Zarai, Yoram; Margaliot, Michael; Tuller, Tamir
2013-01-01
Gene translation is a central stage in the intracellular process of protein synthesis. Gene translation proceeds in three major stages: initiation, elongation, and termination. During the elongation step, ribosomes (intracellular macromolecules) link amino acids together in the order specified by messenger RNA (mRNA) molecules. The homogeneous ribosome flow model (HRFM) is a mathematical model of translation-elongation under the assumption of constant elongation rate along the mRNA sequence. The HRFM includes $(n)$ first-order nonlinear ordinary differential equations, where $(n)$ represents the length of the mRNA sequence, and two positive parameters: ribosomal initiation rate and the (constant) elongation rate. Here, we analyze the HRFM when $(n)$ goes to infinity and derive a simple expression for the steady-state protein synthesis rate. We also derive bounds that show that the behavior of the HRFM for finite, and relatively small, values of $(n)$ is already in good agreement with the closed-form result in the infinite-dimensional case. For example, for $(n=15)$, the relative error is already less than 4 percent. Our results can, thus, be used in practice for analyzing the behavior of finite-dimensional HRFMs that model translation. To demonstrate this, we apply our approach to estimate the mean initiation rate in M. musculus, finding it to be around 0.17 codons per second. PMID:24384716
SALT (System Analysis Language Translater): A steady state and dynamic systems code
Berry, G.; Geyer, H.
1983-01-01
SALT (System Analysis Language Translater) is a lumped parameter approach to system analysis which is totally modular. The modules are all precompiled and only the main program, which is generated by SALT, needs to be compiled for each unique system configuration. This is a departure from other lumped parameter codes where all models are written by MACROS and then compiled for each unique configuration, usually after all of the models are lumped together and sorted to eliminate undetermined variables. The SALT code contains a robust and sophisticated steady-sate finder (non-linear equation solver), optimization capability and enhanced GEAR integration scheme which makes use of sparsity and algebraic constraints. The SALT systems code has been used for various technologies. The code was originally developed for open-cycle magnetohydrodynamic (MHD) systems. It was easily extended to liquid metal MHD systems by simply adding the appropriate models and property libraries. Similarly, the model and property libraries were expanded to handle fuel cell systems, flue gas desulfurization systems, combined cycle gasification systems, fluidized bed combustion systems, ocean thermal energy conversion systems, geothermal systems, nuclear systems, and conventional coal-fired power plants. Obviously, the SALT systems code is extremely flexible to be able to handle all of these diverse systems. At present, the dynamic option has only been used for LMFBR nuclear power plants and geothermal power plants. However, it can easily be extended to other systems and can be used for analyzing control problems. 12 refs.
Skoglof, A; Göthe, P O; Deinum, J
1990-01-01
The kinetics of the steady-state inhibition of angiotension I-converting enzyme (EC 3.4.15.1) at 25 degrees C and 37 degrees C with enalaprilat and ramiprilat can be simulated, assuming only one inhibitor-binding site, consistent with a 1:1 stoichiometry if the protein concentration was determined by amino acid analysis. In this temperature range the apparent inhibition constants for ramiprilat and enalaprilat were roughly doubled by a decrease in the chloride concentration from 0.300 M to 0.120 M. PMID:2176463
Kerzel, Dirk; Born, Sabine; Souto, David
2010-11-01
It is known that visual transients prolong saccadic latency and reduce saccadic frequency. The latter effect was attributed to subcortical structures because it occurred only 60-70 ms after stimulus onset. We examined the effects of large task-irrelevant transients on steady-state pursuit and the generation of catch-up saccades. Two screen-wide stripes of equal contrast (4, 20, or 100%) were briefly flashed at equal eccentricities (3, 6, or 12°) from the pursuit target. About 100 ms after flash onset, we observed that pursuit gain dropped by 6-12% and catch-up saccades were entirely suppressed. The relatively long latency of the inhibition suggests that it results from cortical mechanisms that may act by promoting fixation or the deployment of attention over the visual field. In addition, we show that a loud irrelevant sound is able to generate the same inhibition of saccades as visual transients, whereas it only induces a weak modulation of pursuit gain, indicating a privileged access of acoustic information to the saccadic system. Finally, irrelevant changes in motion direction orthogonal to pursuit had a smaller and later inhibitory effect. PMID:20844111
Duarte, Américo G; Cordas, Cristina M; Moura, José J G; Moura, Isabel
2014-03-01
Nitric oxide reductase (NOR) from denitrifying bacteria is an integral membrane protein that catalyses the two electron reduction of NO to N2O, as part of the denitrification process, being responsible for an exclusive reaction, the NN bond formation, the key step of this metabolic pathway. Additionally, this class of enzymes also presents residual oxidoreductase activity, reducing O2 to H2O in a four electron/proton reaction. In this work we report, for the first time, steady-state kinetics with the Pseudomonas nautica NOR, either in the presence of its physiological electron donor (cyt. c552) or immobilised on a graphite electrode surface, in the presence of its known substrates, namely NO or O2. The obtained results show that the enzyme has high affinity for its natural substrate, NO, and different kinetic profiles according to the electron donor used. The kinetic data, as shown by the pH dependence, is modelled by ionisable amino acid residues nearby the di-nuclear catalytic site. The catalytic mechanism is revised and a mononitrosyl-non-heme Fe complex (FeB(II)-NO) species is favoured as the first catalytic intermediate involved on the NO reduction. PMID:24412239
Kopp, E B; Miglietta, J J; Shrutkowski, A G; Shih, C K; Grob, P M; Skoog, M T
1991-01-01
Steady state kinetics and inhibition by a dipyridodiazepinone of the reverse transcriptase from human immunodeficiency virus type 1 (HIV) were studied using a heteropolymeric RNA template with a sequence from the authentic initiation site on the HIV genome. For addition of the first deoxynucleotide to primer, kcat/KM is 0.05 (nM-min)-1 and KM is 10 nM. When all 4 deoxynucleotide triphosphates are present and processive synthesis occurs, catalysis is less efficient; kcat/KM = .0077 (nM-min)-1 and KM = 100 nM for dATP. These results are consistent with a rate determining conformation change involved in translocation of the enzyme along the template. Inhibition by the dipyridodiazepinone BI-RG-587 is noncompetitive with respect to both nucleotide and template-primer; this compound decreases Vmax but does not affect KM. Thus, this inhibitor binds to a site distinct from the substrate binding sites with Ki of 220 nM. Inhibition by BI-RG-587 results in a uniform decrease in amount of products of all lengths rather than a shift from longer to shorter products, suggesting the inhibitor does not affect processivity of reverse transcriptase. Images PMID:1711678
Grady, S R; Wang, J K; Dekker, E E
1981-04-28
Two sensitive assays, one which fluorometrically measures only the L isomer of 2-keto-4-hydroxyglutarate after decarboxylation to L-malate and the other which spectrophotometrically determines both enantiomers by reductive amination with glutamate dehydrogenase, are described. By use of these assays, the steady-state kinetics of the aldol condensation of pyruvate with glyoxylate, as catalyzed by 2-keto-4-hydroxyglutarate aldolase from either bovine liver or Escherichia coli, were studied as was the inhibition of this reaction by glyoxylate and other anions. For the E. coli aldolase, double-reciprocal plots are linear except at high (above 5 mM) glyoxylate concentrations; apparent Km values increase with increasing concentrations of the fixed substrate. The data are consistent with an ordered reaction sequence. Inhibition by halides follows the lyotropic or Hofmeister series. Esters are not good inhibitors; mono-, di-, and tricarboxylic acids are increasingly inhibitory. Of the substrate analogues tested, hydroxypyruvate is the most potent inhibitor. Inhibition studies with citrate, acetaldehyde, and glyoxylate (all competitive inhibitors) suggest there are two domains at the active site-the Schiff base forming lysyl residue which interacts with carbonyl analogues (like acetaldehyde) and a center of positive charge which binds anions (like citrate). In contrast to the bacterial enzyme, liver 2-keto-4-hydroxyglutarate aldolase is inhibited in a competitive manner by much lower concentrations (0.1 mM or even lower) of glyoxylate. Many salts and some carboxylic acids activate the liver enzyme. Similarly, substrate analogues like 2-ketobutyrate and fluoropyruvate are mild activators; no effect is seen with acetaldehyde. Besides glyoxylate, only glyoxal, 2-ketoglutarate, and hydroxypyruvate inhibit the aldol condensation reaction. A uniform value of 1 is found for the number of inhibitor molecules bound per active site of either liver or E. coli 2-keto-4-hydroxyglutarate
Thermodynamics of Stability of Nonequilibrium Steady States.
ERIC Educational Resources Information Center
Rastogi, R. P.; Shabd, Ram
1983-01-01
Presented is a concise and critical account of developments in nonequilibrium thermodynamics. The criterion for stability of nonequilibrium steady states is critically examined for consecutive and monomolecular triangular reactions, autocatalytic reactions, auto-inhibited reactions, and the Lotka-Volterra model. (JN)
Steady State Dense Gas Dispersion
Energy Science and Technology Software Center (ESTSC)
1995-03-01
SLAB-LLNL is a steady-state one-dimensional program which calculates the atmospheric dispersion of a heavier than air gas that is continuously released at ground level. The model is based on the steady-state crosswind-averaged conservation equations of species, mass, energy, and momentum. It uses the air entrainment concept to account for the turbulent mixing of the gas cloud with the surrounding atmosphere and similarity profiles to determine the crosswind dependence.
ERIC Educational Resources Information Center
Owens, J. A.
1982-01-01
Options for faculty utilization in a steady state are examined, with consideration for their economy or ability to increase turnover or flexibility: early retirement, part retirement, retraining, exchange with other institutions or industry, and fixed-term appointments or lecturer positions. (MSE)
Inconsistencies in steady state thermodynamics
NASA Astrophysics Data System (ADS)
Dickman, Ronald; Motai, Ricardo
2014-03-01
We address the issue of extending thermodynamics to nonequilibrium steady states. Using driven stochastic lattice gases, we ask whether consistent definitions of an effective chemical potential μ, and an effective temperature Te, are possible. These quantities are determined via zero-flux conditions of particles and energy between the driven system and a reservoir. For the models considered here, the fluxes are given in terms of certain stationary average densities, eliminating the need to perturb the system by actually exchanging particles; μ and Te are thereby obtained via open-circuit measurements, using a virtual reservoir. In the lattice gas with nearest-neighbor exclusion, temperature is not relevant, and we find that the effective chemical potential, a function of density and drive strength, satisfies the zeroth law, and correctly predicts the densities of coexisting systems. In the Katz-Lebowitz-Spohn driven lattice gas, both μ and Te need to be defined. We show analytically that the zeroth law is violated, and determine the size of the violations numerically. Our results highlight a fundamental inconsistency in the extension of thermodynamics to nonequilibrium steady states. Research supported by CNPq, Brazil.
Irreversible processes at nonequilibrium steady states
Fox, Ronald Forrest
1979-01-01
It is shown that a Liapunov criterion exists for the stability of nonequilibrium steady states. This criterion is based upon the fluctuation-dissipation relation, as was first pointed out by Keizer. At steady states, the Liapunov function is constructed from the covariance matrix for the thermodynamic variables. Unlike the situation around equilibrium, at steady states the covariance matrix and the “excess entropy” matrix are not equivalent. The excess entropy, which serves as the Liapunov function around equilibrium, does not work in this capacity at steady states. Keizer's Liapunov function must be viewed as the first correct candidate for a proper Liapunov function for steady states. PMID:16592649
Chow, Melissa L; Troussicot, Laura; Martin, Marie; Doumèche, Bastien; Guillière, Florence; Lancelin, Jean-Marc
2016-06-21
Funnel metadynamics is a kind of computational simulation used to enhance the sampling of protein-ligand binding events in solution. By characterization of the binding interaction events, an estimated absolute binding free energy can be calculated. Nuclear magnetic resonance and funnel metadynamics were used to evaluate the binding of pyrocatechol derivatives (catechol, 4-methylcatechol, and 4-tert-butylcatechol) to human peroxiredoxin 5. Human peroxiredoxins are peroxidases involved in cellular peroxide homeostasis. Recently, overexpressed or suppressed peroxiredoxin levels have been linked to various diseases. Here, the catechol derivatives were found to be inhibitors against human peroxiredoxin 5 through a partial mixed type noncompetitive mechanism. Funnel metadynamics provided a microscopic model for interpreting the inhibition mechanism. Correlations were observed between the inhibition constants and the absolute binding free energy. Overall, this study showcases the fact that funnel metadynamics simulations can be employed as a preliminary approach to gain an in-depth understanding of potential enzyme inhibitors. PMID:27239955
Bienvenut, Willy V; Giglione, Carmela; Meinnel, Thierry
2015-07-01
A proteome wide analysis was performed in Escherichia coli to identify the impact on protein N-termini of actinonin, an antibiotic specifically inhibiting peptide deformylase (PDF). A strategy and tool suite (SILProNaQ) was employed to provide large-scale quantitation of N-terminal modifications. In control conditions, more than 1000 unique N-termini were identified with 56% showing initiator methionine removal. Additional modifications corresponded to partial or complete Nα-acetylation (10%) and N-formyl retention (5%). Among the proteins undergoing these N-terminal modifications, 140 unique N-termini from translocated membrane proteins were highlighted. The very early time-course impact of actinonin was followed after addition of bacteriostatic concentrations of the drug. Under these conditions, 26% of all proteins did not undergo deformylation any longer after 10 min, a value reaching more than 60% of all characterized proteins after 40 min of treatment. The N-formylation ratio measured on individual proteins increased with the same trend. Upon early PDF inhibition, two major categories of proteins retained their N-formyl group: a large number of inner membrane proteins and many proteins involved in protein synthesis including factors assisting the nascent chains in early cotranslational events. All MS data have been deposited in the ProteomeXchange with identifiers PXD001979, PXD002012 and PXD001983 (http://proteomecentral.proteomexchange.org/dataset/PXD001979, http://proteomecentral.proteomexchange.org/dataset/PXD002012 and http://proteomecentral.proteomexchange.org/dataset/PXD001983). PMID:26017780
Venusian hydrology: Steady state reconsidered
NASA Technical Reports Server (NTRS)
Grinspoon, David H.
1992-01-01
In 1987, Grinspoon proposed that the data on hydrogen abundance, isotopic composition, and escape rate were consistent with the hypothesis that water on Venus might be in steady state rather than monotonic decline since the dawn of time. This conclusion was partially based on a derived water lifetime against nonthermal escape of approximately 10(exp 8) yr. De Bergh et al., preferring the earlier Pioneer Venus value of 200 ppm water to the significantly lower value detected by Bezard et al., found H2O lifetimes of greater than 10(exp 9) yr. Donahue and Hodges derived H2O lifetimes of 0.4-5 x 10 (exp 9) yr. Both these analyses used estimates of H escape flux between 0.4 x 10(exp 7) and 1 x 10(exp 7) cm(exp -2)s(exp -1) from Rodriguez et al. Yet in more recent Monte Carlo modeling, Hodges and Tinsley found an escape flux due to charge exchange with hot H(+) of 2.8 x 10(exp 7) cm(exp -2)s(exp -1). McElroy et al. estimated an escape flux of 8 x 10(exp 6) cm(exp -2)s(exp -1) from collisions with hot O produced by dissociative recombination of O2(+). Brace et al. estimated an escape flux of 5 x 10(exp 6) cm(exp -2)s(exp -1) from ion escape from the ionotail of Venus. The combined estimated escape flux from all these processes is approximately 4 x 10(exp 7) cm(exp -2)s(exp -1). The most sophisticated analysis to date of near-IR radiation from Venus' nightside reveals a water mixing ratio of approximately 30 ppm, suggesting a lifetime against escape for water of less than 10(exp 8) yr. Large uncertainties remain in these quantities, yet the data point toward a steady state. Further evaluation of these uncertainties, and new evolutionary modeling incorporating estimates of the outgassing rate from post-Magellan estimates of the volcanic resurfacing rate are presented.
Steady State Tokamak Equilibria without Current Drive
Shaing, K.C.; Aydemir, A.Y.; Lin-Liu, Y.R.; Miller, R.L.
1997-11-01
Steady state tokamak equilibria without current drive are found. This is made possible by including the potato bootstrap current close to the magnetic axis. Tokamaks with this class of equilibria do not need seed current or current drive, and are intrinsically steady state. {copyright} {ital 1997} {ital The American Physical Society}
Optimal Control of Transitions between Nonequilibrium Steady States
Zulkowski, Patrick R.; Sivak, David A.; DeWeese, Michael R.
2013-01-01
Biological systems fundamentally exist out of equilibrium in order to preserve organized structures and processes. Many changing cellular conditions can be represented as transitions between nonequilibrium steady states, and organisms have an interest in optimizing such transitions. Using the Hatano-Sasa Y-value, we extend a recently developed geometrical framework for determining optimal protocols so that it can be applied to systems driven from nonequilibrium steady states. We calculate and numerically verify optimal protocols for a colloidal particle dragged through solution by a translating optical trap with two controllable parameters. We offer experimental predictions, specifically that optimal protocols are significantly less costly than naive ones. Optimal protocols similar to these may ultimately point to design principles for biological energy transduction systems and guide the design of artificial molecular machines. PMID:24386112
Steady state response of unsymmetrically laminated plates
Hosokawa, Kenji; Kawashima, Katsuya; Sakata, Toshiyuki
1995-11-01
A numerical approach for analyzing the forced vibration problem of a symmetrically laminated FRP (fiber reinforced plastic) composite plate was proposed by the authors. In the present paper, this approach is modified for application to an unsymmetrically laminated FRP composite plate. Numerical calculations are carried out for the clamped antisymmetrically laminated rectangular and elliptical plates which are a kind of unsymmetrically laminated plate. Then,, the effects of the lamina material and the fiber orientation angle on the steady state response are discussed. Furthermore, it is investigated that what structural damping factor is most influenced on the steady state response of an antisymmetrically laminated plate.
Steady-state inductive spheromak operation
Janos, A.C.; Jardin, S.C.; Yamada, M.
1985-02-20
The inductively formed spheromak configuration (S-1) can be maintained in a highly stable and controlled fashion. The method described eliminates the restriction to pulsed spheromak plasmas or the use of electrodes for steady-state operation, and, therefore, is a reactor-relevant formation and sustainment method.
The Politics of the Steady State
ERIC Educational Resources Information Center
Taylor, Charles
1978-01-01
A steady state society has limits pertaining to population size, non-renewable resources, and production which emits heat or substances into soil, water, or the atmosphere. Respecting these limits means renouncing exponential quantitative growth and accepting a universally available consumption standard. (SW)
Steady-state spheromak reactor studies. Revision
Krakowski, R.A.; Hagenson, R.L.
1985-01-01
After summarizing the essential elements of a gun-sustained spheromak, the potential for a steady-state is explored by means of a comprehensive physics/engineering/costing model. A range of cost-optimized reactor design point is presented, and the sensitivity of cost to key physics, engineering, and operational variables is reported.
Steady state compact toroidal plasma production
Turner, William C.
1986-01-01
Apparatus and method for maintaining steady state compact toroidal plasmas. A compact toroidal plasma is formed by a magnetized coaxial plasma gun and held in close proximity to the gun electrodes by applied magnetic fields or magnetic fields produced by image currents in conducting walls. Voltage supply means maintains a constant potential across the electrodes producing an increasing magnetic helicity which drives the plasma away from a minimum energy state. The plasma globally relaxes to a new minimum energy state, conserving helicity according to Taylor's relaxation hypothesis, and injecting net helicity into the core of the compact toroidal plasma. Controlling the voltage so as to inject net helicity at a predetermined rate based on dissipative processes maintains or increases the compact toroidal plasma in a time averaged steady state mode.
On Typicality in Nonequilibrium Steady States
NASA Astrophysics Data System (ADS)
Evans, Denis J.; Williams, Stephen R.; Searles, Debra J.; Rondoni, Lamberto
2016-06-01
From the statistical mechanical viewpoint, relaxation of macroscopic systems and response theory rest on a notion of typicality, according to which the behavior of single macroscopic objects is given by appropriate ensembles: ensemble averages of observable quantities represent the measurements performed on single objects, because "almost all" objects share the same fate. In the case of non-dissipative dynamics and relaxation toward equilibrium states, "almost all" is referred to invariant probability distributions that are absolutely continuous with respect to the Lebesgue measure. In other words, the collection of initial micro-states (single systems) that do not follow the ensemble is supposed to constitute a set of vanishing, phase space volume. This approach is problematic in the case of dissipative dynamics and relaxation to nonequilibrium steady states, because the relevant invariant distributions attribute probability 1 to sets of zero volume, while evolution commonly begins in equilibrium states, i.e., in sets of full phase space volume. We consider the relaxation of classical, thermostatted particle systems to nonequilibrium steady states. We show that the dynamical condition known as Ω T-mixing is necessary and sufficient for relaxation of ensemble averages to steady state values. Moreover, we find that the condition known as weak T-mixing applied to smooth observables is sufficient for ensemble relaxation to be independent of the initial ensemble. Lastly, we show that weak T-mixing provides a notion of typicality for dissipative dynamics that is based on the (non-invariant) Lebesgue measure, and that we call physical ergodicity.
On Typicality in Nonequilibrium Steady States
NASA Astrophysics Data System (ADS)
Evans, Denis J.; Williams, Stephen R.; Searles, Debra J.; Rondoni, Lamberto
2016-08-01
From the statistical mechanical viewpoint, relaxation of macroscopic systems and response theory rest on a notion of typicality, according to which the behavior of single macroscopic objects is given by appropriate ensembles: ensemble averages of observable quantities represent the measurements performed on single objects, because " almost all" objects share the same fate. In the case of non-dissipative dynamics and relaxation toward equilibrium states, " almost all" is referred to invariant probability distributions that are absolutely continuous with respect to the Lebesgue measure. In other words, the collection of initial micro-states (single systems) that do not follow the ensemble is supposed to constitute a set of vanishing, phase space volume. This approach is problematic in the case of dissipative dynamics and relaxation to nonequilibrium steady states, because the relevant invariant distributions attribute probability 1 to sets of zero volume, while evolution commonly begins in equilibrium states, i.e., in sets of full phase space volume. We consider the relaxation of classical, thermostatted particle systems to nonequilibrium steady states. We show that the dynamical condition known as Ω T-mixing is necessary and sufficient for relaxation of ensemble averages to steady state values. Moreover, we find that the condition known as weak T-mixing applied to smooth observables is sufficient for ensemble relaxation to be independent of the initial ensemble. Lastly, we show that weak T-mixing provides a notion of typicality for dissipative dynamics that is based on the (non-invariant) Lebesgue measure, and that we call physical ergodicity.
Theory of Steady-State Superradiance
NASA Astrophysics Data System (ADS)
Xu, Minghui
In this thesis, I describe the theoretical development of the superradiant laser, or laser in the extreme bad-cavity regime. In this regime, the cavity decay rate is much greater than the atomic dynamics. The atoms emit photons into the cavity mode superradiantly in steady state. We develop group-theoretic methods that enable us to exactly solve mesoscopic systems with hundreds of atoms. We demonstrate the synchronization of atomic dipoles in steady-state superradiance. With this synchronized system, we propose conditional Ramsey spectroscopy which allows us to observe Ramsey fringes indefinitely, even in the presence of atomic decoherence. Furthermore, we explore manifestations of synchronization in the quantum realm with two superradiant atomic ensembles. We show that two such ensembles exhibit a dynamical phase transition from two disparate oscillators to quantum phase-locked dynamics. Finally, we study the mechanical eect of the light-atom interaction in the steady-state superradiance. We find efficient many-body cooling of atoms. The work described in this thesis lays the theoretical foundation for the superradiant laser and for a potential future of active optical frequency standards.
An FGFR1-SPRY2 Signaling Axis Limits Basal Cell Proliferation in the Steady-State Airway Epithelium
Balasooriya, Gayan I.; Johnson, Jo-Anne; Basson, M. Albert; Rawlins, Emma L.
2016-01-01
Summary The steady-state airway epithelium has a low rate of stem cell turnover but can nevertheless mount a rapid proliferative response following injury. This suggests a mechanism to restrain proliferation at steady state. One such mechanism has been identified in skeletal muscle in which pro-proliferative FGFR1 signaling is antagonized by SPRY1 to maintain satellite cell quiescence. Surprisingly, we found that deletion of Fgfr1 or Spry2 in basal cells of the adult mouse trachea caused an increase in steady-state proliferation. We show that in airway basal cells, SPRY2 is post-translationally modified in response to FGFR1 signaling. This allows SPRY2 to inhibit intracellular signaling downstream of other receptor tyrosine kinases and restrain basal cell proliferation. An FGFR1-SPRY2 signaling axis has previously been characterized in cell lines in vitro. We now demonstrate an in vivo biological function of this interaction and thus identify an active signaling mechanism that maintains quiescence in the airway epithelium. PMID:27046834
Siple Dome: Is it in Steady State?
NASA Astrophysics Data System (ADS)
Pettit, E. C.; Waddington, E. D.; Nereson, N. A.; Zumberge, M. A.; Hamilton, G. S.
2001-12-01
Changes in the West Antarctic Ice Sheet since the end of the last ice age have implications for how we interpret its present behavior, in terms of both its stability and its record of climate history. Siple Dome, the ridge between Ice Streams C and D, is not presently thinning and is close to being in balance with present environmental conditions. We present three independent measurements of ice thickness change in the divide region of Siple Dome: a GPS surface horizontal strain network, fiber optic vertical strain measurements at depth, and precision GPS measurements of vertical motion of near-surface ice ("coffee-can" method). From the horizontal strain network, we calculate the divergence of the horizontal velocity. This divergence is equal to the gradient of vertical velocity at the surface and, with some assumptions about the distribution of strain rates with depth, we can calculate the vertical velocity at the surface. For steady state, the vertical velocity must be balanced by the local accumulation rate. The fiber optic instruments provide a profile of the relative vertical velocity with depth. We fit a theoretical vertical velocity pattern to these data and extrapolate to find the surface vertical velocity. Our third method (coffee-can) directly measures the vertical motion of a marker 20 meters deep using precision GPS and compares it with the local long-term rate of snow accumulation to calculate the net rate of ice sheet thickness change. All three methods reach the same conclusion: Siple Dome is currently very close to being in steady state. This result has two implications. First, ice dynamics models developed to interpret radar images or ice core data can assume steady state behavior, simplifying the models. Second, our result suggests that the central part of the Ross Embayment may have had a low-elevation profile during the late Holocene, even though other areas of the WAIS may have been thicker.
Intensity fluctuations in steady-state superradiance
Meiser, D.; Holland, M. J.
2010-06-15
Alkaline-earth-metal-like atoms with ultranarrow optical transitions enable superradiance in steady state. The emitted light promises to have an unprecedented stability with a linewidth as narrow as a few millihertz. In order to evaluate the potential usefulness of this light source as an ultrastable oscillator in clock and precision metrology applications, it is crucial to understand the noise properties of this device. In this paper, we present a detailed analysis of the intensity fluctuations by means of Monte Carlo simulations and semiclassical approximations. We find that the light exhibits bunching below threshold, is to a good approximation coherent in the superradiant regime, and is chaotic above the second threshold.
Intense steady state electron beam generator
Hershcovitch, Ady; Kovarik, Vincent J.; Prelec, Krsto
1990-01-01
An intense, steady state, low emittance electron beam generator is formed by operating a hollow cathode discharge plasma source at critical levels in combination with an extraction electrode and a target electrode that are operable to extract a beam of fast primary electrons from the plasma source through a negatively biased grid that is critically operated to repel bulk electrons toward the plasma source while allowing the fast primary electrons to move toward the target in the desired beam that can be successfully transported for relatively large distances, such as one or more meters away from the plasma source.
Intense steady state electron beam generator
Hershcovitch, A.; Kovarik, V.J.; Prelec, K.
1990-07-17
An intense, steady state, low emittance electron beam generator is formed by operating a hollow cathode discharge plasma source at critical levels in combination with an extraction electrode and a target electrode that are operable to extract a beam of fast primary electrons from the plasma source through a negatively biased grid that is critically operated to repel bulk electrons toward the plasma source while allowing the fast primary electrons to move toward the target in the desired beam that can be successfully transported for relatively large distances, such as one or more meters away from the plasma source. 2 figs.
Inhibiting cytosolic translation and autophagy improves health in mitochondrial disease
Peng, Min; Ostrovsky, Julian; Kwon, Young Joon; Polyak, Erzsebet; Licata, Joseph; Tsukikawa, Mai; Marty, Eric; Thomas, Jeffrey; Felix, Carolyn A.; Xiao, Rui; Zhang, Zhe; Gasser, David L.; Argon, Yair; Falk, Marni J.
2015-01-01
Mitochondrial respiratory chain (RC) disease therapies directed at intra-mitochondrial pathology are largely ineffective. Recognizing that RC dysfunction invokes pronounced extra-mitochondrial transcriptional adaptations, particularly involving dysregulated translation, we hypothesized that translational dysregulation is itself contributing to the pathophysiology of RC disease. Here, we investigated the activities, and effects from direct inhibition, of a central translational regulator (mTORC1) and its downstream biological processes in diverse genetic and pharmacological models of RC disease. Our data identify novel mechanisms underlying the cellular pathogenesis of RC dysfunction, including the combined induction of proteotoxic stress, the ER stress response and autophagy. mTORC1 inhibition with rapamycin partially ameliorated renal disease in B6.Pdss2kd/kd mice with complexes I–III/II–III deficiencies, improved viability and mitochondrial physiology in gas-1(fc21) nematodes with complex I deficiency, and rescued viability across a variety of RC-inhibited human cells. Even more effective was probucol, a PPAR-activating anti-lipid drug that we show also inhibits mTORC1. However, directly inhibiting mTORC1-regulated downstream activities yielded the most pronounced and sustained benefit. Partial inhibition of translation by cycloheximide, or of autophagy by lithium chloride, rescued viability, preserved cellular respiratory capacity and induced mitochondrial translation and biogenesis. Cycloheximide also ameliorated proteotoxic stress via a uniquely selective reduction of cytosolic protein translation. RNAseq-based transcriptome profiling of treatment effects in gas-1(fc21) mutants provide further evidence that these therapies effectively restored altered translation and autophagy pathways toward that of wild-type animals. Overall, partially inhibiting cytosolic translation and autophagy offer novel treatment strategies to improve health across the diverse
Inhibiting cytosolic translation and autophagy improves health in mitochondrial disease.
Peng, Min; Ostrovsky, Julian; Kwon, Young Joon; Polyak, Erzsebet; Licata, Joseph; Tsukikawa, Mai; Marty, Eric; Thomas, Jeffrey; Felix, Carolyn A; Xiao, Rui; Zhang, Zhe; Gasser, David L; Argon, Yair; Falk, Marni J
2015-09-01
Mitochondrial respiratory chain (RC) disease therapies directed at intra-mitochondrial pathology are largely ineffective. Recognizing that RC dysfunction invokes pronounced extra-mitochondrial transcriptional adaptations, particularly involving dysregulated translation, we hypothesized that translational dysregulation is itself contributing to the pathophysiology of RC disease. Here, we investigated the activities, and effects from direct inhibition, of a central translational regulator (mTORC1) and its downstream biological processes in diverse genetic and pharmacological models of RC disease. Our data identify novel mechanisms underlying the cellular pathogenesis of RC dysfunction, including the combined induction of proteotoxic stress, the ER stress response and autophagy. mTORC1 inhibition with rapamycin partially ameliorated renal disease in B6.Pdss2(kd/kd) mice with complexes I-III/II-III deficiencies, improved viability and mitochondrial physiology in gas-1(fc21) nematodes with complex I deficiency, and rescued viability across a variety of RC-inhibited human cells. Even more effective was probucol, a PPAR-activating anti-lipid drug that we show also inhibits mTORC1. However, directly inhibiting mTORC1-regulated downstream activities yielded the most pronounced and sustained benefit. Partial inhibition of translation by cycloheximide, or of autophagy by lithium chloride, rescued viability, preserved cellular respiratory capacity and induced mitochondrial translation and biogenesis. Cycloheximide also ameliorated proteotoxic stress via a uniquely selective reduction of cytosolic protein translation. RNAseq-based transcriptome profiling of treatment effects in gas-1(fc21) mutants provide further evidence that these therapies effectively restored altered translation and autophagy pathways toward that of wild-type animals. Overall, partially inhibiting cytosolic translation and autophagy offer novel treatment strategies to improve health across the diverse array
Steady state phreatic surfaces in sloping aquifers
NASA Astrophysics Data System (ADS)
LoáIciga, Hugo A.
2005-08-01
Steady state groundwater flow driven by constant recharge in an unconfined aquifer overlying sloping bedrock is shown to be represented, using the Dupuit approximation, by an ordinary differential equation of the Abel type y(x) · y'(x) + a · y(x) + x = 0, whose analytical solution is derived in this work. This article first investigates the case of zero saturated thickness at the upstream boundary, a flow system reminiscent of perched groundwater created by percolation of precipitation or irrigation in a sloping aquifer fully draining at its downstream boundary. A variant of this flow system occurs when the phreatic surface mounds and produces groundwater discharge toward the upstream boundary. This variant is a generalization of the classical groundwater flow problem involving two lakes connected by an aquifer, the latter being on sloping terrain in this instance. Analytical solutions for the phreatic surface's steady state geometry are derived for the case of monotonically declining hydraulic head as well as for the case of a mounded phreatic surface. These solutions are of practical interest in drainage studies, slope stability, and runoff formation investigations. It is shown that the flow factor a = -? tan β (where K, N, and tan β are the hydraulic conductivity, vertical recharge, and aquifer slope, respectively) has a commanding role on the phreatic surface's solutions. Two computational examples illustrate the implementation of this article's results.
Steady state phreatic surfaces in sloping aquifers
NASA Astrophysics Data System (ADS)
Loáiciga, Hugo A.
2005-08-01
Steady state groundwater flow driven by constant recharge in an unconfined aquifer overlying sloping bedrock is shown to be represented, using the Dupuit approximation, by an ordinary differential equation of the Abel type y(x) . y'(x) + a . y(x) + x = 0, whose analytical solution is derived in this work. This article first investigates the case of zero saturated thickness at the upstream boundary, a flow system reminiscent of perched groundwater created by percolation of precipitation or irrigation in a sloping aquifer fully draining at its downstream boundary. A variant of this flow system occurs when the phreatic surface mounds and produces groundwater discharge toward the upstream boundary. This variant is a generalization of the classical groundwater flow problem involving two lakes connected by an aquifer, the latter being on sloping terrain in this instance. Analytical solutions for the phreatic surface's steady state geometry are derived for the case of monotonically declining hydraulic head as well as for the case of a mounded phreatic surface. These solutions are of practical interest in drainage studies, slope stability, and runoff formation investigations. It is shown that the flow factor a = -$\\sqrt{{\\rm K}/{\\rm N} tan β (where K, N, and tan β are the hydraulic conductivity, vertical recharge, and aquifer slope, respectively) has a commanding role on the phreatic surface's solutions. Two computational examples illustrate the implementation of this article's results.
An Intuitive Approach to Steady-State Kinetics.
ERIC Educational Resources Information Center
Raines, Ronald T.; Hansen, David E.
1988-01-01
Attempts to provide an intuitive understanding of steady state kinetics. Discusses the meaning of steady state and uses free energy profiles to illustrate and follow complex kinetic and thermodynamic relationships. Provides examples with explanations. (MVL)
High power steady state MPD thrusters
NASA Astrophysics Data System (ADS)
Auweter-Kurtz, Monika; Habiger, Harald; Kurtz, Helmut; Schrade, Herbert; Sleziona, Cristian
1993-04-01
At the Institut fuer Raumfahrtsysteme (IRS) rotation symmetric magnetoplasmadynamic thrusters with self induced magnetic fields are investigated at high current levels in a steady state operation mode. MPD thrusters with different geometrics were compared, and the influence of mass flow rate and power input on the operating conditions of the thrusters explored. By optical and probe measurements, a systematic investigation of the plasma plume has been started. The investigation of the various instabilities of the arc and the plasma flow appearing at high power levels was continued. The computer code development for the geometry optimization of continuous self-field MPD thrusters, running with argon, was modified by considering higher degrees of ionization, which showed better agreement with the experiment.
Structural analysis of kasugamycin inhibition of translation
Schuwirth, Barbara S; Day, J Michael; Hau, Cathy W; Janssen, Gary R; Dahlberg, Albert E; Cate, Jamie H Doudna; Vila-Sanjurjo, Antón
2008-01-01
The prokaryotic ribosome is an important target of antibiotic action. We determined the X-ray structure of the aminoglycoside kasugamycin (Ksg) in complex with the Escherichia coli 70S ribosome at 3.5-Å resolution. The structure reveals that the drug binds within the messenger RNA channel of the 30S subunit between the universally conserved G926 and A794 nucleotides in 16S ribosomal RNA, which are sites of Ksg resistance. To our surprise, Ksg resistance mutations do not inhibit binding of the drug to the ribosome. The present structural and biochemical results indicate that inhibition by Ksg and Ksg resistance are closely linked to the structure of the mRNA at the junction of the peptidyl-tRNA and exit-tRNA sites (P and E sites). PMID:16998486
Rosenblatt, Marcus; Timmer, Jens; Kaschek, Daniel
2016-01-01
Ordinary differential equation models have become a wide-spread approach to analyze dynamical systems and understand underlying mechanisms. Model parameters are often unknown and have to be estimated from experimental data, e.g., by maximum-likelihood estimation. In particular, models of biological systems contain a large number of parameters. To reduce the dimensionality of the parameter space, steady-state information is incorporated in the parameter estimation process. For non-linear models, analytical steady-state calculation typically leads to higher-order polynomial equations for which no closed-form solutions can be obtained. This can be circumvented by solving the steady-state equations for kinetic parameters, which results in a linear equation system with comparatively simple solutions. At the same time multiplicity of steady-state solutions is avoided, which otherwise is problematic for optimization. When solved for kinetic parameters, however, steady-state constraints tend to become negative for particular model specifications, thus, generating new types of optimization problems. Here, we present an algorithm based on graph theory that derives non-negative, analytical steady-state expressions by stepwise removal of cyclic dependencies between dynamical variables. The algorithm avoids multiple steady-state solutions by construction. We show that our method is applicable to most common classes of biochemical reaction networks containing inhibition terms, mass-action and Hill-type kinetic equations. Comparing the performance of parameter estimation for different analytical and numerical methods of incorporating steady-state information, we show that our approach is especially well-tailored to guarantee a high success rate of optimization. PMID:27243005
Rosenblatt, Marcus; Timmer, Jens; Kaschek, Daniel
2016-01-01
Ordinary differential equation models have become a wide-spread approach to analyze dynamical systems and understand underlying mechanisms. Model parameters are often unknown and have to be estimated from experimental data, e.g., by maximum-likelihood estimation. In particular, models of biological systems contain a large number of parameters. To reduce the dimensionality of the parameter space, steady-state information is incorporated in the parameter estimation process. For non-linear models, analytical steady-state calculation typically leads to higher-order polynomial equations for which no closed-form solutions can be obtained. This can be circumvented by solving the steady-state equations for kinetic parameters, which results in a linear equation system with comparatively simple solutions. At the same time multiplicity of steady-state solutions is avoided, which otherwise is problematic for optimization. When solved for kinetic parameters, however, steady-state constraints tend to become negative for particular model specifications, thus, generating new types of optimization problems. Here, we present an algorithm based on graph theory that derives non-negative, analytical steady-state expressions by stepwise removal of cyclic dependencies between dynamical variables. The algorithm avoids multiple steady-state solutions by construction. We show that our method is applicable to most common classes of biochemical reaction networks containing inhibition terms, mass-action and Hill-type kinetic equations. Comparing the performance of parameter estimation for different analytical and numerical methods of incorporating steady-state information, we show that our approach is especially well-tailored to guarantee a high success rate of optimization. PMID:27243005
Steady State Vapor Bubble in Pool Boiling
NASA Astrophysics Data System (ADS)
Zou, An; Chanana, Ashish; Agrawal, Amit; Wayner, Peter C.; Maroo, Shalabh C.
2016-02-01
Boiling, a dynamic and multiscale process, has been studied for several decades; however, a comprehensive understanding of the process is still lacking. The bubble ebullition cycle, which occurs over millisecond time-span, makes it extremely challenging to study near-surface interfacial characteristics of a single bubble. Here, we create a steady-state vapor bubble that can remain stable for hours in a pool of sub-cooled water using a femtosecond laser source. The stability of the bubble allows us to measure the contact-angle and perform in-situ imaging of the contact-line region and the microlayer, on hydrophilic and hydrophobic surfaces and in both degassed and regular (with dissolved air) water. The early growth stage of vapor bubble in degassed water shows a completely wetted bubble base with the microlayer, and the bubble does not depart from the surface due to reduced liquid pressure in the microlayer. Using experimental data and numerical simulations, we obtain permissible range of maximum heat transfer coefficient possible in nucleate boiling and the width of the evaporating layer in the contact-line region. This technique of creating and measuring fundamental characteristics of a stable vapor bubble will facilitate rational design of nanostructures for boiling enhancement and advance thermal management in electronics.
Inconsistencies in steady-state thermodynamics
NASA Astrophysics Data System (ADS)
Dickman, Ronald; Motai, Ricardo
2014-03-01
We address the issue of extending thermodynamics to nonequilibrium steady states. Using driven stochastic lattice gases, we ask whether consistent definitions of an effective chemical potential μ, and an effective temperature Te, are possible. μ and Te are determined via coexistence, i.e., zero flux of particles and energy between the driven system and a reservoir. In the lattice gas with nearest-neighbor exclusion, temperature is not relevant, and we find that the effective chemical potential, a function of density and drive strength, satisfies the zeroth law, and correctly predicts the densities of coexisting systems. In the Katz-Lebowitz-Spohn driven lattice gas both μ and Te need to be defined. We show analytically that in this case the zeroth law is violated for Metropolis exchange rates, and determine the size of the violations numerically. The zeroth law appears to be violated for generic exchange rates. Remarkably, the system-reservoir coupling proposed by Sasa and Tasaki [J. Stat. Phys. 125, 125 (2006), 10.1007/s10955-005-9021-7] is free of inconsistencies, and the zeroth law holds. This is because the rate depends only on the state of the donor system, and is independent of that of the acceptor.
Steady State Vapor Bubble in Pool Boiling.
Zou, An; Chanana, Ashish; Agrawal, Amit; Wayner, Peter C; Maroo, Shalabh C
2016-01-01
Boiling, a dynamic and multiscale process, has been studied for several decades; however, a comprehensive understanding of the process is still lacking. The bubble ebullition cycle, which occurs over millisecond time-span, makes it extremely challenging to study near-surface interfacial characteristics of a single bubble. Here, we create a steady-state vapor bubble that can remain stable for hours in a pool of sub-cooled water using a femtosecond laser source. The stability of the bubble allows us to measure the contact-angle and perform in-situ imaging of the contact-line region and the microlayer, on hydrophilic and hydrophobic surfaces and in both degassed and regular (with dissolved air) water. The early growth stage of vapor bubble in degassed water shows a completely wetted bubble base with the microlayer, and the bubble does not depart from the surface due to reduced liquid pressure in the microlayer. Using experimental data and numerical simulations, we obtain permissible range of maximum heat transfer coefficient possible in nucleate boiling and the width of the evaporating layer in the contact-line region. This technique of creating and measuring fundamental characteristics of a stable vapor bubble will facilitate rational design of nanostructures for boiling enhancement and advance thermal management in electronics. PMID:26837464
Maximal lactate steady state in Judo
de Azevedo, Paulo Henrique Silva Marques; Pithon-Curi, Tania; Zagatto, Alessandro Moura; Oliveira, João; Perez, Sérgio
2014-01-01
Summary Background: the purpose of this study was to verify the validity of respiratory compensation threshold (RCT) measured during a new single judo specific incremental test (JSIT) for aerobic demand evaluation. Methods: to test the validity of the new test, the JSIT was compared with Maximal Lactate Steady State (MLSS), which is the gold standard procedure for aerobic demand measuring. Eight well-trained male competitive judo players (24.3 ± 7.9 years; height of 169.3 ± 6.7cm; fat mass of 12.7 ± 3.9%) performed a maximal incremental specific test for judo to assess the RCT and performed on 30-minute MLSS test, where both tests were performed mimicking the UchiKomi drills. Results: the intensity at RCT measured on JSIT was not significantly different compared to MLSS (p=0.40). In addition, it was observed high and significant correlation between MLSS and RCT (r=0.90, p=0.002), as well as a high agreement. Conclusions: RCT measured during JSIT is a valid procedure to measure the aerobic demand, respecting the ecological validity of Judo. PMID:25332923
Steady State Vapor Bubble in Pool Boiling
Zou, An; Chanana, Ashish; Agrawal, Amit; Wayner, Peter C.; Maroo, Shalabh C.
2016-01-01
Boiling, a dynamic and multiscale process, has been studied for several decades; however, a comprehensive understanding of the process is still lacking. The bubble ebullition cycle, which occurs over millisecond time-span, makes it extremely challenging to study near-surface interfacial characteristics of a single bubble. Here, we create a steady-state vapor bubble that can remain stable for hours in a pool of sub-cooled water using a femtosecond laser source. The stability of the bubble allows us to measure the contact-angle and perform in-situ imaging of the contact-line region and the microlayer, on hydrophilic and hydrophobic surfaces and in both degassed and regular (with dissolved air) water. The early growth stage of vapor bubble in degassed water shows a completely wetted bubble base with the microlayer, and the bubble does not depart from the surface due to reduced liquid pressure in the microlayer. Using experimental data and numerical simulations, we obtain permissible range of maximum heat transfer coefficient possible in nucleate boiling and the width of the evaporating layer in the contact-line region. This technique of creating and measuring fundamental characteristics of a stable vapor bubble will facilitate rational design of nanostructures for boiling enhancement and advance thermal management in electronics. PMID:26837464
Steady state volcanism - Evidence from eruption histories of polygenetic volcanoes
NASA Technical Reports Server (NTRS)
Wadge, G.
1982-01-01
Cumulative volcano volume curves are presented as evidence for steady-state behavior at certain volcanoes and to develop a model of steady-state volcanism. A minimum criteria of five eruptions over a year was chosen to characterize a steady-state volcano. The subsequent model features a constant head of magmatic pressure from a reservoir supplied from depth, a sawtooth curve produced by the magma arrivals or discharge from the subvolcanic reservoir, large volume eruptions with long repose periods, and conditions of nonsupply of magma. The behavior of Mts. Etna, Nyamuragira, and Kilauea are described and show continuous levels of plasma output resulting in cumulative volume increases. Further discussion is made of steady-state andesitic and dacitic volcanism, long term patterns of the steady state, and magma storage, and the lack of a sufficient number of steady-state volcanoes in the world is taken as evidence that further data is required for a comprehensive model.
CA_OPPUSST - Cantera OPUS Steady State
Energy Science and Technology Software Center (ESTSC)
2005-03-01
The Cantera Opus Steady State (ca-opusst) applications solves steady reacting flow problems in opposed-flow geometries. It is a 1-0 application that represents axisymmetnc 3-0 physical systems that can be reduced via a similarity transformation to a 1-0 mathematical representation. The code contain solutions of the general dynamic equations for the particle distribution functions using a sectional model to describe the particle distribution function. Operators for particle nucleation, coagulation, condensation (i.e., growth/etching via reactions with themore » gas ambient), internal particle reactions. particle transport due to convection and due to molecular transport, are included in the particle general dynamics equation. Heat transport due to radiation exchange of the environment with particles in local thermal equilibrium to the surrounding gas will be included in the enthalpy conservation equation that is solved for the coupled gas! particle system in an upcoming version of the code due in June 2005. The codes use Cantera , a C++ Cal Tech code, for determination of gas phase species transport, reaction, and thermodynamics physical properties and source terms. The Codes use the Cantera Aerosol Dynamics Simulator (CADS) package, a general library for aerosol modeling, to calculate properties and source terms for the aerosol general dynamics equation, including particle formation from gas phase reactions, particle surface chemistry (growth and oxidation), bulk particle chemistry, particle transport by Brownian diffusion, thermophoresis, and diffusiophoresis, and thermal radiative transport involving particles. Also included are post-processing programs, cajost and cajrof, to extract ascii data from binary output files to produce plots.« less
Inhibition of insulin synthesis by cyproheptadine: effects on translation.
Hawkins, Belinda S; Fischer, Lawrence J
2004-06-01
The antihistaminic, antiserotonergic drug cyproheptadine (CPH) is known to inhibit insulin synthesis in vivo and in vitro. This inhibition of insulin synthesis occurs without a commensurate decrease in preproinsulin mRNA (PPImRNA) levels, suggesting a post-transcriptional mechanism of action. The goal of the present study was to investigate the direct effects of CPH on translation of PPImRNA in RINm5F cells. Results produced using a subcellular fractionation technique followed by real-time RT-PCR indicated that a 2-h 10 microM CPH treatment resulted in a decrease in the percentage of cellular PPImRNA associated with endoplasmic reticulum (ER) bound polysomes and increases in the percentages of translationally uninitiated and monoribosome-associated PPImRNA. These alterations in PPImRNA distribution were found to be concentration-dependent, chemical structure-specific, and reversible with a time course consistent with a previously reported CPH-induced inhibition of insulin synthesis. Further investigations to examine the possible effect of CPH on translation initiation were then undertaken by examining the phosphorylation state of the translation initiation factors eIF2alpha, eIF4E, and 4E-BP1 after CPH treatment. CPH (10 microM) treatment resulted in increased phosphorylation of eIF2alpha, and decreased phosphorylation of both eIF4E and 4E-BP1. These changes are all consistent with decreased initiation of translation. Taken together, these results suggest that the inhibition of insulin synthesis known to be elicited by CPH treatment of RINm5F cells and intact animals involves alterations of initiation factor phosphorylation leading to a decrease in insulin synthesis and of stored insulin in insulin-producing cells. PMID:15056814
Defining Features of Steady-State Timbres
NASA Astrophysics Data System (ADS)
Hall, Michael D.
1995-01-01
Three experiments were conducted to define steady -state features of timbre for a group of well-trained musicians. Experiment 1 evaluated whether or not pairs of three critical dimensions of timbre--spectral slope (6 or 12 dB/octave), formant structure (/a/ or /i/ vowel), and inharmonicity of partials (harmonic or inharmonic)--were processed in a separable or integral fashion. Accuracy and speed for classification of values along one dimension were examined under different conditions of variability along a second dimension (fixed, correlated, or orthogonal). Spectral slope and formant structure were integral, with classification speed for the target dimension depending upon variability along the orthogonal dimension. In contrast, evidence of asymmetric separability was obtained for inharmonicity. Classification speed for slope and formant structure did not depend on inharmonicity, whereas RT for the target dimension of inharmonicity was strongly influenced by variability along either slope or formant structure. Since the results of Experiment 1 provided a basis for manipulating spectral slope and formant structure as a single feature, these dimensions were correlated in Experiment 2. Subjects searched for targets containing potential features of timbre within arrays of 1-4 inharmonic distractor pitches. Distractors were homogeneous with respect to the dimensions of timbre. When targets had /a/ formants with shallow spectral slopes, search time increased nonlinearly with array size in a manner consistent with the parallel processing of items, and thus feature search. Feature search was not obtained for targets with /i/ formants and steep slopes. Thus, the feature was coded as the presence or absence of /a/ formants with shallow spectral slopes. A search task using heterogeneous distractor values along slope/formant structure was used in Experiment 3 to evaluate whether or not the feature of timbre and pitch were automatically conjoined (integral). Search times for
Diehl, S; Zambrano, J; Carlsson, B
2016-01-01
A reduced model of a completely stirred-tank bioreactor coupled to a settling tank with recycle is analyzed in its steady states. In the reactor, the concentrations of one dominant particulate biomass and one soluble substrate component are modelled. While the biomass decay rate is assumed to be constant, growth kinetics can depend on both substrate and biomass concentrations, and optionally model substrate inhibition. Compressive and hindered settling phenomena are included using the Bürger-Diehl settler model, which consists of a partial differential equation. Steady-state solutions of this partial differential equation are obtained from an ordinary differential equation, making steady-state analysis of the entire plant difficult. A key result showing that the ordinary differential equation can be replaced with an approximate algebraic equation simplifies model analysis. This algebraic equation takes the location of the sludge-blanket during normal operation into account, allowing for the limiting flux capacity caused by compressive settling to easily be included in the steady-state mass balance equations for the entire plant system. This novel approach grants the possibility of more realistic solutions than other previously published reduced models, comprised of yet simpler settler assumptions. The steady-state concentrations, solids residence time, and the wastage flow ratio are functions of the recycle ratio. Solutions are shown for various growth kinetics; with different values of biomass decay rate, influent volumetric flow, and substrate concentration. PMID:26476681
The steady-state assumption in oscillating and growing systems.
Reimers, Alexandra-M; Reimers, Arne C
2016-10-01
The steady-state assumption, which states that the production and consumption of metabolites inside the cell are balanced, is one of the key aspects that makes an efficient analysis of genome-scale metabolic networks possible. It can be motivated from two different perspectives. In the time-scales perspective, we use the fact that metabolism is much faster than other cellular processes such as gene expression. Hence, the steady-state assumption is derived as a quasi-steady-state approximation of the metabolism that adapts to the changing cellular conditions. In this article we focus on the second perspective, stating that on the long run no metabolite can accumulate or deplete. In contrast to the first perspective it is not immediately clear how this perspective can be captured mathematically and what assumptions are required to obtain the steady-state condition. By presenting a mathematical framework based on the second perspective we demonstrate that the assumption of steady-state also applies to oscillating and growing systems without requiring quasi-steady-state at any time point. However, we also show that the average concentrations may not be compatible with the average fluxes. In summary, we establish a mathematical foundation for the steady-state assumption for long time periods that justifies its successful use in many applications. Furthermore, this mathematical foundation also pinpoints unintuitive effects in the integration of metabolite concentrations using nonlinear constraints into steady-state models for long time periods. PMID:27363728
Cotranslational Coat Protein-Mediated Inhibition of Potyviral RNA Translation
Besong-Ndika, Jane; Ivanov, Konstantin I.; Hafrèn, Anders; Michon, Thierry
2015-01-01
ABSTRACT Potato virus A (PVA) is a single-stranded positive-sense RNA virus and a member of the family Potyviridae. The PVA coat protein (CP) has an intrinsic capacity to self-assemble into filamentous virus-like particles, but the mechanism responsible for the initiation of viral RNA encapsidation in vivo remains unclear. Apart from virion assembly, PVA CP is also involved in the inhibition of viral RNA translation. In this study, we show that CP inhibits PVA RNA translation in a dose-dependent manner, through a mechanism involving the CP-encoding region. Analysis of this region, however, failed to identify any RNA secondary structure(s) preferentially recognized by CP, suggesting that the inhibition depends on CP-CP rather than CP-RNA interactions. In agreement with this possibility, insertion of an in-frame stop codon upstream of the CP sequence led to a marked decrease in the inhibition of viral RNA translation. Based on these results, we propose a model in which the cotranslational interactions between excess CP accumulating in trans and CP translated from viral RNA in cis are required to initiate the translational repression. This model suggests a mechanism for how viral RNA can be sequestered from translation and specifically selected for encapsidation at the late stages of viral infection. IMPORTANCE The main functions of the CP during potyvirus infection are to protect viral RNA from degradation and to transport it locally, systemically, and from host to host. Although virion assembly is a key step in the potyviral infectious cycle, little is known about how it is initiated and how viral RNA is selected for encapsidation. The results presented here suggest that CP-CP rather than CP-RNA interactions are predominantly involved in the sequestration of viral RNA away from translation. We propose that the cotranslational nature of these interactions may represent a mechanism for the selection of viral RNA for encapsidation. A better understanding of the
Steady State Growth of Continental Crust?
NASA Astrophysics Data System (ADS)
Bowring, S. A.; Bauer, A.; Dudas, F. O.; Schoene, B.; McLean, N. M.
2012-12-01
any age. If one accepts that the probability of preserving old crust decreases with increasing age, the few exposures of rocks older than 3.5 Ga should not be surprising. The thickness and compositional differences between Archean and younger lithospheric mantle are not fully understood nor is the role of thicker buoyant mantle in preserving continental crust; these lead to the question of whether the preserved rock record is representative of what formed. It is notable that the oldest known rocks, the ca. 4.0 Ga Acasta Gneisses, are tonalities-granodiorites-granites with evidence for the involvement of even older crust and that the oldest detrital zircons from Australia (ca. 4.0-4.4 Ga) are thought to have been derived from granitoid sources. The global Hf and Nd isotope databases are compatible with both depleted and enriched sources being present from at least 4.0 Ga to the present and that the lack of evolution of the MORB source or depleted mantle is due to recycling of continental crust throughout earth history. Using examples from the Slave Province and southern Africa, we argue that Armstrong's concept of steady state crustal growth and recycling via plate tectonics still best explains the modern geological and geochemical data.
Steady states and stability in metabolic networks without regulation.
Ivanov, Oleksandr; van der Schaft, Arjan; Weissing, Franz J
2016-07-21
Metabolic networks are often extremely complex. Despite intensive efforts many details of these networks, e.g., exact kinetic rates and parameters of metabolic reactions, are not known, making it difficult to derive their properties. Considerable effort has been made to develop theory about properties of steady states in metabolic networks that are valid for any values of parameters. General results on uniqueness of steady states and their stability have been derived with specific assumptions on reaction kinetics, stoichiometry and network topology. For example, deep results have been obtained under the assumptions of mass-action reaction kinetics, continuous flow stirred tank reactors (CFSTR), concordant reaction networks and others. Nevertheless, a general theory about properties of steady states in metabolic networks is still missing. Here we make a step further in the quest for such a theory. Specifically, we study properties of steady states in metabolic networks with monotonic kinetics in relation to their stoichiometry (simple and general) and the number of metabolites participating in every reaction (single or many). Our approach is based on the investigation of properties of the Jacobian matrix. We show that stoichiometry, network topology, and the number of metabolites that participate in every reaction have a large influence on the number of steady states and their stability in metabolic networks. Specifically, metabolic networks with single-substrate-single-product reactions have disconnected steady states, whereas in metabolic networks with multiple-substrates-multiple-product reactions manifolds of steady states arise. Metabolic networks with simple stoichiometry have either a unique globally asymptotically stable steady state or asymptotically stable manifolds of steady states. In metabolic networks with general stoichiometry the steady states are not always stable and we provide conditions for their stability. In order to demonstrate the biological
Steady-state solidification of aqueous ammonium chloride
NASA Astrophysics Data System (ADS)
Peppin, S. S. L.; Huppert, Herbert E.; Worster, M. Grae
We report on a series of experiments in which a Hele-Shaw cell containing aqueous solutions of NH4Cl was translated at prescribed rates through a steady temperature gradient. The salt formed the primary solid phase of a mushy layer as the solution solidified, with the salt-depleted residual fluid driving buoyancy-driven convection and the development of chimneys in the mushy layer. Depending on the operating conditions, several morphological transitions occurred. A regime diagram is presented quantifying these transitions as a function of freezing rate and the initial concentration of the solution. In general, for a given concentration, increasing the freezing rate caused the steady-state system to change from a convecting mushy layer with chimneys to a non-convecting mushy layer below a relatively quiescent liquid, and then to a much thinner mushy layer separated from the liquid by a region of active secondary nucleation. At higher initial concentrations the second of these states did not occur. At lower concentrations, but still above the eutectic, the mushy layer disappeared. A simple mathematical model of the system is developed which compares well with the experimental measurements of the intermediate, non-convecting state and serves as a benchmark against which to understand some of the effects of convection. Movies are available with the online version of the paper.
Measurement of non-steady-state free fatty acid turnover
Jensen, M.D.; Heiling, V.; Miles, J.M. )
1990-01-01
The accuracy of non-steady-state equations for measuring changes in free fatty acid rate of appearance (Ra) is unknown. In the present study, endogenous lipolysis (traced with ({sup 14}C)-linoleate) was pharmacologically suppressed in six conscious mongrel dogs. A computer-responsive infusion pump was then used to deliver an intravenous oleic acid emulsion in both constant and linear gradient infusion modes. Both non-steady-state equations with various effective volumes of distribution (V) and steady-state equations were used to measure oleate Ra (({sup 14}C)oleate). Endogenous lipolysis did not change during the experiment. When oleate Ra increased in a linear gradient fashion, only non-steady-state equations with a large (150 ml/kg) V resulted in erroneous values (9% overestimate, P less than 0.05). In contrast, when oleate Ra decreased in a similar fashion, steady-state and standard non-steady-state equations (V = plasma volume = 50 ml/kg) overestimated total oleate Ra (18 and 7%, P less than 0.001 and P less than 0.05, respectively). Overall, non-steady-state equations with an effective V of 90 ml/kg (1.8 x plasma volume) allowed the most accurate estimates of oleate Ra.
Autonomous quantum thermal machine for generating steady-state entanglement
NASA Astrophysics Data System (ADS)
Bohr Brask, Jonatan; Haack, Géraldine; Brunner, Nicolas; Huber, Marcus
2015-11-01
We discuss a simple quantum thermal machine for the generation of steady-state entanglement between two interacting qubits. The machine is autonomous in the sense that it uses only incoherent interactions with thermal baths, but no source of coherence or external control. By weakly coupling the qubits to thermal baths at different temperatures, inducing a heat current through the system, steady-state entanglement is generated far from thermal equilibrium. Finally, we discuss two possible implementations, using superconducting flux qubits or a semiconductor double quantum dot. Experimental prospects for steady-state entanglement are promising in both systems.
Steady-state decoupling and design of linear multivariable systems
NASA Technical Reports Server (NTRS)
Thaler, G. J.
1974-01-01
A constructive criterion for decoupling the steady states of a linear time-invariant multivariable system is presented. This criterion consists of a set of inequalities which, when satisfied, will cause the steady states of a system to be decoupled. Stability analysis and a new design technique for such systems are given. A new and simple connection between single-loop and multivariable cases is found. These results are then applied to the compensation design for NASA STOL C-8A aircraft. Both steady-state decoupling and stability are justified through computer simulations.
A Note on Equations for Steady-State Optimal Landscapes
Liu, H.H.
2010-06-15
Based on the optimality principle (that the global energy expenditure rate is at its minimum for a given landscape under steady state conditions) and calculus of variations, we have derived a group of partial differential equations for describing steady-state optimal landscapes without explicitly distinguishing between hillslopes and channel networks. Other than building on the well-established Mining's equation, this work does not rely on any empirical relationships (such as those relating hydraulic parameters to local slopes). Using additional constraints, we also theoretically demonstrate that steady-state water depth is a power function of local slope, which is consistent with field data.
Einstein's steady-state theory: an abandoned model of the cosmos
NASA Astrophysics Data System (ADS)
O'Raifeartaigh, Cormac; McCann, Brendan; Nahm, Werner; Mitton, Simon
2014-09-01
We present a translation and analysis of an unpublished manuscript by Albert Einstein in which he attempted to construct a `steady-state' model of the universe. The manuscript, which appears to have been written in early 1931, demonstrates that Einstein once explored a cosmic model in which the mean density of matter in an expanding universe is maintained constant by the continuous formation of matter from empty space. This model is very different to previously known Einsteinian models of the cosmos (both static and dynamic) but anticipates the later steady-state cosmology of Hoyle, Bondi and Gold in some ways. We find that Einstein's steady-state model contains a fundamental flaw and suggest that it was abandoned for this reason. We also suggest that he declined to explore a more sophisticated version because he found such theories rather contrived. The manuscript is of historical interest because it reveals that Einstein debated between steady-state and evolving models of the cosmos decades before a similar debate took place in the cosmological community.
Loriaux, Paul Michael; Tesler, Glenn; Hoffmann, Alexander
2013-01-01
The steady states of cells affect their response to perturbation. Indeed, diagnostic markers for predicting the response to therapeutic perturbation are often based on steady state measurements. In spite of this, no method exists to systematically characterize the relationship between steady state and response. Mathematical models are established tools for studying cellular responses, but characterizing their relationship to the steady state requires that it have a parametric, or analytical, expression. For some models, this expression can be derived by the King-Altman method. However, King-Altman requires that no substrate act as an enzyme, and is therefore not applicable to most models of signal transduction. For this reason we developed py-substitution, a simple but general method for deriving analytical expressions for the steady states of mass action models. Where the King-Altman method is applicable, we show that py-substitution yields an equivalent expression, and at comparable efficiency. We use py-substitution to study the relationship between steady state and sensitivity to the anti-cancer drug candidate, dulanermin (recombinant human TRAIL). First, we use py-substitution to derive an analytical expression for the steady state of a published model of TRAIL-induced apoptosis. Next, we show that the amount of TRAIL required for cell death is sensitive to the steady state concentrations of procaspase 8 and its negative regulator, Bar, but not the other procaspase molecules. This suggests that activation of caspase 8 is a critical point in the death decision process. Finally, we show that changes in the threshold at which TRAIL results in cell death is not always equivalent to changes in the time of death, as is commonly assumed. Our work demonstrates that an analytical expression is a powerful tool for identifying steady state determinants of the cellular response to perturbation. All code is available at http://signalingsystems.ucsd.edu/models-and-code/ or
An Operational Definition of the Steady State in Enzyme Kinetics.
ERIC Educational Resources Information Center
Barnsley, E. A.
