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Sample records for channel stabilization

  1. Stability of flowing open fluidic channels

    Directory of Open Access Journals (Sweden)

    Jue Nee Tan

    2013-02-01

    Full Text Available Open fluidic systems have a distinct advantage over enclosed channels in that the fluids exposed nature makes for easy external interaction, this finds uses in introduction of samples by adding liquid droplets or from the surrounding gaseous medium. This work investigates flowing open channels and films, which can potentially make use of the open section of the system as an external interface, before bringing the sample into an enclosed channel. Clearly, in this scenario a key factor is the stability of the flowing open fluid. The open channels investigated include a straight open channel defined by a narrow strip of solid surface, the edges of which allow large contact angle hysteresis, and a wider structure allowing for multiple inputs and outputs. A model is developed for fluid flow, and the findings used to describe the process of failure in both cases.

  2. Theory of hydraulic stability of boiling channels

    International Nuclear Information System (INIS)

    A framework of boiling channel stability theory is analyzed. The fundamental equations are those of STABLE code: Three conservation laws of mass, energy and momentum applied to one-dimensional channel, together with Bankoff' slip and Marinelli-Nelson's pressure drop correlation. These equations are analyzed to yield ''Void Equation'', ''Linearized Void Equation'', ''Volume Conservation Law'' and the ''Flow Impedance'' R(s), defined by the dynamic response of pressure drop to the inlet flow. The impedance contains all the information such a stability index, dominant frequency and damping ratio. It is shown that R is a sum of the form R sub(IA) + N sub(F)-1R sub(D) + N sub(R)R sub(R) + N sub(OR), where N's are non-dimensional parameters and R's characteristic impedances determined by three kinds of parameters, N sub(X), N sub(s) and the power distribution parameter. Systematic edition of the characteristic impedances according to the non-dimensional parameters will reduce the need for case-by-case STABLE calculations. Hydraulic stability of BWR channels under constant system pressure, is a phenomenon with three parameters in view of complexity. Furthermore an analysis is conducted to confirm the above stability structure and three typical instabilities are identified. (auth.)

  3. Stability in channel flow with fiber suspensions

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The constitutive equation of fiber suspensions is established on the basis of fiber orientation tensors. The modified Orr-Sommerfeld stability equation is obtained further and numerically solved by aid of spectral method and finite difference method. The computational results of channel flow without fibers agree well with the experimental data with a higher degree of accuracy than previous numerical results. The results of the channel flow with fiber suspensions indicate that the presence of fibers attenuates the instability of flow, increases the critical Reynolds number, reduces the growth rate of perturbations and narrows the range of unstable waves. The extent of the effect of fibers on the flow stability is in direct proportion to the volume fraction and aspect-ratio of the fibers.

  4. Gramicidin tryptophans mediate formamidinium-induced channel stabilization.

    OpenAIRE

    Seoh, S A; Busath, D

    1995-01-01

    Compared with alkali metal cations, formamidinium ions stabilize the gramicidin A channel molecule in monoolein bilayers (Seoh and Busath, 1993a). A similar effect is observed with N-acetyl gramicidin channel molecules in spite of the modified forces at the dimeric junction (Seoh and Busath, 1993b). Here we use electrophysiological measurements with tryptophan-to-phenylalanine-substituted gramicidin analogs to show that the formamidinium-induced channel molecule stabilization is eliminated wh...

  5. Method of stabilizing single channel analyzers

    International Nuclear Information System (INIS)

    A method and the apparatus to reduce the drift of single channel analyzers are described. Essentially, this invention employs a time-sharing or multiplexing technique to insure that the outputs from two single channel analyzers (SCAS) maintain the same count ratio regardless of variations in the threshold voltage source or voltage changes, the multiplexing technique is accomplished when a flip flop, actuated by a clock, changes state to switch the output from the individual SCAS before these outputs are sent to a ratio counting scalar. In the particular system embodiment disclosed that illustrates this invention, the sulfur content of coal is determined by subjecting the coal to radiation from a neutron producing source. A photomultiplier and detector system equates the transmitted gamma radiation to an analog voltage signal and sends the same signal after amplification, to a SCA system that contains the invention. Therein, at least two single channel analyzers scan the analog signal over different parts of a spectral region. The two outputs may then be sent to a digital multiplexer so that the output from the multiplexer contains counts falling within two distinct segments of the region. By dividing the counts from the multiplexer by each other, the percentage of sulfur within the coal sample under observation may be determined. (U.S.)

  6. Opportunistic Channel Scheduling for Ad Hoc Networks with Queue Stability

    Science.gov (United States)

    Dong, Lei; Wang, Yongchao

    2015-03-01

    In this paper, a distributed opportunistic channel access strategy in ad hoc network is proposed. We consider the multiple sources contend for the transmission opportunity, the winner source decides to transmit or restart contention based on the current channel condition. Owing to real data assumption at all links, the decision still needs to consider the stability of the queues. We formulate the channel opportunistic scheduling as a constrained optimization problem which maximizes the system average throughput with the constraints that the queues of all links are stable. The proposed optimization model is solved by Lyapunov stability in queueing theory. The successive channel access problem is decoupled into single optimal stopping problem at every frame and solved with Lyapunov algorithm. The threshold for every frame is different, and it is derived based on the instantaneous queue information. Finally, computer simulations are conducted to demonstrate the validity of the proposed strategy.

  7. Stability of stratified two-phase flows in inclined channels

    CERN Document Server

    Barmak, Ilya; Ullmann, Amos; Brauner, Neima

    2016-01-01

    Linear stability of stratified gas-liquid and liquid-liquid plane-parallel flows in inclined channels is studied with respect to all wavenumber perturbations. The main objective is to predict parameter regions in which stable stratified configuration in inclined channels exists. Up to three distinct base states with different holdups exist in inclined flows, so that the stability analysis has to be carried out for each branch separately. Special attention is paid to the multiple solution regions to reveal the feasibility of non-unique stable stratified configurations in inclined channels. The stability boundaries of each branch of steady state solutions are presented on the flow pattern map and are accompanied by critical wavenumbers and spatial profiles of the most unstable perturbations. Instabilities of different nature are visualized by streamlines of the neutrally stable perturbed flows, consisting of the critical perturbation superimposed on the base flow. The present analysis confirms the existence of ...

  8. Stability of floodplain-channel components Basin Hukiv.

    OpenAIRE

    Kyryljuk O.V.

    2010-01-01

    Appraised floodplain complex of river basin Gukiv and according mapped schemes is built. Calculations of the to determine the number Lohtina, factor of stability Makkaveyeva, Froude number, and Hryshanina parameter channel for the various phases of the water regime of the river.

  9. Stability of floodplain-channel components Basin Hukiv.

    Directory of Open Access Journals (Sweden)

    Kyryljuk O.V.

    2010-06-01

    Full Text Available Appraised floodplain complex of river basin Gukiv and according mapped schemes is built. Calculations of the to determine the number Lohtina, factor of stability Makkaveyeva, Froude number, and Hryshanina parameter channel for the various phases of the water regime of the river.

  10. Stability of stratified two-phase flows in inclined channels

    Science.gov (United States)

    Barmak, I.; Gelfgat, A. Yu.; Ullmann, A.; Brauner, N.

    2016-08-01

    Linear stability of the stratified gas-liquid and liquid-liquid plane-parallel flows in the inclined channels is studied with respect to all wavenumber perturbations. The main objective is to predict the parameter regions in which the stable stratified configuration in inclined channels exists. Up to three distinct base states with different holdups exist in the inclined flows, so that the stability analysis has to be carried out for each branch separately. Special attention is paid to the multiple solution regions to reveal the feasibility of the non-unique stable stratified configurations in inclined channels. The stability boundaries of each branch of the steady state solutions are presented on the flow pattern map and are accompanied by the critical wavenumbers and the spatial profiles of the most unstable perturbations. Instabilities of different nature are visualized by the streamlines of the neutrally stable perturbed flows, consisting of the critical perturbation superimposed on the base flow. The present analysis confirms the existence of two stable stratified flow configurations in a region of low flow rates in the countercurrent liquid-liquid flows. These configurations become unstable with respect to the shear mode of instability. It was revealed that in slightly upward inclined flows the lower and middle solutions for the holdup are stable in the part of the triple solution region, while the upper solution is always unstable. In the case of downward flows, in the triple solution region, none of the solutions are stable with respect to the short-wave perturbations. These flows are stable only in the single solution region at low flow rates of the heavy phase, and the long-wave perturbations are the most unstable ones.

  11. Stability of stratified two-phase flows in horizontal channels

    CERN Document Server

    Barmak, Ilya; Ullmann, Amos; Brauner, Neima; Vitoshkin, Helen

    2016-01-01

    Linear stability of stratified two-phase flows in horizontal channels to arbitrary wavenumber disturbances is studied. The problem is reduced to Orr-Sommerfeld equations for the stream function disturbances, defined in each sublayer and coupled via boundary conditions that account also for possible interface deformation and capillary forces. Applying the Chebyshev collocation method, the equations and interface boundary conditions are reduced to the generalized eigenvalue problems solved by standard means of numerical linear algebra for the entire spectrum of eigenvalues and the associated eigenvectors. Some additional conclusions concerning the instability nature are derived from the most unstable perturbation patterns. The results are summarized in the form of stability maps showing the operational conditions at which a stratified-smooth flow pattern is stable. It is found that for gas-liquid and liquid-liquid systems the stratified flow with smooth interface is stable only in confined zone of relatively lo...

  12. Enhanced stability of hillslopes and channel beds to mass failure

    Science.gov (United States)

    Prancevic, Jeff; Lamb, Michael; Palucis, Marisa; Venditti, Jeremy

    2016-04-01

    The stability of inclined, unconsolidated sediments subjected to groundwater flow on hillslopes and steep channel beds is important for both landscape evolution and natural hazards. Force-balance models have been used for seven decades to predict the stability of slopes, but they generally underpredict the degree of saturation required to destabilize the sediment. Researchers often appeal to heightened stabilizing forces from root and mineral cohesion, and friction acting on the margins of the failure to explain this underprediction. Surprisingly, infinite-slope stability models in their simplest form have never been tested under controlled laboratory conditions. To address this gap in data, we perform a set of controlled laboratory experiments with slope-parallel seepage in the simplest possible configuration. We performed 47 experiments in a 5 m laboratory flume with 4 grain sizes (D50 = 0.7, 2, 5, and 15 mm) and a wide range in bed angles (20° to 43°), spanning both Darcian and turbulent subsurface flow regimes. Our experiments show that granular slopes were more stable than predicted by simple force balance models in experiments that lack root or mineral cohesion. Despite the smooth plastic walls and the long aspect ratio of our flume, we calculate wall and toe friction to be important. Including these additional resistance terms in the model reduces the model misfit with our experimental results. However, there is considerable remaining misfit (up to 50% underestimation of the saturation level required for failure). We investigate two explanations of this heightened stability: 1) standard frictional resistance terms are underestimated, and 2) seepage stresses are overestimated. Both explanations require that we modify the models used to predict slope stability.

  13. Linear Stability Analysis of Compressible Channel Flow with Porous Walls

    CERN Document Server

    Rahbari, Iman

    2015-01-01

    We have investigated the effects of permeable walls, modeled by linear acoustic impedance with zero reactance, on compressible channel flow via linear stability analysis (LSA). Base flow profiles are taken from impermeable isothermal-wall laminar and turbulent channel flow simulations at bulk Reynolds number, $Re_b$= 6900 and Mach numbers, $M_b$ = 0.2, 0.5, 0.85. For a sufficiently high value of permeability, two dominant modes are excited: a bulk pressure mode, causing symmetric expulsion and suction of mass from the porous walls (Mode 0); a standing-wave-like mode, with a pressure node at the centerline (Mode 1). In the case of turbulent mean flow profiles, both modes generate additional Reynolds shear stresses augmenting the (base) turbulent ones, but concentrated in the viscous sublayer region; the trajectories of the two modes in the complex phase velocity space follow each other very closely for values of wall permeability spanning two orders of magnitude, suggesting their coexistence. The transition fr...

  14. Stability of stratified two-phase flows in horizontal channels

    Science.gov (United States)

    Barmak, I.; Gelfgat, A.; Vitoshkin, H.; Ullmann, A.; Brauner, N.

    2016-04-01

    Linear stability of stratified two-phase flows in horizontal channels to arbitrary wavenumber disturbances is studied. The problem is reduced to Orr-Sommerfeld equations for the stream function disturbances, defined in each sublayer and coupled via boundary conditions that account also for possible interface deformation and capillary forces. Applying the Chebyshev collocation method, the equations and interface boundary conditions are reduced to the generalized eigenvalue problems solved by standard means of numerical linear algebra for the entire spectrum of eigenvalues and the associated eigenvectors. Some additional conclusions concerning the instability nature are derived from the most unstable perturbation patterns. The results are summarized in the form of stability maps showing the operational conditions at which a stratified-smooth flow pattern is stable. It is found that for gas-liquid and liquid-liquid systems, the stratified flow with a smooth interface is stable only in confined zone of relatively low flow rates, which is in agreement with experiments, but is not predicted by long-wave analysis. Depending on the flow conditions, the critical perturbations can originate mainly at the interface (so-called "interfacial modes of instability") or in the bulk of one of the phases (i.e., "shear modes"). The present analysis revealed that there is no definite correlation between the type of instability and the perturbation wavelength.

  15. Selection an Optimal Control Channel for STATCOM-Based Stabilizers to Damp Inter-Area Oscillation

    Directory of Open Access Journals (Sweden)

    A. Samanfar

    2014-01-01

    Full Text Available In static synchronous compensator (STATCOM a controllable AC voltage is generated by a voltage-source converter. There are two control channels for controlling of magnitude and phase of the voltage. When these devices are used for damping inter-are oscillations in multi-machine power systems, a damping stabilizer can be applied for both channels. In this paper, a method by quadratic mathematical programming has been presented to design of the damping stabilizer. By this method, the effect of the stabilizer in both control channels of the STATCOM on damping of inter-area oscillations has been assessed. Obtained results on a 2-area 4-machine power system shows that a STATCOM-based stabilizer in the phase control channel is more effective for damping inter-area oscillations than that of the magnitude control channel.

  16. Channel stability downstream from a dam assessed using aerial photographs and stream-gage information

    Science.gov (United States)

    Juracek, K.E.

    2000-01-01

    The stability of the Neosho River channel downstream from John Redmond Dam, in southeast Kansas, was investigated using multiple-date aerial photographs and stream-gage information. Bankfull channel width was used as the primary indicator variable to assess pre- and post-dam channel change. Five six-mile river reaches and four stream gages were used in the analysis. Results indicated that, aside from some localized channel widening, the overall channel change has been minor with little post-dam change in bankfull channel width. The lack of a pronounced postdam channel change may be attributed to a substantial reduction in the magnitude of the post-dam annual peak discharges in combination with the resistance to erosion of the bed and bank materials. Also, the channel may have been overwidened by a series of large floods that predated construction of the dam, including one with an estimated 500-year recurrence interval.

  17. Harmonic analysis of the stability of reverse routing in channels

    Directory of Open Access Journals (Sweden)

    2007-01-01

    Full Text Available Normal downstream routing of a flood flow is a highly stable process for Froude numbers less than 1 and hence the results are reliable. In contrast, reverse routing in an upstream direction, which may be required for flow control, is potentially unstable. This paper reports the results of a study of the practical limits on channel lengths for reverse routing. Harmonic analysis is applied to the full non-linear solution of the St. Venant equations for three different wave patterns and two different wave periods, for a particular channel with a Froude number of 0.5. Reverse routing can be done for prismatic channels longer than 100 km. For long periods (>10 hours the shape of the upstream hydrograph is recovered well. However, when the wave period is short (<1 hour, the high frequency components of the upstream hydrograph and, thus, its shape, are not recovered. These limits are influenced by the channel morphology and shape of the wave. Further work is needed to determine how these factors interact.

  18. Stability analysis of parallel-channel systems with forced flows under supercritical pressure

    International Nuclear Information System (INIS)

    Highlights: → A frequency-domain model for supercritical flow stability analysis was developed. → The marginal stability boundaries for parallel-channel system were constructed. → The sensitivities of several parameters were studied for system stability boundary. → A time-domain model was developed and applied to nonlinear stability analysis. - Abstract: The flow in the core of supercritical water reactors (SCWRs) experiences drastic change in its thermodynamic properties and transport properties near the pseudo-critical temperature, thus the core flow may be susceptible to density wave oscillation instability, which is a challenge to the system safety and must be studied carefully. This paper studies the dynamic stability characteristics of the fast-spectrum zone of a newly designed mixed-spectrum SCWR (SCWR-M), which is characterized as a parallel-channel system. A frequency-domain model has been developed for linear stability analysis, and marginal stability boundaries under several conditions for the parallel-channel system are generated, which indicate that the system normal operational condition is in the stable region. The stability of parallel-channel systems is dominated by the hottest channel. The higher the power density of the hottest channel is, the less stable the system will be. Increasing mass flow is beneficial for the system stability. Systems with uniformly axial power distribution are less stable than those with cosine-shaped or stair-shaped axial power distributions. In the time-domain, a single-phase one-dimensional model has been developed for non-linear analysis, and several perturbation transients are calculated. The results of analysis show a good agreement with that of the frequency-domain analyses, and the existence of transitional stable region has been verified.

  19. Stability analysis of a heated channel cooled by supercritical water

    International Nuclear Information System (INIS)

    A simple model to study thermal-hydraulic stability of a heated cannel under supercritical conditions is presented. Single cannel stability analysis for the SCWR (Supercritical Water Cooled Reactor) design was performed. The drastic change of fluid density in the reactor core of a SCWR may induce DWO (Density Wave Oscillations) similar to those observed in BWRs. Due to the similarities between subcritical and supercritical systems we may treat the supercritical fluid as a pseudo two-phase system. Thus, we may extend the modeling approach often used for boiling flow stability analysis to supercritical pressure operation conditions. The model developed in this work take into account three regions: a heavy fluid region, similar to an incompressible liquid; a zone where a heavy fluid and a light fluid coexist, similar to two-phase mixture; and a light fluid region which behaves like superheated steam. It was used the homogeneous equilibrium model (HEM) for the pseudo boiling zone, and the ideal gas model for the pseudo superheated steam zone. System stability maps were obtained using linear stability analysis in the frequency domain. Two possible instability mechanisms are observed: DWO and excursive Ledinegg instabilities. Also, a sensitivity analysis showed that frictions in pseudo superheated steam zone, together with acceleration effect, are the most destabilizing effects. On the other hand, frictions in pseudo liquid zone are the most important stabilizing effect.

  20. Multi-channel High Precision Measure System for DC Current Stability of Power Supply

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The DC current stability is an important parameter of the HIRFL power supplies.With the requirement of HIRFL power supplies reconstruction,the multi-channel high precision measurement system for DC current stability of power supply has been developed.The measurement of DC current stability has strict requirement in hardware design and software development,it requhes that the measure system can exelude all sorts of interfere

  1. A theoretical analysis of river bars stability under changing channel width

    Science.gov (United States)

    Zen, S.; Zolezzi, G.; Tubino, M.

    2014-04-01

    In this paper we propose a new theoretical model to investigate the influence of temporal changes in channel width on river bar stability. This is achieved by performing a nonlinear stability analysis, which includes temporal width variations as a small-amplitude perturbation of the basic flow. In order to quantify width variability, channel width is related with the instantaneous discharge using existing empirical formulae proposed for channels with cohesionless banks. Therefore, width can vary (increase and/or decrease) either because it adapts to the temporally varying discharge or, if discharge is constant, through a relaxation relation describing widening of an initially overnarrow channel towards the equilibrium width. Unsteadiness related with changes in channel width is found to directly affect the instantaneous bar growth rate, depending on the conditions under which the widening process occurs. The governing mathematical system is solved by means of a two-parameters (ɛ, δ) perturbation expansion, where ɛ is related to bar amplitude and δ to the temporal width variability. In general width unsteadiness is predicted to play a destabilizing role on free bar stability, namely during the peak stage of a flood event in a laterally unconfined channel and invariably for overnarrow channels fed with steady discharge. In this latter case, width unsteadiness tends to shorten the most unstable bar wavelength compared to the case with constant width, in qualitative agreement with existing experimental observations.

  2. Anytime reliable codes for stabilizing plants over erasure channels

    OpenAIRE

    Sukhavasi, Ravi Teja; Hassibi, Babak

    2011-01-01

    The problem of stabilizing an unstable plant over a noisy communication link is an increasingly important one that arises in problems of distributed control and networked control systems. Although the work of Schulman and Sahai over the past two decades, and their development of the notions of "tree codes" and "anytime capacity", provides the theoretical framework for studying such problems, there has been scant practical progress in this area because explicit constructions of tree codes with...

  3. Stability and Hydrocarbon/Fluorocarbon Sorption of a Metal-Organic Framework with Fluorinated Channels

    Directory of Open Access Journals (Sweden)

    Jijiang Xie

    2016-04-01

    Full Text Available The stabilities and hydrocarbon/fluorocarbon sorption properties of a zeolite-like metal-organic framework (MOF Zn(hfipbb with fluorinated channels has been studied. By the combination of thermogravimetric analysis (TGA and powder X-ray diffraction (PXRD measurements, we confirm that Zn(hfipbb has exceptionally high hydrothermal and thermal stabilities. The adsorption behaviors of water and methanol by Zn(hfipbb indicate that it is highly hydrophobic but with high adsorption of alcohols. Hexane and perfluorohexane adsorption measurements show that the fluorinated channels in Zn(hfipbb have high affinity with hydrocarbon and fluorocarbon. The high fluorophilic nature of the channels and the high stability of the compound suggest its potential utility in practical separation applications.

  4. The role of sodium channels in the mechanism of action of antidepressants and mood stabilizers.

    Science.gov (United States)

    Bourin, Michel; Chenu, Franck; Hascoët, Martine

    2009-11-01

    Antidepressant drugs modify in different ways the activity of neurons, by increasing monoamines levels and by modulating ion channels. Sodium channels are molecular targets for antiepileptic drugs, which can also be mood stabilizers (i.e. lamotrigine, topiramate, phenytoin, carbamazepine, valproic acid). After a short overview on the sodium channels and the interaction with antidepressants and mood stabilizers, a comparison of the activity of both antidepressants and mood stabilizers with the addition of veratrine (sodium channel opener) on the forced swimming test (FST) in mice was presented. By comparing the antidepressant-like effect of the antidepressants (paroxetine, imipramine and desipramine) with the one of anticonvulsants (lamotrigine, phenytoin and topiramate) on the FST, it seems that the mechanism of action of anticonvulsants and antidepressants are different, because veratrine limits the activity of anticonvulsants but not of antidepressants. The anticonvulsants topiramate and phenytoin reduce the immobility time in the FST in a range of time similar to those induced by antidepressants, suggesting that the FST could be sensitive to both drugs. The magnitude of antidepressant-like effect of the lamotrigine (acting through an increase in monoaminergic neurotransmission and a blockade of sodium channels) in the FST is greater than what is obtained after administration of the other drugs, suggesting that this dual activity could be used as an augmentation strategy. Authors conclude that the development of new drugs acting on sodium channels could potentially be of interest as antidepressants, but also as augmentation strategies for classical antidepressants.

  5. Stability and Hydrocarbon/Fluorocarbon Sorption of a Metal-Organic Framework with Fluorinated Channels

    OpenAIRE

    Jijiang Xie; Fuxing Sun; Chunrui Wang; Qikun Pan

    2016-01-01

    The stabilities and hydrocarbon/fluorocarbon sorption properties of a zeolite-like metal-organic framework (MOF) Zn(hfipbb) with fluorinated channels has been studied. By the combination of thermogravimetric analysis (TGA) and powder X-ray diffraction (PXRD) measurements, we confirm that Zn(hfipbb) has exceptionally high hydrothermal and thermal stabilities. The adsorption behaviors of water and methanol by Zn(hfipbb) indicate that it is highly hydrophobic but with high adsorption of alcohols...

  6. Upper Bounds on the Rate of Low Density Stabilizer Codes for the Quantum Erasure Channel

    CERN Document Server

    Delfosse, Nicolas

    2012-01-01

    Using combinatorial arguments, we determine an upper bound on achievable rates of stabilizer codes used over the quantum erasure channel. This allows us to recover the no-cloning bound on the capacity of the quantum erasure channel, R is below 1-2p, for stabilizer codes: we also derive an improved upper bound of the form : R is below 1-2p-D(p) with a function D(p) that stays positive for 0 < p < 1/2 and for any family of stabilizer codes whose generators have weights bounded from above by a constant - low density stabilizer codes. We obtain an application to percolation theory for a family of self-dual tilings of the hyperbolic plane. We associate a family of low density stabilizer codes with appropriate finite quotients of these tilings. We then relate the probability of percolation to the probability of a decoding error for these codes on the quantum erasure channel. The application of our upper bound on achievable rates of low density stabilizer codes gives rise to an upper bound on the critical prob...

  7. Stability characteristics of hyper-concentration flow in open channel

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The flow instability is related to many engineering problems and belongs to a wide-ranging research field. When the problem on the transition from the laminar to the turbulence caused by the instability of the laminar is studied,the "neutral line" and the critical Reynolds number are always taken as the criterion to judge whether a certain kind of flow is stable,whose corresponding flow medium is the clear water,that is,the single-phase Newtonian fluid. And it is not studied in the traditional in-stability theory that the hyper-concentration flow widely exists in rivers. This shortage can be covered by this research. Study shows that the instability of non-Newtonian fluid such as hyper-concentration fluid,compared with Newtonian fluid such as clear water,is influenced by not only Reynolds number,the ratio of the inertia force and the viscous force,but also many other factors such as the sediment concentration,the concentration distribution,the grain size,the volu-metric weight of the sediment and so on,which make the mechanical principle even more complex. So the results of the research can supply the scientific basis for the explanations of "slurrying river",the turbulence intensity of the flow carrying sediment and the variance of the turbulence structure.

  8. Stability and Drag Reduction in Transient Channel Flow of Fibre Suspension

    Institute of Scientific and Technical Information of China (English)

    游振江; 林建忠; 邵雪明; 张卫峰

    2004-01-01

    Drag reduction features in the transition regime of channel flow with fibre suspension were analyzed in terms of the linear stability theory. The modified stability equation was obtained based on the slender-body theory and natural closure approximation. Results of the stability analysis show attenuating effects of fibre additives to the flow instability. For the cases leading to transition, drag reduction rate increases with the characteristic parameter H of fibres. The mechanism of drag reduction by fibres is revealed through the variation of velocity profile and the decrease of wall shear stress. The theoretical results are qualitatively consistent with some typical experiments.

  9. Study of Wave and Tide Influence on Slope Stability of the Navigation Channel of Tianjin Port

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The Tianjin Port is the largest man-made port in China. Since the navigation channel of the Tianjin Port is constructed by dredging, a very important problem, as many people concerned, is the submarine slope stability. As the environment on land is different from that in submarine, it is necessary to evaluate the influence of the environmental loading, such as wave and tide, on the stability of navigation channel slope. In the present study, based on the observed results, the characteristics of the navigation channel slope are summarized, and the causes of creating the special slope shape are analyzed. The roles of waves and tides are evaluated, and failure mechanics are discussed to helq us predict what will happen in the future.

  10. Stability and quench of dual cooling channel cable-in-conduct superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Blau, Bertrand [Ecole Polytechnique Federale de Lausanne, Centre de Recherches en Physique des Plasmas (CRPP), CH-1015 Lausanne (Switzerland)

    1999-11-01

    Presently, the most ambitious experimental project towards controlled thermonuclear fusion is the International Thermonuclear Experimental Reactor ITER. All coils of its magnet system will be superconducting since for magnetic fields in the range between 6 - 13 T high current densities are required. During recent years, in particular for fusion applications, a special configuration of superconductor was favoured: the so-called Cable-In-Conduit Conductor (CICC). The CICCs for ITER consist of a superconducting cable made of a large number of superconducting wires (NbTi or Nb{sub 3}Sn) twisted around a central cooling channel, which are tightly jacketed in a metal conduit, providing the desired mechanical stiffness of the conductor against magnetic forces. Pressurized supercritical helium is pumped through the cable interstices and the central channel. The direct contact between the coolant and the cable provides good thermal stability of the conductor against sudden energy inputs. These disturbances can lead to a transition into the normal state (quench) if the released energy is sufficiently high, so that the temperature of the superconductor exceeds locally its critical temperature and if the energy cannot be absorbed efficiently by the surrounding helium. Stability of superconductors against quenches is one of the most important issues in applied superconductivity. The recovery capabilities of a CICC after thermal disturbances are governed by the heat transfer rate from the strands to the helium. The heat transfer is greatly affected by the flow velocity of the coolant. It has been shown theoretically that a temporal thermal disturbance in a CICC can induce an additional strong helium flow, which enhances the heat transfer rate and, hence, the stability. This self-stabilizing effect is believed to play an important role for the recovery capabilities of a CICC. The scope of this thesis is the experimental assessment of the quench and stability behaviour of dual

  11. Linear stability of a fuel channel uniformly heated considering retrofeeding by vacuum. Theoretical study

    International Nuclear Information System (INIS)

    The Technology, Regulation and Services Management of the National Commission of Nuclear Safety and Safeguards in coordinated form with the IPH Department of the Metropolitan Autonomous-Iztapalapa University, developed the present project to study the linear stability in a fuel channel uniformly heated with effects of retrofeeding by vacuums. In this study the methodology used in the analysis of linear stability of the nuclear reactor unit 1 at Laguna Verde power plant is described which represented by an average channel uniformly heated. The conceptual model consists of two cells which represent the two regions in which is divided the channel according to the cooling is in one and two phases, considering the boiling length dependent in the time. It is used the homogeneous flux models for describing the thermohydraulic behavior of the cooling in the two phases region. The neutron processes with the punctual model of the neutron kinetics with a group of retarded neutrons precursors are described. It is studied the behavior of the system in the frequency domain with the transfer functions obtained and it is characterized in four operation states corresponding to the four corners of the low stability zone in the map power-flow Laguna Verde power plant. For these operation states the characteristic frequency is determined and the corresponding Nyquist diagrams are obtained. The results show that the system stability depends on the power-flow relation and that the operations which implicate a reduction of this relation improve the stability of the system (reducing the power introducing control bars with constant cooling flow or increase cooling flow with bars pattern established). The obtained results with effects of retrofeeding by vacuums show that the value of the characteristic frequency is modified very little with respect to the model without retrofeeding, therefore the thermohydraulic processes seem to determine the response of the stability of the system

  12. Response matrix method and its application to SCWR single channel stability analysis

    International Nuclear Information System (INIS)

    To simulate the reactor system dynamic features during density wave oscillations (DWO), both the non-linear method and the linear method can be used. Although some transient information is lost through model linearization, the high computational efficiency and relatively accurate results make the linear analysis methodology attractive, especially for prediction of the onset of instability. In the linear stability analysis, the system models are simplified through linearization of the complex non-linear differential equations, and then, the linear differential equations are generally solved in the frequency domain through Laplace transformation. In this paper, a system response matrix method was introduced by directly solving the differential equations in the time domain. By using a system response matrix method, the complicated transfer function derivation, which must be done in the frequency domain method, can be avoided. Using the response matrix method, a model was developed and applied to the single channel or parallel channel type instability analyses of the typical proposed SCWR design. The sensitivity of the decay ratio (DR) to the axial mesh size was analyzed and it was found that the DR is not sensitive to mesh size once sufficient number of axial nodes is applied. To demonstrate the effects of the inlet orificing to the stability feature for the supercritical condition, the sensitivity of the stability to inlet orifice coefficient was conducted for hot channel. It is clearly shown that a higher inlet orifice coefficient will make the system more stable. The susceptibility of stability to operating parameters such as mass flow rate, power and system pressure was also performed. And the measure to improve the SCWR stability sensitivity to operating parameters was investigated. It was found that the SCWR stability sensitivity feature can be improved by carefully managing the inlet orifices and choosing proper operating parameters. (author)

  13. The Phase Stability Measure Method for Transmitting and Receiving Channels of Space-borne SAR

    Directory of Open Access Journals (Sweden)

    Xie Dong-dong

    2012-03-01

    Full Text Available Accurate phase stability measurement of Transmitting and Receiving channels in space-borne SAR (Synthetic Aperture Radar system is important to evaluate imaging quality. Based on fewer instruments, matched filtering and interpolation algorithm, two kinds of measure methods which makes the measurement value more accurate are presented and compared in this paper. The test result of one space-borne SAR prototyping system indicates that the methods are feasible and effective.

  14. Assessment of flow stability boundaries in a heated channel with different fluids at supercritical pressure

    Energy Technology Data Exchange (ETDEWEB)

    Ambrosini, Walter, E-mail: walter.ambrosini@ing.unipi.it [Dipartimento di Ingegneria Meccanica Nucleare e della Produzione, Universita di Pisa, Via Diotisalvi 2, 56126 Pisa (Italy)

    2011-02-15

    This paper presents results on the stability of a simple heated channel containing fluids at supercritical pressure with an external imposed pressure drop. Basing on a recent work that discussed stability characteristics in a fluid-to-fluid comparison perspective, additional data are presented in order to discuss relevant parametric effects, also including a more accurate fluid-to-fluid comparison. Three different analysis tools, including a system code and in-house linear and transient analysis programs, were adopted to evaluate stability thresholds at different channel throttling conditions and orientations; four different supercritical fluids were considered. The diversity of the adopted tools and the good level of agreement observed in the comparison of their results provide adequate confidence on the general reliability of the obtained information. Among the addressed phenomena, both Ledinegg and density-wave oscillations are considered, pointing out a fundamental continuity between the two phenomena that occur in adjoining regions of the parameter space. Numerical effects are also highlighted, quantifying the impact of truncation error occurring in the use of system codes in the analysis of flow instabilities. The results obtained by different fluids provide further support to the conclusion that, when an appropriate dimensionless formalism is used, the differences obtained in the stability behaviour at imposed heat flux are relatively small for a number of fluids of interest for experimental analyses.

  15. Robust Stability of Scaled-Four-Channel Teleoperation with Internet Time-Varying Delays

    Directory of Open Access Journals (Sweden)

    Emma Delgado

    2016-04-01

    Full Text Available We describe the application of a generic stability framework for a teleoperation system under time-varying delay conditions, as addressed in a previous work, to a scaled-four-channel (γ-4C control scheme. Described is how varying delays are dealt with by means of dynamic encapsulation, giving rise to mu-test conditions for robust stability and offering an appealing frequency technique to deal with the stability robustness of the architecture. We discuss ideal transparency problems and we adapt classical solutions so that controllers are proper, without single or double differentiators, and thus avoid the negative effects of noise. The control scheme was fine-tuned and tested for complete stability to zero of the whole state, while seeking a practical solution to the trade-off between stability and transparency in the Internet-based teleoperation. These ideas were tested on an Internet-based application with two Omni devices at remote laboratory locations via simulations and real remote experiments that achieved robust stability, while performing well in terms of position synchronization and force transparency.

  16. Linear stability analysis of flow instabilities with a nodalized reduced order model in heated channel

    International Nuclear Information System (INIS)

    The prime objective of the presented work is to develop a Nodalized Reduced Order Model (NROM) to carry linear stability analysis of flow instabilities in a two-phase flow system. The model is developed by dividing the single phase and two-phase region of a uniformly heated channel into N number of nodes followed by time dependent spatial linear approximations for single phase enthalpy and two-phase quality between the consecutive nodes. Moving boundary scheme has been adopted in the model, where all the node boundaries vary with time due to the variation of boiling boundary inside the heated channel. Using a state space approach, the instability thresholds are delineated by stability maps plotted in parameter planes of phase change number (Npch) and subcooling number (Nsub). The prime feature of the present model is that, though the model equations are simpler due to presence of linear-linear approximations for single phase enthalpy and two-phase quality, yet the results are in good agreement with the existing models (Karve [33]; Dokhane [34]) where the model equations run for several pages and experimental data (Solberg [41]). Unlike the existing ROMs, different two-phase friction factor multiplier correlations have been incorporated in the model. The applicability of various two-phase friction factor multipliers and their effects on stability behaviour have been depicted by carrying a comparative study. It is also observed that the Friedel model for friction factor calculations produces the most accurate results with respect to the available experimental data. (authors)

  17. Transmission Control of Two-User Slotted ALOHA Over Gilbert-Elliott Channel: Stability and Delay Analysis

    CERN Document Server

    Fanous, Anthony

    2011-01-01

    In this paper, we consider the problem of calculating the stability region and average delay of two user slotted ALOHA over a Gilbert-Elliott channel, where users have channel state information and adapt their transmission probabilities according to the channel state. Each channel has two states, namely, the 'good' and 'bad' states. In the 'bad' state, the channel is assumed to be in deep fade and the transmission fails with probability one, while in the 'good' state, there is some positive success probability. We calculate the Stability region with and without Multipacket Reception capability as well as the average delay without MPR. Our results show that the stability region of the controlled S-ALOHA is always a superset of the stability region of uncontrolled S-ALOHA. Moreover, if the channel tends to be in the 'bad' state for long proportion of time, then the stability region is a convex Polyhedron strictly containing the TDMA stability region and the optimal transmission strategy is to transmit with prob...

  18. Stability and quench of dual cooling channel cable-in-conduct superconductors

    International Nuclear Information System (INIS)

    Presently, the most ambitious experimental project towards controlled thermonuclear fusion is the International Thermonuclear Experimental Reactor ITER. All coils of its magnet system will be superconducting since for magnetic fields in the range between 6 - 13 T high current densities are required. During recent years, in particular for fusion applications, a special configuration of superconductor was favoured: the so-called Cable-In-Conduit Conductor (CICC). The CICCs for ITER consist of a superconducting cable made of a large number of superconducting wires (NbTi or Nb3Sn) twisted around a central cooling channel, which are tightly jacketed in a metal conduit, providing the desired mechanical stiffness of the conductor against magnetic forces. Pressurized supercritical helium is pumped through the cable interstices and the central channel. The direct contact between the coolant and the cable provides good thermal stability of the conductor against sudden energy inputs. These disturbances can lead to a transition into the normal state (quench) if the released energy is sufficiently high, so that the temperature of the superconductor exceeds locally its critical temperature and if the energy cannot be absorbed efficiently by the surrounding helium. Stability of superconductors against quenches is one of the most important issues in applied superconductivity. The recovery capabilities of a CICC after thermal disturbances are governed by the heat transfer rate from the strands to the helium. The heat transfer is greatly affected by the flow velocity of the coolant. It has been shown theoretically that a temporal thermal disturbance in a CICC can induce an additional strong helium flow, which enhances the heat transfer rate and, hence, the stability. This self-stabilizing effect is believed to play an important role for the recovery capabilities of a CICC. The scope of this thesis is the experimental assessment of the quench and stability behaviour of dual cooling

  19. Machine-Learning Based Channel Quality and Stability Estimation for Stream-Based Multichannel Wireless Sensor Networks.

    Science.gov (United States)

    Rehan, Waqas; Fischer, Stefan; Rehan, Maaz

    2016-01-01

    Wireless sensor networks (WSNs) have become more and more diversified and are today able to also support high data rate applications, such as multimedia. In this case, per-packet channel handshaking/switching may result in inducing additional overheads, such as energy consumption, delays and, therefore, data loss. One of the solutions is to perform stream-based channel allocation where channel handshaking is performed once before transmitting the whole data stream. Deciding stream-based channel allocation is more critical in case of multichannel WSNs where channels of different quality/stability are available and the wish for high performance requires sensor nodes to switch to the best among the available channels. In this work, we will focus on devising mechanisms that perform channel quality/stability estimation in order to improve the accommodation of stream-based communication in multichannel wireless sensor networks. For performing channel quality assessment, we have formulated a composite metric, which we call channel rank measurement (CRM), that can demarcate channels into good, intermediate and bad quality on the basis of the standard deviation of the received signal strength indicator (RSSI) and the average of the link quality indicator (LQI) of the received packets. CRM is then used to generate a data set for training a supervised machine learning-based algorithm (which we call Normal Equation based Channel quality prediction (NEC) algorithm) in such a way that it may perform instantaneous channel rank estimation of any channel. Subsequently, two robust extensions of the NEC algorithm are proposed (which we call Normal Equation based Weighted Moving Average Channel quality prediction (NEWMAC) algorithm and Normal Equation based Aggregate Maturity Criteria with Beta Tracking based Channel weight prediction (NEAMCBTC) algorithm), that can perform channel quality estimation on the basis of both current and past values of channel rank estimation. In the end

  20. Machine-Learning Based Channel Quality and Stability Estimation for Stream-Based Multichannel Wireless Sensor Networks

    Science.gov (United States)

    Rehan, Waqas; Fischer, Stefan; Rehan, Maaz

    2016-01-01

    Wireless sensor networks (WSNs) have become more and more diversified and are today able to also support high data rate applications, such as multimedia. In this case, per-packet channel handshaking/switching may result in inducing additional overheads, such as energy consumption, delays and, therefore, data loss. One of the solutions is to perform stream-based channel allocation where channel handshaking is performed once before transmitting the whole data stream. Deciding stream-based channel allocation is more critical in case of multichannel WSNs where channels of different quality/stability are available and the wish for high performance requires sensor nodes to switch to the best among the available channels. In this work, we will focus on devising mechanisms that perform channel quality/stability estimation in order to improve the accommodation of stream-based communication in multichannel wireless sensor networks. For performing channel quality assessment, we have formulated a composite metric, which we call channel rank measurement (CRM), that can demarcate channels into good, intermediate and bad quality on the basis of the standard deviation of the received signal strength indicator (RSSI) and the average of the link quality indicator (LQI) of the received packets. CRM is then used to generate a data set for training a supervised machine learning-based algorithm (which we call Normal Equation based Channel quality prediction (NEC) algorithm) in such a way that it may perform instantaneous channel rank estimation of any channel. Subsequently, two robust extensions of the NEC algorithm are proposed (which we call Normal Equation based Weighted Moving Average Channel quality prediction (NEWMAC) algorithm and Normal Equation based Aggregate Maturity Criteria with Beta Tracking based Channel weight prediction (NEAMCBTC) algorithm), that can perform channel quality estimation on the basis of both current and past values of channel rank estimation. In the end

  1. High-stability transparent amorphous oxide TFT with a silicon-doped back-channel layer

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Hyoung-Rae; Park, Jea-Gun [Hanyang University, Seoul (Korea, Republic of)

    2014-10-15

    We significantly reduced various electrical instabilities of amorphous indium gallium zinc oxide thin-film transistors (TFTs) by using the co-deposition of silicon on an a-IGZO back channel. This process showed improved stability of the threshold voltage (V{sub th}) under high temperature and humidity and negative gate-bias illumination stress (NBIS) without any reduction of IDS. The enhanced stability was achieved with silicon, which has higher metal-oxide bonding strengths than gallium does. Additionally, SiO{sub x} distributed on the a-IGZO surface reduced the adsorption and the desorption of H{sub 2}O and O{sub 2}. This process is applicable to the TFT manufacturing process with a variable sputtering target.

  2. Stability characteristics of the open channel flow above the asymmetrical irregular sand ripples

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Sandy bed cannot keep its original smoothness as the flows pass. With the increase of the flow intensity, the bed forms will appear as sand ripples and dune in turn. Among these morphologies, the sand ripple scale is the smallest, which is generally symmetrical when it just appears, but as time goes on, the asymmetrical form gradually develops. Just because of this sand ripples asymmetry, it manifests the influence of the flow on the bed morphology and also the impact on the laminar flow dynamical process, especially the stability characteristics. The stability features of laminar flow on open channels with the asymmetrical sand ripples are discussed, and also the results on the symmetrical sand ripples are compared in detail.

  3. Weakly nonlinear stability analysis of non-isothermal Poiseuille flow in a vertical channel

    Science.gov (United States)

    Khandelwal, Manish K.; Bera, P.

    2015-06-01

    A weakly nonlinear stability theory in terms of Landau equation is developed to analyze the nonlinear saturation of stably stratified non-isothermal Poiseuille flow in a vertical channel. The results are presented with respect to fluids: mercury, gases, liquids, and heavy oils. The weakly nonlinear stability results predict only the supercritical instability, in agreement with the published result [Y. C. Chen and J. N. Chung, "A direct numerical simulation of K and H-type flow transition in heated vertical channel," Comput. Fluids 32, 795-822 (2003)] based on direct numerical simulation. Apart from this, the influence of nonlinear interaction among different superimposed waves on the heat transfer rate, real part of wavespeed, and friction coefficient on the wall is also investigated. A substantial enhancement (reduction) in heat transfer rate (friction coefficient) is found for liquids and heavy oils from the basic state beyond the critical Rayleigh number. The amplitude analysis indicates that the equilibrium amplitude decreases on increasing the value of Reynolds number. However, in the case of mercury, influence of nonlinear interaction on the variation of equilibrium amplitude, heat transfer rate, wavespeed, as well as friction coefficient is complex and subtle. The analysis of the nonlinear energy spectra for the disturbance also supports the supercritical instability at and beyond the critical point. Finally, the effect of superimposed waves on the pattern of secondary flow, based on linear stability theory, is also studied. It has been found that the impact of nonlinear interaction of waves on the pattern of secondary flow for mercury is weak compared to gases, which is the consequence of negligible modification in the buoyant production of disturbance kinetic energy of the mercury.

  4. Experimental study on the stability characteristics of two-phase flows in parallel boiling channels under natural-circulation conditions

    International Nuclear Information System (INIS)

    Experimental study has been performed to study periodical-boiling instability in parallel channels, which occurs at low heat fluxes and is of concern in the start-up process of an SBWR. Three channels, made of glass tubes to facilitate visual observation, are placed in bulk water and are heated with electric heaters inserted in the channels. Two types of channels of different length are used to investigate the effect of unheated risers or chimney on periodical boiling. Relationship of bubble development and flow instability is also studied. It is found that slug bubbles are usually followed by rapid boiling, which results in high fluctuation of the flow. Refilling of the subcooled water from the top causes bubble condensation. Sometimes rapid condensation occurs and results in crack sounds. The longer channel does not necessarily have better coolability and stability characteristics; the average flow rate is actually lower and fluctuation amplitude is higher compared to those for the shorter channel

  5. Thermal stability of purified and reconstituted CFTR in a locked open channel conformation.

    Science.gov (United States)

    Aleksandrov, Luba A; Jensen, Timothy J; Cui, Liying; Kousouros, Joseph N; He, Lihua; Aleksandrov, Andrei A; Riordan, John R

    2015-12-01

    CFTR is unique among ABC transporters as the only one functioning as an ion channel and from a human health perspective because mutations in its gene cause cystic fibrosis. Although considerable advances have been made towards understanding CFTR's mechanism of action and the impact of mutations, the lack of a high-resolution 3D structure has hindered progress. The large multi-domain membrane glycoprotein is normally present at low copy number and when over expressed at high levels it aggregates strongly, limiting the production of stable mono-disperse preparations. While the reasons for the strong self-association are not fully understood, its relatively low thermal stability seems likely to be one. The major CF causing mutation, ΔF508, renders the protein very thermally unstable and therefore a great deal of attention has been paid to this property of CFTR. Multiple second site mutations of CFTR in NBD1 where F508 normally resides and small molecule binders of the domain increase the thermal stability of the mutant. These manipulations also stabilize the wild-type protein. Here we have applied ΔF508-stabilizing changes and other modifications to generate wild-type constructs that express at much higher levels in scaled-up suspension cultures of mammalian cells. After purification and reconstitution into liposomes these proteins are active in a locked-open conformation at temperatures as high as 50 °C and remain monodisperse at 4 °C in detergent or lipid for at least a week. The availability of adequate amounts of these and related stable active preparations of homogeneous CFTR will enable stalled structural and ligand binding studies to proceed.

  6. Stability of fluid flow through deformable tubes and channels: An overview

    Indian Academy of Sciences (India)

    V Shankar

    2015-05-01

    The aim of this paper is to provide a systematic overview of the study of instabilities in flow past deformable solid surfaces, with particular emphasis on internal flows through tubes and channels. The subject is certainly more than five decades old, and arguably began with Kramer’s pioneering experiments on drag reduction by compliant surfaces. This was immediately followed by the theoretical studies of Benjamin and Landhal in the early 1960s. Most earlier theoretical studies were focused on stability of external flows such as boundary layers, and used relatively simple wall models composed of spring-backed plates. There has been a resurgence in the field since the mid-1980s, and more attention was focused on internal flows through deformable tubes and channels. The wall deformation was described by both phenomenological spring-backed plate models and continuum linear viscoelastic solid models. All these studies predict several types of instabilities in flow past deformable surfaces. This paper will attempt to place the various theoretical results in perspective, and to classify the instabilities predicted by various studies. Recent studies have also emphasized the importance of using a frame-invariant constitutive model, such as the neo-Hookean model, for the solid deformation. Until recently, however, the field has been dominated by theoretical and numerical studies, with very little experimental observations to corroborate the theoretical predictions. Recent experiments in flow through deformable tubes and channels indeed show instability at Reynolds number much lower than their rigid counterparts, and the experimental observations are in qualitative agreement with some of the theoretical predictions. There have also been a few studies on the non-linear aspects of the instability using the weakly non-linear formulation to determine the nature of the bifurcation at the linear instability. A brief discussion on weakly nonlinear analyses is also provided in

  7. A study on the stability of laminar open-channel flow over a sandy rippled bed

    Institute of Scientific and Technical Information of China (English)

    BAI; Yuchuan; XU; Haijue

    2005-01-01

    The bed of a river often features some kinds of bedform, such as sand ripples, dunes, and so on. Even if the bed is smooth initially, disturbances arising from the bed or other external sources will cause the laminar flow in an open channel to become unstable as soon as the flow develops, thereby leading to the formation of sand ripples on the bed. In return, the formation of the sand ripples will modify the instability path of the laminar flow passing over them. The wavy character of the bed will induce further instability of the flow, which is essentially different from that on a smooth bed: the neutral curve will move forward and the critical Reynolds number will decrease. The flow is unstable in response to a wider range of the disturbance wave number, or the laminar flow instability can happen more easily. The propagation speed of the sand ripples also affects the flow instability, since the stability of open channel flow over a movable bed is fundamentally different from that on a rigid bed. These instability effects are discussed in detail in this paper.

  8. Linear stability analysis and direct numerical simulation of two layer channel flow

    Science.gov (United States)

    Sahu, Kirti; Govindarajan, Rama; Tripathi, Manoj

    2015-11-01

    We study the stability of two-fluid flow through a plane channel at Reynolds numbers of a hundred to a thousand. The two fluids have the same density but different viscosities. The fluids, when miscible, are separated from each other by a mixed layer of small but finite thickness, across which viscosity changes from that of one fluid to that of the other. When immiscible, the interface is sharp. Our study spans a range of Schmidt numbers, viscosity ratios and location and thickness of the mixed layer. Our two-dimensional linear stability results predict well the behaviour displayed by our three-dimensional direct numerical simulations at early times. In both linear and non-linear regimes, the miscible flow is more unstable than the corresponding immiscible one, and the miscible flow breaks spanwise symmetry more readily to go into three-dimensionality. We show that the miscible flow over our range of parameters is always significantly more unstable than the corresponding immiscible case.

  9. Linear stability analysis and direct numerical simulation of two layer channel flow

    CERN Document Server

    Sahu, Kirti Chandra

    2016-01-01

    We study the stability of two-fluid flow through a plane channel at Reynolds numbers of a hundred to a thousand in the linear and nonlinear regimes. The two fluids have the same density but different viscosities. The fluids, when miscible, are separated from each other by a mixed layer of small but finite thickness, across which viscosity changes from that of one fluid to that of the other. When immiscible, the interface is sharp. Our study spans a range of Schmidt numbers, viscosity ratios and location and thickness of the mixed layer. A region of instability distinct from that of the Tollmien-Schlichting mode is obtained at moderate Reynolds numbers. We show that the overlap of the layer of viscosity-stratification with the critical layer of the dominant disturbance provides a mechanism for this instability. At very low values of diffusivity, the miscible flow behaves exactly like the immiscible in terms of stability characteristics. High levels of miscibility make the flow more stable. At intermediate leve...

  10. Tutorial on Feedback Control of Flows, Part I: Stabilization of Fluid Flows in Channels and Pipes

    Directory of Open Access Journals (Sweden)

    Ole M. Aamo

    2002-07-01

    Full Text Available The field of flow control has picked up pace over the past decade or so, on the promise of real-time distributed control on turbulent scales being realizable in the near future. This promise is due to the micromachining technology that emerged in the 1980s and developed at an amazing speed through the 1990s. In lab experiments, so called micro-electro-mechanical systems (MEMS that incorporate the entire detection-decision-actuation process on a single chip, have been batch processed in large numbers and assembled into flexible skins for gluing onto body-fluid interfaces for drag reduction purposes. Control of fluid flows span a wide variety of specialities. In Part I of this tutorial, we focus on the problem of reducing drag in channel and pipe flows by stabilizing the parabolic equilibrium profile using boundary feedback control. The control strategics used for this problem include classical control, based on the Nyquist criteria, and various optimal control techniques (H2, H-Infinity, as well as applications of Lyapunov stability theory.

  11. Phosphatidic acid plays a special role in stabilizing and folding of the tetrameric potassium channel KcsA

    OpenAIRE

    Raja, M.M.; Spelbrink, R E J; de Kruijff, B.; Killian, J A

    2007-01-01

    In this study, we investigated how the presence of anionic lipids influenced the stability and folding properties of the potassium channel KcsA. By using a combination of gel electrophoresis, tryptophan fluorescence and acrylamide quenching experiments, we found that the presence of the anionic lipid phosphatidylglycerol (PG) in a phosphatidylcholine (PC) bilayer slightly stabilized the tetramer and protected it from trifluoroethanol- induced dissociation. Surprisingly, the presence of phosph...

  12. Global stability for the multi-channel Gel'fand-Calder\\'on inverse problem in two dimensions

    CERN Document Server

    Santacesaria, Matteo

    2011-01-01

    We prove a global logarithmic stability estimate for the multi-channel Gel'fand-Calder\\'on inverse problem on a two-dimensional bounded domain, i.e. the inverse boundary value problem for the equation $-\\Delta \\psi + v\\, \\psi = 0$ on $D$, where $v$ is a smooth matrix-valued potential defined on a bounded planar domain $D$.

  13. Electrical Conductivity, Thermal Stability, and Lattice Defect Evolution During Cyclic Channel Die Compression of OFHC Copper

    Science.gov (United States)

    Satheesh Kumar, S. S.; Raghu, T.

    2015-02-01

    Oxygen-free high-conductivity (OFHC) copper samples are severe plastically deformed by cyclic channel die compression (CCDC) technique at room temperature up to an effective plastic strain of 7.2. Effect of straining on variation in electrical conductivity, evolution of deformation stored energy, and recrystallization onset temperatures are studied. Deformation-induced lattice defects are quantified using three different methodologies including x-ray diffraction profile analysis employing Williamson-Hall technique, stored energy based method, and electrical resistivity-based techniques. Compared to other severe plastic deformation techniques, electrical conductivity degrades marginally from 100.6% to 96.6% IACS after three cycles of CCDC. Decrease in recrystallization onset and peak temperatures is noticed, whereas stored energy increases and saturates at around 0.95-1.1J/g after three cycles of CCDC. Although drop in recrystallization activation energy is observed with the increasing strain, superior thermal stability is revealed, which is attributed to CCDC process mechanics. Low activation energy observed in CCDC-processed OFHC copper is corroborated to synergistic influence of grain boundary characteristics and lattice defects distribution. Estimated defects concentration indicated continuous increase in dislocation density and vacancy with strain. Deformation-induced vacancy concentration is found to be significantly higher than equilibrium vacancy concentration ascribed to hydrostatic stress states experienced during CCDC.

  14. Dynamics of bluff-body-stabilized premixed hydrogen/air flames in a narrow channel

    KAUST Repository

    Lee, Bok Jik

    2015-06-01

    Two-dimensional direct numerical simulations were conducted for bluff-body stabilized flames of a lean hydrogen/air mixture at near-blowoff conditions in a meso-scale channel. Parametric simulations were conducted by incrementally varying the inflow velocity in the vicinity of the blowoff limit, and the corresponding flame response was monitored. The present study is a showcase of combustion DNS with embedded boundary representation, and full demonstration of the detailed visualization of the near-blowoff flame characteristics. As the inflow velocity approaches blowoff limit, the flame dynamics exhibit a complex sequence of events, such as periodic local extinction and recovery, and regrowth of the bulk flame by the flame segments attached behind the bluff-body. The total extinction is observed as the attached flames shrink down and are no longer able to regrow the bulk flames. Despite the disparity in the physical scale under study, the observed sequence of the extinction pathway shows a strong similarity with experimental observations at larger scale combustion systems. © 2015 The Combustion Institute.

  15. Mutations Causing Slow-Channel Myasthenia Reveal That a Valine Ring in the Channel Pore of Muscle AChR is Optimized for Stabilizing Channel Gating.

    Science.gov (United States)

    Shen, Xin-Ming; Okuno, Tatsuya; Milone, Margherita; Otsuka, Kenji; Takahashi, Koji; Komaki, Hirofumi; Giles, Elizabeth; Ohno, Kinji; Engel, Andrew G

    2016-10-01

    We identify two novel mutations in acetylcholine receptor (AChR) causing a slow-channel congenital myasthenia syndrome (CMS) in three unrelated patients (Pts). Pt 1 harbors a heterozygous βV266A mutation (p.Val289Ala) in the second transmembrane domain (M2) of the AChR β subunit (CHRNB1). Pts 2 and 3 carry the same mutation at an equivalent site in the ε subunit (CHRNE), εV265A (p.Val285Ala). The mutant residues are conserved across all AChR subunits of all species and are components of a valine ring in the channel pore, which is positioned four residues above the leucine ring. Both βV266A and εV265A reduce the amino acid size and lengthen the channel opening bursts by fourfold by enhancing gating efficiency by approximately 30-fold. Substitution of alanine for valine at the corresponding position in the δ and α subunit prolongs the burst duration four- and eightfold, respectively. Replacing valine at ε codon 265 either by a still smaller glycine or by a larger leucine also lengthens the burst duration. Our analysis reveals that each valine in the valine ring contributes to channel kinetics equally, and the valine ring has been optimized in the course of evolution to govern channel gating.

