Science.gov

Sample records for asymmetric m-b velocity

  1. Asymmetric optimal-velocity car-following model

    NASA Astrophysics Data System (ADS)

    Xu, Xihua; Pang, John; Monterola, Christopher

    2015-10-01

    Taking the asymmetric characteristic of the velocity differences of vehicles into account, we present an asymmetric optimal velocity model for a car-following theory. The asymmetry between the acceleration and the deceleration is represented by the exponential function with an asymmetrical factor, which agrees with the published experiment. This model avoids the disadvantage of the unrealistically high acceleration appearing in previous models when the velocity difference becomes large. This model is simple and only has two independent parameters. The linear stability condition is derived and the phase transition of the traffic flow appears beyond the critical density. The strength of interaction between clusters is shown to increase with the asymmetry factor in our model.

  2. Observations of velocities, sand concentrations, and fluxes under velocity-asymmetric oscillatory flows

    NASA Astrophysics Data System (ADS)

    Ruessink, B. G.; Michallet, H.; Abreu, T.; Sancho, F.; van der A, D. A.; van der Werf, J. J.; Silva, P. A.

    2011-03-01

    U-tube measurements of instantaneous velocities, concentrations, and fluxes for a well-sorted, medium-sized sand in oscillatory sheet flow are analyzed. The experiments involved two velocity-asymmetric flows, the same two flows with an opposing current of 0.4 m/s, and a mixed skewed-asymmetric flow, all with a velocity amplitude of 1.2 m/s and flow period of 7 s. We find that the net positive transport rate beneath velocity-asymmetric oscillatory flow results from large, but opposing sand fluxes during the positive and negative flow phase. With an increase in velocity asymmetry and, in particular, velocity skewness, the difference in the magnitude of the fluxes in the two half cycles increases, leading to larger net transport rates. This trend is consistent with the observed increase in skewness of the oscillatory bed shear stress. Phase-lag effects, whereby sand stirred during the negative flow phase has not settled by the time of the negative-to-positive flow reversal and is subsequently transported during the positive flow phase, are notable but of minor importance to the net transport rate compared to earlier experiments with finer sands. In the vertical, the oscillatory flux is positive above the no-flow bed. Within the sheet flow pick-up layer, the oscillatory flux is negative and similar in magnitude to the positive flux induced by the residual flow. The 0.4 m/s opposing current causes more sand to be picked up during the negative than during the positive flow phase. Above the no-flow bed the resulting negative oscillatory flux is comparable in magnitude to the current-related flux.

  3. The force-velocity curve in passive whole muscle is asymmetric about zero velocity.

    PubMed

    Krause, P C; Choi, J S; McMahon, T A

    1995-09-01

    The force-velocity property of passive muscle was investigated to determine if a discontinuity of slope occurred at zero velocity. Isolated, unstimulated whole frog sartorius muscles were subjected to constant-velocity stretches and releases using a servo-controlled lever. The force due to damping (delta T) was calculated by subtracting the tension measured at a very low speed (1.0 mm s-1) from the tension measured at the same length while the muscle was shortening or lengthening at a particular test speed. The experiments were performed over a range of speeds at each of several lengths and at two temperatures. For comparison, the same experiments were performed using a strip of pure latex rubber and a steel spring. Curves showing the magnitude of delta T vs velocity were nearly symmetric about the zero-velocity axis for the steel spring and the rubber strip, but were markedly asymmetric for passive muscle, showing a positive delta T for lengthening at all speeds that was between four and 11 times the negative delta T for shortening at the same speed, depending on the temperature and initial stretch length. The force due to damping at a given speed increased with extension above the rest length in passive muscle but decreased with increasing length in experiments using the latex strip. Predictions obtained from a mathematical model based on a damping element in series with a lightly damped spring were fitted to the experimental measurements of delta T vs velocity. The damping parameter provisionally representing interfilamentary sliding was between six and 12 times larger for lengthening than for shortening.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7559673

  4. Quantum beats in conductance oscillations in graphene-based asymmetric double velocity wells and electrostatic wells

    SciTech Connect

    Liu, Lei; Li, Yu-Xian; Zhang, Ying-Tao; Liu, Jian-Jun

    2014-01-14

    The transport properties in graphene-based asymmetric double velocity well (Fermi velocity inside the well less than that outside the well) and electrostatic well structures are investigated using the transfer matrix method. The results show that quantum beats occur in the oscillations of the conductance for asymmetric double velocity wells. The beating effect can also be found in asymmetric double electrostatic wells, but only if the widths of the two wells are different. The beat frequency for the asymmetric double well is exactly equal to the frequency difference between the oscillation rates in two isolated single wells with the same structures as the individual wells in the double well structure. A qualitative interpretation is proposed based on the fact that the resonant levels depend upon the sizes of the quantum wells. The beating behavior can provide a new way to identify the symmetry of double well structures.

  5. Asymmetric velocity anisotropies in remnants of collisionless mergers

    SciTech Connect

    Sparre, Martin; Hansen, Steen H. E-mail: hansen@dark-cosmology.dk

    2012-07-01

    Dark matter haloes in cosmological N-body simulations are affected by processes such as mergers, accretion and the gravitational interaction with baryonic matter. Typically the analysis of dark matter haloes is performed in spherical or elliptical bins and the velocity distributions are often assumed to be constant within those bins. However, the velocity anisotropy, which describes differences between the radial and tangential velocity dispersion, has recently been show to have a strong dependence on direction in the triaxial halos formed in cosmological simulations. In this study we derive properties of particles in cones parallel or perpendicular to the collision axis of merger remnants. We find that the velocity anisotropy has a strong dependence on direction. The finding that the direction-dependence of the velocity anisotropy of a halo depends on the merger history, explains the existence of such trends in cosmological simulations. It also explains why a large diversity is seen in the velocity anisotropy profiles in the outer parts of high-resolution simulations of cosmological haloes.

  6. Computational analysis of asymmetric water entry of wedge and ship section at constant velocity

    NASA Astrophysics Data System (ADS)

    Rahaman, Md. Mashiur; Ullah, Al Habib; Afroz, Laboni; Shabnam, Sharmin; Sarkar, M. A. Rashid

    2016-07-01

    Water impact problems receive much attention due to their short duration and large unsteady component of hydrodynamic loads. The effect of water entry has several important applications in various aspects of the naval field. Significant attention has been given to various water entry phenomena such as ship slamming, planning hulls, high-speed hydrodynamics of seaplanes, surface-piercing propellers and the interaction of high-speed liquid drops with structural elements. Asymmetric water entry may be caused by various natural phenomena such as weather conditions or strong winds. Since the determination of hydrodynamic impact load plays a vital role in designing safe and effcient vessels, an accurate and reliable prediction method is necessary to investigate asymmetric water entry problems. In this paper, water entry of a two-dimensional wedge and ship section at constant velocity in asymmetric condition will be analysed numerically and the effects of asymmetric impact on the velocity and pressure distribution will be discussed. The finite volume method is employed to solve the dynamic motion of the wedge in two-phase flow. During the water entry, the air and water interface is described implicitly by the volume of fluid (VOF) scheme. The numerical code and method was first validated for symmetric condition by one of the present author is applied for asymmetric wedge and ship section. The free surface, velocity and pressure distribution for asymmetric water entry are investigated and visualized with contour plots at different time steps.

  7. Reconstruction of velocity profiles in axisymmetric and asymmetric flows using an electromagnetic flow meter

    NASA Astrophysics Data System (ADS)

    Kollár, László E.; Lucas, Gary P.; Meng, Yiqing

    2015-05-01

    An analytical method that was developed formerly for the reconstruction of velocity profiles in asymmetric flows is improved to be applicable for both axisymmetric and asymmetric flows. The method is implemented in Matlab, and predicts the velocity profile from measured electrical potential distributions obtained around the boundary of a multi-electrode electromagnetic flow meter (EMFM). Potential distributions are measured in uniform and non-uniform magnetic fields, and the velocity is assumed as a sum of axisymmetric and polynomial components. The procedure requires three steps. First, the discrete Fourier transform (DFT) is applied to the potential distribution obtained in a uniform magnetic field. Since the direction of polynomial components of order greater than two in the plane of the pipe cross section is not unique multiple solutions exist, therefore all possible polynomial velocity profiles are determined. Then, the DFT is applied to the potential distribution obtained in a specific non-uniform magnetic field, and used to calculate the exponent in a power-law representation of the axisymmetric component. Finally, the potential distribution in the non-uniform magnetic field is calculated for all of the possible velocity profile solutions using weight values, and the velocity profile with the calculated potential distribution which is closest to the measured one provides the optimum solution. The method is validated by reconstructing two quartic velocity profiles, one of which includes an axisymmetric component. The potential distributions are obtained from simulations using COMSOL Multiphysics where a model of the EMFM is constructed. The reconstructed velocity profiles show satisfactory agreement with the input velocity profiles. The main benefits of the method described in this paper are that it provides a velocity distribution in the circular cross section of a pipe as an analytical function of the spatial coordinates which is suitable for both

  8. Control of exit velocity profile of an asymmetric annular diffuser using wall suction

    NASA Technical Reports Server (NTRS)

    Juhasz, A. J.

    1973-01-01

    An asymmetric annular diffuser equipped with wall bleed (suction) capability was tested for controllability of exit velocity profile. The diffuser area ratio was 3.2, and the length to inlet height ratio was 1.6. Results show that the diffuser radial exit velocity profile could be controlled from a hub peaked to a tip peaked form by selective use of bleed on the outer wall or on both diffuser walls. Based on these results, application of the diffuser bleed technique to gas turbine combustors may be possible. Diffuser bleed could be used to tailor the airflow distribution for optimizing combustor performance at a variety of operating conditions.

  9. Asymmetric orbital distribution near mean motion resonance: Application to planets observed by Kepler and radial velocities

    SciTech Connect

    Xie, Ji-Wei E-mail: jwxie@astro.utoronto.ca

    2014-05-10

    Many multiple-planet systems have been found by the Kepler transit survey and various radial velocity (RV) surveys. Kepler planets show an asymmetric feature, namely, there are small but significant deficits/excesses of planet pairs with orbital period spacing slightly narrow/wide of the exact resonance, particularly near the first order mean motion resonance (MMR), such as 2:1 and 3:2 MMR. Similarly, if not exactly the same, an asymmetric feature (pileup wide of 2:1 MMR) is also seen in RV planets, but only for massive ones. We analytically and numerically study planets' orbital evolutions near and in the MMR. We find that their orbital period ratios could be asymmetrically distributed around the MMR center regardless of dissipation. In the case of no dissipation, Kepler planets' asymmetric orbital distribution could be partly reproduced for 3:2 MMR but not for 2:1 MMR, implying that dissipation might be more important to the latter. The pileup of massive RV planets just wide of 2:1 MMR is found to be consistent with the scenario that planets formed separately then migrated toward the MMR. The location of the pileup infers a K value of 1-100 on the order of magnitude for massive planets, where K is the damping rate ratio between orbital eccentricity and semimajor axis during planet migration.

  10. Hummingbirds control turning velocity using body orientation and turning radius using asymmetrical wingbeat kinematics.

    PubMed

    Read, Tyson J G; Segre, Paolo S; Middleton, Kevin M; Altshuler, Douglas L

    2016-03-01

    Turning in flight requires reorientation of force, which birds, bats and insects accomplish either by shifting body position and total force in concert or by using left-right asymmetries in wingbeat kinematics. Although both mechanisms have been observed in multiple species, it is currently unknown how each is used to control changes in trajectory. We addressed this problem by measuring body and wingbeat kinematics as hummingbirds tracked a revolving feeder, and estimating aerodynamic forces using a quasi-steady model. During arcing turns, hummingbirds symmetrically banked the stroke plane of both wings, and the body, into turns, supporting a body-dependent mechanism. However, several wingbeat asymmetries were present during turning, including a higher and flatter outer wingtip path and a lower more deviated inner wingtip path. A quasi-steady analysis of arcing turns performed with different trajectories revealed that changes in radius were associated with asymmetrical kinematics and forces, and changes in velocity were associated with symmetrical kinematics and forces. Collectively, our results indicate that both body-dependent and -independent force orientation mechanisms are available to hummingbirds, and that these kinematic strategies are used to meet the separate aerodynamic challenges posed by changes in velocity and turning radius. PMID:27030042

  11. Calculation and measurement of a neutral air flow velocity impacting a high voltage capacitor with asymmetrical electrodes

    SciTech Connect

    Malík, M. Primas, J.; Kopecký, V.; Svoboda, M.

    2014-01-15

    This paper deals with the effects surrounding phenomenon of a mechanical force generated on a high voltage asymmetrical capacitor (the so called Biefeld-Brown effect). A method to measure this force is described and a formula to calculate its value is also given. Based on this the authors derive a formula characterising the neutral air flow velocity impacting an asymmetrical capacitor connected to high voltage. This air flow under normal circumstances lessens the generated force. In the following part this velocity is measured using Particle Image Velocimetry measuring technique and the results of the theoretically calculated velocity and the experimentally measured value are compared. The authors found a good agreement between the results of both approaches.

  12. Dark matter searches employing asymmetric velocity distributions obtained via the Eddington approach

    NASA Astrophysics Data System (ADS)

    Vergados, J. D.; Moustakidis, Ch. C.; Owen, D.

    2016-08-01

    Starting from WIMP density profiles, in the framework of the Eddington approach, we obtain the energy distribution f(E) of dark matter in our vicinity. Assuming a factorizable phase space function, f(E , L) = F(E) FL(L) , we obtain the velocity dispersions and the anisotropy parameter β in terms of the parameters describing the angular momentum dependence. By employing the derived expression f(E) we construct axially symmetric WIMP velocity distributions. The obtained distributions automatically have a velocity upper bound, as a consequence of the fact that they are associated with a gravitationally bound system, and are characterized by an anisotropy parameter β. We then show how such velocity distributions can be used in determining the event rates, including modulation, both in the standard as well directional WIMP searches.

  13. Asymmetric material impact: Achieving free surfaces velocities nearly double that of the projectile

    SciTech Connect

    Aslam, Tariq; Dattelbaum, Dana; Gustavsen, Richard; Scharff, Robert; Byers, Mark

    2015-05-19

    Hypervelocity impact speeds are often limited by practical considerations in guns and explosive driven systems. In particular, for gas guns (both powder driven and light gas guns), there is the general trend that higher projectile speeds often come at the expense of smaller diameters, and thus less time for examining shock phenomena prior to two dimensional release waves affecting the observed quantities of interest. Similarly, explosive driven systems have their own set of limiting conditions due to limitations in explosive energy and size of devices required as engineering dimensions increase. The focus in this study is to present a methodology of obtaining free surface velocities well in excess of the projectile velocity. The key to this approach is in using a high impedance projectile that impacts a series of progressively lower impedance materials. The free surface velocity (if they were separated) of each of the progressively lower impedance materials would increase for each material. The theory behind this approach, as well as experimental results are presented.

  14. Asymmetric material impact: Achieving free surfaces velocities nearly double that of the projectile

    DOE PAGESBeta

    Aslam, Tariq; Dattelbaum, Dana; Gustavsen, Richard; Scharff, Robert; Byers, Mark

    2015-05-19

    Hypervelocity impact speeds are often limited by practical considerations in guns and explosive driven systems. In particular, for gas guns (both powder driven and light gas guns), there is the general trend that higher projectile speeds often come at the expense of smaller diameters, and thus less time for examining shock phenomena prior to two dimensional release waves affecting the observed quantities of interest. Similarly, explosive driven systems have their own set of limiting conditions due to limitations in explosive energy and size of devices required as engineering dimensions increase. The focus in this study is to present a methodologymore » of obtaining free surface velocities well in excess of the projectile velocity. The key to this approach is in using a high impedance projectile that impacts a series of progressively lower impedance materials. The free surface velocity (if they were separated) of each of the progressively lower impedance materials would increase for each material. The theory behind this approach, as well as experimental results are presented.« less

  15. Performance of an asymmetric short annular diffuser with a nondiverging inner wall using suction. [control of radial profiles of diffuser exit velocity

    NASA Technical Reports Server (NTRS)

    Juhasz, A.

    1974-01-01

    The performance of a short highly asymmetric annular diffuser equipped with wall bleed (suction) capability was evaluated at nominal inlet Mach numbers of 0.188, 0.264, and 0.324 with the inlet pressure and temperature at near ambient values. The diffuser had an area ratio of 2.75 and a length- to inlet-height ratio of 1.6. Results show that the radial profiles of diffuser exit velocity could be controlled from a severely hub peaked to a slightly tip biased form by selective use of bleed. At the same time, other performance parameters were also improved. These results indicate the possible application of the diffuser bleed technique to control flow profiles to gas turbine combustors.

  16. J.B. v. M.B.

    PubMed

    2000-01-01

    Court Decision: 751 Atlantic Reporter, 2d Series 613; 2003 Jun 1 (date of decision). The Superior Court of New Jersey held that a contract made between a now divorced couple and their in vitro fertilization (IVF) provider is not enforceable because it constitutes a contract to procreate, and thus it is contrary to state public policy and is unenforceable. During IVF treatment J.B. became pregnant and gave birth to a healthy child. The extra embryos were cryopreserved. Subsequently J.B. and M.B. divorced. An agreement with their IVF provider specified that control over the frozen embryos was to be relinquished to the provider if the couple divorced, unless specified by a court order. M.B., the former husband, alleged that he and J.B. had agreed to donate the unused embryos to infertile couples. J.B., the former wife, wished to have the embryos destroyed. The court found that enforcing the alleged contract to donate the embryos would impair the former wife's constitutional right to not procreate. Furthermore, M.B.'s right to procreate would not be impaired if the contract were not enforced because M.B. was not infertile and was capable of having children with another person. The Superior Court affirmed the trial court's judgment in favor of the former wife and ordered the destruction of the frozen embryos. PMID:16285110

  17. Observations of asymmetric velocity fields and gas cooling in the NGC 4636 galaxy group X-ray halo

    NASA Astrophysics Data System (ADS)

    Ahoranta, Jussi; Finoguenov, Alexis; Pinto, Ciro; Sanders, Jeremy; Kaastra, Jelle; de Plaa, Jelle; Fabian, Andrew

    2016-08-01

    Aims: This study aims to probe the thermodynamic properties of the hot intragroup medium (IGM) plasma in the core regions of the NGC 4636 galaxy group by detailed measurements of several emission lines and their relative intensities. Methods: We analyzed deep XMM-Newton Reflection Grating Spectrometer (RGS) data in five adjacent spectral regions in the central parts of the NGC 4636 galaxy group. We examined the suppression of the Fe xvii resonance line (15.01 Å) as compared to the forbidden lines of the same ion (17.05 Å and 17.10 Å). The presence and radial dependence of the cooling flow was investigated through spectral modeling. Parallel analysis with deep Chandra Advances CCD Imaging Spectrometer (ACIS) data was conducted to gain additional information about the thermodynamical properties of the IGM. Results: The plasma at the group center to the north shows efficient Fe xvii ion resonant scattering, yielding (Iλ17.05 + Iλ17.10) /Iλ15.01 line ratios up to 2.9 ± 0.4, corresponding toabout twice the predicted line ratio. In contrast, no resonant scattering was detected at the south side. The regions featuring resonant scattering coincide with those embodying large amounts of cool (kT ≲ 0.4 keV) gas phases, and the spectral imprints of cooling gas with a total mass deposition rate of ~0.8 M⊙ yr-1 within the examined region of 2.4' × 5.0'. Conclusions: We interpret the results as possible evidence of asymmetric turbulence distribution in the NGC 4636 IGM: turbulence dominates the gas dynamics to the south, while collective gas motions characterize the dynamics to the north. X-ray images show imprints of energetic AGN at both sides, yet we find evidence of turbulence heating at the south and gas cooling at the north of the core. We infer that the observed asymmetry may be the result of the specific observation angle to the source, or arise from the turbulence driven by core sloshing at south side.

  18. Structure of the velocity distribution of sheath-accelerated secondary electrons in an asymmetric RF-dc discharge

    NASA Astrophysics Data System (ADS)

    Khrabrov, Alexander V.; Kaganovich, Igor D.; Ventzek, Peter L. G.; Ranjan, Alok; Chen, Lee

    2015-10-01

    Low-pressure capacitively-coupled discharges with additional dc bias applied to a separate electrode are utilized in plasma-assisted etching for semiconductor device manufacturing. Measurements of the electron velocity distribution function (EVDF) of the flux impinging on the wafer, as well as in the plasma bulk, show a thermal population and additional peaks within a broad range of energies. That range extends from the thermal level up to the value for the ‘ballistic’ peak, corresponding to the bias potential. The non-thermal electron flux has been correlated to alleviating the electron shading effect and providing etch-resistance properties to masking photoresist layers. ‘Middle-energy peak electrons’ at energies of several hundred eV may provide an additional sustaining mechanism for the discharge. These features in the electron velocity (or energy) distribution functions are possibly caused by secondary electrons emitted from the electrodes and interacting with two high-voltage sheaths: a stationary sheath at the dc electrode and an oscillating self-biased sheath at the powered electrode. Since at those energies the mean free path for large-angle scattering (momentum relaxation length) is comparable to, or exceeds the size of the discharge gap, these ‘ballistic’ electrons will not be fully scattered by the background gas as they traverse the inter-electrode space. We have performed test-particle simulations in which the features in the EVDF of electrons impacting the RF electrode are fully resolved at all energies. An analytical model has been developed to predict existence of peaked and step-like structures in the EVDF. Those features can be explained by analyzing the kinematics of electron trajectories in the discharge gap. Step-like structures in the EVDF near the powered electrode appear due to accumulation of electrons emitted from the dc electrode within a portion of the RF cycle, and their subsequent release. Trapping occurs when the RF

  19. Measurement of the mass difference m(B0)-m(B+)

    NASA Astrophysics Data System (ADS)

    Aubert, B.; Bona, M.; Karyotakis, Y.; Lees, J. P.; Poireau, V.; Prencipe, E.; Prudent, X.; Tisserand, V.; Tico, J. Garra; Grauges, E.; Lopez, L.; Palano, A.; Pappagallo, M.; Eigen, G.; Stugu, B.; Sun, L.; Abrams, G. S.; Battaglia, M.; Brown, D. N.; Button-Shafer, J.; Cahn, R. N.; Jacobsen, R. G.; Kadyk, J. A.; Kerth, L. T.; Kolomensky, Yu. G.; Kukartsev, G.; Lynch, G.; Osipenkov, I. L.; Ronan, M. T.; Tackmann, K.; Tanabe, T.; Wenzel, W. A.; Hawkes, C. M.; Soni, N.; Watson, A. T.; Koch, H.; Schroeder, T.; Walker, D.; Asgeirsson, D. J.; Cuhadar-Donszelmann, T.; Fulsom, B. G.; Hearty, C.; Mattison, T. S.; McKenna, J. A.; Barrett, M.; Khan, A.; Saleem, M.; Teodorescu, L.; Blinov, V. E.; Bukin, A. D.; Buzykaev, A. R.; Druzhinin, V. P.; Golubev, V. B.; Onuchin, A. P.; Serednyakov, S. I.; Skovpen, Yu. I.; Solodov, E. P.; Todyshev, K. Yu.; Bondioli, M.; Curry, S.; Eschrich, I.; Kirkby, D.; Lankford, A. J.; Lund, P.; Mandelkern, M.; Martin, E. C.; Stoker, D. P.; Abachi, S.; Buchanan, C.; Gary, J. W.; Liu, F.; Long, O.; Shen, B. C.; Vitug, G. M.; Yasin, Z.; Zhang, L.; Sharma, V.; Campagnari, C.; Hong, T. M.; Kovalskyi, D.; Mazur, M. A.; Richman, J. D.; Beck, T. W.; Eisner, A. M.; Flacco, C. J.; Heusch, C. A.; Kroseberg, J.; Lockman, W. S.; Schalk, T.; Schumm, B. A.; Seiden, A.; Wang, L.; Wilson, M. G.; Winstrom, L. O.; Cheng, C. H.; Doll, D. A.; Echenard, B.; Fang, F.; Hitlin, D. G.; Narsky, I.; Piatenko, T.; Porter, F. C.; Andreassen, R.; Mancinelli, G.; Meadows, B. T.; Mishra, K.; Sokoloff, M. D.; Blanc, F.; Bloom, P. C.; Ford, W. T.; Gaz, A.; Hirschauer, J. F.; Kreisel, A.; Nagel, M.; Nauenberg, U.; Olivas, A.; Smith, J. G.; Ulmer, K. A.; Wagner, S. R.; Ayad, R.; Gabareen, A. M.; Soffer, A.; Toki, W. H.; Wilson, R. J.; Altenburg, D. D.; Feltresi, E.; Hauke, A.; Jasper, H.; Karbach, M.; Merkel, J.; Petzold, A.; Spaan, B.; Wacker, K.; Klose, V.; Kobel, M. J.; Lacker, H. M.; Mader, W. F.; Nogowski, R.; Schubert, K. R.; Schwierz, R.; Sundermann, J. E.; Volk, A.; Bernard, D.; Bonneaud, G. R.; Latour, E.; Thiebaux, Ch.; Verderi, M.; Clark, P. J.; Gradl, W.; Playfer, S.; Watson, J. E.; Andreotti, M.; Bettoni, D.; Bozzi, C.; Calabrese, R.; Cecchi, A.; Cibinetto, G.; Franchini, P.; Luppi, E.; Negrini, M.; Petrella, A.; Piemontese, L.; Santoro, V.; Anulli, F.; Baldini-Ferroli, R.; Calcaterra, A.; de Sangro, R.; Finocchiaro, G.; Pacetti, S.; Patteri, P.; Peruzzi, I. M.; Piccolo, M.; Rama, M.; Zallo, A.; Buzzo, A.; Contri, R.; Lo Vetere, M.; Macri, M. M.; Monge, M. R.; Passaggio, S.; Patrignani, C.; Robutti, E.; Santroni, A.; Tosi, S.; Chaisanguanthum, K. S.; Morii, M.; Dubitzky, R. S.; Marks, J.; Schenk, S.; Uwer, U.; Bard, D. J.; Dauncey, P. D.; Nash, J. A.; Vazquez, W. Panduro; Tibbetts, M.; Behera, P. K.; Chai, X.; Charles, M. J.; Mallik, U.; Cochran, J.; Crawley, H. B.; Dong, L.; Meyer, W. T.; Prell, S.; Rosenberg, E. I.; Rubin, A. E.; Gao, Y. Y.; Gritsan, A. V.; Guo, Z. J.; Lae, C. K.; Denig, A. G.; Fritsch, M.; Schott, G.; Arnaud, N.; Béquilleux, J.; D'Orazio, A.; Davier, M.; da Costa, J. Firmino; Grosdidier, G.; Höcker, A.; Lepeltier, V.; Le Diberder, F.; Lutz, A. M.; Pruvot, S.; Roudeau, P.; Schune, M. H.; Serrano, J.; Sordini, V.; Stocchi, A.; Wang, W. F.; Wormser, G.; Lange, D. J.; Wright, D. M.; Bingham, I.; Burke, J. P.; Chavez, C. A.; Fry, J. R.; Gabathuler, E.; Gamet, R.; Hutchcroft, D. E.; Payne, D. J.; Touramanis, C.; Bevan, A. J.; George, K. A.; di Lodovico, F.; Sacco, R.; Sigamani, M.; Cowan, G.; Flaecher, H. U.; Hopkins, D. A.; Paramesvaran, S.; Salvatore, F.; Wren, A. C.; Brown, D. N.; Davis, C. L.; Alwyn, K. E.; Barlow, N. R.; Barlow, R. J.; Chia, Y. M.; Edgar, C. L.; Lafferty, G. D.; West, T. J.; Yi, J. I.; Anderson, J.; Chen, C.; Jawahery, A.; Roberts, D. A.; Simi, G.; Tuggle, J. M.; Dallapiccola, C.; Hertzbach, S. S.; Li, X.; Salvati, E.; Saremi, S.; Cowan, R.; Dujmic, D.; Fisher, P. H.; Koeneke, K.; Sciolla, G.; Spitznagel, M.; Taylor, F.; Yamamoto, R. K.; Zhao, M.; McLachlin, S. E.; Patel, P. M.; Robertson, S. H.; Lazzaro, A.; Lombardo, V.; Palombo, F.; Bauer, J. M.; Cremaldi, L.; Eschenburg, V.; Godang, R.; Kroeger, R.; Sanders, D. A.; Summers, D. J.; Zhao, H. W.; Brunet, S.; Côté, D.; Simard, M.; Taras, P.; Viaud, F. B.; Nicholson, H.; de Nardo, G.; Lista, L.; Monorchio, D.; Sciacca, C.; Baak, M. A.; Raven, G.; Snoek, H. L.; Jessop, C. P.; Knoepfel, K. J.; Losecco, J. M.; Benelli, G.; Corwin, L. A.; Honscheid, K.; Kagan, H.; Kass, R.; Morris, J. P.; Rahimi, A. M.; Regensburger, J. J.; Sekula, S. J.; Wong, Q. K.; Blount, N. L.; Brau, J.; Frey, R.; Igonkina, O.; Kolb, J. A.; Lu, M.; Rahmat, R.; Sinev, N. B.; Strom, D.; Strube, J.; Torrence, E.; Castelli, G.; Gagliardi, N.; Margoni, M.; Morandin, M.; Posocco, M.; Rotondo, M.; Simonetto, F.; Stroili, R.; Voci, C.; Del Amo Sanchez, P.; Ben-Haim, E.; Briand, H.; Calderini, G.; Chauveau, J.; David, P.; Del Buono, L.; Hamon, O.; Leruste, Ph.; Ocariz, J.; Perez, A.; Prendki, J.; Gladney, L.; Biasini, M.; Covarelli, R.; Manoni, E.; Angelini, C.; Batignani, G.; Bettarini, S.; Carpinelli, M.; Cervelli, A.; Forti, F.; Giorgi, M. A.; Lusiani, A.; Marchiori, G.; Morganti, M.; Neri, N.; Paoloni, E.; Rizzo, G.; Walsh, J. J.; Biesiada, J.; Pegna, D. Lopes; Lu, C.; Olsen, J.; Smith, A. J. S.; Telnov, A. V.; Baracchini, E.; Cavoto, G.; Del Re, D.; di Marco, E.; Faccini, R.; Ferrarotto, F.; Ferroni, F.; Gaspero, M.; Jackson, P. D.; Gioi, L. Li; Mazzoni, M. A.; Morganti, S.; Piredda, G.; Polci, F.; Renga, F.; Voena, C.; Ebert, M.; Hartmann, T.; Schröder, H.; Waldi, R.; Adye, T.; Franek, B.; Olaiya, E. O.; Roethel, W.; Wilson, F. F.; Emery, S.; Escalier, M.; Esteve, L.; Gaidot, A.; Ganzhur, S. F.; de Monchenault, G. Hamel; Kozanecki, W.; Vasseur, G.; Yèche, Ch.; Zito, M.; Chen, X. R.; Liu, H.; Park, W.; Purohit, M. V.; White, R. M.; Wilson, J. R.; Allen, M. T.; Aston, D.; Bartoldus, R.; Bechtle, P.; Benitez, J. F.; Cenci, R.; Coleman, J. P.; Convery, M. R.; Dingfelder, J. C.; Dorfan, J.; Dubois-Felsmann, G. P.; Dunwoodie, W.; Field, R. C.; Gowdy, S. J.; Graham, M. T.; Grenier, P.; Hast, C.; Innes, W. R.; Kaminski, J.; Kelsey, M. H.; Kim, H.; Kim, P.; Kocian, M. L.; Leith, D. W. G. S.; Li, S.; Lindquist, B.; Luitz, S.; Luth, V.; Lynch, H. L.; Macfarlane, D. B.; Marsiske, H.; Messner, R.; Muller, D. R.; Neal, H.; Nelson, S.; O'Grady, C. P.; Ofte, I.; Perazzo, A.; Perl, M.; Ratcliff, B. N.; Roodman, A.; Salnikov, A. A.; Schindler, R. H.; Schwiening, J.; Snyder, A.; Su, D.; Sullivan, M. K.; Suzuki, K.; Swain, S. K.; Thompson, J. M.; Va'Vra, J.; Wagner, A. P.; Weaver, M.; West, C. A.; Wisniewski, W. J.; Wittgen, M.; Wright, D. H.; Wulsin, H. W.; Yarritu, A. K.; Yi, K.; Young, C. C.; Ziegler, V.; Burchat, P. R.; Edwards, A. J.; Majewski, S. A.; Miyashita, T. S.; Petersen, B. A.; Wilden, L.; Ahmed, S.; Alam, M. S.; Bula, R.; Ernst, J. A.; Pan, B.; Saeed, M. A.; Zain, S. B.; Spanier, S. M.; Wogsland, B. J.; Eckmann, R.; Ritchie, J. L.; Ruland, A. M.; Schilling, C. J.; Schwitters, R. F.; Drummond, B. W.; Izen, J. M.; Lou, X. C.; Ye, S.; Bianchi, F.; Gamba, D.; Pelliccioni, M.; Bomben, M.; Bosisio, L.; Cartaro, C.; Della Ricca, G.; Lanceri, L.; Vitale, L.; Azzolini, V.; Lopez-March, N.; Martinez-Vidal, F.; Milanes, D. A.; Oyanguren, A.; Albert, J.; Banerjee, Sw.; Bhuyan, B.; Choi, H. H. F.; Hamano, K.; Kowalewski, R.; Lewczuk, M. J.; Nugent, I. M.; Roney, J. M.; Sobie, R. J.; Gershon, T. J.; Harrison, P. F.; Ilic, J.; Latham, T. E.; Mohanty, G. B.; Band, H. R.; Chen, X.; Dasu, S.; Flood, K. T.; Pan, Y.; Pierini, M.; Prepost, R.; Vuosalo, C. O.; Wu, S. L.

    2008-07-01

    Using 230×106 B Bmacr events recorded with the BABAR detector at the e+e- storage rings PEP-II, we reconstruct approximately 4100 B0→J/ψK+π- and 9930 B+→J/ψK+ decays with J/ψ→μ+μ- and e+e-. From the measured B-momentum distributions in the e+e- rest frame, we determine the mass difference m(B0)-m(B+)=(+0.33±0.05±0.03)MeV/c2.

  20. Measurement of the Mass Difference m(B0) - m(B+)

    SciTech Connect

    Aubert, B.

    2008-05-19

    Using 230 million B{bar B} events recorded with the BABAR detector at the e{sup +}e{sup -} storage rings PEP-II, they reconstruct approximately 4100 B{sup 0} {yields} J/{psi} K{sup +}{pi}{sup -} and 9930 B{sup +} {yields} J/{psi}K{sup +} decays with J/{psi} {yields} {mu}{sup +}{mu}{sup -} and e{sup +} e{sup -}. From the measured B-momentum distributions in the e{sup +}e{sup -} rest frame, they determine the mass difference m(B{sup 0}) - m(B{sup +}) = (+0.33 {+-} 0.05 {+-} 0.03) MeV/c{sup 2}.

  1. Career Services and the M.B.A. Student.

    ERIC Educational Resources Information Center

    Brooks, Jennifer E.

    2001-01-01

    Aims to dispel misconceptions regarding M.B.A. candidates by focusing on the requirements of M.B.A. students, and clarifying the role of career services in working with this population. Includes advice from a M.B.A. career counselor on the specific professional and personal skills needed for success. (GCP)

  2. The M.B.A.: A Schizophrenic Graduate Program?

    ERIC Educational Resources Information Center

    Rinehart, Shelley M.

    2007-01-01

    The term "M.B.A." is globally recognized as referring to a Masters of Business Administration Program, a degree historically perceived as a graduate's ticket to employment opportunities, generous salaries and the business savvy that garners respect across industries. Recently, however, the value of an M.B.A. has come under fire from many…

  3. Developing Content for an M.B.A. Communications Class.

    ERIC Educational Resources Information Center

    Shelby, Annette N.

    1983-01-01

    Outlines an M.B.A. communications course which includes source materials and content development frameworks for four different topic areas: (1) company, industry, and organization data; (2) management theory and organizational design; (3) crisis communication; and (4) issues management. (RAE)

  4. Asymmetric Ashes

    NASA Astrophysics Data System (ADS)

    2006-11-01

    that oscillate in certain directions. Reflection or scattering of light favours certain orientations of the electric and magnetic fields over others. This is why polarising sunglasses can filter out the glint of sunlight reflected off a pond. When light scatters through the expanding debris of a supernova, it retains information about the orientation of the scattering layers. If the supernova is spherically symmetric, all orientations will be present equally and will average out, so there will be no net polarisation. If, however, the gas shell is not round, a slight net polarisation will be imprinted on the light. This is what broad-band polarimetry can accomplish. If additional spectral information is available ('spectro-polarimetry'), one can determine whether the asymmetry is in the continuum light or in some spectral lines. In the case of the Type Ia supernovae, the astronomers found that the continuum polarisation is very small so that the overall shape of the explosion is crudely spherical. But the much larger polarization in strongly blue-shifted spectral lines evidences the presence, in the outer regions, of fast moving clumps with peculiar chemical composition. "Our study reveals that explosions of Type Ia supernovae are really three-dimensional phenomena," says Dietrich Baade. "The outer regions of the blast cloud is asymmetric, with different materials found in 'clumps', while the inner regions are smooth." "This study was possible because polarimetry could unfold its full strength thanks to the light-collecting power of the Very Large Telescope and the very precise calibration of the FORS instrument," he adds. The research team first spotted this asymmetry in 2003, as part of the same observational campaign (ESO PR 23/03 and ESO PR Photo 26/05). The new, more extensive results show that the degree of polarisation and, hence, the asphericity, correlates with the intrinsic brightness of the explosion. The brighter the supernova, the smoother, or less clumpy

  5. Asymmetric dark matter

    SciTech Connect

    Kumar, Jason

    2014-06-24

    We review the theoretical framework underlying models of asymmetric dark matter, describe astrophysical constraints which arise from observations of neutron stars, and discuss the prospects for detecting asymmetric dark matter.

  6. Transport properties of asymmetric-top molecules.

    PubMed

    Dickinson, A S; Hellmann, R; Bich, E; Vogel, E

    2007-06-14

    Kinetic theory of gases is extended from linear molecules to asymmetric tops. The integration over the velocity of the centre of mass is carried out explicitly and the results are expressed in a form suitable for classical evaluation. These results can also be employed for spherical and symmetric tops. PMID:17538728

  7. m b( Pn) Scale for the Korean Peninsula and Site-Dependent Pn Amplification

    NASA Astrophysics Data System (ADS)

    Hong, Tae-Kyung; Lee, Kiwook

    2012-11-01

    The Korean Peninsula is located in the far-eastern Eurasian plate margin where crustal structures vary laterally, causing significant raypath-dependent modulations of crustal phases. The discriminative variations of crustal phases hinder application of conventional local magnitude scales in the continental margin. The mantle-lid phase is less affected by the crustal structures than the crustal phases, providing a better constraint to magnitude estimation. A regional body-wave magnitude scale based on the mantle-lid P wave ( Pn), m b( Pn), is developed for regional events around the Korean Peninsula. The m b( Pn) scale is determined to be m b( Pn) = 0.380 (±0.299) + log A + 2.012 (±0.122) log d, where A is the peak-to-peak Pn amplitude in μm and d is the epicentral distance in km. The m b( Pn) estimates of regional events around the Korean Peninsula are determined. The m b( Pn) estimates are compared with other available magnitude estimates ( m b( Lg), M L). The influence of structures beneath stations on Pn amplification is investigated from inter-station magnitude residuals. A characteristic spatial variation of inter-station magnitude residuals with strengths mostly between -6 and 6 %, but with maximum strengths of ±10 %, is observed. The inter-station magnitude residuals appears to be correlated well with geological and seismic structures in the crust.

  8. Twin Higgs Asymmetric Dark Matter.

    PubMed

    García García, Isabel; Lasenby, Robert; March-Russell, John

    2015-09-18

    We study asymmetric dark matter (ADM) in the context of the minimal (fraternal) twin Higgs solution to the little hierarchy problem, with a twin sector with gauged SU(3)^{'}×SU(2)^{'}, a twin Higgs doublet, and only third-generation twin fermions. Naturalness requires the QCD^{'} scale Λ_{QCD}^{'}≃0.5-20  GeV, and that t^{'} is heavy. We focus on the light b^{'} quark regime, m_{b^{'}}≲Λ_{QCD}^{'}, where QCD^{'} is characterized by a single scale Λ_{QCD}^{'} with no light pions. A twin baryon number asymmetry leads to a successful dark matter (DM) candidate: the spin-3/2 twin baryon, Δ^{'}∼b^{'}b^{'}b^{'}, with a dynamically determined mass (∼5Λ_{QCD}^{'}) in the preferred range for the DM-to-baryon ratio Ω_{DM}/Ω_{baryon}≃5. Gauging the U(1)^{'} group leads to twin atoms (Δ^{'}-τ^{'}[over ¯] bound states) that are successful ADM candidates in significant regions of parameter space, sometimes with observable changes to DM halo properties. Direct detection signatures satisfy current bounds, at times modified by dark form factors. PMID:26430985

  9. Sources of Error and the Statistical Formulation of M S: m b Seismic Event Screening Analysis

    NASA Astrophysics Data System (ADS)

    Anderson, D. N.; Patton, H. J.; Taylor, S. R.; Bonner, J. L.; Selby, N. D.

    2014-03-01

    The Comprehensive Nuclear-Test-Ban Treaty (CTBT), a global ban on nuclear explosions, is currently in a ratification phase. Under the CTBT, an International Monitoring System (IMS) of seismic, hydroacoustic, infrasonic and radionuclide sensors is operational, and the data from the IMS is analysed by the International Data Centre (IDC). The IDC provides CTBT signatories basic seismic event parameters and a screening analysis indicating whether an event exhibits explosion characteristics (for example, shallow depth). An important component of the screening analysis is a statistical test of the null hypothesis H 0: explosion characteristics using empirical measurements of seismic energy (magnitudes). The established magnitude used for event size is the body-wave magnitude (denoted m b) computed from the initial segment of a seismic waveform. IDC screening analysis is applied to events with m b greater than 3.5. The Rayleigh wave magnitude (denoted M S) is a measure of later arriving surface wave energy. Magnitudes are measurements of seismic energy that include adjustments (physical correction model) for path and distance effects between event and station. Relative to m b, earthquakes generally have a larger M S magnitude than explosions. This article proposes a hypothesis test (screening analysis) using M S and m b that expressly accounts for physical correction model inadequacy in the standard error of the test statistic. With this hypothesis test formulation, the 2009 Democratic Peoples Republic of Korea announced nuclear weapon test fails to reject the null hypothesis H 0: explosion characteristics.

  10. Asymmetrical field emitter

    DOEpatents

    Fleming, J.G.; Smith, B.K.

    1995-10-10

    A method is disclosed for providing a field emitter with an asymmetrical emitter structure having a very sharp tip in close proximity to its gate. One preferred embodiment of the present invention includes an asymmetrical emitter and a gate. The emitter having a tip and a side is coupled to a substrate. The gate is connected to a step in the substrate. The step has a top surface and a side wall that is substantially parallel to the side of the emitter. The tip of the emitter is in close proximity to the gate. The emitter is at an emitter potential, and the gate is at a gate potential such that with the two potentials at appropriate values, electrons are emitted from the emitter. In one embodiment, the gate is separated from the emitter by an oxide layer, and the emitter is etched anisotropically to form its tip and its asymmetrical structure. 17 figs.

  11. Asymmetric ion trap

    DOEpatents

    Barlow, Stephan E.; Alexander, Michael L.; Follansbee, James C.

    1997-01-01

    An ion trap having two end cap electrodes disposed asymmetrically about a center of a ring electrode. The inner surface of the end cap electrodes are conformed to an asymmetric pair of equipotential lines of the harmonic formed by the application of voltages to the electrodes. The asymmetry of the end cap electrodes allows ejection of charged species through the closer of the two electrodes which in turn allows for simultaneously detecting anions and cations expelled from the ion trap through the use of two detectors charged with opposite polarity.

  12. Asymmetric reactions in continuous flow

    PubMed Central

    Mak, Xiao Yin; Laurino, Paola

    2009-01-01

    Summary An overview of asymmetric synthesis in continuous flow and microreactors is presented in this review. Applications of homogeneous and heterogeneous asymmetric catalysis as well as biocatalysis in flow are discussed. PMID:19478913

  13. ON ASYMMETRIC DISTRIBUTIONS OF SATELLITE GALAXIES

    SciTech Connect

    Bowden, A.; Evans, N. W.; Belokurov, V.

    2014-10-01

    We demonstrate that the asymmetric distribution of M31 satellites cannot be produced by tides from the Milky Way as such effects are too weak. However, loosely bound associations and groups of satellites can fall into larger halos and give rise to asymmetries. We compute the survival times for such associations. We prove that the survival time is always shortest in Keplerian potentials, and can be ∼3 times longer in logarithmic potentials. We provide an analytical formula for the dispersal time in terms of the size and velocity dispersion of the infalling structure. We show that, if an association of ∼10 dwarfs fell into the M31 halo, its present aspect would be that of an asymmetric disk of satellites. We also discuss the case of cold substructure in the Andromeda II and Ursa Minor dwarfs.

  14. Asymmetric hydrogenations (Nobel lecture).

    PubMed

    Knowles, William S

    2002-06-17

    The start of the development of catalysts for asymmetric hydrogenation was the concept of replacing the triphenylphosphane ligand of the Wilkinson catalyst with a chiral ligand. With the new catalysts, it should be possible to hydrogenate prochiral olefins. Knowles and his co-workers were convinced that the phosphorus atom played a central role in this selectivity, as only chiral phosphorus ligands such as (R,R)-DIPAMP, whose stereogenic center lies directly on the phosphorus atom, lead to high enantiomeric excesses when used as catalysts in asymmetric hydrogenation reactions. This hypothesis was disproven by the development of ligands with chiral carbon backbones. Although the exact mechanism of action of the phosphane ligands is not incontrovertibly determined to this day, they provide a simple entry to a large number of chiral compounds. PMID:19746594

  15. Multipartite asymmetric quantum cloning

    SciTech Connect

    Iblisdir, S.; Gisin, N.; Acin, A.; Cerf, N.J.; Filip, R.; Fiurasek, J.

    2005-10-15

    We investigate the optimal distribution of quantum information over multipartite systems in asymmetric settings. We introduce cloning transformations that take N identical replicas of a pure state in any dimension as input and yield a collection of clones with nonidentical fidelities. As an example, if the clones are partitioned into a set of M{sub A} clones with fidelity F{sup A} and another set of M{sub B} clones with fidelity F{sup B}, the trade-off between these fidelities is analyzed, and particular cases of optimal N{yields}M{sub A}+M{sub B} cloning machines are exhibited. We also present an optimal 1{yields}1+1+1 cloning machine, which is an example of a tripartite fully asymmetric cloner. Finally, it is shown how these cloning machines can be optically realized.

  16. Asymmetric information and economics

    NASA Astrophysics Data System (ADS)

    Frieden, B. Roy; Hawkins, Raymond J.

    2010-01-01

    We present an expression of the economic concept of asymmetric information with which it is possible to derive the dynamical laws of an economy. To illustrate the utility of this approach we show how the assumption of optimal information flow leads to a general class of investment strategies including the well-known Q theory of Tobin. Novel consequences of this formalism include a natural definition of market efficiency and an uncertainty principle relating capital stock and investment flow.

  17. Asymmetric dipolar ring

    DOEpatents

    Prosandeev, Sergey A.; Ponomareva, Inna V.; Kornev, Igor A.; Bellaiche, Laurent M.

    2010-11-16

    A device having a dipolar ring surrounding an interior region that is disposed asymmetrically on the ring. The dipolar ring generates a toroidal moment switchable between at least two stable states by a homogeneous field applied to the dipolar ring in the plane of the ring. The ring may be made of ferroelectric or magnetic material. In the former case, the homogeneous field is an electric field and in the latter case, the homogeneous field is a magnetic field.

  18. Oscillating asymmetric dark matter

    SciTech Connect

    Tulin, Sean; Yu, Hai-Bo; Zurek, Kathryn M. E-mail: haiboyu@umich.edu

    2012-05-01

    We study the dynamics of dark matter (DM) particle-antiparticle oscillations within the context of asymmetric DM. Oscillations arise due to small DM number-violating Majorana-type mass terms, and can lead to recoupling of annihilation after freeze-out and washout of the DM density. Asymmetric DM oscillations 'interpolate' between symmetric and asymmetric DM freeze-out scenarios, and allow for a larger DM model-building parameter space. We derive the density matrix equations for DM oscillations and freeze-out from first principles using nonequilibrium field theory, and our results are qualitatively different than in previous studies. DM dynamics exhibits particle-vs-antiparticle 'flavor' effects, depending on the interaction type, analogous to neutrino oscillations in a medium. 'Flavor-sensitive' DM interactions include scattering or annihilation through a new vector boson, while 'flavor-blind' interactions include scattering or s-channel annihilation through a new scalar boson. In particular, we find that flavor-sensitive annihilation does not recouple when coherent oscillations begin, and that flavor-blind scattering does not lead to decoherence.

  19. Asymmetric Evolutionary Games

    PubMed Central

    McAvoy, Alex; Hauert, Christoph

    2015-01-01

    Evolutionary game theory is a powerful framework for studying evolution in populations of interacting individuals. A common assumption in evolutionary game theory is that interactions are symmetric, which means that the players are distinguished by only their strategies. In nature, however, the microscopic interactions between players are nearly always asymmetric due to environmental effects, differing baseline characteristics, and other possible sources of heterogeneity. To model these phenomena, we introduce into evolutionary game theory two broad classes of asymmetric interactions: ecological and genotypic. Ecological asymmetry results from variation in the environments of the players, while genotypic asymmetry is a consequence of the players having differing baseline genotypes. We develop a theory of these forms of asymmetry for games in structured populations and use the classical social dilemmas, the Prisoner’s Dilemma and the Snowdrift Game, for illustrations. Interestingly, asymmetric games reveal essential differences between models of genetic evolution based on reproduction and models of cultural evolution based on imitation that are not apparent in symmetric games. PMID:26308326

  20. Asymmetrically driven implosions

    SciTech Connect

    Vaughan, K.; McAlpin, S.; Foster, J. M.; Stevenson, R. M.; Glendinning, S. G.; Sorce, C.

    2010-05-15

    Techniques to achieve uniform near-spherical symmetry of radiation drive on a capsule in a laser-heated hohlraum have received detailed attention in the context of inertial confinement fusion. However, much less attention has been paid to the understanding of the hohlraum physics in cases where the radiation drive departs significantly from spherical symmetry. A series of experiments has been carried out to study the implosion dynamics of a capsule irradiated by a deliberately asymmetric x-ray drive. The experimental data provide a sensitive test of radiation transport in hohlraums in which drive symmetry is modulated by asymmetric laser beam timing and the use of wall materials of different albedos. Data from foam ball and thin-shell capsule experiments are presented together with modeling using consecutively linked Lagrangian and Eulerian calculational schemes. The thin-shell capsules exhibit much stronger sensitivity to early-time asymmetry than do the foam balls, and this sensitivity results in the formation of a well-defined polar jet. These data are shown to challenge computational modeling in this highly asymmetric convergent regime. All of the experiments detailed were carried out at the OMEGA laser facility [J. M. Soures, R. L. McCrory, C. P. Verdon et al., Phys. Plasmas 3, 2108 (1996)] at the Laboratory for Laser Energetics in Rochester, NY.

  1. Asymmetrical Capacitors for Propulsion

    NASA Technical Reports Server (NTRS)

    Canning, Francis X.; Melcher, Cory; Winet, Edwin

    2004-01-01

    Asymmetrical Capacitor Thrusters have been proposed as a source of propulsion. For over eighty years, it has been known that a thrust results when a high voltage is placed across an asymmetrical capacitor, when that voltage causes a leakage current to flow. However, there is surprisingly little experimental or theoretical data explaining this effect. This paper reports on the results of tests of several Asymmetrical Capacitor Thrusters (ACTs). The thrust they produce has been measured for various voltages, polarities, and ground configurations and their radiation in the VHF range has been recorded. These tests were performed at atmospheric pressure and at various reduced pressures. A simple model for the thrust was developed. The model assumed the thrust was due to electrostatic forces on the leakage current flowing across the capacitor. It was further assumed that this current involves charged ions which undergo multiple collisions with air. These collisions transfer momentum. All of the measured data was consistent with this model. Many configurations were tested, and the results suggest general design principles for ACTs to be used for a variety of purposes.

  2. Asymmetrically driven implosionsa)

    NASA Astrophysics Data System (ADS)

    Vaughan, K.; McAlpin, S.; Foster, J. M.; Stevenson, R. M.; Glendinning, S. G.; Sorce, C.

    2010-05-01

    Techniques to achieve uniform near-spherical symmetry of radiation drive on a capsule in a laser-heated hohlraum have received detailed attention in the context of inertial confinement fusion. However, much less attention has been paid to the understanding of the hohlraum physics in cases where the radiation drive departs significantly from spherical symmetry. A series of experiments has been carried out to study the implosion dynamics of a capsule irradiated by a deliberately asymmetric x-ray drive. The experimental data provide a sensitive test of radiation transport in hohlraums in which drive symmetry is modulated by asymmetric laser beam timing and the use of wall materials of different albedos. Data from foam ball and thin-shell capsule experiments are presented together with modeling using consecutively linked Lagrangian and Eulerian calculational schemes. The thin-shell capsules exhibit much stronger sensitivity to early-time asymmetry than do the foam balls, and this sensitivity results in the formation of a well-defined polar jet. These data are shown to challenge computational modeling in this highly asymmetric convergent regime. All of the experiments detailed were carried out at the OMEGA laser facility [J. M. Soures, R. L. McCrory, C. P. Verdon et al., Phys. Plasmas 3, 2108 (1996)] at the Laboratory for Laser Energetics in Rochester, NY.

  3. Asymmetric Kinks: Stabilization by Entropic Forces

    SciTech Connect

    Costantini, G.; Marchesoni, F.

    2001-09-10

    Asymmetric kinks bridging two adjacent potential valleys of equal depth but different curvature are unstable against phonon modes. When coupled to a heat bath, a kink-bearing string tends to cross over into the shallower valley; kinks are thus predicted to drift in the appropriate direction with velocity proportional to the temperature, in close agreement with numerical simulation. When contrasted by a mechanical bias, these entropic forces give rise to a rich phenomenology that includes configurational phase transitions, double-kink dissociation, and noise-directed signal transmission.

  4. External combustion engine having an asymmetrical CAM

    NASA Astrophysics Data System (ADS)

    Duva, Anthony W.

    1994-11-01

    An external combustion engine having an asymmetrical cam is the focus of this patent. The engine includes a combustion chamber for generating a high-pressure, energized gas from a monopropellant fuel and an even number of cylinders for receiving sequentially the energized gas through the rotary valve, the gas performing work on a piston disposed within each cylinder. The pistons transfer energy to a drive shaft through a connection to the asymmetrically shaped cam. The cam is shaped having two identical halves, each half having a power and an exhaust stroke. The identical halves provide that opposing cylinders are in thermodynamic balance, thus reducing rocking vibrations and torque pulsations. Having opposing pistons within the same thermodynamic cycle allows piston stroke to be reduced while maintaining displacement comparable to an engine having individual cycle positions. The reduced stroke diminishes gas flow velocity thus reducing flow induced noise. The power and exhaust strokes within each identical half of the cam are asymmetrical in that the power stroke is of greater duration than the exhaust stroke. The shape and length of the power stroke is optimized for increased efficiency.

  5. Asymmetric fluorocyclizations of alkenes.

    PubMed

    Wolstenhulme, Jamie R; Gouverneur, Véronique

    2014-12-16

    CONSPECTUS: The vicinal fluorofunctionalization of alkenes is an attractive transformation that converts feedstock olefins into valuable cyclic fluorinated molecules for application in the pharmaceutical, agrochemical, medical, and material sectors. The challenges associated with asymmetric fluorocyclizations induced by F(+) reagents are distinct from other types of halocyclizations. Processes initiated by the addition of an F(+) reagent onto an alkene do not involve the reversible formation of bridged fluoronium ions but generate acyclic β-fluorocationic intermediates. This mechanistic feature implies that fluorocyclizations are not stereospecific. A discontinuity exists between the importance of this class of fluorocyclization and the activation modes currently available to implement successful catalysis. Progress toward fluorocyclization has been achieved by investing in neutral and cationic [NF] reagent development. The body of work on asymmetric fluorination using chiral cationic [NF](+) reagents prepared by fluorine transfer from the dicationic [NF](2+) reagent Selectfluor to quinuclidines, inspired the development of asymmetric F(+)-induced fluorocyclizations catalyzed by cinchona alkaloids; for catalysis, the use of N-fluorobenzenesulfonimide, which is less reactive than Selectfluor, ensures that the achiral F(+) source remains unreactive toward the alkene. These organocatalyzed enantioselective fluorocyclizations can be applied to indoles to install the fluorine on a quaternary benzylic stereogenic carbon center and to afford fluorinated analogues of natural products featuring the hexahydropyrrolo[2,3-b]indole or the tetrahydro-2H-furo[2,3-b]indole skeleton. In an alternative approach, the poor solubility of dicationic Selectfluor bis(tetrafluoroborate) in nonpolar solvent was exploited with anionic phase transfer catalysis as the operating activation mode. Exchange of the tetrafluoroborate ions of Selectfluor with bulky lipophilic chiral anions (e

  6. Asymmetric quantum convolutional codes

    NASA Astrophysics Data System (ADS)

    La Guardia, Giuliano G.

    2016-01-01

    In this paper, we construct the first families of asymmetric quantum convolutional codes (AQCCs). These new AQCCs are constructed by means of the CSS-type construction applied to suitable families of classical convolutional codes, which are also constructed here. The new codes have non-catastrophic generator matrices, and they have great asymmetry. Since our constructions are performed algebraically, i.e. we develop general algebraic methods and properties to perform the constructions, it is possible to derive several families of such codes and not only codes with specific parameters. Additionally, several different types of such codes are obtained.

  7. The Asymmetric Piers Hydrosilylation.

    PubMed

    Süsse, Lars; Hermeke, Julia; Oestreich, Martin

    2016-06-01

    An axially chiral, cyclic borane decorated with just one C6F5 group at the boron atom promotes the highly enantioselective hydrosilylation of acetophenone derivatives without assistance of an additional Lewis base (up to 99% ee). The reaction is an unprecedented asymmetric variant of Piers' B(C6F5)3-catalyzed carbonyl hydrosilylation. The steric congestion imparted by the 3,3'-disubstituted binaphthyl backbone of the borane catalyst as well as the use of reactive trihydrosilanes as reducing agents are keys to success. PMID:27212565

  8. Asymmetric tensor analysis for flow visualization.

    PubMed

    Zhang, Eugene; Yeh, Harry; Lin, Zhongzang; Laramee, Robert S

    2009-01-01

    The gradient of a velocity vector field is an asymmetric tensor field which can provide critical insight that is difficult to infer from traditional trajectory-based vector field visualization techniques. We describe the structures in the eigenvalue and eigenvector fields of the gradient tensor and how these structures can be used to infer the behaviors of the velocity field. To illustrate the structures in asymmetric tensor fields, we introduce the notions of eigenvalue and eigenvector manifolds. These concepts afford a number of theoretical results that clarify the connections between symmetric and antisymmetric components in tensor fields. In addition, these manifolds naturally lead to partitions of tensor fields, which we use to design effective visualization strategies. Both eigenvalue manifold and eigenvector manifold are supported by a tensor reparameterization with physical meaning. This allows us to relate our tensor analysis to physical quantities such as rotation, angular deformation, and dilation, which provide physical interpretation of our tensor-driven vector field analysis in the context of fluid mechanics. To demonstrate the utility of our approach, we have applied our visualization techniques and interpretation to the study of the Sullivan Vortex as well as computational fluid dynamics simulation data. PMID:19008559

  9. Irradiated asymmetric Friedmann branes

    NASA Astrophysics Data System (ADS)

    Gergely, László Á.; Keresztes, Zoltán

    2006-01-01

    We consider a Friedmann brane moving in a bulk impregnated with radiation. The set-up is strongly asymmetric, with only one black hole in the bulk. The radiation emitted by this left bulk black hole can be reflected, absorbed or transmitted through the brane. Radiation pressure accelerates the brane, behaving as dark energy. Absorption however generates a competing effect: the brane becomes heavier and gravitational attraction increases. We analyse the model numerically, assuming a total absorption on the brane for k = 1. We conclude that due to the two competing effects, in this asymmetric scenario the Hawking radiation from the bulk black hole is not able to change the recollapsing fate of this brane-world universe. We show that for light branes and early times the radiation pressure is the dominant effect. In contrast, for heavy branes the self-gravity of the absorbed radiation is a much stronger effect. We find the critical value of the initial energy density for which these two effects roughly cancel each other.

  10. Asymmetric inclusion process

    NASA Astrophysics Data System (ADS)

    Reuveni, Shlomi; Eliazar, Iddo; Yechiali, Uri

    2011-10-01

    We introduce and explore the asymmetric inclusion process (ASIP), an exactly solvable bosonic counterpart of the fermionic asymmetric exclusion process (ASEP). In both processes, random events cause particles to propagate unidirectionally along a one-dimensional lattice of n sites. In the ASEP, particles are subject to exclusion interactions, whereas in the ASIP, particles are subject to inclusion interactions that coalesce them into inseparable clusters. We study the dynamics of the ASIP, derive evolution equations for the mean and probability generating function (PGF) of the sites’ occupancy vector, obtain explicit results for the above mean at steady state, and describe an iterative scheme for the computation of the PGF at steady state. We further obtain explicit results for the load distribution in steady state, with the load being the total number of particles present in all lattice sites. Finally, we address the problem of load optimization, and solve it under various criteria. The ASIP model establishes bridges between statistical physics and queueing theory as it represents a tandem array of queueing systems with (unlimited) batch service, and a tandem array of growth-collapse processes.

  11. Models for asymmetric hybrid brane

    NASA Astrophysics Data System (ADS)

    Bazeia, D.; Marques, M. A.; Menezes, R.

    2015-10-01

    We deal with relativistic models described by a single real scalar field, searching for topological structures that behave asymmetrically, connecting minima with a distinct profile. We use such features to build a new braneworld scenario, in which the source scalar field contributes to generate asymmetric hybrid brane.

  12. Preparation of asymmetric porous materials

    DOEpatents

    Coker, Eric N.

    2012-08-07

    A method for preparing an asymmetric porous material by depositing a porous material film on a flexible substrate, and applying an anisotropic stress to the porous media on the flexible substrate, where the anisotropic stress results from a stress such as an applied mechanical force, a thermal gradient, and an applied voltage, to form an asymmetric porous material.

  13. Asymmetric twin Dark Matter

    SciTech Connect

    Farina, Marco

    2015-11-09

    We study a natural implementation of Asymmetric Dark Matter in Twin Higgs models. The mirroring of the Standard Model strong sector suggests that a twin baryon with mass around 5 GeV is a natural Dark Matter candidate once a twin baryon number asymmetry comparable to the SM asymmetry is generated. We explore twin baryon Dark Matter in two different scenarios, one with minimal content in the twin sector and one with a complete copy of the SM, including a light twin photon. The essential requirements for successful thermal history are presented, and in doing so we address some of the cosmological issues common to many Twin Higgs models. The required interactions we introduce predict signatures at direct detection experiments and at the LHC.

  14. Asymmetrically warped spacetimes

    SciTech Connect

    Csaki, C.

    2001-01-01

    We investigate spacetimes in which the speed of light along flat 4D sections varies over the extra dimensions due to different warp factors for the space and the time coordinates ('asymmetrically warped' spacetimes). The main property of such spaces is that while the induced metric is flat, implying Lorentz invariant particle physics on a brane, bulk gravitational effects will cause apparent violations of Lorentz invariance and of causality from the brane observer's point of view. An important experimentally verifiable consequence of this is that gravitational waves may travel with a speed different from the speed of light on the brane, and possibly even faster. We find the most general spacetimes of this sort, which are given by certain types of black hole spacetimes characterized by the m a s and the charge of the black hole. We show how to satisfy the junction conditions and analyze the properties of these space-times.

