Sample records for ohmic heating coil

  1. Plasma current start-up by the outer ohmic heating coils in the Saskatchewan TORus Modified (STOR-M) iron core tokamak

    DOE PAGES

    Mitarai, O.; Xiao, C.; McColl, D.; ...

    2015-03-24

    A plasma current up to 15 kA has been driven with outer ohmic heating (OH) coils in the STOR-M iron core tokamak. Even when the inner OH coil is disconnected, the outer OH coils alone can induce the plasma current as primary windings and initial breakdown are even easier in this coil layout. Our results suggest a possibility to use an iron core in a spherical tokamak to start up the plasma current without a central solenoid. Finally, the effect of the iron core saturation on the extension of the discharge pulse length has been estimated for further experiments inmore » the STOR-M tokamak.« less

  2. Plasma current start-up by the outer ohmic heating coils in the Saskatchewan TORus Modified (STOR-M) iron core tokamak

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Mitarai, O.; Xiao, C.; McColl, D.

    A plasma current up to 15 kA has been driven with outer ohmic heating (OH) coils in the STOR-M iron core tokamak. Even when the inner OH coil is disconnected, the outer OH coils alone can induce the plasma current as primary windings and initial breakdown are even easier in this coil layout. Our results suggest a possibility to use an iron core in a spherical tokamak to start up the plasma current without a central solenoid. Finally, the effect of the iron core saturation on the extension of the discharge pulse length has been estimated for further experiments inmore » the STOR-M tokamak.« less

  3. High magnetic field ohmically decoupled non-contact technology

    DOEpatents

    Wilgen, John [Oak Ridge, TN; Kisner, Roger [Knoxville, TN; Ludtka, Gerard [Oak Ridge, TN; Ludtka, Gail [Oak Ridge, TN; Jaramillo, Roger [Knoxville, TN

    2009-05-19

    Methods and apparatus are described for high magnetic field ohmically decoupled non-contact treatment of conductive materials in a high magnetic field. A method includes applying a high magnetic field to at least a portion of a conductive material; and applying an inductive magnetic field to at least a fraction of the conductive material to induce a surface current within the fraction of the conductive material, the surface current generating a substantially bi-directional force that defines a vibration. The high magnetic field and the inductive magnetic field are substantially confocal, the fraction of the conductive material is located within the portion of the conductive material and ohmic heating from the surface current is ohmically decoupled from the vibration. An apparatus includes a high magnetic field coil defining an applied high magnetic field; an inductive magnetic field coil coupled to the high magnetic field coil, the inductive magnetic field coil defining an applied inductive magnetic field; and a processing zone located within both the applied high magnetic field and the applied inductive magnetic field. The high magnetic field and the inductive magnetic field are substantially confocal, and ohmic heating of a conductive material located in the processing zone is ohmically decoupled from a vibration of the conductive material.

  4. Ohmic Heating: An Emerging Concept in Organic Synthesis.

    PubMed

    Silva, Vera L M; Santos, Luis M N B F; Silva, Artur M S

    2017-06-12

    The ohmic heating also known as direct Joule heating, is an advanced thermal processing method, mainly used in the food industry to rapidly increase the temperature for either cooking or sterilization purposes. Its use in organic synthesis, in the heating of chemical reactors, is an emerging method that shows great potential, the development of which has started recently. This Concept article focuses on the use of ohmic heating as a new tool for organic synthesis. It presents the fundamentals of ohmic heating and makes a qualitative and quantitative comparison with other common heating methods. A brief description of the ohmic reactor prototype in operation is presented as well as recent examples of its use in organic synthesis at laboratory scale, thus showing the current state of the research. The advantages and limitations of this heating method, as well as its main current applications are also discussed. Finally, the prospects and potential implications of ohmic heating in future research in chemical synthesis are proposed. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Effect of ultrahigh-temperature continuous ohmic heating treatment on fresh orange juice.

    PubMed

    Leizerson, Shirly; Shimoni, Eyal

    2005-05-04

    The scope of this study is the effect of ohmic heating thermal treatment on liquid fruit juice made of oranges. Effects of ohmic heating on the quality of orange juice were examined and compared to those of heat pasteurization at 90 degrees C for 50 s. Orange juice was treated at temperatures of 90, 120, and 150 degrees C for 1.13, 0.85, and 0.68 s in an ohmic heating system. Microbial counts showed complete inactivation of bacteria, yeast, and mold during ohmic and conventional treatments. The ohmic heating treatment reduced pectin esterase activity by 98%. The reduction in vitamin C was 15%. Ohmic-heated orange juice maintained higher amounts of the five representative flavor compounds than did heat-pasteurized juice. Sensory evaluation tests showed no difference between fresh and ohmic-heated orange juice. Thus, high-temperature ohmic-heating treatment can be effectively used to pasteurize fresh orange juice with minimal sensory deterioration.

  6. Extended Heat Deposition in Hot Jupiters: Application to Ohmic Heating

    NASA Astrophysics Data System (ADS)

    Ginzburg, Sivan; Sari, Re'em

    2016-03-01

    The observed radii of many giant exoplanets in close orbits exceed theoretical predictions. One suggested origin for this discrepancy is heat deposited deep inside the atmospheres of these “hot Jupiters”. Here, we study extended power sources that distribute heat from the photosphere to the deep interior of the planet. Our analytical treatment is a generalization of a previous analysis of localized “point sources”. We model the deposition profile as a power law in the optical depth and find that planetary cooling and contraction halt when the internal luminosity (I.e., cooling rate) of the planet drops below the heat deposited in the planet’s convective region. A slowdown in the evolutionary cooling prior to equilibrium is possible only for sources that do not extend to the planet’s center. We estimate the ohmic dissipation resulting from the interaction between the atmospheric winds and the planet’s magnetic field, and apply our analytical model to ohmically heated planets. Our model can account for the observed radii of most inflated planets, which have equilibrium temperatures of ≈1500-2500 K and are inflated to a radius of ≈ 1.6{R}J. However, some extremely inflated planets remain unexplained by our model. We also argue that ohmically inflated planets have already reached their equilibrium phase, and no longer contract. Following Wu & Lithwick, who argued that ohmic heating could only suspend and not reverse contraction, we calculate the time it takes ohmic heating to re-inflate a cold planet to its equilibrium configuration. We find that while it is possible to re-inflate a cold planet, the re-inflation timescales are longer by a factor of ≈ 30 than the cooling time.

  7. Analytical models of Ohmic heating and conventional heating in food processing

    NASA Astrophysics Data System (ADS)

    Serventi, A.; Bozzoli, F.; Rainieri, S.

    2017-11-01

    Ohmic heating is a food processing operation in which an electric current is passed through a food and the electrical resistance of the food causes the electric power to be transformed directly into heat. The heat is not delivered through a surface as in conventional heat exchangers but it is internally generated by Joule effect. Therefore, no temperature gradient is required and it origins quicker and more uniform heating within the food. On the other hand, it is associated with high energy costs and its use is limited to a particular range of food products with an appropriate electrical conductivity. Sterilization of foods by Ohmic heating has gained growing interest in the last few years. The aim of this study is to evaluate the benefits of Ohmic heating with respect to conventional heat exchangers under uniform wall temperature, a condition that is often present in industrial plants. This comparison is carried out by means of analytical models. The two different heating conditions are simulated under typical circumstances for the food industry. Particular attention is paid to the uniformity of the heat treatment and to the heating section length required in the two different conditions.

  8. Ohmic Heating Assisted Lye Peeling of Pears.

    PubMed

    Gupta, Sarvesh; Sastry, Sudhir K

    2018-05-01

    Currently, high concentrations (15% to 18%) of lye (sodium hydroxide) are used in peeling pears, constituting a wastewater handling and disposal problem for fruit processors. In this study, the effect of ohmic heating on lye peeling of pears was investigated. Pears were peeled using 0.5%, 1%, 2%, and 3% NaOH under different electric field strengths at two run times and their peeled yields were compared to that obtained at 2% and 18% NaOH with conventional heating. Results revealed that ohmic heating results in greater than 95% peeled yields and the best peel quality at much lower concentrations of lye (2% NaOH at 532 V/m and 3% NaOH at 426 and 479 V/m) than those obtained under conventional heating conditions. Treatment times of 30 and 60 s showed no significant differences. Within the studied range, the effects of increasing field strength yielded no significant additional benefits. These results confirm that the concentration of lye can be significantly lowered in the presence of ohmic heating to achieve high peeled yields and quality. Our work shows that lye concentrations can be greatly reduced while peeling pears, resulting in significant savings in use of caustic chemicals, reduced costs for effluent treatment and waste disposal. © 2018 Institute of Food Technologists®.

  9. Innovative food processing technology using ohmic heating and aseptic packaging for meat.

    PubMed

    Ito, Ruri; Fukuoka, Mika; Hamada-Sato, Naoko

    2014-02-01

    Since the Tohoku earthquake, there is much interest in processed foods, which can be stored for long periods at room temperature. Retort heating is one of the main technologies employed for producing it. We developed the innovative food processing technology, which supersede retort, using ohmic heating and aseptic packaging. Electrical heating involves the application of alternating voltage to food. Compared with retort heating, which uses a heat transfer medium, ohmic heating allows for high heating efficiency and rapid heating. In this paper we ohmically heated chicken breast samples and conducted various tests on the heated samples. The measurement results of water content, IMP, and glutamic acid suggest that the quality of the ohmically heated samples was similar or superior to that of the retort-heated samples. Furthermore, based on the monitoring of these samples, it was observed that sample quality did not deteriorate during storage. © 2013. Published by Elsevier Ltd on behalf of The American Meat Science Association. All rights reserved.

  10. Apple snack enriched with L-arginine using vacuum impregnation/ohmic heating technology.

    PubMed

    Moreno, Jorge; Echeverria, Julian; Silva, Andrea; Escudero, Andrea; Petzold, Guillermo; Mella, Karla; Escudero, Carlos

    2017-07-01

    Modern life has created a high demand for functional food, and in this context, emerging technologies such as vacuum impregnation and ohmic heating have been applied to generate functional foods. The aim of this research was to enrich the content of the semi-essential amino acid L-arginine in apple cubes using vacuum impregnation, conventional heating, and ohmic heating. Additionally, combined vacuum impregnation/conventional heating and vacuum impregnation/ohmic heating treatments were evaluated. The above treatments were applied at 30, 40 and 50  ℃ and combined with air-drying at 40 ℃ in order to obtain an apple snack rich in L-arginine. Both the impregnation kinetics of L-arginine and sample color were evaluated. The impregnated samples created using vacuum impregnation/ohmic heating at 50 ℃ presented a high content of L-arginine, an effect attributed primarily to electropermeabilization. Overall, vacuum impregnation/ohmic heating treatment at 50 ℃, followed by drying at 40 ℃, was the best process for obtaining an apple snack rich in L-arginine.

  11. Remarks on the thermal stability of an Ohmic-heated nanowire

    NASA Astrophysics Data System (ADS)

    Timsit, Roland S.

    2018-05-01

    The rise in temperature of a wire made from specific materials, due to ohmic heating by a DC electrical current, may lead to uncontrollable thermal runaway with ensuing melting. Thermal runaway stems from a steep decrease with increasing temperature of the thermal conductivity of the conducting material and subsequent trapping of the ohmic heat in the wire, i.e., from the inability of the wire to dissipate the heat sufficiently quickly by conduction to the cooler ends of the wire. In this paper, we show that the theory used to evaluate the temperature of contacting surfaces in a bulk electrical contact may be applied to calculate the conditions for thermal runaway in a nanowire. Implications of this effect for electrical contacts are addressed. A possible implication for memory devices using ohmic-heated nanofilms or nanowires is also discussed.

  12. Ohmic Heating of an Electrically Conductive Food Package.

    PubMed

    Kanogchaipramot, Kanyawee; Tongkhao, Kullanart; Sajjaanantakul, Tanaboon; Kamonpatana, Pitiya

    2016-12-01

    Ohmic heating through an electrically conductive food package is a new approach to heat the food and its package as a whole after packing to avoid post-process contamination and to serve consumer needs for convenience. This process has been successfully completed using polymer film integrated with an electrically conductive film to form a conductive package. Orange juice packed in the conductive package surrounded with a conductive medium was pasteurized in an ohmic heater. A mathematical model was developed to simulate the temperature distribution within the package and its surroundings. A 3-D thermal-electric model showed heating uniformity inside the food package while the hot zone appeared in the orange juice adjacent to the conductive film. The accuracy of the model was determined by comparing the experimental results with the simulated temperature and current drawn; the model showed good agreement between the actual and simulated results. An inoculated pack study using Escherichia coli O157:H7 indicated negative growth of viable microorganisms at the target and over target lethal process temperatures, whereas the microorganism was present in the under target temperature treatment. Consequently, our developed ohmic heating system with conductive packaging offers potential for producing safe food. © 2016 Institute of Food Technologists®.

  13. Edge Ohmic Heating Experiment on HT-6M Tokamak

    NASA Astrophysics Data System (ADS)

    Gao, Xiang; Fan, Shuping; Li, Jian'gang; Meng, Yuedong; Luo, Jiarong; Yin, Fuxian; Zeng, Lei; Ding, Liancheng; Lin, Bili; Zhang, Wei; Han, Yuqing; Tong, Xingde; Luo, Lanchang; Gong, Xianzu; Jiang, Jiaguang; Wu, Mingjun; Yin, Fei

    1994-03-01

    An improved ohmic confinement has been achieved on HT-6M tokamak after application of edge ohmic heating pulse which makes plasma current rapidly ramp up (0.4 ms) in a ramp rate of 12 Ma/s. The improved ohmic confinement phase is characterized by (a) energy and particle confinement time increase, (b) non-symmetric increased density ne, (c) reduced Hα radiation, (d) increased Te and steeper Te, ne profile at the edge. The results from soft x-ray sawteeth inversion radius and βp + li/2 implied the anomalous current penetration.

  14. [Acceleration of osmotic dehydration process through ohmic heating of foods: raspberries (Rubus idaeus)].

    PubMed

    Simpson, Ricardo R; Jiménez, Maite P; Carevic, Erica G; Grancelli, Romina M

    2007-06-01

    Raspberries (Rubus idaeus) were osmotically dehydrated by applying a conventional method under the supposition of a homogeneous solution, all in a 62% glucose solution at 50 degrees C. Raspberries (Rubus idaeus) were also osmotically dehydrated by using ohmic heating in a 57% glucose solution at a variable voltage (to maintain temperature between 40 and 50 degrees C) and an electric field intensity <100 V/cm. When comparing the results from both experiments it was evident that processing time is reduced when ohmic heating technique was used. In some cases this reduction reached even 50%. This is explained by the additional effect to the thermal damage that is generated in an ohmic process, denominated electroporation.

  15. Minimum maximum temperature gradient coil design.

    PubMed

    While, Peter T; Poole, Michael S; Forbes, Larry K; Crozier, Stuart

    2013-08-01

    Ohmic heating is a serious problem in gradient coil operation. A method is presented for redesigning cylindrical gradient coils to operate at minimum peak temperature, while maintaining field homogeneity and coil performance. To generate these minimaxT coil windings, an existing analytic method for simulating the spatial temperature distribution of single layer gradient coils is combined with a minimax optimization routine based on sequential quadratic programming. Simulations are provided for symmetric and asymmetric gradient coils that show considerable improvements in reducing maximum temperature over existing methods. The winding patterns of the minimaxT coils were found to be heavily dependent on the assumed thermal material properties and generally display an interesting "fish-eye" spreading of windings in the dense regions of the coil. Small prototype coils were constructed and tested for experimental validation and these demonstrate that with a reasonable estimate of material properties, thermal performance can be improved considerably with negligible change to the field error or standard figures of merit. © 2012 Wiley Periodicals, Inc.

  16. Cryogenic focussing, ohmically heated on-column trap

    NASA Technical Reports Server (NTRS)

    Springston, Stephen R.

    1991-01-01

    A procedure is described for depositing a conductive layer of gold on the exterior of a fused-silica capillary used in gas chromatography. By subjecting a section of the column near the inlet to a thermal cycle of cryogenic cooling and ohmic heating, volatile samples are concentrated and subsequently injected. The performance of this trap as a chromatographic injector is demonstrated. Several additional applications are suggested and the unique properties of this device are discussed.

  17. Mathematical Model of Solid Food Pasteurization by Ohmic Heating: Influence of Process Parameters

    PubMed Central

    2014-01-01

    Pasteurization of a solid food undergoing ohmic heating has been analysed by means of a mathematical model, involving the simultaneous solution of Laplace's equation, which describes the distribution of electrical potential within a food, the heat transfer equation, using a source term involving the displacement of electrical potential, the kinetics of inactivation of microorganisms likely to be contaminating the product. In the model, thermophysical and electrical properties as function of temperature are used. Previous works have shown the occurrence of heat loss from food products to the external environment during ohmic heating. The current model predicts that, when temperature gradients are established in the proximity of the outer ohmic cell surface, more cold areas are present at junctions of electrodes with lateral sample surface. For these reasons, colder external shells are the critical areas to be monitored, instead of internal points (typically geometrical center) as in classical pure conductive heat transfer. Analysis is carried out in order to understand the influence of pasteurisation process parameters on this temperature distribution. A successful model helps to improve understanding of these processing phenomenon, which in turn will help to reduce the magnitude of the temperature differential within the product and ultimately provide a more uniformly pasteurized product. PMID:24574874

  18. Mathematical model of solid food pasteurization by ohmic heating: influence of process parameters.

    PubMed

    Marra, Francesco

    2014-01-01

    Pasteurization of a solid food undergoing ohmic heating has been analysed by means of a mathematical model, involving the simultaneous solution of Laplace's equation, which describes the distribution of electrical potential within a food, the heat transfer equation, using a source term involving the displacement of electrical potential, the kinetics of inactivation of microorganisms likely to be contaminating the product. In the model, thermophysical and electrical properties as function of temperature are used. Previous works have shown the occurrence of heat loss from food products to the external environment during ohmic heating. The current model predicts that, when temperature gradients are established in the proximity of the outer ohmic cell surface, more cold areas are present at junctions of electrodes with lateral sample surface. For these reasons, colder external shells are the critical areas to be monitored, instead of internal points (typically geometrical center) as in classical pure conductive heat transfer. Analysis is carried out in order to understand the influence of pasteurisation process parameters on this temperature distribution. A successful model helps to improve understanding of these processing phenomenon, which in turn will help to reduce the magnitude of the temperature differential within the product and ultimately provide a more uniformly pasteurized product.

  19. Measurement of heating coil temperature for e-cigarettes with a "top-coil" clearomizer.

    PubMed

    Chen, Wenhao; Wang, Ping; Ito, Kazuhide; Fowles, Jeff; Shusterman, Dennis; Jaques, Peter A; Kumagai, Kazukiyo

    2018-01-01

    To determine the effect of applied power settings, coil wetness conditions, and e-liquid compositions on the coil heating temperature for e-cigarettes with a "top-coil" clearomizer, and to make associations of coil conditions with emission of toxic carbonyl compounds by combining results herein with the literature. The coil temperature of a second generation e-cigarette was measured at various applied power levels, coil conditions, and e-liquid compositions, including (1) measurements by thermocouple at three e-liquid fill levels (dry, wet-through-wick, and full-wet), three coil resistances (low, standard, and high), and four voltage settings (3-6 V) for multiple coils using propylene glycol (PG) as a test liquid; (2) measurements by thermocouple at additional degrees of coil wetness for a high resistance coil using PG; and (3) measurements by both thermocouple and infrared (IR) camera for high resistance coils using PG alone and a 1:1 (wt/wt) mixture of PG and glycerol (PG/GL). For single point thermocouple measurements with PG, coil temperatures ranged from 322 ‒ 1008°C, 145 ‒ 334°C, and 110 ‒ 185°C under dry, wet-through-wick, and full-wet conditions, respectively, for the total of 13 replaceable coil heads. For conditions measured with both a thermocouple and an IR camera, all thermocouple measurements were between the minimum and maximum across-coil IR camera measurements and equal to 74% ‒ 115% of the across-coil mean, depending on test conditions. The IR camera showed details of the non-uniform temperature distribution across heating coils. The large temperature variations under wet-through-wick conditions may explain the large variations in formaldehyde formation rate reported in the literature for such "top-coil" clearomizers. This study established a simple and straight-forward protocol to systematically measure e-cigarette coil heating temperature under dry, wet-through-wick, and full-wet conditions. In addition to applied power, the

  20. Effect of ohmic heating of soymilk on urease inactivation and kinetic analysis in holding time.

    PubMed

    Li, Fa-De; Chen, Chen; Ren, Jie; Wang, Ranran; Wu, Peng

    2015-02-01

    To verify the effect of the ohmic heating on the urease activity in the soymilk, the ohmic heating methods with the different electrical field conditions (the frequency and the voltage ranging from 50 to 10 kHz and from 160 to 220 V, respectively) were employed. The results showed that if the value of the urease activity measured with the quantitative spectrophotometry method was lower than 16.8 IU, the urease activity measured with the qualitative method was negative. The urease activity of the sample ohmically heated was significantly lower than that of the sample conventionally heated (P < 0.01) at the same target temperature. It was concluded that the electrical field enhanced the urease inactivation. In addition, the inactivation kinetics of the urease in the soymilk could be described with a biphasic model during holding time at a target temperature. Thus, it was concluded that the urease in the soymilk would contain 2 isoenzymes, one is the thermolabile fraction, the other the thermostable fraction, and that the thermostable isoenzyme could not be completely inactivated when the holding time increased, whether the soymilk was cooked with the conventional method or with the ohmic heating method. Therefore, the electric field had no effect on the inactivation of the thermostable isoenzyme of the urease. © 2015 Institute of Food Technologists®

  1. Density scaling on n  =  1 error field penetration in ohmically heated discharges in EAST

    NASA Astrophysics Data System (ADS)

    Wang, Hui-Hui; Sun, You-Wen; Shi, Tong-Hui; Zang, Qing; Liu, Yue-Qiang; Yang, Xu; Gu, Shuai; He, Kai-Yang; Gu, Xiang; Qian, Jin-Ping; Shen, Biao; Luo, Zheng-Ping; Chu, Nan; Jia, Man-Ni; Sheng, Zhi-Cai; Liu, Hai-Qing; Gong, Xian-Zu; Wan, Bao-Nian; Contributors, EAST

    2018-05-01

    Density scaling of error field penetration in EAST is investigated with different n  =  1 magnetic perturbation coil configurations in ohmically heated discharges. The density scalings of error field penetration thresholds under two magnetic perturbation spectra are br\\propto n_e0.5 and br\\propto n_e0.6 , where b r is the error field and n e is the line averaged electron density. One difficulty in understanding the density scaling is that key parameters other than density in determining the field penetration process may also be changed when the plasma density changes. Therefore, they should be determined from experiments. The estimated theoretical analysis (br\\propto n_e0.54 in lower density region and br\\propto n_e0.40 in higher density region), using the density dependence of viscosity diffusion time, electron temperature and mode frequency measured from the experiments, is consistent with the observed scaling. One of the key points to reproduce the observed scaling in EAST is that the viscosity diffusion time estimated from energy confinement time is almost constant. It means that the plasma confinement lies in saturation ohmic confinement regime rather than the linear Neo-Alcator regime causing weak density dependence in the previous theoretical studies.

  2. Ohmic heating pretreatment of algal slurry for production of biodiesel.

    PubMed

    Yodsuwan, Natthawut; Kamonpatana, Pitiya; Chisti, Yusuf; Sirisansaneeyakul, Sarote

    2018-02-10

    Suspensions of the model microalga Chlorella sp. TISTR 8990 were pretreated by ohmic heating to facilitate release of lipids from the cells in subsequent extraction and lipase-mediated transesterification to biodiesel. After ohmic pretreatment, the moist biomass was suspended in a system of water, hexane, methanol and immobilized lipase for extraction of lipids and simultaneous conversion to biodiesel. The ohmic pretreatment was optimized using an experimental design based on Taguchi method to provide treated biomass that maximized the biodiesel yield in subsequent extraction-transesterification operation. The experimental factors were the frequency of electric current (5-10 5  Hz), the processing temperature (50-70 °C), the algal biomass concentration in the slurry (algal fresh weight to water mass ratio of 1-3) and the incubation time (1-3 min). Extraction-transesterification of the pretreated biomass was carried out at 40 °C for 24 h using a reaction systems of a fixed composition (i.e. biomass, hexane, methanol, water and immobilized enzyme). Compared to control (i.e. untreated biomass), the ohmic pretreatment under optimal conditions (5 Hz current frequency, 70 °C, 1:2 mass ratio of biomass to water, incubation time of 2-min) increased the rate of subsequent transesterification by nearly 2-fold. Copyright © 2017 Elsevier B.V. All rights reserved.

  3. Thermosyphon coil arrangement for heat pump outdoor unit

    DOEpatents

    Draper, R.

    1984-05-22

    For a heat pump, the outdoor unit is provided with a coil and a refrigerant flow arrangement there for which is such that in the heating mode of operation of the heat pump they operate in a thermosyphon fashion. The coil has a feed portion and an exit portion leading to a separator drum from which liquid refrigerant is returned through downcomer line for recirculation to the feed portion. The coil is tilted upwardly from entry to exit by the angle alpha to enhance the clearance of the two phases of refrigerant from each other in the heating mode of operation. There is no thermosyphon function in the cooling mode of operation. 9 figs.

  4. Thermosyphon coil arrangement for heat pump outdoor unit

    DOEpatents

    Draper, Robert

    1984-01-01

    For a heat pump, the outdoor unit is provided with a coil and a refrigerant flow arrangement therefor which is such that in the heating mode of operation of the heat pump they operate in a thermosyphon fashion. The coil 32 has a feed portion 30 and an exit portion 34 leading to a separator drum 36 from which liquid refrigerant is returned through downcomer line 42 for recirculation to the feed portion. The coil is tilted upwardly from entry to exit by the angle alpha to enhance the clearance of the two phases of refrigerant from each other in the heating mode of operation. There is no thermosyphon function in the cooling mode of operation.

  5. Enhancement of ohmic and stochastic heating by resonance effects in capacitive radio frequency discharges: a theoretical approach.

    PubMed

    Mussenbrock, T; Brinkmann, R P; Lieberman, M A; Lichtenberg, A J; Kawamura, E

    2008-08-22

    In low-pressure capacitive radio frequency discharges, two mechanisms of electron heating are dominant: (i) Ohmic heating due to collisions of electrons with neutrals of the background gas and (ii) stochastic heating due to momentum transfer from the oscillating boundary sheath. In this work we show by means of a nonlinear global model that the self-excitation of the plasma series resonance which arises in asymmetric capacitive discharges due to nonlinear interaction of plasma bulk and sheath significantly affects both Ohmic heating and stochastic heating. We observe that the series resonance effect increases the dissipation by factors of 2-5. We conclude that the nonlinear plasma dynamics should be taken into account in order to describe quantitatively correct electron heating in asymmetric capacitive radio frequency discharges.

  6. Tx/Rx Head Coil Induces Less RF Transmit-Related Heating than Body Coil in Conductive Metallic Objects Outside the Active Area of the Head Coil

    PubMed Central

    Nagy, Zoltan; Oliver-Taylor, Aaron; Kuehne, Andre; Goluch, Sigrun; Weiskopf, Nikolaus

    2017-01-01

    The transmit–receive (Tx/Rx) birdcage head coil is often used for excitation instead of the body coil because of the presumably lower risk of heating in and around conductive implants. However, this common practice has not been systematically tested. To investigate whether the Tx/Rx birdcage head coil produces less heating than the body coil when scanning individuals with implants, we used a 3T clinical scanner and made temperature measurements around a straight 15 cm conductor using either the Tx/Rx body or the head coil for excitation. Additionally, the transmitted fields of a Tx/Rx head coil were measured both in air and in gel using a resonant and a non-resonant B field probes as well as a non-resonant E field probe. Simulations using a finite-difference time domain solver were compared with the experimental findings. When the body coil was used for excitation, we observed heating around the 15 cm wire at various anatomical locations (both within and outside of the active volume of the head coil). Outside its active area, no such heating was observed while using the Tx/Rx head coil for excitation. The E and B fields of the Tx/Rx birdcage head coil extended well-beyond the physical dimensions of the coil. In air, the fields were monotonically decreasing, while in gel they were more complex with local maxima at the end of the ASTM phantom. These experimental findings were line with the simulations. While caution must always be exercised when scanning individuals with metallic implants, these findings support the use of the Tx/Rx birdcage head coil in place of the body coil at 3T in order to reduce the risk of heating in and around conductive implants that are remote from the head coil. PMID:28184184

  7. Evaluation of non-thermal effects of electricity on ascorbic acid and carotenoid degradation in acerola pulp during ohmic heating.

    PubMed

    Jaeschke, Débora Pez; Marczak, Ligia Damasceno Ferreira; Mercali, Giovana Domeneghini

    2016-05-15

    The effect of electric field on ascorbic acid and carotenoid degradation in acerola pulp during ohmic heating was evaluated. Ascorbic acid kinetic degradation was evaluated at 80, 85, 90 and 95°C during 60 min of thermal treatment by ohmic and conventional heating. Carotenoid degradation was evaluated at 90 and 95°C after 50 min of treatment. The different temperatures evaluated showed the same effect on degradation rates. To investigate the influence of oxygen concentration on the degradation process, ohmic heating was also carried out under rich and poor oxygen modified atmospheres at 90°C. Ascorbic acid and carotenoid degradation was higher under a rich oxygen atmosphere, indicating that oxygen is the limiting reagent of the degradation reaction. Ascorbic acid and carotenoid degradation was similar for both heating technologies, demonstrating that the presence of the oscillating electric field did not influence the mechanisms and rates of reactions associated with the degradation process. Copyright © 2015 Elsevier Ltd. All rights reserved.

  8. Goat milk free fatty acid characterization during conventional and ohmic heating pasteurization.

    PubMed

    Pereira, R N; Martins, R C; Vicente, A A

    2008-08-01

    The disruption of the milk fat globule membrane can lead to an excessive accumulation of free fatty acids in milk, which is frequently associated with the appearance of rancid flavors. Solid-phase microextraction and gas chromatography techniques have been shown to be useful tools in the quantification of individual free fatty acids in dairy products providing enough sensitivity to detect levels of rancidity in milk. Therefore, the aim of this study was to characterize the short-chain and medium-chain free fatty acid profile in i) raw untreated goat milk; ii) raw goat milk passing through pumps and heating units (plate-and-frame heat exchanger and ohmic heater); and iii) processed goat milk by conventional and ohmic pasteurization to determine the influence of each treatment in the final quality of the milk. Multivariate statistical analysis has shown that the treatments studied were not responsible for the variability found on free fatty acid contents. In particular, it was possible to conclude that ohmic pasteurization at 72 degrees C for 15 s did not promote an extended modification of free fatty acid contents in goat milk when compared with that of conventional pasteurization. Furthermore, principal component analysis showed that the capric acid can be used to discriminate goat's milk with different free fatty acid concentrations. Hierarchical cluster analysis showed evidence of the existence of correlations between contents of short and medium chain free fatty acids in goat milk.

  9. 46 CFR 153.434 - Heat transfer coils within a tank.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 5 2010-10-01 2010-10-01 false Heat transfer coils within a tank. 153.434 Section 153... Cargo Temperature Control Systems § 153.434 Heat transfer coils within a tank. When a cargo tank... the heat transfer fluid at a pressure greater than the pressure exerted on the heating or cooling...

  10. 46 CFR 153.434 - Heat transfer coils within a tank.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 5 2011-10-01 2011-10-01 false Heat transfer coils within a tank. 153.434 Section 153... Cargo Temperature Control Systems § 153.434 Heat transfer coils within a tank. When a cargo tank... the heat transfer fluid at a pressure greater than the pressure exerted on the heating or cooling...

  11. 46 CFR 153.434 - Heat transfer coils within a tank.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 5 2014-10-01 2014-10-01 false Heat transfer coils within a tank. 153.434 Section 153... Cargo Temperature Control Systems § 153.434 Heat transfer coils within a tank. When a cargo tank... the heat transfer fluid at a pressure greater than the pressure exerted on the heating or cooling...

  12. 46 CFR 153.434 - Heat transfer coils within a tank.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 5 2013-10-01 2013-10-01 false Heat transfer coils within a tank. 153.434 Section 153... Cargo Temperature Control Systems § 153.434 Heat transfer coils within a tank. When a cargo tank... the heat transfer fluid at a pressure greater than the pressure exerted on the heating or cooling...

  13. Designing gradient coils with reduced hot spot temperatures.

    PubMed

    While, Peter T; Forbes, Larry K; Crozier, Stuart

    2010-03-01

    Gradient coil temperature is an important concern in the design and construction of MRI scanners. Closely spaced gradient coil windings cause temperature hot spots within the system as a result of Ohmic heating associated with large current being driven through resistive material, and can strongly affect the performance of the coils. In this paper, a model is presented for predicting the spatial temperature distribution of a gradient coil, including the location and extent of temperature hot spots. Subsequently, a method is described for designing gradient coils with improved temperature distributions and reduced hot spot temperatures. Maximum temperature represents a non-linear constraint and a relaxed fixed point iteration routine is proposed to adjust coil windings iteratively to minimise this coil feature. Several examples are considered that assume different thermal material properties and cooling mechanisms for the gradient system. Coil winding solutions are obtained for all cases considered that display a considerable drop in hot spot temperature (>20%) when compared to standard minimum power gradient coils with equivalent gradient homogeneity, efficiency and inductance. The method is semi-analytical in nature and can be adapted easily to consider other non-linear constraints in the design of gradient coils or similar systems. Crown Copyright (c) 2009. Published by Elsevier Inc. All rights reserved.

  14. Enhanced heat transfer and frictional losses in heat exchanger tube with modified helical coiled inserts

    NASA Astrophysics Data System (ADS)

    Verma, Aditya; Kumar, Manoj; Patil, Anil Kumar

    2018-04-01

    The application of compact heat exchangers in any thermal system improves overall performance with a considerable reduction in size and weight. Inserts of different geometrical features have been used as turbulence promoting devices to increase the heat transfer rates. The present study deals with the experimental investigation of heat transfer and fluid flow characteristics of a tubular heat exchanger fitted with modified helical coiled inserts. Experiments have been carried out for a smooth tube without insert, tube fitted with helical coiled inserts, and modified helical coiled inserts. The helical coiled inserts are tested by varying the pitch ratio and wire diameter ratio from 0.5-1.5, and 0.063-0.125, respectively for the Reynolds number range of 1400 to 11,000. Experimental data have also been collected for the modified helical coiled inserts with gradually increasing pitch (GIP) and gradually decreasing pitch (GDP) configurations. The Nusselt number and friction factor values for helical coiled inserts are enhanced in the range of 1.42-2.62, 3.4-27.4, relative to smooth tube, respectively. The modified helical coiled insert showed enhancements in Nusselt number and friction factor values in the range of 1.49-3.14, 11.2-19.9, relative to smooth tube, respectively. The helical coiled and modified helical coiled inserts have thermo-hydraulic performance factor in the range of 0.59-1.29, 0.6-1.39, respectively. The empirical correlations of Nusselt number and friction factor for helical coiled inserts are proposed.

  15. Product formulation for ohmic heating: blanching as a pretreatment method to improve uniformity in heating of solid-liquid food mixtures.

    PubMed

    Sarang, S; Sastry, S K; Gaines, J; Yang, T C S; Dunne, P

    2007-06-01

    The electrical conductivity of food components is critical to ohmic heating. Food components of different electrical conductivities heat at different rates. While equal electrical conductivities of all phases are desirable, real food products may behave differently. In the present study involving chicken chow mein consisting of a sauce and different solid components, celery, water chestnuts, mushrooms, bean sprouts, and chicken, it was observed that the sauce was more conductive than all solid components over the measured temperature range. To improve heating uniformity, a blanching method was developed to increase the ionic content of the solid components. By blanching different solid components in a highly conductive sauce at 100 degrees C for different lengths of time, it was possible to adjust their conductivity to that of the sauce. Chicken chow mein samples containing blanched particulates were compared with untreated samples with respect to ohmic heating uniformity at 60 Hz up to 140 degrees C. All components of the treated product containing blanched solids heated more uniformly than untreated product. In sensory tests, 3 different formulations of the blanched product showed good quality attributes and overall acceptability, demonstrating the practical feasibility of the blanching protocol.

  16. Performance analyses of helical coil heat exchangers. The effect of external coil surface modification on heat exchanger effectiveness

    NASA Astrophysics Data System (ADS)

    Andrzejczyk, Rafał; Muszyński, Tomasz

    2016-12-01

    The shell and coil heat exchangers are commonly used in heating, ventilation, nuclear industry, process plant, heat recovery and air conditioning systems. This type of recuperators benefits from simple construction, the low value of pressure drops and high heat transfer. In helical coil, centrifugal force is acting on the moving fluid due to the curvature of the tube results in the development. It has been long recognized that the heat transfer in the helical tube is much better than in the straight ones because of the occurrence of secondary flow in planes normal to the main flow inside the helical structure. Helical tubes show good performance in heat transfer enhancement, while the uniform curvature of spiral structure is inconvenient in pipe installation in heat exchangers. Authors have presented their own construction of shell and tube heat exchanger with intensified heat transfer. The purpose of this article is to assess the influence of the surface modification over the performance coefficient and effectiveness. The experiments have been performed for the steady-state heat transfer. Experimental data points were gathered for both laminar and turbulent flow, both for co current- and countercurrent flow arrangement. To find optimal heat transfer intensification on the shell-side authors applied the number of transfer units analysis.

  17. Inductance and resistance measurement method for vessel detection and coil powering in all-surface inductive heating systems composed of outer squircle coils

    NASA Astrophysics Data System (ADS)

    Kilic, Veli Tayfun; Unal, Emre; Demir, Hilmi Volkan

    2017-05-01

    In this work, we investigate a method proposed for vessel detection and coil powering in an all-surface inductive heating system composed of outer squircle coils. Besides conventional circular coils, coils with different shapes such as outer squircle coils are used for and enable efficient all-surface inductive heating. Validity of the method, which relies on measuring inductance and resistance values of a loaded coil at different frequencies, is experimentally demonstrated for a coil with shape different from conventional circular coil. Simple setup was constructed with a small coil to model an all-surface inductive heating system. Inductance and resistance maps were generated by measuring coil's inductance and resistance values at different frequencies loaded by a plate made of different materials and located at various positions. Results show that in an induction hob for various coil geometries it is possible to detect a vessel's presence, to identify its material type and to specify its position on the hob surface by considering inductance and resistance of the coil measured on at least two different frequencies. The studied method is important in terms of enabling safe, efficient and user flexible heating in an all-surface inductive heating system by automatically detecting the vessel's presence and powering on only the coils that are loaded by the vessel with predetermined current levels.

  18. Hydrodynamic studies of CNT nanofluids in helical coil heat exchanger

    NASA Astrophysics Data System (ADS)

    Babita; Sharma, S. K.; Mital Gupta, Shipra; Kumar, Arinjay

    2017-12-01

    Helical coils are extensively used in several industrial processes such as refrigeration systems, chemical reactors, recovery processes etc to accommodate a large heat transfer area within a smaller space. Nanofluids are getting great attention due to their enhanced heat transfer capability. In heat transfer equipments, pressure drop is one of the major factors of consideration for pumping power calculations. So, the present work is aimed to study hydrodynamics of CNT nanofluids in helical coils. In this study, pressure drop characteristics of CNT nanofluid flowing inside horizontal helical coils are investigated experimentally. The helical coil to tube diameter was varied from 11.71 to 27.34 keeping pitch of the helical coil constant. Double distilled water was used as basefluid. SDBS and GA surfactants were added to stablilize CNT nanofluids. The volumetric fraction of CNT nanofluid was varied from 0.003 vol% to 0.051 vol%. From the experimental data, it was analyzed that the friction factor in helical coils is greater than that of straight tubes. Concentration of CNT in nanofluids also has a significant influence on the pressure drop/friction factor of helical coils. At a constant concentration of CNT, decreasing helical coil to tube diameter from 27.24 to 11.71, fanning friction factor of helical coil; f c increases for a constant value of p/d t. This increase in the value of fanning friction factor can be attributed to the secondary flow of CNT nanofluid in helical coils.

  19. A Spectroscopic Study of Impurity Behavior in Neutral-beam and Ohmically Heated TFTR Discharges

    DOE R&D Accomplishments Database

    Stratton, B. C.; Ramsey, A. T.; Boody, F. P.; Bush, C. E.; Fonck, R. J.; Groenbner, R. J.; Hulse, R. A.; Richards, R. K.; Schivell, J.

    1987-02-01

    Quantitative spectroscopic measurements of Z{sub eff}, impurity densities, and radiated power losses have been made for ohmic- and neutral-beam-heated TFTR discharges at a plasma current of 2.2 MA and toroidal field of 4.7 T. Variations in these quantities with line-average plasma density (anti n{sub e}) and beam power up to 5.6 MW are presented for discharges on a graphite movable limiter. A detailed discussion of the use of an impurity transport model to infer absolute impurity densities and radiative losses from line intensity and visible continuum measurements is given. These discharges were dominated by low-Z impurities with carbon having a considerably higher density than oxygen, except in high-anti n{sub e} ohmic discharges, where the densities of carbon and oxygen were comparable. Metallic impurity concentrations and radiative losses were small, resulting in hollow radiated power profiles and fractions of the input power radiated being 30 to 50% for ohmic heating and 30% or less with beam heating. Spectroscopic estimates of the radiated power were in good agreement with bolometrically measured values. Due to an increase in the carbon density, Z{sub eff} rose from 2.0 to 2.8 as the beam power increased from 0 to 5.6 MW, pointing to a potentially serious dilution of the neutron-producing plasma ions as the beam power increased. Both the low-Z and metallic impurity concentrations were approximately constant with minor radius, indicating no central impurity accumulation in these discharges.

  20. Calculation of Eddy Currents In the CTH Vacuum Vessel and Coil Frame

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    A. Zolfaghari, A. Brooks, A. Michaels, J. Hanson, and G. Hartwell

    2012-09-25

    Knowledge of eddy currents in the vacuum vessel walls and nearby conducting support structures can significantly contribute to the accuracy of Magnetohydrodynamics (MHD) equilibrium reconstruction in toroidal plasmas. Moreover, the magnetic fields produced by the eddy currents could generate error fields that may give rise to islands at rational surfaces or cause field lines to become chaotic. In the Compact Toroidal Hybrid (CTH) device (R0 = 0.75 m, a = 0.29 m, B ≤ 0.7 T), the primary driver of the eddy currents during the plasma discharge is the changing flux of the ohmic heating transformer. Electromagnetic simulations are usedmore » to calculate eddy current paths and profile in the vacuum vessel and in the coil frame pieces with known time dependent currents in the ohmic heating coils. MAXWELL and SPARK codes were used for the Electromagnetic modeling and simulation. MAXWELL code was used for detailed 3D finite-element analysis of the eddy currents in the structures. SPARK code was used to calculate the eddy currents in the structures as modeled with shell/surface elements, with each element representing a current loop. In both cases current filaments representing the eddy currents were prepared for input into VMEC code for MHD equilibrium reconstruction of the plasma discharge. __________________________________________________« less

  1. Optimum Construction of Heating Coil for Domestic Induction Cooker

    NASA Astrophysics Data System (ADS)

    Sinha, Dola; Bandyopadhyay, Atanu; Sadhu, Pradip Kumar; Pal, Nitai

    2010-10-01

    The design and optimization of the parameters of heating coil is very important for the analytical analysis of high frequency inverter fed induction cooker. Moreover, accurate prediction of high frequency winding loss (i.e., losses due to skin and proximity effects) is necessary as the induction cooker used in power electronics applications. At high frequency current penetration in the induction coil circuit is very difficult for conducting wire due to skin-effect. To eradicate the skin effect heating coil is made up of bundle conductor i.e., litz wire. In this paper inductances and AC resistances of a litz-wire are calculated and optimized by considering the input parameters like wire type, shape, number of strand, number of spiral turn, number of twist per feet of heating coil and operating frequency. A high frequency half bridge series resonant mirror inverter circuit is used in this paper and taking the optimum values of inductance and ac resistance the circuit is simulated through PSPICE simulations. It has been noticed that the results are feasible enough for real implementation.

  2. Studies on convective heat transfer through helical coils

    NASA Astrophysics Data System (ADS)

    Pawar, S. S.; Sunnapwar, Vivek K.

    2013-12-01

    An experimental investigation on steady state convection heat transfer from vertical helical coiled tubes in water was performed for laminar flow regime. Three coils with curvature ratios as 0.0757, 0.064, 0.055 and range of Prandtl number from 3.81 to 4.8, Reynolds number from 3,166 to 9,658 were considered in this work. The heat transfer data were generated from 30 experiments conducted at constant water bath temperature (60 °C) for different cold water flow rates in helical coils. For the first time, an innovative approach of correlating Nusselt number with ‘M’ number is proposed which is not available in the literature and the developed correlations are found to be in good agreement with the work of earlier researchers. Thus, dimensionless number ‘M’ was found to be significant to characterize the hydrodynamics of fluid flow and heat transfer correlations in helical coils. Several other correlations based on experimental data are developed. To cover wide range of industrial applications, suitable generalized correlations based on extended parameters beyond the range of present experimental work are also developed. All these correlations are developed by using least-squares power law fit and multiple-regression analysis of MATLAB software. Correlations so developed were compared with published correlations and were found to be in good agreement. Comparison of heat transfer coefficients, friction factor and Nusselt number for different geometrical conditions is presented in this paper.

  3. Ohmic Inflation of Hot Jupiters: an Analytical Approach

    NASA Astrophysics Data System (ADS)

    Ginzburg, Sivan; Sari, Re'em

    2015-12-01

    Many giant exoplanets in close orbits have observed radii which exceed theoretical predictions.One suggested explanation for this discrepancy is heat deposited deep inside the atmospheres of these hot Jupiters.We present an analytical model for the evolution of such irradiated, and internally heated gas giants, and derive scaling laws for their cooling rates and radii.We estimate the Ohmic dissipation resulting from the interaction between the atmospheric winds and the planet's magnetic field, and apply our model to Ohmically heated planets.Our model can account for the observed radii of many inflated planets, but not the most extreme ones.We show that Ohmically heated planets have already reached their equilibrium phase and they no longer contract.We show that it is possible to re-inflate planets, but we confirm that re-heating timescales are longer by about a factor of 30 than cooling times.

  4. Effect of Electropermeabilization by Ohmic Heating for Inactivation of Escherichia coli O157:H7, Salmonella enterica Serovar Typhimurium, and Listeria monocytogenes in Buffered Peptone Water and Apple Juice

    PubMed Central

    Park, Il-Kyu

    2013-01-01

    The effect of electric field-induced ohmic heating for inactivation of Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium, and Listeria monocytogenes in buffered peptone water (BPW) (pH 7.2) and apple juice (pH 3.5; 11.8 °Brix) was investigated in this study. BPW and apple juice were treated at different temperatures (55°C, 58°C, and 60°C) and for different times (0, 10, 20, 25, and 30 s) by ohmic heating compared with conventional heating. The electric field strength was fixed at 30 V/cm and 60 V/cm for BPW and apple juice, respectively. Bacterial reduction resulting from ohmic heating was significantly different (P < 0.05) from that resulting from conventional heating at 58°C and 60°C in BPW and at 55°C, 58°C, and 60°C in apple juice for intervals of 0, 10, 20, 25, and 30 s. These results show that electric field-induced ohmic heating led to additional bacterial inactivation at sublethal temperatures. Transmission electron microscopy (TEM) observations and the propidium iodide (PI) uptake test were conducted after treatment at 60°C for 0, 10, 20, 25 and 30 s in BPW to observe the effects on cell permeability due to electroporation-caused cell damage. PI values when ohmic and conventional heating were compared were significantly different (P < 0.05), and these differences increased with increasing levels of inactivation of three food-borne pathogens. These results demonstrate that ohmic heating can more effectively reduce bacterial populations at reduced temperatures and shorter time intervals, especially in acidic fruit juices such as apple juice. Therefore, loss of quality can be minimized in a pasteurization process incorporating ohmic heating. PMID:23995939

  5. Effect of electropermeabilization by ohmic heating for inactivation of Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium, and Listeria monocytogenes in buffered peptone water and apple juice.

    PubMed

    Park, Il-Kyu; Kang, Dong-Hyun

    2013-12-01

    The effect of electric field-induced ohmic heating for inactivation of Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium, and Listeria monocytogenes in buffered peptone water (BPW) (pH 7.2) and apple juice (pH 3.5; 11.8 °Brix) was investigated in this study. BPW and apple juice were treated at different temperatures (55°C, 58°C, and 60°C) and for different times (0, 10, 20, 25, and 30 s) by ohmic heating compared with conventional heating. The electric field strength was fixed at 30 V/cm and 60 V/cm for BPW and apple juice, respectively. Bacterial reduction resulting from ohmic heating was significantly different (P<0.05) from that resulting from conventional heating at 58°C and 60°C in BPW and at 55°C, 58°C, and 60°C in apple juice for intervals of 0, 10, 20, 25, and 30 s. These results show that electric field-induced ohmic heating led to additional bacterial inactivation at sublethal temperatures. Transmission electron microscopy (TEM) observations and the propidium iodide (PI) uptake test were conducted after treatment at 60°C for 0, 10, 20, 25 and 30 s in BPW to observe the effects on cell permeability due to electroporation-caused cell damage. PI values when ohmic and conventional heating were compared were significantly different (P<0.05), and these differences increased with increasing levels of inactivation of three food-borne pathogens. These results demonstrate that ohmic heating can more effectively reduce bacterial populations at reduced temperatures and shorter time intervals, especially in acidic fruit juices such as apple juice. Therefore, loss of quality can be minimized in a pasteurization process incorporating ohmic heating.

  6. Three-phase flow? Consider helical-coil heat exchangers

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Haraburda, S.S.

    1995-07-01

    In recent years, chemical process plants are increasingly encountering processes that require heat exchange in three-phase fluids. A typical application, for example, is heating liquids containing solid catalyst particles and non-condensable gases. Heat exchangers designed for three-phase flow generally have tubes with large diameters (typically greater than two inches), because solids can build-up inside the tube and lead to plugging. At the same time, in order to keep heat-transfer coefficients high, the velocity of the process fluid within the tube should also be high. As a result, heat exchangers for three-phase flow may require less than five tubes -- eachmore » having a required linear length that could exceed several hundred feet. Given these limitations, it is obvious that a basic shell-and-tube heat exchanger is not the most practical solution for this purpose. An alternative for three-phase flow is a helical-coil heat exchanger. The helical-coil units offer a number of advantages, including perpendicular, counter-current flow and flexible overall dimensions for the exchanger itself. The paper presents equations for: calculating the tube-side heat-transfer coefficient; calculating the shell-side heat-transfer coefficient; calculating the heat-exchanger size; calculating the tube-side pressure drop; and calculating shell-side pressure-drop.« less

  7. Detail of heating coil for Machine Shop (Bldg. 163) ventilation ...

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

    Detail of heating coil for Machine Shop (Bldg. 163) ventilation system Note portion of fan visible behind coil - Atchison, Topeka, Santa Fe Railroad, Albuquerque Shops, Machine Shop, 908 Second Street, Southwest, Albuquerque, Bernalillo County, NM

  8. Promoted-Combustion Chamber with Induction Heating Coil

    NASA Technical Reports Server (NTRS)

    Richardson, Erin; Hagood, Richard; Lowery, Freida; Herald, Stephen

    2006-01-01

    An improved promoted-combustion system has been developed for studying the effects of elevated temperatures on the flammability of metals in pure oxygen. In prior promoted-combustion chambers, initial temperatures of metal specimens in experiments have been limited to the temperatures of gas supplies, usually near room temperature. Although limited elevated temperature promoted-combustion chambers have been developed using water-cooled induction coils for preheating specimens, these designs have been limited to low-pressure operation due to the hollow induction coil. In contrast, the improved promoted-combustion chamber can sustain a pressure up to 10 kpsi (69 MPa) and, through utilization of a solid induction coil, is capable of preheating a metal specimen up to its melting point [potentially in excess of 2,000 F (approximately equal to 1,100 C)]. Hence, the improved promoted combustion chamber makes a greater range of physical conditions and material properties accessible for experimentation. The chamber consists of a vertical cylindrical housing with an inner diameter of 8 in. (20.32 cm) and an inner height of 20.4 in. (51.81 cm). A threaded, sealing cover at one end of the housing can be unscrewed to gain access for installing a specimen. Inlet and outlet ports for gases are provided. Six openings arranged in a helical pattern in the chamber wall contain sealed sapphire windows for viewing an experiment in progress. The base of the chamber contains pressure-sealed electrical connectors for supplying power to the induction coil. The connectors feature a unique design that prevents induction heating of the housing and the pressure sealing surfaces; this is important because if such spurious induction heating were allowed to occur, chamber pressure could be lost. The induction coil is 10 in. (25.4 cm) long and is fitted with a specimen holder at its upper end. At its lower end, the induction coil is mounted on a ceramic base, which affords thermal insulation to

  9. Quasistationary magnetic field generation with a laser-driven capacitor-coil assembly.

    PubMed

    Tikhonchuk, V T; Bailly-Grandvaux, M; Santos, J J; Poyé, A

    2017-08-01

    Recent experiments are showing possibilities to generate strong magnetic fields on the excess of 500 T with high-energy nanosecond laser pulses in a compact setup of a capacitor connected to a single turn coil. Hot electrons ejected from the capacitor plate (cathode) are collected at the other plate (anode), thus providing the source of a current in the coil. However, the physical processes leading to generation of currents exceeding hundreds of kiloamperes in such a laser-driven diode are not sufficiently understood. Here we present a critical analysis of previous results and propose a self-consistent model for the high current generation in a laser-driven capacitor-coil assembly. It accounts for three major effects controlling the diode current: the space charge neutralization, the plasma magnetization between the capacitor plates, and the Ohmic heating of the external circuit-the coil-shaped connecting wire. The model provides the conditions necessary for transporting strongly super-Alfvenic currents through the diode on the time scale of a few nanoseconds. The model validity is confirmed by a comparison with the available experimental data.

  10. Effect of continuous ohmic heating to inactivate Escherichia coli O157:H7, Salmonella Typhimurium and Listeria monocytogenes in orange juice and tomato juice.

    PubMed

    Lee, S-Y; Sagong, H-G; Ryu, S; Kang, D-H

    2012-04-01

    The purpose of this study was to investigate the efficacy of continuous ohmic heating for reducing Escherichia coli O157:H7, Salmonella Typhimurium and Listeria monocytogenes in orange juice and tomato juice. Orange juice and tomato juice were treated with electric field strengths in the range of 25-40 V cm(-1) for different treatment times. The temperature of the samples increased with increasing treatment time and electric field strength. The rate of temperature change for tomato juice was higher than for orange juice at all voltage gradients applied. Higher electric field strength or longer treatment time resulted in a greater reduction of pathogens. Escherichia coli O157:H7 was reduced by more than 5 log after 60-, 90- and 180-s treatments in orange juice with 40, 35 and 30 V cm(-1) electric field strength, respectively. In tomato juice, treatment with 25 V cm(-1) for 30 s was sufficient to achieve a 5-log reduction in E. coli O157:H7. Similar results were observed in Salm. Typhimurium and L. monocytogenes. The concentration of vitamin C in continuous ohmic heated juice was significantly higher than in conventionally heated juice (P < 0·05). Continuous ohmic heating can be effective in killing foodborne pathogens on orange juice and tomato juice with lower degradation of quality than conventional heating. These results suggest that continuous ohmic heating might be effectively used to pasteurize fruit and vegetable juices in a short operating time and that the effect of inactivation depends on applied electric field strengths, treatment time and electric conductivity. © 2012 The Authors. Journal of Applied Microbiology © 2012 The Society for Applied Microbiology.

  11. Measurement of heating coil temperature for e-cigarettes with a “top-coil” clearomizer

    PubMed Central

    Wang, Ping; Ito, Kazuhide; Fowles, Jeff; Shusterman, Dennis; Jaques, Peter A.; Kumagai, Kazukiyo

    2018-01-01

    Objectives To determine the effect of applied power settings, coil wetness conditions, and e-liquid compositions on the coil heating temperature for e-cigarettes with a “top-coil” clearomizer, and to make associations of coil conditions with emission of toxic carbonyl compounds by combining results herein with the literature. Methods The coil temperature of a second generation e-cigarette was measured at various applied power levels, coil conditions, and e-liquid compositions, including (1) measurements by thermocouple at three e-liquid fill levels (dry, wet-through-wick, and full-wet), three coil resistances (low, standard, and high), and four voltage settings (3–6 V) for multiple coils using propylene glycol (PG) as a test liquid; (2) measurements by thermocouple at additional degrees of coil wetness for a high resistance coil using PG; and (3) measurements by both thermocouple and infrared (IR) camera for high resistance coils using PG alone and a 1:1 (wt/wt) mixture of PG and glycerol (PG/GL). Results For single point thermocouple measurements with PG, coil temperatures ranged from 322 ‒ 1008°C, 145 ‒ 334°C, and 110 ‒ 185°C under dry, wet-through-wick, and full-wet conditions, respectively, for the total of 13 replaceable coil heads. For conditions measured with both a thermocouple and an IR camera, all thermocouple measurements were between the minimum and maximum across-coil IR camera measurements and equal to 74% ‒ 115% of the across-coil mean, depending on test conditions. The IR camera showed details of the non-uniform temperature distribution across heating coils. The large temperature variations under wet-through-wick conditions may explain the large variations in formaldehyde formation rate reported in the literature for such “top-coil” clearomizers. Conclusions This study established a simple and straight-forward protocol to systematically measure e-cigarette coil heating temperature under dry, wet-through-wick, and full

  12. Transient Heat Transfer in TCAP Coils

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Steimke, J.L.

    1999-03-09

    The Thermal Cycling Absorption Process (TCAP) is used to separate isotopes of hydrogen. TCAP involves passing a stream of mixed hydrogen isotopes through palladium deposited on kieselguhr (Pd/k) while cycling the temperature of the Pd/k. Kieselguhr is a silica mineral also called diatomite. To aid in the design of a full scale facility, the Thermal Fluids Laboratory was used by the Chemical and Hydrogen Technology Section to compare the heat transfer properties of three different configurations of stainless steel coils containing kieselguhr and helium. Testing of coils containing Pd/k and hydrogen isotopes would have been more prototypical but would havemore » been too expensive. Three stainless steel coils filled with kieselguhr were tested; one made from 2.0 inch diameter tubing, one made from 2.0 inch diameter tubing with foam copper embedded in the kieselguhr and one made from 1.25 inch diameter tubing. It was known prior to testing that increasing the tubing diameter from 1.25 inch to 2.0 inch would slow the rate of temperature change. The primary purpose of the testing was to measure to what extent the presence of copper foam in a 2.0" tubing coil would compensate for the effect of larger diameter. Each coil was connected to a pressure gage and the coil was evacuated and backfilled with helium gas. Helium was used instead of a mixture of hydrogen isotopes for reasons of safety. Each coil was quickly immersed in a stirred bath of ethylene glycol at a temperature of approximately 100 degrees Celsius. The coil pressure increased, reflecting the increase in average temperature of its contents. The pressure transient was recored as a function of time after immersion. Because of the actual process will use Pd/k instead of kieselguhr, additional tests were run to determine the differences in thermal properties between the two materials. The method was to position a thermocouple at the center of a hollow sphere and pack the sphere with Pd/k. The sphere was sealed

  13. Transient Heat Transfer in TCAP Coils

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Steimke, J.L.

    1999-03-09

    The Thermal Cycling Absorption Process (TCAP) is used to separate isotopes of hydrogen. TCAP involves passing a stream of mixed hydrogen isotopes through palladium deposited on kieselguhr (Pd/k) while cycling the temperature of the Pd/k. Kieselguhr is a silica mineral also called diatomite. To aid in the design of a full scale facility, the Thermal Fluids Laboratory was used by the Chemical and Hydrogen Technology Section to compare the heat transfer properties of three different configurations of stainless steel coils containing kieselguhr and helium. Testing of coils containing Pd/k and hydrogen isotopes would have been more prototypical but would havemore » been too expensive. Three stainless steel coils filled with kieselguhr were tested; one made from 2.0 inch diameter tubing, one made from 2.0 inch diameter tubing with foam copper embedded in the kieselguhr and one made from 1.25 inch diameter tubing. It was known prior to testing that increasing the tubing diameter from 1.25 inch to 2.0 inch would slow the rate of temperature change. The primary purpose of the testing was to measure to what extent the presence of copper foam in a 2.0 tubing coil would compensate for the effect of larger diameter. Each coil was connected to a pressure gage and the coil was evacuated and backfilled with helium gas. Helium was used instead of a mixture of hydrogen isotopes for reasons of safety. Each coil was quickly immersed in a stirred bath of ethylene glycol at a temperature of approximately 100 degrees Celsius. The coil pressure increased, reflecting the increase in average temperature of its contents. The pressure transient was recored as a function of time after immersion. Because of the actual process will use Pd/k instead of kieselguhr, additional tests were run to determine the differences in thermal properties between the two materials. The method was to position a thermocouple at the center of a hollow sphere and pack the sphere with Pd/k. The sphere was sealed

  14. Effect of γ-Al2O3/water nanofluid on the thermal performance of shell and coil heat exchanger with different coil torsions

    NASA Astrophysics Data System (ADS)

    Elshazly, K. M.; Sakr, R. Y.; Ali, R. K.; Salem, M. R.

    2017-06-01

    This work investigated experimentally the thermal performance of shell and coil heat exchanger with different coil torsions (λ) for γ-Al2O3/water nanofluid flow. Five helically coiled tube (HCT) with 0.0442 ≤ λ ≤ 0.1348 were tested within turbulent flow regime. The average size of γ-Al2O3 particles is 40 nm and volume concentration (φ) is varied from 0 to 2%. Results showed that reducing coil torsion enhances the heat transfer rate and increases HCT-friction factor (fc). Also, it is noticed that HCT average Nusselt number (Nut) and fc of nanofluids increase with increasing γ-Al2O3 volume concentration. The thermal performance index, TPI = (ht,nf/ht,bf)/(ΔPc,nf/ΔPc,bf). increases with increasing nanoparticles concentration, coil torsion, HCT-side inlet temperature and nanofluid flow rate. Over the studied range of HCT-Reynolds number, the average value of TPI is of 1.34 and 2.24 at φ = 0.5% and φ = 2%, respectively. The average value of TPI is of 1.64 at λ = 0.0442 while its average value at λ = 0.1348 is of 2.01. One of the main contributions is to provide heat equipments designers with Nut and fc correlations for practical configurations shell and coil heat exchangers with a wide range of nanofluid concentration.

  15. Ohmic cooking of whole beef muscle--evaluation of the impact of a novel rapid ohmic cooking method on product quality.

    PubMed

    Zell, Markus; Lyng, James G; Cronin, Denis A; Morgan, Desmond J

    2010-10-01

    Cylindrical cores of beef semitendinosus (500g) were cooked in a combined ohmic/convection heating system to low (72 degrees C, LTLT) and high (95 degrees C, HTST) target end-point temperatures. A control was also cooked to an end-point temperature of 72 degrees C at the coldest point. Microbial challenge studies on a model meat matrix confirmed product safety. Hunter L-values showed that ohmically heated meat had significantly (p<0.05) lighter surface-colours (63.05 (LTLT) and 62.26 (HTST)) relative to the control (56.85). No significant texture differences (p>/=0.05) were suggested by Warner-Bratzler peak load values (34.09, 36.37 vs. 35.19N). Cook loss was significantly (p<0.05) lower for LTLT samples (29.3%) compared to the other meats (36.3 and 33.8%). Sensory studies largely confirmed these observations. Cook values were lower for LTLT (3.05) while HTST and the control were more comparable (6.09 and 7.71, respectively). These results demonstrate considerable potential for this application of ohmic heating for whole meats. Copyright (c) 2010 The American Meat Science Association. Published by Elsevier Ltd. All rights reserved.

  16. Application of low frequency pulsed ohmic heating for inactivation of foodborne pathogens and MS-2 phage in buffered peptone water and tomato juice.

    PubMed

    Kim, Sang-Soon; Choi, Won; Kang, Dong-Hyun

    2017-05-01

    The purpose of this study was to inactivate foodborne pathogens effectively by ohmic heating in buffered peptone water and tomato juice without causing electrode corrosion and quality degradation. Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes were used as representative foodborne pathogens and MS-2 phage was used as a norovirus surrogate. Buffered peptone water and tomato juice inoculated with pathogens were treated with pulsed ohmic heating at different frequencies (0.06-1 kHz). Propidium iodide uptake values of bacterial pathogens were significantly (p < 0.05) larger at 0.06-0.5 kHz than at 1 kHz, and sub-lethal injury of pathogenic bacteria was reduced by decreasing frequency. MS-2 phage was inactivated more effectively at low frequency, and was more sensitive to acidic conditions than pathogenic bacteria. Electrode corrosion and quality degradation of tomato juice were not observed regardless of frequency. This study suggests that low frequency pulsed ohmic heating is applicable to inactivate foodborne pathogens effectively without causing electrode corrosion and quality degradation in tomato juice. Copyright © 2016. Published by Elsevier Ltd.

  17. Investigation of optimum ohmic heating conditions for inactivation of Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium, and Listeria monocytogenes in apple juice.

    PubMed

    Park, Il-Kyu; Ha, Jae-Won; Kang, Dong-Hyun

    2017-05-19

    Control of foodborne pathogens is an important issue for the fruit juice industry and ohmic heating treatment has been considered as one of the promising antimicrobial interventions. However, to date, evaluation of the relationship between inactivation of foodborne pathogens and system performance efficiency based on differing soluble solids content of apple juice during ohmic heating treatment has not been well studied. This study aims to investigate effective voltage gradients of an ohmic heating system and corresponding sugar concentrations (°Brix) of apple juice for inactivating major foodborne pathogens (E. coli O157:H7, S. Typhimurium, and L. monocytogenes) while maintaining higher system performance efficiency. Voltage gradients of 30, 40, 50, and 60 V/cm were applied to 72, 48, 36, 24, and 18 °Brix apple juices. At all voltage levels, the lowest heating rate was observed in 72 °Brix apple juice and a similar pattern of temperature increase was shown in18-48 °Brix juice samples. System performance coefficients (SPC) under two treatment conditions (30 V/cm in 36 °Brix or 60 V/cm in 48 °Brix juice) were relatively greater than for other combinations. Meanwhile, 5-log reductions of the three foodborne pathogens were achieved after treatment for 60 s in 36 °Brix at 30 V/cm, but this same reduction was observed in 48 °Brix juice at 60 V/cm within 20 s without affecting product quality. With respect to both bactericidal efficiency and SPC values, 60 V/cm in 48 °Brix was the most effective ohmic heating treatment combination for decontaminating apple juice concentrates.

  18. Experimental analysis for heat transfer of nanofluid with wire coil turbulators in a concentric tube heat exchanger

    NASA Astrophysics Data System (ADS)

    Akyürek, Eda Feyza; Geliş, Kadir; Şahin, Bayram; Manay, Eyüphan

    2018-06-01

    Nanofluids are a novel class of heat transfer suspensions of metallic or nonmetallic nanopowders with a size of less than 100 nm in base fluids and they can increase heat transfer potential of the base fluids in various applications. In the last decade, nanofluids have become an intensive research topic because of their improved thermal properties and possible heat transfer applications. For comparison, an experiment using water as the working fluid in the heat exchanger without wire coils was also performed. Turbulent forced convection heat transfer and pressure drop characteristics of Al2O3-water nanofluids in a concentric tube heat exchanger with and without wire coil turbulators were experimentally investigated in this research. Experiments effected particle volume concentrations of 0.4-0.8 to 1.2-1.6 vol% in the Reynolds number range from 4000 to 20,000. Two turbulators with the pitches of 25 mm and 39 mm were used. The average Nusselt number increased with increasing the Reynolds number and particle concentrations. Moreover, the pressure drop of the Al2O3-water nanofluid showed nearly equal to that of pure water at the same Reynolds number range. As a result, nanofluids with lower particle concentrations did not show an important influence on pressure drop change. Nonetheless, when the wire coils used in the heat exchanger, it increased pressure drop as well as the heat transfer coefficient.

  19. Ohmic ITBs in Alcator C-Mod

    NASA Astrophysics Data System (ADS)

    Rowan, William L.; Bespamyatnov, Igor O.; Fiore, C. L.; Dominguez, A.; Hubbard, A. E.; Ince-Cushman, A.; Greenwald, M. J.; Lin, L.; Marmar, E. S.; Reinke, M.; Rice, J. E.; Zhurovich, K.

    2007-11-01

    Internal transport barrier (ITB) plasmas can arise spontaneously in Ohmic Alcator C-Mod plasmas. The operational prescription for the ITB include formation of an EDA H-mode in a toroidal magnetic field that is ramping down and a subsequent increase in the toroidal magnetic field. Like ITBs generated with off-axis ICRF heating, these have peaked pressure profiles which can be suppressed by on-axis ICRF heating. Recent work on onset conditions for the ICRF generated ITB (K. Zhurovich, et al., To be published in Nuclear Fusion) demonstrates that the broadening of the ion temperature profile due to off-axis ICRF reduces the ion temperature gradient and suppreses the ITG instability driven particle flux as the primary mechanism for ITB formation. The object of this study is to examine the characteristics of Ohmic ITBs to find whether this model for onset is supported.

  20. 1. PLENUM INTERIOR, SHOWING HEATING COILS AND BYPASS Hot ...

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

    1. PLENUM INTERIOR, SHOWING HEATING COILS AND BY-PASS - Hot Springs National Park, Bathhouse Row, Fordyce Bathhouse: Mechanical & Piping Systems, State Highway 7, 1 mile north of U.S. Highway 70, Hot Springs, Garland County, AR

  1. Numerical evaluation of laminar heat transfer enhancement in nanofluid flow in coiled square tubes

    PubMed Central

    2011-01-01

    Convective heat transfer can be enhanced by changing flow geometry and/or by enhancing thermal conductivity of the fluid. This study proposes simultaneous passive heat transfer enhancement by combining the geometry effect utilizing nanofluids inflow in coils. The two nanofluid suspensions examined in this study are: water-Al2O3 and water-CuO. The flow behavior and heat transfer performance of these nanofluid suspensions in various configurations of coiled square tubes, e.g., conical spiral, in-plane spiral, and helical spiral, are investigated and compared with those for water flowing in a straight tube. Laminar flow of a Newtonian nanofluid in coils made of square cross section tubes is simulated using computational fluid dynamics (CFD)approach, where the nanofluid properties are treated as functions of particle volumetric concentration and temperature. The results indicate that addition of small amounts of nanoparticles up to 1% improves significantly the heat transfer performance; however, further addition tends to deteriorate heat transfer performance. PMID:21711901

  2. Study of transient behavior of finned coil heat exchangers

    NASA Technical Reports Server (NTRS)

    Rooke, S. P.; Elissa, M. G.