1990-01-01
The Briggs-Haldane assumption is used as the basis for the development of a kinetic model for enzyme catalysis. An alternative definition of the steady state and examples of realistic mechanisms are provided. (KR)
Phencyclidine Disrupts the Auditory Steady State Response in Rats
Leishman, Emma; O’Donnell, Brian F.; Millward, James B.; Vohs, Jenifer L.; Rass, Olga; Krishnan, Giri P.; Bolbecker, Amanda R.; Morzorati, Sandra L.
2015-01-01
The Auditory Steady-State Response (ASSR) in the electroencephalogram (EEG) is usually reduced in schizophrenia (SZ), particularly to 40 Hz stimulation. The gamma frequency ASSR deficit has been attributed to N-methyl-D-aspartate receptor (NMDAR) hypofunction. We tested whether the NMDAR antagonist, phencyclidine (PCP), produced similar ASSR deficits in rats. EEG was recorded from awake rats via intracranial electrodes overlaying the auditory cortex and at the vertex of the skull. ASSRs to click trains were recorded at 10, 20, 30, 40, 50, and 55 Hz and measured by ASSR Mean Power (MP) and Phase Locking Factor (PLF). In Experiment 1, the effect of different subcutaneous doses of PCP (1.0, 2.5 and 4.0 mg/kg) on the ASSR in 12 rats was assessed. In Experiment 2, ASSRs were compared in PCP treated rats and control rats at baseline, after acute injection (5 mg/kg), following two weeks of subchronic, continuous administration (5 mg/kg/day), and one week after drug cessation. Acute administration of PCP increased PLF and MP at frequencies of stimulation below 50 Hz, and decreased responses at higher frequencies at the auditory cortex site. Acute administration had a less pronounced effect at the vertex site, with a reduction of either PLF or MP observed at frequencies above 20 Hz. Acute effects increased in magnitude with higher doses of PCP. Consistent effects were not observed after subchronic PCP administration. These data indicate that acute administration of PCP, a NMDAR antagonist, produces an increase in ASSR synchrony and power at low frequencies of stimulation and a reduction of high frequency (> 40 Hz) ASSR activity in rats. Subchronic, continuous administration of PCP, on the other hand, has little impact on ASSRs. Thus, while ASSRs are highly sensitive to NMDAR antagonists, their translational utility as a cross-species biomarker for NMDAR hypofunction in SZ and other disorders may be dependent on dose and schedule. PMID:26258486
On the time to steady state: insights from numerical modeling
NASA Astrophysics Data System (ADS)
Goren, L.; Willett, S.; McCoy, S. W.; Perron, J.
2013-12-01
How fast do fluvial landscapes approach steady state after an application of tectonic or climatic perturbation? While theory and some numerical models predict that the celerity of the advective wave (knickpoint) controls the response time for perturbations, experiments and other landscape evolution models demonstrate that the time to steady state is much longer than the theoretically predicted response time. We posit that the longevity of transient features and the time to steady state are controlled by the stability of the topology and geometry of channel networks. Evolution of a channel network occurs by a combination of discrete capture events and continuous migration of water divides, processes, which are difficult to represent accurately in landscape evolution models. We therefore address the question of the time to steady state using the DAC landscape evolution model that solves accurately for the location of water divides, using a combination of analytical solution for hillslopes and low-order channels together with a numerical solution for higher order channels. DAC also includes an explicit capture criterion. We have tested fundamental predictions from DAC and show that modeled networks reproduce natural network characteristics such as the Hack's exponent and coefficient and the fractal dimension. We define two steady-state criteria: a topographic steady state, defined by global, pointwise steady elevation, and a topological steady state defined as the state in which no further reorganization of the drainage network takes place. Analyzing block uplift simulations, we find that the time to achieve either topographic or topological steady state exceeds by an order of magnitude the theoretical response time of the fluvial network. The longevity of the transient state is the result of the area feedback, by which, migration of a divide changes the local contributing area. This change propagates downstream as a slope adjustment, forcing further divide migrations
Multiple steady states in coupled flow tank reactors
NASA Astrophysics Data System (ADS)
Hunt, Katharine L. C.; Kottalam, J.; Hatlee, Michael D.; Ross, John
1992-05-01
Coupling between continuous-flow, stirred tank reactors (CSTR's), each having multiple steady states, can produce new steady states with different concentrations of the chemical species in each of the coupled tanks. In this work, we identify a kinetic potential ψ that governs the deterministic time evolution of coupled tank reactors, when the reaction mechanism permits a single-variable description of the states of the individual tanks; examples include the iodate-arsenous acid reaction, a cubic model suggested by Noyes, and two quintic models. Stable steady states correspond to minima of ψ, and unstable steady states to maxima or saddle points; marginally stable states typically correspond to saddle-node points. We illustrate the variation in ψ due to changes in the rate constant for external material intake (k0) and for exchange between tanks (kx). For fixed k0 values, we analyze the changes in numbers and types of steady states as kx increases from zero. We show that steady states disappear by pairwise coalescence; we also show that new steady states may appear with increasing kx, when the reaction mechanism is sufficiently complex. For fixed initial conditions, the steady state ultimately reached in a mixing experiment may depend on the exchange rate constant as a function of time, kx(t) : Adiabatic mixing is obtained in the limit of slow changes in kx(t) and instantaneous mixing in the limit as kx(t)→∞ while t remains small. Analyses based on the potential ψ predict the outcome of mixing experiments for arbitrary kx(t). We show by explicit counterexamples that a prior theory developed by Noyes does not correctly predict the instability points or the transitions between steady states of coupled tanks, to be expected in mixing experiments. We further show that the outcome of such experiments is not connected to the relative stability of steady states in individual tank reactors. We find that coupling may effectively stabilize the tanks. We provide
Steady state in a gas of inelastic rough spheres heated by a uniform stochastic force
NASA Astrophysics Data System (ADS)
Vega Reyes, Francisco; Santos, Andrés
2015-11-01
We study here the steady state attained in a granular gas of inelastic rough spheres that is subject to a spatially uniform random volume force. The stochastic force has the form of the so-called white noise and acts by adding impulse to the particle translational velocities. We work out an analytical solution of the corresponding velocity distribution function from a Sonine polynomial expansion that displays energy non-equipartition between the translational and rotational modes, translational and rotational kurtoses, and translational-rotational velocity correlations. By comparison with a numerical solution of the Boltzmann kinetic equation (by means of the direct simulation Monte Carlo method), we show that our analytical solution provides a good description that is quantitatively very accurate in certain ranges of inelasticity and roughness. We also find three important features that make the forced granular gas steady state very different from the homogeneous cooling state (attained by an unforced granular gas). First, the marginal velocity distributions are always close to a Maxwellian. Second, there is a continuous transition to the purely smooth limit (where the effects of particle rotations are ignored). And third, the angular translational-rotational velocity correlations show a preference for a quasiperpendicular mutual orientation (which is called "lifted-tennis-ball" behavior).
Steady state in a gas of inelastic rough spheres heated by a uniform stochastic force
Vega Reyes, Francisco Santos, Andrés
2015-11-15
We study here the steady state attained in a granular gas of inelastic rough spheres that is subject to a spatially uniform random volume force. The stochastic force has the form of the so-called white noise and acts by adding impulse to the particle translational velocities. We work out an analytical solution of the corresponding velocity distribution function from a Sonine polynomial expansion that displays energy non-equipartition between the translational and rotational modes, translational and rotational kurtoses, and translational-rotational velocity correlations. By comparison with a numerical solution of the Boltzmann kinetic equation (by means of the direct simulation Monte Carlo method), we show that our analytical solution provides a good description that is quantitatively very accurate in certain ranges of inelasticity and roughness. We also find three important features that make the forced granular gas steady state very different from the homogeneous cooling state (attained by an unforced granular gas). First, the marginal velocity distributions are always close to a Maxwellian. Second, there is a continuous transition to the purely smooth limit (where the effects of particle rotations are ignored). And third, the angular translational-rotational velocity correlations show a preference for a quasiperpendicular mutual orientation (which is called “lifted-tennis-ball” behavior)
Poissonian steady states: From stationary densities to stationary intensities
NASA Astrophysics Data System (ADS)
Eliazar, Iddo
2012-10-01
Markov dynamics are the most elemental and omnipresent form of stochastic dynamics in the sciences, with applications ranging from physics to chemistry, from biology to evolution, and from economics to finance. Markov dynamics can be either stationary or nonstationary. Stationary Markov dynamics represent statistical steady states and are quantified by stationary densities. In this paper, we generalize the notion of steady state to the case of general Markov dynamics. Considering an ensemble of independent motions governed by common Markov dynamics, we establish that the entire ensemble attains Poissonian steady states which are quantified by stationary Poissonian intensities and which hold valid also in the case of nonstationary Markov dynamics. The methodology is applied to a host of Markov dynamics, including Brownian motion, birth-death processes, random walks, geometric random walks, renewal processes, growth-collapse dynamics, decay-surge dynamics, Ito diffusions, and Langevin dynamics.
Evaluation of a steady state MPD thruster test facility
Reed, C.B.; Carlson, L.W.; Herman, H.; Doss, E.D.; Kilgore, O.
1985-01-01
The successful development of multimegawatt MPD thrusters depends, to a great extent, on testing them under steady state high altitude space conditions. Steady state testing is required to provide thermal characteristics, life cycle, erosion, and other essential data. the major technical obstacle for ground testing of MPD thrusters in a space simulation facility is the inability of state-of-the-art vacuum systems to handle the tremendous pumping speeds required for multimegawatt MPD thrusters. This is true for other types of electric propulsion devices as well. This paper discusses the results of the first phase of an evaluation of steady state MPD thruster test facilities. The first phase addresses the conceptual design of vacuum systems required to support multimegawatt MPD thruster testing. Three advanced pumping system concepts were evaluated and are presented here.
From Steady-State To Cyclic Metal Forming Processes
NASA Astrophysics Data System (ADS)
Montmitonnet, Pierre
2007-05-01
Continuous processes often exhibit a high proportion of steady state, and have been modeled with steady-state formulations for thirty years, resulting in very CPU-time efficient computations. On the other hand, incremental forming processes generally remain a challenge for FEM software, because of the local nature of deformation compared with the size of the part to be formed, and of the large number of deformation steps needed. Among them however, certain semi-continuous metal forming processes can be characterized as periodic, or cyclic. In this case, an efficient computational strategy can be derived from the ideas behind the steady-state models. This will be illustrated with the example of pilgering, a seamless tube cold rolling process.
40 Hz Auditory Steady-State Response Is a Pharmacodynamic Biomarker for Cortical NMDA Receptors.
Sivarao, Digavalli V; Chen, Ping; Senapati, Arun; Yang, Yili; Fernandes, Alda; Benitex, Yulia; Whiterock, Valerie; Li, Yu-Wen; Ahlijanian, Michael K
2016-08-01
Schizophrenia patients exhibit dysfunctional gamma oscillations in response to simple auditory stimuli or more complex cognitive tasks, a phenomenon explained by reduced NMDA transmission within inhibitory/excitatory cortical networks. Indeed, a simple steady-state auditory click stimulation paradigm at gamma frequency (~40 Hz) has been reproducibly shown to reduce entrainment as measured by electroencephalography (EEG) in patients. However, some investigators have reported increased phase locking factor (PLF) and power in response to 40 Hz auditory stimulus in patients. Interestingly, preclinical literature also reflects this contradiction. We investigated whether a graded deficiency in NMDA transmission can account for such disparate findings by administering subanesthetic ketamine (1-30 mg/kg, i.v.) or vehicle to conscious rats (n=12) and testing their EEG entrainment to 40 Hz click stimuli at various time points (~7-62 min after treatment). In separate cohorts, we examined in vivo NMDA channel occupancy and tissue exposure to contextualize ketamine effects. We report a robust inverse relationship between PLF and NMDA occupancy 7 min after dosing. Moreover, ketamine could produce inhibition or disinhibition of the 40 Hz response in a temporally dynamic manner. These results provide for the first time empirical data to understand how cortical NMDA transmission deficit may lead to opposite modulation of the auditory steady-state response (ASSR). Importantly, our findings posit that 40 Hz ASSR is a pharmacodynamic biomarker for cortical NMDA function that is also robustly translatable. Besides schizophrenia, such a functional biomarker may be of value to neuropsychiatric disorders like bipolar and autism spectrum where 40 Hz ASSR deficits have been documented. PMID:26837462
Brenneisen, P; Briviba, K; Wlaschek, M; Wenk, J; Scharffetter-Kochanek, K
1997-01-01
Reactive oxygen species (ROS) have been shown to be important messenger molecules in the induction of several genes. In human dermal fibroblasts the herbicide paraquat (PQ2+) was used to induce intracellular oxidative stress that was modulated by the inhibition of copper, zinc superoxide dismutase (Cu,ZnSOD), glutathione peroxidase (GSHPx), catalase, and blocking of the Fenton reaction. Interstitial collagenase (MMP-1) mRNA increased time dependently for up to 72 h following paraquat treatment. A correlation with the translation of MMP-1 could, however, only be detected up to 24 h, indicating an uncoupling of transcription and translation. Interleukin-1 alpha and beta mRNA showed two peaks at 6 h and 72 h. The inhibition of catalase by aminotriazol (ATZ), inhibition of GSHPx by buthionine sulfoximine (BSO), and blocking the Fenton reaction by the iron chelator desferrioxamine (DFO) in concert led to an increase in steady-state MMP-1 mRNA levels, possibly dependent on intracellular H2O2 increase. This combined treatment potentiated MMP-1 mRNA induction up to 6.5-fold compared to paraquat treated controls. Furthermore, exogenously added H2O2 caused an increase in MMP-1 mRNA levels. In contrast, inhibition of Cu,ZnSOD by diethyldithiocarbamate (DDC), leading to diminished H2O2 production from O2.-, decreased MMP-1 mRNA induction. Collectively, our data provide evidence that H2O2 is an important intermediate in the downstream signalling pathway finally leading to the induction of increased steady state MMP-1 mRNA levels. The synthesis of MMPs may contribute to connective tissue damage in vivo related to photoaging, inflammatory diseases, and tumor invasion. PMID:8981044
Descriptive Linear modeling of steady-state visual evoked response
NASA Technical Reports Server (NTRS)
Levison, W. H.; Junker, A. M.; Kenner, K.
1986-01-01
A study is being conducted to explore use of the steady state visual-evoke electrocortical response as an indicator of cognitive task loading. Application of linear descriptive modeling to steady state Visual Evoked Response (VER) data is summarized. Two aspects of linear modeling are reviewed: (1) unwrapping the phase-shift portion of the frequency response, and (2) parsimonious characterization of task-loading effects in terms of changes in model parameters. Model-based phase unwrapping appears to be most reliable in applications, such as manual control, where theoretical models are available. Linear descriptive modeling of the VER has not yet been shown to provide consistent and readily interpretable results.
Steady-state CO/sub 2/ laser model
Scott, M.W.; Myers, G.D.
1984-09-01
A steady-state CO/sub 2/ lase model is reported which can be used to predict and evaluate the performance of cw slow-flow and no-flow CO/sub 2/ lasers. Traditional CO/sub 2/ laser models require the solution of several simultaneous differential equations and can be used to model pulsed and fast-flow lasers in addition to cw and slow-flow devices. The model reported here is computationally simpler, requiring only a routine to solve one equation in one unknown, but is only useful for lasers which operate in the steady state.
Steady state decoupling and design of linear multivariable systems
NASA Technical Reports Server (NTRS)
Huang, J. Y.; Thaler, G. J.
1974-01-01
A constructive criterion for decoupling the steady states of linear multivariable systems is developed. The criterion consists of n(n-1) inequalities with the type numbers of the compensator transfer functions as the unknowns. These unknowns can be chosen to satisfy the inequalities and hence achieve a steady state decoupling scheme. It turns out that pure integrators in the loops play an important role. An extended root locus design method is then developed to take care of the stability and transient response. The overall procedure is applied to the compensation design for STOL C-8A aircraft in the approach mode.
Steady-state entanglement activation in optomechanical cavities
NASA Astrophysics Data System (ADS)
Farace, Alessandro; Ciccarello, Francesco; Fazio, Rosario; Giovannetti, Vittorio
2014-02-01
Quantum discord, and related indicators, are raising a relentless interest as a novel paradigm of nonclassical correlations beyond entanglement. Here, we discover a discord-activated mechanism yielding steady-state entanglement production in a realistic continuous-variable setup. This comprises two coupled optomechanical cavities, where the optical modes (OMs) communicate through a fiber. We first use a simplified model to highlight the creation of steady-state discord between the OMs. We show next that such discord improves the level of stationary optomechanical entanglement attainable in the system, making it more robust against temperature and thermal noise.
Non-equilibrium steady state in the hydro regime
NASA Astrophysics Data System (ADS)
Pourhasan, Razieh
2016-02-01
We study the existence and properties of the non-equilibrium steady state which arises by putting two copies of systems at different temperatures into a thermal contact. We solve the problem for the relativistic systems that are described by the energy-momentum of a perfect hydro with general equation of state (EOS). In particular, we examine several simple examples: a hydro with a linear EOS, a holographic CFT perturbed by a relevant operator and a barotropic fluid, i.e., P=P({E}) . Our studies suggest that the formation of steady state is a universal result of the hydro regime regardless of the kind of fluid.
Steady-state coherent transfer by adiabatic passage.
Huneke, Jan; Platero, Gloria; Kohler, Sigmund
2013-01-18
We propose steady-state electron transport based on coherent transfer by adiabatic passage (CTAP) in a linearly arranged triple quantum dot with leads attached to the outer dots. Its main feature is repeated steering of single electrons from the first dot to the last dot without relevant occupation of the middle dot. The coupling to leads enables a steady-state current, whose shot noise is significantly suppressed provided that the CTAP protocol performs properly. This represents an indication for the direct transfer between spatially separated dots and, thus, may resolve the problem of finding experimental evidence for the nonoccupation of the middle dot. PMID:23373941
CONTROL OF CRYPTOSPORIDIUM OOCYSTS BY STEADY-STATE CONVENTIONAL TREATMENT
Pilot-scale experiments have been performed to assess the ability of conventional treatment to control Cryptosporidium oocysts under steady-state conditions. The work was performed with a pilot plant that was designed to minimize flow rates and, as a result, the number of oocyst...
Pressure updating methods for the steady-state fluid equations
NASA Technical Reports Server (NTRS)
Fiterman, A.; Turkel, E.; Vatsa, V.
1995-01-01
We consider the steady state equations for a compressible fluid. Since we wish to solve for a range of speeds we must consider the equations in conservation form. For transonic speeds these equations are of mixed type. Hence, the usual approach is to add time derivatives to the steady state equations and then march these equations in time. One then adds a time derivative of the density to the continuity equation, a derivative of the momentum to the momentum equation and a derivative of the total energy to the energy equation. This choice is dictated by the time consistent equations. However, since we are only interested in the steady state this is not necessary. Thus we shall consider the possibility of adding a time derivative of the pressure to the continuity equation and similar modifications for the energy equation. This can then be generalized to adding combinations of time derivatives to each equation since these vanish in the steady state. When using acceleration techniques such as residual smoothing, multigrid, etc. these are applied to the pressure rather than the density. Hence, the code duplicates the behavior of the incompressible equations for low speeds.
The Development of Strategies for the Steady State.
ERIC Educational Resources Information Center
Wolfman, Brunetta R.; Wolfman, Burton
1980-01-01
Presented is a matrix of institution types and institutional characteristics that can be used in planning for the steady state in colleges and universities. Case studies of six institutions are presented: Harvard University, Boston University, Dartmouth College, Colorado College, University of Massachusetts/Boston, and Massachusetts Community…
Steady-State Pharmacokinetics of Bupropion SR in Juvenile Patients
ERIC Educational Resources Information Center
Daviss, W. Burleson; Perel, James M.; Rudolph, George R.; Axelson, David A.; Gilchrist, Richard; Nuss, Sharon; Birmaher, Boris; Brent, David A.
2005-01-01
Objective: To examine the steady-state pharmacokinetic properties of bupropion sustained release (SR) and their potential developmental differences in youths. Method: Eleven boys and eight girls aged 11 to 17 years old were prescribed bupropion SR monotherapy for attention-deficit/hyperactivity disorder (n = 16) and/or depressive disorders (n =…
Is There More than One Steady State for Nox?
NASA Technical Reports Server (NTRS)
Bakas, G.
1985-01-01
The study of alternative steady states for nitrogen oxides is discussed: The production of these oxides and the reactions they undergo in the atmosphere are described. The computerized modelling of the atmosphere using a one dimensional time dependent photochemical model is attempted.
Effects of curvature on asymmetric steady states in catalyst particles
Lucier, B J
1981-02-01
The effects of curvature on steady states of chemical catalytic reactions are investigated by studying the cases of the catalytic particle being a spherical or cylindrical shell. Existence and stability of solutions are studied. It is shown that the solutions converge to the solutions for the catalytic slab when the curvature goes to 0 in each case.
Equilibrium Binding and Steady-State Enzyme Kinetics.
ERIC Educational Resources Information Center
Dunford, H. Brian
1984-01-01
Points out that equilibrium binding and steady-state enzyme kinetics have a great deal in common and that related equations and error analysis can be cast in identical forms. Emphasizes that if one type of problem solution is taught, the other is also taught. Various methods of data analysis are evaluated. (JM)
Steady-State Multiplicity Features of Chemically Reacting Systems.
ERIC Educational Resources Information Center
Luss, Dan
1986-01-01
Analyzes steady-state multiplicity in chemical reactors, focusing on the use of two mathematical tools, namely, the catastrophe theory and the singularity theory with a distinguished parameter. These tools can be used to determine the maximum number of possible solutions and the different types of bifurcation diagrams. (JN)
Steady State Load Characterization Fact Sheet: 2012 Chevy Volt
Don Scoffield
2015-01-01
This fact sheet characterizes the steady state charging behavior of a 2012 Chevy Volt. Both level 1 charging (120 volt) and level 2 charging (208 volts) is investigated. This fact sheet contains plots of efficiency, power factor, and current harmonics as vehicle charging is curtailed. Prominent current harmonics are also displayed in a histogram for various charge rates.
Experimental study of multiple steady states in homogeneous azeotropic distillation
Guettinger, T.E.; Dorn, C.; Morari, M.
1997-03-01
Bekiaris et al. (1993) explained the existence of multiple steady states in homogeneous ternary azeotropic distillation, on the basis of the analysis of the case of infinite reflux and infinite column length (infinite number of trays). They showed that the predictions of multiple steady states for such infinite columns have relevant implications for columns of finite length operated at finite reflux. In this article, experiments are described for the ternary homogeneous system methanol-methyl butyrate-toluene which demonstrate the existence of multiple steady states (output multiplicities) caused by the vapor-liquid-equilibrium. The experiments on an industrial pilot column show two stable steady states for the same feed flow rate and composition and the same set of operating parameters. The measurements are in excellent agreement with the predictions obtained for infinite columns using the {infinity}/{infinity} analysis tool as well as with stage-by-stage simulation results. These experiments represent the first published study reporting evidence for the predictions and simulations by various researchers showing that type of output multiplicities in distillation.
Steady-State Squeezing in the Micromaser Cavity Field
NASA Technical Reports Server (NTRS)
Nayak, N.
1996-01-01
It is shown that the radiation field in the presently operated micromaser cavity may be squeezed when pumped with polarized atoms. The squeezing is in the steady state field corresponding to the action similar to that of the conventional micromaser, with the effect of cavity dissipation during entire t(sub c) = tau + t(sub cav).
Steady States of the Parametric Rotator and Pendulum
ERIC Educational Resources Information Center
Bouzas, Antonio O.
2010-01-01
We discuss several steady-state rotation and oscillation modes of the planar parametric rotator and pendulum with damping. We consider a general elliptic trajectory of the suspension point for both rotator and pendulum, for the latter at an arbitrary angle with gravity, with linear and circular trajectories as particular cases. We treat the…
Density Functional Theory for Steady-State Nonequilibrium Molecular Junctions
NASA Astrophysics Data System (ADS)
Liu, Shuanglong; Nurbawono, Argo; Zhang, Chun
2015-10-01
We present a density functional theory (DFT) for steady-state nonequilibrium quantum systems such as molecular junctions under a finite bias. Based on the steady-state nonequilibrium statistics that maps nonequilibrium to an effective equilibrium, we show that ground-state DFT (GS-DFT) is not applicable in this case and two densities, the total electron density and the density of current-carrying electrons, are needed to uniquely determine the properties of the corresponding nonequilibrium system. A self-consistent mean-field approach based on two densities is then derived. The theory is implemented into SIESTA computational package and applied to study nonequilibrium electronic/transport properties of a realistic carbon-nanotube (CNT)/Benzene junction. Results obtained from our steady-state DFT (SS-DFT) are compared with those of conventional GS-DFT based transport calculations. We show that SS-DFT yields energetically more stable nonequilibrium steady state, predicts significantly lower electric current, and is able to produce correct electronic structures in local equilibrium under a limiting case.
Combined Steady-State and Dynamic Heat Exchanger Experiment
ERIC Educational Resources Information Center
Luyben, William L.; Tuzla, Kemal; Bader, Paul N.
2009-01-01
This paper describes a heat-transfer experiment that combines steady-state analysis and dynamic control. A process-water stream is circulated through two tube-in-shell heat exchangers in series. In the first, the process water is heated by steam. In the second, it is cooled by cooling water. The equipment is pilot-plant size: heat-transfer areas…
Steady state volcanism: Evidence from eruption histories of polygenetic volcanoes
Wadge, G.
1982-05-10
Some volcanoes erupt magma at average rates which are constant over periods of many years, even through this magma may appear in a complex series of eruptions. This constancy of output is tested by construction of a curve of cumulative volume of erupted magma, which is linear for steady state volcanism, and whose gradient defines the steady state rate Q/sub s/s. The assumption is made that Q/sub s/s is the rate at which magma is supplied to these polygenetic volcanoes. Five general types of eruptive behavior can be distinguished from the cumulative volume studied. These types are interpreted in terms of a simple model of batches of magma rising buoyantly through the crust and interacting with a small-capacity subvolcanic magma reservoir. Recognition of previous steady state behavior at a volcano may enable the cumulative volume curve to be used empirically as a constraint on the timing and volume of the next eruption. The steady state model thus has a limited predictive capability. With the exception of Kilauea (O/sub s/s = 4m/sup 3/ s/sup -1/) all the identified steady state volcanoes have values of Q/sub s/s of a few tenths of one cubic meter per second. These rates are consistent with the minimum flux rates required by theoretical cooling models of batches of magma traversing the crust. The similarity of these Q/sub s/s values of volcanoes (producing basalt, andesite, and dacite magmas) in very different tectonic settings suggests that the common factors of crustal buoyancy forces and the geotherm-controlled cooling rates control the dynamics of magma supply through the crust. Long-term dormancy at active volcanoes may be a manifestation of the steady accumulation of magma in large crustal reservoirs, a process that complements the intermittent periods of steady state output at the surface. This possibility has several implications, the most important of which is that it provides a constraint on the supply rate of new magma to the bases of plutons.
Persistent Probability Currents in Non-equilibrium Steady States
NASA Astrophysics Data System (ADS)
Zia, Royce; Mellor, Andrew; Mobilia, Mauro; Fox-Kemper, Baylor; Weiss, Jeffrey
For many interesting phenomena in nature, from all life forms to the global climate, the fundamental hypothesis of equilibrium statistical mechanics does not apply. Instead, they are perhaps better characterized by non-equilibrium steady states, evolving with dynamical rules which violate detailed balance. In particular, such dynamics leads to the existence of non-trivial, persistent probability currents - a principal characteristic of non-equilibrium steady states. In turn, they give rise to the notion of 'probability angular momentum'. Observable manifestations of such abstract concepts will be illustrated in two distinct contexts: a heterogeneous nonlinear voter model and our ocean heat content. Supported in part by grants from the Bloom Agency (Leeds, UK) and the US National Science Foundation: OCE-1245944. AM acknowledges the support of EPSRC Industrial CASE Studentship, Grant No. EP/L50550X/1.
Nonequilibrium Steady States of a Stochastic Model System.
NASA Astrophysics Data System (ADS)
Zhang, Qiwei
We study the nonequilibrium steady state of a stochastic lattice gas model, originally proposed by Katz, Lebowitz and Spohn (Phys. Rev. B 28: 1655 (1983)). Firstly, we solve the model on some small lattices exactly in order to see the general dependence of the steady state upon different parameters of the model. Nextly, we derive some analytical results for infinite lattice systems by taking some suitable limits. We then present some renormalization group results for the continuum version of the model via field theoretical techniques, the supersymmetry of the critical dynamics in zero field is also explored. Finally, we report some very recent 3-D Monte Carlo simulation results, which have been obtained by applying Multi-Spin-Coding techniques on a CDC vector supercomputer - Cyber 205 at John von Neumann Center.
Hydrodynamics of stratified epithelium: Steady state and linearized dynamics
NASA Astrophysics Data System (ADS)
Yeh, Wei-Ting; Chen, Hsuan-Yi
2016-05-01
A theoretical model for stratified epithelium is presented. The viscoelastic properties of the tissue are assumed to be dependent on the spatial distribution of proliferative and differentiated cells. Based on this assumption, a hydrodynamic description of tissue dynamics at the long-wavelength, long-time limit is developed, and the analysis reveals important insights into the dynamics of an epithelium close to its steady state. When the proliferative cells occupy a thin region close to the basal membrane, the relaxation rate towards the steady state is enhanced by cell division and cell apoptosis. On the other hand, when the region where proliferative cells reside becomes sufficiently thick, a flow induced by cell apoptosis close to the apical surface enhances small perturbations. This destabilizing mechanism is general for continuous self-renewal multilayered tissues; it could be related to the origin of certain tissue morphology, tumor growth, and the development pattern.
Steady States in Fermionic Interacting Dissipative Floquet Systems
NASA Astrophysics Data System (ADS)
Seetharam, Karthik; Bardyn, Charles; Lindner, Netanel; Rudner, Mark; Refael, Gil
The possibility to drive quantum systems periodically in time offers unique ways to deeply modify their fundamental properties, as exemplified by Floquet topological insulators. It also opens the door to a variety of non-equilibrium effects. Resonant driving fields, in particular, lead to excitations which can expose the system to heating. We previously demonstrated that the analog of thermal states can be achieved and controlled in a fermionic Floquet system in the presence of phonon scattering, spontaneous emission, and an energy filtered fermionic bath. However, interactions play an important role in thermalization and present additional sources of heating. We analyze the effects of weak interactions in the presence of dissipation and the role of coherences in determining the steady state of the driven system. Interactions generically create additional excitations and, in contrast to phonons, may sustain inter-Floquet-band coherences at steady state.
Steady-state spin squeezing generation in diamond nanostructures
NASA Astrophysics Data System (ADS)
Ma, Yong-Hong; Zhang, Xue-Feng
2014-04-01
As one kind of many body entangled states, spin squeezed states can be used to implement the high precise measurement beyond the standard quantum limit. Inspired by the novel spin squeezing scheme based on phonon-induced spin-spin interactions [S. D. Bennett et al., Phys. Rev. Lett. 110, 156402 (2013), 10.1103/PhysRevLett.110.156402], we reexamine the steady-state behaviors for the spin ensemble in diamond nanostructures by exerting a controllable microwave field. By using the phase-space approach we calculate analytically fluctuations of collective spin operators. We find that there is bistability and spin squeezing for the steady-state spin ensemble, despite the mechanical damping considered. Moreover, our work shows that bistability and spin squeezing can be controlled by microwave field and Zeeman splitting. The present scheme can be used to increase the stability of spin clocks, magnetometers, and other measurements based on spin-spin interaction in diamond nanostructures.
Analysis of slow transitions between nonequilibrium steady states
NASA Astrophysics Data System (ADS)
Mandal, Dibyendu; Jarzynski, Christopher
2016-06-01
Transitions between nonequilibrium steady states obey a generalized Clausius inequality, which becomes an equality in the quasistatic limit. For slow but finite transitions, we show that the behavior of the system is described by a response matrix whose elements are given by a far-from-equilibrium Green–Kubo formula, involving the decay of correlations evaluated in the nonequilibrium steady state. This result leads to a fluctuation-dissipation relation between the mean and variance of the nonadiabatic entropy production, Δ {{s}\\text{na}} . Furthermore, our results extend—to nonequilibrium steady states—the thermodynamic metric structure introduced by Sivak and Crooks for analyzing minimal-dissipation protocols for transitions between equilibrium states.
Turnover of messenger RNA: Polysome statistics beyond the steady state
NASA Astrophysics Data System (ADS)
Valleriani, A.; Ignatova, Z.; Nagar, A.; Lipowsky, R.
2010-03-01
The interplay between turnover or degradation and ribosome loading of messenger RNA (mRNA) is studied theoretically using a stochastic model that is motivated by recent experimental results. Random mRNA degradation affects the statistics of polysomes, i.e., the statistics of the number of ribosomes per mRNA as extracted from cells. Since ribosome loading of newly created mRNA chains requires some time to reach steady state, a fraction of the extracted mRNA/ribosome complexes does not represent steady state conditions. As a consequence, the mean ribosome density obtained from the extracted complexes is found to be inversely proportional to the mRNA length. On the other hand, the ribosome density profile shows an exponential decrease along the mRNA for prokaryotes and becomes uniform in eukaryotic cells.
Steady-state current transfer and scattering theory.
Ben-Moshe, Vered; Rai, Dhurba; Skourtis, Spiros S; Nitzan, Abraham
2010-08-01
The correspondence between the steady-state theory of current transfer and scattering theory in a system of coupled tight-binding models of one-dimensional wires is explored. For weak interwire coupling both calculations give nearly identical results, except at singular points associated with band edges. The effect of decoherence in each of these models is studied using a generalization of the Liouville-von Neuman equation suitable for steady-state situations. An example of a single impurity model is studied in detail, leading to a lattice model of scattering off target that affects both potential scattering and decoherence. For an impurity level lying inside the energy band, the transmission coefficient diminishes with increasing dephasing rate, while the opposite holds for impurity energy outside the band. The efficiency of current transfer in the coupled wire system decreases with increasing dephasing. PMID:20707524
Master equation based steady-state cluster perturbation theory
NASA Astrophysics Data System (ADS)
Nuss, Martin; Dorn, Gerhard; Dorda, Antonius; von der Linden, Wolfgang; Arrigoni, Enrico
2015-09-01
A simple and efficient approximation scheme to study electronic transport characteristics of strongly correlated nanodevices, molecular junctions, or heterostructures out of equilibrium is provided by steady-state cluster perturbation theory. In this work, we improve the starting point of this perturbative, nonequilibrium Green's function based method. Specifically, we employ an improved unperturbed (so-called reference) state ρ̂S, constructed as the steady state of a quantum master equation within the Born-Markov approximation. This resulting hybrid method inherits beneficial aspects of both the quantum master equation as well as the nonequilibrium Green's function technique. We benchmark this scheme on two experimentally relevant systems in the single-electron transistor regime: an electron-electron interaction based quantum diode and a triple quantum dot ring junction, which both feature negative differential conductance. The results of this method improve significantly with respect to the plain quantum master equation treatment at modest additional computational cost.
Analysis of steady-state characteristics of bistable laser diodes
Zhong Lichen; Guo Yili
1987-05-01
In this paper we analyze the steady-state characteristics of bistable semiconductor laser diode (BILD). A simple model for optical output of BILD is obtained using nonlinear rate equations for electron and photon densities. This model emphasizes the physical mechanisms and parameters responsible for the bistability, gives the state equation and explains the main features of BILD. Bistability with a very large hysteresis in P/sub 0/-P/sub 4/ characteristics is a distinctive feature of BILD.
Steady state magnetic field configurations for the earth's magnetotail
NASA Technical Reports Server (NTRS)
Hau, L.-N.; Wolf, R. A.; Voigt, G.-H.; Wu, C. C.
1989-01-01
A two-dimensional, force-balance magnetic field model is presented. The theoretical existence of a steady state magnetic field configuration that is force-balanced and consistent with slow, lossless, adiabatic, earthward convection within the limit of the ideal MHD is demonstrated. A numerical solution is obtained for a two-dimensional magnetosphere with a rectangular magnetopause and nonflaring tail. The results are consistent with the convection time sequences reported by Erickson (1985).
Intense steady state neutron source. The CNR reactor
Difilippo, F.C.; Moon, R.M.; Gambill, W.R.; Moon, R.M.; Primm, R.T. III; West, C.D.
1986-01-01
The Center for Neutron Research (CNR) has been proposed in response to the needs - neutron flux, spectrum, and experimental facilities - that have been identified through workshops, studies, and discussions by the neutron-scattering, isotope, and materials irradiation research communities. The CNR is a major new experimental facility consisting of a reactor-based steady state neutron source of unprecedented flux, together with extensive facilities and instruments for neutron scattering, isotope production, materials irradiation, and other areas of research.
Transitional steady states of exchange dynamics between finite quantum systems.
Jeon, Euijin; Yi, Juyeon; Kim, Yong Woon
2016-08-01
We examine energy and particle exchange between finite-sized quantum systems and find a new form of nonequilibrium state. The exchange rate undergoes stepwise evolution in time, and its magnitude and sign dramatically change according to system size differences. The origin lies in interference effects contributed by multiply scattered waves at system boundaries. Although such characteristics are utterly different from those of true steady state for infinite systems, Onsager's reciprocal relation remains universally valid. PMID:27627275
Analytic Steady-State Accuracy of a Spacecraft Attitude Estimator
NASA Technical Reports Server (NTRS)
Markley, F. Landis
2000-01-01
This paper extends Farrenkopf's analysis of a single-axis spacecraft attitude estimator using gyro and angle sensor data to include the angle output white noise of a rate-integrating gyro. Analytic expressions are derived for the steady-state pre-update and post-update angle and drift bias variances and for the state update equations. It is shown that only part of the state update resulting from the angle sensor measurement is propagated to future times.
Steady-state superradiance with alkaline-earth-metal atoms
Meiser, D.; Holland, M. J.
2010-03-15
Alkaline-earth-metal-like atoms with ultranarrow transitions open the door to a new regime of cavity quantum electrodynamics. That regime is characterized by a critical photon number that is many orders of magnitude smaller than what can be achieved in conventional systems. We show that it is possible to achieve superradiance in steady state with such systems. We discuss the basic underlying mechanisms as well as the key experimental requirements.
Cyclic steady state stress-strain behavior of UHMW polyethylene.
Krzypow, D J; Rimnac, C M
2000-10-01
To increase the long-term performance of total joint replacements, finite element analyses of ultra high molecular weight polyethylene (UHMWPE) components have been conducted to predict the effect of load on the stress and strain distributions occurring on and within these components. Early models incorporated the monotonic behavior of UHMWPE without considering the unloading and cyclic loading behavior. However, UHMWPE components undergo cyclic loading during use and at least two wear damage modes (pitting and delamination) are thought to be associated with the fatigue fracture properties of UHMWPE. The objective of this study was to examine the fully reversed uniaxial tension/compression cyclic steady state stress-strain behavior of UHMWPE as a first step towards developing a cyclic constitutive relationship for UHMWPE. The hypothesis that cycling results in a permanent change in the stress-strain relationship, that is, that the cyclic steady state represents a new cyclically stabilized state, was examined. It was found that, like other ductile polymers, UHMWPE substantially cyclically softens under fully reversed uniaxial straining. More cyclic softening occurred in tension than in compression. Furthermore, cyclic steady state was attained, but not cyclic stability. It is suggested that it may be more appropriate to base a material constitutive relationship for UHMWPE for finite element analyses of components upon a cyclically modified stress-strain relationship. PMID:10966018
Ideal MHD Stability of ITER Steady State Scenarios with ITBs
F.M. Poli, C.E. Kessel, S. Jardin, J. Manickam, M. Chance, J. Chen
2011-07-27
One of ITER goals is to demonstrate feasibility of continuous operations using non-inductive current drive. Two main candidates have been identified for advanced operations: the long duration, high neutron fluency hybrid scenario and the steady state scenario, both operating at a plasma current lower than the reference ELMy scenario [1][2] to minimize the required current drive. The steady state scenario targets plasmas with current 7-10 MA in the flat-top, 50% of which will be provided by the self-generated, pressure-driven bootstrap current. It has been estimated that, in order to obtain a fusion gain Q > 5 at a current of 9 MA, it should be ΒN > 2.5 and H > 1.5 [3]. This implies the presence of an Internal Transport Barrier (ITB). This work discusses how the stability of steady state scenarios with ITBs is affected by the external heating sources and by perturbations of the equilibrium profiles.
KIR channel activation contributes to onset and steady-state exercise hyperemia in humans.
Crecelius, Anne R; Luckasen, Gary J; Larson, Dennis G; Dinenno, Frank A
2014-09-01
We tested the hypothesis that activation of inwardly rectifying potassium (KIR) channels and Na(+)-K(+)-ATPase, two pathways that lead to hyperpolarization of vascular cells, contributes to both the onset and steady-state hyperemic response to exercise. We also determined whether after inhibiting these pathways nitric oxide (NO) and prostaglandins (PGs) are involved in the hyperemic response. Forearm blood flow (FBF; Doppler ultrasound) was determined during rhythmic handgrip exercise at 10% maximal voluntary contraction for 5 min in the following conditions: control [saline; trial 1 (T1)]; with combined inhibition of KIR channels and Na(+)-K(+)-ATPase alone [via barium chloride (BaCl2) and ouabain, respectively; trial 2 (T2)]; and with additional combined nitric oxide synthase (N(G)-monomethyl-l-arginine) and cyclooxygenase inhibition [ketorolac; trial 3 (T3)]. In T2, the total hyperemic responses were attenuated ~50% from control (P < 0.05) at exercise onset, and there was minimal further effect in T3 (protocol 1; n = 11). In protocol 2 (n = 8), steady-state FBF was significantly reduced during T2 vs. T1 (133 ± 15 vs. 167 ± 17 ml/min; Δ from control: -20 ± 3%; P < 0.05) and further reduced during T3 (120 ± 15 ml/min; -29 ± 3%; P < 0.05 vs. T2). In protocol 3 (n = 8), BaCl2 alone reduced FBF during onset (~50%) and steady-state exercise (~30%) as observed in protocols 1 and 2, respectively, and addition of ouabain had no further impact. Our data implicate activation of KIR channels as a novel contributing pathway to exercise hyperemia in humans. PMID:24973385
Mitoenergetic Dysfunction Triggers a Rapid Compensatory Increase in Steady-State Glucose Flux.
Liemburg-Apers, Dania C; Schirris, Tom J J; Russel, Frans G M; Willems, Peter H G M; Koopman, Werner J H
2015-10-01
ATP can be produced in the cytosol by glycolytic conversion of glucose (GLC) into pyruvate. The latter can be metabolized into lactate, which is released by the cell, or taken up by mitochondria to fuel ATP production by the tricarboxylic acid cycle and oxidative phosphorylation (OXPHOS) system. Altering the balance between glycolytic and mitochondrial ATP generation is crucial for cell survival during mitoenergetic dysfunction, which is observed in a large variety of human disorders including cancer. To gain insight into the kinetic properties of this adaptive mechanism we determined here how acute (30 min) inhibition of OXPHOS affected cytosolic GLC homeostasis. GLC dynamics were analyzed in single living C2C12 myoblasts expressing the fluorescent biosensor FLII(12)Pglu-700μδ6 (FLII). Following in situ FLII calibration, the kinetic properties of GLC uptake (V1) and GLC consumption (V2) were determined independently and used to construct a minimal mathematical model of cytosolic GLC dynamics. After validating the model, it was applied to quantitatively predict V1 and V2 at steady-state (i.e., when V1 = V2 = Vsteady-state) in the absence and presence of OXPHOS inhibitors. Integrating model predictions with experimental data on lactate production, cell volume, and O2 consumption revealed that glycolysis and mitochondria equally contribute to cellular ATP production in control myoblasts. Inhibition of OXPHOS induced a twofold increase in Vsteady-state and glycolytic ATP production flux. Both in the absence and presence of OXPHOS inhibitors, GLC was consumed at near maximal rates, meaning that GLC consumption is rate-limiting under steady-state conditions. Taken together, we demonstrate here that OXPHOS inhibition increases steady-state GLC uptake and consumption in C2C12 myoblasts. This activation fully compensates for the reduction in mitochondrial ATP production, thereby maintaining the balance between cellular ATP supply and demand. PMID:26445438
Stress-induced inhibition of translation independently of eIF2α phosphorylation.
Knutsen, Jon Halvor Jonsrud; Rødland, Gro Elise; Bøe, Cathrine Arnason; Håland, Tine Weise; Sunnerhagen, Per; Grallert, Beáta; Boye, Erik
2015-12-01
Exposure of fission yeast cells to ultraviolet (UV) light leads to inhibition of translation and phosphorylation of the eukaryotic initiation factor-2α (eIF2α). This phosphorylation is a common response to stress in all eukaryotes. It leads to inhibition of translation at the initiation stage and is thought to be the main reason why stressed cells dramatically reduce protein synthesis. Phosphorylation of eIF2α has been taken as a readout for downregulation of translation, but the role of eIF2α phosphorylation in the downregulation of general translation has not been much investigated. We show here that UV-induced global inhibition of translation in fission yeast cells is independent of eIF2α phosphorylation and the eIF2α kinase general control nonderepressible-2 protein (Gcn2). Also, in budding yeast and mammalian cells, the UV-induced translational depression is largely independent of GCN2 and eIF2α phosphorylation. Furthermore, exposure of fission yeast cells to oxidative stress generated by hydrogen peroxide induced an inhibition of translation that is also independent of Gcn2 and of eIF2α phosphorylation. Our findings show that stress-induced translational inhibition occurs through an unknown mechanism that is likely to be conserved through evolution. PMID:26493332
Stress-induced inhibition of translation independently of eIF2α phosphorylation
Knutsen, Jon Halvor Jonsrud; Rødland, Gro Elise; Bøe, Cathrine Arnason; Håland, Tine Weise; Sunnerhagen, Per; Grallert, Beáta; Boye, Erik
2015-01-01
ABSTRACT Exposure of fission yeast cells to ultraviolet (UV) light leads to inhibition of translation and phosphorylation of the eukaryotic initiation factor-2α (eIF2α). This phosphorylation is a common response to stress in all eukaryotes. It leads to inhibition of translation at the initiation stage and is thought to be the main reason why stressed cells dramatically reduce protein synthesis. Phosphorylation of eIF2α has been taken as a readout for downregulation of translation, but the role of eIF2α phosphorylation in the downregulation of general translation has not been much investigated. We show here that UV-induced global inhibition of translation in fission yeast cells is independent of eIF2α phosphorylation and the eIF2α kinase general control nonderepressible-2 protein (Gcn2). Also, in budding yeast and mammalian cells, the UV-induced translational depression is largely independent of GCN2 and eIF2α phosphorylation. Furthermore, exposure of fission yeast cells to oxidative stress generated by hydrogen peroxide induced an inhibition of translation that is also independent of Gcn2 and of eIF2α phosphorylation. Our findings show that stress-induced translational inhibition occurs through an unknown mechanism that is likely to be conserved through evolution. PMID:26493332
Steady-state responses of a belt-drive dynamical system under dual excitations
NASA Astrophysics Data System (ADS)
Ding, Hu
2016-02-01
The stable steady-state periodic responses of a belt-drive system with a one-way clutch are studied. For the first time, the dynamical system is investigated under dual excitations. The system is simultaneously excited by the firing pulsations of the engine and the harmonic motion of the foundation. Nonlinear discrete-continuous equations are derived for coupling the transverse vibration of the belt spans and the rotations of the driving and driven pulleys and the accessory pulley. The nonlinear dynamics is studied under equal and multiple relations between the frequency of the firing pulsations and the frequency of the foundation motion. Furthermore, translating belt spans are modeled as axially moving strings. A set of nonlinear piecewise ordinary differential equations is achieved by using the Galerkin truncation. Under various relations between the excitation frequencies, the time histories of the dynamical system are numerically simulated based on the time discretization method. Furthermore, the stable steady-state periodic response curves are calculated based on the frequency sweep. Moreover, the convergence of the Galerkin truncation is examined. Numerical results demonstrate that the one-way clutch reduces the resonance amplitude of the rotations of the driven pulley and the accessory pulley. On the other hand, numerical examples prove that the resonance areas of the belt spans are decreased by eliminating the torque-transmitting in the opposite direction. With the increasing amplitude of the foundation excitation, the damping effect of the one-way clutch will be reduced. Furthermore, as the amplitude of the firing pulsations of the engine increases, the jumping phenomena in steady-state response curves of the belt-drive system with or without a one-way clutch both occur.
Steady state free radical budgets and ozone photochemistry during TOPSE
NASA Astrophysics Data System (ADS)
Cantrell, Christopher A.; Mauldin, L.; Zondlo, M.; Eisele, F.; Kosciuch, E.; Shetter, R.; Lefer, B.; Hall, S.; Campos, T.; Ridley, B.; Walega, J.; Fried, A.; Wert, B.; Flocke, F.; Weinheimer, A.; Hannigan, J.; Coffey, M.; Atlas, E.; Stephens, S.; Heikes, B.; Snow, J.; Blake, D.; Blake, N.; Katzenstein, A.; Lopez, J.; Browell, E. V.; Dibb, J.; Scheuer, E.; Seid, G.; Talbot, R.
2003-02-01
A steady state model, constrained by a number of measured quantities, was used to derive peroxy radical levels for the conditions of the Tropospheric Ozone Production about the Spring Equinox (TOPSE) campaign. The analysis is made using data collected aboard the NCAR/NSF C-130 aircraft from February through May 2000 at latitudes from 40° to 85°N, and at altitudes from the surface to 7.6 km. HO2 + RO2 radical concentrations were measured during the experiment, which are compared with model results over the domain of the study showing good agreement on the average. Average measurement/model ratios are 1.04 (σ = 0.73) and 0.96 (σ = 0.52) for the MLB and HLB, respectively. Budgets of total peroxy radical levels as well as of individual free radical members were constructed, which reveal interesting differences compared to studies at lower latitudes. The midlatitude part of the study region is a significant net source of ozone, while the high latitudes constitute a small net sink leading to the hypothesis that transport from the middle latitudes can explain the observed increase in ozone in the high latitudes. Radical reservoir species concentrations are modeled and compared with the observations. For most conditions, the model does a good job of reproducing the formaldehyde observations, but the peroxide observations are significantly less than steady state for this study. Photostationary state (PSS) derived total peroxy radical levels and NO/NO2 ratios are compared with the measurements and the model; PSS-derived results are higher than observations or the steady state model at low NO concentrations.
The requirements of a next step large steady state tokamak
NASA Astrophysics Data System (ADS)
Janeschitz, G.; Barabaschi, P.; Federici, G.; Ioki, K.; Ladd, P.; Mukhovatov, V.; Sugihara, M.; Tivey, R.; ITER-JCT; Home Team
2000-06-01
After a decision by the ITER parties to investigate the possibility of designing a reduced cost version of ITER several possible machine layouts with different aspect ratios were studied. Relatively early in this process it became clear that there is no significant cost difference between different aspect ratios and that there is a maximum realistically possible aspect ratio for a machine with 6 m major radius and rather high plasma shaping. Following this study a machine with an intermediate aspect ratio (3.1) called the ITER Fusion Energy Advanced Tokamak (ITER FEAT) was chosen as the basis for the outline design of a reduced cost ITER. Several potential steady state scenarios can be investigated in ITER FEAT, i.e. monotonic or reversed shear at full or reduced minor radius. In addition, so-called hybrid discharges, are feasible where a mixture of inductive and non-inductive current drive as well as bootstrap current allows long pulse discharges of the order of 2500 s. The βN values and H factors required for these discharges are in the same range as those observed on present machines, which provides confidence that such discharges can be studied in ITER FEAT. However, due to uncertainties in physics knowledge, for example the current drive efficiency off-axis, it is impossible at present to generate a completely self-consistent scenario taking all boundary conditions, for example engineering or heating system constraints, into account. In addition, all of these regimes have a potential problem with divertor operation compatibility (low edge density) and with helium exhaust which has to be addressed in existing experiments. For the engineering design of the in-vessel components and for the balance of the plant there is practically no difference between inductive (500 s) and steady state operation. However, the choice of heating systems and the distribution of power between them will be strongly influenced by the envisaged steady state scenarios.
Mimicking Nonequilibrium Steady States with Time-Periodic Driving
NASA Astrophysics Data System (ADS)
Raz, O.; Subaşı, Y.; Jarzynski, C.
2016-04-01
Under static conditions, a system satisfying detailed balance generically relaxes to an equilibrium state in which there are no currents. To generate persistent currents, either detailed balance must be broken or the system must be driven in a time-dependent manner. A stationary system that violates detailed balance evolves to a nonequilibrium steady state (NESS) characterized by fixed currents. Conversely, a system that satisfies instantaneous detailed balance but is driven by the time-periodic variation of external parameters—also known as a stochastic pump (SP)—reaches a periodic state with nonvanishing currents. In both cases, these currents are maintained at the cost of entropy production. Are these two paradigmatic scenarios effectively equivalent? For discrete-state systems, we establish a mapping between nonequilibrium stationary states and stochastic pumps. Given a NESS characterized by a particular set of stationary probabilities, currents, and entropy production rates, we show how to construct a SP with exactly the same (time-averaged) values. The mapping works in the opposite direction as well. These results establish a proof of principle: They show that stochastic pumps are able to mimic the behavior of nonequilibrium steady states, and vice versa, within the theoretical framework of discrete-state stochastic thermodynamics. Nonequilibrium steady states and stochastic pumps are often used to model, respectively, biomolecular motors driven by chemical reactions and artificial molecular machines steered by the variation of external, macroscopic parameters. Our results loosely suggest that anything a biomolecular machine can do, an artificial molecular machine can do equally well. We illustrate this principle by showing that kinetic proofreading, a NESS mechanism that explains the low error rates in biochemical reactions, can be effectively mimicked by a constrained periodic driving.
Yang, Hsin-Sheng; Jansen, Aaron P.; Komar, Anton A.; Zheng, Xiaojing; Merrick, William C.; Costes, Sylvain; Lockett, Stephen J.; Sonenberg, Nahum; Colburn, Nancy H.
2003-01-01
Pdcd4 is a novel transformation suppressor that inhibits tumor promoter-induced neoplastic transformation and the activation of AP-1-dependent transcription required for transformation. A yeast two-hybrid analysis revealed that Pdcd4 associates with the eukaryotic translation initiation factors eIF4AI and eIF4AII. Immunofluorescent confocal microscopy showed that Pdcd4 colocalizes with eIF4A in the cytoplasm. eIF4A is an ATP-dependent RNA helicase needed to unwind 5′ mRNA secondary structure. Recombinant Pdcd4 specifically inhibited the helicase activity of eIF4A and eIF4F. In vivo translation assays showed that Pdcd4 inhibited cap-dependent but not internal ribosome entry site (IRES)-dependent translation. In contrast, Pdcd4D418A, a mutant inactivated for binding to eIF4A, failed to inhibit cap-dependent or IRES-dependent translation or AP-1 transactivation. Recombinant Pdcd4 prevented eIF4A from binding to the C-terminal region of eIF4G (amino acids 1040 to 1560) but not to the middle region of eIF4G(amino acids 635 to 1039). In addition, both Pdcd4 and Pdcd4D418A bound to the middle region of eIF4G. The mechanism by which Pdcd4 inhibits translation thus appears to involve inhibition of eIF4A helicase, interference with eIF4A association-dissociation from eIF4G, and inhibition of eIF4A binding to the C-terminal domain of eIF4G. Pdcd4 binding to eIF4A is linked to its transformation-suppressing activity, as Pdcd4-eIF4A binding and consequent inhibition of translation are required for Pdcd4 transrepression of AP-1. PMID:12482958
Tracking and controlling unstable steady states of dynamical systems
NASA Astrophysics Data System (ADS)
Tamaševičiūtė, Elena; Mykolaitis, Gytis; Bumelienė, Skaidra; Tamaševičius, Arūnas
2014-03-01
An adaptive controller for stabilization of unknown unstable steady states (spirals, nodes and saddles) of nonlinear dynamical systems is considered and its robustness under the changes of the location of the fixed point in the phase space is demonstrated. An analog electronic controller, based on a low-pass filter technique, is described. It can be easily switched between a stable and an unstable mode of operation for stabilizing either spirals/nodes or saddles, respectively. Numerical and experimental results for two autonomous systems, the damped Duffing-Holmes oscillator and the chaotic Lorenz system, are presented.
Steady State Sedimentation in a Liquid Fluidized Bed
NASA Technical Reports Server (NTRS)
Segre, P. N.; Curreri, Peter A. (Technical Monitor)
2002-01-01
The velocity fluctuations and the local particle concentration of a particle suspension exhibiting steady state sedimentation in a fluidized bed are determined as a function of height along the particle column. Both the velocity fluctuations and the particle volume fraction are found to strongly depend on height. We account for the stability of the bed by a simple model evoking a flux balance. Velocity fluctuations driving a downward particle flux are compensated by an upward particle flux stemming from an excess flow velocity due to the concentration gradient of the system.
Steady-State Solution of a Flexible Wing
NASA Technical Reports Server (NTRS)
Karkehabadi, Reza; Chandra, Suresh; Krishnamurthy, Ramesh
1997-01-01
A fluid-structure interaction code, ENSAERO, has been used to compute the aerodynamic loads on a swept-tapered wing. The code has the capability of using Euler or Navier-Stokes equations. Both options have been used and compared in the present paper. In the calculation of the steady-state solution, we are interested in knowing how the flexibility of the wing influences the lift coefficients. If the results of a flexible wing are not affected by the flexibility of the wing significantly, one could consider the wing to be rigid and reduce the problem from fluid-structure interaction to a fluid problem.
Quantum-classical correspondence in steady states of nonadiabatic systems
Fujii, Mikiya; Yamashita, Koichi
2015-12-31
We first present nonadiabatic path integral which is exact formulation of quantum dynamics in nonadiabatic systems. Then, by applying the stationary phase approximations to the nonadiabatic path integral, a semiclassical quantization condition, i.e., quantum-classical correspondence, for steady states of nonadiabatic systems is presented as a nonadiabatic trace formula. The present quantum-classical correspondence indicates that a set of primitive hopping periodic orbits, which are invariant under time evolution in the phase space of the slow degree of freedom, should be quantized. The semiclassical quantization is then applied to a simple nonadiabatic model and accurately reproduces exact quantum energy levels.
Steady State Vacuum Ultraviolet Exposure Facility With Automated Calibration Capability
NASA Technical Reports Server (NTRS)
Stueber, Thomas J.; Sechkar, Edward A.; Dever, Joyce A.; Banks, Bruce A.
2000-01-01
NASA Glenn Research Center at Lewis Field designed and developed a steady state vacuum ultraviolet automated (SSVUVa) facility with in situ VUV intensity calibration capability. The automated feature enables a constant accelerated VUV radiation exposure over long periods of testing without breaking vacuum. This test facility is designed to simultaneously accommodate four isolated radiation exposure tests within the SSVUVa vacuum chamber. Computer-control of the facility for long, term continuous operation also provides control and recording of thermocouple temperatures, periodic recording of VUV lamp intensity, and monitoring of vacuum facility status. This paper discusses the design and capabilities of the SSVUVa facility.
Long Pulse Operation on Tore-Supra: Towards Steady State
Moreau, P.; Bucalossi, J.; Brosset, C.; Dufour, E.; Loarer, T.; Monier-Garbet, P.; Pegourie, B.; Tsitrone, E.; Basiuk, V.; Bremond, S.; Chantant, M.; Colas, L.; Commaux, N.; Geraud, A.; Guirlet, R.; Gunn, J.; Hertout, P.; Hoang, G. T.; Kazarian, F.; Mazon, D.
2006-01-15
The experimental programme of Tore Supra is devoted to the study of technology and physics issues associated to long-duration high performance discharges. This new domain of operation requires simultaneously and in steady state: heat removal capability, particle exhaust, fully non-inductive current drive, advanced technology integration and real time plasma control. The long discharge allows for addressing new time scale physic such as the wall particle retention and erosion. Moreover, the physics of fully non-inductive discharges is full of novelty, namely: the MHD stability, the slow spontaneous oscillation of the central electron temperature or the outstanding inward particle pinch.
Ergodicity, mixing, and time reversibility for atomistic nonequilibrium steady states
Hoover, W.G.; Kum, O.
1997-11-01
Ergodic mixing is prerequisite to any statistical-mechanical calculation of properties derived from atomistic dynamical simulations. Thus the time-reversible thermostats and ergostats used in simulating Gibbsian equilibrium dynamics or nonequilibrium steady-state dynamics should impose ergodicity and mixing. Though it is hard to visualize many-dimensional phase-space distributions, recent developments provide several practical numerical approaches to the problem of ergodic mixing. Here we apply three of these approaches to a useful nonequilibrium test problem, an oscillator in a temperature gradient. {copyright} {ital 1997} {ital The American Physical Society}
A Spreadsheet Program for Steady-State Temperature Distributions
Hutchens, G.J.
2000-11-01
A desktop program is developed in Microsoft EXCEL using Visual Basic for Applications (VBA) to solve a two-dimensional steady state heat conduction problem with a radiation boundary condition. The resulting partial differential equation and boundary conditions are solved using finite difference techniques and the results are compared with a finite element solution using the commercially available software package MSC/THERMAL. The results from the two methods are found to be within 1 percent. The VBA solution demonstrates how spreadsheet programs, like EXCEL, can be used to solve practical engineering problems with good accuracy.
Paleoenvironmental evolution in a steady state foredeep, Taiwan
NASA Astrophysics Data System (ADS)
Nagel, S.; Castelltort, S.; Willett, S. D.; Mouthereau, F.; Lin, A. T.; Granjeon, D.; Kaus, B.
2012-04-01
The evolution of mountain ranges to steady state is an important concept in the study of the interrelationships between climate, mountain building and topography. The young and active Taiwan orogeny situated in the western pacific typhoon belt has often been regarded as the type locality of a steady state orogeny, and an ideal case study for tectonic and climatic geomorphology. One prediction of the steady-state theory applied to mountains is the attainment of a constant sediment flux. Our aim in the present study is to estimate the material flux out of the Taiwan orogeny through its evolution. To do so, we have studied the basin wide sedimentary facies distribution at five key stratigraphic horizons to construct detailed paleogeographic maps that include paleobathymetric information and sediment feeding systems. The maps highlight the complicated basin-wide dynamics of sediment dispersal within an evolving foreland basin. The basin physiography changed very little from the middle Miocene (around 12.5 Ma) to the late Pliocene (around 3 Ma); the paleoenvironments were essentially maintained from the passive margin to the foreland basin stage. At 3 Ma, during deposition of the mud-dominated Chinshui Shale, the main depositional basin started to widen and deepen. This clearly marks the increased subsidence associated with the approach of the growing orogen to the east. The basin started to become filled in the late early Pleistocene when a shallow marine wedge in front of the growing orogen initiated to propagate towards the south. We use Dionisos, a forward stratigraphic model, to simulate the evolution of the Taiwan foreland basin in terms of sediment flux (in and out of the basin) towards steady state. We constrain the model with our paleogeographic and sedimentary reconstructions. As an initial input data we utilize the paleoenvironmental maps and a primary sediment supply from the hinterland (topography). The model enables us to look at the long-term basin
Steady state simulator using alternate left right approach
NASA Astrophysics Data System (ADS)
Ng, Yit Hoe; Hasan, Mohammad Khatim
2013-04-01
Partial difference equation plays important role in simulating a wide variety of science and engineering problem. In this paper, we develop numerical application which implements the iterative methods for steady state simulation and its numerical engine. A new approach names Alternate Left Right is applied onto Successive Overrelaxation (SOR) called as the Alternate Left Right Successive Overrelaxation (ALRSOR) iterative method. The experiment's results are compared amongst SOR and ALRSOR to reveal the performance of these numerical engines. From the results, Alternate Left Right approach successfully increases the speed computation. In conclusion, ALRSOR method performs the fastest amongst the compared method.
Linear modeling of steady-state behavioral dynamics.
Palya, William L; Walter, Donald; Kessel, Robert; Lucke, Robert
2002-01-01
The observed steady-state behavioral dynamics supported by unsignaled periods of reinforcement within repeating 2,000-s trials were modeled with a linear transfer function. These experiments employed improved schedule forms and analytical methods to improve the precision of the measured transfer function, compared to previous work. The refinements include both the use of multiple reinforcement periods that improve spectral coverage and averaging of independently determined transfer functions. A linear analysis was then used to predict behavior observed for three different test schedules. The fidelity of these predictions was determined. PMID:11831782
Skewness of steady-state current fluctuations in nonequilibrium systems
NASA Astrophysics Data System (ADS)
Belousov, Roman; Cohen, E. G. D.; Wong, Chun-Shang; Goree, John A.; Feng, Yan
2016-04-01
A skewness of the probability for instantaneous current fluctuations, in a nonequilibrium steady state, is observed experimentally in a dusty plasma. This skewness is attributed to the spatial asymmetry, which is imminent to the nonequilibrium systems due to the external hydrodynamic gradient. Using the modern framework of the large deviation theory, we extend the Onsager-Machlup ansatz for equilibrium fluctuations to systems with a preferred spatial direction, and provide a modulated Gaussian probability distribution, which is tested by simulations. This probability distribution is also of potential interest for other statistical disciplines. Connections with the principles of statistical mechanics, due to Boltzmann and Gibbs, are discussed as well.