  15. Engineered Asymmetric Synthetic Vesicles

    NASA Astrophysics Data System (ADS)

    Lu, Li; Chiarot, Paul

    2013-11-01

    Synthetic vesicles are small, fluid-filled spheres that are enclosed by a bilayer of lipid molecules. They can be used as models for investigating membrane biology and as delivery vehicles for pharmaceuticals. In practice, it is difficult to simultaneously control membrane asymmetry, unilamellarity, vesicle size, vesicle-to-vesicle uniformity, and luminal content. Membrane asymmetry, where each leaflet of the bilayer is composed of different lipids, is of particular importance as it is a feature of most natural membranes. In this study, we leverage microfluidic technology to build asymmetric vesicles at high-throughput. We use the precise flow control offered by microfluidic devices to make highly uniform emulsions, with controlled internal content, that serve as templates to build the synthetic vesicles. Flow focusing, dielectrophoretic steering, and interfacial lipid self-assembly are critical procedures performed on-chip to produce the vesicles. Fluorescent and confocal microscopy are used to evaluate the vesicle characteristics.

  16. Age‐related aspects of human IgM+ B cell heterogeneity

    PubMed Central

    Martin, Victoria; Wu, Yu‐Chang; Kipling, David

    2015-01-01

    The CD27+IgD+ B cell population, known as IgM memory, reduces with age. It is thought that this population is responsible for pneumococcal polysaccharide T‐independent responses, and that the age‐related reduction might be partially responsible for the increased susceptibility of older people to bacterial pathogens. There are other IgM+ B cell populations that do not express IgD. We compared the different IgM populations using high‐throughput sequencing of the immunoglobulin (Ig) gene repertoire and multidimensional cell phenotyping and found that the different populations of IgM cells, defined by CD27 and IgD expression, have repertoire differences. Some of these differences are likely indicative of different selection pressures in an immune response, although the older individuals were found to have a changed repertoire in naive B cells, which may contribute to some of the changes seen in memory cells. In addition, even within the CD27+IgD+ IgM memory population there are multiple cell types. We show that the level of IgM expression varies substantially and hypothesize that this distinguishes between T‐dependent and T‐independent types of IgM memory cells. Significant age‐related changes in the relative proportions of these populations may exacerbate the reduction in T‐independent responders in old age. PMID:26152370

  17. Metal rolling - Asymmetrical rolling process

    NASA Astrophysics Data System (ADS)

    Alexa, V.; Raţiu, S.; Kiss, I.

    2016-02-01

    The development of theory and practice related to the asymmetric longitudinal rolling process is based on the general theory of metalworking by pressure and symmetric rolling theory, to which a large number of scientists brought their contribution. The rolling of metal materials was a serious problem throughout history, either economically or technically, because the plating technologies enabled the consumption of raw materials (scarce and expensive) to be reduced, while improving the mechanical properties. Knowing the force parameters related to asymmetric rolling leads to the optimization of energy and raw material consumption. This paper presents data on symmetric rolling process, in order to comparatively highlight the particularities of the asymmetric process.

  18. Asymmetric distribution of aftershocks on large faults in California

    NASA Astrophysics Data System (ADS)

    Zaliapin, Ilya; Ben-Zion, Yehuda

    2011-06-01

    We examine the relations between spatial symmetry properties of earthquake patterns along faults in California (CA) and local velocity structure images to test the hypothesis that ruptures on bimaterial faults have statistically preferred propagation directions. The analysis employs seismic catalogues for 25 fault zones in CA. We distinguish between clustered and homogeneous parts of each catalogue, using a recently introduced earthquake cluster analysis, and examine asymmetry of offspring with respect to parent events within the clustered portion of each catalogue. The results indicate strong asymmetric patterns along large faults with prominent bimaterial interfaces (e.g. sections of the San Andreas Fault), with enhanced activities in the directions predicted for the local velocity contrasts, and absence of significant asymmetry along most other faults. Assuming the observed asymmetric properties of seismicity reflect the properties of the parent earthquake ruptures, the discussed methodology and results can be used to develop refined estimates of seismic shaking hazard associated with individual fault zones.

  19. Asymmetric bifurcated halogen bonds.

    PubMed

    Novák, Martin; Foroutan-Nejad, Cina; Marek, Radek

    2015-03-01

    Halogen bonding (XB) is being extensively explored for its potential use in advanced materials and drug design. Despite significant progress in describing this interaction by theoretical and experimental methods, the chemical nature remains somewhat elusive, and it seems to vary with the selected system. In this work we present a detailed DFT analysis of three-center asymmetric halogen bond (XB) formed between dihalogen molecules and variously 4-substituted 1,2-dimethoxybenzene. The energy decomposition, orbital, and electron density analyses suggest that the contribution of electrostatic stabilization is comparable with that of non-electrostatic factors. Both terms increase parallel with increasing negative charge of the electron donor molecule in our model systems. Depending on the orientation of the dihalogen molecules, this bifurcated interaction may be classified as 'σ-hole - lone pair' or 'σ-hole - π' halogen bonds. Arrangement of the XB investigated here deviates significantly from a recent IUPAC definition of XB and, in analogy to the hydrogen bonding, the term bifurcated halogen bond (BXB) seems to be appropriate for this type of interaction. PMID:25656525

  20. Asymmetric Ion-Pairing Catalysis

    PubMed Central

    Brak, Katrien

    2014-01-01

    Charged intermediates and reagents are ubiquitous in organic transformations. The interaction of these ionic species with chiral neutral, anionic, or cationic small molecules has emerged as a powerful strategy for catalytic, enantioselective synthesis. This review describes developments in the burgeoning field of asymmetric ion-pairing catalysis with an emphasis on the insights that have been gleaned into the structural and mechanistic features that contribute to high asymmetric induction. PMID:23192886

  1. Asymmetric morphology of the propagating jet

    NASA Astrophysics Data System (ADS)

    Hardee, Philip E.; Norman, Michael L.

    1990-12-01

    Simulations of slab jets propagating in constant atmospheres are reported for a range of jet velocities and Mach numbers. At early times, the jet maintains approximate axisymmetry within a backflowing cocoon. When the jet has penetrated farther into the external medium, the symmetry is broken by sideways oscillation and the leading edge of the jet moves about within a growing lobe. The oscillation results from nonlinear resonant amplification of the initial perturbation by the Kelvin-Helmholtz instability. Finally, the jet flaps chaotically within the growing lobe. The flapping is driven by turbulent vortices in the lobe. The basic picture of Scheuer's (1982) 'dentist's drill' model of the physical processes underlying asymmetric morphologies in radio galaxies is confirmed. The fluid motions in the lobe are found to govern the location of the drill bit. The morphology is time-dependent on relatively short time scales.

  2. Microstructure and texture of asymmetrically rolled aluminium and titanium after deformation and recrystallization

    NASA Astrophysics Data System (ADS)

    Wronski, M.; Wierzbanowski, K.; Wronski, S.; Bacroix, B.

    2015-08-01

    Asymmetric rolling is used to modify material properties and to reduce forces and torques applied during deformation. This geometry of deformation is relatively easy to implement on existing industrial rolling mills and it can provide large volumes of a material. The results of the study of microstructure and crystallographic texture in asymmetrically rolled aluminium 6061 and titanium (grade 2) are presented in this work. These characteristics were determined using the EBSD technique and X-ray diffraction. The rolling asymmetry was realized using two identical rolls, driven by independent motors, rotating with different angular velocities. It was found that asymmetric rolling leads to microstructural refinement and texture rotation (around the transverse direction). The impact of asymmetric rolling on microstructural refinement appears also in recrystallized samples of both materials. On the other hand, texture rotation, caused by asymmetric rolling, persists after annealing in titanium but not in aluminium samples.

  3. Water Permeability of Asymmetric Planar Lipid Bilayers

    PubMed Central

    Krylov, Andrey V.; Pohl, Peter; Zeidel, Mark L.; Hill, Warren G.

    2001-01-01

    To understand how plasma membranes may limit water flux, we have modeled the apical membrane of MDCK type 1 cells. Previous experiments demonstrated that liposomes designed to mimic the inner and outer leaflet of this membrane exhibited 18-fold lower water permeation for outer leaflet lipids than inner leaflet lipids (Hill, W.G., and M.L. Zeidel. 2000. J. Biol. Chem. 275:30176–30185), confirming that the outer leaflet is the primary barrier to permeation. If leaflets in a bilayer resist permeation independently, the following equation estimates single leaflet permeabilities: 1/PAB = 1/PA + 1/PB (Eq. l), where PAB is the permeability of a bilayer composed of leaflets A and B, PA is the permeability of leaflet A, and PB is the permeability of leaflet B. Using for the MDCK leaflet–specific liposomes gives an estimated value for the osmotic water permeability (Pf) of 4.6 × 10−4 cm/s (at 25°C) that correlated well with experimentally measured values in intact cells. We have now constructed both symmetric and asymmetric planar lipid bilayers that model the MDCK apical membrane. Water permeability across these bilayers was monitored in the immediate membrane vicinity using a Na+-sensitive scanning microelectrode and an osmotic gradient induced by addition of urea. The near-membrane concentration distribution of solute was used to calculate the velocity of water flow (Pohl, P., S.M. Saparov, and Y.N. Antonenko. 1997. Biophys. J. 72:1711–1718). At 36°C, Pf was 3.44 ± 0.35 × 10−3 cm/s for symmetrical inner leaflet membranes and 3.40 ± 0.34 × 10−4 cm/s for symmetrical exofacial membranes. From , the estimated permeability of an asymmetric membrane is 6.2 × 10−4 cm/s. Water permeability measured for the asymmetric planar bilayer was 6.7 ± 0.7 × 10−4 cm/s, which is within 10% of the calculated value. Direct experimental measurement of Pf for an asymmetric planar membrane confirms that leaflets in a bilayer offer independent and additive resistances to

  4. Disk Galaxy Stellar Velocity Ellipsoids

    NASA Astrophysics Data System (ADS)

    Westfall, Kyle B.; Bershady, M. A.; Verheijen, M. A. W.; Andersen, D. R.; Swaters, R. A.

    2007-12-01

    We have measured the disk stellar velocity ellipsoids in a subset of spiral galaxies observed for the Disk-Mass Survey, which provide information on disk stability and secular heating mechanisms. Our methodology invokes our 2D ionized gas and stellar kinematics and a suite of dynamical assumptions based on the Jeans' equations. When combined with orthogonal axes from our 2D data, either the epicycle approximation (EA) or asymmetric drift (AD) equation may close the necessary equation set, individually. We have isolated large observational and inherent systematic effects via EA-only, AD-only, and EA+AD ellipsoid decomposition methodologies. In an attempt to minimize these effects and generate robust ellipsoid measurements we explore constraints provided by higher order expansions of the Jeans' equations and direct orbital integrations. We compare our best ellipsoid axial ratio estimates to similar measurements made by, e.g., van der Kruit & de Grijs (1999, A&A, 352, 129) and Shapiro et al. (2003, AJ, 126, 2707). Finally, we discuss possibilities for the measurement of vertical velocity dispersions in low-surface-brightness galaxies by applying the characterization of the stellar velocity ellipsoid in late-type galaxies. This work is supported by the National Science Foundation (AST-0607516).

  5. Top Business Schools Seek To Ride a Bull Market in On-Line M.B.A.'s.

    ERIC Educational Resources Information Center

    Mangan, Katherine S.

    1999-01-01

    Internet-based master's programs in business administration (M.B.A.s) serve a market that could bring significant revenues to business schools, providing new access to mid- to upper-level managers who want degrees to advance their careers but who cannot take time from work, or to young executives whose bosses offer to pay for the degree but not…

  6. Asymmetric mass models of disk galaxies. I. Messier 99

    NASA Astrophysics Data System (ADS)

    Chemin, Laurent; Huré, Jean-Marc; Soubiran, Caroline; Zibetti, Stefano; Charlot, Stéphane; Kawata, Daisuke

    2016-04-01

    Mass models of galactic disks traditionally rely on axisymmetric density and rotation curves, paradoxically acting as if their most remarkable asymmetric features, such as lopsidedness or spiral arms, were not important. In this article, we relax the axisymmetry approximation and introduce a methodology that derives 3D gravitational potentials of disk-like objects and robustly estimates the impacts of asymmetries on circular velocities in the disk midplane. Mass distribution models can then be directly fitted to asymmetric line-of-sight velocity fields. Applied to the grand-design spiral M 99, the new strategy shows that circular velocities are highly nonuniform, particularly in the inner disk of the galaxy, as a natural response to the perturbed gravitational potential of luminous matter. A cuspy inner density profile of dark matter is found in M 99, in the usual case where luminous and dark matter share the same center. The impact of the velocity nonuniformity is to make the inner profile less steep, although the density remains cuspy. On another hand, a model where the halo is core dominated and shifted by 2.2-2.5 kpc from the luminous mass center is more appropriate to explain most of the kinematical lopsidedness evidenced in the velocity field of M 99. However, the gravitational potential of luminous baryons is not asymmetric enough to explain the kinematical lopsidedness of the innermost regions, irrespective of the density shape of dark matter. This discrepancy points out the necessity of an additional dynamical process in these regions: possibly a lopsided distribution of dark matter.

  7. SIO MASERS IN ASYMMETRIC MIRAS. I. R LEONIS

    SciTech Connect

    Cotton, W. D.; Ragland, S.; Pluzhnik, E.; Danchi, W. C.; Traub, W. A.; Lacasse, M. G.

    2009-10-10

    This is the first paper in a series of multi-epoch observations of the SiO masers at 7 mm wavelength in several asymptotic giant branch (AGB) stars. This is a sample of Mira variable stars showing evidence of asymmetric structure in the infrared which were observed interferometrically in the infrared by Infrared Optical Telescope Array and with Very Long Baseline Array measurements of the SiO masers. In this paper, we present the observations of R Leonis (R Leo). During the period of observations, this star shows extended emission with large-scale coherent patterns in the radial velocity, possibly the result of ejecting a substantial amount of material, largely to the west. This is interpreted as an event in which material is expelled in a collimated flow, possibly following an energetic event. If common, these events may help explain the asymmetric nature of the planetary nebulae that develop from AGB stars. The systemic velocity of R Leo is estimated to be +1.0 +-0.3 km s{sup -1}. All observed radial velocities are well below the escape velocity.

  8. Hydroxamic acids in asymmetric synthesis.

    PubMed

    Li, Zhi; Yamamoto, Hisashi

    2013-02-19

    Metal-catalyzed stereoselective reactions are a central theme in organic chemistry research. In these reactions, the stereoselection is achieved predominantly by introducing chiral ligands at the metal catalyst's center. For decades, researchers have sought better chiral ligands for asymmetric catalysis and have made great progress. Nevertheless, to achieve optimal stereoselectivity and to catalyze new reactions, new chiral ligands are needed. Because of their high metal affinity, hydroxamic acids play major roles across a broad spectrum of fields from biochemistry to metal extraction. Dr. K. Barry Sharpless first revealed their potential as chiral ligands for asymmetric synthesis in 1977: He published the chiral vanadium-hydroxamic-acid-catalyzed, enantioselective epoxidation of allylic alcohols before his discovery of Sharpless asymmetric epoxidation, which uses the titanium-tartrate complex as the chiral reagent. However, researchers have reported few highly enantioselective reactions using metal-hydroxamic acid as catalysts since then. This Account summarizes our research on metal-catalyzed asymmetric epoxidation using hydroxamic acids as chiral ligands. We designed and synthesized a series of new hydroxamic acids, most notably the C2-symmetric bis-hydroxamic acid (BHA) family. V-BHA-catalyzed epoxidation of allylic and homoallylic alcohols achieved higher activity and stereoselectivity than Sharpless asymmetric epoxidation in many cases. Changing the metal species led to a series of unprecedented asymmetric epoxidation reactions, such as (i) single olefins and sulfides with Mo-BHA, (ii) homoallylic and bishomoallylic alcohols with Zr- and Hf-BHA, and (iii) N-alkenyl sulfonamides and N-sulfonyl imines with Hf-BHA. These reactions produce uniquely functionalized chiral epoxides with good yields and enantioselectivities. PMID:23157425

  9. Hydroxamic Acids in Asymmetric Synthesis

    PubMed Central

    Li, Zhi; Yamamoto, Hisashi

    2012-01-01

    Metal-catalyzed stereoselective reactions are a central theme in organic chemistry research. In these reactions, the stereoselection is achieved predominantly by introducing chiral ligands at the metal catalyst’s center. For decades, researchers have sought better chiral ligands for asymmetric catalysis and have made great progress. Nevertheless, to achieve optimal stereoselectivity and to catalyze new reactions, new chiral ligands are needed. Due to their high metal affinity, hydroxamic acids play major roles across a broad spectrum of fields from biochemistry to metal extraction. Dr. K. Barry Sharpless first revealed their potential as chiral ligands for asymmetric synthesis in 1977: He published the chiral vanadium-hydroxamic-acid-catalyzed, enantioselective epoxidation of allylic alcohols before his discovery of Sharpless Asymmetric Epoxidation, which uses titanium-tartrate complex as the chiral reagent. However, researchers have reported few highly enantioselective reactions using metal-hydroxamic acid as catalysts since then. This Account summarizes our research on metal-catalyzed asymmetric epoxidation using hydroxamic acids as chiral ligands. We designed and synthesized a series of new hydroxamic acids, most notably the C2-symmetric bis-hydroxamic acid (BHA) family. V-BHA-catalyzed epoxidation of allylic and homoallylic alcohols achieved higher activity and stereoselectivity than Sharpless Asymmetric Epoxidation in many cases. Changing the metal species led to a series of unprecedented asymmetric epoxidation reactions, such as (i) single olefins and sulfides with Mo-BHA, (ii) homoallylic and bishomoallylic alcohols with Zr- and Hf-BHA, and (iii) N-alkenyl sulfonamides and N-sulfonyl imines with Hf-BHA. These reactions produce uniquely functionalized chiral epoxides with good yields and enantioselectivities. PMID:23157425

  10. Asymmetric counterpropagating fronts without flow.

    PubMed

    Andrade-Silva, I; Clerc, M G; Odent, V

    2015-06-01

    Out-of-equilibrium systems exhibit domain walls between different states. These walls, depending on the type of connected states, can display rich spatiotemporal dynamics. In this Rapid Communication, we investigate the asymmetrical counterpropagation of fronts in an in-plane-switching cell filled with a nematic liquid crystal. Experimentally, we characterize the different front shapes and propagation speeds. These fronts present dissimilar elastic deformations that are responsible for their asymmetric speeds. Theoretically, using a phenomenological model, we describe the observed dynamics with fair agreement. PMID:26172647

  11. [Photosensitization in cattle grazing on pastures of Brahciaria decumbens Stapf infested with Pithomyces chartarum (Berk. & Curt.) M.B. Ellis].

    PubMed

    Andrade, S O; da Silva Lopes, H O; de Almeida Barros, M; Leite, G G; Dias, S M; Saueressig, M; Nobre, D; Temperini, J A

    1978-01-01

    Aspects of photosensitization in bovines grazing on pastures of Brachiaria decumbens Stapf infested with Pithomyces chartarum (Berk. & Curt.) M.B. Ellis infested all pastures 45(2):117-136, 1978. This paper reports experimental studies on photosensitization in bovines grazing on different pastures of Brachiaria decumbens Stapf in the "Cerrados" region (Planaltina, DF). Climatic conditions, zinc content and occurence of fungi on pastures were investigated. Pithomyces chartarum (Berk. & Curt.) M.B. Ellis infested all pastures examined. Photosensitization was observed in one animal maintained on a pasture of B. decumbens formed with seeds from Australia. Clinical and necropsy data were similar to those related in literature for sporidesmin-intoxicated animals. An isolate of P. chartarum and samples of bovine bile were assayed for sporidesmin presence. PMID:573108

  12. Asymmetrical Switch Costs in Children

    ERIC Educational Resources Information Center

    Ellefson, Michelle R.; Shapiron, Laura R.; Chater, Nick

    2006-01-01

    Switching between tasks produces decreases in performance as compared to repeating the same task. Asymmetrical switch costs occur when switching between two tasks of unequal difficulty. This asymmetry occurs because the cost is greater when switching to the less difficult task than when switching to the more difficult task. Various theories about…

  13. Thomson scattering measurements from asymmetric interpenetrating plasma flows.

    PubMed

    Ross, J S; Moody, J D; Fiuza, F; Ryutov, D; Divol, L; Huntington, C M; Park, H-S

    2014-11-01

    Imaging Thomson scattering measurements of collective ion-acoustic fluctuations have been utilized to determine ion temperature and density from laser produced counter-streaming asymmetric flows. Two foils are heated with 8 laser beams each, 500 J per beam, at the Omega Laser facility. Measurements are made 4 mm from the foil surface using a 60 J 2ω probe laser with a 200 ps pulse length. Measuring the electron density and temperature from the electron-plasma fluctuations constrains the fit of the multi-ion species, asymmetric flows theoretical form factor for the ion feature such that the ion temperatures, ion densities, and flow velocities for each plasma flow are determined. PMID:25430359

  14. Directed transport of active particles over asymmetric energy barriers.

    PubMed

    Koumakis, N; Maggi, C; Di Leonardo, R

    2014-08-21

    We theoretically and numerically investigate the transport of active colloids to target regions, delimited by asymmetric energy barriers. We show that it is possible to introduce a generalized effective temperature that is related to the local variance of particle velocities. The stationary probability distributions can be derived from a simple diffusion equation in the presence of an inhomogeneous effective temperature resulting from the action of external force fields. In particular, transition rates over asymmetric energy barriers can be unbalanced by having different effective temperatures over the two slopes of the barrier. By varying the type of active noise, we find that equal values of diffusivity and persistence time may produce strongly varied effective temperatures and thus stationary distributions. PMID:24978345

  15. A computational study of asymmetric glottal jet deflection during phonation.

    PubMed

    Zheng, X; Mittal, R; Bielamowicz, S

    2011-04-01

    Two-dimensional numerical simulations are used to explore the mechanism for asymmetric deflection of the glottal jet during phonation. The model employs the full Navier-Stokes equations for the flow but a simple laryngeal geometry and vocal-fold motion. The study focuses on the effect of Reynolds number and glottal opening angle with a particular emphasis on examining the importance of the so-called "Coanda effect" in jet deflection. The study indicates that the glottal opening angle has no substantial effect on glottal jet deflection. Deflection in the glottal jet is always preceded by large-scale asymmetry in the downstream portion of the glottal jet. A detailed analysis of the velocity and vorticity fields shows that these downstream asymmetric vortex structures induce a flow at the glottal exit which is the primary driver for glottal jet deflection. PMID:21476669

  16. Induced Motion by Asymmetric Enzymatic Degradation of Hydrogels

    NASA Astrophysics Data System (ADS)

    Hou, Jennifer; Cohen, Adam

    2012-02-01

    Biological hydrogels are continuously turned over through secretion and degradation. This non-equilibrium flux is critical to understanding cellular and molecular transport through biogels such as mucus and the extracellular matrix. Gel-digesting enzymes can drastically change the physical and chemical properties of the hydrogel environment. We report that a spatial gradient in the degradation of two gel/enzyme systems--gelatin/trypsin and hyaluronan/hyaluronidase--leads to directional motion of particles embedded in the gel in the direction of higher enzyme concentration. We study the rate at which the degradation front propagates through the gel and the ensuing velocity of the embedded particles, as functions of enzyme and gel concentrations. We propose that asymmetric degradation leads to asymmetric swelling, which transports particles up the enzyme concentration gradient.

  17. Thomson scattering measurements from asymmetric interpenetrating plasma flows

    SciTech Connect

    Ross, J. S. Moody, J. D.; Fiuza, F.; Ryutov, D.; Divol, L.; Huntington, C. M.; Park, H.-S.

    2014-11-15

    Imaging Thomson scattering measurements of collective ion-acoustic fluctuations have been utilized to determine ion temperature and density from laser produced counter-streaming asymmetric flows. Two foils are heated with 8 laser beams each, 500 J per beam, at the Omega Laser facility. Measurements are made 4 mm from the foil surface using a 60 J 2ω probe laser with a 200 ps pulse length. Measuring the electron density and temperature from the electron-plasma fluctuations constrains the fit of the multi-ion species, asymmetric flows theoretical form factor for the ion feature such that the ion temperatures, ion densities, and flow velocities for each plasma flow are determined.

  18. A computational study of asymmetric glottal jet deflection during phonation

    PubMed Central

    Zheng, X.; Mittal, R.; Bielamowicz, S.

    2011-01-01

    Two-dimensional numerical simulations are used to explore the mechanism for asymmetric deflection of the glottal jet during phonation. The model employs the full Navier–Stokes equations for the flow but a simple laryngeal geometry and vocal-fold motion. The study focuses on the effect of Reynolds number and glottal opening angle with a particular emphasis on examining the importance of the so-called “Coanda effect” in jet deflection. The study indicates that the glottal opening angle has no substantial effect on glottal jet deflection. Deflection in the glottal jet is always preceded by large-scale asymmetry in the downstream portion of the glottal jet. A detailed analysis of the velocity and vorticity fields shows that these downstream asymmetric vortex structures induce a flow at the glottal exit which is the primary driver for glottal jet deflection. PMID:21476669

  19. Pore Velocity Estimation Uncertainties

    NASA Astrophysics Data System (ADS)

    Devary, J. L.; Doctor, P. G.

    1982-08-01

    Geostatistical data analysis techniques were used to stochastically model the spatial variability of groundwater pore velocity in a potential waste repository site. Kriging algorithms were applied to Hanford Reservation data to estimate hydraulic conductivities, hydraulic head gradients, and pore velocities. A first-order Taylor series expansion for pore velocity was used to statistically combine hydraulic conductivity, hydraulic head gradient, and effective porosity surfaces and uncertainties to characterize the pore velocity uncertainty. Use of these techniques permits the estimation of pore velocity uncertainties when pore velocity measurements do not exist. Large pore velocity estimation uncertainties were found to be located in the region where the hydraulic head gradient relative uncertainty was maximal.

  20. Reconstruction of velocity fields in electromagnetic flow tomography.

    PubMed

    Lehtikangas, Ossi; Karhunen, Kimmo; Vauhkonen, Marko

    2016-06-28

    Electromagnetic flow meters (EMFMs) are the gold standard in measuring flow velocity in process industry. The flow meters can measure the mean flow velocity of conductive liquids and slurries. A drawback of this approach is that the velocity field cannot be determined. Asymmetric axial flows, often encountered in multiphase flows, pipe elbows and T-junctions, are problematic and can lead to serious systematic errors. Recently, electromagnetic flow tomography (EMFT) has been proposed for measuring velocity fields using several coils and a set of electrodes attached to the surface of the pipe. In this work, a velocity field reconstruction method for EMFT is proposed. The method uses a previously developed finite-element-based computational forward model for computing boundary voltages and a Bayesian framework for inverse problems. In the approach, the vz-component of the velocity field along the longitudinal axis of the pipe is estimated on the pipe cross section. Different asymmetric velocity fields encountered near pipe elbows, solids-in-water flows in inclined pipes and in stratified or multiphase flows are tested. The results suggest that the proposed reconstruction method could be used to estimate velocity fields in complicated pipe flows in which the conventional EMFMs have limited accuracy. This article is part of the themed issue 'Supersensing through industrial process tomography'. PMID:27185961

  1. Electron jet of asymmetric reconnection

    NASA Astrophysics Data System (ADS)

    Khotyaintsev, Yu. V.; Graham, D. B.; Norgren, C.; Eriksson, E.; Li, W.; Johlander, A.; Vaivads, A.; André, M.; Pritchett, P. L.; Retinò, A.; Phan, T. D.; Ergun, R. E.; Goodrich, K.; Lindqvist, P.-A.; Marklund, G. T.; Le Contel, O.; Plaschke, F.; Magnes, W.; Strangeway, R. J.; Russell, C. T.; Vaith, H.; Argall, M. R.; Kletzing, C. A.; Nakamura, R.; Torbert, R. B.; Paterson, W. R.; Gershman, D. J.; Dorelli, J. C.; Avanov, L. A.; Lavraud, B.; Saito, Y.; Giles, B. L.; Pollock, C. J.; Turner, D. L.; Blake, J. D.; Fennell, J. F.; Jaynes, A.; Mauk, B. H.; Burch, J. L.

    2016-06-01

    We present Magnetospheric Multiscale observations of an electron-scale current sheet and electron outflow jet for asymmetric reconnection with guide field at the subsolar magnetopause. The electron jet observed within the reconnection region has an electron Mach number of 0.35 and is associated with electron agyrotropy. The jet is unstable to an electrostatic instability which generates intense waves with E∥ amplitudes reaching up to 300 mV m-1 and potentials up to 20% of the electron thermal energy. We see evidence of interaction between the waves and the electron beam, leading to quick thermalization of the beam and stabilization of the instability. The wave phase speed is comparable to the ion thermal speed, suggesting that the instability is of Buneman type, and therefore introduces electron-ion drag and leads to braking of the electron flow. Our observations demonstrate that electrostatic turbulence plays an important role in the electron-scale physics of asymmetric reconnection.

  2. CO2 capture and separation from N2/CH4 mixtures by Co@B8/Co@B8(-) and M@B9/M@B9(-) (M = Ir, Rh, Ru) clusters: a theoretical study.

    PubMed

    Wang, Weihua; Zhang, Xiaoxiao; Li, Ping; Sun, Qiao; Li, Zhen; Ren, Cong; Guo, Chao

    2015-01-29

    The discovery of advanced materials with high selectivity and efficiency is essential to realize practical carbon capture and sequestration. Here, we have investigated the interactions of the Co@B8/Co@B8(-) and M@B9/M@B9(-) (M = Ir, Rh, Ru) clusters with CO2, N2, and CH4 gas molecules theoretically. We found that neutral boron clusters have weak interaction with CO2, N2, and CH4 molecules. Similarly, the clusters with their negative charge states have also weak interaction with N2 and CH4 molecules. However, anionic clusters have a strong interaction with CO2, which can be explained by the Lewis acid-base interaction as CO2 (Lewis acid) can gain electron easily from the electron-rich anionic clusters. Moreover, the kinetic stability of the formed complexes after CO2 capture has been validated by ab initio molecular dynamics. In all, the present study demonstrates, for the first time, that the anionic boron wheel ring clusters can be used as potential advanced materials for CO2 capture and separation from flue gas and natural gas mixtures. PMID:25594368

  3. Asymmetric information and macroeconomic dynamics

    NASA Astrophysics Data System (ADS)

    Hawkins, Raymond J.; Aoki, Masanao; Roy Frieden, B.

    2010-09-01

    We show how macroeconomic dynamics can be derived from asymmetric information. As an illustration of the utility of this approach we derive the equilibrium density, non-equilibrium densities and the equation of motion for the response to a demand shock for productivity in a simple economy. Novel consequences of this approach include a natural incorporation of time dependence into macroeconomics and a common information-theoretic basis for economics and other fields seeking to link micro-dynamics and macro-observables.

  4. Nerve conduction velocity

    MedlinePlus

    ... page: //medlineplus.gov/ency/article/003927.htm Nerve conduction velocity To use the sharing features on this page, please enable JavaScript. Nerve conduction velocity (NCV) is a test to see how ...

  5. Resonant discharge simulations with asymmetric electrodes

    SciTech Connect

    Smith, H.B.; Bowers, K.J.; Birdsall, C.K.

    1999-07-01

    Bounded plasmas exhibit two basic natural resonances--the plasma frequency and the series resonance frequency. The latter is associated with the edge of the plasma, and involves density perturbations in the sheath; it is also the cut-off frequency for waves propagating along the wall. Series resonant discharges have been previously simulated in planar 1d3v (one spatial dimension, 3 velocity dimensions) models. Results from these simulations are found to compare well with experimental measurements. In this paper the authors will look at 1d3v simulations of series resonant discharges between concentric cylinders and concentric spheres, also 1d3v. First, the natural series resonant frequency is determined by simulating an undriven plasma between short-circuited electrodes, looking for the resonance in the current; this frequency will be checked with simple circuit modeling. Second, they driven the same model near this resonance, in order to obtain a self-sustained discharge. They will report in detail on the differences between the driven symmetric and asymmetric discharges with respect to start-up, lock-on and steady state behavior, as well as on scaling laws.

  6. Asymmetric effect on single-file dense pedestrian flow

    NASA Astrophysics Data System (ADS)

    Kuang, Hua; Cai, Mei-Jing; Li, Xing-Li; Song, Tao

    2015-11-01

    In this paper, an extended optimal velocity model is proposed to simulate single-file dense pedestrian flow by considering asymmetric interaction (i.e. attractive force and repulsive force), which depends on the different distances between pedestrians. The stability condition of this model is obtained by using the linear stability theory. The phase diagram comparison and analysis show that asymmetric effect plays an important role in strengthening the stabilization of system. The modified Korteweg-de Vries (mKdV) equation near the critical point is derived by applying the reductive perturbation method. The pedestrian jam could be described by the kink-antikink soliton solution for the mKdV equation. From the simulation of space-time evolution of the pedestrians distance, it can be found that the asymmetric interaction is more efficient compared to the symmetric interaction in suppressing the pedestrian jam. Furthermore, the simulation results are consistent with the theoretical analysis as well as reproduce experimental phenomena better.

  7. Dust particle velocity measurement

    NASA Technical Reports Server (NTRS)

    Thielman, L. O.

    1976-01-01

    A laser Doppler velocimeter was used to measure the velocity distributions for particles entering a vacuum chamber from the atmosphere through calibrated leaks. The relative number of particles per velocity interval was obtained for particulates of three size distributions and two densities passing through six different leak geometries. The velocity range 15 to 320 meters per second was investigated. Peak particle velocities were found to occur in the 15 to 150 meters per second range depending upon type of particle and leak geometry. A small fraction of the particles were found to have velocities in the 150 to 320 meters per second range.

  8. Dry deposition velocities

    SciTech Connect

    Sehmel, G.A.

    1984-03-01

    Dry deposition velocities are very difficult to predict accurately. In this article, reported values of dry deposition velocities are summarized. This summary includes values from the literature on field measurements of gas and particle dry deposition velocities, and the uncertainties inherent in extrapolating field results to predict dry deposition velocities are discussed. A new method is described for predicting dry deposition velocity using a least-squares correlation of surface mass transfer resistances evaluated in wind tunnel experiments. 14 references, 4 figures, 1 table.

  9. Electronic properties of asymmetrically doped twisted graphene bilayers

    NASA Astrophysics Data System (ADS)

    Trambly de Laissardière, Guy; Namarvar, Omid Faizy; Mayou, Didier; Magaud, Laurence

    2016-06-01

    Rotated graphene bilayers form an exotic class of nanomaterials with fascinating electronic properties governed by the rotation angle θ . For large rotation angles, the electron eigenstates are restricted to one layer and the bilayer behaves like two decoupled graphene layers. At intermediate angles, Dirac cones are preserved but with a lower velocity and van Hove singularities are induced at energies where the two Dirac cones intersect. At very small angles, eigenstates become localized in peculiar moiré zones. We analyze here the effect of an asymmetric doping for a series of commensurate rotated bilayers on the basis of tight-binding calculations of their band dispersions, density of states, participation ratio, and diffusive properties. While a small doping level preserves the θ dependence of the rotated bilayer electronic structure, larger doping induces a further reduction of the band velocity in the same way as a further reduction of the rotation angle.

  10. Asymmetric Schiff bases derived from diaminomaleonitrile and their metal complexes

    NASA Astrophysics Data System (ADS)

    Yang, Jianjie; Shi, Rufei; Zhou, Pei; Qiu, Qiming; Li, Hui

    2016-02-01

    Asymmetric Schiff bases, due to its asymmetric structure, can be used as asymmetric catalyst, antibacterial, and mimic molecules during simulate biological processes, etc. In recent years, research on synthesis and properties of asymmetric Schiff bases have become an increase interest of chemists. This review summarizes asymmetric Schiff bases derived from diaminomaleonitrile (DAMN) and DAMN-based asymmetric Schiff bases metal complexes. Applications of DAMN-based asymmetric Schiff bases are also discussed in this review.

  11. LG tools for asymmetric wargaming

    NASA Astrophysics Data System (ADS)

    Stilman, Boris; Yakhnis, Alex; Yakhnis, Vladimir

    2002-07-01

    Asymmetric operations represent conflict where one of the sides would apply military power to influence the political and civil environment, to facilitate diplomacy, and to interrupt specified illegal activities. This is a special type of conflict where the participants do not initiate full-scale war. Instead, the sides may be engaged in a limited open conflict or one or several sides may covertly engage another side using unconventional or less conventional methods of engagement. They may include peace operations, combating terrorism, counterdrug operations, arms control, support of insurgencies or counterinsurgencies, show of force. An asymmetric conflict can be represented as several concurrent interlinked games of various kinds: military, transportation, economic, political, etc. Thus, various actions of peace violators, terrorists, drug traffickers, etc., can be expressed via moves in different interlinked games. LG tools allow us to fully capture the specificity of asymmetric conflicts employing the major LG concept of hypergame. Hypergame allows modeling concurrent interlinked processes taking place in geographically remote locations at different levels of resolution and time scale. For example, it allows us to model an antiterrorist operation taking place simultaneously in a number of countries around the globe and involving wide range of entities from individuals to combat units to governments. Additionally, LG allows us to model all sides of the conflict at their level of sophistication. Intelligent stakeholders are represented by means of LG generated intelligent strategies. TO generate those strategies, in addition to its own mathematical intelligence, the LG algorithm may incorporate the intelligence of the top-level experts in the respective problem domains. LG models the individual differences between intelligent stakeholders. The LG tools make it possible to incorporate most of the known traits of a stakeholder, i.e., real personalities involved in

  12. Spontaneous baryogenesis from asymmetric inflaton

    NASA Astrophysics Data System (ADS)

    Takahashi, Fuminobu; Yamada, Masaki

    2016-05-01

    We propose a variant scenario of spontaneous baryogenesis from asymmetric inflaton based on current-current interactions between the inflaton and matter fields with a non-zero B - L charge. When the inflaton starts to oscillate around the minimum after inflation, it may lead to excitation of a CP-odd component, which induces an effective chemical potential for the B - L number through the current-current interactions. We study concrete inflation models and show that the spontaneous baryogenesis scenario can be naturally implemented in the chaotic inflation in supergravity.

  13. Diffusion on asymmetric fractal networks

    NASA Astrophysics Data System (ADS)

    Haynes, Christophe P.; Roberts, Anthony P.

    2010-12-01

    We derive a renormalization method to calculate the spectral dimension d¯ of deterministic self-similar networks with arbitrary base units and branching constants. The generality of the method allows the affect of a multitude of microstructural details to be quantitatively investigated. In addition to providing models for physical networks, the results allow precise tests of theories of diffusive transport. For example, the properties of a class of nonrecurrent trees (d¯>2) with asymmetric elements and branching violate the Alexander-Orbach scaling law.

  14. Theoretical electronic structures and relative stabilities of the spinel oxynitrides M3NO3 (M=B,Al,Ga,In)

    NASA Astrophysics Data System (ADS)

    Okeke, Onyekwelu U.; Lowther, J. E.

    2008-03-01

    A spinel structure of an oxynitride material in the form M3NO3 ( M=B , Al, Ga, or In) is considered to be derived from a reaction of the form MN+M2O3→M3NO3 . Various possible phases of MN and M2O3 , which could lead to the M3NO3 spinel material, are considered. The spinels containing B and Al exhibit higher resistance to compression and shear than those containing Ga and In, and these are suggested to be potentially important hard materials possibly formed under extreme conditions. Calculated energetics of the proposed reaction favor the formation of spinels containing Ga and In with such materials having potentially significant optoelectronic applications.

  15. Asymmetric cell division in plant development.

    PubMed

    Heidstra, Renze

    2007-01-01

    Plant embryogenesis creates a seedling with a basic body plan. Post-embryonically the seedling elaborates with a lifelong ability to develop new tissues and organs. As a result asymmetric cell divisions serve essential roles during embryonic and postembryonic development to generate cell diversity. This review highlights selective cases of asymmetric division in the model plant Arabidopsis thaliana and describes the current knowledge on fate determinants and mechanisms involved. Common themes that emerge are: 1. role of the plant hormone auxin and its polar transport machinery; 2. a MAP kinase signaling cascade and; 3. asymmetric segregating transcription factors that are involved in several asymmetric cell divisions. PMID:17585494

  16. ASYMMETRIC SOLAR POLAR FIELD REVERSALS

    SciTech Connect

    Svalgaard, Leif; Kamide, Yohsuke

    2013-01-20

    The solar polar fields reverse because magnetic flux from decaying sunspots moves toward the poles, with a preponderance of flux from the trailing spots. If there is a strong asymmetry, in the sense that most activity is in the northern hemisphere, then that excess flux will move toward the north pole and reverse that pole first. If there is more activity in the south later on, then that flux will help to reverse the south pole. In this way, two humps in the solar activity and a corresponding difference in the time of reversals develop (in the ideal case). Such a difference was originally noted in the very first observation of polar field reversal just after the maximum of the strongly asymmetric solar cycle 19, when the southern hemisphere was most active before sunspot maximum and the south pole duly reversed first, followed by the northern hemisphere more than a year later, when that hemisphere became most active. Solar cycles since then have had the opposite asymmetry, with the northern hemisphere being most active before solar maximum. We show that polar field reversals for these cycles have all happened in the north first, as expected. This is especially noteworthy for the present solar cycle 24. We suggest that the association of two or more peaks of solar activity when separated by hemispheres with correspondingly different times of polar field reversals is a general feature of the cycle, and that asymmetric polar field reversals are simply a consequence of the asymmetry of solar activity.

  17. Asymmetric Laguerre-Gaussian beams

    NASA Astrophysics Data System (ADS)

    Kovalev, A. A.; Kotlyar, V. V.; Porfirev, A. P.

    2016-06-01

    We introduce a family of asymmetric Laguerre-Gaussian (aLG) laser beams. The beams have been derived via a complex-valued shift of conventional LG beams in the Cartesian plane. While propagating in a uniform medium, the first bright ring of the aLG beam becomes less asymmetric and the energy is redistributed toward peripheral diffraction rings. The projection of the orbital angular momentum (OAM) onto the optical axis is calculated. The OAM is shown to grow quadratically with increasing asymmetry parameter of the aLG beam, which equals the ratio of the shift to the waist radius. Conditions for the OAM becoming equal to the topological charge have been derived. For aLG beams with zero radial index, we have deduced an expression to define the intensity maximum coordinates and shown the crescent-shaped intensity pattern to rotate during propagation. Results of the experimental generation and rotation of aLG beams agree well with theoretical predictions.

  18. Active matter on asymmetric substrates

    NASA Astrophysics Data System (ADS)

    Olson Reichhardt, C. J.; Drocco, J.; Mai, T.; Wan, M. B.; Reichhardt, C.

    2011-10-01

    For collections of particles in a thermal bath interacting with an asymmetric substrate, it is possible for a ratchet effect to occur where the particles undergo a net dc motion in response to an ac forcing. Ratchet effects have been demonstrated in a variety of systems including colloids as well as magnetic vortices in type-II superconductors. Here we examine the case of active matter or self-driven particles interacting with asymmetric substrates. Active matter systems include self-motile colloidal particles undergoing catalysis, swimming bacteria, artificial swimmers, crawling cells, and motor proteins. We show that a ratchet effect can arise in this type of system even in the absence of ac forcing. The directed motion occurs for certain particle-substrate interaction rules and its magnitude depends on the amount of time the particles spend swimming in one direction before turning and swimming in a new direction. For strictly Brownian particles there is no ratchet effect. If the particles reflect off the barriers or scatter from the barriers according to Snell's law there is no ratchet effect; however, if the particles can align with the barriers or move along the barriers, directed motion arises. We also find that under certain motion rules, particles accumulate along the walls of the container in agreement with experiment. We also examine pattern formation for synchronized particle motion. We discuss possible applications of this system for self-assembly, extracting work, and sorting as well as future directions such as considering collective interactions and flocking models.

  19. Scatterometry measurement of asymmetric gratings

    NASA Astrophysics Data System (ADS)

    Li, Jie; Hwu, Justin J.; Liu, Yongdong; Rabello, Silvio; Liu, Zhuan; Hu, Jiangtao

    2009-12-01

    Scatterometry has been used extensively for the characterization of critical dimensions (CD) and detailed sidewall profiles of periodic structures in microelectronics fabrication processes. So far the majority of applications are for symmetric gratings. In most cases devices are designed to be symmetric although errors could occur during fabrication process and result in undesired asymmetry. The problem with conventional optical scatterometry techniques lies in the lack of capability to distinguish between left and right asymmetries. In this work we investigate the possibility of measuring grating asymmetry using Mueller matrix spectroscopic ellipsometry (MM-SE). A patterned hard disk prepared by nano-imprint technique is used for the study. The relief image on the disk sometimes has asymmetrical sidewall profile, presumably due to the uneven separation of the template from the disk. The undesired tilting resist profile causes difficulties to the downstream processes or even makes them fail. Cross-section SEM reveals that the asymmetrical resist lines are typically tilted towards the outer diameter direction. The simulation and experimental data show that certain Mueller matrix elements are proportional to the direction and amplitude of profile asymmetry, providing a direct indication to the sidewall tilting. The tilting parameter can be extracted using rigorous optical critical dimension (OCD) modeling or calibration method. We demonstrate that this technique has good sensitivity for measuring and distinguishing left and right asymmetry caused by sidewall tilting, and can therefore be used for monitoring processes, such as lithography and etch processing, for which symmetric structures are desired.

  20. Geometry-induced asymmetric diffusion

    PubMed Central

    Shaw, Robert S.; Packard, Norman; Schröter, Matthias; Swinney, Harry L.

    2007-01-01

    Past work has shown that ions can pass through a membrane more readily in one direction than the other. We demonstrate here in a model and an experiment that for a mixture of small and large particles such asymmetric diffusion can arise solely from an asymmetry in the geometry of the pores of the membrane. Our deterministic simulation considers a two-dimensional gas of elastic disks of two sizes diffusing through a membrane, and our laboratory experiment examines the diffusion of glass beads of two sizes through a metal membrane. In both experiment and simulation, the membrane is permeable only to the smaller particles, and the asymmetric pores lead to an asymmetry in the diffusion rates of these particles. The presence of even a small percentage of large particles can clog a membrane, preventing passage of the small particles in one direction while permitting free flow of the small particles in the other direction. The purely geometric kinetic constraints may play a role in common biological contexts such as membrane ion channels. PMID:17522257

  1. Asymmetric Wettability Directs Leidenfrost Droplets

    NASA Astrophysics Data System (ADS)

    Agapov, Rebecca; Boreyko, Jonathan; Briggs, Dayrl; Srijanto, Bernadeta; Retterer, Scott; Collier, C. Patrick; Lavrik, Nickolay

    2014-03-01

    Exploration of Leidenfrost droplets on nano- and microstructured surfaces are of great importance for increasing control over heat transfer in high power density systems using boiling phenomena. They also provide an elegant way to direct droplet motion in a variety of emerging fluidic systems. Here, we report the fabrication and characterization of tilted nanopillar arrays (TNPAs) that exhibit directional Leidenfrost water droplets under dynamic conditions. The batch fabrication of the TNPAs was achieved by glancing-angle anisotropic reactive ion etching of a thermally dewet platinum mask. In contrast to previously implemented macro- and microscopic Leidenfrost ratchets, our TNPAs induce no preferential directional movement of Leidenfrost droplets under conditions approaching steady-state film boiling. This suggests that the observed droplet directionality is not a result of asymmetric vapor flow. Phase diagrams were constructed for the boiling behavior upon droplet impact onto TNPAs, straight nanopillar arrays, and smooth silicon surfaces. Asymmetric wettability and directional trajectory of droplets was exclusive to the TNPAs for impacts corresponding to the transition boiling regime, revealing this to be the mechanism for the droplet directionality. This work was conducted at the Center for Nanophase Materials Sciences, which is sponsored at Oak Ridge National Lab by the Division of Scientific User Facilities, US Dept. of Energy.

  2. Migration in asymmetric, random environments

    NASA Astrophysics Data System (ADS)

    Deem, Michael; Wang, Dong

    Migration is a key mechanism for expansion of communities. As a population migrates, it experiences a changing environment. In heterogeneous environments, rapid adaption is key to the evolutionary success of the population. In the case of human migration, environmental heterogeneity is naturally asymmetric in the North-South and East-West directions. We here consider migration in random, asymmetric, modularly correlated environments. Knowledge about the environment determines the fitness of each individual. We find that the speed of migration is proportional to the inverse of environmental change, and in particular we find that North-South migration rates are lower than East-West migration rates. Fast communication within the population of pieces of knowledge between individuals, similar to horizontal gene transfer in genetic systems, can help to spread beneficial knowledge among individuals. We show that increased modularity of the relation between knowledge and fitness enhances the rate of evolution. We investigate the relation between optimal information exchange rate and modularity of the dependence of fitness on knowledge. These results for the dependence of migration rate on heterogeneity, asymmetry, and modularity are consistent with existing archaeological facts.

  3. Aberrations in asymmetrical electron lenses.

    PubMed

    Fitzgerald, J P S; Word, R C; Könenkamp, R

    2012-08-01

    Starting from well established knowledge in light-optics we explore the question if electron-optical aberration can be improved in asymmetrical electron lenses. We show that spherical as well as chromatic aberration coefficients are reduced in asymmetric electrostatic einzel lenses when the center electrode is moved away from the center position towards the entrance electrode. Relative improvements up to 40% for both the chromatic and the spherical aberration coefficients can be obtained. We use analytical and numerical calculations to confirm this result for exemplary cases of a lens with fixed length and working distance. The agreement of the two calculation methods is very good. We then derive an estimate for the electron-optical aberration coefficients from light-optics. The derived expressions for chromatic and spherical aberrations are somewhat simpler than the ones derived from electron-optics as they involve integrals only over the electrostatic potential, not over the electron paths. The estimated formulas still agree well with the electron optical calculations. Overall, we are tempted to suggest that the enormous knowledge base of light optics can provide considerable guidance for electron-optical applications. PMID:22206603

  4. Excitons in asymmetric quantum wells

    NASA Astrophysics Data System (ADS)

    Grigoryev, P. S.; Kurdyubov, A. S.; Kuznetsova, M. S.; Ignatiev, I. V.; Efimov, Yu. P.; Eliseev, S. A.; Petrov, V. V.; Lovtcius, V. A.; Shapochkin, P. Yu.

    2016-09-01

    Resonance dielectric response of excitons is studied for the high-quality InGaAs/GaAs heterostructures with wide asymmetric quantum wells (QWs). To highlight effects of the QW asymmetry, we have grown and studied several heterostructures with nominally square QWs as well as with triangle-like QWs. Several quantum confined exciton states are experimentally observed as narrow exciton resonances. A standard approach for the phenomenological analysis of the profiles is generalized by introducing different phase shifts for the light waves reflected from the QWs at different exciton resonances. Good agreement of the phenomenological fit to the experimentally observed exciton spectra for high-quality structures allowed us to reliably obtain parameters of the exciton resonances: the exciton transition energies, the radiative broadenings, and the phase shifts. A direct numerical solution of the Schrödinger equation for the heavy-hole excitons in asymmetric QWs is used for microscopic modeling of the exciton resonances. Remarkable agreement with the experiment is achieved when the effect of indium segregation is taken into account. The segregation results in a modification of the potential profile, in particular, in an asymmetry of the nominally square QWs.

  5. Effect of Geometric Azimuthal Asymmetrics of PPM Stack on Electron Beam Characteristics

    NASA Technical Reports Server (NTRS)

    Kory, Carol L.

    2000-01-01

    A three-dimensional (3D) beam optics model has been developed using the electromagnetic particle-in-cell (PIC) code MAFIA. The model includes an electron beam with initial transverse velocity distribution focused by a periodic permanent magnet (PPM) stack. All components of the model are simulated in three dimensions allowing several azimuthally asymmetric traveling wave tube (TWT) characteristics to be investigated for the first time. These include C-magnets, shunts and magnet misalignment and their effects on electron beam behavior. The development of the model is presented and 3D TWT electron beam characteristics are compared in the absence of and under the influence of the azimuthally asymmetric characteristics described.

  6. Complete temporal characterization of asymmetric pulse compression in a laser wakefield.

    PubMed

    Schreiber, J; Bellei, C; Mangles, S P D; Kamperidis, C; Kneip, S; Nagel, S R; Palmer, C A J; Rajeev, P P; Streeter, M J V; Najmudin, Z

    2010-12-01

    We present complete experimental characterization of the temporal shape of an intense ultrashort 200-TW laser pulse driving a laser wakefield. The phase of the pulse was uniquely measured by using (second-order) frequency-resolved optical gating. The pulses are asymmetrically compressed and exhibit a positive chirp consistent with the expected asymmetric self-phase-modulation due to photon acceleration or deceleration in a relativistic plasma wave. The measured pulse duration decreases linearly with increasing length and density of the plasma, in quantitative agreement with the intensity-dependent group velocity variation in the plasma wave. PMID:21231474

  7. Angular velocity discrimination

    NASA Technical Reports Server (NTRS)

    Kaiser, Mary K.

    1990-01-01

    Three experiments designed to investigate the ability of naive observers to discriminate rotational velocities of two simultaneously viewed objects are described. Rotations are constrained to occur about the x and y axes, resulting in linear two-dimensional image trajectories. The results indicate that observers can discriminate angular velocities with a competence near that for linear velocities. However, perceived angular rate is influenced by structural aspects of the stimuli.

  8. Dynamic responses of asymmetric vortices over slender bodies to a rotating tip perturbation

    NASA Astrophysics Data System (ADS)

    Ma, Bao-Feng; Huang, Yu; Deng, Xue-Ying

    2016-04-01

    The dynamic responses of asymmetric vortices over a slender body to a rotating tip perturbation were investigated experimentally in a wind tunnel. A small rotating nose with an artificial micro-perturbation on the nose tip was driven by a servomotor with various rates to change azimuthal locations of tip perturbation. Wall pressures and spatial velocity fields were measured using pressure scanner and particle image velocimetry based on a phase-locked method. The results show that the spinning tip perturbation enables asymmetric vortices to exhibit significantly dynamic characteristics different from a case with a static perturbation. The orientations of asymmetric vortices and associated side forces show apparent phase delay that are enlarged with increasing rotational rates of the nose. The switching rates of asymmetric vortices among various orientations also increase with the rotational rates increasing, but asymmetry level of vortices is lowered, which reveals that the asymmetric vortices change requires an amount of time to switch from one orientation to another. The phase delays of vortices, however, are determined by the amount of time required for the propagation of disturbance waves along a body axis. As the rotational frequencies are sufficiently high, the orientations of vortices almost hold to be unchanged. The unchanged orientation of vortices is asymmetric, depending on the directions of rotation. The asymmetric vortices arising from high-frequency rotation of the nose are attributed to wall effects induced by the rotating nose with a finite length. In addition, there exist small intrinsic vortex oscillations which are superimposed on the average vortex structures with symmetric and asymmetric orientations for the cases of static and rotational tip perturbations.

  9. About measuring velocity dispersions

    NASA Astrophysics Data System (ADS)

    Fellhauer, M.

    A lot of our knowledge about the dynamics and total masses of pressure dominated stellar systems relies on measuring the internal velocity disper- sion of the system. We assume virial equilibrium and that we are able to measure only the bound stars of the system without any contamination. This article shows how likely it is to measure the correct velocity dispersion in reality. It will show that as long as we have small samples of velocity mea- surements the distribution of possible outcomes can be very large and as soon as we have a source of error the velocity dispersion can wrong by several standard deviations especially in large samples.

  10. An Asymmetric Stereodivergent Strategy Towards Aminocyclitols

    PubMed Central

    Malhotra, Sushant

    2014-01-01

    A concise asymmetric synthesis of aminocyclitols such as diastereomeric 2-deoxystreptamine analogues and conduramine A is described. The Pd-catalyzed asymmetric desymmetrization of meso 1,4-dibenzolate enables the synthesis of highly oxidized cyclohaxane architectures. These scaffolds can potentially be used to access novel aminoglycoside antibiotics and enantiomerically pure α-glucosidase inhibitors. PMID:24889256

  11. Defect-free ultrahigh flux asymmetric membranes

    DOEpatents

    Pinnau, Ingo; Koros, William J.

    1990-01-01

    Defect-free, ultrahigh flux integrally-skinned asymmetric membranes having extremely thin surface layers (<0.2 .mu.m) comprised of glassy polymers are disclosed. The membranes are formed by casting an appropriate drope followed by forced convective evaporation of solvent to obtain a dry phase separated asymmetrical structure. The structure is then washed in a precipitation liquid and dried.

  12. Separator for Heavy ELement Spectroscopy - velocity filter SHELS

    NASA Astrophysics Data System (ADS)

    Popeko, A. G.; Yeremin, A. V.; Malyshev, O. N.; Chepigin, V. I.; Isaev, A. V.; Popov, Yu. A.; Svirikhin, A. I.; Haushild, K.; Lopez-Martens, A.; Rezynkina, K.; Dorvaux, O.

    2016-06-01

    The SHELS velocity filter originated upon reconstruction of the VASSILISSA electrostatic separator used for investigations of heavy nuclei produced in complete fusion reactions. The goals of this modernization were to increase the transmission of products of asymmetric reactions and to extend the region of reactions to be investigated up to symmetric combinations. The first tests of the set-up were performed with the beams of accelerated 22Ne, 40Ar, 48Ca, and 50Ti ions.

  13. Superfluidity in asymmetric nuclear matter

    SciTech Connect

    Sedrakian, A.; Alm, T.; Lombardo, U.

    1997-02-01

    The onset of superfluidity in isospin-asymmetric nuclear matter is investigated within the BCS theory. A neutron-proton superfluid state in the channel {sup 3}S{sub 1}-{sup 3}D{sub 1} comes about from the interplay between thermal excitations and separation {delta}{mu} of the two Fermi surfaces. The superfluid state disappears above the threshold value of the density-asymmetry parameter {alpha}=(n{sub n}{minus}n{sub p})/n{approx_equal}0.35. For large enough shift between the two Fermi surfaces {delta}{mu}=(1)/(2)({mu}{sub n}{minus}{mu}{sub p}) the transition to the normal state becomes a first-order transition and a second gap solution develops. This solution, however, corresponds to a metastable superfluid state which is unstable with respect to the transition to the normal state. {copyright} {ital 1997} {ital The American Physical Society}

  14. Asymmetric catalysis: An enabling science

    PubMed Central

    Trost, Barry M.

    2004-01-01

    Chirality of organic molecules plays an enormous role in areas ranging from medicine to material science, yet the synthesis of such entities in one enantiomeric form is one of the most difficult challenges. The advances being made stem from the convergence of a broader understanding of theory and how structure begets function, the developments in the interface between organic and inorganic chemistry and, most notably, the organic chemistry of the transition metals, and the continuing advancements in the tools to help define structure, especially in solution. General themes for designing catalysts to effect asymmetric induction are helping to make this strategy more useful, in general, with the resultant effect of a marked enhancement of synthetic efficiency. PMID:14990801

  15. New asymmetric quantum codes over Fq

    NASA Astrophysics Data System (ADS)

    Ma, Yuena; Feng, Xiaoyi; Xu, Gen

    2016-07-01

    Two families of new asymmetric quantum codes are constructed in this paper. The first family is the asymmetric quantum codes with length n=qm-1 over Fq, where qge 5 is a prime power. The second one is the asymmetric quantum codes with length n=3m-1. These asymmetric quantum codes are derived from the CSS construction and pairs of nested BCH codes. Moreover, let the defining set T1=T2^{-q}, then the real Z-distance of our asymmetric quantum codes are much larger than δ _max+1, where δ _max is the maximal designed distance of dual-containing narrow-sense BCH code, and the parameters presented here have better than the ones available in the literature.

  16. Designing asymmetric multiferroics with strong magnetoelectric coupling

    NASA Astrophysics Data System (ADS)

    Lu, X. Z.; Xiang, H. J.

    2014-09-01

    Multiferroics offer exciting opportunities for electric-field control of magnetism. Single-phase multiferroics suitable for such applications at room temperature need much more study. Here, we propose the concept of an alternative type of multiferroics, namely, the "asymmetric multiferroic." In asymmetric multiferroics, two locally stable ferroelectric states are not symmetrically equivalent, leading to different magnetic properties between these two states. Furthermore, we predict from first principles that a Fe-Cr-Mo superlattice with the LiNbO3-type structure is such an asymmetric multiferroic. The strong ferrimagnetism, high ferroelectric polarization, and significant dependence of the magnetic transition temperature on polarization make this asymmetric multiferroic an ideal candidate for realizing electric-field control of magnetism at room temperature. Our study suggests that the asymmetric multiferroic may provide an alternative playground for voltage control of magnetism and find its applications in spintronics and quantum computing.

  17. Designing asymmetric multiferroics with strong magnetoelectric coupling

    NASA Astrophysics Data System (ADS)

    Lu, Xuezeng; Xiang, Hongjun; Rondinelli, James; Materials Theory; Design Group Team

    2015-03-01

    Multiferroics offer exciting opportunities for electric-field control of magnetism. Single-phase multiferroics suitable for such applications at room temperature need much more study. Here, we propose the concept of an alternative type of multiferroics, namely, the ``asymmetric multiferroic.'' In asymmetric multiferroics, two locally stable ferroelectric states are not symmetrically equivalent, leading to different magnetic properties between these two states. Furthermore, we predict from first principles that a Fe-Cr-Mo superlattice with the LiNbO3-type structure is such an asymmetric multiferroic. The strong ferrimagnetism, high ferroelectric polarization, and significant dependence of the magnetic transition temperature on polarization make this asymmetric multiferroic an ideal candidate for realizing electric-field control of magnetism at room temperature. Our study suggests that the asymmetric multiferroic may provide an alternative playground for voltage control of magnetism and find its applications in spintronics and quantum computing.

  18. New asymmetric quantum codes over Fq

    NASA Astrophysics Data System (ADS)

    Ma, Yuena; Feng, Xiaoyi; Xu, Gen

    2016-04-01

    Two families of new asymmetric quantum codes are constructed in this paper. The first family is the asymmetric quantum codes with length n=qm-1 over Fq , where q≥ 5 is a prime power. The second one is the asymmetric quantum codes with length n=3m-1 . These asymmetric quantum codes are derived from the CSS construction and pairs of nested BCH codes. Moreover, let the defining set T1=T2^{-q} , then the real Z-distance of our asymmetric quantum codes are much larger than δ _max+1 , where δ _max is the maximal designed distance of dual-containing narrow-sense BCH code, and the parameters presented here have better than the ones available in the literature.

  19. Ice crystal terminal velocities.

    NASA Technical Reports Server (NTRS)

    Heymsfield, A.

    1972-01-01

    Terminal velocities of different ice crystal forms were calculated, using the most recent ice crystal drag coefficients, aspect ratios, and densities. The equations derived were primarily for use in calculating precipitation rates by sampling particles with an aircraft in cirrus clouds, and determining particle size in cirrus clouds by Doppler radar. However, the equations are sufficiently general for determining particle terminal velocity at any altitude, and almost any crystal type. Two sets of equations were derived. The 'general' equations provide a good estimate of terminal velocities at any altitude. The 'specific' equations are a set of equations for ice crystal terminal velocities at 1000 mb. The calculations are in good agreement with terminal velocity measurements. The results from the present study were also compared to prior calculations by others and seem to give more reasonable results, particularly at higher altitudes.

  20. Stepwise shockwave velocity determinator

    NASA Technical Reports Server (NTRS)

    Roth, Timothy E.; Beeson, Harold

    1992-01-01

    To provide an uncomplicated and inexpensive method for measuring the far-field velocity of a surface shockwave produced by an explosion, a stepwise shockwave velocity determinator (SSVD) was developed. The velocity determinator is constructed of readily available materials and works on the principle of breaking discrete sensors composed of aluminum foil contacts. The discrete sensors have an average breaking threshold of approximately 7 kPa. An incremental output step of 250 mV is created with each foil contact breakage and is logged by analog-to-digital instrumentation. Velocity data obtained from the SSVD is within approximately 11 percent of the calculated surface shockwave velocity of a muzzle blast from a 30.06 rifle.

  1. How required reserve ratio affects distribution and velocity of money

    NASA Astrophysics Data System (ADS)

    Xi, Ning; Ding, Ning; Wang, Yougui

    2005-11-01

    In this paper the dependence of wealth distribution and the velocity of money on the required reserve ratio is examined based on a random transfer model of money and computer simulations. A fractional reserve banking system is introduced to the model where money creation can be achieved by bank loans and the monetary aggregate is determined by the monetary base and the required reserve ratio. It is shown that monetary wealth follows asymmetric Laplace distribution and latency time of money follows exponential distribution. The expression of monetary wealth distribution and that of the velocity of money in terms of the required reserve ratio are presented in a good agreement with simulation results.

  2. FAME Radial Velocity Survey

    NASA Astrophysics Data System (ADS)

    Salim, S.; Gould, A.

