated that an implantable silicone (MED-4050) device, impregnated with ACV protected against HSV-1 both in vitro and in vivo. Here, we extend our in vitro observations to include protection against both HSV-2 and VZV. We also demonstrate protection against HSV-2 in vitro using MED-4750, a silicone polymer designed for long-term use in humans. When release of ACV from MED-4750 is quantitated on a daily basis, an initial burst of 5 days is observed, followed by a long period of slow release with near-zero-order kinetics, with an average daily release of 1.3923 ± 0.5908 μg ACV over days 20–60. Development of a slow-release implant has the potential to significantly impact the treatment of human alpha herpesvirus infections. PMID:23983683

  20. Controlling the reproducibility of Coulomb blockade phenomena for gold nanoparticles on an organic monolayer/silicon system.

    PubMed

    Caillard, L; Sattayaporn, S; Lamic-Humblot, A-F; Casale, S; Campbell, P; Chabal, Y J; Pluchery, O

    2015-02-13

    Two types of highly ordered organic layers were prepared on silicon modified with an amine termination for binding gold nanoparticles (AuNPs). These two grafted organic monolayers (GOMs), consisting of alkyl chains with seven or 11 carbon atoms, were grafted on oxide-free Si(111) surfaces as tunnel barriers between the silicon electrode and the AuNPs. Three kinds of colloidal AuNPs were prepared by reducing HAuCl4 with three different reactants: citrate (Turkevich synthesis, diameter ∼16 nm), ascorbic acid (diameter ∼9 nm), or NaBH4 (Natan synthesis, diameter ∼7 nm). Scanning tunnel spectroscopy (STS) was performed in a UHV STM at 40 K, and Coulomb blockade behaviour was observed. The reproducibility of the Coulomb behavior was analysed as a function of several chemical and physical parameters: size, crystallinity of the AuNPs, influence of surrounding surfactant molecules, and quality of the GOM/Si interface (degree of oxidation after the full processing). Samples were characterized with scanning tunneling microscope, STS, atomic force microscope, Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy (XPS), and high resolution transmission electronic microscope. We show that the reproducibility in observing Coulomb behavior can be as high as ∼80% with the Natan synthesis of AuNPs and GOMs with short alkyl chains. PMID:25611611

  1. Controlling the reproducibility of Coulomb blockade phenomena for gold nanoparticles on an organic monolayer/silicon system

    NASA Astrophysics Data System (ADS)

    Caillard, L.; Sattayaporn, S.; Lamic-Humblot, A.-F.; Casale, S.; Campbell, P.; Chabal, Y. J.; Pluchery, O.

    2015-02-01

    Two types of highly ordered organic layers were prepared on silicon modified with an amine termination for binding gold nanoparticles (AuNPs). These two grafted organic monolayers (GOMs), consisting of alkyl chains with seven or 11 carbon atoms, were grafted on oxide-free Si(111) surfaces as tunnel barriers between the silicon electrode and the AuNPs. Three kinds of colloidal AuNPs were prepared by reducing HAuCl4 with three different reactants: citrate (Turkevich synthesis, diameter ˜16 nm), ascorbic acid (diameter ˜9 nm), or NaBH4 (Natan synthesis, diameter ˜7 nm). Scanning tunnel spectroscopy (STS) was performed in a UHV STM at 40 K, and Coulomb blockade behaviour was observed. The reproducibility of the Coulomb behavior was analysed as a function of several chemical and physical parameters: size, crystallinity of the AuNPs, influence of surrounding surfactant molecules, and quality of the GOM/Si interface (degree of oxidation after the full processing). Samples were characterized with scanning tunneling microscope, STS, atomic force microscope, Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy (XPS), and high resolution transmission electronic microscope. We show that the reproducibility in observing Coulomb behavior can be as high as ˜80% with the Natan synthesis of AuNPs and GOMs with short alkyl chains.

  2. Low-temperature linear thermal rectifiers based on Coriolis forces

    NASA Astrophysics Data System (ADS)

    Suwunnarat, Suwun; Li, Huanan; Fleischmann, Ragnar; Kottos, Tsampikos

    2016-04-01

    We demonstrate that a three-terminal harmonic symmetric chain in the presence of a Coriolis force, produced by a rotating platform that is used to place the chain, can produce thermal rectification. The direction of heat flow is reconfigurable and controlled by the angular velocity Ω of the rotating platform. A simple three-terminal triangular lattice is used to demonstrate the proposed principle.

  3. Intermediate Bandgap Solar Cells From Nanostructured Silicon

    SciTech Connect

    Black, Marcie

    2014-10-30

    This project aimed to demonstrate increased electronic coupling in silicon nanostructures relative to bulk silicon for the purpose of making high efficiency intermediate bandgap solar cells using silicon. To this end, we formed nanowires with controlled crystallographic orientation, small diameter, <111> sidewall faceting, and passivated surfaces to modify the electronic band structure in silicon by breaking down the symmetry of the crystal lattice. We grew and tested these silicon nanowires with <110>-growth axes, which is an orientation that should produce the coupling enhancement.

  4. Hydrogen-silicon carbide interactions

    NASA Technical Reports Server (NTRS)

    Eckel, Andrew J.; Misra, Ajay K.; Humphrey, Donald L.; Jacobson, Nathan S.

    1990-01-01

    A study of the thermochemistry and kinetics of hydrogen environmental attack of silicon carbide was conducted for temperatures in the range from 1100 C to 1400 C. Thermodynamics maps based on the parameters of pressure and oxygen/moisture content were constructed. With increasing moisture levels, four distinct regions of attack were identified. Each region is defined by the thermodynamically stable solid phases. The theoretically stable solid phases of region 1 are silicon carbide and silicon. Experimental evidence is provided to support this thermodynamic prediction. Silicone carbide is the single stable solid phase in region 2. Active attack of the silicon carbide in this region occurs by the formation of gases of SiO, CO, CH4, SiH4 and SiH. Analyses of the kinetics of reaction for region 2 at 1300 C show the attack of the silicon carbide to be controlled by gas phase diffusion of H2O to the sample. Silicon carbide and silica are the stable phases common to regions 3 and 4. These two regions are characterized by the passive oxidation of silicon carbide and formation of a protective silica layer.

  5. Hydrogen-silicon carbide interactions

    NASA Technical Reports Server (NTRS)

    Eckel, Andrew J.; Jacobson, Nathan S.; Misra, Ajay K.; Humphrey, Donald L.

    1989-01-01

    A study of the thermochemistry and kinetics of hydrogen environmental attack of silicon carbide was conducted for temperatures in the range from 1100 C to 1400 C. Thermodynamic maps based on the parameters of pressure and oxygen/moisture content were constructed. With increasing moisture levels, four distinct regions of attack were identified. Each region is defined by the thermodynamically stable solid phases. The theoretically stable solid phases of Region 1 are silicon carbide and silicon. Experimental evidence is provided to support this thermodynamic prediction. Silicon carbide is the single stable solid phase in Region 2. Active attack of the silicon carbide in this region occurs by the formation of gases of SiO, CO, CH4, SiH4, and SiH. Analysis of the kinetics of reaction for Region 2 at 1300 C show the attack of the silicon carbide to be controlled by gas phase diffusion of H2O to the sample. Silicon carbide and silica are the stable phases common to Regions 3 and 4. These two regions are characterized by the passive oxidation of silicon carbide and formation of a protective silica layer.

  6. Characterization of deep electron traps in 4H-SiC Junction Barrier Schottky rectifiers

    NASA Astrophysics Data System (ADS)

    Gelczuk, Ł.; Dąbrowska-Szata, M.; Sochacki, M.; Szmidt, J.

    2014-04-01

    Conventional deep level transient spectroscopy (DLTS) technique was used to study deep electron traps in 4H-SiC Junction Barrier Schottky (JBS) rectifiers. 4H-SiC epitaxial layers, doped with nitrogen and grown on standard n+-4H-SiC substrates were exposed to low-dose aluminum ion implantation process under the Schottky contact in order to form both JBS grid and junction termination extension (JTE), and assure good rectifying properties of the diodes. Several deep electron traps were revealed and attributed to impurities or intrinsic defects in 4H-SiC epitaxial layers, on the basis of comparison of their electrical parameters (i.e. activation energies, apparent capture cross sections and concentrations) with previously published results.

  7. Aviram-Ratner rectifying mechanism for DNA base-pair sequencing through graphene nanogaps

    PubMed Central

    Agapito, Luis A.; Gayles, Jacob; Wolowiec, Christian; Kioussis, Nicholas

    2012-01-01

    We demonstrate that biological molecules such as Watson-Crick DNA base pairs can behave as biological Aviram-Ratner electrical rectifiers because of the spatial separation and weak hydrogen bonding between the nucleobases. We have performed a parallel computational implementation of the ab-initio non-equilibrium Green’s function (NEGF) theory to determine the electrical response of graphene—base-pair—graphene junctions. The results show an asymmetric (rectifying) current-voltage response for the Cytosine-Guanine base pair adsorbed on a graphene nanogap. In sharp contrast we find a symmetric response for the Thymine-Adenine case. We propose applying the asymmetry of the current-voltage response as a sensing criterion to the technological challenge of rapid DNA sequencing via graphene nanogaps. PMID:22418779

  8. A High Power Density Single-Phase PWM Rectifier With Active Ripple Energy Storage

    SciTech Connect

    Wang, Ruxi; Wang, Fei; Boroyevich, Dushan; Burgos, Rolando; Lai, Rixin; Ning, Puqi; Rajashekara, Kaushik

    2011-01-01

    It is well known that single-phase pulse width modulation rectifiers have second-order harmonic currents and corresponding ripple voltages on the dc bus. The low-frequency harmonic current is normally filtered using a bulk capacitor in the bus, which results in low power density. However, pursuing high power density in converter design is a very important goal in the aerospace applications. This paper studies methods for reducing the energy storage capacitor for single-phase rectifiers. The minimum ripple energy storage requirement is derived independently of a specific topology. Based on theminimum ripple energy requirement, the feasibility of the active capacitor s reduction schemes is verified. Then, we propose a bidirectional buck boost converter as the ripple energy storage circuit, which can effectively reduce the energy storage capacitance. The analysis and design are validated by simulation and experimental results.

  9. Hydrogen Sulfide Regulates Inward-Rectifying K+ Channels in Conjunction with Stomatal Closure1[OPEN

    PubMed Central

    Papanatsiou, Maria; Scuffi, Denisse; Blatt, Michael R.; García-Mata, Carlos

    2015-01-01

    Hydrogen sulfide (H2S) is the third biological gasotransmitter, and in animals, it affects many physiological processes by modulating ion channels. H2S has been reported to protect plants from oxidative stress in diverse physiological responses. H2S closes stomata, but the underlying mechanism remains elusive. Here, we report the selective inactivation of current carried by inward-rectifying K+ channels of tobacco (Nicotiana tabacum) guard cells and show its close parallel with stomatal closure evoked by submicromolar concentrations of H2S. Experiments to scavenge H2S suggested an effect that is separable from that of abscisic acid, which is associated with water stress. Thus, H2S seems to define a unique and unresolved signaling pathway that selectively targets inward-rectifying K+ channels. PMID:25770153

  10. Hydrogen sulfide regulates inward-rectifying K+ channels in conjunction with stomatal closure.

    PubMed

    Papanatsiou, Maria; Scuffi, Denisse; Blatt, Michael R; García-Mata, Carlos

    2015-05-01

    Hydrogen sulfide (H2S) is the third biological gasotransmitter, and in animals, it affects many physiological processes by modulating ion channels. H2S has been reported to protect plants from oxidative stress in diverse physiological responses. H2S closes stomata, but the underlying mechanism remains elusive. Here, we report the selective inactivation of current carried by inward-rectifying K(+) channels of tobacco (Nicotiana tabacum) guard cells and show its close parallel with stomatal closure evoked by submicromolar concentrations of H2S. Experiments to scavenge H2S suggested an effect that is separable from that of abscisic acid, which is associated with water stress. Thus, H2S seems to define a unique and unresolved signaling pathway that selectively targets inward-rectifying K(+) channels. PMID:25770153

  11. Analysis of UHF RFID CMOS rectifier structures and input impedance characteristics

    NASA Astrophysics Data System (ADS)

    Jamali, Behnam; Ranasinghe, Damith C.; Cole, Peter H.

    2005-12-01

    Passive radio frequency identification (RFID) systems deployment efforts are revolutionizing supply chain logistics by providing unprecedented supply chain visibility. The widely used bandwidth of operation in modern systems is the UHF ISM (industrial, scientific, and medical) band. The performance of UHF RFID systems are largely reliant on low power CMOS circuits, efficient power rectification and the ability of RFID label antennas to match to the input impedance of the RFID label IC. This paper examines a new rectifying structure and considers it for its merits in RFID applications while analysing contribution of the rectifying structure to the input impedance of RFID chips as this is an important consideration in impedance matching to an external antenna.

  12. Inwardly rectifying currents in hair cells and supporting cells in the goldfish sacculus.

    PubMed Central

    Sugihara, I; Furukawa, T

    1996-01-01

    1. Inwardly rectifying ionic currents were studied using patch-clamp recording methods in oscillatory-type and spike-type hair cells and supporting cells dissociated from the goldfish sacculus. These cells had different types of inwardly rectifying currents. The biophysical properties of these currents were investigated. 2. A unique potassium current (Isc) was the sole ionic current recognized in supporting cells. Isc was active throughout the membrane potential range between +30 and -170 mV, but showed weak inward rectification and no inactivation. 3. In spike-type hair cells, inwardly rectifying current (Ik1) was selectively permeable to K+ (K+:Na+ permeability ratio, 1:0.0021). Ik1 could underlie the high negative resting potential of these hair cells because it is partially active at this potential. The strong inward rectification of Ik1 contributed to the low negative plateau potential seen in spike-type hair cells. 4. In oscillatory-type hair cells, hyperpolarization-activated potassium-sodium current (Ih), which had properties similar to that in photoreceptor and other neurons, was present instead of inwardly rectifying K+ current. 5. In the cell-attached and inside-out modes with 125 microM external K+ ([K+]o), IK1 channel had a unitary conductance of 27 pS and showed inactivation with increasing hyperpolarization. Putative Ih and Iso single channels had unitary conductances of 7 and 61 pS, respectively, in the cell-attached mode with 125 microM Ko+. Images Figure 1 PMID:8887774

  13. Vacuolar malate uptake is mediated by an anion-selective inward rectifier.

    PubMed

    Hafke, Jens B; Hafke, Yuliya; Smith, J Andrew C; Lüttge, Ulrich; Thiel, Gerhard

    2003-07-01

    Electrophysiological studies using the patch-clamp technique were performed on isolated vacuoles from leaf mesophyll cells of the crassulacean acid metabolism (CAM) plant Kalanchoë daigremontiana to characterize the malate transport system responsible for nocturnal malic acid accumulation. In the presence of malate on both sides of the membrane, the current-voltage relations of the tonoplast were dominated by a strongly inward-rectifying anion-selective channel that was active at cytoplasmic-side negative voltages. Rectification of the macroscopic conductance was reflected in the voltage-dependent gating of a 3-pS malate-selective ion channel, which showed a half-maximal open probability at -43 mV. Also, the time-averaged unitary currents following a step to a negative voltage corresponded to the time-dependent kinetics of the macroscopic currents, suggesting that the activity of this channel underlies the anion-selective inward rectifier. The inward rectifier showed saturation kinetics with respect to malate (apparent Km of 2.5 mm malate2- activity), a selectivity sequence of fumarate2- > malate2- > Cl- > maleate2- approximately citrate3-, and greater activity at higher pH values (with an apparent pK of 7.1 and maximum activity at around pH 8.0). All these properties were in close agreement with the characteristics of malate transport observed in isolated tonoplast vesicles. Further, 100 microM niflumate reversibly blocked the activity of the 3-pS channel and inhibited both macroscopic currents and malate transport into tonoplast vesicles to the same extent. The macroscopic current densities recorded at physiological voltages and the estimated channel density of 0.2 microm-2 are sufficient to account for the observed rates of nocturnal malic acid accumulation in this CAM plant, suggesting that the 3-pS, inward-rectifying, anion-selective channel represents the principal pathway for malate influx into the vacuole. PMID:12834407

  14. Use of neural network method to characterize pressure controlled charge density of silicon nitride films deposited by PECVD

    NASA Astrophysics Data System (ADS)

    Kim, Byungwhan; Kim, Su Yeon

    2008-05-01

    A prediction model of charge density of silicon nitride (SiN) films was constructed by using a generalized regression neural network (GRNN). The SiN film was deposited by a plasma enhanced chemical vapor deposition (PECVD) system and the deposition process was characterized by means of a statistical experiment. The prediction performance of GRNN was optimized by using a genetic algorithm (GA) and yielded an improved prediction of about 63% over statistical regression model. The optimized model was utilized to qualitatively investigate the effect of process parameters under various pressures. A refractive index model was effectively utilized to validate charge density variations. For the variations in process parameters, charge density was strongly dependent on [N-H]. Effects of NH 3 or SiH 4 flow rates were significant only under high collision rate. Effect of pressure-induced collision rate was noticeable only at higher NH 3 flow rate or lower SiH 4 flow rate.

  15. TOPICAL REVIEW: Black silicon method X: a review on high speed and selective plasma etching of silicon with profile control: an in-depth comparison between Bosch and cryostat DRIE processes as a roadmap to next generation equipment

    NASA Astrophysics Data System (ADS)

    Jansen, H V; de Boer, M J; Unnikrishnan, S; Louwerse, M C; Elwenspoek, M C

    2009-03-01

    An intensive study has been performed to understand and tune deep reactive ion etch (DRIE) processes for optimum results with respect to the silicon etch rate, etch profile and mask etch selectivity (in order of priority) using state-of-the-art dual power source DRIE equipment. The research compares pulsed-mode DRIE processes (e.g. Bosch technique) and mixed-mode DRIE processes (e.g. cryostat technique). In both techniques, an inhibitor is added to fluorine-based plasma to achieve directional etching, which is formed out of an oxide-forming (O2) or a fluorocarbon (FC) gas (C4F8 or CHF3). The inhibitor can be introduced together with the etch gas, which is named a mixed-mode DRIE process, or the inhibitor can be added in a time-multiplexed manner, which will be termed a pulsed-mode DRIE process. Next, the most convenient mode of operation found in this study is highlighted including some remarks to ensure proper etching (i.e. step synchronization in pulsed-mode operation and heat control of the wafer). First of all, for the fabrication of directional profiles, pulsed-mode DRIE is far easier to handle, is more robust with respect to the pattern layout and has the potential of achieving much higher mask etch selectivity, whereas in a mixed-mode the etch rate is higher and sidewall scalloping is prohibited. It is found that both pulsed-mode CHF3 and C4F8 are perfectly suited to perform high speed directional etching, although they have the drawback of leaving the FC residue at the sidewalls of etched structures. They show an identical result when the flow of CHF3 is roughly 30 times the flow of C4F8, and the amount of gas needed for a comparable result decreases rapidly while lowering the temperature from room down to cryogenic (and increasing the etch rate). Moreover, lowering the temperature lowers the mask erosion rate substantially (and so the mask selectivity improves). The pulsed-mode O2 is FC-free but shows only tolerable anisotropic results at -120 °C. The downside of needing liquid nitrogen to perform cryogenic etching can be improved by using a new approach in which both the pulsed and mixed modes are combined into the so-called puffed mode. Alternatively, the use of tetra-ethyl-ortho-silicate (TEOS) as a silicon oxide precursor is proposed to enable sufficient inhibiting strength and improved profile control up to room temperature. Pulsed-mode processing, the second important aspect, is commonly performed in a cycle using two separate steps: etch and deposition. Sometimes, a three-step cycle is adopted using a separate step to clean the bottom of etching features. This study highlights an issue, known by the authors but not discussed before in the literature: the need for proper synchronization between gas and bias pulses to explore the benefit of three steps. The transport of gas from the mass flow controller towards the wafer takes time, whereas the application of bias to the wafer is relatively instantaneous. This delay causes a problem with respect to synchronization when decreasing the step time towards a value close to the gas residence time. It is proposed to upgrade the software with a delay time module for the bias pulses to be in pace with the gas pulses. If properly designed, the delay module makes it possible to switch on the bias exactly during the arrival of the gas for the bottom removal step and so it will minimize the ionic impact because now etch and deposition steps can be performed virtually without bias. This will increase the mask etch selectivity and lower the heat impact significantly. Moreover, the extra bottom removal step can be performed at (also synchronized!) low pressure and therefore opens a window for improved aspect ratios. The temperature control of the wafer, a third aspect of this study, at a higher etch rate and longer etch time, needs critical attention, because it drastically limits the DRIE performance. It is stressed that the exothermic reaction (high silicon loading) and ionic impact (due to metallic masks and/or exposed silicon) are the main sources of heat that might raise the wafer temperature uncontrollably, and they show the weakness of the helium backside technique using mechanical clamping. Electrostatic clamping, an alternative technique, should minimize this problem because it is less susceptible to heat transfer when its thermal resistance and the gap of the helium backside cavity are minimized; however, it is not a subject of the current study. Because oxygen-growth-based etch processes (due to their ultra thin inhibiting layer) rely more heavily on a constant wafer temperature than fluorocarbon-based processes, oxygen etches are more affected by temperature fluctuations and drifts during the etching. The fourth outcome of this review is a phenomenological model, which explains and predicts many features with respect to loading, flow and pressure behaviour in DRIE equipment including a diffusion zone. The model is a reshape of the flow model constructed by Mogab, who studied the loading effect in plasma etching. Despite the downside of needing a cryostat, it is shown that—when selecting proper conditions—a cryogenic two-step pulsed mode can be used as a successful technique to achieve high speed and selective plasma etching with an etch rate around 25 µm min-1 (<1% silicon load) with nearly vertical walls and resist etch selectivity beyond 1000. With the model in hand, it can be predicted that the etch rate can be doubled (50 µm min-1 at an efficiency of 33% for the fluorine generation from the SF6 feed gas) by minimizing the time the free radicals need to pass the diffusion zone. It is anticipated that this residence time can be reduced sufficiently by a proper inductive coupled plasma (ICP) source design (e.g. plasma shower head and concentrator). In order to preserve the correct profile at such high etch rates, the pressure during the bottom removal step should be minimized and, therefore, the synchronized three-step pulsed mode is believed to be essential to reach such high etch rates with sufficient profile control. In order to improve the etch rate even further, the ICP power should be enhanced; the upgrading of the turbopump seems not yet to be relevant because the throttle valve in the current study had to be used to restrict the turbo efficiency. In order to have a versatile list of state-of-the-art references, it has been decided to arrange it in subjects. The categories concerning plasma physics and applications are, for example, books, reviews, general topics, fluorine-based plasmas, plasma mixtures with oxygen at room temperature, wafer heat transfer and high aspect ratio trench (HART) etching. For readers 'new' to this field, it is advisable to study at least one (but rather more than one) of the reviews concerning plasma as found in the first 30 references. In many cases, a paper can be classified into more than one category. In such cases, the paper is directed to the subject most suited for the discussion of the current review. For example, many papers on heat transfer also treat cryogenic conditions and all the references dealing with highly anisotropic behaviour have been directed to the category HARTs. Additional pointers could get around this problem but have the disadvantage of creating a kind of written spaghetti. I hope that the adapted organization structure will help to have a quick look at and understanding of current developments in high aspect ratio plasma etching. Enjoy reading... Henri Jansen 18 June 2008