  16. Establishment and application of Kuosheng BWR/6 channel flow stability map with RETRANO2/MOD5 code

    International Nuclear Information System (INIS)

    The primary objective of this paper is to determine the channel flow stability map using the RETRAN02/MOD5 code under natural circulation conditions for the Kuosheng Nuclear Power Plant (KNPP). Meanwhile, two transient loci of a KNPP recirculation pump trip (RPT) with decreasing feedwater enthalpy are also drawn on the stability map to assess whether such power oscillation phenomena as the LaSalle-2 event may occur at KNPP. To avoid numerical oscillation of flow stability in time domain analysis, several sensitivity studies are also carried out. The results indicate that both transient loci have sufficient stability margins to unstable boundaries and reveal that KNPP's operations will be stable under such RPT's with decreasing feedwater enthalpy transients. (author)

  17. Phosphatidic acid plays a special role in stabilizing and folding of the tetrameric potassium channel KcsA.

    Science.gov (United States)

    Raja, Mobeen; Spelbrink, Robin E J; de Kruijff, Ben; Killian, J Antoinette

    2007-12-11

    In this study, we investigated how the presence of anionic lipids influenced the stability and folding properties of the potassium channel KcsA. By using a combination of gel electrophoresis, tryptophan fluorescence and acrylamide quenching experiments, we found that the presence of the anionic lipid phosphatidylglycerol (PG) in a phosphatidylcholine (PC) bilayer slightly stabilized the tetramer and protected it from trifluoroethanol-induced dissociation. Surprisingly, the presence of phosphatidic acid (PA) had a much larger effect on the stability of KcsA and this lipid, in addition, significantly influenced the folding properties of the protein. The data indicate that PA creates some specificity over PG, and that it most likely stabilizes the tetramer via both electrostatic and hydrogen bond interactions. PMID:18036565

  18. Vegetative impacts upon bedload transport capacity and channel stability for differing alluvial planforms in the Yellow River source zone

    Science.gov (United States)

    Li, Zhi Wei; Yu, Guo An; Brierley, Gary; Wang, Zhao Yin

    2016-07-01

    The influence of vegetation upon bedload transport and channel morphodynamics is examined along a channel stability gradient ranging from meandering to anabranching to anabranching-braided to fully braided planform conditions along trunk and tributary reaches of the Upper Yellow River in western China. Although the regional geology and climate are relatively consistent across the study area, there is a distinct gradient in the presence and abundance of riparian vegetation for these reaches atop the Qinghai-Tibet Plateau (elevations in the study area range from 2800 to 3400 m a.s.l.). To date, the influence of vegetative impacts upon channel planform and bedload transport capacity of alluvial reaches of the Upper Yellow River remains unclear because of a lack of hydrological and field data. In this region, the types and pattern of riparian vegetation vary with planform type as follows: trees exert the strongest influence in the anabranching reach, the meandering reach flows through meadow vegetation, the anabranching-braided reach has a grass, herb, and sparse shrub cover, and the braided reach has no riparian vegetation. A non-linear relation between vegetative cover on the valley floor and bedload transport capacity is evident, wherein bedload transport capacity is the highest for the anabranching reach, roughly followed by the anabranching-braided, braided, and meandering reaches. The relationship between the bedload transport capacity of a reach and sediment supply from upstream exerts a significant influence upon channel stability. Bedload transport capacity during the flood season (June-September) in the braided reach is much less than the rate of sediment supply, inducing bed aggradation and dynamic channel adjustments. Rates of channel adjustment are less pronounced for the anabranching-braided and anabranching reaches, while the meandering reach is relatively stable (i.e., this is a passive meandering reach).

  19. The contribution of riparian vegetation to the stability of agricultural channels banks in the Lombardy plane

    Science.gov (United States)

    Spelta, E.; Chiaradia, E. A.; Bischetti, G. B.

    2009-04-01

    limitations, we have modified the model to account for the distribution of root cohesion (cR) within the soil and the non-simultaneous root breaking: ‘N cR = k′k′′ (Trar)i i=1 where Tr is the tensile strength and ar is the Root Area Ratio (RAR) for roots belonging to diameter class i, N is the number of classes considered, k′ is the factor accounting for the decomposition of root tensile strength and k′′ is a factor accounting for the non-simultaneous breaking of roots. In the present work the modified W&W model has been adopted to estimate the root cohesion due to the riparian vegetation, and the bank stability, for six study sites belonging to two small agricultural channel of the Lombardy plane. The study sites consist of very steep banks (45-50˚ ) with the following riparian vegetation, typical of the considered landscape: Sambucus nigra, Acer campestre, Rubus spp., Populus Canadensis. Several samples of roots have been taken at each site, in order to carry out laboratory tensile strength tests and to develop the strength-diameter relationships, which are requested to estimate the tensile strength of the roots of the different size according to their species. Trenches have been excavated into the bank at each site in order to identify all the roots of different size present at each depth, and to estimate RAR distribution with depth. Estimated root cohesion values for each site have been then used into a bank stability model to evaluate the current Factor of Safety values, that have been compared with those resulting from banks without vegetation. Results show that in the selected cases, riparian vegetation is crucial in determining the stability of the banks. Neglecting the estimated values of cohesion, in fact, banks result extremely unstable, according to their soil properties and their steepness.

  20. NEAR-BLOWOFF DYNAMICS OF BLUFF-BODY-STABILIZED PREMIXED HYDROGEN/AIR FLAMES IN A NARROW CHANNEL

    KAUST Repository

    Lee, Bok Jik

    2015-06-07

    The flame stability is known to be significantly enhanced when the flame is attached to a bluff-body. The main interest of this study is on the stability of the flame in a meso-scale channel, considering applications such as combustion-based micro power generators. We investigate the dynamics of lean premixed hydrogen/air flames stabilized behind a square box in a two-dimensional meso-scale channel with high-fidelity numerical simulations. Characteristics of both non-reacting flows and reacting flows over the bluff-body are studied for a range of the mean inflow velocity. The flame stability in reacting flows is investigated by ramping up the mean inflow velocity step by step. As the inlet velocity is increased, the initially stable steady flames undergo a transition to an unsteady mode of regular asymmetric fluctuation. When the inlet velocity is further increased, the flame is eventually blown off. Between the regular fluctuation mode and blowoff limit, there exists a narrow range of the inlet velocity where the flames exhibit periodic local extinction and recovery. Approaching further to blowoff limit, the local extinction and recovery becomes highly transient and a failure of recovery leads blowoff and extinction of the flame kernel.

  1. Impacts of warm water on Antarctic ice shelf stability through basal channel formation

    Science.gov (United States)

    Alley, Karen E.; Scambos, Ted A.; Siegfried, Matthew R.; Fricker, Helen Amanda

    2016-04-01

    Antarctica's ice shelves provide resistance to the flow of grounded ice towards the ocean. If this resistance is decreased as a result of ice shelf thinning or disintegration, acceleration of grounded ice can occur, increasing rates of sea-level rise. Loss of ice shelf mass is accelerating, especially in West Antarctica, where warm seawater is reaching ocean cavities beneath ice shelves. Here we use satellite imagery, airborne ice-penetrating radar and satellite laser altimetry spanning the period from 2002 to 2014 to map extensive basal channels in the ice shelves surrounding Antarctica. The highest density of basal channels is found in West Antarctic ice shelves. Within the channels, warm water flows northwards, eroding the ice shelf base and driving channel evolution on annual to decadal timescales. Our observations show that basal channels are associated with the development of new zones of crevassing, suggesting that these channels may cause ice fracture. We conclude that basal channels can form and grow quickly as a result of warm ocean water intrusion, and that they can structurally weaken ice shelves, potentially leading to rapid ice shelf loss in some areas.

  2. Extracellular potassium inhibits Kv7.1 potassium channels by stabilizing an inactivated state

    DEFF Research Database (Denmark)

    Larsen, Anders Peter; Steffensen, Annette Buur; Grunnet, Morten;

    2011-01-01

    Kv7.1 (KCNQ1) channels are regulators of several physiological processes including vasodilatation, repolarization of cardiomyocytes, and control of secretory processes. A number of Kv7.1 pore mutants are sensitive to extracellular potassium. We hypothesized that extracellular potassium also...... modulates wild-type Kv7.1 channels. The Kv7.1 currents were measured in Xenopus laevis oocytes at different concentrations of extracellular potassium (1-50 mM). As extracellular potassium was elevated, Kv7.1 currents were reduced significantly more than expected from theoretical calculations based...... on the Goldman-Hodgkin-Katz flux equation. Potassium inhibited the steady-state current with an IC(50) of 6.0 ± 0.2 mM. Analysis of tail-currents showed that potassium increased the fraction of channels in the inactivated state. Similarly, the recovery from inactivation was slowed by potassium, suggesting...

  3. Using CEOS reference standard test sites to track the calibration stability of NOAA-19 AVHRR reflective solar channels

    Science.gov (United States)

    Wu, Aisheng; Angal, Amit; Xiong, Jack; Cao, Changyong

    2010-10-01

    In recent years, there is an increasing interest to establish a global integrated network of calibration sites for the purpose of tracking sensor performance, conducting cross-sensor comparison and assessing data quality and consistency. Based on such a need, the Committee on Earth Observation Satellites (CEOS) proposed eight instrumented sites for which surface measurements can be acquired through field campaigns and five pseudo-invariant desert sites typically consisting of sand dunes. In this study, we select one site from each category to study the calibration stability of reflective solar channels of NOAA- 19 Advanced Very High Resolution Radiometer (AVHRR) (launched on February 6, 2009). Since AVHRR does not have an onboard calibrator for the reflective solar channels and vicarious calibration often needs long-term observations to derive reliable trends, this study will provide an early assessment of sensor on-orbit calibration performance and establish a preliminary trend to examine its calibration consistency with other sensors. The Antarctic Dome C site is selected primarily to monitor the on-orbit calibration performance whereas Libya 4 test site is used to evaluate the cross-calibration consistency of AVHRR with other sensors. A site-specific Bi-directional Reflectance Distribution Function (BRDF) model developed based on observations made by Moderate Resolution Imaging Spectroradiometer (MODIS) is used to normalize AVHRR observed Top-of-Atmosphere (TOA) reflectances. Impact due to calibration applied to NOAA-19 AVHRR L1B is assessed separately using a constant detector response. Results show that for NOAA-19 AVHRR solar channels 1 and 2, variations in reflectance during the first year after launch are still around 6% and more than 10%, respectively, either due to sensor change or improper adjustment of calibration coefficients. While two sites provide consistent trends for the visible channel, the Dome C site is more suitable for the near

  4. Transient calnexin interaction confers long-term stability on folded K+ channel protein in the ER.

    Science.gov (United States)

    Khanna, Rajesh; Lee, Eun Jeon; Papazian, Diane M

    2004-06-15

    We recently showed that an unglycosylated form of the Shaker potassium channel protein is retained in the endoplasmic reticulum (ER) and degraded by proteasomes in mammalian cells despite apparently normal folding and assembly. These results suggest that channel proteins with a native structure can be substrates for ER-associated degradation. We have now tested this hypothesis using the wild-type Shaker protein. Wild-type Shaker is degraded by cytoplasmic proteasomes when it is trapped in the ER and prevented from interacting with calnexin. Neither condition alone is sufficient to destabilize the protein. Proteasomal degradation of the wild-type protein is abolished when ER mannosidase I trimming of the core glycan is inhibited. Our results indicate that transient interaction with calnexin provides long-term protection from ER-associated degradation. PMID:15161937

  5. Stabilization Control for Linear Switching Stochastic Systems Against Time-Delay in Communication Channel

    Institute of Scientific and Technical Information of China (English)

    Dongfang Lv; Shen Cong

    2015-01-01

    The paper is concerned with stabilization problem for a class of stochastic switching systems with time⁃delay in the detection of switching signal. By using binomial model, Poisson process, and Wiener process to describe time⁃delay, switching signal, and exogenous disturbance, respectively, the system under investigation is entirely set in a stochastic framework. The influence of the random time⁃delay is combined into reconstructing the switching signal of overall closed⁃loop system and changes the distribution property of switching points. Therefore, based on the asymptotical behaviors of Poisson processes and Wiener processes, the almost surely exponential stability conditions are established. Furthermore, a design methodology is posed for solving the stabilization control.

  6. Preliminary assessment of channel stability and bed-material transport along Hunter Creek, southwestern Oregon

    Science.gov (United States)

    Jones, Krista L.; Wallick, J. Rose; O'Connor, Jim E.; Keith, Mackenzie K.; Mangano, Joseph F.; Risley, John C.

    2011-01-01

    This preliminary assessment of (1) bed-material transport in the Hunter Creek basin, (2) historical changes in channel condition, and (3) supplementary data needed to inform permitting decisions regarding instream gravel extraction revealed the following: Along the lower 12.4 km (kilometers) of Hunter Creek from its confluence with the Little South Fork Hunter Creek to its mouth, the river has confined and unconfined segments and is predominately alluvial in its lowermost 11 km. This 12.4-km stretch of river can be divided into two geomorphically distinct study reaches based primarily on valley physiography. In the Upper Study Reach (river kilometer [RKM] 12.4-6), the active channel comprises a mixed bed of bedrock, boulders, and smaller grains. The stream is confined in the upper 1.4 km of the reach by a bedrock canyon and in the lower 2.4 km by its valley. In the Lower Study Reach (RKM 6-0), where the area of gravel bars historically was largest, the stream flows over bed material that is predominately alluvial sediments. The channel alternates between confined and unconfined segments. The primary human activities that likely have affected bed-material transport and the extent and area of gravel bars are (1) historical and ongoing aggregate extraction from gravel bars in the study area and (2) timber harvest and associated road construction throughout the basin. These anthropogenic activities likely have varying effects on sediment transport and deposition throughout the study area and over time. Although assessing the relative effects of these anthropogenic activities on sediment dynamics would be challenging, the Hunter Creek basin may serve as a case study for such an assessment because it is mostly free of other alterations to hydrologic and geomorphic processes such as flow regulation, dredging, and other navigation improvements that are common in many Oregon coastal basins. Several datasets are available that may support a more detailed physical assessment

  7. An investigation of turbulent catalytically stabilized channel flow combustion of lean hydrogen - air mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Mantzaras, I.; Benz, P.; Schaeren, R.; Bombach, R. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1999-08-01

    The catalytically stabilised thermal combustion (CST) of lean hydrogen-air mixtures was investigated numerically in a turbulent channel flow configuration using a two-dimensional elliptic model with detailed heterogeneous and homogeneous chemical reactions. Comparison between turbulent and laminar cases having the same incoming mean properties shows that turbulence inhibits homogeneous ignition due to increased heat transport away from the near-wall layer. The peak root-mean-square temperature and species fluctuations are always located outside the extent of the homogeneous reaction zone indicating that thermochemical fluctuations have no significant influence on gaseous combustion. (author) 4 figs., 6 refs.

  8. STABILITY AND VIBRATION OF DRILL STRINGS WITH INTERNAL FLOWS OF LIQUIDS IN THE CHANNELS OF HORIZONTAL BORE-HOLES

    Directory of Open Access Journals (Sweden)

    Andrusenko E.N.

    2015-12-01

    Full Text Available In connection with elaboration of new technologies of hydrocarbons extraction from shales, in the oil and gas industry, the great attention is payed to the problems of drilling inclined and horizontal bore-holes. The peculiarities of these bore-hole drivage consist in essential influence of friction and contact forces on proceeding of drilling processes. In this paper, the problem about bifurcational buckling and small bending vibration of a rotating drill string lying in the channel of a horizontal bore-hole is stated. With allowance made for friction forces and additional constraint reactions, differential equations are deduced, their eigen-value solutions describing stability and vibration of the drill string of finite and infinite lengths are received.

  9. Linear stability of optimal streaks in the log-layer of turbulent channel flows

    Science.gov (United States)

    Alizard, Frédéric

    2015-10-01

    The importance of secondary instability of streaks for the generation of vortical structures attached to the wall in the logarithmic region of turbulent channels is studied. The streaks and their linear instability are computed by solving equations associated with the organized motion that include an eddy-viscosity modeling the effect of incoherent fluctuations. Three friction Reynolds numbers, Reτ = 2000, 3000, and 5000, are investigated. For all flow cases, optimal streamwise vortices (i.e., having the highest potential for linear transient energy amplification) are used as initial conditions. Due to the lift-up mechanism, these optimal perturbations lead to the nonlinear growth of streaks. Based on a Floquet theory along the spanwise direction, we observe the onset of streak secondary instability for a wide range of spanwise wavelengths when the streak amplitude exceeds a critical value. Under neutral conditions, it is shown that streak instability modes have their energy mainly concentrated in the overlap layer and propagate with a phase velocity equal to the mean streamwise velocity of the log-layer. These neutral log-layer modes exhibit a sinuous pattern and have characteristic sizes that are proportional to the wall distance in both streamwise and spanwise directions, in agreement with the Townsend's attached eddy hypothesis (A. Townsend, the structure of turbulent shear flow, Cambridge university press, 1976 2nd edition). In particular, for a distance from the wall varying from y+ ≈ 100 (in wall units) to y ≈ 0.3h, where h is half the height of the channel, the neutral log-layer modes are self-similar with a spanwise width of λz ≈ y/0.3 and a streamwise length of λx ≈ 3λz, independently of the Reynolds number. Based on this observation, it is suggested that compact vortical structures attached to the wall can be ascribed to streak secondary instabilities. In addition, spatial distributions of fluctuating vorticity components show that the onset

  10. Stabilizing ER Ca2+ channel function as an early preventative strategy for Alzheimer's disease.

    Directory of Open Access Journals (Sweden)

    Shreaya Chakroborty

    Full Text Available Alzheimer's disease (AD is a devastating neurodegenerative condition with no known cure. While current therapies target late-stage amyloid formation and cholinergic tone, to date, these strategies have proven ineffective at preventing disease progression. The reasons for this may be varied, and could reflect late intervention, or, that earlier pathogenic mechanisms have been overlooked and permitted to accelerate the disease process. One such example would include synaptic pathology, the disease component strongly associated with cognitive impairment. Dysregulated Ca(2+ homeostasis may be one of the critical factors driving synaptic dysfunction. One of the earliest pathophysiological indicators in mutant presenilin (PS AD mice is increased intracellular Ca(2+ signaling, predominantly through the ER-localized inositol triphosphate (IP(3 and ryanodine receptors (RyR. In particular, the RyR-mediated Ca(2+ upregulation within synaptic compartments is associated with altered synaptic homeostasis and network depression at early (presymptomatic AD stages. Here, we offer an alternative approach to AD therapeutics by stabilizing early pathogenic mechanisms associated with synaptic abnormalities. We targeted the RyR as a means to prevent disease progression, and sub-chronically treated AD mouse models (4-weeks with a novel formulation of the RyR inhibitor, dantrolene. Using 2-photon Ca(2+ imaging and patch clamp recordings, we demonstrate that dantrolene treatment fully normalizes ER Ca(2+ signaling within somatic and dendritic compartments in early and later-stage AD mice in hippocampal slices. Additionally, the elevated RyR2 levels in AD mice are restored to control levels with dantrolene treatment, as are synaptic transmission and synaptic plasticity. Aβ deposition within the cortex and hippocampus is also reduced in dantrolene-treated AD mice. In this study, we highlight the pivotal role of Ca(2+ aberrations in AD, and propose a novel strategy to

  11. Optimization of power compression and stability of relativistic and ponderomotive self-channeling of 248 nm laser pulses in underdense plasmas

    International Nuclear Information System (INIS)

    The controlled formation in an underdense plasma of stable multi-PW relativistic micrometer-scale channels, which conduct a confined power at 248 nm exceeding 104 critical powers and establish a peak channel intensity of ∼1023 W/cm2, can be achieved with the use of an appropriate gradient in the electron density in the initial launching phase of the confined propagation. This mode of channel formation optimizes both the power compression and the stability by smoothing the transition from the incident spatial profile to that associated with the lowest channel eigenmode, the dynamically robust structure that governs the confined propagation. A chief outcome is the ability to stably conduct coherent energy at fluences greater than 109 J/cm2

  12. Hydrophobic interactions between the S5 segment and the pore helix stabilizes the closed state of Slo2.1 potassium channels.

    Science.gov (United States)

    Suzuki, Tomoyuki; Hansen, Angela; Sanguinetti, Michael C

    2016-04-01

    Under normal physiological conditions, Slo2.1K(+) channels are in a closed state unless activated by an elevation in [Na(+)]i. Fenamates such as niflumic acid also activate Slo2.1. Previous studies suggest that activation of Slo2.1 channels is mediated by a conformational change in the selectivity filter, and not a widening of the aperture formed by the S6 segment bundle crossing as occurs in voltage-gated K(+) channels. It is unclear how binding of Na(+) or fenamates is allosterically linked to opening of the presumed selectivity filter activation gate in Slo2.1. Here we examined the role of the S5 transmembrane segment in the activation of Slo2.1. Channels were heterologously expressed in Xenopus laevis oocytes and whole cell currents measured with the voltage-clamp technique. Ala substitution of five residues located on a single face of the S5 α-helical segment induced constitutive channel activity. Leu-209, predicted to face towards Phe-240 in the pore helix was investigated by further mutagenesis. Mutation of Leu-209 to Glu or Gln induced maximal channel activation as did the combined mutation to Ala of all three hydrophobic S5 residues predicted to be adjacent to Phe-240. Together these results suggest that hydrophobic interactions between residues in S5 and the C-terminal end of the pore helix stabilize Slo2.1 channels in a closed state.

  13. Improving electrical performance and bias stability of HfInZnO-TFT with optimizing the channel thickness

    Directory of Open Access Journals (Sweden)

    Jun Li

    2013-10-01

    Full Text Available RF magnetron sputtered HfInZnO film and atomic layer deposition (ALD Al2O3 film were employed for thin film transistors (TFTs as channel layer and gate insulator, respectively. To achieve HfInZnO-TFT with high performance and good bias stability, the thickness of HfInZnO active layer was optimized. The performance of HfInZnO-TFTs was found to be thickness dependent. As the HfInZnO active layer got thicker, the leakage current greatly increased from 1.73 × 10−12 to 2.54 × 10−8 A, the threshold voltage decreased from 7.4 to −4.7 V, while the subthreshold swing varied from 0.41 to 1.07 V/decade. Overall, the HfInZnO film showed superior performance, such as saturation mobility of 6.4 cm2/V s, threshold voltage of 4.2 V, subthreshold swing of 0.43 V/decade, on/off current ratio of 3 × 107 and Vth shift of 3.6 V under VGS = 10 V for 7200 s. The results demonstrate the possibility of fabricating TFTs using HfInZnO film as active layer and using ALD Al2O3 as gate insulator.

  14. Effects of electric field and Coriolis force on electrohydrodynamic stability of poorly conducting couple stress parallel fluid flow in a channel

    International Nuclear Information System (INIS)

    The linear stability of electrohydrodynamic poorly conducting couple stress viscous parallel fluid flow in a channel is studied in the presence of a non-uniform transverse electric field and Coriolis force using energy method and supplemented with Galerkin Technique. The sufficient condition for stability is obtained for sufficiently small values of the Reynolds number, Re. From this condition we show that strengthening or weakening of the stability criterion is dictated by the values of the strength of electric field, the coefficient of couple stress fluid and independent of Taylor number. In particular, it is shown that the interaction of electric field with couple stress is more effective in stabilizing the poorly conducting couple stress fluid compared to that in an ordinary Newtonian viscous fluid. (author)

  15. Linear stability of a fuel channel uniformly heated considering retrofeeding by vacuum. Theoretical study; Estabilidad lineal de un canal combustible uniformemente calentado considerando retroalimentacion por vacios

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez M, V. [Comision Nacional de Seguridad Nuclear y Salvaguardias, 03000 Mexico D.F. (Mexico); Salinas H, J.G.; Espinosa P, G. [Universidad Autonoma Metropolitana-Iztapalapa, 09000 Mexico D.F. (Mexico)

    2000-07-01

    The Technology, Regulation and Services Management of the National Commission of Nuclear Safety and Safeguards in coordinated form with the IPH Department of the Metropolitan Autonomous-Iztapalapa University, developed the present project to study the linear stability in a fuel channel uniformly heated with effects of retrofeeding by vacuums. In this study the methodology used in the analysis of linear stability of the nuclear reactor unit 1 at Laguna Verde power plant is described which represented by an average channel uniformly heated. The conceptual model consists of two cells which represent the two regions in which is divided the channel according to the cooling is in one and two phases, considering the boiling length dependent in the time. It is used the homogeneous flux models for describing the thermohydraulic behavior of the cooling in the two phases region. The neutron processes with the punctual model of the neutron kinetics with a group of retarded neutrons precursors are described. It is studied the behavior of the system in the frequency domain with the transfer functions obtained and it is characterized in four operation states corresponding to the four corners of the low stability zone in the map power-flow Laguna Verde power plant. For these operation states the characteristic frequency is determined and the corresponding Nyquist diagrams are obtained. The results show that the system stability depends on the power-flow relation and that the operations which implicate a reduction of this relation improve the stability of the system (reducing the power introducing control bars with constant cooling flow or increase cooling flow with bars pattern established). The obtained results with effects of retrofeeding by vacuums show that the value of the characteristic frequency is modified very little with respect to the model without retrofeeding, therefore the thermohydraulic processes seem to determine the response of the stability of the system

  16. Maintenance of Road Embankment Cross Channels Stability in Cryolithozone%寒区隧道的路基稳定性维护

    Institute of Scientific and Technical Information of China (English)

    M.M. Dubina

    2004-01-01

    In cryolithozone conditions the control facilities a three-dimensional temperature mode of a place of crossing by the road embankment cross channel of various assignment for maintenance of structure stability are considered. The management is carried out through regulation by conditions of heat exchange on borders of a structure and in a ground massif. The software complex of thermal and mechanical behaviour computer modeling of structures considered class is created for the decision of control facilities designing tasks. The results of computing experiments show efficiency of application of such means, including as compensatory measures for maintenance of a considered structure stability at possible of a climate warming.

  17. A novel mechanism for fine-tuning open-state stability in a voltage-gated potassium channel

    DEFF Research Database (Denmark)

    Pless, Stephan Alexander; Niciforovic, Ana P; Galpin, Jason D;

    2013-01-01

    Voltage-gated potassium channels elicit membrane hyperpolarization through voltage-sensor domains that regulate the conductive status of the pore domain. To better understand the inherent basis for the open-closed equilibrium in these channels, we undertook an atomistic scan using synthetic fluor...

  18. Stabilization

    Directory of Open Access Journals (Sweden)

    Muhammad H. Al-Malack

    2016-07-01

    Full Text Available Fuel oil flyash (FFA produced in power and water desalination plants firing crude oils in the Kingdom of Saudi Arabia is being disposed in landfills, which increases the burden on the environment, therefore, FFA utilization must be encouraged. In the current research, the effect of adding FFA on the engineering properties of two indigenous soils, namely sand and marl, was investigated. FFA was added at concentrations of 5%, 10% and 15% to both soils with and without the addition of Portland cement. Mixtures of the stabilized soils were thoroughly evaluated using compaction, California Bearing Ratio (CBR, unconfined compressive strength (USC and durability tests. Results of these tests indicated that stabilized sand mixtures could not attain the ACI strength requirements. However, marl was found to satisfy the ACI strength requirement when only 5% of FFA was added together with 5% of cement. When the FFA was increased to 10% and 15%, the mixture’s strength was found to decrease to values below the ACI requirements. Results of the Toxicity Characteristics Leaching Procedure (TCLP, which was performed on samples that passed the ACI requirements, indicated that FFA must be cautiously used in soil stabilization.

  19. Mutation of light-dependent phosphorylation sites of the Drosophila transient receptor potential-like (TRPL) ion channel affects its subcellular localization and stability.

    Science.gov (United States)

    Cerny, Alexander C; Oberacker, Tina; Pfannstiel, Jens; Weigold, Sebastian; Will, Carina; Huber, Armin

    2013-05-31

    The Drosophila phototransduction cascade terminates in the opening of the ion channel transient receptor potential (TRP) and TRP-like (TRPL). Contrary to TRP, TRPL undergoes light-dependent subcellular trafficking between rhabdomeric photoreceptor membranes and an intracellular storage compartment, resulting in long term light adaptation. Here, we identified in vivo phosphorylation sites of TRPL that affect TRPL stability and localization. Quantitative mass spectrometry revealed a light-dependent change in the TRPL phosphorylation pattern. Mutation of eight C-terminal phosphorylation sites neither affected multimerization of the channels nor the electrophysiological response of flies expressing the mutated channels. However, these mutations resulted in mislocalization and enhanced degradation of TRPL after prolonged dark-adaptation. Mutation of subsets of the eight C-terminal phosphorylation sites also led to a reduction of TRPL content and partial mislocalization in the dark. This suggests that a light-dependent switch in the phosphorylation pattern of the TRPL channel mediates stable expression of TRPL in the rhabdomeres upon prolonged dark-adaptation. PMID:23592784

  20. Mutation of Light-dependent Phosphorylation Sites of the Drosophila Transient Receptor Potential-like (TRPL) Ion Channel Affects Its Subcellular Localization and Stability*

    Science.gov (United States)

    Cerny, Alexander C.; Oberacker, Tina; Pfannstiel, Jens; Weigold, Sebastian; Will, Carina; Huber, Armin

    2013-01-01

    The Drosophila phototransduction cascade terminates in the opening of the ion channel transient receptor potential (TRP) and TRP-like (TRPL). Contrary to TRP, TRPL undergoes light-dependent subcellular trafficking between rhabdomeric photoreceptor membranes and an intracellular storage compartment, resulting in long term light adaptation. Here, we identified in vivo phosphorylation sites of TRPL that affect TRPL stability and localization. Quantitative mass spectrometry revealed a light-dependent change in the TRPL phosphorylation pattern. Mutation of eight C-terminal phosphorylation sites neither affected multimerization of the channels nor the electrophysiological response of flies expressing the mutated channels. However, these mutations resulted in mislocalization and enhanced degradation of TRPL after prolonged dark-adaptation. Mutation of subsets of the eight C-terminal phosphorylation sites also led to a reduction of TRPL content and partial mislocalization in the dark. This suggests that a light-dependent switch in the phosphorylation pattern of the TRPL channel mediates stable expression of TRPL in the rhabdomeres upon prolonged dark-adaptation. PMID:23592784

  1. Regional flexibility in the S4-S5 linker regulates hERG channel closed-state stabilization.

    Science.gov (United States)

    Hull, Christina M; Sokolov, Stanislav; Van Slyke, Aaron C; Claydon, Tom W

    2014-10-01

    hERG K(+) channel function is vital for normal cardiac rhythm, yet the mechanisms underlying the unique biophysical characteristics of the channel, such as slow activation and deactivation gating, are incompletely understood. The S4-S5 linker is thought to transduce voltage sensor movement to opening of the pore gate, but may also integrate signals from cytoplasmic domains. Previously, we showed that substitutions of G546 within the S4-S5 linker destabilize the closed state of the channel. Here, we present results of a glycine-scan in the background of 546L. We demonstrate site-specific restoration of WT-like activation which suggests that flexibility in the N-terminal portion of the S4-S5 linker is critical for the voltage dependence of hERG channel activation. In addition, we show that the voltage dependence of deactivation, which was recently shown to be left-shifted from that of activation due to voltage sensor mode-shift, is also modulated by the S4-S5 linker. The G546L mutation greatly attenuated the coupling of voltage sensor mode-shift to the pore gate without altering the mode-shift itself. Indeed, all of the S4-S5 linker mutations tested similarly reduced coupling of the mode-shift to the pore gate. These data demonstrate a key role for S4-S5 linker in the unique activation and deactivation gating of hERG channels. Furthermore, uncoupling of the mode-shift to the pore by S4-S5 linker mutations parallels the effects of mutations in the N-terminus suggestive of functional interactions between the two regions.

  2. Modelling temporal stability of EPI time series using magnitude images acquired with multi-channel receiver coils.

    Directory of Open Access Journals (Sweden)

    Chloe Hutton

    Full Text Available In 2001, Krueger and Glover introduced a model describing the temporal SNR (tSNR of an EPI time series as a function of image SNR (SNR(0. This model has been used to study physiological noise in fMRI, to optimize fMRI acquisition parameters, and to estimate maximum attainable tSNR for a given set of MR image acquisition and processing parameters. In its current form, this noise model requires the accurate estimation of image SNR. For multi-channel receiver coils, this is not straightforward because it requires export and reconstruction of large amounts of k-space raw data and detailed, custom-made image reconstruction methods. Here we present a simple extension to the model that allows characterization of the temporal noise properties of EPI time series acquired with multi-channel receiver coils, and reconstructed with standard root-sum-of-squares combination, without the need for raw data or custom-made image reconstruction. The proposed extended model includes an additional parameter κ which reflects the impact of noise correlations between receiver channels on the data and scales an apparent image SNR (SNR'(0 measured directly from root-sum-of-squares reconstructed magnitude images so that κ = SNR'(0/SNR(0 (under the condition of SNR(0>50 and number of channels ≤32. Using Monte Carlo simulations we show that the extended model parameters can be estimated with high accuracy. The estimation of the parameter κ was validated using an independent measure of the actual SNR(0 for non-accelerated phantom data acquired at 3T with a 32-channel receiver coil. We also demonstrate that compared to the original model the extended model results in an improved fit to human task-free non-accelerated fMRI data acquired at 7T with a 24-channel receiver coil. In particular, the extended model improves the prediction of low to medium tSNR values and so can play an important role in the optimization of high-resolution fMRI experiments at lower SNR levels.

  3. High-power dense wavelength division multiplexing (HP-DWDM) of frequency stabilized 9xx diode laser bars with a channel spacing of 1.5 nm

    Science.gov (United States)

    Hengesbach, Stefan; Holly, Carlo; Krauch, Niels; Witte, Ulrich; Westphalen, Thomas; Traub, Martin; Hoffmann, Dieter

    2014-03-01

    We present a compact High-Power DenseWavelength Division Multiplexer (HP-DWDM) based on Volume Bragg Gratings (VBGs) for spectrally stabilized diode lasers with a low average beam quality M2 <=50. The center wavelengths of the five input channels with a spectral spacing of 1.5 nm are 973 nm, 974.5 nm, 976 nm, 977.5 nm and 979 nm. Multiplexing efficiencies of 97%+/-2% have been demonstrated with single mode, frequency stabilized laser radiation. Since the diffraction efficiency strongly depends on the beam quality, the multiplexing efficiency decreases to 94% (M2 = 25) and 85%+/-3% (M2 = 45) if multimode radiation is overlaid. Besides, the calculated multiplexing efficiency of the radiation with M2 = 45 amounts to 87:5 %. Thus, calculations and measurements are in good agreement. In addition, we developed a dynamic temperature control for the multiplexing VBGs which adapts the Bragg wavelengths to the diode laser center wavelengths. In short, the prototype with a radiance of 70GWm-2 sr-1 consists of five spectrally stabilized and passively cooled diode laser bars with 40Woutput after beam transformation. To achieve a good stabilization performance ELOD (Extreme LOw Divergence) diode laser bars have been chosen in combination with an external resonator based on VBGs. As a result, the spectral width defined by 95% power inclusion is < 120pm for each beam source across the entire operating range from 30 A to 120 A. Due to the spectral stabilization, the output power of each bar decreases in the range of < 5 %.

  4. 应答式ALOHA-CDMA信道的吞吐量及稳定性分析%Analysis of throughput and stability for ACK-ALOHA-CDMA channel

    Institute of Scientific and Technical Information of China (English)

    邵建华; 殷奎喜; 赵华

    2009-01-01

    A new acknowledgment-type slotted-ALOHA code division multiple access(ACK-ALOHA-CDMA) channel which can be used in the inbound channels of very small aperture terminal(VSAT) networks is proposed in order to simplify the synchronization equipment of networks in the slotted-ALOHA-CDMA systems. By dividing all VSAT stations into M subsystems and sending out periodic inquiry signals from the Hub station to the VSAT station, the channel model is established. By the means of deriving multi-access interference(MAI) and packet detecting probability, steady-state throughput is calculated. By applying diffusion process theory to the analysis of the stability of the ACK-ALOHA-CDMA channel, the drift parameter a(r), the diffusion parameter b (r) and the steady transition probability density p (r) are investigated. Simulation results indicate that significant performance improvement and high-bandwidth efficiency can be gained and one or two steady equilibrium points can be obtained by using this channel. Consequently, the ACK-ALOHA-CDMA channel is very suitable for cutting down on the expense of satellite VSAT systems and distributed packet radio networks.%为了简化时隙ALOHA-CDMA系统的时间同步设备,提出了一种可用于卫星VSAT网络内向信道的应答式时隙ALOHA-CDMA信道模型.将端站分为M个子系统,利用主站发出周期性询问信号,建立了信道模型;通过扩频多址干扰(MAI)和分组检测概率的推导,计算出该信道的稳态吞吐量;并将扩散过程理论用于该信道的稳定性分析,得到扩散系数a(r)、漂移系数b(r)和信道平稳分布P(r).仿真结果表明,该系统可以显著提高信道吞吐性能和信道利用率,且存在1~2个稳定平衡点.应答式时隙ALOHA-CDMA信道可以降低卫星VSAT系统及分组无线网络系统的组网成本.

  5. Electrohydrodynamic linear stability of two immiscible fluids in channel flow under the influence of a parallel electric field

    Science.gov (United States)

    Kerem Uguz, A.; Aubry, Nadine

    2007-11-01

    The instability of a flat interface between two viscous, immiscible and incompressible liquids in plane Poiseuille flow is studied in the presence of an electric field parallel to the flat interface. In practice, either the stability or instability of the interface is desired depending on the application such as material deposition, mixing, or droplet formation. For that purpose the effect of various parameters was studied via linear stability analysis. The electric field was found to be either stabilizing or destabilizing depending on the electrical properties of the fluids. An interesting feature of this problem is the presence of a second window of stability, namely for some parameters there exist two regions of wavenumbers in which the system is stable. Our results are compared with the case where the electric field is normal to the fluid-fluid interface [1, 2]. [1] O. Ozen, N. Aubry, D. T. Papageorgiou and P. G. Petropoulos, Electrochimica Acta, 51, 5316-5323 (2006) [2] F. Li, O. Ozen, N. Aubry, D.T. Papageorgiou and P.G. Petropoulos, Journal of Fluid Mechanics, 583, 347-377 (2007)

  6. Influence of microstructural stability on the creep mechanism of Al-7wt% Si alloy processed by equal channel angular pressing

    OpenAIRE

    Orozco-Caballero, A.; Menon, S.K.; Cepeda-Jiménez, C.M.; Hidalgo-Manrique, P.; McNelley, T.R.; Ruano, O.A.; Carreño, F.

    2014-01-01

    The article of record as published may be located at http://dx.doi.org/10.1016/j.msea.2014.06.017 A Na-modified, as-cast Al-7 wt% Si alloy was processed by equal channel angular pressing (ECAP) up to 8 passes by route A at ambient temperature using a 90 degree square section die, obtaining improved strength ductility and work fracture. From the first pass, porosity is removed, the eutectic constituent is refined and the eutectic silicon particles are partially redistributed...

  7. Modelling temporal stability of EPI time series using magnitude images acquired with multi-channel receiver coils.

    OpenAIRE

    Chloe Hutton; Evelyne Balteau; Antoine Lutti; Oliver Josephs; Nikolaus Weiskopf

    2012-01-01

    In 2001, Krueger and Glover introduced a model describing the temporal SNR (tSNR) of an EPI time series as a function of image SNR (SNR(0)). This model has been used to study physiological noise in fMRI, to optimize fMRI acquisition parameters, and to estimate maximum attainable tSNR for a given set of MR image acquisition and processing parameters. In its current form, this noise model requires the accurate estimation of image SNR. For multi-channel receiver coils, this is not straightforwar...

  8. THE LOSS OF STABILITY OF LAMINAR FLOW IN OPEN CHANNEL AND THE MECHANISM OF SAND RIPPLE FORMATION

    Institute of Scientific and Technical Information of China (English)

    白玉川; 罗纪生

    2002-01-01

    In the flow on a mobile bed in an open channel, sand ripple often appears after the sediment begins to move. Different scholars have different views on the formation of sand ripples. This paper holds that as the ripple in general is very small, its formation is due to the instability of the laminar flow or the evolution of the small-scale coherent structures in the sublayer adjacent to the wall of the open channel. When the shear stresses caused by the disturbing waves or the coherent structure near the bed surface boundary and the water flow itself are greater than the shields stresses, responses on the bed surface appear and the sand ripple forms. If the frequency of the shear stress caused by the disturbance is close to the natural frequency of the sand grains that produced resonance,such a phenomenon is called the "detection property" of the sediment. It is at this point that the maximum resonance appears and the sand ripple develops rapidly.

  9. Intracellular potassium stabilizes human ether-à-go-go-related gene channels for export from endoplasmic reticulum.

    Science.gov (United States)

    Wang, Lu; Dennis, Adrienne T; Trieu, Phan; Charron, Francois; Ethier, Natalie; Hebert, Terence E; Wan, Xiaoping; Ficker, Eckhard

    2009-04-01

    Several therapeutic compounds have been identified that prolong the QT interval on the electrocardiogram and cause torsade de pointes arrhythmias not by direct block of the cardiac potassium channel human ether-à-go-go-related gene (hERG) but via disruption of hERG trafficking to the cell surface membrane. One example of a clinically important compound class that potently inhibits hERG trafficking are cardiac glycosides. We have shown previously that inhibition of hERG trafficking by cardiac glycosides is initiated via direct block of Na(+)/K(+) pumps and not via off-target interactions with hERG or any other protein. However, it was not known how pump inhibition at the cell surface is coupled to hERG processing in the endoplasmic reticulum. Here, we show that depletion of intracellular K(+)-either indirectly after long-term exposure to cardiac glycosides or directly after exposure to gramicidin in low sodium media-is sufficient to disrupt hERG trafficking. In K(+)-depleted cells, hERG trafficking can be restored by permeating K(+) or Rb(+) ions, incubation at low temperature, exposure to the pharmacological chaperone astemizole, or specific mutations in the selectivity filter of hERG. Our data suggest a novel mechanism for drug-induced trafficking inhibition in which cardiac glycosides produce a [K(+)](i)-mediated conformational defect directly in the hERG channel protein. PMID:19139152

  10. Streak instability and generation of hairpin-vortices by a slotted jet in channel crossflow: Experiments and linear stability analysis

    Science.gov (United States)

    Philip, Jimmy; Karp, Michael; Cohen, Jacob

    2016-01-01

    Streaks and hairpin-vortices are experimentally generated in a laminar plane Poiseuille crossflow by injecting a continuous jet through a streamwise slot normal to the crossflow, with air as the working media. Small disturbances form stable streaks, however, higher disturbances cause the formation of streaks which undergo instability leading to the generation of hairpin vortices. Particular emphasis is placed on the flow conditions close to the generation of hairpin-vortices. Measurements are carried out in the cases of natural and phase-locked disturbance employing smoke visualisation, particle image velocimetry, and hot-wire anemometry, which include, the dominant frequency, wavelength, and the disturbance shape (or eigenfunctions) associated with the coherent part of the velocity field. A linear stability analysis for both one- and two-dimensional base-flows is carried out to understand the mechanism of instability and good agreement of wavelength and eigenfunctions are obtained when compared to the experimental data, and a slight under-prediction of the growth-rates by the linear stability analysis consistent with the final nonlinear stages in transitional flows. Furthermore, an energy analysis for both the temporal and spatial stability analysis revels the dominance of the symmetric varicose mode, again, in agreement with the experiments, which is found to be governed by the balance of the wallnormal shear and dissipative effects rather than the spanwise shear. In all cases the anti-symmetric sinuous modes governed by the spanwise shear are found to be damped both in analysis and in our experiments.

  11. Cyclisation Increases the Stability of the Sea Anemone Peptide APETx2 but Decreases Its Activity at Acid-Sensing Ion Channel 3

    Directory of Open Access Journals (Sweden)

    Lachlan D. Rash

    2012-07-01

    Full Text Available APETx2 is a peptide isolated from the sea anemone Anthopleura elegantissima. It is the most potent and selective inhibitor of acid-sensing ion channel 3 (ASIC3 and it is currently in preclinical studies as a novel analgesic for the treatment of chronic inflammatory pain. As a peptide it faces many challenges in the drug development process, including the potential lack of stability often associated with therapeutic peptides. In this study we determined the susceptibility of wild-type APETx2 to trypsin and pepsin and tested the applicability of backbone cyclisation as a strategy to improve its resistance to enzymatic degradation. Cyclisation with either a six-, seven- or eight-residue linker vastly improved the protease resistance of APETx2 but substantially decreased its potency against ASIC3. This suggests that either the N- or C-terminus of APETx2 is involved in its interaction with the channel, which we confirmed by making N- and C-terminal truncations. Truncation of either terminus, but especially the N-terminus, has detrimental effects on the ability of APETx2 to inhibit ASIC3. The current work indicates that cyclisation is unlikely to be a suitable strategy for stabilising APETx2, unless linkers can be engineered that do not interfere with binding to ASIC3.

  12. Stability boundary calculation of thermal-hydraulic channels with RAMONA5, ATHLET and a reduced order model. A comparative study

    International Nuclear Information System (INIS)

    In the framework of the design study comprehensive system code analyses are performed with ATHLET and RAMONA. RAMONA is used in the current analysis because it has a broad validation basis for stability and transient analysis. On the other hand ATHLET has some advantages compared to RAMONA (free geometry and nodalization definition), which will be important to model and analyse the above mentioned test facility. One objective is to predict and confirm the operating conditions and transient behaviour for different facility designs. Thereby one aspect is the prediction of the thermal-hydraulic conditions at which self sustained density wave oscillations (ssDWOs) may occur under constant pressure drop boundary conditions. This paper is devoted to the latter investigation, only. In particular, we will discuss the question under which conditions the results of the measurement and simulation of the ssDWO onset are comparable to each other using the system codes ATHLET and RAMONA and, beside, an advanced reduced thermal-hydraulic model (TH-ROM). It will be shown why a precise measurement of the steady state axial profiles (void fraction, velocity of the liquid and gas phases and the axial pressure drop distribution) is of paramount importance in the scope of the present comparative study. (orig.)

  13. 槽道纤维悬浮流动转捩阶段稳定性与减阻研究%Stability and drag reduction in transient channel flow of fibre suspension

    Institute of Scientific and Technical Information of China (English)

    游振江; 林建忠; 邵雪明; 张卫峰

    2004-01-01

    Drag reduction features in the transition regime of channel flow with fibre suspension were analyzed in terms of the linear stability theory.The modified stability equation was obtained based on the slender-body theory and natural closure approximation.Results of the stability analysis show attenuating effects of fibre additives to the flow instability.For the cases leading to transition,drag reduction rate increases with the characteristic parameter H of fibres.The mechanism of drag reduction by fibres is revealed through the variation of velocity profile and the decrease of wall shear stress.The theoretical results are qualitatively consistent with some typical experiments.

  14. Medium timescale stability of tidal mudflats in Bridgwater Bay, Bristol Channel, UK: Influence of tides, waves and climate

    Science.gov (United States)

    Kirby, Jason R.; Kirby, Robert

    2008-11-01

    This paper presents the results of an 11-year study into mudflat elevation changes within the intertidal zone at Stert Flats in Bridgwater Bay, Somerset. This site is located in the outer Severn Estuary/inner Bristol Channel which is a macro-hypertidal regime dominated by physical processes, characterized by strong tidal currents, high turbidity and a significant degree of exposure to wind generated waves. Two transects of stakes were installed perpendicular to the coast, extending seawards 300 m from the edge of the saltmarsh onto the mudflats, against which variations in accretion or erosion could be measured. The mudflats themselves consisted of an underlying consolidated clay of Holocene age and a surface veneer of fluid mud and/or mobile sand patches which varied both spatially and temporally. Mudflat development was recorded over both short-term (monthly/seasonal) and medium-term (inter-annual) timescales. The results display a significant degree of scatter over all timescales. Such variability in response may be expected in such a dynamic system where noise can be attributed to a combination of factors such as the mobility of surface fluid mud and sand patches and the migration of the underlying ridge-runnel drainage network. Despite this, the expected short-term variations related to neap-spring tidal conditions and seasonal influences were observed at a number of locations on the transects although these were weakly expressed. The over-riding feature of the profiles is a consistent long-term trend of erosion which appears to be masking shorter term trends within the dataset. Viewed over the 11-year period, the changes in mudflat elevation closely match the pattern of the index of the North Atlantic Oscillation (NAO) during the 1990s, suggesting a strong climatic control over mudflat development on a medium-term/decadal scale. Most profiles display a strong erosional trend during the early 1990s when the NAO index was positive. The erosional trend peaked in

  15. Characterization of Jupiter's Deep Circulation and Static Stability through Wide Channel Numerical Simulations of the Dynamics and Interactions of Southern Midlatitudes Vortices

    Science.gov (United States)

    Morales-Juberias, Raul; Dowling, T. E.

    2012-10-01

    Previous studies have shown that the observed features and dynamics of Jovian vortices are sensitive to the underlying environmental structure of Jupiter’s atmosphere, in particular to the vertical wind shear and the static stability, and that forward modeling techniques can be successfully used to eliminate a large range of possibilities in a self-consistent manner and hence constrain the atmospheric structure below the cloud regions (Youseff and Marcus 2003, Morales-Juberias et al. 2005). However, these studies have generally been done on a narrow latitude-band basis (˜15°). Here we present wide channel simulations (˜40°) of two major meteorological events observed in the southern atmosphere of Jupiter involving the interaction of the Great Red Spot (GRS) with other nearby vortices. Namely, the spots associated with the recirculation of the South Tropical Disturbance of 1979 (Smith et al. 1979) and the White Ovals (WOS) in 2000 when ovals BE and FA merged to form BA (Sanchez-Lavega et al. 2001). By studying these two events using wide channel simulations, not unlike the strategy used in terrestrial synoptic meteorology, we show that we can gain new insights into the patterns governing Jupiter's global circulations, drawing a coherent picture of the vertical structure of the atmosphere for the whole southern mid-latitudinal regions of Jupiter over time. In particular, we find that the model output best captures the dynamics of the individual vortices and the morphology of their interactions when the deformation length in this region is like that derived by Read et al. 2006 and the deep winds vary following a dependence like that derived by Dowling 1995 in which the westward jets remain constant with depth but the eastward jets increase with depth. Computational resources were provided by the New Mexico Computing Applications Center and NMT. This work was supported by PATM grants NNX08AE91G and NNX08AE64G.

  16. Preliminary assessment of channel stability and bed-material transport in the Tillamook Bay tributaries and Nehalem River basin, northwestern Oregon

    Science.gov (United States)

    Jones, Krista L.; Keith, Mackenzie K.; O'Connor, Jim E.; Mangano, Joseph F.; Wallick, J. Rose

    2012-01-01

    subject to incision and aggradation as well as lateral shifts in thalweg position and bank deposition and erosion. * In fluvial reaches, unit bar area declined a net 5.3-83.6 percent from 1939 to 2009. The documented reduction in bar area may be attributable to several factors, including vegetation establishment and stabilization of formerly active bar surfaces, lateral channel changes and resulting alterations in sediment deposition and erosion patterns, and streamflow and/or tide differences between photographs. Other factors that may be associated with the observed reduction in bar area but not assessed in this reconnaissance level study include changes in the sediment and hydrology regimes of these rivers over the analysis period. * In tidal reaches, unit bar area increased on the Tillamook and Nehalem Rivers (98.0 and 14.7 percent, respectively), but declined a net 24.2 to 83.1 percent in the other four tidal reaches. Net increases in bar area in the Tidal Tillamook and Nehalem Reaches were possibly attributable to tidal differences between the photographs as well as sediment deposition behind log booms and pile structures on the Tillamook River between 1939 and 1967. * The armoring ratio (ratio of the median grain sizes of a bar's surface and subsurface layers) was 1.6 at Lower Waldron Bar on the Miami River, tentatively indicating a relative balance between transport capacity and sediment supply at this location. Armoring ratios, however, ranged from 2.4 to 5.5 at sites on the Trask, Wilson, Kilchis, and Nehalem Rivers; these coarse armor layers probably reflect limited bed-material supply at these sites. * On the basis of mapping results, measured armoring ratios, and channel cross section surveys, preliminary conclusions are that the fluvial reaches on the Tillamook, Trask, Kilchis, and Nehalem Rivers are currently sediment supply-limited in terms of bed material - that is, the transport capacity of the channel generally exceeds the supply of bed material. The

  17. Microstructure stability of ultra-fine grained magnesium alloy AZ31 processed by extrusion and equal-channel angular pressing (EX–ECAP)

    Energy Technology Data Exchange (ETDEWEB)

    Stráská, Jitka, E-mail: straska.jitka@gmail.com [Department of Physics of Materials, Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 5, 121 16 Praha 2 (Czech Republic); Janeček, Miloš, E-mail: janecek@met.mff.cuni.cz [Department of Physics of Materials, Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 5, 121 16 Praha 2 (Czech Republic); Čížek, Jakub, E-mail: jcizek@mbox.troja.mff.cuni.cz [Department of Low Temperature Physics, Faculty of Mathematics and Physics, Charles University in Prague, V Holešovičkách 2, 180 00 Praha 8 (Czech Republic); Stráský, Josef, E-mail: josef.strasky@gmail.com [Department of Physics of Materials, Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 5, 121 16 Praha 2 (Czech Republic); Hadzima, Branislav, E-mail: branislav.hadzima@fstroj.uniza.sk [University of Žilina, Research Centre, Univerzitná 1, 010 26 Žilina (Slovakia); Department of Materials Engineering, Faculty of Mechanical Engineering, University of Žilina, Univerzitná 1, 010 26 Žilina (Slovakia)

    2014-08-15

    Thermal stability of the ultra-fine grained (UFG) microstructure of magnesium AZ31 alloy was investigated. UFG microstructure was achieved by a combined two-step severe plastic deformation process: the extrusion (EX) and subsequent equal-channel angular pressing (ECAP). This combined process leads to refined microstructure and enhanced microhardness. Specimens with UFG microstructure were annealed isochronally at temperatures 150–500 °C for 1 h. The evolution of microstructure, mechanical properties and dislocation density was studied by electron backscatter diffraction (EBSD), microhardness measurements and positron annihilation spectroscopy (PAS). The coarsening of the fine-grained structure at higher temperatures was accompanied by a gradual decrease of the microhardness and decrease of dislocation density. Mechanism of grain growth was studied by general equation for grain growth and Arrhenius equation. Activation energies for grain growth were calculated to be 115, 33 and 164 kJ/mol in temperature ranges of 170–210 °C, 210–400 °C and 400–500 °C (443–483 K, 483–673 K and 673–773 K), respectively. - Highlights: • Microhardness of UFG AZ31 alloy decreases with increasing annealing temperature. • This fact has two reasons: dislocation annihilations and/or grain growth. • The activation energies for grain growth were calculated for all temperature ranges.

  18. Quantitative determination of capsaicin, a transient receptor potential channel vanilloid 1 agonist, by liquid chromatography quadrupole ion trap mass spectrometry: evaluation of in vitro metabolic stability.

    Science.gov (United States)

    Beaudry, Francis; Vachon, Pascal

    2009-02-01

    Capsaicin is the most abundant pungent molecule present in red peppers and it is widely used for food flavoring, in pepper spray in self-defense devices and more recently in ointments for the relief of neuropathic pain. Capsaicin is a selective agonist of transient receptor potential channel, vanilloid subfamily member 1. A selective and sensitive quantitative method for the determination of capsaicin by LC-ESI/MS/MS was developed. The method consisted of a protein precipitation extraction followed by analysis using liquid chromatography electrospray quadrupole ion trap mass spectrometry. The chromatographic separation was achieved using a 100 x 2 mm C(18) Waters Symmetry column combined with a gradient mobile phase composed of acetonitrile and 0.1% formic acid aqueous solution at a flow rate of 220 microL/min. The mass spectrometer was operating in full-scan MS/MS mode using two-segment analysis. An analytical range of 10-5000 ng/mL was used in the calibration curve constructed in rat plasma. The interbatch precision and accuracy observed were 6.5, 6.7, 5.3 and 101.2, 102.7, 103.5% at 50, 500 and 5000 ng/mL, respectively. An in vitro metabolic stability study was performed in rat, dog and mouse liver microsomes and the novel analytical method was adapted and used to determine intrinsic clearance of capsaicin. Results suggest very rapid degradation with T(1/2) ranging from 2.3 to 4.1 min and high clearance values suggesting that drug bioavailability will be considerably reduced, consequently affecting drug response and efficacy. PMID:18816461

  19. 明渠网络中基于带权Lyapunov函数的边界反馈控制稳定性%Stability of Boundary Feedback Control Based on Weighted Lyapunov Function in Networks of Open Channels

    Institute of Scientific and Technical Information of China (English)

    岑丽辉; 席裕庚

    2009-01-01

    A Lyapunov function is constructed based on the weighted sum of entropies for the case of two open channels in cascade, which is described by the Saint-Venant equations. A class of boundary feedback controllers is presented to guaran-tee the local closed-loop asymptotic stability in a neighborhood of the equilibrium point by means of the Lyapunov design ap-proach.

  20. Improved Mobility and Bias Stability of Thin Film Transistors Using the Double-Layer a-InGaZnO/a-InGaZnO:N Channel.

    Science.gov (United States)

    Yu, H; Zhang, L; Li, X H; Xu, H Y; Liu, Y C

    2016-04-01

    The amorphous indium-gallium-zinc oxide (a-IGZO) thin film transistors (TFTs) were demonstrated based on a double-layer channel structure, where the channel is composed of an ultrathin nitro-genated a-IGZO (a-IGZO:N) layer and an undoped a-IGZO layer. The double-layer channel device showed higher saturation mobility and lower threshold-voltage shift (5.74 cm2/Vs, 2.6 V) compared to its single-layer counterpart (0.17 cm2/Vs, 7.23 V). The improvement can be attributed to three aspects: (1) improved carrier transport properties of the channel by the a-IGZO:N layer with high carrier mobility and the a-IGZO layer with high carrier concentration, (2) reduced interfacial trap density between the active channel and the gate insulator, and (3) higher surface flatness of the double-layer channel. Our study reveals key insights into double-layer channel, involving selecting more suitable electrical property for back-channel layer and more suitable interface modification for active layer. Meanwhile, room temperature fabrication amorphous TFTs offer certain advantages on better flexibility and higher uniformity over a large area. PMID:27451684

  1. Parametric study of the stability properties of a thermo hydraulic channel coupled to punctual kinetics; Estudio parametrico de las propiedades de estabilidad de un canal termohidraulico acoplado a cinetica puntual

    Energy Technology Data Exchange (ETDEWEB)

    Cecenas F, M.; Campos G, R.M. [Instituto de Investigaciones Electricas, Reforma 113, Col. Palmira, Temixco, Morelos (Mexico)]. e-mail: mcf@iie.org.mx

    2005-07-01

    The reason of decay is the indicator of stability usually used in the literature to evaluate stability of boiling water reactors, however, in the operation of this type of reactors is considered the length of boiling like an auxiliary parameter for the evaluation of stability. In this work its are studied the variation of these two indicators when modifying a given an operation parameter in a model of a thermo hydraulic channel coupled to punctual kinetics, maintaining all the other input constant variables. The parameters selected for study are the axial profile of power, the subcooling, the flow of coolant and the thermal power. The study is supplemented by means of real data of plant using the one Benchmark of Ringhals, and the results for the case of the ratio of decay its are compared with the decay reasons obtained by means of autoregression models of the local instrumentation of neutron flux. (Author)

  2. Athermalized channeled spectropolarimeter enhancement.

    Energy Technology Data Exchange (ETDEWEB)

    Jones, Julia Craven; Way, Brandyn Michael; Mercier, Jeffrey Alan; Hunt, Jeffery P.