    2000-12-01

    Full-Sky Astrometric Mapping Explorer (FAME) belongs to a new generation of astrometry satellites and will probe the surrounding space some 20 times deeper than its predecessor Hipparcos. As a result we will acquire precise knowledge of 5 out of 6 components of phase-space for millions of stars. The remaining coordinate, radial velocity, will remain unknown. In this study, we look at how the knowledge of radial velocity affects the determination of the structure of the Galaxy, and its gravitational potential. We therefore propose a radial velocity survey of FAME stars, and discuss its feasibility and technical requirements.

  3. Asymmetrical division of Saccharomyces cerevisiae.

    PubMed Central

    Lord, P G; Wheals, A E

    1980-01-01

    The unequal division model proposed for budding yeast (L. H. Hartwell and M. W. Unger, J. Cell Biol. 75:422-435, 1977) was tested by bud scar analyses of steady-state exponential batch cultures of Saccharomyces cerevisiae growing at 30 degrees C at 19 different rates, which were obtained by altering the carbon source. The analyses involved counting the number of bud scars, determining the presence or absence of buds on at least 1,000 cells, and independently measuring the doubling times (gamma) by cell number increase. A number of assumptions in the model were tested and found to be in good agreement with the model. Maximum likelihood estimates of daughter cycle time (D), parent cycle time (P), and the budded phase (B) were obtained, and we concluded that asymmetrical division occurred at all growth rates tested (gamma, 75 to 250 min). D, P, and B are all linearly related to gamma, and D, P, and gamma converge to equality (symmetrical division) at gamma = 65 min. Expressions for the genealogical age distribution for asymmetrically dividing yeast cells were derived. The fraction of daughter cells in steady-state populations is e-alpha P, and the fraction of parent cells of age n (where n is the number of buds that a cell has produced) is (e-alpha P)n-1(1-e-alpha P)2, where alpha = IN2/gamma; thus, the distribution changes with growth rate. The frequency of cells with different numbers of bud scars (i.e., different genealogical ages) was determined for all growth rates, and the observed distribution changed with the growth rate in the manner predicted. In this haploid strain new buds formed adjacent to the previous buds in a regular pattern, but at slower growth rates the pattern was more irregular. The median volume of the cells and the volume at start in the cell cycle both increased at faster growth rates. The implications of these findings for the control of the cell cycle are discussed. PMID:6991494

  4. Nerve conduction velocity

    MedlinePlus

    Nerve conduction velocity (NCV) is a test to see how fast electrical signals move through a nerve. ... normal body temperature. Being too cold slows nerve conduction. Tell your doctor if you have a cardiac ...

  5. Investigation of Slipstream Velocity

    NASA Technical Reports Server (NTRS)

    Crowley, J W , Jr

    1925-01-01

    These experiments were made at the request of the Bureau of Aeronautics, Navy Department, to investigate the velocity of the air in the slipstream in horizontal and climbing flight to determine the form of expression giving the slipstream velocity in terms of the airspeed of the airplane. The method used consisted in flying the airplane both on a level course and in climb at full throttle and measuring the slipstream velocity at seven points in the slipstream for the whole speed range of the airplane in both conditions. In general the results show that for both condition, horizontal and climbing flights, the slipstream velocity v subscript 3 and airspeed v can be represented by straight lines and consequently the equations are of the form: v subscript s = mv+b where m and b are constant. (author)

  6. High Velocity Gas Gun

    NASA Technical Reports Server (NTRS)

    1988-01-01

    A video tape related to orbital debris research is presented. The video tape covers the process of loading a High Velocity Gas Gun and firing it into a mounted metal plate. The process is then repeated in slow motion.

  7. Velocity of Sound

    ERIC Educational Resources Information Center

    Gillespie, A.

    1975-01-01

    Describes a method for the determination of the velocity of sound using a dual oscilloscope on which is displayed the sinusoidal input into a loudspeaker and the signal picked up by a microphone. (GS)

  8. Regenerating a symmetry in asymmetric dark matter.

    PubMed

    Buckley, Matthew R; Profumo, Stefano

    2012-01-01

    Asymmetric dark matter theories generically allow for mass terms that lead to particle-antiparticle mixing. Over the age of the Universe, dark matter can thus oscillate from a purely asymmetric configuration into a symmetric mix of particles and antiparticles, allowing for pair-annihilation processes. Additionally, requiring efficient depletion of the primordial thermal (symmetric) component generically entails large annihilation rates. We show that unless some symmetry completely forbids dark matter particle-antiparticle mixing, asymmetric dark matter is effectively ruled out for a large range of masses, for almost any oscillation time scale shorter than the age of the Universe. PMID:22304253

  9. Nondeterministic self-assembly with asymmetric interactions.

    PubMed

    Tesoro, S; Göpfrich, K; Kartanas, T; Keyser, U F; Ahnert, S E

    2016-08-01

    We investigate general properties of nondeterministic self-assembly with asymmetric interactions, using a computational model and DNA tile assembly experiments. By contrasting symmetric and asymmetric interactions we show that the latter can lead to self-limiting cluster growth. Furthermore, by adjusting the relative abundance of self-assembly particles in a two-particle mixture, we are able to tune the final sizes of these clusters. We show that this is a fundamental property of asymmetric interactions, which has potential applications in bioengineering, and provides insights into the study of diseases caused by protein aggregation. PMID:27627332

  10. Nondeterministic self-assembly with asymmetric interactions

    NASA Astrophysics Data System (ADS)

    Tesoro, S.; Göpfrich, K.; Kartanas, T.; Keyser, U. F.; Ahnert, S. E.

    2016-08-01

    We investigate general properties of nondeterministic self-assembly with asymmetric interactions, using a computational model and DNA tile assembly experiments. By contrasting symmetric and asymmetric interactions we show that the latter can lead to self-limiting cluster growth. Furthermore, by adjusting the relative abundance of self-assembly particles in a two-particle mixture, we are able to tune the final sizes of these clusters. We show that this is a fundamental property of asymmetric interactions, which has potential applications in bioengineering, and provides insights into the study of diseases caused by protein aggregation.

  11. Twin Higgs Asymmetric Dark Matter

    NASA Astrophysics Data System (ADS)

    García García, Isabel; Lasenby, Robert; March-Russell, John

    2015-09-01

    We study asymmetric dark matter (ADM) in the context of the minimal (fraternal) twin Higgs solution to the little hierarchy problem, with a twin sector with gauged SU(3)'×SU(2)', atwin Higgs doublet, and only third-generation twin fermions. Naturalness requires the QCD' scale ΛQCD'≃0.5 - 20 GeV , and that t' is heavy. We focus on the light b' quark regime, mb'≲ΛQCD', where QCD' is characterized by a single scale ΛQCD' with no light pions. A twin baryon number asymmetry leads to a successful dark matter (DM) candidate: the spin-3 /2 twin baryon, Δ'˜b'b'b', with a dynamically determined mass (˜5 ΛQCD') in the preferred range for the DM-to-baryon ratio ΩDM/Ωbaryon≃5 . Gauging the U (1 )' group leads to twin atoms (Δ'-τ' ¯ bound states) that are successful ADM candidates in significant regions of parameter space, sometimes with observable changes to DM halo properties. Direct detection signatures satisfy current bounds, at times modified by dark form factors.

  12. Why Do Nucleosomes Unwrap Asymmetrically?

    PubMed

    de Bruin, Lennart; Tompitak, Marco; Eslami-Mossallam, Behrouz; Schiessel, Helmut

    2016-07-01

    Nucleosomes, DNA spools with a protein core, engage about three-quarters of eukaryotic DNA and play a critical role in chromosomal processes, ranging from gene regulation, recombination, and replication to chromosome condensation. For more than a decade, micromanipulation experiments where nucleosomes are put under tension, as well as the theoretical interpretations of these experiments, have deepened our understanding of the stability and dynamics of nucleosomes. Here we give a theoretical explanation for a surprising new experimental finding: nucleosomes wrapped onto the 601 positioning sequence (the sequence used in most laboratories) respond highly asymmetrically to external forces by always unwrapping from the same end. Using a computational nucleosome model, we show that this asymmetry can be explained by differences in the DNA mechanics of two very short stretches on the wrapped DNA portion. Our finding suggests that the physical properties of nucleosomes, here the response to forces, can be tuned locally by the choice of the underlying base-pair sequence. This leads to a new view of nucleosomes: a physically highly varied set of DNA-protein complexes whose properties can be tuned on evolutionary time scales to their specific function in the genomic context. PMID:26991771

  13. Chaos suppression through asymmetric coupling

    NASA Astrophysics Data System (ADS)

    Bragard, J.; Vidal, G.; Mancini, H.; Mendoza, C.; Boccaletti, S.

    2007-12-01

    We study pairs of identical coupled chaotic oscillators. In particular, we have used Roessler (in the funnel and no funnel regimes), Lorenz, and four-dimensional chaotic Lotka-Volterra models. In all four of these cases, a pair of identical oscillators is asymmetrically coupled. The main result of the numerical simulations is that in all cases, specific values of coupling strength and asymmetry exist that render the two oscillators periodic and synchronized. The values of the coupling strength for which this phenomenon occurs is well below the previously known value for complete synchronization. We have found that this behavior exists for all the chaotic oscillators that we have used in the analysis. We postulate that this behavior is presumably generic to all chaotic oscillators. In order to complete the study, we have tested the robustness of this phenomenon of chaos suppression versus the addition of some Gaussian noise. We found that chaos suppression is robust for the addition of finite noise level. Finally, we propose some extension to this research.

  14. Purification of water by electrocoagulation with an alternating asymmetrical current for stripping voltammetry

    SciTech Connect

    Gorodovykh, V.E.; Kaplin, A.A.; Svishchenko, N.M.; Obraztsov, S.V.

    1987-11-20

    The influence of the flow velocity and the current density on the degree of purification of water by electrocoagulation with an alternating asymmetrical current has been studied. It has been demonstrated that under optimum conditions at pH/sub c/ 11.0-11.5 the residual metal content in the purified water drops to the level n x 10/sup -4/ g/ml; this allows its use in the practice of stripping voltammetry.

  15. Numerical study of Williamson nano fluid flow in an asymmetric channel

    NASA Astrophysics Data System (ADS)

    Akbar, Noreen Sher; Nadeem, S.; Lee, Changhoon; Khan, Zafar Hayat; Haq, Rizwan Ul

    This article investigates with the peristaltic flow of a Williamson nano fluid in an asymmetric channel. The related modeling of the problem has been done in Cartesian coordinate system. Problem has been simplified with the reliable assumptions i.e. long wave length and small Reynolds number. Numerical solutions have been evaluated for stream function, velocity profile, temperature profile, nano particle phenomena and pressure rise. Graphical results have been presented and discussed for various involved parameters.

  16. Luminal pulse velocity in a superluminal medium

    NASA Astrophysics Data System (ADS)

    Amano, Heisuke; Tomita, Makoto

    2015-12-01

    To investigate the physical meaning of pulse peak in fast and slow light media, we investigated propagation of differently shaped pulses experimentally, controlling the sharpness of the pulse peak. Symmetric behavior with respect to fast and slow light was observed in traditional Gaussian pulses; that is, propagated pulses were advanced or delayed, respectively, whereas the pulse shape remained unchanged. This symmetry broke down when the pulse peak was sharpened; in the fast light medium, the sharp pulse peak propagated with luminal velocity, and the transmitted pulse deformed into a characteristic asymmetric profile. In contrast, in the slow light medium, a time-delayed smooth peak appeared with a bending point at t =0 . This symmetry breaking with respect to fast and slow light is a universal characteristic of pulse propagation in causal dispersive systems. The sharp pulse peak can be recognized as a bending nonanalytical point and may be capable of transferring information.

  17. Catalytic asymmetric sulfenylation to structurally diverse dithioketals.

    PubMed

    Liao, Kui; Zhou, Feng; Yu, Jin-Sheng; Gao, Wei-Ming; Zhou, Jian

    2015-11-21

    We report the first example of the highly enantioselective synthesis of structurally diverse chiral dithioketals via asymmetric sulfenylation of various types of S-based nucleophiles, catalyzed by a cheap cinchona alkaloid derivative, dihydroquinine. PMID:26399606

  18. GPM Sees Tropical Storm Danny's Asymmetric Rainfall

    NASA Video Gallery

    On Aug. 19, GPM saw Danny's rain structure was still asymmetric as noted by the large rain band (identified by the green arc indicating moderate rain) being located mainly on the eastern side of th...

  19. Asymmetric cryptography based on wavefront sensing

    NASA Astrophysics Data System (ADS)

    Peng, Xiang; Wei, Hengzheng; Zhang, Peng

    2006-12-01

    A system of asymmetric cryptography based on wavefront sensing (ACWS) is proposed for the first time to our knowledge. One of the most significant features of the asymmetric cryptography is that a trapdoor one-way function is required and constructed by analogy to wavefront sensing, in which the public key may be derived from optical parameters, such as the wavelength or the focal length, while the private key may be obtained from a kind of regular point array. The ciphertext is generated by the encoded wavefront and represented with an irregular array. In such an ACWS system, the encryption key is not identical to the decryption key, which is another important feature of an asymmetric cryptographic system. The processes of asymmetric encryption and decryption are formulized mathematically and demonstrated with a set of numerical experiments.

  20. Asymmetric cryptography based on wavefront sensing.

    PubMed

    Peng, Xiang; Wei, Hengzheng; Zhang, Peng

    2006-12-15

    A system of asymmetric cryptography based on wavefront sensing (ACWS) is proposed for the first time to our knowledge. One of the most significant features of the asymmetric cryptography is that a trapdoor one-way function is required and constructed by analogy to wavefront sensing, in which the public key may be derived from optical parameters, such as the wavelength or the focal length, while the private key may be obtained from a kind of regular point array. The ciphertext is generated by the encoded wavefront and represented with an irregular array. In such an ACWS system, the encryption key is not identical to the decryption key, which is another important feature of an asymmetric cryptographic system. The processes of asymmetric encryption and decryption are formulized mathematically and demonstrated with a set of numerical experiments. PMID:17130909

  1. Velocity Based Modulus Calculations

    NASA Astrophysics Data System (ADS)

    Dickson, W. C.

    2007-12-01

    A new set of equations are derived for the modulus of elasticity E and the bulk modulus K which are dependent only upon the seismic wave propagation velocities Vp, Vs and the density ρ. The three elastic moduli, E (Young's modulus), the shear modulus μ (Lamé's second parameter) and the bulk modulus K are found to be simple functions of the density and wave propagation velocities within the material. The shear and elastic moduli are found to equal the density of the material multiplied by the square of their respective wave propagation-velocities. The bulk modulus may be calculated from the elastic modulus using Poisson's ratio. These equations and resultant values are consistent with published literature and values in both magnitude and dimension (N/m2) and are applicable to the solid, liquid and gaseous phases. A 3D modulus of elasticity model for the Parkfield segment of the San Andreas Fault is presented using data from the wavespeed model of Thurber et al. [2006]. A sharp modulus gradient is observed across the fault at seismic depths, confirming that "variation in material properties play a key role in fault segmentation and deformation style" [Eberhart-Phillips et al., 1993] [EPM93]. The three elastic moduli E, μ and K may now be calculated directly from seismic pressure and shear wave propagation velocities. These velocities may be determined using conventional seismic reflection, refraction or transmission data and techniques. These velocities may be used in turn to estimate the density. This allows velocity based modulus calculations to be used as a tool for geophysical analysis, modeling, engineering and prospecting.

  2. Diffusivity in asymmetric Yukawa ionic mixtures in dense plasmas

    NASA Astrophysics Data System (ADS)

    Haxhimali, Tomorr; Rudd, Robert E.; Cabot, William H.; Graziani, Frank R.

    2014-08-01

    In this paper we present molecular dynamics (MD) calculations of the interdiffusion coefficient for asymmetric mixed plasma for thermodynamic conditions relevant to astrophysical and inertial confinement fusion plasmas. Specifically, we consider mixtures of deuterium and argon at temperatures of 100-500 eV and a number density ˜1025 ions/cm3. The motion of 30 000-120 000 ions is simulated in which the ions interact via the Yukawa (screened Coulomb) potential. The electric field of the electrons is included in this effective interaction; the electrons are not simulated explicitly. The species diffusivity is then calculated using the Green-Kubo approach using an integral of the interdiffusion current autocorrelation function, a quantity calculated in the equilibrium MD simulations. Our MD simulation results show that a widely used expression relating the interdiffusion coefficient with the concentration-weighted sum of self-diffusion coefficients overestimates the interdiffusion coefficient. We argue that this effect due to cross-correlation terms in velocities is characteristic of asymmetric mixed plasmas. Comparison of the MD results with predictions of kinetic theories also shows a discrepancy with MD giving effectively a larger Coulomb logarithm.

  3. Diffusivity in asymmetric Yukawa ionic mixtures in dense plasmas.

    PubMed

    Haxhimali, Tomorr; Rudd, Robert E; Cabot, William H; Graziani, Frank R

    2014-08-01

    In this paper we present molecular dynamics (MD) calculations of the interdiffusion coefficient for asymmetric mixed plasma for thermodynamic conditions relevant to astrophysical and inertial confinement fusion plasmas. Specifically, we consider mixtures of deuterium and argon at temperatures of 100-500 eV and a number density ∼10(25) ions/cm(3). The motion of 30,000-120,000 ions is simulated in which the ions interact via the Yukawa (screened Coulomb) potential. The electric field of the electrons is included in this effective interaction; the electrons are not simulated explicitly. The species diffusivity is then calculated using the Green-Kubo approach using an integral of the interdiffusion current autocorrelation function, a quantity calculated in the equilibrium MD simulations. Our MD simulation results show that a widely used expression relating the interdiffusion coefficient with the concentration-weighted sum of self-diffusion coefficients overestimates the interdiffusion coefficient. We argue that this effect due to cross-correlation terms in velocities is characteristic of asymmetric mixed plasmas. Comparison of the MD results with predictions of kinetic theories also shows a discrepancy with MD giving effectively a larger Coulomb logarithm. PMID:25215836

  4. Optimization of backward giant circle technique on the asymmetric bars.

    PubMed

    Hiley, Michael J; Yeadon, Maurice R

    2007-11-01

    The release window for a given dismount from the asymmetric bars is the period of time within which release results in a successful dismount. Larger release windows are likely to be associated with more consistent performance because they allow a greater margin for error in timing the release. A computer simulation model was used to investigate optimum technique for maximizing release windows in asymmetric bars dismounts. The model comprised four rigid segments with the elastic properties of the gymnast and bar modeled using damped linear springs. Model parameters were optimized to obtain a close match between simulated and actual performances of three gymnasts in terms of rotation angle (1.5 degrees ), bar displacement (0.014 m), and release velocities (<1%). Three optimizations to maximize the release window were carried out for each gymnast involving no perturbations, 10-ms perturbations, and 20-ms perturbations in the timing of the shoulder and hip joint movements preceding release. It was found that the optimizations robust to 20-ms perturbations produced release windows similar to those of the actual performances whereas the windows for the unperturbed optimizations were up to twice as large. It is concluded that robustness considerations must be included in optimization studies in order to obtain realistic results and that elite performances are likely to be robust to timing perturbations of the order of 20 ms. PMID:18089928

  5. The cosmology of asymmetric brane modified gravity

    SciTech Connect

    O'Callaghan, Eimear; Gregory, Ruth; Pourtsidou, Alkistis E-mail: ppxap1@nottingham.ac.uk

    2009-09-01

    We consider the asymmetric branes model of modified gravity, which can produce late time acceleration of the universe and compare the cosmology of this model to the standard ΛCDM model and to the DGP braneworld model. We show how the asymmetric cosmology at relevant physical scales can be regarded as a one-parameter extension of the DGP model, and investigate the effect of this additional parameter on the expansion history of the universe.

  6. Modeling Asymmetric Rolling Process of Mg alloys

    SciTech Connect

    Cho, Jaehyung; Kim, Hyung-Wuk; Kang, Suk-Bong

    2010-06-15

    Asymmetric deformation during rolling can arise in various ways: difference in the radii, speeds, frictions of the top and bottom rolls. Asymmetric warm rolling processes of magnesium alloys were modeled using a lagrangian incremental approach. A constitutive equation representing flow behaviors of AZ31 magnesium alloys during warm deformation was implemented to the modeling. Various roll speed ratios were introduced to investigate deformation behaviors of the magnesium alloys. Bending and texturing of the strips were examined.

  7. Determination of the functioning parameters in asymmetrical flow field-flow fractionation with an exponential channel.

    PubMed

    Déjardin, P

    2013-08-30

    The flow conditions in normal mode asymmetric flow field-flow fractionation are determined to approach the high retention limit with the requirement d≪l≪w, where d is the particle diameter, l the characteristic length of the sample exponential distribution and w the channel height. The optimal entrance velocity is determined from the solute characteristics, the channel geometry (exponential to rectangular) and the membrane properties, according to a model providing the velocity fields all over the cell length. In addition, a method is proposed for in situ determination of the channel height. PMID:23885667

  8. SiO MASERS IN ASYMMETRIC MIRAS. II. R CANCRI

    SciTech Connect

    Cotton, W. D.; Ragland, S.; Pluzhnik, E. A.; Danchi, W. C.; Traub, W. A.; Lacasse, M. G.

    2009-12-01

    This is the second paper in a series of multi-epoch observations of the SiO masers at 7 mm wavelength in several asymptotic giant branch stars from a sample of Mira variable stars showing evidence of asymmetric structure in the infrared. These stars have been observed interferometrically in the infrared by the Infrared Optical Telescope Array and with Very Long Baseline Array measurements of the SiO masers. In this paper, we present the observations of R Cancri (R Cnc). The systemic velocity of R Cnc is estimated to be 15.8 {+-} 0.2 km s{sup -1}. A comparison is made with the model calculations of Gray et al. which predict some but not all observed features.

  9. The basic mechanics of bipedal walking lead to asymmetric behavior.

    PubMed

    Gregg, Robert D; Degani, Amir; Dhaher, Yasin; Lynch, Kevin M

    2011-01-01

    This paper computationally investigates whether gait asymmetries can be attributed in part to basic bipedal mechanics independent of motor control. Using a symmetrical rigid-body model known as the compass-gait biped, we show that changes in environmental or physiological parameters can facilitate asymmetry in gait kinetics at fast walking speeds. In the environmental case, the asymmetric family of high-speed gaits is in fact more stable than the symmetric family of low-speed gaits. These simulations suggest that lower extremity mechanics might play a direct role in functional and pathological asymmetries reported in human walking, where velocity may be a common variable in the emergence and growth of asymmetry. PMID:22275657

  10. [Asymmetric dimethylarginine: predictor of cardiovascular diseases?].

    PubMed

    Németh, Balázs; Kustán, Péter; Németh, Ádám; Lenkey, Zsófia; Cziráki, Attila; Kiss, István; Sulyok, Endre; Ajtay, Zénó

    2016-03-27

    Cardiovascular diseases are the most common diseases worldwide. They are responsible for one third of global deaths and they are the leading cause of disability, too. The usage of different levels of prevention in combination with effective risk assessment improved these statistical data. Risk assessment based on classic risk factors has recently been supported with several new markers, such as asymmetric dimethylarginine, which is an endogenous competitive inhibitor of nitric oxide synthase. Elevated levels of asymmetric dimethylarginine have been reported in obese, smoker, hypercholesterolemic, hypertensive and diabetic patients. According to previous studies, asymmetric dimethylarginine is a suitable indicator of endothelial dysfunction, which is held to be the preceding condition before atherosclerosis. Several researches found positive correlation between higher levels of asymmetric dimethylarginine and coronary artery disease onset, or progression of existing coronary disease. According to a study involving 3000 patients, asymmetric dimethylarginine is an independent risk factor of cardiovascular mortality in patients with coronary artery disease. This article summarizes the role of asymmetric dimethylarginine in prediction of cardiovascular diseases, and underlines its importance in cardiovascular prevention. PMID:26996894

  11. On the wake flow of asymmetrically beveled trailing edges

    NASA Astrophysics Data System (ADS)

    Guan, Yaoyi; Pröbsting, Stefan; Stephens, David; Gupta, Abhineet; Morris, Scott C.

    2016-05-01

    Trailing edge and wake flows are of interest for a wide range of applications. Small changes in the design of asymmetrically beveled or semi-rounded trailing edges can result in significant difference in flow features which are relevant for the aerodynamic performance, flow-induced structural vibration and aerodynamically generated sound. The present study describes in detail the flow field characteristics around a family of asymmetrically beveled trailing edges with an enclosed trailing-edge angle of 25° and variable radius of curvature R. The flow fields over the beveled trailing edges are described using data obtained by particle image velocimetry (PIV) experiments. The flow topology for different trailing edges was found to be strongly dependent on the radius of curvature R, with flow separation occurring further downstream as R increases. This variation in the location of flow separation influences the aerodynamic force coefficients, which were evaluated from the PIV data using a control volume approach. Two-point correlations of the in-plane velocity components are considered to assess the structure in the flow field. The analysis shows large-scale coherent motions in the far wake, which are associated with vortex shedding. The wake thickness parameter yf is confirmed as an appropriate length scale to characterize this large-scale roll-up motion in the wake. The development in the very near wake was found to be critically dependent on R. In addition, high-speed PIV measurements provide insight into the spectral characteristics of the turbulent fluctuations. Based on the time-resolved flow field data, the frequency range associated with the shedding of coherent vortex pairs in the wake is identified. By means of time-correlation of the velocity components, turbulent structures are found to convect from the attached or separated shear layers without distinct separation point into the wake.

  12. Asymmetric supernova remnants generated by Galactic, massive runaway stars

    NASA Astrophysics Data System (ADS)

    Meyer, D. M.-A.; Langer, N.; Mackey, J.; Velázquez, P. F.; Gusdorf, A.

    2015-07-01

    After the death of a runaway massive star, its supernova shock wave interacts with the bow shocks produced by its defunct progenitor, and may lose energy, momentum and its spherical symmetry before expanding into the local interstellar medium (ISM). We investigate whether the initial mass and space velocity of these progenitors can be associated with asymmetric supernova remnants. We run hydrodynamical models of supernovae exploding in the pre-shaped medium of moving Galactic core-collapse progenitors. We find that bow shocks that accumulate more than about 1.5 M⊙ generate asymmetric remnants. The shock wave first collides with these bow shocks 160-750 yr after the supernova, and the collision lasts until 830-4900 yr. The shock wave is then located 1.35-5 pc from the centre of the explosion, and it expands freely into the ISM, whereas in the opposite direction it is channelled into the region of undisturbed wind material. This applies to an initially 20 M⊙ progenitor moving with velocity 20 km s-1 and to our initially 40 M⊙ progenitor. These remnants generate mixing of ISM gas, stellar wind and supernova ejecta that is particularly important upstream from the centre of the explosion. Their light curves are dominated by emission from optically thin cooling and by X-ray emission of the shocked ISM gas. We find that these remnants are likely to be observed in the [O III] λ 5007 spectral line emission or in the soft energy-band of X-rays. Finally, we discuss our results in the context of observed Galactic supernova remnants such as 3C 391 and the Cygnus Loop.

  13. Quantitative velocity modulation spectroscopy.

    PubMed

    Hodges, James N; McCall, Benjamin J

    2016-05-14

    Velocity Modulation Spectroscopy (VMS) is arguably the most important development in the 20th century for spectroscopic study of molecular ions. For decades, interpretation of VMS lineshapes has presented challenges due to the intrinsic covariance of fit parameters including velocity modulation amplitude, linewidth, and intensity. This limitation has stifled the growth of this technique into the quantitative realm. In this work, we show that subtle changes in the lineshape can be used to help address this complexity. This allows for determination of the linewidth, intensity relative to other transitions, velocity modulation amplitude, and electric field strength in the positive column of a glow discharge. Additionally, we explain the large homogeneous component of the linewidth that has been previously described. Using this component, the ion mobility can be determined. PMID:27179476

  14. Fluidic angular velocity sensor

    NASA Technical Reports Server (NTRS)

    Berdahl, C. M. (Inventor)

    1986-01-01

    A fluidic sensor providing a differential pressure signal proportional to the angular velocity of a rotary input is described. In one embodiment the sensor includes a fluid pump having an impeller coupled to a rotary input. A housing forming a constricting fluid flow chamber is connected to the fluid input of the pump. The housing is provided with a fluid flow restrictive input to the flow chamber and a port communicating with the interior of the flow chamber. The differential pressure signal measured across the flow restrictive input is relatively noise free and proportional to the square of the angular velocity of the impeller. In an alternative embodiment, the flow chamber has a generally cylindrical configuration and plates having flow restrictive apertures are disposed within the chamber downstream from the housing port. In this embodiment, the differential pressure signal is found to be approximately linear with the angular velocity of the impeller.

  15. Quantitative velocity modulation spectroscopy

    NASA Astrophysics Data System (ADS)

    Hodges, James N.; McCall, Benjamin J.

    2016-05-01

    Velocity Modulation Spectroscopy (VMS) is arguably the most important development in the 20th century for spectroscopic study of molecular ions. For decades, interpretation of VMS lineshapes has presented challenges due to the intrinsic covariance of fit parameters including velocity modulation amplitude, linewidth, and intensity. This limitation has stifled the growth of this technique into the quantitative realm. In this work, we show that subtle changes in the lineshape can be used to help address this complexity. This allows for determination of the linewidth, intensity relative to other transitions, velocity modulation amplitude, and electric field strength in the positive column of a glow discharge. Additionally, we explain the large homogeneous component of the linewidth that has been previously described. Using this component, the ion mobility can be determined.

  16. MSE velocity survey

    NASA Astrophysics Data System (ADS)

    Schimd, C.; Courtois, H.; Koda, J.

    2015-12-01

    A huge velocity survey based on the Maunakea Spectroscopic Explorer facility (MSE) is proposed, aiming at investigating the structure and dynamics of the cosmic web over 3π steradians up to ˜1 Gpc and at unprecedented spatial resolution, its relationship with the galaxy formation process, and the bias between galaxies and dark matter during the last three billions years. The cross-correlation of velocity and density fields will further allow the probe any deviation from General Relativity by measuring the the linear-growth rate of cosmic structures at precision competitive with high-redshift spectroscopic redshift surveys.

  17. DVL Angular Velocity Recorder

    NASA Technical Reports Server (NTRS)

    Liebe, Wolfgang

    1944-01-01

    In many studies, especially of nonstationary flight motion, it is necessary to determine the angular velocities at which the airplane rotates about its various axes. The three-component recorder is designed to serve this purpose. If the angular velocity for one flight attitude is known, other important quantities can be derived from its time rate of change, such as the angular acceleration by differentiations, or - by integration - the angles of position of the airplane - that is, the angles formed by the airplane axes with the axis direction presented at the instant of the beginning of the motion that is to be investigated.

  18. Velocity pump reaction turbine

    DOEpatents

    House, P.A.

    An expanding hydraulic/two-phase velocity pump reaction turbine including a dual concentric rotor configuration with an inter-rotor annular flow channel in which the inner rotor is mechanically driven by the outer rotor. In another embodiment, the inner rotor is immobilized and provided with gas recovery ports on its outer surface by means of which gas in solution may be recovered. This velocity pump reaction turbine configuration is capable of potential energy conversion efficiencies of up to 70%, and is particularly suited for geothermal applications.

  19. Velocity pump reaction turbine

    DOEpatents

    House, Palmer A.

    1984-01-01

    An expanding hydraulic/two-phase velocity pump reaction turbine including a dual concentric rotor configuration with an inter-rotor annular flow channel in which the inner rotor is mechanically driven by the outer rotor. In another embodiment, the inner rotor is immobilized and provided with gas recovery ports on its outer surface by means of which gas in solution may be recovered. This velocity pump reaction turbine configuration is capable of potential energy conversion efficiencies of up to 70%, and is particularly suited for geothermal applications.

  20. Velocity pump reaction turbine

    DOEpatents

    House, Palmer A.

    1982-01-01

    An expanding hydraulic/two-phase velocity pump reaction turbine including a dual concentric rotor configuration with an inter-rotor annular flow channel in which the inner rotor is mechanically driven by the outer rotor. In another embodiment, the inner rotor is immobilized and provided with gas recovery ports on its outer surface by means of which gas in solution may be recovered. This velocity pump reaction turbine configuration is capable of potential energy conversion efficiencies of up to 70%, and is particularly suited for geothermal applications.

  1. Modeling Terminal Velocity

    ERIC Educational Resources Information Center

    Brand, Neal; Quintanilla, John A.

    2013-01-01

    Using a simultaneously falling softball as a stopwatch, the terminal velocity of a whiffle ball can be obtained to surprisingly high accuracy with only common household equipment. This classroom activity engages students in an apparently daunting task that nevertheless is tractable, using a simple model and mathematical techniques at their…

  2. New insights into the nature of the asymmetrical flow of shear-thinning polymer solutions in transitional pipe flow

    NASA Astrophysics Data System (ADS)

    Wen, Chaofan; Poole, Robert; Dennis, David

    2014-11-01

    Previous studies of shear-thinning fluids in pipe flow discovered that, although the time-averaged velocity profile was axisymmetric when the flow was laminar or fully turbulent, contrary to expectations it was asymmetric in the laminar-turbulent transition regime. The general consensus of these previous experiments was that the location of the peak velocity remained at a fixed point in space. We present new experimental data which demonstrates that this is in fact not the case. The experiment was performed using an aqueous solution of Xanthan Gum (0.15 wt%), a shear-thinning polymer solution. Stereoscopic particle image velocimetry (SPIV) was used to measure the 3C velocity vectors over the entire circular cross-section of the pipe, 220 pipe diameters downstream of the inlet. The exhibition of significant departures from axisymmetry in transitional flows of shear-thinning fluids was observed and in addition it was discovered that the asymmetric flow pattern is not stationary, although the peak velocity does preferentially arise at certain azimuthal locations. The ensemble average of all the SPIV data results in the recovery of the velocity profile measured using laser Doppler velocimetry in previous studies: still asymmetric but to a lesser extent than the instantaneous flow.

  3. Tunable symmetric and asymmetric resonances in an asymmetrical split-ring metamaterial

    NASA Astrophysics Data System (ADS)

    Shi, J. H.; Zhu, Z.; Ma, H. F.; Jiang, W. X.; Cui, T. J.

    2012-10-01

    We demonstrate the coexistence of two tunable symmetric and asymmetric resonances in a metamaterial composed of asymmetrical split-rings (ASRs) patterned on a dielectric layer numerically and experimentally. The full-wave simulation and measurement results demonstrate that the metamaterial reveals a symmetric cross-polarization transmission band with a ripple-free peak and asymmetric co-polarization transmission bands characterized by trapped-mode resonances. Both symmetric and asymmetric resonances can be easily tuned via the incident angle of electromagnetic waves. The resonant excitation and coupling of the electric and magnetic dipole moments contribute to the conversion of two orthogonal linear polarizations. The ASR metamaterial shows a directionally asymmetric transmission for both linearly and circularly polarized waves for large angles of incidence. The proposed ASR metamaterial is of importance to develop novel metamaterial-based devices.

  4. Asymmetric biocatalysis with microbial enzymes and cells.

    PubMed

    Wohlgemuth, Roland

    2010-06-01

    Microbial enzymes and cells continue to be important tools and nature's privileged chiral catalysts for performing asymmetric biocatalysis from the analytical small scale to the preparative and large scale in synthesis and degradation. The application of biocatalysts for preparing molecular asymmetry has achieved high efficiency, enantioselectivity and yield and is experiencing today a worldwide renaissance. Recent developments in the discovery, development and production of stable biocatalysts, in the design of new biocatalytic processes and in the product recovery and purification processes have made biocatalytic approaches using microbial cells and enzymes attractive choices for the synthesis of chiral compounds. The methodologies of kinetic resolution and kinetic asymmetric transformation, dynamic kinetic resolution and deracemization, desymmetrization, asymmetric synthesis with or without diastereo control and multi-step asymmetric biocatalysis are finding increasing applications in research. The ever-increasing use of hydrolytic enzymes has been accompanied by new applications of oxidoreductases, transferases and lyases. Isomerases, already used in large-scale processes, and ligases, are emerging as interesting biocatalysts for new synthetic applications. The production of a wide variety of industrial products by asymmetric biocatalysis has even become the preferred method of production. PMID:20434391

  5. Control of apoptosis by asymmetric cell division.

    PubMed

    Hatzold, Julia; Conradt, Barbara

    2008-04-01

    Asymmetric cell division and apoptosis (programmed cell death) are two fundamental processes that are important for the development and function of multicellular organisms. We have found that the processes of asymmetric cell division and apoptosis can be functionally linked. Specifically, we show that asymmetric cell division in the nematode Caenorhabditis elegans is mediated by a pathway involving three genes, dnj-11 MIDA1, ces-2 HLF, and ces-1 Snail, that directly control the enzymatic machinery responsible for apoptosis. Interestingly, the MIDA1-like protein GlsA of the alga Volvox carteri, as well as the Snail-related proteins Snail, Escargot, and Worniu of Drosophila melanogaster, have previously been implicated in asymmetric cell division. Therefore, C. elegans dnj-11 MIDA1, ces-2 HLF, and ces-1 Snail may be components of a pathway involved in asymmetric cell division that is conserved throughout the plant and animal kingdoms. Furthermore, based on our results, we propose that this pathway directly controls the apoptotic fate in C. elegans, and possibly other animals as well. PMID:18399720

  6. Pd and Mo Catalyzed Asymmetric Allylic Alkylation

    PubMed Central

    Trost, Barry M.

    2012-01-01

    The ability to control the alkylation of organic substrates becomes ever more powerful by using metal catalysts. Among the major benefits of metal catalysis is the possibility to perform such processes asymmetrically using only catalytic amounts of the chiral inducing agent which is a ligand to the metal of the catalyst. A unique aspect of asymmetric metal catalyzed processes is the fact that many mechanisms exist for stereoinduction. Furthermore, using the same catalyst system, many types of bonds including but not limited to C-C, C-N, C-O, C-S, C-P, and C-H can be formed asymmetrically. An overview of this process using palladium and molybdenum based metals being developed in my laboratories and how they influence strategy in synthesizing bioactive molecular targets is presented. PMID:22736934

  7. Asymmetric catalytic transformations in supercritical carbon dioxide

    SciTech Connect

    Feng, Shaoguang; Tumas, W.; Gross, M.F.; Burk, M.J.

    1996-12-31

    Supercritical carbon dioxide can be a useful environmentally benign solvent for a wide range of catalytic reactions. We have been exploring the utility of supercritical carbon dioxide as a reaction medium for catalytic asymmetric transformations. We will present results on the asymmetric hydrogenation of prochiral olefins, ketones, and unsaturated acids by Rh and Ru catalysts containing chiral phosphine ligands using hydrogen or hydrogen transfer agents. We have found that asymmetric catalytic hydrogenation reactions of enamide esters work as well or better in CO{sub 2} than in conventional solvents. We have been able to effect high conversions and ee`s using hydrogen transfer systems such as HCOOH/NEt{sub 3}, We will discuss temperature, pressure and solvent density effects on selectivity and reactivity. Kinetic studies will also be presented in order to understand the enhanced enantioselectivity that we observed in SC CO{sub 2}.

  8. Asymmetric catalysis in complex target synthesis

    PubMed Central

    Taylor, Mark S.; Jacobsen, Eric N.

    2004-01-01

    This article describes three distinct strategies by which stereochemically complex molecules are synthesized and the ways asymmetric catalysis can impact on all three. The development of general methods to prepare synthetically useful building blocks leads to an expanded “chiral pool” of potential starting materials for asymmetric synthesis. The possibility of discovering new reactions to access new types of building blocks is particularly attractive and serves to help define the frontiers of the field. Asymmetric catalysis can also be applied to diastereoselective synthesis such that the stereochemistry of the catalyst, and not that of the substrate, determines the relative configuration of the product. Finally, in reactions where multiple stereocenters are generated simultaneously or in tandem, catalyst and substrate control can operate in a complementary manner to achieve one of many possible stereochemical outcomes selectively. PMID:15020767

  9. Asymmetric soft-error resistant memory

    NASA Technical Reports Server (NTRS)

    Buehler, Martin G. (Inventor); Perlman, Marvin (Inventor)

    1991-01-01

    A memory system is provided, of the type that includes an error-correcting circuit that detects and corrects, that more efficiently utilizes the capacity of a memory formed of groups of binary cells whose states can be inadvertently switched by ionizing radiation. Each memory cell has an asymmetric geometry, so that ionizing radiation causes a significantly greater probability of errors in one state than in the opposite state (e.g., an erroneous switch from '1' to '0' is far more likely than a switch from '0' to'1'. An asymmetric error correcting coding circuit can be used with the asymmetric memory cells, which requires fewer bits than an efficient symmetric error correcting code.

  10. Asymmetric Magnon Excitation by Spontaneous Toroidal Ordering

    NASA Astrophysics Data System (ADS)

    Hayami, Satoru; Kusunose, Hiroaki; Motome, Yukitoshi

    2016-05-01

    The effects of spontaneous toroidal ordering on magnetic excitation are theoretically investigated for a localized spin model that includes a staggered Dzyaloshinsky-Moriya interaction and anisotropic exchange interactions, which arise from the antisymmetric spin-orbit coupling and the multiorbital correlation effect. We show that the model exhibits a Néel-type antiferromagnetic order, which simultaneously accompanies a ferroic toroidal order. We find that the occurrence of toroidal order modulates the magnon dispersion in an asymmetric way with respect to the wave number: a toroidal dipole order on the zigzag chain leads to a band-bottom shift, while a toroidal octupole order on the honeycomb lattice gives rise to a valley splitting. These asymmetric magnon excitations could be a source of unusual magnetic responses, such as nonreciprocal magnon transport. A variety of modulations are discussed while changing the lattice and magnetic symmetries. The implications regarding candidate materials for asymmetric magnon excitations are presented.

  11. IS FS Tau B DRIVING AN ASYMMETRIC JET?

    SciTech Connect

    Liu, Chun-Fan; Shang, Hsien; Takami, Michihiro; Yan, Chi-Hung; Wang, Shiang-Yu; Ohashi, Nagayoshi; Pyo, Tae-Soo; Walter, Frederick M.; Hayashi, Masahiko

    2012-04-10

    FS Tau B is one of the few T Tauri stars that possess a jet and a counterjet as well as an optically visible cavity wall. We obtained images and spectra of its jet-cavity system in the near-infrared H and K bands using the Subaru/Infrared Camera and Spectrograph and detected the jet and the counterjet in the [Fe II] 1.644 {mu}m line for the first time. Within 2'' the blueshifted jet is brighter, whereas beyond {approx}5'' the redshifted counterjet dominates the [Fe II] emission. The innermost blueshifted knot is spectrally resolved to have a large line width of {approx}110 km s{sup -1}, while the innermost redshifted knot appears spectrally unresolved. The velocity ratio of the jet to the counterjet is {approx}1.34, which suggests that FS Tau B is driving an asymmetric jet, similar to those found in several T Tauri stars. Combining with optical observations in the literature, we showed that the blueshifted jet has a lower density and higher excitation than the redshifted counterjet. We suggest that the asymmetry in brightness and velocity is the manifestation of a bipolar outflow driving at different mass-loss rates, while maintaining balance of linear momentum. A full explanation of the asymmetry in the FS Tau B system awaits detail modeling and further investigation of the kinematic structure of the wind-associated cavity walls.

  12. Keep-Left Behavior Induced by Asymmetrically Profiled Walls

    NASA Astrophysics Data System (ADS)

    Oliveira, C. L. N.; Vieira, A. P.; Helbing, D.; Andrade, J. S.; Herrmann, H. J.

    2016-01-01

    We show, computationally and analytically, that asymmetrically shaped walls can organize the flow of pedestrians driven in opposite directions through a corridor. Precisely, a two-lane ordered state emerges in which people always walk on the left-hand side (or right-hand side), controlled by the system's parameters. This effect depends on features of the channel geometry, such as the asymmetry of the profile and the channel width, as well as on the density and the drift velocity of pedestrians, and the intensity of noise. We investigate in detail the influence of these parameters on the flow and discover a crossover between ordered and disordered states. Our results show that an ordered state only appears within a limited range of drift velocities. Moreover, increasing noise may suppress such flow organization, but the flow is always sustained. This is in contrast with the "freezing by heating" phenomenon according to which pedestrians tend to clog in smooth channels for strong noise [Phys. Rev. Lett. 84, 1240 (2000)]. Therefore, the ratchetlike effect proposed here acts on the system not only to induce a "keep-left" behavior but also to prevent the freezing by heating clogging phenomenon. Besides pedestrian flow, this new phenomenon has other potential applications in microfluidics systems.

  13. Microfluidic device with asymmetric electrodes for cell and reagent delivery

    NASA Astrophysics Data System (ADS)

    Lee, Daniel; Xu, Guolin; Tay, Hong Kiat; Yang, Chun; Ying, Jackie Y.

    2006-12-01

    We present the design and fabrication of a micro-electromechanical system (MEMS) device for cell and particle delivery using a combination of AC electrokinetic fluidic flow and negative dielectrophoresis (DEP) force. An array of interdigitated asymmetric microelectrode pairs were used in the planar device. The electrodes produced a net charge in the surrounding fluid, generating an AC electrokinetic fluidic motion. A non-uniform electric field with low actuation frequency from the microelectrode pairs resulted in a negative DEP force, which was responsible for pushing delivery particles away from sedimentation. The experimental results showed that the flow velocity increased rapidly from 267 μm/min to 394 μm/min when the applied frequency was increased from 10 kHz to 70 kHz for a cell-suspending medium buffer solution with a conductivity of 4.7 μS/cm. A maximum delivery velocity of 801 μm/min was obtained when the buffer conductivity was increased to 47 μS/cm with an actuation frequency of 100 kHz.

  14. Asymmetric Membrane Osmotic Capsules for Terbutaline Sulphate

    PubMed Central

    Gobade, N. G.; Koland, Marina; Harish, K. H.

    2012-01-01

    The aim of the present study was to design an asymmetric membrane capsule, an osmotic pump-based drug delivery system of ethyl cellulose for controlled release of terbutaline sulphate. asymmetric membrane capsules contains pore-forming water soluble additive, sorbitol in different concentrations in the capsule shell membrane, which after coming in contact with water, dissolves, resulting in an in situ formation of a microporous structure. The terbutaline sulphate is a β-adrenoreceptor agonist widely used in the treatment of asthma. The oral dosage regimen of terbutaline sulphate is 5 mg twice or thrice daily, the plasma half-life is approximate 3-4 h and it produces GI irritation with extensive first pass metabolism. Hence, terbutaline sulphate was chosen as a model drug with an aim to develop controlled release system. Different formulations of ethyl cellulose were prepared by phase inversion technique using different concentrations of sorbitol as pore forming agent. It was found that the thickness of the prepared asymmetric membrane capsules was increased with increase in concentration of ethyl cellulose and pore forming agent, i.e. sorbitol. The dye release study in water and 10% sodium chloride solution indicates that, the asymmetric membrane capsules follow osmotic principle to release content. The pores formed due to sorbitol were confirmed by microscopic observation of transverse section of capsule membrane. Data of in vitro release study of terbutaline sulphate from asymmetric membrane capsules indicated that, the capsules prepared with 10% and 12.5% of ethyl cellulose and 25% of sorbitol released as much as 97.44% and 76.27% in 12 h, respectively with zero order release rate. Hence asymmetric membrane capsule of 10% ethyl cellulose and 25% of sorbitol is considered as optimum for controlled oral delivery of terbutaline sulphate. PMID:23204625

  15. Asymmetric membrane osmotic capsules for terbutaline sulphate.

    PubMed

    Gobade, N G; Koland, Marina; Harish, K H

    2012-01-01

    The aim of the present study was to design an asymmetric membrane capsule, an osmotic pump-based drug delivery system of ethyl cellulose for controlled release of terbutaline sulphate. asymmetric membrane capsules contains pore-forming water soluble additive, sorbitol in different concentrations in the capsule shell membrane, which after coming in contact with water, dissolves, resulting in an in situ formation of a microporous structure. The terbutaline sulphate is a β-adrenoreceptor agonist widely used in the treatment of asthma. The oral dosage regimen of terbutaline sulphate is 5 mg twice or thrice daily, the plasma half-life is approximate 3-4 h and it produces GI irritation with extensive first pass metabolism. Hence, terbutaline sulphate was chosen as a model drug with an aim to develop controlled release system. Different formulations of ethyl cellulose were prepared by phase inversion technique using different concentrations of sorbitol as pore forming agent. It was found that the thickness of the prepared asymmetric membrane capsules was increased with increase in concentration of ethyl cellulose and pore forming agent, i.e. sorbitol. The dye release study in water and 10% sodium chloride solution indicates that, the asymmetric membrane capsules follow osmotic principle to release content. The pores formed due to sorbitol were confirmed by microscopic observation of transverse section of capsule membrane. Data of in vitro release study of terbutaline sulphate from asymmetric membrane capsules indicated that, the capsules prepared with 10% and 12.5% of ethyl cellulose and 25% of sorbitol released as much as 97.44% and 76.27% in 12 h, respectively with zero order release rate. Hence asymmetric membrane capsule of 10% ethyl cellulose and 25% of sorbitol is considered as optimum for controlled oral delivery of terbutaline sulphate. PMID:23204625

  16. Asymmetric acoustic transmission in multiple frequency bands

    SciTech Connect

    Sun, Hong-xiang; Yuan, Shou-qi; Zhang, Shu-yi

    2015-11-23

    We report both experimentally and numerically that the multi-band device of the asymmetric acoustic transmission is realized by placing two periodic gratings with different periods on both sides of two brass plates immersed in water. The asymmetric acoustic transmission can exist in four frequency bands below 1500 kHz, which arises from the interaction between various diffractions from the two gratings and Lamb modes in the brass plates immersed in water. The results indicate that the device has the advantages of multiple band, broader bandwidth, and simpler structure. Our finding should have great potential applications in ultrasonic devices.

  17. Asymmetric counter propagation of domain walls

    NASA Astrophysics Data System (ADS)

    Andrade-Silva, I.; Clerc, M. G.; Odent, V.

    2016-07-01

    Far from equilibrium systems show different states and domain walls between them. These walls, depending on the type of connected equilibria, exhibit a rich spatiotemporal dynamics. Here, we investigate the asymmetrical counter propagation of domain walls in an in-plane-switching cell filled with a nematic liquid crystal. Experimentally, we characterize the shape and speed of the domain walls. Based on the molecular orientation, we infer that the counter propagative walls have different elastic deformations. These deformations are responsible of the asymmetric counter propagating fronts. Theoretically, based on symmetry arguments, we propose a simple bistable model under the influence of a nonlinear gradient, which qualitatively describes the observed dynamics.

  18. Combined trellis coding with asymmetric modulations

    NASA Technical Reports Server (NTRS)

    Divsalar, D.; Simon, M. K.

    1985-01-01

    The use of asymmetric signal constellations combined with optimized trellis coding to improve the performance of coded systems without increasing the average or peak power, or changing the bandwidth constraints of a system is discussed. The trellis code, asymmetric signal set, and Viterbi decoder of the system model are examined. The procedures for assigning signals to state transitions of the trellis code are described; the performance of the trellis coding system is evaluated. Examples of AM, QAM, and MPSK modulations with short memory trellis codes are presented.

  19. Asymmetric and Unilateral Hearing Loss in Children

    PubMed Central

    Vila, Peter; Lieu, Judith E. C.

    2015-01-01

    Asymmetric and unilateral hearing losses in children have traditionally been underappreciated, but health care practitioners are now beginning to understand their effect on development and the underlying pathophysiologic mechanisms. The common wisdom among medical and educational professionals has been that at least one normal hearing or near-normal hearing ear was sufficient for typical speech and language development in children. The objective of this review is to illustrate to the non-otolaryngologist the consequences of asymmetric and unilateral hearing loss in children on developmental and educational outcomes. In the process, etiology, detection, and management are discussed. Lastly, implications for further research are considered. PMID:26004144

  20. Cell-sized asymmetric lipid vesicles facilitate the investigation of asymmetric membranes.

    PubMed

    Kamiya, Koki; Kawano, Ryuji; Osaki, Toshihisa; Akiyoshi, Kazunari; Takeuchi, Shoji

    2016-09-01

    Asymmetric lipid giant vesicles have been used to model the biochemical reactions in cell membranes. However, methods for producing asymmetric giant vesicles lead to the inclusion of an organic solvent layer that affects the mechanical and physical characteristics of the membrane. Here we describe the formation of asymmetric giant vesicles that include little organic solvent, and use them to investigate the dynamic responses of lipid molecules in the vesicle membrane. We formed the giant vesicles via the inhomogeneous break-up of a lipid microtube generated by applying a jet flow to an asymmetric planar lipid bilayer. The asymmetric giant vesicles showed a lipid flip-flop behaviour in the membrane, superficially similar to the lipid flip-flop activity observed in apoptotic cells. In vitro synthesis of membrane proteins into the asymmetric giant vesicles revealed that the lipid asymmetry in bilayer membranes improves the reconstitution ratio of membrane proteins. Our asymmetric giant vesicles will be useful in elucidating lipid-lipid and lipid-membrane protein interactions involved in the regulation of cellular functions. PMID:27554415

  1. Bell-inequality tests using asymmetric entangled coherent states in asymmetric lossy environments

    NASA Astrophysics Data System (ADS)

    Park, Chae-Yeun; Jeong, Hyunseok

    2015-04-01

    We study an asymmetric form of the two-mode entangled coherent state (ECS), where the two local amplitudes have different values, as a tool for testing the Bell-Clauser-Horne-Shimony-Holt (Bell-CHSH) inequality. We find that the asymmetric ECSs have obvious advantages over the symmetric form of ECSs in testing the Bell-CHSH inequality. We further study an asymmetric strategy in distributing an ECS over a lossy environment and find that such a scheme can significantly increase violation of the inequality.

  2. The settling velocity and shape distortion of drops in a uniform electric field

    NASA Astrophysics Data System (ADS)

    Homsy, G. M.

    2005-11-01

    We theoretically and experimentally investigate the settling velocity and deformation of a dielectric liquid drop in a second dielectric liquid subject to a uniform electric field, E. Both shape distortion and charge convection, when coupled with the asymmetric velocity profiles, will produce a net drag and a shift in the settling speed. Perturbation methods for small shape distortion and small charge convection are used to solve the problem. Corrections to the settling velocity from both contributions are combined linearly at the lowest order, and show a dependence on the drop size. The shape distortion due to charge convection is given up to second order, with the result that the distortion is asymmetric. Experiments are performed to measure the settling velocity and deformation of PhenylMethylsiloxane-DiMethylsiloxane (PMM) drops in castor oil. The experimental results are in qualitative agreement with the theory: the symmetric and asymmetric deformations and the change in settling velocity are all proportional to E^2, as predicted, and the settling speed shows the correct trends with drop size. Quantitative agreement is lacking, presumably due to the imprecision of the fluid properties, but the theory can fit all the data with reasonable choices for these properties.

  3. The settling velocity and shape distortion of drops in a uniform electric field

    NASA Astrophysics Data System (ADS)

    Xu, Xiumei; Homsy, G. M.

    2006-10-01

    We theoretically and experimentally investigate the settling velocity and deformation of a leaky dielectric liquid drop in a second leaky dielectric liquid subject to a uniform electric field, E. Both shape distortion and charge convection, when coupled with the asymmetric velocity profiles, will produce a net drag and a shift in the settling speed. Perturbation methods for small shape distortion and small charge convection are used to solve the problem. Corrections to the settling velocity from both contributions are combined linearly at the lowest order, and show a dependence on the drop size. The shape distortion due to charge convection is known to be asymmetric. Experiments are performed to measure the settling velocity and deformation of phenylmethylsiloxane-dimethylsiloxane (PMM) drops in castor oil. The experimental results are in qualitative agreement with the theory: the symmetric and asymmetric deformations and the change in settling velocity are all proportional to E(2) , as predicted, and the settling speed shows the correct trends with drop size. Quantitative agreement is lacking, presumably due to the imprecision of the fluid properties, but the theory can fit all the data with reasonable choices for these properties.

  4. Sensitivity to Auditory Velocity Contrast.

    PubMed

    Locke, Shannon M; Leung, Johahn; Carlile, Simon

    2016-01-01

    A natural auditory scene often contains sound moving at varying velocities. Using a velocity contrast paradigm, we compared sensitivity to velocity changes between continuous and discontinuous trajectories. Subjects compared the velocities of two stimulus intervals that moved along a single trajectory, with and without a 1 second inter stimulus interval (ISI). We found thresholds were threefold larger for velocity increases in the instantaneous velocity change condition, as compared to instantaneous velocity decreases or thresholds for the delayed velocity transition condition. This result cannot be explained by the current static "snapshot" model of auditory motion perception and suggest a continuous process where the percept of velocity is influenced by previous history of stimulation. PMID:27291488

  5. Sensitivity to Auditory Velocity Contrast

    PubMed Central

    Locke, Shannon M.; Leung, Johahn; Carlile, Simon

    2016-01-01

    A natural auditory scene often contains sound moving at varying velocities. Using a velocity contrast paradigm, we compared sensitivity to velocity changes between continuous and discontinuous trajectories. Subjects compared the velocities of two stimulus intervals that moved along a single trajectory, with and without a 1 second inter stimulus interval (ISI). We found thresholds were threefold larger for velocity increases in the instantaneous velocity change condition, as compared to instantaneous velocity decreases or thresholds for the delayed velocity transition condition. This result cannot be explained by the current static “snapshot” model of auditory motion perception and suggest a continuous process where the percept of velocity is influenced by previous history of stimulation. PMID:27291488

  6. Measurement of the flow velocity in unmagnetized plasmas by counter propagating ion-acoustic waves

    SciTech Connect

    Ma, J.X.; Li Yangfang; Xiao Delong; Li Jingju; Li Yiren

    2005-06-15

    The diffusion velocity of an inhomogeneous unmagnetized plasma is measured by means of the phase velocities of ion-acoustic waves propagating along and against the direction of the plasma flow. Combined with the measurement of the plasma density distributions by usual Langmuir probes, the method is applied to measure the ambipolar diffusion coefficient and effective ion collision frequency in inhomogeneous plasmas formed in an asymmetrically discharged double-plasma device. Experimental results show that the measured flow velocities, diffusion coefficients, and effective collision frequencies are in agreement with ion-neutral collision dominated diffusion theory.

  7. Velocity distribution of neutral species during magnetron sputtering by Fabry-Perot interferometry

    SciTech Connect

    Britun, N.; Han, J. G.; Oh, S.-G.

    2008-04-07

    The velocity distribution of a metallic neutral species sputtered in a dc magnetron discharge was measured using a planar Fabry-Perot interferometer and a hollow cathode lamp as a reference source. The measurement was performed under different angles of view relative to the target surface. The velocity distribution function in the direction perpendicular to the target becomes asymmetrical as the Ar pressure decreases, whereas it remains nearly symmetrical when the line of sight is parallel to the target surface. The average velocity of the sputtered Ti atoms was measured to be about 2 km/s.

  8. Acoustic velocity meter systems

    USGS Publications Warehouse

    Laenen, Antonius

    1985-01-01

    Acoustic velocity meter (AVM) systems operate on the principles that the point-to-point upstream traveltime of an acoustic pulse is longer than the downstream traveltime and that this difference in traveltime can be accurately measured by electronic devices. An AVM system is capable of recording water velocity (and discharge) under a wide range of conditions, but some constraints apply: 1. Accuracy is reduced and performance is degraded if the acoustic path is not a continuous straight line. The path can be bent by reflection if it is too close to a stream boundary or by refraction if it passes through density gradients resulting from variations in either water temperature or salinity. For paths of less than 100 m, a temperature gradient of 0.1' per meter causes signal bending less than 0.6 meter at midchannel, and satisfactory velocity results can be obtained. Reflection from stream boundaries can cause signal cancellation if boundaries are too close to signal path. 2. Signal strength is attenuated by particles or bubbles that absorb, spread, or scatter sound. The concentration of particles or bubbles that can be tolerated is a function of the path length and frequency of the acoustic signal. 3. Changes in streamline orientation can affect system accuracy if the variability is random. 4. Errors relating to signal resolution are much larger for a single threshold detection scheme than for multiple threshold schemes. This report provides methods for computing the effect of various conditions on the accuracy of a record obtained from an AVM. The equipment must be adapted to the site. Field reconnaissance and preinstallation analysis to detect possible problems are critical for proper installation and operation of an AVM system.

  9. Dark Matter Velocity Spectroscopy.

    PubMed

    Speckhard, Eric G; Ng, Kenny C Y; Beacom, John F; Laha, Ranjan

    2016-01-22

    Dark matter decays or annihilations that produce linelike spectra may be smoking-gun signals. However, even such distinctive signatures can be mimicked by astrophysical or instrumental causes. We show that velocity spectroscopy-the measurement of energy shifts induced by relative motion of source and observer-can separate these three causes with minimal theoretical uncertainties. The principal obstacle has been energy resolution, but upcoming experiments will have the precision needed. As an example, we show that the imminent Astro-H mission can use Milky Way observations to separate possible causes of the 3.5-keV line. We discuss other applications. PMID:26849582

  10. Dark Matter Velocity Spectroscopy

    NASA Astrophysics Data System (ADS)

    Speckhard, Eric G.; Ng, Kenny C. Y.; Beacom, John F.; Laha, Ranjan

    2016-01-01

    Dark matter decays or annihilations that produce linelike spectra may be smoking-gun signals. However, even such distinctive signatures can be mimicked by astrophysical or instrumental causes. We show that velocity spectroscopy—the measurement of energy shifts induced by relative motion of source and observer—can separate these three causes with minimal theoretical uncertainties. The principal obstacle has been energy resolution, but upcoming experiments will have the precision needed. As an example, we show that the imminent Astro-H mission can use Milky Way observations to separate possible causes of the 3.5-keV line. We discuss other applications.

  11. Asymmetric Time Evolution and Indistinguishable Events

    SciTech Connect

    Bryant, P. W.

    2010-11-25

    With a time asymmetric theory, in which quantum mechanical time evolution is given by a semigroup of operators rather than by a group, the states of open systems are represented by density operators exhibiting a branching behavior. To treat the indistinguishably of the members of experimental ensembles, we hypothesize that environmental interference occurs during events that are themselves fundamentally indistinguishable.

  12. Asymmetric hindwing foldings in rove beetles

    PubMed Central

    Saito, Kazuya; Yamamoto, Shuhei; Maruyama, Munetoshi; Okabe, Yoji

    2014-01-01

    Foldable wings of insects are the ultimate deployable structures and have attracted the interest of aerospace engineering scientists as well as entomologists. Rove beetles are known to fold their wings in the most sophisticated ways that have right–left asymmetric patterns. However, the specific folding process and the reason for this asymmetry remain unclear. This study reveals how these asymmetric patterns emerge as a result of the folding process of rove beetles. A high-speed camera was used to reveal the details of the wing-folding movement. The results show that these characteristic asymmetrical patterns emerge as a result of simultaneous folding of overlapped wings. The revealed folding mechanisms can achieve not only highly compact wing storage but also immediate deployment. In addition, the right and left crease patterns are interchangeable, and thus each wing internalizes two crease patterns and can be folded in two different ways. This two-way folding gives freedom of choice for the folding direction to a rove beetle. The use of asymmetric patterns and the capability of two-way folding are unique features not found in artificial structures. These features have great potential to extend the design possibilities for all deployable structures, from space structures to articles of daily use. PMID:25368178

  13. Symmetric and Asymmetric Matching of Joint Presentations

    ERIC Educational Resources Information Center

    Luce, R. Duncan

    2004-01-01

    The global psychophysical theory of summation and magnitude production of R. D. Luce (2002) had joint presentations of pairs of intensities (measured above threshold) being matched asymmetrically, with 1 component being 0 intensity and the other the matching intensity. For loudness, an intensity pair to the 2 ears is matched by an intensity in…

  14. Asymmetric demand for energy: A cointegration approach

    NASA Astrophysics Data System (ADS)

    Maclean, Thomas Frank

    1997-12-01

    This paper uses time series data in a study of the demand for energy. One goal is to compare the results from the traditional autoregressive distributed lag (ADL) model to the error correction model (ECM) using cointegration. The second goal is to determine if the demand elasticity is asymmetric with respect to increasing and decreasing prices. This paper discusses three topics that are important to the use of time series data. The first topic is the presence and consequences unit roots which are common in time series data. The second topic is the identification of cointegrated variables and the third topic is a development of the ECM. This results in a model that can be used in either a single equation or multivariate system context and it will estimate both long run and short run elasticities. Asymmetry theory and its implications are studied along with an investigation into competing methods of creating the asymmetric variables. Simulations provided evidence that the use of dummy variables results in biased estimates and that the cumulative difference method of Wolffram/Houck gives valid estimates. The results of the empirical part of the paper show that the short run estimates of the ADL model are like those of the error correction model, but the cointegration method's long run estimates are better since they are known to be consistent and asymptotically unbiased. Tests for asymmetry do not support the theory of asymmetric long run price elasticities; however there is evidence to support the presence of asymmetric demand in the short run.