  16. Rectifying Properties of Oligo(Phenylene Ethynylene) Heterometallic Molecular Junctions: Molecular Length and Side Group Effects

    PubMed Central

    Fu, Xiao-Xiao; Zhang, Rui-Qin; Zhang, Guang-Ping; Li, Zong-Liang

    2014-01-01

    The rectifying properties of α,ω-dithiol terminated oligo(phenylene ethynylene) molecules sandwiched between heterometallic electrodes, including the molecular length and side group effects, are theoretically investigated using the fully self-consistent nonequilibrium Green's function method combined with density functional theory. The results show nonlinear variation with changes in molecule length: when the molecule becomes longer, the current decreases at first and then increases while the rectification shifts in the opposite direction. This stems from the change in molecular eigenstates and the coupling between the molecule and electrodes caused by different molecular lengths. The rectifying behavior of heterometallic molecular junctions can be attributed to the asymmetric molecule-electrode contacts, which lead to asymmetric electronic tunneling spectra, molecular eigenvalues, molecular orbitals, and potential drop at reversed equivalent bias voltages. Our results provide a fundamental understanding of the rectification of heterometallic molecular junction, and a prediction of rectifiers with different rectification properties from those in the experiment, using electrodes with reduced sizes. PMID:25220880

  17. Microfluidic rectifier based on poly(dimethylsiloxane) membrane and its application to a micropump.

    PubMed

    Wang, Yao-Nan; Tsai, Chien-Hsiung; Fu, Lung-Ming; Lin Liou, Lung-Kai

    2013-01-01

    A microfluidic rectifier incorporating an obstructed microchannel and a PDMS membrane is proposed. During forward flow, the membrane deflects in the upward direction; thereby allowing the fluid to pass over the obstacle. Conversely, during reverse flow, the membrane seals against the obstacle, thereby closing the channel and preventing flow. It is shown that the proposed device can operate over a wide pressure range by increasing or decreasing the membrane thickness as required. A microfluidic pump is realized by integrating the rectifier with a simple stepper motor mechanism. The experimental results show that the pump can achieve a vertical left height of more than 2 m. Moreover, it is shown that a maximum flow rate of 6.3 ml/min can be obtained given a membrane thickness of 200 μm and a motor velocity of 80 rpm. In other words, the proposed microfluidic rectifier not only provides an effective means of preventing reverse flow but also permits the realization of a highly efficient microfluidic pump. PMID:24404051

  18. Multi-Service Highly Sensitive Rectifier for Enhanced RF Energy Scavenging

    PubMed Central

    Shariati, Negin; Rowe, Wayne S. T.; Scott, James R.; Ghorbani, Kamran

    2015-01-01

    Due to the growing implications of energy costs and carbon footprints, the need to adopt inexpensive, green energy harvesting strategies are of paramount importance for the long-term conservation of the environment and the global economy. To address this, the feasibility of harvesting low power density ambient RF energy simultaneously from multiple sources is examined. A high efficiency multi-resonant rectifier is proposed, which operates at two frequency bands (478–496 and 852–869 MHz) and exhibits favorable impedance matching over a broad input power range (−40 to −10 dBm). Simulation and experimental results of input reflection coefficient and rectified output power are in excellent agreement, demonstrating the usefulness of this innovative low-power rectification technique. Measurement results indicate an effective efficiency of 54.3%, and an output DC voltage of 772.8 mV is achieved for a multi-tone input power of −10 dBm. Furthermore, the measured output DC power from harvesting RF energy from multiple services concurrently exhibits a 3.14 and 7.24 fold increase over single frequency rectification at 490 and 860 MHz respectively. Therefore, the proposed multi-service highly sensitive rectifier is a promising technique for providing a sustainable energy source for low power applications in urban environments. PMID:25951137

  19. Increased inwardly rectifying potassium currents in HEK-293 cells expressing murine transient receptor potential 4.

    PubMed Central

    Zhang, Z; Tang, Y; Zhu, M X

    2001-01-01

    Drosophila transient receptor potential (Trp) and its mammalian homologues are postulated to form capacitative Ca2+ entry or store-operated channels. Here we show that expression of murine Trp4 in HEK 293 cells also leads to an increase in inwardly rectifying K+ currents. No similar increase was found in cell lines expressing Trp1, Trp3 or Trp6. Consistent with typical characteristics of inward rectifiers, the K+ currents in Trp4-expressing cells were blocked by low millimolar concentrations of Cs+ and Ba2+, but not by 1.2 mM Ca2+, and were only slightly inhibited by 5 mM tetraethylammonium. Single channel recordings of excised inside-out patches revealed the presence of two conducting states of 51 pS and 94 pS in Trp4-expressing cells. The outward current in the excised patches was blocked by 1 mM spermine, but not by 1 mM Mg2+. How Trp4 expression causes the increase in the K+ currents is not known. We propose that Trp4 either participates in the formation of a novel K+ channel or up-regulates the expression or activity of endogenous inwardly rectifying K+ channels. PMID:11237877

  20. Low cost, p-ZnO/n-Si, rectifying, nano heterojunction diode: Fabrication and electrical characterization.

    PubMed

    Kabra, Vinay; Aamir, Lubna; Malik, M M

    2014-01-01

    A low cost, highly rectifying, nano heterojunction (p-ZnO/n-Si) diode was fabricated using solution-processed, p-type, ZnO nanoparticles and an n-type Si substrate. p-type ZnO nanoparticles were synthesized using a chemical synthesis route and characterized by XRD and a Hall effect measurement system. The device was fabricated by forming thin film of synthesized p-ZnO nanoparticles on an n-Si substrate using a dip coating technique. The device was then characterized by current-voltage (I-V) and capacitance-voltage (C-V) measurements. The effect of UV illumination on the I-V characteristics was also explored and indicated the formation of a highly rectifying, nano heterojunction with a rectification ratio of 101 at 3 V, which increased nearly 2.5 times (232 at 3 V) under UV illumination. However, the cut-in voltage decreases from 1.5 V to 0.9 V under UV illumination. The fabricated device could be used in switches, rectifiers, clipper and clamper circuits, BJTs, MOSFETs and other electronic circuitry. PMID:25551049

  1. Decrease in an Inwardly Rectifying Potassium Conductance in Mouse Mammary Secretory Cells after Forced Weaning

    PubMed Central

    Kamikawa, Akihiro; Sugimoto, Shota; Ichii, Osamu; Kondoh, Daisuke

    2015-01-01

    Mammary glands are physiologically active in female mammals only during nursing. Immediately after weaning, most lactation-related genes are downregulated and milk production ceases. In our previous study, we have detected an inwardly rectifying potassium channel (Kir) 2.1-like current in mammary secretory (MS) cells freshly isolated from lactating mice. This current is highly sensitive to external Ba2+. The potassium permeability of the Kir channels may contribute to the secretion and/or preservation of ions in milk. We hypothesized that the functions of the Kir channels in MS cells are regulated after weaning. To test this hypothesis, we examined the effect of forced weaning on the Ba2+-sensitive Kir current and Kir2.1 expression in the mouse mammary glands. Twenty-four hours after weaning, the lumina of mammary acini were histologically enlarged by milk accumulation. The whole-cell patch-clamp analyses showed that the Ba2+-sensitive Kir current in the post-weaning MS cells was smaller than in the lactating MS cells. The inward conductances of the current in the lactating and post-weaning cells were 4.25 ± 0.77 and 0.93 ± 0.34 nS, respectively. Furthermore, real-time PCR and Western blot analyses showed that Kir2.1 mRNA and protein expression decreased in the post-weaning mammary gland (mRNA, 90% reduction; protein, 47% reduction). Moreover, the local milk accumulation caused by teat sealing decreased Kir conductance in MS cells (2.74 ± 0.45 and 0.36 ± 0.27 nS for control and sealed mammary glands, respectively). This was concomitant with the reduction in the Kir2.1 mRNA expression. Our results suggest that milk stasis after weaning immediately decreases the Kir conductance in MS cells. This decrease in the Kir conductance may be partly caused by the reduction in the Kir2.1 mRNA and protein expression. These alterations during the post-weaning period may be involved in the cessation of ion secretion and/or preservation in the milk. PMID:26484867

  2. Thermal emission control by evanescent wave coupling between guided mode of resonant grating and surface phonon polariton on silicon carbide plate

    NASA Astrophysics Data System (ADS)

    Ito, Kota; Matsui, Takayuki; Iizuka, Hideo

    2014-02-01

    Dielectric guided mode resonant gratings exhibit a sharp spectral and angular response of high reflectivity for propagation wave, and strong evanescent waves are excited. We show that in such a resonant grating positioned above the silicon carbide (SiC) plate, incident light is absorbed in the SiC plate via the evanescent wave coupling when the lateral wavenumber of a guided mode of the grating coincides with that of surface phonon polaritons on the SiC plate. This coupling scheme using the thermally transparent grating enables a sharp spectral and angular emission in the infrared region with capabilities of emissivity modulation and spatially asymmetric emissivity. Thermally transparent subwavelength structures electromagnetically coupled to polar material thermal bodies are crucial in enabling components for thermal emission control.

  3. Preparation of Aligned Ultra-long and Diameter-controlled Silicon Oxide Nanotubes by Plasma Enhanced Chemical Vapor Deposition Using Electrospun PVP Nanofiber Template.

    PubMed

    Zhou, Ming; Zhou, Jinyuan; Li, Ruishan; Xie, Erqing

    2009-01-01

    Well-aligned and suspended polyvinyl pyrrolidone (PVP) nanofibers with 8 mm in length were obtained by electrospinning. Using the aligned suspended PVP nanofibers array as template, aligned ultra-long silicon oxide (SiOx) nanotubes with very high aspect ratios have been prepared by plasma-enhanced chemical vapor deposition (PECVD) process. The inner diameter (20-200 nm) and wall thickness (12-90 nm) of tubes were controlled, respectively, by baking the electrospun nanofibers and by coating time without sacrificing the orientation degree and the length of arrays. The micro-PL spectrum of SiOx nanotubes shows a strong blue-green emission with a peak at about 514 nm accompanied by two shoulders around 415 and 624 nm. The blue-green emission is caused by the defects in the nanotubes. PMID:21711837

  4. Preparation of Aligned Ultra-long and Diameter-controlled Silicon Oxide Nanotubes by Plasma Enhanced Chemical Vapor Deposition Using Electrospun PVP Nanofiber Template

    PubMed Central

    2010-01-01

    Well-aligned and suspended polyvinyl pyrrolidone (PVP) nanofibers with 8 mm in length were obtained by electrospinning. Using the aligned suspended PVP nanofibers array as template, aligned ultra-long silicon oxide (SiOx) nanotubes with very high aspect ratios have been prepared by plasma-enhanced chemical vapor deposition (PECVD) process. The inner diameter (20–200 nm) and wall thickness (12–90 nm) of tubes were controlled, respectively, by baking the electrospun nanofibers and by coating time without sacrificing the orientation degree and the length of arrays. The micro-PL spectrum of SiOx nanotubes shows a strong blue–green emission with a peak at about 514 nm accompanied by two shoulders around 415 and 624 nm. The blue–green emission is caused by the defects in the nanotubes. PMID:21711837

  5. Silicon microdosimetry.

    PubMed

    Agosteo, Stefano; Pola, Andrea

    2011-02-01

    Silicon detectors are being studied as microdosemeters since they can provide sensitive volumes of micrometric dimensions. They can be applied for assessing single-event effects in electronic instrumentation exposed to complex fields around high-energy accelerators or in space missions. When coupled to tissue-equivalent converters, they can be used for measuring the quality of radiation therapy beams or for dosimetry. The use of micrometric volumes avoids the contribution of wall effects to the measured spectra. Further advantages of such detectors are their compactness, cheapness, transportability and a low sensitivity to vibrations. The following problems need to be solved when silicon devices are used for microdosimetry: (i) the sensitive volume has to be confined in a region of well-known dimensions; (ii) the electric noise limits the minimum detectable energy; (iii) corrections for tissue-equivalency should be made; (iv) corrections for shape equivalency should be made when referring to a spherical simulated site of tissue; (v) the angular response should be evaluated carefully; (vi) the efficiency of a single detector of micrometric dimensions is very poor and detector arrays should be considered. Several devices have been proposed as silicon microdosemeters, based on different technologies (telescope detectors, silicon on insulator detectors and arrays of cylindrical p-n junctions with internal amplification), in order to satisfy the issues mentioned above. PMID:21112892

  6. A novel recovery of silicon nanoparticles from a waste silicon sludge.

    PubMed

    Jang, Hee Dong; Kim, Hyekyoung; Kil, Dae Sup; Chang, Hankwon

    2013-03-01

    As the semiconductor and photovoltaic industry undergo rapid growth, a large amount of silicon sludge is generated from the cutting process of silicon ingots. However, it is not effectively recycled. Recovery of nanometer-sized silicon (Si) particles from the sludge has become an important concern because the silicon sludge contains valuable resources including high purity silicon. In the present study, we investigated the novel recovery of Si nanoparticles from waste silicon sludge. The waste silicon sludge also contained surfactant, silicon carbide particles and metallic fragments. After removal of the surfactant by distillation, the Si nanoparticles were recovered by applying controlled ultrasonic waves and centrifugation in series. Metallic impurities in the recovered Si nanoparticles were purified by HCl treatment. The overall maximum yield and purity of the Si nanoparticles were about 80% and 99.7%, respectively. PMID:23755688

  7. Damage Mechanisms and Controlled Crack Propagation in a Hot Pressed Silicon Nitride Ceramic. Ph.D. Thesis - Northwestern Univ., 1993

    NASA Technical Reports Server (NTRS)

    Calomino, Anthony Martin

    1994-01-01

    The subcritical growth of cracks from pre-existing flaws in ceramics can severely affect the structural reliability of a material. The ability to directly observe subcritical crack growth and rigorously analyze its influence on fracture behavior is important for an accurate assessment of material performance. A Mode I fracture specimen and loading method has been developed which permits the observation of stable, subcritical crack extension in monolithic and toughened ceramics. The test specimen and procedure has demonstrated its ability to generate and stably propagate sharp, through-thickness cracks in brittle high modulus materials. Crack growth for an aluminum oxide ceramic was observed to be continuously stable throughout testing. Conversely, the fracture behavior of a silicon nitride ceramic exhibited crack growth as a series of subcritical extensions which are interrupted by dynamic propagation. Dynamic initiation and arrest fracture resistance measurements for the silicon nitride averaged 67 and 48 J/sq m, respectively. The dynamic initiation event was observed to be sudden and explosive. Increments of subcritical crack growth contributed to a 40 percent increase in fracture resistance before dynamic initiation. Subcritical crack growth visibly marked the fracture surface with an increase in surface roughness. Increments of subcritical crack growth loosen ceramic material near the fracture surface and the fracture debris is easily removed by a replication technique. Fracture debris is viewed as evidence that both crack bridging and subsurface microcracking may be some of the mechanisms contributing to the increase in fracture resistance. A Statistical Fracture Mechanics model specifically developed to address subcritical crack growth and fracture reliability is used together with a damaged zone of material at the crack tip to model experimental results. A Monte Carlo simulation of the actual experiments was used to establish a set of modeling input parameters. It was demonstrated that a single critical parameter does not characterize the conditions required for dynamic initiation. Experimental measurements for critical crack lengths, and the energy release rates exhibit significant scatter. The resulting output of the model produces good agreement with both the average values and scatter of experimental measurements.

  8. High Efficiency Silicon Photonic Interconnects

    NASA Astrophysics Data System (ADS)

    Cao, Liang

    Silicon photonic has provided an opportunity to enhance future processor speed by replacing copper interconnects with an on chip optical network. Although photonics are supposed to be efficient in terms of power consumption, speed, and bandwidth, the existing silicon photonic technologies involve problems limiting their efficiency. Examples of limitations to efficiency are transmission loss, coupling loss, modulation speed limited by electro-optical effect, large amount of energy required for thermal control of devices, and the bandwidth limit of existing optical routers. The objective of this dissertation is to investigate novel materials and methods to enhance the efficiency of silicon photonic devices. The first part of this dissertation covers the background, theory and design of on chip optical interconnects, specifically silicon photonic interconnects. The second part describes the work done to build a 300mm silicon photonic library, including its process flow, comprised of basic elements like electro-optical modulators, germanium detectors, Wavelength Division Multiplexing (WDM) interconnects, and a high efficiency grating coupler. The third part shows the works done to increase the efficiency of silicon photonic modulators, unitizing the chi(3) nonlinear effect of silicon nanocrystals to make DC Kerr effect electro-optical modulator, combining silicon with lithium niobate to make chi(2) electro-optical modulators on silicon, and increasing the efficiency of thermal control by incorporating micro-oven structures in electro-optical modulators. The fourth part introduces work done on dynamic optical interconnects including a broadband optical router, single photon level adiabatic wavelength conversion, and optical signal delay. The final part summarizes the work and talks about future development.

  9. Advances in the understanding of low molecular weight silicon formation and implications for control by AMC filters

    NASA Astrophysics Data System (ADS)

    Lobert, Jürgen M.; Cate, Philip W.; Ruede, David J.; Wildgoose, Joseph R.; Miller, Charles M.; Gaudreau, John C.

    2010-03-01

    Trimethylsilanol (TMS) is a low molecular weight / low boiling point silicon-containing, airborne contaminant that has received increased interest over the past few years as an important cause for contamination of optical surfaces in lithography equipment. TMS is not captured well by carbon-based filters, and hexamethyldisiloxane (HMDSO), even though captured well, can be converted to TMS when using acidic filter media commonly used for ammonia removal. TMS and HMDSO co-exist in a chemical equilibrium, which is affected by the acidity and moisture of their environment. This publication shows that HMDSO is converted to TMS by acidic media at concentrations typically found in cleanroom environments. This is contrary to published results that show a re-combination of TMS to HMDSO on acid media. We also demonstrate that, based on its conversion to TMS, HMDSO is not a suitable test compound for hybrid chemical filter performance, as the apparent lifetime/capacity of the filter can be substantially skewed towards larger numbers when conversion to TMS is involved. We show lifetime test results with toluene and HMDSO on acidic and non-acidic filter media. Appropriately designed, asymmetric hybrid chemical filters significantly minimize or eliminate the conversion of HMDSO to TMS, thereby reducing the risk to scanner optical elements. Similarly, such filters can also prevent or reduce acid-sensitive reactions of other AMC when passing through filter systems.

  10. Versatile control of metal-assisted chemical etching for vertical silicon microwire arrays and their photovoltaic applications.

    PubMed

    Um, Han-Don; Kim, Namwoo; Lee, Kangmin; Hwang, Inchan; Hoon Seo, Ji; Yu, Young J; Duane, Peter; Wober, Munib; Seo, Kwanyong

    2015-01-01

    A systematic study was conducted into the use of metal-assisted chemical etching (MacEtch) to fabricate vertical Si microwire arrays, with several models being studied for the efficient redox reaction of reactants with silicon through a metal catalyst by varying such parameters as the thickness and morphology of the metal film. By optimizing the MacEtch conditions, high-quality vertical Si microwires were successfully fabricated with lengths of up to 23.2 μm, which, when applied in a solar cell, achieved a conversion efficiency of up to 13.0%. These solar cells also exhibited an open-circuit voltage of 547.7 mV, a short-circuit current density of 33.2 mA/cm(2), and a fill factor of 71.3% by virtue of the enhanced light absorption and effective carrier collection provided by the Si microwires. The use of MacEtch to fabricate high-quality Si microwires therefore presents a unique opportunity to develop cost-effective and highly efficient solar cells. PMID:26060095

  11. Versatile control of metal-assisted chemical etching for vertical silicon microwire arrays and their photovoltaic applications

    PubMed Central

    Um, Han-Don; Kim, Namwoo; Lee, Kangmin; Hwang, Inchan; Hoon Seo, Ji; Yu, Young J.; Duane, Peter; Wober, Munib; Seo, Kwanyong

    2015-01-01

    A systematic study was conducted into the use of metal-assisted chemical etching (MacEtch) to fabricate vertical Si microwire arrays, with several models being studied for the efficient redox reaction of reactants with silicon through a metal catalyst by varying such parameters as the thickness and morphology of the metal film. By optimizing the MacEtch conditions, high-quality vertical Si microwires were successfully fabricated with lengths of up to 23.2 μm, which, when applied in a solar cell, achieved a conversion efficiency of up to 13.0%. These solar cells also exhibited an open-circuit voltage of 547.7 mV, a short-circuit current density of 33.2 mA/cm2, and a fill factor of 71.3% by virtue of the enhanced light absorption and effective carrier collection provided by the Si microwires. The use of MacEtch to fabricate high-quality Si microwires therefore presents a unique opportunity to develop cost-effective and highly efficient solar cells. PMID:26060095

  12. Versatile control of metal-assisted chemical etching for vertical silicon microwire arrays and their photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Um, Han-Don; Kim, Namwoo; Lee, Kangmin; Hwang, Inchan; Hoon Seo, Ji; Yu, Young J.; Duane, Peter; Wober, Munib; Seo, Kwanyong

    2015-06-01

    A systematic study was conducted into the use of metal-assisted chemical etching (MacEtch) to fabricate vertical Si microwire arrays, with several models being studied for the efficient redox reaction of reactants with silicon through a metal catalyst by varying such parameters as the thickness and morphology of the metal film. By optimizing the MacEtch conditions, high-quality vertical Si microwires were successfully fabricated with lengths of up to 23.2 μm, which, when applied in a solar cell, achieved a conversion efficiency of up to 13.0%. These solar cells also exhibited an open-circuit voltage of 547.7 mV, a short-circuit current density of 33.2 mA/cm2, and a fill factor of 71.3% by virtue of the enhanced light absorption and effective carrier collection provided by the Si microwires. The use of MacEtch to fabricate high-quality Si microwires therefore presents a unique opportunity to develop cost-effective and highly efficient solar cells.

