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Sample records for activity state stability

  1. Steel passive state stability in activated fly ash mortars

    Directory of Open Access Journals (Sweden)

    Fernández-Jiménez, A.

    2010-12-01

    Full Text Available The present study explores the behaviour of structural steel embedded in Portland cement (OPC mortars and NaOH- and NaOH-waterglass-activated fly ash, in the presence and absence of 2 % Cl- (CaCl2. Variations were determined in the corrosion potential (Ecorr, linear polarization resistance (Rp and corrosion current density (icorr under different environmental conditions (90 days at 95 % relative humidity (RH, 30 days at ≈ 30 % RH, 760 days at ≈ 95 % RH. In the absence of Cl-, fly ash mortars were able to passivate steel reinforcement, although the stability of the passive state in changing environmental conditions was found to depend heavily on the activating solution used. Steel corrosion in the presence of 2 % Cl- was observed to be similar to the corrosion reported for the material in OPC mortars.

    En el presente trabajo se estudia el comportamiento del acero estructural embebido en morteros de cemento Pórtland (OPC y de cenizas volantes activadas con NaOH y una mezcla de NaOH y waterglass, en ausencia y en presencia de un 2% de Cl- (CaCl2. Se determino la evolución del potencial de corrosión (Ecorr, la resistencia de polarización lineal (Rp y la intensidad de corrosión (icorr, variando las condiciones ambientales (90 días al 95% de humedad relativa (HR-30 días a ≈ 30% HR- 760 días a ≈ 95% HR. En ausencia de Cl- los morteros de cenizas volantes activadas pueden pasivar los refuerzos de acero, si bien la estabilidad del estado pasivo ante cambios en las condiciones ambientales parece mostrar una fuerte dependencia de la solución activadora empleada. En presencia de un 2% de Cl- los aceros se corroen mostrando en comportamiento similar al observado en morteros en base OPC.

  2. Visualization of the Differential Transition State Stabilization within the Active Site Environment

    Directory of Open Access Journals (Sweden)

    Jerzy Leszczynski

    2004-05-01

    Full Text Available Abstract: Increasing interest in the enzymatic reaction mechanisms and in the nature of catalytic effects in enzymes causes the need of appropriate visualization methods. A new interactive method to investigate catalytic effects using differential transition state stabilization approach (DTSS [1, 2] is presented. The catalytic properties of the active site of cytidine deaminase (E.C. 3.5.4.5 is visualized in the form of differential electrostatic properties. The visualization was implemented using scripting interface of VMD [3]. Cumulative Atomic Multipole Moments (CAMM [4,5,6] were utilized for efficient yet accurate evaluation of the electrostatic properties. The implementation is efficient enough for interactive presentation of catalytic effects in the active site of the enzyme due to transition state or substrate movement. This system of visualization of DTTS approach can be potentially used to validate hypotheses regarding the catalytic mechanism or to study binding properties of transition state analogues.

  3. Correlations in background activity control persistent state stability and allow execution of working memory tasks

    Directory of Open Access Journals (Sweden)

    Mario eDipoppa

    2013-10-01

    Full Text Available Working memory (WM is tightly capacity limited, it requires selective information gating, active information maintenance, and rapid active updating. Hence performing a WM task needs rapid and controlled transitions between neural persistent activity and the resting state. We propose that changes in spike-time correlations in neural activity provides a mechanism for the required working memory operations. As a proof of principle, we implement sustained activity and working memory in a recurrently-coupled spiking network with neurons receiving excitatory random background activity where background correlations are induced by a common noise source. We first characterize how the level of background correlations controls the stability of the persistent state. With sufficiently high correlations, the sustained state becomes practically unstable, so it cannot be initiated by a transient stimulus. We exploit this in a working memory model implementing the delay match to sample task by modulating flexibly in time the correlation level at different phases of the task. The modulation sets the network in different working regimes: more prompt to gate in a signal or clear the memory. The findings presented in this manuscript can form the basis for a new paradigm about how correlations are flexibly controlled by the cortical circuits to execute WM operations.

  4. Correlations in background activity control persistent state stability and allow execution of working memory tasks.

    Science.gov (United States)

    Dipoppa, Mario; Gutkin, Boris S

    2013-01-01

    Working memory (WM) requires selective information gating, active information maintenance, and rapid active updating. Hence performing a WM task needs rapid and controlled transitions between neural persistent activity and the resting state. We propose that changes in correlations in neural activity provides a mechanism for the required WM operations. As a proof of principle, we implement sustained activity and WM in recurrently coupled spiking networks with neurons receiving excitatory random background activity where background correlations are induced by a common noise source. We first characterize how the level of background correlations controls the stability of the persistent state. With sufficiently high correlations, the sustained state becomes practically unstable, so it cannot be initiated by a transient stimulus. We exploit this in WM models implementing the delay match to sample task by modulating flexibly in time the correlation level at different phases of the task. The modulation sets the network in different working regimes: more prompt to gate in a signal or clear the memory. We examine how the correlations affect the ability of the network to perform the task when distractors are present. We show that in a winner-take-all version of the model, where two populations cross-inhibit, correlations make the distractor blocking robust. In a version of the mode where no cross inhibition is present, we show that appropriate modulation of correlation levels is sufficient to also block the distractor access while leaving the relevant memory trace in tact. The findings presented in this manuscript can form the basis for a new paradigm about how correlations are flexibly controlled by the cortical circuits to execute WM operations.

  5. Comparative Solid-State Stability of Perindopril Active Substance vs. Pharmaceutical Formulation

    Science.gov (United States)

    Buda, Valentina; Andor, Minodora; Ledeti, Adriana; Ledeti, Ionut; Vlase, Gabriela; Vlase, Titus; Cristescu, Carmen; Voicu, Mirela; Suciu, Liana; Tomescu, Mirela Cleopatra

    2017-01-01

    This paper presents the results obtained after studying the thermal stability and decomposition kinetics of perindopril erbumine as a pure active pharmaceutical ingredient as well as a solid pharmaceutical formulation containing the same active pharmaceutical ingredient (API). Since no data were found in the literature regarding the spectroscopic description, thermal behavior, or decomposition kinetics of perindopril, our goal was the evaluation of the compatibility of this antihypertensive agent with the excipients in the tablet under ambient conditions and to study the effect of thermal treatment on the stability of perindopril erbumine. ATR-FTIR (Attenuated Total Reflectance Fourier Transform Infrared) spectroscopy, thermal analysis (thermogravimetric mass curve (TG—thermogravimetry), derivative thermogravimetric mass curve (DTG), and heat flow (HF)) and model-free kinetics were chosen as investigational tools. Since thermal behavior is a simplistic approach in evaluating the thermal stability of pharmaceuticals, in-depth kinetic studies were carried out by classical kinetic methods (Kissinger and ASTM E698) and later with the isoconversional methods of Friedman, Kissinger-Akahira-Sunose and Flynn-Wall-Ozawa. It was shown that the main thermal degradation step of perindopril erbumine is characterized by activation energy between 59 and 69 kJ/mol (depending on the method used), while for the tablet, the values were around 170 kJ/mol. The used excipients (anhydrous colloidal silica, microcrystalline cellulose, lactose, and magnesium stearate) should be used in newly-developed generic solid pharmaceutical formulations, since they contribute to an increased thermal stability of perindopril erbumine. PMID:28098840

  6. Comparative Solid-State Stability of Perindopril Active Substance vs. Pharmaceutical Formulation

    Directory of Open Access Journals (Sweden)

    Valentina Buda

    2017-01-01

    Full Text Available This paper presents the results obtained after studying the thermal stability and decomposition kinetics of perindopril erbumine as a pure active pharmaceutical ingredient as well as a solid pharmaceutical formulation containing the same active pharmaceutical ingredient (API. Since no data were found in the literature regarding the spectroscopic description, thermal behavior, or decomposition kinetics of perindopril, our goal was the evaluation of the compatibility of this antihypertensive agent with the excipients in the tablet under ambient conditions and to study the effect of thermal treatment on the stability of perindopril erbumine. ATR-FTIR (Attenuated Total Reflectance Fourier Transform Infrared spectroscopy, thermal analysis (thermogravimetric mass curve (TG—thermogravimetry, derivative thermogravimetric mass curve (DTG, and heat flow (HF and model-free kinetics were chosen as investigational tools. Since thermal behavior is a simplistic approach in evaluating the thermal stability of pharmaceuticals, in-depth kinetic studies were carried out by classical kinetic methods (Kissinger and ASTM E698 and later with the isoconversional methods of Friedman, Kissinger-Akahira-Sunose and Flynn-Wall-Ozawa. It was shown that the main thermal degradation step of perindopril erbumine is characterized by activation energy between 59 and 69 kJ/mol (depending on the method used, while for the tablet, the values were around 170 kJ/mol. The used excipients (anhydrous colloidal silica, microcrystalline cellulose, lactose, and magnesium stearate should be used in newly-developed generic solid pharmaceutical formulations, since they contribute to an increased thermal stability of perindopril erbumine.

  7. Structure of a nanobody-stabilized active state of the β(2) adrenoceptor

    DEFF Research Database (Denmark)

    Rasmussen, Søren Gøgsig Faarup; Choi, Hee-Jung; Fung, Juan Jose;

    2011-01-01

    G protein coupled receptors (GPCRs) exhibit a spectrum of functional behaviours in response to natural and synthetic ligands. Recent crystal structures provide insights into inactive states of several GPCRs. Efforts to obtain an agonist-bound active-state GPCR structure have proven difficult due...... to the inherent instability of this state in the absence of a G protein. We generated a camelid antibody fragment (nanobody) to the human β(2) adrenergic receptor (β(2)AR) that exhibits G protein-like behaviour, and obtained an agonist-bound, active-state crystal structure of the receptor-nanobody complex....... Comparison with the inactive β(2)AR structure reveals subtle changes in the binding pocket; however, these small changes are associated with an 11 Å outward movement of the cytoplasmic end of transmembrane segment 6, and rearrangements of transmembrane segments 5 and 7 that are remarkably similar to those...

  8. Quantum Contextuality with Stabilizer States

    Directory of Open Access Journals (Sweden)

    Jiri Vala

    2013-06-01

    Full Text Available The Pauli groups are ubiquitous in quantum information theory because of their usefulness in describing quantum states and operations and their readily understood symmetry properties. In addition, the most well-understood quantum error correcting codes—stabilizer codes—are built using Pauli operators. The eigenstates of these operators—stabilizer states—display a structure (e.g., mutual orthogonality relationships that has made them useful in examples of multi-qubit non-locality and contextuality. Here, we apply the graph-theoretical contextuality formalism of Cabello, Severini and Winter to sets of stabilizer states, with particular attention to the effect of generalizing two-level qubit systems to odd prime d-level qudit systems. While state-independent contextuality using two-qubit states does not generalize to qudits, we show explicitly how state-dependent contextuality associated with a Bell inequality does generalize. Along the way we note various structural properties of stabilizer states, with respect to their orthogonality relationships, which may be of independent interest.

  9. Active Stabilization of Aeromechanical Systems

    Science.gov (United States)

    1993-01-05

    feedback, the resulting two-mode proportonal control law further extended the stable range of operation of the compresor . Stall flow coefficient was...active control of surge and stall in gas turbine engines. The use of small amplitude waves predicted by theory as stall precursors were tested with...stabilization system for rotating stall which was tested on both a single-stage and a three-stage axial compressor, increasing the stable operating range

  10. Incorporation of low energy activated nitrogen onto HOPG surface: Chemical states and thermal stability studies by in-situ XPS and Raman spectroscopy

    Science.gov (United States)

    Chandran, Maneesh; Shasha, Michal; Michaelson, Shaul; Hoffman, Alon

    2016-09-01

    In this paper we report the chemical states analysis of activated nitrogen incorporated highly oriented pyrolytic graphite (HOPG) surface under well-controlled conditions. Nitrogen incorporation is carried out by two different processes: an indirect RF nitrogen plasma and low energy (1 keV) N2+ implantation. Bonding configuration, concentration and thermal stability of the incorporated nitrogen species by aforesaid processes are systematically compared by in-situ X-ray photoelectron spectroscopy (XPS). Relatively large concentration of nitrogen is incorporated onto RF nitride HOPG surface (16.2 at.%), compared to N2+ implanted HOPG surface (7.7 at.%). The evolution of N 1s components (N1, N2, N3) with annealing temperature is comprehensively discussed, which indicates that the formation and reorganization of local chemical bonding states are determined by the process of nitridation and not by the prior chemical conditioning (i.e., amorphization or hydrogenation) of the HOPG surface. A combined XPS and Raman spectroscopy studies revealed that N2+ implantation process resulted in a high level of defects to the HOPG surface, which cannot be annealed-out by heat treatment up to 1000 °C. On the other hand, the RF nitrogen plasma process did not produce a high level of surface defects, while incorporating nearly the same amount of stable nitrogen species.

  11. State-space Correlations and Stabilities

    CERN Document Server

    Bellucci, Stefano

    2010-01-01

    The state-space pair correlation functions and notion of stability of extremal and non-extremal black holes in string theory and M-theory are considered from the viewpoints of thermodynamic Ruppeiner geometry. From the perspective of intrinsic Riemannian geometry, the stability properties of these black branes are divulged from the positivity of principle minors of the space-state metric tensor. We have explicitly analyzed the state-space configurations for (i) the two and three charge extremal black holes, (ii) the four and six charge non-extremal black branes, which both arise from the string theory solutions. An extension is considered for the $D_6$-$D_4$-$D_2$-$D_0$ multi-centered black branes, fractional small black branes and two charge rotating fuzzy rings in the setup of Mathur's fuzzball configurations. The state-space pair correlations and nature of stabilities have been investigated for three charged bubbling black brane foams, and thereby the M-theory solutions are brought into the present conside...

  12. Video tonal stabilization via color states smoothing.

    Science.gov (United States)

    Wang, Yinting; Tao, Dacheng; Li, Xiang; Song, Mingli; Bu, Jiajun; Tan, Ping

    2014-11-01

    We address the problem of removing video color tone jitter that is common in amateur videos recorded with hand-held devices. To achieve this, we introduce color state to represent the exposure and white balance state of a frame. The color state of each frame can be computed by accumulating the color transformations of neighboring frame pairs. Then, the tonal changes of the video can be represented by a time-varying trajectory in color state space. To remove the tone jitter, we smooth the original color state trajectory by solving an L1 optimization problem with PCA dimensionality reduction. In addition, we propose a novel selective strategy to remove small tone jitter while retaining extreme exposure and white balance changes to avoid serious artifacts. Quantitative evaluation and visual comparison with previous work demonstrate the effectiveness of our tonal stabilization method. This system can also be used as a preprocessing tool for other video editing methods.

  13. Nanobody stabilization of G protein coupled receptor conformational states

    Science.gov (United States)

    Steyaert, Jan; K Kobilka, Brian

    2011-01-01

    Remarkable progress has been made in the field of G protein coupled receptor (GPCR) structural biology during the past four years. Several obstacles to generating diffraction quality crystals of GPCRs have been overcome by combining innovative methods ranging from protein engineering to lipid-based screens and microdiffraction technology. The initial GPCR structures represent energetically stable inactive-state conformations. However, GPCRs signal through different G protein isoforms or G protein-independent effectors upon ligand binding suggesting the existence of multiple ligand-specific active states. These active-state conformations are unstable in the absence of specific cytosolic signaling partners representing new challenges for structural biology. Camelid single chain antibody fragments (nanobodies) show promise for stabilizing active GPCR conformations and as chaperones for crystallogenesis. PMID:21782416

  14. Activating Welfare States

    DEFF Research Database (Denmark)

    Kvist, Jon

    This paper investigates how welfare states may actively contribute to promote employment opportunities, i.e. participation in the labour market through various operations and policies. The principal operations concern in particular the de-familiarisation of caring tasks through social services...

  15. Towards Stabilizing Parametric Active Contours

    DEFF Research Database (Denmark)

    Liu, Jinchao; Fan, Zhun; Olsen, Søren Ingvor;

    2014-01-01

    Numerical instability often occurs in evolving of parametric active contours. This is mainly due to the undesired change of parametrization during evolution. In this paper, we propose a new tangential diffusion term to compensate this undesired change. As a result, the parametrization will converge...

  16. Emotional stability, anxiety, and natural killer activity under examination stress.

    Science.gov (United States)

    Borella, P; Bargellini, A; Rovesti, S; Pinelli, M; Vivoli, R; Solfrini, V; Vivoli, G

    1999-08-01

    This study was performed to evaluate the relation between a stable personality trait, a mood state and immune response to an examination stress. A self-reported measure of emotional stability (BFQ-ES scale) was obtained in a sample (n = 39) randomly selected from 277 cadets; this personality trait was also investigated by completing a neuroticism scale (Eysenck personality inventory) and a trait-anxiety scale (STAI). Natural killer (NK) cell activity was measured at baseline, long before the examination time and the examination day. The state-anxiety scale evaluated the response to the stressful stimulus. Taking subjects all together, the academic task did not result in significant modification over baseline in NK cell activity. Subjects were then divided into three groups based on emotional stability and state-anxiety scores: high emotional stability/low anxiety, medium, and low emotional stability/high anxiety. Examination stress induced significant increases in NK cell activity in the high emotional stability/low anxiety group, no effect in the medium group, and significant decreases in the low emotional stability/high anxiety group. The repeated-measure ANOVA revealed a significant interaction of group x period (baseline vs. examination) for both lytic units and percent cytolysis. The results did not change after introducing coffee and smoking habits as covariates. Our findings suggest that the state-anxiety acts in concert with a stable personality trait to modulate NK response in healthy subjects exposed to a psychological naturalistic stress. The relation between anxiety and poor immune control has been already described, whereas the ability of emotional stability to associate with an immunoenhancement has not yet reported. The peculiarity of our population, a very homogeneous and healthy group for life style and habits, can have highlighted the role of emotional stability, and may account for the difference with other studies.

  17. Vehicle lateral dynamics stabilization using active suspension

    Directory of Open Access Journals (Sweden)

    Drobný V.

    2008-12-01

    Full Text Available The paper deals with the investigation of active nonlinear suspension control in order to stabilize the lateral vehicle motion in similar way as systems like ESP do. The lateral stabilization of vehicle based on braking forces can be alternatively provided by the different setting of suspension forces. The basis of this control is the nonlinear property of the tyres. The vehicle has at least four wheels and it gives one or more redundant vertical forces that can be used for the different distribution of vertical suspension forces in such a way that resulting lateral and/or longitudinal forces create the required correction moment for lateral dynamic vehicle stabilization.

  18. Active Risk Management and Banking Stability

    NARCIS (Netherlands)

    Silva Buston, C.F.

    2013-01-01

    Abstract: This paper analyzes the net impact of two opposing effects of active risk management at banks on their stability: higher risk-taking incentives and better isolation of credit supply from varying economic conditions. We present a model where banks actively manage their portfolio risk by buy

  19. Active Risk Management and Banking Stability

    NARCIS (Netherlands)

    Silva Buston, C.F.

    2013-01-01

    Abstract: This paper analyzes the net impact of two opposing effects of active risk management at banks on their stability: higher risk-taking incentives and better isolation of credit supply from varying economic conditions. We present a model where banks actively manage their portfolio risk by

  20. Entanglement on mixed stabilizer states: normal forms and reduction procedures

    Energy Technology Data Exchange (ETDEWEB)

    Audenaert, Koenraad M R; Plenio, Martin B [Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2BW (United Kingdom); Institute for Mathematical Sciences, Imperial College London, Exhibition Road, London SW7 2BW (United Kingdom)

    2005-08-01

    The stabilizer formalism allows the efficient description of a sizeable class of pure as well as mixed quantum states of n-qubit systems. That same formalism has important applications in the field of quantum error correcting codes, where mixed stabilizer states correspond to projectors on subspaces associated with stabilizer codes. In this paper, we derive efficient reduction procedures to obtain various useful normal forms for stabilizer states. We explicitly prove that these procedures will always converge to the correct result and that these procedures are efficient in that they only require a polynomial number of operations on the generators of the stabilizers. On one hand, we obtain two single-party normal forms. The first, the row-reduced echelon form, is obtained using only permutations and multiplications of generators. This form is useful to calculate partial traces of stabilizer states. The second is the fully reduced form, where the reduction procedure invokes single-qubit operations and CNOT operations as well. This normal form allows for the efficient calculation of the overlap between two stabilizer states, as well as of the Uhlmann fidelity between them, and their Bures distance. On the other hand, we also find a reduction procedure of bipartite stabilizer states, where the operations involved are restricted to be local ones. The two-party normal form thus obtained lays bare a very simple bipartite entanglement structure of stabilizer states. To wit, we prove that every bipartite mixed stabilizer state is locally equivalent to a direct product of a number of maximally entangled states and, potentially, a separable state. As a consequence, using this normal form we can efficiently calculate every reasonable bipartite entanglement measure of mixed stabilizer states.

  1. Basin stability measure of different steady states in coupled oscillators.

    Science.gov (United States)

    Rakshit, Sarbendu; Bera, Bidesh K; Majhi, Soumen; Hens, Chittaranjan; Ghosh, Dibakar

    2017-04-05

    In this report, we investigate the stabilization of saddle fixed points in coupled oscillators where individual oscillators exhibit the saddle fixed points. The coupled oscillators may have two structurally different types of suppressed states, namely amplitude death and oscillation death. The stabilization of saddle equilibrium point refers to the amplitude death state where oscillations are ceased and all the oscillators converge to the single stable steady state via inverse pitchfork bifurcation. Due to multistability features of oscillation death states, linear stability theory fails to analyze the stability of such states analytically, so we quantify all the states by basin stability measurement which is an universal nonlocal nonlinear concept and it interplays with the volume of basins of attractions. We also observe multi-clustered oscillation death states in a random network and measure them using basin stability framework. To explore such phenomena we choose a network of coupled Duffing-Holmes and Lorenz oscillators which are interacting through mean-field coupling. We investigate how basin stability for different steady states depends on mean-field density and coupling strength. We also analytically derive stability conditions for different steady states and confirm by rigorous bifurcation analysis.

  2. Basin stability measure of different steady states in coupled oscillators

    Science.gov (United States)

    Rakshit, Sarbendu; Bera, Bidesh K.; Majhi, Soumen; Hens, Chittaranjan; Ghosh, Dibakar

    2017-01-01

    In this report, we investigate the stabilization of saddle fixed points in coupled oscillators where individual oscillators exhibit the saddle fixed points. The coupled oscillators may have two structurally different types of suppressed states, namely amplitude death and oscillation death. The stabilization of saddle equilibrium point refers to the amplitude death state where oscillations are ceased and all the oscillators converge to the single stable steady state via inverse pitchfork bifurcation. Due to multistability features of oscillation death states, linear stability theory fails to analyze the stability of such states analytically, so we quantify all the states by basin stability measurement which is an universal nonlocal nonlinear concept and it interplays with the volume of basins of attractions. We also observe multi-clustered oscillation death states in a random network and measure them using basin stability framework. To explore such phenomena we choose a network of coupled Duffing-Holmes and Lorenz oscillators which are interacting through mean-field coupling. We investigate how basin stability for different steady states depends on mean-field density and coupling strength. We also analytically derive stability conditions for different steady states and confirm by rigorous bifurcation analysis. PMID:28378760

  3. Stabilization of memory States by stochastic facilitating synapses.

    Science.gov (United States)

    Miller, Paul

    2013-12-06

    Bistability within a small neural circuit can arise through an appropriate strength of excitatory recurrent feedback. The stability of a state of neural activity, measured by the mean dwelling time before a noise-induced transition to another state, depends on the neural firing-rate curves, the net strength of excitatory feedback, the statistics of spike times, and increases exponentially with the number of equivalent neurons in the circuit. Here, we show that such stability is greatly enhanced by synaptic facilitation and reduced by synaptic depression. We take into account the alteration in times of synaptic vesicle release, by calculating distributions of inter-release intervals of a synapse, which differ from the distribution of its incoming interspike intervals when the synapse is dynamic. In particular, release intervals produced by a Poisson spike train have a coefficient of variation greater than one when synapses are probabilistic and facilitating, whereas the coefficient of variation is less than one when synapses are depressing. However, in spite of the increased variability in postsynaptic input produced by facilitating synapses, their dominant effect is reduced synaptic efficacy at low input rates compared to high rates, which increases the curvature of neural input-output functions, leading to wider regions of bistability in parameter space and enhanced lifetimes of memory states. Our results are based on analytic methods with approximate formulae and bolstered by simulations of both Poisson processes and of circuits of noisy spiking model neurons.

  4. Active Stabilization of Ion Trap Radiofrequency Potentials

    CERN Document Server

    Johnson, K G; Neyenhuis, B; Mizrahi, J; Monroe, C

    2016-01-01

    We actively stabilize the harmonic oscillation frequency of a laser-cooled atomic ion confined in a rf Paul trap by sampling and rectifying the high voltage rf applied to the trap electrodes. We are able to stabilize the 1 MHz atomic oscillation frequency to better than 10 Hz, or 10 ppm. This represents a suppression of ambient noise on the rf circuit by 34 dB. This technique could impact the sensitivity of ion trap mass spectrometry and the fidelity of quantum operations in ion trap quantum information applications.

  5. Functional Stability of Plasminogen Activator Inhibitor-1

    Directory of Open Access Journals (Sweden)

    Songul Yasar Yildiz

    2014-01-01

    Full Text Available Plasminogen activator inhibitor-1 (PAI-1 is the main inhibitor of plasminogen activators, such as tissue-type plasminogen activator (t-PA and urokinase-type plasminogen activator (u-PA, and a major regulator of the fibrinolytic system. PAI-1 plays a pivotal role in acute thrombotic events such as deep vein thrombosis (DVT and myocardial infarction (MI. The biological effects of PAI-1 extend far beyond thrombosis including its critical role in fibrotic disorders, atherosclerosis, renal and pulmonary fibrosis, type-2 diabetes, and cancer. The conversion of PAI-1 from the active to the latent conformation appears to be unique among serpins in that it occurs spontaneously at a relatively rapid rate. Latency transition is believed to represent a regulatory mechanism, reducing the risk of thrombosis from a prolonged antifibrinolytic action of PAI-1. Thus, relying solely on plasma concentrations of PAI-1 without assessing its function may be misleading in interpreting the role of PAI-1 in many complex diseases. Environmental conditions, interaction with other proteins, mutations, and glycosylation are the main factors that have a significant impact on the stability of the PAI-1 structure. This review provides an overview on the current knowledge on PAI-1 especially importance of PAI-1 level and stability and highlights the potential use of PAI-1 inhibitors for treating cardiovascular disease.

  6. Stability of edge states and edge magnetism in graphene nanoribbons

    OpenAIRE

    Kunstmann, Jens; Özdoğan, Cem; Quandt, Alexander; Fehske, Holger

    2010-01-01

    We critically discuss the stability of edge states and edge magnetism in zigzag edge graphene nanoribbons (ZGNRs). We point out that magnetic edge states might not exist in real systems, and show that there are at least three very natural mechanisms - edge reconstruction, edge passivation, and edge closure - which dramatically reduce the effect of edge states in ZGNRs or even totally eliminate them. Even if systems with magnetic edge states could be made, the intrinsic magnetism would not be ...

  7. 76 FR 59036 - State Fiscal Stabilization Fund Program

    Science.gov (United States)

    2011-09-23

    ..., definitions, and approval criteria for the State Fiscal Stabilization Fund (SFSF) program (November 2009..., the number and percentage of core academic courses taught, in the highest-poverty and lowest-poverty...-poverty and lowest-poverty schools, by teachers who are highly qualified. Because States will have...

  8. EnviroAtlas - Climate Stabilization Metrics for Conterminous United States

    Data.gov (United States)

    U.S. Environmental Protection Agency — This EnviroAtlas web service supports research and online mapping activities related to EnviroAtlas (https://www.epa.gov/enviroatlas). The Climate Stabilization...

  9. Room temperature skyrmion ground state stabilized through interlayer exchange coupling

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Gong, E-mail: gchenncem@gmail.com; Schmid, Andreas K. [NCEM, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Mascaraque, Arantzazu [Depto. Física de Materiales, Universidad Complutense de Madrid, 28040 Madrid (Spain); Unidad Asociada IQFR (CSIC) - UCM, 28040 Madrid (Spain); N' Diaye, Alpha T. [Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

    2015-06-15

    Possible magnetic skyrmion device applications motivate the search for structures that extend the stability of skyrmion spin textures to ambient temperature. Here, we demonstrate an experimental approach to stabilize a room temperature skyrmion ground state in chiral magnetic films via exchange coupling across non-magnetic spacer layers. Using spin polarized low-energy electron microscopy to measure all three Cartesian components of the magnetization vector, we image the spin textures in Fe/Ni films. We show how tuning the thickness of a copper spacer layer between chiral Fe/Ni films and perpendicularly magnetized Ni layers permits stabilization of a chiral stripe phase, a skyrmion phase, and a single domain phase. This strategy to stabilize skyrmion ground states can be extended to other magnetic thin film systems and may be useful for designing skyrmion based spintronics devices.

  10. Extending stability through hierarchical clusters in Echo State Networks

    Directory of Open Access Journals (Sweden)

    Sarah Jarvis

    2010-07-01

    Full Text Available Echo State Networks (ESN are reservoir networks that satisfy well-established criteria for stability when constructed as feedforward networks. Recent evidence suggests that stability criteria are altered in the presence of reservoir substructures, such as clusters. Understanding how the reservoir architecture affects stability is thus important for the appropriate design of any ESN. To quantitatively determine the influence of the most relevant network parameters, we analysed the impact of reservoir substructures on stability in hierarchically clustered ESNs (HESN, as they allow a smooth transition from highly structured to increasingly homogeneous reservoirs. Previous studies used the largest eigenvalue of the reservoir connectivity matrix (spectral radius as a predictor for stable network dynamics. Here, we evaluate the impact of clusters, hierarchy and intercluster connectivity on the predictive power of the spectral radius for stability. Both hierarchy and low relative cluster sizes extend the range of spectral radius values, leading to stable networks, while increasing intercluster connectivity decreased maximal spectral radius.

  11. Stabilizing unstable steady states using multiple delay feedback control.

    Science.gov (United States)

    Ahlborn, Alexander; Parlitz, Ulrich

    2004-12-31

    Feedback control with different and independent delay times is introduced and shown to be an efficient method for stabilizing fixed points (equilibria) of dynamical systems. In comparison to other delay based chaos control methods multiple delay feedback control is superior for controlling steady states and works also for relatively large delay times (sometimes unavoidable in experiments due to system dead times). To demonstrate this approach for stabilizing unstable fixed points we present numerical simulations of Chua's circuit and a successful experimental application for stabilizing a chaotic frequency doubled Nd-doped yttrium aluminum garnet laser.

  12. Changing climate states and stability: from Pliocene to present

    Energy Technology Data Exchange (ETDEWEB)

    Livina, V.N.; Lenton, T.M. [University of East Anglia, School of Environmental Sciences, Norwich (United Kingdom); Kwasniok, F. [University of Exeter, College of Engineering, Mathematics and Physical Sciences, Exeter (United Kingdom); Lohmann, G. [Alfred Wegener Institute for Polar and Marine Research, Bremerhaven (Germany); Kantelhardt, J.W. [Martin-Luther-Universitaet Halle-Wittenberg, Institute of Physics, Theory group, Halle (Germany)

    2011-12-15

    We present a recently developed method of potential analysis of time series data, which comprises (1) derivation of the number of distinct global states of a system from time series data, and (2) derivation of the potential coefficients describing the location and stability of these states, using the unscented Kalman filter (UKF). We test the method on artificial data and then apply it to climate records spanning progressively shorter time periods from 5.3 Myr ago to the recent observational record. We detect various changes in the number and stability of states in the climate system. The onset of Northern Hemisphere glaciation roughly 3 Myr BP is detected as the appearance of a second climate state. During the last ice age in Greenland, there is a bifurcation representing the loss of stability of the warm interstadial state, followed by the total loss of this state around 25 kyr BP. The Holocene is generally characterized by a single stable climate state, especially at large scales. However, in the historical record, at the regional scale, the European monthly temperature anomaly temporarily exhibits a second, highly degenerate (unstable) state during the latter half of the eighteenth century. At the global scale, temperature is currently undergoing a forced movement of a single stable state rather than a bifurcation. The method can be applied to a wide range of geophysical systems with time series of sufficient length and temporal resolution, to look for bifurcations and their precursors. (orig.)

  13. Sampled-Data State Feedback Stabilization of Boolean Control Networks.

    Science.gov (United States)

    Liu, Yang; Cao, Jinde; Sun, Liangjie; Lu, Jianquan

    2016-04-01

    In this letter, we investigate the sampled-data state feedback control (SDSFC) problem of Boolean control networks (BCNs). Some necessary and sufficient conditions are obtained for the global stabilization of BCNs by SDSFC. Different from conventional state feedback controls, new phenomena observed the study of SDSFC. Based on the controllability matrix, we derive some necessary and sufficient conditions under which the trajectories of BCNs can be stabilized to a fixed point by piecewise constant control (PCC). It is proved that the global stabilization of BCNs under SDSFC is equivalent to that by PCC. Moreover, algorithms are given to construct the sampled-data state feedback controllers. Numerical examples are given to illustrate the efficiency of the obtained results.

  14. Stability of Cassie-Baxter wetting states on microstructured surfaces

    Science.gov (United States)

    Guo, Hao-Yuan; Li, Bo; Feng, Xi-Qiao

    2016-10-01

    A stable Cassie-Baxter (CB) wetting state is indispensable for the superhydrophobicity of solid surfaces. In this paper, we analyze the equilibrium and stability of CB wetting states. Using an energy approach, the stability criteria of CB wetting states are established for solid surfaces with either two- or three-dimensional symmetric microstructures. A generic method is presented to calculate the critical pressure at which the CB state on a microstructured solid surface collapses. The method holds for microstructures with arbitrary generatrix, and explicit solutions are derived for a few representative microstructures with a straight or circular generatrix. In addition, some possible strategies are proposed to design surface structures with stable CB wetting states from the viewpoints of geometry and chemistry.

  15. Stability properties of nonlinear dynamical systems and evolutionary stable states

    Energy Technology Data Exchange (ETDEWEB)

    Gleria, Iram, E-mail: iram@fis.ufal.br [Instituto de Física, Universidade Federal de Alagoas, 57072-970 Maceió-AL (Brazil); Brenig, Leon [Faculté des Sciences, Université Libre de Bruxelles, 1050 Brussels (Belgium); Rocha Filho, Tarcísio M.; Figueiredo, Annibal [Instituto de Física and International Center for Condensed Matter Physics, Universidade de Brasília, 70919-970 Brasília-DF (Brazil)

    2017-03-18

    Highlights: • We address the problem of equilibrium stability in a general class of non-linear systems. • We link Evolutionary Stable States (ESS) to stable fixed points of square quasi-polynomial (QP) systems. • We show that an interior ES point may be related to stable interior fixed points of QP systems. - Abstract: In this paper we address the problem of stability in a general class of non-linear systems. We establish a link between the concepts of asymptotic stable interior fixed points of square Quasi-Polynomial systems and evolutionary stable states, a property of some payoff matrices arising from evolutionary games.

  16. Steady states and stability in metabolic networks without regulation.

    Science.gov (United States)

    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

  17. A Comparison of Vanadate to a 2'-5' Linkage at the Active Site of a Small Ribozyme Suggests a Role for Water in Transition-State Stabilization

    Energy Technology Data Exchange (ETDEWEB)

    Torelli, A.T.; Krucinska, J.; Wedekind, J.E.

    2009-06-04

    The potential for water to participate in RNA catalyzed reactions has been the topic of several recent studies. Here, we report crystals of a minimal, hinged hairpin ribozyme in complex with the transition-state analog vanadate at 2.05 A resolution. Waters are present in the active site and are discussed in light of existing views of catalytic strategies employed by the hairpin ribozyme. A second structure harboring a 2',5'-phosphodiester linkage at the site of cleavage was also solved at 2.35 A resolution and corroborates the assignment of active site waters in the structure containing vanadate. A comparison of the two structures reveals that the 2',5' structure adopts a conformation that resembles the reaction intermediate in terms of (1) the positioning of its nonbridging oxygens and (2) the covalent attachment of the 2'-O nucleophile with the scissile G+1 phosphorus. The 2',5'-linked structure was then overlaid with scissile bonds of other small ribozymes including the glmS metabolite-sensing riboswitch and the hammerhead ribozyme, and suggests the potential of the 2',5' linkage to elicit a reaction-intermediate conformation without the need to form metalloenzyme complexes. The hairpin ribozyme structures presented here also suggest how water molecules bound at each of the nonbridging oxygens of G+1 may electrostatically stabilize the transition state in a manner that supplements nucleobase functional groups. Such coordination has not been reported for small ribozymes, but is consistent with the structures of protein enzymes. Overall, this work establishes significant parallels between the RNA and protein enzyme worlds.

  18. Adaptive steady-state stabilization for nonlinear dynamical systems

    Science.gov (United States)

    Braun, David J.

    2008-07-01

    By means of LaSalle’s invariance principle, we propose an adaptive controller with the aim of stabilizing an unstable steady state for a wide class of nonlinear dynamical systems. The control technique does not require analytical knowledge of the system dynamics and operates without any explicit knowledge of the desired steady-state position. The control input is achieved using only system states with no computer analysis of the dynamics. The proposed strategy is tested on Lorentz, van der Pol, and pendulum equations.

  19. Purification and switching protocols for dissipatively stabilized entangled qubit states

    Science.gov (United States)

    Hein, Sven M.; Aron, Camille; Türeci, Hakan E.

    2016-06-01

    Pure dephasing processes limit the fidelities achievable in driven-dissipative schemes for stabilization of entangled states of qubits. We propose a scheme which, combined with already existing entangling methods, purifies the desired entangled state by driving out of equilibrium auxiliary dissipative cavity modes coupled to the qubits. We lay out the specifics of our scheme and compute its efficiency in the particular context of two superconducting qubits in a cavity-QED architecture, where the strongly coupled auxiliary modes provided by collective cavity excitations can drive and sustain the qubits in maximally entangled Bell states with fidelities reaching 90% for experimentally accessible parameters.

  20. String Models, Stability and Regge Trajectories for Hadron States

    CERN Document Server

    Sharov, G S

    2013-01-01

    Various string models of mesons and baryons include a string carrying 2 or 3 massive points (quarks or antiquarks). Rotational states (planar uniform rotations) of these systems generate quasilinear Regge trajectories and may be used for describing excited hadron states on these trajectories. For different string models of baryon we are to solve the problem of choice between them and the stability problem for their rotational states. An unexpected result is that for the Y string baryon model these rotations are unstable with respect to small disturbances on the classical level. This instability has specific feature, disturbances grow linearly, whereas for the linear string baryon model they grow exponentially and may increase predictions for baryon's width $\\Gamma$. The classical instability of rotational states and nonstandard Regge slope are the arguments in favor of the stable simplest model of string with massive ends both for baryons and mesons. Rotational states of this model with two types of spin-orbi...

  1. Improved physical stability of amorphous state through acid base interactions.

    Science.gov (United States)

    Telang, Chitra; Mujumdar, Siddharthya; Mathew, Michael

    2009-06-01

    To investigate role of specific interactions in aiding formation and stabilization of amorphous state in ternary and binary dispersions of a weakly acidic drug. Indomethacin (IMC), meglumine (MU), and polyvinyl pyrollidone (PVP) were the model drug, base, and polymer, respectively. Dispersions were prepared using solvent evaporation. Physical mixtures were cryogenically coground. XRPD, PLM, DSC, TGA, and FTIR were used for characterization. MU has a high crystallization tendency and is characterized by a low T(g) (17 degrees C). IMC crystallization was inhibited in ternary dispersion with MU compared to IMC/PVP alone. An amorphous state formed readily even in coground mixtures. Spectroscopic data are indicative of an IMC-MU amorphous salt and supports solid-state proton transfer. IMC-MU salt displays a low T(g) approximately 50 degrees C, but is more physically stable than IMC, which in molecular mixtures with MU, resisted crystallization even when present in stoichiometric excess of base. This is likely due to a disrupted local structure of amorphous IMC due to specific interactions. IMC showed improved physical stability on incorporating MU in polymer, in spite of low T(g) of the base indicating that chemical interactions play a dominant role in physical stabilization. Salt formation could be induced thermally and mechanically.

  2. Analysis of stability of a homogeneous state of anisotropic plasma

    Energy Technology Data Exchange (ETDEWEB)

    Zakharov, V. Yu., E-mail: vladiyuz@mail.ru; Chernova, T. G., E-mail: chernova-tg@yandex.ru; Stepanov, S. E., E-mail: stepanov@bmstu-kaluga.ru [Bauman Moscow State Technical University, Kaluga Branch (Russian Federation)

    2015-04-15

    Small-amplitude waves in collisionless magnetized plasma are considered in the framework of one-fluid anisotropic magnetohydrodynamics with allowance for the anisotropy of the pressure and thermal flux. Stability of a homogeneous plasma state is analyzed using an eighth-order dispersion relation. Restrictions on the parameters of the homogeneous state at which the dispersion relation has no complex roots at any value of the angle between the wave vector and the unperturbed magnetic field are obtained. The applied method also makes it possible to determine the types of unstable waves.

  3. State and Health (1900-2013: Political Stability and Resources

    Directory of Open Access Journals (Sweden)

    Carla Leão

    2016-02-01

    Full Text Available Portuguese public health policies do not surpass eighty years in terms of concerted decision-making, and it is inappropriate to speak of a national health policy before the second half of the twentieth century. This article describes the pathway of policymaking from 1900 to 2013, concerning Portuguese Welfare State emergence. It systematises the main stages of the Portuguese health policies, and analyses its stronger lines, highlighting the relationship between political stability, resources and the State's intervention, strongly related to the emergence of the Welfare State. It summarises the milestones of health policy decisions and describes each of them since 1910. A larger description of changes occurred after the democratic regime and the origins of the Welfare State, embodied in the creation of the National Health Service are given, emphasising the process of epidemiological transition, the decline of infant mortality rate and the growth of life expectancy average levels.

  4. Loss of Consciousness Is Associated with Stabilization of Cortical Activity.

    Science.gov (United States)

    Solovey, Guillermo; Alonso, Leandro M; Yanagawa, Toru; Fujii, Naotaka; Magnasco, Marcelo O; Cecchi, Guillermo A; Proekt, Alex

    2015-07-29

    What aspects of neuronal activity distinguish the conscious from the unconscious brain? This has been a subject of intense interest and debate since the early days of neurophysiology. However, as any practicing anesthesiologist can attest, it is currently not possible to reliably distinguish a conscious state from an unconscious one on the basis of brain activity. Here we approach this problem from the perspective of dynamical systems theory. We argue that the brain, as a dynamical system, is self-regulated at the boundary between stable and unstable regimes, allowing it in particular to maintain high susceptibility to stimuli. To test this hypothesis, we performed stability analysis of high-density electrocorticography recordings covering an entire cerebral hemisphere in monkeys during reversible loss of consciousness. We show that, during loss of consciousness, the number of eigenmodes at the edge of instability decreases smoothly, independently of the type of anesthetic and specific features of brain activity. The eigenmodes drift back toward the unstable line during recovery of consciousness. Furthermore, we show that stability is an emergent phenomenon dependent on the correlations among activity in different cortical regions rather than signals taken in isolation. These findings support the conclusion that dynamics at the edge of instability are essential for maintaining consciousness and provide a novel and principled measure that distinguishes between the conscious and the unconscious brain. What distinguishes brain activity during consciousness from that observed during unconsciousness? Answering this question has proven difficult because neither consciousness nor lack thereof have universal signatures in terms of most specific features of brain activity. For instance, different anesthetics induce different patterns of brain activity. We demonstrate that loss of consciousness is universally and reliably associated with stabilization of cortical dynamics

  5. State stability analysis for the fermionic projector in the continuum

    Energy Technology Data Exchange (ETDEWEB)

    Hoch, Stefan Ludwig

    2008-07-01

    The principle of the fermionic projector in the continuum gives an indication that there might be a deeper reason why elementary particles only appear with a few definite masses. In this thesis the existence of approximately state-stable configurations is shown. In order to achieve that, we make use of a variational principle for the fermionic projector in the continuum which contains certain contributions supported on the light cone. In a certain sense, these extra terms contain the structure of the underlying discrete spacetime. Lorentz invariant distributions and their convolutions are studied. Some of these are well-defined because the convolution integrals have compactly supported integrands. Other convolutions can be regularized such that the property of being ill-defined only plays a role on the light cone. These results are used to analyze the variational principle and to give criteria for state stability, which can be numerically analyzed. Some plots are presented to allow a decision about state stability and to show how possible configurations could look like. (orig.)

  6. Evaluation of a steady-state test of foam stability

    Science.gov (United States)

    Hutzler, Stefan; Lösch, Dörte; Carey, Enda; Weaire, Denis; Hloucha, Matthias; Stubenrauch, Cosima

    2011-02-01

    We have evaluated a steady-state test of foam stability, based on the steady-state height of a foam produced by a constant velocity of gas flow. This test is mentioned in the book by Bikerman [Foams, Springer, Berlin, 1973] and an elementary theory was developed for it by Verbist et al. [J. Phys. Condens. Matter 8 (1996) p. 3715]. For the study, we used an aqueous solution of the cationic surfactant dodecyl trimethylammonium bromide, C12TAB, at a concentration of two times the critical micelle concentration (2 cmc). During foam generation, bubbles collapse at the top of the column which, in turn, eventually counterbalances the rate of bubble production at the bottom. The resulting balance can be described mathematically by an appropriate solution of the foam drainage equation under specified boundary conditions. Our experimental findings are in agreement with the theoretical predictions of a diverging foam height at a critical gas velocity and a finite foam height in the limit of zero velocity. We identify a critical liquid fraction below which a foam is unstable as an important parameter for characterizing foam stability. Furthermore, we deduce an effective viscosity of the liquid which flows through the foam. Currently unexplained are two experimental observations, namely sudden changes of the steady-state foam height in experiments that run over several hours and a reduction in foam height once an overflow of the foam from the containing vessel has occurred.

  7. Edge States at Phase Boundaries and Their Stability

    CERN Document Server

    Asorey, M; Perez-Pardo, J M

    2015-01-01

    We analyse the effects of Robin boundary conditions on quantum field theories of spin 0, 1 and 1/2. In particular, we show that these conditions always lead to the appearance of edge states that play a significant role in quantum Hall effect and topological insulators. We prove in a rigorous way the existence of spectral lower bounds on the kinetic term of the Hamiltonian, which guarantees the stability and consistency of massive field theories when the mass is larger than the lower bound of the kinetic term. We also find an upper bound for the deepest edge state. The explicit dependence of both bounds on the boundary conditions and the size of the system is derived under very general conditions. For fermionic systems we analyse the case of Atiyah-Patodi-Singer and chiral bag boundary conditions. We point out the existence of edge states also in these cases and show that they disappear for small enough systems. Stability is granted in this case.

  8. A Notion of Stochastic Input-to-State Stability and Its Application to Stability of Cascaded Stochastic Nonlinear Systems

    Institute of Scientific and Technical Information of China (English)

    Shu-jun Liu; Ji-feng Zhang; Zhong-ping Jiang

    2008-01-01

    In this paper, the property of practical input-to-state stability and its application to stability of cascaded nonlinear systems are investigated in the stochastic framework. Firstly, the notion of (practical)stochastic input-to-state stability with respect to a stochastic input is introduced, and then by the method of changing supply functions, (a) an (practical) SISS-Lyapunov function for the overall system is obtained from the corresponding Lyapunov functions for cascaded (practical) SISS subsystems.

  9. Stability investigation of an airfoil section with active flap control

    DEFF Research Database (Denmark)

    Bergami, Leonardo; Gaunaa, Mac

    2010-01-01

    This work presents a method to determine flutter and divergence instability limits for a two-dimensional (2-D) airfoil section fitted with an actively controlled trailing edge flap. This flap consists of a deformable trailing edge, which deformation is governed by control algorithms based...... for fatigue load alleviation. The structural model of the 2-D airfoil section contains three degrees of freedom: heave translation, pitch rotation and flap deflection. A potential flow model provides the aerodynamic forces and their distribution. The unsteady aerodynamics are described using an indicial...... function approximation. Stability of the full aeroservoelastic system is determined through eigenvalue analysis by state-space formulation of the indicial approximation. Validation is carried out against an implementation of the recursive method by Theodorsen and Garrick for flexure-torsion-aileron flutter...

  10. Stability of spontaneous electrodermal activity in the kitten.

    Science.gov (United States)

    Delerm, B; Delsaut, M; Freixa i Baqué, E

    1981-06-01

    Recordings of spontaneous electrodermal activity (EDA) were made in eight kittens, between 1 and 29 days of age, in order to obtain an estimation of reliability. Both frequency (number of SSPRs/min) and amplitude (in mV) of spontaneous electrodermal responses were computed during several waking-sleeping sessions. The results show that: (a) the reliability of records taken during the first week appears to be very low; (b) the frequency of SSPRs reaches the same level of stability as that of the adult at about three weeks of life; and (c) reliability of spontaneous EDA is considerably higher in sleeping than in waking kitten. The results are discussed in terms of ontogeny and 'trait' vs. 'state' characteristics of spontaneous EDA.

  11. Active zone stability: insights from fly neuromuscular junction

    Directory of Open Access Journals (Sweden)

    Xiaolin Tian

    2015-01-01

    Full Text Available The presynaptic active zone is a dynamic structure that orchestrates regulated release of neurotransmitters. Developmental and aging processes, and changes in neuronal network activity can all modulate the number, size and composition of active zone and thereby synaptic efficacy. However, very little is known about the mechanism that controls the structural stability of active zone. By studying a model synapse, the Drosophila neuromuscular junction, our recent work shed light on how two scaffolding proteins at the active zone regulate active zone stability by promoting a localized dephosphorylation event at the nerve terminal. Here we discuss the major insights from our findings and their implications for future research.

  12. Task-specific stability of multifinger steady-state action.

    Science.gov (United States)

    Reschechtko, Sasha; Zatsiorsky, Vladimir M; Latash, Mark L

    2015-01-01

    The authors explored task-specific stability during accurate multifinger force production tasks with different numbers of instructed fingers. Subjects performed steady-state isometric force production tasks and were instructed not to interfere voluntarily with transient lifting-and-lowering perturbations applied to the index finger. The main results were (a) intertrial variance in the space of finger modes at steady states was larger within the subspace that had no effect on the total force (the uncontrolled manifold [UCM]); (b) perturbations caused large deviations of finger modes within the UCM (motor equivalence); and (c) deviations caused by the perturbation showed larger variance within the UCM. No significant effects of the number of task fingers were noted in any of the 3 indicators. The results are discussed within the frameworks of the UCM and referent configuration hypotheses. The authors conclude, in particular, that all the tasks were effectively 4-finger tasks with different involvement of task and nontask fingers.

  13. Passive stability and active control in a rhythmic task

    NARCIS (Netherlands)

    Wei, Kunlin; Dijkstra, Tjeerd M. H.; Sternad, Dagmar

    2007-01-01

    Rhythmically bouncing a ball with a racket is a task that affords passively stable solutions as demonstrated by stability analyses of a mathematical model of the task. Passive stability implies that no active control is needed as errors die out without requiring corrective actions. Empirical results

  14. Design of biomimetic catalysts by molecular imprinting in synthetic polymers: the role of transition state stabilization.

    Science.gov (United States)

    Wulff, Günter; Liu, Junqiu

    2012-02-21

    The impressive efficiency and selectivity of biological catalysts has engendered a long-standing effort to understand the details of enzyme action. It is widely accepted that enzymes accelerate reactions through their steric and electronic complementarity to the reactants in the rate-determining transition states. Thus, tight binding to the transition state of a reactant (rather than to the corresponding substrate) lowers the activation energy of the reaction, providing strong catalytic activity. Debates concerning the fundamentals of enzyme catalysis continue, however, and non-natural enzyme mimics offer important additional insight in this area. Molecular structures that mimic enzymes through the design of a predetermined binding site that stabilizes the transition state of a desired reaction are invaluable in this regard. Catalytic antibodies, which can be quite active when raised against stable transition state analogues of the corresponding reaction, represent particularly successful examples. Recently, synthetic chemistry has begun to match nature's ability to produce antibody-like binding sites with high affinities for the transition state. Thus, synthetic, molecularly imprinted polymers have been engineered to provide enzyme-like specificity and activity, and they now represent a powerful tool for creating highly efficient catalysts. In this Account, we review recent efforts to develop enzyme models through the concept of transition state stabilization. In particular, models for carboxypeptidase A were prepared through the molecular imprinting of synthetic polymers. On the basis of successful experiments with phosphonic esters as templates to arrange amidinium groups in the active site, the method was further improved by combining the concept of transition state stabilization with the introduction of special catalytic moieties, such as metal ions in a defined orientation in the active site. In this way, the imprinted polymers were able to provide both an

  15. On stability of odd-frequency superconducting state

    Energy Technology Data Exchange (ETDEWEB)

    Lenov, Bmitry [Los Alamos National Laboratory; Martin, Ivar [Los Alamos National Laboratory; Mozyrsky, Dima [Los Alamos National Laboratory

    2008-01-01

    Odd-frequency pairing mechanism has been investigated for several decades. Nevertheless the properties of such superconducting phase as well as its thermodynamic stability have remained unclear. In particular it has been argued by numerous authors that the odd-frequency state is thermodynamically unstable, has an unphysical Meissner effect (at least within the mean-field approximation), and therefore can not exist as a homogeneous phase in equilibrium physical systems. We argue that such a conclusion is incorrect because it relies on an inappropriate assumption that the odd-frequency superconductor can be described by an effective Hamiltonian that breaks the U(l) symmetry. We show that the odd-frequency state can be appropriately formulated within the functional integral representation by using the effective action to describe such a superconducting state within the mean field approximation. We find that the odd-frequency superconductor is thermodynamically stable and exhibits ordinary Meissner effect, and therefore, in principle, it can be realized in equilibrium solid state systems.

  16. Generalized exponential input-to-state stability of nonlinear systems with time delay

    Science.gov (United States)

    Sun, Fenglan; Gao, Lingxia; Zhu, Wei; Liu, Feng

    2017-03-01

    This paper studies the general input-to-state stability problem of the nonlinear delay systems. By employing Lypaunov-Razumikhin technique, several general input-to-state stability concepts, that is generalized globally exponential integral input-to-state stability (GGE-iISS), generalized globally integral exponential integral input-to-state stability (GGIE-iISS), and eλt-weighted generalized globally integral exponential integral input-to-state stability (eλt-weighted GGIE-iISS) are studied. An example is given to illustrate the correctness of the obtained theoretical results.

  17. Modeling, Stability Analysis and Active Stabilization of Multiple DC-Microgrids Clusters

    DEFF Research Database (Denmark)

    Shafiee, Qobad; Dragicevic, Tomislav; Vasquez, Juan Carlos

    2014-01-01

    ), and more especially during interconnection with other MGs, creating dc MG clusters. This paper develops a small signal model for dc MGs from the control point of view, in order to study stability analysis and investigate effects of CPLs and line impedances between the MGs on stability of these systems......DC microgrids (MGs), as an alternative option, have attracted increasing interest in recent years due to many potential advantages as compare to the ac system. Stability of these systems can be an important issue under high penetration of load converters which behaves as constant power loads (CPLs....... This model can be also used to synthesis and study dynamics of control loops in dc MGs and also dc MG clusters. An active stabilization method is proposed to be implemented as a dc active power filter (APF) inside the MGs in order to not only increase damping of dc MGs at the presence of CPLs but also...

  18. Neighborhood Stabilization Program (NSP) Activities by Tract

    Data.gov (United States)

    Department of Housing and Urban Development — The data being displayed are census tract level counts of NSP-funded activities and is derived from an extract of HUD's Community Planning and Development’s (CPD)...

  19. Active Disturbance Rejection Fuzzy Controller for Roll Stabilization of Autonomous Underwater Vehicle under Wave Disturbance

    OpenAIRE

    Lin-Lin Wang; Hong-Jian Wang; Li-Xin Pan; Jun-Xi Guo

    2015-01-01

    Considering the case of autonomous underwater vehicle navigating with low speed near water surface, a new method for designing of roll motion controller is proposed in order to restrain wave disturbance effectively and improve roll stabilizing performance under different sea conditions. Active disturbance rejection fuzzy control is applied, which is based on nonlinear motion model of autonomous underwater vehicle and the principle of zero-speed fin stabilizer. Extended state observer is used...

  20. Edge states at phase boundaries and their stability

    Science.gov (United States)

    Asorey, M.; Balachandran, A. P.; Pérez-Pardo, J. M.

    2016-10-01

    We analyze the effects of Robin-like boundary conditions on different quantum field theories of spin 0, 1/2 and 1 on manifolds with boundaries. In particular, we show that these conditions often lead to the appearance of edge states. These states play a significant role in physical phenomena like quantum Hall effect and topological insulators. We prove in a rigorous way the existence of spectral lower bounds on the kinetic term of different Hamiltonians, even in the case of Abelian gauge fields where it is a non-elliptic differential operator. This guarantees the stability and consistency of massive field theories with masses larger than the lower bound of the kinetic term. Moreover, we find an upper bound for the deepest edge state. In the case of Abelian gauge theories, we analyze a generalization of Robin boundary conditions. For Dirac fermions, we analyze the cases of Atiyah-Patodi-Singer and chiral bag boundary conditions. The explicit dependence of the bounds on the boundary conditions and the size of the system is derived under general assumptions.

  1. Ideal MHD Stability of ITER Steady State Scenarios with ITBs

    Energy Technology Data Exchange (ETDEWEB)

    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.

  2. Chelation and stabilization of berkelium in oxidation state +IV

    Science.gov (United States)

    Deblonde, Gauthier J.-P.; Sturzbecher-Hoehne, Manuel; Rupert, Peter B.; An, Dahlia D.; Illy, Marie-Claire; Ralston, Corie Y.; Brabec, Jiri; de Jong, Wibe A.; Strong, Roland K.; Abergel, Rebecca J.

    2017-09-01

    Berkelium (Bk) has been predicted to be the only transplutonium element able to exhibit both +III and +IV oxidation states in solution, but evidence of a stable oxidized Bk chelate has so far remained elusive. Here we describe the stabilization of the heaviest 4+ ion of the periodic table, under mild aqueous conditions, using a siderophore derivative. The resulting Bk(IV) complex exhibits luminescence via sensitization through an intramolecular antenna effect. This neutral Bk(IV) coordination compound is not sequestered by the protein siderocalin—a mammalian metal transporter—in contrast to the negatively charged species obtained with neighbouring trivalent actinides americium, curium and californium (Cf). The corresponding Cf(III)-ligand-protein ternary adduct was characterized by X-ray diffraction analysis. Combined with theoretical predictions, these data add significant insight to the field of transplutonium chemistry, and may lead to innovative Bk separation and purification processes.

  3. A state-wide assessment: marital stability and client outcomes.

    Science.gov (United States)

    Hartmann, D J; Sullivan, W P; Wolk, J L

    1991-12-01

    This paper presents results of Missouri's first statewide evaluation of alcohol and drug treatment programs. The study utilized a 1-year follow-up sample of 242 respondents to explore the nature and patterns of post-treatment functioning. This paper focuses on the impact of client marital stability on post-treatment substance use. The data supported the expected result that marital status was related to post-treatment relapse. Further analysis suggests that transitional periods between marriage and divorce are especially important in understanding the pattern of relapse after treatment. Multivariate analysis indicates that the marital status effect is important both directly and in interaction with program completion. The data suggest that attention to transitional states and interpersonal functioning should be incorporated into client follow-up.

  4. Stability of thalamocortical synaptic transmission across awake brain states.

    Science.gov (United States)

    Stoelzel, Carl R; Bereshpolova, Yulia; Swadlow, Harvey A

    2009-05-27

    Sensory cortical neurons are highly sensitive to brain state, with many neurons showing changes in spatial and/or temporal response properties and some neurons becoming virtually unresponsive when subjects are not alert. Although some of these changes are undoubtedly attributable to state-related filtering at the thalamic level, another likely source of such effects is the thalamocortical (TC) synapse, where activation of nicotinic receptors on TC terminals have been shown to enhance synaptic transmission in vitro. However, monosynaptic TC synaptic transmission has not been directly examined during different states of alertness. Here, in awake rabbits that shifted between alert and non-alert EEG states, we examined the monosynaptic TC responses and short-term synaptic dynamics generated by spontaneous impulses of single visual and somatosensory TC neurons. We did this using spike-triggered current source-density analysis, an approach that enables assessment of monosynaptic extracellular currents generated in different cortical layers by impulses of single TC afferents. Spontaneous firing rates of TC neurons were higher, and burst rates were much lower in the alert state. However, we found no state-related changes in the amplitude of monosynaptic TC responses when TC spikes with similar preceding interspike interval were compared. Moreover, the relationship between the preceding interspike interval of the TC spike and postsynaptic response amplitude was not influenced by state. These data indicate that TC synaptic transmission and dynamics are highly conserved across different states of alertness and that observed state-related changes in receptive field properties that occur at the cortical level result from other mechanisms.

  5. State Dependence and Trait Stability of Perfectionism: A Short-Term Longitudinal Study

    Science.gov (United States)

    Rice, Kenneth G.; Aldea, Mirela A.

    2006-01-01

    The authors examined state dependency on depression, trait stability, and state-trait characteristics of perfectionism in a short-term longitudinal study of university students. Relative stability of perfectionism was assessed with test-retest correlations across 3 time points, and results showed higher rank order and relative stability for…

  6. Enhanced muscle activity during lumbar extension exercise with pelvic stabilization.

    Science.gov (United States)

    Lee, Ho-Seong

    2015-12-01

    The purpose of this study was to investigate whether pelvic stabilization affects multifidus (MF) and iliocostalis lumborum (IL) muscle activities during dynamic extension exercise. Nine males (age, 25.1±6.3 yr; height, 176.6±2.4 cm; body mass, 74.9±6.7 kg) performed an isometric lumbar extension strength test and dynamic exercise in an upright seated position with or without pelvic stabilization. The electromyography and muscle strength of the MF and IL muscles were measured when the subjects performed the isometric lumbar extension strength test at the trunk angle 110°, 146°, and 182°. In addition, the trunk extensor muscle activities were measured using 50% muscle strength of maximum isometric strength during a dynamic trunk extension exercise. The MF and IL muscle activities were significantly higher at 110°, 146°, and 182° with pelvic stabilization than that without pelvic stabilization during the isometric lumbar extension strength test (Plumbar extension exercise with pelvic stabilization may be more effective for MF and IL muscle activity compared to that without pelvic stabilization.

  7. An active interferometer-stabilization scheme with linear phase control

    DEFF Research Database (Denmark)

    Vardhan Krishnamachari, Vishnu; Andresen, Esben Ravn; Potma, Eric Olaf

    2006-01-01

    We report a simple and robust computer-based active interferometer stabilization scheme which does not require modulation of the interfering beams and relies on an error signal which is linearly related to the optical path difference. In this setup, a non-collinearly propagating reference laser...... beam stabilizes the interference output of the laser light propagating collinearly through the interferometer. This stabilization scheme enables adjustable phase control with 20 ms switching times in the range from 0.02π radians to 6π radians at 632.8 nm....