  15. Asymmetric conditional volatility in international stock markets

    NASA Astrophysics Data System (ADS)

    Ferreira, Nuno B.; Menezes, Rui; Mendes, Diana A.

    2007-08-01

    Recent studies show that a negative shock in stock prices will generate more volatility than a positive shock of similar magnitude. The aim of this paper is to appraise the hypothesis under which the conditional mean and the conditional variance of stock returns are asymmetric functions of past information. We compare the results for the Portuguese Stock Market Index PSI 20 with six other Stock Market Indices, namely the SP 500, FTSE 100, DAX 30, CAC 40, ASE 20, and IBEX 35. In order to assess asymmetric volatility we use autoregressive conditional heteroskedasticity specifications known as TARCH and EGARCH. We also test for asymmetry after controlling for the effect of macroeconomic factors on stock market returns using TAR and M-TAR specifications within a VAR framework. Our results show that the conditional variance is an asymmetric function of past innovations raising proportionately more during market declines, a phenomenon known as the leverage effect. However, when we control for the effect of changes in macroeconomic variables, we find no significant evidence of asymmetric behaviour of the stock market returns. There are some signs that the Portuguese Stock Market tends to show somewhat less market efficiency than other markets since the effect of the shocks appear to take a longer time to dissipate.

  16. Beam-beam issues in asymmetric colliders

    SciTech Connect

    Furman, M.A.

    1992-07-01

    We discuss generic beam-beam issues for proposed asymmetric e{sup +}- e{sup -} colliders. We illustrate the issues by choosing, as examples, the proposals by Cornell University (CESR-B), KEK, and SLAC/LBL/LLNL (PEP-II).

  17. Stochastic Differential Games with Asymmetric Information

    SciTech Connect

    Cardaliaguet, Pierre Rainer, Catherine

    2009-02-15

    We investigate a two-player zero-sum stochastic differential game in which the players have an asymmetric information on the random payoff. We prove that the game has a value and characterize this value in terms of dual viscosity solutions of some second order Hamilton-Jacobi equation.

  18. Asymmetric hindwing foldings in rove beetles.

    PubMed

    Saito, Kazuya; Yamamoto, Shuhei; Maruyama, Munetoshi; Okabe, Yoji

    2014-11-18

    Foldable wings of insects are the ultimate deployable structures and have attracted the interest of aerospace engineering scientists as well as entomologists. Rove beetles are known to fold their wings in the most sophisticated ways that have right-left asymmetric patterns. However, the specific folding process and the reason for this asymmetry remain unclear. This study reveals how these asymmetric patterns emerge as a result of the folding process of rove beetles. A high-speed camera was used to reveal the details of the wing-folding movement. The results show that these characteristic asymmetrical patterns emerge as a result of simultaneous folding of overlapped wings. The revealed folding mechanisms can achieve not only highly compact wing storage but also immediate deployment. In addition, the right and left crease patterns are interchangeable, and thus each wing internalizes two crease patterns and can be folded in two different ways. This two-way folding gives freedom of choice for the folding direction to a rove beetle. The use of asymmetric patterns and the capability of two-way folding are unique features not found in artificial structures. These features have great potential to extend the design possibilities for all deployable structures, from space structures to articles of daily use. PMID:25368178

  19. Attentional Control and Asymmetric Associative Priming

    ERIC Educational Resources Information Center

    Hutchison, Keith A.; Heap, Shelly J.; Neely, James H.; Thomas, Matthew A.

    2014-01-01

    Participants completed a battery of 3 attentional control (AC) tasks (OSPAN, antisaccade, and Stroop, as in Hutchison, 2007) and performed a lexical decision task with symmetrically associated (e.g., "sister-brother") and asymmetrically related primes and targets presented in both the forward (e.g., "atom-bomb") and backward…

  20. Mach bands change asymmetrically during solar eclipses.

    PubMed

    Ross, John; Diamond, Mark R; Badcock, David R

    2003-01-01

    Observations made during two partial eclipses of the Sun show that the Mach bands on shadows cast by the Sun disappear and reappear asymmetrically as an eclipse progresses. These changes can be explained as due to changes in the shape of the penumbras of shadows as the visible portion of the Sun forms crescents of different orientation. PMID:12892435

  1. Magnetically Retrievable Catalysts for Asymmetric Synthesis

    EPA Science Inventory

    Surface modification of magnetic nanoparticles with chiral scaffolds for asymmetric catalytic applications is an elegant way of providing a special pseudo homogenous phase which could be separated using an external magnet. In this review, we summarize the use of magnetic nanopart...

  2. Synthesis and photochromic properties of asymmetric diarylethenes

    NASA Astrophysics Data System (ADS)

    Zhou, Xinhong; Zhang, Fushi; Guo, Haobo; Sun, Fan; Pu, Shouzhi; Yuan, Peng

    2002-09-01

    Two asymmetric photochromic diarylethenes with different spectra in open and closed form were synthesized simultaneously. Irradiation of the open form with UV light results in essentially quantitative photocyclization to the deeply colored form. The compounds show attractive optical properties and are expected to be used in optical storage and photoswitch.

  3. Asymmetric Bulkheads for Cylindrical Pressure Vessels

    NASA Technical Reports Server (NTRS)

    Ford, Donald B.

    2007-01-01

    Asymmetric bulkheads are proposed for the ends of vertically oriented cylindrical pressure vessels. These bulkheads, which would feature both convex and concave contours, would offer advantages over purely convex, purely concave, and flat bulkheads (see figure). Intended originally to be applied to large tanks that hold propellant liquids for launching spacecraft, the asymmetric-bulkhead concept may also be attractive for terrestrial pressure vessels for which there are requirements to maximize volumetric and mass efficiencies. A description of the relative advantages and disadvantages of prior symmetric bulkhead configurations is prerequisite to understanding the advantages of the proposed asymmetric configuration: In order to obtain adequate strength, flat bulkheads must be made thicker, relative to concave and convex bulkheads; the difference in thickness is such that, other things being equal, pressure vessels with flat bulkheads must be made heavier than ones with concave or convex bulkheads. Convex bulkhead designs increase overall tank lengths, thereby necessitating additional supporting structure for keeping tanks vertical. Concave bulkhead configurations increase tank lengths and detract from volumetric efficiency, even though they do not necessitate additional supporting structure. The shape of a bulkhead affects the proportion of residual fluid in a tank that is, the portion of fluid that unavoidably remains in the tank during outflow and hence cannot be used. In this regard, a flat bulkhead is disadvantageous in two respects: (1) It lacks a single low point for optimum placement of an outlet and (2) a vortex that forms at the outlet during outflow prevents a relatively large amount of fluid from leaving the tank. A concave bulkhead also lacks a single low point for optimum placement of an outlet. Like purely concave and purely convex bulkhead configurations, the proposed asymmetric bulkhead configurations would be more mass-efficient than is the flat

  4. Synthetic RR Lyrae velocity curves

    SciTech Connect

    Liu, Tianxing Boston Univ., MA )

    1991-02-01

    An amplitude correlation between the pulsation velocity curves and visual light curves of ab-type RR Lyrae stars is derived from a large number of RR Lyrae that have high-precision radial-velocity and photometric data. Based on the determined AVp, AV ralation, a synthetic radial-velocity curve for a typical ab-type RR Lyrae star is constructed. This would be of particular use in determining the systemic velocities of RR Lyrae. 17 refs.

  5. The velocity distribution of cometary hydrogen - Evidence for high velocities?

    NASA Technical Reports Server (NTRS)

    Brown, Michael E.; Spinrad, Hyron

    1993-01-01

    The Hamilton Echelle spectrograph on the 3-m Shane telescope at Lick Observatory was used to obtain high-velocity and spatial resolution 2D spectra of H-alpha 6563-A emission in Comets Austin and Levy. The presence of the components expected from water dissociation and collisional thermalization in the inner coma is confirmed by the hydrogen velocity distribution. In Comet Austin, the potential high-velocity hydrogen includes velocities of up to about 40 km/s and is spatially symmetric with respect to the nucleus. In Comet Levy, the high-velocity hydrogen reaches velocities of up to 50 km/s and is situated exclusively on the sunward side of the nucleus. The two distinct signatures of high-velocity hydrogen imply two distinct sources.

  6. Unitaxial constant velocity microactuator

    DOEpatents

    McIntyre, Timothy J.

    1994-01-01

    A uniaxial drive system or microactuator capable of operating in an ultra-high vacuum environment. The mechanism includes a flexible coupling having a bore therethrough, and two clamp/pusher assemblies mounted in axial ends of the coupling. The clamp/pusher assemblies are energized by voltage-operated piezoelectrics therewithin to operatively engage the shaft and coupling causing the shaft to move along its rotational axis through the bore. The microactuator is capable of repeatably positioning to sub-manometer accuracy while affording a scan range in excess of 5 centimeters. Moreover, the microactuator generates smooth, constant velocity motion profiles while producing a drive thrust of greater than 10 pounds. The system is remotely controlled and piezoelectrically driven, hence minimal thermal loading, vibrational excitation, or outgassing is introduced to the operating environment.

  7. Phobos: Low Velocity Impacts

    NASA Astrophysics Data System (ADS)

    Smith, Heather; Lee, Pascal; Hamilton, Douglas

    2014-11-01

    Mars’s inner moon, Phobos, is located deep in the planet’s gravity well and orbits far below the planet’s synchronous orbit. Images of the surface of Phobos, in particular from Viking Orbiter 1, MGS, MRO, and MEX, reveal a rich collisional history, including fresh-looking impact craters and subdued older ones, very large impact structures (compared to the size of Phobos), such as Stickney, and much smaller ones.Sources of impactors colliding with Phobos include a priori: A) Impactors from outside the martian system (asteroids, comets, and fragments thereof); B) Impactors from Mars itself (ejecta from large impacts on Mars); and C) Impactors from Mars orbit, including impact ejecta launched from Deimos and ejecta launched from, and reintercepted by, Phobos. In addition to individual craters on Phobos, the networks of grooves on this moon have also been attributed in part or in whole to impactors from some of these sources, particularly B. We report the preliminary results of a systematic survey of the distribution, morphology, albedo, and color characteristics of fresh impact craters and associated ejecta deposits on Phobos. Considering that the different potential impactor sources listed above are expected to display distinct dominant compositions and different characteristic impact velocity regimes, we identify specific craters on Phobos that are more likely the result of low velocity impacts by impactors derived from Mars orbit than from any alternative sources. Our finding supports the hypothesis that the spectrally “Redder Unit” on Phobos may be a superficial veneer of accreted ejecta from Deimos, and that Phobos’s bulk might be distinct in composition from Deimos.

  8. Theoretical analysis of electrokinetic flow and heat transfer in a microchannel under asymmetric boundary conditions.

    PubMed

    Soong, C Y; Wang, S H

    2003-09-01

    The main theme of the present work is to investigate the electrokinetic effects on liquid flow and heat transfer in a flat microchannel of two parallel plates under asymmetric boundary conditions including wall-sliding motion, unequal zeta potentials, and unequal heat fluxes on two walls. Based on the Debye-Huckel approximation, an electrical potential solution to the linearized Poisson-Boltzmann equation is obtained and employed in the analysis. The analytic solutions of the electrical potential, velocity distributions, streaming potential, friction coefficient, temperature distribution, and heat transfer rate are obtained, and thereby the effects of electrokinetic separation distance (K), zeta-potential level (zeta;(1)), ratio of two zeta potentials (r(zeta) identical with zeta;(2)/zeta;(1)), wall-sliding velocity (u(w)), and heat flux ratio (r(q) identical with q"(2)/q"(1)) are investigated. The present results reveal the effects of wall-sliding and zeta-potential ratio on the hydrodynamic nature of microchannel flow, and they are used to provide physical interpretations for the resultant electrokinetic effects and the underlying electro-hydrodynamic interaction mechanisms. In the final part the results of potential and velocity fields are applied in solving the energy equation. The temperature distributions and heat transfer characteristics under the asymmetrical kinematic, electric, and thermal boundary conditions considered presently are dealt with. PMID:12927184

  9. Particle-in-cell simulation study of the scaling of asymmetric magnetic reconnection with in-plane flow shear

    NASA Astrophysics Data System (ADS)

    Doss, C. E.; Cassak, P. A.; Swisdak, M.

    2016-08-01

    We investigate magnetic reconnection in systems simultaneously containing asymmetric (anti-parallel) magnetic fields, asymmetric plasma densities and temperatures, and arbitrary in-plane bulk flow of plasma in the upstream regions. Such configurations are common in the high-latitudes of Earth's magnetopause and in tokamaks. We investigate the convection speed of the X-line, the scaling of the reconnection rate, and the condition for which the flow suppresses reconnection as a function of upstream flow speeds. We use two-dimensional particle-in-cell simulations to capture the mixing of plasma in the outflow regions better than is possible in fluid modeling. We perform simulations with asymmetric magnetic fields, simulations with asymmetric densities, and simulations with magnetopause-like parameters where both are asymmetric. For flow speeds below the predicted cutoff velocity, we find good scaling agreement with the theory presented in Doss et al. [J. Geophys. Res. 120, 7748 (2015)]. Applications to planetary magnetospheres, tokamaks, and the solar wind are discussed.

  10. Velocity and velocity bounds in static spherically symmetric metrics

    NASA Astrophysics Data System (ADS)

    Arraut, Ivan; Batic, Davide; Nowakowski, Marek

    2011-08-01

    We find simple expressions for velocity of massless particles with dependence on the distance, r, in Schwarzschild coordinates. For massive particles these expressions give an upper bound for the velocity. Our results apply to static spherically symmetric metrics. We use these results to calculate the velocity for different cases: Schwarzschild, Schwarzschild-de Sitter and Reissner-Nordström with and without the cosmological constant. We emphasize the differences between the behavior of the velocity in the different metrics and find that in cases with naked singularity there always exists a region where the massless particle moves with a velocity greater than the velocity of light in vacuum. In the case of Reissner-Nordström-de Sitter we completely characterize the velocity and the metric in an algebraic way. We contrast the case of classical naked singularities with naked singularities emerging from metric inspired by noncommutative geometry where the radial velocity never exceeds one. Furthermore, we solve the Einstein equations for a constant and polytropic density profile and calculate the radial velocity of a photon moving in spaces with interior metric. The polytropic case of radial velocity displays an unexpected variation bounded by a local minimum and maximum.

  11. Effects of asymmetric sitting on spinal balance

    PubMed Central

    Woo, Hee Soon; Oh, Jong Chi; Won, Sung Yoon

    2016-01-01

    [Purpose] To investigate the effects of two common asymmetric sitting positions on spinal balance. [Subjects and Methods] Thirty-seven healthy subjects in their twenties were enrolled and randomly divided into two groups. Asymmetric positions of resting the chin on a hand and crossing the legs were performed by each group for 1 hour. After 1 hour, the subjects lay in the supine position again and spinal imbalance was measured using a device. [Results] After 1 hour of resting with the chin on a hand, sagittal imbalance, coronal imbalance, pelvic obliquity and lordosis angle presented spinal imbalance worsening of 1 hour of crossing legs, sagittal imbalance, pelvic torsion showed in mainly learned spinal imbalance living. [Conclusion] Good posture could be an innate ability, however it through habits. So this study is meaningful from the perspective of the importance of good posture. PMID:27065291

  12. Asymmetric twins in rhombohedral boron carbide

    SciTech Connect

    Fujita, Takeshi Guan, Pengfei; Madhav Reddy, K.; Hirata, Akihiko; Guo, Junjie; Chen, Mingwei

    2014-01-13

    Superhard materials consisting of light elements have recently received considerable attention because of their ultrahigh specific strength for a wide range of applications as structural and functional materials. However, the failure mechanisms of these materials subjected to high stresses and dynamic loading remain to be poorly known. We report asymmetric twins in a complex compound, boron carbide (B{sub 4}C), characterized by spherical-aberration-corrected transmission electron microscopy. The atomic structure of boron-rich icosahedra at rhombohedral vertices and cross-linked carbon-rich atomic chains can be clearly visualized, which reveals unusual asymmetric twins with detectable strains along the twin interfaces. This study offers atomic insights into the structure of twins in a complex material and has important implications in understanding the planar defect-related failure of superhard materials under high stresses and shock loading.

  13. Design of Asymmetric Peptide Bilayer Membranes.

    PubMed

    Li, Sha; Mehta, Anil K; Sidorov, Anton N; Orlando, Thomas M; Jiang, Zhigang; Anthony, Neil R; Lynn, David G

    2016-03-16

    Energetic insights emerging from the structural characterization of peptide cross-β assemblies have enabled the design and construction of robust asymmetric bilayer peptide membranes. Two peptides differing only in their N-terminal residue, phosphotyrosine vs lysine, coassemble as stacks of antiparallel β-sheets with precisely patterned charged lattices stabilizing the bilayer leaflet interface. Either homogeneous or mixed leaflet composition is possible, and both create nanotubes with dense negative external and positive internal solvent exposed surfaces. Cross-seeding peptide solutions with a preassembled peptide nanotube seed leads to domains of different leaflet architecture within single nanotubes. Architectural control over these cross-β assemblies, both across the bilayer membrane and along the nanotube length, provides access to highly ordered asymmetric membranes for the further construction of functional mesoscale assemblies. PMID:26942690

  14. Asymmetric-hysteresis compensation in piezoelectric actuators

    NASA Astrophysics Data System (ADS)

    Aguirre, Gorka; Janssens, Thierry; Van Brussel, Hendrik; Al-Bender, Farid

    2012-07-01

    The advantages of using piezoelectric actuators in ultra-precision applications are often impaired by nonlinear effects, in particular hysteresis, which may lead to positioning uncertainties of up to 15% of the actuator's stroke. Model-based compensation strategies are often prescribed in order to overcome this limitation and achieve better dynamical accuracy. This comes, however, at the expense of increasing identification and implementation complexity, especially when hysteresis is of the asymmetric type, such as prevalent in hard piezoceramic materials. This paper proposes a new compensation strategy based upon (i) treating hysteresis as being separate from other dynamical effects and (ii) formulating a new, simplified model to deal with asymmetric hysteresis, based on applying a linear operator to the conventional hysteresis models. After developing the theoretical background of the compensation strategy, the accuracy improvement due to the new hysteresis-compensation method is demonstrated experimentally.

  15. Asymmetric Redox-Annulation of Cyclic Amines

    PubMed Central

    2015-01-01

    Cyclic amines such as 1,2,3,4-tetrahydroisoquinoline undergo regiodivergent annulation reactions with 4-nitrobutyraldehydes. These redox-neutral transformations enable the asymmetric synthesis of highly substituted polycyclic ring systems in just two steps from commercial materials. The utility of this process is illustrated in a rapid synthesis of (−)-protoemetinol. Computational studies provide mechanistic insights and implicate the elimination of acetic acid from an ammonium nitronate intermediate as the rate-determining step. PMID:26348653

  16. Asymmetric Total Synthesis of (-)-Maoecrystal V.

    PubMed

    Zhang, Wei-bin; Shao, Wen-bin; Li, Fu-zhuo; Gong, Jian-xian; Yang, Zhen

    2015-09-01

    The asymmetric total synthesis of (-)-maoecrystal V, a novel cytotoxic pentacyclic ent-kaurane diterpene, has been accomplished. Key steps of the current strategy involve an early-stage semipinacol rearrangement reaction for the construction of the C10 quaternary stereocenter, a rhodium-catalyzed intramolecular O-H insertion reaction, and a sequential Wessely oxidative dearomatization/intramolecular Diels-Alder reaction to forge the pentacyclic framework of maoecrystal V. PMID:26136342

  17. Bidirectional and Asymmetric Quantum Controlled Teleportation

    NASA Astrophysics Data System (ADS)

    Zhang, Da; Zha, Xin-Wei; Duan, Ya-Jun

    2015-05-01

    We propose a new protocol of bidirectional and asymmetric quantum controlled teleportation, using a maximally seven-qubit entangled state as the quantum channel. That is to say Alice wants to transmit an arbitrary single qubit state (an arbitrary two-qubit state) to Bob and Bob wants to transmit an arbitrary two-qubit state (an arbitrary single state) to Alice via the control of the supervisor Charlie.

  18. Iron-catalyzed asymmetric haloamination reactions.

    PubMed

    Cai, Yunfei; Liu, Xiaohua; Zhou, Pengfei; Kuang, Yulong; Lin, Lili; Feng, Xiaoming

    2013-09-21

    The first iron(III)/N,N'-dioxide-catalyzed asymmetric haloamination of 3-alkylidene- and 3-arylidene-indolin-2-ones was developed, affording the corresponding chiral oxindole derivatives bearing vicinal haloamine substituents with excellent results (up to 99% yield, 99% ee, >19 : 1 dr). This iron catalyst also exhibits perfect enantioselectivity for chalcone derivatives. The cooperative activation of the substrate and the reagent in concert guarantees the high stereoselectivity. PMID:23903004

  19. Development of a laser-Doppler system for measurement of velocity fields in PVT crystal growth systems

    NASA Technical Reports Server (NTRS)

    Jones, O. C.; Glicksman, M. E.; Lin, J. T.; Kim, G. T.; Singh, N. B.

    1991-01-01

    A laser-Doppler velocimetry (LDV) system capable of measuring velocities as low as 10 exp -5 m/s is presented, and a calibration system for determining the accuracy of the LDV system at these velocities is described. The results obtained in mercurous chloride crystal grown in cylindrical ampoules at 300 C, using physical vapor transport (PVT) methods, are presented. It is concluded that the overall flow pattern observed is a unicellular, asymmetric pattern between Rayleigh number of 125 and 250.

  20. Asymmetric nuclear matter equation of state

    SciTech Connect

    Bombaci, I.; Lombardo, U. Istituto Nazionale di Fisica Nucleare, Sezione di Catania, Corso Italia 57, I-95129 Catania )

    1991-11-01

    Systematic calculations of asymmetric nuclear matter have been performed in the framework of the Brueckner-Bethe-Goldstone approach in a wide range of both density and asymmetry parameter. The empirical parabolic law fulfilled by the binding energy per nucleon is confirmed by the present results in all the range of the asymmetry parameter values. The predominant role of the {sup 3}{ital S}{sub 1-}{sup 3}{ital D}{sub 1} component of the {ital NN} interaction is elucidated. A linear variation of the proton and neutron single-particle potentials is found as increasing the neutron excess; a deviation from the phenomenological potentials occurs for highly asymmetric matter as an effect of the self-consistency. The present calculations of the incompressibility predict a strong softening of the equation of state going from symmetric to asymmetric nuclear matter. The proton fraction in equilibrium with neutron matter has been determined from the beta-stability condition and its relevance to the superfluidity of neutron stars has been investigated.

  1. Recent developments in asymmetric multicomponent reactions.

    PubMed

    de Graaff, Corien; Ruijter, Eelco; Orru, Romano V A

    2012-05-21

    Multicomponent reactions (MCRs) receive increasing attention because they address both diversity and complexity in organic synthesis. Thus, in principle diverse sets of relatively complex structures can be generated from simple starting materials in a single reaction step. The ever increasing need for optically pure compounds for pharmaceutical and agricultural applications as well as for catalysis promotes the development of asymmetric multicomponent reactions. In recent years, asymmetric multicomponent reactions have been applied to the total synthesis of various enantiopure natural products and commercial drugs, reducing the number of required reaction steps significantly. Although many developments in diastereoselective MCRs have been reported, the field of catalytic enantioselective MCRs has just started to blossom. This critical review describes developments in both diastereoselective and catalytic enantioselective multicomponent reactions since 2004. Significantly broadened scopes, new techniques, more environmentally benign methods and entirely novel MCRs reflect the increasingly inventive paths that synthetic chemist follow in this field. Until recently, enantioselective transition metal-catalyzed MCRs represented the majority of catalytic enantioselective MCRs. However, metal contamination is highly undesirable for drug synthesis. The emergence of organocatalysis greatly influences the quest for new asymmetric MCRs. PMID:22546840

  2. Flapping flight: effect of asymmetric kinematics

    NASA Astrophysics Data System (ADS)

    Pande, Nakul; Krithivasan, Siddharth; K. R., Sreenivas

    2014-11-01

    Flapping flight has received considerable attention in the past with its relevance in the design of micro-air vehicles. In this regard, asymmetric flapping of wings offers simple kinematics. Nevertheless, it leads to symmetry-breaking in the flow field and generation of sustained lift. It has been observed previously with flow visualization experiments and Discrete Vortex Method (DVM) simulations that if the down-stroke time period is lesser than the up-stroke time, there is a net downward momentum imparted to the fluid. This is seen as a switching the flow field from a four-jet (symmetric) to a two-jet (asymmetric) configuration when the stroke-time ratio is progressively varied. This symmetry breaking has been studied experimentally using Particle Image Velocimetry (PIV) across a range of Reynolds Numbers and asymmetry ratios. Results are also corroborated with results from 3-D numerical simulations. Study helps in shedding light on the effectiveness of asymmetric kinematics as a lift generation mechanism.

  3. Asymmetric threat data mining and knowledge discovery

    NASA Astrophysics Data System (ADS)

    Gilmore, John F.; Pagels, Michael A.; Palk, Justin

    2001-03-01

    Asymmetric threats differ from the conventional force-on- force military encounters that the Defense Department has historically been trained to engage. Terrorism by its nature is now an operational activity that is neither easily detected or countered as its very existence depends on small covert attacks exploiting the element of surprise. But terrorism does have defined forms, motivations, tactics and organizational structure. Exploiting a terrorism taxonomy provides the opportunity to discover and assess knowledge of terrorist operations. This paper describes the Asymmetric Threat Terrorist Assessment, Countering, and Knowledge (ATTACK) system. ATTACK has been developed to (a) data mine open source intelligence (OSINT) information from web-based newspaper sources, video news web casts, and actual terrorist web sites, (b) evaluate this information against a terrorism taxonomy, (c) exploit country/region specific social, economic, political, and religious knowledge, and (d) discover and predict potential terrorist activities and association links. Details of the asymmetric threat structure and the ATTACK system architecture are presented with results of an actual terrorist data mining and knowledge discovery test case shown.

  4. Measurement of Asymmetric Optical Pumping of Ions Accelerating in a Magnetic-field Gradient

    SciTech Connect

    Xuan Sun; Earl Scime; Mahmood Miah; Samuel Cohen; Frederick Skiff

    2004-10-28

    We report observations of asymmetric optical pumping of argon ions accelerating in a magnetic field gradient. The signature is a difference in the laser-induced-fluorescence (LIF) emission amplitude from a pair of Zeeman-split states. A model that reproduces the dependence of the asymmetry on magnetic-field and ion-velocity gradients is described. With the model, the fluorescence intensity ratio provides a new method of measuring ion collisionality. This phenomenon has implications for interpreting stellar plasma spectroscopy data which often exhibit unequal Zeeman state intensities.

  5. Asymmetric Distribution of Histones during Drosophila Male Germline Stem Cell Asymmetric Divisions

    PubMed Central

    Tran, Vuong; Feng, Lijuan; Chen, Xin

    2014-01-01

    It has long been known that epigenetic changes are inheritable. However, except for DNA methylation, little is known about the molecular mechanisms of epigenetic inheritance. Many types of stem cells undergo asymmetric cell division to generate a self-renewed stem cell and a daughter cell committed for differentiation. Still, whether and how stem cells retain their epigenetic memory remain questions to be elucidated. During the asymmetric division of Drosophila male germline stem cell (GSC), our recent studies revealed that the preexisting histone 3 (H3) are selectively segregated to the GSC, whereas newly synthesized H3 deposited during DNA replication are enriched in the differentiating daughter cell. We propose a two-step model to explain this asymmetric histone distribution. First, prior to mitosis, preexisting histones and newly synthesized histones are differentially distributed at two sets of sister chromatids. Next, during mitosis, the set of sister chromatids that mainly consist of preexisting histones are segregated to GSCs, while the other set of sister chromatids enriched with newly synthesized histones are partitioned to the daughter cell committed for differentiation. In this review, we apply current knowledge about epigenetic inheritance and asymmetric cell division to inform our discussion of potential molecular mechanisms and the cellular basis underlying this asymmetric histone distribution pattern. We will also discuss whether this phenomenon contributes to the maintenance of stem cell identity and resetting chromatin structure in the other daughter cell for differentiation. PMID:23681658

  6. Factors influencing perceived angular velocity

    NASA Technical Reports Server (NTRS)

    Kaiser, Mary K.; Calderone, Jack B.

    1991-01-01

    Angular velocity perception is examined for rotations both in depth and in the image plane and the influence of several object properties on this motion parameter is explored. Two major object properties are considered, namely, texture density which determines the rate of edge transitions for rotations in depth, i.e., the number of texture elements that pass an object's boundary per unit of time, and object size which determines the tangential linear velocities and 2D image velocities of texture elements for a given angular velocity. Results of experiments show that edge-transition rate biased angular velocity estimates only when edges were highly salient. Element velocities had an impact on perceived angular velocity; this bias was associated with 2D image velocity rather than 3D tangential velocity. Despite these biases judgements were most strongly determined by the true angular velocity. Sensitivity to this higher order motion parameter appeared to be good for rotations both in depth (y-axis) and parallel to the line of sight (z-axis).

  7. Particle Velocity Measuring System

    NASA Technical Reports Server (NTRS)

    Arndt, G. Dickey (Inventor); Carl, James R. (Inventor)

    1998-01-01

    Method and apparatus are provided for determining the velocity of individual food particles within a liquid/solid food mixture that is cooked by an aseptic cooking method whereby the food mixture is heated as it flows through a flowline. At least one upstream and at least one downstream microwave transducer are provided to determine the minimum possible travel time of the fastest food particle through the flowline. In one embodiment, the upstream detector is not required. In another embodiment, a plurality of small dipole antenna markers are secured to a plurality of food particles to provide a plurality of signals as the markers pass the upstream and downstream transducers. The dipole antenna markers may also include a non-linear element to reradiate a harmonic frequency of a transmitter frequency. Upstream and downstream transducers include dipole antennas that are matched to the impedance of the food slurry and a signal transmission cable by various impedance matching means including unbalanced feed to the antennas.

  8. Velocity dependant splash behaviour

    NASA Astrophysics Data System (ADS)

    Hamlett, C. A. E.; Shirtcliffe, N. J.; McHale, G.; Ahn, S.; Doerr, S. H.; Bryant, R.; Newton, M. I.

    2012-04-01

    Extreme soil water repellency can occur in nature via condensation of volatile organic compounds released during wildfires and can lead to increased erosion rate. Such extreme water repellent soil can be classified as superhydrophobic and shares similar chemical and topographical features to specifically designed superhydrophobic surfaces. Previous studies using high speed videography to investigate single droplet impact behaviour on artificial superhydrophobic have revealed three distinct modes of splash behaviour (rebound, pinned and fragmentation) which are dependent on the impact velocity of the droplet. In our studies, using high-speed videography, we show that such splash behaviour can be replicated on fixed 'model' water repellent soils (hydrophobic glass beads/particles). We show that the type of splash behaviour is dependent on both the size and chemical nature of the fixed particles. The particle shape also influences the splash behaviour as shown by drop impact experiments on fixed sand samples. We have also studied soil samples, as collected from the field, which shows that the type of droplet splash behaviour can lead to enhanced soil particle transport.

  9. Metallic glass velocity sensor

    SciTech Connect

    Butler, J.L.; Butler, S.C.; Massa, D.P.; Cavanagh, G.H.

    1996-04-01

    A metallic glass accelerometer has been developed for use as an underwater sound velocity sensor. The device uses the metallic glass material Metglas 2605SC which has been processed to achieve a virgin coupling coefficient of 0.96. The mechanical to electrical conversion is based on the detection of the change in the inductance of the device as a result of bending motion. The detection method uses a carrier frequency signal which is amplitude modulated by the received signal. This scheme was originally described by Wun-Fogle, Savage and Clark [{open_quote}{open_quote}Sensitive wide frequency range magnetostrictive strain gauge,{close_quote}{close_quote} Sensors and Actuators, 1{underscore}2{underscore}, 323{endash}331 (1987)]. The bender is in the form of a three layered laminate with a closed magnetic path window frame structure. The theory of operation along with measured and calculated results are presented for a prototype element with approximate dimensions 1.5{times}1.0{times}0.1 inches. Calculated and measured results agree for a reduced effective coupling coefficient of 0.72 and operation with a carrier field intensity of 0.87 Oe and carrier frequency of 20 kHz. {copyright} {ital 1996 American Institute of Physics.}

  10. Hydrokinetic canal measurements: inflow velocity, wake flow velocity, and turbulence

    DOE Data Explorer

    Gunawan, Budi

    2014-06-11

    The dataset consist of acoustic Doppler current profiler (ADCP) velocity measurements in the wake of a 3-meter diameter vertical-axis hydrokinetic turbine deployed in Roza Canal, Yakima, WA, USA. A normalized hub-centerline wake velocity profile and two cross-section velocity contours, 10 meters and 20 meters downstream of the turbine, are presented. Mean velocities and turbulence data, measured using acoustic Doppler velocimeter (ADV) at 50 meters upstream of the turbine, are also presented. Canal dimensions and hydraulic properties, and turbine-related information are also included.

  11. Epitaxial growth in dislocation-free strained asymmetric alloy films

    SciTech Connect

    Desai, Rashmi C.; Kim, Ho Kwon; Chatterji, Apratim; Ngai, Darryl; Chen Si; Yang Nan

    2010-06-15

    Epitaxial growth in strained asymmetric, dislocation-free, coherent, alloy films is explored. Linear-stability analysis is used to theoretically analyze the coupled instability arising jointly from the substrate-film lattice mismatch (morphological instability) and the spinodal decomposition mechanism. Both the static and growing films are considered. Role of various parameters in determining stability regions for a coherent growing alloy film is investigated. In addition to the usual parameters: lattice mismatch {epsilon}, solute-expansion coefficient {eta}, growth velocity V, and growth temperature T, we consider the alloy asymmetry arising from its mean composition. The dependence of elastic moduli on composition fluctuations and the coupling between top surface and underlying bulk of the film also play important roles. The theory is applied to group III-V films such as GaAsN, InGaN, and InGaP and to group IV Si-Ge films at temperatures below the bare critical temperature T{sub c} for strain-free spinodal decomposition. The dependences of various material parameters on mean concentration and temperature lead to significant qualitative changes.

  12. Animating streamlines with repeated asymmetric patterns for steady flow visualization

    NASA Astrophysics Data System (ADS)

    Yeh, Chih-Kuo; Liu, Zhanping; Lee, Tong-Yee

    2012-01-01

    Animation provides intuitive cueing for revealing essential spatial-temporal features of data in scientific visualization. This paper explores the design of Repeated Asymmetric Patterns (RAPs) in animating evenly-spaced color-mapped streamlines for dense accurate visualization of complex steady flows. We present a smooth cyclic variable-speed RAP animation model that performs velocity (magnitude) integral luminance transition on streamlines. This model is extended with inter-streamline synchronization in luminance varying along the tangential direction to emulate orthogonal advancing waves from a geometry-based flow representation, and then with evenly-spaced hue differing in the orthogonal direction to construct tangential flow streaks. To weave these two mutually dual sets of patterns, we propose an energy-decreasing strategy that adopts an iterative yet efficient procedure for determining the luminance phase and hue of each streamline in HSL color space. We also employ adaptive luminance interleaving in the direction perpendicular to the flow to increase the contrast between streamlines.

  13. Critical Differences of Asymmetric Magnetic Reconnection from Standard Models

    NASA Astrophysics Data System (ADS)

    Nitta, S.; Wada, T.; Fuchida, T.; Kondoh, K.

    2016-09-01

    We have clarified the structure of asymmetric magnetic reconnection in detail as the result of the spontaneous evolutionary process. The asymmetry is imposed as ratio k of the magnetic field strength in both sides of the initial current sheet (CS) in the isothermal equilibrium. The MHD simulation is carried out by the HLLD code for the long-term temporal evolution with very high spatial resolution. The resultant structure is drastically different from the symmetric case (e.g., the Petschek model) even for slight asymmetry k = 2. (1) The velocity distribution in the reconnection jet clearly shows a two-layered structure, i.e., the high-speed sub-layer in which the flow is almost field aligned and the acceleration sub-layer. (2) Higher beta side (HBS) plasma is caught in a lower beta side plasmoid. This suggests a new plasma mixing process in the reconnection events. (3) A new large strong fast shock in front of the plasmoid forms in the HBS. This can be a new particle acceleration site in the reconnection system. These critical properties that have not been reported in previous works suggest that we contribute to a better and more detailed knowledge of the reconnection of the standard model for the symmetric magnetic reconnection system.

  14. Velocity correlations of galaxy clusters

    NASA Technical Reports Server (NTRS)

    Cen, Renyue; Bahcall, Neta A.; Gramann, Mirt

    1994-01-01

    We determine the velocity correlation function, pairwise peculiar velocity difference, and rms pairwise peculiar velocity dispersion of rich clusters of galaxies, as a function of pair separation, for three cosmological models: Omega = 1 and Omega = 0.3 cold dark matter (CDM), and Omega = 0.3 primeval baryonic isocurvature (PBI) models (all flat and Cosmic Background Explorer (COBE)-normalized). We find that close cluster pairs, with separation r is less than or equal to 10/h Mpc, exhibit strong attractive peculiar velocities in all models; the cluster pairwise velocities depend sensitively on the model. The mean pairwise attractive velocity of clusters on 5/h Mpc scale ranges from approximately 1700 km/s for Omega = 1 CDM to approximately 1000 km/s for PBI to approximately 700 km/s for Omega = 0.3 CDM. The small-scale pairwise velocities depend also on cluster mass: richer, more massive clusters exhibit stronger attractive velocities than less massive clusters. On large scales, from approximately 20 to 200/h Mpc, the cluster peculiar velocities are increasingly dominated by bulk and random motions; they are independent of cluster mass. The cluster velocity correlation function is negative on small scales for Omega = 1 and Omega = 0.3 CDM, indicating strong pairwise motion relative to bulk motion on small scales; PBI exhibits relatively larger bulk motions. The cluster velocity correlation function is positive on very large scales, from r approximately 10/h Mpc to r approximately 200/h Mpc, for all models. These positive correlations, which decrease monotonically with scale, indicate significant bulk motions of clusters up to approximately 200/h Mpc. The strong dependence of the cluster velocity functions on models, especially at small separations, makes them useful tools in constraining cosmological models when compared with observations.

  15. The Local Stellar Velocity Field via Vector Spherical Harmonics

    NASA Technical Reports Server (NTRS)

    Makarov, V. V.; Murphy, D. W.

    2007-01-01

    We analyze the local field of stellar tangential velocities for a sample of 42,339 nonbinary Hipparcos stars with accurate parallaxes, using a vector spherical harmonic formalism.We derive simple relations between the parameters of the classical linear model (Ogorodnikov-Milne) of the local systemic field and low-degree terms of the general vector harmonic decomposition. Taking advantage of these relationships, we determine the solar velocity with respect to the local stars of (V(sub X), V(sub Y), V(sub Z)) = (10.5, 18.5, 7.3) +/- 0.1 km s(exp -1) not for the asymmetric drift with respect to the local standard of rest. If only stars more distant than 100 pc are considered, the peculiar solar motion is (V(sub X), V(sub Y), V(sub Z)) = (9.9, 15.6, 6.9) +/- 0.2 km s(exp -1). The adverse effects of harmonic leakage, which occurs between the reflex solar motion represented by the three electric vector harmonics in the velocity space and higher degree harmonics in the proper-motion space, are eliminated in our analysis by direct subtraction of the reflex solar velocity in its tangential components for each star...

  16. Velocity Dispersions Across Bulge Types

    SciTech Connect

    Fabricius, Maximilian; Bender, Ralf; Hopp, Ulrich; Saglia, Roberto; Drory, Niv; Fisher, David

    2010-06-08

    We present first results from a long-slit spectroscopic survey of bulge kinematics in local spiral galaxies. Our optical spectra were obtained at the Hobby-Eberly Telescope with the LRS spectrograph and have a velocity resolution of 45 km/s (sigma*), which allows us to resolve the velocity dispersions in the bulge regions of most objects in our sample. We find that the velocity dispersion profiles in morphological classical bulge galaxies are always centrally peaked while the velocity dispersion of morphologically disk-like bulges stays relatively flat towards the center--once strongly barred galaxies are discarded.

  17. A diagnostic study of the asymmetric distribution of rainfall during the landfall of typhoon Haitang (2005)

    NASA Astrophysics Data System (ADS)

    Yue, Caijun; Gao, Shouting; Liu, Lu; Li, Xiaofan

    2015-10-01

    The precipitation during landfall of typhoon Haitang (2005) showed asymmetric structures (left side/right side of the track). Analysis of Weather Research and Forecasting model simulation data showed that rainfall on the right side was more than 15 times stronger than on the left side. The causes were analyzed by focusing on comparing the water vapor flux, stability and upward motion between the two sides. The major results were as follows: (1) Relative humidity on both sides was over 80%, whereas the convergence of water vapor flux in the lower troposphere was about 10 times larger on the right side than on the left side. (2) Both sides featured conditional symmetric instability [MPV (moist potential vorticity) <0], but the right side was more unstable than the left side. (3) Strong (weak) upward motion occurred throughout the troposphere on the right (left) side. The Q vector diagnosis suggested that large-scale and mesoscale forcing accounted for the difference in vertical velocity. Orographic lift and surface friction forced the development of the asymmetric precipitation pattern. On the right side, strong upward motion from the forcing of different scale weather systems and topography caused a substantial release of unstable energy and the transportation of water vapor from the lower to the upper troposphere, which produced torrential rainfall. However, the above conditions on the left side were all much weaker, which led to weaker rainfall. This may have been the cause of the asymmetric distribution of rainfall during the landfall of typhoon Haitang.

  18. Numerical solution of the asymmetric water impact of a wedge in three degrees of freedom

    NASA Astrophysics Data System (ADS)

    Ghazizade-Ahsaee, H.; Nikseresht, A. H.

    2013-06-01

    Impact problems associated with water entry have important applications in various aspects of naval architecture and ocean engineering. Estimation of hydrodynamic impact forces especially during the first instances after the impact is very important and is of interest. Since the estimation of hydrodynamic impact load plays an important role in safe design and also in evaluation of structural weight and costs, it is better to use a reliable and accurate prediction method instead of a simple estimation resulted by analyzing methods. In landing of flying boats, some phenomena such as weather conditions and strong winds can cause asymmetric instead of symmetric descent. In this paper, a numerical simulation of the asymmetric impact of a wedge, as the step of a flying boat, considering dynamic equations in two-phase flow is taken into account. The dynamic motion of the wedge in two-phase flow is solved based on finite volume method with volume of fluid (VOF) scheme considering dynamic equations. Then the effects of different angles of impact and water depth on the velocity change and slamming forces in an asymmetric impact are investigated. The comparison between the simulation results and experimental data verifies the accuracy of the method applied in the present study.

  19. Sodium Velocity Maps on Mercury

    NASA Technical Reports Server (NTRS)

    Potter, A. E.; Killen, R. M.

    2011-01-01

    The objective of the current work was to measure two-dimensional maps of sodium velocities on the Mercury surface and examine the maps for evidence of sources or sinks of sodium on the surface. The McMath-Pierce Solar Telescope and the Stellar Spectrograph were used to measure Mercury spectra that were sampled at 7 milliAngstrom intervals. Observations were made each day during the period October 5-9, 2010. The dawn terminator was in view during that time. The velocity shift of the centroid of the Mercury emission line was measured relative to the solar sodium Fraunhofer line corrected for radial velocity of the Earth. The difference between the observed and calculated velocity shift was taken to be the velocity vector of the sodium relative to Earth. For each position of the spectrograph slit, a line of velocities across the planet was measured. Then, the spectrograph slit was stepped over the surface of Mercury at 1 arc second intervals. The position of Mercury was stabilized by an adaptive optics system. The collection of lines were assembled into an images of surface reflection, sodium emission intensities, and Earthward velocities over the surface of Mercury. The velocity map shows patches of higher velocity in the southern hemisphere, suggesting the existence of sodium sources there. The peak earthward velocity occurs in the equatorial region, and extends to the terminator. Since this was a dawn terminator, this might be an indication of dawn evaporation of sodium. Leblanc et al. (2008) have published a velocity map that is similar.

  20. Airflow acceleration performance of asymmetric surface dielectric barrier discharge actuators at different exposed needle electrode heights

    NASA Astrophysics Data System (ADS)

    Yang, Liang; Yan, Hui-Jie; Qi, Xiao-Hua; Hua, Yue; Ren, Chun-Sheng

    2015-12-01

    The use of plasma, created by asymmetric surface dielectric barrier discharge (ASDBD), as aerodynamic actuators to control airflows, has been of widespread concern over the past decades. For the single ASDBD, the actuator performance is dependent on the geometry of actuator and the produced plasma. In this work, a new electrode configuration, i.e., a row of needle, is taken as an exposed electrode for the ASDBD plasma actuator, and the electrode height is adjustable. The effects of different electrode heights on the airflow acceleration behavior are experimentally investigated by measuring surface potential distribution, ionic wind velocity, and mean thrust force production. It is demonstrated that the airflow velocity and thrust force increase with the exposed electrode height and the best actuator performance can be obtained when the exposed electrode is adjusted to an appropriate height. The difference, as analyzed, is mainly due to the distinct plasma spatial distributions at different exposed electrode heights.

  1. Highly asymmetric magnetic domain wall propagation due to coupling to a periodic pinning potential

    NASA Astrophysics Data System (ADS)

    Novak, R. L.; Metaxas, P. J.; Jamet, J.-P.; Weil, R.; Ferré, J.; Mougin, A.; Rohart, S.; Stamps, R. L.; Zermatten, P.-J.; Gaudin, G.; Baltz, V.; Rodmacq, B.

    2015-06-01

    Magneto-optical microscopy and magnetometry have been used to study magnetization reversal in an ultrathin magnetically soft (Pt/Co)2 ferromagnetic film coupled to an array of magnetically harder (Co/Pt)4 nanodots via a predominantly dipolar interaction across a 3 nm Pt spacer. This interaction generates a spatially periodic pinning potential for domain walls propagating through the continuous magnetic film. When reversing the applied field with respect to the static nanodot array magnetization orientation, strong asymmetries in the wall velocity and switching fields are observed. Asymmetric switching fields mean that hysteresis of the film is characterized by a large bias field of dipolar origin which is linked to the wall velocity asymmetry. This latter asymmetry, though large at low fields, vanishes at high fields where the domains become round and compact. A field-polarity-controlled transition from dendritic to compact faceted domain structures is also seen at intermediate fields and a model is proposed to interpret the transition.

  2. Asymmetric electroosmotic flow and mobility measurements at nonstationary positions in the rectangular chamber

    NASA Technical Reports Server (NTRS)

    1985-01-01

    The electrophoretic mobility of a cell in solution is defined by its velocity divided by the electric field strength it experiences. An obvious way to measure the mobility of cells is to apply a constant electric field to a suspension of cells in a glass chamber and clock the velocities of individual cells through a microscope. This microscope method is the classic technique in cell electrophoresis and it has been used for the bulk of research in this field. Two aspects of the microscope method can critically affect the accuracy and consistency of its cell mobility measurements: (1) the electroosmotic fluctuations in the chamber from measurement to measurement; and (2) the number of cells which can be practically measured for statistically meaningful results. A new method of analyzing microelectrophoretic data using a computer program has been developed which addresses both of these aspects. It makes possible the mobility measurements of individual cells as positions throughout the rectangular chamber depth during asymmetric electroosmotic flow.

  3. Asymmetric angular-selective thermal emission

    NASA Astrophysics Data System (ADS)

    Sakr, Enas; Dhaka, Shailja; Bermel, Peter

    2016-03-01

    Thermal emission from blackbodies and flat metallic surfaces is non-directional, following the Lambert cosine law. However, highly directional thermal emission could be useful for improving the efficiency of a broad range of different applications, including thermophotovoltaics, spectroscopy and infra-red light sources. This is particularly true if strong symmetry breaking could ensure emission only in one particular direction. In this work, we investigate the possibility of tailoring asymmetric thermal emission using structured metasurfaces. These are built from surface grating unit elements that support asymmetric localization of thermal surface plasmon polaritons. The angular dependence of emissivity is studied using a rigorous coupled wave analysis (RCWA) of absorption, plus Kirchhoff's law of thermal radiation. It is further validated using a direct thermal simulation of emission originating from the metal. Asymmetric angular selectivity with near-blackbody emissivity is demonstrated for different shallow blazed grating structures. We study the effect of changing the period, depth and shape of the grating unit cell on the direction angle, angular spread, and magnitude of coupled radiation mode. In particular, a periodic sawtooth structure with a period of 1.5λ and angle of 8°was shown to create significant asymmetry of at least a factor of 3. Such structures can be considered arbitrary directional sources that can be carefully patterned on metallic surfaces to yield thermal lenses with designed focal lengths, targeted to particular concentration ratios. The benefit of this approach is that it can enhance the view factor between thermal emitters and receivers, without restricting the area ratio or separation distance.

  4. Synthesis of asymmetric tetracarboxylic acids and corresponding dianhydrides

    NASA Technical Reports Server (NTRS)

    Chuang, Chun-Hua (Inventor)

    2008-01-01

    This invention relates to processes for preparing asymmetrical biphenyl tetracarboxylic acids and the corresponding asymmetrical dianhydrides, namely 2,3,3',4'-biphenyl dianhydride (a-BPDA), 2,3,3',4'-benzophenone dianhydride (a-BTDA) and 3,4'-methylenediphthalic anhydride (-MDPA). By cross-coupling reactions of reactive metal substituted o-xylenes or by cross-coupling o-xylene derivatives in the presence of catalysts, this invention specifically produces asymmetrical biphenyl intermediates that are subsequently oxidized or hydrolyzed and oxidized to provide asymmetric biphenyl tetracarboxylic acids in comparatively high yields. These asymmetrical biphenyl tetracarboxylic acids are subsequently converted to the corresponding asymmetrical dianhydrides without contamination by symmetrical biphenyl dianhydrides.

  5. Asymmetric-Structure Analysis of Carbon and Energy Markets

    NASA Astrophysics Data System (ADS)

    Xu, Wei; Cao, Guangxi

    2016-02-01

    This study aimed to investigate the asymmetric structure between the carbon and energy markets from two aspects of different trends (up or down) and volatility-transmission direction using asymmetric detrended cross-correlation analysis (DCCA) cross-correlation coefficient test, multifractal asymmetric DCCA (MF-ADCCA) method, asymmetric volatility-constrained correlation metric and time rate of information-flow approach. We sampled 1283 observations from January 2008 to December 2012 among pairs of carbon and energy markets for analysis. Empirical results show that the (1) asymmetric characteristic from the cross-correlation between carbon and returns in the energy markets is significant, (2) asymmetric cross-correlation between carbon and energy market price returns is persistent and multifractral and (3) volatility of the base assets of energy market returns is more influential to the base asset of the carbon market than that of the energy market.

  6. Definition of Contravariant Velocity Components

    NASA Technical Reports Server (NTRS)

    Hung, Ching-Mao; Kwak, Dochan (Technical Monitor)

    2002-01-01

    This is an old issue in computational fluid dynamics (CFD). What is the so-called contravariant velocity or contravariant velocity component? In the article, we review the basics of tensor analysis and give the contravariant velocity component a rigorous explanation. For a given coordinate system, there exist two uniquely determined sets of base vector systems - one is the covariant and another is the contravariant base vector system. The two base vector systems are reciprocal. The so-called contravariant velocity component is really the contravariant component of a velocity vector for a time-independent coordinate system, or the contravariant component of a relative velocity between fluid and coordinates, for a time-dependent coordinate system. The contravariant velocity components are not physical quantities of the velocity vector. Their magnitudes, dimensions, and associated directions are controlled by their corresponding covariant base vectors. Several 2-D (two-dimensional) linear examples and 2-D mass-conservation equation are used to illustrate the details of expressing a vector with respect to the covariant and contravariant base vector systems, respectively.

  7. Instantaneous Velocity Using Photogate Timers

    ERIC Educational Resources Information Center

    Wolbeck, John

    2010-01-01

    Photogate timers are commonly used in physics laboratories to determine the velocity of a passing object. In this application a card attached to a moving object breaks the beam of the photogate timer providing the time for the card to pass. The length L of the passing card can then be divided by this time to yield the average velocity (or speed)…

  8. Multi-Velocity Component LDV

    NASA Technical Reports Server (NTRS)

    Johnson, Dennis A. (Inventor)

    1996-01-01

    A laser doppler velocimeter uses frequency shifting of a laser beam to provide signal information for each velocity component. A composite electrical signal generated by a light detector is digitized and a processor produces a discrete Fourier transform based on the digitized electrical signal. The transform includes two peak frequencies corresponding to the two velocity components.

  9. Massless sunset diagrams in finite asymmetric volumes

    NASA Astrophysics Data System (ADS)

    Niedermayer, F.; Weisz, P.

    2016-06-01

    This paper discusses the methods and the results used in an accompanying paper describing the matching of effective chiral Lagrangians in dimensional and lattice regularizations. We present methods to compute 2-loop massless sunset diagrams in finite asymmetric volumes in the framework of these regularizations. We also consider 1-loop sums in both regularizations, extending the results of Hasenfratz and Leutwyler for the case of dimensional regularization and we introduce a new method to calculate precisely the expansion coefficients of the 1-loop lattice sums.

  10. Plasma current resonance in asymmetric toroidal systems

    SciTech Connect

    Hazeltine, R. D.; Catto, Peter J.

    2015-09-15

    The well-known singularity in the magnetic differential equation for plasma current in an asymmetric toroidal confinement system is resolved by including in the pressure tensor corrections stemming from finite Larmor radius. The result provides an estimate of the amplitude of spikes in the parallel current that occur on rational magnetic surfaces. Resolution of the singularity is shown to depend on both the ambipolarity condition—the requirement of zero surface-averaged radial current—and the form of the magnetic differential equation near the rational surface.

  11. Asymmetric chemical reactions by polarized quantum beams

    NASA Astrophysics Data System (ADS)

    Takahashi, Jun-Ichi; Kobayashi, Kensei

    One of the most attractive hypothesis for the origin of homochirality in terrestrial bio-organic compounds (L-amino acid and D-sugar dominant) is nominated as "Cosmic Scenario"; a chiral impulse from asymmetric excitation sources in space triggered asymmetric reactions on the surfaces of such space materials as meteorites or interstellar dusts prior to the existence of terrestrial life. 1) Effective asymmetric excitation sources in space are proposed as polarized quantum beams, such as circularly polarized light and spin polarized electrons. Circularly polarized light is emitted as synchrotron radiation from tightly captured electrons by intense magnetic field around neutron stars. In this case, either left-or right-handed polarized light can be observed depending on the direction of observation. On the other hand, spin polarized electrons is emitted as beta-ray in beta decay from radioactive nuclei or neutron fireballs in supernova explosion. 2) The spin of beta-ray electrons is longitudinally polarized due to parity non-conservation in the weak interaction. The helicity (the the projection of the spin onto the direction of kinetic momentum) of beta-ray electrons is universally negative (left-handed). For the purpose of verifying the asymmetric structure emergence in bio-organic compounds by polarized quantum beams, we are now carrying out laboratory simulations using circularly polarized light from synchrotron radiation facility or spin polarized electron beam from beta-ray radiation source. 3,4) The target samples are solid film or aqueous solution of racemic amino acids. 1) K.Kobayashi, K.Kaneko, J.Takahashi, Y.Takano, in Astrobiology: from simple molecules to primitive life; Ed. V.Basiuk; American Scientific Publisher: Valencia, 2008. 2) G.A.Gusev, T.Saito, V.A.Tsarev, A.V.Uryson, Origins Life Evol. Biosphere. 37, 259 (2007). 3) J.Takahashi, H.Shinojima, M.Seyama, Y.Ueno, T.Kaneko, K.Kobayashi, H.Mita, M.Adachi, M.Hosaka, M.Katoh, Int. J. Mol. Sci. 10, 3044

  12. Constructions of Asymmetric Quantum Alternant Codes

    NASA Astrophysics Data System (ADS)

    Fan, Jihao; Chen, Hanwu; Xu, Juan

    2016-01-01

    Asymmetric quantum error-correcting codes (AQCs) have been proposed to deal with the significant asymmetry in many quantum channels, which may have more flexbility than general quantum error-correcting codes (QECs). In this paper, we construct AQCs based on Alternant codes. Firstly, we propose a new subclass of Alternant codes and combine them with BCH codes to construct AQCs. Then we construct AQCs based on series of nested pairs of subclasses of Alternant codes such as nested Goppa codes. As an illustrative example, we get three [[55, 6, 19/4

  13. Flory Theorem for Structurally Asymmetric Mixtures

    NASA Astrophysics Data System (ADS)

    Dobrynin, Andrey; Sun, Frank; Shirvanyants, David; Rubinstein, Gregory; Rubinstein, Michael; Sheiko, Sergei; Lee, Hyung-Il; Matyjaszewski, Krzysztof

    2008-03-01

    The generalization of the Flory theorem for structurally asymmetric mixtures was derived and tested by direct visualization of conformational transformations of brushlike macromolecules embedded in a melt of linear chains. Swelling of a brush molecule was shown to be controlled not only by the degree of polymerization of the surrounding linear chains, NB, but also by the degree of polymerization of the brush's side chains, N, which determines the structural asymmetry of the mixed species. The boundaries of the swelling region were established by scaling analysis as N^2

  14. Flory Theorem for Structurally Asymmetric Mixtures

    NASA Astrophysics Data System (ADS)

    Sun, Frank C.; Dobrynin, Andrey V.; Shirvanyants, David; Lee, Hyung-Il; Matyjaszewski, Krzysztof; Rubinstein, Gregory J.; Rubinstein, Michael; Sheiko, Sergei S.

    2007-09-01

    The generalization of the Flory theorem for structurally asymmetric mixtures was derived and tested by direct visualization of conformational transformations of brushlike macromolecules embedded in a melt of linear chains. Swelling of a brush molecule was shown to be controlled not only by the degree of polymerization (DP) of the surrounding linear chains, NB, but also by the DP of the brush’s side chains, N, which determines the structural asymmetry of the mixed species. The boundaries of the swelling region were established by scaling analysis as N2

  15. Quantum optics of lossy asymmetric beam splitters.

    PubMed

    Uppu, Ravitej; Wolterink, Tom A W; Tentrup, Tristan B H; Pinkse, Pepijn W H

    2016-07-25

    We theoretically investigate quantum interference of two single photons at a lossy asymmetric beam splitter, the most general passive 2×2 optical circuit. The losses in the circuit result in a non-unitary scattering matrix with a non-trivial set of constraints on the elements of the scattering matrix. Our analysis using the noise operator formalism shows that the loss allows tunability of quantum interference to an extent not possible with a lossless beam splitter. Our theoretical studies support the experimental demonstrations of programmable quantum interference in highly multimodal systems such as opaque scattering media and multimode fibers. PMID:27464096

  16. Excluding Light Asymmetric Bosonic Dark Matter

    NASA Astrophysics Data System (ADS)

    Kouvaris, Chris; Tinyakov, Peter

    2011-08-01

    We argue that current neutron star observations exclude asymmetric bosonic noninteracting dark matter in the range from 2 keV to 16 GeV, including the 5-15 GeV range favored by DAMA and CoGeNT. If bosonic weakly interacting massive particles (WIMPs) are composite of fermions, the same limits apply provided the compositeness scale is higher than ˜1012GeV (for WIMP mass ˜1GeV). In the case of repulsive self-interactions, we exclude the large range of WIMP masses and interaction cross sections which complements the constraints imposed by observations of the Bullet Cluster.

  17. Asymmetric Hydrogenation of 3-Substituted Pyridinium Salts.

    PubMed

    Renom-Carrasco, Marc; Gajewski, Piotr; Pignataro, Luca; de Vries, Johannes G; Piarulli, Umberto; Gennari, Cesare; Lefort, Laurent

    2016-07-01

    The use of an equivalent amount of an organic base leads to high enantiomeric excess in the asymmetric hydrogenation of N-benzylated 3-substituted pyridinium salts into the corresponding piperidines. Indeed, in the presence of Et3 N, a Rh-JosiPhos catalyst reduced a range of pyridinium salts with ee values up to 90 %. The role of the base was elucidated with a mechanistic study involving the isolation of the various reaction intermediates and isotopic labeling experiments. Additionally, this study provided some evidence for an enantiodetermining step involving a dihydropyridine intermediate. PMID:27140832

  18. Asymmetric catalytic aziridination of cyclic enones.

    PubMed

    De Vincentiis, Francesco; Bencivenni, Giorgio; Pesciaioli, Fabio; Mazzanti, Andrea; Bartoli, Giuseppe; Galzerano, Patrizia; Melchiorre, Paolo

    2010-07-01

    The first catalytic method for the asymmetric aziridination of cyclic enones is described. The presented organocatalytic strategy is based on the use of an easily available organocatalyst that is able to convert a wide range of cyclic enones into the desired aziridines with very high enantiomeric purity and good chemical yield. Such a method may very well open up new opportunities to stereoselectively prepare complex chiral molecules that possess an indane moiety, a framework that is found in a large number of bioactive and pharmaceutically important molecules. PMID:20512797

  19. RHIC operation with asymmetric collisions in 2015

    SciTech Connect

    Liu, C.; Aschenauer, C.; Atoian, G.; Blaskiewicz, M.; Brown, K. A.; Bruno, D.; Connolly, R.; Ottavio, T. D.; Drees, K. A.; Fischer, W.; Gardner, C. J.; Gu, X.; Hayes, T.; Huang, H.; Laster, J. S.; Luo, Y.; Makdisi, Y.; Marr, G.; Marusic, A.; Meot, F.; Mernick, K.; Michnoff, R.; Minty, M.; Montag, C.; Morris, J.; Narayan, G.; Nayak, S.; Nemesure, S.; Pile, P.; Poblaguev, A.; Ranjbar, V.; Robert-Demolaize, G.; Roser, T.; Schmidke, B.; Schoefer, V.; Severino, F.; Shrey, T.; Smith, K.; Steski, D.; Tepikian, S.; Trbojevic, D.; Tsoupas, N.; Wang, G.; White, S.; Yip, K.; Zaltsman, A.; Zeno, K.; Zhang, S. Y.

    2015-08-07

    To study low-x shadowing/saturation physics as well as other nuclear effects [1], [2], proton-gold (p-Au, for 5 weeks) and proton-Aluminum (p-Al, for 2 weeks) collisions were provided for experiments in 2015 at the Relativistic Heavy Ion Collider (RHIC), with polarized proton beam in the Blue ring and Au/Al beam in the Yellow ring. The special features of the asymmetric run in 2015 will be introduced. The operation experience will be reviewed as well in the report.

  20. Crossflow in two-dimensional asymmetric nozzles

    NASA Technical Reports Server (NTRS)

    Sebacher, D. I.; Lee, L. P.

    1975-01-01

    An experimental investigation of the crossflow effects in three contoured, two-dimensional asymmetric nozzles is described. The data were compared with theoretical predictions of nozzle flow by using an inviscid method of characteristics solution and two-dimensional turbulent boundary-layer calculations. The effect of crossflow as a function of the nozzle maximum expansion angle was studied by use of oil-flow techniques, static wall-pressure measurements, and impact-pressure surveys at the nozzle exit. Reynolds number effects on crossflow were investigated.

  1. New ligands for the asymmetric dihydroxylation

    SciTech Connect

    Becker, H.; King, S.B.; Richardson, P.

    1995-12-31

    The asymmetric dibydroxylation of olefins in the presence of cinchona alkaloid derivatives (the AD reaction) has proven to be a reliable method in organic syntheses. For most olefins, the enantioselectivities using the {open_quotes}standard{close_quotes} phathalazine ligands are excellent; however, facial selectivity is still moderate for some olefins. 2,3-Diphenyl pyrazinopyridazine (DPP) and anthraquinone (AQN) as spacers for the {open_quotes}pseudo enantiomeric{close_quotes} alkaloids dihydroquinidine (DHQD) or dihydroquinine (DHQ) give superior enantioselectivities for almost all olefins.