  13. Distinct pharmacological and molecular properties of the acid-sensitive outwardly rectifying (ASOR) anion channel from those of the volume-sensitive outwardly rectifying (VSOR) anion channel.

    PubMed

    Sato-Numata, Kaori; Numata, Tomohiro; Inoue, Ryuji; Okada, Yasunobu

    2016-05-01

    Expressed by many cell types, acid-sensitive outwardly rectifying (ASOR) anion channels are known to be activated by extracellular acidification and involved in acidotoxic necrotic cell death. In contrast, ubiquitously expressed volume-sensitive outwardly rectifying (VSOR) anion channels are activated by osmotic cell swelling and involved in cell volume regulation and apoptotic cell death. Distinct inhibitors to distinguish ASOR from VSOR anion channels have not been identified. Although leucine-rich repeats containing 8A (LRRC8A) was recently found to be an essential component of VSOR anion channels, the possibility of an LRRC8 family member serving as a component of ASOR anion channels has not been examined. In this study, we explored the effects of 12 known VSOR channel inhibitors and small interfering RNA (siRNA)-mediated knockdown of LRRC8 family members on ASOR and VSOR currents in HeLa cells. Among these inhibitors, eight putative VSOR blockers, including 4-(2-butyl-6,7-dichlor-2-cyclopentylindan-1-on-5-yl) oxobutyric acid (DCPIB) and 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB), were totally ineffective at blocking ASOR channel activity, whereas suramin, R-(+)-[(2-n-butyl-6,7-dichloro-2-cyclopentyl-2,3-dihydro-1-oxo-1H-inden-5-yl)oxy] acetic acid (DIOA), arachidonic acid, and niflumic acid were found to be effective ASOR anion channel antagonists. In addition, gene-silencing studies showed that no LRRC8 family members are essentially involved in ASOR anion channel activity, whereas LRRC8A is involved in VSOR anion channel activity in HeLa cells. PMID:26743872

  14. Production of electronic grade lunar silicon by disproportionation of silicon difluoride

    NASA Technical Reports Server (NTRS)

    Agosto, William N.

    1993-01-01

    Waldron has proposed to extract lunar silicon by sodium reduction of sodium fluorosilicate derived from reacting sodium fluoride with lunar silicon tetrafluoride. Silicon tetrafluoride is obtained by the action of hydrofluoric acid on lunar silicates. While these reactions are well understood, the resulting lunar silicon is not likely to meet electronic specifications of 5 nines purity. Dale and Margrave have shown that silicon difluoride can be obtained by the action of silicon tetrafluoride on elemental silicon at elevated temperatures (1100-1200 C) and low pressures (1-2 torr). The resulting silicon difluoride will then spontaneously disproportionate into hyperpure silicon and silicon tetrafluoride in vacuum at approximately 400 C. On its own merits, silicon difluoride polymerizes into a tough waxy solid in the temperature range from liquid nitrogen to about 100 C. It is the silicon analog of teflon. Silicon difluoride ignites in moist air but is stable under lunar surface conditions and may prove to be a valuable industrial material that is largely lunar derived for lunar surface applications. The most effective driver for lunar industrialization may be the prospects for industrial space solar power systems in orbit or on the moon that are built with lunar materials. Such systems would require large quantities of electronic grade silicon or compound semiconductors for photovoltaics and electronic controls. Since silicon is the most abundant semimetal in the silicate portion of any solar system rock (approximately 20 wt percent), lunar silicon production is bound to be an important process in such a solar power project. The lunar silicon extraction process is discussed.

  15. High-rate, low-temperature synthesis of composition controlled hydrogenated amorphous silicon carbide films in low-frequency inductively coupled plasmas

    NASA Astrophysics Data System (ADS)

    Cheng, Qijin; Xu, S.; Long, J. D.; Ni, Z. H.; Rider, A. E.; Ostrikov, K.

    2008-03-01

    It is commonly believed that in order to synthesize high-quality hydrogenated amorphous silicon carbide (a-Si1-xCx : H) films at competitive deposition rates it is necessary to operate plasma discharges at high power regimes and with heavy hydrogen dilution. Here we report on the fabrication of hydrogenated amorphous silicon carbide films with different carbon contents x (ranging from 0.09 to 0.71) at high deposition rates using inductively coupled plasma (ICP) chemical vapour deposition with no hydrogen dilution and at relatively low power densities (~0.025 W cm-3) as compared with existing reports. The film growth rate Rd peaks at x = 0.09 and x = 0.71, and equals 18 nm min-1 and 17 nm min-1, respectively, which is higher than other existing reports on the fabrication of a-Si1-xCx : H films. The extra carbon atoms for carbon-rich a-Si1-xCx : H samples are incorporated via diamond-like sp3 C-C bonding as deduced by Fourier transform infrared absorption and Raman spectroscopy analyses. The specimens feature a large optical band gap, with the maximum of 3.74 eV obtained at x = 0.71. All the a-Si1-xCx : H samples exhibit low-temperature (77 K) photoluminescence (PL), whereas only the carbon-rich a-Si1-xCx : H samples (x >= 0.55) exhibit room-temperature (300 K) PL. Such behaviour is explained by the static disorder model. High film quality in our work can be attributed to the high efficiency of the custom-designed ICP reactor to create reactive radical species required for the film growth. This technique can be used for a broader range of material systems where precise compositional control is required.

  16. Impurity diffusion process for silicon semiconductors is fast and precise

    NASA Technical Reports Server (NTRS)

    Mc louski, R. M.; Mc Louski, R. M.; Skouson, G. W.

    1965-01-01

    Impurity diffusion process produces precision silicon semiconductor junctions economically and fast. Oxide is deposited on a silicon wafer and a controlled concentration of impurity atoms in gaseous form is simultaneously introduced into the reaction.

  17. Failure rates for accelerated acceptance testing of silicon transistors

    NASA Technical Reports Server (NTRS)

    Toye, C. R.

    1968-01-01

    Extrapolation tables for the control of silicon transistor product reliability have been compiled. The tables are based on a version of the Arrhenius statistical relation and are intended to be used for low- and medium-power silicon transistors.

  18. Post-transcriptional regulation of GORK channels by superoxide anion contributes to increases in outward-rectifying K⁺ currents.

    PubMed

    Tran, Daniel; El-Maarouf-Bouteau, Hayat; Rossi, Marika; Biligui, Bernadette; Briand, Joël; Kawano, Tomonori; Mancuso, Stefano; Bouteau, François

    2013-06-01

    · Ion fluxes are ubiquitous processes in the plant and animal kingdoms, controlled by fine-tuned regulations of ion channel activity. Yet the mechanism that cells employ to achieve the modification of ion homeostasis at the molecular level still remains unclear. This is especially true when it comes to the mechanisms that lead to cell death. · In this study, Arabidopsis thaliana cells were exposed to ozone (O₃). Ion flux variations were analyzed by electrophysiological measurements and their transcriptional regulation by RT-PCR. Reactive oxygen species (ROS) generation was quantified by luminescence techniques and caspase-like activities were investigated by laser confocal microscopy. · We highlighted the delayed activation of K(+) outward-rectifying currents after an O₃ -induced oxidative stress leading to programmed cell death (PCD). Caspase-like activities are detected under O₃ exposure and could be decreased by K(+) channel blocker. Molecular experiments revealed that the sustained activation of K(+) outward current could be the result of an unexpected O₂ ·⁻ post-transcriptional regulation of the guard cell outward-rectifying K(+) (GORK) channels. · This consists of a likely new mode of regulating the processing of the GORK mRNA, in a ROS-dependent manner, to allow sustained K(+) effluxes during PCD. These data provide new mechanistic insights into K(+) channel regulation during an oxidative stress response. PMID:23517047

  19. Large area silicon sheet by EFG

    NASA Technical Reports Server (NTRS)

    1977-01-01

    Some hypotheses to explain both of these features are advanced and the possible implications for solar cell performance are touched upon. The multiple ribbon growth system has shown a number of flaws with respect to the reliability of the basic furnace design. These definitely need to be rectified before any significant demonstration of multiple ribbon growth can proceed. The cartridges, however, have performed quite well. The work on 3" cartridge design and automatic controls has proceeded nearly on schedule and the report contains a detailed description of the approach and the equipment to be used for automatic control of ribbon growth.

  20. Silicon Nanowire Devices

    NASA Astrophysics Data System (ADS)

    Kamins, Theodore

    2006-03-01

    Metal-catalyzed, self-assembled, one-dimensional semiconductor nanowires are being considered as possible device elements to augment and supplant conventional electronics and to extend the use of CMOS beyond the physical and economic limits of conventional technology. Such nanowires can create nanostructures without the complexity and cost of extremely fine scale lithography. The well-known and controllable properties of silicon make silicon nanowires especially attractive. Easy integration with conventional electronics will aid their acceptance and incorporation. For example, connections can be formed to both ends of a nanowire by growing it laterally from a vertical surface formed by etching the top silicon layer of a silicon-on-insulator structure into isolated electrodes. Field-effect structures are one class of devices that can be readily built in silicon nanowires. Because the ratio of surface to volume in a thin nanowire is high, conduction through the nanowire is very sensitive to surface conditions, making it effective as the channel of a field-effect transistor or as the transducing element of a gas or chemical sensor. As the nanowire diameter decreases, a greater fraction of the mobile charge can be modulated by a given external charge, increasing the sensitivity. Having the gate of a nanowire transistor completely surround the nanowire also enhances the sensitivity. For a field-effect sensor to be effective, the charge must be physically close to the nanowire so that the majority of the compensating charge is induced in the nanowire and so that ions in solution do not screen the charge. Because only induced charge is being sensed, a coating that selectively binds the target species should be added to the nanowire surface to distinguish between different species in the analyte. The nanowire work at Hewlett-Packard Laboratories was supported in part by the Defense Advanced Research Projects Agency.

  1. Role of slow delayed rectifying potassium current in dynamics of repolarization and electrical memory in swine ventricles.

    PubMed

    Jing, Linyuan; Brownson, Kathleen; Patwardhan, Abhijit

    2014-05-01

    Dynamics of repolarization, quantified as restitution and electrical memory, impact conduction stability. Relatively less is known about role of slow delayed rectifying potassium current, I(Ks), in dynamics of repolarization and memory compared to the rapidly activating current I(Kr). Trans-membrane potentials were recorded from right ventricular tissues from pigs during reduction (chromanol 293B) and increases in I(Ks) (mefenamic acid). A novel pacing protocol was used to explicitly control diastolic intervals to quantify memory. Restitution hysteresis, a consequence of memory, increased after chromanol 293B (loop thickness and area increased 27 and 38 %) and decreased after mefenamic acid (52 and 53 %). Standard and dynamic restitutions showed an increase in average slope after chromanol 293B and a decrease after mefenamic acid. Increase in slope and memory are hypothesized to have opposite effects on electrical stability; therefore, these results suggest that reduction and enhancement of I(Ks) likely also have offsetting components that affect stability. PMID:24682806

  2. Stress-induced glucocorticoid signaling remodels neurovascular coupling through impairment of cerebrovascular inwardly rectifying K+ channel function

    PubMed Central

    Longden, Thomas A.; Dabertrand, Fabrice; Hill-Eubanks, David C.; Hammack, Sayamwong E.; Nelson, Mark T.

    2014-01-01

    Studies of stress effects on the brain have traditionally focused on neurons, without considering the cerebral microcirculation. Here we report that stress impairs neurovascular coupling (NVC), the process that matches neuronal activity with increased local blood flow. A stressed phenotype was induced in male rats by administering a 7-d heterotypical stress paradigm. NVC was modeled by measuring parenchymal arteriole (PA) vasodilation in response to neuronal stimulation in amygdala brain slices. After stress, vasodilation of PAs to neuronal stimulation was greatly reduced, and dilation of isolated PAs to external K+ was diminished, suggesting a defect in smooth muscle inwardly rectifying K+ (KIR) channel function. Consistent with these observations, stress caused a reduction in PA KIR2.1 mRNA and smooth muscle KIR current density, and blocking KIR channels significantly inhibited NVC in control, but not in stressed, slices. Delivery of corticosterone for 7 d (without stressors) or RU486 (before stressors) mimicked and abrogated NVC impairment by stress, respectively. We conclude that stress causes a glucocorticoid-mediated decrease in functional KIR channels in amygdala PA myocytes. This renders arterioles less responsive to K+ released from astrocytic endfeet during NVC, leading to impairment of this process. Because the fidelity of NVC is essential for neuronal health, the impairment characterized here may contribute to the pathophysiology of brain disorders with a stress component. PMID:24808139

  3. High-fat diet-dependent modulation of the delayed rectifier K(+) current in adult guinea pig atrial myocytes.

    PubMed

    Aromolaran, Ademuyiwa S; Colecraft, Henry M; Boutjdir, Mohamed

    2016-06-01

    Obesity is associated with hyperlipidemia, electrical remodeling of the heart, and increased risk of supraventricular arrhythmias in both male and female patients. The delayed rectifier K(+) current (IK), is an important regulator of atrial repolarization. There is a paucity of studies on the functional role of IK in response to obesity. Here, we assessed the obesity-mediated functional modulation of IK in low-fat diet (LFD), and high-fat diet (HFD) fed adult guinea pigs. Guinea pigs were randomly divided into control and obese groups fed, ad libitum, with a LFD (10 kcal% fat) or a HFD (45 kcal% fat) respectively. Action potential duration (APD), and IK were studied in atrial myocytes and IKr and IKs in HEK293 cells using whole-cell patch clamp electrophysiology. HFD guinea pigs displayed a significant increase in body weight, total cholesterol and total triglycerides within 50 days. Atrial APD at 30% (APD30) and 90% (APD90) repolarization were shorter, while atrial IK density was significantly increased in HFD guinea pigs. Exposure to palmitic acid (PA) increased heterologously expressed IKr and IKs densities, while oleic acid (OA), severely reduced IKr and had no effect on IKs. The data are first to show that in obese guinea pigs abbreviated APD is due to increased IK density likely through elevations of PA. Our findings may have crucial implications for targeted treatment options for obesity-related arrhythmias. PMID:27130822

  4. Molecular and functional characterization of Anopheles gambiae inward rectifier potassium (Kir1) channels: A novel role in egg production

    PubMed Central

    Raphemot, Rene; Estévez-Lao, Tania Y.; Rouhier, Matthew F.; Piermarini, Peter M.; Denton, Jerod S.; Hillyer, Julián F.

    2014-01-01

    Inward rectifier potassium (Kir) channels play essential roles in regulating diverse physiological processes. Although Kir channels are encoded in mosquito genomes, their functions remain largely unknown. In this study, we identified the members of the Anopheles gambiae Kir gene family and began to investigate their function. Notably, we sequenced the A. gambiae Kir1 (AgKir1) gene and showed that it encodes all the canonical RIP features of a Kir channel: an ion pore that is composed of a pore helix and a selectivity filter, two transmembrane domains that flank the ion pore, and the so-called G-loop. Heterologous expression of AgKir1 in Xenopus oocytes revealed that this gene encodes a functional, barium-sensitive Kir channel. Quantitative RT-PCR experiments then showed that relative AgKir1 mRNA levels are highest in the pupal stage, and that AgKir1 mRNA is enriched in the adult ovaries. Gene silencing of AgKir1 by RNA interference did not affect the survival of female mosquitoes following a blood in mosquito fecundity, and further validates them as promising molecular targets for the meal, but decreased their egg output. These data provide evidence for a new role of Kir channels development of a new class of mosquitocides to be used in vector control. PMID:24855023

  5. Identification of common synaptic inputs to motor neurons from the rectified electromyogram

    PubMed Central

    Farina, Dario; Negro, Francesco; Jiang, Ning

    2013-01-01

    Oscillatory common inputs of cortical or peripheral origin can be identified from the motor neuron output with coherence analysis. Linear transmission is possible despite the motor neuron non-linearity because the same input is sent commonly to several neurons. Because of the linear transmission, common input components to motor neurons can be investigated from the surface EMG, for example by EEG–EMG or EMG–EMG coherence. In these studies, there is an open debate on the utility and appropriateness of EMG rectification. The present study addresses this issue using an analytical, simulation and experimental approach. The main novel theoretical contribution that we report is that the spectra of both the rectified and the raw EMG contain input spectral components to motor neurons. However, they differ by the contribution of amplitude cancellation which influences the rectified EMG spectrum when extracting common oscillatory inputs. Therefore, the degree of amplitude cancellation has an impact on the effectiveness of EMG rectification in extracting input spectral peaks. The theoretical predictions were exactly confirmed by realistic simulations of a pool of motor neurons innervating a muscle in a cylindrical volume conductor of EMG generation and by experiments conducted on the first dorsal interosseous and the abductor pollicis brevis muscles of seven healthy subjects during pinching. It was concluded that when the contraction level is relatively low, EMG rectification may be preferable for identifying common inputs to motor neurons, especially when the energy of the action potentials in the low frequency range is low. Nonetheless, different levels of cancellation across conditions influence the relative estimates of the degree of linear transmission of oscillatory inputs to motor neurons when using the rectified EMG. PMID:23507877

  6. Operating a three-phase diode rectifier with a low-input current distortion using a series-connected dual boost converter

    SciTech Connect

    Salmon, J.C.

    1996-07-01

    This paper describes a technique for shaping the input current to a three-phase diode rectifier using a two-switch series-connected dual boost converter and a three-phase bidirectional switch circuit. Circuits are described for generating a single voltage dc output, single dc-rail, or a dual output dc voltage using center-tapped capacitors, split dc-rail. Both rectifier types can be operated with the boost inductors located either on the dc or the ac side of the rectifier. The resultant rectifier circuit configurations have an excellent immunity to the shoot-through fault condition and use active switching elements with low per-unit current ratings and low switching losses. These features increase the reliability factor and lower the cost penalty associated with unity fundamental power factor three-phase rectifiers. Test results are presented for the rectifiers using simulation and experimental results.

  7. High-voltage 4H-SiC trench MOS barrier Schottky rectifier with low forward voltage drop using enhanced sidewall layer

    NASA Astrophysics Data System (ADS)

    Cho, Doohyung; Sim, Seulgi; Park, Kunsik; Won, Jongil; Kim, Sanggi; Kim, Kwangsoo

    2015-12-01

    In this paper, a 4H-SiC trench MOS barrier Schottky (TMBS) rectifier with an enhanced sidewall layer (ESL) is proposed. The proposed structure has a high doping concentration at the trench sidewall. This high doping concentration improves both the reverse blocking and forward characteristics of the structure. The ESL-TMBS rectifier has a 7.4% lower forward voltage drop and a 24% higher breakdown voltage. However, this structure has a reverse leakage current that is approximately three times higher than that of a conventional TMBS rectifier owing to the reduction in energy barrier height. This problem is solved when ESL is used partially, since its use provides a reverse leakage current that is comparable to that of a conventional TMBS rectifier. Thus, the forward voltage drop and breakdown voltage improve without any loss in static and dynamic characteristics in the ESL-TMBS rectifier compared with the performance of a conventional TMBS rectifier.

  8. Programmable controller system for wind tunnel diversion vanes

    NASA Technical Reports Server (NTRS)

    King, R. F.

    1982-01-01

    A programmable controller (PC) system automatic sequence control, which acts as a supervisory controller for the servos, selects the proper drives, and automatically sequences the vanes, was developed for use in a subsonic wind tunnel. Tunnel modifications include a new second test section (80 ft x 100 ft with a maximum air speed capability of 110 knots) and an increase in maximum velocity flow from 200 knots to 300 knots. A completely automatic sequence control is necessary in order to allow intricate motion of the 14 triangularly arranged vanes which can be as large as 70 ft high x 35 ft wide and which require precise acceleration and deceleration control. Rate servos on each drive aid in this control, and servo cost was minimized by using four silicon controlled rectifier controllers to control the 20 dc drives. The PC has a programming capacity which facilitated the implementation of extensive logic design. A series of diagrams sequencing the vanes and a block diagram of the system are included.

  9. Rectifying the Optical-Field-Induced Current in Dielectrics: Petahertz Diode

    NASA Astrophysics Data System (ADS)

    Lee, J. D.; Yun, Won Seok; Park, Noejung

    2016-02-01

    Investigating a theoretical model of the optical-field-induced current in dielectrics driven by strong few-cycle laser pulses, we propose an asymmetric conducting of the current by forming a heterojunction made of two distinct dielectrics with a low hole mass (mh*≪me*) and low electron mass (me*≪mh* ), respectively. This proposition introduces the novel concept of a petahertz (1015 Hz ) diode to rectify the current in the petahertz domain, which should be a key ingredient for the electric signal manipulation of future light-wave electronics. Further, we suggest the candidate dielectrics for the heterojunction.