  8. Stabilizing Niger

    DEFF Research Database (Denmark)

    Hahonou, Eric Komlavi

    international intervention in Niger. Their main objective is to secure their own strategic, economic and political interests by strengthening the Nigerien authorities through direct intervention and capacity building activities. For western states reinforcing state security institutions and stabilizing elite...

  9. Alpha-haemoglobin stabilizing protein (AHSP) stabilizes apo-α-haemoglobin in a partially folded state

    Science.gov (United States)

    Krishna Kumar, Kaavya; Dickson, Claire F.; Weiss, Mitchell J.; Mackay, Joel P.; Gell, David A.

    2015-01-01

    SYNOPSIS To produce functional haemoglobin, nascent α-globin (αo) and β-globin (βo) chains must each bind a single haem molecule (to form αh and βh) and interact together to form heterodimers. The precise sequence of binding events is unknown, and it has been suggested that additional factors might enhance the efficiency of Hb folding. The α-haemoglobin stabilizing protein (AHSP) has previously been shown to bind αh and regulate redox activity of the haem iron. Here, we use a combination of classical and dynamic light scattering and NMR spectroscopy to demonstrate that AHSP forms a heterodimeric complex with αo that inhibits αo aggregation and promotes αo folding in the absence of haem. These findings indicate that AHSP may function as an αo-specific chaperone, and suggest an important role for αo in guiding Hb assembly by stabilizing βo and inhibiting off-pathway self-association of βh. PMID:20860551

  10. AHSP (α-haemoglobin-stabilizing protein) stabilizes apo-α-haemoglobin in a partially folded state.

    Science.gov (United States)

    Krishna Kumar, Kaavya; Dickson, Claire F; Weiss, Mitchell J; Mackay, Joel P; Gell, David A

    2010-12-01

    To produce functional Hb (haemoglobin), nascent α-globin (αo) and β-globin (βo) chains must each bind a single haem molecule (to form αh and βh) and interact together to form heterodimers. The precise sequence of binding events is unknown, and it has been suggested that additional factors might enhance the efficiency of Hb folding. AHSP (α-haemoglobin-stabilizing protein) has been shown previously to bind αh and regulate redox activity of the haem iron. In the present study, we used a combination of classical and dynamic light scattering and NMR spectroscopy to demonstrate that AHSP forms a heterodimeric complex with αo that inhibits αo aggregation and promotes αo folding in the absence of haem. These findings indicate that AHSP may function as an αo-specific chaperone, and suggest an important role for αo in guiding Hb assembly by stabilizing βo and inhibiting off-pathway self-association of βh.

  11. Flow stabilization with active hydrodynamic cloaks

    CERN Document Server

    Urzhumov, Yaroslav A; 10.1103/PhysRevE.86.056313

    2012-01-01

    We demonstrate that fluid flow cloaking solutions based on active hydrodynamic metamaterials exist for two-dimensional flows past a cylinder in a wide range of Reynolds numbers, up to approximately 200. Within the framework of the classical Brinkman equation for homogenized porous flow, we demonstrate using two different methods that such cloaked flows can be dynamically stable for $Re$ in the range 5-119. The first, highly efficient, method is based on a linearization of the Brinkman-Navier-Stokes equation and finding the eigenfrequencies of the least stable eigen-perturbations; the second method is a direct, numerical integration in the time domain. We show that, by suppressing the Karman vortex street in the weekly turbulent wake, porous flow cloaks can raise the critical Reynolds number up to about 120, or five times greater than for a bare, uncloaked cylinder.

  12. Protein's native state stability in a chemically induced denaturation mechanism.

    Science.gov (United States)

    Olivares-Quiroz, L; Garcia-Colin, L S

    2007-05-21

    In this work, we present a generalization of Zwanzig's protein unfolding analysis [Zwanzig, R., 1997. Two-state models of protein folding kinetics. Proc. Natl Acad. Sci. USA 94, 148-150; Zwanzig, R., 1995. Simple model of protein folding kinetics. Proc. Natl Acad. Sci. USA 92, 9801], in order to calculate the free energy change Delta(N)(D)F between the protein's native state N and its unfolded state D in a chemically induced denaturation. This Extended Zwanzig Model (EZM) is both based on an equilibrium statistical mechanics approach and the inclusion of experimental denaturation curves. It enables us to construct a suitable partition function Z and to derive an analytical formula for Delta(N)(D)F in terms of the number K of residues of the macromolecule, the average number nu of accessible states for each single amino acid and the concentration C(1/2) where the midpoint of the ND transition occurs. The results of the EZM for proteins where chemical denaturation follows a sigmoidal-type profile, as it occurs for the case of the T70N human variant of lysozyme (PDB code: T70N) [Esposito, G., et al., 2003. J. Biol. Chem. 278, 25910-25918], can be splitted into two lines. First, EZM shows that for sigmoidal denaturation profiles, the internal degrees of freedom of the chain play an outstanding role in the stability of the native state. On the other hand, that under certain conditions DeltaF can be written as a quadratic polynomial on concentration C(1/2), i.e., DeltaF approximately aC(1/2)(2)+bC(1/2)+c, where a,b,c are constant coefficients directly linked to protein's size K and the averaged number of non-native conformations nu. Such functional form for DeltaF has been widely known to fit experimental measures in chemically induced protein denaturation [Yagi, M., et al., 2003. J. Biol. Chem. 278, 47009-47015; Asgeirsson, B., Guojonsdottir, K., 2006. Biochim. Biophys. Acta 1764, 190-198; Sharma, S., et al., 2006. Protein Pept. Lett. 13(4), 323-329; Salem, M., et al

  13. Substituent Effects on the Stability and Antioxidant Activity of Spirodiazaselenuranes

    Directory of Open Access Journals (Sweden)

    Devappa S. Lamani

    2015-07-01

    Full Text Available Spirodiazaselenuranes are structurally interesting compounds and the stability of these compounds depends highly on the nature of the substituents attached to the nitrogen atoms. Aromatic substituents are known to play important roles in stabilizing the Se-N bonds in spiro compounds. In this study, several spirodiazaselenuranes are synthesized by introducing benzylic and aliphatic substituents to understand their effect on the stability of the Se-N bonds and the antioxidant activity. Replacement of phenyl substituent by benzyl/alkyl groups significantly reduces the stability of the spirodiazaselenuranes and slows down the oxidative cyclization process. The selenium centre in the spiro compounds undergoes further oxidation to produce the corresponding selenurane oxides, which are stable at room temperature. Comparison of the glutathione peroxidase (GPx mimetic activity of the compounds showed that the diaryl selenides having heterocyclic rings are significantly more active due to the facile oxidation of the selenium centre. However, the activity is reduced significantly for compounds having aliphatic substituents. In addition to GPx activity, the compounds also inhibit peroxynitrite-mediated nitration and oxidation reaction of protein and small molecules, respectively. The experimental observations suggest that the antioxidant activity is increased considerably upon substitution of the aromatic group with the benzylic/aliphatic substituents on the nitrogen atoms.

  14. Stabilization of actinides and lanthanides in unusually high oxidation states

    Energy Technology Data Exchange (ETDEWEB)

    Eller, P.G.; Penneman, R.A.

    1986-01-01

    Chemical environments can be chosen which stabilize actinides and lanthanides in unusually high or low oxidation states and in unusual coordination. In many cases, one can rationalize the observed species as resulting from strong charge/size influences provided by specific sites in host lattices (e.g., Tb(IV) in BaTbO/sub 3/ or Am(IV) in polytungstate anions). In other cases, the unusual species can be considered from an acid-base viewpoint (e.g., U(III) in AsF/sub 5//HF solution or Pu(VII) in Li/sub 5/PuO/sub 6/). In still other cases, an interplay of steric and redox effects can lead to interesting comparisons (e.g., instability of double fluoride salts of Pu(V) and Pu(VI) relative to U, Np, and Am analogues). Generalized ways to rationalize compounds containing actinides and lanthanides in unusual valences (particularly high valences), including the above and numerous other examples, will form the focus of this paper. Recently developed methods for synthesizing high valent f-element fluorides using superoxidizers and superacids at low temperatures will also be described. 65 refs., 8 figs., 9 tabs.

  15. Social status and personality: stability in social state can promote consistency of behavioural responses.

    Science.gov (United States)

    Favati, Anna; Leimar, Olof; Radesäter, Tommy; Løvlie, Hanne

    2014-01-07

    Stability of 'state' has been suggested as an underlying factor explaining behavioural stability and animal personality (i.e. variation among, and consistency within individuals in behavioural responses), but the possibility that stable social relationships represent such states remains unexplored. Here, we investigated the influence of social status on the expression and consistency of behaviours by experimentally changing social status between repeated personality assays. We used male domestic fowl (Gallus gallus domesticus), a social species that forms relatively stable dominance hierarchies, and showed that behavioural responses were strongly affected by social status, but also by individual characteristics. The level of vigilance, activity and exploration changed with social status, whereas boldness appeared as a stable individual property, independent of status. Furthermore, variation in vocalization predicted future social status, indicating that individual behaviours can both be a predictor and a consequence of social status, depending on the aspect in focus. Our results illustrate that social states contribute to both variation and stability in behavioural responses, and should therefore be taken into account when investigating and interpreting variation in personality.

  16. Non-probabilistic stability reliability measure for active vibration control system with interval parameters

    Science.gov (United States)

    Li, Yunlong; Wang, Xiaojun; Wang, Lei; Fan, Weichao; Qiu, Zhiping

    2017-01-01

    A systematic non-probabilistic reliability analysis procedure for structural vibration active control system with unknown-but-bounded parameters is proposed. The state-space representation of active vibration control system with uncertain parameters is presented. Compared with the robust control theory, which is always over-conservative, the reliability-based analysis method is more suitable to deal with uncertain problem. Stability is the core of the closed-loop feedback control system design, so stability criterion is adopted to act as the limited state function for reliability analysis. The uncertain parameters without enough samples are modeled as interval variables. Interval perturbation method is employed to estimate the interval bounds of eigenvalues, which can be used to characterize the stability of the closed-loop active control system. Formulation of defining the reliability of active control system based on stability is discussed. A novel non-probabilistic reliability measurement index is discussed and used to determine the probability of the stability based on the area ratio. The feasibility and efficiency of the proposed method are demonstrated by two numerical examples.

  17. Stabilizing State-Feedback Design via the Moving Horizon Method.

    Science.gov (United States)

    1982-01-01

    aide if necessary and identify by block number) Stabilizing control design; linear time varying systems; fixed depth horizon; index optimization methods...dual system. 20. ABSTRACT (Continue an reverse side If necessary and Identify by block number) Li _ A stabilizing control design for general linear...Apprvyed for pb~ ~~* 14 ~dl Stri but ion uni imit Oe, ABSTRACT A stabilizing control design for general linear time vary- invariant systems through

  18. Active and passive stabilization of body pitch in insect flight.

    Science.gov (United States)

    Ristroph, Leif; Ristroph, Gunnar; Morozova, Svetlana; Bergou, Attila J; Chang, Song; Guckenheimer, John; Wang, Z Jane; Cohen, Itai

    2013-08-01

    Flying insects have evolved sophisticated sensory-motor systems, and here we argue that such systems are used to keep upright against intrinsic flight instabilities. We describe a theory that predicts the instability growth rate in body pitch from flapping-wing aerodynamics and reveals two ways of achieving balanced flight: active control with sufficiently rapid reactions and passive stabilization with high body drag. By glueing magnets to fruit flies and perturbing their flight using magnetic impulses, we show that these insects employ active control that is indeed fast relative to the instability. Moreover, we find that fruit flies with their control sensors disabled can keep upright if high-drag fibres are also attached to their bodies, an observation consistent with our prediction for the passive stability condition. Finally, we extend this framework to unify the control strategies used by hovering animals and also furnish criteria for achieving pitch stability in flapping-wing robots.

  19. Protein stability and enzyme activity at extreme biological temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Feller, Georges, E-mail: gfeller@ulg.ac.b [Laboratory of Biochemistry, Centre for Protein Engineering, Institute of Chemistry B6a, University of Liege, B-4000 Liege (Belgium)

    2010-08-18

    Psychrophilic microorganisms thrive in permanently cold environments, even at subzero temperatures. To maintain metabolic rates compatible with sustained life, they have improved the dynamics of their protein structures, thereby enabling appropriate molecular motions required for biological activity at low temperatures. As a consequence of this structural flexibility, psychrophilic proteins are unstable and heat-labile. In the upper range of biological temperatures, thermophiles and hyperthermophiles grow at temperatures > 100 {sup 0}C and synthesize ultra-stable proteins. However, thermophilic enzymes are nearly inactive at room temperature as a result of their compactness and rigidity. At the molecular level, both types of extremophilic proteins have adapted the same structural factors, but in opposite directions, to address either activity at low temperatures or stability in hot environments. A model based on folding funnels is proposed accounting for the stability-activity relationships in extremophilic proteins. (topical review)

  20. Integral input-to-state stability of nonlinear control systems with delays

    Energy Technology Data Exchange (ETDEWEB)

    Zhu Wenli [Department of Economics Mathematics, South Western University of Finance and Economics, Chengdu 610074 (China)]. E-mail: zhuwl@swufe.edu.cn; Yi Zhang [Computational Intelligence Laboratory, School of Computer Science and Engineering, University of Electronic Science and Technology of China, Chengdu 610054 (China)]. E-mail: zhangyi@uestc.edu.cn

    2007-10-15

    Integral input-to-state stability is an interesting concept that has been recently introduced to nonlinear control systems. This paper generalizes this concept to nonlinear control systems with delays. These delays can be bounded, unbounded, and even infinite. Theorems for integral input-to-state stability are derived by developing the method of Razumikhin technique in the theory of functional differential equations.

  1. Global exponential stability conditions for generalized state-space systems with time-varying delays

    Energy Technology Data Exchange (ETDEWEB)

    Yu, K.-W. [Department of Marine Engineering, National Kaohsiung Marine University, Kaohsiung 811, Taiwan (China)], E-mail: kwyu@mail.nkmu.edu.tw; Lien, C.-H. [Department of Marine Engineering, National Kaohsiung Marine University, Kaohsiung 811, Taiwan (China)], E-mail: chlien.ee@msa.hinet.net

    2008-05-15

    A unified approach is proposed to deal with the exponential stability for generalized state-space systems with time-varying delays. Many systems models can be regarded as special cases of the considered systems; such as neutral time-delay systems and delayed cellular neural networks. Delay-dependent stability criteria are proposed to guarantee the global exponential stability for generalized state-space systems with two cases of uncertainties. Two numerical examples are given to show the effectiveness of our method.

  2. 146 SOCIAL STABILITY WITHIN THE NIGERIAN STATE Charles ...

    African Journals Online (AJOL)

    User

    political philosophy, social stability features as a core concern of social ... Both in Origin of Species and. Descent of ... The reality of society is anchored on man's tendency to come .... This understanding is fundamental and forms a veritable.

  3. Using state diagrams for predicting colloidal stability of whey protein beverages.

    Science.gov (United States)

    Wagoner, Ty B; Ward, Loren; Foegeding, E Allen

    2015-05-06

    A method for evaluating aspects of colloidal stability of whey protein beverages after thermal treatment was established. Three state diagrams for beverages (pH 3-7) were developed representing protein solubility, turbidity, and macroscopic state after two ultrahigh-temperature (UHT) treatments. Key transitions of stability in the state diagrams were explored using electrophoresis and chromatography to determine aggregation propensities of β-lactoglobulin, α-lactalbumin, bovine serum albumin, and glycomacropeptide. The state diagrams present an overlapping view of high colloidal stability at pH 3 accompanied by high solubility of individual whey proteins. At pH 5, beverages were characterized by poor solubility, high turbidity, and aggregation/gelation of whey proteins with the exception of glycomacropeptide. Stability increased at pH 6, due to increased solubility of α-lactalbumin. The results indicate that combinations of state diagrams can be used to identify key regions of stability for whey protein containing beverages.

  4. Elliptically Bent X-ray Mirrors with Active Temperature Stabilization

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, Sheng; Church, Matthew; Yashchuk, Valeriy V.; Goldberg, Kenneth A.; Celestre, Rich; McKinney, Wayne R.; Kirschman, Jonathan; Morrison, Greg; Noll, Tino; Warwick, Tony; Padmore, Howard A.

    2010-01-31

    We present details of design of elliptically bent Kirkpatrick-Baez mirrors developed and successfully used at the Advanced Light Source for submicron focusing. A distinctive feature of the mirror design is an active temperature stabilization based on a Peltier element attached directly to the mirror body. The design and materials have been carefully optimized to provide high heat conductance between the mirror body and substrate. We describe the experimental procedures used when assembling and precisely shaping the mirrors, with special attention paid to laboratory testing of the mirror-temperature stabilization. For this purpose, the temperature dependence of the surface slope profile of a specially fabricated test mirror placed inside a temperature-controlled container was measured. We demonstrate that with active mirror-temperature stabilization, a change of the surrounding temperature by more than 3K does not noticeably affect the mirror figure. Without temperature stabilization, the surface slope changes by approximately 1.5 ?mu rad rms (primarily defocus) under the same conditions.

  5. Robustness and robust stability of the active sliding mode synchronization

    Energy Technology Data Exchange (ETDEWEB)

    Naseh, Majid Reza [Electrical Engineering Department, Islamic Azad University, Birjand Branch (Iran, Islamic Republic of)], E-mail: naseh@ee.src.aiu.ir; Haeri, Mohammad [Advanced Control System Lab., Electrical Engineering Department, Sharif University Technology, Tehran (Iran, Islamic Republic of)], E-mail: haeri@sina.sharif.edu

    2009-01-15

    We have developed relations between uncertainties and signals bounds in one side and the control parameters on the other side in the case of the active sliding mode synchronization. Using Lyapunov stability theorem, we have determined uncertainties levels for which synchronization is achieved for a given set of the control parameters. We have run a nonlinear programming algorithm to determine the control parameters for specific range of the uncertainties. Finally, numerical simulations are presented to verify the derived relations.

  6. Exercise of mechanisms of dynamic stability improves the stability state after an unexpected gait perturbation in elderly.

    Science.gov (United States)

    Bierbaum, Stefanie; Peper, Andreas; Arampatzis, Adamantios

    2013-10-01

    Unexpected changes during gait challenge elderly individuals to a greater degree than young adults. However, the adaptive potential of elderly seems to be retained, and therefore, the training of the mechanisms of dynamic stability as well as muscle strength training may improve the dynamic stability after unexpected perturbations. Thirty-eight subjects (65-75 years) participated in the study, divided into two experimental groups (stability training group, ST, n = 14 and mixed training group, MT, n = 14) and a control group (CG, n = 10). Both experimental groups performed exercises which focused on the mechanisms of dynamic stability. Additionally, the MT group executed a training to improve muscle strength. Session volume and duration were equal for both groups (14 weeks, twice a week, ~1.5 h per session). Pre- and post-intervention, subjects performed a gait protocol with an induced unexpected perturbation. Post-intervention, the margin of stability was significantly increased after the unexpected perturbation in the ST group, indicating an improvement in stability state (pre, -30.3 ± 5.9 cm; post, -24.1 ± 5.2 cm). Further, both intervention groups increased their base of support after the intervention to regain balance after gait perturbation, whereas only the ST group showed a statistically significant improvement (STpre, 90.9 ± 6.6 cm, STpost, 98.2 ± 8.5 cm; MTpre, 91.4 ± 6.2 cm; MTpost, 97.9 ± 12.7 cm). The CG showed no differences between pre- and post-measurements. The exercise of the mechanisms of dynamic stability led to a better application of these mechanisms after an unexpected perturbation during gait. We suggest that the repeated exercise of the mechanisms of dynamic stability contributes to significant improvements in postural stability. Additional strength training for healthy elderly individuals, however, shows no further effect on the ability to recover balance after unexpected perturbations during gait.

  7. Stability of synchronous state in networks of chaotic maps by matrix measure approach

    Directory of Open Access Journals (Sweden)

    F Aghaei

    2015-07-01

    Full Text Available Stability of synchronous state is a fundamental problem in synchronization. We study Matrix Measure as an approach for investigating of stability of synchronous states of chaotic maps on complex networks. Matrix Measure is a measure which depends on network structure. Using this measure and comparing with synchronization threshold which depends on the function of the map, show us how the synchronous state can be stabilized. We use these methods for networks with different parameters and topologies. Our numerical calculation shows that synchronous states on more dense networks are more stable. Network’s size is another effective parameter that order of value and extent of stability interval is determined by network’s size. Our results also show that among dense networks, Random and Scale-Free networks have larger stability interval of coupling strength. Finally, we use Error Function to test a prediction of Matrix Measure approach.

  8. Frozen steady states in active systems

    CERN Document Server

    Schaller, Volker; Hammerich, Benjamin; Frey, Erwin; Bausch, Andreas R

    2011-01-01

    Even simple active systems can show a plethora of intriguing phenomena and often we find complexity were we would have expected simplicity. One striking example is the occurrence of a quiescent or absorbing state with frozen fluctuations that at first sight seems to be impossible for active matter driven by the incessant input of energy. While such states were reported for externally driven systems through macroscopic shear or agitation, the investigation of frozen active states in inherently active systems like cytoskeletal suspensions or active gels is still at large. Using high density motility assay experiments, we demonstrate that frozen steady states can arise in active systems if active transport is coupled to growth processes. The experiments are complemented by agent-based simulations which identify the coupling between self-organization, growth and mechanical properties to be responsible for the pattern formation process.

  9. Screening Effects on the Binding Energy and Stability of Quarkonia States

    CERN Document Server

    Bhatt, Palak; Patel, Smruti; Vinodkumar, P C

    2016-01-01

    We have studied the thermal stability of Quarkonia states by computing the effects of color-screening and vacuum screening based on a temperature dependent screened coulomb plus power potential for the quark-antiquark interaction. Medium effects on the properties of charmonia and bottomonia states are studied. The color screening and the vacuum screening effects on the stability of the quarkonia states are also separately calculated for comparison.

  10. An empirically based steady state friction law and implications for fault stability

    Science.gov (United States)

    Spagnuolo, E.; Nielsen, S.; Violay, M.; Di Toro, G.

    2016-04-01

    Empirically based rate-and-state friction laws (RSFLs) have been proposed to model the dependence of friction forces with slip and time. The relevance of the RSFL for earthquake mechanics is that few constitutive parameters define critical conditions for fault stability (i.e., critical stiffness and frictional fault behavior). However, the RSFLs were determined from experiments conducted at subseismic slip rates (V 0.1 m/s) remains questionable on the basis of the experimental evidence of (1) large dynamic weakening and (2) activation of particular fault lubrication processes at seismic slip rates. Here we propose a modified RSFL (MFL) based on the review of a large published and unpublished data set of rock friction experiments performed with different testing machines. The MFL, valid at steady state conditions from subseismic to seismic slip rates (0.1 µm/s arrest.

  11. Generating and stabilizing the GHZ state in circuit QED: Joint measurement, Zeno effect and feedback

    CERN Document Server

    Feng, Wei; Ding, Xinmei; Xu, Luting; Li, Xin-Qi

    2011-01-01

    In solid-state circuit QED system, we extend the previous study of generating and stabilizing two-qubit Bell state [Phys. Rev. A 82, 032335 (2010)], to three-qubit GHZ state. In dispersive regime, we employ the homodyne joint readout for multiple qubits to infer the state for further processing, and in particular use it to stabilize the state directly by means of an alternate-flip-interrupted Zeno (AFIZ) scheme. Moreover, the state-of-the-art feedback action based on the filtered current enables not only a deterministic generation of the pre-GHZ state in the initial stage, but also a fast recovery from the environment-caused degradation in the later stabilization process. We show that the proposed scheme can maintain the state with high fidelity if the efficient quantum measurement and rapid single-qubit rotations are available.

  12. Active Disturbance Rejection Fuzzy Controller for Roll Stabilization of Autonomous Underwater Vehicle under Wave Disturbance

    Directory of Open Access Journals (Sweden)

    Lin-Lin Wang

    2015-01-01

    Full Text Available Considering the case of autonomous underwater vehicle navigating with low speed near water surface, a new method for designing of roll motion controller is proposed in order to restrain wave disturbance effectively and improve roll stabilizing performance under different sea conditions. Active disturbance rejection fuzzy control is applied, which is based on nonlinear motion model of autonomous underwater vehicle and the principle of zero-speed fin stabilizer. Extended state observer is used for estimation of roll motion state and unknown wave disturbance. Wave moment is counteracted by introducing compensation term into the roll control law which is founded on nonlinear feedback. Fuzzy reasoning is used for parameter adjustment of the controller online. Simulation experiments on roll motion are conducted under different sea conditions, and the results show better robustness improved by active disturbance rejection fuzzy controller of autonomous underwater vehicle navigating near water surface.

  13. Origin of Activity and Stability Enhancement for Ag3PO4 Photocatalyst after Calcination

    Directory of Open Access Journals (Sweden)

    Pengyu Dong

    2016-11-01

    Full Text Available Pristine Ag3PO4 microspheres were synthesized by a co-precipitation method, followed by being calcined at different temperatures to obtain a series of calcined Ag3PO4 photocatalysts. This work aims to investigate the origin of activity and stability enhancement for Ag3PO4 photocatalyst after calcination based on the systematical analyses of the structures, morphologies, chemical states of elements, oxygen defects, optical absorption properties, separation and transfer of photogenerated electron-hole pairs, and active species. The results indicate that oxygen vacancies (VO˙˙ are created and metallic silver nanoparticles (Ag NPs are formed by the reaction of partial Ag+ in Ag3PO4 semiconductor with the thermally excited electrons from Ag3PO4 and then deposited on the surface of Ag3PO4 microspheres during the calcination process. Among the calcined Ag3PO4 samples, the Ag3PO4-200 sample exhibits the best photocatalytic activity and greatly enhanced photocatalytic stability for photodegradation of methylene blue (MB solution under visible light irradiation. Oxygen vacancies play a significantly positive role in the enhancement of photocatalytic activity, while metallic Ag has a very important effect on improving the photocatalytic stability. Overall, the present work provides some powerful evidences and a deep understanding on the origin of activity and stability enhancement for the Ag3PO4 photocatalyst after calcination.

  14. Stability of Flip and Exchange Symmetric Entangled State Classes

    Science.gov (United States)

    Zafer Gedik, Mehmet

    2010-03-01

    Flip and exchange symmetric (FES) many-qubit states, which can be obtained from a state with the same symmetries by means of invertible local operations (ILO), constitute a one-parameter family of curves in the Hilbert space. Eigenstates of FES ILOs correspond to vectors that cannot be transformed to other FES states. Therefore, equivalence classes of states under ILO can be determined in a systematic way for an arbitrary number of qubits. More important, for entangled states, at the boundaries of neighboring equivalence classes, one can show that when the fidelity between the final state after an ILO and a state of the neighboring class approaches unity, probability of success decreases to zero. In other words, the classes are stable under ILOs.

  15. Dermal nanocrystals from medium soluble actives - physical stability and stability affecting parameters.

    Science.gov (United States)

    Zhai, Xuezhen; Lademann, Jürgen; Keck, Cornelia M; Müller, Rainer H

    2014-09-01

    Nanocrystals are meanwhile applied to increase the dermal penetration of drugs, but were applied by now only to poorly soluble drugs (e.g. 1-10 μg/ml). As a new concept nanocrystals from medium soluble actives were produced, using caffeine as model compound (solubility 16 mg/ml at 20 °C). Penetration should be increased by (a) further increase in solubility and (b) mainly by increased hair follicle targeting of nanocrystals compared to pure solution. Caffeine nanocrystal production in water lead to pronounced crystal growth. Therefore the stability of nanocrystals in water-ethanol (1:9) and ethanol-propylene glycol (3:7) mixtures with lower dielectric constant D was investigated, using various stabilizers. Both mixtures in combination with Carbopol 981 (non-neutralized) yielded stable nanosuspensions over 2 months at 4 °C and room temperature. Storage at 40 °C lead to crystal growth, attributed to too strong solubility increase, supersaturation and Ostwald ripening effects. Stability of caffeine nanocrystals at lower temperatures could not only be attributed to lower solubility, because the solubilities of caffeine in mixtures and in water are not that much different. Other effects such as quantified by reduced dielectric constant D, and specific interactions between dispersion medium and crystal surface seem to play a role. With the 2 mixtures and Carbopol 981, a basic formulation composition for this type of nanocrystals has been established, to be used in the in vivo proof of principle of the new concept.

  16. Preparation and bactericide activity of gallic acid stabilized gold nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Moreno-Alvarez, S. A. [UASLP, Doctorado Institucional en Ingenieria y Ciencia de Materiales (Mexico); Martinez-Castanon, G. A., E-mail: mtzcastanon@fciencias.uaslp.m [UASLP, Maestria en Ciencias Odontologicas, Facultad de Estomatologia (Mexico); Nino-Martinez, N. [UASLP, Facultad de Ciencias (Mexico); Reyes-Macias, J. F.; Patino-Marin, N.; Loyola-Rodriguez, J. P. [UASLP, Maestria en Ciencias Odontologicas, Facultad de Estomatologia (Mexico); Ruiz, Facundo [UASLP, Facultad de Ciencias (Mexico)

    2010-10-15

    In this work, gold nanoparticles with three different sizes (13.7, 39.4, and 76.7 nm) were prepared using a simple aqueous method with gallic acid as the reducing and stabilizing agent, the different sizes were obtained varying some experimental parameters as the pH of the reaction and the amount of the gallic acid. The prepared nanoparticles were characterized using X-ray diffraction, transmission electron microscopy, dynamic light scattering, and UV-Vis spectroscopy. Samples were identified as elemental gold and present spherical morphology, a narrow size distribution and good stabilization according to TEM and DLS results. The antibacterial activity of this gallic acid stabilized gold nanoparticles against S. mutans (the etiologic agent of dental caries) was assessed using a microdilution method obtaining a minimum inhibitory concentration of 12.31, 12.31, and 49.25 {mu}g/mL for 13.7, 39.4, and 76.7 nm gold nanoparticles, respectively. The antibacterial assay showed that gold nanoparticles prepared in this work present a bactericide activity by a synergistic action with gallic acid. The MIC found for this nanoparticles are much lower than those reported for mixtures of gold nanoparticles and antibiotics.

  17. Preparation and bactericide activity of gallic acid stabilized gold nanoparticles

    Science.gov (United States)

    Moreno-Álvarez, S. A.; Martínez-Castañón, G. A.; Niño-Martínez, N.; Reyes-Macías, J. F.; Patiño-Marín, N.; Loyola-Rodríguez, J. P.; Ruiz, Facundo

    2010-10-01

    In this work, gold nanoparticles with three different sizes (13.7, 39.4, and 76.7 nm) were prepared using a simple aqueous method with gallic acid as the reducing and stabilizing agent, the different sizes were obtained varying some experimental parameters as the pH of the reaction and the amount of the gallic acid. The prepared nanoparticles were characterized using X-ray diffraction, transmission electron microscopy, dynamic light scattering, and UV-Vis spectroscopy. Samples were identified as elemental gold and present spherical morphology, a narrow size distribution and good stabilization according to TEM and DLS results. The antibacterial activity of this gallic acid stabilized gold nanoparticles against S. mutans (the etiologic agent of dental caries) was assessed using a microdilution method obtaining a minimum inhibitory concentration of 12.31, 12.31, and 49.25 μg/mL for 13.7, 39.4, and 76.7 nm gold nanoparticles, respectively. The antibacterial assay showed that gold nanoparticles prepared in this work present a bactericide activity by a synergistic action with gallic acid. The MIC found for this nanoparticles are much lower than those reported for mixtures of gold nanoparticles and antibiotics.

  18. Stabilization of neutral-type indirect control systems to absolute stability state

    NARCIS (Netherlands)

    Shatyrko, A.; Van Nooyen, R.R.P.; Kolechkina, A.; Khusainov, D.

    2015-01-01

    This paper provides sufficient conditions for absolute stability of an indirect control Lur’e problem of neutral type. The conditions are derived using a Lyapunov-Krasovskii functional and are given in terms of a system of matrix algebraic inequalities. From these matrix inequalities a sufficient co

  19. Activity and Stability of Nanoscale Oxygen Reduction Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Shao-Horn, Yang

    2015-07-28

    Design of highly active and stable nanoscale catalysts for electro-oxidation of small organic molecules is of great importance to the development of efficient fuel cells. The amount and instability of Pt-based catalysts in the cathode limits the cost, efficiency and lifetime of proton exchange membrane fuel cells. We developed a microscopic understanding of the factors governing activity and stability in Pt and PtM alloys. Experimental efforts were focused on probing the size and shape dependence of ORR activity of Pt-based nanoparticles supported on carbon nanotubes. A microscopic understanding of the activity was achieved by correlating voltammetry and rotating ring disk electrodes to surface atomic and electronic structures, which were elucidated predominantly by high-resolution transmission electron microscopy (HRTEM), Scanning transmission electron microscopy energy dispersive X-ray Spectroscopy (STEM-EDS) and synchrotron X-ray absorption spectroscopy (XAS).

  20. ℋ∞ constant gain state feedback stabilization of stochastic hybrid systems with Wiener process

    Directory of Open Access Journals (Sweden)

    E. K. Boukas

    2004-01-01

    Full Text Available This paper considers the stabilization problem of the class of continuous-time linear stochastic hybrid systems with Wiener process. The ℋ∞ state feedback stabilization problem is treated. A state feedback controller with constant gain that does not require access to the system mode is designed. LMI-based conditions are developed to design the state feedback controller with constant gain that stochastically stabilizes the studied class of systems and, at the same time, achieve the disturbance rejection of a desired level. The minimum disturbance rejection is also determined. Numerical examples are given to show the usefulness of the proposed results.

  1. Reconciling Ligase Ribozyme Activity with Fatty Acid Vesicle Stability

    Directory of Open Access Journals (Sweden)

    Fabrizio Anella

    2014-12-01

    Full Text Available The “RNA world” and the “Lipid world” theories for the origin of cellular life are often considered incompatible due to the differences in the environmental conditions at which they can emerge. One obstacle resides in the conflicting requirements for divalent metal ions, in particular Mg2+, with respect to optimal ribozyme activity, fatty acid vesicle stability and protection against RNA strand cleavage. Here, we report on the activity of a short L1 ligase ribozyme in the presence of myristoleic acid (MA vesicles at varying concentrations of Mg2+. The ligation rate is significantly lower at low-Mg2+ conditions. However, the loss of activity is overcompensated by the increased stability of RNA leading to a larger amount of intact ligated substrate after long reaction periods. Combining RNA ligation assays with fatty acid vesicles we found that MA vesicles made of 5 mM amphiphile are stable and do not impair ligase ribozyme activity in the presence of approximately 2 mM Mg2+. These results provide a scenario in which catalytic RNA and primordial membrane assembly can coexist in the same environment.

  2. The effect of some osmolytes on the activity and stability of mushroom tyrosinase

    Indian Academy of Sciences (India)

    N Gheibi; A A Saboury; K Haghbeen; A A Moosavi-Movahedi

    2006-09-01

    The thermodynamical stability and remained activity of mushroom tyrosinase (MT) from Agaricus bisporus in 10 mM phosphate buffer, pH 6.8, stored at two temperatures of 4 and 40°C were investigated in the presence of three different amino acids (His, Phe and Asp) and also trehalose as osmolytes, for comparing with the results obtained in the absence of any additive. Kinetics of inactivation obeye the first order law. Inactivation rate constant (kinact) value is the best parameter describing effect of osmolytes on kinetic stability of the enzyme. Trehalose and His have the smallest value of kinact (0.7×10–4 s–1) in comparison with their absence (2.5×10–4 s–1). Moreover, to obtain effect of these four osmolytes on thermodynamical stability of the enzyme, protein denaturation by dodecyl trimethylammonium bromide (DTAB) and thermal scanning was investigated. Sigmoidal denaturation curves were analysed according to the two states model of Pace theory to find the Gibbs free energy change of denaturation process in aqueous solution at room temperature, as a very good thermodynamic criterion indicating stability of the protein. Although His, Phe and Asp induced constriction of MT tertiary structure, its secondary structure had not any change and the result was a chemical and thermal stabilization of MT. The enzyme shows a proper coincidence of thermodyanamic and structural changes with the presence of trehalose. Thus, among the four osmolytes, trehalose is an exceptional protein stabilizer.

  3. The effect of some osmolytes on the activity and stability of mushroom tyrosinase.

    Science.gov (United States)

    Gheibi, N; Saboury, A A; Haghbeen, K; Moosavi-Movahedi, A A

    2006-09-01

    The thermodynamical stability and remained activity of mushroom tyrosinase (MT) from Agaricus bisporus in 10 mM phosphate buffer, pH 6.8, stored at two temperatures of 4 and 40 degrees C were investigated in the presence of three different amino acids (His, Phe and Asp) and also trehalose as osmolytes, for comparing with the results obtained in the absence of any additive. Kinetics of inactivation obey the first order law. Inactivation rate constant (kinact) value is the best parameter describing effect of osmolytes on kinetic stability of the enzyme. Trehalose and His have the smallest value of kinact (0.7x10(-4) s-1) in comparison with their absence (2.5x10(-4) s-1). Moreover, to obtain effect of these four osmolytes on thermodynamical stability of the enzyme, protein denaturation by dodecyl trimethylammonium bromide (DTAB) and thermal scanning was investigated. Sigmoidal denaturation curves were analysed according to the two states model of Pace theory to find the Gibbs free energy change of denaturation process in aqueous solution at room temperature, as a very good thermodynamic criterion indicating stability of the protein. Although His, Phe and Asp induced constriction of MT tertiary structure, its secondary structure had not any change and the result was a chemical and thermal stabilization of MT. The enzyme shows a proper coincidence of thermodynamic and structural changes with the presence of trehalose. Thus, among the four osmolytes, trehalose is an exceptional protein stabilizer.

  4. Delay-dependent state feedback robust stabilization for uncertain singular time-delay systems

    Institute of Scientific and Technical Information of China (English)

    Gao Huanli; Xu Bugong

    2008-01-01

    The problem of robust stabilization for uncertain singular time-delay systems is studied.First,a new delay-dependent asymptotic stability criteria for normal singular time-delay systems is given,which is less conservative.Using this result,the problem of state feedback robust stabilization for uncertain singular time-delay systems is discussed.Finally,two examples are given to illustrate the effectiveness of the results.

  5. Stability analysis of uniform equilibrium foam states for EOR processes

    NARCIS (Netherlands)

    Ashoori, E.; Marchesin, D.; Rossen, W.R.

    2011-01-01

    The use of foam for mobility control is a promising mean to improve sweep efficiency in EOR. Experimental studies discovered that foam exhibits three different states (weak foam, intermediate foam, and strong foam). The intermediate-foam state is found to be unstable in the lab whereas the weak- and

  6. IMPROVEMENT OF TRANSIENT STABILITY OF POWER SYSTEM USING SOLID STATE CIRCUIT BREAKER

    Directory of Open Access Journals (Sweden)

    Kalai Murugan Amirthalingam

    2013-01-01

    Full Text Available The aim of this study is to use a solid state circuit breaker for the improvement of transient stability margin. Long distance AC transmission is often subject to stability problems, which limits the transmission capability. Interconnected power systems suffer from weakly damped swings between synchronous generator and sub systems. The development of modern power system has lead to an increasing complexity in the study of power system and also presents new challenges to power system stability and in particular to the aspects of transient stability and small signal stability. Transient stability control plays a significant role in ensuring the stable operation of power systems in the event of large disturbances and faults and is thus a significant area of research. This study investigates the improvement of transient stability of a two area system, using Solid State Circuit Breaker which is capable of fast switching in case of faults and thus controlling the real and reactive power flows in a faulted transmission line. Simulations are carried out in Matlab/Simulink environment for two area system model with Solid State Circuit Breaker to analyze the effects of SSCB on transient stability performance of the system. From the simulation results, swing curves of the three phase faulted power system without SSCB gets increases monotonically and thus the system can be considered as unstable whereas the swing curves of the system with an SSCB reaches to a steady state.

  7. On exponential stability for systems with state delays

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    This paper considers the issue of delay-dependent exponential stability for time-delay systems. Both nominal and uncertain systems are investigated. New sufficient conditions in terms of linear matrix inequalities (LMIs) are obtained. These criteria are simple owing to the use of an integral inequality. The model transformation approaches, bounding techniques for cross terms and slack matrices are all avoided in the derivation. Rigorous proof and numerical examples showed that the proposed criteria and those based on introducing slack matrices are equivalent.

  8. Diversity of Active States in TMT Opsins.

    Directory of Open Access Journals (Sweden)

    Kazumi Sakai

    Full Text Available Opn3/TMT opsins belong to one of the opsin groups with vertebrate visual and non-visual opsins, and are widely distributed in eyes, brains and other internal organs in various vertebrates and invertebrates. Vertebrate Opn3/TMT opsins are further classified into four groups on the basis of their amino acid identities. However, there is limited information about molecular properties of these groups, due to the difficulty in preparing the recombinant proteins. Here, we successfully expressed recombinant proteins of TMT1 and TMT2 opsins of medaka fish (Oryzias latipes in cultured cells and characterized their molecular properties. Spectroscopic and biochemical studies demonstrated that TMT1 and TMT2 opsins functioned as blue light-sensitive Gi/Go-coupled receptors, but exhibited spectral properties and photo-convertibility of the active state different from each other. TMT1 opsin forms a visible light-absorbing active state containing all-trans-retinal, which can be photo-converted to 7-cis- and 9-cis-retinal states in addition to the original 11-cis-retinal state. In contrast, the active state of TMT2 opsin is a UV light-absorbing state having all-trans-retinal and does not photo-convert to any other state, including the original 11-cis-retinal state. Thus, TMT opsins are diversified so as to form a different type of active state, which may be responsible for their different functions.

  9. Evaluation of pancreatin stability through enzyme activity determination

    Directory of Open Access Journals (Sweden)

    Terra Gleysson De Paula

    2016-09-01

    Full Text Available Pancreatin is a biotechnological product containing an enzyme complex, obtained from porcine pancreas, that is employed in treating pancreatic diseases. Experiments regarding the stability of the pharmaceutical formulation containing pancreatin were performed using standard binary mixtures with 6 excipients in a 1:1 ratio (m/m and a commercial formulation. To accomplish these goals, samples were stored for 1, 3 and 6 months at 40 ± 1 °C and 75 ± 5 % relative humidity (RH and 40 ± 1 °C and 0 % RH. Stress testing was also performed. All samples were analyzed to evaluate the α-amylase, lipase and protease activities through UV/Vis spectrophotometry. The results revealed that the excipient proprieties and the storage conditions affected enzyme stability. Humidity was a strong influencing factor in the reduction of α-amylase and protease activities. Stress testing indicated that pH 9.0 and UV light did not induce substantial alterations in enzyme activity.

  10. Oscillations and multiple steady states in active membrane transport models.

    Science.gov (United States)

    Vieira, F M; Bisch, P M

    1994-01-01

    The dynamic behavior of some non-linear extensions of the six-state alternating access model for active membrane transport is investigated. We use stoichio-metric network analysis to study the stability of steady states. The bifurcation analysis has been done through standard numerical methods. For the usual six-state model we have proved that there is only one steady state, which is globally asymptotically stable. When we added an autocatalytic step we found self-oscillations. For the competition between a monomer cycle and a dimer cycle, with steps of dimer formation, we have also found self-oscillations. We have also studied models involving the formation of a complex with other molecules. The addition of two steps for formation of a complex of the monomer with another molecule does not alter either the number or the stability of steady states of the basic six-state model. The model which combines the formation of a complex with an autocatalytic step shows both self-oscillations and multiple steady states. The results lead us to conclude that oscillations could be produced by active membrane transport systems if the transport cycle contains a sufficiently large number of steps (six in the present case) and is coupled to at least one autocatalytic reaction,. Oscillations are also predicted when the monomer cycle is coupled to a dimer cycle. In fact, the autocatalytic reaction can be seen as a simplification of the model involving competition between monomer and dimer cycles, which seems to be a more realistic description of biological systems. A self-regulation mechanism of the pumps, related to the multiple stationary states, is expected only for a combined effect of autocatalysis and formation of complexes with other molecules. Within the six-state model this model also leads to oscillation.

  11. Flatness-based control in successive loops for stabilization of heart's electrical activity

    Science.gov (United States)

    Rigatos, Gerasimos; Melkikh, Alexey

    2016-12-01

    The article proposes a new flatness-based control method implemented in successive loops which allows for stabilization of the heart's electrical activity. Heart's pacemaking function is modeled as a set of coupled oscillators which potentially can exhibit chaotic behavior. It is shown that this model satisfies differential flatness properties. Next, the control and stabilization of this model is performed with the use of flatness-based control implemented in cascading loops. By applying a per-row decomposition of the state-space model of the coupled oscillators a set of nonlinear differential equations is obtained. Differential flatness properties are shown to hold for the subsystems associated with the each one of the aforementioned differential equations and next a local flatness-based controller is designed for each subsystem. For the i-th subsystem, state variable xi is chosen to be the flat output and state variable xi+1 is taken to be a virtual control input. Then the value of the virtual control input which eliminates the output tracking error for the i-th subsystem becomes reference setpoint for the i + 1-th subsystem. In this manner the control of the entire state-space model is performed by successive flatness-based control loops. By arriving at the n-th row of the state-space model one computes the control input that can be actually exerted on the aforementioned biosystem. This real control input of the coupled oscillators' system, contains recursively all virtual control inputs associated with the previous n - 1 rows of the state-space model. This control approach achieves asymptotically the elimination of the chaotic oscillation effects and the stabilization of the heart's pulsation rhythm. The stability of the proposed control scheme is proven with the use of Lyapunov analysis.

  12. Towards Stability Analysis of Jump Linear Systems with State-Dependent and Stochastic Switching

    Science.gov (United States)

    Tejada, Arturo; Gonzalez, Oscar R.; Gray, W. Steven

    2004-01-01

    This paper analyzes the stability of hierarchical jump linear systems where the supervisor is driven by a Markovian stochastic process and by the values of the supervised jump linear system s states. The stability framework for this class of systems is developed over infinite and finite time horizons. The framework is then used to derive sufficient stability conditions for a specific class of hybrid jump linear systems with performance supervision. New sufficient stochastic stability conditions for discrete-time jump linear systems are also presented.

  13. Environmental stability of actively mode locked fibre lasers

    Science.gov (United States)

    Hill, Calum H.; Lee, Stephen T.; Reid, Derryck T.; Baili, Ghaya; Davies, John

    2016-10-01

    Lasers developed for defence related applications typically encounter issues with reliability and meeting desired specification when taken from the lab to the product line. In particular the harsh environmental conditions a laser has to endure can lead to difficulties. This paper examines a specific class of laser, namely actively mode-locked fibre lasers (AMLFLs), and discusses the impact of environmental perturbations. Theoretical and experimental results have assisted in developing techniques to improve the stability of a mode-locked pulse train for continuous operation. Many of the lessons learned in this research are applicable to a much broader category of lasers. The AMLFL consists of a fibre ring cavity containing a semiconductor optical amplifier (SOA), an isolator, an output coupler, a circulator, a bandpass filter and a modulator. The laser produces a train of 6-ps pulses at 800 nm with a repetition rate in the GHz regime and a low-noise profile. This performance is realisable in a laboratory environment. However, even small changes in temperature on the order of 0.1 °C can cause a collapse of mode-locked dynamics such that the required stability cannot be achieved without suitable feedback. Investigations into the root causes of this failure were performed by changing the temperature of components that constitute the laser resonator and observing their properties. Several different feedback mechanisms have been investigated to improve laser stability in an environment with dynamic temperature changes. Active cavity length control will be discussed along with DC bias control of the Mach-Zehnder modulator (MZM).

  14. Solid State Stability of Extemporaneously Prepared Levothyroxine Aliquots and Capsules.

    Science.gov (United States)

    Fortner, Jeff; Salton, Jason; Carlson, Christie; Wheeler, Rich; Cote, Brianna; Rao, Deepa

    2015-01-01

    The purpose of this research was to collect, analyze, and compare stability data for levothyroxine (T4) powder in the anhydrous and pentahydrate form when prepared as an aliquot and in capsules. Two different compounding pharmacies, Central Iowa Compounding and Gateway Medical Pharmacy, used different forms of T4 and aliquot formulations, which were studied to determine the beyond-use date at ±5% or ±10% of labeled strength. T4 was extracted from aliquot and capsule formulations and assessed using reverse-phase high- performance liquid chromatography validated to differentiate between the degraded and original forms of T4. The results indicate that T4 1:100 aliquot formulation prepared with silica gel or Avicel as filler are stable for 120 days at ±10% labeled potency, but at ±5% labeled potency, the silica gel and Avicel aliquot formulations are stable for 45 and 30 days, respectively. The silica gel capsules prepared from fresh aliquot were stable for 120 days at ±10% labeled potency and 90 days at ±5% labeled potency, while the Avicel capsules prepared from fresh aliquot were stable for 180 days at both ±10% and ±5% labeled potency. Avicel capsules prepared from old aliquot (120 days) and fresh aliquot (1 day) were also compared for stability. The old aliquot Avicel capsules were stable for 14 days at ±5% labeled potency and 150 days at ±10% labeled potency, while new aliquot Avicel capsules were stable for 180 days at both ±10% and ±5% labeled potency. Based on our data, there can be significant variation in the beyond-use dates assigned to T4 capsules based on the diluents used for aliquots, the final capsule formulations, and the potency standards applied. These results also indicate that pharmacists must exercise caution when using older aliquots and may have to assign shorter beyond-use dates.

  15. Increasing protein stability: Importance of ΔCp and the denatured state

    Science.gov (United States)

    Fu, Hailong; Grimsley, Gerald; Scholtz, J Martin; Pace, C Nick

    2010-01-01

    Increasing the conformational stability of proteins is an important goal for both basic research and industrial applications. In vitro selection has been used successfully to increase protein stability, but more often site-directed mutagenesis is used to optimize the various forces that contribute to protein stability. In previous studies, we showed that improving electrostatic interactions on the protein surface and improving the β-turn sequences were good general strategies for increasing protein stability, and used them to increase the stability of RNase Sa. By incorporating seven of these mutations in RNase Sa, we increased the stability by 5.3 kcal/mol. Adding one more mutation, D79F, gave a total increase in stability of 7.7 kcal/mol, and a melting temperature 28°C higher than the wild-type enzyme. Surprisingly, the D79F mutation lowers the change in heat capacity for folding, ΔCp, by 0.6 kcal/mol/K. This suggests that this mutation stabilizes structure in the denatured state ensemble. We made other mutants that give some insight into the structure present in the denatured state. Finally, the thermodynamics of folding of these stabilized variants of RNase Sa are compared with those observed for proteins from thermophiles. PMID:20340133

  16. Robust stability analysis of uncertain discrete-time systems with state delay

    Institute of Scientific and Technical Information of China (English)

    任正云; 张立群; 邵惠鹤

    2004-01-01

    The sufficient conditions of stability for uncertain discrete-time systems with state delay have been proposed by some researchers in the past few years, yet these results may be conservative in application. The stability analysis of these systems is discussed, and the necessary and sufficient condition of stability is derived by method other than constructing Lyapunov function and solving Riccati inequality. The root locations of system characteristic polynomial, which is obtained by augmentation approach and Laplace expansion, determine the stability of uncertain discrete-time systems with state delay, the system is stable if and only if all roots lie within the unit circle. In order to analyze robust stability of system characteristic polynomial effectively, Kharitonov theorem and edge theorem are applied. Example shows the practicability of these methods.

  17. Enhanced biological activity of carotenoids stabilized by phenyl groups.

    Science.gov (United States)

    You, Ji Suk; Jeon, Sunhwa; Byun, Youn Jung; Koo, Sangho; Choi, Shin Sik

    2015-06-15

    Carotenoids are lipid soluble food ingredients with multifunction including antioxidant and anticancer activities. However, carotenoids are destructively oxidized upon reaction with radicals resulting in toxic effects on biological systems. Two synthetic carotenoids (BAS and BTS) containing the aromatic phenyl groups with a para-substituent (OMe and Me, respectively) at C-13 and C-13' position were prepared in order to overcome a structural instability of carotenoid. Both BAS and BTS exerted stronger radical scavenging activity than β-carotene in DPPH and ABTS assays. In particular, BTS significantly reduced in vivo ROS (reactive oxygen species) levels and improved body growth and reproduction of Caenorhabditiselegans. BTS has a great potential for the advanced and modified carotenoid material with stability leading to enhanced bioavailability.

  18. ONLINE MONITORING STEADY STATE STABILITY LIMIT PADA SISTEM INTERKONEKSI SULSELRABAR

    OpenAIRE

    2015-01-01

    Pada beberapa dekade terakhir, fenomena black-out (pemadaman total)akibat voltage collapse mengalami peningkatan.Hal ini disebabkan oleh peningkatan konsumen pemakai listrik yang tidak sebanding dengan peningkatan pembangkit dan pengembangan jaringan transmisi. Berdasarkan kenyataan dilapangan, ketidakstabilan steady state sangat berhubungan dengan rendahnya ketersediaan daya aktif/reaktif, level tegangan yang rendah, dan besarnya perubahan tegangan untuk perubahan beban atau daya pembangkit....

  19. 77 FR 4674 - State Fiscal Stabilization Fund Program

    Science.gov (United States)

    2012-01-31

    ... by January 31, 2012. Waiver of Delayed Effective Date The Administrative Procedure Act (5 U.S.C. 553..., the President's priorities, or the principles stated in the Executive order. It has been determined... principles, structures, and definitions governing regulatory review established in Executive Order 12866....

  20. Theory, Investigation and Stability of Cathode Electrocatalytic Activity

    Energy Technology Data Exchange (ETDEWEB)

    Ding, Dong; Liu, Mingfei; Lai, Samson; Blinn, Kevin; Liu, Meilin

    2012-09-30

    The main objective of this project is to systematically characterize the surface composition, morphology, and electro-catalytic properties of catalysts coated on LSCF, aiming to establish the scientific basis for rational design of high-performance cathodes by combining a porous backbone (such as LSCF) with a thin catalyst coating. The understanding gained will help us to optimize the composition and morphology of the catalyst layer and microstructure of the LSCF backbone for better performance. More specifically, the technical objectives include: (1) to characterize the surface composition, morphology, and electro-catalytic properties of catalysts coated on LSCF; (2) to characterize the microscopic details and stability of the LSCF-catalyst (e.g., LSM) interfaces; (3) to establish the scientific basis for rational design of high-performance cathodes by combining a porous backbone (such as LSCF) with a thin catalyst coating; and (4) to demonstrate that the performance and stability of porous LSCF cathodes can be enhanced by the application of a thin-film coating of LSM through a solution infiltration process in small homemade button cells and in commercially available cells of larger dimension. We have successfully developed dense, conformal LSM films with desired structure, composition, morphology, and thickness on the LSCF surfaces by two different infiltration processes: a non-aqueous and a water-based sol-gel process. It is demonstrated that the activity and stability of LSCF cathodes can be improved by the introduction of a thin-film LSM coating through an infiltration process. Surface and interface of the LSM-coated LSCF cathode were systematically characterized using advanced microscopy and spectroscopy techniques. TEM observation suggests that a layer of La and Sr oxide was formed on LSCF surfaces after annealing. With LSM infiltration, in contrast, we no longer observe such La/Sr oxide layer on the LSM-coated LSCF samples after annealing under similar

  1. Exploiting Stabilizers and Parallelism in State Space Generation with the Symmetry Method

    DEFF Research Database (Denmark)

    Lorentsen, Louise; Kristensen, Lars Michael

    2001-01-01

    The symmetry method is a main reduction paradigm for alleviating the state explosion problem. For large symmetry groups deciding whether two states are symmetric becomes time expensive due to the apparent high time complexity of the orbit problem. The contribution of this paper is to alleviate th...... the negative impact of the orbit problem by the specification of canonical representatives for equivalence classes of states in Coloured Petri Nets, and by giving algorithms exploiting stabilizers and parallelism for computing the condensed state space....

  2. Electrostatic transition state stabilization rather than reactant destabilization provides the chemical basis for efficient chorismate mutase catalysis.

    Science.gov (United States)

    Burschowsky, Daniel; van Eerde, André; Ökvist, Mats; Kienhöfer, Alexander; Kast, Peter; Hilvert, Donald; Krengel, Ute

    2014-12-09

    For more than half a century, transition state theory has provided a useful framework for understanding the origins of enzyme catalysis. As proposed by Pauling, enzymes accelerate chemical reactions by binding transition states tighter than substrates, thereby lowering the activation energy compared with that of the corresponding uncatalyzed process. This paradigm has been challenged for chorismate mutase (CM), a well-characterized metabolic enzyme that catalyzes the rearrangement of chorismate to prephenate. Calculations have predicted the decisive factor in CM catalysis to be ground state destabilization rather than transition state stabilization. Using X-ray crystallography, we show, in contrast, that a sluggish variant of Bacillus subtilis CM, in which a cationic active-site arginine was replaced by a neutral citrulline, is a poor catalyst even though it effectively preorganizes chorismate for the reaction. A series of high-resolution molecular snapshots of the reaction coordinate, including the apo enzyme, and complexes with substrate, transition state analog and product, demonstrate that an active site, which is only complementary in shape to a reactive substrate conformer, is insufficient for effective catalysis. Instead, as with other enzymes, electrostatic stabilization of the CM transition state appears to be crucial for achieving high reaction rates.

  3. Stability analysis and active damping for LLCL-filter based grid-connected inverters

    DEFF Research Database (Denmark)

    Huang, Min; Blaabjerg, Frede; Loh, Poh Chiang

    2014-01-01

    A higher order passive power filter (LLCL-filter) for the grid-tied inverter is becoming attractive for the industrial applications due to the possibility to reduce the cost of the copper and the magnetic material. To avoid the well-known stability problems of the LLCL-filter it is requested to use...... either passive or active damping methods. This paper analyzes the stability when damping is required and when damping is not necessary considering sampling and transport delay. Basic LLCL resonance damping properties of different feedback states are also studied. Then an active damping method which...... is using the capacitor current feedback for LLCL-filter is introduced. Based on this method, a design procedure for the control method is given. Last, both simulation and experimental results are provided to validate the theoretical analysis of this paper....

  4. Design of hydraulic active stabilizer bar test platform based on dSPACE

    Directory of Open Access Journals (Sweden)

    Shan CHEN

    2016-12-01

    Full Text Available For the study of the influence of hydraulic active stabilizer bar to vehicle lateral stability under high speed steering maneuver, the hydraulic active stabilizer bar HIL test platform is implemented. The HIL test platform is designed with single/double axles universal test bench to experiment on single or double axles active stabilizer bar, using MC9S12DG128 microcontroller as the core controller and running vehicle dynamics model in the dSPACE. This HIL platform is used to study the effect of the hydraulic active stabilizer bar on the vehicle roll stability under different types of the road and typical steering maneuvers. The experiment results illustrate that the hydraulic active stabilizer bar HIL test platform can simulate the experiment environment and provide a powerful support for the development of active stabilizer bar system.

  5. Nanobody stabilization of G protein coupled receptor conformational states

    OpenAIRE

    Steyaert, Jan; K Kobilka, Brian

    2011-01-01

    Remarkable progress has been made in the field of G protein coupled receptor (GPCR) structural biology during the past four years. Several obstacles to generating diffraction quality crystals of GPCRs have been overcome by combining innovative methods ranging from protein engineering to lipid-based screens and microdiffraction technology. The initial GPCR structures represent energetically stable inactive-state conformations. However, GPCRs signal through different G protein isoforms or G pro...

  6. Linear Quantum Systems: Non-Classical States and Robust Stability

    Science.gov (United States)

    2016-06-29

    terms of transfer functions which describe the memory behaviour for arbitrary inputs and operating regimes. This allows us to go beyond previous works...characterize the condition required on the pulse shape achieving the perfect state transfer from the light field to the memory subsystem. The key idea to...illustrate the efficacy of this idea . Ian R. Petersen, Notes on coherent feedback control for linear quantum systems. In Australian Control

  7. A steady-state analytical slope stability model for complex hillslopes

    NARCIS (Netherlands)

    Talebi, A.; Troch, P.A.; Uijlenhoet, R.

    2008-01-01

    This paper presents a steady-state analytical hillslope stability model to study the role of topography on rain-induced shallow landslides. We combine a bivariate continuous function of the topographic surface, a steady-state hydrological model of hillslope saturated storage, and the infinite slope

  8. A steady-state analytical slope stability model for complex hillslopes

    NARCIS (Netherlands)

    Talebi, A.; Troch, P.A.; Uijlenhoet, R.

    2008-01-01

    This paper presents a steady-state analytical hillslope stability model to study the role of topography on rain-induced shallow landslides. We combine a bivariate continuous function of the topographic surface, a steady-state hydrological model of hillslope saturated storage, and the infinite slope

  9. Stability Analysis and Active Damping for LLCL-filter-Based Grid-Connected Inverters

    DEFF Research Database (Denmark)

    Huang, Min; Wang, Xiongfei; Loh, Poh Chiang

    2015-01-01

    to use either passive or active damping methods. This paper analyzes the stability of the LLCL-filter based grid-connected inverter and identifies a critical resonant frequency for the LLCL-filter when sampling and transport delays are considered. In a high resonant frequency region the active damping...... is not required but in a low resonant frequency region the active damping is necessary. The basic LLCL resonance damping properties of different feedback states based on a notch filter concept are also studied. Then an active damping method which is using the capacitor current feedback for LLCL......-filter is introduced. Based on this active damping method, a design procedure for the controller is given. Last, both simulation and experimental results are provided to validate the theoretical analysis of this paper....

  10. (Mutual Security Mutual Affluence) Negative Factors = Sustained Stability: A Framework for Establishing Stability Between Like States

    Science.gov (United States)

    2017-03-31

    United States, Great Britain’s vote to leave the European Union (BREXIT), and the 2015 election results in the Philippines, Brazil, Sweden , and Denmark.6...Slovenia, Spain, and Sweden . The United Kingdom, though technically still considered a part of the EU voted to exit the union and was therefore removed...Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden , and Switzerland, AXA Assistnace Insurance Group, Map of the Schengen

  11. Asymptotic Stabilization of Continuous-Time Linear Systems with Input and State Quantizations

    Directory of Open Access Journals (Sweden)

    Sung Wook Yun

    2014-01-01

    Full Text Available This paper discusses the asymptotic stabilization problem of linear systems with input and state quantizations. In order to achieve asymptotic stabilization of such systems, we propose a state-feedback controller comprising two control parts: the main part is used to determine the fundamental characteristics of the system associated with the cost, and the additional part is employed to eliminate the effects of input and state quanizations. In particular, in order to implement the additional part, we introduce a quantizer with a region-decision making process (RDMP for a certain linear switching surface. The simulation results show the effectiveness of the proposed controller.