  2. Catalytic asymmetric formal synthesis of beraprost

    PubMed Central

    Kobayashi, Yusuke; Kuramoto, Ryuta

    2015-01-01

    Summary The first catalytic asymmetric synthesis of the key intermediate for beraprost has been achieved through an enantioselective intramolecular oxa-Michael reaction of an α,β-unsaturated amide mediated by a newly developed benzothiadiazine catalyst. The Weinreb amide moiety and bromo substituent of the Michael adduct were utilized for the C–C bond formations to construct the scaffold. All four contiguous stereocenters of the tricyclic core were controlled via Rh-catalyzed stereoselective C–H insertion and the subsequent reduction from the convex face. PMID:26734111

  3. Plasmonic photodetectors based on asymmetric nanogap electrodes

    NASA Astrophysics Data System (ADS)

    Ge, Junyu; Luo, Manlin; Zou, Wanghui; Peng, Wei; Duan, Huigao

    2016-08-01

    Hot electrons excited by plasmon resonance in nanostructure can be employed to enhance the properties of photodetectors, even when the photon energy is lower than the bandgap of the semiconductor. However, current research has seldom considered how to realize the efficient collection of hot electrons, which restricts the responsivity of the device. In this paper, a type of plasmonic photodetector based on asymmetric nanogap electrodes is proposed. Owing to this structure, the device achieves responsivities as high as 0.45 and 0.25 mA/W for wavelengths of 1310 and 1550 nm, respectively. These insights can aid the realization of efficient plasmon-enhanced photodetectors for infrared detection.

  4. de Sitter and double asymmetric brane worlds

    SciTech Connect

    Guerrero, Rommel; Rodriguez, R. Omar; Torrealba, Rafael

    2005-12-15

    Asymmetric brane worlds with dS expansion and static double kink topology are obtained from a recently proposed method and their properties are analyzed. These domain walls interpolate between two spacetimes with different cosmological constants. In the dynamic case, the vacua correspond to dS and AdS geometry, unlike the static case where they correspond to AdS background. We show that it is possible to confine gravity on such branes. In particular, the double-brane world hosts two different walls, so that the gravity is localized on one of them.

  5. Dynamics of adaptive agents with asymmetric information

    NASA Astrophysics Data System (ADS)

    DeMartino, Andrea; Galla, Tobias

    2005-08-01

    We apply path integral techniques to study the dynamics of agent-based models with asymmetric information structures. In particular, we devise a batch version of a model proposed originally by Berg et al (2001 Quantitative Finance 1 203), and convert the coupled multi-agent processes into an effective-agent problem from which the dynamical order parameters in ergodic regimes can be derived self-consistently together with the corresponding phase structure. Our dynamical study complements and extends the available static theory. Results are confirmed by numerical simulations.

  6. Horizontal Velocity Structure in Waterspouts.

    NASA Astrophysics Data System (ADS)

    Schwiesow, R. L.

    1981-04-01

    We have measured the spatial variation of a single horizontal component of the velocity in a number of waterspouts using an airborne infrared Doppler lidar. In 21 data sets, maximum velocities range from 4.2 to 33.6 m s1 and visible funnel diameters from 6.6 to 90 m. Data were taken at altitudes between 675 m, near cloud base, and 95 m above the surface. The sequences show time development of the velocity as a function of radius at a fixed altitude and the velocity structure at different altitudes and sequential times with a horizontal resolution of 0.75 m between data points. The variation in velocity structure between waterspouts is large, with some showing marked azimuthal asymmetry and mixing with the ambient flow, and others showing multiple concentric vortex shells.

  7. Asymmetric multifractal scaling behavior in the Chinese stock market: Based on asymmetric MF-DFA

    NASA Astrophysics Data System (ADS)

    Cao, Guangxi; Cao, Jie; Xu, Longbing

    2013-02-01

    We utilized asymmetric multifractal detrended fluctuation analysis in this study to examine the asymmetric multifractal scaling behavior of Chinese stock markets with uptrends or downtrends. Results show that the multifractality degree of Chinese stock markets with uptrends is stronger than that of Chinese stock markets with downtrends. Correlation asymmetries are more evident in large fluctuations than in small fluctuations. By discussing the source of asymmetric multifractality, we find that multifractality is related to long-range correlations when the market is going up, whereas it is related to fat-tailed distribution when the market is going down. The main source of asymmetric scaling behavior in the Shanghai stock market are long-range correlations, whereas that in the Shenzhen stock market is fat-tailed distribution. An analysis of the time-varying feature of scaling asymmetries shows that the evolution trends of these scaling asymmetries are similar in the two Chinese stock markets. Major financial and economical events may enhance scaling asymmetries.

  8. Asymmetrical Capacitors for Propulsion and the ISR Asymmetrical Capacitator Thruster, Experimental Results and Improved Designs

    NASA Technical Reports Server (NTRS)

    Canning, Francis; Winet, Ed; Ice, Bob; Melcher, Cory; Pesavento, Phil; Holmes, Alan; Butler, Carey; Cole, John; Campbell, Jonathan

    2004-01-01

    The outline of this viewgraph presentation on asymmetrical capacitor thruster development includes: 1) Test apparatus; 2) Devices tested; 3) Circuits used; 4) Data collected (Time averaged, Time resolved); 5) Patterns observed; 6) Force calculation; 7) Electrostatic modeling; 8) Understand it all.

  9. Benzene analogues of (quasi-)planar M@B{sub n}H{sub n} compounds (M = V{sup −}, Cr, Mn{sup +}): A theoretical investigation

    SciTech Connect

    Li, Lifen; Xu, Chang; Jin, Baokang; Cheng, Longjiu

    2013-11-07

    The stability of M@B{sub n}H{sub n} (M = V{sup −}, Cr, Mn{sup +}; n = 5–8) is investigated by density functional theory. For n = 6–8, the isomers possess (quasi-)planar local minima showed by geometry optimization at TPSSh/6-311+G{sup **} level. All the optimized structures are thermodynamics stable according to the large HOMO-LUMO gap, binding energy, vertical ionization potential, and vertical electron affinity analysis. The peripheral and central atomic radius fit each other best at n = 7 confirmed by the variation of the binding energy values. The availability of d atom orbitals in M for participation in the π-delocalized bonding with the peripheral ring leads to the aromaticity of the (quasi-)planar structures and makes them the benzene analogues. This work establishes firmly the metal-doped borane rings as a new type of aromatic molecule.

  10. Velocity Distributions of Runaway Stars Produced by Supernovae in the Galaxy

    NASA Astrophysics Data System (ADS)

    Yisikandeer, Abudusaimaitijiang; Zhu, Chunhua; Wang, Zhaojun; Lü, Guoliang

    2016-09-01

    Using a method of population synthesis, we investigate the runaway stars produced by disrupted binaries via asymmetric core collapse supernova explosions (CC-RASs) and thermonuclear supernova explosions (TN-RASs). We find the velocities of CC-RASs in the range of about 30-100 km s -1. The runaway stars observed in the galaxy are possibly CC-RASs. Due to differences in stellar chemical components and structures, TN-RASs are divided into hydrogen-rich TN-RASs and helium-rich TN-RASs. The velocities of the former are about 100-500 km s -1, while the velocities of the latter are mainly between 600 and 1100 km s -1. The hypervelocity stars observed in the galaxy may originate from thermonuclear supernova explosions. Our results possibly cover the US 708 which is a compact helium star and travels with a velocity of 1157 ±53 km s-1 in our galaxy.

  11. Lane-changing behavior and its effect on energy dissipation using full velocity difference model

    NASA Astrophysics Data System (ADS)

    Wang, Jian; Ding, Jian-Xun; Shi, Qin; Kühne, Reinhart D.

    2016-07-01

    In real urban traffic, roadways are usually multilane with lane-specific velocity limits. Most previous researches are derived from single-lane car-following theory which in the past years has been extensively investigated and applied. In this paper, we extend the continuous single-lane car-following model (full velocity difference model) to simulate the three-lane-changing behavior on an urban roadway which consists of three lanes. To meet incentive and security requirements, a comprehensive lane-changing rule set is constructed, taking safety distance and velocity difference into consideration and setting lane-specific speed restriction for each lane. We also investigate the effect of lane-changing behavior on distribution of cars, velocity, headway, fundamental diagram of traffic and energy dissipation. Simulation results have demonstrated asymmetric lane-changing “attraction” on changeable lane-specific speed-limited roadway, which leads to dramatically increasing energy dissipation.

  12. Evolutionary Stability in the Asymmetric Volunteer's Dilemma

    PubMed Central

    Li, Yao-Tang

    2014-01-01

    It is often assumed that in public goods games, contributors are either strong or weak players and each individual has an equal probability of exhibiting cooperation. It is difficult to explain why the public good is produced by strong individuals in some cooperation systems, and by weak individuals in others. Viewing the asymmetric volunteer's dilemma game as an evolutionary game, we find that whether the strong or the weak players produce the public good depends on the initial condition (i.e., phenotype or initial strategy of individuals). These different evolutionarily stable strategies (ESS) associated with different initial conditions, can be interpreted as the production modes of public goods of different cooperation systems. A further analysis revealed that the strong player adopts a pure strategy but mixed strategies for the weak players to produce the public good, and that the probability of volunteering by weak players decreases with increasing group size or decreasing cost-benefit ratio. Our model shows that the defection probability of a “strong” player is greater than the “weak” players in the model of Diekmann (1993). This contradicts Selten's (1980) model that public goods can only be produced by a strong player, is not an evolutionarily stable strategy, and will therefore disappear over evolutionary time. Our public good model with ESS has thus extended previous interpretations that the public good can only be produced by strong players in an asymmetric game. PMID:25111781

  13. Internally architectured materials with directionally asymmetric friction.

    PubMed

    Bafekrpour, Ehsan; Dyskin, Arcady; Pasternak, Elena; Molotnikov, Andrey; Estrin, Yuri

    2015-01-01

    Internally Architectured Materials (IAMs) that exhibit different friction forces for sliding in the opposite directions are proposed. This is achieved by translating deformation normal to the sliding plane into a tangential force in a manner that is akin to a toothbrush with inclined bristles. Friction asymmetry is attained by employing a layered material or a structure with parallel 'ribs' inclined to the direction of sliding. A theory of directionally asymmetric friction is presented, along with prototype IAMs designed, fabricated and tested. The friction anisotropy (the ξ-coefficient) is characterised by the ratio of the friction forces for two opposite directions of sliding. It is further demonstrated that IAM can possess very high levels of friction anisotropy, with ξ of the order of 10. Further increase in ξ is attained by modifying the shape of the ribs to provide them with directionally dependent bending stiffness. Prototype IAMs produced by 3D printing exhibit truly giant friction asymmetry, with ξ in excess of 20. A novel mechanical rectifier, which can convert oscillatory movement into unidirectional movement by virtue of directionally asymmetric friction, is proposed. Possible applications include locomotion in a constrained environment and energy harvesting from oscillatory noise and vibrations. PMID:26040634

  14. Particle identification at an asymmetric B Factory

    SciTech Connect

    Coyle, P.; Eigen, G.; Hitlin, D.; Oddone, P.; Ratcliff, B.; Roe, N.; Va'vra, J.; Ypsilantis, T.

    1991-09-01

    Particle identification systems are an important component of any detector at a high-luminosity, asymmetric B Factory. In particular, excellent hadron identification is required to probe CP violation in B{sup 0} decays to CP eigenstates. The particle identification systems discussed below also provide help in separating leptons from hadrons at low momenta. We begin this chapter with a discussion of the physics motivation for providing particle identification, the inherent limitations due to interactions and decays in flight, and the requirements for hermiticity and angular coverage. A special feature of an asymmetric B Factory is the resulting asymmetry in the momentum distribution as a function of polar angle; this will also be quantified and discussed. In the next section the three primary candidates, time-of-flight (TOF), energy loss (dE/dx), and Cerenkov counters, both ring-imaging and threshold, will be briefly described and evaluated. Following this, one of the candidates, a long-drift Cerenkov ring-imaging device, is described in detail to provide a reference design. Design considerations for a fast RICH are then described. A detailed discussion of aerogel threshold counter designs and associated R D conclude the chapter. 56 refs., 64 figs., 13 tabs.

  15. Characterization of Asymmetric Coplanar Waveguide Discontinuities

    NASA Technical Reports Server (NTRS)

    Dib, Nihad I.; Katehi, Linda P. B.; Gupta, Minoo; Ponchak, George E.

    1993-01-01

    A general technique to characterize asymmetric coplanar waveguide (CPW) discontinuities with air bridges where both the fundamental coplanar and slotline modes may be excited together is presented. First, the CPW discontinuity without air bridges is analyzed using the space-domain integral equation (SDIE) approach. Second, the parameters (phase, amplitude, and wavelength) of the coplanar and slotline modes are extracted from an amplitude modulated-like standing wave existing in the CPW feeding lines. Then a 2n x 2n generalized scattering matrix of the n-port discontinuity without air bridges is derived which includes the occurring mode conversion. Finally, this generalized scattering matrix is reduced to an n x n matrix by enforcing suitable conditions at the ports which correspond to the excited slotline mode. For the purpose of illustration, the method is applied to a shielded asymmetric short-end CPW shunt stub, the scattering parameters of which are compared with those of a symmetric one. Experiments are performed on both discontinuities and the results are in good agreement with theoretical data. The advantages of using air bridges in CPW circuits as opposed to bond wires are also discussed.

  16. Asymmetric catalysis: science and opportunities (Nobel lecture).

    PubMed

    Noyori, Ryoji

    2002-06-17

    Asymmetric catalysis, in its infancy in the 1960s, has dramatically changed the procedures of chemical synthesis, and resulted in an impressive progression to a level that technically approximates or sometimes even exceeds that of natural biological processes. The recent exceptional advances in this area attest to a range of conceptual breakthroughs in chemical sciences in general, and to the practical benefits of organic synthesis, not only in laboratories but also in industry. The growth of this core technology has given rise to enormous economic potential in the manufacture of pharmaceuticals, animal health products, agrochemicals, fungicides, pheromones, flavors, and fragrances. Practical asymmetric catalysis is of growing importance to a sustainable modern society, in which environmental protection is of increasing concern. This subject is an essential component of molecular science and technology in the 21st century. Most importantly, recent progress has spurred various interdisciplinary research efforts directed toward the creation of molecularly engineered novel functions. The origin and progress of my research in this field are discussed. PMID:19746595

  17. Internally architectured materials with directionally asymmetric friction

    PubMed Central

    Bafekrpour, Ehsan; Dyskin, Arcady; Pasternak, Elena; Molotnikov, Andrey; Estrin, Yuri

    2015-01-01

    Internally Architectured Materials (IAMs) that exhibit different friction forces for sliding in the opposite directions are proposed. This is achieved by translating deformation normal to the sliding plane into a tangential force in a manner that is akin to a toothbrush with inclined bristles. Friction asymmetry is attained by employing a layered material or a structure with parallel ‘ribs’ inclined to the direction of sliding. A theory of directionally asymmetric friction is presented, along with prototype IAMs designed, fabricated and tested. The friction anisotropy (the ξ-coefficient) is characterised by the ratio of the friction forces for two opposite directions of sliding. It is further demonstrated that IAM can possess very high levels of friction anisotropy, with ξ of the order of 10. Further increase in ξ is attained by modifying the shape of the ribs to provide them with directionally dependent bending stiffness. Prototype IAMs produced by 3D printing exhibit truly giant friction asymmetry, with ξ in excess of 20. A novel mechanical rectifier, which can convert oscillatory movement into unidirectional movement by virtue of directionally asymmetric friction, is proposed. Possible applications include locomotion in a constrained environment and energy harvesting from oscillatory noise and vibrations. PMID:26040634

  18. Asymmetric Uncertainty Expression for High Gradient Aerodynamics

    NASA Technical Reports Server (NTRS)

    Pinier, Jeremy T

    2012-01-01

    When the physics of the flow around an aircraft changes very abruptly either in time or space (e.g., flow separation/reattachment, boundary layer transition, unsteadiness, shocks, etc), the measurements that are performed in a simulated environment like a wind tunnel test or a computational simulation will most likely incorrectly predict the exact location of where (or when) the change in physics happens. There are many reasons for this, includ- ing the error introduced by simulating a real system at a smaller scale and at non-ideal conditions, or the error due to turbulence models in a computational simulation. The un- certainty analysis principles that have been developed and are being implemented today do not fully account for uncertainty in the knowledge of the location of abrupt physics changes or sharp gradients, leading to a potentially underestimated uncertainty in those areas. To address this problem, a new asymmetric aerodynamic uncertainty expression containing an extra term to account for a phase-uncertainty, the magnitude of which is emphasized in the high-gradient aerodynamic regions is proposed in this paper. Additionally, based on previous work, a method for dispersing aerodynamic data within asymmetric uncer- tainty bounds in a more realistic way has been developed for use within Monte Carlo-type analyses.

  19. An asymmetric B factory based on PEP

    SciTech Connect

    Not Available

    1991-02-01

    In this report we describe a design for a high-luminosity Asymmetric B Factory to be built in the PEP tunnel on the SLAC site. This proposal, a collaborative effort SLAC, LBL, and LLNL, is the culmination of more than two years of effort aimed at the design and construction of an asymmetric e{sup +}e{sup {minus}} collider capable of achieving a luminosity of L = 3 {times} 10{sup 33} cm{sup {minus}2} s{sup {minus}1}. The configuration adopted utilizes two storage rings, and electron ring operating at 9 GeV and a positron ring at 3.1 GeV, each with a circumference of 2200 m. The high-energy ring is an upgrade of the PEP storage ring at SLAC; all PEP magnets and most power supplies will be reused. The upgrade consists primarily of replacing the PEP vacuum chamber and RF system with newly designed versions optimized for the high-current environment of the B Factory. The low-energy ring will be newly constructed and will be situated atop the high-energy ring in the PEP tunnel. Utilities already installed in the PEP tunnel are largely sufficient to operate the two B Factory storage rings.

  20. Asymmetric Vesicle Instability in Extensional Flow

    NASA Astrophysics Data System (ADS)

    Spann, Andrew; Zhao, Hong; Shaqfeh, Eric

    2012-11-01

    Previous researchers have chronicled the breakup of drops in an extensional flow as they stretch into a dumbbell shape with a long thin neck. Motivated by recent experimental observations, we study an apparently similar problem with vesicles, which are deformable but incompressible membranes that conserve area and volume. First, we simulate vesicles in an unbounded uniaxial extensional flow which are given general radial perturbations from an initially stable symmetric equilibrium state. For sufficiently low reduced volume (< 0.74 at matched inner/outer viscosity) there exists a capillary number at which an asymmetric perturbation mode will grow, resulting in the formation of an asymmetric dumbbell shape with a thin connecting cylindrical bridge analogous to the shapes associated with drop breakup. Our simulations help elucidate a mechanism for this instability based on a competition between internal pressure differentials in the vesicle resulting from the membrane bending force and ambient flow. We compare and contrast this transition to the ``standard'' drop breakup transition. Funded by NSF GRFP and Stanford Graduate Fellowship.

  1. Limit laws for the asymmetric inclusion process.

    PubMed

    Reuveni, Shlomi; Eliazar, Iddo; Yechiali, Uri

    2012-12-01

    The Asymmetric Inclusion Process (ASIP) is a unidirectional lattice-gas flow model which was recently introduced as an exactly solvable 'Bosonic' counterpart of the 'Fermionic' asymmetric exclusion process. An iterative algorithm that allows the computation of the probability generating function (PGF) of the ASIP's steady state exists but practical considerations limit its applicability to small ASIP lattices. Large lattices, on the other hand, have been studied primarily via Monte Carlo simulations and were shown to display a wide spectrum of intriguing statistical phenomena. In this paper we bypass the need for direct computation of the PGF and explore the ASIP's asymptotic statistical behavior. We consider three different limiting regimes: heavy-traffic regime, large-system regime, and balanced-system regime. In each of these regimes we obtain-analytically and in closed form-stochastic limit laws for five key ASIP observables: traversal time, overall load, busy period, first occupied site, and draining time. The results obtained yield a detailed limit-laws perspective of the ASIP, numerical simulations demonstrate the applicability of these laws as useful approximations. PMID:23367919

  2. Explosive synchronization with asymmetric frequency distribution

    NASA Astrophysics Data System (ADS)

    Zhou, Wenchang; Chen, Lumin; Bi, Hongjie; Hu, Xin; Liu, Zonghua; Guan, Shuguang

    2015-07-01

    In this work, we study the synchronization in a generalized Kuramoto model with frequency-weighted coupling. In particular, we focus on the situations in which the frequency distributions of oscillators are asymmetric. For typical unimodal frequency distributions, such as Lorentzian, Gaussian, triangle, and even special Rayleigh, we find that the synchronization transition in the model generally converts from the first order to the second order as the central frequency shifts toward positive direction. We characterize two interesting coherent states in the system: In the former, two phase-locking clusters are formed, rotating with the same frequency. They correspond to those oscillators with relatively high frequencies while the oscillators with relatively small frequencies are not entrained. In the latter, two phase-locking clusters rotate with different frequencies, leading to the oscillation of the order parameter. We further conduct theoretical analysis to reveal the relation between the asymmetric frequency distribution and the conversion of synchronization type, and justify the coherent states observed in the system.

  3. Survey of Reflection-Asymmetric Nuclear Deformations

    NASA Astrophysics Data System (ADS)

    Olsen, Erik; Birge, Noah; Erler, Jochen; Nazarewicz, Witek; Perhac, Alex; Schunck, Nicolas; Stoitsov, Mario; Nuclei Collaboration

    2015-10-01

    Due to spontaneous symmetry breaking it is possible for a nucleus to have a deformed shape in its ground state. It is theorized that atoms whose nuclei have reflection-asymmetric or pear-like deformations could have non-zero electric dipole moments (EDMs). Such a trait would be evidence of CP-violation, a feature that goes beyond the Standard Model of Physics. It is the purpose of this project to predict which nuclei exhibit a reflection-asymmetric deformation and which of those would be the best candidates for an EDM measuring experiment. Using nuclear Density Functional Theory along with the new computer code AxialHFB and massively parallel computing we calculated ground state nuclear properties for thousands of even-even nuclei across the nuclear chart: from light to superheavy and from stable to short-lived systems. Six different Energy Density Functionals (EDFs) were used to assess systematic errors in our calculations. Overall, 140 even-even nuclei (near and among the lantanides and actinides and in the superheavy region near N = 184) were predicted by all 6 EDFs to have a pear-like deformation. The case of 112Xe also proved curious as it was predicted by 5 EDFs to have a pear-like deformation despite its proximity to the two-proton drip line. Deceased.

  4. Asymmetric negotiation in structured language games

    NASA Astrophysics Data System (ADS)

    Yang, Han-Xin; Wang, Wen-Xu; Wang, Bing-Hong

    2008-02-01

    We propose an asymmetric negotiation strategy to investigate the influence of high-degree agents on the agreement dynamics in a structured language game, the naming game. We introduce a model parameter, which governs the frequency of high-degree agents acting as speakers in communication. It is found that there exists an optimal value of the parameter that induces the fastest convergence to a global consensus on naming an object for both scale-free and small-world naming games. This phenomenon indicates that, although a strong influence of high-degree agents favors consensus achievement, very strong influences inhibit the convergence process, making it even slower than in the absence of influence of high-degree agents. Investigation of the total memory used by agents implies that there is some trade-off between the convergence speed and the required total memory. Other quantities, including the evolution of the number of different names and the relationship between agents’ memories and their degrees, are also studied. The results are helpful for better understanding of the dynamics of the naming game with asymmetric negotiation strategy.

  5. Asymmetric negotiation in structured language games.

    PubMed

    Yang, Han-Xin; Wang, Wen-Xu; Wang, Bing-Hong

    2008-02-01

    We propose an asymmetric negotiation strategy to investigate the influence of high-degree agents on the agreement dynamics in a structured language game, the naming game. We introduce a model parameter, which governs the frequency of high-degree agents acting as speakers in communication. It is found that there exists an optimal value of the parameter that induces the fastest convergence to a global consensus on naming an object for both scale-free and small-world naming games. This phenomenon indicates that, although a strong influence of high-degree agents favors consensus achievement, very strong influences inhibit the convergence process, making it even slower than in the absence of influence of high-degree agents. Investigation of the total memory used by agents implies that there is some trade-off between the convergence speed and the required total memory. Other quantities, including the evolution of the number of different names and the relationship between agents' memories and their degrees, are also studied. The results are helpful for better understanding of the dynamics of the naming game with asymmetric negotiation strategy. PMID:18352158

  6. Asymmetric Reconnection in the Terrestrial Reconnection EXperiment

    NASA Astrophysics Data System (ADS)

    Olson, Joseph; Egedal, Jan; Forest, Cary; Wallace, John; TREX Team; MPDX Team

    2014-10-01

    The Terrestrial Reconnection EXperiment (TREX) is a new and versatile addition to the Wisconsin Plasma Astrophysics Laboratory (WiPAL) at the University of Wisconsin-Madison. TREX is optimized for the study of kinetic reconnection in various regimes and to provide the first laboratory evidence in support of a new model describing the dynamics of trapped electrons and correlating pressure anisotropy. The initial configuration implemented in TREX is specially designed to study asymmetric reconnection scenarios. These are particularly relevant to the dayside magnetopause in which the plasma beta of the solar wind and of the magnetosphere can differ by factors of 100-1000. The configuration utilizes the Helmholtz coils to produce a static, uniform magnetic field up to 275 G through the 3 m spherical vacuum vessel. Plasma is produced on a 10 s rep rate while two internal coils are pulsed, creating an opposing magnetic field to induce reconnection with asymmetric high and low beta inflows. A Langmuir and Bdot probe array is swept in between pulses to build up the magnetic profiles in the reconnection region. Preliminary data from these initial runs will be presented.

  7. New GNSS velocity field and preliminary velocity model for Ecuador

    NASA Astrophysics Data System (ADS)

    Luna-Ludeña, Marco P.; Staller, Alejandra; Gaspar-Escribano, Jorge M.; Belén Benito, M.

    2016-04-01

    In this work, we present a new preliminary velocity model of Ecuador based on the GNSS data of the REGME network (continuous monitoring GNSS network). To date, there is no velocity model available for the country. The only existing model in the zone is the regional model VEMOS2009 for South America and Caribbean (Drewes and Heidbach, 2012). This model was developed from the SIRGAS station positions, the velocities of the SIRGAS-CON stations, and several geodynamics projects performed in the region. Just two continuous GNSS (cGNSS) stations of Ecuador were taking into account in the VEMOS2009 model. The first continuous station of the REGME network was established in 2008. At present, it is composed by 32 continuous GNSS stations, covering the country. All the stations provided data during at least two years. We processed the data of the 32 GNSS stations of REGME for the 2008-2014 period, as well as 20 IGS stations in order to link to the global reference frame IGb08 (ITRF2008). GPS data were processed using Bernese 5.0 software (Dach et al., 2007). We obtained and analyzed the GNSS coordinate time series of the 32 REGME stations and we calculated the GPS-derived horizontal velocity field of the country. Velocities in ITRF2008 were transformed into a South American fixed reference frame, using the Euler pole calculated from 8 cGNSS stations throughout this plate. Our velocity field is consistent with the tectonics of the country and contributes to a better understanding of it. From the horizontal velocity field, we determined a preliminary model using the kriging geostatistical technique. To check the results we use the cross-validation method. The differences between the observed and estimated values range from ± 5 mm. This is a new velocity model obtained from GNSS data for Ecuador.

  8. Robust, automatic GPS station velocities and velocity time series

    NASA Astrophysics Data System (ADS)

    Blewitt, G.; Kreemer, C.; Hammond, W. C.

    2014-12-01

    Automation in GPS coordinate time series analysis makes results more objective and reproducible, but not necessarily as robust as the human eye to detect problems. Moreover, it is not a realistic option to manually scan our current load of >20,000 time series per day. This motivates us to find an automatic way to estimate station velocities that is robust to outliers, discontinuities, seasonality, and noise characteristics (e.g., heteroscedasticity). Here we present a non-parametric method based on the Theil-Sen estimator, defined as the median of velocities vij=(xj-xi)/(tj-ti) computed between all pairs (i, j). Theil-Sen estimators produce statistically identical solutions to ordinary least squares for normally distributed data, but they can tolerate up to 29% of data being problematic. To mitigate seasonality, our proposed estimator only uses pairs approximately separated by an integer number of years (N-δt)<(tj-ti )<(N+δt), where δt is chosen to be small enough to capture seasonality, yet large enough to reduce random error. We fix N=1 to maximally protect against discontinuities. In addition to estimating an overall velocity, we also use these pairs to estimate velocity time series. To test our methods, we process real data sets that have already been used with velocities published in the NA12 reference frame. Accuracy can be tested by the scatter of horizontal velocities in the North American plate interior, which is known to be stable to ~0.3 mm/yr. This presents new opportunities for time series interpretation. For example, the pattern of velocity variations at the interannual scale can help separate tectonic from hydrological processes. Without any step detection, velocity estimates prove to be robust for stations affected by the Mw7.2 2010 El Mayor-Cucapah earthquake, and velocity time series show a clear change after the earthquake, without any of the usual parametric constraints, such as relaxation of postseismic velocities to their preseismic values.

  9. Single-drop impingement onto a wavy liquid film and description of the asymmetrical cavity dynamics.

    PubMed

    van Hinsberg, Nils Paul; Charbonneau-Grandmaison, Marie

    2015-07-01

    The present paper is devoted to an experimental investigation of the cavity formed upon a single-drop impingement onto a traveling solitary surface wave on a deep pool of the same liquid. The dynamics of the cavity throughout its complete expansion and receding phase are analyzed using high-speed shadowgraphy and compared to the outcomes of drop impingements onto steady liquid surface films having equal thickness. The effects of the surface wave velocity, amplitude and phase, drop impingement velocity, and liquid viscosity on the cavity's diameter and depth evolution are accurately characterized at various time instants. The wave velocity induces a distinct and in time increasing inclination of the cavity in the wave propagation direction. In particular for strong waves an asymmetrical distribution of the radial expansion and retraction velocity along the cavity's circumference is observed. A linear dependency between the absolute Weber number and the typical length and time scales associated with the cavity's maximum depth and maximum diameter is reported. PMID:26274267

  10. Single-drop impingement onto a wavy liquid film and description of the asymmetrical cavity dynamics

    NASA Astrophysics Data System (ADS)

    van Hinsberg, Nils Paul; Charbonneau-Grandmaison, Marie

    2015-07-01

    The present paper is devoted to an experimental investigation of the cavity formed upon a single-drop impingement onto a traveling solitary surface wave on a deep pool of the same liquid. The dynamics of the cavity throughout its complete expansion and receding phase are analyzed using high-speed shadowgraphy and compared to the outcomes of drop impingements onto steady liquid surface films having equal thickness. The effects of the surface wave velocity, amplitude and phase, drop impingement velocity, and liquid viscosity on the cavity's diameter and depth evolution are accurately characterized at various time instants. The wave velocity induces a distinct and in time increasing inclination of the cavity in the wave propagation direction. In particular for strong waves an asymmetrical distribution of the radial expansion and retraction velocity along the cavity's circumference is observed. A linear dependency between the absolute Weber number and the typical length and time scales associated with the cavity's maximum depth and maximum diameter is reported.

  11. Iron-, Cobalt-, and Nickel-Catalyzed Asymmetric Transfer Hydrogenation and Asymmetric Hydrogenation of Ketones.

    PubMed

    Li, Yan-Yun; Yu, Shen-Luan; Shen, Wei-Yi; Gao, Jing-Xing

    2015-09-15

    Chiral alcohols are important building blocks in the pharmaceutical and fine chemical industries. The enantioselective reduction of prochiral ketones catalyzed by transition metal complexes, especially asymmetric transfer hydrogenation (ATH) and asymmetric hydrogenation (AH), is one of the most efficient and practical methods for producing chiral alcohols. In both academic laboratories and industrial operations, catalysts based on noble metals such as ruthenium, rhodium, and iridium dominated the asymmetric reduction of ketones. However, the limited availability, high price, and toxicity of these critical metals demand their replacement with abundant, nonprecious, and biocommon metals. In this respect, the reactions catalyzed by first-row transition metals, which are more abundant and benign, have attracted more and more attention. As one of the most abundant metals on earth, iron is inexpensive, environmentally benign, and of low toxicity, and as such it is a fascinating alternative to the precious metals for catalysis and sustainable chemical manufacturing. However, iron catalysts have been undeveloped compared to other transition metals. Compared with the examples of iron-catalyzed asymmetric reduction, cobalt- and nickel-catalyzed ATH and AH of ketones are even seldom reported. In early 2004, we reported the first ATH of ketones with catalysts generated in situ from iron cluster complex and chiral PNNP ligand. Since then, we have devoted ourselves to the development of ATH and AH of ketones with iron, cobalt, and nickel catalysts containing novel chiral aminophosphine ligands. In our study, the iron catalyst containing chiral aminophosphine ligands, which are expected to control the stereochemistry at the metal atom, restrict the number of possible diastereoisomers, and effectively transfer chiral information, are successful catalysts for enantioselective reduction of ketones. Among these novel chiral aminophosphine ligands, 22-membered macrocycle P2N4

  12. Velocity of Sound in Solids.

    ERIC Educational Resources Information Center

    Frank, Michael T.; Kluk, Edward

    1991-01-01

    Presents experiments to measure the velocity of sound through metals and other amorphous materials. Describes the equipment used to make the measurements and the possibility of interfacing with a microcomputer. (MDH)

  13. GMTI radar minimum detectable velocity.

    SciTech Connect

    Richards, John Alfred

    2011-04-01

    Minimum detectable velocity (MDV) is a fundamental consideration for the design, implementation, and exploitation of ground moving-target indication (GMTI) radar imaging modes. All single-phase-center air-to-ground radars are characterized by an MDV, or a minimum radial velocity below which motion of a discrete nonstationary target is indistinguishable from the relative motion between the platform and the ground. Targets with radial velocities less than MDV are typically overwhelmed by endoclutter ground returns, and are thus not generally detectable. Targets with radial velocities greater than MDV typically produce distinct returns falling outside of the endoclutter ground returns, and are thus generally discernible using straightforward detection algorithms. This document provides a straightforward derivation of MDV for an air-to-ground single-phase-center GMTI radar operating in an arbitrary geometry.

  14. Kriging interpolating cosmic velocity field

    NASA Astrophysics Data System (ADS)

    Yu, Yu; Zhang, Jun; Jing, Yipeng; Zhang, Pengjie

    2015-10-01

    Volume-weighted statistics of large-scale peculiar velocity is preferred by peculiar velocity cosmology, since it is free of the uncertainties of galaxy density bias entangled in observed number density-weighted statistics. However, measuring the volume-weighted velocity statistics from galaxy (halo/simulation particle) velocity data is challenging. Therefore, the exploration of velocity assignment methods with well-controlled sampling artifacts is of great importance. For the first time, we apply the Kriging interpolation to obtain the volume-weighted velocity field. Kriging is a minimum variance estimator. It predicts the most likely velocity for each place based on the velocity at other places. We test the performance of Kriging quantified by the E-mode velocity power spectrum from simulations. Dependences on the variogram prior used in Kriging, the number nk of the nearby particles to interpolate, and the density nP of the observed sample are investigated. First, we find that Kriging induces 1% and 3% systematics at k ˜0.1 h Mpc-1 when nP˜6 ×1 0-2(h-1 Mpc )-3 and nP˜6 ×1 0-3(h-1 Mpc )-3 , respectively. The deviation increases for decreasing nP and increasing k . When nP≲6 ×1 0-4(h-1 Mpc )-3 , a smoothing effect dominates small scales, causing significant underestimation of the velocity power spectrum. Second, increasing nk helps to recover small-scale power. However, for nP≲6 ×1 0-4(h-1 Mpc )-3 cases, the recovery is limited. Finally, Kriging is more sensitive to the variogram prior for a lower sample density. The most straightforward application of Kriging on the cosmic velocity field does not show obvious advantages over the nearest-particle method [Y. Zheng, P. Zhang, Y. Jing, W. Lin, and J. Pan, Phys. Rev. D 88, 103510 (2013)] and could not be directly applied to cosmology so far. However, whether potential improvements may be achieved by more delicate versions of Kriging is worth further investigation.

  15. Measurement of surface velocity fields

    NASA Technical Reports Server (NTRS)

    Mann, J. A., Jr.

    1979-01-01

    A new technique for measuring surface velocity fields is briefly described. It determines the surface velocity vector as a function of location and time by the analysis of thermal fluctuations of the surface profile in a small domain around the point of interest. The apparatus now being constructed will be used in a series of experiments involving flow fields established by temperature gradients imposed along a surface.

  16. High geocentric velocity meteor ablation

    NASA Astrophysics Data System (ADS)

    Hill, K. A.; Rogers, L. A.; Hawkes, R. L.

    2005-12-01

    Interstellar origin meteoroids have now been detected using radar, image intensified video, large aperture radar and space dust impact techniques. Dynamical and radiation production mechanisms will eject some meteoroids from other planetary systems into orbits which will impact Earth with high geocentric velocities. In this paper we numerically model the ablation of high geocentric velocity (71 to 500~km s-1) meteors in order to predict the heights, light curves and trail lengths to be expected. We modeled three compositions and structures: asteroidal, cometary and porous cometary. Meteoroid masses ranging from 10-6 to 10-13~kg were used in the model. As expected, these high geocentric velocity meteors, when compared to other meteors, ablate higher in the atmosphere. For example a 300~km s-1 cometary structure meteor of mass 10-9~kg will have a peak luminosity at about 190 km. They will also have significantly longer trail lengths. The same 300~km s-1, 10-9~kg cometary meteor would be within 2 mag of its peak brightness for a vertical displacement of 60 km if incident at a zenith angle of 45°. The peak light intensity of these high geocentric velocity meteors changes only slowly with velocity. Although the incident kinetic energy per unit time increases dramatically, this is largely offset by a decrease in the optical luminous efficiency in this velocity regime according to our luminous efficiency model. The 300~km s-1, 10-9~kg cometary meteor would have an absolute meteor magnitude at peak luminosity of about +8.5 mag. Our results suggest that at least those high geocentric velocity meteors larger than about 10-8~kg should be observable with current meteor electro-optical technology although there may be observational biases against their detection. The results of this paper can be used to help optimize a search strategy for these very high geocentric velocity meteors.

  17. Effect of asymmetric auxin application on Helianthus hypocotyl curvature

    NASA Technical Reports Server (NTRS)

    Migliaccio, F.; Rayle, D. L.

    1989-01-01

    Indole-3-acetic acid was applied asymmetrically to the hypocotyls of sunflower (Helianthus annuus L.) seedlings. After 5 hours on a clinostat, auxin gradients as small as 1 to 1.3 produced substantial (more than 60 degrees) hypocotyl curvature. This result suggests the asymmetric growth underlying hypocotyl gravitropism can be explained by lateral auxin redistribution.

  18. Asymmetric catalysis on the nanoscale: the organocatalytic approach to helicenes.

    PubMed

    Kötzner, Lisa; Webber, Matthew J; Martínez, Alberto; De Fusco, Claudia; List, Benjamin

    2014-05-12

    The first asymmetric organocatalytic synthesis of helicenes is reported. A novel SPINOL-derived phosphoric acid, bearing extended π-substituents, catalyzes the asymmetric synthesis of helicenes through an enantioselective Fischer indole reaction. A variety of azahelicenes and diazahelicenes could be obtained with good to excellent yields and enantioselectivities. PMID:24737692

  19. Effects of Noise on Asymmetric Bidirectional Controlled Teleportation

    NASA Astrophysics Data System (ADS)

    Nie, Yi-you; Sang, Ming-huang

    2016-07-01

    We present a scheme for asymmetric bidirectional controlled teleportation via a six-qubit cluster state in noisy environments, which includes the phase-damping and amplitude-damping channels. We analytically derive the fidelities of the asymmetric bidirectional controlled teleportation process in these two noise channels. We show that the fidelities only depend on the initial state and the noisy rate.

  20. Catalytic Asymmetric Formal Total Synthesis of (-)-Triptophenolide and (+)-Triptolide.

    PubMed

    Xu, Wen-Dan; Li, Liang-Qun; Li, Ming-Ming; Geng, Hui-Chun; Qin, Hong-Bo

    2016-06-01

    Catalytic asymmetric formal synthesis of (-)-Triptophenolide and (+)-Triptolide have been achieved. Key reaction involves Palladium catalyzed asymmetric conjugate addition of aryl boronic acid to 3-methyl cyclohexe-1-none to form quaternary carbon. Claisen rearrangement and subsequent aldol reaction furnished trans-decaline key intermediate, which assured a formal total synthesis of (-)-Triptophenolide and (+)-Triptolide. PMID:27095015

  1. Microscale Synthesis of Chiral Alcohols via Asymmetric Catalytic Transfer Hydrogenation

    ERIC Educational Resources Information Center

    Peeters, Christine M.; Deliever, Rik; De Vos, Dirk

    2009-01-01

    Synthesis of pure enantiomers is a key issue in industry, especially in areas connected to life sciences. Catalytic asymmetric synthesis has emerged as a powerful and practical tool. Here we describe an experiment on racemic reduction and asymmetric reduction via a catalytic hydrogen transfer process. Acetophenone and substituted acetophenones are…

  2. Ultrathin-skinned asymmetric membranes by immiscible solvents treatment

    DOEpatents

    Friesen, Dwayne T.; Babcock, Walter C.

    1989-01-01

    Improved semipermeable asymmetric fluid separation membranes useful in gas, vapor and liquid separations are disclosed. The membranes are prepared by substantially filling the pores of asymmetric cellulosic semipermeable membranes having a finely porous layer on one side thereof with a water immiscible organic liquid, followed by contacting the finely porous layer with water.

  3. Ultrathin-skinned asymmetric membranes by immiscible solvents treatment

    DOEpatents

    Friesen, D.T.; Babcock, W.C.

    1989-11-28

    Improved semipermeable asymmetric fluid separation membranes useful in gas, vapor and liquid separations are disclosed. The membranes are prepared by substantially filling the pores of asymmetric cellulosic semipermeable membranes having a finely porous layer on one side thereof with a water immiscible organic liquid, followed by contacting the finely porous layer with water.

  4. Asymmetric perfectly matched layer for the absorption of waves

    SciTech Connect

    Vay, Jean-Luc

    2002-02-10

    The Perfectly Matched Layer (PML) has become a standard for comparison in the techniques that have been developed to close the system of Maxwell equations (more generally wave equations) when simulating an open system. The original Berenger PML formulation relies on a split version of Maxwell equations with numerical electric and magnetic conductivities. They present here an extension of this formulation which introduces counterparts of the electric and magnetic conductivities affecting the term which is spatially differentiated in the equations. they phase velocity along each direction is also multiplied by an additional coefficient. They show that, under certain constraints on the additional numerical coefficients, this ''medium'' does not generate any reflection at any angle and any frequency and is then a Perfectly Matched Layer. Technically it is a super-set of Berenger's PML to which it reduces for a specific set of parameters and like it, it is anisotropic. However, unlike the PML, it introduces some asymmetry in the absorption rate and is therefore labeled an APML for Asymmetric Perfectly Matched Layer. They present here the numerical considerations that have led them to introduce such a medium as well as its theory. Several finite-different numerical implementations are derived (in one, two and three dimensions) and the performance of the APML is contrasted with that of the PML in one and two dimensions. Using plane wave analysis, they show that the APML implementations lead to higher absorption rates than the considered PML implementations. Although they have considered in this paper the finite-different discretization of Maxwell-like equations only, the APML system of equations may be used with other discretization schemes, such as finite-elements, and may be applied to other equations, for applications beyond electromagnetics.

  5. Magnetoresistive system with concentric ferromagnetic asymmetric nanorings

    SciTech Connect

    Avila, J. I. Tumelero, M. A.; Pasa, A. A.; Viegas, A. D. C.

    2015-03-14

    A structure consisting of two concentric asymmetric nanorings, each displaying vortex remanent states, is studied with micromagnetic calculations. By orienting in suitable directions, both the asymmetry of the rings and a uniform magnetic field, the vortices chiralities can be switched from parallel to antiparallel, obtaining in this way the analogue of the ferromagnetic and antiferromagnetic configurations found in bar magnets pairs. Conditions on the thickness of single rings to obtain vortex states, as well as formulas for their remanent magnetization are given. The concentric ring structure enables the creation of magnetoresistive systems comprising the qualities of magnetic nanorings, such as low stray fields and high stability. A possible application is as contacts in spin injection in semiconductors, and estimations obtained here of magnetoresistance change for a cylindrical spin injection based device show significant variations comparable to linear geometries.

  6. Optical Nonreciprocity in Asymmetric Optomechanical Couplers

    NASA Astrophysics Data System (ADS)

    Wang, Zheqi; Shi, Lei; Liu, Yi; Xu, Xinbiao; Zhang, Xinliang

    2015-03-01

    We propose an all-optical integrated nonreciprocal device on the optomechanical platform with a large nonreciprocal bandwidth and low operating power. The device is based on an asymmetric silicon coupler consisting of two branches. One of them is a conventional strip waveguide fixed on the substrate, and the other is a freestanding nanostring suspended above a groove in the substrate. When light is launched into the coupler, the optical gradient force between the freestanding nanostring and the underlying substrate leads to the deflection of the nanostring, and finally results in destruction of the initial phase-matching condition between the two branches. The suspended branch would achieve distinct deflections when light is incident from different ports. The simulation results show a nonreciprocal bandwidth of 13.1 nm with operating power of 390 μW. With the advantages of simple structure, low power consumption and large operating bandwidth, our work provides a promising solution for on-chip passive nonreciprocal device.

  7. Dynamics in asymmetric double-well condensates

    NASA Astrophysics Data System (ADS)

    Cataldo, H. M.; Jezek, D. M.

    2014-10-01

    The dynamics of Bose-Einstein condensates in asymmetric double wells is studied. We construct a two-mode model and analyze the properties of the corresponding phase-space diagram, showing in particular that the minimum of the phase-space portrait becomes shifted from the origin as a consequence of the nonvanishing overlap between the ground and excited states from which the localized states are derived. We further incorporate effective interaction corrections in the set of two-mode model parameters. Such a formalism is applied to a recent experimentally explored system, which is confined by a toroidal trap with radial barriers forming an arbitrary angle between them. We confront the model results with Gross-Pitaevskii simulations for various angle values finding a very good agreement. We also analyze the accuracy of a previously employed simple model for moving barriers, exploring a possible improvement that could cover a wider range of trap asymmetries.

  8. Asymmetric pneumatization of the petrous apex.

    PubMed

    Roland, P S; Meyerhoff, W L; Judge, L O; Mickey, B E

    1990-07-01

    Three patients with high-intensity MR signals from one petrous apex, but nonpathologic fine-cut computed tomography are reported. In two of the three patients, normal bone marrow within the petrous apex on one side is believed to have generated the high-intensity signal. In one of the three patients, the etiology of the MR image remains obscure, but may represent the earliest stages of petrous cholesterol granuloma or mucocele. We have reviewed 500 head CT scans performed for non-otologic reasons, in an attempt to establish the frequency of this finding. The literature on MR and CT imaging of the petrous apex and asymmetric pneumatization of the petrous apex is reviewed. PMID:2117735

  9. Medium polarization in asymmetric nuclear matter

    NASA Astrophysics Data System (ADS)

    Zhang, S. S.; Cao, L. G.; Lombardo, U.; Schuck, P.

    2016-04-01

    The influence of the medium polarization on the effective nuclear interaction of asymmetric nuclear matter is calculated in the framework of the induced interaction theory. The strong isospin dependence of the density and spin-density fluctuations is studied as it is driven by the interplay between the neutron and proton medium polarizations. Going from symmetric nuclear matter to pure neutron matter, the crossover of the induced interaction from attractive to repulsive in the spin-singlet state is determined as a function of the isospin imbalance. The density range in which the crossover occurs is also determined. For the spin-triplet state the induced interaction turns out to be always repulsive. The implications of the results for neutron star superfluid phases are briefly discussed.

  10. Asymmetric flameholder for gas turbine engine afterburner

    SciTech Connect

    Gulati, A.; Bigelow, E.C.

    1992-03-17

    This patent describes an afterburner flameholder for a gas turbine engine, the engine having an afterburner region including a central diffuser cone, a generally cylindrical outer shell and fuel spray means in the region between the shell and the cone. It comprises an annular member having an asymmetric V-shape in cross section, the annular member including a first and a second circular sidewall member, each sidewall member being joined together at one end forming an apex, the annular member adapted to be secured to the engine in the afterburner region with the apex facing upstream in an axial direction towards the fuel spray means, the annular member in cross section forming a V with unequal length sidewall members, the distance between the distal ends of the first and second circular members measured in the direction of the included angle bisector being approximately equal to the distance between the distal ends measured in a direction perpendicular to the bisector.

  11. Asymmetric Synthesis of Spiroketals with Aminothiourea Catalysts.

    PubMed

    Yoneda, Naoki; Fukata, Yukihiro; Asano, Keisuke; Matsubara, Seijiro

    2015-12-14

    Chiral spiroketal skeletons are found as core structures in a range of bioactive compounds. These natural compounds and their analogues have attracted much attention in the field of drug discovery. However, methods for their enantioselective construction are limited, and easily available optically active spiroketals are rare. We demonstrate a novel catalytic asymmetric synthesis of spiroketal compounds that proceeds through an intramolecular hemiacetalization/oxy-Michael addition cascade mediated by a bifunctional aminothiourea catalyst. This results in spiroketal structures through the relay formation of contiguous oxacycles, in which multipoint recognition by the catalyst through hydrogen bonding imparts high enantioselectivity. This method offers facile access to spiroketal frameworks bearing an alkyl group at the 2-position, which are prevalent in insect pheromones. Optically active (2S,5S)-chalcogran, a pheromone of the six-spined spruce bark beetle, and an azide derivative could be readily synthesized from the bicyclic reaction product. PMID:26510921

  12. Hydrazones as Singular Reagents in Asymmetric Organocatalysis.

    PubMed

    de Gracia Retamosa, María; Matador, Esteban; Monge, David; Lassaletta, José M; Fernández, Rosario

    2016-09-12

    This Minireview summarizes strategies and developments regarding the use of hydrazones as reagents in asymmetric organocatalysis, their distinct roles in nucleophile-electrophile, cycloaddition, and cyclization reactions. The key structural elements governing the reactivity of these reagents in a preferred pathway will be discussed, as well as their different interactions with organocatalysts, leading to diverse activation modes. Along these studies, the synthetic equivalence of N-monoalkyl, N,N-dialkyl, and N-acyl hydrazones with several synthons is also highlighted. Emphasis is also put on the mechanistic studies performed to understand the observed reactivities. Finally, the functional group transformations performed from the available products has also been analyzed, highlighting the synthetic value of these methodologies, which served to access numerous families of valuable multifunctional compounds and nitrogen-containing heterocycles. PMID:27552942

  13. An Asymmetric B Factory based on PEP

    SciTech Connect

    Hutton, A.; Zisman, M.S.

    1991-05-01

    An Asymmetric B Factory to be installed in the PEP tunnel has been under study at SLAC, LBL and LLNL for several years. A mature design for a 9 GeV {times} GeV electron-positron collider with a design luminosity of 3 {times} 10{sup 33} cm{sup {minus}2}s{sup {minus}1} is presented. Solutions new exist for all the technical problems, including issues rlated high currents (e.g. beam instabilities, feedback systems, vacuum chamber design, lifetime degradation and radiation power dissipation in the interaction region) and those related to the related to the different energies of the beams (e.g. beam separation, beam -- beam interaction and detector requirements). The status of the design, including prototype development will be discussed.

  14. Asymmetric charge distributions in planar bilayer systems.

    PubMed Central

    McQuarrie, D A; Mulás, P

    1977-01-01

    Using the simple argument based on irreversible thermodynamics and the Gouy-Chapman theory of the double layer, we show that the equilibrium distribution of charged lipid molecules between the two surfaces of a bilayer is asymmetric if the two solutions bathing the surfaces have the same ionic strength but contain ions of different valencies. For example, if one bathing solution contains 0.10 M NaCl and the other contains 0.70 M NaCl and 0.10 M CaCl2, the ratio of charged lipid molecules of the two surfaces in a membrane that contains 50% total negative lipids is 1.46, leading to a transbilayer potential of 18 mV. A complete set of such numerical results is presented in four figures. PMID:836930

  15. Asymmetric charge distributions in planar bilayer systems.

    PubMed

    McQuarrie, D A; Mulás, P

    1977-02-01

    Using the simple argument based on irreversible thermodynamics and the Gouy-Chapman theory of the double layer, we show that the equilibrium distribution of charged lipid molecules between the two surfaces of a bilayer is asymmetric if the two solutions bathing the surfaces have the same ionic strength but contain ions of different valencies. For example, if one bathing solution contains 0.10 M NaCl and the other contains 0.70 M NaCl and 0.10 M CaCl2, the ratio of charged lipid molecules of the two surfaces in a membrane that contains 50% total negative lipids is 1.46, leading to a transbilayer potential of 18 mV. A complete set of such numerical results is presented in four figures. PMID:836930

  16. Polyimides Derived from Novel Asymmetric Benzophenone Dianhydrides

    NASA Technical Reports Server (NTRS)

    Chuang, Chun-Hua (Inventor)

    2015-01-01

    This invention relates to the composition and processes for preparing thermoset polyimides derived from an asymmetric dianhydride, namely 2,3,3',4'-benzophenone dianhydride (a-BTDA) with at least one diamine, and a monofunctional terminal endcaps. The monofunctional terminating groups include 4-phenylethynylphthalic anhydride ester-acid derivatives, phenylethyl trimellitic anhydride (PETA) and its ester derivatives as well as 3-phenylethynylaniline. The process of polyimide composite comprises impregnating monomer reactants of dianhydride or its ester-acid derivatives, diamine and with monofunctional reactive endcaps into glass, carbon, quartz or synthetic fibers and fabrics, and then stack up into laminates and subsequently heated to between 150-375.degree. C. either at atmosphere or under pressure to promote the curing and crosslinking of the reactive endcaps to form a network of thermoset polyimides.

  17. Disordered contact process with asymmetric spreading

    NASA Astrophysics Data System (ADS)

    Juhász, Róbert

    2013-02-01

    An asymmetric variant of the contact process where the activity spreads with different and independent random rates to the left and to the right is introduced. A real space renormalization scheme is formulated for the model by means of which it is shown that the local asymmetry of spreading is irrelevant on large scales if the model is globally (statistically) symmetric. Otherwise, in the presence of a global bias in either direction, the renormalization method predicts two distinct phase transitions, which are related to the spreading of activity in and against the direction of the bias. The latter is found to be described by an infinite randomness fixed point while the former is not.

  18. Baryon destruction by asymmetric dark matter

    SciTech Connect

    Davoudiasl H.; Morrissey, D.; Sigurdson, K.; Tulin, S.

    2011-11-10

    We investigate new and unusual signals that arise in theories where dark matter is asymmetric and carries a net antibaryon number, as may occur when the dark matter abundance is linked to the baryon abundance. Antibaryonic dark matter can cause induced nucleon decay by annihilating visible baryons through inelastic scattering. These processes lead to an effective nucleon lifetime of 10{sup 29}-10{sup 32} yrs in terrestrial nucleon decay experiments, if baryon number transfer between visible and dark sectors arises through new physics at the weak scale. The possibility of induced nucleon decay motivates a novel approach for direct detection of cosmic dark matter in nucleon decay experiments. Monojet searches (and related signatures) at hadron colliders also provide a complementary probe of weak-scale dark-matter-induced baryon number violation. Finally, we discuss the effects of baryon-destroying dark matter on stellar systems and show that it can be consistent with existing observations.

  19. Baryon destruction by asymmetric dark matter

    SciTech Connect

    Davoudiasl, Hooman; Morrissey, David E.; Tulin, Sean; Sigurdson, Kris

    2011-11-01

    We investigate new and unusual signals that arise in theories where dark matter is asymmetric and carries a net antibaryon number, as may occur when the dark matter abundance is linked to the baryon abundance. Antibaryonic dark matter can cause induced nucleon decay by annihilating visible baryons through inelastic scattering. These processes lead to an effective nucleon lifetime of 10{sup 29}-10{sup 32} yrs in terrestrial nucleon decay experiments, if baryon number transfer between visible and dark sectors arises through new physics at the weak scale. The possibility of induced nucleon decay motivates a novel approach for direct detection of cosmic dark matter in nucleon decay experiments. Monojet searches (and related signatures) at hadron colliders also provide a complementary probe of weak-scale dark-matter-induced baryon number violation. Finally, we discuss the effects of baryon-destroying dark matter on stellar systems and show that it can be consistent with existing observations.

  20. Asymmetric neutron emissions from sonicated steel

    NASA Astrophysics Data System (ADS)

    Petrucci, Andrea; Rosada, Alberto; Santoro, Emilio

    2015-05-01

    Following up published works in which we studied and experimentally verified the assumptions of the theory of "Deformed Space-Time" in relation to piezonuclear emissions, and according to previous experiments of sonication by ultrasounds performed on solid materials with high density, cylindrical bars of AISI 304 steel have been sonicated by ultrasounds of the power of 330 Watts and frequency of 20 KHz. We verified by means of passive detectors CR39 (PADC) pulsed emissions of neutrons. In this work, following a recent proposal, it was decided to perform a stereoscopic measurement of neutron emission. It has been verified that they are characterized by a distribution which is anisotropic and asymmetric in the space. The work shows a wide and accurate description of the experiment and the results of neutron emissions, and we stress that there exist two directions corresponding to maximum emission (maximum dose) and zero emission (null dose).

  1. Seismic signals from asymmetric underground nuclear explosions

    SciTech Connect

    Davis, C.G.

    1993-09-01

    The methods discussed to estimate the effect on the seismic signals from asymmetric underground nuclear explosions, depends on the use of large-scale numerical codes and high-speed computers. The use of a two-dimensional (2D) radiation diffusion coupled Eulerian hydrodynamic code (SOIL) for the early time phenomenology is discussed. The results from this calculation are then coupled into a 2D Lagrangian code that treats the strength of the materials and the effects of fractures, ground reflections and spells. The final step in the simulation is the use of a seismic code (which uses the representation theory) to develop the actual far field seismic signals. These calculations were run on the CRAY YMP computers at the Los Alamos National Laboratory.

  2. Fractional domain asymmetric cryptosystem and cryptanalysis

    NASA Astrophysics Data System (ADS)

    Rajput, Sudheesh K.; Nishchal, Naveen K.

    2013-06-01

    Most of the reported optical techniques of encryption in literature belong to the category of symmetric cryptosystems, in which the keys used for encryption are identical to the decryption keys. In an environment of network security, a symmetric cryptosystem would suffer from problems in key distribution, management, and delivery. In this paper, we present the results of an asymmetric cryptosystem that uses fractional Fourier transform domain amplitude- and phase- truncation approach. The input image/data used are gray-scale and color patterns. The conventional random phase masks are replaced with structured phase masks to further enhance the key size and hence security of cryptosystem. The scheme also uses the concept of interference and polarization selective diffractive optical element. Cryptanalysis has been carried out considering various types of attacks using phase retrieval algorithm. Numerical simulation results have been presented.

  3. Catalytic Asymmetric Synthesis of Chiral Allylic Esters

    PubMed Central

    Cannon, Jeffrey S.; Kirsch, Stefan F.; Overman, Larry E.

    2010-01-01

    A broadly useful catalytic enantioselective synthesis of branched allylic esters from prochiral (Z)-2-alkene-1-ols has been developed. The starting allylic alcohol is converted to its trichloroacetimidate intermediate by reaction with trichloroacetonitrile, either in situ or in a separate step, and this intermediate undergoes clean enantioselective SN2′ substitution with a variety of carboxylic acids in the presence of the palladium(II) catalyst (Rp,S)-di-μ -acetatobis[(η5-2-(2'-(4'-methylethyl)oxazolinyl)cyclopentadienyl,1-C,3'-N)(η4-tetraphenylcyclobutadiene)cobalt]dipalladium, (Rp,S)-[COP-OAc]2 or its enantiomer. The scope and limitations of this useful catalytic asymmetric allylic esterification are defined. PMID:15740118

  4. Cylindrical Asymmetrical Capacitor Devices for Space Applications

    NASA Technical Reports Server (NTRS)

    Campbell, Jonathan W. (Inventor)

    2004-01-01

    An asymmetrical capacitor system is provided which creates a thrust force. The system is adapted for use in space applications and includes a capacitor device provided with a first conductive element and a second conductive element axially spaced from the first conductive element and of smaller axial extent. A shroud supplied with gas surrounds the capacitor device. The second conductive element can be a wire ring or mesh mounted on dielectric support posts affixed to a dielectric member which separates the conductive elements or a wire or mesh annulus surrounding a barrel-shaped dielectric member on which the h t element is also mounted. A high voltage source is connected across the conductive elements and applies a high voltage to the conductive elements of sufficient value to create a thrust force on the system inducing movement thereof.

  5. Performance of an AGATA asymmetric detector

    SciTech Connect

    Boston, A. J.; Dimmock, M. R.; Unsworth, C.; Boston, H. C.; Cooper, R. J.; Grint, A. N.; Harkness, L. J.; Jones, M.; Nolan, P. J.; Oxley, D. C.; Slee, M.; Lazarus, I. H.; Simpson, J.

    2008-11-11

    Each major technical advance in gamma-ray detection devices has resulted in significant new insights into the structure of atomic nuclei. The next major step in gamma-ray spectroscopy involves achieving the goal of a 4{pi} ball of germanium detectors by using the technique of gamma-ray energy tracking in electrically segmented germanium crystals. The resulting spectrometer will have an unparalleled level of detection power for nuclear electromagnetic radiation. Collaborations have been established in Europe (AGATA)[1] and the USA (GRETA/GRETINA)[2] to build gamma-ray tracking spectrometers. This paper discusses the performance of the first AGATA (Advanced GAmma Tracking Array) asymmetric detector that has been tested at the University of Liverpool. The use of a fully digital data acquisition system has allowed detector charge pulse shapes from a selection of well defined photon interaction positions to be analysed, yielding important information on the position sensitivity of the detector.

  6. Asymmetric cortical extension shifts cleavage furrow position in Drosophila neuroblasts

    PubMed Central

    Connell, Marisa; Cabernard, Clemens; Ricketson, Derek; Doe, Chris Q.; Prehoda, Kenneth E.

    2011-01-01

    The cytokinetic cleavage furrow is typically positioned symmetrically relative to the cortical cell boundaries, but it can also be asymmetric. The mechanisms that control furrow site specification have been intensively studied, but how polar cortex movements influence ultimate furrow position remains poorly understood. We measured the position of the apical and the basal cortex in asymmetrically dividing Drosophila neuroblasts and observed preferential displacement of the apical cortex that becomes the larger daughter cell during anaphase, effectively shifting the cleavage furrow toward the smaller daughter cell. Asymmetric cortical extension is correlated with the presence of cortical myosin II, which is polarized in neuroblasts. Loss of myosin II asymmetry by perturbing heterotrimeric G-protein signaling results in symmetric extension and equal-sized daughter cells. We propose a model in which contraction-driven asymmetric polar extension of the neuroblast cortex during anaphase contributes to asymmetric furrow position and daughter cell size. PMID:21937716

  7. HMI Measured Doppler Velocity Contamination from the SDO Orbit Velocity

    NASA Astrophysics Data System (ADS)

    Scherrer, Philip H.; SDO HMI Team

    2016-05-01

    The Helioseismic and Magnetic Imager (HMI) instrument on the Solar Dynamics Observatory (SDO) measures sets of filtergrams which are converted into velocity and magnetic field maps each 45-seconds with its front camera and each 12 minutes with its side camera. In addition to solar phototspheric motions the velocity measurements include a direct component from the line-of-sight component of the SDO orbit. Since the magnetic field is computed as the difference between the velocity measured in left and right circular polarization the orbit velocity is canceled only if the celocity is properly calibrated. When the orbit component of the velocity is subtracted for each pixel the remaining "solar" velocity shows a residual signal which is equal to about 2% of the c. +- 3000 m/s orbit velocity in a nearly linear relationship. This implies an error in our knowledge of some of the details of as-built filter components. The model instrument transmission profile is required for calibration of all HMI level 1.5 “observable” quantities. This systematic error is very likely the source of 12- and 24-hour variations in most HMI data products. Over the years since launch a substantial effort has been dedicated to understanding the origin of this problem. While the instrument as presently calibrated (Couvidat et al. 2012 and 2016) meets all of the “Level-1” mission requirements it fails to meet the stated goal of 10 m/s accuracy for velocity data products and some not stated but generally assumed goals for other products. For the velocity measurements this has not been a significant problem since the prime HMI goals of obtaining data for helioseismology are not affected by this systematic error. However the orbit signal leaking into the magnetograms and vector magnetograms degrades the ability to accomplish some of the mission science goals at the expected levels of accuracy. This poster presents the current state of understanding of the source of this systematic error and

  8. Scaffold of Asymmetric Organic Compounds - Magnetite Plaquettes

    NASA Technical Reports Server (NTRS)

    Chan, Q. H. S.; Zolensky, M. E.; Martinez, J.