  10. Current-driven antivortex core resonance measured by the rectifying effect

    NASA Astrophysics Data System (ADS)

    Goto, Minori; Nozaki, Yukio

    2016-02-01

    We demonstrate the current-driven resonance of a single antivortex core confined in a cross-shaped Ni81Fe19 wire. The antivortex core dynamics can be excited purely by spin transfer torque; therefore, it is significant to understand the current-induced magnetization dynamics. The antivortex core resonance can be measured from the frequency dependence of a rectified voltage generated by an alternating current application. We found that the resonance frequency and peak amplitude greatly depend on the external magnetic field. This result is in good agreement with micromagnetic simulation.

  11. Molecular motors that digest their track to rectify Brownian motion: processive movement of exonuclease enzymes

    NASA Astrophysics Data System (ADS)

    Xie, Ping

    2009-09-01

    A general model is presented for the processive movement of molecular motors such as λ-exonuclease, RecJ and exonuclease I that use digestion of a DNA track to rectify Brownian motion along this track. Using this model, the translocation dynamics of these molecular motors is studied. The sequence-dependent pausing of λ-exonuclease, which results from a site-specific high affinity DNA interaction, is also studied. The theoretical results are consistent with available experimental data. Moreover, the model is used to predict the lifetime distribution and force dependence of these paused states.

  12. Rectifying the Optical-Field-Induced Current in Dielectrics: Petahertz Diode.

    PubMed

    Lee, J D; Yun, Won Seok; Park, Noejung

    2016-02-01

    Investigating a theoretical model of the optical-field-induced current in dielectrics driven by strong few-cycle laser pulses, we propose an asymmetric conducting of the current by forming a heterojunction made of two distinct dielectrics with a low hole mass (m_{h}^{*}≪m_{e}^{*}) and low electron mass (m_{e}^{*}≪m_{h}^{*}), respectively. This proposition introduces the novel concept of a petahertz (10^{15}  Hz) diode to rectify the current in the petahertz domain, which should be a key ingredient for the electric signal manipulation of future light-wave electronics. Further, we suggest the candidate dielectrics for the heterojunction. PMID:26894731

  13. Rectifying performance and negative differential behavior in graphite—chain—carbon nanotube junctions

    SciTech Connect

    Qiu, Ming; Li, Jiangfan; Liew, K. M.; Yuan, Chris

    2014-01-13

    In this paper, the (5, 5) capped carbon nanotubes (CNTs) in contact with different lengths of sp monoatomic chains grown on the surface of graphite substrate are fabricated and its electronic transport properties sandwiched between CNT and graphite electrodes are investigated. The first-principles calculations based on nonequilibrium Green's function in combination with density-functional theory show that their rectifying performance and negative differential resistance behavior are observed under very low biases and obviously are enhanced when the length increases. From our analysis, the charge transfer, transmission spectra, projected density of states and evolutions of molecular orbitals are responsible for these phenomena.

  14. Development of thermal rectifier using unusual electron thermal conductivity of icosahedral quasicrystals

    NASA Astrophysics Data System (ADS)

    Takeuchi, Tsunehiro

    2015-03-01

    The bulk thermal rectifiers usable at high temperature were developed using the unusual increase of electron thermal conductivity of icosahedral quasicrystals (ICQ's) at high temperature. Our previously performed analyses in terms of linear response theory suggested that the unusual increase of electron thermal conductivity of ICQ was brought about by the synergy effect of quasiperiodicity and narrow pseudogap at the Fermi level. Since the linear response theory suggests that the unusual increase of electron thermal conductivity is coupled with the small magnitude of Seebeck coefficient, the composition of Al-Cu-Fe ICQ, where the thermal conductivity shows the most significant increase with increasing temperature, was determined with a great help of Seebeck coefficient measurements. Consequently obtained Al61.5Cu26.5Fe12.0 ICQ, which was characterized by the small magnitude of Seebeck coefficient, possessed 9 times larger value of thermal conductivity at 1000 K than that observed at 300 K. The increasing tendency of electron thermal conductivity with increasing temperature was further enhanced by means of small amount of Re substitution for Fe. This substitution definitely reduced the lattice thermal conductivity while the electron thermal conductivity was kept unchanged. The lattice thermal conductivity was reduced by 35 % under the presence of 0.5 at.% Re, and the thermal conductivity at 1000 K consequently became about 11 times larger than that at 300 K. The thermal rectifiers were constructed using our newly developed ICQ (Al61.5Cu26.5Fe12.0 or Al61.0Si0.5Cu26.5Fe11.5Re0.5) together with one of the selected materials (Si, Al2O3, CuGeTe2 or Ag2Te) that possess thermal conductivity decreasing with increasing temperature. The heat current flowing in the rectifiers was confirmed to show significant direction dependence. The consequently obtained TRR =|Jlarge|/ |Jsmall | for the composite consisting of Al61.0Si0.5Cu26.5Fe11.5Re0.5/ CuGeTe2 reached 2.24, and that is the largest value ever reported for the bulk thermal rectifiers.

  15. Properties of the inwardly rectifying K+ conductance in the toad retinal pigment epithelium.

    PubMed Central

    Segawa, Y; Hughes, B A

    1994-01-01

    An inwardly rectifying K+ current was analysed in isolated toad retinal pigment epithelial (RPE) cells using the perforated-patch clamp technique. The zero-current potential (Vo) of RPE cells averaged -71 mV when the extracellular K+ concentration ([K+]o) was 2 mM. Increasing [K+]o from 0.5 to 5 mM shifted V0 by +43 mV, indicating a relative K+ conductance (TK) of 0.74. At [K+]o greater than 5 mM, TK decreased to 0.53. Currents were larger in response to hyperpolarizing voltage pulses than depolarizing pulses, indicating an inwardly rectifying conductance. Currents were time independent except in response to voltage pulses to potentials positive to 0 mV, where the outward current decayed with an exponential time course. Both the inwardly rectifying current and the transient outward current were eliminated by the addition of 0.5 mM Ba2+, 5 mM Cs+ or 2 mM Rb+ to the extracellular solution. The current blocked by these ions reversed near the K+ equilibrium potential (EK) over a wide range of [K+]o, indicating a highly selective K+ channel. The current-voltage relationship of the isolated K+ current exhibited mild inward rectification at voltages negative to -20 mV and a negative slope conductance at voltages positive to -20 mV. The Cs(+)- and Ba(2+)-induced blocks of the K+ current were concentration dependent but voltage independent. The apparent dissociation constants were 0.8 mM for Cs+ and 40 microM for Ba2+. The K+ conductance decreased when extracellular Na+ was removed. Increasing [K+]o decreased the K+ chord conductance (gK) at negative membrane potentials. In the physiological voltage range, increasing [K+]o from 2 to 5 mM caused gK to decrease by approximately 25%. We conclude that the inwardly rectifying K+ conductance represents the resting K+ conductance of the toad RPE apical membrane. The unusual properties of this conductance may enhance the ability of the RPE to buffer [K+]o changes that take place in the subretinal space at the transition between dark and light. PMID:8046634

  16. In situ ZnO nanowire growth to promote the PVDF piezo phase and the ZnO-PVDF hybrid self-rectified nanogenerator as a touch sensor.

    PubMed

    Li, Zetang; Zhang, Xu; Li, Guanghe

    2014-03-28

    A PVDF-ZnO nanowires (NWs) hybrid generator (PZHG) was designed. A simple, cost effective method to produce the PVDF β phase by nano force is introduced. With the ZnO NWs growing, the in situ nano extension force promotes the phase change. A theoretical analysis of the ZnO NWs acting as a self-rectifier of the nano generator is established. The ZnO NWs acted as a self-adjustment diode to control the current output of the PZHG by piezo-electric and semi-conductive effects. Based on the self-controllability of the piezoelectric output, three kinds of finger touching are distinguished by the output performances of the PZHG, which is applicable to an LCD touch pad. PMID:24515250

  17. Semiconductor systems utilizing materials that form rectifying junctions in both N and P-type doping regions, whether metallurgically or field induced, and methods of use

    DOEpatents

    Welch, James D.

    2000-01-01

    Disclosed are semiconductor systems, such as integrated circuits utilizing Schotky barrier and/or diffused junction technology, which semiconductor systems incorporate material(s) that form rectifying junctions in both metallurgically and/or field induced N and P-type doping regions, and methods of their use. Disclosed are Schottky barrier based inverting and non-inverting gate voltage channel induced semiconductor single devices with operating characteristics similar to multiple device CMOS systems and which can be operated as modulators, N and P-channel MOSFETS and CMOS formed therefrom, and (MOS) gate voltage controlled rectification direction and gate voltage controlled switching devices, and use of such material(s) to block parasitic current flow pathways. Simple demonstrative five mask fabrication procedures for inverting and non-inverting gate voltage channel induced semiconductor single devices with operating characteristics similar to multiple device CMOS systems are also presented.

  18. Ultrafast laser functionalized rare phased gold-silicon/silicon oxide nanostructured hybrid biomaterials.

    PubMed

    Premnath, P; Tan, B; Venkatakrishnan, K

    2015-12-01

    We introduce a hybrid nanostructured biomaterial that is a combination of rare phases of immiscible gold and silicon oxide, functionalized via ultrafast laser synthesis. For the first time, we show cancer controlling properties of rare phases of gold silicides, which include Au7Si, Au5Si, Au0.7Si2.3 and Au8Si2. Conventionally, pure forms of gold and silicon/silicon oxide are extensively employed in targeted therapy and drug delivery systems due to their unique properties. While silicon and silicon oxide nanoparticles have shown biocompatibility, gold nanoparticles show conflicting results based on their size and material properties. Several studies have shown that gold and silicon combinations produce cell controlling properties, however, these studies were not able to produce a homogenous combination of gold and silicon, owing to its immiscibility. A homogenous combination of gold and silicon may potentially enable properties that have not previously been reported. We describe rare phased gold-silicon oxide nanostructured hybrid biomaterials and its unique cancer controlling properties, owing to material properties, concentration, size and density. The gold-silicon oxide nanostructured hybrid is composed of individual gold-silicon oxide nanoparticles in various concentrations of gold and silicon, some nanoparticles possess a gold-core and silicon-shell like structure. The individual nanoparticles are bonded together forming a three dimensional nanostructured hybrid. The interaction of the nanostructured hybrids with cervical cancer cells showed a 96% reduction in 24h. This engineered nanostructured hybrid biomaterial presents significant potential due to the combination of immiscible gold and silicon oxide in varying phases and can potentially satiate the current vacuum in cancer therapy. PMID:26539809

  19. Correlation between barrier inhomogeneities of 4H-SiC 1 A/600 V Schottky rectifiers and deep-level defects revealed by DLTS and Laplace DLTS

    NASA Astrophysics Data System (ADS)

    Gelczuk, Ł.; Kamyczek, P.; Płaczek-Popko, E.; Dąbrowska-Szata, M.

    2014-09-01

    Electrical properties of commercial silicon carbide (SiC) Schottky rectifiers are investigated through the measurement and analysis of the forward current-voltage (I-V) and reverse capacitance-voltage (C-V) characteristics in a large temperature range. Some of devices show distinct discrepancies in specific ranges of their electrical characteristics, especially the excess current dominates at voltage <1 V and temperature <300 K. Standard deep level transient spectroscopy (DLTS) revealed the presence of a single deep-level defect with activation energy of about 0.3 eV, exhibiting the features characteristic for extended defects (e.g. dislocations), such as logarithmic capture kinetics. Furthermore, high-resolution Laplace DLTS showed that this deep level consists actually of three closely spaced levels with activation energies ranging from about 0.26 eV to 0.29 eV. A strong correlation between these two techniques implies that the revealed trap level is due to extended defects surrounded by point traps or clusters of defects. On the basis of obtained specific features of the deep-level defect, it was proposed that this defect is arguably responsible for the observed Schottky barrier inhomogeneities.

  20. Comparison between Phase-Shift Full-Bridge Converters with Noncoupled and Coupled Current-Doubler Rectifier

    PubMed Central

    Tsai, Cheng-Tao; Tseng, Sheng-Yu

    2013-01-01

    This paper presents comparison between phase-shift full-bridge converters with noncoupled and coupled current-doubler rectifier. In high current capability and high step-down voltage conversion, a phase-shift full-bridge converter with a conventional current-doubler rectifier has the common limitations of extremely low duty ratio and high component stresses. To overcome these limitations, a phase-shift full-bridge converter with a noncoupled current-doubler rectifier (NCDR) or a coupled current-doubler rectifier (CCDR) is, respectively, proposed and implemented. In this study, performance analysis and efficiency obtained from a 500 W phase-shift full-bridge converter with two improved current-doubler rectifiers are presented and compared. From their prototypes, experimental results have verified that the phase-shift full-bridge converter with NCDR has optimal duty ratio, lower component stresses, and output current ripple. In component count and efficiency comparison, CCDR has fewer components and higher efficiency at full load condition. For small size and high efficiency requirements, CCDR is relatively suitable for high step-down voltage and high efficiency applications. PMID:24381521

  1. Comparison between phase-shift full-bridge converters with noncoupled and coupled current-doubler rectifier.

    PubMed

    Tsai, Cheng-Tao; Su, Jye-Chau; Tseng, Sheng-Yu

    2013-01-01

    This paper presents comparison between phase-shift full-bridge converters with noncoupled and coupled current-doubler rectifier. In high current capability and high step-down voltage conversion, a phase-shift full-bridge converter with a conventional current-doubler rectifier has the common limitations of extremely low duty ratio and high component stresses. To overcome these limitations, a phase-shift full-bridge converter with a noncoupled current-doubler rectifier (NCDR) or a coupled current-doubler rectifier (CCDR) is, respectively, proposed and implemented. In this study, performance analysis and efficiency obtained from a 500 W phase-shift full-bridge converter with two improved current-doubler rectifiers are presented and compared. From their prototypes, experimental results have verified that the phase-shift full-bridge converter with NCDR has optimal duty ratio, lower component stresses, and output current ripple. In component count and efficiency comparison, CCDR has fewer components and higher efficiency at full load condition. For small size and high efficiency requirements, CCDR is relatively suitable for high step-down voltage and high efficiency applications. PMID:24381521

  2. Making silicon stronger.

    SciTech Connect

    Boyce, Brad Lee

    2010-11-01

    Silicon microfabrication has seen many decades of development, yet the structural reliability of microelectromechanical systems (MEMS) is far from optimized. The fracture strength of Si MEMS is limited by a combination of poor toughness and nanoscale etch-induced defects. A MEMS-based microtensile technique has been used to characterize the fracture strength distributions of both standard and custom microfabrication processes. Recent improvements permit 1000's of test replicates, revealing subtle but important deviations from the commonly assumed 2-parameter Weibull statistical model. Subsequent failure analysis through a combination of microscopy and numerical simulation reveals salient aspects of nanoscale flaw control. Grain boundaries, for example, suffer from preferential attack during etch-release thereby forming failure-critical grain-boundary grooves. We will discuss ongoing efforts to quantify the various factors that affect the strength of polycrystalline silicon, and how weakest-link theory can be used to make worst-case estimates for design.

  3. Role of an inwardly rectifying potassium current in rabbit ventricular action potential.

    PubMed Central

    Shimoni, Y; Clark, R B; Giles, W R

    1992-01-01

    1. Whole-cell voltage-clamp measurements were made of the time- and voltage-dependent properties of the inwardly rectifying background potassium current IK1, in single myocytes from rabbit ventricle. The main goal of these experiments was to define the role of IK1 in the plateau and repolarization phases of the action potential (AP). 2. Action potentials from single ventricular myocytes were used as the command signals for voltage-clamp measurements. In these 'action potential voltage-clamp' experiments, IK1 was isolated from other membrane currents by taking the difference between control currents and currents in K(+)-free bathing solution. The results show that IK1 is small during the plateau, but then rapidly increases during repolarization and declines in early diastole. 3. Evidence of an important functional role for IK1 in AP repolarization was obtained by comparing the magnitude of IK1 and the rate of change of membrane potential (dVm/dt) in the same cell during the AP. The time courses of IK1 and dVm/dt during the AP were closely correlated, indicating that IK1 was the principal current responsible for final repolarization. 4. Rectangular voltage-clamp steps were used to study time- and voltage-dependent changes in IK1 at membrane potentials corresponding to the repolarization phase of the AP. 'Slow' relaxations or tail currents, lasting 100-300 ms, were consistently recorded when the cell was repolarized to potentials in the range -30 to -70 mV, following depolarizations between +10 and -10 mV. 5. The close correlation between the magnitude of the steady-state IK1 (in an external K+ concentration of 5.4 mM), which was outward for membrane potentials in the range -30 to -70 mV, and the magnitude of the tail currents, suggests that they resulted from a slow increase, or reactivation, of IK1. 6. The component of the slow tails due to reactivation of IK1 can be separated from a previously described component due to Na(+)-Ca2+ exchange since the IK1 component: (i) does not depend on the presence of the calcium current, ICa; (ii) can be recorded when internal EGTA (5 mM) suppresses large changes in [Ca2+]i; (iii) does not depend on the Na+ electrochemical gradient; (iv) is abolished in K(+)-free external solution; and (v) is not present in rabbit atrial myocytes, in which IK1 is very small. 7. The time- and voltage-dependent properties of IK1 revealed by these tail current experiments suggest that the measured magnitude of IK1 will be dependent on the voltage-clamp protocol.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:1593485

  4. Crystalline Silicon Solar Cells

    NASA Astrophysics Data System (ADS)

    Green, Martin A.

    2015-10-01

    The following sections are included: * Overview * Silicon cell development * Substrate production * Cell processing * Cell costs * Opportunities for improvement * Silicon-supported thin films * Summary * Acknowledgement * References

  5. Silicon Micromachined Microlens Array for THz Antennas

    NASA Technical Reports Server (NTRS)

    Lee, Choonsup; Chattopadhyay, Goutam; Mehdi, IImran; Gill, John J.; Jung-Kubiak, Cecile D.; Llombart, Nuria

    2013-01-01

    5 5 silicon microlens array was developed using a silicon micromachining technique for a silicon-based THz antenna array. The feature of the silicon micromachining technique enables one to microfabricate an unlimited number of microlens arrays at one time with good uniformity on a silicon wafer. This technique will resolve one of the key issues in building a THz camera, which is to integrate antennas in a detector array. The conventional approach of building single-pixel receivers and stacking them to form a multi-pixel receiver is not suited at THz because a single-pixel receiver already has difficulty fitting into mass, volume, and power budgets, especially in space applications. In this proposed technique, one has controllability on both diameter and curvature of a silicon microlens. First of all, the diameter of microlens depends on how thick photoresist one could coat and pattern. So far, the diameter of a 6- mm photoresist microlens with 400 m in height has been successfully microfabricated. Based on current researchers experiences, a diameter larger than 1-cm photoresist microlens array would be feasible. In order to control the curvature of the microlens, the following process variables could be used: 1. Amount of photoresist: It determines the curvature of the photoresist microlens. Since the photoresist lens is transferred onto the silicon substrate, it will directly control the curvature of the silicon microlens. 2. Etching selectivity between photoresist and silicon: The photoresist microlens is formed by thermal reflow. In order to transfer the exact photoresist curvature onto silicon, there needs to be etching selectivity of 1:1 between silicon and photoresist. However, by varying the etching selectivity, one could control the curvature of the silicon microlens. The figure shows the microfabricated silicon microlens 5 x5 array. The diameter of the microlens located in the center is about 2.5 mm. The measured 3-D profile of the microlens surface has a smooth curvature. The measured height of the silicon microlens is about 280 microns. In this case, the original height of the photoresist was 210 microns. The change was due to the etching selectivity of 1.33 between photoresist and silicon. The measured surface roughness of the silicon microlens shows the peak-to-peak surface roughness of less than 0.5 microns, which is adequate in THz frequency. For example, the surface roughness should be less than 7 microns at 600 GHz range. The SEM (scanning electron microscope) image of the microlens confirms the smooth surface. The beam pattern at 550 GHz shows good directivity.

  6. Self-contained sub-millimeter wave rectifying antenna integrated circuit

    NASA Technical Reports Server (NTRS)

    Siegel, Peter H. (Inventor)

    2004-01-01

    The invention is embodied in a monolithic semiconductor integrated circuit in which is formed an antenna, such as a slot dipole antenna, connected across a rectifying diode. In the preferred embodiment, the antenna is tuned to received an electromagnetic wave of about 2500 GHz so that the device is on the order of a wavelength in size, or about 200 microns across and 30 microns thick. This size is ideal for mounting on a microdevice such as a microrobot for example. The antenna is endowed with high gain in the direction of the incident radiation by providing a quarter-wavelength (30 microns) thick resonant cavity below the antenna, the cavity being formed as part of the monolithic integrated circuit. Preferably, the integrated circuit consists of a thin gallium arsenide membrane overlying the resonant cavity and supporting an epitaxial Gallium Arsenide semiconductor layer. The rectifying diode is a Schottky diode formed in the GaAs semiconductor layer and having an area that is a very small fraction of the wavelength of the 2500 GHz incident radiation. The cavity provides high forward gain in the antenna and isolation from surrounding structure.