  12. Stabilization of a scalar equation with delay in the state and control variables

    OpenAIRE

    SHAYAKHMETOVA LILIYA VLADIMIROVNA; KHARITONOV VLADIMIR LEONIDOVICH

    2014-01-01

    The contribution is dedicated to the stabilization problem of systems with input and state delay. We derive a stabilizing control law for the case of a scalar equation with several state and two input delays. We start with a control law of the form, where the right hand side contains future values of the state predicted by Cauchy formula. The presented control law is of the form of an integral equation. It is shown that the characteristic function of the closed-loop system consists of two fac...

  13. Robust stabilization of rotor-active magnetic bearing systems

    Science.gov (United States)

    Li, Guoxin

    Active magnetic bearings (AMBs) are emerging as a beneficial technology for high-speed and high-performance suspensions in rotating machinery applications. A fundamental feedback control problem is robust stabilization in the presence of uncertain destabilizing mechanisms in aeroelastic, hydroelastic dynamics, and AMB feedback. As rotating machines are evolving in achieving high speed, high energy density, and high performance, the rotor and the support structure become increasingly flexible, and highly coupled. This makes rotor-AMB system more challenging to stabilize. The primary objective of this research is to develop a systematic control synthesis procedure for achieving highly robust stabilization of rotor-AMB systems. Of special interest is the stabilization of multivariable systems such as the AMB supported flexible rotors and gyroscopic rotors, where the classical control design may encounter difficulties. To this end, we first developed a systematic modeling procedure. This modeling procedure exploited the best advantages of technology developed in rotordynamics and the unique system identification tool provided by the AMBs. A systematic uncertainty model for rotor-AMB systems was developed, eliminating the iterative process of selecting uncertainty structures. The consequences of overestimation or underestimation of uncertainties were made transparent to control engineers. To achieve high robustness, we explored the fundamental performance/robustness limitations due to rotor-AMB system unstable poles. We examined the mixed sensitivity performance that is closely related to the unstructured uncertainty. To enhance transparency of the synthesis, we analyzed multivariable controllers from classical control perspectives. Based on these results, a systematic robust control synthesis procedure was established. For a strong gyroscopic rotor over a wide speed range, we applied the advanced gain-scheduled synthesis, and compared two synthesis frameworks in

  14. Adaptive neural networks control for camera stabilization with active suspension system

    Directory of Open Access Journals (Sweden)

    Feng Zhao

    2015-08-01

    Full Text Available The camera always suffers from image instability on the moving vehicle due to unintentional vibrations caused by road roughness. This article presents an adaptive neural network approach mixed with linear quadratic regulator control for a quarter-car active suspension system to stabilize the image captured area of the camera. An active suspension system provides extra force through the actuator which allows it to suppress vertical vibration of sprung mass. First, to deal with the road disturbance and the system uncertainties, radial basis function neural network is proposed to construct the map between the state error and the compensation component, which can correct the optimal state-feedback control law. The weights matrix of radial basis function neural network is adaptively tuned online. Then, the closed-loop stability and asymptotic convergence performance is guaranteed by Lyapunov analysis. Finally, the simulation results demonstrate that the proposed controller effectively suppresses the vibration of the camera and enhances the stabilization of the entire camera, where different excitations are considered to validate the system performance.

  15. Phosphorylation regulates NCC stability and transporter activity in vivo.

    Science.gov (United States)

    Yang, Sung-Sen; Fang, Yu-Wei; Tseng, Min-Hua; Chu, Pei-Yi; Yu, I-Shing; Wu, Han-Chung; Lin, Shu-Wha; Chau, Tom; Uchida, Shinichi; Sasaki, Sei; Lin, Yuh-Feng; Sytwu, Huey-Kang; Lin, Shih-Hua

    2013-10-01

    A T60M mutation in the thiazide-sensitive sodium chloride cotransporter (NCC) is common in patients with Gitelman's syndrome (GS). This mutation prevents Ste20-related proline and alanine-rich kinase (SPAK)/oxidative stress responsive kinase-1 (OSR1)-mediated phosphorylation of NCC and alters NCC transporter activity in vitro. Here, we examined the physiologic effects of NCC phosphorylation in vivo using a novel Ncc T58M (human T60M) knock-in mouse model. Ncc(T58M/T58M) mice exhibited typical features of GS with a blunted response to thiazide diuretics. Despite expressing normal levels of Ncc mRNA, these mice had lower levels of total Ncc and p-Ncc protein that did not change with a low-salt diet that increased p-Spak. In contrast to wild-type Ncc, which localized to the apical membrane of distal convoluted tubule cells, T58M Ncc localized primarily to the cytosolic region and caused an increase in late distal convoluted tubule volume. In MDCK cells, exogenous expression of phosphorylation-defective NCC mutants reduced total protein expression levels and membrane stability. Furthermore, our analysis found diminished total urine NCC excretion in a cohort of GS patients with homozygous NCC T60M mutations. When Wnk4(D561A/+) mice, a model of pseudohypoaldosteronism type II expressing an activated Spak/Osr1-Ncc, were crossed with Ncc(T58M/T58M) mice, total Ncc and p-Ncc protein levels decreased and the GS phenotype persisted over the hypertensive phenotype. Overall, these data suggest that SPAK-mediated phosphorylation of NCC at T60 regulates NCC stability and function, and defective phosphorylation at this residue corrects the phenotype of pseudohypoaldosteronism type II.

  16. Contribution of linker stability to the activities of anticancer immunoconjugates.

    Science.gov (United States)

    Alley, Stephen C; Benjamin, Dennis R; Jeffrey, Scott C; Okeley, Nicole M; Meyer, Damon L; Sanderson, Russell J; Senter, Peter D

    2008-03-01

    The linker component of antibody-drug conjugates (ADC) is a key feature in developing optimized therapeutic agents that are highly active at well tolerated doses. For maximal intratumoral drug delivery, linkers are required that are highly stable in the systemic circulation, yet allow for efficient drug release at the target site. In this respect, amide bond-based technologies constitute a technological advancement, since the linker half-lives in circulation ( t 1/2 approximately 7 days) are much longer than earlier generation linkers that break down within 1-2 days. The amide linkers, some of which contain peptides, are appended to the mAb carriers through thioether/maleimide adducts. Here, we describe that use of a bromoacetamidecaproyl (bac) in place of the maleimidocaproyl (mc) increases the plasma stability of resulting thioether ADCs. One such ADC, 1F6-C4v2-bac-MMAF, which is directed against the CD70 antigen on lymphomas and renal cell carcinoma, was prepared containing a bac thioether spacer between the drug (MMAF) and the mAb carrier (1F6-C4v2). There was no measurable systemic drug release from this ADC for 2 weeks postadministration in mice. In order to assess the impact of improving linker stability beyond mc containing ADCs, a series of mc and bac-linked 1F6-MMAF conjugates were compared for tolerability, intratumoral drug delivery, and therapeutic efficacy in nude mice with renal cell carcinoma xenografts. There were no statistically significant efficacy differences between sets of mc and bac containing ADCs, although the bac linker technology led to 25% higher intratumoral drug exposure over a 7 day period compared to the corresponding mc linker. The mechanism of drug release from maleimide-adducts likely involves a retro-Michael reaction that takes place in plasma, based on in vitro studies demonstrating that some of the released drug-maleimide derivative became covalently bound to cysteine-34 of serum albumin. In summary, the data indicate that new

  17. Structural Distortion Stabilizing the Antiferromagnetic and Semiconducting Ground State of BaMn2As2

    Directory of Open Access Journals (Sweden)

    Ekkehard Krüger

    2016-09-01

    Full Text Available We report evidence that the experimentally found antiferromagnetic structure as well as the semiconducting ground state of BaMn 2 As 2 are caused by optimally-localized Wannier states of special symmetry existing at the Fermi level of BaMn 2 As 2 . In addition, we find that a (small tetragonal distortion of the crystal is required to stabilize the antiferromagnetic semiconducting state. To our knowledge, this distortion has not yet been established experimentally.

  18. Adaptive Stabilization for a Class of Dynamical Systems with Nonlinear Delayed State Perturbations

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The problem of adaptive stabilization for a class of systems with nonlinear delayed state perturbations is considered. The bound of the perturbations is assumed to be unknown, by using the adaptive control method, an adaptive controller is designed. Based on the Lyapunov- Karasovskii functional, it is shown that the dynamical system can be stabilized by the adaptive controller. The effectiveness of the proposed controller is demonstrated by some simulations.

  19. Stability and Bifurcation in a State-Dependent Delayed Predator-Prey System

    Science.gov (United States)

    Hou, Aiyu; Guo, Shangjiang

    In this paper, we consider a class of predator-prey equations with state-dependent delayed feedback. Firstly, we investigate the local stability of the positive equilibrium and the existence of the Hopf bifurcation. Then we use perturbation methods to determine the sub/supercriticality of Hopf bifurcation and hence the stability of Hopf bifurcating periodic solutions. Finally, numerical simulations supporting our theoretical results are also provided.

  20. Metal Fluoride Inhibition of a P-type H+ Pump: STABILIZATION OF THE PHOSPHOENZYME INTERMEDIATE CONTRIBUTES TO POST-TRANSLATIONAL PUMP ACTIVATION

    National Research Council Canada - National Science Library

    Pedersen, Jesper Torbøl; Falhof, Janus; Ekberg, Kira; Buch-Pedersen, Morten Jeppe; Palmgren, Michael

    2015-01-01

    .... In contrast to findings for other P-type ATPases, inhibition of the plasma membrane H(+)-ATPase by metal fluorides was partly reversible, and the stability of the inhibition varied with the activation state...

  1. Exact stabilization of entangled states in finite time by dissipative quantum circuits

    Science.gov (United States)

    Johnson, Peter D.; Ticozzi, Francesco; Viola, Lorenza

    2017-07-01

    Open quantum systems evolving according to discrete-time dynamics are capable, unlike continuous-time counterparts, to converge to a stable equilibrium in finite time with zero error. We consider dissipative quantum circuits consisting of sequences of quantum channels subject to specified quasi-locality constraints, and determine conditions under which stabilization of a pure multipartite entangled state of interest may be exactly achieved in finite time. Special emphasis is devoted to characterizing scenarios where finite-time stabilization may be achieved robustly with respect to the order of the applied quantum maps, as suitable for unsupervised control architectures. We show that if a decomposition of the physical Hilbert space into virtual subsystems is found, which is compatible with the locality constraint and relative to which the target state factorizes, then robust stabilization may be achieved by independently cooling each component. We further show that if the same condition holds for a scalable class of pure states, a continuous-time quasi-local Markov semigroup ensuring rapid mixing can be obtained. Somewhat surprisingly, we find that the commutativity of the canonical parent Hamiltonian one may associate to the target state does not directly relate to its finite-time stabilizability properties, although in all cases where we can guarantee robust stabilization, a (possibly noncanonical) commuting parent Hamiltonian may be found. Aside from graph states, quantum states amenable to finite-time robust stabilization include a class of universal resource states displaying two-dimensional symmetry-protected topological order, along with tensor network states obtained by generalizing a construction due to Bravyi and Vyalyi [Quantum Inf. Comput. 5, 187 (2005)]. Extensions to representative classes of mixed graph-product and thermal states are also discussed.

  2. Full-State Linearization and Stabilization of SISO Markovian Jump Nonlinear Systems

    Directory of Open Access Journals (Sweden)

    Zhongwei Lin

    2013-01-01

    Full Text Available This paper investigates the linearization and stabilizing control design problems for a class of SISO Markovian jump nonlinear systems. According to the proposed relative degree set definition, the system can be transformed into the canonical form through the appropriate coordinate changes followed with the Markovian switchings; that is, the system can be full-state linearized in every jump mode with respect to the relative degree set n,…,n. Then, a stabilizing control is designed through applying the backstepping technique, which guarantees the asymptotic stability of Markovian jump nonlinear systems. A numerical example is presented to illustrate the effectiveness of our results.

  3. Real-time quantum feedback prepares and stabilizes photon number states

    CERN Document Server

    Sayrin, Clément; Zhou, Xingxing; Peaudecerf, Bruno; Rybarczyk, Théo; Gleyzes, Sébastien; Rouchon, Pierre; Mirrahimi, Mazyar; Amini, Hadis; Brune, Michel; Raimond, Jean-Michel; Haroche, Serge

    2011-01-01

    Feedback loops are at the heart of most classical control procedures. A controller compares the signal measured by a sensor with the target value. It adjusts then an actuator in order to stabilize the signal towards its target. Generalizing this scheme to stabilize a micro-system's quantum state relies on quantum feedback, which must overcome a fundamental difficulty: the measurements by the sensor have a random back-action on the system. An optimal compromise employs weak measurements providing partial information with minimal perturbation. The controller should include the effect of this perturbation in the computation of the actuator's unitary operation bringing the incrementally perturbed state closer to the target. While some aspects of this scenario have been experimentally demonstrated for the control of quantum or classical micro-system variables, continuous feedback loop operations permanently stabilizing quantum systems around a target state have not yet been realized. We have implemented such a rea...

  4. A complete characterization of all-versus-nothing arguments for stabilizer states.

    Science.gov (United States)

    Abramsky, Samson; Barbosa, Rui Soares; Carù, Giovanni; Perdrix, Simon

    2017-11-13

    An important class of contextuality arguments in quantum foundations are the all-versus-nothing (AvN) proofs, generalizing a construction originally due to Mermin. We present a general formulation of AvN arguments and a complete characterization of all such arguments that arise from stabilizer states. We show that every AvN argument for an n-qubit stabilizer state can be reduced to an AvN proof for a three-qubit state that is local Clifford-equivalent to the tripartite Greenberger-Horne-Zeilinger state. This is achieved through a combinatorial characterization of AvN arguments, the AvN triple theorem, whose proof makes use of the theory of graph states. This result enables the development of a computational method to generate all the AvN arguments in [Formula: see text] on n-qubit stabilizer states. We also present new insights into the stabilizer formalism and its connections with logic.This article is part of the themed issue 'Second quantum revolution: foundational questions'. © 2017 The Author(s).

  5. Iron metallodrugs: stability, redox activity and toxicity against Artemia salina.

    Science.gov (United States)

    Vitorino, Hector Aguilar; Mantovanelli, Luca; Zanotto, Flavia Pinheiro; Espósito, Breno Pannia

    2015-01-01

    Iron metallodrugs comprise mineral supplements, anti-hypertensive agents and, more recently, magnetic nanomaterials, with both therapeutic and diagnostic roles. As biologically-active metal compounds, concern has been raised regarding the impact of these compounds when emitted to the environment and associated ecotoxicological effects for the fauna. In this work we assessed the relative stability of several iron compounds (supplements based on glucoheptonate, dextran or glycinate, as well as 3,5,5-trimethylhexanoyl (TMH) derivatives of ferrocene) against high affinity models of biological binding, calcein and aprotransferrin, via a fluorimetric method. Also, the redox-activity of each compound was determined in a physiologically relevant medium. Toxicity toward Artemia salina at different developmental stages was measured, as well as the amount of lipid peroxidation. Our results show that polymer-coated iron metallodrugs are stable, non-redox-active and non-toxic at the concentrations studied (up to 300 µM). However, TMH derivatives of ferrocene were less stable and more redox-active than the parent compound, and TMH-ferrocene displayed toxicity and lipid peroxidation to A. salina, unlike the other compounds. Our results indicate that iron metallodrugs based on polymer coating do not present direct toxicity at low levels of emission; however other iron species (eg. metallocenes), may be deleterious for aquatic organisms. We suggest that ecotoxicity depends more on metal speciation than on the total amount of metal present in the metallodrugs. Future studies with discarded metallodrugs should consider the chemical speciation of the metal present in the composition of the drug.

  6. Synthesis, thermal stability, and photocatalytic activity of nanocrystalline titanium carbide

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Youjian; Zhang, Hong [College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, Zhejiang 325027 (China); Ma, DeKun [College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, Zhejiang 325027 (China); Nanomaterials and Chemistry Key Laboratory, Advanced Materials Research Center of Wenzhou, Wenzhou University, Wenzhou, Zhejiang 325027 (China); Ma, Jianhua, E-mail: mjh820@ustc.edu [College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, Zhejiang 325027 (China); Nanomaterials and Chemistry Key Laboratory, Advanced Materials Research Center of Wenzhou, Wenzhou University, Wenzhou, Zhejiang 325027 (China); Ye, Hongnan; Qian, Gaojin; Ye, Yi [Oujiang College, Wenzhou University, Wenzhou, Zhejiang 325027 (China)

    2011-11-15

    Highlights: {yields} The synthesized temperature is lower than some conventional methods. {yields} These raw materials are safe; all manipulations are rather safe and convenient. {yields} The product exhibits photocatalytic activity in degradation of Rhodamine-B. -- Abstract: Titanium carbide (TiC) was prepared via one simple route by the reaction of metallic magnesium powders with titanium dioxide (TiO{sub 2}) and potassium acetate (CH{sub 3}COOK) in an autoclave at 600 {sup o}C and 8 h. Phase structure and morphology were characterized by X-ray powder diffraction (XRD) and Scanning electron microscopy (SEM). The results indicated that the product was cubic TiC, which consisted of particles with an average size of about 100 nm in diameter. The product was also studied by the thermogravimetric analysis (TGA) and its photocatalysis. It had good thermal stability and oxidation resistance below 350 {sup o}C in air. In addition, we discovered that the cubic TiC powders exhibited photocatalytic activity in degradation of Rhodamine-B (RhB) under 500 W mercury lamp light irradiation.

  7. Frequency stabilization of a solid-state microwave generator at a passing four-pole resonator antiparasitic load

    Directory of Open Access Journals (Sweden)

    V. V. Dzyubenko

    1987-12-01

    Full Text Available The analysis of the quality of the parametric frequency stabilization of solid state microwave generators in the four-pole through-inclusion of stabilizing resonator absorbing load. Lredlozhena technique optimal setting generators.

  8. Frequency stabilization of a solid-state microwave generator at a passing four-pole resonator antiparasitic load

    OpenAIRE

    V. V. Dzyubenko; E. A. Zaritskaya; E. A. Machusskii

    1987-01-01

    The analysis of the quality of the parametric frequency stabilization of solid state microwave generators in the four-pole through-inclusion of stabilizing resonator absorbing load. Lredlozhena technique optimal setting generators.

  9. Active quadrupole stabilization for future linear particle colliders

    CERN Document Server

    Collette, Christophe; Kuzmin, Andrey; Janssens, Stef; Sylte, Magnus; Guinchard, Michael; Hauviller, Claude

    2010-01-01

    The future Compact LInear particle Collider (CLIC) under study at CERN will require to stabilize heavy electromagnets, and also to provide them some positioning capabilities. Firstly, this paper presents the concept adopted to address both requirements. Secondly, the control strategy adopted for the stabilization is studied numerically, showing that the quadrupole can be stabilized in both lateral and vertical direction. Finally, the strategy is validated experimentally on a single degree of freedom scaled test bench.

  10. Advances in simultaneous DSC-FTIR microspectroscopy for rapid solid-state chemical stability studies: some dipeptide drugs as examples.

    Science.gov (United States)

    Lin, Shan-Yang; Wang, Shun-Li

    2012-04-01

    The solid-state chemistry of drugs has seen growing importance in the pharmaceutical industry for the development of useful API (active pharmaceutical ingredients) of drugs and stable dosage forms. The stability of drugs in various solid dosage forms is an important issue because solid dosage forms are the most common pharmaceutical formulation in clinical use. In solid-state stability studies of drugs, an ideal accelerated method must not only be selected by different complicated methods, but must also detect the formation of degraded product. In this review article, an analytical technique combining differential scanning calorimetry and Fourier-transform infrared (DSC-FTIR) microspectroscopy simulates the accelerated stability test, and simultaneously detects the decomposed products in real time. The pharmaceutical dipeptides aspartame hemihydrate, lisinopril dihydrate, and enalapril maleate either with or without Eudragit E were used as testing examples. This one-step simultaneous DSC-FTIR technique for real-time detection of diketopiperazine (DKP) directly evidenced the dehydration process and DKP formation as an impurity common in pharmaceutical dipeptides. DKP formation in various dipeptides determined by different analytical methods had been collected and compiled. Although many analytical methods have been applied, the combined DSC-FTIR technique is an easy and fast analytical method which not only can simulate the accelerated drug stability testing but also at the same time enable to explore phase transformation as well as degradation due to thermal-related reactions. This technique offers quick and proper interpretations.

  11. A genetic timer through noise-induced stabilization of an unstable state.

    Science.gov (United States)

    Turcotte, Marc; Garcia-Ojalvo, Jordi; Süel, Gürol M

    2008-10-14

    Stochastic fluctuations affect the dynamics of biological systems. Typically, such noise causes perturbations that can permit genetic circuits to escape stable states, triggering, for example, phenotypic switching. In contrast, studies have shown that noise can surprisingly also generate new states, which exist solely in the presence of fluctuations. In those instances noise is supplied externally to the dynamical system. Here, we present a mechanism in which noise intrinsic to a simple genetic circuit effectively stabilizes a deterministically unstable state. Furthermore, this noise-induced stabilization represents a unique mechanism for a genetic timer. Specifically, we analyzed the effect of noise intrinsic to a prototypical two-component gene-circuit architecture composed of interacting positive and negative feedback loops. Genetic circuits with this topology are common in biology and typically regulate cell cycles and circadian clocks. These systems can undergo a variety of bifurcations in response to parameter changes. Simulations show that near one such bifurcation, noise induces oscillations around an unstable spiral point and thus effectively stabilizes this unstable fixed point. Because of the periodicity of these oscillations, the lifetime of the noise-dependent stabilization exhibits a polymodal distribution with multiple, well defined, and regularly spaced peaks. Therefore, the noise-induced stabilization presented here constitutes a minimal mechanism for a genetic circuit to function as a timer that could be used in the engineering of synthetic circuits.

  12. Stabilization of nonclassical states of the radiation field in a cavity by reservoir engineering.

    Science.gov (United States)

    Sarlette, A; Raimond, J M; Brune, M; Rouchon, P

    2011-07-01

    We propose an engineered reservoir inducing the relaxation of a cavity field towards nonclassical states. It is made up of two-level atoms crossing the cavity one at a time. Each atom-cavity interaction is first dispersive, then resonant, then dispersive again. The reservoir pointer states are those produced by an effective Kerr Hamiltonian acting on a coherent field. We thereby stabilize squeezed states and quantum superpositions of multiple coherent components in a cavity having a finite damping time. This robust decoherence protection method could be implemented in state-of-the-art experiments.

  13. Stabilization of unstable steady states of a continuous stirred tank bioreactor with predator-prey kinetics.

    Science.gov (United States)

    Tabiś, Bolesław; Skoneczny, Szymon

    2013-07-20

    Nonlinear properties of a bioreactor with a developed microbiological predator-prey food chain are discussed. The presence of the predator microorganism completely changes the position and stability of the stationary states. A wide range of unstable steady states appears, associated with high amplitude oscillations of the state variables. Without automatic control such a system can only operate in transient states, with the yield undergoing periodic changes following the dynamics of the stable limit cycle. Technologically, this is undesirable. It has been shown that the oscillations can be removed by employing continuous P or PI controllers. Moreover, with a PI-controller, the predator can be eliminated from the system.

  14. Delay-dependent robust stability of uncertain networked control systems with multiple state time-delays

    Institute of Scientific and Technical Information of China (English)

    Huaicheng YAN; Xinhan HUANG; Min WANG

    2007-01-01

    In this paper, delay-dependent robust stability for a class of uncertain networked control systems (NCSs)with multiple state time-delays is investigated. Modeling of multi-input and multi-output (MIMO) NCSs with networkinduced delays and uncertainties through new methods are proposed. Some new stability criteria in terms of LMIs are derived by using Lyapunov stability theory combined with linear matrix inequalities (LMIs) techniques. We analyze the delay-dependent asymptotic stability and obtain maximum allowable delay bound (MADB) for the NCSs with the proposed methods. Compared with the reported results, the proposed results obtain a much less conservative MADB which are more general. Numerical example and simulation is used to illustrate the effectiveness of the proposed methods.

  15. Amplitude and frequency stabilized solid-state lasers in the near infrared

    Energy Technology Data Exchange (ETDEWEB)

    Laporta, P. [INFM, Dipartimento di Fisica del Politecnico di Milano and CEQSE-CNR Piazza Leonardo da Vinci 32, Milan (Italy)]. E-mail: paolo.laporta@polimi.it; Taccheo, S.; Marano, M.; Svelto, O. [INFM, Dipartimento di Fisica del Politecnico di Milano and CEQSE-CNR Piazza Leonardo da Vinci 32, Milan (Italy); Bava, E.; Galzerano, G.; Svelto, C. [INFM, Dipartimento di Elettronica e Informazione, Politecnico di Milano and CNR-CSTS Piazza Leonardo da Vinci 32, Milan (Italy)

    2001-08-21

    In this article we present a comprehensive review of the work done by our group on the amplitude and frequency stabilization of diode-pumped near-infrared solid-state lasers. In particular, we describe experiments based on single-mode Nd:YAG (1064 nm), Er-Yb:glass (1530-1560 nm), and Tm-Ho:YAG (2097 nm) lasers, end-pumped by semiconductor laser diodes. Amplitude stabilization is achieved by means of optoelectronic control loops sensing the laser intensity fluctuations and feeding back the error signal to the current of the pump diodes. Frequency stabilization is pursued using rovibrational molecular lines as absolute frequency references by means of various frequency locking techniques. The most interesting stability results are described in some detail whereas the wide literature cited through the paper provides for a useful reference list of related topics and experiments. (author)

  16. Evaluation of phenotypic stability of cassava clones by AMMI analysis in northwestern Paraná state

    Directory of Open Access Journals (Sweden)

    Marcus Vinícius Kvitschal

    2006-01-01

    Full Text Available High yield stability and adaptability of storage root are highly desirable attributes of cassava clones. Theobjective of this study was therefore to evaluate the effect of the genotype x environment interaction (G x E and the stability ofcassava clones developed at IAC. A subset of eight cassava genotypes was chosen in trials of storage root yield, arranged ina randomized complete block design with four replications, in two counties (Araruna and Maringá, in the northwesternregion of Paraná State, over five growing seasons (1997-2001. The G x E interaction was evaluated by joint varianceanalysis and stability and adaptability by AMMI analysis. The G x E interaction was significant (P<0.05 for storage rootyield. Results indicated AMMI analysis as an efficient tool for the evaluation of phenotypic adaptability and stability of cassavaclones and IAC 190 as the most promising clone.

  17. Stabilizing a Platinum1 Single-Atom Catalyst on Supported Phosphomolybdic Acid without Compromising Hydrogenation Activity.

    Science.gov (United States)

    Zhang, Bin; Asakura, Hiroyuki; Zhang, Jia; Zhang, Jiaguang; De, Sudipta; Yan, Ning

    2016-07-11

    In coordination chemistry, catalytically active metal complexes in a zero- or low-valent state often adopt four-coordinate square-planar or tetrahedral geometry. By applying this principle, we have developed a stable Pt1 single-atom catalyst with a high Pt loading (close to 1 wt %) on phosphomolybdic acid(PMA)-modified active carbon. This was achieved by anchoring Pt on the four-fold hollow sites on PMA. Each Pt atom is stabilized by four oxygen atoms in a distorted square-planar geometry, with Pt slightly protruding from the oxygen planar surface. Pt is positively charged, absorbs hydrogen easily, and exhibits excellent performance in the hydrogenation of nitrobenzene and cyclohexanone. It is likely that the system described here can be extended to a number of stable SACs with superior catalytic activities.

  18. Effect of axial ligands on the molecular configurations, stability, reactivity, and photodynamic activities of silicon phthalocyanines.

    Science.gov (United States)

    Luan, Liqiang; Ding, Lanlan; Shi, Jiawei; Fang, Wenjuan; Ni, Yuxing; Liu, Wei

    2014-12-01

    To demonstrate the effect of axial ligands on the structure-activity relationship, a series of axially substituted silicon phthalocyanines (SiPcs) have been synthesized with changes to the axial ligands. The reactivity of the axial ligand upon shielding by the phthalocyanine ring current, along with their stability, photophysical, and photodynamic therapy (PDT) activities were compared and evaluated for the first time. As revealed by single-crystal XRD analysis, rotation of the axial -OMe ligands was observed in SiPc 3, which resulted in two molecular configurations coexisting synchronously in both the solid and solution states and causing a split of the phthalocyanine α protons in the (1)H NMR spectra that is significantly different from all SiPcs reported so far. The remarkable photostability, good singlet oxygen quantum yield, and efficient in vitro photodynamic activity synergistically show that compound 3 is one of the most promising photosensitizers for PDT.

  19. Micron: an Actively Stabilized Handheld Tool for Microsurgery

    Science.gov (United States)

    MacLachlan, Robert A.; Becker, Brian C.; Tabarés, Jaime Cuevas; Podnar, Gregg W.; Lobes, Louis A.; Riviere, Cameron N.

    2011-01-01

    We describe the design and performance of a hand-held actively stabilized tool to increase accuracy in micro-surgery or other precision manipulation. It removes involuntary motion such as tremor by actuating the tip to counteract the effect of the undesired handle motion. The key components are a three-degree-of-freedom piezoelectric manipulator that has 400 μm range of motion, 1 N force capability, and bandwidth over 100 Hz, and an optical position measurement subsystem that acquires the tool pose with 4 μm resolution at 2000 samples/s. A control system using these components attenuates hand motion by at least 15 dB (a fivefold reduction). By considering the effect of the frequency response of Micron on the human visual feedback loop, we have developed a filter that reduces unintentional motion, yet preserves intuitive eye-hand coordination. We evaluated the effectiveness of Micron by measuring the accuracy of the human/machine system in three simple manipulation tasks. Handheld testing by three eye surgeons and three non-surgeons showed a reduction in position error of between 32% and 52%, depending on the error metric. PMID:23028266

  20. Stability of stationary states of non-local equations with singular interaction potentials

    KAUST Repository

    Fellner, Klemens

    2011-04-01

    We study the large-time behaviour of a non-local evolution equation for the density of particles or individuals subject to an external and an interaction potential. In particular, we consider interaction potentials which are singular in the sense that their first derivative is discontinuous at the origin.For locally attractive singular interaction potentials we prove under a linear stability condition local non-linear stability of stationary states consisting of a finite sum of Dirac masses. For singular repulsive interaction potentials we show the stability of stationary states of uniformly bounded solutions under a convexity condition.Finally, we present numerical simulations to illustrate our results. © 2010 Elsevier Ltd.

  1. A steady-state solver and stability calculator for nonlinear internal wave flows

    Science.gov (United States)

    Viner, Kevin C.; Epifanio, Craig C.; Doyle, James D.

    2013-10-01

    A steady solver and stability calculator is presented for the problem of nonlinear internal gravity waves forced by topography. Steady-state solutions are obtained using Newton's method, as applied to a finite-difference discretization in terrain-following coordinates. The iteration is initialized using a boundary-inflation scheme, in which the nonlinearity of the flow is gradually increased over the first few Newton steps. The resulting method is shown to be robust over the full range of nonhydrostatic and rotating parameter space. Examples are given for both nonhydrostatic and rotating flows, as well as flows with realistic upstream shear and static stability profiles. With a modest extension, the solver also allows for a linear stability analysis of the steady-state wave fields. Unstable modes are computed using a shifted-inverse method, combined with a parameter-space search over a set of realistic target values. An example is given showing resonant instability in a nonhydrostatic mountain wave.

  2. Longitudinal Stability of the Beck Depression Inventory II: A Latent Trait-State-Occasion Model

    Science.gov (United States)

    Wu, Pei-Chen

    2016-01-01

    In a six-wave longitudinal study with two cohorts (660 adolescents and 630 young adults), this study investigated the longitudinal stability of the Beck Depression Inventory II (BDI-II) using the Trait-State-Occasion (TSO) model. The results revealed that the full TSO model was the best fitting representation of the depression measured by the…

  3. Stabilization of nonlinear sandwich systems via state feedback-Discrete-time systems

    NARCIS (Netherlands)

    Wang, Xu; Stoorvogel, Anton A.; Saberi, Ali; Grip, H°avard Fjær; Sannuti, Peddapullaiah

    2011-01-01

    A recent paper (IEEE Trans. Aut. Contr. 2010; 55(9):2156–2160) considered stabilization of a class of continuous-time nonlinear sandwich systems via state feedback. This paper is a discrete-time counterpart of it. The class of nonlinear sandwich systems consists of saturation elements sandwiched bet

  4. On the stability of diffusion processes with state-dependent switching

    Institute of Scientific and Technical Information of China (English)

    XI Fubao; ZHAO Liqin

    2006-01-01

    In this paper we consider the stability for diffusion processes with state-dependent switching. We first prove their Feller continuity by the coupling methods. Furthermore, we also prove their strong Feller continuity and their exponential ergodicity under some reasonable conditions. Finally, we append a very brief discussion about the regularity of these processes.

  5. The challenge of stabilizing control for queueing systems with unobservable server states

    NARCIS (Netherlands)

    Nazarathy, Y.; Taimre, T.; Asanjarani, A.; Kuhn, J.; Patch, B.; Vuorinen, A.

    2016-01-01

    We address the problem of stabilizing control for complex queueing systems where servers follow unobservable Markovian environments. The controller needs to assign servers to queues without full information about the servers' states. A control challenge is to devise a policy that matches servers to

  6. Infinite-Dimensional Feedback Systems : The Circle Criterion and Input-to-State Stability

    NARCIS (Netherlands)

    Jayawardhana, Bayu; Logemann, Hartmut; Ryan, Eugene P.

    2008-01-01

    An input-to-state stability theory, which subsumes results of circle criterion type, is developed in the context of a class of infinite-dimensional systems. The generic system is of Lur’e type: a feedback interconnection of a well-posed infinite-dimensional linear system and a nonlinearity. The

  7. State-space-based harmonic stability analysis for paralleled grid-connected inverters

    DEFF Research Database (Denmark)

    Wang, Yanbo; Wang, Xiongfei; Chen, Zhe

    2016-01-01

    This paper addresses a state-space-based harmonic stability analysis of paralleled grid-connected inverters system. A small signal model of individual inverter is developed, where LCL filter, the equivalent delay of control system, and current controller are modeled. Then, the overall small signa...

  8. Predictors of Placement Stability at the State Level: The Use of Logistic Regression to Inform Practice

    Science.gov (United States)

    Courtney, Jon R.; Prophet, Retta

    2011-01-01

    Placement instability is often associated with a number of negative outcomes for children. To gain state level contextual knowledge of factors associated with placement stability/instability, logistic regression was applied to selected variables from the New Mexico Adoption and Foster Care Administrative Reporting System dataset. Predictors…

  9. Stabilization of three-dimensional chaotic systems via single state feedback controller

    Energy Technology Data Exchange (ETDEWEB)

    Yu Wenguang, E-mail: smilewgyu@163.co [School of Statistics and Mathematics, Shandong Economic University, Jinan 250014 (China)

    2010-03-29

    This Letter investigates the stabilization of three-dimensional chaotic systems, and proposes a novel simple adaptive-feedback controller for chaos control. In comparison with previous methods, the present controller which only contains single state feedback, to our knowledge, is the simplest control scheme for controlling the three-dimensional chaotic system. The results are validated using numerical simulations.

  10. Wavelet modeling and prediction of the stability of states: the Roman Empire and the European Union

    Science.gov (United States)

    Yaroshenko, Tatyana Y.; Krysko, Dmitri V.; Dobriyan, Vitalii; Zhigalov, Maksim V.; Vos, Hendrik; Vandenabeele, Peter; Krysko, Vadim A.

    2015-09-01

    How can the stability of a state be quantitatively determined and its future stability predicted? The rise and collapse of empires and states is very complex, and it is exceedingly difficult to understand and predict it. Existing theories are usually formulated as verbal models and, consequently, do not yield sharply defined, quantitative prediction that can be unambiguously validated with data. Here we describe a model that determines whether the state is in a stable or chaotic condition and predicts its future condition. The central model, which we test, is that growth and collapse of states is reflected by the changes of their territories, populations and budgets. The model was simulated within the historical societies of the Roman Empire (400 BC to 400 AD) and the European Union (1957-2007) by using wavelets and analysis of the sign change of the spectrum of Lyapunov exponents. The model matches well with the historical events. During wars and crises, the state becomes unstable; this is reflected in the wavelet analysis by a significant increase in the frequency ω (t) and wavelet coefficients W (ω, t) and the sign of the largest Lyapunov exponent becomes positive, indicating chaos. We successfully reconstructed and forecasted time series in the Roman Empire and the European Union by applying artificial neural network. The proposed model helps to quantitatively determine and forecast the stability of a state.

  11. Antibacterial activity of silver nanoparticles stabilized on tannin-grafted collagen fiber

    Energy Technology Data Exchange (ETDEWEB)

    He Li [National Engineering Laboratory for Clean Technology of Leather Manufacture, Sichuan University, Chengdu 610065 (China); Gao Siying; Wu Hao [Department of Biomass Chemistry and Engineering, Sichuan University, Chengdu 610065 (China); Liao Xuepin, E-mail: xpliao@scu.edu.cn [Department of Biomass Chemistry and Engineering, Sichuan University, Chengdu 610065 (China); He Qiang [National Engineering Laboratory for Clean Technology of Leather Manufacture, Sichuan University, Chengdu 610065 (China); Shi Bi, E-mail: sibitannin@vip.163.com [National Engineering Laboratory for Clean Technology of Leather Manufacture, Sichuan University, Chengdu 610065 (China) and Department of Biomass Chemistry and Engineering, Sichuan University, Chengdu 610065 (China)

    2012-07-01

    Bayberry tannin (BT), a typical plant polyphenol, was grafted on collagen fiber (CF) in different mass ratios. Subsequently, the BT-grafted CF (BT-CF) was used as carrier and stabilizer to prepare BT-CF stabilized silver nanoparticles (BT-CF-AgNPs). Scanning Electron Microscopy image of BT-CF-AgNPs showed that the BT-CF-AgNPs was in ordered fibrous state. X-ray Diffraction patterns and Transmission Electron Microscopy images offered evidence that the Ag nanoparticles were well dispersed on BT-CF. Fourier Transform-Infrared Spectroscopy (FTIR) and X-ray Photoelectron Spectroscopy (XPS) investigations revealed that the Ag NPs were stabilized by the phenolic hydroxyls and quinones of BT on CF through electron donation/acception interaction. Antibacterial experiments demonstrated that BT-CF-AgNPs exhibited high antibacterial activity. When cell suspensions of Escherichia coli and Staphylococcus aureus (10{sup 4}-10{sup 5} cfu/mL) were contacted with BT{sub 0.19}-CF-AgNPs (mass ratio of BT to CF = 0.19, conc. of Ag = 8 {mu}g/mL) at 310 K under constant shaking, the number of cells went down to zero within 2 h. In addition, the minimal inhibitory concentration of BT{sub 0.19}-CF-AgNPs against Escherichia coli, Staphylococcus aureus, Penicillium glaucum and Saccharomyces cerevisiae was 2 {mu}g/mL, 4 {mu}g/mL, 6 {mu}g/mL and 12 {mu}g/mL Ag, respectively. During recycling use, the antibacterial activity of BT{sub 0.19}-CF-AgNPs against Escherichia coli can last for 5 cycles. These facts suggest that BT-CF-AgNPs can be used as a new and effective antibacterial agent. - Highlights: Black-Right-Pointing-Pointer Bayberry tannin-grafted collagen fiber can be acted as carrier and stabilizer for the preparation of nano-silver (AgNPs) with different particle size. Black-Right-Pointing-Pointer Bayberry tannin-grafted collagen fiber stabilized silver nanoparticles (BT-CF-AgNPs) were characterized by SEM, XRD, TEM, FTIR and XPS. Black-Right-Pointing-Pointer BT-CF-AgNPs has the

  12. Stabilization

    Directory of Open Access Journals (Sweden)

    Muhammad H. Al-Malack

    2016-07-01

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

  13. Supramolecular stabilization of metastable tautomers in solution and the solid state.

    Science.gov (United States)

    Juribašić, Marina; Bregović, Nikola; Stilinović, Vladimir; Tomišić, Vladislav; Cindrić, Marina; Sket, Primož; Plavec, Janez; Rubčić, Mirta; Užarević, Krunoslav

    2014-12-22

    This work presents a successful application of a recently reported supramolecular strategy for stabilization of metastable tautomers in cocrystals to monocomponent, non-heterocyclic, tautomeric solids. Quantum-chemical computations and solution studies show that the investigated Schiff base molecule, derived from 3-methoxysalicylaldehyde and 2-amino-3-hydroxypyridine (ap), is far more stable as the enol tautomer. In the solid state, however, in all three obtained polymorphic forms it exists solely as the keto tautomer, in each case stabilized by an unexpected hydrogen-bonding pattern. Computations have shown that hydrogen bonding of the investigated Schiff base with suitable molecules shifts the tautomeric equilibrium to the less stable keto form. The extremes to which supramolecular stabilization can lead are demonstrated by the two polymorphs of molecular complexes of the Schiff base with ap. The molecules of both constituents of molecular complexes are present as metastable tautomers (keto anion and protonated pyridine, respectively), which stabilize each other through a very strong hydrogen bond. All the obtained solid forms proved stable in various solid-state and solvent-mediated methods used to establish their relative thermodynamic stabilities and possible interconversion conditions.

  14. Stabilizing Effect of Various Polyols on the Native and the Denatured States of Glucoamylase

    Directory of Open Access Journals (Sweden)

    Mohammed Suleiman Zaroog

    2013-01-01

    Full Text Available Different spectral probes were employed to study the stabilizing effect of various polyols, such as, ethylene glycol (EG, glycerol (GLY, glucose (GLC and trehalose (TRE on the native (N, the acid-denatured (AD and the thermal-denatured (TD states of Aspergillus niger glucoamylase (GA. Polyols induced both secondary and tertiary structural changes in the AD state of enzyme as reflected from altered circular dichroism (CD, tryptophan (Trp, and 1-anilinonaphthalene-8-sulfonic acid (ANS fluorescence characteristics. Thermodynamic analysis of the thermal denaturation curve of native GA suggested significant increase in enzyme stability in the presence of GLC, TRE, and GLY (in decreasing order while EG destabilized it. Furthermore, CD and fluorescence characteristics of the TD state at 71°C in the presence of polyols showed greater effectiveness of both GLC and TRE in inducing native-like secondary and tertiary structures compared to GLY and EG.

  15. Estimation of LISS(local input-to-state stability) properties for nonlinear systems

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Compared with input-to-state stability(ISS) in global version,the concept of local input-to-state stability(LISS) is more relevant and meaningful in practice.The key of assessing LISS properties lies in investigating three main ingredients,the local region of initial states,the local region of external inputs and the asymptotic gain.It is the objective of this paper to propose a numerical algorithm for estimating LISS properties on the theoretical foundation of quadratic form LISS-Lyapunov function.Given developments of linear matrix inequality(LMI) methods,this algorithm is effective and powerful.A typical power electronics based system with common DC bus is served as a demonstration for quantitative results.

  16. United States Military Presence in Central Asia: Implications of United States Basing for Central Asian Stability

    Science.gov (United States)

    2006-06-01

    Europe and reducing the number of military personnel by 40,000 to 60,000. According to United States Air Force General Charles Wald , there are...The Deputy Secretary of Defense Paul Wolfowitz is quoted as saying United States presence “…may be more political than actually military” and that

  17. Selective Electrocatalytic Activity of Ligand Stabilized Copper Oxide Nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Kauffman, Douglas R; Ohodnicki, Paul R; Kail, Brian W; Matranga, Christopher

    2011-01-01

    Ligand stabilization can influence the surface chemistry of Cu oxide nanoparticles (NPs) and provide unique product distributions for electrocatalytic methanol (MeOH) oxidation and CO{sub 2} reduction reactions. Oleic acid (OA) stabilized Cu{sub 2}O and CuO NPs promote the MeOH oxidation reaction with 88% and 99.97% selective HCOH formation, respectively. Alternatively, CO{sub 2} is the only reaction product detected for bulk Cu oxides and Cu oxide NPs with no ligands or weakly interacting ligands. We also demonstrate that OA stabilized Cu oxide NPs can reduce CO{sub 2} into CO with a {approx}1.7-fold increase in CO/H{sub 2} production ratios compared to bulk Cu oxides. The OA stabilized Cu oxide NPs also show 7.6 and 9.1-fold increases in CO/H{sub 2} production ratios compared to weakly stabilized and non-stabilized Cu oxide NPs, respectively. Our data illustrates that the presence and type of surface ligand can substantially influence the catalytic product selectivity of Cu oxide NPs.

  18. Origin of stabilization and destabilization in solid-state redox reaction of oxide ions for lithium-ion batteries

    Science.gov (United States)

    Yabuuchi, Naoaki; Nakayama, Masanobu; Takeuchi, Mitsue; Komaba, Shinichi; Hashimoto, Yu; Mukai, Takahiro; Shiiba, Hiromasa; Sato, Kei; Kobayashi, Yuki; Nakao, Aiko; Yonemura, Masao; Yamanaka, Keisuke; Mitsuhara, Kei; Ohta, Toshiaki

    2016-12-01

    Further increase in energy density of lithium batteries is needed for zero emission vehicles. However, energy density is restricted by unavoidable theoretical limits for positive electrodes used in commercial applications. One possibility towards energy densities exceeding these limits is to utilize anion (oxide ion) redox, instead of classical transition metal redox. Nevertheless, origin of activation of the oxide ion and its stabilization mechanism are not fully understood. Here we demonstrate that the suppression of formation of superoxide-like species on lithium extraction results in reversible redox for oxide ions, which is stabilized by the presence of relatively less covalent character of Mn4+ with oxide ions without the sacrifice of electronic conductivity. On the basis of these findings, we report an electrode material, whose metallic constituents consist only of 3d transition metal elements. The material delivers a reversible capacity of 300 mAh g-1 based on solid-state redox reaction of oxide ions.

  19. Chemical stability of a cold-active cellulase with high tolerance toward surfactants and chaotropic agent

    Directory of Open Access Journals (Sweden)

    Thaís V. Souza

    2016-03-01

    Full Text Available CelE1 is a cold-active endo-acting glucanase with high activity at a broad temperature range and under alkaline conditions. Here, we examined the effects of pH on the secondary and tertiary structures, net charge, and activity of CelE1. Although variation in pH showed a small effect in the enzyme structure, the activity was highly influenced at acidic conditions, while reached the optimum activity at pH 8. Furthermore, to estimate whether CelE1 could be used as detergent additives, CelE1 activity was evaluated in the presence of surfactants. Ionic and nonionic surfactants were not able to reduce CelE1 activity significantly. Therefore, CelE1 was found to be promising candidate for use as detergent additives. Finally, we reported a thermodynamic analysis based on the structural stability and the chemical unfolding/refolding process of CelE1. The results indicated that the chemical unfolding proceeds as a reversible two-state process. These data can be useful for biotechnological applications.

  20. Input-to-state stabilization of the perturbed systems in the generalized triangular form

    CERN Document Server

    Dashkovskiy, Sergey

    2010-01-01

    We consider nonlinear control systems of the so-called generalized triangular form (GTF) with time-varying and periodic dynamics which linearly depends on some external disturbances. Our purpose is to construct a feedback controller which provides the global input-to-state stability of the corresponding closed-loop w.r.t. the disturbances. To do this, we combine the method proposed in the earlier work \\cite{pavlichkov_ge_2009} devoted the the global asymptotic stabilization of the GTF systems without disturbances with the ISS theory for time-varying systems proposed in \\cite{wang}. Following this pattern we construct a feedback which provides the properties of uniform global stability and asymptotic gain w.r.t the disturbances. Then we obtain the semi-uniform ISS of the closed-loop system.

  1. PSO Based State Feedback Controller Design for SVC to Enhance the Stability of Power System

    Directory of Open Access Journals (Sweden)

    Saeid Jalilzadeh

    2012-08-01

    Full Text Available SVC is one of the most significant devices in FACTS technology, which is used in parallel compensation, enhancing the transient stability, limiting the low frequency oscillations and, etc. designing a proper controller is effective in operation of SVC. In this paper, a simplified analysis of the effect of a SVC on the stability of a Single Machine Infinite Bus (SMIB system is presented. The SVC which is located at the terminal of the generator has the state feedback controller in which the coefficients of state feedback are optimized by the Particle Swarm Optimization (PSO algorithm in order to damp the Low Frequency Oscillations (LFO. The equations that describe the proposed system have been linearized, and then the optimum state feedback controller has been designed for SVC which its optimal coefficients have been earned by PSO algorithm. The system with proposed controller has been simulated for a special disturbance in nominal loading condition. Thereafter, for three states viz light loading condition, normal loading condition and heavy loading condition, to show the robustness of the proposed controller, the previous disturbance has been applied again. Then the dynamic responses of the generator have been presented. The simulation results showed that the system composed with proposed controller has a suitable operation in fast damping of oscillations of the power system. to ensure stability and tracking. Simulations is carried out to verify the theoretical results.

  2. Wind Lidar Activities in the United States

    Energy Technology Data Exchange (ETDEWEB)

    Clifton, Andrew; Newman, Jennifer; St. Pe, Alexandra; Iungo, G. Valerio; Wharton, Sonia; Herges, Tommy; Filippelli, Matthew; Pontbriand, Philippe; Osler, Evan

    2017-06-28

    IEA Wind Task 32 seeks to identify and mitigate the barriers to the adoption of lidar for wind energy applications. This work is partly achieved by sharing experience across researchers and practitioners in the United States and worldwide. This presentation is a short summary of some wind lidar-related activities taking place in the country, and was presented by Andrew Clifton at the Task 32 meeting in December 2016 in his role as the U.S. Department of Energy-nominated country representative to the task.

  3. Stability of Einstein static state universe in the spatially flat branemodels

    Science.gov (United States)

    Zhang, Kaituo; Wu, Puxun; Yu, Hongwei; Luo, Ling-Wei

    2016-07-01

    With the assumption that a perfect fluid with a constant equation of state is the only energy component on the brane, we study the stability of Einstein static state solution under homogeneous and inhomogeneous scalar perturbations in both spatially flat Randall-Sundrum (RS) and Shtanov-Sahni (SS) braneworlds. We find that if the perfect fluid has a phantom-like property and the "Weyl fluid" originating from the projection of the bulk Weyl tensor onto the brane behaves like a radiation with positive energy density, the Einstein static state solution is stable in the SS braneworld, but unstable in the RS one. Furthermore, we demonstrate that the static state solution is also stable in the bulk with a timelike extra dimension. Thus, in the model where the extra dimension is timelike, our universe can stay at the Einstein static state past-eternally, which means that the big bang singularity might be resolved successfully by an emergent scenario.

  4. Stability of Einstein static state universe in the spatially flat branemodels

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Kaituo [Department of Physics, Anhui Normal University, Wuhu, Anhui 241000 (China); Wu, Puxun [Center for Nonlinear Science and Department of Physics, Ningbo University, Ningbo, Zhejiang 315211 (China); Synergetic Innovation Center for Quantum Effects and Applications, Hunan Normal University, Changsha, Hunan 410081 (China); Center for High Energy Physics, Peking University, Beijing 100080 (China); Yu, Hongwei, E-mail: hwyu@hunnu.edu.cn [Synergetic Innovation Center for Quantum Effects and Applications, Hunan Normal University, Changsha, Hunan 410081 (China); Center for Nonlinear Science and Department of Physics, Ningbo University, Ningbo, Zhejiang 315211 (China); Luo, Ling-Wei [Institute of Physics, Chiao Tung University, Hsinchu 300, Taiwan (China)

    2016-07-10

    With the assumption that a perfect fluid with a constant equation of state is the only energy component on the brane, we study the stability of Einstein static state solution under homogeneous and inhomogeneous scalar perturbations in both spatially flat Randall–Sundrum (RS) and Shtanov–Sahni (SS) braneworlds. We find that if the perfect fluid has a phantom-like property and the “Weyl fluid” originating from the projection of the bulk Weyl tensor onto the brane behaves like a radiation with positive energy density, the Einstein static state solution is stable in the SS braneworld, but unstable in the RS one. Furthermore, we demonstrate that the static state solution is also stable in the bulk with a timelike extra dimension. Thus, in the model where the extra dimension is timelike, our universe can stay at the Einstein static state past-eternally, which means that the big bang singularity might be resolved successfully by an emergent scenario.

  5. Active Stabilization of a Diode Laser Injection Lock

    CERN Document Server

    Saxberg, Brendan; Gupta, Subhadeep

    2016-01-01

    We report on a device to electronically stabilize the optical injection lock of a semiconductor diode laser. Our technique uses as discriminator the peak height of the laser's transmission signal on a scanning Fabry-Perot cavity and feeds back to the diode current, thereby maintaining maximum optical power in the injected mode. A two-component feedback algorithm provides constant optimization of the injection lock, keeping it robust to slow thermal drifts and allowing fast recovery from sudden failures such as temporary occlusion of the injection beam. We demonstrate the successful performance of our stabilization method in a diode laser setup at 399 nm used for laser cooling of Yb atoms. The device eases the requirements on passive stabilization and can benefit any diode laser injection lock application, particularly those where several such locks are employed.

  6. Active stabilization of a diode laser injection lock

    Science.gov (United States)

    Saxberg, Brendan; Plotkin-Swing, Benjamin; Gupta, Subhadeep

    2016-06-01

    We report on a device to electronically stabilize the optical injection lock of a semiconductor diode laser. Our technique uses as discriminator the peak height of the laser's transmission signal on a scanning Fabry-Perot cavity and feeds back to the diode current, thereby maintaining maximum optical power in the injected mode. A two-component feedback algorithm provides constant optimization of the injection lock, keeping it robust to slow thermal drifts and allowing fast recovery from sudden failures such as temporary occlusion of the injection beam. We demonstrate the successful performance of our stabilization method in a diode laser setup at 399 nm used for laser cooling of Yb atoms. The device eases the requirements on passive stabilization and can benefit any diode laser injection lock application, particularly those where several such locks are employed.

  7. Further results on saturated globally stabilizing linear state feedback control laws for single-input neutrally stable planar systems

    NARCIS (Netherlands)

    Yang, Tao; Stoorvogel, Anton A.; Saberi, Ali; Johansson, Karl H.

    2013-01-01

    It is known that for single-input neutrally stable planar systems, there exists a class of saturated globally stabilizing linear state feedback control laws. The goal of this paper is to characterize the dynamic behavior for such a system under arbitrary locally stabilizing linear state feedback con

  8. Further results on saturated globally stabilizing linear state feedback control laws for single-input neutrally stable planar systems

    NARCIS (Netherlands)

    Yang, Tao; Stoorvogel, Antonie Arij; Saberi, Ali; Johansson, Karl H.

    2013-01-01

    It is known that for single-input neutrally stable planar systems, there exists a class of saturated globally stabilizing linear state feedback control laws. The goal of this paper is to characterize the dynamic behavior for such a system under arbitrary locally stabilizing linear state feedback

  9. Defying the activity-stability trade-off in enzymes: taking advantage of entropy to enhance activity and thermostability.

    Science.gov (United States)

    Siddiqui, Khawar Sohail

    2017-05-01

    The biotechnological applications of enzymes are limited due to the activity-stability trade-off, which implies that an increase in activity is accompanied by a concomitant decrease in protein stability. This premise is based on thermally adapted homologous enzymes where cold-adapted enzymes show high intrinsic activity linked to enhanced thermolability. In contrast, thermophilic enzymes show low activity around ambient temperatures. Nevertheless, genetically and chemically modified enzymes are beginning to show that the activity-stability trade-off can be overcome. In this review, the origin of the activity-stability trade-off, the thermodynamic basis for enhanced activity and stability, and various approaches for escaping the activity-stability trade-off are discussed. The role of entropy in enhancing both the activity and the stability of enzymes is highlighted with a special emphasis placed on the involvement of solvent water molecules. This review is concluded with suggestions for further research, which underscores the implications of these findings in the context of productivity curves, the Daniel-Danson equilibrium model, catalytic antibodies, and life on cold planets.

  10. Asymptotic formation and orbital stability of phase-locked states for the Kuramoto model

    Science.gov (United States)

    Choi, Young-Pil; Ha, Seung-Yeal; Jung, Sungeun; Kim, Yongduck

    2012-04-01

    We discuss the asymptotic formation and nonlinear orbital stability of phase-locked states arising from the ensemble of non-identical Kuramoto oscillators. We provide an explicit lower bound for a coupling strength on the formation of phase-locked states, which only depends on the diameters of natural frequencies and initial phase configurations. We show that, when the phases of non-identical oscillators are distributed over the half circle and the coupling strength is sufficiently large, the dynamics of Kuramoto oscillators exhibits two stages (transition and relaxation stages). In a transition stage, initial configurations shrink to configurations whose diameters are strictly less than {π}/{2} in a finite-time, and then the configurations tend to phase-locked states asymptotically. This improves previous results on the formation of phase-locked states by Chopra-Spong (2009) [26] and Ha-Ha-Kim (2010) [27] where their attention were focused only on the latter relaxation stage. We also show that the Kuramoto model is ℓ1-contractive in the sense that the ℓ1-distance along two smooth Kuramoto flows is less than or equal to that of initial configurations. In particular, when two initial configurations have the same averaged phases, the ℓ1-distance between them decays to zero exponentially fast. For the configurations with different phase averages, we use the method of average adjustment and translation-invariant of the Kuramoto model to show that one solution converges to the translation of the other solution exponentially fast. This establishes the orbital stability of the phase-locked states. Our stability analysis does not employ any standard linearization technique around the given phase-locked states, but instead, we use a robust ℓ1-metric functional as a Lyapunov functional. In the formation process of phase-locked states, we estimate the number of collisions between oscillators, and lower-upper bounds of the transversal phase differences.

  11. Novel active stabilization technology in highly crosslinked UHMWPEs for superior stability

    Science.gov (United States)

    Oral, Ebru; Neils, Andrew L.; Wannomae, Keith K.; Muratoglu, Orhun K.

    2014-12-01

    Radiation cross-linked ultrahigh molecular weight polyethylene (UHMWPE) is the bearing of choice in joint arthroplasty. The demands on the longevity of this polymer are likely to increase with the recently advancing deterioration of the performance of alternative metal-on-metal implants. Vitamin E-stabilized, cross-linked UHMWPEs are considered the next generation of improved UHMWPE bearing surfaces for improving the oxidation resistance of the polymer. It was recently discovered that in the absence of radiation-induced free radicals, lipids absorbed into UHMWPE from the synovial fluid can initiate oxidation and result in new free radical-mediated oxidation mechanisms. In the presence of radiation-induced free radicals, it is possible for the polymer to oxidize through both existing free radicals at the time of implantation and through newly formed free radicals in vivo. Thus, we showed that reducing the radiation-induced free radicals in vitamin E-stabilized UHMWPE would increase its oxidative stability and presumably lead to improved longevity. We describe mechanical annealing and warm irradiation of irradiated vitamin E blends as novel methods to eliminate 99% of radiation-induced free radicals without sacrificing crystallinity. These are significant improvements in the processing of highly cross-linked UHMWPE for joint implants with improved longevity.

  12. Active feedback stabilization of flute instability in a mirror trap

    Science.gov (United States)

    Be'Ery, Ilan; Seemann, Omri; Fruchtman, Amnon; Fisher, Amnon; Ron, Amiram

    2013-10-01

    The flute instability in a table-top mirror machine has been stabilized by a feedback system consisting of optical probes, digital signal processor, and needle electrodes. The total response time of the system is 5 μs, which is considerably faster than the typical flute growth time. Simulation and a dynamic model of the plasma's response to the needle actuators were tested against cyclic bias experiments. The plasma density is increased by the stabilization by a factor of two and is limited by other decay processes.

  13. Carrier-Envelope Offset Stabilized Ultrafast Diode-Pumped Solid-State Lasers

    Directory of Open Access Journals (Sweden)

    Stéphane Schilt

    2015-10-01

    Full Text Available Optical frequency combs have been revolutionizing many research areas and are finding a growing number of real-world applications. While initially dominated by Ti:Sapphire and fiber lasers, optical frequency combs from modelocked diode-pumped solid-state lasers (DPSSLs have become an attractive alternative with state-of-the-art performance. In this article, we review the main achievements in ultrafast DPSSLs for frequency combs. We present the current status of carrier-envelope offset (CEO frequency-stabilized DPSSLs based on various approaches and operating in different wavelength regimes. Feedback to the pump current provides a reliable scheme for frequency comb CEO stabilization, but also other methods with faster feedback not limited by the lifetime of the gain material have been applied. Pumping DPSSLs with high power multi-transverse-mode diodes enabled a new class of high power oscillators and gigahertz repetition rate lasers, which were initially not believed to be suitable for CEO stabilization due to the pump noise. However, this challenge has been overcome, and recently both high power and gigahertz DPSSL combs have been demonstrated. Thin disk lasers have demonstrated the highest pulse energy and average power emitted from any ultrafast oscillator and present a high potential for the future generation of stabilized frequency combs with hundreds of watts average output power.

  14. Radial pulsations and stability of anisotropic stars with quasi-local equation of state

    CERN Document Server

    Horvat, Dubravko; Marunovic, Anja

    2010-01-01

    Quasi-local variables, i.e. quantities whose values can be derived from physics accessible within an arbitrarily small neighborhood of a spacetime point, are used to construct the equation of state for the anisotropic fluid in spherical symmetry. One parameter families of equilibrium solutions are obtained making it possible to assess stability properties by means of the standard M(R) method. Normal modes of radial pulsation are computed as well and are found to confirm the onset of instability as predicted by the M(R) method. As an example, a stable configuration with outwardly increasing energy density in the core is obtained with a simple quasi-local extension of the polytropic equation of state. It is also found that the loss of stability occurs at higher surface compactness when the anisotropy of pressures is present.

  15. Long-lived charge-separated states in ligand-stabilized silver clusters

    KAUST Repository

    Pelton, Matthew

    2012-07-25

    Recently developed synthesis methods allow for the production of atomically monodisperse clusters of silver atoms stabilized in solution by aromatic thiol ligands, which exhibit intense absorption peaks throughout the visible and near-IR spectral regions. Here we investigated the time-dependent optical properties of these clusters. We observed two kinetic processes following ultrafast laser excitation of any of the absorption peaks: a rapid decay, with a time constant of 1 ps or less, and a slow decay, with a time constant that can be longer than 300 ns. Both time constants decrease as the polarity of the solvent increases, indicating that the two processes correspond to the formation and recombination, respectively, of a charge-separated state. The long lifetime of this state and the broad optical absorption spectrum mean that the ligand-stabilized silver clusters are promising materials for solar energy harvesting. © 2012 American Chemical Society.