    2015-01-01

    Life on Earth shows preference towards the set of organics with particular spatial configurations, this 'selectivity' is a crucial criterion for life. With only rare exceptions, life prefers the left- (L-) form over the right- (D-) form of amino acids, resulting in an L-enantiomeric excess (L-ee). Recent studies have shown Lee for alpha-methyl amino acids in some chondrites. Since these amino acids have limited terrestrial occurrence, the origin of their stereoselectivity is nonbiological, and it seems appropriate to conclude that chiral asymmetry, the molecular characteristic that is common to all terrestrial life form, has an abiotic origin. A possible abiotic mechanism that can produce chiral asymmetry in meteoritic amino acids is their formation with the presence of asymmetric catalysts, as mineral crystallization can produce spatially asymmetric structures. Magnetite is shown to be an effective catalyst for the formation of amino acids that are commonly found in chondrites. Magnetite 'plaquettes' (or 'platelets'), first described by Jedwab, show an interesting morphology of barrel-shaped stacks of magnetite disks with an apparent dislocation-induced spiral growth that seem to be connected at the center. A recent study by Singh et al. has shown that magnetites can self-assemble into helical superstructures. Such molecular asymmetry could be inherited by adsorbed organic molecules. In order to understand the distribution of 'spiral' magnetites in different meteorite classes, as well as to investigate their apparent spiral configurations and possible correlation to molecular asymmetry, we observed polished sections of carbonaceous chondrites (CC) using scanning electron microscope (SEM) imaging. The sections were also studied by electron backscattered diffraction (EBSD) in order to reconstruct the crystal orientation along the stack of magnetite disks.

  9. Asymmetric protonation of EmrE.

    PubMed

    Morrison, Emma A; Robinson, Anne E; Liu, Yongjia; Henzler-Wildman, Katherine A

    2015-12-01

    The small multidrug resistance transporter EmrE is a homodimer that uses energy provided by the proton motive force to drive the efflux of drug substrates. The pKa values of its "active-site" residues--glutamate 14 (Glu14) from each subunit--must be poised around physiological pH values to efficiently couple proton import to drug export in vivo. To assess the protonation of EmrE, pH titrations were conducted with (1)H-(15)N TROSY-HSQC nuclear magnetic resonance (NMR) spectra. Analysis of these spectra indicates that the Glu14 residues have asymmetric pKa values of 7.0 ± 0.1 and 8.2 ± 0.3 at 45°C and 6.8 ± 0.1 and 8.5 ± 0.2 at 25°C. These pKa values are substantially increased compared with typical pKa values for solvent-exposed glutamates but are within the range of published Glu14 pKa values inferred from the pH dependence of substrate binding and transport assays. The active-site mutant, E14D-EmrE, has pKa values below the physiological pH range, consistent with its impaired transport activity. The NMR spectra demonstrate that the protonation states of the active-site Glu14 residues determine both the global structure and the rate of conformational exchange between inward- and outward-facing EmrE. Thus, the pKa values of the asymmetric active-site Glu14 residues are key for proper coupling of proton import to multidrug efflux. However, the results raise new questions regarding the coupling mechanism because they show that EmrE exists in a mixture of protonation states near neutral pH and can interconvert between inward- and outward-facing forms in multiple different protonation states. PMID:26573622

  10. Algebraic Davis Decomposition and Asymmetric Doob Inequalities

    NASA Astrophysics Data System (ADS)

    Hong, Guixiang; Junge, Marius; Parcet, Javier

    2016-04-01

    In this paper we investigate asymmetric forms of Doob maximal inequality. The asymmetry is imposed by noncommutativity. Let {({M}, τ)} be a noncommutative probability space equipped with a filtration of von Neumann subalgebras {({M}_n)_{n ≥ 1}} , whose union {bigcup_{n≥1}{M}_n} is weak-* dense in {{M}} . Let {{E}_n} denote the corresponding family of conditional expectations. As an illustration for an asymmetric result, we prove that for {1 < p < 2} and {x in L_p({M},τ)} one can find {a, b in L_p({M},τ)} and contractions {u_n, v_n in {M}} such that {E}_n(x) = a u_n + v_n b quad and quad max big{ |a|_p,|b|_p big} ≤ c_p |x|_p. Moreover, it turns out that {a u_n} and {v_n b} converge in the row/column Hardy spaces {{H}_p^r({M})} and {{H}_p^c({M})} respectively. In particular, this solves a problem posed by the Defant and Junge in 2004. In the case p = 1, our results establish a noncommutative form of the Davis celebrated theorem on the relation betwe en martingale maximal and square functions in L 1, whose noncommutative form has remained open for quite some time. Given {1 ≤ p ≤ 2} , we also provide new weak type maximal estimates, which imply in turn left/right almost uniform convergence of {{E}_n(x)} in row/column Hardy spaces. This improves the bilateral convergence known so far. Our approach is based on new forms of Davis martingale decomposition which are of independent interest, and an algebraic atomic description for the involved Hardy spaces. The latter results are new even for commutative von Neumann algebras.

  11. Catalytic Asymmetric Umpolung Reactions of Imines

    PubMed Central

    Wu, Yongwei; Hu, Lin; Li, Zhe; Deng, Li

    2015-01-01

    Imines, carbon-nitrogen double bonds, are fundamentally important functional groups in organic chemistry. This is largely due to the fact that imines act as electrophiles in C–C bond forming reactions towards carbon nucleophiles, thereby serving one of the most widely used precursors for the formation of amines in both synthetic and biosynthetic settings.1–5 If the carbon atom of the imine could be rendered electron-rich, the imine could react as a nucleophile instead of as an electrophile. Such a reversal in the electronic characteristics of the imine functionality would facilitate the development of new chemical transformations that convert imines into amines via C–C bond forming reactions with carbon electrophiles, thereby creating new opportunities for the efficient synthesis of amines. The development of asymmetric ‘umpolung’ reactions of imines remains an uncharted ground, in spite of the far-reaching impact of such reactions in organic synthesis. Here we report the discovery and development of new chiral phase transfer catalysts that promote the highly efficient asymmetric umpolung reactions of imines and enals. These catalysts mediate the deprotonation of imines and direct the 2-azaallylanions thus formed to react in a highly chemoselective, regioselective, diastereoselective and enantioselective fashion with enals. The reaction tolerates a broad range of imines and enals, and can be carried out in high yield with as little as 0.01 mol % catalyst with a moisture and air-tolerant operational protocol. These umpolung reactions provide a conceptually new and practical approach towards chiral amino compounds. PMID:26201597

  12. Modeling Normal Shock Velocity Curvature Relation for Heterogeneous Explosives

    NASA Astrophysics Data System (ADS)

    Yoo, Sunhee; Crochet, Michael; Pemberton, Steve

    2015-06-01

    The normal shock velocity and curvature, Dn(κ) , relation on a detonation shock surface has been an important functional quantity to measure to understand the shock strength exerted against the material interface between a main explosive charge and the case of an explosive munition. The Dn(κ) relation is considered an intrinsic property of an explosive, and can be experimentally deduced by rate stick tests at various charge diameters. However, experimental measurements of the Dn(κ) relation for heterogeneous explosives such as PBXN-111 are challenging due to the non-smoothness and asymmetry usually observed in the experimental streak records of explosion fronts. Out of the many possibilities, the asymmetric character may be attributed to the heterogeneity of the explosives, a hypothesis which begs two questions: (1) is there any simple hydrodynamic model that can explain such an asymmetric shock evolution, and (2) what statistics can be derived for the asymmetry using simulations with defined structural heterogeneity in the unreacted explosive? Saenz, Taylor and Stewart studied constitutive models for derivation of the Dn(κ) relation on porous `homogeneous' explosives and carried out simulations in a spherical coordinate frame. In this paper, we extend their model to account for `heterogeneity' and present shock evolutions in heterogeneous explosives using 2-D hydrodynamic simulations with some statistical examination. (96TW-2015-0004)

  13. Turbulent flow separation in three-dimensional asymmetric diffusers

    NASA Astrophysics Data System (ADS)

    Jeyapaul, Elbert

    2011-12-01

    Turbulent three-dimensional flow separation is more complicated than 2-D. The physics of the flow is not well understood. Turbulent flow separation is nearly independent of the Reynolds number, and separation in 3-D occurs at singular points and along convergence lines emanating from these points. Most of the engineering turbulence research is driven by the need to gain knowledge of the flow field that can be used to improve modeling predictions. This work is motivated by the need for a detailed study of 3-D separation in asymmetric diffusers, to understand the separation phenomena using eddy-resolving simulation methods, assess the predictability of existing RANS turbulence models and propose modeling improvements. The Cherry diffuser has been used as a benchmark. All existing linear eddy-viscosity RANS models k--o SST,k--epsilon and v2- f fail in predicting such flows, predicting separation on the wrong side. The geometry has a doubly-sloped wall, with the other two walls orthogonal to each other and aligned with the diffuser inlet giving the diffuser an asymmetry. The top and side flare angles are different and this gives rise to different pressure gradient in each transverse direction. Eddyresolving simulations using the Scale adaptive simulation (SAS) and Large Eddy Simulation (LES) method have been used to predict separation in benchmark diffuser and validated. A series of diffusers with the same configuration have been generated, each having the same streamwise pressure gradient and parametrized only by the inlet aspect ratio. The RANS models were put to test and the flow physics explored using SAS-generated flow field. The RANS model indicate a transition in separation surface from top sloped wall to the side sloped wall at an inlet aspect ratio much lower than observed in LES results. This over-sensitivity of RANS models to transverse pressure gradients is due to lack of anisotropy in the linear Reynolds stress formulation. The complexity of the flow

  14. Molecular line emission in asymmetric envelopes of evolved stars

    NASA Astrophysics Data System (ADS)

    Sanchez, Andres Felipe Perez

    2014-06-01

    Stars with initial masses of 0.8 < M⊙ < 9M⊙ eject most of their mass when evolving along the asymptotic giant branch (AGB) phase. The ejected material eventually cools down, which leads it to condensate and to form dust grains and molecular gas around the star, creating an extended circumstellar envelope (CSE). The mechanism responsible for the expansion of the dusty and dense CSEs is not completely understood. It is suggested that stellar radiation pressure on the dust particles can accelerate them outwards. Then, by collisional exchange of momentum, the dust particles drag along the molecular gas. However, this scenario cannot explain the onset of asymmetries in the CSEs observed towards more evolved sources such as post-AGB sources and Planetary nebulae. Part of the research in this thesis is focused on the study of the role that the stellar magnetic field plays on the formation of the collimated high-velocity outflows observed towards post-AGB sources. Polarized maser emission towards (post-)AGB stars has become an useful tool to determine the properties of the stellar magnetic fields permeating their CSEs. However, the polarization fraction detected can be affected by non-Zeeman effects. Here I present the results of our analysis of the polarization properties of SiO, H2O and HCN maser emission in the (sub-)millimetre wavelength range. The goal of this analysis is to determine whether polarized maser emission of these molecular species can be used as reliable tracer of the magnetic field from observations at (sub-)millimetre wavelengths. I also present the results of radio interferometric observations of both continuum and polarized maser emission towards post-AGB stars. The sources observed are characterized by H2O maser emission arising from their collimated, high-velocity outflows. The observations have been carried out with the Australian Telescope Compact Array aiming to detect both polarized maser emission and non-thermal radio continuum emission

  15. Asymmetric turbulent boundary layers along long thin circular cylinders at low-Re

    NASA Astrophysics Data System (ADS)

    Jordan, Stephen A.

    2015-09-01

    Notable deviations of the asymmetric turbulent boundary layer (TBL) statistics from their axisymmetric counterpart along long thin circular cylinders are vitally important to the naval and oceanographic jurisdictions. Although the available experimental evidence backs their concern, the realm of parametric variability (both geometric and kinematic) is extremely limited to draw solid conclusions. We know that only small misalignments which quantify less than one degree of incidence between the freestream and the straight cylinder axis can substantially alter the boundary layer thicknesses, mean axial velocity, and Reynolds stresses. But the statistical database is plainly inadequate to justify modifying the design tools that were founded solely for axisymmetric flow conditions. Herein, we begin rectifying this drawback by numerical means. The investigation centers on low turbulent Reynolds numbers (500 ≤ Rea ≤ 2500) and small angles-of-incidence (0° < α < 9°) to validate and complement the lions-share of the present database (Rea = aUo/ν, where a, Uo, and ν are the cylinder radius, freestream velocity, and kinematic viscosity, respectively). In particular, we numerically resolved the statistical responses of the TBL, mean axial velocity, Reynolds stresses, and skin friction under angles-of-incidence up to the earliest signs of Strouhal-type shedding. Clearly, the first prominent response was the thinning and thickening of the TBL along the respective windward and leeward sides to only a minor misalignment. Tilting the straight cylinder to slightly higher yaw angles transformed the TBL to a transitional boundary layer along the windward side for all simulated Reynolds numbers. For yaw angles α > 2°, all turbulent statistics of the asymmetric boundary layer were measurably dissimilar to those of the axisymmetric state.

  16. Current driven asymmetric domain wall propagation

    NASA Astrophysics Data System (ADS)

    Garg, Chirag; Pushp, Aakash; Phung, Timothy; Yang, See-Hun; Hughes, Brian P.; Rettner, Charles; Parkin, Stuart S. P.

    In ultrathin magnetic heterostructures, the presence of spin-orbit coupling gives rise to chiral Neel walls which are stabilized by the Dzyaloshinskii-Moriya Interaction (DMI), and also to a highly efficient chiral spin torque mechanism. In straight nanowires, the current-driven propagation of alternating Néel DWs without the presence of an in-plane field is equivalent, leading to the lock-step motion of several DWs in a nanowire. Here, we show that by engineering the structure in which the domain walls propagate, which in our case is in the shape of a Y-shaped junction, the DW propagation process becomes selective to the polarity of the DWs even in the absence of any externally applied magnetic fields. We remarkably find that after splitting at the Y-shaped junction, the DW velocity in one branch remains largely unaffected compared to its initial velocity whereas simultaneously the DW velocity in the other branch decreases by as much as 10-90%. We show that this large change in the DW velocity in a particular branch depends on the relative angle between the local magnetization of the DW and the spin current emanating from the underlying heavy-metal layer in these nanowires.

  17. Asymmetric dominance and asymmetric mate choice oppose premating isolation after allopatric divergence

    PubMed Central

    Sefc, Kristina M; Hermann, Caroline M; Steinwender, Bernd; Brindl, Hanna; Zimmermann, Holger; Mattersdorfer, Karin; Postl, Lisbeth; Makasa, Lawrence; Sturmbauer, Christian; Koblmüller, Stephan

    2015-01-01

    Assortative mating promotes reproductive isolation and allows allopatric speciation processes to continue in secondary contact. As mating patterns are determined by mate preferences and intrasexual competition, we investigated male–male competition and behavioral isolation in simulated secondary contact among allopatric populations. Three allopatric color morphs of the cichlid fish Tropheus were tested against each other. Dyadic male–male contests revealed dominance of red males over bluish and yellow-blotch males. Reproductive isolation in the presence of male–male competition was assessed from genetic parentage in experimental ponds and was highly asymmetric among pairs of color morphs. Red females mated only with red males, whereas the other females performed variable degrees of heteromorphic mating. Discrepancies between mating patterns in ponds and female preferences in a competition-free, two-way choice paradigm suggested that the dominance of red males interfered with positive assortative mating of females of the subordinate morphs and provoked asymmetric hybridization. Between the nonred morphs, a significant excess of negative assortative mating by yellow-blotch females with bluish males did not coincide with asymmetric dominance among males. Hence, both negative assortative mating preferences and interference of male–male competition with positive assortative preferences forestall premating isolation, the latter especially in environments unsupportive of competition-driven spatial segregation. PMID:25937900

  18. Asymmetric dominance and asymmetric mate choice oppose premating isolation after allopatric divergence.

    PubMed

    Sefc, Kristina M; Hermann, Caroline M; Steinwender, Bernd; Brindl, Hanna; Zimmermann, Holger; Mattersdorfer, Karin; Postl, Lisbeth; Makasa, Lawrence; Sturmbauer, Christian; Koblmüller, Stephan

    2015-04-01

    Assortative mating promotes reproductive isolation and allows allopatric speciation processes to continue in secondary contact. As mating patterns are determined by mate preferences and intrasexual competition, we investigated male-male competition and behavioral isolation in simulated secondary contact among allopatric populations. Three allopatric color morphs of the cichlid fish Tropheus were tested against each other. Dyadic male-male contests revealed dominance of red males over bluish and yellow-blotch males. Reproductive isolation in the presence of male-male competition was assessed from genetic parentage in experimental ponds and was highly asymmetric among pairs of color morphs. Red females mated only with red males, whereas the other females performed variable degrees of heteromorphic mating. Discrepancies between mating patterns in ponds and female preferences in a competition-free, two-way choice paradigm suggested that the dominance of red males interfered with positive assortative mating of females of the subordinate morphs and provoked asymmetric hybridization. Between the nonred morphs, a significant excess of negative assortative mating by yellow-blotch females with bluish males did not coincide with asymmetric dominance among males. Hence, both negative assortative mating preferences and interference of male-male competition with positive assortative preferences forestall premating isolation, the latter especially in environments unsupportive of competition-driven spatial segregation. PMID:25937900

  19. Singularity of the Velocity Distribution Function in Molecular Velocity Space

    NASA Astrophysics Data System (ADS)

    Chen, I.-Kun; Funagane, Hitoshi; Liu, Tai-Ping; Takata, Shigeru

    2016-01-01

    We study the boundary singularity of the solutions to the Boltzmann equation in the kinetic theory. The solution has a jump discontinuity in the microscopic velocity {ζ} on the boundary and a secondary singularity of logarithmic type around the velocity tangential to the boundary, {ζn ˜ 0-}, where {ζn} is the component of molecular velocity normal to the boundary, pointing to the gas. We demonstrate this secondary singularity by obtaining an asymptotic formula for the derivative of the solution on the boundary with respect to {ζn} that diverges logarithmically when {ζn ˜ 0-}. Our study is for the thermal transpiration problem between two plates for the hard sphere gases with sufficiently large Knudsen number and with the diffuse reflection boundary condition. The solution is constructed and its singularity is studied by an iteration procedure.

  20. Effect of delta tabs on mixing and axis switching in jets from asymmetric nozzles

    NASA Technical Reports Server (NTRS)

    Zaman, K. B. M. Q.

    1994-01-01

    The effect of delta tabs on mixing and the phenomenon of axis switching in free air jets from various asymmetric nozzles was studied experimentally. Flow visualization and Pitot probe surveys were carried out with a set of small nozzles (D = 1.47 cm) at a jet Mach number, Mj = 1.63. Hot wire measurements for streamwise vorticity were carried out with larger nozzles (D = 6.35 cm) at Mj = 0.31. Jet mixing with the asymmetric nozzles, as indicated by the mass fluxes downstream, was found to be higher than that produced by a circular nozzle. The circular nozzle with four delta tabs, however, produced fluxes much higher than that produced by a asymmetric nozzles themselves or by most of the tab configurations tried with them. Even higher fluxes could be obtained with only a few cases, e.g., with 3:1 rectangular nozzle with two large delta tabs placed on the narrow edges. In this case, the jet 'fanned out' at a large angle after going through one axis switch. The axis switching could be either stopped or augmented with suitable choice of the tab configurations. Two mechanisms are identified governing the phenomenon. One, as described in Ref. 12 and referred to here as the omega(sub Theta)-induced dynamics, is due to differential induced velocities of different segments of a rolled up azimuthal vortical structure. The other is the omega(sub x)-induced dynamics due to the induced velocities of streamwise vortex pairs in the flow. While the former dynamics are responsible for rapid axis switching in periodically forced jets, the effect of the tabs is governed mainly by the latter. It is inferred that both dynamics are active in a natural asymmetric jet issuing from a nozzle having an upstream contraction. The tendency for axis switching caused by the omega(sub Theta)-induced dynamics is resisted by the omega(sub x)-induced dynamics, leading to a delayed or no switch over in that case. In jets from orifices and in screeching jets, the omega(sub Theta)-induced dynamics

  1. Calculation of symmetric and asymmetric vortex seperation on cones and tangent ogives based on discrete vortex models

    NASA Technical Reports Server (NTRS)

    Chin, S.; Lan, C. Edward

    1988-01-01

    An inviscid discrete vortex model, with newly derived expressions for the tangential velocity imposed at the separation points, is used to investigate the symmetric and asymmetric vortex separation on cones and tangent ogives. The circumferential locations of separation are taken from experimental data. Based on a slender body theory, the resulting simultaneous nonlinear algebraic equations in a cross-flow plane are solved with Broyden's modified Newton-Raphson method. Total force coefficients are obtained through momentum principle with new expressions for nonconical flow. It is shown through the method of function deflation that multiple solutions exist at large enough angles of attack, even with symmetric separation points. These additional solutions are asymmetric in vortex separation and produce side force coefficients which agree well with data for cones and tangent ogives.

  2. Double aromaticity in transition metal centered double-ring boron clusters M@B2n (M = Ti, Cr, Fe, Ni, Zn; n = 6, 7, 8)

    NASA Astrophysics Data System (ADS)

    Xu, Chang; Cheng, Longjiu; Yang, Jinlong

    2014-09-01

    It is well known that double-ring boron clusters have got the special double aromaticity with delocalized π orbitals in two directions (tangential and radial), which are potential ligands centered by a transition metal. In this article, the transition metal centered double-ring boron clusters M@B2n (M = Ti, Cr, Fe, Ni, Zn; n = 6, 7, 8) are theoretically investigated by density functional theory calculations. These endohedral compounds have also got double aromaticity in both tangential and radial directions. Interestingly, the tangential delocalized π orbitals of boron ligands following the Huckle's (4n + 2) rule do not interact with the central metal, while the radial π orbitals of boron ligands are bonded with the central mental to form spd-π endohedral bonding. The spd-π endohedral bonding follows the 18e-principle in Ni@B14 and Fe@B16. However, due to the flat shape of the compounds, 14e (Cr@B14) and 16e (Ni@B12) can also be electronically very stable where the energy levels of the spd-π orbitals delocalized in z-direction rise up. This intriguing bonding model makes sense in further study of the boron chemistry.

  3. Structural phase stability, electronic structure and mechanical properties of alkali metal hydrides AMH4 (A=Li, Na; M=B, AL)

    NASA Astrophysics Data System (ADS)

    Santhosh, M.; Rajeswarapalanichamy, R.

    2016-01-01

    The structural stability of Alkali metal hydrides AMH4 (A=Li, Na; M=B, Al) is analyzed among the various crystal structures, namely hexagonal (P63mc), tetragonal (P42/nmc), tetragonal (P-421c), tetragonal (I41/a), orthorhombic (Pnma) and monoclinic (P21/c). It is observed that, orthorhombic (Pnma) phase is the most stable structure for LiBH4, monoclinic (P21/c) for LiAlH4, tetragonal (P42/nmc) for NaBH4 and tetragonal (I41/a) for NaAlH4 at normal pressure. Pressure induced structural phase transitions are observed in LiBH4, LiAlH4, NaBH4 and NaAlH4 at the pressures of 4 GPa, 36.1 GPa, 26.5 GPa and 46 GPa respectively. The electronic structure reveals that these metal hydrides are wide band gap insulators. The calculated elastic constants indicate that these metal hydrides are mechanically stable at normal pressure.

  4. Neutrino and Superluminal Limiting Velocity

    NASA Astrophysics Data System (ADS)

    Soln, Josip

    2013-04-01

    From the relativistic kinematics one derives the relativistic bicubic equation for the particle limiting velocity in the arbitrary reference frame. The three solutions, in quadratic forms, depending on the particle mass, m, energy, E, and the ordinary velocity, v, are all given in exact forms. In a frame where mv^2/E is very small, the solutions are given as Taylor series from which one recognizes just one solution as physically acceptable and denoting it as C. For a massless particle, m=o, C=v, the particle velocity,while for a photon C becomes luminal, C=c, with c the light velocity. In the OPERA experiment [1], one measures the muon neutrino velocity with E=17GeV at a distance of 730 km. The mass of the neutrino pushes the C values upward from c which, however is neutralized by a large value of E and could be neglected. Restricting ourselves to the OPERA results for which v >,=c,and for the sake of completeness, assuming m=0.05eV, the solution for C turns out to be slightly larger than c, C >,=c, with the largest value C=1.000002c.[4pt] [1] T. Adam et al., arXiv:1212.1276

  5. Geostatistical Modeling of Pore Velocity

    SciTech Connect

    Devary, J.L.; Doctor, P.G.

    1981-06-01

    A significant part of evaluating a geologic formation as a nuclear waste repository involves the modeling of contaminant transport in the surrounding media in the event the repository is breached. The commonly used contaminant transport models are deterministic. However, the spatial variability of hydrologic field parameters introduces uncertainties into contaminant transport predictions. This paper discusses the application of geostatistical techniques to the modeling of spatially varying hydrologic field parameters required as input to contaminant transport analyses. Kriging estimation techniques were applied to Hanford Reservation field data to calculate hydraulic conductivity and the ground-water potential gradients. These quantities were statistically combined to estimate the groundwater pore velocity and to characterize the pore velocity estimation error. Combining geostatistical modeling techniques with product error propagation techniques results in an effective stochastic characterization of groundwater pore velocity, a hydrologic parameter required for contaminant transport analyses.

  6. Cosmic string induced peculiar velocities

    NASA Technical Reports Server (NTRS)

    Van Dalen, Anthony; Schramm, David N.

    1988-01-01

    This paper considers the scenario of a flat universe with a network of heavy cosmic strings as the primordial fluctuation spectrum. The joint probability of finding streaming velocities of at least 600 km/s on large scales and local peculiar velocities of less than 800 km/s is calculated. It is shown how the effects of loops breaking up and being born with a spectrum of sizes can be estimated. It is found that to obtain large-scale streaming velocities of at least 600 km/s, it is necessary that either a large value for beta G mu exist or the effect of loop fissioning and production details be considerable.

  7. Asymmetric modes decomposition in an overmoded relativistic backward wave oscillator

    SciTech Connect

    Zhang, Dian; Zhang, Jun Zhong, Huihuang; Jin, Zhenxing; Ju, Jinchuan

    2014-09-15

    Most of the investigated overmoded relativistic backward wave oscillators (RBWOs) are azimuthally symmetric; thus, they are designed through two dimensional (2-D) particle-in-cell (PIC) simulations. However, 2-D PIC simulations cannot reveal the effect of asymmetric modes on beam-wave interaction. In order to investigate whether asymmetric mode competition needs to be considered in the design of overmoded RBWOs, a numerical method of determining the composition of both symmetric and asymmetric modes in three dimensional (3-D) PIC simulations is introduced in this paper. The 2-D and 3-D PIC simulation results of an X-band overmoded RBWO are analyzed. Our analysis indicates that the 2-D and 3-D PIC simulation results of our device are quite different due to asymmetric mode competition. In fact, asymmetric surface waves, especially EH{sub 11} mode, can lead to serious mode competition when electron beam propagates near the surface of slow wave structures (SWSs). Therefore, additional method of suppressing asymmetric mode competition, such as adjusting the reflections at both ends of SWSs to decrease the Q-factor of asymmetric modes, needs to be utilized in the design of overmoded RBWOs. Besides, 3-D PIC simulation and modes decomposition are essential for designing overmoded RBWOs.

  8. Estimating Shear Velocity and Roughness Length From Velocity Profiles

    NASA Astrophysics Data System (ADS)

    Bergeron, Normand E.; Abrahams, Athol D.

    1992-08-01

    In turbulent boundary layer flows, shear velocity u*, and roughness length z0 are commonly derived from semilogarithmic flow velocity profiles by fitting a straight line by ordinary least squares regression to the profile and calculating estimates of u*, and z0 from the slope and intercept of the computed regression equation. However, it is not clear from the literature whether the appropriate regression is of flow velocity u on the logarithm of height above the bed In z or of ln z on u. In order to calculate estimates of u* and z0, the true or structural relation between u and In z must be established. Because u is generally observed with much greater error than is In z, the structural relation may be estimated by regressing u on ln z; regressing ln z on u is incorrect. An analysis of 24 stream channel flow velocity profiles indicates that even in situations where the correlation between u and ln z exceeds 0.9, performing the incorrect regression can result in the considerable overestimation of u* and z0.

  9. Microbunching Instability in Velocity Bunching

    SciTech Connect

    Xiang, D; Wu, J.; /SLAC

    2009-05-26

    Microbunching instability is one of the most challenging threats to FEL performances. The most effective ways to cure the microbunching instability include suppression of the density modulation sources and suppression of the amplification process. In this paper we study the microbunching instability in velocity bunching. Our simulations show that the initial current and energy modulations are suppressed in velocity bunching process, which may be attributed to the strong plasma oscillation and Landau damping from the relatively low beam energy and large relative slice energy spread. A heating effect that may be present in a long solenoid is also preliminarily analyzed.

  10. Velocity fluctuations of fission fragments

    NASA Astrophysics Data System (ADS)

    Llanes-Estrada, Felipe J.; Carmona, Belén Martínez; Martínez, Jose L. Muñoz

    2016-02-01

    We propose event by event velocity fluctuations of nuclear fission fragments as an additional interesting observable that gives access to the nuclear temperature in an independent way from spectral measurements and relates the diffusion and friction coefficients for the relative fragment coordinate in Kramers-like models (in which some aspects of fission can be understood as the diffusion of a collective variable through a potential barrier). We point out that neutron emission by the heavy fragments can be treated in effective theory if corrections to the velocity distribution are needed.

  11. SOLAR CONSTRAINTS ON ASYMMETRIC DARK MATTER

    SciTech Connect

    Lopes, Ilidio; Silk, Joseph E-mail: silk@astro.ox.ac.uk

    2012-10-01

    The dark matter content of the universe is likely to be a mixture of matter and antimatter, perhaps comparable to the measured asymmetric mixture of baryons and antibaryons. During the early stages of the universe, the dark matter particles are produced in a process similar to baryogenesis, and dark matter freezeout depends on the dark matter asymmetry and the annihilation cross section (s-wave and p-wave annihilation channels) of particles and antiparticles. In these {eta}-parameterized asymmetric dark matter ({eta}ADM) models, the dark matter particles have an annihilation cross section close to the weak interaction cross section, and a value of dark matter asymmetry {eta} close to the baryon asymmetry {eta}{sub B}. Furthermore, we assume that dark matter scattering of baryons, namely, the spin-independent scattering cross section, is of the same order as the range of values suggested by several theoretical particle physics models used to explain the current unexplained events reported in the DAMA/LIBRA, CoGeNT, and CRESST experiments. Here, we constrain {eta}ADM by investigating the impact of such a type of dark matter on the evolution of the Sun, namely, the flux of solar neutrinos and helioseismology. We find that dark matter particles with a mass smaller than 15 GeV, a spin-independent scattering cross section on baryons of the order of a picobarn, and an {eta}-asymmetry with a value in the interval 10{sup -12}-10{sup -10}, would induce a change in solar neutrino fluxes in disagreement with current neutrino flux measurements. This result is also confirmed by helioseismology data. A natural consequence of this model is suppressed annihilation, thereby reducing the tension between indirect and direct dark matter detection experiments, but the model also allows a greatly enhanced annihilation cross section. All the cosmological {eta}ADM scenarios that we discuss have a relic dark matter density {Omega}h {sup 2} and baryon asymmetry {eta}{sub B} in agreement with

  12. Asymmetric protonation of EmrE

    PubMed Central

    Morrison, Emma A.; Robinson, Anne E.; Liu, Yongjia

    2015-01-01

    The small multidrug resistance transporter EmrE is a homodimer that uses energy provided by the proton motive force to drive the efflux of drug substrates. The pKa values of its “active-site” residues—glutamate 14 (Glu14) from each subunit—must be poised around physiological pH values to efficiently couple proton import to drug export in vivo. To assess the protonation of EmrE, pH titrations were conducted with 1H-15N TROSY-HSQC nuclear magnetic resonance (NMR) spectra. Analysis of these spectra indicates that the Glu14 residues have asymmetric pKa values of 7.0 ± 0.1 and 8.2 ± 0.3 at 45°C and 6.8 ± 0.1 and 8.5 ± 0.2 at 25°C. These pKa values are substantially increased compared with typical pKa values for solvent-exposed glutamates but are within the range of published Glu14 pKa values inferred from the pH dependence of substrate binding and transport assays. The active-site mutant, E14D-EmrE, has pKa values below the physiological pH range, consistent with its impaired transport activity. The NMR spectra demonstrate that the protonation states of the active-site Glu14 residues determine both the global structure and the rate of conformational exchange between inward- and outward-facing EmrE. Thus, the pKa values of the asymmetric active-site Glu14 residues are key for proper coupling of proton import to multidrug efflux. However, the results raise new questions regarding the coupling mechanism because they show that EmrE exists in a mixture of protonation states near neutral pH and can interconvert between inward- and outward-facing forms in multiple different protonation states. PMID:26573622

  13. Theory and Modeling of Asymmetric Catalytic Reactions.

    PubMed

    Lam, Yu-Hong; Grayson, Matthew N; Holland, Mareike C; Simon, Adam; Houk, K N

    2016-04-19

    Modern density functional theory and powerful contemporary computers have made it possible to explore complex reactions of value in organic synthesis. We describe recent explorations of mechanisms and origins of stereoselectivities with density functional theory calculations. The specific functionals and basis sets that are routinely used in computational studies of stereoselectivities of organic and organometallic reactions in our group are described, followed by our recent studies that uncovered the origins of stereocontrol in reactions catalyzed by (1) vicinal diamines, including cinchona alkaloid-derived primary amines, (2) vicinal amidophosphines, and (3) organo-transition-metal complexes. Two common cyclic models account for the stereoselectivity of aldol reactions of metal enolates (Zimmerman-Traxler) or those catalyzed by the organocatalyst proline (Houk-List). Three other models were derived from computational studies described in this Account. Cinchona alkaloid-derived primary amines and other vicinal diamines are venerable asymmetric organocatalysts. For α-fluorinations and a variety of aldol reactions, vicinal diamines form enamines at one terminal amine and activate electrophilically with NH(+) or NF(+) at the other. We found that the stereocontrolling transition states are cyclic and that their conformational preferences are responsible for the observed stereoselectivity. In fluorinations, the chair seven-membered cyclic transition states is highly favored, just as the Zimmerman-Traxler chair six-membered aldol transition state controls stereoselectivity. In aldol reactions with vicinal diamine catalysts, the crown transition states are favored, both in the prototype and in an experimental example, shown in the graphic. We found that low-energy conformations of cyclic transition states occur and control stereoselectivities in these reactions. Another class of bifunctional organocatalysts, the vicinal amidophosphines, catalyzes the (3 + 2) annulation

  14. Cophasal horizontal wideband array antennas for transmitting with asymmetric output

    NASA Astrophysics Data System (ADS)

    Belousov, S. P.; Kliger, G. A.; Eskin, N. A.

    1985-03-01

    Type SGDRA cophasal horizontal wideband antennas for transmitters with asymmetric (single-stage) output are described. An antenna of this kind consists of rigid shunt vibrators and an asymmetric feeder channel. The latter is formed by symmetric overhead feeders, a symmetrizing device being available for operation with a single-stage transmitter. Two typical construction are: one tower section with four tiers of vibrator groups and two tower sections with eight tiers of vibrator groups on each, with an adapter from symmetric to asymmetric feeder channel in each case. Various arrangements for power feed are possible, coaxial cables being most suitable for this purpose. The performance characteristics of these antennas are discussed.

  15. Study of asymmetric supersonic jet flow for ejectors

    SciTech Connect

    Ho, C.M. . Dept. of Aerospace Engineering); Knoke, G.S. ); Geller, E.W.; Liu, H.T. ); Jou, W.H. ); Chen, F.C.; Murphy, R.W. )

    1990-01-01

    An asymmetric subsonic jet nozzle with a small aspect ratio can entrain a mass several times higher than a circular jet can entrain in a low subsonic flow. In this study, we extend the Mach number of the jet to 2.5. The advantage an asymmetric jet has over a circular jet in enhancing mass transfer still exists in the supersonic range. The main objective of this study is to explore the possibility of applying the asymmetric jet to a supersonic ejector with pressure build-up. The wall confinement was found to have a strong effect on the entrainment.

  16. Asymmetric Dimethylarginine, Race, and Mortality in Hemodialysis Patients

    PubMed Central

    Drew, David A.; Tighiouart, Hocine; Scott, Tammy; Kantor, Amy; Fan, Li; Artusi, Carlo; Plebani, Mario; Weiner, Daniel E.

    2014-01-01

    Background and objectives Levels of asymmetric dimethylarginine, an inhibitor of nitric oxide synthase, are elevated in kidney disease and associated with mortality in white European hemodialysis populations. Nitric oxide production and degradation are partially genetically determined and differ by racial background. No studies have measured asymmetric dimethylarginine in African Americans on dialysis and assessed whether differences exist in its association with mortality by race. Design, setting, participants, & measurements Asymmetric dimethylarginine was measured in 259 patients on maintenance hemodialysis assembled from 2004 to 2012 in Boston area outpatient centers. Cox proportional hazards models were used to determine the association between asymmetric dimethylarginine and all-cause mortality, and an interaction with race was tested. Results Mean (SD) age was 63 (17) years, 46% were women, and 22% were African American. Mean asymmetric dimethylarginine in non–African Americans was 0.79 µmol/L (0.16) versus 0.70 µmol/L (0.11) in African Americans (P<0.001); 130 patients died over a median follow-up of 2.3 years. African Americans had lower mortality risk than non–African Americans (hazard ratio, 0.27; 95% confidence interval, 0.15 to 0.50) that was robust to adjustment for age, comorbidity, and asymmetric dimethylarginine (hazard ratio, 0.35; 95% confidence interval, 0.17 to 0.69). An interaction was noted between race and asymmetric dimethylarginine (P=0.03), such that asymmetric dimethylarginine was associated with higher mortality in non–African Americans (adjusted hazard ratio, 1.29; 95% confidence interval, 1.06 to 1.57 per 1 SD higher asymmetric dimethylarginine) but not in African Americans (adjusted hazard ratio, 0.57; 95% confidence interval, 0.28 to 1.18). Additional adjustment for fibroblast growth factor 23 partially attenuated the association for non–African Americans (adjusted hazard ratio, 1.22; 95% confidence interval, 0.98 to 1

  17. Asymmetric dark matter and effective number of neutrinos

    NASA Astrophysics Data System (ADS)

    Kitabayashi, Teruyuki; Kurosawa, Yoshihiro

    2016-02-01

    We study the effect of the MeV-scale asymmetric dark matter annihilation on the effective number of neutrinos Neff at the epoch of the big bang nucleosynthesis. If the asymmetric dark matter χ couples more strongly to the neutrinos ν than to the photons γ and electrons e-, Γχ γ ,χ e≪Γχ ν , or Γχ γ ,χ e≫Γχ ν, the lower mass limit on the asymmetric dark matter is about 18 MeV for Neff≃3.0 .

  18. Modified transfer matrix method for asymmetric rotor-bearing systems

    NASA Astrophysics Data System (ADS)

    Kang, Yuan; Lee, An-Chen; Shih, Yuan-Pin

    1994-07-01

    A modified transfer matrix method (MTMM) is developed to analyze rotor-bearing systems with an asymmetric shaft and asymmetric disks. The rotating shaft is modeled by a Rayleigh-Euler beam considering the effects of the rotary inertia and gyroscopic moments. Specifically, a transfer matrix of the asymmetric shaft segments is derived in a continuous-system sense to give accurate solutions. The harmonic balance method is incorporated in the transfer matrix equations, so that steady-state responses of synchronous and superharmonic whirls can be determined. A numerical example is presented to demonstrate the effectiveness of this approach.

  19. Generic approach for synthesizing asymmetric nanoparticles and nanoassemblies

    SciTech Connect

    Sun, Yugang; Hu, Yongxing

    2015-05-26

    A generic route for synthesis of asymmetric nanostructures. This approach utilizes submicron magnetic particles (Fe.sub.3O.sub.4--SiO.sub.2) as recyclable solid substrates for the assembly of asymmetric nanostructures and purification of the final product. Importantly, an additional SiO.sub.2 layer is employed as a mediation layer to allow for selective modification of target nanoparticles. The partially patched nanoparticles are used as building blocks for different kinds of complex asymmetric nanostructures that cannot be fabricated by conventional approaches. The potential applications such as ultra-sensitive substrates for surface enhanced Raman scattering (SERS) have been included.

  20. Magnetic Properties and Microstructure of Melt--Spun Sm(Co-Fe-Cu-Zr)_zMx (M = B or C) Nanocomposite Magnets

    NASA Astrophysics Data System (ADS)

    Manrakhan, W.; Withanawasam, L.; Meng-Burany, X.; Chen, Z. M.; Hadjipanayis, G. C.

    1997-03-01

    Nanocomposite magnets have attracted much interest recently because of their potential application in less expensive and medium performance permanent magnets. We produced a nanocrystalline structure consisting of magnetically hard Sm_2Co_17 and SmCo5 phases and soft Fe(Co) phases with a high M_r/Ms ratio without significant loss of coercivity, by first making cast Sm(Co_0.65Fe_0.28Cu_0.05Zr_0.02)_zMx magnets with M = B or C, z = 7.7-9.5, and x = 0-1, and then melt--spinning and subsequently annealing small pieces of the original ingot. DSC and XRD studies showed that the as--spun Sm(Co_0.65Fe_0.28Cu_0.05Zr_0.02)z ribbons are crystalline and that the addition of the B or C makes the ribbons more glassy/amorphous. After annealing at 600-900^circ C for 15 minutes, all the samples showed a M_r/Ms ratio greater than 0.5, indicating exchange coupling among the nanosize phases. The coercivity ranged from less than 1 kOe to 12.5 kOe, and decreased with increasing B or C content. TEM and XRD studies revealed that the samples were composed of a Sm_2Co_17 (and SmCo_5) matrix with an average grain size around 100 nm and a soft Fe(Co) phase which increases with the B or C content. It was also found that B--containing samples have a finer microstructure and higher M_r/Ms than the C--containing samples.

  1. Ångström (B1Σ+ →A1Π) 0-1 and 1-1 bands in isotopic CO molecules: further investigations

    NASA Astrophysics Data System (ADS)

    Kȩpa, R.; Ostrowska-Kopeć, M.; Piotrowska, I.; Zachwieja, M.; Hakalla, R.; Szajna, W.; Kolek, P.

    2014-02-01

    In the emission spectrum of six 12C16O, 13C16O, 12C18O, 14C16O, 13C18O and 14C18O isotopologues of the carbon monoxide molecule, new recordings and analyses or new reanalyses of the selected and strongest bands belonging to the Ångström (B1Σ+ - A1Π) system were carried out. Under high resolution, emission spectra of the 0-1 and 1-1 bands were recorded and reanalysed, representing both the 0 - v″ and 1 - v″ progressions of this system. Unobserved so far, new spectral lines were identified, and for the 12C16O, 13C16O, 12C18O, 14C16O and 14C18O molecules new parameters of the rovibronic structure B0, B1, D0 and D1 of the v = 0 and v = 1 levels of the B1Σ+ state and band origins ν0 of the 0-1 and 1-1 bands of the B - A transition were determined. A detailed analysis included the predissociation regions of the spectra observed in all analysed bands and isotopologues. The values of rotational quantum numbers and rovibronic terms of the highest nonpredissociated Jh as well as the first, already predissociated Jf levels were determined. On that basis, a new and more precise value of dissociation energy of the CO molecule was determined: {D}_e=(90\\,679.1+/- 6.0) cm-1. Also, atomic states of the dissociation products of this molecule, which correspond to this energy, were identified as C(3P0) + O(3P2) i.e. as both triplet ground atomic sublevels.

  2. Asymmetrical and heterogeneous elasto-static deformation along the El Pilar Fault in Northeastern Venezuela

    NASA Astrophysics Data System (ADS)

    Reinoza, C.; Jouanne, F.; Audemard, F. A.; Beck, C.

    2013-05-01

    Velocities field in both sides of the El Pilar fault, the most important right-lateral strike-slip fault of the Caribbean-South America plate boundary, present an important asymmetry. This pattern suggests a change in elastic properties when crossing the fault. We have applied an asymmetric model to simulate observed velocities with 20 mm/yr creep at depth, corresponding at the relative velocity of Caribbean plate versus South America plate. The preferred model indicated a shallow locking depth at 4.5 km. In a second part, a near-fault low-rigidity compliant zone from 3 km of depth with a 30 per cent of rigidity reduction respect to the environment is proposed using a 3D elasto-static model. We use GPS data from 23 stations collected in 2002 and 2005 like input parameters as well as geometry parameters based in previous work. The shallow locking depth and the interseismic velocities used in the asymmetry and compliant zone models respectively support: i) the hypothesis of a partially locked seismogenic upper part, ii) the concentration of the Caribbean- South America relative displacement entirely along the El Pilar Fault. Reinoza Carlos PhD thesis and stay in ISTerre Laboratory is funded through Venezuela's FUNDAYACUCHO Grant N° 756514C. This research is a contribution to FONACIT-ECOS Nord grant 2009000818 (French code V10U01). Observed velocities (white) from 2002 and 2005 GPS campaign measurements data with error ellipses drawn for 66% confidence level expressed in the South America plate reference frame.

  3. Instrument remotely measures wind velocities

    NASA Technical Reports Server (NTRS)

    Margolis, J. S.; Mccleese, D. J.; Seaman, C. H.; Shumate, M. S.

    1980-01-01

    Doppler-shift spectrometer makes remote satellite measurements of atmospheric wind velocity and temperature at specified altitudes. As in correlation spectrometer, spectrum of gas in reference cell and spectrum of same gas in atmosphere are correlated both in emission and absorption.

  4. Asymmetric Dark Matter and Dark Radiation

    SciTech Connect

    Blennow, Mattias; Martinez, Enrique Fernandez; Mena, Olga; Redondo, Javier; Serra, Paolo E-mail: enfmarti@cern.ch E-mail: redondo@mppmu.mpg.de

    2012-07-01

    Asymmetric Dark Matter (ADM) models invoke a particle-antiparticle asymmetry, similar to the one observed in the Baryon sector, to account for the Dark Matter (DM) abundance. Both asymmetries are usually generated by the same mechanism and generally related, thus predicting DM masses around 5 GeV in order to obtain the correct density. The main challenge for successful models is to ensure efficient annihilation of the thermally produced symmetric component of such a light DM candidate without violating constraints from collider or direct searches. A common way to overcome this involves a light mediator, into which DM can efficiently annihilate and which subsequently decays into Standard Model particles. Here we explore the scenario where the light mediator decays instead into lighter degrees of freedom in the dark sector that act as radiation in the early Universe. While this assumption makes indirect DM searches challenging, it leads to signals of extra radiation at BBN and CMB. Under certain conditions, precise measurements of the number of relativistic species, such as those expected from the Planck satellite, can provide information on the structure of the dark sector. We also discuss the constraints of the interactions between DM and Dark Radiation from their imprint in the matter power spectrum.

  5. Optical nonreciprocity in asymmetric optomechanical couplers.

    PubMed

    Wang, Zheqi; Shi, Lei; Liu, Yi; Xu, Xinbiao; Zhang, Xinliang

    2015-01-01

    We propose an all-optical integrated nonreciprocal device on the optomechanical platform with a large nonreciprocal bandwidth and low operating power. The device is based on an asymmetric silicon coupler consisting of two branches. One of them is a conventional strip waveguide fixed on the substrate, and the other is a freestanding nanostring suspended above a groove in the substrate. When light is launched into the coupler, the optical gradient force between the freestanding nanostring and the underlying substrate leads to the deflection of the nanostring, and finally results in destruction of the initial phase-matching condition between the two branches. The suspended branch would achieve distinct deflections when light is incident from different ports. The simulation results show a nonreciprocal bandwidth of 13.1 nm with operating power of 390 μW. With the advantages of simple structure, low power consumption and large operating bandwidth, our work provides a promising solution for on-chip passive nonreciprocal device. PMID:25728978

  6. An asymmetric solar wind termination shock.

    PubMed

    Stone, Edward C; Cummings, Alan C; McDonald, Frank B; Heikkila, Bryant C; Lal, Nand; Webber, William R

    2008-07-01

    Voyager 2 crossed the solar wind termination shock at 83.7 au in the southern hemisphere, approximately 10 au closer to the Sun than found by Voyager 1 in the north. This asymmetry could indicate an asymmetric pressure from an interstellar magnetic field, from transient-induced shock motion, or from the solar wind dynamic pressure. Here we report that the intensity of 4-5 MeV protons accelerated by the shock near Voyager 2 was three times that observed concurrently by Voyager 1, indicating differences in the shock at the two locations. (Companion papers report on the plasma, magnetic field, plasma-wave and lower energy particle observations at the shock.) Voyager 2 did not find the source of anomalous cosmic rays at the shock, suggesting that the source is elsewhere on the shock or in the heliosheath. The small intensity gradient of Galactic cosmic ray helium indicates that either the gradient is further out in the heliosheath or the local interstellar Galactic cosmic ray intensity is lower than expected. PMID:18596802

  7. Experimental study of asymmetric heart valve prototype

    NASA Astrophysics Data System (ADS)

    Vukicevic, M.; Fortini, S.; Querzoli, G.; Cenedese, A.; Pedrizzetti, G.

    2011-11-01

    The mechanical heart valves (MHVs) are extremely important medical devices, commonly used for diseased heart valves replacement. Despite the long term of use and constant design refinement, the MHVs are very far from ideal and their performance is very diverse from that of the native ones. It has been approved that small variations in geometry of valvular leaflets influence the significant change in the intraventricular vortical flow, known as one of the most important factors for the overall functionality of the heart. We have experimentally examined the home-made heart valve prototypes, exclusively modeled for the mitral valve replacement. The performance and energetic properties of the prototypes have been compared with those in the presence of standard MHVs. The analysis was based on the testing of intraventricular fluid dynamics, usually missing criteria for the quality of the valve performance. It has been shown that the asymmetric prototype, with unequal leaflets and D-shaped orifice produces flow patterns and energetic properties close to those found in the healthy subjects. Thus, the break of symmetry in the standard bi-leaflet MHV prosthesis, at least from the fluid dynamics point of view, is worthwhile to be considered for the design of MHVs for the mitral valve replacement.

  8. Waveguide switches using asymmetric coupled quantum wells

    NASA Astrophysics Data System (ADS)

    Ritter, Kenneth J.; Horst, Scott C.

    1994-07-01

    This report contains the results of a three-year effort to investigate the use of Asymmetric Coupled Quantum Well in optical waveguide cross bar switches. The two types of devices investigated are the standard delta beta switch and the delta alpha switch. The delta alpha switch uses the imaginary part of the refractive index to modulate the intensity along different waveguide paths in the switch structure. Both types of switch were fabricated and tested. The delta beta switches produced are suitable as 1-input 2-output devices. The delta alpha switches were demonstrated as 2 by 2 cross bar switches with up to 40% throughput. To compensate for losses in the switches the use of amplifying elements was investigated. To provide gain at a longer wavelength than that of the excitons in the modulation waveguides, the quantum wells in the modulation waveguides were blue shifted using vacancy induced disordering (VID). The VID shifted quantum wells showed less Stark shift than the unshifted quantum wells. This effect is explained by the nearly parabolic shape of the disordered wells. Coupled quantum wells can be used to create a structure that will maintain a strongly Stark shifted spatially indirect transition even after VID. Modeling of the various waveguide structures used is also discussed.

  9. Asymmetric Wormholes via Electrically Charged Lightlike Branes

    SciTech Connect

    Guendelman, E.; Kaganovich, A.; Nissimov, E.; Pacheva, S.

    2010-06-17

    We consider a self-consistent Einstein-Maxwell-Kalb-Ramond system in the bulk D = 4 space-time interacting with a variable-tension electrically charged lightlike brane. The latter serves both as a material and charge source for gravity and electromagnetism, as well as it dynamically generates a bulk space varying cosmological constant. We find an asymmetric wormhole solution describing two 'universes' with different spherically symmetric black-hole-type geometries connected through a 'throat' occupied by the lightlike brane. The electrically neutral 'left universe' comprises the exterior region of Schwarzschild-de-Sitter (or pure Schwarzschild) space-time above the inner(Schwarzschild-type) horizon, whereas the electrically charged 'right universe' consists of the exterior Reissner-Nordstroem (or Reissner-Nordstroem-de-Sitter) black hole region beyond the outer Reissner-Nordstroem horizon. All physical parameters of the wormhole are uniquely determined by two free parameters - the electric charge and Kalb-Ramond coupling of the lightlike brane.

  10. Particle Transport through Hydrogels Is Charge Asymmetric

    PubMed Central

    Zhang, Xiaolu; Hansing, Johann; Netz, Roland R.; DeRouchey, Jason E.

    2015-01-01

    Transport processes within biological polymer networks, including mucus and the extracellular matrix, play an important role in the human body, where they serve as a filter for the exchange of molecules and nanoparticles. Such polymer networks are complex and heterogeneous hydrogel environments that regulate diffusive processes through finely tuned particle-network interactions. In this work, we present experimental and theoretical studies to examine the role of electrostatics on the basic mechanisms governing the diffusion of charged probe molecules inside model polymer networks. Translational diffusion coefficients are determined by fluorescence correlation spectroscopy measurements for probe molecules in uncharged as well as cationic and anionic polymer solutions. We show that particle transport in the charged hydrogels is highly asymmetric, with diffusion slowed down much more by electrostatic attraction than by repulsion, and that the filtering capability of the gel is sensitive to the solution ionic strength. Brownian dynamics simulations of a simple model are used to examine key parameters, including interaction strength and interaction range within the model networks. Simulations, which are in quantitative agreement with our experiments, reveal the charge asymmetry to be due to the sticking of particles at the vertices of the oppositely charged polymer networks. PMID:25650921

  11. Crystallization in mass and charge asymmetric bilayers

    NASA Astrophysics Data System (ADS)

    Bonitz, Michael; Ludwig, Patrick; Filinov, Alexei; Lozovik, Yurii; Stolz, Heinrich

    2007-11-01

    We consider Coulomb crystal formation in quantum electron-ion (hole) bilayers. Varying the mass ratio M of ions and electrons between 1 and 100 for a fixed layer separation d at low temperature and high density, one can tune the hole behavior from delocalized (quantum) to localized (quasi-classical) while the electrons remain delocalized all the time. While in 3D plasmas [1], ions crystallize if the mass ratio exceeds a critical value of Mcr˜80, in bilayers Mcr can be drastically reduced by properly choosing d and the in-layer particle density. The complicated overlap of correlation and quantum effects of both, electrons and holes, is fully taken care of by performing first-principle path integral Monte Carlo simulations. [1] M. Bonitz, V.S. Filinov, V.E. Fortov. P.R. Levashov, and H. Fehske, Phys. Rev. Lett. 95, 235006 (2005) and J. Phys. A: Math. Gen. 39, 4717 (2006). [2] P. Ludwig, A. Filinov, Yu. Lozovik, H. Stolz, and M. Bonitz, Crystallization in mass-asymmetric electron-hole bilayers, Contrib. Plasma Phys. (2007), ArXiv: cond-mat/0611556

  12. Computation in Dynamically Bounded Asymmetric Systems

    PubMed Central

    Rutishauser, Ueli; Slotine, Jean-Jacques; Douglas, Rodney

    2015-01-01

    Previous explanations of computations performed by recurrent networks have focused on symmetrically connected saturating neurons and their convergence toward attractors. Here we analyze the behavior of asymmetrical connected networks of linear threshold neurons, whose positive response is unbounded. We show that, for a wide range of parameters, this asymmetry brings interesting and computationally useful dynamical properties. When driven by input, the network explores potential solutions through highly unstable ‘expansion’ dynamics. This expansion is steered and constrained by negative divergence of the dynamics, which ensures that the dimensionality of the solution space continues to reduce until an acceptable solution manifold is reached. Then the system contracts stably on this manifold towards its final solution trajectory. The unstable positive feedback and cross inhibition that underlie expansion and divergence are common motifs in molecular and neuronal networks. Therefore we propose that very simple organizational constraints that combine these motifs can lead to spontaneous computation and so to the spontaneous modification of entropy that is characteristic of living systems. PMID:25617645

  13. Asymmetric translation between multiple representations in chemistry

    NASA Astrophysics Data System (ADS)

    Lin, Yulan I.; Son, Ji Y.; Rudd, James A., II

    2016-03-01

    Experts are more proficient in manipulating and translating between multiple representations (MRs) of a given concept than novices. Studies have shown that instruction using MR can increase student understanding of MR, and one model for MR instruction in chemistry is the chemistry triplet proposed by Johnstone. Concreteness fading theory suggests that presenting concrete representations before abstract representations can increase the effectiveness of MR instruction; however, little work has been conducted on varying the order of different representations during instruction and the role of concreteness in assessment. In this study, we investigated the application of concreteness fading to MR instruction and assessment in teaching chemistry. In two experiments, undergraduate students in either introductory psychology courses or general chemistry courses were given MR instruction on phase changes using different orders of presentation and MR assessment questions based on the representations in the chemistry triplet. Our findings indicate that the order of presentation based on levels of concreteness in MR chemistry instruction is less important than implementation of comprehensive MR assessments. Even after MR instruction, students display an asymmetric understanding of the chemical phenomenon on the MR assessments. Greater emphasis on MR assessments may be an important component in MR instruction that effectively moves novices toward more expert MR understanding.

  14. Polyimides Derived from Novel Asymmetric Dianhydrides

    NASA Technical Reports Server (NTRS)

    Chuang, Chun-Hua (Inventor)

    2012-01-01

    This invention relates to the compositions and processes for preparing thermoset and thermoplastic polyimides derived from novel asymmetrical dianhydrides: specifically 2,3,3',4' benzophenone dianhydride (a-BTDA), and 3,4'-(hexafluoroisopropylidene)diphthalic anhydride (a-6FDA). The a-BTDA anhydride is prepared by Suzuki coupling with catalysts from a mixed anhydride of 3,4-dimethylbenzoic acid or 2,3-dimethylbenzoic acid with 2,3-dimethylphenylboronic acid or 3,4-dimethylphenylboronic acid respectively, to form 2,3,3',4'-tetramethylbenzophenone which is oxidized to form 2,3,3',4'-benzophenonetetracarboxylic acid followed by cyclodehydration to obtain a-BTDA. The a-6FDA is prepared by nucleophilic triflouoromethylation of 2,3,3',4'-tetramethylbenzophenone with trifluoromethyltrimethylsilane to form 3,4'-(trifluoromethylmethanol)-bis(o-xylene) which is converted to 3,4'-(hexafluoroisopropylidene-bis(o-xylene). The 3,4'-(hexafluoroisopropylidene)-bis(o-xylene) is oxidized to the corresponding tetraacid followed by cyclodehydration to yield a-6FDA.

  15. Asymmetric Dimethylarginine, Endothelial Dysfunction and Renal Disease

    PubMed Central

    Aldámiz-Echevarría, Luis; Andrade, Fernando

    2012-01-01

    l-Arginine (Arg) is oxidized to l-citrulline and nitric oxide (NO) by the action of endothelial nitric oxide synthase (NOS). In contrast, protein-incorporated Arg residues can be methylated with subsequent proteolysis giving rise to methylarginine compounds, such as asymmetric dimethylarginine (ADMA) that competes with Arg for binding to NOS. Most ADMA is degraded by dimethylarginine dimethyaminohydrolase (DDAH), distributed widely throughout the body and regulates ADMA levels and, therefore, NO synthesis. In recent years, several studies have suggested that increased ADMA levels are a marker of atherosclerotic change, and can be used to assess cardiovascular risk, consistent with ADMA being predominantly absorbed by endothelial cells. NO is an important messenger molecule involved in numerous biological processes, and its activity is essential to understand both pathogenic and therapeutic mechanisms in kidney disease and renal transplantation. NO production is reduced in renal patients because of their elevated ADMA levels with associated reduced DDAH activity. These factors contribute to endothelial dysfunction, oxidative stress and the progression of renal damage, but there are treatments that may effectively reduce ADMA levels in patients with kidney disease. Available data on ADMA levels in controls and renal patients, both in adults and children, also are summarized in this review. PMID:23109853

  16. Unitarity Constraints on Asymmetric Freeze-In

    SciTech Connect

    Hook, Anson; /SLAC

    2011-08-15

    This paper considers unitarity and CPT constraints on asymmetric freeze-in, the use of freeze-in to store baryon number in a dark sector. In this scenario, Sakharov's out of equilibrium condition is satisfied by placing the visible and hidden sectors at different temperatures while a net visible baryon number is produced by storing negative baryon number in a dark sector. It is shown that unitarity and CPT lead to unexpected cancellations. In particular, the transfer of baryon number cancels completely at leading order. This note has shown that if two sectors are in thermal equilibrium with themselves, but not with each other, then the leading effect transferring conserved quantities between the two sectors is of order the the weak coupling connecting them to the third power. When freeze-in is used to produce a net baryon number density, the leading order effect comes from {Omicron}({lambda}{sup 3}) diagrams where the intermediate state that goes on-shell has a different visible baryon number than the final state visible baryon number. Models in which the correct baryon number is generated with freeze-in as the dominant source of abundance, typically require {lambda} {approx}> 10{sup -6} and m{sub bath} {approx}> TeV. m{sub bath} is the mass of the visible particle which communicates with the hidden sector. The lower window is potentially observable at the LHC.

  17. Asymmetric versus symmetric pulses for cortical microstimulation.

    PubMed

    Koivuniemi, Andrew S; Otto, Kevin J

    2011-10-01

    Intracortical microstimulation (ICMS), which has shown promise in the visual, auditory and somatosensory systems as a platform for sensory prostheses, typically relies on charged balanced, symmetric, biphasic stimulation. However, neural stimulation models as well as experiments conducted in cochlear implant users have suggested that charge balanced asymmetric pulses could generate lower detection thresholds for stimulation in terms of charge per phase. For this study, rats were chronically implanted with microelectrode arrays unilaterally in their right auditory cortex and then trained to detect ICMS delivered through a single electrode site in order to determine their behavioral threshold. This model was used in two experiments. The first experiment addressed the effect of lead phase direction, asymmetry, and phase duration on detection threshold. The second experiment fixed the cathode phase duration at 123 μs and varied only the phase asymmetry and lead phase direction. Taken together, the results of these experiments suggest that, for ICMS, the primary determinant of threshold level is cathode phase duration, and that asymmetry provides no significant advantage when compared to symmetric, cathode leading pulses. However, symmetric anode leading pulses of less than or equal to 205 μs per phase consistently showed higher thresholds when compared to all other pulses of equal cathode phase duration. PMID:21968793

  18. Asymmetric Electrostatic Radiation Shielding for Spacecraft

    NASA Technical Reports Server (NTRS)

    Metzger, Philip T.; Youngquist, Robert C.; Lane, John E.

    2005-01-01

    A paper describes the types, sources, and adverse effects of energetic-particle radiation in interplanetary space, and explores a concept of using asymmetric electrostatic shielding to reduce the amount of such radiation impinging on spacecraft. Typically, such shielding would include a system of multiple inflatable, electrically conductive spheres deployed in clusters in the vicinity of a spacecraft on lightweight structures that would maintain the spheres in a predetermined multipole geometry. High-voltage generators would maintain the spheres at potential differences chosen in conjunction with the multipole geometry so that the resulting multipole field would gradually divert approaching energetic atomic nuclei from a central region occupied by the spacecraft. The spheres nearest the center would be the most positive, so as to repel the positively charged impinging nuclei from the center. At the same time, the monopole potential of the overall spacecraft-and-shielding system would be made negative so as to repel thermal electrons. The paper presents results of computational simulations of energetic-particle trajectories and shield efficiency for a trial system of 21 spheres arranged in three clusters in an overall linear quadrupole configuration. Further development would be necessary to make this shielding concept practical.

  19. Asymmetric Cherenkov acoustic reverse in topological insulators

    NASA Astrophysics Data System (ADS)

    Smirnov, Sergey

    2014-09-01

    A general phenomenon of the Cherenkov radiation known in optics or acoustics of conventional materials is a formation of a forward cone of, respectively, photons or phonons emitted by a particle accelerated above the speed of light or sound in those materials. Here we suggest three-dimensional topological insulators as a unique platform to fundamentally explore and practically exploit the acoustic aspect of the Cherenkov effect. We demonstrate that by applying an in-plane magnetic field to a surface of a three-dimensional topological insulator one may suppress the forward Cherenkov sound up to zero at a critical magnetic field. Above the critical field the Cherenkov sound acquires pure backward nature with the polar distribution differing from the forward one generated below the critical field. Potential applications of this asymmetric Cherenkov reverse are in the design of low energy electronic devices such as acoustic ratchets or, in general, in low power design of electronic circuits with a magnetic field control of the direction and magnitude of the Cherenkov dissipation.