    2013-09-01

    Channeled spectropolarimetry can measure the complete polarization state of light as a function of wavelength. Typically, a channeled spectropolarimeter uses high order retarders made of uniaxial crystal to amplitude modulate the measured spectrum with the spectrally-dependent Stokes polarization information. A primary limitation of conventional channeled spectropolarimeters is related to the thermal variability of the retarders. Thermal variation often forces frequent system recalibration, particularly for field deployed systems. However, implementing thermally stable retarders, made of biaxial crystal, results in an athermal channeled spectropolarimeter that relieves the need for frequent recalibration. This report presents experimental results for an anthermalized channeled spectropolarimeter prototype produced using potassium titanyl phosphate. The results of this prototype are compared to the current thermal stabilization state of the art. Finally, the application of the technique to the thermal infrared is studied, and the athermalization concept is applied to an infrared imaging spectropolarimeter design.

  3. RFI channels

    Science.gov (United States)

    Mceliece, R. J.

    1980-01-01

    A class of channel models is presented which exhibit varying burst error severity much like channels encountered in practice. An information-theoretic analysis of these channel models is made, and conclusions are drawn that may aid in the design of coded communication systems for realistic noisy channels.

  4. DMT of weighted Parallel Channels: Application to Broadcast Channel

    CERN Document Server

    Mroueh, Lina; Othman, Ghaya Rekaya-Ben; Belfiore, Jean-Claude

    2008-01-01

    In a broadcast channel with random packet arrival and transmission queues, the stability of the system is achieved by maximizing a weighted sum rate capacity with suitable weights that depend on the queue size. The weighted sum rate capacity using Dirty Paper Coding (DPC) and Zero Forcing (ZF) is asymptotically equivalent to the weighted sum capacity over parallel single-channels. In this paper, we study the Diversity Multiplexing Tradeoff (DMT) of the fading broadcast channel under a fixed weighted sum rate capacity constraint. The DMT of both identical and different parallel weighted MISO channels is first derived. Finally, we deduce the DMT of a broadcast channel using DPC and ZF precoders.

  5. L596-W733 bond between the start of the S4-S5 linker and the TRP box stabilizes the closed state of TRPV4 channel.

    Science.gov (United States)

    Teng, Jinfeng; Loukin, Stephen H; Anishkin, Andriy; Kung, Ching

    2015-03-17

    Unlike other cation channels, each subunit of most transient receptor potential (TRP) channels has an additional TRP-domain helix with an invariant tryptophan immediately trailing the gate-bearing S6. Recent cryo-electron microscopy of TRP vanilloid subfamily, member 1 structures revealed that this domain is a five-turn amphipathic helix, and the invariant tryptophan forms a bond with the beginning of the four-turn S4-S5 linker helix. By homology modeling, we identified the corresponding L596-W733 bond in TRP vanilloid subfamily, member 4 (TRPV4). The L596P mutation blocks bone development in Kozlowski-type spondylometaphyseal dysplasia in human. Our previous screen also isolated W733R as a strong gain-of-function (GOF) mutation that suppresses growth when the W733R channel is expressed in yeast. We show that, when expressed in Xenopus oocytes, TRPV4 with the L596P or W733R mutation displays normal depolarization-induced activation and outward rectification. However, these mutant channels have higher basal open probabilities and limited responses to the agonist GSK1016790A, explaining their biological GOF phenotypes. In addition, W733R current fails to inactivate during depolarization. Systematic replacement of W733 with amino acids of different properties produced similar electrophysiological and yeast phenotypes. The results can be interpreted consistently in the context of the homology model of TRPV4 molecule we have developed and refined using simulations in explicit medium. We propose that this bond maintains the orientation of the S4-S5 linker to keep the S6 gate closed. Further, the two partner helices, both amphipathic and located at the polar-nonpolar interface of the inner lipid monolayer, may receive and integrate various physiological stimuli.

  6. DMT of weighted Parallel Channels: Application to Broadcast Channel

    OpenAIRE

    Mroueh, Lina; Rouquette-Léveil, Stéphanie; Othman, Ghaya Rekaya-Ben; Belfiore, Jean-Claude

    2008-01-01

    In a broadcast channel with random packet arrival and transmission queues, the stability of the system is achieved by maximizing a weighted sum rate capacity with suitable weights that depend on the queue size. The weighted sum rate capacity using Dirty Paper Coding (DPC) and Zero Forcing (ZF) is asymptotically equivalent to the weighted sum capacity over parallel single-channels. In this paper, we study the Diversity Multiplexing Tradeoff (DMT) of the fading broadcast channel under a fixed w...

  7. Analysis of trafficking, stability and function of human connexin 26 gap junction channels with deafness-causing mutations in the fourth transmembrane helix.

    Directory of Open Access Journals (Sweden)

    Cinzia Ambrosi

    Full Text Available Human Connexin26 gene mutations cause hearing loss. These hereditary mutations are the leading cause of childhood deafness worldwide. Mutations in gap junction proteins (connexins can impair intercellular communication by eliminating protein synthesis, mis-trafficking, or inducing channels that fail to dock or have aberrant function. We previously identified a new class of mutants that form non-functional gap junction channels and hemichannels (connexons by disrupting packing and inter-helix interactions. Here we analyzed fourteen point mutations in the fourth transmembrane helix of connexin26 (Cx26 that cause non-syndromic hearing loss. Eight mutations caused mis-trafficking (K188R, F191L, V198M, S199F, G200R, I203K, L205P, T208P. Of the remaining six that formed gap junctions in mammalian cells, M195T and A197S formed stable hemichannels after isolation with a baculovirus/Sf9 protein purification system, while C202F, I203T, L205V and N206S formed hemichannels with varying degrees of instability. The function of all six gap junction-forming mutants was further assessed through measurement of dye coupling in mammalian cells and junctional conductance in paired Xenopus oocytes. Dye coupling between cell pairs was reduced by varying degrees for all six mutants. In homotypic oocyte pairings, only A197S induced measurable conductance. In heterotypic pairings with wild-type Cx26, five of the six mutants formed functional gap junction channels, albeit with reduced efficiency. None of the mutants displayed significant alterations in sensitivity to transjunctional voltage or induced conductive hemichannels in single oocytes. Intra-hemichannel interactions between mutant and wild-type proteins were assessed in rescue experiments using baculovirus expression in Sf9 insect cells. Of the four unstable mutations (C202F, I203T, L205V, N206S only C202F and N206S formed stable hemichannels when co-expressed with wild-type Cx26. Stable M195T hemichannels

  8. Effects of electric field and Coriolis force on electrohydrodynamic stability of poorly conducting couple stress parallel fluid flow in a channel

    International Nuclear Information System (INIS)

    The effective functioning of microfluidic devices in chemical, electrical and mechanical engineering involving fluidics particularly those having vibrations and petroleum products containing organic, inorganic and other microfluidics require understanding and control of stability of poorly conducting parallel fluid flows. The electrical conductivity, σ, of a poorly conducting fluidics, increases with the temperature and the concentration of freely suspended particles like RBC, WBC and so on in the blood, the hylauronic acid (HA) and nutrients of synovial fluid in synovial joints will spin producing microrotation, forming micropolar fluid of Eringen. The presence of Deuterium - Tritium (DT) in inertial fusion target (IFT) may also be modeled using micropolar fluid theory of Eringen. A particular case of micropolar fluid theory when microrotation balances with the natural vorticity of a poorly conducting fluidics in the presence of an electric field is called ‘electrohydrodynamic couple stress fluid’ (EHDCF). These EHDCFs exhibit a variation of electrical conductivity, ∇ σ, increasing with temperature and concentration of freely suspended particles, releases the charges from the nuclei forming distribution of charge density, ρe. These charges induce an electric field, 1Ei. If need be, we can apply an electric field, 1Ea, by embedding electrodes of different potentials at the boundaries. The total electric field, 1E = 1Ei + 1Ea, produces a current density, 1J = ρσ1E, according to Ohm’s law and also produces an electric force, 1Fσ = σ1E. This current 1J acts as sensing and the force, 1Fσ acts as actuation. These two properties make the poorly conducting couple stress fluid to act as a smart material. The objective of this paper is to show that EHDCV in presence of coriolis force plays a significant role in controlling the stability of parallel flows which is essential for an effective functioning of machineries that occur in practical mentioned above. A

  9. Flag flapping in a channel

    Science.gov (United States)

    Alben, Silas; Shoele, Kourosh; Mittal, Rajat; Jha, Sourabh; Glezer, Ari

    2015-11-01

    We study the flapping of a flag in an inviscid channel flow. We focus especially on how quantities vary with channel spacing. As the channel walls move inwards towards the flag, heavier flags become more unstable, while light flags' stability is less affected. We use a vortex sheet model to compute large-amplitude flapping, and find that the flag undergoes a series of jumps to higher flapping modes as the channel walls are moved towards the flag. Meanwhile, the drag on the flag and the energy lost to the wake first rise as the walls become closer, then drop sharply as the flag moves to a higher flapping mode.

  10. 西台吉乃尔盐湖采卤渠及周边稳定性分析%Analysis of the stability of brine channel and the surrounding in Xitaijinair Salt Lake

    Institute of Scientific and Technical Information of China (English)

    王涛; 李国荣; 朱海丽

    2015-01-01

    Salt lake chemical industry is the pillar industry in Qinghai province.Taking the Xitaiji-nair Salt Lake as an example,the stability of goaf in the salt lake was investigated.According to the corresponding parameters obtained by saline soil physical mechanics experiment,model was built by applying FLAC2D on the specific positions of the salt lake.Combining the model and field survey, the stability of the Xitaijinair Salt Lake brine channels is stable under the natural condition.%以西台吉乃尔盐湖为例,对盐湖开采后的采空区稳定性进行研究.通过盐湖盐渍土物理力学实验获取相应参数,应用FLAC2D对盐湖特定部位进行建模,结合实地考察对西台吉乃尔盐湖采卤渠及其周边稳定性进行分析,得出在自然情况下采空区处于稳定的结论.

  11. CHANNEL WIDENING DURING DEGRADATION OF ALLUVIAL RIVERS

    Institute of Scientific and Technical Information of China (English)

    Guangqian WANG; Junqiang XIA

    2001-01-01

    This paper first describes the phenomenon of channel widening during degradation of alluvial rivers,explains the mechanisms of channel widening, and analyzes the stability of cohesive riverbank. Then a one-dimensional mathematical model is developed to simulate the transport of non-uniform suspended sediments, with a sub-model for the simulation of channel widening, and is used to study the process of channel widening during degradation. The effects of different incident flow and sediment conditions and different riverbank material characteristics on channel widening and bed degradation are compared.Finally, main factors that control the deformation processes are identified.

  12. Brands & Channels

    Institute of Scientific and Technical Information of China (English)

    Alice Yang

    2009-01-01

    @@ "Brands" and "Channels" are the two most important things in Ku-Hai Chen's eyes when doing business with Main-land China. Ku-Hai Chen, Executive Director of the International Trade Institute of Taiwan External Trade Development Council (TAITRA), flies frequently between Chinese Taipei and Mainland China, and was in Beijing earlier this month for his seminar.

  13. Intra-membrane molecular interactions of K+ channel proteins :

    Energy Technology Data Exchange (ETDEWEB)

    Moczydlowski, Edward G.

    2013-07-01

    Ion channel proteins regulate complex patterns of cellular electrical activity and ionic signaling. Certain K+ channels play an important role in immunological biodefense mechanisms of adaptive and innate immunity. Most ion channel proteins are oligomeric complexes with the conductive pore located at the central subunit interface. The long-term activity of many K+ channel proteins is dependent on the concentration of extracellular K+; however, the mechanism is unclear. Thus, this project focused on mechanisms underlying structural stability of tetrameric K+ channels. Using KcsA of Streptomyces lividans as a model K+ channel of known structure, the molecular basis of tetramer stability was investigated by: 1. Bioinformatic analysis of the tetramer interface. 2. Effect of two local anesthetics (lidocaine, tetracaine) on tetramer stability. 3. Molecular simulation of drug docking to the ion conduction pore. The results provide new insights regarding the structural stability of K+ channels and its possible role in cell physiology.

  14. Channel Power in Multi-Channel Environments

    NARCIS (Netherlands)

    M.G. Dekimpe (Marnik); B. Skiera (Bernd)

    2004-01-01

    textabstractIn the literature, little attention has been paid to instances where companies add an Internet channel to their direct channel portfolio. However, actively managing multiple sales channels requires knowing the customers’ channel preferences and the resulting channel power. Two key compon

  15. Information geometry of Gaussian channels

    International Nuclear Information System (INIS)

    We define a local Riemannian metric tensor in the manifold of Gaussian channels and the distance that it induces. We adopt an information-geometric approach and define a metric derived from the Bures-Fisher metric for quantum states. The resulting metric inherits several desirable properties from the Bures-Fisher metric and is operationally motivated by distinguishability considerations: It serves as an upper bound to the attainable quantum Fisher information for the channel parameters using Gaussian states, under generic constraints on the physically available resources. Our approach naturally includes the use of entangled Gaussian probe states. We prove that the metric enjoys some desirable properties like stability and covariance. As a by-product, we also obtain some general results in Gaussian channel estimation that are the continuous-variable analogs of previously known results in finite dimensions. We prove that optimal probe states are always pure and bounded in the number of ancillary modes, even in the presence of constraints on the reduced state input in the channel. This has experimental and computational implications. It limits the complexity of optimal experimental setups for channel estimation and reduces the computational requirements for the evaluation of the metric: Indeed, we construct a converging algorithm for its computation. We provide explicit formulas for computing the multiparametric quantum Fisher information for dissipative channels probed with arbitrary Gaussian states and provide the optimal observables for the estimation of the channel parameters (e.g., bath couplings, squeezing, and temperature).

  16. Quartz Channel Fabrication for Electrokinetically Driven Separations

    Energy Technology Data Exchange (ETDEWEB)

    Arnold, D.W.; Ashby, C.I.H.; Bailey, C.G.; Kravitz, S.H., Warren, M.E.; Matzke, C.M.

    1998-12-01

    For well resolved electrokinetic separation, we L tilize crystalline quartz to micromachine a uniformly packe Q&iKLmnel. Packing features are posts 5 Vm on a side with:} pm spacing and etched 42 Vm deep. In addition to anisotropic wet etch characteristics for micromachining, quartz propmties are compatible with chemical soiutioits, ekctrokinetic high voltage operation, and stationary phase film depositions. To seal these channels, we employ a room temperature silicon-oxynhride deposition to forma membrane, that is subsequently coated for mechanical stability. Using this technique, particulate issues and global warp, that make large area wafer bon ding methods difficult, are avoided, and a room temperature process, in contrast to high temperature bonding techniques, accommodate preprocessing of metal films for electrical interconnect. After sealing channels, a number of macro-assembly steps are required to attach a micro-optical detection system and fluid interconnects. Keywords: microcharmel, integrated channel, micromachined channel, packed channel, electrokinetic channel, eleetrophoretic channel

  17. Channel Networks

    Science.gov (United States)

    Rinaldo, Andrea; Rodriguez-Iturbe, Ignacio; Rigon, Riccardo

    This review proceeds from Luna Leopold's and Ronald Shreve's lasting accomplishments dealing with the study of random-walk and topologically random channel networks. According to the random perspective, which has had a profound influence on the interpretation of natural landforms, nature's resiliency in producing recurrent networks and landforms was interpreted to be the consequence of chance. In fact, central to models of topologically random networks is the assumption of equal likelihood of any tree-like configuration. However, a general framework of analysis exists that argues that all possible network configurations draining a fixed area are not necessarily equally likely. Rather, a probability P(s) is assigned to a particular spanning tree configuration, say s, which can be generally assumed to obey a Boltzmann distribution: P(s) % e^-H(s)/T, where T is a parameter and H(s) is a global property of the network configuration s related to energetic characters, i.e. its Hamiltonian. One extreme case is the random topology model where all trees are equally likely, i.e. the limit case for T6 4 . The other extreme case is T 6 0, and this corresponds to network configurations that tend to minimize their total energy dissipation to improve their likelihood. Networks obtained in this manner are termed optimal channel networks (OCNs). Observational evidence suggests that the characters of real river networks are reproduced extremely well by OCNs. Scaling properties of energy and entropy of OCNs suggest that large network development is likely to effectively occur at zero temperature (i.e. minimizing its Hamiltonian). We suggest a corollary of dynamic accessibility of a network configuration and speculate towards a thermodynamics of critical self-organization. We thus conclude that both chance and necessity are equally important ingredients for the dynamic origin of channel networks---and perhaps of the geometry of nature.

  18. Opening the Shaker K+ channel with hanatoxin

    OpenAIRE

    Milescu, Mirela; Lee, Hwa C.; Bae, Chan Hyung; Kim, Jae Il; Swartz, Kenton J.

    2013-01-01

    Voltage-activated ion channels open and close in response to changes in membrane voltage, a property that is fundamental to the roles of these channels in electrical signaling. Protein toxins from venomous organisms commonly target the S1–S4 voltage-sensing domains in these channels and modify their gating properties. Studies on the interaction of hanatoxin with the Kv2.1 channel show that this tarantula toxin interacts with the S1–S4 domain and inhibits opening by stabilizing a closed state....

  19. Modeling of channel patterns in short tidal basins

    NARCIS (Netherlands)

    Marciano, R.; Wang, Z.B.; Hibma, A.; De Vriend, H.J.; Defina, A.

    2005-01-01

    We model branching channel patterns in short tidal basins with two methods. A theoretical stability analysis leads to a relationship between the number of channels and physical parameters of the tidal system. The analysis reveals that width and spacing of the channels should decrease as the slope of

  20. Channeling experiment

    International Nuclear Information System (INIS)

    Channeling of water flow and tracer transport in real fractures in a granite body at Stripa have been investigated experimentally. The experimental site was located 360 m below the ground level. Two kinds of experiments were performed. In the single hole experiments, 20 cm diameter holes were drilled about 2.5 m into the rock in the plane of the fracture. Specially designed packers were used to inject water into the fracture in 5 cm intervals all along the fracture trace in the hole. The variation of the injection flowrates along the fracture were used to determine the transmissivity variations in the fracture plane. Detailed photographs were taken from inside the hole and the visual fracture aperture was compared with the injection flowrates in the same locations. Geostatistical methods were used to evaluate the results. Five holes were measured in great detail. In addition 7 holes were drilled and scanned by simpler packer systems. A double hole experiment was performed where two parallel holes were drilled in the same fracture plane at nearly 2 m distance. Pressure pulse tests were made between the holes in both directions. Tracers were injected in 5 locations in one hole and monitored for in many locations in the other hole. The single hole experiment and the double hole experiment show that most of the fracture planes are tight but that there are open sections which form connected channels over distances of at least 2 meters. It was also found in the double hole experiment that the investigated fracture was intersected by at least one fracture between the two holes which diverted a large amount of the injected tracers to several distant locations at the tunnel wall. (authours)

  1. NONLINEAR STABILITY FOR EADY'S MODEL

    Institute of Scientific and Technical Information of China (English)

    LIU Yong-ming; QIU Ling-cun

    2005-01-01

    Poincaré type integral inequality plays an important role in the study of nonlinear stability ( in the sense of Arnold's second theorem) for three-dimensional quasigeostophic flow. The nonlinear stability of Eady's model is one of the most important cases in the application of the method. But the best nonlinear stability criterion obtained so far and the linear stability criterion are not coincident. The two criteria coincide only when the period of the channel is infinite.additional conservation law of momentum and by rigorous estimate of integral inequality. So the new nonlinear stability criterion was obtained, which shows that for Eady 's model in the periodic channel, the linear stable implies the nonlinear stable.

  2. Study on the sediment dynamics and stability of the Kushuiyang tidal channel at radial sand ridges in the southern Yellow Sea%南黄海辐射沙脊群苦水洋海域的沉积动力特征及稳定性研究

    Institute of Scientific and Technical Information of China (English)

    倪文斐; 汪亚平; 邹欣庆; 高建华

    2013-01-01

    Based on the data from hydrological observation and sediment sampling in Kushuiyang during a tide cycle from 3rd July 2011 to 4th July 2011, the water and sediment transport rates are calculated to specify the sediment dynamic characteristics along the tidal channel. The geomorphological evolution and stability of the channel are also discussed on the basis of the comparison between historic sea charts and new topographic surveys. The main results turn out that tidal currents are strong in the channel. Sediments are mainly transported in the form of suspended loads. The net transport direction is landward in the nearshore part of channel, while it is generally pointed seaward in the part of channel east of sand bank (121.606oE,33.029oN). Over the past thirty years, the deep trough of west Kushuiyang channel has gradually connected to the north part of channel, leading the whole channel to be straighter.%根据2011年7月3日-4日在苦水洋海域获取的全潮水文资料和底质样品,计算潮周期水、沙输运率,分析了其沉积动力特征。基于1979年历史海图资料与最新测量的水道地形进行对比,进一步探讨苦水洋水道的地形演变过程及稳定性。结果表明,苦水洋潮流作用较强,水道内沉积物主要以悬移质形式输运,在近岸段沿水道向岸净输沙,但在(121.606º E,33.029ºN)以东以向海输运为主。近三十多年来,苦水洋西水道深槽与口门北水道逐渐贯通,水道整体趋于顺直。

  3. Cable Stability

    CERN Document Server

    Bottura, L

    2014-01-01

    Superconductor stability is at the core of the design of any successful cable and magnet application. This chapter reviews the initial understanding of the stability mechanism, and reviews matters of importance for stability such as the nature and magnitude of the perturbation spectrum and the cooling mechanisms. Various stability strategies are studied, providing criteria that depend on the desired design and operating conditions.

  4. Channel strategy adaptation

    OpenAIRE

    Rangan, V. Kasturi; Nueno, Jose L

    1999-01-01

    Using transaction cost theory, considerable research in marketing has focused on the conditions under which firms would use direct or vertically integrated versus indirect or arms length channels of distribution. Data from the field, however, indicate that channel configurations are more varied and complex, with multiple channels and composite channels being just as common as direct and indirect channels. In an attempt to explain this variety, this paper revisits the influence on channel stru...

  5. River channel adjustments in Southern Italy over the past 150 years and implications for channel recovery

    Science.gov (United States)

    Scorpio, Vittoria; Aucelli, Pietro P. C.; Giano, Salvatore I.; Pisano, Luca; Robustelli, Gaetano; Rosskopf, Carmen M.; Schiattarella, Marcello

    2015-12-01

    Multi-temporal GIS analysis of topographic maps and aerial photographs along with topographic and geomorphological surveys are used to assess evolutionary trends and key control factors of channel adjustments for five major rivers in southern Italy (the Trigno, Biferno, Volturno, Sinni and Crati rivers) to support assessment of channel recovery and river restoration. Three distinct phases of channel adjustment are identified over the past 150 years primarily driven by human disturbances. Firstly, slight channel widening dominated from the last decades of the nineteenth century to the 1950s. Secondly, from the 1950s to the end of the 1990s, altered sediment fluxes induced by in-channel mining and channel works brought about moderate to very intense incision (up to 6-7 m) accompanied by strong channel narrowing (up to 96%) and changes in channel configuration from multi-threaded to single-threaded patterns. Thirdly, the period from around 2000 to 2015 has been characterized by channel stabilization and local widening. Evolutionary trajectories of the rivers studied are quite similar to those reconstructed for other Italian rivers, particularly regarding the second phase of channel adjustments and ongoing transitions towards channel recovery in some reaches. Analyses of river dynamics, recovery potential and connectivity with sediment sources of the study reaches, framed in their catchment context, can be used as part of a wider interdisciplinary approach that views effective river restoration alongside sustainable and risk-reduced river management.

  6. Dual Turbo MIMO-OFDM Channel Estimation Based on Puncher Technique via UWA Channels

    Directory of Open Access Journals (Sweden)

    Gang Qiao

    2013-02-01

    Full Text Available In this study, various techniques of UWA (Underwater Acoustic, UWA channel estimation for underwater MIMO-OFDM system are studied. Dual turbo channel estimation algorithm based on channel puncture technique is proposed. In order to judge the criteria of channel compensation, difference between the raw received signal and the re-coded information signal is carried out. The uncertain sub-channels are punched by using channel puncture technique and replaced by the responses estimated by MMSE (Minimum Mean Square Error, MMSE or OMP (Orthogonal Matching Pursuit, OMP algorithms. Compared with the conventional existing algorithms, the proposed algorithm can effectively reduce the occupancy of pilots, offer confined error propagation and significantly increase the stability of the system with Monte Caro simulation. The results of in-tank-experiment further indorse the reliable performance with improved efficiency of 1.51 bits/s/Hz.

  7. Mobile radio channels

    CERN Document Server

    Pätzold, Matthias

    2011-01-01

    Providing a comprehensive overview of the modelling, analysis and simulation of mobile radio channels, this book gives a detailed understanding of fundamental issues and examines state-of-the-art techniques in mobile radio channel modelling. It analyses several mobile fading channels, including terrestrial and satellite flat-fading channels, various types of wideband channels and advanced MIMO channels, providing a fundamental understanding of the issues currently being investigated in the field. Important classes of narrowband, wideband, and space-time wireless channels are explored in deta

  8. Impacts of salt marsh plants on tidal channel initiation and inheritance

    Science.gov (United States)

    Schwarz, C.; Ye, Q. H.; Wal, D.; Zhang, L. Q.; Bouma, T.; Ysebaert, T.; Herman, P. M. J.

    2014-02-01

    At the transition between mudflat and salt marsh, vegetation is traditionally regarded as a sustaining factor for previously incised mudflat channels, able to conserve the channel network via bank stabilization following plant colonization (i.e., vegetation-stabilized channel inheritance). This is in contrast to recent studies revealing vegetation as the main driver of tidal channel emergence through vegetation-induced channel erosion. We present a coupled hydrodynamic morphodynamic plant growth model to simulate plant expansion and channel formation by our model species (Spartina alterniflora) during a mudflat-salt marsh transition with various initial bathymetries (flat, shoal dense, shoal sparse, and deep dense channels). This simulated landscape development is then compared to remote sensing images of the Yangtze estuary, China, and the Scheldt estuary in Netherlands. Our results propose the existence of a threshold in preexisting mudflat channel depth, which favors either vegetation-stabilized channel inheritance or vegetation-induced channel erosion processes. The increase in depth of preexisting mudflat channels favors flow routing through them, consequently leaving less flow and momentum remaining for vegetation-induced channel erosion processes. This threshold channel depth will be influenced by field specific parameters such as hydrodynamics (tidal range and flow), sediment characteristics, and plant species. Hence, our study shows that the balance between vegetation-stabilized channel inheritance and vegetation-induced channel erosion depends on ecosystem properties.

  9. Channel nut tool

    Energy Technology Data Exchange (ETDEWEB)

    Olson, Marvin

    2016-01-12

    A method, system, and apparatus for installing channel nuts includes a shank, a handle formed on a first end of a shank, and an end piece with a threaded shaft configured to receive a channel nut formed on the second end of the shaft. The tool can be used to insert or remove a channel nut in a channel framing system and then removed from the channel nut.

  10. Localized Algorithm for Channel Assignment in Cognitive Radio Networks

    Directory of Open Access Journals (Sweden)

    Harpreet Kaur

    2015-12-01

    Full Text Available Cognitive Radio has been emerged as a revolutionary solution to migrate the current shortage of spectrum allocation in wireless networks. In this paper, an improved localized channel allocation algorithm based on channel weight is proposed. A factor of channel stability is introduced based on link environment, which efficiently assigns the best channels to the links. Based on the framework, a conflict resolution strategy is used to make the scheme adaptable to different network conditions. Calculations indicate that this algorithm can reduce the conflicts, increase the delivery rate and link assignment rate compared with the basic channel assignment algorithm.

  11. The Earliest Ion Channels

    Science.gov (United States)

    Pohorille, A.; Wilson, M. A.; Wei, C.

    2009-12-01

    Supplying protocells with ions required assistance from channels spanning their membrane walls. The earliest channels were most likely short proteins that formed transmembrane helical bundles surrounding a water-filled pore. These simple aggregates were capable of transporting ions with efficiencies comparable to those of complex, contemporary ion channels. Channels with wide pores exhibited little ion selectivity but also imposed only modest constraints on amino acid sequences of channel-forming proteins. Channels with small pores could have been selective but also might have required a more precisely defined sequence of amino acids. In contrast to modern channels, their protocellular ancestors had only limited capabilities to regulate ion flux. It is postulated that subsequent evolution of ion channels progressed primarily to acquire precise regulation, and not high efficiency or selectivity. It is further proposed that channels and the surrounding membranes co-evolved.

  12. Gramicidin Channels: Versatile Tools

    Science.gov (United States)

    Andersen, Olaf S.; Koeppe, Roger E., II; Roux, Benoît

    Gramicidin channels are miniproteins in which two tryptophan-rich subunits associate by means of transbilayer dimerization to form the conducting channels. That is, in contrast to other ion channels, gramicidin channels do not open and close; they appear and disappear. Each subunit in the bilayer-spanning channel is tied to the bilayer/solution interface through hydrogen bonds that involve the indole NH groups as donors andwater or the phospholipid backbone as acceptors. The channel's permeability characteristics are well-defined: gramicidin channels are selective for monovalent cations, with no measurable permeability to anions or polyvalent cations; ions and water move through a pore whose wall is formed by the peptide backbone; and the single-channel conductance and cation selectivity vary when the amino acid sequence is varied, even though the permeating ions make no contact with the amino acid side chains. Given the plethora of available experimental information—for not only the wild-type channels but also for channels formed by amino acid-substituted gramicidin analogues—gramicidin channels continue to provide important insights into the microphysics of ion permeation through bilayer-spanning channels. For similar reasons, gramicidin channels constitute a system of choice for evaluating computational strategies for obtaining mechanistic insights into ion permeation through the more complex channels formed by integral membrane proteins.

  13. Multi-Channel Retailing

    Directory of Open Access Journals (Sweden)

    Dirk Morschett, Dr.,

    2005-01-01

    Full Text Available Multi-channel retailing entails the parallel use by retailing enterprises of several sales channels. The results of an online buyer survey which has been conducted to investigate the impact of multi-channel retailing (i.e. the use of several retail channels by one retail company on consumer behaviour show that the frequently expressed concern that the application of multi-channel systems in retailing would be associated with cannibalization effects, has proven unfounded. Indeed, the appropriate degree of similarity, consistency, integration and agreement achieves the exact opposite. Different channels create different advantages for consumers. Therefore the total benefit an enterprise which has a multi-channel system can offer to its consumers is larger, the greater the number of available channels. The use of multi-channel systems is associated with additional purchases in the different channels. Such systems are thus superior to those offering only one sales channel to their customers. Furthermore, multi-channel systems with integrated channels are superior to those in which the channels are essentially autonomous and independent of one another. In integrated systems, consumers can achieve synergy effects in the use of sales-channel systems. Accordingly, when appropriately formulated, multi-channel systems in retailing impact positively on consumers. They use the channels more frequently, buy more from them and there is a positive customer-loyalty impact. Multi-channel systems are strategic options for achieving customer loyalty, exploiting customer potential and for winning new customers. They are thus well suited for approaching differing and varied target groups.

  14. Channel guiding for advanced accelerators

    Energy Technology Data Exchange (ETDEWEB)

    Milchberg, H.M. [Institute for Physical Science and Technology (United States); Durfee, C.G. III [Institute for Physical Science and Technology (United States); Antonsen, T.M. [Institute for Plasma Research, University of Maryland, College Park, Maryland, (United States) 20742; Mora, P. [Centre de Physique Theorique, Ecole Polytechnique, 91128 Palaiseau (France)

    1996-02-01

    The recent demonstration of optical guiding of high intensity laser pulses in plasma waveguides [C. G. Durfee III and H. M. Milchberg, Phys. Rev. Lett 71, 2409 (1993)] has opened the way to new advances in the development of compact laser-driven electron particle accelerators. We review plasma waveguide properties relevant to intense pulse guiding and electron acceleration and show that the shock driven channels described here are well suited for stabilization of a large class of laser-plasma instabilities deleterious to high intensity guiding over long distances. {copyright} {ital 1996 American Institute of Physics.}

  15. Calcium channel blocker overdose

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/article/002580.htm Calcium channel blocker overdose To use the sharing features on this page, please enable JavaScript. Calcium channel blockers are a type of medicine used ...

  16. Flag flutter in inviscid channel flow

    CERN Document Server

    Alben, Silas

    2014-01-01

    Using nonlinear vortex-sheet simulations, we determine the region in parameter space in which a straight flag in a channel-bounded inviscid flow is unstable to flapping motions. We find that for heavier flags, greater confinement increases the size of the region of instability. For lighter flags, confinement has little influence. We then compute the stability boundaries analytically for an infinite flag, and find similar results. For the finite flag we also consider the effect of channel walls on the large-amplitude periodic flapping dynamics. We find that multiple flapping states are possible but rare at a given set of parameters, when periodic flapping occurs. As the channel walls approach the flag, its flapping amplitude decreases roughly in proportion to the near-wall distance, for both symmetric and asymmetric channels. Meanwhile, its dominant flapping frequency and mean number of deflection extrema (or "wavenumber") increase in a nearly stepwise fashion. That is, they remain nearly unchanged over a wide...

  17. Dynamic channel allocation

    OpenAIRE

    Kaminsky, Andrew D.

    2003-01-01

    Approved for public release; distribution in unlimited. Dynamic Channel Allocation (DCA) offers the possibility of capturing unused channel capacity by allocating unused resources between competing network nodes. This can reduce or possibly eliminate channels sitting idle while information awaits transmission. This holds potential for increasing throughput on bandwidth constrained networks. The purpose of this thesis is to examine the techniques used to allocate channels on demand and acc...

  18. A Micromechanical RF Channelizer

    Science.gov (United States)

    Akgul, Mehmet

    The power consumption of a radio generally goes as the number and strength of the RF signals it must process. In particular, a radio receiver would consume much less power if the signal presented to its electronics contained only the desired signal in a tiny percent bandwidth frequency channel, rather than the typical mix of signals containing unwanted energy outside the desired channel. Unfortunately, a lack of filters capable of selecting single channel bandwidths at RF forces the front-ends of contemporary receivers to accept unwanted signals, and thus, to operate with sub-optimal efficiency. This dissertation focuses on the degree to which capacitive-gap transduced micromechanical resonators can achieve the aforementioned RF channel-selecting filters. It aims to first show theoretically that with appropriate scaling capacitive-gap transducers are strong enough to meet the needed coupling requirements; and second, to fully detail an architecture and design procedure needed to realize said filters. Finally, this dissertation provides an actual experimentally demonstrated RF channel-select filter designed using the developed procedures and confirming theoretical predictions. Specifically, this dissertation introduces four methods that make possible the design and fabrication of RF channel-select filters. The first of these introduces a small-signal equivalent circuit for parallel-plate capacitive-gap transduced micromechanical resonators that employs negative capacitance to model the dependence of resonance frequency on electrical stiffness in a way that facilitates the analysis of micromechanical circuits loaded with arbitrary electrical impedances. The new circuit model not only correctly predicts the dependence of electrical stiffness on the impedances loading the input and output electrodes of parallel-plate capacitive-gap transduced micromechanical device, but does so in a visually intuitive way that identifies current drive as most appropriate for

  19. Desynched channels on IRCnet

    CERN Document Server

    Hansen, Michael

    2008-01-01

    In this paper we describe what a desynchronised channel on IRC is. We give procedures on how to create such a channel and how to remove desynchronisation. We explain which types of desynchronisation there are, what properties desynchronised channels have, and which properties can be exploited.

  20. Quantum Binary Symmetric Channels

    Institute of Scientific and Technical Information of China (English)

    陈小余; 仇佩亮

    2001-01-01

    Quantum binary symmetric channels are defined via the invariance of fidelity under unitary transformations ofthe input density operators. In this definition, they not only include the most studied case of the depolarizingchannel but also other channels. We investigate the character of the latter and find the maximum of the coherentinformation to estimate the capacities of the channels.

  1. Quantum Multiple Access Channel

    Institute of Scientific and Technical Information of China (English)

    侯广; 黄民信; 张永德

    2002-01-01

    We consider the transmission of classical information over a quantum channel by many senders, which is a generalization of the two-sender case. The channel capacity region is shown to be a convex hull bound by the yon Neumann entropy and the conditional yon Neumann entropies. The result allows a reasonable distribution of channel capacity over the senders.

  2. Cardiac potassium channel subtypes

    DEFF Research Database (Denmark)

    Schmitt, Nicole; Grunnet, Morten; Olesen, Søren-Peter

    2014-01-01

    About 10 distinct potassium channels in the heart are involved in shaping the action potential. Some of the K(+) channels are primarily responsible for early repolarization, whereas others drive late repolarization and still others are open throughout the cardiac cycle. Three main K(+) channels...

  3. KV7 potassium channels

    DEFF Research Database (Denmark)

    Stott, Jennifer B; Jepps, Thomas Andrew; Greenwood, Iain A

    2014-01-01

    Potassium channels are key regulators of smooth muscle tone, with increases in activity resulting in hyperpolarisation of the cell membrane, which acts to oppose vasoconstriction. Several potassium channels exist within smooth muscle, but the KV7 family of voltage-gated potassium channels have been...

  4. Stability performance of the SBWR

    International Nuclear Information System (INIS)

    The stability of boiling water reactors (BWRs) has been a consideration of designers, operators, and regulators since the start-up of early BWRs. Recently, instability phenomena of two different modes (corewide oscillations and regional oscillations) were observed in several BWR plants. These raised additional concerns related to BWR stability. For the simplified BWR (SBWR) design, the approach is to eliminate instability as a concern by assuring a large margin to the stability limits. A conservative set of stability criteria (core decay ratio ≤ 0.4 and channel decay ratio ≤ 0.3 for all expected steady-state operating conditions and moderate frequency transients) is imposed on the SBWR design. During the initial SBWR design, engineering judgment based on operating experience was relied on to select plant parameters that have significant effects on reactor stability. A comparison between the SBWR design and an operating BWR, which had stability test data available, to show that the SBWR design is thermal-hydraulically stable was performed to illustrate this process. After the design was selected, stability analysis was performed to confirm whether the stability criteria had been met. Several iterations were required to obtain the optimal SBWR design. This paper presents a qualitative comparison between the SBWR design and an operating BWR, and the SBWR stability performance as analyzed by a frequency domain code and a three-dimensional thermal-hydraulic code, TRACG

  5. 长江河口南港采砂对河床稳定性的影响%The Effect of Sand Digging to Bedfrom Stability of the Nangang Channel in the Changjiang River Mouth

    Institute of Scientific and Technical Information of China (English)

    李茂田; 程和琴; 周丰年; 吴敬文; 李伯昌

    2011-01-01

    利用多波束测深及数字高程模型技术发现:南港主槽有若干长50~100m,深3~5m的采砂坑;瑞丰沙体南侧存在高0.5~1.2m,长约1800m的两级陡坎,陡坎下有长1850m、宽400m、体积124.5万立方米的滑坡体.近8年来,瑞丰沙冲刷减少3724万立方米.采砂坑、陡坎与滑坡体形成的主要受采砂及其引起的瑞丰沙顶部水沙通量调整控制,采砂引起瑞丰沙顶部过水断面增加8240m2,涨潮从南小泓分流0.96亿立方米,落潮从南港主槽分流1.43亿立方米.%According to the bed-form data measured by multi-beam echo-sounding system (MBES) and digital elevation model (DEM), this parer is to examine the impacts of pumping-sand on the river bed-form evolution of the Nangang Channel in the Changjiang River mouth. The results is that there were 5 huge sandpits with 50-100m long and 3-5m depth,2 ranges steep ridge with 1800m long and 0.5-1.2m high and 1 huge landslide with 1850m long and 400m wide in Ruifeng shoal edge nearly sandpits in the Nangang Channel ,and the volume of landslide reached 1.245 × 106m3. Furthermore, our data have further demonstrated such bed-from evolutions mainly resulted from human pumping-sand. Reifeng shoal were obviously eroded and the volume decreased 3.724×107m3 recently 8years. It decreased 8240m2 of longitudinal profile area of the middle Ruifeng shoal,and that resulted in water discharge increasing separately 0.966×l08m3 in flood tide and 1.43× 108 m3 in ebb tide.

  6. On 1-qubit channels

    OpenAIRE

    Uhlmann, Armin

    2000-01-01

    The entropy H_T(rho) of a state rho with respect to a channel T and the Holevo capacity of the channel require the solution of difficult variational problems. For a class of 1-qubit channels, which contains all the extremal ones, the problem can be significantly simplified by associating an Hermitian antilinear operator theta to every channel of the considered class. The concurrence of the channel can be expressed by theta and turns out to be a flat roof. This allows to write down an explicit...

  7. On 1-qubit channels

    CERN Document Server

    Uhlmann, A

    2001-01-01

    The entropy H_T(rho) of a state rho with respect to a channel T and the Holevo capacity of the channel require the solution of difficult variational problems. For a class of 1-qubit channels, which contains all the extremal ones, the problem can be significantly simplified by associating an Hermitian antilinear operator theta to every channel of the considered class. The concurrence of the channel can be expressed by theta and turns out to be a flat roof. This allows to write down an explicit expression for H_T. Its maximum would give the Holevo (1-shot) capacity.

  8. Source and Channel Coding for Correlated Sources Over Multiuser Channels

    OpenAIRE

    Gunduz, Deniz; Erkip, Elza; Goldsmith, Andrea; Poor, H. Vincent

    2008-01-01

    Source and channel coding over multiuser channels in which receivers have access to correlated source side information is considered. For several multiuser channel models necessary and sufficient conditions for optimal separation of the source and channel codes are obtained. In particular, the multiple access channel, the compound multiple access channel, the interference channel and the two-way channel with correlated sources and correlated receiver side information are considered, and the o...

  9. C. elegans TRP channels.

    Science.gov (United States)

    Xiao, Rui; Xu, X Z Shawn

    2011-01-01

    Transient receptor potential (TRP) channels represent a superfamily of cation channels found in all eukaryotes. The C. elegans genome encodes seventeen TRP channels covering all of the seven TRP subfamilies. Genetic analyses in C. elegans have implicated TRP channels in a wide spectrum of behavioral and physiological processes, ranging from sensory transduction (e.g. chemosensation, touch sensation, proprioception and osmosensation) to fertilization, drug dependence, organelle biogenesis, apoptosis, gene expression, and neurotransmitter/hormone release. Many C. elegans TRP channels share similar activation and regulatory mechanisms with their vertebrate counterparts. Studies in C. elegans have also revealed some previously unrecognized functions and regulatory mechanisms of TRP channels. C. elegans represents an excellent genetic model organism for the study of function and regulation of TRP channels in vivo. PMID:21290304

  10. Ensuring Stability

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    "Stable"will be a key word for China’s economy in 2012.That’s the beat set at the annual Central Economic Work Conference held in Beijing on December 12-14,which reviewed this year’s development and mapped out plans for the next year.Policymakers at the conference decided to keep macroeconomic policies stable,seek a stable and relatively fast economic growth,stabilize consumer prices and maintain social stability in 2012.On the basis of stability,the government will transform the development model,deepen reform and improve people’s livelihood.

  11. Against Stabilization

    Directory of Open Access Journals (Sweden)

    Roger Mac Ginty

    2012-11-01

    Full Text Available This is a polemic against the concept and practice of stabilization as practiced by leading states from the global north in peace support interventions. It is not an argument against stability. Instead, it depicts stabilization as an essentially conservative doctrine that runs counter to its stated aims of enhancing local participation and legitimacy. It is an agenda of control that privileges notions of assimilation with international (western standards and mainstreams the military into peace-support operations. As a result, the value of peace is undercut.

  12. Frequency Dependence of Measured Massive MIMO Channel Properties

    DEFF Research Database (Denmark)

    Oliveras Martínez, Àlex; Carvalho, Elisabeth De; Nielsen, Jesper Ødum;

    2016-01-01

    A multi-user massive MIMO measurement campaign is conducted to study the channel propagation characteristics (e.g. user correlation, sum of eigenvalues and condition number), focusing on the stability over frequencies and the impact of the array aperture. We use 3 arrays with 64 antennas (6m linear...... array, 2m linear array and 25cm by 28cm squared 2D array) serving 8 users holding a handset with 2 antennas. The study of the measurements shows that the propagation characteristics of the channel are stable for all the measured frequencies. We also observe that user proximity and user handgrip...... stabilize the studied properties of the channel across the frequencies, and in such case the larger the aperture of the array the more stable the properties. The number of base station antennas improves the propagation characteristics of the channel and stabilizes the properties in the frequency domain....

  13. Compound Wiretap Channels

    Directory of Open Access Journals (Sweden)

    Kramer Gerhard

    2009-01-01

    Full Text Available Abstract This paper considers the compound wiretap channel, which generalizes Wyner's wiretap model to allow the channels to the (legitimate receiver and to the eavesdropper to take a number of possible states. No matter which states occur, the transmitter guarantees that the receiver decodes its message and that the eavesdropper is kept in full ignorance about the message. The compound wiretap channel can also be viewed as a multicast channel with multiple eavesdroppers, in which the transmitter sends information to all receivers and keeps the information secret from all eavesdroppers. For the discrete memoryless channel, lower and upper bounds on the secrecy capacity are derived. The secrecy capacity is established for the degraded channel and the semideterministic channel with one receiver. The parallel Gaussian channel is further studied. The secrecy capacity and the secrecy degree of freedom ( are derived for the degraded case with one receiver. Schemes to achieve the for the case with two receivers and two eavesdroppers are constructed to demonstrate the necessity of a prefix channel in encoder design. Finally, the multi-antenna (i.e., MIMO compound wiretap channel is studied. The secrecy capacity is established for the degraded case and an achievable is given for the general case.

  14. Compound Wiretap Channels

    Directory of Open Access Journals (Sweden)

    Shlomo Shamai (Shitz

    2009-01-01

    Full Text Available This paper considers the compound wiretap channel, which generalizes Wyner's wiretap model to allow the channels to the (legitimate receiver and to the eavesdropper to take a number of possible states. No matter which states occur, the transmitter guarantees that the receiver decodes its message and that the eavesdropper is kept in full ignorance about the message. The compound wiretap channel can also be viewed as a multicast channel with multiple eavesdroppers, in which the transmitter sends information to all receivers and keeps the information secret from all eavesdroppers. For the discrete memoryless channel, lower and upper bounds on the secrecy capacity are derived. The secrecy capacity is established for the degraded channel and the semideterministic channel with one receiver. The parallel Gaussian channel is further studied. The secrecy capacity and the secrecy degree of freedom (s.d.o.f. are derived for the degraded case with one receiver. Schemes to achieve the s.d.o.f. for the case with two receivers and two eavesdroppers are constructed to demonstrate the necessity of a prefix channel in encoder design. Finally, the multi-antenna (i.e., MIMO compound wiretap channel is studied. The secrecy capacity is established for the degraded case and an achievable s.d.o.f. is given for the general case.

  15. Channel capacity and error exponents of variable rate adaptive channel coding for Rayleigh fading channels

    OpenAIRE

    Lau, KN

    1999-01-01

    We have evaluated the information theoretical performance of variable rate adaptive channel coding for Rayleigh fading channels. The channel states are detected at the receiver and fed back to the transmitter by means of a noiseless feedback link. Based on the channel state informations, the transmitter can adjust the channel coding scheme accordingly. Coherent channel and arbitrary channel symbols with a fixed average transmitted power constraint are assumed. The channel capacity and the err...

  16. Quantum broadcast channels

    CERN Document Server

    Yard, J; Devetak, I; Yard, Jon; Hayden, Patrick; Devetak, Igor

    2006-01-01

    We analyze quantum broadcast channels, which are quantum channels with a single sender and many receivers. Focusing on channels with two receivers for simplicity, we generalize a number of results from the network Shannon theory literature which give the rates at which two senders can receive a common message, while a personalized one is sent to one of them. Our first collection of results applies to channels with a classical input and quantum outputs. The second class of theorems we prove concern sending a common classical message over a quantum broadcast channel, while sending quantum information to one of the receivers. The third group of results we obtain concern communication over an isometry, giving the rates at quantum information can be sent to one receiver, while common quantum information is sent to both, in the sense that tripartite GHZ entanglement is established. For each scenario, we provide an additivity proof for an appropriate class of channels, yielding single-letter characterizations of the...

  17. HIPPI and Fibre Channel

    International Nuclear Information System (INIS)

    The High-Performance Parallel Interface (HIPPI) and Fibre Channel are near-gigabit per second data communications interfaces being developed in ANSI standards Task Group X3T9.3. HIPPI is the current interface of choice in the high-end and supercomputer arena, and Fibre Channel is a follow-on effort. HIPPI came from a local area network background, and Fibre Channel came from a mainframe to peripheral interface background

  18. Stabilization of networked control systems over signal-to-noise ratio constrained channels%基于信噪比受限通道的网络控制系统镇定

    Institute of Scientific and Technical Information of China (English)

    邓玮璍; 费敏锐; 杜大军; 宋杨

    2012-01-01

    This paper investigates the problem of stabilization for linear system considering communication and network characteristics together. Firstly, the minimal signal-to-noise ratios(SNRs) required for stabilisability are obtained in continuous-time networked control system(NCS) with varying delay by using linear matrix inequality(LMI) approach. Then the similar results are extended to a kind of discrete-time heterogeneous networked control system. The proposed multisensors stochastic delays model which is more practical can depict the characteristic of token-passing bus control network. Finally, the above theories are tested by numerical examples, and relations among unstable poles, delays and SNRs are illustrated explicitly.%研究了同时考虑通信和网络特性的线性系统镇定问题.首先针对连续时间网络控制系统,使用线性矩阵不等式方法得到了系统镇定所需要的最小信噪比;然后将问题推广到一类更为复杂的离散时间异构网络控制系统并得到了相似的结论.其中建立的多传感器随机时滞模型很好地刻画了token—passing总线控制网络,它更具有实际意义;最后通过数值例子对以上理论进行了仿真验证,有效表明了系统镇定时被控对象不稳定极点、网络时滞和信噪比之间的关系.

  19. On Nonlinear Stability Theorems of 3D Quasi-geostrophic Flow

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Nonlinear stability criteria for quasi-geostrophic zonally symmetric flow are improved by establishing an invariant of zonal momentum. When applied to the Eady model in a periodic channel with finite zonal length, the improved nonlinear stability criterion is identical to the linear normal-mode stability criterion provided the channel meridional width is no greater than 0.8605... times its channel length (which is the geophysically relevant case).

  20. Ponderomotive laser channelling and multi-channelling in homogeneous underdense plasma

    CERN Document Server

    Naseri, Neda; Rozmus, Wojciech

    2016-01-01

    We have studied laser pulse channeling in underdense plasma by means of analytical theory and 3D PIC simulations. The most significant result of this paper is the demonstration of the single fully evacuated stationary channel solution can be reached an asymptotic state in PIC simulations. In the lower density and for a laser power above channeling power, we were able to reproduce in PIC simulations the analytical curve. We showed that single channels are stable structures against symmetric perturbations. We also studied the formation of the ring structure in theory and simulations. An evacuated ring enclosed by an electron filament was observed in our 3D simulations. However they always coexist with the main laser mode. The threshold power for ring structure formation is found. Our studies on stability of the rings against asymmetric perturbations show that ring structure is not stable against azimuthal perturbations. The growth rate of the instability is shorter for higher densities and it is therefore more ...

  1. A linearization of quantum channels

    Science.gov (United States)

    Crowder, Tanner

    2015-06-01

    Because the quantum channels form a compact, convex set, we can express any quantum channel as a convex combination of extremal channels. We give a Euclidean representation for the channels whose inverses are also valid channels; these are a subset of the extreme points. They form a compact, connected Lie group, and we calculate its Lie algebra. Lastly, we calculate a maximal torus for the group and provide a constructive approach to decomposing any invertible channel into a product of elementary channels.

  2. PARALLEL STABILIZATION

    Institute of Scientific and Technical Information of China (English)

    J.L.LIONS

    1999-01-01

    A new algorithm for the stabilization of (possibly turbulent, chaotic) distributed systems, governed by linear or non linear systems of equations is presented. The SPA (Stabilization Parallel Algorithm) is based on a systematic parallel decomposition of the problem (related to arbitrarily overlapping decomposition of domains) and on a penalty argument. SPA is presented here for the case of linear parabolic equations: with distrjbuted or boundary control. It extends to practically all linear and non linear evolution equations, as it will be presented in several other publications.

  3. RFI channels, 2

    Science.gov (United States)

    Mceliece, R. J.

    1981-01-01

    The cutoff parameters for a class of channel models exhibiting burst noise behavior were calculated and the performance of interleaved coding strategies was evaluated. It is concluded that, provided the channel memory is large enough and is properly exploited, interleaved coding is nearly optimal.

  4. Channelling versus inversion

    DEFF Research Database (Denmark)

    Gale, A.S.; Surlyk, Finn; Anderskouv, Kresten

    2013-01-01

    . Within this channel were smaller erosional structures (<10 m deep) that truncate originally horizontal bedding, are floored by hardgrounds, and locally have a basal fill of granular phosphorite. The entire channel system was progressively infilled by chalk, as demonstrated by the expanded succession of...... the lower Campanian Culver Chalk Formation. The beds of the channel fill are cut by small step faults, resulting from gravitational collapse. Complete burial had taken place by the base of the upper Campanian Portsdown Chalk Formation, which is of even thickness across the region. The structures are......Evidence from regional stratigraphical patterns in Santonian−Campanian chalk is used to infer the presence of a very broad channel system (5 km across) with a depth of at least 50 m, running NNW−SSE across the eastern Isle of Wight; only the western part of the channel wall and fill is exposed...

  5. Stabilizing Movements

    DEFF Research Database (Denmark)

    Norbäck, Maria; Helin, Jenny; Raviola, Elena

    2014-01-01

    of turbulent times. Departing from a process perspective to organizational change and insights from Bakhtin's notion of ‘double-voicing’, which means that people borrow other people's words in their own talk, two main contributions are offered. First, we show how stability cannot be taken for granted...

  6. Before Stabilization

    DEFF Research Database (Denmark)

    Plesner, Ursula; Horst, Maja

    2013-01-01

    to the literature on the relationship between ICTs and organizing, but with a distinct focus on innovation communication and distributed innovation processes taking place before ICTs are stabilized, issues which cannot be captured by studies of diffusion and adaptation of new ICTs within single organizations....

  7. Macroeconomic stability

    DEFF Research Database (Denmark)

    Jespersen, Jesper

    2004-01-01

    It is demonstrated that full employment and sustainable development not necessarily are conflicting goals. On the other hand macroeconomic stability cannot be obtained without a deliberate labour sharing policy and a shift in the composition of private consumption away from traditional material...

  8. Beam Stability at the Advanced Photon Source

    CERN Document Server

    Decker, Glenn

    2005-01-01

    The Advanced Photon Source has been in operation since 1996. Since that time, extensive incremental improvements to orbit stabilization systems have been made. This includes the addition of 80 channels of narrowband rf beam position monitors (bpm's), 40 channels of bending magnet photon bpm's, and most recently the inclusion of 36 insertion device photon bpm's into the orbit correction response matrix. In addition, considerable improvements have been made in the area of power supply regulation, both for the main multipole magnets and the steering corrector magnets. The present status of overall performance will be discussed, including long term pointing stability, reproducibility, and AC beam motion.

  9. Controlled beta-quenching of fuel channels using inert gas

    International Nuclear Information System (INIS)

    The trend towards higher fuel assembly discharge burnups poses new challenges for fuel channels in terms of their dimensional behavior and corrosion resistance. This led AREVA NP to develop a new technique for beta quenching of fuel channels that combines the effect of beta-quenching with the optimization of the microstructure. The first set of fuel channels with these optimized material properties have been placed in the core of a German boiling water reactor (BWR) nuclear power plant in spring of 2004. Some more channels have been sited in the core of a Scandinavian BWR in fall of 2007 to broaden the in-pile experience with these channels. Dimensional stability is the major requirement that is applied to fuel channels. High corrosion resistance and low hydrogen pickup are certainly required as well. However, corrosion and hydrogen pickup are usually not life limiting factors due to the large wall thickness of the material. Since thick layers of oxide may spall off extensively at high burnup and cause increase of the dose rate for the personnel, high corrosion resistance of fuel channels is mandatory. The fuel channels which surround BWR fuel assemblies are exposed to neutron irradiation as well as to loads induced by the reactor coolant flowing through them. These service conditions induce material growth and creep which cause permanent changes in the dimensions of the channels. Especially, fuel channel bow is of certain interest as increased channel bow may lead to some friction with control blades. Fuel channel bow is mainly induced by fluence gradients. However, there may be additional influences such as oxidation and hydrogen uptake to cause increased channel bow. The effect of hydrogen is currently discussed in the nuclear community to explain the unexpected high fuel channel bow that has been observed in some nuclear power plants. (orig.)

  10. Channel Choice: A Literature Review

    DEFF Research Database (Denmark)

    Østergaard Madsen, Christian; Kræmmergaard, Pernille

    2015-01-01

    The channel choice branch of e-government studies citizens’ and businesses’ choice of channels for interacting with government, and how government organizations can integrate channels and migrate users towards the most cost-efficient channels. In spite of the valuable contributions offered no sys...... no systematic overview exist of channel choice. We present a literature review of channel choice studies in government to citizen context identifying authors, countries, methods, concepts, units of analysis, and theories, and offer suggestionsfor future studies....

  11. A Simple Water Channel

    Science.gov (United States)

    White, A. S.

    1976-01-01

    Describes a simple water channel, for use with an overhead projector. It is run from a water tap and may be used for flow visualization experiments, including the effect of streamlining and elementary building aerodynamics. (MLH)

  12. 28-Channel rotary transformer

    Science.gov (United States)

    Mclyman, W. T.

    1981-01-01

    Transformer transmits power and digital data across rotating interface. Array has many parallel data channels, each with potential l megabaud data rate. Ferrite-cored transformers are spaced along rotor; airgap between them reduces crosstalk.