  16. State-space-based harmonic stability assessment of paralleled grid-connected inverters system

    DEFF Research Database (Denmark)

    Wang, Yanbo; Wang, Xiongfei; Chen, Zhe;

    2016-01-01

    model of paralleled grid-connected inverters is built. Finally, the state space-based stability analysis approach is developed to explain the harmonic resonance phenomenon. The eigenvalue traces associated with time delay and coupled grid impedance are obtained, which accounts for how the unstable......This paper addresses a state-space-based harmonic stability analysis of paralleled grid-connected inverters system. A small signal model of individual inverter is developed, where LCL filter, the equivalent delay of control system, and current controller are modeled. Then, the overall small signal...... inverter produces the harmonic resonance and leads to the instability of whole paralleled system. The proposed approach reveals the contributions of the grid impedance as well as the coupled effect on other grid-connected inverters under different grid conditions. Simulation and experimental results...

  17. Higher Education Spending and the State Fiscal Stabilization Fund, Part 3: State Case Studies

    Science.gov (United States)

    Cohen, Jennifer

    2011-01-01

    By late 2008, the United States was in the midst of its most severe economic recession since the 1930s, brought on by a collapse in real estate prices and exacerbated by the failure of many large banks and financial institutions. Heeding calls from economists, Congress and the Obama administration passed an historic law in early 2009 to stimulate…

  18. Cdk and APC activities limit the spindle-stabilizing function of Fin1 to anaphase.

    Science.gov (United States)

    Woodbury, Erika L; Morgan, David O

    2007-01-01

    The fidelity of chromosome segregation depends on proper regulation of mitotic spindle behaviour. In anaphase, spindle stability is promoted by the dephosphorylation of cyclin-dependent kinase (Cdk) substrates, which results from Cdk inactivation and phosphatase activation. Few of the critical Cdk targets have been identified. Here, we identify the budding-yeast protein Fin1 (ref. 7) as a spindle-stabilizing protein whose activity is strictly limited to anaphase by changes in its phosphorylation state and rate of degradation. Phosphorylation of Fin1 from S phase to metaphase, by the cyclin-dependent kinase Clb5-Cdk1, inhibits Fin1 association with the spindle. In anaphase, when Clb5-Cdk1 is inactivated, Fin1 is dephosphorylated by the phosphatase Cdc14. Fin1 dephosphorylation targets it to the poles and microtubules of the elongating spindle, where it contributes to spindle integrity. A non-phosphorylatable Fin1 mutant localizes to the spindle before anaphase and impairs efficient chromosome segregation. As cells complete mitosis and disassemble the spindle, the ubiqutin ligase APC(Cdh1) targets Fin1 for destruction. Our studies illustrate how phosphorylation-dependent changes in the behaviour of Cdk1 substrates influence complex mitotic processes.

  19. Infinite-Dimensional Feedback Systems: The Circle Criterion and Input-to-State Stability

    OpenAIRE

    2008-01-01

    An input-to-state stability theory, which subsumes results of circle criterion type, is developed in the context of a class of infinite-dimensional systems. The generic system is of Lur’e type: a feedback interconnection of a well-posed infinite-dimensional linear system and a nonlinearity. The class of nonlinearities is subject to a (generalized) sector condition and contains, as particular subclasses, both static nonlinearities and hysteresis operators of Preisach type.

  20. Improved steady-state stability of power grids with a communication infrastructure

    OpenAIRE

    Gajduk, Andrej; Todorovski, Mirko; Kocarev, Ljupco

    2014-01-01

    Efficient control of power systems is becoming increasingly difficult as they gain in complexity and size. We propose an automatic control strategy that regulates the mechanical power output of the generators in a power grid based on information obtained via a communication infrastructure. An algorithm that optimizes steady-state stability of a power grid by iteratively adding communication links is presented. The proposed control scheme is successfully applied to the IEEE New England and IEE...

  1. Effects of pelvic stabilization on lumbar muscle activity during dynamic exercise.

    Science.gov (United States)

    San Juan, Jun G; Yaggie, James A; Levy, Susan S; Mooney, Vert; Udermann, Brian E; Mayer, John M

    2005-11-01

    Many commonly utilized low-back exercise devices offer mechanisms to stabilize the pelvis and to isolate the lumbar spine, but the value of these mechanisms remains unclear. The purpose of this study was to examine the effect of pelvic stabilization on the activity of the lumbar and hip extensor muscles during dynamic back extension exercise. Fifteen volunteers in good general health performed dynamic extension exercise in a seated upright position on a lumbar extension machine with and without pelvic stabilization. During exercise, surface electromyographic activity of the lumbar multifidus and biceps femoris was recorded. The activity of the multifidus was 51% greater during the stabilized condition, whereas there was no difference in the activity of the biceps femoris between conditions. This study demonstrates that pelvic stabilization enhances lumbar muscle recruitment during dynamic exercise on machines. Exercise specialists can use these data when designing exercise programs to develop low back strength.

  2. Physicochemical properties and thermal stability of quercetin hydrates in the solid state

    Energy Technology Data Exchange (ETDEWEB)

    Borghetti, G.S., E-mail: greicefarm@yahoo.com.br [Programa de Pos-Graduacao em Ciencias Farmaceuticas, Faculdade de Farmacia, Universidade Federal do Rio Grande do Sul, Av. Ipiranga 2752, CEP 90.610-000, Porto Alegre, RS (Brazil); Carini, J.P. [Programa de Pos-Graduacao em Ciencias Farmaceuticas, Faculdade de Farmacia, Universidade Federal do Rio Grande do Sul, Av. Ipiranga 2752, CEP 90.610-000, Porto Alegre, RS (Brazil); Honorato, S.B.; Ayala, A.P. [Departamento de Fisica, Universidade Federal do Ceara, Caixa Postal 6030, CEP 60.455-970, Fortaleza, CE (Brazil); Moreira, J.C.F. [Departamento de Bioquimica, Instituto de Ciencias Basicas da Saude, Universidade Federal do Rio Grande do Sul, Rua Ramiro Barcelos 2600, CEP 90035-003, Porto Alegre, RS (Brazil); Bassani, V.L. [Programa de Pos-Graduacao em Ciencias Farmaceuticas, Faculdade de Farmacia, Universidade Federal do Rio Grande do Sul, Av. Ipiranga 2752, CEP 90.610-000, Porto Alegre, RS (Brazil)

    2012-07-10

    Highlights: Black-Right-Pointing-Pointer Quercetin raw materials may present different degree of hydration. Black-Right-Pointing-Pointer Thermal stability of quercetin in the solid state depends on its degree of hydration. Black-Right-Pointing-Pointer Quercetin dehydrate is thermodynamically more stable than the other crystal forms. - Abstract: In the present work three samples of quercetin raw materials (QCTa, QCTb and QCTc), purchased from different Brazilian suppliers, were characterized employing scanning electron microscopy, Raman spectroscopy, simultaneous thermogravimetry and infrared spectroscopy, differential scanning calorimetry, and variable temperature-powder X-ray diffraction, in order to know their physicochemical properties, specially the thermal stability in solid state. The results demonstrated that the raw materials of quercetin analyzed present distinct crystalline structures, ascribed to the different degree of hydration of their crystal lattice. The thermal stability of these quercetin raw materials in the solid state was highly dependent on their degree of hydration, where QCTa (quercetin dihydrate) was thermodynamically more stable than the other two samples.

  3. Cat-state generation and stabilization for a nuclear spin through electric quadrupole interaction

    Science.gov (United States)

    Bulutay, Ceyhun

    2017-07-01

    Spin cat states are superpositions of two or more coherent spin states (CSSs) that are distinctly separated over the Bloch sphere. Additionally, the nuclei with angular momenta greater than 1/2 possess a quadrupolar charge distribution. At the intersection of these two phenomena, we devise a simple scheme for generating various types of nuclear-spin cat states. The native biaxial electric quadrupole interaction that is readily available in strained solid-state systems plays a key role here. However, the fact that built-in strain cannot be switched off poses a challenge for the stabilization of target cat states once they are prepared. We remedy this by abruptly diverting via a single rotation pulse the state evolution to the neighborhood of the fixed points of the underlying classical Hamiltonian flow. Optimal process parameters are obtained as a function of electric field gradient biaxiality and nuclear-spin angular momentum. The overall procedure is seen to be robust under 5% deviations from optimal values. We show that higher-level cat states with four superposed CSS can also be formed using three rotation pulses. Finally, for open systems subject to decoherence we extract the scaling of cat-state fidelity damping with respect to the spin quantum number. This reveals rates greater than the dephasing of individual CSSs. Yet, our results affirm that these cat states can preserve their fidelities for practically useful durations under the currently attainable decoherence levels.

  4. Stability

    Directory of Open Access Journals (Sweden)

    Nada S. Abdelwahab

    2017-05-01

    Full Text Available The present work concerns with the development of stability indicating the RP-HPLC method for simultaneous determination of guaifenesin (GUF and pseudoephedrine hydrochloride (PSH in the presence of guaifenesin related substance (Guaiacol. GUC, and in the presence of syrup excepients with minimum sample pre-treatment. In the developed RP-HPLC method efficient chromatographic separation was achieved for GUF, PSH, GUC and syrup excepients using ODS column as a stationary phase and methanol: water (50:50, v/v, pH = 4 with orthophosphoric acid as a mobile phase with a flow rate of 1 mL min−1 and UV detection at 210 nm. The chromatographic run time was approximately 10 min. Calibration curves were drawn relating the integrated area under peak to the corresponding concentrations of PSH, GUF and GUC in the range of 1–8, 1–20, 0.4–8 μg mL−1, respectively. The developed method has been validated and met the requirements delineated by ICH guidelines with respect to linearity, accuracy, precision, specificity and robustness. The validated method was successfully applied for determination of the studied drugs in triaminic chest congestion® syrup; moreover its results were statistically compared with those obtained by the official method and no significant difference was found between them.

  5. Stability of the electroweak ground state in the Standard Model and its extensions

    Directory of Open Access Journals (Sweden)

    Luca Di Luzio

    2016-02-01

    Full Text Available We review the formalism by which the tunnelling probability of an unstable ground state can be computed in quantum field theory, with special reference to the Standard Model of electroweak interactions. We describe in some detail the approximations implicitly adopted in such calculation. Particular attention is devoted to the role of scale invariance, and to the different implications of scale-invariance violations due to quantum effects and possible new degrees of freedom. We show that new interactions characterized by a new energy scale, close to the Planck mass, do not invalidate the main conclusions about the stability of the Standard Model ground state derived in absence of such terms.

  6. On the Gross–Pitaevskii Equation with Pumping and Decay: Stationary States and Their Stability

    KAUST Repository

    Sierra Nunez, Jesus Alfredo

    2015-02-11

    We investigate the behavior of solutions of the complex Gross–Pitaevskii equation, a model that describes the dynamics of pumped decaying Bose–Einstein condensates. The stationary radially symmetric solutions of the equation are studied, and their linear stability with respect to two-dimensional perturbations is analyzed. Using numerical continuation, we calculate not only the ground state of the system, but also a number of excited states. Accurate numerical integration is employed to study the general nonlinear evolution of the system from the unstable stationary solutions to the formation of stable vortex patterns.

  7. Magnetic states stabilization in Ni51Mn33.4In15.6 Heusler alloy

    Directory of Open Access Journals (Sweden)

    Mohammadreza Ghahremani

    2015-12-01

    Full Text Available The rate-independent stabilization of magnetic states with iterations in a Heusler alloy has been studied. The direct measurement of the adiabatic temperature change, ΔTad, of a Ni51Mn33.4In15.6 alloy near the magnetostructural phase transition is presented. The adiabatic temperature change at a given temperature within the temperature range of the magnetostructural transition is history dependent and varies considerably with the iteration count of the field cycle. The data show the transition from the low magnetization state to the high magnetization state during low to high (L–H temperature change direction and from high magnetization to low magnetization state during high to low (H–L temperature change direction require several field cycles to stabilize the ΔTad measurement, similar to the accommodation phenomenon in hysteretic materials. In the mixed magnetic state inside the first-order transition, both low and high magnetization portions of the alloy exist and it varies considerably with the induced fields. This original observation emphasizes that it is incorrect to assess the performance of a magnetic refrigeration system through a single measurement, and that achieving a stable, utilizable, adiabatic temperature change requires several field-induced transitions.

  8. Stabilization of generalized fractional order chaotic systems using state feedback control

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad, Wajdi M. E-mail: wajdi@sharjah.ac.ae; El-Khazali, Reyad E-mail: khazali@ece.ac.ae; Al-Assaf, Yousef E-mail: yassaf@aus.ac.ae

    2004-10-01

    In this paper, we address the problem of chaos control of three types of fractional order systems using simple state feedback gains. Electronic chaotic oscillators, mechanical 'jerk' systems, and the Chen system are investigated when they assume generalized fractional orders. We design the static gains to place the eigenvalues of the system Jacobian matrices in a stable region whose boundaries are determined by the orders of the fractional derivatives. We numerically demonstrate the effectiveness of the controller in eliminating the chaotic behavior from the state trajectories, and driving the states to the nearest equilibrium point in the basin of attraction. For the recently introduced Chen system, in particular, we demonstrate that with a proper choice of model parameters, chaotic behavior is preserved when the system order becomes fractional. Both state and output feedback controllers are then designed to stabilize a generalized fractional order Chen system.

  9. On the stability of KMS states in perturbative algebraic quantum field theories

    CERN Document Server

    Drago, Nicolo; Pinamonti, Nicola

    2016-01-01

    We analyze the stability properties shown by KMS states for interacting massive scalar fields propagating over Minkowski spacetime, recently constructed in the framework of perturbative algebraic quantum field theories by Fredenhagen and Lindner \\cite{FredenhagenLindner}. In particular, we prove the validity of the return to equilibrium property when the interaction Lagrangean has compact spatial support. Surprisingly, this does not hold anymore, if the adiabatic limit is considered, namely when the interaction Lagrangean is invariant under spatial translations. Consequently, an equilibrium state under the adiabatic limit for a perturbative interacting theory evolved with the free dynamics does not converge anymore to the free equilibrium state. Actually, we show that its ergodic mean converges to a non equilibrium steady state for the free theory.

  10. Influence of rhenium speciation on the stability and activity of Re/Pd bimetal catalysts used for perchlorate reduction.

    Science.gov (United States)

    Choe, Jong Kwon; Shapley, John R; Strathmann, Timothy J; Werth, Charles J

    2010-06-15

    Recent work demonstrates reduction of aqueous perchlorate by hydrogen at ambient temperatures and pressures using a novel rhenium-palladium bimetal catalyst immobilized on activated carbon (Re/Pd-AC). This study examines the influence of Re speciation on catalyst activity and stability. Rates of perchlorate reduction are linearly dependent on Re content from 0-6 wt %, but no further increases are observed at higher Re contents. Surface-immobilized Re shows varying stability and speciation both in oxic versus H(2)-reducing environments and as a function of Re content. In oxic solutions, Re immobilization is dictated by sorption of the Re(VII) precursor, perrhenate (ReO(4)(-)), to activated carbon via electrostatic interactions. Under H(2)-reducing conditions, Re immobilization is significantly improved and leaching is minimized by ReO(4)(-) reduction to more reduced species on the catalyst surface. X-ray photoelectron spectroscopy shows two different Re binding energy states under H(2)-reducing conditions that correspond most closely to Re(V)/Re(IV) and Re(I) reference standards, respectively. The distribution of the two redox states varies with Re content, with the latter predominating at lower Re contents where catalyst activity is more strongly dependent on Re content. Results demonstrate that both lower Re contents and the maintenance of H(2)-reducing conditions are key elements in stabilizing the active Re surface species that are needed for sustained catalytic perchlorate treatment.

  11. Stability in Bank Income through Fee-based Activities

    Directory of Open Access Journals (Sweden)

    R. K. Uppal

    2010-12-01

    Full Text Available This paper is an attempt to study the trends in non-interest income which is a vital source of stability in bank income. For this, the study takes some parameters like interest and non-interest income as a percentage to total income, share of non-interest income components like exchange & brokerage, sale in investment and exchange transaction. On the basis of these parameters the study concludes that interest income is continuously declining due to deregulation in interest rates and non-interest income is rising. Among the non-interest income components, commodity exchange & brokerage witnessed a large share while exchange transaction witnessed a meager part. The paper also gives some ways and means to bring stability in the total income.

  12. Active Stabilization of a Diode Laser Injection Lock

    OpenAIRE

    Saxberg, Brendan; Plotkin-Swing, Benjamin; Gupta, Subhadeep

    2016-01-01

    We report on a device to electronically stabilize the optical injection lock of a semiconductor diode laser. Our technique uses as discriminator the peak height of the laser's transmission signal on a scanning Fabry-Perot cavity and feeds back to the diode current, thereby maintaining maximum optical power in the injected mode. A two-component feedback algorithm provides constant optimization of the injection lock, keeping it robust to slow thermal drifts and allowing fast recovery from sudde...

  13. Active Stabilization of a Diode Laser Injection Lock

    OpenAIRE

    Saxberg, Brendan; Plotkin-Swing, Benjamin; Gupta, Subhadeep

    2016-01-01

    We report on a device to electronically stabilize the optical injection lock of a semiconductor diode laser. Our technique uses as discriminator the peak height of the laser's transmission signal on a scanning Fabry-Perot cavity and feeds back to the diode current, thereby maintaining maximum optical power in the injected mode. A two-component feedback algorithm provides constant optimization of the injection lock, keeping it robust to slow thermal drifts and allowing fast recovery from sudde...

  14. Stability Simulation of a Vehicle with Wheel Active Steering

    Directory of Open Access Journals (Sweden)

    Brabec Pavel

    2016-01-01

    Full Text Available This paper deals with the possibility of increasing the vehicle driving stability at a higher speed. One of the ways how to achieve higher stability is using the 4WS system. Mathematical description of vehicle general movement is a very complex task. For simulation, models which are aptly simplified are used. For the first approach, so-called single-truck vehicle model (often linear is usually used. For the simulation, we have chosen to extend the model into a two-truck one, which includes the possibility to input more vehicle parameters. Considering the 4WS system, it is possible to use a number of potential regulations. In our simulation model, the regulation system with compound coupling was used. This type of regulation turns the rear wheels depending on the input parameters of the system (steering angle of the front wheels and depending on the output moving quantities of the vehicle, most frequently the yaw rate. Criterion for compensation of lateral deflection centre of gravity angle is its zero value, or more precisely the zero value of its first-order derivative. Parameters and set-up of the simulation model were done in conjunction with the dSAPACE software. Reference performances of the vehicle simulation model were made through the defined manoeuvres. But the simulation results indicate that the rear-wheels steering can have a positive effect on the vehicle movement stability, especially when changing the driving direction at high speed.

  15. Complete stability of delayed recurrent neural networks with Gaussian activation functions.

    Science.gov (United States)

    Liu, Peng; Zeng, Zhigang; Wang, Jun

    2017-01-01

    This paper addresses the complete stability of delayed recurrent neural networks with Gaussian activation functions. By means of the geometrical properties of Gaussian function and algebraic properties of nonsingular M-matrix, some sufficient conditions are obtained to ensure that for an n-neuron neural network, there are exactly 3(k) equilibrium points with 0≤k≤n, among which 2(k) and 3(k)-2(k) equilibrium points are locally exponentially stable and unstable, respectively. Moreover, it concludes that all the states converge to one of the equilibrium points; i.e., the neural networks are completely stable. The derived conditions herein can be easily tested. Finally, a numerical example is given to illustrate the theoretical results. Copyright © 2016 Elsevier Ltd. All rights reserved.

  16. The roles of entropy and enthalpy in stabilizing ion-pairs at transition states in zeolite acid catalysis.

    Science.gov (United States)

    Gounder, Rajamani; Iglesia, Enrique

    2012-02-21

    Acidic zeolites are indispensable catalysts in the petrochemical industry because they select reactants and their chemical pathways based on size and shape. Voids of molecular dimensions confine reactive intermediates and transition states that mediate chemical reactions, stabilizing them by van der Waals interactions. This behavior is reminiscent of the solvation effects prevalent within enzyme pockets and has analogous consequences for catalytic specificity. Voids provide the "right fit" for certain transition states, reflected in their lower free energies, thus extending the catalytic diversity of zeolites well beyond simple size discrimination. This catalytic diversity is even more remarkable because acid strength is essentially unaffected by confinement among known crystalline aluminosilicates. In this Account, we discuss factors that determine the "right fit" for a specific chemical reaction, exploring predictive criteria that extend the prevailing discourse based on size and shape. We link the structures of reactants, transition states, and confining voids to chemical reactivity and selectivity. Confinement mediates enthalpy-entropy compromises that determine the Gibbs free energies of transition states and relevant reactants; these activation free energies determine turnover rates via transition state theory. At low temperatures (400-500 K), dimethyl ether carbonylation occurs with high specificity within small eight-membered ring (8-MR) voids in FER and MOR zeolite structures, but at undetectable rates within larger voids (MFI, BEA, FAU, and SiO(2)-Al(2)O(3)). More effective van der Waals stabilization within 8-MR voids leads to lower ion-pair enthalpies but also lower entropies; taken together, carbonylation activation free energies are lower within 8-MR voids. The "right fit" is a "tight fit" at low temperatures, a consequence of how temperature appears in the defining equation for Gibbs free energy. In contrast, entropy effects dominate in high

  17. Enhanced activity and stability of papain immobilized on CNBr-activated sepharose.

    Science.gov (United States)

    Homaei, Ahmad

    2015-04-01

    Immobilization of papain was carried out by covalent attachment on Sepharose 6B activated by using cyanogen bromide. Immobilization process brought about significant enhancement of storage and thermal stability, stability at extreme pHs, and resistance against the inhibitory effects of various bivalent metal ions with respect to papain. The optimum temperature of papain increased by 20 °C (from 60 to 80 °C) and its optimum pH was shifted from 6.5 to 8.0 upon immobilization. The activation energy of the enzymatic reaction for immobilized papain showed a significant increase as compared with its free form (1.87 kcal mol(-1) K(-1) for free and 4.69 kcal mol(-1) K(-1) for immobilized enzyme). The kinetic parameters, Km and kcat, were estimated to be 0.62 μM and 162 × 10(-4) s(-1) for free and 0.79 μM and 102 × 10(-4) s(-1) for immobilized papain, respectively.

  18. Stability and activity of molybdenum carbide catalysts for the oxidative reforming of methane

    Science.gov (United States)

    Lamont, David Charles

    Molybdenum carbide catalysts have been studied for oxidative reforming, in particular, the effect on reforming activity of the method by which they were synthesized, their stability under conditions of varying mass transfer, and the measurement of their inherent reaction kinetics. These catalysts show promise as possible alternatives to both conventional supported nickel catalysts, as well as to the rare and expensive noble metal catalysts. Samples of Mo 2C were synthesized in house and compared to a commercial sample of Mo2C for the CO2 (dry) reforming of methane. It was found that high surface areas, previously thought to be important for activity, were not a property of the Mo2C, but instead were attributable to large amounts of excess carbon. This carbon had a detrimental effect on catalyst stability under dry reforming conditions, because it enhanced deposition of refractory carbon via methane cracking. The commercial sample of Mo 2C, while of low surface area and containing no excess carbon, behaved more stably over time. In another investigation, Mo2C was studied for its stability under varying mass transfer conditions, because of evidence showing that the Mo2C can undergo redox chemistry at reforming conditions. Under dry reforming conditions, it was found that some feed mixtures are net oxidizing, but that oxidation in the presence of such feed mixtures could be prevented by operating under mass transfer limited conditions, which resulted in sufficiently high partial pressures of CO and H2 in the catalyst boundary layer. Similar stability was achieved by co-feeding CO to the catalyst bed, which allowed for stable operation under conditions that were not mass transfer limited. Using this approach, measurements of the intrinsic reaction kinetics of Mo2C for dry reforming were successfully achieved. These results pointed to a strong dependence of dry reforming rate on both CH4 and CO2 partial pressures, as well as evidence for a reaction mechanism unique from

  19. Von Neumann stability of the WONDY wavecode for thermodynamic equations of state

    Energy Technology Data Exchange (ETDEWEB)

    Hicks, D.L.

    1977-11-01

    Previous analyses of the von Neumann stability of the WONDY wavecode (based on the von Neumann--Richtmyer artificial viscosity method) assumed a mechanical stress--strain relation; i.e., they assumed the stress, p, to depend only on the mass density, rho. In a thermodynamic equation of state p is allowed to depend also on the specific entropy, S (or on the specific internal energy, epsilon). If p does not depend on epsilon (or S), then the Grueneisen parameter, GAMMA, is zero. Herein a von Neumann stability analysis of WONDY is done for the more general case when GAMMA is not equal to 0. The result of this analysis is the requirement that the timestep be less than the product of the material increment and a certain function f of the acoustic impedance (a); artificial viscosity coefficient, ..lambda..; and GAMMA. In a region of compression, if ..lambda.. GAMMA is greater than 0, then f(a,..lambda..,GAMMA) is smaller than f(a,..lambda..,0). Therefore, the more general stability analysis yields the result that the timestep restriction now in WONDY may be insufficient for stability in certain regions of certain calculations.

  20. A switched state feedback law for the stabilization of LTI systems.

    Energy Technology Data Exchange (ETDEWEB)

    Santarelli, Keith R.

    2009-09-01

    Inspired by prior work in the design of switched feedback controllers for second order systems, we develop a switched state feedback control law for the stabilization of LTI systems of arbitrary dimension. The control law operates by switching between two static gain vectors in such a way that the state trajectory is driven onto a stable n - 1 dimensional hyperplane (where n represents the system dimension). We begin by briefly examining relevant geometric properties of the phase portraits in the case of two-dimensional systems to develop intuition, and we then show how these geometric properties can be expressed as algebraic constraints on the switched vector fields that are applicable to LTI systems of arbitrary dimension. We then derive necessary and sufficient conditions to ensure stabilizability of the resulting switched system (characterized primarily by simple conditions on eigenvalues), and describe an explicit procedure for designing stabilizing controllers. We then show how the newly developed control law can be applied to the problem of minimizing the maximal Lyapunov exponent of the corresponding closed-loop state trajectories, and we illustrate the closed-loop transient performance of these switched state feedback controllers via multiple examples.

  1. Reduced Fluorescent Protein Switching Fatigue by Binding-Induced Emissive State Stabilization

    Directory of Open Access Journals (Sweden)

    Thijs Roebroek

    2017-09-01

    Full Text Available Reversibly switchable fluorescent proteins (RSFPs enable advanced fluorescence imaging, though the performance of this imaging crucially depends on the properties of the labels. We report on the use of an existing small binding peptide, named Enhancer, to modulate the spectroscopic properties of the recently developed rsGreen series of RSFPs. Fusion constructs of Enhancer with rsGreen1 and rsGreenF revealed an increased molecular brightness and pH stability, although expression in living E. coli or HeLa cells resulted in a decrease of the overall emission. Surprisingly, Enhancer binding also increased off-switching speed and resistance to switching fatigue. Further investigation suggested that the RSFPs can interconvert between fast- and slow-switching emissive states, with the overall protein population gradually converting to the slow-switching state through irradiation. The Enhancer modulates the spectroscopic properties of both states, but also preferentially stabilizes the fast-switching state, supporting the increased fatigue resistance. This work demonstrates how the photo-physical properties of RSFPs can be influenced by their binding to other small proteins, which opens up new horizons for applications that may require such modulation. Furthermore, we provide new insights into the photoswitching kinetics that should be of general consideration when developing new RSFPs with improved or different photochromic properties.

  2. Stabilization of Parametric Roll Resonance with Active U-Tanks via Lyapunov Control Design

    DEFF Research Database (Denmark)

    Holden, Christian; Galeazzi, Roberto; Fossen, Thor Inge;

    2009-01-01

    design of an active u-tank stabilizer is carried out using Lyapunov theory. A nonlinear backstepping controller is developed to provide global exponential stability of roll. An extension of commonly used u-tank models is presented to account for large roll angles, and the control design is tested via...

  3. Charge State of the Globular Histone Core Controls Stability of the Nucleosome

    Science.gov (United States)

    Fenley, Andrew T.; Adams, David A.; Onufriev, Alexey V.

    2010-01-01

    Presented here is a quantitative model of the wrapping and unwrapping of the DNA around the histone core of the nucleosome that suggests a mechanism by which this transition can be controlled: alteration of the charge state of the globular histone core. The mechanism is relevant to several classes of posttranslational modifications such as histone acetylation and phosphorylation; several specific scenarios consistent with recent in vivo experiments are considered. The model integrates a description based on an idealized geometry with one based on the atomistic structure of the nucleosome, and the model consistently accounts for both the electrostatic and nonelectrostatic contributions to the nucleosome free energy. Under physiological conditions, isolated nucleosomes are predicted to be very stable (38 ± 7 kcal/mol). However, a decrease in the charge of the globular histone core by one unit charge, for example due to acetylation of a single lysine residue, can lead to a significant decrease in the strength of association with its DNA. In contrast to the globular histone core, comparable changes in the charge state of the histone tail regions have relatively little effect on the nucleosome's stability. The combination of high stability and sensitivity explains how the nucleosome is able to satisfy the seemingly contradictory requirements for thermodynamic stability while allowing quick access to its DNA informational content when needed by specific cellular processes such as transcription. PMID:20816070

  4. Influence of the initial state of carbon nanotubes on their colloidal stability under natural conditions

    Energy Technology Data Exchange (ETDEWEB)

    Schwyzer, Irene [Empa - Swiss Federal Laboratories for Materials Science and Technology, CH-9014 St. Gallen (Switzerland); Eawag - Swiss Federal Institute of Aquatic Science and Technology, CH-8600 Duebendorf (Switzerland); Kaegi, Ralf; Sigg, Laura [Eawag - Swiss Federal Institute of Aquatic Science and Technology, CH-8600 Duebendorf (Switzerland); Magrez, Arnaud [EPFL - Ecole Polytechnique Federale de Lausanne, CH-1015 Lausanne (Switzerland); Nowack, Bernd, E-mail: nowack@empa.ch [Empa - Swiss Federal Laboratories for Materials Science and Technology, CH-9014 St. Gallen (Switzerland)

    2011-06-15

    The colloidal stability of dry and suspended carbon nanotubes (CNTs) in the presence of amphiphilic compounds (i.e. natural organic matter or surfactants) at environmentally realistic concentrations was investigated over several days. The suspensions were analyzed for CNT concentration (UV-vis spectroscopy), particle size (nanoparticle tracking analysis), and CNT length and dispersion quality (TEM). When added in dry form, around 1% of the added CNTs remained suspended. Pre-dispersion in organic solvent or anionic detergent stabilized up to 65% of the added CNTs after 20 days of mild shaking and 5 days of settling. The initial state of the CNTs (dry vs. suspended) and the medium composition hence are critical determinants for the partitioning of CNTs between sediment and the water column. TEM analysis revealed that single suspended CNTs were present in all suspensions and that shaking and settling resulted in a fractionation of the CNTs with shorter CNTs remaining predominantly in suspension. - Highlights: > Individually suspended CNTs are present under environment relevant conditions. > The number of suspended CNTs varies depending on the medium composition. > Surfactants at environmental concentrations have no suspending effect on dry CNTs. > Pre-dispersed CNTs are more stable in suspension than dry CNTs. - The colloidal stability of CNTs varies a lot depending on the initial state of the CNTs (dry vs. pre-dispersed), the applied dispersant for pre-suspension, and the composition of the medium.

  5. The periplasmic loop provides stability to the open state of the CorA magnesium channel.

    Science.gov (United States)

    Palombo, Isolde; Daley, Daniel O; Rapp, Mikaela

    2012-08-10

    Crystal structures of the CorA Mg(2+) channel have suggested that metal binding in the cytoplasmic domain stabilizes the pentamer in a closed conformation. The open "metal free" state of the channel is, however, still structurally uncharacterized. Here, we have attempted to map conformational states of CorA from Thermotoga maritima by determining which residues support the pentameric structure in the presence or absence of Mg(2+). We find that when Mg(2+) is present, the pentamer is stabilized by the putative gating sites (M1/M2) in the cytoplasmic domain. Strikingly however, we find that the conserved and functionally important periplasmic loop is vital for the integrity of the pentamer when Mg(2+) is absent from the M1/M2 sites. Thus, although the periplasmic loops were largely disordered in the x-ray structures of the closed channel, our data suggests a prominent role for the loops in stabilizing the open conformation of the CorA channels.

  6. Exploiting Transient Protein States for the Design of Small-Molecule Stabilizers of Mutant p53

    Science.gov (United States)

    Joerger, Andreas C.; Bauer, Matthias R.; Wilcken, Rainer; Baud, Matthias G.J.; Harbrecht, Hannes; Exner, Thomas E.; Boeckler, Frank M.; Spencer, John; Fersht, Alan R.

    2015-01-01

    Summary The destabilizing p53 cancer mutation Y220C creates an extended crevice on the surface of the protein that can be targeted by small-molecule stabilizers. Here, we identify different classes of small molecules that bind to this crevice and determine their binding modes by X-ray crystallography. These structures reveal two major conformational states of the pocket and a cryptic, transiently open hydrophobic subpocket that is modulated by Cys220. In one instance, specifically targeting this transient protein state by a pyrrole moiety resulted in a 40-fold increase in binding affinity. Molecular dynamics simulations showed that both open and closed states of this subsite were populated at comparable frequencies along the trajectories. Our data extend the framework for the design of high-affinity Y220C mutant binders for use in personalized anticancer therapy and, more generally, highlight the importance of implementing protein dynamics and hydration patterns in the drug-discovery process. PMID:26636255

  7. Steady-state analysis of the effect of reactive generation limits in voltage stability

    Energy Technology Data Exchange (ETDEWEB)

    Echavarren, F.M.; Lobato, E.; Rouco, L. [School of Engineering of Universidad Pontificia Comillas, C/Alberto Aguilera, 23, 28015 Madrid (Spain)

    2009-09-15

    Voltage collapse phenomena are highly affected by reactive power generation limits. Saturation of the reactive power generation limits of a unit may result in a deterioration of the voltage stability. However, in some cases when the power network is operating close to the voltage collapse point, the reactive power generation saturation of a unit can change the system voltages immediately from stable to unstable; thus, a dynamic voltage collapse leading to blackout may follow. This paper presents a steady-state analysis of the immediate instability caused by reactive power generation saturation phenomena. For this purpose, the paper proposes a novel index that evaluates ''when'' and ''why'' a reactive power generation saturation will only result in a deterioration of the system voltage stability or, on the contrary, it will make the system voltages immediately unstable. (author)

  8. Topologically stable magnetization states on a spherical shell: Curvature-stabilized skyrmions

    Science.gov (United States)

    Kravchuk, Volodymyr P.; Rößler, Ulrich K.; Volkov, Oleksii M.; Sheka, Denis D.; van den Brink, Jeroen; Makarov, Denys; Fuchs, Hagen; Fangohr, Hans; Gaididei, Yuri

    2016-10-01

    Topologically stable structures include vortices in a wide variety of matter, skyrmions in ferro- and antiferromagnets, and hedgehog point defects in liquid crystals and ferromagnets. These are characterized by integer-valued topological quantum numbers. In this context, closed surfaces are a prominent subject of study as they form a link between fundamental mathematical theorems and real physical systems. Here we perform an analysis on the topology and stability of equilibrium magnetization states for a thin spherical shell with easy-axis anisotropy in normal directions. Skyrmion solutions are found for a range of parameters. These magnetic skyrmions on a spherical shell have two distinct differences compared to their planar counterpart: (i) they are topologically trivial and (ii) can be stabilized by curvature effects, even when Dzyaloshinskii-Moriya interactions are absent. Due to its specific topological nature a skyrmion on a spherical shell can be simply induced by a uniform external magnetic field.

  9. Fuzzy Stabilization for Nonlinear Discrete Ship Steering Stochastic Systems Subject to State Variance and Passivity Constraints

    Directory of Open Access Journals (Sweden)

    Wen-Jer Chang

    2014-01-01

    Full Text Available For nonlinear discrete-time stochastic systems, a fuzzy controller design methodology is developed in this paper subject to state variance constraint and passivity constraint. According to fuzzy model based control technique, the nonlinear discrete-time stochastic systems considered in this paper are represented by the discrete-time Takagi-Sugeno fuzzy models with multiplicative noise. Employing Lyapunov stability theory, upper bound covariance control theory, and passivity theory, some sufficient conditions are derived to find parallel distributed compensation based fuzzy controllers. In order to solve these sufficient conditions, an iterative linear matrix inequality algorithm is applied based on the linear matrix inequality technique. Finally, the fuzzy stabilization problem for nonlinear discrete ship steering stochastic systems is investigated in the numerical example to illustrate the feasibility and validity of proposed fuzzy controller design method.

  10. SOYBEAN (GLYCINE MAX UREASE: STEADY STATE KINETICS, STABILITY AND THERMAL INACTIVATION STUDIES

    Directory of Open Access Journals (Sweden)

    Sandeep Kumar

    2017-06-01

    Full Text Available The soybean (Glycine max urease was characterized with respect to kinetic parameters, stability studies and thermal inactivation. The stability temperature and stability pH of the purified urease was found to be 4 °C and 7.6, respectively. The optimum pH and optimum temperature were 7.0 oC and 65 oC, respectively. The energy of activation (Ea was 15.40 kJ/mol. Further, the Km and Vmax were determined by Lineweaver Burk plot and the values were 2.70 ± 0.10 mM and 2.85 x102 µmol NH3/min/mg protein,respectively. Thermal inactivation studies at 65 oC, revealed the mono-phasic kinetics, which indicated the loss in activity in single phase. However, at higher temperatures (70 oC, 75 oC and 77 oC, the kinetic pattern was mainly bi-phasic. At 80 oC, there was complete loss in activity thereby showing the denaturation of enzyme. Thermal inactivation studies strongly support the oligomeric nature of urease.

  11. Wellbore stability analysis in chemically active shale formations

    Directory of Open Access Journals (Sweden)

    Shi Xiang-Chao

    2016-01-01

    Full Text Available Maintaining wellbore stability involves significant challenges when drilling in low-permeability reactive shale formations. In the present study, a non-linear thermo-chemo-poroelastic model is provided to investigate the effect of chemical, thermal, and hydraulic gradients on pore pressure and stress distributions near the wellbores. The analysis indicates that when the solute concentration of the drilling mud is higher than that of the formation fluid, the pore pressure and the effective radial and tangential stresses decrease, and v. v. Cooling of the lower salinity formation decreases the pore pressure, radial and tangential stresses. Hole enlargement is the combined effect of shear and tensile failure when drilling in high-temperature shale formations. The shear and tensile damage indexes reveal that hole enlargement occurs in the vicinity of the wellbore at an early stage of drilling. This study also demonstrates that shale wellbore stability exhibits a time-delay effect due to changes in the pore pressure and stress. The delay time computed with consideration of the strength degradation is far less than that without strength degradation.

  12. An adaptive mutation in adenylate kinase that increases organismal fitness is linked to stability-activity trade-offs

    National Research Council Canada - National Science Library

    Couñago, Rafael; Wilson, Corey J; Peña, Matthew I; Wittung-Stafshede, Pernilla; Shamoo, Yousif

    Protein function is a balance between activity and stability. However, the relevance of stability-activity trade-offs for protein evolution and their impact on organismal fitness have been difficult to determine...

  13. Macroeconomic policy interaction: State dependency and implications for financial stability in UK: A systemic review

    Directory of Open Access Journals (Sweden)

    Muhammad Ali Nasir

    2016-12-01

    Full Text Available The association between economic and financial stabilities and influence of macroeconomic policies on the financial sector creates scope of active policy role in financial stability. As a contribution to the existing body of knowledge, this study has analysed the implications of macroeconomic policy interaction/coordination for financial stability, proxied by financial assets, i.e. equity and bonds price oscillation. The critical review and analysis of the existing literature on the subject suggests that there is also ample evidence of interdependence between monetary and fiscal policies and this interrelation necessitates coordination between them for the sake of financial stability. There is also a case for analysing the symmetry of financial markets responses to macroeconomic policy interaction. On methodological and empirical grounds, it is vital to test the robustness of policy recommendations to overcome the limitation of a single empirical approach (Jeffrey–Lindley’s paradox. Hence, the Frequentist and Bayesian approaches should be used in commentary manner. The policy interaction and optimal policy combination should also be analysed in the context of institutional design and major financial events to gain insight into the implications of policy interaction in the periods of stable economic and financial environments as well as period of financial and economic distress.

  14. Gas-phase synthesis of solid state DNA nanoparticles stabilized by l-leucine.

    Science.gov (United States)

    Raula, Janne; Hanzlíková, Martina; Rahikkala, Antti; Hautala, Juho; Kauppinen, Esko I; Urtti, Arto; Yliperttula, Marjo

    2013-02-28

    Aerosol flow reactor is used to generate solid-state nanoparticles in a one-step process that is based on drying of aerosol droplets in continuous flow. We investigated the applicability of aerosol flow reactor method to prepare solid state DNA nanoparticles. Precursor solutions of plasmid DNA with or without complexing agent (polyethylenimine), coating material (l-leucine) and mannitol (bulking material) were dispersed to nanosized droplets and instantly dried in laminar heat flow. Particle morphology, integrity and stability were studied by scanning electron microscopy. The stability of DNA was studied by gel electrophoresis. Plasmid DNA as such degraded in the aerosol flow process. Complexing agent protected DNA from degradation and coating material enabled production of dispersed, non-aggregated, nanoparticles. The resulting nanoparticles were spherical and their mean diameter ranged from 65 to 125nm. The nanoparticles were structurally stable at room temperature and their DNA content was about 10%. We present herein the proof of principle for the production of dispersed solid state nanoparticles with relevant size and intact plasmid DNA.

  15. Possible Mechanism of Formation and Stability of Anomalous States of Water

    CERN Document Server

    Wong, C Y; Wong, Cheuk-Yin; Lo, Shui-Yin

    1998-01-01

    We examine the physical processes which are involved in the formation and stability of the anomalous states of water reported recently. The initial step of adding a small amount of ionic compound XY to pure water leads to the formation of water clusters (X^+)(H2O)_n and (Y^-)(H2O)_n with n>>1. The structure of the cluster around the ion depends strongly on the equation of state. We explore the consequences of possible polymorphic states of H2O in the liquid phase at room temperature. If there are low-lying polymorphic states, the local dipole moment and the local density will change discontinuously as a function of the radial distance from the ion, and regions of different polymorphic states will be found at different separations from the ion. Fragmentation of the cluster by vigorous shaking may break up the cluster into small domains to allow subsequent coalescence of these domains or the growth of the domains as seeds to form greater domains of polymorphic states. Further experimental and theoretical analys...

  16. Stabilizing the urinary activity of fructose-1,6-bisphosphatase with EDTA and mercaptoethanol.

    Science.gov (United States)

    Kepka, Alina; Szajda, Sławomir Dariusz; Waszkiewicz, Napoleon; Zalewska, Anna; Płudowski, Paweł; Zwierz-Gugała, Dorota; Zalewska-Szajda, Beata; Borzym-Kluczyk, Małgorzata; Kryśkiewicz, Edyta; Zwierz, Krzysztof

    2009-09-01

    The study aim was to establish conditions for stabilization the activity of fructose-1,6-bisphosphatase (FBP-1) in stored urine. The FBP-1 was determined by the method Kepka et. al in a collected fraction of purified urine. EDTA and mercaptoethanol stabilized FBP-1 activity in stored urine. At optimal conditions urine may be stored up to 7 days at a temperature of 4 degrees C.

  17. An appraisal of the enzyme stability-activity trade-off.

    Science.gov (United States)

    Miller, Scott R

    2017-07-01

    A longstanding idea in evolutionary physiology is that an enzyme cannot jointly optimize performance at both high and low temperatures due to a trade-off between stability and activity. Although a stability-activity trade-off has been observed for well-characterized examples, such a trade-off is not imposed by any physical chemical constraint. To better understand the pervasiveness of this trade-off, I investigated the stability-activity relationship for comparative biochemical studies of purified orthologous enzymes identified by a literature search. The nature of this relationship varied greatly among studies. Notably, studies of enzymes with low mean synonymous nucleotide sequence divergence were less likely to exhibit the predicted negative correlation between stability and activity. Similarly, a survey of directed evolution investigations of the stability-activity relationship indicated that these traits are often uncoupled among nearly identical yet phenotypically divergent enzymes. This suggests that the presumptive trade-off often reported for investigations of enzymes with high mean sequence divergence may in some cases instead be a consequence of the degeneration over time of enzyme function in unselected environments, rather than a direct effect of thermal adaptation. The results caution against the general assertion of a stability-activity trade-off during enzyme adaptation. © 2017 The Author(s). Evolution © 2017 The Society for the Study of Evolution.

  18. Delay-dependent stabilization of singular Markovian jump systems with state delay

    Institute of Scientific and Technical Information of China (English)

    Zhengguang WU; Hongye SU; Jian CHU

    2009-01-01

    This paper deals with the delay-dependent stabilization problem for singular systems with Markovian jump parameters and time delays.A delay-dependent condition is established for the considered system to be regular,impulse free and stochastically stable.Based on the condition,a design algorithm of the desired state feedback controller which guarantees the resultant closed-loop system to be regular,impulse free and stochastically stable is proposed in terms of a set of strict linear matrix inequalities (LMIs).Numerical examples show the effectiveness of the proposed methods.

  19. Delay-dependent observer-based stabilizing controller design for linear multiple state-delayed systems

    Institute of Scientific and Technical Information of China (English)

    Dejin WANG

    2003-01-01

    This article concerns a coupled LMIs approach to delay-dependent observer-based output feedback stabilizing controller design for linear continuous-time systems with multiple state delays. The advantage of our proposed delay-dependent coupled LMIs criterion lies in that: (1) it can optimize one of multiple time delays with others selected properly, and at the same time, the feedback-gain and observer-gain can be obtained, respectively. (2) it is less conservative than the existing delay-independent ones in the literature. Algorithm to solve the coupled LMIs is also given. Numerical examples illustrate the effectiveness of our method.

  20. On the stability of two-step predictive controller based on state observer

    Institute of Scientific and Technical Information of China (English)

    Cao Muliang; Wu Zhiming; Ding Baocang; Wang Chuanxu

    2006-01-01

    For input saturated Hammerstein systems, the two-step predictive control strategy is adopted. The first step calculates the desired intermediate variable applying unconstrained linear model and predictive control. The second step obtains the real-time control action by solving algebraic equation and desaturation. The case of measurable state is considered where the observer gain matrix is solved by Sylvester equation. The sufficient closed-loop stability condition is given and the designing and tuning algorithm for the domain of attraction is proposed. The theoretical results are validated by an example.

  1. STABILITY AND NATURAL VIBRATIONS OF INHOMOGENEOUS SHELLS TAKING INTO ACCOUNT THE STRESS STATE

    Directory of Open Access Journals (Sweden)

    Bazhenov V.A.

    2015-12-01

    Full Text Available The work is devoted to the problem of developing a unified methodology based on the efficient numerical analysis of problems of stability and natural vibrations of a wide class of inhomogeneous shells, thin and medium thickness. In problems of its natural vibrations takes into account the presence of a pre-stressed state of the structure from the action of static loads, which significantly affect the spectrum of natural vibrations and allows determining the bifurcation point and the value of the critical force of buckling by dynamic criteria.

  2. Stability and hierarchy of quasi-stationary states: financial markets as an example

    Science.gov (United States)

    Stepanov, Yuriy; Rinn, Philip; Guhr, Thomas; Peinke, Joachim; Schäfer, Rudi

    2015-08-01

    We combine geometric data analysis and stochastic modeling to describe the collective dynamics of complex systems. As an example we apply this approach to financial data and focus on the non-stationarity of the market correlation structure. We identify the dominating variable and extract its explicit stochastic model. This allows us to establish a connection between its time evolution and known historical events on the market. We discuss the dynamics, the stability and the hierarchy of the recently proposed quasi-stationary market states.

  3. Leisure Activities and Change in Cognitive Stability: A Multivariate Approach

    Science.gov (United States)

    Mella, Nathalie; Grob, Emmanuelle; Döll, Salomé; Ghisletta, Paolo; de Ribaupierre, Anik

    2017-01-01

    Aging is traditionally associated with cognitive decline, attested by slower reaction times and poorer performance in various cognitive tasks, but also by an increase in intraindividual variability (IIV) in cognitive performance. Results concerning how lifestyle activities protect from cognitive decline are mixed in the literature and all focused on how it affects mean performance. However, IIV has been proven to be an index more sensitive to age differences, and very little is known about the relationships between lifestyle activities and change in IIV in aging. This longitudinal study explores the association between frequency of physical, social, intellectual, artistic, or cultural activities and age-related change in various cognitive abilities, considering both mean performance and IIV. Ninety-six participants, aged 64–93 years, underwent a battery of cognitive tasks at four measurements over a seven-year period, and filled out a lifestyle activity questionnaire. Linear multilevel models were used to analyze the associations between change in cognitive performance and five types of activities. Results showed that the practice of leisure activities was more strongly associated with IIV than with mean performance, both when considering overall level and change in performance. Relationships with IIV were dependent of the cognitive tasks considered and overall results showed protective effects of cultural, physical and intellectual activities on IIV. These results underline the need for considering IIV in the study of age-related cognitive change. PMID:28257047

  4. Exponential stability for a class of state-dependent delay equations via the Crandall-Liggett approach

    Science.gov (United States)

    Louihi, M.; Hbid, M. L.

    2007-05-01

    In this paper we are concerned with the exponential asymptotic stability of the solution of a class of differential equations with state dependent delays. Our approach is based on the Crandall-Liggett approximation and the properties of semigroups.

  5. Statistical optimization of activity and stability of β-xylanase ...

    African Journals Online (AJOL)

    STORAGESEVER

    2008-10-20

    Oct 20, 2008 ... analysis of treatment combinations showed that a regression models of optimization of xylanase activity and ..... Compendium of soil fungi. Regenburg;. ... Integration of Science & Technology for Sustainable Development,.

  6. Beta activity in the premotor cortex is increased during stabilized as compared to normal walking

    Directory of Open Access Journals (Sweden)

    Sjoerd M. Bruijn

    2015-10-01

    Full Text Available Walking on two legs is inherently unstable. Still, we humans perform remarkable well at it, mostly without falling. To gain more understanding of the role of the brain in controlling gait stability we measured brain activity using electro-encephalography (EEG during stabilized and normal walking.Subjects walked on a treadmill in two conditions, each lasting 10 minutes; normal, and while being laterally stabilized by elastic cords. Kinematics of trunk and feet, electro-myography (EMG of neck muscles, as well as 64-channel EEG were recorded. To assess gait stability the local divergence exponent, step width, and trunk range of motion were calculated from the kinematic data. We used independent component analysis to remove movement, EMG, and eyeblink artifacts from the EEG, after which dynamic imaging of coherent sources beamformers were determined to identify cortical sources that showed a significant difference between conditions. Stabilized walking led to a significant increase in gait stability, i.e. lower local divergence exponents. Beamforming analysis of the beta band activity revealed significant sources in bilateral pre-motor cortices. Projection of sensor data on these sources showed a significant difference only in the left premotor area, with higher beta power during stabilized walking, specifically around push-off, although only significant around contralateral push-off. It appears that even during steady gait the cortex is involved in the control of stability.

  7. Relative stability of network states in Boolean network models of gene regulation in development.

    Science.gov (United States)

    Zhou, Joseph Xu; Samal, Areejit; d'Hérouël, Aymeric Fouquier; Price, Nathan D; Huang, Sui

    2016-01-01

    Progress in cell type reprogramming has revived the interest in Waddington's concept of the epigenetic landscape. Recently researchers developed the quasi-potential theory to represent the Waddington's landscape. The Quasi-potential U(x), derived from interactions in the gene regulatory network (GRN) of a cell, quantifies the relative stability of network states, which determine the effort required for state transitions in a multi-stable dynamical system. However, quasi-potential landscapes, originally developed for continuous systems, are not suitable for discrete-valued networks which are important tools to study complex systems. In this paper, we provide a framework to quantify the landscape for discrete Boolean networks (BNs). We apply our framework to study pancreas cell differentiation where an ensemble of BN models is considered based on the structure of a minimal GRN for pancreas development. We impose biologically motivated structural constraints (corresponding to specific type of Boolean functions) and dynamical constraints (corresponding to stable attractor states) to limit the space of BN models for pancreas development. In addition, we enforce a novel functional constraint corresponding to the relative ordering of attractor states in BN models to restrict the space of BN models to the biological relevant class. We find that BNs with canalyzing/sign-compatible Boolean functions best capture the dynamics of pancreas cell differentiation. This framework can also determine the genes' influence on cell state transitions, and thus can facilitate the rational design of cell reprogramming protocols.

  8. Analysis of stability of a Power System by using Delay Static State Feedback

    Directory of Open Access Journals (Sweden)

    Sindy Paola Amaya

    2012-12-01

    Full Text Available This article presents the analysis of stability of a power system modeled as Infinite Bus Connected Generator with delay static state feedback. The model of the power system is described by nonlinear differential- algebraic equations. For controller design, we linealize the nonlinear differential-algebraic model around an operation point to obtain a lineal differential-algebraic model. As of this model obtains the Kronecker -Weierstrass model which designs the controller. To obtain the K gain of the controller outline inequalities matrix lineal (LMI's . Then it makes a study of the maximum delay that it supports in the state feedback. At the end of the article present the results and the conclusions.

  9. STEADY-STATE RESPONSES AND THEIR STABILITY OF NONLINEAR VIBRATION OF AN AXIALLY ACCELERATING STRING

    Institute of Scientific and Technical Information of China (English)

    吴俊; 陈立群

    2004-01-01

    The steady-state transverse vibration of an axially moving string with geometric nonlinearity was investigated. The transport speed was assumed to be a constant mean speed with small harmonic variations. The nonlinear partial-differential equation that governs the transverse vibration of the string was derived by use of the Hamilton principle. The method of multiple scales was applied directly to the equation. The solvability condition of eliminating the secular terms was established. Closed form solutions for the amplitude and the existence conditions of nontrivial steady-state response of the two-to-one parametric resonance were obtained. Some numerical examples showing effects of the mean transport speed, the amplitude and the frequency of speed variation were presented. The Liapunov linearized stability theory was employed to derive the instability conditions of the trivial solution and the nontrivial solutions for the two-to-one parametric resonance. Some numerical examples highlighting influences of the related parameters on the instability conditions were presented.

  10. Stabilization of the Activated hERG Channel Voltage Sensor by Depolarization Involves the S4-S5 Linker.

    Science.gov (United States)

    Thouta, Samrat; Hull, Christina M; Shi, Yu Patrick; Sergeev, Valentine; Young, James; Cheng, Yen M; Claydon, Thomas W

    2017-01-24

    Slow deactivation of hERG channels is critical for preventing cardiac arrhythmia yet the mechanistic basis for the slow gating transition is unclear. Here, we characterized the temporal sequence of events leading to voltage sensor stabilization upon membrane depolarization. Progressive increase in step depolarization duration slowed voltage-sensor return in a biphasic manner (τfast = 34 ms, τslow = 2.5 s). The faster phase of voltage-sensor return slowing correlated with the kinetics of pore opening. The slower component occurred over durations that exceeded channel activation and was consistent with voltage sensor relaxation. The S4-S5 linker mutation, G546L, impeded the faster phase of voltage sensor stabilization without attenuating the slower phase, suggesting that the S4-S5 linker is important for communications between the pore gate and the voltage sensor during deactivation. These data also demonstrate that the mechanisms of pore gate-opening-induced and relaxation-induced voltage-sensor stabilization are separable. Deletion of the distal N-terminus (Δ2-135) accelerated off-gating current, but did not influence the relative contribution of either mechanism of stabilization of the voltage sensor. Lastly, we characterized mode-shift behavior in hERG channels, which results from stabilization of activated channel states. The apparent mode-shift depended greatly on recording conditions. By measuring slow activation and deactivation at steady state we found the "true" mode-shift to be ∼15 mV. Interestingly, the "true" mode-shift of gating currents was ∼40 mV, much greater than that of the pore gate. This demonstrates that voltage sensor return is less energetically favorable upon repolarization than pore gate closure. We interpret this to indicate that stabilization of the activated voltage sensor limits the return of hERG channels to rest. The data suggest that this stabilization occurs as a result of reconfiguration of the pore gate upon opening by

  11. Active stabilization of thin-wall structures under compressive loading

    Science.gov (United States)

    Welham, Jared; Calius, Emilio P.; Chase, J. Geoffrey

    2003-08-01

    The active suppression of elastic buckling instability has the potential to significantly increase the effective strength of thin-wall structures. Despite all the interest in smart structures, the active suppression of buckling has received comparatively little attention. This paper addresses the effects of embedded actuation on the compression buckling strength of laminated composite plates through analysis and simulation. Numerical models are formulated that include the influence of essential features such as sensor uncertainty and noise, actuator saturation and control architecture on the buckling process. Silicon-based strain sensors and diffuse laser distance sensors are both considered for use in the detection of incipient buckling behavior due to their increased sensitivity. Actuation is provided by paired distributions of piezo-electric material incorporated into both sides of the laminate. Optimal controllers are designed to command the structure to deform in ways that interfere with the development of buckling mode shapes. Commercial software packages are used to solve the resulting non-linear equations, and some of the tradeoffs are enumerated. Overall, the results show that active buckling control can considerably enhance resistance to instability under compressive loads. These buckling load predictions demonstrate the viability of optimal control and piezo-electric actuation for implementing active buckling control. Due to the importance of early detection, the relative effectiveness of active buckling control is shown to be strongly dependent on the performance of the sensing scheme, as well as on the characteristics of the structure.

  12. Effect of titanium on passive state stability of austenitic stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Cihal, V.; Blahetova, M.; Krhutova, Z.; Lasek, St.; Mikel, P. [Ostrava VSB-Technical Univ. (Czech Republic); Cihal, V.; Kalabisova, E. [SVUOM Ltd. Prague (Czech Republic); Burda, J.; Karnik, D. [Nuclear Research Institute Rez, plc. (Czech Republic)

    2009-07-01

    In view of the wide application range of austenitic stainless steels and alloys, it is indispensable for these materials to retain adequate passivity when exposed to aggressive media under a variety of conditions. Stability of the passive state is the function mainly of the chemical composition, structural sensitivity, and the state of stressing of the metal, coupled with the specific chemistry of the environment, as is also the case e.g., with boiling water and pressure water reactors. Sensitization of higher-carbon steels was eventually coped with by stabilization i.e., bonding the carbon with titanium and columbium, and by lowering the carbon content. In the case of steels stabilized with titanium and columbium, the effects of these elements when present in the form of carbides as well as their influence in the solid solution on potential passive film breakdown require attention, owing to the danger of provoking pitting corrosion, stress corrosion cracking, intergranular corrosion, or dissolution in highly oxidizing media. The effects of titanium and columbium in the solid solution on passive state stability of CrNi and CrNiMo steels as well as on their localized corrosion are compared. Experimental heats of low-carbon (max 0.02%) alloys containing 17.5-18.0% Cr, 12-15% Ni and 2.5-2.7% Mo, modified with graduated additions of Ti and Nb (0.4-1.2%), were subjected to chemical and metallographic analyses and to phase identification procedures. Electrochemical polarization measurements involving reactivation from the outset of the passive region (at 0.1 or 0.0 V{sub SCE}) indicated a reduction of the critical reactivation current density for the titanium-stabilized steels. The reactivation ratios derived from measurements by the DL-EPR method (according to ISO12732-2006) exhibit slightly lower values, on the average, for the steels with titanium than for those with columbium. The significant effect of titanium has also been confirmed by reactivation measurements run

  13. Study on Active Oxygen Quantum Yield, Insecticidal Activities and Stability of Diphenylthiophene

    Institute of Scientific and Technical Information of China (English)

    CHEN Xiao-jun; XU Han-hong; WANG Yu-jian; HU Shan; ZHANG Zhi-xiang; ZHANG Yao-mou

    2007-01-01

    Active oxygen quantum yield, insecticidal activities and stability of diphenylthiophene were studied for the first time. The results showed that maximum diphenylthiophene absorbency variety was 0.438 after irradiation for 280 min and that of α-terthienyl (α-T) was 0.480 after irradiation for 200 min with UV. LC50 values ofdiphenylthiophene and α-T against 3rd instar larvae of Aedes albopictus were 9.18 × 10-3 and 9.69 × 10-4 μg mL-1 when treated for 24 h, respectively. LC50 values of the two chemicals against the 3rd instar larvae of Plutella xylostella were 267.87 and 222.22 μg mL-1 when treated for 24 h, respectively. The half lives of diphenylthiophene and α-T in methanol were 113.62 and 10.65 h. Difference between quantum yield of diphenylthiophene and α-T was not significant and they all possessed high toxicity to Aedes albopictus and Plutella xylostella, but diphenylthiophene was more stable than α-T. It could be concluded that diphenylthiophene has overcome the deficiency of photoactivated insecticides which degraded quickly in the environment and could not be applied on the field. Diphenylthiophene could kill the insects and accelerate the degradation rate of triazophos. The benefits of diphenylthiophene can be further exploited and applied on the field.

  14. FAD binding overcomes defects in activity and stability displayed by cancer-associated variants of human NQO1.

    Science.gov (United States)

    Pey, Angel L; Megarity, Clare F; Timson, David J

    2014-11-01

    NAD(P)H quinone oxidoreductase 1 is involved in antioxidant defence and protection from cancer, stabilizing the apoptosis regulator p53 towards degradation. Here, we studied the enzymological, biochemical and biophysical properties of two cancer-associated variants (p.R139W and p.P187S). Both variants (especially p.187S) have lower thermal stability and greater susceptibility to proteolysis compared to the wild-type. p.P187S also has reduced activity due to a lower binding affinity for the FAD cofactor as assessed by activity measurements and direct titrations. Native gel electrophoresis and dynamic light scattering also suggest that p.P187S has a higher tendency to populate unfolded states under native conditions. Detailed thermal stability studies showed that all variants irreversibly denature causing dimer dissociation, while addition of FAD restores the stability of the polymorphic forms to wild-type levels. The kinetic destabilization induced by polymorphisms as well as the kinetic protection exerted by FAD was confirmed by measuring denaturation kinetics at temperatures close to physiological. Our data suggest that the main molecular mechanisms associated with these cancer-related variants are their low binding affinity for FAD and/or kinetic instability. Thus, pharmacological chaperones may be useful in the treatment of patients bearing these polymorphisms.

  15. Metabolic stabilization of acetylcholine receptors in vertebrate neuromuscular junction by muscle activity

    Energy Technology Data Exchange (ETDEWEB)

    Rotzler, S.; Brenner, H.R. (Univ. of Basel (Switzerland))

    1990-08-01

    The effects of muscle activity on the growth of synaptic acetylcholine receptor (AChR) accumulations and on the metabolic AChR stability were investigated in rat skeletal muscle. Ectopic end plates induced surgically in adult soleus muscle were denervated early during development when junctional AChR number and stability were still low and, subsequently, muscles were either left inactive or they were kept active by chronic exogenous stimulation. AChR numbers per ectopic AChR cluster and AChR stabilities were estimated from the radioactivity and its decay with time, respectively, of end plate sites whose AChRs had been labeled with {sup 125}I-alpha-bungarotoxin (alpha-butx). The results show that the metabolic stability of the AChRs in ectopic clusters is reversibly increased by muscle activity even when innervation is eliminated very early in development. 1 d of stimulation is sufficient to stabilize the AChRs in ectopic AChR clusters. Muscle stimulation also produced an increase in the number of AChRs at early denervated end plates. Activity-induced cluster growth occurs mainly by an increase in area rather than in AChR density, and for at least 10 d after denervation is comparable to that in normally developing ectopic end plates. The possible involvement of AChR stabilization in end plate growth is discussed.