  20. On the Origin of the Asymmetric Helicity Injection in Emerging Active Regions

    NASA Astrophysics Data System (ADS)

    Fan, Y.; Alexander, D.; Tian, L.

    2009-12-01

    To explore the possible causes of the observed asymmetric helicity flux in emerging active regions between the leading and following polarities reported in a recent study by Tian & Alexander, we examine the subsurface evolution of buoyantly rising Ω-shaped flux tubes using three-dimensional, spherical-shell anelastic MHD simulations. We find that due to the asymmetric stretching of the Ω-shaped tube by the Coriolis force, the leading side of the emerging tube has a greater field strength, is more buoyant, and remains more cohesive compared to the following side. As a result, the magnetic field lines in the leading leg show more coherent values of local twist α ≡ (∇ × B) · B/B 2, whereas the values in the following leg show large fluctuations and are of mixed sign. On average, however, the field lines in the leading leg do not show a systematically greater mean twist compared to the following leg. Due to the higher rise velocity of the leading leg, the upward helicity flux through a horizontal cross section at each depth in the upper half of the convection zone is significantly greater in the leading polarity region than that in the following leg. This may contribute to the observed asymmetric helicity flux in emerging active regions. Furthermore, based on a simplified model of active region flux emergence into the corona by Longcope & Welsch, we show that a stronger field strength in the leading tube can result in a faster rotation of the leading polarity sunspot driven by torsional Alfvén waves during flux emergence into the corona, contributing to a greater helicity injection rate in the leading polarity of an emerging active region.

  1. ON THE ORIGIN OF THE ASYMMETRIC HELICITY INJECTION IN EMERGING ACTIVE REGIONS

    SciTech Connect

    Fan, Y.; Alexander, D.; Tian, L.

    2009-12-10

    To explore the possible causes of the observed asymmetric helicity flux in emerging active regions between the leading and following polarities reported in a recent study by Tian and Alexander, we examine the subsurface evolution of buoyantly rising OMEGA-shaped flux tubes using three-dimensional, spherical-shell anelastic MHD simulations. We find that due to the asymmetric stretching of the OMEGA-shaped tube by the Coriolis force, the leading side of the emerging tube has a greater field strength, is more buoyant, and remains more cohesive compared to the following side. As a result, the magnetic field lines in the leading leg show more coherent values of local twist alpha ident to (nabla x B) centre dot B/B {sup 2}, whereas the values in the following leg show large fluctuations and are of mixed sign. On average, however, the field lines in the leading leg do not show a systematically greater mean twist compared to the following leg. Due to the higher rise velocity of the leading leg, the upward helicity flux through a horizontal cross section at each depth in the upper half of the convection zone is significantly greater in the leading polarity region than that in the following leg. This may contribute to the observed asymmetric helicity flux in emerging active regions. Furthermore, based on a simplified model of active region flux emergence into the corona by Longcope and Welsch, we show that a stronger field strength in the leading tube can result in a faster rotation of the leading polarity sunspot driven by torsional Alfven waves during flux emergence into the corona, contributing to a greater helicity injection rate in the leading polarity of an emerging active region.

  2. Spontaneous curvature of bilayer membranes from molecular simulations: Asymmetric lipid densities and asymmetric adsorption

    NASA Astrophysics Data System (ADS)

    RóŻycki, Bartosz; Lipowsky, Reinhard

    2015-02-01

    Biomimetic and biological membranes consist of molecular bilayers with two leaflets which are typically exposed to different aqueous environments and may differ in their molecular density or composition. Because of these asymmetries, the membranes prefer to curve in a certain manner as quantitatively described by their spontaneous curvature. Here, we study such asymmetric membranes via coarse-grained molecular dynamics simulations. We consider two mechanisms for the generation of spontaneous curvature: (i) different lipid densities within the two leaflets and (ii) leaflets exposed to different concentrations of adsorbing particles. We focus on membranes that experience no mechanical tension and describe two methods to compute the spontaneous curvature. The first method is based on the detailed structure of the bilayer's stress profile which can hardly be measured experimentally. The other method starts from the intuitive view that the bilayer represents a thin fluid film bounded by two interfaces and reduces the complexity of the stress profile to a few membrane parameters that can be measured experimentally. For the case of asymmetric adsorption, we introduce a simulation protocol based on two bilayers separated by two aqueous compartments with different adsorbate concentrations. The adsorption of small particles with a size below 1 nm is shown to generate large spontaneous curvatures up to about 1/(24 nm). Our computational approach is quite general: it can be applied to any molecular model of bilayer membranes and can be extended to other mechanisms for the generation of spontaneous curvatures as provided, e.g., by asymmetric lipid composition or depletion layers of solute molecules.

  3. The velocity of climate change.

    PubMed

    Loarie, Scott R; Duffy, Philip B; Hamilton, Healy; Asner, Gregory P; Field, Christopher B; Ackerly, David D

    2009-12-24

    The ranges of plants and animals are moving in response to recent changes in climate. As temperatures rise, ecosystems with 'nowhere to go', such as mountains, are considered to be more threatened. However, species survival may depend as much on keeping pace with moving climates as the climate's ultimate persistence. Here we present a new index of the velocity of temperature change (km yr(-1)), derived from spatial gradients ( degrees C km(-1)) and multimodel ensemble forecasts of rates of temperature increase ( degrees C yr(-1)) in the twenty-first century. This index represents the instantaneous local velocity along Earth's surface needed to maintain constant temperatures, and has a global mean of 0.42 km yr(-1) (A1B emission scenario). Owing to topographic effects, the velocity of temperature change is lowest in mountainous biomes such as tropical and subtropical coniferous forests (0.08 km yr(-1)), temperate coniferous forest, and montane grasslands. Velocities are highest in flooded grasslands (1.26 km yr(-1)), mangroves and deserts. High velocities suggest that the climates of only 8% of global protected areas have residence times exceeding 100 years. Small protected areas exacerbate the problem in Mediterranean-type and temperate coniferous forest biomes. Large protected areas may mitigate the problem in desert biomes. These results indicate management strategies for minimizing biodiversity loss from climate change. Montane landscapes may effectively shelter many species into the next century. Elsewhere, reduced emissions, a much expanded network of protected areas, or efforts to increase species movement may be necessary. PMID:20033047

  4. Asymmetric drag in oscillatory motion: ratchet effect without an asymmetric potential.

    PubMed

    Fomin, Vladimir M; Smith, Elliot J; Karnaushenko, Dmitriy D; Makarov, Denys; Schmidt, Oliver G

    2013-05-01

    Asymmetry of magnetic objects in a fluid under an oscillating magnetic field leads to a wealth of nonequilibrium dynamics phenomena including a novel ratchet effect without an asymmetric substrate. These nonlinear dynamics are explained in the framework of the Stokes' model by a drag coefficient, which depends on the direction of motion. This approach is general and is independent of the physical mechanism responsible for this directional dependence of the drag coefficient as well as the size of the object. The theoretical model is experimentally verified for two systems, a nonrigid magnetic microcoil and a chiral magnetic macroobject immersed in a bounded fluid. PMID:23767502

  5. Chiral Brønsted Acids for Asymmetric Organocatalysis

    NASA Astrophysics Data System (ADS)

    Kampen, Daniela; Reisinger, Corinna M.; List, Benjamin

    Chiral Brønsted acid catalysis is an emerging area of organocatalysis. Since the pioneering studies of the groups of Akiyama and Terada in 2004 on the use of chiral BINOL phosphates as powerful Brønsted acid catalysts in asymmetric Mannich-type reactions, numerous catalytic asymmetric transformations involving imine activation have been realized by means of this catalyst class, including among others Friedel-Crafts, Pictet-Spengler, Strecker, cycloaddition reactions, transfer hydrogenations, and reductive aminations. More recently, chiral BINOL phosphates found application in multicomponent and cascade reactions as for example in an asymmetric version of the Biginelli reaction. With the introduction of chiral BINOL-derived N-triflyl phosphoramides in 2006, asymmetric Brønsted acid catalysis is no longer restricted to reactive substrates. Also certain carbonyl compounds can be activated through these stronger Brønsted acid catalysts. In dealing with sensitive substrate classes, chiral dicarboxylic acids proved of particular value.

  6. A novel and practical asymmetric synthesis of dapoxetine hydrochloride.

    PubMed

    Zhu, Yijun; Liu, Zhenren; Li, Hongyan; Ye, Deyong; Zhou, Weicheng

    2015-01-01

    A novel and practical asymmetric synthesis of dapoxetine hydrochloride by using the chiral auxiliary (S)-tert-butanesulfinamide was explored. The synthesis was concise, mild, and easy to perform. The overall yield and stereoselectivity were excellent. PMID:26734109

  7. Ferroelectricity and tunneling electroresistance effect in asymmetric ferroelectric tunnel junctions

    NASA Astrophysics Data System (ADS)

    Tao, L. L.; Wang, J.

    2016-06-01

    We report the investigation on the ferroelectricity and tunneling electroresistance (TER) effect in PbTiO3 (PTO)-based ferroelectric tunnel junctions (FTJs) using first-principles calculations. For symmetric FTJs, we have calculated the average polarizations of PTO film and effective screening lengths of different metal electrodes for a number of FTJs, which is useful for experimental research. For asymmetric FTJs, significant asymmetric ferroelectric displacements in PTO film are observed, which is attributed to the intrinsic field generated by the two dissimilar electrodes. Moreover, by performing quantum transport calculations on those asymmetric FTJs, a sizable TER effect is observed. It is found that the asymmetry of ferroelectric displacements in PTO barrier, which is determined by the difference of work functions of the electrodes, controls the observed TER effect. Our results will help unravel the TER mechanism of asymmetric FTJs in most experiments and will be useful for the designing of FTJ-based devices.

  8. A novel and practical asymmetric synthesis of dapoxetine hydrochloride

    PubMed Central

    Zhu, Yijun; Liu, Zhenren; Li, Hongyan

    2015-01-01

    Summary A novel and practical asymmetric synthesis of dapoxetine hydrochloride by using the chiral auxiliary (S)-tert-butanesulfinamide was explored. The synthesis was concise, mild, and easy to perform. The overall yield and stereoselectivity were excellent. PMID:26734109

  9. Optimal multicopy asymmetric Gaussian cloning of coherent states

    SciTech Connect

    Fiurasek, Jaromir; Cerf, Nicolas J.

    2007-05-15

    We investigate the asymmetric Gaussian cloning of coherent states which produces M copies from N input replicas in such a way that the fidelity of each copy may be different. We show that the optimal asymmetric Gaussian cloning can be performed with a single phase-insensitive amplifier and an array of beam splitters. We obtain a simple analytical expression characterizing the set of optimal asymmetric Gaussian cloning machines and prove the optimality of these cloners using the formalism of Gaussian completely positive maps and semidefinite programming techniques. We also present an alternative implementation of the asymmetric cloning machine where the phase-insensitive amplifier is replaced with a beam splitter, heterodyne detector, and feedforward.

  10. Polarization dependent switching of asymmetric nanorings with a circular field

    NASA Astrophysics Data System (ADS)

    Pradhan, Nihar R.; Tuominen, Mark T.; Aidala, Katherine E.

    2016-01-01

    We experimentally investigated the switching from onion to vortex states in asymmetric cobalt nanorings by an applied circular field. An in-plane field is applied along the symmetric or asymmetric axis of the ring to establish domain walls (DWs) with symmetric or asymmetric polarization. A circular field is then applied to switch from the onion state to the vortex state, moving the DWs in the process. The asymmetry of the ring leads to different switching fields depending on the location of the DWs and direction of applied field. For polarization along the asymmetric axis, the field required to move the DWs to the narrow side of the ring is smaller than the field required to move the DWs to the larger side of the ring. For polarization along the symmetric axis, establishing one DW in the narrow side and one on the wide side, the field required to switch to the vortex state is an intermediate value.

  11. Asymmetric Aldol Reaction with Formaldehyde: a Challenging Process.

    PubMed

    Meninno, Sara; Lattanzi, Alessandra

    2016-08-01

    The asymmetric aldol reaction with formaldehyde is a fundamental carbon-carbon bond-forming reaction in organic synthesis, as well as in the quest of the origin of life, as it is thought to have been the first "molecular brick" involved in the synthetic path to complex sugars. Products of aldol reactions, i.e., the β-hydroxy carbonyl compounds, are versatile building blocks used to access a great variety of functionalised molecules. The employment of formaldehyde, as a C1 symmetric electrophile, in aldol reactions can be likely considered the most challenging, yet simplest, process to introduce a hydroxymethyl group in an asymmetric fashion. In this account, an overview of the progress achieved in the asymmetric metal- and organocatalysed aldol reaction, using readily available formalin or paraformaldehyde sources, is illustrated. Our recent contribution to this area, with the application of asymmetric hydroxymethylation in cascade processes for the synthesis of γ-butyrolactones, is also shown. PMID:27328802

  12. The Asymmetrical "Sticking" Behavior of Two Balls on an Incline.

    ERIC Educational Resources Information Center

    Mallinckrodt, A. John

    1999-01-01

    Offers a relatively simple analysis of the asymmetrical "sticking" and rolling behavior of two balls, one steel and one rubber, on an incline. Describes an Interactive Physics (TM) simulation designed to study the problem and gives rough experimental results. (WRM)

  13. Hopf bifurcation analysis for a dissipative system with asymmetric interaction: Analytical explanation of a specific property of highway traffic.

    PubMed

    Nomura, Yasuyuki; Saito, Satoshi; Ishiwata, Ryosuke; Sugiyama, Yuki

    2016-01-01

    A dissipative system with asymmetric interaction, the optimal velocity model, shows a Hopf bifurcation concerned with the transition from a homogeneous motion to the formation of a moving cluster, such as the emergence of a traffic jam. We investigate the properties of Hopf bifurcation depending on the particle density, using the dynamical system for the traveling cluster solution of the continuum system derived from the original discrete system of particles. The Hopf bifurcation is revealed as a subcritical one, and the property explains well the specific phenomena in highway traffic: the metastability of jamming transition and the hysteresis effect in the relation of car density and flow rate. PMID:26871081

  14. Hopf bifurcation analysis for a dissipative system with asymmetric interaction: Analytical explanation of a specific property of highway traffic

    NASA Astrophysics Data System (ADS)

    Nomura, Yasuyuki; Saito, Satoshi; Ishiwata, Ryosuke; Sugiyama, Yuki

    2016-01-01

    A dissipative system with asymmetric interaction, the optimal velocity model, shows a Hopf bifurcation concerned with the transition from a homogeneous motion to the formation of a moving cluster, such as the emergence of a traffic jam. We investigate the properties of Hopf bifurcation depending on the particle density, using the dynamical system for the traveling cluster solution of the continuum system derived from the original discrete system of particles. The Hopf bifurcation is revealed as a subcritical one, and the property explains well the specific phenomena in highway traffic: the metastability of jamming transition and the hysteresis effect in the relation of car density and flow rate.

  15. Response to ``Comment on `Scaling of asymmetric magnetic reconnection: General theory and collisional simulations' '' [Phys. Plasmas 16, 034701 (2009)

    NASA Astrophysics Data System (ADS)

    Cassak, P. A.; Shay, M. A.

    2009-03-01

    The comment by Semenov et al. has called into question our derivation of the outflow velocity in asymmetric magnetic reconnection. We present three reasons that the analysis presented in the comment is incorrect. Most importantly, the authors of the comment have incorrectly applied results from one-dimensional shock theory to the problem of conservation through a two-dimensional dissipation region. For completeness, we compare their predictions to numerical simulation results, finding that their theory does not describe the data. We conclude the analysis in the comment is without merit.

  16. Plasma and Energetic Particle Behaviors During Asymmetric Magnetic Reconnection at the Magnetopause

    NASA Technical Reports Server (NTRS)

    Lee, S. H.; Zhang, H.; Zong, Q.-G.; Otto, A.; Sibeck, D. G.; Wang, Y.; Glassmeier, K.-H.; Daly, P.W.; Reme, H.

    2014-01-01

    The factors controlling asymmetric reconnection and the role of the cold plasma population in the reconnection process are two outstanding questions. We present a case study of multipoint Cluster observations demonstrating that the separatrix and flow boundary angles are greater on the magnetosheath than on the magnetospheric side of the magnetopause, probably due to the stronger density than magnetic field asymmetry at this boundary. The motion of cold plasmaspheric ions entering the reconnection region differs from that of warmer magnetosheath and magnetospheric ions. In contrast to the warmer ions, which are probably accelerated by reconnection in the diffusion region near the subsolar magnetopause, the colder ions are simply entrained by ??×?? drifts at high latitudes on the recently reconnected magnetic field lines. This indicates that plasmaspheric ions can sometimes play only a very limited role in asymmetric reconnection, in contrast to previous simulation studies. Three cold ion populations (probably H+, He+, and O+) appear in the energy spectrum, consistent with ion acceleration to a common velocity.

  17. Equation of State for Isospin Asymmetric Nuclear Matter Using Lane Potential

    NASA Astrophysics Data System (ADS)

    Basu, D. N.; Chowdhury, P. Roy; Samanta, C.

    2006-10-01

    A mean field calculation for obtaining the equation of state (EOS) for symmetric nuclear matter from a density dependent M3Y interaction supplemented by a zero-range potential is described. The energy per nucleon is minimized to obtain the ground state of symmetric nuclear matter. The saturation energy per nucleon used for nuclear matter calculations is determined from the co-efficient of the volume term of Bethe--Weizsäcker mass formula which is evaluated by fitting the recent experimental and estimated atomic mass excesses from Audi--Wapstra--Thibault atomic mass table by minimizing the mean square deviation. The constants of density dependence of the effective interaction are obtained by reproducing the saturation energy per nucleon and the saturation density of spin and isospin symmetric cold infinite nuclear matter. The EOS of symmetric nuclear matter, thus obtained, provide reasonably good estimate of nuclear incompressibility. Once the constants of density dependence are determined, EOS for asymmetric nuclear matter is calculated by adding to the isoscalar part, the isovector component of the M3Y interaction that do not contribute to the EOS of symmetric nuclear matter. These EOS are then used to calculate the pressure, the energy density and the velocity of sound in symmetric as well as isospin asymmetric nuclear matter.

  18. Study of the energy inventory during asymmetric magnetic reconnection in a laboratory plasma

    NASA Astrophysics Data System (ADS)

    Yoo, Jongsoo; Yamada, Masaaki; Na, Ben; Jara-Almonte, Jonathan; Ji, Hantao; Fox, Will; Chien, Abe

    2015-11-01

    The energy inventory of a magnetic reconnection layer is studied in a laboratory plasma with a significant density asymmetry across the current sheet. The upstream density ratio of about 7 is generated by the in-plane inductive electric field during the plasma formation in MRX. Compared to the symmetric case where the ion energy gain is about twice more than that of electrons, the ion energy gain becomes smaller and the electron energy gain is larger. The reduction in the ion energy gain is mainly caused by the asymmetric profile of the in-plane electrostatic potential, which is generated to balance the Lorentz force in the electron momentum equation. Since the out-of-plane electron fluid velocity on the high-density side is small due to the high density, the potential drop on the high-density side becomes also small. The potential drop on the low-density side is also smaller than expected from the general scaling (~B2 / n), since it is suppressed by a large density gradient across the low-density side separatrices. As a result, the ion energy gain from the in-plane electrostatic field is smaller than the symmetric case, thereby decreasing the total ion energy gain. Discussion on the electron energization process during asymmetric reconnection is also presented. This research is supported by DoE Contract Number DE-AC02-09CH11466.

  19. Exploring the effects of seated whole body vibration exposure on repetitive asymmetric lifting tasks.

    PubMed

    Mehta, Jay P; Lavender, Steven A; Jagacinski, Richard J; Sommerich, Carolyn M

    2015-01-01

    This study investigated changes in the physiological and behavioral responses to repetitive asymmetric lifting activity after exposure to whole body vibrations. Seventeen healthy volunteers repeatedly lifted a box (15% of lifter's capacity) positioned in front of them at ankle level to a location on their left side at waist level at the rate of 10 lifts/min for a period of 60 minutes. Prior to lifting, participants were seated on a vibrating platform for 60 minutes; in one of the two sessions the platform did not vibrate. Overall, the physiological responses assessed using near-infrared spectroscopy signals for the erector spinae muscles decreased significantly over time during the seating and the lifting tasks (p < 0.001). During repetitive asymmetric lifting, behavioral changes included increases in peak forward bending motion, twisting movement, and three-dimensional movement velocities of the spine. The lateral bending movement of the spine and the duration of each lift decreased significantly over the 60 minutes of repetitive lifting. With exposure to whole body vibration, participants twisted farther (p = 0.046) and twisted faster (p = 0.025). These behavioral changes would suggest an increase in back injury risk when repetitive lifting tasks are preceded by whole body vibration exposure. PMID:25264920

  20. Tailor-made asymmetric PVDF hollow fibers for soluble gas removal

    SciTech Connect

    Li, K.; Kong, J.F.; Wang, D.; Teo, W.K.

    1999-06-01

    Tailor-made polyvinylidene fluoride (PVDF) asymmetric hollow-fiber membranes and their membrane modules were employed for soluble gas removal, such as H{sub 2}S from waste gas streams. This study focused on the techniques of fabricating and characterizing the PVDF asymmetric hollow-fiber membranes and their membrane modules for removal of H{sub 2}S using an aqueous solution containing 10% NaOH. A laminar parabolic velocity profile was used to characterize the flow of the H{sub 2}S gas mixture in the hollow-fiber lumen. Effects of operating conditions and the morphological structures of the membranes on the membrane`s coefficient, k{sub AM}, were examined both theoretically and experimentally. The capabilities of the hollow-fiber membranes developed for removal of H{sub 2}S from waste gas streams were evaluated and compared with conventional symmetric hydrophobic hollow-fiber membranes, such as polypropylene. An analysis of H{sub 2}S transfer across the more developed PVDF membranes reveals that the membrane`s coefficient, k{sub AM}, evaluated from its structure parameters, such as the effective surface porosity and mean radius, agreed well with the experimental data obtained from absorption experiments.

  1. A laboratory study of asymmetric magnetic reconnection in strongly-driven plasmas

    DOE PAGESBeta

    Rosenberg, M. J.; Li, C. K.; Fox, W.; Igumenshchev, I.; Seguin, F. H.; Town, R.P. J.; Frenje, J. A.; Stoeckl, C.; Glebov, V.; Petrasso, R. D.

    2015-02-04

    Magnetic reconnection, the annihilation and rearrangement of magnetic fields in a plasma, is a universal phenomenon that frequently occurs when plasmas carrying oppositely-directed field lines collide. In most natural circumstances the collision is asymmetric (the two plasmas having different properties), but laboratory research to date has been limited to symmetric configurations. Additionally, the regime of strongly-driven magnetic reconnection, where the ram pressure of the plasma dominates the magnetic pressure, as in several astrophysical environments, has also received little experimental attention. Thus, we have designed experiments to probe reconnection in asymmetric, strongly-driven, laser-generated plasmas. Here we show that, in this strongly-drivenmore » system, the rate of magnetic flux annihilation is dictated by the relative flow velocities of the opposing plasmas and is insensitive to initial asymmetries. Additionally, out-of-plane magnetic fields that arise from asymmetries in the three-dimensional plasma geometry have minimal impact on the reconnection rate, due to the strong flows.« less

  2. A laboratory study of asymmetric magnetic reconnection in strongly-driven plasmas

    SciTech Connect

    Rosenberg, M. J.; Li, C. K.; Fox, W.; Igumenshchev, I.; Seguin, F. H.; Town, R.P. J.; Frenje, J. A.; Stoeckl, C.; Glebov, V.; Petrasso, R. D.

    2015-02-04

    Magnetic reconnection, the annihilation and rearrangement of magnetic fields in a plasma, is a universal phenomenon that frequently occurs when plasmas carrying oppositely-directed field lines collide. In most natural circumstances the collision is asymmetric (the two plasmas having different properties), but laboratory research to date has been limited to symmetric configurations. Additionally, the regime of strongly-driven magnetic reconnection, where the ram pressure of the plasma dominates the magnetic pressure, as in several astrophysical environments, has also received little experimental attention. Thus, we have designed experiments to probe reconnection in asymmetric, strongly-driven, laser-generated plasmas. Here we show that, in this strongly-driven system, the rate of magnetic flux annihilation is dictated by the relative flow velocities of the opposing plasmas and is insensitive to initial asymmetries. Additionally, out-of-plane magnetic fields that arise from asymmetries in the three-dimensional plasma geometry have minimal impact on the reconnection rate, due to the strong flows.

  3. Modelling crystal growth: Convection in an asymmetrically heated ampoule

    NASA Technical Reports Server (NTRS)

    Alexander, J. Iwan D.; Rosenberger, Franz; Pulicani, J. P.; Krukowski, S.; Ouazzani, Jalil

    1990-01-01

    The objective was to develop and implement a numerical method capable of solving the nonlinear partial differential equations governing heat, mass, and momentum transfer in a 3-D cylindrical geometry in order to examine the character of convection in an asymmetrically heated cylindrical ampoule. The details of the numerical method, including verification tests involving comparison with results obtained from other methods, are presented. The results of the study of 3-D convection in an asymmetrically heated cylinder are described.

  4. Circular motion of asymmetric self-propelling particles.

    PubMed

    Kümmel, Felix; ten Hagen, Borge; Wittkowski, Raphael; Buttinoni, Ivo; Eichhorn, Ralf; Volpe, Giovanni; Löwen, Hartmut; Bechinger, Clemens

    2013-05-10

    Micron-sized self-propelled (active) particles can be considered as model systems for characterizing more complex biological organisms like swimming bacteria or motile cells. We produce asymmetric microswimmers by soft lithography and study their circular motion on a substrate and near channel boundaries. Our experimental observations are in full agreement with a theory of Brownian dynamics for asymmetric self-propelled particles, which couples their translational and orientational motion. PMID:23705745

  5. Circular Motion of Asymmetric Self-Propelling Particles

    NASA Astrophysics Data System (ADS)

    Kümmel, Felix; ten Hagen, Borge; Wittkowski, Raphael; Buttinoni, Ivo; Eichhorn, Ralf; Volpe, Giovanni; Löwen, Hartmut; Bechinger, Clemens

    2013-05-01

    Micron-sized self-propelled (active) particles can be considered as model systems for characterizing more complex biological organisms like swimming bacteria or motile cells. We produce asymmetric microswimmers by soft lithography and study their circular motion on a substrate and near channel boundaries. Our experimental observations are in full agreement with a theory of Brownian dynamics for asymmetric self-propelled particles, which couples their translational and orientational motion.

  6. Water in asymmetric organocatalytic systems: a global perspective.

    PubMed

    Jimeno, Ciril

    2016-07-14

    Asymmetric organocatalysis often operates under near ambient conditions, which means it is air and moisture compatible. However, in many examples water is indeed necessary for achieving excellent catalytic results. Ranging from the addition of small amounts of water to a reaction, to complex catalytic systems in the presence of water as the only reaction medium, this review offers an illustrative classification of the uses of water in asymmetric organocatalysis. PMID:27215302

  7. Protease-catalysed Direct Asymmetric Mannich Reaction in Organic Solvent

    NASA Astrophysics Data System (ADS)

    Xue, Yang; Li, Ling-Po; He, Yan-Hong; Guan, Zhi

    2012-10-01

    We reported the first enzyme-catalysed, direct, three-component asymmetric Mannich reaction using protease type XIV from Streptomyces griseus (SGP) in acetonitrile. Yields of up to 92% with enantioselectivities of up to 88% e.e. and diastereoselectivities of up to 92:8 (syn:anti) were achieved under the optimised conditions. This enzyme's catalytic promiscuity expands the application of this biocatalyst and provides a potential alternative method for asymmetric Mannich reactions.

  8. Evolutionary dynamics on measurable strategy spaces: Asymmetric games

    NASA Astrophysics Data System (ADS)

    Mendoza-Palacios, Saul; Hernández-Lerma, Onésimo

    2015-12-01

    The theory of evolutionary dynamics in asymmetric games has been mainly studied for games with a finite strategy space. In this paper we introduce an evolutionary dynamics model for asymmetric games where the strategy sets are measurable spaces (separable metric spaces). Under this hypothesis the replicator dynamics is in a Banach Space. We specify conditions under which the replicator dynamics has a solution. Furthermore, under suitable assumptions, a critical point of the system is stable. Finally, an example illustrates our results.

  9. Protease-catalysed direct asymmetric Mannich reaction in organic solvent.

    PubMed

    Xue, Yang; Li, Ling-Po; He, Yan-Hong; Guan, Zhi

    2012-01-01

    We reported the first enzyme-catalysed, direct, three-component asymmetric Mannich reaction using protease type XIV from Streptomyces griseus (SGP) in acetonitrile. Yields of up to 92% with enantioselectivities of up to 88% e.e. and diastereoselectivities of up to 92:8 (syn:anti) were achieved under the optimised conditions. This enzyme's catalytic promiscuity expands the application of this biocatalyst and provides a potential alternative method for asymmetric Mannich reactions. PMID:23094136

  10. Protease-catalysed Direct Asymmetric Mannich Reaction in Organic Solvent

    PubMed Central

    Xue, Yang; Li, Ling-Po; He, Yan-Hong; Guan, Zhi

    2012-01-01

    We reported the first enzyme-catalysed, direct, three-component asymmetric Mannich reaction using protease type XIV from Streptomyces griseus (SGP) in acetonitrile. Yields of up to 92% with enantioselectivities of up to 88% e.e. and diastereoselectivities of up to 92:8 (syn:anti) were achieved under the optimised conditions. This enzyme's catalytic promiscuity expands the application of this biocatalyst and provides a potential alternative method for asymmetric Mannich reactions. PMID:23094136

  11. Asymmetric exclusion process and extremal statistics of random sequences.

    PubMed

    Bundschuh, R

    2002-03-01

    A mapping is established between sequence alignment, one of the most commonly used tools of computational biology, at a certain choice of scoring parameters and the asymmetric exclusion process, one of the few exactly solvable models of nonequilibrium physics. The statistical significance of sequence alignments is characterized through studying the total hopping current of the discrete time and space version of the asymmetric exclusion process. PMID:11909113

  12. Asymmetric formal synthesis of schulzeines A and C.

    PubMed

    Jang, Jaebong; Jung, Jong-Wha; Ahn, Jaeseung; Sim, Jaehoon; Chang, Dong-Jo; Kim, Dae-Duk; Suh, Young-Ger

    2012-07-21

    The asymmetric formal synthesis of schulzeines A and C is described. Key features of the synthesis include the efficient and stereoselective construction of the benzoquinolizidine skeleton via the aza-Claisen rearrangement-induced ring expansion of the 1-vinyl-N-glycyl-isoquinoline, which was prepared by the highly enantioselective asymmetric allylation of the 8-benzyloxy-substituted dihydroisoquinoline and by the acid-catalyzed transannulation of the resulting 10-membered lactam. PMID:22692049

  13. Controllable asymmetric double well and ring potential on an atom chip

    NASA Astrophysics Data System (ADS)

    Kim, S. J.; Yu, H.; Gang, S. T.; Anderson, D. Z.; Kim, J. B.

    2016-03-01

    We have constructed an asymmetric matter-wave beam splitter and a ring potential on an atom chip with Bose-Einstein condensates using radio-frequency dressing. By applying rf field parallel to the quantization axis in the vicinity of the static trap minima added to perpendicular rf fields, versatile controllability on the asymmetry of rf-dressed potentials is realized. Asymmetry of the rf-induced double well is controlled over a wide range without discernible displacement of each well. Formation of an isotropic ring potential on an atom chip is achieved by compensating the gradient due to gravity and inhomogeneous coupling strength. In addition, position and rotation velocity of a BEC along the ring geometry are controlled by the relative phase and the frequency difference between the rf fields, respectively.

  14. Asymmetric dihedral angle offsets for large-size lunar laser ranging retroreflectors

    NASA Astrophysics Data System (ADS)

    Otsubo, Toshimichi; Kunimori, Hiroo; Noda, Hirotomo; Hanada, Hideo; Araki, Hiroshi; Katayama, Masato

    2011-08-01

    The distribution of two-dimensional velocity aberration is off-centered by 5 to 6 microradians in lunar laser ranging, due to the stable measurement geometry in the motion of the Earth and the Moon. The optical responses of hollow-type retroreflectors are investigated through numerical simulations, especially focusing on large-size, single-reflector targets that can ultimately minimize the systematic error in future lunar laser ranging. An asymmetric dihedral angle offset, i.e. setting unequal angles between the three back faces, is found to be effective for retroreflectors that are larger than 100 mm in diameter. Our numerical simulation results reveal that the optimized return energy increases approximately 3.5 times more than symmetric dihedral angle cases, and the optimized dihedral angle offsets are 0.65-0.8 arcseconds for one angle, and zeroes for the other two angles.

  15. Route guidance strategies revisited: Comparison and evaluation in an asymmetric two-route traffic network

    NASA Astrophysics Data System (ADS)

    He, Zhengbing; Chen, Bokui; Jia, Ning; Guan, Wei; Lin, Benchuan; Wang, Binghong

    2014-12-01

    To alleviate traffic congestion, a variety of route guidance strategies have been proposed for intelligent transportation systems. A number of strategies are introduced and investigated on a symmetric two-route traffic network over the past decade. To evaluate the strategies in a more general scenario, this paper conducts eight prevalent strategies on an asymmetric two-route traffic network with different slowdown behaviors on alternative routes. The results show that only mean velocity feedback strategy (MVFS) is able to equalize travel time, i.e. approximate user optimality (UO); while the others fail due to incapability of establishing relations between the feedback parameters and travel time. The paper helps better understand these strategies, and suggests MVFS if the authority intends to achieve user optimality.

  16. Progress in the Large-Eddy Simulation of an Asymmetric Plane Diffuser

    NASA Technical Reports Server (NTRS)

    Fatica, Massimiliano; Mittal, Rajat

    1996-01-01

    The flow through a plane asymmetric diffuser is a good test case for assessing the capability of LES since it contains features such as large scale unsteady separation and strong intermittency which are difficult to capture using conventional modeling approaches. Previous attempts to simulate this flow (Kaltenbach, 1994) have significantly underpredicted the extent of separation. The objective of the present research is to understand why the previous simulations did not predict the flow separation correctly. This study focuses on mesh refinement and matching of the inlet velocity profile. In order to perform this study, the flow solver of Kaltenbach (1994) was modified to increase its accuracy and efficiency. The improved algorithm allows for better resolution at affordable CPU cost.

  17. Application of multivariate outlier detection to fluid velocity measurements

    NASA Astrophysics Data System (ADS)

    Griffin, John; Schultz, Todd; Holman, Ryan; Ukeiley, Lawrence S.; Cattafesta, Louis N.

    2010-07-01

    A statistical-based approach to detect outliers in fluid-based velocity measurements is proposed. Outliers are effectively detected from experimental unimodal distributions with the application of an existing multivariate outlier detection algorithm for asymmetric distributions (Hubert and Van der Veeken, J Chemom 22:235-246, 2008). This approach is an extension of previous methods that only apply to symmetric distributions. For fluid velocity measurements, rejection of statistical outliers, meaning erroneous as well as low probability data, via multivariate outlier rejection is compared to a traditional method based on univariate statistics. For particle image velocimetry data, both tests are conducted after application of the current de facto standard spatial filter, the universal outlier detection test (Westerweel and Scarano, Exp Fluids 39:1096-1100, 2005). By doing so, the utility of statistical outlier detection in addition to spatial filters is demonstrated, and further, the differences between multivariate and univariate outlier detection are discussed. Since the proposed technique for outlier detection is an independent process, statistical outlier detection is complementary to spatial outlier detection and can be used as an additional validation tool.

  18. Quantitative analysis of protein dynamics during asymmetric cell division.

    PubMed

    Mayer, Bernd; Emery, Gregory; Berdnik, Daniela; Wirtz-Peitz, Frederik; Knoblich, Juergen A

    2005-10-25

    In dividing Drosophila sensory organ precursor (SOP) cells, the fate determinant Numb and its associated adaptor protein Pon localize asymmetrically and segregate into the anterior daughter cell, where Numb influences cell fate by repressing Notch signaling. Asymmetric localization of both proteins requires the protein kinase aPKC and its substrate Lethal (2) giant larvae (Lgl). Because both Numb and Pon localization require actin and myosin, lateral transport along the cell cortex has been proposed as a possible mechanism for their asymmetric distribution. Here, we use quantitative live analysis of GFP-Pon and Numb-GFP fluorescence and fluorescence recovery after photobleaching (FRAP) to characterize the dynamics of Numb and Pon localization during SOP division. We demonstrate that Numb and Pon rapidly exchange between a cytoplasmic pool and the cell cortex and that preferential recruitment from the cytoplasm is responsible for their asymmetric distribution during mitosis. Expression of a constitutively active form of aPKC impairs membrane recruitment of GFP-Pon. This defect can be rescued by coexpression of nonphosphorylatable Lgl, indicating that Lgl is the main target of aPKC. We propose that a high-affinity binding site is asymmetrically distributed by aPKC and Lgl and is responsible for asymmetric localization of cell-fate determinants during mitosis. PMID:16243032

  19. Flexible Asymmetric Encapsulation for Dehydration-Responsive Hybrid Microfibers.

    PubMed

    Chaurasia, Ankur S; Sajjadi, Shahriar

    2016-08-01

    A new class of smart alginate microfibers with asymmetric oil encapsulates is introduced. These fibers are produced by injecting an aqueous alginate solution into an outer aqueous calcium chloride solution to form alginate fibers, which are asymmetrically loaded with oil entities through eccentrically aligned inner capillaries. The fiber morphology and its degree of asymmetry can be tuned via altering the size, location, and frequency of the oil encapsulates. These asymmetric fibers reveal significant potential for applications where conventional symmetric fibers fail to perform. It is shown how asymmetric oil-encapsulated fibers can become dehydration-sensitive, and trigger the release of encapsulates if their hydration level drops below a critical value. It is also shown how the triggered response could be switched off on demand by stabilizing the oil encapsulates. The capability of asymmetric fibers to carry and release multiple cargos in parallel is demonstrated. The fibers loaded with equal-sized spheres are more asymmetric than those containing unequal drops, have a higher tensile strength, and show better potential for a triggered response. PMID:27352241

  20. A method for automated control of belt velocity changes with an instrumented treadmill.

    PubMed

    Hinkel-Lipsker, Jacob W; Hahn, Michael E

    2016-01-01

    Increased practice difficulty during asymmetrical split-belt treadmill rehabilitation has been shown to improve gait outcomes during retention and transfer tests. However, research in this area has been limited by manual treadmill operation. In the case of variable practice, which requires stride-by-stride changes to treadmill belt velocities, the treadmill control must be automated. This paper presents a method for automation of asymmetrical split-belt treadmill walking, and evaluates how well this method performs with regards to timing of gait events. One participant walked asymmetrically for 100 strides, where the non-dominant limb was driven at their self-selected walking speed, while the other limb was driven randomly on a stride-by-stride basis. In the control loop, the key factors to insure that the treadmill belt had accelerated to its new velocity safely during the swing phase were the sampling rate of the A/D converter, processing time within the controller software, and acceleration of the treadmill belt. The combination of these three factors resulted in a total control loop time during each swing phase that satisfied these requirements with a factor of safety that was greater than 4. Further, a polynomial fit indicated that belt acceleration was the largest contributor to changes in this total time. This approach appears to be safe and reliable for stride-by-stride adjustment of treadmill belt speed, making it suitable for future asymmetrical split-belt walking studies. Further, it can be incorporated into virtual reality rehabilitation paradigms that utilize split-belt treadmill walking. PMID:26654110

  1. Asymmetric inhibitory treatment effects in multilingual aphasia

    PubMed Central

    Goral, Mira; Naghibolhosseini, Maryam; Conner, Peggy

    2014-01-01

    Findings from recent psycholinguistic studies of bilingual processing support the hypothesis that both languages of a bilingual are always active and that bilinguals continually engage in processes of language selection. This view aligns with the convergence hypothesis of bilingual language representation (Abutalebi & Green, 2008). Furthermore, it is hypothesized that when bilinguals perform a task in one language they need to inhibit their other, non-target language(s) (e.g., Costa, Miozzo, & Caramazza, 1999) and that stronger inhibition is required when the task is performed in the weaker language than in the stronger one (e.g., Costa & Santesteban, 2004). The study of multilingual individuals who acquire aphasia resulting from a focal brain lesion offers a unique opportunity to test the convergence hypothesis and the inhibition asymmetry. We report on a trilingual person with chronic non-fluent aphasia who at the time of testing demonstrated greater impairment in her first acquired language (Persian) than in her third, later-learned language (English). She received treatment in English followed by treatment in Persian. An examination of her connected language production revealed improvement in her grammatical skills in each language following intervention in that language, but decreased grammatical accuracy in English following treatment in Persian. The increased error rate was evident in structures that are not shared by the two languages (e.g., use of auxiliary verbs). The results support the prediction that greater inhibition is applied to the stronger language than to the weaker language, regardless of their age of acquisition. We interpret the findings as consistent with convergence theories that posit overlapping neuronal representation and simultaneous activation of multiple languages, and with proficiency-dependent asymmetric inhibition in multilinguals. PMID:24499302

  2. Asymmetric Planetary Nebulae VI: the conference summary

    NASA Astrophysics Data System (ADS)

    De Marco, O.

    2014-04-01

    The Asymmetric Planetary Nebulae conference series, now in its sixth edition, aims to resolve the shaping mechanism of PN. Eighty percent of PN have non spherical shapes and during this conference the last nails in the coffin of single stars models for non spherical PN have been put. Binary theories abound but observational tests are lagging. The highlight of APN6 has been the arrival of ALMA which allowed us to measure magnetic fields on AGB stars systematically. AGB star halos, with their spiral patterns are now connected to PPN and PN halos. New models give us hope that binary parameters may be decoded from these images. In the post-AGB and pre-PN evolutionary phase the naked post-AGB stars present us with an increasingly curious puzzle as complexity is added to the phenomenologies of objects in transition between the AGB and the central star regimes. Binary central stars continue to be detected, including the first detection of longer period binaries, however a binary fraction is still at large. Hydro models of binary interactions still fail to give us results, if we make an exception for the wider types of binary interactions. More promise is shown by analytical considerations and models driven by simpler, 1D simulations such as those carried out with the code MESA. Large community efforts have given us more homogeneous datasets which will yield results for years to come. Examples are the ChanPlaN and HerPlaNe collaborations that have been working with the Chandra and Herschel space telescopes, respectively. Finally, the new kid in town is the intermediate-luminosity optical transient, a new class of events that may have contributed to forming several peculiar PN and pre-PN.

  3. Collective modes in asymmetric ultracold Fermi systems

    SciTech Connect

    Gubankova, Elena; Mannarelli, Massimo; Sharma, Rishi

    2010-09-15

    We derive the long wavelength effective action for the collective modes in systems of fermions interacting via a short-range s-wave attraction, featuring unequal chemical potentials for the two fermionic species (asymmetric systems). As a consequence of the attractive interaction, fermions form a condensate that spontaneously breaks the U(1) symmetry associated with total number conservation. Therefore at sufficiently small temperatures and asymmetries, the system is a superfluid. We reproduce previous results for the stability conditions of the system as a function of the four-fermion coupling and asymmetry. We obtain these results analyzing the coefficients of the low energy effective Lagrangian of the modes describing fluctuations in the magnitude (Higgs mode) and in the phase (Nambu-Goldstone, or Anderson-Bogoliubov, mode) of the difermion condensate. We find that for certain values of parameters, the mass of the Higgs mode decreases with increasing mismatch between the chemical potentials of the two populations, if we keep the scattering length and the gap parameter constant. Furthermore, we find that the energy cost for creating a position dependent fluctuation of the condensate is constant in the gapped region and increases in the gapless region. These two features may lead to experimentally detectable effects. As an example, we argue that if the superfluid is put in rotation, the square of the radius of the outer core of a vortex should sharply increase on increasing the asymmetry, when we pass through the relevant region in the gapless superfluid phase. Finally, by gauging the global U(1) symmetry, we relate the coefficients of the effective Lagrangian of the Nambu-Goldstone mode with the screening masses of the gauge field.

  4. Asymmetric Magnetization Reversal in Exchange Bias Systems*

    NASA Astrophysics Data System (ADS)

    Fitzsimmons, Michael

    2001-03-01

    Polarized neutron reflectometry measured the in-plane projection of the net-magnetization vector of polycrystalline Fe films exchange-coupled to (110) FeF2 antiferromagnetic (AF) films of controlled crystalline quality. For the sample with the single crystal AF film, we observed perpendicular exchange coupling across the ferromagnetic (F)-AF interface on either side of the hysteresis loop at coercivity. Perpendicular exchange coupling was observed regardless of cooling field orientation parallel or perpendicular to the AF anisotropy axis. Yet, for one orientation the exchange bias was zero; thus, perpendicular exchange coupling is not a sufficient condition for exchange bias. For samples with twinned AF films, an asymmetry in the spin flip scattering on either side of the hysteresis loop, and consequently in the magnetization reversal process, was observed. The origin of the asymmetry is explained by frustration of perpendicular exchange coupling, which enhances exchange bias and leads to 45° exchange coupling across the F-AF interface. The easy axis in the ferromagnet, which gives rise to asymmetric magnetization reversal in the twinned samples, is not present in samples with (110) textured polycrystalline AF films; and consequently exchange bias is reduced. *Work supported by the U.S. Department of Energy, BES-DMS under Contract No. W-7405-Eng-36, Grant No. DE-FG03-87ER-45332 and funds from the University of California Collaborative University and Laboratory Assisted Research. ÝWork in collaboration with A. Hoffmann, P. Yashar, J. Groves, R. Springer, P. Arendt (LANL), C. Leighton, K. Liu, Ivan K. Schuller (UCSD), J. Nogués (UAB), C.F. Majkrzak, J.A. Dura (NIST), H. Fritzsche (HMI), V. Leiner, H. Lauter (ILL).

  5. 2d PDE Linear Asymmetric Matrix Solver

    Energy Science and Technology Software Center (ESTSC)

    1983-10-01

    ILUCG2 (Incomplete LU factorized Conjugate Gradient algorithm for 2d problems) was developed to solve a linear asymmetric matrix system arising from a 9-point discretization of two-dimensional elliptic and parabolic partial differential equations found in plasma physics applications, such as plasma diffusion, equilibria, and phase space transport (Fokker-Planck equation) problems. These equations share the common feature of being stiff and requiring implicit solution techniques. When these parabolic or elliptic PDE''s are discretized with finite-difference or finite-elementmore » methods, the resulting matrix system is frequently of block-tridiagonal form. To use ILUCG2, the discretization of the two-dimensional partial differential equation and its boundary conditions must result in a block-tridiagonal supermatrix composed of elementary tridiagonal matrices. A generalization of the incomplete Cholesky conjugate gradient algorithm is used to solve the matrix equation. Loops are arranged to vectorize on the Cray1 with the CFT compiler, wherever possible. Recursive loops, which cannot be vectorized, are written for optimum scalar speed. For problems having a symmetric matrix ICCG2 should be used since it runs up to four times faster and uses approximately 30% less storage. Similar methods in three dimensions are available in ICCG3 and ILUCG3. A general source, containing extensions and macros, which must be processed by a pre-compiler to obtain the standard FORTRAN source, is provided along with the standard FORTRAN source because it is believed to be more readable. The pre-compiler is not included, but pre-compilation may be performed by a text editor as described in the UCRL-88746 Preprint.« less

  6. Asymmetrical Stimulus Generalization following Differential Fear Conditioning

    PubMed Central

    Bang, Sun Jung; Allen, Timothy A.; Jones, Lauren K.; Boguszewski, Pawel; Brown, Thomas H.

    2008-01-01

    Rodent ultrasonic vocalizations (USVs) are ethologically critical social signals. Rats emit 22 kHz USVs and 50 kHz USVs, respectively, in conjunction with negative and positive affective states. Little is known about what controls emotional reactivity to these social signals. Using male Sprague-Dawley rats, we examined unconditional and conditional freezing behavior in response to the following auditory stimuli: three 22 kHz USVs, a discontinuous tone whose frequency and on-off pattern matched one of the USVs, a continuous tone with the same or lower frequencies, a 4 kHz discontinuous tone with an on-off pattern matched to one of the USVs, and a 50 kHz USV. There were no differences among these stimuli in terms of the unconditional elicitation of freezing behavior. Thus, the stimuli were equally neutral before conditioning. During differential fear conditioning, one of these stimuli (the CS+) always co-terminated with a footshock unconditional stimulus (US) and another stimulus (the CS−) was explicitly unpaired with the US. There were no significant differences among these cues in CS+-elicited freezing behavior. Thus, the stimuli were equally salient or effective as cues in supporting fear conditioning. When the CS+ was a 22 kHz USV or a similar stimulus, rats discriminated based on the principal frequency and/or the temporal pattern of the stimulus. However, when these same stimuli served as the CS−, discrimination failed due to generalization from the CS+. Thus, the stimuli differed markedly in the specificity of conditioning. This strikingly asymmetrical stimulus generalization is a novel bias in discrimination. PMID:18434217

  7. Chilly dark sectors and asymmetric reheating

    NASA Astrophysics Data System (ADS)

    Adshead, Peter; Cui, Yanou; Shelton, Jessie

    2016-06-01

    In a broad class of theories, the relic abundance of dark matter is determined by interactions internal to a thermalized dark sector, with no direct involvement of the Standard Model (SM). We point out that these theories raise an immediate cosmological question: how was the dark sector initially populated in the early universe? Motivated in part by the difficulty of accommodating large amounts of entropy carried in dark radiation with cosmic microwave background measurements of the effective number of relativistic species at recombination, N eff , we aim to establish which admissible cosmological histories can populate a thermal dark sector that never reaches thermal equilibrium with the SM. The minimal cosmological origin for such a dark sector is asymmetric reheating, when the same mechanism that populates the SM in the early universe also populates the dark sector at a lower temperature. Here we demonstrate that the resulting inevitable inflaton-mediated scattering between the dark sector and the SM can wash out a would-be temperature asymmetry, and establish the regions of parameter space where temperature asymmetries can be generated in minimal reheating scenarios. Thus obtaining a temperature asymmetry of a given size either restricts possible inflaton masses and couplings or necessitates a non-minimal cosmology for one or both sectors. As a side benefit, we develop techniques for evaluating collision terms in the relativistic Boltzmann equation when the full dependence on Bose-Einstein or Fermi-Dirac phase space distributions must be retained, and present several new results on relativistic thermal averages in an appendix.

  8. A three-dimensional asymmetric magnetopause model

    NASA Astrophysics Data System (ADS)

    Lin, R. L.; Zhang, X. X.; Liu, S. Q.; Wang, Y. L.; Gong, J. C.

    2010-04-01

    A new three-dimensional asymmetric magnetopause model has been developed for corrected GSM coordinates and parameterized by the solar wind dynamic and magnetic pressures (Pd + Pm), the interplanetary magnetic field (IMF) Bz, and the dipole tilt angle. On the basis of the magnetopause crossings from Geotail, IMP 8, Interball, TC1, Time History of Events and Macroscale Interactions during Substorms (THEMIS), Wind, Cluster, Polar, Los Alamos National Laboratory (LANL), GOES, and Hawkeye, and the corresponding upstream solar wind parameters from ACE, Wind, or OMNI, this model is constructed by the Levenberg-Marquardt method for nonlinear multiparameter fitting step-by-step over the divided regions. The asymmetries of the magnetopause and the indentations near the cusps are appropriately described in this new model. In addition, the saturation effect of IMF Bz on the subsolar distance and the extrapolation for the distant tail magnetopause are also considered. On the basis of this model, the power law index for the subsolar distance versus Pd + Pm is a bit less than -1/6, the northward IMF Bz almost does not influence the magnetopause, and the dipole tilt angle is very important to the north-south asymmetry and the location of indentations. In comparison with the previous empirical magnetopause models based on our database, the new model improves prediction capability to describe the three-dimensional structure of the magnetopause. It is shown that this new model can be used to quantitatively study how Pd + Pm compresses the magnetopause, how the southward IMF Bz erodes the magnetopause, and how the dipole tilt angle influences the north-south asymmetry and the indentations.

  9. Asymmetric vs. symmetric deep lithospheric architecture of intra-plate continental orogens

    NASA Astrophysics Data System (ADS)

    Calignano, Elisa; Sokoutis, Dimitrios; Willingshofer, Ernst; Gueydan, Frédéric; Cloetingh, Sierd

    2015-08-01

    The initiation and subsequent evolution of intra-plate orogens, resulting from continental plate interior deformation due to transmission of stresses over large distances from the active plate boundaries, is controlled by lateral and vertical strength contrasts in the lithosphere. We present lithospheric-scale analogue models combining 1) lateral strength variations in the continental lithosphere, and 2) different vertical rheological stratifications. The experimental continental lithosphere has a four-layer brittle-ductile rheological stratification. Lateral heterogeneity is implemented in all models by increased crustal strength in a central narrow block. The main investigated parameters are strain rate and strength of the lithospheric mantle, both playing an important role in crust-mantle coupling. The experiments show that the presence of a strong crustal domain is effective in localizing deformation along its boundaries. After deformation is localized, the evolution of the orogenic system is governed by the mechanical properties of the lithosphere such that the final geometry of the intra-plate mountain depends on the interplay between crust-mantle coupling and folding versus fracturing of the lithospheric mantle. Underthrusting is the main deformation mode in case of high convergence velocity and/or thick brittle mantle with a final asymmetric architecture of the deep lithosphere. In contrast, lithospheric folding is dominant in case of low convergence velocity and low strength brittle mantle, leading to the development of a symmetric lithospheric root. The presented analogue modelling results provide novel insights for 1) strain localization and 2) the development of the asymmetric architecture of the Pyrenees.

  10. Axis switching and spreading of an asymmetric jet: Role of vorticity dynamics

    NASA Technical Reports Server (NTRS)

    Zaman, K. B. M. Q.

    1994-01-01

    The effects of vortex generators and periodic excitation on vorticity dynamics and the phenomenon of axis switching in a free asymmetric jet are studied experimentally. Most of the data reported are for a 3:1 rectangular jet at a Reynolds number of 450,000 and a Mach number of 0.31. The vortex generators are in the form of 'delta tabs', triangular shaped protrusions into the flow, placed at the nozzle exit. With suitable placement of the tabs, axis switching could be either stopped or augmented. Two mechanisms are identified governing the phenomenon. One, as described by previous researchers and referred to here as the omega(sub theta)-induced dynamics, is due to difference in induced velocities for different segments of a rolled up azimuthal vortical structure. The other, omega(sub x)-induced dynamics, is due to the induced velocities of streamwise vortex pairs in the flow. Both dynamics can be active in a natural asymmetric jet; the tendency for axis switching caused by the omega(sub theta)-induced dynamics may be, depending on the streamwise vorticity distribution, either resisted or enhanced by the omega(sub x)-induced dynamics. While this simple framework qualitatively explains the various observations made on axis switching, mechanisms actually in play may be much more complex. The two dynamics are not independent as the flow field is replete with both azimuthal and streamwise vortical structures which continually interact. Phase averaged flow field data for a periodically forced case, over a volume of the flow field, are presented and discussed in an effort to gain insight into the dynamics of these vortical structures.

  11. Preflare magnetic and velocity fields

    NASA Technical Reports Server (NTRS)

    Hagyard, M. J.; Gaizauskas, V.; Chapman, G. A.; Deloach, A. C.; Gary, G. A.; Jones, H. P.; Karpen, J. T.; Martres, M.-J.; Porter, J. G.; Schmeider, B.

    1986-01-01

    A characterization is given of the preflare magnetic field, using theoretical models of force free fields together with observed field structure to determine the general morphology. Direct observational evidence for sheared magnetic fields is presented. The role of this magnetic shear in the flare process is considered within the context of a MHD model that describes the buildup of magnetic energy, and the concept of a critical value of shear is explored. The related subject of electric currents in the preflare state is discussed next, with emphasis on new insights provided by direct calculations of the vertical electric current density from vector magnetograph data and on the role of these currents in producing preflare brightenings. Results from investigations concerning velocity fields in flaring active regions, describing observations and analyses of preflare ejecta, sheared velocities, and vortical motions near flaring sites are given. This is followed by a critical review of prevalent concepts concerning the association of flux emergence with flares

  12. Definition of Contravariant Velocity Components

    NASA Technical Reports Server (NTRS)

    Hung, Ching-moa; Kwak, Dochan (Technical Monitor)

    2002-01-01

    In this paper we have reviewed the basics of tensor analysis in an attempt to clarify some misconceptions regarding contravariant and covariant vector components as used in fluid dynamics. We have indicated that contravariant components are components of a given vector expressed as a unique combination of the covariant base vector system and, vice versa, that the covariant components are components of a vector expressed with the contravariant base vector system. Mathematically, expressing a vector with a combination of base vector is a decomposition process for a specific base vector system. Hence, the contravariant velocity components are decomposed components of velocity vector along the directions of coordinate lines, with respect to the covariant base vector system. However, the contravariant (and covariant) components are not physical quantities. Their magnitudes and dimensions are controlled by their corresponding covariant (and contravariant) base vectors.

  13. Multilogarithmic velocity renormalization in graphene

    NASA Astrophysics Data System (ADS)

    Sharma, Anand; Kopietz, Peter

    2016-06-01

    We reexamine the effect of long-range Coulomb interactions on the quasiparticle velocity in graphene. Using a nonperturbative functional renormalization group approach with partial bosonization in the forward scattering channel and momentum transfer cutoff scheme, we calculate the quasiparticle velocity, v (k ) , and the quasiparticle residue, Z , with frequency-dependent polarization. One of our most striking results is that v (k ) ∝ln[Ck(α ) /k ] where the momentum- and interaction-dependent cutoff scale Ck(α ) vanishes logarithmically for k →0 . Here k is measured with respect to one of the charge neutrality (Dirac) points and α =2.2 is the strength of dimensionless bare interaction. Moreover, we also demonstrate that the so-obtained multilogarithmic singularity is reconcilable with the perturbative expansion of v (k ) in powers of the bare interaction.

  14. An examination of a group-velocity criterion for the breakdown of an idealized vortex flow

    NASA Technical Reports Server (NTRS)

    Tsai, C. Y.; Widnall, S. E.

    1979-01-01

    The phenomenon of vortex breakdown is believed to be associated with a finite amplitude wave that has become trapped at the critical or breakdown location. The conditions at which the propagating waves become trapped at a certain axial location were examined by use of a group-velocity criterion implied by Landahl's general theory of wave trapping. An ideal vortex having constant vorticity and uniform axial velocity at the inlet of a slowly diverging duct was studied. The linear wave propagation analysis is applied to the base flow at several axial stations for several values of the ratio of swirl velocity to axial velocity at the inlet of the divergent duct, assuming a locally parallel flow. The dipsersion relations and hence the group velocities of both the symmetric (n = 0) and asymmetric modes (n = + or - 1) were investigated. The existence of a critical state in the flow (at which the group velocity vanishes), and its relationship to the stagnation point on the axis of the duct and to the occurrence of an irregular singularity in the equations governing wave propagation in the flow field are discussed.

  15. Gaussian Velocity Distributions in Avalanches

    NASA Astrophysics Data System (ADS)

    Shattuck, Mark

    2004-03-01

    Imagine a world where gravity is so strong that if an ice cube is tilted the shear forces melt the surface and water avalanches down. Further imagine that the ambient temperature is so low that the water re-freezes almost immediately. This is the world of granular flows. As a granular solid is tilted the surface undergoes a sublimation phase transition and a granular gas avalanches down the surface, but the inelastic collisions rapidly remove energy from the flow lowering the granular temperature (kinetic energy per particle) until the gas solidifies again. It is under these extreme conditions that we attempt to uncover continuum granular flow properties. Typical continuum theories like Navier-Stokes equation for fluids follow the space-time evolution of the first few moments of the velocity distribution. We study continuously avalanching flow in a rotating two-dimensional granular drum using high-speed video imaging and extract the position and velocities of the particles. We find a universal near Gaussian velocity distribution throughout the flowing regions, which are characterized by a liquid-like radial distribution function. In the remaining regions, in which the radial distribution function develops sharp crystalline peaks, the velocity distribution has a Gaussian peak but is much broader in the tails. In a companion experiment on a vibrated two-dimensional granular fluid under constant pressure, we find a clear gas-solid phase transition in which both the temperature and density change discontinuously. This suggests that a low temperature crystal and a high temperature gas can coexist in steady state. This coexistence could result in a narrower, cooler, Gaussian peak and a broader, warmer, Gaussian tail like the non-Gaussian behavior seen in the crystalline portions of the rotating drum.

  16. Simulations of High Velocity Clouds

    NASA Astrophysics Data System (ADS)

    Shelton, Robin

    Recently, a great deal of progress has been made toward understanding clouds of fast moving material within and near our Galaxy. Not only have observations revealed more clouds and enabled better distance estimates, but they have found large numbers of high velocity high ions. Observations of faint stars have revealed that our Galaxy is threaded with streams of stars, the likely remnants of subsumed dwarf galaxies. It has become apparent that the gas stripped from such galaxies likely contributed to the population of high velocity clouds (HVCs), making HVCs signposts of the Milky Way's growth via accretion. Theoretical and simulational work on this explanation for HVCs have advanced as have theoretical and simulational work on other explanations and on HVC-galaxy interactions. But, much work has yet to be done. Here, we propose a suite of multi-dimensional simulations of HVC-galaxy interactions designed to determine how HVCs affect the Galaxy and designed to determine the characteristics of the clouds and environmental gas that enable high velocity gas to be rich in high stage ions. This work will contribute toward NASA's strategic goal to discover how the universe works and evolves. The project will employ simulations and theory, while also producing results that will be helpful for deciphering vast numbers of observations taken by NASA telescopes.

  17. Measurement of retinal blood velocity

    NASA Astrophysics Data System (ADS)

    Winchester, Leonard W., Jr.; Chou, Nee-Yin

    2006-02-01

    A fundus camera was modified to illuminate the retina of a rabbit model with low power laser light in order to obtain laser speckle images. A fast-exposure charge-coupled device (CCD) camera was used to capture laser speckle images of the retina. Image acquisition was synchronized with the arterial pulses of the rabbit to ensure that all images are obtained at the same point in the cardiac cycle. The rabbits were sedated and a speculum was inserted to prevent the eyelid from closing. Both albino (New Zealand; pigmented (Dutch belted) rabbits were used in the study. The rabbit retina is almost avascular. The measurements are obtained for choroidal tissue as well as retinal tissue. Because the retina is in a region of high metabolism, blood velocity is strongly affected by blood oxygen saturation. Measurements of blood velocity obtained over a wide range of O II saturations (58%-100%) showed that blood velocity increases with decreasing O II saturation. For most experiments, the left eye of the rabbit was used for laser measurements whereas the right eye served as a control. No observable difference between pre- and post-experimented eye was noted. Histological examinations of retinal tissue subjected to repeated laser measurements showed no indication of tissue damage.

  18. Three axis velocity probe system

    DOEpatents

    Fasching, George E.; Smith, Jr., Nelson S.; Utt, Carroll E.

    1992-01-01

    A three-axis velocity probe system for determining three-axis positional velocities of small particles in fluidized bed systems and similar applications. This system has a sensor head containing four closely-spaced sensing electrodes of small wires that have flat ends to establish a two axis plane, e.g. a X-Y plane. Two of the sensing electrodes are positioned along one of the axes and the other two are along the second axis. These four sensing electrodes are surrounded by a guard electrode, and the outer surface is a ground electrode and support member for the sensing head. The electrodes are excited by, for example, sinusoidal voltage having a peak-to-peak voltage of up to 500 volts at a frequency of 2 MHz. Capacitive currents flowing between the four sensing electrodes and the ground electrode are influenced by the presence and position of a particle passing the sensing head. Any changes in these currents due to the particle are amplified and synchronously detected to produce positional signal values that are converted to digital form. Using these digital forms and two values of time permit generation of values of the three components of the particle vector and thus the total velocity vector.