  7. High-performance microfluidic rectifier based on sudden expansion channel with embedded block structure.

    PubMed

    Tsai, Chien-Hsiung; Lin, Che-Hsin; Fu, Lung-Ming; Chen, Hui-Chun

    2012-06-01

    A high-performance microfluidic rectifier incorporating a microchannel and a sudden expansion channel is proposed. In the proposed device, a block structure embedded within the expansion channel is used to induce two vortex structures at the end of the microchannel under reverse flow conditions. The vortices reduce the hydraulic diameter of the microchannel and, therefore, increase the flow resistance. The rectification performance of the proposed device is evaluated by both experimentally and numerically. The experimental and numerical values of the rectification performance index (i.e., the diodicity, Di) are found to be 1.54 and 1.76, respectively. Significantly, flow rectification is achieved without the need for moving parts. Thus, the proposed device is ideally suited to the high pressure environment characteristic of most micro-electro-mechanical-systems (MEMS)-based devices. Moreover, the rectification performance of the proposed device is superior to that of existing valveless rectifiers based on Tesla valves, simple nozzle/diffuser structures, or cascaded nozzle/diffuser structures. PMID:22655019

  8. Rectifier of aberrant mRNA splicing recovers tRNA modification in familial dysautonomia.

    PubMed

    Yoshida, Mayumi; Kataoka, Naoyuki; Miyauchi, Kenjyo; Ohe, Kenji; Iida, Kei; Yoshida, Suguru; Nojima, Takayuki; Okuno, Yukiko; Onogi, Hiroshi; Usui, Tomomi; Takeuchi, Akihide; Hosoya, Takamitsu; Suzuki, Tsutomu; Hagiwara, Masatoshi

    2015-03-01

    Familial dysautonomia (FD), a hereditary sensory and autonomic neuropathy, is caused by missplicing of exon 20, resulting from an intronic mutation in the inhibitor of kappa light polypeptide gene enhancer in B cells, kinase complex-associated protein (IKBKAP) gene encoding IKK complex-associated protein (IKAP)/elongator protein 1 (ELP1). A newly established splicing reporter assay allowed us to visualize pathogenic splicing in cells and to screen small chemicals for the ability to correct the aberrant splicing of IKBKAP. Using this splicing reporter, we screened our chemical libraries and identified a compound, rectifier of aberrant splicing (RECTAS), that rectifies the aberrant IKBKAP splicing in cells from patients with FD. Here, we found that the levels of modified uridine at the wobble position in cytoplasmic tRNAs are reduced in cells from patients with FD and that treatment with RECTAS increases the expression of IKAP and recovers the tRNA modifications. These findings suggest that the missplicing of IKBKAP results in reduced tRNA modifications in patients with FD and that RECTAS is a promising therapeutic drug candidate for FD. PMID:25675486

  9. Rectifier of aberrant mRNA splicing recovers tRNA modification in familial dysautonomia

    PubMed Central

    Yoshida, Mayumi; Kataoka, Naoyuki; Miyauchi, Kenjyo; Ohe, Kenji; Iida, Kei; Yoshida, Suguru; Nojima, Takayuki; Okuno, Yukiko; Onogi, Hiroshi; Usui, Tomomi; Takeuchi, Akihide; Hosoya, Takamitsu; Suzuki, Tsutomu; Hagiwara, Masatoshi

    2015-01-01

    Familial dysautonomia (FD), a hereditary sensory and autonomic neuropathy, is caused by missplicing of exon 20, resulting from an intronic mutation in the inhibitor of kappa light polypeptide gene enhancer in B cells, kinase complex-associated protein (IKBKAP) gene encoding IKK complex-associated protein (IKAP)/elongator protein 1 (ELP1). A newly established splicing reporter assay allowed us to visualize pathogenic splicing in cells and to screen small chemicals for the ability to correct the aberrant splicing of IKBKAP. Using this splicing reporter, we screened our chemical libraries and identified a compound, rectifier of aberrant splicing (RECTAS), that rectifies the aberrant IKBKAP splicing in cells from patients with FD. Here, we found that the levels of modified uridine at the wobble position in cytoplasmic tRNAs are reduced in cells from patients with FD and that treatment with RECTAS increases the expression of IKAP and recovers the tRNA modifications. These findings suggest that the missplicing of IKBKAP results in reduced tRNA modifications in patients with FD and that RECTAS is a promising therapeutic drug candidate for FD. PMID:25675486

  10. Simulation and Analysis of Three-Phase Rectifiers for Aerospace Power Applications

    NASA Technical Reports Server (NTRS)

    Truong, Long V.; Birchenough, Arthur G.

    2004-01-01

    Due to the nature of planned planetary missions, fairly large advanced power systems are required for the spacecraft. These future high power spacecrafts are expected to use dynamic power conversion systems incorporating high speed alternators as three-phase AC electrical power source. One of the early design considerations in such systems is the type of rectification to be used with the AC source for DC user loads. This paper address the issues involved with two different rectification methods, namely the conventional six and twelve pulses. Two circuit configurations which involved parallel combinations of the six and twelve-pulse rectifiers were selected for the simulation. The rectifier s input and output power waveforms will be thoroughly examined through simulations. The effects of the parasitic load for power balancing and filter components for reducing the ripple voltage at the DC loads are also included in the analysis. Details of the simulation circuits, simulation results, and design examples for reducing risk from damaging of spacecraft engines will be presented and discussed.

  11. Power spectrum of the rectified EMG: when and why is rectification beneficial for identifying neural connectivity?

    NASA Astrophysics Data System (ADS)

    Negro, Francesco; Keenan, Kevin; Farina, Dario

    2015-06-01

    Objective. The identification of common oscillatory inputs to motor neurons in the electromyographic (EMG) signal power spectrum is often preceded by EMG rectification for enhancing the low-frequency oscillatory components. However, rectification is a nonlinear operator and its influence on the EMG signal spectrum is not fully understood. In this study, we aim at determining when EMG rectification is beneficial in the study of oscillatory inputs to motor neurons. Approach. We provide a full mathematical description of the power spectrum of the rectified EMG signal and the influence of the average shape of the motor unit action potentials on it. We also provide a validation of these theoretical results with both simulated and experimental EMG signals. Main results. Simulations using an advanced computational model and experimental results demonstrated the accuracy of the theoretical derivations on the effect of rectification on the EMG spectrum. These derivations proved that rectification is beneficial when assessing the strength of low-frequency (delta and alpha bands) common synaptic inputs to the motor neurons, when the duration of the action potentials is short, and when the level of cancellation is relatively low. On the other hand, rectification may distort the estimation of common synaptic inputs when studying higher frequencies (beta and gamma), in a way dependent on the duration of the action potentials, and may introduce peaks in the coherence function that do not correspond to physiological shared inputs. Significance. This study clarifies the conditions when rectifying the surface EMG is appropriate for studying neural connectivity.

  12. Filament Guides for Silicon-Ribbon Growth

    NASA Technical Reports Server (NTRS)

    Morrison, A. D.

    1985-01-01

    Contamination reduced in modified growth system. In Silicon-ribbongrowth apparatus, capillary filament guides are integral parts of crucible, extending from bottom to top of melt. Addition of guides expected to result in better thermal control of growth process and higher silicon purity.

  13. Sodium Spray Would Speed Silicon Production

    NASA Technical Reports Server (NTRS)

    Sancier, K. M.

    1983-01-01

    Production rate of solar-grade silicon in sodium/silicon tetrafluoride reactor increase by spray feed. Liquid-sodium droplet size is controlled by pressure of argon gas and by nozzle design. Baffle helps to prevent reactor opening from becoming clogged by reaction products.

  14. Producing High-Purity Silicon With Sodium

    NASA Technical Reports Server (NTRS)

    Sanjurjo, A.

    1982-01-01

    Simple technique for producing silicon for solar cells employs solid sodium to reduce silicon fluoride. Since solid rather than liquid sodium is used, careful temperature control is unnecessary, and simple feed equipment is used. Technique is energy-efficient, since reaction produces enough heat to sustain itself.

  15. Asymmetric Die Grows Purer Silicon Ribbon

    NASA Technical Reports Server (NTRS)

    Kalejs, J. P.; Chalmers, B.; Surek, T.

    1983-01-01

    Concentration of carbide impurities in silicon ribbon is reduced by growing crystalline ribbon with die one wall higher than other. Height difference controls shape of meniscus at liquid/crystal interface and concentrates silicon carbide impurity near one of broad faces. Opposite face is left with above-average purity. Significantly improves efficiency of solar cells made from ribbon.

  16. Plasmas in saline solutions sustained using rectified ac voltages: polarity and frequency effects on the discharge behaviour

    NASA Astrophysics Data System (ADS)

    Chang, Hung-wen; Hsu, Cheng-che

    2012-06-01

    In this work, three major problems, namely severe electrode damage, poor plasma stability and excess power consumption, arising in ac-driven plasmas in saline solutions are solved using a rectified power source. Diagnostic studies on the effects of power source polarity and frequency on the plasma behaviour are performed. Examination of I-V characteristics and temporally resolved light emission shows that the polarity significantly influences the current amplitude when the plasma exists, while the frequency alters the bubble dynamics, which in turn affects the plasma ignition voltage. When the plasma is driven by a rectified ac power source, the electrode erosion is reduced substantially. With a low frequency, moderate applied voltage and positively rectified ac power source (e.g. 100 Hz and 350 V), a stable plasma is ignited in nearly every power cycle.

  17. Control and expression of -NH2, -SH, -COOH and SiO2 on the surface of silicon carbide quantum dots

    NASA Astrophysics Data System (ADS)

    Mwania, Munuve; Aguirre-Medel, Susana; Kroll, Peter

    2015-03-01

    We present simple protocols for reliably tailoring the surfaces of zinc blende silicon carbide quantum dots (β-SiC QDs). The SiC QDs are synthesized via photo-assisted electrochemical corrosion of bulk powders at different temperatures and time scales. After washing the residual acid and resuspending in H2O, the surfaces of SiC QDs were controllably coated with four different functional groups, specifically -NH2, -SH, and -COOH and -SiO2. We began by covalently attaching primary amines (-NH2) to the QD surface. The amine terminations were then converted to amine/thiolate (-NH2/SH) and amine/carboxylate (-NH2/COOH) functional groups. SiO2 shells around SiC QDs (to create SiC@SiO2nano-structures) were grown using a TEOS-mediated Stöber method. The presence of amine and thiol groups was confirmed by fluoresceamine assay test, X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (FTIR). While a negative fluoresceamine assay test confirmed the replacement of amine groups by thiol groups, the thiolation of the surface was also confirmed through Ellman's assay, XPS and FTIR. The presence of the SiO2 shells was examined using transmission electron microscopy and XPS. Our results open up possibilities to manipulate SiC QDs for various applications.

  18. Synthesis of Silicon Nanocrystals in Microplasma Reactor

    NASA Astrophysics Data System (ADS)

    Nozaki, Tomohiro; Sasaki, Kenji; Ogino, Tomohisa; Asahi, Daisuke; Okazaki, Ken

    Nanocrystalline silicon particles with a grain size of at least less than 10 nm are widely recognized as one of the key materials in optoelectronic devices, electrodes of lithium battery, bio-medical labels. There is also important character that silicon is safe material to the environment and easily gets involved in existing silicon technologies. To date, several synthesis methods such as sputtering, laser ablation, and plasma enhanced chemical vapor deposition (PECVD) based on low-pressure silane chemistry (SiH4) have been developed for precise control of size and density distributions of silicon nanocrystals. We explore the possibility of microplasma technologies for the efficient production of mono-dispersed nanocrystalline silicon particles in a micrometer-scale, continuous-flow plasma reactor operated at atmospheric pressure. Mixtures of argon, hydrogen, and silicon tetrachloride were activated using very high frequency (VHF = 144 MHz) power source in a capillary glass tube with a volume of less than 1 μ-liter. Fundamental plasma parameters of VHF capacitively coupled microplasma were characterized by optical emission spectroscopy, showing electron density of approximately 1015 cm-3 and rotational temperature of 1500 K, respectively. Such high-density non-thermal reactive plasma has a capability of decomposing silicon tetrachloride into atomic silicon to produce supersaturated atomic silicon vapor, followed by gas phase nucleation via three-body collision. The particle synthesis in high-density plasma media is beneficial for promoting nucleation process. In addition, further growth of silicon nuclei was able to be favorably terminated in a short-residence time reactor. Micro Raman scattering spectrum showed that as-deposited particles were mostly amorphous silicon with small fraction of silicon nanocrystals. Transmission electron micrograph confirmed individual silicon nanocrystals of 3-15 nm size. Although those particles were not mono-dispersed, they were well separated and not coagulated.

  19. Silicon Nanocrystal Synthesis in Microplasma Reactor

    NASA Astrophysics Data System (ADS)

    Nozaki, Tomohiro; Sasaki, Kenji; Ogino, Tomohisa; Asahi, Daisuke; Okazaki, Ken

    Nanocrystalline silicon particles with grains smaller than 5 nm are widely recognized as a key material in optoelectronic devices, lithium battery electrodes, and bio-medical labels. Another important characteristic is that silicon is an environmentally safe material that is used in numerous silicon technologies. To date, several synthesis methods such as sputtering, laser ablation, and plasma-enhanced chemical vapor deposition (PECVD) based on low-pressure silane chemistry (SiH4) have been developed for precise control of size and density distributions of silicon nanocrystals. In this study, we explore the possibility of microplasma technologies for efficient production of mono-dispersed nanocrystalline silicon particles on a micrometer-scale, continuous-flow plasma reactor operated at atmospheric pressure. Mixtures of argon, hydrogen, and silicon tetrachloride were activated using a very-high-frequency (144 MHz) power source in a capillary glass tube with volume of less than 1 μl. Fundamental plasma parameters of the microplasma were characterized using optical emission spectroscopy, which respectively indicated electron density of 1015 cm-3, argon excitation temperature of 5000 K, and rotational temperature of 1500 K. Such high-density non-thermal reactive plasma can decompose silicon tetrachloride into atomic silicon to produce supersaturated silicon vapor, followed by gas-phase nucleation via three-body collision: particle synthesis in high-density plasma media is beneficial for promoting nucleation processes. In addition, further growth of silicon nuclei can be terminated in a short-residence-time reactor. Micro-Raman scattering spectra showed that as-deposited particles are mostly amorphous silicon with a small fraction of silicon nanocrystals. Transmission electron micrography confirmed individual 3-15 nm silicon nanocrystals. Although particles were not mono-dispersed, they were well separated and not coagulated.

  20. Long-term stability of neural prosthetic control signals from silicon cortical arrays in rhesus macaque motor cortex

    NASA Astrophysics Data System (ADS)

    Chestek, Cynthia A.; Gilja, Vikash; Nuyujukian, Paul; Foster, Justin D.; Fan, Joline M.; Kaufman, Matthew T.; Churchland, Mark M.; Rivera-Alvidrez, Zuley; Cunningham, John P.; Ryu, Stephen I.; Shenoy, Krishna V.

    2011-08-01

    Cortically-controlled prosthetic systems aim to help disabled patients by translating neural signals from the brain into control signals for guiding prosthetic devices. Recent reports have demonstrated reasonably high levels of performance and control of computer cursors and prosthetic limbs, but to achieve true clinical viability, the long-term operation of these systems must be better understood. In particular, the quality and stability of the electrically-recorded neural signals require further characterization. Here, we quantify action potential changes and offline neural decoder performance over 382 days of recording from four intracortical arrays in three animals. Action potential amplitude decreased by 2.4% per month on average over the course of 9.4, 10.4, and 31.7 months in three animals. During most time periods, decoder performance was not well correlated with action potential amplitude (p > 0.05 for three of four arrays). In two arrays from one animal, action potential amplitude declined by an average of 37% over the first 2 months after implant. However, when using simple threshold-crossing events rather than well-isolated action potentials, no corresponding performance loss was observed during this time using an offline decoder. One of these arrays was effectively used for online prosthetic experiments over the following year. Substantial short-term variations in waveforms were quantified using a wireless system for contiguous recording in one animal, and compared within and between days for all three animals. Overall, this study suggests that action potential amplitude declines more slowly than previously supposed, and performance can be maintained over the course of multiple years when decoding from threshold-crossing events rather than isolated action potentials. This suggests that neural prosthetic systems may provide high performance over multiple years in human clinical trials.

  1. Long-term stability of neural prosthetic control signals from silicon cortical arrays in rhesus macaque motor cortex

    PubMed Central

    Chestek, Cynthia A.; Gilja, Vikash; Nuyujukian, Paul; Foster, Justin D.; Fan, Joline M.; Kaufman, Matthew T.; Churchland, Mark M.; Rivera-Alvidrez, Zuley; Cunningham, John P.; Ryu, Stephen I.; Shenoy, Krishna V.

    2013-01-01

    Cortically-controlled prosthetic systems aim to help disabled patients by translating neural signals from the brain into control signals for guiding prosthetic devices. Recent reports have demonstrated reasonably high levels of performance and control of computer cursors and prosthetic limbs, but to achieve true clinical viability the long-term operation of these systems must be better understood. In particular, the quality and stability of the electrically-recorded neural signals requires further characterization. Here, we quantify action potential changes and offline neural decoder performance over 382 days of recording from 4 intracortical arrays in 3 animals. Action potential amplitude decreased by 2.4% per month on average over the course of 9.4, 10.4, and 31.7 months in 3 animals. During most time periods, decoder performance was not well correlated with action potential amplitude (p > 0.05 for 3 of 4 arrays). In two arrays from one animal, action potential amplitude declined by an average of 37% over the first 2 months after implant. However, when using simple threshold crossing events rather than well isolated action potentials, no corresponding performance loss was observed during this time using an offline decoder. One of these arrays was effectively used for online prosthetic experiments over the following year. Substantial short-term variations in waveforms were quantified using a wireless system for contiguous recording in one animal, and compared within and between days for all three animals. Overall, this study suggests that action potential amplitude declines more slowly than previously supposed, and performance can be maintained over the course of multiple years when decoding from threshold crossing events rather than isolated action potentials. This suggests that neural prosthetic systems may provide high performance over multiple years in human clinical trials. PMID:21775782

  2. Thermal Conductivity of Size-Controlled Bulk Silicon Nanocrystals Using Self-Limiting Oxidation and HF Etching

    NASA Astrophysics Data System (ADS)

    Suzuki, Takayuki; Ohishi, Yuji; Kurosaki, Ken; Muta, Hiroaki; Yamanaka, Shinsuke

    2012-08-01

    We propose a new method of obtaining low thermal conductivity in bulk Si. In this method, which we call “HF-etching nanosize-controlling process for powder” (HNPP), self-limiting oxidation coupled with HF etching is applied to nanopowder Si. The application of HNPP to nanopowder Si reduces the average diameter from 58 to 35 nm. The thermal conductivity is reduced from 25.7 to 13.5 W m-1 K-1 at 300 K. Theoretical calculation including grain boundary transmission and frequency-dependent grain boundary scattering shows that these thermal conductivity reductions can be attributed to phonon scattering at grain boundaries.

  3. Controlled self-assembly and photovoltaic characteristics of porphyrin derivatives on a silicon surface at solid-liquid interfaces.

    PubMed

    Cai, Jinhua; Chen, Haihui; Huang, Jiangen; Wang, Jingxia; Tian, Dongliang; Dong, Huanli; Jiang, Lei

    2014-04-21

    Two meso-tetraphenylporphyrin (H2TPP) derivatives with different central metal ions, namely ZnTPP, CuTPP, were synthesized, and characterized by a series of spectroscopic methods. Their self-assembly behaviors in mixed solvents without surfactant were systematically investigated. The morphology of the thus produced nanoarchitectures could be efficiently controlled. Nanoslices can be manufactured when a volume of cyclohexane is involved, octahedrons can be produced when a mixed solvent of chloroform and isopropanol is employed, while four-leaf clover-shaped structures can be produced with a large volume of methanol injected. The nanostructures have been characterized by electronic absorption, scanning electron microscopy (SEM) and photoelectric conversion techniques. The internal structures of the nanostructures are well described by XRD. The nanostructures exhibit a power conversion under illumination intensity of 2.3 mW cm(-2). The present result appears to represent an effort toward controlling the morphology of self-assembled nanostructures of porphyrin derivatives via synthesis through introduction of metal-ligand and solvent interaction. Nevertheless, the fundamental study will be helpful to understand photoinduced energy/charge transport in an organic interface and this might also serve as promising building blocks for nanoscale power sources for potential application in solar energy technologies and organic electronics and optoelectronics. PMID:24647426

  4. Silicon Wafer Cleaning Using New Liquid Aerosol with Controlled Droplet Velocity and Size by Rotary Atomizer Method

    NASA Astrophysics Data System (ADS)

    Seike, Yoshiyuki; Miyachi, Keiji; Shibata, Tatsuo; Kobayashi, Yoshinori; Kurokawa, Syuhei; Doi, Toshiro

    2010-06-01

    A liquid aerosol, which sprays cleaning liquid with a carrier gas, is widely used for cleaning semiconductor devices. The liquid aerosol using a conventional two-fluid nozzle may cause pattern damage on the wafer. To resolve this problem, we have made a prototype new rotary atomizing two-fluid cleaning nozzle (RAC nozzle), which can control the velocity distribution and size distribution of flying liquid droplets separately. It was confirmed by measuring flying liquid droplets using a shadow Doppler particle analyzer system that the mean volumetric diameter of the droplets could be atomized to 20 µm or less at a rotational speed of the air turbine of 50,000 min-1 and that the mean velocity of the flying liquid droplets could be controlled in the range under 65 m/s independently. It was confirmed in a cleaning experiment using polystyrene latex (PSL) particles on a wafer that particle removal efficiency increased when shaping air pressure increased. Also, the particle removal efficiency was improved with the finer atomization promoted by a higher rotational speed of the air turbine.

  5. Silicon Wafer Cleaning Using New Liquid Aerosol with Controlled Droplet Velocity and Size by Rotary Atomizer Method

    NASA Astrophysics Data System (ADS)

    Yoshiyuki Seike,; Keiji Miyachi,; Tatsuo Shibata,; Yoshinori Kobayashi,; Syuhei Kurokawa,; Toshiro Doi,

    2010-06-01

    A liquid aerosol, which sprays cleaning liquid with a carrier gas, is widely used for cleaning semiconductor devices. The liquid aerosol using a conventional two-fluid nozzle may cause pattern damage on the wafer. To resolve this problem, we have made a prototype new rotary atomizing two-fluid cleaning nozzle (RAC nozzle), which can control the velocity distribution and size distribution of flying liquid droplets separately. It was confirmed by measuring flying liquid droplets using a shadow Doppler particle analyzer system that the mean volumetric diameter of the droplets could be atomized to 20 μm or less at a rotational speed of the air turbine of 50,000 min-1 and that the mean velocity of the flying liquid droplets could be controlled in the range under 65 m/s independently. It was confirmed in a cleaning experiment using polystyrene latex (PSL) particles on a wafer that particle removal efficiency increased when shaping air pressure increased. Also, the particle removal efficiency was improved with the finer atomization promoted by a higher rotational speed of the air turbine.