    1993-01-01

    The status of research on the transient behavior of finned coil cross-flow heat exchangers using single phase fluids is reviewed. Applications with available analytical or numerical solutions are discussed. Investigation of water-to-air type cross-flow finned tube heat exchangers is examined through the use of simplified governing equations and an up-wind finite difference scheme. The degenerate case of zero air-side capacitance rate is compared with available exact solution. Generalization of the numerical model is discussed for application to multi-row multi-circuit heat exchangers.

  3. Induction heating using induction coils in series-parallel circuits

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Matsen, Marc Rollo; Geren, William Preston; Miller, Robert James

    A part is inductively heated by multiple, self-regulating induction coil circuits having susceptors, coupled together in parallel and in series with an AC power supply. Each of the circuits includes a tuning capacitor that tunes the circuit to resonate at the frequency of AC power supply.

  4. Entropy Generation Analysis through Helical Coil Heat Exchanger in an Agitated Vessel

    NASA Astrophysics Data System (ADS)

    Ashok Reddy, K.

    2018-03-01

    Entropy Generation have been obtained while conducting the experiments for different sodium carboxymethyl cellulose concentrations 0.05%,0.1%,0.15% and 0.2% of Newtonian and non Newtonian fluids and the data made available by passing the test fluid at different flow rates through a helical coil in a mixing coil using paddle impeller. Heating of fluids depend on operational parameters, geometry of the mixing vessel and the type of impeller used. A new design of heating element was design and fabricated by providing kanthal wire inserted into a glove knitted with fiber glass yarn as glass fabric is flexible, heat resistant and can accommodate to adopt small difference in size of the vessel, perfectly. The knitted fabric is made to the shape of vessel used in the experiment and the heating elements are inserted so that it gets embedded and forms part of the glove knitted with yarn of fiber glass.

  5. Effects of design parameters and puff topography on heating coil temperature and mainstream aerosols in electronic cigarettes

    NASA Astrophysics Data System (ADS)

    Zhao, Tongke; Shu, Shi; Guo, Qiuju; Zhu, Yifang

    2016-06-01

    Emissions from electronic cigarettes (ECs) may contribute to both indoor and outdoor air pollution and the number of users is increasing rapidly. ECs operate based on the evaporation of e-liquid by a high-temperature heating coil. Both puff topography and design parameters can affect this evaporation process. In this study, both mainstream aerosols and heating coil temperature were measured concurrently to study the effects of design parameters and puff topography. The heating coil temperatures and mainstream aerosols varied over a wide range across different brands and within same brand. The peak heating coil temperature and the count median diameter (CMD) of EC aerosols increased with a longer puff duration and a lower puff flow rate. The particle number concentration was positively associated with the puff duration and puff flow rate. These results provide a better understanding of how EC emissions are affected by design parameters and puff topography and emphasize the urgent need to better regulate EC products.

  6. Effect of Frequency and Waveform on Inactivation of Escherichia coli O157:H7 and Salmonella enterica Serovar Typhimurium in Salsa by Ohmic Heating

    PubMed Central

    Lee, Su-Yeon; Ryu, Sangryeol

    2013-01-01

    The effect of frequency of alternating current during ohmic heating on electrode corrosion, heating rate, inactivation of food-borne pathogens, and quality of salsa was investigated. The impact of waveform on heating rate was also investigated. Salsa was treated with various frequencies (60 Hz to 20 kHz) and waveforms (sine, square, and sawtooth) at a constant electric field strength of 12.5 V/cm. Electrode corrosion did not occur when the frequency exceeded 1 kHz. The heating rate of the sample was dependent on frequency up to 500 Hz, but there was no significant difference (P > 0.05) in the heating rate when the frequency was increased above 1 kHz. The electrical conductivity of the sample increased with a rise in the frequency. At a frequency of 60 Hz, the square wave produced a lower heating rate than that of sine and sawtooth waves. The heating rate between waveforms was not significantly (P > 0.05) different when the frequency was >500 Hz. As the frequency increased, the treatment time required to reduce Escherichia coli O157:H7 and Salmonella enterica serovar Typhimurium to below the detection limit (1 log CFU/g) decreased without affecting product quality. These results suggest that ohmic heating can be effectively used to pasteurize salsa and that the effect of inactivation is dependent on frequency and electrical conductivity rather than waveform. PMID:23023752

  7. Effect of frequency and waveform on inactivation of Escherichia coli O157:H7 and Salmonella enterica Serovar Typhimurium in salsa by ohmic heating.

    PubMed

    Lee, Su-Yeon; Ryu, Sangryeol; Kang, Dong-Hyun

    2013-01-01

    The effect of frequency of alternating current during ohmic heating on electrode corrosion, heating rate, inactivation of food-borne pathogens, and quality of salsa was investigated. The impact of waveform on heating rate was also investigated. Salsa was treated with various frequencies (60 Hz to 20 kHz) and waveforms (sine, square, and sawtooth) at a constant electric field strength of 12.5 V/cm. Electrode corrosion did not occur when the frequency exceeded 1 kHz. The heating rate of the sample was dependent on frequency up to 500 Hz, but there was no significant difference (P > 0.05) in the heating rate when the frequency was increased above 1 kHz. The electrical conductivity of the sample increased with a rise in the frequency. At a frequency of 60 Hz, the square wave produced a lower heating rate than that of sine and sawtooth waves. The heating rate between waveforms was not significantly (P > 0.05) different when the frequency was >500 Hz. As the frequency increased, the treatment time required to reduce Escherichia coli O157:H7 and Salmonella enterica serovar Typhimurium to below the detection limit (1 log CFU/g) decreased without affecting product quality. These results suggest that ohmic heating can be effectively used to pasteurize salsa and that the effect of inactivation is dependent on frequency and electrical conductivity rather than waveform.

  8. CFD analysis of the two-phase bubbly flow characteristics in helically coiled rectangular and circular tube heat exchangers

    NASA Astrophysics Data System (ADS)

    Hussain, Alamin; Fsadni, Andrew M.

    2016-03-01

    Due to their ease of manufacture, high heat transfer efficiency and compact design, helically coiled heat exchangers are increasingly being adopted in a number of industries. The higher heat transfer efficiency over straight pipes is due to the secondary flow that develops as a result of the centrifugal force. In spite of the widespread use of helically coiled heat exchangers, and the presence of bubbly two-phase flow in a number of systems, very few studies have investigated the resultant flow characteristics. This paper will therefore present the results of CFD simulations for the two-phase bubbly flow in helically coiled heat exchangers as a function of the volumetric void fraction and the tube cross-section design. The CFD results are compared to the scarce flow visualisation experimental results available in the open literature.

  9. Application of horizontal spiral coil heat exchanger for volatile organic compounds (VOC) emission control.

    PubMed

    Deshpande, P M; Dawande, S D

    2013-04-01

    The petroleum products have wide range of volatility and are required to be stored in bulk. The evaporation losses are significant and it is a economic as well as environmental concern, since evaporative losses of petroleum products cause increased VOC in ambient air. Control of these losses poses a major problem for the storage tank designers. Ever rising cost of petroleum products further adds to the gravity of the problem. Condensation is one of the technologies for reducing volatile organic compounds emissions. Condensation is effected by condenser, which is basically a heat exchanger and the heat exchanger configuration plays an important role. The horizontal spiral coil heat exchanger is a promising configuration that finds an application in VOC control. This paper attempts to understand underlying causes of emissions and analyse the option of horizontal spiral coil heat exchanger as vent condenser.

  10. RF HEATING OF MRI-ASSISTED CATHETER STEERING COILS FOR INTERVENTIONAL MRI

    PubMed Central

    Settecase, Fabio; Hetts, Steven W.; Martin, Alastair J.; Roberts, Timothy P. L.; Bernhardt, Anthony F.; Evans, Lee; Malba, Vincent; Saeed, Maythem; Arenson, Ronald L.; Kucharzyk, Walter; Wilson, Mark W.

    2010-01-01

    RATIONALE AND OBJECTIVES To assess magnetic resonance imaging (MRI) radiofrequency (RF) related heating of conductive wire coils used in magnetically steerable endovascular catheters. MATERIALS AND METHODS A 3-axis microcoil was fabricated onto a 1.8 Fr catheter tip. In vitro testing was performed in a 1.5 T MRI system using an agarose gel filled vessel phantom, a transmit/receive body RF coil and a steady state free precession (SSFP) pulse sequence, and a fluoroptic thermometry system. Temperature was measured without simulated blood flow at varying distances from magnet isocenter and varying flip angles. Additional experiments were performed with laser-lithographed single-axis microcoil-tipped microcatheters in air and in a saline bath with varied grounding of the microcoil wires. Preliminary in vivo evaluation of RF heating was performed in pigs at 1.5 T with coil-tipped catheters in various positions in the common carotid arteries with SSFP pulse sequence on and off, and under physiologic flow and zero flow conditions. RESULTS In tissue-mimicking agarose gel, RF heating resulted in a maximal temperature increase of 0.35°C after 15 minutes of imaging, 15 cm from magnet isocenter. For a single axis microcoil, maximal temperature increases were 0.73-1.91°C in air and 0.45-0.55°C in saline. In vivo, delayed contrast enhanced MRI revealed no evidence of vascular injury and histopathological sections from the common carotid arteries confirmed the lack of vascular damage. CONCLUSIONS Microcatheter tip microcoils for endovascular catheter steering in MRI experience minimal RF heating under the conditions tested. These data provide the basis for further in vivo testing of this promising technology for endovascular interventional MRI. PMID:21075019

  11. RF Heating of MRI-Assisted Catheter Steering Coils for Interventional MRI.

    PubMed

    Settecase, Fabio; Hetts, Steven W; Martin, Alastair J; Roberts, Timothy P L; Bernhardt, Anthony F; Evans, Lee; Malba, Vincent; Saeed, Maythem; Arenson, Ronald L; Kucharzyk, Walter; Wilson, Mark W

    2011-03-01

    The aim of this study was too assess magnetic resonance imaging (MRI) radiofrequency (RF)-related heating of conductive wire coils used in magnetically steerable endovascular catheters. A three-axis microcoil was fabricated onto a 1.8Fr catheter tip. In vitro testing was performed on a 1.5-T MRI system using an agarose gel-filled vessel phantom, a transmit-receive body RF coil, a steady-state free precession pulse sequence, and a fluoroptic thermometry system. Temperature was measured without simulated blood flow at varying distances from the magnet isocenter and at varying flip angles. Additional experiments were performed with laser-lithographed single-axis microcoil-tipped microcatheters in air and in a saline bath with varied grounding of the microcoil wires. Preliminary in vivo evaluation of RF heating was performed in pigs at 1.5 T with coil-tipped catheters in various positions in the common carotid arteries with steady-state free precession pulse sequence on and off and under physiologic-flow and zero-flow conditions. In tissue-mimicking agarose gel, RF heating resulted in a maximal temperature increase of 0.35°C after 15 minutes of imaging, 15 cm from the magnet isocenter. For a single-axis microcoil, maximal temperature increases were 0.73°C to 1.91°C in air and 0.45°C to 0.55°C in saline. In vivo, delayed contrast-enhanced MRI revealed no evidence of vascular injury, and histopathologic sections from the common carotid arteries confirmed the lack of vascular damage. Microcatheter tip microcoils for endovascular catheter steering in MRI experience minimal RF heating under the conditions tested. These data provide the basis for further in vivo testing of this promising technology for endovascular interventional MRI. Copyright © 2011 AUR. Published by Elsevier Inc. All rights reserved.

  12. Coil Welding Aid

    NASA Technical Reports Server (NTRS)

    Wiesenbach, W. T.; Clark, M. C.

    1983-01-01

    Positioner holds coil inside cylinder during tack welding. Welding aid spaces turns of coil inside cylinder and applies contact pressure while coil is tack-welded to cylinder. Device facilitates fabrication of heat exchangers and other structures by eliminating hand-positioning and clamping of individual coil turns.

  13. Universal Scaling of Robust Thermal Hot Spot and Ionic Current Enhancement by Focused Ohmic Heating in a Conic Nanopore

    PubMed Central

    Pan, Zehao; Wang, Ceming; Li, Meng; Chang, Hsueh-Chia

    2017-01-01

    A stable nanoscale thermal hot spot, with temperature approaching 100 °C, is shown to be sustained by localized Ohmic heating of a focused electric field at the tip of a slender conic nanopore. The self-similar (length-independent) conic geometry allows us to match the singular heat source at the tip to the singular radial heat loss from the slender cone to obtain a self-similar steady temperature profile along the cone and the resulting ionic current conductance enhancement due to viscosity reduction. The universal scaling, which depends only on a single dimensionless parameter Z, collapses the measured conductance data and computed temperature profiles in ion-track conic nanopores and conic nanopipettes. The collapsed numerical data reveal universal values for the hot-spot location and temperature in an aqueous electrolyte. PMID:27715110

  14. Universal Scaling of Robust Thermal Hot Spot and Ionic Current Enhancement by Focused Ohmic Heating in a Conic Nanopore

    NASA Astrophysics Data System (ADS)

    Pan, Zehao; Wang, Ceming; Li, Meng; Chang, Hsueh-Chia

    2016-09-01

    A stable nanoscale thermal hot spot, with temperature approaching 100 °C , is shown to be sustained by localized Ohmic heating of a focused electric field at the tip of a slender conic nanopore. The self-similar (length-independent) conic geometry allows us to match the singular heat source at the tip to the singular radial heat loss from the slender cone to obtain a self-similar steady temperature profile along the cone and the resulting ionic current conductance enhancement due to viscosity reduction. The universal scaling, which depends only on a single dimensionless parameter Z , collapses the measured conductance data and computed temperature profiles in ion-track conic nanopores and conic nanopipettes. The collapsed numerical data reveal universal values for the hot-spot location and temperature in an aqueous electrolyte.

  15. Universal Scaling of Robust Thermal Hot Spot and Ionic Current Enhancement by Focused Ohmic Heating in a Conic Nanopore.

    PubMed

    Pan, Zehao; Wang, Ceming; Li, Meng; Chang, Hsueh-Chia

    2016-09-23

    A stable nanoscale thermal hot spot, with temperature approaching 100 °C, is shown to be sustained by localized Ohmic heating of a focused electric field at the tip of a slender conic nanopore. The self-similar (length-independent) conic geometry allows us to match the singular heat source at the tip to the singular radial heat loss from the slender cone to obtain a self-similar steady temperature profile along the cone and the resulting ionic current conductance enhancement due to viscosity reduction. The universal scaling, which depends only on a single dimensionless parameter Z, collapses the measured conductance data and computed temperature profiles in ion-track conic nanopores and conic nanopipettes. The collapsed numerical data reveal universal values for the hot-spot location and temperature in an aqueous electrolyte.

  16. Influence of infrared final cooking on color, texture and cooking characteristics of ohmically pre-cooked meatball.

    PubMed

    Yildiz Turp, Gulen; Icier, Filiz; Kor, Gamze

    2016-04-01

    The objective of the current study was to improve the quality characteristics of ohmically pre-cooked beef meatballs via infrared cooking as a final stage. Samples were pre-cooked in a specially designed-continuous type ohmic cooker at a voltage gradient of 15.26 V/cm for 92 s. Infrared cooking was then applied to the pre-cooked samples at different combinations of heat fluxes (3.706, 5.678, and 8.475 kW/m(2)), application distances (10.5, 13.5, and 16.5 cm) and application durations (4, 8, and 12min). Effects of these parameters on color, texture and cooking characteristics of ohmically pre-cooked beef meatballs were investigated. The appearance of ohmically pre-cooked meatball samples was improved via infrared heating. A dark brown layer desired in cooked meatballs formed on the surface of the meatballs with lowest application distance (10.5 cm) and longest application duration (12 min). The texture of the samples was also improved with these parameters. However the cooking yield of the samples decreased at the longest application duration of infrared heating. Copyright © 2015 Elsevier Ltd. All rights reserved.

  17. Experimental investigation of TiO2/water nanofluid laminar forced convective heat transfer through helical coiled tube

    NASA Astrophysics Data System (ADS)

    Kahani, M.; Zeinali Heris, S.; Mousavi, S. M.

    2014-05-01

    Coiled tubes and nanofludics are two significant techniques to enhance the heat transfer ability of thermal equipments. The forced convective heat transfer and the pressure drop of nanofluid inside straight tube and helical coiled one with a constant wall heat flux were studied experimentally. Distilled water was used as a host fluid and Nanofluids of aqueous TiO2 nanoparticles (50 nm) suspensions were prepared in various volume concentrations of 0.25-2 %. The heat transfer coefficient of nanofluids is obtained for different nanoparticle concentrations as well as various Reynolds numbers. The experiments covered a range of Reynolds number of 500-4,500. The results show the considerable enhancement of heat transfer rate, which is due to the nanoparticles present in the fluid. Heat transfer coefficient increases by increasing the volume concentration of nanoparticles as well as Reynolds number. Moreover, due to the curvature of the tube when fluid flows inside helical coiled tube instead of straight one, both convective heat transfer coefficient and the pressure drop of fluid grow considerably. Also, the thermal performance factors for tested nanofluids are greater than unity and the maximum thermal performance factor of 3.72 is found with the use of 2.0 % volume concentration of nanofluid at Reynolds number of 1,750.

  18. Turbulent convective heat transfer of methane at supercritical pressure in a helical coiled tube

    NASA Astrophysics Data System (ADS)

    Wang, Chenggang; Sun, Baokun; Lin, Wei; He, Fan; You, Yingqiang; Yu, Jiuyang

    2018-02-01

    The heat transfer of methane at supercritical pressure in a helically coiled tube was numerically investigated using the Reynolds Stress Model under constant wall temperature. The effects of mass flux ( G), inlet pressure ( P in) and buoyancy force on the heat transfer behaviors were discussed in detail. Results show that the light fluid with higher temperature appears near the inner wall of the helically coiled tube. When the bulk temperature is less than or approach to the pseudocritical temperature ( T pc ), the combined effects of buoyancy force and centrifugal force make heavy fluid with lower temperature appear near the outer-right of the helically coiled tube. Beyond the T pc , the heavy fluid with lower temperature moves from the outer-right region to the outer region owing to the centrifugal force. The buoyancy force caused by density variation, which can be characterized by Gr/ Re 2 and Gr/ Re 2.7, enhances the heat transfer coefficient ( h) when the bulk temperature is less than or near the T pc , and the h experiences oscillation due to the buoyancy force. The oscillation is reduced progressively with the increase of G. Moreover, h reaches its peak value near the T pc . Higher G could improve the heat transfer performance in the whole temperature range. The peak value of h depends on P in. A new correlation was proposed for methane at supercritical pressure convective heat transfer in the helical tube, which shows a good agreement with the present simulated results.

  19. Edge ohmic heating and improved confinement on HT-6M Tokamak

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Gao, X.

    1995-04-01

    An improved confinement has been observed on HT-6M tokamak after application of Edge Ohmic Heating (EOH) which makes plasma current rapidly ramp up from an initial steady state (I{sub p}=55 kA) within a small time scale (0.4 ms) to a second steady state (I{sub p}=60 kA) with a ramp rate of 12 MA/sec. The improved confinement is characterized by (a) increased average density n{sub e}; (b) reduced H{sub alpha} radiation; (c) reduced density fluctuations both in the center and at the edge; (d) a steeper n{sub e} and T{sub e} profile at the edge; (e) the changed profiles of plasmamore » parameters n{sub e}(r), q(r) and j(r); (f) transferred the oscillation modes of the soft-X ray signals from Mirnov fluctuation (12 kHz) to sawtooth oscillation (1.7 kHz). The changes of edge fluctuation, radial electric field and bremsstrahlung during EOH were measured and discussed in details. The measured values of {beta}{sub p}+l{sub i}/2 and soft-X ray sawtooth inversion radius implied the anomalous current penetration. 10 refs., 2 figs.« less

  20. Uniform magnetic fields and double-wrapped coil systems: improved techniques for the design of bioelectromagnetic experiments.

    PubMed

    Kirschvink, J L

    1992-01-01

    A common mistake in biomagnetic experimentation is the assumption that Helmholtz coils provide uniform magnetic fields; this is true only for a limited volume at their center. Substantial improvements on this design have been made during the past 140 years with systems of three, four, and five coils. Numerical comparisons of the field uniformity generated by these designs are made here, along with a table of construction details and recommendations for their use in experiments in which large volumes of uniform intensity magnetic exposures are needed. Double-wrapping, or systems of bifilar windings, can also help control for the non-magnetic effects of the electric coils used in many experiments. In this design, each coil is wrapped in parallel with two separate, adjacent strands of copper wire, rather than the single strand used normally. If currents are flowing in antiparallel directions, the magnetic fields generated by each strand will cancel and yield virtually no external magnetic field, whereas parallel currents will yield an external field. Both cases will produce similar non-magnetic effects of ohmic heating, and simple measures can reduce the small vibration and electric field differences. Control experiments can then be designed such that the only major difference between treated and untreated groups is the presence or absence of the magnetic field. Double-wrapped coils also facilitate the use of truly double-blind protocol, as the same apparatus can be used either for experimental or control groups.

  1. Unsteady heat dissipation in accelerator superconducting coils insulated with porous ceramic insulation in normal and supercritical helium conditions

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Pietrowicz, S.; Four, A.; Baudouy, B.

    To investigate the unsteady heat dissipation in accelerator superconducting coils insulated with porous ceramic insulation, two experimental mock-ups reproducing the thermal and the mechanical conditions of a superconducting coils were produced. The mock-ups with compressive load of 10 MPa and 20 MPa were tested at normal (T = 4.23 K and p = 1 bar) and supercritical helium conditions (T = 4.23 K and p = 2.0 to 3.75 bar) during unsteady heat dissipation. The paper presents the experimental results of temperature rise in both superconducting coils as a function of time for a wide range of a localized heatmore » load varying from 0.1 kJ/m{sup 3} up to 12.8 MJ m{sup −3} per pulse. A numerical model of the transient process in these coils has been developed and the computations are compared with the experimental results.« less

  2. Quantitative comparison of electron temperature fluctuations to nonlinear gyrokinetic simulations in C-Mod Ohmic L-mode discharges

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sung, C., E-mail: csung@physics.ucla.edu; White, A. E.; Greenwald, M.

    2016-04-15

    Long wavelength turbulent electron temperature fluctuations (k{sub y}ρ{sub s} < 0.3) are measured in the outer core region (r/a > 0.8) of Ohmic L-mode plasmas at Alcator C-Mod [E. S. Marmar et al., Nucl. Fusion 49, 104014 (2009)] with a correlation electron cyclotron emission diagnostic. The relative amplitude and frequency spectrum of the fluctuations are compared quantitatively with nonlinear gyrokinetic simulations using the GYRO code [J. Candy and R. E. Waltz, J. Comput. Phys. 186, 545 (2003)] in two different confinement regimes: linear Ohmic confinement (LOC) regime and saturated Ohmic confinement (SOC) regime. When comparing experiment with nonlinear simulations, it is found that local,more » electrostatic ion-scale simulations (k{sub y}ρ{sub s} ≲ 1.7) performed at r/a ∼ 0.85 reproduce the experimental ion heat flux levels, electron temperature fluctuation levels, and frequency spectra within experimental error bars. In contrast, the electron heat flux is robustly under-predicted and cannot be recovered by using scans of the simulation inputs within error bars or by using global simulations. If both the ion heat flux and the measured temperature fluctuations are attributed predominantly to long-wavelength turbulence, then under-prediction of electron heat flux strongly suggests that electron scale turbulence is important for transport in C-Mod Ohmic L-mode discharges. In addition, no evidence is found from linear or nonlinear simulations for a clear transition from trapped electron mode to ion temperature gradient turbulence across the LOC/SOC transition, and also there is no evidence in these Ohmic L-mode plasmas of the “Transport Shortfall” [C. Holland et al., Phys. Plasmas 16, 052301 (2009)].« less

  3. Bayesian Analysis of Hot Jupiter Radius Anomalies Points to Ohmic Dissipation

    NASA Astrophysics Data System (ADS)

    Thorngren, Daniel; Fortney, Jonathan

    2018-01-01

    The cause of the unexpectedly large radii of hot Jupiters has been the subject of many hypotheses over the past 15 years and is one of the long-standing open issues in exoplanetary physics. In our work, we seek to examine the population of 300 hot Jupiters to identify a model that best explains their radii. Using a hierarchical Bayesian framework, we match structure evolution models to the observed giant planets’ masses, radii, and ages, with a prior for bulk composition based on the mass from Thorngren et al. (2016). We consider various models for the relationship between heating efficiency (the fraction of flux absorbed into the interior) and incident flux. For the first time, we are able to derive this heating efficiency as a function of planetary T_eq. Models in which the heating efficiency decreases at the higher temperatures (above ~1600 K) are strongly and statistically significantly preferred. Of the published models for the radius anomaly, only the Ohmic dissipation model predicts this feature, which it explains as being the result of magnetic drag reducing atmospheric wind speeds. We interpret our results as evidence in favor of the Ohmic dissipation model.

  4. Alfvén oscillations in ohmic discharges with runaway electrons in the TUMAN-3M tokamak

    NASA Astrophysics Data System (ADS)

    Tukachinsky, A. S.; Askinazi, L. G.; Balachenkov, I. M.; Belokurov, A. A.; Gin, D. B.; Zhubr, N. A.; Kornev, V. A.; Lebedev, S. V.; Khil'kevich, E. M.; Chugunov, I. N.; Shevelev, A. E.

    2016-12-01

    Studying the mechanism of Alfvén wave generation in plasma is important, since the interaction of these waves with energetic particles in tokamak-type reactors can increase the losses of energy and particles with the corresponding decrease in the efficiency of plasma heating and, under certain conditions, lead to the damage of structural elements of the system. Despite the previous detailed investigations of the excitation of Alfvén waves by superthermal particles in regimes with additional heating, the physics of Alfvén mode generation in discharges with ohmic heating of plasma is still not sufficiently studied. We have established that a significant factor inf luencing the development of Alfvén oscillations in ohmic discharge is the presence of runaway electrons. A physical mechanism explaining this relationship is proposed.

  5. Ohmic ignition with high engineering beta based on the RFP

    NASA Astrophysics Data System (ADS)

    Sarff, J. S.; Anderson, J. K.; Chapman, B. E.; McCollam, K. J.

    2017-10-01

    The RFP configuration allows the possibility of ohmic ignition for fusion energy, eliminating the need for auxiliary heating by rf or neutral beam injection. Complex plasma-facing antennas and NBI sources are therefore not required, simplifying the difficult fusion materials challenge. While all toroidal configurations require a volume-average 〈 B 〉 >= 5 T, the field strength at the magnet in the RFP is only Bcoil 3T since plasma current generates almost all of the field. Engineering beta is therefore maximized. We summarize access to ohmic ignition by examining a Lawson-like power balance for an RFP fusion plasma comparable to the ARIES-AT advanced tokamak, which generates neutron wall loading Pn / A 5 MW/m2. The required energy confinement for ohmic ignition in an RFP is similar to that for a tokamak. Confinement in MST is comparable to a same-size, same-field tokamak plasma, but 〈 B 〉 in MST is only 1/20th that required for fusion. While transport could ultimately be dominated by micro turbulence, extrapolation of stochastic transport using Lundquist number scaling for MHD tearing indicates standard RFP confinement (not enhanced by current profile control) could be sufficient to access ohmic ignition. This bolsters the possibility for steady-state inductive sustainment using oscillating field current drive. The high beta and classical energetic ion confinement measured in MST also bolster the RFP's fusion potential. Work supported by U.S. DoE.

  6. Destruction of Bacillus cereus spores in a thick soy bean paste (doenjang) by continuous ohmic heating with five sequential electrodes.

    PubMed

    Ryang, J H; Kim, N H; Lee, B S; Kim, C T; Rhee, M S

    2016-07-01

    This study selected spores from Bacillus cereus FSP-2 strain (the isolate from a commercial doenjang processing line) as the test strain which showed significantly higher thermal resistance (P < 0·05) than B. cereus reference strain (ATCC 27348). The spores in doenjang were subjected to ohmic heating (OH) at 95, 105, 115 and 125°C for 30, 60 or 90 s using a five sequential electrode system (electrical field: 26·7 V cm(-1) ; alternating current frequency: 25 kHz). OH at 105°C for 30-90 s reduced the B. cereus spore count in doenjang samples to <4 log CFU g(-1) . Since OH treatment at 115 and 125°C caused a perceivable colour change in the product (>1·5 National Bureau of Standards units), treatment at 105°C for 60 s was selected and applied on a large scale (500 kg of product). Reliable and reproducible destruction of B. cereus spores occurred; the reductions achieved (to < 4 log CFU g(-1) ) met the Korean national standards. Scanning electron microscopy revealed microstructural alterations in the spores (shrinkage and a distorted outer spore coat). OH is an effective method for destroying B. cereus spores to ensure the microbiological quality and safety of a thick, highly viscous sauce. This study shows that an ohmic heating (OH) using a five sequential electrode system can effectively destroy highly heat-resistant Bacillus cereus spores which have been frequently found in a commercial doenjang processing line without perceivable quality change in the product. In addition, it may demonstrate high potential of the unique OH system used in this study that will further contribute to ensure microbiological quality and safety of crude sauces containing high levels of electrolyte other than doenjang as well. © 2016 The Society for Applied Microbiology.

  7. Study on Matching a 300 MVA Motor Generator with an Ohmic Heating Power Supply in HL-2M

    NASA Astrophysics Data System (ADS)

    Peng, Jianfei; Xuan, Weimin; Wang, Haibing; Li, Huajun; Wang, Yingqiao; Wang, Shujin

    2013-03-01

    A new 300 MVA/1350 MJ motor generator (MG) will be built to feed all of the poloidal field power supplies (PFPS) and auxiliary heating power supplies of the HL-2M tokamak. The MG has a vertical-shaft salient pole 6-phase synchronous generator and a coaxial 8500 kW induction motor. The Ohmic heating power supply (OHPS) consisting of 4-quadrant DC pulsed convertor is the one with the highest parameters among the PFPS. Therefore, the match between the generator and the OHPS is very important. The matching study with Matlab/Simulink is described in this paper. The simulation results show that the subtransient reactance of the generator is closely related to the inversion operation of the OHPS. By setting various subtransient reactance in the simulation generator model and considering the cost reduction, the optimized parameters are obtained as x″d = 0.405 p.u. at 100 Hz for the generator. The models built in the simulation can be used as an important tool for studying the dynamic characteristics and the control strategy of other HL-2M PFPSes.

  8. Hydronic Heating Coil Versus Propane Furnace, Rehoboth Beach, Delaware (Fact Sheet)

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    None, None

    2014-01-01

    Insight Homes constructed two houses in Rehoboth Beach, Delaware, with identical floor plans and thermal envelopes but different heating and domestic hot water (DHW) systems. Each house is 1,715-ft 2 with a single story, three bedrooms, two bathrooms, and the heating, ventilation, and air conditioning (HVAC) systems and ductwork located in conditioned crawlspaces. The standard house, which the builder offers as its standard production house, uses an air source heat pump (ASHP) with supplemental propane furnace heating. The Building America test house uses the same ASHP unit with supplemental heat provided by the DHW heater (a combined DHW and hydronicmore » heating system, where the hydronic heating element is in the air handler). Both houses were occupied during the test period. Results indicate that efficiency of the two heating systems was not significantly different. Three issues dominate these results; lower system design performance resulting from the indoor refrigerant coil selected for the standard house, an incorrectly functioning defrost cycle in the standard house, and the low resolution of the natural gas monitoring equipment. The thermal comfort of both houses fell outside the ASHRAE Standard 55 heating range but was within the ACCA room-to-room temperature range when compared to the thermostat temperature. The monitored DHW draw schedules were input into EnergyPlus to evaluate the efficiency of the tankless hot water heater model using the two monitored profiles and the Building America House Simulation Protocols. The results indicate that the simulation is not significantly impacted by the draw profiles.« less

  9. Alternating current losses in superconducting coils

    NASA Technical Reports Server (NTRS)

    Wipf, S. L.; Guderjahn, C. A.

    1972-01-01

    Report examines relationship between coil loss and frequency and heat loss in coil as a function of the magnetic field H. Information is of value to manufacturers of superconducting magnets, motors and generators.

  10. Coupling and power transfer efficiency enhancement of modular and array of planar coils using in-plane ring-shaped inner ferrites for inductive heating applications

    NASA Astrophysics Data System (ADS)

    Kilic, V. T.; Unal, E.; Demir, H. V.

    2017-07-01

    We propose and demonstrate a highly effective method of enhancing coupling and power transfer efficiency in inductive heating systems composed of planar coils. The proposed method is based on locating ring-shaped ferrites in the inner side of the coils in the same plane. Measurement results of simple inductive heating systems constructed with either a single or a pair of conventional circular coils show that, with the in-plane inner ferrites, the total dissipated power of the system is increased by over 65%. Also, with three-dimensional full electromagnetic solutions, it is found that power transfer efficiency of the system is increased up to 92% with the inner ferrite placement. The proposed method is promising to be used for efficiency enhancement in inductive heating applications, especially in all-surface induction hobs.

  11. Performance of the Conduction-Cooled LDX Levitation Coil

    NASA Astrophysics Data System (ADS)

    Michael, P. C.; Schultz, J. H.; Smith, B. A.; Titus, P. H.; Radovinsky, A.; Zhukovsky, A.; Hwang, K. P.; Naumovich, G. J.; Camille, R. J.

    2004-06-01

    The Levitated Dipole Experiment (LDX) was developed to study plasma confinement in a dipole magnetic field. Plasma is confined in the magnetic field of a 680-kg Nb3Sn Floating Coil (F-coil) that is electromagnetically supported at the center of a 5-m diameter by 3-m tall vacuum chamber. The Levitation Coil (L-coil) is a 2800-turn, double pancake winding that supports the weight of the F-coil and controls its vertical position within the vacuum chamber. The use of high-temperature superconductor (HTS) Bi-2223 for the L-coil minimizes the electrical and cooling power needed for levitation. The L-coil winding pack and support plate are suspended within the L-coil cryostat and cooled by conduction to a single-stage cryocooler rated for 25-W heat load at approximately 20 K. The coil current leads consist of conduction-cooled copper running from room temperature to 80 K and a pair of commercially-available, 150-A HTS leads. An automatically filled liquid-nitrogen reservoir provides cooling for the coil's radiation shield and for the leads' 80-K heat stations. This paper discusses the L-coil system design and its observed cryogenic performance.

  12. RELAP5-3D Modeling of Heat Transfer Components (Intermediate Heat Exchanger and Helical-Coil Steam Generator) for NGNP Application

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    N. A. Anderson; P. Sabharwall

    2014-01-01

    The Next Generation Nuclear Plant project is aimed at the research and development of a helium-cooled high-temperature gas reactor that could generate both electricity and process heat for the production of hydrogen. The heat from the high-temperature primary loop must be transferred via an intermediate heat exchanger to a secondary loop. Using RELAP5-3D, a model was developed for two of the heat exchanger options a printed-circuit heat exchanger and a helical-coil steam generator. The RELAP5-3D models were used to simulate an exponential decrease in pressure over a 20 second period. The results of this loss of coolant analysis indicate thatmore » heat is initially transferred from the primary loop to the secondary loop, but after the decrease in pressure in the primary loop the heat is transferred from the secondary loop to the primary loop. A high-temperature gas reactor model should be developed and connected to the heat transfer component to simulate other transients.« less

  13. Lack of dependence on resonant error field of locked mode island size in ohmic plasmas in DIII-D

    NASA Astrophysics Data System (ADS)

    La Haye, R. J.; Paz-Soldan, C.; Strait, E. J.

    2015-02-01

    DIII-D experiments show that fully penetrated resonant n = 1 error field locked modes in ohmic plasmas with safety factor q95 ≳ 3 grow to similar large disruptive size, independent of resonant error field correction. Relatively small resonant (m/n = 2/1) static error fields are shielded in ohmic plasmas by the natural rotation at the electron diamagnetic drift frequency. However, the drag from error fields can lower rotation such that a bifurcation results, from nearly complete shielding to full penetration, i.e., to a driven locked mode island that can induce disruption. Error field correction (EFC) is performed on DIII-D (in ITER relevant shape and safety factor q95 ≳ 3) with either the n = 1 C-coil (no handedness) or the n = 1 I-coil (with ‘dominantly’ resonant field pitch). Despite EFC, which allows significantly lower plasma density (a ‘figure of merit’) before penetration occurs, the resulting saturated islands have similar large size; they differ only in the phase of the locked mode after typically being pulled (by up to 30° toroidally) in the electron diamagnetic drift direction as they grow to saturation. Island amplification and phase shift are explained by a second change-of-state in which the classical tearing index changes from stable to marginal by the presence of the island, which changes the current density profile. The eventual island size is thus governed by the inherent stability and saturation mechanism rather than the driving error field.

  14. Improved Ohmic-contact to AlGaN/GaN using Ohmic region recesses by self-terminating thermal oxidation assisted wet etching technique

    NASA Astrophysics Data System (ADS)

    Liu, J.; Wang, J.; Wang, H.; Zhu, L.; Wu, W.

    2017-06-01

    Lower Ti/Al/Ni/Au Ohmic contact resistance on AlGaN/GaN with wider rapid thermal annealing (RTA) temperature window was achieved using recessed Ohmic contact structure based on self-terminating thermal oxidation assisted wet etching technique (STOAWET), in comparison with conventional Ohmic contacts. Even at lower temperature such as 650°C, recessed structure by STOAWET could still obtain Ohmic contact with contact resistance of 1.97Ω·mm, while conventional Ohmic structure mainly featured as Schottky contact. Actually, both Ohmic contact recess and mesa isolation processes could be accomplished by STOAWET in one process step and the process window of STOAWET is wide, simplifying AlGaN/GaN HEMT device process. Our experiment shows that the isolation leakage current by STOAWET is about one order of magnitude lower than that by inductivity coupled plasma (ICP) performed on the same wafer.

  15. Theoretical transport modeling of Ohmic cold pulse experiments

    NASA Astrophysics Data System (ADS)

    Kinsey, J. E.; Waltz, R. E.; St. John, H. E.

    1998-11-01

    The response of several theory-based transport models in Ohmically heated tokamak discharges to rapid edge cooling due to trace impurity injection is studied. Results are presented for the Institute for Fusion Studies—Princeton Plasma Physics Laboratory (IFS/PPPL), gyro-Landau-fluid (GLF23), Multi-mode (MM), and the Itoh-Itoh-Fukuyama (IIF) transport models with an emphasis on results from the Texas Experimental Tokamak (TEXT) [K. W. Gentle, Nucl. Technol./Fusion 1, 479 (1981)]. It is found that critical gradient models containing a strong ion and electron temperature ratio dependence can exhibit behavior that is qualitatively consistent with experimental observation while depending solely on local parameters. The IFS/PPPL model yields the strongest response and demonstrates both rapid radial pulse propagation and a noticeable increase in the central electron temperature following a cold edge temperature pulse (amplitude reversal). Furthermore, the amplitude reversal effect is predicted to diminish with increasing electron density and auxiliary heating in agreement with experimental data. An Ohmic pulse heating effect due to rearrangement of the current profile is shown to contribute to the rise in the core electron temperature in TEXT, but not in the Joint European Tokamak (JET) [A. Tanga and the JET Team, in Plasma Physics and Controlled Nuclear Fusion Research 1986 (International Atomic Energy Agency, Vienna, 1987), Vol. 1, p. 65] and the Tokamak Fusion Test Reactor (TFTR) [R. J. Hawryluk, V. Arunsalam, M. G. Bell et al., in Plasma Physics and Controlled Nuclear Fusion Research 1986 (International Atomic Energy Agency, Vienna, 1987), Vol. 1, p. 51]. While this phenomenon is not necessarily a unique signature of a critical gradient, there is sufficient evidence suggesting that the apparent plasma response to edge cooling may not require any underlying nonlocal mechanism and may be explained within the context of the intrinsic properties of electrostatic drift

  16. Whey acerola-flavoured drink submitted ohmic heating processing: Is there an optimal combination of the operational parameters?

    PubMed

    Cappato, Leandro P; Ferreira, Marcus Vinícius S; Pires, Roberto P S; Cavalcanti, Rodrigo N; Bisaggio, Rodrigo C; Freitas, Mônica Q; Silva, Marcia C; Cruz, Adriano G

    2018-04-15

    Whey acerola-flavoured drink was treated using ohmic heating (OH) at 65°C for 30min to evaluate different frequencies (10, 100 and 1000Hz with 25V) and voltages (45, 60 and 80V at 60Hz) and by conventional heating (CH) with the same temperature profile (65°C/30min). Rheology parameters, color changes (h°, C∗, ΔE) microstructure (optical microscopy), and ascorbic acid (AA) degradation kinetics were performed. AA degradation rates ranged from 1.7 to 29.3% and from 2.8 to 24.8% for OH and CH, respectively. The beverages treated with both processes exhibited a pseudo-plastic behavior (n<1), higher saturation (C∗), lesser reddish color (h°), and higher color variations (ΔE∗). In microstructure analysis, OH (1000Hz-25V and 80V-60Hz) was able to rupture the cell structure. The best results were observed at low frequencies and voltage OH processes on whey acerola-flavoured drinks should be performed at low frequencies and voltages (≤100Hz and 45V), an alternating current (A/C). However, despite the use of inert electrodes, the existence of corrosion was not evaluated, being an important information to be investigated. Copyright © 2017 Elsevier Ltd. All rights reserved.

  17. Formation of ohmic contacts to MOCVD grown p-GaN by controlled activation of Mg

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kaminska, E.; Piotrowska, A.; Barcz, A.

    2000-11-27

    We report on the formation of low resistivity ohmic contacts to p-GaN, r{sub c} < 10{sup {minus}4}{Omega}cm{sup 2}, by increasing the concentration of the active Mg in the subcontact zone, via Zr-mediated release of hydrogen. We have investigated the process of evolution of hydrogen from MOCVD grown p-GaN via Zr-based metallization, and determined the optimum processing conditions (temperature and gas ambient) for fabrication of low resistance ohmic contacts. When the process is conducted in N{sub 2} flow, the metallization remains stable at temperatures required to achieve the ohmic behavior, and the morphology of the metal/semiconductor interface is unaltered by suchmore » a heat treatment. The processing in O{sub 2}, on the contrary, causes the interdiffusion of metallization constituents and the incorporation of oxygen into the semiconductor subcontact region, which could be responsible for increased resistivity of these contacts.« less

  18. Auxiliary coil controls temperature of RF induction heater

    NASA Technical Reports Server (NTRS)

    1966-01-01

    Auxiliary coil controls the temperature of an RF induction furnace that is powered by a relatively unstable RF generator. Manual or servoed adjustments of the relative position of the auxiliary coil, which is placed in close proximity to the RF coil, changes the looseness of the RF coil and hence the corresponding heating effect of its RF field.

  19. Heat Transfer Characteristics of Fan Coil Unit (FCU) Under The Effect of Chilled Water Volume Flowrate

    NASA Astrophysics Data System (ADS)

    Wijaya Sunu, Putu; Anakottapary, Daud Simon; Mulawarman, A. A. N. B.; Cipta Santosa, I. D. M.; Putu Sastra Negara, I.

    2018-01-01

    In this paper, the volume flowrate of chilled water in the water chiller simulation apparatus was optimized using experimental studied. The experimental analysis was performed on the fan coil unit (FCU) of the system. The chilled water flows in tube side and the air as a hot fluid flows throughout the tube and fin of FCU. The thermal performance and analysis of the heat transfer is examined using various chilled water flowrate e.g. 11, 12, 13, 14, 15 lpm. The effect of the flowrate to the important parameter such as LMTD temperature, heat absorb used for investigate the heat transfer characteristics. The result showed that the heat transfer characteristics has been increased with the increased of chilled water volume flowrate.

  20. A magnetic induction heating system with multi-cascaded coils and adjustable magnetic circuit for hyperthermia.

    PubMed

    Huang, Chi-Fang; Chao, Hsuan-Yi; Chang, Hsun-Hao; Lin, Xi-Zhang

    2016-01-01

    Based on the characteristics of cancer cells that cannot survive in an environment with temperature over 42 °C, a magnetic induction heating system for cancer treatment is developed in this work. First, the methods and analyses for designing the multi-cascaded coils magnetic induction hyperthermia system are proposed, such as internal impedance measurement of power generator, impedance matching of coils, and analysis of the system. Besides, characteristics of the system are simulated by a full-wave package for engineering optimization. Furthermore, by considering the safety factor of patients, a two-sectional needle is designed for hyperthermia. Finally, this system is employed to test the liver of swine in ex-vivo experiments, and through Hematoxylin and Eosin (H&E) stain and NADPH oxidase activity assay, the feasibility of this system is verified.

  1. Characterization and optimization of spiral eddy current coils for in-situ crack detection

    NASA Astrophysics Data System (ADS)

    Mandache, Catalin

    2018-03-01

    In-situ condition-based maintenance is making strides in the aerospace industry and it is seen as an alternative to scheduled, time-based maintenance. With fatigue cracks originating from fastener holes as the main reason for structural failures, embedded eddy current coils are a viable non-invasive solution for their timely detection. The development and potential broad use of these coils are motivated by a few consistent arguments: (i) inspection of structures of complicated geometries and hard to access areas, that often require disassembly, (ii) alternative to regular inspection actions that could introduce inadvertent damage, (iii) for structures that have short inspection intervals, and (iv) for repaired structures where fastener holes contain bushings and prevent further bolt-hole inspections. Since the spiral coils are aiming at detecting radial cracks emanating from the fastener holes, their design parameters should allow for high inductance, low ohmic losses and power requirements, as well as optimal size and high sensitivity to discontinuities. In this study, flexible, surface conformable, spiral eddy current coils are empirically investigated on mock-up specimens, while numerical analysis is performed for their optimization and design improvement.

  2. Enhancing Induction Coil Reliability

    NASA Astrophysics Data System (ADS)

    Kreter, K.; Goldstein, R.; Yakey, C.; Nemkov, V.

    2014-12-01

    In induction hardening, thermal fatigue is one of the main copper failure modes of induction heat treating coils. There have been papers published that describe this failure mode and others that describe some good design practices. The variables previously identified as the sources of thermal fatigue include radiation from the part surface, frequency, current, concentrator losses, water pressure and coil wall thickness. However, there is very little quantitative data on the factors that influence thermal fatigue in induction coils is available in the public domain. By using finite element analysis software this study analyzes the effect of common design variables of inductor cooling, and quantifies the relative importance of these variables. A comprehensive case study for a single shot induction coil with Fluxtrol A concentrator applied is used for the analysis.

  3. The influence of Dean Number on heat transfer to Newtonian fluid through spiral coils with constant wall temperature in laminar flow

    NASA Astrophysics Data System (ADS)

    Patil, Rahul Harishchandra; Nadar, Mariappan Dharmaraj; Ali, Rashed

    2017-05-01

    The influence of Dean Number on the heat transfer to petroleum base oils (SN70, SN150 and SN300, flowing through four spiral coils, maintained at constant wall temperature and having average curvature ratio of 0.01568, 0.019, 0.02466 and 0.03011 are investigated in the present study. The fluid, with fully developed velocity profile and underdeveloped temperature profile (the Graetz problem), flows inside the tube at the entrance. Four correlations are developed which are valid for a range of Dean Number from 2 to 1043, Prandtl Number from 76 to 298, and Reynold's Number from 12 to 6013. These correlations are not available in literature and are developed for the first time for the given conditions. The correlations are compared with the correlations developed by earlier investigators and it is found that they are in good agreement. The developed correlations are corrected to account for the variable property relations for the viscous fluids used in the experiment. The average deviations in the developed correlations and the readings obtained by experiment are found to be <± 3%. The comparison of the developed correlations with the correlations of other investigators on helical coils showed an increase in heat transfer in spiral coils than the helical coils. The reason for this is that the magnitude of the secondary flow varied continuously with an increase in the mixing of the fluid particles occurring throughout the length of the spiral coil.

  4. Faraday Shields within a Solenoidal Coil to Reduce Sample Heating: Numerical Comparison of Designs and Experimental Verification

    PubMed Central

    Park, BuSik; Neuberger, Thomas; Webb, Andrew G.; Bigler, Don C.; Collins, Christopher M.

    2009-01-01

    A comparison of methods to decrease RF power dissipation and related heating in conductive samples using passive conductors surrounding a sample in a solenoid coil is presented. Full-Maxwell finite difference time domain numerical calculations were performed to evaluate the effect of the passive conductors by calculating conservative and magnetically-induced electric field and magnetic field distributions. To validate the simulation method, experimental measurements of temperature increase were conducted using a solenoidal coil (diameter 3 mm), a saline sample (10 mM NaCl) and passive copper shielding wires (50 μm diameter). The temperature increase was 58% lower with the copper wires present for several different input powers to the coil. This was in good agreement with simulation for the same geometry, which indicated 57% lower power dissipated in the sample with conductors present. Simulations indicate that some designs should be capable of reducing temperature increase by more than 85%. PMID:19879784

  5. Ohmic contacts to semiconducting diamond

    NASA Astrophysics Data System (ADS)

    Zeidler, James R.; Taylor, M. J.; Zeisse, Carl R.; Hewett, C. A.; Delahoussaye, Paul R.

    1990-10-01

    Work was carried out to improve the electron beam evaporation system in order to achieve better deposited films. The basic system is an ion pumped vacuum chamber, with a three-hearth, single-gun e-beam evaporator. Four improvements were made to the system. The system was thoroughly cleaned and new ion pump elements, an e-gun beam adjust unit, and a more accurate crystal monitor were installed. The system now has a base pressure of 3 X 10(exp -9) Torr, and can easily deposit high-melting-temperature metals such as Ta with an accurately controlled thickness. Improved shadow masks were also fabricated for better alignment and control of corner contacts for electrical transport measurements. Appendices include: A Thermally Activated Solid State Reaction Process for Fabricating Ohmic Contacts to Semiconducting Diamond; Tantalum Ohmic Contacts to Diamond by a Solid State Reaction Process; Metallization of Semiconducting Diamond: Mo, Mo/Au, and Mo/Ni/Au; Specific Contact Resistance Measurements of Ohmic Contracts to Diamond; and Electrical Activation of Boron Implanted into Diamond.

  6. Numerical investigation of heat transfer in annulus laminar flow of multi tubes-in-tube helical coil

    NASA Astrophysics Data System (ADS)

    Nada, S. A.; Elattar, H. F.; Fouda, A.; Refaey, H. A.

    2018-03-01

    In the present study, a CFD analysis using ANSYS-FLUENT 14.5 CFD package is used to investigate the characteristics of heat transfer of laminar flow in annulus formed by multi tubes in tube helically coiled heat exchanger. The numerical results are validated by comparison with previous experimental data and fair agreements were existed. The influences of the design and operation parameters such as heat flux, Reynolds numbers and annulus geometry on the heat transfer characteristics are investigated. Different annulus of different numbers of inner tubes, specifically 1, 2, 3, 4 and 5 tubes, are tested. The Results showed that for all the studied annulus, the heat flux has no effect on the Nusselt number and compactness parameter. The annulus formed by using five inner tubes showed the best heat transfer performance and compactness parameter. Correlation of predicting Nusselt number in terms of Reynolds number and number of inner tubes are presented.

  7. Fabrication of a helical coil shape memory alloy actuator

    NASA Astrophysics Data System (ADS)

    Odonnell, R. E.

    1992-02-01

    A fabrication process was developed to form, heat treat, and join NiTi shape memory alloy helical coils for use as mechanical actuators. Tooling and procedures were developed to wind both extension and compression-type coils on a manual lathe. Heat treating fixtures and techniques were used to set the 'memory' of the NiTi alloy to the desired configuration. A swaging process was devised to fasten shape memory alloy extension coils to end fittings for use in actuator testing and for potential attachment to mechanical devices. The strength of this mechanical joint was evaluated.

  8. An explicit scheme for ohmic dissipation with smoothed particle magnetohydrodynamics

    NASA Astrophysics Data System (ADS)

    Tsukamoto, Yusuke; Iwasaki, Kazunari; Inutsuka, Shu-ichiro

    2013-09-01

    In this paper, we present an explicit scheme for Ohmic dissipation with smoothed particle magnetohydrodynamics (SPMHD). We propose an SPH discretization of Ohmic dissipation and solve Ohmic dissipation part of induction equation with the super-time-stepping method (STS) which allows us to take a longer time step than Courant-Friedrich-Levy stability condition. Our scheme is second-order accurate in space and first-order accurate in time. Our numerical experiments show that optimal choice of the parameters of STS for Ohmic dissipation of SPMHD is νsts ˜ 0.01 and Nsts ˜ 5.

  9. A Modified Alderman-Grant Coil makes possible an efficient cross-coil probe for high field solid-state NMR of lossy biological samples

    NASA Astrophysics Data System (ADS)

    Grant, Christopher V.; Yang, Yuan; Glibowicka, Mira; Wu, Chin H.; Park, Sang Ho; Deber, Charles M.; Opella, Stanley J.

    2009-11-01

    The design, construction, and performance of a cross-coil double-resonance probe for solid-state NMR experiments on lossy biological samples at high magnetic fields are described. The outer coil is a Modified Alderman-Grant Coil (MAGC) tuned to the 1H frequency. The inner coil consists of a multi-turn solenoid coil that produces a B 1 field orthogonal to that of the outer coil. This results in a compact nested cross-coil pair with the inner solenoid coil tuned to the low frequency detection channel. This design has several advantages over multiple-tuned solenoid coil probes, since RF heating from the 1H channel is substantially reduced, it can be tuned for samples with a wide range of dielectric constants, and the simplified circuit design and high inductance inner coil provides excellent sensitivity. The utility of this probe is demonstrated on two electrically lossy samples of membrane proteins in phospholipid bilayers (bicelles) that are particularly difficult for conventional NMR probes. The 72-residue polypeptide embedding the transmembrane helices 3 and 4 of the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) (residues 194-241) requires a high salt concentration in order to be successfully reconstituted in phospholipid bicelles. A second application is to paramagnetic relaxation enhancement applied to the membrane-bound form of Pf1 coat protein in phospholipid bicelles where the resistance to sample heating enables high duty cycle solid-state NMR experiments to be performed.

  10. Correlation of volatile carbonyl yields emitted by e-cigarettes with the temperature of the heating coil and the perceived sensorial quality of the generated vapours.

    PubMed

    Geiss, Otmar; Bianchi, Ivana; Barrero-Moreno, Josefa

    2016-05-01

    E-liquids generally contain four main components: nicotine, flavours, water and carrier liquids. The carrier liquid dissolves flavours and nicotine and vaporises at a certain temperature on the atomizer of the e-cigarette. Propylene glycol and glycerol, the principal carriers used in e-liquids, undergo decomposition in contact with the atomizer heating-coil forming volatile carbonyls. Some of these, such as formaldehyde, acetaldehyde and acrolein, are of concern due to their adverse impact on human health when inhaled at sufficient concentrations. The aim of this study was to correlate the yield of volatile carbonyls emitted by e-cigarettes with the temperature of the heating coil. For this purpose, a popular commercial e-liquid was machine-vaped on a third generation e-cigarette which allowed the variation of the output wattage (5-25W) and therefore the heat generated on the atomizer heating-coil. The temperature of the heating-coil was determined by infrared thermography and the vapour generated at each temperature underwent subjective sensorial quality evaluation by an experienced vaper. A steep increase in the generated carbonyls was observed when applying a battery-output of at least 15W corresponding to 200-250°C on the heating coil. However, when considering concentrations in each inhaled puff, the short-term indoor air guideline value for formaldehyde was already exceeded at the lowest wattage of 5W, which is the wattage applied in most 2nd generation e-cigarettes. Concentrations of acetaldehyde in each puff were several times below the short-term irritation threshold value for humans. Acrolein was only detected from 20W upwards. The negative sensorial quality evaluation by the volunteering vaper of the vapour generated at 20W demonstrated the unlikelihood that such a wattage would be realistically set by a vaper. This study highlights the importance to develop standardised testing methods for the assessment of carbonyl-emissions and emissions of other

  11. Flexible heating head for induction heating

    NASA Technical Reports Server (NTRS)

    Fox, Robert L. (Inventor); Johnson, Samuel D. (Inventor); Coultrip, Robert H. (Inventor); Phillips, W. Morris (Inventor)

    1993-01-01

    An induction heating head includes a length of wire having first and second opposite ends and being wound in a flat spiral shape to form an induction coil, a capacitor connected to the first and second ends of the wire, the induction coil and capacitor defining a tank circuit, and a flexible, elastomeric body molded to encase the induction coil. When a susceptor is placed in juxtaposition to the body, and the tank circuit is powered, the susceptor is inductively heated.

  12. Flexible heating head for induction heating

    NASA Astrophysics Data System (ADS)

    Fox, Robert L.; Johnson, Samuel D.; Coultrip, Robert H.; Phillips, W. Morris

    1993-11-01

    An induction heating head includes a length of wire having first and second opposite ends and being wound in a flat spiral shape to form an induction coil, a capacitor connected to the first and second ends of the wire, the induction coil and capacitor defining a tank circuit, and a flexible, elastomeric body molded to encase the induction coil. When a susceptor is placed in juxtaposition to the body, and the tank circuit is powered, the susceptor is inductively heated.

  13. Heat tube device

    NASA Technical Reports Server (NTRS)

    Khattar, Mukesh K. (Inventor)

    1990-01-01

    The present invention discloses a heat tube device through which a working fluid can be circulated to transfer heat to air in a conventional air conditioning system. The heat tube device is disposable about a conventional cooling coil of the air conditioning system and includes a plurality of substantially U-shaped tubes connected to a support structure. The support structure includes members for allowing the heat tube device to be readily positioned about the cooling coil. An actuatable adjustment device is connected to the U-shaped tubes for allowing, upon actuation thereof, for the heat tubes to be simultaneously rotated relative to the cooling coil for allowing the heat transfer from the heat tube device to air in the air conditioning system to be selectively varied.

  14. Influence of infrared final cooking on polycyclic aromatic hydrocarbon formation in ohmically pre-cooked beef meatballs.

    PubMed

    Kendirci, Perihan; Icier, Filiz; Kor, Gamze; Onogur, Tomris Altug

    2014-06-01

    Effects of infrared cooking on polycyclic aromatic hydrocarbon (PAH) formation in ohmically pre-cooked beef meatballs were investigated. Samples were pre-cooked in a specially designed-continuous type ohmic cooking at a voltage gradient of 15.26V/cm for 92s. Infrared cooking was applied as a final cooking method at different combinations of heat fluxes (3.706, 5.678, 8.475kW/m(2)), application distances (10.5, 13.5, 16.5cm) and application durations (4, 8, 12min). PAHs were analyzed by using high performance liquid chromatography (HPLC) equipped with a fluorescence detector. The total PAH levels were detected to be between 4.47 and 64μg/kg. Benzo[a] pyrene (B[a]P) and PAH4 (sum of B[a]P, chrysene (Chr), benzo[a]anthracene (B[a]A) and benzo[b]fluoranthene (B[b]F)) levels detected in meatballs were below the EC limits. Ohmic pre-cooking followed by infrared cooking may be regarded as a safe cooking procedure of meatballs from a PAH contamination point of view. Copyright © 2014 Elsevier Ltd. All rights reserved.

  15. Heat Transfer Enhancement in a Helically Coiled Tube with Al2O3/WATER Nanofluid Under Laminar Flow Condition

    NASA Astrophysics Data System (ADS)

    Kumar, P. C. Mukesh; Kumar, J.; Suresh, S.; Babu, K. Praveen

    2012-10-01

    In this experimental investigation, the heat transfer coefficients of a shell and helically coiled tube heat exchanger using Al2O3/water nanofluid under laminar flow condition were studied. The Al2O3 nanoparticles were characterized by X-Ray diffraction (XRD). The Al2O3/water nanofluid at 0.1%, 0.4% and 0.8% particle volume concentration were prepared by using two step method. The prepared nanofluid was characterized by scanning electron microscope (SEM). It is observed that the overall heat transfer coefficient, inner heat transfer coefficient and experimental inner Nusselt number increase while increasing particle volume concentration and increasing inner Dean number. The enhancement of overall heat transfer coefficient was found to be 7%, 16.9% and 24.2% at 0.1%, 0.4% and 0.8% Al2O3/water nanofluid respectively when compared with water. The enhancement of tube side experimental Nusselt number was found to be 17%, 22.9% and 28% at 0.1%, 0.4% and 0.8% particle volume concentration of Al2O3/water nanofluid respectively when compared with water at fixed Dean number. The tests were conducted in the range of 1600 < De < 2700, and 5200 < Re < 8600 under laminar flow condition and counter flow configuration. These enhancements are due to higher thermal conductivity of nanofluid while increasing particle volume concentration and Brownian motion of nanoparticles. It is studied that there is no negative impact on formation of secondary flow and mixing of fluid when nanofluid passes through the helically coiled tube.

  16. Oval gradient coils for an open magnetic resonance imaging system with a vertical magnetic field.

    PubMed

    Matsuzawa, Koki; Abe, Mitsushi; Kose, Katsumi; Terada, Yasuhiko

    2017-05-01

    Existing open magnetic resonance imaging (MRI) systems use biplanar gradient coils for the spatial encoding of signals. We propose using novel oval gradient coils for an open vertical-field MRI. We designed oval gradients for a 0.3T open MRI system and showed that such a system could outperform a traditional biplanar gradient system while maintaining adequate gradient homogeneity and subject accessibility. Such oval gradient coils would exhibit high efficiency, low inductance and resistance, and high switching capability. Although the designed oval Y and Z coils showed more heat dissipation and less cooling capability than biplanar coils with the same gap, they showed an efficient heat-dissipation path to the surrounding air, which would alleviate the heat problem. The performance of the designed oval-coil system was demonstrated experimentally by imaging a human hand. Copyright © 2017 Elsevier Inc. All rights reserved.

  17. Multi-turn transmit coil to increase b1 efficiency in current source amplification.

    PubMed

    Gudino, N; Griswold, M A

    2013-04-01

    A multi-turn transmit surface coil design was presented to improve B1 efficiency when used with current source amplification. Three different coil designs driven by an on-coil current-mode class-D amplifier with current envelope feedback were tested on the benchtop and through imaging in a 1.5 T scanner. Case temperature of the power field-effect transistor at the amplifier output stage was measured to evaluate heat dissipation for the different current levels and coil configurations. In addition, a lower power rated device was tested to exploit the potential gain in B1 obtained with the multi-turn coil. As shown both on the benchtop and in a 1.5 T scanner, B1 was increased by almost 3-fold without increasing heat dissipation on the power device at the amplifier's output using a multi-turn surface coil. Similar gain was obtained when connecting a lower power rated field-effect transistor to the multi-turn coil. In addition to reduce heat dissipation per B1 in the device, higher B1 per current efficiency allows the use of field-effect transistors with lower current ratings and lower port capacitances, which could improve the overall performance of the on-coil current source transmit system. Copyright © 2013 Wiley Periodicals, Inc.

  18. Multi-turn transmit coil to increase B1 efficiency in current source amplification

    PubMed Central

    Gudino, N.; Griswold, M.A.

    2013-01-01

    Purpose A multi-turn transmit surface coil design was presented to improve B1 efficiency when used with current source amplification. Methods Three different coil designs driven by an on-coil current-mode class-D (CMCD) amplifier with current envelope feedback were tested on the benchtop and through imaging in a 1.5 T scanner. Case temperature of the power field-effect transistor (FET) at the amplifier output stage was measured to evaluate heat dissipation for the different current levels and coil configurations. In addition, a lower power rated device was tested to exploit the potential gain in B1 obtained with the multi-turn coil. Results As shown both on the benchtop and in a 1.5 T scanner, B1 was increased by almost three-fold without increasing heat dissipation on the power device at the amplifier's output using a multi-turn surface coil. Similar gain was obtained when connecting a lower power rated FET to the multi-turn coil. Conclusion In addition to reduce heat dissipation per B1 in the device, higher B1 per current efficiency allows the use of FETs with lower current ratings and lower port capacitances which could improve the overall performance of the on-coil current source transmit system. PMID:23401060

  19. α/β coiled coils

    PubMed Central

    Hartmann, Marcus D; Mendler, Claudia T; Bassler, Jens; Karamichali, Ioanna; Ridderbusch, Oswin; Lupas, Andrei N; Hernandez Alvarez, Birte

    2016-01-01

    Coiled coils are the best-understood protein fold, as their backbone structure can uniquely be described by parametric equations. This level of understanding has allowed their manipulation in unprecedented detail. They do not seem a likely source of surprises, yet we describe here the unexpected formation of a new type of fiber by the simple insertion of two or six residues into the underlying heptad repeat of a parallel, trimeric coiled coil. These insertions strain the supercoil to the breaking point, causing the local formation of short β-strands, which move the path of the chain by 120° around the trimer axis. The result is an α/β coiled coil, which retains only one backbone hydrogen bond per repeat unit from the parent coiled coil. Our results show that a substantially novel backbone structure is possible within the allowed regions of the Ramachandran space with only minor mutations to a known fold. DOI: http://dx.doi.org/10.7554/eLife.11861.001 PMID:26771248

  20. Investigation of impurity transport using laser blow-off technique in the HL-2A Ohmic and ECRH plasmas

    NASA Astrophysics Data System (ADS)

    Kai, Zhang; Zheng-Ying, Cui; Ping, Sun; Chun-Feng, Dong; Wei, Deng; Yun-Bo, Dong; Shao-Dong, Song; Min, Jiang; Yong-Gao, Li; Ping, Lu; Qing-Wei, Yang

    2016-06-01

    Impurity transports in two neighboring discharges with and without electron cyclotron resonance heating (ECRH) are studied in the HL-2A tokamak by laser blow-off (LBO) technique. The progression of aluminium ions as the trace impurity is monitored by soft x-ray (SXR) and bolometer detector arrays with good temporal and spatial resolutions. Obvious difference in the time trace of the signal between the Ohmic and ECRH L-mode discharges is observed. Based on the numerical simulation with one-dimensional (1D) impurity transport code STRAHL, the radial profiles of impurity diffusion coefficient D and convective velocity V are obtained for each shot. The result shows that the diffusion coefficient D significantly increases throughout the plasma minor radius for the ECRH case with respect to the Ohmic case, and that the convection velocity V changes from negative (inward) for the Ohmic case to partially positive (outward) for the ECRH case. The result on HL-2A confirms the pump out effect of ECRH on impurity profile as reported on various other devices.

  1. Ohmic ITBs in Alcator C-Mod

    NASA Astrophysics Data System (ADS)

    Fiore, C. L.; Rowan, W. L.; Dominguez, A.; Hubbard, A. E.; Ince-Cushman, A.; Greenwald, M. J.; Lin, L.; Marmar, E. S.; Reinke, M.; Rice, J. E.; Zhurovich, K.

    2007-11-01

    Internal transport barrier plasmas can arise spontaneously in ohmic Alcator C-Mod plasmas where an EDA H-mode has been developed by magnetic field ramping. These ohmic ITBs share the hallmarks of ITBs created with off-axis ICRF injection in that they have highly peaked density and pressure profiles and the peaking can be suppressed by on-axis ICRF. There is a reduction of particle and thermal flux in the barrier region which then allows the neoclassical pinch to peak the central density. Recent work on ITB onset conditions [1] which was motivated by turbulence studies [2] points to the broadening of the Ti profile with off-axis ICRF acting to reduce the ion temperature gradient. This suppresses ITG instability driven particle fluxes, which is thought to be the primary mechanism for ITB formation. The object of this study is to examine the characteristics of ohmic ITBs to find whether the stability of plasmas and the plasma parameters support the onset model. [1]K. Zhurovich, et al., To be published in Nuclear Fusion [2] D. R. Ernst, et al., Phys. Plasmas 11, 2637 (2004)

  2. Aging behavior of Au-based ohmic contacts to GaAs

    NASA Technical Reports Server (NTRS)

    Fatemi, Navid S.

    1989-01-01

    Gold based alloys, commonly used as ohmic contacts for solar cells, are known to react readily with GaAs. It is shown that the contact interaction with the underlying GaAs can continue even at room temperature upon aging, altering both the electrical characteristics of the contacts and the nearby pn junction. Au-Ge-Ni as-deposited (no heat-treatment) contacts made to thin emitter (0.15 microns) GaAs diodes have shown severe shunting of the pn junction upon aging for several months at room temperature. The heat-treated contacts, despite showing degradation in contact resistance, did not affect the underlying pn junction. Au-Zn-Au contacts to p-GaAs emitter (0.2 microns) diodes, however, showed slight improvement in contact resistance upon 200 C isothermal annealing for several months, without degrading the pn junction. The effect of aging on electrical characteristics of the as-deposited and heat-treated contacts and the nearby pn junction, as well as on the surface morphology of the contacts are presented.

  3. Aging behavior of Au-based ohmic contacts to GaAs

    NASA Technical Reports Server (NTRS)

    Fatemi, Navid S.

    1988-01-01

    Gold based alloys, commonly used as ohmic contacts for solar cells, are known to react readily with GaAs. It is shown that the contact interaction with the underlying GaAs can continue even at room temperature upon aging, altering both the electrical characteristics of the contacts and the nearby pn junction. Au-Ge-Ni as-deposited (no heat treatment) contacts made to thin emitter (0.15 micrometer) GaAs diodes have shown severe shunting of the pn junction upon aging for several months at room temperature. The heat-treated contacts, despite showing degradation in contact resistance did not affect the underlying pn junction. Au-Zn-Au contacts to p-GaAs emitter (0.2 micrometer) diodes, however, showed slight improvement in contact resistance upon 200 C isothermal annealing for several months, without degrading the pn junction. The effect of aging on electrical characteristics of the as-deposited and heat-treated contacts and the nearby pn junction, as well as on the surface morphology of the contacts are presented.

  4. Dual ohmic contact to N- and P-type silicon carbide

    NASA Technical Reports Server (NTRS)

    Okojie, Robert S. (Inventor)

    2013-01-01

    Simultaneous formation of electrical ohmic contacts to silicon carbide (SiC) semiconductor having donor and acceptor impurities (n- and p-type doping, respectively) is disclosed. The innovation provides for ohmic contacts formed on SiC layers having n- and p-doping at one process step during the fabrication of the semiconductor device. Further, the innovation provides a non-discriminatory, universal ohmic contact to both n- and p-type SiC, enhancing reliability of the specific contact resistivity when operated at temperatures in excess of 600.degree. C.

  5. Flexible heating head for induction heating apparatus and method

    NASA Astrophysics Data System (ADS)

    Coultrip, Robert H.; Copeland, Carl E.; Fox, Robert L.; Johnson, Samuel D., Jr.; Phillips, W. Morris; Buckley, John D.