  13. Channelized Streams in Iowa

    Data.gov (United States)

    Iowa State University GIS Support and Research Facility — This draft dataset consists of all ditches or channelized pieces of stream that could be identified using three input datasets; namely the1:24,000 National...

  14. CHANNEL ESTIMATION TECHNIQUE

    DEFF Research Database (Denmark)

    2015-01-01

    A method includes determining a sequence of first coefficient estimates of a communication channel based on a sequence of pilots arranged according to a known pilot pattern and based on a receive signal, wherein the receive signal is based on the sequence of pilots transmitted over the communicat......A method includes determining a sequence of first coefficient estimates of a communication channel based on a sequence of pilots arranged according to a known pilot pattern and based on a receive signal, wherein the receive signal is based on the sequence of pilots transmitted over the...... communication channel. The method further includes determining a sequence of second coefficient estimates of the communication channel based on a decomposition of the first coefficient estimates in a dictionary matrix and a sparse vector of the second coefficient estimates, the dictionary matrix including...

  15. Sensing with Ion Channels

    CERN Document Server

    Martinac, Boris

    2008-01-01

    All living cells are able to detect and translate environmental stimuli into biologically meaningful signals. Sensations of touch, hearing, sight, taste, smell or pain are essential to the survival of all living organisms. The importance of sensory input for the existence of life thus justifies the effort made to understand its molecular origins. Sensing with Ion Channels focuses on ion channels as key molecules enabling biological systems to sense and process the physical and chemical stimuli that act upon cells in their living environment. Its aim is to serve as a reference to ion channel specialists and as a source of new information to non specialists who want to learn about the structural and functional diversity of ion channels and their role in sensory physiology.

  16. TRP channels in disease.

    Science.gov (United States)

    Jordt, S E; Ehrlich, B E

    2007-01-01

    The transient receptor potential (TRP) channels are a large family of proteins with six main subfamilies termed the TRPC (canonical), TRPV (vanilloid), TRPM (melastatin), TRPP (polycystin), TRPML (mucolipin), and TRPA (ankyrin) groups. The sheer number of different TRPs with distinct functions supports the statement that these channels are involved in a wide range of processes ranging from sensing of thermal and chemical signals to reloading intracellular stores after responding to an extracellular stimulus. Mutations in TRPs are linked to pathophysiology and specific diseases. An understanding of the role of TRPs in normal physiology is just beginning; the progression from mutations in TRPs to pathophysiology and disease will follow. In this review, we focus on two distinct aspects of TRP channel physiology, the role of TRP channels in intracellular Ca2+ homeostasis, and their role in the transduction of painful stimuli in sensory neurons. PMID:18193640

  17. Chloride channels in stroke

    Institute of Scientific and Technical Information of China (English)

    Ya-ping ZHANG; Hao ZHANG; Dayue Darrel DUAN

    2013-01-01

    Vascular remodeling of cerebral arterioles,including proliferation,migration,and apoptosis of vascular smooth muscle cells (VSMCs),is the major cause of changes in the cross-sectional area and diameter of the arteries and sudden interruption of blood flow or hemorrhage in the brain,ie,stroke.Accumulating evidence strongly supports an important role for chloride (Clˉ) channels in vascular remodeling and stroke.At least three Clˉ channel genes are expressed in VSMCs:1) the TMEM16A (or Ano1),which may encode the calcium-activated Clˉ channels (CACCs); 2) the CLC-3 Clˉ channel and Clˉ/H+ antiporter,which is closely related to the volume-regulated Clˉ channels (VRCCs); and 3) the cystic fibrosis transmembrane conductance regulator (CFTR),which encodes the PKA-and PKC-activated Clˉ channels.Activation of the CACCs by agonist-induced increase in intracellular Ca2+ causes membrane depolarization,vasoconstriction,and inhibition of VSMC proliferation.Activation of VRCCs by cell volume increase or membrane stretch promotes the production of reactive oxygen species,induces proliferation and inhibits apoptosis of VSMCs.Activation of CFTR inhibits oxidative stress and may prevent the development of hypertension.In addition,Clˉ current mediated by gammaaminobutyric acid (GABA) receptor has also been implicated a role in ischemic neuron death.This review focuses on the functional roles of Clˉ channels in the development of stroke and provides a perspective on the future directions for research and the potential to develop Clˉ channels as new targets for the prevention and treatment of stroke.

  18. Physics of Ion Channels

    OpenAIRE

    Kuyucak, Serdar; Bastug, Turgut

    2003-01-01

    We review the basic physics involved in transport of ions across membrane channels in cells. Electrochemical forces that control the diffusion of ions are discussed both from microscopic and macroscopic perspectives. A case is made for use of Brownian dynamics as the minimal phenomenological model that provides a bridge between experiments and more fundamental theoretical approaches. Application of Brownian and molecular dynamics methods to channels with known molecular structures is discussed.

  19. Identification Via Quantum Channels

    OpenAIRE

    Winter, Andreas

    2012-01-01

    We review the development of the quantum version of Ahlswede and Dueck's theory of identification via channels. As is often the case in quantum probability, there is not just one but several quantizations: we know at least two different concepts of identification of classical information via quantum channels, and three different identification capacities for quantum information. In the present summary overview we concentrate on conceptual points and open problems, referring the reader to the ...

  20. Quantum Feedback Channels

    OpenAIRE

    Bowen, Garry

    2002-01-01

    In Shannon information theory the capacity of a memoryless communication channel cannot be increased by the use of feedback. In quantum information theory the no-cloning theorem means that noiseless copying and feedback of quantum information cannot be achieved. In this paper, quantum feedback is defined as the unlimited use of a noiseless quantum channel from receiver to sender. Given such quantum feedback, it is shown to provide no increase in the entanglement--assisted capacities of a memo...

  1. Chaos in quantum channels

    OpenAIRE

    Hosur, Pavan; Qi, Xiao-Liang; Roberts, Daniel; Yoshida, Beni(Institute for Quantum Information & Matter and Walter Burke Institute for Theoretical Physics, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA, 91125, U.S.A.)

    2016-01-01

    We study chaos and scrambling in unitary channels by considering their entanglement properties as states. Using out-of-time-order correlation functions to diagnose chaos, we characterize the ability of a channel to process quantum information. We show that the generic decay of such correlators implies that any input subsystem must have near vanishing mutual information with almost all partitions of the output. Additionally, we propose the negativity of the tripartite information of the channe...

  2. Course on Ionic Channels

    CERN Document Server

    1986-01-01

    This book is based on a series of lectures for a course on ionic channels held in Santiago, Chile, on November 17-20, 1984. It is intended as a tutorial guide on the properties, function, modulation, and reconstitution of ionic channels, and it should be accessible to graduate students taking their first steps in this field. In the presentation there has been a deliberate emphasis on the spe­ cific methodologies used toward the understanding of the workings and function of channels. Thus, in the first section, we learn to "read" single­ channel records: how to interpret them in the theoretical frame of kinetic models, which information can be extracted from gating currents in re­ lation to the closing and opening processes, and how ion transport through an open channel can be explained in terms of fluctuating energy barriers. The importance of assessing unequivocally the origin and purity of mem­ brane preparations and the use of membrane vesicles and optical tech­ niques in the stUGY of ionic channels a...

  3. Behaviour of organised disturbances in fully developed turbulent channel flow

    Indian Academy of Sciences (India)

    P K Sen; Srinivas V Veeravali

    2000-10-01

    In our earlier work we have shown the relevance of stability theory in understanding the sustenance of turbulence in turbulent boundary layers. Here we adopt the same model to study the evolution of organised disturbances in turbulent channel flow. Since the dominant modes are wall modes we find that the stability characteristics in the two flows are nearly identical although the boundary conditions (at the edge of the boundary layer and at the centre of the channel) are different. Comparisons with the experiments of Hussain and Reynolds are also presented.

  4. Integrin receptors and ligand-gated channels.

    Science.gov (United States)

    Morini, Raffaella; Becchetti, Andrea

    2010-01-01

    Plastic expression of different integrin subunits controls the different stages of neural development, whereas in the adult integrins regulate synaptic stability. Evidence of integrin-channel crosstalk exists for ionotropic glutamate receptors. As is often the case in other tissues, integrin engagement regulates channel activity through complex signaling pathways that often include tyrosine phosphorylation cascades. The specific pathways recruited by integrin activation depend on cerebral region and cell type. In turn, ion channels control integrin expression onto the plasma membrane and their ligand binding affinity. The most extensive studies concern the hippocampus and suggest implications for neuronal circuit plasticity. The physiological relevance of these findings depends on whether adhesion molecules, aside from determining tissue stability, contribute to synaptogenesis and the responsiveness of mature synapses, thus contributing to long-term circuit consolidation. Little evidence is available for other ligand-gated channels, with the exception of nicotinic receptors. These exert a variety of functions in neurons and non neural tissue, both in development and in the adult, by regulating cell cycle, synaptogenesis and synaptic circuit refinement. Detailed studies in epidermal keratinocytes have shed some light on the possible mechanisms through which ACh can regulate cell motility, which may be of general relevance for morphogenetic processes. As to the control of mature synapses, most results concern the integrinic control of nicotinic receptors in the neuromuscular junction. Following this lead, a few studies have addressed similar topics in adult cerebral synapses. However, pursuing and interpreting these results in the brain is especially difficult because of the complexity of the nicotinic roles and the widespread contribution of nonsynaptic, paracrine transmission. From a pathological point of view, considering the well-known contribution of both

  5. Morphodynamics of Floodplain Chute Channels

    Science.gov (United States)

    David, S. R.; Edmonds, D. A.

    2015-12-01

    Floodplain chute channel formation is a key process that can enable rivers to transition from single-thread to multi-thread planform geometries. Floodplain chute channels are usually incisional channels connecting topographic lows across point bars and in the floodplain. Surprisingly, it is still not clear what conditions promote chute channel formation and what governs their morphodynamic behavior. Towards this end we have initiated an empirical and theoretical study of floodplain chute channels in Indiana, USA. Using elevation models and satellite imagery we mapped 3064 km2 of floodplain in Indiana, and find that 37.3% of mapped floodplains in Indiana have extensive chute channel networks. These chute channel networks consist of two types of channel segments: meander cutoffs of the main channel and chute channels linking the cutoffs together. To understand how these chute channels link meander cutoffs together and eventually create floodplain channel networks we use Delft3D to explore floodplain morphodynamics. Our first modeling experiment starts from a generic floodplain prepopulated with meander cutoffs to test under what conditions chute channels form.We find that chute channel formation is optimized at an intermediate flood discharge. If the flood discharge is too large the meander cutoffs erosively diffuse, whereas if the floodwave is too small the cutoffs fill with sediment. A moderately sized floodwave reworks the sediment surrounding the topographic lows, enhancing the development of floodplain chute channels. Our second modeling experiments explore how floodplain chute channels evolve on the West Fork of the White River, Indiana, USA. We find that the floodplain chute channels are capable of conveying the entire 10 yr floodwave (Q=1330m3/s) leaving the inter-channel areas dry. Moreover, the chute channels can incise into the floodplain while the margins of channels are aggrading, creating levees. Our results suggest that under the right conditions

  6. Premixed Flame Dynamics in Narrow 2D Channels

    CERN Document Server

    Ayoobi, Mohsen

    2015-01-01

    Premixed flames propagating within small channels show complex combustion phenomena that differ from flame propagation at conventional scales. Available experimental and numerical studies have documented stationary/non-stationary and/or asymmetric modes that depend on properties of the incoming reactant flow as well as channel geometry and wall temperatures. The present work seeks to illuminate mechanisms leading to symmetry-breaking and limit cycle behavior that are fundamental to these combustion modes. Specifically, four cases of lean premixed methane/air combustion -- two equivalence ratios (0.53 and 0.7) and two channel widths (2 and 5mm) -- are investigated in a 2D configuration with constant channel length and bulk inlet velocity, where numerical simulations are performed using detailed chemistry. External wall heating is simulated by imposing a linear temperature gradient as a boundary condition on both walls. In the 2mm-channel, both equivalence ratios produce flames that stabilize with symmetric fla...

  7. Stability of non-parallel flow in a channel

    Directory of Open Access Journals (Sweden)

    Philip G. Drazin

    1991-05-01

    Full Text Available This is a review of several generalizations of Hiemenz's classic solution for steady two-dimensional flow of a uniform incompressible viscous fluid near a stagnation point on a bluff body. These generalizations are diverse exact solutions, steady and unsteady, two- and three-dimensional, of the Navier-Stokes equations. The solutions exhibit many types of instability and bifurcation. There are turning points, trans critical bifurcations, pitchfork bifurcations, Hopf bifurcations and Takens-Bogdanov bifurcations. The solutions also take the period-doubling and Ruelle-Takens routes to chaos.

  8. Stone stability under decelerating open-channel flow

    NARCIS (Netherlands)

    Hoan, N.T.; Booij, R.; Hofland, B.; Stive, M.J.F.; Verhagen, H.J.

    2007-01-01

    The current research is aimed at finding a proper relation between flow forces acting on the bed and the bed response. To this end, experiments were carried out in which both the bed response (quantified by a dimensionless entrainment rate) and the flow field (velocity and turbulence intensity distr

  9. CAREM-25 Steam Generator Stability Analysis

    International Nuclear Information System (INIS)

    In this work the stability of a once-through CAREM-25 steam generator is analyzed.A fix nodes numerical model, that allows the modelling of the liquid, two-phase and superheated steam zones, is implemented.This model was checked against a mobile finite elements model under saturated steam conditions at the channel exit and a good agreement was obtained.Finally the stability of a CAREM steam generator is studied and the range of in let restrictions that a assure the system stability is analyzed

  10. MEMS in microfluidic channels.

    Energy Technology Data Exchange (ETDEWEB)

    Ashby, Carol Iris Hill; Okandan, Murat; Michalske, Terry A.; Sounart, Thomas L.; Matzke, Carolyn M.

    2004-03-01

    Microelectromechanical systems (MEMS) comprise a new class of devices that include various forms of sensors and actuators. Recent studies have shown that microscale cantilever structures are able to detect a wide range of chemicals, biomolecules or even single bacterial cells. In this approach, cantilever deflection replaces optical fluorescence detection thereby eliminating complex chemical tagging steps that are difficult to achieve with chip-based architectures. A key challenge to utilizing this new detection scheme is the incorporation of functionalized MEMS structures within complex microfluidic channel architectures. The ability to accomplish this integration is currently limited by the processing approaches used to seal lids on pre-etched microfluidic channels. This report describes Sandia's first construction of MEMS instrumented microfluidic chips, which were fabricated by combining our leading capabilities in MEMS processing with our low-temperature photolithographic method for fabricating microfluidic channels. We have explored in-situ cantilevers and other similar passive MEMS devices as a new approach to directly sense fluid transport, and have successfully monitored local flow rates and viscosities within microfluidic channels. Actuated MEMS structures have also been incorporated into microfluidic channels, and the electrical requirements for actuation in liquids have been quantified with an elegant theory. Electrostatic actuation in water has been accomplished, and a novel technique for monitoring local electrical conductivities has been invented.

  11. Mitochondrial Ion Channels

    Science.gov (United States)

    O’Rourke, Brian

    2009-01-01

    In work spanning more than a century, mitochondria have been recognized for their multifunctional roles in metabolism, energy transduction, ion transport, inheritance, signaling, and cell death. Foremost among these tasks is the continuous production of ATP through oxidative phosphorylation, which requires a large electrochemical driving force for protons across the mitochondrial inner membrane. This process requires a membrane with relatively low permeability to ions to minimize energy dissipation. However, a wealth of evidence now indicates that both selective and nonselective ion channels are present in the mitochondrial inner membrane, along with several known channels on the outer membrane. Some of these channels are active under physiological conditions, and others may be activated under pathophysiological conditions to act as the major determinants of cell life and death. This review summarizes research on mitochondrial ion channels and efforts to identify their molecular correlates. Except in a few cases, our understanding of the structure of mitochondrial ion channels is limited, indicating the need for focused discovery in this area. PMID:17059356

  12. Channel Identification Machines

    Directory of Open Access Journals (Sweden)

    Aurel A. Lazar

    2012-01-01

    Full Text Available We present a formal methodology for identifying a channel in a system consisting of a communication channel in cascade with an asynchronous sampler. The channel is modeled as a multidimensional filter, while models of asynchronous samplers are taken from neuroscience and communications and include integrate-and-fire neurons, asynchronous sigma/delta modulators and general oscillators in cascade with zero-crossing detectors. We devise channel identification algorithms that recover a projection of the filter(s onto a space of input signals loss-free for both scalar and vector-valued test signals. The test signals are modeled as elements of a reproducing kernel Hilbert space (RKHS with a Dirichlet kernel. Under appropriate limiting conditions on the bandwidth and the order of the test signal space, the filter projection converges to the impulse response of the filter. We show that our results hold for a wide class of RKHSs, including the space of finite-energy bandlimited signals. We also extend our channel identification results to noisy circuits.

  13. The effect of wall heating on instability of channel flow

    OpenAIRE

    Sameen, A; Govindarajan, Rama

    2006-01-01

    A comprehensive study of the effect of wall heating or cooling on the linear, transient and secondary growth of instability in channel flow is conducted. The effect of viscosity stratification, heat diffusivity and of buoyancy are estimated separately, with some unexpected results. From linear stability results, it has been accepted that heat diffusivity does not affect stability. However, we show that realistic Prandtl numbers cause a transient growth of disturbances that is an order of magn...

  14. QKD Quantum Channel Authentication

    CERN Document Server

    Kosloski, J T

    2006-01-01

    Several simple yet secure protocols to authenticate the quantum channel of various QKD schemes, by coupling the photon sender's knowledge of a shared secret and the QBER Bob observes, are presented. It is shown that Alice can encrypt certain portions of the information needed for the QKD protocols, using a sequence whose security is based on computational-complexity, without compromising all of the sequence's entropy. It is then shown that after a Man-in-the-Middle attack on the quantum and classical channels, there is still enough entropy left in the sequence for Bob to detect the presence of Eve by monitoring the QBER. Finally, it is shown that the principles presented can be implemented to authenticate the quantum channel associated with any type of QKD scheme, and they can also be used for Alice to authenticate Bob.

  15. Dequantization Via Quantum Channels

    Science.gov (United States)

    Andersson, Andreas

    2016-10-01

    For a unital completely positive map {Φ} ("quantum channel") governing the time propagation of a quantum system, the Stinespring representation gives an enlarged system evolving unitarily. We argue that the Stinespring representations of each power {Φ^m} of the single map together encode the structure of the original quantum channel and provide an interaction-dependent model for the bath. The same bath model gives a "classical limit" at infinite time {mto∞} in the form of a noncommutative "manifold" determined by the channel. In this way, a simplified analysis of the system can be performed by making the large- m approximation. These constructions are based on a noncommutative generalization of Berezin quantization. The latter is shown to involve very fundamental aspects of quantum-information theory, which are thereby put in a completely new light.

  16. Dequantization Via Quantum Channels

    Science.gov (United States)

    Andersson, Andreas

    2016-08-01

    For a unital completely positive map {Φ} ("quantum channel") governing the time propagation of a quantum system, the Stinespring representation gives an enlarged system evolving unitarily. We argue that the Stinespring representations of each power {Φ^m} of the single map together encode the structure of the original quantum channel and provide an interaction-dependent model for the bath. The same bath model gives a "classical limit" at infinite time {mto∞} in the form of a noncommutative "manifold" determined by the channel. In this way, a simplified analysis of the system can be performed by making the large-m approximation. These constructions are based on a noncommutative generalization of Berezin quantization. The latter is shown to involve very fundamental aspects of quantum-information theory, which are thereby put in a completely new light.

  17. Entanglement-saving channels

    Science.gov (United States)

    Lami, L.; Giovannetti, V.

    2016-03-01

    The set of Entanglement Saving (ES) quantum channels is introduced and characterized. These are completely positive, trace preserving transformations which when acting locally on a bipartite quantum system initially prepared into a maximally entangled configuration, preserve its entanglement even when applied an arbitrary number of times. In other words, a quantum channel ψ is said to be ES if its powers ψn are not entanglement-breaking for all integers n. We also characterize the properties of the Asymptotic Entanglement Saving (AES) maps. These form a proper subset of the ES channels that is constituted by those maps that not only preserve entanglement for all finite n but which also sustain an explicitly not null level of entanglement in the asymptotic limit n → ∞. Structure theorems are provided for ES and for AES maps which yield an almost complete characterization of the former and a full characterization of the latter.

  18. Chaos in quantum channels

    CERN Document Server

    Hosur, Pavan; Roberts, Daniel A; Yoshida, Beni

    2015-01-01

    We study chaos and scrambling in unitary channels by considering their entanglement properties as states. Using out-of-time-order correlation functions to diagnose chaos, we characterize the ability of a channel to process quantum information. We show that the generic decay of such correlators implies that any input subsystem must have near vanishing mutual information with almost all partitions of the output. Additionally, we propose the negativity of the tripartite information of the channel as a general diagnostic of scrambling. This measures the delocalization of information and is closely related to the decay of out-of-time-order correlators. We back up our results with numerics in two non-integrable models and analytic results in a perfect tensor network model of chaotic time evolution. These results show that the butterfly effect in quantum systems implies the information-theoretic definition of scrambling.

  19. Voltage-Gated Proton Channels

    OpenAIRE

    DeCoursey, Thomas E.

    2008-01-01

    Voltage-gated proton channels, HV1, have vaulted from the realm of the esoteric into the forefront of a central question facing ion channel biophysicists, namely the mechanism by which voltage-dependent gating occurs. This transformation is the result of several factors. Identification of the gene in 2006 revealed that proton channels are homologues of the voltage-sensing domain of most other voltage-gated ion channels. Unique, or at least eccentric, properties of proton channels include dime...

  20. Stabilizing brokerage.

    Science.gov (United States)

    Stovel, Katherine; Golub, Benjamin; Milgrom, Eva M Meyersson

    2011-12-27

    A variety of social and economic arrangements exist to facilitate the exchange of goods, services, and information over gaps in social structure. Each of these arrangements bears some relationship to the idea of brokerage, but this brokerage is rarely like the pure and formal economic intermediation seen in some modern markets. Indeed, for reasons illuminated by existing sociological and economic models, brokerage is a fragile relationship. In this paper, we review the causes of instability in brokerage and identify three social mechanisms that can stabilize fragile brokerage relationships: social isolation, broker capture, and organizational grafting. Each of these mechanisms rests on the emergence or existence of supporting institutions. We suggest that organizational grafting may be the most stable and effective resolution to the tensions inherent in brokerage, but it is also the most institutionally demanding.

  1. STABILIZED OSCILLATOR

    Science.gov (United States)

    Jessen, P.L.; Price, H.J.

    1958-03-18

    This patent relates to sine-wave generators and in particular describes a generator with a novel feedback circuit resulting in improved frequency stability. The generator comprises two triodes having a common cathode circuit connected to oscillate at a frequency and amplitude at which the loop galn of the circutt ls unity, and another pair of triodes having a common cathode circuit arranged as a conventional amplifier. A signal is conducted from the osciliator through a frequency selective network to the amplifier and fed back to the osciliator. The unique feature of the feedback circuit is the amplifier operates in the nonlinear portion of its tube characteristics thereby providing a relatively constant feedback voltage to the oscillator irrespective of the amplitude of its input signal.

  2. The neutron channeling phenomenon.

    Science.gov (United States)

    Khanouchi, A; Sabir, A; Boulkheir, M; Ichaoui, R; Ghassoun, J; Jehouani, A

    1997-01-01

    Shields, used for protection against radiation, are often pierced with vacuum channels for passing cables and other instruments for measurements. The neutron transmission through these shields is an unavoidable phenomenon. In this work we study and discuss the effect of channels on neutron transmission through shields. We consider an infinite homogeneous slab, with a fixed thickness (20 lambda, with lambda the mean free path of the neutron in the slab), which contains a vacuum channel. This slab is irradiated with an infinite source of neutrons on the left side and on the other side (right side) many detectors with windows equal to 2 lambda are placed in order to evaluate the neutron transmission probabilities (Khanouchi, A., Aboubekr, A., Ghassoun, J. and Jehouani, A. (1994) Rencontre Nationale des Jeunes Chercheurs en Physique. Casa Blanca Maroc; Khanouchi, A., Sabir, A., Ghassoun, J. and Jehouani, A. (1995) Premier Congré International des Intéractions Rayonnements Matière. Eljadida Maroc). The neutron history within the slab is simulated by the Monte Carlo method (Booth, T. E. and Hendricks, J. S. (1994) Nuclear Technology 5) and using the exponential biasing technique in order to improve the Monte Carlo calculation (Levitt, L. B. (1968) Nuclear Science and Engineering 31, 500-504; Jehouani, A., Ghassoun, J. and Aboubker, A. (1994) In Proceedings of the 6th International Symposium on Radiation Physics, Rabat, Morocco). Then different geometries of the vacuum channel have been studied. For each geometry we have determined the detector response and calculated the neutron transmission probability for different detector positions. This neutron transmission probability presents a peak for the detectors placed in front of the vacuum channel. This study allowed us to clearly identify the neutron channeling phenomenon. One application of our study is to detect vacuum defects in materials. PMID:9463884

  3. BLIND CHANNEL ESTIMATION IN DELAY DIVERSITY FOR FREQUENCY SELECTIVE CHANNELS

    Institute of Scientific and Technical Information of China (English)

    Zhao Zheng; Jia Ying; Yin Qinye

    2003-01-01

    Delay diversity is an effective transmit diversity technique to combat adverse ef-fects of fading. Thus far, previous work in delay diversity assumed that perfect estimates ofcurrent channel fading conditions are available at the receiver and training symbols are requiredto estimate the channel from the transmitter to the receiver. However, increasing the number ofthe antennas increases the required training interval and reduces the available time within whichdata may be transmitted. Learning the channel coefficients becomes increasingly difficult for thefrequency selective channels. In this paper, with the subspace method and the delay character ofdelay diversity, a channel estimation method is proposed, which does not use training symbols. Itaddresses the transmit diversity for a frequency selective channel from a single carrier perspectivein the form of a simple equivalent fiat fading model. Monte Carlo simulations give the perfor-mance of channel estimation and the performance comparison of our channel-estimation-baseddetector with decision feedback equalization, which uses the perfect channel information.

  4. K(v)7 channels: function, pharmacology and channel modulators.

    Science.gov (United States)

    Dalby-Brown, William; Hansen, Henrik H; Korsgaard, Mads P G; Mirza, Naheed; Olesen, Søren-P

    2006-01-01

    K(v)7 channels are unique among K(+) channels, since four out of the five channel subtypes have well-documented roles in the development of human diseases. They have distinct physiological functions in the heart and in the nervous system, which can be ascribed to their voltage-gating properties. The K(v)7 channels also lend themselves to pharmacological modulation, and synthetic openers as well as blockers of the channels, regulating neuronal excitability, have existed even before the K(v)7 channels were identified by cloning. In the present review we give an account on the focused efforts to develop selective modulators, openers as well as blockers, of the K(v)7 channel subtypes, which have been undertaken during recent years, along with a discussion of the K(v)7 ion channel physiology and therapeutic indications for modulators of the neuronal K(v)7 channels.

  5. Channelization of plumes beneath ice shelves

    KAUST Repository

    Dallaston, M. C.

    2015-11-11

    © 2015 Cambridge University Press. We study a simplified model of ice-ocean interaction beneath a floating ice shelf, and investigate the possibility for channels to form in the ice shelf base due to spatial variations in conditions at the grounding line. The model combines an extensional thin-film description of viscous ice flow in the shelf, with melting at its base driven by a turbulent ocean plume. Small transverse perturbations to the one-dimensional steady state are considered, driven either by ice thickness or subglacial discharge variations across the grounding line. Either forcing leads to the growth of channels downstream, with melting driven by locally enhanced ocean velocities, and thus heat transfer. Narrow channels are smoothed out due to turbulent mixing in the ocean plume, leading to a preferred wavelength for channel growth. In the absence of perturbations at the grounding line, linear stability analysis suggests that the one-dimensional state is stable to initial perturbations, chiefly due to the background ice advection.

  6. Scheduling with Rate Adaptation under Incomplete Knowledge of Channel/Estimator Statistics

    CERN Document Server

    Ouyang, Wenzhuo; Eryilmaz, Atilla; Shroff, Ness B

    2010-01-01

    In time-varying wireless networks, the state of the communication channels are subject to random variations, and hence need to be estimated for efficient rate adaptation and scheduling. The estimation mechanism possesses inaccuracies that need to be tackled in a probabilistic framework. In this work, we study scheduling with rate adaptation in single-hop queueing networks under two levels of channel uncertainty: when the channel estimates are inaccurate but complete knowledge of the channel/estimator joint statistics is available at the scheduler; and when the knowledge of the joint statistics is incomplete. In the former case, we characterize the network stability region and show that a maximum-weight type scheduling policy is throughput-optimal. In the latter case, we propose a joint channel statistics - scheduling policy. With an associated trade-off in average packet delay and convergence time, the proposed policy has a stability region arbitrarily close to the stability region of the network under full k...

  7. Numerical simulation of spinning detonation in circular section channels

    Science.gov (United States)

    Levin, V. A.; Manuylovich, I. S.; Markov, V. V.

    2016-06-01

    Numerical simulation of three-dimensional structures of gas detonation in circular section channels that emerge due to the instability when the one-dimensional flow is initiated by energy supply at the closed end of the channel is performed. It is found that in channels with a large diameter, an irregular three-dimensional cellular detonation structure is formed. Furthermore, it is found that in channels with a small diameter circular section, the initially plane detonation wave is spontaneously transformed into a spinning detonation wave, while passing through four phases. A critical value of the channel diameter that divides the regimes with the three-dimensional cellular detonation and spinning detonation is determined. The stability of the spinning detonation wave under perturbations occurring when the wave passes into a channel with a greater (a smaller) diameter is investigated. It is found that the spin is preserved if the diameter of the next channel (into which the wave passes) is smaller (respectively, greater) than a certain critical value. The computations were performed on the Lomonosov supercomputer using from 0.1 to 10 billions of computational cells. All the computations of the cellular and spinning detonation were performed in the whole long three-dimensional channel (up to 1 m long) rather than only in its part containing the detonation wave; this made it possible to adequately simulate and investigate the features of the transformation of the detonation structure in the process of its propagation.

  8. Chemistry in Microfluidic Channels

    Science.gov (United States)

    Chia, Matthew C.; Sweeney, Christina M.; Odom, Teri W.

    2011-01-01

    General chemistry introduces principles such as acid-base chemistry, mixing, and precipitation that are usually demonstrated in bulk solutions. In this laboratory experiment, we describe how chemical reactions can be performed in a microfluidic channel to show advanced concepts such as laminar fluid flow and controlled precipitation. Three sets of…

  9. Beyond the Manual Channel

    DEFF Research Database (Denmark)

    the manual channel. Not surprisingly, most papers deal with non-manuals on the face. Once again, the papers at this workshop clearly identify the potentials of even closer cooperation between sign linguists and sign language engineers, and we think it is events like this that contribute a lot to a better...

  10. TRP channels: an overview

    DEFF Research Database (Denmark)

    Pedersen, Stine Falsig; Owsianik, Grzegorz; Nilius, Bernd

    2005-01-01

    to a plethora of data on the roles of TRPs in a variety of tissues and species, including mammals, insects, and yeast. The present review summarizes the most pertinent recent evidence regarding the structural and functional properties of TRP channels, focusing on the regulation and physiology of mammalian TRPs....

  11. All channels open

    NARCIS (Netherlands)

    Frank Huysmans; Jos de Haan

    2010-01-01

    Original title: Alle kanalen staan open. The rapid changes taking place in the media landscape in the Netherlands - characterised by digitisation and convergence of media technologies - raise the question of how the Dutch are dealing with the many new opportunities that have opened up. All channels

  12. Channeling through Bent Crystals

    Energy Technology Data Exchange (ETDEWEB)

    Mack, Stephanie; /Ottawa U. /SLAC

    2012-09-07

    Bent crystals have demonstrated potential for use in beam collimation. A process called channeling is when accelerated particle beams are trapped by the nuclear potentials in the atomic planes within a crystal lattice. If the crystal is bent then the particles can follow the bending angle of the crystal. There are several different effects that are observed when particles travel through a bent crystal including dechanneling, volume capture, volume reflection and channeling. With a crystal placed at the edge of a particle beam, part of the fringe of the beam can be deflected away towards a detector or beam dump, thus helping collimate the beam. There is currently FORTRAN code by Igor Yazynin that has been used to model the passage of particles through a bent crystal. Using this code, the effects mentioned were explored for beam energy that would be seen at the Facility for Advanced Accelerator Experimental Tests (FACET) at a range of crystal orientations with respect to the incoming beam. After propagating 5 meters in vacuum space past the crystal the channeled particles were observed to separate from most of the beam with some noise due to dechanneled particles. Progressively smaller bending radii, with corresponding shorter crystal lengths, were compared and it was seen that multiple scattering decreases with the length of the crystal therefore allowing for cleaner detection of the channeled particles. The input beam was then modified and only a portion of the beam sent through the crystal. With the majority of the beam not affected by the crystal, most particles were not deflected and after propagation the channeled particles were seen to be deflected approximately 5mm. After a portion of the beam travels through the crystal, the entire beam was then sent through a quadrupole magnet, which increased the separation of the channeled particles from the remainder of the beam to a distance of around 20mm. A different code, which was developed at SLAC, was used to

  13. Multiple Description Coding for Closed Loop Systems over Erasure Channels

    DEFF Research Database (Denmark)

    Østergaard, Jan; Quevedo, Daniel

    2013-01-01

    ) and the decoder (plant). The feedback channel from the decoder to the encoder is assumed noiseless. Since the forward channel is digital, we need to employ quantization.We combine two techniques to enhance the reliability of the system. First, in order to guarantee that the system remains stable during packet......In this paper, we consider robust source coding in closed-loop systems. In particular, we consider a (possibly) unstable LTI system, which is to be stabilized via a network. The network has random delays and erasures on the data-rate limited (digital) forward channel between the encoder (controller....... In particular, we transmit M redundant packets, which are constructed such that when receiving any J packets, the current control signal as well as J-1 future control signals can be reliably reconstructed at the decoder. We prove stability subject to quantization constraints, random dropouts, and delays...

  14. Analysis of nonlinear channel friction inverse problem

    Institute of Scientific and Technical Information of China (English)

    CHENG Weiping; LIU Guohua

    2007-01-01

    Based on the Backus-Gilbert inverse theory, the singular value decomposition (SVD) for general inverse matrices and the optimization algorithm are used to solve the channel friction inverse problem. The resolution and covari- ance friction inverse model in matrix form is developed to examine the reliability of solutions. Theoretical analyses demonstrate that the convergence rate of the general Newton optimization algorithm is in the second-order. The Wiggins method is also incorporated into the algorithm. Using the method, noise can be suppressed effectively, and the results are close to accurate solutions with proper control parameters. Also, the numerical stability can be improved.

  15. Improving Virtual Channel Discrimination in a Multi-Channel Context

    OpenAIRE

    Srinivasan, Arthi G.; Shannon, Robert V.; Landsberger, David M.

    2012-01-01

    Improving spectral resolution in cochlear implants is key to improving performance in difficult listening conditions (e.g. speech in noise, music, etc.). Current focusing might reduce channel interaction, thereby increasing spectral resolution. Previous studies have shown that combining current steering and current focusing reduces spread of excitation and improves virtual channel discrimination in a single-channel context. It is unclear whether the single-channel benefits from current focusi...

  16. The earliest ion channels in protocellular membranes

    Science.gov (United States)

    Mijajlovic, Milan; Pohorille, Andrew; Wilson, Michael; Wei, Chenyu

    Cellular membranes with their hydrophobic interior are virtually impermeable to ions. Bulk of ion transport through them is enabled through ion channels. Ion channels of contemporary cells are complex protein molecules which span the membrane creating a cylindrical pore filled with water. Protocells, which are widely regarded as precursors to modern cells, had similarly impermeable membranes, but the set of proteins in their disposal was much simpler and more limited. We have been, therefore, exploring an idea that the first ion channels in protocellular membranes were formed by much smaller peptide molecules that could spontaneously self-assemble into short-lived cylindrical bundles in a membrane. Earlier studies have shown that a group of peptides known as peptaibols is capable of forming ion channels in lipid bilayers when they are exposed to an electric field. Peptaibols are small, non-genetically encoded peptides produced by some fungi as a part of their system of defense against bacteria. They are usually only 14-20 residues long, which is just enough to span the membrane. Their sequence is characterized by the presence of non-standard amino acids which, interestingly, are also expected to have existed on the early earth. In particular, the presence of 2-aminoisobutyric acid (AIB) gives peptaibols strong helix forming propensities. Association of the helices inside membranes leads to the formation of cylindrical bundles, typically containing 4 to 10 monomers. Although peptaibols are excellent candidates for models of the earliest ion channels their struc-tures, which are stabilized only by van der Waals forces and occasional hydrogen bonds between neighboring helices, are not very stable. Although it might properly reflect protobiological real-ity, it is also a major obstacle in studying channel behavior. For this reason we focused on two members of the peptaibol family, trichotoxin and antiamoebin, which are characterized by a single conductance level. This

  17. The Earliest Ion Channels in Protocellular Membranes

    Science.gov (United States)

    Mijajlovic, Milan; Pohorille, Andrew; Wilson, Michael; Wei, Chenyu

    2010-01-01

    Cellular membranes with their hydrophobic interior are virtually impermeable to ions. Bulk of ion transport through them is enabled through ion channels. Ion channels of contemporary cells are complex protein molecules which span the membrane creating a cylindrical pore filled with water. Protocells, which are widely regarded as precursors to modern cells, had similarly impermeable membranes, but the set of proteins in their disposal was much simpler and more limited. We have been, therefore, exploring an idea that the first ion channels in protocellular membranes were formed by much smaller peptide molecules that could spontaneously selfassemble into short-lived cylindrical bundles in a membrane. Earlier studies have shown that a group of peptides known as peptaibols is capable of forming ion channels in lipid bilayers when they are exposed to an electric field. Peptaibols are small, non-genetically encoded peptides produced by some fungi as a part of their system of defense against bacteria. They are usually only 14-20 residues long, which is just enough to span the membrane. Their sequence is characterized by the presence of non-standard amino acids which, interestingly, are also expected to have existed on the early earth. In particular, the presence of 2-aminoisobutyric acid (AIB) gives peptaibols strong helix forming propensities. Association of the helices inside membranes leads to the formation of cylindrical bundles, typically containing 4 to 10 monomers. Although peptaibols are excellent candidates for models of the earliest ion channels their structures, which are stabilized only by van der Waals forces and occasional hydrogen bonds between neighboring helices, are not very stable. Although it might properly reflect protobiological reality, it is also a major obstacle in studying channel behavior. For this reason we focused on two members of the peptaibol family, trichotoxin and antiamoebin, which are characterized by a single conductance level. This

  18. Geysering in boiling channels

    Energy Technology Data Exchange (ETDEWEB)

    Aritomi, Masanori; Takemoto, Takatoshi [Tokyo Institute of Technology, Tokyo (Japan); Chiang, Jing-Hsien [Japan NUS Corp. Ltd., Toyko (Japan)] [and others

    1995-09-01

    A concept of natural circulation BWRs such as the SBWR has been proposed and seems to be promising in that the primary cooling system can be simplified. The authors have been investigating thermo-hydraulic instabilities which may appear during the start-up in natural circulation BWRs. In our previous works, geysering was investigated in parallel boiling channels for both natural and forced circulations, and its driving mechanism and the effect of system pressure on geysering occurrence were made clear. In this paper, geysering is investigated in a vertical column and a U-shaped vertical column heated in the lower parts. It is clarified from the results that the occurrence mechanism of geysering and the dependence of system pressure on geysering occurrence coincide between parallel boiling channels in circulation systems and vertical columns in non-circulation systems.

  19. Lipid Ion Channels

    CERN Document Server

    Heimburg, Thomas

    2010-01-01

    The interpretation electrical phenomena in biomembranes is usually based on the assumption that the experimentally found discrete ion conduction events are due to a particular class of proteins called ion channels while the lipid membrane is considered being an inert electrical insulator. The particular protein structure is thought to be related to ion specificity, specific recognition of drugs by receptors and to macroscopic phenomena as nerve pulse propagation. However, lipid membranes in their chain melting regime are known to be highly permeable to ions, water and small molecules, and are therefore not always inert. In voltage-clamp experiments one finds quantized conduction events through protein-free membranes in their melting regime similar to or even undistinguishable from those attributed to proteins. This constitutes a conceptual problem for the interpretation of electrophysiological data obtained from biological membrane preparations. Here, we review the experimental evidence for lipid ion channels...

  20. Ion Channels, Natural Nanovalves

    OpenAIRE

    Eisenberg, Bob

    2012-01-01

    Ion channels are proteins with holes down their middle that control the flow of ions and electric current across otherwise impermeable biological membranes. The flow of sodium, potassium, calcium (divalent), and chloride ions have been central issues in biology for more than a century. The flow of current is responsible for the signals of the nervous system that propagate over long distances (meters). The concentration of divalent calcium ions is a 'universal' signal that controls many differ...

  1. Proton channel models

    OpenAIRE

    Pupo, Amaury; Baez-Nieto, David; Martínez, Agustín; Latorre, Ramón; González, Carlos

    2014-01-01

    Voltage-gated proton channels are integral membrane proteins with the capacity to permeate elementary particles in a voltage and pH dependent manner. These proteins have been found in several species and are involved in various physiological processes. Although their primary topology is known, lack of details regarding their structures in the open conformation has limited analyses toward a deeper understanding of the molecular determinants of their function and regulation. Consequently, the f...

  2. Athermal channeled spectropolarimeter

    Energy Technology Data Exchange (ETDEWEB)

    Jones, Julia Craven

    2015-12-08

    A temperature insensitive (athermal) channeled spectropolarimeter (CSP) is described. The athermal CSP includes a crystal retarder formed of a biaxial crystal. The crystal retarder has three crystal axes, wherein each axis has its own distinct index of refraction. The axes are oriented in a particular manner, causing an amplitude modulating carrier frequency induced by the crystal retarder to be thermally invariant. Accordingly, a calibration beam technique can be used over a relatively wide range of ambient temperatures, with a common calibration data set.

  3. Radar channel balancing with commutation

    Energy Technology Data Exchange (ETDEWEB)

    Doerry, Armin Walter

    2014-02-01

    When multiple channels are employed in a pulse-Doppler radar, achieving and maintaining balance between the channels is problematic. In some circumstances the channels may be commutated to achieve adequate balance. Commutation is the switching, trading, toggling, or multiplexing of the channels between signal paths. Commutation allows modulating the imbalance energy away from the balanced energy in Doppler, where it can be mitigated with filtering.

  4. Ion channeling revisited

    Energy Technology Data Exchange (ETDEWEB)

    Doyle, Barney Lee [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Corona, Aldo [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Nguyen, Anh [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2014-09-01

    A MS Excel program has been written that calculates accidental, or unintentional, ion channeling in cubic bcc, fcc and diamond lattice crystals or polycrystalline materials. This becomes an important issue when simulating the creation by energetic neutrons of point displacement damage and extended defects using beams of ions. All of the tables and graphs in the three Ion Beam Analysis Handbooks that previously had to be manually looked up and read from were programed into Excel in handy lookup tables, or parameterized, for the case of the graphs, using rather simple exponential functions with different powers of the argument. The program then offers an extremely convenient way to calculate axial and planar half-angles and minimum yield or dechanneling probabilities, effects on half-angles of amorphous overlayers, accidental channeling probabilities for randomly oriented crystals or crystallites, and finally a way to automatically generate stereographic projections of axial and planar channeling half-angles. The program can generate these projections and calculate these probabilities for axes and [hkl] planes up to (555).

  5. The alpha channeling effect

    Energy Technology Data Exchange (ETDEWEB)

    Fisch, N. J.

    2015-12-10

    Alpha particles born through fusion reactions in a tokamak reactor tend to slow down on electrons, but that could take up to hundreds of milliseconds. Before that happens, the energy in these alpha particles can destabilize on collisionless timescales toroidal Alfven modes and other waves, in a way deleterious to energy confinement. However, it has been speculated that this energy might be instead be channeled into useful energy, so as to heat fuel ions or to drive current. Such a channeling needs to be catalyzed by waves Waves can produce diffusion in energy of the alpha particles in a way that is strictly coupled to diffusion in space. If these diffusion paths in energy-position space point from high energy in the center to low energy on the periphery, then alpha particles will be cooled while forced to the periphery. The energy from the alpha particles is absorbed by the wave. The amplified wave can then heat ions or drive current. This process or paradigm for extracting alpha particle energy collisionlessly has been called alpha channeling. While the effect is speculative, the upside potential for economical fusion is immense. The paradigm also operates more generally in other contexts of magnetically confined plasma.

  6. Capsule-train stability

    Science.gov (United States)

    Bryngelson, Spencer H.; Freund, Jonathan B.

    2016-07-01

    Elastic capsules flowing in small enough tubes, such as red blood cells in capillaries, are well known to line up into regular single-file trains. The stability of such trains in somewhat wider channels, where this organization is not observed, is studied in a two-dimensional model system that includes full coupling between the viscous flow and suspended capsules. A diverse set of linearly amplifying disturbances, both long-time asymptotic (modal) and transient (nonmodal) perturbations, is identified and analyzed. These have a range of amplification rates and their corresponding forms are wavelike, typically dominated by one of five principal perturbation classes: longitudinal and transverse translations, tilts, and symmetric and asymmetric shape distortions. Finite-amplitude transiently amplifying perturbations are shown to provide a mechanism that can bypass slower asymptotic modal linear growth and precipitate the onset of nonlinear effects. Direct numerical simulations are used to verify the linear analysis and track the subsequent transition of the regular capsule trains into an apparently chaotic flow.

  7. Cascading blockages in channel bundles.

    Science.gov (United States)

    Barré, C; Talbot, J

    2015-11-01

    Flow in channel networks may involve a redistribution of flux following the blockage or failure of an individual link. Here we consider a simplified model consisting of N(c) parallel channels conveying a particulate flux. Particles enter these channels according to a homogeneous Poisson process and an individual channel blocks if more than N particles are simultaneously present. The behavior of the composite system depends strongly on how the flux of entering particles is redistributed following a blockage. We consider two cases. In the first, the intensity on each open channel remains constant while in the second the total intensity is evenly redistributed over the open channels. We obtain exact results for arbitrary N(c) and N for a system of independent channels and for arbitrary N(c) and N=1 for coupled channels. For N>1 we present approximate analytical as well as numerical results. Independent channels block at a decreasing rate due to a simple combinatorial effect, while for coupled channels the interval between successive blockages remains constant for N=1 but decreases for N>1. This accelerating cascade is due to the nonlinear dependence of the mean blocking time of a single channel on the entering particle flux that more than compensates for the decrease in the number of active channels.

  8. Micro-channel plate detector

    Energy Technology Data Exchange (ETDEWEB)

    Elam, Jeffrey W.; Lee, Seon W.; Wang, Hsien -Hau; Pellin, Michael J.; Byrum, Karen; Frisch, Henry J.

    2015-09-22

    A method and system for providing a micro-channel plate detector. An anodized aluminum oxide membrane is provided and includes a plurality of nanopores which have an Al coating and a thin layer of an emissive oxide material responsive to incident radiation, thereby providing a plurality of radiation sensitive channels for the micro-channel plate detector.

  9. Nomenclature for Ion channel Subunits

    OpenAIRE

    Bradley, Jonathan; Frings, Stephan; Yau, King-Wai; Reed, Randall

    2001-01-01

    Presents the nomenclature for ion channel subunits. Role of ion channels in the mediation of visual and olfactory signal transduction; Expression of ion channels in cell types and tissues; Assessment on the nucleotide sensitivity, ion conductance and calcium modulation in heteromers.

  10. Computer Simulation Studies of Ion Channels at High Temperatures

    Science.gov (United States)

    Song, Hyun Deok

    The gramicidin channel is the smallest known biological ion channel, and it exhibits cation selectivity. Recently, Dr. John Cuppoletti's group at the University of Cincinnati showed that the gramicidin channel can function at high temperatures (360 ˜ 380K) with significant currents. This finding may have significant implications for fuel cell technology. In this thesis, we have examined the gramicidin channel at 300K, 330K, and 360K by computer simulation. We have investigated how the temperature affects the current and differences in magnitude of free energy between the two gramicidin forms, the helical dimer (HD) and the double helix (DH). A slight decrease of the free energy barrier inside the gramicidin channel and increased diffusion at high temperatures result in an increase of current. An applied external field of 0.2V/nm along the membrane normal results in directly observable ion transport across the channels at high temperatures for both HD and DH forms. We found that higher temperatures also affect the probability distribution of hydrogen bonds, the bending angle, the distance between dimers, and the size of the pore radius for the helical dimer structure. These findings may be related to the gating of the gramicidin channel. Methanococcus jannaschii (MJ) is a methane-producing thermophile, which was discovered at a depth of 2600m in a Pacific Ocean vent in 1983. It has the ability to thrive at high temperatures and high pressures, which are unfavorable for most life forms. There have been some experiments to study its stability under extreme conditions, but still the origin of the stability of MJ is not exactly known. MJ0305 is the chloride channel protein from the thermophile MJ. After generating a structure of MJ0305 by homology modeling based on the Ecoli ClC templates, we examined the thermal stability, and the network stability from the change of network entropy calculated from the adjacency matrices of the protein. High temperatures increase the

  11. Validation of the radiometric stability of the Atmospheric Infrared Sounder

    Science.gov (United States)

    Aumann, H. H.; Elliott, D.; Strow, L. L.

    2012-09-01

    It has been widely accepted that an infrared sounder in low polar orbit is capable of producing climate quality data, if the spectral brightness temperatures have instrumental trends of less than 10 mK/yr. Achieving measurement stability at this level is not only very demanding of the design of the instrument, it is also pushes the state of art of measuring on orbit what stability is actually achieved. We discuss this using Atmospheric Infrared Sounder (AIRS) L1B data collected between 2002 and 2011. We compare the L1B brightness temperature observed in cloud filtered night tropical ocean spectra (obs) to the brightness temperature calculated based on the known surface emissivity, temperature and water vapor profiles from the ECMWF ReAnalysis (ERA) and the growth rates of CO2 , N2O and Ozone. The trend in (obscalc) is a powerful tool for the evaluation of the stability of the 2378 AIRS channels. We divided the channels into seven classes: All channels which sound in the stratosphere (at pressure levels below 150 hPa), 14 um CO2 sounding, 4 um CO2 P-branch sounding, 4um CO2 R-branch sounding, water vapor sounding, shortwave surface sounding and longwave surface sounding. The peak in the weighting function at 1050 hPa separates sounding and surface channels. The boundary between shortwave and longwave is 5 μm. Except for the stratosphere sounding channels, the remaining six groups have (obs-calc) trends of less than 20 mK/yr. The longwave surface channels have trends of 2 mK/yr, significantly less than the 8 mK/yr trend seem in the shortwave window channels. Based on the design of the instrument, trends within a group of channels should be the same. While the longwave and shortwave trends are less than the canonical 10 mK/yr, the larger trend in the shortwave channels could be an artifact of using the pre-launch determined calibration coefficients. This is currently under evaluation. The trend in (obs-calc) for the non-surface sounding channels, in particular for

  12. Rapid Fabrication Techniques for Liquid Rocket Channel Wall Nozzles

    Science.gov (United States)

    Gradl, Paul R.

    2016-01-01

    The functions of a regeneratively-cooled nozzle are to (1) expand combustion gases to increase exhaust gas velocity while, (2) maintaining adequate wall temperatures to prevent structural failure, and (3) transfer heat from the hot gases to the coolant fluid to promote injector performance and stability. Regeneratively-cooled nozzles are grouped into two categories: tube-wall nozzles and channel wall nozzles. A channel wall nozzle is designed with an internal liner containing a series of integral coolant channels that are closed out with an external jacket. Manifolds are attached at each end of the nozzle to distribute coolant to and away from the channels. A variety of manufacturing techniques have been explored for channel wall nozzles, including state of the art laser-welded closeouts and pressure-assisted braze closeouts. This paper discusses techniques that NASA MSFC is evaluating for rapid fabrication of channel wall nozzles that address liner fabrication, slotting techniques and liner closeout techniques. Techniques being evaluated for liner fabrication include large-scale additive manufacturing of freeform-deposition structures to create the liner blanks. Abrasive water jet milling is being evaluated for cutting the complex coolant channel geometries. Techniques being considered for rapid closeout of the slotted liners include freeform deposition, explosive bonding and Cold Spray. Each of these techniques, development work and results are discussed in further detail in this paper.

  13. Stability evaluation of vaccines: WHO approach.

    Science.gov (United States)

    Knezevic, Ivana

    2009-11-01

    The stability of vaccines has a major impact on the success of immunization programmes worldwide. In line with this, clear definition of the stability characteristics of a vaccine is of critical importance. One of the concerns at country level is whether vaccines will remain potent on its way from the manufacturer, through the distribution channels, to the final users and vaccine recipients. In response to the requests for assistance in defining stability profile of vaccines, the Expert Committee on Biological Standardization (ECBS) in October 2006 agreed that new WHO guidelines be established on stability evaluation of vaccines (http://www.who.int/biologicals/publications/trs/areas/vaccines/stability/en/index.html). This document applies to all vaccines against infectious diseases. The aim of this guideline is to provide the scientific basis and guiding principles for evaluation of vaccine stability for the purpose of clinical trial approval, licensing, and post-licensure monitoring. As part of its initiative to promote use of vaccines of assured quality, WHO emphasizes the role of National Regulatory Authorities (NRAs) and National Control Laboratories (NCLs) in overall vaccine evaluation, including stability assessment. While recognizing that manufacturers are responsible for the quality of the vaccines they produce, compliance with vaccine quality specifications is part of regulatory oversight. This article provides basic information about WHO international standards as well as key definitions and principles for stability evaluation of vaccines that are elaborated in detail in the above mentioned guidance document.

  14. Definition of two agonist types at the mammalian cold-activated channel TRPM8.

    Science.gov (United States)

    Janssens, Annelies; Gees, Maarten; Toth, Balazs Istvan; Ghosh, Debapriya; Mulier, Marie; Vennekens, Rudi; Vriens, Joris; Talavera, Karel; Voets, Thomas

    2016-01-01

    Various TRP channels act as polymodal sensors of thermal and chemical stimuli, but the mechanisms whereby chemical ligands impact on TRP channel gating are poorly understood. Here we show that AITC (allyl isothiocyanate; mustard oil) and menthol represent two distinct types of ligands at the mammalian cold sensor TRPM8. Kinetic analysis of channel gating revealed that AITC acts by destabilizing the closed channel, whereas menthol stabilizes the open channel, relative to the transition state. Based on these differences, we classify agonists as either type I (menthol-like) or type II (AITC-like), and provide a kinetic model that faithfully reproduces their differential effects. We further demonstrate that type I and type II agonists have a distinct impact on TRPM8 currents and TRPM8-mediated calcium signals in excitable cells. These findings provide a theoretical framework for understanding the differential actions of TRP channel ligands, with important ramifications for TRP channel structure-function analysis and pharmacology. PMID:27449282

  15. QKD Quantum Channel Authentication

    OpenAIRE

    Kosloski, J. T.

    2006-01-01

    Several simple yet secure protocols to authenticate the quantum channel of various QKD schemes, by coupling the photon sender's knowledge of a shared secret and the QBER Bob observes, are presented. It is shown that Alice can encrypt certain portions of the information needed for the QKD protocols, using a sequence whose security is based on computational-complexity, without compromising all of the sequence's entropy. It is then shown that after a Man-in-the-Middle attack on the quantum and c...

  16. Scheduling for Stable and Reliable Communication over Multiaccess Channels and Degraded Broadcast Channels

    CERN Document Server

    Sayee, K C V K S

    2006-01-01

    Information-theoretic arguments focus on modeling the reliability of information transmission, assuming availability of infinite data at sources, thus ignoring randomness in message generation times at the respective sources. However, in information transport networks, not only is reliable transmission important, but also stability, i.e., finiteness of mean delay incurred by messages from the time of generation to the time of successful reception. Usually, delay analysis is done separately using queueing-theoretic arguments, whereas reliable information transmission is studied using information theory. In this thesis, we investigate these two important aspects of data communication jointly by suitably combining models from these two fields. In particular, we model scheduled communication of messages, that arrive in a random process, (i) over multiaccess channels, with either independent decoding or joint decoding, and (ii) over degraded broadcast channels. The scheduling policies proposed permit up to a certa...

  17. Improving virtual channel discrimination in a multi-channel context.

    Science.gov (United States)

    Srinivasan, Arthi G; Shannon, Robert V; Landsberger, David M

    2012-04-01

    Improving spectral resolution in cochlear implants is key to improving performance in difficult listening conditions (e.g. speech in noise, music, etc.). Current focusing might reduce channel interaction, thereby increasing spectral resolution. Previous studies have shown that combining current steering and current focusing reduces spread of excitation and improves virtual channel discrimination in a single-channel context. It is unclear whether the single-channel benefits from current focusing extend to a multi-channel context, in which the physical and perceptual interference of multiple stimulated channels might overwhelm the benefits of improved spectral resolution. In this study, signal discrimination was measured with and without current focusing, in the presence of competing stimuli on nearby electrodes. Results showed that signal discrimination was consistently better with current focusing than without, regardless of the amplitude of the competing stimuli. Therefore, combining current steering and current focusing may provide more effective spectral cues than are currently available. PMID:22616092

  18. EFFICIENT UTILIZATION OF CHANNELS USING DYNAMIC GUARD CHANNEL ALLOCATION WITH CHANNEL BORROWING STRATEGY IN HANDOFFS

    Directory of Open Access Journals (Sweden)

    Alagu S

    2012-05-01

    Full Text Available User mobility in wireless data networks is increasing because of technological advances and the desire for voice and multimedia applications. These applications, however, require fast handoffs between base stations to maintain the quality of the connections. In this paper, the authors describe the use of novel and efficient data structure which dynamically allocates guard channel for handoffs and introduces the concept of channel borrowing strategy. The proposed scheme allocates the guard channels for handoff requests dynamically, based on the traffic load for certain time period. A new originating call in the cell coverage area also uses these guard channels if they are unused. Our basic idea is to allow Guard channels to be shared between new calls and handoff calls. This approach maximizes the channel utilization. The simulation results prove that the channel borrowing scheme improves the overall throughput.