  6. Multi-ion distributions in the cytoplasmic domain of inward rectifier potassium channels.

    PubMed

    Robertson, J L; Palmer, L G; Roux, B

    2012-08-01

    Inward rectifier potassium (Kir) channels act as cellular diodes, allowing unrestricted flow of potassium (K(+)) into the cell while preventing currents of large magnitude in the outward direction. The rectification mechanism by which this occurs involves a coupling between K(+) and intracellular blockers-magnesium (Mg(2+)) or polyamines-that simultaneously occupy the permeation pathway. In addition to the transmembrane pore, Kirs possess a large cytoplasmic domain (CD) that provides a favorable electronegative environment for cations. Electrophysiological experiments have shown that the CD is a key regulator of both conductance and rectification. In this study, we calculate and compare averaged equilibrium probability densities of K(+) and Cl(-) in open-pore models of the CDs of a weak (Kir1.1-ROMK) and a strong (Kir2.1-IRK) rectifier through explicit-solvent molecular-dynamics simulations in ~1 M KCl. The CD of both channels concentrates K(+) ions greater than threefold inside the cytoplasmic pore while IRK shows an additional K(+) accumulation region near the cytoplasmic entrance. Simulations carried out with Mg(2+) or spermine (SPM(4+)) show that these ions interact with pore-lining residues, shielding the surface charge and reducing K(+) in both channels. The results also show that SPM(4+) behaves differently inside these two channels. Although SPM(4+) remains inside the CD of ROMK, it diffuses around the entire volume of the pore. In contrast, this polyatomic cation finds long-lived conformational states inside the IRK pore, interacting with residues E224, D259, and E299. The strong rectifier CD is also capable of sequestering an additional SPM(4+) at the cytoplasmic entrance near a cluster of negative residues D249, D274, E275, and D276. Although understanding the actual mechanism of rectification blockade will require high-resolution structural information of the blocked state, these simulations provide insight into how sequence variation in the CD can affect the multi-ion distributions that underlie the mechanisms of conduction, rectification affinity, and kinetics. PMID:22947859

  7. Silicon Micromachining

    NASA Astrophysics Data System (ADS)

    Elwenspoek, Miko; Jansen, Henri V.

    2004-08-01

    This comprehensive book provides an overview of the key techniques used in the fabrication of micron-scale structures in silicon. Recent advances in these techniques have made it possible to create a new generation of microsystem devices, such as microsensors, accelerometers, micropumps, and miniature robots. The authors underpin the discussion of each technique with a brief review of the fundamental physical and chemical principles involved. They pay particular attention to methods such as isotropic and anisotropic wet chemical etching, wafer bonding, reactive ion etching, and surface micromachining. There is a special section on bulk micromachining, and the authors also discuss release mechanisms for movable microstructures. The book is a blend of detailed experimental and theoretical material, and will be of great interest to graduate students and researchers in electrical engineering and materials science whose work involves the study of micro-electromechanical systems (MEMS).

  8. Thin silicon solar cells

    SciTech Connect

    Hall, R.B.; Bacon, C.; DiReda, V.; Ford, D.H.; Ingram, A.E.; Cotter, J.; Hughes-Lampros, T.; Rand, J.A.; Ruffins, T.R.; Barnett, A.M.

    1992-12-01

    The silicon-film design achieves high performance by using a dun silicon layer and incorporating light trapping. Optimally designed thin crystalline solar cells (<50 microns thick) have performance advantages over conventional thick devices. The high-performance silicon-film design employs a metallurgical barrier between the low-cost substrate and the thin silicon layer. Light trapping properties of silicon-film on ceramic solar cells are presented and analyzed. Recent advances in process development are described here.

  9. Silicon Web Process Development

    NASA Technical Reports Server (NTRS)

    Duncan, C. S.; Seidensticker, R. G.; Hopkins, R. H.; Mchugh, J. P.; Hill, F. E.; Heimlich, M. E.; Driggers, J. M.

    1978-01-01

    Progress in the development of techniques to grow silicon web at 25 wq cm/min output rate is reported. Feasibility of web growth with simultaneous melt replenishment is discussed. Other factors covered include: (1) tests of aftertrimmers to improve web width; (2) evaluation of growth lid designs to raise speed and output rate; (3) tests of melt replenishment hardware; and (4) investigation of directed gas flow systems to control unwanted oxide deposition in the system and to improve convective cooling of the web. Compatibility with sufficient solar cell performance is emphasized.

  10. Surface rippling by oblique ion incidence during plasma etching of silicon: Experimental demonstration using sheath control plates

    NASA Astrophysics Data System (ADS)

    Nakazaki, Nobuya; Matsumoto, Haruka; Eriguchi, Koji; Ono, Kouichi

    2015-09-01

    In the microfabrication of 3D transistors (e.g. Fin-FET), the sidewall roughness, such as LER and LWR caused by off-normal or oblique ion incidence during plasma etching, is a critical issue to be resolved, which in turn requires a better understanding of the effects of ion incidence angle θi on surface roughening. This paper presents surface roughening and rippling by oblique ion incidence during inductively coupled plasma etching of Si in Cl2, using the experimental setup as in our previous study. The oblique ion incidence was achieved by sheath control plates, which were placed on and electrically connected to the wafer stage. The plates had slits to vary the sheath structure thereon and to extract ions from plasma to samples on the bottom and/or side of the slits. The results indicated that at θi ~ 40° or oblique incidence; ripple structures were formed on surfaces perpendicularly to the direction of ion incidence, on the other hand, at θi ~ 80° or grazing incidence, small ripples or slit like grooves were formed on surfaces parallel to the direction of ion incidence, as predicted in our previous numerical investigations.

  11. Geometrically controlled ratchet effect with collective vortex motion

    NASA Astrophysics Data System (ADS)

    Rouco, V.; Palau, A.; Monton, C.; Del-Valle, N.; Navau, C.; Sanchez, A.; Obradors, X.; Puig, T.

    2015-07-01

    Rectified flux motion arising from the collective effect of many interacting vortices is obtained in a specially designed superconducting device. Ratchet structures with different asymmetric pinning potentials are generated by tuning the size, depth, and distribution of triangular blind-antidots in a high-temperature superconducting film. We experimentally and theoretically demonstrate that the amplitude and sign of the rectified vortex motion can be finely tuned with the pattern geometry. Two different dynamical regimes depending on the nature of vortices initiating the dissipation are identified, which can control the rectified vortex motion.

  12. Effect of guide vanes on the performance of a variable chord self-rectifying air turbine

    NASA Astrophysics Data System (ADS)

    Govardhan, M.; Dhanasekaran, T. S.

    1998-12-01

    Wells turbine is a self rectifying air flow turbine capable of converting pneumatic power of the periodically reversing air stream in Oscillating Water Column into mechanical energy. One of the principal reasons for the low efficiency of the Wells turbine is its lower tangential force compared to its axial force. Guide vanes before and after the rotor suggest a means to improve the tangential force, hence its efficiency. Experimental investigations are carried out on the Wells turbine with a variable chord (VACR) blade rotor fitted with inlet and outlet guide vanes to understand the aerodynamics especially improvement in efficiency and starting characteristics. Numerical simulation has been made to clarify the unsteady characteristics of the turbine with guide vanes. Studies are done at various flow coefficients covering the entire range of flow coefficients over which the turbine is operable. The efficiency, starting characteristics of the Wells turbine has improved when compared with the turbine without guide vanes.

  13. Rectifying properties of ZnO thin films deposited on FTO by electrodeposition technique

    NASA Astrophysics Data System (ADS)

    Lv, Jianguo; Sun, Yue; Zhao, Min; Cao, Li; Xu, Jiayuan; He, Gang; Zhang, Miao; Sun, Zhaoqi

    2016-03-01

    ZnO thin films were successfully grown on fluorine-doped tin oxide glass by electrodeposition technique. The crystal structure, surface morphology and optical properties of the thin films were investigated. The average crystallite size and intensity of A1(LO) mode increase with improving the absolute value of deposition potential. The best preferential orientation along c-axis and the richest oxygen interstitial defects have been observed in the sample deposited at -0.8 V. A heterojunction device consisting of ZnO thin film and n-type fluorine-doped tin oxide was fabricated. The current-voltage (I-V) characteristic of the p-n heterojunction device deposited at -0.8 V shows the best rectifying diode behavior. The p-type conductivity of the ZnO thin film could be attributed to complex defect of unintentional impurity and interstitial oxygen.

  14. Computational Design of Intrinsic Molecular Rectifiers Based on Asymmetric Functionalization of N-Phenylbenzamide.

    PubMed

    Ding, Wendu; Koepf, Matthieu; Koenigsmann, Christopher; Batra, Arunabh; Venkataraman, Latha; Negre, Christian F A; Brudvig, Gary W; Crabtree, Robert H; Schmuttenmaer, Charles A; Batista, Victor S

    2015-12-01

    We report a systematic computational search of molecular frameworks for intrinsic rectification of electron transport. The screening of molecular rectifiers includes 52 molecules and conformers spanning over 9 series of structural motifs. N-Phenylbenzamide is found to be a promising framework with both suitable conductance and rectification properties. A targeted screening performed on 30 additional derivatives and conformers of N-phenylbenzamide yielded enhanced rectification based on asymmetric functionalization. We demonstrate that electron-donating substituent groups that maintain an asymmetric distribution of charge in the dominant transport channel (e.g., HOMO) enhance rectification by raising the channel closer to the Fermi level. These findings are particularly valuable for the design of molecular assemblies that could ensure directionality of electron transport in a wide range of applications, from molecular electronics to catalytic reactions. PMID:26642992

  15. Study of atrial activities for abnormality detection by phase rectified signal averaging technique.

    PubMed

    Maji, U; Pal, S; Mitra, M

    2015-01-01

    Non-invasive detection of Atrial Fibrillation (AF) and Atrial Flutter (AFL) from ECG at the time of their onset can prevent forthcoming dangers for patients. In most of the previous detection algorithms, one of the steps includes filtering of the signal to remove noise and artefacts present in the signal. In this paper, a method of AF and AFL detection is proposed from ECG without the conventional filtering stage. Here Phase Rectified Signal Average (PRSA) technique is used with a novel optimized windowing method to achieve an averaged signal without quasi-periodicities. Both time domain and statistical features are extracted from a novel SQ concatenated section of the signal for non-linear Support Vector Machine (SVM) based classification. The performance of the proposed algorithm is tested with the MIT-BIH Arrhythmia database and good performance parameters are obtained, as indicated in the result section. PMID:26084877

  16. OsKAT2 is the prevailing functional inward rectifier potassium channels in rice guard cell

    PubMed Central

    Hwang, Hyunsik; Yoon, Jin-Young; Cho, Hana; Kim, Beom-Gi

    2013-01-01

    AtKAT1 plays roles as a major channel to uptake K+ in guard cell when stomata open in dicot model plant Arabidopsis. In a recent publication, we isolated 3 KAT-like potassium channels in rice. We expressed them in CHO cell to identify electrophysiological characteristics of the channels. OsKAT2 showed much bigger inwardly rectifying potassium channel activities among them. The histochemical X-glu staining of transgenic rice leaf blades expressing β-glucuronidase fused with OsKAT2 promoter showed that the OsKAT2 is dominantly expressed in rice guard cell. These findings indicate that OsKAT2 may be a functional ortholog of AtKAT1 in rice. Thus this gene will be the prime target for engineering the guard cell movement to improve drought tolerance in monocot plants, including most major crops. PMID:24103920

  17. Delayed rectifier K channels contribute to contrast adaptation in mammalian retinal ganglion cells

    PubMed Central

    Weick, Michael; Demb, Jonathan B.

    2011-01-01

    SUMMARY Retinal ganglion cells adapt by reducing their sensitivity during periods of high contrast. Contrast adaptation in the firing response depends on both presynaptic and intrinsic mechanisms. Here, we investigated intrinsic mechanisms for contrast adaptation in OFF Alpha ganglion cells in the in vitro guinea pig retina. Using either visual stimulation or current injection, we show that brief depolarization evoked spiking and suppressed firing during subsequent depolarization. The suppression could be explained by Na channel inactivation, as shown in salamander cells. However, brief hyperpolarization in the physiological range (5–10 mV) also suppressed firing during subsequent depolarization. This suppression was sensitive selectively to blockers of delayed-rectifier K channels (KDR). Somatic membrane patches showed TEA-sensitive KDR currents with activation near −25 mV and removal of inactivation at voltages negative to Vrest. Brief periods of hyperpolarization apparently remove KDR inactivation and thereby increase the channel pool available to suppress excitability during subsequent depolarization. PMID:21745646

  18. Crowdsourcing Aquatic Resource Data Collection: Exploring Effective Methods to Collect and Rectify Citizen Contributed Data

    NASA Astrophysics Data System (ADS)

    Soderberg, J.

    2011-12-01

    Increasing use of mobile computing and geopositioning technology has provided the environmental sciences with vast new pools of data. Prominent among the gathering methods which produce this data is "crowdsourcing", in which citizen scientists volunteer data. Environmental data collected by crowdsourcing may need to be rectified prior to use by the scientific community. Using mobile applications to educate the crowd, support for the targeted environmental data desired, coupled with thoughtful design of mobile applications can potentially aid the process of rectification. This presentation will outline the use of crowdsourced data, cohort groups and design options for mobile applications that can be used to collect aquatic resource information. If rectification challenges can be overcome, the collective power of the crowd can be harnessed to gather standards-based geographic data, information about environmental conditions, and detailed biological data about aquatic resources. Key Words: Crowdsource, Citizen Scientist, Volunteer Data, Geopositioning Aquatic Resource Geographic Data Author Jon Eric Soderberg

  19. Pacemaker Created in Human Ventricle by Depressing Inward-Rectifier K+ Current: A Simulation Study

    PubMed Central

    Zhang, Yue; Li, Qince; Zhang, Henggui

    2016-01-01

    Cardiac conduction disorders are common diseases which cause slow heart rate and syncope. The best way to treat these diseases by now is to implant electronic pacemakers, which, yet, have many disadvantages, such as the limited battery life and infection. Biopacemaker has been expected to replace the electronic devices. Automatic ventricular myocytes (VMs) could show pacemaker activity, which was induced by depressing inward-rectifier K+ current (IK1). In this study, a 2D model of human biopacemaker was created from the ventricular endocardial myocytes. We examined the stability of the created biopacemaker and investigated its driving capability by finding the suitable size and spatial distribution of the pacemaker for robust pacing and driving the surrounding quiescent cardiomyocytes. Our results suggest that the rhythm of the pacemaker is similar to that of the single cell at final stable state. The driving force of the biopacemaker is closely related to the pattern of spatial distribution of the pacemaker. PMID:26998484

  20. Bipolar resistive switching with self-rectifying effects in Al/ZnO/Si structure

    NASA Astrophysics Data System (ADS)

    Chen, C.; Pan, F.; Wang, Z. S.; Yang, J.; Zeng, F.

    2012-01-01

    We report the electrical characteristics of room-temperature-fabricated Al/ZnO/Si memory devices. Stable and reproducible clockwise bipolar resistive switching phenomena with self-rectifying effects in the low resistance state were observed in this complementary metal oxide semiconductor compatible memory structure. The current-voltage curve in different temperatures and the corresponding Arrhenius plot confirm the semiconducting conduction behavior of both the high resistance state and the low resistance state. The conduction mechanisms are explained by the Poole-Frenkel emission and space-charge-limited conduction mechanisms for the high resistance state and the low resistance state, respectively. It is proposed that the resistive switching originates from the formation and dissolution of the AlOx barrier layer which are induced by the migration of the oxygen ions.

  1. Rectifying performance and negative differential resistance behavior in graphite-chain-nanoribbon junctions

    NASA Astrophysics Data System (ADS)

    Qiu, Ming; Liew, K. M.

    2013-03-01

    Electronic transport properties of graphite-nanoribbon conjunctions bridged by carbon atomic chains have been investigated. The first-principles calculations show that their I-V characteristics display odd-even effects. Specifically, current in odd-numbered chains is carried by resonances originating from the hybridization of the surface of the graphite electrode, chain and nanoribbon states, while even-numbered chains are mediated by tunneling between the graphite electrode and chain states. The rectifying performance in our models was found to be a result of asymmetric distortions of conducting resonances of the graphite electrode and chain states. It was also found that odd-numbered chains exhibit NDR behaviors caused by depressed chain states.

  2. Multiple PIP2 binding sites in Kir2.1 inwardly rectifying potassium channels.

    PubMed

    Soom, M; Schönherr, R; Kubo, Y; Kirsch, C; Klinger, R; Heinemann, S H

    2001-02-01

    Inwardly rectifying potassium channels require binding of phosphatidylinositol-4,5-bisphosphate (PIP2) for channel activity. Three independent sites (aa 175-206, aa 207-246, aa 324-365) were located in the C-terminal domain of Kir2.1 channels by assaying the binding of overlapping fragments to PIP2 containing liposomes. Mutations in the first site, which abolished channel activity, reduced PIP2 binding of this fragment but not of the complete C-terminus. Point mutations in the third site also reduced both, channel activity and PIP2 binding of this segment. The relevance of the third PIP2 binding site provides a basis for the understanding of constitutively active Kir2 channels. PMID:11172809

  3. Pacemaker Created in Human Ventricle by Depressing Inward-Rectifier K(+) Current: A Simulation Study.

    PubMed

    Zhang, Yue; Wang, Kuanquan; Li, Qince; Zhang, Henggui

    2016-01-01

    Cardiac conduction disorders are common diseases which cause slow heart rate and syncope. The best way to treat these diseases by now is to implant electronic pacemakers, which, yet, have many disadvantages, such as the limited battery life and infection. Biopacemaker has been expected to replace the electronic devices. Automatic ventricular myocytes (VMs) could show pacemaker activity, which was induced by depressing inward-rectifier K(+) current (I K1). In this study, a 2D model of human biopacemaker was created from the ventricular endocardial myocytes. We examined the stability of the created biopacemaker and investigated its driving capability by finding the suitable size and spatial distribution of the pacemaker for robust pacing and driving the surrounding quiescent cardiomyocytes. Our results suggest that the rhythm of the pacemaker is similar to that of the single cell at final stable state. The driving force of the biopacemaker is closely related to the pattern of spatial distribution of the pacemaker. PMID:26998484

  4. Negative differential resistance and rectifying performance induced by doped graphene nanoribbons p-n device

    NASA Astrophysics Data System (ADS)

    Zhou, Yuhong; Qiu, Nianxiang; Li, Runwei; Guo, Zhansheng; Zhang, Jian; Fang, Junfeng; Huang, Aisheng; He, Jian; Zha, Xianhu; Luo, Kan; Yin, Jingshuo; Li, Qiuwu; Bai, Xiaojing; Huang, Qing; Du, Shiyu

    2016-03-01

    Employing nonequilibrium Green's Functions in combination with density functional theory, the electronic transport properties of armchair graphene nanoribbon (GNR) devices with various widths are investigated in this work. In the adopted model, two semi-infinite graphene electrodes are periodically doped with boron or nitrogen atoms. Our calculations reveal that these devices have a striking nonlinear feature and show notable negative differential resistance (NDR). The results also indicate the diode-like properties are reserved and the rectification ratios are high. It is found the electronic transport properties are strongly dependent on the width of doped nanoribbons and the positions of dopants and three distinct families are elucidated for the current armchair GNR devices. The NDR as well as rectifying properties can be well explained by the variation of transmission spectra and the relative shift of discrete energy states with applied bias voltage. These findings suggest that the doped armchair GNR is a promising candidate for the next generation nanoscale device.

  5. Docetaxel modulates the delayed rectifier potassium current (IK) and ATP-sensitive potassium current (IKATP) in human breast cancer cells.

    PubMed

    Sun, Tao; Song, Zhi-Guo; Jiang, Da-Qing; Nie, Hong-Guang; Han, Dong-Yun

    2015-04-01

    Ion channel expression and activity may be affected during tumor development and cancer growth. Activation of potassium (K(+)) channels in human breast cancer cells is reported to be involved in cell cycle progression. In this study, we investigated the effects of docetaxel on the delayed rectifier potassium current (I K) and the ATP-sensitive potassium current (I KATP) in two human breast cancer cell lines, MCF-7 and MDA-MB-435S, using the whole-cell patch-clamp technique. Our results show that docetaxel inhibited the I K and I KATP in both cell lines in a dose-dependent manner. Compared with the control at a potential of +60 mV, treatment with docetaxel at doses of 0.1, 1, 5, and 10 µM significantly decreased the I K in MCF-7 cells by 16.1 ± 3.5, 30.2 ± 5.2, 42.5 ± 4.3, and 46.4 ± 9% (n = 5, P < 0.05), respectively and also decreased the I KATP at +50 mV. Similar results were observed in MDA-MB-435S cells. The G-V curves showed no significant changes after treatment of either MCF-7 or MDA-MB-435S cells with 10 μM docetaxel. The datas indicate that the possible mechanisms of I K and I KATP inhibition by docetaxel may be responsible for its effect on the proliferation of human breast cancer cells. PMID:25421218

  6. Reduced volume-regulated outwardly rectifying anion channel activity in ventricular myocyte of type 1 diabetic mice.

    PubMed

    Yamamoto, Shintaro; Ichishima, Kunihiko; Ehara, Tsuguhisa

    2009-03-01

    The currents through the volume-regulated outwardly rectifying anion channel (VRAC) were measured in single ventricular myocytes obtained from streptozotocin (STZ)-induced diabetic mice, using whole-cell voltage-clamp method. In myocytes from STZ-diabetic mice, the density of VRAC current induced by hypotonic perfusion was markedly reduced, compared with that in the cells form normal control mice. Video-image analysis showed that the regulatory volume decrease (RVD), which was seen in normal cells after osmotic swelling, was almost lost in myocytes from STZ-diabetic mice. Some mice were pretreated with 3-O-methylglucose before STZ injection, to prevent the STZ's beta cell toxicity. In the myocytes obtained from such mice, the magnitude of VRAC current and the degree of RVD seen during hypotonic challenge were almost normal. Incubation of the myocytes from STZ-diabetic mice with insulin reversed the attenuation of VRAC current. These findings suggested that the STZ-induced chronic insulin-deficiency was an important causal factor for the attenuation of VRAC current. Intracellular loading of the STZ-diabetic myocytes with phosphatidylinositol 3,4,5-trisphosphate (PIP3), but not phosphatidylinositol 4,5-bisphosphate (PIP2), also reversed the attenuation of VRAC current. Furthermore, treatment of the normal cells with wortmannin, a phosphatidylinositol 3-kinase (PI3K) inhibitor, suppressed the development of VRAC current. We postulate that an impairment PI3K-PIP3 pathway, which may be insulin-dependent, is responsible for the attenuation of VRAC currents in STZ-diabetic myocytes. PMID:19340548

  7. Characterization and control of crystal nucleation in amorphous electron beam evaporated silicon for thin film solar cells

    SciTech Connect

    Sontheimer, Tobias; Scherf, Simone; Klimm, Carola; Becker, Christiane; Rech, Bernd

    2011-09-15

    The kinetics of crystal nucleation in high-rate electron beam evaporated amorphous Si for polycrystalline thin film solar cells was systematically studied on SiN and selected ZnO:Al-coated glass substrates with dissimilar surface topographies by employing Raman spectroscopy, transmission electron microscopy, and optical microscopy. The influence of the surface topography of the substrate and the disorder of the deposited amorphous Si could be correlated to the respective characteristics of the transient and steady state regime of the nucleation rate. The steady state nucleation rate I{sub ss}, its corresponding activation energy E{sub Iss}, and consequently the size of the grains in the crystallized Si were found to be governed by the interplay between the surface roughness and the deposition temperature. The steady state nucleation rate I{sub ss} increased gradually upon increasing the substrate roughness, while lowering the deposition temperature of the amorphous Si on rough textures resulted in a decline of I{sub ss}. The time-lag {tau}, which represents a distinctive parameter for the transient regime, was only slightly affected by the substrate topography. The deposition temperature, however, had a significant influence on {tau}, with {tau} increasing by a factor of 8 upon lowering the deposition temperature from 300 to 200 deg. C for all substrate topographies. These characteristics could be correlated with the increasing structural disorder of the deposited a-Si upon decreasing the deposition temperature. Based on this analysis, we could determine design rules for the controlled preparation of large-grained poly-Si in minimized processing time on any of the used substrate types by individually adjusting the deposition temperature and implementing nucleation layers.