    1991-10-01

    An induction heating head includes: a length of wire having first and second opposite ends and being wound in a flat spiral shape to form an induction coil; a capacitor connected to the first and second ends of the wire, the induction coil and capacitor defining a tank circuit; and a flexible, elastomeric body molded to encase the induction coil. When a susceptor is placed in juxtaposition to the body, and the tank circuit is powered, the susceptor is inductively heated.

  6. Flexible heating head for induction heating apparatus and method

    NASA Astrophysics Data System (ADS)

    Fox, Robert L.; Johnson, Samuel D.; Coultrip, Robert H.; Phillips, W. Morris

    1991-10-01

    An induction heating head includes a length of wire having first and second opposite ends and being wound in a flat spiral shape to form an induction coil, a capacitor connected to the first and second ends of the wire, the induction coil and capacitor defining a tank circuit, and a flexible, elastomeric body molded to encase the induction coil. When a susceptor is placed in juxtaposition to the body, and the tank circuit is powered, the susceptor is inductively heated.

  7. Bayesian Analysis of Hot-Jupiter Radius Anomalies: Evidence for Ohmic Dissipation?

    NASA Astrophysics Data System (ADS)

    Thorngren, Daniel P.; Fortney, Jonathan J.

    2018-05-01

    The cause of hot-Jupiter radius inflation, where giant planets with {T}eq} > 1000 K are significantly larger than expected, is an open question and the subject of many proposed explanations. Many of these hypotheses postulate an additional anomalous power that heats planets’ convective interiors, leading to larger radii. Rather than examine these proposed models individually, we determine what anomalous powers are needed to explain the observed population’s radii, and consider which models are most consistent with this. We examine 281 giant planets with well-determined masses and radii and apply thermal evolution and Bayesian statistical models to infer the anomalous power as a fraction of (and varying with) incident flux ɛ(F) that best reproduces the observed radii. First, we observe that the inflation of planets below about M = 0.5 M J appears very different than their higher-mass counterparts, perhaps as the result of mass loss or an inefficient heating mechanism. As such, we exclude planets below this threshold. Next, we show with strong significance that ɛ(F) increases with {T}eq} toward a maximum of ∼2.5% at T eq ≈ 1500 K, and then decreases as temperatures increase further, falling to ∼0.2% at T eff = 2500 K. This high-flux decrease in inflation efficiency was predicted by the Ohmic dissipation model of giant planet inflation but not other models. We also show that the thermal tides model predicts far more variance in radii than is observed. Thus, our results provide evidence for the Ohmic dissipation model and a functional form for ɛ(F) that any future theories of hot-Jupiter radii can be tested against.

  8. Minimizing hot spot temperature in asymmetric gradient coil design.

    PubMed

    While, Peter T; Forbes, Larry K; Crozier, Stuart

    2011-08-01

    Heating caused by gradient coils is a considerable concern in the operation of magnetic resonance imaging (MRI) scanners. Hot spots can occur in regions where the gradient coil windings are closely spaced. These problem areas are particularly common in the design of gradient coils with asymmetrically located target regions. In this paper, an extension of an existing coil design method is described, to enable the design of asymmetric gradient coils with reduced hot spot temperatures. An improved model is presented for predicting steady-state spatial temperature distributions for gradient coils. A great amount of flexibility is afforded by this model to consider a wide range of geometries and system material properties. A feature of the temperature distribution related to the temperature gradient is used in a relaxed fixed point iteration routine for successively altering coil windings to have a lower hot spot temperature. Results show that significant reductions in peak temperature are possible at little or no cost to coil performance when compared to minimum power coils of equivalent field error.

  9. Conductor analysis of the ITER FEAT poloidal field coils during a plasma scenario

    NASA Astrophysics Data System (ADS)

    Nicollet, S.; Hertout, P.; Duchateau, J. L.; Bleyer, A.; Bessette, D.

    2002-05-01

    In the framework of the ITER (International Thermonuclear Experimental Reactor) FEAT (Fusion Energy Advanced Tokamak) project, a fully superconducting PF (Poloidal Field) system has been designed in detail. The Central Solenoid and the 6 equilibrium coils constituting the PF system provide the magnetic fields which develop, shape and control the 15 MA plasma during the 1800 s of a typical plasma scenario. The 6 PF coils will be wound two-in-hand from a 45 kA niobium-titanium CICC (Cable-In-Conduit-Conductor). These coils will experience severe heat loads specially during the 400 s of the plasma burn: nuclear heating due to the 400 MW of fusion power, thermal radiation and AC losses (30 to 300 kJ). The AC losses along the PF coil pancakes are deduced from accurate magnetic field computations performed with a 3D magnetostatic code, TRAPS. The nuclear heating and the thermal radiation are assumed to be uniform over a given face of the PF coils. These heat loads are used as input to perform the thermal and hydraulic analysis with a finite element code, GANDALF. The temperature increases (0.1 to 0.4 K) are computed, the margins and performances of the conductor are evaluated.

  10. Fabrication and Analysis of 150-mm-Aperture Nb 3Sn MQXF Coils

    DOE PAGES

    Holik, E. F.; Ambrosio, G.; Anerella, M.; ...

    2016-01-12

    The U.S. LHC Accelerator Research Program (LARP) and CERN are combining efforts for the HiLumi-LHC upgrade to design and fabricate 150-mm-aperture, interaction region quadrupoles with a nominal gradient of 130 T/m using Nb 3Sn. To successfully produce the necessary long MQXF triplets, the HiLumi-LHC collaboration is systematically reducing risk and design modification by heavily relying upon the experience gained from the successful 120-mm-aperture LARP HQ program. First generation MQXF short (MQXFS) coils were predominately a scaling up of the HQ quadrupole design allowing comparable cable expansion during Nb 3Sn formation heat treatment and increased insulation fraction for electrical robustness. Amore » total of 13 first generation MQXFS coils were fabricated between LARP and CERN. Systematic differences in coil size, coil alignment symmetry, and coil length contraction during heat treatment are observed and likely due to slight variances in tooling and insulation/cable systems. Analysis of coil cross sections indicate that field-shaping wedges and adjacent coil turns are systematically displaced from the nominal location and the cable is expanding less than nominally designed. Lastly, a second generation MQXF coil design seeks to correct the expansion and displacement discrepancies by increasing insulation and adding adjustable shims at the coil pole and midplanes to correct allowed magnetic field harmonics.« less

  11. Genome-Wide Identification of Arabidopsis Coiled-Coil Proteins and Establishment of the ARABI-COIL Database1

    PubMed Central

    Rose, Annkatrin; Manikantan, Sankaraganesh; Schraegle, Shannon J.; Maloy, Michael A.; Stahlberg, Eric A.; Meier, Iris

    2004-01-01

    Increasing evidence demonstrates the importance of long coiled-coil proteins for the spatial organization of cellular processes. Although several protein classes with long coiled-coil domains have been studied in animals and yeast, our knowledge about plant long coiled-coil proteins is very limited. The repeat nature of the coiled-coil sequence motif often prevents the simple identification of homologs of animal coiled-coil proteins by generic sequence similarity searches. As a consequence, counterparts of many animal proteins with long coiled-coil domains, like lamins, golgins, or microtubule organization center components, have not been identified yet in plants. Here, all Arabidopsis proteins predicted to contain long stretches of coiled-coil domains were identified by applying the algorithm MultiCoil to a genome-wide screen. A searchable protein database, ARABI-COIL (http://www.coiled-coil.org/arabidopsis), was established that integrates information on number, size, and position of predicted coiled-coil domains with subcellular localization signals, transmembrane domains, and available functional annotations. ARABI-COIL serves as a tool to sort and browse Arabidopsis long coiled-coil proteins to facilitate the identification and selection of candidate proteins of potential interest for specific research areas. Using the database, candidate proteins were identified for Arabidopsis membrane-bound, nuclear, and organellar long coiled-coil proteins. PMID:15020757

  12. Heterogeneous Superconducting Low-Noise Sensing Coils

    NASA Technical Reports Server (NTRS)

    Hahn, Inseob; Penanen, Konstantin I.; Ho Eom, Byeong

    2008-01-01

    A heterogeneous material construction has been devised for sensing coils of superconducting quantum interference device (SQUID) magnetometers that are subject to a combination of requirements peculiar to some advanced applications, notably including low-field magnetic resonance imaging for medical diagnosis. The requirements in question are the following: The sensing coils must be large enough (in some cases having dimensions of as much as tens of centimeters) to afford adequate sensitivity; The sensing coils must be made electrically superconductive to eliminate Johnson noise (thermally induced noise proportional to electrical resistance); and Although the sensing coils must be cooled to below their superconducting- transition temperatures with sufficient cooling power to overcome moderate ambient radiative heat leakage, they must not be immersed in cryogenic liquid baths. For a given superconducting sensing coil, this combination of requirements can be satisfied by providing a sufficiently thermally conductive link between the coil and a cold source. However, the superconducting coil material is not suitable as such a link because electrically superconductive materials are typically poor thermal conductors. The heterogeneous material construction makes it possible to solve both the electrical- and thermal-conductivity problems. The basic idea is to construct the coil as a skeleton made of a highly thermally conductive material (typically, annealed copper), then coat the skeleton with an electrically superconductive alloy (typically, a lead-tin solder) [see figure]. In operation, the copper skeleton provides the required thermally conductive connection to the cold source, while the electrically superconductive coating material shields against Johnson noise that originates in the copper skeleton.

  13. Experimental and numerical investigations of wire bending by linear winding of rectangular tooth coils

    NASA Astrophysics Data System (ADS)

    Komodromos, A.; Tekkaya, A. E.; Hofmann, J.; Fleischer, J.

    2018-05-01

    Since electric motors are gaining in importance in many fields of application, e.g. hybrid electric vehicles, optimization of the linear coil winding process greatly contributes to an increase in productivity and flexibility. For the investigation of the forming behavior of the winding wire the material behavior is characterized in different experimental setups. Numerical examinatons of the linear winding process are carried out in a case study for a rectangular bobbin in order to analyze the influence of forming parameters on the resulting properties of the wound coil. Besides the numerical investigation of the linear winding method by using the finite element method (FEM), a multi-body dynamics (MBD) simulation is carried out. The multi-body dynamics simulation is necessary to represent the movement of the bodies as well as the connection of the components during winding. The finite element method is used to represent the material behavior of the copper wire and the plastic strain distribution within the wire. It becomes clear that the MBD simulation is not sufficient for analyzing the process and the wire behavior in its entirety. Important parameters that define the final coil properties cannot be analyzed in the manner of a precise manifestation, e.g. the clearance between coil bobbin and wire as well as the wire deformation behavior in form of a diameter reduction which negatively affects the ohmic resistance. Finally, the numerical investigations are validated experimentally by linear winding tests.

  14. Heat exchanger with auxiliary cooling system

    DOEpatents

    Coleman, John H.

    1980-01-01

    A heat exchanger with an auxiliary cooling system capable of cooling a nuclear reactor should the normal cooling mechanism become inoperable. A cooling coil is disposed around vertical heat transfer tubes that carry secondary coolant therethrough and is located in a downward flow of primary coolant that passes in heat transfer relationship with both the cooling coil and the vertical heat transfer tubes. A third coolant is pumped through the cooling coil which absorbs heat from the primary coolant which increases the downward flow of the primary coolant thereby increasing the natural circulation of the primary coolant through the nuclear reactor.

  15. Molecular basis of coiled-coil oligomerization-state specificity.

    PubMed

    Ciani, Barbara; Bjelic, Saša; Honnappa, Srinivas; Jawhari, Hatim; Jaussi, Rolf; Payapilly, Aishwarya; Jowitt, Thomas; Steinmetz, Michel O; Kammerer, Richard A

    2010-11-16

    Coiled coils are extensively and successfully used nowadays to rationally design multistranded structures for applications, including basic research, biotechnology, nanotechnology, materials science, and medicine. The wide range of applications as well as the important functions these structures play in almost all biological processes highlight the need for a detailed understanding of the factors that control coiled-coil folding and oligomerization. Here, we address the important and unresolved question why the presence of particular oligomerization-state determinants within a coiled coil does frequently not correlate with its topology. We found an unexpected, general link between coiled-coil oligomerization-state specificity and trigger sequences, elements that are indispensable for coiled-coil formation. By using the archetype coiled-coil domain of the yeast transcriptional activator GCN4 as a model system, we show that well-established trimer-specific oligomerization-state determinants switch the peptide's topology from a dimer to a trimer only when inserted into the trigger sequence. We successfully confirmed our results in two other, unrelated coiled-coil dimers, ATF1 and cortexillin-1. We furthermore show that multiple topology determinants can coexist in the same trigger sequence, revealing a delicate balance of the resulting oligomerization state by position-dependent forces. Our experimental results should significantly improve the prediction of the oligomerization state of coiled coils. They therefore should have major implications for the rational design of coiled coils and consequently many applications using these popular oligomerization domains.

  16. Electrical and thermal characteristics of Bi2212/Ag HTS coils for conduction-cooled SMES

    NASA Astrophysics Data System (ADS)

    Hayakawa, N.; Noguchi, S.; Kurupakorn, C.; Kojima, H.; Endo, F.; Hirano, N.; Nagaya, S.; Okubo, H.

    2006-06-01

    In this paper, we investigated the electrical and thermal performance of conduction-cooled Bi2212/Ag HTS coils with 4K-GM cryocooler system. First, we measured the critical current Ic for different ambient temperatures T0 at 4.2 K - 40 K. Experimental results revealed that Ic increased with the decrease in T0 and was saturated at T0 < 10 K. We carried out thermal analysis considering heat generation, conduction and transfer under conduction-cooling condition, and reproduced the electrical and thermal characteristics of the conduction-cooled HTS coil, taking account of temperature dependence of specific heat and thermal conductivity of the materials. We also measured the temperature rise of Bi2212/Ag HTS coil for different continuous current levels at T0 = 4.8 K. Experimental results revealed the criterion of thermal runaway, which was discussed in terms of heat generation and propagation in the test coil.

  17. A Study on Ohmic Contact to Dry-Etched p-GaN

    NASA Astrophysics Data System (ADS)

    Hu, Cheng-Yu; Ao, Jin-Ping; Okada, Masaya; Ohno, Yasuo

    Low-power dry-etching process has been adopted to study the influence of dry-etching on Ohmic contact to p-GaN. When the surface layer of as-grown p-GaN was removed by low-power SiCl4/Cl2-etching, no Ohmic contact can be formed on the low-power dry-etched p-GaN. The same dry-etching process was also applied on n-GaN to understand the influence of the low-power dry-etching process. By capacitance-voltage (C-V) measurement, the Schottky barrier heights (SBHs) of p-GaN and n-GaN were measured. By comparing the change of measured SBHs on p-GaN and n-GaN, it was suggested that etching damage is not the only reason responsible for the degraded Ohmic contacts to dry-etched p-GaN and for Ohmic contact formatin, the original surface layer of as-grown p-GaN have some special properties, which were removed by dry-etching process. To partially recover the original surface of as-grown p-GaN, high temperature annealing (1000°C 30s) was tried on the SiCl4/Cl2-etched p-GaN and Ohmic contact was obtained.

  18. The structure of the GemC1 coiled coil and its interaction with the Geminin family of coiled-coil proteins

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Caillat, Christophe; Fish, Alexander; Pefani, Dafni-Eleftheria

    The GemC1 coiled-coil structure has subtle differences compared with its homologues Geminin and Idas. Co-expression experiments in cells and biophysical stability analysis of the Geminin-family coiled coils suggest that the GemC1 coiled coil alone is unstable. GemC1, together with Idas and Geminin, an important regulator of DNA-replication licensing and differentiation decisions, constitute a superfamily sharing a homologous central coiled-coil domain. To better understand this family of proteins, the crystal structure of a GemC1 coiled-coil domain variant engineered for better solubility was determined to 2.2 Å resolution. GemC1 shows a less typical coiled coil compared with the Geminin homodimer and themore » Geminin–Idas heterodimer structures. It is also shown that both in vitro and in cells GemC1 interacts with Geminin through its coiled-coil domain, forming a heterodimer that is more stable that the GemC1 homodimer. Comparative analysis of the thermal stability of all of the possible superfamily complexes, using circular dichroism to follow the unfolding of the entire helix of the coiled coil, or intrinsic tryptophan fluorescence of a unique conserved N-terminal tryptophan, shows that the unfolding of the coiled coil is likely to take place from the C-terminus towards the N-terminus. It is also shown that homodimers show a single-state unfolding, while heterodimers show a two-state unfolding, suggesting that the dimer first falls apart and the helices then unfold according to the stability of each protein. The findings argue that Geminin-family members form homodimers and heterodimers between them, and this ability is likely to be important for modulating their function in cycling and differentiating cells.« less

  19. Whey acerola-flavoured drink submitted Ohmic Heating: Bioactive compounds, antioxidant capacity, thermal behavior, water mobility, fatty acid profile and volatile compounds.

    PubMed

    Cappato, Leandro P; Ferreira, Marcus Vinicius S; Moraes, Jeremias; Pires, Roberto P S; Rocha, Ramon S; Silva, Ramon; Neto, Roberto P C; Tavares, Maria Inês B; Freitas, Mônica Q; Rodrigues, Flavio N; Calado, Veronica M A; Raices, Renata S L; Silva, Marcia C; Cruz, Adriano G

    2018-10-15

    Whey acerola-flavoured drink was subjected to Ohmic Heating (OH) under different operational conditions (45, 60, 80 V at 60 Hz and 10, 100, 1000 Hz with 25 V, 65 °C/30 min) and conventional pasteurization (65 °C/30 min). Bioactive compounds (total phenolics, DPPH, FRAP, ACE levels), fatty acid profile, volatile compounds (CG-MS), thermal behaviors (DSC) and water mobility (TD-NMR) were performed. Reduction of frequency (1000-10 Hz) resulted in a lower bioactive compounds and antioxidant capacity of the samples, except for the DPPH values. Concerning the thermal behaviors, fatty acids profile and volatile compounds, different findings were observed as a function of the parameters used (voltage and frequency). In respect of TD-NMR parameters, OH led to a slightly reduction of the relaxation time when compared to the conventional treatment, suggesting more viscous beverages. Overall, OH may be interesting option to whey acerola-flavoured drink processing. Copyright © 2018 Elsevier Ltd. All rights reserved.

  20. Current COIL research in Samara

    NASA Astrophysics Data System (ADS)

    Nikolaev, Valeri D.

    1996-02-01

    Development of the high pressure singlet oxygen generator (SOG) is a very important aspect for chemical oxygen-iodine laser (COIL). Increasing of oxygen pressure up to 30 torr and more at conserving high O2(1(Delta) ) yield and maintaining BHP temperature at minus (10 divided by 20) degrees Celsius permits us to decrease ration [H2O]/[O2] to 5% and less. In this case COIL can operate successfully without a water vapor trap. With raising the total pressure Reynolds number increases too, diminishing boundary layers in supersonic nozzles and improving pressure recovery. The weight and dimensions of the SOG and laser become reduced for the same gas flow rate. For solving these problems the jet SOG has been suggested and developed in Lebedev Physical Institute, Samara Branch. The advantages of the jet SOG consist of the following: (1) Large and controlled specific surface of contact liquid-gas provides for high mass transfer efficiency. (2) High jets velocity guarantees fast basic hydrogen peroxide (BHP) surface renovation. (3) High gas velocity in the reaction zone diminishes O2(1(Delta) ) quenching. (4) Efficient gas-liquid heat exchange eliminates the gas heating and generation water vapor due O2(1(Delta) ) quenching. (5) Counterflowing design of the jet SOG produces the best conditions for self-cleaning gas flow of droplets in the reaction zone and gives the possibility of COIL operation without droplets separator. High pressure jet SOG has some features connected with intrachannel jet formation, free space jets reconstruction, interaction jets ensemble with counter moving gas flow and drag part of gas by jets, disintegrating jets, generation and separation of droplets, heat effects, surface renovation, impoverishment BHP surface by HO2- ions, moving solution film on the reaction zone walls, etc. In this communication our current understanding of the major processes in the jet SOG is set forth. The complex gas and hydrodynamic processes with heat and mass transfer

  1. Experimental measurement of coil-rod-coil block copolymer tracer diffusion through entangled coil homopolymers

    PubMed Central

    Wang, Muzhou; Timachova, Ksenia; Olsen, Bradley D.

    2014-01-01

    The diffusion of coil-rod-coil triblock copolymers in entangled coil homopolymers is experimentally measured and demonstrated to be significantly slower than rod or coil homopolymers of the same molecular weight. A model coil-rod-coil triblock was prepared by expressing rodlike alanine-rich α-helical polypeptides in E. coli and conjugating coillike poly(ethylene oxide) (PEO) to both ends to form coil-rod-coil triblock copolymers. Tracer diffusion through entangled PEO homopolymer melts was measured using forced Rayleigh scattering at various rod lengths, coil molecular weights, and coil homopolymer concentrations. For rod lengths, L, that are close to the entanglementh length, a, the ratio between triblock diffusivity and coil homopolymer diffusivity decreases monotonically and is only a function of L/a, in quantitative agreement with previous simulation results. For large rod lengths, diffusion follows an arm retraction scaling, which is also consistent with previous theoretical predictions. These experimental results support the key predictions of theory and simulation, suggesting that the mismatch in curvature between rod and coil entanglement tubes leads to the observed diffusional slowing. PMID:25484454

  2. A periodic table of coiled-coil protein structures.

    PubMed

    Moutevelis, Efrosini; Woolfson, Derek N

    2009-01-23

    Coiled coils are protein structure domains with two or more alpha-helices packed together via interlacing of side chains known as knob-into-hole packing. We analysed and classified a large set of coiled-coil structures using a combination of automated and manual methods. This led to a systematic classification that we termed a "periodic table of coiled coils," which we have made available at http://coiledcoils.chm.bris.ac.uk/ccplus/search/periodic_table. In this table, coiled-coil assemblies are arranged in columns with increasing numbers of alpha-helices and in rows of increased complexity. The table provides a framework for understanding possibilities in and limits on coiled-coil structures and a basis for future prediction, engineering and design studies.

  3. Buried polar residues in coiled-coil interfaces.

    PubMed

    Akey, D L; Malashkevich, V N; Kim, P S

    2001-05-29

    Coiled coils, estimated to constitute 3-5% of the encoded residues in most genomes, are characterized by a heptad repeat, (abcdefg)(n), where the buried a and d positions form the interface between multiple alpha-helices. Although generally hydrophobic, a substantial fraction ( approximately 20%) of these a- and d-position residues are polar or charged. We constructed variants of the well-characterized coiled coil GCN4-p1 with a single polar residue (Asn, Gln, Ser, or Thr) at either an a or a d position. The stability and oligomeric specificity of each variant were measured, and crystal structures of coiled-coil trimers with threonine or serine at either an a or a d position were determined. The structures show how single polar residues in the interface affect not only local packing, but also overall coiled-coil geometry as seen by changes in the Crick supercoil parameters and core cavity volumes.

  4. Method for forming low-resistance ohmic contacts on semiconducting oxides

    DOEpatents

    Narayan, J.

    1979-10-01

    The invention provides a new method for the formation of high-quality ohmic contacts on wide-band-gap semiconducting oxides. As exemplified by the formation of an ohmic contact on n-type BaTiO/sub 3/ containing a p-n junction, the invention entails depositing a film of a metallic electroding material on the BaTiO/sub 3/ surface and irradiating the film with a Q-switched laser pulse effecting complete melting of the film and localized melting of the surface layer of oxide immediately underlying the film. The resulting solidified metallic contact is ohmic, has unusually low contact resistance, and is thermally stable, even at elevated temmperatures. The contact does not require cleaning before attachment of any suitable electrical lead. This method is safe, rapid, reproducible, and relatively inexpensive.

  5. Ohmic contacts to Al-rich AlGaN heterostructures

    DOE PAGES

    Douglas, E. A.; Reza, S.; Sanchez, C.; ...

    2017-06-06

    Due to the ultra-wide bandgap of Al-rich AlGaN, up to 5.8 eV for the structures in this study, obtaining low resistance ohmic contacts is inherently difficult to achieve. A comparative study of three different fabrication schemes is presented for obtaining ohmic contacts to an Al-rich AlGaN channel. Schottky-like behavior was observed for several different planar metallization stacks (and anneal temperatures), in addition to a dry-etch recess metallization contact scheme on Al 0.85Ga 0.15N/Al 0.66Ga 0.34N. However, a dry etch recess followed by n +-GaN regrowth fabrication process is reported as a means to obtain lower contact resistivity ohmic contacts onmore » a Al 0.85Ga 0.15N/Al 0.66Ga 0.34N heterostructure. In conclusion, specific contact resistivity of 5×10 -3 Ω cm 2 was achieved after annealing Ti/Al/Ni/Au metallization.« less

  6. Ultra-thin ohmic contacts for p-type nitride light emitting devices

    DOEpatents

    Raffetto, Mark [Raleigh, NC; Bharathan, Jayesh [Cary, NC; Haberern, Kevin [Cary, NC; Bergmann, Michael [Chapel Hill, NC; Emerson, David [Chapel Hill, NC; Ibbetson, James [Santa Barbara, CA; Li, Ting [Ventura, CA

    2012-01-03

    A semiconductor based Light Emitting Device (LED) can include a p-type nitride layer and a metal ohmic contact, on the p-type nitride layer. The metal ohmic contact can have an average thickness of less than about 25 .ANG. and a specific contact resistivity less than about 10.sup.-3 ohm-cm.sup.2.

  7. ZnO Schottky barriers and Ohmic contacts

    NASA Astrophysics Data System (ADS)

    Brillson, Leonard J.; Lu, Yicheng

    2011-06-01

    ZnO has emerged as a promising candidate for optoelectronic and microelectronic applications, whose development requires greater understanding and control of their electronic contacts. The rapid pace of ZnO research over the past decade has yielded considerable new information on the nature of ZnO interfaces with metals. Work on ZnO contacts over the past decade has now been carried out on high quality material, nearly free from complicating factors such as impurities, morphological and native point defects. Based on the high quality bulk and thin film crystals now available, ZnO exhibits a range of systematic interface electronic structure that can be understood at the atomic scale. Here we provide a comprehensive review of Schottky barrier and ohmic contacts including work extending over the past half century. For Schottky barriers, these results span the nature of ZnO surface charge transfer, the roles of surface cleaning, crystal quality, chemical interactions, and defect formation. For ohmic contacts, these studies encompass the nature of metal-specific interactions, the role of annealing, multilayered contacts, alloyed contacts, metallization schemes for state-of-the-art contacts, and their application to n-type versus p-type ZnO. Both ZnO Schottky barriers and ohmic contacts show a wide range of phenomena and electronic behavior, which can all be directly tied to chemical and structural changes on an atomic scale.

  8. Annealing effects on electrical behavior of gold nanoparticle film: Conversion of ohmic to non-ohmic conductivity

    NASA Astrophysics Data System (ADS)

    Ebrahimpour, Zeinab; Mansour, Nastaran

    2017-02-01

    This paper reports on the electrical behavior of self-assembled gold nanoparticle films before and after high-temperature annealing in ambient environment. These films are made by depositing gold nanoparticles from a colloidal solution on glass substrates using centrifuge deposition technique. The current-voltage (I-V) characteristics of these films exhibits ohmic and non-ohmic properties for un-annealed and annealed films respectively. As the annealing time duration increases, the onset of non-ohmic behavior occurs at higher voltages. To understand the underlying mechanisms for the observed electrical conduction behavior in these films and how electrical conduction is effected by film morphology and structural properties before and after annealing, systematic comparative studies based on scanning electron microscopy (SEM), UV-vis absorption spectroscopy and X-ray photoelectron spectroscopy (XPS) have been performed. The morphology of the films shows that the assembled gold nanoparticles are distributed on the substrate in a random way before annealing. After 2 h annealing gold nanoparticles exhibit a higher filling fraction when examined by SEM, which means that they coalesce, upon annealing, with respect to un-annealed films. The UV-vis absorption spectra of the films show that there is a red-shift and broadening in the absorption band for the annealed films. The observed phenomenon is related to the plasmon near-field coupling effect and suggests that the nanoparticle ensembles interspacing has decreased. The structural and crystallinity of the films exhibit amorphous structure before annealing and pure crystalline phases with a preferential growth direction along the (111) plane after annealing. The XPS analysis further suggests the existence of the stable thin oxide layer in the phase of Au2O3 in the annealed films. The I-V characteristics have been described by Simmons' model for tunnel transport through metal-insulator-metal (MIM) junctions. The Fowler

  9. Dynamic allostery of protein alpha helical coiled-coils

    PubMed Central

    Hawkins, Rhoda J; McLeish, Tom C.B

    2005-01-01

    Alpha helical coiled-coils appear in many important allosteric proteins such as the dynein molecular motor and bacteria chemotaxis transmembrane receptors. As a mechanism for transmitting the information of ligand binding to a distant site across an allosteric protein, an alternative to conformational change in the mean static structure is an induced change in the pattern of the internal dynamics of the protein. We explore how ligand binding may change the intramolecular vibrational free energy of a coiled-coil, using parameterized coarse-grained models, treating the case of dynein in detail. The models predict that coupling of slide, bend and twist modes of the coiled-coil transmits an allosteric free energy of ∼2kBT, consistent with experimental results. A further prediction is a quantitative increase in the effective stiffness of the coiled-coil without any change in inherent flexibility of the individual helices. The model provides a possible and experimentally testable mechanism for transmission of information through the alpha helical coiled-coil of dynein. PMID:16849225

  10. Predicting helix orientation for coiled-coil dimers

    PubMed Central

    Apgar, James R.; Gutwin, Karl N.; Keating, Amy E.

    2008-01-01

    The alpha-helical coiled coil is a structurally simple protein oligomerization or interaction motif consisting of two or more alpha helices twisted into a supercoiled bundle. Coiled coils can differ in their stoichiometry, helix orientation and axial alignment. Because of the near degeneracy of many of these variants, coiled coils pose a challenge to fold recognition methods for structure prediction. Whereas distinctions between some protein folds can be discriminated on the basis of hydrophobic/polar patterning or secondary structure propensities, the sequence differences that encode important details of coiled-coil structure can be subtle. This is emblematic of a larger problem in the field of protein structure and interaction prediction: that of establishing specificity between closely similar structures. We tested the behavior of different computational models on the problem of recognizing the correct orientation - parallel vs. antiparallel - of pairs of alpha helices that can form a dimeric coiled coil. For each of 131 examples of known structure, we constructed a large number of both parallel and antiparallel structural models and used these to asses the ability of five energy functions to recognize the correct fold. We also developed and tested three sequenced-based approaches that make use of varying degrees of implicit structural information. The best structural methods performed similarly to the best sequence methods, correctly categorizing ∼81% of dimers. Steric compatibility with the fold was important for some coiled coils we investigated. For many examples, the correct orientation was determined by smaller energy differences between parallel and antiparallel structures distributed over many residues and energy components. Prediction methods that used structure but incorporated varying approximations and assumptions showed quite different behaviors when used to investigate energetic contributions to orientation preference. Sequence based methods were

  11. Method to reduce non-specific tissue heating of small animals in solenoid coils.

    PubMed

    Kumar, Ananda; Attaluri, Anilchandra; Mallipudi, Rajiv; Cornejo, Christine; Bordelon, David; Armour, Michael; Morua, Katherine; Deweese, Theodore L; Ivkov, Robert

    2013-01-01

    Solenoid coils that generate time-varying or alternating magnetic fields (AMFs) are used in biomedical devices for research, imaging and therapy. Interactions of AMF and tissue produce eddy currents that deposit power within tissue, thus limiting effectiveness and safety. We aim to develop methods that minimise excess heating of mice exposed to AMFs for cancer therapy experiments. Numerical and experimental data were obtained to characterise thermal management properties of water using a continuous, custom water jacket in a four-turn simple solenoid. Theoretical data were obtained with method-of-moments (MoM) numerical field calculations and finite element method (FEM) thermal simulations. Experimental data were obtained from gel phantoms and mice exposed to AMFs having amplitude >50 kA/m and frequency of 160 kHz. Water has a high specific heat and thermal conductivity, is diamagnetic, polar, and nearly transparent to magnetic fields. We report at least a two-fold reduction of temperature increase from gel phantom and animal models when a continuous layer of circulating water was placed between the sample and solenoid, compared with no water. Thermal simulations indicate the superior efficiency in thermal management by the developed continuous single chamber cooling system over a double chamber non-continuous system. Further reductions of heating were obtained by regulating water temperature and flow for active cooling. These results demonstrate the potential value of a contiguous layer of circulating water to permit sustained exposure to high intensity alternating magnetic fields at this frequency for research using small animal models exposed to AMFs.

  12. Method to reduce non-specific tissue heating of small animals in solenoid coils

    PubMed Central

    KUMAR, ANANDA; ATTALURI, ANILCHANDRA; MALLIPUDI, RAJIV; CORNEJO, CHRISTINE; BORDELON, DAVID; ARMOUR, MICHAEL; MORUA, KATHERINE; DEWEESE, THEODORE L.; IVKOV, ROBERT

    2014-01-01

    Purpose Solenoid coils that generate time-varying or alternating magnetic fields (AMFs) are used in biomedical devices for research, imaging and therapy. Interactions of AMF and tissue produce eddy currents that deposit power within tissue, thus limiting effectiveness and safety. We aim to develop methods that minimise excess heating of mice exposed to AMFs for cancer therapy experiments. Materials and methods Numerical and experimental data were obtained to characterise thermal management properties of water using a continuous, custom water jacket in a four-turn simple solenoid. Theoretical data were obtained with method-of-moments (MoM) numerical field calculations and finite element method (FEM) thermal simulations. Experimental data were obtained from gel phantoms and mice exposed to AMFs having amplitude >50kA/m and frequency of 160 kHz. Results Water has a high specific heat and thermal conductivity, is diamagnetic, polar, and nearly transparent to magnetic fields. We report at least a two-fold reduction of temperature increase from gel phantom and animal models when a continuous layer of circulating water was placed between the sample and solenoid, compared with no water. Thermal simulations indicate the superior efficiency in thermal management by the developed continuous single chamber cooling system over a double chamber non-continuous system. Further reductions of heating were obtained by regulating water temperature and flow for active cooling. Conclusions These results demonstrate the potential value of a contiguous layer of circulating water to permit sustained exposure to high intensity alternating magnetic fields at this frequency for research using small animal models exposed to AMFs. PMID:23402327

  13. Wound tube heat exchanger

    DOEpatents

    Ecker, Amir L.

    1983-01-01

    What is disclosed is a wound tube heat exchanger in which a plurality of tubes having flattened areas are held contiguous adjacent flattened areas of tubes by a plurality of windings to give a double walled heat exchanger. The plurality of windings serve as a plurality of effective force vectors holding the conduits contiguous heat conducting walls of another conduit and result in highly efficient heat transfer. The resulting heat exchange bundle is economical and can be coiled into the desired shape. Also disclosed are specific embodiments such as the one in which the tubes are expanded against their windings after being coiled to insure highly efficient heat transfer.

  14. Shielding of Sensitive Electronic Devices in Magnetic Nanoparticle Hyperthermia Using Arrays of Coils

    NASA Astrophysics Data System (ADS)

    Spirou, S. V.; Tsialios, P.; Loudos, G.

    2015-09-01

    In Magnetic Nanoparticle Hyperthermia (MNH) an externally applied electromagnetic field transfers energy to the magnetic nanoparticles in the body, which in turn convert this energy into heat, thus locally heating the tissue they are located in. This external electromagnetic field is sufficiently strong so as to cause interference and affect sensitive electronic equipment. Standard shielding of magnetic fields involves Faraday cages or coating with high-permeability shielding alloys; however, these techniques cannot be used with optically sensitive devices, such as those employed in Optical Coherence Tomography or radionuclide imaging. In this work we present a method to achieve magnetic shielding using an array of coils. The magnetic field generated by a single coil was calculated using the COMSOL physics simulation toolkit. Software was written in C/C++ to import the single-coil data, and then calculate the positions, number of turns and currents in the shielding coils in order to minimize the magnetic field strength at the desired location. Simulations and calculations have shown that just two shielding coils can reduce the magnetic field by 2-3 orders of magnitude.

  15. Ultra-thin ohmic contacts for p-type nitride light emitting devices

    DOEpatents

    Raffetto, Mark; Bharathan, Jayesh; Haberern, Kevin; Bergmann, Michael; Emerson, David; Ibbetson, James; Li, Ting

    2014-06-24

    A flip-chip semiconductor based Light Emitting Device (LED) can include an n-type semiconductor substrate and an n-type GaN epi-layer on the substrate. A p-type GaN epi-layer can be on the n-type GaN epi-layer and a metal ohmic contact p-electrode can be on the p-type GaN epi-layer, where the metal ohmic contact p-electrode can have an average thickness less than about 25 .ANG.. A reflector can be on the metal ohmic contact p-electrode and a metal stack can be on the reflector. An n-electrode can be on the substrate opposite the n-type GaN epi-layer and a bonding pad can be on the n-electrode.

  16. Minimization of Ohmic losses for domain wall motion in ferromagnetic nanowires

    NASA Astrophysics Data System (ADS)

    Abanov, Artem; Tretiakov, Oleg; Liu, Yang

    2011-03-01

    We study current-induced domain-wall motion in a narrow ferromagnetic wire. We propose a way to move domain walls with a resonant time-dependent current which dramatically decreases the Ohmic losses in the wire and allows driving of the domain wall with higher speed without burning the wire. For any domain wall velocity we find the time-dependence of the current needed to minimize the Ohmic losses. Below a critical domain-wall velocity specified by the parameters of the wire the minimal Ohmic losses are achieved by dc current. Furthermore, we identify the wire parameters for which the losses reduction from its dc value is the most dramatic. This work was supported by the NSF Grant No. 0757992 and Welch Foundation (A-1678).

  17. Features of Stationary Photoconductivity of High-Ohmic Semiconductors Under Local Illumination

    NASA Astrophysics Data System (ADS)

    Lysenko, A. P.; Belov, A. G.; Kanevskii, V. E.; Odintsova, E. A.

    2018-04-01

    Photoconductivity has been thoroughly studied for a long time. However, most researchers have examined photoconductivity of semiconductors while illuminating the entire surface of samples. The present paper examines the effect of local exposure that ensures a high level of injection of free charge carriers upon the conductivity of high-ohmic cadmium telluride and semi-insulating gallium arsenide samples and upon the properties of ohmic contacts to samples. The authors found that regardless of the exposure area the value of transition resistance of ohmic contacts decreases and the concentration of the main charge carriers increases in the sample in proportion to radiation intensity. This research uncovered a number of previously unknown effects that are interesting from the physical point of view. This paper focuses on discussing these effects.

  18. Minimization of Ohmic Losses for Domain Wall Motion in a Ferromagnetic Nanowire

    NASA Astrophysics Data System (ADS)

    Tretiakov, O. A.; Liu, Y.; Abanov, Ar.

    2010-11-01

    We study current-induced domain-wall motion in a narrow ferromagnetic wire. We propose a way to move domain walls with a resonant time-dependent current which dramatically decreases the Ohmic losses in the wire and allows driving of the domain wall with higher speed without burning the wire. For any domain-wall velocity we find the time dependence of the current needed to minimize the Ohmic losses. Below a critical domain-wall velocity specified by the parameters of the wire the minimal Ohmic losses are achieved by dc current. Furthermore, we identify the wire parameters for which the losses reduction from its dc value is the most dramatic.

  19. Heating and Large Scale Dynamics of the Solar Corona

    NASA Technical Reports Server (NTRS)

    Schnack, Dalton D.

    2000-01-01

    The effort was concentrated in the areas: coronal heating mechanism, unstructured adaptive grid algorithms, numerical modeling of magnetic reconnection in the MRX experiment: effect of toroidal magnetic field and finite pressure, effect of OHMIC heating and vertical magnetic field, effect of dynamic MESH adaption.

  20. Laser method for forming low-resistance ohmic contacts on semiconducting oxides

    DOEpatents

    Narayan, Jagdish

    1981-01-01

    This invention is a new method for the formation of high-quality ohmic contacts on wide-band-gap semiconducting oxides. As exemplified by the formation of an ohmic contact on n-type BaTiO.sub.3 containing a p-n junction, the invention entails depositing a film of a metallic electroding material on the BaTiO.sub.3 surface and irradiating the film with a Q-switched laser pulse effecting complete melting of the film and localized melting of the surface layer of oxide immediately underlying the film. The resulting solidified metallic contact is ohmic, has unusually low contact resistance, and is thermally stable, even at elevated temperatures. The contact does not require cleaning before attachment of any suitable electrical lead. This method is safe, rapid, reproducible, and relatively inexpensive.

  1. Development of Numerical Methods to Estimate the Ohmic Breakdown Scenarios of a Tokamak

    NASA Astrophysics Data System (ADS)

    Yoo, Min-Gu; Kim, Jayhyun; An, Younghwa; Hwang, Yong-Seok; Shim, Seung Bo; Lee, Hae June; Na, Yong-Su

    2011-10-01

    The ohmic breakdown is a fundamental method to initiate the plasma in a tokamak. For the robust breakdown, ohmic breakdown scenarios have to be carefully designed by optimizing the magnetic field configurations to minimize the stray magnetic fields. This research focuses on development of numerical methods to estimate the ohmic breakdown scenarios by precise analysis of the magnetic field configurations. This is essential for the robust and optimal breakdown and start-up of fusion devices especially for ITER and its beyond equipped with low toroidal electric field (ET <= 0.3 V/m). A field-line-following analysis code based on the Townsend avalanche theory and a particle simulation code are developed to analyze the breakdown characteristics of actual complex magnetic field configurations including the stray magnetic fields in tokamaks. They are applied to the ohmic breakdown scenarios of tokamaks such as KSTAR and VEST and compared with experiments.

  2. Self-focusing and defocusing of Gaussian laser beams in collisional underdense magnetized plasmas with considering the nonlinear ohmic heating and ponderomotive force effects

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ettehadi Abari, Mehdi; Sedaghat, Mahsa; Shokri, Babak, E-mail: b-shokri@sbu.ac.ir

    2015-10-15

    The propagation characteristics of a Gaussian laser beam in collisional magnetized plasma are investigated by considering the ponderomotive and ohmic heating nonlinearities. Here, by taking into account the effect of the external magnetic field, the second order differential equation of the dimensionless beam width parameter is solved numerically. Furthermore, the nonlinear dielectric permittivity of the mentioned plasma medium in the paraxial approximation and its dependence on the propagation characteristics of the Gaussian laser pulse is obtained, and its variation in terms of the dimensionless plasma length is analyzed at different initial normalized plasma and cyclotron frequencies. The results show thatmore » the dimensionless beam width parameter is strongly affected by the initial plasma frequency, magnetic strength, and laser pulse intensity. Furthermore, it is found that there exists a certain intensity value below which the laser pulse tends to self focus, while the beam diverges above of this value. In addition, the results confirm that, by increasing the plasma and cyclotron frequencies (plasma density and magnetic strength), the self-focusing effect can occur intensively.« less

  3. Retrofitting coils

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Merrill, D.G.

    1995-12-01

    This article provides guidelines for maintaining efficiency by determining which coils require replacement and the selection of replacement coils to match the originals in terms of size, performance, materials, and material thickness. Coils in the Rio Hondo College have been in use 24 years. The author recently found an installation where the coils installed 20 years ago look like new, which is the result of a highly effective preventive maintenance program. But these exceptions are countered by some installations lasting considerably less time. Periodic coil inspections are the best way to find leaks and deterioration. Leaking coils have an unhappymore » way of announcing their presence through unwanted water on ceilings, walls, and machine room floors. Minuscule streams of water impinge on nonwater-tight housings or are picked up in the air stream to leak out of the ductwork. Coil return bends and headers seem to have the greater incidence of failure and should be checked first for pinhole or joint leaks. Also, check along the points where the tubes penetrate the tube sheets. The coil headers should be checked as should the tubes along the front and backside of the coil. The more rows the coil has, the more difficult this latter assignment becomes.« less

  4. High performance 3-coil wireless power transfer system for the 512-electrode epiretinal prosthesis.

    PubMed

    Zhao, Yu; Nandra, Mandheerej; Yu, Chia-Chen; Tai, Yu-chong

    2012-01-01

    The next-generation retinal prostheses feature high image resolution and chronic implantation. These features demand the delivery of power as high as 100 mW to be wireless and efficient. A common solution is the 2-coil inductive power link, used by current retinal prostheses. This power link tends to include a larger-size extraocular receiver coil coupled to the external transmitter coil, and the receiver coil is connected to the intraocular electrodes through a trans-sclera trans-choroid cable. In the long-term implantation of the device, the cable may cause hypotony (low intraocular pressure) and infection. However, when a 2-coil system is constructed from a small-size intraocular receiver coil, the efficiency drops drastically which may induce over heat dissipation and electromagnetic field exposure. Our previous 2-coil system achieved only 7% power transfer. This paper presents a fully intraocular and highly efficient wireless power transfer system, by introducing another inductive coupling link to bypass the trans-sclera trans-choroid cable. With the specific equivalent load of our customized 512-electrode stimulator, the current 3-coil inductive link was measured to have the overall power transfer efficiency around 36%, with 1-inch separation in saline. The high efficiency will favorably reduce the heat dissipation and electromagnetic field exposure to surrounding human tissues. The effect of the eyeball rotation on the power transfer efficiency was investigated as well. The efficiency can still maintain 14.7% with left and right deflection of 30 degree during normal use. The surgical procedure for the coils' implantation into the porcine eye was also demonstrated.

  5. Fabrication of optically reflecting ohmic contacts for semiconductor devices

    DOEpatents

    Sopori, B.L.

    1995-07-04

    A method is provided to produce a low-resistivity ohmic contact having high optical reflectivity on one side of a semiconductor device. The contact is formed by coating the semiconductor substrate with a thin metal film on the back reflecting side and then optically processing the wafer by illuminating it with electromagnetic radiation of a predetermined wavelength and energy level through the front side of the wafer for a predetermined period of time. This method produces a thin epitaxial alloy layer between the semiconductor substrate and the metal layer when a crystalline substrate is used. The alloy layer provides both a low-resistivity ohmic contact and high optical reflectance. 5 figs.

  6. Fabrication of optically reflecting ohmic contacts for semiconductor devices

    DOEpatents

    Sopori, Bhushan L.

    1995-01-01

    A method is provided to produce a low-resistivity ohmic contact having high optical reflectivity on one side of a semiconductor device. The contact is formed by coating the semiconductor substrate with a thin metal film on the back reflecting side and then optically processing the wafer by illuminating it with electromagnetic radiation of a predetermined wavelength and energy level through the front side of the wafer for a predetermined period of time. This method produces a thin epitaxial alloy layer between the semiconductor substrate and the metal layer when a crystalline substrate is used. The alloy layer provides both a low-resistivity ohmic contact and high optical reflectance.

  7. Modelling and Optimization of Four-Segment Shielding Coils of Current Transformers

    PubMed Central

    Gao, Yucheng; Zhao, Wei; Wang, Qing; Qu, Kaifeng; Li, He; Shao, Haiming; Huang, Songling

    2017-01-01

    Applying shielding coils is a practical way to protect current transformers (CTs) for large-capacity generators from the intensive magnetic interference produced by adjacent bus-bars. The aim of this study is to build a simple analytical model for the shielding coils, from which the optimization of the shielding coils can be calculated effectively. Based on an existing stray flux model, a new analytical model for the leakage flux of partial coils is presented, and finite element method-based simulations are carried out to develop empirical equations for the core-pickup factors of the models. Using the flux models, a model of the common four-segment shielding coils is derived. Furthermore, a theoretical analysis is carried out on the optimal performance of the four-segment shielding coils in a typical six-bus-bars scenario. It turns out that the “all parallel” shielding coils with a 45° starting position have the best shielding performance, whereas the “separated loop” shielding coils with a 0° starting position feature the lowest heating value. Physical experiments were performed, which verified all the models and the conclusions proposed in the paper. In addition, for shielding coils with other than the four-segment configuration, the analysis process will generally be the same. PMID:28587137

  8. Modelling and Optimization of Four-Segment Shielding Coils of Current Transformers.

    PubMed

    Gao, Yucheng; Zhao, Wei; Wang, Qing; Qu, Kaifeng; Li, He; Shao, Haiming; Huang, Songling

    2017-05-26

    Applying shielding coils is a practical way to protect current transformers (CTs) for large-capacity generators from the intensive magnetic interference produced by adjacent bus-bars. The aim of this study is to build a simple analytical model for the shielding coils, from which the optimization of the shielding coils can be calculated effectively. Based on an existing stray flux model, a new analytical model for the leakage flux of partial coils is presented, and finite element method-based simulations are carried out to develop empirical equations for the core-pickup factors of the models. Using the flux models, a model of the common four-segment shielding coils is derived. Furthermore, a theoretical analysis is carried out on the optimal performance of the four-segment shielding coils in a typical six-bus-bars scenario. It turns out that the "all parallel" shielding coils with a 45° starting position have the best shielding performance, whereas the "separated loop" shielding coils with a 0° starting position feature the lowest heating value. Physical experiments were performed, which verified all the models and the conclusions proposed in the paper. In addition, for shielding coils with other than the four-segment configuration, the analysis process will generally be the same.

  9. Aneurysm permeability following coil embolization: packing density and coil distribution

    PubMed Central

    Chueh, Ju-Yu; Vedantham, Srinivasan; Wakhloo, Ajay K; Carniato, Sarena L; Puri, Ajit S; Bzura, Conrad; Coffin, Spencer; Bogdanov, Alexei A; Gounis, Matthew J

    2015-01-01

    Background Rates of durable aneurysm occlusion following coil embolization vary widely, and a better understanding of coil mass mechanics is desired. The goal of this study is to evaluate the impact of packing density and coil uniformity on aneurysm permeability. Methods Aneurysm models were coiled using either Guglielmi detachable coils or Target coils. The permeability was assessed by taking the ratio of microspheres passing through the coil mass to those in the working fluid. Aneurysms containing coil masses were sectioned for image analysis to determine surface area fraction and coil uniformity. Results All aneurysms were coiled to a packing density of at least 27%. Packing density, surface area fraction of the dome and neck, and uniformity of the dome were significantly correlated (p<0.05). Hence, multivariate principal components-based partial least squares regression models were used to predict permeability. Similar loading vectors were obtained for packing and uniformity measures. Coil mass permeability was modeled better with the inclusion of packing and uniformity measures of the dome (r2=0.73) than with packing density alone (r2=0.45). The analysis indicates the importance of including a uniformity measure for coil distribution in the dome along with packing measures. Conclusions A densely packed aneurysm with a high degree of coil mass uniformity will reduce permeability. PMID:25031179

  10. Testing of machine wound second generation HTS tape Vacuum Pressure Impregnated coils

    NASA Astrophysics Data System (ADS)

    Swaffield, D.; Lewis, C.; Eugene, J.; Ingles, M.; Peach, D.

    2014-05-01

    Delamination of second generation (2G) High Temperature Superconducting (HTS) tapes has previously been reported when using resin based insulation systems for wound coils. One proposed root cause is the differential thermal contraction between the coil former and the resin encapsulated coil turns resulting in the tape c-axis tensile stress being exceeded. Importantly, delamination results in unacceptable degradation of the superconductor critical current level. To mitigate the delamination risk and prove winding, jointing and Vacuum Pressure Impregnation (VPI) processes in the production of coils for superconducting rotating machines at GE Power Conversion two scaled trial coils have been wound and extensively tested. The coils are wound from 12mm wide 2G HTS tape supplied by AMSC onto stainless steel 'racetrack' coil formers. The coils are wound in two layers which include both in-line and layer-layer joints subject to in-process test. The resin insulation system chosen is VPI and oven cured. Tests included; insulation resistance, repeat quench and recovery of the superconductor, heat runs and measurement of n-value, before and after multiple thermal cycling between ambient and 35 Kelvin. No degradation of coil performance is evidenced.

  11. Applying graph theory to protein structures: an atlas of coiled coils.

    PubMed

    Heal, Jack W; Bartlett, Gail J; Wood, Christopher W; Thomson, Andrew R; Woolfson, Derek N

    2018-05-02

    To understand protein structure, folding and function fully and to design proteins de novo reliably, we must learn from natural protein structures that have been characterised experimentally. The number of protein structures available is large and growing exponentially, which makes this task challenging. Indeed, computational resources are becoming increasingly important for classifying and analysing this resource. Here, we use tools from graph theory to define an atlas classification scheme for automatically categorising certain protein substructures. Focusing on the α-helical coiled coils, which are ubiquitous protein-structure and protein-protein interaction motifs, we present a suite of computational resources designed for analysing these assemblies. iSOCKET enables interactive analysis of side-chain packing within proteins to identify coiled coils automatically and with considerable user control. Applying a graph theory-based atlas classification scheme to structures identified by iSOCKET gives the Atlas of Coiled Coils, a fully automated, updated overview of extant coiled coils. The utility of this approach is illustrated with the first formal classification of an emerging subclass of coiled coils called α-helical barrels. Furthermore, in the Atlas, the known coiled-coil universe is presented alongside a partial enumeration of the 'dark matter' of coiled-coil structures; i.e., those coiled-coil architectures that are theoretically possible but have not been observed to date, and thus present defined targets for protein design. iSOCKET is available as part of the open-source GitHub repository associated with this work (https://github.com/woolfson-group/isocket). This repository also contains all the data generated when classifying the protein graphs. The Atlas of Coiled Coils is available at: http://coiledcoils.chm.bris.ac.uk/atlas/app.

  12. Aneurysm permeability following coil embolization: packing density and coil distribution.

    PubMed

    Chueh, Ju-Yu; Vedantham, Srinivasan; Wakhloo, Ajay K; Carniato, Sarena L; Puri, Ajit S; Bzura, Conrad; Coffin, Spencer; Bogdanov, Alexei A; Gounis, Matthew J

    2015-09-01

    Rates of durable aneurysm occlusion following coil embolization vary widely, and a better understanding of coil mass mechanics is desired. The goal of this study is to evaluate the impact of packing density and coil uniformity on aneurysm permeability. Aneurysm models were coiled using either Guglielmi detachable coils or Target coils. The permeability was assessed by taking the ratio of microspheres passing through the coil mass to those in the working fluid. Aneurysms containing coil masses were sectioned for image analysis to determine surface area fraction and coil uniformity. All aneurysms were coiled to a packing density of at least 27%. Packing density, surface area fraction of the dome and neck, and uniformity of the dome were significantly correlated (p<0.05). Hence, multivariate principal components-based partial least squares regression models were used to predict permeability. Similar loading vectors were obtained for packing and uniformity measures. Coil mass permeability was modeled better with the inclusion of packing and uniformity measures of the dome (r(2)=0.73) than with packing density alone (r(2)=0.45). The analysis indicates the importance of including a uniformity measure for coil distribution in the dome along with packing measures. A densely packed aneurysm with a high degree of coil mass uniformity will reduce permeability. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

  13. A new twist in the coil: functions of the coiled-coil domain of structural maintenance of chromosome (SMC) proteins.

    PubMed

    Matityahu, Avi; Onn, Itay

    2018-02-01

    The higher-order organization of chromosomes ensures their stability and functionality. However, the molecular mechanism by which higher order structure is established is poorly understood. Dissecting the activity of the relevant proteins provides information essential for achieving a comprehensive understanding of chromosome structure. Proteins of the structural maintenance of chromosome (SMC) family of ATPases are the core of evolutionary conserved complexes. SMC complexes are involved in regulating genome dynamics and in maintaining genome stability. The structure of all SMC proteins resembles an elongated rod that contains a central coiled-coil domain, a common protein structural motif in which two α-helices twist together. In recent years, the imperative role of the coiled-coil domain to SMC protein activity and regulation has become evident. Here, we discuss recent advances in the function of the SMC coiled coils. We describe the structure of the coiled-coil domain of SMC proteins, modifications and interactions that are mediated by it. Furthermore, we assess the role of the coiled-coil domain in conformational switches of SMC proteins, and in determining the architecture of the SMC dimer. Finally, we review the interplay between mutations in the coiled-coil domain and human disorders. We suggest that distinctive properties of coiled coils of different SMC proteins contribute to their distinct functions. The discussion clarifies the mechanisms underlying the activity of SMC proteins, and advocates future studies to elucidate the function of the SMC coiled coil domain.

  14. Flexible carbon-based ohmic contacts for organic transistors

    NASA Technical Reports Server (NTRS)

    Brandon, Erik (Inventor)

    2007-01-01

    The present invention relates to a system and method of organic thin-film transistors (OTFTs). More specifically, the present invention relates to employing a flexible, conductive particle-polymer composite material for ohmic contacts (i.e. drain and source).

  15. In Vivo Radiofrequency Heating in Swine in a 3T (123.2 MHz) Birdcage Whole-Body Coil

    PubMed Central

    Shrivastava, Devashish; Utecht, Lynn; Tian, Jinfeng; Hughes, John; Vaughan, J. Thomas

    2014-01-01

    Purpose To study in vivo radiofrequency (RF) heating produced due to power deposition from a 3T (Larmour frequency = 123.2 MHz), birdcage, whole-body coil. Methods The RF heating was simulated in a digital swine by solving the mechanistic generic bioheat transfer model (GBHTM) and the conventional, empirical Pennes bioheat transfer equation for the following two cases: (1) when the porcine head was in the isocenter, and (2) when the porcine trunk was in the isocenter. The simulation results were validated by making direct fluoroptic temperature measurements in the skin, brain, simulated hot regions, and rectum of ten swine (Case 1, N= 5, mean animal weight = 84.03 ± 6.85 kg, Whole-body average SAR = 2.65 ± 0.22 W/kg; Case 2, N= 5, mean animal weight = 81.59 ± 6.23 kg, Whole-body average SAR = 2.77 ± 0.26 W/kg) during one hour of exposure to a turbo spin echo sequence. Results The GBHTM simulated the RF heating more accurately compared to the Pennes equation. In vivo temperatures exceeded safe temperature thresholds with allowable SAR exposures. Hot regions may be produced deep inside the body, away from the skin. Conclusion SAR exposures to produce safe temperature thresholds may need re-investigation. PMID:24259413

  16. Fabricating Ohmic contact on Nb-doped SrTiO{sub 3} surface in nanoscale

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wang, Yuhang; National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, Chinese Academy of Engineering Physics, Mianyang, Sichuan 621999; Shi, Xiaolan

    2016-05-09

    Fabricating reliable nano-Ohmic contact on wide gap semiconductors is an important yet difficult step in oxide nanoelectronics. We fabricated Ohmic contact on the n-type wide gap oxide Nb-doped SrTiO{sub 3} in nanoscale by mechanically scratching the surface using an atomic force microscopy tip. Although contacted to high work function metal, the scratched area exhibits nearly linear IV behavior with low contact resistance, which maintains for hours in vacuum. In contrast, the unscratched area shows Fowler–Nordheim tunneling dominated Schottky rectifying behavior with high contact resistance. It was found that the Ohmic conductivity in the scratched area was drastically suppressed by oxygenmore » gas indicating the oxygen vacancy origin of the Ohmic behavior. The surface oxygen vacancy induced barrier width reduction was proposed to explain the phenomena. The nanoscale approach is also applicable to macroscopic devices and has potential application in all-oxide devices.« less

  17. Manufacturing of a REBCO racetrack coil using thermoplastic resin aiming at Maglev application

    NASA Astrophysics Data System (ADS)

    Mizuno, Katsutoshi; Ogata, Masafumi; Hasegawa, Hitoshi

    2015-11-01

    The REBCO coated conductor is a promising technology for the Maglev application in terms of its high critical temperature. The operating temperature of the on-board magnets can be around 40-50 K with the coated conductor. The REBCO coils are cooled by cryocoolers directly, and hence the thermal design of the REBCO coils significantly changes from that of LTS coils. We have developed a novel REBCO coil structure using thermoplastic resin. The coil is not impregnated and the thermoplastic resin is used to bond the coil winding and the heat transfer members, e.g. copper and aluminum plates. The viscosity of the thermoplastic resin is high enough for the thermoplastic resin not to permeate between the turns in the coil. Therefore, the thermal stress does not occur and the risk of degradation is removed. This paper contains the following three topics. First, the thermal resistance of the thermoplastic resin was measured at cryogenic temperature. Then, a small round REBCO coil was experimentally produced. It has been confirmed that the thermoplastic resin does not cause the degradation and, the adhesion between the coil winding and copper plates withstands the thermal stress. Finally, we successfully produced a full-scale racetrack REBCO coil applying the coil structure with the thermoplastic resin.

  18. Magnetic Field Generation by a Laser-Driven Capacitor-Coil Target

    NASA Astrophysics Data System (ADS)

    Cheng, Jessica; Gao, Lan

    2016-10-01

    Magnetic fields generated by currents flowing through a capacitor-coil target were characterized using ultrafast proton radiography at the OMEGA EP Laser System. Two 1.25 kJ, 1-ns laser pulses propagated through the laser entrance holes in one foil of the capacitor, and were focused to the other with an intensity of 3 ×1016 W/cm2. The intense laser-solid interaction induced a high voltage between the foils and generated a large current in the connecting coil. The proton data show tens of kA current producing tens of Tesla magnetic fields at the center of the coil. Theoretical lumped circuit models based on the experimental parameters were developed to simulate the target behavior and calculate the time evolution of the current in the coil. The models take into account important elements such as plasmas conditions for building up the voltage, the capacitance between the gap, the resistive heating and skin effect to gain insights on the field generation mechanism. Applications to other coil geometries and magnetic field configurations will also be described.

  19. Computational assessment of folding energy landscapes in heterodimeric coiled coils.

    PubMed

    André, Ingemar; Bjelic, Sinisa

    2018-07-01

    The coiled coil structural motif consists of alpha helices supercoiling around each other to form staggered knobs-into-holes packing. Such structures are deceptively simple, especially as they often can be described with parametric equations, but are known to exist in various conformations. Even the simplest systems, consisting of 2 monomers, can assemble into a wide range of states. They can form canonical as well as noncanonical coiled coils, be parallel or antiparallel, where helices associate with different degrees of shift, tilt, and rotation. Here, we investigate the energy landscape of heterodimeric coiled coils by carrying out de novo folding simulations starting from amino acid sequence. We folded a diverse set of 22 heterodimers and demonstrate that the approach is capable of identifying the atomic details in the experimental structure in the majority of cases. Our methodology also enables exploration of alternative states that can be accessible in solution beyond the experimentally determined structure. For many systems, we observe folding energy landscapes with multiple energy minima and several isoenergetic states. By comparing coiled coils from single domains and those extracted from larger proteins, we find that standalone coiled coils have deeper energy wells at the experimentally determined conformation. By folding the competing homodimeric states in addition to the heterodimers, we observe that the structural specificity towards the heteromeric state is often small. Taken together, our results demonstrate that de novo folding simulations can be a powerful tool to characterize structural specificity of coiled coils when coupled to assessment of energy landscapes. © 2018 Wiley Periodicals, Inc.

  20. Crystal Structure of a Coiled-Coil Domain from Human ROCK I

    PubMed Central

    Tu, Daqi; Li, Yiqun; Song, Hyun Kyu; Toms, Angela V.; Gould, Christopher J.; Ficarro, Scott B.; Marto, Jarrod A.; Goode, Bruce L.; Eck, Michael J.

    2011-01-01

    The small GTPase Rho and one of its targets, Rho-associated kinase (ROCK), participate in a variety of actin-based cellular processes including smooth muscle contraction, cell migration, and stress fiber formation. The ROCK protein consists of an N-terminal kinase domain, a central coiled-coil domain containing a Rho binding site, and a C-terminal pleckstrin homology domain. Here we present the crystal structure of a large section of the central coiled-coil domain of human ROCK I (amino acids 535–700). The structure forms a parallel α-helical coiled-coil dimer that is structurally similar to tropomyosin, an actin filament binding protein. There is an unusual discontinuity in the coiled-coil; three charged residues (E613, R617 and D620) are positioned at what is normally the hydrophobic core of coiled-coil packing. We speculate that this conserved irregularity could function as a hinge that allows ROCK to adopt its autoinhibited conformation. PMID:21445309

  1. Mitochondrial Hsp90 is a ligand-activated molecular chaperone coupling ATP binding to dimer closure through a coiled-coil intermediate

    PubMed Central

    Sung, Nuri; Lee, Jungsoon; Kim, Ji-Hyun; Chang, Changsoo; Joachimiak, Andrzej; Lee, Sukyeong; Tsai, Francis T. F.

    2016-01-01

    Heat-shock protein of 90 kDa (Hsp90) is an essential molecular chaperone that adopts different 3D structures associated with distinct nucleotide states: a wide-open, V-shaped dimer in the apo state and a twisted, N-terminally closed dimer with ATP. Although the N domain is known to mediate ATP binding, how Hsp90 senses the bound nucleotide and facilitates dimer closure remains unclear. Here we present atomic structures of human mitochondrial Hsp90N (TRAP1N) and a composite model of intact TRAP1 revealing a previously unobserved coiled-coil dimer conformation that may precede dimer closure and is conserved in intact TRAP1 in solution. Our structure suggests that TRAP1 normally exists in an autoinhibited state with the ATP lid bound to the nucleotide-binding pocket. ATP binding displaces the ATP lid that signals the cis-bound ATP status to the neighboring subunit in a highly cooperative manner compatible with the coiled-coil intermediate state. We propose that TRAP1 is a ligand-activated molecular chaperone, which couples ATP binding to dramatic changes in local structure required for protein folding. PMID:26929380

  2. Two-phase pressure drop in a helical coil flow boiling system

    NASA Astrophysics Data System (ADS)

    Hardik, B. K.; Prabhu, S. V.

    2018-05-01

    The objective of the present work is to study the two-phase pressure drop in helical coils. Literature on the two-phase pressure drop in a helical coil suggests the complexity in flow boiling inside a helical coil due to secondary flow. Most of correlations reported in the literature on the two-phase pressure drop in a helical coil are limited to a specific operating range. No general correlation is available for a helical coil which is applicable for all fluids. In the present study, an experimental databank collected containing a total of 832 data points includes the data from the present study and from the literature. The data includes diabatic pressure drop of two fluids namely water and R123. Data covers a range of parameters namely a mass flux of 120-2058 kg/m2 s, a heat flux of 18-2831 kW/m2, an exit quality of 0.03-1, a density ratio of 32-1404 and a coil to tube diameter ratio of 14-58. The databank is compared with eighteen empirical correlations which include well referred correlations of straight tubes and the available correlations of helical coils. The straight tube correlations are not working well for the present data set. The helical coil correlations work reasonably well for the present databank. A correlation is suggested to predict the two-phase pressure drop in helical coils. The present study suggests that the influence of a helical coil is completely included in the single phase pressure drop correlation for helical coils.

  3. Optimization of Coil Element Configurations for a Matrix Gradient Coil.

    PubMed

    Kroboth, Stefan; Layton, Kelvin J; Jia, Feng; Littin, Sebastian; Yu, Huijun; Hennig, Jurgen; Zaitsev, Maxim

    2018-01-01

    Recently, matrix gradient coils (also termed multi-coils or multi-coil arrays) were introduced for imaging and B 0 shimming with 24, 48, and even 84 coil elements. However, in imaging applications, providing one amplifier per coil element is not always feasible due to high cost and technical complexity. In this simulation study, we show that an 84-channel matrix gradient coil (head insert for brain imaging) is able to create a wide variety of field shapes even if the number of amplifiers is reduced. An optimization algorithm was implemented that obtains groups of coil elements, such that a desired target field can be created by driving each group with an amplifier. This limits the number of amplifiers to the number of coil element groups. Simulated annealing is used due to the NP-hard combinatorial nature of the given problem. A spherical harmonic basis set up to the full third order within a sphere of 20-cm diameter in the center of the coil was investigated as target fields. We show that the median normalized least squares error for all target fields is below approximately 5% for 12 or more amplifiers. At the same time, the dissipated power stays within reasonable limits. With a relatively small set of amplifiers, switches can be used to sequentially generate spherical harmonics up to third order. The costs associated with a matrix gradient coil can be lowered, which increases the practical utility of matrix gradient coils.

  4. Voice Coil Percussive Mechanism Concept for Hammer Drill

    NASA Technical Reports Server (NTRS)

    Okon, Avi

    2009-01-01

    A hammer drill design of a voice coil linear actuator, spring, linear bearings, and a hammer head was proposed. The voice coil actuator moves the hammer head to produce impact to the end of the drill bit. The spring is used to store energy on the retraction and to capture the rebound energy after each impact for use in the next impact. The maximum actuator stroke is 20 mm with the hammer mass being 200 grams. This unit can create impact energy of 0.4 J with 0.8 J being the maximum. This mechanism is less complex than previous devices meant for the same task, so it has less mass and less volume. Its impact rate and energy are easily tunable without changing major hardware components. The drill can be driven by two half-bridges. Heat is removed from the voice coil via CO2 conduction.

  5. Thermodynamic analysis of cavity creating mutations in an engineered leucine zipper and energetics of glycerol-induced coiled coil stabilization.

    PubMed

    Dürr, E; Jelesarov, I

    2000-04-18

    Protein stability in vitro can be influenced either by introduction of mutations or by changes in the chemical composition of the solvent. Recently, we have characterized the thermodynamic stability and the rate of folding of the engineered dimeric leucine zipper A(2), which has a strengthened hydrophobic core [Dürr, E., Jelesarov, I., and Bosshard, H. R. (1999) Biochemistry 38, 870-880]. Here we report on the energetic consequences of a cavity introduced by Leu/Ala substitution at the tightly packed dimeric interface and how addition of 30% glycerol affects the folding thermodynamics of A(2) and the cavity mutants. Folding could be described by a two-state transition from two unfolded monomers to a coiled coil dimer. Removal of six methylene groups by Leu/Ala substitutions destabilized the dimeric coiled coil by 25 kJ mol(-1) at pH 3.5 and 25 degrees C in aqueous buffer. Destabilization was purely entropic at around room temperature and became increasingly enthalpic at elevated temperatures. Mutations were accompanied by a decrease of the unfolding heat capacity by 0.5 kJ K(-1) mol(-1). Addition of 30% glycerol increased the free energy of folding of A(2) and the cavity mutants by 5-10 kJ mol(-1) and lowered the unfolding heat capacity by 25% for A(2) and by 50% for the Leu/Ala mutants. The origin of the stabilizing effect of glycerol varied with temperature. Stabilization of the parent leucine zipper A(2) was enthalpic with an unfavorable entropic component between 0 and 100 degrees C. In the case of cavity mutants, glycerol induced enthalpic stabilization below 50 degrees C and entropic stabilization above 50 degrees C. The effect of glycerol could not be accounted for solely by the enthalpy and entropy of transfer or protein surface from water to glycerol/water mixture. We propose that in the presence of glycerol the folded coiled coil dimer is better packed and displays less intramolecular fluctuations, leading to enhanced enthalpic interactions and to an

  6. A Synthetic Coiled-Coil Interactome Provides Heterospecific Modules for Molecular Engineering

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Reinke, Aaron W.; Grant, Robert A.; Keating, Amy E.