  19. BENCAP, LLC: CAPSULE VELOCITY TEST

    SciTech Connect

    Meidinger, Brian

    2005-09-07

    Ben Cap, LLC, has a technology that utilizes bebtonite to plug wells. The bentonite is encapsulated in a cardboard capsule, droped down to the bottom of the well where it is allowed to hydrate, causing the bentonite to expand and plug the well. This method of plugging a well is accepted in some, but not all states. This technology can save a significant amount of money when compared to cementing methods currently used to plug and abandon wells. The test objective was to obtain the terminal velocity of the capsule delivery system as it drops through a column of water in a wellbore. Once the terminal velocity is known, the bentonite swelling action can be timed not to begin swelling until it reaches the bottom of the well bore. The results of the test showed that an average speed of 8.93 plus or minus 0.12 ft/sec was achieved by the capsule as it was falling through a column of water. Plotting the data revealed a very linear function with the capsules achieving terminal velocity shortly after being released. The interference of the capsule impacting the casing was not readily apparent in any of the runs, but a siginal sampling anomaly was present in one run. Because the anomaly was so brief and not present in any of the other runs, no solid conclusions could be drawn. Additional testing would be required to determine the effects of capsules impacting a fluid level that is not at surface.

  20. Influence of thermal and velocity slip on the peristaltic flow of Cu-water nanofluid with magnetic field

    NASA Astrophysics Data System (ADS)

    Akbar, Noreen Sher

    2016-03-01

    The peristaltic flow of an incompressible viscous fluid containing copper nanoparticles in an asymmetric channel is discussed with thermal and velocity slip effects. The copper nanoparticles for the peristaltic flow water as base fluid is not explored so far. The equations for the purposed fluid model are developed first time in literature and simplified using long wavelength and low Reynolds number assumptions. Exact solutions have been calculated for velocity, pressure gradient, the solid volume fraction of the nanoparticles and temperature profile. The influence of various flow parameters on the flow and heat transfer characteristics is obtained.

  1. The Asymmetric Wind in M82

    NASA Astrophysics Data System (ADS)

    Shopbell, P. L.; Bland-Hawthorn, J.

    1998-01-01

    We have obtained detailed Fabry-Perot imaging observations of the nearby galaxy M82 in order to understand the physical association between the high-velocity outflow and the starburst nucleus. The high spatial and kinematic resolution of our observations has allowed us to perform photometric analyses of Hα, [N II], and [O III] spectral lines at roughly 100,000 positions across the extent of the galaxy. The observed velocities of the emitting gas in M82 reveal a bipolar outflow of material, originating from the bright starburst regions in the galaxy's inner disk but misaligned with respect to the galaxy spin axis. The deprojected outflow velocity indicated by the optical filaments increases with radius from 525 to 655 km s-1. All three spectral lines show double components in the centers of the outflowing lobes, with the Hα line split by ~300 km s-1 over a region almost 1 kpc in size. The filamentary lobes lie along an axis tilted by 15° with respect to the spin axis, a finding confirmed by the regions of line splitting and by the ionization pattern over the outflow. The filaments are not simple surfaces of revolution, nor is the emission distributed evenly over the surfaces. We model these lobes as a composite of cylindrical and conical structures, collimated in the inner ~500 pc but expanding at a larger opening angle of ~25° beyond that radius. We compare our kinematic model with simulations of starburst-driven winds in which disk material surrounding the source is entrained by the wind. There is some evidence for rotation of the wind filaments about the outflow axis in support of entrainment, and we find strong similarities between the observed and predicted structures. The data reveal a remarkably low [N II]/Hα ratio in the region of the outflow, indicating that photoionization by the nuclear starburst may play a significant role in the excitation of the optical filament gas, particularly near the nucleus. An increase in the [O III]/Hα ratio along the

  2. Asymmetric photoredox transition-metal catalysis activated by visible light

    NASA Astrophysics Data System (ADS)

    Huo, Haohua; Shen, Xiaodong; Wang, Chuanyong; Zhang, Lilu; Röse, Philipp; Chen, Liang-An; Harms, Klaus; Marsch, Michael; Hilt, Gerhard; Meggers, Eric

    2014-11-01

    Asymmetric catalysis is seen as one of the most economical strategies to satisfy the growing demand for enantiomerically pure small molecules in the fine chemical and pharmaceutical industries. And visible light has been recognized as an environmentally friendly and sustainable form of energy for triggering chemical transformations and catalytic chemical processes. For these reasons, visible-light-driven catalytic asymmetric chemistry is a subject of enormous current interest. Photoredox catalysis provides the opportunity to generate highly reactive radical ion intermediates with often unusual or unconventional reactivities under surprisingly mild reaction conditions. In such systems, photoactivated sensitizers initiate a single electron transfer from (or to) a closed-shell organic molecule to produce radical cations or radical anions whose reactivities are then exploited for interesting or unusual chemical transformations. However, the high reactivity of photoexcited substrates, intermediate radical ions or radicals, and the low activation barriers for follow-up reactions provide significant hurdles for the development of efficient catalytic photochemical processes that work under stereochemical control and provide chiral molecules in an asymmetric fashion. Here we report a highly efficient asymmetric catalyst that uses visible light for the necessary molecular activation, thereby combining asymmetric catalysis and photocatalysis. We show that a chiral iridium complex can serve as a sensitizer for photoredox catalysis and at the same time provide very effective asymmetric induction for the enantioselective alkylation of 2-acyl imidazoles. This new asymmetric photoredox catalyst, in which the metal centre simultaneously serves as the exclusive source of chirality, the catalytically active Lewis acid centre, and the photoredox centre, offers new opportunities for the `green' synthesis of non-racemic chiral molecules.

  3. Asymmetric bias in user guided segmentations of brain structures.

    PubMed

    Maltbie, Eric; Bhatt, Kshamta; Paniagua, Beatriz; Smith, Rachel G; Graves, Michael M; Mosconi, Matthew W; Peterson, Sarah; White, Scott; Blocher, Joseph; El-Sayed, Mohammed; Hazlett, Heather C; Styner, Martin A

    2012-01-16

    Brain morphometric studies often incorporate comparative hemispheric asymmetry analyses of segmented brain structures. In this work, we present evidence that common user guided structural segmentation techniques exhibit strong left-right asymmetric biases and thus fundamentally influence any left-right asymmetry analyses. In this study, MRI scans from ten pediatric subjects were employed for studying segmentations of amygdala, globus pallidus, putamen, caudate, and lateral ventricle. Additionally, two pediatric and three adult scans were used for studying hippocampus segmentation. Segmentations of the sub-cortical structures were performed by skilled raters using standard manual and semi-automated methods. The left-right mirrored versions of each image were included in the data and segmented in a random order to assess potential left-right asymmetric bias. Using shape analysis we further assessed whether the asymmetric bias is consistent across subjects and raters with the focus on the hippocampus. The user guided segmentation techniques on the sub-cortical structures exhibited left-right asymmetric volume bias with the hippocampus displaying the most significant asymmetry values (p<0.01). The hippocampal shape analysis revealed the bias to be strongest on the lateral side of the body and medial side of the head and tail. The origin of this asymmetric bias is considered to be based in laterality of visual perception; therefore segmentations with any degree of user interaction contain an asymmetric bias. The aim of our study is to raise awareness in the neuroimaging community regarding the presence of the asymmetric bias and its influence on any left-right hemispheric analyses. We also recommend reexamining previous research results in the light of this new finding. PMID:21889995

  4. Satellite-tracked cumulus velocities. [for determining wind velocity

    NASA Technical Reports Server (NTRS)

    Fujita, T. T.; Pearl, E. W.; Shenk, W. E.

    1973-01-01

    The research indicates that extreme caution must be exercised in converting cloud velocities into winds. The motion of fair-weather cumuli obtained by tracking their shadows over Springfield, Missouri revealed that the standard deviation in the individual cloud motion is several times the tracking error. The motion of over-ocean cumuli near Barbados clearly indicated the complicated nature of cumulus velocities. Analysis of whole-sky images obtained near Tampa, Florida failed to show significant continuity and stability of cumulus plumes, less than 0.3 mile in diameter. Cumulus turrets with 0.3 to 2 mile in size appear to be the best target to infer the mean wind within the subcloud layers. Cumulus or stratocumulus cells consisting of x number of turrets do not always move with wind. The addition and deletion of turrets belonging to a specific cell appear to be the cause of the erratic motion of a tracer cell. It may by concluded that the accuracy of wind estimates is unlikely to be better than 2m/sec unless the physical and dynamical characteristics of cumulus motion is futher investigated.

  5. Spatio-temporal linear stability analysis of stratified planar wakes: Velocity and density asymmetry effects

    NASA Astrophysics Data System (ADS)

    Emerson, Benjamin; Jagtap, Swapnil; Quinlan, J. Mathew; Renfro, Michael W.; Cetegen, Baki M.; Lieuwen, Tim

    2016-04-01

    This paper explores the hydrodynamic stability of bluff body wakes with non-uniform mean density, asymmetric mean density, and velocity profiles. This work is motivated by experiments [S. Tuttle et al., "Lean blow off behavior of asymmetrically-fueled bluff body-stabilized flames," Combust. Flame 160, 1677 (2013)], which investigated reacting wakes with equivalence ratio stratification and, hence, asymmetry in the base flow density profiles. They showed that highly stratified cases exhibited strong, narrowband oscillations, suggestive of global hydrodynamic instability. In this paper, we present a local hydrodynamic stability analysis for non-uniform density wakes that includes base flow asymmetry. The results show that increasing the degree of base density asymmetry generally has a destabilizing effect and that increasing base velocity asymmetry tends to be stabilizing. Furthermore, we show that increasing base density asymmetry slightly decreases the absolute frequency and that increasing the base velocity asymmetry slightly increases the absolute frequency. In addition, we show that increasing the degree of base density asymmetry distorts the most absolutely unstable hydrodynamic mode from its nominally sinuous structure. This distorted mode exhibits higher amplitude pressure and velocity oscillations near the interface with the smaller density jump than near the one with the bigger density jump. This would then be anticipated to lead to strongly non-symmetric amplitudes of flame flapping, with much stronger flame flapping on the side with lower density ratio. These predictions are shown to be consistent with experimental data. These comparisons support the analytical predictions that increased base density asymmetry are destabilizing and that hydrodynamic velocity fluctuation amplitudes should be greatest at the flame with the lowest density jump.

  6. Coupling Between Velocities in a Radial Supercharger

    NASA Astrophysics Data System (ADS)

    Pavlechko, V. N.; Petrov, O. A.

    2014-03-01

    We have analyzed the velocities of the medium and impeller in a radial supercharger with consideration of the Coriolis acceleration. We have derived an expression for determining the angular velocity of the medium that differs from the angular velocity of the impeller. Dependences have been obtained to determine the velocity of the medium at the exit from the impeller on the inclination angle of the supercharger blades and their coupling with the circumferential velocity of the impeller in the absence of energy losses. Graphical dependences of velocities on the inclination angle of the blades at different ratios of inside radius to outside radius have been constructed.

  7. Velocity distribution of fragments of catastrophic impacts

    NASA Technical Reports Server (NTRS)

    Takagi, Yasuhiko; Kato, Manabu; Mizutani, Hitoshi

    1992-01-01

    Three dimensional velocities of fragments produced by laboratory impact experiments were measured for basalts and pyrophyllites. The velocity distribution of fragments obtained shows that the velocity range of the major fragments is rather narrow, at most within a factor of 3 and that no clear dependence of velocity on the fragment mass is observed. The NonDimensional Impact Stress (NDIS) defined by Mizutani et al. (1990) is found to be an appropriate scaling parameter to describe the overall fragment velocity as well as the antipodal velocity.

  8. Study of Estimation Method for Unsteady Inflow Velocity in Two-Dimensional Ultrasonic-Measurement-Integrated Blood Flow Simulation.

    PubMed

    Kadowaki, Hiroko; Hayase, Toshiyuki; Funamoto, Kenichi; Taniguchi, Nobuyuki

    2016-02-01

    Information on hemodynamics is essential for elucidation of mechanisms and development of novel diagnostic methods for circulatory diseases. Two-dimensional ultrasonic-measurement-integrated (2D-UMI) simulation can correctly reproduce an intravascular blood flow field and hemodynamics by feeding back an ultrasonic measurement to the numerical blood flow simulation. In this method, it is critically important to give the correct cross-sectional average inflow velocity (inflow velocity) as the boundary condition. However, systematic study has not been done on the relative validity and effectiveness of existing inflow velocity estimation methods for various target flow fields. The aim of this study was to examine the existing methods systematically and to establish a method to accurately estimate inflow velocities for various vessel geometries and flow conditions in 2D-UMI simulations. A numerical experiment was performed for 2D-UMI simulation of blood flow models in a straight vessel with inflow velocity profiles symmetric and asymmetric to the vessel axis using existing evaluation functions based on Doppler velocity error for the inflow velocity estimation. As a result, it was clarified that a significantly large estimation error occurs in the asymmetric flow due to a nonfeedback domain near the downstream end of the calculation domain. Hence, a new inflow velocity estimation method of 2D-UMI simulation is proposed in which the feedback and evaluation domains are extended to the downstream end. Further numerical experiments of 2D-UMI simulation for two realistic vessel geometries of a healthy blood vessel and a stenosed one confirmed the effectiveness of the proposed method. PMID:26241967

  9. PRECISION RADIAL VELOCITIES WITH CSHELL

    SciTech Connect

    Crockett, Christopher J.; Prato, L.; Mahmud, Naved I.; Johns-Krull, Christopher M.; Jaffe, Daniel T.; Beichman, Charles A. E-mail: lprato@lowell.edu E-mail: cmj@rice.edu

    2011-07-10

    Radial velocity (RV) identification of extrasolar planets has historically been dominated by optical surveys. Interest in expanding exoplanet searches to M dwarfs and young stars, however, has motivated a push to improve the precision of near-infrared RV techniques. We present our methodology for achieving 58 m s{sup -1} precision in the K band on the M0 dwarf GJ 281 using the CSHELL spectrograph at the 3 m NASA Infrared Telescope Facility. We also demonstrate our ability to recover the known 4 M{sub JUP} exoplanet Gl 86 b and discuss the implications for success in detecting planets around 1-3 Myr old T Tauri stars.

  10. Newberry EGS Seismic Velocity Model

    DOE Data Explorer

    Templeton, Dennise

    2013-10-01

    We use ambient noise correlation (ANC) to create a detailed image of the subsurface seismic velocity at the Newberry EGS site down to 5 km. We collected continuous data for the 22 stations in the Newberry network, together with 12 additional stations from the nearby CC, UO and UW networks. The data were instrument corrected, whitened and converted to single bit traces before cross correlation according to the methodology in Benson (2007). There are 231 unique paths connecting the 22 stations of the Newberry network. The additional networks extended that to 402 unique paths crossing beneath the Newberry site.

  11. Velocity Condensation for Magnetotactic Bacteria.

    PubMed

    Rupprecht, Jean-François; Waisbord, Nicolas; Ybert, Christophe; Cottin-Bizonne, Cécile; Bocquet, Lydéric

    2016-04-22

    Magnetotactic swimmers tend to align along magnetic field lines against stochastic reorientations. We show that the swimming strategy, e.g., active Brownian motion versus run-and-tumble dynamics, strongly affects the orientation statistics. The latter can exhibit a velocity condensation whereby the alignment probability density diverges. As a consequence, we find that the swimming strategy affects the nature of the phase transition to collective motion, indicating that Lévy run-and-tumble walks can outperform active Brownian processes as strategies to trigger collective behavior. PMID:27152825

  12. Velocity Condensation for Magnetotactic Bacteria

    NASA Astrophysics Data System (ADS)

    Rupprecht, Jean-François; Waisbord, Nicolas; Ybert, Christophe; Cottin-Bizonne, Cécile; Bocquet, Lydéric

    2016-04-01

    Magnetotactic swimmers tend to align along magnetic field lines against stochastic reorientations. We show that the swimming strategy, e.g., active Brownian motion versus run-and-tumble dynamics, strongly affects the orientation statistics. The latter can exhibit a velocity condensation whereby the alignment probability density diverges. As a consequence, we find that the swimming strategy affects the nature of the phase transition to collective motion, indicating that Lévy run-and-tumble walks can outperform active Brownian processes as strategies to trigger collective behavior.

  13. Distribution of quantum Fisher information in asymmetric cloning machines

    NASA Astrophysics Data System (ADS)

    Xiao, Xing; Yao, Yao; Zhou, Lei-Ming; Wang, Xiaoguang

    2014-12-01

    An unknown quantum state cannot be copied and broadcast freely due to the no-cloning theorem. Approximate cloning schemes have been proposed to achieve the optimal cloning characterized by the maximal fidelity between the original and its copies. Here, from the perspective of quantum Fisher information (QFI), we investigate the distribution of QFI in asymmetric cloning machines which produce two nonidentical copies. As one might expect, improving the QFI of one copy results in decreasing the QFI of the other copy. It is perhaps also unsurprising that asymmetric phase-covariant cloning outperforms universal cloning in distributing QFI since a priori information of the input state has been utilized. However, interesting results appear when we compare the distributabilities of fidelity (which quantifies the full information of quantum states), and QFI (which only captures the information of relevant parameters) in asymmetric cloning machines. Unlike the results of fidelity, where the distributability of symmetric cloning is always optimal for any d-dimensional cloning, we find that any asymmetric cloning outperforms symmetric cloning on the distribution of QFI for d <= 18, whereas some but not all asymmetric cloning strategies could be worse than symmetric ones when d > 18.

  14. Depth Structure from Asymmetric Shading Supports Face Discrimination

    PubMed Central

    Chen, Chien-Chung; Chen, Chin-Mei; Tyler, Christopher W.

    2013-01-01

    To examine the effect of illumination direction on the ability of observers to discriminate between faces, we manipulated the direction of illumination on scanned 3D face models. In order to dissociate the surface reflectance and illumination components of front-view face images, we introduce a symmetry algorithm that can separate the symmetric and asymmetric components of the face in both low and high spatial frequency bands. Based on this approach, hybrid faces stimuli were constructed with different combinations of symmetric and asymmetric spatial content. Discrimination results with these images showed that asymmetric illumination information biased face perception toward the structure of the shading component, while the symmetric illumination information had little, if any, effect. Measures of perceived depth showed that this property increased systematically with the asymmetric but not the symmetric low spatial frequency component. Together, these results suggest that (1) the asymmetric 3D shading information dramatically affects both the perceived facial information and the perceived depth of the facial structure; and (2) these effects both increase as the illumination direction is shifted to the side. Thus, our results support the hypothesis that face processing has a strong 3D component. PMID:23457484

  15. Asymmetric MRI magnet design using a hybrid numerical method.

    PubMed

    Zhao, H; Crozier, S; Doddrell, D M

    1999-12-01

    This paper describes a hybrid numerical method for the design of asymmetric magnetic resonance imaging magnet systems. The problem is formulated as a field synthesis and the desired current density on the surface of a cylinder is first calculated by solving a Fredholm equation of the first kind. Nonlinear optimization methods are then invoked to fit practical magnet coils to the desired current density. The field calculations are performed using a semi-analytical method. A new type of asymmetric magnet is proposed in this work. The asymmetric MRI magnet allows the diameter spherical imaging volume to be positioned close to one end of the magnet. The main advantages of making the magnet asymmetric include the potential to reduce the perception of claustrophobia for the patient, better access to the patient by attending physicians, and the potential for reduced peripheral nerve stimulation due to the gradient coil configuration. The results highlight that the method can be used to obtain an asymmetric MRI magnet structure and a very homogeneous magnetic field over the central imaging volume in clinical systems of approximately 1.2 m in length. Unshielded designs are the focus of this work. This method is flexible and may be applied to magnets of other geometries. PMID:10579958

  16. Asymmetric multiscale detrended fluctuation analysis of California electricity spot price

    NASA Astrophysics Data System (ADS)

    Fan, Qingju

    2016-01-01

    In this paper, we develop a new method called asymmetric multiscale detrended fluctuation analysis, which is an extension of asymmetric detrended fluctuation analysis (A-DFA) and can assess the asymmetry correlation properties of series with a variable scale range. We investigate the asymmetric correlations in California 1999-2000 power market after filtering some periodic trends by empirical mode decomposition (EMD). Our findings show the coexistence of symmetric and asymmetric correlations in the price series of 1999 and strong asymmetric correlations in 2000. What is more, we detect subtle correlation properties of the upward and downward price series for most larger scale intervals in 2000. Meanwhile, the fluctuations of Δα(s) (asymmetry) and | Δα(s) | (absolute asymmetry) are more significant in 2000 than that in 1999 for larger scale intervals, and they have similar characteristics for smaller scale intervals. We conclude that the strong asymmetry property and different correlation properties of upward and downward price series for larger scale intervals in 2000 have important implications on the collapse of California power market, and our findings shed a new light on the underlying mechanisms of power price.

  17. Efficient wavelength multiplexers based on asymmetric response filters.

    PubMed

    Wade, Mark T; Popović, Miloš A

    2013-05-01

    We propose integrated photonic wavelength multiplexers based on serially cascaded channel add-drop filters with an asymmetric frequency response. By utilizing the through-port rejection of the previous channel to advantage, the asymmetric response provides optimal rejection of the adjacent channels at each wavelength channel. We show theoretically the basic requirements to realize an asymmetric filter response, and propose and evaluate the possible implementations using coupled resonators. For one implementation, we provide detailed design formulas based on a coupled-mode theory model, and more generally we provide broad guidelines that enumerate all structures that can provide asymmetric passbands in the context of a pole-zero design approach to engineering the device response. Using second-order microring resonator filter stages as an example, we show that the asymmetric multiplexer can provide 2.4 times higher channel packing (bandwidth) density than a multiplexer using the same order stages (number of resonators) using conventional all-pole maximally-flat designs. We also address the sensitivities and constraints of various implementations of our proposed approach, as it affects their applicability to CMOS photonic interconnects. PMID:23669947

  18. Numerical simulation of steady and unsteady asymmetric vortical flow

    NASA Technical Reports Server (NTRS)

    Kandil, Osama A.; Wong, Tin-Chee; Liu, C. H.

    1992-01-01

    The unsteady, compressible, thin-layer, Navier-Stokes (NS) equations are solved to simulate steady and unsteady, asymmetric, vortical laminar flow around cones at high incidences and supersonic Mach numbers. The equations are solved by using an implicit, upwind, flux-difference splitting (FDS), finite-volume scheme. The locally conical flow assumption is used and the solutions are obtained by forcing the conserved components of the flowfield vector to be equal at two axial stations located at 0.95 and 1.0. Computational examples cover steady and unsteady asymmetric flows around a circular cone and its control using side strakes. The unsteady asymmetric flow solution around the circular cone has also been validated using the upwind, flux-vector splitting (FVS) scheme with the thin-layer NS equations and the upwind FDS with the full NS equations. The results are in excellent agreement with each other. Unsteady asymmetric flows are also presented for elliptic- and diamond-section cones, which model asymmetric vortex shedding around round- and sharp-edged delta winds.

  19. Evaluation of Asymmetric Immunoliposomal Nanoparticles for Cellular Uptake

    PubMed Central

    Whittenton, Jeremiah; Pitchumani, Ramanan; Thevananther, Sundararajah; Mohanty, Kishore

    2013-01-01

    Effective and targeted in vivo delivery of polynucleotide therapeutics is the key for the treatment of many diseases. Asymmetric immunoliposomes can be used as vehicles to deliver polynucleotides effectively because the two leaflets of the bilayer can have different compositions, which enhance the delivery capacity. The formation and in vitro cellular uptake of asymmetric immunoliposomes containing polynucleotide cargoes were studied here. Maleimide functionalized DSPE-PEG (2000) were incorporated into the outer leaflet to produce asymmetric liposomes capable of covalently attaching antibodies. Thiolated antibodies from both human and rabbit origin were conjugated to produce asymmetric pendant-type immunoliposomes that retain their specificity towards detection antibodies through the formation process. Human IgG conjugated asymmetric immunoliposomes were readily internalized (> 20 per cell) by macrophage, HEPG2, and CV-1 monkey kidney cells. The cells internalized the liposomal nanoparticles by the endocytic pathway. The immunoliposome-encapsulated endosomes were intact for at least 5 days and sequestered the plasmid from expression by the cell. PMID:22742513

  20. Contributing factors for increased bat swing velocity.

    PubMed

    Szymanski, David J; DeRenne, Coop; Spaniol, Frank J

    2009-07-01

    Bat swing velocity is an important characteristic of successful hitters in baseball and softball. The purpose of this literature review is threefold. First, before describing what components and training methods have been investigated to improve bat swing velocity, it is necessary to discuss the importance of bat swing velocity and batted-ball velocity. The second purpose is to discuss bat weight during on-deck circle warm-up, bat weight during resistance training, resistance training with an overload of force, performance of additional supplemental resistance exercises, the relationship between strength, power, lean body mass, and angular velocity and bat swing velocity, and the relationship between improvements in strength, power, lean body mass, and angular velocity and improvements in bat swing velocity. The third purpose of this review is to recommend some practical applications based on research results. PMID:19528868

  1. Azimuthally Anisotropic 3D Velocity Continuation

    DOE PAGESBeta

    Burnett, William; Fomel, Sergey

    2011-01-01

    We extend time-domain velocity continuation to the zero-offset 3D azimuthally anisotropic case. Velocity continuation describes how a seismic image changes given a change in migration velocity. This description turns out to be of a wave propagation process, in which images change along a velocity axis. In the anisotropic case, the velocity model is multiparameter. Therefore, anisotropic image propagation is multidimensional. We use a three-parameter slowness model, which is related to azimuthal variations in velocity, as well as their principal directions. This information is useful for fracture and reservoir characterization from seismic data. We provide synthetic diffraction imaging examples to illustratemore » the concept and potential applications of azimuthal velocity continuation and to analyze the impulse response of the 3D velocity continuation operator.« less

  2. Inexpensive Time-of-Flight Velocity Measurements.

    ERIC Educational Resources Information Center

    Everett, Glen E.; Wild, R. L.

    1979-01-01

    Describes a circuit designed to measure time-of-flight velocity and shows how to use it to determine bullet velocity in connection with the ballistic pendulum demonstration of momentum conservation. (Author/GA)

  3. Calculating the Velocity in the Moss

    NASA Technical Reports Server (NTRS)

    Womebarger, Amy R.; Tripathi, Durgesh; Mason, Helen

    2011-01-01

    The velocity of the warm (1 MK) plasma in the footpoint of the hot coronal loops (commonly called moss) could help discriminate between different heating frequencies in the active region core. Strong velocities would indicated low-frequency heating, while velocities close to zero would indicate high-frequency heating. Previous results have found disparaging observations, with both strong velocities and velocities close to zero reported. Previous results are based on observations from Hinode/EIS. The wavelength arrays for EIS spectra are typically calculated by assuming quiet Sun velocities are zero. In this poster, we determine the velocity in the moss using observations with SoHO/SUMER. We rely on neutral or singly ionized spectral lines to determine accurately the wavelength array associated with the spectra. SUMER scanned the active region twice, so we also report the stability of the velocity.

  4. Enhancement of electron mobility in asymmetric coupled quantum well structures

    SciTech Connect

    Das, S.; Nayak, R. K.; Sahu, T. Panda, A. K.

    2014-02-21

    We study the low temperature multisubband electron mobility in a structurally asymmetric GaAs/Al{sub x}Ga{sub 1-x}As delta doped double quantum well. We calculate the subband energy levels and wave functions through selfconsistent solution of the coupled Schrodinger equation and Poisson's equation. We consider ionized impurity scattering, interface roughness scattering, and alloy disorder scattering to calculate the electron mobility. The screening of the scattering potentials is obtained by using static dielectric response function formalism within the random phase approximation. We analyze, for the first time, the effect of asymmetric structure parameters on the enhancement of multisubband electron mobility through intersubband interactions. We show that the asymmetric variation of well width, doping concentration, and spacer width considerably influences the interplay of scattering mechanisms on mobility. Our results of asymmetry induced enhancement of electron mobility can be utilized for low temperature device applications.

  5. Experimental Quantification of Asymmetric Einstein-Podolsky-Rosen Steering.

    PubMed

    Sun, Kai; Ye, Xiang-Jun; Xu, Jin-Shi; Xu, Xiao-Ye; Tang, Jian-Shun; Wu, Yu-Chun; Chen, Jing-Ling; Li, Chuan-Feng; Guo, Guang-Can

    2016-04-22

    Einstein-Podolsky-Rosen (EPR) steering describes the ability of one observer to nonlocally "steer" the other observer's state through local measurements. EPR steering exhibits a unique asymmetric property; i.e., the steerability can differ between observers, which can lead to one-way EPR steering in which only one observer obtains steerability in the steering process. This property is inherently different from the symmetric concepts of entanglement and Bell nonlocality, and it has attracted increasing interest. Here, we experimentally demonstrate asymmetric EPR steering for a class of two-qubit states in the case of two measurement settings. We propose a practical method to quantify the steerability. We then provide a necessary and sufficient condition for EPR steering and clearly demonstrate one-way EPR steering. Our work provides new insight into the fundamental asymmetry of quantum nonlocality and has potential applications in asymmetric quantum information processing. PMID:27152778

  6. Three-dimensional infrared metamaterial with asymmetric transmission

    DOE PAGESBeta

    Kenanakis, George; Xomalis, Aggelos; Selimis, Alexandros; Vamvakaki, Maria; Farsari, Maria; Kafesaki, Maria; Soukoulis, Costas M.; Economou, Eleftherios N.

    2015-01-14

    A novel three-dimensional (3D) metallic metamaterial structure with asymmetric transmission for linear polarization is demonstrated in the infrared spectral region. The structure was fabricated by direct laser writing and selective electroless silver coating, a straightforward, novel technique producing mechanically and chemically stable 3D photonic structures. The structure unit cell is composed of a pair of conductively coupled magnetic resonators, and the asymmetric transmission response results from interplay of electric and magnetic responses; this equips the structure with almost total opaqueness along one propagation direction versus satisfying transparency along the opposite one. It also offers easily adjustable impedance, 90° one-way puremore » optical activity and backward propagation possibility, resulting thus in unique capabilities in polarization control and isolation applications. We show also that scaling down the structure can make it capable of exhibiting its asymmetric transmission and its polarization capabilities in the optical region.« less

  7. Three-dimensional infrared metamaterial with asymmetric transmission

    SciTech Connect

    Kenanakis, George; Xomalis, Aggelos; Selimis, Alexandros; Vamvakaki, Maria; Farsari, Maria; Kafesaki, Maria; Soukoulis, Costas M.; Economou, Eleftherios N.

    2015-01-14

    A novel three-dimensional (3D) metallic metamaterial structure with asymmetric transmission for linear polarization is demonstrated in the infrared spectral region. The structure was fabricated by direct laser writing and selective electroless silver coating, a straightforward, novel technique producing mechanically and chemically stable 3D photonic structures. The structure unit cell is composed of a pair of conductively coupled magnetic resonators, and the asymmetric transmission response results from interplay of electric and magnetic responses; this equips the structure with almost total opaqueness along one propagation direction versus satisfying transparency along the opposite one. It also offers easily adjustable impedance, 90° one-way pure optical activity and backward propagation possibility, resulting thus in unique capabilities in polarization control and isolation applications. We show also that scaling down the structure can make it capable of exhibiting its asymmetric transmission and its polarization capabilities in the optical region.

  8. Cooperative optical trapping in asymmetric plasmon nanocavity arrays.

    PubMed

    Guo, Ling; Sun, Zhijun

    2015-11-30

    We propose a scheme using cooperative interaction of antiphase resonance modes to enhance optical trapping in plasmonic nanostructures. This is implemented with a subwavelength array of asymmetric binary nanogrooves (e.g. different depths) in metal. When damping and inter-coupling of antiphase fields in the nanogrooves are mediated satisfying a critical condition, light can be cooperatively trapped in the nanogrooves, demonstrating perfect absorption at nearly the intrinsic resonance frequency of the deeper nanogrooves. A harmonic oscillator model is developed to interpret the cooperative interaction processes. The phenomenon has been also implemented in asymmetric ternary nanogroove arrays. In terms of compositions and intra-coupling mechanisms, the asymmetric binary/ternary plasmonic nanostructure arrays are crystalline molecular-metamaterials, analogous to electronic crystals composed of covalence-bond molecules. PMID:26698759

  9. Continuous Flavor Symmetries and the Stability of Asymmetric Dark Matter

    SciTech Connect

    Bishara, Fady; Zupan, Jure

    2015-01-19

    Generically, the asymmetric interactions in asymmetric dark matter (ADM) models could lead to decaying DM. We show that, for ADM that carries nonzero baryon number, continuous flavor symmetries that generate the flavor structure in the quark sector also imply a looser lower bound on the mass scale of the asymmetric mediators between the dark and visible sectors. Furthermore, the mediators for B = 2 ADM that can produce a signal in the future indirect dark matter searches can thus also be searched for at the LHC. For two examples of the mediator models, with either the MFV or Froggatt-Nielsen flavor breaking pattern, we derive the FCNC constraints and discuss the search strategies at the LHC.

  10. Symmetric/asymmetric bifurcation behaviours of a bogie system

    NASA Astrophysics Data System (ADS)

    Xue-jun, Gao; Ying-hui, Li; Yuan, Yue; True, Hans

    2013-02-01

    Based on the bifurcation and stability theory of dynamical systems, the symmetric/asymmetric bifurcation behaviours and chaotic motions of a railway bogie system under a complex nonlinear wheel-rail contact relation are investigated in detail by the 'resultant bifurcation diagram' method with slowly increasing and decreasing speed. It is found that the stationary equilibrium solution and the periodic motions coexist due to the sub-critical Hopf bifurcation in the railway bogie system. It is also found that multiple solutions coexist in many speed ranges. The coexistence of multiple solutions may result in a jump and hysteresis of the oscillating amplitude for different kinds of disturbances. It should be avoided in the normal operation. Furthermore, it is found that symmetry-breaking of the system through a pitchfork bifurcation leads to asymmetric chaotic motions in the railway bogie system. The speed ranges of asymmetric chaotic motions are, however, small.

  11. Asymmetric transformations of achiral 2,5-cyclohexadienones

    PubMed Central

    Kalstabakken, Kyle A.; Harned, Andrew M.

    2014-01-01

    Cyclohexadienones are versatile platforms for performing asymmetric synthesis as evidenced by the numerous natural product syntheses that exploit their diverse reactivity profile. However, there are few general methods available for the direct asymmetric synthesis of chiral cyclohexadienones. To circumvent this problem, several researchers have developed catalytic asymmetric methods that employ readily available achiral 2,5-cyclohexadienones as substrates. Many of these reactions are desymmetrizations in which one of the enantiotopic alkenes of an achiral dienone is transformed. Others involve selective reaction at one alkene of an unsymmetrically substituted, achiral dienone. This review will cover advances in this area over the last 20 years and the application of these strategies in complex molecule synthesis. PMID:26688596

  12. Pentamodal behaviors and acoustic bandgaps of asymmetric pentamode elastic metamaterials

    NASA Astrophysics Data System (ADS)

    Huang, Yan; Lu, Xuegang; Liang, Gongying; Xu, Zhuo

    2016-04-01

    The asymmetric pentamode metamaterial structure which is built by connecting double-cones with different cross-section shapes (regular triangle, square, pentagon and hexagon) to form diamond lattice is proposed in this paper. Then its phonon band structure is calculated by finite-element method (FEM), and its pentamodal behaviors and acoustic bandgaps are studied in detail. Results show that in the process of adjusting geometrical parameters, the asymmetric case performs similar pentamodal behaviors [ratio of bulk modulus to shear modulus B/G and single-mode bandgap (SBG)] with the symmetric cases. And the asymmetric case not only remains the intrinsic complete bandgap (CBG) of mode 12-13 like symmetric cases, but also opens new and wide CBG of mode 10-11 and mode 14-15 for appropriate parameters. Therefore, introducing structural asymmetry should be an effective way to open CBG in pentamode elastic metamaterials.

  13. Plasmon coupling of magnetic resonances in an asymmetric gold semishell

    NASA Astrophysics Data System (ADS)

    Ye, Jian; Kong, Yan; Liu, Cheng

    2016-05-01

    The generation of magnetic dipole resonances in metallic nanostructures is of great importance for constructing near-zero or even negative refractive index metamaterials. Commonly, planar two-dimensional (2D) split-ring resonators or relevant structures are basic elements of metamaterials. In this work, we introduce a three-dimensional (3D) asymmetric Au semishell composed of two nanocups with a face-to-face geometry and demonstrate two distinct magnetic resonances spontaneously in the visible–near infrared optical wavelength regime. These two magnetic resonances are from constructive and destructive hybridization of magnetic dipoles of individual nanocups in the asymmetric semishell. In contrast, complete cancellation of magnetic dipoles in the symmetric semishell leads to only a pronounced electric mode with near-zero magnetic dipole moment. These 3D asymmetric resonators provide new ways for engineering hybrid resonant modes and ultra-high near-field enhancement for the design of 3D metamaterials.

  14. Experimental Quantification of Asymmetric Einstein-Podolsky-Rosen Steering

    NASA Astrophysics Data System (ADS)

    Sun, Kai; Ye, Xiang-Jun; Xu, Jin-Shi; Xu, Xiao-Ye; Tang, Jian-Shun; Wu, Yu-Chun; Chen, Jing-Ling; Li, Chuan-Feng; Guo, Guang-Can

    2016-04-01

    Einstein-Podolsky-Rosen (EPR) steering describes the ability of one observer to nonlocally "steer" the other observer's state through local measurements. EPR steering exhibits a unique asymmetric property; i.e., the steerability can differ between observers, which can lead to one-way EPR steering in which only one observer obtains steerability in the steering process. This property is inherently different from the symmetric concepts of entanglement and Bell nonlocality, and it has attracted increasing interest. Here, we experimentally demonstrate asymmetric EPR steering for a class of two-qubit states in the case of two measurement settings. We propose a practical method to quantify the steerability. We then provide a necessary and sufficient condition for EPR steering and clearly demonstrate one-way EPR steering. Our work provides new insight into the fundamental asymmetry of quantum nonlocality and has potential applications in asymmetric quantum information processing.

  15. Gravity-induced asymmetric distribution of a plant growth hormone

    NASA Technical Reports Server (NTRS)

    Bandurski, R. S.; Schulze, A.; Momonoki, Y.

    1984-01-01

    Dolk (1936) demonstrated that gravistimulation induced an asymmetric distribution of auxin in a horizontally-placed shoot. An attempt is made to determine where and how that asymmetry arises, and to demonstrate that the endogenous auxin, indole-3-acetic acid, becomes asymmetrically distributed in the cortical cells of the Zea mays mesocotyl during 3 min of geostimulation. Further, indole-3-acetic acid derived by hydrolysis of an applied transport form of the hormone, indole-3-acetyl-myo-inositol, becomes asymmetrically distributed within 15 min of geostimulus time. From these and prior data is developed a working theory that the gravitational stimulus induces a selective leakage, or secretion, of the hormone from the vascular tissue to the cortical cells of the mesocotyl.

  16. Continuous Flavor Symmetries and the Stability of Asymmetric Dark Matter

    DOE PAGESBeta

    Bishara, Fady; Zupan, Jure

    2015-01-19

    Generically, the asymmetric interactions in asymmetric dark matter (ADM) models could lead to decaying DM. We show that, for ADM that carries nonzero baryon number, continuous flavor symmetries that generate the flavor structure in the quark sector also imply a looser lower bound on the mass scale of the asymmetric mediators between the dark and visible sectors. Furthermore, the mediators for B = 2 ADM that can produce a signal in the future indirect dark matter searches can thus also be searched for at the LHC. For two examples of the mediator models, with either the MFV or Froggatt-Nielsen flavormore » breaking pattern, we derive the FCNC constraints and discuss the search strategies at the LHC.« less

  17. Ultrasonic monitoring of asymmetric carbon fibre reinforced aluminum laminates

    NASA Astrophysics Data System (ADS)

    Zhao, Junqing; Yang, Fan; Wang, Rongguo

    2013-08-01

    Asymmetric carbon fibre reinforced aluminum alloy laminates was manufactured for the purpose with repeat tensile test, which will be applied in composite pressure vessel. Ultrasonic C scan and A scan approach are used to evaluate the damage of the asymmetric CFRP-Al (carbon fibre reinforced aluminum alloy) laminates. Nondestructive detection is carried out for the CFRP-Al laminates before and after tensile test. Comparison results and pulse echo analysis show that when subjected to repeat tensile test with 70% elastic limit strain load of the CFRP laminates, the interface debonding between CFRP and Al will not occur but the delamination within CFRP laminates becomes the main damage of the asymmetric CFRP-Al laminates. This investigation indicated that combined ultrasonic C scan and A scan is available for damage evaluation of fibre metal laminates.

  18. Ballistic thermal rectification in asymmetric three-terminal graphene nanojunctions

    NASA Astrophysics Data System (ADS)

    Ouyang, Tao; Chen, Yuanping; Xie, Yuee; Wei, X. L.; Yang, Kaike; Yang, Ping; Zhong, Jianxin

    2010-12-01

    Graphene nanojunctions (GNJs) are important components of future nanodevices and nanocircuits. Using the nonequilibrium Green’s function method, we investigate the phononic properties of three-terminal GNJs (TGNJs). The results show that the heat flux runs preferentially along the direction from narrow to wide terminals, presenting an evident ballistic thermal rectification effect in the asymmetric TGNJs. The rectification efficiency is strongly dependent on the asymmetry of the nanojunctions, which increases rapidly with the width discrepancy between the left and right terminals. Meanwhile, the corner form of the TGNJs also plays an important role in the rectification effect. The mechanism of this thermal rectification is explained by a qualitative analysis. Compared to previous thermal rectifiers based on other materials, the asymmetric nanojunctions based on graphene possess much high rectification ratio which can approach about 200%. These indicate that asymmetric TGNJs might be a promising candidate for excellent ballistic thermal (phononic) devices.

  19. Solitary waves in asymmetric electron-positron-ion plasmas

    NASA Astrophysics Data System (ADS)

    Lu, Ding; Li, Zi-Liang; Xie, Bai-Song

    2015-10-01

    > By solving the coupled equations of the electromagnetic field and electrostatic potential, we investigate solitary waves in an asymmetric electron-positron plasma and/or electron-positron-ion plasmas with delicate features. It is found that the solutions of the coupled equations can capture multipeak structures of solitary waves in the case of cold plasma, which are left out by using the long-wavelength approximation. By considering the effect of ion motion with respect to non-relativistic and ultra-relativistic temperature plasmas, we find that the ions' mobility can lead to larger-amplitude solitary waves; especially, this becomes more obvious for a high-temperature plasma. The effects of asymmetric temperature between electrons and positrons and the ion fraction on the solitary waves are also studied and presented. It is shown that the amplitudes of solitary waves decrease with positron temperature in asymmetric temperature electron-positron plasmas and decrease also with ion concentration.

  20. Dynamic JUNQ inclusion bodies are asymmetrically inherited in mammalian cell lines through the asymmetric partitioning of vimentin

    PubMed Central

    Ogrodnik, Mikołaj; Salmonowicz, Hanna; Brown, Rachel; Turkowska, Joanna; Średniawa, Władysław; Pattabiraman, Sundararaghavan; Amen, Triana; Abraham, Ayelet-chen; Eichler, Noam; Lyakhovetsky, Roman; Kaganovich, Daniel

    2014-01-01

    Aging is associated with the accumulation of several types of damage: in particular, damage to the proteome. Recent work points to a conserved replicative rejuvenation mechanism that works by preventing the inheritance of damaged and misfolded proteins by specific cells during division. Asymmetric inheritance of misfolded and aggregated proteins has been shown in bacteria and yeast, but relatively little evidence exists for a similar mechanism in mammalian cells. Here, we demonstrate, using long-term 4D imaging, that the vimentin intermediate filament establishes mitotic polarity in mammalian cell lines and mediates the asymmetric partitioning of damaged proteins. We show that mammalian JUNQ inclusion bodies containing soluble misfolded proteins are inherited asymmetrically, similarly to JUNQ quality-control inclusions observed in yeast. Mammalian IPOD-like inclusion bodies, meanwhile, are not always inherited by the same cell as the JUNQ. Our study suggests that the mammalian cytoskeleton and intermediate filaments provide the physical scaffold for asymmetric inheritance of dynamic quality-control JUNQ inclusions. Mammalian IPOD inclusions containing amyloidogenic proteins are not partitioned as effectively during mitosis as their counterparts in yeast. These findings provide a valuable mechanistic basis for studying the process of asymmetric inheritance in mammalian cells, including cells potentially undergoing polar divisions, such as differentiating stem cells and cancer cells. PMID:24843142

  1. Saltwater injection systems can tolerate higher velocities

    SciTech Connect

    Salama, M.M. )

    1993-07-12

    The API erosional velocity limit is overly conservative for saltwater injection systems constructed from corrosion-resistant material and containing no solids in the water. Under such conditions and providing that pressure drop is not of concern, a flow velocity of 50 fps can be safely used without concern for erosion. The paper discusses the selection of flow velocity, the API criterion, velocity limits, and a calculation example.

  2. Effect of asymmetrical flow field-flow fractionation channel geometry on separation efficiency.

    PubMed

    Ahn, Ji Yeon; Kim, Ki Hun; Lee, Ju Yong; Williams, P Stephen; Moon, Myeong Hee

    2010-06-11

    The separation efficiencies of three different asymmetrical flow field-flow fractionation (AF4) channel designs were evaluated using polystyrene latex standards. Channel breadth was held constant for one channel (rectangular profile), and was reduced either linearly (trapezoidal profile) or exponentially (exponential profile) along the length for the other two. The effective void volumes of the three channel types were designed to be equivalent. Theoretically, under certain flow conditions, the mean channel flow velocity of the exponential channel could be arranged to remain constant along the channel length, thereby improving separation in AF4. Particle separation obtained with the exponential channel was compared with particle separation obtained with the trapezoidal and rectangular channels. We demonstrated that at a certain flow rate condition (outflow/inflow rate=0.2), the exponential channel design indeed provided better performance with respect to the separation of polystyrene nanoparticles in terms of reducing band broadening. While the trapezoidal channel exhibited a little poorer performance than the exponential, the strongly decreasing mean flow velocity in the rectangular channel resulted in serious band broadening, a delay in retention time, and even failure of larger particles to elute. PMID:20439106

  3. A theoretical model of asymmetric wave ripples

    PubMed Central

    Blondeaux, P.; Foti, E.; Vittori, G.

    2015-01-01

    The time development of ripples under sea waves is investigated by means of the weakly nonlinear stability analysis of a flat sandy bottom subjected to the viscous oscillatory flow that is present in the boundary layer at the bottom of propagating sea waves. Second-order effects in the wave steepness are considered, to take into account the presence of the steady drift generated by the surface waves. Hence, the work of Vittori & Blondeaux (1990 J. Fluid Mech. 218, 19–39 (doi:10.1017/S002211209000091X)) is extended by considering steeper waves and/or less deep waters. As shown by the linear analysis of Blondeaux et al. (2000 Eur. J. Mech. B 19, 285–301 (doi:10.1016/S0997-7546(90)00106-I)), because of the presence of a steady velocity component in the direction of wave propagation, ripples migrate at a constant rate that depends on sediment and wave characteristics. The weakly nonlinear analysis shows that the ripple profile is no longer symmetric with respect to ripple crests and troughs and the symmetry index is computed as a function of the parameters of the problem. In particular, a relationship is determined between the symmetry index and the strength of the steady drift. A fair agreement between model results and laboratory data is obtained, albeit further data and analyses are necessary to determine the behaviour of vortex ripples and to be conclusive. PMID:25512587

  4. A theoretical model of asymmetric wave ripples.

    PubMed

    Blondeaux, P; Foti, E; Vittori, G

    2015-01-28

    The time development of ripples under sea waves is investigated by means of the weakly nonlinear stability analysis of a flat sandy bottom subjected to the viscous oscillatory flow that is present in the boundary layer at the bottom of propagating sea waves. Second-order effects in the wave steepness are considered, to take into account the presence of the steady drift generated by the surface waves. Hence, the work of Vittori & Blondeaux (1990 J. Fluid Mech. 218, 19-39 (doi:10.1017/S002211209000091X)) is extended by considering steeper waves and/or less deep waters. As shown by the linear analysis of Blondeaux et al. (2000 Eur. J. Mech. B 19, 285-301 (doi:10.1016/S0997-7546(90)00106-I)), because of the presence of a steady velocity component in the direction of wave propagation, ripples migrate at a constant rate that depends on sediment and wave characteristics. The weakly nonlinear analysis shows that the ripple profile is no longer symmetric with respect to ripple crests and troughs and the symmetry index is computed as a function of the parameters of the problem. In particular, a relationship is determined between the symmetry index and the strength of the steady drift. A fair agreement between model results and laboratory data is obtained, albeit further data and analyses are necessary to determine the behaviour of vortex ripples and to be conclusive. PMID:25512587

  5. A symmetric inhibitor binds HIV-1 protease asymmetrically.

    PubMed

    Dreyer, G B; Boehm, J C; Chenera, B; DesJarlais, R L; Hassell, A M; Meek, T D; Tomaszek, T A; Lewis, M

    1993-01-26

    Potential advantages of C2-symmetric inhibitors designed for the symmetric HIV-1 protease include high selectivity, potency, stability, and bioavailability. Pseudo-C2-symmetric monools and C2-symmetric diols, containing central hydroxymethylene and (R,R)-dihydroxyethylene moieties flanked by a variety of hydrophobic P1/P1' side chains, were studied as HIV-1 protease inhibitors. The monools and diols were synthesized in 8-10 steps from D-(+)-arabitol and D-(+)-mannitol, respectively. Monools with ethyl or isobutyl P1/P1' side chains were weak inhibitors of recombinant HIV-1 protease (Ki > 10 microM), while benzyl P1/P1' side chains afforded a moderately potent inhibitor (apparent Ki = 230 nM). Diols were 100-10,000x more potent than analogous monools, and a wider range of P1/P1' side chains led to potent inhibition. Both classes of compounds exhibited lower apparent Ki values under high-salt conditions. Surprisingly, monool and diol HIV-1 protease inhibitors were potent inhibitors of porcine pepsin, a prototypical asymmetric monomeric aspartic protease. These results were evaluated in the context of the pseudosymmetric structure of monomeric aspartic proteases and their evolutionary kinship with the retroviral proteases. The X-ray crystal structure of HIV-1 protease complexed with a symmetric diol was determined at 2.6 A. Contrary to expectations, the diol binds the protease asymmetrically and exhibits 2-fold disorder in the electron density map. Molecular dynamics simulations were conducted beginning with asymmetric and symmetric HIV-1 protease/inhibitor model complexes. A more stable trajectory resulted from the asymmetric complex, in agreement with the observed asymmetric binding mode. A simple four-point model was used to argue more generally that van der Waals and electrostatic force fields can commonly lead to an asymmetric association between symmetric molecules. PMID:8422397

  6. Connection between Magnetic Topology, Mixing and the Reconnection Rate in Asymmetric Layers

    NASA Astrophysics Data System (ADS)

    Daughton, W. S.; Nakamura, T.; Roytershteyn, V.; Karimabadi, H.; Hesse, M.; Loring, B.

    2013-12-01

    The entry of solar wind plasma into the magnetosphere occurs in thin boundary layers, which are typically asymmetric and have large magnetic and/or velocity shear across them. Magnetic reconnection is the dominant entry mechanism, but in regions with strong nearly perpendicular velocity shear, the Kelvin-Helmholtz instability dominates and can lead to vortex induced reconnection [1]. In both of these limits, recent fully kinetic simulations feature the development of 3D turbulence, characterized by electron-scale current sheets and interacting magnetic flux ropes. The 3D magnetic field, characterized by the Lyapunov exponent, reveals a chaotic structure within the reconnection layer in which neighboring field lines undergo rapid separation. In the presence of this complex 3D dynamics, defining and accurately computing the time evolving reconnection rate is a major challenge. One of the leading theoretical ideas [2] for computing the rate is based on integrating the parallel electric field. However, applying this approach is complicated by the chaotic magnetic field, which can lead to different answers on closely neighboring field lines. Furthermore, it is difficult to cleanly identify a transition back into an ideal region where the integration can be terminated. Here we explore a new approach that exploits the connection between the magnetic topology and the mixing of electrons that originate from separate sides of the asymmetric current layer. This idea is motivated by a clear correlation between the Lyapunov exponent for the magnetic field and the boundaries between mixed and unmixed regions. This correlation implies that mixing is a good proxy for quickly identifying 3D surfaces separating different topologies, and thus accurately measuring the time changing flux between topologies. The 3D reconnection rate obtained from this approach is contrasted with corresponding 2D simulations in the limits of both weak and strong velocity shear. [1] T.K.M Nakamura et al

  7. Application of Vectors to Relative Velocity

    ERIC Educational Resources Information Center

    Tin-Lam, Toh

    2004-01-01

    The topic 'relative velocity' has recently been introduced into the Cambridge Ordinary Level Additional Mathematics syllabus under the application of Vectors. In this note, the results of relative velocity and the 'reduction to rest' technique of teaching relative velocity are derived mathematically from vector algebra, in the hope of providing…

  8. Origin of the Low Velocity Zone

    NASA Astrophysics Data System (ADS)

    Stixrude, L. P.; Lithgow-Bertelloni, C. R.

    2014-12-01

    The origin of the low velocity zone is still not well understood, although the mechanisms responsible have important implications for the thermal evolution of the Earth and the origin of plate tectonics. The null hypothesis (a geotherm consisting of an adiabat and a conductive thermal boundary layer, and free of melt, water, and attenuation) accounts for many properties of the low velocity zone, including the depth at which the minimum velocity occurs and its variation with age, but the value of the minimum velocity is greater than that seen by seismology (the velocity deficit). Attenuation, as found in global seismic attenuation tomography, can explain much of the velocity deficit, but still leaves two features of the boundaries of the low velocity zone unexplained: an apparently abrupt upper boundary to the low velocity (G discontinuity, sometimes also associated with the "lithosphere-asthenosphere boundary"), and a high gradient zone beneath in which velocity increases with depth very rapidly. Here we show that by adding to the null hypothesis attenuation as recently measured experimentally, the entire velocity deficit is explained. Moreover, the upper boundary of the low velocity zone is remarkably abrupt, although possibly less sharp than receiver function analyses indicate. The high gradient zone is explained by variations in the entropy with depth, i.e. cooling with increasing depth at depths beneath the low velocity zone, a property of the geotherm that is expected on the basis of mantle convection simulations.

  9. Questions Students Ask: About Terminal Velocity.

    ERIC Educational Resources Information Center

    Meyer, Earl R.; Nelson, Jim

    1984-01-01

    If a ball were given an initial velocity in excess of its terminal velocity, would the upward force of air resistance (a function of velocity) be greater than the downward force of gravity and thus push the ball back upwards? An answer to this question is provided. (JN)

  10. Velocity distribution in horizontal slug flow

    SciTech Connect

    Kvernvold, O.; Saasen, A.; Selmor-Olsen, S.; Sontvedt, T.; Vindoy, V.

    1984-08-01

    An experimental device for measurement of the velocity distribution in a two-phase slug is developed. Velocity profiles both in the film and the liquid slug besides velocity variation along the pipe bottom (at a distance of 1 mm) through the slug front are presented.

  11. The Local Stellar Velocity Field via Vector Spherical Harmonics

    NASA Astrophysics Data System (ADS)

    Makarov, V. V.; Murphy, D. W.

    2007-07-01

    We analyze the local field of stellar tangential velocities for a sample of 42,339 nonbinary Hipparcos stars with accurate parallaxes, using a vector spherical harmonic formalism. We derive simple relations between the parameters of the classical linear model (Ogorodnikov-Milne) of the local systemic field and low-degree terms of the general vector harmonic decomposition. Taking advantage of these relationships, we determine the solar velocity with respect to the local stars of (VX,VY,VZ)=(10.5,18.5,7.3)+/-0.1 km s-1 not corrected for the asymmetric drift with respect to the local standard of rest. If only stars more distant than 100 pc are considered, the peculiar solar motion is (VX,VY,VZ)=(9.9,15.6,6.9)+/-0.2 km s-1. The adverse effects of harmonic leakage, which occurs between the reflex solar motion represented by the three electric vector harmonics in the velocity space and higher degree harmonics in the proper-motion space, are eliminated in our analysis by direct subtraction of the reflex solar velocity in its tangential components for each star. The Oort parameters determined by a straightforward least-squares adjustment in vector spherical harmonics are A=14.0+/-1.4, B=-13.1+/-1.2, K=1.1+/-1.8, and C=-2.9+/-1.4 km s-1 kpc-1. The physical meaning and the implications of these parameters are discussed in the framework of a general linear model of the velocity field. We find a few statistically significant higher degree harmonic terms that do not correspond to any parameters in the classical linear model. One of them, a third-degree electric harmonic, is tentatively explained as the response to a negative linear gradient of rotation velocity with distance from the Galactic plane, which we estimate at ~-20 km s-1 kpc-1. A similar vertical gradient of rotation velocity has been detected for more distant stars representing the thick disk (z>1 kpc), but here we surmise its existence in the thin disk at z<200 pc. The most unexpected and unexplained term within

  12. The Local Stellar Velocity Field via Vector Spherical Harmonics

    NASA Technical Reports Server (NTRS)

    Markarov, V. V.; Murphy, D. W.

    2007-01-01

    We analyze the local field of stellar tangential velocities for a sample of 42,339 nonbinary Hipparcos stars with accurate parallaxes, using a vector spherical harmonic formalism. We derive simple relations between the parameters of the classical linear model (Ogorodnikov-Milne) of the local systemic field and low-degree terms of the general vector harmonic decomposition. Taking advantage of these relationships, we determine the solar velocity with respect to the local stars of (V(sub X), V(sub Y), V(sub Z)) (10.5, 18.5, 7.3) +/- 0.1 km s(exp -1) not corrected for the asymmetric drift with respect to the local standard of rest. If only stars more distant than 100 pc are considered, the peculiar solar motion is (V(sub X), V(sub Y), V(sub Z)) (9.9, 15.6, 6.9) +/- 0.2 km s(exp -1). The adverse effects of harmonic leakage, which occurs between the reflex solar motion represented by the three electric vector harmonics in the velocity space and higher degree harmonics in the proper-motion space, are eliminated in our analysis by direct subtraction of the reflex solar velocity in its tangential components for each star. The Oort parameters determined by a straightforward least-squares adjustment in vector spherical harmonics are A=14.0 +/- 1.4, B=13.1 +/- 1.2, K=1.1 +/- 1.8, and C=2.9 +/- 1.4 km s(exp -1) kpc(exp -1). The physical meaning and the implications of these parameters are discussed in the framework of a general linear model of the velocity field. We find a few statistically significant higher degree harmonic terms that do not correspond to any parameters in the classical linear model. One of them, a third-degree electric harmonic, is tentatively explained as the response to a negative linear gradient of rotation velocity with distance from the Galactic plane, which we estimate at approximately -20 km s(exp -1) kpc(exp -1). A similar vertical gradient of rotation velocity has been detected for more distant stars representing the thick disk (z greater than 1 kpc

  13. Strongly asymmetric discrete Painlevé equations: The multiplicative case

    NASA Astrophysics Data System (ADS)

    Grammaticos, B.; Ramani, A.; Tamizhmani, K. M.; Tamizhmani, T.; Satsuma, J.

    2016-04-01

    We examine a class of multiplicative discrete Painlevé equations which may possess a strongly asymmetric form. When the latter occurs, the equation is written as a system of two equations the right hand sides of which have different functional forms. The present investigation focuses upon two canonical families of the Quispel-Roberts-Thompson classification which contain equations associated with the affine Weyl groups D5 ( 1 ) and E6 ( 1 ) (or groups appearing lower in the degeneration cascade of these two). Many new discrete Painlevé equations with strongly asymmetric forms are obtained.

  14. 10 Step Asymmetric Total Synthesis and Stereochemistry of (+)-Dragmacidin D

    PubMed Central

    Jackson, Jeffrey J.; Kobayashi, Hiroyuki; Steffens, Sophia D.

    2015-01-01

    The asymmetric synthesis of dragmacidin D (1) has been completed in 10 steps. Its sole stereocenter was set using direct asymmetric alkylation enabled by a C2-symmetric tetramine and lithium N-(trimethylsilyl)-tert-butylamide as the enolization reagent. A central Larock indole synthesis was employed in a convergent assembly of heterocyclic subunits. The stereochemical evidence from this work strongly supports the predicted S configuration at 6′″ position consistent with other members of the dragmacidin family of natural products. PMID:26130270

  15. Chaos-assisted emission from asymmetric resonant cavity microlasers

    SciTech Connect

    Shinohara, Susumu; Hentschel, Martina; Harayama, Takahisa; Sunada, Satoshi; Fukushima, Takehiro; Narimanov, Evgenii E.

    2011-05-15

    We study emission from quasi-one-dimensional modes of an asymmetric resonant cavity that are associated with a stable periodic ray orbit confined inside the cavity by total internal reflection. It is numerically demonstrated that such modes exhibit directional emission, which is explained by chaos-assisted emission induced by dynamical tunneling. Fabricating semiconductor microlasers with an asymmetric resonant cavity, we experimentally demonstrate the selective excitation of the quasi-one-dimensional modes by employing the device structure to preferentially inject currents to these modes and observe directional emission in good accordance with the theoretical prediction based on chaos-assisted emission.

  16. Possible origin of transition from symmetric to asymmetric fission

    NASA Astrophysics Data System (ADS)

    Paşca, H.; Andreev, A. V.; Adamian, G. G.; Antonenko, N. V.

    2016-09-01

    The charged distributions of fragments produced in the electromagnetic-induced fission of the even-even isotopes of Rn, Ra, Th, and U are described within an improved scission-point model and compared with the available experimental data. The three-equal-peaked charge distributions are predicted for several fissioning nuclei with neutron number N = 136. The possible explanation of the transition from a symmetric fission mode to an asymmetric one around N ∼ 136 is presented. The excitation energy dependencies of the asymmetric and symmetric fission modes are anticipated.

  17. Tilted Liquid Crystal Alignment on Asymmetrically Grooved Porous Alumina Film

    NASA Astrophysics Data System (ADS)

    Maeda, Tsuyoshi; Hiroshima, Kohki

    2005-06-01

    This paper reports the achievement of tilted liquid crystal (LC) alignment on an anodic porous alumina (APA) film using microgrooves with asymmetric shapes and dozens of minute pores. The microgrooves with asymmetric shapes were formed by a rubbing technique. The minute pores were then produced by anodization. The LC pretilt angle was controlled by the shapes of the microgrooves and pores. The LC director was orientated in the same inclining direction as that of a rubbed polyimide (PI) film. The pretilt angle was in the range of 20 to 90°. This tilted LC alignment remains very stable against external forces such as thermal shock and intense light.

  18. Asymmetric Mutualism in Two- and Three-Dimensional Range Expansions

    NASA Astrophysics Data System (ADS)

    Lavrentovich, Maxim O.; Nelson, David R.

    2014-04-01

    Genetic drift at the frontiers of two-dimensional range expansions of microorganisms can frustrate local cooperation between different genetic variants, demixing the population into distinct sectors. In a biological context, mutualistic or antagonistic interactions will typically be asymmetric between variants. By taking into account both the asymmetry and the interaction strength, we show that the much weaker demixing in three dimensions allows for a mutualistic phase over a much wider range of asymmetric cooperative benefits, with mutualism prevailing for any positive, symmetric benefit. We also demonstrate that expansions with undulating fronts roughen dramatically at the boundaries of the mutualistic phase, with severe consequences for the population genetics along the transition lines.

  19. Asymmetric laser sideband generation with a tapered semiconductor amplifier

    NASA Astrophysics Data System (ADS)

    Yanakas, Michael; Lim, Michael

    2013-03-01

    We have constructed a free-space, frequency-shifted feedback amplifier using a tapered semiconductor gain element. The general layout of the system is similar to that described in Littler, et al., Opt. Comm. 88, 523 (1992). Traveling-wave feedback is demonstrated with the m = - 1 order of several different acousto-optic modulators driven at variable frequency. Asymmetric sideband production is observed in the rf spectrum of a fast photodiode and in the transmission of a scanning Fabry-Perot interferometer. The number of asymmetric modes is controlled with the AOM rf drive power and the seed laser optical power. Supported by NSF PHY-0613659

  20. Tunable Dirac points and perfect transmission in asymmetric graphene superlattices

    NASA Astrophysics Data System (ADS)

    Zhang, Rui-Li; Li, Jin-Jing; Zhou, Yu; Peng, Ru-Wen; Huang, Run-Sheng; Wang, Mu

    2015-08-01

    We investigated the electronic band structures and transport properties in asymmetric graphene superlattices (AGSLs). Their asymmetric distribution of potentials can induce extra Dirac points (DPs) that are absent in periodic and symmetric graphene superlattices. The emergence and location of the DPs in the k space can be manipulated by selecting the special structure of the AGSL. As a result, tunable perfect transmissions are obtained in the system. Moreover, the conductance and Fano factor present interesting oscillatory behaviors. These findings may be used for the design of graphene-based electronic devices.