Steady-state flow properties of amorphous materials
NASA Astrophysics Data System (ADS)
Jadhao, Vikram; O'Connor, Thomas; Robbins, Mark
2015-03-01
Molecular dynamics (MD) simulations are used to investigate the steady-state shear flow curves of a standard glass model: the bidisperse Lennard-Jones system. For a wide range of temperatures in the neighborhood of the glass transition temperature Tg predicted by the mode coupling theory, we compute the steady-state shear stress and viscosity as a function of the shear rate γ ˙. At temperatures near and above Tg, the stress crosses over from linear Newtonian behavior at low rates to power law shear-thinning at high rates. As T decreases below Tg, the stress shows a plateau, becoming nearly rate-independent at low γ ˙. There is a weak increase in stress that is consistent with Eyring theory for activated flow of a solid. We find that when the strain rate is reduced to extremely low values, Newtonian behavior appears once more. Insights gained from these simulations are applied to the computation of flow curves of a well-established boundary lubricant: squalane. In the elastohydrodynamic regime, squalane responds like a glassy solid with an Eyring-like response, but at low rates it has a relatively small Newtonian viscosity. Supported by the Army Research Laboratory under Grant W911NF-12-2-0022.
Mechanisms of steady-state nucleate pool boiling in microgravity.
Lee, Ho Sung
2002-10-01
Research on nucleate pool boiling in microgravity using R-113 as a working fluid was conducted using a five-second drop tower and five space flights at a/g approximately 10(-4). A 19 x 38-mm flat gold film heater was used that allowed cine camera viewing both from the side and the bottom of the heater. It was concluded that for both subcooled and saturated liquids long-term steady-state pool boiling can take place in reduced gravity, but the effectiveness of the boiling heat transfer appears to depend on the heater geometry and on the size and the properties of fluids. Heat transfer is enhanced at lower heat flux levels and the CHF increases as the subcooling increases. It was found that several mechanisms are responsible for the steady-state nucleate pool boiling in the absence of buoyancy. The mechanisms considered here are defined and summarized as bubble removal, bubble coalescence, thermocapillary flow, bubble migration, and latent heat transport. PMID:12446341
Zeroth law and nonequilibrium thermodynamics for steady states in contact
NASA Astrophysics Data System (ADS)
Chatterjee, Sayani; Pradhan, Punyabrata; Mohanty, P. K.
2015-06-01
We ask what happens when two nonequilibrium systems in steady state are kept in contact and allowed to exchange a quantity, say mass, which is conserved in the combined system. Will the systems eventually evolve to a new stationary state where a certain intensive thermodynamic variable, like equilibrium chemical potential, equalizes following the zeroth law of thermodynamics and, if so, under what conditions is it possible? We argue that an equilibriumlike thermodynamic structure can be extended to nonequilibrium steady states having short-ranged spatial correlations, provided that the systems interact weakly to exchange mass with rates satisfying a balance condition—reminiscent of a detailed balance condition in equilibrium. The short-ranged correlations would lead to subsystem factorization on a coarse-grained level and the balance condition ensures both equalization of an intensive thermodynamic variable as well as ensemble equivalence, which are crucial for construction of a well-defined nonequilibrium thermodynamics. This proposition is proved and demonstrated in various conserved-mass transport processes having nonzero spatial correlations.
Driven, steady-state RFP computations. [reversed field pinch
NASA Technical Reports Server (NTRS)
Dahlburg, J. P.; Montgomery, D.; Doolen, G. D.; Turner, L.
1988-01-01
The pseudospectral three-dimensional MHD code of Dahlburg et al. (1986 and 1987) is used to compute the dynamical behavior of a channel of magnetofluid carrying an axial current and magnetic flux. This situation contains the essential MHD behavior of the reversed-field pinch (RFP). An externally imposed electric field is applied to an initially current-free magnetofluid and drives currents that rise and eventually fluctuate about values corresponding to pinch ratios Theta of about 1.3, 2.2, and 4.5. A period of violent turbulence leads to an approximately force-free core, surrounded by an active MHD boundary layer that is not force-free. A steady state is reached that can apparently be sustained indefinitely (for several hundred Alfven transit times or longer). The turbulence level and time variability in the steady state increase with increasing Theta. The average toroidal magnetic field at the wall reverses for Theta = 2.2 and 4.5, but not for Theta = 1.3. Negative toroidal current filaments are observed. The Lundquist numbers are of the order of a few hundred.
Integrated stoichiometric, thermodynamic and kinetic modelling of steady state metabolism
Fleming, R.M.T.; Thiele, I.; Provan, G.; Nasheuer, H.P.
2010-01-01
The quantitative analysis of biochemical reactions and metabolites is at frontier of biological sciences. The recent availability of high-throughput technology data sets in biology has paved the way for new modelling approaches at various levels of complexity including the metabolome of a cell or an organism. Understanding the metabolism of a single cell and multi-cell organism will provide the knowledge for the rational design of growth conditions to produce commercially valuable reagents in biotechnology. Here, we demonstrate how equations representing steady state mass conservation, energy conservation, the second law of thermodynamics, and reversible enzyme kinetics can be formulated as a single system of linear equalities and inequalities, in addition to linear equalities on exponential variables. Even though the feasible set is non-convex, the reformulation is exact and amenable to large-scale numerical analysis, a prerequisite for computationally feasible genome scale modelling. Integrating flux, concentration and kinetic variables in a unified constraint-based formulation is aimed at increasing the quantitative predictive capacity of flux balance analysis. Incorporation of experimental and theoretical bounds on thermodynamic and kinetic variables ensures that the predicted steady state fluxes are both thermodynamically and biochemically feasible. The resulting in silico predictions are tested against fluxomic data for central metabolism in E. coli and compare favourably with in silico prediction by flux balance analysis. PMID:20230840
Integrated stoichiometric, thermodynamic and kinetic modelling of steady state metabolism.
Fleming, R M T; Thiele, I; Provan, G; Nasheuer, H P
2010-06-01
The quantitative analysis of biochemical reactions and metabolites is at frontier of biological sciences. The recent availability of high-throughput technology data sets in biology has paved the way for new modelling approaches at various levels of complexity including the metabolome of a cell or an organism. Understanding the metabolism of a single cell and multi-cell organism will provide the knowledge for the rational design of growth conditions to produce commercially valuable reagents in biotechnology. Here, we demonstrate how equations representing steady state mass conservation, energy conservation, the second law of thermodynamics, and reversible enzyme kinetics can be formulated as a single system of linear equalities and inequalities, in addition to linear equalities on exponential variables. Even though the feasible set is non-convex, the reformulation is exact and amenable to large-scale numerical analysis, a prerequisite for computationally feasible genome scale modelling. Integrating flux, concentration and kinetic variables in a unified constraint-based formulation is aimed at increasing the quantitative predictive capacity of flux balance analysis. Incorporation of experimental and theoretical bounds on thermodynamic and kinetic variables ensures that the predicted steady state fluxes are both thermodynamically and biochemically feasible. The resulting in silico predictions are tested against fluxomic data for central metabolism in Escherichia coli and compare favourably with in silico prediction by flux balance analysis. PMID:20230840
Steady-state wear and friction in boundary lubrication studies
NASA Technical Reports Server (NTRS)
Loomis, W. R.; Jones, W. R., Jr.
1980-01-01
A friction and wear study was made at 20 C to obtain improved reproducibility and reliability in boundary lubrication testing. Ester-base and C-ether-base fluids were used to lubricate a pure iron rider in sliding contact with a rotating M-50 steel disk in a friction and wear apparatus. Conditions included loads of 1/2 and 1 kg and sliding velocities of 3.6 to 18.2 m/min in a dry air atmosphere and stepwise time intervals from 1 to 250 min for wear measurements. The wear rate results were compared with those from previous studies where a single 25 min test period was used. Satisfactory test conditions for studying friction and wear in boundary lubrication for this apparatus were found to be 1 kg load; sliding velocities of 7.1 to 9.1 m/min (50 rpm disk speed); and use of a time stepwise test procedure. Highly reproducible steady-state wear rates and steady-state friction coefficients were determined under boundary conditions. Wear rates and coefficients of friction were constant following initially high values during run-in periods.
Drug Sanctuaries, Low Steady State Viral Loads and Viral Blips.
Perelson, Alan S.,; Callaway, D.; Pomerantz, R. J.; Chen, H. Y.; Markowitz, M.; Ho, David D.; Di Mascio, M.
2002-01-01
Patients on HAART for long periods of time obtain viral loads (VLs) below 50 copies/ml. Ultrasensitive VL assays show that some of these patients obtain a low steady state VL, while others continue to exhibit VL declines to below 5 copies/ml. Low steady states can be explained by two-compartment models that incorporate a drug sanctuary. Interestingly, when patients exhibit continued declines below 50 copies/ml the rate of decline has a half-life of {approx} 6 months, consistent with some estimates of the rate of latent cell decline. Some patients, despite having sustained undetectable VLs show periods of transient viremia (blips). I will present some statistical characterization of the blips observed in a set of 123 patients, suggesting that blips are generated largely by random processes, that blips tend to correspond to periods of a few weeks in which VLs are elevated, and that VL decay from the peak of a blip may have two-phases. Using new results suggesting that the viral burst size, N {approx} 5 x 10{sup 4}, we estimate the number of cells needed to produce a blip.
Steady State Erosion of Granular Particles by Shear Flow
NASA Astrophysics Data System (ADS)
Allen, Benjamin; Kudrolli, Arshad
2015-11-01
Despite decades of scientific observation of rivers, streams and laboratory experiments the process of erosion still is not understood. Empirical fits are used to determine when erosion starts with more than an order of magnitude scatter or a shifting power law determining how much material erodes away. In order to study the many body problem of multiple particles we first need to understand the basics of a single particle eroding from a potential well in laminar flow. Using different particle densities and different barrier heights we looked at the onset of erosion and the balance of forces and torques to create a predictive model of when a single particle will erode over a barrier of a given height as a function of shear rate and viscosity. We then create a steady state system in which to image erosion as it happens and simultaneously measure flow velocity and particle movement. Measuring particle movement allows us to determine when steady state erosion occurs and calculate the fluxes and slip velocities at the beginning of the erosion process as we transition from rolling particles to particles suspended in the fluid flow. NSF Grant Number CBET 1335928.
Nonequilibrium many-body steady states via Keldysh formalism
NASA Astrophysics Data System (ADS)
Maghrebi, Mohammad F.; Gorshkov, Alexey V.
2016-01-01
Many-body systems with both coherent dynamics and dissipation constitute a rich class of models which are nevertheless much less explored than their dissipationless counterparts. The advent of numerous experimental platforms that simulate such dynamics poses an immediate challenge to systematically understand and classify these models. In particular, nontrivial many-body states emerge as steady states under nonequilibrium dynamics. While these states and their phase transitions have been studied extensively with mean-field theory, the validity of the mean-field approximation has not been systematically investigated. In this paper, we employ a field-theoretic approach based on the Keldysh formalism to study nonequilibrium phases and phase transitions in a variety of models. In all cases, a complete description via the Keldysh formalism indicates a partial or complete failure of the mean-field analysis. Furthermore, we find that an effective temperature emerges as a result of dissipation, and the universal behavior including the dynamics near the steady state is generically described by a thermodynamic universality class.
Steady state magnetic field configurations for the earth's magnetotail
Hau, L.N.; Wolf, R.A.; Voigt, G.H. ); Wu, C.C. )
1989-02-01
The authors present a two-dimensional, force-balanced magnetic field model in which flux tubes have constant pV{gamma} throughout an extended region of the nightside plasma sheet, between approximately 36 R{sub E} geocentric distance and the region of the inner edge of the plasma sheet. They have thus demonstrated the theoretical existence of a steady state magnetic field configuration that is force-balanced and also consistent with slow, lossless, adiabatic, earthward convection within the limit of the ideal MHD (isotropic pressure, perfect conductivity). The numerical solution was constructed for a two-dimensional magnetosphere with a rectangular magnetopause and nonflaring tail. The primary characteristics of the steady state convection solution are (1) a pressure maximum just tailward of the inner edge of the plasma sheet and (2) a deep, broad minimum in equatorial magnetic field strength B{sub ze}, also just tailward of the inner edge. The results are consistent with Erickson's (1985) convection time sequences, which exhibited analogous pressure peaks and B{sub ze} minima. Observations do not indicate the existence of a B{sub ze} minimum, on the average. They suggest that the configurations with such deep minima in B{sub ze} may be tearing-mode unstable, thus leading to substorm onset in the inner plasma sheet.
Non-steady state tidal heating of Enceladus
NASA Astrophysics Data System (ADS)
Shoji, D.; Hussmann, H.; Sohl, F.; Kurita, K.
2014-06-01
Enceladus is one of the most geologically active bodies in the Solar System. The satellite's diverse surface suggests that Enceladus was subject to past episodic heating. It is largely probable that the activity of Enceladus is not in a steady state. In order to analyze the non-steady state heating, thermal and orbital coupled calculation is needed because they affect each other. We perform the coupled calculation assuming conductive ice layer and low melting temperature. Although the heating state of Enceladus strongly depends on the rheological parameters used, episodic heating is induced if the Q-value of Saturn is less than 23,000 and Enceladus' core radius is less than 161 km. The duration of one episodic heating cycle is around one hundred million years. The cyclic change in ice thickness is consistent with the origin of a partial ocean which is suggested by plume emissions and diverse surface states of Enceladus. Although the obtained tidal heating rate is smaller than the observed heat flux of a few giga watt, other heating mechanisms involving e.g., liquid water and/or specific chemical reactions may be initiated by the formation of a partial or global subsurface ocean.
Gas-turbine engine steady-state behavior
NASA Astrophysics Data System (ADS)
Curnock, Barry
A set of graphics with explanations illustrating gas turbine engine steady state behavior are presented. Typical combinations of compressors and nozzles which occur in a gas turbine engine are shown. The basic effect of a nozzle is explained by considering a compressor on a test rig: typical compressor, fan, and turbine characteristics are illustrated. The following are discussed: the degrees of freedom of an aeroengine (the flow and the power); the 'working lines' of components (the locus of the off design steady state operating points of a component plotted on a chart of that components characteristics); bleed and whirl; offtakes; P1 effects (performance changes which modify the basic nondimensional behavior an engine (caused by the effect on Reynolds number levels and on engine mechanical configuration of basic engine inlet pressure level)), and T1 effects (performance changes which modify the basic nondimensional behavior of an engine and are caused by the effects of engine inlet temperature level on Reynolds number level, on engine mechanical configuration and on specific heat level); variable nozzles; and turbojet matching.
Steady-State ALPS for Real-Valued Problems
NASA Technical Reports Server (NTRS)
Hornby, Gregory S.
2009-01-01
The two objectives of this paper are to describe a steady-state version of the Age-Layered Population Structure (ALPS) Evolutionary Algorithm (EA) and to compare it against other GAs on real-valued problems. Motivation for this work comes from our previous success in demonstrating that a generational version of ALPS greatly improves search performance on a Genetic Programming problem. In making steady-state ALPS some modifications were made to the method for calculating age and the method for moving individuals up layers. To demonstrate that ALPS works well on real-valued problems we compare it against CMA-ES and Differential Evolution (DE) on five challenging, real-valued functions and on one real-world problem. While CMA-ES and DE outperform ALPS on the two unimodal test functions, ALPS is much better on the three multimodal test problems and on the real-world problem. Further examination shows that, unlike the other GAs, ALPS maintains a genotypically diverse population throughout the entire search process. These findings strongly suggest that the ALPS paradigm is better able to avoid premature convergence then the other GAs.
Tomao, Luigi; Sbardella, Diego; Gioia, Magda; Di Masi, Alessandra; Marini, Stefano; Ascenzi, Paolo; Coletta, Massimo
2014-01-01
Prostate-specific antigen (PSA), an enzyme of 30 kDa grouped in the kallikrein family is synthesized to high levels by normal and malignant prostate epithelial cells. Therefore, it is the main biomarker currently used for early diagnosis of prostate cancer. Here, presteady-state and steady-state kinetics of the PSA-catalyzed hydrolysis of the fluorogenic substrate Mu-His-Ser-Ser-Lys-Leu-Gln-AMC (spanning from pH 6.5 to pH 9.0, at 37.0°C) are reported. Steady-state kinetics display at every pH value a peculiar feature, represented by an initial “burst” phase of the fluorescence signal before steady-state conditions are taking place. This behavior, which has been already observed in other members of the kallikrein family, suggests the occurrence of a proteolytic mechanism wherefore the acylation step is faster than the deacylation process. This feature allows to detect the acyl intermediate, where the newly formed C-terminal carboxylic acid of the cleaved substrate forms an ester bond with the -OH group of the Ser195 catalytic residue, whereas the AMC product has been already released. Therefore, the pH-dependence of the two enzymatic steps (i.e., acylation and deacylation) has been separately characterized, allowing the determination of pKa values. On this basis, possible residues are tentatively identified in PSA, which might regulate these two steps by interacting with the two portions of the substrate. PMID:25068395
Dowling, Ryan J O; Zakikhani, Mahvash; Fantus, I George; Pollak, Michael; Sonenberg, Nahum
2007-11-15
Metformin is used for the treatment of type 2 diabetes because of its ability to lower blood glucose. The effects of metformin are explained by the activation of AMP-activated protein kinase (AMPK), which regulates cellular energy metabolism. Recently, we showed that metformin inhibits the growth of breast cancer cells through the activation of AMPK. Here, we show that metformin inhibits translation initiation. In MCF-7 breast cancer cells, metformin treatment led to a 30% decrease in global protein synthesis. Metformin caused a dose-dependent specific decrease in cap-dependent translation, with a maximal inhibition of 40%. Polysome profile analysis showed an inhibition of translation initiation as metformin treatment of MCF-7 cells led to a shift of mRNAs from heavy to light polysomes and a concomitant increase in the amount of 80S ribosomes. The decrease in translation caused by metformin was associated with mammalian target of rapamycin (mTOR) inhibition, and a decrease in the phosphorylation of S6 kinase, ribosomal protein S6, and eIF4E-binding protein 1. The effects of metformin on translation were mediated by AMPK, as treatment of cells with the AMPK inhibitor compound C prevented the inhibition of translation. Furthermore, translation in MDA-MB-231 cells, which lack the AMPK kinase LKB1, and in tuberous sclerosis complex 2 null (TSC2(-/-)) mouse embryonic fibroblasts was unaffected by metformin, indicating that LKB1 and TSC2 are involved in the mechanism of action of metformin. These results show that metformin-mediated AMPK activation leads to inhibition of mTOR and a reduction in translation initiation, thus providing a possible mechanism of action of metformin in the inhibition of cancer cell growth. PMID:18006825
Seeing the talker’s face supports executive processing of speech in steady state noise
Mishra, Sushmit; Lunner, Thomas; Stenfelt, Stefan; Rönnberg, Jerker; Rudner, Mary
2013-01-01
Listening to speech in noise depletes cognitive resources, affecting speech processing. The present study investigated how remaining resources or cognitive spare capacity (CSC) can be deployed by young adults with normal hearing. We administered a test of CSC (CSCT; Mishra et al., 2013) along with a battery of established cognitive tests to 20 participants with normal hearing. In the CSCT, lists of two-digit numbers were presented with and without visual cues in quiet, as well as in steady-state and speech-like noise at a high intelligibility level. In low load conditions, two numbers were recalled according to instructions inducing executive processing (updating, inhibition) and in high load conditions the participants were additionally instructed to recall one extra number, which was the always the first item in the list. In line with previous findings, results showed that CSC was sensitive to memory load and executive function but generally not related to working memory capacity (WMC). Furthermore, CSCT scores in quiet were lowered by visual cues, probably due to distraction. In steady-state noise, the presence of visual cues improved CSCT scores, probably by enabling better encoding. Contrary to our expectation, CSCT performance was disrupted more in steady-state than speech-like noise, although only without visual cues, possibly because selective attention could be used to ignore the speech-like background and provide an enriched representation of target items in working memory similar to that obtained in quiet. This interpretation is supported by a consistent association between CSCT scores and updating skills. PMID:24324411
Gruys, K J; Marzabadi, M R; Pansegrau, P D; Sikorski, J A
1993-08-01
Recently it has been found that the kinetic mechanism for Escherichia coli 5-enolpyruvoylshikimate-3-phosphate synthase (EPSPS) in the forward direction is random with synergistic binding of substrates and inhibitors (K. J. Gruys, M. C. Walker, and J. A. Sikorski, 1992, Biochemistry 31, 5534). This work, however, did not address the reverse reaction with 5-enolpyruvoylshikimate-3-phosphate (EPSP) and phosphate (Pi) as substrates where a similar question of random versus ordered addition of substrates remained. Previous transient-state kinetic results led to a proposal for an equilibrium-ordered mechanism, where binding of EPSP occurs first followed by Pi (K. S. Anderson, and K. A. Johnson, 1990, Chem. Rev. 90, 1131). Steady-state kinetic results of the reverse reaction presented here suggest that, like the forward reaction, addition of substrates occurs randomly. Initial velocity studies with EPSP and Pi show a normal intersecting pattern in the reciprocal plots, consistent with a random or steady-state-ordered mechanism, but not with equilibrium-ordered addition of substrates. Inhibition of the EPSPS reverse reaction by 5-amino-S3P or the S3P-glyphosate hybrid molecule gave the expected competitive patterns versus EPSP, but mixed noncompetitive patterns versus Pi. These results also disfavor an equilibrium-ordered model, but again are consistent with a random or steady-state-ordered mechanism. A more quantitative mechanistic analysis of the inhibition data to determine the true rather than apparent Ki values provides evidence for a random over a steady-state-ordered addition of substrates. These results in combination with previous findings lead to the conclusion that the mechanism is random addition of EPSP and Pi since it is the only possible model for substrate addition that is consistent with the cumulative data from all kinetic (transient- as well as steady-state) and direct binding studies. PMID:8346911
Adaptation of the Steady-state PERG in Early Glaucoma
Porciatti, Vittorio; Bosse, Brandon; Parekh, Prashant K.; Shif, Olga A.; Feuer, William J.; Ventura, Lori M.
2013-01-01
Purpose Previous studies have shown that the onset of high-contrast, fast reversing patterned stimuli induces rapid blood flow increase in retinal vessels in association with slow changes of the steady-state PERG signal. We tested the hypothesis that adaptive PERG changes of normal controls (NC) differed from those of glaucoma suspects (GS) and patients with early manifest glaucoma (EMG). Methods Subjects were 42 GS (SAP MD −0.89 ±1.8 dB), 22 EMG (MD −2.12 ±2.4 dB) with visual acuity of ≥20/20 and 16 age-matched NC from a previous study. The PERG signal was sampled every ~15 s over 4 minutes in response to gratings (1.6 cyc/deg, 100% contrast) reversing 16.28 times/s. Amplitude/phase values of successive PERG samples were fitted with a non-parametric LOWESS smoothing function to retrieve the initial and final values and calculate their difference (delta) and the residual standard deviation around the fitted function (SDr). The magnitude of PERG adaptive change compared to random variability was calculated as log10 of percentage coefficient of variation CoV=100*SDr ÷ |delta|. Grand-average PERGs were also obtained by averaging all samples of the same series. Results The grand-average PERG amplitude (ANOVA, p=0.02), but not phase (ANOVA, p=0.63), decreased with increasing severity of disease. Adaptive changes (log10 (CoV) of PERG amplitude were not significantly associated with disease severity (ANOVA, p=0.27), but adaptive changes (log10 (CoV) of PERG phase were (ANOVA, p=0.037; linear trend, p=0.011). Conclusions The steady-state PERG signal displayed slow adaptive changes over time that could be isolated from random variability. PERG adaptive changes differed from those of grand-average PERGs (corresponding the standard steady-state PERG), thus representing a new source of biological information about retinal ganglion cell function that may have potential in the study of glaucoma and optic nerve diseases. PMID:23429613
Steady-state hydrodynamics of a viscous incompressible fluid with spinning particles.
Felderhof, B U
2011-12-21
The steady-state hydrodynamics of a viscous incompressible fluid with spinning particles is studied on the basis of extended Stokes equations. The profiles of flow velocity and spin velocity in simple flow situations may be used to determine the vortex viscosity and spin viscosity of the molecular liquid or fluid suspension. As an example, one situation studied is the flow generated by a uniform torque density in a planar layer of infinite fluid. The spinning particles drive a nearly uniform flow on either side of the layer, in opposite directions on the two sides. The Green function of the extended Stokes equations is derived. The translational and rotational friction coefficients of a sphere with no-slip boundary conditions, and the corresponding flow profiles, are calculated. PMID:22191899
Steady state model of an industrial FCC unit
Lopez-Isunza, F.; Ancheyta-Juarez, J.
1996-12-31
A reactor model has been developed to simulate the steady-state of an industrial fluid catalytic cracking unit using a three-lump kinetic expression with parameters estimated from experiments in a microactivity test reactor. The model considers a transported bed reactor (riser) where gas-oil and catalyst are in contact to perform the endothermic cracking reactions, interacting with a two-phase moving bed regenerator with recirculation where the combustion of the coke deposited on the catalyst takes place. The model is used to find best operating conditions for maximizing gasoline yield in terms of gas-oil feed temperature (To) and recycled catalyst to gas-oil ratio (C/O). 12 refs., 4 figs.
Steady State Temperature Profile in a Cylinder Heated by Microwaves
NASA Technical Reports Server (NTRS)
Jackson, H. W.; Barmatz, M.; Wagner, P.
1995-01-01
A new theory has been developed to calculate the steady state temperature profile in a cylindrical sample positioned along the entire axis of a cylindrical microwave cavity. Temperature profiles where computed for- alumina rods of various radii contained in a cavity excite in one of the TM(sub OnO) modes with n = 1, 2 or 3. Calculations where also performed with a concentric outer cylindrical tube surrounding the rod to investigate hybrid heating. The parameters studies of the sample center and surface temperature where performed as a function of the total power transmitted into the cavity. Also, the total hemispherical emissivity was varied at boundaries of the rod, surrounding tube, and cavity walls. The result are discussed in the context of controlling the average rod temperature and the temperature distribution in the rod during microwave processing.
Steady-State Density Functional Theory for Finite Bias Conductances.
Stefanucci, G; Kurth, S
2015-12-01
In the framework of density functional theory, a formalism to describe electronic transport in the steady state is proposed which uses the density on the junction and the steady current as basic variables. We prove that, in a finite window around zero bias, there is a one-to-one map between the basic variables and both local potential on as well as bias across the junction. The resulting Kohn-Sham system features two exchange-correlation (xc) potentials, a local xc potential, and an xc contribution to the bias. For weakly coupled junctions the xc potentials exhibit steps in the density-current plane which are shown to be crucial to describe the Coulomb blockade diamonds. At small currents these steps emerge as the equilibrium xc discontinuity bifurcates. The formalism is applied to a model benzene junction, finding perfect agreement with the orthodox theory of Coulomb blockade. PMID:26571349
The thermal vacuum for non-equilibrium steady state
NASA Astrophysics Data System (ADS)
Imai, Ryosuke; Kuwahara, Yukiro; Nakamura, Yusuke; Yamanaka, Yoshiya
Our purpose is to construct a theoretical description of non-equilibrium steady state (NESS), employing thermo field dynamics (TFD). TFD is the operator-based formalism of thermal quautum field theory, where every degree of freedom is doubled and thermal averages are given by expectation values of the thermal vacuum. To specify the thermal vacuum for NESS is a non-trivial issue, and we attempt it on the analogy between the superoperator formalism and TFD. Using the thermal vacuum thus obtained, we analyze the NESS which is realized in the two-reservoir model. It will be shown that the NESS vacuum of the model coincides with the fixed point solutions of the quantum transport equation derived by the self-consistent renormalization of the self-energy in non-equilibrium TFD.
Entropy Production and Non-Equilibrium Steady States
NASA Astrophysics Data System (ADS)
Suzuki, Masuo
2013-01-01
The long-term issue of entropy production in transport phenomena is solved by separating the symmetry of the non-equilibrium density matrix ρ(t) in the von Neumann equation, as ρ(t) = ρs(t) + ρa(t) with the symmetric part ρs(t) and antisymmetric part ρa(t). The irreversible entropy production (dS/dt)irr is given in M. Suzuki, Physica A 390(2011)1904 by (dS/dt)irr = Tr( {H}(dρ s{(t)/dt))}/T for the Hamiltonian {H} of the relevant system. The general formulation of the extended von Neumann equation with energy supply and heat extraction is reviewed from the author's paper (M. S.,Physica A391(2012)1074). irreversibility; entropy production; transport phenomena; electric conduction; thermal conduction; linear response; Kubo formula; steady state; non-equilibrium density matrix; energy supply; symmetry-separated von Neumann equation; unboundedness.
Steady-state plasma transition in the Venus ionosheath
NASA Technical Reports Server (NTRS)
Perez-De-tejada, H.; Intriligator, D. S.; Strangeway, R. J.
1991-01-01
The results of an extended analysis of the plasma and electric field data of the Pioneer Venus Orbiter (PVO) are presented. The persistent presence of a plasma transition embedded in the flanks of the Venus ionosheath between the bow shock and the ionopause is reported. This transition is identified by the repeated presence of characteristic bursts in the 30 kHz channel of the electric field detector of the PVO. The observed electric field signals coincide with the onset of different plasma conditions in the inner ionosheath where more rarified plasma fluxes are measured. The repeated identification of this intermediate ionosheath transition in the PVO data indicates that it is present as a steady state feature of the Venus plasma environment. The distribution of PVO orbits in which the transition is observed suggests that it is more favorably detected in the vicinity of and downstream from the terminator.
Fueling Requirements for Steady State high butane current fraction discharges
R.Raman
2003-10-08
The CT injector originally used for injecting CTs into 1T toroidal field discharges in the TdeV tokamak was shipped PPPL from the Affiliated Customs Brokers storage facility in Montreal during November 2002. All components were transported safely, without damage, and are currently in storage at PPPL, waiting for further funding in order to begin advanced fueling experiments on NSTX. The components are currently insured through the University of Washington. Several technical presentations were made to investigate the feasibility of the CT injector installation on NSTX. These technical presentations, attached to this document, were: (1) Motivation for Compact Toroida Injection in NSTX; (2) Assessment of the Engineering Feasibility of Installing CTF-II on NSTX; (3) Assessment of the Cost for CT Installation on NSTX--A Peer Review; and (4) CT Fueling for NSTX FY 04-08 steady-state operation needs.
NASA Lewis Steady-State Heat Pipe Code Architecture
NASA Technical Reports Server (NTRS)
Mi, Ye; Tower, Leonard K.
2013-01-01
NASA Glenn Research Center (GRC) has developed the LERCHP code. The PC-based LERCHP code can be used to predict the steady-state performance of heat pipes, including the determination of operating temperature and operating limits which might be encountered under specified conditions. The code contains a vapor flow algorithm which incorporates vapor compressibility and axially varying heat input. For the liquid flow in the wick, Darcy s formula is employed. Thermal boundary conditions and geometric structures can be defined through an interactive input interface. A variety of fluid and material options as well as user defined options can be chosen for the working fluid, wick, and pipe materials. This report documents the current effort at GRC to update the LERCHP code for operating in a Microsoft Windows (Microsoft Corporation) environment. A detailed analysis of the model is presented. The programming architecture for the numerical calculations is explained and flowcharts of the key subroutines are given
Taylor dispersion in equilibrium gradient focusing at steady state.
Ivory, Cornelius F
2015-03-01
An analytic expression is presented for the effective dispersion coefficient in the case where a solute is focused in a parabolic flow against a linear gradient in a restoring force. This expression was derived by employing a minor variation on the method of moments used by Aris in his development of the dispersion coefficients for a time-dependent, isocratic system. In the present case, dispersion is controlled by two dimensionless groups, a Peclet number which is proportional to the parabolic component of the flow, and a gradient number which is proportional to the slope of the restoring force. These results confirm that the Aris-Taylor expression for the dispersion coefficient should not be applied in cases where a solute is focused to a stationary steady state. PMID:25521436
Nuclide Importance and the Steady-State Burnup Equation
Sekimoto, Hiroshi; Nemoto, Atsushi
2000-05-15
Conventional methods for evaluating some characteristic values of nuclides relating to burnup in a given neutron spectrum are reviewed in a mathematically systematic way, and a new method based on the importance theory is proposed. In this method, these characteristic values of a nuclide are equivalent to the importances of the nuclide. By solving the equation adjoint to the steady-state burnup equation with a properly chosen source term, the importances for all nuclides are obtained simultaneously.The fission number importance, net neutron importance, fission neutron importance, and absorbed neutron importance are evaluated and discussed. The net neutron importance is a measure directly estimating neutron economy, and it can be evaluated simply by calculating the fission neutron importance minus the absorbed neutron importance, where only the absorbed neutron importance depends on the fission product. The fission neutron importance and absorbed neutron importance are analyzed separately, and detailed discussions of the fission product effects are given for the absorbed neutron importance.
Quasi-steady-state analysis of coupled flashing ratchets
NASA Astrophysics Data System (ADS)
Levien, Ethan; Bressloff, Paul C.
2015-10-01
We perform a quasi-steady-state (QSS) reduction of a flashing ratchet to obtain a Brownian particle in an effective potential. The resulting system is analytically tractable and yet preserves essential dynamical features of the full model. We first use the QSS reduction to derive an explicit expression for the velocity of a simple two-state flashing ratchet. In particular, we determine the relationship between perturbations from detailed balance, which are encoded in the transitions rates of the flashing ratchet, and a tilted-periodic potential. We then perform a QSS analysis of a pair of elastically coupled flashing ratchets, which reduces to a Brownian particle moving in a two-dimensional vector field. We suggest that the fixed points of this vector field accurately approximate the metastable spatial locations of the coupled ratchets, which are, in general, impossible to identify from the full system.
[Auditory steady-state responses--the state of art].
Szymańska, Anna; Gryczyński, Maciej; Pajor, Anna
2010-01-01
The auditory steady-state responses (ASSR) is quite a new method of electrophysiological threshold estimation with no clinical standards. It was the aim of this study to review practical and theoretical thesis of ASSR and mention recent recommendations and achievements of this technique. The most common application of ASSR is diagnosis of hearing loss in children together with ABR test. In this paper we mentioned information about influence of physiological factors (age, sex, state of arousal, handedness) and type of recording technique (electrodes placement, air and bone stimulation, occlusion effect, amplitude and frequency stimulation, multiple or single frequency stimulation, dichotic and monotic recording technique and type of hearing loss) on ASSR. We conclude that putting ASSR in clinical use as an standardized method it is necessary to do research with numerous groups of patients using the same equipment and parameters of tests. PMID:21166136
Steady state asymmetric planetary electrical induction. [by solar wind
NASA Technical Reports Server (NTRS)
Horning, B. L.; Schubert, G.
1974-01-01
An analytic solution is presented for the steady state electric and magnetic fields induced by the motional electric field of the solar wind in the atmosphere or interior of a planet that is asymmetrically surrounded by solar wind plasma. The electrically conducting ionosphere or interior must be in direct electrical contact with the solar wind over the day side of the planet. The conducting region of the planet is modeled by a sphere or a spherical shell of arbitrarily stratified electrical conductivity. A monoconducting cylindrical cavity is assumed to extend downstream on the night side of the planet. The solar wind is assumed to be highly conducting so that the induced fields are confined to the planet and cavity. Induced currents close as sheet currents at the solar wind-cavity and solar wind-planet interfaces. Numerical evaluations of the analytic formulas are carried out for a uniformly conducting spherical model.
Steady States in SIRS Epidemical Model of Mobile Individuals
NASA Astrophysics Data System (ADS)
Zhang, Duan-Ming; He, Min-Hua; Yu, Xiao-Ling; Pan, Gui-Jun; Sun, Hong-Zhang; Su, Xiang-Ying; Sun, Fan; Yin, Yan-Ping; Li, Rui; Liu, Dan
2006-01-01
We consider an epidemical model within socially interacting mobile individuals to study the behaviors of steady states of epidemic propagation in 2D networks. Using mean-field approximation and large scale simulations, we recover the usual epidemic behavior with critical thresholds δc and pc below which infectious disease dies out. For the population density δ far above δc, it is found that there is linear relationship between contact rate λ and the population density δ in the main. At the same time, the result obtained from mean-field approximation is compared with our numerical result, and it is found that these two results are similar by and large but not completely the same.
Modelling of pulsed and steady-state DEMO scenarios
NASA Astrophysics Data System (ADS)
Giruzzi, G.; Artaud, J. F.; Baruzzo, M.; Bolzonella, T.; Fable, E.; Garzotti, L.; Ivanova-Stanik, I.; Kemp, R.; King, D. B.; Schneider, M.; Stankiewicz, R.; Stępniewski, W.; Vincenzi, P.; Ward, D.; Zagórski, R.
2015-07-01
Scenario modelling for the demonstration fusion reactor (DEMO) has been carried out using a variety of simulation codes. Two DEMO concepts have been analysed: a pulsed tokamak, characterized by rather conventional physics and technology assumptions (DEMO1) and a steady-state tokamak, with moderately advanced physics and technology assumptions (DEMO2). Sensitivity to impurity concentrations, radiation, and heat transport models has been investigated. For DEMO2, the impact of current driven non-inductively by neutral beams has been studied by full Monte Carlo simulations of the fast ion distribution. The results obtained are a part of a more extensive research and development (R&D) effort carried out in the EU in order to develop a viable option for a DEMO reactor, to be adopted after ITER for fusion energy research.
Dust remobilization in fusion plasmas under steady state conditions
NASA Astrophysics Data System (ADS)
Tolias, P.; Ratynskaia, S.; De Angeli, M.; De Temmerman, G.; Ripamonti, D.; Riva, G.; Bykov, I.; Shalpegin, A.; Vignitchouk, L.; Brochard, F.; Bystrov, K.; Bardin, S.; Litnovsky, A.
2016-02-01
The first combined experimental and theoretical studies of dust remobilization by plasma forces are reported. The main theoretical aspects of remobilization in fusion devices under steady state conditions are analyzed. In particular, the dominant role of adhesive forces is highlighted and generic remobilization conditions—direct lift-up, sliding, rolling—are formulated. A novel experimental technique is proposed, based on controlled adhesion of dust grains on tungsten samples combined with detailed mapping of the dust deposition profile prior and post plasma exposure. Proof-of-principle experiments in the TEXTOR tokamak and the EXTRAP-T2R reversed-field pinch are presented. The versatile environment of the linear device Pilot-PSI allowed for experiments with different magnetic field topologies and varying plasma conditions that were complemented with camera observations.
Waveguides formed by quasi-steady-state photorefractive spatial solitons
NASA Astrophysics Data System (ADS)
Morin, Matthew; Duree, Galen; Salamo, Gregory; Segev, Mordechai
1995-10-01
We show that a quasi-steady-state photorefractive spatial soliton forms a waveguide structure in the bulk of a photorefractive material. Although the optically induced waveguide is formed by a very low-power (microwatts) soliton beam, it can guide a powerful (watt) beam of a longer wavelength at which the medium is nonphotosensitive. Furthermore, the waveguide survives, either in the dark or when guiding the longer-wavelength beam, for a long time after the soliton beam is turned off. We take advantage of the solitons' property of evolution from a relatively broad input beam into a narrow channel and show that the soliton induces a tapered waveguide (an optical funnel) that improves the coupling efficiency of light into the waveguiding structure.
Computational complexity of nonequilibrium steady states of quantum spin chains
NASA Astrophysics Data System (ADS)
Marzolino, Ugo; Prosen, Tomaž
2016-03-01
We study nonequilibrium steady states (NESS) of spin chains with boundary Markovian dissipation from the computational complexity point of view. We focus on X X chains whose NESS are matrix product operators, i.e., with coefficients of a tensor operator basis described by transition amplitudes in an auxiliary space. Encoding quantum algorithms in the auxiliary space, we show that estimating expectations of operators, being local in the sense that each acts on disjoint sets of few spins covering all the system, provides the answers of problems at least as hard as, and believed by many computer scientists to be much harder than, those solved by quantum computers. We draw conclusions on the hardness of the above estimations.
Typical pure nonequilibrium steady states and irreversibility for quantum transport.
Monnai, Takaaki; Yuasa, Kazuya
2016-07-01
It is known that each single typical pure state in an energy shell of a large isolated quantum system well represents a thermal equilibrium state of the system. We show that such typicality holds also for nonequilibrium steady states (NESS's). We consider a small quantum system coupled to multiple infinite reservoirs. In the long run, the total system reaches a unique NESS. We identify a large Hilbert space from which pure states of the system are to be sampled randomly and show that the typical pure states well describe the NESS. We also point out that the irreversible relaxation to the unique NESS is important to the typicality of the pure NESS's. PMID:27575115
Steady-state magma discharge at Etna 1971-81
NASA Technical Reports Server (NTRS)
Wadge, G.; Guest, J. E.
1981-01-01
Throughout the past decade Mount Etna has been in almost continuous activity and even during periods of repose incandescent lava has often been visible in at least one of the summit vents. Using observations by Italian, British and French volcanological teams, the volumes of lava produced by each eruption from 1971 to July 1981 have been estimated. The computed output of magma for this period approximates to a rate of 0.7 cu m/s. This is compared with the output rate estimates for Etna's historic past. The steady-state nature of the output during the past decade has implications for the interpretation of the volcano's internal plumbing and the petrology of its lavas, and the assumption that this state will be maintained allows a discussion of the timing and magnitude of future eruptions.
Non-Equilibrium Steady States for Chains of Four Rotors
NASA Astrophysics Data System (ADS)
Cuneo, N.; Eckmann, J.-P.
2016-07-01
We study a chain of four interacting rotors (rotators) connected at both ends to stochastic heat baths at different temperatures. We show that for non-degenerate interaction potentials the system relaxes, at a stretched exponential rate, to a non-equilibrium steady state (NESS). Rotors with high energy tend to decouple from their neighbors due to fast oscillation of the forces. Because of this, the energy of the central two rotors, which interact with the heat baths only through the external rotors, can take a very long time to dissipate. By appropriately averaging the oscillatory forces, we estimate the dissipation rate and construct a Lyapunov function. Compared to the chain of length three (considered previously by C. Poquet and the current authors), the new difficulty with four rotors is the appearance of resonances when both central rotors are fast. We deal with these resonances using the rapid thermalization of the two external rotors.
Locating CVBEM collocation points for steady state heat transfer problems
Hromadka, T.V., II
1985-01-01
The Complex Variable Boundary Element Method or CVBEM provides a highly accurate means of developing numerical solutions to steady state two-dimensional heat transfer problems. The numerical approach exactly solves the Laplace equation and satisfies the boundary conditions at specified points on the boundary by means of collocation. The accuracy of the approximation depends upon the nodal point distribution specified by the numerical analyst. In order to develop subsequent, refined approximation functions, four techniques for selecting additional collocation points are presented. The techniques are compared as to the governing theory, representation of the error of approximation on the problem boundary, the computational costs, and the ease of use by the numerical analyst. ?? 1985.
Building steady-state simulators via hierarchical feedback decomposition
Rouquette, N.
1996-12-31
In recent years, compositional modeling and self-explanatory simulation techniques have simplified the process of building dynamic simulators of physical systems. Building steady-state simulators is, conceptually, a simpler task consisting in solving a set algebraic equations. This simplicity hides delicate technical issues of convergence and search-space size due to the potentially large number of unknown parameters. We present an automated technique for reducing the dimensionality of the problem by (1) automatically identifying feedback loops (a generally NP-complete problem), (2) hierarchically decomposing the set of equations in terms of feedback loops, and (3) structuring a simulator where equations are solved either serially without search or in isolation within a feedback loop. This paper describes the key algorithms and the results of their implementation on building simulators for a two-phase evaporator loop system across multiple combinations of causal and non-causal approximations.
Electrically Evoked Auditory Steady State Responses in Cochlear Implant Users
Wouters, Jan
2009-01-01
Auditory steady state responses are neural potentials in response to repeated auditory stimuli. This study shows that electrically evoked auditory steady state responses (EASSRs) to low-rate pulse trains can be reliably recorded by electrodes placed on the scalp of a cochlear implant (CI) user and separated from the artifacts generated by the electrical stimulation. Response properties are described, and the predictive value of EASSRs for behaviorally hearing thresholds is analyzed. For six users of a Cochlear Nucleus CI, EASSRs to symmetric biphasic pulse trains with rates between 35 and 47 Hz were recorded with seven scalp electrodes. The influence of various stimulus parameters was assessed: pulse rate, stimulus intensity, monopolar or bipolar stimulation mode, and presentation of either one pulse train on one electrode or interleaved pulse trains with different pulse rates on multiple electrodes. To compensate for the electrical artifacts caused by the stimulus pulses and radio frequency transmission, different methods of artifact reduction were employed. The validity of the recorded responses was confirmed by recording on–off responses, determination of response latency across the measured pulse rates, and comparison of amplitude growth of stimulus artifact and response amplitude. For stimulation in the 40 Hz range, response latencies of 35.6 ms (SD = 5.3 ms) were obtained. Responses to multiple simultaneous stimuli on different electrodes can be evoked, and the electrophysiological thresholds determined from EASSR amplitude growth in the 40 Hz range correlate well with behaviorally determined threshold levels for pulse rates of 41 Hz. PMID:20033246
A mathematical model of pan evaporation under steady state conditions
NASA Astrophysics Data System (ADS)
Lim, Wee Ho; Roderick, Michael L.; Farquhar, Graham D.
2016-09-01
In the context of changing climate, global pan evaporation records have shown a spatially-averaged trend of ∼ -2 to ∼ -3 mm a-2 over the past 30-50 years. This global phenomenon has motivated the development of the "PenPan" model (Rotstayn et al., 2006). However, the original PenPan model has yet to receive an independent experimental evaluation. Hence, we constructed an instrumented US Class A pan at Canberra Airport (Australia) and monitored it over a three-year period (2007-2010) to uncover the physics of pan evaporation under non-steady state conditions. The experimental investigations of pan evaporation enabled theoretical formulation and parameterisation of the aerodynamic function considering the wind, properties of air and (with or without) the bird guard effect. The energy balance investigation allowed for detailed formulation of the short- and long-wave radiation associated with the albedos and the emissivities of the pan water surface and the pan wall. Here, we synthesise and generalise those earlier works to develop a new model called the "PenPan-V2" model for application under steady state conditions (i.e., uses a monthly time step). Two versions (PenPan-V2C and PenPan-V2S) are tested using pan evaporation data available across the Australian continent. Both versions outperformed the original PenPan model with better representation of both the evaporation rate and the underlying physics of a US Class A pan. The results show the improved solar geometry related calculations (e.g., albedo, area) for the pan system led to a clear improvement in representing the seasonal cycle of pan evaporation. For general applications, the PenPan-V2S is simpler and suited for applications including an evaluation of long-term trends in pan evaporation.
Steady-state spectroscopy of new biological probes
NASA Astrophysics Data System (ADS)
Abou-Zied, Osama K.
2007-02-01
The steady state absorption and fluorescence spectroscopy of 2-(2'-hydroxyphenyl)benzoxazole (HBO) and (2,2'-bipyridine)-3,3'-diol (BP(OH) II) were studied here free in solution and in human serum albumin (HSA) in order to test their applicability as new biological probes. HBO and BP(OH) II are known to undergo intramolecular proton transfers in the excited state. Their absorption and fluorescence spectra are sensitive to environmental change from hydrophilic to hydrophobic, thus allowing the opportunity to use them as environment-sensitive probes. The effect of water on the steady state spectra of the two molecules also shows unique features which may position them as water sensors in biological systems. For HBO in buffer, fluorescence is only due to the syn-keto tautomer, whereas in HSA the fluorescence is due to four species in equilibrium in the excited state (the syn-keto tautomer, the anti-enol tautomer, the solvated syn-enol tautomer, and the anion species of HBO). Analysis of the fluorescence spectra of HBO in HSA indicates that HBO is exposed to less water in the HBO:HSA complex. For the BP(OH) II molecule, unique absorption due to water was observed in the spectral region of 400-450 nm. This absorption decreases in the presence of HSA due to less accessibility to water as a result of binding to HSA. Fluorescence of BP(OH) II is due solely to the di-keto tautomer after double proton transfer in the excited state. The fluorescence peak of BP(OH) II shows a red-shift upon HSA recognition which is attributed to the hydrophobic environment inside the binding site of HSA. We discuss also the effect of probe-inclusion inside well-defined hydrophobic cavities of cyclodextrins.
Torque-balanced Steady States of Single-component Plasmas
NASA Astrophysics Data System (ADS)
Danielson, James R.
2005-10-01
Penning-Malmberg traps provide an excellent method to confine single-component plasmas. Specially tailored, high-density plasmas can be created in these devices by the application of azimuthally phased rf fields [i.e., the so-called ``rotating wall'' (RW) technique]. Recently, we reported a new regime of RW compression of electron (or positron) plasmas ootnotetextJ. R. Danielson and C. M. Surko, Phys. Rev. Lett. 95, 035001 (2005).. In this ``strong-drive'' regime, plasmas are compressed until the E x B rotation frequency, φE (with φE plasma density) approaches the applied frequency, φRW. Good compression is achieved over a broad range of RW frequencies, without the need to tune to a mode in the plasma. The resulting steady-state density is found to be only weakly dependent on the applied RW amplitude. A simple nonlinear dynamical model explains these observations as convergence to an attracting fixed point - the torque-balanced steady state. The applied RW torque, τRW, can be understood as a generic, linear coupling between the plasma and the Debye- shielded RW electric field. The thermodynamic equations ootnotetextT. M. O'Neil and D. H. E. Dubin, Phys. Plasmas 5, 2163 (1998). governing the evolution will be discussed and compared to the experiments. This new regime facilitates improved compression and colder plasmas (since less transport means less plasma heating). Factors limiting the utility of the technique and applications will be discussed, including the development of a multicell trap to confine large numbers (i.e., N >=10^ 12) of positrons ootnotetextC. M. Surko and R. G. Greaves, Phys. Plasmas 11, 2333 (2004)..
Steady-state creep of metal-ceramic multilayered materials
Shen, Y.L.; Suresh, S.
1996-04-01
A general approach is presented for analyzing the steady-state creep response and its underlying mechanisms in metal-ceramic multilayers subjected to monotonic or cyclic variations in temperature. This approach combines the plate or beam theories of continuum mechanics with the mechanism-based classical constitutive equations for steady-state creep. The method is capable of predicting the evolution of overall curvature in the layered solid, the generation of thermal stresses within each layer, and the dominant deformation mechanisms at any through-thickness location of each layer at any instant of time or temperature for prescribed layer geometries, thermo-mechanical properties of the constituent layers, and the applied thermal history. Simulations are presented for Al-Al{sub 2}O{sub 3} bilayer and Al{sub 2}O{sub 3}-Al-Al{sub 2}O{sub 3} trilayer model systems. The predicted results are compared with appropriate experimental measurements for the bilayers subjected to thermal cycling up to 450 C. It is found that the multilayer creep calculations capture the essential features of cyclic thermal response; the extent of stress relaxation in the Al layer, however, is somewhat overestimated, especially at higher temperatures. Possible reasons for such discrepancy are discussed, and the significance and limitations of the overall approach are highlighted. The effects of the rate of heating or cooling on deformation, and the correlations between the present creep analyses and rate-independent elastoplastic formulations for multilayers are also considered. The influence of layer thickness on the evolution of creep mechanisms is also examined from thick multilayers to the limiting case of a thin metallic film on a brittle substrate.
Steady state plasma operation in RF dominated regimes on EAST
Zhang, X. J.; Zhao, Y. P.; Gong, X. Z.; Hu, C. D.; Liu, F. K.; Hu, L. Q.; Wan, B. N. Li, J. G.
2015-12-10
Significant progress has recently been made on EAST in the 2014 campaign, including the enhanced CW H&CD system over 20MW heating power (LHCD, ICRH and NBI), more than 70 diagnostics, ITER-like W-monoblock on upper divertor, two inner cryo-pumps and RMP coils, enabling EAST to investigate long pulse H mode operation with dominant electron heating and low torque to address the critical issues for ITER. H-mode plasmas were achieved by new H&CD system or 4.6GHz LHCD alone for the first time. Long pulse high performance H mode has been obtained by LHCD alone up to 28s at H{sub 98}∼1.2 or by combing of ICRH and LHCD, no or small ELM was found in RF plasmas, which is essential for steady state operation in the future Tokamak. Plasma operation in low collision regimes were implemented by new 4.6GHz LHCD with core Te∼4.5keV. The non-inductive scenarios with high performance at high bootstrap current fraction have been demonstrated in RF dominated regimes for long pulse operation. Near full non-inductive CD discharges have been achieved. In addition, effective heating and decoupling method under multi-transmitter for ICRF system were developed in this campaign, etc. EAST could be in operation with over 30MW CW heating and current drive power (LHCD ICRH NBI and ECRH), enhanced diagnostic capabilities and full actively-cooled metal wall from 2015. It will therefore allow to access new confinement regimes and to extend these regimes towards to steady state operation.
Okunishi, Katsuhide; DeGraaf, Angela J.; Zasłona, Zbigniew; Peters-Golden, Marc
2014-01-01
Prostaglandin E2 (PGE2) regulates numerous biological processes by modulating transcriptional activation, epigenetic control, proteolysis, and secretion of various proteins. Scar formation depends on fibroblast elaboration of matrix proteins such as collagen, and this process is strongly suppressed by PGE2 through activation of cAMP-dependent protein kinase A (PKA). However, the actual mechanism by which PGE2-PKA signaling inhibits collagen expression in fibroblasts has never been delineated, and that was the objective of this study. PGE2 unexpectedly induced a rapid reduction in procollagen I protein expression in adult lung fibroblasts, with a half-maximum effect at 1.5 h. This effect reflected its inhibition of translation rather than transcription. Global protein synthesis was also inhibited by PGE2. This action was mediated by PKA and involved both activation of ribosomal protein (rpS6) and suppression of mammalian target of rapamycin (mTOR). Similar effects of PGE2 were demonstrated in mouse peritoneal macrophages (PMs). These findings identify inhibition of translation as a new mechanism by which PGE2 regulates cellular function and a novel example of translational inhibition mediated by opposing actions on two distinct translational control pathways. Translational inhibition would be expected to contribute to dynamic alterations in cell function that accompany the changing PGE2 levels observed in disease states and with various pharmacotherapies.—Okunishi K., DeGraaf, A. J., Zasłona, Z., Peters-Golden, M. Inhibition of protein translation as a novel mechanism for prostaglandin E2 regulation of cell functions. PMID:24072780
Martins, O B; Tuena de Gómez-Puyou, M; Gómez-Puyou, A
1988-09-20
ATPase activities were measured in 10 mM MgCl2, 5 mM ATP, 1 mM ADP, and 1 microM FCCP with submitochondrial particles from bovine heart that had been stimulated by delta mu H+-forming substrates and with particles whose natural inhibitor protein was partially removed by heating. The activities were not linear with time. With both particles, the rate of ATP hydrolysis in the 7-fold greater than that in the steady state. Pre-steady-state and steady-state kinetic studies showed that the decrease of ATPase activity was due to the binding of ADP in a high-affinity site of the enzyme (K0.5 of 10 microM). Inhibition of ATP hydrolysis was accompanied by the binding of approximately 1 mol of ADP/mol of particulate F1; 10 microM ADP gave half-maximal binding. ADP could be replaced by IDP, but with an affinity 50-fold lower (K0.5 of 0.5 mM). Maximal inhibition by ADP and IDP was achieved in less than 5 s. Inhibition was enhanced by uncouplers. Even in the presence of pyruvate kinase and phosphoenolpyruvate, the rates of hydrolysis were about 2.5-fold higher in the first seconds of reaction than in the steady state. This decrease of ATPase activity also correlated with the binding of nearly 1 mol of ADP/mol of F1. This inhibitory ADP remained bound to the enzyme after several thousand turnovers. Apparently, it is possible to observe maximal rates of hydrolysis only in the first few catalytic cycles of the enzyme. PMID:2974725
Critical Concavity of a Drainage Basin for Steady-State
NASA Astrophysics Data System (ADS)
Byun, Jongmin; Paik, Kyungrock
2015-04-01
Longitudinal profiles of natural streams are known to show concave forms. Saying A as drainage area, channel gradient S can be expressed as the power-law, S≈A-θ (Flint, 1974), which is one of the scale-invariant features of drainage basin. According to literature, θ of most natural streams falls into a narrow range (0.4 < θ < 0.7) (Tucker and Whipple, 2002). It leads to fundamental questions: 'Why does θ falls into such narrow range?' and 'How is this related with other power-law scaling relationships reported in natural drainage basins?' To answer above questions, we analytically derive θ for a steady-state drainage basin following Lane's equilibrium (Lane, 1955) throughout the corridor and named this specific case as the 'critical concavity'. In the derivation, sediment transport capacity is estimated by unit stream power model (Yang, 1976), yielding a power function of upstream area. Stability of channel at a local point occurs when incoming flux equals outgoing flux at the point. Therefore, given the drainage at steady-state where all channel beds are stable, the exponent of the power function should be zero. From this, we can determine the critical concavity. Considering ranges of variables associated in this derivation, critical concavity cannot be resolved as a single definite value, rather a range of critical concavity is suggested. This range well agrees with the widely reported range of θ (0.4 < θ < 0.7) in natural streams. In this theoretical study, inter-relationships between power-laws such as hydraulic geometry (Leopold and Maddock, 1953), dominant discharge-drainage area (Knighton et al., 1999), and concavity, are coupled into the power-law framework of stream power sediment transport model. This allows us to explore close relationships between their power-law exponents: their relative roles and sensitivity. Detailed analysis and implications will be presented. References Flint, J. J., 1974, Stream gradient as a function of order, magnitude
Regulatory T cell homeostasis: steady-state maintenance and modulation during inflammation
Smigiel, Kate S.; Srivastava, Shivani; Stolley, J. Michael; Campbell, Daniel J.
2014-01-01
Summary Regulatory T (Treg) cells play a vital role in the prevention of autoimmunity and the maintenance of self-tolerance but also have an active role in inhibiting immune responses during viral, bacterial and parasitic infections. Whereas excessive Treg activity can lead to immunodeficiency, chronic infection and cancer, too little Treg activity results in autoimmunity and immunopathology, and impairs the quality of pathogen-specific responses. Recent studies have helped define the homeostatic mechanisms that support the diverse pool of peripheral Treg cells under steady-state conditions, and delineate how the abundance and function of Treg cells changes during inflammation. These findings are highly relevant for developing effective strategies to manipulate Treg cell activity to promote allograft tolerance and treat autoimmunity, chronic infection and cancer. PMID:24712458
Nonequilibrium steady states of ideal bosonic and fermionic quantum gases
NASA Astrophysics Data System (ADS)
Vorberg, Daniel; Wustmann, Waltraut; Schomerus, Henning; Ketzmerick, Roland; Eckardt, André
2015-12-01
We investigate nonequilibrium steady states of driven-dissipative ideal quantum gases of both bosons and fermions. We focus on systems of sharp particle number that are driven out of equilibrium either by the coupling to several heat baths of different temperature or by time-periodic driving in combination with the coupling to a heat bath. Within the framework of (Floquet-)Born-Markov theory, several analytical and numerical methods are described in detail. This includes a mean-field theory in terms of occupation numbers, an augmented mean-field theory taking into account also nontrivial two-particle correlations, and quantum-jump-type Monte Carlo simulations. For the case of the ideal Fermi gas, these methods are applied to simple lattice models and the possibility of achieving exotic states via bath engineering is pointed out. The largest part of this work is devoted to bosonic quantum gases and the phenomenon of Bose selection, a nonequilibrium generalization of Bose condensation, where multiple single-particle states are selected to acquire a large occupation [Phys. Rev. Lett. 111, 240405 (2013), 10.1103/PhysRevLett.111.240405]. In this context, among others, we provide a theory for transitions where the set of selected states changes, describe an efficient algorithm for finding the set of selected states, investigate beyond-mean-field effects, and identify the dominant mechanisms for heat transport in the Bose-selected state.
Steady-state and transient results on insulation materials
Graves, R.S.; Yarbrough, D.W.; McElroy, D.L.; Fine, H.A.
1991-01-01
The Unguarded Thin-Heater Apparatus (UTHA, ASTM C 1114) was used to determine the thermal conductivity (k), specific heat (C), and thermal diffusivity ({alpha}) of selected building materials from 24 to 50{degree}C. Steady-state and transient measurements yielded data on four types of material: gypsum wall board containing 0, 15, and 30 wt % wax; calcium silicate insulations with densities ({rho}) of 307, 444, and 605 kg/m{sup 3}; three wood products: southern yellow pine flooring (575 kg/m{sup 3}), Douglas fir plywood (501 kg/m{sup 3}), and white spruce flooring (452 kg/m{sup 3}); and two cellular plastic foams: extruded polystyrene (30 kg/m{sup 3}) blown with HCFC-142b and polyisocyanurate rigid board (30.2 kg/m{sup 3}) blown with CFC-11. The extruded polystyrene was measured several times after production (25 days, 45 days, 74 days, 131 days, and 227 days). The UTHA is an absolute technique that yields k with an uncertainty of less than {plus minus}2% as determined by modeling, by determinate error analyses, and by use of Standard Reference Materials SRM-1450b and SRM-1451. 37 refs., 5 figs., 10 tabs.
NASA Lewis steady-state heat pipe code users manual
NASA Technical Reports Server (NTRS)
Tower, Leonard K.; Baker, Karl W.; Marks, Timothy S.
1992-01-01
The NASA Lewis heat pipe code was developed to predict the performance of heat pipes in the steady state. The code can be used as a design tool on a personal computer or with a suitable calling routine, as a subroutine for a mainframe radiator code. A variety of wick structures, including a user input option, can be used. Heat pipes with multiple evaporators, condensers, and adiabatic sections in series and with wick structures that differ among sections can be modeled. Several working fluids can be chosen, including potassium, sodium, and lithium, for which monomer-dimer equilibrium is considered. The code incorporates a vapor flow algorithm that treats compressibility and axially varying heat input. This code facilitates the determination of heat pipe operating temperatures and heat pipe limits that may be encountered at the specified heat input and environment temperature. Data are input to the computer through a user-interactive input subroutine. Output, such as liquid and vapor pressures and temperatures, is printed at equally spaced axial positions along the pipe as determined by the user.
Steady-State Movement Related Potentials for Brain Computer Interfacing
Nazarpour, Kianoush; Praamstra, Peter; Miall, R. Chris; Sanei, Saeid
2012-01-01
An approach for brain computer interfacing (BCI) by analysis of steady-state movement related potentials (ssMRP) produced during rhythmic finger movements is proposed in this paper. The neurological background of ssMRPs is briefly reviewed. Averaged ssMRPs represented the development of a lateralized rhythmic potential and the energy of the electroencephalogram (EEG) signals at the finger tapping frequency can be used for single trial ssMRP classification. The proposed ssMRP-based BCI approach is tested using the classic Fisher’s linear discriminant (FLD) classifier. Moreover, the influence of the current source density transform on the performance of BCI system is investigated. The averaged correct classification rates (CCR) as well as averaged information transfer rates (ITR) for different sliding time windows are reported. Reliable single trial classification rates of 88%-100% accuracy are achievable at relatively high ITRs. Furthermore, we have been able to achieve CCRs of up to 93% in classification of the sMRPs recorded during imagined rhythmic finger movements. The merit of this approach is in the application of rhythmic cues for BCI, the relatively simple recording setup, and straightforward computations which make the real-time implementations plausible. PMID:19403356
Steady state quantum discord for circularly accelerated atoms
NASA Astrophysics Data System (ADS)
Hu, Jiawei; Yu, Hongwei
2015-12-01
We study, in the framework of open quantum systems, the dynamics of quantum entanglement and quantum discord of two mutually independent circularly accelerated two-level atoms in interaction with a bath of fluctuating massless scalar fields in the Minkowski vacuum. We assume that the two atoms rotate synchronically with their separation perpendicular to the rotating plane. The time evolution of the quantum entanglement and quantum discord of the two-atom system is investigated. For a maximally entangled initial state, the entanglement measured by concurrence diminishes to zero within a finite time, while the quantum discord can either decrease monotonically to an asymptotic value or diminish to zero at first and then followed by a revival depending on whether the initial state is antisymmetric or symmetric. When both of the two atoms are initially excited, the generation of quantum entanglement shows a delayed feature, while quantum discord is created immediately. Remarkably, the quantum discord for such a circularly accelerated two-atom system takes a nonvanishing value in the steady state, and this is distinct from what happens in both the linear acceleration case and the case of static atoms immersed in a thermal bath.
Steady State Turbulent Transport in Magnetic Fusion Plasmas
Lee, W. W.; Ethier, S.; Kolesnikov, R.; Wang, W. X.; Tang, W. M.
2007-12-20
For more than a decade, the study of microturbulence, driven by ion temperature gradient (ITG) drift instabilities in tokamak devices, has been an active area of research in magnetic fusion science for both experimentalists and theorists alike. One of the important impetus for this avenue of research was the discovery of the radial streamers associated the ITG modes in the early nineties using a Particle-In-Cell (PIC) code. Since then, ITG simulations based on the codes with increasing realism have become possible with the dramatic increase in computing power. The notable examples were the demonstration of the importance of nonlinearly generated zonal flows in regulating ion thermal transport and the transition from Bohm to GyroBoham scaling with increased device size. In this paper, we will describe another interesting nonlinear physical process associated with the parallel acceleration of the ions, that is found to play an important role for the steady state turbulent transport. Its discovery is again through the use of the modern massively parallel supercomputers.