    2010-06-21

    The versatile coiled-coil protein motif is widely used to induce and control macromolecular interactions in biology and materials science. Yet the types of interaction patterns that can be constructed using known coiled coils are limited. Here we greatly expand the coiled-coil toolkit by measuring the complete pairwise interactions of 48 synthetic coiled coils and 7 human bZIP coiled coils using peptide microarrays. The resulting 55-member protein 'interactome' includes 27 pairs of interacting peptides that preferentially heteroassociate. The 27 pairs can be used in combinations to assemble sets of 3 to 6 proteins that compose networks of varying topologies. Of specialmore » interest are heterospecific peptide pairs that participate in mutually orthogonal interactions. Such pairs provide the opportunity to dimerize two separate molecular systems without undesired crosstalk. Solution and structural characterization of two such sets of orthogonal heterodimers provide details of their interaction geometries. The orthogonal pair, along with the many other network motifs discovered in our screen, provide new capabilities for synthetic biology and other applications.« less

  7. Functional Investigation of the Plant-Specific Long Coiled-Coil Proteins PAMP-INDUCED COILED-COIL (PICC) and PICC-LIKE (PICL) in Arabidopsis thaliana

    PubMed Central

    Venkatakrishnan, Sowmya; Mackey, David; Meier, Iris

    2013-01-01

    We have identified and characterized two Arabidopsis long coiled-coil proteins PAMP-INDUCED COILED-COIL (PICC) and PICC-LIKE (PICL). PICC (147 kDa) and PICL (87 kDa) are paralogs that consist predominantly of a long coiled-coil domain (expanded in PICC), with a predicted transmembrane domain at the immediate C-terminus. Orthologs of PICC and PICL were found exclusively in vascular plants. PICC and PICL GFP fusion proteins are anchored to the cytoplasmic surface of the endoplasmic reticulum (ER) membrane by a C-terminal transmembrane domain and a short tail domain, via a tail-anchoring mechanism. T-DNA-insertion mutants of PICC and PICL as well as the double mutant show an increased sensitivity to the plant abiotic stress hormone abscisic acid (ABA) in a post-germination growth response. PICC, but not PICL gene expression is induced by the bacterial pathogen-associated molecular pattern (PAMP) flg22. T-DNA insertion alleles of PICC, but not PICL, show increased susceptibility to the non-virulent strain P. syringae pv. tomato DC3000 hrcC, but not to the virulent strain P. syringae pv. tomato DC3000. This suggests that PICC mutants are compromised in PAMP-triggered immunity (PTI). The data presented here provide first evidence for the involvement of a plant long coiled-coil protein in a plant defense response. PMID:23451199

  8. Estimation of performance of a J-T refrigerators operating with nitrogen-hydrocarbon mixtures and a coiled tubes-in-tube heat exchanger

    NASA Astrophysics Data System (ADS)

    Satya Meher, R.; Venkatarathnam, G.

    2018-06-01

    The exergy efficiency of Joule-Thomson (J-T) refrigerators operating with mixtures (MRC systems) strongly depends on the choice of refrigerant mixture and the performance of the heat exchanger used. Helically coiled, multiple tubes-in-tube heat exchangers with an effectiveness of over 96% are widely used in these types of systems. All the current studies focus only on the different heat transfer correlations and the uncertainty in predicting performance of the heat exchanger alone. The main focus of this work is to estimate the uncertainty in cooling capacity when the homogenous model is used by comparing the theoretical and experimental studies. The comparisons have been extended to some two-phase models present in the literature as well. Experiments have been carried out on a J-T refrigerator at a fixed heat load of 10 W with different nitrogen-hydrocarbon mixtures in the evaporator temperature range of 100-120 K. Different heat transfer models have been used to predict the temperature profiles as well as the cooling capacity of the refrigerator. The results show that the homogenous two-phase flow model is probably the most suitable model for rating the cooling capacity of a J-T refrigerator operating with nitrogen-hydrocarbon mixtures.

  9. Nonazeotropic Heat Pump

    NASA Technical Reports Server (NTRS)

    Ealker, David H.; Deming, Glenn

    1991-01-01

    Heat pump collects heat from water circulating in heat-rejection loop, raises temperature of collected heat, and transfers collected heat to water in separate pipe. Includes sealed motor/compressor with cooling coils, evaporator, and condenser, all mounted in outer housing. Gradients of temperature in evaporator and condenser increase heat-transfer efficiency of vapor-compression cycle. Intended to recover relatively-low-temperature waste heat and use it to make hot water.

  10. ITER Side Correction Coil Quench model and analysis

    NASA Astrophysics Data System (ADS)

    Nicollet, S.; Bessette, D.; Ciazynski, D.; Duchateau, J. L.; Gauthier, F.; Lacroix, B.

    2016-12-01

    Previous thermohydraulic studies performed for the ITER TF, CS and PF magnet systems have brought some important information on the detection and consequences of a quench as a function of the initial conditions (deposited energy, heated length). Even if the temperature margin of the Correction Coils is high, their behavior during a quench should also be studied since a quench is likely to be triggered by potential anomalies in joints, ground fault on the instrumentation wires, etc. A model has been developed with the SuperMagnet Code (Bagnasco et al., 2010) for a Side Correction Coil (SCC2) with four pancakes cooled in parallel, each of them represented by a Thea module (with the proper Cable In Conduit Conductor characteristics). All the other coils of the PF cooling loop are hydraulically connected in parallel (top/bottom correction coils and six Poloidal Field Coils) are modeled by Flower modules with equivalent hydraulics properties. The model and the analysis results are presented for five quench initiation cases with/without fast discharge: two quenches initiated by a heat input to the innermost turn of one pancake (case 1 and case 2) and two other quenches initiated at the innermost turns of four pancakes (case 3 and case 4). In the 5th case, the quench is initiated at the middle turn of one pancake. The impact on the cooling circuit, e.g. the exceedance of the opening pressure of the quench relief valves, is detailed in case of an undetected quench (i.e. no discharge of the magnet). Particular attention is also paid to a possible secondary quench detection system based on measured thermohydraulic signals (pressure, temperature and/or helium mass flow rate). The maximum cable temperature achieved in case of a fast current discharge (primary detection by voltage) is compared to the design hot spot criterion of 150 K, which includes the contribution of helium and jacket.

  11. Triple Halo Coil: Development and Comparison with Other TMS Coils

    NASA Astrophysics Data System (ADS)

    Rastogi, Priyam; Hadimani, Ravi; Jiles, David

    Transcranial Magnetic Stimulation (TMS) is a non-invasive stimulation technique that can be used for the treatment of various neurological disorders such as Parkinson's Disease, PTSD, TBI and anxiety by regulating synaptic activity. TMS is FDA approved for the treatment of major depressive disorder. There is a critical need to develop deep TMS coils that can stimulate deeper regions of the brain without excessively stimulating the cortex in order to provide an alternative to surgical methods. We have developed a novel multi-coil configuration called ``Triple Halo Coil'' (THC) that can stimulate deep brain regions. Investigation of induced electric and magnetic field in these regions have been achieved by computer modelling. Comparison of the results due to THC configuration have been conducted with other TMS coils such as ``Halo Coil'', circular coil and ``Figure of Eight'' coil. There was an improvement of more than 15 times in the strength of magnetic field, induced by THC configuration at 10 cm below the vertex of the head when compared with the ``Figure of Eight'' coil alone. Carver Charitable Trust.

  12. Biomaterials Made from Coiled-Coil Peptides.

    PubMed

    Conticello, Vincent; Hughes, Spencer; Modlin, Charles

    The development of biomaterials designed for specific applications is an important objective in personalized medicine. While the breadth and prominence of biomaterials have increased exponentially over the past decades, critical challenges remain to be addressed, particularly in the development of biomaterials that exhibit highly specific functions. These functional properties are often encoded within the molecular structure of the component molecules. Proteins, as a consequence of their structural specificity, represent useful substrates for the construction of functional biomaterials through rational design. This chapter provides an in-depth survey of biomaterials constructed from coiled-coils, one of the best-understood protein structural motifs. We discuss the utility of this structurally diverse and functionally tunable class of proteins for the creation of novel biomaterials. This discussion illustrates the progress that has been made in the development of coiled-coil biomaterials by showcasing studies that bridge the gap between the academic science and potential technological impact.

  13. Critical heat flux test apparatus

    DOEpatents

    Welsh, Robert E.; Doman, Marvin J.; Wilson, Edward C.

    1992-01-01

    An apparatus for testing, in situ, highly irradiated specimens at high temperature transients is provided. A specimen, which has a thermocouple device attached thereto, is manipulated into test position in a sealed quartz heating tube by a robot. An induction coil around a heating portion of the tube is powered by a radio frequency generator to heat the specimen. Sensors are connected to monitor the temperatures of the specimen and the induction coil. A quench chamber is located below the heating portion to permit rapid cooling of the specimen which is moved into this quench chamber once it is heated to a critical temperature. A vacuum pump is connected to the apparatus to collect any released fission gases which are analyzed at a remote location.

  14. Crystal structure of a designed, thermostable, heterotrimeric coiled coil.

    PubMed Central

    Nautiyal, S.; Alber, T.

    1999-01-01

    Electrostatic interactions are often critical for determining the specificity of protein-protein complexes. To study the role of electrostatic interactions for assembly of helical bundles, we previously designed a thermostable, heterotrimeric coiled coil, ABC, in which charged residues were employed to drive preferential association of three distinct, 34-residue helices. To investigate the basis for heterotrimer specificity, we have used multiwavelength anomalous diffraction (MAD) analysis to determine the 1.8 A resolution crystal structure of ABC. The structure shows that ABC forms a heterotrimeric coiled coil with the intended arrangement of parallel chains. Over half of the ion pairs engineered to restrict helix associations were apparent in the experimental electron density map. As seen in other trimeric coiled coils, ABC displays acute knobs-into-holes packing and a buried anion coordinated by core polar amino acids. These interactions validate the design strategy and illustrate how packing and polar contacts determine structural uniqueness. PMID:10210186

  15. Performance of Upgraded Cooling System for Lhd Helical Coils

    NASA Astrophysics Data System (ADS)

    Hamaguchi, S.; Imagawa, S.; Obana, T.; Yanagi, N.; Moriuchi, S.; Sekiguchi, H.; Oba, K.; Mito, T.; Motojima, O.; Okamura, T.; Semba, T.; Yoshinaga, S.; Wakisaka, H.

    2008-03-01

    Helical coils of the Large Helical Device (LHD) are large scale superconducting magnets for heliotron plasma experiments. The helical coils had been cooled by saturated helium at 4.4 K, 120 kPa until 2005. An upgrade of the cooling system was carried out in 2006 in order to improve the cryogenic stability of the helical coils and then it has been possible to supply the coils with subcooled helium at 3.2 K, 120 kPa. A designed mass flow of the supplied subcooled helium is 50 g/s. The subcooled helium is generated at a heat exchanger in a saturated helium bath. A series of two centrifugal cold compressors with gas foil bearing is utilized to lower the helium pressure in the bath. The supplied helium temperature is regulated by rotational speed of the cold compressors and power of a heater in the bath. The mass flow of the supplied helium is also controlled manually by a supply valve and its surplus is evaporated by ten heaters at the outlet above the coils. In the present study, the performance of the cooling system has been investigated and a stable operating method has also developed. As the result, it was confirmed that the performance of the upgraded cooling system satisfies the requirements.

  16. Quench of non-Markovian coherence in the deep sub-Ohmic spin–boson model: A unitary equilibration scheme

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Yao, Yao, E-mail: yaoyao@fudan.edu.cn

    The deep sub-Ohmic spin–boson model shows a longstanding non-Markovian coherence at low temperature. Motivating to quench this robust coherence, the thermal effect is unitarily incorporated into the time evolution of the model, which is calculated by the adaptive time-dependent density matrix renormalization group algorithm combined with the orthogonal polynomials theory. Via introducing a unitary heating operator to the bosonic bath, the bath is heated up so that a majority portion of the bosonic excited states is occupied. It is found in this situation the coherence of the spin is quickly quenched even in the coherent regime, in which the non-Markovianmore » feature dominates. With this finding we come up with a novel way to implement the unitary equilibration, the essential term of the eigenstate-thermalization hypothesis, through a short-time evolution of the model.« less

  17. Voltage Controlled Hot Carrier Injection Enables Ohmic Contacts Using Au Island Metal Films on Ge.

    PubMed

    Ganti, Srinivas; King, Peter J; Arac, Erhan; Dawson, Karl; Heikkilä, Mikko J; Quilter, John H; Murdoch, Billy; Cumpson, Peter; O'Neill, Anthony

    2017-08-23

    We introduce a new approach to creating low-resistance metal-semiconductor ohmic contacts, illustrated using high conductivity Au island metal films (IMFs) on Ge, with hot carrier injection initiated at low applied voltage. The same metallization process simultaneously allows ohmic contact to n-Ge and p-Ge, because hot carriers circumvent the Schottky barrier formed at metal/n-Ge interfaces. A 2.5× improvement in contact resistivity is reported over previous techniques to achieve ohmic contact to both n- and p- semiconductor. Ohmic contacts at 4.2 K confirm nonequilibrium current transport. Self-assembled Au IMFs are strongly orientated to Ge by annealing near the Au/Ge eutectic temperature. Au IMF nanostructures form, provided the Au layer is below a critical thickness. We anticipate that optimized IMF contacts may have applicability to many material systems. Optimizing this new paradigm for metal-semiconductor contacts offers the prospect of improved nanoelectronic systems and the study of voltage controlled hot holes and electrons.

  18. AlGaN channel field effect transistors with graded heterostructure ohmic contacts

    NASA Astrophysics Data System (ADS)

    Bajaj, Sanyam; Akyol, Fatih; Krishnamoorthy, Sriram; Zhang, Yuewei; Rajan, Siddharth

    2016-09-01

    We report on ultra-wide bandgap (UWBG) Al0.75Ga0.25N channel metal-insulator-semiconductor field-effect transistors (MISFETs) with heterostructure engineered low-resistance ohmic contacts. The low intrinsic electron affinity of AlN (0.6 eV) leads to large Schottky barriers at the metal-AlGaN interface, resulting in highly resistive ohmic contacts. In this work, we use a reverse compositional graded n++ AlGaN contact layer to achieve upward electron affinity grading, leading to a low specific contact resistance (ρsp) of 1.9 × 10-6 Ω cm2 to n-Al0.75Ga0.25N channels (bandgap ˜5.3 eV) with non-alloyed contacts. We also demonstrate UWBG Al0.75Ga0.25N channel MISFET device operation employing the compositional graded n++ ohmic contact layer and 20 nm atomic layer deposited Al2O3 as the gate-dielectric.

  19. A Mechanical Coil Insertion System for Endovascular Coil Embolization of Intracranial Aneurysms

    PubMed Central

    Haraguchi, K.; Miyachi, S.; Matsubara, N.; Nagano, Y.; Yamada, H.; Marui, N.; Sano, A.; Fujimoto, H.; Izumi, T.; Yamanouchi, T.; Asai, T.; Wakabayashi, T.

    2013-01-01

    Summary Like other fields of medicine, robotics and mechanization might be introduced into endovascular coil embolization of intracranial aneurysms for effective treatment. We have already reported that coil insertion force could be smaller and more stable when the coil delivery wire is driven mechanically at a constant speed. Another background is the difficulty in synchronizing operators' minds and hands when two operators control the microcatheter and the coil respectively. We have therefore developed a mechanical coil insertion system enabling a single operator to insert coils at a fixed speed while controlling the microcatheter. Using our new system, the operator manipulated the microcatheter with both hands and drove the coil using foot switches simultaneously. A delivery wire force sensor previously reported was used concurrently, allowing the operator to detect excessive stress on the wire. In vitro coil embolization was performed using three methods: simple mechanical advance of the coil; simple mechanical advance of the coil with microcatheter control; and driving (forward and backward) of the coil using foot switches in addition to microcatheter control. The system worked without any problems, and did not interfere with any procedures. In experimental coil embolization, delivery wire control using the foot switches as well as microcatheter manipulation helped to achieve successful insertion of coils. This system could offer the possibility of developing safer and more efficient coil embolization. Although we aim at total mechanization and automation of procedures in the future, microcatheter manipulation and synchronized delivery wire control are still indispensable using this system. PMID:23693038

  20. Cross-linking reveals laminin coiled-coil architecture

    PubMed Central

    Armony, Gad; Jacob, Etai; Moran, Toot; Levin, Yishai; Mehlman, Tevie; Levy, Yaakov; Fass, Deborah

    2016-01-01

    Laminin, an ∼800-kDa heterotrimeric protein, is a major functional component of the extracellular matrix, contributing to tissue development and maintenance. The unique architecture of laminin is not currently amenable to determination at high resolution, as its flexible and narrow segments complicate both crystallization and single-particle reconstruction by electron microscopy. Therefore, we used cross-linking and MS, evaluated using computational methods, to address key questions regarding laminin quaternary structure. This approach was particularly well suited to the ∼750-Å coiled coil that mediates trimer assembly, and our results support revision of the subunit order typically presented in laminin schematics. Furthermore, information on the subunit register in the coiled coil and cross-links to downstream domains provide insights into the self-assembly required for interaction with other extracellular matrix and cell surface proteins. PMID:27815530

  1. Eddy current heating in magnetic refrigerators

    NASA Technical Reports Server (NTRS)

    Kittel, Peter

    1990-01-01

    Eddy current heating can be a significant source of parasitic heating in low temperature magnetic refrigerators. To study this problem a technique to approximate the heating due to eddy currents has been developed. A formula is presented for estimating the heating within a variety of shapes commonly found in magnetic refrigerators. These shapes include circular, square, and rectangular rods; cylindrical and split cylindrical shells; wire loops; and 'coil foil. One set of components evaluated are different types of thermal radiation shields. This comparison shows that a simple split shield is almost as effective (only 23 percent more heating) as using a shield, with the same axial thermal conductivity, made of 'coil foil'.

  2. Coiled-coil intermediate filament stutter instability and molecular unfolding.

    PubMed

    Arslan, Melis; Qin, Zhao; Buehler, Markus J

    2011-05-01

    Intermediate filaments (IFs) are the key components of cytoskeleton in eukaryotic cells and are critical for cell mechanics. The building block of IFs is a coiled-coil alpha-helical dimer, consisting of several domains that include linkers and other structural discontinuities. One of the discontinuities in the dimer's coiled-coil region is the so-called 'stutter' region. The stutter is a region where a variation of the amino acid sequence pattern from other parts of the alpha-helical domains of the protein is found. It was suggested in earlier works that due to this sequence variation, the perfect coiled-coil arrangement ceases to exist. Here, we show using explicit water molecular dynamics and well-tempered metadynamics that for the coil2 domain of vimentin IFs the stutter is more stable in a non-alpha-helical, unfolded state. This causes a local structural disturbance in the alpha helix, which has a global effect on the nanomechanics of the structure. Our analysis suggests that the stutter features an enhanced tendency to unfolding even under the absence of external forces, implying a much greater structural instability than previously assumed. As a result it features a smaller local bending stiffness than other segments and presents a seed for the initiation of molecular bending and unfolding at large deformation.

  3. Evaluation of feasibility of 1.5 Tesla prostate MRI using body coil RF transmit in a patient with an implanted vagus nerve stimulator.

    PubMed

    Favazza, Christopher P; Edmonson, Heidi A; Ma, Chi; Shu, Yunhong; Felmlee, Joel P; Watson, Robert E; Gorny, Krzysztof R

    2017-11-01

    To assess risks of RF-heating of a vagus nerve stimulator (VNS) during 1.5 T prostate MRI using body coil transmit and to compare these risks with those associated with MRI head exams using a transmit/receive head coil. Spatial distributions of radio-frequency (RF) B1 fields generated by transmit/receive (T/R) body and head coils were empirically assessed along the long axis of a 1.5 T MRI scanner bore. Measurements were obtained along the center axis of the scanner and laterally offset by 15 cm (body coil) and 7 cm (head coil). RF-field measurements were supplemented with direct measurements of RF-heating of 15 cm long copper wires affixed to and submerged in the "neck" region of the gelled saline-filled (sodium chloride and polyacrylic acid) "head-and-torso" phantom. Temperature elevations at the lead tips were measured using fiber-optic thermometers with the phantom positioned at systematically increased distances from the scanner isocenter. B1 field measurements demonstrated greater than 10 dB reduction in RF power at distances beyond 28 cm and 24 cm from isocenter for body and head coil, respectively. Moreover, RF power from body coil transmit at distances greater than 32 cm from isocenter was found to be lower than from the RF power from head coil transmit measured at locations adjacent to the coil array at its opening. Correspondingly, maximum temperature elevations at the tips of the copper wires decreased with increasing distance from isocenter - from 7.4°C at 0 cm to no appreciable heating at locations beyond 40 cm. For the particular scanner model evaluated in this study, positioning an implanted VNS farther than 32 cm from isocenter (configuration achievable for prostate exams) can reduce risks of RF-heating resulting from the body coil transmit to those associated with using a T/R head coil. © 2017 American Association of Physicists in Medicine.

  4. Comparison of nickel silicide and aluminium ohmic contact metallizations for low-temperature quantum transport measurements.

    PubMed

    Polley, Craig M; Clarke, Warrick R; Simmons, Michelle Y

    2011-10-03

    We examine nickel silicide as a viable ohmic contact metallization for low-temperature, low-magnetic-field transport measurements of atomic-scale devices in silicon. In particular, we compare a nickel silicide metallization with aluminium, a common ohmic contact for silicon devices. Nickel silicide can be formed at the low temperatures (<400°C) required for maintaining atomic precision placement in donor-based devices, and it avoids the complications found with aluminium contacts which become superconducting at cryogenic measurement temperatures. Importantly, we show that the use of nickel silicide as an ohmic contact at low temperatures does not affect the thermal equilibration of carriers nor contribute to hysteresis in a magnetic field.

  5. Conformational switching in the coiled-coil domains of a proteasomal ATPase regulates substrate processing.

    PubMed

    Snoberger, Aaron; Brettrager, Evan J; Smith, David M

    2018-06-18

    Protein degradation in all domains of life requires ATPases that unfold and inject proteins into compartmentalized proteolytic chambers. Proteasomal ATPases in eukaryotes and archaea contain poorly understood N-terminally conserved coiled-coil domains. In this study, we engineer disulfide crosslinks in the coiled-coils of the archaeal proteasomal ATPase (PAN) and report that its three identical coiled-coil domains can adopt three different conformations: (1) in-register and zipped, (2) in-register and partially unzipped, and (3) out-of-register. This conformational heterogeneity conflicts with PAN's symmetrical OB-coiled-coil crystal structure but resembles the conformational heterogeneity of the 26S proteasomal ATPases' coiled-coils. Furthermore, we find that one coiled-coil can be conformationally constrained even while unfolding substrates, and conformational changes in two of the coiled-coils regulate PAN switching between resting and active states. This switching functionally mimics similar states proposed for the 26S proteasome from cryo-EM. These findings thus build a mechanistic framework to understand regulation of proteasome activity.

  6. The tripartite motif coiled-coil is an elongated antiparallel hairpin dimer.

    PubMed

    Sanchez, Jacint G; Okreglicka, Katarzyna; Chandrasekaran, Viswanathan; Welker, Jordan M; Sundquist, Wesley I; Pornillos, Owen

    2014-02-18

    Tripartite motif (TRIM) proteins make up a large family of coiled-coil-containing RING E3 ligases that function in many cellular processes, particularly innate antiviral response pathways. Both dimerization and higher-order assembly are important elements of TRIM protein function, but the atomic details of TRIM tertiary and quaternary structure have not been fully understood. Here, we present crystallographic and biochemical analyses of the TRIM coiled-coil and show that TRIM proteins dimerize by forming interdigitating antiparallel helical hairpins that position the N-terminal catalytic RING domains at opposite ends of the dimer and the C-terminal substrate-binding domains at the center. The dimer core comprises an antiparallel coiled-coil with a distinctive, symmetric pattern of flanking heptad and central hendecad repeats that appear to be conserved across the entire TRIM family. Our studies reveal how the coiled-coil organizes TRIM25 to polyubiquitylate the RIG-I/viral RNA recognition complex and how dimers of the TRIM5α protein are arranged within hexagonal arrays that recognize the HIV-1 capsid lattice and restrict retroviral replication.

  7. The tripartite motif coiled-coil is an elongated antiparallel hairpin dimer

    PubMed Central

    Sanchez, Jacint G.; Okreglicka, Katarzyna; Chandrasekaran, Viswanathan; Welker, Jordan M.; Sundquist, Wesley I.; Pornillos, Owen

    2014-01-01

    Tripartite motif (TRIM) proteins make up a large family of coiled-coil-containing RING E3 ligases that function in many cellular processes, particularly innate antiviral response pathways. Both dimerization and higher-order assembly are important elements of TRIM protein function, but the atomic details of TRIM tertiary and quaternary structure have not been fully understood. Here, we present crystallographic and biochemical analyses of the TRIM coiled-coil and show that TRIM proteins dimerize by forming interdigitating antiparallel helical hairpins that position the N-terminal catalytic RING domains at opposite ends of the dimer and the C-terminal substrate-binding domains at the center. The dimer core comprises an antiparallel coiled-coil with a distinctive, symmetric pattern of flanking heptad and central hendecad repeats that appear to be conserved across the entire TRIM family. Our studies reveal how the coiled-coil organizes TRIM25 to polyubiquitylate the RIG-I/viral RNA recognition complex and how dimers of the TRIM5α protein are arranged within hexagonal arrays that recognize the HIV-1 capsid lattice and restrict retroviral replication. PMID:24550273

  8. Plasma-assisted ohmic contact for AlGaN/GaN heterostructure field-effect transistors

    NASA Astrophysics Data System (ADS)

    Zhang, Jiaqi; Wang, Lei; Wang, Qingpeng; Jiang, Ying; Li, Liuan; Zhu, Huichao; Ao, Jin-Ping

    2016-03-01

    An Al-based ohmic process assisted by an inductively coupled plasma (ICP) recess treatment is proposed for AlGaN/GaN heterostructure field-effect transistors (HFETs) to realize ohmic contact, which is only needed to anneal at 500 °C. The recess treatment was done with SiCl4 plasma with 100 W ICP power for 20 s and annealing at 575 °C for 1 min. Under these conditions, contact resistance of 0.52 Ωmm was confirmed. To suppress the ball-up phenomenon and improve the surface morphology, an Al/TiN structure was also fabricated with the same conditions. The contact resistance was further improved to 0.30 Ωmm. By using this plasma-assisted ohmic process, a gate-first HFET was fabricated. The device showed high drain current density and high transconductance. The leakage current of the TiN-gate device decreased to 10-9 A, which was 5 orders of magnitude lower than that of the device annealed at 800 °C. The results showed that the low-temperature ohmic contact process assisted by ICP treatment is promising for the fabrication of gate-first and self-aligned gate HFETs.

  9. Superconducting magnetic coil

    DOEpatents

    Aized, Dawood; Schwall, Robert E.

    1999-06-22

    A superconducting magnetic coil includes a plurality of sections positioned axially along the longitudinal axis of the coil, each section being formed of an anisotropic high temperature superconductor material wound about a longitudinal axis of the coil and having an associated critical current value that is dependent on the orientation of the magnetic field of the coil. The cross section of the superconductor, or the type of superconductor material, at sections along the axial and radial axes of the coil are changed to provide an increased critical current at those regions where the magnetic field is oriented more perpendicularly to the conductor plane, to thereby increase the critical current at these regions and to maintain an overall higher critical current of the coil.

  10. Superconducting magnetic coil

    DOEpatents

    Aized, Dawood; Schwall, Robert E.

    1996-06-11

    A superconducting magnetic coil includes a plurality of sections positioned axially along the longitudinal axis of the coil, each section being formed of an anisotropic high temperature superconductor material wound about a longitudinal axis of the coil and having an associated critical current value that is dependent on the orientation of the magnetic field of the coil. The cross section of the superconductor, or the type of superconductor material, at sections along the axial and radial axes of the coil are changed to provide an increased critical current at those regions where the magnetic field is oriented more perpendicularly to the conductor plane, to thereby increase the critical current at these regions and to maintain an overall higher critical current of the coil.

  11. Superconducting magnetic coil

    DOEpatents

    Aized, D.; Schwall, R.E.

    1999-06-22

    A superconducting magnetic coil includes a plurality of sections positioned axially along the longitudinal axis of the coil, each section being formed of an anisotropic high temperature superconductor material wound about a longitudinal axis of the coil and having an associated critical current value that is dependent on the orientation of the magnetic field of the coil. The cross section of the superconductor, or the type of superconductor material, at sections along the axial and radial axes of the coil are changed to provide an increased critical current at those regions where the magnetic field is oriented more perpendicularly to the conductor plane, to thereby increase the critical current at these regions and to maintain an overall higher critical current of the coil. 15 figs.

  12. Accommodation of structural rearrangements in the huntingtin-interacting protein 1 coiled-coil domain.

    PubMed

    Wilbur, Jeremy D; Hwang, Peter K; Brodsky, Frances M; Fletterick, Robert J

    2010-03-01

    Huntingtin-interacting protein 1 (HIP1) is an important link between the actin cytoskeleton and clathrin-mediated endocytosis machinery. HIP1 has also been implicated in the pathogenesis of Huntington's disease. The binding of HIP1 to actin is regulated through an interaction with clathrin light chain. Clathrin light chain binds to a flexible coiled-coil domain in HIP1 and induces a compact state that is refractory to actin binding. To understand the mechanism of this conformational regulation, a high-resolution crystal structure of a stable fragment from the HIP1 coiled-coil domain was determined. The flexibility of the HIP1 coiled-coil region was evident from its variation from a previously determined structure of a similar region. A hydrogen-bond network and changes in coiled-coil monomer interaction suggest that the HIP1 coiled-coil domain is uniquely suited to allow conformational flexibility.

  13. Design and analysis of permanent magnet moving coil type generator used in a micro-CHP generation system

    NASA Astrophysics Data System (ADS)

    Oros Pop, Susana Teodora; Berinde, Ioan; Vadan, Ioan

    2015-12-01

    This paper presents the design and analysis of a permanent magnet moving coil type generator driven by a free piston Stirling engine. This assemble free piston Stirling engine - permanent magnet moving coil type generator will be used in a combined heat and power (CHP) system for producing heat and power in residential area. The design procedure for moving coil type linear generator starts from the rated power imposed and finally uses the Faraday law of induction. The magneto-static magnetic field generated by permanent magnets is analyzed by means of Reluctance method and Finite Element Method in order to evaluate the magnetic flux density in the air gap, which is a design data imposed in the design stage, and the results are compared.

  14. Nuclear magnetic resonance apparatus having semitoroidal rf coil for use in topical NMR and NMR imaging

    DOEpatents

    Fukushima, Eiichi; Roeder, Stephen B. W.; Assink, Roger A.; Gibson, Atholl A. V.

    1986-01-01

    An improved nuclear magnetic resonance (NMR) apparatus for use in topical magnetic resonance (TMR) spectroscopy and other remote sensing NMR applications includes a semitoroidal radio-frequency (rf) coil. The semitoroidal rf coil produces an effective alternating magnetic field at a distance from the poles of the coil, so as to enable NMR measurements to be taken from selected regions inside an object, particularly including human and other living subjects. The semitoroidal rf coil is relatively insensitive to magnetic interference from metallic objects located behind the coil, thereby rendering the coil particularly suited for use in both conventional and superconducting NMR magnets. The semitoroidal NMR coil can be constructed so that it emits little or no excess rf electric field associated with the rf magnetic field, thus avoiding adverse effects due to dielectric heating of the sample or to any other interaction of the electric field with the sample.

  15. Wireless Metal Detection and Surface Coverage Sensing for All-Surface Induction Heating

    PubMed Central

    Kilic, Veli Tayfun; Unal, Emre; Demir, Hilmi Volkan

    2016-01-01

    All-surface induction heating systems, typically comprising small-area coils, face a major challenge in detecting the presence of a metallic vessel and identifying its partial surface coverage over the coils to determine which of the coils to power up. The difficulty arises due to the fact that the user can heat vessels made of a wide variety of metals (and their alloys). To address this problem, we propose and demonstrate a new wireless detection methodology that allows for detecting the presence of metallic vessels together with uniquely sensing their surface coverages while also identifying their effective material type in all-surface induction heating systems. The proposed method is based on telemetrically measuring simultaneously inductance and resistance of the induction coil coupled with the vessel in the heating system. Here, variations in the inductance and resistance values for an all-surface heating coil loaded by vessels (made of stainless steel and aluminum) at different positions were systematically investigated at different frequencies. Results show that, independent of the metal material type, unique identification of the surface coverage is possible at all freqeuncies. Additionally, using the magnitude and phase information extracted from the coupled coil impedance, unique identification of the vessel effective material is also achievable, this time independent of its surface coverage. PMID:26978367

  16. Accommodation of structural rearrangements in the huntingtin-interacting protein 1 coiled-coil domain

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wilbur, Jeremy D., E-mail: jwilbur@msg.ucsf.edu; Hwang, Peter K.; Brodsky, Frances M.

    2010-03-01

    Variable packing interaction related to the conformational flexibility within the huntingtin-interacting protein 1 coiled coil domain. Huntingtin-interacting protein 1 (HIP1) is an important link between the actin cytoskeleton and clathrin-mediated endocytosis machinery. HIP1 has also been implicated in the pathogenesis of Huntington’s disease. The binding of HIP1 to actin is regulated through an interaction with clathrin light chain. Clathrin light chain binds to a flexible coiled-coil domain in HIP1 and induces a compact state that is refractory to actin binding. To understand the mechanism of this conformational regulation, a high-resolution crystal structure of a stable fragment from the HIP1 coiled-coilmore » domain was determined. The flexibility of the HIP1 coiled-coil region was evident from its variation from a previously determined structure of a similar region. A hydrogen-bond network and changes in coiled-coil monomer interaction suggest that the HIP1 coiled-coil domain is uniquely suited to allow conformational flexibility.« less

  17. Protective link for superconducting coil

    DOEpatents

    Umans, Stephen D [Belmont, MA

    2009-12-08

    A superconducting coil system includes a superconducting coil and a protective link of superconducting material coupled to the superconducting coil. A rotating machine includes first and second coils and a protective link of superconducting material. The second coil is operable to rotate with respect to the first coil. One of the first and second coils is a superconducting coil. The protective link is coupled to the superconducting coil.

  18. Universal strategy for Ohmic hole injection into organic semiconductors with high ionization energies

    NASA Astrophysics Data System (ADS)

    Kotadiya, Naresh B.; Lu, Hao; Mondal, Anirban; Ie, Yutaka; Andrienko, Denis; Blom, Paul W. M.; Wetzelaer, Gert-Jan A. H.

    2018-02-01

    Barrier-free (Ohmic) contacts are a key requirement for efficient organic optoelectronic devices, such as organic light-emitting diodes, solar cells, and field-effect transistors. Here, we propose a simple and robust way of forming an Ohmic hole contact on organic semiconductors with a high ionization energy (IE). The injected hole current from high-work-function metal-oxide electrodes is improved by more than an order of magnitude by using an interlayer for which the sole requirement is that it has a higher IE than the organic semiconductor. Insertion of the interlayer results in electrostatic decoupling of the electrode from the semiconductor and realignment of the Fermi level with the IE of the organic semiconductor. The Ohmic-contact formation is illustrated for a number of material combinations and solves the problem of hole injection into organic semiconductors with a high IE of up to 6 eV.

  19. Universal strategy for Ohmic hole injection into organic semiconductors with high ionization energies.

    PubMed

    Kotadiya, Naresh B; Lu, Hao; Mondal, Anirban; Ie, Yutaka; Andrienko, Denis; Blom, Paul W M; Wetzelaer, Gert-Jan A H

    2018-04-01

    Barrier-free (Ohmic) contacts are a key requirement for efficient organic optoelectronic devices, such as organic light-emitting diodes, solar cells, and field-effect transistors. Here, we propose a simple and robust way of forming an Ohmic hole contact on organic semiconductors with a high ionization energy (IE). The injected hole current from high-work-function metal-oxide electrodes is improved by more than an order of magnitude by using an interlayer for which the sole requirement is that it has a higher IE than the organic semiconductor. Insertion of the interlayer results in electrostatic decoupling of the electrode from the semiconductor and realignment of the Fermi level with the IE of the organic semiconductor. The Ohmic-contact formation is illustrated for a number of material combinations and solves the problem of hole injection into organic semiconductors with a high IE of up to 6 eV.

  20. The interaction of pulsed eddy current with metal surface crack for various coils

    NASA Astrophysics Data System (ADS)

    Yang, Hung-Chi; Tai, Cheng-Chi

    2002-05-01

    We study the interaction of pulsed eddy current (PEC) with metal surface cracks using various coils that have different geometric sizes. In the previous work, we have showed that the PEC technique can be used to inspect electrical-discharge-machined (EDM) notches with depth from 0.5 mm to 9 mm. The results showed that the relationship between PEC signals and crack depth is obvious. In this work, we further try a series of coils with different radii, heights, turns and shapes. We will discuss the effects of these coil parameters on the PEC signal. Some other critical problems of PEC measurements such as signal drift that caused by heating effect of coil currents will be studied. We also show more experiments on fatigue cracks to demonstrate the capability of PEC technique for cracks inspection.

  1. High-resolution structures of a heterochiral coiled coil

    DOE PAGES

    Mortenson, David E.; Steinkruger, Jay D.; Kreitler, Dale F.; ...

    2015-10-12

    Interactions between polypeptide chains containing amino acid residues with opposite absolute configurations have long been a source of interest and speculation, but there is very little structural information for such heterochiral associations. The need to address this lacuna has grown in recent years because of increasing interest in the use of peptides generated from D amino acids (D peptides) as specific ligands for natural proteins, e.g., to inhibit deleterious protein–protein interactions. Coiled–coil interactions, between or among α-helices, represent the most common tertiary and quaternary packing motif in proteins. Heterochiral coiled–coil interactions were predicted over 50 years ago by Crick, andmore » limited experimental data obtained in solution suggest that such interactions can indeed occur. To address the dearth of atomic-level structural characterization of heterochiral helix pairings, we report in this paper two independent crystal structures that elucidate coiled-coil packing between L- and D-peptide helices. Both structures resulted from racemic crystallization of a peptide corresponding to the transmembrane segment of the influenza M2 protein. Networks of canonical knobs-into-holes side-chain packing interactions are observed at each helical interface. Finally, however, the underlying patterns for these heterochiral coiled coils seem to deviate from the heptad sequence repeat that is characteristic of most homochiral analogs, with an apparent preference for a hendecad repeat pattern.« less

  2. Crystal Structure of the Central Coiled-Coil Domain from Human Liprin-[beta]2

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Stafford, Ryan L.; Tang, Ming-Yun; Sawaya, Michael R.

    2012-02-07

    Liprins are a conserved family of scaffolding proteins important for the proper regulation and development of neuronal synapses. Humans have four liprin-{alpha}s and two liprin-{beta}s which all contain long coiled-coil domains followed by three tandem SAM domains. Complex interactions between the coiled-coil and SAM domains are thought to create liprin scaffolds, but the structural and biochemical properties of these domains remain largely uncharacterized. In this study we find that the human liprin-{beta}2 coiled-coil forms an extended dimer. Several protease-resistant subdomains within the liprin-{beta}1 and liprin-{beta}2 coiled-coils were also identified. A 2.0 {angstrom} crystal structure of the central, protease-resistant core ofmore » the liprin-{beta}2 coiled-coil reveals a parallel helix orientation. These studies represent an initial step toward determining the overall architecture of liprin scaffolds and understanding the molecular basis for their synaptic functions.« less

  3. Flexible, Carbon-Based Ohmic Contacts for Organic Transistors

    NASA Technical Reports Server (NTRS)

    Brandon, Erik

    2005-01-01

    A low-temperature process for fabricating flexible, ohmic contacts for use in organic thin-film transistors (OTFTs) has been developed. Typical drainsource contact materials used previously for OTFTs include (1) vacuum-deposited noble-metal contacts and (2) solution-deposited intrinsically conducting molecular or polymeric contacts. Both of these approaches, however, have serious drawbacks.

  4. Kinetic studies on strand displacement in de novo designed parallel heterodimeric coiled coils.

    PubMed

    Groth, Mike C; Rink, W Mathis; Meyer, Nils F; Thomas, Franziska

    2018-05-14

    Among the protein folding motifs, which are accessible by de novo design, the parallel heterodimeric coiled coil is most frequently used in bioinspired applications and chemical biology in general. This is due to the straightforward sequence-to-structure relationships, which it has in common with all coiled-coil motifs, and the heterospecificity, which allows control of association. Whereas much focus was laid on designing orthogonal coiled coils, systematic studies on controlling association, for instance by strand displacement, are rare. As a contribution to the design of dynamic coiled-coil-based systems, we studied the strand-displacement mechanism in obligate heterodimeric coiled coils to investigate the suitability of the dissociation constants ( K D ) as parameters for the prediction of the outcome of strand-displacement reactions. We use two sets of heterodimeric coiled coils, the previously reported N-A x B y and the newly characterized C-A x B y . Both comprise K D values in the μM to sub-nM regime. Strand displacement is explored by CD titration and a FRET-based kinetic assay and is proved to be an equilibrium reaction with half-lifes from a few seconds up to minutes. We could fit the displacement data by a competitive binding model, giving rate constants and overall affinities of the underlying association and dissociation reactions. The overall affinities correlate well with the ratios of K D values determined by CD-thermal denaturation experiments and, hence, support the dissociative mechanism of strand displacement in heterodimeric coiled coils. From the results of more than 100 different displacement reactions we are able to classify three categories of overall affinities, which allow for easy prediction of the equilibrium of strand displacement in two competing heterodimeric coiled coils.

  5. Dryout occurrence in a helically coiled steam generator for nuclear power application

    NASA Astrophysics Data System (ADS)

    Santini, L.; Cioncolini, A.; Lombardi, C.; Ricotti, M.

    2014-03-01

    Dryout phenomena have been experimentally investigated in a helically coiled steam generator tube. The experiences carried out in the present work are part of a wide experimental program devoted to the study of a GEN III+ innovative nuclear power plant [1].The experimental facility consists in an electrically heated AISI 316L stainless steel coiled tube. The tube is 32 meters long, 12.53 mm of inner diameter, with a coil diameter of 1m and a pitch of 0.79 m, resulting in a total height of the steam generator of 8 meters. The thermo-hydraulics conditions for dryout investigations covered a spectrum of mass fluxes between 199 and 810 kg/m2s, the pressures ranges from 10.7 to 60.7 bar, heat fluxes between 43.6 to 209.3 kW/m2.Very high first qualities dryout, between 0.72 and 0.92, were found in the range of explored conditions, comparison of our results with literature available correlations shows the difficulty in predicting high qualities dryout in helical coils., immediately following the heading. The text should be set to 1.15 line spacing. The abstract should be centred across the page, indented 15 mm from the left and right page margins and justified. It should not normally exceed 200 words.

  6. Comparison of nickel silicide and aluminium ohmic contact metallizations for low-temperature quantum transport measurements

    PubMed Central

    2011-01-01

    We examine nickel silicide as a viable ohmic contact metallization for low-temperature, low-magnetic-field transport measurements of atomic-scale devices in silicon. In particular, we compare a nickel silicide metallization with aluminium, a common ohmic contact for silicon devices. Nickel silicide can be formed at the low temperatures (<400°C) required for maintaining atomic precision placement in donor-based devices, and it avoids the complications found with aluminium contacts which become superconducting at cryogenic measurement temperatures. Importantly, we show that the use of nickel silicide as an ohmic contact at low temperatures does not affect the thermal equilibration of carriers nor contribute to hysteresis in a magnetic field. PMID:21968083

  7. Coil geometry effects on scanning single-coil magnetic induction tomography

    NASA Astrophysics Data System (ADS)

    Feldkamp, Joe R.; Quirk, Stephen

    2017-09-01

    Alternative coil designs for single coil magnetic induction tomography are considered in this work, with the intention of improving upon the standard design used previously. In particular, we note that the blind spot associated with this coil type, a portion of space along its axis where eddy current generation can be very weak, has an important effect on performance. The seven designs tested here vary considerably in the size of their blind spot. To provide the most discerning test possible, we use laboratory phantoms containing feature dimensions similar to blind spot size. Furthermore, conductivity contrasts are set higher than what would occur naturally in biological systems, which has the effect of weakening eddy current generation at coil locations that straddle the border between high and low conductivity features. Image reconstruction results for the various coils show that coils with smaller blind spots give markedly better performance, though improvements in signal-to-noise ratio could alter that conclusion.

  8. Magnetic heating of stellar chromospheres and coronae

    NASA Astrophysics Data System (ADS)

    van Ballegooijen, A. A.

    The theoretical discussion of magnetic heating focuses on heating by dissipation of field-aligned electric currents. Several mechanisms are set forth to account for the very high current densities needed to generate the heat, but observed radiative losses do not justify the resultant Ohmic heating rate. Tearing modes, 'turbulent resistivity', and 'hyper-resistivity' are considered to resolve the implied inefficiency of coronal heating. Because the mechanisms are not readily applicable to the sun, transverse magnetic energy flows and magnetic flare release are considered to account for the magnitude of observed radiative loss. High-resolution observations of the sun are concluded to be an efficient way to examine the issues of magnetic heating in spite of the very small spatial scales of the heating processes.

  9. COUPLED EVOLUTIONS OF THE STELLAR OBLIQUITY, ORBITAL DISTANCE, AND PLANET'S RADIUS DUE TO THE OHMIC DISSIPATION INDUCED IN A DIAMAGNETIC HOT JUPITER AROUND A MAGNETIC T TAURI STAR

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chang, Yu-Ling; Gu, Pin-Gao; Bodenheimer, Peter H.

    We revisit the calculation of the ohmic dissipation in a hot Jupiter presented by Laine et al. by considering more realistic interior structures, stellar obliquity, and the resulting orbital evolution. In this simplified approach, the young hot Jupiter of one Jupiter mass is modeled as a diamagnetic sphere with a finite resistivity, orbiting across tilted stellar magnetic dipole fields in vacuum. Since the induced ohmic dissipation occurs mostly near the planet's surface, we find that the dissipation is unable to significantly expand the young hot Jupiter. Nevertheless, the planet inside a small corotation orbital radius can undergo orbital decay bymore » the dissipation torque and finally overfill its Roche lobe during the T Tauri star phase. The stellar obliquity can evolve significantly if the magnetic dipole is parallel/antiparallel to the stellar spin. Our results are validated by the general torque-dissipation relation in the presence of the stellar obliquity. We also run the fiducial model of Laine et al. and find that the planet's radius is sustained at a nearly constant value by the ohmic heating, rather than being thermally expanded to the Roche radius as suggested by the authors.« less

  10. Scalable Nernst thermoelectric power using a coiled galfenol wire

    NASA Astrophysics Data System (ADS)

    Yang, Zihao; Codecido, Emilio A.; Marquez, Jason; Zheng, Yuanhua; Heremans, Joseph P.; Myers, Roberto C.

    2017-09-01

    The Nernst thermopower usually is considered far too weak in most metals for waste heat recovery. However, its transverse orientation gives it an advantage over the Seebeck effect on non-flat surfaces. Here, we experimentally demonstrate the scalable generation of a Nernst voltage in an air-cooled metal wire coiled around a hot cylinder. In this geometry, a radial temperature gradient generates an azimuthal electric field in the coil. A Galfenol (Fe0.85Ga0.15) wire is wrapped around a cartridge heater, and the voltage drop across the wire is measured as a function of axial magnetic field. As expected, the Nernst voltage scales linearly with the length of the wire. Based on heat conduction and fluid dynamic equations, finite-element method is used to calculate the temperature gradient across the Galfenol wire and determine the Nernst coefficient. A giant Nernst coefficient of -2.6 μV/KT at room temperature is estimated, in agreement with measurements on bulk Galfenol. We expect that the giant Nernst effect in Galfenol arises from its magnetostriction, presumably through enhanced magnon-phonon coupling. Our results demonstrate the feasibility of a transverse thermoelectric generator capable of scalable output power from non-flat heat sources.

  11. Induction heating coupler

    NASA Technical Reports Server (NTRS)

    Fox, Robert L. (Inventor); Copeland, Carl E. (Inventor); Swaim, Robert J. (Inventor); Coultrip, Robert H. (Inventor); Johnston, David F. (Inventor); Phillips, W. Morris (Inventor); Johnson, Samuel D. (Inventor); Dinkins, James R. (Inventor); Buckley, John D. (Inventor)

    1994-01-01

    An induction heating device includes a handle having a hollow interior and two opposite ends, a wrist connected to one end of the handle, a U-shaped pole piece having two spaced apart ends, a tank circuit including an induction coil wrapped around the pole piece and a capacitor connected to the induction coil, a head connected to the wrist and including a housing for receiving the U-shaped pole piece, the two spaced apart ends of the pole piece extending outwardely beyond the housing, and a power source connected to the tank circuit. When the tank circuit is energized and a susceptor is placed in juxtaposition to the ends of the U-shaped pole piece, the susceptor is heated by induction heating due to magnetic flux passing between the two ends of the pole piece.

  12. Improved nuclear magnetic resonance apparatus having semitoroidal rf coil for use in topical NMR and NMR imaging

    DOEpatents

    Fukushima, E.; Roeder, S.B.W.; Assink, R.A.; Gibson, A.A.V.

    1984-01-01

    An improved nuclear magnetic resonance (NMR) apparatus for use in topical magnetic resonance (TMR) spectroscopy and other remote sensing NMR applications includes a semitoroidal radio frequency (rf) coil. The semitoroidal rf coil produces an effective alternating magnetic field at a distance from the poles of the coil, so as to enable NMR measurements to be taken from selected regions inside an object, particularly including human and other living subjects. The semitoroidal rf coil is relatively insensitive to magnetic interference from metallic objects located behind the coil, thereby rendering the coil particularly suited for use in both conventional and superconducting NMR magnets. The semitoroidal NMR coil can be constructed so that it emits little or no excess rf electric field associated with the rf magnetic field, thus avoiding adverse effects due to dielectric heating of the sample or to any other interaction of the electric field with the sample.

  13. Coiled-coil forming peptides for the induction of silver nanoparticles

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Božič Abram, Sabina; Graduate School of Biomedicine, University of Ljubljana, Ljubljana 1000; Aupič, Jana

    Biopolymers with defined sequence patterns offer an attractive alternative for the formation of silver nanoparticle (AgNP). A set of coiled-coil dimer forming peptides was tested for their AgNP formation ability. Seventeen of those peptides mediated the formation of AgNPs in aqueous solution at neutral pH, while the formation of a coiled-coil dimer inhibited the nanoparticle generation. A QSAR regression model on the relationship between sequence and function suggests that in this peptide type the patterns KXQQ and KXEE are favorable, whereas Ala residues appear to have an inhibitory effect. UV–VIS spectra of the obtained nanoparticles gave a peak at aroundmore » 420 nm, typical for AgNPs in the size range around 40 nm, which was confirmed by dynamic light scattering and transmission electron microscopy. Peptide-induced AgNPs exhibited good antibacterial activity, even after a 15 min contact time, while they had low toxicity to human cells at the same concentrations. These results show that our designed peptides generate AgNPs with antibacterial activity at mild conditions and might be used for antibacterial coatings. - Highlights: • 17 of the 30 tested coiled-coil forming peptides induce AgNP formation. • Coiled-coil dimer formation suppresses AgNP generation of individual peptides. • Size of the peptide-induced silver nanoparticles is around 40 nm. • QSAR analysis points to the importance of KXQQ and KXEE motifs for AgNP generation. • Peptide-induced silver nanoparticles exhibit antibacterial activity.« less

  14. Design and Optimization of a 3-Coil Inductive Link for Efficient Wireless Power Transmission.

    PubMed

    Kiani, Mehdi; Jow, Uei-Ming; Ghovanloo, Maysam

    2011-07-14

    Inductive power transmission is widely used to energize implantable microelectronic devices (IMDs), recharge batteries, and energy harvesters. Power transfer efficiency (PTE) and power delivered to the load (PDL) are two key parameters in wireless links, which affect the energy source specifications, heat dissipation, power transmission range, and interference with other devices. To improve the PTE, a 4-coil inductive link has been recently proposed. Through a comprehensive circuit based analysis that can guide a design and optimization scheme, we have shown that despite achieving high PTE at larger coil separations, the 4-coil inductive links fail to achieve a high PDL. Instead, we have proposed a 3-coil inductive power transfer link with comparable PTE over its 4-coil counterpart at large coupling distances, which can also achieve high PDL. We have also devised an iterative design methodology that provides the optimal coil geometries in a 3-coil inductive power transfer link. Design examples of 2-, 3-, and 4-coil inductive links have been presented, and optimized for 13.56 MHz carrier frequency and 12 cm coupling distance, showing PTEs of 15%, 37%, and 35%, respectively. At this distance, the PDL of the proposed 3-coil inductive link is 1.5 and 59 times higher than its equivalent 2- and 4-coil links, respectively. For short coupling distances, however, 2-coil links remain the optimal choice when a high PDL is required, while 4-coil links are preferred when the driver has large output resistance or small power is needed. These results have been verified through simulations and measurements.

  15. Manufacture and Quality Control of Insert Coil with Real ITER TF Conductor

    DOE PAGES

    Ozeki, H.; Isono, T.; Uno, Y.; ...

    2016-03-02

    JAEA successfully completed the manufacture of the toroidal field (TF) insert coil (TFIC) for a performance test of the ITER TF conductor in the final design in cooperation with Hitachi, Ltd. The TFIC is a single-layer 8.875-turn solenoid coil with 1.44-m diameter. This will be tested for 68-kA current application in a 13-T external magnetic field. TFIC was manufactured in the following order: winding of the TF conductor, lead bending, fabrication of the electrical termination, heat treatment, turn insulation, installation of the coil into the support mandrel structure, vacuum pressure impregnation (VPI), structure assembly, and instrumentation. Here in this presentation,more » manufacture process and quality control status for the TFIC manufacturing are reported.« less

  16. Coiled-coil length: Size does matter.

    PubMed

    Surkont, Jaroslaw; Diekmann, Yoan; Ryder, Pearl V; Pereira-Leal, Jose B

    2015-12-01

    Protein evolution is governed by processes that alter primary sequence but also the length of proteins. Protein length may change in different ways, but insertions, deletions and duplications are the most common. An optimal protein size is a trade-off between sequence extension, which may change protein stability or lead to acquisition of a new function, and shrinkage that decreases metabolic cost of protein synthesis. Despite the general tendency for length conservation across orthologous proteins, the propensity to accept insertions and deletions is heterogeneous along the sequence. For example, protein regions rich in repetitive peptide motifs are well known to extensively vary their length across species. Here, we analyze length conservation of coiled-coils, domains formed by an ubiquitous, repetitive peptide motif present in all domains of life, that frequently plays a structural role in the cell. We observed that, despite the repetitive nature, the length of coiled-coil domains is generally highly conserved throughout the tree of life, even when the remaining parts of the protein change, including globular domains. Length conservation is independent of primary amino acid sequence variation, and represents a conservation of domain physical size. This suggests that the conservation of domain size is due to functional constraints. © 2015 Wiley Periodicals, Inc.

  17. Automated de novo phasing and model building of coiled-coil proteins.

    PubMed

    Rämisch, Sebastian; Lizatović, Robert; André, Ingemar

    2015-03-01

    Models generated by de novo structure prediction can be very useful starting points for molecular replacement for systems where suitable structural homologues cannot be readily identified. Protein-protein complexes and de novo-designed proteins are examples of systems that can be challenging to phase. In this study, the potential of de novo models of protein complexes for use as starting points for molecular replacement is investigated. The approach is demonstrated using homomeric coiled-coil proteins, which are excellent model systems for oligomeric systems. Despite the stereotypical fold of coiled coils, initial phase estimation can be difficult and many structures have to be solved with experimental phasing. A method was developed for automatic structure determination of homomeric coiled coils from X-ray diffraction data. In a benchmark set of 24 coiled coils, ranging from dimers to pentamers with resolutions down to 2.5 Å, 22 systems were automatically solved, 11 of which had previously been solved by experimental phasing. The generated models contained 71-103% of the residues present in the deposited structures, had the correct sequence and had free R values that deviated on average by 0.01 from those of the respective reference structures. The electron-density maps were of sufficient quality that only minor manual editing was necessary to produce final structures. The method, named CCsolve, combines methods for de novo structure prediction, initial phase estimation and automated model building into one pipeline. CCsolve is robust against errors in the initial models and can readily be modified to make use of alternative crystallographic software. The results demonstrate the feasibility of de novo phasing of protein-protein complexes, an approach that could also be employed for other small systems beyond coiled coils.

  18. Coiled-coil protein composition of 22 proteomes--differences and common themes in subcellular infrastructure and traffic control.

    PubMed

    Rose, Annkatrin; Schraegle, Shannon J; Stahlberg, Eric A; Meier, Iris

    2005-11-16

    Long alpha-helical coiled-coil proteins are involved in diverse organizational and regulatory processes in eukaryotic cells. They provide cables and networks in the cyto- and nucleoskeleton, molecular scaffolds that organize membrane systems and tissues, motors, levers, rotating arms, and possibly springs. Mutations in long coiled-coil proteins have been implemented in a growing number of human diseases. Using the coiled-coil prediction program MultiCoil, we have previously identified all long coiled-coil proteins from the model plant Arabidopsis thaliana and have established a searchable Arabidopsis coiled-coil protein database. Here, we have identified all proteins with long coiled-coil domains from 21 additional fully sequenced genomes. Because regions predicted to form coiled-coils interfere with sequence homology determination, we have developed a sequence comparison and clustering strategy based on masking predicted coiled-coil domains. Comparing and grouping all long coiled-coil proteins from 22 genomes, the kingdom-specificity of coiled-coil protein families was determined. At the same time, a number of proteins with unknown function could be grouped with already characterized proteins from other organisms. MultiCoil predicts proteins with extended coiled-coil domains (more than 250 amino acids) to be largely absent from bacterial genomes, but present in archaea and eukaryotes. The structural maintenance of chromosomes proteins and their relatives are the only long coiled-coil protein family clearly conserved throughout all kingdoms, indicating their ancient nature. Motor proteins, membrane tethering and vesicle transport proteins are the dominant eukaryote-specific long coiled-coil proteins, suggesting that coiled-coil proteins have gained functions in the increasingly complex processes of subcellular infrastructure maintenance and trafficking control of the eukaryotic cell.

  19. Exchanging Ohmic Losses in Metamaterial Absorbers with Useful Optical Absorption for Photovoltaics

    PubMed Central

    Vora, Ankit; Gwamuri, Jephias; Pala, Nezih; Kulkarni, Anand; Pearce, Joshua M.; Güney, Durdu Ö.

    2014-01-01

    Using metamaterial absorbers, we have shown that metallic layers in the absorbers do not necessarily constitute undesired resistive heating problem for photovoltaics. Tailoring the geometric skin depth of metals and employing the natural bulk absorbance characteristics of the semiconductors in those absorbers can enable the exchange of undesired resistive losses with the useful optical absorbance in the active semiconductors. Thus, Ohmic loss dominated metamaterial absorbers can be converted into photovoltaic near-perfect absorbers with the advantage of harvesting the full potential of light management offered by the metamaterial absorbers. Based on experimental permittivity data for indium gallium nitride, we have shown that between 75%–95% absorbance can be achieved in the semiconductor layers of the converted metamaterial absorbers. Besides other metamaterial and plasmonic devices, our results may also apply to photodectors and other metal or semiconductor based optical devices where resistive losses and power consumption are important pertaining to the device performance. PMID:24811322

  20. Designed Coiled-Coil Peptides Inhibit the Type Three Secretion System of Enteropathogenic Escherichia coli

    PubMed Central

    Larzábal, Mariano; Mercado, Elsa C.; Vilte, Daniel A.; Salazar-González, Hector; Cataldi, Angel; Navarro-Garcia, Fernando

    2010-01-01

    Background Enteropathogenic E. coli (EPEC) and enterohemorrhagic E. coli (EHEC) are two categories of E. coli strains associated with human disease. A major virulence factor of both pathotypes is the expression of a type three secretion system (TTSS), responsible for their ability to adhere to gut mucosa causing a characteristic attaching and effacing lesion (A/E). The TTSS translocates effector proteins directly into the host cell that subvert mammalian cell biochemistry. Methods/Principal Findings We examined synthetic peptides designed to inhibit the TTSS. CoilA and CoilB peptides, both representing coiled-coil regions of the translocator protein EspA, and CoilD peptide, corresponding to a coiled–coil region of the needle protein EscF, were effective in inhibiting the TTSS dependent hemolysis of red blood cells by the EPEC E2348/69 strain. CoilA and CoilB peptides also reduced the formation of actin pedestals by the same strain in HEp-2 cells and impaired the TTSS-mediated protein translocation into the epithelial cell. Interestingly, CoilA and CoilB were able to block EspA assembly, destabilizing the TTSS and thereby Tir translocation. This blockage of EspA polymerization by CoilA or CoilB peptides, also inhibited the correct delivery of EspB and EspD as detected by immunoblotting. Interestingly, electron microscopy of bacteria incubated with the CoilA peptide showed a reduction of the length of EspA filaments. Conclusions Our data indicate that coiled-coil peptides can prevent the assembly and thus the functionality of the TTSS apparatus and suggest that these peptides could provide an attractive tool to block EPEC and EHEC pathogenesis. PMID:20140230

  1. Electromagnetic characteristics of eccentric figure-eight coils for transcranial magnetic stimulation: A numerical study

    NASA Astrophysics Data System (ADS)

    Kato, Takuya; Sekino, Masaki; Matsuzaki, Taiga; Nishikawa, Atsushi; Saitoh, Youichi; Ohsaki, Hiroyuki

    2012-04-01

    Repetitive transcranial magnetic stimulation (rTMS) is effective for treatment of several neurological and psychiatric diseases. We proposed an eccentric figure-eight coil, which induces strong eddy currents in the target brain tissue. In this study, numerical analyses were carried out to obtain magnetic field distribution of the eccentric figure-eight coil and eddy current in the brain. The analyses were performed with various coil design parameters, such as the outer and inner diameters and number of turns, to investigate the influence of these parameters on the coil characteristics. Increases in the inner diameter, outer diameter, and number of turns caused increases in the maximum eddy current densities. Coil inductance, working voltage, and heat generation also became higher with the increases in these design parameters. In order to develop a compact stimulator system for use at home, we need to obtain strong eddy current density, keeping the working voltage as low as possible. Our results show that it is effective to enlarge the outer diameter.

  2. Doped polymer semiconductors with ultrahigh and ultralow work functions for ohmic contacts.

    PubMed

    Tang, Cindy G; Ang, Mervin C Y; Choo, Kim-Kian; Keerthi, Venu; Tan, Jun-Kai; Syafiqah, Mazlan Nur; Kugler, Thomas; Burroughes, Jeremy H; Png, Rui-Qi; Chua, Lay-Lay; Ho, Peter K H

    2016-11-24

    To make high-performance semiconductor devices, a good ohmic contact between the electrode and the semiconductor layer is required to inject the maximum current density across the contact. Achieving ohmic contacts requires electrodes with high and low work functions to inject holes and electrons respectively, where the work function is the minimum energy required to remove an electron from the Fermi level of the electrode to the vacuum level. However, it is challenging to produce electrically conducting films with sufficiently high or low work functions, especially for solution-processed semiconductor devices. Hole-doped polymer organic semiconductors are available in a limited work-function range, but hole-doped materials with ultrahigh work functions and, especially, electron-doped materials with low to ultralow work functions are not yet available. The key challenges are stabilizing the thin films against de-doping and suppressing dopant migration. Here we report a general strategy to overcome these limitations and achieve solution-processed doped films over a wide range of work functions (3.0-5.8 electronvolts), by charge-doping of conjugated polyelectrolytes and then internal ion-exchange to give self-compensated heavily doped polymers. Mobile carriers on the polymer backbone in these materials are compensated by covalently bonded counter-ions. Although our self-compensated doped polymers superficially resemble self-doped polymers, they are generated by separate charge-carrier doping and compensation steps, which enables the use of strong dopants to access extreme work functions. We demonstrate solution-processed ohmic contacts for high-performance organic light-emitting diodes, solar cells, photodiodes and transistors, including ohmic injection of both carrier types into polyfluorene-the benchmark wide-bandgap blue-light-emitting polymer organic semiconductor. We also show that metal electrodes can be transformed into highly efficient hole- and electron

  3. Historical review: another 50th anniversary--new periodicities in coiled coils.

    PubMed

    Gruber, Markus; Lupas, Andrei N

    2003-12-01

    In 1953, Francis Crick and Linus Pauling both proposed models of supercoiled alpha helices ('coiled coils') for the structure of keratin. These were the first attempts at modelling the tertiary structure of a protein. Crick emphasized the packing mode of the side-chains ('knobs-into-holes'), which required a periodicity of seven residues over two helical turns (7/2) and a supercoil in the opposite sense of the constituent helices. By contrast, Pauling envisaged a broader set of periodicities (4/1, 7/2, 18/5, 15/4, 11/3) and supercoils of both senses. Crick's model became canonical and the 'heptad repeat' essentially synonymous with coiled coils, but 50 years later new crystal structures and protein sequences show that the less common periodicities envisaged by Pauling also occur in coiled coils, adding a variant packing mode ('knobs-to-knobs') to the standard model. Pauling's laboratory notebooks suggest that he searched unsuccessfully for this packing mode in 1953.

  4. Coiled-Coil Proteins Facilitated the Functional Expansion of the Centrosome

    PubMed Central

    Kuhn, Michael; Hyman, Anthony A.; Beyer, Andreas

    2014-01-01

    Repurposing existing proteins for new cellular functions is recognized as a main mechanism of evolutionary innovation, but its role in organelle evolution is unclear. Here, we explore the mechanisms that led to the evolution of the centrosome, an ancestral eukaryotic organelle that expanded its functional repertoire through the course of evolution. We developed a refined sequence alignment technique that is more sensitive to coiled coil proteins, which are abundant in the centrosome. For proteins with high coiled-coil content, our algorithm identified 17% more reciprocal best hits than BLAST. Analyzing 108 eukaryotic genomes, we traced the evolutionary history of centrosome proteins. In order to assess how these proteins formed the centrosome and adopted new functions, we computationally emulated evolution by iteratively removing the most recently evolved proteins from the centrosomal protein interaction network. Coiled-coil proteins that first appeared in the animal–fungi ancestor act as scaffolds and recruit ancestral eukaryotic proteins such as kinases and phosphatases to the centrosome. This process created a signaling hub that is crucial for multicellular development. Our results demonstrate how ancient proteins can be co-opted to different cellular localizations, thereby becoming involved in novel functions. PMID:24901223

  5. State transition of a non-Ohmic damping system in a corrugated plane.

    PubMed

    Lü, Kun; Bao, Jing-Dong

    2007-12-01

    Anomalous transport of a particle subjected to non-Ohmic damping of the power delta in a tilted periodic potential is investigated via Monte Carlo simulation of the generalized Langevin equation. It is found that the system exhibits two relative motion modes: the locked state and the running state. In an environment of sub-Ohmic damping (0Ohmic damping (1=2D_(eff)(delta){t(delta_eff} . Our result shows that the effective power index delta_(eff) can be enhanced and is a nonmonotonic function of the temperature and the driving force. The mixture of the two motion modes also leads to a breakdown of the hysteresis loop of the mobility.

  6. CCBuilder 2.0: Powerful and accessible coiled-coil modeling.

    PubMed

    Wood, Christopher W; Woolfson, Derek N

    2018-01-01

    The increased availability of user-friendly and accessible computational tools for biomolecular modeling would expand the reach and application of biomolecular engineering and design. For protein modeling, one key challenge is to reduce the complexities of 3D protein folds to sets of parametric equations that nonetheless capture the salient features of these structures accurately. At present, this is possible for a subset of proteins, namely, repeat proteins. The α-helical coiled coil provides one such example, which represents ≈ 3-5% of all known protein-encoding regions of DNA. Coiled coils are bundles of α helices that can be described by a small set of structural parameters. Here we describe how this parametric description can be implemented in an easy-to-use web application, called CCBuilder 2.0, for modeling and optimizing both α-helical coiled coils and polyproline-based collagen triple helices. This has many applications from providing models to aid molecular replacement for X-ray crystallography, in silico model building and engineering of natural and designed protein assemblies, and through to the creation of completely de novo "dark matter" protein structures. CCBuilder 2.0 is available as a web-based application, the code for which is open-source and can be downloaded freely. http://coiledcoils.chm.bris.ac.uk/ccbuilder2. We have created CCBuilder 2.0, an easy to use web-based application that can model structures for a whole class of proteins, the α-helical coiled coil, which is estimated to account for 3-5% of all proteins in nature. CCBuilder 2.0 will be of use to a large number of protein scientists engaged in fundamental studies, such as protein structure determination, through to more-applied research including designing and engineering novel proteins that have potential applications in biotechnology. © 2017 The Authors Protein Science published by Wiley Periodicals, Inc. on behalf of The Protein Society.

  7. Intra-coil interactions in split gradient coils in a hybrid MRI-LINAC system

    NASA Astrophysics Data System (ADS)

    Tang, Fangfang; Freschi, Fabio; Sanchez Lopez, Hector; Repetto, Maurizio; Liu, Feng; Crozier, Stuart

    2016-04-01

    An MRI-LINAC system combines a magnetic resonance imaging (MRI) system with a medical linear accelerator (LINAC) to provide image-guided radiotherapy for targeting tumors in real-time. In an MRI-LINAC system, a set of split gradient coils is employed to produce orthogonal gradient fields for spatial signal encoding. Owing to this unconventional gradient configuration, eddy currents induced by switching gradient coils on and off may be of particular concern. It is expected that strong intra-coil interactions in the set will be present due to the constrained return paths, leading to potential degradation of the gradient field linearity and image distortion. In this study, a series of gradient coils with different track widths have been designed and analyzed to investigate the electromagnetic interactions between coils in a split gradient set. A driving current, with frequencies from 100 Hz to 10 kHz, was applied to study the inductive coupling effects with respect to conductor geometry and operating frequency. It was found that the eddy currents induced in the un-energized coils (hereby-referred to as passive coils) positively correlated with track width and frequency. The magnetic field induced by the eddy currents in the passive coils with wide tracks was several times larger than that induced by eddy currents in the cold shield of cryostat. The power loss in the passive coils increased with the track width. Therefore, intra-coil interactions should be included in the coil design and analysis process.