  16. Enhancement of the Antibacterial Activity of Silver Nanoparticles against Phytopathogenic Bacterium Ralstonia solanacearum by Stabilization

    Directory of Open Access Journals (Sweden)

    Juanni Chen

    2016-01-01

    Full Text Available In this paper, the enhanced antibacterial activity of silver nanoparticles (AgNPs against the phytopathogenic bacterium Ralstonia solanacearum after stabilization using selected surfactants (SDS, SDBS, TX-100, and Tween 80 was examined, in comparison with silver ion. Tween 80 was found to be the most preferable stabilizer of AgNPs due to the beneficial synergistic effects of the AgNPs and surfactant. However, all the surfactants nearly had no effects on the antibacterial activity of Ag+. In vitro, Tween 80-stabilized AgNPs showed the highest bactericidal activity against R. solanacearum. Further measurements using TEM, fluorescence microscopy, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE revealed that though Ag+ and Tween 80-Ag+ induced high toxicity, Tween 80-stabilized AgNPs displayed most severe damage when in direct contact with cells, causing mechanistic injury to the cell membrane and strongly modifying and destructing the cellular proteins. Meanwhile, in vivo, the pot experiments data indicated that the control efficiency of Tween 80-stabilized AgNPs on tobacco bacterial wilt was 96.71%, 90.11%, and 84.21%, at 7 days, 14 days, and 21 days, respectively. Based on the results evidencing their advantageous low dosage requirements and strong antimicrobial activity, Tween 80-stabilized AgNPs are a promising antibacterial agent for use in alternative crop disease control approaches.

  17. Validity Evidence for the State Mindfulness Scale for Physical Activity

    Science.gov (United States)

    Cox, Anne E.; Ullrich-French, Sarah; French, Brian F.

    2016-01-01

    Being attentive to and aware of one's experiences in the present moment with qualities of acceptance and openness reflects the state of mindfulness. Positive associations exist between state mindfulness and state autonomous motivation for everyday activities. Though this suggests that state mindfulness links with adaptive motivational experiences,…

  18. Carbonless footprints: promoting health and climate stabilization through active transportation.

    Science.gov (United States)

    Frank, Lawrence D; Greenwald, Michael J; Winkelman, Steve; Chapman, James; Kavage, Sarah

    2010-01-01

    Our objective was to describe how active transportation can help meet health and greenhouse gas emissions goals, and the ability of urban form strategies to impact both issues. In addition, we wanted to assess if there is an inverse relationship between active and motorized forms of travel. A cross-sectional analysis of travel diary data was used to measure relationships among energy (kcal) burned from walking, energy (kcal) burned from motorized transportation, and the ratio of the two (the transport energy index) with regional accessibility and local walkability when adjusting for demographic factors. Multiple linear regression and descriptive statistics were employed to estimate these relationships. Transit accessibility, residential density, and intersection density were positive predictors of walk energy and the energy index and inverse predictors of motorized energy. The land use mix variable was negatively and significantly associated with energy burned from walking and from motorized transportation, with no significant impact on the transport energy index. Because a mixed land use pattern places destinations closer together, it reduces distances and thus energy demands for both walking and driving. The results support the concept, previously untested empirically, that similar urban form strategies can have cobenefits for both physical activity and climate change.

  19. STATE-FEEDBACK ADAPTIVE STABILIZING CONTROL DESIGN FOR A CLASS OF HIGH-ORDER NONLINEAR SYSTEMS WITH UNKNOWN CONTROL COEFFICIENTS

    Institute of Scientific and Technical Information of China (English)

    Zongyao SUN; Yungang LIU

    2007-01-01

    In this paper, a new approach is successfully addressed to design the state-feedback adaptive stabilizing control law for a class of high-order nonlinear systems in triangular form and with unknown and nonidentical control coefficients, whose stabilizing control has been investigated recently under the knowledge that the lower bounds of the control coefficients are exactly known. In the present paper,without any knowledge of the lower bounds of the control coefficients, based on the adaptive technique and appropriately choosing design parameters, we give the recursive design procedure of the stabilizing control law by utilizing the approach of adding a power integrator together with tuning functions. The state-feedback adaptive control law designed not only preserves the equilibrium at the origin, but also guarantees the global asymptotic stability of the closed-loop states and the uniform boundedness of all the other closed-loop signals.

  20. ALD Functionalized Nanoporous Gold: Thermal Stability, Mechanical Properties, and Catalytic Activity

    Energy Technology Data Exchange (ETDEWEB)

    Biener, M M; Biener, J; Wichmann, A; Wittstock, A; Baumann, T F; Baeumer, M; Hamza, A V

    2011-03-24

    Nanoporous metals have many technologically promising applications but their tendency to coarsen limits their long-term stability and excludes high temperature applications. Here, we demonstrate that atomic layer deposition (ALD) can be used to stabilize and functionalize nanoporous metals. Specifically, we studied the effect of nanometer-thick alumina and titania ALD films on thermal stability, mechanical properties, and catalytic activity of nanoporous gold (np-Au). Our results demonstrate that even only one-nm-thick oxide films can stabilize the nanoscale morphology of np-Au up to 1000 C, while simultaneously making the material stronger and stiffer. The catalytic activity of np-Au can be drastically increased by TiO{sub 2} ALD coatings. Our results open the door to high temperature sensor, actuator, and catalysis applications and functionalized electrodes for energy storage and harvesting applications.

  1. Voltage stability in low voltage microgrids in aspects of active and reactive power demand

    Directory of Open Access Journals (Sweden)

    Parol Mirosław

    2016-03-01

    Full Text Available Low voltage microgrids are autonomous subsystems, in which generation, storage and power and electrical energy consumption appear. In the paper the main attention has been paid to the voltage stability issue in low voltage microgrid for different variants of its operation. In the introduction a notion of microgrid has been presented, and also the issue of influence of active and reactive power balance on node voltage level has been described. Then description of voltage stability issue has been presented. The conditions of voltage stability and indicators used to determine voltage stability margin in the microgrid have been described. Description of the low voltage test microgrid, as well as research methodology along with definition of considered variants of its operation have been presented further. The results of exemplary calculations carried out for the daily changes in node load of the active and reactive power, i.e. the voltage and the voltage stability margin indexes in nodes have been presented. Furthermore, the changes of voltage stability margin indexes depending on the variant of the microgrid operation have been presented. Summary and formulation of conclusions related to the issue of voltage stability in microgrids have been included at the end of the paper.

  2. Active Affordance Learning in Continuous State and Action Spaces

    NARCIS (Netherlands)

    Wang, C.; Hindriks, K.V.; Babuska, R.

    2014-01-01

    Learning object affordances and manipulation skills is essential for developing cognitive service robots. We propose an active affordance learning approach in continuous state and action spaces without manual discretization of states or exploratory motor primitives. During exploration in the action

  3. Electronic metal-support interaction enhanced oxygen reduction activity and stability of boron carbide supported platinum

    Science.gov (United States)

    Jackson, Colleen; Smith, Graham T.; Inwood, David W.; Leach, Andrew S.; Whalley, Penny S.; Callisti, Mauro; Polcar, Tomas; Russell, Andrea E.; Levecque, Pieter; Kramer, Denis

    2017-06-01

    Catalysing the reduction of oxygen in acidic media is a standing challenge. Although activity of platinum, the most active metal, can be substantially improved by alloying, alloy stability remains a concern. Here we report that platinum nanoparticles supported on graphite-rich boron carbide show a 50-100% increase in activity in acidic media and improved cycle stability compared to commercial carbon supported platinum nanoparticles. Transmission electron microscopy and x-ray absorption fine structure analysis confirm similar platinum nanoparticle shapes, sizes, lattice parameters, and cluster packing on both supports, while x-ray photoelectron and absorption spectroscopy demonstrate a change in electronic structure. This shows that purely electronic metal-support interactions can significantly improve oxygen reduction activity without inducing shape, alloying or strain effects and without compromising stability. Optimizing the electronic interaction between the catalyst and support is, therefore, a promising approach for advanced electrocatalysts where optimizing the catalytic nanoparticles themselves is constrained by other concerns.

  4. Stability and phase transfer of catalytically active platinum nanoparticle suspensions

    Energy Technology Data Exchange (ETDEWEB)

    Sriram, Indira; Curtin, Alexandra E.; Chiaramonti, Ann N.; Cuchiaro, J. Hunter; Weidner, Andrew R.; Tingley, Tegan M.; Greenlee, Lauren F.; Jeerage, Kavita M., E-mail: jeerage@boulder.nist.gov [National Instrument of Standards and Technology, Applied Chemicals and Materials Division (United States)

    2015-05-15

    In this work, we present a robust synthesis protocol for platinum nanoparticles that yields a monomodal dispersion of particles that are approximately 100 nm in diameter. We determine that these particles are actually agglomerates of much smaller particles, creating a “raspberry” morphology. We demonstrate that these agglomerates are stable at room temperature for at least 8 weeks by dynamic light scattering. Furthermore, we demonstrate consistent electrocatalytic activity for methanol oxidation. Finally, we quantitatively explore the relationship between dispersion solvent and particle agglomeration; specifically, particles are found to agglomerate abruptly as solvent polarity decreases.

  5. Prevalence and Stability of Active Play, Restricted Movement and Television Viewing in Infants

    Science.gov (United States)

    Hesketh, Kylie D.; Crawford, David A.; Abbott, Gavin; Campbell, Karen J.; Salmon, Jo

    2015-01-01

    This study describes engagement in and stability of physical activity and sedentary behaviours in early life, and assesses associations with sex, maternal education and developmental stage. Maternal-report data at child age 4, 9 and 20 months were collected from 542 families in the Melbourne Infant Feeding Activity and Nutrition Trial Program.…

  6. Influence of Soil Humic and Fulvic Acid on the Activity and Stability of Lysozyme and Urease

    NARCIS (Netherlands)

    Li, Yan; Tan, WenFeng; Koopal, Luuk K.; Wang, MingXia; Liu, Fan; Norde, Willem

    2013-01-01

    Humic substances (HS), including humic acids (HA) and fulvic acids (FA), are important components of soil systems. HS form strong complexes with oppositely charged proteins, which will lead to changes in the enzyme activity. The effect of soil HS on the activity and stability of two enzymes was inve

  7. Influence of soil humic and fulvic acid on the activity and stability of lysozyme and urease

    NARCIS (Netherlands)

    Li, Y.; Tan, W.; Koopal, L.K.; Wang, M.; Liu, Fan; Norde, W.

    2013-01-01

    Humic substances (HS), including humic acids (HA) and fulvic acids (FA), are important components of soil systems. HS form strong complexes with oppositely charged proteins, which will lead to changes in the enzyme activity. The effect of soil HS on the activity and stability of two enzymes was inve

  8. Chemical modification of L-asparaginase from Cladosporium sp. for improved activity and thermal stability.

    Science.gov (United States)

    Mohan Kumar, N S; Kishore, Vijay; Manonmani, H K

    2014-01-01

    L-Asparaginase (ASNase), an antileukemia enzyme, is facing problems with antigenicity in the blood. Modification of L-asparaginase from Cladosporium sp. was tried to obtain improved stability and improved functionality. In our experiment, modification of the enzyme was tried with bovine serum albumin, ovalbumin by crosslinking using glutaraldehyde, N-bromosuccinimide, and mono-methoxy polyethylene glycol. Modified enzymes were studied for activity, temperature stability, rate constants (kd), and protection to proteolytic digestion. Modification with ovalbumin resulted in improved enzyme activity that was 10-fold higher compared to native enzyme, while modification with bovine serum albumin through glutaraldehyde cross-linking resulted in high stability of L-asparaginase that was 8.5- and 7.62-fold more compared to native enzyme at 28°C and 37°C by the end of 24 hr. These effects were dependent on the quantity of conjugate formed. Modification also markedly prolonged L-asparaginase half-life and serum stability. N-Bromosuccinimide-modified ASNase presented greater stability with prolonged in vitro half-life of 144 hr to proteolytic digestion relative to unmodified enzyme (93 h). The present work could be seen as producing a modified L-asparaginase with improved activity and stability and can be a potential source for developing therapeutic agents for cancer treatment.

  9. Stabilizing Niger

    DEFF Research Database (Denmark)

    Hahonou, Eric Komlavi

    international intervention in Niger. Their main objective is to secure their own strategic, economic and political interests by strengthening the Nigerien authorities through direct intervention and capacity building activities. For western states reinforcing state security institutions and stabilizing elite...... rule constitute the only realistic path to defend their own interests. The report suggests that international support of Nigerien security forces could be counter-productive for the re-establishment of state authority and legitimacy in the long-term. Brutal repression and violation of human rights...

  10. Stated Uptake of Physical Activity Rewards Programmes Among Active and Insufficiently Active Full-Time Employees.

    Science.gov (United States)

    Ozdemir, Semra; Bilger, Marcel; Finkelstein, Eric A

    2017-04-22

    Employers are increasingly relying on rewards programmes in an effort to promote greater levels of activity among employees; however, if enrolment in these programmes is dominated by active employees, then they are unlikely to be a good use of resources. This study uses a stated-preference survey to better understand who participates in rewards-based physical activity programmes, and to quantify stated uptake by active and insufficiently active employees. The survey was fielded to a national sample of 950 full-time employees in Singapore between 2012 and 2013. Participants were asked to choose between hypothetical rewards programmes that varied along key dimensions and whether or not they would join their preferred programme if given the opportunity. A mixed logit model was used to analyse the data and estimate predicted uptake for specific programmes. We then simulated employer payments based on predictions for the percentage of each type of employee likely to meet the activity goal. Stated uptake ranged from 31 to 67% of employees, depending on programme features. For each programme, approximately two-thirds of those likely to enrol were insufficiently active. Results showed that insufficiently active employees, who represent the majority, are attracted to rewards-based physical activity programmes, and at approximately the same rate as active employees, even when enrolment fees are required. This suggests that a programme with generous rewards and a modest enrolment fee may have strong employee support and be within the range of what employers may be willing to spend.

  11. UP states protect ongoing cortical activity from thalamic inputs.

    Directory of Open Access Journals (Sweden)

    Brendon O Watson

    Full Text Available Cortical neurons in vitro and in vivo fluctuate spontaneously between two stable membrane potentials: a depolarized UP state and a hyperpolarized DOWN state. UP states temporally correspond with multineuronal firing sequences which may be important for information processing. To examine how thalamic inputs interact with ongoing cortical UP state activity, we used calcium imaging and targeted whole-cell recordings of activated neurons in thalamocortical slices of mouse somatosensory cortex. Whereas thalamic stimulation during DOWN states generated multineuronal, synchronized UP states, identical stimulation during UP states had no effect on the subthreshold membrane dynamics of the vast majority of cells or on ongoing multineuronal temporal patterns. Both thalamocortical and corticocortical PSPs were significantly reduced and neuronal input resistance was significantly decreased during cortical UP states -- mechanistically consistent with UP state insensitivity. Our results demonstrate that cortical dynamics during UP states are insensitive to thalamic inputs.

  12. Transition state trajectory stability determines barrier crossing rates in chemical reactions induced by time-dependent oscillating fields

    CERN Document Server

    Craven, Galen T; Hernandez, Rigoberto

    2015-01-01

    When a chemical reaction is driven by an external field, the transition state that the system must pass through as it changes from reactant to product -for example, an energy barrier- becomes time-dependent. We show that for periodic forcing the rate of barrier crossing can be determined through stability analysis of the non-autonomous transition state. Specifically, strong agreement is observed between the difference in the Floquet exponents describing stability of the transition state trajectory, which defines a recrossing-free dividing surface [G. T. Craven, T. Bartsch, and R. Hernandez, Phys. Rev. E 89, 040801(R) (2014)], and the rates calculated by simulation of ensembles of trajectories. This result opens the possibility to extract rates directly from the intrinsic stability of the transition state, even when it is time-dependent, without requiring a numerically-expensive simulation of the long-time dynamics of a large ensemble of trajectories.

  13. Adaptive Neural Stabilizing Controller for a Class of Mismatched Uncertain Nonlinear Systems by State and Output Feedback.

    Science.gov (United States)

    Arefi, Mohammad Mehdi; Jahed-Motlagh, Mohammad Reza; Karimi, Hamid Reza

    2015-08-01

    In this paper, first, an adaptive neural network (NN) state-feedback controller for a class of nonlinear systems with mismatched uncertainties is proposed. By using a radial basis function NN (RBFNN), a bound of unknown nonlinear functions is approximated so that no information about the upper bound of mismatched uncertainties is required. Then, an observer-based adaptive controller based on RBFNN is designed to stabilize uncertain nonlinear systems with immeasurable states. The state-feedback and observer-based controllers are based on Lyapunov and strictly positive real-Lyapunov stability theory, respectively, and it is shown that the asymptotic convergence of the closed-loop system to zero is achieved while maintaining bounded states at the same time. The presented methods are more general than the previous approaches, handling systems with no restriction on the dimension of the system and the number of inputs. Simulation results confirm the effectiveness of the proposed methods in the stabilization of mismatched nonlinear systems.

  14. Ionic and Covalent Stabilization of Intermediates and Transition States in Catalysis by Solid Acids

    Energy Technology Data Exchange (ETDEWEB)

    Deshlahra, Prashant; Carr, Robert T.; Iglesia, Enrique

    2014-10-29

    Reactivity descriptors describe catalyst properties that determine the stability of kinetically relevant transition states and adsorbed intermediates. Theoretical descriptors, such as deprotonation energies (DPE), rigorously account for Brønsted acid strength for catalytic solids with known structure. Here, mechanistic interpretations of methanol dehydration turnover rates are used to assess how charge reorganization (covalency) and electrostatic interactions determine DPE and how such interactions are recovered when intermediates and transition states interact with the conjugate anion in W and Mo polyoxometalate (POM) clusters and gaseous mineral acids. Turnover rates are lower and kinetically relevant species are less stable on Mo than W POM clusters with similar acid strength, and such species are more stable on mineral acids than that predicted from W-POM DPE–reactivity trends, indicating that DPE and acid strength are essential but incomplete reactivity descriptors. Born–Haber thermochemical cycles indicate that these differences reflect more effective charge reorganization upon deprotonation of Mo than W POM clusters and the much weaker reorganization in mineral acids. Such covalency is disrupted upon deprotonation but cannot be recovered fully upon formation of ion pairs at transition states. Predictive descriptors of reactivity for general classes of acids thus require separate assessments of the covalent and ionic DPE components. Here, we describe methods to estimate electrostatic interactions, which, taken together with energies derived from density functional theory, give the covalent and ionic energy components of protons, intermediates, and transition states. In doing so, we provide a framework to predict the reactive properties of protons for chemical reactions mediated by ion-pair transition states.

  15. Ionic and covalent stabilization of intermediates and transition states in catalysis by solid acids.

    Science.gov (United States)

    Deshlahra, Prashant; Carr, Robert T; Iglesia, Enrique

    2014-10-29

    Reactivity descriptors describe catalyst properties that determine the stability of kinetically relevant transition states and adsorbed intermediates. Theoretical descriptors, such as deprotonation energies (DPE), rigorously account for Brønsted acid strength for catalytic solids with known structure. Here, mechanistic interpretations of methanol dehydration turnover rates are used to assess how charge reorganization (covalency) and electrostatic interactions determine DPE and how such interactions are recovered when intermediates and transition states interact with the conjugate anion in W and Mo polyoxometalate (POM) clusters and gaseous mineral acids. Turnover rates are lower and kinetically relevant species are less stable on Mo than W POM clusters with similar acid strength, and such species are more stable on mineral acids than that predicted from W-POM DPE-reactivity trends, indicating that DPE and acid strength are essential but incomplete reactivity descriptors. Born-Haber thermochemical cycles indicate that these differences reflect more effective charge reorganization upon deprotonation of Mo than W POM clusters and the much weaker reorganization in mineral acids. Such covalency is disrupted upon deprotonation but cannot be recovered fully upon formation of ion pairs at transition states. Predictive descriptors of reactivity for general classes of acids thus require separate assessments of the covalent and ionic DPE components. Here, we describe methods to estimate electrostatic interactions, which, taken together with energies derived from density functional theory, give the covalent and ionic energy components of protons, intermediates, and transition states. In doing so, we provide a framework to predict the reactive properties of protons for chemical reactions mediated by ion-pair transition states.

  16. Occurrence and stability of chimera states in coupled externally excited oscillators

    Science.gov (United States)

    Dudkowski, Dawid; Maistrenko, Yuri; Kapitaniak, Tomasz

    2016-11-01

    We studied the phenomenon of chimera states in networks of non-locally coupled externally excited oscillators. Units of the considered networks are bi-stable, having two co-existing attractors of different types (chaotic and periodic). The occurrence of chimeras is discussed, and the influence of coupling radius and coupling strength on their co-existence is analyzed (including typical bifurcation scenarios). We present a statistical analysis and investigate sensitivity of the probability of observing chimeras to the initial conditions and parameter values. Due to the fact that each unit of the considered networks is individually excited, we study the influence of the excitation failure on stability of observed states. Typical transitions are shown, and changes in network's dynamics are discussed. We analyze systems of coupled van der Pol-Duffing oscillators and the Duffing ones. Described chimera states are robust as they are observed in the wide regions of parameter values, as well as in other networks of coupled forced oscillators.

  17. Solid-state amorphization of rebamipide and investigation on solubility and stability of the amorphous form.

    Science.gov (United States)

    Xiong, Xinnuo; Xu, Kailin; Li, Shanshan; Tang, Peixiao; Xiao, Ying; Li, Hui

    2017-02-01

    Solid-state amorphization of crystalline rebamipide (RBM) was realized by ball milling and spray drying. The amorphous content of samples milled for various time was quantified using X-ray powder diffraction. Crystalline RBM and three amorphous RBM obtained by milling and spray drying were characterized by morphological analysis, X-ray diffraction, thermal analysis and vibrational spectroscopy. The crystal structure of RBM was first determined by single-crystal X-ray diffraction. In addition, the solubility and dissolution rate of the RBM samples were investigated in different media. Results indicated that the solubility and the dissolution rates of spray-dried RBM-PVP in different media were highly improved compared with crystalline RBM. The physical stabilities of the three amorphous RBM were systematically investigated, and the stability orders under different storage temperatures and levels of relative humidity (RH) were both as follows: spray dried RBM < milled RBM < spray dried RBM-PVP. A direct glass-to-crystal transformation was induced under high RH, and the transformation rate rose with increasing RH. However, amorphous RBM could stay stable at RH levels lower than 57.6% (25 °C).

  18. Comprehensive transient-state study for CARMENES NIR high-thermal stability

    Science.gov (United States)

    Becerril, Santiago; Sánchez, Miguel A.; Cárdenas, M. C.; Rabaza, Ovidio; Ramón, Alejandro; Abril, Miguel; Costillo, Luis P.; Morales, Rafael; Rodríguez, Alicia; Amado, Pedro J.

    2010-07-01

    CARMENES has been proposed as a next-generation instrument for the 3.5m Calar Alto Telescope. Its objective is finding habitable exoplanets around M dwarfs through radial velocity measurements (m/s level) in the near-infrared. Consequently, the NIR spectrograph is highly constraint regarding thermal/mechanical requirements. Indeed, the requirements used for the present study limit the thermal stability to +/-0.01K (within year period) over a working temperature of 243K in order to minimise radial velocity drifts. This can be achieved by implementing a solution based on several temperature-controlled rooms (TCR), whose smallest room encloses the vacuum vessel which houses the spectrograph's optomechanics. Nevertheless, several options have been taken into account to minimise the complexity of the thermal design: 1) Large thermal inertia of the system, where, given a thermal instability of the environment (typically, +/-0.1K), the optomechanical system remains stable within +/-0.01K in the long run; 2) Environment thermal control, where thermal stability is ensured by controlling the temperature of the environment surrounding the vacuum vessel. The present article also includes the comprehensive transient-state thermal analyses which have been implemented in order to make the best choice, as well as to give important inputs for the thermal layout of the instrument.

  19. Non-linear ultimate strength and stability limit state analysis of a wind turbine blade

    DEFF Research Database (Denmark)

    Rosemeier, Malo; Berring, Peter; Branner, Kim

    2016-01-01

    flap-wise loading has been compared with a linear response to determine the blade's resistance in the ultimate strength and stability limit states. The linear analysis revealed an unrealistic failure mechanism and failure mode. Further, it did not capture the highly non-linear response of the blade...... of an imperfection. The more realistic non-linear approaches yielded more optimistic results than the mandatory linear bifurcation analysis. Consequently, the investigated blade designed after the lesser requirements was sufficient. Using the non-linear approaches, considering inter-fibre failure as the critical...... failure mode, yielded still a significant safety margin for the designer (7–28%). The non-linear response was significantly dependent on the scaling of the imperfection. Eurocode's method of applying an imperfection appeared more realistic than the GL method. Since the considered blade withstood 135...

  20. Comprehensive transient-state study for CARMENES-NIR high thermal stability

    CERN Document Server

    Becerril, S; Cárdenas, M C; Rabaza, O; Ramón, A; Abril, M; Costillo, L P; Morales, R; Rodríguez, A; Amado, P J

    2010-01-01

    CARMENES has been proposed as a next-generation instrument for the 3.5m Calar Alto Telescope. Its objective is finding habitable exoplanets around M dwarfs through radial velocity measurements (m/s level) in the near-infrared. Consequently, the NIR spectrograph is highly constraint regarding thermal/mechanical requirements. As a first approach, the thermal stability has been limited to \\pm 0.01K (within year period) over a working temperature of 243K. This can be achieved by means of several temperature-controlled rooms. The options considered to minimise the complexity of the thermal design are here presented, as well as the transient-state thermal analyses realised to make the best choice.

  1. Stability of strange stars (SS) derived from a realistic equation of state

    CERN Document Server

    Sinha, M N; Dey, M; Ray, S; Bhowmick, S; Sinha, Monika; Dey, Jishnu; Dey, Mira; Ray, Subharthi; Bhowmick, Siddhartha

    2002-01-01

    A realistic equation of state (EOS) leads to realistic strange stars (ReSS) which are compact in the mass radius plot, close to the Schwarzchild limiting line (Dey et al 1998). Many of the observed stars fit in with this kind of compactness, irrespective of whether they are X-ray pulsars, bursters or soft $\\gamma$ repeaters or even radio pulsars. We point out that a change in the radius of a star can be small or large, when its mass is increasing and this depends on the position of a particular star on the mass radius curve. We carry out a stability analysis against radial oscillations and compare with the EOS of other strange star (SS) models. We find that the ReSS is stable and an M-R region can be identified to that effect.

  2. Effects of temperature and relative humidity on the solid-state chemical stability of ranitidine hydrochloride.

    Science.gov (United States)

    Teraoka, R; Otsuka, M; Matsuda, Y

    1993-06-01

    The chemical stability of ranitidine HCl in solution and in the solid state at various temperatures was investigated by high-performance liquid chromatography. Ranitidine HCl was unstable in lower pH buffer solutions, and the percent degradation after 72 h increased as the pH of the buffer solution was reduced. The percent degradation in the unbuffered solution increased dose dependently. The critical relative humidity (CRH) of the ranitidine HCl bulk powder was approximately 67% relative humidity (RH). The amount of water adsorbed onto the sample above the CRH was proportional to the RH level. The percent degradation of the powder below 50% RH was almost negligible because, at this level, it was a solid. The percent degradation at 60-70% RH was higher than that above 70% RH. Ranitidine HCl powder was unstable around the CRH.

  3. Effects of Time Delay on Stability of an Unstable State in a Bistable System with Correlated Noises

    Institute of Scientific and Technical Information of China (English)

    LI Chun; MEI Dong-Cheng

    2011-01-01

    @@ Effects of time delay on stability of an unstable state in a time-delayed bistable system are investigated.The analytic expression of the transition rate W(xu,τ)from unstable state xu to stable state x+ is derived.The numerical calculation results of W(xu,τ)indicate that W(xu,τ)decreases with the increasing multiplicative noise intensity, the additive noise intensi by and the strength of correlations between the multiplicative and the additive noise increase, but W(xu,τ)increases with increasing delay time.Namely, the multiplicative noise, the additive noise and the correlations between the multiplicative and the additive noises enhance the stability of the unstable state in the time-delayed bistable system but the stability is weakened by time delay.%Effects of time delay on stability of an unstable state in a time-delayed bistable system are investigated. The analytic expression of the transition rate W(xu, T) from unstable state xu to stable state x+ is derived. The numerical calculation results of W(xu, T) indicate that W(xu, T) decreases with the increasing multiplicative noise intensity, the additive noise intensity and the strength of correlations between the multiplicative and the additive noise increase, but W(xu, T) increases with increasing delay time. Namely, the multiplicative noise, the additive noise and the correlations between the multiplicative and the additive noises enhance the stability of the unstable state in the time-delayed bistable system but the stability is weakened by time delay.

  4. High stability of the hinge region in the membrane-active peptide helix of zervamicin: paramagnetic relaxation enhancement studies.

    Science.gov (United States)

    Shenkarev, Zakhar O; Paramonov, Alexander S; Balashova, Tamara A; Yakimenko, Zoya A; Baru, Michael B; Mustaeva, Leila G; Raap, Jan; Ovchinnikova, Tatyana V; Arseniev, Alexander S

    2004-12-17

    Zervamicin IIB is a 16 amino acid peptaibol that forms voltage dependent ion channels with multilevel conductance states in planar lipid bilayers and vesicular systems. Stability of the hinge region and intermolecular interactions were investigated in the N- and C-terminally spin-labelled peptide analogues. Intermolecular and intramolecular paramagnetic enhancement indicates that zervamicin behaves as a rigid helical rod in methanol solution. There are no high amplitude hinge-bending motions, and the peptaibol is monomeric up to concentration 1.5 mM. Stability of the hinge region illustrates the helix stabilising propensity of the Pro residue in membrane mimic environments and implies absence of significant conformational rearrangement due to voltage peptaibol activation.

  5. Social Media Activism and State Censorship

    NARCIS (Netherlands)

    T. Poell

    2015-01-01

    This chapter interrogates how activist social media communication in authoritarian contexts is shaped through the mutual articulation of social media user practices, business models, and technological architectures, as well as through the controlling efforts of states. It specifically focuses on soc

  6. Distributed Dynamic State Estimator, Generator Parameter Estimation and Stability Monitoring Demonstration

    Energy Technology Data Exchange (ETDEWEB)

    Meliopoulos, Sakis [Georgia Inst. of Technology, Atlanta, GA (United States); Cokkinides, George [Georgia Inst. of Technology, Atlanta, GA (United States); Fardanesh, Bruce [New York Power Authority, NY (United States); Hedrington, Clinton [U.S. Virgin Islands Water and Power Authority (WAPA), St. Croix (U.S. Virgin Islands)

    2013-12-31

    This is the final report for this project that was performed in the period: October1, 2009 to June 30, 2013. In this project, a fully distributed high-fidelity dynamic state estimator (DSE) that continuously tracks the real time dynamic model of a wide area system with update rates better than 60 times per second is achieved. The proposed technology is based on GPS-synchronized measurements but also utilizes data from all available Intelligent Electronic Devices in the system (numerical relays, digital fault recorders, digital meters, etc.). The distributed state estimator provides the real time model of the system not only the voltage phasors. The proposed system provides the infrastructure for a variety of applications and two very important applications (a) a high fidelity generating unit parameters estimation and (b) an energy function based transient stability monitoring of a wide area electric power system with predictive capability. Also the dynamic distributed state estimation results are stored (the storage scheme includes data and coincidental model) enabling an automatic reconstruction and “play back” of a system wide disturbance. This approach enables complete play back capability with fidelity equal to that of real time with the advantage of “playing back” at a user selected speed. The proposed technologies were developed and tested in the lab during the first 18 months of the project and then demonstrated on two actual systems, the USVI Water and Power Administration system and the New York Power Authority’s Blenheim-Gilboa pumped hydro plant in the last 18 months of the project. The four main thrusts of this project, mentioned above, are extremely important to the industry. The DSE with the achieved update rates (more than 60 times per second) provides a superior solution to the “grid visibility” question. The generator parameter identification method fills an important and practical need of the industry. The “energy function” based

  7. Active-Flux-Based, V/f-with-Stabilizing-Loops Versus Sensorless Vector Control of IPMSM Drives

    DEFF Research Database (Denmark)

    Moldovan, Ana; Blaabjerg, Frede; Boldea, Ion

    2011-01-01

    . By this control strategy, a fast dynamic speed response, without steady state error and without speed or current regulators, for all AC machines is obtained. The second control method is a sensorless vector control strategy which also has been implemented and tested, just for comparison.......This paper proposes two control methods for Interior Permanent Magnet Synchronous Motor (IPMSM) Drives. The first one is a V/f control with two stabilizing loops: one loop based on active flux balance for voltage magnitude correction and a second, based on speed error, with voltage phase correction...

  8. Phenotypic stability of hybrids of Gália melon in Rio Grande do Norte state, Brazil

    Directory of Open Access Journals (Sweden)

    Glauber H.S. Nunes

    2011-12-01

    Full Text Available The objectives of this study were to determine the importance of simple and complex components of the interaction genotype × environment and to evaluate the adaptability and stability of Gália melon hybrids. Nine hybrids were tested in twelve environments of Rio Grande Norte State from 2000 to 2001. The experiments were carried out in a randomized complete block design with three replications. The statistical methods of Toler and Burrows, Wricke and AMMI (Additive Main effect and Multiplicative Interaction were used to study the adaptability and stability. The complex component is responsible for most of the genotype × environment interaction for the yield and content of solids soluble of fruits. The environments associated with Mossoró and Assu municipalities are the most suitable to evaluate melon hybrids in the state. The hybrid DRG 1537 was the most likely to be grown in the Agro-industrial Complex Mossoró-Assu due to its stability, high productivity and high content of soluble solids.Os objetivos deste estudo foram determinar a importância das componentes simples e complexa da interação genótipo × ambiente e avaliar a adaptabilidade e estabilidade de híbridos de melão Gália. Nove híbridos foram testados em doze ambientes do Estado do Rio Grande Norte no período de 2000 a2001. Os experimentos foram conduzidos em blocos completos casualizados com três repetições. Os métodos estatísticos de Toler e Burrows, Wricke e AMMI (Additive Main effect and Multiplicative Interaction foram usados para estudar a adaptabilidade e estabilidade. A componente complexa é responsável pela maior parte da interação genótipo × ambiente para a produtividade e teor de sólidos solúveis dos frutos. Os ambientes associados com Mossoró e Assu são os mais adequados para a avaliação de melão híbrido. O híbrido DRG1537 é o mais promissor para o cultivo no Complexo Agro-industrial Mossoró-Assu, devido à sua estabilidade, alta

  9. Active Erk Regulates Microtubule Stability in H-ras-Transformed Cells

    Directory of Open Access Journals (Sweden)

    Rene E. Harrison

    2001-01-01

    Full Text Available Increasing evidence suggests that activated erk regulates cell functions, at least in part, by mechanisms that do not require gene transcription. Here we show that the map kinase, erk, decorates microtubules (MTs and mitotic spindles in both parental and mutant active rastransfected 10T1 /2 fibroblasts and MCF10A breast epithelial cells. Approximately 20% of total cellular erk decorated MTs in both cell lines. A greater proportion of activated erk was associated with MTs in the presence of mutant active H-ras than in parental cells. Activation of erk by the ras pathway coincided with a decrease in the stability of MT, as detected by a stability marker. The MKK1 inhibitor, PD98059 and transfection of a dominant negative MKK1 blocked ras-induced instability of MTs but did not modify the association of erk with MTs or affect MT stability of the parental cells. These results indicate that the subset of active erk kinase that associates with MTs contributes to their instability in the presence of a mutant active ras. The MT-associated subset of active erk likely contributes to the enhanced invasive and proliferative abilities of cells containing mutant active H-ras.

  10. Novel conditions on exponential stability of a class of delayed neural networks with state-dependent switching.

    Science.gov (United States)

    Zhang, Guodong; Shen, Yi

    2015-11-01

    This paper is concerned with the global exponential stability on a class of delayed neural networks with state-dependent switching. Under the novel conditions, some sufficient criteria ensuring exponential stability of the proposed system are obtained. In particular, the obtained conditions complement and improve earlier publications on conventional neural networks with continuous or discontinuous right-hand side. Numerical simulations are also presented to illustrate the effectiveness of the obtained results.

  11. Enhanced photocatalytic activity of a self-stabilized synthetic flavin anchored on a TiO2 surface.

    Science.gov (United States)

    Pandiri, Manjula; Hossain, Mohammad S; Foss, Frank W; Rajeshwar, Krishnan; Paz, Yaron

    2016-07-21

    Synthetic flavin molecules were anchored on Degussa P25 titanium dioxide (TiO2). The effect of their presence on the photocatalytic (PC) activity of TiO2 was studied. Under UV light, an increase in the degradation rate of ethanol was observed. This increase was accompanied by stabilization of the anchored flavin against self-degradation. The unprecedented stabilization effect was found also in the absence of a reducing agent such as ethanol. In contrast, under the less energetic visible light, fast degradation of the anchored flavin was observed. These rather surprising observations were attributed to the propensity for charge transport from excited flavin molecules to the semiconductor and to the role that such charge transfer may play in stabilizing the overall assembly. Anchored flavins excited by UV light to their S2, S3 electronic states were able to transfer the excited electrons to the TiO2 phase whereas anchored flavin molecules that were excited by visible light to the S1 state were less likely to transfer the photo-excited electrons and therefore were destabilized. These findings may be relevant not only to anchored flavins in general but to other functionalized photocatalysts, and may open up new vistas in the implementation of sensitizers in PC systems.

  12. Memory State-Feedback Stabilization for a Class of Time-Delay Systems with a Type of Adaptive Strategy

    Directory of Open Access Journals (Sweden)

    Lin Chai

    2013-01-01

    Full Text Available Stabilization of a class of systems with time delay is studied using adaptive control. With the help of the “error to error” technique and the separated “descriptor form” technique, the memory state-feedback controller is designed. The adaptive controller designed can guarantee asymptotical stability of the closed-loop system via a suitable Lyapunov-Krasovskii functional. Some sufficient conditions are derived for the stabilization together with the linear matrix inequality (LMI design approach. Finally, the effectiveness of the proposed control design methodology is demonstrated in numerical simulations.

  13. Finite-size-induced stability of a permanent magnet levitating over a superconductor in the Meissner state

    Science.gov (United States)

    Perez-Diaz, Jose Luis; Garcia-Prada, Juan Carlos

    2007-10-01

    The force between a magnetic dipole and a finite superconductor in the Meissner state (Hstability. The finiteness of a piece of superconductor therefore suffices to explain a stability for the levitation of a magnet over it or even the suspension of one of them under the other one. This does not contradict the existence of flux penetration. However, this makes the flux penetration not necessary to explain both stability and attractiveness, as has been assumed until now.

  14. Spin-state dependent radical stabilization in nitrenes: the unusually small singlet-triplet splitting in 2-furanylnitrene.

    Science.gov (United States)

    Wenthold, Paul G

    2012-01-06

    Geometries and energies of the triplet and singlet states of 2-furanylnitrene and 3-furanylnitrene have been calculated by using spin-flip coupled-cluster methods. Calculations with triple-ζ basis sets predict a singlet-triplet splitting of 10.9 kcal/mol for 2-furanylnitrene, 4.5 kcal/mol smaller than that in phenylnitrene. In contrast, the singlet-triplet splitting in 3-furanylnitrene is computed to be 1.9 kcal/mol larger than that in phenylnitrene. The differences in the singlet-triplet splittings for the furanylnitrenes are attributed to the differences in the radical stabilizing abilities of the 2-furanyl- and 3-furanyl-groups compared to a phenyl ring. Comparison of the singlet-triplet splittings of more than 20 substituted aromatic nitrenes and the radical stabilizing ability of the aromatic systems reveals a high degree of correlation between the singlet-triplet splitting and the radical stabilizing ability, indicating that singlet states of aromatic nitrenes are preferentially stabilized by radical stabilizing substituents. The preferential stabilization of the singlet states is attributed to the decrease in electron pair repulsion resulting from increased delocalization of the radical electron.

  15. UV and visible light active aqueous titanium dioxide colloids stabilized by surfactants.

    Science.gov (United States)

    Pacia, Michał; Warszyński, Piotr; Macyk, Wojciech

    2014-09-07

    Attempts to increase the stability of photocatalytically active nanodispersions of titanium dioxide over a wide range of pH (3-10) were undertaken. Polyethylene glycols (PEGs) with different molecular weights and polyoxyethylenesorbitan monooleate (Tween® 80) were tested as stabilizing agents of TiO2 nanoparticles. The results of DLS measurements proved the stabilizing effect of Tween® 80 while the systems involving PEGs, independently of the polymer concentration, showed a tendency to form aggregates in neutral solutions. The colloids stabilized with Tween® 80 were photosensitized with 2,3-naphthalenediol (nd) or 2-hydroxy-3-naphthoic acid (hn) or catechol (cat). The photocatalytic activity of such colloids has been assessed in an azure B degradation reaction using both UV and visible light. The nd@TiO2 + Tween colloid appeared particularly photoactive upon visible light irradiation. Moreover, the comparison of activities of nd@TiO2 + Tween and TiO2 + Tween revealed a significantly better performance of the former nanodispersion, independently of the irradiation conditions (UV or visible light). This effect has been explained by different structures of micelles formed in the case of TiO2 and nd@TiO2 stabilized with Tween® 80.

  16. Stability of silanols and grafted alkylsilane monolayers on plasma-activated mica surfaces.

    Science.gov (United States)

    Liberelle, Benoît; Banquy, Xavier; Giasson, Suzanne

    2008-04-01

    We investigated the effect of physical and chemical modifications of mica surfaces induced by water vapor-based plasma treatments on the stability of silanols and grafted alkylsilane monolayers. The plasma-activated substrates were characterized using XPS, TOF-SIMS, and contact angle measurements. They revealed a large surface coverage of silanol groups (Si-OH) and a loss of aluminum atoms compared to freshly cleaved mica surfaces. The stability of plasma-induced silanol groups was investigated by contact angle measurements using ethylene glycol as a probe liquid. The Si-OH surface coverage decreased rapidly under vacuum or thermal treatment to give rise to hydrophobic dehydrated surfaces. The stability of end-grafted monofunctionalized n-alkylsilanes was investigated in different solvents and at different pH using water contact angle measurements. The degrafting of alkylsilanes from the activated mica was promoted in acidic aqueous solutions. This detachment was associated with the hydrolysis of covalent bonds between the alkylsilanes and the mica surface. The monolayer stability was enhanced by increasing the length of the alkyl chains that probably act as a hydrophobic protective layer against hydrolysis reactions. Stable alkylsilane monolayers in water with pH greater than 5.5 were obtained on mica surfaces activated at low plasma pressure. We attributed this stability to the loss of surface Al atoms induced by the plasma treatment.

  17. Antibacterial Activity of DNA-Stabilized Silver Nanoclusters Tuned by Oligonucleotide Sequence.

    Science.gov (United States)

    Javani, Siamak; Lorca, Romina; Latorre, Alfonso; Flors, Cristina; Cortajarena, Aitziber L; Somoza, Álvaro

    2016-04-27

    Silver nanoclusters (AgNCs) stabilized by DNA are promising materials with tunable fluorescent properties, which have been employed in a plethora of sensing systems. In this report, we explore their antimicrobial properties in Gram-positive and Gram-negative bacteria. After testing 9 oligonucleotides with different sequence and length, we found that the antibacterial activity depends on the sequence of the oligonucleotide employed. The sequences tested yielded fluorescent AgNCs, which can be grouped in blue, yellow, and red emitters. Interestingly, blue emitters yielded poor antibacterial activity, whereas yellow and red emitters afforded an activity similar to silver nitrate. Furthermore, structural studies using circular dichroism indicate the formation of complexes with different stability and structure, which might be one of the factors that modulate their activity. Finally, we prepared a trimeric structure containing the sequence that afforded the best antimicrobial activity, which inhibited the growth of Gram-positive and negative bacteria in the submicromolar range.

  18. Postural stability of older female Scottish country dancers in comparison with physically active controls.

    Science.gov (United States)

    Dewhurst, Susan; Peacock, Leslie; Bampouras, Theodoros M

    2015-01-01

    Physical activity assists older individuals' functional ability and postural stability. Recently, Scottish country dance (SCD) was reported as being a beneficial form of physical activity for functional ability in older females. This study aims to examine the effect of SCD on postural stability. Scottish country dancers (n = 20) were compared with physically active controls (n = 33) for static postural sway measured on a force platform. The Romberg and Tandem stances were used under 'eyes open' and 'eyes closed' conditions. Ninety-five percent ellipse area and sway velocity were calculated from the center of pressure displacement. Ninety-five percent ellipse area was the same for both groups in all tests. The control group had greater sway velocity for all tests (P < .01) except Tandem eyes closed. SCD participation resulted in similar postural sway as participation in other physical activities, however nondancers may need a greater amount of regulatory activity to maintain balance.

  19. Influence of reactive oxygen species on the enzyme stability and activity in the presence of ionic liquids.

    Directory of Open Access Journals (Sweden)

    Pankaj Attri

    Full Text Available In this paper, we have examined the effect of ammonium and imidazolium based ionic liquids (ILs on the stability and activity of proteolytic enzyme α-chymotrypsin (CT in the presence of cold atmospheric pressure plasma jet (APPJ. The present work aims to illustrate the state of art implementing the combined action of ILs and APPJ on the enzyme stability and activity. Our circular dichroism (CD, fluorescence and enzyme activity results of CT have revealed that buffer and all studied ILs {triethylammonium hydrogen sulphate (TEAS from ammonium family and 1-butyl-3-methyl imidazolium chloride ([Bmim][Cl], 1-methylimidazolium chloride ([Mim][Cl] from imidazolium family} are notable to act as protective agents against the deleterious action of the APPJ, except triethylammonium dihydrogen phosphate (TEAP ammonium IL. However, TEAP attenuates strongly the deleterious action of reactive oxygen species (ROS created by APPJ on native structure of CT. Further, TEAP is able to retain the enzymatic activity after APPJ exposure which is absent in all the other systems.This study provides the first combined effect of APPJ and ILs on biomolecules that may generate many theoretical and experimental opportunities. Through this methodology, we can utilise both enzyme and plasma simultaneously without affecting the enzyme structure and activity on the material surface; which can prove to be applicable in various fields.

  20. Enzyme Stability and Activity in Non-Aqueous Reaction Systems: A Mini Review

    Directory of Open Access Journals (Sweden)

    Shihui Wang

    2016-02-01

    Full Text Available Enormous interest in biocatalysis in non-aqueous phase has recently been triggered due to the merits of good enantioselectivity, reverse thermodynamic equilibrium, and no water-dependent side reactions. It has been demonstrated that enzyme has high activity and stability in non-aqueous media, and the variation of enzyme activity is attributed to its conformational modifications. This review comprehensively addresses the stability and activity of the intact enzymes in various non-aqueous systems, such as organic solvents, ionic liquids, sub-/super-critical fluids and their combined mixtures. It has been revealed that critical factors such as Log P, functional groups and the molecular structures of the solvents define the microenvironment surrounding the enzyme molecule and affect enzyme tertiary and secondary structure, influencing enzyme catalytic properties. Therefore, it is of high importance for biocatalysis in non-aqueous media to elucidate the links between the microenvironment surrounding enzyme surface and its stability and activity. In fact, a better understanding of the correlation between different non-aqueous environments and enzyme structure, stability and activity can contribute to identifying the most suitable reaction medium for a given biotransformation.

  1. State and actuator fault estimation observer design integrated in a riderless bicycle stabilization system.

    Science.gov (United States)

    Brizuela Mendoza, Jorge Aurelio; Astorga Zaragoza, Carlos Manuel; Zavala Río, Arturo; Pattalochi, Leo; Canales Abarca, Francisco

    2016-03-01

    This paper deals with an observer design for Linear Parameter Varying (LPV) systems with high-order time-varying parameter dependency. The proposed design, considered as the main contribution of this paper, corresponds to an observer for the estimation of the actuator fault and the system state, considering measurement noise at the system outputs. The observer gains are computed by considering the extension of linear systems theory to polynomial LPV systems, in such a way that the observer reaches the characteristics of LPV systems. As a result, the actuator fault estimation is ready to be used in a Fault Tolerant Control scheme, where the estimated state with reduced noise should be used to generate the control law. The effectiveness of the proposed methodology has been tested using a riderless bicycle model with dependency on the translational velocity v, where the control objective corresponds to the system stabilization towards the upright position despite the variation of v along the closed-loop system trajectories.

  2. Modified Quasi-Steady State Model of DC System for Transient Stability Simulation under Asymmetric Faults

    Directory of Open Access Journals (Sweden)

    Jun Liu

    2015-01-01

    Full Text Available As using the classical quasi-steady state (QSS model could not be able to accurately simulate the dynamic characteristics of DC transmission and its controlling systems in electromechanical transient stability simulation, when asymmetric fault occurs in AC system, a modified quasi-steady state model (MQSS is proposed. The model firstly analyzes the calculation error induced by classical QSS model under asymmetric commutation voltage, which is mainly caused by the commutation voltage zero offset thus making inaccurate calculation of the average DC voltage and the inverter extinction advance angle. The new MQSS model calculates the average DC voltage according to the actual half-cycle voltage waveform on the DC terminal after fault occurrence, and the extinction advance angle is also derived accordingly, so as to avoid the negative effect of the asymmetric commutation voltage. Simulation experiments show that the new MQSS model proposed in this paper has higher simulation precision than the classical QSS model when asymmetric fault occurs in the AC system, by comparing both of them with the results of detailed electromagnetic transient (EMT model of the DC transmission and its controlling system.

  3. Interference stabilization of autoionizing states in molecular $N_2$ studied by time- and angular-resolved photoelectron spectroscopy

    CERN Document Server

    Eckstein, Martin; Yang, Chung-Hsin; Sansone, Giuseppe; Vrakking, Marc J J; Ivanov, Misha; Kornilov, Oleg

    2016-01-01

    An autoionizing resonance in molecular N$_2$ is excited by an ultrashort XUV pulse and probed by a subsequent weak IR pulse, which ionizes the contributing Rydberg states. Time- and angular-resolved photoelectron spectra recorded with a velocity map imaging spectrometer reveal two electronic contributions with different angular distributions. One of them has an exponential decay rate of $20\\pm5$ fs, while the other one is shorter than 10 fs. This observation is interpreted as a manifestation of interference stabilization involving the two overlapping discrete Rydberg states. A formalism of interference stabilization for molecular ionization is developed and applied to describe the autoionizing resonance. The results of calculations reveal, that the effect of the interference stabilization is facilitated by rotationally-induced couplings of electronic states with different symmetry.

  4. Comment on `Stability analysis and controller synthesis for discrete linear time-delay systems with state saturation nonlinearities'

    Science.gov (United States)

    Tadepalli, Siva Kumar; Krishna Rao Kandanvli, V.; Kar, Haranath

    2015-11-01

    A recently reported paper (Ji, X., Liu, T., Sun, Y., and Su, H. (2011), 'Stability analysis and controller synthesis for discrete linear time-delay systems with state saturation nonlinearities', International Journal of Systems Science, 42, 397-406) for the global asymptotic stability analysis and controller synthesis for a class of discrete linear time delay systems employing state saturation nonlinearities is reviewed. It is claimed in Ji, Liu, Sun and Su (2011) that a previous approach by Kandanvli and Kar (Kandanvli, V.K.R and Kar, H. (2009), 'Robust stability of discrete-time state-delayed systems with saturation nonlinearities: Linear matrix inequality approach', Signal Processing, 89, 161-173) is recovered from their approach as a special case. It is shown that this claim is not justified.

  5. STABILITY OF THE PHOTON INDICES IN Z-SOURCE GX 340+0 FOR SPECTRAL STATES

    Energy Technology Data Exchange (ETDEWEB)

    Seifina, Elena [Moscow State University/Sternberg Astronomical Institute, Universitetsky Prospect 13, Moscow 119992 (Russian Federation); Titarchuk, Lev; Frontera, Filippo, E-mail: seif@sai.msu.ru, E-mail: titarchuk@fe.infn.it, E-mail: lev@milkyway.gsfc.nasa.gov, E-mail: frontera@fe.infn.it [Dipartimento di Fisica, Universita di Ferrara, Via Saragat 1, I-44122 Ferrara (Italy)

    2013-03-20

    We show an analysis of the spectral and timing properties of X-ray radiation from Z-source GX 340+0 during its evolution when the electron temperature of the transition layer (TL) kT{sub e} monotonically decreases from 21 to 3 keV. We analyze episodes observed with BeppoSAX and RXTE. We reveal that the X-ray broadband energy spectra during all spectral states can be reproduced by a physical model composed of a soft Blackbody component and two Comptonized components (both due to the presence of the TL that upscatters both seed photons of T{sub s1} {approx}< 1 keV coming from the disk (first component Comptb1), and seed photons of temperature T{sub s2} {approx}< 1.5 keV coming from the neutron star (second component Comptb2) and the iron-line (Gaussian) component. Spectral analysis using this model indicates that the photon power-law indices {Gamma}{sub com1} and {Gamma}{sub com2} of the Comptonized components are almost constant, {Gamma}{sub com1} and {Gamma}{sub com2} {approx} 2 when kT{sub e} changes from 3 to 21 keV along the Z-track. We interpret the detected quasi-stability of the indices of Comptonized components to be near a value of 2. Furthermore, this index stability now found for the Comptonized spectral components of Z-source GX 340+0 is similar to that previously established in the atoll sources 4U 1728-34 and GX 3+1, and earlier proposed for a number of X-ray neutron stars (NSs). This behavior of NSs both for atoll and Z-sources is essentially different from that observed in black hole binaries where {Gamma}{sub com} increases during a spectral evolution from the low state to the high state and ultimately saturates at a high mass accretion rate.

  6. Gyrase-dependent stabilization of pSC101 plasmid inheritance by transcriptionally active promoters.

    Science.gov (United States)

    Beaucage, S L; Miller, C A; Cohen, S N

    1991-09-01

    The pSC101 plasmid encodes a cis-acting genetic locus termed par that ensures the stable inheritance of plasmids in a population of dividing cells. In the absence of selection, par-defective plasmids are lost rapidly from the bacterial population. We report here that the stability of par-deleted pSC101 derivatives is restored by introducing certain adventitious bacterial promoters onto the plasmid. Stabilization requires active transcription from the inserted promoter and is affected by the site and orientation of the insertion, the length of the nascent transcript and DNA gyrase activity. While a promotor-associated overall increase in negative superhelicity of plasmid DNA was observed, stabilized inheritance appeared to be dependent on localized rather than generalized supercoiling. Our demonstration that promoter-induced DNA supercoiling can mimic the effects of the pSC101 par locus provides evidence that the previously reported superhelicity-generating effects of par are intrinsic to its function.

  7. A Review of Active Yaw Control System for Vehicle Handling and Stability Enhancement

    Directory of Open Access Journals (Sweden)

    M. K. Aripin

    2014-01-01

    Full Text Available Yaw stability control system plays a significant role in vehicle lateral dynamics in order to improve the vehicle handling and stability performances. However, not many researches have been focused on the transient performances improvement of vehicle yaw rate and sideslip tracking control. This paper reviews the vital elements for control system design of an active yaw stability control system; the vehicle dynamic models, control objectives, active chassis control, and control strategies with the focus on identifying suitable criteria for improved transient performances. Each element is discussed and compared in terms of their underlying theory, strengths, weaknesses, and applicability. Based on this, we conclude that the sliding mode control with nonlinear sliding surface based on composite nonlinear feedback is a potential control strategy for improving the transient performances of yaw rate and sideslip tracking control.

  8. Evaluation of Membrane Stabilizing Activity, Total Phenolic Content, Brine Shrimp Lethality Bioassay, Thrombolytic and Antimicrobial Activities of Tagetes patula L.

    Directory of Open Access Journals (Sweden)

    Md. Ruhul Kuddus

    2012-11-01

    Full Text Available The methanol extract of leaf of Tagetes patula L. as well as its n-hexane, carbon tetrachloride, chloroform and aqueous soluble partitionates were subjected to screening for total phenolic content, brine shrimp lethality, membrane stabilizing, thrombolytic and antimicrobial activity. The membrane stabilizing activity was assessed by hypotonic solution-and heat-induced methods and was compared with acetyl salicylic acid. In the present studies, the n-hexane soluble fraction demonstrated strong membrane stabilizing activity in both hypotonic solution-and heat-induced methods with 44.48% and 42.68% inhibition of haemolysis, respectively. The total phenolic content was also determined and expressed in gallic acid equivalent. In brine shrimp bioassay, the crude methanol extract of leaf showed strong cytotoxic activity with LC50 value of 8.58 μg/ml compared to that of 0.451 μg/ml exhibited by standard vincristine sulphate. During assay for thrombolytic activity, the n-hexane soluble fraction revealed 43.7% lysis of clot while standard streptokinase and water, used as positive and negative controls, demonstrated 65.8% and 3.62% lysis of clot, respectively. In antimicrobial assay by disc diffusion method, all the samples exhibited moderate to significant antimicrobial activity (zone of inhibition = 9.0-22.0 mm against all the test organisms. Among all the samples, the carbon tetrachloride soluble fraction displayed strong antimicrobial activity against Escherichia coli (22.0 mm.

  9. State observer-based sliding mode control for semi-active hydro-pneumatic suspension

    Science.gov (United States)

    Ren, Hongbin; Chen, Sizhong; Zhao, Yuzhuang; Liu, Gang; Yang, Lin

    2016-02-01

    This paper proposes an improved virtual reference model for semi-active suspension to coordinate the vehicle ride comfort and handling stability. The reference model combines the virtues of sky-hook with ground-hook control logic, and the hybrid coefficient is tuned according to the longitudinal and lateral acceleration so as to improve the vehicle stability especially in high-speed condition. Suspension state observer based on unscented Kalman filter is designed. A sliding mode controller (SMC) is developed to track the states of the reference model. The stability of the SMC strategy is proven by means of Lyapunov function taking into account the nonlinear damper characteristics and sprung mass variation of the vehicle. Finally, the performance of the controller is demonstrated under three typical working conditions: the random road excitation, speed bump road and sharp acceleration and braking. The simulation results indicated that, compared with the traditional passive suspension, the proposed control algorithm can offer a better coordination between vehicle ride comfort and handling stability. This approach provides a viable alternative to costlier active suspension control systems for commercial vehicles.

  10. Electromyographic activity of selected trunk muscles during stabilization exercises using a gym ball.

    Science.gov (United States)

    Mori, A

    2004-01-01

    Trunk stabilization is very important for the injured lower back. The use of a gym ball, the surface of which is labile, is becoming more popular for strengthening the trunk muscles and challenging the motor control system in trunk stabilization exercises. However, little is known about the activity of the trunk muscles during such exercises. The purpose of this study was to compare the electromyographic (EMG) activity of the trunk muscles during seven stabilization exercises using a gym ball. Eleven healthy men (19.9 +/- 1.8 years old) without low back pain volunteered to participate in the study. Bipolar surface electrodes were attached to the right side of the upper and lower rectus abdominis, the obliquus externus abdominis and the upper and lower back extensor muscles. EMG signals were recorded during seven types of stabilization exercises using a gym ball and normalized to maximal voluntary contraction (% MVC). A two-way analysis of variance (ANOVA) was performed on % MVC from each task for each of the five trunk muscle sites (p gym ball and toes on the floor in prone position, resulted in the highest activity of all abdominal muscles, and an exercise of the lifting the gym ball up, holding it actively between both legs with both knees flexed in supine position resulted in the lowest. Lifting up of the pelvis in a bridged position exercise, supporting the head with the gym ball and with the feet on the floor in supine position, resulted in higher muscle activity of the back extensor muscles than another exercise. It is very important for physical therapists to make clear the purpose of the trunk stabilization exercises, because different kinds of exercises with the gym ball demand various levels of muscular activity and use of various parts of the trunk muscles.

  11. Further results on global state feedback stabilization of high-order nonlinear systems with time-varying delays.

    Science.gov (United States)

    Gao, Fangzheng; Wu, Yuqiang

    2015-03-01

    This paper considers the problem of global stabilization by state feedback for a class of high-order nonlinear systems with time-varying delays. Comparing with the existing relevant literature, the systems under investigation allow more uncertainties, to which the existing control methods are inapplicable. By introducing sign function and necessarily modifying the method of adding a power integrator, a state feedback controller is successfully constructed to preserve the equilibrium at the origin and guarantee the global asymptotic stability of the resulting closed-loop system. Finally, two simulation examples are provided to illustrate the effectiveness of the proposed approach.

  12. Application of the stabilization method to the molecular states of LiHeT : Energies and radial couplings

    Energy Technology Data Exchange (ETDEWEB)

    Macias, A.; Mendizabal, R.; Pelayo, F.; Riera, A.; Yaez, M.

    1986-01-01

    We have used the stabilization method to perform calculations on autoionizing states of the LiHeT system which are involved in LiT +He collisions. The molecular energies and radial couplings are calculated with use of programs developed at our laboratory. For both short and large internuclear distances, the stabilization treatment is complemented by block-diagonalization techniques. Our calculations allow us to draw conclusions on the conditions under which these methods can be used to calculate energy positions and radial couplings for states that lie in an ionization continuum.

  13. Influence of different carbon nanostructures on the electrocatalytic activity and stability of Pt supported electrocatalysts

    DEFF Research Database (Denmark)

    Stamatin, Serban Nicolae; Borghei, Maryam; Andersen, Shuang Ma;

    2014-01-01

    Commercially available graphitized carbon nanofibers and multi-walled carbon nanotubes, two carbon materials with very different structure, have been functionalized in a nitric–sulfuric acid mixture. Further on, the materials have been platinized by a microwave assisted polyol method. The relative...... that the functionalization improves the stability for multi-walled carbon nanotubes, at the cost of decreased activity....

  14. Design of a robot for in-pipe inspection using omnidirectional wheels and active stabilization

    NARCIS (Netherlands)

    Dertien, Edwin; Mozaffari Foumashi, Mohammad; Pulles, Kees; Stramigioli, Stefano

    2014-01-01

    This paper discusses the design of a vehicle for in-pipe inspection using omnidirectional wheels and active stabilizing control. A novel propulsion mechanism is discussed using omnidirectional wheels (or omni-wheels) is presented which allows direct control of the orientation in the pipe. This paper

  15. Cellulase variants with improved expression, activity and stability, and use thereof

    Energy Technology Data Exchange (ETDEWEB)

    Aehle, Wolfgang; Bott, Richard R.; Bower, Benjamin S.; Caspi, Jonathan; Goedegebuur, Frits; Hommes, Ronaldus Wilhelmus Joannes; Kaper, Thijs; Kelemen, Bradley R.; Kralj, Slavko; Van Lieshout, Johannes Franciscus Thomas; Nikolaev, Igor; Wallace, Louise; Van Stigt Thans, Sander; Vogtentanz, Gudrun; Sandgren, Mats

    2016-12-20

    The present disclosure relates to cellulase variants. In particular the present disclosure relates to cellulase variants having improved expression, activity and/or stability. Also described are nucleic acids encoding the cellulase variants, compositions comprising the cellulase variants, and methods of use thereof.