The Path of Carbon in Photosynthesis XX. The Steady State
DOE R&D Accomplishments Database
Calvin, M.; Massini, Peter
1952-09-01
The separation of the phenomenon of photosynthesis in green plants into a photochemical reaction and into the light-dependent reduction of carbon dioxide is discussed, The reduction of carbon dioxide and the fate of the assimilated carbon were investigated with the help of the tracer technique (exposure of the planks to the radioactive C{sup 14}O{sub 2}) and of paper chromatography. A reaction cycle is proposed in which phosphoglyceric acid is the first isolable assimilations product. Analyses of the algal extracts which had assimilated radioactive carbon dioxide in a stationary condition ('steady-state' photosynthesis) for a long time provided further information concerning the proposed cycle and permitted the approximate estimation, for a number of compounds of what fraction of each compound was taking part in the cycle. The earlier supposition that light influences the respiration cycle was confirmed. The possibility of the assistance of {alpha}-lipoic acid, or of a related substance, in this influence and in the photosynthesis cycle, is discussed.
Steady State Response Analysis of a Tubular Piezoelectric Print Head.
Chang, Jiaqing; Liu, Yaxin; Huang, Bo
2016-01-01
In recent years, inkjet technology has played an important role in industrial materials printing and various sensors fabrication, but the mechanisms of the inkjet print head should be researched more elaborately. The steady state deformation analysis of a tubular piezoelectric print head, which can be classified as a plane strain problem because the radii of the tubes are considerably smaller than the lengths, is discussed in this paper. The geometric structure and the boundary conditions are all axisymmetric, so a one-dimensional mathematical model is constructed. By solving the model, the deformation field and stress field, as well as the electric potential distribution of the piezoelectric tube and glass tube, are obtained. The results show that the deformations are on the nanometer scale, the hoop stress is larger than the radial stress on the whole, and the potential is not linearly distributed along the radial direction. An experiment is designed to validate these computations. A discussion of the effect of the tubes' thicknesses on the system deformation status is provided. PMID:26771612
Steady-state growth of the marine diatom Thalassiosira pseudonana
Olson, R.J.; SooHoo, J.B.; Kiefer, D.A.
1980-09-01
Seasonal studies of the vertical distribution of nitrate, nitrite, and phytoplankton in the oceans and studies using /sup 15/N as a tracer of nitrate metabolism indicate that the reduction of nitrate by phytoplankton is a source of nitrite in the upper waters of the ocean. To better understand this process, the relationship between nitrate uptake and nitrite production has been examined with continuous cultures of the small marine diatom Thalassiosira pseudonana. In a turbidostat culture, the rates of nitrite production by T. Pseudonana increase with light intensity. This process is only loosely coupled to rates of nitrate assimilation since the ratio of net nitrite production to total nitrate assimilation increases with increased rates of growth. In continuous cultures where steady-state concentrations of nitrate and nitrite were varied, T. pseudonana produced nitrite at rates which increased with increasing concentrations of nitrate. Again, the rates of nitrite production were uncoupled from rates of nitrate assimilation. The study was used to derive a mathematical description of nitrate and nitrite metabolism by T. pseudonana. The validity of this model was supported by the results of a study in which /sup 15/N-labeled nitrite was introduced into the continuous culture, and the model was used to examine patterns in distribution of nitrite in the Antarctic Ocean and the Sargasso Sea.
Magnetocentrifugal Winds in 3D: Nonaxisymmetric Steady State
Anderson, Jeffrey M.; Li, Zhi-Yun; Krasnopolsky, Ruben; Blandford, Roger D.; /SLAC
2006-11-28
Outflows can be loaded and accelerated to high speeds along rapidly rotating, open magnetic field lines by centrifugal forces. Whether such magnetocentrifugally driven winds are stable is a longstanding theoretical problem. As a step towards addressing this problem, we perform the first large-scale 3D MHD simulations that extend to a distance {approx} 10{sup 2} times beyond the launching region, starting from steady 2D (axisymmetric) solutions. In an attempt to drive the wind unstable, we increase the mass loading on one half of the launching surface by a factor of {radical}10, and reduce it by the same factor on the other half. The evolution of the perturbed wind is followed numerically. We find no evidence for any rapidly growing instability that could disrupt the wind during the launching and initial phase of propagation, even when the magnetic field of the magnetocentrifugal wind is toroidally dominated all the way to the launching surface. The strongly perturbed wind settles into a new steady state, with a highly asymmetric mass distribution. The distribution of magnetic field strength is, in contrast, much more symmetric. We discuss possible reasons for the apparent stability, including stabilization by an axial poloidal magnetic field, which is required to bend field lines away from the vertical direction and produce a magnetocentrifugal wind in the first place.
Quasi-steady state aerodynamics of the cheetah tail
Boje, Edward; Fisher, Callen; Louis, Leeann; Lane, Emily
2016-01-01
ABSTRACT During high-speed pursuit of prey, the cheetah (Acinonyx jubatus) has been observed to swing its tail while manoeuvring (e.g. turning or braking) but the effect of these complex motions is not well understood. This study demonstrates the potential of the cheetah's long, furry tail to impart torques and forces on the body as a result of aerodynamic effects, in addition to the well-known inertial effects. The first-order aerodynamic forces on the tail are quantified through wind tunnel testing and it is observed that the fur nearly doubles the effective frontal area of the tail without much mass penalty. Simple dynamic models provide insight into manoeuvrability via simulation of pitch, roll and yaw tail motion primitives. The inertial and quasi-steady state aerodynamic effects of tail actuation are quantified and compared by calculating the angular impulse imparted onto the cheetah's body and its shown aerodynamic effects contribute to the tail's angular impulse, especially at the highest forward velocities. PMID:27412267
Estimation of the Maximal Lactate Steady State in Endurance Runners.
Llodio, I; Gorostiaga, E M; Garcia-Tabar, I; Granados, C; Sánchez-Medina, L
2016-06-01
This study aimed to predict the velocity corresponding to the maximal lactate steady state (MLSSV) from non-invasive variables obtained during a maximal multistage running field test (modified University of Montreal Track Test, UMTT), and to determine whether a single constant velocity test (CVT), performed several days after the UMTT, could estimate the MLSSV. Within 4-5 weeks, 20 male runners performed: 1) a modified UMTT, and 2) several 30 min CVTs to determine MLSSV to a precision of 0.25 km·h(-1). Maximal aerobic velocity (MAV) was the best predictor of MLSSV. A regression equation was obtained: MLSSV=1.425+(0.756·MAV); R(2)=0.63. Running velocity during the CVT (VCVT) and blood lactate at 6 (La6) and 30 (La30) min further improved the MLSSV prediction: MLSSV=VCVT+0.503 - (0.266·ΔLa30-6); R(2)=0.66. MLSSV can be estimated from MAV during a single maximal multistage running field test among a homogeneous group of trained runners. This estimation can be further improved by performing an additional CVT. In terms of accuracy, simplicity and cost-effectiveness, the reported regression equations can be used for the assessment and training prescription of endurance runners. PMID:27116348
Steady State Response Analysis of a Tubular Piezoelectric Print Head
Chang, Jiaqing; Liu, Yaxin; Huang, Bo
2016-01-01
In recent years, inkjet technology has played an important role in industrial materials printing and various sensors fabrication, but the mechanisms of the inkjet print head should be researched more elaborately. The steady state deformation analysis of a tubular piezoelectric print head, which can be classified as a plane strain problem because the radii of the tubes are considerably smaller than the lengths, is discussed in this paper. The geometric structure and the boundary conditions are all axisymmetric, so a one-dimensional mathematical model is constructed. By solving the model, the deformation field and stress field, as well as the electric potential distribution of the piezoelectric tube and glass tube, are obtained. The results show that the deformations are on the nanometer scale, the hoop stress is larger than the radial stress on the whole, and the potential is not linearly distributed along the radial direction. An experiment is designed to validate these computations. A discussion of the effect of the tubes’ thicknesses on the system deformation status is provided. PMID:26771612
Steady state model of electrochemical gas sensors with multiple reactions
Brailsford, A.D.; Yussouff, M.; Logothetis, E.M.
1996-12-31
A general first-principles model of the steady state response of metal oxide gas sensors was developed by the authors and applied to the case of both electrochemical and resistive type oxygen sensors. It can describe many features of the experimentally observed response of commercial electrochemical zirconia sensors exposed to non-equilibrium gas mixtures consisting of O{sub 2} and one or more reducing species (CO, H{sub 2} , etc). However, the calculated sensor emf as a function of R`= 2p{sub O2}/P{sub CO} (or 2p{sub O2}/P{sub H2}) always showed a sharp transition from high to low values at some R` value and had a small value for R` >> 1. These results do not agree with the broad transitions and relatively high emf values for large R`, as observed experimentally at low temperatures. This paper discusses an extension of the model which is able to describe all aspects of the observed response.
Modeling biofiltration of VOC mixtures under steady-state conditions
Baltzis, B.C.; Wojdyla, S.M.; Zarook, S.M.
1997-06-01
Treatment of air streams contaminated with binary volatile organic compound (VOC) mixtures in classical biofilters under steady-state conditions of operation was described with a general mathematical model. The model accounts for potential kinetic interactions among the pollutants, effects of oxygen availability on biodegradation, and biomass diversification in the filter bed. While the effects of oxygen were always taken into account, two distinct cases were considered for the experimental model validation. The first involves kinetic interactions, but no biomass differentiation, used for describing data from biofiltration of benzene/toluene mixtures. The second case assumes that each pollutant is treated by a different type of biomass. Each biomass type is assumed to form separate patches of biofilm on the solid packing material, thus kinetic interference does not occur. This model was used for describing biofiltration of ethanol/butanol mixtures. Experiments were performed with classical biofilters packed with mixtures of peat moss and perlite (2:3, volume:volume). The model equations were solved through the use of computer codes based on the fourth-order Runge-Kutta technique for the gas-phase mass balances and the method of orthogonal collocation for the concentration profiles in the biofilms. Good agreement between model predictions and experimental data was found in almost all cases. Oxygen was found to be extremely important in the case of polar VOCs (ethanol/butanol).
Steady state solutions to dynamically loaded periodic structures
NASA Technical Reports Server (NTRS)
Kalinowski, A. J.
1980-01-01
The general problem of solving for the steady state (time domain) dynamic response (i.e., NASTRAN rigid format-8) of a general elastic periodic structure subject to a phase difference loading of the type encountered in traveling wave propagation problems was studied. Two types of structural configurations were considered; in the first type, the structure has a repeating pattern over a span that is long enough to be considered, for all practical purposes, as infinite; in the second type, the structure has structural rotational symmetry in the circumferential direction. The theory and a corresponding set of DMAP instructions which permits the NASTRAN user to automatically alter the rigid format-8 sequence to solve the intended class of problems are presented. Final results are recovered as with any ordinary rigid format-8 solution, except that the results are only printed for the typical periodic segment of the structure. A simple demonstration problem having a known exact solution is used to illustrate the implementation of the procedure.
Mimicking Nonequilibrium Steady States with Time-Periodic Driving
NASA Astrophysics Data System (ADS)
Raz, Oren; Subasi, Yigit; Jarzynski, Christopher
Under static conditions, a system satisfying detailed balance generically relaxes to an equilibrium state in which there are no currents: to generate persistent currents, either detailed balance must be broken or the system must be driven in a time-dependent manner. A stationary system that violates detailed balance evolves to a nonequilibrium steady state (NESS) characterized by fixed currents. Conversely, a system that satisfies instantaneous detailed balance but is driven by the time-periodic variation of external parameters - also known as a stochastic pump (SP) - reaches a periodic state with non-vanishing currents. In both cases, these currents are maintained at the cost of entropy production. Are these two paradigmatic scenarios effectively equivalent? For discrete-state systems we establish a mapping between NESS and SP. Given a NESS characterized by a particular set of stationary probabilities, currents and entropy production rates, we show how to construct a SP with exactly the same (time-averaged) values. The mapping works in the opposite direction as well. These results establish a proof of principle: they show that SP are able to mimic the behavior of NESS, and vice-versa, within the theoretical framework of discrete-state stochastic thermodynamics.
Nonequilibrium steady states of ideal bosonic and fermionic quantum gases.
Vorberg, Daniel; Wustmann, Waltraut; Schomerus, Henning; Ketzmerick, Roland; Eckardt, André
2015-12-01
We investigate nonequilibrium steady states of driven-dissipative ideal quantum gases of both bosons and fermions. We focus on systems of sharp particle number that are driven out of equilibrium either by the coupling to several heat baths of different temperature or by time-periodic driving in combination with the coupling to a heat bath. Within the framework of (Floquet-)Born-Markov theory, several analytical and numerical methods are described in detail. This includes a mean-field theory in terms of occupation numbers, an augmented mean-field theory taking into account also nontrivial two-particle correlations, and quantum-jump-type Monte Carlo simulations. For the case of the ideal Fermi gas, these methods are applied to simple lattice models and the possibility of achieving exotic states via bath engineering is pointed out. The largest part of this work is devoted to bosonic quantum gases and the phenomenon of Bose selection, a nonequilibrium generalization of Bose condensation, where multiple single-particle states are selected to acquire a large occupation [Phys. Rev. Lett. 111, 240405 (2013)]. In this context, among others, we provide a theory for transitions where the set of selected states changes, describe an efficient algorithm for finding the set of selected states, investigate beyond-mean-field effects, and identify the dominant mechanisms for heat transport in the Bose-selected state. PMID:26764644
Dynamic steady state of periodically driven quantum systems
NASA Astrophysics Data System (ADS)
Yudin, V. I.; Taichenachev, A. V.; Basalaev, M. Yu.
2016-01-01
Using the density matrix formalism, we prove the existence of the periodic steady state for an arbitrary periodically driven system described by linear dynamic equations. This state has the same period as the modulated external influence, and it is realized as an asymptotic solution (t →+∞ ) due to relaxation processes. The presented derivation simultaneously contains a simple and effective computational algorithm (without using either the Floquet or Fourier formalisms), which automatically guarantees a full account of all frequency components. As a particular example, for three-level Λ system we calculate the line shape and field-induced shift of the dark resonance formed by the field with a periodically modulated phase. Also we have analytically solved a basic theoretical problem of the direct frequency comb spectroscopy, when the two-level system is driven by the periodic sequence of rectangular pulses. In this case, the radical dependence of the spectroscopy line shape on pulse area is found. Moreover, the existence of quasiforbidden spectroscopic zones, in which the Ramsey fringes are significantly reduced, is predicted. Our results have a wide area of applications in laser physics, spectroscopy, atomic clocks, and magnetometry. Also they can be useful for any area of quantum physics where periodically driven systems are considered.
Flavour fields in steady state: stress tensor and free energy
NASA Astrophysics Data System (ADS)
Banerjee, Avik; Kundu, Arnab; Kundu, Sandipan
2016-02-01
The dynamics of a probe brane in a given gravitational background is governed by the Dirac-Born-Infeld action. The corresponding open string metric arises naturally in studying the fluctuations on the probe. In Gauge-String duality, it is known that in the presence of a constant electric field on the worldvolume of the probe, the open string metric acquires an event horizon and therefore the fluctuation modes on the probe experience an effective temperature. In this article, we bring together various properties of such a system to a formal definition and a subsequent narration of the effective thermodynamics and the stress tensor of the corresponding flavour fields, also including a non-vanishing chemical potential. In doing so, we point out a potentially infinitely-degenerate scheme-dependence of regularizing the free energy, which nevertheless yields a universal contribution in certain cases. This universal piece appears as the coefficient of a log-divergence in free energy when a space-filling probe brane is embedded in AdS d+1-background, for d = 2, 4, and is related to conformal anomaly. For the special case of d = 2, the universal factor has a striking resemblance to the well-known heat current formula in (1 + 1)-dimensional conformal field theory in steady-state, which endows a plausible physical interpretation to it. Interestingly, we observe a vanishing conformal anomaly in d = 6.
NASA Lewis steady-state heat pipe code users manual
Tower, L.K.; Baker, K.W.; Marks, T.S.
1992-06-01
The NASA Lewis heat pipe code has been developed to predict the performance of heat pipes in the steady state. The code can be used as a design tool on a personal computer or, with a suitable calling routine, as a subroutine for a mainframe radiator code. A variety of wick structures, including a user input option, can be used. Heat pipes with multiple evaporators, condensers, and adiabatic sections in series and with wick structures that differ among sections can be modeled. Several working fluids can be chosen, including potassium, sodium, and lithium, for which the monomer-dimer equilibrium is considered. The code incorporates a vapor flow algorithm that treats compressibility and axially varying heat input. This code facilitates the determination of heat pipe operating temperatures and heat pipe limits that may be encountered at the specified heat input and environment temperature. Data are input to the computer through a user-interactive input subroutine. Output, such as liquid and vapor pressures and temperatures, is printed at equally spaced axial positions along the pipe as determined by the user.
Hyperbolic method for magnetic reconnection process in steady state magnetohydrodynamics
NASA Astrophysics Data System (ADS)
Baty, Hubert; Nishikawa, Hiroaki
2016-06-01
A recent numerical approach for solving the advection-diffusion and Navier-Stokes equations is extended for the first time to a magnetohydrodynamic (MHD) model, aiming in particular consistent improvements over classical methods for investigating the magnetic reconnection process. In this study, we mainly focus on a two-dimensional incompressible set of resistive MHD equations written in flux-vorticity scalar variables. The originality of the method is based on hyperbolic reformulation of the dissipative terms, leading to the construction of an equivalent hyperbolic first-order (spatial derivatives) system. This enables the use of approximate Riemann solvers for handling dissipative and advective flux in the same way. A simple second-order finite-volume discretization on rectangular grids using an upwind flux is employed. The advantages of this method are illustrated by a comparison to two particular analytical steady state solutions of the inviscid magnetic reconnection mechanism, namely the magnetic annihilation and the reconnective diffusion problems. In particular, the numerical solution is obtained with the same order of accuracy for the solution and gradient for a wide range of magnetic Reynolds numbers, without any deterioration characteristic of more conventional schemes. The amelioration of the hyperbolic method and its extension to time-dependent MHD problems related to solar flares mechanisms is also discussed.
Quasi-steady state aerodynamics of the cheetah tail.
Patel, Amir; Boje, Edward; Fisher, Callen; Louis, Leeann; Lane, Emily
2016-01-01
During high-speed pursuit of prey, the cheetah (Acinonyx jubatus) has been observed to swing its tail while manoeuvring (e.g. turning or braking) but the effect of these complex motions is not well understood. This study demonstrates the potential of the cheetah's long, furry tail to impart torques and forces on the body as a result of aerodynamic effects, in addition to the well-known inertial effects. The first-order aerodynamic forces on the tail are quantified through wind tunnel testing and it is observed that the fur nearly doubles the effective frontal area of the tail without much mass penalty. Simple dynamic models provide insight into manoeuvrability via simulation of pitch, roll and yaw tail motion primitives. The inertial and quasi-steady state aerodynamic effects of tail actuation are quantified and compared by calculating the angular impulse imparted onto the cheetah's body and its shown aerodynamic effects contribute to the tail's angular impulse, especially at the highest forward velocities. PMID:27412267
Methionine sustituted polyamides are RNAse mimics that inhibit translation.
Kumar, Rohtash; Garneau, Philippe; Nguyen, Nhi; William Lown, J; Pelletier, Jerry
2004-04-01
RNAse mimics are small molecules that can cleave RNA in a fashion similar to ribonucleases. These compounds would be very useful as gene specific reagents if their activities could be regulated and targeted. We demonstrate here that polyamides with methionine substituents show enhanced RNA cleavage activity relative to other polyamides. Conjugation of these compounds to aminoglycosides produced RNAse mimics that are capable of inhibiting eukaryotic protein synthesis. As a new class of compounds capable of interacting with nucleic acids, these novel aminoglycoside-polyamides constitute promising scaffolds for the construction of nuclease mimics with biological activity. PMID:15203891
Hempstead, Andrew D.; Isberg, Ralph R.
2015-01-01
Cells of the innate immune system recognize bacterial pathogens by detecting common microbial patterns as well as pathogen-specific activities. One system that responds to these stimuli is the IRE1 branch of the unfolded protein response (UPR), a sensor of endoplasmic reticulum (ER) stress. Activation of IRE1, in the context of Toll-like receptor (TLR) signaling, induces strong proinflammatory cytokine induction. We show here that Legionella pneumophila, an intravacuolar pathogen that replicates in an ER-associated compartment, blocks activation of the IRE1 pathway despite presenting pathogen products that stimulate this response. L. pneumophila TLR ligands induced the splicing of mRNA encoding XBP1s, the main target of IRE1 activity. L. pneumophila was able to inhibit both chemical and bacterial induction of XBP1 splicing via bacterial translocated proteins that interfere with host protein translation. A strain lacking five translocated translation elongation inhibitors was unable to block XBP1 splicing, but this could be rescued by expression of a single such inhibitor, consistent with limitation of the response by translation elongation inhibitors. Chemical inhibition of translation elongation blocked pattern recognition receptor-mediated XBP1 splicing, mimicking the effects of the bacterial translation inhibitors. In contrast, host cell-promoted inhibition of translation initiation in response to the pathogen was ineffective in blocking XBP1 splicing, demonstrating the need for the elongation inhibitors for protection from the UPR. The inhibition of host translation elongation may be a common strategy used by pathogens to limit the innate immune response by interfering with signaling via the UPR. PMID:26598709
Whole Plant and Leaf Steady State Gas Exchange during Ethylene Exposure in Xanthium strumarium L. 1
Woodrow, Lorna; Jiao, Jirong; Tsujita, M. James; Grodzinski, Bernard
1989-01-01
The effects of ethylene evolved from ethephon on leaf and whole plant photosynthesis in Xanthium strumarium L. were examined. Ethylene-induced epinasty reduced light interception by the leaves of ethephon treated plants by up to 60%. Gas exchange values of individual, attached leaves under identical assay conditions were not inhibited even after 36 hours of ethylene exposure, although treated leaves required a longer induction period to achieve steady state photosynthesis. The speed of translocation of recently fixed 11C-assimilate movement was not seriously impaired following ethephon treatment; however, a greater proportion of the assimilate was partitioned downward toward the roots. Within 24 hours of ethephon treatment, the whole plant net carbon exchange rate expressed on a per plant basis or a leaf area basis had dropped by 35%. The apparent inhibition of net carbon exchange rate was reversed by physically repositioning the leaves with respect to the light source. Ethylene exposure also inhibited expansion of young leaves which was partially reversed when the leaves were repositioned. The data indicated that ethylene indirectly affected net C gain and plant growth through modification of light interception and altered sink demand without directly inhibiting leaf photosynthesis. Images Figure 1 PMID:16666773
There are no steady state processes in compaction
NASA Astrophysics Data System (ADS)
Dysthe, D. K.
2003-04-01
Compaction of sediments is normally thought to start with grain sliding and cataclastic grain crushing. Then the ductile dissolution-precipitation creep processes take over. Modeling of this process normally neglects all collective rearrangement processes and regard simple packings of grains that slowly deform by steady state pressure solution creep. From simple geometrical reasoning we know, however that imperfect packings of plastic grains must undergo rearrangement during compaction. Such rearrangement will drastically alter the microscopic, or "primitive processes" of compaction. Recent research has questioned the fundamental mechanisms ("primitive processes") of dissolution-precipitation creep. Do grain contacts heal or dissolve? Why is there asymmetric dissolution? Does pressure solution creep in single contacts ever reach steady state? Can transient free face dissolution feed back on pressure solution creep in the contacts? The emerging radical change in our understanding of dissolution-precipitation creep as a dynamic, transient process is driven by new experiments and reevaluation of the fundamental theory. The same change in viewpoint is necessary on all time and length scales. I will present experiments [1-8] and simulations [9-11] of complex compaction behaviour [1], transient primitive processes of pressure solution creep in the contacts [2-4], free face dissolution [5] and crack healing [6]. I will also show that macroscopic observation of compaction shows smooth, universal behaviour [7]. Microscopic observation of compaction shows transient collective behaviour at all scales. Evidence points in the direction that compaction is dominated by transient processes with interacting instabilities. The interaction causes intermittency or switching between processes. A new, more complex theory of compaction is necessary to explain how the cooperative microscopic phenomena contribute to the simple, universal, macroscopic behaviour. 1. Uri, L., et. al., in
Steady state growth of E. Coli in low ammonium environment
NASA Astrophysics Data System (ADS)
Kim, Minsu; Deris, Barret; Zhang, Zhongge; Hwa, Terry
2011-03-01
Ammonium is the preferred nitrogen source for many microorganisms. In medium with low ammonium concentrations, enteric bacteria turn on the nitrogen responsive (ntr) genes to assimilate ammonium. Two proteins in E. coli, Glutamine synthetase (GS) and the Ammonium/methylammonium transporter AmtB play crucial roles in this regard. GS is the major ammonium assimilation enzyme below 1mM of NH4 + . AmtB is an inner membrane protein that transports NH4 + across the cell membrane against a concentration gradient. In order to study ammonium uptake at low NH4 + concentration at neutral pH, we developed a microfluidic flow chamber that maintains a homogenous nutrient environment during the course of exponential cell growth, even at very low concentration of nutrients. Cell growth can be accurately monitored using time-lapse microscopy. We followed steady state growth down to micro-molar range of NH4 + for the wild type and Δ amtB strains. The wild type strain is able to maintain the growth rate from 10mM down to a few uM of NH4 + , while the mutant exhibited reduced growth below ~ 20 ~uM of NH4 + . Simultaneous characterization of the expression levels of GS and AmtB using fluorescence reporters reveals that AmtB is turned on already at 1mM, but contributes to function only below ~ 30 ~uM in the wild-type. Down to ~ 20 ~uM of NH4 + , E.~coli can compensate the loss of AmtB by GS alone.
Kinematical Analysis along Maximal Lactate Steady State Swimming Intensity
Figueiredo, Pedro; Nazario, Rafael; Sousa, Marisa; Pelarigo, Jailton Gregório; Vilas-Boas, João Paulo; Fernandes, Ricardo
2014-01-01
The purpose of this study was to conduct a kinematical analysis during swimming at the intensity corresponding to maximal lactate steady state (MLSS). Thirteen long distance swimmers performed, in different days, an intermittent incremental protocol of n x 200 m until exhaustion and two to four 30-min submaximal constant speed bouts to determine the MLSS. The video analysis, using APAS System (Ariel Dynamics Inc., USA), allowed determining the following relevant swimming determinants (in five moments of the 30-min test: 0, 25, 50, 75, and 100%): stroke rate, stroke length, trunk incline, intracyclic velocity variation, propelling efficiency, index of coordination and the time allotted to propulsion per distance unit. An ANOVA for repeated measures was used to compare the parameters mean values along each moment of analysis. Stoke rate tended to increase and stroke length to decrease along the test; a tendency to decrease was also found for intracyclic velocity variation and propelling efficiency whereas the index of coordination and the propulsive impulse remained stable during the MLSS test. It can be concluded that the MLSS is not only an intensity to maintain without a significant increase of blood lactate concentration, but a concomitant stability for some biomechanical parameters exists (after an initial adaptation). However, efficiency indicators seem to be more sensitive to changes occurring during swimming at this threshold intensity. Key Points In MLSS swimming intensity, stability of the stroke length and stroke frequency occurs after an initial adaptation. Efficiency indicators seem to be more sensitive to possible changes occurring through time at MLSS intensity. MLSS is a useful and practical swimming intensity to be maintained for a long period of time, but some constraints in technique can occur. PMID:25177189
Impact of aquifer desaturation on steady-state river seepage
NASA Astrophysics Data System (ADS)
Morel-Seytoux, Hubert J.; Miracapillo, Cinzia; Mehl, Steffen
2016-02-01
Flow exchange between surface and ground water is of great importance be it for beneficial allocation and use of the water resources or for the proper exercise of water rights. That exchange can take place under a saturated or unsaturated flow regime. Which regimes occur depend on conditions in the vicinity of the interactive area. Withdrawals partially sustained by seepage may not bring about desaturation but greater amounts eventually will. The problem considered in this paper deals only with the steady-state case. It is meant as a first step toward a simple, yet accurate and physically based treatment of the transient situation. The primary purpose of the article is to provide simple criteria for determination of the initiation of desaturation in an aquifer originally in saturated hydraulic connection with a river or a recharge area. The extent of the unsaturated zone in the aquifer will increase with increasing withdrawals while at the same time the seepage rate from the river increases. However the seepage increase will stop once infiltration takes place strictly by gravity in the aquifer and is no longer opposed by the capillary rise from the water table below the riverbed. Following desaturation simple criteria are derived and simple analytical formulae provided to estimate the river seepage based on the position of the water table mound below the clogging layer and at some distance away from the river bank. They fully account for the unsaturated flow phenomena, including the existence of a drainage entry pressure. Two secondary objectives were to verify that (1) the assumption of uniform vertical flow through a clogging layer and that (2) the approximation of the water table mound below the seepage area as a flat surface were both reasonably legitimate. This approach will be especially advantageous for the implementation of the methodology in large-scale applications of integrated hydrologic models used for management.
A steady-state model of the lunar ejecta cloud
NASA Astrophysics Data System (ADS)
Christou, Apostolos
2014-05-01
Every airless body in the solar system is surrounded by a cloud of ejecta produced by the impact of interplanetary meteoroids on its surface [1]. Such ``dust exospheres'' have been observed around the Galilean satellites of Jupiter [2,3]. The prospect of long-term robotic and human operations on the Moon by the US and other countries has rekindled interest on the subject [4]. This interest has culminated with the - currently ongoing - investigation of the Moon's dust exosphere by the LADEE spacecraft [5]. Here a model is presented of a ballistic, collisionless, steady state population of ejecta launched vertically at randomly distributed times and velocities and moving under constant gravity. Assuming a uniform distribution of launch times I derive closed form solutions for the probability density functions (pdfs) of the height distribution of particles and the distribution of their speeds in a rest frame both at the surface and at altitude. The treatment is then extended to particle motion with respect to a moving platform such as an orbiting spacecraft. These expressions are compared with numerical simulations under lunar surface gravity where the underlying ejection speed distribution is (a) uniform (b) a power law. I discuss the predictions of the model, its limitations, and how it can be validated against near-surface and orbital measurements.[1] Gault, D. Shoemaker, E.M., Moore, H.J., 1963, NASA TN-D 1767. [2] Kruger, H., Krivov, A.V., Hamilton, D. P., Grun, E., 1999, Nature, 399, 558. [3] Kruger, H., Krivov, A.V., Sremcevic, M., Grun, E., 2003, Icarus, 164, 170. [4] Grun, E., Horanyi, M., Sternovsky, Z., 2011, Planetary and Space Science, 59, 1672. [5] Elphic, R.C., Hine, B., Delory, G.T., Salute, J.S., Noble, S., Colaprete, A., Horanyi, M., Mahaffy, P., and the LADEE Science Team, 2014, LPSC XLV, LPI Contr. 1777, 2677.
Storkebaum, Erik
2016-09-01
Recent evidence indicates that inhibition of protein translation may be a common pathogenic mechanism for peripheral neuropathy associated with mutant tRNA synthetases (aaRSs). aaRSs are enzymes that ligate amino acids to their cognate tRNA, thus catalyzing the first step of translation. Dominant mutations in five distinct aaRSs cause Charcot-Marie-Tooth (CMT) peripheral neuropathy, characterized by length-dependent degeneration of peripheral motor and sensory axons. Surprisingly, loss of aminoacylation activity is not required for mutant aaRSs to cause CMT. Rather, at least for some mutations, a toxic-gain-of-function mechanism underlies CMT-aaRS. Interestingly, several mutations in two distinct aaRSs were recently shown to inhibit global protein translation in Drosophila models of CMT-aaRS, by a mechanism independent of aminoacylation, suggesting inhibition of translation as a common pathogenic mechanism. Future research aimed at elucidating the molecular mechanisms underlying the translation defect induced by CMT-mutant aaRSs should provide novel insight into the molecular pathogenesis of these incurable diseases. PMID:27352040
Neutrophil-derived alpha defensins control inflammation by inhibiting macrophage mRNA translation.
Brook, Matthew; Tomlinson, Gareth H; Miles, Katherine; Smith, Richard W P; Rossi, Adriano G; Hiemstra, Pieter S; van 't Wout, Emily F A; Dean, Jonathan L E; Gray, Nicola K; Lu, Wuyuan; Gray, Mohini
2016-04-19
Neutrophils are the first and most numerous cells to arrive at the site of an inflammatory insult and are among the first to die. We previously reported that alpha defensins, released from apoptotic human neutrophils, augmented the antimicrobial capacity of macrophages while also inhibiting the biosynthesis of proinflammatory cytokines. In vivo, alpha defensin administration protected mice from inflammation, induced by thioglychollate-induced peritonitis or following infection withSalmonella entericaserovar Typhimurium. We have now dissected the antiinflammatory mechanism of action of the most abundant neutrophil alpha defensin, Human Neutrophil Peptide 1 (HNP1). Herein we show that HNP1 enters macrophages and inhibits protein translation without inducing the unfolded-protein response or affecting mRNA stability. In a cell-free in vitro translation system, HNP1 powerfully inhibited both cap-dependent and cap-independent mRNA translation while maintaining mRNA polysomal association. This is, to our knowledge, the first demonstration of a peptide released from one cell type (neutrophils) directly regulating mRNA translation in another (macrophages). By preventing protein translation, HNP1 functions as a "molecular brake" on macrophage-driven inflammation, ensuring both pathogen clearance and the resolution of inflammation with minimal bystander tissue damage. PMID:27044108
In vitro reconstitution and steady-state analysis of the fatty acid synthase from Escherichia coli
Yu, Xingye; Liu, Tiangang; Zhu, Fayin; Khosla, Chaitan
2011-01-01
Microbial fatty acid derivatives are emerging as promising alternatives to fossil fuel derived transportation fuels. Among bacterial fatty acid synthases (FAS), the Escherichia coli FAS is perhaps the most well studied, but little is known about its steady-state kinetic behavior. Here we describe the reconstitution of E. coli FAS using purified protein components and report detailed kinetic analysis of this reconstituted system. When all ketosynthases are present at 1 μM, the maximum rate of free fatty acid synthesis of the FAS exceeded 100 μM/ min. The steady-state turnover frequency was not significantly inhibited at high concentrations of any substrate or cofactor. FAS activity was saturated with respect to most individual protein components when their concentrations exceeded 1 μM. The exceptions were FabI and FabZ, which increased FAS activity up to concentrations of 10 μM; FabH and FabF, which decreased FAS activity at concentrations higher than 1 μM; and holo-ACP and TesA, which gave maximum FAS activity at 30 μM concentrations. Analysis of the S36T mutant of the ACP revealed that the unusual dependence of FAS activity on holo-ACP concentration was due, at least in part, to the acyl-phosphopantetheine moiety. MALDI-TOF mass spectrometry analysis of the reaction mixture further revealed medium and long chain fatty acyl-ACP intermediates as predominant ACP species. We speculate that one or more of such intermediates are key allosteric regulators of FAS turnover. Our findings provide a new basis for assessing the scope and limitations of using E. coli as a biocatalyst for the production of diesel-like fuels. PMID:22042840
Translation Inhibition of Capped and Uncapped Viral RNAs Mediated by Ribosome-Inactivating Proteins.
Vivanco, Jorge M; Tumer, Nilgun E
2003-05-01
ABSTRACT Ribosome-inactivating proteins (RIPs) are N-glycosidases that remove specific purine residues from the sarcin/ricin (S/R) loop of the large rRNA and arrest protein synthesis at the translocation step. In addition to their enzymatic activity, RIPs have been reputed to be potent antiviral agents against many plant, animal, and human viruses. We recently showed that pokeweed antiviral protein (PAP), an RIP from pokeweed, inhibits translation in cell extracts by binding to the cap structure of eukaryotic mRNA and viral RNAs and depurinating these RNAs at multiple sites downstream of the cap structure. In this study, we examined the activity of three different RIPs against capped and uncapped viral RNAs. PAP, Mirabilis expansa RIP (ME1), and the Saponaria officinalis RIP (saporin) depurinated the capped Tobacco mosaic virus and Brome mosaic virus RNAs, but did not depurinate the uncapped luciferase RNA, indicating that other type I RIPs besides PAP can distinguish between capped and uncapped RNAs. We did not detect depurination of Alfalfa mosaic virus (AMV) RNAs at multiple sites by PAP or ME1. Because AMV RNAs are capped, these results indicate that recognition of the cap structure alone is not sufficient for depurination of the RNA at multiple sites throughout its sequence. Furthermore, PAP did not cause detectable depurination of uncapped RNAs from Tomato bushy stunt virus (TBSV), Satellite panicum mosaic virus (SPMV), and uncapped RNA containing poliovirus internal ribosome entry site (IRES). However, in vitro translation experiments showed that PAP inhibited translation of AMV, TBSV, SPMV RNAs, and poliovirus IRES dependent translation. These results demonstrate that PAP does not depurinate every capped RNA and that PAP can inhibit translation of uncapped viral RNAs in vitro without causing detectable depurination at multiple sites. Thus, the cap structure is not the only determinant for inhibition of translation by PAP. PMID:18942981
Saito, Kazuki; Horikawa, Wataru; Ito, Koichi
2015-01-01
Incidental ribosome stalling during translation elongation is an aberrant phenomenon during protein synthesis and is subjected to quality control by surveillance systems, in which mRNA and a nascent protein are rapidly degraded. Their detailed molecular mechanisms as well as responsible factors for these processes are beginning to be understood. However, the initial processes for detecting stalled translation that result in degradation remain to be determined. Among the factors identified to date, two E3 ubiquitin ligases have been reported to function in distinct manners. Because ubiquitination is one of the most versatile of cellular signals, these distinct functions of E3 ligases suggested diverse ubiquitination pathways during surveillance for stalled translation. In this study, we report experimental evidences for a unique role of non-proteasomal K63 polyubiquitination during quality control for stalled translation. Inhibiting K63 polyubiquitination by expressing a K63R ubiquitin mutation in Saccharomyces cerevisiae cells markedly abolished the quality control responses for stalled translation. More detailed analyses indicated that the effects of K63R mutants were independent of the proteasome and that K63 polyubiquitination is dependent on Hel2, one of the E3 ligases. Moreover, a K63R ubiquitin mutant barely inhibited the quality control pathway for nonstop translation, indicating distinct mechanisms for these highly related quality control pathways. Our results suggest that non-proteasomal K63 polyubiquitination is included in the initial surveillance process of stalled translation and presumably triggers protein degradation steps upon translational stall. These findings provide crucial information regarding the detailed molecular mechanisms for the initial steps involved in quality control systems and their classification. PMID:25909477
Progress Towards High Performance, Steady-state Spherical Torus
M. Ono; M.G. Bell; R.E. Bell; T. Bigelow; M. Bitter; W. Blanchard; J. Boedo; C. Bourdelle; C. Bush; W. Choe; J. Chrzanowski; D.S. Darrow; S.J. Diem; R. Doerner; P.C. Efthimion; J.R. Ferron; R.J. Fonck; E.D. Fredrickson; G.D. Garstka; D.A. Gates; T. Gray; L.R. Grisham; W. Heidbrink; K.W. Hill; D. Hoffman; T.R. Jarboe; D.W. Johnson; R. Kaita; S.M. Kaye; C. Kessel; J.H. Kim; M.W. Kissick; S. Kubota; H.W. Kugel; B.P. LeBlanc; K. Lee; S.G. Lee; B.T. Lewicki; S. Luckhardt; R. Maingi; R. Majeski; J. Manickam; R. Maqueda; T.K. Mau; E. Mazzucato; S.S. Medley; J. Menard; D. Mueller; B.A. Nelson; C. Neumeyer; N. Nishino; C.N. Ostrander; D. Pacella; F. Paoletti; H.K. Park; W. Park; S.F. Paul; Y.-K. M. Peng; C.K. Phillips; R. Pinsker; P.H. Probert; S. Ramakrishnan; R. Raman; M. Redi; A.L. Roquemore; A. Rosenberg; P.M. Ryan; S.A. Sabbagh; M. Schaffer; R.J. Schooff; R. Seraydarian; C.H. Skinner; A.C. Sontag; V. Soukhanovskii; J. Spaleta; T. Stevenson; D. Stutman; D.W. Swain; E. Synakowski; Y. Takase; X. Tang; G. Taylor; J. Timberlake; K.L. Tritz; E.A. Unterberg; A. Von Halle; J. Wilgen; M. Williams; J.R. Wilson; X. Xu; S.J. Zweben; R. Akers; R.E. Barry; P. Beiersdorfer; J.M. Bialek; B. Blagojevic; P.T. Bonoli; M.D. Carter; W. Davis; B. Deng; L. Dudek; J. Egedal; R. Ellis; M. Finkenthal; J. Foley; E. Fredd; A. Glasser; T. Gibney; M. Gilmore; R.J. Goldston; R.E. Hatcher; R.J. Hawryluk; W. Houlberg; R. Harvey; S.C. Jardin; J.C. Hosea; H. Ji; M. Kalish; J. Lowrance; L.L. Lao; F.M. Levinton; N.C. Luhmann; R. Marsala; D. Mastravito; M.M. Menon; O. Mitarai; M. Nagata; G. Oliaro; R. Parsells; T. Peebles; B. Peneflor; D. Piglowski; G.D. Porter; A.K. Ram; M. Rensink; G. Rewoldt; P. Roney; K. Shaing; S. Shiraiwa; P. Sichta; D. Stotler; B.C. Stratton; R. Vero; W.R. Wampler; G.A. Wurden
2003-10-02
Research on the Spherical Torus (or Spherical Tokamak) is being pursued to explore the scientific benefits of modifying the field line structure from that in more moderate aspect-ratio devices, such as the conventional tokamak. The Spherical Tours (ST) experiments are being conducted in various U.S. research facilities including the MA-class National Spherical Torus Experiment (NSTX) at Princeton, and three medium-size ST research facilities: Pegasus at University of Wisconsin, HIT-II at University of Washington, and CDX-U at Princeton. In the context of the fusion energy development path being formulated in the U.S., an ST-based Component Test Facility (CTF) and, ultimately a Demo device, are being discussed. For these, it is essential to develop high-performance, steady-state operational scenarios. The relevant scientific issues are energy confinement, MHD stability at high beta (B), noninductive sustainment, ohmic-solenoid-free start-up, and power and particle handling. In the confinement area, the NSTX experiments have shown that the confinement can be up to 50% better than the ITER-98-pby2 H-mode scaling, consistent with the requirements for an ST-based CTF and Demo. In NSTX, CTF-relevant average toroidal beta values bT of up to 35% with the near unity central betaT have been obtained. NSTX will be exploring advanced regimes where bT up to 40% can be sustained through active stabilization of resistive wall modes. To date, the most successful technique for noninductive sustainment in NSTX is the high beta-poloidal regime, where discharges with a high noninductive fraction ({approx}60% bootstrap current + neutral-beam-injected current drive) were sustained over the resistive skin time. Research on radio-frequency-based heating and current drive utilizing HHFW (High Harmonic Fast Wave) and EBW (Electron Bernstein Wave) is also pursued on NSTX, Pegasus, and CDX-U. For noninductive start-up, the Coaxial Helicity Injection (CHI), developed in HIT/HIT-II, has been
Progress towards high-performance, steady-state spherical torus
Ono, M.; Bell, M. G.; Bell, R. E.; Bigelow, T.; Bitter, M.; Blanchard, W.; Boedo, J.; Bourdelle, C.; Bush, C.; Choe, W.; Chrzanowski, J.; Darrow, D. S.; Diem, S. J.; Doerner, R.; Efthimion, P. C.; Ferron, J. R.; Fonck, R. J.; Fredrickson, E. D.; Garstka, G. D.; Gates, D A; Gray, T.; Grisham, L. R.; Heidbrink, W.; Hill, K. W.; Hoffman, D.; Jarboe, T. R.; Johnson, D. W.; Kaita, R.; Kaye, S. M.; Kessel, C.; Kim, J. H.; Kissick, M. W.; Kubota, S.; Kugel, H. W.; LeBlanc, B. P.; Lee, K.; Lee, S. G.; Lewicki, B. T.; Luckhardt, S.; Maingi, R.; Majeski, R.; Manickam, J.; Maqueda, R.; Mau, T. K.; Mazzucato, E.; Medley, S. S.; Menard, J.; Mueller, D.; Nelson, B. A.; Neumeyer, C.; Nishino, N.; Ostrander, C. N.; Pacella, D.; Paoletti, F.; Park, H. K.; Park, W.; Paul, S. F.; Peng, Y-K M.; Phillips, C. K.; Pinsker, R.; Probert, P. H.; Ramakrishnan, S.; Raman, R.; Redi, M.; Roquemore, A. L.; Rosenberg, A.; Ryan, P. M.; Sabbagh, S. A.; Schaffer, M.; Schooff, R. J.; Seraydarian, R.; Skinner, C. H.; Sontag, A. C.; Soukhanovskii, V.; Spaleta, J.; Stevenson, T.; Stutman, D.; Swain, D. W.; Synakowski, E.; Takase, Y.; Tang, X.; Taylor, G.; Timberlake, J.; Tritz, K. L.; Unterberg, E. A.; Halle, A. Von.; Wilgen, J.; Williams, M.; Wilson, J. R.; Xu, X.; Zweben, S. J.; Akers, R.; Barry, R. E.; Beiersdorfer, P.; Bialek, J. M.; Blagojevic, B.; Bonoli, P. T.; Carter, M. D.; Davis, W.; Deng, B.; Dudek, L.; Egedal, J.; Ellis, R.; Finkenthal, M.; Foley, J.; Fredd, E.; Glasser, A.; Gibney, T.; Gilmore, M.; Goldston, R. J.; Hatcher, R. E.; Hawryluk, R. J.; Houlberg, W.; Harvey, R.; Jardin, S. C.; Hosea, J. C.; Ji, H.; Kalish, M.; Lowrance, J.; Lao, L. L.; Levinton, F. M.; Luhmann, N. C.; Marsala, R.; Mastravito, D.; Menon, M. M.; Mitarai, O.; Nagata, M.; Oliaro, G.; Parsells, R.; Peebles, T.; Peneflor, B.; Piglowski, D.; Porter, G. D.; Ram, A. K.; Rensink, M.; Rewoldt, G.; Robinson, J.; Roney, P.; Shaing, K.; Shiraiwa, S.; Sichta, P.; Stotler, D.; Stratton, B. C.; Vero, R.; Wampler, W. R.; Wurden, G. A.
2003-12-01
Research on the spherical torus (or spherical tokamak) (ST) is being pursued to explore the scientific benefits of modifying the field line structure from that in more moderate aspect ratio devices, such as the conventional tokamak. The ST experiments are being conducted in various US research facilities including the MA-class National Spherical Torus Experiment (NSTX) at Princeton, and three medium sized ST research facilities: PEGASUS at University of Wisconsin, HIT-II at University of Washington, and CDX-U at Princeton. In the context of the fusion energy development path being formulated in the US, an ST-based Component Test Facility (CTF) and, ultimately a Demo device, are being discussed. For these, it is essential to develop high performance, steady-state operational scenarios. The relevant scientific issues are energy confinement, MHD stability at high beta (β), non-inductive sustainment, Ohmic-solenoid-free start-up, and power and particle handling. In the confinement area, the NSTX experiments have shown that the confinement can be up to 50% better than the ITER-98-pby2 H-mode scaling, consistent with the requirements for an ST-based CTF and Demo. In NSTX, CTF-relevant average toroidal beta values β_{T} of up to 35% with a near unity central β_{T} have been obtained. NSTX will be exploring advanced regimes where β_{T} up to 40% can be sustained through active stabilization of resistive wall modes. To date, the most successful technique for non-inductive sustainment in NSTX is the high beta poloidal regime, where discharges with a high non-inductive fraction (~ 60% bootstrap current+NBI current drive) were sustained over the resistive skin time. Research on radio-frequency (RF) based heating and current drive utilizing high harmonic fast wave and electron Bernstein wave is also pursued on NSTX, PEGASUS, and CDX-U. For non-inductive start-up, the coaxial helicity injection, developed in HIT/HIT-II, has been adopted on NSTX to
Progress towards high-performance, steady-state spherical torus
NASA Astrophysics Data System (ADS)
Ono, M.; Bell, M. G.; Bell, R. E.; Bigelow, T.; Bitter, M.; Blanchard, W.; Boedo, J.; Bourdelle, C.; Bush, C.; Choe, W.; Chrzanowski, J.; Darrow, D. S.; Diem, S. J.; Doerner, R.; Efthimion, P. C.; Ferron, J. R.; Fonck, R. J.; Fredrickson, E. D.; Garstka, G. D.; Gates, D. A.; Gray, T.; Grisham, L. R.; Heidbrink, W.; Hill, K. W.; Hoffman, D.; Jarboe, T. R.; Johnson, D. W.; Kaita, R.; Kaye, S. M.; Kessel, C.; Kim, J. H.; Kissick, M. W.; Kubota, S.; Kugel, H. W.; LeBlanc, B. P.; Lee, K.; Lee, S. G.; Lewicki, B. T.; Luckhardt, S.; Maingi, R.; Majeski, R.; Manickam, J.; Maqueda, R.; Mau, T. K.; Mazzucato, E.; Medley, S. S.; Menard, J.; Mueller, D.; Nelson, B. A.; Neumeyer, C.; Nishino, N.; Ostrander, C. N.; Pacella, D.; Paoletti, F.; Park, H. K.; Park, W.; Paul, S. F.; Peng, Y.-K. M.; Phillips, C. K.; Pinsker, R.; Probert, P. H.; Ramakrishnan, S.; Raman, R.; Redi, M.; Roquemore, A. L.; Rosenberg, A.; Ryan, P. M.; Sabbagh, S. A.; Schaffer, M.; Schooff, R. J.; Seraydarian, R.; Skinner, C. H.; Sontag, A. C.; Soukhanovskii, V.; Spaleta, J.; Stevenson, T.; Stutman, D.; Swain, D. W.; Synakowski, E.; Takase, Y.; Tang, X.; Taylor, G.; Timberlake, J.; Tritz, K. L.; Unterberg, E. A.; Von Halle, A.; Wilgen, J.; Williams, M.; Wilson, J. R.; Xu, X.; Zweben, S. J.; Akers, R.; Barry, R. E.; Beiersdorfer, P.; Bialek, J. M.; Blagojevic, B.; Bonoli, P. T.; Carter, M. D.; Davis, W.; Deng, B.; Dudek, L.; Egedal, J.; Ellis, R.; Finkenthal, M.; Foley, J.; Fredd, E.; Glasser, A.; Gibney, T.; Gilmore, M.; Goldston, R. J.; Hatcher, R. E.; Hawryluk, R. J.; Houlberg, W.; Harvey, R.; Jardin, S. C.; Hosea, J. C.; Ji, H.; Kalish, M.; Lowrance, J.; Lao, L. L.; Levinton, F. M.; Luhmann, N. C.; Marsala, R.; Mastravito, D.; Menon, M. M.; Mitarai, O.; Nagata, M.; Oliaro, G.; Parsells, R.; Peebles, T.; Peneflor, B.; Piglowski, D.; Porter, G. D.; Ram, A. K.; Rensink, M.; Rewoldt, G.; Robinson, J.; Roney, P.; Shaing, K.; Shiraiwa, S.; Sichta, P.; Stotler, D.; Stratton, B. C.; Vero, R.; Wampler, W. R.; Wurden, G. A.
2003-12-01
Research on the spherical torus (or spherical tokamak) (ST) is being pursued to explore the scientific benefits of modifying the field line structure from that in more moderate aspect ratio devices, such as the conventional tokamak. The ST experiments are being conducted in various US research facilities including the MA-class National Spherical Torus Experiment (NSTX) at Princeton, and three medium sized ST research facilities: PEGASUS at University of Wisconsin, HIT-II at University of Washington, and CDX-U at Princeton. In the context of the fusion energy development path being formulated in the US, an ST-based Component Test Facility (CTF) and, ultimately a Demo device, are being discussed. For these, it is essential to develop high performance, steady-state operational scenarios. The relevant scientific issues are energy confinement, MHD stability at high beta (bgr), non-inductive sustainment, Ohmic-solenoid-free start-up, and power and particle handling. In the confinement area, the NSTX experiments have shown that the confinement can be up to 50% better than the ITER-98-pby2 H-mode scaling, consistent with the requirements for an ST-based CTF and Demo. In NSTX, CTF-relevant average toroidal beta values bgrT of up to 35% with a near unity central bgrT have been obtained. NSTX will be exploring advanced regimes where bgrT up to 40% can be sustained through active stabilization of resistive wall modes. To date, the most successful technique for non-inductive sustainment in NSTX is the high beta poloidal regime, where discharges with a high non-inductive fraction (~60% bootstrap current+NBI current drive) were sustained over the resistive skin time. Research on radio-frequency (RF) based heating and current drive utilizing high harmonic fast wave and electron Bernstein wave is also pursued on NSTX, PEGASUS, and CDX-U. For non-inductive start-up, the coaxial helicity injection, developed in HIT/HIT-II, has been adopted on NSTX to test the method up to Ip ~ 500 k
Oxygen consumption dynamics in steady-state tumour models.
Grimes, David Robert; Fletcher, Alexander G; Partridge, Mike
2014-09-01
Oxygen levels in cancerous tissue can have a significant effect on treatment response: hypoxic tissue is both more radioresistant and more chemoresistant than well-oxygenated tissue. While recent advances in medical imaging have facilitated real-time observation of macroscopic oxygenation, the underlying physics limits the resolution to the millimetre domain, whereas oxygen tension varies over a micrometre scale. If the distribution of oxygen in the tumour micro-environment can be accurately estimated, then the effect of potential dose escalation to these hypoxic regions could be better modelled, allowing more realistic simulation of biologically adaptive treatments. Reaction-diffusion models are commonly used for modelling oxygen dynamics, with a variety of functional forms assumed for the dependence of oxygen consumption rate (OCR) on cellular status and local oxygen availability. In this work, we examine reaction-diffusion models of oxygen consumption in spherically and cylindrically symmetric geometries. We consider two different descriptions of oxygen consumption: one in which the rate of consumption is constant and one in which it varies with oxygen tension in a hyperbolic manner. In each case, we derive analytic approximations to the steady-state oxygen distribution, which are shown to closely match the numerical solutions of the equations and accurately predict the extent to which oxygen can diffuse. The derived expressions relate the limit to which oxygen can diffuse into a tissue to the OCR of that tissue. We also demonstrate that differences between these functional forms are likely to be negligible within the range of literature estimates of the hyperbolic oxygen constant, suggesting that the constant consumption rate approximation suffices for modelling oxygen dynamics for most values of OCR. These approximations also allow the rapid identification of situations where hyperbolic consumption forms can result in significant differences from constant
Progress Towards High-Performance, Steady-State Spherical Torus
Lawrence Livermore National Laboratory
2004-01-04
Research on the spherical torus (or spherical tokamak) (ST) is being pursued to explore the scientific benefits of modifying the field line structure from that in more moderate aspect ratio devices, such as the conventional tokamak. The ST experiments are being conducted in various US research facilities including the MA-class National Spherical Torus Experiment (NSTX) at Princeton, and three medium sized ST research facilities: PEGASUS at University of Wisconsin, HIT-II at University of Washington, and CDX-U at Princeton. In the context of the fusion energy development path being formulated in the US, an ST-based Component Test Facility (CTF) and, ultimately a Demo device, are being discussed. For these, it is essential to develop high performance, steady-state operational scenarios. The relevant scientific issues are energy confinement, MHD stability at high beta ({beta}), non-inductive sustainment, Ohmic-solenoid-free start-up, and power and particle handling. In the confinement area, the NSTX experiments have shown that the confinement can be up to 50% better than the ITER-98-pby2 H-mode scaling, consistent with the requirements for an ST-based CTF and Demo. In NSTX, CTF-relevant average toroidal beta values {beta}{sub T} of up to 35% with a near unity central {beta}{sub T} have been obtained. NSTX will be exploring advanced regimes where {beta}{sub T} up to 40% can be sustained through active stabilization of resistive wall modes. To date, the most successful technique for non-inductive sustainment in NSTX is the high beta poloidal regime, where discharges with a high non-inductive fraction ({approx}60% bootstrap current+NBI current drive) were sustained over the resistive skin time. Research on radio-frequency (RF) based heating and current drive utilizing high harmonic fastwave and electron Bernstein wave is also pursued on NSTX, PEGASUS, and CDX-U. For non-inductive start-up, the coaxial helicity injection, developed in HIT/HIT-II, has been adopted on NSTX
Progress towards high-performance, steady-state spherical torus.
Lee, S.G; Kugel, W.; Efthimion, P. C.; Kissick, M. W.; Bourdelle, C.; Kim, J.H; Gray, T.; Garstka, G. D.; Fonck, R. J.; Doerner, R.; Diem, S.J.; Pacella, D.; Nishino, N.; Ferron, J. R.; Skinner, C. H.; Stutman, D.; Soukhanovskii, V.; Choe, W.; Chrzanowski, J.; Mau, T.K.; Bell, Michael G.; Raman, R.; Peng, Y-K. M.; Ono, M.; Park, W.; Hoffman, D.; Maqueda, R.; Kaye, S. M.; Kaita, R.; Jarboe, T.R.; Hill, K.W.; Heidbrink, W.; Spaleta, J.; Sontag, A.C; Seraydarian, R.; Schooff, R.J.; Sabbagh, S.A.; Menard, J.; Mazzucato, E.; Lee, K.; LeBlanc, B.; Probert, P. H.; Blanchard, W.; Wampler, William R.; Swain, D. W.; Ryan, P.M.; Rosenberg, A.; Ramakrishnan, S.; Phillips, C.K.; Park, H.K.; Roquemore, A. L.; Paoletti, F.; Medley, S. S.; Fredrickson, E. D.; Kessel, C. E.; Stevenson, T.; Darrow, D. S.; Majeski, R.; Bitter, M.; Neumeyer, C.; Nelson, B.A.; Paul, S. F.; Manickam, J.; Ostrander, C. N.; Mueller, D.; Lewicki, B.T; Luckhardt, S.; Johnson, D.W.; Grisham, L.R.; Kubota, Shigeru; Gates, D.A.; Bush, C.; Synakowski, E.J.; Schaffer, M.; Boedo, J.; Maingi, R.; Redi, M.; Pinsker, R.; Bigelow, T.; Bell, R. E.
2004-06-01
Research on the spherical torus (or spherical tokamak) (ST) is being pursued to explore the scientific benefits of modifying the field line structure from that in more moderate aspect ratio devices, such as the conventional tokamak. The ST experiments are being conducted in various US research facilities including the MA-class National Spherical Torus Experiment (NSTX) at Princeton, and three medium sized ST research facilities: PEGASUS at University of Wisconsin, HIT-II at University of Washington, and CDX-U at Princeton. In the context of the fusion energy development path being formulated in the US, an ST-based Component Test Facility (CTF) and, ultimately a Demo device, are being discussed. For these, it is essential to develop high performance, steady-state operational scenarios. The relevant scientific issues are energy confinement, MHD stability at high beta ({beta}), non-inductive sustainment, Ohmic-solenoid-free start-up, and power and particle handling. In the confinement area, the NSTX experiments have shown that the confinement can be up to 50% better than the ITER-98-pby2 H-mode scaling, consistent with the requirements for an ST-based CTF and Demo. In NSTX, CTF-relevant average toroidal beta values {beta}{sub T} of up to 35% with a near unity central {beta}{sub T} have been obtained. NSTX will be exploring advanced regimes where {beta}{sub T} up to 40% can be sustained through active stabilization of resistive wall modes. To date, the most successful technique for non-inductive sustainment in NSTX is the high beta poloidal regime, where discharges with a high non-inductive fraction ({approx}60% bootstrap current+NBI current drive) were sustained over the resistive skin time. Research on radio-frequency (RF) based heating and current drive utilizing high harmonic fast wave and electron Bernstein wave is also pursued on NSTX, PEGASUS, and CDX-U. For non-inductive start-up, the coaxial helicity injection, developed in HIT/HIT-II, has been adopted on NSTX
40 CFR 92.130 - Determination of steady-state concentrations.
Code of Federal Regulations, 2014 CFR
2014-07-01
... concentrations. 92.130 Section 92.130 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR....130 Determination of steady-state concentrations. (a)(1) For HC and NOX emissions, a steady-state concentration measurement, measured after 300 seconds (or 840 seconds for notch 8) of testing shall be...
40 CFR 92.130 - Determination of steady-state concentrations.
Code of Federal Regulations, 2013 CFR
2013-07-01
... concentrations. 92.130 Section 92.130 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR....130 Determination of steady-state concentrations. (a)(1) For HC and NOX emissions, a steady-state concentration measurement, measured after 300 seconds (or 840 seconds for notch 8) of testing shall be...
40 CFR 92.130 - Determination of steady-state concentrations.
Code of Federal Regulations, 2012 CFR
2012-07-01
... concentrations. 92.130 Section 92.130 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR....130 Determination of steady-state concentrations. (a)(1) For HC and NOX emissions, a steady-state concentration measurement, measured after 300 seconds (or 840 seconds for notch 8) of testing shall be...
40 CFR 92.130 - Determination of steady-state concentrations.
Code of Federal Regulations, 2011 CFR
2011-07-01
... concentrations. 92.130 Section 92.130 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR....130 Determination of steady-state concentrations. (a)(1) For HC and NOX emissions, a steady-state concentration measurement, measured after 300 seconds (or 840 seconds for notch 8) of testing shall be...
40 CFR 92.130 - Determination of steady-state concentrations.
Code of Federal Regulations, 2010 CFR
2010-07-01
... concentrations. 92.130 Section 92.130 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR....130 Determination of steady-state concentrations. (a)(1) For HC and NOX emissions, a steady-state concentration measurement, measured after 300 seconds (or 840 seconds for notch 8) of testing shall be...
Steady-State Axial Temperature and Flow Velocity in Triga Channel.
Energy Science and Technology Software Center (ESTSC)
2007-02-28
Version 00 TRISTAN-IJS is a computer program for calculating steady-state axial temperature distribution and flow velocity through a vertical coolant channel in low power TRIGA reactor core, cooled by natural circulation. It is designed for steady-state thermohydraulic analysis of TRIGA research reactors operating at a low power level of 1-2 MW.
NEW APPROACHES: Keeping moving to stay where you are: energy flows and steady states
NASA Astrophysics Data System (ADS)
Boohan, Richard
1996-01-01
Many systems need to be actively maintained to keep them in a steady state - centrally-heated rooms, living things, the Earth. The use of commercially available 'temperature sensitive film' allows qualitative ideas about steady-state systems to be easily investigated by pupils from lower secondary school onwards. Some examples of more advanced quantitative ideas which can be developed are given.
40 CFR 85.2225 - Steady state test exhaust analysis system-EPA 91.
Code of Federal Regulations, 2010 CFR
2010-07-01
... 40 Protection of Environment 18 2010-07-01 2010-07-01 false Steady state test exhaust analysis... Performance Warranty Short Tests § 85.2225 Steady state test exhaust analysis system—EPA 91. (a) Special... feet (above mean sea level). At any given altitude and ambient conditions specified in paragraphs...
40 CFR 85.2225 - Steady state test exhaust analysis system-EPA 91.
Code of Federal Regulations, 2011 CFR
2011-07-01
... 40 Protection of Environment 18 2011-07-01 2011-07-01 false Steady state test exhaust analysis... Performance Warranty Short Tests § 85.2225 Steady state test exhaust analysis system—EPA 91. (a) Special... feet (above mean sea level). At any given altitude and ambient conditions specified in paragraphs...
Comprehensive identification of translation start sites by tetracycline-inhibited ribosome profiling
Nakahigashi, Kenji; Takai, Yuki; Kimura, Michiko; Abe, Nozomi; Nakayashiki, Toru; Shiwa, Yuh; Yoshikawa, Hirofumi; Wanner, Barry L.; Ishihama, Yasushi; Mori, Hirotada
2016-01-01
Tetracycline-inhibited ribosome profiling (TetRP) provides a powerful new experimental tool for comprehensive genome-wide identification of translation initiation sites in bacteria. We validated TetRP by confirming the translation start sites of protein-coding genes in accordance with the 2006 version of Escherichia coli K-12 annotation record (GenBank U00096.2) and found ∼150 new start sites within 60 nucleotides of the annotated site. This analysis revealed 72 per cent of the genes whose initiation site annotations were changed from the 2006 GenBank record to the newer 2014 annotation record (GenBank U00096.3), indicating a high sensitivity. Also, results from reporter fusion and proteomics of N-terminally enriched peptides showed high specificity of the TetRP results. In addition, we discovered over 300 translation start sites within non-coding, intergenic regions of the genome, using a threshold that retains ∼2,000 known coding genes. While some appear to correspond to pseudogenes, others may encode small peptides or have previously unforeseen roles. In summary, we showed that ribosome profiling upon translation inhibition by tetracycline offers a simple, reliable and comprehensive experimental tool for precise annotation of translation start sites of expressed genes in bacteria. PMID:27013550
The steady-state phase distribution of the motor switch complex model of Halobacterium salinarum.
del Rosario, Ricardo C H; Diener, Francine; Diener, Marc; Oesterhelt, Dieter
2009-12-01
Steady-state analysis is performed on the kinetic model for the switch complex of the flagellar motor of Halobacterium salinarum (Nutsch et al.). The existence and uniqueness of a positive steady-state of the system is established and it is demonstrated why the steady-state is centered around the competent phase, a state of the motor in which it is able to respond to light stimuli. It is also demonstrated why the steady-state shifts to the refractory phase when the steady-state value of the response regulator CheYP increases. This work is one aspect of modeling in systems biology wherein the mathematical properties of a model are established. PMID:19857501
Steady- and non-steady-state carbonate-silicate controls on atmospheric CO2
Sundquist, E.T.