  8. Passivation of InGaAs(001)-(2 × 4) by Self-Limiting Chemical Vapor Deposition of a Silicon Hydride Control Layer.

    PubMed

    Edmonds, Mary; Kent, Tyler; Chagarov, Evgueni; Sardashti, Kasra; Droopad, Ravi; Chang, Mei; Kachian, Jessica; Park, Jun Hong; Kummel, Andrew

    2015-07-01

    A saturated Si-Hx seed layer for gate oxide or contact conductor ALD has been deposited via two separate self-limiting and saturating CVD processes on InGaAs(001)-(2 × 4) at substrate temperatures of 250 and 350 °C. For the first self-limiting process, a single silicon precursor, Si3H8, was dosed at a substrate temperature of 250 °C, and XPS results show the deposited silicon hydride layer saturated at about 4 monolayers of silicon coverage with hydrogen termination. STS results show the surface Fermi level remains unpinned following the deposition of the saturated silicon hydride layer, indicating the InGaAs surface dangling bonds are electrically passivated by Si-Hx. For the second self-limiting process, Si2Cl6 was dosed at a substrate temperature of 350 °C, and XPS results show the deposited silicon chloride layer saturated at about 2.5 monolayers of silicon coverage with chlorine termination. Atomic hydrogen produced by a thermal gas cracker was subsequently dosed at 350 °C to remove the Si-Cl termination by replacing with Si-H termination as confirmed by XPS, and STS results confirm the saturated Si-Hx bilayer leaves the InGaAs(001)-(2 × 4) surface Fermi level unpinned. Density function theory modeling of silicon hydride surface passivation shows an Si-Hx monolayer can remove all the dangling bonds and leave a charge balanced surface on InGaAs. PMID:26070022

  9. Mechanisms rectifying the annual mean response of tropical Atlantic rainfall to precessional forcing

    NASA Astrophysics Data System (ADS)

    Tigchelaar, Michelle; Timmermann, Axel

    2015-09-01

    Numerous reconstructions of tropical hydroclimate in the Pleistocene display substantial variability on precessional timescales. Precessionally-induced insolation variations, with a mean period of {˜ }21{,}000 years, affect the strength of the seasonal cycle, but not annual mean insolation. The existence of variations in annual mean climate on precessional timescales therefore hints at the existence of nonlinear mechanisms that rectify the zero annual mean forcing into a non-zero annual mean response. The aim of this study is to identify these nonlinear rectification mechanisms. The traditional view of precessionally-forced precipitation changes is that tropical precipitation increases with summer insolation. By comparing two simulations with an earth system model (CESM1.0.3) we find that this paradigm is true for continental but not for oceanic changes in precipitation. Focusing on the Atlantic intertropical convergence zone (ITCZ), we find that the continental temperature and precipitation response to precessional forcing are key rectifiers of annual mean precipitation over the ocean. A boundary layer response to temperature changes over northern Africa affects the meridional position of the ITCZ over the North Atlantic in boreal spring and summer, but not in fall and winter. Over the equatorial and South Atlantic, the intensity of precipitation is strongly impacted by diabatic forcing from the continents through an adjustment of the full troposphere. Although the top of atmosphere insolation forcing is seasonally symmetric, continental precipitation changes are largest in boreal summer, thus skewing the annual mean response. These results show that it is important to take into account the seasonality of climatic forcings, even when studying annual mean climate change.

  10. Inward rectifier potassium conductance regulates membrane potential of canine colonic smooth muscle.

    PubMed

    Flynn, E R; McManus, C A; Bradley, K K; Koh, S D; Hegarty, T M; Horowitz, B; Sanders, K M

    1999-07-01

    1. The membrane potential of gastrointestinal smooth muscles determines the open probability of ion channels involved in rhythmic electrical activity. The role of Ba2+-sensitive K+ conductances in the maintenance of membrane potential was examined in canine proximal colon circular muscle. 2. Application of Ba2+ (1-100 microM) to strips of tunica muscularis produced depolarization of cells along the submucosal surface of the circular muscle layer. Significantly higher concentrations of Ba2+ were needed to depolarize preparations from which the submucosal and myenteric pacemaker regions were removed. 3. Elevation of extracellular [K+]o (from 5.9 to 12 mM) brought membrane potentials closer to EK (the Nernst potential for K+ ions), suggesting activation of a K+ conductance. This occurred at potentials much more negative than the activation range for delayed rectifier channels (Kv). 4. Forskolin (1 microM) caused hyperpolarization and a leftward shift in the dose-response relationship for Ba2+, suggesting that forskolin may activate a Ba2+-sensitive conductance. 5. Patch-clamp recordings from interstitial cells of Cajal (ICC) revealed the presence of a Ba2+-sensitive inward rectifier potassium conductance. Far less of this conductance was present in smooth muscle cells. 6. Kir2.1 was expressed in the circular muscle layer of the canine proximal colon, duodenum, jejunum and ileum. Kir2.1 mRNA was expressed in greater abundance along the submucosal surface of the circular muscle layer in the colon. 7. These results demonstrate that ICC express a Ba2+-sensitive conductance (possibly encoded by Kir2.1). This conductance contributes to the generation and maintenance of negative membrane potentials between slow waves. PMID:10373706

  11. Buried oxide layer in silicon

    DOEpatents

    Sadana, Devendra Kumar; Holland, Orin Wayne

    2001-01-01

    A process for forming Silicon-On-Insulator is described incorporating the steps of ion implantation of oxygen into a silicon substrate at elevated temperature, ion implanting oxygen at a temperature below 200.degree. C. at a lower dose to form an amorphous silicon layer, and annealing steps to form a mixture of defective single crystal silicon and polycrystalline silicon or polycrystalline silicon alone and then silicon oxide from the amorphous silicon layer to form a continuous silicon oxide layer below the surface of the silicon substrate to provide an isolated superficial layer of silicon. The invention overcomes the problem of buried isolated islands of silicon oxide forming a discontinuous buried oxide layer.

  12. Colloidal characterization of silicon nitride and silicon carbide

    NASA Technical Reports Server (NTRS)

    Feke, Donald L.

    1986-01-01

    The colloidal behavior of aqueous ceramic slips strongly affects the forming and sintering behavior and the ultimate mechanical strength of the final ceramic product. The colloidal behavior of these materials, which is dominated by electrical interactions between the particles, is complex due to the strong interaction of the solids with the processing fluids. A surface titration methodology, modified to account for this interaction, was developed and used to provide fundamental insights into the interfacial chemistry of these systems. Various powder pretreatment strategies were explored to differentiate between true surface chemistry and artifacts due to exposure history. The colloidal behavior of both silicon nitride and carbide is dominated by silanol groups on the powder surfaces. However, the colloid chemistry of silicon nitride is apparently influenced by an additional amine group. With the proper powder treatments, silicon nitride and carbide powder can be made to appear colloidally equivalent. The impact of these results on processing control will be discussed.

  13. Perceived Harm of Online Drug-Encouraging Messages: Third-Person Effect and Adolescents' Support for Rectifying Measures

    ERIC Educational Resources Information Center

    Leung, Wan Chi; Lo, Ven-Hwei

    2015-01-01

    This study examines third-person perceptions (TPP) of two types of online messages--antisocial messages that encourage drug abuse and prosocial messages in the youth anti-drug campaign--and their relationship with support for three types of rectifying measures: restrictive, corrective, and promotional. A survey of 778 secondary school students

  14. Perceived Harm of Online Drug-Encouraging Messages: Third-Person Effect and Adolescents' Support for Rectifying Measures

    ERIC Educational Resources Information Center

    Leung, Wan Chi; Lo, Ven-Hwei

    2015-01-01

    This study examines third-person perceptions (TPP) of two types of online messages--antisocial messages that encourage drug abuse and prosocial messages in the youth anti-drug campaign--and their relationship with support for three types of rectifying measures: restrictive, corrective, and promotional. A survey of 778 secondary school students…

  15. A transparent diode with high rectifying ratio using amorphous indium-gallium-zinc oxide/SiNx coupled junction

    NASA Astrophysics Data System (ADS)

    Choi, Myung-Jea; Kim, Myeong-Ho; Choi, Duck-Kyun

    2015-08-01

    We introduce a transparent diode that shows both high rectifying ratio and low leakage current at process temperature below 250 °C. This device is clearly distinguished from all previous transparent diodes in that the rectifying behavior results from the junction between a semiconductor (amorphous indium-gallium-zinc oxide (a-IGZO)) and insulator (SiNx). We systematically study the properties of each junction within the device structure and demonstrate that the a-IGZO/SiNx junction is the source of the outstanding rectification. The electrical characteristics of this transparent diode are: 2.8 A/cm2 on-current density measured at -7 V; lower than 7.3 × 10-9 A/cm2 off-current density; 2.53 ideality factor; and high rectifying ratio of 108-109. Furthermore, the diode structure has a transmittance of over 80% across the visible light range. The operating principle of the indium-tin oxide (ITO)/a-IGZO/SiNx/ITO device was examined with an aid of the energy band diagram and we propose a preliminary model for the rectifying behavior. Finally, we suggest further directions for research on this transparent diode.

  16. A Voltage Controlled Oscillator for a Phase-Locked Loop Frequency Synthesizer in a Silicon-on-Sapphire Process

    SciTech Connect

    Garrison, Sean

    2009-05-21

    Engineers from a government-owned engineering and manufacturing facility were contracted by government-owned research laboratory to design and build an S-band telemetry transmitter using Radio Frequency Integrated Circuit (RFIC) technology packaged in a Low-Temperature Co-fired Ceramic (LTCC) Multi-Chip Module. The integrated circuit technology chosen for the Phase-Locked Loop Frequency Synthesizer portion of the telemetry transmitter was a 0.25 um CMOS process that utilizes a sapphire substrate and is fabricated by Peregrine Semiconductor corporation. This thesis work details the design of the Voltage Controlled Oscillator (VCO) portion of the PLL frequency synthesizer and constitutes an fully integrated VCO core circuit and a high-isolation buffer amplifier. The high-isolation buffer amplifier was designed to provide 16 dB of gain for 2200-3495 MHz as well as 60 dB of isolation for the oscillator core to provide immunity to frequency pulling due to RF load mismatch. Actual measurements of the amplifier gain and isolation showed the gain was approximately 5 dB lower than the simulated gain when all bond-wire and test substrate parasitics were taken into account. The isolation measurements were shown to be 28 dB at the high end of the frequency band but the measurement was more than likely compromised due to the aforementioned bond-wire and test substrate parasitics. The S-band oscillator discussed in this work was designed to operate over a frequency range of 2200 to 2300 MHz with a minimum output power of 0 dBm with a phase-noise of -92 dBc/Hz at a 100 kHz offset from the carrier. The tuning range was measured to be from 2215 MHz to 2330 MHz with a minimum output power of -7 dBm over the measured frequency range. A phase-noise of -90 dBc was measured at a 100 kHz offset from the carrier.

  17. TrkB Activation by Brain-derived Neurotrophic Factor Inhibits the G Protein-gated Inward Rectifier Kir3 by Tyrosine Phosphorylation of the Channel*

    PubMed Central

    Rogalski, Sherri L.; Appleyard, Suzanne M.; Pattillo, Aaron; Terman, Gregory W.; Chavkin, Charles

    2005-01-01

    G protein-activated inwardly rectifying potassium channels (Kir3) are widely expressed throughout the brain, and regulation of their activity modifies neuronal excitability and synaptic transmission. In this study, we show that the neurotrophin brain-derived neurotrophic factor (BDNF), through activation of TrkB receptors, strongly inhibited the basal activity of Kir3. This inhibition was subunit dependent as functional homomeric channels of either Kir3.1 or Kir3.4 were significantly inhibited, whereas homomeric channels composed of Kir3.2 were insensitive. The general tyrosine kinase inhibitors genistein, Gö 6976, and K252a but not the serine/threonine kinase inhibitor staurosporine blocked the BDNF-induced inhibition of the channel. BDNF was also found to directly stimulate channel phosphorylation because Kir3.1 immunoprecipitated from BDNF-stimulated cells showed enhanced labeling by anti-phosphotyrosine-specific antibodies. The BDNF effect required specific tyrosine residues in the amino terminus of Kir3.1 and Kir3.4 channels. Mutations of either Tyr-12, Tyr-67, or both in Kir3.1 or mutation of either Tyr-32, Tyr-53, or both of Kir3.4 channels to phenylalanine significantly blocked the BDNF-induced inhibition. The insensitive Kir3.2 was made sensitive to BDNF by adding a tyrosine (D41Y) and a lysine (P32K) upstream to generate a phosphorylation site motif analogous to that present in Kir3.4. These results suggest that neurotrophin activation of TrkB receptors may physiologically control neuronal excitability by direct tyrosine phosphorylation of the Kir3.1 and Kir3.4 subunits of G protein-gated inwardly rectifying potassium channels. PMID:10833508

  18. Localization and role of inward rectifier K(+) channels in Malpighian tubules of the yellow fever mosquito Aedes aegypti.

    PubMed

    Piermarini, Peter M; Dunemann, Sonja M; Rouhier, Matthew F; Calkins, Travis L; Raphemot, Rene; Denton, Jerod S; Hine, Rebecca M; Beyenbach, Klaus W

    2015-12-01

    Malpighian tubules of adult female yellow fever mosquitoes Aedes aegypti express three inward rectifier K(+) (Kir) channel subunits: AeKir1, AeKir2B and AeKir3. Here we 1) elucidate the cellular and membrane localization of these three channels in the Malpighian tubules, and 2) characterize the effects of small molecule inhibitors of AeKir1 and AeKir2B channels (VU compounds) on the transepithelial secretion of fluid and electrolytes and the electrophysiology of isolated Malpighian tubules. Using subunit-specific antibodies, we found that AeKir1 and AeKir2B localize exclusively to the basolateral membranes of stellate cells and principal cells, respectively; AeKir3 localizes within intracellular compartments of both principal and stellate cells. In isolated tubules bathed in a Ringer solution containing 34 mM K(+), the peritubular application of VU590 (10 μM), a selective inhibitor of AeKir1, inhibited transepithelial fluid secretion 120 min later. The inhibition brings rates of transepithelial KCl and fluid secretion to 54% of the control without a change in transepithelial NaCl secretion. VU590 had no effect on the basolateral membrane voltage (Vbl) of principal cells, but it significantly reduced the cell input conductance (gin) to values 63% of the control within ∼90 min. In contrast, the peritubular application of VU625 (10 μM), an inhibitor of both AeKir1 and AeKir2B, started to inhibit transepithelial fluid secretion as early as 60 min later. At 120 min after treatment, VU625 was more efficacious than VU590, inhibiting transepithelial KCl and fluid secretion to ∼35% of the control without a change in transepithelial NaCl secretion. Moreover, VU625 caused the Vbl and gin of principal cells to respectively drop to values 62% and 56% of the control values within only ∼30 min. Comparing the effects of VU590 with those of VU625 allowed us to estimate that AeKir1 and AeKir2B respectively contribute to 46% and 20% of the transepithelial K(+) secretion when the tubules are bathed in a Ringer solution containing 34 mM K(+). Thus, we uncover an important role of AeKir1 and stellate cells in transepithelial K(+) transport under conditions of peritubular K(+) challenge. The physiological role of AeKir3 in intracellular membranes of both stellate and principal cells remains to be determined. PMID:26079629

  19. Purified silicon production system

    DOEpatents

    Wang, Tihu; Ciszek, Theodore F.

    2004-03-30

    Method and apparatus for producing purified bulk silicon from highly impure metallurgical-grade silicon source material at atmospheric pressure. Method involves: (1) initially reacting iodine and metallurgical-grade silicon to create silicon tetraiodide and impurity iodide byproducts in a cold-wall reactor chamber; (2) isolating silicon tetraiodide from the impurity iodide byproducts and purifying it by distillation in a distillation chamber; and (3) transferring the purified silicon tetraiodide back to the cold-wall reactor chamber, reacting it with additional iodine and metallurgical-grade silicon to produce silicon diiodide and depositing the silicon diiodide onto a substrate within the cold-wall reactor chamber. The two chambers are at atmospheric pressure and the system is open to allow the introduction of additional source material and to remove and replace finished substrates.

  20. Speed control for synchronous motors

    NASA Technical Reports Server (NTRS)

    Packard, H.; Schott, J.

    1981-01-01

    Feedback circuit controls fluctuations in speed of synchronous ac motor. Voltage proportional to phase angle is developed by phase detector, rectified, amplified, compared to threshold, and reapplied positively or negatively to motor excitation circuit. Speed control reduces wow and flutter of audio turntables and tape recorders, and enhances hunting in gyroscope motors.

  1. Photoinduced Charge Separation in Molecular Silicon.

    PubMed

    Zhou, Jiawang; Surampudi, Sravan K; Bragg, Arthur E; Klausen, Rebekka S

    2016-04-25

    Interest in molecular silicon semiconductors arises from the properties shared with bulk silicon like earth abundance and the unique architectures accessible from a structure distinctly different than rigid π-conjugated organic semiconductors. We report ultrafast spectroscopic evidence for direct, photoinduced charge separation in molecular silicon semiconductors that supports the viability of molecular silicon as donor materials in optoelectronic devices. The materials in this study are σ-π hybrids, in which electron-deficient aromatic acceptors flank a σ-conjugated silicon chain. Transient absorption and femtosecond-stimulated Raman spectroscopy (FSRS) techniques revealed signatures consistent with direct, optical charge transfer from the silane chain to the acceptor; these signatures were only observed by probing excited-state structure. Our findings suggest new opportunities for controlling charge separation in molecular electronics. PMID:26919126

  2. Silicon quantum dots for biological applications.

    PubMed

    Chinnathambi, Shanmugavel; Chen, Song; Ganesan, Singaravelu; Hanagata, Nobutaka

    2014-01-01

    Semiconductor nanoparticles (or quantum dots, QDs) exhibit unique optical and electronic properties such as size-controlled fluorescence, high quantum yields, and stability against photobleaching. These properties allow QDs to be used as optical labels for multiplexed imaging and in drug delivery detection systems. Luminescent silicon QDs and surface-modified silicon QDs have also been developed as potential minimally toxic fluorescent probes for bioapplications. Silicon, a well-known power electronic semiconductor material, is considered an extremely biocompatible material, in particular with respect to blood. This review article summarizes existing knowledge related to and recent research progress made in the methods for synthesizing silicon QDs, as well as their optical properties and surface-modification processes. In addition, drug delivery systems and in vitro and in vivo imaging applications that use silicon QDs are also discussed. PMID:23949967

  3. Dual Mode Inverter Control Test Verification

    SciTech Connect

    Bailey, J.M.

    2001-04-25

    Permanent Magnet Motors with either sinusoidal back emf (permanent magnet synchronous motor [PMSM]) or trapezoidal back emf (brushless dc motor [BDCM]) do not have the ability to alter the air gap flux density (field weakening). Since the back emf increases with speed, the system must be designed to operate with the voltage obtained at its highest speed. Oak Ridge National Laboratory's (ORNL) Power Electronics and Electric Machinery Research Center (PEEMRC) has developed a dual mode inverter controller (DMIC) that overcomes this disadvantage. This report summarizes the results of tests to verify its operation. The standard PEEMRC 75 kW hard-switched inverter was modified to implement the field weakening procedure (silicon controlled rectifier enabled phase advance). A 49.5 hp motor rated at 2800 rpm was derated to a base of 400 rpm and 7.5 hp. The load developed by a Kahn Industries hydraulic dynamometer, was measured with a MCRT9-02TS Himmelstein and Company torque meter. At the base conditions a current of 212 amperes produced the 7.5 hp. Tests were run at 400, 1215, and 2424 rpm. In each run, the current was no greater than 214 amperes. The horsepower obtained in the three runs were 7.5, 9.3, and 8.12. These results verified the basic operation of the DMIC in producing a Constant Power Speed Ratios (CPSR) of six.

  4. Fracture of silicon wafers

    NASA Astrophysics Data System (ADS)

    McLaughlin, J. C.; Willoughby, A. F. W.