  19. Front shock behavior of stable curved detonation waves in rectangular-cross-section curved channels

    OpenAIRE

    Nakayama, Hisahiro; Kasahara, Jiro; Matsuo, Akiko; Funaki, Ikkoh

    2013-01-01

    The propagation of curved detonation waves of gaseous explosives stabilized in rectangular-cross-section curved channels is investigated. Three types of stoichiometric test gases, C2H4 + 3O2, 2H2 + O2, and 2C2H2 + 5O2 + 7Ar, are evaluated. The ratio of the inner radius of the curved channel (ri) to the normal detonation cell width (λ) is an important factor in stabilizing curved detonation waves. The lower boundary of stabilization is around ri/λ = 23, regardless of the test gas. The stabiliz...

  20. Evolution and stability of tidal river bifurcations

    Science.gov (United States)

    Kleinhans, M. G.

    2011-12-01

    At bifurcations, water and sediment are partitioned, so that long-term evolution of fluvial and deltaic channels is determined by the bifurcation stability. Recent work in fluvial environments showed that bifurcations are commonly unstable so that avulsion results. For tidal rivers it could be argued that the discharge fluctuation enhances transport so that it simply closes of faster than in steady flow, but it could also be argued that tidal phase differences between the bifurcates cause a residual flow that counteracts the closing trend and keeps both bifurcates open. A physics-based numerical model (Delft3D) was used to model fixed-bank fork-shaped bifurcations with and without tides, and with short and long length relative to tidal wavelength. In all cases the bifurcations remained as unstable as without tides and ended invariably in avulsion. Tidal bifurcations unbalanced more rapidly than fluvial bifurcations, because of the increased ebb current and nonlinearity of sediment transport. On the other hand, discharge partitioning at the final bifurcation was much less asymmetrical with tides than without. Tidal wave deformation and production of higher harmonics in the longer channels affected sediment partitioning in the unstable phase but seems to have no effect on equilibrium morphology. Significant phase differences between the bifurcates caused a tidal floss effect, which scoured the bifurcation. In conclusion, symmetrical bifurcations affected by tides are unstable, but their final equilibrium is more symmetrical than without tides unless bifurcates have significant tidal phase differences. Furthermore I modelled growing deltas with self-formed distributary channels with and without cohesive sediment and with and without tides. Here, tides cause the flow to be more focussed in fewer and larger channels, whilst the few bifurcations are relatively stable. Combined fluvial discharge and tidal ebb flow in the channels transports more sediment than in fluvial

  1. Multiuser MIMO Channel Estimation

    Directory of Open Access Journals (Sweden)

    G.Indumathi

    2016-05-01

    Full Text Available In this paper, three beamforming design are considered for multi user MIMO system. First, transmit beamformers are fixed and the receive (RX beamformers are calculated. Transmit beamformer (TX-BFis projectedas a null space of appropriate channels. It reduces the interference for each user. Then the receiver beamformer is determined which maximize the SNR. This beamforming design provides less computation time. The second case is joint TX and RX beamformer for SNR maximization. In this transmitter and receiver beamformer are calculated using extended alternating optimization (EAO algorithm. The third one is joint transmitter and receiver beamforming for SNR and SINR maximization using EAO algorithm. This algorithm provides better error performance and sum rate performance. All the design cases are simulated by using standard multipath channel model. Our simulation results illustrate that compared to the least square design and zero forcing design, the joint TX and RX beamforming design using EAO algorithm provides faster beamforming and improved error performance and sum rate.

  2. Plutonium inventories for stabilization and stabilized materials

    Energy Technology Data Exchange (ETDEWEB)

    Williams, A.K.

    1996-05-01

    The objective of the breakout session was to identify characteristics of materials containing plutonium, the need to stabilize these materials for storage, and plans to accomplish the stabilization activities. All current stabilization activities are driven by the Defense Nuclear Facilities Safety Board Recommendation 94-1 (May 26, 1994) and by the recently completed Plutonium ES&H Vulnerability Assessment (DOE-EH-0415). The Implementation Plan for accomplishing stabilization of plutonium-bearing residues in response to the Recommendation and the Assessment was published by DOE on February 28, 1995. This Implementation Plan (IP) commits to stabilizing problem materials within 3 years, and stabilizing all other materials within 8 years. The IP identifies approximately 20 metric tons of plutonium requiring stabilization and/or repackaging. A further breakdown shows this material to consist of 8.5 metric tons of plutonium metal and alloys, 5.5 metric tons of plutonium as oxide, and 6 metric tons of plutonium as residues. Stabilization of the metal and oxide categories containing greater than 50 weight percent plutonium is covered by DOE Standard {open_quotes}Criteria for Safe Storage of Plutonium Metals and Oxides{close_quotes} December, 1994 (DOE-STD-3013-94). This standard establishes criteria for safe storage of stabilized plutonium metals and oxides for up to 50 years. Each of the DOE sites and contractors with large plutonium inventories has either started or is preparing to start stabilization activities to meet these criteria.

  3. Trapped particle stability for the kinetic stabilizer

    Science.gov (United States)

    Berk, H. L.; Pratt, J.

    2011-08-01

    A kinetically stabilized axially symmetric tandem mirror (KSTM) uses the momentum flux of low-energy, unconfined particles that sample only the outer end-regions of the mirror plugs, where large favourable field-line curvature exists. The window of operation is determined for achieving magnetohydrodynamic (MHD) stability with tolerable energy drain from the kinetic stabilizer. Then MHD stable systems are analysed for stability of the trapped particle mode. This mode is characterized by the detachment of the central-cell plasma from the kinetic-stabilizer region without inducing field-line bending. Stability of the trapped particle mode is sensitive to the electron connection between the stabilizer and the end plug. It is found that the stability condition for the trapped particle mode is more constraining than the stability condition for the MHD mode, and it is challenging to satisfy the required power constraint. Furthermore, a severe power drain may arise from the necessary connection of low-energy electrons in the kinetic stabilizer to the central region.

  4. Coupling tests of parallel channels to modal neutronic kinetics

    International Nuclear Information System (INIS)

    In this work the initial results of the joining of an arrangement of 36 channels in parallel are studied to a modal neutronic kinetic model to represent the core of a BWR type reactor. The set of channels is obtained group the assemblies of that it consists the core in an arrangement of concentric rings, for later on to subdivide each ring in four parts to assign each segment to a quadrant of the core. The obtained channels are coupled to a modal kinetics model that considers the fundamental way and the first harmonic. The obtained solution represents the radial distribution and power azimuthal, the one which is feedback to the channels to update the thermohydraulic variables. The restriction that the pressure drop is same for each channel it is only imposed as initial condition, like part of the stationary state, and it is allowed that the pressure drop in the assemblies them it is different in each channel during a reactivity interference. For the tests to the system, it is convenient to select a relatively big core and that it operates near their stability frontier, for that the channels are dimensioning according to the case 9 of the Stability Benchmark of the Ringhals Swedish plant, organized by the Nuclear Energy Agency in 1994. In general, they reproduce the results of this benchmark, when reproducing oscillations outside of phase, with the additional results that the quadrants 1 and 2 of the core present oscillations of more width that the quadrants 3 and 4. The set group nuclear-thermohydraulics it is solved numerically by means of the outline master-slave of distributed calculation implemented by means of Parallel Virtual Machine (PVM). (Author)

  5. Calcium ion channel and epilepsy

    Institute of Scientific and Technical Information of China (English)

    Yudan Lü; Weihong Lin; Dihui Ma

    2006-01-01

    OBJECTIVE: To review the relationship between calcium ion channel and epilepsy for well investigating the pathogenesis of epilepsy and probing into the new therapeutic pathway of epilepsy.DATA SOURCES: A computer-based online research Calcium ion channel and epilepsy related articles published between January 1994 and December 2006 in the CKNI and Wanfang database with the key words of "calcium influxion, epilepsy, calcium-channel blocker". The language was limited to Chinese. At the same time,related articles published between January 1993 and December 2006 in Pubmed were searched for on online with the key words of "calcium influxion, epilepsy" in English.STUDY SELECTION: The materials were selected firstly. Inclusive criteria: ① Studies related to calcium ion channel and the pat1hogenesis of epilepsy. ② Studies on the application of calcium ion channel blocker in the treatment of epilepsy. Exclusive criteria: repetitive or irrelated studies.DATA EXTRACTION: According to the criteria, 123 articles were retrieved and 93 were excluded due to repetitive or irrelated studies. Altogether 30 articles met the inclusive criteria, 11 of them were about the structure and characters of calcium ion channel, 10 about calcium ion channel and the pathogenesis of epilepsy and 9 about calcium blocker and the treatment of epilepsy.DATA SYNTHESIS: Calcium ion channels mainly consist of voltage dependent calcium channel and receptor operated calcium channel. Depolarization caused by voltage gating channel-induced influxion is the pathological basis of epileptic attack, and it is found in many studies that many anti-epileptic drugs have potential and direct effect to rivalizing voltage-dependent calcium ion channel.CONCLUSION: Calcium influxion plays an important role in the seizure of epilepsy. Some calcium antagonists seen commonly are being tried in the clinical therapy of epilepsy that is being explored, not applied in clinical practice. If there are enough evidences to

  6. Secure refinements of communication channels

    OpenAIRE

    Cheval, Vincent; Cortier, Véronique; Le Morvan, Eric

    2015-01-01

    International audience It is a common practice to design a protocol (say Q) assuming some secure channels. Then the secure channels are implemented using any standard protocol, e.g. TLS. In this paper, we study when such a practice is indeed secure. We provide a characterization of both confidential and authenticated channels. As an application, we study several protocols of the literature including TLS and BAC protocols. Thanks to our result, we can consider a larger number of sessions wh...

  7. Determining nitrogen laser channel parameters

    International Nuclear Information System (INIS)

    This paper reports the measurement of the nitrogen laser channel current using a magnetic probe. For a 46 cm laser channel of gap 16 mm operated at 10 kV, 60 torr with foil capacitors of 58 and 28 nF, the channel current, inductance and resistance are found to be 42 kA, l.6 nH and 0.1 Ω respectively. (author)

  8. Highly permeable artificial water channels that can self-assemble into two-dimensional arrays.

    Science.gov (United States)

    Shen, Yue-Xiao; Si, Wen; Erbakan, Mustafa; Decker, Karl; De Zorzi, Rita; Saboe, Patrick O; Kang, You Jung; Majd, Sheereen; Butler, Peter J; Walz, Thomas; Aksimentiev, Aleksei; Hou, Jun-li; Kumar, Manish

    2015-08-11

    Bioinspired artificial water channels aim to combine the high permeability and selectivity of biological aquaporin (AQP) water channels with chemical stability. Here, we carefully characterized a class of artificial water channels, peptide-appended pillar[5]arenes (PAPs). The average single-channel osmotic water permeability for PAPs is 1.0(± 0.3) × 10(-14) cm(3)/s or 3.5(± 1.0) × 10(8) water molecules per s, which is in the range of AQPs (3.4 ∼ 40.3 × 10(8) water molecules per s) and their current synthetic analogs, carbon nanotubes (CNTs, 9.0 × 10(8) water molecules per s). This permeability is an order of magnitude higher than first-generation artificial water channels (20 to ∼ 10(7) water molecules per s). Furthermore, within lipid bilayers, PAP channels can self-assemble into 2D arrays. Relevant to permeable membrane design, the pore density of PAP channel arrays (∼ 2.6 × 10(5) pores per μm(2)) is two orders of magnitude higher than that of CNT membranes (0.1 ∼ 2.5 × 10(3) pores per μm(2)). PAP channels thus combine the advantages of biological channels and CNTs and improve upon them through their relatively simple synthesis, chemical stability, and propensity to form arrays. PMID:26216964

  9. Trapped Particle Stability for the Kinetic Stabilizer

    CERN Document Server

    Berk, H L

    2011-01-01

    A kinetically stabilized axially symmetric tandem mirror (KSTM) uses the momentum flux of low-energy, unconfined particles that sample only the outer end-regions of the mirror plugs, where large favorable field-line curvature exists. The window of operation is determined for achieving MHD stability with tolerable energy drain from the kinetic stabilizer. Then MHD stable systems are analyzed for stability of the trapped particle mode. This mode is characterized by the detachment of the central-cell plasma from the kinetic stabilizer region without inducing field-line bending. Stability of the trapped particle mode is sensitive to the electron connection between the stabilizer and the end plug. It is found that the stability condition for the trapped particle mode is more constraining than the stability condition for the MHD mode, and it is challenging to satisfy the required power constraint. Furthermore a severe power drain may arise from the necessary connection of low-energy electrons in the kinetic stabili...

  10. Demystifying Mechanosensitive Piezo Ion Channels.

    Science.gov (United States)

    Xu, X Z Shawn

    2016-06-01

    Mechanosensitive channels mediate touch, hearing, proprioception, and blood pressure regulation. Piezo proteins, including Piezo1 and Piezo2, represent a new class of mechanosensitive channels that have been reported to play key roles in most, if not all, of these modalities. The structural architecture and molecular mechanisms by which Piezos act as mechanosensitive channels, however, remain mysterious. Two new studies have now provided critical insights into the atomic structure and molecular basis of the ion permeation and mechano-gating properties of the Piezo1 channel.

  11. Geometric pumping in autophoretic channels

    CERN Document Server

    Michelin, Sebastien; De Canio, Gabriele; Lobato-Dauzier, Nicolas; Lauga, Eric

    2015-01-01

    Many microfluidic devices use macroscopic pressure differentials to overcome viscous friction and generate flows in microchannels. In this work, we investigate how the chemical and geometric properties of the channel walls can drive a net flow by exploiting the autophoretic slip flows induced along active walls by local concentration gradients of a solute species. We show that chemical patterning of the wall is not required to generate and control a net flux within the channel, rather channel geometry alone is sufficient. Using numerical simulations, we determine how geometric characteristics of the wall influence channel flow rate, and confirm our results analytically in the asymptotic limit of lubrication theory.

  12. Demystifying Mechanosensitive Piezo Ion Channels.

    Science.gov (United States)

    Xu, X Z Shawn

    2016-06-01

    Mechanosensitive channels mediate touch, hearing, proprioception, and blood pressure regulation. Piezo proteins, including Piezo1 and Piezo2, represent a new class of mechanosensitive channels that have been reported to play key roles in most, if not all, of these modalities. The structural architecture and molecular mechanisms by which Piezos act as mechanosensitive channels, however, remain mysterious. Two new studies have now provided critical insights into the atomic structure and molecular basis of the ion permeation and mechano-gating properties of the Piezo1 channel. PMID:27164907

  13. A Beacon Transmission Power Control Algorithm Based on Wireless Channel Load Forecasting in VANETs.

    Directory of Open Access Journals (Sweden)

    Yuanfu Mo

    Full Text Available In a vehicular ad hoc network (VANET, the periodic exchange of single-hop status information broadcasts (beacon frames produces channel loading, which causes channel congestion and induces information conflict problems. To guarantee fairness in beacon transmissions from each node and maximum network connectivity, adjustment of the beacon transmission power is an effective method for reducing and preventing channel congestion. In this study, the primary factors that influence wireless channel loading are selected to construct the KF-BCLF, which is a channel load forecasting algorithm based on a recursive Kalman filter and employs multiple regression equation. By pre-adjusting the transmission power based on the forecasted channel load, the channel load was kept within a predefined range; therefore, channel congestion was prevented. Based on this method, the CLF-BTPC, which is a transmission power control algorithm, is proposed. To verify KF-BCLF algorithm, a traffic survey method that involved the collection of floating car data along a major traffic road in Changchun City is employed. By comparing this forecast with the measured channel loads, the proposed KF-BCLF algorithm was proven to be effective. In addition, the CLF-BTPC algorithm is verified by simulating a section of eight-lane highway and a signal-controlled urban intersection. The results of the two verification process indicate that this distributed CLF-BTPC algorithm can effectively control channel load, prevent channel congestion, and enhance the stability and robustness of wireless beacon transmission in a vehicular network.

  14. A Beacon Transmission Power Control Algorithm Based on Wireless Channel Load Forecasting in VANETs.

    Science.gov (United States)

    Mo, Yuanfu; Yu, Dexin; Song, Jun; Zheng, Kun; Guo, Yajuan

    2015-01-01

    In a vehicular ad hoc network (VANET), the periodic exchange of single-hop status information broadcasts (beacon frames) produces channel loading, which causes channel congestion and induces information conflict problems. To guarantee fairness in beacon transmissions from each node and maximum network connectivity, adjustment of the beacon transmission power is an effective method for reducing and preventing channel congestion. In this study, the primary factors that influence wireless channel loading are selected to construct the KF-BCLF, which is a channel load forecasting algorithm based on a recursive Kalman filter and employs multiple regression equation. By pre-adjusting the transmission power based on the forecasted channel load, the channel load was kept within a predefined range; therefore, channel congestion was prevented. Based on this method, the CLF-BTPC, which is a transmission power control algorithm, is proposed. To verify KF-BCLF algorithm, a traffic survey method that involved the collection of floating car data along a major traffic road in Changchun City is employed. By comparing this forecast with the measured channel loads, the proposed KF-BCLF algorithm was proven to be effective. In addition, the CLF-BTPC algorithm is verified by simulating a section of eight-lane highway and a signal-controlled urban intersection. The results of the two verification process indicate that this distributed CLF-BTPC algorithm can effectively control channel load, prevent channel congestion, and enhance the stability and robustness of wireless beacon transmission in a vehicular network.

  15. A Beacon Transmission Power Control Algorithm Based on Wireless Channel Load Forecasting in VANETs.

    Science.gov (United States)

    Mo, Yuanfu; Yu, Dexin; Song, Jun; Zheng, Kun; Guo, Yajuan

    2015-01-01

    In a vehicular ad hoc network (VANET), the periodic exchange of single-hop status information broadcasts (beacon frames) produces channel loading, which causes channel congestion and induces information conflict problems. To guarantee fairness in beacon transmissions from each node and maximum network connectivity, adjustment of the beacon transmission power is an effective method for reducing and preventing channel congestion. In this study, the primary factors that influence wireless channel loading are selected to construct the KF-BCLF, which is a channel load forecasting algorithm based on a recursive Kalman filter and employs multiple regression equation. By pre-adjusting the transmission power based on the forecasted channel load, the channel load was kept within a predefined range; therefore, channel congestion was prevented. Based on this method, the CLF-BTPC, which is a transmission power control algorithm, is proposed. To verify KF-BCLF algorithm, a traffic survey method that involved the collection of floating car data along a major traffic road in Changchun City is employed. By comparing this forecast with the measured channel loads, the proposed KF-BCLF algorithm was proven to be effective. In addition, the CLF-BTPC algorithm is verified by simulating a section of eight-lane highway and a signal-controlled urban intersection. The results of the two verification process indicate that this distributed CLF-BTPC algorithm can effectively control channel load, prevent channel congestion, and enhance the stability and robustness of wireless beacon transmission in a vehicular network. PMID:26571042

  16. MONETARY TRANSMISSION CHANNELS IN ROMANIA – THE CREDIT CHANNEL

    Directory of Open Access Journals (Sweden)

    Magdalena RĂDULESCU

    2009-12-01

    Full Text Available The theoretical – intuitive analysis applied to the segment of monetary transmission evidences the fact that forming the traditional monetary impulses transmission channels are in a starting phase due to the long financial non – intermediary process which Romanian economy had known. In these conditions, the exchange rate channel, and also NBR currency purchases was, for a long time, an important way through which monetary authorities actions influenced macro economical behaviors. But starting with 2000, it is observed a credit channel reactivation and, especially, interest rate channel. Anyhow, the credit channel continues to be undermined by the existence of liquidity surplus within the system, by the phenomena of substitution of national currency credit with currency credits, and also moral hazardous displays. Albeit some of these phenomena also affect the interest rate channel, its role in sending monetary policy impulses is in a continuous progress. Apparently, it acts by way of nominal interest rates, their real level seeming less relevant. Once with remaking the two traditional channels, the companies and households balance is configured and consolidated, which shall potentate in the future the efficiency of the monetary policy. This paper analyses the credit channel in Romania, through an unrestricted VAR analysis.. It shows the responses of exchange rate, inflation rate, GDP, interest rate, imports and exports to a shock on non-governmental credit

  17. CHANNEL ESTIMATION FOR ITERATIVE DECODING OVER FADING CHANNELS

    Institute of Scientific and Technical Information of China (English)

    K. H. Sayhood; Wu Lenan

    2002-01-01

    A method of coherent detection and channel estimation for punctured convolutional coded binary Quadrature Amplitude Modulation (QAM) signals transmitted over a frequency-flat Rayleigh fading channels used for a digital radio broadcasting transmission is presented. Some known symbols are inserted in the encoded data stream to enhance the channel estimation process.The pilot symbols are used to replace the existing parity symbols so no bandwidth expansion is required. An iterative algorithm that uses decoding information as well as the information contained in the known symbols is used to improve the channel parameter estimate. The scheme complexity grows exponentially with the channel estimation filter length. The performance of the system is compared for a normalized fading rate with both perfect coherent detection (corresponding to a perfect knowledge of the fading process and noise variance) and differential detection of Differential Amplitude Phase Shift Keying (DAPSK). The tradeoff between simplicity of implementation and bit-error-rate performance of different techniques is also compared.

  18. Asymptotic stability region of slotted-Aloha

    CERN Document Server

    Bordenave, Charles; Proutiere, Alexandre

    2008-01-01

    We analyze the stability of standard, buffered, slotted-Aloha systems. Specifically, we consider a set of $N$ users, each equipped with an infinite buffer. Packets arrive into user $i$'s buffer according to some stationary ergodic Markovian process of intensity $\\lambda_i$. At the beginning of each slot, if user $i$ has packets in its buffer, it attempts to transmit a packet with fixed probability $p_i$ over a shared resource / channel. The transmission is successful only when no other user attempts to use the channel. The stability of such systems has been open since their very first analysis in 1979 by Tsybakov and Mikhailov. In this paper, we propose an approximate stability condition, that is provably exact when the number of users $N$ grows large. We provide theoretical evidence and numerical experiments to explain why the proposed approximate stability condition is extremely accurate even for systems with a restricted number of users (even two or three). We finally extend the results to the case of more...

  19. Flow characteristics on the blade channel vortex in the Francis turbine

    Science.gov (United States)

    Guo, P. C.; Wang, Z. N.; Luo, X. Q.; Wang, Y. L.; Zuo, J. L.

    2016-05-01

    Depending on the long-term hydraulic development of Francis turbine, the blade channel vortex phenomenon was investigated systematically from hydraulic design, experimental and numerical computation in this paper. The blade channel vortex difference between the high water head and low water head turbine was also analyzed. Meanwhile, the relationship between the blade channel vortex and the operating stability of hydraulic turbine was also investigated. The results show that the phenomenon of blade channel vortex is an intrinsic property for Francis turbine under small flow rate condition, the turning-point of the blade channel vortex inception curve appears at low unit speed region, and the variation trend of the blade channel vortex inception curve is closely related to the blade inlet edge profile. In addition to, the vortex of the high water head turbine can generally be excluded from the stable operation region, while which is more different for the one of the low water head turbine.

  20. Workshop on Feedback Stabilization of MHD Stabilities

    Energy Technology Data Exchange (ETDEWEB)

    McGuire, K.; Kugel, H. [Princeton Univ., NJ (United States). Plasma Physics Lab.; La Haye, R. [General Atomics, San Diego, CA (United States); Mauel, M. [Columbia Univ., New York, NY (United States). Dept. of Applied Physics; Nevins, W. [Lawrence Livermore National Lab., CA (United States); Prager, S. [Wisconsin Univ., Madison, WI (United States). Dept. of Physics

    1996-12-31

    The feedback stabilization of MHD instabilities is an area of research that is critical for improving the performance and economic attractiveness of magnetic confinement devices. A Workshop dedicated to feedback stabilization of MHD instabilities was held from December 11-13, 1996 at the Princeton Plasma Physics Laboratory, Princeton NJ, USA. The resulting presentations, conclusions, and recommendations are summarized.

  1. Engineering of metabolic pathways by artificial enzyme channels

    Directory of Open Access Journals (Sweden)

    Marlene ePröschel

    2015-10-01

    Full Text Available Application of industrial enzymes for production of valuable chemical compounds has greatly benefited from recent developments in Systems and Synthetic Biology. Both, in vivo and in vitro systems have been established, allowing conversion of simple into complex compounds. Metabolic engineering in living cells needs to be balanced which is achieved by controlling gene expression levels, translation, scaffolding, compartmentation and flux control. In vitro applications are often hampered by limited protein stability/half-life and insufficient rates of substrate conversion. To improve stability and catalytic activity, proteins are post-translationally modified and arranged in artificial metabolic channels. Within the review article we will first discuss the supramolecular organization of enzymes in living systems and secondly summarize current and future approaches to design artificial metabolic channels by additive manufacturing for the efficient production of desired products.

  2. Stabilizing membrane domains antagonizes anesthesia

    CERN Document Server

    Machta, Benjamin B; Nouri, Mariam; McCarthy, Nicola L C; Gray, Erin M; Miller, Ann L; Brooks, Nicholas J; Veatch, Sarah L

    2016-01-01

    Diverse molecules induce general anesthesia with potency strongly correlated both with their hydrophobicity and their effects on certain ion channels. We recently observed that several anesthetics inhibit heterogeneity in plasma membrane derived vesicles by lowering the critical temperature ($T_c$) for phase separation. Here we exploit conditions that stabilize membrane heterogeneity to test the correlation between the anesthetic potency of n-alcohols and effects on $T_c$. First we show that hexadecanol acts oppositely to anesthetics on membrane mixing and antagonizes ethanol induced anesthesia in a tadpole behavioral assay. Second, we show that two previously described `intoxication reversers' raise $T_c$ in vesicles and counter ethanol's effects in vesicles, mimicking the findings of previous electrophysiological measurements. Third, we find that hydrostatic pressure, long known to reverse anesthesia, also raises $T_c$ in vesicles with a magnitude that counters the effect of an anesthetic at relevant concen...

  3. Improving stability of stabilized and multiscale formulations in flow simulations at small time steps

    KAUST Repository

    Hsu, Ming-Chen

    2010-02-01

    The objective of this paper is to show that use of the element-vector-based definition of stabilization parameters, introduced in [T.E. Tezduyar, Computation of moving boundaries and interfaces and stabilization parameters, Int. J. Numer. Methods Fluids 43 (2003) 555-575; T.E. Tezduyar, Y. Osawa, Finite element stabilization parameters computed from element matrices and vectors, Comput. Methods Appl. Mech. Engrg. 190 (2000) 411-430], circumvents the well-known instability associated with conventional stabilized formulations at small time steps. We describe formulations for linear advection-diffusion and incompressible Navier-Stokes equations and test them on three benchmark problems: advection of an L-shaped discontinuity, laminar flow in a square domain at low Reynolds number, and turbulent channel flow at friction-velocity Reynolds number of 395. © 2009 Elsevier B.V. All rights reserved.

  4. Channel's Concurrence and Quantum Teleportation

    Institute of Scientific and Technical Information of China (English)

    LING Yin-Sheng

    2005-01-01

    Concurrence can measure the entanglement property of a system. If the channel is a pure state, positive concurrence state can afford the good performance in the teleportation process. If the channel ia a mixed state, positive concurrence state cannot assure the good performance in the teleportation. The conditions of the positive concurrence and the quantum teleportation in the Heisenberg spin ring is derived.

  5. Channel's Concurrence and Quantum Teleportation

    International Nuclear Information System (INIS)

    Concurrence can measure the entanglement property of a system. If the channel is a pure state, positive concurrence state can afford the good performance in the teleportation process. If the channel ia a mixed state, positive concurrence state cannot assure the good performance in the teleportation. The conditions of the positive concurrence and the quantum teleportation in the Heisenberg spin ring is derived.

  6. An improved channel assessment scheme

    KAUST Repository

    Bader, Ahmed

    2014-05-01

    A source node in a multihop network determines whether to transmit in a channel based on whether the channel is occupied by a packet transmission with a large number of relays; whether the source node is in the data tones back-off zone; and the source node is in the busy tone back-off zone.

  7. Defect Distributions in Channeling Experiments

    DEFF Research Database (Denmark)

    Andersen, Hans Henrik; Sigmund, P.

    1965-01-01

    of radiation damage by channeled particles. As an application, one gets a necessary criterion for the occurence of super tails in channeling experiments. The theory involves some assumptions on the behaviour of Born-Mayer potentials which are verified by comparison to experimental displacement energies....

  8. Synchronization strategies for RFI channels

    Science.gov (United States)

    Mceliece, R. J.; Vantilborg, H.; Tung, S.

    1977-01-01

    An RFI channel to be a multiple-access channel is defined in which no sender can know when any other starts, and the problem of determining the relative phases of the senders at the receiver is studied. A new result is proved about binary DEBruijn sequences.

  9. Hydraulic jumps in a channel

    DEFF Research Database (Denmark)

    Bonn, D.; Andersen, Anders Peter; Bohr, Tomas

    2009-01-01

    We present a study of hydraulic jumps with flow predominantly in one direction, created either by confining the flow to a narrow channel with parallel walls or by providing an inflow in the form of a narrow sheet. In the channel flow, we find a linear height profile upstream of the jump as expected...

  10. Molecular Diversity and Functional Evolution of Scorpion Potassium Channel Toxins*

    OpenAIRE

    Zhu, Shunyi; Peigneur, Steve; Gao, Bin; Luo, Lan; Jin, Di; Zhao, Yong; Tytgat, Jan

    2010-01-01

    Scorpion toxins affecting K+ channels (KTxs) represent important pharmacological tools and potential drug candidates. Here, we report molecular characterization of seven new KTxs in the scorpion Mesobuthus eupeus by cDNA cloning combined with biochemical approaches. Comparative modeling supports that all these KTxs share a conserved cysteine-stabilized α-helix/β-sheet structural motif despite the differences in protein sequence and size. We investigated functional diversification of two ortho...

  11. Lipid Regulation of Sodium Channels.

    Science.gov (United States)

    D'Avanzo, N

    2016-01-01

    The lipid landscapes of cellular membranes are complex and dynamic, are tissue dependent, and can change with the age and the development of a variety of diseases. Researchers are now gaining new appreciation for the regulation of ion channel proteins by the membrane lipids in which they are embedded. Thus, as membrane lipids change, for example, during the development of disease, it is likely that the ionic currents that conduct through the ion channels embedded in these membranes will also be altered. This chapter provides an overview of the complex regulation of prokaryotic and eukaryotic voltage-dependent sodium (Nav) channels by fatty acids, sterols, glycerophospholipids, sphingolipids, and cannabinoids. The impact of lipid regulation on channel gating kinetics, voltage-dependence, trafficking, toxin binding, and structure are explored for Nav channels that have been examined in heterologous expression systems, native tissue, and reconstituted into artificial membranes. Putative mechanisms for Nav regulation by lipids are also discussed. PMID:27586290

  12. Quantum channel capacities - multiparty communication

    CERN Document Server

    Demianowicz, M; Demianowicz, Maciej; Horodecki, Pawel

    2006-01-01

    We analyze different aspects of multiparty communication over quantum memoryless channels and generalize some of key results known from bipartite channels to that of multiparty scenario. In particular, we introduce multiparty versions of minimal subspace transmission fidelity and entanglement transmission fidelity. We also provide alternative, local, versions of fidelities and show their equivalence to the global ones in context of capacity regions defined. The equivalence of two different capacity notions with respect to two types of the fidelities is proven. In analogy to bipartite case it is shown, via sufficiency of isometric encoding theorem, that additional classical forward side channel does not increase capacity region of any quantum channel with $k$ senders and $m$ receivers which represents a compact unit of general quantum networks theory. The result proves that recently provided capacity region of multiple access channel ([M. Horodecki et al, Nature {\\bf 436} 673 (2005)], [J.Yard et al, quant-ph/0...

  13. Voltage-gated proton channels.

    Science.gov (United States)

    Decoursey, Thomas E

    2012-04-01

    Voltage-gated proton channels, HV1, have vaulted from the realm of the esoteric into the forefront of a central question facing ion channel biophysicists, namely, the mechanism by which voltage-dependent gating occurs. This transformation is the result of several factors. Identification of the gene in 2006 revealed that proton channels are homologues of the voltage-sensing domain of most other voltage-gated ion channels. Unique, or at least eccentric, properties of proton channels include dimeric architecture with dual conduction pathways, perfect proton selectivity, a single-channel conductance approximately 10(3) times smaller than most ion channels, voltage-dependent gating that is strongly modulated by the pH gradient, ΔpH, and potent inhibition by Zn(2+) (in many species) but an absence of other potent inhibitors. The recent identification of HV1 in three unicellular marine plankton species has dramatically expanded the phylogenetic family tree. Interest in proton channels in their own right has increased as important physiological roles have been identified in many cells. Proton channels trigger the bioluminescent flash of dinoflagellates, facilitate calcification by coccolithophores, regulate pH-dependent processes in eggs and sperm during fertilization, secrete acid to control the pH of airway fluids, facilitate histamine secretion by basophils, and play a signaling role in facilitating B-cell receptor mediated responses in B-lymphocytes. The most elaborate and best-established functions occur in phagocytes, where proton channels optimize the activity of NADPH oxidase, an important producer of reactive oxygen species. Proton efflux mediated by HV1 balances the charge translocated across the membrane by electrons through NADPH oxidase, minimizes changes in cytoplasmic and phagosomal pH, limits osmotic swelling of the phagosome, and provides substrate H(+) for the production of H2O2 and HOCl, reactive oxygen species crucial to killing pathogens.

  14. Reduced fine sediment flux and channel change in response to the managed diversion of an upland river channel

    Science.gov (United States)

    Perks, Matthew Thomas; Warburton, Jeff

    2016-09-01

    This paper describes the implementation of a novel mitigation approach and subsequent adaptive management, designed to reduce the transfer of fine sediment (indicates a reduction in residuals through time (p < 0.001), with the developed LOWESS model over-predicting sediment concentrations as the channel stabilizes. However, the channel is continuing to adjust to the reconfigured morphology, with evidence of a headward propagating knickpoint which has migrated 120 m at an exponentially decreasing rate over the last 7 years since diversion. The study demonstrates that channel reconfiguration can be effective in mitigating fine sediment flux in headwater streams but the full value of this may take many years to achieve whilst the fluvial system slowly readjusts.

  15. Opening Channels of Communication

    Directory of Open Access Journals (Sweden)

    Clarice Moura Costa

    2009-03-01

    Full Text Available Psychosis, as described through a psychodynamic perspective, is conceptualized as an attempt to deny the enveloping reality to avoid contact with the other. Music therapy is a way to break this barrier of non-communication raised by the patients. The music therapy process is configured as a trinomial – action (making music/ relationship (action with the other/communication (musical or verbal voluntary expression of feelings and conflicts, which, although intrinsically connected, is perceived in a sequential process. Aulagnier asserts that psychic activity represents the conjunction of three modes of functioning: the original process, the primary process and the secondary process. The perception of sound passes through three phases, corresponding to each manner of functioning of the psychic system – the pleasure of hearing, the desire to listen (to the other and the imperative of meaning. The music therapy process offers a significant similarity with the theory proposed by Aulagnier. We propose the hypothesis that in music therapy, there is an opportunity to (reexperience very archaic phases in the constitution of the ego, but in a new manner, so helping to open communication channels. This theoretical hypothesis is illustrated by real examples of patients.

  16. Single-Channel Recording of Ligand-Gated Ion Channels.

    Science.gov (United States)

    Plested, Andrew J R

    2016-01-01

    Single-channel recordings reveal the microscopic properties of individual ligand-gated ion channels. Such recordings contain much more information than measurements of ensemble behavior and can yield structural and functional information about the receptors that participate in fast synaptic transmission in the brain. With a little care, a standard patch-clamp electrophysiology setup can be adapted for single-channel recording in a matter of hours. Thenceforth, it is a realistic aim to record single-molecule activity with microsecond resolution from arbitrary cell types, including cell lines and neurons. PMID:27480725

  17. M channel enhancers and physiological M channel block.

    Science.gov (United States)

    Linley, John E; Pettinger, Louisa; Huang, Dongyang; Gamper, Nikita

    2012-02-15

    M-type (Kv7, KCNQ) K(+) channels control the resting membrane potential of many neurons, including peripheral nociceptive sensory neurons. Several M channel enhancers were suggested as prospective analgesics, and targeting M channels specifically in peripheral nociceptors is a plausible strategy for peripheral analgesia. However, receptor-induced inhibition of M channels in nociceptors is often observed in inflammation and may contribute to inflammatory pain. Such inhibition is predominantly mediated by phospholipase C. We investigated four M channel enhancers (retigabine, flupirtine, zinc pyrithione and H(2)O(2)) for their ability to overcome M channel inhibition via two phospholipase C-mediated mechanisms, namely depletion of membrane phosphatidylinositol 4,5-bisphosphate (PIP(2)) and a rise in intracellular Ca(2+) (an action mediated by calmodulin). Data from overexpressed Kv7.2/Kv7.3 heteromers and native M currents in dorsal root ganglion neurons suggest the following conclusions. (i) All enhancers had a dual effect on M channel activity, a negative shift in voltage dependence and an increase of the maximal current at saturating voltages. The enhancers differed in their efficacy to produce these effects. (ii) Both PIP(2) depletion and Ca(2+)/calmodulin strongly reduced the M current amplitude; however, at voltages near the threshold for M channel activation (-60 mV) all enhancers were able to restore M channel activity to a control level or above, while at saturating voltages the effects were more variable. (iii) Receptor-mediated inhibition of M current in nociceptive dorsal root ganglion neurons did not reduce the efficacy of retigabine or flupirtine to hyperpolarize the resting membrane potential. In conclusion, we show that all four M channel enhancers tested could overcome both PIP(2) and Ca(2+)-calmodulin-induced inhibition of Kv7.2/7.3 at voltages close to the threshold for action potential firing (-60 mV) but generally had reduced efficacy at a

  18. Stability of Dolos Slopes

    DEFF Research Database (Denmark)

    Brorsen, Michael; Burcharth, Hans F.; Larsen, Torben

    The stability of dolos armour blocks against wave attack has been investigated in wave model studies.......The stability of dolos armour blocks against wave attack has been investigated in wave model studies....

  19. Opposite Effects of the S4-S5 Linker and PIP(2) on Voltage-Gated Channel Function: KCNQ1/KCNE1 and Other Channels.

    Science.gov (United States)

    Choveau, Frank S; Abderemane-Ali, Fayal; Coyan, Fabien C; Es-Salah-Lamoureux, Zeineb; Baró, Isabelle; Loussouarn, Gildas

    2012-01-01

    Voltage-gated potassium (Kv) channels are tetramers, each subunit presenting six transmembrane segments (S1-S6), with each S1-S4 segments forming a voltage-sensing domain (VSD) and the four S5-S6 forming both the conduction pathway and its gate. S4 segments control the opening of the intracellular activation gate in response to changes in membrane potential. Crystal structures of several voltage-gated ion channels in combination with biophysical and mutagenesis studies highlighted the critical role of the S4-S5 linker (S4S5(L)) and of the S6 C-terminal part (S6(T)) in the coupling between the VSD and the activation gate. Several mechanisms have been proposed to describe the coupling at a molecular scale. This review summarizes the mechanisms suggested for various voltage-gated ion channels, including a mechanism that we described for KCNQ1, in which S4S5(L) is acting like a ligand binding to S6(T) to stabilize the channel in a closed state. As discussed in this review, this mechanism may explain the reverse response to depolarization in HCN-like channels. As opposed to S4S5(L), the phosphoinositide, phosphatidylinositol 4,5-bisphosphate (PIP(2)), stabilizes KCNQ1 channel in an open state. Many other ion channels (not only voltage-gated) require PIP(2) to function properly, confirming its crucial importance as an ion channel cofactor. This is highlighted in cases in which an altered regulation of ion channels by PIP(2) leads to channelopathies, as observed for KCNQ1. This review summarizes the state of the art on the two regulatory mechanisms that are critical for KCNQ1 and other voltage-gated channels function (PIP(2) and S4S5(L)), and assesses their potential physiological and pathophysiological roles.

  20. K stability and stability of chiral ring

    CERN Document Server

    Collins, Tristan C; Yau, Shing-Tung

    2016-01-01

    We define a notion of stability for chiral ring of four dimensional N=1 theory by introducing test chiral rings and generalized a maximization. We conjecture that a chiral ring is the chiral ring of a superconformal field theory if and only if it is stable. We then study N=1 field theory derived from D3 branes probing a three-fold singularity X, and show that the K stability which implies the existence of Ricci-flat conic metric on X is equivalent to the stability of chiral ring of the corresponding field theory.

  1. Stability of parallel flows

    CERN Document Server

    Betchov, R

    2012-01-01

    Stability of Parallel Flows provides information pertinent to hydrodynamical stability. This book explores the stability problems that occur in various fields, including electronics, mechanics, oceanography, administration, economics, as well as naval and aeronautical engineering. Organized into two parts encompassing 10 chapters, this book starts with an overview of the general equations of a two-dimensional incompressible flow. This text then explores the stability of a laminar boundary layer and presents the equation of the inviscid approximation. Other chapters present the general equation

  2. In-service inspection and testing of TAPS square fuel channels

    International Nuclear Information System (INIS)

    Tarapur Atomic Power Station is a twin unit Boiling Water Reactor. The initial each unit design was for 210 MWe. Subsequently due to Secondary Steam Generator tube leak problem, the units were de-rated to 160 MWe in the year 1985-86. Since then each unit is operating at 160 MWe. The station has completed 32 years of successful commercial operation. Presently each reactor is re-rated to 530 MWth. There are 284 fuel assemblies in each reactor. Each fuel assembly utilizes fuel channel made of Zircaloy-4 material. The fuel channel is a square tube and it surrounds the fuel bundle. The channel is secured to the fuel bundle by means of channel fastener assembly. The fuel channel length is 158.625 and wall thickness is 0.060. The fuel channel directs the coolant flow to fuel rods. It is also used as a guide for control blade movement inside the core. It provides for the structural stability of the fuel assembly. Initially during fabrication of the fuel channel, care is taken to control its dimensions very stringently by following quality assurance plan. However, once the channels are loaded into core along with fuel bundle, it undergoes dimensional changes due to neutron exposure. The fuel channels are monitored for its dimensions due to the neutron exposure and taken out of core at appropriate time. The paper prescribes the methodology adopted for inspecting the channels and the findings of the inspection. (author)

  3. Ion Channels in Brain Metastasis.

    Science.gov (United States)

    Klumpp, Lukas; Sezgin, Efe C; Eckert, Franziska; Huber, Stephan M

    2016-01-01

    Breast cancer, lung cancer and melanoma exhibit a high metastatic tropism to the brain. Development of brain metastases severely worsens the prognosis of cancer patients and constrains curative treatment options. Metastasizing to the brain by cancer cells can be dissected in consecutive processes including epithelial-mesenchymal transition, evasion from the primary tumor, intravasation and circulation in the blood, extravasation across the blood-brain barrier, formation of metastatic niches, and colonization in the brain. Ion channels have been demonstrated to be aberrantly expressed in tumor cells where they regulate neoplastic transformation, malignant progression or therapy resistance. Moreover, many ion channel modulators are FDA-approved drugs and in clinical use proposing ion channels as druggable targets for future anti-cancer therapy. The present review article aims to summarize the current knowledge on the function of ion channels in the different processes of brain metastasis. The data suggest that certain channel types involving voltage-gated sodium channels, ATP-release channels, ionotropic neurotransmitter receptors and gap junction-generating connexins interfere with distinct processes of brain metastazation. PMID:27618016

  4. Entanglement Cost of Quantum Channels

    CERN Document Server

    Berta, Mario; Christandl, Matthias; Wehner, Stephanie

    2011-01-01

    A natural question in characterizing the information theoretic power of quantum channels is to ask at what rate entanglement is needed in order to asymptotically simulate a quantum channel in the presence of free classical communication. We call this the entanglement cost of a channel, and prove a formula describing it for all channels. We discuss two applications. Firstly, our result has consequences for the study of the strong converse property of the quantum capacity. More precisely, we show that any coding scheme sending quantum information through a quantum channel at a rate larger than the entanglement cost of the channel is exponentially 'bad' in the number of channel uses. Secondly, and independently of the first application, we are able to link the security in the noisy-storage model to a problem of sending quantum rather than classical information through the adversary's storage device. This not only greatly improves the range of parameters where security could be shown previously, but allows us to ...

  5. Thermal stability of nanocrystalline microstructures

    Science.gov (United States)

    Darling, Kris Allen

    The objective of the proposed research is to develop the experimental data and scientific basis that can optimize the thermodynamic stabilization of a nanoscale microstructure during consolidation of Fe powder particles through select solute diffusion to grain boundaries. Fe based alloys were high energy ball milled to produce supersaturated solid solutions with a nominal grain size of ˜10nm. Solutes such as Y, W, Ta, Ni and Zr were selected based on their propensity to grain boundary segregated in Fe. Based on preliminary heat treatments Zr was selected as the solute of choice. Upon further heat treating experiments and microstructural analysis it was found that Zr solute additions of contamination was high due to the extensive cold welding exhibited by this system. The as-milled alloy showed an increase in hardness from ˜6.5GPa to ˜10GPa after heat treating at 1000°C for 1 hour. Based on these hardness measurements this alloy exhibits high thermal stability up to 1000°C. However, after heat treating at 1273°C the formation of Zr oxides were detected. Occurring simultaneously with the secondary phase formation was a rapid decrease in Vickers hardness from ˜10GPa to ˜3GPa. Ion channeling contrast images reveled that a nanocrystalline microstructure was not maintained at 1273°C. While these results are in conflict with what was reported in literature additional work is needed to confirm the results, however a presentation of the collected data is presented.

  6. Channel Coding in Random Access Communication over Compound Channels

    CERN Document Server

    Wang, Zheng

    2011-01-01

    Due to the short and bursty incoming messages, channel access activities in a wireless random access system are often fractional. The lack of frequent data support consequently makes it difficult for the receiver to estimate and track the time varying channel states with high precision. This paper investigates random multiple access communication over a compound wireless channel where channel realization is known neither at the transmitters nor at the receiver. An achievable rate and error probability tradeoff bound is derived under the non-asymptotic assumption of a finite codeword length. The results are then extended to the random multiple access system where the receiver is only interested in decoding messages from a user subset.

  7. Channel estimation in TDD mode

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yi; GU Jian; YANG Da-cheng

    2006-01-01

    An efficient solution is proposed in this article for the channel estimation in time division duplex (TDD) mode wireless communication systems. In the proposed solution, the characteristics of fading channels in TDD mode systems are fully exploited to estimate the path delay of the fading channel.The corresponding amplitude is estimated using the minimum mean square error (MMSE) criterion. As a result, it is shown that the proposed novel solution is more accurate and efficient than the traditional solution, and the improvement is beneficial to the performance of Joint Detection.

  8. Marine Toxins Targeting Ion Channels

    Directory of Open Access Journals (Sweden)

    Hugo R. Arias

    2006-04-01

    Full Text Available Abstract: This introductory minireview points out the importance of ion channels for cell communication. The basic concepts on the structure and function of ion channels triggered by membrane voltage changes, the so-called voltage-gated ion channels (VGICs, as well as those activated by neurotransmitters, the so-called ligand-gated ion channel (LGICs, are introduced. Among the most important VGIC superfamiles, we can name the voltage-gated Na+ (NaV, Ca2+ (CaV, and K+ (KV channels. Among the most important LGIC super families, we can include the Cys-loop or nicotinicoid, the glutamate-activated (GluR, and the ATP-activated (P2XnR receptor superfamilies. Ion channels are transmembrane proteins that allow the passage of different ions in a specific or unspecific manner. For instance, the activation of NaV, CaV, or KV channels opens a pore that is specific for Na+, Ca2+, or K+, respectively. On the other hand, the activation of certain LGICs such as nicotinic acetylcholine receptors, GluRs, and P2XnRs allows the passage of cations (e.g., Na+, K+, and/or Ca2+, whereas the activation of other LGICs such as type A γ-butyric acid and glycine receptors allows the passage of anions (e.g., Cl− and/or HCO3−. In this regard, the activation of NaV and CaV as well as ligand-gated cation channels produce membrane depolarization, which finally leads to stimulatory effects in the cell, whereas the activation of KV as well as ligand-gated anion channels induce membrane hyperpolarization that finally leads to inhibitory effects in the cell. The importance of these ion channel superfamilies is emphasized by considering their physiological functions throughout the body as well as their pathophysiological implicance in several neuronal diseases. In this regard, natural molecules, and especially marine toxins, can be potentially used as modulators (e.g., inhibitors or prolongers of ion channel functions to treat or to alleviate a specific

  9. Neural KCNQ (Kv7) channels

    OpenAIRE

    Brown, David A.; Passmore, Gayle M.

    2009-01-01

    KCNQ genes encode five Kv7 K+ channel subunits (Kv7.1–Kv7.5). Four of these (Kv7.2–Kv7.5) are expressed in the nervous system. Kv7.2 and Kv7.3 are the principal molecular components of the slow voltage-gated M-channel, which widely regulates neuronal excitability, although other subunits may contribute to M-like currents in some locations. M-channels are closed by receptors coupled to Gq such as M1 and M3 muscarinic receptors; this increases neuronal excitability and underlies some forms of c...

  10. Calcium channel-dependent molecular maturation of photoreceptor synapses.

    Directory of Open Access Journals (Sweden)

    Nawal Zabouri

    Full Text Available Several studies have shown the importance of calcium channels in the development and/or maturation of synapses. The Ca(V1.4(α(1F knockout mouse is a unique model to study the role of calcium channels in photoreceptor synapse formation. It features abnormal ribbon synapses and aberrant cone morphology. We investigated the expression and targeting of several key elements of ribbon synapses and analyzed the cone morphology in the Ca(V1.4(α(1F knockout retina. Our data demonstrate that most abnormalities occur after eye opening. Indeed, scaffolding proteins such as Bassoon and RIM2 are properly targeted at first, but their expression and localization are not maintained in adulthood. This indicates that either calcium or the Ca(V1.4 channel, or both are necessary for the maintenance of their normal expression and distribution in photoreceptors. Other proteins, such as Veli3 and PSD-95, also display abnormal expression in rods prior to eye opening. Conversely, vesicle related proteins appear normal. Our data demonstrate that the Ca(V1.4 channel is important for maintaining scaffolding proteins in the ribbon synapse but less vital for proteins related to vesicular release. This study also confirms that in adult retinae, cones show developmental features such as sprouting and synaptogenesis. Overall we present evidence that in the absence of the Ca(V1.4 channel, photoreceptor synapses remain immature and are unable to stabilize.

  11. Feedback stabilization initiative

    International Nuclear Information System (INIS)

    Much progress has been made in attaining high confinement regimes in magnetic confinement devices. These operating modes tend to be transient, however, due to the onset of MHD instabilities, and their stabilization is critical for improved performance at steady state. This report describes the Feedback Stabilization Initiative (FSI), a broad-based, multi-institutional effort to develop and implement methods for raising the achievable plasma betas through active MHD feedback stabilization. A key element in this proposed effort is the Feedback Stabilization Experiment (FSX), a medium-sized, national facility that would be specifically dedicated to demonstrating beta improvement in reactor relevant plasmas by using a variety of MHD feedback stabilization schemes

  12. A multichannel dual-mixer stability analyzer: progress report

    Science.gov (United States)

    Stevens, C. A.; Kirk, A.; Stevens, G. L.

    2001-01-01

    A stability analyzer is being developed for frequency standards in JPL's Deep Space Network. Prototype hardware and software have been built. Initial tests on 100-MHz sources show an Allan deviation noise floor of about 7 X 10(sup -15) at 1 second for a dual-mixer channel.

  13. The Degraded Poisson Wiretap Channel

    CERN Document Server

    Laourine, Amine

    2010-01-01

    Providing security guarantees for wireless communication is critically important for today's applications. While previous work in this area has concentrated on radio frequency (RF) channels, providing security guarantees for RF channels is inherently difficult because they are prone to rapid variations due small scale fading. Wireless optical communication, on the other hand, is inherently more secure than RF communication due to the intrinsic aspects of the signal propagation in the optical and near-optical frequency range. In this paper, secure communication over wireless optical links is examined by studying the secrecy capacity of a direct detection system. For the degraded Poisson wiretap channel, a closed-form expression of the secrecy capacity is given. A complete characterization of the general rate-equivocation region is also presented. For achievability, an optimal code is explicitly constructed by using the structured code designed by Wyner for the Poisson channel. The converse is proved in two dif...

  14. FMCG companies specific distribution channels

    Directory of Open Access Journals (Sweden)

    Ioana Barin

    2009-12-01

    Full Text Available Distribution includes all activities undertaken by the producer, alone or in cooperation, since the end of the final finished products or services until they are in possession of consumers. The distribution consists of the following major components: distribution channels or marketing channels, which together form a distribution network; logistics o rphysical distribution. In order to effective achieve, distribution of goods requires an amount of activities and operational processes related to transit of goods from producer to consumer, the best conditions, using existing distribution channels and logistics system. One of the essential functions of a distribution is performing acts of sale, through which, with the actual movement of goods, their change of ownership takes place, that the successive transfer of ownership from producer to consumer. This is an itinerary in the economic cycle of goods, called the distribution channel.

  15. Message Authentication over Noisy Channels

    Directory of Open Access Journals (Sweden)

    Fanfan Zheng

    2015-01-01

    Full Text Available The essence of authentication is the transmission of unique and irreproducible information. In this paper, the authentication becomes a problem of the secure transmission of the secret key over noisy channels. A general analysis and design framework for message authentication is presented based on the results of Wyner’s wiretap channel. Impersonation and substitution attacks are primarily investigated. Information-theoretic lower and upper bounds on the opponent’s success probability are derived, and the lower bound and the upper bound are shown to match. In general, the fundamental limits on message authentication over noisy channels are fully characterized. Analysis results demonstrate that introducing noisy channels is a reliable way to enhance the security of authentication.

  16. Aquaglyceroporins: ancient channels for metalloids

    OpenAIRE

    Bhattacharjee, Hiranmoy; Mukhopadhyay, Rita; Thiyagarajan, Saravanamuthu; Rosen, Barry P.

    2008-01-01

    The identification of aquaglyceroporins as uptake channels for arsenic and antimony shows how these toxic elements can enter the food chain, and suggests that food plants could be genetically modified to exclude arsenic while still accumulating boron and silicon.

  17. Thermosyphon boiling in vertical channels

    Science.gov (United States)

    Bar-Cohen, A.; Schweitzer, H.

    The thermal characteristics of ebullient cooling systems for VHSIC and VLSI microelectronic component thermal control are studied by experimentally and analytically investigating boiling heat transfer from a pair of flat, closely spaced, isoflux plates immersed in saturated water. A theoretical model for liquid flow rate through the channel is developed and used as a basis for correlating the rate of heat transfer from the channel walls. Experimental results for wall temperature as a function of axial location, heat flux, and plate spacing are presented. The finding that the wall superheat at constant imposed heat flux decreases as the channel is narrowed is explained with the aid of a boiling thermosiphon analysis which yields the mass flux through the channel.

  18. Catalytic reaction in confined flow channel

    Energy Technology Data Exchange (ETDEWEB)

    Van Hassel, Bart A.

    2016-03-29

    A chemical reactor comprises a flow channel, a source, and a destination. The flow channel is configured to house at least one catalytic reaction converting at least a portion of a first nanofluid entering the channel into a second nanofluid exiting the channel. The flow channel includes at least one turbulating flow channel element disposed axially along at least a portion of the flow channel. A plurality of catalytic nanoparticles is dispersed in the first nanofluid and configured to catalytically react the at least one first chemical reactant into the at least one second chemical reaction product in the flow channel.

  19. Pharmacological modulation of SK3 channels

    DEFF Research Database (Denmark)

    Grunnet, M; Jespersen, Thomas; Angelo, K;

    2001-01-01

    Small-conductance, calcium-activated K+ channels (SK channels) are voltage-insensitive channels that have been identified molecularly within the last few years. As SK channels play a fundamental role in most excitable cells and participate in afterhyperpolarization (AHP) and spike-frequency adapt......Small-conductance, calcium-activated K+ channels (SK channels) are voltage-insensitive channels that have been identified molecularly within the last few years. As SK channels play a fundamental role in most excitable cells and participate in afterhyperpolarization (AHP) and spike...

  20. Highly stable thin film transistors using multilayer channel structure

    KAUST Repository

    Nayak, Pradipta K.

    2015-03-09

    We report highly stable gate-bias stress performance of thin film transistors (TFTs) using zinc oxide (ZnO)/hafnium oxide (HfO2) multilayer structure as the channel layer. Positive and negative gate-bias stress stability of the TFTs was measured at room temperature and at 60°C. A tremendous improvement in gate-bias stress stability was obtained in case of the TFT with multiple layers of ZnO embedded between HfO2 layers compared to the TFT with a single layer of ZnO as the semiconductor. The ultra-thin HfO2 layers act as passivation layers, which prevent the adsorption of oxygen and water molecules in the ZnO layer and hence significantly improve the gate-bias stress stability of ZnO TFTs.

  1. FMCG companies specific distribution channels

    OpenAIRE

    Ioana Barin

    2009-01-01

    Distribution includes all activities undertaken by the producer, alone or in cooperation, since the end of the final finished products or services until they are in possession of consumers. The distribution consists of the following major components: distribution channels or marketing channels, which together form a distribution network; logistics o rphysical distribution. In order to effective achieve, distribution of goods requires an amount of activities and operational processes related t...

  2. Integrating food web diversity, structure and stability.

    Science.gov (United States)

    Rooney, Neil; McCann, Kevin S

    2012-01-01

    Given the unprecedented rate of species extinctions facing the planet, understanding the causes and consequences of species diversity in ecosystems is of paramount importance. Ecologists have investigated both the influence of environmental variables on species diversity and the influence of species diversity on ecosystem function and stability. These investigations have largely been carried out without taking into account the overarching stabilizing structures of food webs that arise from evolutionary and successional processes and that are maintained through species interactions. Here, we argue that the same large-scale structures that have been purported to convey stability to food webs can also help to understand both the distribution of species diversity in nature and the relationship between species diversity and food web stability. Specifically, the allocation of species diversity to slow energy channels within food webs results in the skewed distribution of interactions strengths that has been shown to confer stability to complex food webs. We end by discussing the processes that might generate and maintain the structured, stable and diverse food webs observed in nature. PMID:21944861

  3. Improved stability of free-standing lipid bilayers based on nanoporous alumina films

    Science.gov (United States)

    Hirano-Iwata, Ayumi; Taira, Tasuku; Oshima, Azusa; Kimura, Yasuo; Niwano, Michio

    2010-05-01

    In this study, we propose a method for improving the stability of free-standing bilayer lipid membranes (BLMs) by preparing BLMs across nanoporous alumina films. The use of porous alumina reduced individual membrane size to improve the BLM stability. The BLMs were stable under an applied voltage of ±1 V. The lifetime of the BLMs was 16-30 h with and without incorporated gramicidin channels. Electric properties of the BLMs as a platform for channel-current recordings are also discussed. Since the total area of the BLMs is still large to facilitate protein incorporation, our approach is useful for designing highly sensitive biosensors based on channel proteins.