1991-01-01
Two contrasting hypotheses have recently been proposed for the past long-term relation between atmospheric CO2 and the carbonate-silicate geochemical cycle. One approach (Berner, 1990) suggests that CO2 levels have varied in a manner that has maintained chemical weathering and carbonate sedimentation at a steady state with respect to tectonically controlled decarbonation reactions. A second approach (Raymo et al., 1988), applied specificlly to the late Cenozoic, suggests a decrease in CO2 caused by an uplift-induced increase in chemical weathering, without regard to the rate of decarbonation. According to the steady-state (first) hypothesis, increased weathering and carbonate sedimentation are generally associated with increasing atmospheric CO2, whereas the uplift (second) hypothesis implies decreasing CO2 under the same conditions. An ocean-atmosphere-sediment model has been used to assess the response of atmospheric CO2 and carbonate sedimentation to global perturbations in chemical weathering and decarbonation reactions. Although this assessment is theoretical and cannot yet be related to the geologic record, the model simulations compare steady-state and non-steady-state carbonate-silicate cycle response. The e-fold response time of the 'CO2-weathering' feedback mechanism is between 300 and 400 ka. The response of carbonate sedimentation is much more rapid. These response times provide a measure of the strength of steady-state assumptions, and imply that certain systematic relations are sustained throughout steady-state and non-steady-state scenarios for the carbonate-silicate cycle. The simulations suggest that feedbacks can maintain the system near a steady state, but that non-steady-state effects may contribute to long-term trends. The steady-state and uplift hypotheses are not necessarily incompatible over time scales of a few million years. ?? 1991.
Inhibition of tumor cell growth by Sigma1 ligand mediated translational repression
Kim, Felix J.; Schrock, Joel M.; Spino, Christina M.; Marino, Jacqueline C.; Pasternak, Gavril W.
2012-09-21
Highlights: Black-Right-Pointing-Pointer Sigma1 ligand treatment mediates decrease in tumor cell mass. Black-Right-Pointing-Pointer Identification of a Sigma1 ligand with reversible translational repressor actions. Black-Right-Pointing-Pointer Demonstration of a role for Sigma1 in cellular protein synthesis. -- Abstract: Treatment with sigma1 receptor (Sigma1) ligands can inhibit cell proliferation in vitro and tumor growth in vivo. However, the cellular pathways engaged in response to Sigma1 ligand treatment that contribute to these outcomes remain largely undefined. Here, we show that treatment with putative antagonists of Sigma1 decreases cell mass. This effect corresponds with repressed cap-dependent translation initiation in multiple breast and prostate cancer cell lines. Sigma1 antagonist treatment suppresses phosphorylation of translational regulator proteins p70S6K, S6, and 4E-BP1. RNAi-mediated knockdown of Sigma1 also results in translational repression, consistent with the effects of antagonist treatment. Sigma1 antagonist mediated translational repression and decreased cell size are both reversible. Together, these data reveal a role for Sigma1 in tumor cell protein synthesis, and demonstrate that small molecule Sigma1 ligands can be used as modulators of protein translation.
Yagi, T; Matsuno-Yagi, A; Vik, S B; Hatefi, Y
1984-02-28
In oxidative phosphorylation and ATP-driven uphill electron transfer from succinate to NAD, double-reciprocal plots of rates vs. substrate concentrations of the energy-driven reactions are a family of parallel lines at several fixed subsaturating concentrations of the substrates or at several moderate concentrations of the inhibitors of the energy-yielding reactions. Thus, as shown elsewhere [Hatefi, Y., Yagi, T., Phelps, D. C., Wong, S.-Y., Vik, S. B., & Galante, Y. M. (1982) Proc. Natl. Acad. Sci. U.S.A. 79, 1756-1760], partial uncoupling decreases the Vappmax and increases the Kappm of the substrates of the energy-driven reactions, resulting in a decrease of Vmax/Km as a function of increased uncoupling. However, partial limitation of the flow rates of the energy-yielding reactions decreases both the Vappmax and the Kappm of the substrates of the energy-driven reactions, resulting in no change in Vmax/Km. This is true as long as the rate limitation is moderate (e.g., less than 60%), under which conditions the steady-state membrane potential (delta psi) remains essentially unchanged. At high inhibition of the energy-yielding reactions, or at moderate inhibition in the presence of low levels of an uncoupler to cause partial uncoupling, then the family of double-reciprocal plots is no longer parallel and tends to converge toward the left. Under these conditions, steady-state delta psi and Vmax/Km also decrease as inhibition is increased. The relationship between the magnitude of steady-state delta psi and the rate of the energy-driven reaction was studied in oxidative phosphorylation, ATP-driven electron transfer from succinate to NAD, and respiration-driven uniport calcium transport by intact mitochondria.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:6712922
The 40-Hz auditory steady-state response: a selective biomarker for cortical NMDA function.
Sivarao, Digavalli V
2015-05-01
When subjected to a phasic input, sensory cortical neurons display a remarkable ability to entrain faithfully to the driving stimuli. The entrainment to rhythmic sound stimuli is often referred to as the auditory steady-state response (ASSR) and can be captured using noninvasive techniques, such as scalp-recorded electroencephalography (EEG). An ASSR to a driving frequency of approximately 40 Hz is particularly interesting in that it shows, in relative terms, maximal power, synchrony, and synaptic activity. Moreover, the 40-Hz ASSR has been consistently found to be abnormal in schizophrenia patients across multiple studies. The nature of the reported abnormality has been less consistent; while most studies report a deficit in entrainment, several studies have reported increased signal power, particularly when there are concurrent positive symptoms, such as auditory hallucinations. However, the neuropharmacological basis for the 40-Hz ASSR, as well as its dysfunction in schizophrenia, has been unclear until recently. On the basis of several recent reports, it is argued that the 40-Hz ASSR represents a specific marker for cortical NMDA transmission. If confirmed, the 40-Hz ASSR may be a simple and easy-to-access pharmacodynamic biomarker for testing the integrity of cortical NMDA neurotransmission that is robustly translational across species. PMID:25809615
Steady-state kinetics and chemical mechanism of octopus hepatopancreatic glutathione transferase.
Tang, S S; Chang, G G
1995-01-01
The kinetic mechanism of glutathione S-transferase (GST) from Octopus vulgaris hepatopancreas was investigated by steady-state analysis. Initial-velocity studies showed an intersecting pattern, which suggests a sequential kinetic mechanism for the enzyme. Product-inhibition patterns by chloride and the conjugate product were all non-competitive with respect to glutathione or 1-chloro-2,4-dinitrobenzene (CDNB), which indicates that the octopus digestive gland GST conforms to a steady-state sequential random Bi Bi kinetic mechanism. Dead-end inhibition patterns indicate that ethacrynic acid ([2,3-dichloro-4-(2-methyl-enebutyryl) phenoxy]acetic acid) binds at the hydrophobic H-site, norophthalmic acid (gamma-glutamylalanylglycine) binds at the glutathione G-site, and glutathione-ethacrynate conjugate occupied both H- and G-sites of the enzyme. The chemical mechanism of the enzyme was examined by pH and kinetic solvent-isotope effects. At pH (and p2H) = 8.011, in which kcat. was independent of pH or p2H, the solvent isotope effects on V and V/KmGSH were near unity, in the range 1.069-1.175. An inverse isotope effect was observed for V/KmCDNB (0.597), presumably resulting from the hydrogen-bonding of enzyme-bound glutathione, which has pKa of 6.83 +/- 0.04, a value lower by 2.34 pH units than the pKa of glutathione in aqueous solution. This lowering of the pKa value for the sulphydryl group of the bound glutathione was presumably due to interaction with the active site Tyr7, which had a pKa value of 8.46 +/- 0.09 that was raised to 9.63 +/- 0.08 in the presence of glutathione thiolate. Subsequent chemical reaction involves attacking of thiolate anion at the electrophilic substrate with the formation of a negatively charged Meisenheimer complex, which is the rate-limiting step of the reaction. Images Scheme 2 PMID:7619078
Translation control during prolonged mTORC1 inhibition mediated by 4E-BP3.
Tsukumo, Yoshinori; Alain, Tommy; Fonseca, Bruno D; Nadon, Robert; Sonenberg, Nahum
2016-01-01
Targeting mTORC1 is a highly promising strategy in cancer therapy. Suppression of mTORC1 activity leads to rapid dephosphorylation of eIF4E-binding proteins (4E-BP1-3) and subsequent inhibition of mRNA translation. However, how the different 4E-BPs affect translation during prolonged use of mTOR inhibitors is not known. Here we show that the expression of 4E-BP3, but not that of 4E-BP1 or 4E-BP2, is transcriptionally induced during prolonged mTORC1 inhibition in vitro and in vivo. Mechanistically, our data reveal that 4E-BP3 expression is controlled by the transcription factor TFE3 through a cis-regulatory element in the EIF4EBP3 gene promoter. CRISPR/Cas9-mediated EIF4EBP3 gene disruption in human cancer cells mitigated the inhibition of translation and proliferation caused by prolonged treatment with mTOR inhibitors. Our findings show that 4E-BP3 is an important effector of mTORC1 and a robust predictive biomarker of therapeutic response to prolonged treatment with mTOR-targeting drugs in cancer. PMID:27319316
Translation control during prolonged mTORC1 inhibition mediated by 4E-BP3
Tsukumo, Yoshinori; Alain, Tommy; Fonseca, Bruno D.; Nadon, Robert; Sonenberg, Nahum
2016-01-01
Targeting mTORC1 is a highly promising strategy in cancer therapy. Suppression of mTORC1 activity leads to rapid dephosphorylation of eIF4E-binding proteins (4E-BP1–3) and subsequent inhibition of mRNA translation. However, how the different 4E-BPs affect translation during prolonged use of mTOR inhibitors is not known. Here we show that the expression of 4E-BP3, but not that of 4E-BP1 or 4E-BP2, is transcriptionally induced during prolonged mTORC1 inhibition in vitro and in vivo. Mechanistically, our data reveal that 4E-BP3 expression is controlled by the transcription factor TFE3 through a cis-regulatory element in the EIF4EBP3 gene promoter. CRISPR/Cas9-mediated EIF4EBP3 gene disruption in human cancer cells mitigated the inhibition of translation and proliferation caused by prolonged treatment with mTOR inhibitors. Our findings show that 4E-BP3 is an important effector of mTORC1 and a robust predictive biomarker of therapeutic response to prolonged treatment with mTOR-targeting drugs in cancer. PMID:27319316
HIV-1 Vif binds to APOBEC3G mRNA and inhibits its translation
Mercenne, Gaëlle; Bernacchi, Serena; Richer, Delphine; Bec, Guillaume; Henriet, Simon; Paillart, Jean-Christophe; Marquet, Roland
2010-01-01
The HIV-1 viral infectivity factor (Vif) allows productive infection of non-permissive cells (including most natural HIV-1 targets) by counteracting the cellular cytosine deaminases APOBEC-3G (hA3G) and hA3F. The Vif-induced degradation of these restriction factors by the proteasome has been extensively studied, but little is known about the translational repression of hA3G and hA3F by Vif, which has also been proposed to participate in Vif function. Here, we studied Vif binding to hA3G mRNA and its role in translational repression. Filter binding assays and fluorescence titration curves revealed that Vif tightly binds to hA3G mRNA. Vif overall binding affinity was higher for the 3′UTR than for the 5′UTR, even though this region contained at least one high affinity Vif binding site (apparent Kd = 27 ± 6 nM). Several Vif binding sites were identified in 5′ and 3′UTRs using RNase footprinting. In vitro translation evidenced that Vif inhibited hA3G translation by two mechanisms: a main time-independent process requiring the 5′UTR and an additional time-dependent, UTR-independent process. Results using a Vif protein mutated in the multimerization domain suggested that the molecular mechanism of translational control is more complicated than a simple physical blockage of scanning ribosomes. PMID:19910370
HIV-1 Vif binds to APOBEC3G mRNA and inhibits its translation.
Mercenne, Gaëlle; Bernacchi, Serena; Richer, Delphine; Bec, Guillaume; Henriet, Simon; Paillart, Jean-Christophe; Marquet, Roland
2010-01-01
The HIV-1 viral infectivity factor (Vif) allows productive infection of non-permissive cells (including most natural HIV-1 targets) by counteracting the cellular cytosine deaminases APOBEC-3G (hA3G) and hA3F. The Vif-induced degradation of these restriction factors by the proteasome has been extensively studied, but little is known about the translational repression of hA3G and hA3F by Vif, which has also been proposed to participate in Vif function. Here, we studied Vif binding to hA3G mRNA and its role in translational repression. Filter binding assays and fluorescence titration curves revealed that Vif tightly binds to hA3G mRNA. Vif overall binding affinity was higher for the 3'UTR than for the 5'UTR, even though this region contained at least one high affinity Vif binding site (apparent K(d) = 27 +/- 6 nM). Several Vif binding sites were identified in 5' and 3'UTRs using RNase footprinting. In vitro translation evidenced that Vif inhibited hA3G translation by two mechanisms: a main time-independent process requiring the 5'UTR and an additional time-dependent, UTR-independent process. Results using a Vif protein mutated in the multimerization domain suggested that the molecular mechanism of translational control is more complicated than a simple physical blockage of scanning ribosomes. PMID:19910370
NASA Astrophysics Data System (ADS)
Bansal, Pikesh; Chattopadhyay, Ajit Kumar; Agrawal, Vishnu Prakash
2016-04-01
The aim of the present study is to theoretically determine the steady state characteristics of hydrodynamic oil journal bearings considering the effect of deformation of liner and with micropolar lubrication. Modified Reynolds equation based on micropolar lubrication theory is solved using finite difference method to obtain steady state film pressures. Minimum film thickness is calculated taking into consideration the deformation of the liner. Parametric study has been conducted and steady state characteristics for journal bearing with elasticity of bearing liner are plotted for various values of eccentricity ratio, deformation factor, characteristic length and coupling number.
The condensation of ampholytes in steady state moving boundaries - Analysis by computer simulation
NASA Technical Reports Server (NTRS)
Mosher, Richard A.; Thormann, Wolfgang
1986-01-01
A digital simulation of the behavior of amphoteric sample components in moving steady state boundaries is presented. Complete computer simulation data, including profiles of concentration, conductivity and pH as functions of time, are given for both cationic and anionic electrolyte configurations which incorporate one amphoteric sample constituent. The condensation of ampholytes in steady state moving boundaries is shown to proceed via an isotachophoretic mechanism and not by isoelectric focusing. Mobility (velocity) relationships necessary for sample components to form steady state zones are discussed.
Type I and Type II Interferons Inhibit the Translation of Murine Norovirus Proteins▿
Changotra, Harish; Jia, Yali; Moore, Tara N.; Liu, Guangliang; Kahan, Shannon M.; Sosnovtsev, Stanislav V.; Karst, Stephanie M.
2009-01-01
Human noroviruses are responsible for more than 95% of nonbacterial epidemic gastroenteritis worldwide. Both onset and resolution of disease symptoms are rapid, suggesting that components of the innate immune response are critical in norovirus control. While the study of the human noroviruses has been hampered by the lack of small animal and tissue culture systems, our recent discovery of a murine norovirus (MNV) and its in vitro propagation have allowed us to begin addressing norovirus replication strategies and immune responses to norovirus infection. We have previously demonstrated that interferon responses are critical to control MNV-1 infection in vivo and to directly inhibit viral replication in vitro. We now extend these studies to define the molecular basis for interferon-mediated inhibition. Viral replication intermediates were not detected in permissive cells pretreated with type I interferon after either infection or transfection of virion-associated RNA, demonstrating a very early block to virion production that is after virus entry and uncoating. A similar absence of viral replication intermediates was observed in infected primary macrophages and dendritic cells pretreated with type I IFN. This was not due to degradation of incoming genomes in interferon-pretreated cells since similar levels of genomes were present in untreated and pretreated cells through 6 h of infection, and these genomes retained their integrity. Surprisingly, this block to the translation of viral proteins was not dependent on the well-characterized interferon-induced antiviral molecule PKR. Similar results were observed in cells pretreated with type II interferon, except that the inhibition of viral translation was dependent on PKR. Thus, both type I and type II interferon signaling inhibit norovirus translation in permissive myeloid cells, but they display distinct dependence on PKR for this inhibition. PMID:19297466
Ascenzi, Paolo; Bocedi, Alessio; Visca, Paolo; Antonini, Giovanni; Gradoni, Luigi
2003-09-26
Cysteine proteinases are relevant to several aspects of the parasite life cycle and of parasite-host relationship. Moreover, they appear as promising targets for antiparasite chemotherapy. Here, the first quantitative investigation on the steady-state and pre-steady-state kinetics of the papain-like cysteine proteinases from epimastigotes of Trypanosoma cruzi (cruzipain), the agent of Chagas' disease, and from promastigotes of Leishmania infantum, an agent of visceral and cutaneous leishmaniases, is reported. The results indicate that kinetics for the parasite proteinase catalyzed hydrolysis of N-alpha-benzyloxycarbonyl-L-phenylalanyl-L-arginine-(7-amino-4-methylcoumarin) may be consistently fitted to the minimum three-step mechanism involving the acyl.enzyme intermediate E.P: [mechanism: see text] At neutral pH, the k(+3) step (deacylation process) is rate limiting in enzyme catalysis, whereas, at pH<6, the k(+2) step (acylation process) becomes rate limiting. This illustrates the potential danger in interpreting both kcat versus pH profile, given that the acylation or the deacylation step is rate limiting throughout the whole pH range explored, and Km as the true affinity constant for the E:S complex formation. Comparison with the steady-state and pre-steady-state kinetics of homologous plant enzymes suggests that the parasite cysteine proteinase catalytic behavior appears to be of general significance. PMID:12963041
Strain-dependent cross-bridge cycle for muscle. II. Steady-state behavior.
Smith, D A; Geeves, M A
1995-01-01
Quantitative predictions of steady-state muscle properties from the strain-dependent cross-bridge for muscle are presented. With a stiffness of 5.4 x 10(-4) N/m per head, a throw distance of 11 nm, and three allowed actin sites/head, isometric properties and their dependence on phosphate and nucleotide levels are well described if the tension-generating step occurs before phosphate release. At very low ATP levels, rigorlike states with negative strain are predicted. The rate-limiting step for cycling and ATP consumption is strain-blocked ADP release for isometric and slowly shortening muscle. Under rapid shortening, ATP hydrolysis on detached heads is the rate-limiting step, and the ratio of bound ATP to bound ADP.Pi increases by a factor of 7. At large positive strains, bound heads must be forcibly detached from actin to account for tension in rapid extension, but forced detachment in shortening has no effect without destroying isometric attached states. Strain-blocked phosphate release as proposed produces modest inhibition of the ATPase rate under rapid shortening, sufficient to give a maximum for one actin site per helix turn. Alternative cross-bridge models are discussed in the light of these predictions. PMID:8527668
Deng, Xin; Liang, Haihua; Ulanovskaya, Olesya A; Ji, Quanjiang; Zhou, Tianhong; Sun, Fei; Lu, Zhike; Hutchison, Alan L; Lan, Lefu; Wu, Min; Cravatt, Benjamin F; He, Chuan
2014-07-01
Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) from human pathogens Staphylococcus aureus and Pseudomonas aeruginosa can be readily inhibited by reactive oxygen species (ROS)-mediated direct oxidation of their catalytic active cysteines. Because of the rapid degradation of H2O2 by bacterial catalase, only steady-state but not one-dose treatment with H2O2 rapidly induces glycolysis and the pentose phosphate pathway (PPP). We conducted transcriptome sequencing (RNA-seq) analyses to globally profile the bacterial transcriptomes in response to a steady level of H2O2, which revealed profound transcriptional changes, including the induced expression of glycolytic genes in both bacteria. Our results revealed that the inactivation of GAPDH by H2O2 induces metabolic levels of glycolysis and the PPP; the elevated levels of fructose 1,6-biphosphate (FBP) and 2-keto-3-deoxy-6-phosphogluconate (KDPG) lead to dissociation of their corresponding glycolytic repressors (GapR and HexR, respectively) from their cognate promoters, thus resulting in derepression of the glycolytic genes to overcome H2O2-stalled glycolysis in S. aureus and P. aeruginosa, respectively. Both GapR and HexR may directly sense oxidative stresses, such as menadione. PMID:24769698
Deng, Xin; Liang, Haihua; Ulanovskaya, Olesya A.; Ji, Quanjiang; Zhou, Tianhong; Sun, Fei; Lu, Zhike; Hutchison, Alan L.; Lan, Lefu; Wu, Min; Cravatt, Benjamin F.
2014-01-01
Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) from human pathogens Staphylococcus aureus and Pseudomonas aeruginosa can be readily inhibited by reactive oxygen species (ROS)-mediated direct oxidation of their catalytic active cysteines. Because of the rapid degradation of H2O2 by bacterial catalase, only steady-state but not one-dose treatment with H2O2 rapidly induces glycolysis and the pentose phosphate pathway (PPP). We conducted transcriptome sequencing (RNA-seq) analyses to globally profile the bacterial transcriptomes in response to a steady level of H2O2, which revealed profound transcriptional changes, including the induced expression of glycolytic genes in both bacteria. Our results revealed that the inactivation of GAPDH by H2O2 induces metabolic levels of glycolysis and the PPP; the elevated levels of fructose 1,6-biphosphate (FBP) and 2-keto-3-deoxy-6-phosphogluconate (KDPG) lead to dissociation of their corresponding glycolytic repressors (GapR and HexR, respectively) from their cognate promoters, thus resulting in derepression of the glycolytic genes to overcome H2O2-stalled glycolysis in S. aureus and P. aeruginosa, respectively. Both GapR and HexR may directly sense oxidative stresses, such as menadione. PMID:24769698
The Effects of High Steady State Auxin Levels on Root Cell Elongation in Brachypodium.
Pacheco-Villalobos, David; Díaz-Moreno, Sara M; van der Schuren, Alja; Tamaki, Takayuki; Kang, Yeon Hee; Gujas, Bojan; Novak, Ondrej; Jaspert, Nina; Li, Zhenni; Wolf, Sebastian; Oecking, Claudia; Ljung, Karin; Bulone, Vincent; Hardtke, Christian S
2016-05-01
The long-standing Acid Growth Theory of plant cell elongation posits that auxin promotes cell elongation by stimulating cell wall acidification and thus expansin action. To date, the paucity of pertinent genetic materials has precluded thorough analysis of the importance of this concept in roots. The recent isolation of mutants of the model grass species Brachypodium distachyon with dramatically enhanced root cell elongation due to increased cellular auxin levels has allowed us to address this question. We found that the primary transcriptomic effect associated with elevated steady state auxin concentration in elongating root cells is upregulation of cell wall remodeling factors, notably expansins, while plant hormone signaling pathways maintain remarkable homeostasis. These changes are specifically accompanied by reduced cell wall arabinogalactan complexity but not by increased proton excretion. On the contrary, we observed a tendency for decreased rather than increased proton extrusion from root elongation zones with higher cellular auxin levels. Moreover, similar to Brachypodium, root cell elongation is, in general, robustly buffered against external pH fluctuation in Arabidopsis thaliana However, forced acidification through artificial proton pump activation inhibits root cell elongation. Thus, the interplay between auxin, proton pump activation, and expansin action may be more flexible in roots than in shoots. PMID:27169463
The Effects of High Steady State Auxin Levels on Root Cell Elongation in Brachypodium[OPEN
Pacheco-Villalobos, David; Tamaki, Takayuki; Gujas, Bojan; Jaspert, Nina; Oecking, Claudia; Bulone, Vincent; Hardtke, Christian S.
2016-01-01
The long-standing Acid Growth Theory of plant cell elongation posits that auxin promotes cell elongation by stimulating cell wall acidification and thus expansin action. To date, the paucity of pertinent genetic materials has precluded thorough analysis of the importance of this concept in roots. The recent isolation of mutants of the model grass species Brachypodium distachyon with dramatically enhanced root cell elongation due to increased cellular auxin levels has allowed us to address this question. We found that the primary transcriptomic effect associated with elevated steady state auxin concentration in elongating root cells is upregulation of cell wall remodeling factors, notably expansins, while plant hormone signaling pathways maintain remarkable homeostasis. These changes are specifically accompanied by reduced cell wall arabinogalactan complexity but not by increased proton excretion. On the contrary, we observed a tendency for decreased rather than increased proton extrusion from root elongation zones with higher cellular auxin levels. Moreover, similar to Brachypodium, root cell elongation is, in general, robustly buffered against external pH fluctuation in Arabidopsis thaliana. However, forced acidification through artificial proton pump activation inhibits root cell elongation. Thus, the interplay between auxin, proton pump activation, and expansin action may be more flexible in roots than in shoots. PMID:27169463
Green, J; Dalton, H
1986-01-01
A steady-state kinetic analysis of purified soluble methane mono-oxygenase of Methylococcus capsulatus (Bath) was performed. The enzyme was found to follow a concerted-substitution mechanism. Methane binds to the enzyme followed by NADH, which reacts to yield reduced enzyme and NAD+. The reduced enzyme-methane complex binds O2 to give a second ternary complex, which breaks down to release water and methanol. In this way the enzyme can control the supply of electrons to the active site to coincide with the arrival of methane. Product-inhibition studies (with propylene as substrate) supported the reaction mechanism proposed. Ki values for NAD+ and propylene oxide are reported. The Km for NADH varied from 25 microM to 300 microM, depending on the nature of the hydrocarbon substrate, and thus supports the proposed reaction sequence. With methane as substrate the Km values for methane, NADH and O2 were shown to be 3 microM, 55.8 microM and 16.8 microM respectively. With propylene as substrate the Km values for propylene, NADH and O2 were 0.94 microM, 25.2 microM and 12.7-15.9 microM respectively. Methane mono-oxygenase was shown to be well adapted to the oxidation of methane compared with other straight-chain alkanes. PMID:3098230
Streit, Bennett R.; DuBois, Jennifer L.
2013-01-01
Chlorite dismutase carries out the heme-catalyzed decomposition of ClO2– to Cl– and O2, an unusual transformation with biotechnological and bioremediative applications. The enzyme has been successfully overexpressed for the first time in highly functional form in Escherichia coli and its steady state kinetics studied. The purified enzyme is abundant (55 mg/L cell culture), highly active (~4.7 × 103 μmol of ClO2– min–1 mg–1 subunit) and nearly stoichiometric in heme; further, it shares spectroscopic and physicochemical features with chlorite dismutases previously isolated from three organisms. A careful study of the enzyme's steady state kinetics has been carried out. ClO2– consumption and O2 release rates were measured, yielding comparable values of kcat (4.5 × 105 min–1), Km (~215 μM), and kcat/Km (3.5 × 107 M–1 s–1) via either method (4 °C, pH 6.8; all values referenced per heme-containing subunit). ClO2–:O2 stoichiometry exhibited a 1:1 relationship under all conditions measured. Though the value of kcat/Km indicates near diffusion control of the reaction, viscosogens had no effect on kcat/Km or Vmax. The product O2 did not inhibit the reaction at saturating [O2], but Cl– is a mixed inhibitor with relatively high values of KI (225 mM for enzyme and 95.6 mM for the enzyme–substrate complex), indicating a relatively low affinity of the heme iron for halogen ions. Chlorite irreversibly inactivates the enzyme after ~1.7 × 104 turnovers (per heme) and with a half-life of 0.39 min, resulting in bleaching of the heme chromophore. The inactivation KI (Kinact) of 166 μM is similar in magnitude to Km, consistent with a common Michaelis complex on the pathway to both reaction and inactivation. The one-electron peroxidase substrate guaiacol offers incomplete protection of the enzyme from inactivation. Mechanisms in keeping with the available data and the properties of other well-described heme enzymes are proposed. PMID:18422344
Measurements of Gene Expression at Steady State Improve the Predictability of Part Assembly.
Zhang, Haoqian M; Chen, Shuobing; Shi, Handuo; Ji, Weiyue; Zong, Yeqing; Ouyang, Qi; Lou, Chunbo
2016-03-18
Mathematical modeling of genetic circuits generally assumes that gene expression is at steady state when measurements are performed. However, conventional methods of measurement do not necessarily guarantee that this assumption is satisfied. In this study, we reveal a bi-plateau mode of gene expression at the single-cell level in bacterial batch cultures. The first plateau is dynamically active, where gene expression is at steady state; the second plateau, however, is dynamically inactive. We further demonstrate that the predictability of assembled genetic circuits in the first plateau (steady state) is much higher than that in the second plateau where conventional measurements are often performed. By taking the nature of steady state into consideration, our method of measurement promises to directly capture the intrinsic property of biological parts/circuits regardless of circuit-host or circuit-environment interactions. PMID:26652307
Determination of multiple steady states in a family of allosteric models for glycolysis
NASA Astrophysics Data System (ADS)
Li, Hsing-Ya
1998-11-01
To predict glycolytic oscillations, Goldbeter and Lefever [Biophys. J. 12, 1302 (1972)] proposed a complex allosteric model, consisting of 14 species and 32 reactions. Under the usual assumption of a quasisteady state for all the enzymatic forms, they simplified it to a two-variable model and ruled out the possibility of multiple steady states. In this work, the original network is determined to admit multiplicity of steady states by a zero eigenvalue analysis. It is shown that the existence of the multiplicity in the original network can be determined by a subnetwork with five species and eight reactions. The fourteen-species network can be treated as containing four such subnetworks. The analysis is extended to a general modified allosteric model, consisting of n active subunits. It can be shown that the general network has no steady-state multiplicity if all the four subnetworks follow the case of n=1; otherwise, multiple steady states can occur.
A model for electrophoretic transport of charged particles through membrane before steady state
NASA Astrophysics Data System (ADS)
de Souza, Tatiana Miranda; Fragoso, Viviane Muniz da Silva; Cruz, Frederico Alan de Oliveira
2015-12-01
In this paper, we are presenting a model for electrophoretic motion of a charged particle through the membrane before it reaches the steady state, based on concepts of Physics. Some results from analysis of the model are discussed.
Aspects of steady-state operation of the Wendelstein 7-X stellarator
Geiger, J.; Wolf, R. C.; Beidler, C.; Cardella, A.; Chlechowitz, E.; Erckmann, V.; Gantenbein, G.; Hathiramani, D.; Hirsch, M.; Kasparek, W.; Kißlinger, J.; König, R.; Kornejew, P.; Laqua, H. P.; Lechte, C.; Lore, J.; Lumsdaine, A.; Maaßberg, H.; Marushchenko, N. B.; Michel, G.; Otte, M.; Peacock, A.; Sunn Pedersen, T.; Thumm, M.; Turkin, Y.; Werner, A.; Zhang, D.
2012-12-17
The objective of Wendelstein 7-X is to demonstrate steady-state operation at -values of up to 5%, at ion temperatures of several keV and plasma densities of up to 2 1020 m 3. The second operational phase foresees a fully steady-state high heat flux (HHF) divertor. Preparations are underway to cope with residual bootstrap currents, either by electron cyclotron current drive or by HHF protection elements. The main steady-state heating system is an electron cyclotron resonance heating facility. Various technical improvements of the gyrotrons have been implemented recently. They enable a reliable operation at the 1MW power level. Some of the technical issues preparing plasma diagnostics for steady-state operation are exemplified. This includes the protection against non-absorbed microwave radiation.
Technical challenges in the construction of the steady-state stellarator Wendelstein 7-X
Bosch, H.-S.; Wolf, R. C.; Andreeva, T.; Cardella, A; Erckmann, V.; Gantenbein, G; Hathiramani, D; Kasparek, W; Klinger, T.; Koenig, R; Kornejew, P; Laqua, H P; Lechte, C; Michel, G; Peacock, A.; Sunn Pedersen, T; Thumm, M; Turkin, Yu.; Wegener, Lutz; Werner, A.; Zhang, D; Beidler, C.; Bozhenkov, S.; Brown, T.; Geiger, J.; Harris, Jeffrey H; Heitzenroeder, P.; Lumsdaine, Arnold; Maassberg, H.; Marushchenko, N B; Neilson, G. H.; Otte, M; Rummel, Thomas; Spong, Donald A; Tretter, Jorg
2013-01-01
The next step in the Wendelstein stellarator line is the large superconducting device Wendelstein 7-X, currently under construction in Greifswald, Germany. Steady-state operation is an intrinsic feature of stellarators, and one key element of the Wendelstein 7-X mission is to demonstrate steady-state operation under plasma conditions relevant for a fusion power plant. Steady-state operation of a fusion device, on the one hand, requires the implementation of special technologies, giving rise to technical challenges during the design, fabrication and assembly of such a device. On the other hand, also the physics development of steady-state operation at high plasma performance poses a challenge and careful preparation. The electron cyclotron resonance heating system, diagnostics, experiment control and data acquisition are prepared for plasma operation lasting 30 min. This requires many new technological approaches for plasma heating and diagnostics as well as new concepts for experiment control and data acquisition.
Quasi steady-state aerodynamic model development for race vehicle simulations
NASA Astrophysics Data System (ADS)
Mohrfeld-Halterman, J. A.; Uddin, M.
2016-01-01
Presented in this paper is a procedure to develop a high fidelity quasi steady-state aerodynamic model for use in race car vehicle dynamic simulations. Developed to fit quasi steady-state wind tunnel data, the aerodynamic model is regressed against three independent variables: front ground clearance, rear ride height, and yaw angle. An initial dual range model is presented and then further refined to reduce the model complexity while maintaining a high level of predictive accuracy. The model complexity reduction decreases the required amount of wind tunnel data thereby reducing wind tunnel testing time and cost. The quasi steady-state aerodynamic model for the pitch moment degree of freedom is systematically developed in this paper. This same procedure can be extended to the other five aerodynamic degrees of freedom to develop a complete six degree of freedom quasi steady-state aerodynamic model for any vehicle.
Steady State Performance Characteristics of a Single Pad Externally Adjustable Fluid Film Bearing
NASA Astrophysics Data System (ADS)
Shenoy, Satish B.; Pai, Raghuvir
The steady state performance characteristics of centrally loaded 60 degree single pad externally adjustable partial arc bearing is studied theoretically. Principal feature of the bearing is the facility to control its radial clearance and circumferential film thickness gradient, during operation. The bearing has aspect ratios of 1.0, 0.5 and 0.25 and operates over a wide range of eccentricity ratios and adjustments. Steady state performance characteristics of the bearing are presented in terms of attitude angle, load carrying capacity, oil flow and friction variable. The steady state form of Reynolds equation in two dimensions is solved numerically using the finite difference method. The effect of tilt and the radial adjustments on the steady state performance characteristics are presented in the form of plots. A comparative study predicts that negative radial and negative tilt adjustment results in better load carrying capacity with reduced oil flow and friction.
Detection meeting control: Unstable steady states in high-dimensional nonlinear dynamical systems.
Ma, Huanfei; Ho, Daniel W C; Lai, Ying-Cheng; Lin, Wei
2015-10-01
We articulate an adaptive and reference-free framework based on the principle of random switching to detect and control unstable steady states in high-dimensional nonlinear dynamical systems, without requiring any a priori information about the system or about the target steady state. Starting from an arbitrary initial condition, a proper control signal finds the nearest unstable steady state adaptively and drives the system to it in finite time, regardless of the type of the steady state. We develop a mathematical analysis based on fast-slow manifold separation and Markov chain theory to validate the framework. Numerical demonstration of the control and detection principle using both classic chaotic systems and models of biological and physical significance is provided. PMID:26565299
Semi-continuous organic carbon concentrations were measured through several experiments of statically generated secondary organic aerosol formed by hydrocarbon + NOx irradiations. Repeated, randomized measurements of these steady state aerosols reveal decreases in the observed c...
Representation of Type 4 wind turbine generator for steady state short-circuit calculations
NASA Astrophysics Data System (ADS)
Kamara, Wouleye
Various technical impacts are associated to the interconnection of wind turbine generators to the grid. Among them, the increase of short-circuit levels along with its effect on the settings of protecting relays has long acted as an important inhibiting factor for the interconnection of new wind power plants to the grid. This is especially true at the medium voltage level where networks operate close to their short-circuit design value [1]. As renewable energies are progressively replacing traditional power generation sources, short-circuit studies need to adequately assess the impact of newly interconnected wind power plants on the fault level of the network. For planning and design purposes, short-circuit studies are usually performed using steady-state short-circuit programs. Unfortunately, very few have developed models of wind turbine generators that accurately estimate their fault contribution in the phase domain. In particular, no commercial fault-flow analysis program specifically addresses the modeling of inverter-based wind turbine generators which behavior is based on the inverter's characteristics rather than the generator's. The main contribution of this research work is the development of a simplified and yet accurate model of full-scale converter based wind turbine generator, also called Type 4 wind turbine generator, for steady-state short-circuit calculations. The model reproduces the real behavior of the Type 4 wind turbine generator under fault conditions by correctly accounting for the effect of the full-scale converter. The data used for the model is easily accessible to planning engineers. An additional contribution of this research work is the development of a short-circuit algorithm adapted to support the proposed model of Type 4 wind-turbine generator. Short-circuit algorithm based on modified-augmented-nodal analysis (MANA) is solved iteratively to accommodate the proposed model. The algorithm is successfully implemented in CYME 7.0, a
Zhang, J; Ma, L; Li, W; Yang, P; Qin, L
2016-06-01
As disturbance in auditory steady-state response (ASSR) has been consistently found in many neuropsychiatric disorders, such as autism spectrum disorder and schizophrenia, there is considerable interest in the development of translational rat models to elucidate the underlying neural and neurochemical mechanisms involved in ASSR. This is the first study to investigate the effects of the non-selective muscarinic antagonist scopolamine and the cholinesterase inhibitor donepezil (also in combination with scopolamine) on ASSR. We recorded the local field potentials through the chronic microelectrodes implanted in the auditory cortex of freely moving rat. ASSRs were recorded in response to auditory stimuli delivered over a range of frequencies (10-80Hz) and averaged over 60 trials. We found that a single dose of scopolamine produced a temporal attenuation in response to auditory stimuli; the most attenuation occurred at 40Hz. Time-frequency analysis revealed deficits in both power and phase-locking to 40Hz. Donepezil augmented 40-Hz steady-state power and phase-locking. Scopolamine combined with donepezil had an enhanced effect on the phase-locking, but not power of ASSR. These changes induced by cholinergic drugs suggest an involvement of muscarinic neurotransmission in auditory processing and provide a rodent model investigating the neurochemical mechanism of neurophysiological deficits seen in patients. PMID:26964684
NASA Astrophysics Data System (ADS)
Rao, Wei
2011-10-01
The constant modulus algorithm (CMA) for blind equalization requires a separate carrier-recovery system for phase recovery. A modified CMA, called the multimodulus algorithm (MMA), which may perform joint blind equalization and carrier recovery without the need for a separate carrier-recovery system for quadrature amplitude modulation (QAM) signal constellations. This letter mathematically analyzes the steady-state mean square error (MSE) of MMA. Analysis results indicate that MMA produces 50% fewer steady-state MSE than CMA.
A comparison and review of steady-state and time-varying reconnection
NASA Technical Reports Server (NTRS)
Semenov, V. S.; Kubyshkin, I. V.; Lebedeva, V. V.; Rijnbeek, R. P.; Heyn, M. F.; Biernat, H. K.; Farrugia, C. J.
1992-01-01
Extensions of Petschek's (1964) analysis are reviewed and used to investigate the steady-state and time-dependent reconnection in a current sheet geometry of the type observed at the magnetopause. It is shown that steady-state reconnection appears as a very special case in a time-dependent analysis. A single theoretical framework is proposed for interpreting reconnection phenomena at the magnetopause and for investigating the characteristics of dayside reconnection.
The effect of oxygen on denitrification during steady-state growth of Paracoccus halodenitrificans
NASA Technical Reports Server (NTRS)
Hochstein, L. I.; Betlach, M.; Kritikos, G.
1984-01-01
Steady-state cultures of Paracoccus halodenitrificans were grown anaerobically prior to establishing steady states at different concentrations of oxygen. In the absence of oxygen, nitrate-limited cultures produced dinitrogen, and as the oxygen supply increased, these cultures produced nitrous oxide, then nitrite. These changes reflected two phenomena: the inactivation of nitrous oxide reductase by oxygen and the diversion of electrons from nitrite to oxygen.
Inner bremsstrahlung as a source of X-rays in the steady-state universe.
NASA Technical Reports Server (NTRS)
Petrosian, V.; Ramaty, R.
1972-01-01
Consideration of the compatibility of matter creation in steady-state cosmology with certain X-ray observations. It is shown that, because of inner bremsstrahlung from neutron decay, the steady-state universe with neutron creation in diffuse regions is inconsistent with X-ray observations around 100 keV, unless the particle density of the universe is less than 0.1 per cu m.
Gain in the non-steady-state free-electron laser
Wu, D.; Min, Y.
1995-09-01
The non-steady-state self-consistent equation in the linear regime of the free-electron laser (FEL) and the low gain formulas in the non-steady-state FEL are derived in this paper. It is found that due to slippage the nonuniformity effect in the longitudinal distribution of the electron beam density is dominant in the influence of the electron pulse length on the gain of the FEL. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.
Steady-state 2. pi. pulses under conditions of passive locking of laser modes
Komarov, K.P.; Ugozhaev, V.D.
1984-06-01
A theoretical study is made of laser mode locking in the regime of self-induced transparency of a passive filter. It is shown that there is a solution in the form of ultrashort steady-state 2..pi.. pulses. The range of stability of this regime and its characteristics are determined. By way of example, estimates are obtained of parameters of a steady-state pulse emitted by an alexandrite laser with a potassium absorption cell.
Steady-state entanglement of a Bose-Einstein condensate and a nanomechanical resonator
Asjad, Muhammad; Saif, Farhan
2011-09-15
We analyze the steady-state entanglement between Bose-Einstein condensate trapped inside an optical cavity with a moving end mirror (nanomechanical resonator) driven by a single mode laser. The quantized laser field mediates the interaction between the Bose-Einstein condensate and nanomechanical resonator. In particular, we study the influence of temperature on the entanglement of the coupled system, and note that the steady-state entanglement is fragile with respect to temperature.
Theory of second-harmonic generation of molecular systems: The steady-state case
Lin, S.H.; Alden, R.G. ); Villaeys, A.A.; Pflumio, V. )
1993-10-01
In this paper, a general formalism for treating both steady-state and time-resolved second-harmonic generation for molecular systems is presented. Here, only the steady-state case will be reported. The adiabatic approximation is introduced. Four important cases, resonance-resonance, resonance--off-resonance, off-resonance--resonance, and off-resonance--off-resonance transitions, have been considered. Finally, numerical calculations of rhodamine 6G are performed to demonstrate the applications of theoretical results.
Non-equilibrium Steady States in Kac's Model Coupled to a Thermostat
NASA Astrophysics Data System (ADS)
Evans, Josephine
2016-09-01
This paper studies the existence, uniqueness and convergence to non-equilibrium steady states in Kac's model with an external coupling. We work in both Fourier distances and Wasserstein distances. Our methods work in the case where the external coupling is not a Maxwellian equilibrium. This provides an example of a non-equilibrium steady state. We also study the behaviour as the number of particles goes to infinity and show quantitative estimates on the convergence rate of the first marginal.
Steady state effects in a two-pulse diffusion-weighted sequence
Zubkov, Mikhail; Stait-Gardner, Timothy; Price, William S.; Stilbs, Peter
2015-04-21
In conventional nuclear magnetic resonance (NMR) diffusion measurements a significant amount of experimental time is used up by magnetization recovery, serving to prevent the formation of the steady state, as in the latter case the manifestation of diffusion is modulated by multiple applications of the pulse sequence and conventional diffusion coefficient inference procedures are generally not applicable. Here, an analytical expression for diffusion-related effects in a two-pulse NMR experiment (e.g., pulsed-gradient spin echo) in the steady state mode (with repetition times less than the longitudinal relaxation time of the sample) is derived by employing a Fourier series expansion within the solution of the Bloch-Torrey equations. Considerations are given for the transition conditions between the full relaxation and the steady state experiment description. The diffusion coefficient of a polymer solution (polyethylene glycol) is measured by a two-pulse sequence in the full relaxation mode and for a range of repetition times, approaching the rapid steady state experiment. The precision of the fitting employing the presented steady state solution by far exceeds that of the conventional fitting. Additionally, numerical simulations are performed yielding results strongly supporting the proposed description of the NMR diffusion measurements in the steady state.
Farley, J R; Cryns, D F; Yang, Y H; Segel, I H
1976-07-25
The kinetic mechanism of ATP sulfurylase was established from initial velocity, product inhibition, and dead-end inhibition studies. In the forward direction, the reaction is steady state ordered, with MgATP=A, sulfate=B, MgPP1=P, and APS=Q.KmA=0.38 mM, Kia=0.71 mM, KmB=0.50 mM. Nitrate and chlorate are competive with sulfate and uncompetitive with MgATP. KiNO3-=0.25 mM; KiC1O3-= 0.15 mM. AMP and various MgATP analogs are competitive with MgATP and mixed-type inhibitors with respect to SO42-. The Ki for AMP is 0.55 mM. The reaction is rapid equilibrium ordered in the reverse direction with Kiq=0.3 to 1.0 muM and Kmp=0.65 muM. Adenosine 5'-phosphosulfate (APS) exhibits competitive substrate inhibition (KIQ=0.3 mM). The ratio Vmaxf/Vmaxr is 0.018. In the forward direction the ratio VmaxMoO42-/VmaxSO42- is 20. The Keq at pH 8.0 and 30 degrees calculated from the Haldane equation is 6 X 10(-9) to 3.3 X 10(-8) (depending on the Kiq value chosen). The experimental Keq is about 2.5 X 10(-9). The fact that Vmax/Vmaxr is about 1 million times greater than Keq is consistent with the assumed physiological role of the enzyme (APS synthesis). The mechanistic basis of the ordered binding sequence was probed by multiple inhibition analysis. Dead-end inhibitors competitive with MgATP (such as free ATP, Mg alpha,beta-methylene ATP, CrATP, and CaATP) do not induce substrate inhibition by sulfate or alter the inhibition patterns displayed by nitrate. This result suggests (but does not prove) that catalytic action on MgATP must precede the formation of the sulfate binding site. PMID:819440
2013-01-01
Background In a previous study (Vaghefi et al. 2012) we described a 3D computer model that used finite element modeling to capture the structure and function of the ocular lens. This model accurately predicted the steady state properties of the lens including the circulating ionic and fluid fluxes that are believed to underpin the lens internal microcirculation system. In the absence of a blood supply, this system brings nutrients to the core of the lens and removes waste products faster than would be achieved by passive diffusion alone. Here we test the predictive properties of our model by investigating whether it can accurately mimic the experimentally measured changes to lens steady-state properties induced by either depolarising the lens potential or reducing Na+ pump rate. Methods To mimic experimental manipulations reported in the literature, the boundary conditions of the model were progressively altered and the model resolved for each new set of conditions. Depolarisation of lens potential was implemented by increasing the extracellular [K+], while inhibition of the Na+ pump was stimulated by utilising the inherent temperature sensitivity of the pump and changing the temperature at which the model was solved. Results Our model correctly predicted that increasing extracellular [K+] depolarizes the lens potential, reducing and then reversing the magnitude of net current densities around the lens. While lowering the temperature reduced Na+ pump activity and caused a reduction in circulating current, it had a minimal effect on the lens potential, a result consistent with published experimental data. Conclusion We have shown that our model is capable of accurately simulating the effects of two known experimental manipulations on lens steady-state properties. Our results suggest that the model will be a valuable predictive tool to support ongoing studies of lens structure and function. PMID:23988187
Corr, David T; Herzog, Walter
2016-03-21
Force depression (FD), the reduction of isometric force following active shortening, is a phenomenon of skeletal muscle that has received significant attention in biomechanical and physiological literature, yet the mechanisms underlying FD remain unknown. Recent experiments identified a slower rate of force redevelopment with increasing amounts of steady-state FD, suggesting that FD may be caused, at least in part, by a decrease in cross-bridge binding rate (Corr and Herzog, 2005; Koppes et al., 2014). Herein, we develop a cross-bridge based model of FD in which the binding rate function, f, decreases with the mechanical work performed during shortening. This modification incorporates a direct relationship between steady-state FD and muscle mechanical work (Corr and Herzog, 2005; Herzog et al., 2000; Kosterina et al., 2008), and is consistent with a proposed mechanism attributing FD to stress-induced inhibition of cross-bridge attachments (Herzog, 1998; Maréchal and Plaghki, 1979). Thus, for an increase in mechanical work, the model should predict a slower force redevelopment (decreased attachment rate) to a more depressed steady-state force (fewer attached cross-bridges), and a reduction in contractile element stiffness (Ford et al., 1981). We hypothesized that since this modification affects the cross-bridge kinetics, a corresponding model would be able to account for both transient and steady-state FD behaviors. Comparisons to prior experiments (Corr and Herzog, 2005; Herzog et al., 2000; Kosterina et al., 2008) show that both steady-state and transient aspects of FD, as well as the relationship of FD with respect to speed and amplitude of shortening, are well captured by this model. Thus, this relatively simple cross-bridge based model of FD lends support to a mechanism involving the inhibition of cross-bridge binding, and indicates that cross-bridge kinetics may play a critical role in FD. PMID:26928777
ERIC Educational Resources Information Center
Kosman, Daniel J.
2009-01-01
The steady-state is a fundamental aspect of biochemical pathways in cells; indeed, the concept of steady-state is a definition of life itself. In a simple enzyme kinetic scheme, the steady-state condition is easy to define analytically but experimentally often difficult to capture because of its evanescent quality; the initial, constant velocity…
Steady-state transposon mutagenesis in inbred maize.
McCarty, Donald R; Settles, Andrew Mark; Suzuki, Masaharu; Tan, Bao Cai; Latshaw, Susan; Porch, Tim; Robin, Kevin; Baier, John; Avigne, Wayne; Lai, Jinsheng; Messing, Joachim; Koch, Karen E; Hannah, L Curtis
2005-10-01
We implement a novel strategy for harnessing the power of high-copy transposons for functional analysis of the maize genome, and report behavioral features of the Mutator system in a uniform inbred background. The unique UniformMu population and database facilitate high-throughput molecular analysis of Mu-tagged mutants and gene knockouts. Key features of the population include: (i) high mutation frequencies (7% independent seed mutations) and moderation of copy number (approximately 57 total Mu elements; 1-2 MuDR copies per plant) were maintained by continuous back-crossing into a phenotypically uniform inbred background; (ii) a bz1-mum9 marker enabled selection of stable lines (loss of MuDR), inhibiting further transpositions in lines selected for molecular analysis; (iii) build-up of mutation load was prevented by screening Mu-active parents to exclude plants carrying pre-existing seed mutations. To create a database of genomic sequences flanking Mu insertions, selected mutant lines were analyzed by sequencing of MuTAIL PCR clone libraries. These sequences were annotated and clustered to facilitate bioinformatic subtraction of ancestral elements and identification of insertions unique to mutant lines. New insertions targeted low-copy, gene-rich sequences, and in silico mapping revealed a random distribution of insertions over the genome. Our results indicate that Mu populations differ markedly in the occurrence of Mu insertion hotspots and the frequency of suppressible mutations. We suggest that controlled MuDR copy number in UniformMu lines is a key determinant of these differences. The public database (http://uniformmu.org; http://endosperm.info) includes pedigree and phenotypic data for over 2000 independent seed mutants selected from a population of 31 548 F2 lines and integrated with analyses of 34 255 MuTAIL sequences. PMID:16167895
Inhibition of translation by cytotrienin A—a member of the ansamycin family
Lindqvist, Lisa; Robert, Francis; Merrick, William; Kakeya, Hideaki; Fraser, Christopher; Osada, Hiroyuki; Pelletier, Jerry
2010-01-01
The ansamycins are a diverse and often physiologically active group of compounds that include geldanamycin and rifamycin, inhibitors of heat shock protein 90 and prokaryotic DNA-dependent RNA synthesis, respectively. Cytotrienin A is an ansamycin-type small molecule with potent antiproliferative and proapoptotic properties. Here, we report that this compound inhibits eukaryotic protein synthesis by targeting translation elongation and interfering with eukaryotic elongation factor 1A function. We also find that cytotrienin A prevents HUVEC tube formation and diminishes microvessel formation in the chorioallantoic membrane assay. These results provide a molecular understanding into cytotrienin A's previously reported properties as an anticancer apoptosis-inducing drug. PMID:20943818
Hong, Changki; Hwang, Jeewon; Cho, Kwang-Hyun; Shin, Insik
2015-01-01
Boolean networks have been widely used to model biological processes lacking detailed kinetic information. Despite their simplicity, Boolean network dynamics can still capture some important features of biological systems such as stable cell phenotypes represented by steady states. For small models, steady states can be determined through exhaustive enumeration of all state transitions. As the number of nodes increases, however, the state space grows exponentially thus making it difficult to find steady states. Over the last several decades, many studies have addressed how to handle such a state space explosion. Recently, increasing attention has been paid to a satisfiability solving algorithm due to its potential scalability to handle large networks. Meanwhile, there still lies a problem in the case of large models with high maximum node connectivity where the satisfiability solving algorithm is known to be computationally intractable. To address the problem, this paper presents a new partitioning-based method that breaks down a given network into smaller subnetworks. Steady states of each subnetworks are identified by independently applying the satisfiability solving algorithm. Then, they are combined to construct the steady states of the overall network. To efficiently apply the satisfiability solving algorithm to each subnetwork, it is crucial to find the best partition of the network. In this paper, we propose a method that divides each subnetwork to be smallest in size and lowest in maximum node connectivity. This minimizes the total cost of finding all steady states in entire subnetworks. The proposed algorithm is compared with others for steady states identification through a number of simulations on both published small models and randomly generated large models with differing maximum node connectivities. The simulation results show that our method can scale up to several hundreds of nodes even for Boolean networks with high maximum node connectivity. The
Apigenin Restricts FMDV Infection and Inhibits Viral IRES Driven Translational Activity
Qian, Suhong; Fan, Wenchun; Qian, Ping; Zhang, Dong; Wei, Yurong; Chen, Huanchun; Li, Xiangmin
2015-01-01
Foot-and-mouth disease (FMD) is a highly contagious disease of domestic and wild ruminants that is caused by FMD virus (FMDV). FMD outbreaks have occurred in livestock-containing regions worldwide. Apigenin, which is a flavonoid naturally existing in plant, possesses various pharmacological effects, including anti-inflammatory, anticancer, antioxidant and antiviral activities. Results show that apigenin can inhibit FMDV-mediated cytopathogenic effect and FMDV replication in vitro. Further studies demonstrate the following: (i) apigenin inhibits FMDV infection at the viral post-entry stage; (ii) apigenin does not exhibit direct extracellular virucidal activity; and (iii) apigenin interferes with the translational activity of FMDV driven by internal ribosome entry site. Studies on applying apigein in vivo are required for drug development and further identification of potential drug targets against FDMV infection. PMID:25835532
Baranwal, V K; Tumer, Nilgun E; Kapoor, H C
2002-10-01
An antiviral protein (25 kD) isolated from leaves of Celosia cristata (CCP 25) was tested for depurination study on ribosomal RNA from yeast. Ribosomal RNA yielded 360 nucleotide base fragment after treatment with CCP 25 indicating that CCP 25 was a ribosome inactivating protein. CCP 25 also inhibited translation of brome mosaic virus (BMV) and pokeweed mosaic virus (PMV) RNAs in rabbit reticulocyte translation system. The radioactive assay showed that incorporation of [35S]-methionine was less in translation proteins of BMV nucleic acid when CCP 25 was added to translation system. This indicated that antiviral protein from Celosia cristata not only depurinated ribosomal RNA but also inhibited translation of viral RNA in vitro. PMID:12693705
McLaren, David G; Previs, Stephen F; Phair, Robert D; Stout, Steven J; Xie, Dan; Chen, Ying; Salituro, Gino M; Xu, Suoyu S; Castro-Perez, Jose M; Opiteck, Gregory J; Akinsanya, Karen O; Cleary, Michele A; Dansky, Hayes M; Johns, Douglas G; Roddy, Thomas P
2016-03-01
Studies in lipoprotein kinetics almost exclusively rely on steady-state approaches to modeling. Herein, we have used a non-steady-state experimental design to examine the role of cholesteryl ester transfer protein (CETP) in mediating HDL-TG flux in vivo in rhesus macaques, and therefore, we developed an alternative strategy to model the data. Two isotopomers ([(2)H11] and [(13)C18]) of oleic acid were administered (orally and intravenously, respectively) to serve as precursors for labeling TGs in apoB-containing lipoproteins. The flux of a specific TG (52:2) from these donor lipoproteins to HDL was used as the measure of CETP activity; calculations are also presented to estimate total HDL-TG flux. Based on our data, we estimate that the peak total postprandial TG flux to HDL via CETP is ∼ 13 mg · h(-1) · kg(-1) and show that this transfer was inhibited by 97% following anacetrapib treatment. Collectively, these data demonstrate that HDL TG flux can be used as a measure of CETP activity in vivo. The fact that the donor lipoproteins can be labeled in situ using well-established stable isotope tracer techniques suggests ways to measure this activity for native lipoproteins in free-living subjects under any physiological conditions. PMID:26658238
Yates, J L; Arfsten, A E; Nomura, M
1980-01-01
Escherichia coli ribosomal protein L1 (0.5 micro M) was found to inhibit the synthesis of both proteins of the L11 operon, L11 and L1, but not the synthesis of other proteins directed by lambda rifd 18 DNA. Similarly, S4 (1 micro M) selectively inhibited the synthesis of three proteins of the alpha operon, S13, S11, and S4, directed by lambda spcI DNA or a restriction enzyme fragment obtained from this DNA. S8 (3.6 micro M) also showed preferential inhibitory effects on the synthesis of some proteins encoded in the spc operon, L24 and L5 (and probably S14 and S8), directed by lambda spcl DNA or a restriction enzyme fragment carrying the genes for these proteins. The inhibitory effect of L1 was observed only with L1 and not with other proteins examined, including S4 and S8. Similarly, the effect of S4 was not observed with L1 or S8, and that of S8 was not seen with L1 or S4. Inhibition was shown to take place at the level of translation rather than transcription. Thus, at least some ribosomal proteins (L1 S4, and S8) have the ability to cause selective translational inhibition of the synthesis of certain ribosomal proteins whose genes are in the same operon as their own. These results support the hypothesis that certain free ribosomal proteins not assembled into ribosomes act as "autogenous" feedback inhibitors to regulate the synthesis of ribosomal proteins. Images PMID:6445562
Inhibition of translation in living eukaryotic cells by an RNA G-quadruplex motif
Arora, Amit; Dutkiewicz, Mariola; Scaria, Vinod; Hariharan, Manoj; Maiti, Souvik; Kurreck, Jens
2008-01-01
Guanine-rich sequences can adopt intramolecular four-stranded structures, called G-quadruplexes. These motifs have been intensively investigated on the DNA level, but their overall biological relevance remains elusive. Only recently has research concerning the function of G-quadruplexes in RNAs commenced. Here, we demonstrate for the first time, that an RNA G-quadruplex structure inhibits translation in vivo in eukaryotic cells. We investigated the function of a highly conserved, thermodynamically stable RNA G-quadruplex in the 5′-UTR of the mRNA of the human Zic-1 zinc-finger protein. Using dual luciferase reporter assay, we demonstrate that the Zic-1 RNA G-quadruplex represses protein synthesis inside eukaryotic cells. Quantitative RT-PCR assays confirmed that the reduction of protein synthesis is due to regulation of the translation process and not a consequence of reduced transcription. Western blot analysis revealed that expression of Zic-1 is strongly reduced by a 73 nucleotides-long fragment of the UTR containing the G-quadruplex motif. These structures might add to the more recently discovered elements in untranslated regions of mRNAs that regulate their translation. PMID:18515550
Rodriguez, Paloma; Pérez-Morgado, M Isabel; Gonzalez, Víctor M; Martín, M Elena; Nieto, Amelia
2016-01-01
The genetic diversity of the influenza virus hinders the use of broad spectrum antiviral drugs and favors the appearance of resistant strains. Single-stranded DNA aptamers represent an innovative approach with potential application as antiviral compounds. The mRNAs of influenza virus possess a 5'cap structure and a 3'poly(A) tail that makes them structurally indistinguishable from cellular mRNAs. However, selective translation of viral mRNAs occurs in infected cells through a discriminatory mechanism, whereby viral polymerase and NS1 interact with components of the translation initiation complex, such as the eIF4GI and PABP1 proteins. We have studied the potential of two specific aptamers that recognize PABP1 (ApPABP7 and ApPABP11) to act as anti-influenza drugs. Both aptamers reduce viral genome expression and the production of infective influenza virus particles. The interaction of viral polymerase with the eIF4GI translation initiation factor is hindered by transfection of infected cells with both PABP1 aptamers, and ApPABP11 also inhibits the association of NS1 with PABP1 and eIF4GI. These results indicate that aptamers targeting the host factors that interact with viral proteins may potentially have a broad therapeutic spectrum, reducing the appearance of escape mutants and resistant subtypes. PMID:27070300
Lactate and Acrylate Metabolism by Megasphaera elsdenii under Batch and Steady-State Conditions
Prabhu, Rupal; Altman, Elliot
2012-01-01
The growth of Megasphaera elsdenii on lactate with acrylate and acrylate analogues was studied under batch and steady-state conditions. Under batch conditions, lactate was converted to acetate and propionate, and acrylate was converted into propionate. Acrylate analogues 2-methyl propenoate and 3-butenoate containing a terminal double bond were similarly converted into their respective saturated acids (isobutyrate and butyrate), while crotonate and lactate analogues 3-hydroxybutyrate and (R)-2-hydroxybutyrate were not metabolized. Under carbon-limited steady-state conditions, lactate was converted to acetate and butyrate with no propionate formed. As the acrylate concentration in the feed was increased, butyrate and hydrogen formation decreased and propionate was increasingly generated, while the calculated ATP yield was unchanged. M. elsdenii metabolism differs substantially under batch and steady-state conditions. The results support the conclusion that propionate is not formed during lactate-limited steady-state growth because of the absence of this substrate to drive the formation of lactyl coenzyme A (CoA) via propionyl-CoA transferase. Acrylate and acrylate analogues are reduced under both batch and steady-state growth conditions after first being converted to thioesters via propionyl-CoA transferase. Our findings demonstrate the central role that CoA transferase activity plays in the utilization of acids by M. elsdenii and allows us to propose a modified acrylate pathway for M. elsdenii. PMID:23023753
Perception of steady-state vowels and vowelless syllables by adults and children
NASA Astrophysics Data System (ADS)
Nittrouer, Susan
2005-04-01
Vowels can be produced as long, isolated, and steady-state, but that is not how they are found in natural speech. Instead natural speech consists of almost continuously changing (i.e., dynamic) acoustic forms from which mature listeners recover underlying phonetic form. Some theories suggest that children need steady-state information to recognize vowels (and so learn vowel systems), even though that information is sparse in natural speech. The current study examined whether young children can recover vowel targets from dynamic forms, or whether they need steady-state information. Vowel recognition was measured for adults and children (3, 5, and 7 years) for natural productions of /dæd/, /dUd/ /æ/, /U/ edited to make six stimulus sets: three dynamic (whole syllables; syllables with middle 50-percent replaced by cough; syllables with all but the first and last three pitch periods replaced by cough), and three steady-state (natural, isolated vowels; reiterated pitch periods from those vowels; reiterated pitch periods from the syllables). Adults scored nearly perfectly on all but first/last three pitch period stimuli. Children performed nearly perfectly only when the entire syllable was heard, and performed similarly (near 80%) for all other stimuli. Consequently, children need dynamic forms to perceive vowels; steady-state forms are not preferred.
Synchronous machine steady-state stability analysis using an artificial neural network
Chen, C.R.; Hsu, Y.Y. . Dept. of Electrical Engineering)
1991-03-01
A new type of artificial neural network is proposed for the steady-state stability analysis of a synchronous generator. In the developed artificial neutral network, those system variables which play an important role in steady-state stability such as generator outputs and power system stabilizer parameters are employed as the inputs. The output of the neural net provides the information on steady-state stability. Once the connection weights of the neural network have been learned using a set of training data derived off-line, the neural net can be applied to analyze the steady-state stability of the system time. To demonstrate the effectiveness of the proposed neural net, steady-state stability analysis is performed on a synchronous generator connected to a large power system. It is found that the proposed neural net requires much less training time than the multilayer feedforward network with backpropagation-momentum learning algorithm. It is also concluded from the test results that correct stability assessment can be achieved by the neural network.
Analytical Solution of Steady State Equations for Chemical Reaction Networks with Bilinear Rate Laws
Halász, Ádám M.; Lai, Hong-Jian; McCabe, Meghan M.; Radhakrishnan, Krishnan; Edwards, Jeremy S.
2014-01-01
True steady states are a rare occurrence in living organisms, yet their knowledge is essential for quasi-steady state approximations, multistability analysis, and other important tools in the investigation of chemical reaction networks (CRN) used to describe molecular processes on the cellular level. Here we present an approach that can provide closed form steady-state solutions to complex systems, resulting from CRN with binary reactions and mass-action rate laws. We map the nonlinear algebraic problem of finding steady states onto a linear problem in a higher dimensional space. We show that the linearized version of the steady state equations obeys the linear conservation laws of the original CRN. We identify two classes of problems for which complete, minimally parameterized solutions may be obtained using only the machinery of linear systems and a judicious choice of the variables used as free parameters. We exemplify our method, providing explicit formulae, on CRN describing signal initiation of two important types of RTK receptor-ligand systems, VEGF and EGF-ErbB1. PMID:24334389
Dynamic evolution of initial instability during non-steady-state growth.