  8. Crystal structure of a super leucine zipper, an extended two-stranded super long coiled coil

    PubMed Central

    Diao, Jiasheng

    2010-01-01

    Coiled coil is a ubiquitous structural motif in proteins, with two to seven alpha helices coiled together like the strands of a rope, and coiled coil folding and assembly is not completely understood. A GCN4 leucine zipper mutant with four mutations of K3A, D7A, Y17W, and H18N has been designed, and the crystal structure has been determined at 1.6 Å resolution. The peptide monomer shows a helix trunk with short curved N- and C-termini. In the crystal, two monomers cross in 35° and form an X-shaped dimer, and each X-shaped dimer is welded into the next one through sticky hydrophobic ends, thus forming an extended two-stranded, parallel, super long coiled coil rather than a discrete, two-helix coiled coil of the wild-type GCN4 leucine zipper. Leucine residues appear at every seventh position in the super long coiled coil, suggesting that it is an extended super leucine zipper. Compared to the wild-type leucine zipper, the N-terminus of the mutant has a dramatic conformational change and the C-terminus has one more residue Glu 32 determined. The mutant X-shaped dimer has a large crossing angle of 35° instead of 18° in the wild-type dimer. The results show a novel assembly mode and oligomeric state of coiled coil, and demonstrate that mutations may affect folding and assembly of the overall coiled coil. Analysis of the formation mechanism of the super long coiled coil may help understand and design self-assembling protein fibers. PMID:20027625

  9. Crystal Structure of a Super Leucine Zipper an Extended Two-Stranded Super Long Coiled Coil

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    J Diao

    2011-12-31

    Coiled coil is a ubiquitous structural motif in proteins, with two to seven alpha helices coiled together like the strands of a rope, and coiled coil folding and assembly is not completely understood. A GCN4 leucine zipper mutant with four mutations of K3A, D7A, Y17W, and H18N has been designed, and the crystal structure has been determined at 1.6 {angstrom} resolution. The peptide monomer shows a helix trunk with short curved N- and C-termini. In the crystal, two monomers cross in 35{sup o} and form an X-shaped dimer, and each X-shaped dimer is welded into the next one through stickymore » hydrophobic ends, thus forming an extended two-stranded, parallel, super long coiled coil rather than a discrete, two-helix coiled coil of the wild-type GCN4 leucine zipper. Leucine residues appear at every seventh position in the super long coiled coil, suggesting that it is an extended super leucine zipper. Compared to the wild-type leucine zipper, the N-terminus of the mutant has a dramatic conformational change and the C-terminus has one more residue Glu 32 determined. The mutant X-shaped dimer has a large crossing angle of 35{sup o} instead of 18{sup o} in the wild-type dimer. The results show a novel assembly mode and oligomeric state of coiled coil, and demonstrate that mutations may affect folding and assembly of the overall coiled coil. Analysis of the formation mechanism of the super long coiled coil may help understand and design self-assembling protein fibers.« less

  10. Experiments and Simulations of ITER-like Plasmas in Alcator C-Mod

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    .R. Wilson, C.E. Kessel, S. Wolfe, I.H. Hutchinson, P. Bonoli, C. Fiore, A.E. Hubbard, J. Hughes, Y. Lin, Y. Ma, D. Mikkelsen, M. Reinke, S. Scott, A.C.C. Sips, S. Wukitch and the C-Mod Team

    Alcator C-Mod is performing ITER-like experiments to benchmark and verify projections to 15 MA ELMy H-mode Inductive ITER discharges. The main focus has been on the transient ramp phases. The plasma current in C-Mod is 1.3 MA and toroidal field is 5.4 T. Both Ohmic and ion cyclotron (ICRF) heated discharges are examined. Plasma current rampup experiments have demonstrated that (ICRF and LH) heating in the rise phase can save voltseconds (V-s), as was predicted for ITER by simulations, but showed that the ICRF had no effect on the current profile versus Ohmic discharges. Rampdown experiments show an overcurrent inmore » the Ohmic coil (OH) at the H to L transition, which can be mitigated by remaining in H-mode into the rampdown. Experiments have shown that when the EDA H-mode is preserved well into the rampdown phase, the density and temperature pedestal heights decrease during the plasma current rampdown. Simulations of the full C-Mod discharges have been done with the Tokamak Simulation Code (TSC) and the Coppi-Tang energy transport model is used with modified settings to provide the best fit to the experimental electron temperature profile. Other transport models have been examined also. __________________________________________________« less

  11. Coiling of viscous jets

    NASA Astrophysics Data System (ADS)

    Ribe, Neil M.

    2004-11-01

    A stream of viscous fluid falling from a sufficient height onto a surface forms a series of regular coils. I use a numerical model for a deformable fluid thread to predict the coiling frequency as a function of the thread's radius, the flow rate, the fall height, and the fluid viscosity. Three distinct modes of coiling can occur: viscous (e.g. toothpaste), gravitational (honey falling from a moderate height) and inertial (honey falling from a great height). When inertia is significant, three states of steady coiling with different frequencies can exist over a range of fall heights. The numerically predicted coiling frequencies agree well with experimental measurements in the inertial coiling regime.

  12. Analysis of Coiled-Coil Interactions between Core Proteins of the Spindle Pole Body

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zizlsperger, N.; Malashkevich, V; Pillay, S

    2008-01-01

    The spindle pole body (SPB) is a multiprotein complex that organizes microtubules in yeast. Due to its large size and association with the nuclear membrane, little is known about its detailed structure. In particular, although many SPB components and some of the interactions between them have been identified, the molecular details of how most of these interactions occur are not known. The prevalence of predicted coiled-coil regions in SPB proteins suggests that some interactions may occur via coiled coils. Here this hypothesis is supported by biochemical characterization of isolated coiled-coil peptides derived from SPB proteins. Formation of four strongly self-associatingmore » coiled-coil complexes from Spc29, Spc42, and Spc72 was demonstrated by circular dichroism (CD) spectroscopy and a fluorescence resonance energy transfer (FRET) assay. Many weaker self- and heteroassociations were also detected by CD, FRET, and/or cross-linking. The thermal stabilities of nine candidate homooligomers were assessed; six unfolded cooperatively with melting temperatures ranging from <11 to >50 C. Solution studies established that coiled-coil peptides derived from Spc42 and Spc72 form parallel dimers, and this was confirmed for Spc42 by a high-resolution crystal structure. These data contribute to a growing body of knowledge that will ultimately provide a detailed model of the SPB structure.« less

  13. Dual coil ignition system

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Huberts, Garlan J.; Qu, Qiuping; Czekala, Michael Damian

    2017-03-28

    A dual coil ignition system is provided. The dual coil ignition system includes a first inductive ignition coil including a first primary winding and a first secondary winding, and a second inductive ignition coil including a second primary winding and a second secondary winding, the second secondary winding connected in series to the first secondary winding. The dual coil ignition system further includes a diode network including a first diode and a second diode connected between the first secondary winding and the second secondary winding.

  14. A study on geometry effect of transmission coil for micro size magnetic induction coil

    NASA Astrophysics Data System (ADS)

    Lee, Kyung Hwa; Jun, Byoung Ok; Kim, Seunguk; Lee, Gwang Jun; Ryu, Mingyu; Choi, Ji-Woong; Jang, Jae Eun

    2016-05-01

    The effects of transmission (Tx) coil structure have been studied for micro-size magnetic induction coil. The size of the receiving (Rx) coil should be shrunk to the micrometer level for the various new applications such as micro-robot and wireless body implanted devices. In case of the macro-scale magnetic induction coil, the power transmission efficiency is generally considered to be higher as the inductance of the transmission coil became larger; however, the large size difference between macro-size Tx coil and micro-size Rx coil can decrease the power transmission efficiency due to the difference of resonance frequency. Here, we study a correlation of the power transmission with the size and distance between the macro-size Tx and micro-size Rx coils using magnetic induction technique. The maximum power efficiency was 0.28/0.23/0.13/0.12% at the distance of 0.3/1/3/5 cm between Rx and Tx coil. In addition, more efficient wireless power transferring method is suggested with a floating coil for the body implantable devices. The voltage output increased up to 5.4 mV than the original one Tx coil system. The results demonstrated the foundational wireless power transferring system with enhanced power efficiency.

  15. Sintered Cr/Pt and Ni/Au ohmic contacts to B 12P 2

    DOE PAGES

    Frye, Clint D.; Kucheyev, Sergei O.; Edgar, James H.; ...

    2015-04-09

    With this study, icosahedral boron phosphide (B 12P 2) is a wide-bandgap semiconductor possessing interesting properties such as high hardness, chemical inertness, and the reported ability to self-heal from irradiation by high energy electrons. Here, the authors developed Cr/Pt and Ni/Au ohmic contacts to epitaxially grown B 12P 2 for materials characterization and electronic device development. Cr/Pt contacts became ohmic after annealing at 700 °C for 30 s with a specific contact resistance of 2×10 –4 Ω cm 2, as measured by the linear transfer length method. Ni/Au contacts were ohmic prior to any annealing, and their minimum specific contactmore » resistance was ~l–4 × 10 –4 Ω cm 2 after annealing over the temperature range of 500–800 °C. Rutherford backscattering spectrometry revealed a strong reaction and intermixing between Cr/Pt and B 12P 2 at 700 °C and a reaction layer between Ni and B 12P 2 thinner than ~25 nm at 500 °C.« less

  16. Intra-coil interactions in split gradient coils in a hybrid MRI-LINAC system.

    PubMed

    Tang, Fangfang; Freschi, Fabio; Sanchez Lopez, Hector; Repetto, Maurizio; Liu, Feng; Crozier, Stuart

    2016-04-01

    An MRI-LINAC system combines a magnetic resonance imaging (MRI) system with a medical linear accelerator (LINAC) to provide image-guided radiotherapy for targeting tumors in real-time. In an MRI-LINAC system, a set of split gradient coils is employed to produce orthogonal gradient fields for spatial signal encoding. Owing to this unconventional gradient configuration, eddy currents induced by switching gradient coils on and off may be of particular concern. It is expected that strong intra-coil interactions in the set will be present due to the constrained return paths, leading to potential degradation of the gradient field linearity and image distortion. In this study, a series of gradient coils with different track widths have been designed and analyzed to investigate the electromagnetic interactions between coils in a split gradient set. A driving current, with frequencies from 100 Hz to 10 kHz, was applied to study the inductive coupling effects with respect to conductor geometry and operating frequency. It was found that the eddy currents induced in the un-energized coils (hereby-referred to as passive coils) positively correlated with track width and frequency. The magnetic field induced by the eddy currents in the passive coils with wide tracks was several times larger than that induced by eddy currents in the cold shield of cryostat. The power loss in the passive coils increased with the track width. Therefore, intra-coil interactions should be included in the coil design and analysis process. Copyright © 2016 Elsevier Inc. All rights reserved.

  17. Coiled Coils - A Model System for the 21st Century.

    PubMed

    Lupas, Andrei N; Bassler, Jens

    2017-02-01

    α-Helical coiled coils were described more than 60 years ago as simple, repetitive structures mediating oligomerization and mechanical stability. Over the past 20 years, however, they have emerged as one of the most diverse protein folds in nature, enabling many biological functions beyond mechanical rigidity, such as membrane fusion, signal transduction, and solute transport. Despite this great diversity, their structures can be described by parametric equations, making them uniquely suited for rational protein design. Far from having been exhausted as a source of structural insight and a basis for functional engineering, coiled coils are poised to become even more important for protein science in the coming decades. Copyright © 2016 Elsevier Ltd. All rights reserved.

  18. Four signature motifs define the first class of structurally related large coiled-coil proteins in plants.

    PubMed Central

    Gindullis, Frank; Rose, Annkatrin; Patel, Shalaka; Meier, Iris

    2002-01-01

    Background Animal and yeast proteins containing long coiled-coil domains are involved in attaching other proteins to the large, solid-state components of the cell. One subgroup of long coiled-coil proteins are the nuclear lamins, which are involved in attaching chromatin to the nuclear envelope and have recently been implicated in inherited human diseases. In contrast to other eukaryotes, long coiled-coil proteins have been barely investigated in plants. Results We have searched the completed Arabidopsis genome and have identified a family of structurally related long coiled-coil proteins. Filament-like plant proteins (FPP) were identified by sequence similarity to a tomato cDNA that encodes a coiled-coil protein which interacts with the nuclear envelope-associated protein, MAF1. The FPP family is defined by four novel unique sequence motifs and by two clusters of long coiled-coil domains separated by a non-coiled-coil linker. All family members are expressed in a variety of Arabidopsis tissues. A homolog sharing the structural features was identified in the monocot rice, indicating conservation among angiosperms. Conclusion Except for myosins, this is the first characterization of a family of long coiled-coil proteins in plants. The tomato homolog of the FPP family binds in a yeast two-hybrid assay to a nuclear envelope-associated protein. This might suggest that FPP family members function in nuclear envelope biology. Because the full Arabidopsis genome does not appear to contain genes for lamins, it is of interest to investigate other long coiled-coil proteins, which might functionally replace lamins in the plant kingdom. PMID:11972898

  19. Coiled-coil protein composition of 22 proteomes – differences and common themes in subcellular infrastructure and traffic control

    PubMed Central

    Rose, Annkatrin; Schraegle, Shannon J; Stahlberg, Eric A; Meier, Iris

    2005-01-01

    Background Long alpha-helical coiled-coil proteins are involved in diverse organizational and regulatory processes in eukaryotic cells. They provide cables and networks in the cyto- and nucleoskeleton, molecular scaffolds that organize membrane systems and tissues, motors, levers, rotating arms, and possibly springs. Mutations in long coiled-coil proteins have been implemented in a growing number of human diseases. Using the coiled-coil prediction program MultiCoil, we have previously identified all long coiled-coil proteins from the model plant Arabidopsis thaliana and have established a searchable Arabidopsis coiled-coil protein database. Results Here, we have identified all proteins with long coiled-coil domains from 21 additional fully sequenced genomes. Because regions predicted to form coiled-coils interfere with sequence homology determination, we have developed a sequence comparison and clustering strategy based on masking predicted coiled-coil domains. Comparing and grouping all long coiled-coil proteins from 22 genomes, the kingdom-specificity of coiled-coil protein families was determined. At the same time, a number of proteins with unknown function could be grouped with already characterized proteins from other organisms. Conclusion MultiCoil predicts proteins with extended coiled-coil domains (more than 250 amino acids) to be largely absent from bacterial genomes, but present in archaea and eukaryotes. The structural maintenance of chromosomes proteins and their relatives are the only long coiled-coil protein family clearly conserved throughout all kingdoms, indicating their ancient nature. Motor proteins, membrane tethering and vesicle transport proteins are the dominant eukaryote-specific long coiled-coil proteins, suggesting that coiled-coil proteins have gained functions in the increasingly complex processes of subcellular infrastructure maintenance and trafficking control of the eukaryotic cell. PMID:16288662

  20. Experiments Demonstrate Geothermal Heating Process

    ERIC Educational Resources Information Center

    Roman, Harry T.

    2012-01-01

    When engineers design heat-pump-based geothermal heating systems for homes and other buildings, they can use coil loops buried around the perimeter of the structure to gather low-grade heat from the earth. As an alternative approach, they can drill well casings and store the summer's heat deep in the earth, then bring it back in the winter to warm…

  1. INTERNATIONAL CONFERENCE ON SEMICONDUCTOR INJECTION LASERS SELCO-87: Multilayer CrPtCr/NiAu ohmic contacts with p-type GaAs in heterojunction laser structures

    NASA Astrophysics Data System (ADS)

    Wójcik, I.; Stareev, G.; Barcz, A.; Domański, M.

    1988-11-01

    Multilayer CrPtCr/NiAu metallization was deposited by sputtering in a magnetron on the p-type side of GaAs in a pulsed laser heterostructure. Heat treatment at 490 °C for 3 min produced a reliable ohmic contact with a specific resistance of 10- 6-10- 5 Ω · cm2, depending on the substrate doping. Secondary-ion mass spectroscopy and Rutherford backscattering methods were used to study the mechanism of formation of a contact.

  2. Magnetic propulsion of a magnetic device using three square-Helmholtz coils and a square-Maxwell coil.

    PubMed

    Ha, Yong H; Han, Byung H; Lee, Soo Y

    2010-02-01

    We introduce a square coil system for remote magnetic navigation of a magnetic device without any physical movements of the coils. We used three square-Helmholtz coils and a square-Maxwell coil for magnetic propulsion of a small magnet along the desired path. All the square coils are mountable on a cubic frame that has an opening to accommodate a living subject. The square-Helmholtz coils control the magnetic propulsion direction by generating uniform magnetic field along the desired direction while the square-Maxwell coil controls the propulsion force by generating magnetic gradient field. We performed magnetic propulsion experiments with a down-scaled coil set and a three-channel coil driver. Experimental results demonstrate that we can use the square coil set for magnetic navigation of a magnetic device without any physical movements of the coils.

  3. Quadruple Cone Coil with improved focality than Figure-8 coil in Transcranial Magnetic Stimulation

    NASA Astrophysics Data System (ADS)

    Rastogi, Priyam; Lee, Erik G.; Hadimani, Ravi L.; Jiles, David C.

    Transcranial Magnetic Stimulation (TMS) is a non-invasive therapy which uses a time varying magnetic field to induce an electric field in the brain and to cause neuron depolarization. Magnetic coils play an important role in the TMS therapy since their coil geometry determines the focality and penetration's depth of the induced electric field in the brain. Quadruple Cone Coil (QCC) is a novel coil with an improved focality when compared to commercial Figure-8 coil. The results of this newly designed QCC coil are compared with the Figure-8 coil at two different positions of the head - vertex and dorsolateral prefrontal cortex, over the 50 anatomically realistic MRI derived head models. Parameters such as volume of stimulation, maximum electric, area of stimulation and location of maximum electric field are determined with the help of computer modelling of both coils. There is a decrease in volume of brain stimulated by 11.6 % and a modest improvement of 8 % in the location of maximum electric field due to QCC in comparison to the Figure-8 coil. The Carver Charitable Trust and The Galloway Foundation.

  4. Cooling a solar telescope enclosure: plate coil thermal analysis

    NASA Astrophysics Data System (ADS)

    Gorman, Michael; Galapon, Chriselle; Montijo, Guillermo; Phelps, LeEllen; Murga, Gaizka

    2016-08-01

    The climate of Haleakalā requires the observatories to actively adapt to changing conditions in order to produce the best possible images. Observatories need to be maintained at a temperature closely matching ambient or the images become blurred and unusable. The Daniel K. Inouye Solar Telescope is a unique telescope as it will be active during the day as opposed to the other night-time stellar observatories. This means that it will not only need to constantly match the ever-changing temperature during the day, but also during the night so as not to sub-cool and affect the view field of other telescopes while they are in use. To accomplish this task, plate coil heat exchanger panels will be installed on the DKIST enclosure that are designed to keep the temperature at ambient temperature +0°C/-4°C. To verify the feasibility of this and to validate the design models, a test rig has been installed at the summit of Haleakalā. The project's purpose is to confirm that the plate coil panels are capable of maintaining this temperature throughout all seasons and involved collecting data sets of various variables including pressures, temperatures, coolant flows, solar radiations and wind velocities during typical operating hours. Using MATLAB, a script was written to observe the plate coil's thermal performance. The plate coil did not perform as expected, achieving a surface temperature that was generally 2ºC above ambient temperature. This isn't to say that the plate coil does not work, but the small chiller used for the experiment was undersized resulting in coolant pumped through the plate coil that was not supplied at a low enough temperature. Calculated heat depositions were about 23% lower than that used as the basis of the design for the hillers to be used on the full system, a reasonable agreement given the fact that many simplifying assumptions were used in the models. These were not carried over into the testing. The test rig performance showing a 23% margin

  5. Suitability of miniature inductively coupled RF coils as MR-visible markers for clinical purposes.

    PubMed

    Garnov, Nikita; Thormer, Gregor; Trampel, Robert; Grunder, Wilfried; Kahn, Thomas; Moche, Michael; Busse, Harald

    2011-11-01

    MR-visible markers have already been used for various purposes such as image registration, motion detection, and device tracking. Inductively coupled RF (ICRF) coils, in particular, provide a high contrast and do not require connecting wires to the scanner, which makes their application highly flexible and safe. This work aims to thoroughly characterize the MR signals of such ICRF markers under various conditions with a special emphasis on fully automatic detection. The small markers consisted of a solenoid coil that was wound around a glass tube containing the MR signal source and tuned to the resonance frequency of a 1.5 T MRI. Marker imaging was performed with a spoiled gradient echo sequence (FLASH) and a balanced steady-state free precession (SSFP) sequence (TrueFISP) in three standard projections. The signal intensities of the markers were recorded for both pulse sequences, three source materials (tap water, distilled water, and contrast agent solution), different flip angles and coil alignments with respect to the B(0) direction as well as for different marker positions in the entire imaging volume (field of view, FOV). Heating of the ICRF coils was measured during 10-min RF expositions to three conventional pulse sequences. Clinical utility of the markers was assessed from their performance in computer-aided detection and in defining double oblique scan planes. For almost the entire FOV (±215 mm) and an estimated 82% of all possible RF coil alignments with respect to B(0), the ICRF markers generated clearly visible MR signals and could be reliably localized over a large range of flip angles, in particular with the TrueFISP sequence (0.3°-4.0°). Generally, TrueFISP provided a higher marker contrast than FLASH. RF exposition caused a moderate heating (≤5 °C) of the ICRF coils only. Small ICRF coils, imaged at low flip angles with a balanced SSFP sequence showed an excellent performance under a variety of experimental conditions and therefore make for a

  6. Development of high temperature stable Ohmic and Schottky contacts on n-gallium nitride

    NASA Astrophysics Data System (ADS)

    Khanna, Rohit

    In this work the effort was made to towards develop and investigate high temperature stable Ohmic and Schottky contacts for n type GaN. Various borides and refractory materials were incorporated in metallization scheme to best attain the desired effect of minimal degradation of contacts when placed at high temperatures. This work focuses on achieving a contact scheme using different borides which include two Tungsten Borides (namely W2B, W2B 5), Titanium Boride (TiB2), Chromium Boride (CrB2) and Zirconium Boride (ZrB2). Further a high temperature metal namely Iridium (Ir) was evaluated as a potential contact to n-GaN, as part of continuing improved device technology development. The main goal of this project was to investigate the most promising boride-based contact metallurgies on GaN, and finally to fabricate a High Electron Mobility Transistor (HEMT) and compare its reliability to a HEMT using present technology contact. Ohmic contacts were fabricated on n GaN using borides in the metallization scheme of Ti/Al/boride/Ti/Au. The characterization of the contacts was done using current-voltage measurements, scanning electron microscopy (SEM) and Auger Electron Spectroscopy (AES) measurements. The contacts formed gave specific contact resistance of the order of 10-5 to 10-6 Ohm-cm2. A minimum contact resistance of 1.5x10-6 O.cm 2 was achieved for the TiB2 based scheme at an annealing temperature of 850-900°C, which was comparable to a regular ohmic contact of Ti/Al/Ni/Au on n GaN. When some of borides contacts were placed on a hot plate or in hot oven for temperature ranging from 200°C to 350°C, the regular metallization contacts degraded before than borides ones. Even with a certain amount of intermixing of the metallization scheme the boride contacts showed minimal roughening and smoother morphology, which, in terms of edge acuity, is crucial for very small gate devices. Schottky contacts were also fabricated and characterized using all the five boride

  7. Modified van Vaals-Bergman coaxial cable coil (lambda coil) for high-field imaging.

    PubMed

    Matsuzawa, H; Nakada, T

    1996-03-01

    An easily constructed, low-capacitive coupling volume coil based on the van Vaals-Bergman coaxial cable coil for high field imaging is described. The coil (designated "lambda coil") was constructed using two 5/4 length 50 omega coaxial cables matched to a 50 omega transmission line with LC bridge balun. The standing wave on the single 5/4 lambda length coaxial cable provides two points of current maxima in oppositional direction. Therefore, the four current elements necessary for effective B1 field generation can be obtained by two 5/4 lambda length coaxial cables arranged analogous to 1/2 lambda T-antenna. Capacitive coupling between the coil elements and conductive samples (i.e. animals) is minimized by simply retaining the shield of the coaxial cable for the area of voltage maxima. The lambda coil exhibited excellent performance as a volume coil with a high quality factor and highly homogeneous rf fields. Because of its dramatically simple architecture and excellent performance, the lambda coil configuration appears to be an economical alternative to the original van Vaals-Bergman design, especially for research facilities with a high field magnet and limited bore space.

  8. Effect of interfacial composition on Ag-based Ohmic contact of GaN-based vertical light emitting diodes

    NASA Astrophysics Data System (ADS)

    Wu, Ning; Xiong, Zhihua; Qin, Zhenzhen

    2018-02-01

    By investigating the effect of a defective interface structure on Ag-based Ohmic contact of GaN-based vertical light-emitting diodes, we found a direct relationship between the interfacial composition and the Schottky barrier height of the Ag(111)/GaN(0001) interface. It was demonstrated that the Schottky barrier height of a defect-free Ag(111)/GaN(0001) interface was 2.221 eV, and it would be dramatically decreased to 0.375 eV with the introduction of one Ni atom and one Ga vacancy at the interface structure. It was found that the tunability of the Schottky barrier height can be attributed to charge accumulations around the interfacial defective regions and an unpinning of the Fermi level, which explains the experimental phenomenon of Ni-assisted annealing improving the p-type Ohmic contact characteristic. Lastly, we propose a new method of using Cu as an assisted metal to realize a novel Ag-based Ohmic contact. These results provide a guideline for the fabrication of high-quality Ag-based Ohmic contact of GaN-based vertical light-emitting diodes.

  9. CCBuilder: an interactive web-based tool for building, designing and assessing coiled-coil protein assemblies.

    PubMed

    Wood, Christopher W; Bruning, Marc; Ibarra, Amaurys Á; Bartlett, Gail J; Thomson, Andrew R; Sessions, Richard B; Brady, R Leo; Woolfson, Derek N

    2014-11-01

    The ability to accurately model protein structures at the atomistic level underpins efforts to understand protein folding, to engineer natural proteins predictably and to design proteins de novo. Homology-based methods are well established and produce impressive results. However, these are limited to structures presented by and resolved for natural proteins. Addressing this problem more widely and deriving truly ab initio models requires mathematical descriptions for protein folds; the means to decorate these with natural, engineered or de novo sequences; and methods to score the resulting models. We present CCBuilder, a web-based application that tackles the problem for a defined but large class of protein structure, the α-helical coiled coils. CCBuilder generates coiled-coil backbones, builds side chains onto these frameworks and provides a range of metrics to measure the quality of the models. Its straightforward graphical user interface provides broad functionality that allows users to build and assess models, in which helix geometry, coiled-coil architecture and topology and protein sequence can be varied rapidly. We demonstrate the utility of CCBuilder by assembling models for 653 coiled-coil structures from the PDB, which cover >96% of the known coiled-coil types, and by generating models for rarer and de novo coiled-coil structures. CCBuilder is freely available, without registration, at http://coiledcoils.chm.bris.ac.uk/app/cc_builder/. © The Author 2014. Published by Oxford University Press.

  10. Electromagnetic pump stator coil

    DOEpatents

    Fanning, A.W.; Dahl, L.R.

    1996-06-25

    An electrical stator coil for an electromagnetic pump includes a continuous conductor strip having first and second terminals at opposite ends thereof and an intermediate section disposed therebetween. The strip is configured in first and second coil halves, with the first coil half including a plurality of windings extending from the first terminal to the intermediate section, and the second coil half including a plurality of windings extending from the second terminal to the intermediate section. The first and second coil halves are disposed coaxially, and the first and second terminals are disposed radially inwardly therefrom with the intermediate section being disposed radially outwardly therefrom. 9 figs.

  11. Electromagnetic pump stator coil

    DOEpatents

    Fanning, Alan W.; Dahl, Leslie R.

    1996-01-01

    An electrical stator coil for an electromagnetic pump includes a continuous conductor strip having first and second terminals at opposite ends thereof and an intermediate section disposed therebetween. The strip is configured in first and second coil halves, with the first coil half including a plurality of windings extending from the first terminal to the intermediate section, and the second coil half including a plurality of windings extending from the second terminal to the intermediate section. The first and second coil halves are disposed coaxially, and the first and second terminals are disposed radially inwardly therefrom with the intermediate section being disposed radially outwardly therefrom.

  12. Development of an Extreme High Temperature n-type Ohmic Contact to Silicon Carbide

    NASA Technical Reports Server (NTRS)

    Evans, Laura J.; Okojie, Robert S.; Lukco, Dorothy

    2011-01-01

    We report on the initial demonstration of a tungsten-nickel (75:25 at. %) ohmic contact to silicon carbide (SiC) that performed for up to fifteen hours of heat treatment in argon at 1000 C. The transfer length method (TLM) test structure was used to evaluate the contacts. Samples showed consistent ohmic behavior with specific contact resistance values averaging 5 x 10-4 -cm2. The development of this contact metallization should allow silicon carbide devices to operate more reliably at the present maximum operating temperature of 600 C while potentially extending operations to 1000 C. Introduction Silicon Carbide (SiC) is widely recognized as one of the materials of choice for high temperature, harsh environment sensors and electronics due to its ability to survive and continue normal operation in such environments [1]. Sensors and electronics in SiC have been developed that are capable of operating at temperatures of 600 oC. However operating these devices at the upper reliability temperature threshold increases the potential for early degradation. Therefore, it is important to raise the reliability temperature ceiling higher, which would assure increased device reliability when operated at nominal temperature. There are also instances that require devices to operate and survive for prolonged periods of time above 600 oC [2, 3]. This is specifically needed in the area of hypersonic flight where robust sensors are needed to monitor vehicle performance at temperature greater than 1000 C, as well as for use in the thermomechanical characterization of high temperature materials (e.g. ceramic matrix composites). While SiC alone can withstand these temperatures, a major challenge is to develop reliable electrical contacts to the device itself in order to facilitate signal extraction

  13. Second-generation coil design of the Nb 3Sn low-β quadrupole for the high luminosity LHC

    DOE PAGES

    Bermudez, S. Izquierdo; Ambrosio, G.; Ballarino, A.; ...

    2016-01-18

    As part of the Large Hadron Collider Luminosity upgrade (HiLumi-LHC) program, the US LARP collaboration and CERN are working together to design and build a 150 mm aperture Nb 3Sn quadrupole for the LHC interaction regions. A first series of 1.5 m long coils were fabricated and assembled in a first short model. A detailed visual inspection of the coils was carried out to investigate cable dimensional changes during heat treatment and the position of the windings in the coil straight section and in the end region. The analyses allow identifying a set of design changes which, combined with amore » fine tune of the cable geometry and a field quality optimization, were implemented in a new, second-generation, coil design. In this study, we review the main characteristics of the first generation coils, describe the modification in coil lay-out, and discuss their impact on parts design and magnet analysis.« less

  14. Ohmic contact formation between metal and AlGaN/GaN heterostructure via graphene insertion

    NASA Astrophysics Data System (ADS)

    Sung Park, Pil; Reddy, Kongara M.; Nath, Digbijoy N.; Yang, Zhichao; Padture, Nitin P.; Rajan, Siddharth

    2013-04-01

    A simple method for the creation of Ohmic contact to 2D electron gas in AlGaN/GaN high electron-mobility transistors using Cr/graphene layer is demonstrated. A weak temperature dependence of this Ohmic contact observed in the range 77 to 300 K precludes thermionic emission or trap-assisted hopping as possible carrier-transport mechanisms. It is suggested that the Cr/graphene combination acts akin to a doped n-type semiconductor in contact with AlGaN/GaN heterostructure, and promotes carrier transport along percolating Al-lean paths through the AlGaN layer. This use of graphene offers a simple method for making Ohmic contacts to AlGaN/GaN heterostructures, circumventing complex additional processing steps involving high temperatures. These results could have important implications for the fabrication and manufacturing of AlGaN/GaN-based microelectronic and optoelectronic devices/sensors of the future.

  15. Coiled coil interactions for the targeting of liposomes for nucleic acid delivery

    NASA Astrophysics Data System (ADS)

    Oude Blenke, Erik E.; van den Dikkenberg, Joep; van Kolck, Bartjan; Kros, Alexander; Mastrobattista, Enrico

    2016-04-01

    Coiled coil interactions are strong protein-protein interactions that are involved in many biological processes, including intracellular trafficking and membrane fusion. A synthetic heterodimeric coiled-coil forming peptide pair, known as E3 (EIAALEK)3 and K3 (KIAALKE)3 was used to functionalize liposomes encapsulating a splice correcting oligonucleotide or siRNA. These peptide-functionalized vesicles are highly stable in solution but start to cluster when vesicles modified with complementary peptides are mixed together, demonstrating that the peptides quickly coil and crosslink the vesicles. When one of the peptides was anchored to the cell membrane using a hydrophobic cholesterol anchor, vesicles functionalized with the complementary peptide could be docked to these cells, whereas non-functionalized cells did not show any vesicle tethering. Although the anchored peptides do not have a downstream signaling pathway, microscopy pictures revealed that after four hours, the majority of the docked vesicles were internalized by endocytosis. Finally, for the first time, it was shown that the coiled coil assembly at the interface between the vesicles and the cell membrane induces active uptake and leads to cytosolic delivery of the nucleic acid cargo. Both the siRNA and the splice correcting oligonucleotide were functionally delivered, resulting respectively in the silencing or recovery of luciferase expression in the appropriate cell lines. These results demonstrate that the docking to the cell by coiled coil interaction can induce active uptake and achieve the successful intracellular delivery of otherwise membrane impermeable nucleic acids in a highly specific manner.Coiled coil interactions are strong protein-protein interactions that are involved in many biological processes, including intracellular trafficking and membrane fusion. A synthetic heterodimeric coiled-coil forming peptide pair, known as E3 (EIAALEK)3 and K3 (KIAALKE)3 was used to functionalize liposomes

  16. Linear Rogowski coil

    NASA Astrophysics Data System (ADS)

    Nassisi, V.; Delle Side, D.

    2017-02-01

    Nowadays, the employment and development of fast current pulses require sophisticated systems to perform measurements. Rogowski coils are used to diagnose cylindrical shaped beams; therefore, they are designed and built with a toroidal structure. Recently, to perform experiments of radiofrequency biophysical stresses, flat transmission lines have been developed. Therefore, in this work we developed a linear Rogowski coil to detect current pulses inside flat conductors. The system is first approached by means of transmission line theory. We found that, if the pulse width to be diagnosed is comparable with the propagation time of the signal in the detector, it is necessary to impose a uniform current as input pulse, or to use short coils. We further analysed the effect of the resistance of the coil and the influence of its magnetic properties. As a result, the device we developed is able to record pulses lasting for some hundreds of nanoseconds, depending on the inductance, load impedance, and resistance of the coil. Furthermore, its response is characterized by a sub-nanosecond rise time (˜100 ps). The attenuation coefficient depends mainly on the turn number of the coil, while the fidelity of the response depends both on the magnetic core characteristics and on the current distribution along the plane conductors.

  17. Experimental approach to investigate the constrained recovery behavior of coiled monofilament polymer fibers

    NASA Astrophysics Data System (ADS)

    Mendes, S. S.; Nunes, L. C. S.

    2017-11-01

    The aim of this work is to propose a new approach for investigating the thermo-mechanical behavior of coiled oriented polymer fibers with fixed ends and promote an understanding of the actuation response of coiled polymers in constrained recovery applications. In the proposed experimental methodology, a coiled fiber was pre-stretched by 50% and the distance between its ends remained constant, then it was subjected to a heating-cooling cycle ranging from 30 °C to 120 °C and the induced restoring force was measured. Based on these measurements, axial deformation and shear strain were obtained from full-field displacements extracted by the digital image correlation method from images of the coiled fiber. Three coiled fibers with different initial pitch angles were manufactured, and samples with lengths of 15 mm and 20 mm were tested. Bias angles and coil radius were also estimated using the experimental data associated with the helical spring theory. Results show that significant shape changes can be noticed above the glass transition temperature (47 °C), and these changes induce variation in the resultant forces. The effects of thermal softening and thermal contraction for a modest negative thermal expansion coefficient became evident at temperatures ranging from ∼47 °C to ∼90 °C, while the response of a coiled homochiral polymer fiber was achieved at temperatures close to 90 °C. During the cooling process, saturated states of the axial deformation and shear strain of the coiled fibers were observed at temperatures between 120 °C and 100 °C.

  18. Degradation mechanisms of Ti/Al/Ni/Au-based Ohmic contacts on AlGaN/GaN HEMTs

    DOE PAGES

    Hwang, Ya-Hsi; Ahn, Shihyun; Dong, Chen; ...

    2015-04-27

    We investigated the degradation mechanism of Ti/Al/Ni/Au-based Ohmic metallization on AlGaN/GaN high electron mobility transistors upon exposure to buffer oxide etchant (BOE). The major effect of BOE on the Ohmic metal was an increase of sheet resistance from 2.89 to 3.69 Ω/ₜafter 3 min BOE treatment. The alloyed Ohmic metallization consisted 3–5 μm Ni-Al alloy islands surrounded by Au-Al alloy-rings. The morphology of both the islands and ring areas became flatter after BOE etching. Lastly, we used energy dispersive x-ray analysis and Auger electron microscopy to analyze the compositions and metal distributions in the metal alloys prior to and aftermore » BOE exposure.« less

  19. Conceptual design and thermal analysis of a modular cryostat for one single coil of a 10 MW offshore superconducting wind turbine

    NASA Astrophysics Data System (ADS)

    Sun, Jiuce; Sanz, Santiago; Neumann, Holger

    2015-12-01

    Superconducting generators show the potential to reduce the head mass of large offshore wind turbines. A 10 MW offshore superconducting wind turbine has been investigated in the SUPRAPOWER project. The superconducting coils based on MgB2 tapes are supposed to work at cryogenic temperature of 20 K. In this paper, a novel modular rotating cryostat was presented for one single coil of the superconducting wind turbine. The modular concept and cryogen-free cooling method were proposed to fulfil the requirements of handling, maintenance, reliability of long term and offshore operations. Two stage Gifford-McMahon cryocoolers were used to provide cooling source. Supporting rods made of titanium alloy were selected as support structures of the cryostat in aim of reducing the heat load. The thermal performance in the modular cryostat was carefully investigated. The heat load applied to the cryocooler second stage was 2.17 W@20 K per coil. The corresponding temperature difference along the superconducting coil was only around 1 K.

  20. Unraveling double stranded alpha-helical coiled coils: an x-ray diffraction study on hard alpha-keratin fibers.

    PubMed

    Kreplak, L; Doucet, J; Briki, F

    2001-04-15

    Transformations of proteins secondary and tertiary structures are generally studied in globular proteins in solution. In fibrous proteins, such as hard alpha-keratin, that contain long and well-defined double stranded alpha-helical coiled coil domains, such study can be directly done on the native fibrous tissue. In order to assess the structural behavior of the coiled coil domains under an axial mechanical stress, wide angle x-ray scattering and small angle x-ray scattering experiments have been carried out on stretched horse hair fibers at relative humidity around 30%. Our observations of the three major axial spacings as a function of the applied macroscopic strain have shown two rates. Up to 4% macroscopic strain the coiled coils were slightly distorted but retained their overall conformation. Above 4% the proportion of coiled coil domains progressively decreased. The main and new result of our study is the observation of the transition from alpha-helical coiled coils to disordered chains instead of the alpha-helical coiled coil to beta-sheet transition that occurs in wet fibers.

  1. High Temperature Characteristics of Pt/TaSi2/Pt/W and Pt/Ti/W Diffusion Barrier Systems for Ohmic Contacts to 4H-SiC

    NASA Technical Reports Server (NTRS)

    Okojie, Robert S.; Lukco, Dorothy

    2017-01-01

    The degradation of ohmic contacts to 4H-SiC pressure sensors over time at high temperature is primarily due to two failure mechanisms: migrating bond pad Au and atmospheric O toward the ohmic contact SiC interface and the inter-metallic mixing between diffusion barrier systems (DBS) and the underlying ohmic contact metallization. We investigated the effectiveness of Pt/TaSi2/Pt/W (DBS-A) and Pt/Ti/W (DBS-B) in preventing Au and O diffusion through the underlying binary Ti/W or alloyed W50:Ni50 ohmic contacts to 4H-SiC and the DBS ohmic contact intermixing at temperature up to 700 C.

  2. Heat exchanger-accumulator

    DOEpatents

    Ecker, Amir L.

    1980-01-01

    What is disclosed is a heat exchanger-accumulator for vaporizing a refrigerant or the like, characterized by an upright pressure vessel having a top, bottom and side walls; an inlet conduit eccentrically and sealingly penetrating through the top; a tubular overflow chamber disposed within the vessel and sealingly connected with the bottom so as to define an annular outer volumetric chamber for receiving refrigerant; a heat transfer coil disposed in the outer volumetric chamber for vaporizing the liquid refrigerant that accumulates there; the heat transfer coil defining a passageway for circulating an externally supplied heat exchange fluid; transferring heat efficiently from the fluid; and freely allowing vaporized refrigerant to escape upwardly from the liquid refrigerant; and a refrigerant discharge conduit penetrating sealingly through the top and traversing substantially the length of the pressurized vessel downwardly and upwardly such that its inlet is near the top of the pressurized vessel so as to provide a means for transporting refrigerant vapor from the vessel. The refrigerant discharge conduit has metering orifices, or passageways, penetrating laterally through its walls near the bottom, communicating respectively interiorly and exteriorly of the overflow chamber for controllably carrying small amounts of liquid refrigerant and oil to the effluent stream of refrigerant gas.

  3. A new type of coil structure called pan-shaped coil of wireless charging system based on magnetic resonance

    NASA Astrophysics Data System (ADS)

    Yue, Z. K.; Liu, Z. Z.; Hou, Y. J.; Zeng, H.; Liang, L. H.; Cui, S.

    2017-11-01

    The problem that misalignment between the transmitting coil and the receiving coil significantly impairs the transmission power and efficiency of the system has been attached more and more attention. In order to improve the uniformity of the magnetic field between the two coils to solve this problem, a new type of coil called pan-shaped coil is proposed. Three-dimension simulation models of the planar-core coil and the pan-shaped coil are established using Ansoft Maxwell software. The coupling coefficient between the transmitting coil and the receiving coil is obtained by simulating the magnetic field with the receiving coil misalignment or not. And the maximum percentage difference strength along the radial direction which is defined as the magnetic field uniformity factor is calculated. According to the simulation results of the two kinds of coil structures, it is found that the new type of coil structure can obviously improve the uniformity of the magnetic field, coupling coefficient and power transmission properties between the transmitting coil and the receiving coil.

  4. A Thermal Performance Analysis and Comparison of Fiber Coils with the D-CYL Winding and QAD Winding Methods.

    PubMed

    Li, Xuyou; Ling, Weiwei; He, Kunpeng; Xu, Zhenlong; Du, Shitong

    2016-06-16

    The thermal performance under variable temperature conditions of fiber coils with double-cylinder (D-CYL) and quadrupolar (QAD) winding methods is comparatively analyzed. Simulation by the finite element method (FEM) is done to calculate the temperature distribution and the thermal-induced phase shift errors in the fiber coils. Simulation results reveal that D-CYL fiber coil itself has fragile performance when it experiences an axially asymmetrical temperature gradient. However, the axial fragility performance could be improved when the D-CYL coil meshes with a heat-off spool. Through further simulations we find that once the D-CYL coil is provided with an axially symmetrical temperature environment, the thermal performance of fiber coils with the D-CYL winding method is better than that with the QAD winding method under the same variable temperature conditions. This valuable discovery is verified by two experiments. The D-CYL winding method is thus promising to overcome the temperature fragility of interferometric fiber optic gyroscopes (IFOGs).

  5. A Thermal Performance Analysis and Comparison of Fiber Coils with the D-CYL Winding and QAD Winding Methods

    PubMed Central

    Li, Xuyou; Ling, Weiwei; He, Kunpeng; Xu, Zhenlong; Du, Shitong

    2016-01-01

    The thermal performance under variable temperature conditions of fiber coils with double-cylinder (D-CYL) and quadrupolar (QAD) winding methods is comparatively analyzed. Simulation by the finite element method (FEM) is done to calculate the temperature distribution and the thermal-induced phase shift errors in the fiber coils. Simulation results reveal that D-CYL fiber coil itself has fragile performance when it experiences an axially asymmetrical temperature gradient. However, the axial fragility performance could be improved when the D-CYL coil meshes with a heat-off spool. Through further simulations we find that once the D-CYL coil is provided with an axially symmetrical temperature environment, the thermal performance of fiber coils with the D-CYL winding method is better than that with the QAD winding method under the same variable temperature conditions. This valuable discovery is verified by two experiments. The D-CYL winding method is thus promising to overcome the temperature fragility of interferometric fiber optic gyroscopes (IFOGs). PMID:27322271

  6. Performance evaluation of matrix gradient coils.

    PubMed

    Jia, Feng; Schultz, Gerrit; Testud, Frederik; Welz, Anna Masako; Weber, Hans; Littin, Sebastian; Yu, Huijun; Hennig, Jürgen; Zaitsev, Maxim

    2016-02-01

    In this paper, we present a new performance measure of a matrix coil (also known as multi-coil) from the perspective of efficient, local, non-linear encoding without explicitly considering target encoding fields. An optimization problem based on a joint optimization for the non-linear encoding fields is formulated. Based on the derived objective function, a figure of merit of a matrix coil is defined, which is a generalization of a previously known resistive figure of merit for traditional gradient coils. A cylindrical matrix coil design with a high number of elements is used to illustrate the proposed performance measure. The results are analyzed to reveal novel features of matrix coil designs, which allowed us to optimize coil parameters, such as number of coil elements. A comparison to a scaled, existing multi-coil is also provided to demonstrate the use of the proposed performance parameter. The assessment of a matrix gradient coil profits from using a single performance parameter that takes the local encoding performance of the coil into account in relation to the dissipated power.

  7. Development of model for studies on momentum transfer in electrochemical cells with entry region coil as turbulence promoter

    NASA Astrophysics Data System (ADS)

    Penta Rao, Tamarba; Rajendra Prasad, P.

    2018-04-01

    Entry region swirl promoters gain importance in industry because of its effectiveness in augmentation of mass and heat transfer augmentation. Design of equipment needs momentum transfer data along with mass or heat transfer data. Hence an experimental investigation was carried out with coaxially placed entry region spiral coil as turbulence promoters on momentum transfer in forced convection flow of electrolyte in circular conduits. Aqueous solution of sodium hydroxide and 0.01 M equimolal Ferri-ferro cyanide system was chosen for the study. The study covered parameters like effect of pitch of the coil, effect of length of the coil, diameter of the coil, diameter of the coil wire, diameter of the annular rod. The promoter is measured by limiting current technique using diffusion controlled electrochemical reactions. The study comprises of evaluation of momentum transfer rates at the outer wall of the electrochemical cell. Pressure drop measurements were also made to obtain the energy consumption pattern. Within the range of variables covered. The results are correlated by the momentum transfer similarity function. Momentum transfer coefficients were evaluated from measured limiting currents. Effect of each parameter was studied in terms of friction factor. A model was developed for momentum transfer. The experimental data on momentum transfer was modeled in terms of momentum transfer function and Reynolds number, geometric parameters.

  8. Induction heating coupler and annealer

    NASA Technical Reports Server (NTRS)

    Fox, Robert L. (Inventor); Johnson, Samuel D. (Inventor); Copeland, Carl E. (Inventor); Coultrip, Robert H. (Inventor); Phillips, W. Morris (Inventor); Johnston, David F. (Inventor); Swaim, Robert J. (Inventor); Dinkins, James R. (Inventor)

    1994-01-01

    An induction heating device includes a handle having a hollow interior and two opposite ends, a wrist connected to one end of the handle, a U-shaped pole piece having- two spaced apart ends, a tank circuit including an induction coil wrapped around the pole piece and a capacitor connected to the induction coil, a head connected to the wrist and including a housing for receiving the U-shaped pole piece, the two spaced apart ends of the pole piece extending outwardly beyond the housing, and a power source connected to the tank circuit. When the tank circuit is energized and a susceptor is placed in juxtaposition to the ends of the U-shaped pole piece, the susceptor is heated by induction heating due to a magnetic flux passing between the two ends of the pole piece.

  9. Computational study for the effects of coil configuration on blood flow characteristics in coil-embolized cerebral aneurysm.

    PubMed

    Otani, Tomohiro; Ii, Satoshi; Shigematsu, Tomoyoshi; Fujinaka, Toshiyuki; Hirata, Masayuki; Ozaki, Tomohiko; Wada, Shigeo

    2017-05-01

    Coil embolization of cerebral aneurysms with inhomogeneous coil distribution leads to an incomplete occlusion of the aneurysm. However, the effects of this factor on the blood flow characteristics are still not fully understood. This study investigates the effects of coil configuration on the blood flow characteristics in a coil-embolized aneurysm using computational fluid dynamics (CFD) simulation. The blood flow analysis in the aneurysm with coil embolization was performed using a coil deployment (CD) model, in which the coil configuration was constructed using a physics-based simulation of the CD. In the CFD results, total flow momentum and kinetic energy in the aneurysm gradually decayed with increasing coil packing density (PD), regardless of the coil configuration attributed to deployment conditions. However, the total shear rate in the aneurysm was relatively high and the strength of the local shear flow varied based on the differences in coil configuration, even at adequate PDs used in clinical practice (20-25 %). Because the sufficient shear rate reduction is a well-known factor in the blood clot formation occluding the aneurysm inside, the present study gives useful insight into the effects of coil configuration on the treatment efficiency of coil embolization.

  10. Suppression of skeletal muscle signal using a crusher coil: A human cardiac (31) p-MR spectroscopy study at 7 tesla.

    PubMed

    Schaller, Benoit; Clarke, William T; Neubauer, Stefan; Robson, Matthew D; Rodgers, Christopher T

    2016-03-01

    The translation of sophisticated phosphorus MR spectroscopy ((31)P-MRS) protocols to 7 Tesla (T) is particularly challenged by the issue of radiofrequency (RF) heating. Legal limits on RF heating make it hard to reliably suppress signals from skeletal muscle that can contaminate human cardiac (31)P spectra at 7T. We introduce the first surface-spoiling crusher coil for human cardiac (31)P-MRS at 7T. A planar crusher coil design was optimized with simulations and its performance was validated in phantoms. Crusher gradient pulses (100 μs) were then applied during human cardiac (31)P-MRS at 7T. In a phantom, residual signals were 50 ± 10% with BISTRO (B1 -insensitive train to obliterate signal), and 34 ± 8% with the crusher coil. In vivo, residual signals in skeletal muscle were 49 ± 4% using BISTRO, and 24 ± 5% using the crusher coil. Meanwhile, in the interventricular septum, spectral quality and metabolite quantification did not differ significantly between BISTRO (phosphocreatine/adenosine triphosphate [PCr/ATP] = 2.1 ± 0.4) and the crusher coil (PCr/ATP = 1.8 ± 0.4). However, the specific absorption rate (SAR) decreased from 96 ± 1% of the limit (BISTRO) to 16 ± 1% (crusher coil). A crusher coil is an SAR-efficient alternative for selectively suppressing skeletal muscle during cardiac (31)P-MRS at 7T. A crusher coil allows the use of sequence modules that would have been SAR-prohibitive, without compromising skeletal muscle suppression. © 2015 The Authors. Magnetic Resonance in Medicine Published by Wiley Periodicals, Inc. on behalf of International Society of Medicine in Resonance.

  11. Formation and characterization of Ni/Al Ohmic contact on n+-type GeSn

    NASA Astrophysics Data System (ADS)

    Zhang, Xu; Zhang, Dongliang; Zheng, Jun; Liu, Zhi; He, Chao; Xue, Chunlai; Zhang, Guangze; Li, Chuanbo; Cheng, Buwen; Wang, Qiming

    2015-12-01

    In this study, a Ni/Al Ohmic contact on a highly doped n-type GeSn has been investigated. A specific contact resistivity as low as (2.26 ± 0.11) × 10-4 Ω cm2 was obtained with the GeSn sample annealed at a temperature of 450 °C for 30 s. The linear Ohmic behavior was attributed to the low resistance of the Ni(GeSn) phase; this behavior was determined using glancing-angle X-ray diffraction, and the quantum tunneling current through the Schottky barrier narrowed because of high doping; this phenomenon was confirmed from the contact resistance characteristics at different temperatures from 45 to 205 K.

  12. Inductively coupled wireless RF coil arrays.

    PubMed

    Bulumulla, S B; Fiveland, E; Park, K J; Foo, T K; Hardy, C J

    2015-04-01

    As the number of coils increases in multi-channel MRI receiver-coil arrays, RF cables and connectors become increasingly bulky and heavy, degrading patient comfort and slowing workflow. Inductive coupling of signals provides an attractive "wireless" approach, with the potential to reduce coil weight and cost while simplifying patient setup. In this work, multi-channel inductively coupled anterior arrays were developed and characterized for 1.5T imaging. These comprised MR receiver coils inductively (or "wirelessly") linked to secondary or "sniffer" coils whose outputs were transmitted via preamps to the MR system cabinet. The induced currents in the imaging coils were blocked by passive diode circuits during RF transmit. The imaging arrays were totally passive, obviating the need to deliver power to the coils, and providing lightweight, untethered signal reception with easily positioned coils. Single-shot fast spin echo images were acquired from 5 volunteers using a 7-element inductively coupled coil array and a conventionally cabled 7-element coil array of identical geometry, with the inductively-coupled array showing a relative signal-to-noise ratio of 0.86 +/- 0.07. The concept was extended to a larger 9-element coil array to demonstrate the effect of coil element size on signal transfer and RF-transmit blocking. Copyright © 2015 Elsevier Inc. All rights reserved.

  13. Fifty years of coiled-coils and alpha-helical bundles: a close relationship between sequence and structure.

    PubMed

    Parry, David A D; Fraser, R D Bruce; Squire, John M

    2008-09-01

    alpha-Helical coiled coils are remarkable for the diversity of related conformations that they adopt in both fibrous and globular proteins, and for the range of functions that they exhibit. The coiled coils are based on a heptad (7-residue), hendecad (11-residue) or a related quasi-repeat of apolar residues in the sequences of the alpha-helical regions involved. Most of these, however, display one or more sequence discontinuities known as stutters or stammers. The resulting coiled coils vary in length, in the number of chains participating, in the relative polarity of the contributing alpha-helical regions (parallel or antiparallel), and in the pitch length and handedness of the supercoil (left- or right-handed). Functionally, the concept that a coiled coil can act only as a static rod is no longer valid, and the range of roles that these structures have now been shown to exhibit has expanded rapidly in recent years. An important development has been the recognition that the delightful simplicity that exists between sequence and structure, and between structure and function, allows coiled coils with specialized features to be designed de novo.

  14. Electrical, Chemical, And Microstructural Analysis of the Thermal Stability of Nickel-based Ohmic Contacts to Silicon Carbide for High-Temperature Electronics

    NASA Astrophysics Data System (ADS)

    Virshup, Ariel R.

    With increasing attention on curbing the emission of pollutants into the atmosphere, chemical sensors that can be used to monitor and control these unwanted emissions are in great demand. Examples include monitoring of hydrocarbons from automobile engines and monitoring of flue gases such as CO emitted from power plants. One of the critical limitations in high-temperature SiC gas sensors, however, is the degradation of the metal-SiC contacts over time. In this dissertation, we investigated the high-temperature stability of Pt/TaSix/Ni/SiC ohmic contacts, which have been implemented in SiC-based gas sensors developed for applications in diesel engines and power plants. The high-temperature stability of a Pt/TaSi2/Ni/SiC ohmic contact metallization scheme was characterized using a combination of current-voltage measurements, Auger electron spectroscopy, secondary ion mass spectrometry, and transmission electron microscope imaging and associated analytical techniques. Increasing the thicknesses of the Pt and TaSi2 layers promoted electrical stability of the contacts, which remained ohmic at 600°C in air for over 300 h; the specific contact resistance showed only a gradual increase from an initial value of 5.2 x 10-5 O-cm 2. We observed a continuous silicon-oxide layer in the thinner contact structures, which failed after 36 h of heating. It was found that the interface between TaSix and NiySi was weakened by the accumulation of free carbon (produced by the reaction of Ni and SiC), which in turn facilitated oxygen diffusion from the contact edges. Additional oxygen diffusion occurred along grain boundaries in the Pt overlayer. Meanwhile, thicker contacts, with less interfacial free carbon and enhanced electrical stability contained a much lower oxygen concentration that was distributed across the contact layers, precluding the formation of an electrically insulating contact structure.

  15. Heat pump system with selective space cooling

    DOEpatents

    Pendergrass, J.C.

    1997-05-13

    A reversible heat pump provides multiple heating and cooling modes and includes a compressor, an evaporator and heat exchanger all interconnected and charged with refrigerant fluid. The heat exchanger includes tanks connected in series to the water supply and a condenser feed line with heat transfer sections connected in counterflow relationship. The heat pump has an accumulator and suction line for the refrigerant fluid upstream of the compressor. Sub-cool transfer tubes associated with the accumulator/suction line reclaim a portion of the heat from the heat exchanger. A reversing valve switches between heating/cooling modes. A first bypass is operative to direct the refrigerant fluid around the sub-cool transfer tubes in the space cooling only mode and during which an expansion valve is utilized upstream of the evaporator/indoor coil. A second bypass is provided around the expansion valve. A programmable microprocessor activates the first bypass in the cooling only mode and deactivates the second bypass, and vice-versa in the multiple heating modes for said heat exchanger. In the heating modes, the evaporator may include an auxiliary outdoor coil for direct supplemental heat dissipation into ambient air. In the multiple heating modes, the condensed refrigerant fluid is regulated by a flow control valve. 4 figs.

  16. Heat pump system with selective space cooling

    DOEpatents

    Pendergrass, Joseph C.

    1997-01-01

    A reversible heat pump provides multiple heating and cooling modes and includes a compressor, an evaporator and heat exchanger all interconnected and charged with refrigerant fluid. The heat exchanger includes tanks connected in series to the water supply and a condenser feed line with heat transfer sections connected in counterflow relationship. The heat pump has an accumulator and suction line for the refrigerant fluid upstream of the compressor. Sub-cool transfer tubes associated with the accumulator/suction line reclaim a portion of the heat from the heat exchanger. A reversing valve switches between heating/cooling modes. A first bypass is operative to direct the refrigerant fluid around the sub-cool transfer tubes in the space cooling only mode and during which an expansion valve is utilized upstream of the evaporator/indoor coil. A second bypass is provided around the expansion valve. A programmable microprocessor activates the first bypass in the cooling only mode and deactivates the second bypass, and vice-versa in the multiple heating modes for said heat exchanger. In the heating modes, the evaporator may include an auxiliary outdoor coil for direct supplemental heat dissipation into ambient air. In the multiple heating modes, the condensed refrigerant fluid is regulated by a flow control valve.

  17. High frequency-heated air turbojet

    NASA Technical Reports Server (NTRS)

    Miron, J. H. D.

    1986-01-01

    A description is given of a method to heat air coming from a turbojet compressor to a temperature necessary to produce required expansion without requiring fuel. This is done by high frequency heating, which heats the walls corresponding to the combustion chamber in existing jets, by mounting high frequency coils in them. The current transformer and high frequency generator to be used are discussed.

  18. Manufacturing and test of 2G-HTS coils for rotating machines: Challenges, conductor requirements, realization

    NASA Astrophysics Data System (ADS)

    Oomen, Marijn; Herkert, Werner; Bayer, Dietmar; Kummeth, Peter; Nick, Wolfgang; Arndt, Tabea

    2012-11-01

    We investigate the use of 2nd-generation High-Temperature Superconductors (2G-HTSs) in the rotors of electrical motors and generators. For these devices the conductor must be wound into robust impregnated coils, which are operated in vacuum at temperatures around 30 K, in strong magnetic fields of about 2T. Differences in thermal contraction between the coil former, conductor constituents, impregnation resin, bandage and heat-sink materials (assembled at room temperature) cause mechanical stresses at operating temperature. Rotating-machine operation adds Lorentz forces and challenging centripetal accelerations up to thousands of g. Second generation-HTS conductors withstand large tensile stresses in axial direction and compression in normal direction. However, shear stresses, axial compression, and tension normal to the conductor can cause degradation in superconducting properties. Such stresses can be mitigated by correct choice of materials, coil lay-out and manufacturing process. A certain stress level will remain, which the conductor must withstand. We have manufactured many impregnated round and race-track coils, using different 2G-HTS conductors, and tested them at temperatures from 25 K to 77 K. Degradation of the superconductor in early coils was traced to the mentioned differences in thermal contraction, and was completely avoided in coils produced later. We will discuss appropriate coil-winding techniques to assure robust and reliable superconductor performance.

  19. Eight channel transmit array volume coil using on-coil radiofrequency current sources

    PubMed Central

    Kurpad, Krishna N.; Boskamp, Eddy B.

    2014-01-01

    Background At imaging frequencies associated with high-field MRI, the combined effects of increased load-coil interaction and shortened wavelength results in degradation of circular polarization and B1 field homogeneity in the imaging volume. Radio frequency (RF) shimming is known to mitigate the problem of B1 field inhomogeneity. Transmit arrays with well decoupled transmitting elements enable accurate B1 field pattern control using simple, non-iterative algorithms. Methods An eight channel transmit array was constructed. Each channel consisted of a transmitting element driven by a dedicated on-coil RF current source. The coil current distributions of characteristic transverse electromagnetic (TEM) coil resonant modes were non-iteratively set up on each transmitting element and 3T MRI images of a mineral oil phantom were obtained. Results B1 field patterns of several linear and quadrature TEM coil resonant modes that typically occur at different resonant frequencies were replicated at 128 MHz without having to retune the transmit array. The generated B1 field patterns agreed well with simulation in most cases. Conclusions Independent control of current amplitude and phase on each transmitting element was demonstrated. The transmit array with on-coil RF current sources enables B1 field shimming in a simple and predictable manner. PMID:24834418

  20. Dimensional changes of Nb 3Sn Rutherford cables during heat treatment

    DOE PAGES

    Rochepault, E.; Ferracin, P.; Ambrosio, G.; ...

    2016-06-01

    In high field magnet applications, Nb 3Sn coils undergo a heat treatment step after winding. During this stage, coils radially expand and longitudinally contract due to the Nb 3Sn phase change. In order to prevent residual strain from altering superconducting performances, the tooling must provide the adequate space for these dimensional changes. The aim of this paper is to understand the behavior of cable dimensions during heat treatment and to provide estimates of the space to be accommodated in the tooling for coil expansion and contraction. In addition, this paper summarizes measurements of dimensional changes on strands, single Rutherford cables,more » cable stacks, and coils performed between 2013 and 2015. These samples and coils have been performed within a collaboration between CERN and the U.S. LHC Accelerator Research Program to develop Nb 3Sn quadrupole magnets for the HiLumi LHC. The results are also compared with other high field magnet projects.« less

  1. Effect of reflective p-type ohmic contact on thermal reliability of vertical InGaN/GaN LEDs

    NASA Astrophysics Data System (ADS)

    Son, Jun Ho; Song, Yang Hee; Kim, Buem Joon; Lee, Jong-Lam

    2014-11-01

    We report on the enhanced thermal reliability of vertical-LEDs (VLEDs) using novel reflective p-type ohmic contacts with good thermal stability. The reflective p-type ohmic contacts with Ni/Ag-Cu alloy multi-layer structure shows low contact resistivity, as low as 9.3 × 10-6 Ωcm2, and high reflectance of 86% after annealing at 450°C. The V-LEDs with Ni/Ag-Cu alloy multi-layer structure show good thermal reliability with stress time at 300°C in air ambient. The improved thermal stability of the reflective ohmic contacts to p-type GaN is believed to play a critical role in the thermal reliability of V-LEDs. [Figure not available: see fulltext.

  2. Transparent ohmic contacts for solution-processed, ultrathin CdTe solar cells

    DOE PAGES

    Kurley, J. Matthew; Panthani, Matthew G.; Crisp, Ryan W.; ...

    2016-12-19

    Recently, solution-processing became a viable route for depositing CdTe for use in photovoltaics. Ultrathin (~500 nm) solar cells have been made using colloidal CdTe nanocrystals with efficiencies exceeding 12% power conversion efficiency (PCE) demonstrated by using very simple device stacks. Further progress requires an effective method for extracting charge carriers generated during light harvesting. Here, we explored solution-based methods for creating transparent Ohmic contacts to the solution-deposited CdTe absorber layer and demonstrated molecular and nanocrystal approaches to Ohmic hole-extracting contacts at the ITO/CdTe interface. Furthermore, we used scanning Kelvin probe microscopy to further show how the above approaches improved carriermore » collection by reducing the potential drop under reverse bias across the ITO/CdTe interface. Other methods, such as spin-coating CdTe/A 2CdTe 2 (A = Na, K, Cs, N 2H 5), can be used in conjunction with current/light soaking to improve PCE further.« less

  3. Evaluation of persistent-mode operation in a superconducting MgB2 coil in solid nitrogen

    NASA Astrophysics Data System (ADS)

    Patel, Dipak; Hossain, Md Shahriar Al; See, Khay Wai; Qiu, Wenbin; Kobayashi, Hiroki; Ma, Zongqing; Kim, Seong Jun; Hong, Jonggi; Park, Jin Yong; Choi, Seyong; Maeda, Minoru; Shahabuddin, Mohammed; Rindfleisch, Matt; Tomsic, Mike; Xue Dou, Shi; Kim, Jung Ho

    2016-04-01

    We report the fabrication of a magnesium diboride (MgB2) coil and evaluate its persistent-mode operation in a system cooled by a cryocooler with solid nitrogen (SN2) as a cooling medium. The main purpose of SN2 was to increase enthalpy of the cold mass. For this work, an in situ processed carbon-doped MgB2 wire was used. The coil was wound on a stainless steel former in a single layer (22 turns), with an inner diameter of 109 mm and height of 20 mm without any insulation. The two ends of the coil were then joined to make a persistent-current switch to obtain the persistent-current mode. After a heat treatment, the whole coil was installed in the SN2 chamber. During operation, the resultant total circuit resistance was estimated to be <7.4 × 10-14 Ω at 19.5 K ± 1.5 K, which meets the technical requirement for magnetic resonance imaging application.

  4. Reduction of resonant RF heating in intravascular catheters using coaxial chokes.

    PubMed

    Ladd, M E; Quick, H H

    2000-04-01

    The incorporation of RF coils into the tips of intravascular devices has been shown to enable the localization of catheters and guidewires under MR guidance. Furthermore, such coils can be used for endoluminal imaging. The long cable required to connect the coil with the scanner input inadvertently acts as a dipole antenna which picks up RF energy from the body coil during transmit. Currents are induced on the cable which can lead to localized heating of surrounding tissue. Cables of various lengths were measured to determine if a resonance in the heating as a function of cable length could be found. Coaxial chokes with a length of lambda/4 were added to coaxial cables to reduce the amplitude of the currents induced on the cable shield. A 0.7-mm diameter triaxial cable, small enough to fit into a standard intravascular device, was developed and measured both with and without a coaxial choke. It is demonstrated that resonant heating does occur and that it can be significantly reduced by avoiding a resonant length of cable and by including coaxial chokes on the cable.

  5. Nanoscale electro-structural characterisation of ohmic contacts formed on p-type implanted 4H-SiC

    NASA Astrophysics Data System (ADS)

    Frazzetto, Alessia; Giannazzo, Filippo; Lo Nigro, Raffaella; di Franco, Salvatore; Bongiorno, Corrado; Saggio, Mario; Zanetti, Edoardo; Raineri, Vito; Roccaforte, Fabrizio

    2011-12-01

    This work reports a nanoscale electro-structural characterisation of Ti/Al ohmic contacts formed on p-type Al-implanted silicon carbide (4H-SiC). The morphological and the electrical properties of the Al-implanted layer, annealed at 1700°C with or without a protective capping layer, and of the ohmic contacts were studied using atomic force microscopy [AFM], transmission line model measurements and local current measurements performed with conductive AFM. The characteristics of the contacts were significantly affected by the roughness of the underlying SiC. In particular, the surface roughness of the Al-implanted SiC regions annealed at 1700°C could be strongly reduced using a protective carbon capping layer during annealing. This latter resulted in an improved surface morphology and specific contact resistance of the Ti/Al ohmic contacts formed on these regions. The microstructure of the contacts was monitored by X-ray diffraction analysis and a cross-sectional transmission electron microscopy, and correlated with the electrical results.

  6. Passive radiative cooling of a HTS coil for attitude orbit control in micro-spacecraft

    NASA Astrophysics Data System (ADS)

    Inamori, Takaya; Ozaki, Naoya; Saisutjarit, Phongsatorn; Ohsaki, Hiroyuki

    2015-02-01

    This paper proposes a novel radiative cooling system for a high temperature superconducting (HTS) coil for an attitude orbit control system in nano- and micro-spacecraft missions. These days, nano-spacecraft (1-10 kg) and micro-spacecraft (10-100 kg) provide space access to a broader range of spacecraft developers and attract interest as space development applications. In planetary and high earth orbits, most previous standard-size spacecraft used thrusters for their attitude and orbit control, which are not available for nano- and micro-spacecraft missions because of the strict power consumption, space, and weight constraints. This paper considers orbit and attitude control methods that use a superconducting coil, which interacts with on-orbit space plasmas and creates a propulsion force. Because these spacecraft cannot use an active cooling system for the superconducting coil because of their mass and power consumption constraints, this paper proposes the utilization of a passive radiative cooling system, in which the superconducting coil is thermally connected to the 3 K cosmic background radiation of deep space, insulated from the heat generation using magnetic holders, and shielded from the sun. With this proposed cooling system, the HTS coil is cooled to 60 K in interplanetary orbits. Because the system does not use refrigerators for its cooling system, the spacecraft can achieve an HTS coil with low power consumption, small mass, and low cost.

  7. Correction coil cable

    DOEpatents

    Wang, S.T.

    1994-11-01

    A wire cable assembly adapted for the winding of electrical coils is taught. A primary intended use is for use in particle tube assemblies for the Superconducting Super Collider. The correction coil cables have wires collected in wire array with a center rib sandwiched therebetween to form a core assembly. The core assembly is surrounded by an assembly housing having an inner spiral wrap and a counter wound outer spiral wrap. An alternate embodiment of the invention is rolled into a keystoned shape to improve radial alignment of the correction coil cable on a particle tube in a particle tube assembly. 7 figs.

  8. ELECTRICAL COIL STRUCTURE

    DOEpatents

    Baker, W.R.; Hartwig, A.

    1962-09-25

    A compactly wound electrical coil is designed for carrying intense pulsed currents such as are characteristic of controlled thermonuclear reaction devices. A flat strip of conductor is tightly wound in a spiral with a matching flat strip of insulator. To provide for a high fluid coolant flow through the coil with minimum pumping pressure, a surface of the conductor is scored with parallel transverse grooves which form short longitudinal coolant pasaages when the conductor is wound in the spiral configuration. Owing to this construction, the coil is extremely resistant to thermal and magnetic shock from sudden high currents. (AEC)

  9. Au-Doped Indium Tin Oxide Ohmic Contacts to p-Type GaN

    NASA Astrophysics Data System (ADS)

    Guo, H.; Andagana, H. B.; Cao, X. A.