  4. CHANNEL ESTIMATION FOR ITERATIVE DECODING OVER FADING CHANNELS

    Institute of Scientific and Technical Information of China (English)

    K.H.Sayhood; WuLenan

    2002-01-01

    A method of coherent detection and channel estimation for punctured convolutional coded binary Quadrature Amplitude Modulation (QAM) signals transmitted over a frequency-flat Rayleigh fading channels used for a digital radio broadcasting transmission is presented.Some known symbols are inserted in the encoded data stream to enhance the channel estimation process.The puilot symbols are used to replace the existing parity symbols so no bandwidth expansion is required.An iterative algorithm that uses decoding information as well as the information contained in the known symbols is used to improve the channel parameter estimate.The scheme complexity grows exponentially with the channel estimation filter length,The performance of the system is compared for a normalized fading rate with both perfect coherent detection(Corresponding to a perfect knowledge of the fading process and noise variance)and differential detection of Differential Amplitude Phase Shift Keying (DAPSK).The tradeoff between simplicity of implementation and bit-error-rate performance of different techniques is also compared.

  5. Causes and effects of morphological changes of the regulated channel of the river Toplica

    Directory of Open Access Journals (Sweden)

    Đeković Vojislav

    2005-01-01

    Full Text Available The regulation of small torrential watercourses outside the urbanized areas is often based on the so-called field type of regulation. In the selection of this concept, after the regulation works, the new channel is left to the natural process of the morphological formation of the water cross-section taking care not to disturb the general stability of the regulated channel. We present the process of morphological development of the regulated channel of the river Toplica, tributary of the river Kolubara, in the period 1982-2004 i.e. from immediately after the regulation works to the present day.

  6. Design of step composition gradient thin film transistor channel layers grown by atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Ahn, Cheol Hyoun; Hee Kim, So; Gu Yun, Myeong; Koun Cho, Hyung, E-mail: chohk@skku.edu [School of Advanced Materials Science and Engineering, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon, Gyeonggi-do 440-746 (Korea, Republic of)

    2014-12-01

    In this study, we proposed the artificially designed channel structure in oxide thin-film transistors (TFTs) called a “step-composition gradient channel.” We demonstrated Al step-composition gradient Al-Zn-O (AZO) channel structures consisting of three AZO layers with different Al contents. The effects of stacking sequence in the step-composition gradient channel on performance and electrical stability of bottom-gate TFT devices were investigated with two channels of inverse stacking order (ascending/descending step-composition). The TFT with ascending step-composition channel structure (5 → 10 → 14 at. % Al composition) showed relatively negative threshold voltage (−3.7 V) and good instability characteristics with a reduced threshold voltage shift (Δ 1.4 V), which was related to the alignment of the conduction band off-set within the channel layer depending on the Al contents. Finally, the reduced Al composition in the initial layer of ascending step-composition channel resulted in the best field effect mobility of 4.5 cm{sup 2}/V s. We presented a unique active layer of the “step-composition gradient channel” in the oxide TFTs and explained the mechanism of adequate channel design.

  7. Evolution and distribution of macroscopic gas channels in an overburden strata

    Institute of Scientific and Technical Information of China (English)

    Liu Hongtao; Ma Nianjie; Ma Wang; Ren Guoqiang

    2012-01-01

    The evolution of gas bearing channels in the roof,and their spatial distribution,was studied.A complete consideration of gas flow changes through the stress-strain changes in the roof near a working face is made.The theoretical abutment pressure distribution using displacement monitors and borehole visual recording instruments allow a theoretical analysis.Field test research determined the conditions for formation of macroscopic gas channels.These appear along the working face roof,normally distributed to it.These results show that the coal rock stratification becomes a macroscopic gas channel boundary if its deformation is less than the lower layer,or greater than the layer above it.At the same time the stability is greater than the distance from the roof for hanging dew conditions.The working face advances and the roof gas channels experience a cycle of development.Microscopic channels dominate the initial stage then macroscopic gas channels form,develop,and close.The evolution of the macroscopic channels depends on the ratio between the distances from the new compaction area in the goaf to the initial stress area in front of the working face.The amount of daily advance of the face also affects channel development.The experimental observations in one mining area showed that the main gas channels are located about 2 and 6.2 m above the lower surface of the roof and that they have an evolution period 7 to 11 days long.

  8. Differential distribution of the sodium-activated potassium channels slick and slack in mouse brain.

    Science.gov (United States)

    Rizzi, Sandra; Knaus, Hans-Günther; Schwarzer, Christoph

    2016-07-01

    The sodium-activated potassium channels Slick (Slo2.1, KCNT2) and Slack (Slo2.2, KCNT1) are high-conductance potassium channels of the Slo family. In neurons, Slick and Slack channels are involved in the generation of slow afterhyperpolarization, in the regulation of firing patterns, and in setting and stabilizing the resting membrane potential. The distribution and subcellular localization of Slick and Slack channels in the mouse brain have not yet been established in detail. The present study addresses this issue through in situ hybridization and immunohistochemistry. Both channels were widely distributed and exhibited distinct distribution patterns. However, in some brain regions, their expression overlapped. Intense Slick channel immunoreactivity was observed in processes, varicosities, and neuronal cell bodies of the olfactory bulb, granular zones of cortical regions, hippocampus, amygdala, lateral septal nuclei, certain hypothalamic and midbrain nuclei, and several regions of the brainstem. The Slack channel showed primarily a diffuse immunostaining pattern, and labeling of cell somata and processes was observed only occasionally. The highest Slack channel expression was detected in the olfactory bulb, lateral septal nuclei, basal ganglia, and distinct areas of the midbrain, brainstem, and cerebellar cortex. In addition, comparing our data obtained from mouse brain with a previously published study on rat brain revealed some differences in the expression and distribution of Slick and Slack channels in these species. J. Comp. Neurol. 524:2093-2116, 2016. © 2015 The Authors The Journal of Comparative Neurology Published by Wiley Periodicals, Inc. PMID:26587966

  9. Nav1.5 cardiac sodium channels, regulation and clinical implications

    Directory of Open Access Journals (Sweden)

    Henry Humberto León-Ariza

    2014-10-01

    Full Text Available Voltage-gated sodium channels constitute a group of membrane proteins widely distributed thought the body. In the heart, there are at least six different isoforms, being the Nav1.5 the most abundant. The channel is composed of an α subunit that is formed by four domains of six segments each, and four much smaller β subunits that provide stability and integrate other channels into the α subunit. The function of the Nav1.5 channel is modulated by intracellular cytoskeleton proteins, extracellular proteins, calcium concentration, free radicals, and medications, among other things. The study of the channel and its alterations has grown thanks to its association with pathogenic conditions such as Long QT syndrome, Brugada syndrome, atrial fibrillation, arrhythmogenic ventricular dysplasia and complications during ischemic processes.

  10. High basal melting forming a channel at the grounding line of Ross Ice Shelf, Antarctica

    Science.gov (United States)

    Marsh, Oliver J.; Fricker, Helen A.; Siegfried, Matthew R.; Christianson, Knut; Nicholls, Keith W.; Corr, Hugh F. J.; Catania, Ginny

    2016-01-01

    Antarctica's ice shelves are thinning at an increasing rate, affecting their buttressing ability. Channels in the ice shelf base unevenly distribute melting, and their evolution provides insight into changing subglacial and oceanic conditions. Here we used phase-sensitive radar measurements to estimate basal melt rates in a channel beneath the currently stable Ross Ice Shelf. Melt rates of 22.2 ± 0.2 m a-1 (>2500% the overall background rate) were observed 1.7 km seaward of Mercer/Whillans Ice Stream grounding line, close to where subglacial water discharge is expected. Laser altimetry shows a corresponding, steadily deepening surface channel. Two relict channels to the north suggest recent subglacial drainage reorganization beneath Whillans Ice Stream approximately coincident with the shutdown of Kamb Ice Stream. This rapid channel formation implies that shifts in subglacial hydrology may impact ice shelf stability.

  11. Mechanical properties of lipid bilayers and regulation of mechanosensitive function: from biological to biomimetic channels.

    Science.gov (United States)

    Balleza, Daniel

    2012-01-01

    Material properties of lipid bilayers, including thickness, intrinsic curvature and compressibility regulate the function of mechanosensitive (MS) channels. This regulation is dependent on phospholipid composition, lateral packing and organization within the membrane. Therefore, a more complete framework to understand the functioning of MS channels requires insights into bilayer structure, thermodynamics and phospholipid structure, as well as lipid-protein interactions. Phospholipids and MS channels interact with each other mainly through electrostatic forces and hydrophobic matching, which are also crucial for antimicrobial peptides. They are excellent models for studying the formation and stabilization of membrane pores. Importantly, they perform equivalent responses as MS channels: (1) tilting in response to tension and (2) dissipation of osmotic gradients. Lessons learned from pore forming peptides could enrich our knowledge of mechanisms of action and evolution of these channels. Here, the current state of the art is presented and general principles of membrane regulation of mechanosensitive function are discussed. PMID:22790280

  12. Internet Addiction: Stability and Change

    Science.gov (United States)

    Huang, Chiungjung

    2010-01-01

    This longitudinal study examined five indices of stability and change in Internet addiction: structural stability, mean-level stability, differential stability, individual-level stability, and ipsative stability. The study sample was 351 undergraduate students from end of freshman year to end of junior year. Convergent findings revealed stability…

  13. Information transfer through quantum channels

    International Nuclear Information System (INIS)

    This PhD thesis represents work done between Aug. 2003 and Dec. 2006 in Reinhard F. Werner's quantum information theory group at Technische Universitaet Braunschweig, and Artur Ekert's Centre for Quantum Computation at the University of Cambridge. My thesis falls into the field of abstract quantum information theory. This work investigates both fundamental properties of quantum channels and their asymptotic capacities for classical as well as quantum information transfer. Stinespring's theorem is the basic structure theorem for quantum channels. It implies that every quantum channel can be represented as a unitary evolution on an enlarged system. In Ch. 3 we present a continuity theorem for Stinespring's representation: two quantum channels are similar if and only if it is possible to find unitary implementations that are likewise similar, with dimension-independent norm bounds. The continuity theorem allows to derive a formulation of the information-disturbance tradeoff in terms of quantum channels, and a continuity estimate for the no-broadcasting principle. In Ch. 4 we then apply the continuity theorem to give a strengthened no-go proof for quantum bit commitment, an important cryptographic primitive. This result also provides a natural characterization of those protocols that fall outside the standard setting of unconditional security, and thus may allow secure bit commitment. We present a new such protocol whose security relies on decoherence in the receiver's lab. Ch. 5 reviews the capacities of quantum channels for the transfer of both classical and quantum information, and investigates several variations in the notion of channel capacity. Memory effects are then investigated in detail in Ch. 6. We advertise a model which is sufficiently general to encompass all causal automata: every quantum process in which the outputs up to any given time t do not depend on the inputs at times t'>t can be represented as a concatenated memory channel. We then explain how

  14. Information transfer through quantum channels

    Energy Technology Data Exchange (ETDEWEB)

    Kretschmann, D.

    2007-03-12

    This PhD thesis represents work done between Aug. 2003 and Dec. 2006 in Reinhard F. Werner's quantum information theory group at Technische Universitaet Braunschweig, and Artur Ekert's Centre for Quantum Computation at the University of Cambridge. My thesis falls into the field of abstract quantum information theory. This work investigates both fundamental properties of quantum channels and their asymptotic capacities for classical as well as quantum information transfer. Stinespring's theorem is the basic structure theorem for quantum channels. It implies that every quantum channel can be represented as a unitary evolution on an enlarged system. In Ch. 3 we present a continuity theorem for Stinespring's representation: two quantum channels are similar if and only if it is possible to find unitary implementations that are likewise similar, with dimension-independent norm bounds. The continuity theorem allows to derive a formulation of the information-disturbance tradeoff in terms of quantum channels, and a continuity estimate for the no-broadcasting principle. In Ch. 4 we then apply the continuity theorem to give a strengthened no-go proof for quantum bit commitment, an important cryptographic primitive. This result also provides a natural characterization of those protocols that fall outside the standard setting of unconditional security, and thus may allow secure bit commitment. We present a new such protocol whose security relies on decoherence in the receiver's lab. Ch. 5 reviews the capacities of quantum channels for the transfer of both classical and quantum information, and investigates several variations in the notion of channel capacity. Memory effects are then investigated in detail in Ch. 6. We advertise a model which is sufficiently general to encompass all causal automata: every quantum process in which the outputs up to any given time t do not depend on the inputs at times t'>t can be represented as a concatenated memory

  15. Memory effects in quantum channel discrimination

    OpenAIRE

    Chiribella G.; D'Ariano G.M.; Perinotti P.

    2008-01-01

    We consider quantum-memory assisted protocols for discriminating quantum channels. We show that for optimal discrimination of memory channels, memory assisted protocols are needed. This leads to a new notion of distance for channels with memory. For optimal discrimination and estimation of sets of unitary channels memory-assisted protocols are not required.

  16. Transient receptor potential channels in essential hypertension

    DEFF Research Database (Denmark)

    Liu, Daoyan; Scholze, Alexandra; Zhu, Zhiming;

    2006-01-01

    The role of nonselective cation channels of the transient receptor potential channel (TRPC) family in essential hypertension has not yet been investigated.......The role of nonselective cation channels of the transient receptor potential channel (TRPC) family in essential hypertension has not yet been investigated....

  17. Continuous Time Channels with Interference

    CERN Document Server

    Ivan, Ioana; Thaler, Justin; Yuen, Henry

    2012-01-01

    Khanna and Sudan studied a natural model of continuous time channels where signals are corrupted by the effects of both noise and delay, and showed that, surprisingly, in some cases both are not enough to prevent such channels from achieving unbounded capacity. Inspired by their work, we consider channels that model continuous time communication with adversarial delay errors. The sender is allowed to subdivide time into arbitrarily large number $M$ of micro-units in which binary symbols may be sent, but the symbols are subject to unpredictable delays and may interfere with each other. We model interference by having symbols that land in the same micro-unit of time be summed, and a $k$-interference channels allows receivers to distinguish sums up to the value $k$. We consider both a channel adversary that has a limit on the maximum number of steps it can delay each symbol, and a more powerful adversary that only has a bound on the average delay. We give precise characterizations of the threshold between finite...

  18. Charged and Neutral Particles Channeling Phenomena Channeling 2008

    Science.gov (United States)

    Dabagov, Sultan B.; Palumbo, Luigi

    2010-04-01

    On the discovery of coherent Bremsstrahlung in a single crystal at the Frascati National Laboratories / C. Barbiellini, G. P. Murtas and S. B. Dabagov -- Advances in coherent Bremsstrahlung and LPM-effect studies (to the lOOth anniversary from the birth of L. D. Landau) / N. F. Shul'ga -- Spectra of radiation and created particles at intermediate energy in oriented crystal taking into account energy loss / V. N. Baier and V. M. Katkov -- The coherent Bremsstrahlung beam at MAX-lab facility / K. Fissum ... [et al.] -- Radiation from thin, structured targets (CERN NA63) / A. Dizdar -- Hard incoherent radiation in thick crystals / N. F. Shul'ga, V. V. Syshchenko and A. I. Tarnovsky -- Coherent Bremsstrahlung in periodically deformed crystals with a complex base / A. R. Mkrtchyan, A. A. Saharian and V. V. Parazian -- Induction of coherent x-ray Bremsstrahlung in crystals under the influence of acoustic waves / A. R. Mkrtchyan and V. V. Parazian -- Coherent processes in bent single crystals / V. A. Maisheev -- Experimental and theoretical investigation of complete transfer phenomenon for media with various heat exchange coefficients / A. R. Mkrtchyan, A. E. Movsisyan and V. R. Kocharyan -- Coherent pair production in crystals / A. R. Mkrtchyan, A. A. Saharian and V. V. Parazian -- Negative particle planar and axial channeling and channeling collimation / R. A. Carrigan, Jr. -- CERN crystal-based collimation in modern hadron colliders / W. Scandale -- Studies and application of bent crystals for beam steering at 70 GeV IHEP accelerator / A. G. Afonin ... [et al.] -- Crystal collimation studies at the Tevatron (T-980) / N. V. Mokhov ... [et al.] -- Fabrication of crystals for channeling of particles in accellerators / A. Mazzolari ... [et al.] -- New possibilities to facilitate collimation of both positively and negatively charged particle beams by crystals / V. Guidi, A. Mazzolari and V. V. Tikhomirov -- Increase of probability of particle capture into the channeling

  19. Quantum channels with a finite memory

    CERN Document Server

    Bowen, G; Bowen, Garry; Mancini, Stefano

    2004-01-01

    In this paper we study quantum communication channels with correlated noise effects, i.e., quantum channels with memory. We derive a model for correlated noise channels that includes a channel memory state. We examine the case where the memory is finite, and derive bounds on the classical and quantum capacities. For the entanglement-assisted and unassisted classical capacities it is shown that these bounds are attainable for certain classes of channel. Also, we show that the structure of any finite memory state is unimportant in the asymptotic limit, and specifically, for a perfect finite-memory channel where no information is lost to the environment, the channel is asymptotically noiseless.

  20. Researches toward potassium channels on tumor progressions.

    Science.gov (United States)

    Shen, Zheng; Yang, Qian; You, Qidong

    2009-01-01

    As trans-membrane proteins located in cytoplasm and organelle membrane, potassium (K(+)) channels are generally divided into four super-families: voltage-gated K(+) channels (K(v)), Ca(2+)-activated K(+) channels (K(Ca)), inwardly rectifying K(+) channels (K(ir)) and two-pore domain K(+) channels (K(2P)). Since dysfunctions of K(+) channels would induce many diseases, various studies toward their functions in physiologic and pathologic process have been extensively launched. This review focuses on the recent advances of K(+) channels in tumor progression, including the brief introduction of K(+) channels, the role of K(+) channels in tumor cells, the possible mechanism of action at cellular level, and the possible application of K(+) channel modulators in cancer chemotherapy.

  1. Gain Stabilization of SiPMs

    CERN Document Server

    Cvach, Jaroslav; Kvasnicka, Jiri; Polak, Ivo; van der Kraiij, Erik; Zalieckas, Justas

    2014-01-01

    The gain of SiPMs depends both on bias voltage and on temperature. For stable operations, both need to be kept constant. In an ILC calorimeter with millions of channels, this is a challenging task. It is, therefore, desirable to compensate for temperature variations by automatically readjusting the bias voltage. We have designed a bias voltage regulator board to achieve this task. We anticipate an uncertainty on the gain stability at the level of $< 1\\%$. First, we present measurements of the gain dependence on temperature and bias voltage for several SiPMs from three different manufacturers and determine their dV/dT dependence. Next, we demonstrate the performance of the gain stability with the bias voltage regulator test board on four SiPMs.

  2. Sodium Channel Inhibiting Marine Toxins

    Science.gov (United States)

    Llewellyn, Lyndon E.

    Saxitoxin (STX), tetrodotoxin (TTX) and their many chemical relatives are part of our daily lives. From killing people who eat seafood containing these toxins, to being valuable research tools unveiling the invisible structures of their pharmacological receptor, their global impact is beyond measure. The pharmacological receptor for these toxins is the voltage-gated sodium channel which transports Na ions between the exterior to the interior of cells. The two structurally divergent families of STX and TTX analogues bind at the same location on these Na channels to stop the flow of ions. This can affect nerves, muscles and biological senses of most animals. It is through these and other toxins that we have developed much of our fundamental understanding of the Na channel and its part in generating action potentials in excitable cells.

  3. Information geometry of Gaussian channels

    CERN Document Server

    Monras, Alex

    2009-01-01

    We define a local Riemannian metric tensor in the manifold of Gaussian channels and the distance that it induces. We adopt an information-geometric approach and define a metric derived from the Bures-Fisher metric for quantum states. The resulting metric inherits several desirable properties from the Bures-Fisher metric and is operationally motivated from distinguishability considerations: It serves as an upper bound to the attainable quantum Fisher information for the channel parameters using Gaussian states, under some restriction on the available resources. We prove that optimal states are always pure and bounded in the number of ancillary modes that are needed. This has experimental and computational advantages: It limits the complexity of optimal experimental setups for channel estimation and reduces the computational requirements for the evaluation of the metric. Indeed, we construct a converging algorithm for computing the metric. We provide explicit formulae for computing the multiparametric quantum F...

  4. Resolvability of positron decay channels

    International Nuclear Information System (INIS)

    Many data analysis treatments of positron experiments attempt to resolve two or more positron decay or exist channels which may be open simultaneously. Examples of the need to employ such treatments of the experimental results can be found in the resolution of the constituents of a defect ensemble, or in the analysis of the complex spectra which arise from the interaction of slow positrons at or near the surfaces of solids. Experimental one- and two-dimensional angular correlation of annihilation radiation experiments in Al single crystals have shown that two defect species (mono- and divacancies) can be resolved under suitable conditions. Recent experiments at LLNL indicate that there are a variety of complex exit channels open to positrons interacting at surfaces, and ultimely these decay channels must also be suitably resolved from one another. 6 refs., 4 figs

  5. Quantum channels with a finite memory

    OpenAIRE

    Bowen, Garry; Mancini, Stefano

    2003-01-01

    In this paper we study quantum communication channels with correlated noise effects, i.e., quantum channels with memory. We derive a model for correlated noise channels that includes a channel memory state. We examine the case where the memory is finite, and derive bounds on the classical and quantum capacities. For the entanglement-assisted and unassisted classical capacities it is shown that these bounds are attainable for certain classes of channel. Also, we show that the structure of any ...

  6. Insect sodium channels and insecticide resistance

    OpenAIRE

    Dong, Ke

    2007-01-01

    Voltage-gated sodium channels are essential for the generation and propagation of action potentials (i.e., electrical impulses) in excitable cells. Although most of our knowledge about sodium channels is derived from decades of studies of mammalian isoforms, research on insect sodium channels is revealing both common and unique aspects of sodium channel biology. In particular, our understanding of the molecular dynamics and pharmacology of insect sodium channels has advanced greatly in recent...

  7. Mobile Radio Channels Modeling in MATLAB

    OpenAIRE

    N. Kostov

    2003-01-01

    In this paper, a MATLAB based approach for mobile radio channels modeling is presented. Specifically, the paper introduces the basic concepts for modeling flat fading channels in MATLAB by means of user-defined m-files. Typical small-scale fading channel models are derived such as uncorrelated Rician fading channel and Rayleigh fading channel with Doppler shift. Further, simple and useful MATLAB constructions for approximation of cumulative distribution functions (CDFs) and probability densit...

  8. Conformational stability of calreticulin

    DEFF Research Database (Denmark)

    Jørgensen, Charlotte S; Trandum, Christa; Larsen, Nanna Brink;

    2005-01-01

    The conformational stability of calreticulin was investigated. Apparent unfolding temperatures (Tm) increased from 31 degrees C at pH 5 to 51 degrees C at pH 9, but electrophoretic analysis revealed that calreticulin oligomerized instead of unfolding. Structural analyses showed that the single C......-terminal alpha-helix was of major importance to the conformational stability of calreticulin....

  9. Temperature stabilized phase detector

    Science.gov (United States)

    Lo, Y.

    1981-01-01

    The construction, tests, and performance of a temperature stabilized phase detector are discussed. It has a frequency stability of 5 parts in 10 to the 16th power at 100 MHz, with a temperature step of 20 C (15 to 35 C).

  10. Conformational stability of calreticulin

    DEFF Research Database (Denmark)

    Jørgensen, C.S.; Trandum, C.; Larsen, N.;

    2005-01-01

    The conformational stability of calreticulin was investigated. Apparent unfolding temperatures (T-m) increased from 31 degrees C at pH 5 to 51 degrees C at pH 9, but electrophoretic analysis revealed that calreticulin oligomerized instead of unfolding. Structural analyses showed that the single C......-terminal a-helix was of major importance to the conformational stability of calreticulin....

  11. Radion Cosmology and Stabilization

    CERN Document Server

    Chakraborty, Sumanta

    2014-01-01

    We have solved the Einstein equation in 5D spacetime for Randall Sundrum Brane world model with time dependent radion field. We have shown how inflation could compactify the extra dimension such that it become unobservable today. We also propose a mechanism for stabilizing the time dependent radion field following Goldberger Wise mechanism and have obtained the stabilized value.

  12. Stability: general considerations

    International Nuclear Information System (INIS)

    This chapter is concerned with determining the stability properties of ideal MHD equilibria. The problem of stability can be stated qualitatively as follows. The existence of an MHD equilibrium state implies a situation where the sum of the forces acting on the plasma is zero. If the plasma is perturbed from this state, the resulting perturbed forces either restore the plasma to its original equilibrium (stability) or cause a further enhancement of the initial disturbance (instability). Chapter 8 begins with a discussion of a mathematical definition of stability particularly applicable to ideal MHD. Next, a short derivation is presented of the dispersion relation for waves in an infinite homogeneous MHD plasma. These waves play an important role in providing intuition into the dynamical behavior of an MHD plasma. Following this is a rather extensive discussion of the formulation of the general linearized stability problem, starting with the equations of motion and culminating with the development of the Energy Principle, a powerful method for testing stability. Having established the Energy Principle, it is then possible to address the role of plasma compressibility on ideal MHD stability in a general manner. This demonstrates the relationship between the ideal and collisionless MHD stability boundaries. Next, a rather subtle point is investigated concerning whether the region outside the main plasma core is more accurately described by a vacuum or by a relatively cold, but still perfectly conducting, force-free plasma. Finally, a brief discussion is presented of the general classification of ideal MHD instabilities

  13. Stability of charged membranes

    OpenAIRE

    Bensimon, D; David, F.; Leibler, S.; Pumir, A.

    1990-01-01

    The electrostatic contribution to the bending elastic modulus of charged phospholipid bilayers in an ionic solution is computed. It is found to be the same for conducting and non-conducting membranes and is always stabilizing. This stability for free membranes is shown to be a simple consequence of the vanishing of the physical surface tension.

  14. Channel incision and water quality

    Science.gov (United States)

    Shields, F. D.

    2009-12-01

    Watershed development often triggers channel incision that leads to radical changes in channel morphology. Although morphologic evolution due to channel incision has been documented and modeled by others, ecological effects, particularly water quality effects, are less well understood. Furthermore, environmental regulatory frameworks for streams frequently focus on stream water quality and underemphasize hydrologic and geomorphic issues. Discharge, basic physical parameters, solids, nutrients (nitrogen and phosphorus), chlorophyll and bacteria were monitored for five years at two sites along a stream in a mixed cover watershed characterized by rapid incision of the entire channel network. Concurrent data were collected from two sites on a nearby stream draining a watershed of similar size and cultivation intensity, but without widespread incision. Data sets describing physical aquatic habitat and fish fauna of each stream were available from other studies. The second stream was impacted by watershed urbanization, but was not incised, so normal channel-floodplain interaction maintained a buffer zone of floodplain wetlands between the study reach and the urban development upstream. The incised stream had mean channel depth and width that were 1.8 and 3.5 times as large as for the nonincised stream, and was characterized by flashier hydrology. The median rise rate for the incised stream was 6.4 times as great as for the nonincised stream. Correlation analyses showed that hydrologic perturbations were associated with water quality degradation, and the incised stream had levels of turbidity and solids that were two to three times higher than the nonincised, urbanizing stream. Total phosphorus, total Kjeldahl N, and chlorophyll a concentrations were significantly higher in the incised stream, while nitrate was significantly greater in the nonincised, urbanizing stream (p urbanizing stream were superior, as it supported almost twice as many species and yielded more than

  15. Conformational heterogeneity in closed and open states of the KcsA potassium channel in lipid bicelles.

    Science.gov (United States)

    Kim, Dorothy M; Dikiy, Igor; Upadhyay, Vikrant; Posson, David J; Eliezer, David; Nimigean, Crina M

    2016-08-01

    The process of ion channel gating-opening and closing-involves local and global structural changes in the channel in response to external stimuli. Conformational changes depend on the energetic landscape that underlies the transition between closed and open states, which plays a key role in ion channel gating. For the prokaryotic, pH-gated potassium channel KcsA, closed and open states have been extensively studied using structural and functional methods, but the dynamics within each of these functional states as well as the transition between them is not as well understood. In this study, we used solution nuclear magnetic resonance (NMR) spectroscopy to investigate the conformational transitions within specific functional states of KcsA. We incorporated KcsA channels into lipid bicelles and stabilized them into a closed state by using either phosphatidylcholine lipids, known to favor the closed channel, or mutations designed to trap the channel shut by disulfide cross-linking. A distinct state, consistent with an open channel, was uncovered by the addition of cardiolipin lipids. Using selective amino acid labeling at locations within the channel that are known to move during gating, we observed at least two different slowly interconverting conformational states for both closed and open channels. The pH dependence of these conformations and the predictable disruptions to this dependence observed in mutant channels with altered pH sensing highlight the importance of conformational heterogeneity for KcsA gating. PMID:27432996

  16. CONTRIBUTIONS OF INTRACELLULAR IONS TO Kv CHANNEL VOLTAGE SENSOR DYNAMICS.

    Directory of Open Access Journals (Sweden)

    Samuel eGoodchild

    2012-06-01

    Full Text Available Voltage sensing domains of Kv channels control ionic conductance through coupling of the movement of charged residues in the S4 segment to conformational changes at the cytoplasmic region of the pore domain, that allow K+ ions to flow. Conformational transitions within the voltage sensing domain caused by changes in the applied voltage across the membrane field are coupled to the conducting pore region and the gating of ionic conductance. However, several other factors not directly linked to the voltage dependent movement of charged residues within the voltage sensor impact the dynamics of the voltage sensor, such as inactivation, ionic conductance, intracellular ion identity and block of the channel by intracellular ligands. The effect of intracellular ions on voltage sensor dynamics is of importance in the interpretation of gating current measurements and the physiology of pore/voltage sensor coupling. There is a significant amount of variability in the reported kinetics of voltage sensor deactivation kinetics of Kv channels attributed to different mechanisms such as open state stabilization, immobilization and relaxation processes of the voltage sensor. Here we separate these factors and focus on the causal role that intracellular ions can play in allosterically modulating the dynamics of Kv voltage sensor deactivation kinetics. These considerations are of critical importance in understanding the molecular determinants of the complete channel gating cycle from activation to deactivation.

  17. A multi-channel fiber optic proximity sensor

    International Nuclear Information System (INIS)

    In this investigation, we propose an efficient multi-channel optical proximity sensor based on the spectrally-resolved interferometric principle. This sensor consists of a single optical source, a spectrometer and fiber optic components such as an optical circulator, a coarse wavelength division multiplexer (CWDM) and fiber optic probes. A spectrometer is used to detect the spectral interferograms of the measuring probes according to their own spectral bandwidths and the interference signals can be separated by the spectral filtering by a CWDM. The principle of the proposed sensor system was verified with feasibility experiments with the home-built 4 channel sensor system. The measuring range of each channel was 1 mm and the resolution was a few tens of nanometers determined by the deviation of linear motions. The stability of the sensor was less than 30 nm. With the aid of a broadband source and a spectrometer, the measurement channel can be extended further by using a suitable CWDM. (paper)

  18. Serial DNA immobilization in micro- and extended nanospace channels.

    Science.gov (United States)

    Renberg, Björn; Sato, Kae; Mawatari, Kazuma; Idota, Naokazu; Tsukahara, Takehiko; Kitamori, Takehiko

    2009-06-01

    That focused arrays, even with a small set of ligands, provide more data than single point experiments is well established in the DNA microarray research field, but microarray technology has yet to be transferred to fused silica microchips. Fused silica microchips have several attractive features such as stability to pressure, solvents, acids and bases, and can be fabricated with minute dimensions, making them good candidates for nanofluidic research. However, due to harsh bonding conditions, DNA ligands must be immobilized after fabrication, thus preventing standard microarray spotting techniques from being used. In this paper, we provide tools for serial DNA immobilization in fused silica microchips using UV. We report the synthesis of a new UV-linker which was used to covalently couple functional DNA oligos to the inside of channels in fused silica microchips. With some simple modifications to our mask aligner, we were able to transfer OHP mask patterns, which allows the creation of basically any pattern in the channels. The functionality of the oligos was measured through the binding of fluorophore-labeled complementary target oligos. We examined parameters influencing DNA immobilization, and carry-over between spots after consecutive immobilizations inside the same channel. We also report the first successful multiple immobilizations of functional DNA oligos inside single channels of extended nanospace depth (460 nm). PMID:19458857

  19. 2D IR spectroscopy reveals the role of water in the binding of channel-blocking drugs to the influenza M2 channel

    Energy Technology Data Exchange (ETDEWEB)

    Ghosh, Ayanjeet, E-mail: ayanjeet@sas.upenn.edu, E-mail: gai@sas.upenn.edu; Gai, Feng, E-mail: ayanjeet@sas.upenn.edu, E-mail: gai@sas.upenn.edu; Hochstrasser, Robin M. [Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104 (United States); Wang, Jun; DeGrado, William F. [Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California 94143 (United States); Moroz, Yurii S.; Korendovych, Ivan V. [Department of Chemistry, Syracuse University, Syracuse, New York 13244 (United States); Zanni, Martin [Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706 (United States)

    2014-06-21

    Water is an integral part of the homotetrameric M2 proton channel of the influenza A virus, which not only assists proton conduction but could also play an important role in stabilizing channel-blocking drugs. Herein, we employ two dimensional infrared (2D IR) spectroscopy and site-specific IR probes, i.e., the amide I bands arising from isotopically labeled Ala30 and Gly34 residues, to probe how binding of either rimantadine or 7,7-spiran amine affects the water dynamics inside the M2 channel. Our results show, at neutral pH where the channel is non-conducting, that drug binding leads to a significant increase in the mobility of the channel water. A similar trend is also observed at pH 5.0 although the difference becomes smaller. Taken together, these results indicate that the channel water facilitates drug binding by increasing its entropy. Furthermore, the 2D IR spectral signatures obtained for both probes under different conditions collectively support a binding mechanism whereby amantadine-like drugs dock in the channel with their ammonium moiety pointing toward the histidine residues and interacting with a nearby water cluster, as predicted by molecular dynamics simulations. We believe these findings have important implications for designing new anti-influenza drugs.

  20. Algebraic disturbances and their consequences in rotating channel flow transition

    CERN Document Server

    Jose, Sharath; Pier, Benoît; Govindarajan, Rama

    2016-01-01

    It is now established that subcritical mechanisms play a crucial role in the transition to turbulence of non-rotating plane shear flows. The role of these mechanisms in rotating channel flow is examined here in the linear and nonlinear stages. Distinct patterns of behaviour are found: the transient growth leading to nonlinearity at low rotation rates $Ro$, a highly chaotic intermediate $Ro$ regime, a localised weak chaos at higher $Ro$, and complete stabilization of transient disturbances at very high $Ro$. At very low $Ro$, the transient growth amplitudes are close to those for non-rotating flow, but Coriolis forces already assert themselves by producing distinct asymmetry about the channel centreline. Nonlinear processes are then triggered, in a streak-breakdown mode of transition. The high $Ro$ regimes do not show these signatures, here the leading eigenmode emerges as dominant in the early stages. Elongated structures plastered close to one wall are seen at higher rotation rates. Rotation is shown to redu...

  1. Two-phase flow instabilities in a vertical annular channel

    Energy Technology Data Exchange (ETDEWEB)

    Babelli, I.; Nair, S.; Ishii, M. [Purdue Univ., West Lafayette, IN (United States)

    1995-09-01

    An experimental test facility was built to study two-phase flow instabilities in vertical annular channel with emphasis on downward flow under low pressure and low flow conditions. The specific geometry of the test section is similar to the fuel-target sub-channel of the Savannah River Site (SRS) Mark 22 fuel assembly. Critical Heat Flux (CHF) was observed following flow excursion and flow reversal in the test section. Density wave instability was not recorded in this series of experimental runs. The results of this experimental study show that flow excursion is the dominant instability mode under low flow, low pressure, and down flow conditions. The onset of instability data are plotted on the subcooling-Zuber (phase change) numbers stability plane.

  2. Braiding of submarine channels controlled by aspect ratio similar to rivers

    Science.gov (United States)

    Foreman, Brady Z.; Lai, Steven Y. J.; Komatsu, Yuhei; Paola, Chris

    2015-09-01

    The great majority of submarine channels formed by turbidity and density currents are meandering in planform; they consist of a single, sinuous channel that transports a turbid, dense flow of sediment from submarine canyons to ocean floor environments. Braided turbidite systems consisting of multiple, interconnected channel threads are conspicuously rare. Furthermore, such systems may not represent the spontaneous planform instability of true braiding, but instead result from erosive processes or bathymetric variability. In marked contrast to submarine environments, both meandering and braided planforms are common in fluvial systems. Here we present experiments of subaqueous channel formation conducted at two laboratory facilities. We find that density currents readily produce a braided planform for flow aspect ratios of depth to width that are similar to those that produce river braiding. Moreover, we find that stability model theory for river planform morphology successfully describes submarine channels in both experiments and the field. On the basis of these observations, we propose that the rarity of braided submarine channels is explained by the generally greater flow depths in submarine systems, which necessitate commensurately greater widths to achieve the required aspect ratio, along with feedbacks among flow thickness, suspended sediment concentration and channel relief that induce greater levee deposition rates and limit channel widening.

  3. Hydrodynamics and morphodynamics of shallow tidal channels and intertidal flats. Doctoral thesis

    Energy Technology Data Exchange (ETDEWEB)

    Friedrichs, C.T.

    1993-02-01

    In this thesis, mechanisms which control morphodynamics of shallow tidal embayments are investigated analytically. In the process of exploring these mechanisms (specifically asymmetries in bottom stress), Tau, basis momentum and mass balances which govern flow in these systems are clarified. Temporal asymmetries in Tau are investigated via a new perturbation scheme which quantifies nonlinear processes and combines geometric controls on asymmetry into a single non-dimensional parameter. Implications of spatial asymmetries in Tau are investigated through stability criteria based on a uniform distribution of Tau. Morphologic observations of both tidal channels and intertidal flats are consistent with a uniform distribution of Tau at equilibrium. Investigation of morphodynamic mechanisms leads to scalings of momentum and continuity which diverge from classical models. Scalings for prismatic channels with strong tidal asymmetries indicate friction often dominates acceleration in the momentum equation. The resulting zero-inertia balance gives a time-varying diffusion equation which requires along-channel amplitude to decay. Uniform Tau justifies a new scaling of continuity for exponentially-shaped channels. In such channels, along-channel gradients in tidal velocity are small and are often dominated by gradients in cross-sectional area. The resulting first-order wave equation allows only amplitude, forward propagating waveforms which are independent of channel length. Tidal channels Hydrodynamics, Tidal flats.

  4. The role of MscL amphipathic N terminus indicates a blueprint for bilayer-mediated gating of mechanosensitive channels.

    Science.gov (United States)

    Bavi, Navid; Cortes, D Marien; Cox, Charles D; Rohde, Paul R; Liu, Weihong; Deitmer, Joachim W; Bavi, Omid; Strop, Pavel; Hill, Adam P; Rees, Douglas; Corry, Ben; Perozo, Eduardo; Martinac, Boris

    2016-01-01

    The bacterial mechanosensitive channel MscL gates in response to membrane tension as a result of mechanical force transmitted directly to the channel from the lipid bilayer. MscL represents an excellent model system to study the basic biophysical principles of mechanosensory transduction. However, understanding of the essential structural components that transduce bilayer tension into channel gating remains incomplete. Here using multiple experimental and computational approaches, we demonstrate that the amphipathic N-terminal helix of MscL acts as a crucial structural element during tension-induced gating, both stabilizing the closed state and coupling the channel to the membrane. We propose that this may also represent a common principle in the gating cycle of unrelated mechanosensitive ion channels, allowing the coupling of channel conformation to membrane dynamics. PMID:27329693

  5. Vascular potassium channels in NVC.

    Science.gov (United States)

    Yamada, K

    2016-01-01

    It has long been proposed that the external potassium ion ([K(+)]0) works as a potent vasodilator in the dynamic regulation of local cerebral blood flow. Astrocytes may play a central role for producing K(+) outflow possibly through calcium-activated potassium channels on the end feet, responding to a rise in the intracellular Ca(2+) concentration, which might well reflect local neuronal activity. A mild elevation of [K(+)]0 in the end feet/vascular smooth muscle space could activate Na(+)/K(+)-ATPase concomitant with inwardly rectifying potassium (Kir) channels in vascular smooth muscle cells, leading to a hyperpolarization of vascular smooth muscle and relaxation of smooth muscle actin-positive vessels. Also proposed notion is endothelial calcium-activated potassium channels and/or inwardly rectifying potassium channel-mediated hyperpolarization of vascular smooth muscle. A larger elevation of [K(+)]0, which may occur pathophysiologically in such as spreading depression or stroke, can trigger a depolarization of vascular smooth muscle cells and vasoconstriction instead. PMID:27130411

  6. Multi channel beam profile digitizer

    International Nuclear Information System (INIS)

    Beam of ions in an accelerator are focussed with the help of focussing magnets to achieve very narrow circular beam. To verify the beam profile along its length, Beam Profile Monitors (BPM) are installed at number of points. The signal generated from these units convey information about the shape and axial error of the beam. Presently BPM signals are monitored on oscilloscope. One oscilloscope is required per BPM channel to be monitored and normally 2 oscilloscopes are kept for viewing beam at two successive points along with one channel selector to select the channel to be monitored. The 8 channel beam profile digitizer being developed is a low cost intelligent PC-add on card, built around Intel's 8751 microcontroller, which can be easily integrated with PC based data acquisition and control system for accelerators. Microcontroller digitizes the signal and stores information on FIFO for PC to read and graphically display the profile. User can select up to 8 profiles to view simultaneously on the screen. (author). 1 ref., 2 figs

  7. Sales promotion and channel coordination

    NARCIS (Netherlands)

    Wierenga, B.; Soethoudt, J.M.

    2010-01-01

    Consumer sales promotions are usually the result of the decisions of two marketing channel parties, the manufacturer and the retailer. In making these decisions, each party normally follows its own interest: i.e. maximizes its own profit. Unfortunately, this results in a suboptimal outcome for the c

  8. Sales promotions and channel coordination

    NARCIS (Netherlands)

    B. Wierenga (Berend); H. Soethoudt (Han)

    2009-01-01

    textabstractConsumer sales promotions are usually the result of the decisions of two marketing channel parties, the manufacturer and the retailer. In making these decisions, each party normally follows its own interest: i.e. maximizes its own profit. Unfortunately, this results in a suboptimal outco

  9. Wireless Communication over Dispersive Channels

    NARCIS (Netherlands)

    Fang, K.

    2010-01-01

    Broadband wireless communication systems require high transmission rates, where the bandwidth of the transmitted signal is larger than the channel coherence bandwidth. This gives rise to time dispersion of the transmitted symbols or frequency-selectivity with different frequency components exhibitin

  10. Visualizing multi-channel networks

    DEFF Research Database (Denmark)

    Antemijczuk, Paweł; Magiera, Marta; Jørgensen, Sune Lehmann;

    2014-01-01

    In this paper, we propose a visualization to illustrate social interactions, built from multiple distinct channels of communication. The visualization displays a summary of dense personal information in a compact graphical notation. The starting point is an abstract drawing of a spider’s web. Bel...

  11. Potential flow through channel constriction.

    Science.gov (United States)

    Lee, J.K.

    1984-01-01

    Potential flow through an eccentric, normal constriction of zero thickness in an infinitely long, straight channel of constant width and unit depth is studied by use of a Schwarz-Christoffel transformation. The transformation is integrated by a direct approach. Parametric equations for streamlines are obtained and used to compute an average streamline length for a potential-flow field. -from ASCE Publications Information

  12. Hidden systematics of fission channels

    Directory of Open Access Journals (Sweden)

    Schmidt Karl-Heinz

    2013-12-01

    Full Text Available It is a common procedure to describe the fission-fragment mass distributions of fissioning systems in the actinide region by a sum of at least 5 Gaussian curves, one for the symmetric component and a few additional ones, together with their complementary parts, for the asymmetric components. These components have been attributed to the influence of fragment shells, e.g. in the statistical scission-point model of Wilkins, Steinberg and Chasman. They have also been associated with valleys in the potential-energy landscape between the outer saddle and the scission configuration in the multi-channel fission model of Brosa. When the relative yields, the widths and the mean mass-asymmetry values of these components are fitted to experimental data, the mass distributions can be very well reproduced. Moreover, these fission channels are characterised by specific values of charge polarisation, total kinetic energy and prompt-neutron yields. The present contribution investigates the systematic variation of the characteristic fission-channel properties as a function of the composition and the excitation energy of the fissioning system. The mean position of the asymmetric fission channels in the heavy fragment is almost constant in atomic number. The deformation of the nascent fragments at scission, which is the main source of excitation energy of the separated fission fragments ending up in prompt-neutron emission, is found to be a unique function of Z for the light and the heavy fragment of the asymmetric fission channels. A variation of the initial excitation energy of the fissioning system above the fission saddle is only seen in the neutron yield of the heavy fragment. The charge polarisation in the two most important asymmetric fission channels is found to be constant and to appreciably exceed the macroscopic value. The variation of the relative yields and of the positions of the fission channels as a function of the composition and excitation energy

  13. CONDUCTIVE CHANNEL FOR ENERGY TRANSMISSION

    Directory of Open Access Journals (Sweden)

    V. V. Apollonov

    2014-01-01

    Full Text Available Laser spark obtained by using a conical optics is much more appropriate to form conducting channels in atmosphere. Only two types of lasers are actively considered to be used in forming high-conductivity channels in atmosphere, controlled by laser spark: pulsed sub-microsecond gas and chemical lasers (CO2, DF and short pulse solid-state and UV lasers. Main advantage of short pulse lasers is their ability in forming of super long ionized channels with a characteristic diameter of ~100  µ  in atmosphere along the  beam propagation direction. At estimated electron densities below  10 ⋅ 16 cm–3 in these filaments and laser wavelengths in the range of 0,5–1,0 mm, the plasma barely absorbs laser radiation.  In this case, the length of the track composed of many filaments is determined by the laser intensity and may reach many kilometers at a femtosecond pulse energy of ~100 mJ. However, these lasers could not be used to form high-conductivity long channels in atmosphere. The ohmic resistance of this type a conducting channels turned out to be very high, and the gas in the channels could not be strongly heated (< 1 J. An electric breakdown controlled by radiation of femtosecond solid-state laser was implemented in only at a length of 3 m with a voltage of 2 MV across the discharge gap (670 kV/m.Not so long ago scientific group from P. N. Lebedev has improved that result, the discharge gap – 1 m had been broken under KrF laser irradiation when switching high-voltage (up to 390 kV/m electric discharge by 100-ns UV pulses. Our previous result  –  16 m long conducting channel controlled by a  laser spark at the voltage  –  3 MV  – was obtained more than 20 years ago in Russia and Japan by using pulsed CO2  laser with energy  –  0,5 kJ. An average electric field strength  was < 190 kV/m. It is still too much for efficient applications.

  14. Molecular pharmacology of the calcium channel: evidence for subtypes, multiple drug-receptor sites, channel subunits, and the development of a radioiodinated 1,4-dihydropyridine calcium channel label, (/sup 125/I)iodipine

    Energy Technology Data Exchange (ETDEWEB)

    Glossmann, H.; Ferry, D.R.; Goll, A.; Rombusch, M.

    1984-01-01

    Radiolabeled Ca2+ antagonists (1,4-dihydropyridines, verapamil, and D-cis-diltiazem) were used to study voltage-operated Ca2+ channels in different excitable tissues. The concept of three subtypes of Ca2+ channels, represented by brain, heart, and skeletal-muscle isoreceptors for 1,4-dihydropyridines, is developed. The three subtypes are characterized by a variety of criteria. Despite the biochemical differences between the subtypes, they have the same Mr in situ by target-size analysis (Mr approximately equal to 180,000, when evaluated by (/sub 3/H)nimodipine). The concept of the metalloprotein nature of the channel and the interaction of channel drugs with the Me2+ binding sites of the ionic pore is demonstrated. Distinct but interacting drug-receptor sites of the Ca2+ channel are found by direct labeling as well as indirectly by drug competition studies. The authors distinguish between the 1,4-dihydropyridine site, the verapamil site, and the D-cis-diltiazem site. Each receptor site can exist in high and low-affinity state; the distribution of receptor sites in these states is regulated by temperature, ions, and drugs. The concept of intrinsic activity of drugs to stabilize the high-affinity state is exemplified for the 1,4-dihydropyridines. A change in the channel architecture is induced by binding of D-cis-diltiazem to its drug receptor site. This is proven by target-size analysis of the channel in situ. Partially purified t-tubule membranes from skeletal muscle are an extremely rich source of Ca2+ channel drug-receptor sites. The stoichiometry was determined in this preparation and found to be four verapamil:two 1,4-dihydropyridine:one D-cis-diltiazem site. A novel Ca2+ channel probe, (/sup 125/I)iodipine (2,200 Ci/mmol), was synthetized, and the properties of this ligand are presented.

  15. Plutonium-237: comparative uptake in chelated and non-chelated form by channel catfish (Ictalurus punctatus)

    International Nuclear Information System (INIS)

    Chelation can either enhance or reduce the uptake of ingested plutonium relative to PuOH (monomer) in channel catfish. Reduced uptake of 237Pu-fulvate is due either to the molecular weight of the complex or its stability in metabolic systems. Increased uptake of 237Pu-citrate is attributable to instability of the complex in metabolic systems. (author)

  16. The design of multi-channel pulse amplitude analyzer based on ARM micro controller

    International Nuclear Information System (INIS)

    It introduces the design of multi-channel pulse amplitude analyzer based on embedded ARM micro-controller. The embedded and real-time system μC/OS-II builds up the real-time and stability of the system and advances the integration. (authors)

  17. Thermal unfolding of a mammalian pentameric ligand-gated ion channel proceeds at consecutive, distinct steps

    NARCIS (Netherlands)

    Tol, Menno B.; Deluz, Cédric; Hassaine, Gherici; Graff, Alexandra; Stahlberg, Henning; Vogel, Horst

    2013-01-01

    Background: The 5-hydroxytryptamine receptor (5-HT3R) is a prototypical pentameric ligand-gated ion channel. Results: The receptor's thermal stability was investigated in native plasma membranes, in detergent solution, and in reconstituted lipid bilayers. Conclusion: Unfolding of the 5-HT3R occurs v

  18. Transmural expression of ion channels and transporters in human nondiseased and end-stage failing hearts

    DEFF Research Database (Denmark)

    Soltysinska, Ewa; Olesen, Søren-Peter; Christ, Torsten;

    2009-01-01

    The cardiac action potential is primarily shaped by the orchestrated function of several different types of ion channels and transporters. One of the regional differences believed to play a major role in the progression and stability of the action potential is the transmural gradient of electrica...

  19. Drilling string stabilizer

    Energy Technology Data Exchange (ETDEWEB)

    Reznik, L.A.; Gurevich, D.A.; Korsakov, N.T.; Savich, M.S.; Ulitskiy, Ye.N.; Zinchenko, V.K.

    1981-04-15

    A stabilizer of a drilling string is suggested which is installed in the turning of a rod and contains two half shells with graduated mutually joining surfaces and fixing connecting element made in the form of a pin. In order to improve the reliable operation and to simplify the assembly-disassembly, the mutually joining surfaces of the half shells are made with a Z-shape, while the connecting fixing element is made in the form of a clamp and is placed between the ends of the stabilizer and the broad turning. The connecting surfaces of the rod of the stabilizer have an unrounded shape.

  20. The Seabed Stability Zonation in Chinese Offshore

    Science.gov (United States)

    Du, J.

    2013-12-01

    There are abundant natural resources and energy in Chinese offshore continental shelf, and which should be the most development potential region now and in the future. But the seabed of Chinese offshore is often under the instable status caused by many factors which deeply affects the safety of marine development. Marine geohazards is an active one among the influence factors. The marine geohazards means the geological factors developed in the seabed surface and the strata below the seabed, such as fault, shallow gas, landslide, coastal erosion, buried river channel, sand wave and sand ridge, easily liquefied sand layer etc., which will cause damage to the human life and property. In this paper, the seabed stability were analyzed and divided it into five grades based on the marine geohazards evaluation result which made by fuzzy mathematic model. Firstly, by collecting the analyzing the marine geohazards which distributed on the seabed or under the seabed, the marine geohazards maps in Chinese offshore were made and the classification system of marine geohazards was established. Then, the evaluation index system of seabed stability was set which included the seismic peak acceleration, geomorphology, direct geohazards and restricted geohazards. And the weighted value of each indicator was calculated by using analytic hierarchy process. And, a group of appropriate number with normal distribution was selected to replace the membership grade function. Based on above, a fuzzy evaluation model for seabed stability is established. Using the maps of marine geohazards, geomorphology maps and seismic peak acceleration maps as data source, using the fuzzy matrix as calculated method, based on the principles of maximum membership grade of fuzzy mathematics, we get the evaluation result of Chinese offshore with 6' by 6' grid unit. The maximum membership grade should be taken as the stability level in each unit. Above all, the seabed stability of Chinese offshore is divided into

  1. STUDY ON DOUBLE-CHANNEL CYCLONE-TYPE PULVERIZED COAL BURNER WITH INNER-POSITIONED FLAME-STABILIZING BODY AND ITS APPLICATION ON 410 t/h BOILER%加内置稳焰体的双通道旋流煤粉燃烧器研究及其在410 t/h锅炉上的应用

    Institute of Scientific and Technical Information of China (English)

    熊立红; 唐必光; 顾昌; 顾山; 高茂; 刘玲; 蔡建国

    2001-01-01

    The combustion-stabilizing mechanism of the title burner has been analyzed.The results of test,measurement and study of cold-state simulation have been given.Based on the results of study,the cyclone-type burner of boiler No 3 in Huozhou Power Plant,Shanxi province,has been retrofitted.The results of commercial experiments show,this kind of burner has better fire-stabilizing capability.%分析了加内置稳焰体的双通道旋流煤粉燃烧器的稳燃机理,给出了冷态模拟试验测量及研究结果,根据研究结果对山西霍州电厂3号炉的旋流燃烧器进行了改造。工业试验结果表明,该燃烧器具有较好的稳燃性能。

  2. Molecular diversity and functional evolution of scorpion potassium channel toxins.

    Science.gov (United States)

    Zhu, Shunyi; Peigneur, Steve; Gao, Bin; Luo, Lan; Jin, Di; Zhao, Yong; Tytgat, Jan

    2011-02-01

    Scorpion toxins affecting K(+) channels (KTxs) represent important pharmacological tools and potential drug candidates. Here, we report molecular characterization of seven new KTxs in the scorpion Mesobuthus eupeus by cDNA cloning combined with biochemical approaches. Comparative modeling supports that all these KTxs share a conserved cysteine-stabilized α-helix/β-sheet structural motif despite the differences in protein sequence and size. We investigated functional diversification of two orthologous α-KTxs (MeuTXKα1 from M. eupeus and BmP01 from Mesobuthus martensii) by comparing their K(+) channel-blocking activities. Pharmacologically, MeuTXKα1 selectively blocked Kv1.3 channel with nanomolar affinity (IC(50), 2.36 ± 0.9 nM), whereas only 35% of Kv1.1 currents were inhibited at 3 μM concentration, showing more than 1271-fold selectivity for Kv1.3 over Kv1.1. This peptide displayed a weak effect on Drosophila Shaker channel and no activity on Kv1.2, Kv1.4, Kv1.5, Kv1.6, and human ether-a-go-go-related gene (hERG) K(+) channels. Although BmB01 and MeuTXKα1 have a similar channel spectrum, their affinity and selectivity for these channels largely varies. In comparison with MeuTXKα1, BmP01 only exhibits a submicromolar affinity (IC(50), 133.72 ± 10.98 nM) for Kv1.3, showing 57-fold less activity than MeuTXKα1. Moreover, it lacks the ability to distinguish between Kv1.1 and Kv1.3. We also found that MeuTXKα1 inhibited the proliferation of activated T cells induced by phorbol myristate acetate and ionomycin at micromolar concentrations. Our results demonstrate that accelerated evolution drives affinity variations of orthologous α-KTxs on Kv channels and indicate that MeuTXKα1 is a promising candidate to develop an immune modulation agent for human autoimmune diseases. PMID:20889474

  3. Integrated criteria for covert channel auditing

    Institute of Scientific and Technical Information of China (English)

    Chang-da WANG; Shi-guang JU

    2008-01-01

    A new concept, the security level difference of a covert channel, is presented, which means the security level span from the sender to the receiver of the covert channel. Based on this, the integrated criteria for covert channel auditing are given. Whereas TCSEC (Trusted Computer System Evaluation Criteria) or CC (Common Criteria for Information Technology Security Evaluation) only use the bandwidth to evaluate the threat of covert channels, our new criteria integrate the security level difference, the bandwidth sensitive parameter, bandwidth, duration and instantaneous time of covert channels, so as to give a comprehensive evaluation of the threat of covert channels in a multilevel security system.

  4. Electromagnetic channel capacity for practical purposes

    CERN Document Server

    Giovannetti, Vittorio; Maccone, Lorenzo; Shapiro, Jeffrey H

    2012-01-01

    We give analytic upper bounds to the channel capacity C for transmission of classical information in electromagnetic channels (bosonic channels with thermal noise). In the practically relevant regimes of high noise and low transmissivity, by comparison with know lower bounds on C, our inequalities determine the value of the capacity up to corrections which are irrelevant for all practical purposes. Examples of such channels are radio communication, infrared or visible-wavelength free space channels. We also provide bounds to active channels that include amplification.

  5. Joint Scheduling for Dual-Hop Block-Fading Broadcast Channels

    KAUST Repository

    Ammar, Zafar

    2012-09-16

    In this paper, we propose joint user-and-hop scheduling over dual-hop block-fading broadcast channels in order to exploit multi-user diversity gains and multi-hop diversity gains all together. To achieve this objective, the first and second hops are scheduled opportunistically based on the channel state information and as a prerequisite we assume that the relay, which is half-duplex and operates using decode-and-forward, is capable of storing the received packets from the source until the channel condition of the destined user becomes good to be scheduled. We formulate the joint scheduling problem as maximizing the weighted sum of the long term achievable rates by the users under a stability constraint, which means that on the long term the rate received by the relay should equal the rate transmitted by it, in addition to constant or variable power constraints. We show that this problem is equivalent to a single-hop broadcast channel by treating the source as a virtual user with an optimal priority weight that maintains the stability constraint. We show how to obtain the source weight either off-line based on channel statistics or on real-time based on channel measurements. Furthermore, we consider special cases including the maximum sum rate scheduler and the proportional fair scheduler. We demonstrate via numerical results that our proposed joint scheduling scheme enlarges the rate region as compared with a scheme that employs multi-user scheduling alone.