Dong, Zhibo; Zheng, Wenjian; Wei, Yanhong; Song, Kuijing
2014-06-01
Dynamic evolution of initial instability is investigated by an analytic model obtained by modifying the theory of Warren and Langer [Phys. Rev. E 47, 2702 (1993)] and the quantitative phase-field model in directional solidification under transient conditions for realistic parameters of a dilute alloy. The evolutions of tip velocity and concentration in the liquid side of the interface predicted by the analytic model agree very well with that from the phase-field simulation in the linear growth stage of the non-steady-state growth, indicating that the model could be used as a convenient method to study the initial instability during non-steady-state growth. The influences of non-steady-state conditions which include the increasing rate of pulling speed and temperature gradient at the onset of initial instability are investigated, and we find that, the initial instability seems to depend strongly on the non-steady-state conditions and the non-steady-state history, and thus, it should be primarily considered in the study of the transient growth. PMID:25019790
Dynamic evolution of initial instability during non-steady-state growth
NASA Astrophysics Data System (ADS)
Dong, Zhibo; Zheng, Wenjian; Wei, Yanhong; Song, Kuijing
2014-06-01
Dynamic evolution of initial instability is investigated by an analytic model obtained by modifying the theory of Warren and Langer [Phys. Rev. E 47, 2702 (1993), 10.1103/PhysRevE.47.2702] and the quantitative phase-field model in directional solidification under transient conditions for realistic parameters of a dilute alloy. The evolutions of tip velocity and concentration in the liquid side of the interface predicted by the analytic model agree very well with that from the phase-field simulation in the linear growth stage of the non-steady-state growth, indicating that the model could be used as a convenient method to study the initial instability during non-steady-state growth. The influences of non-steady-state conditions which include the increasing rate of pulling speed and temperature gradient at the onset of initial instability are investigated, and we find that, the initial instability seems to depend strongly on the non-steady-state conditions and the non-steady-state history, and thus, it should be primarily considered in the study of the transient growth.
Steady-State Operation Scenario and the First Experimental Result on QUEST
Hanada, K; Peng, Yueng Kay Martin
2010-01-01
QUEST focuses on the steady state operation of the spherical tokamak by controlled PWI and electron Bernstein wave current drive. One of the main purposes of QUEST is an achievement of long duration discharge with MW-class injected power. As the result, QUEST should be operated in the challenging region on heat and particle handling. To do the particle handling, high temperature all metal wall up to 623 K and closed divertors are planned, which is to realize the steady-state operation under recycling ratio, R = 1. This is a dispensable check to DEMO, because wall pumping should be avoided as possible in the view of tritium retention. The QUEST project will be developed in increment step such as, I. low steady state operation in limiter configuration, II. low steady state operation in divertor configuration, III. relatively high steady state operation in closed divertor configuration. Phase I in the project corresponds to these two years, and final goal of phase I is to make full current drive plasma up to 20 kA. Closed divertor will be designed and tested in the Phase II. QUEST is running from Oct., 2008 and the first results are introduced.
Ota, Yu; Chinen, Takumi; Yoshida, Keisuke; Kudo, Shun; Nagumo, Yoko; Shiwa, Yuh; Yamada, Ryosuke; Umihara, Hirotatsu; Iwasaki, Kotaro; Masumoto, Hiroshi; Yokoshima, Satoshi; Yoshikawa, Hirofumi; Fukuyama, Tohru; Kobayashi, Junichi; Usui, Takeo
2016-09-01
Eudistomin C (EudiC), a natural product, shows potent antitumor and antiviral activities, but the target molecule and the mechanism of action remain to be revealed. Here, we show that the 40S ribosome is the target in EudiC cytotoxicity. We isolated EudiC-resistant mutants from a multidrug-sensitive yeast strain, and a genetic analysis classified these YER (yeast EudiC resistance) mutants into three complementation groups. A genome-wide study revealed that the YER1-6 mutation is in the uS11 gene (RPS14A). Biotinylated EudiC pulled down Rps14p-containing complexes from 40S and 80S ribosomes, but not from the 60S ribosome. EudiC strongly inhibited translation of the wild-type strain but not of YER1-6 in cells and in vitro. These results indicate that EudiC is a protein synthesis inhibitor targeting the uS11-containing ribosomal subunit, and shows cytotoxicity by inhibiting protein translation. PMID:27304596
Realistic expectations of prepulse inhibition in translational models for schizophrenia research
Swerdlow, Neal R.; Weber, Martin; Qu, Ying; Light, Gregory A.; Braff, David L.
2009-01-01
Introduction Under specific conditions, a weak lead stimulus, or “prepulse”, can inhibit the startling effects of a subsequent intense abrupt stimulus. This startle-inhibiting effect of the prepulse, termed “prepulse inhibition” (PPI), is widely used in translational models to understand the biology of brain based inhibitory mechanisms and their deficiency in neuropsychiatric disorders. In 1981, four published reports with “prepulse inhibition” as an index term were listed on Medline; over the past 5 years, new published Medline reports with “prepulse inhibition” as an index term have appeared at a rate exceeding once every 2.7 days (n = 678). Most of these reports focus on the use of PPI in translational models of impaired sensorimotor gating in schizophrenia. This rapid expansion and broad application of PPI as a tool for understanding schizophrenia has, at times, outpaced critical thinking and falsifiable hypotheses about the relative strengths vs. limitations of this measure. Objectives This review enumerates the realistic expectations for PPI in translational models for schizophrenia research, and provides cautionary notes for the future applications of this important research tool. Conclusion In humans, PPI is not “diagnostic”; levels of PPI do not predict clinical course, specific symptoms, or individual medication responses. In preclinical studies, PPI is valuable for evaluating models or model organisms relevant to schizophrenia, “mapping” neural substrates of deficient PPI in schizophrenia, and advancing the discovery and development of novel therapeutics. Across species, PPI is a reliable, robust quantitative phenotype that is useful for probing the neurobiology and genetics of gating deficits in schizophrenia. PMID:18568339
Joseph, David; Schobelock, Michael J; Riesenberg, Robert R; Vince, Bradley D; Webster, Lynn R; Adeniji, Abidemi; Elgadi, Mabrouk; Huang, Fenglei
2015-01-01
The effects of steady-state faldaprevir on the safety, pharmacokinetics, and pharmacodynamics of steady-state methadone and buprenorphine-naloxone were assessed in 34 healthy male and female subjects receiving stable addiction management therapy. Subjects continued receiving a stable oral dose of either methadone (up to a maximum dose of 180 mg per day) or buprenorphine-naloxone (up to a maximum dose of 24 mg-6 mg per day) and also received oral faldaprevir (240 mg) once daily (QD) for 8 days following a 480-mg loading dose. Serial blood samples were taken for pharmacokinetic analysis. The pharmacodynamics of the opioid maintenance regimens were evaluated by the objective and subjective opioid withdrawal scales. Coadministration of faldaprevir with methadone or buprenorphine-naloxone resulted in geometric mean ratios for the steady-state area under the concentration-time curve from 0 to 24 h (AUC(0-24,ss)), the steady-state maximum concentration of the drug in plasma (C(max,ss)), and the steady-state concentration of the drug in plasma at 24 h (C(24,ss)) of 0.92 to 1.18 for (R)-methadone, (S)-methadone, buprenorphine, norbuprenorphine, and naloxone, with 90% confidence intervals including, or very close to including, 1.00 (no effect), suggesting a limited overall effect of faldaprevir. Although individual data showed moderate variability in the exposures between subjects and treatments, there was no evidence of symptoms of opiate overdose or withdrawal either during the coadministration of faldaprevir with methadone or buprenorphine-naloxone or after faldaprevir dosing was stopped. Similar faldaprevir exposures were observed in the methadone- and buprenorphine-naloxone-treated subjects. In conclusion, faldaprevir at 240 mg QD can be coadministered with methadone or buprenorphine-naloxone without dose adjustment, although given the relatively narrow therapeutic windows of these agents, monitoring for opiate overdose and withdrawal may still be appropriate. (This
Joseph, David; Schobelock, Michael J.; Riesenberg, Robert R.; Vince, Bradley D.; Webster, Lynn R.; Adeniji, Abidemi; Elgadi, Mabrouk
2014-01-01
The effects of steady-state faldaprevir on the safety, pharmacokinetics, and pharmacodynamics of steady-state methadone and buprenorphine-naloxone were assessed in 34 healthy male and female subjects receiving stable addiction management therapy. Subjects continued receiving a stable oral dose of either methadone (up to a maximum dose of 180 mg per day) or buprenorphine-naloxone (up to a maximum dose of 24 mg-6 mg per day) and also received oral faldaprevir (240 mg) once daily (QD) for 8 days following a 480-mg loading dose. Serial blood samples were taken for pharmacokinetic analysis. The pharmacodynamics of the opioid maintenance regimens were evaluated by the objective and subjective opioid withdrawal scales. Coadministration of faldaprevir with methadone or buprenorphine-naloxone resulted in geometric mean ratios for the steady-state area under the concentration-time curve from 0 to 24 h (AUC0–24,ss), the steady-state maximum concentration of the drug in plasma (Cmax,ss), and the steady-state concentration of the drug in plasma at 24 h (C24,ss) of 0.92 to 1.18 for (R)-methadone, (S)-methadone, buprenorphine, norbuprenorphine, and naloxone, with 90% confidence intervals including, or very close to including, 1.00 (no effect), suggesting a limited overall effect of faldaprevir. Although individual data showed moderate variability in the exposures between subjects and treatments, there was no evidence of symptoms of opiate overdose or withdrawal either during the coadministration of faldaprevir with methadone or buprenorphine-naloxone or after faldaprevir dosing was stopped. Similar faldaprevir exposures were observed in the methadone- and buprenorphine-naloxone-treated subjects. In conclusion, faldaprevir at 240 mg QD can be coadministered with methadone or buprenorphine-naloxone without dose adjustment, although given the relatively narrow therapeutic windows of these agents, monitoring for opiate overdose and withdrawal may still be appropriate. (This study
Equilibrium and Steady State of Dense Z-Pinches Superposing a Small Amount of Axial Flux
NASA Astrophysics Data System (ADS)
Hashimoto, Mitsuhiro; Miyamoto, Tetsu
2016-07-01
The pressure equilibrium and steady state of z-pinches trapping a small amount of axial magnetic flux are studied. The Bennett relation and the Pease-Braginskii-current are modified, taking into account the superposed axial field. The line energy density decreases in the modified Bennett relation, but the decrease is only of the order ɛ2, where ɛ = (the axial field strength at the axis)/(the azimuthal field strength at the plasma periphery) ≪ 1. On the other hand, the current in the steady state can increase without being limited by the Pease-Braginskii-current. Hence, the radiation collapse is prevented. The decrease of line energy density in the modified Bennett relation is almost canceled in the steady state.
Obtaining pure steady states in nonequilibrium quantum systems with strong dissipative couplings
NASA Astrophysics Data System (ADS)
Popkov, Vladislav; Presilla, Carlo
2016-02-01
Dissipative preparation of a pure steady state usually involves a commutative action of a coherent and a dissipative dynamics on the target state. Namely, the target pure state is an eigenstate of both the coherent and dissipative parts of the dynamics. We show that working in the Zeno regime, i.e., for infinitely large dissipative coupling, one can generate a pure state by a noncommutative action, in the above sense, of the coherent and dissipative dynamics. A corresponding Zeno regime pureness criterion is derived. We illustrate the approach, looking at both its theoretical and applicative aspects, in the example case of an open X X Z spin-1 /2 chain, driven out of equilibrium by boundary reservoirs targeting different spin orientations. Using our criterion, we find two families of pure nonequilibrium steady states, in the Zeno regime, and calculate the dissipative strengths effectively needed to generate steady states which are almost indistinguishable from the target pure states.
NASA Astrophysics Data System (ADS)
Zhang, C.; Tang, Y.; Liang, S.; Ren, L.; Wang, Z.; Xu, Y.
This paper presents the electromagnetic analysis of a high voltage saturated-core superconducting fault current limiter (SCSFCL). The numerical analyses of a three-dimensional (3D) model is shown, and the specific parameters are given. The model focus on the steady-state impedance of the limiter when connected to the power grid. It analyzed the dependence of steady-state impedance on the AC coil current, and the relationship between oil gap and coil inductance. The results suggest that, adding oil gap between slice of silicon steel can reduce the core cross-section, restrain the ultraharmonic and decrease the steady-state impedance. As the core cross-section of AC limb decreased from 4344 cm2 to 3983 cm2, the total harmonic distortion for voltage decreased from 2.4% to 1.8%, and the impedance decreased from 1.082 Ω to 1.069 Ω(Idc=400A,Iac=1296A).
Mechanism of Non-Steady State Dissolution of Goethite in the Presence of Siderophores
NASA Astrophysics Data System (ADS)
Reichard, P. U.; Kretzschmar, R.; Kraemer, S. M.
2003-12-01
Iron is an essential micronutrient for almost all known organisms. Bacteria, fungi, and graminaceous plants are capable of exuding siderophores as part of an iron acquisition strategy. The production of these strong iron chelating ligands is induced by iron limited conditions. Grasses under iron stress, for example, exude phytosiderophores into the rhizosphere in a special diurnal rhythm (Roemheld and Marschner 1986). A few hours after sunrise the exudation starts, culminates around noon and is shut down again until about 4 hours after noon. The phytosiderophores diffuse into the rhizosphere (Marschner et al. 1986) and are passively back transported to the plants by advective flow induced by high transpiration around noon. Despite a fairly short residence time of the phytosiderophores in the rhizosphere, it is a very effective strategy for iron acquisition. To investigate the effect of such pulse inputs of siderophores on iron acquisition, we studied the dissolution mechanism of goethite (alpha-FeOOH), a mineral phase common in soils, under non-steady state conditions. In consideration of the chemical complexity of the rhizosphere, we also investigated the effect of other organic ligands commonly found in the rhizosphere (e. g. oxalate) on the dissolution kinetics. The dissolution experiments were conducted in batch reactors with a constant goethite solids concentration of 2.5 g/l, an ionic strength of 0.01 M, a pH of 6 and 100 microM oxalate. To induce non-steady state conditions, 3 mM phytosiderophores were added to a batch after the goethite-oxalate suspension reacted for a certain time period. Before the siderophore was added to the goethite-oxalate suspension, no dissolution of iron was observed. But, with the addition of the siderophore, a high rate was observed for the iron mobilization under these non-steady state conditions that subsequently was followed by a slow steady state dissolution rate. The results of these non-steady state experiments are very
NASA Astrophysics Data System (ADS)
Or, D.; Aminzadeh, M.; Roderick, M. L.
2015-12-01
The definition of potential evaporation remains widely debated despite its centrality for hydrologic and climatic models. We employed an analytical pore-scale representation of evaporation from porous surfaces to define potential evaporation using a hypothetical steady-state reference temperature for air and evaporating surface. The feedback between drying land surfaces and overlaying air properties is implicitly incorporated in the hypothetical steady-state where the sensible heat flux vanishes and available energy is consumed by evaporation. Potential evaporation based on steady-state surface temperature was in surprisingly good agreement with class A pan evaporation measurements suggesting that pan evaporation occurs with negligible sensible heat flux. The model facilitates a new analytical generalization of the asymmetric complementary relationship across a wide range of meteorological conditions with good agreement between measured and predicted actual evaporation.
Current Control in ITER Steady State Plasmas With Neutral Beam Steering
R.V. Budny
2009-09-10
Predictions of quasi steady state DT plasmas in ITER are generated using the PTRANSP code. The plasma temperatures, densities, boundary shape, and total current (9 - 10 MA) anticipated for ITER steady state plasmas are specified. Current drive by negative ion neutral beam injection, lower-hybrid, and electron cyclotron resonance are calculated. Four modes of operation with different combinations of current drive are studied. For each mode, scans with the NNBI aimed at differing heights in the plasma are performed to study effects of current control on the q profile. The timeevolution of the currents and q are calculated to evaluate long duration transients. Quasi steady state, strongly reversed q profiles are predicted for some beam injection angles if the current drive and bootstrap currents are sufficiently large.
NASA Astrophysics Data System (ADS)
Mu, Baojie; Li, Yaoyu; Seem, John E.
2016-08-01
A major class of extremum seeking control (ESC) is based on the use of periodic dither perturbation of plant input for extracting the gradient information. Presence of the dither input into the steady state operation is undesirable in practice due to the possible excessive wear of actuators. It is thus beneficial to stop the dithering action after the ESC reaches its steady state. In this paper, we propose a method for automatically discriminating between the steady state and the transient state modes of extremum seeking control process using the sinusoidal detection techniques. Some design guidelines are proposed for the parameter selection of the relevant sinusoidal detection scheme. The proposed scheme is validated with simulation study on dynamic virtual plant of two building HVAC systems.
Steady-state solutions of a diffusive energy-balance climate model and their stability
NASA Technical Reports Server (NTRS)
Ghil, M.
1975-01-01
A diffusive energy-balance climate model, governed by a nonlinear parabolic partial differential equation, was studied. Three positive steady-state solutions of this equation are found; they correspond to three possible climates of our planet: an interglacial (nearly identical to the present climate), a glacial, and a completely ice-covered earth. Models similar to the main one are considered, and the number of their steady states was determined. All the models have albedo continuously varying with latitude and temperature, and entirely diffusive horizontal heat transfer. The stability under small perturbations of the main model's climates was investigated. A stability criterion is derived, and its application shows that the present climate and the deep freeze are stable, whereas the model's glacial is unstable. The dependence was examined of the number of steady states and of their stability on the average solar radiation.
Wang, Qian; Li, Bincheng
2015-09-28
Spatially resolved steady-state photocarrier radiometric (PCR) imaging technique is developed to characterize the electronic transport properties of silicon wafers. Based on a nonlinear PCR theory, simulations are performed to investigate the effects of electronic transport parameters (the carrier lifetime, the carrier diffusion coefficient, and the front surface recombination velocity) on the steady-state PCR intensity profiles. The electronic transport parameters of an n-type silicon wafer are simultaneously determined by fitting the measured steady-state PCR intensity profiles to the three-dimensional nonlinear PCR model. The determined transport parameters are in good agreement with the results obtained by the conventional modulated PCR technique with multiple pump beam radii.
The steady-state visual evoked potential in vision research: A review
Norcia, Anthony M.; Appelbaum, L. Gregory; Ales, Justin M.; Cottereau, Benoit R.; Rossion, Bruno
2015-01-01
Periodic visual stimulation and analysis of the resulting steady-state visual evoked potentials were first introduced over 80 years ago as a means to study visual sensation and perception. From the first single-channel recording of responses to modulated light to the present use of sophisticated digital displays composed of complex visual stimuli and high-density recording arrays, steady-state methods have been applied in a broad range of scientific and applied settings.The purpose of this article is to describe the fundamental stimulation paradigms for steady-state visual evoked potentials and to illustrate these principles through research findings across a range of applications in vision science. PMID:26024451
Pre-Steady-State Kinetic Analysis of Single-Nucleotide Incorporation by DNA Polymerases.
Su, Yan; Peter Guengerich, F
2016-01-01
Pre-steady-state kinetic analysis is a powerful and widely used method to obtain multiple kinetic parameters. This protocol provides a step-by-step procedure for pre-steady-state kinetic analysis of single-nucleotide incorporation by a DNA polymerase. It describes the experimental details of DNA substrate annealing, reaction mixture preparation, handling of the RQF-3 rapid quench-flow instrument, denaturing polyacrylamide DNA gel preparation, electrophoresis, quantitation, and data analysis. The core and unique part of this protocol is the rationale for preparation of the reaction mixture (the ratio of the polymerase to the DNA substrate) and methods for conducting pre-steady-state assays on an RQF-3 rapid quench-flow instrument, as well as data interpretation after analysis. In addition, the methods for the DNA substrate annealing and DNA polyacrylamide gel preparation, electrophoresis, quantitation and analysis are suitable for use in other studies. © 2016 by John Wiley & Sons, Inc. PMID:27248785
Mass transport in salt repositories: Steady-state transport through interbeds
Hwang, Y.; Lee, W.W.-L.; Chambre, P.L.; Pigford, T.H. . Dept. of Nuclear Engineering)
1989-03-01
Salt has long been a candidate for geologic disposal of nuclear waste. Because salt is extremely soluble in water, the existence of rock salt in the ground atest to the long-term stability of the salt. Both bedded salt and salt domes have been considered for nuclear waste disposal in the United States and Europe. While the salt is known to be quite pure in salt domes, bedded salt is interlaced with beds of sediments. Traditionally rock salt has not been considered water-conducting, but sediments layers would be classical porous media, capable of conducting water. Therefore there is interest in determining whether interbeds in bedded salt constitute pathway for radionuclide migration. In this report we consider steady-state migration of radionuclides from a single waste cylinder into a single interbed. Two approaches are used. In 1982 Neretnieks proposed an approach for calculating the steady-state transport of oxidants to a copper container. We have adapted that approach for calculating steady-state radionuclide migration away from the waste package, as a first approximation. We have also analyzed the problem of time-dependent radionuclide diffusion from a container through a backfill layer into a fracture, and we used the steady-state solution from that problem for comparison. Section 2 gives a brief summary of the geology of interbeds in bedded salt. Section 3 presents the mass transfer resistances approach of Neretnieks, summarizing the formulation and giving numerical illustrations of the steady-state two-dimensional diffusion analysis. Section 4 gives a brief statement of the steady-state result from a related analysis. Conclusions are stated in Section 5. 13 refs., 5 figs., 2 tabs.
Foster, Carl; Farland, Courtney V.; Guidotti, Flavia; Harbin, Michelle; Roberts, Brianna; Schuette, Jeff; Tuuri, Andrew; Doberstein, Scott T.; Porcari, John P.
2015-01-01
High intensity interval training (HIIT) has become an increasingly popular form of exercise due to its potentially large effects on exercise capacity and small time requirement. This study compared the effects of two HIIT protocols vs steady-state training on aerobic and anaerobic capacity following 8-weeks of training. Fifty-five untrained college-aged subjects were randomly assigned to three training groups (3x weekly). Steady-state (n = 19) exercised (cycle ergometer) 20 minutes at 90% of ventilatory threshold (VT). Tabata (n = 21) completed eight intervals of 20s at 170% VO2max/10s rest. Meyer (n = 15) completed 13 sets of 30s (20 min) @ 100% PVO2 max/ 60s recovery, average PO = 90% VT. Each subject did 24 training sessions during 8 weeks. Results: There were significant (p < 0.05) increases in VO2max (+19, +18 and +18%) and PPO (+17, +24 and +14%) for each training group, as well as significant increases in peak (+8, + 9 and +5%) & mean (+4, +7 and +6%) power during Wingate testing, but no significant differences between groups. Measures of the enjoyment of the training program indicated that the Tabata protocol was significantly less enjoyable (p < 0.05) than the steady state and Meyer protocols, and that the enjoyment of all protocols declined (p < 0.05) across the duration of the study. The results suggest that although HIIT protocols are time efficient, they are not superior to conventional exercise training in sedentary young adults. Key points Steady state training equivalent to HIIT in untrained students Mild interval training presents very similar physiologic challenge compared to steady state training HIIT (particularly very high intensity variants were less enjoyable than steady state or mild interval training Enjoyment of training decreases across the course of an 8 week experimental training program PMID:26664271
Dynamic modeling and sensitivity analysis of dAFM in the transient and steady state motions.
Payam, Amir Farokh
2016-10-01
In this paper, based on the slow time varying function theory, dynamical equations for the amplitude and phase of the dynamic atomic force microscope are derived. Then, the sensitivity of the amplitude and phase to the dissipative and conservative parts of interaction force is investigated. The most advantage of this dynamical model is the ability to simulate and analysis the dynamics behavior of amplitude and phase of the AFM tip motion not only in the steady state but also in the transient regime. Using numerical analysis the transient and steady state behavior of amplitude and phase is studied and the sensitivity of amplitude and phase to the interaction force is analyzed. PMID:27448201
Arbitrary Steady-State Solutions with the K-epsilon Model
NASA Technical Reports Server (NTRS)
Rumsey, Christopher L.; Pettersson Reif, B. A.; Gatski, Thomas B.
2006-01-01
Widely-used forms of the K-epsilon turbulence model are shown to yield arbitrary steady-state converged solutions that are highly dependent on numerical considerations such as initial conditions and solution procedure. These solutions contain pseudo-laminar regions of varying size. By applying a nullcline analysis to the equation set, it is possible to clearly demonstrate the reasons for the anomalous behavior. In summary, the degenerate solution acts as a stable fixed point under certain conditions, causing the numerical method to converge there. The analysis also suggests a methodology for preventing the anomalous behavior in steady-state computations.
A quaternionic map for the steady states of the Heisenberg spin-chain
NASA Astrophysics Data System (ADS)
Mehta, Mitaxi P.; Dutta, Souvik; Tiwari, Shubhanshu
2014-01-01
We show that the steady states of the classical Heisenberg XXX spin-chain in an external magnetic field can be found by iterations of a quaternionic map. A restricted model, e.g., the xy spin-chain is known to have spatially chaotic steady states and the phase space occupied by these chaotic states is known to go through discrete changes as the field strength is varied. The same phenomenon is studied for the xxx spin-chain. It is seen that in this model the phase space volume varies smoothly with the external field.
The Transient to Steady-State Transition during the Spray-Rolling Process
Yaojun Lin; Kevin M. McHugh; Yizhang Zhou; Enrique J. Lavernia
2004-11-01
From the geometrical standpoint, this article presents a qualitative theoretical analysis and prediction of the transient to steady-state transition during the spray-rolling process, a novel manufacturing technique for aluminum strips. The analytical results indicate that, when the deposited materials at the specific points on one roll surface overlap their counter-parts on the other roll surface, spray rolling transits from the transient state to the steady state. The specific points are the limiting depositon position of the atomized droplets on the roll surface initially.
Experimental investigation of a steady-state dynamical phase transition in a Jaynes-Cummings dimer
NASA Astrophysics Data System (ADS)
Raftery, James; Sadri, Darius; Mandt, Stephan; Tureci, Hakan; Houck, Andrew
Experimental progress in circuit-QED has made it possible to study non-equilibrium many-body physics using strongly correlated photons. Such open and driven systems can display new types of dynamical phase transitions. A steady state transition has also been predicted for a Jaynes-Cummings dimer where the photon current between the two cavities acts as an order parameter. Here, we discuss the theory and report measurements of the steady-state behavior of a circuit-QED dimer with in situ tunable inter-cavity coupling and on-site photon-photon interaction. Recently deceased.
Global stability of steady states in the classical Stefan problem for general boundary shapes
Hadžić, Mahir; Shkoller, Steve
2015-01-01
The classical one-phase Stefan problem (without surface tension) allows for a continuum of steady-state solutions, given by an arbitrary (but sufficiently smooth) domain together with zero temperature. We prove global-in-time stability of such steady states, assuming a sufficient degree of smoothness on the initial domain, but without any a priori restriction on the convexity properties of the initial shape. This is an extension of our previous result (Hadžić & Shkoller 2014 Commun. Pure Appl. Math. 68, 689–757 (doi:10.1002/cpa.21522)) in which we studied nearly spherical shapes. PMID:26261359
Steady-State Kinetic Analysis of DNA Polymerase Single-Nucleotide Incorporation Products
O'Flaherty, Derek K.
2014-01-01
This unit describes the experimental procedures for the steady-state kinetic analysis of DNA synthesis across DNA nucleotides (native or modified) by DNA polymerases. In vitro primer extension experiments with a single nucleoside triphosphate species followed by denaturing polyacrylamide gel electrophoresis of the extended products is described. Data analysis procedures and fitting to steady-state kinetic models is presented to highlight the kinetic differences involved in the bypass of damaged versus undamaged DNA. Moreover, explanations concerning problems encountered in these experiments are addressed. This approach provides useful quantitative parameters for the processing of damaged DNA by DNA polymerases. PMID:25501593
The puzzle of the steady-state rotation of a reverse sprinkler
NASA Astrophysics Data System (ADS)
Rueckner, Wolfgang
2015-04-01
The continuous rotation of the reverse sprinkler has been a puzzle for over two decades. This article presents a series of experiments that demonstrate that a properly designed reverse sprinkler experiences no steady-state torque and does not rotate. Ignoring transients when the flow starts and stops, if any sustained rotation of the reverse sprinkler occurs, it is because a force couple produces a torque accompanied by vortex flow inside the body of the sprinkler. No steady-state rotation occurs if the vortex is suppressed or prevented from forming in the first place. Demonstrative proof is given that an ideal reverse sprinkler does not rotate.
SUPERENERGY-2: a multiassembly, steady-state computer code for LMFBR core thermal-hydraulic analysis
Basehore, K.L.; Todreas, N.E.
1980-08-01
Core thermal-hydraulic design and performance analyses for Liquid Metal Fast Breeder Reactors (LMFBRs) require repeated detailed multiassembly calculations to determine radial temperature profiles and subchannel outlet temperatures for various core configurations and subassembly structural analyses. At steady-state, detailed core-wide temperature profiles are required for core restraint calculations and subassembly structural analysis. In addition, sodium outlet temperatures are routinely needed for each reactor operating cycle. The SUPERENERGY-2 thermal-hydraulic code was designed specifically to meet these designer needs. It is applicable only to steady-state, forced-convection flow in LMFBR core geometries.
TRIGA Mark II benchmark experiment; Part I: Steady-state operation
Mele, I.; Ravnik, M.; Trkov, A. )
1994-01-01
The experimental results of startup tests after reconstruction and modification of the TRIGA Mark II reactor in Ljubljana are presented. The experiments were performed with a completely fresh, compact, and uniform core. The operating conditions were well defined and controlled, so that the results can be used as a benchmark test case for TRIGA reactor calculations. Both steady-state and pulse mode operation were tested. In this paper, the following steady-state experiments are treated: critical core and excess reactivity, control rod worths, fuel element reactivity worth distribution, fuel temperature distribution, and fuel temperature reactivity coefficient.
NASA Astrophysics Data System (ADS)
Iadecola, Thomas; Campbell, David; Chamon, Claudio; Hou, Chang-Yu; Jackiw, Roman; Pi, So-Young; Kusminskiy, Silvia Viola
2013-04-01
Controlling the properties of materials by driving them out of equilibrium is an exciting prospect that has only recently begun to be explored. In this Letter we give a striking theoretical example of such materials design: a tunable gap in monolayer graphene is generated by exciting a particular optical phonon. We show that the system reaches a steady state whose transport properties are the same as if the system had a static electronic gap, controllable by the driving amplitude. Moreover, the steady state displays topological phenomena: there are chiral edge currents, which circulate a fractional charge e/2 per rotation cycle, with the frequency set by the optical phonon frequency.
The Dynamics of Life, V. Applying the Steady-State Theory of Mutations to Human Cancer
Erying, Henry; Stover, Betsy J.; Brown, Russell A.
1971-01-01
In papers I, II, and III of this series the steady-state theory of mutations was developed and applied to the extensive data on the effect of radiation on beagles acquired here during the past twenty years. In this paper the theory is used to interpret H. B. Dorn's data on the incidence of 21 kinds of cancer in both male and female Americans. The theory shows the nature of the heterogeneity in the population of various disorders. The agreement found confirms the steady-state theory of mutations in an interesting way. PMID:5288751
Hill, T L; Eisenberg, E; Chalovich, J M
1981-01-01
Recent theoretical work on the cooperative equilibrium binding of myosin subfragment-1-ADP to regulated actin, as influenced by Ca2+, is extended here to the cooperative steady-state ATPase activity of myosin subfragment-1 on regulated actin. Exact solution of the general steady-state problem will require Monte Carlo calculations. Three interrelated special cases are discussed in some detail and sample computer (not Monte Carlo) solutions are given. The eventual objective is to apply these considerations to in vitro experimental data and to in vivo muscle models. PMID:6455170
Devauges, Viviane; Matthews, Daniel R.; Aluko, Justin; Nedbal, Jakub; Levitt, James A.; Poland, Simon P.; Coban, Oana; Weitsman, Gregory; Monypenny, James; Ng, Tony; Ameer-Beg, Simon M.
2014-01-01
We present a novel imaging system combining total internal reflection fluorescence (TIRF) microscopy with measurement of steady-state acceptor fluorescence anisotropy in order to perform live cell Förster Resonance Energy Transfer (FRET) imaging at the plasma membrane. We compare directly the imaging performance of fluorescence anisotropy resolved TIRF with epifluorescence illumination. The use of high numerical aperture objective for TIRF required correction for induced depolarization factors. This arrangement enabled visualisation of conformational changes of a Raichu-Cdc42 FRET biosensor by measurement of intramolecular FRET between eGFP and mRFP1. Higher activity of the probe was found at the cell plasma membrane compared to intracellularly. Imaging fluorescence anisotropy in TIRF allowed clear differentiation of the Raichu-Cdc42 biosensor from negative control mutants. Finally, inhibition of Cdc42 was imaged dynamically in live cells, where we show temporal changes of the activity of the Raichu-Cdc42 biosensor. PMID:25360776
Maitra, Dhiman; Shaeib, Faten; Abdulhamid, Ibrahim; Abdulridha, Rasha M.; Saed, Ghassan M.; Diamond, Michael P.; Pennathur, Subramaniam; Abu-Soud, Husam M.
2013-01-01
Myeloperoxidase (MPO) is a heme-containing enzyme that generates hypochlorous acid (HOCl) from chloride (Cl−) and hydrogen peroxide (H2O2). It is implicated in the pathology of several chronic inflammatory conditions such as cardiovascular and pulmonary diseases and cancer. Recently we have shown that HOCl can destroy the heme prosthetic group of hemoproteins. Here, we investigated whether the HOCl formed during steady-state catalysis is able to destroy the MPO heme moiety and thereby function as a major source of free iron. UV–visible spectra and H2O2-specific electrode measurements recorded during steady-state HOCl synthesis by MPO showed that the degree of MPO heme destruction increased after multiple additions of H2O2 (10 μM), precluding the enzyme from functioning at maximum activity (80–90% inhibition). MPO heme destruction occurred only in the presence of Cl−. Stopped-flow measurements revealed that the HOCl-mediated MPO heme destruction was complex and occurred through transient ferric species whose formation and decay kinetics indicated it participates in heme destruction along with subsequent free iron release. MPO heme depletion was confirmed by the buildup of free iron utilizing the ferrozine assay. Hypochlorous acid, once generated, first equilibrates in the solution as a whole before binding to the heme iron and initiating heme destruction. Eliminating HOCl from the MPO milieu by scavenging HOCl, destabilizing the MPO–Compound I–Cl complex that could be formed during catalysis, and/or inhibiting MPO catalytic activity partially or completely protects MPO from HOCl insults. Collectively, this study elucidates the bidirectional relationship between MPO and HOCl, which highlights the potential role of MPO as a source of free iron. PMID:23624305
Non-steady state effects in diurnal 180 discrimination by Picea sitchensis branches in the field.
Seibt, U; Wingate, L; Berry, J A; Lloyd, J
2006-05-01
We report diurnal variations in 18O discrimination (18 delta) during photosynthesis (18 delta A) and respiration (18 delta R) of Picea sitchensis branches measured in branch chambers in the field. These observations were compared with predicted 18 delta (18 delta pred) based on concurrent measurements of branch gas exchange to evaluate steady state and non-steady state (NSS) models of foliage water 18O enrichment for predicting the impact of this ecosystem on the Delta 18O of atmospheric CO2. The non-steady state approach substantially improved the agreement between 18 delta pred and observed 18 delta (18 delta obs) compared with the assumption of isotopic steady state (ISS) for the Delta 18O signature of foliage water. In addition, we found direct observational evidence for NSS effects: extremely high apparent 18 delta values at dusk, dawn and during nocturnal respiration. Our experiments also show the importance of bidirectional foliage gas exchange at night (isotopic equilibration in addition to the net flux). Taken together, neglecting these effects leads to an underestimation of daily net canopy isofluxes from this forest by up to 30%. We expect NSS effects to be most pronounced in species with high specific leaf water content such as conifers and when stomata are open at night or when there is high relative humidity, and we suggest modifications to ecosystem and global models of delta 18O of CO2. PMID:17087476
NASA Technical Reports Server (NTRS)
Giebler, K. N.
1966-01-01
Computer program evaluates heat transfer modes and calculates either the transient or steady-state temperature distributions throughout an object of complex shape when heat sources are applied to specified points on the object. It uses an electrothermal model to simulate the conductance, heat capacity, and temperature potential of the object.
40 CFR 86.1362-2007 - Steady-state testing with a ramped-modal cycle.
Code of Federal Regulations, 2011 CFR
2011-07-01
... in 40 CFR 1065.650 and cycle statistics as described in 40 CFR 1065.514. (b) Measure emissions by... Steady-state 168 Warm Idle 0 1 Speed terms are defined in 40 CFR part 1065. 2 Advance from one mode to... maximum test torque. (d) (e) See 40 CFR part 1065 for detailed specifications of tolerances...
40 CFR 86.1362-2010 - Steady-state testing with a ramped-modal cycle.
Code of Federal Regulations, 2011 CFR
2011-07-01
... described in 40 CFR 1065.650 and cycle statistics as described in 40 CFR 1065.514. (b) Measure emissions by... Transition Linear Transition. 14 Steady-state 168 Warm Idle 0 1 Speed terms are defined in 40 CFR part 1065.... (c) During idle mode, operate the engine at its warm idle as described in 40 CFR part 1065. (d)...
An implicit steady-state initialization package for the RELAP5 computer code
Paulsen, M.P.; Peterson, C.E.; Odar, F.
1995-08-01
A direct steady-state initialization (DSSI) method has been developed and implemented in the RELAP5 hydrodynamic analysis program. It provides a means for users to specify a small set of initial conditions which are then propagated through the remainder of the system. The DSSI scheme utilizes the steady-state form of the RELAP5 balance equations for nonequilibrium two-phase flow. It also employs the RELAP5 component models and constitutive model packages for wall-to-phase and interphase momentum and heat exchange. A fully implicit solution of the linearized hydrodynamic equations is implemented. An implicit coupling scheme is used to augment the standard steady-state heat conduction solution for steam generator use. It solves the primary-side tube region energy equations, heat conduction equations, wall heat flux boundary conditions, and overall energy balance equation as a coupled system of equations and improves convergence. The DSSI method for initializing RELAP5 problems to steady-state conditions has been compared with the transient solution scheme using a suite of test problems including; adiabatic single-phase liquid and vapor flow through channels with and without healing and area changes; a heated two-phase test bundle representative of BWR core conditions; and a single-loop PWR model.
Abnormal Attention in Autism Shown by Steady-State Visual Evoked Potentials.
ERIC Educational Resources Information Center
Belmonte, Matthew
2000-01-01
Eight males with autism were required to shift attention between rapidly flashed targets alternating between left and right visual hemifields. When targets were separated by less than 700 ms, steady-state brain electrical response in both hemispheres was augmented and background EEG decreased for rightward shifts as compared with leftward shifts.…
A Steady State Visually Evoked Potential Investigation of Memory and Ageing
ERIC Educational Resources Information Center
Macpherson, Helen; Pipingas, Andrew; Silberstein, Richard
2009-01-01
Old age is generally accompanied by a decline in memory performance. Specifically, neuroimaging and electrophysiological studies have revealed that there are age-related changes in the neural correlates of episodic and working memory. This study investigated age-associated changes in the steady state visually evoked potential (SSVEP) amplitude and…
NASA Astrophysics Data System (ADS)
Marenduzzo, D.; Orlandini, E.; Cates, M. E.; Yeomans, J. M.
2007-09-01
We report hybrid lattice Boltzmann (HLB) simulations of the hydrodynamics of an active nematic liquid crystal sandwiched between confining walls with various anchoring conditions. We confirm the existence of a transition between a passive phase and an active phase, in which there is spontaneous flow in the steady state. This transition is attained for sufficiently “extensile” rods, in the case of flow-aligning liquid crystals, and for sufficiently “contractile” ones for flow-tumbling materials. In a quasi-one-dimensional geometry, deep in the active phase of flow-aligning materials, our simulations give evidence of hysteresis and history-dependent steady states, as well as of spontaneous banded flow. Flow-tumbling materials, in contrast, rearrange themselves so that only the two boundary layers flow in steady state. Two-dimensional simulations, with periodic boundary conditions, show additional instabilities, with the spontaneous flow appearing as patterns made up of “convection rolls.” These results demonstrate a remarkable richness (including dependence on anchoring conditions) in the steady-state phase behavior of active materials, even in the absence of external forcing; they have no counterpart for passive nematics. Our HLB methodology, which combines lattice Boltzmann for momentum transport with a finite difference scheme for the order parameter dynamics, offers a robust and efficient method for probing the complex hydrodynamic behavior of active nematics.
Analysis of steady state creep of southeastern New Mexico bedded salt
Herrmann, W.; Wawersik, W.R.; Lauson, H.S.
1980-03-01
Steady state creep rates have been obtained from a large suite of existing experimental creep data relating to bedded rock salt from the Salado formation of S.E. New Mexico. Experimental conditions covered an intermediate temperature range from 22/sup 0/C to 200/sup 0/C, and shear stresses from 1000 psi (7 MPa) to 6000 psi (31 MPa). An expression, based on a single diffusion controlled dislocation climb mechanism, has been found to fit the observed dependence of steady state creep rate on shear stress and temperature, yielding an activation energy of 12 kcal/mole (50 kJ/mole) and a stress exponent of 4.9. Multiple regression analysis revealed a dependence on stratigraphy, but no statistically significant dependence on pressure of specimen size. No consistent dilatancy or compaction associated with steady state creep was found, although some individual specimens dilated or compacted during creep. The steady state creep data were found to agree very well with creep data for both bedded and dome salt from a variety of other locations.
Thermal shock behaviour of blisters on W surface during combined steady-state/pulsed plasma loading
NASA Astrophysics Data System (ADS)
Jia, Y. Z.; Liu, W.; Xu, B.; Luo, G.-N.; Li, C.; Qu, S. L.; Morgan, T. W.; De Temmerman, G.
2015-09-01
The thermal shock behaviour of blister-covered W surfaces during combined steady-state/pulsed plasma loading was studied by scanning electron microscopy and electron backscatter diffraction. The W samples were first exposed to steady-state D plasma to induce blisters on the surface, and then the blistered surfaces were exposed to steady-state/pulsed plasma. Growth and cracking of blisters were observed after the exposure to the steady-state/pulsed plasma, while no obvious damage occurred on the surface area not covered with blisters. The results confirm that blisters induced by D plasma might represent weak spots on the W surface when exposed to transient heat load of ELMs. The cracks on blisters were different from the cracks due to the transient heat loads reported before, and they were assumed to be caused by stress and strain due to the gas expansion inside the blisters during the plasma pulses. Moreover, most of cracks were found to appear on the blisters formed on grains with surface orientation near [1 1 1].
Current Pressure Transducer Application of Model-based Prognostics Using Steady State Conditions
NASA Technical Reports Server (NTRS)
Teubert, Christopher; Daigle, Matthew J.
2014-01-01
Prognostics is the process of predicting a system's future states, health degradation/wear, and remaining useful life (RUL). This information plays an important role in preventing failure, reducing downtime, scheduling maintenance, and improving system utility. Prognostics relies heavily on wear estimation. In some components, the sensors used to estimate wear may not be fast enough to capture brief transient states that are indicative of wear. For this reason it is beneficial to be capable of detecting and estimating the extent of component wear using steady-state measurements. This paper details a method for estimating component wear using steady-state measurements, describes how this is used to predict future states, and presents a case study of a current/pressure (I/P) Transducer. I/P Transducer nominal and off-nominal behaviors are characterized using a physics-based model, and validated against expected and observed component behavior. This model is used to map observed steady-state responses to corresponding fault parameter values in the form of a lookup table. This method was chosen because of its fast, efficient nature, and its ability to be applied to both linear and non-linear systems. Using measurements of the steady state output, and the lookup table, wear is estimated. A regression is used to estimate the wear propagation parameter and characterize the damage progression function, which are used to predict future states and the remaining useful life of the system.
A study was conducted of the relative performance of anaerobic digestion systems under mesophilic and thermophilic conditions. Fifty liter laboratory scale digesters were fed primary sludge from the Allentown, PA Waste Water Treatment Plant. Long-term, steady-state performance da...
COMPARATIVE EVALUATION OF MESOPHILIC AND THERMOPHILIC DIGESTION - PHASE II. STEADY STATE STUDIES
A study of the relative performance of anaerobic digestion systems under mesophilic and thermophilic conditions was conducted. Fifty liter laboratory scale digesters were fed primary sludge from the Allentown, PA Waste Water Treatment Plant. Long-term, steady-state performance da...
TRANSIENT AND STEADY STATE STUDY OF PURE AND MIXED REFRIGERANTS IN A RESIDENTIAL HEAT PUMP
The report gives results of an experimental and theoretical investigation of the transient and steady state performance of a residential air-conditioning/heat pump (AC/HP) operating with different refrigerants. (NOTE: The project was motivated by environmental concerns related to...
Incorporation of wind generation to the Mexican power grid: Steady state analysis
Tovar, J.H.; Guardado, J.L.; Cisneros, F.; Cadenas, R.; Lopez, S.
1997-09-01
This paper describes a steady state analysis related with the incorporation of large amounts of eolic generation into the Mexican power system. An equivalent node is used to represent individual eolic generators in the wind farm. Possible overloads, losses, voltage and reactive profiles and estimated severe contingencies are analyzed. Finally, the conclusions of this study are presented.
40 CFR Appendix C to Subpart S of... - Steady-State Short Test Standards
Code of Federal Regulations, 2010 CFR
2010-07-01
... 40 Protection of Environment 2 2010-07-01 2010-07-01 false Steady-State Short Test Standards C Appendix C to Subpart S of Part 51 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED.../Maintenance Program Requirements Pt. 51, Subpt. S, App. C Appendix C to Subpart S of Part...
40 CFR Appendix D to Subpart S of... - Steady-State Short Test Equipment
Code of Federal Regulations, 2010 CFR
2010-07-01
... Appendix D to Subpart S of Part 51 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED.../Maintenance Program Requirements Pt. 51, Subpt. S, App. D Appendix D to Subpart S of Part 51—Steady-State... capable of applying a load to the vehicle's driving tire surfaces at the horsepower and speed...
Elimination of thermodynamically infeasible loops in steady-state metabolic models.
Schellenberger, Jan; Lewis, Nathan E; Palsson, Bernhard Ø
2011-02-01
The constraint-based reconstruction and analysis (COBRA) framework has been widely used to study steady-state flux solutions in genome-scale metabolic networks. One shortcoming of current COBRA methods is the possible violation of the loop law in the computed steady-state flux solutions. The loop law is analogous to Kirchhoff's second law for electric circuits, and states that at steady state there can be no net flux around a closed network cycle. Although the consequences of the loop law have been known for years, it has been computationally difficult to work with. Therefore, the resulting loop-law constraints have been overlooked. Here, we present a general mixed integer programming approach called loopless COBRA (ll-COBRA), which can be used to eliminate all steady-state flux solutions that are incompatible with the loop law. We apply this approach to improve flux predictions on three common COBRA methods: flux balance analysis, flux variability analysis, and Monte Carlo sampling of the flux space. Moreover, we demonstrate that the imposition of loop-law constraints with ll-COBRA improves the consistency of simulation results with experimental data. This method provides an additional constraint for many COBRA methods, enabling the acquisition of more realistic simulation results. PMID:21281568
Quasisteady and steady states in global gyrokinetic particle-in-cell simulations
Jolliet, S.; McMillan, B. F.; Vernay, T.; Villard, L.; Bottino, A.; Angelino, P.
2009-05-15
Collisionless delta-f gyrokinetic particle-in-cell simulations suffer from the entropy paradox, in which the entropy grows linearly in time while low-order moments are saturated. As a consequence, these simulations do not reach a steady state and are unsuited to make quantitative predictions. A solution to this issue is the introduction of artificial dissipation. The notion of steady state in gyrokinetic simulations is studied by deriving an evolution equation for the fluctuation entropy and applying it to the global collisionless particle-in-cell code ORB5 [S. Jolliet et al., Comput. Phys. Commun. 177, 409 (2007)]. It is shown that a recently implemented noise-control algorithm [B. F. McMillan et al., Phys. Plasmas 15, 052308 (2008)] based on a W-stat provides the necessary dissipation to reach a steady state. The two interesting situations of decaying and driven turbulence are considered. In addition, it is shown that a separate heating algorithm, not based on a W-stat, does not lead to a statistical steady state.
Marenduzzo, D; Orlandini, E; Cates, M E; Yeomans, J M
2007-09-01
We report hybrid lattice Boltzmann (HLB) simulations of the hydrodynamics of an active nematic liquid crystal sandwiched between confining walls with various anchoring conditions. We confirm the existence of a transition between a passive phase and an active phase, in which there is spontaneous flow in the steady state. This transition is attained for sufficiently "extensile" rods, in the case of flow-aligning liquid crystals, and for sufficiently "contractile" ones for flow-tumbling materials. In a quasi-one-dimensional geometry, deep in the active phase of flow-aligning materials, our simulations give evidence of hysteresis and history-dependent steady states, as well as of spontaneous banded flow. Flow-tumbling materials, in contrast, rearrange themselves so that only the two boundary layers flow in steady state. Two-dimensional simulations, with periodic boundary conditions, show additional instabilities, with the spontaneous flow appearing as patterns made up of "convection rolls." These results demonstrate a remarkable richness (including dependence on anchoring conditions) in the steady-state phase behavior of active materials, even in the absence of external forcing; they have no counterpart for passive nematics. Our HLB methodology, which combines lattice Boltzmann for momentum transport with a finite difference scheme for the order parameter dynamics, offers a robust and efficient method for probing the complex hydrodynamic behavior of active nematics. PMID:17930285
Steady-State Clinical Pharmacokinetics of Bupropion Extended-Release In Youths
ERIC Educational Resources Information Center
Daviss, W. Burleson; Perel, James M.; Birmaher, Boris; Rudolph, George R.; Melhem, Imad; Axelson, David A.; Brent, David A.
2006-01-01
Objective: To examine in children and adolescents the 24-hour, steady-state clinical pharmacokinetics of an extended-release (XL) formulation of bupropion (Wellbutrin XL). Method: Subjects were six male and four female patients (ages 11.5-16.2 years) prescribed bupropion XL in morning daily doses of either 150 mg (n = 5) or 300 mg (n = 5) for at…
Steady-state choice between four alternatives obeys the constant-ratio rule.
Bensemann, Joshua; Lobb, Brenda; Podlesnik, Christopher A; Elliffe, Douglas
2015-07-01
We investigated why violations to the constant-ratio rule, an assumption of the generalized matching law, occur in procedures that arrange frequent changes to reinforcer ratios. Our investigation produced steady-state data and compared them with data from equivalent, frequently changing procedures. Six pigeons responded in a four-alternative concurrent-schedule experiment with an arranged reinforcer-rate ratio of 27:9:3:1. The same four variable-interval schedules were used in every condition, for 50 sessions, and the physical location of each schedule was changed across conditions. The experiment was a steady-state version of a frequently changing procedure in which the locations of four VI schedules were changed every 10 reinforcers. We found that subjects' responding was consistent with the constant-ratio rule in the steady-state procedure. Additionally, local analyses showed that preference after reinforcement was towards the alternative that was likely to produce the next reinforcer, instead of being towards the just-reinforced alternative as in frequently changing procedures. This suggests that the effect of a reinforcer on preference is fundamentally different in rapidly changing and steady-state environments. Comparing this finding to the existing literature suggests that choice is more influenced by reinforcer-generated signals when the reinforcement contingencies often change. PMID:25989016
Pellet Injectors Developed at the Pelin Laboratory for Steady-State Plasma Fuelling
NASA Astrophysics Data System (ADS)
Vinyar, I.; Geraud, A.; Yamada, H.; Sakamoto, R.; Oda, Y.; Lukin, A.; Umov, A.; Skoblikov, S.; Gros, G.; Saksaganskii, G.; Reznichenko, P.; Krasilnikov, I.; Panchenko, V.
2004-06-01
Pneumatic and centrifugal injectors for steady-state plasma refuelling by solid hydrogen, deuterium and tritium pellets have been designed at the PELIN Laboratory to meet requirements of LHD, TORE SUPRA, and ITER. Presented here is a review of these injectors' designs and results.
The Cost Structure of Higher Education: Implications for Governmental Policy in Steady State.
ERIC Educational Resources Information Center
Lyell, Edward H.
The historical pattern of resource allocation in American higher education as exemplified by public colleges in Colorado was examined. The reliance upon average cost information in making resource allocation decisions was critiqued for the special problems that arise from student enrollment decline or steady state. A model of resource allocation…
Analytical steady-state solutions for water-limited cropping systems using saline irrigation water
Technology Transfer Automated Retrieval System (TEKTRAN)
Due to the diminishing availability of good quality water for irrigation, it is increasingly important that irrigation and salinity management tools be able to target submaximal crop yields and support the use of marginal quality waters. In this work, we present a steady-state irrigated systems mod...
Steady-state chlorophyll flourescence (Fs) as a tool to monitor plant heat and drought stress
Technology Transfer Automated Retrieval System (TEKTRAN)
Crop yield decreases when photosynthesis is limited by heat or drought conditions. Yet farmers do not monitor crop photosynthesis because it is difficult to measure at the field scale in real time. Steady-state chlorophyll fluorescence (Fs) can be used at the field level as an indirect measure of p...
HU, T.A.
2005-10-27
Assess the steady-state flammability level at normal and off-normal ventilation conditions. The hydrogen generation rate was calculated for 177 tanks using the rate equation model. Flammability calculations based on hydrogen, ammonia, and methane were performed for 177 tanks for various scenarios.
System and method for generating steady state confining current for a toroidal plasma fusion reactor
Fisch, Nathaniel J.
1981-01-01
A system for generating steady state confining current for a toroidal plasma fusion reactor providing steady-state generation of the thermonuclear power. A dense, hot toroidal plasma is initially prepared with a confining magnetic field with toroidal and poloidal components. Continuous wave RF energy is injected into said plasma to establish a spectrum of traveling waves in the plasma, where the traveling waves have momentum components substantially either all parallel, or all anti-parallel to the confining magnetic field. The injected RF energy is phased to couple to said traveling waves with both a phase velocity component and a wave momentum component in the direction of the plasma traveling wave components. The injected RF energy has a predetermined spectrum selected so that said traveling waves couple to plasma electrons having velocities in a predetermined range .DELTA.. The velocities in the range are substantially greater than the thermal electron velocity of the plasma. In addition, the range is sufficiently broad to produce a raised plateau having width .DELTA. in the plasma electron velocity distribution so that the plateau electrons provide steady-state current to generate a poloidal magnetic field component sufficient for confining the plasma. In steady state operation of the fusion reactor, the fusion power density in the plasma exceeds the power dissipated in the plasma.
System and method for generating steady state confining current for a toroidal plasma fusion reactor
Bers, Abraham
1981-01-01
A system for generating steady state confining current for a toroidal plasma fusion reactor providing steady-state generation of the thermonuclear power. A dense, hot toroidal plasma is initially prepared with a confining magnetic field with toroidal and poloidal components. Continuous wave RF energy is injected into said plasma to estalish a spectrum of traveling waves in the plasma, where the traveling waves have momentum components substantially either all parallel, or all anti-parallel to the confining magnetic field. The injected RF energy is phased to couple to said traveling waves with both a phase velocity component and a wave momentum component in the direction of the plasma traveling wave components. The injected RF energy has a predetermined spectrum selected so that said traveling waves couple to plasma electrons having velocities in a predetermined range .DELTA.. The velocities in the range are substantially greater than the thermal electron velocity of the plasma. In addition, the range is sufficiently broad to produce a raised plateau having width .DELTA. in the plasma electron velocity distribution so that the plateau electrons provide steady-state current to generate a poloidal magnetic field component sufficient for confining the plasma. In steady state operation of the fusion reactor, the fusion power density in the plasma exceeds the power dissipated inthe plasma.
HU TA
2009-10-26
Assess the steady-state flammability level at normal and off-normal ventilation conditions. The hydrogen generation rate was calculated for 177 tanks using the rate equation model. Flammability calculations based on hydrogen, ammonia, and methane were performed for 177 tanks for various scenarios.
Quantifying biases in non-steady state chamber measurements of soil-atmosphere gas exchange
Technology Transfer Automated Retrieval System (TEKTRAN)
Limitations of non-steady state (NSS) chamber methods for determining soil-to-atmosphere trace gas exchange rates have been recognized for several decades. Of these limitations, the so-called “chamber effect” is one of the most challenging to overcome. The chamber effect can be defined as the inhere...
TRACE GAS EMISSIONS IN CHAMBERS: A NON-STEADY-STATE DIFFUSION MODEL
Technology Transfer Automated Retrieval System (TEKTRAN)
Non-steady-state (NSS) chambers are widely used to measure trace gas emissions from the Earth’s surface in the atmosphere. Unfortunately, traditional interpretations of time-dependent chamber concentrations often systematically underestimate predeployment exchange rates because they do not accuratel...
Steady-state BOLD Response to Higher-order Cognition Modulates Low-Frequency Neural Oscillations.
Wang, Yi-Feng; Dai, Gang-Shu; Liu, Feng; Long, Zhi-Liang; Yan, Jin H; Chen, Hua-Fu
2015-12-01
Steady-state responses (SSRs) reflect the synchronous neural oscillations evoked by noninvasive and consistently repeated stimuli at the fundamental or harmonic frequencies. The steady-state evoked potentials (SSEPs; the representative form of the SSRs) have been widely used in the cognitive and clinical neurosciences and brain-computer interface research. However, the steady-state evoked potentials have limitations in examining high-frequency neural oscillations and basic cognition. In addition, synchronous neural oscillations in the low frequency range (<1 Hz) and in higher-order cognition have received a little attention. Therefore, we examined the SSRs in the low frequency range using a new index, the steady-state BOLD responses (SSBRs) evoked by semantic stimuli. Our results revealed that the significant SSBRs were induced at the fundamental frequency of stimuli and the first harmonic in task-related regions, suggesting the enhanced variability of neural oscillations entrained by exogenous stimuli. The SSBRs were independent of neurovascular coupling and characterized by sensorimotor bias, an indication of regional-dependent neuroplasticity. Furthermore, the amplitude of SSBRs may predict behavioral performance and show the psychophysiological relevance. Our findings provide valuable insights into the understanding of the SSRs evoked by higher-order cognition and how the SSRs modulate low-frequency neural oscillations. PMID:26284992
Proteome analysis of the Escherichia coli heat shock response under steady-state conditions
Lüders, Svenja; Fallet, Claas; Franco-Lara, Ezequiel
2009-01-01
In this study a proteomic approach was used to investigate the steady-state response of Escherichia coli to temperature up-shifts in a cascade of two continuously operated bioreactors. The first reactor served as cell source with optimal settings for microbial growth, while in the second chemostat the cells were exposed to elevated temperatures. By using this reactor configuration, which has not been reported to be used for the study of bacterial stress responses so far, it is possible to study temperature stress under well-defined, steady-state conditions. Specifically the effect on the cellular adaption to temperature stress using two-dimensional gel electrophoresis was examined and compared at the cultivation temperatures of 37°C and 47.5°C. As expected, the steady-state study with the double bioreactor configuration delivered a different protein spectrum compared to that obtained with standard batch experiments in shaking flasks and bioreactors. Setting a high cut-out spot-to-spot size ratio of 5, proteins involved in defence against oxygen stress, functional cell envelope proteins, chaperones and proteins involved in protein biosynthesis, the energy metabolism and the amino acid biosynthesis were found to be differently expressed at high cultivation temperatures. The results demonstrate the complexity of the stress response in a steady-state culture not reported elsewhere to date. PMID:19772559
NASA Technical Reports Server (NTRS)
Sellers, J. F.; Daniele, C. J.
1975-01-01
The DYNGEN, a digital computer program for analyzing the steady state and transient performance of turbojet and turbofan engines, is described. The DYNGEN is based on earlier computer codes (SMOTE, GENENG, and GENENG 2) which are capable of calculating the steady state performance of turbojet and turbofan engines at design and off-design operating conditions. The DYNGEN has the combined capabilities of GENENG and GENENG 2 for calculating steady state performance; to these the further capability for calculating transient performance was added. The DYNGEN can be used to analyze one- and two-spool turbojet engines or two- and three-spool turbofan engines without modification to the basic program. A modified Euler method is used by DYNGEN to solve the differential equations which model the dynamics of the engine. This new method frees the programmer from having to minimize the number of equations which require iterative solution. As a result, some of the approximations normally used in transient engine simulations can be eliminated. This tends to produce better agreement when answers are compared with those from purely steady state simulations. The modified Euler method also permits the user to specify large time steps (about 0.10 sec) to be used in the solution of the differential equations. This saves computer execution time when long transients are run. Examples of the use of the program are included, and program results are compared with those from an existing hybrid-computer simulation of a two-spool turbofan.
Integrated modelling of DEMO-FNS current ramp-up scenario and steady-state regime
NASA Astrophysics Data System (ADS)
Dnestrovskij, A. Yu.; Kuteev, B. V.; Bykov, A. S.; Ivanov, A. A.; Lukash, V. E.; Medvedev, S. Yu.; Sergeev, V. Yu.; Sychugov, D. Yu.; Khayrutdinov, R. R.
2015-06-01
An approach to the integrated modelling of plasma regimes in the projected neutron source DEMO-FNS based on different codes is developed. The consistency check of the steady-state regime is carried out, namely, the possibility of the plasma current ramp-up, acceptance of growth rates of MHD modes in the steady-state regime, heat loads to the wall and divertor plates and neutron yield value. The following codes are employed for the integrated modelling. ASTRA transport code for calculation of plasma parameters in the steady-state regime, NUBEAM Monte Carlo code for NBI incorporated into the ASTRA code, DINA free boundary equilibrium and evolution code, SPIDER free boundary equilibrium and equilibrium reconstruction code, KINX ideal MHD stability code, TOKSTAB rigid shift vertical stability code, edge and divertor plasma B2SOLPS5.2 code and Semi-analytic Hybrid Model (SHM) code for self-consistent description of the core, edge and divertor plasmas based on the experimental scaling laws. The consistent steady-state regime for the DEMO-FNS plasma and the plasma current ramp-up scenario are developed using the integrated modelling approach. Passive copper coils are suggested to reduce the plasma vertical instability growth rate to below ˜30 s-1.The outer divertor operation in the ‘high-recycling’ regime is numerically demonstrated with a maximal heat flux density of 7-9 MW m-2 that is technically acceptable.
Diagrams of the state of a steady-state arc discharge in hydrogen and helium
NASA Astrophysics Data System (ADS)
Vasil'ev, E. N.
2014-12-01
The temperature, electric field strength, and specific and integrated powers of energy mechanisms of an axisymmetric steady-state equilibrium arc discharge in hydrogen and helium under atmospheric pressure are calculated for various values of the current and radius. The results of calculations are presented in the form of state diagrams intended for estimating the main energy characteristics of electric arcs.
Vector interactions of steady-state planar solitons in biased photorefractive media
NASA Astrophysics Data System (ADS)
Singh, S. R.; Carvalho, M. I.; Christodoulides, D. N.
1995-11-01
A theory describing the steady-state propagation of orthogonally polarized planar bright beams in biased photorefractive media is developed. Interactions between soliton states of each polarization in a strontium barium niobate photorefractive crystal are then investigated numerically. Our results indicate that such vector interactions can lead to a number of interesting effects such as beam compression and beam steering.
40 CFR Appendix C to Subpart S of... - Steady-State Short Test Standards
Code of Federal Regulations, 2014 CFR
2014-07-01
... 40 Protection of Environment 2 2014-07-01 2014-07-01 false Steady-State Short Test Standards C Appendix C to Subpart S of Part 51 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED.../Maintenance Program Requirements Pt. 51, Subpt. S, App. C Appendix C to Subpart S of Part...
40 CFR Appendix C to Subpart S of... - Steady-State Short Test Standards
Code of Federal Regulations, 2012 CFR
2012-07-01
... 40 Protection of Environment 2 2012-07-01 2012-07-01 false Steady-State Short Test Standards C Appendix C to Subpart S of Part 51 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED.../Maintenance Program Requirements Pt. 51, Subpt. S, App. C Appendix C to Subpart S of Part...
Existence and uniqueness of steady state solutions of a nonlocal diffusive logistic equation
NASA Astrophysics Data System (ADS)
Sun, Linan; Shi, Junping; Wang, Yuwen
2013-08-01
In this paper, we consider a dynamical model of population biology which is of the classical Fisher type, but the competition interaction between individuals is nonlocal. The existence, uniqueness, and stability of the steady state solution of the nonlocal problem on a bounded interval with homogeneous Dirichlet boundary conditions are studied.
Technology Transfer Automated Retrieval System (TEKTRAN)
Several flux-calculation (FC) schemes are available for determining soil-to-atmosphere emissions of nitrous oxide (N2O) and other trace gases using data from non-steady-state flux chambers. Recently developed methods claim to provide more accuracy in estimating the true pre-deployment flux (f0) comp...
Walkway Length Determination for Steady State Walking in Young and Older Adults
ERIC Educational Resources Information Center
Macfarlane, Pamela A.; Looney, Marilyn A.