    2010-05-01

    Indium tin oxide (ITO) thin films doped with Au, Ni, or Pt (3.5 at.% to 10.5 at.%) were deposited on p-GaN epilayers (Mg ~4 × 1019 cm-3) using direct-current (DC) sputter codeposition. It was found that undoped ITO con- tacts to p-GaN exhibited leaky Schottky behavior, whereas the incorporation of a small amount of Au (3.5 at.% to 10.5 at.%) significantly improved their ohmic characteristics. Compared with standard Ni/ITO contacts, the Au-doped ITO contacts had a similar specific contact resistance in the low 10-2 Ω cm-2 range, but were more stable above 600°C and more transparent at blue wavelengths. These results provide support for the use of Au-doped ITO ohmic contact to p-type GaN in high-brightness blue light-emitting diodes.

  10. Planarized arrays of aligned, untangled multiwall carbon nanotubes with Ohmic back contacts

    DOE PAGES

    Rochford, C.; Limmer, S. J.; Howell, S. W.; ...

    2014-11-26

    Vertically aligned, untangled planarized arrays of multiwall carbon nanotubes (MWNTs) with Ohmic back contacts were grown in nanopore templates on arbitrary substrates. The templates were prepared by sputter depositing Nd-doped Al films onto W-coated substrates, followed by anodization to form an aluminum oxide nanopore array. The W underlayer helps eliminate the aluminum oxide barrier that typically occurs at the nanopore bottoms by instead forming a thin WO 3 layer. The WO 3 can be selectively etched to enable electrodeposition of Co catalysts with control over the Co site density. This led to control of the site density of MWNTs grownmore » by thermal chemical vapor deposition, with the W also serving as a back electrical contact. As a result, Ohmic contact to MWNTs was confirmed, even following ultrasonic cutting of the entire array to a uniform height.« less

  11. An “ohmic-first” self-terminating gate-recess technique for normally-off Al2O3/GaN MOSFET

    NASA Astrophysics Data System (ADS)

    Wang, Hongyue; Wang, Jinyan; Li, Mengjun; He, Yandong; Wang, Maojun; Yu, Min; Wu, Wengang; Zhou, Yang; Dai, Gang

    2018-04-01

    In this article, an ohmic-first AlGaN/GaN self-terminating gate-recess etching technique was demonstrated where ohmic contact formation is ahead of gate-recess-etching/gate-dielectric-deposition (GRE/GDD) process. The ohmic contact exhibits few degradations after the self-terminating gate-recess process. Besides, when comparing with that using the conventional fabrication process, the fabricated device using the ohmic-first fabrication process shows a better gate dielectric quality in terms of more than 3 orders lower forward gate leakage current, more than twice higher reverse breakdown voltage as well as better stability. Based on this proposed technique, the normally-off Al2O3/GaN MOSFET exhibits a threshold voltage (V th) of ˜1.8 V, a maximum drain current of ˜328 mA/mm, a forward gate leakage current of ˜10-6 A/mm and an off-state breakdown voltage of 218 V at room temperature. Meanwhile, high temperature characteristics of the device was also evaluated and small variations (˜7.6%) of the threshold voltage was confirmed up to 300 °C.

  12. Suppression of skeletal muscle signal using a crusher coil: A human cardiac 31p‐MR spectroscopy study at 7 tesla

    PubMed Central

    Clarke, William T.; Neubauer, Stefan; Robson, Matthew D.; Rodgers, Christopher T.

    2015-01-01

    Purpose The translation of sophisticated phosphorus MR spectroscopy (31P‐MRS) protocols to 7 Tesla (T) is particularly challenged by the issue of radiofrequency (RF) heating. Legal limits on RF heating make it hard to reliably suppress signals from skeletal muscle that can contaminate human cardiac 31P spectra at 7T. We introduce the first surface‐spoiling crusher coil for human cardiac 31P‐MRS at 7T. Methods A planar crusher coil design was optimized with simulations and its performance was validated in phantoms. Crusher gradient pulses (100 μs) were then applied during human cardiac 31P‐MRS at 7T. Results In a phantom, residual signals were 50 ± 10% with BISTRO (B1‐insensitive train to obliterate signal), and 34 ± 8% with the crusher coil. In vivo, residual signals in skeletal muscle were 49 ± 4% using BISTRO, and 24 ± 5% using the crusher coil. Meanwhile, in the interventricular septum, spectral quality and metabolite quantification did not differ significantly between BISTRO (phosphocreatine/adenosine triphosphate [PCr/ATP] = 2.1 ± 0.4) and the crusher coil (PCr/ATP = 1.8 ± 0.4). However, the specific absorption rate (SAR) decreased from 96 ± 1% of the limit (BISTRO) to 16 ± 1% (crusher coil). Conclusion A crusher coil is an SAR‐efficient alternative for selectively suppressing skeletal muscle during cardiac 31P‐MRS at 7T. A crusher coil allows the use of sequence modules that would have been SAR‐prohibitive, without compromising skeletal muscle suppression. Magn Reson Med 75:962–972, 2016. © 2015 The Authors. Magnetic Resonance in Medicine Published by Wiley Periodicals, Inc. on behalf of International Society of Medicine in Resonance. PMID:25924813

  13. Beam heated linear theta-pinch device for producing hot plasmas

    DOEpatents

    Bohachevsky, Ihor O.

    1981-01-01

    A device for producing hot plasmas comprising a single turn theta-pinch coil, a fast discharge capacitor bank connected to the coil, a fuel element disposed along the center axis of the coil, a predetermined gas disposed within the theta-pinch coil, and a high power photon, electron or ion beam generator concentrically aligned to the theta-pinch coil. Discharge of the capacitor bank generates a cylindrical plasma sheath within the theta-pinch coil which heats the outer layer of the fuel element to form a fuel element plasma layer. The beam deposits energy in either the cylindrical plasma sheath or the fuel element plasma layer to assist the implosion of the fuel element to produce a hot plasma.

  14. Stabilization of coiled-coil peptide domains by introduction of trifluoroleucine.

    PubMed

    Tang, Y; Ghirlanda, G; Vaidehi, N; Kua, J; Mainz, D T; Goddard III, W A; DeGrado, W F; Tirrell, D A

    2001-03-06

    Substitution of leucine residues by 5,5,5-trifluoroleucine at the d-positions of the leucine zipper peptide GCN4-p1d increases the thermal stability of the coiled-coil structure. The midpoint thermal unfolding temperature of the fluorinated peptide is elevated by 13 degrees C at 30 microM peptide concentration. The modified peptide is more resistant to chaotropic denaturants, and the free energy of folding of the fluorinated peptide is 0.5-1.2 kcal/mol larger than that of the hydrogenated form. A similarly fluorinated form of the DNA-binding peptide GCN4-bZip binds to target DNA sequences with affinity and specificity identical to those of the hydrogenated form, while demonstrating enhanced thermal stability. Molecular dynamics simulation on the fluorinated GCN4-p1d peptide using the Surface Generalized Born implicit solvation model revealed that the coiled-coil binding energy is 55% more favorable upon fluorination. These results suggest that fluorination of hydrophobic substructures in peptides and proteins may provide new means of increasing protein stability, enhancing protein assembly, and strengthening receptor-ligand interactions.

  15. Self-assembled nanocages based on the coiled coil bundle motif

    NASA Astrophysics Data System (ADS)

    Sinha, Nairiti; Villegas, Jose; Saven, Jeffery; Kiick, Kristi; Pochan, Darrin

    Computational design of coiled coil peptide bundles that undergo solution phase self-assembly presents a diverse toolbox for engineering new materials with tunable and pre-determined nanostructures that can have various end applications such as in drug delivery, biomineralization and electronics. Self-assembled cages are especially advantageous as the cage geometry provides three distinct functional sites: the interior, the exterior and the solvent-cage interface. In this poster, syntheses and characterization of a peptide cage based on computationally designed homotetrameric coiled coil bundles as building blocks is discussed. Techniques such as Transmission Electron Microscopy (TEM), Small-Angle Neutron Scattering (SANS) and Analytical Ultracentrifugation (AUC) are employed to characterize the size, shape and molecular weight of the self-assembled peptide cages under different pH and temperature conditions. Various self-assembly pathways such as dialysis and thermal quenching are shown to have a significant impact on the final structure of these peptides in solution. Comparison of results with the target cage design can be used to iteratively improve the peptide design and provide greater understanding of its interactions and folding.

  16. Nylon screws make inexpensive coil forms

    NASA Technical Reports Server (NTRS)

    Aucoin, G.; Rosenthal, C.

    1978-01-01

    Standard nylon screws act as coil form copper wire laid down in spiral thread. Completed coil may be bonded to printed-circuit board. However, it is impossible to tune coil by adjusting spacing between windings, technique sometimes used with air-core coils.

  17. Preliminary Process Design of ITER ELM Coil Bracket Brazing

    NASA Astrophysics Data System (ADS)

    LI, Xiangbin; SHI, Yi

    2015-03-01

    With the technical requirement of the International Thermonuclear Experimental Reactor (ITER) project, the manufacture and assembly technology of the mid Edge Localized Modes (ELM) coil was developed by the Institute of Plasma Physics, Chinese Academy of Science (ASIPP). As the gap between the bracket and the Stainless Steel jacketed and Mineral Insulated Conductor (SSMIC) can be larger than 0.5 mm instead of 0.01 mm to 0.1 mm as in normal industrial cases, the process of mid ELM coil bracket brazing to the SSMICT becomes quiet challenging, from a technical viewpoint. This paper described the preliminary design of ELM coil bracket brazing to the SSMIC process, the optimal bracket brazing curve and the thermal simulation of the bracket furnace brazing method developed by ANSYS. BAg-6 foil (Bag50Cu34Zn16) plus BAg-1a paste (Bag45CuZnCd) solders were chosen as the brazing filler. By testing an SSMICT prototype, it is shown that the average gap between the bracket and the SSMIC could be controlled to 0.2-0.3 mm, and that there were few voids in the brazing surface. The results also verified that the preliminary design had a favorable heat conducting performance in the bracket.

  18. Design and testing of a coil-unit barrel for helical coil electromagnetic launcher.

    PubMed

    Yang, Dong; Liu, Zhenxiang; Shu, Ting; Yang, Lijia; Ouyang, Jianming

    2018-01-01

    A coil-unit barrel for a helical coil electromagnetic launcher is described. It provides better features of high structural strength and flexible adjustability. It is convenient to replace the damaged coil units and easy to adjust the number of turns in the stator coils due to the modular design. In our experiments, the highest velocity measured for a 4.5-kg projectile is 47.3 m/s and the mechanical reinforcement of the launcher could bear 35 kA peak current. The relationship between the energy conversion efficiency and the inductance gradient of the launcher is also studied. In the region of low inductance gradient, the efficiency is positively correlated with the inductance gradient. However, in the region of high inductance gradient, the inter-turn arc erosion becomes a major problem of limiting the efficiency and velocity of the launcher. This modular barrel allows further studies in the inter-turn arc and the variable inductance gradient helical coil launcher.

  19. Design and testing of a coil-unit barrel for helical coil electromagnetic launcher

    NASA Astrophysics Data System (ADS)

    Yang, Dong; Liu, Zhenxiang; Shu, Ting; Yang, Lijia; Ouyang, Jianming

    2018-01-01

    A coil-unit barrel for a helical coil electromagnetic launcher is described. It provides better features of high structural strength and flexible adjustability. It is convenient to replace the damaged coil units and easy to adjust the number of turns in the stator coils due to the modular design. In our experiments, the highest velocity measured for a 4.5-kg projectile is 47.3 m/s and the mechanical reinforcement of the launcher could bear 35 kA peak current. The relationship between the energy conversion efficiency and the inductance gradient of the launcher is also studied. In the region of low inductance gradient, the efficiency is positively correlated with the inductance gradient. However, in the region of high inductance gradient, the inter-turn arc erosion becomes a major problem of limiting the efficiency and velocity of the launcher. This modular barrel allows further studies in the inter-turn arc and the variable inductance gradient helical coil launcher.

  20. Directed surface attachment of nanomaterials via coiled-coil-driven self-assembly

    NASA Astrophysics Data System (ADS)

    White, Simon J.; Johnson, Steven; Szymonik, Michal; Wardingley, Richard A.; Pye, Douglas; Davies, A. Giles; Wälti, Christoph; Stockley, Peter G.

    2012-12-01

    Numerous nanoscale devices and materials have been fabricated in recent years using a variety of biological scaffolds. However, the interfacing of these devices and materials into existing circuits and ordered arrays has proved problematic. Here, we describe a simple solution to this problem using self-assembly of the peptide coiled-coil heterodimer ACID:BASE to immobilize M13 bacteriophage particles to specific locations on a patterned gold surface. Surface plasmon resonance demonstrated that free ACID peptides will assemble onto a surface derivatized with BASE. We then displayed the ACID peptide on the pIX coat protein of M13 and showed that these phage particles permit formation of the coiled-coil resulting in specific surface attachment. The ACID:immobilized BASE affinities appear to be similar for free peptide and phage-displayed ACID. Finally, we fabricated two gold electrodes, separated by a 200 nm gap, coated one of them with BASE and showed that this allows localization of the M13:ACID onto the functionalized electrode.

  1. Coiled-coil coactivators play a structural role mediating interactions in hypoxia-inducible factor heterodimerization

    DOE PAGES

    Guo, Yirui; Scheuermann, Thomas H.; Partch, Carrie L.; ...

    2015-01-27

    The hypoxia-inducible factor complex (HIF-α·aryl hydrocarbon receptor nuclear translocator (ARNT)) requires association with several transcription coactivators for a successful cellular response to hypoxic stress. In addition to the conventional global transcription coactivator CREB-binding protein/p300 (CBP/p300) that binds to the HIF-α transactivation domain, a new group of transcription coactivators called the coiled-coil coactivators (CCCs) interact directly with the second PER-ARNT-SIM (PAS) domain of ARNT (ARNT PAS-B). These less studied transcription coactivators play essential roles in the HIF-dependent hypoxia response, and CCC misregulation is associated with several forms of cancer. To better understand CCC protein recruitment by the heterodimeric HIF transcription factor,more » we used x-ray crystallography, NMR spectroscopy, and biochemical methods to investigate the structure of the ARNT PAS-B domain in complex with the C-terminal fragment of a coiled-coil coactivator protein, transforming acidic coiled-coil coactivator 3 (TACC3). We found that the HIF-2α PAS-B domain also directly interacts with TACC3, motivating an NMR data-derived model suggesting a means by which TACC3 could form a ternary complex with HIF-2α PAS-B and ARNT PAS-B via β-sheet/coiled-coil interactions. Furthermore, these findings suggest that TACC3 could be recruited as a bridge to cooperatively mediate between the HIF-2α PAS-B·ARNT PAS-B complex, thereby participating more directly in HIF-dependent gene transcription than previously anticipated.« less

  2. Optimized Geometry for Superconducting Sensing Coils

    NASA Technical Reports Server (NTRS)

    Eom, Byeong Ho; Pananen, Konstantin; Hahn, Inseob

    2008-01-01

    An optimized geometry has been proposed for superconducting sensing coils that are used in conjunction with superconducting quantum interference devices (SQUIDs) in magnetic resonance imaging (MRI), magnetoencephalography (MEG), and related applications in which magnetic fields of small dipoles are detected. In designing a coil of this type, as in designing other sensing coils, one seeks to maximize the sensitivity of the detector of which the coil is a part, subject to geometric constraints arising from the proximity of other required equipment. In MRI or MEG, the main benefit of maximizing the sensitivity would be to enable minimization of measurement time. In general, to maximize the sensitivity of a detector based on a sensing coil coupled with a SQUID sensor, it is necessary to maximize the magnetic flux enclosed by the sensing coil while minimizing the self-inductance of this coil. Simply making the coil larger may increase its self-inductance and does not necessarily increase sensitivity because it also effectively increases the distance from the sample that contains the source of the signal that one seeks to detect. Additional constraints on the size and shape of the coil and on the distance from the sample arise from the fact that the sample is at room temperature but the coil and the SQUID sensor must be enclosed within a cryogenic shield to maintain superconductivity.

  3. An Induction Heating Method with Traveling Magnetic Field for Long Structure Metal

    NASA Astrophysics Data System (ADS)

    Sekine, Takamitsu; Tomita, Hideo; Obata, Shuji; Saito, Yukio

    A novel dismantlable adhesion method for recycling operation of interior materials is proposed. This method is applied a high frequency induction heating and a thermoplastic adhesive. For an adhesion of interior material to long steel stud, a conventional spiral coil as like IH cooking heater gives inadequateness for uniform heating to the stud. Therefore, we have proposed an induction heating method with traveling magnetic field for perfect long structures bonding. In this paper, we describe on the new adhesion method using the 20kHz, three-phase 200V inverter and linear induction coil. From induction heating characteristics to thin steel plates and long studs, the method is cleared the usefulness for uniform heating to long structures.

  4. Structure of bacteriophage T4 fibritin: a segmented coiled coil and the role of the C-terminal domain.

    PubMed

    Tao, Y; Strelkov, S V; Mesyanzhinov, V V; Rossmann, M G

    1997-06-15

    Oligomeric coiled-coil motifs are found in numerous protein structures; among them is fibritin, a structural protein of bacteriophage T4, which belongs to a class of chaperones that catalyze a specific phage-assembly process. Fibritin promotes the assembly of the long tail fibers and their subsequent attachment to the tail baseplate; it is also a sensing device that controls the retraction of the long tail fibers in adverse environments and, thus, prevents infection. The structure of fibritin had been predicted from sequence and biochemical analyses to be mainly a triple-helical coiled coil. The determination of its structure at atomic resolution was expected to give insights into the assembly process and biological function of fibritin, and the properties of modified coiled-coil structures in general. The three-dimensional structure of fibritin E, a deletion mutant of wild-type fibritin, was determined to 2.2 A resolution by X-ray crystallography. Three identical subunits of 119 amino acid residues form a trimeric parallel coiled-coil domain and a small globular C-terminal domain about a crystallographic threefold axis. The coiled-coil domain is divided into three segments that are separated by insertion loops. The C-terminal domain, which consists of 30 residues from each subunit, contains a beta-propeller-like structure with a hydrophobic interior. The residues within the C-terminal domain make extensive hydrophobic and some polar intersubunit interactions. This is consistent with the C-terminal domain being important for the correct assembly of fibritin, as shown earlier by mutational studies. Tight interactions between the C-terminal residues of adjacent subunits counteract the latent instability that is suggested by the structural properties of the coiled-coil segments. Trimerization is likely to begin with the formation of the C-terminal domain which subsequently initiates the assembly of the coiled coil. The interplay between the stabilizing effect of the C

  5. Processing and plating helical metallic coils

    NASA Technical Reports Server (NTRS)

    1972-01-01

    The results of research efforts to develop an optimized nickel cobalt coating suitable as a recording medium are outlined. The coating is to be used directly on a BeCu helical coil substrate of a helical coil NASA recorder. Specifically, efforts were made to: optimize the coating thickness; establish processes and techniques adaptable for the production of finalized plated helical coils; design and fabricate the equipment required for production and testing of the coils; and deliver finalized helical coils to NASA.

  6. Endovascular rescue method for undesirably stretched coil.

    PubMed

    Cho, Jae Hoon

    2014-10-01

    Undesirable detachment or stretching of coils within the parent artery during aneurysm embolization can be related with thrombus formation, which can be caused occlusion of parent artery or embolic event(s). To escape from this situation, several rescue methods have been reported. A case with undesirably stretched coil in which another rescue method was used, is presented. When the stretched coil is still located in the coil delivery microcatheter, the stretched coil can be removed safely using a snare and a handmade monorail microcatheter. After a snare is lodged in the handmade monorail microcatheter, the snare is introduced over the coil delivery micorcatheter and located in the distal part of the stretched coil. After then, the handmade monorail microcatheter captures the stretched coil and the snare as one unit. This technique using a handmade monorail microcatheter and a snare can be a good rescue modality for the undesirably stretched coil, still remained within the coil delivery microcatheter.

  7. Endovascular Rescue Method for Undesirably Stretched Coil

    PubMed Central

    2014-01-01

    Undesirable detachment or stretching of coils within the parent artery during aneurysm embolization can be related with thrombus formation, which can be caused occlusion of parent artery or embolic event(s). To escape from this situation, several rescue methods have been reported. A case with undesirably stretched coil in which another rescue method was used, is presented. When the stretched coil is still located in the coil delivery microcatheter, the stretched coil can be removed safely using a snare and a handmade monorail microcatheter. After a snare is lodged in the handmade monorail microcatheter, the snare is introduced over the coil delivery micorcatheter and located in the distal part of the stretched coil. After then, the handmade monorail microcatheter captures the stretched coil and the snare as one unit. This technique using a handmade monorail microcatheter and a snare can be a good rescue modality for the undesirably stretched coil, still remained within the coil delivery microcatheter. PMID:25371791

  8. Ohmic resistance in a multi-anode MxCs

    EPA Pesticide Factsheets

    A-3txf_sequence summary.xksx: Abundance of contigs or unique sequences for each biofilm samples from anodes in the MEC reactorHodon Waterloo final_fasta_working.docx: Raw sequences with their identification numbersRNA S1_MEC.docx: Representative sequences with their ID number and taxonomyThis dataset is associated with the following publication:Santodomingo, J., H. Ryu, B. Dhar, and H. Lee. Ohmic resistance affects microbial community and electrochemical kinetics in a multi-anode microbial electrochemical cell. JOURNAL OF POWER SOURCES. Elsevier Science Ltd, New York, NY, USA, 331: 315-321, (2016).

  9. Improved ohmic contact of Ga-Doped ZnO to p-GaN by using copper sulfide intermediate layers

    NASA Astrophysics Data System (ADS)

    Gu, Wen; Xu, Tao; Zhang, Jianhua

    2013-11-01

    Copper sulfide (CuS) was used as the intermediate layer to build ohmic contact of Ga-Doped ZnO (GZO) transparent conduction layer (TCL) to p-GaN. The CuS and GZO layers were prepared by thermal evaporation and RF magnetron sputtering, respectively. Although the GZO-only contacts to p-GaN exhibit nonlinear behavior, ohmic contact with a specific contact resistance of 1.6 × 10-2 Ω cm2 has been realized by inserting 3 nm CuS layer between GZO and p-GaN. The optical transmittance of CuS/GZO film was measured to be higher than 80% in the range of 450-600 nm wavelength. The possible mechanism for the ohmic contact behavior can be attributed to the increased hole concentration of p-GaN surface induced by CuS films after annealing. The forward voltage of LEDs with CuS/GZO TCL has been reduced by 1.7 V at 20 mA and the output power has been increased by 29.6% at 100 mA compared with LEDs without CuS interlayer. These results indicated that using CuS intermediate layer could be a potential ohmic contact method to realize high-efficiency LEDs.

  10. Evidence-based pathology: umbilical cord coiling.

    PubMed

    Khong, T Y

    2010-12-01

    The generation of a pathology test result must be based on criteria that are proven to be acceptably reproducible and clinically relevant to be evidence-based. This review de-constructs the umbilical cord coiling index to illustrate how it can stray from being evidence-based. Publications related to umbilical cord coiling were retrieved and analysed with regard to how the umbilical coiling index was calculated, abnormal coiling was defined and reference ranges were constructed. Errors and other influences that can occur with the measurement of the length of the umbilical cord or of the number of coils can compromise the generation of the coiling index. Definitions of abnormal coiling are not consistent in the literature. Reference ranges defining hypocoiling or hypercoiling have not taken those potential errors or the possible effect of gestational age into account. Even the way numerical test results in anatomical pathology are generated, as illustrated by the umbilical coiling index, warrants a critical analysis into its evidence base to ensure that they are reproducible or free from errors.

  11. The significant impact of framing coils on long-term outcomes in endovascular coiling for intracranial aneurysms: how to select an appropriate framing coil.

    PubMed

    Ishida, Wataru; Sato, Masayuki; Amano, Tatsuo; Matsumaru, Yuji

    2016-09-01

    OBJECTIVE The importance of a framing coil (FC)-the first coil inserted into an aneurysm during endovascular coiling, also called a lead coil or a first coil-is recognized, but its impact on long-term outcomes, including recanalization and retreatment, is not well established. The purposes of this study were to test the hypothesis that the FC is a significant factor for aneurysmal recurrence and to provide some insights on appropriate FC selection. METHODS The authors retrospectively reviewed endovascular coiling for 280 unruptured intracranial aneurysms and gathered data on age, sex, aneurysm location, aneurysm morphology, maximal size, neck width, adjunctive techniques, recanalization, retreatment, follow-up periods, total volume packing density (VPD), volume packing density of the FC, and framing coil percentage (FCP; the percentage of FC volume in total coil volume) to clarify the associated factors for aneurysmal recurrence. RESULTS Of 236 aneurysms included in this study, 33 (14.0%) had recanalization, and 18 (7.6%) needed retreatment during a mean follow-up period of 37.7 ± 16.1 months. In multivariate analysis, aneurysm size (odds ratio [OR] = 1.29, p < 0.001), FCP < 32% (OR 3.54, p = 0.009), and VPD < 25% (OR 2.96, p = 0.015) were significantly associated with recanalization, while aneurysm size (OR 1.25, p < 0.001) and FCP < 32% (OR 6.91, p = 0.017) were significant predictors of retreatment. VPD as a continuous value or VPD with any cutoff value could not predict retreatment with statistical significance in multivariate analysis. CONCLUSIONS FCP, which is equal to the FC volume as a percentage of the total coil volume and is unaffected by the morphology of the aneurysm or the measurement error in aneurysm length, width, or height, is a novel predictor of recanalization and retreatment and is more significantly predictive of retreatment than VPD. To select FCs large enough to meet the condition of FCP ≥ 32% is a potential relevant factor for better

  12. Investigation on quench initiation and propagation characteristics of GdBCO coil co-wound with a stainless steel tape as turn-to-turn metallic insulation.

    PubMed

    Kim, Y G; Song, J B; Choi, Y H; Yang, D G; Kim, S G; Lee, H G

    2016-11-01

    This paper investigates the quench initiation and propagation characteristics of a metallic insulation (MI) coil by conducting thermal quench tests for a GdBCO single-pancake coil co-wound with a stainless steel tape as the turn-to-turn MI. The test results confirmed that the MI coil exhibited superior thermal and electrical stabilities compared to the conventional coils co-wound with organic insulation material because the operating current could flow along the radial direction due to the existence of a turn-to-turn contact when a local hot spot was generated. The results of the quench test at a heater current (I h ) of 12, 13, and 14 A indicate that the MI coil possesses a self-protecting characteristic resulting from the "current bypass" through the turn-to-turn contact. However, the test coil was not self-protecting at I h = 15 A because the Joule heat energy generated by the radial current flow was not completely dissipated due to the characteristic resistance of the metallic insulation tape and the non-superconducting materials, including the substrate, stabilizer, and buffer layers within the high-temperature superconductor (HTS) tape. Even though the MI coil possesses superior thermal and electrical stability relative to those of conventional HTS coils co-wound with an organic material as turn-to-turn insulation, it is essential to consider the critical role of the Joule heat energy resulting from the operating current and stored magnetic energy as well as the characteristic resistances in order to further develop self-protective 2G HTS magnets.

  13. Overview of ground coupled heat pump research and technology transfer activities

    NASA Astrophysics Data System (ADS)

    Baxter, V. D.; Mei, V. C.

    Highlights of DOE-sponsored ground coupled heat pump (GCHP) research at Oak Ridge National Laboratory (ORNL) are presented. ORNL, in cooperation with Niagara Mohawk Power Company, Climate Master, Inc., and Brookhaven National Laboratory developed and demonstrated an advanced GCHP design concept with shorter ground coils that can reduce installed costs for northern climates. In these areas it can also enhance the competitiveness of GCHP systems versus air-source heat pumps by lowering their payback from 6 to 7 years to 3 to 5 years. Ground coil heat exchanger models (based primarily on first principles) have been developed and used by others to generate less conservative ground coil sizing methods. An aggressive technology transfer initiative was undertaken to publicize results of this research and make it available to the industry. Included in this effort were an international workshop, trade press releases and articles, and participation in a live teleconference on GCHP technology.

  14. Formation of Ohmic contact to semipolar (11-22) p-GaN by electrical breakdown method

    NASA Astrophysics Data System (ADS)

    Jeong, Seonghoon; Lee, Sung-Nam; Kim, Hyunsoo

    2018-01-01

    The electrical breakdown (EBD) method was used to obtain Ohmic contact to semipolar (11-20) p-GaN surfaces using the Ti/SiO2/ p-GaN structure. The EBD method by which the electrical stress voltage was increased up to 70 V with a compliance current of 30 mA resulted in an Ohmic contact with a specific contact resistance of 3.1×10-3 Ωcm2. The transmission electron microscope (TEM) analysis revealed that the oxygen was slightly out-diffused from SiO2 layer toward Ti surface and the oxidation occurred at the Ti surface, while the GaN remained unchanged.

  15. Magnetic Microhelix Coil Structures

    NASA Astrophysics Data System (ADS)

    Smith, Elliot J.; Makarov, Denys; Sanchez, Samuel; Fomin, Vladimir M.; Schmidt, Oliver G.

    2011-08-01

    Together with the well-known ferro- and antiferromagnetic ordering, nature has created a variety of complex helical magnetic configurations. Here, we design and investigate three-dimensional microhelix coil structures that are radial-, corkscrew-, and hollow-bar-magnetized. The magnetization configurations of the differently magnetized coils are experimentally revealed by probing their specific dynamic response to an external magnetic field. Helix coils offer an opportunity to realize microscale geometries of the magnetic toroidal moment, observed so far only in bulk multiferroic materials.

  16. On the breakdown modes and parameter space of Ohmic Tokamak startup

    NASA Astrophysics Data System (ADS)

    Peng, Yanli; Jiang, Wei; Zhang, Ya; Hu, Xiwei; Zhuang, Ge; Innocenti, Maria; Lapenta, Giovanni

    2017-10-01

    Tokamak plasma has to be hot. The process of turning the initial dilute neutral hydrogen gas at room temperature into fully ionized plasma is called tokamak startup. Even with over 40 years of research, the parameter ranges for the successful startup still aren't determined by numerical simulations but by trial and errors. However, in recent years it has drawn much attention due to one of the challenges faced by ITER: the maximum electric field for startup can't exceed 0.3 V/m, which makes the parameter range for successful startup narrower. Besides, this physical mechanism is far from being understood either theoretically or numerically. In this work, we have simulated the plasma breakdown phase driven by pure Ohmic heating using a particle-in-cell/Monte Carlo code, with the aim of giving a predictive parameter range for most tokamaks, even for ITER. We have found three situations during the discharge, as a function of the initial parameters: no breakdown, breakdown and runaway. Moreover, breakdown delay and volt-second consumption under different initial conditions are evaluated. In addition, we have simulated breakdown on ITER and confirmed that when the electric field is 0.3 V/m, the optimal pre-filling pressure is 0.001 Pa, which is in good agreement with ITER's design.

  17. Borehole induction coil transmitter

    DOEpatents

    Holladay, Gale; Wilt, Michael J.

    2002-01-01

    A borehole induction coil transmitter which is a part of a cross-borehole electromagnetic field system that is used for underground imaging applications. The transmitter consists of four major parts: 1) a wound ferrite or mu-metal core, 2) an array of tuning capacitors, 3) a current driver circuit board, and 4) a flux monitor. The core is wound with several hundred turns of wire and connected in series with the capacitor array, to produce a tuned coil. This tuned coil uses internal circuitry to generate sinusoidal signals that are transmitted through the earth to a receiver coil in another borehole. The transmitter can operate at frequencies from 1-200 kHz and supplies sufficient power to permit the field system to operate in boreholes separated by up to 400 meters.

  18. Rod-Coil Block Polyimide Copolymers

    NASA Technical Reports Server (NTRS)

    Meador, Mary Ann B. (Inventor); Kinder, James D. (Inventor)

    2005-01-01

    This invention is a series of rod-coil block polyimide copolymers that are easy to fabricate into mechanically resilient films with acceptable ionic or protonic conductivity at a variety of temperatures. The copolymers consist of short-rigid polyimide rod segments alternating with polyether coil segments. The rods and coil segments can be linear, branched or mixtures of linear and branched segments. The highly incompatible rods and coil segments phase separate, providing nanoscale channels for ion conduction. The polyimide segments provide dimensional and mechanical stability and can be functionalized in a number of ways to provide specialized functions for a given application. These rod-coil black polyimide copolymers are particularly useful in the preparation of ion conductive membranes for use in the manufacture of fuel cells and lithium based polymer batteries.

  19. A history of detachable coils: 1987-2012.

    PubMed

    Hui, Ferdinand K; Fiorella, David; Masaryk, Thomas J; Rasmussen, Peter A; Dion, Jacques E

    2014-03-01

    The development of detachable coils is one of the most pivotal developments in neurointervention, providing a tool that could be used to treat a wide variety of hemorrhagic stroke. From the original Guglielmi detachable coil, a number of different coil designs and delivery designs have evolved. This article reviews the history of commercially available detachable coils. A timeline of detachable coils was constructed and coil design philosophies were reviewed. A complete list of commercially available coils is presented in a timeline format. Detachable coil technology continues to evolve. Advances in construction and design have yielded products which may benefit patients in terms of safety, radiation dose reduction and cost of treatment. Continued evolution is expected, irrespective of competing disruptive technologies.

  20. Mathematic analysis of incremental packing density with detachable coils: does that last coil matter much?

    PubMed

    Taussky, P; Kallmes, D F; Cloft, H

    2012-05-01

    Higher packing attenuation of coils in cerebral aneurysms is associated with a decreased recurrence rate. However, geometric relationships suggest that an additional coil may have very little effect on packing attenuation as aneurysm size increases. We mathematically evaluated the relationship between aneurysm size and incremental packing attenuation for coils currently available.

  1. Electric current heating calibration of a laser holographic nondestructive test system

    NASA Technical Reports Server (NTRS)

    Liu, H.-K.; Kurtz, R. L.

    1975-01-01

    Holographic NDT was used to measure small surface displacements controlled by electric heating by detecting the difference of the interference fringe patterns as viewed through the hologram on a real time basis. A perforated aluminum test plate, with the holes used to position thin metal foils, was used in the experiment. One of the foils was connected to an electric power source and small displacements of the foil were caused and controlled by Ohmic heating. An He-Ne laser was used to perform the holography.

  2. Stellarator Saddle Coils

    NASA Astrophysics Data System (ADS)

    Boozer, Allen H.

    1999-11-01

    Modern stellarators are designed using J. Nuehrenberg’s method of varying Fourier coefficients in the shape of the plasma boundary to maximize a target function. The matrix of second derivatives of the target function at the optimum determines a quality matrix. This matrix gives the degradation in the quality of the configuration as the normal magnetic field is varied on a control surface, which lies on or outside the plasma surface. The task is finding saddle coils that produce the desired configuration in the presence of a given toroidal field. An eigenvector of the quality matrix can be important for two reasons: (1) the normal field that must be produced by the saddles is large or (2) the eigenvalue is large (an island-causing resonant perturbation). The rank of the important part of the quality matrix is the number of important eigenvectors. The current in each saddle coil produces a normal field on the control surface, which can be described by an inductance matrix. The relevant part of the inductance matrix has large eigenvalues. The coils can produce the configuration if the rank of the important part of the quality matrix and its product with the relevant part of the inductance matrix are the same. Existing coil design codes, pioneered by P. Merkel, approximate the quality matrix by the unit matrix. Stellarator flexibility could be enhanced by using a more realistic quality matrix and by using trim coils to balance large eigenvalues.

  3. Strong contributions from vertical triads to helix-partner preferences in parallel coiled coils.

    PubMed

    Steinkruger, Jay D; Bartlett, Gail J; Woolfson, Derek N; Gellman, Samuel H

    2012-09-26

    Pairing preferences in heterodimeric coiled coils are determined by complementarities among side chains that pack against one another at the helix-helix interface. However, relationships between dimer stability and interfacial residue identity are not fully understood. In the context of the "knobs-into-holes" (KIH) packing pattern, one can identify two classes of interactions between side chains from different helices: "lateral", in which a line connecting the adjacent side chains is perpendicular to the helix axes, and "vertical", in which the connecting line is parallel to the helix axes. We have previously analyzed vertical interactions in antiparallel coiled coils and found that one type of triad constellation (a'-a-a') exerts a strong effect on pairing preferences, while the other type of triad (d'-d-d') has relatively little impact on pairing tendencies. Here, we ask whether vertical interactions (d'-a-d') influence pairing in parallel coiled-coil dimers. Our results indicate that vertical interactions can exert a substantial impact on pairing specificity, and that the influence of the d'-a-d' triad depends on the lateral a' contact within the local KIH motif. Structure-informed bioinformatic analyses of protein sequences reveal trends consistent with the thermodynamic data derived from our experimental model system in suggesting that heterotriads involving Leu and Ile are preferred over homotriads involving Leu and Ile.

  4. Invited review the coiled coil silk of bees, ants, and hornets.

    PubMed

    Sutherland, Tara D; Weisman, Sarah; Walker, Andrew A; Mudie, Stephen T

    2012-06-01

    In this article, we review current knowledge about the silk produced by the larvae of bees, ants, and hornets [Apoidea and Vespoidea: Hymenoptera]. Different species use the silk either alone or in composites for a variety of purposes including mechanical reinforcement, thermal regulation, or humidification. The characteristic molecular structure of this silk is α-helical proteins assembled into tetrameric coiled coils. Gene sequences from seven species are available, and each species possesses a copy of each of four related silk genes that encode proteins predicted to form coiled coils. The proteins are ordered at multiple length scales within the labial gland of the final larval instar before spinning. The insects control the morphology of the silk during spinning to produce either fibers or sheets. The silk proteins are small and non repetitive and have been produced artificially at high levels by fermentation in E. coli. The artificial silk proteins can be fabricated into materials with structural and mechanical properties similar to those of native silks. Copyright © 2011 Wiley Periodicals, Inc.

  5. Toroid cavity/coil NMR multi-detector

    DOEpatents

    Gerald, II, Rex E.; Meadows, Alexander D.; Gregar, Joseph S.; Rathke, Jerome W.

    2007-09-18

    An analytical device for rapid, non-invasive nuclear magnetic resonance (NMR) spectroscopy of multiple samples using a single spectrometer is provided. A modified toroid cavity/coil detector (TCD), and methods for conducting the simultaneous acquisition of NMR data for multiple samples including a protocol for testing NMR multi-detectors are provided. One embodiment includes a plurality of LC resonant circuits including spatially separated toroid coil inductors, each toroid coil inductor enveloping its corresponding sample volume, and tuned to resonate at a predefined frequency using a variable capacitor. The toroid coil is formed into a loop, where both ends of the toroid coil are brought into coincidence. Another embodiment includes multiple micro Helmholtz coils arranged on a circular perimeter concentric with a central conductor of the toroid cavity.

  6. Heat operated cryogenic electrical generator

    NASA Technical Reports Server (NTRS)

    Wang, T. G.; Saffren, M. M.; Elleman, D. D. (Inventor)

    1975-01-01

    An electrical generator useful for providing electrical power in deep space, is disclosed. The electrical generator utilizes the unusual hydrodynamic property exhibited by liquid helium as it is converted to and from a superfluid state to cause opposite directions of rotary motion for a rotor cell thereof. The physical motion of the rotor cell was employed to move a magnetic field provided by a charged superconductive coil mounted on the exterior of the cell. An electrical conductor was placed in surrounding proximity to the cell to interact with the moving magnetic field provided by the superconductive coil and thereby generate electrical energy. A heat control arrangement was provided for the purpose of causing the liquid helium to be partially converted to and from a superfluid state by being cooled and heated, respectively.

  7. Thermal conductivity measurements of impregnated Nb3Sn coil samples in the temperature range of 3.5 K to 100 K

    NASA Astrophysics Data System (ADS)

    Koettig, T.; Maciocha, W.; Bermudez, S.; Rysti, J.; Tavares, S.; Cacherat, F.; Bremer, J.

    2017-02-01

    In the framework of the luminosity upgrade of the LHC, high-field magnets are under development. Magnetic flux densities of up to 13 T require the use of Nb3Sn superconducting coils. Quench protection becomes challenging due to the high stored energy density and the low stabilizer fraction. The thermal conductivity and diffusivity of the combination of insulating layers and Nb3Sn based cables are an important thermodynamic input parameter for quench protection systems and superfluid helium cooling studies. A two-stage cryocooler based test stand is used to measure the thermal conductance of the coil sample in two different heat flow directions with respect to the coil package geometry. Variable base temperatures of the experimental platform at the cryocooler allow for a steady-state heat flux method up to 100 K. The heat is applied at wedges style copper interfaces of the Rutherford cables. The respective temperature difference represents the absolute value of thermal conductance of the sample arrangement. We report about the measurement methodology applied to this kind of non-uniform sample composition and the evaluation of the used resin composite materials.

  8. Performance investigation and comparison of different turbulator shapes in solar water heating collector system

    NASA Astrophysics Data System (ADS)

    Khargotra, Rohit; Dhingra, Sunil; Chauhan, Ranchan; Singh, Tej

    2018-05-01

    The effective use of solar energy is hindered by the intermittent nature of its availability, limiting its use and effectiveness in domestic and industrial applications especially in water heating. In the present paper, the performance of different turbulator shapes in solar water heating collector system has been studied experimentally and comparison on the output performance has been carried out. Effects of insertion of coil-spring turbulator on heat transfer rate, mass flow rate, heat gain by the fluid etc. is studied by disturbing the flow inside the absorber tubes in a solar flat plate collector. The coil-spring used as a turbulator is placed inside the absorber tube which creates a continuous swirling flow along the tube wall. The results of the heat transfer have been compared well with the available results. The heat transfer rate in the collector has been found to be increased by 18% to 70%. Solar water heater having inserts in the flow tubes perform better than the conventional plain ones. It has been observed that heat losses are reduced consequently increasing the thermal performance to about 70% over the plain water heater under same operating conditions. The coil-spring used as a turbulator is placed inside the riser tube while the twisted tape is inserted into the wire coil to create a continuous swirling flow along the tube wall. The results of the heat transfer have been compared with the available results. Solar water heater having inserts in the flow tubes perform better than the conventional plain ones.

  9. Coil Embolization for Intracranial Aneurysms

    PubMed Central

    2006-01-01

    Executive Summary Objective To determine the effectiveness and cost-effectiveness of coil embolization compared with surgical clipping to treat intracranial aneurysms. The Technology Endovascular coil embolization is a percutaneous approach to treat an intracranial aneurysm from within the blood vessel without the need of a craniotomy. In this procedure, a microcatheter is inserted into the femoral artery near the groin and navigated to the site of the aneurysm. Small helical platinum coils are deployed through the microcatheter to fill the aneurysm, and prevent it from further expansion and rupture. Health Canada has approved numerous types of coils and coil delivery systems to treat intracranial aneurysms. The most favoured are controlled detachable coils. Coil embolization may be used with other adjunct endovascular devices such as stents and balloons. Background Intracranial Aneurysms Intracranial aneurysms are the dilation or ballooning of part of a blood vessel in the brain. Intracranial aneurysms range in size from small (<12 mm in diameter) to large (12–25 mm), and to giant (>25 mm). There are 3 main types of aneurysms. Fusiform aneurysms involve the entire circumference of the artery; saccular aneurysms have outpouchings; and dissecting aneurysms have tears in the arterial wall. Berry aneurysms are saccular aneurysms with well-defined necks. Intracranial aneurysms may occur in any blood vessel of the brain; however, they are most commonly found at the branch points of large arteries that form the circle of Willis at the base of the brain. In 85% to 95% of patients, they are found in the anterior circulation. Aneurysms in the posterior circulation are less frequent, and are more difficult to treat surgically due to inaccessibility. Most intracranial aneurysms are small and asymptomatic. Large aneurysms may have a mass effect, causing compression on the brain and cranial nerves and neurological deficits. When an intracranial aneurysm ruptures and bleeds

  10. Graphene in ohmic contact for both n-GaN and p-GaN

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhong, Haijian; Liu, Zhenghui; Shi, Lin

    The wrinkles of single layer graphene contacted with either n-GaN or p-GaN were found both forming ohmic contacts investigated by conductive atomic force microscopy. The local I–V results show that some of the graphene wrinkles act as high-conductive channels and exhibiting ohmic behaviors compared with the flat regions with Schottky characteristics. We have studied the effects of the graphene wrinkles using density-functional-theory calculations. It is found that the standing and folded wrinkles with zigzag or armchair directions have a tendency to decrease or increase the local work function, respectively, pushing the local Fermi level towards n- or p-type GaN andmore » thus improving the transport properties. These results can benefit recent topical researches and applications for graphene as electrode material integrated in various semiconductor devices.« less

  11. Rotor assembly including superconducting magnetic coil

    DOEpatents

    Snitchler, Gregory L.; Gamble, Bruce B.; Voccio, John P.

    2003-01-01

    Superconducting coils and methods of manufacture include a superconductor tape wound concentrically about and disposed along an axis of the coil to define an opening having a dimension which gradually decreases, in the direction along the axis, from a first end to a second end of the coil. Each turn of the superconductor tape has a broad surface maintained substantially parallel to the axis of the coil.

  12. Correction coil cable

    DOEpatents

    Wang, Sou-Tien

    1994-11-01

    A wire cable assembly (10, 310) adapted for the winding of electrical coils is taught. A primary intended use is for use in particle tube assemblies (532) for the superconducting super collider. The correction coil cables (10, 310) have wires (14, 314) collected in wire arrays (12, 312) with a center rib (16, 316) sandwiched therebetween to form a core assembly (18, 318 ). The core assembly (18, 318) is surrounded by an assembly housing (20, 320) having an inner spiral wrap (22, 322) and a counter wound outer spiral wrap (24, 324). An alternate embodiment (410) of the invention is rolled into a keystoned shape to improve radial alignment of the correction coil cable (410) on a particle tube (733) in a particle tube assembly (732).

  13. Update on High-Temperature Coils for Electromagnets

    NASA Technical Reports Server (NTRS)

    Kascak, Albert F.; Montague, Gerald T.; Palazzolo, Alan; Preuss, Jason; Carter, Bart; Tucker, Randall; Hunt, Andrew

    2005-01-01

    A report revisits the subject matter of "High-Temperature Coils for Electromagnets" (LEW-17164), NASA Tech Briefs, Vol. 26, No. 8, (August 2002) page 38. To recapitulate: Wires have been developed for use in electromagnets that operate at high temperatures. The starting material for a wire of this type can be either a nickel-clad, ceramic-insulated copper wire or a bare silver wire. The wire is covered by electrical-insulation material that is intended to withstand operating temperatures in the range from 800 to 1,300 F (.430 to .700 C): The starting wire is either primarily wrapped with S-glass as an insulating material or else covered with another insulating material wrapped in S-glass prior to the winding process. A ceramic binding agent is applied as a slurry during the winding process to provide further insulating capability. The turns are pre-bent during winding to prevent damage to the insulation. The coil is then heated to convert the binder into ceramic. The instant report mostly reiterates the prior information and presents some additional information on the application of the ceramic binding agent and the incorporation of high-temperature wire into the windings.

  14. GBNV encoded movement protein (NSm) remodels ER network via C-terminal coiled coil domain

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Singh, Pratibha; Savithri, H.S., E-mail: bchss@biochem.iisc.ernet.in

    Plant viruses exploit the host machinery for targeting the viral genome–movement protein complex to plasmodesmata (PD). The mechanism by which the non-structural protein m (NSm) of Groundnut bud necrosis virus (GBNV) is targeted to PD was investigated using Agrobacterium mediated transient expression of NSm and its fusion proteins in Nicotiana benthamiana. GFP:NSm formed punctuate structures that colocalized with mCherry:plasmodesmata localized protein 1a (PDLP 1a) confirming that GBNV NSm localizes to PD. Unlike in other movement proteins, the C-terminal coiled coil domain of GBNV NSm was shown to be involved in the localization of NSm to PD, as deletion of thismore » domain resulted in the cytoplasmic localization of NSm. Treatment with Brefeldin A demonstrated the role of ER in targeting GFP NSm to PD. Furthermore, mCherry:NSm co-localized with ER–GFP (endoplasmic reticulum targeting peptide (HDEL peptide fused with GFP). Co-expression of NSm with ER–GFP showed that the ER-network was transformed into vesicles indicating that NSm interacts with ER and remodels it. Mutations in the conserved hydrophobic region of NSm (residues 130–138) did not abolish the formation of vesicles. Additionally, the conserved prolines at positions 140 and 142 were found to be essential for targeting the vesicles to the cell membrane. Further, systematic deletion of amino acid residues from N- and C-terminus demonstrated that N-terminal 203 amino acids are dispensable for the vesicle formation. On the other hand, the C-terminal coiled coil domain when expressed alone could also form vesicles. These results suggest that GBNV NSm remodels the ER network by forming vesicles via its interaction through the C-terminal coiled coil domain. Interestingly, NSm interacts with NP in vitro and coexpression of these two proteins in planta resulted in the relocalization of NP to PD and this relocalization was abolished when the N-terminal unfolded region of NSm was deleted. Thus, the NSm

  15. Creep life prediction of super heater coils used in coal based thermal power plants subjected to fly ash erosion and oxide scale formation

    NASA Astrophysics Data System (ADS)

    Srinivasan, P.; Kushwaha, Shashank

    2018-04-01

    Super heater coils of the coal based thermal power plants and subjected to severe operating conditions from both steam side and gas side. Formation of oxide scale due to prolonged service lead to temperature raise of the tube and erosion due to fly ash present in the combusted gases leads to tube thinning. Both these factors lead to creep rupture of the coils much before the designed service life. Failure of super heater coils during service of the boiler leads to power loss and huge monitory loss to the power plants. An attempt is made to model the creep damage caused to the super heater coils using heat transfer analysis tube thinning due to erosive wear of the tubes. Combined effects of these parameters are taken into consideration to predict the life of the super heater coils. This model may be used to estimate the life of the coils operating under the severe operating conditions to prevent the unexpected failure of the coils.

  16. Design of a single-chain polypeptide tetrahedron assembled from coiled-coil segments.

    PubMed

    Gradišar, Helena; Božič, Sabina; Doles, Tibor; Vengust, Damjan; Hafner-Bratkovič, Iva; Mertelj, Alenka; Webb, Ben; Šali, Andrej; Klavžar, Sandi; Jerala, Roman

    2013-06-01

    Protein structures evolved through a complex interplay of cooperative interactions, and it is still very challenging to design new protein folds de novo. Here we present a strategy to design self-assembling polypeptide nanostructured polyhedra based on modularization using orthogonal dimerizing segments. We designed and experimentally demonstrated the formation of the tetrahedron that self-assembles from a single polypeptide chain comprising 12 concatenated coiled coil-forming segments separated by flexible peptide hinges. The path of the polypeptide chain is guided by a defined order of segments that traverse each of the six edges of the tetrahedron exactly twice, forming coiled-coil dimers with their corresponding partners. The coincidence of the polypeptide termini in the same vertex is demonstrated by reconstituting a split fluorescent protein in the polypeptide with the correct tetrahedral topology. Polypeptides with a deleted or scrambled segment order fail to self-assemble correctly. This design platform provides a foundation for constructing new topological polypeptide folds based on the set of orthogonal interacting polypeptide segments.

  17. Spaced-based search coil magnetometers

    NASA Astrophysics Data System (ADS)

    Hospodarsky, George B.

    2016-12-01

    Search coil magnetometers are one of the primary tools used to study the magnetic component of low-frequency electromagnetic waves in space. Their relatively small size, mass, and power consumption, coupled with a good frequency range and sensitivity, make them ideal for spaceflight applications. The basic design of a search coil magnetometer consists of many thousands of turns of wire wound on a high permeability core. When a time-varying magnetic field passes through the coil, a time-varying voltage is induced due to Faraday's law of magnetic induction. The output of the coil is usually attached to a preamplifier, which amplifies the induced voltage and conditions the signal for transmission to the main electronics (usually a low-frequency radio receiver). Search coil magnetometers are usually used in conjunction with electric field antenna to measure electromagnetic plasma waves in the frequency range of a few hertz to a few tens of kilohertzs. Search coil magnetometers are used to determine the properties of waves, such as comparing the relative electric and magnetic field amplitudes of the waves, or to investigate wave propagation parameters, such as Poynting flux and wave normal vectors. On a spinning spacecraft, they are also sometimes used to determine the background magnetic field. This paper presents some of the basic design criteria of search coil magnetometers and discusses design characteristics of sensors flown on a number of spacecraft.

  18. Novel Use of Water Soluble "Aquapour" As A Temporary Spacer During Coil Winding For The NSTX-U Centerstack

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Mardenfeld, Michael

    A major facility upgrade to the National Spherical Torus eXperiment (NSTX-U) is currently underway at Princeton Plasma Physics Laboratory (PPPL). A key component of NSTX-U is the fabrication of a new, higher field centerstack (CS). In order to simultaneously provide robust joints between the inner and outer legs of the Toroidal Field Coils (TF) and minimize radial build, the NSTX-U CS design requires that the Ohmic Heating solenoid (OH) be wound directly on the inner TF bundle. To protect the OH against thermal expansion stress during scenarios where the inner TF bundle is hot but the OH is relatively cool,more » the completed CS will have a 0.100 inch annular gap between the outer diameter of the TF bundle and the inner diameter of the OH solenoid. "Aquapour", a proprietary material produced by the Advanced Ceramics Manufacturing Company will be used during manufacture to produce this gap. After the TF bundle is vacuum pressure impregnated and cured, a cylindrical "clam shell" mold will be assembled around it, and a slurry of powdered Aquapour and water will be pumped into the annular space between the mold and TF bundle. Subsequent baking will turn the Aquapour solid, and a protective layer of wet lay-up fiberglass and resin will be added. The OH solenoid will be wound directly on this wet lay-up shell. After vacuum pressure impregnation of the OH, the water soluble Aquapour will be washed away, leaving the required radial clearance between the TF and OH. This paper will describe prototyping and testing of this process, and plans for use on the actual CS fabrication.« less

  19. Membrane-Based Absorption Refrigeration Systems: Nanoengineered Membrane-Based Absorption Cooling for Buildings Using Unconcentrated Solar & Waste Heat

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    None

    BEETIT Project: UFL is improving a refrigeration system that uses low quality heat to provide the energy needed to drive cooling. This system, known as absorption refrigeration system (ARS), typically consists of large coils that transfer heat. Unfortunately, these large heat exchanger coils are responsible for bulkiness and high cost of ARS. UFL is using new materials as well as system design innovations to develop nanoengineered membranes to allow for enhanced heat exchange that reduces bulkiness. UFL’s design allows for compact, cheaper and more reliable use of ARS that use solar or waste heat.

  20. 46 CFR 153.436 - Heat transfer fluids: compatibility with cargo.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 5 2011-10-01 2011-10-01 false Heat transfer fluids: compatibility with cargo. 153.436... Equipment Cargo Temperature Control Systems § 153.436 Heat transfer fluids: compatibility with cargo. A heat transfer fluid separated from the cargo by only one wall (for example, the heat transfer fluid in a coil...

  1. 46 CFR 153.436 - Heat transfer fluids: compatibility with cargo.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 5 2010-10-01 2010-10-01 false Heat transfer fluids: compatibility with cargo. 153.436... Equipment Cargo Temperature Control Systems § 153.436 Heat transfer fluids: compatibility with cargo. A heat transfer fluid separated from the cargo by only one wall (for example, the heat transfer fluid in a coil...

  2. 46 CFR 153.436 - Heat transfer fluids: compatibility with cargo.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 5 2012-10-01 2012-10-01 false Heat transfer fluids: compatibility with cargo. 153.436... Equipment Cargo Temperature Control Systems § 153.436 Heat transfer fluids: compatibility with cargo. A heat transfer fluid separated from the cargo by only one wall (for example, the heat transfer fluid in a coil...

  3. 46 CFR 153.436 - Heat transfer fluids: compatibility with cargo.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 5 2014-10-01 2014-10-01 false Heat transfer fluids: compatibility with cargo. 153.436... Equipment Cargo Temperature Control Systems § 153.436 Heat transfer fluids: compatibility with cargo. A heat transfer fluid separated from the cargo by only one wall (for example, the heat transfer fluid in a coil...

  4. 46 CFR 153.436 - Heat transfer fluids: compatibility with cargo.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 5 2013-10-01 2013-10-01 false Heat transfer fluids: compatibility with cargo. 153.436... Equipment Cargo Temperature Control Systems § 153.436 Heat transfer fluids: compatibility with cargo. A heat transfer fluid separated from the cargo by only one wall (for example, the heat transfer fluid in a coil...

  5. Coiled-coil destabilizing residues in the group A Streptococcus M1 protein are required for functional interaction.

    PubMed

    Stewart, Chelsea M; Buffalo, Cosmo Z; Valderrama, J Andrés; Henningham, Anna; Cole, Jason N; Nizet, Victor; Ghosh, Partho

    2016-08-23

    The sequences of M proteins, the major surface-associated virulence factors of the widespread bacterial pathogen group A Streptococcus, are antigenically variable but have in common a strong propensity to form coiled coils. Paradoxically, these sequences are also replete with coiled-coil destabilizing residues. These features are evident in the irregular coiled-coil structure and thermal instability of M proteins. We present an explanation for this paradox through studies of the B repeats of the medically important M1 protein. The B repeats are required for interaction of M1 with fibrinogen (Fg) and consequent proinflammatory activation. The B repeats sample multiple conformations, including intrinsically disordered, dissociated, as well as two alternate coiled-coil conformations: a Fg-nonbinding register 1 and a Fg-binding register 2. Stabilization of M1 in the Fg-nonbinding register 1 resulted in attenuation of Fg binding as expected, but counterintuitively, so did stabilization in the Fg-binding register 2. Strikingly, these register-stabilized M1 proteins gained the ability to bind Fg when they were destabilized by a chaotrope. These results indicate that M1 stability is antithetical to Fg interaction and that M1 conformational dynamics, as specified by destabilizing residues, are essential for interaction. A "capture-and-collapse" model of association accounts for these observations, in which M1 captures Fg through a dynamic conformation and then collapses into a register 2-coiled coil as a result of stabilization provided by binding energy. Our results support the general conclusion that destabilizing residues are evolutionarily conserved in M proteins to enable functional interactions necessary for pathogenesis.

  6. Coil Migration, Malposition, Stretching and Retrieval

    PubMed Central

    Abe, T.; Hirohata, M.; Tanaka, N.; Uchiyama, Y.; Morimitsu, H.; Kojima, K.; Hayabuchi, N.

    2000-01-01

    Summary In this educational program for complicated coil placements, we report several cases of coil malposition, migration, and retrieval. We emphasize that a decrease in the expected one-to-one motion of the coil is the earliest sign of a possible imminent complication, and the over the core wire technique with a fixed-loop snare (Gooseneck microsnare) is a very effective potential solution for elongated coil retrieval. PMID:20667237

  7. Non-Markovian dynamics of fermionic and bosonic systems coupled to several heat baths

    NASA Astrophysics Data System (ADS)

    Hovhannisyan, A. A.; Sargsyan, V. V.; Adamian, G. G.; Antonenko, N. V.; Lacroix, D.

    2018-03-01

    Employing the fermionic and bosonic Hamiltonians for the collective oscillator linearly FC-coupled with several heat baths, the analytical expressions for the collective occupation number are derived within the non-Markovian quantum Langevin approach. The master equations for the occupation number of collective subsystem are derived and discussed. In the case of Ohmic dissipation with Lorenzian cutoffs, the possibility of reduction of the system with several heat baths to the system with one heat bath is analytically demonstrated. For the fermionic and bosonic systems, a comparative analysis is performed between the collective subsystem coupled to two heat baths and the reference case of the subsystem coupled to one bath.

  8. B1- non-uniformity correction of phased-array coils without measuring coil sensitivity.

    PubMed

    Damen, Frederick C; Cai, Kejia

    2018-04-18

    Parallel imaging can be used to increase SNR and shorten acquisition times, albeit, at the cost of image non-uniformity. B 1 - non-uniformity correction techniques are confounded by signal that varies not only due to coil induced B 1 - sensitivity variation, but also the object's own intrinsic signal. Herein, we propose a method that makes minimal assumptions and uses only the coil images themselves to produce a single combined B 1 - non-uniformity-corrected complex image with the highest available SNR. A novel background noise classifier is used to select voxels of sufficient quality to avoid the need for regularization. Unique properties of the magnitude and phase were used to reduce the B 1 - sensitivity to two joint additive models for estimation of the B 1 - inhomogeneity. The complementary corruption of the imaged object across the coil images is used to abate individual coil correction imperfections. Results are presented from two anatomical cases: (a) an abdominal image that is challenging in both extreme B 1 - sensitivity and intrinsic tissue signal variation, and (b) a brain image with moderate B 1 - sensitivity and intrinsic tissue signal variation. A new relative Signal-to-Noise Ratio (rSNR) quality metric is proposed to evaluate the performance of the proposed method and the RF receiving coil array. The proposed method has been shown to be robust to imaged objects with widely inhomogeneous intrinsic signal, and resilient to poorly performing coil elements. Copyright © 2018. Published by Elsevier Inc.

  9. Measurement of tokamak error fields using plasma response and its applicability to ITER

    DOE PAGES

    Strait, Edward J.; Buttery, Richard J.; Casper, T. A.; ...

    2014-04-17

    The nonlinear response of a low-beta tokamak plasma to non-axisymmetric fields offers an alternative to direct measurement of the non-axisymmetric part of the vacuum magnetic fields, often termed “error fields”. Possible approaches are discussed for determination of error fields and the required current in non-axisymmetric correction coils, with an emphasis on two relatively new methods: measurement of the torque balance on a saturated magnetic island, and measurement of the braking of plasma rotation in the absence of an island. The former is well suited to ohmically heated discharges, while the latter is more appropriate for discharges with a modest amountmore » of neutral beam heating to drive rotation. Both can potentially provide continuous measurements during a discharge, subject to the limitation of a minimum averaging time. The applicability of these methods to ITER is discussed, and an estimate is made of their uncertainties in light of the specifications of ITER’s diagnostic systems. Furthermore, the use of plasma response-based techniques in normal ITER operational scenarios may allow identification of the error field contributions by individual central solenoid coils, but identification of the individual contributions by the outer poloidal field coils or other sources is less likely to be feasible.« less

  10. Rho-associated coiled-coil containing kinases (ROCK)

    PubMed Central

    Julian, Linda; Olson, Michael F

    2014-01-01

    Rho-associated coiled-coil containing kinases (ROCK) were originally identified as effectors of the RhoA small GTPase.1–5 They belong to the AGC family of serine/threonine kinases6 and play vital roles in facilitating actomyosin cytoskeleton contractility downstream of RhoA and RhoC activation. Since their discovery, ROCK kinases have been extensively studied, unveiling their manifold functions in processes including cell contraction, migration, apoptosis, survival, and proliferation. Two mammalian ROCK homologs have been identified, ROCK1 (also called ROCK I, ROKβ, Rho-kinase β, or p160ROCK) and ROCK2 (also known as ROCK II, ROKα, or Rho kinase), hereafter collectively referred to as ROCK. In this review, we will focus on the structure, regulation, and functions of ROCK. PMID:25010901

  11. New flange correction formula applied to interfacial resistance measurements of ohmic contacts to GaAs

    NASA Technical Reports Server (NTRS)

    Lieneweg, Udo; Hannaman, David J.

    1987-01-01

    A quasi-two-dimensional analytical model is developed to account for vertical and horizontal current flow in and adjacent to a square ohmic contact between a metal and a thin semiconducting strip which is wider than the contact. The model includes side taps to the contact area for voltage probing and relates the 'apparent' interfacial resistivity to the (true) interfacial resistivity, the sheet resistance of the semiconducting layer, the contact size, and the width of the 'flange' around the contact. This relation is checked against numerical simulations. With the help of the model, interfacial resistivities of ohmic contacts to GaAs were extracted and found independent of contact size in the range of 1.5-10 microns.

  12. Innovations in compact stellarator coil design

    NASA Astrophysics Data System (ADS)

    Pomphrey, N.; Berry, L.; Boozer, A.; Brooks, A.; Hatcher, R. E.; Hirshman, S. P.; Ku, L.-P.; Miner, W. H.; Mynick, H. E.; Reiersen, W.; Strickler, D. J.; Valanju, P. M.

    2001-03-01

    Experimental devices for the study of the physics of high beta (β gtrsim 4%), low aspect ratio (A lesssim 4.5) stellarator plasmas require coils that will produce plasmas satisfying a set of physics goals, provide experimental flexibility and be practical to construct. In the course of designing a flexible coil set for the National Compact Stellarator Experiment, several innovations have been made that may be useful in future stellarator design efforts. These include: the use of singular value decomposition methods for obtaining families of smooth current potentials on distant coil winding surfaces from which low current density solutions may be identified; the use of a control matrix method for identifying which few of the many detailed elements of a stellarator boundary must be targeted if a coil set is to provide fields to control the essential physics of the plasma; the use of a genetic algorithm for choosing an optimal set of discrete coils from a continuum of potential contours; the evaluation of alternate coil topologies for balancing the trade-off between physics objectives and engineering constraints; the development of a new coil optimization code for designing modular coils and the identification of a `natural' basis for describing current sheet distributions.

  13. Multiple-Coil, Pulse-Induction Metal Detector

    NASA Technical Reports Server (NTRS)

    Lesky, Edward S.; Reid, Alan M.; Bushong, Wilton E.; Dickey, Duane P.

    1988-01-01

    Multiple-head, pulse-induction metal detector scans area of 72 feet squared with combination of eight detector heads, each 3 ft. square. Head includes large primary coil inducing current in smaller secondary coils. Array of eight heads enables searcher to cover large area quickly. Pulses applied to primary coil, induced in secondary coils measured to determine whether metal present within range of detector head. Detector designed for recovery of Space Shuttle debris.

  14. Improved Sensing Coils for SQUIDs

    NASA Technical Reports Server (NTRS)

    Penanen, Konstantin; Hahn, Inseob; Eom, Byeong Ho

    2007-01-01

    An improvement in the design and fabrication of sensing coils of superconducting quantum interference device (SQUID) magnetometers has been proposed to increase sensitivity. It has been estimated that, in some cases, it would be possible to increase sensitivity by about half or to reduce measurement time correspondingly. The pertinent aspects of the problems of design and fabrication can be summarized as follows: In general, to increase the sensitivity of a SQUID magnetometer, it is necessary to maximize the magnetic flux enclosed by the sensing coil while minimizing the self-inductance of this coil. It is often beneficial to fabricate the coil from a thicker wire to reduce its self-inductance. Moreover, to optimize the design of the coil with respect to sensitivity, it may be necessary to shape the wire to other than a commonly available circular or square cross-section. On the other hand, it is not practical to use thicker superconducting wire for the entire superconducting circuit, especially if the design of a specific device requires a persistent-current loop enclosing a remotely placed SQUID sensor. It may be possible to bond a thicker sensing-coil wire to thinner superconducting wires leading to a SQUID sensor, but it could be difficult to ensure reliable superconducting connections, especially if the bonded wires are made of different materials. The main idea is to mold the sensing coil in place, to more nearly optimum cross sectional shape, instead of making the coil by winding standard pre-fabricated wire. For this purpose, a thin superconducting wire loop that is an essential part of the SQUID magnetometer would be encapsulated in a form that would serve as a mold. A low-melting-temperature superconducting metal (e.g., indium, tin, or a lead/tin alloy) would be melted into the form, which would be sized and shaped to impart the required cross section to the coil thus formed.

  15. Displacement control of an antagonistic-type twisted and coiled polymer actuator

    NASA Astrophysics Data System (ADS)

    Suzuki, Motoya; Kamamichi, Norihiro

    2018-03-01

    A novel artificial muscle actuator referred to as a twisted and coiled polymer actuator can be easily fabricated by commercially available nylon fibers. It can be thermally activated and has remarkable properties such as large deformation and flexibility. The actuator uses conductive nylon fibers and can be activated by Joule heating and is easily controlled electrically. However, asymmetric response characteristics due to a speed difference in heating-cooling are a problem. In the case of actuation in air, the cooling speed depends on the external temperature, and is slower than the heating speed. To solve these problems, we apply an antagonistic structure. The validity of the applied method is investigated through numerical simulations and experiments. The response characteristics of the PID feedback control and the 2-DOF control of the displacement are investigated.

  16. Family-specific Kinesin Structures Reveal Neck-linker Length Based on Initiation of the Coiled-coil*

    PubMed Central

    Phillips, Rebecca K.; Peter, Logan G.; Gilbert, Susan P.

    2016-01-01

    Kinesin-1, -2, -5, and -7 generate processive hand-over-hand 8-nm steps to transport intracellular cargoes toward the microtubule plus end. This processive motility requires gating mechanisms to coordinate the mechanochemical cycles of the two motor heads to sustain the processive run. A key structural element believed to regulate the degree of processivity is the neck-linker, a short peptide of 12–18 residues, which connects the motor domain to its coiled-coil stalk. Although a shorter neck-linker has been correlated with longer run lengths, the structural data to support this hypothesis have been lacking. To test this hypothesis, seven kinesin structures were determined by x-ray crystallography. Each included the neck-linker motif, followed by helix α7 that constitutes the start of the coiled-coil stalk. In the majority of the structures, the neck-linker length differed from predictions because helix α7, which initiates the coiled-coil, started earlier in the sequence than predicted. A further examination of structures in the Protein Data Bank reveals that there is a great disparity between the predicted and observed starting residues. This suggests that an accurate prediction of the start of a coiled-coil is currently difficult to achieve. These results are significant because they now exclude simple comparisons between members of the kinesin superfamily and add a further layer of complexity when interpreting the results of mutagenesis or protein fusion. They also re-emphasize the need to consider factors beyond the kinesin neck-linker motif when attempting to understand how inter-head communication is tuned to achieve the degree of processivity required for cellular function. PMID:27462072

  17. Structural basis for cargo binding and autoinhibition of Bicaudal-D1 by a parallel coiled-coil with homotypic registry

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Terawaki, Shin-ichi, E-mail: terawaki@gunma-u.ac.jp; SPring-8 Center, RIKEN, 1-1-1 Koto, Sayo-cho, Sayo-gun, Hyogo 679-5148; Yoshikane, Asuka

    Bicaudal-D1 (BICD1) is an α-helical coiled-coil protein mediating the attachment of specific cargo to cytoplasmic dynein. It plays an essential role in minus end-directed intracellular transport along microtubules. The third C-terminal coiled-coil region of BICD1 (BICD1 CC3) has an important role in cargo sorting, including intracellular vesicles associating with the small GTPase Rab6 and the nuclear pore complex Ran binding protein 2 (RanBP2), and inhibiting the association with cytoplasmic dynein by binding to the first N-terminal coiled-coil region (CC1). The crystal structure of BICD1 CC3 revealed a parallel homodimeric coiled-coil with asymmetry and complementary knobs-into-holes interactions, differing from Drosophila BicDmore » CC3. Furthermore, our binding study indicated that BICD1 CC3 possesses a binding surface for two distinct cargos, Rab6 and RanBP2, and that the CC1-binding site overlaps with the Rab6-binding site. These findings suggest a molecular basis for cargo recognition and autoinhibition of BICD proteins during dynein-dependent intracellular retrograde transport. - Highlights: • BICD1 CC3 is a parallel homodimeric coiled-coil with axial asymmetry. • The coiled-coil packing of BICD1 CC3 is adapted to the equivalent heptad position. • BICD1 CC3 has distinct binding sites for two classes of cargo, Rab6 and RanBP2. • The CC1-binding site of BICD1 CC3 overlaps with the Rab6-binding site.« less

  18. Multi-Canted Coils, Tubes, and Structures

    NASA Technical Reports Server (NTRS)

    Jaster, Mark L. (Inventor)

    2015-01-01

    Coil, tube, and other structures configured with a plurality of individual coils, internal structures, legs or extensions with each having multiple cants per coil, internal structure, leg or extension, and wherein the cants formed therein allow for a load-deflection force when each is compressed. In addition, any horizontal or moment forces are substantially reduced and/or eliminated when a downward vertical force is applied, as minimal or no torsion is created in the individual coils, legs or extensions.