  6. Alternative splicing modulates inactivation of type 1 voltage-gated sodium channels by toggling an amino acid in the first S3-S4 linker.

    Science.gov (United States)

    Fletcher, Emily V; Kullmann, Dimitri M; Schorge, Stephanie

    2011-10-21

    Voltage-gated sodium channels underlie the upstroke of action potentials and are fundamental to neuronal excitability. Small changes in the behavior of these channels are sufficient to change neuronal firing and trigger seizures. These channels are subject to highly conserved alternative splicing, affecting the short linker between the third transmembrane segment (S3) and the voltage sensor (S4) in their first domain. The biophysical consequences of this alternative splicing are incompletely understood. Here we focus on type 1 sodium channels (Nav1.1) that are implicated in human epilepsy. We show that the functional consequences of alternative splicing are highly sensitive to recording conditions, including the identity of the major intracellular anion and the recording temperature. In particular, the inactivation kinetics of channels containing the alternate exon 5N are more sensitive to intracellular fluoride ions and to changing temperature than channels containing exon 5A. Moreover, Nav1.1 channels containing exon 5N recover from inactivation more rapidly at physiological temperatures. Three amino acids differ between exons 5A and 5N. However, the changes in sensitivity and stability of inactivation were reproduced by a single conserved change from aspartate to asparagine in channels containing exon 5A, which was sufficient to make them behave like channels containing the complete exon 5N sequence. These data suggest that splicing at this site can modify the inactivation of sodium channels and reveal a possible interaction between splicing and anti-epileptic drugs that stabilize sodium channel inactivation.

  7. Nonlinear hydrodynamic stability

    CERN Document Server

    Isichenko, M B

    1998-01-01

    The variational principle of V. I. Arnold [J. Appl. Math. Mech. Vol. 29, P. 1002 (1965)] is extended to the general conservative inhomogeneous, compressible, and conducting fluid. The concept of iso-vortical flows is generalized to an "invariant foliation" of the phase space. The foliation, which may or may not correspond to explicit conservation laws, is derived from the equations of motion and used for Lyapunov stability. A nonlinear three-dimensional (magneto-) hydrodynamic stability criterion is formulated.

  8. Thermodynamic Stability of Wormholes

    CERN Document Server

    Sajadi, S N

    2016-01-01

    In the context of GR, we study the thermodynamic stability of evolving Lorentzian wormholes at the apparent horizon. The average pressure of the anisotrropic components is considered as the pressure of the wormhole. According to the requirements of stable equilibrium in conventional thermodynamics, we calculate the heat capacity at constant pressure and Gibbs free energy and analyze the local and global thermodynamic stability of the wormhole.

  9. Automatic Fiscal Stabilizers

    Directory of Open Access Journals (Sweden)

    Narcis Eduard Mitu

    2013-11-01

    Full Text Available Policies or institutions (built into an economic system that automatically tend to dampen economic cycle fluctuations in income, employment, etc., without direct government intervention. For example, in boom times, progressive income tax automatically reduces money supply as incomes and spendings rise. Similarly, in recessionary times, payment of unemployment benefits injects more money in the system and stimulates demand. Also called automatic stabilizers or built-in stabilizers.

  10. PFP solution stabilization

    International Nuclear Information System (INIS)

    This Functional Design Criteria (FDC) addresses remediation of the plutonium-bearing solutions currently in inventory at the Plutonium Finishing Plant (PFP). The recommendation from the Environmental Impact Statement (EIS) is that the solutions be treated thermally and stabilized as a solid for long term storage. For solutions which are not discardable, the baseline plan is to utilize a denitration process to stabilize the solutions prior to packaging for storage

  11. Stability of settlement space

    OpenAIRE

    Fikfak, Alenka

    2015-01-01

    Characteristics of settlements patterns and forms are encompassed between stability and instability. We evaluate them according to their historical value, but their image, as perceived today after centuries of changing, adapting and transformation, cannot be recognised in its original form. Time is the "super-factor" that balances, determines and transforms internal forces of settlement structures, and is decisively conditioned by social links. Instability can change to stability and vice ver...

  12. COLLAGEN STRUCTURE AND STABILITY

    OpenAIRE

    Shoulders, Matthew D.; Raines, Ronald T.

    2009-01-01

    Collagen is the most abundant protein in animals. This fibrous, structural protein comprises a right-handed bundle of three parallel, left-handed polyproline II-type helices. Much progress has been made in elucidating the structure of collagen triple helices and the physicochemical basis for their stability. New evidence demonstrates that stereoelectronic effects and preorganization play a key role in that stability. The fibrillar structure of type I collagen–the prototypical collagen fibril–...

  13. Food Fortification Stability Study

    Science.gov (United States)

    Sirmons, T. A.; Cooper, M. R.; Douglas, G. L.

    2016-01-01

    This study aims to assess the stability of vitamin content, sensory acceptability and color variation in fortified spaceflight foods over a period of 2 years. Findings will identify optimal formulation, processing, and storage conditions to maintain stability and acceptability of commercially available fortification nutrients. Changes in food quality are being monitored to indicate whether fortification affects quality over time (compared to the unfortified control), thus indicating their potential for use on long-duration missions.

  14. The effect of wall heating on instability of channel flow

    CERN Document Server

    Sameen, A; Govindarajan, Rama

    2006-01-01

    A comprehensive study of the effect of wall heating or cooling on the linear, transient and secondary growth of instability in channel flow is conducted. The effect of viscosity stratification, heat diffusivity and of buoyancy are estimated separately, with some unexpected results. From linear stability results, it has been accepted that heat diffusivity does not affect stability. However, we show that realistic Prandtl numbers cause a transient growth of disturbances that is an order of magnitude higher than at zero Prandtl number. Buoyancy, even at fairly low levels, gives rise to high levels of subcritical energy growth. Unusually for transient growth, both of these are spanwise-independent and not in the form of streamwise vortices. At moderate Grashof numbers, exponential growth dominates, with distinct Rayleigh-Benard and Poiseuille modes for Grashof numbers upto $\\sim 25000$, which merge thereafter. Wall heating has a converse effect on the secondary instability compared to the primary, destabilising s...

  15. Actin Dynamics Regulates Voltage-Dependent Calcium-Permeable Channels of the Vicia faba Guard Cell Plasma Membrane

    Institute of Scientific and Technical Information of China (English)

    Wei Zhang; Liu-Min Fan

    2009-01-01

    Free cytosolic Ca~(2+) ([Ca~(2+)]_(cyt)) is an ubiquitous second messenger in plant cell signaling, and [Ca~(2+)]_(cyt) elevation is associated with Ca~(2+)-permeable channels in the plasma membrane and endomembranes regulated by a wide range of stimuli. However, knowledge regarding Ca~(2+) channels and their regulation remains limited in planta. A type of voltage-dependent Ca~(2+)-permeable channel was identified and characterized for the Vicia faba L. guard cell plasma membrane by using patch-clamp techniques. These channels are permeable to both Ba~(2+) and Ca~(2+), and their activities can be inhibited by micromolar Gd~(3+). The unitary conductance and the reversal potential of the channels depend on the Ca~(2+) or Ba~(2+) gradients across the plasma membrane. The inward whole-cell Ca~(2+) (Ba~(2+)) current, as well as the unitary current amplitude and NP. of the single Ca~(2+) channel, increase along with the membrane hyperpolarization. Pharmacological experiments suggest that actin dynamics may serve as an upstream regulator of this type of calcium channel of the guard cell plasma membrane. Cytochalasin D, an actin polymerization blocker, activated the NP_o of these channels at the single channel level and increased the current amplitude at the whole-cell level. But these channel activations and current increments could be restrained by pretreatment with an F-actin stabilizer, phalloidin. The potential physiological significance of this regulatory mechanism is also discussed.

  16. Channel estimation in DCT-based OFDM.

    Science.gov (United States)

    Wang, Yulin; Zhang, Gengxin; Xie, Zhidong; Hu, Jing

    2014-01-01

    This paper derives the channel estimation of a discrete cosine transform-(DCT-) based orthogonal frequency-division multiplexing (OFDM) system over a frequency-selective multipath fading channel. Channel estimation has been proved to improve system throughput and performance by allowing for coherent demodulation. Pilot-aided methods are traditionally used to learn the channel response. Least square (LS) and mean square error estimators (MMSE) are investigated. We also study a compressed sensing (CS) based channel estimation, which takes the sparse property of wireless channel into account. Simulation results have shown that the CS based channel estimation is expected to have better performance than LS. However MMSE can achieve optimal performance because of prior knowledge of the channel statistic.

  17. Modulation of ERG channels by XE991

    DEFF Research Database (Denmark)

    Elmedyb, Pernille; Calloe, Kirstine; Schmitt, Nicole;

    2007-01-01

    In neuronal tissue, KCNQ2-5 channels conduct the physiologically important M-current. In some neurones, the M-current may in addition be conducted partly by ERG potassium channels, which have widely overlapping expression with the KCNQ channel subunits. XE991 and linopiridine are known to be...... standard KCNQ potassium channel blockers. These compounds have been used in many different tissues as specific pharmacological tools to discern native currents conducted by KCNQ channels from other potassium currents. In this article, we demonstrate that ERG1-2 channels are also reversibly inhibited by XE......991 in the micromolar range (EC(50) 107 microM for ERG1). The effect has been characterized in Xenopus laevis oocytes expressing ERG1-2 and in the mammalian HEK293 cell line stably expressing ERG1 channels. The IC(50) values for block of KCNQ channels by XE991 range 1-65 microM. In conclusion, great...

  18. Chloride Channels: Often enigmatic, rarely predictable

    Science.gov (United States)

    Duran, Charity; Thompson, Christopher H.; Xiao, Qinghuan; Hartzell, Criss

    2010-01-01

    Until recently, anion (Cl−) channels have received considerably less attention than cation channels. One reason for this may be that many Cl− channels perform functions that might be considered cell biological, like fluid secretion and cell volume regulation, whereas cation channels have historically been associated with cellular excitability that typically happens more rapidly. In this review, we discuss the recent explosion of interest in Cl− channels with special emphasis on new and often surprising developments over the last 5 years. This is exemplified by the findings that more than half of the ClC family members are antiporters, and not channels as was previously thought, and that bestrophins, previously prime candidates for Ca2+-activated Cl− channels, have been supplanted by the newly discovered anoctamins and now hold a tenuous position in the Cl− channel world. PMID:19827947

  19. The quantum capacity with symmetric side channels

    CERN Document Server

    Smith, G; Winter, A; Smith, Graeme; Smolin, John A.; Winter, Andreas

    2006-01-01

    We present an upper bound for the quantum channel capacity that is both additive and convex. Our bound can be interpreted as the capacity of a channel for high-fidelity communication when assisted by the family of all channels mapping symmetrically to their output and environment. The bound seems to be quite tight, and for degradable quantum channels it coincides with the unassisted channel capacity. Using this symmetric side channel capacity, we find new upper bounds on the capacity of the depolarizing channel. We also briefly indicate an analogous notion for distilling entanglement using the same class of (one-way) channels, yielding one of the few genuinely 1-LOCC monotonic entanglement measures.

  20. Coastal Maintained Channels in US waters

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This layer shows coastal channels and waterways that are maintained and surveyed by the U.S. Army Corps of Engineers (USACE). These channels are necessary...

  1. BK channel modulators: a comprehensive overview

    DEFF Research Database (Denmark)

    Nardi, Antonio; Olesen, Søren-Peter

    2008-01-01

    and blockers 4) Marketed and/or investigational drugs with BK-modulating side properties and structural analogues 5) Naturally-occurring BK channel openers and structural analogues 6) Synthetic BK channel openers. This review is intended to provide readers with current opinion on the BK channel as a drug......The large Ca(2+)-activated K(+) channel (BK channel) reflects per excellence the dilemma of the molecular target driven drug discovery process. Significant experimental evidence suggests that the BK channels play a pivotal and specific role in many pathophysiological conditions supporting...... the notion that the channel represents an innovative and promising drug target. However, after more than ten years of intense research effort both in academia and industry, scientists have yet to witness the approval of a single BK channel modulator for clinical use. On the contrary, three BK openers...

  2. Membrane lipid modulations remove divalent open channel block from TRP-like and NMDA channels.

    Science.gov (United States)

    Parnas, Moshe; Katz, Ben; Lev, Shaya; Tzarfaty, Vered; Dadon, Daniela; Gordon-Shaag, Ariela; Metzner, Henry; Yaka, Rami; Minke, Baruch

    2009-02-25

    Open channel block is a process in which ions bound to the inside of a channel pore block the flow of ions through that channel. Repulsion of the blocking ions by depolarization is a known mechanism of open channel block removal. For the NMDA channel, this mechanism is necessary for channel activation and is involved in neuronal plasticity. Several types of transient receptor potential (TRP) channels, including the Drosophila TRP and TRP-like (TRPL) channels, also exhibit open channel block. Therefore, removal of open channel block is necessary for the production of the physiological response to light. Because there is no membrane depolarization before the light response develops, it is not clear how the open channel block is removed, an essential step for the production of a robust light response under physiological conditions. Here we present a novel mechanism to alleviate open channel block in the absence of depolarization by membrane lipid modulations. The results of this study show open channel block removal by membrane lipid modulations in both TRPL and NMDA channels of the photoreceptor cells and CA1 hippocampal neurons, respectively. Removal of open channel block is characterized by an increase in the passage-rate of the blocking cations through the channel pore. We propose that the profound effect of membrane lipid modulations on open channel block alleviation, allows the productions of a robust current in response to light in the absence of depolarization.

  3. Theoretical investigations on two-phase flow instability in parallel channels under axial non-uniform heating

    International Nuclear Information System (INIS)

    Highlights: • We developed a model based on homogeneous flow model to analyze two-phase flow instability in parallel channels. • The influence of axial non-uniform heating on the system stability has been investigated. • Influences of various factors on system instability under cosine heat flux have been studied. • The system under top-peaked heat flux is the most stable system. - Abstract: Two-phase flow instability in parallel channels heated by axial non-uniform heat flux has been theoretically studied in this paper. The system control equations of parallel channels were established based on the homogeneous flow model in two-phase region. Semi-implicit finite-difference scheme and staggered mesh method were used to discretize the equations, and the difference equations were solved by chasing method. Cosine, bottom-peaked and top-peaked heat fluxes were used to study the influence of non-uniform heating on two-phase flow instability of the parallel channels system. The marginal stability boundaries (MSB) of parallel channels and three-dimensional instability spaces (or instability reefs) under different heat flux conditions have been obtained. Compared with axial uniform heating, axial non-uniform heating will affect the system stability. Cosine and bottom-peaked heat fluxes can destabilize the system stability in high inlet subcooling region, while the opposite effect can be found in low inlet subcooling region. However, top-peaked heat flux can enhance the system stability in the whole region. In addition, for cosine heat flux, increasing the system pressure or inlet resistance coefficient can strengthen the system stability, and increasing the heating power will destabilize the system stability. The influence of inlet subcooling number on the system stability is multi-valued under cosine heat flux

  4. GMSK co-channel demodulation

    Science.gov (United States)

    Nelson, D. J.; Hopkins, J. R.

    2009-08-01

    Gaussian Minimum Shift Keying (GMSK) is a modulation method used by GSM phone networks and the Automatic Identification System (AIS) used by commercial ships. Typically these systems transmit data in short bursts and accomodate a large number of users by time, frequency and power management. Co-channel interference is not a problem unless the system is heavily loaded. This system load is a function of the density of users and the footprint of the receiver. We consider the problem of demodulation of burst GMSK signals in the presence of severe noise and co-channel interference. We further examine the problem of signal detection and blind estimation and tracking of all of the parameters required in the demodulation process. These parameters include carrier frequency, carrier phase, baud rate, baud phase, modulation index and the start and duration of the signal.

  5. Backward reflection analysis of transmitting channel of active laser ranging optics

    Science.gov (United States)

    Hong, Jinsuk; Koh, Hae Seog

    2013-09-01

    The designed Active LDR(Laser Detection and Ranging) System contains high-power Laser and its diameter is approximately 24mm. Although the laser transmitting channel and receiving optic channel are completely separated from each other and doesn't share any of the optical components in design, each channel shares 4 wedge scanners, which are to overcome the narrow FOV(Field of View) of the optical system. Any backward reflection back to the fiber laser end must be carefully studied since it can damage the LD(Laser Diodes), the inner components of the laser unit because of the high amplification factor of the laser unit. In this study, the stray light caused by the transmitting channel's laser and inner reflection by optical components were analyzed by ASAP(Advanced System Analysis Program) software. We also can confirm the operability and stability of the system by more than 6 months of operation of the system.

  6. Adaptive Four-Channel Neuro-Fuzzy Control of a Master-Slave Robot

    Directory of Open Access Journals (Sweden)

    Watcharin Po-Ngaen

    2013-03-01

    Full Text Available In bilateral control of tele‐manipulation based on a conventional approach, there are deficiencies in stability robustness and manoeuvrability against variations in the dynamics of the master input device and the task environment. In this study, an adaptive four‐channel neuro‐fuzzy bilateral control scheme is proposed. To evaluate whether the proposed algorithm is a suitable technique for improving the robustness and manoeuvrability of tele‐robot implementation, four‐channel neuro‐fuzzy and classical bilateral control frameworks have been investigated in a simulation experiment. Distinct bilateral control schemes in the form of four‐channel intelligent control and the classic form of position–force and position‐position have been implemented and compared using a one degree of freedom (DOF master‐slave system. The experimental results show that the application of a four‐channel neuro‐fuzzy control strategy effectively improves the overall performance.

  7. Gramicidin channel kinetics under tension.

    OpenAIRE

    Goulian, M; Mesquita, O. N.; Fygenson, D K; Nielsen, C; Andersen, O S; Libchaber, A.

    1998-01-01

    We have measured the effect of tension on dimerization kinetics of the channel-forming peptide gramicidin A. By aspirating large unilamellar vesicles into a micropipette electrode, we are able to simultaneously monitor membrane tension and electrical activity. We find that the dimer formation rate increases by a factor of 5 as tension ranges from 0 to 4 dyn/cm. The dimer lifetime also increases with tension. This behavior is well described by a phenomenological model of membrane elasticity in...

  8. Wireless Channel Propagation Models Evaluation

    OpenAIRE

    Raikel Bordón López; Reinier Alonso Quintana; Samuel Montejo Sánchez

    2012-01-01

    In the design of wireless communications systems, channel modelling is an efficient alternative to predict the path loss. In this paper we present a comparative study between Okumura, Hata, Walfisch-Bertoni and Walfisch-Ikegami propagation models. We present a developed software tool, which is useful to evaluate these models from a graphical user interface. The main objective is to analyze and compare path loss predictions, taking into account different environment conditions and a common val...

  9. SOCIAL NETWORKS AS MARKETING CHANNELS

    OpenAIRE

    Sonja Petrov, Vesna Zubac, Miroslav Milojeviæ

    2015-01-01

    Fast technological development in social media offers many opportunities for companies in order to have better connection with their customers. Traditional tools become less effective and companies are working intensively to be present on the web. This paper will try to answer the question what are the advantages of social media as a marketing channels compared to conventional way of advertising. The authors will specially pay attention to how can companies improve and increase their presence...

  10. Degenerate RFID Channel Modeling for Positioning Applications

    Directory of Open Access Journals (Sweden)

    A. Povalac

    2012-12-01

    Full Text Available This paper introduces the theory of channel modeling for positioning applications in UHF RFID. It explains basic parameters for channel characterization from both the narrowband and wideband point of view. More details are given about ranging and direction finding. Finally, several positioning scenarios are analyzed with developed channel models. All the described models use a degenerate channel, i.e. combined signal propagation from the transmitter to the tag and from the tag to the receiver.

  11. Interference Channels with Correlated Receiver Side Information

    OpenAIRE

    Liu, Nan; Gunduz, Deniz; Goldsmith, Andrea J.; Poor, H. Vincent

    2008-01-01

    The problem of joint source-channel coding in transmitting independent sources over interference channels with correlated receiver side information is studied. When each receiver has side information correlated with its own desired source, it is shown that source-channel code separation is optimal. When each receiver has side information correlated with the interfering source, sufficient conditions for reliable transmission are provided based on a joint source-channel coding scheme using the ...

  12. Southern California Channel Islands Bibliography, through 1992

    OpenAIRE

    Channel Islands National Marine Sanctuary

    1992-01-01

    The Southern California Channel Islands Bibliography, through 1992, comprises 4035 references to the scientific literature on Southern California's Channel Islands. The Bibliography was compiled by the Channel Islands National Marine Sanctuary and is presented here in a February 1993 version. The Santa Barbara Museum of Natural History presents a California Channel Islands Bibliography on its website. It has more recent references and overlaps considerably with this bibliography. How...

  13. Ions in Fluctuating Channels: Transistors Alive

    OpenAIRE

    Eisenberg, Bob

    2005-01-01

    Ion channels are proteins with a hole down the middle embedded in cell membranes. Membranes form insulating structures and the channels through them allow and control the movement of charged particles, spherical ions, mostly Na+, K+, Ca++, and Cl-. Membranes contain hundreds or thousands of types of channels, fluctuating between open conducting, and closed insulating states. Channels control an enormous range of biological function by opening and closing in response to specific stimuli using ...

  14. Artificial water channels--incipient innovative developments.

    Science.gov (United States)

    Barboiu, Mihail

    2016-04-28

    Aquaporins (AQPs) are biological water channels known for fast water transport (∼10(8)-10(9) water molecules per s per channel), with complete proton/ion exclusion. Few synthetic channels have been designed to mimic this high water permeability and to reject ions at a significant level. This Feature Article will discuss the incipient developments of the first artificial water channel systems. PMID:27046217

  15. Customer Evolution in Sales Channel Migration

    OpenAIRE

    Valentini, Sara

    2008-01-01

    This research has been triggered by an emergent trend in customer behavior: customers have rapidly expanded their channel experiences and preferences beyond traditional channels (such as stores) and they expect the company with which they do business to have a presence on all these channels. This evidence has produced an increasing interest in multichannel customer behavior and it has motivated several researchers to study the customers’ channel choices dynamics in multichannel environment. W...

  16. Radio propagation measurement and channel modelling

    CERN Document Server

    Salous, Sana

    2013-01-01

    While there are numerous books describing modern wireless communication systems that contain overviews of radio propagation and radio channel modelling, there are none that contain detailed information on the design, implementation and calibration of radio channel measurement equipment, the planning of experiments and the in depth analysis of measured data. The book would begin with an explanation of the fundamentals of radio wave propagation and progress through a series of topics, including the measurement of radio channel characteristics, radio channel sounders, measurement strategies

  17. Stability and Halo Formation in Axisymmetric Intense Beams

    CERN Document Server

    Gluckstern, R L; Gluckstern, Robert L.; Kurennoy, Sergey S.

    1998-01-01

    Beam stability and halo formation in high-intensity axisymmetric 2D beams in a uniform focusing channel are analyzed using particle-in-cell simulations. The tune depression - mismatch space is explored for the uniform (KV) distribution of the particle transverse-phase-space density, as well as for more realistic ones (in particular, the water-bag distribution), to determine the stability limits and halo parameters. The numerical results show an agreement with predictions of the analytical model for halo formation (R.L. Gluckstern, Phys. Rev. Letters, 73 (1994) 1247).

  18. Stability and Halo Formation in Axisymmetric Intense Beams.

    Science.gov (United States)

    Gluckstern, Robert L.; Kurennoy, Sergey S.

    1997-05-01

    Beam stability and halo formation in high-intensity axisymmetric 2D beams in a uniform focusing channel are analyzed using particle-in-cell simulations. The tune depression - mismatch space is explored for the uniform distribution of the particle transverse phase space density (Kapchinsky-Vladimirsky), as well as for more realistic ones (in particular, the water-bag distribution), to determine the stability limits and halo parameters. The numerical results obtained are compared and show an agreement with the predictions of the analytical model for halo formation developed earlier (R.L. Gluckstern, Phys. Rev. Lett., 73), 1247 (1994)..

  19. Stability and halo formation in axisymmetric intense beams

    Energy Technology Data Exchange (ETDEWEB)

    Gluckstern, R.L. [Univ. of Maryland, College Park, MD (United States); Kurennoy, S.S. [Los Alamos National Lab., NM (United States)

    1997-10-01

    Beam stability and halo formation in high-intensity axisymmetric 2D beams in a uniform focusing channel are analyzed using particle-in-cell simulations. The tune depression-mismatch space is explored for the uniform (KV) distribution of the particle transverse-phase-space density, as well as for more realistic ones (in particular, the water-bag distribution), to determine the stability limits and halo parameters. The numerical results show an agreement with predictions of the analytical model for halo formation.

  20. Interference Channels with Strong Secrecy

    CERN Document Server

    He, Xiang

    2009-01-01

    It is known that given the real sum of two independent uniformly distributed lattice points from the same nested lattice codebook, the eavesdropper can obtain at most 1 bit of information per channel regarding the value of one of the lattice points. In this work, we study the effect of this 1 bit information on the equivocation expressed in three commonly used information theoretic measures, i.e., the Shannon entropy, the Renyi entropy and the min entropy. We then demonstrate its applications in an interference channel with a confidential message. In our previous work, we showed that nested lattice codes can outperform Gaussian codes for this channel when the achieved rate is measured with the weak secrecy notion. Here, with the Renyi entropy and the min entropy measure, we prove that the same secure degree of freedom is achievable with the strong secrecy notion as well. A major benefit of the new coding scheme is that the strong secrecy is generated from a single lattice point instead of a sequence of lattic...

  1. Water channels in peritoneal dialysis.

    Science.gov (United States)

    Devuyst, Olivier

    2010-01-01

    Peritoneal dialysis involves diffusive and convective transports and osmosis through the highly vascularized peritoneal membrane. Several lines of evidence have demonstrated that the water channel aquaporin-1 (AQP1) corresponds to the ultrasmall pore predicted by the modelization of peritoneal transport. Proof-of-principle studies have shown that up-regulation of the expression of AQP1 in peritoneal capillaries is reflected by increased water permeability and ultrafiltration, without affecting the osmotic gradient and the permeability for small solutes. Inversely, studies in Aqp1 mice have shown that haploinsufficiency in AQP1 is reflected by significant attenuation of water transport. Recent studies have identified lead compounds that could act as agonists of aquaporins, as well as putative binding sites and potential mechanisms of gating the water channel. By modulating water transport, these pharmacological agents could have clinically relevant effects in targeting specific tissues or disease states. These studies on the peritoneal membrane also provide an experimental framework to investigate the role of water channels in the endothelium and various cell types.

  2. Aquifer stability investigations

    Energy Technology Data Exchange (ETDEWEB)

    Allen, R.D.; Doherty, T.J.

    1981-09-01

    The study of compressed air energy storage (CAES) in porous rock reservoirs is carried out within the Reservoir Stability Studies Program at Pacific Northwest Laboratory. The goal of the study is to establish criteria for long-term stability of aquifer CAES reservoirs. These criteria are intended to be guidelines and check lists that utilities and architect-engineering firms may use to evaluate reservoir stability at candidate CAES sites. These criteria will be quantitative where possible, qualitative where necessary, and will provide a focal point for CAES relevant geotechnical knowledge, whether developed within this study or available from petroleum, mining or other geotechnical practices using rock materials. The Reservoir Stability Studies Program had four major activities: a state-of-the-art survey to establish preliminary stability criteria and identify areas requiring research and development; numerical modeling; laboratory testing to provide data for use in numerical models and to investigate fundamental rock mechanics, thermal, fluid, and geochemical response of aquifer materials; and field studies to verify the feasibility of air injection and recovery under CAES conditions in an aquifer, to validate and refine the stability criteria, and to evaluate the accuracy and adequacy of the numerical and experimental methodologies developed in previous work. Three phases of study, including preliminary criteria formulation, numerical model development, and experimental assessment of CAES reservoir materials have been completed. Present activity consists of construction and operation of the aquifer field test, and associated numerical and experimental work in support of that activity. Work is presently planned to be complete by 1983 at the end of the field test. At that time the final stability criteria for aquifers will be issued. Attached here also are preliminary criteria for aquifers.

  3. Two-dimensional nonlinear travelling waves in magnetohydrodynamic channel flow

    CERN Document Server

    Hagan, Jonathan

    2013-01-01

    The present study is concerned with the stability of a flow of viscous conducting liquid driven by pressure gradient in the channel between two parallel walls subject to a transverse magnetic field. Although the magnetic field has a strong stabilizing effect, this flow, similarly to its hydrodynamic counterpart -- plane Poiseuille flow, is known to become turbulent significantly below the threshold predicted by linear stability theory. We investigate the effect of the magnetic field on 2D nonlinear travelling-wave states which are found at substantially subcritical Reynolds numbers starting from $Re_n=2939$ without the magnetic field and from $Re_n\\sim6.50\\times10^3Ha$ in a sufficiently strong magnetic field defined by the Hartmann number $Ha.$ Although the latter value is by a factor of seven lower than the linear stability threshold $Re_l\\sim4.83\\times10^4Ha$,it is still more by an order of magnitude higher than the experimentally observed value for the onset of turbulence in this flow.

  4. Tyrosine Residues from the S4-S5 Linker of Kv11.1 Channels Are Critical for Slow Deactivation.

    Science.gov (United States)

    Ng, Chai-Ann; Gravel, Andrée E; Perry, Matthew D; Arnold, Alexandre A; Marcotte, Isabelle; Vandenberg, Jamie I

    2016-08-12

    Slow deactivation of Kv11.1 channels is critical for its function in the heart. The S4-S5 linker, which joins the voltage sensor and pore domains, plays a critical role in this slow deactivation gating. Here, we use NMR spectroscopy to identify the membrane-bound surface of the S4S5 linker, and we show that two highly conserved tyrosine residues within the KCNH subfamily of channels are membrane-associated. Site-directed mutagenesis and electrophysiological analysis indicates that Tyr-542 interacts with both the pore domain and voltage sensor residues to stabilize activated conformations of the channel, whereas Tyr-545 contributes to the slow kinetics of deactivation by primarily stabilizing the transition state between the activated and closed states. Thus, the two tyrosine residues in the Kv11.1 S4S5 linker play critical but distinct roles in the slow deactivation phenotype, which is a hallmark of Kv11.1 channels.

  5. Control of intrabunch dynamics at CERN SPS ring using 3.2 GS/s digital feedback channel

    CERN Document Server

    Rivetta, C; Cesaratto, J M; Dusatko, J; Pivi, M; Pollock, K; Turgut, O; Bartosik, H; Hofle, W; Kotzian, G; Li, K

    2013-01-01

    The feedback control of intra-bunch instabilities driven by electron-cloud or strong head-tail interaction requires bandwidth sufficient to sense the vertical position and apply correction fields to multiple sections of a nanosecondscale bunch. These requirements impose challenges and limits in the design of the feedback channel. We present experimental measurements taken from the CERN SPS machine development studies with an intrabunch feedback channel prototype. The performance of a 3.2 GS/s digital processing system is evaluated, quantifying the effect of noise and limits of the feedback channel in the bunch stability as well as transient and steady state motion of the bunch. The controllers implemented are general purpose 16 tap FIR filters and the impact on the bunch stability of controller parameters are analyzed and quantified. These studies, based on the limited feedback prototype, are crucial to validate reduced models of the system and macroparticle simulation codes, including the feedback channel. T...

  6. Mechanosensitive Channels: In Touch with Piezo

    OpenAIRE

    Xiao, Rui; Xu, X. Z. Shawn

    2010-01-01

    Mechanosensory transduction underlies touch, hearing and proprioception and requires mechanosensitive channels that are directly gated by forces; however, the molecular identities of these channels remain largely elusive. A new study has identified Piezo1 and Piezo2 as a novel class of mechanosensitive channels.

  7. Channel One: But What about the Advertising?

    Science.gov (United States)

    Greenberg, Bradley S.; Brand, Jeffrey E.

    1994-01-01

    A survey of students in Channel One and control schools showed that regular viewing of Channel One reinforces materialistic attitudes. Youngsters are bombarded daily with advertising from adolescent-oriented radio stations, magazines, and TV programs outside school. Channel One does provide educators with a excellent opportunity to educate youth…

  8. One-mode quantum Gaussian channels

    OpenAIRE

    Holevo, A. S.

    2006-01-01

    A classification of one-mode Gaussian channels is given up to canonical unitary equivalence. A complementary to the quantum channel with additive classical Gaussian noise is described providing an example of one-mode Gaussian channel which is neither degradable nor anti-degradable.

  9. 47 CFR 95.29 - Channels available.

    Science.gov (United States)

    2010-10-01

    ... no more than 5 watts ERP. (g) Fixed stations in GMRS systems authorized before March 18, 1968... transmission of another GMRS station on a different channel or channels), the licensee of the GMRS system must... GMRS system from the following 462 MHz channels: 462.5500, 462.5750, 462.6000, 462.6250, 462.6500,...

  10. Language Planning, Channel Management, and ESP.

    Science.gov (United States)

    Kennedy, Chris

    Channel management, a concept developed in marketing to refer to the process by which a product is moved from production to consumption, uses a channel of distribution operating at several levels, each responsible for one or more of the activities of moving the product forward to the consumer. The function of channel management is to select the…

  11. ANALYSIS AND ESTIMATION OF HYDRAULIC STABILITY OF FRANCIS HYDRO TURBINE

    Institute of Scientific and Technical Information of China (English)

    LAI Xi-de

    2004-01-01

    With the development of large-capacity hydro turbines, the hydraulic instability of bydro turbines has become one of the most important problems that affect the stable operation of the hydro-electric units. The hydraulic vibration and unstable operation of Francis hydro turbines are primarily caused by the unsteady pressure pulsations inside draft tubes.The forced rotating vortex core at the runner exit and the channel vortices inside Francis turbine runners are origins of the unsteady pressure pulsations when operating at partial load. This paper briefly analyzes the hydraulic instability of operation caused by the vortex core and channel vortices at partial load, then, presents a way to estimate the hydraulic stability by calculation of the flow behavior at the runner exit.The validity of estimation is examined by comparison with experimental data. This will be helpful to evaluate the alternative design and predict the hydraulic stability for both the prototype and model hydro turbines.

  12. Channel instability in a forested catchment: a case study from Jones Creek, East Gippsland, Australia

    Science.gov (United States)

    Cohen, Tim J.; Brierley, Gary J.

    2000-02-01

    Jones Creek, a forested sub-catchment of the Genoa River, Victoria, Australia has experienced channel metamorphosis induced by a series of floods since 1971. In the flood of record, in 1971, the Genoa River widened by up to two times at the confluence with Jones Creek. This effectively shortened the course of Jones Creek, resulting in a lagged tributary response. Incision and bed steepening during floods in 1975 and 1978 triggered significant changes in channel form along Jones Creek. Channel changes between 1972-1997 resulted in a four-fold increase in cross-sectional area. Channel depth increased by up to 1.5 m, but has subsequently refilled by around 0.6 m. Initially, incision resulted in increased stream power as a result of increased mean depth, while sinuosity was maintained. This was followed by channel widening, a reduction in sinuosity and a continued increase in slope. Estimated stream power remains high as the channel continues to laterally adjust. This study highlights the dynamic nature of tributary-trunk stream relationships in a cut-and-fill landscape, demonstrating how trunk stream adjustments can induce profound tributary instability in a forested subcatchment. Channel widening of the trunk stream primed the tributary for change. Bedlevel incision and increases in bedslope breached the threshold of landscape stability in this steep alluvial tributary. Three periods of channel change can be identified, reflecting the complex response of the system to channel incision. Rather than developing simple cutoffs, Jones Creek now exhibits a range of lateral adjustment and realignment features. Responses to external disturbance provide insights into 'natural' recovery mechanisms in this forested setting. Lateral adjustment and associated sediment deposition have been accompanied by rapid rates of vegetation colonisation and stabilisation of realignment features, effectively reducing the volume of sediment that is available to be reworked through the channel

  13. Inception of supraglacial channelization under turbulent flow conditions

    Science.gov (United States)

    Mantelli, E.; Camporeale, C.; Ridolfi, L.

    2013-12-01

    Glacier surfaces exhibit an amazing variety of meltwater-induced morphologies, ranging from small scale ripples and dunes on the bed of supraglacial channels to meandering patterns, till to large scale drainage networks. Even though the structure and geometry of these morphologies play a key role in the glacier melting processes, the physical-based modeling of such spatial patterns have attracted less attention than englacial and subglacial channels. In order to partially fill this gap, our work concerns the large scale channelization occurring on the ice slopes and focuses on the role of turbulence on the wavelength selection processes during the channelization inception. In a recent study[1], two of us showed that the morphological instability induced by a laminar film flowing over an ice bed is characterized by transversal length scales of order of centimeters. Being these scales much smaller than the spacing observed in the channelization of supraglacial drainage networks (that are of order of meters) and considering that the water films flowing on glaciers can exhibit Reynolds numbers larger than 104, we investigated the role of turbulence in the inception of channelization. The flow-field is modeled by means of two-dimensional shallow water equations, where Reynolds stresses are also considered. In the depth-averaged heat balance equation an incoming heat flux from air is assumed and forced convection heat exchange with the wall is taken into account, in addition to convection and diffusion in the liquid. The temperature profile in the ice is finally coupled to the liquid through Stefan equation. We then perform a linear stability analysis and, under the assumption of small Stefan number, we solve the differential eigenvalue problem analytically. As main outcome of such an analysis, the morphological instability of the ice-water interface is detected and investigated in a wide range of the independent parameters: longitudinal and transversal wavenumbers

  14. Plasma channel and Z-pinch dynamics for heavy ion transport

    Energy Technology Data Exchange (ETDEWEB)

    Ponce-Marquez, David

    2002-07-09

    A self stabilized, free standing, z-pinch plasma channel has been proposed to deliver the high intensity heavy ion beam from the end of a driver to the fuel target in a heavy ion inertial fusion power plant. The z-pinch relaxes emittance and energy spread requirements requiring a lower cost driver. A z-pinch transport would reduce the number of beam entry port holes to the target chamber from over a hundred to four as compared to neutralized ballistic focusing thus reducing the driver hardware exposure to neutron flux. Experiments where a double pulse discharge technique is used, z-pinch plasma channels with enhanced stability are achieved. Typical parameters are 7 kV pre-pulse discharge and 30 kV main bank discharge with 50 kA of channel current in a 7 torr background gas atmosphere. This work is an experimental study of these plasma channels examining the relevant physics necessary to understand and model such plasmas. Laser diagnostics measured the dynamical properties of neutrals and plasma. Schlieren and phase contrast techniques probe the pre-pulse gas dynamics and infrared interferometry and faraday effect polarimetry are used on the z-pinch to study its electron density and current distribution. Stability and repeatability of the z-pinch depend on the initial conditions set by the pre-pulse. Results show that the z-pinch channel is wall stabilized by an on-axis gas density depression created by the pre-pulse through hydrodynamic expansion where the ratio of the initial gas density to the final gas density is > 10/1. The low on-axis density favors avalanching along the desired path for the main bank discharge. Pinch time is around 2 s from the main bank discharge initiation with a FWHM of {approx} 2 cm. Results also show that typical main bank discharge plasma densities reach 10{sup 17} cm{sup -3} peak on axis for a 30 kV, 7 torr gas nitrogen discharge. Current rise time is limited by the circuit-channel inductance with the highest contribution to the

  15. Highly Sensitive and Patchable Pressure Sensors Mimicking Ion-Channel-Engaged Sensory Organs.

    Science.gov (United States)

    Chun, Kyoung-Yong; Son, Young Jun; Han, Chang-Soo

    2016-04-26

    Biological ion channels have led to much inspiration because of their unique and exquisite operational functions in living cells. Specifically, their extreme and dynamic sensing abilities can be realized by the combination of receptors and nanopores coupled together to construct an ion channel system. In the current study, we demonstrated that artificial ion channel pressure sensors inspired by nature for detecting pressure are highly sensitive and patchable. Our ion channel pressure sensors basically consisted of receptors and nanopore membranes, enabling dynamic current responses to external forces for multiple applications. The ion channel pressure sensors had a sensitivity of ∼5.6 kPa(-1) and a response time of ∼12 ms at a frequency of 1 Hz. The power consumption was recorded as less than a few μW. Moreover, a reliability test showed stability over 10 000 loading-unloading cycles. Additionally, linear regression was performed in terms of temperature, which showed no significant variations, and there were no significant current variations with humidity. The patchable ion channel pressure sensors were then used to detect blood pressure/pulse in humans, and different signals were clearly observed for each person. Additionally, modified ion channel pressure sensors detected complex motions including pressing and folding in a high-pressure range (10-20 kPa).

  16. An SK3 channel/nWASP/Abi-1 complex is involved in early neurogenesis.

    Directory of Open Access Journals (Sweden)

    Stefan Liebau

    Full Text Available BACKGROUND: The stabilization or regulated reorganization of the actin cytoskeleton is essential for cellular structure and function. Recently, we could show that the activation of the SK3-channel that represents the predominant SK-channel in neural stem cells, leads to a rapid local outgrowth of long filopodial processes. This observation indicates that the rearrangement of the actin based cytoskeleton via membrane bound SK3-channels might selectively be controlled in defined micro compartments of the cell. PRINCIPAL FINDINGS: We found two important proteins for cytoskeletal rearrangement, the Abelson interacting protein 1, Abi-1 and the neural Wiskott Aldrich Syndrome Protein, nWASP, to be in complex with SK3- channels in neural stem cells (NSCs. Moreover, this interaction is also found in spines and postsynaptic compartments of developing primary hippocampal neurons and regulates neurite outgrowth during early phases of differentiation. Overexpression of the proteins or pharmacological activation of SK3 channels induces obvious structural changes in NSCs and hippocampal neurons. In both neuronal cell systems SK3 channels and nWASP act synergistic by strongly inducing filopodial outgrowth while Abi-1 behaves antagonistic to its interaction partners. CONCLUSIONS: Our results give good evidence for a functional interplay of a trimeric complex that transforms incoming signals via SK3-channel activation into the local rearrangement of the cytoskeleton in early steps of neuronal differentiation involving nWASP and Abi-1 actin binding proteins.

  17. Open State Destabilization by Atp Occupancy Is Mechanism Speeding Burst Exit Underlying KATP Channel Inhibition by Atp

    OpenAIRE

    Li, Lehong; Geng, Xuehui; Drain, Peter

    2002-01-01

    The ATP-sensitive potassium (KATP) channel is named after its characteristic inhibition by intracellular ATP. The inhibition is a centerpiece of how the KATP channel sets electrical signaling to the energy state of the cell. In the β cell of the endocrine pancreas, for example, ATP inhibition results from high blood glucose levels and turns on electrical activity leading to insulin release. The underlying gating mechanism (ATP inhibition gating) includes ATP stabilization of closed states, bu...

  18. Na+ channel β subunits: Overachievers of the ion channel family

    OpenAIRE

    LoriLIsom; WilliamJBrackenbury

    2011-01-01

    Voltage gated Na+ channels (VGSCs) in mammals contain a pore-forming α subunit and one or more β subunits. There are five mammalian β subunits in total: β1, β1B, β2, β3, and β4, encoded by four genes: SCN1B-SCN4B. With the exception of the SCN1B splice variant, β1B, the β subunits are type I topology transmembrane proteins. In contrast, β1B lacks a transmembrane domain and is a secreted protein. A growing body of work shows that VGSC β subunits are multifunctional. While they do not form the...

  19. Analytical study of magnetohydrodynamic propulsion stability

    Science.gov (United States)

    Abdollahzadeh Jamalabadi, M. Y.

    2014-09-01

    In this paper an analytical solution for the stability of the fully developed flow drive in a magneto-hydro-dynamic pump with pulsating transverse Eletro-magnetic fields is presented. To do this, a theoretical model of the flow is developed and the analytical results are obtained for both the cylindrical and Cartesian configurations that are proper to use in the propulsion of marine vessels. The governing parabolic momentum PDEs are transformed into an ordinary differential equation using approximate velocity distribution. The numerical results are obtained and asymptotic analyses are built to discover the mathematical behavior of the solutions. The maximum velocity in a magneto-hydro-dynamic pump versus time for various values of the Stuart number, electro-magnetic interaction number, Reynolds number, aspect ratio, as well as the magnetic and electrical angular frequency and the shift of the phase angle is presented. Results show that for a high Stuart number there is a frequency limit for stability of the fluid flow in a certain direction of the flow. This stability frequency is dependent on the geometric parameters of a channel.

  20. Analytical Study of Magnetohydrodynamic Propulsion Stability

    Institute of Scientific and Technical Information of China (English)

    M.Y.Abdollahzadeh Jamalabadi

    2014-01-01

    In this paper an analytical solution for the stability of the fully developed flow drive in a magneto-hydro-dynamic pump with pulsating transverse Eletro-magnetic fields is presented. To do this, a theoretical model of the flow is developed and the analytical results are obtained for both the cylindrical and Cartesian configurations that are proper to use in the propulsion of marine vessels. The governing parabolic momentum PDEs are transformed into an ordinary differential equation using approximate velocity distribution. The numerical results are obtained and asymptotic analyses are built to discover the mathematical behavior of the solutions. The maximum velocity in a magneto-hydro-dynamic pump versus time for various values of the Stuart number, electro-magnetic interaction number, Reynolds number, aspect ratio, as well as the magnetic and electrical angular frequency and the shift of the phase angle is presented. Results show that for a high Stuart number there is a frequency limit for stability of the fluid flow in a certain direction of the flow. This stability frequency is dependent on the geometric parameters of a channel.

  1. A simple channel estimator for space-time coded OFDM systems in rapid fading channels

    Institute of Scientific and Technical Information of China (English)

    单淑伟; 罗汉文; 宋文涛

    2004-01-01

    A simple channel estimator for space-time coded orthogonal frequency division multiplexing (OFDM) systems in rapid fading channels is proposed. The channels at the training bauds are estimated using the EM (expectation-maximization) algorithm, while the channels at the data bauds are estimated based on the method for modelling the time-varying channel as the linear combination of several time-invariant " Doppler channels". Computer simulations showed that this estimator outperforms the decision-directed tracking in rapid fading channels and that the performance of this method can be improved by iteration.

  2. A simple channel estimator for space-time coded OFDM systems in rapid fading channels

    Institute of Scientific and Technical Information of China (English)

    SHAN Shu-wei(单淑伟); LUO Han-wen(罗汉文); SONG Wen-tao(宋文涛)

    2004-01-01

    A simple channel estimator for space-time coded orthogonal frequency division multiplexing (OFDM) systems in rapid fading channels is proposed. The channels at the training bauds are estimated using the EM (expectation-maximization) algorithm, while the channels at the data bauds are estimated based on the method for modelling the time-varying channel as the linear combination of several time-invariant "Doppler channels". Computer simulations showed that this estimator outperforms the decision-directed tracking in rapid fading channels and that the performance of this method can be improved by iteration.

  3. Laser Frequency Stabilization

    Science.gov (United States)

    Donelan, Darsa; Mueller, Guido; Thorpe, James; Livas, Jeffrey

    2011-01-01

    Laser ranging and interferometry are essential technologies allowing for many astounding new spacebased missions such as the Laser Interferometer Space Antenna (LISA) to measure gravitational radiation emitted from distant super massive black hole mergers or distributed aperture telescopes with unprecedented angular resolution in the NIR or visible regime. The requirements on laser frequency noise depend on the residual motion and the distances between the spacecraft forming the interferometer. The intrinsic frequency stability of commercial lasers is several orders of magnitude above these requirements. Therefore, it is necessary for lasers to be stabilized to an ultrastable frequency reference so that they can be used to sense and control distances between spacecraft. Various optical frequency references and frequency stabilization schemes are considered and investigated for the applicability and usefulness for space-based interferometry missions.

  4. Generalized Lotka stability.

    Science.gov (United States)

    Smith, J D H; Zhang, C

    2015-08-01

    The recently developed macroscopic approach to demography describes the age distribution of mothers and the net maternity function for a given human population entirely in terms of five parameters. Tracking of these parameters provides a number of new tools for analyzing populations and predicting their future states. Within the macroscopic approach, the new concept of generalized Lotka stability is presented in this paper, as an extension of a strong version of classic Lotka stability. The two leading parameters of the macroscopic approach, the Malthusian parameter r and the perturbation s, are computed from population data and plotted in two-dimensional parameter space. Generalized Lotka stability is then defined in terms of the movement of the (r,s)-vector over time. It may be observed in a number of human populations at specific periods of their history.

  5. HYDRAULICS OF COMPOUND CHANNEL WITH VEGETATED FLOODPLAINS

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Experimental researches were conducted on flood carrying capacity of compound open channels with wide and narrow floodplains as well as hydrodynamic behavior of overbank flow across vegetated floodplains. Results show that hydrodynamic behavior of compound channels with narrow floodplains is different from that of the wide floodplains. In such compound channels with narrow vegetated floodplains as in the Pearl River delta nework, it has been found that vegetated domains become really impenetrable when the length of vegetated domain is larger than Lm, the length of flow in floodplain coming into the main channel, and that the influence of vegetated floodplains upon flood stages of a channel is not very significant.

  6. Generation of single plasma channel in air

    International Nuclear Information System (INIS)

    The conditions of generating a single plasma channel in air are studied by using picosecond and femtosecond laser pulse. A stable and single plasma channel can be generated by a picosecond laser pulse with energy of 8-12 mJ and focusing length of 15 cm. The self-generated light emission is observed to be confined in the plasma channel and propagates in the channel. When using short focal length lenses it is easy to generate a single plasma channel in air with femtosecond laser with energy less than 10 mJ. (authors)

  7. Box model for channels of human migration

    CERN Document Server

    Vitanov, Nikolay K

    2016-01-01

    We discuss a mathematical model of migration channel based on the truncated Waring distribution. The truncated Waring distribution is obtained for a more general model of motion of substance through a channel containing finite number of boxes. The model is applied then for case of migrants moving through a channel consisting of finite number of countries or cities. The number of migrants in the channel strongly depends on the number of migrants that enter the channel through the country of entrance. It is shown that if the final destination country is very popular then large percentage of migrants may concentrate there.

  8. The Hydrophobic Effect Contributes to the Closed State of a Simplified Ion Channel through a Conserved Hydrophobic Patch at the Pore-Helix Crossing.

    Directory of Open Access Journals (Sweden)

    Michael eYonkunas

    2015-11-01

    Full Text Available Ion selectivity-filter structures are strikingly similar throughout the large family of K+ channels and other p-loop-like receptors (i.e., glutamate receptors. At the same time, the triggers for opening these channels, or gating, are diverse. Two questions that remain unanswered regarding these channels are: 1 what force(s stabilize the closed non-conducting channel-pore conformation? And 2 what is the free energy associated with transitioning from a closed (non-conducting to an open (conducting channel-pore conformation? The effects of charge and hydrophobicity on the conformational states of a model tetrameric biological ion channel are shown utilizing the amino acid sequence from the K+ channel KcsA as the model channel. Its widely conserved hydrophobic bundle crossing located adjacent to the lipid head-groups at the intracellular side of the membrane was calculated to have a 5 kcal/mol free energy difference between modeled open and closed conformations. Simulated mutants of amino acids within the hydrophobic region significantly contribute to the size of this difference. Specifically for KcsA, these residues are part of the pH sensor important for channel gating and our results are in agreement with published electrophysiology data. Our simulations support the idea that the hydrophobic effect contributes significantly to the stability of the closed conformation in tetrameric ion channels with a hydrophobic bundle crossing positioned in proximity to the lipid head groups of the biological membrane.

  9. Magnetohydrodynamic stability of tokamaks

    CERN Document Server

    Zohm, Hartmut

    2014-01-01

    This book bridges the gap between general plasma physics lectures and the real world problems in MHD stability. In order to support the understanding of concepts and their implication, it refers to real world problems such as toroidal mode coupling or nonlinear evolution in a conceptual and phenomenological approach. Detailed mathematical treatment will involve classical linear stability analysis and an outline of more recent concepts such as the ballooning formalism. The book is based on lectures that the author has given to Master and PhD students in Fusion Plasma Physics. Due its strong lin

  10. Progress on plutonium stabilization

    Energy Technology Data Exchange (ETDEWEB)

    Hurt, D. [Defense Nuclear Facilities Safety Board, Washington, DC (United States)

    1996-05-01

    The Defense Nuclear Facilities Safety Board has safety oversight responsibility for most of the facilities where unstable forms of plutonium are being processed and packaged for interim storage. The Board has issued recommendations on plutonium stabilization and has has a considerable influence on DOE`s stabilization schedules and priorities. The Board has not made any recommendations on long-term plutonium disposition, although it may get more involved in the future if DOE develops plans to use defense nuclear facilities for disposition activities.

  11. Thermodynamic Stability of Nanobubbles

    CERN Document Server

    Attard, Phil

    2015-01-01

    The observed stability of nanobubbles contradicts the well-known result in classical nucleation theory, that the critical radius is both microscopic and thermodynamically unstable. Here nanoscopic stability is shown to be the combined result of two non-classical mechanisms. It is shown that the surface tension decreases with increasing supersaturation, and that this gives a nanoscopic critical radius. Whilst neither a free spherical bubble nor a hemispherical bubble mobile on an hydrophobic surface are stable, it is shown that an immobilized hemispherical bubble with a pinned contact rim is stable and that the total entropy is a maximum at the critical radius.

  12. Stability of dynamical systems

    CERN Document Server

    Liao, Xiaoxin; Yu, P 0

    2007-01-01

    The main purpose of developing stability theory is to examine dynamic responses of a system to disturbances as the time approaches infinity. It has been and still is the object of intense investigations due to its intrinsic interest and its relevance to all practical systems in engineering, finance, natural science and social science. This monograph provides some state-of-the-art expositions of major advances in fundamental stability theories and methods for dynamic systems of ODE and DDE types and in limit cycle, normal form and Hopf bifurcation control of nonlinear dynamic systems.ʺ Presents

  13. Anisotropic Stars II Stability

    CERN Document Server

    Dev, K; Dev, Krsna; Gleiser, Marcelo

    2003-01-01

    We investigate the stability of self-gravitating spherically symmetric anisotropic spheres under radial perturbations. We consider both the Newtonian and the full general-relativistic perturbation treatment. In the general-relativistic case, we extend the variational formalism for spheres with isotropic pressure developed by Chandrasekhar. We find that, in general, when the tangential pressure is greater than the radial pressure, the stability of the anisotropic sphere is enhanced when compared to isotropic configurations. In particular, anisotropic spheres are found to be stable for smaller values of the adiabatic index $\\gamma$.

  14. Stellarator theory and stability

    International Nuclear Information System (INIS)

    This report summarizes our work in the past year on stellarator transport theory and stability. We have developed two methods of calculating diffusion rates due to ripple transport: a ''hybrid'' bounce-averaged/guiding-center Monte Carlo code, and a numerical method of solving the bounce-averaged Fokker-Planck equation. We have modified a one-dimensional transport code to describe the Wisconsin stellarator experiments and applied it to interpret experimental results, and we have studied stability in stellarators by writing a computer code which solves the linearized ''double-adiabatic'' equations as an initial value problem. 20 refs., 7 figs

  15. Stability of heterodyne terahertz receivers

    NARCIS (Netherlands)

    Kooi, J.W.; Baselmans, J.J.A.; Baryshev, A.; Schieder, R.; Hajenius, M.; Gao, J.R.; Klapwijk, T.M.; Voronov, B.; Gol'tsman, G.

    2006-01-01

    In this paper we discuss the stability of heterodyne terahertz receivers based on small volume NbN phonon cooled hot electron bolometers (HEBs). The stability of these receivers can be broken down in two parts: the intrinsic stability of the HEB mixer and the stability of the local oscillator (LO) s

  16. The structure of GlpF, a glycerol conducting channel.

    Science.gov (United States)

    Fu, Dax; Libson, Andrew; Stroud, Robert

    2002-01-01

    The passage of water or small neutral solutes across the cell membrane in animals, plants and bacteria is facilitated by a family of homologous membrane channels, variously known as aquaporins though perhaps more correctly as aquaglyceroporins. The glycerol facilitator (GlpF) is a 28 kDa aquaglyceroporin that catalyses transmembrane diffusion of glycerol and certain linear polyhydric alcohols in Escherichia coli. X-ray crystallographic analysis of GlpF to 2.2 A resolution revealed an alpha-barrel structure, surrounded by six full-length transmembrane helices and two half-spanning helices that are joined head-to-head in the middle of the membrane. These helices are arranged to a quasi twofold manner relative to the central membrane plane, where highly conserved residues make helix-to-helix contacts that stabilize the relative position and orientation of the helices in the structure. This sequence-structure correlation suggests that the evolutionary divergence of aquaporins and aquaglyceroporins is constrained by a conserved structural framework within which specialized function may be developed. Three glycerol molecules were resolved in the central channel through the GlpF monomer, thereby defining a transmembrane channel for glycerol permeation. The structure of glycerol GlpF complex provides insight into the chemical basis for transmembrane selective permeability. PMID:12027015

  17. Results From a Channel Restoration Project: Hydraulic Design Considerations

    Science.gov (United States)

    Karle, K.F.; Densmore, R.V.

    2001-01-01

    Techniques for the hydraulic restoration of placer-mined streams and floodplains were developed in Denali National Park and Preserve, Alaska. The two-year study at Glen Creek focused on a design of stream and floodplain geometry using hydraulic capacity and shear stress equations. Slope and sinuosity values were based on regional relationships. Design requirements included a channel capacity for a bankfull discharge and a floodplain capacity for a 1.5- to 100-year discharge. Several bio-engineering techniques using alder and willow, including anchored brush bars, streambank hedge layering, seedlings, and cuttings, were tested to dissipate floodwater energy and encourage sediment deposition until natural revegetation stabilized the new floodplains. Permanently monumented cross-sections installed throughout the project site were surveyed every one to three years. Nine years after the project began, a summer flood caused substantial damage to the channel form, including a change in width/depth ratio, slope, and thalweg location. Many of the alder brush bars were heavily damaged or destroyed, resulting in significant bank erosion. This paper reviews the original hydraulic design process, and describes changes to the channel and floodplain geometry over time, based on nine years of cross-section surveys.