    1987-11-01

    In spite of the increasing use of silicon in applications where mechanical stresses are deliberately applied to the material, such as in transducers, and the fatal nature of cracking in silicon devices, there is very limited characterisation and understanding of the fracture behaviour of silicon wafers at room temperature. This understanding is of increasing importance with the use of larger diameter wafers in modern technology. This paper examines the fracture strength of a wide range of silicon material both as-grown and after processing. The wafers tested were from crystals grwon by float-zone and Czochralski techniques and the effects of oxidation, ion-implantation and annealing in various environments have been studied. The technique used to measure the fracture stress involved simply supporting the wafer on an aluminium ring concentric to the load axis. The load was gradually increased until the wafer fractured. This method was chosen to avoid edge effects, and has proved to have adequate reproducibility. Typical values of the fracture stress obtained by this method, for different crystals, vary between 2 and 3.5 GPa. In the first part of the study, the role of the surface on the fracture behaviour has been investigated in detail. While the surface perfection of the tensile surface has a major effect on the fracture stress (as shown in previous studies), some of the results were found to be sensitive to the compressive surface as well. In the case where the results are sensitive to the compressive surface finish the fracture stress rose from 3.7 to 8.8 GPa as the surface finish was improved while in the cases where they were not sensitive the fracture stress remained at about 3.5-4.6 GPa. Only in the float-zone material were fracture stresses approaching 8.8 GPa observed. At this level of fracture stress, the behaviour is believed to be sensitive to surface defects less than 0.01 ?m in size. These results can be analyzed in terms of surface controlled defects under conditions where surface defects are dominant and bulk controlled defects where these defects are dominant. In this manner bulk effects can be isolated from surface ones. This gives the opportunity to study the effects of specific defects on the fracture stress and the results in this paper are discussed in terms of the role of surface and internal defects on the fracture stress.

  5. Graphene as transparent and current spreading electrode in silicon solar cell

    SciTech Connect

    Behura, Sanjay K. Nayak, Sasmita; Jani, Omkar; Mahala, Pramila

    2014-11-15

    Fabricated bi-layer graphene (BLG) has been studied as transparent and current spreading electrode (TCSE) for silicon solar cell, using TCAD-Silvaco 2D simulation. We have carried out comparative study using both Ag grids and BLG as current spreading electrode (CSE) and TCSE, respectively. Our study reveals that BLG based solar cell shows better efficiency of 24.85% than Ag-based cell (21.44%), in all of the critical aspects, including generation rate, recombination rate, electric field, potential and quantum efficiency. Further BLG based cell exhibits pronounce rectifying behavior, low saturation current, and good turn-on voltage while studying in dark.

  6. Axial p-n junctions realized in silicon nanowires by ion implantation.

    PubMed

    Hoffmann, S; Bauer, J; Ronning, C; Stelzner, Th; Michler, J; Ballif, C; Sivakov, V; Christiansen, S H

    2009-04-01

    The electrical properties of vertically aligned silicon nanowires doped by ion implantation are studied in this paper by a combination of electron beam-induced current imaging and two terminal current-voltage measurements. By varying the implantation parameters in several process steps, uniform p- and n-doping profiles as well as p-n junctions along the nanowire axis are realized. The effective doping is demonstrated by electron beam-induced current imaging on single nanowires, and current-voltage measurements show their well-defined rectifying behavior. PMID:19256535

  7. Distribution of neurones expressing inwardly rectifying and Ca(2+)-permeable AMPA receptors in rat hippocampal slices.

    PubMed Central

    Isa, T; Itazawa, S; Iino, M; Tsuzuki, K; Ozawa, S

    1996-01-01

    1. Current-voltage (I-V) relationships and Ca2+ permeability of receptor channels activated by bath application of kainate, a non-desensitizing agonist of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, were examined in various types of neurones in hippocampal slices of 5- to 13-day-old rats by using the tight-seal patch clamp recording technique. 2. Three types of responses were observed: type I response with outwardly rectifying I-V relationship, type II response with I-V relationship of marked inward rectification, and intermediate response with I-V relationship of weaker inward rectification. Neurones with type I, type II and intermediate I-V relationships of kainate responses were referred to as type I, type II and intermediate neurones, respectively. 3. Permeability of Ca2+ ions was estimated by the reversal potential of kainate response in the outside-out patch in Na(+)-free extracellular solution containing 100 mM Ca2+. The reversal potentials were -44.4 +/- 14.0 mV (mean +/- S.D.) for type I (n = 7), +11.8 +/- 3.6 mV for type II (n = 5), and -8.7 +/- 7.4 mV for the intermediate neurones (n = 7). The values of PCa/PCs, the ratios of the permeability coefficients of Ca2+ and Cs+, estimated according to the constant-field equation were 0.08 for type I, 1.71 for type II, and 0.50 for the intermediate neurones. 4. Type II and intermediate responses were observed mainly in non-pyramidal neurones in various areas of the hippocampus, most frequently observed in the stratum molecular of the dentate gyrus and in the stratum radiatum and the stratum lacunosum-molecular of both the CA1 and CA3 regions. Both type II and intermediate neurones stained with biocytin had round- or ellipsoidal-shaped somata and issued divergent axonal projections to the surrounding structures. 5. Excitatory postsynaptic currents (EPSCs) recorded in type II neurones had 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX)-sensitive fast and D-2-amino-5-phosphonovalerate (APV)-sensitive slow components. The I-V relationship of the fast component showed a strong inward rectification, indicating that inwardly rectifying AMPA receptors are involved in excitatory synaptic transmission. Images Figure 4 Figure 5 PMID:8815206

  8. Modulation of inwardly rectifying potassium channels in cultured bovine pulmonary artery endothelial cells.

    PubMed Central

    Kamouchi, M; Van Den Bremt, K; Eggermont, J; Droogmans, G; Nilius, B

    1997-01-01

    1. We have used the patch-clamp technique to study modulation of the inwardly rectifying K+ current (IK(IR)) in cultured bovine pulmonary artery endothelial cells (CPAE cells). In whole-cell mode, IK(IR) was defined as the Ba(2+)-sensitive current. In single channel recordings, we observed a strongly inwardly rectifying and K(+)-selective channel with a conductance of 31 +/- 3 pS. 2. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis and functional data suggest that the endothelial IRK is most probably Kir2.1. 3. Intracellular ATP is required to prevent run-down of IRK in whole-cell mode. Single channel activity disappeared in inside-out patches exposed to ATP-free solution and in cell-attached patches on cells exposed to metabolic inhibition (KCN, 2-deoxyglucose). 4. The non-hydrolysable ATP analogues, ATP gamma S and adenylyl imidodiphosphate (AMP-PNP), did not prevent run-down. Run-down did not occur in the presence of okadaic acid, a phosphatase inhibitor, but was enhanced in the presence of protamine, an activator of phosphatase 2A (PP2A). 5. GTP gamma S and AlF4- inhibited IRK, also in the presence of ATP. GTP beta S antagonized the GTP gamma S effect. Pretreatment of the cells with PTX did not affect the GTP gamma S-induced inhibition. Okadaic acid, however, slowed this inhibition. 6. Neither activation of protein kinase A (PKA) nor activation of protein kinase C (PKC) affected IRK. Additionally, neither cytochalasin B nor a high concentration of intracellular Ca2+ affected the time course of IRK run-down. 7. We conclude that run-down of IRK is probably due to dephosphorylation by PP2A. Activation of a PTX-insensitive G protein inhibits this current by a mechanism that is neither mediated via the PKA and PKC pathways nor by intracellular Ca2+, but supposedly by a G protein-dependent activation of a phosphatase. Images Figure 3 PMID:9401963

  9. Characterization of the outward rectifying potassium channel in a novel mouse intestinal smooth muscle cell preparation.

    PubMed Central

    Molleman, A; Thuneberg, L; Huizinga, J D

    1993-01-01

    1. The outward rectifying K+ conductance and underlying single channel behaviour in mouse small intestine (MSI) smooth muscle cells was studied using microelectrode impalement and the patch clamp technique. 2. At 37 degrees C, smooth muscle cells in MSI explants had a resting membrane potential around -65 mV and showed spontaneous electrical and mechanical activity. 3. Under whole-cell voltage clamp, depolarization of smooth muscle cells in the explants evoked a methoxyverapamil (D600)-sensitive, partially inactivating inward current and a non-inactivating outward current. The outward current was also observed in enzymatically dispersed cells from neonatal mouse small intestine. 4. The reversal potential of the outward current as established in tail current experiments was -70.2 mV. Tail currents could be fitted with a single exponential, suggesting the participation of only one population of channels. 5. The outward current was sensitive to 4-aminopyridine (10(-4) M), Ba2+ (1 mM) and to the presence of Cs+ in the pipette, but not to D600 (10(-6) M), or the presence of ATP (1 mM) in the pipette. 6. In the cell-attached patch configuration, a unitary outward current was observed that showed increased activity upon depolarization of the patch. The current-voltage relationship was close to linear with a slope conductance of 186 pS. 7. With normal K+ (6 mM) in the pipette, the extrapolated reversal potential for the unitary current was around -75 mV, while with high K+ (120 mM) the reversal potential was close to 0 mV. 8. Averaging single channel traces recorded under a depolarizing pulse protocol resulted in a trace with similar time characteristics as the outward current observed in the whole-cell configuration. 9. The burst behaviour of the channel was described by a simple model consisting of two closed states, Cf (intraburst closed state) and Cs (interburst closed state) and an open state (O). The rate constants in the model showed differential sensitivity to potential changes, channel blockade by Ba2+ and equimolar K+ conditions. 10. It was concluded that the outward rectifying potassium current in MSI smooth muscle cells is mediated by a 186 pS bursting channel. Voltage dependency and Ba2+ blockade are mainly reflected by changes in the transition rate from the open channel state to the interburst closed state. PMID:8308726

  10. Process for producing silicon

    DOEpatents

    Olson, Jerry M.; Carleton, Karen L.

    1984-01-01

    A process for producing silicon includes forming an alloy of copper and silicon and positioning the alloy in a dried, molten salt electrolyte to form a solid anode structure therein. An electrically conductive cathode is placed in the electrolyte for plating silicon thereon. The electrolyte is then purified to remove dissolved oxides. Finally, an electrical potential is applied between the anode and cathode in an amount sufficient to form substantially pure silicon on the cathode in the form of substantially dense, coherent deposits.

  11. Process for producing silicon

    DOEpatents

    Olson, J.M.; Carleton, K.L.

    1982-06-10

    A process of producing silicon includes forming an alloy of copper and silicon and positioning the alloy in a dried, molten salt electrolyte to form a solid anode structure therein. An electrically conductive cathode is placed in the electrolyte for plating silicon thereon. The electrolyte is then purified to remove dissolved oxides. Finally, an electrical potential is applied between the anode and cathode in an amount sufficient to form substantially pure silicon on the cathode in the form of substantially dense, coherent deposits.

  12. Bonding silicones with epoxies

    SciTech Connect

    Tira, J.S.

    1980-01-01

    It is shown that silicones, both room temperature vulcanizing (RTV) and millable rubber (press cured) can be successfully bonded to other materials using plasma treatment and epoxy adhesives. The plasma treatment using dry air atmosphere increases the surface energy of the silicone and thus provides a lower water contact angle. This phenomenon allows the epoxy adhesive to wet the silicone surface and ultimately bond. Bond strengths are sufficiently high to result in failures in the silicone materials rather than the adhesive bond.

  13. Laser sintering of silicon powder and carbon nanofibers for porous composite thick films

    NASA Astrophysics Data System (ADS)

    Iwabuchi, Yuki; Yan, Jiwang

    2015-02-01

    We attempted the laser sintering of a mixture of waste silicon powder from silicon wafer slicing processes and carbon nanofibers. Thick films with high porosity were successfully generated by a strong combination of silicon and carbon nanofibers. The surface porosity of the thick films and the crystallinity of silicon were controllable by varying the scanning speed of the laser beam. These findings indicate the feasibility of a new fabrication method for silicon anodes for future lithium-ion batteries.

  14. Advanced SEM/EDS Analysis using Stage Control and an annular Silicon Drift Detector: Applications in Impact Studies from Centimetre below Micrometre Scale

    NASA Astrophysics Data System (ADS)

    Salge, Tobias; Berlin, Jana; Terborg, Ralf; Howard, Kieren; Newsom, Horton; Wozniakiewicz, Penny; Price, Mark; Burchell, Mark; Cole, Mike; Kearsley, Anton

    2013-04-01

    Introduction: Imaging of ever smaller structures, in situ within large samples, requires low electron beam energy (HV<6 kV) to enhance spatial resolution, and therefore also the use of low energy X-ray lines for element analysis. To separate significantly overlapping peaks e.g. N-K (392 eV) and Ti-Ll (395 eV), the incorporation of line deconvolution algorithms in energy dispersive X-ray software is of crucial importance. Methods: Without adequate X-ray count statistics, deconvolution is unlikely to be effective. We therefore used an annular Silicon Drift Detector (SDD), the Bruker XFlash® 5060F which is placed between the pole piece and sample. High take-off angle and collection of X-rays from four different directions allow data collection across samples with substantial surface topography. Automated stage control and spectrum imaging allow large data sets to be acquired within a short time. Applications: (A) Large area, high resolution images (with tiling or stitching of neighbouring areas) is useful for understanding processes in the formation of tektites [1], revealing flow textures and layering, without destructive section preparation. Coalescence textures formed during the transition from melt to solid, surface pitting produced by micro-impact collisions in the impact plume, and surface etching by chemical attack in the impact plume, or later weathering, can all be revealed. (B) Spectrum imaging of the matrix in the impact melt breccia of the Chicxulub impact crater (Yaxcopoil-1 borehole, Unit 5 861.72 m) reveals secondary mineral formation, such as NaCl (<500 nm) and Fe-Ti-oxides (<150 nm) associated with garnet resorption. It documents the role of multiple episodes of precipitation of Mg-rich phyllosilicates as well as the formation and dissolution of accessory minerals in a relatively high temperature (>300°C) hydrothermal event [2]. (C) In experimental hypervelocity impact craters, spectrum images readily find locations of projectile residue throughout all the complex topography. The very high count rate at even low beam energy and current reveals inhomogeneous compositions and textures below micrometre scale [3]. These results help us understand preservation and modification of structure and composition in the fine-grained cometary dust aggregates which made aluminium foil craters on the Stardust spacecraft during its encounter with comet Wild 2. Acknowledgements: International Continental Scientific Drilling Program and the Museum of Natural History Berlin for providing samples. References: [1] K.T. Howard 2011. Geological Society of London: 573-591. [2] M. Nelson et al. 2012. GCA 86: 1-20. [3] A. T. Kearsley et al. 2013. Submitted to LPSC #1910.

  15. The SNAP trial: a double blind multi-center randomized controlled trial of a silicon nitride versus a PEEK cage in transforaminal lumbar interbody fusion in patients with symptomatic degenerative lumbar disc disorders: study protocol

    PubMed Central

    2014-01-01

    Background Polyetheretherketone (PEEK) cages have been widely used in the treatment of lumbar degenerative disc disorders, and show good clinical results. Still, complications such as subsidence and migration of the cage are frequently seen. A lack of osteointegration and fibrous tissues surrounding PEEK cages are held responsible. Ceramic implants made of silicon nitride show better biocompatible and osteoconductive qualities, and therefore are expected to lower complication rates and allow for better fusion. Purpose of this study is to show that fusion with the silicon nitride cage produces non-inferior results in outcome of the Roland Morris Disability Questionnaire at all follow-up time points as compared to the same procedure with PEEK cages. Methods/Design This study is designed as a double blind multi-center randomized controlled trial with repeated measures analysis. 100 patients (18–75 years) presenting with symptomatic lumbar degenerative disorders unresponsive to at least 6 months of conservative treatment are included. Patients will be randomly assigned to a PEEK cage or a silicon nitride cage, and will undergo a transforaminal lumbar interbody fusion with pedicle screw fixation. Primary outcome measure is the functional improvement measured by the Roland Morris Disability Questionnaire. Secondary outcome parameters are the VAS leg, VAS back, SF-36, Likert scale, neurological outcome and radiographic assessment of fusion. After 1 year the fusion rate will be measured by radiograms and CT. Follow-up will be continued for 2 years. Patients and clinical observers who will perform the follow-up visits will be blinded for type of cage used during follow-up. Analyses of radiograms and CT will be performed independently by two experienced radiologists. Discussion In this study a PEEK cage will be compared with a silicon nitride cage in the treatment of symptomatic degenerative lumbar disc disorders. To our knowledge, this is the first randomized controlled trial in which the silicon nitride cage is compared with the PEEK cage in patients with symptomatic degenerative lumbar disc disorders. Trial registration NCT01557829 PMID:24568365

  16. Electrodeposition of molten silicon

    DOEpatents

    De Mattei, Robert C.; Elwell, Dennis; Feigelson, Robert S.

    1981-01-01

    Silicon dioxide is dissolved in a molten electrolytic bath, preferably comprising barium oxide and barium fluoride. A direct current is passed between an anode and a cathode in the bath to reduce the dissolved silicon dioxide to non-alloyed silicon in molten form, which is removed from the bath.

  17. Formation of iron disilicide on amorphous silicon

    NASA Astrophysics Data System (ADS)

    Erlesand, U.; Östling, M.; Bodén, K.

    1991-11-01

    Thin films of iron disilicide, β-FeSi 2 were formed on both amorphous silicon and on crystalline silicon. The β-phase is reported to be semiconducting with a direct band-gap of about 0.85-0.89 eV. This phase is known to form via a nucleation-controlled growth process on crystalline silicon and as a consequence a rather rough silicon/silicide interface is usually formed. In order to improve the interface a bilayer structure of amorphous silicon and iron was sequentially deposited on Czochralski <111> silicon in an e-gun evaporation system. Secondary ion mass spectrometry profiling (SIMS) and scanning electron micrographs revealed an improvement of the interface sharpness. Rutherford backscattering spectrometry (RBS) and X-ray diffractiometry showed β-FeSi 2 formation already at 525°C. It was also observed that the silicide growth was diffusion-controlled, similar to what has been reported for example in the formation of NiSi 2 for the reaction of nickel on amorphous silicon. The kinetics of the FeSi 2 formation in the temperature range 525-625°C was studied by RBS and the activation energy was found to be 1.5 ± 0.1 eV.

  18. Spectroscopic ellipsometry characterization of silicon/silicon-dioxide superlattices for photoluminescence and electroluminescence

    NASA Astrophysics Data System (ADS)

    Creazzo, Tim; Prather, Lindsay; Redding, Brandon; Shi, Shouyuan; Prather, Dennis

    2008-02-01

    Silicon based light emitting materials are of particular interest for integrating electric and photonic devices into an allsilicon platform. The progress of nano-scale fabrication has led to the ability to realize silicon emitters based on quantum confinement mechanisms. Quantum confinement in nano-structured silicon overcomes the indirect bandgap present in bulk silicon allowing for radiative emissions. Silicon/silicon dioxide superlattices employ two-dimensional confinement leading to light emission. Strong photoluminescence (PL) has been demonstrated in Si/SiO II superlattices, confirming the presence of quantum confinement effects. Our super lattice structures are grown using plasma enhanced chemical vapor deposition (PECVD) with alternating layers of silicon and silicon dioxide. Sub-10 nanometer periods are confirmed via transmission electron microscopy (TEM) and x-ray reflectivity (XRR) studies. However, consistent and predictable PL and electroluminescence (EL) relies on precise measurement and characterization of the deposition process. Spectroscopic ellipsometry (SE) offers a non-destructive extremely sensitive method of optical characterization which provides us with the required control. We present characterization of our superlattice structures using spectroscopic ellipsometry. The ellipsometer allows us to measure optical properties of the individual layers of ultra-thin silicon as a part of Si/SiO II superlattices. We demonstrate the change in the imaginary part of the dielectric function and the bandgap for a-Si. We also generate deposition rate curves for very specific PECVD recipes and apply this information to further SE characterization and modeling of multi-period superlattice structures.

  19. Bond Testing for Effects of Silicone Contamination

    NASA Technical Reports Server (NTRS)

    Plaia, James; Evans, Kurt

    2005-01-01

    In 2003 ATK Thiokol discovered that the smocks and coveralls worn by its operations personnel for safety and contamination control were themselves contaminated with a silicone defoamer and a silicone oil. As a growing list of items have been identified as having this form of contamination, it was desirable to devise a test method to determine if the contamination level detected could cause subsequent processing concerns. The smocks and coveralls could potentially contact bonding surfaces during processing so the test method focused on dry transfer of the silicone from the clothing to the bonding surface.

  20. Inhibition of g protein-activated inwardly rectifying k channels by phencyclidine.

    PubMed

    Kobayashi, Toru; Nishizawa, Daisuke; Ikeda, Kazutaka

    2011-03-01

    Addictive drugs, such as opioids, ethanol, cocaine, amphetamine, and phencyclidine (PCP), affect many functions of the nervous system and peripheral organs, resulting in severe health problems. G protein-activated inwardly rectifying K(+) (GIRK, Kir3) channels play an important role in regulating neuronal excitability through activation of various Gi/o protein-coupled receptors including opioid and CB(1) cannabinoid receptors. Furthermore, the channels are directly activated by ethanol and inhibited by cocaine at toxic levels, but not affected by methylphenidate, methamphetamine, and 3,4-methylenedioxymethamphetamine (MDMA) at toxic levels. The primary pharmacological action of PCP is blockade of N-methyl-D-aspartate (NMDA) receptor channels that are associated with its psychotomimetic effects. PCP also interacts with several receptors and channels at relatively high concentrations. However, the molecular mechanisms underlying the various effects of PCP remain to be clarified. Here, we investigated the effects of PCP on GIRK channels using the Xenopus oocyte expression system. PCP weakly but significantly inhibited GIRK channels at micromolar concentrations, but not Kir1.1 and Kir2.1 channels. The PCP concentrations effective in inhibiting GIRK channels overlap clinically relevant brain concentrations in severe intoxication. The results suggest that partial inhibition of GIRK channels by PCP may contribute to some of the toxic effects after overdose. PMID:21886598