  19. An analysis of 3D solvation structure in biomolecules: application to coiled coil serine and bacteriorhodopsin.

    PubMed

    Hirano, Kenji; Yokogawa, Daisuke; Sato, Hirofumi; Sakaki, Shigeyoshi

    2010-06-17

    Three-dimensional (3D) solvation structure around coiled coil serine (Coil-Ser) and inner 3D hydration structure in bacteriorhodopsin (bR) were studied using a recently developed method named multicenter molecular Ornstein-Zernike equation (MC-MOZ) theory. In addition, a procedure for analyzing the 3D solvent distribution was proposed. The method enables us to calculate the coordination number of solvent water as well as the strength of hydrogen bonding between the water molecule and the protein. The results for Coil-Ser and bR showed very good agreement with the experimental observations.

  20. Cold Heat Storage Characteristics of O/W-type Latent Heat Emulsion Including Continuum Phase of Water Treated with a Freezing Point Depression

    NASA Astrophysics Data System (ADS)

    Inaba, Hideo; Morita, Shin-Ichi

    This paper deals with flow and cold heat storage characteristics of the oil (tetradecane, C14H30, freezing point 278.9 K, Latent heat 229 kJ/kg)/water emulsion as a latent heat storage material having a low melting point. The test emulsion includes a water-urea solution as a continuum phase. The freezing point depression of the continuum phase permits enhancement of the heat transfer rate of the emulison, due to the large temperature difference between the latent heat storage material and water-urea solution. The velocity of emulsion flow and the inlet temperature of coolant in a coiled double tube heat exchanger are chosen as the experimental parameters. The pressure drop, the heat transfer coefficient of the emulsion in the coiled tube are measured in the temperture region over solid and liquid phase of the latent heat storage material. The finishing time of the cold heat storage is defined experimentally in the range of sensible and latent heat storage. It is clarified that the flow behavior of the emulsion as a non-Newtonian fluid has an important role in cold heat storage. The useful nondimentional correlation equations for the additional pressure loss coefficient, the heat transfer coefficient and the finishing time of the cold heat storage are derived in terms of Dean number and heat capacity ratio.

  1. Two-step deposition of Al-doped ZnO on p-GaN to form ohmic contacts.

    PubMed

    Su, Xi; Zhang, Guozhen; Wang, Xiao; Chen, Chao; Wu, Hao; Liu, Chang

    2017-12-01

    Al-doped ZnO (AZO) thin films were deposited directly on p-GaN substrates by using a two-step deposition consisting of polymer assisted deposition (PAD) and atomic layer deposition (ALD) methods. Ohmic contacts of the AZO on p-GaN have been formed. The lowest sheet resistance of the two-step prepared AZO films reached to 145 Ω/sq, and the specific contact resistance reduced to 1.47 × 10 -2 Ω·cm 2 . Transmittance of the AZO films remained above 80% in the visible region. The combination of PAD and ALD technique can be used to prepare p-type ohmic contacts for optoelectronics.

  2. Two-step deposition of Al-doped ZnO on p-GaN to form ohmic contacts

    NASA Astrophysics Data System (ADS)

    Su, Xi; Zhang, Guozhen; Wang, Xiao; Chen, Chao; Wu, Hao; Liu, Chang

    2017-07-01

    Al-doped ZnO (AZO) thin films were deposited directly on p-GaN substrates by using a two-step deposition consisting of polymer assisted deposition (PAD) and atomic layer deposition (ALD) methods. Ohmic contacts of the AZO on p-GaN have been formed. The lowest sheet resistance of the two-step prepared AZO films reached to 145 Ω/sq, and the specific contact resistance reduced to 1.47 × 10-2 Ω·cm2. Transmittance of the AZO films remained above 80% in the visible region. The combination of PAD and ALD technique can be used to prepare p-type ohmic contacts for optoelectronics.

  3. Coil Design for Low Aspect Ratio Stellarators

    NASA Astrophysics Data System (ADS)

    Miner, W. H., Jr.; Valanju, P. M.; Wiley, J. C.; Hirshman, S. P.; Whitson, J. C.

    1998-11-01

    Two compact stellarator designs have recently been under investigation because of their potential as a reactor featuring steady-state, disruption-free operation, low recirculating power and good confinement and beta. Both quasi-axisymmetric (QA) equilibria and quasi-omnigenous (QO) equilibria have been obtained by using the 3-D MHD equilibrium code VMEC. In order to build an experiment, coil sets must be obtained that are compatable with these equilibria. We have been using both the NESCOIL(Merkel, P., Nucl. Fus. 27, 5 (1987) 867.) code and the COILOPT code to find coilsets for both of these types of equilibria. We are considering three types of coil configurations. The first is a combination of modular coils and vertical field coils. The second configuration is a combination of toroidal field coils, vertical field coils and saddle coils. A third configuration is a combination of modular coils and a single helical winding. The quality of each coil set will be evaluated by computing its magnetic field and using that as input to VMEC in free boundary mode to see how accurately the original equilibrium can be reconstructed.

  4. Analysis and experimental study of wireless power transfer with HTS coil and copper coil as the intermediate resonators system

    NASA Astrophysics Data System (ADS)

    Wang, Xiufang; Nie, Xinyi; Liang, Yilang; Lu, Falong; Yan, Zhongming; Wang, Yu

    2017-01-01

    Intermediate resonator (repeater) between transmitter and receiver can significantly increase the distance of wireless power transfer (WPT) and the efficiency of wireless power transfer. The wireless power transfer via strongly coupled magnetic resonances with an high temperature superconducting (HTS) coil and copper coil as intermediate resonators was presented in this paper. The electromagnetic experiment system under different conditions with different repeating coils were simulated by finite element software. The spatial distribution patterns of magnetic induction intensity at different distances were plotted. In this paper, we examined transfer characteristics with HTS repeating coil and copper repeating coil at 77 K and 300 K, respectively. Simulation and experimental results show that HTS and copper repeating coil can effectively enhance the space magnetic induction intensity, which has significant effect on improving the transmission efficiency and lengthening transmission distance. We found that the efficiency and the distance of wireless power transfer system with an HTS coil as repeater is much higher by using of copper coil as repeater.

  5. Mounting improves heat-sink contact with beryllia washer

    NASA Technical Reports Server (NTRS)

    1966-01-01

    To conduct heat away from electrical components that must be electrically insulated from a metal heat sink, a metal washer and a coil spring are placed between one end of the electrical component and the beryllia washer mounted on the heat sink. The thermal paths are formed by the component lead and base, the metal and beryllia washers, and the compressed spring.

  6. BI-ground microstrip array coil vs. conventional microstrip array coil for mouse imaging at 7 tesla

    NASA Astrophysics Data System (ADS)

    Hernández, Ricardo; Terrones, M. A. López; Jakob, P. M.

    2012-10-01

    At high field strengths, the need for more efficient high frequency coils has grown. Since the radiation losses and the interaction between coil and sample increase proportionally to field strength, the quality factor (Q) and the sensitivity of the coil decrease as consequence of these negative effects. Since Zhang et al proposed in 2001 a new surface coil based on the microstrip transmission line for high frequency, different Tx-Rx phased arrays based on this concept have been already introduced in animal and whole body systems at high field strengths, each of them with different modifications in order to get better field homogeneity, SNR or isolation between coil elements in the array. All these arrays for animals systems have been built for rat imaging. One of these modifications is called BI-Ground Microstrip Array Coil (BIGMAC). The implementation of a smaller two-channel BIGMAC design for mouse imaging is studied and its performance compared to a two-channel conventional Microstrip array at 7 Tesla, the higher isolation by using BIGMAC elements in comparison with conventional Microstrip elements is shown in this work.

  7. Two-slot coiled coaxial cable resonator: reaching critical coupling at a reduced number of coils.

    PubMed

    Hefferman, Gerald; Chen, Zhen; Wei, Tao

    2014-11-01

    This paper reports the experimental demonstration of a coiled coaxial cable resonator capable of meeting the critical coupling condition using a reduced number of coils relative to previously reported coiled resonators. By introducing a second slot along the length of the device, a two-slot coiled coaxial cable resonator was fabricated and critical coupling observed at 22 turns. An additional device with one-slot, but otherwise identically constructed, was also fabricated. After 44 turns, the one-slot device had yet to reach critical coupling. An ultrahigh signal-to-noise ratio (greater than 70 dB) was observed at critical coupling of the two-slot device. This reduction in number of slots necessary to reach critical coupling, and the corresponding reduction of physical length of the device, makes this demonstration of the control of critical coupling a potentially important step towards the successful application of coiled coaxial cable resonators to microwave communication and robust sensing applications.

  8. A new method of making ohmic contacts to p-GaN

    NASA Astrophysics Data System (ADS)

    Hernández-Gutierrez, C. A.; Kudriavtsev, Yu.; Mota, Esteban; Hernández, A. G.; Escobosa-Echavarría, A.; Sánchez-Resendiz, V.; Casallas-Moreno, Y. L.; López-López, M.

    2016-12-01

    The structural, chemical, and electrical characteristics of In+ ion-implanted Au/Ni, Au/Nb and Au/W ohmic contacts to p-GaN were investigated. After the preparation of Ni, Nb and W electrode on the surface of p-GaN, the metal/p-GaN contact interface was implanted by 30 keV In+ ions with an implantation dose of 5 × 1015 ions/cm2 at room temperature to form a thin layer of InxGa1-xN located at the metal-semiconductor interface, achieved to reduce the specific contact resistance due to the improving quantum tunneling transport trough to the structure. The characterization was carried out by high-resolution X-ray diffraction, scanning electron microscopy, Raman spectroscopy, and secondary ion mass spectrometry to investigate the formation of ternary alloy, re-crystallization by rapid thermal annealing process after In+ implantation, and the redistribution of elements. The specific contact resistance was extracted by current-voltage (I-V) curves using transmission line method; the lowest specific contact resistance of 2.5 × 10-4 Ωcm2 was achieved for Au/Ni/p-InxGa1-xN/p-GaN ohmic contacts.

  9. Radio frequency coil technology for small-animal MRI.

    PubMed

    Doty, F David; Entzminger, George; Kulkarni, Jatin; Pamarthy, Kranti; Staab, John P

    2007-05-01

    A review of the theory, technology, and use of radio frequency (RF) coils for small-animal MRI is presented. It includes a brief overview of MR signal-to-noise (S/N) analysis and discussions of the various coils commonly used in small-animal MR: surface coils, linear volume coils, birdcages, and their derivatives. The scope is limited to mid-range coils, i.e. coils where the product (fd) of the frequency f and the coil diameter d is in the range 2-30 MHz-m. Common applications include mouse brain and body coils from 125 to 750 MHz, rat body coils up to 500 MHz, and small surface coils at all fields. In this regime, all the sources of loss (coil, capacitor, sample, shield, and transmission lines) are important. All such losses may be accurately captured in some modern full-wave 3D electromagnetics software, and new simulation results are presented for a selection of surface coils using Microwave Studio 2006 by Computer Simulation Technology, showing the dramatic importance of the "lift-off effect". Standard linear circuit simulators have been shown to be useful in optimization of complex coil tuning and matching circuits. There appears to be considerable potential for trading S/N for speed using phased arrays, especially for a larger field of view. Circuit simulators are shown to be useful for optimal mismatching of ultra-low-noise preamps based on the enhancement-mode pseudomorphic high-electron-mobility transistor for optimal coil decoupling in phased arrays. Cryogenically cooled RF coils are shown to offer considerable opportunity for future gains in S/N in smaller samples.

  10. 46 CFR 153.434 - Heat transfer coils within a tank.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... SHIPS CARRYING BULK LIQUID, LIQUEFIED GAS, OR COMPRESSED GAS HAZARDOUS MATERIALS Design and Equipment... the heat transfer fluid at a pressure greater than the pressure exerted on the heating or cooling...

  11. Induction-heating MOCVD reactor with significantly improved heating efficiency and reduced harmful magnetic coupling

    NASA Astrophysics Data System (ADS)

    Li, Kuang-Hui; Alotaibi, Hamad S.; Sun, Haiding; Lin, Ronghui; Guo, Wenzhe; Torres-Castanedo, Carlos G.; Liu, Kaikai; Valdes-Galán, Sergio; Li, Xiaohang

    2018-04-01

    In a conventional induction-heating III-nitride metalorganic chemical vapor deposition (MOCVD) reactor, the induction coil is outside the chamber. Therefore, the magnetic field does not couple with the susceptor well, leading to compromised heating efficiency and harmful coupling with the gas inlet and thus possible overheating. Hence, the gas inlet has to be at a minimum distance away from the susceptor. Because of the elongated flow path, premature reactions can be more severe, particularly between Al- and B-containing precursors and NH3. Here, we propose a structure that can significantly improve the heating efficiency and allow the gas inlet to be closer to the susceptor. Specifically, the induction coil is designed to surround the vertical cylinder of a T-shaped susceptor comprising the cylinder and a top horizontal plate holding the wafer substrate within the reactor. Therefore, the cylinder coupled most magnetic field to serve as the thermal source for the plate. Furthermore, the plate can block and thus significantly reduce the uncoupled magnetic field above the susceptor, thereby allowing the gas inlet to be closer. The results show approximately 140% and 2.6 times increase in the heating and susceptor coupling efficiencies, respectively, as well as a 90% reduction in the harmful magnetic flux on the gas inlet.

  12. Demonstration of Scalable Nernst Voltage in a Coiled Galfenol Wire

    NASA Astrophysics Data System (ADS)

    Codecido, Emilio; Yang, Zihao; Marquez, Jason; Zheng, Yuanhua; Heremans, Joseph; Myers, Roberto

    Transverse thermopower by the Nernst effect is usually considered far too weak an effect for waste heat recovery and power generation. We propose that magnetostriction provides a pathway to enhance the Nernst effect because it increases phonon and magnon coupling. Here, we measure the Nernst coefficient in the magnetostrictive alloy, Galfenol (Fe0.85Ga0.15) and observe an extraordinarily large Nernst coefficient at room temperature of 4 μV/KT. Next we demonstrate a new geometry for efficient and low cost power generation by wrapping Galfenol wire around a hot cylinder. This coil geometry results in a radial temperature gradient direction. With a magnetic field applied in the axial direction, a uniform Nernst electric field is produced along the azimuthal direction at every point along the coil. As a result of this geometry, the Nernst voltage is shown to increase linearly with wire length, proving the concept of scalable Nernst thermal power generation.

  13. Coil spring venting arrangement

    DOEpatents

    McCugh, R.M.

    1975-10-21

    A simple venting device for trapped gas pockets in hydraulic systems is inserted through a small access passages, operated remotely, and removed completely. The device comprises a small diameter, closely wound coil spring which is pushed through a guide temporarily inserted in the access passage. The guide has a central passageway which directs the coil spring radially upward into the pocket, so that, with the guide properly positioned for depth and properly oriented, the coil spring can be pushed up into the top of the pocket to vent it. By positioning a seal around the free end of the guide, the spring and guide are removed and the passage is sealed.

  14. Feasibility of Applying Ohmic Heating and Split-Phase Aseptic Processing for Ration Entree Preservation

    DTIC Science & Technology

    1994-08-01

    study demonstrated that either of these reduced- temperature sterilization processes will produce an acceptable product that is an alternative to thermal...and uniform heating of liquids and solids simultaneously, even of large particles, up to sterilization temperatures . Uniform heating means shorter...potential cost reduction by substitution of continuous processing of a high- temperature /short-time ( HTST ) nature for traditional batch retort

  15. Ohmic contacts to p-GaN Using Au/Ni-Mg-O Metallization

    NASA Astrophysics Data System (ADS)

    Liday, Jozef; Vogrinčič, Peter; Hotový, Ivan; Bonanni, Alberta; Sitter, Helmut; Lalinský, Tibor; Vanko, Gabriel; Řeháček, Vlastimil; Breza, Juraj; Ecke, Gernot

    2010-11-01

    Electrical characteristics and elemental depth profiles of ohmic contacts to p-GaN using Au/Ni-Mg-Ox metallization have been investigated. The objective was to examine the possibilities of increasing the charge carrier concentration in the surface region of GaN by adding Mg, thus of a p-type dopant into the Au/NiOx metallization structure. For this purpose, a Ni-Mg-Ox layer with a low concentration of Mg was deposited on p-GaN by dc reactive magnetron sputtering. The top Au layer was deposited in a similar way. The fabricated contact structures were annealed in N2. When the Ni-Mg layer in the Au/Ni-Mg-Ox/p-GaN structure was deposited in an atmosphere with a low concentration of oxygen (0.2 at%), the structure exhibited a low resistance ohmic nature. The contact resistance was lower than in the case of a Au/Ni-Ox/p-GaN structure without the Mg dopant in the metallic layer. An increase in the concentration of oxygen in the working atmosphere resulted in higher values of the contact resistance of the Au/Ni-Mg-Ox/p-GaN structure. In our opinion the ohmic nature of the contact structure is related to the existence of a metal/p-NiO/p-GaN scheme. The measured values of the contact resistance in the Au/Ni-Mg-Ox/p-GaN structure in comparison with the Au/Ni-Ox/p-GaN structure are caused by an increased charge carrier concentration in the surface region of p-GaN, which is a consequence of Mg diffusion from the Ni-Mg-Ox layer.

  16. Inductive ion acceleration and heating in picket fence geometry: Theory and simulations

    NASA Astrophysics Data System (ADS)

    Leboeuf, J. N.; Dawson, J. M.; Ratliff, S. T.; Rhodes, M.; Luhmann, N. C., Jr.

    1982-11-01

    Particle simulations and analytic theory confirm the experimental observation of preferential ion acceleration and heating by an inductive electric field Edc in picket-fence geometry. The ions which are unmagnetized over most of the current channel are freely accelerated by the inductive field; the magnetized electrons are tied to the field lines and do not run away as long as the binding ev×B/c force is greater than the detrapping inductive force eEdc. Consequently, most of the current is carried by the ions which are also Ohmically heated.

  17. A study of the Au/Ni ohmic contact on p-GaN

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Qiao, D.; Yu, L. S.; Lau, S. S.

    2000-10-01

    The formation mechanism of the ohmic Au/Ni/p-GaN contact has been investigated. We found that it is essential to (i) deposit a structure of Au and Ni in the proper deposition sequence, and (ii) anneal the bilayer structure in an oxygen containing ambient. Our findings indicated that oxygen assists the layer-reversal reactions of the metallized layers to form a structure of NiO/Au/p-GaN. The presence of oxygen during annealing appears to increase the conductivity of the p-GaN. It is further suggested that Ni removes or reduces the surface contamination of the GaN sample before or during layer reversal. In the final contactmore » structure, an Au layer, which has a large work function, is in contact with the p-GaN substrate. The presence of Au in the entire contacting layer improves the conductivity of the contact. An ohmic formation mechanism based on our experimental results is proposed and discussed in this work. (c) 2000 American Institute of Physics.« less

  18. Lack of dependence on resonant error field of locked mode island size in ohmic plasmas in DIII-D

    DOE PAGES

    Haye, R. J. La; Paz-Soldan, C.; Strait, E. J.

    2015-01-23

    DIII-D experiments show that fully penetrated resonant n=1 error field locked modes in Ohmic plasmas with safety factor q 95≳3 grow to similar large disruptive size, independent of resonant error field correction. Relatively small resonant (m/n=2/1) static error fields are shielded in Ohmic plasmas by the natural rotation at the electron diamagnetic drift frequency. However, the drag from error fields can lower rotation such that a bifurcation results, from nearly complete shielding to full penetration, i.e., to a driven locked mode island that can induce disruption.

  19. In situ ohmic contact formation for n-type Ge via non-equilibrium processing

    NASA Astrophysics Data System (ADS)

    Prucnal, S.; Frigerio, J.; Napolitani, E.; Ballabio, A.; Berencén, Y.; Rebohle, L.; Wang, M.; Böttger, R.; Voelskow, M.; Isella, G.; Hübner, R.; Helm, M.; Zhou, S.; Skorupa, W.

    2017-11-01

    Highly scaled nanoelectronics requires effective channel doping above 5 × 1019 cm-3 together with ohmic contacts with extremely low specific contact resistivity. Nowadays, Ge becomes very attractive for modern optoelectronics due to the high carrier mobility and the quasi-direct bandgap, but n-type Ge doped above 5 × 1019 cm-3 is metastable and thus difficult to be achieved. In this letter, we report on the formation of low-resistivity ohmic contacts in highly n-type doped Ge via non-equilibrium thermal processing consisting of millisecond-range flash lamp annealing. This is a single-step process that allows for the formation of a 90 nm thick NiGe layer with a very sharp interface between NiGe and Ge. The measured carrier concentration in Ge is above 9 × 1019 cm-3 with a specific contact resistivity of 1.2 × 10-6 Ω cm2. Simultaneously, both the diffusion and the electrical deactivation of P are fully suppressed.

  20. Better Ohmic Contacts For InP Semiconductor Devices

    NASA Technical Reports Server (NTRS)

    Weizer, Victor G.; Fatemi, Navid S.

    1995-01-01

    Four design modifications enable fabrication of improved ohmic contacts on InP-based semiconductor devices. First modification consists of insertion of layer of gold phosphide between n-doped InP and metal or other overlayer of contact material. Second, includes first modification plus use of particular metal overlayer to achieve very low contact resistivities. Third, also involves deposition of Au(2)P(3) interlayer; in addition, refractory metal (W or Ta) deposited to form contact overlayer. In fourth, contact layer of Auln alloy deposited directly on InP. Improved contacts exhibit low electrical resistances and fabricated without exposing devices to destructive predeposition or postdeposition treatments.

  1. Development of Ground Coils with Low Eddy Current Loss by Applying the Compression Molding Method after the Coil Winding

    NASA Astrophysics Data System (ADS)

    Suzuki, Masao; Aiba, Masayuki; Takahashi, Noriyuki; Ota, Satoru; Okada, Shigenori

    In a magnetically levitated transportation (MAGLEV) system, a huge number of ground coils will be required because they must be laid for the whole line. Therefore, stable performance and reduced cost are essential requirements for the ground coil development. On the other hand, because the magnetic field changes when the superconducting magnet passes by, an eddy current will be generated in the conductor of the ground coil and will result in energy loss. The loss not only increases the magnetic resistance for the train running but also brings an increase in the ground coil temperature. Therefore, the reduction of the eddy current loss is extremely important. This study examined ground coils in which both the eddy current loss and temperature increase were small. Furthermore, quantitative comparison for the eddy current loss of various magnet wire samples was performed by bench test. On the basis of the comparison, a round twisted wire having low eddy current loss was selected as an effective ground coil material. In addition, the ground coils were manufactured on trial. A favorable outlook to improve the size accuracy of the winding coil and uneven thickness of molded resin was obtained without reducing the insulation strength between the coil layers by applying a compression molding after winding.

  2. Vapor compression heat pump system field tests at the TECH complex

    NASA Astrophysics Data System (ADS)

    Baxter, V. D.

    1985-07-01

    The Tennessee Energy Conservation In Housing (TECH) complex has been utilized since 1977 as a field test site for several novel and conventional heat pump systems for space conditioning and water heating. Systems tested include the Annual Cycle Energy System (ACES), solar assisted heat pumps (SAHP) both parallel and series, two conventional air-to-air heat pumps, an air-to-air heat pump with desuperheater water heater, and horizontal coil and multiple shallow vertical coil ground-coupled heat pumps (GCHP). A direct comparison of the measured annual performance of the test systems was not possible. However, a cursory examination revealed that the ACES had the best performance. However, its high cost makes it unlikely that it will achieve widespread use. Costs for the SAHP systems are similar to those of the ACES but their performance is not as good. Integration of water heating and space conditioning functions with a desuperheater yielded significant efficiency improvement at modest cost. The GCHP systems performed much better for heating than for cooling and may well be the most efficient alternative for residences in cold climates.

  3. Vapor compression heat pump system field tests at the tech complex

    NASA Astrophysics Data System (ADS)

    Baxter, Van D.

    1985-11-01

    The Tennessee Energy Conservation In Housing (TECH) complex has been utilized since 1977 as a field test site for several novel and conventional heat pump systems for space conditioning and water heating. Systems tested include the Annual Cycle Energy System (ACES), solar assisted heat pumps (SAHP) both parallel and series, two conventional air-to-air heat pumps, an air-to-air heat pump with desuperheater water heater, and horizontal coil and multiple shallow vertical coil ground-coupled heat pumps (GCHP). A direct comparison of the measured annual performance of the test systems was not possible. However, a cursory examination revealed that the ACES had the best performance, however, its high cost makes it unlikely that it will achieve wide-spread use. Costs for the SAHP systems are similar to those of the ACES but their performance is not as good. Integration of water heating and space conditioning functions with a desuperheater yielded significant efficiency improvement at modest cost. The GCHP systems performed much better for heating than for cooling and may well be the most efficient alternative for residences in cold climates.

  4. A switch from parallel to antiparallel strand orientation in a coiled-coil X-ray structure via two core hydrophobic mutations

    DOE PAGES

    Malashkevich, Vladimir N.; Higgins, Chelsea D.; Almo, Steven C.; ...

    2015-05-06

    The coiled-coil is one of the most ubiquitous and well studied protein structural motifs. Significant effort has been devoted to dissecting subtle variations of the typical heptad repeat sequence pattern that can designate larger topological features such as relative α-helical orientation and oligomer size. Here in this paper we report the X-ray structure of a model coiled-coil peptide, HA2-Del-L2seM, which forms an unanticipated core antiparallel dimer with potential sites for discrete higher-order multimerization (trimer or tetramer). In the X-ray structure, a third, partially-ordered α-helix is weakly associated with the antiparallel dimer and analytical ultracentrifugation experiments indicate the peptide forms amore » well-defined tetramer in solution. The HA2-Del-L2seM sequence is closely related to a parent model peptide, HA2-Del, which we previously reported adopts a parallel trimer; HA2-Del-L2seM differs by only hydrophobic leucine to selenomethione mutations and thus this subtle difference is sufficient to switch both relative α-helical topology and number of α-helices participating in the coiled-coil. Comparison of the X-ray structures of HA2-Del-L2seM (reported here) with the HA2-Del parent (reported previously) reveals novel interactions involving the selenomethionine residues that promote antiparallel coiled-coil configuration and preclude parallel trimer formation. Finally, these novel atomic insights are instructive for understanding subtle features that can affect coiled-coil topology and provide additional information for design of antiparallel coiled-coils.« less

  5. Effects of Gradient Coil Noise and Gradient Coil Replacement on the Reproducibility of Resting State Networks.

    PubMed

    Bagarinao, Epifanio; Tsuzuki, Erina; Yoshida, Yukina; Ozawa, Yohei; Kuzuya, Maki; Otani, Takashi; Koyama, Shuji; Isoda, Haruo; Watanabe, Hirohisa; Maesawa, Satoshi; Naganawa, Shinji; Sobue, Gen

    2018-01-01

    The stability of the MRI scanner throughout a given study is critical in minimizing hardware-induced variability in the acquired imaging data set. However, MRI scanners do malfunction at times, which could generate image artifacts and would require the replacement of a major component such as its gradient coil. In this article, we examined the effect of low intensity, randomly occurring hardware-related noise due to a faulty gradient coil on brain morphometric measures derived from T1-weighted images and resting state networks (RSNs) constructed from resting state functional MRI. We also introduced a method to detect and minimize the effect of the noise associated with a faulty gradient coil. Finally, we assessed the reproducibility of these morphometric measures and RSNs before and after gradient coil replacement. Our results showed that gradient coil noise, even at relatively low intensities, could introduce a large number of voxels exhibiting spurious significant connectivity changes in several RSNs. However, censoring the affected volumes during the analysis could minimize, if not completely eliminate, these spurious connectivity changes and could lead to reproducible RSNs even after gradient coil replacement.

  6. Effects of Gradient Coil Noise and Gradient Coil Replacement on the Reproducibility of Resting State Networks

    PubMed Central

    Bagarinao, Epifanio; Tsuzuki, Erina; Yoshida, Yukina; Ozawa, Yohei; Kuzuya, Maki; Otani, Takashi; Koyama, Shuji; Isoda, Haruo; Watanabe, Hirohisa; Maesawa, Satoshi; Naganawa, Shinji; Sobue, Gen

    2018-01-01

    The stability of the MRI scanner throughout a given study is critical in minimizing hardware-induced variability in the acquired imaging data set. However, MRI scanners do malfunction at times, which could generate image artifacts and would require the replacement of a major component such as its gradient coil. In this article, we examined the effect of low intensity, randomly occurring hardware-related noise due to a faulty gradient coil on brain morphometric measures derived from T1-weighted images and resting state networks (RSNs) constructed from resting state functional MRI. We also introduced a method to detect and minimize the effect of the noise associated with a faulty gradient coil. Finally, we assessed the reproducibility of these morphometric measures and RSNs before and after gradient coil replacement. Our results showed that gradient coil noise, even at relatively low intensities, could introduce a large number of voxels exhibiting spurious significant connectivity changes in several RSNs. However, censoring the affected volumes during the analysis could minimize, if not completely eliminate, these spurious connectivity changes and could lead to reproducible RSNs even after gradient coil replacement. PMID:29725294

  7. Anomalous Ion Heating, Intrinsic and Induced Rotation in the Pegasus Toroidal Experiment

    NASA Astrophysics Data System (ADS)

    Burke, M. G.; Barr, J. L.; Bongard, M. W.; Fonck, R. J.; Hinson, E. T.; Perry, J. M.; Redd, A. J.; Thome, K. E.

    2014-10-01

    Pegasus plasmas are initiated through either standard, MHD stable, inductive current drive or non-solenoidal local helicity injection (LHI) current drive with strong reconnection activity, providing a rich environment to study ion dynamics. During LHI discharges, a large amount of anomalous impurity ion heating has been observed, with Ti ~ 800 eV but Te < 100 eV. The ion heating is hypothesized to be a result of large-scale magnetic reconnection activity, as the amount of heating scales with increasing fluctuation amplitude of the dominant, edge localized, n = 1 MHD mode. Chordal Ti spatial profiles indicate centrally peaked temperatures, suggesting a region of good confinement near the plasma core surrounded by a stochastic region. LHI plasmas are observed to rotate, perhaps due to an inward radial current generated by the stochastization of the plasma edge by the injected current streams. H-mode plasmas are initiated using a combination of high-field side fueling and Ohmic current drive. This regime shows a significant increase in rotation shear compared to L-mode plasmas. In addition, these plasmas have been observed to rotate in the counter-Ip direction without any external momentum sources. The intrinsic rotation direction is consistent with predictions from the saturated Ohmic confinement regime. Work supported by US DOE Grant DE-FG02-96ER54375.

  8. Completely transparent ohmic electrode on p-type AlGaN for UV LEDs with core-shell Cu@alloy nanosilk network (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Cai, Duanjun; Wang, Huachun; Huang, Youyang; Wu, Chenping; Chen, Xiaohong; Gao, Na; Wei, Tongbo T.; Wang, Junxi; Li, Shuping; Kang, Junyong

    2016-09-01

    Metal nanowire networks hold a great promise, which have been supposed the only alternative to ITO as transparent electrodes for their excellent performance in touch screen, LED and solar cell. It is well known that the difficulty in making transparent ohmic electrode to p-type high-Al-content AlGaN conducting layer has highly constrained the further development of UV LEDs. On the IWN-2014, we reported the ohmic contact to n, p-GaN with direct graphene 3D-coated Cu nanosilk network and the fabrication of complete blue LED. On the ICNS-2015, we reported the ohmic contact to n-type AlGaN conducting layer with Cu@alloy nanosilk network. Here, we further demonstrate the latest results that a novel technique is proposed for fabricating transparent ohmic electrode to high-Al-content AlGaN p-type conducting layer in UV LEDs using Cu@alloy core-shell nanosilk network. The superfine copper nanowires (16 nm) was synthesized for coating various metals such as Ni, Zn, V or Ti with different work functions. The transmittance showed a high transparency (> 90%) over a broad wavelength range from 200 to 3000 nm. By thermal annealing, ohmic contact was achieved on p-type Al0.5Ga0.5N layer with Cu@Ni nanosilk network, showing clearly linear I-V curve. By skipping the p-type GaN cladding layer, complete UV LED chip was fabricated and successfully lit with bright emission at 276 nm.

  9. Improvement of electrical and optical properties of p-GaN Ohmic metals under ultraviolet light irradiation annealing processes

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chae, S.W.; Yoon, S.K.; Kwak, J.S.

    2006-05-15

    We report the improvement of electrical and optical properties of p-GaN Ohmic metals, ZnNi(10 nm)/Au(10 nm), by ultraviolet (UV) light irradiation. After UV light irradiation, the specific contact resistance of p-GaN decreased slightly from 2.99x10{sup -4} to 2.54x10{sup -4} {omega} cm{sup 2}, while the transmittance of the contact layer increased form 75% to 85% at a wavelength of 460 nm. In addition, the forward voltage of InGaN/GaN light-emitting diode chip at 20 mA decreased from 3.55 to 3.45 V, and the output power increased form 18 to 25 mW by UV light irradiation. The low resistance and high transmittance ofmore » the p-GaN Ohmic metals are attributed to the reduced Shottky barrier by the formation of gallium oxide and the increased oxidation of p-Ohmic metals, respectively, due to ozone generated form oxygen during UV light irradiation.« less

  10. Immersed finger-type indium tin oxide ohmic contacts on p-GaN photoelectrodes for photoelectrochemical hydrogen generation.

    PubMed

    Liu, Shu-Yen; Sheu, J K; Lee, M L; Lin, Yu-Chuan; Tu, S J; Huang, F W; Lai, W C

    2012-03-12

    In this study, we demonstrated photoelectrochemical (PEC) hydrogen generation using p-GaN photoelectrodes associated with immersed finger-type indium tin oxide (IF-ITO) ohmic contacts. The IF-ITO/p-GaN photoelectrode scheme exhibits higher photocurrent and gas generation rate compared with p-GaN photoelectrodes without IF-ITO ohmic contacts. In addition, the critical external bias for detectable hydrogen generation can be effectively reduced by the use of IF-ITO ohmic contacts. This finding can be attributed to the greatly uniform distribution of the IF-ITO/p-GaN photoelectrode applied fields over the whole working area. As a result, the collection efficiency of photo-generated holes by electrode contacts is higher than that of p-GaN photoelectrodes without IF-ITO contacts. Microscopy revealed a tiny change on the p-GaN surfaces before and after hydrogen generation. In contrast, photoelectrodes composed of n-GaN have a short lifetime due to n-GaN corrosion during hydrogen generation. Findings of this study indicate that the ITO finger contacts on p-GaN layer is a potential candidate as photoelectrodes for PEC hydrogen generation.

  11. System and method of adjusting the equilibrium temperature of an inductively-heated susceptor

    DOEpatents

    Matsen, Marc R; Negley, Mark A; Geren, William Preston

    2015-02-24

    A system for inductively heating a workpiece may include an induction coil, at least one susceptor face sheet, and a current controller coupled. The induction coil may be configured to conduct an alternating current and generate a magnetic field in response to the alternating current. The susceptor face sheet may be configured to have a workpiece positioned therewith. The susceptor face sheet may be formed of a ferromagnetic alloy having a Curie temperature and being inductively heatable to an equilibrium temperature approaching the Curie temperature in response to the magnetic field. The current controller may be coupled to the induction coil and may be configured to adjust the alternating current in a manner causing a change in at least one heating parameter of the susceptor face sheet.

  12. Eccentric figure-eight coils for transcranial magnetic stimulation.

    PubMed

    Sekino, Masaki; Ohsaki, Hiroyuki; Takiyama, Yoshihiro; Yamamoto, Keita; Matsuzaki, Taiga; Yasumuro, Yoshihiro; Nishikawa, Atsushi; Maruo, Tomoyuki; Hosomi, Koichi; Saitoh, Youichi

    2015-01-01

    Previously we proposed an eccentric figure-eight coil that can cause threshold stimulation in the brain at lower driving currents. In this study, we performed numerical simulations and magnetic stimulations to healthy subjects for evaluating the advantages of the eccentric coil. The simulations were performed using a simplified spherical brain model and a realistic human brain model. We found that the eccentric coil required a driving current intensity of approximately 18% less than that required by the concentric coil to cause comparable eddy current densities within the brain. The eddy current localization of the eccentric coil was slightly higher than that of the concentric coil. A prototype eccentric coil was designed and fabricated. Instead of winding a wire around a bobbin, we cut eccentric-spiral slits on the insulator cases, and a wire was woven through the slits. The coils were used to deliver magnetic stimulation to healthy subjects; among our results, we found that the current slew rate corresponding to motor threshold values for the concentric and eccentric coils were 86 and 78 A/µs, respectively. The results indicate that the eccentric coil consistently requires a lower driving current to reach the motor threshold than the concentric coil. Future development of compact magnetic stimulators will enable the treatment of some intractable neurological diseases at home. © 2014 Wiley Periodicals, Inc.

  13. Trimeric, Coiled-coil Extension on Peptide Fusion Inhibitor of HIV-1 Influences Selection of Resistance Pathways*

    PubMed Central

    Zhuang, Min; Wang, Wei; De Feo, Christopher J.; Vassell, Russell; Weiss, Carol D.

    2012-01-01

    Peptides corresponding to N- and C-terminal heptad repeat regions (HR1 and HR2, respectively) of viral fusion proteins can block infection of viruses in a dominant negative manner by interfering with refolding of the viral HR1 and HR2 to form a six-helix bundle (6HB) that drives fusion between viral and host cell membranes. The 6HB of the HIV gp41 (endogenous bundle) consists of an HR1 coiled-coil trimer with grooves lined by antiparallel HR2 helices. HR1 peptides form coiled-coil oligomers that may bind to gp41 HR2 as trimers to form a heterologous 6HB (inhibitor bundle) or to gp41 HR1 as monomers or dimers to form a heterologous coiled coil. To gain insights into mechanisms of Env entry and inhibition by HR1 peptides, we compared resistance to a peptide corresponding to 36 residues in gp41 HR1 (N36) and the same peptide with a coiled-coil trimerization domain fused to its N terminus (IZN36) that stabilizes the trimer and increases inhibitor potency (Eckert, D. M., and Kim, P. S. (2001) Proc. Nat. Acad. Sci. U.S.A. 98, 11187–11192). Whereas N36 selected two genetic pathways with equal probability, each defined by an early mutation in either HR1 or HR2, IZN36 preferentially selected the HR1 pathway. Both pathways conferred cross-resistance to both peptides. Each HR mutation enhanced the thermostability of the endogenous 6HB, potentially allowing the virus to simultaneously escape inhibitors targeting either gp41 HR1 or HR2. These findings inform inhibitor design and identify regions of plasticity in the highly conserved gp41 that modulate virus entry and escape from HR1 peptide inhibitors. PMID:22235115

  14. Parametric Study of HTS Coil Quench Protection Strategies

    NASA Astrophysics Data System (ADS)

    Seibert, Joseph; Zarnstorff, Michael; Zhai, Yuhu

    2016-10-01

    Next generation fusion devices require high magnetic fields to adequately contain burning plasmas. Use of high temperature superconducting (HTS) coils to generate these magnetic fields would lower energy cost of operation as well as increase stability of the superconducting state compared to low temperature superconducting coils. However, use of HTS coils requires developing quench protection strategies to prevent damage to the coils. One technique involves the utilization of copper discs and other conductors mutually coupled to the HTS coil to quickly extract the current from the coil. Another technique allows conduction between HTS turns to reduce the current in the coil during quench. This project describes a parametric study of the HTS coil and resistive-conductor setup in order to determine limiting cases of the geometry in an attempt to optimize current extraction and coil protection during quench scenarios. This work was supported in part by the U.S. Department of Energy, Office of Science, Office of Workforce Development for Teachers and Scientists (WDTS) under the Science Undergraduate Laboratory Internship (SULI) program.

  15. Energy dissipation of composite multifilamentary superconductors for high-current ramp-field magnet applications

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Gung, C.Y.

    1993-01-01

    Energy dissipation, which is also called AC loss, of a composite multifilamentary superconducting wire is one of the most fundamental concerns in building a stable superconducting magnet. Characterization and reduction of AC losses are especially important in designing a superconducting magnet for generating transient magnetic fields. The goal of this thesis is to improve the understanding of AC-loss properties of superconducting wires developed for high-current ramp-field magnet applications. The major tasks include: (1) building an advanced AC-loss measurement system, (2) measuring AC losses of superconducting wires under simulated pulse magnet operations, (3) developing an analytical model for explaining the newmore » AC-loss properties found in the experiment, and (4) developing a computational methodology for comparing AC losses of a superconducting wire with those of a cable for a superconducting pulse magnet. A new experimental system using an isothermal calorimetric method was designed and constructed to measure the absolute AC losses in a composite superconductor. This unique experimental setup is capable of measuring AC losses of a brittle Nb{sub 3}Sn wire carrying high AC current in-phase with a large-amplitude pulse magnetic field. Improvements of the accuracy and the efficiency of this method are discussed. Three different types of composite wire have been measured: a Nb{sub 3}Sn modified jelly-roll (MJR) internal-tin wire used in a prototype ohmic heating coil, a Nb{sub 3}Sn internal-tin wire developed for a fusion reactor ohmic heating coil, and a NbTi wire developed for the magnets in a particle accelerator. The cross sectional constructions of these wires represent typical commercial wires manufactured for pulse magnet applications.« less

  16. Split Coil Forms for Rotary Transformers

    NASA Technical Reports Server (NTRS)

    Mclyman, C. W. T.

    1982-01-01

    Split cores for rotor and stator windings of rotary transformer mounted around their respective coils (which are in bobbins) and cemented together. This arrangement simplifies winding of stator coil to go in a slot in inner diameter of stator coil. One practical application of rotary transformers fabricated according to this technique is for centrifuges, in which conventional sliprings are of uncertain reliability.

  17. Service life of counter-current chromatography coils.

    PubMed

    Conway, Walter D

    2007-06-01

    A multilayer coil of PTFE tubing, which failed after being used each workday for about 3 years in a type J centrifuge, was examined. Two types of defects were found. One, called crazes, occurs throughout the coil and does not leak initially, but may eventually lead to a short, axially oriented slit. Another, called indentations, is seen primarily in the innermost and other nearby layers. They are elongated, about 5 mm, indentations, usually on the central side of the tubing. These eventually crack and leak. PTFE tubing is permeable to air and hexane and expands by more than 1% when immersed in hexane, heptane or chloroform for a few days. It is suggested that the crazes result from exposure of the somewhat flexible tubing to the undulating centripetal force field in the coil-planet centrifuge, especially when further softened by solvent absorption. The indentations may result from carriage of the excess tubing length, created by solvent absorption, from the coil periphery to the coil center by the centripetal force field, which continuously travels from the peripheral tail to the central head of the coil. A 1% increase in coil length creates 74 cm of excess tubing in the 160-ml coils examined in this study. It is suggested that fluorinated ethylene propylene (FEP) tubing, especially when etched on the outside, may provide more stable CCC coils, since its expansion when exposed to organic solvents is 0.1 or less than that of PTFE.

  18. Novel transcranial magnetic stimulation coil for mice

    NASA Astrophysics Data System (ADS)

    March, Stephen; Stark, Spencer; Crowther, Lawrence; Hadimani, Ravi; Jiles, David

    2014-03-01

    Transcranial magnetic stimulation (TMS) shows potential for non-invasive treatment of various neurological disorders. Significant work has been performed on the design of coils used for TMS on human subjects but few reports have been made on the design of coils for use on the brains of animals such as mice. This work is needed as TMS studies utilizing mice can allow rapid preclinical development of TMS for human disorders but the coil designs developed for use on humans are inadequate for optimal stimulation of the much smaller mouse brain. A novel TMS coil has been developed with the goal of inducing strong and focused electric fields for the stimulation of small animals such as mice. Calculations of induced electric fields were performed utilizing an MRI derived inhomogeneous model of an adult male mouse. Mechanical and thermal analysis of this new TMS helmet-coil design have also been performed at anticipated TMS operating conditions to ensure mechanical stability of the new coil and establish expected linear attraction and rotational force values. Calculated temperature increases for typical stimulation periods indicate the helmet-coil system is capable of operating within established medical standards. A prototype of the coil has been fabricated and characterization results are presented.

  19. Characteristics of bowl-shaped coils for transcranial magnetic stimulation

    NASA Astrophysics Data System (ADS)

    Yamamoto, Keita; Suyama, Momoko; Takiyama, Yoshihiro; Kim, Dongmin; Saitoh, Youichi; Sekino, Masaki

    2015-05-01

    Transcranial magnetic stimulation (TMS) has recently been used as a method for the treatment of neurological and psychiatric diseases. Daily TMS sessions can provide continuous therapeutic effectiveness, and the installation of TMS systems at patients' homes has been proposed. A figure-eight coil, which is normally used for TMS therapy, induces a highly localized electric field; however, it is challenging to achieve accurate coil positioning above the targeted brain area using this coil. In this paper, a bowl-shaped coil for stimulating a localized but wider area of the brain is proposed. The coil's electromagnetic characteristics were analyzed using finite element methods, and the analysis showed that the bowl-shaped coil induced electric fields in a wider area of the brain model than a figure-eight coil. The expanded distribution of the electric field led to greater robustness of the coil to the coil-positioning error. To improve the efficiency of the coil, the relationship between individual coil design parameters and the resulting coil characteristics was numerically analyzed. It was concluded that lengthening the outer spherical radius and narrowing the width of the coil were effective methods for obtaining a more effective and more uniform distribution of the electric field.

  20. Transcranial Magnetic Stimulation-coil design with improved focality

    NASA Astrophysics Data System (ADS)

    Rastogi, P.; Lee, E. G.; Hadimani, R. L.; Jiles, D. C.

    2017-05-01

    Transcranial Magnetic Stimulation (TMS) is a technique for neuromodulation that can be used as a non-invasive therapy for various neurological disorders. In TMS, a time varying magnetic field generated from an electromagnetic coil placed on the scalp is used to induce an electric field inside the brain. TMS coil geometry plays an important role in determining the focality and depth of penetration of the induced electric field responsible for stimulation. Clinicians and basic scientists are interested in stimulating a localized area of the brain, while minimizing the stimulation of surrounding neural networks. In this paper, a novel coil has been proposed, namely Quadruple Butterfly Coil (QBC) with an improved focality over the commercial Figure-8 coil. Finite element simulations were conducted with both the QBC and the conventional Figure-8 coil. The two coil's stimulation profiles were assessed with 50 anatomically realistic MRI derived head models. The coils were positioned on the vertex and the scalp over the dorsolateral prefrontal cortex to stimulate the brain. Computer modeling of the coils has been done to determine the parameters of interest-volume of stimulation, maximum electric field, location of maximum electric field and area of stimulation across all 50 head models for both coils.

  1. Pure silver ohmic contacts to N- and P- type gallium arsenide materials

    DOEpatents

    Hogan, Stephen J.

    1986-01-01

    Disclosed is an improved process for manufacturing gallium arsenide semiconductor devices having as its components an n-type gallium arsenide substrate layer and a p-type gallium arsenide diffused layer. The improved process comprises forming a pure silver ohmic contact to both the diffused layer and the substrate layer, wherein the n-type layer comprises a substantially low doping carrier concentration.

  2. [Surface coils for magnetic-resonance images].

    PubMed

    Rodríguez-González, Alfredo Odón; Amador-Baheza, Ricardo; Rojas-Jasso, Rafael; Barrios-Alvarez, Fernando Alejandro

    2005-01-01

    Since the introduction of magnetic resonance imaging in Mexico, the development of this important medical imaging technology has been almost non-existing in our country. The very first surface coil prototypes for clinical applications in magnetic resonance imaging has been developed at the Center of Research in Medical Imaging and Instrumentation of the Universidad Autónoma Metropolitana Iztapalapa (Metropolitan Autonomous University, Campus Iztapalapa). Two surface coil prototypes were built: a) a circular-shaped coil and b) a square-shaped coil for multiple regions of the body, such as heart, brain, knee, hands, and ankles. These coils were tested on the 1.5T imager of the ABC Hospital-Tacubaya, located in Mexico City. Brain images of healthy volunteers were obtained in different orientations: sagittal, coronal, and axial. Since images showed a good-enough clinical quality for diagnosis, it is fair to say that these coil prototypes can be used in the clinical environment, and with small modifications, they can be made compatible with almost any commercial scanner. This type of development can offer new alternatives for further collaboration between the research centers and the radiology community, in the search of new applications and developments of this imaging technique.

  3. Radiation-hard electrical coil and method for its fabrication

    DOEpatents

    Grieggs, R.J.; Blake, R.D.; Gac, F.D.

    1982-06-29

    A radiation-hard insulated electrical coil and method for making the same are disclosed. In accordance with the method, a conductor, preferably copper, is wrapped with an aluminum strip and then tightly wound into a coil. The aluminum-wrapped coil is then annealed to relax the conductor in the coiled configuration. The annealed coil is then immersed in an alkaline solution to dissolve the aluminum strip, leaving the bare conductor in a coiled configuration with all of the windings closely packed yet uniformly spaced from one another. The coil is then insulated with a refractory insulating material. In the preferred embodiment, the coil is insulated by coating it with a vitreous enamel and subsequently potting the enamelled coil in a castable ceramic concrete. The resulting coil is substantially insensitive to radiation and may be operated continuously in high radiation environments for long periods of time.

  4. Safety of Radioembolization with {sup 90}Yttrium Resin Microspheres Depending on Coiling or No-Coiling of Aberrant/High-Risk Vessels

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Paprottka, P. M., E-mail: philipp.paprottka@med.lmu.de, E-mail: philipp.paprottka@med.uni-muenchen.de; Paprottka, K. J., E-mail: karolin.paprottka@med.lmu.de; Walter, A., E-mail: alexandra.Walter@campus.lmu.de

    2015-08-15

    PurposeTo evaluate the safety of radioembolization (RE) with {sup 90}Yttrium ({sup 90}Y) resin microspheres depending on coiling or no-coiling of aberrant/high-risk vessels.Materials and MethodsEarly and late toxicity after 566 RE procedures were analyzed retrospectively in accordance with the National Cancer Institute’s Common Terminology Criteria for Adverse Events (CTCAE v3.0). For optimal safety, aberrant vessels were either coil embolized (n = 240/566, coiling group) or a more peripheral position of the catheter tip was chosen to treat right or left liver lobes (n = 326/566, no-coiling group).ResultsClinically relevant late toxicities (≥Grade 3) were observed in 1 % of our overall cohort. The no-coiling group had significantlymore » less “any” (P = 0.0001) or “clinically relevant” (P = 0.0003) early toxicity. There was no significant difference (P > 0.05) in delayed toxicity in the coiling versus the no-coiling group. No RE-induced liver disease was noted after all 566 procedures.ConclusionRE with {sup 90}Y resin microspheres is a safe and effective treatment option. Performing RE without coil embolization of aberrant vessels prior to treatment could be an alternative for experienced centers.« less

  5. Embolization of the Gastroduodenal Artery Before Selective Internal Radiotherapy: A Prospectively Randomized Trial Comparing Standard Pushable Coils with Fibered Interlock Detachable Coils

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Dudeck, Oliver, E-mail: oliver.dudeck@med.ovgu.de; Bulla, Karsten; Wieners, Gero

    2011-02-15

    The purpose of this study was compare embolization of the gastroduodenal artery (GDA) using standard pushable coils with the Interlock detachable coil (IDC), a novel fibered mechanically detachable long microcoil, in patients scheduled for selective internal radiotherapy (SIRT). Fifty patients (31 male and 19 female; median age 66.6 {+-} 8.1 years) were prospectively randomized for embolization using either standard coils or IDCs. Procedure time, radiation dose, number of embolization devices, complications, and durability of vessel occlusion at follow-up angiography were recorded. The procedures differed significantly in time (14:32 {+-} 5:56 min for standard coils vs. 2:13 {+-} 1:04 min formore » IDCs; p < 0.001); radiation dose for coil deployment (2479 {+-} 1237 cGycm Superscript-Two for standard coils vs. 275 {+-} 268 cGycm Superscript-Two for IDCs; p < 0.001); and vessel occlusion (17:18 {+-} 6:39 min for standard coils vs. 11:19 {+-} 7:54 min for IDCs; p = 0.002). A mean of 6.2 {+-} 1.8 coils (n = 27) were used in the standard coil group, and 1.3 {+-} 0.9 coils (p < 0.0001) were used in the IDC group (n = 23) because additional pushable coils were required to achieve GDA occlusion in 4 patients. In 2 patients, the IDC could not be deployed through a Soft-VU catheter. One standard coil dislodged in the hepatic artery and was retrieved. Vessel reperfusion was noted in only 1 patient in the standard coil group. Controlled embolization of the GDA with fibered IDCs was achieved more rapidly than with pushable coils. However, vessel occlusion may not be obtained using a single device only, and the use of sharply angled guiding catheters hampered coil pushability.« less

  6. Study on stabilization and quench protection of coils wound of HTS coated conductors considering quench origins - Proposal of criteria for stabilization and quench protection

    NASA Astrophysics Data System (ADS)

    Tsukamoto, Osami; Fujimoto, Yasutaka; Takao, Tomoaki

    2014-09-01

    It has been considered that HTS coils are hard to be quenched because of high quench energy due to high critical temperature and high specific heat of HTS wires. Therefore, attention to quench protection was not much paid. However, HTS coils still have possibility to be quenched during operation by mainly the following two origins, (a) presence of non-recoverable local defects in the conductors and (b) temperature rise of long part of the conductor. Actually, severe quench accidents, such as burning coils, are occurring in various places as scales of HTS increased. Purposes of this paper are to study on behaviors of normal zone and hot spot temperature of wires during quench detect/energy dump sequence and to find criteria for the stability and quench protection. In the paper, criteria are proposed for stability and quench protection of HTS coils. A criterion for the stability is that a coil can be operated stably without a quench against defects in coil windings and that for quench protection is that a coil can be safely protected from damages caused by a quench due to temperature rise of long part of coil wires. The criteria are used as design rules for HTS coils.

  7. Coiled-Coil Irregularities and Instabilities in Group A Streptococcus M1 Are Required for Virulence

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    McNamara, Case; Zinkernagel, Annelies S.; Macheboeuf, Pauline

    2008-07-21

    Antigenically variable M proteins are major virulence factors and immunogens of the human pathogen group A Streptococcus (GAS). Here, we report the -3 angstrom resolution structure of a GAS M1 fragment containing the regions responsible for eliciting type-specific, protective immunity and for binding fibrinogen, which promotes M1 proinflammatory and antiphagocytic functions. The structure revealed substantial irregularities and instabilities throughout the coiled coil of the M1 fragment. Similar structural irregularities occur in myosin and tropomyosin, explaining the patterns of cross-reactivity seen in autoimmune sequelae of GAS infection. Sequence idealization of a large segment of the M1 coiled coil enhanced stability butmore » diminished fibrinogen binding, proinflammatory effects, and antibody cross-reactivity, whereas it left protective immunogenicity undiminished. Idealized M proteins appear to have promise as vaccine immunogens.« less

  8. Method and device for determining bond separation strength using induction heating

    NASA Technical Reports Server (NTRS)

    Coultrip, Robert H. (Inventor); Johnson, Samuel D. (Inventor); Copeland, Carl E. (Inventor); Phillips, W. Morris (Inventor); Fox, Robert L. (Inventor)

    1994-01-01

    An induction heating device includes an induction heating gun which includes a housing, a U-shaped pole piece having two spaced apart opposite ends defining a gap there between, the U-shaped pole piece being mounted in one end of the housing, and a tank circuit including an induction coil wrapped around the pole piece and a capacitor connected to the induction coil. A power source is connected to the tank circuit. A pull test machine is provided having a stationary chuck and a movable chuck, the two chucks holding two test pieces bonded together at a bond region. The heating gun is mounted on the pull test machine in close proximity to the bond region of the two test pieces, whereby when the tank circuit is energized, the two test pieces are heated by induction heating while a tension load is applied to the two test pieces by the pull test machine to determine separation strength of the bond region.

  9. Synthesis, characterisation and applications of coiled carbon nanotubes.

    PubMed

    Hanus, Monica J; Harris, Andrew T

    2010-04-01

    Coiled carbon nanotubes are helical carbon structures formed when heptagonal and pentagonal rings are inserted into the hexagonal backbone of a 'straight' nanotube. Coiled carbon nanotubes have been reported with both regular and irregular helical structures. In this work the structure, growth mechanism(s), synthesis, properties and potential applications of coiled carbon nanotubes are reviewed. Published data suggests that coiled carbon nanotube synthesis occurs due to nonuniform extrusion of carbon from a catalyst surface. To date, coiled carbon nanotubes have been synthesised using catalyst modification techniques including: (i) the addition of S or P containing compounds during synthesis; (ii) the use of binary or ternary metal catalysts; (iii) the use of microwaves to create a local temperature gradient around individual catalyst particles and; (iv) the use of pH control during catalyst preparation. In most instances coiled carbon nanotubes are produced as a by-product; high yield and/or large-scale synthesis of coiled carbon nanotubes remains problematic. The qualitative analysis of coiled carbon nanotubes is currently hindered by the absence of specific characterisation data in the literature, e.g., oxidation profiles measured by thermogravimetric analysis and Raman spectra of pure coiled carbon nanotube samples.

  10. Coil Compression for Accelerated Imaging with Cartesian Sampling

    PubMed Central

    Zhang, Tao; Pauly, John M.; Vasanawala, Shreyas S.; Lustig, Michael

    2012-01-01

    MRI using receiver arrays with many coil elements can provide high signal-to-noise ratio and increase parallel imaging acceleration. At the same time, the growing number of elements results in larger datasets and more computation in the reconstruction. This is of particular concern in 3D acquisitions and in iterative reconstructions. Coil compression algorithms are effective in mitigating this problem by compressing data from many channels into fewer virtual coils. In Cartesian sampling there often are fully sampled k-space dimensions. In this work, a new coil compression technique for Cartesian sampling is presented that exploits the spatially varying coil sensitivities in these non-subsampled dimensions for better compression and computation reduction. Instead of directly compressing in k-space, coil compression is performed separately for each spatial location along the fully-sampled directions, followed by an additional alignment process that guarantees the smoothness of the virtual coil sensitivities. This important step provides compatibility with autocalibrating parallel imaging techniques. Its performance is not susceptible to artifacts caused by a tight imaging fieldof-view. High quality compression of in-vivo 3D data from a 32 channel pediatric coil into 6 virtual coils is demonstrated. PMID:22488589

  11. Heat Setting Procedures for Helical Coiled Springs

    DTIC Science & Technology

    1976-12-01

    Springs, M -aw-Hill Book Company, Inc., New York, New York, 1963. 1 - 1i) Music Wire, QQ-9-JM7 •r ’Wire diameter = 0.043 iALCh Stress relieve: Heat at... music wire and chrome vanadium materials c) 100,000 psi corresponds to 1.580 inches b) 150,0O0 psi corresponds to 1.020 inches For stainless steel...frequency which would produce spring set with the minimun amount of sprirg breakage. It was determined that the music wire springs should be cycled

  12. Magnetic induced heating of nanoparticle solutions

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Murph, S. Hunyadi; Brown, M.; Coopersmith, K.

    2016-12-02

    Magnetic induced heating of nanoparticles (NP) provides a useful advantage for many energy transfer applications. This study aims to gain an understanding of the key parameters responsible for maximizing the energy transfer leading to nanoparticle heating through the use of simulations and experimental results. It was found that magnetic field strength, NP concentration, NP composition, and coil size can be controlled to generate accurate temperature profiles in NP aqueous solutions.

  13. Electron cyclotron resonance ion sources with arc-shaped coils.

    PubMed

    Suominen, P; Wenander, F

    2008-02-01

    The minimum-B magnetic field structure of electron cyclotron resonance ion sources (ECRIS) has conventionally been formed with a combination of solenoids and a hexapole magnet. However, minimum-B structure can also be formed with arc-shaped coils. Recently it was shown that multiply charged heavy-ions can be produced with an ECRIS based on such a structure. In the future, the ARC-ECRIS magnetic field structure can be an interesting option for radioactive ion-beam sources and charge-breeders as well as for high performance ECRIS allowing for 100 GHz plasma heating. This paper presents some design aspects of the ARC-ECRIS.

  14. Microstructure, electrical properties, and thermal stability of Au-based ohmic contacts to p-GaN

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Smith, L.L.; Davis, R.F.; Kim, M.J.

    1997-09-01

    The work described in this paper is part of a systematic study of ohmic contact strategies for GaN-based semiconductors. Au contacts exhibited ohmic behavior on p-GaN when annealed at high temperature. The specific contact resistivity ({rho}{sub c}) calculated from TLM measurements on Au/p-GaN contacts was 53{Omega}{center_dot}cm{sup 2} after annealing at 800{degree}C. Multilayer Au/Mg/Au/p-GaN contacts exhibited linear, ohmic current-voltage (I-V) behavior in the as-deposited condition with {rho}{sub c}=214{Omega}{center_dot}cm{sup 2}. The specific contact resistivity of the multilayer contact increased significantly after rapid thermal annealing (RTA) through 725{degree}C. Cross-sectional microstructural characterization of the Au/p-GaN contact system via high-resolution electron microscopy (HREM) revealed thatmore » interfacial secondary phase formation occurred during high-temperature treatments, which coincided with the improvement of contact performance. In the as-deposited multilayer Au/Mg/Au/p-GaN contact, the initial 32 nm Au layer was found to be continuous. However, Mg metal was found in direct contact with the GaN in many places in the sample after annealing at 725{degree}C for 15 s. The resultant increase in contact resistance is believed to be due to the barrier effect increased by the presence of the low work function Mg metal. {copyright} {ital 1997 Materials Research Society.}« less

  15. Ion and electron heating characteristics of magnetic reconnection in tokamak plasma merging experiments

    NASA Astrophysics Data System (ADS)

    Ono, Y.; Tanabe, H.; Yamada, T.; Inomoto, M.; T, Ii; Inoue, S.; Gi, K.; Watanabe, T.; Gryaznevich, M.; Scannell, R.; Michael, C.; Cheng, C. Z.

    2012-12-01

    Recently, the TS-3 and TS-4 tokamak merging experiments revealed significant plasma heating during magnetic reconnection. A key question is how and where ions and electrons are heated during magnetic reconnection. Two-dimensional measurements of ion and electron temperatures and plasma flow made clear that electrons are heated inside the current sheet mainly by the Ohmic heating and ions are heated in the downstream areas mainly by the reconnection outflows. The outflow kinetic energy is thermalized by the fast shock formation and viscous damping. The magnetic reconnection converts the reconnecting magnetic field energy mostly to the ion thermal energy in the outflow region whose size is much larger than the current sheet size for electron heating. The ion heating energy is proportional to the square of the reconnection magnetic field component B_p^2 . This scaling of reconnection heating indicates the significant ion heating effect of magnetic reconnection, which leads to a new high-field reconnection heating experiment for fusion plasmas.

  16. Correcting coils in end magnets of accelerators

    NASA Astrophysics Data System (ADS)

    Kassab, L. R.; Gouffon, P.

    1998-05-01

    We present an empirical investigation of the correcting coils behavior used to homogenize the field distribution of the race-track microtron accelerator end magnets. These end magnets belong to the second stage of the 30.0 MeV cw electron accelerator under construction at IFUSP, the race-track microtron booster, in which the beam energy is raised from 1.97 to 5.1 MeV. The correcting coils are attached to the pole faces and are based on the inhomogeneities of the magnetic field measured. The performance of these coils, when operating the end magnets with currents that differ by +/-10% from the one used in the mappings that originated the coils copper leads, is presented. For one of the magnets, adjusting conveniently the current of the correcting coils makes it possible to homogenize field distributions of different intensities, once their shapes are practically identical to those that originated the coils. For the other one, the shapes are changed and the coils are less efficient. This is related to intrinsic factors that determine the inhomogeneities. However, we obtained uniformity of 0.001% in both cases.

  17. Single-coil and dual-coil defibrillator leads and association with clinical outcomes in a complete Danish nationwide ICD cohort.

    PubMed

    Larsen, Jacob M; Hjortshøj, Søren P; Nielsen, Jens C; Johansen, Jens B; Petersen, Helen H; Haarbo, Jens; Johansen, Martin B; Thøgersen, Anna Margrethe

    2016-03-01

    The best choice of defibrillator lead in patients with routine implantable cardioverter-defibrillator (ICD) is not settled. Traditionally, most physicians prefer dual-coil leads but the use of single-coil leads is increasing. The purpose of this study was to compare clinical outcomes in patients with single- and dual-coil leads. All 4769 Danish patients 18 years or older with first-time ICD implants from 2007 to 2011 were included from the Danish Pacemaker and ICD Register. Defibrillator leads were 38.9% single-coil leads and 61.1% dual-coil leads. The primary end point was all-cause mortality. Secondary end points were lowest successful energy at implant defibrillation testing, first shock failure in spontaneous arrhythmias, structural lead failure, and lead extraction outcomes. Single-coil leads were associated with lower all-cause mortality with an adjusted hazard ratio of 0.85 (95% confidence interval 0.73-0.99; P = .04). This finding was robust in a supplementary propensity score-matched analysis. However, dual-coil leads were used in patients with slightly higher preimplant morbidity, making residual confounding by indication the most likely explanation for the observed association between lead type and mortality. The lowest successful defibrillation energy was higher using single-coil leads (23.2 ± 4.3 J vs 22.1 ± 3.9 J; P < .001). No significant differences were observed for other secondary end points showing high shock efficacies and low rates of lead failures and extraction complications. Shock efficacy is high for modern ICD systems. The choice between single-coil and dual-coil defibrillator leads is unlikely to have a clinically significant impact on patient outcomes in routine ICD implants. Copyright © 2016 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.

  18. Measurement of Diffusion in Entangled Rod-Coil Triblock Copolymers

    NASA Astrophysics Data System (ADS)

    Olsen, B. D.; Wang, M.

    2012-02-01

    Although rod-coil block copolymers have attracted increasing attention for functional nanomaterials, their dynamics relevant to self-assembly and processing have not been widely investigated. Because the rod and coil blocks have different reptation behavior and persistence lengths, the mechanism by which block copolymers will diffuse is unclear. In order to understand the effect of the rigid block on reptation, tracer diffusion of a coil-rod-coil block copolymer through an entangled coil polymer matrix was experimentally measured. A monodisperse, high molecular weight coil-rod-coil triblock was synthesized using artificial protein engineering to prepare the helical rod and bioconjugaiton of poly(ethylene glycol) coils to produce the final triblock. Diffusion measurements were performed using Forced Rayleigh scattering (FRS), at varying ratios of the rod length to entanglement length, where genetic engineering is used to control the protein rod length and the polymer matrix concentration controls the entanglement length. As compared to PEO homopolymer tracers, the coil-rod-coil triblocks show markedly slower diffusion, suggesting that the mismatch between rod and coil reptation mechanisms results in hindered diffusion of these molecules in the entangled state.

  19. The structure of human SFPQ reveals a coiled-coil mediated polymer essential for functional aggregation in gene regulation

    PubMed Central

    Lee, Mihwa; Sadowska, Agata; Bekere, Indra; Ho, Diwei; Gully, Benjamin S.; Lu, Yanling; Iyer, K. Swaminathan; Trewhella, Jill; Fox, Archa H.; Bond, Charles S.

    2015-01-01

    SFPQ, (a.k.a. PSF), is a human tumor suppressor protein that regulates many important functions in the cell nucleus including coordination of long non-coding RNA molecules into nuclear bodies. Here we describe the first crystal structures of Splicing Factor Proline and Glutamine Rich (SFPQ), revealing structural similarity to the related PSPC1/NONO heterodimer and a strikingly extended structure (over 265 Å long) formed by an unusual anti-parallel coiled-coil that results in an infinite linear polymer of SFPQ dimers within the crystals. Small-angle X-ray scattering and transmission electron microscopy experiments show that polymerization is reversible in solution and can be templated by DNA. We demonstrate that the ability to polymerize is essential for the cellular functions of SFPQ: disruptive mutation of the coiled-coil interaction motif results in SFPQ mislocalization, reduced formation of nuclear bodies, abrogated molecular interactions and deficient transcriptional regulation. The coiled-coil interaction motif thus provides a molecular explanation for the functional aggregation of SFPQ that directs its role in regulating many aspects of cellular nucleic acid metabolism. PMID:25765647

  20. Formation of low resistance ohmic contacts in GaN-based high electron mobility transistors with BCl3 surface plasma treatment

    NASA Astrophysics Data System (ADS)

    Fujishima, Tatsuya; Joglekar, Sameer; Piedra, Daniel; Lee, Hyung-Seok; Zhang, Yuhao; Uedono, Akira; Palacios, Tomás

    2013-08-01

    A BCl3 surface plasma treatment technique to reduce the resistance and to increase the uniformity of ohmic contacts in AlGaN/GaN high electron mobility transistors with a GaN cap layer has been established. This BCl3 plasma treatment was performed by an inductively coupled plasma reactive ion etching system under conditions that prevented any recess etching. The average contact resistances without plasma treatment, with SiCl4, and with BCl3 plasma treatment were 0.34, 0.41, and 0.17 Ω mm, respectively. Also, the standard deviation of the ohmic contact resistance with BCl3 plasma treatment was decreased. This decrease in the standard deviation of contact resistance can be explained by analyzing the surface condition of GaN with x-ray photoelectron spectroscopy and positron annihilation spectroscopy. We found that the proposed BCl3 plasma treatment technique can not only remove surface oxide but also introduce surface donor states that contribute to lower the ohmic contact resistance.