  18. Kalman filter application in auto spectrum stabilization in airborne spectroscopy investigation

    International Nuclear Information System (INIS)

    Considered airborne spectrum's characteristic of low counter rate,high statistics fluctuation when measured in short time period, kalman filter algorithm was adopted to smooth the noise within the airborne spectrum. Compared the effect of several normal used smooth methods with kalman filter method, and finally decided to use this method smooth spectrum, then search the peak position to realize auto spectrum stabilization in airborne spectrum. The result is: spectrum drift less than 1 channel when resolution is 1024 channels. (authors)

  19. Dynamic Channel Allocation in Sectored Cellular Systems

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    It is known that dynamic channel assignment(DCA) strategy outperforms the fixed channel assignment(FCA) strategy in omni-directional antenna cellular systems. One of the most important methods used in DCA was channel borrowing. But with the emergence of cell sectorization and spatial division multiple access(SDMA) which are used to increase the capacity of cellular systems, the channel assignment faces a series of new problems. In this paper, a dynamic channel allocation scheme based on sectored cellular systems is proposed. By introducing intra-cell channel borrowing (borrowing channels from neighboring sectors) and inter-cell channel borrowing (borrowing channels from neighboring cells) methods, previous DCA strategies, including compact pattern based channel borrowing(CPCB) and greedy based dynamic channel assignment(GDCA) schemes proposed by the author, are improved significantly. The computer simulation shows that either intra-cell borrowing scheme or inter-cell borrowing scheme is efficient enough to uniform and non-uniform traffic service distributions.

  20. The Holevo-Schumacher-Westmoreland Channel Capacity for a Class of Qudit Unital Channels

    OpenAIRE

    Cortese, John A.

    2002-01-01

    The Holevo-Schumacher-Westmoreland (HSW) classical (entanglement-unassisted) channel capacity for a class of qudit unital channels is shown to be C = log2(d) - Smin, where d is the dimension of the qudit, and Smin is the minimum possible von Neumann entropy at the channel output. The HSW channel capacity for tensor products of this class of unital qudit channels is shown to obey the same formula.

  1. VARIABLE-RATE MULTIUSER DIVERSITY IN CORRELATED MIMO CHANNEL VIA VIRTUAL CHANNEL REPRESENTATION

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    This paper studies the multiuser diversity with constellation selection based on a virtual representation of realistic Multiple Input Multiple Output (MIMO) correlated channels. To realize multiuser diversity in slow fading channels, random beamforming is adopted. Random beamforming matrix exploiting virtual channel representation is constructed, which can match the channel matrix of the desired user better. Simultaneously, adaptive coded modulation is applied to each sub-channel of the selected user to improve the system performance further.

  2. The Holevo-Schumacher-Westmoreland Channel Capacity for a Class of Qudit Unital Channels

    CERN Document Server

    Cortese, J A

    2004-01-01

    The Holevo-Schumacher-Westmoreland (HSW) classical (entanglement-unassisted) channel capacity for a class of qudit unital channels is shown to be C = log2(d) - Smin, where d is the dimension of the qudit, and Smin is the minimum possible von Neumann entropy at the channel output. The HSW channel capacity for tensor products of this class of unital qudit channels is shown to obey the same formula.

  3. Joint design of fixed-rate source codes and UEP channel codes for fading channels

    OpenAIRE

    Tie, Hai-Xin; Goldsmith, Andrea; Effros, Michelle

    1998-01-01

    We study an iterative design algorithm that jointly optimizes source and channel codes for image transmission over Rayleigh fading channels. The joint design combines channel-optimized vector quantization (COVQ) for the source code with a family of rate-compatible punctured convolutional codes for the unequal-error-protection (UEP) channel code. We consider both hard-decision and soft-decision decoding for these channel codes. Our objective is to minimize the average end-to-end distortion, av...

  4. Progress in Development of Improved Ion-Channel Biosensors

    Science.gov (United States)

    Nadeau, Jay L.; White, Victor E.; Maurer, Joshua A.; Dougherty, Dennis A.

    2008-01-01

    Further improvements have recently been made in the development of the devices described in Improved Ion-Channel Biosensors (NPO-30710), NASA Tech Briefs, Vol. 28, No. 10 (October 2004), page 30. As discussed in more detail in that article, these sensors offer advantages of greater stability, greater lifetime, and individual electrical addressability, relative to prior ion-channel biosensors. In order to give meaning to a brief description of the recent improvements, it is necessary to recapitulate a substantial portion of the text of the cited previous article. The figure depicts one sensor that incorporates the recent improvements, and can be helpful in understanding the recapitulated text, which follows: These sensors are microfabricated from silicon and other materials compatible with silicon. Typically, the sensors are fabricated in arrays in silicon wafers on glass plates. Each sensor in the array can be individually electrically addressed, without interference with its neighbors. Each sensor includes a well covered by a thin layer of silicon nitride, in which is made a pinhole for the formation of a lipid bilayer membrane. In one stage of fabrication, the lower half of the well is filled with agarose, which is allowed to harden. Then the upper half of the well is filled with a liquid electrolyte (which thereafter remains liquid) and a lipid bilayer is painted over the pinhole. The liquid contains a protein that forms an ion channel on top of the hardened agarose. The combination of enclosure in the well and support by the hardened agarose provides the stability needed to keep the membrane functional for times as long as days or even weeks. An electrode above the well, another electrode below the well, and all the materials between the electrodes together constitute a capacitor. What is measured is the capacitive transient current in response to an applied voltage pulse. One notable feature of this sensor, in comparison with prior such sensors, is a

  5. Analytical Expression for the MIMO Channel Capacity

    Institute of Scientific and Technical Information of China (English)

    ZHAO Yifei; ZHAO Ming; XIAO Limin; WANG Jing

    2006-01-01

    This paper presents analytical expressions for the multiple-input multiple-output (MIMO) channel capacity in frequency-flat Rayleigh fading environments. An exact analytical expression is given for the ergodic capacity for single-input multiple-output (SIMO) channels. The analysis shows that the SIMO channel capacity can be approximated by a Gaussian random variable and that the MIMO channel capacity can be approximated as the sum of multiple SIMO capacities. The SIMO channel results are used to derive approximate closed-form expressions for the MIMO channel ergodic capacity and the complementary cumulative distribution function (CCDF) of the MIMO channel capacity (outage capacity). Simulations show that these theoretical results are good approximations for MIMO systems with an arbitrary number of transmit or receive antennas. Moreover, these analytical expressions are relatively simple which makes them very useful for practical computations.

  6. Quantum channels with a finite memory

    International Nuclear Information System (INIS)

    In this paper we study quantum communication channels with correlated noise effects, i.e., quantum channels with memory. We derive a model for correlated noise channels that includes a channel memory state. We examine the case where the memory is finite, and derive bounds on the classical and quantum capacities. For the entanglement-assisted and unassisted classical capacities it is shown that these bounds are attainable for certain classes of channel. Also, we show that the structure of any finite-memory state is unimportant in the asymptotic limit, and specifically, for a perfect finite-memory channel where no information is lost to the environment, achieving the upper bound implies that the channel is asymptotically noiseless

  7. Quantum channels with a finite memory

    Science.gov (United States)

    Bowen, Garry; Mancini, Stefano

    2004-01-01

    In this paper we study quantum communication channels with correlated noise effects, i.e., quantum channels with memory. We derive a model for correlated noise channels that includes a channel memory state. We examine the case where the memory is finite, and derive bounds on the classical and quantum capacities. For the entanglement-assisted and unassisted classical capacities it is shown that these bounds are attainable for certain classes of channel. Also, we show that the structure of any finite-memory state is unimportant in the asymptotic limit, and specifically, for a perfect finite-memory channel where no information is lost to the environment, achieving the upper bound implies that the channel is asymptotically noiseless.

  8. Post-Translational Modifications of TRP Channels

    Directory of Open Access Journals (Sweden)

    Olaf Voolstra

    2014-04-01

    Full Text Available Transient receptor potential (TRP channels constitute an ancient family of cation channels that have been found in many eukaryotic organisms from yeast to human. TRP channels exert a multitude of physiological functions ranging from Ca2+ homeostasis in the kidney to pain reception and vision. These channels are activated by a wide range of stimuli and undergo covalent post-translational modifications that affect and modulate their subcellular targeting, their biophysical properties, or channel gating. These modifications include N-linked glycosylation, protein phosphorylation, and covalent attachment of chemicals that reversibly bind to specific cysteine residues. The latter modification represents an unusual activation mechanism of ligand-gated ion channels that is in contrast to the lock-and-key paradigm of receptor activation by its agonists. In this review, we summarize the post-translational modifications identified on TRP channels and, when available, explain their physiological role.

  9. Fundamental channeling questions at ultra relativistic energies

    Energy Technology Data Exchange (ETDEWEB)

    Carrigan, Richard A., Jr.; /Fermilab

    2006-08-01

    TeV-range bent crystal channeling has interesting advantages for several applications at high energy accelerators. Observations of enhanced deflection over the whole arc of a bent crystal at RHIC and recently at the Tevatron may be due to a process called ''volume reflection''. More investigations of volume reflection and of the complimentary process, volume capture, are needed. So-called quasimosaic bending processes also deserve additional study. Negative particle channeling may be relevant to channeling collimation for electron machines. Electron and positron channeling and channeling radiation are interwoven so that the impact of channeling radiation on applications needs to be better understood. Beams in the 0.1 to 1 GeV range may be useful for some of these investigations. Finally there has been little or no study of positive and negative muon channeling. The current understanding of these topics and the desirability of further work is reviewed.

  10. Stability monitoring of a natural-circulation-cooled boiling water reactor

    International Nuclear Information System (INIS)

    Methods for monitoring the stability of a boiling water reactor (BWR) are discussed. Surveillance of BWR stability is of importance as problems were encountered in several large reactors. Moreover, surveying stability allows plant owners to operate at high power with acceptable stability margins. The results of experiments performed on the Dodewaard BWR (the Netherlands) are reported. This type reactor is cooled by natural circulation, a cooling principle that is also being considered for new reactor designs. The stability of this reactor was studied both with deterministic methods and by noise analysis. Three types of stability are distinguished and were investigated separately: reactor-kinetic stability, thermal-hydraulic stability and total-plant stability. It is shown that the Dodewaard reactor has very large stability margins. A simple yet reliable stability criterion is introduced. It can be derived on-line from thhe noise signal of ex-vessel neutron detectors during normal operation. The sensitivity of neutron detectors to in-core flux perturbations - reflected in the field-of-view of the detector - was calculated in order to insure proper stability surveillance. A novel technique is presented which enables the determination of variations of the in-core coolant velocity by noise correlation. The velocity measured was interpreted on the basis of experiments performed on the air/water flow in a model of a BWR coolant channel. It appeared from this analysis that the velocity measured was much higher than the volume-averaged water and air velocities and the volumetric flux. The applicability of the above-mentioned technique to monitoring of local channel-flow stability was tested. It was observed that stability effects on the coolant velocity are masked by other effects originating from the local flow pattern. Experimental and theoretical studies show a shorter effective fuel time constant in a BWR than was assumed. (author). 118 refs.; 73 figs.; 21 tabs

  11. Multicarrier chaotic communications in multipath fading channels without channel estimation

    Directory of Open Access Journals (Sweden)

    Shilian Wang

    2015-01-01

    Full Text Available A multi-carrier chaotic shift keying(MC-CSK communication scheme with low probability of interception(LPI is proposed in this article. We apply chaotic spreading sequences in the frequency domain, mapping a different chip of a chaotic sequence to an individual orthogonal frequency division multiplexing(OFDM subcarrier. In each block size of $M$ OFDM symbols, we use one pilot OFDM symbol inserted time-spaced in all-frequency to transmit the reference chaotic signal and use the other M-1 OFDM symbols to transmit the information-bearing signals each spreaded by the reference chaotic signal. At the receiver, we construct a differential detector after DFT and recover the information bits from the correlations between the pilot OFDM symbol and the other M-1 OFDM symbols in each block size of M. Performance analysis and computer simulations show that the MC-CSK outperforms differential chaos shift keying(DCSK in AWGN channels with high bandwidth efficiency for the block size of M=2 and that the MC-CSK exploits effectively the frequent diversity of the multipath channel.

  12. Multicarrier chaotic communications in multipath fading channels without channel estimation

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Shilian, E-mail: wangsl@nudt.edu.cn; Zhang, Zhili [College of Electrical Science and Engineering, National University of Defense Technology, Changsha, 410073, P R China (China)

    2015-01-15

    A multi-carrier chaotic shift keying(MC-CSK) communication scheme with low probability of interception(LPI) is proposed in this article. We apply chaotic spreading sequences in the frequency domain, mapping a different chip of a chaotic sequence to an individual orthogonal frequency division multiplexing(OFDM) subcarrier. In each block size of $M$ OFDM symbols, we use one pilot OFDM symbol inserted time-spaced in all-frequency to transmit the reference chaotic signal and use the other M-1 OFDM symbols to transmit the information-bearing signals each spreaded by the reference chaotic signal. At the receiver, we construct a differential detector after DFT and recover the information bits from the correlations between the pilot OFDM symbol and the other M-1 OFDM symbols in each block size of M. Performance analysis and computer simulations show that the MC-CSK outperforms differential chaos shift keying(DCSK) in AWGN channels with high bandwidth efficiency for the block size of M=2 and that the MC-CSK exploits effectively the frequent diversity of the multipath channel.

  13. Multicarrier chaotic communications in multipath fading channels without channel estimation

    International Nuclear Information System (INIS)

    A multi-carrier chaotic shift keying(MC-CSK) communication scheme with low probability of interception(LPI) is proposed in this article. We apply chaotic spreading sequences in the frequency domain, mapping a different chip of a chaotic sequence to an individual orthogonal frequency division multiplexing(OFDM) subcarrier. In each block size of $M$ OFDM symbols, we use one pilot OFDM symbol inserted time-spaced in all-frequency to transmit the reference chaotic signal and use the other M-1 OFDM symbols to transmit the information-bearing signals each spreaded by the reference chaotic signal. At the receiver, we construct a differential detector after DFT and recover the information bits from the correlations between the pilot OFDM symbol and the other M-1 OFDM symbols in each block size of M. Performance analysis and computer simulations show that the MC-CSK outperforms differential chaos shift keying(DCSK) in AWGN channels with high bandwidth efficiency for the block size of M=2 and that the MC-CSK exploits effectively the frequent diversity of the multipath channel

  14. Nav Channels in Damaged Membranes.

    Science.gov (United States)

    Morris, C E; Joos, B

    2016-01-01

    Sick excitable cells (ie, Nav channel-expressing cells injured by trauma, ischemia, inflammatory, and other conditions) typically exhibit "acquired sodium channelopathies" which, we argue, reflect bleb-damaged membranes rendering their Nav channels "leaky." The situation is excitotoxic because untreated Nav leak exacerbates bleb damage. Fast Nav inactivation (a voltage-independent process) is so tightly coupled, kinetically speaking, to the inherently voltage-dependent process of fast activation that when bleb damage accelerates and thus left-shifts macroscopic fast activation, fast inactivation accelerates to the same extent. The coupled g(V) and availability(V) processes and their window conductance regions consequently left-shift by the same number of millivolts. These damage-induced hyperpolarizing shifts, whose magnitude increases with damage intensity, are called coupled left shift (CLS). Based on past work and modeling, we discuss how to test for Nav-CLS, emphasizing the virtue of sawtooth ramp clamp. We explain that it is the inherent mechanosensitivity of Nav activation that underlies Nav-CLS. Using modeling of excitability, we show the known process of Nav-CLS is sufficient to predict a wide variety of "sick excitable cell" phenomena, from hyperexcitability through to depolarizing block. When living cells are mimicked by inclusion of pumps, mild Nav-CLS produces a wide array of burst phenomena and subthreshold oscillations. Dynamical analysis of mild damage scenarios shows how these phenomena reflect changes in spike thresholds as the pumps try to counteract the leaky Nav channels. Smart Nav inhibitors designed for sick excitable cells would target bleb-damaged membrane, buying time for cell-mediated removal or repair of Nav-bearing membrane that has become bleb-damaged (ie, detached from the cytoskeleton). PMID:27586295

  15. Precipitation patterns during channel flow

    Science.gov (United States)

    Jamtveit, B.; Hawkins, C.; Benning, L. G.; Meier, D.; Hammer, O.; Angheluta, L.

    2013-12-01

    Mineral precipitation during channelized fluid flow is widespread in a wide variety of geological systems. It is also a common and costly phenomenon in many industrial processes that involve fluid flow in pipelines. It is often referred to as scale formation and encountered in a large number of industries, including paper production, chemical manufacturing, cement operations, food processing, as well as non-renewable (i.e. oil and gas) and renewable (i.e. geothermal) energy production. We have studied the incipient stages of growth of amorphous silica on steel plates emplaced into the central areas of the ca. 1 meter in diameter sized pipelines used at the hydrothermal power plant at Hellisheidi, Iceland (with a capacity of ca 300 MW electricity and 100 MW hot water). Silica precipitation takes place over a period of ca. 2 months at approximately 120°C and a flow rate around 1 m/s. The growth produces asymmetric ca. 1mm high dendritic structures ';leaning' towards the incoming fluid flow. A novel phase-field model combined with the lattice Boltzmann method is introduced to study how the growth morphologies vary under different hydrodynamic conditions, including non-laminar systems with turbulent mixing. The model accurately predicts the observed morphologies and is directly relevant for understanding the more general problem of precipitation influenced by turbulent mixing during flow in channels with rough walls and even for porous flow. Reference: Hawkins, C., Angheluta, L., Hammer, Ø., and Jamtveit, B., Precipitation dendrites in channel flow. Europhysics Letters, 102, 54001

  16. TRANSITIONAL FLOW IN CHANNEL JUNCTIONS

    Institute of Scientific and Technical Information of China (English)

    NI Han-gen; LIU Ya-kun

    2004-01-01

    On the basis of energy and continuity equations a simple one-dimensional formulation was proposed to predict the transitional flow at an open-channel junction. An empilical relation between the junction losses, the junction angle, and the discharge ratio was suggested which agrees well with the experimental results. The results calculated by the present formulation for the depth ratio were compared with the results of earlier one-dimensional formulations and experiments. It is found that the present results coincide better with experiments than those of others.

  17. Magnetohydrodynamic (MHD) channel corner seal

    Science.gov (United States)

    Spurrier, Francis R.

    1980-01-01

    A corner seal for an MHD duct includes a compressible portion which contacts the duct walls and an insulating portion which contacts the electrodes, sidewall bars and insulators. The compressible portion may be a pneumatic or hydraulic gasket or an open-cell foam rubber. The insulating portion is segmented into a plurality of pieces of the same thickness as the electrodes, insulators and sidewall bars and aligned therewith, the pieces aligned with the insulator being of a different size from the pieces aligned with the electrodes and sidewall bars to create a stepped configuration along the corners of the MHD channel.

  18. Exploiting Multi-user Diversity and Multi-hop Diversity in Dual-hop Broadcast Channels

    KAUST Repository

    Zafar, Ammar

    2013-05-21

    We propose joint user-and-hop scheduling over dual-hop block-fading broadcast channels in order to exploit multi-user diversity gains and multi-hop diversity gains all together. To achieve this objective, the first and second hops are scheduled opportunistically based on the channel state information. The joint scheduling problem is formulated as maximizing the weighted sum of the long term achievable rates of the users under a stability constraint, which means that in the long term the rate received by the relay should equal the rate transmitted by it, in addition to power constraints. We show that this problem is equivalent to a single-hop broadcast channel by treating the source as a virtual user with an optimal weight that maintains the stability constraint. We show how to obtain the source weight either off-line based on channel statistics or on real-time based on channel measurements. Furthermore, we consider special cases including the maximum sum-rate scheduler and the proportional fair scheduler. We also show how to extend the scheme into one that allows multiple user scheduling via superposition coding with successive decoding. Numerical results demonstrate that our proposed joint scheduling scheme enlarges the rate region as compared to scheduling schemes that exploit the diversity gains partially.

  19. Real-time visualization of oxygen partial pressures in straight channels of running polymer electrolyte fuel cell with water plugging

    Science.gov (United States)

    Nagase, Katsuya; Suga, Takeo; Nagumo, Yuzo; Uchida, Makoto; Inukai, Junji; Nishide, Hiroyuki; Watanabe, Masahiro

    2015-01-01

    Visualization inside polymer electrolyte fuel cells (PEFCs) for elucidating the reaction distributions is expected to improve the performance, durability, and stability. An oxygen-sensitive film of a luminescent porphyrin was used to visualize the oxygen partial pressures in five straight gas-flow channels of a running PEFC with liquid-water blockages formed at the end of the channels. The blockage greatly lowered and unstabilized the cell voltage. The oxygen partial pressure decreased nearly to 0 kPa in the blocked channel. With a water blockage in a channel, the oxygen partial pressures in the adjacent channels were lowered due to an extra demand of oxygen consumption. When the number of the blocked channels increased, the oxygen partial pressure in the unblocked channels became much lowered. When the water blockages disappeared, the oxygen partial pressures quickly returned to the values before plugging. The influence of the cross flows of air through the gas diffusion layers in straight channels was much smaller than that in serpentine flow channels.

  20. Sprinkler Bifurcations and Stability

    Science.gov (United States)

    Sorensen, Jody; Rykken, Elyn

    2010-01-01

    After discussing common bifurcations of a one-parameter family of single variable functions, we introduce sprinkler bifurcations, in which any number of new fixed points emanate from a single point. Based on observations of these and other bifurcations, we then prove a number of general results about the stabilities of fixed points near a…

  1. Tetraphenylborate Solids Stability Tests

    International Nuclear Information System (INIS)

    Tetraphenylborate solids provide a potentially large source of benzene in the slurries produced in the In-Tank Precipitation process. The stability of the solids is an important consideration in the safety analysis of the process and we desire an understanding of the factors that influence the rate of conversion of the solids to benzene

  2. STABILIZED PINCH MACHINE

    Science.gov (United States)

    Anderson, O.A.

    1962-04-24

    A device for heating and confining a high temperature gas or plasma utilizing the linear pinch effect is described. The pinch discharge produced is the form of an elongated cylinder. The electrical discharge current is returned in parallel along an axial and a concentric conductor whereby the magnetic field of the conductors compresses and stabilizes the pinch discharge against lateral instability. (AEC)

  3. Robust Stabilization of Linear Switching Systems with Both Input and Communication Delays

    Directory of Open Access Journals (Sweden)

    Lili Jia

    2014-01-01

    Full Text Available This work is concerned with stabilization control of a class of linear switching systems with time-delays in both the input and the communication channels. It is observed that the time-delay in communication channel leads to the mismatch between the plant and the controller. Such a phenomenon can be accounted for by reconstructing switching signal for the overall closed-loop system. Therefore, we derive some sufficient stability conditions by using multiple Lyapunov functions approach and, moreover, present a robust controller design methodology. A numerical example is presented to demonstrate the effectiveness of the proposed method.

  4. Axisymmetric annular curtain stability

    International Nuclear Information System (INIS)

    A temporal stability analysis was carried out to investigate the stability of an axially moving viscous annular liquid jet subject to axisymmetric disturbances in surrounding co-flowing viscous gas media. We investigated in this study the effects of inertia, surface tension, the gas-to-liquid density ratio, the inner-to-outer radius ratio and the gas-to-liquid viscosity ratio on the stability of the jet. With an increase in inertia, the growth rate of the unstable disturbances is found to increase. The dominant (or most unstable) wavenumber decreases with increasing Reynolds number for larger values of the gas-to-liquid viscosity ratio. However, an opposite tendency for the most unstable wavenumber is predicted for small viscosity ratio in the same inertia range. The surrounding gas density, in the presence of viscosity, always reduces the growth rate, hence stabilizing the flow. There exists a critical value of the density ratio above which the flow becomes stable for very small viscosity ratio, whereas for large viscosity ratio, no stable flow appears in the same range of the density ratio. The curvature has a significant destabilizing effect on the thin annular jet, whereas for a relatively thick jet, the maximum growth rate decreases as the inner radius increases, irrespective of the surrounding gas viscosity. The degree of instability increases with Weber number for a relatively large viscosity ratio. In contrast, for small viscosity ratio, the growth rate exhibits a dramatic dependence on the surface tension. There is a small Weber number range, which depends on the viscosity ratio, where the flow is stable. The viscosity ratio always stabilizes the flow. However, the dominant wavenumber increases with increasing viscosity ratio. The range of unstable wavenumbers is affected only by the curvature effect. (paper)

  5. Instream wood in a steep headwater channel: geomorphic significance of large and small wood

    Science.gov (United States)

    Galia, Tomáš; Šilhán, Karel; Ruiz-Villanueva, Virginia; Tichavský, Radek

    2016-04-01

    Besides the well-known significance of large wood (LW), also small woody pieces (SW; here defined as pieces with dimensions at least 0.5 m length and 0.05 m diameter), can play an important role in steep narrow headwaters. We inventoried instream wood in the 0.4 km long Mazák headwater channel, Moravskoslezské Beskydy Mts, Czech Republic (2attached by bed sediments or other wood), % of influenced channel width by a wood, the geomorphic function of a wood (step, wood jam) and % of length of a wood in channel were assessed. The total number of inventoried instream wood was 90 LWs and 199 SWs. In addition, dendrogeomorphic dating of 36 LWs and 17 SWs was performed to obtain residence time of local instream wood and to provide some insights into its mobility. Practically all investigated pieces were European beeches (Fagus sylvatica L.); only two pieces were Norway spruces (Picea abies (L.) Karst.). First results showed an increase in the number of LWs in channel-reaches confined by the steepest adjacent hillslopes (especially at 0.15-0.20 km). Increasing downstream amount of SW most likely reflected transport processes in the stream, and the later deposition of SWs on the lowest channel gradients. Also LWs and SWs in the downstream channel-reaches were more decayed than wood presented in the upper reaches. The orientation of instream wood was connected with its length and stability, and LWs longer than 5 m were usually attached to adjacent hillslopes. Pieces longer than 2 m, which were unattached or were somehow stabilized in the channel bed, had often orientation of 0° or 337°. LWs were mostly unattached in the upstream channel-reaches, while often stabilized by adjacent hillslopes in the middle part. At 0.05-0.10 km, there were also many logs stabilized by bed sediments. By contrast, SWs were mostly unattached in the whole longitudinal profile. We observed higher % of influenced channel width by SWs than LWs. Also, SWs were usually entirely located in the

  6. Geometric pumping in autophoretic channels

    Science.gov (United States)

    Michelin, Sebastien; Montenegro Johnson, Thomas; de Canio, Gabriele; Lobatto-Dauzier, Nicolas; Lauga, Eric

    2015-11-01

    Pumping at the microscale has important applications from biological fluid handling to lab-on-a-chip systems. It can be achieved either from a global (e.g. imposed pressure gradient) or local forcing (e.g. ciliary pumping). Phoretic slip flows generated from concentration or temperature gradients are examples of such local flow forcing. Autophoresis is currently receiving much attention for the design of self-propelled particles achieving force- and torque-free locomotion by combining two essential surface properties: (i) an activity that modifies the solute content of the particle's environment (e.g. catalytic reaction or solute release), and (ii) a mobility that generates a slip flow from the resulting local concentration gradients. Recent work showed that geometric asymmetry is sufficient for a chemically-homogeneous particle to self-propel. Here we extend this idea to micro-pumping in active channels whose walls possess both chemical activity and phoretic mobility. Using a combination of theoretical analysis and numerical simulations, we show that geometrically-asymmetric but chemically-homogeneous channels can generate pumping and analyze the resulting flow patterns.

  7. Channel simulation via interactive communications

    CERN Document Server

    Yassaee, Mohammad Hossein; Aref, Mohammad Reza

    2012-01-01

    In this paper, we study the problem of channel simulation via interactive communication, known as the coordination capacity, in a two-terminal network. We assume that two terminals observe i.i.d.\\ copies of two random variables and would like to generate i.i.d.\\ copies of two other random variables jointly distributed with the observed random variables. The terminals are provided with two-way communication links, and shared common randomness, all at limited rates. Two special cases of this problem are the interactive function computation studied by Ma and Ishwar, and the tradeoff curve between one-way communication and shared randomness studied by Cuff. The latter work had inspired Gohari and Anantharam to study the general problem of channel simulation via interactive communication stated above. However only inner and outer bounds for the special case of no shared randomness were obtained in their work. In this paper we settle this problem by providing an exact computable characterization of the multi-round ...

  8. Design of a high-resolution high-stability positioning mechanism for crystal optics

    Energy Technology Data Exchange (ETDEWEB)

    Shu, D.; Toellner, T. S.; Alp, E. E.

    1999-10-11

    The authors present a novel miniature multi-axis driving structure that will allow positioning of two crystals with better than 50-nrad angular resolution and nanometer linear driving sensitivity.The precision and stability of this structure allow the user to align or adjust an assembly of crystals to achieve the same performance as does a single channel-cut crystal, so they call it an artificial channel-cut crystal. In this paper, the particular designs and specifications, as well as the test results,for a two-axis driving structure for a high-energy-resolution artificial channel-cut crystal monochromator are presented

  9. The molecular physiology of CRAC channels

    Science.gov (United States)

    Prakriya, Murali

    2011-01-01

    Summary The Ca2+release-activated Ca2+ (CRAC) channel is a highly Ca2+-selective store-operated channel expressed in T cells, mast cells, and various other tissues. CRAC channels regulate critical cellular processes such as gene expression, motility, and the secretion of inflammatory mediators. The identification of Orai1, a key subunit of the CRAC channel pore, and STIM1, the endoplasmic reticulum (ER) Ca2+ sensor, have provided the tools to illuminate the mechanisms of regulation and the pore properties of CRAC channels. Recent evidence indicates that the activation of CRAC channels by store depletion involves a coordinated series of steps, which include the redistributions of STIM1 and Orai1, direct physical interactions between these proteins, and conformational changes in Orai1, culminating in channel activation. Additional studies have revealed that the high Ca2+ selectivity of CRAC channels arises from the presence of an intrapore Ca2+ binding site, the properties of which are finely honed to occlude the permeation of the much more prevalent Na+. Structure-function studies have led to the identification of the potential pore-binding sites for Ca2+, providing a firm framework for understanding the mechanisms of selectivity and gating of the CRAC channel. This review summarizes recent progress in understanding the mechanisms of CRAC channel activation, pore properties, and modulation. PMID:19754891

  10. VKCDB: Voltage-gated potassium channel database

    Directory of Open Access Journals (Sweden)

    Gallin Warren J

    2004-01-01

    Full Text Available Abstract Background The family of voltage-gated potassium channels comprises a functionally diverse group of membrane proteins. They help maintain and regulate the potassium ion-based component of the membrane potential and are thus central to many critical physiological processes. VKCDB (Voltage-gated potassium [K] Channel DataBase is a database of structural and functional data on these channels. It is designed as a resource for research on the molecular basis of voltage-gated potassium channel function. Description Voltage-gated potassium channel sequences were identified by using BLASTP to search GENBANK and SWISSPROT. Annotations for all voltage-gated potassium channels were selectively parsed and integrated into VKCDB. Electrophysiological and pharmacological data for the channels were collected from published journal articles. Transmembrane domain predictions by TMHMM and PHD are included for each VKCDB entry. Multiple sequence alignments of conserved domains of channels of the four Kv families and the KCNQ family are also included. Currently VKCDB contains 346 channel entries. It can be browsed and searched using a set of functionally relevant categories. Protein sequences can also be searched using a local BLAST engine. Conclusions VKCDB is a resource for comparative studies of voltage-gated potassium channels. The methods used to construct VKCDB are general; they can be used to create specialized databases for other protein families. VKCDB is accessible at http://vkcdb.biology.ualberta.ca.

  11. A Perspective on the MIMO Wiretap Channel

    KAUST Repository

    Oggier, Frederique

    2015-10-01

    A wiretap channel is a communication channel between a transmitter Alice and a legitimate receiver Bob, in the presence of an eavesdropper Eve. The goal of communication is to achieve reliability between Alice and Bob, but also confidentiality despite Eve’s presence. Wiretap channels are declined in all kinds of flavors, depending on the underlying channels used by the three players: discrete memoryless channels, additive Gaussian noise channels, or fading channels, to name a few. In this survey, we focus on the case where the three players use multiple-antenna channels with Gaussian noise to communicate. After summarizing known results for multiple-input–multiple-output (MIMO) channels, both in terms of achievable reliable data rate (capacity) and code design, we introduce the MIMO wiretap channel. We then state the MIMO wiretap capacity, summarize the idea of the proof(s) behind this result, and comment on the insights given by the proofs on the physical meaning of the secrecy capacity. We finally discuss design criteria for MIMO wiretap codes.

  12. ASIC3 channels in multimodal sensory perception.

    Science.gov (United States)

    Li, Wei-Guang; Xu, Tian-Le

    2011-01-19

    Acid-sensing ion channels (ASICs), which are members of the sodium-selective cation channels belonging to the epithelial sodium channel/degenerin (ENaC/DEG) family, act as membrane-bound receptors for extracellular protons as well as nonproton ligands. At least five ASIC subunits have been identified in mammalian neurons, which form both homotrimeric and heterotrimeric channels. The highly proton sensitive ASIC3 channels are predominantly distributed in peripheral sensory neurons, correlating with their roles in multimodal sensory perception, including nociception, mechanosensation, and chemosensation. Different from other ASIC subunit composing ion channels, ASIC3 channels can mediate a sustained window current in response to mild extracellular acidosis (pH 7.3-6.7), which often occurs accompanied by many sensory stimuli. Furthermore, recent evidence indicates that the sustained component of ASIC3 currents can be enhanced by nonproton ligands including the endogenous metabolite agmatine. In this review, we first summarize the growing body of evidence for the involvement of ASIC3 channels in multimodal sensory perception and then discuss the potential mechanisms underlying ASIC3 activation and mediation of sensory perception, with a special emphasis on its role in nociception. We conclude that ASIC3 activation and modulation by diverse sensory stimuli represent a new avenue for understanding the role of ASIC3 channels in sensory perception. Furthermore, the emerging implications of ASIC3 channels in multiple sensory dysfunctions including nociception allow the development of new pharmacotherapy. PMID:22778854

  13. Inertial (non-Darcian) channeled seepage flow

    Science.gov (United States)

    Foda, Mostafa A.

    1994-10-01

    A slow wave solution is identified for an infinite elastic medium intersected by a two-dimensional fluid channel. Because the wave speed is much slower than the medium's elastic shear wave, the response in the elastic medium is governed by elastostatics. The inertia of the wave is essentially focused in the fluid channel. Furthermore, wave damping is caused by fluid viscous friction on the channel in an elastic solid. It is proposed that these solutions may also be used in the case of a granular porous medium. The seepage channels would then represent a network of preferential flow paths. Therefore we would allow, in this case, the channel porosity to be different from the average granular porosity. For a strongly channel seepage flow or for a low channel porosity the solution is shown to approach that of a single-channel solution, giving rise to a slow propagating wave mode. On the other hand, for weak channeling or nearly `homogeneous' seepage flow the solution is shown to reproduce Biot's (1956) critically damped wave of the second kind. It is proposed that the resonance observed by Foda and Tzang (1994) are in the form of these strongly channeled wave modes.

  14. Experimental studies on the flow through soft tubes and channels

    Indian Academy of Sciences (India)

    V Kumaran

    2015-05-01

    Experiments conducted in channels/tubes with height/diameter less than 1 mm with soft walls made of polymer gels show that the transition Reynolds number could be significantly lower than the corresponding value of 1200 for a rigid channel or 2100 for a rigid tube. Experiments conducted with very viscous fluids show that there could be an instability even at zero Reynolds number provided the surface is sufficiently soft. Linear stability studies show that the transition Reynolds number is linearly proportional to the wall shear modulus in the low Reynolds number limit, and it increases as the 1/2 and 3/4 power of the shear modulus for the ‘inviscid’ and ‘wall mode’ instabilities at high Reynolds number. While the inviscid instability is similar to that in the flow in a rigid channel, the mechanisms of the viscous and wall mode instabilities are qualitatively different. These involve the transfer of energy from the mean flow to the fluctuations due to the shear work done at the interface. The experimental results for the viscous instability mechanism are in quantitative agreement with theoretical predictions. At high Reynolds number, the instability mechanism has characteristics similar to the wall mode instability. The experimental transition Reynolds number is smaller, by a factor of about 10, than the theoretical prediction for the parabolic flow through rigid tubes and channels. However, if the modification in the tube shape due to the pressure gradient, and the consequent modification in the velocity profile and pressure gradient, are incorporated, there is quantitative agreement between theoretical predictions and experimental results. The transition has important practical consequences, since there is a significant enhancement of mixing after transition.

  15. Electrostatic properties of two porin channels from Escherichia coli.

    Science.gov (United States)

    Karshikoff, A; Spassov, V; Cowan, S W; Ladenstein, R; Schirmer, T

    1994-07-22

    The electrostatic interactions in the channels of OmpF and PhoE porins from Escherichia coli were analysed on the basis of a macroscopic multi-dielectric model of the protein-membrane complex derived from the respective porin X-ray structures. The membrane was represented as layers of distinct dielectric constants corresponding to the aliphatic core and the polar head groups of the lipids. The pKa values of the titratable groups and the electrostatic field in the region of the channel were calculated by the finite difference technique. In spite of the differences in sequences and charge constellations, the calculated electrostatic properties of the two porins are similar in several aspects: (1) unusual titration behaviour (pKa below 7) was found for some groups of the cluster of basic residues at the constriction of the pore; (2) a number of acidic groups buried between the internal loop and the barrel wall are stabilized in their protonated forms at neutral pH; (3) there is a strong transverse electrostatic field in the channel characterized by a screw-like form. The strength of the field is greatest at the region of the constriction zone. This would facilitate the diffusion of solutes with a large dipole moment such as free amino acids. Differences between the electrostatic fields of OmpF and PhoE are mainly confined to that end of the pore that faces the cell exterior in vivo. In OmpF the electrostatic potential is close to zero in this region of the channel, whereas a positive potential was found in PhoE. It was shown that the experimentally observed difference in ion selectivity of the two porins can largely be attributed to this distinct electrostatic property. PMID:8035460

  16. Interacting tilt and kink instabilities in repelling current channels

    International Nuclear Information System (INIS)

    We present a numerical study in resistive magnetohydrodynamics (MHD) where the initial equilibrium configuration contains adjacent, oppositely directed, parallel current channels. Since oppositely directed current channels repel, the equilibrium is liable to an ideal magnetohydrodynamic tilt instability. This tilt evolution, previously studied in planar settings, involves two magnetic islands or flux ropes, which on Alfvénic timescales undergo a combined rotation and separation. This in turn leads to the creation of (near) singular current layers, posing severe challenges to numerical approaches. Using our open-source grid-adaptive MPI-AMRVAC software, we revisit the planar evolution case in compressible MHD, as well as its extension to two-and-a-half-dimensional (2.5D) and full three-dimensional (3D) scenarios. As long as the third dimension can be ignored, pure tilt evolutions result that are hardly affected by out of plane magnetic field components. In all 2.5D runs, our simulations do show secondary tearing type disruptions throughout the near singular current sheets in the far nonlinear saturation regime. In full 3D runs, both current channels can be liable to additional ideal kink deformations. We discuss the effects of having both tilt and kink instabilities acting simultaneously in the violent, reconnection-dominated evolution. In 3D, both the tilt and the kink instabilities can be stabilized by tension forces. As a concrete space plasma application, we argue that interacting tilt-kink instabilities in repelling current channels provide a novel route to initiate solar coronal mass ejections, distinctly different from the currently favored pure kink or torus instability routes.

  17. Functional role of voltage gated Ca2+ channels in heart automaticity

    Directory of Open Access Journals (Sweden)

    Pietro eMesirca

    2015-02-01

    Full Text Available Pacemaker activity of automatic cardiac myocytes controls the heartbeat in everyday life. Cardiac automaticity is under the control of several neurotransmitters and hormones and is constantly regulated by the autonomic nervous system to match the physiological needs of the organism. Several classes of ion channels and proteins involved in intracellular Ca2+ dynamics contribute to pacemaker activity. The functional role of voltage-gated calcium channels (VGCCs in heart automaticity and impulse conduction has been matter of debate for 30 years. However, growing evidence shows that VGCCs are important regulators of the pacemaker mechanisms and play also a major role in atrio-ventricular impulse conduction. Incidentally, studies performed in genetically modified mice lacking L-type Cav1.3 (Cav1.3-/- or T-type Cav3.1 (Cav3.1-/- channels show that genetic inactivation of these channels strongly impacts pacemaking. In cardiac pacemaker cells, VGCCs activate at negative voltages at the beginning of the diastolic depolarization and importantly contribute to this phase by supplying inward current. Loss-of-function of these channels also impairs atrio-ventricular conduction. Furthermore, inactivation of Cav1.3 channels promotes also atrial fibrillation and flutter in knockout mice suggesting that these channels can play a role in stabilizing atrial rhythm. Genomic analysis demonstrated that Cav1.3 and Cav3.1 channels are widely expressed in pacemaker tissue of mice, rabbits and humans. Importantly, human diseases of pacemaker activity such as congenital bradycardia and heart block have been attributed to loss-of-function of Cav1.3 and Cav3.1 channels. In this article, we will review the current knowledge on the role of VGCCs in the generation and regulation of heart rate and rhythm. We will discuss also how loss of Ca2+ entry through VGCCs could influence intracellular Ca2+ handling and promote atrial arrhythmias.

  18. Decoding with approximate channel statistics for band-limited nonlinear satellite channels

    Science.gov (United States)

    Biederman, L.; Omura, J. K.; Jain, P. C.

    1981-11-01

    Expressions for the cutoff rate of memoryless channels and certain channels with memory are derived assuming decoding with approximate channel statistics. For channels with memory, two different decoding techniques are examined: conventional decoders in conjunction with ideal interleaving/deinterleaving, and maximum likelihood decoders that take advantage of the channel memory. As a practical case of interest, the cutoff rate for the band-limited nonlinear satellite channel is evaluated where the modulation is assumed to be M-ary phase shift keying (MPSK). The channel nonlinearity is introduced by a limiter in cascade with a traveling wave tube amplifier (TWTA) at the satellite repeater while the channel memory is created by channel filters in the transmission path.

  19. Control works in debris-flow channels: influence on morphology and sediment transfer

    Science.gov (United States)

    Marchi, L.

    2012-04-01

    Extensive torrent control works, such as grade-control dams, debris basins, deflecting walls, etc. have been implemented in the European Alps since the last decades of 19th century. These structural measures, aimed at stabilizing channels and to control sediment transport, are also widespread in Japan and are increasingly present in other mountain regions. As debris flows are one of the most destructive processes in steep mountain channels, hydraulic works are often intended to attenuate debris-flow hazard. Multi-temporal aerial photos and historic records permit evaluating the long term effects of torrent control works on the morphological settings of the channels and the delivery of sediment. The experience arising from over one century of torrent control works in debris-flow channels of the Alps permits also to improve the management of steep headwater catchments. A basic issue in the management of debris-flow channels is the recognition of success versus failure of engineering control works. Successful debris-flow control works provide benchmarks for further implementations, whereas the failure in reducing debris-flow hazard may lead to refinements in planning and design of control works or to the choice of preferring non-structural measures for coping with debris flows. Data from historical archives on debris-flow occurrence and on the performance of control works are the basic sources of information for these analyses. Moreover, when dealing with hydraulic structures for debris-flow control, it should be reminded that the artificial morphology resulting from the construction of check dams provides only a temporary stability to the channel and adjacent banks. This stresses the importance of evaluating the state of conservation and the effectiveness of control works and implies the need for their careful and continuous maintenance. Inventories of hydraulic structures, coupled with detailed data on catchment and channel topography, sediment sources and supply

  20. Chopper-stabilized phase detector

    Science.gov (United States)

    Hopkins, P. M.

    1978-01-01

    Phase-detector circuit for binary-tracking loops and other binary-data acquisition systems minimizes effects of drift, gain imbalance, and voltage offset in detector circuitry. Input signal passes simultaneously through two channels where it is mixed with early and late codes that are alternately switched between channels. Code switching is synchronized with polarity switching of detector output of each channel so that each channel uses each detector for half time. Net result is that dc offset errors are canceled, and effect of gain imbalance is simply change in sensitivity.

  1. Statistical-mechanical analysis of multiuser channel capacity with imperfect channel state information

    Institute of Scientific and Technical Information of China (English)

    Wang Hui-Song; Zeng Gui-Hua

    2008-01-01

    In this paper,the effect of imperfect channel state information at the receiver, which is caused by noise and other interference, on the multi-access channel capacity is analysed through a statistical-mechanical approach. Replica analyses focus on analytically studying how the minimum mean square error (MMSE) channel estimation error appears in a multiuser channel capacity formula. And the relevant mathematical expressions are derived. At the same time,numerical simulation results are demonstrated to validate the Replica analyses. The simulation results show how the system parameters, such as channel estimation error, system load and signal-to-noise ratio, affect the channel capacity.

  2. K-user Interference Channels: General Outer Bound and Sum-capacity for Certain Gaussian Channels

    CERN Document Server

    Tuninetti, Daniela

    2011-01-01

    This paper derives an outer bound on the capacity region of a general memoryless interference channel with an arbitrary number of users. The derivation follows from a generalization of the techniques developed by Kramer and by Etkin et al for the Gaussian two-user channel. The derived bound is the first known outer bound valid for any memoryless channel. In Gaussian noise, classes of channels for which the proposed bound gives the sum-rate capacity are identified, including degraded channels and a class of Z-channels.

  3. Parameter estimation in channel network flow simulation

    Institute of Scientific and Technical Information of China (English)

    Han Longxi

    2008-01-01

    Simulations of water flow in channel networks require estimated values of roughness for all the individual channel segments that make up a network. When the number of individual channel segments is large, the parameter calibration workload is substantial and a high level of uncertainty in estimated roughness cannot be avoided. In this study, all the individual channel segments are graded according to the factors determining the value of roughness. It is assumed that channel segments with the same grade have the same value of roughness. Based on observed hydrological data, an optimal model for roughness estimation is built. The procedure of solving the optimal problem using the optimal model is described. In a test of its efficacy, this estimation method was applied successfully in the simulation of tidal water flow in a large complicated channel network in the lower reach of the Yangtze River in China.

  4. Interference Channels with One Cognitive Transmitter

    CERN Document Server

    Cao, Yi

    2009-01-01

    This paper studies the problem of interference channels with one cognitive transmitter (ICOCT) where "cognitive" is defined from both the noncausal and causal perspectives. For the noncausal ICOCT, referred to as interference channels with degraded message sets (IC-DMS), we propose a new achievable rate region that generalizes existing achievable rate regions for IC-DMS. In the absence of the noncognitive transmitter, the proposed region coincides with Marton's region for the broadcast channel. Based on this result, the capacity region of a class of semi-deterministic IC-DMS is established. For the causal ICOCT, due to the complexity of the channel model, we focus primarily on the cognitive Z interference channel (ZIC), where the interference link from the cognitive transmitter to the primary receiver is assumed to be absent due to practical design considerations. Capacity bounds for such channels in different parameter regimes are obtained and the impact of such causal cognitive ability is carefully studied....

  5. Rateless Coding for MIMO Block Fading Channels

    CERN Document Server

    Fan, Yijia; Erkip, Elza; Poor, H Vincent

    2008-01-01

    In this paper the performance limits and design principles of rateless codes over fading channels are studied. The diversity-multiplexing tradeoff (DMT) is used to analyze the system performance for all possible transmission rates. It is revealed from the analysis that the design of such rateless codes follows the design principle of approximately universal codes for parallel multiple-input multiple-output (MIMO) channels, in which each sub-channel is a MIMO channel. More specifically, it is shown that for a single-input single-output (SISO) channel, the previously developed permutation codes of unit length for parallel channels having rate LR can be transformed directly into rateless codes of length L having multiple rate levels (R, 2R, . . ., LR), to achieve the DMT performance limit.

  6. Parameter estimation in channel network flow simulation

    Directory of Open Access Journals (Sweden)

    Han Longxi

    2008-03-01

    Full Text Available Simulations of water flow in channel networks require estimated values of roughness for all the individual channel segments that make up a network. When the number of individual channel segments is large, the parameter calibration workload is substantial and a high level of uncertainty in estimated roughness cannot be avoided. In this study, all the individual channel segments are graded according to the factors determining the value of roughness. It is assumed that channel segments with the same grade have the same value of roughness. Based on observed hydrological data, an optimal model for roughness estimation is built. The procedure of solving the optimal problem using the optimal model is described. In a test of its efficacy, this estimation method was applied successfully in the simulation of tidal water flow in a large complicated channel network in the lower reach of the Yangtze River in China.

  7. Electrical conductivity channel for a shock tube

    Science.gov (United States)

    Lu, Frank K.; Liu, Hsuan-Cheng; Wilson, Donald R.

    2005-09-01

    The design of an electrical conductivity measurement channel for a shock tube is described. This measurement channel is used for the study of weakly ionized, high-enthalpy flows of gases seeded with alkali salts. The theory for determining the dimensions of the measurement channel and the electrical power supply for the channel is based on Ohm's law. Data are shown which demonstrate that the channel performs well. However, the measured electrical conductivity was one or two orders less than theoretical values. The current traces for each case show that the peak current occurred behind the contact surface, which indicates that some of the seed was entrained behind the test gas originally in the driven tube. An analysis of the effect of Joule heating on the measured conductivity was conducted. The result of increased temperature due to Joule heating in the measurement channel is believed to be minimal. Reasons for the discrepancy are given.

  8. Optimum performance characteristics of a conduction channel

    Energy Technology Data Exchange (ETDEWEB)

    Okulov, N.A.

    1978-01-01

    Steady laminar flow of an incompressible viscous and electrically conducting fluid is considered in an infinitely long cylindrical conduction channel. A set of permanent magnets outside produces a transverse magnetic field which does not vary over the channel length. An external electric dc generator or load maintains on the channel-fluid boundary a distribution of electric potential which also does not vary over the channel length. The power efficiency of such a channel is calculated and the distribution of electric potential is then optimized to yield the maximum efficiency for a given pressure head and flow rate, with a given scalar magnetic potential. Two mathematical theorems are proved for solving the optimization problem, i.e., the problem of minimizing a functional. An upper estimate of the efficiency is made on the basis of a third theorem. An estimate is also made of the flow rate in a conduction channel with a passive electrical system (load without generator). 3 references.

  9. Stability Criterion for Humanoid Running

    Institute of Scientific and Technical Information of China (English)

    LIZhao-Hui; HUANGQiang; LIKe-Jie

    2005-01-01

    A humanoid robot has high mobility but possibly risks of tipping over. Until now, one main topic on humanoid robots is to study the walking stability; the issue of the running stability has rarely been investigated. The running is different from the walking, and is more difficult to maintain its dynamic stability. The objective of this paper is to study the stability criterion for humanoid running based on the whole dynamics. First, the cycle and the dynamics of running are analyzed. Then, the stability criterion of humanoid running is presented. Finally, the effectiveness of the proposed stability criterion is illustrated by a dynamic simulation example using a dynamic analysis and design system (DADS).

  10. Uncertainties, monetary policy and financial stability: challenges on inflation targeting

    Directory of Open Access Journals (Sweden)

    Gabriel Caldas Montes

    2010-03-01

    Full Text Available This work aims at presenting the challenges that inflation targeting central banks may face since uncertainties represent a harmful element for the effectiveness of monetary policy, and since financial instabilities may disturb the transmission mechanisms - in particular, the expectation channel - and thus the economic stability. Financial stability must not be considered as a simple goal of monetary policy, but a precondition for central banks operate their policies and reach the goals of inflation and output stability. The work identifies different sources of uncertainties that surround central banks' decisions; and approaches the role that inflation targeting central banks should play according to some basic principles that can serve as useful guides for central banks to help them achieve successful outcomes in their conduct of monetary policy.

  11. Stabilization/Solidification Remediation Method for Contaminated Soil: A Review

    Science.gov (United States)

    Tajudin, S. A. A.; Azmi, M. A. M.; Nabila, A. T. A.

    2016-07-01

    Stabilization/Solidification (S/S) is typically a process that involves a mixing of waste with binders to reduce the volume of contaminant leachability by means of physical and chemical characteristics to convert waste in the environment that goes to landfill or others possibly channels. Stabilization is attempts to reduce the solubility or chemical reactivity of the waste by changing the physical and chemical properties. While, solidification attempt to convert the waste into easily handled solids with low hazardous level. These two processes are often discussed together since they have a similar purpose of improvement than containment of potential pollutants in treated wastes. The primary objective of this review is to investigate the materials used as a binder in Stabilization/Solidification (S/S) method as well as the ability of these binders to remediate the contaminated soils especially by heavy metals.

  12. Stability of Organic Nanowires

    DEFF Research Database (Denmark)

    Balzer, F.; Schiek, M.; Wallmann, I.;

    2011-01-01

    The morphological stability of organic nanowires over time and under thermal load is of major importance for their use in any device. In this study the growth and stability of organic nanowires from a naphthyl end-capped thiophene grown by organic molecular beam deposition is investigated via...... atomic force microscopy (AFM). Aging experiments under ambient conditions already show substantial morphological changes. Nanoscopic organic clusters, which initially coexist with the nanowires, vanish within hours. Thermal annealing of nanowire samples leads to even more pronounced morphology changes......, such as a strong decrease in nanowire number density, a strong increase in nanowire height, and the formation of new types of crystallites. This happens even before sublimation of organic material starts. These experiments also shine new light on the formation process of the nanowires....

  13. Hillslope hydrology and stability

    Science.gov (United States)

    Lu, Ning; Godt, Jonathan

    2012-01-01

    Landslides are caused by a failure of the mechanical balance within hillslopes. This balance is governed by two coupled physical processes: hydrological or subsurface flow and stress. The stabilizing strength of hillslope materials depends on effective stress, which is diminished by rainfall. This book presents a cutting-edge quantitative approach to understanding hydro-mechanical processes across variably saturated hillslope environments and to the study and prediction of rainfall-induced landslides. Topics covered include historic synthesis of hillslope geomorphology and hydrology, total and effective stress distributions, critical reviews of shear strength of hillslope materials and different bases for stability analysis. Exercises and homework problems are provided for students to engage with the theory in practice. This is an invaluable resource for graduate students and researchers in hydrology, geomorphology, engineering geology, geotechnical engineering and geomechanics and for professionals in the fields of civil and environmental engineering and natural hazard analysis.

  14. The effect of grain boundaries state on the thermal stability of a submicrocrystalline titanium alloy structure

    Science.gov (United States)

    Chuvil'deev, V. N.; Kopylov, V. I.; Nokhrin, A. V.; Lopatin, Yu. G.; Kozlova, N. A.; Tabachkova, N. Yu.; Semenycheva, A. V.; Smirnova, E. S.; Gryaznov, M. Yu.; Pirozhnikova, O. E.

    2015-06-01

    The thermal stability of the structure and the mechanical properties of submicrocrystalline (SMC) titanium alloy Ti-4Al-2V (industrial designation PT3V) are investigated. The alloy was produced by equal-channel angular pressing (ECAP). It is demonstrated that the enhanced thermal stability of the SMC alloy structure is associated with a change in the concentration of aluminum at the grain boundaries during ECAP.

  15. Stability of Coulomb crystals in a linear Paul trap with storage-ring-like confinement

    DEFF Research Database (Denmark)

    Kjærgaard, Niels; Mølhave, Kristian; Drewsen, Michael

    2002-01-01

    We report experiments on the stability of ion Coulomb crystals in a linear Paul trap with storage-ring-like confinement. The transverse dynamics of charged particles in a trap of this type is analogous to that of a fast beam traveling through a channel with periodic, magnetic alternating gradient...... confinement. The experimentally observed stability conditions for stationary crystals comply remarkably well with current theory of crystalline plasmas and beams....

  16. Catalytically stabilized combustion of lean methane-air-mixtures: a numerical model

    Energy Technology Data Exchange (ETDEWEB)

    Dogwiler, U.; Benz, P.; Mantharas, I. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-06-01

    The catalytically stabilized combustion of lean methane/air mixtures has been studied numerically under conditions closely resembling the ones prevailing in technical devices. A detailed numerical model has been developed for a laminar, stationary, 2-D channel flow with full heterogeneous and homogeneous reaction mechanisms. The computations provide direct information on the coupling between heterogeneous-homogeneous combustion and in particular on the means of homogeneous ignitions and stabilization. (author) 4 figs., 3 refs.

  17. A father protocol for quantum broadcast channels

    OpenAIRE

    Dupuis, Frédéric; Hayden, Patrick; Li, Ke

    2006-01-01

    A new protocol for quantum broadcast channels based on the fully quantum Slepian-Wolf protocol is presented. The protocol yields an achievable rate region for entanglement-assisted transmission of quantum information through a quantum broadcast channel that can be considered the quantum analogue of Marton's region for classical broadcast channels. The protocol can be adapted to yield achievable rate regions for unassisted quantum communication and for entanglement-assisted classical communica...

  18. Chromatic effects in long periodic transport channels

    Energy Technology Data Exchange (ETDEWEB)

    Litvinenko V. N.; Hao, Y.; Jing, Y.

    2015-05-03

    Long periodic transport channels are frequently used in accelerator complexes and suggested for using in high-energy ERLs for electron-hadron colliders. Without proper chromaticity compensation, such transport channels exhibit high sensitivity to the random orbit errors causing significant emittance growth. Such emittance growth can come from both the correlated and the uncorrelated energy spread. In this paper we present results of our theoretical and numerical studies of such effects and develop a criteria for acceptable chromaticity in such channels.

  19. Two-channel Optimal Quantum Teleportation

    OpenAIRE

    Quan, Quan; Fei, Shao-Ming; Fan, Heng; Yang, Wen-Li(Institute of Modern Physics, Northwest University, Xian, 710069, China)

    2015-01-01

    We investigate two-channel scenarios of optimal quantum teleportation based on Bell measurements and GHZ measurements. The detailed protocols are presented and the general expressions of the optimal teleportation fidelities are derived, which turn out to be functions of two-channel fully entangled fractions -- invariants under local unitary transformations. We prove that the set of states which are useful for two-channel teleportation is convex and compact. Hence witness operators exist to se...

  20. Natural Products and Ion Channel Pharmacology

    OpenAIRE

    Teichert, Russell W.; Olivera, Baldomero M.

    2010-01-01

    An accelerated rate of natural-product discovery is critical for the future of ion channel pharmacology. For the full potential of natural products to be realized, an interdisciplinary initiative is required that combines chemical ecology and ion channel physiology. A prime source of future drug leads targeted to ion channels is the vast assortment of compounds that mediate biotic interactions in the marine environment. Many animals have evolved a chemical strategy to change the behavior of t...