2008-01-01
The primary purpose of this study was to determine acceleration (AC) and deceleration (DC) distances that would accommodate young and older adults walking at their preferred and fast speeds. A secondary purpose was to determine the minimal walkway length needed to record six steady state (SS) steps (three full gait cycles) for younger and older…
A general theory of kinetics and thermodynamics of steady-state copolymerization.
Shu, Yao-Gen; Song, Yong-Shun; Ou-Yang, Zhong-Can; Li, Ming
2015-06-17
Kinetics of steady-state copolymerization has been investigated since the 1940s. Irreversible terminal and penultimate models were successfully applied to a number of comonomer systems, but failed for systems where depropagation is significant. Although a general mathematical treatment of the terminal model with depropagation was established in the 1980s, a penultimate model and higher-order terminal models with depropagation have not been systematically studied, since depropagation leads to hierarchically-coupled and unclosed kinetic equations which are hard to solve analytically. In this work, we propose a truncation method to solve the steady-state kinetic equations of any-order terminal models with depropagation in a unified way, by reducing them into closed steady-state equations which give the exact solution of the original kinetic equations. Based on the steady-state equations, we also derive a general thermodynamic equality in which the Shannon entropy of the copolymer sequence is explicitly introduced as part of the free energy dissipation of the whole copolymerization system. PMID:25992648
User's instructions for the 41-node thermoregulatory model (steady state version)
NASA Technical Reports Server (NTRS)
Leonard, J. I.
1974-01-01
A user's guide for the steady-state thermoregulatory model is presented. The model was modified to provide conversational interaction on a remote terminal, greater flexibility for parameter estimation, increased efficiency of convergence, greater choice of output variable and more realistic equations for respiratory and skin diffusion water losses.
40 CFR Appendix D to Subpart S of... - Steady-State Short Test Equipment
Code of Federal Regulations, 2012 CFR
2012-07-01
... 40 Protection of Environment 2 2012-07-01 2012-07-01 false Steady-State Short Test Equipment D Appendix D to Subpart S of Part 51 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED.../Maintenance Program Requirements Pt. 51, Subpt. S, App. D Appendix D to Subpart S of Part...
40 CFR Appendix D to Subpart S of... - Steady-State Short Test Equipment
Code of Federal Regulations, 2014 CFR
2014-07-01
... 40 Protection of Environment 2 2014-07-01 2014-07-01 false Steady-State Short Test Equipment D Appendix D to Subpart S of Part 51 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED.../Maintenance Program Requirements Pt. 51, Subpt. S, App. D Appendix D to Subpart S of Part...
HU, T.A.
2000-04-27
This work is to assess the steady-state flammability level at normal and off-normal ventilation conditions in the tank dome space for 177 double-shell and single-shell tanks at Hanford. Hydrogen generation rate was calculated for 177 tanks using rate equation model developed recently.
Programmable calculator uses equation to figure steady-state gas-pipeline flow
Holmberg, E.
1982-04-26
Because it is accurate and consistent over a wide range of variables, the Colebrook-White (C-W) formula serves as the basis for many methods of calculating turbulent flow in gas pipelines. Oilconsult reveals a simple way to adapt the C-W formula to calculate steady-state pipeline flow using the TI-59 programmable calculator.
Steady-State Fluorescence Anisotropy to Investigate Flavonoids Binding to Proteins
ERIC Educational Resources Information Center
Ingersoll, Christine M.; Strollo, Christen M.
2007-01-01
The steady-state fluorescence anisotropy is employed to study the binding of protein of a model protein, human serum albumin, to a commonly used flavonoid, quercetin. The experiment describes the thermodynamics, as well as the biochemical interactions of such binding effectively.
Transient and steady state photoelectronic analysis in TlInSe{sub 2} crystals
Qasrawi, A.F.; Gasanly, N.M.
2011-08-15
Highlights: {yields} The steady state and time dependent photoconductivity kinetics of the TlInSe{sub 2} crystals are investigated in the temperature region of 100-350 K. {yields} The photocurrent of the sample exhibited linear, sublinear, and supralinear recombination mechanisms, at, above and below 160 K, respectively. {yields} Steady state photoconductivity revealed two recombination centres located at 234 and 94 meV. {yields} The transient photoconductivity is limited by a trapping center located at 173 meV. {yields} The capture coefficient of the trap for holes was determined as 3.11 x 10{sup -22} cm{sup -2}. -- Abstract: The temperature and illumination effects on the transient and steady state photoconductivities of TlInSe{sub 2} crystals have been studied. Namely, two recombination centres located at 234 and at 94 meV and one trap center located at 173 meV were determined from the temperature-dependent steady state and transient photoconductivities, respectively. The illumination dependence of photoconductivity indicated the domination of sublinear and supralinear recombination mechanisms above and below 160 K, respectively. The change in the recombination mechanism is attributed to the exchange of roles between the linear recombination at the surface and trapping centres in the crystal, which become dominant as temperature decreases. The transient photoconductivity measurement allowed the determination of the capture coefficient of traps for holes as 3.11 x 10{sup -22} cm{sup -2}.
40 CFR Appendix C to Subpart S of... - Steady-State Short Test Standards
Code of Federal Regulations, 2011 CFR
2011-07-01
... 40 Protection of Environment 2 2011-07-01 2011-07-01 false Steady-State Short Test Standards C... Short Test Standards (I) Short Test Standards for 1981 and Later Model Year Light-Duty Vehicles For 1981... altitude to which high altitude certification standards of 1.5 gpm HC and 15 gpm CO or less apply),...
ROLE OF NMDA, NICOTINIC, AND GABA RECEPTORS IN THE STEADY STATE VISUAL EVOKED POTENTIAL IN RATS.
This manuscript characterizes the receptor pathways involved in pattern-evoked potential generation in rats
" NMDA and nicotinic acetylcholine receptors appear to be involved in the generation of the steady-state pattern evoked response in vivo.
" The pattern evok...
Dissipative production of a maximally entangled steady state of two quantum bits
NASA Astrophysics Data System (ADS)
Lin, Y.; Gaebler, J. P.; Reiter, F.; Tan, T. R.; Bowler, R.; Sørensen, A. S.; Leibfried, D.; Wineland, D. J.
2013-12-01
Entangled states are a key resource in fundamental quantum physics, quantum cryptography and quantum computation. Introduction of controlled unitary processes--quantum gates--to a quantum system has so far been the most widely used method to create entanglement deterministically. These processes require high-fidelity state preparation and minimization of the decoherence that inevitably arises from coupling between the system and the environment, and imperfect control of the system parameters. Here we combine unitary processes with engineered dissipation to deterministically produce and stabilize an approximate Bell state of two trapped-ion quantum bits (qubits), independent of their initial states. Compared with previous studies that involved dissipative entanglement of atomic ensembles or the application of sequences of multiple time-dependent gates to trapped ions, we implement our combined process using trapped-ion qubits in a continuous time-independent fashion (analogous to optical pumping of atomic states). By continuously driving the system towards the steady state, entanglement is stabilized even in the presence of experimental noise and decoherence. Our demonstration of an entangled steady state of two qubits represents a step towards dissipative state engineering, dissipative quantum computation and dissipative phase transitions. Following this approach, engineered coupling to the environment may be applied to a broad range of experimental systems to achieve desired quantum dynamics or steady states. Indeed, concurrently with this work, an entangled steady state of two superconducting qubits was demonstrated using dissipation.
40 CFR Appendix II to Part 1042 - Steady-State Duty Cycles
Code of Federal Regulations, 2014 CFR
2014-07-01
... transition Linear transition in torque. 6Steady-state 171 Warm idle 0. 1 Speed terms are defined in 40 CFR... Engine Governed 25 0.15 1 Speed terms are defined in 40 CFR part 1065. 2 The percent torque is relative to the maximum test torque as defined in 40 CFR part 1065. (2) The following duty cycle applies...
40 CFR 86.1362 - Steady-state testing with a ramped-modal cycle.
Code of Federal Regulations, 2014 CFR
2014-07-01
... 40 CFR part 1065. 2 Advance from one mode to the next within a 20-second transition phase. During the... commanded engine speed. (b) Perform the ramped-modal test as described in 40 CFR part 1065. (c) For 2007... Transition. 14 Steady-state 168 Warm Idle 0. 1 Speed terms are defined in 40 CFR part 1065. 2 Advance...
40 CFR 86.1362-2007 - Steady-state testing with a ramped-modal cycle.
Code of Federal Regulations, 2013 CFR
2013-07-01
... maximum test torque. (d) (e) See 40 CFR part 1065 for detailed specifications of tolerances and... in 40 CFR 1065.650 and cycle statistics as described in 40 CFR 1065.514. (b) Measure emissions by... Steady-state 168 Warm Idle 0 1 Speed terms are defined in 40 CFR part 1065. 2 Advance from one mode...
40 CFR 86.1362-2007 - Steady-state testing with a ramped-modal cycle.
Code of Federal Regulations, 2010 CFR
2010-07-01
... maximum test torque. (d) (e) See 40 CFR part 1065 for detailed specifications of tolerances and... in 40 CFR 1065.650 and cycle statistics as described in 40 CFR 1065.514. (b) Measure emissions by... Steady-state 168 Warm Idle 0 1 Speed terms are defined in 40 CFR part 1065. 2 Advance from one mode...
40 CFR 86.1362-2010 - Steady-state testing with a ramped-modal cycle.
Code of Federal Regulations, 2013 CFR
2013-07-01
... described in 40 CFR 1065.650 and cycle statistics as described in 40 CFR 1065.514. (b) Measure emissions by... Transition Linear Transition. 14 Steady-state 168 Warm Idle 0 1 Speed terms are defined in 40 CFR part 1065.... (c) During idle mode, operate the engine at its warm idle as described in 40 CFR part 1065. (d)...
40 CFR 86.1362-2010 - Steady-state testing with a ramped-modal cycle.
Code of Federal Regulations, 2010 CFR
2010-07-01
... described in 40 CFR 1065.650 and cycle statistics as described in 40 CFR 1065.514. (b) Measure emissions by... Transition Linear Transition. 14 Steady-state 168 Warm Idle 0 1 Speed terms are defined in 40 CFR part 1065.... (c) During idle mode, operate the engine at its warm idle as described in 40 CFR part 1065. (d)...
40 CFR Appendix II to Part 1042 - Steady-State Duty Cycles
Code of Federal Regulations, 2010 CFR
2010-07-01
... transition Linear transition in torque. 6Steady-state 171 Warm idle 0. 1 Speed terms are defined in 40 CFR... Engine Governed 25 0.15 1 Speed terms are defined in 40 CFR part 1065. 2 The percent torque is relative to the maximum test torque as defined in 40 CFR part 1065. (2) The following duty cycle applies...
40 CFR Appendix II to Part 1042 - Steady-State Duty Cycles
Code of Federal Regulations, 2013 CFR
2013-07-01
... transition Linear transition in torque. 6Steady-state 171 Warm idle 0. 1 Speed terms are defined in 40 CFR... Engine Governed 25 0.15 1 Speed terms are defined in 40 CFR part 1065. 2 The percent torque is relative to the maximum test torque as defined in 40 CFR part 1065. (2) The following duty cycle applies...
40 CFR 86.1362-2007 - Steady-state testing with a ramped-modal cycle.
Code of Federal Regulations, 2012 CFR
2012-07-01
... maximum test torque. (d) (e) See 40 CFR part 1065 for detailed specifications of tolerances and... in 40 CFR 1065.650 and cycle statistics as described in 40 CFR 1065.514. (b) Measure emissions by... Steady-state 168 Warm Idle 0 1 Speed terms are defined in 40 CFR part 1065. 2 Advance from one mode...
40 CFR Appendix II to Part 1042 - Steady-State Duty Cycles
Code of Federal Regulations, 2012 CFR
2012-07-01
... transition Linear transition in torque. 6Steady-state 171 Warm idle 0. 1 Speed terms are defined in 40 CFR... Engine Governed 25 0.15 1 Speed terms are defined in 40 CFR part 1065. 2 The percent torque is relative to the maximum test torque as defined in 40 CFR part 1065. (2) The following duty cycle applies...
Steady-state Relativistic Stellar Dynamics Around a Massive Black hole
NASA Astrophysics Data System (ADS)
Bar-Or, Ben; Alexander, Tal
2016-04-01
A massive black hole (MBH) consumes stars whose orbits evolve into the small phase-space volume of unstable orbits, the “loss cone,” which take them into the MBH, or close enough to interact strongly with it. The resulting phenomena, e.g., tidal heating and disruption, binary capture and hyper-velocity star ejection, gravitational wave (GW) emission by inspiraling compact remnants, or hydrodynamical interactions with an accretion disk, can produce observable signatures and thereby reveal the MBH, affect its mass and spin evolution, test strong gravity, and probe stars and gas near the MBH. These continuous stellar loss and resupply processes shape the central stellar distribution. We investigate relativistic stellar dynamics near the loss cone of a non-spinning MBH in steady state, analytically and by Monte Carlo simulations of the diffusion of the orbital parameters. These take into account Newtonian mass precession due to enclosed stellar mass, in-plane precession due to general relativity, dissipation by GW, uncorrelated two-body relaxation, correlated resonant relaxation (RR), and adiabatic invariance due to secular precession, using a rigorously derived description of correlated post-Newtonian dynamics in the diffusion limit. We argue that general maximal entropy considerations strongly constrain the orbital diffusion in steady state, irrespective of the relaxation mechanism. We identify the exact phase-space separatrix between plunges and inspirals, and predict their steady-state rates. We derive the dependence of the rates on the mass of the MBH, show that the contribution of RR in steady state is small, and discuss special cases where unquenched RR in restricted volumes of phase-space may affect the steady state substantially.
Analytical models of steady-state plumes undergoing sequential first-order degradation.
Burnell, Daniel K; Mercer, James W; Sims, Lawrence S
2012-01-01
An exact, closed-form analytical solution is derived for one-dimensional (1D), coupled, steady-state advection-dispersion equations with sequential first-order degradation of three dissolved species in groundwater. Dimensionless and mathematical analyses are used to examine the sensitivity of longitudinal dispersivity in the parent and daughter analytical solutions. The results indicate that the relative error decreases to less than 15% for the 1D advection-dominated and advection-dispersion analytical solutions of the parent and daughter when the Damköhler number of the parent decreases to less than 1 (slow degradation rate) and the Peclet number increases to greater than 6 (advection-dominated). To estimate first-order daughter product rate constants in advection-dominated zones, 1D, two-dimensional (2D), and three-dimensional (3D) steady-state analytical solutions with zero longitudinal dispersivity are also derived for three first-order sequentially degrading compounds. The closed form of these exact analytical solutions has the advantage of having (1) no numerical integration or evaluation of complex-valued error function arguments, (2) computational efficiency compared to problems with long times to reach steady state, and (3) minimal effort for incorporation into spreadsheets. These multispecies analytical solutions indicate that BIOCHLOR produces accurate results for 1D steady-state, applications with longitudinal dispersion. Although BIOCHLOR is inaccurate in multidimensional applications with longitudinal dispersion, these multidimensional multispecies analytical solutions indicate that BIOCHLOR produces accurate steady-state results when the longitudinal dispersion is zero. As an application, the 1D advection-dominated analytical solution is applied to estimate field-scale rate constants of 0.81, 0.74, and 0.69/year for trichloroethene, cis-1,2-dichloroethene, and vinyl chloride, respectively, at the Harris Palm Bay, FL, CERCLA site. PMID:21883193
Hydrogen sulfide inhibits the translational expression of hypoxia-inducible factor-1α
Wu, Bo; Teng, Huajian; Yang, Guangdong; Wu, Lingyun; Wang, Rui
2012-01-01
BACKGROUND AND PURPOSE The accumulation of hypoxia-inducible factor-1α (HIF-1α) is under the influence of hydrogen sulfide (H2S), which regulates hypoxia responses. The regulation of HIF-1α accumulation by H2S has been shown, but the mechanisms for this effect are largely elusive and controversial. This study aimed at addressing the controversial mechanisms for and the functional importance of the interaction of H2S and HIF-1α protein. EXPERIMENTAL APPROACH HIF-1α protein levels and HIF-1α transcriptional activity were detected by Western blotting and luciferase assay. The mechanisms for H2S-regulated HIF-1α protein levels were determined using short interfering RNA transfection, co-immunoprecipitation and 7-methyl-GTP sepharose 4B pull-down assay. Angiogenic activity was evaluated using tube formation assay in EA.hy926 cells. KEY RESULTS The accumulation of HIF-1α protein under hypoxia (1% O2) or hypoxia-mimetic conditions was reversed by sodium hydrosulfide (NaHS). This effect of NaHS was not altered after blocking the ubiquitin-proteasomal pathway for HIF-1α degradation; however, blockade of protein translation with cycloheximide abolished the effect of NaHS on the half-life of HIF-1α protein. Knockdown of eukaryotic translation initiation factor 2α (eIF2α) suppressed the effect of NaHS on HIF-1α protein accumulation under hypoxia. NaHS inhibited the expression of VEGF under hypoxia. It also decreased in vitro capillary tube formation and cell proliferation of EA.hy926 cells under hypoxia, but stimulated the tube formation under normoxia. CONCLUSIONS AND IMPLICATIONS H2S suppresses HIF-1α translation by enhancing eIF2α phosphorylation under hypoxia. The interaction of H2S and HIF-1α inhibits the angiogenic activity of vascular endothelial cells under hypoxia through the down-regulation of VEGF. PMID:22831549
A pre-steady state and steady state kinetic analysis of the N-ribosyl hydrolase activity of hCD157.
Preugschat, Frank; Carter, Luke H; Boros, Eric E; Porter, David J T; Stewart, Eugene L; Shewchuk, Lisa M
2014-12-15
hCD157 catalyzes the hydrolysis of nicotinamide riboside (NR) and nicotinic acid riboside (NAR). The release of nicotinamide or nicotinic acid from NR or NAR was confirmed by spectrophotometric, HPLC and NMR analyses. hCD157 is inactivated by a mechanism-based inhibitor, 2'-deoxy-2'-fluoro-nicotinamide arabinoside (fNR). Modification of the enzyme during the catalytic cycle by NR, NAR, or fNR increased the intrinsic protein fluorescence by approximately 50%. Pre-steady state and steady state data were used to derive a minimal kinetic scheme for the hydrolysis of NR. After initial complex formation a reversible step (360 and 30s(-1)) is followed by a slow irreversible step (0.1s(-1)) that defined the rate limiting step, or kcat. The calculated KMapp value for NR in the hydrolytic reaction is 6nM. The values of the kinetic constants suggest that one biological function of cell-surface hCD157 is to bind and slowly hydrolyze NR, possibly converting it to a ligand-activated receptor. Differences in substrate preference between hCD157 and hCD38 were rationalized through a comparison of the crystal structures of the two proteins. This comparison identified several residues in hCD157 (F108 and F173) that can potentially hinder the binding of dinucleotide substrates (NAD+). PMID:25250980
Compatible operation of the power system for steady state and pulse modes in a magnetic torus KT-5D
NASA Astrophysics Data System (ADS)
Yu, Yi; Wang, Zhi-jiang; Xu, Min; Zhu, Zhen-hua; Lu, Rong-hua; Wen, Yi-zhi; Yu, Chang-xuan; Wan, Shu-de; Liu, Wan-dong; Wang, Jun; Xu, Xiao-yuan; Hu, Ling-ying
2006-12-01
Compatible operation of steady state mode and pulse mode is realized in the KT-5D device. New power supplies with the operation control systems for the steady state toroidal magnetic field as well as for the vertical field are added, and the rf wave injection systems for sustaining steady state plasmas are upgraded. After the modification, the device now can work not only as a tokomak with pulsed plasma currents as it was but also as a simple magnetized torus with steady state plasma discharges. It allows more flexible and efficient experimental researches on the magnetically confined plasmas to be carried on in the same device.
Culjkovic-Kraljacic, Biljana; Fernando, Tharu M.; Marullo, Rossella; Calvo-Vidal, Nieves; Verma, Akanksha; Yang, ShaoNing; Tabbò, Fabrizio; Gaudiano, Marcello; Zahreddine, Hiba; Goldstein, Rebecca L.; Patel, Jayeshkumar; Taldone, Tony; Chiosis, Gabriela; Ladetto, Marco; Ghione, Paola; Machiorlatti, Rodolfo; Elemento, Olivier; Inghirami, Giorgio; Melnick, Ari; Borden, Katherine L. B.
2016-01-01
Aggressive double- and triple-hit (DH/TH) diffuse large B-cell lymphomas (DLBCLs) feature activation of Hsp90 stress pathways. Herein, we show that Hsp90 controls posttranscriptional dynamics of key messenger RNA (mRNA) species including those encoding BCL6, MYC, and BCL2. Using a proteomics approach, we found that Hsp90 binds to and maintains activity of eIF4E. eIF4E drives nuclear export and translation of BCL6, MYC, and BCL2 mRNA. eIF4E RNA-immunoprecipitation sequencing in DLBCL suggests that nuclear eIF4E controls an extended program that includes B-cell receptor signaling, cellular metabolism, and epigenetic regulation. Accordingly, eIF4E was required for survival of DLBCL including the most aggressive subtypes, DH/TH lymphomas. Indeed, eIF4E inhibition induces tumor regression in cell line and patient-derived tumorgrafts of TH-DLBCL, even in the presence of elevated Hsp90 activity. Targeting Hsp90 is typically limited by counterregulatory elevation of Hsp70B, which induces resistance to Hsp90 inhibitors. Surprisingly, we identify Hsp70 mRNA as an eIF4E target. In this way, eIF4E inhibition can overcome drug resistance to Hsp90 inhibitors. Accordingly, rational combinatorial inhibition of eIF4E and Hsp90 inhibitors resulted in cooperative antilymphoma activity in DH/TH DLBCL in vitro and in vivo. PMID:26603836
NASA Astrophysics Data System (ADS)
Boulin, P. F.; Bretonnier, P.; Gland, N.
2010-12-01
Very low permeability geomaterials (order of nanoDarcy (10-21 m2)), such as clays rocks, are studied for many industrial applications such as production from unconventional reserves of oil and gas, CO2 geological storage and deep geological disposal of high-level long-lived nuclear wastes. For these last two applications, clay efficiency as barrier relies mainly on their very low permeability. Laboratory measurement of low permeability to water (below 10-19 m2) remains a technical challenge. Some authors argue that steady state methods are irrelevant due to the time required to stabilize water fluxes in such low permeability media. Most of the authors measuring low permeabilities use a transient technique called pulse decay. This study aims to compare objectively these different types of permeability tests performed on a single clay sample. For the steady state method, a high precision pump was used to impose a pressure gradient and to measure the small resulting water flow rate at steady state. We show that with a suitable set-up, the steady state method enables to measure a very low permeability of 8 10-22 m2 in a period of three days. For a comparable duration, the pulse decay test, most commonly used for such low permeability measurements, provides only an average estimate of the permeability. Permeability measurements by pulse decay require to perform simulations to interpret the pressure relaxation signals. Many uncertainties remain such as the determination of the reservoirs storage factor, micro leakage effect, or the determination of the initial pulse pressure. All these uncertainties have a very significant impact on the determination of sample permeability and specific storage. Opposite to the wide-spread idea that transient techniques are required to measure very low permeability, we show that direct steady state measurement of water permeability with suitable equipments can be much faster and more accurate than measurement by pulse decay, especially in
Steady-State Cycle Deck Launcher Developed for Numerical Propulsion System Simulation
NASA Technical Reports Server (NTRS)
VanDrei, Donald E.
1997-01-01
One of the objectives of NASA's High Performance Computing and Communications Program's (HPCCP) Numerical Propulsion System Simulation (NPSS) is to reduce the time and cost of generating aerothermal numerical representations of engines, called customer decks. These customer decks, which are delivered to airframe companies by various U.S. engine companies, numerically characterize an engine's performance as defined by the particular U.S. airframe manufacturer. Until recently, all numerical models were provided with a Fortran-compatible interface in compliance with the Society of Automotive Engineers (SAE) document AS681F, and data communication was performed via a standard, labeled common structure in compliance with AS681F. Recently, the SAE committee began to develop a new standard: AS681G. AS681G addresses multiple language requirements for customer decks along with alternative data communication techniques. Along with the SAE committee, the NPSS Steady-State Cycle Deck project team developed a standard Application Program Interface (API) supported by a graphical user interface. This work will result in Aerospace Recommended Practice 4868 (ARP4868). The Steady-State Cycle Deck work was validated against the Energy Efficient Engine customer deck, which is publicly available. The Energy Efficient Engine wrapper was used not only to validate ARP4868 but also to demonstrate how to wrap an existing customer deck. The graphical user interface for the Steady-State Cycle Deck facilitates the use of the new standard and makes it easier to design and analyze a customer deck. This software was developed following I. Jacobson's Object-Oriented Design methodology and is implemented in C++. The AS681G standard will establish a common generic interface for U.S. engine companies and airframe manufacturers. This will lead to more accurate cycle models, quicker model generation, and faster validation leading to specifications. The standard will facilitate cooperative work between
MicroRNAs inhibit the translation of target mRNAs on the endoplasmic reticulum in Arabidopsis.
Li, Shengben; Liu, Lin; Zhuang, Xiaohong; Yu, Yu; Liu, Xigang; Cui, Xia; Ji, Lijuan; Pan, Zhiqiang; Cao, Xiaofeng; Mo, Beixin; Zhang, Fuchun; Raikhel, Natasha; Jiang, Liwen; Chen, Xuemei
2013-04-25
Translation inhibition is a major but poorly understood mode of action of microRNAs (miRNAs) in plants and animals. In particular, the subcellular location where this process takes place is unknown. Here, we show that the translation inhibition, but not the mRNA cleavage activity, of Arabidopsis miRNAs requires ALTERED MERISTEM PROGRAM1 (AMP1). AMP1 encodes an integral membrane protein associated with endoplasmic reticulum (ER) and ARGONAUTE1, the miRNA effector and a peripheral ER membrane protein. Large differences in polysome association of miRNA target RNAs are found between wild-type and the amp1 mutant for membrane-bound, but not total, polysomes. This, together with AMP1-independent recruitment of miRNA target transcripts to membrane fractions, shows that miRNAs inhibit the translation of target RNAs on the ER. This study demonstrates that translation inhibition is an important activity of plant miRNAs, reveals the subcellular location of this activity, and uncovers a previously unknown function of the ER. PMID:23622241
miR-17 regulates melanoma cell motility by inhibiting the translation of ETV1.
Cohen, Ronit; Greenberg, Eyal; Nemlich, Yael; Schachter, Jacob; Markel, Gal
2015-08-01
Melanoma is an aggressive malignancy with a high metastatic potential. microRNA-17 (miR-17) is a member of the oncogenic miR-17/92 cluster. Here we study the effect of miR-17 on melanoma cell motility. Over expression of the mature or pri-microRNA form of miR-17 in WM-266-4 and 624mel melanoma lines enhances cell motility, evident in both wound healing and transwell migration assays. TargetScan algorithm predicts the PEA3-subfamily member ETV1 as a direct target of miR-17. Indeed, a 3-4-fold decrease of ETV1 protein levels are observed following miR-17 transfection into the various melanoma lines, with no significant change in ETV1 mRNA expression. Dual luciferase experiments demonstrate direct binding of miR-17 to the 3'-untranslated region of ETV1, confirmed by abolishing point mutations in the putative binding site. These combined results suggest regulation of ETV1 by miR-17 by a direct translational repression. Further, in both melanoma cell lines ETV1 knockdown by selective siRNA successfully pheno-copies the facilitated cell migration, while overexpression of ETV1 inhibits cell motility and migration. Altered ETV1 expression does not affect melanoma net-proliferation. In conclusion, we show a new role for miR-17 in melanoma, facilitating cell motility, by targeting the translation of ETV1 protein, which may support the development of metastasis. PMID:26158900
An S6:S18 complex inhibits translation of E. coli rpsF
Babina, Arianne M.; Soo, Mark W.; Fu, Yang; Meyer, Michelle M.
2015-01-01
More than half of the ribosomal protein operons in Escherichia coli are regulated by structures within the mRNA transcripts that interact with specific ribosomal proteins to inhibit further protein expression. This regulation is accomplished using a variety of mechanisms and the RNA structures responsible for regulation are often not conserved across bacterial phyla. A widely conserved mRNA structure preceding the ribosomal protein operon containing rpsF and rpsR (encoding S6 and S18) was recently identified through comparative genomics. Examples of this RNA from both E. coli and Bacillus subtilis were shown to interact in vitro with an S6:S18 complex. In this work, we demonstrate that in E. coli, this RNA structure regulates gene expression in response to the S6:S18 complex. β-galactosidase activity from a lacZ reporter translationally fused to the 5′ UTR and first nine codons of E. coli rpsF is reduced fourfold by overexpression of a genomic fragment encoding both S6 and S18 but not by overexpression of either protein individually. Mutations to the mRNA structure, as well as to the RNA-binding site of S18 and the S6–S18 interaction surfaces of S6 and S18, are sufficient to derepress β-galactosidase activity, indicating that the S6:S18 complex is the biologically active effector. Measurement of transcript levels shows that although reporter levels do not change upon protein overexpression, levels of the native transcript are reduced fourfold, suggesting that the mRNA regulator prevents translation and this effect is amplified on the native transcript by other mechanisms. PMID:26447183
NASA Astrophysics Data System (ADS)
Dubbert, Maren; Kübert, Angelika; Cuntz, Matthias; Werner, Christiane
2015-04-01
Isotope techniques are widely applied in ecosystem studies. For example, isoflux models are used to separate soil evaporation from transpiration in ecosystems. These models often assume that plant transpiration occurs at isotopic steady state, i.e. that the transpired water shows the same isotopic signature as the source water. Yet, several studies found that transpiration did not occur at isotopic steady state, under both controlled and field conditions. Here we focused on identifying the internal and external factors which drive the isotopic signature of leaf transpiration. Using cavity ring-down spectroscopy (CRDS), the effect of both environmental variables and leaf physiological traits on δ18OT was investigated under controlled conditions. Six plant species with distinct leaf physiological traits were exposed to step changes in relative air humidity (RH), their response in δ18OT and gas exchange parameters and their leaf physiological traits were assessed. Moreover, two functionally distinct plant types (tree, i.e. Quercus suber, and grassland) of a semi-arid Mediterranean oak-woodland where observed under natural conditions throughout an entire growth period in the field. The species differed substantially in their leaf physiological traits and their turn-over times of leaf water. They could be grouped in species with fast (<60 min.), intermediate (ca. 120 min.) and slow (>240 min.) turn-over times, mostly due to differences in stomatal conductance, leaf water content or a combination of both. Changes in RH caused an immediate response in δ18OT, which were similarly strong in all species, while leaf physiological traits affected the subsequent response in δ18OT. The turn-over time of leaf water determined the speed of return to the isotopic steady or a stable δ18OT value (Dubbert & Kübert et al., in prep.). Under natural conditions, changes in environmental conditions over the diurnal cycle had a huge impact on the diurnal development of δ18OT in both
Steady states and global dynamics of electrical activity in the cerebral cortex
NASA Astrophysics Data System (ADS)
Robinson, P. A.; Rennie, C. J.; Wright, J. J.; Bourke, P. D.
1998-09-01
Steady states and global dynamics of electrical activity in the cerebral cortex are investigated within the framework of a recent continuum model. It is shown that for a particular physiologically realistic class of models, at most three steady states can occur, two of which are stable. The global dynamics of spatially uniform activity states is studied and it is shown that in a physiologically realistic class of models, the adiabatic dynamics is governed by a second-order differential equation equivalent to that for the motion of a Newtonian particle in a potential in the presence of friction. This result is used to derive a simplified dynamical equation in the friction-dominated limit. Solutions of these equations are compared with those of the full global dynamics equations and it is found that they are adequate for time scales longer than approximately 100 ms provided dendritic integration times are less than approximately 10 ms.
NASA Astrophysics Data System (ADS)
Darko, Godfred; Goethals, Annelies; Torto, Nelson; De Clerck, Karen
2015-10-01
Electrospinning is the most promising method for the large-scale production of nanofiber membranes. Multi-nozzle systems have already proven to be successful in producing polyamide nanofiber membranes suitable for water filtration. In this contribution, conditions for steady state electrospinning of polyethersulphone were investigated. Steady state electrospinning of PES was only possible for a limited number of electrospinning parameter combinations. Only a polymer concentration of 25 and 26 wt% resulted in defect-free nanofiber membranes. The solvent ratio of DMF:NMP can be varied from 95:5 (v:v%) to 85:15 (v:v%) to generate uniform nanofibers with average diameters varying from 300 to 730 nm all with relatively narrow standard deviation as low as 20 %. These results, thus, allow for a well-chosen set of electrospinning parameters for scaling up electrospinning of polyethersulphone nanofiber membranes.
Numerical determination of entropy associated with excess heat in steady-state thermodynamics
NASA Astrophysics Data System (ADS)
Chiba, Yoshiyuki; Nakagawa, Naoko
2016-08-01
We numerically determine the global entropy for heat-conducting states, which is connected to the so-called excess heat considered as a basic quantity for steady-state thermodynamics in nonequilibrium. We adopt an efficient method to estimate the global entropy from the bare heat current and find that the obtained entropy agrees with the familiar local equilibrium hypothesis well. Our method possesses a wider applicability than local equilibrium and opens a possibility to compare thermodynamic properties of complex systems in nonequilibrium with those in the local equilibrium. We further investigate the global entropy for heat-conducting states and find that it exhibits both extensive and additive properties; however, the two properties do not degenerate each other differently from those at equilibrium. The separation of the extensivity and additivity makes it difficult to apply powerful thermodynamic methods to the nonequilibrium steady states.
An Insightful Steady-State Performance of a Squirrel Cage Induction Generator Enhanced with STATCOM
NASA Astrophysics Data System (ADS)
Ojo, Olorunfemi; Khayamy, Mehdy; Bule, Mehari
2014-06-01
This paper presents the regulation of the terminal voltage and reactive power of a grid-connected squirrel cage induction generator. A shunt connected voltage source inverter (VSI) with a capacitor in the DC side operating as a Static Compensator (STATCOM) and a shunt capacitor are used for regulating the generator terminal voltage and limit the reactive power demand from the grid. Simulation results for steady-state operation for a wide variation of speed in the super-synchronous region are presented as well as the dynamic stability of the system. Closed-form steady-state characteristics equations for the system are used to determine key variables and to demonstrate how the operation of the system depends on various parameters. This characteristics curve which contains all of the equations of the system provides the all in one insightful view to the inherent characteristics of the system and the effect of the parameter variation on the terminal voltage plane.
Padma, S; Hariharan, G
2016-06-01
In this paper, we have developed an efficient wavelet based approximation method to biofilm model under steady state arising in enzyme kinetics. Chebyshev wavelet based approximation method is successfully introduced in solving nonlinear steady state biofilm reaction model. To the best of our knowledge, until now there is no rigorous wavelet based solution has been addressed for the proposed model. Analytical solutions for substrate concentration have been derived for all values of the parameters δ and SL. The power of the manageable method is confirmed. Some numerical examples are presented to demonstrate the validity and applicability of the wavelet method. Moreover the use of Chebyshev wavelets is found to be simple, efficient, flexible, convenient, small computation costs and computationally attractive. PMID:26661721
Shock waves, rarefaction waves, and nonequilibrium steady states in quantum critical systems
NASA Astrophysics Data System (ADS)
Lucas, Andrew; Schalm, Koenraad; Doyon, Benjamin; Bhaseen, M. J.
2016-07-01
We reexamine the emergence of a universal nonequilibrium steady state following a local quench between quantum critical heat baths in spatial dimensions greater than one. We show that energy transport proceeds by the formation of an instantaneous shock wave and a broadening rarefaction wave on either side of the interface, and not by two shock waves as previously proposed. For small temperature differences the universal steady state energy currents of the two-shock and rarefaction-shock solutions coincide. Over a broad range of parameters, the difference in the energy flow across the interface between these two solutions is at the level of 2%. The properties of the energy flow remain fully universal and independent of the microscopic theory. We briefly discuss the width of the shock wave in a viscous fluid, the effects of momentum relaxation, and the generalization to charged fluids.
Moving-Surface Plasma-Facing Components for Particle Control in Steady State Magnetic Fusion Devices
Hirooka, Yoshi; Fukushima, Hoju; Ohno, Noriyasu; Takamura, Shuichi; Nishikawa, Masahiro
2004-01-15
This paper will report on the proof-of-principle (POP) experiments conducted to demonstrate reduced wall recycling, using a laboratory-scale test unit, constructed based on the concept of moving-surface plasma-facing component (MS-PFC). In this concept, the moving-surface exposed to edge plasmas in steady state magnetic fusion devices is continuously deposited ex-situ with a getter material, so that particle trapping capabilities can be regenerated prior to the subsequent exposure. In our previous paper, the construction details of the MS-PFC test unit and the first results in the case of titanium gettering was reported, but in the present paper preliminary results in the case of lithium gettering will be presented for comparison. Results indicate that the H{sub {alpha}} light intensity used as the measure of hydrogen recycling is reduced by {approx}6% due to titanium gettering and by {approx}12% due to lithium gettering, both at steady state.
Kabir, M. Z.; Imam, Safayat-Al
2013-04-15
A theoretical model for describing bias-dependent transient and steady-state behaviors of dark current in amorphous selenium (a-Se) avalanche detector structures has been developed. The analytical model considers bulk thermal generation current from mid-gap sates, transient carrier depletion, and carrier injection from the electrodes incorporating avalanche multiplication. The proposed physics-based dark current model is compared with the published experimental results on three potential a-Se avalanche detector structures. The steady-state dark current is the minimum for the structures that have effective blocking layers for both holes and electrons. The transient decay time to reach a plateau decreases considerably with increasing electric field.
Steady State Properties of Lock-On Current Filaments in GaAs
NASA Astrophysics Data System (ADS)
Kambour, K.; Kang, Samsoo; Myles, Charles W.; Hjalmarson, Harold P.
1999-10-01
Collective impact ionization has been used by Hjalmarson et al.(H. Hjalmarson, F. Zutavern, G. Loubriel, A. Baca, and D. Wake, Sandia Report SAND93-3972(1996).) to explain the lock-on effect, observed in optically activated, semi-insulating GaAs switches. We have used this theory to study some of the steady state properties of the lock-on current filaments which accompany this effect. In steady state, the energy gained from the electric field is exactly compensated for by the the energy lost due to the phonon cooling of the hot carriers. In the simplest approximation, the carrier distribution approaches a quasi-equilibrium Maxwell-Boltzmann distribution. In this presentation we report preliminary results on the validity of this quasi-equilibrium approximation. We find that this approximation leads to a filament carrier density which is much lower than the high density needed to achieve a quasi-equilibrium distribution. Further work is in progress.
PEBBLE: a two-dimensional steady-state pebble bed reactor thermal hydraulics code
Vondy, D.R.
1981-09-01
This report documents the local implementation of the PEBBLE code to treat the two-dimensional steady-state pebble bed reactor thermal hydraulics problem. This code is implemented as a module of a computation system used for reactor core history calculations. Given power density data, the geometric description in (RZ), and basic heat removal conditions and thermal properties, the coolant properties, flow conditions, and temperature distributions in the pebble fuel elements are predicted. The calculation is oriented to the continuous fueling, steady state condition with consideration of the effect of the high energy neutron flux exposure and temperature history on the thermal conductivity. The coolant flow conditions are calculated for the same geometry as used in the neutronics calculation, power density and fluence data being used directly, and temperature results are made available for subsequent use.
On the Numerical Convergence to Steady State of Hypersonic Flows Over Bodies with Concavities
NASA Technical Reports Server (NTRS)
Gnoffo, Peter A.
2002-01-01
Two recent numerical studies of hypersonic flows over bodies with concavities revealed problems with convergence to a steady state with an oft-used application of local-time-stepping. Both simulated flows showed a time-like, periodic shedding of vortices in a subsonic domain bounded by supersonic external flow although the simulations, using local-time-stepping, were not time accurate. Simple modifications to the numerical algorithm were implemented to enable implicit, first-order accurate in time simulations. Subsequent time-accurate simulations of the two test problems converged to a steady state. The baseline algorithm and modifications for temporal accuracy are described. The requirement for sub-iterations to achieve convergence is demonstrated. Failure to achieve convergence without time accuracy is conjectured to arise from temporal errors being continuously refocused into a subsonic domain.
NASA Astrophysics Data System (ADS)
Darko, Godfred; Goethals, Annelies; Torto, Nelson; De Clerck, Karen
2016-08-01
Electrospinning is the most promising method for the large-scale production of nanofiber membranes. Multi-nozzle systems have already proven to be successful in producing polyamide nanofiber membranes suitable for water filtration. In this contribution, conditions for steady state electrospinning of polyethersulphone were investigated. Steady state electrospinning of PES was only possible for a limited number of electrospinning parameter combinations. Only a polymer concentration of 25 and 26 wt% resulted in defect-free nanofiber membranes. The solvent ratio of DMF:NMP can be varied from 95:5 (v:v%) to 85:15 (v:v%) to generate uniform nanofibers with average diameters varying from 300 to 730 nm all with relatively narrow standard deviation as low as 20 %. These results, thus, allow for a well-chosen set of electrospinning parameters for scaling up electrospinning of polyethersulphone nanofiber membranes.
A computer simulation using spreadsheets for learning concept of steady-state equilibrium
NASA Astrophysics Data System (ADS)
Sharda, Vandana; Sastri, O. S. K. S.; Bhardwaj, Jyoti; Jha, Arbind K.
2016-03-01
In this paper, we present a simple spreadsheet based simulation activity that can be performed by students at the undergraduate level. This simulation is implemented in free open source software (FOSS) LibreOffice Calc, which is available for both Windows and Linux platform. This activity aims at building the probability distribution for the possible macro-states of a system. This has been achieved by randomly sampling the configuration space consisting of all the possible microstates and determining the corresponding macrostate for each of the samples, which is akin to Monte-Carlo simulation. This simulation could act as a very useful tool in engaging students for learning the concepts of microstates, macrostates and steady state equilibrium, once the ideas have been introduced in the classroom. Further, the effect of the number of particles on the quality of steady state equilibrium achieved demonstrates the idea of thermodynamic limit.
Fu, H.; Haken, H.
1988-05-01
A semiclassical theory of dye lasers is presented in which the relevant energy-level diagram of a dye molecule is assumed to consist of a bandlike ground state with many sublevels and an excited single state. This theory not only describes the single-frequency operation, which has a low instability threshold, but also describes the two-frequency and multifrequency steady states of operation and the transitions between the different steady states. The general solution of a multifrequency operation is given explicitly and differs essentially from the well-known Rabi oscillation. The theoretical predictions are in good agreement with recent experiments done by Hillman et al. (Phys. Rev. Lett. 52, 1605 (1984)), which cannot be explained by the conventional Maxwell--Bloch laser theory derived from two-level atoms.
Steady-state boundary lubrication with formulated C-ethers to 260 C
NASA Technical Reports Server (NTRS)
Loomis, W. R.
1981-01-01
Steady state wear and friction studies were made at boundary lubrication conditions in a pin on disk (pure iron on rotating CVM M 50 steel) sliding friction apparatus with five C ether formulated fluids (modified polyphenyl ether containing phosphrous ester, organic acid, and other additives). Conditions included 20, 150, and 260 C disk temperatures, dry air test atmosphere, 1 kilogram load, 50 rpm disk speed, and test times to 130 minutes. Results were compared with those obtained with a formulated MIL L 27502 candidate ester and the C ether base fluid. Three of the C ether formulations gave better lubrication than both reference fluids under most conditions. The other two C ether formulations yielded higher wear rates and friction coefficients than the C ether base fluid for most of the temperature range. Only one C ether formulation showed consistently higher steady state wear rates than the ester.
Transition from homogeneous to inhomogeneous steady states in oscillators under cyclic coupling
NASA Astrophysics Data System (ADS)
Bera, Bidesh K.; Hens, Chittaranjan; Bhowmick, Sourav K.; Pal, Pinaki; Ghosh, Dibakar
2016-01-01
We report a transition from homogeneous steady state to inhomogeneous steady state in coupled oscillators, both limit cycle and chaotic, under cyclic coupling and diffusive coupling as well when an asymmetry is introduced in terms of a negative parameter mismatch. Such a transition appears in limit cycle systems via pitchfork bifurcation as usual. Especially, when we focus on chaotic systems, the transition follows a transcritical bifurcation for cyclic coupling while it is a pitchfork bifurcation for the conventional diffusive coupling. We use the paradigmatic Van der Pol oscillator as the limit cycle system and a Sprott system as a chaotic system. We verified our results analytically for cyclic coupling and numerically check all results including diffusive coupling for both the limit cycle and chaotic systems.
Development of repetitive railgun pellet accelerator and steady-state pellet supply system
Oda, Y.; Onozuka, M.; Azuma, K.; Kasai, S.; Hasegawa, K.
1995-12-31
A railgun system for repetitive high-speed pellet acceleration and steady-state pellet supply system has been developed and investigated. Using a 2m-long railgun system, the hydrogen pellet was accelerated to 2.6km/sec by the supplied energy of 1.7kJ. It is expected that the hydrogen pellet can be accelerated to 3km/sec using the present pneumatic pellet accelerator and a 2m-long augment railgun. Screw-driven hydrogen-isotope filament extruding system has been fabricated and will be tested to examine its applicability to the steady-state extrusion of the solid hydrogen-isotope filament.
Comparison of steady-state and transient CVS cycle emission of an automotive Stirling engine
NASA Technical Reports Server (NTRS)
Farrell, R. A.; Bolton, R. J.
1983-01-01
The Automotive Stirling Engine Development Program is to demonstrate a number of goals for a Stirling-powered vehicle. These goals are related to an achievement of specified maximum emission rates, a combined cycle fuel economy 30 percent better than a comparable internal-combustion engine-powered automobile, multifuel capability, competitive cost and reliability, and a meeting of Federal standards concerning noise and safety. The present investigation is concerned with efforts related to meeting the stringent emission goals. Attention is given to the initial development of a procedure for predicting transient CVS urban cycle gaseous emissions from steady-state engine data, taking into account the employment of the test data from the first-generation automotive Stirling engine. A large amount of steady-state data from three Mod I automotive Stirling engines were used to predict urban CVS cycle emissions for the Mod I Lerma vehicle.
Steady-State Dynamic Behavior of a Flexible Rotor With Auxiliary Support From a Clearance Bearing
NASA Technical Reports Server (NTRS)
Xie, Huajun; Flowers, George T.; Feng, Li; Lawrence, Charles T.
1996-01-01
This paper investigates the steady-state responses of a rotor system supported by auxiliary bearings in which there is a clearance between the rotor and the inner race of the bearing. A simulation model based upon the rotor of a production jet engine is developed and its steady-state behavior is explored over a wide range of operating conditions for various parametric configurations. Specifically, the influence of rotor imbalance, clearance, support stiffness and damping is studied. Bifurcation diagrams are used as a tool to examine the dynamic behavior of this system as a function of the afore mentioned parameters. The harmonic balance method is also employed for synchronous response cases. The observed dynamical responses is discussed and some insights into the behavior of such systems are presented.
Steady-State Somatosensory Evoked Potential for Brain-Computer Interface—Present and Future
Ahn, Sangtae; Kim, Kiwoong; Jun, Sung Chan
2016-01-01
Brain-computer interface (BCI) performance has achieved continued improvement over recent decades, and sensorimotor rhythm-based BCIs that use motor function have been popular subjects of investigation. However, it remains problematic to introduce them to the public market because of their low reliability. As an alternative resolution to this issue, visual-based BCIs that use P300 or steady-state visually evoked potentials (SSVEPs) seem promising; however, the inherent visual fatigue that occurs with these BCIs may be unavoidable. For these reasons, steady-state somatosensory evoked potential (SSSEP) BCIs, which are based on tactile selective attention, have gained increasing attention recently. These may reduce the fatigue induced by visual attention and overcome the low reliability of motor activity. In this literature survey, recent findings on SSSEP and its methodological uses in BCI are reviewed. Further, existing limitations of SSSEP BCI and potential future directions for the technique are discussed. PMID:26834611
NASA Astrophysics Data System (ADS)
Meerson, Baruch
2015-05-01
Suppose that a point-like steady source at x = 0 injects particles into a half-infinite line. The particles diffuse and die. At long times a non-equilibrium steady state sets in, and we assume that it involves many particles. If the particles are non-interacting, their total number N in the steady state is Poisson-distributed with mean \\bar{N} predicted from a deterministic reaction-diffusion equation. Here we determine the most likely density history of this driven system conditional on observing a given N. We also consider two prototypical examples of interacting diffusing particles: (i) a family of mortal diffusive lattice gases with constant diffusivity (as illustrated by the simple symmetric exclusion process with mortal particles), and (ii) random walkers that can annihilate in pairs. In both examples we calculate the variances of the (non-Poissonian) stationary distributions of N.
Iterative solutions to the steady-state density matrix for optomechanical systems.
Nation, P D; Johansson, J R; Blencowe, M P; Rimberg, A J
2015-01-01
We present a sparse matrix permutation from graph theory that gives stable incomplete lower-upper preconditioners necessary for iterative solutions to the steady-state density matrix for quantum optomechanical systems. This reordering is efficient, adding little overhead to the computation, and results in a marked reduction in both memory and runtime requirements compared to other solution methods, with performance gains increasing with system size. Either of these benchmarks can be tuned via the preconditioner accuracy and solution tolerance. This reordering optimizes the condition number of the approximate inverse and is the only method found to be stable at large Hilbert space dimensions. This allows for steady-state solutions to otherwise intractable quantum optomechanical systems. PMID:25679739
Diagnostics and control for the steady state and pulsed tokamak DEMO
NASA Astrophysics Data System (ADS)
Orsitto, F. P.; Villari, R.; Moro, F.; Todd, T. N.; Lilley, S.; Jenkins, I.; Felton, R.; Biel, W.; Silva, A.; Scholz, M.; Rzadkiewicz, J.; Duran, I.; Tardocchi, M.; Gorini, G.; Morlock, C.; Federici, G.; Litnovsky, A.
2016-02-01
The present paper is devoted to a first assessment of the DEMO diagnostics systems and controls in the context of pulsed and steady state reactor design under study in Europe. In particular, the main arguments treated are: (i) The quantities to be measured in DEMO and the requirements for the measurements; (ii) the present capability of the diagnostic and control technology, determining the most urgent gaps, and (iii) the program and strategy of the research and development (R&D) needed to fill the gaps. Burn control, magnetohydrodynamic stability, and basic machine protection require improvements to the ITER technology, and moderated efforts in R&D can be dedicated to infrared diagnostics (reflectometry, electron cyclotron emission, polarimetry) and neutron diagnostics. Metallic Hall sensors appear to be a promising candidate for magnetic measurements in the high neutron fluence and long/steady state discharges of DEMO.
Liu, H. H.
2010-09-15
Optimality principles have been used for investigating physical processes in different areas. This work attempts to apply an optimal principle (that water flow resistance is minimized on global scale) to steady-state unsaturated flow processes. Based on the calculus of variations, we show that under optimal conditions, hydraulic conductivity for steady-state unsaturated flow is proportional to a power function of the magnitude of water flux. This relationship is consistent with an intuitive expectation that for an optimal water flow system, locations where relatively large water fluxes occur should correspond to relatively small resistance (or large conductance). Similar results were also obtained for hydraulic structures in river basins and tree leaves, as reported in other studies. Consistence of this theoretical result with observed fingering-flow behavior in unsaturated soils and an existing model is also demonstrated.
Development of a plasma control system for steady-state operation on QUEST
NASA Astrophysics Data System (ADS)
Hasegwa, Makoto; Nakamura, Kazuo; Zushi, Hideki; Hanada, Kazuaki; Fujisawa, Akihide; Matsuoka, Keisuke; Idei, Hiroshi; Nagashima, Yoshihiko; Tokunaga, Kazutoshi; Kawasaki, Shoji; Nakashima, Hisatoshi; Higashijima, Aki
2014-10-01
A drift error correction technique with machine vision and a real-time equilibrium calculation code have been developed on the QUEST (Q-shu university experiment with the steady-state spherical tokamak) for steady-state operation. The drift error caused by the long time-integration of magnetic raw signals has to be removed. With a captured image of the plasma's cross section, the plasma's position is identified by use of image filters. The measured magnetic flux values are corrected to the calculated flux values estimated by using this plasma position. The correction with the captured image work as expected in the preliminary result using a flashlight instead of a plasma.
Robust random number generation using steady-state emission of gain-switched laser diodes
Yuan, Z. L. Lucamarini, M.; Dynes, J. F.; Fröhlich, B.; Plews, A.; Shields, A. J.
2014-06-30
We demonstrate robust, high-speed random number generation using interference of the steady-state emission of guaranteed random phases, obtained through gain-switching a semiconductor laser diode. Steady-state emission tolerates large temporal pulse misalignments and therefore significantly improves the interference quality. Using an 8-bit digitizer followed by a finite-impulse-response unbiasing algorithm, we achieve random number generation rates of 8 and 20 Gb/s, for laser repetition rates of 1 and 2.5 GHz, respectively, with a ±20% tolerance in the interferometer differential delay. We also report a generation rate of 80 Gb/s using partially phase-correlated short pulses. In relation to the field of quantum key distribution, our results confirm the gain-switched laser diode as a suitable light source, capable of providing phase-randomized coherent pulses at a clock rate of up to 2.5 GHz.
NASA Technical Reports Server (NTRS)
Wang, Jai-Ching
1994-01-01
The lateral solute segregation that results from a curved solid-liquid interface shape during steady state unidirectional solidification of a binary alloy system has been studied both analytically and numerically by Coriell, Bosivert, Rehm, and Sekerka. The system under their study is a two dimensional rectangular system. However, most real growth systems are cylindrical systems. Thus, in a previous study, we have followed Coriell etc. formalism and obtained analytical results for lateral solute segregation for an azimuthal symmetric cylindrical binary melt system during steady state solidification process. The solid-liquid interface shape is expressed as a series combination of Bessel functions. In this study a computer program has been developed to simulate the lateral solute segregation.
An analytical solution for the steady-state aerosol size distribution achieved in a steady-state, continuous flow chamber is derived, where particle growth is occurring by gas-to-particle conversion and particle loss is occurring by deposition to the walls of the chamber. The s...
NASA Technical Reports Server (NTRS)
Bowman, L. M.
1984-01-01
An interactive steady state frequency response computer program with graphics is documented. Single or multiple forces may be applied to the structure using a modal superposition approach to calculate response. The method can be reapplied to linear, proportionally damped structures in which the damping may be viscous or structural. The theoretical approach and program organization are described. Example problems, user instructions, and a sample interactive session are given to demonstate the program's capability in solving a variety of problems.
Non-steady-state transport of superthermal electrons in the plasmasphere
NASA Technical Reports Server (NTRS)
Khazanov, George V.; Liemohn, Michael W.; Gombosi, Tamas I.; Nagy, Andrew F.
1993-01-01
Numerical solutions to the time-dependent kinetic equation, which describes the transport of superthermal electrons in the splasmasphere between the two conjugate ionospheres, are presented. The model calculates the distribution function as a function of time, field-aligned distance, energy, and pitch-angle. The processes of refilling, depleting, and establishing steady-state conditions of superthermal electrons in the plasmasphere are discussed.
Brennan, Rachel A.; Sanford, Robert A.
2002-01-01
Tenax-TA, a solid-phase sorbent, was used as an alternative to hexadecane for continuous delivery of tetrachloroethene (PCE) to Desulfuromonas strain BB1, a chloro-respiring microorganism. In both batch and bioreactor configurations, Tenax not only maintained low, steady-state concentrations of PCE in an active culture for several months but also adsorbed the product of dechlorination, cis-1,2-dichloroethene, before it approached toxic levels. PMID:11872503
Evidence for forcing-dependent steady states in a turbulent swirling flow.
Saint-Michel, B; Dubrulle, B; Marié, L; Ravelet, F; Daviaud, F
2013-12-01
We study the influence on steady turbulent states of the forcing in a von Karman flow, at constant impeller speed, or at constant torque. We find that the different forcing conditions change the nature of the stability of the steady states and reveal dynamical regimes that bear similarities to low-dimensional systems. We suggest that this forcing dependence may be applicable to other turbulent systems. PMID:24476277
Resonant loop antenna design with a 2-D steady state analysis
Chen, G.I.; Ryan, P.M.; Hoffman, D.J.; Baity, F.W.; Swain, D.W.; Whealton, J.H.
1987-01-01
Evaluation of resonant loop antenna designs for ICRF heating of plasmas requires information concerning the electrical characteristics of the structure. Our 2-D steady state model described herein provides us with current strap inductance and capacitance, surface current distributions, and flux linkage to the plasma. These are used to determine the current and voltage requirements, ohmic dissipation, frequency limits and matching requirements, maximum electric fields, and plasma loading in order to compare antenna designs.
Ascon-Cabrera, M A; Thomas, D; Lebeault, J M
1995-01-01
The maintenance of a steady-state biofilm in a continuous-flow fixed-bed reactor, as a consequence of the reproduction-detachment of cells (an interfacial cell physiology phenomenon of steady-state biofilm) during the biodegradation of 2,4,6-trichlorophenol by Pseudomonas cells, was determined. After cell adhesion on an open-pore glass support, the biofilm was formed in a packed-bed recirculated reactor. After the steady-state biofilm was reached, the mechanisms of the interfacial cell detachment (at the biofilm-liquid interface) were determined. It was established that (i) the hydrophobicity of immobilized sessile cells (parent cells) increased (from 50 to 80%) as the dilution rate increased, while the hydrophobicity of detached suspended cells (daughter cells) remained constant (about 45%); and (ii) the immediately detached suspended cells showed a synchronized growth in about three generations. These results indicate that (i) the immobilized sessile and suspended detached cells grew synchronically at the end and at the beginning of the cell cycle, respectively; and (ii) the hydrophobicity difference of immobilized sessile and suspended detached cells permitted the cells detachment. Therefore, it is probable that independent of shear stress (due to recirculated flow), the synchronized growth and hydrophobicity of cells (which vary during the cell cycle) are the main factors permitting the maintenance of a steady-state xenobiotic-degrading biofilm reactor (in which the overall accumulation of biofilm is determined by the average growth rate of the biofilm cells minus the rate of detachment of cells from the biofilm). PMID:7793923
Steady-state and dynamic flux balance analysis of ethanol production by Saccharomyces cerevisiae.
Hjersted, J L; Henson, M A
2009-05-01
Steady-state and dynamic flux balance analysis (DFBA) was used to investigate the effects of metabolic model complexity and parameters on ethanol production predictions for wild-type and engineered Saccharomyces cerevisiae. Three metabolic network models ranging from a single compartment representation of metabolism to a genome-scale reconstruction with seven compartments and detailed charge balancing were studied. Steady-state analysis showed that the models generated similar wild-type predictions for the biomass and ethanol yields, but for ten engineered strains the seven compartment model produced smaller ethanol yield enhancements. Simplification of the seven compartment model to two intracellular compartments produced increased ethanol yields, suggesting that reaction localisation had an impact on mutant phenotype predictions. Further analysis with the seven compartment model demonstrated that steady-state predictions can be sensitive to intracellular model parameters, with the biomass yield exhibiting high sensitivity to ATP utilisation parameters and the biomass composition. The incorporation of gene expression data through the zeroing of metabolic reactions associated with unexpressed genes was shown to produce negligible changes in steady-state predictions when the oxygen uptake rate was suitably constrained. Dynamic extensions of the single and seven compartment models were developed through the addition of glucose and oxygen uptake expressions and transient extracellular balances. While the dynamic models produced similar predictions of the optimal batch ethanol productivity for the wild type, the single compartment model produced significantly different predictions for four implementable gene insertions. A combined deletion/overexpression/insertion mutant with improved ethanol productivity capabilities was computationally identified by dynamically screening multiple combinations of the ten metabolic engineering strategies. The authors concluded that
Comparison of experimental data to a model for bicycle steady-state turning
NASA Astrophysics Data System (ADS)
Cain, Stephen M.; Perkins, Noel C.
2012-08-01
The steady-state turning of a bicycle arises when the bicycle/rider system negotiates a constant radius turn with constant speed and roll angle. This paper explores steady-state turning by employing a bicycle instrumented to measure steering torque, steering angle, and bicycle speed, acceleration, and angular velocity. We report data obtained from 134 trials using two subjects executing steady turns defined by nine different radii, three speeds, and three rider lean conditions. A model for steady-state turning, based on the Whipple bicycle model, is used to interpret the experimental results. Overall, the model explains 95.6% of the variability in the estimated bicycle roll angle, 99.4% of the variability in the measured steering angle, and 6.5% of the variability in the measured steering torque. However, the model explains 56.6% of the variability in steering torque for the subset of trials without exaggerated rider lean relative to the bicycle frame. Thus, the model, which assumes a rigid and non-leaning rider, reasonably predicts bicycle roll and steering angles for all rider lean conditions and steering torque without exaggerated rider lean. The findings demonstrate that lateral shifting of the bicycle/rider centre of mass strongly influences the steering torque, suggesting that rider lean plays an important role in bicycle control during steady-state turning. By contrast, the required steering angle is largely insensitive to rider lean, suggesting that the steering angle serves as a superior cue for bicycle control relative to the steering torque.
Predicts the Steady-State Heating and Cooling Performance of Electric Heat Pump
Energy Science and Technology Software Center (ESTSC)
1993-01-13
Oak Ridge National Laboratory (ORNL) is a leader in the development of analytical tools for the design of electrically driven, air-to-air heat pumps. Foremost among these tools is the ORNL Heat Pump Design Model, which can be used to predict the steady-state heating and cooling performance of an electrically driven, air-source heat pump. This version is three to five times faster than the earlier version, easier to use and more versatile.
Analytical determination of transition time between transient and steady state water infiltration
NASA Astrophysics Data System (ADS)
Lassabatere, Laurent; Angulo-Jaramillo, Rafael; di Prima, Simone; Bagarello, Vincenzo; Iovino, Massimo
2016-04-01
The hydraulic characterization of soil hydraulic properties is a prerequisite to the modelling of flow in the vadose zone. Since many years, numerous methods were developed to determine soil hydraulic properties. Many of these methods rely on water infiltration experiments and their analysis using analytical or numerical models. At the beginning, most models were developed for water infiltration at steady state. These models had the advantage to be easy to develop from a theoretical point of view. Yet, many drawbacks remain including the need to wait for a long time, leading to time-consuming experiments, the risk to infiltrate water in large volumes of soil, leading to a response affected by soil variability, and the uncertainty regarding the attainment of steady state (i.e. constant infiltration rate). More recently, infiltration models and mathematical developments addressed the case of consecutive transient and steady states. Yet, one main problem remain. In the field, the operator is never sure about the state of water infiltration data. This paper present analytical formulations for the estimation of a transition time. We consider the model developed by Haverkamp et al. (1994) linking 1D infiltration flux to cumulative infiltration and related approximated expansions. An analytical method based on scaling is proposed to define transition time values in terms of both scaled cumulative infiltration and times. Dimensional times are then calculated for a large variety of soils and initial conditions. These time database can be considered as a relevant tool for the guidance for operators who conduct water infiltration experiments and wants to know when to stop and also for modelers who want to know how to select the data to fit transient or steady state models. Haverkamp, R., Ross, P. J., Smetten, K. R. J., Parlange, J. Y. (1994), Three-dimensional analysis of infiltration from the disc infiltrometer: 2 Physically based infiltration equation. Water Resour. Res
Infinite product expansion of the Fokker–Planck equation with steady-state solution
Martin, R. J.; Craster, R. V.; Kearney, M. J.
2015-01-01
We present an analytical technique for solving Fokker–Planck equations that have a steady-state solution by representing the solution as an infinite product rather than, as usual, an infinite sum. This method has many advantages: automatically ensuring positivity of the resulting approximation, and by design exactly matching both the short- and long-term behaviour. The efficacy of the technique is demonstrated via comparisons with computations of typical examples. PMID:26346100
Steady-state tokamak reactor with non-divertor impurity control: STARFIRE
Baker, C.C.
1980-01-01
STARFIRE is a conceptual design study of a commercial tokamak fusion electric power plant. Particular emphasis has been placed on simplifying the reactor concept by developing design concepts to produce a steady-state tokamak with non-divertor impurity control and helium ash removal. The concepts of plasma current drive using lower hybrid rf waves and a limiter/vacuum system for reactor applications are described.
Maximum efficiency of steady-state heat engines at arbitrary power
NASA Astrophysics Data System (ADS)
Ryabov, Artem; Holubec, Viktor
2016-05-01
We discuss the efficiency of a heat engine operating in a nonequilibrium steady state maintained by two heat reservoirs. Within the general framework of linear irreversible thermodynamics we derive a universal upper bound on the efficiency of the engine operating at arbitrary fixed power. Furthermore, we show that a slight decrease of the power below its maximal value can lead to a significant gain in efficiency. The presented analysis yields the exact expression for this gain and the corresponding upper bound.