  16. Dietary fiber stabilizes blood glucose and insulin levels and reduces physical activity in sows (Sus scrofa)

    NARCIS (Netherlands)

    Leeuw, de J.A.; Jongbloed, A.W.; Verstegen, M.W.A.

    2004-01-01

    The aim of this study was to test whether a diet with a high level of fermentable dietary fiber can stabilize interprandial blood glucose and insulin levels, prevent declines below basal levels, and reduce physical activity in limited-fed breeding sows. Stable levels of glucose and insulin may preve

  17. Habit in the physical activity domain: integration with intention stability and action control

    NARCIS (Netherlands)

    Rhodes, R.E.; de Bruijn, G.J.; Matheson, D.

    2010-01-01

    The purpose of this study was to explore the role of habit in predicting physical activity with the theory of planned behavior (TPB). The study extended previous research by (a) including a measure of temporal intention stability in the regression equation, and (b) unpacking the intention x behavior

  18. An active damper for stabilizing power-electronics-based AC systems

    DEFF Research Database (Denmark)

    Wang, Xiongfei; Blaabjerg, Frede; Liserre, Marco

    2014-01-01

    The interactions among the parallel grid-connected converters coupled through the grid impedance tend to result in stability and power quality problems. To address them, this paper proposes an active damper based on a high bandwidth power electronics converter. The general idea behind this propos...

  19. An active damper for stabilizing power electronics-based AC systems

    DEFF Research Database (Denmark)

    Wang, Xiongfei; Blaabjerg, Frede; Liserre, Marco

    2013-01-01

    The mutual interactions between the parallel grid-connected converters coupled through the grid impedance tend to result in a number of stability and power quality challenges. To address them, this paper proposes an active damper concept based on a low-power, high-bandwidth power converter. The b...

  20. The Broadening of Activities in the Financial System : Implications for Financial Stability and Regulation

    NARCIS (Netherlands)

    Wagner, W.B.

    2006-01-01

    Conglomeration and consolidation in the financial system broaden the activities financial institutions are undertaking and cause them to become more homogenous.Although resulting diversification gains make each institution appear less risky, we argue that financial stability may not improve as total

  1. Dietary fiber stabilizes blood glucose and insulin levels and reduces physical activity in sows (Sus scrofa)

    NARCIS (Netherlands)

    Leeuw, de J.A.; Jongbloed, A.W.; Verstegen, M.W.A.

    2004-01-01

    The aim of this study was to test whether a diet with a high level of fermentable dietary fiber can stabilize interprandial blood glucose and insulin levels, prevent declines below basal levels, and reduce physical activity in limited-fed breeding sows. Stable levels of glucose and insulin may preve

  2. Effect of active arm swing to local dynamic stability during walking.

    Science.gov (United States)

    Wu, Yu; Li, Yue; Liu, An-Min; Xiao, Fei; Wang, Yin-Zhi; Hu, Fei; Chen, Jin-Ling; Dai, Ke-Rong; Gu, Dong-Yun

    2016-02-01

    Arm swing is an essential component in regulating dynamic stability of the whole body during walking, while the contribution of active arm swing to local dynamic stability of different motion segments remains unclear. This study investigated the effects of arm swing under natural arm swing condition and active arm swing condition on local dynamic stability and gait variability of the trunk segments (C7 and T10 joint) and lower extremity joints (hip, knee and ankle joint). The local divergence exponents (λs) and mean standard deviation over strides (MeanSD) of 24 young healthy adults were calculated while they were walking on treadmill with two arm swing conditions at their preferred walking speed (PWS). We found that in medial-lateral direction, both λs and MeanSD values of the trunk segments (C7 and T10 joint) in active arm swing condition were significantly lower than those in natural arm swing condition (pknee and ankle joint) was found between two arm swing conditions (p>0.05, respectively). In anterior-posterior and vertical direction, neither λs nor MeanSD values of all body segments showed significant difference between two arm swing conditions (p>0.05, respectively). These findings indicate that active arm swing may help to improve the local dynamic stability of the trunk segments in medial-lateral direction.

  3. Nanocaged enzymes with enhanced catalytic activity and increased stability against protease digestion.

    Science.gov (United States)

    Zhao, Zhao; Fu, Jinglin; Dhakal, Soma; Johnson-Buck, Alexander; Liu, Minghui; Zhang, Ting; Woodbury, Neal W; Liu, Yan; Walter, Nils G; Yan, Hao

    2016-02-10

    Cells routinely compartmentalize enzymes for enhanced efficiency of their metabolic pathways. Here we report a general approach to construct DNA nanocaged enzymes for enhancing catalytic activity and stability. Nanocaged enzymes are realized by self-assembly into DNA nanocages with well-controlled stoichiometry and architecture that enabled a systematic study of the impact of both encapsulation and proximal polyanionic surfaces on a set of common metabolic enzymes. Activity assays at both bulk and single-molecule levels demonstrate increased substrate turnover numbers for DNA nanocage-encapsulated enzymes. Unexpectedly, we observe a significant inverse correlation between the size of a protein and its activity enhancement. This effect is consistent with a model wherein distal polyanionic surfaces of the nanocage enhance the stability of active enzyme conformations through the action of a strongly bound hydration layer. We further show that DNA nanocages protect encapsulated enzymes against proteases, demonstrating their practical utility in functional biomaterials and biotechnology.

  4. The study of the antimicrobial activity of colloidal solutions of silver nanoparticles prepared using food stabilizers.

    Science.gov (United States)

    Balandin, G V; Suvorov, O A; Shaburova, L N; Podkopaev, D O; Frolova, Yu V; Ermolaeva, G A

    2015-06-01

    The bactericidal effect of colloidal solutions of silver nanoparticles based on food stabilizers, gum arabic and chitosan, against bacterial cultures of microorganisms in food production is described. The antibacterial activity of nanotechnology products containing different amounts of stabilizing additives when applied to solid pH-neutral substrates is studied. For its evaluation a method making it possible to take into account the capability of nanoparticles to diffuse in solid media was applied. Minimal inhibitory concentrations of nanoparticles used against Erwinia herbicola, Pseudomonas fluorescens, Bacillus subtilis, Sarcina flava were found. A suggestion was made concerning the influence of the spatial structure of bacteria on the antibacterial activity of colloidal solutions of silver nanoparticles. The data concerning the antibacterial activity and minimal inhibiting concentrations of nanoparticles may be used for development of products suppressing activity of microorganisms hazardous for food production.

  5. Storage stability and antioxidant activity of complex of astaxanthin with hydroxypropyl-β-cyclodextrin.

    Science.gov (United States)

    Yuan, Chao; Du, Lei; Jin, Zhengyu; Xu, Xueming

    2013-01-02

    Storage stability of astaxanthin/hydroxypropyl-β-cyclodextrin (HPCD) inclusion complex was evaluated and which was compared with native astaxanthin. The storage stability of astaxanthin was enhanced after included in HPCD under 4 °C and 25 °C storage conditions. Antioxidant activity of astaxanthin/HPCD inclusion complex was also assayed using ascorbic acid as a control sample. The reducing power and DPPH radical scavenging activity of native astaxanthin were lower than ascorbic acid, while which of the complex were higher at low concentration for the good water solubility. The hydroxyl radical scavenging activities of astaxanthin and astaxanthin/HPCD complex far outclassed that of ascorbic acid, and the activity of the complex was a little lower than that of the native astaxanthin.

  6. Site selection of active damper for stabilizing power electronics based power distribution system

    DEFF Research Database (Denmark)

    Yoon, Changwoo; Wang, Xiongfei; Bak, Claus Leth

    2015-01-01

    Stability in the nowadays distribution power system is endangered by interaction problems that may arise from newly added power-electronics based power devices. Recently, a new concept to deal with this higher frequency instability, the active damper, has been proposed. The active damper is a power...... electronics based power device, which provides an adjustable damping capability to the power system where the voltage harmonic instability is measured. It can stabilize by adjusting the equivalent node impedance with its plug and play feature. This feature gives many degrees of freedom of its installation...... point when the system has many nodes. Therefore, this paper addresses the proper placement of an active damper in an unstable small-scale power distribution system. A time-domain model of the Cigre benchmark low-vltage network is used as a test field. The result shows the active damper location...

  7. Nanocaged enzymes with enhanced catalytic activity and increased stability against protease digestion

    Science.gov (United States)

    Zhao, Zhao; Fu, Jinglin; Dhakal, Soma; Johnson-Buck, Alexander; Liu, Minghui; Zhang, Ting; Woodbury, Neal W.; Liu, Yan; Walter, Nils G.; Yan, Hao

    2016-01-01

    Cells routinely compartmentalize enzymes for enhanced efficiency of their metabolic pathways. Here we report a general approach to construct DNA nanocaged enzymes for enhancing catalytic activity and stability. Nanocaged enzymes are realized by self-assembly into DNA nanocages with well-controlled stoichiometry and architecture that enabled a systematic study of the impact of both encapsulation and proximal polyanionic surfaces on a set of common metabolic enzymes. Activity assays at both bulk and single-molecule levels demonstrate increased substrate turnover numbers for DNA nanocage-encapsulated enzymes. Unexpectedly, we observe a significant inverse correlation between the size of a protein and its activity enhancement. This effect is consistent with a model wherein distal polyanionic surfaces of the nanocage enhance the stability of active enzyme conformations through the action of a strongly bound hydration layer. We further show that DNA nanocages protect encapsulated enzymes against proteases, demonstrating their practical utility in functional biomaterials and biotechnology. PMID:26861509

  8. The effect of trunk stabilization exercises with a swiss ball on core muscle activation in the elderly.

    Science.gov (United States)

    Kim, Seong Gil; Yong, Min Sik; Na, Sang Su

    2014-09-01

    [Purpose] The purpose of this study was to investigate the effects of trunk stabilization exercise on the muscle EMG activations related to core stability. [Subjects and Methods] Fifteen elderly people in a geriatric hospital performed trunk stabilization exercises with a Swiss ball for 20 minutes five times per week for 8 weeks. Trunk muscle activations were measured using electromyography before and after the intervention. [Results] After the intervention, the muscle activations of the rectus abdominis, erector spinae, lateral low-back (quadratus lumborum and external oblique), and gluteus medius muscles increased significantly. [Conclusion] The trunk stabilization exercise with a Swiss ball significantly increased the muscle activities of the elderly.

  9. Robust Fault-Tolerant Control for Satellite Attitude Stabilization Based on Active Disturbance Rejection Approach with Artificial Bee Colony Algorithm

    Directory of Open Access Journals (Sweden)

    Fei Song

    2014-01-01

    Full Text Available This paper proposed a robust fault-tolerant control algorithm for satellite stabilization based on active disturbance rejection approach with artificial bee colony algorithm. The actuating mechanism of attitude control system consists of three working reaction flywheels and one spare reaction flywheel. The speed measurement of reaction flywheel is adopted for fault detection. If any reaction flywheel fault is detected, the corresponding fault flywheel is isolated and the spare reaction flywheel is activated to counteract the fault effect and ensure that the satellite is working safely and reliably. The active disturbance rejection approach is employed to design the controller, which handles input information with tracking differentiator, estimates system uncertainties with extended state observer, and generates control variables by state feedback and compensation. The designed active disturbance rejection controller is robust to both internal dynamics and external disturbances. The bandwidth parameter of extended state observer is optimized by the artificial bee colony algorithm so as to improve the performance of attitude control system. A series of simulation experiment results demonstrate the performance superiorities of the proposed robust fault-tolerant control algorithm.

  10. State opportunities for action: Update of states' combined heat and power activities

    Energy Technology Data Exchange (ETDEWEB)

    Brown, Elizabeth [American Council for an Energy-Efficient Economy, Washington, D.C. (United States); Elliott, R. Neal [American Council for an Energy-Efficient Economy, Washington, D.C. (United States)

    2003-10-01

    This report updates the review of state policies with regard to CHP that the American Council for and Energy Efficient Economy completed in 2002. It describes the current activities of states with programs during the initial survey and also reviews new programs offered by the states.

  11. The thermal stability of the framework, hydroxyl groups, and active sites of faujasites

    Energy Technology Data Exchange (ETDEWEB)

    Mishin, I.V.; Kalinin, V.P.; Nissenbaum, V.D. [Zelinskii Institute of Organic Chemistry, Moscow (Russian Federation); Beyer, H.K. [Hungarian Academy of Sciences, Budapest (Hungary); Karge, H.G. [Fritz Haber Institute of the Max Planck Soceity, Berlin (Germany)

    1994-07-01

    The effect of the framework composition on the crystallinity and {open_quotes}density{close_quotes} of hydroxyl groups and the concentration of active sites is reported for hydrogen forms of Y zeolites preheated at 400 - 1000{degrees}C. The increase in the Si/Al ratios results in improved resistance of the framework atoms and hydroxyl groups to high temperatures and in enhanced thermal stability of the sites that are active in the cracking of isooctane and disproportionation of ethylbenzene.

  12. Muscle activation during four Pilates core stability exercises in quadruped position.

    Science.gov (United States)

    Queiroz, Bergson C; Cagliari, Mariana F; Amorim, César F; Sacco, Isabel C

    2010-01-01

    Queiroz BC, Cagliari MF, Amorim CF, Sacco IC. Muscle activation during four Pilates core stability exercises in quadruped position. To compare the activity of stabilizing trunk and hip muscles in 4 variations of Pilates stabilizing exercises in the quadruped position. Repeated-measures descriptive study. A biomechanics laboratory at a university school of medicine. Healthy subjects (N=19; mean age +/- SD, 31+/-5y; mean weight +/- SD, 60+/-11kg; mean height +/- SD, 166+/-9cm) experienced in Pilates routines. Surface electromyographic signals of iliocostalis, multifidus, gluteus maximus, rectus abdominis, and external and internal oblique muscles were recorded in 4 knee stretch exercises: retroverted pelvis with flexed trunk; anteverted pelvis with extended trunk; neutral pelvis with inclined trunk; and neutral pelvis with trunk parallel to the ground. Root mean square values of each muscle and exercise in both phases of hip extension and flexion, normalized by the maximal voluntary isometric contraction. The retroverted pelvis with flexed trunk position led to significantly increased external oblique and gluteus maximus muscle activation. The anteverted pelvis with trunk extension significantly increased multifidus muscle activity. The neutral pelvis position led to significantly lower activity of all muscles. Rectus abdominis muscle activation to maintain body posture was similar in all exercises and was not influenced by position of the pelvis and trunk. Variations in the pelvic and trunk positions in the knee stretch exercises change the activation pattern of the multifidus, gluteus maximus, rectus abdominis, and oblique muscles. The lower level of activation of the rectus abdominis muscle suggests that pelvic stability is maintained in the 4 exercise positions. Copyright (c) 2010 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

  13. Measurement and Modelling of Tearing Mode Stability for Steady-State Plasmas in DIII-D

    Energy Technology Data Exchange (ETDEWEB)

    Turco, F; Luce, T; Ferron, J; Petty, C; Politzer, P; Turnbull, A; Brennan, D; Murakami, M; LoDestro, L; Pearlstein, L; Casper, T; Jayakumar, R; Holcomb, C

    2009-06-23

    High-beta, quasi-steady state scenarios represent a fundamental step towards the performance required for future fusion reactors. In DIII-D steady-state scenario discharges, the normalized beta {beta}{sub N} {triple_bond} {beta}(%) {center_dot} a(m) {center_dot} B{sub T}(T)/I{sub p}(MA) (where {beta} is the ratio of the plasma pressure to the magnetic field pressure, {alpha} the plasma minor radius, B{sub T} the toroidal magnetic field and I{sub p} the plasma current) exceeds the no-wall ideal kink beta limit. The performance of this scenario is limited by the onset of an n = 1 tearing mode, which appears on the resistive evolution time-scale (1-2 s) at constant pressure and causes both a loss of confinement and a radial redistribution of the current density from which the available current drive sources cannot recover. It is routinely observed that the injection of electron cyclotron current drive (ECCD), with a broad deposition localized around {rho} {approx} 0.35, can prevent the mode from appearing. It must be noted that this is not a case of a direct stabilization due to the interaction with the mode's rational surface. These variations of the scenario are illustrated in Fig. 1, where the total injected power [neutral beam injection (NBI) and ECCD], {beta}{sub N} and the n = 1 magnetic perturbation at the outer wall are shown. In case (a), the onset of the n = 1 mode is observed when the EC power is not present or if it is stopped before the end of the high {beta} phase, whereas in case (b) the difference is pointed out between broad and narrow current deposition (with the narrow deposition case becoming unstable). The current density profile evolution and the MHD modes of several sets of significant discharges with and without ECCD (at different locations) have been analyzed, using motional Stark effect (MSE) spectroscopy measurements for the former and edge magnetic probes measurements, toroidal rotation profiles and fast electron cyclotron emission

  14. Lidocaine stabilizes the open state of CNS voltage-dependent sodium channels.

    Science.gov (United States)

    Castañeda-Castellanos, David R; Nikonorov, Igor; Kallen, Roland G; Recio-Pinto, E

    2002-03-28

    We have previously reported that the lidocaine action is different between CNS and muscle batrachotoxin-modified Na+ channels [Salazar et al., J. Gen. Physiol. 107 (1996) 743-754; Brain Res. 699 (1995) 305-314]. In this study we examined lidocaine action on CNS Na+ currents, to investigate the mechanism of lidocaine action on this channel isoform and to compare it with that proposed for muscle Na+ currents. Na+ currents were measured with the whole cell voltage clamp configuration in stably transfected cells expressing the brain alpha-subunit (type IIA) by itself (alpha-brain) or together with the brain beta(1)-subunit (alphabeta(1)-brain), or the cardiac alpha-subunit (hH1) (alpha-cardiac). Lidocaine (100 microM) produced comparable levels of Na+ current block at positive potentials and of hyperpolarizing shift of the steady-state inactivation curve in alpha-brain and alphabeta(1)-brain Na+ currents. Lidocaine accelerated the rates of activation and inactivation, produced an hyperpolarizing shift in the steady-state activation curve and increased the current magnitude at negative potentials in alpha-brain but not in alphabeta(1)-brain Na+ currents. The lidocaine action in alphabeta(1)-brain resembled that observed in alpha-cardiac Na+ currents. The lidocaine-induced increase in current magnitude at negative potentials and the hyperpolarizing shift in the steady-state activation curve of alpha-brain, are novel effects and suggest that lidocaine treatment does not always lead to current reduction/block when it interacts with Na+ channels. The data are explained by using a modified version of the model proposed by Vedantham and Cannon [J. Gen. Physiol., 113 (1999) 7-16] in which we postulate that the difference in lidocaine action between alpha-brain and alphabeta(1)-brain Na+ currents could be explained by differences in the lidocaine action on the open channel state.

  15. Stimulating Investment Development through Transformation of State Banks Activity

    Directory of Open Access Journals (Sweden)

    Kulpinska Lidiya K.

    2013-12-01

    Full Text Available The article considers significance of state corporations and state financial institutions in stimulation of investments into the fixed capital of the country and considers problems of increase of efficiency of activity of these institutions in the world and Ukraine. It considers the state sector of the developing countries through the prism of activity of state financial and non-financial corporations. It analyses theories of positive and negative features of carrying out state investing through state-owned banks. It analyses the role of state financial corporations in Ukraine, in particular, in crediting and expansion of the portfolio of acquired governmental bonds and offers ways of its increase in the context of necessity of directing funds into investment development.

  16. Moderating strain without sacrificing reactivity: design of fast and tunable noncatalyzed alkyne-azide cycloadditions via stereoelectronically controlled transition state stabilization.

    Science.gov (United States)

    Gold, Brian; Dudley, Gregory B; Alabugin, Igor V

    2013-01-30

    Recently, we have identified two strategies for selective transition state (TS) stabilization in catalyst-free azide/alkyne cycloadditions. In particular, the transition states for the formation of both 1,4- and 1,5-isomers can be stabilized via hyperconjugative assistance for the C···N bond formation, whereas the 1,5-TS can be stabilized via C-H···X H-bonding interactions. When the hyperconjugative assistance is maximized by the antiperiplanar arrangement of propargylic σ-acceptors relative to the forming bonds, the combination of these TS-stabilizing effects was predicted to lead to ~1 million fold acceleration of the cycloaddition with methyl azide. The present work investigated whether hyperconjugative assistance and H-bonding can be combined with strain activation for the design of even more reactive alkynes and whether reactivity can be turned "on demand." When stereoelectronic amplification is achieved by optimal positioning of σ-acceptors at the endocyclic bonds antiperiplanar to the breaking alkyne π-bonds, the stabilization of the bent alkyne geometry leads to a significant decrease in strain in cyclic alkynes without compromising their reactivity in alkyne-azide cycloadditions. The approach can be used in a modular fashion where the TS stabilizing effects are introduced sequentially until the desired level of reactivity is achieved. A significant increase in reactivity upon the protonation of an endocyclic NH-group suggests a new strategy for the design of click reactions triggered by a pH-change or introduction of an external Lewis acid.

  17. Active Learning of Nondeterministic Finite State Machines

    Directory of Open Access Journals (Sweden)

    Warawoot Pacharoen

    2013-01-01

    Full Text Available We consider the problem of learning nondeterministic finite state machines (NFSMs from systems where their internal structures are implicit and nondeterministic. Recently, an algorithm for inferring observable NFSMs (ONFSMs, which are the potentially learnable subclass of NFSMs, has been proposed based on the hypothesis that the complete testing assumption is satisfied. According to this assumption, with an input sequence (query, the complete set of all possible output sequences is given by the so-called Teacher, so the number of times for asking the same query is not taken into account in the algorithm. In this paper, we propose LNM*, a refined ONFSM learning algorithm that considers the amount for repeating the same query as one parameter. Unlike the previous work, our approach does not require all possible output sequences in one answer. Instead, it tries to observe the possible output sequences by asking the same query many times to the Teacher. We have proved that LNM* can infer the corresponding ONFSMs of the unknown systems when the number of tries for the same query is adequate to guarantee the complete testing assumption. Moreover, the proof shows that our algorithm will eventually terminate no matter whether the assumption is fulfilled or not. We also present the theoretical time complexity analysis of LNM*. In addition, experimental results demonstrate the practical efficiency of our approach.

  18. Active stabilization of a Michelson interferometer at an arbitrary phase with sub-nm resolution

    CERN Document Server

    Grassani, Davide; Bajoni, Daniele

    2013-01-01

    We report on the active stabilization of a Michelson interferometer at an arbitrary phase angle with a precision better than one degree at $\\lambda = 632.8$ nm, which corresponds to an optical path difference between the two arms of less than 1 nm. The stabilization method is ditherless and the error signal is computed from the spatial shift of the interference pattern of a reference laser, measured in real-time with a CCD array detector. We discuss the usefulness of this method for nanopositioning, optical interferometry and quantum optical experiments.

  19. Active stabilization of a Michelson interferometer at an arbitrary phase with subnanometer resolution

    Science.gov (United States)

    Grassani, Davide; Galli, Matteo; Bajoni, Daniele

    2014-04-01

    We report on the active stabilization of a Michelson interferometer at an arbitrary phase angle with a precision better than one degree at $\\lambda = 632.8$ nm, which corresponds to an optical path difference between the two arms of less than 1 nm. The stabilization method is ditherless and the error signal is computed from the spatial shift of the interference pattern of a reference laser, measured in real-time with a CCD array detector. We discuss the usefulness of this method for nanopositioning, optical interferometry and quantum optical experiments.

  20. Active stabilization of a Michelson interferometer at an arbitrary phase with subnanometer resolution.

    Science.gov (United States)

    Grassani, Davide; Galli, Matteo; Bajoni, Daniele

    2014-04-15

    We report on the active stabilization of a Michelson interferometer at an arbitrary phase angle with a precision better than 1° at λ=632.8  nm, which corresponds to a precision in the optical path difference between the two arms of less than 1 nm. The stabilization method is ditherless, and the error signal is computed from the spatial shift of the interference pattern of a reference laser, measured in real-time with a CCD array detector. We discuss the usefulness of this method for nanopositioning, optical interferometry, and quantum optical experiments.

  1. CMS Grid Activities in the United States

    Institute of Scientific and Technical Information of China (English)

    I.Fisk; J.Amundson; 等

    2001-01-01

    The CMS groups in the USA are actively involved in several grid-elated projects,including the DoE-funded Particle Physics Data Grid(PPDG)and the NSFfunded Grid Physics Network(GriPhyN).We present developments of :the Grid data Management Pilot (GDMP) software;a Java Analysis Studio-based prototype remote analysis service for CMS data;tools for automating job submission schemes for large scale distributed simulation and reconstruction runs for CMS;modeling and development of job scheduling schemes using the MONARC toolkit;a robust execution service for distributed processors.The deployment and use of these tools at prototype Tier1 and Tier2 computing centers in the USA is described.

  2. An active film-coating approach to enhance chemical stability of a potent drug molecule.

    Science.gov (United States)

    Desai, Divyakant; Rao, Venkatramana; Guo, Hang; Li, Danping; Stein, Daniel; Hu, Frank Y; Kiesnowski, Chris

    2012-01-01

    Peliglitazar, a PPAR α/γ agonist, was found to undergo acid as well as base catalyzed degradation. The acid catalyzed degradation led to the formation of benzylic alcohol and glycine carbamate and the base catalyzed degradation led to formation of p-hydroxyanisole and an amine degradant. In capsule formulations, the capsules with the lowest drug-loading exhibited maximum instability even at 25 °C/60% RH storage condition. Incorporation of pH-modifiers to maintain 'micro-environmental pH' acidic did not prevent the formation of the base-catalyzed degradants. Traditional dry granulated tablet formulation which is qualitatively similar to the capsule formulations showed the presence of acid-catalyzed degradants even without the presence of an acidifying agent. On the other hand, traditional wet granulated tablet formulation showed mainly base-catalyzed degradants. Stability problems of the tablet formulation were aggravated because the potent molecule required low tablet strengths which resulted in low drug to excipient ratio. To stabilize the molecule, an active film-coating approach was explored. In this approach, the drug was sprayed with the coating material onto non-active containing tablet cores. This approach of trapping the drug particles into the coating material provided tablets with satisfactory chemical stability. The stability enhancement observed in the active coating approach is attributed to the higher drug to excipient ratio in the film coat of non-reactive coating material compared to that in the traditional dry or wet granulated formulations.

  3. Effect of Alkaline Activator to Fly Ash Ratio for Geopolymer Stabilized Soil

    Directory of Open Access Journals (Sweden)

    Abdullah Muhammad Sofian

    2017-01-01

    Full Text Available Geopolymer technology have been developed and explored especially in the construction material field. However, lack of research related to geopolymer stabilized soil. In this research, the utilization of geopolymer has been investigated to stabilize the soil including the factors that affecting the geopolymerization process. Unconfined compressive test (UCT used as indicator to the strength development and hence evaluating the performance of geopolymer stabilized soil. This paper focusing on the effect of fly ash/alkaline activator ratio, Na2SiO3/NaOH ratio and curing time on geopolymer stabilized soil. A various mix design at different fly ash/alkaline activator ratio, Na2SiO3/NaOH ratio were prepared and cured for 7 and 28 days. Molarity and the percentage of geopolymer to soil were fixed at 10 molar and 8 percent respectively. Then, the UCT tests were carried out on 38mm diameter x 76mm height specimens. The highest strength obtained at the fly ash/alkaline activator ratio 2.5 and Na2SiO3/NaOH ratio 2.0 at 28 days curing time.

  4. Stability and electrocatalytic activity for oxygen reduction in WC + Ta catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Kunchan; Ishihara, Akimitsu; Mitsushima, Shigenori; Kamiya, Nobuyuki; Ota, Ken-ichiro

    2004-09-01

    Tantalum (Ta)-added tungsten carbide (WC) (WC+Ta) was examined in order to obtain surperior characteristics in stability and electrocatalytic activity for the oxygen reduction reaction (ORR) in acid electrolyte. The stability and the electrocatalytic activity of the WC+Ta catalyst were electrochemically investigated and compared to the pure WC. It was proved that the stability of the tungsten carbide was significantly increased by the addition of tantalum compared to the pure WC. The enhanced stability might be due to the formation of the W-Ta alloy in the WC+Ta catalyst. The reduction current of the WC+Ta catalyst for the ORR was observed at a potential of 0.8 V (versus dynamin hydrogen eletrode (DHE)) or less noble potential. This value was about 0.35 V higher than that of the pure WC. The enhanced electrocatalytic activity for the ORR might be caused by the presence of tungsten carbide, which exists on the surface and/or sub-surface.

  5. Transition State Charge Stabilization and Acid-Base Catalysis of mRNA Cleavage by the Endoribonuclease RelE.

    Science.gov (United States)

    Dunican, Brian F; Hiller, David A; Strobel, Scott A

    2015-12-01

    The bacterial toxin RelE is a ribosome-dependent endoribonuclease. It is part of a type II toxin-antitoxin system that contributes to antibiotic resistance and biofilm formation. During amino acid starvation, RelE cleaves mRNA in the ribosomal A-site, globally inhibiting protein translation. RelE is structurally similar to microbial RNases that employ general acid-base catalysis to facilitate RNA cleavage. The RelE active site is atypical for acid-base catalysis, in that it is enriched with positively charged residues and lacks the prototypical histidine-glutamate catalytic pair, making the mechanism of mRNA cleavage unclear. In this study, we use a single-turnover kinetic analysis to measure the effect of pH and phosphorothioate substitution on the rate constant for cleavage of mRNA by wild-type RelE and seven active-site mutants. Mutation and thio effects indicate a major role for stabilization of increased negative change in the transition state by arginine 61. The wild-type RelE cleavage rate constant is pH-independent, but the reaction catalyzed by many of the mutants is strongly dependent on pH, suggestive of general acid-base catalysis. pH-rate curves indicate that wild-type RelE operates with the pK(a) of at least one catalytic residue significantly downshifted by the local environment. Mutation of any single active-site residue is sufficient to disrupt this microenvironment and revert the shifted pK(a) back above neutrality. pH-rate curves are consistent with K54 functioning as a general base and R81 as a general acid. The capacity of RelE to effect a large pK(a) shift and facilitate a common catalytic mechanism by uncommon means furthers our understanding of other atypical enzymatic active sites.

  6. Control of gene expression during T cell activation: alternate regulation of mRNA transcription and mRNA stability

    Directory of Open Access Journals (Sweden)

    Gorospe Myriam

    2005-05-01

    Full Text Available Abstract Background Microarray technology has become highly valuable for identifying complex global changes in gene expression patterns. The effective correlation of observed changes in gene expression with shared transcription regulatory elements remains difficult to demonstrate convincingly. One reason for this difficulty may result from the intricate convergence of both transcriptional and mRNA turnover events which, together, directly influence steady-state mRNA levels. Results In order to investigate the relative contribution of gene transcription and changes in mRNA stability regulation to standard analyses of gene expression, we used two distinct microarray methods which individually measure nuclear gene transcription and changes in polyA mRNA gene expression. Gene expression profiles were obtained from both polyA mRNA (whole-cell and nuclear run-on (newly transcribed RNA across a time course of one hour following the activation of human Jurkat T cells with PMA plus ionomycin. Comparative analysis revealed that regulation of mRNA stability may account for as much as 50% of all measurements of changes in polyA mRNA in this system, as inferred by the absence of any corresponding regulation of nuclear gene transcription activity for these groups of genes. Genes which displayed dramatic elevations in both mRNA and nuclear run-on RNA were shown to be inhibited by Actinomycin D (ActD pre-treatment of cells while large numbers of genes regulated only through altered mRNA turnover (both up and down were ActD-resistant. Consistent patterns across the time course were observed for both transcribed and stability-regulated genes. Conclusion We propose that regulation of mRNA stability contributes significantly to the observed changes in gene expression in response to external stimuli, as measured by high throughput systems.

  7. Stability and Linear Quadratic Differential Games of Discrete-Time Markovian Jump Linear Systems with State-Dependent Noise

    Directory of Open Access Journals (Sweden)

    Huiying Sun

    2014-01-01

    Full Text Available We mainly consider the stability of discrete-time Markovian jump linear systems with state-dependent noise as well as its linear quadratic (LQ differential games. A necessary and sufficient condition involved with the connection between stochastic Tn-stability of Markovian jump linear systems with state-dependent noise and Lyapunov equation is proposed. And using the theory of stochastic Tn-stability, we give the optimal strategies and the optimal cost values for infinite horizon LQ stochastic differential games. It is demonstrated that the solutions of infinite horizon LQ stochastic differential games are concerned with four coupled generalized algebraic Riccati equations (GAREs. Finally, an iterative algorithm is presented to solve the four coupled GAREs and a simulation example is given to illustrate the effectiveness of it.

  8. Multi-Objective Sliding Mode Control on Vehicle Cornering Stability with Variable Gear Ratio Actuator-Based Active Front Steering Systems.

    Science.gov (United States)

    Ma, Xinbo; Wong, Pak Kin; Zhao, Jing; Xie, Zhengchao

    2016-12-28

    Active front steering (AFS) is an emerging technology to improve the vehicle cornering stability by introducing an additional small steering angle to the driver's input. This paper proposes an AFS system with a variable gear ratio steering (VGRS) actuator which is controlled by using the sliding mode control (SMC) strategy to improve the cornering stability of vehicles. In the design of an AFS system, different sensors are considered to measure the vehicle state, and the mechanism of the AFS system is also modelled in detail. Moreover, in order to improve the cornering stability of vehicles, two dependent objectives, namely sideslip angle and yaw rate, are considered together in the design of SMC strategy. By evaluating the cornering performance, Sine with Dwell and accident avoidance tests are conducted, and the simulation results indicate that the proposed SMC strategy is capable of improving the cornering stability of vehicles in practice.

  9. On the Stability of Classical Orbits of the Hydrogen Ground State in Stochastic Electrodynamics

    Directory of Open Access Journals (Sweden)

    Theodorus M. Nieuwenhuizen

    2016-04-01

    Full Text Available De la Peña 1980 and Puthoff 1987 show that circular orbits in the hydrogen problem of Stochastic Electrodynamics connect to a stable situation, where the electron neither collapses onto the nucleus nor gets expelled from the atom. Although the Cole-Zou 2003 simulations support the stability, our recent numerics always lead to self-ionisation. Here the de la Peña-Puthoff argument is extended to elliptic orbits. For very eccentric orbits with energy close to zero and angular momentum below some not-small value, there is on the average a net gain in energy for each revolution, which explains the self-ionisation. Next, an 1 / r 2 potential is added, which could stem from a dipolar deformation of the nuclear charge by the electron at its moving position. This shape retains the analytical solvability. When it is enough repulsive, the ground state of this modified hydrogen problem is predicted to be stable. The same conclusions hold for positronium.

  10. Steady states and linear stability analysis of precipitation pattern formation at geothermal hot springs

    Science.gov (United States)

    Chan, Pak Yuen; Goldenfeld, Nigel

    2007-10-01

    A dynamical theory of geophysical precipitation pattern formation is presented and applied to irreversible calcium carbonate (travertine) deposition. Specific systems studied here are the terraces and domes observed at geothermal hot springs, such as those at Yellowstone National Park, and speleothems, particularly stalactites and stalagmites. The theory couples the precipitation front dynamics with shallow water flow, including corrections for turbulent drag and curvature effects. In the absence of capillarity and with a laminar flow profile, the theory predicts a one-parameter family of steady state solutions to the moving boundary problem describing the precipitation front. These shapes match the measured shapes near the vent at the top of observed travertine domes well. Closer to the base of the dome, the solutions deviate from observations and circular symmetry is broken by a fluting pattern, which we show is associated with capillary forces causing thin film break-up. We relate our model to that recently proposed for stalactite growth, and calculate the linear stability spectrum of both travertine domes and stalactites. Lastly, we apply the theory to the problem of precipitation pattern formation arising from turbulent flow down an inclined plane and identify a linear instability that underlies scale-invariant travertine terrace formation at geothermal hot springs.

  11. Interplay between surface and surface resonance states on height selective stability of fcc Dy(111) film at nanoscale.

    Science.gov (United States)

    Liu, Xiaojie; Wang, Cai-Zhuang; Hupalo, Myron; Ho, Kai-Ming; Thiel, Patricia A; Tringides, Michael C

    2016-11-16

    Using first-principles calculations we show that face-centered cubic Dy(111) ultrathin films exhibit height selective stability. The origin of such height selection can be attributed to the interplay between the localized surface states and surface resonance states due to electron confinement effects. Such effect could be utilized to manipulate the film thickness at the atomic level to achieve desirable film properties or to control the growth of nanostructures on the thin film for various applications.

  12. The Stability, Sustained Release and Cellular Antioxidant Activity of Curcumin Nanoliposomes

    Directory of Open Access Journals (Sweden)

    Xing Chen

    2015-08-01

    Full Text Available Curcumin is a multifunctional and natural agent considered to be pharmacologically safe. However, its application in the food and medical industry is greatly limited by its poor water solubility, physicochemical instability and inadequate bioavailability. Nanoliposome encapsulation could significantly enhance the solubility and stability of curcumin. Curcumin nanoliposomes exhibited good physicochemical properties (entrapment efficiency = 57.1, particle size = 68.1 nm, polydispersity index = 0.246, and zeta potential = −3.16 mV. Compared with free curcumin, curcumin nanoliposomes exhibited good stability against alkaline pH and metal ions as well as good storage stability at 4 °C. Curcumin nanoliposomes also showed good sustained release properties. Compared with free curcumin, curcumin nanoliposomes presented an equal cellular antioxidant activity, which is mainly attributed to its lower cellular uptake as detected by fluorescence microscopy and flow cytometry. This study provide theoretical and practical guides for the further application of curcumin nanoliposomes.

  13. Encapsulation of phycocyanin-alginate for high stability and antioxidant activity

    Science.gov (United States)

    Hadiyanto; Suzery, Meiny; Setyawan, Deny; Majid, Dian; Sutanto, Heri

    2017-02-01

    The aim of this study was to obtain optimal condition of phycocyanin-alginate encapsulation, encapsulation efficiency and phycocyanin load, physicochemical properties of beads, in vitro release study, stability and antioxidant activity. The result product with alginate content 1,5% (w/v) and 2% (w/v) produced were in spherical shape than product with alginate content 2,5% (w/v) by ratio of phycocyanin 1:1. Increasing alginate content on encapsulation process will increase of encapsulation efficiency and phycocyanin load. In vitro released study showed that phycocyanin-alginate beads were more resistant in simulated gastric fluid, while rapidly release in simulated intestinal fluid. The antioxidant activity showed that phycocyanin antioxidant activity decreased after encapsulation process due to duration of storage and the possibility of a cracking which will cause reduced stability of phycocyanin.

  14. Laser frequency stabilization based on steady-state spectral-hole burning in Eu$^{3+}$:Y$_2$SiO$_5$

    CERN Document Server

    Cook, Shon; Leibrandt, David R

    2015-01-01

    We present and analyze a method of laser frequency stabilization via steady-state patterns of spectral holes in Eu$^{3+}$:Y$_2$SiO$_5$. Three regions of spectral holes are created, spaced in frequency by the ground state hyperfine splittings of $~^{151}$Eu$^{3+}$. The absorption pattern is shown not to degrade after days of laser frequency stabilization. An optical frequency comparison of a laser locked to such a steady-state spectral-hole pattern with an independent cavity-stabilized laser and a Yb optical lattice clock demonstrates a spectral-hole fractional frequency instability of $1.0\\times10^{-15}~ \\tau^{-\\frac{1}{2}}$ that averages to $8.5^{+4.8}_{-1.8}\\times10^{-17}$ at $\\tau = 73$ s. Residual amplitude modulation at the frequency of the RF drive applied to the fiber-coupled electro-optic modulator is reduced to less than $1\\times10^{-6}$ fractional amplitude modulation at $\\tau>$ 1 s by an active servo. The contribution of residual amplitude modulation to the laser frequency instability is further re...

  15. Effect of oxidation treatment on the adsorption and the stability of mercury on activated carbon

    Institute of Scientific and Technical Information of China (English)

    HU Chang-xing; ZHOU Jin-song; LUO Zhong-yang; HE Sheng; WANG Guang-kai; CEN Ke-fa

    2006-01-01

    Oxidation treatment on the adsorption and the stability of Hg on activated carbon (AC) was inrestigated. Both MnO2-AC and FeCl3-AC were produced during oxidation treatment. The measurement of modified AC's mercury adsorption capacity was conducted in a simulated coal-fired flue gas by adsorbing test apparatus. TCLP and column leaching methods were used to test the stability of mercury adsorbed on ACs. The results indicate that the oxidation treatment changed the pore structure of the AC and modified the carbon surface by creating chemical components such as MnO4-, Mn4+, O, NO3-, Fe3+, Cl-, etc. The Hg sorption capacity on MnO2-AC or FeCl3-AC was about three times higher than that of untreated carbon. In addition, the mercury control cost of each of the formers was about the half cost of the untreated carbon. The stability of Hg absorption was studied, it found that mercury adsorbed on the oxidation treated AC was not better than that of untreated carbon. It could concluded that the insoluble form of Hg is very important to the stability of mercury adsorbed on AC. This study suggests that the FeCl3-AC is the best absorbent for Hg with high adsorption capacity, better Hg adsorption stability in leaching environment, and lower cost among the three ACs tested.

  16. Effect of oxidation treatment on the adsorption and the stability of mercury on activated carbon

    Energy Technology Data Exchange (ETDEWEB)

    Hu, C.X.; Zhou, J.S.; Luo, Z.Y.; He, S.; Wang, G.K.; Cen, K.F. [Zhejiang University, Hangzhou (China)

    2006-07-01

    Oxidation treatment on the adsorption and the stability of Hg on activated carbon (AC) was investigated. Both MnO{sub 2}-AC and FeCl{sub 3}-AC were produced during oxidation treatment. The measurement of modified AC's mercury adsorption capacity was conducted in a simulated coal-fired flue gas by adsorbing test apparatus. TCLP and column leaching methods were used to test the stability of mercury adsorbed on ACs. The results indicate that the oxidation treatment changed the pore structure of the AC and modified the carbon surface by creating chemical components such as MnO{sub 4}{sup -}, Mn{sup 4+}, NO{sub 3}{sup -}, Fe{sup 3+} Cl{sup -}, etc. The Hg sorption capacity on MnO{sub 2}-AC or FeCl3-AC was about three times higher than that of untreated carbon. In addition, the mercury control cost of each of the formers was about the half cost of the untreated carbon. The stability of Hg absorption was studied. It was found that mercury adsorbed on the oxidation treated AC was not better than that of untreated carbon. It could be concluded that the insoluble form of Hg is very important to the stability of mercury adsorbed on AC. This study suggests that the FeCl3-AC is the best absorbent for Hg with high adsorption capacity, better Hg adsorption stability in leaching environment, and lower cost among the three ACs tested.

  17. On the chemical stability of post-lithiated garnet Al-stabilized Li7La3Zr2O12 solid state electrolyte thin films.

    Science.gov (United States)

    Rawlence, Michael; Garbayo, Inigo; Buecheler, Stephan; Rupp, J L M

    2016-08-21

    Garnet-based Al-doped Li7La3Zr2O12 has the potential to be used as a solid state electrolyte for future lithium microbattery architectures, due to its relatively high Li(+) conductivity and stability against Li. Through this work, a model experiment is presented in which the effect of post-lithiation on phase formation and chemical stability is studied for pulsed laser deposited Al-doped Li7La3Zr2O12 thin films on MgO substrates. We report the implications of the newly suggested post-lithiation route for films with thicknesses between 90 and 380 nm. The phase changes from cubic, to a mix of cubic and tetragonal Li7La3Zr2O12, to a cubic Li7La3Zr2O12 and La2Zr2O7 containing film is accompanied by a reduction in the degree of de-wetting as the thickness increases. This study reveals that the thicker, dense, and continuous films remain predominantly in a mixed phase containing cubic Li7La3Zr2O12 and the lithium free La2Zr2O7 phase whereas the thinner, de-wetted films exhibit improved lithium incorporation resulting in the absence of the lithium free phase. For tuning the electrical conductivity and effective use of these structures in future batteries, understanding this material system is of great importance as the chemical stability of the cubic Li7La3Zr2O12 phase in the thin film system will control its effective use. We report a conductivity of 1.2 × 10(-3) S cm(-1) at 325 °C for a 380 nm thick solid state electrolyte film on MgO for potential operation in future all solid state battery assemblies.

  18. Power system stabilization by superconducting magnetic energy storage with solid-state phase shifter

    Energy Technology Data Exchange (ETDEWEB)

    Mitani, Y.; Uranaka, T.; Tsuji, K. [Osaka Univ., Suita, Osaka (Japan). Dept. of Electrical Engineering

    1995-08-01

    In this paper, a new configuration of power system controller with a combination of superconducting magnetic energy storage and phase shifter, is proposed to improve the stability of a long distance bulk power transmission system. A power system stabilizing control scheme is also proposed. A related simulation shows that the proposed controller is effective for enhancement of power system stability independent of the location of controller in a long distance bulk power transmission system.

  19. United States-Russia: Environmental management activities, Summer 1998

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-09-01

    A Joint Coordinating Committee for Environmental Restoration and Waste Management (JCCEM) was formed between the US and Russia. This report describes the areas of research being studied under JCCEM, namely: Efficient separations; Contaminant transport and site characterization; Mixed wastes; High level waste tank remediation; Transuranic stabilization; Decontamination and decommissioning; and Emergency response. Other sections describe: Administrative framework for cooperation; Scientist exchange; Future actions; Non-JCCEM DOE-Russian activities; and JCCEM publications.

  20. Finite-time robust stabilization of uncertain delayed neural networks with discontinuous activations via delayed feedback control.

    Science.gov (United States)

    Wang, Leimin; Shen, Yi; Sheng, Yin

    2016-04-01

    This paper is concerned with the finite-time robust stabilization of delayed neural networks (DNNs) in the presence of discontinuous activations and parameter uncertainties. By using the nonsmooth analysis and control theory, a delayed controller is designed to realize the finite-time robust stabilization of DNNs with discontinuous activations and parameter uncertainties, and the upper bound of the settling time functional for stabilization is estimated. Finally, two examples are provided to demonstrate the effectiveness of the theoretical results.

  1. Activity and stability of a Rhizomucor miehei lipase in hydrophobic media.

    Science.gov (United States)

    Dellamora-Ortiz, G M; Martins, R C; Rocha, W L; Dias, A P

    1997-08-01

    The effects of detergents and organic solvents on a commercial lipase (Lipozyme) from Rhizomucor miehei were investigated. It was shown that the detergent sodium cholate is possibly an activator of the enzyme, increasing lipase activity 2.5 times (250% of the control) when the enzyme was preincubated with 7 mM cholate. Lipozyme activity was over twice as high (230% of the control) in the presence of 80 mM Tween 80 or 90 mM Tween 20 (polyoxyethylenesorbitan monolaurate), apparently through an additional emulsifying action on the substrate. Preincubation with Tween 80 (polyoxyethylenesorbitan mono-oleate) did not affect enzyme activity. In contrast, lipase activity was completely inhibited in the presence of an 8.9 mM concentration of another non-ionic detergent, Brij 58, whereas with a 16.4 mM concentration of the cationic detergent cetyltrimethylammonium bromide (CTAB), enzyme activity was reduced by 80%. Preincubation of Lipozyme with the same concentrations of Brij 58 [poly(oxyethylene)20 cetyl ether] and CTAB promoted total inactivation of the enzyme. Organic solvents had different effects on lipase activity and stability. Of the tested solvents, hexane was least deleterious to lipase activity and did not alter enzyme stability on preincubation. These results suggest that Lipozyme can be used in esterification reactions with hexane as solvent or in hydrolysis reactions with Tween 20 or Tween 80 as emulsifying agents, after pretreatment with sodium cholate.

  2. Stabilization of a raw starch digesting amylase from Aspergillus carbonarius via immobilization on activated and non-activated agarose gel.

    Science.gov (United States)

    Nwagu, Tochukwu N; Okolo, Bartho N; Aoyagi, Hideki

    2012-01-01

    Applications of raw starch digesting amylases (RSDAs) are limited due to instability, product inhibition of enzyme and contamination. RSDA from Aspergillus carbonarius was stabilized through immobilization on agarose gel by adsorption, spontaneous crosslinking and conjugation using glycidol, glutaraldehyde or polyglutaraldehyde. Effects of immobilization on kinetics, catalytic, storage and operational stability of immobilized enzyme were evaluated. Polyglutaraldehyde activated agarose RSDA (PGAg-RSDA) gave the highest immobilization yield (100%) with expressed activity of 86.7% while that of glycidol activated RSDA (GlyAg-RSDA) was 80.4%. A shift in pH from optimum of 5 for the soluble enzyme to 6 for RSDA adsorbed on agarose followed by crosslinking with glutaraldehyde (AgRSDA-CROSS) and simultaneous adsorption and crosslinking (AgRSDA-RET), and pH 7 for PGAg-RSDA was seen. PGAg-RSDA and AgRSDA-CROSS were most pH stable and retained over 82% of their activities between pH 3.5 and 9 compared to 59% for the soluble enzyme. Thermoinactivation studies showed that immobilized RSDAs with the exception of GAg-RSDA retained over 90% of their activities at 60°C for 120 min while soluble enzyme retained only 76% activity under the same condition. AgRSDA-CROSS, PGAg-RSDA, Gly-RSDA and GAg-RSDA retained approximately 100% of their activities after 30 days storage at 4°C. GlyAg-RSDA retained 99.6%, PGAg-RSDA 94%, AgRSDA-CROSS 90%, GAg-RSDA 86.5% and Ag-RSDA-RET 80% activity after 10 batch reactions. Immobilization stabilized RSDA and permits processing at higher temperatures to reduce contamination.

  3. Monitoring Affect States during Effortful Problem Solving Activities

    Science.gov (United States)

    D'Mello, Sidney K.; Lehman, Blair; Person, Natalie

    2010-01-01

    We explored the affective states that students experienced during effortful problem solving activities. We conducted a study where 41 students solved difficult analytical reasoning problems from the Law School Admission Test. Students viewed videos of their faces and screen captures and judged their emotions from a set of 14 states (basic…

  4. 34 CFR 300.814 - Other State-level activities.

    Science.gov (United States)

    2010-07-01

    ... 34 Education 2 2010-07-01 2010-07-01 false Other State-level activities. 300.814 Section 300.814 Education Regulations of the Offices of the Department of Education (Continued) OFFICE OF SPECIAL EDUCATION AND REHABILITATIVE SERVICES, DEPARTMENT OF EDUCATION ASSISTANCE TO STATES FOR THE EDUCATION...

  5. Physical activity in Georgia state parks: A pilot study

    Science.gov (United States)

    Lincoln R. Larson; Jason W. Whiting; Gary T. Green

    2012-01-01

    This pilot study assessed the role of Georgia State Parks in the promotion of physical activity among different racial/ethnic and age groups. Data were collected at three state parks in north Georgia during the summer of 2009 using two research methods: behavior observations (N=2281) and intercept surveys (N=473).

  6. Stabilization of lethal and hemolytic activities of box jellyfish (Chironex fleckeri) venom.

    Science.gov (United States)

    Comis, A; Hartwick, R F; Howden, M E

    1989-01-01

    The stability of both the lethal and hemolytic activities of box jellyfish (Chironex fleckeri) tentacle extract was assessed after various extraction procedures. Both activities were higher when no buffers or water were used during the initial extraction. Also, when the extract was first filtered through a Sep-pak C18 cartridge, the residual lethal titre, after incubation for 24 hr at room temperature, was increased 16-fold and hemolysis was increased 2.6-fold. Evidence for proteolytic activity in the extract was also obtained and monitored by size exclusion HPLC.

  7. Global Stability Analysis for Periodic Solution in Discontinuous Neural Networks with Nonlinear Growth Activations

    Directory of Open Access Journals (Sweden)

    Wu Huaiqin

    2009-01-01

    Full Text Available This paper considers a new class of additive neural networks where the neuron activations are modelled by discontinuous functions with nonlinear growth. By Leray-Schauder alternative theorem in differential inclusion theory, matrix theory, and generalized Lyapunov approach, a general result is derived which ensures the existence and global asymptotical stability of a unique periodic solution for such neural networks. The obtained results can be applied to neural networks with a broad range of activation functions assuming neither boundedness nor monotonicity, and also show that Forti's conjecture for discontinuous neural networks with nonlinear growth activations is true.

  8. Nanocrystalline brookite with enhanced stability and photocatalytic activity: influence of lanthanum(III) doping.

    Science.gov (United States)

    Perego, Céline; Wang, Yu-Heng; Durupthy, Olivier; Cassaignon, Sophie; Revel, Renaud; Jolivet, Jean-Pierre

    2012-02-01

    Metastable TiO(2) polymorphs are more promising materials than rutile for specific applications such as photocatalysis or catalysis support. This was clearly demonstrated for the anatase phase but still under consideration for brookite, which is difficult to obtain as pure phase. Moreover, the surface doping of anatase with lanthanum ions is known to both increase the thermal stability of the metastable phase and improve its photocatalytic activity. In this study, TiO(2) nanoparticles of almost only the brookite structure were prepared by a simple sol-gel procedure in aqueous solution. The nanoparticles were then doped with lanthanum(III) ions. The thermal stability of the nanoparticles was analyzed by X-ray diffraction and kinetic models were successfully applied to quantify phases evolutions. The presence of surface-sorbed lanthanum(III) ions increased the phase stability of at least 200 °C and this temperature shift was attributed to the selective phase stabilization of metastable TiO(2) polymorphs. Moreover, the combination of the surface doping ions and the thermal treatment induces the vanishing of the secondary anatase phase, and the photocatalytic tests on the doped brookite nanoparticles demonstrated that the doping increased photocatalytic activity and that the extent depended on the duration of the sintering treatment.

  9. Adaptive Neural-Sliding Mode Control of Active Suspension System for Camera Stabilization

    Directory of Open Access Journals (Sweden)

    Feng Zhao

    2015-01-01

    Full Text Available The camera always suffers from image instability on the moving vehicle due to the unintentional vibrations caused by road roughness. This paper presents a novel adaptive neural network based on sliding mode control strategy to stabilize the image captured area of the camera. The purpose is to suppress vertical displacement of sprung mass with the application of active suspension system. Since the active suspension system has nonlinear and time varying characteristics, adaptive neural network (ANN is proposed to make the controller robustness against systematic uncertainties, which release the model-based requirement of the sliding model control, and the weighting matrix is adjusted online according to Lyapunov function. The control system consists of two loops. The outer loop is a position controller designed with sliding mode strategy, while the PID controller in the inner loop is to track the desired force. The closed loop stability and asymptotic convergence performance can be guaranteed on the basis of the Lyapunov stability theory. Finally, the simulation results show that the employed controller effectively suppresses the vibration of the camera and enhances the stabilization of the entire camera, where different excitations are considered to validate the system performance.

  10. Modeling the effect of water activity and storage temperature on chemical stability of coffee brews.

    Science.gov (United States)

    Manzocco, Lara; Nicoli, Maria Cristina

    2007-08-08

    This work was addressed to study the chemical stability of coffee brew derivatives as a function of water activity (aw) and storage temperature. To this purpose, coffee brew was freeze-dried, equilibrated at increasing aw values, and stored for up to 10 months at different temperatures from -30 to 60 degrees C. The chemical stability of the samples was assessed by measuring H3O+ formation during storage. Independently of storage temperature, the rate of H3O+ formation was considerably low only when aw was reduced below 0.5 (94% w/w). Beyond this critical boundary, the rate increased, reaching a maximum value at ca. 0.8 aw (78% w/w). Further hydration up to the aw of the freshly prepared beverage significantly increased chemical stability. It was suggested that mechanisms other than lactones' hydrolysis, probably related to nonenzymatic browning pathways, could contribute to the observed increase in acidity during coffee staling. The temperature dependence of H3O+ formation was well-described by the Arrhenius equation in the entire aw range considered. However, aw affected the apparent activation energy and frequency factor. These effects were described by simple equations that were used to set up a modified Arrhenius equation. This model was validated by comparing experimental values, not used to generate the model, with those estimated by the model itself. The model allowed efficient prediction of the chemical stability of coffee derivatives on the basis of only the aw value and storage temperature.

  11. Metal Hydride Nanoparticles with Ultrahigh Structural Stability and Hydrogen Storage Activity Derived from Microencapsulated Nanoconfinement.

    Science.gov (United States)

    Zhang, Jiguang; Zhu, Yunfeng; Lin, Huaijun; Liu, Yana; Zhang, Yao; Li, Shenyang; Ma, Zhongliang; Li, Liquan

    2017-06-01

    Metal hydrides (MHs) have recently been designed for hydrogen sensors, switchable mirrors, rechargeable batteries, and other energy-storage and conversion-related applications. The demands of MHs, particular fast hydrogen absorption/desorption kinetics, have brought their sizes to nanoscale. However, the nanostructured MHs generally suffer from surface passivation and low aggregation-resisting structural stability upon absorption/desorption. This study reports a novel strategy named microencapsulated nanoconfinement to realize local synthesis of nano-MHs, which possess ultrahigh structural stability and superior desorption kinetics. Monodispersed Mg2 NiH4 single crystal nanoparticles (NPs) are in situ encapsulated on the surface of graphene sheets (GS) through facile gas-solid reactions. This well-defined MgO coating layer with a thickness of ≈3 nm efficiently separates the NPs from each other to prevent aggregation during hydrogen absorption/desorption cycles, leading to excellent thermal and mechanical stability. More interestingly, the MgO layer shows superior gas-selective permeability to prevent further oxidation of Mg2 NiH4 meanwhile accessible for hydrogen absorption/desorption. As a result, an extremely low activation energy (31.2 kJ mol(-1) ) for the dehydrogenation reaction is achieved. This study provides alternative insights into designing nanosized MHs with both excellent hydrogen storage activity and thermal/mechanical stability exempting surface modification by agents. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. STABILIZATION OF ACTIVE SLUDGE AFTER WASTEWATER TREATMENT CONTAMINATED BY PETROLEUM PRODUCTS

    Directory of Open Access Journals (Sweden)

    Olena Semenova

    2016-06-01

    Full Text Available Purpose: Biochemical purification of wastewater containing refined petroleum products takes place due to the oxidation of pollutants by active sludge organisms. As a result of this process the intense consumption of pollutants by active sludge and its growth occurs. Therefore, the possibility to use active sludge containing refined petroleum products after wastewater treatment requires its stabilization. Methods: In this work the oxidation by a 30% hydrogen peroxide solution was studied for its use as a stabilizer. Chemical oxidizers, including hydrogen peroxide destroy organic polymers retaining free water thus promoting water release from the structure of sludge particles. On the other hand remains of fine structured oxidized biopolymers can lead to filter clogging, that is, reduce moisture exchange of sludge. Results: The experiment was carried out to find out the correlation between the doses of hydrogen peroxide and the resistivity value of sludge filtration. Discussion: Stabilized active sludge can be used as a fuel for boiler rooms, which in its turn will reduce natural gas consumption for the enterprise needs.

  13. Stability, compatibility and microbiological activity studies of meropenem-clavulanate potassium.

    Science.gov (United States)

    Cielecka-Piontek, Judyta; Szymanowska-Powałowska, Daria; Paczkowska, Magdalena; Łysakowski, Piotr; Zalewski, Przemysław; Garbacki, Piotr

    2015-01-01

    Meropenem (MEM) and clavulanate potassium have been reported to demonstrate highly effective activity against Mycobacterium tuberculosis. There have been no reports on research into the complex of these chemotherapeutics concerning their mutually dependent stability or microbiological action on other microorganisms. Stability and compatibility studies of MEM/clavulanate potassium were conducted by using an HPLC-DAD method. The antibacterial activity of MEM/clavulanate potassium was tested in vitro against a selection of indicator bacteria strains by determining the MIC as well as analyzing the kinetics of changes in the concentrations of Pseudomonas aeruginosa, Staphylococcus aureus and Listeria monocytogenes caused by the action of MEM/clavulanate potassium. The stability and compatibility of MEM/clavulanate potassium were examined in aqua pro iniectione, 0.9% NaCl and 5% glucose at room temperature and at 5 °C. The degradation rates of MEM/clavulanate potassium depended on the type of infusion solvent used. Although in aqueous solutions of MEM/clavulanate potassium neither compound showed any mutual impact on the rate of degradation, clavulanate potassium was more labile than MEM. The synergy between these two resulted in a significantly lower value of MIC as compared to the values observed for the individual activity of either compound. The infusion solvent in which compatibility is observed between the components of the mixture MEM/clavulanate potassium is aqua pro iniectione. The complex MEM/clavulanate potassium demonstrates synergic antibacterial activity against P. aeruginosa, S. aureus and L. monocytogenes.

  14. Alkyl caffeates improve the antioxidant activity, antitumor property and oxidation stability of edible oil.

    Directory of Open Access Journals (Sweden)

    Jun Wang

    Full Text Available Caffeic acid (CA is distributed widely in nature and possesses strong antioxidant activity. However, CA has lower solubility in non-polar media, which limits its application in fat-soluble food. To increase the lipophilicity of natural antioxidant CA, a series of alkyl caffeates were synthesized and their antioxidant and antitumor activities were investigated. The antioxidant parameters, including the induction period, acid value and unsaturated fatty acid content, of the alkyl caffeates in edible oil were firstly investigated. The results indicated that alkyl caffeates had a lower DPPH IC₅₀ (14-23 µM compared to CA, dibutyl hydroxy toluene (BHT and Vitamin C (24-51 µM, and significantly inhibited four human cancer cells (SW620, SW480, SGC7901 and HepG2 with inhibition ratio of 71.4-78.0% by a MTT assay. With regard to the induction period and acid value assays, methyl and butyl caffeates had higher abilities than BHT to restrain the oxidation process and improve the stability of edible oil. The addition of ethyl caffeate to oil allowed maintenance of a higher unsaturated fatty acid methyl ester content (68.53% at high temperatures. Overall, the alkyl caffeats with short chain length (n<5 assessed better oxidative stability than those with long chain length. To date, this is the first report to the correlations among the antioxidant activity, anticancer activity and oxidative stability of alkyl caffeates.