  1. MRI surface-coil pair with strong inductive coupling.

    PubMed

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

    2016-12-01

    A novel inductively coupled coil pair was used to obtain magnetic resonance phantom images. Rationale for using such a structure is described in R. R. Mett et al. [Rev. Sci. Instrum. 87, 084703 (2016)]. The original rationale was to increase the Q-value of a small diameter surface coil in order to achieve dominant loading by the sample. A significant improvement in the vector reception field (VRF) is also seen. The coil assembly consists of a 3-turn 10 mm tall meta-metallic self-resonant spiral (SRS) of inner diameter 10.4 mm and outer diameter 15.1 mm and a single-loop equalization coil of 25 mm diameter and 2 mm tall. The low-frequency parallel mode was used in which the rf currents on each coil produce magnetic fields that add constructively. The SRS coil assembly was fabricated and data were collected using a tissue-equivalent 30% polyacrylamide phantom. The large inductive coupling of the coils produces phase-coherency of the rf currents and magnetic fields. Finite-element simulations indicate that the VRF of the coil pair is about 4.4 times larger than for a single-loop coil of 15 mm diameter. The mutual coupling between coils influences the current ratio between the coils, which in turn influences the VRF and the signal-to-noise ratio (SNR). Data on a tissue-equivalent phantom at 9.4 T show a total SNR increase of 8.8 over the 15 mm loop averaged over a 25 mm depth and diameter. The experimental results are shown to be consistent with the magnetic resonance theory of the emf induced by spins in a coil, the theory of inductively coupled resonant circuits, and the superposition principle. The methods are general for magnetic resonance and other types of signal detection and can be used over a wide range of operating frequencies.

  2. Optically tracked, single-coil, scanning magnetic induction tomography

    NASA Astrophysics Data System (ADS)

    Feldkamp, Joe R.; Quirk, Stephen

    2017-03-01

    Recent work has shown the feasibility of single-coil, magnetic induction tomography, for visualizing a 3D distribution of electrical conductivity in portions of the human body. Loss is measured in a single, planar coil consisting of concentric circular loops while the coil is relocated to various non-redundant positions and orientations in the vicinity of the target. These loss values, together with measured coil position and orientation, are processed by a quantitative mapping equation that enables reconstruction of an electrical conductivity image. Up until now, the position of the coil had to be established by a template, which required assignment of locations for the coil to visit without necessarily giving any prior consideration to target geometry. We have now added optical tracking to our existing single-coil device so that position and orientation are tracked automatically, allowing collection of coil loss data at arbitrary positions or orientations as needed. Optical tracking is accomplished via a set of IR reflective spheres mounted on the same enclosure that supports the coil. Position for a select sphere within the set, together with the four quaternions specifying optical body orientation, is fed to a laptop at the same time coil loss data is streamed to the same laptop via Bluetooth. The coil center can be tracked with sub-millimeter accuracy while orientation angle is known to a fraction of a degree. This work illustrates the use of single-coil MIT in full, position-orientation-tracked scan mode while imaging laboratory phantoms. Phantoms are based upon simple materials having biologic conductivity (< 5 S/m), including a cut of bone-in steak. The goal is not just to reconstruct an image that contains the features of the actual target, but also return correct conductivity values for the various features within the image.

  3. Low resolution crystal structure of Arenicola erythrocruorin: influence of coiled coils on the architecture of a megadalton respiratory protein.

    PubMed

    Royer, William E; Omartian, Michael N; Knapp, James E

    2007-01-05

    Annelid erythrocruorins are extracellular respiratory complexes assembled from 180 subunits into hexagonal bilayers. Cryo-electron microscopic experiments have identified two different architectural classes. In one, designated type I, the vertices of the two hexagonal layers are partially staggered, with one hexagonal layer rotated by about 16 degrees relative to the other layer, whereas in the other class, termed type II, the vertices are essentially eclipsed. We report here the first crystal structure of a type II erythrocruorin, that from Arenicola marina, at 6.2 A resolution. The structure reveals the presence of long continuous triple-stranded coiled-coil "spokes" projecting towards the molecular center from each one-twelfth unit; interdigitation of these spokes provides the only contacts between the two hexagonal layers of the complex. This arrangement contrasts with that of a type I erythrocruorin from Lumbricus terrestris in which the spokes are broken into two triple-stranded coiled coils with a disjointed connection. The disjointed connection allows formation of a more compact structure in the type I architecture, with the two hexagonal layers closer together and additional extensive contacts between the layers. Comparison of sequences of the coiled-coil regions of various linker subunits shows that the linker subunits from type II erythrocruorins possess continuous heptad repeats, whereas a sequence gap places these repeats out of register in the type I linker subunits, consistent with a disjointed coiled-coil arrangement.

  4. Self-aligned Ni-P ohmic contact scheme for silicon solar cells by electroless deposition

    NASA Astrophysics Data System (ADS)

    Lee, Eun Kyung; Lim, Dong Chan; Lee, Kyu Hwan; Lim, Jae-Hong

    2012-08-01

    We report a Ni-P metallization scheme for low resistance ohmic contacts to n-type Si for silicon solar cells. As-deposited Ni-P contacts to n-type Si showed a specific contact resistance of 6.42 × 10-4 Ω·cm2. The specific contact resistance decreased with increasing thermal annealing temperature. When the Ni-P contact was annealed at 600°C for 30 min in ambient air, the specific contact resistance was greatly decreased, to 6.37 × 10-5Ω·cm2. The improved ohmic property was attributed to the decrease in the work function due to the formation of Ni-silicides from Ni in-diffusion during the thermal annealing process. Effects of the annealing process on the electrical and crystal properties of the contacts were investigated by means of various resistivity measurements (circular transmission line method (c-TLM), 4-point probe), glancing angle x-ray diffraction (GAXRD), and x-ray photoelectron spectroscopy (XPS).

  5. Observation of quasi-coherent edge fluctuations in Ohmic plasmas on National Spherical Torus Experiment

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Banerjee, Santanu; Diallo, A.; Zweben, S. J.

    A quasi-coherent edge density mode with frequency f{sub mode} ∼ 40 kHz is observed in Ohmic plasmas in National Spherical Torus Experiment using the gas puff imaging diagnostic. This mode is located predominantly just inside the separatrix, with a maximum fluctuation amplitude significantly higher than that of the broadband turbulence in the same frequency range. The quasi-coherent mode has a poloidal wavelength λ{sub pol} ∼ 16 cm and a poloidal phase velocity of V{sub pol} ∼ 4.9 ± 0.3 km s{sup −1} in the electron diamagnetic direction, which are similar to the characteristics expected from a linear drift-wave-like mode in the edge. This is the first observation of amore » quasi-coherent edge mode in an Ohmic diverted tokamak, and so may be useful for validating tokamak edge turbulence codes.« less

  6. Coiled-Coil Antagonism Regulates Activity of Venus Flytrap-Domain-Containing Sensor Kinases of the BvgS Family

    PubMed Central

    Lesne, Elodie; Dupré, Elian; Lensink, Marc F.; Locht, Camille

    2018-01-01

    ABSTRACT Bordetella pertussis controls the expression of its virulence regulon through the two-component system BvgAS. BvgS is a prototype for a family of multidomain sensor kinases. In BvgS, helical linkers connect periplasmic Venus flytrap (VFT) perception domains to a cytoplasmic Per-Arnt-Sim (PAS) domain and the PAS domain to the dimerization/histidine phosphotransfer (DHp) domain of the kinase. The two linkers can adopt coiled-coil structures but cannot do so simultaneously. The first linker forms a coiled coil in the kinase mode and the second in the phosphatase mode, with the other linker in both cases showing an increase in dynamic behavior. The intervening PAS domain changes its quaternary structure between the two modes. In BvgS homologues without a PAS domain, a helical “X” linker directly connects the VFT and DHp domains. Here, we used BvgS as a platform to characterize regulation in members of the PAS-less subfamily. BvgS chimeras of homologues with natural X linkers displayed various regulation phenotypes. We identified two distinct coiled-coil registers in the N- and C-terminal portions of the X linkers. Stable coil formation in the C-terminal moiety determines the phosphatase mode, similarly to BvgS; in contrast, coil formation in the N-terminal moiety along the other register leads to the kinase mode. Thus, antagonism between two registers in the VFT-DHp linker forms the basis for activity regulation in the absence of the PAS domain. The N and C moieties of the X linker play roles similar to those played by the two independent linkers in sensor kinases with a PAS domain, providing a unified mechanism of regulation for the entire family. PMID:29487240

  7. Ohmic contacts for laser diodes

    NASA Technical Reports Server (NTRS)

    Ladany, I.; Marinelli, D. P.

    1983-01-01

    Requirements for ohmic contacts to laser diodes are discussed, and properties of Schottky barrier tunneling contacts are reviewed. A procedure is described for measuring contact resistance on fabricated laser material without the need for specially constructed samples and contact configurations. Measurements of contact resistance and estimates of specific contact resistance are given for Ti/Pt/Au contacts to surfaces with three different doping levels. It was found that below a p-type carrier concentration of 1 x 10 to the 19th per cu cm the contact resistance is likely to be too high for good device performance. At higher doping levels, a specific contact resistance as low as 2 x 10 to the -6th ohm sq cm was obtained. Oxide stripe lasers provided with the type of contact discussed in this paper have been operated without failures for periods up to 7 years at a current density at the contact of 6-8 kA/sq cm. It appears therefore that these contacts satisfy the need for low resistance and durability and that, at the same time, they do not cause any obvious material degradation.

  8. Structural propensities and entropy effects in peptide helix-coil transitions

    NASA Astrophysics Data System (ADS)

    Chemmama, Ilan E.; Pelea, Adam Colt; Bhandari, Yuba R.; Chapagain, Prem P.; Gerstman, Bernard S.

    2012-09-01

    The helix-coil transition in peptides is a critical structural transition leading to functioning proteins. Peptide chains have a large number of possible configurations that must be accounted for in statistical mechanical investigations. Using hydrogen bond and local helix propensity interaction terms, we develop a method for obtaining and incorporating the degeneracy factor that allows the exact calculation of the partition function for a peptide as a function of chain length. The partition function is used in calculations for engineered peptide chains of various lengths that allow comparison with a variety of different types of experimentally measured quantities, such as fraction of helicity as a function of both temperature and chain length, heat capacity, and denaturation studies. When experimental sensitivity in helicity measurements is properly accounted for in the calculations, the calculated curves fit well with the experimental curves. We determine values of interaction energies for comparison with known biochemical interactions, as well as quantify the difference in the number of configurations available to an amino acid in a random coil configuration compared to a helical configuration.

  9. Comparison of equilibrium ohmic and nonequilibrium swarm models for monitoring conduction electron evolution in high-altitude EMP calculations

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Pusateri, Elise N.; Morris, Heidi E.; Nelson, Eric

    2016-10-17

    Here, atmospheric electromagnetic pulse (EMP) events are important physical phenomena that occur through both man-made and natural processes. Radiation-induced currents and voltages in EMP can couple with electrical systems, such as those found in satellites, and cause significant damage. Due to the disruptive nature of EMP, it is important to accurately predict EMP evolution and propagation with computational models. CHAP-LA (Compton High Altitude Pulse-Los Alamos) is a state-of-the-art EMP code that solves Maxwell inline images equations for gamma source-induced electromagnetic fields in the atmosphere. In EMP, low-energy, conduction electrons constitute a conduction current that limits the EMP by opposing themore » Compton current. CHAP-LA calculates the conduction current using an equilibrium ohmic model. The equilibrium model works well at low altitudes, where the electron energy equilibration time is short compared to the rise time or duration of the EMP. At high altitudes, the equilibration time increases beyond the EMP rise time and the predicted equilibrium ionization rate becomes very large. The ohmic model predicts an unphysically large production of conduction electrons which prematurely and abruptly shorts the EMP in the simulation code. An electron swarm model, which implicitly accounts for the time evolution of the conduction electron energy distribution, can be used to overcome the limitations exhibited by the equilibrium ohmic model. We have developed and validated an electron swarm model previously in Pusateri et al. (2015). Here we demonstrate EMP damping behavior caused by the ohmic model at high altitudes and show improvements on high-altitude, upward EMP modeling obtained by integrating a swarm model into CHAP-LA.« less

  10. Comparison of equilibrium ohmic and nonequilibrium swarm models for monitoring conduction electron evolution in high-altitude EMP calculations

    NASA Astrophysics Data System (ADS)

    Pusateri, Elise N.; Morris, Heidi E.; Nelson, Eric; Ji, Wei

    2016-10-01

    Atmospheric electromagnetic pulse (EMP) events are important physical phenomena that occur through both man-made and natural processes. Radiation-induced currents and voltages in EMP can couple with electrical systems, such as those found in satellites, and cause significant damage. Due to the disruptive nature of EMP, it is important to accurately predict EMP evolution and propagation with computational models. CHAP-LA (Compton High Altitude Pulse-Los Alamos) is a state-of-the-art EMP code that solves Maxwell's equations for gamma source-induced electromagnetic fields in the atmosphere. In EMP, low-energy, conduction electrons constitute a conduction current that limits the EMP by opposing the Compton current. CHAP-LA calculates the conduction current using an equilibrium ohmic model. The equilibrium model works well at low altitudes, where the electron energy equilibration time is short compared to the rise time or duration of the EMP. At high altitudes, the equilibration time increases beyond the EMP rise time and the predicted equilibrium ionization rate becomes very large. The ohmic model predicts an unphysically large production of conduction electrons which prematurely and abruptly shorts the EMP in the simulation code. An electron swarm model, which implicitly accounts for the time evolution of the conduction electron energy distribution, can be used to overcome the limitations exhibited by the equilibrium ohmic model. We have developed and validated an electron swarm model previously in Pusateri et al. (2015). Here we demonstrate EMP damping behavior caused by the ohmic model at high altitudes and show improvements on high-altitude, upward EMP modeling obtained by integrating a swarm model into CHAP-LA.

  11. Assessing the Electromagnetic Fields Generated by a Radiofrequency MRI Body Coil at 64 MHz: Defeaturing vs. Accuracy

    PubMed Central

    Lucano, Elena; Liberti, Micaela; Mendoza, Gonzalo G.; Lloyd, Tom; Iacono, Maria Ida; Apollonio, Francesca; Wedan, Steve; Kainz, Wolfgang; Angelone, Leonardo M.

    2016-01-01

    Goal This study aims at a systematic assessment of five computational models of a birdcage coil for magnetic resonance imaging (MRI) with respect to accuracy and computational cost. Methods The models were implemented using the same geometrical model and numerical algorithm, but different driving methods (i.e., coil “defeaturing”). The defeatured models were labeled as: specific (S2), generic (G32, G16), and hybrid (H16, H16fr-forced). The accuracy of the models was evaluated using the “Symmetric Mean Absolute Percentage Error” (“SMAPE”), by comparison with measurements in terms of frequency response, as well as electric (||E⃗||) and magnetic (||B⃗||) field magnitude. Results All the models computed the ||B⃗|| within 35 % of the measurements, only the S2, G32, and H16 were able to accurately model the ||E⃗|| inside the phantom with a maximum SMAPE of 16 %. Outside the phantom, only the S2 showed a SMAPE lower than 11 %. Conclusions Results showed that assessing the accuracy of ||B⃗|| based only on comparison along the central longitudinal line of the coil can be misleading. Generic or hybrid coils – when properly modeling the currents along the rings/rungs – were sufficient to accurately reproduce the fields inside a phantom while a specific model was needed to accurately model ||E⃗|| in the space between coil and phantom. Significance Computational modeling of birdcage body coils is extensively used in the evaluation of RF-induced heating during MRI. Experimental validation of numerical models is needed to determine if a model is an accurate representation of a physical coil. PMID:26685220

  12. Structure and Misfolding of the Flexible Tripartite Coiled-Coil Domain of Glaucoma-Associated Myocilin.

    PubMed

    Hill, Shannon E; Nguyen, Elaine; Donegan, Rebecca K; Patterson-Orazem, Athéna C; Hazel, Anthony; Gumbart, James C; Lieberman, Raquel L

    2017-11-07

    Glaucoma-associated myocilin is a member of the olfactomedins, a protein family involved in neuronal development and human diseases. Molecular studies of the myocilin N-terminal coiled coil demonstrate a unique tripartite architecture: a Y-shaped parallel dimer-of-dimers with distinct tetramer and dimer regions. The structure of the dimeric C-terminal 7-heptad repeats elucidates an unexpected repeat pattern involving inter-strand stabilization by oppositely charged residues. Molecular dynamics simulations reveal an alternate accessible conformation in which the terminal inter-strand disulfide limits the extent of unfolding and results in a kinked configuration. By inference, full-length myocilin is also branched, with two pairs of C-terminal olfactomedin domains. Selected variants within the N-terminal region alter the apparent quaternary structure of myocilin but do so without compromising stability or causing aggregation. In addition to increasing our structural knowledge of naturally occurring extracellular coiled coils and biomedically important olfactomedins, this work broadens the scope of protein misfolding in the pathogenesis of myocilin-associated glaucoma. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. Structure and Misfolding of the Flexible Tripartite Coiled-Coil Domain of Glaucoma-Associated Myocilin

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hill, Shannon E.; Nguyen, Elaine; Donegan, Rebecca K.

    2017-11-01

    Glaucoma-associated myocilin is a member of the olfactomedins, a protein family involved in neuronal development and human diseases. Molecular studies of the myocilin N-terminal coiled coil demonstrate a unique tripartite architecture: a Y-shaped parallel dimer-of-dimers with distinct tetramer and dimer regions. The structure of the dimeric C-terminal 7-heptad repeats elucidates an unexpected repeat pattern involving inter-strand stabilization by oppositely charged residues. Molecular dynamics simulations reveal an alternate accessible conformation in which the terminal inter-strand disulfide limits the extent of unfolding and results in a kinked configuration. By inference, full-length myocilin is also branched, with two pairs of C-terminal olfactomedin domains.more » Selected variants within the N-terminal region alter the apparent quaternary structure of myocilin but do so without compromising stability or causing aggregation. In addition to increasing our structural knowledge of naturally occurring extracellular coiled coils and biomedically important olfactomedins, this work broadens the scope of protein misfolding in the pathogenesis of myocilin-associated glaucoma.« less

  14. Structure of a designed, right-handed coiled-coil tetramer containing all biological amino acids

    PubMed Central

    Sales, Mark; Plecs, Joseph J.; Holton, James M.; Alber, Tom

    2007-01-01

    The previous design of an unprecedented family of two-, three-, and four-helical, right-handed coiled coils utilized nonbiological amino acids to efficiently pack spaces in the oligomer cores. Here we show that a stable, right-handed parallel tetrameric coiled coil, called RH4B, can be designed entirely using biological amino acids. The X-ray crystal structure of RH4B was determined to 1.1 Å resolution using a designed metal binding site to coordinate a single Yb2+ ion per 33-amino acid polypeptide chain. The resulting experimental phases were particularly accurate, and the experimental electron density map provided an especially clear, unbiased view of the molecule. The RH4B structure closely matched the design, with equivalent core rotamers and an overall root-mean-square deviation for the N-terminal repeat of the tetramer of 0.24 Å. The clarity and resolution of the electron density map, however, revealed alternate rotamers and structural differences between the three sequence repeats in the molecule. These results suggest that the RH4B structure populates an unanticipated variety of structures. PMID:17766380

  15. Structure of a designed, right-handed coiled-coil tetramer containing all biological amino acids.

    PubMed

    Sales, Mark; Plecs, Joseph J; Holton, James M; Alber, Tom

    2007-10-01

    The previous design of an unprecedented family of two-, three-, and four-helical, right-handed coiled coils utilized nonbiological amino acids to efficiently pack spaces in the oligomer cores. Here we show that a stable, right-handed parallel tetrameric coiled coil, called RH4B, can be designed entirely using biological amino acids. The X-ray crystal structure of RH4B was determined to 1.1 Angstrom resolution using a designed metal binding site to coordinate a single Yb(2+) ion per 33-amino acid polypeptide chain. The resulting experimental phases were particularly accurate, and the experimental electron density map provided an especially clear, unbiased view of the molecule. The RH4B structure closely matched the design, with equivalent core rotamers and an overall root-mean-square deviation for the N-terminal repeat of the tetramer of 0.24 Angstrom. The clarity and resolution of the electron density map, however, revealed alternate rotamers and structural differences between the three sequence repeats in the molecule. These results suggest that the RH4B structure populates an unanticipated variety of structures.

  16. Intermittent fluctuations in the Alcator C-Mod scrape-off layer for ohmic and high confinement mode plasmas

    NASA Astrophysics Data System (ADS)

    Garcia, O. E.; Kube, R.; Theodorsen, A.; LaBombard, B.; Terry, J. L.

    2018-05-01

    Plasma fluctuations in the scrape-off layer of the Alcator C-Mod tokamak in ohmic and high confinement modes have been analyzed using gas puff imaging data. In all cases investigated, the time series of emission from a single spatially resolved view into the gas puff are dominated by large-amplitude bursts, attributed to blob-like filament structures moving radially outwards and poloidally. There is a remarkable similarity of the fluctuation statistics in ohmic plasmas and in edge localized mode-free and enhanced D-alpha high confinement mode plasmas. Conditionally averaged waveforms have a two-sided exponential shape with comparable temporal scales and asymmetry, while the burst amplitudes and the waiting times between them are exponentially distributed. The probability density functions and the frequency power spectral densities are similar for all these confinement modes. These results provide strong evidence in support of a stochastic model describing the plasma fluctuations in the scrape-off layer as a super-position of uncorrelated exponential pulses. Predictions of this model are in excellent agreement with experimental measurements in both ohmic and high confinement mode plasmas. The stochastic model thus provides a valuable tool for predicting fluctuation-induced plasma-wall interactions in magnetically confined fusion plasmas.

  17. Imaging performance of a dedicated radiation transparent RF coil on a 1.0 Tesla inline MRI-linac.

    PubMed

    Liney, Gary P; Dong, Bin; Weber, Ewald; Rai, Robba; Destruel, Aurelien; Garcia-Alvarez, Roberto; Manton, David; Jelen, Urszula; Zhang, Kevin; Barton, Michael; Keall, Paul J; Crozier, Stuart

    2018-05-25

    This work describes the first imaging studies on a 1.0 Tesla inline MRI-Linac using a dedicated transmit/receive RF body coil that has been designed to be completely radio transparent and provide optimum imaging performance over a large patient opening. Methods: A series of experiments was performed on the MRI-Linac to investigate the performance and imaging characteristics of a new dedicated volumetric RF coil: (1) numerical electromagnetic simulations were used to measure transmit efficiency in two patient positions; (2) image quality metrics of signal-to-noise ratio (SNR), ghosting and uniformity were assessed in a large diameter phantom with no radiation beam; (3) radiation induced effects were investigated in both the raw data (k-space) and image sequences acquired with simultaneous irradiation; (4) radiation dose was measured with and without image acquisition; (5) RF heating was studied using an MR-compatible fluoroptic thermometer and; (6) the in vivo image quality and versatility of the coil was demonstrated in normal healthy subjects for both supine and standing positions. Results: Daily phantom measurements demonstrated excellent imaging performance with stable SNR over a period of 3 months (42.6 ± 0.9). Simultaneous irradiation produced no statistical change in image quality (p>0.74) and no interference in raw data for a 20  20 cm radiation field. The coil was found to be efficient over large volumes and negligible RF heating was observed. Volunteer scans acquired in both supine and standing positions provided artefact free images with good anatomical visualisation. Conclusions: The first completely radio transparent RF coil for use on a 1.0 Tesla MRI-Linac has been described. There is no impact on either the imaging or dosimetry performance with a simultaneous radiation beam. The open design enables imaging and radiotherapy guidance in a variety of positons. . © 2018 Institute of Physics and Engineering in Medicine.

  18. Liquid Crystalline Assembly of Coil-Rod-Coil Molecules with Lateral Methyl Groups into 3-D Hexagonal and Tetragonal Assemblies

    PubMed Central

    Wang, Zhuoshi; Lan, Yu; Zhong, Keli; Liang, Yongri; Chen, Tie; Jin, Long Yi

    2014-01-01

    In this paper, we report the synthesis and self-assembly behavior of coil-rod-coil molecules, consisting of three biphenyls linked through a vinylene unit as a conjugated rod segment and poly(ethylene oxide) (PEO) with a degree of polymerization (DP) of 7, 12 and 17, incorporating lateral methyl groups between the rod and coil segments as the coil segment. Self-organized investigation of these molecules by means of differential scanning calorimetry (DSC), thermal polarized optical microscopy (POM) and X-ray diffraction (XRD) reveals that the lateral methyl groups attached to the surface of rod and coil segments, dramatically influence the self-assembling behavior in the liquid-crystalline mesophase. Molecule 1 with a relatively short PEO coil length (DP = 7) self-assembles into rectangular and oblique 2-dimensional columnar assemblies, whereas molecules 2 and 3 with DP of 12 and 17 respectively, spontaneously self-organize into unusual 3-dimensional hexagonal close-packed or body-centered tetragonal assemblies. PMID:24699045

  19. Theory of the tensile actuation of fiber reinforced coiled muscles

    NASA Astrophysics Data System (ADS)

    Lamuta, C.; Messelot, S.; Tawfick, S.

    2018-05-01

    There is a strong need for compact artificial muscles capable of applying large contractile strokes and lift heavy weights. Coiled fibers recently emerged as attractive candidates for these purposes, owing to their simple construction and the possibility of their thermal, electrical and chemical actuation. An intuitive theoretical understanding of the mechanics of actuation of these muscles is essential for the enhancement of their performance and can pave the way for the development of new applications and technologies. In this paper, a complete theoretical model for the tensile actuation of fiber reinforced artificial muscles is presented and experimentally validated. The model demonstrates that all muscles made from the same material have a universal behavior, which can be described by a single master curve. It enables the systematic design and understanding of coiled muscles for specific performance owing to a comprehensive mathematical correlation among the geometry, materials properties, and actuation. Carbon fibers (CF)/polydimethylsiloxane coiled muscles are demonstrated as simple to fabricate yet powerful muscles owing to the availability of high strength CF. In addition to showing excellent agreement with the theoretical models, they can be actuated by joule heating or chemical swelling, lift up to 12 600 times their own weight, support up to 60 MPa of mechanical stress, provide tensile strokes higher than 25%, and a specific work up to 758 J kg‑1, the latter is more than 18 times higher than that of natural muscles.

  20. Solar heating and hot water system installed at Arlington Raquetball Club, Arlington, Virginia

    NASA Technical Reports Server (NTRS)

    1981-01-01

    A solar space and water heating system is described. The solar energy system consists of 2,520 sq. ft. of flat plate solar collectors and a 4,000 gallon solar storage tank. The transfer medium in the forced closed loop is a nontoxic antifreeze solution (50 percent water, 50 percent propylene glycol). The service hot water system consists of a preheat coil (60 ft. of 1 1/4 in copper tubing) located in the upper third of the solar storage tank and a recirculation loop between the preheat coil and the existing electric water heaters. The space heating system consists of two separate water to air heat exchangers located in the ducts of the existing space heating/cooling systems. The heating water is supplied from the solar storage tank. Extracts from site files, specification references for solar modifications to existing building heating and hot water systems, and installation, operation and maintenance instructions are included.

  1. Solar coronal loop heating by cross-field wave transport

    NASA Technical Reports Server (NTRS)

    Amendt, Peter; Benford, Gregory

    1989-01-01

    Solar coronal arches heated by turbulent ion-cyclotron waves may suffer significant cross-field transport by these waves. Nonlinear processes fix the wave-propagation speed at about a tenth of the ion thermal velocity, which seems sufficient to spread heat from a central core into a large cool surrounding cocoon. Waves heat cocoon ions both through classical ion-electron collisions and by turbulent stochastic ion motions. Plausible cocoon sizes set by wave damping are in roughly kilometers, although the wave-emitting core may be only 100 m wide. Detailed study of nonlinear stabilization and energy-deposition rates predicts that nearby regions can heat to values intermediate between the roughly electron volt foot-point temperatures and the about 100 eV core, which is heated by anomalous Ohmic losses. A volume of 100 times the core volume may be affected. This qualitative result may solve a persistent problem with current-driven coronal heating; that it affects only small volumes and provides no way to produce the extended warm structures perceptible to existing instruments.

  2. Measurement of the controlled variable during heating of Ti6Al4V for thixoforging

    NASA Astrophysics Data System (ADS)

    Gerlach, O.; Lechler, A.; Verl, A.

    2018-02-01

    Controlled heating of metal billets into the semi-solid state for thixoforming is a challenging task, mainly due to the difficulties in measuring the liquid fraction of the billet during heating. Past research primarily focused on methods measuring the liquid fraction during heating of low-melting aluminium alloys. One of these methods is time constant measurement, a contactless measurement method that uses the heating coil as a sensor. The current through the coil is used to determine the electrical time constant of the heating circuit, which itself is influenced by the specific resistance of the billet inside the coil. While previous works focused on the suitability of this method for industrial applications using aluminum alloys, this paper extends this research to the high-melting titanium alloy Ti6Al4V. This alloys shows high strength, low density and excellent corrosion resistance. It is therefore used to produce light-weight and durable components for medical and aerospace applications. Ti6Al4V is an expensive and difficult to machine alloy. Thus, it is an interesting alloy for thixoforging. However, heating of the billet into a homogeneous state of defined liquid fraction is difficult due to the poor thermal conductivity of Ti6Al4V. This paper analyses the potential of using time constant measurement for controlled heating of Ti6Al4V into the semi-solid state.

  3. Surface coil proton MR imaging at 2 T.

    PubMed

    Röschmann, P; Tischler, R

    1986-10-01

    We describe the design and application of surface coils for magnetic resonance (MR) imaging at high resonance frequencies (85 MHz). Circular, rectangular-frame, and reflector-type surface coils were used in the transmit-and-receive mode. With these coils, the required radio frequency power is reduced by factors of two up to 100 with respect to head and body coils. With the small, circular coils, high-resolution images of a small region of interest can be obtained that are free of foldback and motion artifacts originating outside the field of interest. With the rectangular-frame and reflector coils, large fields of view are also accessible. As examples of applications, single- and multiple-section images of the eye, knee, head and shoulder, and spinal cord are provided.

  4. Critical current studies of a HTS rectangular coil

    NASA Astrophysics Data System (ADS)

    Zhong, Z.; Chudy, M.; Ruiz, H. S.; Zhang, X.; Coombs, T.

    2017-05-01

    Nowadays, superconducting high field magnets are used in numerous applications due to their superior properties. High temperature superconductors (HTS) are usually used for production of circular pancake or racetrack coils. However different geometries of HTS coils might be required for some specific applications. In this study, the HTS coil wound on a rectangular frame was fully characterized in homogeneous DC background field. The study contains measurements of critical current angular dependencies. The critical current of the entire coil and two selected strands under different magnitudes and orientations of external magnetic fields are measured. The critical regions of the coil in different angular regimes are determined. This study brings better understanding of the in- field performance of HTS coils wound on frames with right-angles.

  5. Cooling arrangement for a superconducting coil

    DOEpatents

    Herd, K.G.; Laskaris, E.T.

    1998-06-30

    A superconducting device is disclosed, such as a superconducting rotor for a generator or motor. A vacuum enclosure has an interior wall surrounding a cavity containing a vacuum. A superconductive coil is placed in the cavity. A generally-annularly-arranged, thermally-conductive sheet has an inward-facing surface contacting generally the entire outward-facing surface of the superconductive coil. A generally-annularly-arranged coolant tube contains a cryogenic fluid and contacts a generally-circumferential portion of the outward-facing surface of the sheet. A generally-annularly-arranged, thermally-insulative coil overwrap generally circumferentially surrounds the sheet. The coolant tube and the inward-facing surface of the coil overwrap together contact generally the entire outward-facing surface of the sheet. 3 figs.

  6. Optimization of the current potential for stellarator coils

    NASA Astrophysics Data System (ADS)

    Boozer, Allen H.

    2000-02-01

    Stellarator plasma confinement devices have no continuous symmetries, which makes the design of appropriate coils far more subtle than for axisymmetric devices such as tokamaks. The modern method for designing coils for stellarators was developed by Peter Merkel [P. Merkel, Nucl. Fusion 27, 867 (1987)]. Although his method has yielded a number of successful stellarator designs, Merkel's method has a systematic tendency to give coils with a larger current than that required to produce a stellarator plasma with certain properties. In addition, Merkel's method does not naturally lead to a coil set with the flexibility to produce a number of interesting plasma configurations. The issues of coil efficiency and flexibility are addressed in this paper by a new method of optimizing the current potential, the first step in Merkel's method. The new method also allows the coil design to be based on a freer choice for the plasma-coil separation and to be constrained so space is preserved for plasma access.

  7. Laminated magnet field coil sheath

    DOEpatents

    Skaritka, J.R.

    1987-05-15

    A method for manufacturing a magnetic cable trim coil in a sheath assembly for use in a cryogenic particle accelerator. A precisely positioned pattern of trim coil turns is bonded to a flexible substrate sheath that is capable of withstanding cryogenic operating conditions. In the method of the invention the flexible substrate sheath, with the trim coil pattern precisely location relative to a bore tube assembly of an accelerator and is then bonded to the bore tube with a tape suitable for cryogenic application. The resultant assembly can be readily handled and installed within an iron magnet yoke assembly of a suitable cryogenic particle accelerator. 1 fig.

  8. 3 Tesla MRI of patients with a vagus nerve stimulator: initial experience using a T/R head coil under controlled conditions.

    PubMed

    Gorny, Krzysztof R; Bernstein, Matt A; Watson, Robert E

    2010-02-01

    To assess safety of clinical MRI of the head in patients with implanted model 100, 102, and 103 vagus nerve stimulation (VNS) Therapy Systems (Cyberonics, Inc., Houston, TX) in 3.0 Tesla MRI (GE Healthcare, Milwaukee, WI). The distributions of the radiofrequency B(1) (+)-field produced by the clinically used transmit/receive (T/R) head coil (Advanced Imaging Research Incorporated, Cleveland, OH) and body coil were measured in a head and shoulders phantom. These measurements were supplemented by temperature measurements on the lead tips and the implantable pulse generator (IPG) of the VNS devices in a head and torso phantom with the same two coils. Clinical 3T MRI head scans were then acquired under highly controlled conditions in a series of 17 patients implanted with VNS. Phantom studies showed only weak B(1) (+) fields at the location of the VNS IPG and leads for MRI scans using the T/R head coil. The MRI-related heating on a VNS scanned in vitro at 3T was also found to be minimal (0.4-0.8 degrees C at the leads, negligible at the IPG). The patient MRI examinations were completed successfully without any adverse incidents. No patient reported any heating, discomfort, or any other unusual sensation. Safe clinical MRI head scanning of patients with implanted VNS is shown to be feasible on a GE Signa Excite 3T MRI system using one specific T/R head coil. These results apply to this particular MRI system configuration. Extrapolation or generalization of these results to more general or less controlled imaging situations without supporting data of safety is highly discouraged.

  9. The challenges of heat sterilization of peritoneal dialysis solutions: is there an alternative?

    PubMed

    Hanrahan, Conor T; Himmele, Rainer; Diaz-Buxo, Jose A

    2012-01-01

    Peritoneal dialysis (PD) solutions are currently sterilized in an autoclave using high-temperature saturated steam. Although thermal methods are an effective means of sterilization, the heating of PD solutions results in the formation of toxic glucose degradation products (GDPs). Here, we review basic concepts in the sterilization of PD solutions and discuss possible alternatives to steam sterilization, including filtration, ohmic heat, ionizing radiation, and pulsed ultraviolet light. Although the latter methods have several advantages, many also have prohibitive limitations or have not been adequately studied for use on PD solutions. Thus, in the absence of suitable alternatives, conventional heat sterilization, in combination with low-GDP manufacturing practices, remains the best option at the present time.

  10. Bias induced transition from an ohmic to a non-ohmic interface in supramolecular tunneling junctions with Ga2O3/EGaIn top electrodes.

    PubMed

    Wimbush, Kim S; Fratila, Raluca M; Wang, Dandan; Qi, Dongchen; Liang, Cao; Yuan, Li; Yakovlev, Nikolai; Loh, Kian Ping; Reinhoudt, David N; Velders, Aldrik H; Nijhuis, Christian A

    2014-10-07

    This study describes that the current rectification ratio, R ≡ |J|(-2.0 V)/|J|(+2.0 V) for supramolecular tunneling junctions with a top-electrode of eutectic gallium indium (EGaIn) that contains a conductive thin (0.7 nm) supporting outer oxide layer (Ga2O3), increases by up to four orders of magnitude under an applied bias of >+1.0 V up to +2.5 V; these junctions did not change their electrical characteristics when biased in the voltage range of ±1.0 V. The increase in R is caused by the presence of water and ions in the supramolecular assemblies which react with the Ga2O3/EGaIn layer and increase the thickness of the Ga2O3 layer. This increase in the oxide thickness from 0.7 nm to ∼2.0 nm changed the nature of the monolayer-top-electrode contact from an ohmic to a non-ohmic contact. These results unambiguously expose the experimental conditions that allow for a safe bias window of ±1.0 V (the range of biases studies of charge transport using this technique are normally conducted) to investigate molecular effects in molecular electronic junctions with Ga2O3/EGaIn top-electrodes where electrochemical reactions are not significant. Our findings also show that the interpretation of data in studies involving applied biases of >1.0 V may be complicated by electrochemical side reactions which can be recognized by changes of the electrical characteristics as a function voltage cycling or in current retention experiments.

  11. Molecular clamp mechanism of substrate binding by hydrophobic coiled-coil residues of the archaeal chaperone prefoldin

    PubMed Central

    Lundin, Victor F.; Stirling, Peter C.; Gomez-Reino, Juan; Mwenifumbo, Jill C.; Obst, Jennifer M.; Valpuesta, José M.; Leroux, Michel R.

    2004-01-01

    Prefoldin (PFD) is a jellyfish-shaped molecular chaperone that has been proposed to play a general role in de novo protein folding in archaea and is known to assist the biogenesis of actins, tubulins, and potentially other proteins in eukaryotes. Using point mutants, chimeras, and intradomain swap variants, we show that the six coiledcoil tentacles of archaeal PFD act in concert to bind and stabilize nonnative proteins near the opening of the cavity they form. Importantly, the interaction between chaperone and substrate depends on the mostly buried interhelical hydrophobic residues of the coiled coils. We also show by electron microscopy that the tentacles can undergo an en bloc movement to accommodate an unfolded substrate. Our data reveal how archael PFD uses its unique architecture and intrinsic coiled-coil properties to interact with nonnative polypeptides. PMID:15070724

  12. Force delivery of Ni-Ti coil springs.

    PubMed

    Manhartsberger, C; Seidenbusch, W

    1996-01-01

    Sentalloy springs (GAC, Central Islip, N.Y.) of the open and closed type were investigated with a special designed device. The closed coil springs were subjected to a tensile and the open coil springs to a compression test. After a first measurement, the springs were activated for a period of 4 weeks and then reinvestigated with the same procedure. It could be shown distinctly that, with the different coil springs, the force delivery given by the producer could be achieved only within certain limits. To remain in the martensitic plateau, changed activation ranges, and for the Sentalloy coil springs white and red of the open and closed type, also changed force deliveries had to be taken into account. There was a distinct decrease in force delivery between the first and second measurement. After considering the loading curves of all the Sentalloy coil springs and choosing the right activation range respective to the force delivery, it was found that the coil springs deliver a superior clinical behavior and open new treatment possibilities.

  13. Divertor Coil Design and Implementation on Pegasus

    NASA Astrophysics Data System (ADS)

    Shriwise, P. C.; Bongard, M. W.; Cole, J. A.; Fonck, R. J.; Kujak-Ford, B. A.; Lewicki, B. T.; Winz, G. R.

    2012-10-01

    An upgraded divertor coil system is being commissioned on the Pegasus Toroidal Experiment in conjunction with power system upgrades in order to achieve higher β plasmas, reduce impurities, and possibly achieve H-mode operation. Design points for the divertor coil locations and estimates of their necessary current ratings were found using predictive equilibrium modeling based upon a 300 kA target plasma. This modeling represented existing Pegasus coil locations and current drive limits. The resultant design calls for 125 kA-turns from the divertor system to support the creation of a double null magnetic topology in plasmas with Ip<=300 kA. Initial experiments using this system will employ 900 V IGBT power supply modules to provide IDIV<=4 kA. The resulting 20 kA-turn capability of the existing divertor coil will be augmented by a new coil providing additional A-turns in series. Induced vessel wall current modeling indicates the time response of a 28 turn augmentation coil remains fast compared to the poloidal field penetration rate through the vessel. First results operating the augmented system are shown.

  14. Laterality in coiling behaviour of snakes: another interpretation.

    PubMed

    Heatwole, Harold; King, Peter; Levine, Samuel G

    2007-11-01

    The direction of coiling was periodically recorded for two species of viperid snakes--copperheads (Agkistrodon contortrix) and cottonmouths (Agkistrodon piscivorus). Overall, neither species showed a significant preference for coiling in a particular direction. Only 1 of 22 snakes exhibited an individual preference, a result within expectation for random direction of coiling when using a 5% rejection level for statistical testing. A previously published claim for laterality in coiling direction by cottonmouths presented similar results but came to the opposite conclusion. The data from the combined studies suggest that if laterality in coiling direction does occur, it is extremely weak and inconsistent.

  15. Human LINE-1 retrotransposition requires a metastable coiled coil and a positively charged N-terminus in L1ORF1p

    PubMed Central

    Khazina, Elena

    2018-01-01

    LINE-1 (L1) is an autonomous retrotransposon, which acted throughout mammalian evolution and keeps contributing to human genotypic diversity, genetic disease and cancer. L1 encodes two essential proteins: L1ORF1p, a unique RNA-binding protein, and L1ORF2p, an endonuclease and reverse transcriptase. L1ORF1p contains an essential, but rapidly evolving N-terminal portion, homo-trimerizes via a coiled coil and packages L1RNA into large assemblies. Here, we determined crystal structures of the entire coiled coil domain of human L1ORF1p. We show that retrotransposition requires a non-ideal and metastable coiled coil structure, and a strongly basic L1ORF1p amino terminus. Human L1ORF1p therefore emerges as a highly calibrated molecular machine, sensitive to mutation but functional in different hosts. Our analysis rationalizes the locally rapid L1ORF1p sequence evolution and reveals striking mechanistic parallels to coiled coil-containing membrane fusion proteins. It also suggests how trimeric L1ORF1p could form larger meshworks and indicates critical novel steps in L1 retrotransposition. PMID:29565245

  16. Coupled coils, magnets and Lenz's law

    NASA Astrophysics Data System (ADS)

    Thompson, Frank

    2010-03-01

    Great scientists in the past have experimented with coils and magnets. Here we have a variation where coupling occurs between two coils and the oscillatory motion of two magnets to give somewhat surprising results.

  17. Effect of Inductive Coil Geometry on the Thrust Efficiency of a Microwave Assisted Discharge Inductive Plasma Accelerator

    NASA Technical Reports Server (NTRS)

    Hallock, Ashley; Polzin, Kurt; Emsellem, Gregory

    2012-01-01

    Pulsed inductive plasma thrusters [1-3] are spacecraft propulsion devices in which electrical energy is capacitively stored and then discharged through an inductive coil. The thruster is electrodeless, with a time-varying current in the coil interacting with a plasma covering the face of the coil to induce a plasma current. Propellant is accelerated and expelled at a high exhaust velocity (O(10-100 km/s)) by the Lorentz body force arising from the interaction of the magnetic field and the induced plasma current. While this class of thruster mitigates the life-limiting issues associated with electrode erosion, pulsed inductive plasma thrusters require high pulse energies to inductively ionize propellant. The Microwave Assisted Discharge Inductive Plasma Accelerator (MAD-IPA) [4, 5] is a pulsed inductive plasma thruster that addressees this issue by partially ionizing propellant inside a conical inductive coil via an electron cyclotron resonance (ECR) discharge. The ECR plasma is produced using microwaves and permanent magnets that are arranged to create a thin resonance region along the inner surface of the coil, restricting plasma formation, and in turn current sheet formation, to a region where the magnetic coupling between the plasma and the inductive coil is high. The use of a conical theta-pinch coil is under investigation. The conical geometry serves to provide neutral propellant containment and plasma plume focusing that is improved relative to the more common planar geometry of the Pulsed Inductive Thruster (PIT) [2, 3], however a conical coil imparts a direct radial acceleration of the current sheet that serves to rapidly decouple the propellant from the coil, limiting the direct axial electromagnetic acceleration in favor of an indirect acceleration mechanism that requires significant heating of the propellant within the volume bounded by the current sheet. In this paper, we describe thrust stand measurements performed to characterize the performance

  18. Flux pumping for non-insulated and metal-insulated HTS coils

    NASA Astrophysics Data System (ADS)

    Ma, Jun; Geng, Jianzhao; Coombs, T. A.

    2018-01-01

    High-temperature superconducting (HTS) coils wound from coated conductors without turn-to-turn insulation (non-insulated (NI) coils) have been proven with excellent electrical and thermal performances. However, the slow charging of NI coils has been a long-lasting problem. In this work, we explore using a transformer-rectifier HTS flux pump to charge an NI coil and a metal-insulated coil. The charging performance comparison is made between different coils. Comprehensive study is done to thoroughly understand the electrical-magnetic transience in charging these coils. We will show that the low-voltage high-current flux pump is especially suitable for charging NI coils with very low characteristic resistance.

  19. Outdoor unit construction for an electric heat pump

    DOEpatents

    Draper, Robert; Lackey, Robert S.

    1984-01-01

    The outdoor unit for an electric heat pump is provided with an upper portion 10 containing propeller fan means 14 for drawing air through the lower portion 12 containing refrigerant coil means 16 in the form of four discrete coils connected together in a subassembly forming a W shape, the unit being provided with four adjustable legs 64 which are retracted in shipment, and are adjusted on site to elevate the unit to a particular height suitable for the particular location in which the unit is installed.

  20. Outdoor unit construction for an electric heat pump

    DOEpatents

    Draper, R.; Lackey, R.S.

    1984-09-11

    The outdoor unit for an electric heat pump is provided with an upper portion containing propeller fan means for drawing air through the lower portion containing refrigerant coil means in the form of four discrete coils connected together in a subassembly forming a W shape, the unit being provided with four adjustable legs which are retracted in shipment, and are adjusted on site to elevate the unit to a particular height suitable for the particular location in which the unit is installed. 4 figs.

  1. 77 FR 8178 - Test Procedures for Central Air Conditioners and Heat Pumps: Public Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-14

    ... distribution of those central air conditioning systems and heat pump systems manufactured after January 1, 2010... system central air conditioners and heat pumps be tested using ``the evaporator coil that is likely to... issued two guidance documents surrounding testing central air conditioner and heat pump systems utilizing...

  2. Laminated magnet field coil sheath

    DOEpatents

    Skaritka, John R.

    1987-12-01

    a method for manufacturing a magnet cable trim coil in a sheath assembly for use in a cryogenic particle accelerator. A precisely positioned pattern of trim coil turns is bonded to a flexible substrate sheath that is capable of withstanding cryogenic operating conditions. In the method of the invention the flexible sheath, with the trim coil pattern precisely positioned thereon, is accurately positioned at a precise location relative to a bore tube assembly of an accelerator and is then bonded to the bore tube with a tape suitable for cryogenic application. The resultant assembly can be readily handled and installed within an iron magnet yoke assembly of a suitable cryogenic particle accelerator.

  3. The coiled-coil domain of MURC/cavin-4 is involved in membrane trafficking of caveolin-3 in cardiomyocytes.

    PubMed

    Naito, Daisuke; Ogata, Takehiro; Hamaoka, Tetsuro; Nakanishi, Naohiko; Miyagawa, Kotaro; Maruyama, Naoki; Kasahara, Takeru; Taniguchi, Takuya; Nishi, Masahiro; Matoba, Satoaki; Ueyama, Tomomi

    2015-12-15

    Muscle-restricted coiled-coil protein (MURC), also referred to as cavin-4, is a member of the cavin family that works cooperatively with caveolins in caveola formation and function. Cavins are cytoplasmic proteins with coiled-coil domains and form heteromeric complexes, which are recruited to caveolae in cells expressing caveolins. Among caveolins, caveolin-3 (Cav3) is exclusively expressed in muscle cells, similar to MURC/cavin-4. In the heart, Cav3 overexpression contributes to cardiac protection, and its deficiency leads to progressive cardiomyopathy. Mutations in the MURC/cavin-4 gene have been identified in patients with dilated cardiomyopathy. In the present study, we show the role of MURC/cavin-4 as a caveolar component in the heart. In H9c2 cells, MURC/cavin-4 was localized at the plasma membrane, whereas a MURC/cavin-4 mutant lacking the coiled-coil domain (ΔCC) was primarily localized to the cytoplasm. ΔCC bound to Cav3 and impaired membrane localization of Cav3 in cardiomyocytes. Additionally, although ΔCC did not alter Cav3 mRNA expression, ΔCC decreased the Cav3 protein level. MURC/cavin-4 and ΔCC similarly induced cardiomyocyte hypertrophy; however, ΔCC showed higher hypertrophy-related fetal gene expression than MURC/cavin-4. ΔCC induced ERK activation in cardiomyocytes. Transgenic mice expressing ΔCC in the heart (ΔCC-Tg mice) showed impaired cardiac function accompanied by cardiomyocyte hypertrophy and marked interstitial fibrosis. Hearts from ΔCC-Tg mice showed a reduction of the Cav3 protein level and activation of ERK. These results suggest that MURC/cavin-4 requires its coiled-coil domain to target the plasma membrane and to stabilize Cav3 at the plasma membrane of cardiomyocytes and that MURC/cavin-4 functions as a crucial caveolar component to regulate cardiac function. Copyright © 2015 the American Physiological Society.

  4. Wind and React MgB2 Rotor Coils

    NASA Astrophysics Data System (ADS)

    Bohnenstiehl, S. D.; Sumption, M. D.; Majoros, M.; Tomsic, M.; Rindfleisch, M.; Phillips, J.; Yue, J.; Collings, E. W.

    2008-03-01

    Five rotor coils (four plus a spare) intended for a prototype 2 MW generator were fabricated and tested. For each coil, multifilamentary MgB2 strand was wound around a stepped former in a wind and react mode using S-glass insulation in combination with vacuum epoxy impregnation. The stepped, ellipsoidal coils had maximum in-plane dimensions of 26.7 cm×13.1 cm and a total thickness of 5.4 cm, and were wound with approximately 580 m of MgB2 strand per coil. Each of the coils were measured separately for Ic and magnetic field in the bore at 4.2 K and for one coil Ic and B were also measured as a function of temperature. The bore field as a function of position along the z-axis was also determined near the critical current at 4.2 K. The coils typically reached 186 A at 4.2 K generating a 1.7 T field, while at 20 K the Ic was 117 A with a bore field of 1.1 T field.

  5. Optimization of the current potential for stellarator coils

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Boozer, Allen H.; Max-Planck-Institut fuer Plasmaphysik, EURATOM-Association, D-85748 Garching,

    2000-02-01

    Stellarator plasma confinement devices have no continuous symmetries, which makes the design of appropriate coils far more subtle than for axisymmetric devices such as tokamaks. The modern method for designing coils for stellarators was developed by Peter Merkel [P. Merkel, Nucl. Fusion 27, 867 (1987)]. Although his method has yielded a number of successful stellarator designs, Merkel's method has a systematic tendency to give coils with a larger current than that required to produce a stellarator plasma with certain properties. In addition, Merkel's method does not naturally lead to a coil set with the flexibility to produce a number ofmore » interesting plasma configurations. The issues of coil efficiency and flexibility are addressed in this paper by a new method of optimizing the current potential, the first step in Merkel's method. The new method also allows the coil design to be based on a freer choice for the plasma-coil separation and to be constrained so space is preserved for plasma access. (c) 2000 American Institute of Physics.« less

  6. Deep brain transcranial magnetic stimulation using variable "Halo coil" system

    NASA Astrophysics Data System (ADS)

    Meng, Y.; Hadimani, R. L.; Crowther, L. J.; Xu, Z.; Qu, J.; Jiles, D. C.

    2015-05-01

    Transcranial Magnetic Stimulation has the potential to treat various neurological disorders non-invasively and safely. The "Halo coil" configuration can stimulate deeper regions of the brain with lower surface to deep-brain field ratio compared to other coil configurations. The existing "Halo coil" configuration is fixed and is limited in varying the site of stimulation in the brain. We have developed a new system based on the current "Halo coil" design along with a graphical user interface system that enables the larger coil to rotate along the transverse plane. The new system can also enable vertical movement of larger coil. Thus, this adjustable "Halo coil" configuration can stimulate different regions of the brain by adjusting the position and orientation of the larger coil on the head. We have calculated magnetic and electric fields inside a MRI-derived heterogeneous head model for various positions and orientations of the coil. We have also investigated the mechanical and thermal stability of the adjustable "Halo coil" configuration for various positions and orientations of the coil to ensure safe operation of the system.

  7. Enhanced heat transfer with full circumferential ribs in helical pipe

    NASA Astrophysics Data System (ADS)

    Chang, S. W.; Su, L. M.; Yang, T. L.

    2002-08-01

    This paper describes an experimental study of heat transfers in the smooth-walled and rib-roughened helical pipes with reference to the design of enhanced cooling passages in the cylinder head and liner of a marine propulsive diesel engine. The manner in which the repeated ribs modify the forced heat convection in the helical pipe is considered for the case where the flow is turbulent upon entering the coil but laminar in further downstream. A selection of experimental results illustrates the individual and interactive effects of Dean vortices and rib-flows on heat transfer along the inner and outer helixes of coils. The experimental-based observations reveal that the centrifugal force modifies the heat transfer in a manner to generate circumferential heat transfer variation with better cooling performance on the outer edge relative to its inner counterpart even with the agitated flow field caused by the repeated ribs. Heat transfer augmentation factor in the range of 1.3 - 3 times of the smooth-walled level is achieved using the present ribbing geometry. A set of empirical correlations based on the experimental data has been developed to permit the evaluation of heat transfers along the inner and outer helixes of the smooth-walled and rib-roughened helical pipes.

  8. Structural mapping of the coiled-coil domain of a bacterial condensin and comparative analyses across all domains of life suggest conserved features of SMC proteins.

    PubMed

    Waldman, Vincent M; Stanage, Tyler H; Mims, Alexandra; Norden, Ian S; Oakley, Martha G

    2015-06-01

    The structural maintenance of chromosomes (SMC) proteins form the cores of multisubunit complexes that are required for the segregation and global organization of chromosomes in all domains of life. These proteins share a common domain structure in which N- and C- terminal regions pack against one another to form a globular ATPase domain. This "head" domain is connected to a central, globular, "hinge" or dimerization domain by a long, antiparallel coiled coil. To date, most efforts for structural characterization of SMC proteins have focused on the globular domains. Recently, however, we developed a method to map interstrand interactions in the 50-nm coiled-coil domain of MukB, the divergent SMC protein found in γ-proteobacteria. Here, we apply that technique to map the structure of the Bacillus subtilis SMC (BsSMC) coiled-coil domain. We find that, in contrast to the relatively complicated coiled-coil domain of MukB, the BsSMC domain is nearly continuous, with only two detectable coiled-coil interruptions. Near the middle of the domain is a break in coiled-coil structure in which there are three more residues on the C-terminal strand than on the N-terminal strand. Close to the head domain, there is a second break with a significantly longer insertion on the same strand. These results provide an experience base that allows an informed interpretation of the output of coiled-coil prediction algorithms for this family of proteins. A comparison of such predictions suggests that these coiled-coil deviations are highly conserved across SMC types in a wide variety of organisms, including humans. © 2015 Wiley Periodicals, Inc.

  9. Improved efficiency and precise temperature control of low-frequency induction-heating pure iron vapor source on ECR ion source

    NASA Astrophysics Data System (ADS)

    Kato, Y.; Takenaka, T.; Yano, K.; Kiriyama, R.; Kurisu, Y.; Nozaki, D.; Muramatsu, M.; Kitagawa, A.; Uchida, T.; Yoshida, Y.; Sato, F.; Iida, T.

    2012-11-01

    Multiply charged ions to be used prospectively are produced from solid pure material in an electron cyclotron resonance ion source (ECRIS). Recently a pure iron source is also required for the production of caged iron ions in the fullerene in order to control cells in vivo in bio-nano science and technology. We adopt directly heating iron rod by induction heating (IH) because it has non-contact with insulated materials which are impurity gas sources. We choose molybdenum wire for the IH coils because it doesn't need water cooling. To improve power efficiency and temperature control, we propose to the new circuit without previously using the serial and parallel dummy coils (SPD) for matching and safety. We made the circuit consisted of inductively coupled coils which are thin-flat and helix shape, and which insulates the IH power source from the evaporator. This coupling coils circuit, i.e. insulated induction heating coil transformer (IHCT), can be move mechanically. The secondary current can be adjusted precisely and continuously. Heating efficiency by using the IHCT is much higher than those of previous experiments by using the SPD, because leakage flux is decreased and matching is improved simultaneously. We are able to adjust the temperature in heating the vapor source around melting point. And then the vapor pressure can be controlled precisely by using the IHCT. We can control ±10K around 1500°C by this method, and also recognize to controlling iron vapor flux experimentally in the extreme low pressures. Now we come into next stage of developing induction heating vapor source for materials with furthermore high temperature melting points above 2000K with the IHCT, and then apply it in our ECRIS.

  10. Direct matching methods for coils and preamplifiers in MRI

    NASA Astrophysics Data System (ADS)

    Cao, Xueming; Fischer, Elmar; Hennig, Jürgen; Zaitsev, Maxim

    2018-05-01

    In this paper, direct matching methods for coils and preamplifiers in receiver arrays are presented. Instead of compensating the reactance of the input impedance of preamplifiers, in our method, the reactance was used to resonate with the coil matching networks and thus to decouple the coils. Furthermore, coil matching networks and preamplifier input matching networks were combined, meaning the coil loop can be matched to the transistor in the preamplifier directly. These matching methods and, for comparison, the conventional matching method were implemented with custom-made preamplifiers and coils. Decoupling and noise-matching performance were compared between these three configurations. Phase shifting networks between coils and preamplifiers are not necessary in our matching methods. With fewer components, these matching networks showed lower noise factors, while similar preamplifier-decoupling performance was found for all three methods.

  11. Rapid Covalent Fluorescence Labeling of Membrane Proteins on Live Cells via Coiled-Coil Templated Acyl Transfer.

    PubMed

    Reinhardt, Ulrike; Lotze, Jonathan; Mörl, Karin; Beck-Sickinger, Annette G; Seitz, Oliver

    2015-10-21

    Fluorescently labeled proteins enable the microscopic imaging of protein localization and function in live cells. In labeling reactions targeted against specific tag sequences, the size of the fluorophore-tag is of major concern. The tag should be small to prevent interference with protein function. Furthermore, rapid and covalent labeling methods are desired to enable the analysis of fast biological processes. Herein, we describe the development of a method in which the formation of a parallel coiled coil triggers the transfer of a fluorescence dye from a thioester-linked coil peptide conjugate onto a cysteine-modified coil peptide. This labeling method requires only small tag sequences (max 23 aa) and occurs with high tag specificity. We show that size matching of the coil peptides and a suitable thioester reactivity allow the acyl transfer reaction to proceed within minutes (rather than hours). We demonstrate the versatility of this method by applying it to the labeling of different G-protein coupled membrane receptors including the human neuropeptide Y receptors 1, 2, 4, 5, the neuropeptide FF receptors 1 and 2, and the dopamine receptor 1. The labeled receptors are fully functional and able to bind the respective ligand with high affinity. Activity is not impaired as demonstrated by activation, internalization, and recycling experiments.

  12. Dual levitated coils for antihydrogen production

    NASA Astrophysics Data System (ADS)

    Wofford, J. D.; Ordonez, C. A.

    2013-04-01

    Two coaxial superconducting magnetic coils that carry currents in the same direction and that are simultaneously levitated may serve for antihydrogen plasma confinement. The configuration may be suitable for use by a collaboration at the CERN Antiproton Decelerator facility to test fundamental symmetries between the properties of hydrogen and antihydrogen. Nested Penning traps are currently used to confine recombining antihydrogen plasma. Symmetry studies require the production of sufficiently cold antihydrogen. However, plasma drifts within nested Penning traps can increase the kinetic energy of antiprotons that form antihydrogen atoms. Dual levitated coils may serve to confine relatively large, cold, dense non-drifting recombining antihydrogen plasmas. A minimum-B magnetic field that is produced by the coils could provide for atom trapping. A toroidal plasma is confined between the coils. High density plasmas may be possible, by allowing plasma pressure to balance mechanical pressure to keep the coils apart. Progress is reported on theoretical and experimental efforts. The theoretical effort includes the development of a classical trajectory Monte Carlo simulation of confinement. The experimental effort includes levitation of a NdFeB permanent ring magnet, which produces a magnetic field that is qualitatively similar to the field that would be produced by the two coaxial superconducting magnetic coils. Liquid-nitrogen-cooled Bi-2223 high-temperature-superconducting components, with a critical temperature of 108 K, were used to levitate the ring magnet. An issue concerning keeping the plane of the levitated ring horizontal is discussed.

  13. Fabrication of Ohmic contact on semi-insulating 4H-SiC substrate by laser thermal annealing

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Cheng, Yue; Lu, Wu-yue; Wang, Tao

    The Ni contact layer was deposited on semi-insulating 4H-SiC substrate by magnetron sputtering. The as-deposited samples were treated by rapid thermal annealing (RTA) and KrF excimer laser thermal annealing (LTA), respectively. The RTA annealed sample is rectifying while the LTA sample is Ohmic. The specific contact resistance (ρ{sub c}) is 1.97 × 10{sup −3} Ω·cm{sup 2}, which was determined by the circular transmission line model. High resolution transmission electron microscopy morphologies and selected area electron diffraction patterns demonstrate that the 3C-SiC transition zone is formed in the near-interface region of the SiC after the as-deposited sample is treated by LTA,more » which is responsible for the Ohmic contact formation in the semi-insulating 4H-SiC.« less

  14. RF Magnetic Field Uniformity of Rectangular Planar Coils for Resonance Imaging

    DTIC Science & Technology

    2016-02-04

    coil with square -shaped overlapping turns along the 135mm length of the coil. This paper compares these two coils to determine which has a more...in which, the coil arrays consist of a few square or circular coils side-by-side or overlapping. Mobile unilateral NMR/MRI scanners were...magnetic field along the length of a normal rectangular coil (NRC) and a rectangular coil with overlapping square -shaped turns (RCOS). The RCOS coil is

  15. Three-axis orthogonal transceiver coil for eddy current sounding

    NASA Astrophysics Data System (ADS)

    Sukhanov, D.; Zavyalova, K.; Goncharik, M.

    2017-08-01

    We propose the new structure of three-axis transceiver magnetic-induction coil for eddy current probing. Due to the orientation of the coils, the direct signal from the transmitting coil to the receiving coil is minimized, which provided a high dynamic range. Sensitivity in all directions is provided by combining coils of different orientations. Numerical simulation and experimental studies of such a system have been carried out and confirmed the applicability of the proposed method and the mathematical model.

  16. Optimizing stellarator coil winding surfaces with Regcoil

    NASA Astrophysics Data System (ADS)

    Bader, Aaron; Landreman, Matt; Anderson, David; Hegna, Chris

    2017-10-01

    We show initial attempts at optimizing a coil winding surface using the Regcoil code [1] for selected quasi helically symmetric equilibria. We implement a generic optimization scheme which allows for variation of the winding surface to allow for improved diagnostic access and allow for flexible divertor solutions. Regcoil and similar coil-solving algorithms require a user-input winding surface, on which the coils lie. Simple winding surfaces created by uniformly expanding the plasma boundary may not be ideal. Engineering constraints on reactor design require a coil-plasma separation sufficient for the introduction of neutron shielding and a tritium generating blanket. This distance can be the limiting factor in determining reactor size. Furthermore, expanding coils in other regions, where possible, can be useful for diagnostic and maintenance access along with providing sufficient room for a divertor. We minimize a target function that includes as constraints, the minimum coil-plasma distance, the winding surface volume, and the normal magnetic field on the plasma boundary. Results are presented for two quasi-symmetric equilibria at different aspect ratios. Work supported by the US DOE under Grant DE-FG02-93ER54222.

  17. Development of a compact HTS lead unit for the SC correction coils of the SuperKEKB final focusing magnet system

    NASA Astrophysics Data System (ADS)

    Zong, Zhanguo; Ohuchi, Norihito; Tsuchiya, Kiyosumi; Arimoto, Yasushi

    2016-09-01

    Forty-three superconducting (SC) correction coils with maximum currents of about 60 A are installed in the SuperKEKB final focusing magnet system. Current leads to energize the SC correction coils should have an affordable heat load and fit the spatial constraints in the service cryostat where the current leads are installed. To address the requirements, design optimization of individual lead was performed with vapor cooled current lead made of a brass material, and a compact unit was designed to accommodate eight current leads together in order to be installed with one port in the service cryostat. The 2nd generation high temperature SC (HTS) tape was adopted and soldered at the cold end of the brass current lead to form a hybrid HTS lead structure. A prototype of the compact lead unit with HTS tape was constructed and tested with liquid helium (LHe) environment. This paper presents a cryogenic measurement system to simulate the real operation conditions in the service cryostat, and analysis of the experimental results. The measured results showed excellent agreement with the theoretical analysis and numerical simulation. In total, 11 sets of the compact HTS lead units were constructed for the 43 SC correction coils at KEK. One set from the mass production was tested in cryogenic conditions, and exhibited the same performance as the prototype. The compact HTS lead unit can feed currents to four SC correction coils simultaneously with the simple requirement of controlling and monitoring helium vapor flow, and has a heat load of about 0.762 L/h in terms of LHe consumption.

  18. Influence of a heptad repeat stutter on the pH-dependent conformational behavior of the central coiled-coil from influenza hemagglutinin HA2.

    PubMed

    Higgins, Chelsea D; Malashkevich, Vladimir N; Almo, Steven C; Lai, Jonathan R

    2014-09-01

    The coiled-coil is one of the most common protein structural motifs. Amino acid sequences of regions that participate in coiled-coils contain a heptad repeat in which every third then forth residue is occupied by a hydrophobic residue. Here we examine the consequences of a "stutter," a deviation of the idealized heptad repeat that is found in the central coiled-coil of influenza hemagluttinin HA2. Characterization of a peptide containing the native stutter-containing HA2 sequence, as well as several variants in which the stutter was engineered out to restore an idealized heptad repeat pattern, revealed that the stutter is important for allowing coiled-coil formation in the WT HA2 at both neutral and low pH (7.1 and 4.5). By contrast, all variants that contained idealized heptad repeats exhibited marked pH-dependent coiled-coil formation with structures forming much more stably at low pH. A crystal structure of one variant containing an idealized heptad repeat, and comparison to the WT HA2 structure, suggest that the stutter distorts the optimal interhelical core packing arrangement, resulting in unwinding of the coiled-coil superhelix. Interactions between acidic side chains, in particular E69 and E74 (present in all peptides studied), are suggested to play a role in mediating these pH-dependent conformational effects. This conclusion is partially supported by studies on HA2 variant peptides in which these positions were altered to aspartic acid. These results provide new insight into the structural role of the heptad repeat stutter in HA2. © 2014 Wiley Periodicals, Inc.

  19. Measurement of a Conduction Cooled Nb3Sn Racetrack Coil

    NASA Astrophysics Data System (ADS)

    Kim, HS; Kovacs, C.; Rochester, J.; Sumption, MD; Tomsic, M.; Peng, X.; Doll, D.

    2017-12-01

    Use of superconducting coils for wind turbines and electric aircraft is of interest because of the potential for high power density and weight reduction. Here we test a racetrack coil developed as a proof-of-concept for cryogen-free superconducting motors and generators. The coil was wound with 1209 m of 0.7-mm-diameter insulated tube-type Nb3Sn wire. The coil was epoxy-impregnated, instrumented, covered with numerous layers of aluminized mylar insulation, and inserted vertically into a dewar. The system was cooled to 4.2 K, and a few inches of liquid helium was allowed to collect at the bottom of the dewar but below the coil. The coil was cooled by conduction via copper cooling bars were attached to the coil but also were immersed in the liquid helium at their lower ends. Several current tests were performed on the coil, initially in voltage mode, and one run in current mode. The maximum coil Ic at 4.2 K was 480 A, generating 3.06 T at the surface of the coil. The coil met the design targets with a noticeable margin.

  20. Defining the minimum size of a hydrophobic cluster in two-stranded α-helical coiled-coils: Effects on protein stability

    PubMed Central

    Lu, Stephen M.; Hodges, Robert S.

    2004-01-01

    The α-helical coiled-coil motif is characterized by a heptad repeat pattern (abcdefg)n in which residues a and d form the hydrophobic core. Long coiled-coils (e.g., tropomyosin, 284 residues per polypeptide chain) typically do not have a continuous hydrophobic core of stabilizing residues, but rather one that consists of alternating clusters of stabilizing and destabilizing residues. We have arbitrarily defined a cluster as a minimum of three consecutive stabilizing or destabilizing residues in the hydrophobic core. We report here on a series of two-stranded, disulfide-bridged parallel α-helical coiled-coils that contain a central cassette of three consecutive hydrophobic core positions (d, a, and d) with a destabilizing cluster of three consecutive Ala residues in the hydrophobic core on each side of the cassette. The effect of adding one to three stabilizing hydrophobes in these positions (Leu or Ile; denoted as •) was investigated. Alanine residues (denoted as ○) are used to represent destabilizing residues. The peptide with three Ala residues in the d a d cassette positions (○○○) was among the least stable coiled-coil (Tm = 39.3°C and Urea1/2 = 1.9 M). Surprisingly, the addition of one stabilizing hydrophobe (Leu) to the cassette or two stabilizing hydrophobes (Leu), still interspersed by an Ala in the cassette (•○•), also did not lead to any gain in stability. However, peptides with two adjacent hydrophobes in the cassette (••○)(○••) did show a gain in stability of 0.9 kcal/mole over the peptide with two interspersed hydrophobes (•○•). Because the latter three peptides have the same inherent hydrophobicity, the juxtaposition of stabilizing hydrophobes leads to a synergistic effect, and thus a clustering effect. The addition of a third stabilizing hydrophobe to the cassette (•••) resulted in a further synergistic gain in stability of 1.7 kcal/mole (Tm = 54.1°C and Urea1/2 = 3.3M). Therefore, the role of hydrophobicity