Alarcón, Tomás
2014-05-14
In this paper, we propose two methods to carry out the quasi-steady state approximation in stochastic models of enzyme catalytic regulation, based on WKB asymptotics of the chemical master equation or of the corresponding partial differential equation for the generating function. The first of the methods we propose involves the development of multiscale generalisation of a WKB approximation of the solution of the master equation, where the separation of time scales is made explicit which allows us to apply the quasi-steady state approximation in a straightforward manner. To the lowest order, the multi-scale WKB method provides a quasi-steady state, Gaussian approximation of the probability distribution. The second method is based on the Hamilton-Jacobi representation of the stochastic process where, as predicted by large deviation theory, the solution of the partial differential equation for the corresponding characteristic function is given in terms of an effective action functional. The optimal transition paths between two states are then given by those paths that maximise the effective action. Such paths are the solutions of the Hamilton equations for the Hamiltonian associated to the effective action functional. The quasi-steady state approximation is applied to the Hamilton equations thus providing an approximation to the optimal transition paths and the transition time between two states. Using this approximation we predict that, unlike the mean-field quasi-steady approximation result, the rate of enzyme catalysis depends explicitly on the initial number of enzyme molecules. The accuracy and validity of our approximated results as well as that of our predictions regarding the behaviour of the stochastic enzyme catalytic models are verified by direct simulation of the stochastic model using Gillespie stochastic simulation algorithm. PMID:24832255
A fully implicit method for 3D quasi-steady state magnetic advection-diffusion.
Siefert, Christopher; Robinson, Allen Conrad
2009-09-01
We describe the implementation of a prototype fully implicit method for solving three-dimensional quasi-steady state magnetic advection-diffusion problems. This method allows us to solve the magnetic advection diffusion equations in an Eulerian frame with a fixed, user-prescribed velocity field. We have verified the correctness of method and implementation on two standard verification problems, the Solberg-White magnetic shear problem and the Perry-Jones-White rotating cylinder problem.
Analysis and Modelling of the Steady-State and Dynamic-State Discharge in SMES System
NASA Astrophysics Data System (ADS)
Chen, Xiao Yuan; Jin, Jian Xun
The steady-state and dynamic-state discharge processes have been discussed to develop a superconducting magnetic energy storage (SMES) model in the paper. The SMES model allows the integrated analysis and optimization of the SMES devices, and their control systems, and can also serve as an independent storage module in the practical SMES application circuits, thus provide a method to link superconductivity technology to conventional power electronics in a SMES device.
Central resetting of neuromuscular steady states may underlie rhythmical arm movements.
Ustinova, Ksenia I; Feldman, Anatol G; Levin, Mindy F
2006-09-01
Changing the steady-state configuration of the body or its segments may be an important function of central pattern generators for locomotion and other rhythmical movements. Thereby, muscle activation, forces, and movement may emerge following a natural tendency of the neuromuscular system to achieve the current steady-state configuration. To verify that transitions between different steady states occur during rhythmical movements, we asked standing subjects to swing one or both arms synchronously or reciprocally at approximately 0.8 Hz from the shoulder joints. In randomly selected cycles, one arm was transiently arrested by an electromagnetic device. Swinging resumed after some delay and phase resetting. During bilateral swinging, the nonperturbed arm often stopped before resuming swinging at a position that was close to either the extreme forward or the extreme backward arm position observed before the perturbation. Oscillations usually resumed when both arms arrived at similar extreme positions when a synchronous bilateral pattern was initially produced or at the opposite positions if the initial pattern was reciprocal. Results suggest that a central generator controls both arms as a coherent unit by producing transitions between its steady state (equilibrium) positions. By controlling these positions, the system may define the spatial boundaries of movement. At these positions, the system may halt the oscillations, resume them at a new phase (as observed in the present study), or initiate a new motor action. Our findings are relevant to locomotion and suggest that walking may also be generated by transitions between several equilibrium configurations of the body, possibly accomplished by modulation and gating of proprioceptive reflexes. PMID:16707712
40 CFR 86.1363-2007 - Steady-state testing with a discrete-mode cycle.
Code of Federal Regulations, 2011 CFR
2011-07-01
... 0.08 2 11 C 25 0.05 2 12 C 75 0.05 2 13 C 50 0.05 2 1 Speed terms are defined in 40 CFR part 1065. 2... Exhaust Test Procedures § 86.1363-2007 Steady-state testing with a discrete-mode cycle. This section... taking a sample proportional to the exhaust mass flow during each individual mode of the cycle. This...
40 CFR 86.1363-2007 - Steady-state testing with a discrete-mode cycle.
Code of Federal Regulations, 2010 CFR
2010-07-01
... 0.08 2 11 C 25 0.05 2 12 C 75 0.05 2 13 C 50 0.05 2 1 Speed terms are defined in 40 CFR part 1065. 2... Exhaust Test Procedures § 86.1363-2007 Steady-state testing with a discrete-mode cycle. This section... taking a sample proportional to the exhaust mass flow during each individual mode of the cycle. This...
Alarcón, Tomás
2014-05-14
In this paper, we propose two methods to carry out the quasi-steady state approximation in stochastic models of enzyme catalytic regulation, based on WKB asymptotics of the chemical master equation or of the corresponding partial differential equation for the generating function. The first of the methods we propose involves the development of multiscale generalisation of a WKB approximation of the solution of the master equation, where the separation of time scales is made explicit which allows us to apply the quasi-steady state approximation in a straightforward manner. To the lowest order, the multi-scale WKB method provides a quasi-steady state, Gaussian approximation of the probability distribution. The second method is based on the Hamilton-Jacobi representation of the stochastic process where, as predicted by large deviation theory, the solution of the partial differential equation for the corresponding characteristic function is given in terms of an effective action functional. The optimal transition paths between two states are then given by those paths that maximise the effective action. Such paths are the solutions of the Hamilton equations for the Hamiltonian associated to the effective action functional. The quasi-steady state approximation is applied to the Hamilton equations thus providing an approximation to the optimal transition paths and the transition time between two states. Using this approximation we predict that, unlike the mean-field quasi-steady approximation result, the rate of enzyme catalysis depends explicitly on the initial number of enzyme molecules. The accuracy and validity of our approximated results as well as that of our predictions regarding the behaviour of the stochastic enzyme catalytic models are verified by direct simulation of the stochastic model using Gillespie stochastic simulation algorithm.
Revised Model of the Steady-state Solar Wind Halo Electron Velocity Distribution Function
NASA Astrophysics Data System (ADS)
Yoon, Peter H.; Kim, Sunjung; Choe, G. S.; moon, Y.-J.
2016-08-01
A recent study discussed the steady-state model for solar wind electrons during quiet time conditions. The electrons emanating from the Sun are treated in a composite three-population model—the low-energy Maxwellian core with an energy range of tens of eV, the intermediate ∼102–103 eV energy-range (“halo”) electrons, and the high ∼103–105 eV energy-range (“super-halo”) electrons. In the model, the intermediate energy halo electrons are assumed to be in resonance with transverse EM fluctuations in the whistler frequency range (∼102 Hz), while the high-energy super-halo electrons are presumed to be in steady-state wave–particle resonance with higher-frequency electrostatic fluctuations in the Langmuir frequency range (∼105 Hz). A comparison with STEREO and WIND spacecraft data was also made. However, ignoring the influence of Langmuir fluctuations on the halo population turns out to be an unjustifiable assumption. The present paper rectifies the previous approach by including both Langmuir and whistler fluctuations in the construction of the steady-state velocity distribution function for the halo population, and demonstrates that the role of whistler-range fluctuation is minimal unless the fluctuation intensity is arbitrarily raised. This implies that the Langmuir-range fluctuations, known as the quasi thermal noise, are important for both halo and super-halo electron velocity distribution.
Arc plasma generator of atomic driver for steady-state negative ion source.
Ivanov, A A; Belchenko, Yu I; Davydenko, V I; Ivanov, I A; Kolmogorov, V V; Listopad, A A; Mishagin, V V; Putvinsky, S V; Shulzhenko, G I; Smirnov, A
2014-02-01
The paper reviews the results of development of steady-state arc-discharge plasma generator with directly heated LaB6 cathode. This arc-discharge plasma generator produces a plasma jet which is to be converted into an atomic one after recombination on a metallic plate. The plate is electrically biased relative to the plasma in order to control the atom energies. Such an intensive jet of hydrogen atoms can be used in negative ion sources for effective production of negative ions on a cesiated surface of plasma grid. All elements of the plasma generator have an augmented water cooling to operate in long pulse mode or in steady state. The thermo-mechanical stresses and deformations of the most critical elements of the plasma generator were determined by simulations. Magnetic field inside the discharge chamber was optimized to reduce the local power loads. The first tests of the steady-state arc plasma generator prototype have performed in long-pulse mode. PMID:24593569
Amri, Amina; Pulko, Susan Helen; Wilkinson, Anthony James
2016-01-01
Breast thermography still has inherent limitations that prevent it from being fully accepted as a breast screening modality in medicine. The main challenges of breast thermography are to reduce false positive results and to increase the sensitivity of a thermogram. Further, it is still difficult to obtain information about tumour parameters such as metabolic heat, tumour depth and diameter from a thermogram. However, infrared technology and image processing have advanced significantly and recent clinical studies have shown increased sensitivity of thermography in cancer diagnosis. The aim of this paper is to study numerically the possibilities of extracting information about the tumour depth from steady state thermography and transient thermography after cold stress with no need to use any specific inversion technique. Both methods are based on the numerical solution of Pennes bioheat equation for a simple three-dimensional breast model. The effectiveness of two approaches used for depth detection from steady state thermography is assessed. The effect of breast density on the steady state thermal contrast has also been studied. The use of a cold stress test and the recording of transient contrasts during rewarming were found to be potentially suitable for tumour depth detection during the rewarming process. Sensitivity to parameters such as cold stress temperature and cooling time is investigated using the numerical model and simulation results reveal two prominent depth-related characteristic times which do not strongly depend on the temperature of the cold stress or on the cooling period. PMID:26522612
A theoretical analysis of steady-state photocurrents in simple silicon diodes
NASA Technical Reports Server (NTRS)
Edmonds, L.
1995-01-01
A theoretical analysis solves for the steady-state photocurrents produced by a given photo-generation rate function with negligible recombination in simple silicon diodes, consisting of a uniformly doped quasi-neutral region (called 'substrate' below) adjacent to a p-n junction depletion region (DR). Special attention is given to conditions that produce 'funneling' (a term used by the single-eventeffects community) under steady-state conditions. Funneling occurs when carriers are generated so fast that the DR becomes flooded and partially or completely collapses. Some or nearly all of the applied voltage, plus built-in potential normally across the DR, is now across the substrate. This substrate voltage drop affects substrate currents. The steady-state problem can provide some qualitative insights into the more difficult transient problem. First, it was found that funneling can be induced from a distance, i.e., from carriers generated at locations outside of the DR. Secondly, it was found that the substrate can divide into two subregions, with one controlling substrate resistance and the other characterized by ambipolar diffusion. Finally, funneling was found to be more difficult to induce in the p(sup +)/n diode than in the n(sup +)/p diode. The carrier density exceeding the doping density in the substrate and at the DR boundary is not a sufficient condition to collapse a DR.
Generating large steady-state optomechanical entanglement by the action of Casimir force
NASA Astrophysics Data System (ADS)
Nie, WenJie; Lan, YueHeng; Li, Yong; Zhu, ShiYao
2014-12-01
In this paper, we study an optomechanical device consisting of a Fabry-Pérot cavity with two dielectric nanospheres trapped near the cavity mirrors by an external driving laser. In the condition where the distances between the nanospheres and cavity mirrors are small enough, the Casimir force helps the optomechanical coupling to induce a steady-state optomechanical entanglement of the mechanical and optical modes in a certain regime of parameters. We investigate in detail the dependence of the steady-state optomechanical entanglement on external control parameters of the system, i.e., the effective detuning, the pump powers of the cavity, the cavity decay rate and the wavelength of the driving field. It is found that the large steady-state optomechanical entanglement, i.e. E N = 5.76, can be generated with experimentally feasible parameters, i.e. the pump power P = 18.2 μW, the cavity decay rate κ = 0.5 MHz and the wavelength of the laser λ L=1064 nm, which should be checked by optical measurement.
Hu, J S; Sun, Z; Guo, H Y; Li, J G; Wan, B N; Wang, H Q; Ding, S Y; Xu, G S; Liang, Y F; Mansfield, D K; Maingi, R; Zou, X L; Wang, L; Ren, J; Zuo, G Z; Zhang, L; Duan, Y M; Shi, T H; Hu, L Q
2015-02-01
A critical challenge facing the basic long-pulse high-confinement operation scenario (H mode) for ITER is to control a magnetohydrodynamic (MHD) instability, known as the edge localized mode (ELM), which leads to cyclical high peak heat and particle fluxes at the plasma facing components. A breakthrough is made in the Experimental Advanced Superconducting Tokamak in achieving a new steady-state H mode without the presence of ELMs for a duration exceeding hundreds of energy confinement times, by using a novel technique of continuous real-time injection of a lithium (Li) aerosol into the edge plasma. The steady-state ELM-free H mode is accompanied by a strong edge coherent MHD mode (ECM) at a frequency of 35-40 kHz with a poloidal wavelength of 10.2 cm in the ion diamagnetic drift direction, providing continuous heat and particle exhaust, thus preventing the transient heat deposition on plasma facing components and impurity accumulation in the confined plasma. It is truly remarkable that Li injection appears to promote the growth of the ECM, owing to the increase in Li concentration and hence collisionality at the edge, as predicted by GYRO simulations. This new steady-state ELM-free H-mode regime, enabled by real-time Li injection, may open a new avenue for next-step fusion development. PMID:25699449
Cluster Mean-Field Approach to the Steady-State Phase Diagram of Dissipative Spin Systems
NASA Astrophysics Data System (ADS)
Jin, Jiasen; Biella, Alberto; Viyuela, Oscar; Mazza, Leonardo; Keeling, Jonathan; Fazio, Rosario; Rossini, Davide
2016-07-01
We show that short-range correlations have a dramatic impact on the steady-state phase diagram of quantum driven-dissipative systems. This effect, never observed in equilibrium, follows from the fact that ordering in the steady state is of dynamical origin, and is established only at very long times, whereas in thermodynamic equilibrium it arises from the properties of the (free) energy. To this end, by combining the cluster methods extensively used in equilibrium phase transitions to quantum trajectories and tensor-network techniques, we extend them to nonequilibrium phase transitions in dissipative many-body systems. We analyze in detail a model of spin-1 /2 on a lattice interacting through an X Y Z Hamiltonian, each of them coupled to an independent environment that induces incoherent spin flips. In the steady-state phase diagram derived from our cluster approach, the location of the phase boundaries and even its topology radically change, introducing reentrance of the paramagnetic phase as compared to the single-site mean field where correlations are neglected. Furthermore, a stability analysis of the cluster mean field indicates a susceptibility towards a possible incommensurate ordering, not present if short-range correlations are ignored.
A steady-state Kalman filter for assimilating data from a single polar orbiting satellite
NASA Technical Reports Server (NTRS)
Banfield, Don; Ingersoll, Andrew P.; Keppenne, Christian L.
1995-01-01
A steady-state scheme for data assimilation in the context of a single, short period (relative to a day), sun-synchronous, polar-orbiting satellite is examined. If the satellite takes observations continuously, the gains, which are the weights for blending observations and predictions together, are steady in time. For a linear system forced by random noise, the optimal steady-state gains (Wiener gains) are equivalent to those of a Kalman filter. Computing the Kalman gains increases the computational cost of the model by a large factor, but computing the Wiener gains does not. The latter are computed by iteration using prior estimates of the gains to assimilate simulated observations of one run of the model, termed 'truth' into another run termed 'prediction'. At each stage, the prediction errors form the basis for the next estimate of the gains. Steady state is achieved after three or four iterations. Further simplification is achieved by making the gains depend on longitudinal distance from the observation point, not on absolute longitude. For a single-layer primitive equation model, the scheme works well even if only the mass field is observed but not the velocity field. Although the scheme was developed for Mars Observer, it should be applicable to data retrieved from Earth atmosphere satellites, for example, UARS.
Self-consistent inhomogeneous steady states in Hamiltonian mean-field dynamics
NASA Astrophysics Data System (ADS)
de Buyl, Pierre; Mukamel, David; Ruffo, Stefano
2011-12-01
Long-lived quasistationary states, associated with stationary stable solutions of the Vlasov equation, are found in systems with long-range interactions. Studies of the relaxation time in a model of N globally coupled particles moving on a ring, the Hamiltonian mean-field model (HMF), have shown that it diverges as Nγ for large N, with γ≃1.7 for some initial conditions with homogeneously distributed particles. We propose a method for identifying exact inhomogeneous steady states in the thermodynamic limit, based on analyzing models of uncoupled particles moving in an external field. For the HMF model, we show numerically that the relaxation time of these states diverges with N with the exponent γ≃1. The method, applicable to other models with globally coupled particles, also allows an exact evaluation of the stability limit of homogeneous steady states. In some cases, it provides a good approximation for the correspondence between the initial condition and the final steady state.
Steady-state and dynamic models for particle engulfment during solidification
NASA Astrophysics Data System (ADS)
Tao, Yutao; Yeckel, Andrew; Derby, Jeffrey J.
2016-06-01
Steady-state and dynamic models are developed to study the physical mechanisms that determine the pushing or engulfment of a solid particle at a moving solid-liquid interface. The mathematical model formulation rigorously accounts for energy and momentum conservation, while faithfully representing the interfacial phenomena affecting solidification phase change and particle motion. A numerical solution approach is developed using the Galerkin finite element method and elliptic mesh generation in an arbitrary Lagrangian-Eulerian implementation, thus allowing for a rigorous representation of forces and dynamics previously inaccessible by approaches using analytical approximations. We demonstrate that this model accurately computes the solidification interface shape while simultaneously resolving thin fluid layers around the particle that arise from premelting during particle engulfment. We reinterpret the significance of premelting via the definition an unambiguous critical velocity for engulfment from steady-state analysis and bifurcation theory. We also explore the complicated transient behaviors that underlie the steady states of this system and posit the significance of dynamical behavior on engulfment events for many systems. We critically examine the onset of engulfment by comparing our computational predictions to those obtained using the analytical model of Rempel and Worster [29]. We assert that, while the accurate calculation of van der Waals repulsive forces remains an open issue, the computational model developed here provides a clear benefit over prior models for computing particle drag forces and other phenomena needed for the faithful simulation of particle engulfment.
Effects of aging in catastrophe on the steady state and dynamics of a microtubule population
NASA Astrophysics Data System (ADS)
Jemseena, V.; Gopalakrishnan, Manoj
2015-05-01
Several independent observations have suggested that the catastrophe transition in microtubules is not a first-order process, as is usually assumed. Recent in vitro observations by Gardner et al. [M. K. Gardner et al., Cell 147, 1092 (2011), 10.1016/j.cell.2011.10.037] showed that microtubule catastrophe takes place via multiple steps and the frequency increases with the age of the filament. Here we investigate, via numerical simulations and mathematical calculations, some of the consequences of the age dependence of catastrophe on the dynamics of microtubules as a function of the aging rate, for two different models of aging: exponential growth, but saturating asymptotically, and purely linear growth. The boundary demarcating the steady-state and non-steady-state regimes in the dynamics is derived analytically in both cases. Numerical simulations, supported by analytical calculations in the linear model, show that aging leads to nonexponential length distributions in steady state. More importantly, oscillations ensue in microtubule length and velocity. The regularity of oscillations, as characterized by the negative dip in the autocorrelation function, is reduced by increasing the frequency of rescue events. Our study shows that the age dependence of catastrophe could function as an intrinsic mechanism to generate oscillatory dynamics in a microtubule population, distinct from hitherto identified ones.
Data acquisition system for steady-state experiments at multiple sites
NASA Astrophysics Data System (ADS)
Nakanishi, H.; Ohsuna, M.; Kojima, M.; Imazu, S.; Nonomura, M.; Yamamoto, T.; Emoto, M.; Yoshida, M.; Iwata, C.; Shoji, M.; Nagayama, Y.; Kawahata, K.; Hasegawa, M.; Higashijima, A.; Nakamura, K.; Ono, Y.; Yoshikawa, M.; Urushidani, S.
2011-11-01
A high-performance data acquisition (DAQ) system has been developed for steady-state fusion experiments at the Large Helical Device (LHD). Its significant characteristics are 110 MB s-1 continuous DAQ capability and the performance scalability using an unlimited number of DAQ units. Incoming data streams are first transferred temporarily onto the shared random access memory, and then cut into definite time chunks to be stored. They are also thinned out to 1/N to be served for the real-time monitoring clients. In LHD steady-state experiment, the DAQ cluster has established the world record for acquiring 90 GB/shot. The established technology of this steady-state acquisition and store can contribute to the ITER experiments whose data amount is estimated in the range 100 or 1000 GB/shot. This system also acquires experimental data from multiple remote sites through the fusion-dedicated virtual private network in Japan. The speed lowering problem in long-distance TCP/IP data transfer has been improved by the packet pacing optimization. The demonstrated collaboration scheme will be analogous to that of ITER and the supporting machines.
Steady-state ELM-suppressed H-modes from KSTAR to ITER and beyond
NASA Astrophysics Data System (ADS)
in, Yongkyoon; Kwak, J. G.; KSTAR Team
2014-10-01
Long-pulse, steady-state high-performance plasma is not only an important mission in KSTAR, but also directly relevant to ITER. While demonstrating the pulse-length of more than 20 sec H-mode flat-top in 2013, KSTAR has been exploring various means to achieve and sustain steady-state, ELM-suppressed/mitigated H-modes using versatile in-vessel control coils (IVCC), ECCD/ECH, and/or SMBI. In particular, taking advantage of the versatile 3-rows of IVCC, KSTAR accomplished both n = 1 and n = 2 RMP-driven, ELM-suppressed regimes that lasted up to 4 sec so far (limited by the discharge pulse length, not by any physics constraints, and will be extended up to 10 sec in 2014.) We also found the use of n = 2 RMP has prevented a locked-mode from being disruptive (at least within the RMP phase). To cope with run-away electrons and/or off-normal events, a soft landing algorithm has been developed and confirmed capable of ramping down the plasma current safely. The enhanced understanding and demonstration of steady-state, high-performance plasmas in KSTAR will elevate the level of confidence about the success of ITER and beyond. Supported by Ministry of Science, ICT, and Future Planning in Korea.
NASA Astrophysics Data System (ADS)
Shojania Feizabadi, Mitra; Spillman, William B.
2005-03-01
Microtubules are the target for a large number of anti-mitotic agents including colchicine. Colchicine is a well studied inhibitor that is believed to act by disrupting the microtubule requirements for chromosome movement during mitosis. The mechanism of action of colchicine in vitro and at low concentration is due to kinetic stabilization of spindle microtubule dynamics. In this study we investigate the behavior of free T-tubulin concentration in the microtubule steady state and in the presence colchicine. We assume that there is an excess of GTP (guanosine tri-phosphate) available in the solution, and that the D-tubulin in the solution will exchange its unit of GDP (guanosine di-phosphate) with a unit of GTP. By numerical analysis, the concentration of T-tubulin in the steady state as a function of regeneration rate was investigated in the presence and absence of colchicine. Our results show that low concentration of colchicine in the steady state does not significantly alter the amount of free total T-tubulin concentration or the polymer mass, in good agreement with experimental observations.
Characters of basic steady state solutions for superfluid Fermi gas in Bessel optical lattices
NASA Astrophysics Data System (ADS)
Zhang, Ke-Zhi; Chen, Yan; He, Yong-Lin; Liu, Zheng-Lai
2015-08-01
We consider a dynamical model for superfluid Fermi gas, trapped in the central well of an axially symmetric Bessel optical lattice potential. The equation includes nonlinear power-law form of the chemical potential μ(n) = C|ψ|2γ, for γ = 2 3, which accounts for Fermi pressure. Reducing the equation to two-dimensional (2D) form, we obtain the basic steady state solutions of the system along the Bose-Einstein condensation (BEC) side to Bardeen-Cooper-Schrieffer (BCS) side by employing the energy balance condition, which are guided by the variational approximation. It is found that the strength ɛ and the radial scale r of the Bessel optical lattice have an extreme effect on the characters of basic steady state solution. Analytically, we deduce the atomic density distribution, the average atom number and the average energy of basic steady state, where the atom distribution of the system presents on periodic change with r, and increases faster at unitarity than in the BEC limit. Furthermore, because of the Fermi pressure, the atomic density distribution at the unitarity is more extensive than that in the BEC limit. In particular, there exist very interesting changes, the average energy intends to collapse state with r, however it emerges as a stable state with varying L both in the BEC limit and at unitarity.
Revised Model of the Steady-state Solar Wind Halo Electron Velocity Distribution Function
NASA Astrophysics Data System (ADS)
Yoon, Peter H.; Kim, Sunjung; Choe, G. S.; moon, Y.-J.
2016-08-01
A recent study discussed the steady-state model for solar wind electrons during quiet time conditions. The electrons emanating from the Sun are treated in a composite three-population model—the low-energy Maxwellian core with an energy range of tens of eV, the intermediate ˜102–103 eV energy-range (“halo”) electrons, and the high ˜103–105 eV energy-range (“super-halo”) electrons. In the model, the intermediate energy halo electrons are assumed to be in resonance with transverse EM fluctuations in the whistler frequency range (˜102 Hz), while the high-energy super-halo electrons are presumed to be in steady-state wave–particle resonance with higher-frequency electrostatic fluctuations in the Langmuir frequency range (˜105 Hz). A comparison with STEREO and WIND spacecraft data was also made. However, ignoring the influence of Langmuir fluctuations on the halo population turns out to be an unjustifiable assumption. The present paper rectifies the previous approach by including both Langmuir and whistler fluctuations in the construction of the steady-state velocity distribution function for the halo population, and demonstrates that the role of whistler-range fluctuation is minimal unless the fluctuation intensity is arbitrarily raised. This implies that the Langmuir-range fluctuations, known as the quasi thermal noise, are important for both halo and super-halo electron velocity distribution.
Nonequilibrium Lifshitz theory as a steady state of a full dynamical quantum system
NASA Astrophysics Data System (ADS)
Lombardo, Fernando C.; Mazzitelli, Francisco D.; López, Adrián E. Rubio; Turiaci, Gustavo J.
2016-07-01
In this work we analyze the validity of Lifshitz's theory for the case of nonequilibrium scenarios from a full quantum dynamical approach. We show that Lifshitz's framework for the study of the Casimir pressure is the result of considering the long-time regime (or steady state) of a well-defined fully quantized problem, subjected to initial conditions for the electromagnetic field interacting with real materials. For this, we implement the closed time path formalism developed in previous works to study the case of two half spaces (modeled as composite environments, consisting in quantum degrees of freedom plus thermal baths) interacting with the electromagnetic field. Starting from initial uncorrelated free subsystems, we solve the full time evolution, obtaining general expressions for the different contributions to the pressure that take part on the transient stage. Using the analytic properties of the retarded Green functions, we obtain the long-time limit of these contributions to the total Casimir pressure. We show that, in the steady state, only the baths' contribute, in agreement with the results of previous works, where this was assumed without justification. We also study in detail the physics of the initial conditions' contribution and the concept of modified vacuum modes, giving insights about in which situations one would expect a nonvanishing contribution at the steady state of a nonequilibrium scenario. This would be the case when considering finite width slabs instead of half-spaces.
A Series RCL Circuit Theory for Analyzing Non-Steady-State Water Uptake of Maize Plants
Zhuang, Jie; Yu, Gui-Rui; Nakayama, Keiichi
2014-01-01
Understanding water uptake and transport through the soil-plant continuum is vital for ecosystem management and agricultural water use. Plant water uptake under natural conditions is a non-steady transient flow controlled by root distribution, plant configuration, soil hydraulics, and climatic conditions. Despite significant progress in model development, a mechanistic description of transient water uptake has not been developed or remains incomplete. Here, based on advanced electrical network theory (RLC circuit theory), we developed a non-steady state biophysical model to mechanistically analyze the fluctuations of uptake rates in response to water stress. We found that the non-steady-state model captures the nature of instantaneity and hysteresis of plant water uptake due to the considerations of water storage in plant xylem and coarse roots (capacitance effect), hydraulic architecture of leaf system (inductance effect), and soil-root contact (fuse effect). The model provides insights into the important role of plant configuration and hydraulic heterogeneity in helping plants survive an adverse environment. Our tests against field data suggest that the non-steady-state model has great potential for being used to interpret the smart water strategy of plants, which is intrinsically determined by stem size, leaf size/thickness and distribution, root system architecture, and the ratio of fine-to-coarse root lengths. PMID:25335512
Steady-state propagation speed of rupture fronts along one-dimensional frictional interfaces
NASA Astrophysics Data System (ADS)
Amundsen, David Skâlid; Trømborg, Jørgen Kjoshagen; Thøgersen, Kjetil; Katzav, Eytan; Malthe-Sørenssen, Anders; Scheibert, Julien
2015-09-01
The rupture of dry frictional interfaces occurs through the propagation of fronts breaking the contacts at the interface. Recent experiments have shown that the velocities of these rupture fronts range from quasistatic velocities proportional to the external loading rate to velocities larger than the shear wave speed. The way system parameters influence front speed is still poorly understood. Here we study steady-state rupture propagation in a one-dimensional (1D) spring-block model of an extended frictional interface for various friction laws. With the classical Amontons-Coulomb friction law, we derive a closed-form expression for the steady-state rupture velocity as a function of the interfacial shear stress just prior to rupture. We then consider an additional shear stiffness of the interface and show that the softer the interface, the slower the rupture fronts. We provide an approximate closed form expression for this effect. We finally show that adding a bulk viscosity on the relative motion of blocks accelerates steady-state rupture fronts and we give an approximate expression for this effect. We demonstrate that the 1D results are qualitatively valid in 2D. Our results provide insights into the qualitative role of various key parameters of a frictional interface on its rupture dynamics. They will be useful to better understand the many systems in which spring-block models have proved adequate, from friction to granular matter and earthquake dynamics.
A series RCL circuit theory for analyzing non-steady-state water uptake of maize plants.
Zhuang, Jie; Yu, Gui-Rui; Nakayama, Keiichi
2014-01-01
Understanding water uptake and transport through the soil-plant continuum is vital for ecosystem management and agricultural water use. Plant water uptake under natural conditions is a non-steady transient flow controlled by root distribution, plant configuration, soil hydraulics, and climatic conditions. Despite significant progress in model development, a mechanistic description of transient water uptake has not been developed or remains incomplete. Here, based on advanced electrical network theory (RLC circuit theory), we developed a non-steady state biophysical model to mechanistically analyze the fluctuations of uptake rates in response to water stress. We found that the non-steady-state model captures the nature of instantaneity and hysteresis of plant water uptake due to the considerations of water storage in plant xylem and coarse roots (capacitance effect), hydraulic architecture of leaf system (inductance effect), and soil-root contact (fuse effect). The model provides insights into the important role of plant configuration and hydraulic heterogeneity in helping plants survive an adverse environment. Our tests against field data suggest that the non-steady-state model has great potential for being used to interpret the smart water strategy of plants, which is intrinsically determined by stem size, leaf size/thickness and distribution, root system architecture, and the ratio of fine-to-coarse root lengths. PMID:25335512
A Series RCL Circuit Theory for Analyzing Non-Steady-State Water Uptake of Maize Plants
NASA Astrophysics Data System (ADS)
Zhuang, Jie; Yu, Gui-Rui; Nakayama, Keiichi
2014-10-01
Understanding water uptake and transport through the soil-plant continuum is vital for ecosystem management and agricultural water use. Plant water uptake under natural conditions is a non-steady transient flow controlled by root distribution, plant configuration, soil hydraulics, and climatic conditions. Despite significant progress in model development, a mechanistic description of transient water uptake has not been developed or remains incomplete. Here, based on advanced electrical network theory (RLC circuit theory), we developed a non-steady state biophysical model to mechanistically analyze the fluctuations of uptake rates in response to water stress. We found that the non-steady-state model captures the nature of instantaneity and hysteresis of plant water uptake due to the considerations of water storage in plant xylem and coarse roots (capacitance effect), hydraulic architecture of leaf system (inductance effect), and soil-root contact (fuse effect). The model provides insights into the important role of plant configuration and hydraulic heterogeneity in helping plants survive an adverse environment. Our tests against field data suggest that the non-steady-state model has great potential for being used to interpret the smart water strategy of plants, which is intrinsically determined by stem size, leaf size/thickness and distribution, root system architecture, and the ratio of fine-to-coarse root lengths.
On the Kaolinite Floc Size at the Steady State of Flocculation in a Turbulent Flow.
Zhu, Zhongfan; Wang, Hongrui; Yu, Jingshan; Dou, Jie
2016-01-01
The flocculation of cohesive fine-grained sediment plays an important role in the transport characteristics of pollutants and nutrients absorbed on the surface of sediment in estuarine and coastal waters through the complex processes of sediment transport, deposition, resuspension and consolidation. Many laboratory experiments have been carried out to investigate the influence of different flow shear conditions on the floc size at the steady state of flocculation in the shear flow. Most of these experiments reported that the floc size decreases with increasing shear stresses and used a power law to express this dependence. In this study, we performed a Couette-flow experiment to measure the size of the kaolinite floc through sampling observation and an image analysis system at the steady state of flocculation under six flow shear conditions. The results show that the negative correlation of the floc size on the flow shear occurs only at high shear conditions, whereas at low shear conditions, the floc size increases with increasing turbulent shear stresses regardless of electrolyte conditions. Increasing electrolyte conditions and the initial particle concentration could lead to a larger steady-state floc size. PMID:26901652
Timmons, J A; Poucher, S M; Constantin-Teodosiu, D; Macdonald, I A; Greenhaff, P L
1997-08-01
Skeletal muscle contraction during ischemia, such as that experienced by peripheral vascular disease patients, is characterized by rapid fatigue. Using a canine gracilis model, we tested the hypothesis that a critical factor determining force production during ischemia is the metabolic response during the transition from rest to steady state. Dichloroacetate (DCA) administration before gracilis muscle contraction increased pyruvate dehydrogenase complex activation and resulted in acetylation of 80% of the free carnitine pool to acetylcarnitine. After 1 min of contraction, phosphocreatine (PCr) degradation in the DCA group was approximately 50% lower than in the control group (P < 0.05) during conditions of identical force production. After 6 min of contraction, steady-state force production was approximately 30% higher in the DCA group (P < 0.05), and muscle ATP, PCr, and glycogen degradation and lactate accumulation were lower (P < 0.05 in all cases). It appears, therefore, that an important determinant of contractile function during ischemia is the mechanisms by which ATP regeneration occurs during the period of rest to steady-state transition. PMID:9277374
Relative intelligibility of dynamically extracted transient versus steady-state components of speech
NASA Astrophysics Data System (ADS)
Boston, J. R.; Yoo, Sungyub; Li, C. C.; El-Jaroudi, Amro; Durrant, J. D.; Kovacyk, Kristie; Karn, Stacey
2001-05-01
Consonants are recognized to dominate higher frequencies of the speech spectrum and to carry more information than vowels, but both demonstrate quasi-steady state and transient components, such as vowel to consonant transitions. Fixed filters somewhat separate these effects, but probably not optimally, given diverse words, speakers, and situations. To enhance the transient characteristics of speech, this study used time-varying adaptive filters [Rao and Kumaresan, IEEE Trans. Speech Audio Process. 8, 240-254 (2000)], following high-pass filtering at 700 Hz (well-known to have minimal effect on intelligibility), to extract predominantly steady-state components of speech material (CVC words, NU-6). The transient component was the difference between the sum of the filter outputs and the original signal. Psychometric functions were determined in five subjects with and without background noise and fitted by ogives. The transient components averaged filtered speech energy, but PBmax was not significantly different (nonparametric ANOVA) from that of either the original or highpass filtered speech. The steady-state components yielded significantly lower PBmax (p 3D 0.003) despite their much greater energy, as expected. These results suggest a potential approach to dynamic enhancement of speech intelligibility. [Work supported by ONR.
A Robust and Efficient Method for Steady State Patterns in Reaction-Diffusion Systems
Lo, Wing-Cheong; Chen, Long; Wang, Ming; Nie, Qing
2012-01-01
An inhomogeneous steady state pattern of nonlinear reaction-diffusion equations with no-flux boundary conditions is usually computed by solving the corresponding time-dependent reaction-diffusion equations using temporal schemes. Nonlinear solvers (e.g., Newton’s method) take less CPU time in direct computation for the steady state; however, their convergence is sensitive to the initial guess, often leading to divergence or convergence to spatially homogeneous solution. Systematically numerical exploration of spatial patterns of reaction-diffusion equations under different parameter regimes requires that the numerical method be efficient and robust to initial condition or initial guess, with better likelihood of convergence to an inhomogeneous pattern. Here, a new approach that combines the advantages of temporal schemes in robustness and Newton’s method in fast convergence in solving steady states of reaction-diffusion equations is proposed. In particular, an adaptive implicit Euler with inexact solver (AIIE) method is found to be much more efficient than temporal schemes and more robust in convergence than typical nonlinear solvers (e.g., Newton’s method) in finding the inhomogeneous pattern. Application of this new approach to two reaction-diffusion equations in one, two, and three spatial dimensions, along with direct comparisons to several other existing methods, demonstrates that AIIE is a more desirable method for searching inhomogeneous spatial patterns of reaction-diffusion equations in a large parameter space. PMID:22773849
Dougherty, T.; Maciuca, C.; McAssey, E.V. Jr.; Reddy, D.G.; Yang, B.W.
1991-07-01
This report presents results for the steady state portion of the finless single annulus test program. The objective of the experimental study was to investigate the onset of flow instability in an annular geometry similar to the MARK 22 reactor. The test program involved testing of both a finless or ribless heater and a ribbed heater. The latter program is currently underway and will be reported separately. For finless heater, testing was conducted in both a steady state and transient mode. The present report presents steady state results for a series of experiments with uniform and asymmetric heating. The demand curves obtained under uniform heating yielded OFI flow-rates which were slightly below those obtained for a circular tube geometry with the same L/D ratio; however, the single annulus had a hydraulic diameter which was approximately fifty percent larger than the circular tube. The asymmetric heating cases were selected to provide the same average power input as the uniform cases. The results for these tests indicated that the flow-rate at OFI increased with the degree of asymmetry.
Steady-state and transient analysis of a squeeze film damper bearing for rotor stability
NASA Technical Reports Server (NTRS)
Barrett, L. E.; Gunter, E. J.
1975-01-01
A study of the steady-state and transient response of the squeeze film damper bearing is presented. Both the steady-state and transient equations for the hydrodynamic bearing forces are derived. The bearing equivalent stiffness and damping coefficients are determined by steady-state equations. These coefficients are used to find the bearing configuration which will provide the optimum support characteristics based on a stability analysis of the rotor-bearing system. The transient analysis of rotor-bearing systems is performed by coupling the bearing and journal equations and integrating forward in time. The effects of unbalance, cavitation, and retainer springs are included in the analysis. Methods of determining the stability of a rotor-bearing system under the influence of aerodynamic forces and internal shaft friction are discussed with emphasis on solving the system characteristic frequency equation and on producing stability maps. It is shown that for optimum stability and low force transmissability the squeeze bearing should operate at an eccentricity ratio epsilon 0.4.
Effective bias and potentials in steady-state quantum transport: A NEGF reverse-engineering study
NASA Astrophysics Data System (ADS)
Karlsson, Daniel; Verdozzi, Claudio
2016-03-01
Using non-equilibrium Green's functions combined with many-body perturbation theory, we have calculated steady-state densities and currents through short interacting chains subject to a finite electric bias. By using a steady-state reverse-engineering procedure, the effective potential and bias which reproduce such densities and currents in a non-interacting system have been determined. The role of the effective bias is characterised with the aid of the so-called exchange-correlation bias, recently introduced in a steady-state density-functional- theory formulation for partitioned systems. We find that the effective bias (or, equivalently, the exchange-correlation bias) depends strongly on the interaction strength and the length of the central (chain) region. Moreover, it is rather sensitive to the level of many-body approximation used. Our study shows the importance of the effective/exchange-correlation bias out of equilibrium, thereby offering hints on how to improve the description of density- functional-theory based approaches to quantum transport.
Steady-State and Transient Boundary Element Methods for Coupled Heat Conduction
NASA Technical Reports Server (NTRS)
Kontinos, Dean A.
1997-01-01
Boundary element algorithms for the solution of steady-state and transient heat conduction are presented. The algorithms are designed for efficient coupling with computational fluid dynamic discretizations and feature piecewise linear elements with offset nodal points. The steady-state algorithm employs the fundamental solution approach; the integration kernels are computed analytically based on linear shape functions, linear elements, and variably offset nodal points. The analytic expressions for both singular and nonsingular integrands are presented. The transient algorithm employs the transient fundamental solution; the temporal integration is performed analytically and the nonsingular spatial integration is performed numerically using Gaussian quadrature. A series solution to the integration is derived for the instance of a singular integrand. The boundary-only character of the algorithm is maintained by integrating the influence coefficients from initial time. Numerical results are compared to analytical solutions to verify the current boundary element algorithms. The steady-state and transient algorithms are numerically shown to be second-order accurate in space and time, respectively.
Steady-state bumpless transfer under controller uncertainty using the state/output feedback topology
Zheng, K.; Lee, A.H.; Bentsman, J.; Taft, C.W.
2006-01-15
Linear quadratic (LQ) bumpless transfer design introduced recently by Turner and Walker gives a very convenient and straightforward computational procedure for the steady-state bumpless transfer operator synthesis. It is, however, found to be incapable of providing convergence of the output of the offline controller to that of the online controller in several industrial applications, producing bumps in the plant output in the wake of controller transfer. An examination of this phenomenon reveals that the applications in question are characterized by a significant mismatch, further referred to as controller uncertainty, between the dynamics of the implemented controllers and their models used in the transfer operator computation. To address this problem, while retaining the convenience of the Turner and Walker design, a novel state/output feedback bumpless transfer topology is introduced that employs the nominal state of the offline controller and, through the use of an additional controller/model mismatch compensator, also the offline controller output. A corresponding steady-state bumpless transfer design procedure along with the supporting theory is developed for a large class of systems. Due to these features, it is demonstrated to solve a long-standing problem of high-quality steady-state bumpless transfer from the industry standard low-order nonlinear multiloop PID-based controllers to the modern multiinput-multioutput (MIMO) robust controllers in the megawatt/throttle pressure control of a typical coal-fired boiler/turbine unit.
Arc plasma generator of atomic driver for steady-state negative ion source
Ivanov, A. A.; Belchenko, Yu. I.; Davydenko, V. I.; Ivanov, I. A.; Kolmogorov, V. V.; Listopad, A. A. Mishagin, V. V.; Shulzhenko, G. I.; Putvinsky, S. V.; Smirnov, A.
2014-02-15
The paper reviews the results of development of steady-state arc-discharge plasma generator with directly heated LaB{sub 6} cathode. This arc-discharge plasma generator produces a plasma jet which is to be converted into an atomic one after recombination on a metallic plate. The plate is electrically biased relative to the plasma in order to control the atom energies. Such an intensive jet of hydrogen atoms can be used in negative ion sources for effective production of negative ions on a cesiated surface of plasma grid. All elements of the plasma generator have an augmented water cooling to operate in long pulse mode or in steady state. The thermo-mechanical stresses and deformations of the most critical elements of the plasma generator were determined by simulations. Magnetic field inside the discharge chamber was optimized to reduce the local power loads. The first tests of the steady-state arc plasma generator prototype have performed in long-pulse mode.
The orbital PDF: general inference of the gravitational potential from steady-state tracers
NASA Astrophysics Data System (ADS)
Han, Jiaxin; Wang, Wenting; Cole, Shaun; Frenk, Carlos S.
2016-02-01
We develop two general methods to infer the gravitational potential of a system using steady-state tracers, i.e. tracers with a time-independent phase-space distribution. Combined with the phase-space continuity equation, the time independence implies a universal orbital probability density function (oPDF) dP(λ|orbit) ∝ dt, where λ is the coordinate of the particle along the orbit. The oPDF is equivalent to Jeans theorem, and is the key physical ingredient behind most dynamical modelling of steady-state tracers. In the case of a spherical potential, we develop a likelihood estimator that fits analytical potentials to the system and a non-parametric method (`phase-mark') that reconstructs the potential profile, both assuming only the oPDF. The methods involve no extra assumptions about the tracer distribution function and can be applied to tracers with any arbitrary distribution of orbits, with possible extension to non-spherical potentials. The methods are tested on Monte Carlo samples of steady-state tracers in dark matter haloes to show that they are unbiased as well as efficient. A fully documented C/PYTHON code implementing our method is freely available at a GitHub repository linked from http://icc.dur.ac.uk/data/#oPDF.
On the Kaolinite Floc Size at the Steady State of Flocculation in a Turbulent Flow
Zhu, Zhongfan; Wang, Hongrui; Yu, Jingshan; Dou, Jie
2016-01-01
The flocculation of cohesive fine-grained sediment plays an important role in the transport characteristics of pollutants and nutrients absorbed on the surface of sediment in estuarine and coastal waters through the complex processes of sediment transport, deposition, resuspension and consolidation. Many laboratory experiments have been carried out to investigate the influence of different flow shear conditions on the floc size at the steady state of flocculation in the shear flow. Most of these experiments reported that the floc size decreases with increasing shear stresses and used a power law to express this dependence. In this study, we performed a Couette-flow experiment to measure the size of the kaolinite floc through sampling observation and an image analysis system at the steady state of flocculation under six flow shear conditions. The results show that the negative correlation of the floc size on the flow shear occurs only at high shear conditions, whereas at low shear conditions, the floc size increases with increasing turbulent shear stresses regardless of electrolyte conditions. Increasing electrolyte conditions and the initial particle concentration could lead to a larger steady-state floc size. PMID:26901652
Tromberg, Bruce J.; Berger, Andrew J.; Cerussi, Albert E.; Bevilacqua, Frederic; Jakubowski, Dorota
2008-09-23
A technique for measuring broadband near-infrared absorption spectra of turbid media that uses a combination of frequency-domain and steady-state reflectance methods. Most of the wavelength coverage is provided by a white-light steady-state measurement, whereas the frequency-domain data are acquired at a few selected wavelengths. Coefficients of absorption and reduced scattering derived from the frequency-domain data are used to calibrate the intensity of the steady-state measurements and to determine the reduced scattering coefficient at all wavelengths in the spectral window of interest. The absorption coefficient spectrum is determined by comparing the steady-state reflectance values with the predictions of diffusion theory, wavelength by wavelength. Absorption spectra of a turbid phantom and of human breast tissue in vivo, derived with the combined frequency-domain and steady-state technique, agree well with expected reference values.
Chung, Ching-Hu; Chang, Chien-Hsin; Chen, Shiou-Sheng; Wang, Hsueh-Hsiao; Yen, Juei-Yu; Hsiao, Che-Jen; Wu, Nan-Lin; Chen, Yen-Ling; Huang, Tur-Fu; Wang, Po-Chuan; Yeh, Hung-I; Wang, Shih-Wei
2013-01-01
Compelling evidence indicates that bone marrow-derived endothelial progenitor cells (EPCs) can contribute to postnatal neovascularization and tumor angiogenesis. EPCs have been shown to play a “catalytic” role in metastatic progression by mediating the angiogenic switch. Understanding the pharmacological functions and molecular targets of natural products is critical for drug development. Butein, a natural chalcone derivative, has been reported to exert potent anticancer activity. However, the antiangiogenic activity of butein has not been addressed. In this study, we found that butein inhibited serum- and vascular endothelial growth factor- (VEGF-) induced cell proliferation, migration, and tube formation of human EPCs in a concentration dependent manner without cytotoxic effect. Furthermore, butein markedly abrogated VEGF-induced vessels sprouting from aortic rings and suppressed microvessel formation in the Matrigel implant assay in vivo. In addition, butein concentration-dependently repressed the phosphorylation of Akt, mTOR, and the major downstream effectors, p70S6K, 4E-BP1, and eIF4E in EPCs. Taken together, our results demonstrate for the first time that butein exhibits the antiangiogenic effect both in vitro and in vivo by targeting the translational machinery. Butein is a promising angiogenesis inhibitor with the potential for treatment of cancer and other angiogenesis-related diseases. PMID:23840271
FORMULATION OF NON-STEADY-STATE DUST FORMATION PROCESS IN ASTROPHYSICAL ENVIRONMENTS
Nozawa, Takaya; Kozasa, Takashi
2013-10-10
The non-steady-state formation of small clusters and the growth of grains accompanied by chemical reactions are formulated under the consideration that the collision of key gas species (key molecule) controls the kinetics of dust formation process. The formula allows us to evaluate the size distribution and condensation efficiency of dust formed in astrophysical environments. We apply the formulation to the formation of C and MgSiO{sub 3} grains in the ejecta of supernovae, as an example, to investigate how the non-steady effect influences the formation process, condensation efficiency f{sub con,{sub ∞}}, and average radius a{sub ave,{sub ∞}} of newly formed grains in comparison with the results calculated with the steady-state nucleation rate. We show that the steady-state nucleation rate is a good approximation if the collision timescale of key molecule τ{sub coll} is much smaller than the timescale τ{sub sat} with which the supersaturation ratio increases; otherwise the effect of the non-steady state becomes remarkable, leading to a lower f{sub con,{sub ∞}} and a larger a{sub ave,{sub ∞}}. Examining the results of calculations, we reveal that the steady-state nucleation rate is applicable if the cooling gas satisfies Λ ≡ τ{sub sat}/τ{sub coll} ∼> 30 during the formation of dust, and find that f{sub con,{sub ∞}} and a{sub ave,{sub ∞}} are uniquely determined by Λ{sub on} at the onset time t{sub on} of dust formation. The approximation formulae for f{sub con,{sub ∞}} and a{sub ave,{sub ∞}} as a function of Λ{sub on} could be useful in estimating the mass and typical size of newly formed grains from observed or model-predicted physical properties not only in supernova ejecta but also in mass-loss winds from evolved stars.
NASA Astrophysics Data System (ADS)
Cruz, L.; Teyssier, C.; Annia, F.; Take, A.
2005-12-01
The evolution of orogens is highly affected by surface processes that control mass distribution. Transportation and redistribution of mass at the Earth's surface modifies the gravitational load and alters the stress field and kinematics within orogens. We explore the role of asymmetric erosion, indenter dip angle, and flux steady/non-steady state in determining the patterns of deformation and exhumation in doubly-sided orogenic wedges. In our analogue model, shortening of the orogen is driven by rigid indenters, represented by Plexiglas wedged blocks (35 and 70 degrees) that deform a non-cohesive dry Coulomb material (walnut shells) representing crustal material. Three end-member erosional scenarios are considered. In the first case, erosion is not applied, and thus the doubly-sided orogenic wedge evolves without restraints (non-steady state). In the second case, erosion is concentrated solely on the indenters side of the orogen (retrowedge), and in the third case, erosion is focused on the flank opposite to the indenter side (prowedge). In the last two cases, steady-state conditions were present in the middle stages of shortening. Strain and exhumation were calculated using displacement fields from 2D particle image velocimetry (PIV analysis). In the three cases, the model deforms as a combination of lateral compaction and localization of strain in shear bands. In the early stages of deformation, a "pop-up" structure develops, bounded by a fore-shear on the front and a back-shear toward the indenter. As deformation continues, a new fore-shear develops, and the previous one remains inactive and is passively pushed up the wedge. In the case of no erosion, the old fore-shears rotate slightly toward the indenter, and the shear bands evolve to steeply dipping structures. In the case of retrowedge erosion, the old fore-shears back rotate toward the indenter, and the shear bands evolve to shallowly dipping structures. In the case of prowedge erosion, old fore
NASA Astrophysics Data System (ADS)
Nagel, Hannes; Janke, Wolfhard
2016-05-01
Driven diffusive systems such as the zero-range process (ZRP) and the pair-factorized steady states (PFSS) stochastic transport process are versatile tools that lend themselves to the study of transport phenomena on a generic level. While their mathematical structure is simple enough to allow significant analytical treatment, they offer a variety of interesting phenomena. With appropriate dynamics, the ZRP and PFSS models feature a condensation transition where, for a supercritical density, the translational symmetry breaks spontaneously and excess particles form a single-site or spatially extended condensate, respectively. In this paper we numerically study the typical time scales of the two stages of this condensation process: Nucleation and coarsening. Nucleation is the first stage of condensation where the bulk system relaxes to its stationary distribution and droplet nuclei form in the system. These droplets then gradually grow or evaporate in the coarsening regime to coalesce in a single condensate when the system finally relaxes to the stationary state. We use the ZRP condensation model to discuss the choice of the estimation method for the nucleation time scale and present scaling exponents for the ZRP and PFSS condensation models with respect to the choice of the typical droplet nuclei mass. We then proceed to present scaling exponents in the coarsening regime of the ZRP for partially asymmetric dynamics and the PFSS model for symmetric and asymmetric dynamics.
Christiansen, Torben; Nielsen, Jens
2002-08-28
The production of the extracellular alkaline protease Savinase (EC 3.4.21.62) and glucose uptake in a non-sporulating strain of Bacillus clausii were investigated by analysing steady-state and transients during continuous cultivations. The specific production rate was found to have an optimum at a dilution rate between 0.14 and 0.17 h(-1), whereas the yield of Savinase on glucose was found to increase with decreasing specific growth rate. A linear relationship between the ribosomal RNA content and the specific production rate was found, indicating that the translational capacity may be limiting for product formation. The dynamics of the production of Savinase were studied during step changes in the dilution rate. During a step down in the dilution rate the specific production rate decreased immediately until it reached a new steady value. During a step-up an initial cease in the production rate was observed, but when glucose stopped to accumulate the production rate was regained. The glucose uptake was further investigated when chemostat cultures growing at different dilution rates were exposed to glucose pulses. The maximal glucose uptake capacity was found to be dependent on the initial specific growth rate. Furthermore, the adaptation to high glucose concentrations was faster at high dilution rates than at low dilution rates. PMID:12084482
Region-Specific Activation of oskar mRNA Translation by Inhibition of Bruno-Mediated Repression
Kim, Goheun; Pai, Chin-I; Sato, Keiji; Person, Maria D.; Nakamura, Akira; Macdonald, Paul M.
2015-01-01
A complex program of translational repression, mRNA localization, and translational activation ensures that Oskar (Osk) protein accumulates only at the posterior pole of the Drosophila oocyte. Inappropriate expression of Osk disrupts embryonic axial patterning, and is lethal. A key factor in translational repression is Bruno (Bru), which binds to regulatory elements in the osk mRNA 3′ UTR. After posterior localization of osk mRNA, repression by Bru must be alleviated. Here we describe an in vivo assay system to monitor the spatial pattern of Bru-dependent repression, separate from the full complexity of osk regulation. This assay reveals a form of translational activation—region-specific activation—which acts regionally in the oocyte, is not mechanistically coupled to mRNA localization, and functions by inhibiting repression by Bru. We also show that Bru dimerizes and identify mutations that disrupt this interaction to test its role in vivo. Loss of dimerization does not disrupt repression, as might have been expected from an existing model for the mechanism of repression. However, loss of dimerization does impair regional activation of translation, suggesting that dimerization may constrain, not promote, repression. Our work provides new insight into the question of how localized mRNAs become translationally active, showing that repression of osk mRNA is locally inactivated by a mechanism acting independent of mRNA localization. PMID:25723530
Gebauer, F; Merendino, L; Hentze, M W; Valcárcel, J
1998-01-01
Male-specific expression of the protein male-specific-lethal 2 (MSL-2) controls dosage compensation in Drosophila. msl-2 gene expression is inhibited in females by Sex-lethal (SXL), an RNA binding protein known to regulate pre-mRNA splicing. An intron present at the 5' untranslated region (UTR) of msl-2 mRNA contains putative SXL binding sites and is retained in female flies. Here we show that SXL plays a dual role in the inhibition of msl-2 expression. Cotransfection of Drosophila Schneider cells with an SXL expression vector and a reporter containing the 5' UTR of msl-2 mRNA resulted in retention of the 5' UTR intron and efficient accumulation of the unspliced mRNA in the cytoplasm, where its translation was blocked by SXL, but not by the intron per se. Both splicing and translation inhibition by SXL were recapitulated in vitro and found to be dependent upon SXL binding to high-affinity sites within the intron, showing that SXL directly regulates these events. Our data reveal a coordinated mechanism for the regulation of msl-2 expression by the same regulatory factor: SXL enforces intron retention in the nucleus and subsequent translation inhibition in the cytoplasm. PMID:9570314
Jiao, J.; Grodzinski, B.
1996-01-01
Export and photosynthesis in leaves of Salvia splendens were measured concurrently during steady-state 14CO2 labeling conditions. Under ambient CO2 and O2 conditions, photosynthesis and export rates were similar at 15 and 25[deg]C, but both declined as leaf temperature was raised from 25 to 40[deg]C. Suppressing photorespiration between 15 and 40[deg]C by manipulating CO2 and O2 levels resulted in higher rates of leaf photosynthesis, total sugar synthesis, and export. There was a linear relationship between the rate of photosynthesis and the rate of export between 15 and 35[deg]C. At these temperatures, 60 to 80% of the carbon fixed was readily exported with sucrose, raffinose, and stachyose, which together constituted over 90% of phloem mobile assimilates. Above 35[deg]C, however, export during photosynthesis was inhibited both in photorespiratory conditions, which inhibited photosynthesis, and in nonphotorespiratory conditions, which did not inhibit photosynthesis. Sucrose and raffinose but not stachyose accumulated in the leaf at 40[deg]C. When leaves were preincubated at 40[deg]C and then cooled to 35[deg]C, export recovered more slowly than photosynthesis. These data are consistent with the view that impairment of export processes, rather than photosynthetic processes associated with light trapping, carbon reduction, and sucrose synthesis, accounted for the marked reduction in export between 35 and 40[deg]C. Taken together, the data indicated that temperature changes between 15 and 40[deg]C had two effects on photosynthesis and concurrent export. At all temperatures, suppressing photorespiration increased both photosynthesis and export, but above 35[deg]C, export processes were more directly inhibited independent of changes in photorespiration and photosynthesis. PMID:12226282
Lin, Yuan-Pin; Wang, Yijun; Wei, Chun-Shu; Jung, Tzyy-Ping
2014-01-01
Recent advances in mobile electroencephalogram (EEG) systems, featuring non-prep dry electrodes and wireless telemetry, have enabled and promoted the applications of mobile brain-computer interfaces (BCIs) in our daily life. Since the brain may behave differently while people are actively situated in ecologically-valid environments versus highly-controlled laboratory environments, it remains unclear how well the current laboratory-oriented BCI demonstrations can be translated into operational BCIs for users with naturalistic movements. Understanding inherent links between natural human behaviors and brain activities is the key to ensuring the applicability and stability of mobile BCIs. This study aims to assess the quality of steady-state visual-evoked potentials (SSVEPs), which is one of promising channels for functioning BCI systems, recorded using a mobile EEG system under challenging recording conditions, e.g., walking. To systematically explore the effects of walking locomotion on the SSVEPs, this study instructed subjects to stand or walk on a treadmill running at speeds of 1, 2, and 3 mile (s) per hour (MPH) while concurrently perceiving visual flickers (11 and 12 Hz). Empirical results of this study showed that the SSVEP amplitude tended to deteriorate when subjects switched from standing to walking. Such SSVEP suppression could be attributed to the walking locomotion, leading to distinctly deteriorated SSVEP detectability from standing (84.87 ± 13.55%) to walking (1 MPH: 83.03 ± 13.24%, 2 MPH: 79.47 ± 13.53%, and 3 MPH: 75.26 ± 17.89%). These findings not only demonstrated the applicability and limitations of SSVEPs recorded from freely behaving humans in realistic environments, but also provide useful methods and techniques for boosting the translation of the BCI technology from laboratory demonstrations to practical applications. PMID:24744718
Using Cosmogenic Nuclides to Examine Erosional Steady-State in the Western Alps
NASA Astrophysics Data System (ADS)
Perg, L. A.; von Blanckenburg, F.; Kubik, P.
2002-12-01
Geomorphologists have long been interested in the amount of time needed for landscapes to reach equilibrium after climate or tectonic perturbation. Cosmogenic nuclides provide a means to determine whether landscapes have reached equilibrium after glacial retreat. The cosmogenic nuclide budget should be mostly balanced (input through production equals output through erosion) after removal of one spallation length scale, about 60 cm of material. If a catchment has achieved steady-state erosional loss of cosmogenic nuclides, the cosmogenic nuclide concentration of the river sediment will provide the long-term basin-averaged denudation rate. If a deglaciated catchment has not reached steady-state, the apparent erosion rates will be too high. The apparent erosion rates obtained using cosmogenic nuclides can be compared with the denudation rates obtained from sediment accumulation in glacial lakes and valleys to determine whether the landscape has reached steady-state. Different sediment sources were sampled along a NS transect through the Western Alps from the highland (1 mm/yr uplift) to the foreland (no uplift, net deposition). Samples include: subglacial outwash; intraglacial sediment; moraines (surface and deeply buried material); currently glaciated, formerly glaciated and never glaciated catchments; and large river samples that integrate these sediment sources. Sediment traps indicate a long-term erosion rate of about 0.12 m / k.y. in the W. Alps during the Holocene (Hinderer, 2001). At this rate of denudation, the cosmogenic nuclide concentrations should approach steady-state in 5-6 k.y. However, the apparent cosmogenic nuclide erosion rates are much higher (0.3 m / k.y. in the foreland and 2 m / k.y. in the highland) indicating that the landscape has not reached equilibrium in two to three times that length of time. One possible explanation is intermediate sediment storage, such as alluvial fans, with higher concentration sediment not yet reaching the streams
Steady state estimation of soil organic carbon using satellite-derived canopy leaf area index
Fang, Yilin; Liu, Chongxuan; Huang, Maoyi; Li, Hongyi; Leung, Lai-Yung R.
2014-12-02
Soil organic carbon (SOC) plays a key role in the global carbon cycle that is important for decadal-to-century climate prediction. Estimation of soil organic carbon stock using model-based methods typically requires spin-up (time marching transient simulation) of the carbon-nitrogen (CN) models by performing hundreds to thousands years long simulations until the carbon-nitrogen pools reach dynamic steady-state. This has become a bottleneck for global modeling and analysis, especially when testing new physical and/or chemical mechanisms and evaluating parameter sensitivity. Here we report a new numerical approach to estimate global soil carbon stock that can avoid the long term spin-up of themore » CN model. The approach uses canopy leaf area index (LAI) from satellite data and takes advantage of a reaction-based biogeochemical module NGBGC (Next Generation BioGeoChemical Module) that was recently developed and incorporated in version 4 of the Community Land Model (CLM4). Although NGBGC uses the same CN mechanisms as used in CLM4CN, it can be easily configured to run prognostic or steady state simulations. In this approach, monthly LAI from the multi-year Moderate Resolution Imaging Spectroradiometer (MODIS) data was used to calculate potential annual average gross primary production (GPP) and leaf carbon for the period of the atmospheric forcing. The calculated potential annual average GPP and leaf C are then used by NGBGC to calculate the steady-state distributions of carbon and nitrogen in different vegetation and soil pools by solving the steady-state reaction-network in NGBGC using the Newton-Raphson method. The new approach was applied at point and global scales and compared with SOC derived from long spin-up by running NGBGC in prognostic mode, and SOC from the empirical data of the Harmonized World Soil Database (HWSD). The steady-state solution is comparable to the spin-up value when the MODIS LAI is close to the LAI from the spin-up solution, and largely
Steady state estimation of soil organic carbon using satellite-derived canopy leaf area index
Fang, Yilin; Liu, Chongxuan; Huang, Maoyi; Li, Hongyi; Leung, Lai-Yung R.
2014-12-02
Soil organic carbon (SOC) plays a key role in the global carbon cycle that is important for decadal-to-century climate prediction. Estimation of soil organic carbon stock using model-based methods typically requires spin-up (time marching transient simulation) of the carbon-nitrogen (CN) models by performing hundreds to thousands years long simulations until the carbon-nitrogen pools reach dynamic steady-state. This has become a bottleneck for global modeling and analysis, especially when testing new physical and/or chemical mechanisms and evaluating parameter sensitivity. Here we report a new numerical approach to estimate global soil carbon stock that can avoid the long term spin-up of the CN model. The approach uses canopy leaf area index (LAI) from satellite data and takes advantage of a reaction-based biogeochemical module NGBGC (Next Generation BioGeoChemical Module) that was recently developed and incorporated in version 4 of the Community Land Model (CLM4). Although NGBGC uses the same CN mechanisms as used in CLM4CN, it can be easily configured to run prognostic or steady state simulations. In this approach, monthly LAI from the multi-year Moderate Resolution Imaging Spectroradiometer (MODIS) data was used to calculate potential annual average gross primary production (GPP) and leaf carbon for the period of the atmospheric forcing. The calculated potential annual average GPP and leaf C are then used by NGBGC to calculate the steady-state distributions of carbon and nitrogen in different vegetation and soil pools by solving the steady-state reaction-network in NGBGC using the Newton-Raphson method. The new approach was applied at point and global scales and compared with SOC derived from long spin-up by running NGBGC in prognostic mode, and SOC from the empirical data of the Harmonized World Soil Database (HWSD). The steady-state solution is comparable to the spin-up value when the MODIS LAI is close to the LAI from the spin-up solution, and largely
NASA Technical Reports Server (NTRS)
Pogorzelski, Ronald J.
2004-01-01
When electronic oscillators are coupled to nearest neighbors to form an array on a hexagonal lattice, the planar phase distributions desired for excitation of a phased array antenna are not steady state solutions of the governing non-linear equations describing the system. Thus the steady state phase distribution deviates from planar. It is shown to be possible to obtain an exact solution for the steady state phase distribution and thus determine the deviation from the desired planar distribution as a function of beam steering angle.