  15. Active assignment of eigenvalues and eigen-sensitivities for robust stabilization of friction-induced vibration

    Science.gov (United States)

    Liang, Yao; Yamaura, Hiroshi; Ouyang, Huajiang

    2017-06-01

    As friction couples tangential and lateral degrees-of-freedom of a structure at contact interfaces, the resulting asymmetric dynamic system is prone to dynamic instability. Using state-feedback control, such a frictional asymmetric system can be stabilized through assigning the system desirable eigenvalues; but uncertainties in system parameters can cause assigned eigenvalues to deviate from desired locations and thus stability may be lost. This study presents a robust stabilization method that assigns both desirable eigenvalues and their sensitivities and thus render assigned eigenvalues stable and insensitive to perturbations in uncertain contact parameters (the friction coefficient, contact damping, and contact stiffness). This method utilizes receptances of the corresponding symmetric part of the asymmetric system. The optimal control input location is first determined by minimizing the Frobenius norm of the normalized eigen-sensitivity matrix. The normalized eigen-sensitivities indicate that the friction coefficient and contact stiffness intrinsically have similar crucial effects on the stability of the system. To demonstrate the application of the proposed control method, the eigen-sensitivities with respect to only the friction coefficient are assigned. A constrained over-determined least-squares problem is solved to assign both required eigenvalues and eigen-sensitivities. Numerical examples validate the effectiveness of the proposed robust control scheme by Monte Carlo simulations.

  16. High Telomerase Activity Correlates with the Stabilities of Genome and DNA Ploidy in Renal Cell Carcinoma

    Directory of Open Access Journals (Sweden)

    Hideki Izumi

    2002-01-01

    Full Text Available Malignant tumors have telomerase activity, which is thought to play a critical role in tumor growth. However, the relation between telomerase activity and genomic DNA status in tumor cells is poorly understood. In the present study, we examined telomerase activity in 13 clear cell type renal cell carcinomas (CRCCs with similar clinicopathologic features by telomeric repeat amplification protocol assay (TRAP. Based on TRAP assay results, we divided the CRCCs into two groups: a high telomerase activity group and a low/no telomerase activity group. We then analyzed genomic aberration, DNA ploidy, and telomere status in these two groups by comparative genomic hybridization (CGH, laser scanning cytometry (LSC, and telomere-specific fluorescence in situ hybridization (T-FISH, respectively. CGH showed the high telomerase activity group to have fewer genomic changes than the low/no telomerase activity group, which had many genomic aberrations. Moreover, with LSC, DNA diploid cells were found more frequently in the high telomerase activity group than in the low/no telomerase activity group. In addition, T-FISH revealed strong telomere signal intensity in the high telomerase activity group compared with that of the low/no telomerase activity group. These results suggest that telomerase activity is linked to genomic DNA status and that high telomerase activity is associated with genomic stability, DNA ploidy, and telomere length in CRCC.

  17. Communication: Transition state trajectory stability determines barrier crossing rates in chemical reactions induced by time-dependent oscillating fields.

    Science.gov (United States)

    Craven, Galen T; Bartsch, Thomas; Hernandez, Rigoberto

    2014-07-28

    When a chemical reaction is driven by an external field, the transition state that the system must pass through as it changes from reactant to product--for example, an energy barrier--becomes time-dependent. We show that for periodic forcing the rate of barrier crossing can be determined through stability analysis of the non-autonomous transition state. Specifically, strong agreement is observed between the difference in the Floquet exponents describing stability of the transition state trajectory, which defines a recrossing-free dividing surface [G. T. Craven, T. Bartsch, and R. Hernandez, "Persistence of transition state structure in chemical reactions driven by fields oscillating in time," Phys. Rev. E 89, 040801(R) (2014)], and the rates calculated by simulation of ensembles of trajectories. This result opens the possibility to extract rates directly from the intrinsic stability of the transition state, even when it is time-dependent, without requiring a numerically expensive simulation of the long-time dynamics of a large ensemble of trajectories.

  18. THE CONFORMATIONAL STABILITY OF THE REDOX STATES OF LIPOAMIDE DEHYDROGENASE FROM AZOTOBACTER-VINELANDII

    NARCIS (Netherlands)

    VANBERKEL, WJH; REGELINK, AG; BEINTEMA, JJ; KOK, A

    1991-01-01

    The conformational stability of holo-lipoamide and apo-lipoamide dehydrogenase from Azotobacter vinelandii was studied by thermoinactivation, unfolding and limited proteolysis. The oxidized holoenzyme is thermostable, showing a melting temperature, t(m) = 80-degrees-C. The thermal stability of the h

  19. Numerical Analysis of Relative Equilibrium States and Its Stability of a String System with a Rigid Body

    Institute of Scientific and Technical Information of China (English)

    JianhuaCHENG; JunfengLI; 等

    1996-01-01

    In this paper a mnechanical system is studied in which a rotor rotates around a fixed axis with a string suspended symmetric rigid body.All relative equilibrium strates and their stability are discussed.Considering the spinning angular velocity ω around the fixed vertical axis as a parameter,algebraic equations with this parameter are obtained,Every solution of the equations is relevant to a relative equilibrium state of the system.The existence of two important relative equilibrium states is discussed by numerical method developed in bifurcation theory in this paper,In addition,The lagrange's Theorem is used to determine the stability of the relative equilibrium state relevant to the solution of the algebraic equations.

  20. Homoleptic Ce(III) and Ce(IV) Nitroxide Complexes: Significant Stabilization of the 4+ Oxidation State

    Energy Technology Data Exchange (ETDEWEB)

    Bogart, Justin A.; Lewis, Andrew J.; Medling, Scott A.; Piro, Nicholas A.; Carroll, Patrick J.; Booth, Corwin H.; Schelter, Eric J.

    2014-06-25

    Electrochemical experiments performed on the complex Ce-IV[2-((BuNO)-Bu-t)py](4), where [2-((BuNO)-Bu-t)py](-) = N-tert-butyl-N-2-pyridylnitroxide, indicate a 2.51 V stabilization of the 4+ oxidation state of Ce compared to [(Bu4N)-Bu-n](2)[Ce(NO3)(6)] in acetonitrile and a 2.95 V stabilization compared to the standard potential for the ion under aqueous conditions. Density functional theory calculations suggest that this preference for the higher oxidation state is a result of the tetrakis(nitroxide) ligand framework at the Ce cation, which allows for effective electron donation into, and partial covalent overlap with, vacant 4f orbitals with delta symmetry. The results speak to the behavior of CeO2 and related solid solutions in oxygen uptake and transport applications, in particular an inherent local character of bonding that stabilizes the 4+ oxidation state. The results indicate a cerium(IV) complex that has been stabilized to an unprecedented degree through tuning of its ligand-field environment.

  1. Homoleptic cerium(III) and cerium(IV) nitroxide complexes: significant stabilization of the 4+ oxidation state.

    Science.gov (United States)

    Bogart, Justin A; Lewis, Andrew J; Medling, Scott A; Piro, Nicholas A; Carroll, Patrick J; Booth, Corwin H; Schelter, Eric J

    2013-10-07

    Electrochemical experiments performed on the complex Ce(IV)[2-((t)BuNO)py]4, where [2-((t)BuNO)py](-) = N-tert-butyl-N-2-pyridylnitroxide, indicate a 2.51 V stabilization of the 4+ oxidation state of Ce compared to [(n)Bu4N]2[Ce(NO3)6] in acetonitrile and a 2.95 V stabilization compared to the standard potential for the ion under aqueous conditions. Density functional theory calculations suggest that this preference for the higher oxidation state is a result of the tetrakis(nitroxide) ligand framework at the Ce cation, which allows for effective electron donation into, and partial covalent overlap with, vacant 4f orbitals with δ symmetry. The results speak to the behavior of CeO2 and related solid solutions in oxygen uptake and transport applications, in particular an inherent local character of bonding that stabilizes the 4+ oxidation state. The results indicate a cerium(IV) complex that has been stabilized to an unprecedented degree through tuning of its ligand-field environment.

  2. Stability Analysis for Isolated AC Microgrids Based on PV-Active Generators

    DEFF Research Database (Denmark)

    Aldana, Nelson Leonardo Diaz; Coelho, Ernane A. A.; Quintero, Juan Carlos Vasquez;

    2015-01-01

    The current trend in isolated microgrids is oriented to distributed renewable energy generators, such as photovoltaic (PV) generators and their corresponding distributed energy storage systems (ESS) as an unit denoted as active generator (PV+ESS). In an isolated microgrid, every distributed...... for all the distributed generators. In particular, ESS’s based on batteries require at least two different mode of charge. As consequence, the topological operation mode of the microgrid is affected by the changes of the operation mode of each distributed generator. Typically, droop control loops are used...... for interconnecting several different distributed generators in parallel to a common bus, whose parameters determine the stability and damping of the microgrid operation. In this paper, a small-signal stability analysis is applied to an isolated AC microgrid composed of (PV+ESS) active generators, regarding three...

  3. Anthocyanins, pigment stability and antioxidant activity in jabuticaba [Myrciaria cauliflora (Mart. O. Berg

    Directory of Open Access Journals (Sweden)

    Annete de Jesus Boari Lima

    2011-09-01

    Full Text Available Different solvents were evaluated for the extraction of jabuticaba anthocyanin pigments, identifying, quantifying and verifying the stability of the anthocyanins, as well as the conduction of three antioxidant activity assays and determination of the vitamin C levels. The maceration with ethanol acidified with HCl 1.5 mol L-1 (85:15 provides better pigment extraction and stability. The skin is anthocyanin rich, presenting 1.59 and 2.06 g 100 g-1 of dry matter in the Paulista and Sabará varieties, respectively. Cyanidin 3-glucoside is the majority pigment of the skins, followed by delphinidin 3-glucoside. The highest level of vitamin C was found in the skins and seeds of both varieties. It was verified that the skins, presented more antioxidant activity, in free radical capture, as well as in retarding the lipid oxidation process.

  4. Improvement of activity, thermo-stability and fruit juice clarification characteristics of fungal exo-polygalacturonase.

    Science.gov (United States)

    Amin, Faiza; Bhatti, Haq Nawaz; Bilal, Muhammad; Asgher, Muhammad

    2017-02-01

    An extracellular exo-polygalacturonase (exo-PG) from Penicillium notatum was immobilized in sodium-alginate matrix through two different protocols, viz. covalent bonding and adsorption to enhance its catalytic activity, thermal stability and life-time properties for industrial applications. Covalent immobilization was more efficient in terms of high relative activity (45.89%) and immobilization yield (71.6%) as compared to adsorption. Immobilized exo-PG derivatives displayed maximum activities at pH 5.5 and 55°C as compared to free enzyme which showed its optimum activity at pH 6.0 and 50°C. The affinity of enzyme towards its substrate (Km(app)) was reduced after immobilization and Vmax of covalently immobilized exo-PG decreased to 66.7% while the Vmax value of adsorbed enzyme increased up to 150% as compared to free counterpart. Both immobilization techniques greatly enhanced the thermal stability profile of the enzyme. At 60°C, immobilized exo-PGs retained more than 90% of their residual activities after 60min of heating, while free enzyme did not show any activity at the same temperature. Thermodynamic properties (i.e., Ea, ΔH*, ΔS*and ΔG*) of the free and immobilized enzymes were also investigated. Sodium-alginate covalently immobilized and adsorbed enzymes showed excellent recycling efficiencies and retained 50.0% and 41.0% of original activities, respectively after seven consecutive batch reactions. Moreover, the immobilized enzymes treatment achieved promising results in turbidity and viscosity reduction as well as clarity amelioration in various fruit juices. Altogether catalytic, thermo-stability and fruit juices clarification characteristics of the immobilized ex-PGs suggest a high potential for biotechnological exploitability. Copyright © 2016 Elsevier B.V. All rights reserved.

  5. On the way of classifying new states of active matter

    Science.gov (United States)

    Menzel, Andreas M.

    2016-07-01

    With ongoing research into the collective behavior of self-propelled particles, new states of active matter are revealed. Some of them are entirely based on the non-equilibrium character and do not have an immediate equilibrium counterpart. In their recent work, Romanczuk et al (2016 New J. Phys. 18 063015) concentrate on the characterization of smectic-like states of active matter. A new type, referred to by the authors as smectic P, is described. In this state, the active particles form stacked layers and self-propel along them. Identifying and classifying states and phases of non-equilibrium matter, including the transitions between them, is an up-to-date effort that will certainly extend for a longer period into the future.

  6. Ideal Stabilization

    CERN Document Server

    Nesterenko, Mikhail

    2009-01-01

    We define and explore the concept of ideal stabilization. The program is ideally stabilizing if its every state is legitimate. Ideal stabilization allows the specification designer to prescribe with arbitrary degree of precision not only the fault-free program behavior but also its recovery operation. Specifications may or may not mention all possible states. We identify approaches to designing ideal stabilization to both kinds of specifications. For the first kind, we state the necessary condition for an ideally stabilizing solution. On the basis of this condition we prove that there is no ideally stabilizing solution to the leader election problem. We illustrate the utility of the concept by providing examples of well-known programs and proving them ideally stabilizing. Specifically, we prove ideal stabilization of the conflict manager, the alternator, the propagation of information with feedback and the alternating bit protocol.

  7. Antianaphylactic and mast cell stabilization activity of Strychnos potatorum Linn. seed

    Directory of Open Access Journals (Sweden)

    Umesh Jayantarao Patil

    2011-01-01

    Full Text Available Aim: The antianaphylactic activity of Strychnos potatorum Linn seed extract was evaluated by using compound 48/80 induced anaphylaxis and mast cell stabilization was studied by using peritoneal mast cells of rats. The possible antianaphylactic and mast cell stabilization mechanism was evaluated by using compound 48/80 induced mast cell activation and level of nitric oxide in rat peritoneal mast cells. Materials and Methods: Anaphylactic shock in mice was induced by the intraperitoneal administration of 8 mg/kg compound 48/80, prior to induction of anaphylaxis the animals were treated with S. potatorum Linn. seed extract administered orally 1 h before administration of compound 48/80, the rate mortality was observed in each group of animals. Mast cell stabilization was seen by preincubation of mast cells with the compound 48/80 and the extracts. Results: This study indicates that the chloroform, petroleum ether, and methanolic extracts were shown potent and has significant (P < 0.01 and P < 0.001 inhibitory effects on compound 48/80 induced anaphylactic reaction and mast cell activation. This compound also inhibited significantly compound 48/80 induced increased level of nitric oxide in rat peritoneal mast cells. Conclusion: We conclude from this study that the different extracts of S. potatorum seed have potent antianaphylactic activity through mast cell stabilization and inhibition of nitric oxide synthesis. The inhibitory effect of S. potatorum Linn. on release of histamine and nitric oxide protects from compound 48/80 induced anaphylactic reaction may be through blocking vasodilatation, decrease vascular resistance, hypotension and tachycardia induced by immunogenic agent used in this study.

  8. Stability and biological activity evaluations of PEGylated human basic fibroblast growth factor

    OpenAIRE

    Hadadian, Shahin; Shamassebi, Dariush Norouzian; Mirzahoseini, Hasan; Shokrgozar, Mohamad Ali; Bouzari, Saeid; Sepahi, Mina

    2015-01-01

    Background: Human basic fibroblast growth factor (hBFGF) is a heparin-binding growth factor and stimulates the proliferation of a wide variety of cells and tissues causing survival properties and its stability and biological activity improvements have received much attention. Materials and Methods: In the present work, hBFGF produced by engineered Escherichia coli and purified by cation exchange and heparin affinity chromatography, was PEGylated under appropriate condition employing 10 kD pol...

  9. Rotation in a reversed field pinch with active feedback stabilization of resistive wall modes

    Science.gov (United States)

    Cecconello, M.; Menmuir, S.; Brunsell, P. R.; Kuldkepp, M.

    2006-09-01

    Active feedback stabilization of multiple resistive wall modes (RWMs) has been successfully proven in the EXTRAP T2R reversed field pinch. One of the features of plasma discharges operated with active feedback stabilization, in addition to the prolongation of the plasma discharge, is the sustainment of the plasma rotation. Sustained rotation is observed both for the internally resonant tearing modes (TMs) and the intrinsic impurity oxygen ions. Good quantitative agreement between the toroidal rotation velocities of both is found: the toroidal rotation is characterized by an acceleration phase followed, after one wall time, by a deceleration phase that is slower than in standard discharges. The TMs and the impurity ions rotate in the same poloidal direction with also similar velocities. Poloidal and toroidal velocities have comparable amplitudes and a simple model of their radial profile reproduces the main features of the helical angular phase velocity. RWMs feedback does not qualitatively change the TMs behaviour and typical phenomena such as the dynamo and the 'slinky' are still observed. The improved sustainment of the plasma and TMs rotation occurs also when feedback only acts on internally non-resonant RWMs. This may be due to an indirect positive effect, through non-linear coupling between TMs and RWMs, of feedback on the TMs or to a reduced plasma-wall interaction affecting the plasma flow rotation. Electromagnetic torque calculations show that with active feedback stabilization the TMs amplitude remains well below the locking threshold condition for a thick shell. Finally, it is suggested that active feedback stabilization of RWMs and current profile control techniques can be employed simultaneously thus improving both the plasma duration and its confinement properties.

  10. Active stabilization of the optical part in fiber optic quantum cryptography

    Science.gov (United States)

    Balygin, K. A.; Klimov, A. N.; Kulik, S. P.; Molotkov, S. N.

    2016-03-01

    The method of active stabilization of the polarization and other parameters of the optical part of a two-pass fiber optic quantum cryptography has been proposed and implemented. The method allows the completely automated maintenance of the visibility of interference close to an ideal value ( V ≥ 0.99) and the reduction of the instrumental contribution to the error in primary keys (QBER) to 0.5%.

  11. Strategic Priorities for Physical Activity Surveillance in the United States.

    Science.gov (United States)

    Fulton, Janet E; Carlson, Susan A; Ainsworth, Barbara E; Berrigan, David; Carlson, Cynthia; Dorn, Joan M; Heath, Gregory W; Kohl, Harold W; Lee, I-Min; Lee, Sarah M; Másse, Louise C; Morrow, James R; Gabriel, Kelley Pettee; Pivarnik, James M; Pronk, Nicolaas P; Rodgers, Anne B; Saelens, Brian E; Sallis, James F; Troiano, Richard P; Tudor-Locke, Catrine; Wendel, Arthur

    2016-10-01

    Develop strategic priorities to guide future physical activity surveillance in the United States. The Centers for Disease Control and Prevention and the American College of Sports Medicine convened a scientific roundtable of physical activity and measurement experts. Participants summarized the current state of aerobic physical activity surveillance for adults, focusing on practice and research needs in three areas: 1) behavior, 2) human movement, and 3) community supports. Needs and challenges for each area were identified. At the conclusion of the meeting, experts identified one overarching strategy and five strategic priorities to guide future surveillance. The identified overarching strategy was to develop a national plan for physical activity surveillance similar to the U.S. National Physical Activity Plan for promotion. The purpose of the plan would be to enhance coordination and collaboration within and between sectors, such as transportation and public health, and to address specific strategic priorities identified at the roundtable. These strategic priorities were used 1) to identify and prioritize physical activity constructs; 2) to assess the psychometric properties of instruments for physical activity surveillance; 3) to provide training and technical assistance for those collecting, analyzing, or interpreting surveillance data; 4) to explore accessing data from alternative sources; and 5) to improve communication, translation, and dissemination about estimates of physical activity from surveillance systems. This roundtable provided strategic priorities for physical activity surveillance in the United States. A first step is to develop a national plan for physical activity surveillance that would provide an operating framework from which to execute these priorities.

  12. Cadmium Activates Multiple Signaling Pathways That Coordinately Stimulate Akt Activity to Enhance c-Myc mRNA Stability.

    Directory of Open Access Journals (Sweden)

    Jia-Shiuan Tsai

    Full Text Available Cadmium is a known environmental carcinogen. Exposure of Cd leads to the activation of several proto-oncogenes in cells. We investigated here the mechanism of c-Myc expression in hepatic cells under Cd treatment. The c-Myc protein and mRNA levels increased in dose- and time-dependent manners in HepG2 cells with Cd treatment. This increase was due to an increase in c-Myc mRNA stability. To explore the mechanism involved in enhancing the mRNA stability, several cellular signaling factors that evoked by Cd treatment were analyzed. PI3K, p38, ERK and JNK were activated by Cd. However, ERK did not participate in the Cd-induced c-Myc expression. Further analysis revealed that mTORC2 was a downstream factor of p38. PI3K, JNK and mTORC2 coordinately activated Akt. Akt was phosphorylated at Thr450 in the untreated cells. Cd treatment led to additional phosphorylation at Thr308 and Ser473. Blocking any of the three signaling factors resulted in the reduction of phosphorylation level at all three Akt sites. The activated Akt phosphorylated Foxo1 and allowed the modified protein to translocate into the cytoplasm. We conclude that Cd-induced accumulation of c-Myc requires the activation of several signaling pathways. The signals act coordinately for Akt activation and drive the Foxo1 from the nucleus to the cytoplasm. Reduction of Foxo1 in the nucleus reduces the transcription of its target genes that may affect c-Myc mRNA stability, resulting in a higher accumulation of the c-Myc proteins.

  13. Hammerhead ribozyme activity and oligonucleotide duplex stability in mixed solutions of water and organic compounds

    Directory of Open Access Journals (Sweden)

    Shu-ichi Nakano

    2014-01-01

    Full Text Available Nucleic acids are useful for biomedical targeting and sensing applications in which the molecular environment is different from that of a dilute aqueous solution. In this study, the influence of various types of mixed solutions of water and water-soluble organic compounds on RNA was investigated by measuring the catalytic activity of the hammerhead ribozyme and the thermodynamic stability of an oligonucleotide duplex. The compounds with a net neutral charge, such as poly(ethylene glycol, small primary alcohols, amide compounds, and aprotic solvent molecules, added at high concentrations changed the ribozyme-catalyzed RNA cleavage rate, with the magnitude of the effect dependent on the NaCl concentration. These compounds also changed the thermodynamic stability of RNA base pairs of an oligonucleotide duplex and its dependence on the NaCl concentration. Specific interactions with RNA molecules and reduced water activity could account for the inhibiting effects on the ribozyme catalysis and destabilizing effects on the duplex stability. The salt concentration dependence data correlated with the dielectric constant, but not with water activity, viscosity, and the size of organic compounds. This observation suggests the significance of the dielectric constant effects on the RNA reactions under molecular crowding conditions created by organic compounds.

  14. Activity and Stability of Biofilm Uricase of Lactobacillus plantarum for Uric Acid Biosensor

    Science.gov (United States)

    Iswantini, Dyah; Rachmatia, Rescy; Diana, Novita Rose; Nurhidayat, Novik; Akhiruddin; Saprudin, Deden

    2016-01-01

    Research of uric acid biosensor used a Lactobacillus plantarum was successfully conducted. Lactobacillus plantarum could produce uricase that could be used as uric acid biosensor. Therefore, lifetime of bacteria were quite short that caused the bacteria could not detect uric acid for a long time. To avoid this problem, development of biofilm for uric acid biosensor is important. Biofilms is a structured community of bacterial cells, stick together and are able to maintain a bacteria in an extreme environments. The purpose of present study was to determine and compare the activity of uricase produced by L. plantarum, deposited whithin biofilm and planktonic bacteria on glassy carbon electrode (GCEb & GCE), also to determine the stability of biofilm. The optimization process was conducted by using temperature, pH, and substrate concentration as the parameters. It showed that the activity of uricase within biofilm was able to increase the oxidation current. GCEb and GCE yielded the oxidation current in the amount of 47.24 μA and 23.04 μA, respectively, under the same condition. Results indicated that the optimum condition for uric acid biosensor using biofilm were pH 10, temperature of 40 oC, and uric acid concentration of 5 mM. The stability of GCEb decreased after 10 hours used, with decreasing percentage over 86.33%. This low stability probably caused by the unprotected active site of the enzyme that the enzyme is easier to experience the denaturation.

  15. Antioxidative activity and stability of the extracts of liquorice root (Glycyrrhiza glabra

    Directory of Open Access Journals (Sweden)

    Simona PATRICHE

    2015-12-01

    Full Text Available The active principles from the aqueous liquorice plant extracts were investigated and quantified by evaluation of bioactive compounds (saponins through phytochemical reactions. The presence of saponins was evaluated by measuring the foam index, which was around 500. A major component was Glycyrrhizic acid, responsible for the antioxidant activity, found in concentration of 5.82 % at plant maturity. A time-dependent decrease in concentration of the bioactive compounds from aqueous liquorice extracts was observed. The antimicrobial activity of the extracts was tested by the agar diffusion method, showing a moderate inhibitory activity against Bacillus sp. and strong inhibitory activity against coliforms. A liquorice syrup was obtained and subsequently could be used as nutraceutical additive in bread with good results, showing characteristic, optical and antimicrobial properties and good stability in time. Adding liquorice syrup in food products could be an alternative to improve nutraceutical potential.

  16. Resveratrol serves as a protein-substrate interaction stabilizer in human SIRT1 activation

    Science.gov (United States)

    Hou, Xuben; Rooklin, David; Fang, Hao; Zhang, Yingkai

    2016-11-01

    Resveratrol is a natural compound found in red wine that has been suggested to exert its potential health benefit through the activation of SIRT1, a crucial member of the mammalian NAD+-dependent deacetylases. SIRT1 has emerged as an attractive therapeutic target for many aging related diseases, however, how its activity can only be activated toward some specific substrates by resveratrol has been poorly understood. Herein, by employing extensive molecular dynamics simulations as well as fragment-centric topographical mapping of binding interfaces, we have clarified current controversies in the literature and elucidated that resveratrol plays an important activation role by stabilizing SIRT1/peptide interactions in a substrate-specific manner. This new mechanism highlights the importance of the N-terminal domain in substrate recognition, explains the activity restoration role of resveratrol toward some “loose-binding” substrates of SIRT1, and has significant implications for the rational design of new substrate-specific SIRT1 modulators.

  17. Delay-dependent stability analysis for discrete-time systems with time varying state delay

    Directory of Open Access Journals (Sweden)

    Stojanović Sreten B.

    2011-01-01

    Full Text Available The stability of discrete systems with time-varying delay is considered. Some sufficient delaydependent stability conditions are derived using an appropriate model transformation of the original system. The criteria are presented in the form of LMI, which are dependent on the minimum and maximum delay bounds. It is shown that the stability criteria are approximately the same conservative as the existing ones, but have much simpler mathematical form. The numerical example is presented to illustrate the applicability of the developed results.

  18. Structure-Activity Relationship Analysis of the Thermal Stabilities of Nitroaromatic Compounds Following Different Decomposition Mechanisms.

    Science.gov (United States)

    Li, Jiazhong; Liu, Huanxiang; Huo, Xing; Gramatica, Paola

    2013-02-01

    The decomposition behavior of energetic materials is very important for the safety problems concerning their production, transportation, use and storage, because molecular decomposition is intimately connected to their explosive properties. Nitroaromatic compounds, particularly nitrobenzene derivatives, are often considered as prototypical energetic molecules, and some of them are commonly used as high explosives. Quantitative structure-activity relationship (QSAR) represents a potential tool for predicting the thermal stability properties of energetic materials. But it is reported that constructing general reliable models to predict their stability and their potential explosive properties is a very difficult task. In this work, we make our efforts to investigate the relationship between the molecular structures and corresponding thermal stabilities of 77 nitrobenzene derivatives with various substituent functional groups (in ortho, meta and/or para positions). The proposed best MLR model, developed by the new software QSARINS, based on Genetic Algorithm for variable selection and with various validation tools, is robust, stable and predictive with R(2) of 0.86, QLOO (2) of 0.79 and CCC of 0.90. The results indicated that, though difficult, it is possible to build predictive, externally validated QSAR models to estimate the thermal stability of nitroaromatic compounds. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Deletion of loop fragment adjacent to active site diminishes the stability and activity of exo-inulinase.

    Science.gov (United States)

    Arjomand, Maryam Rezaei; Habibi-Rezaei, Mehran; Ahmadian, Gholamreza; Hassanzadeh, Malihe; Karkhane, Ali Asghar; Asadifar, Mandana; Amanlou, Massoud

    2016-11-01

    Inulinases are classified as hydrolases and widely used in the food and medical industries. Here, we report the deletion of a six-membered adjacent active site loop fragment ((74)YGSDVT(79) sequence) from third Ω-loop of the exo-inulinase containing aspartate residue from Aspergillus niger to study its structural and functional importance. Site-directed mutagenesis was used to create the mutant of the exo-inulinase (Δ6SL). To investigate the stability of the region spanning this loop, MD simulations were performed 80ns for 20-85 residues. Molecular docking was performed to compare the interactions in the active sites of enzymes with fructose as a ligand. Accordingly, the functional thermostability of the exo-inulinase was significantly decreased upon loop fragment deletion. Evaluation of the kinetics parameters (Vmax, Km, kcat and, kcat/Km) and activation energy (Ea) of the catalysis of enzymes indicated the importance of the deleted sequence on the catalytic performance of the enzyme. In conclusion, six-membered adjacent active site loop fragment not only plays a crucial role in the stability of the enzyme, but also it involves in the enzyme catalysis through lowering the activation energy of the catalysis and effective improving the catalytic performance. Copyright © 2016. Published by Elsevier B.V.

  20. Stability Analysis of State Saturation 2D Discrete Time-Delay Systems Based on F-M Model

    Directory of Open Access Journals (Sweden)

    Dongyan Chen

    2013-01-01

    Full Text Available The problem of stability analysis is investigated for a class of state saturation two-dimensional (2D discrete time-delay systems described by the Fornasini-Marchesini (F-M model. The delay is allowed to be a bounded time-varying function. By constructing the delay-dependent 2D discrete Lyapunov functional and introducing a nonnegative scalar β, a sufficient condition is proposed to guarantee the global asymptotic stability of the addressed systems. Subsequently, the criterion is converted into the linear matrix inequalities (LMIs which can be easily tested by using the standard numerical software. Finally, two numerical examples are given to show the effectiveness of the proposed stability criterion.

  1. Solid-state nanoparticle coated emulsions for encapsulation and improving the chemical stability of all-trans-retinol.

    Science.gov (United States)

    Ghouchi-Eskandar, Nasrin; Simovic, Spomenka; Prestidge, Clive A

    2012-02-28

    Submicron oil-in-water (o/w) emulsions stabilised with conventional surfactants and silica nanoparticles were prepared and freeze-dried to obtain free-flowing powders with good redispersibility and a three-dimensional porous matrix structure. Solid-state emulsions were characterised for visual appearance, particle size distribution, zeta potential and reconstitution properties after freeze-drying with various sugars and at a range of sugar to oil ratios. Comparative degradation kinetics of all-trans-retinol from freeze-dried and liquid emulsions was investigated as a function of storage temperatures. Optimum stability was observed for silica-coated oleylamine emulsions at 4 °C in their wet state. The half-life of all-trans-retinol was 25.66 and 22.08 weeks for silica incorporation from the oil and water phases respectively. This was ∼4 times higher compared to the equivalent solid-state emulsions with drug half-life of 6.18 and 6.06 weeks at 4 °C. Exceptionally, at a storage temperature of 40 °C, the chemical stability of the drug was 3 times higher in the solid-state compared to the wet emulsions which confirmed that freeze-drying is a promising approach to improve the chemical stability of water-labile compounds provided that the storage conditions are optimised.

  2. Active Climate Stabilization: Practical Physics-Based Approaches to Prevention of Climate Change

    Energy Technology Data Exchange (ETDEWEB)

    Teller, E; Hyde, T; Wood, L

    2002-04-18

    We offer a case for active technical management of the radiative forcing of the temperatures of the Earth's fluid envelopes, rather than administrative management of atmospheric greenhouse gas inputs, in order to stabilize both the global- and time-averaged climate and its mesoscale features. We suggest that active management of radiative forcing entails negligible--indeed, likely strongly negative--economic costs and environmental impacts, and thus best complies with the pertinent mandate of the UN Framework Convention on Climate Change. We propose that such approaches be swiftly evaluated in sub-scale in the course of an intensive international program.

  3. Active Climate Stabilization: Practical Physics-Based Approaches to Prevention of Climate Change

    Science.gov (United States)

    Teller, E.; Hyde, T.; Wood, L.

    2002-04-18

    We offer a case for active technical management of the radiative forcing of the temperatures of the Earth's fluid envelopes, rather than administrative management of atmospheric greenhouse gas inputs, in order to stabilize both the global- and time-averaged climate and its mesoscale features. We suggest that active management of radiative forcing entails negligible--indeed, likely strongly negative--economic costs and environmental impacts, and thus best complies with the pertinent mandate of the UN Framework Convention on Climate Change. We propose that such approaches be swiftly evaluated in sub-scale in the course of an intensive international program.

  4. Confrontation Between Judicial Activism and State of Exception

    Directory of Open Access Journals (Sweden)

    Alexandre Pedro Moura D’Almeida

    2017-01-01

    Full Text Available The judiciary has excelled in the international and national scene, reaching role of great importance, thus creating opposition to the legislative and executive powers. The center of gravity of the sovereign power of the state moves toward the judiciary, that happens to have a more active role and controlling of the others powers, but also appears as a great defender of social and fundamental rights causes, seeking to make an effective constitution. Its great public notoriety has attracted great distrust of various sectors of society, especially by the two powers that have an increasing interference. Arises, therefore, a speech that the judiciary would be reversing into a big and uncontrollable power, increasing the suspicion that now it would be living in a real dictatorship of the judiciary through judicial activism. There is a growing concern with the expansion of activism and the role of the judiciary. The purpose of this work is to conceptualize and approach the judicial activism and the state of exception to search and reveal if there is any similarity, to then draw up a possible answer to the concern of forming a dictatorship of the judiciary. The state of exception is one of the rule of law paradoxes, while activism is a political manifestation of the judiciary. The similarity between the institutes appears as appalling in a dynamic expansion of political power of a state institution exercising judicial function, putting in check who would be the sovereign in a rule of law and democratic state.

  5. A small RNA activates CFA synthase by isoform-specific mRNA stabilization.

    Science.gov (United States)

    Fröhlich, Kathrin Sophie; Papenfort, Kai; Fekete, Agnes; Vogel, Jörg

    2013-11-13

    Small RNAs use a diversity of well-characterized mechanisms to repress mRNAs, but how they activate gene expression at the mRNA level remains not well understood. The predominant activation mechanism of Hfq-associated small RNAs has been translational control whereby base pairing with the target prevents the formation of an intrinsic inhibitory structure in the mRNA and promotes translation initiation. Here, we report a translation-independent mechanism whereby the small RNA RydC selectively activates the longer of two isoforms of cfa mRNA (encoding cyclopropane fatty acid synthase) in Salmonella enterica. Target activation is achieved through seed pairing of the pseudoknot-exposed, conserved 5' end of RydC to an upstream region of the cfa mRNA. The seed pairing stabilizes the messenger, likely by interfering directly with RNase E-mediated decay in the 5' untranslated region. Intriguingly, this mechanism is generic such that the activation is equally achieved by seed pairing of unrelated small RNAs, suggesting that this mechanism may be utilized in the design of RNA-controlled synthetic circuits. Physiologically, RydC is the first small RNA known to regulate membrane stability.

  6. Urease immobilized polymer hydrogel: Long-term stability and enhancement of enzymatic activity.

    Science.gov (United States)

    Kutcherlapati, S N Raju; Yeole, Niranjan; Jana, Tushar

    2016-02-01

    A method has been developed in which an enzyme namely urease was immobilized inside hydrogel matrix to study the stability and enzymatic activity in room temperature (∼27-30°C). This urease coupled hydrogel (UCG) was obtained by amine-acid coupling reaction and this procedure is such that it ensured the wider opening of mobile flap of enzyme active site. A systematic comparison of urea-urease assay and the detailed kinetic data clearly revealed that the urease shows activity for more than a month when stored at ∼27-30°C in case of UCG whereas it becomes inactive in case of free urease (enzyme in buffer solution). The aqueous microenvironment inside the hydrogel, unusual morphological features and thermal behaviour were believed to be the reasons for unexpected behaviour. UCG displayed enzyme activity at basic pH and up to 60°C. UCG showed significant enhancement in activity against thermal degradation compared to free urease. In summary, this method is a suitable process to stabilize the biomacromolecules in standard room temperature for many practical uses.

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

    Science.gov (United States)

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

    2016-04-01

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

  8. Stability and Antioxidant Activity of Semi-synthetic Derivatives of 4-Nerolidylcatechol

    Directory of Open Access Journals (Sweden)

    Emerson Silva Lima

    2012-12-01

    Full Text Available 4-nerolidylcatechol (4-NC is an unstable natural product that exhibits important antioxidant, anti-inflammatory and other properties. It is readily obtainable on a multi-gram scale through straightforward solvent extraction of the roots of cultivated Piper peltatum or P. umbellatum, followed by column chromatography on the resulting extract. Semi-synthetic derivatives of 4-NC with one or two substituent groups (methyl, acetyl, benzyl, benzoyl on the O atoms have been introduced that have increased stability compared to 4-NC and significant in vitro inhibitory activity against the human malaria parasite Plasmodium falciparum. Antioxidant and anti-inflammatory properties may be important for the antiplasmodial mode of action of 4-NC derivatives. Thus, we decided to investigate the antioxidant properties, cytotoxicity and stability of 4-NC derivatives as a means to explore the potential utility of these compounds. 4-NC showed high antioxidant activity in the DPPH and ABTS assays and in 3T3-L1 cells (mouse embryonic fibroblast, however 4-NC was more cytotoxic (IC50 = 31.4 µM and more unstable than its derivatives and lost more than 80% of its antioxidant activity upon storage in solution at −20 °C for 30 days. DMSO solutions of mono-O-substituted derivatives of 4-NC exhibited antioxidant activity and radical scavenging activity in the DPPH and ABTS assays that was comparable to that of BHA and BHT. In the cell-based antioxidant model, most DMSO solutions of derivatives of 4-NC were less active on day 1 than 4-NC, quercetin and BHA and more active antioxidants than BHT. After storage for 30 days at −20 °C, DMSO solutions of most of the derivatives of 4-NC were more stable and exhibited more antioxidant activity than 4-NC, quercetin and BHA and exhibited comparable antioxidant activity to BHT. These findings point to the potential of derivatives of 4-NC as antioxidant compounds.

  9. Influence of structured sidewalls on the wetting states and superhydrophobic stability of surfaces with dual-scale roughness

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Huaping, E-mail: wuhuaping@gmail.com [Key Laboratory of E& M (Zhejiang University of Technology), Ministry of Education & Zhejiang Province, Hangzhou 310014 (China); State Key Laboratory of Structural Analysis for Industrial Equipment, Dalian University of Technology, Dalian 116024 (China); Zhu, Kai; Wu, Bingbing [Key Laboratory of E& M (Zhejiang University of Technology), Ministry of Education & Zhejiang Province, Hangzhou 310014 (China); Lou, Jia [Piezoelectric Device Laboratory, Department of Mechanics and Engineering Science, Ningbo University, Ningbo, Zhejiang 315211 (China); Zhang, Zheng [Key Laboratory of E& M (Zhejiang University of Technology), Ministry of Education & Zhejiang Province, Hangzhou 310014 (China); Chai, Guozhong, E-mail: chaigz@zjut.edu.cn [Key Laboratory of E& M (Zhejiang University of Technology), Ministry of Education & Zhejiang Province, Hangzhou 310014 (China)

    2016-09-30

    Highlights: • Apparent contact angle equation of all wetting states on dual-scale rough surfaces is derived. • Structured sidewalls can improve superhydrophobicity than smooth sidewalls. • Structured sidewalls can enlarge ACA than smooth sidewalls. • Structured sidewalls present an advantage over smooth sidewalls in terms of enhancing superhydrophobic stability. - Abstract: The superhydrophobicity of biological surfaces with dual-scale roughness has recently received considerable attention because of the unique wettability of such surfaces. Based on this, artificial micro/nano hierarchical structures with structured sidewalls and smooth sidewalls were designed and the influences of sidewall configurations (i.e., structured and smooth) on the wetting state of micro/nano hierarchical structures were systematically investigated based on thermodynamics and the principle of minimum free energy. Wetting transition and superhydrophobic stability were then analyzed for a droplet on dual-scale rough surfaces with structured and smooth sidewalls. Theoretical analysis results show that dual-scale rough surfaces with structured sidewalls have a larger “stable superhydrophobic region” than those with smooth sidewalls. The dual-scale rough surfaces with smooth sidewalls can enlarge the apparent contact angle (ACA) without improvement in the superhydrophobic stability. By contrast, dual-scale rough surfaces with structured sidewalls present an advantage over those with smooth sidewalls in terms of enlarging ACA and enhancing superhydrophobic stability. The proposed thermodynamic model is valid when compared with previous experimental data and numerical analysis results, which is helpful for designing and understanding the wetting states and superhydrophobic stability of surfaces with dual-scale roughness.

  10. Heat shock modulates the subcellular localization, stability, and activity of HIPK2

    Energy Technology Data Exchange (ETDEWEB)

    Upadhyay, Mamta; Bhadauriya, Pratibha; Ganesh, Subramaniam, E-mail: sganesh@iitk.ac.in

    2016-04-15

    The homeodomain-interacting protein kinase-2 (HIPK2) is a highly conserved serine/threonine kinase and is involved in transcriptional regulation. HIPK2 is a highly unstable protein, and is kept at a low level under normal physiological conditions. However, exposure of cells to physiological stress – such as hypoxia, oxidative stress, or UV damage – is known to stabilize HIPK2, leading to the HIPK2-dependent activation of p53 and the cell death pathway. Therefore HIPK2 is also known as a stress kinase and as a stress-activated pro-apoptotic factor. We demonstrate here that exposure of cells to heat shock results in the stabilization of HIPK2 and the stabilization is mediated via K63-linked ubiquitination. Intriguingly, a sub-lethal heat shock (42 °C, 1 h) results in the cytoplasmic localization of HIPK2, while a lethal heat shock (45 °C, 1 h) results in its nuclear localization. Cells exposed to the lethal heat shock showed significantly higher levels of the p53 activity than those exposed to the sub-lethal thermal stress, suggesting that both the level and the nuclear localization are essential for the pro-apoptotic activity of HIPK2 and that the lethal heat shock could retain the HIPK2 in the nucleus to promote the cell death. Taken together our study underscores the importance of HIPK2 in stress mediated cell death, and that the HIPK2 is a generic stress kinase that gets activated by diverse set of physiological stressors.

  11. Influence of structured sidewalls on the wetting states and superhydrophobic stability of surfaces with dual-scale roughness

    Science.gov (United States)

    Wu, Huaping; Zhu, Kai; Wu, Bingbing; Lou, Jia; Zhang, Zheng; Chai, Guozhong

    2016-09-01

    The superhydrophobicity of biological surfaces with dual-scale roughness has recently received considerable attention because of the unique wettability of such surfaces. Based on this, artificial micro/nano hierarchical structures with structured sidewalls and smooth sidewalls were designed and the influences of sidewall configurations (i.e., structured and smooth) on the wetting state of micro/nano hierarchical structures were systematically investigated based on thermodynamics and the principle of minimum free energy. Wetting transition and superhydrophobic stability were then analyzed for a droplet on dual-scale rough surfaces with structured and smooth sidewalls. Theoretical analysis results show that dual-scale rough surfaces with structured sidewalls have a larger "stable superhydrophobic region" than those with smooth sidewalls. The dual-scale rough surfaces with smooth sidewalls can enlarge the apparent contact angle (ACA) without improvement in the superhydrophobic stability. By contrast, dual-scale rough surfaces with structured sidewalls present an advantage over those with smooth sidewalls in terms of enlarging ACA and enhancing superhydrophobic stability. The proposed thermodynamic model is valid when compared with previous experimental data and numerical analysis results, which is helpful for designing and understanding the wetting states and superhydrophobic stability of surfaces with dual-scale roughness.

  12. Hydrogen peroxide sensing and cytotoxicity activity of Acacia lignin stabilized silver nanoparticles.

    Science.gov (United States)

    Aadil, Keshaw Ram; Barapatre, Anand; Meena, Avtar Singh; Jha, Harit

    2016-01-01

    The study is aimed at detection of hydrogen peroxide (H2O2) using Acacia lignin mediated silver nanoparticles (AGNPs). The synthesis of AGNPs was achieved at conditions optimized as, 3 ml of 0.02% lignin and 1mM silver nitrate incubated for 30 min at 80°C and pH 9. Initial screening of AGNPs was performed by measuring the surface plasmon resonance peak at 410-430 nm using UV-vis spectrophotometer. Transmission electron microscopy, atomic force microscopy, X-ray diffraction and particle size analysis confirmed the spherical shaped face centered cubic structure and 10-50 nm size of AGNPs. The infrared spectroscopy study further revealed that the active functional groups present in lignin were responsible for the reduction of silver ions (Ag(+)) to metallic silver (Ag(0)). Lignin stabilized silver nanoparticles showed good sensitivity and a linear response over wide concentrations of H2O2 (10(-1) to 10(-6)M). Further, the in vitrocytotoxicity activity of the lignin mediated AGNPs (5-500 μg/ml) demonstrated toxicity effects in MCF-7 and A375 cell lines. Thus, lignin stabilized silver nanoparticles based optical sensor for H2O2 could be potentially applied in the determination of reactive oxygen species and toxic chemicals which further expands the importance of lignin stabilized silver nanoparticles.

  13. Electromyographic activity of trunk and hip muscles during stabilization exercises in four-point kneeling in healthy volunteers

    OpenAIRE

    Stevens, Veerle K.; Vleeming, Andry; Bouche, Katie G.; Mahieu, Nele N; Vanderstraeten, Guy G.; Danneels, Lieven A

    2006-01-01

    Stabilization exercises are intended to optimize function of the muscles that are believed to govern trunk stability. Debate exists whether certain muscles are more important than others in optimally performing these exercises. Thirty healthy volunteers were asked to perform three frequently prescribed stabilization exercises in four-point kneeling. The electromyographic activity of different trunk and hip muscles was evaluated. Average amplitudes obtained during the exercises were normalized...

  14. The near optimality of the stabilizing control in a weakly nonlinear system with state-dependent coefficients

    Science.gov (United States)

    Dmitriev, Mikhail G.; Makarov, Dmitry A.

    2016-08-01

    We carried out analysis of near optimality of one computationally effective nonlinear stabilizing control built for weakly nonlinear systems with coefficients depending on the state and the formal small parameter. First investigation of that problem was made in [M. G. Dmitriev, and D. A. Makarov, "The suboptimality of stabilizing regulator in a quasi-linear system with state-depended coefficients," in 2016 International Siberian Conference on Control and Communications (SIBCON) Proceedings, National Research University, Moscow, 2016]. In this paper, another optimal control and gain matrix representations were used and theoretical results analogous to cited work above were obtained. Also as in the cited work above the form of quality criterion on which this close-loop control is optimal was constructed.

  15. Slow State Transitions of Sustained Neural Oscillations by Activity-Dependent Modulation of Intrinsic Excitability

    Science.gov (United States)

    Fröhlich, Flavio; Bazhenov, Maxim; Timofeev, Igor; Steriade, Mircea; Sejnowski, Terrence J.

    2010-01-01

    Little is known about the dynamics and mechanisms of transitions between tonic firing and bursting in cortical networks. Here, we use a computational model of a neocortical circuit with extracellular potassium dynamics to show that activity-dependent modulation of intrinsic excitability can lead to sustained oscillations with slow transitions between two distinct firing modes: fast run (tonic spiking or fast bursts with few spikes) and slow bursting. These transitions are caused by a bistability with hysteresis in a pyramidal cell model. Balanced excitation and inhibition stabilizes a network of pyramidal cells and inhibitory interneurons in the bistable region and causes sustained periodic alternations between distinct oscillatory states. During spike-wave seizures, neocortical paroxysmal activity exhibits qualitatively similar slow transitions between fast run and bursting. We therefore predict that extracellular potassium dynamics can cause alternating episodes of fast and slow oscillatory states in both normal and epileptic neocortical networks. PMID:16763023

  16. Active serine involved in the stabilization of the active site loop in the Humicola lanuginosa lipase

    DEFF Research Database (Denmark)

    Peters, Günther H.j.; Svendsen, A.; Langberg, H.;

    1998-01-01

    reveal that the hinges of the active site lid are more flexible in the wild-type Hll than in S146A. In contrast, larger fluctuations are observed in the middle region of the active site loop in S 146A than in Hll. These findings reveal that the single mutation (S146A) of the active site serine leads......We have investigated the binding properties of and dynamics in Humicola lanuginosa lipase (HII) and the inactive mutant S146A (active Ser146 substituted with Ala) using fluorescence spectroscopy and molecular dynamics simulations, respectively. Hll and S146A show significantly different binding......, whereas only small changes are observed for I-Ill suggesting that the active site Lid in the latter opens more easily and hence more lipase molecules are bound to the liposomes. These observations are in agreement with molecular dynamics simulations and subsequent essential dynamics analyses. The results...

  17. Resting state brain activity and functional brain mapping

    Institute of Scientific and Technical Information of China (English)

    Zhao Xiaohu; Wang Peijun; Tang Xiaowei

    2007-01-01

    Functional brain imaging studies commonly use either resting or passive task states as their control conditions, and typically identify the activation brain region associated with a specific task by subtracting the resting from the active task conditions. Numerous studies now suggest, however, that the resting state may not reflect true mental "rest" conditions. The mental activity that occurs during"rest" might therefore greatly influence the functional neuroimaging observations that are collected through the usual subtracting analysis strategies. Exploring the ongoing mental processes that occur during resting conditions is thus of particular importance for deciphering functional brain mapping results and obtaining a more comprehensive understanding of human brain functions. In this review article, we will mainly focus on the discussion of the current research background of functional brain mapping at resting state and the physiological significance of the available neuroimaging data.

  18. Evolution of a transition state: role of Lys100 in the active site of isocitrate dehydrogenase.

    Science.gov (United States)

    Miller, Stephen P; Gonçalves, Susana; Matias, Pedro M; Dean, Antony M

    2014-05-26

    An active site lysine essential to catalysis in isocitrate dehydrogenase (IDH) is absent from related enzymes. As all family members catalyze the same oxidative β-decarboxylation at the (2R)-malate core common to their substrates, it seems odd that an amino acid essential to one is not found in all. Ordinarily, hydride transfer to a nicotinamide C4 neutralizes the positive charge at N1 directly. In IDH, the negatively charged C4-carboxylate of isocitrate stabilizes the ground state positive charge on the adjacent nicotinamide N1, opposing hydride transfer. The critical lysine is poised to stabilize-and perhaps even protonate-an oxyanion formed on the nicotinamide 3-carboxamide, thereby enabling the hydride to be transferred while the positive charge at N1 is maintained. IDH might catalyze the same overall reaction as other family members, but dehydrogenation proceeds through a distinct, though related, transition state. Partial activation of lysine mutants by K(+) and NH4 (+) represents a throwback to the primordial state of the first promiscuous substrate family member.

  19. Structure, activity, and stability of platinum alloys as catalysts for the oxygen reduction reaction

    DEFF Research Database (Denmark)

    Vej-Hansen, Ulrik Grønbjerg

    and dealloying due to kinetic barriers, despite the thermodynamic driving force for dissolution. This is followed by our results on trying to decouple the strain and ligand effects for platinum skin structures, and determining whether there is any correlation between adsorption energy and surface stability...... in these systems. We find that there is such a correlation for some adsorbates, indicating that there exists a limit for the stability of an overlayer for a given adsorption strength. Finally, we introduce our work on platinum alloy nanoparticles, and our attempt to isolate the features which result...... in the increased activity that has been seen experimentally. We show how the platinum-platinum distance at the surface is decreased for a variety of alloy phases in the core, with greater compression of the overlayer for core phases with lattice parameters which are either much smaller or much larger than pure...

  20. Frequency domain stability analysis of nonlinear active disturbance rejection control system.

    Science.gov (United States)

    Li, Jie; Qi, Xiaohui; Xia, Yuanqing; Pu, Fan; Chang, Kai

    2015-05-01

    This paper applies three methods (i.e., root locus analysis, describing function method and extended circle criterion) to approach the frequency domain stability analysis of the fast tool servo system using nonlinear active disturbance rejection control (ADRC) algorithm. Root locus qualitative analysis shows that limit cycle is generated because the gain of the nonlinear function used in ADRC varies with its input. The parameters in the nonlinear function are adjustable to suppress limit cycle. In the process of root locus analysis, the nonlinear function is transformed based on the concept of equivalent gain. Then, frequency domain description of the nonlinear function via describing function is presented and limit cycle quantitative analysis including estimating prediction error is presented, which virtually and theoretically demonstrates that the describing function method cannot guarantee enough precision in this case. Furthermore, absolute stability analysis based on extended circle criterion is investigated as a complement.

  1. Binding, stability, and antioxidant activity of quercetin with soy protein isolate particles.

    Science.gov (United States)

    Wang, Yufang; Wang, Xiaoyong

    2015-12-01

    This work is to study the potential of particles fabricated from soy protein isolate (SPI) as a protective carrier for quercetin. When the concentration of SPI particles increases from 0 to 0.35 g/L, quercetin gives a gradually increased fluorescence intensity and fluorescence anisotropy. The addition of quercetin can highly quench the intrinsic fluorescence of SPI particles. These results are explained in terms of the binding of quercetin to the hydrophobic pockets of SPI particles mainly through the hydrophobic force together with the hydrogen bonding. The small difference in the binding constants at 25 and 40 °C suggests the structural stability of SPI particles. The relative changes in values of Gibbs energy, enthalpy, and entropy indicate that the binding of quercetin with SPI particles is spontaneous and hydrophobic interaction is the major force. Furthermore, SPI particles are superior to native SPI for improving the stability and radical scavenging activity of quercetin.

  2. ON THE STABILITY OF THE POSITIVE RADIAL STEADY STATES FOR A SEMILINEAR CAUCHY PROBLEM INVOLVING CRITICAL EXPONENTS

    Institute of Scientific and Technical Information of China (English)

    Deng Yinbin; Yang Fen

    2008-01-01

    This article is contributed to the Cauchy problem u/t = △u + K(ㄧxㄧ)up in Rn x (0,T), u(x,0) =(ψ)(x) in Rn; with initial function(ψ)≠0. The stability of positive radial steady state, which are positive solutions of △u + K(ㄧxㄧ)up =0, is obtained when p is critical for general K(ㄧxㄧ).

  3. Applications of exact linearization techniques for steady-state stability enhancement in a weak ac/dc system

    Energy Technology Data Exchange (ETDEWEB)

    Kaprielian, S.; Clements, K. (Dept. of Electrical Engineering, Worcester Polytechnic Inst., Worcester, MA (US)); Turi, J. (Texas Univ., Richardson, TX (United States))

    1992-05-01

    A nonlinear control strategy to improve the steady-state stability of a weak AC/DC power system is presented. The approach described in this paper is based on the extension of feedback linearization techniques to nonlinear descriptor system models. This method produces a nonlinear control strategy which is capable of enhancing system performance for various system operating conditions. This claim is supported with simulation results.

  4. Antimicrobial activity, toxicity and stability of phytol as a novel surface disinfectant

    Directory of Open Access Journals (Sweden)

    Mohammad Taghi Ghaneian

    2015-01-01

    Full Text Available Background: Although various surface disinfectants have been introduced, most of them are toxic. The use of natural antimicrobial agent e.g. phytol, extracted from Leptadeniapyrotechnicais a new strategy. The aim of this study was to evaluate the antimicrobial activity, toxicity, and stability of phytol. Methods: The serial concentrations of phytol were prepared, and separately incubated with four microbial isolates. Then, its Minimum Inhibitory Concentration (MIC was measured for each microorganism. For toxicity test, serial concentrations (62.5, 125, 250, 500 and 1000 μg/mL of phytol were incubated with mouse skin cells, and then cell viability was calculated by MTT assay. For stability test, three common surfaces (stone, steel, and MDF were considered. Then, 100 μL of phytol was separately spread over their surface, and they have been kept at lab panel for 12, 24 and 36 hours. After incubation, two samples were obtained from each surface and inoculated on nutrient agar plates. Finally, colony count was read for each surface. T-test was used to evaluate the significant differences between groups, and P>0.05 considered as level of significant difference. Results: The MIC50 of phytol against E.coli, C.albicans, and A.nigerwas 62.5 μg/mL, and against S.aureuswas >1000 μg/mL. MTT assay showed that the toxicity of phytol was dose and time dependent. The stability test demonstrated that phytol was stable on the stone, MDF, and steel surfaces until 36 hours. Conclusion: It can be concluded that phytol has high antimicrobial activity, high stability, and low toxicity. This substance must be evaluated at actual conditions.

  5. Interactions between Carotenoids from Marine Bacteria and Other Micronutrients: Impact on Stability and Antioxidant Activity.

    Science.gov (United States)

    Sy, Charlotte; Dangles, Olivier; Borel, Patrick; Caris-Veyrat, Catherine

    2015-11-19

    Recently isolated spore-forming pigmented marine bacteria Bacillus indicus HU36 are sources of oxygenated carotenoids with original structures (about fifteen distinct yellow and orange pigments with acylated d-glucosyl groups). In this study, we evaluated the stability (sensitivity to iron-induced autoxidation) and antioxidant activity (inhibition of iron-induced lipid peroxidation) of combinations of bacterial HU36 carotenoids with the bacterial vitamin menaquinone MQ-7 and with phenolic antioxidants (vitamin E, chlorogenic acid, rutin). Unexpectedly, MQ-7 strongly improves the ability of HU36 carotenoids to inhibit Fe(II)-induced lipid peroxidation, although MQ-7 was not consumed in the medium. We propose that their interaction modifies the carotenoid antioxidant mechanism(s), possibly by allowing carotenoids to scavenge the initiating radicals. For comparison, β-carotene and lycopene in combination were shown to exhibit a slightly higher stability toward iron-induced autoxidation, as well as an additive antioxidant activity as compared to the carotenoids, individually. HU36 carotenoids and phenolic antioxidants displayed synergistic activities in the inhibition of linoleic acid peroxidation induced by heme iron, but not by free iron. Synergism could arise from antioxidants interacting via electron transfer through the porphyrin nucleus of heme iron. Overall, combining antioxidants acting via complementary mechanisms could be the key for optimizing the activity of this bacterial carotenoid cocktail.

  6. Glycolipid Biosurfactants Activate, Dimerize, and Stabilize Thermomyces lanuginosus Lipase in a pH-Dependent Fashion.

    Science.gov (United States)

    Madsen, Jens Kvist; Kaspersen, Jørn Døvling; Andersen, Camilla Bertel; Nedergaard Pedersen, Jannik; Andersen, Kell Kleiner; Pedersen, Jan Skov; Otzen, Daniel E

    2017-08-15

    We present a study of the interactions between the lipase from Thermomyces lanuginosus (TlL) and the two microbially produced biosurfactants (BSs), rhamnolipid (RL) and sophorolipid (SL). Both RL and SL are glycolipids; however, RL is anionic, while SL is a mixture of anionic and non-ionic species. We investigate the interactions of RL and SL with TlL at pH 6 and 8 and observe different effects at the two pH values. At pH 8, neither RL nor SL had any major effect on TlL stability or activity. At pH 6, in contrast, both surfactants increase TlL's thermal stability and fluorescence and activity measurements indicate interfacial activation of TlL, resulting in 3- and 6-fold improved activity in SL and RL, respectively. Nevertheless, isothermal titration calorimetry reveals binding of only a few BS molecules per lipase. Size-exclusion chromatography and small-angle X-ray scattering suggest formation of TlL dimers with binding of small amounts of either RL or SL at the dimeric interface, forming an elongated complex. We conclude that RL and SL are compatible with TlL and constitute promising green alternatives to traditional surfactants.

  7. Psychological traits and platelet monoamine oxidase activity in eating disorder patients: their relationship and stability.

    Science.gov (United States)

    Podar, Iris; Jaanisk, Maiken; Allik, Jüri; Harro, Jaanus

    2007-01-30

    Self-reported behavior and attitudes towards eating [Eating Disorder Inventory-2; Garner DM (1991). Eating Disorder Inventory-2: Professional Manual. Odessa, Fl.: Psychological Assessment Resources; Estonian version Podar I, Hannus A, Allik J (1999). Personality and Affectivity Characteristics Associated With Eating Disorders: a Comparison of Eating Disordered, Weight-Preoccupied, and Normal Samples. J Pers Assess; 73(1), 133-147] and the activity of platelet monoamine oxidase (MAO) was studied in 11 patients with anorexia nervosa (AN), 43 patients with bulimia nervosa (BN) and a healthy control group (n=138). Nineteen patients filled in the EDI-2 questionnaire and donated blood samples three times with three month intervals in order to determine platelet MAO activity. Eating disordered (ED) patients scored higher on all EDI-2 subscales and had lower MAO activity compared to the control group. They also scored higher than the control group on the Neuroticism domain but lower on the Extraversion, Openness, and Conscientiousness domains of the NEO-PI-R questionnaire. The average stability of MAO on different occasions (r=.56) was slightly smaller than the stability of the EDI-2 scores (r=.70). The lack of correlations between personality dispositions and MAO activity indicates that they have independent influence on eating disorders. A possible relationship between neurochemical mechanisms and psychological symptoms of eating disordered behavior is discussed.

  8. Astaxanthin: Sources, Extraction, Stability, Biological Activities and Its Commercial Applications—A Review

    Directory of Open Access Journals (Sweden)

    Ranga Rao Ambati

    2014-01-01

    Full Text Available There is currently much interest in biological active compounds derived from natural resources, especially compounds that can efficiently act on molecular targets, which are involved in various diseases. Astaxanthin (3,3′-dihydroxy-β, β′-carotene-4,4′-dione is a xanthophyll carotenoid, contained in Haematococcus pluvialis, Chlorella zofingiensis, Chlorococcum, and Phaffia rhodozyma. It accumulates up to 3.8% on the dry weight basis in H. pluvialis. Our recent published data on astaxanthin extraction, analysis, stability studies, and its biological activities results were added to this review paper. Based on our results and current literature, astaxanthin showed potential biological activity in in vitro and in vivo models. These studies emphasize the influence of astaxanthin and its beneficial effects on the metabolism in animals and humans. Bioavailability of astaxanthin in animals was enhanced after feeding Haematococcus biomass as a source of astaxanthin. Astaxanthin, used as a nutritional supplement, antioxidant and anticancer agent, prevents diabetes, cardiovascular diseases, and neurodegenerative disorders, and also stimulates immunization. Astaxanthin products are used for commercial applications in the dosage forms as tablets, capsules, syrups, oils, soft gels, creams, biomass and granulated powders. Astaxanthin patent applications are available in food, feed and nutraceutical applications. The current review provides up-to-date information on astaxanthin sources, extraction, analysis, stability, biological activities, health benefits and special attention paid to its commercial applications.

  9. Astaxanthin: sources, extraction, stability, biological activities and its commercial applications--a review.

    Science.gov (United States)

    Ambati, Ranga Rao; Phang, Siew Moi; Ravi, Sarada; Aswathanarayana, Ravishankar Gokare

    2014-01-07

    There is currently much interest in biological active compounds derived from natural resources, especially compounds that can efficiently act on molecular targets, which are involved in various diseases. Astaxanthin (3,3'-dihydroxy-β, β'-carotene-4,4'-dione) is a xanthophyll carotenoid, contained in Haematococcus pluvialis, Chlorella zofingiensis, Chlorococcum, and Phaffia rhodozyma. It accumulates up to 3.8% on the dry weight basis in H. pluvialis. Our recent published data on astaxanthin extraction, analysis, stability studies, and its biological activities results were added to this review paper. Based on our results and current literature, astaxanthin showed potential biological activity in in vitro and in vivo models. These studies emphasize the influence of astaxanthin and its beneficial effects on the metabolism in animals and humans. Bioavailability of astaxanthin in animals was enhanced after feeding Haematococcus biomass as a source of astaxanthin. Astaxanthin, used as a nutritional supplement, antioxidant and anticancer agent, prevents diabetes, cardiovascular diseases, and neurodegenerative disorders, and also stimulates immunization. Astaxanthin products are used for commercial applications in the dosage forms as tablets, capsules, syrups, oils, soft gels, creams, biomass and granulated powders. Astaxanthin patent applications are available in food, feed and nutraceutical applications. The current review provides up-to-date information on astaxanthin sources, extraction, analysis, stability, biological activities, health benefits and special attention paid to its commercial applications.

  10. Interactions between Carotenoids from Marine Bacteria and Other Micronutrients: Impact on Stability and Antioxidant Activity

    Directory of Open Access Journals (Sweden)

    Charlotte Sy

    2015-11-01

    Full Text Available Recently isolated spore-forming pigmented marine bacteria Bacillus indicus HU36 are sources of oxygenated carotenoids with original structures (about fifteen distinct yellow and orange pigments with acylated d-glucosyl groups. In this study, we evaluated the stability (sensitivity to iron-induced autoxidation and antioxidant activity (inhibition of iron-induced lipid peroxidation of combinations of bacterial HU36 carotenoids with the bacterial vitamin menaquinone MQ-7 and with phenolic antioxidants (vitamin E, chlorogenic acid, rutin. Unexpectedly, MQ-7 strongly improves the ability of HU36 carotenoids to inhibit FeII-induced lipid peroxidation, although MQ-7 was not consumed in the medium. We propose that their interaction modifies the carotenoid antioxidant mechanism(s, possibly by allowing carotenoids to scavenge the initiating radicals. For comparison, β-carotene and lycopene in combination were shown to exhibit a slightly higher stability toward iron-induced autoxidation, as well as an additive antioxidant activity as compared to the carotenoids, individually. HU36 carotenoids and phenolic antioxidants displayed synergistic activities in the inhibition of linoleic acid peroxidation induced by heme iron, but not by free iron. Synergism could arise from antioxidants interacting via electron transfer through the porphyrin nucleus of heme iron. Overall, combining antioxidants acting via complementary mechanisms could be the key for optimizing the activity of this bacterial carotenoid cocktail.

  11. Influence of cysteine and methionine availability on protein peroxide scavenging activity and phenolic stability in emulsions.

    Science.gov (United States)

    Zhou, Lisa; Elias, Ryan J

    2014-03-01

    Plant phenolics are secondary metabolites that have been shown to confer beneficial health effects in humans. However, many of these compounds undergo metal-catalysed oxidation reactions, leading to the generation of hydrogen peroxide (H2O2) and other reactive oxygen species that may negatively impact product stability. In proteins, methionine (Met) and cysteine (Cys) are capable of reacting directly with peroxides. Thus, the dairy proteins, casein (CAS) and β-lactoglobulin (BLG), were examined for their ability to scavenge H2O2 (400μM) and influence (-)-epigallocatechin-3-gallate (EGCG) oxidation (400μM) in Tween- or sodium dodecyl sulphate (SDS)-stabilised hexadecane emulsions. To examine the effect that the accessibility of these amino acids have on their peroxide scavenging activities, proteins were pre-treated with tert-butyl hydroperoxide (TBHP), a bulky peroxide, to oxidise only solvent accessible Met residues or H2O2, the smallest peroxide, to oxidise buried Met residues. In CAS treatments, higher Met content yielded greater peroxide scavenging activity and EGCG stability. CAS treatments also showed significantly higher peroxide scavenging activity compared to the corresponding BLG treatment. However, BLG peroxide scavenging activity was greatly enhanced in SDS-stabilised emulsions due to protein denaturation and subsequent exposure of previously buried Cys residues.

  12. Superior acidic catalytic activity and stability of Fe-doped HTaWO6 nanotubes

    KAUST Repository

    Liu, He

    2017-07-26

    Fe-doped HTaWO6 (H1-3xFexTaWO6, x = 0.23) nanotubes as highly active solid acid catalysts were prepared via an exfoliation-scrolling-exchange process. The specific surface area and pore volume of undoped nanotubes (20.8 m2 g-1, 0.057 cm3 g-1) were remarkably enhanced through Fe3+ ion-exchange (>100 m2 g-1, 0.547 cm3 g-1). Doping Fe ions into the nanotubes endowed them with improved thermal stability due to the stronger interaction between the intercalated Fe3+ ions and the host layers. This interaction also facilitated the preservation of effective Brønsted acid sites and the generation of new acid sites. The integration of these functional roles resulted in Fe-doped nanotubes with high acidic catalytic activities in the Friedel-Crafts alkylation of anisole and the esterification of acetic acid. Facile accessibility to active sites, generation of effective Brønsted acid sites, high stability of the tubular structure and strong acid sites were found to synergistically contribute to the excellent acidic catalytic efficiency. Additionally, the activity of cycled nanocatalysts can be easily recovered through annealing treatment.

  13. Phosphate-Activated Cyclin-Dependent Kinase Stabilizes G1 Cyclin To Trigger Cell Cycle Entry

    Science.gov (United States)

    Menoyo, S.; Ricco, N.; Bru, S.; Hernández-Ortega, S.; Escoté, X.; Aldea, M.

    2013-01-01

    G1 cyclins, in association with a cyclin-dependent kinase (CDK), are universal activators of the transcriptional G1-S machinery during entry into the cell cycle. Regulation of cyclin degradation is crucial for coordinating progression through the cell cycle, but the mechanisms that modulate cyclin stability to control cell cycle entry are still unknown. Here, we show that a lack of phosphate downregulates Cln3 cyclin and leads to G1 arrest in Saccharomyces cerevisiae. The stability of Cln3 protein is diminished in strains with low activity of Pho85, a phosphate-sensing CDK. Cln3 is an in vitro substrate of Pho85, and both proteins interact in vivo. More interestingly, cells that carry a CLN3 allele encoding aspartic acid substitutions at the sites of Pho85 phosphorylation maintain high levels of Cln3 independently of Pho85 activity. Moreover, these cells do not properly arrest in G1 in the absence of phosphate and they die prematurely. Finally, the activity of Pho85 is essential for accumulating Cln3 and for reentering the cell cycle after phosphate refeeding. Taken together, our data indicate that Cln3 is a molecular target of the Pho85 kinase that is required to modulate cell cycle entry in response to environmental changes in nutrient availability. PMID:23339867

  14. Stability and activity of doped transition metal zeolites in the hydrothermal processing

    Directory of Open Access Journals (Sweden)

    Thomas François Robin

    2015-12-01

    Full Text Available This study investigates the stability and activity of HZSM-5 doped with metals such as molybdenum, nickel, copper and iron in under hydrothermal conditions used for the direct liquefaction of microalgae. Catalysts have been prepared by ion exchange techniques, and MoZSM-5 was also prepared by wet incipient impregnation for comparison. Hydrothermal liquefaction is considered as a potential route to convert microalgae into a sustainable fuel. One of the drawbacks of this process is that the bio-crude produced contains significant levels of nitrogen and oxygen compounds which have an impact on the physical and chemical propriety of the fuel. Heterogeneous catalysts have been shown to improve the quality of the bio-crude by reducing nitrogen and oxygen contents. Zeolites, such as HZSM-5, are strong candidates due to their low cost compared to noble metal catalysts but their stability and activity under hydrothermal conditions is not well understood. The stability of the catalysts has been determined under hydrothermal conditions at 350 °C. Catalysts have been characterised before and after treatment using XRD, BET physisorption and STEM microscopy. Metal leaching was determined by analysis of the water phase following hydrothermal treatment. The inserted cation following ion-exchange can influence the physical properties of HZSM-5 for example molybdenum improves the crystallinity of the zeolite. In general, metal doped zeolites were relatively stable under subcritical water. Activity of the catalysts for processing lipids, protein and microalgae has been assessed. Four feedstocks were selected: sunflower oil, soya proteins, Chlorella and P. ellipsoidea. The catalysts exhibited greater activity towards converting lipids for example MoZSM-5 enhanced the formation of aromatic compounds. NiZSM-5 and CuZSM-5 were observed to be more efficient for deoxygenation.

  15. Mitochondrial functional state impacts spontaneous neocortical activity and resting state FMRI.

    Directory of Open Access Journals (Sweden)

    Basavaraju G Sanganahalli

    Full Text Available Mitochondrial Ca(2+ uptake, central to neural metabolism and function, is diminished in aging whereas enhanced after acute/sub-acute traumatic brain injury. To develop relevant translational models for these neuropathologies, we determined the impact of perturbed mitochondrial Ca(2+ uptake capacities on intrinsic brain activity using clinically relevant markers. From a multi-compartment estimate of probable baseline Ca(2+ ranges in the brain, we hypothesized that reduced or enhanced mitochondrial Ca(2+ uptake capacity would decrease or increase spontaneous neuronal activity respectively. As resting state fMRI-BOLD fluctuations and stimulus-evoked BOLD responses have similar physiological origins [1] and stimulus-evoked neuronal and hemodynamic responses are modulated by mitochondrial Ca(2+ uptake capacity [2], [3] respectively, we tested our hypothesis by measuring hemodynamic fluctuations and spontaneous neuronal activities during normal and altered mitochondrial functional states. Mitochondrial Ca(2+ uptake capacity was perturbed by pharmacologically inhibiting or enhancing the mitochondrial Ca(2+ uniporter (mCU activity. Neuronal electrical activity and cerebral blood flow (CBF fluctuations were measured simultaneously and integrated with fMRI-BOLD fluctuations at 11.7T. mCU inhibition reduced spontaneous neuronal activity and the resting state functional connectivity (RSFC, whereas mCU enhancement increased spontaneous neuronal activity but reduced RSFC. We conclude that increased or decreased mitochondrial Ca(2+ uptake capacities lead to diminished resting state modes of brain functional connectivity.

  16. Aspartame-stabilized gold-silver bimetallic biocompatible nanostructures with plasmonic photothermal properties, antibacterial activity, and long-term stability.

    Science.gov (United States)

    Fasciani, Chiara; Silvero, M Jazmin; Anghel, Maria Alexandra; Argüello, Gerardo A; Becerra, Maria Cecilia; Scaiano, Juan C

    2014-12-17

    Gold-silver core-shell nanoparticles stabilized with a common sweetener, aspartame (AuNP@Ag@Asm), combine the antimicrobial properties of silver with the photoinduced plasmon-mediated photothermal effects of gold. The particles were tested with several bacterial strains, while biocompatibility was verified with human dermal fibroblasts.

  17. Insulin analog with additional disulfide bond has increased stability and preserved activity

    DEFF Research Database (Denmark)

    Vinther, Tine N.; Norrman, Mathias; Ribel, Ulla;

    2013-01-01

    bond may enhance insulin structural stability which would be highly desirable in a pharmaceutical use. To address this hypothesis, we designed insulin with an additional interchain disulfide bond in positions A10/B4 based on Cα-Cα distances, solvent exposure, and side-chain orientation in human insulin...... (HI) structure. This insulin analog had increased affinity for the insulin receptor and apparently augmented glucodynamic potency in a normal rat model compared with HI. Addition of the disulfide bond also resulted in a 34.6°C increase in melting temperature and prevented insulin fibril formation...... the classical insulin structure. Furthermore, the additional disulfide bond prevented this insulin analog from adopting the R-state conformation and thus showing that the R-state conformation is not a prerequisite for binding to insulin receptor as previously suggested. In summary, this is the first example...

  18. Radioactive nuclear waste stabilization - Aspects of solid-state molecular engineering and applied geochemistry

    Science.gov (United States)

    Haggerty, S. E.

    1983-01-01

    Stabilization techniques for the storage of radioactive wastes are surveyed, with emphasis on immobilization in a primary barrier of synthetic rock. The composition, half-life, and thermal-emission characteristics of the wastes are shown to require thermally stable immobilization enduring at least 100,000 years. Glass materials are determined to be incapable of withstanding the expected conditions, average temperatures of 100-500 C for the first 100 years. The geological-time stability of crystalline materials, ceramics or synthetic rocks, is examined in detail by comparing their components with similar naturally occurring minerals, especially those containing the same radioactive elements. The high-temperature environment over the first 100 years is seen as stabilizing, since it can recrystallize radiation-induced metamicts. The synthetic-rock stabilization technique is found to be essentially feasible, and improvements are suggested, including the substitution of nepheline with freudenbergite and priderite for alkaline-waste stabilization, the maintenance of low oxygen fugacity, and the dilution of the synthetic-rock pellets into an inert medium.

  19. Radioactive nuclear waste stabilization - Aspects of solid-state molecular engineering and applied geochemistry

    Science.gov (United States)

    Haggerty, S. E.

    1983-01-01

    Stabilization techniques for the storage of radioactive wastes are surveyed, with emphasis on immobilization in a primary barrier of synthetic rock. The composition, half-life, and thermal-emission characteristics of the wastes are shown to require thermally stable immobilization enduring at least 100,000 years. Glass materials are determined to be incapable of withstanding the expected conditions, average temperatures of 100-500 C for the first 100 years. The geological-time stability of crystalline materials, ceramics or synthetic rocks, is examined in detail by comparing their components with similar naturally occurring minerals, especially those containing the same radioactive elements. The high-temperature environment over the first 100 years is seen as stabilizing, since it can recrystallize radiation-induced metamicts. The synthetic-rock stabilization technique is found to be essentially feasible, and improvements are suggested, including the substitution of nepheline with freudenbergite and priderite for alkaline-waste stabilization, the maintenance of low oxygen fugacity, and the dilution of the synthetic-rock pellets into an inert medium.

  20. Mood stabilizers for patients with bipolar disorder: the state of the art.

    Science.gov (United States)

    Altamura, A Carlo; Lietti, Licia; Dobrea, Cristina; Benatti, Beatrice; Arici, Chiara; Dell'Osso, Bernardo

    2011-01-01

    Bipolar disorder (BD) is a prevalent and disabling condition, often comorbid with other medical and psychiatric conditions and frequently misdiagnosed. International treatment guidelines for BD recommend the use of mood stabilizers - either in monotherapy or in association - as the gold standard in both acute and long-term therapy. Commonly used in the clinical practice of BD, mood stabilizers have represented an evolving field over the last few years. The concept of stabilization, in fact, has been stressed as the ultimate objective of the treatment of BD, given the chronic and recurrent nature of the illness, which accounts for its significant levels of impairment and disability. To date, different compounds are included within the broad class of mood stabilizers, with lithium, anticonvulsants and, more recently, atypical antipsychotics being the most representative agents. This article is aimed at providing an updated review of the available literature in relation to the role of mood stabilizers in BD, with particular emphasis on their mechanism of action, main clinical aspects and specific use in the different phases of BD treatment, according to the most recently published international treatment guidelines.

  1. Robust H∞ Stabilization of Uncertain Linear Time-Delay System with Delayed/Undelayed State Feedback Controllers

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    This paper focuses on the H∞ controller design for linear systems with time-varying delays and norm bounded parameter perturbetions in the system state and control/disturbance. On the existence of delayed/undelayed full state feedback controllers, we present a sufficient condition and give a design method in the form of Riccati equation. The controller can not only stabilize the time-delay system, but also make the H∞ norm of the closed-loop system be less than a given bound. This result practically generalizes the related results in current literature.

  2. Neuroticism and State Differences in Partisanship in the USA: Emotional Stability, Ideological Orientation, and Republican Preference

    Directory of Open Access Journals (Sweden)

    Stewart J. H. McCann

    2014-09-01

    Full Text Available Relations between Neuroticism, Republican-Democrat preference, and conservative-liberal ideological orientation were examined with the states of the USA as units of analysis. State-aggregated Neuroticism scores were based on 1999-2005 responses of 619,397 residents to the 44-item Big Five Inventory. State Republican-Democrat preference was based on the 2002 occupancy of the U.S. Presidency, U.S. House, U.S. Senate, state House, state Senate, and state Governorship, as well as state-aggregated partisanship responses of 110,305 persons to 1998-2002 CBS/New York Times national polls. State conservative-liberal ideological orientation was based on 1998-2002 state-aggregated responses of 103,828 persons to CBS/New York Times national polls. Using correlation, partial correlation, and hierarchical multiple regression, it was determined that lower state resident Neuroticism is associated with Republican preference, and that both conservative-liberal ideological orientation and state resident Neuroticism account independently for variance in Republican-Democrat preference. These relations were found when 1998-2002 state socioeconomic status, white percent, and urban percent were statistically considered and controlled in partial correlation and hierarchical regression analysis. In contrast, corresponding analyses involving the other Big Five showed that only Openness and Conscientiousness showed any relation to partisanship, albeit infrequent and inconsistent. State resident Neuroticism is the primary state-level Big Five predictor of Republican/Democratic Party choice.

  3. Data inconsistencies from states with unconventional oil and gas activity.

    Science.gov (United States)

    Malone, Samantha; Kelso, Matthew; Auch, Ted; Edelstein, Karen; Ferrar, Kyle; Jalbert, Kirk

    2015-01-01

    The quality and availability of unconventional oil and gas (O&G) data in the United States have never been compared methodically state-to-state. By conducting such an assessment, this study seeks to better understand private and publicly sourced data variability and to identify data availability gaps. We developed an exploratory data-grading tool - Data Accessibility and Usability Index (DAUI) - to guide the review of O&G data quality. Between July and October 2013, we requested, collected, and assessed 5 categories of unconventional O&G data (wells drilled, violations, production, waste, and Class II disposal wells) from 10 states with active drilling activity. We based our assessment on eight data quality parameters (accessibility, usability, point location, completeness, metadata, agency responsiveness, accuracy, and cost). Using the DAUI, two authors graded the 10 states and then averaged their scores. The average score received across all states, data categories, and parameters was 67.1 out of 100, largely insufficient for proper data transparency. By state, Pennsylvania received the highest average ( = 93.5) and ranked first in all but one data category. The lowest scoring state was Texas ( = 44) largely due to its policy of charging for certain data. This article discusses the various reasons for scores received, as well as methodological limitations of the assessment metrics. We argue that the significant variability of unconventional O&G data-and its availability to the public-is a barrier to regulatory and industry transparency. The lack of transparency also impacts public education and broader participation in industry governance. This study supports the need to develop a set of data best management practices (BMPs) for state regulatory agencies and the O&G industry, and suggests potential BMPs for this purpose.

  4. Electrocatalytic properties and stability of titanium anodes activated by the inorganic sol–gel procedure

    Directory of Open Access Journals (Sweden)

    VLADIMIR V. PANIC

    2008-10-01

    Full Text Available The properties of activated titanium anodes, RuO2–TiO2/Ti and RuO2–TiO2–IrO2/Ti, prepared from oxide sols by the sol–gel procedure, are reviewed. RuO2 and TiO2 sols were synthesized by forced hydrolysis of the corresponding chlorides in acid medium. The morphology of the prepared sols was investigated by transmission electron microscopy. The chemical composition of the RuO2 sol was determined by X-ray diffraction and thermogravimetric analysis. The loss of electrocatalytic activity of a RuO2–TiO2/Ti anode during an accelerated stability test was investigated by examination of the changes in the electrochemical characteristics in the potential region of the chlorine and oxygen evolution reaction, as well as on the open circuit potential. These electrochemical characteristics were investigated by cyclic voltammetry, electrochemical impedance spectroscopy and polarization measurements. The changes in electrochemical characteristics of the anode prepared by the sol–gel procedure were compared to the changes registered for an anode prepared by the traditional thermal decomposition of metal chlorides. The comparison indicated that the main cause for the activity loss of the sol–gel prepared anode was the electrochemical dissolution of RuO2, while in the case of thermally prepared anode the loss was mainly caused by the formation of an insulating TiO2 layer in the coating/Ti substrate interphase. The results of an accelerated stability test on RuO2–TiO2/Ti and RuO2–TiO2–IrO2/Ti anodes showed that the ternary coating is considerably more stable than the binary one, which is the consequence of the greater stability of IrO2 in comparison to RuO2.

  5. Design of an optimal active stabilizer mechanism for enhancing vehicle rolling resistance

    Institute of Scientific and Technical Information of China (English)

    Yaghoub Pourasad; Mehdi Mahmoodi-k; Majid Oveisi

    2016-01-01

    Improving rollover and stability of the vehicles is the indispensable part of automotive research to prevent vehicle rollover and crashes. The main objective of this work is to develop active control mechanism based on fuzzy logic controller (FLC) and linear quadratic regulator (LQR) for improving vehicle path following, roll and handling performances simultaneously. 3-DOF vehicle model including yaw rate, lateral velocity (lateral dynamic) and roll angle (roll dynamic) were developed. The controller produces optimal moment to increase stability and roll margin of vehicle by receiving the steering angle as an input and vehicle variables as a feedback signal. The effectiveness of proposed controller and vehicle model were evaluated during fishhook and single lane-change maneuvers. Simulation results demonstrate that in both cases (FLC and LQR controllers) by reducing roll angle, lateral acceleration and side slip angles remain under 0.6g and 4° during maneuver, which ensures vehicle stability and handling properties. Finally, the sensitivity and robustness analysis of developed controller for varying longitudinal speeds were investigated.

  6. Mechanochemically Activated, Calcium Oxide-Based, Magnesium Oxide-Stabilized Carbon Dioxide Sorbents.

    Science.gov (United States)

    Kurlov, Alexey; Broda, Marcin; Hosseini, Davood; Mitchell, Sharon J; Pérez-Ramírez, Javier; Müller, Christoph R

    2016-09-01

    Carbon dioxide capture and storage (CCS) is a promising approach to reduce anthropogenic CO2 emissions and mitigate climate change. However, the costs associated with the capture of CO2 using the currently available technology, that is, amine scrubbing, are considered prohibitive. In this context, the so-called calcium looping process, which relies on the reversible carbonation of CaO, is an attractive alternative. The main disadvantage of naturally occurring CaO-based CO2 sorbents, such as limestone, is their rapid deactivation caused by thermal sintering. Here, we report a scalable route based on wet mechanochemical activation to prepare MgO-stabilized, CaO-based CO2 sorbents. We optimized the synthesis conditions through a fundamental understanding of the underlying stabilization mechanism, and the quantity of MgO required to stabilize CaO could be reduced to as little as 15 wt %. This allowed the preparation of CO2 sorbents that exceed the CO2 uptake of the reference limestone by 200 %.

  7. Application of contact stabilization activated sludge for enhancing biological phosphorus removal (EBPR in domestic wastewater

    Directory of Open Access Journals (Sweden)

    Ehab M. Rashed

    2014-04-01

    Full Text Available The experiment has been performed in order to investigate the effect of using contact stabilization activated sludge as an application of enhancing biological phosphorous removal (EBPR by using contact tank as a phosphorus uptake zone and using thickening tank as a phosphorus release zone. The study involved the construction of a pilot plant which was setup in Quhafa waste water treatment plant (WWTP that included contact, final sedimentation, stabilization and thickening tanks, respectively with two returns sludge in this system one of them to contact tank and another to stabilization tank. Then observation of the uptake and release of total phosphorus by achievement through two batch test using sludge samples from thickener and final sedimentations. Results showed the removal efficiencies of COD, BOD and TP for this pilot plant with the range of 94%, 85.44% and 80.54%, respectively. On the other hand the results of batch tests showed that the reason of high ability of phosphorus removal for this pilot plant related to the high performance of microorganisms for phosphorus accumulating. Finally the mechanism of this pilot plant depends on the removal of the phosphorus from the domestic waste water as a concentrated TP solution from the supernatant above the thickening zone not through waste sludge like traditional systems.

  8. A translational regulator, PUM2, promotes both protein stability and kinase activity of Aurora-A.

    Directory of Open Access Journals (Sweden)

    Yei-Hsuan Huang

    Full Text Available Aurora-A, a centrosomal serine-threonine kinase, orchestrates several key aspects of cell division. However, the regulatory pathways for the protein stability and kinase activity of Aurora-A are still not completely understood. In this study, PUM2, an RNA-binding protein, is identified as a novel substrate and interacting protein of Aurora-A. Overexpression of the PUM2 mutant which fails to interact with Aurora-A, and depletion of PUM2 result in a decrease in the amount of Aurora-A. PUM2 physically binds to the D-box of Aurora-A, which is recognized by APC/C(Cdh1. Overexpression of PUM2 prevents ubiquitination and enhances the protein stability of Aurora-A, suggesting that PUM2 protects Aurora-A from APC/C(Cdh1-mediated degradation. Moreover, association of PUM2 with Aurora-A not only makes Aurora-A more stable but also enhances the kinase activity of Aurora-A. Our study suggests that PUM2 plays two different but important roles during cell cycle progression. In interphase, PUM2 localizes in cytoplasm and plays as translational repressor through its RNA binding domain. However, in mitosis, PUM2 physically associates with Aurora-A to ensure enough active Aurora-A at centrosomes for mitotic entry. This is the first time to reveal the moonlight role of PUM2 in mitosis.

  9. On the stability of adaptation process in active noise control systems.

    Science.gov (United States)

    Ardekani, Iman Tabatabaei; Abdulla, Waleed H

    2011-01-01

    The stability analysis of the adaptation process, performed by the filtered-x least mean square algorithm on weights of active noise controllers, has not been fully investigated. The main contribution of this paper is conducting a theoretical stability analysis for this process without utilizing commonly used simplifying assumptions regarding the secondary electro-acoustic channel. The core of this analysis is based on the root locus theory. The general rules for constructing the root locus plot of the adaptation process are derived by obtaining root locus parameters, including start points, end points, asymptote lines, and breakaway points. The conducted analysis leads to the derivation of a general upper-bound for the adaptation step-size beyond which the mean weight vector of the active noise controller becomes unstable. Also, this analysis yields the optimum step-size for which the adaptive active noise controller has its fastest dynamic performance. The proposed upper-bound and optimum values apply to general secondary electro-acoustic channels, unlike the commonly used ones which apply to only pure delay channels. The results are found to agree very well with those obtained from numerical analyses and computer simulation experiments.

  10. Synthesis, characterization and antimicrobial activity of dextran sulphate stabilized silver nanoparticles

    Science.gov (United States)

    Cakić, Milorad; Glišić, Slobodan; Nikolić, Goran; Nikolić, Goran M.; Cakić, Katarina; Cvetinov, Miroslav

    2016-04-01

    Dextran sulphate stabilized silver nanoparticles (AgNPs - DS) were synthesized from aqueous solution of silver nitrate (AgNO3) and dextran sulphate sodium salt (DS). The characterization of AgNPs - DS was performed by ultraviolet-visible spectroscopy (UV-VIS), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and antimicrobial activity. The formation of AgNPs - DS was monitored by colour changes of the reaction mixture from yellowish to brown and by measuring the surface plasmon resonance absorption peak in UV-VIS spectra at 420 nm. The SEM analysis was used for size and shape determination of AgNPs - DS. The presence of elemental silver and its crystalline structure in AgNPs - DS were confirmed by EDX and XRD analyses. The possible functional groups of DS responsible for the reduction and stabilization of AgNPs were determinated by FTIR spectroscopy. The AgNPs - DS showed strong antibacterial activity against Staphylococcus aureus ATCC 25923, Bacillus cereus ATCC 11778, Bacillus luteus in haus strain, Bacillus subtilis ATTC 6633, Listeria monocytogenes ATCC 15313, Escherichia coli ATTC 25922, Pseudomonas aeruginosa ATTC 27853, Klebsiella pneumoniae ATTC 700603, Proteus vulgaris ATTC 8427, and antifungal activity against Candida albicans ATTC 2091.

  11. INVESTMENT ACTIVITY OF NON-STATE FOUNDS OF RUSSIA

    Directory of Open Access Journals (Sweden)

    Kobylinsky S. V.

    2016-04-01

    Full Text Available Currently, pension by virtue of their social significance in favor of one of the main socially important guarantee of stable development of society, to ensure the financial and budgetary sphere of the state. Private pension founds are viewed as an instrument to raise the material well-being of pensioners. The social significance of non-state pension funds is to involve the population in the sphere of voluntary pension insurance. The author analyzed the role of non-state pension funds in acting to pension system. The article subjected to a detailed analysis of the norms of a number of Federal laws, fixing the investment activity of non-state pension found. The author concludes that there is a need to improve existing legislation on investment activity of non-state pension found. As well, the authors indicated some legal problems that occur in practice arising from owners of the investment portfolio. The authors have analyzed the performance of pension funds and formed an opinion about the state of the whole system. Following consideration of the practical problems has been offered for both theoretical and practical ways to address them in order to prevent violation

  12. High Frequency State-Variable Biquadratic Active Filters

    Directory of Open Access Journals (Sweden)

    T. Dostal

    1998-04-01

    Full Text Available The state-variable (KHN active RC biquadratic filters with good performance in high frequency range , flexibility of outputs (LP, HP, BP, low sensitivities in novel current and hybrid modes, using current conveyors, transimpedance, trans-admittance and current operational amplifiers, are given in this paper.

  13. Steady-state organization of binary mixtures by active impurities

    DEFF Research Database (Denmark)

    Sabra, Mads Christian; Gilhøj, Henriette; Mouritsen, Ole G.

    1998-01-01

    The structural reorganization of a phase-separated binary mixture in the presence of an annealed dilution of active impurities is studied by computer-simulation techniques via a simple two-dimensional lattice-gas model. The impurities, each of which has two internal states with different affinity...

  14. 34 CFR 300.704 - State-level activities.

    Science.gov (United States)

    2010-07-01

    ... certify to the Secretary that the arrangements to establish responsibility for services pursuant to... transition of students with disabilities to postsecondary activities; (vii) To assist LEAs in meeting... State Medicaid program under Title XIX of the Social Security Act. (9) Funds reserved under paragraph...

  15. The Current State of Marketing Activity among Higher Education Institutions.

    Science.gov (United States)

    Newman, Cynthia M.

    2002-01-01

    Investigated the current state of marketing, marketing research, and planning practices at four-year higher education institutions. Builds upon previous studies by Blackburn (1979) and Goldgehn (1982 and 1989). Determined whether the use and apparent understanding of marketing and its attendant activities by admissions and enrollment management…

  16. Ground state destabilization by anionic nucleophiles contributes to the activity of phosphoryl transfer enzymes.

    Directory of Open Access Journals (Sweden)

    Logan D Andrews

    2013-07-01

    Full Text Available Enzymes stabilize transition states of reactions while limiting binding to ground states, as is generally required for any catalyst. Alkaline Phosphatase (AP and other nonspecific phosphatases are some of Nature's most impressive catalysts, achieving preferential transition state over ground state stabilization of more than 10²²-fold while utilizing interactions with only the five atoms attached to the transferred phosphorus. We tested a model that AP achieves a portion of this preference by destabilizing ground state binding via charge repulsion between the anionic active site nucleophile, Ser102, and the negatively charged phosphate monoester substrate. Removal of the Ser102 alkoxide by mutation to glycine or alanine increases the observed Pi affinity by orders of magnitude at pH 8.0. To allow precise and quantitative comparisons, the ionic form of bound P(i was determined from pH dependencies of the binding of Pi and tungstate, a P(i analog lacking titratable protons over the pH range of 5-11, and from the ³¹P chemical shift of bound P(i. The results show that the Pi trianion binds with an exceptionally strong femtomolar affinity in the absence of Ser102, show that its binding is destabilized by ≥10⁸-fold by the Ser102 alkoxide, and provide direct evidence for ground state destabilization. Comparisons of X-ray crystal structures of AP with and without Ser102 reveal the same active site and P(i binding geometry upon removal of Ser102, suggesting that the destabilization does not result from a major structural rearrangement upon mutation of Ser102. Analogous Pi binding measurements with a protein tyrosine phosphatase suggest the generality of this ground state destabilization mechanism. Our results have uncovered an important contribution of anionic nucleophiles to phosphoryl transfer catalysis via ground state electrostatic destabilization and an enormous capacity of the AP active site for specific and strong recognition of the

  17. Actively stabilized wavelength-insensitive carrier elimination from an electro-optically modulated laser beam

    CERN Document Server

    Cooper, Nathan; Dunning, Alexander; Freegarde, Tim

    2012-01-01

    We demonstrate a simple and robust technique for removal of the carrier wave from a phase-modulated laser beam, using a non-interferometric method that is insensitive to the modulation frequency and instead exploits the polarization-dependence of electro-optic modulation. An actively stabilized system using feedback via a liquid crystal cell yields long-term carrier suppression in excess of 28 dB at the expense of a 6.5 dB reduction in sideband power.

  18. Active and passive stabilization of a high-power UV frequency-doubled diode laser

    CERN Document Server

    Eismann, Ulrich; Simeonidis, Konstantinos; Keller, Felix; Rohde, Felix; Opalevs, Dmitrijs; Scholz, Matthias; Kaenders, Wilhelm; Stuhler, Jürgen

    2016-01-01

    We present a resonantly frequency-doubled tapered amplified semiconductor laser system emitting up to 2.6 W blue light at 400 nm. The output power is stable on both short and long timescales with 0.12% RMS relative intensity noise, and less than 0.15%/h relative power loss over 16 hours of free running continuous operation. Furthermore, the output power can be actively stabilized, and the alignment of the input beams of the tapered amplifier chip, the frequency doubling cavity and-in case of fiber output-the fiber can be optimized automatically using computer-controlled mirrors.

  19. Activity and stability of Fenton-like species supported over different silica structures

    Energy Technology Data Exchange (ETDEWEB)

    Calleja, G.; Melero, J.A.; Martinez, F.; Molina, R. [Dept. of Chemical, Environmental and Materials Technology, ESCET, Rey Juan Carlos Univ., Mostoles (Madrid) (Spain)

    2003-07-01

    Different strategies of synthesis for the preparation of iron containing materials and using different silica supports (amorphous, mesostructured and zeolitic materials) have been evaluated with the purpose of enhancing the activity and stability of metal species in heterogeneous Fenton-like processes. Their catalytic performance in wet peroxide oxidation processes has been monitored in terms of phenol and total organic carbon (TOC) conversions, products distribution and degree of metal leaching into liquid phase reaction. The environment and type of iron species induce significant changes on the catalytic performance of the catalysts. (orig.)

  20. THE EUROPEAN MODEL OF STATE REGULATION OF TOURISM ACTIVITIES

    Directory of Open Access Journals (Sweden)

    О. Davydova

    2013-11-01

    Full Text Available In the article the existing model of state regulation of the development of tourism. Expediency of the European model of state regulation of tourism development in Ukraine. It is noted that the European model of state regulation of tourism activities based on the coordination of marketing activities and the development of cooperation between the public and private sectors. The basic forms of public-private partnerships and the advantages of using cluster model of development of tourism, namely, contracts, production sharing agreement, lease, joint venture. Promising areas of application of the PPP identified the transport sector, housing and utilities, energy and tourism sector. The features of cluster formations in the country and the prospects for tourism clusters.

  1. An in silico study of the molecular basis of B-RAF activation and conformational stability

    Directory of Open Access Journals (Sweden)

    Jónsdóttir Svava

    2009-07-01

    Full Text Available Abstract Background B-RAF kinase plays an important role both in tumour induction and maintenance in several cancers and it is an attractive new drug target. However, the structural basis of the B-RAF activation is still not well understood. Results In this study we suggest a novel molecular basis of B-RAF activation based on molecular dynamics (MD simulations of B-RAFWT and the B-RAFV600E, B-RAFK601E and B-RAFD594V mutants. A strong hydrogen bond network was identified in B-RAFWT in which the interactions between Lys601 and the well known catalytic residues Lys483, Glu501 and Asp594 play an important role. It was found that several mutations, which directly or indirectly destabilized the interactions between these residues within this network, contributed to the changes in B-RAF activity. Conclusion Our results showed that the above mechanisms lead to the disruption of the electrostatic interactions between the A-loop and the αC-helix in the activating mutants, which presumably contribute to the flipping of the activation segment to an active form. Conversely, in the B-RAFD594V mutant that has impaired kinase activity, and in B-RAFWT these interactions were strong and stabilized the kinase inactive form.

  2. PKCθ-Mediated PDK1 Phosphorylation Enhances T Cell Activation by Increasing PDK1 Stability

    Science.gov (United States)

    Kang, Jung-Ah; Choi, Hyunwoo; Yang, Taewoo; Cho, Steve K.; Park, Zee-Yong; Park, Sung-Gyoo

    2017-01-01

    PDK1 is essential for T cell receptor (TCR)-mediated activation of NF-κB, and PDK1-induced phosphorylation of PKCθ is important for TCR-induced NF-κB activation. However, inverse regulation of PDK1 by PKCθ during T cell activation has not been investigated. In this study, we found that PKCθ is involved in human PDK1 phosphorylation and that its kinase activity is crucial for human PDK1 phosphorylation. Mass spectrometry analysis of wild-type PKCθ or of kinase-inactive form of PKCθ revealed that PKCθ induced phosphorylation of human PDK1 at Ser-64. This PKCθ-induced PDK1 phosphorylation positively regulated T cell activation and TCR-induced NF-κB activation. Moreover, phosphorylation of human PDK1 at Ser-64 increased the stability of human PDK1 protein. These results suggest that Ser-64 is an important phosphorylation site that is part of a positive feedback loop for human PDK1-PKCθ-mediated T cell activation. PMID:28152304

  3. The stress stability of olanzapine: studies of interactions with excipients in solid state pharmaceutical formulations.

    Science.gov (United States)

    Djordjević Filijović, Nataša; Antonijević, Milan D; Pavlović, Aleksandar; Vučković, Ivan; Nikolić, Katarina; Agbaba, Danica

    2015-03-01

    Stress stability testing represents an important part of the drug development process. It is used as an important tool for the identification of degradation products and degradation pathways, as well as for the assessment of changes in physical form of drug molecules. The impact of excipients on the stability of olanzapine confirms that levels of impurities and degradants are limiting parameters and are therefore used for stability evaluation. The major degradation product of olanzapine was identified as 2-methyl-5,10-dihydro-4H-thieno[2,3-b][1,5]benzodiazepine-4-one (III). The structure of III was determined by using LC-MS, IR and NMR. Compatibility and stress stability results demonstrated that tablet formulations of olanzapine are sensitive to temperature and moisture. In samples protected from moisture, the increase in concentration of III was shown to be highly temperature dependent and the degradation followed zero-order kinetics. In addition, studies of olanzapine with excipients and in formulated tablets revealed polymorphic phase changes in some samples, influenced by a combination of stress temperature and humidity conditions. Polymorphic transitions were monitored using x-ray powder diffraction (XRPD) analysis and exhibited no correlation between the phase change (appearance of a new polymorph) and the degradation process.

  4. On-call duty effects on sleep-state physiological stability in male medical interns.

    Directory of Open Access Journals (Sweden)

    Yu-Hsuan Lin

    Full Text Available BACKGROUND: On-call duty among medical interns is characterized by sleep deprivation and stressful working conditions, both of which alter cardiac autonomic modulation. We hypothesized that sleep stability decreased in medical interns during on-call duty. We used cardiopulmonary-coupling (CPC analysis to test our hypothesis. METHODS: We used electrocardiogram (ECG-based CPC analysis to quantify physiological parameters of sleep stability in 13 medical interns during on-call and on-call duty-free periods. There were ten 33.5-h on-call duty shifts per month for interns, each followed by 2 on-call duty-free days, over 3 months. Measurements during sleep were collected before, during, and after an on-call shift. Measurements were repeated 3 months later during an on-call duty-free period. RESULTS: The medical interns had significantly reduced stable sleep, and displayed increased latency to the first epoch of stable sleep during the on-call night shift, compared to the pre-call and on-call duty-free nights. Interns also had significantly increased rapid-eye-movement (REM sleep during the on-call night shift, compared to the pre-call and on-call duty-free nights. CONCLUSION: Medical interns suffer disrupted sleep stability and continuity during on-call night shifts. The ECG-based CPC analysis provides a straightforward means to quantify sleep quality and stability in medical staff performing shift work under stressful conditions.

  5. Existence, uniqueness and stability of positive steady states to a prey-predator diffusion system

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    In the paper, we study the positive solutions of an elliptic system coming from a preypredator model with modified Leslie-Gower and Holling-Type II schemes. We study the existence, non-existence, bifurcation, uniqueness and stability of positive solutions. In particular, we obtain a continuum of positive solutions connecting a semitrivial solution to the unique positive solution of the limiting system.

  6. Vehicle state estimator based regenerative braking implementation on an electric vehicle to improve lateral vehicle stability

    NARCIS (Netherlands)

    Jansen, S.T.H.; Boekel, J.J.P. van; Iersel, S.S. van; Besselink, I.J.M.; Nijmeijer, H.

    2013-01-01

    The driving range of electric vehicles can be extended using regenerative braking. Regenerative braking uses the elctric drive system, and therefore only the driven wheels, for decelerating the vehicle. Braking on one axle affects the stability of the vehicle, especially for road conditions with

  7. Stability, Crisis, and Other Reasons for Optimism: University Foreign Language Education in the United States

    Science.gov (United States)

    Levine, Glenn S.

    2011-01-01

    This article presents a brief overview of the state of university language education in the United States. Despite the impact of the world economic crisis on university language education in the United States, the profession has not yet been impacted to the extent many believe it has. Current scholarly debates allow for both a sober assessment of…

  8. Stability of the Fe3 +  state in ZnO

    DEFF Research Database (Denmark)

    Naidoo, D.; Gunnlaugsson, Haraldur Pall; Mølholt, T.E.

    2013-01-01

    are dominated by the Fe3 +  state exhibiting a slow paramagnetic relaxation. We show that the Fe3 +  state in ZnO saturated by 760 K or storage at room temperature for 12 months, after which they show dominantly the Fe2...... +  state for diffusion and/or annihilation of implantation-induced defects....

  9. Enhanced stability and activity of cellulase in an ionic liquid and the effect of pretreatment on cellulose hydrolysis.

    Science.gov (United States)

    Bose, Sayantan; Barnes, Charles A; Petrich, Jacob W

    2012-02-01

    We discuss the hydrolysis of cellulose using a pure cellulase: endo-1,4-β-D-glucanase (EG) from the fungus, Aspergillus niger, in buffer, the pure ionic liquid (IL), tris-(2-hydroxyethyl)-methylammonium methylsulfate (HEMA), and various mixtures of the two at different temperatures. Steady-state fluorescence and absorbance studies were performed to monitor the stability and activity of EG using cellulose azure as the substrate. EG attains its highest activity at 45°C in buffer and denatures at ∼55°C. On the other hand, HEMA imparts substantial stability to the enzyme, permitting the activity to peak at 75°C. The relative roles of temperature, viscosity, pH, polarity, and the constituent ions of the ILs on the hydrolysis reaction are examined. It is demonstrated that pretreatment of cellulose with ILs such as BMIM Cl, MIM Cl, and HEMA results in more rapid conversion to glucose than hydrolysis with cellulose that is not pretreated. The percent conversion to glucose from pretreated cellulose is increased when the temperature is increased from 45 to 60°C. Two different ILs are used to increase the efficiency of cellulose conversion to glucose. Cellulose is pretreated with BMIM Cl. Subsequent hydrolysis of the pretreated cellulose in 10-20% solutions of HEMA in buffer provides higher yields of glucose at 60°C. Finally, to our knowledge, this is the first study dealing with a pure endoglucanase from commercial A. niger. This enzyme not only shows higher tolerance to ILs, such as HEMA, but also has enhanced thermostability in the presence of the IL. Copyright © 2011 Wiley Periodicals, Inc.

  10. Stability analysis of fractional-order generalized chaotic susceptible–infected–recovered epidemic model and its synchronization using active control method

    Indian Academy of Sciences (India)

    Sana P Ansari; Saurabh K Agrawal; Subir Das

    2015-01-01

    This paper presents the synchronization between a pair of identical susceptible–infected–recovered (SIR) epidemic chaotic systems and fractional-order time derivative using active control method. The fractional derivative is described in Caputo sense. Numerical simulation results show that the method is effective and reliable for synchronizing the fractional-order chaotic systems while it allows the system to remain in chaotic state. The striking features of this paper are: the successful presentation of the stability of the equilibrium state and the revelation that time for synchronization varies with the variation in fractional-order derivatives close to the standard one for different specified values of the parameters of the system.

  11. Experimental study of the stability and activity of brines on the surface of Mars

    Science.gov (United States)

    Altheide, Travis S.

    This work contributes to the understanding of liquid water stability, with an emphasis on the role that dissolved solutes may have had on liquid water formation on Mars, past and present. In chapter 2, the stability of liquid water under martian conditions is explored through experiments on ferric sulfate brines. First, it is demonstrated that such brines can be formed starting from typical martian mineralogy. Ferric sulfates are quite soluble, up to 48 wt%, and can form solutions which remain liquid down to 205 +/-1 K at the eutectic. As a result of low water activities, these solutions exhibit evaporation rates 20 times lower than pure water. The combination of a low eutectic point and low evaporation rates allow subsurface liquids to be stable at high martian latitudes, where the majority of gullies and viscous flow features are located. Thus, the characteristics of ferric sulfate brines were further investigated in chapter 3, where the viscous properties of such solutions were measured, with respect to changing temperature and concentration. Using these results, the viscosity of these solutions on the formation of gullies was considered, where calculated fluid flow velocities were found to be in accordance with some estimates from image analyses of gully formations. In chapter 4, other Mars-relevant brines were studied and characterized under martian surface conditions. Magnesium and ferrous sulfate, and magnesium and ferric chloride brines were found to stabilize water, through lower evaporation rates and freezing point depression, much like the ferric sulfate brines. For these sulfate brines, it was found that the thermodynamic process of phase change, i.e. ice formation and/or salt crystallization, can affect the kinetic process of evaporation, through very low water activities in solution. Furthermore, in chapter 5 these studies were extended to recent results from the Phoenix mission, by examining the stability of perchlorate brines under conditions

  12. Effect of milling conditions on solid-state amorphization of glipizide, and characterization and stability of solid forms.

    Science.gov (United States)

    Xu, Kailin; Xiong, Xinnuo; Zhai, Yuanming; Wang, Lili; Li, Shanshan; Yan, Jin; Wu, Di; Ma, Xiaoli; Li, Hui

    2016-09-10

    In this study, the amorphization of glipizide was systematically investigated through high-energy ball milling at different temperatures. The results of solid-state amorphization through milling indicated that glipizide underwent direct crystal-to-glass transformation at 15 and 25°C and crystal-to-glass-to-crystal conversion at 35°C; hence, milling time and temperature had significant effects on the amorphization of glipizide, which should be effectively controlled to obtain totally amorphous glipizide. Solid forms of glipizide were detailedly characterized through analyses of X-ray powder diffraction, morphology, thermal curves, vibrational spectra, and solid-state nuclear magnetic resonance. The physical stability of solid forms was investigated under different levels of relative humidity (RH) at 25°C. Forms I and III are kinetically stable and do not form any new solid-state forms at various RH levels. By contrast, Form II is kinetically unstable, undergoing direct glass-to-crystal transformation when RH levels higher than 32.8%. Therefore, stability investigation indicated that Form II should be stored under relatively dry conditions to prevent rapid crystallization. High temperatures can also induce the solid-state transformation of Form II; the conversion rate increased with increasing temperature.

  13. Accelerated Stability Studies on Dried Extracts of Centella asiatica Through Chemical, HPLC, HPTLC, and Biological Activity Analyses.

    Science.gov (United States)

    Kaur, Ishtdeep; Suthar, Nancy; Kaur, Jasmeen; Bansal, Yogita; Bansal, Gulshan

    2016-10-01

    Regulatory guidelines recommend systematic stability studies on a herbal product to establish its shelf life. In the present study, commercial extracts (Types I and II) and freshly prepared extract (Type III) of Centella asiatica were subjected to accelerated stability testing for 6 months. Control and stability samples were evaluated for organoleptics, pH, moisture, total phenolic content (TPC), asiatic acid, kaempherol, and high-performance thin layer chromatography fingerprints, and for antioxidant and acetylcholinesterase inhibitory activities. Markers and TPC and both the activities of each extract decreased in stability samples with respect to control. These losses were maximum in Type I extract and minimum in Type III extract. Higher stability of Type III extract than others might be attributed to the additional phytoconstituents and/or preservatives in it. Pearson correlation analysis of the results suggested that TPC, asiatic acid, and kaempferol can be taken as chemical markers to assess chemical and therapeutic shelf lives of herbal products containing Centella asiatica.

  14. Nonequilibrium Equation of State in Suspensions of Active Colloids

    Science.gov (United States)

    Ginot, Félix; Theurkauff, Isaac; Levis, Demian; Ybert, Christophe; Bocquet, Lydéric; Berthier, Ludovic; Cottin-Bizonne, Cécile

    2015-01-01

    Active colloids constitute a novel class of materials composed of colloidal-scale particles locally converting chemical energy into motility, mimicking micro-organisms. Evolving far from equilibrium, these systems display structural organizations and dynamical properties distinct from thermalized colloidal assemblies. Harvesting the potential of this new class of systems requires the development of a conceptual framework to describe these intrinsically nonequilibrium systems. We use sedimentation experiments to probe the nonequilibrium equation of state of a bidimensional assembly of active Janus microspheres and conduct computer simulations of a model of self-propelled hard disks. Self-propulsion profoundly affects the equation of state, but these changes can be rationalized using equilibrium concepts. We show that active colloids behave, in the dilute limit, as an ideal gas with an activity-dependent effective temperature. At finite density, increasing the activity is similar to increasing adhesion between equilibrium particles. We quantify this effective adhesion and obtain a unique scaling law relating activity and effective adhesion in both experiments and simulations. Our results provide a new and efficient way to understand the emergence of novel phases of matter in active colloidal suspensions.

  15. Nonequilibrium Equation of State in Suspensions of Active Colloids

    Directory of Open Access Journals (Sweden)

    Félix Ginot

    2015-01-01

    Full Text Available Active colloids constitute a novel class of materials composed of colloidal-scale particles locally converting chemical energy into motility, mimicking micro-organisms. Evolving far from equilibrium, these systems display structural organizations and dynamical properties distinct from thermalized colloidal assemblies. Harvesting the potential of this new class of systems requires the development of a conceptual framework to describe these intrinsically nonequilibrium systems. We use sedimentation experiments to probe the nonequilibrium equation of state of a bidimensional assembly of active Janus microspheres and conduct computer simulations of a model of self-propelled hard disks. Self-propulsion profoundly affects the equation of state, but these changes can be rationalized using equilibrium concepts. We show that active colloids behave, in the dilute limit, as an ideal gas with an activity-dependent effective temperature. At finite density, increasing the activity is similar to increasing adhesion between equilibrium particles. We quantify this effective adhesion and obtain a unique scaling law relating activity and effective adhesion in both experiments and simulations. Our results provide a new and efficient way to understand the emergence of novel phases of matter in active colloidal suspensions.

  16. Flash NanoPrecipitation of organic actives via confined micromixing and block copolymer stabilization

    Science.gov (United States)

    Johnson, Brian K.

    This dissertation provides a method and the understanding required to produce nanoparticles of organic actives using Flash NanoPrecipitation . The process comprises mixing a solvent phase containing molecularly dissolved amphiphilic block copolymer and an organic active with an anti-solvent. One block of the copolymer precipitates to alter the nucleation and growth of the organic active while the other remains in solution for particle stabilization. A custom built confined impinging jets (CIJ) mixer provides optimum micromixing at the laboratory or full scale within milliseconds. Comparison to other reactor designs is provided. The resulting nanoparticles have functional surfaces tailored to meet the needs of pharmaceutical or specialty chemical formulations. Example beta-carotene nanoparticles with a polyethylene oxide surface are produced at high concentration, high yield, low stabilizer content, and a size suitable for sterile filtration or larger. The technical challenges in nanoparticle production are explained via the characteristic times for mixing, copolymer aggregation, and organic active particle formation. The time for Flash NanoPrecipitation is shown to depend strongly on the time for copolymer aggregation, and control of the organic nucleation versus growth is critical to achieve nanoparticles. Mixing operating lines explain the impact of solubility differences between the colloidal stabilizer and the organic active as function of mixing rate. Techniques to measure the solubility of the copolymer and DeltaG° , DeltaH°, and DeltaS° of micellization are demonstrated. An analytical CIJ mixer is developed by quantifying the characteristic time and physical mechanism of mixing. The methodology described to find an absolute mixing lifetime is also applied to a vortex mixer at a spectrum of flow ratios away from one. Dimensional analysis using the process Damkohler number, defined as the ratio of the mixing to the process time, is applied to precipitation

  17. Stability of Flip and Exchange Symmetric Entangled State Classes under Invertible Local Operations

    CERN Document Server

    Gedik, Zafer

    2009-01-01

    Flip and exchange symmetric (FES) many-qubit states, which can be obtained from a state with the same symmetries by means of invertible local operations (ILO), constitute a one-parameter family of curves in the Hilbert space. Eigenstates of FES ILOs correspond to vectors that cannot be transformed to other FES states. This means equivalence classes of states under ILO can be determined in a systematic way for an arbitrary number of qubits. More important, for entangled states, at the boundaries of neighboring equivalence classes, one can show that when the fidelity between the final state after an ILO and a state of the neighboring class approaches unity, probability of success decreases to zero. Therefore, the classes are stable under ILOs.

  18. Stability of flip and exchange symmetric entangled state classes under invertible local operations

    Science.gov (United States)

    Gedik, Z.

    2011-01-01

    Flip and exchange symmetric (FES) many-qubit states, which can be obtained from a state with the same symmetries by means of invertible local operations (ILO), constitute a set of curves in the Hilbert space. Eigenstates of FES ILOs correspond to vectors that cannot be transformed to other FES states. This means equivalence classes of states under ILO can be determined in a systematic way for an arbitrary number of qubits. More important, for entangled states, at the boundaries of neighboring equivalence classes, one can show that when the fidelity between the final state after an ILO and a state of the neighboring class approaches unity, the probability of success decreases to zero. Therefore, the classes are stable under ILOs.

  19. Preparation of lactoperoxidase incorporated hybrid nanoflower and its excellent activity and stability.

    Science.gov (United States)

    Altinkaynak, Cevahir; Yilmaz, Ismail; Koksal, Zeynep; Özdemir, Hasan; Ocsoy, Ismail; Özdemir, Nalan

    2016-03-01

    We report a green approach to synthesize lactoperoxidase (LPO) enzyme and metal ions hybrid nanoflowers (HNFs) and investigate mechanism underlying formation and enhanced catalytic activity and stability under different experimental parameters. The HNFs formed of LPO enzyme purified from bovine milk and copper ions (Cu(2+)) were synthesized at two different temperatures (+4 °C and 20 °C) in PBS (pH 7.4). The effects of experimental conditions, pH and storage temperatures, on the activity and stability of LPO-copper phosphate HNFs were evaluated using guaiacol as a substrate in the presence of hydrogen peroxide (H2O2). Optimum pHs were determined as pH 8 and pH 6 for LPO-copper phosphate HNF and free LPO, respectively. LPO-copper phosphate HNF has higher activity than free LPO at each pHs. Activities of LPO-copper phosphate HNF at pH 6 and pH 8 were calculated as 70.48 EU/mg, 107.23 EU/mg, respectively while free LPO shows 45.78 EU/mg and 30.12 EU/mg, respectively. Compared with free LPO, LPO-copper phosphate HNFs exhibited ∼160% and ∼360% increase in activities at pH 6 and pH 8, respectively. Additionally, LPO-copper phosphate HNFs displayed perfect reusability after six cycles. Finally, we demonstrated that LPO-copper phosphate HNFs can be utilized as a nanosensor for detection of dopamine and epinephrine.

  20. Human cystathionine β-synthase (CBS) contains two classes of binding sites for S-adenosylmethionine (SAM): complex regulation of CBS activity and stability by SAM.

    Science.gov (United States)

    Pey, Angel L; Majtan, Tomas; Sanchez-Ruiz, Jose M; Kraus, Jan P

    2013-01-01

    CBS (cystathionine β-synthase) is a multidomain tetrameric enzyme essential in the regulation of homocysteine metabolism, whose activity is enhanced by the allosteric regulator SAM (S-adenosylmethionine). Missense mutations in CBS are the major cause of inherited HCU (homocystinuria). In the present study we apply a novel approach based on a combination of calorimetric methods, functional assays and kinetic modelling to provide structural and energetic insight into the effects of SAM on the stability and activity of WT (wild-type) CBS and seven HCU-causing mutants. We found two sets of SAM-binding sites in the C-terminal regulatory domain with different structural and energetic features: a high affinity set of two sites, probably involved in kinetic stabilization of the regulatory domain, and a low affinity set of four sites, which are involved in the enzyme activation. We show that the regulatory domain displays a low kinetic stability in WT CBS, which is further decreased in many HCU-causing mutants. We propose that the SAM-induced stabilization may play a key role in modulating steady-state levels of WT and mutant CBS in vivo. Our strategy may be valuable for understanding ligand effects on proteins with a complex architecture and their role in human genetic diseases and for the development of novel pharmacological strategies.

  1. Stability and activity of lactate dehydrogenase on biofunctional layers deposited by activated vapor silanization (AVS) and immersion silanization (IS)

    Science.gov (United States)

    Calvo, Jorge Nieto-Márquez; Elices, Manuel; Guinea, Gustavo V.; Pérez-Rigueiro, José; Arroyo-Hernández, María

    2017-09-01

    The interaction between surfaces and biological elements, in particular, proteins is critical for the performance of biomaterials and biosensors. This interaction can be controlled by modifying the surface in a process known as biofunctionalization. In this work, the enzyme lactate dehydrogenase (LDH) is used to study the stability of the interaction between a functional protein and amine-functionalized surfaces. Two different functionalization procedures were compared: Activated Vapor Silanization (AVS) and Immersion Silanization (IS). Adsorption kinetics is shown to follow the Langmuir model for AVS-functionalized samples, while IS-functionalized samples show a certain instability if immersed in an aqueous medium for several hours. In turn, the enzymatic activity of LDH is preserved for longer times by using glutaraldehyde as crosslinker between the AVS biofunctional surface and the enzyme.

  2. Enhanced cycling stability of NiCo2S4@NiO core-shell nanowire arrays for all-solid-state asymmetric supercapacitors.

    Science.gov (United States)

    Huang, Yuanyuan; Shi, Tielin; Jiang, Shulan; Cheng, Siyi; Tao, Xiangxu; Zhong, Yan; Liao, Guanglan; Tang, Zirong

    2016-12-07

    As a new class of pseudocapacitive material, metal sulfides possess high electrochemical performance. However, their cycling performance as conventional electrodes is rather poor for practical applications. In this article, we report an original composite electrode based on NiCo2S4@NiO core-shell nanowire arrays (NWAs) with enhanced cycling stability. This three-dimensional electrode also has a high specific capacitance of 12.2 F cm(-2) at the current density of 1 mA cm(-2) and excellent cycling stability (about 89% retention after 10,000 cycles). Moreover, an all-solid-state asymmetric supercapacitor (ASC) device has been assembled with NiCo2S4@NiO NWAs as the positive electrode and active carbon (AC) as the negative electrode, delivering a high energy density of 30.38 W h kg(-1) at 0.288 KW kg(-1) and good cycling stability (about 109% retention after 5000 cycles). The results show that NiCo2S4@NiO NWAs are promising for high-performance supercapacitors with stable cycling based on the unique core-shell structure and well-designed combinations.

  3. Enhanced cycling stability of NiCo2S4@NiO core-shell nanowire arrays for all-solid-state asymmetric supercapacitors

    Science.gov (United States)

    Huang, Yuanyuan; Shi, Tielin; Jiang, Shulan; Cheng, Siyi; Tao, Xiangxu; Zhong, Yan; Liao, Guanglan; Tang, Zirong

    2016-12-01

    As a new class of pseudocapacitive material, metal sulfides possess high electrochemical performance. However, their cycling performance as conventional electrodes is rather poor for practical applications. In this article, we report an original composite electrode based on NiCo2S4@NiO core-shell nanowire arrays (NWAs) with enhanced cycling stability. This three-dimensional electrode also has a high specific capacitance of 12.2 F cm-2 at the current density of 1 mA cm-2 and excellent cycling stability (about 89% retention after 10,000 cycles). Moreover, an all-solid-state asymmetric supercapacitor (ASC) device has been assembled with NiCo2S4@NiO NWAs as the positive electrode and active carbon (AC) as the negative electrode, delivering a high energy density of 30.38 W h kg-1 at 0.288 KW kg-1 and good cycling stability (about 109% retention after 5000 cycles). The results show that NiCo2S4@NiO NWAs are promising for high-performance supercapacitors with stable cycling based on the unique core-shell structure and well-designed combinations.

  4. A carbamate-based approach to primaquine prodrugs: antimalarial activity, chemical stability and enzymatic activation.

    Science.gov (United States)

    Mata, Graça; do Rosário, Virgílio E; Iley, Jim; Constantino, Luís; Moreira, Rui

    2012-01-15

    O-Alkyl and O-aryl carbamate derivatives of the antimalarial drug primaquine were synthesised as potential prodrugs that prevent oxidative deamination to the inactive metabolite carboxyprimaquine. Both O-alkyl and O-aryl carbamates undergo hydrolysis in alkaline and pH 7.4 phosphate buffers to the parent drug, with O-aryl carbamates being ca. 10(6)-10(10) more reactive than their O-alkyl counterparts. In human plasma O-alkyl carbamates were stable, whereas in contrast their O-aryl counterparts rapidly released the corresponding phenol product, with primaquine being released only slowly over longer incubation periods. Activation of the O-aryl carbamates in human plasma appears to be catalysed by butyrylcholinesterase (BuChE), which leads to carbamoylation of the catalytic serine of the enzyme followed by subsequent slow enzyme reactivation and release of parent drug. Most of the O-aryl and O-alkyl carbamates are activated in rat liver homogenates with half-lives ranging from 9 to 15 h, while the 4-nitrophenyl carbamate was hydrolysed too rapidly to determine an accurate rate constant. Antimalarial activity was studied using a model consisting of Plasmodium berghei, Balb C mice and Anopheles stephensi mosquitoes. When compared to controls, ethyl and n-hexyl carbamates were able to significantly reduce the percentage of infected mosquitos as well as the mean number of oocysts per infected mosquito, thus indicating that O-alkyl carbamates of primaquine have the potential to be developed as transmission-blocking antimalarial agents. Copyright © 2011 Elsevier Ltd. All rights reserved.

  5. Excitation Spectra In Nongravitational Theories Marginal Stability, String Webs, Bound States In Gauge Theories And Hot Little Strings

    CERN Document Server

    Narayan, K S

    2002-01-01

    In this thesis, we discuss two topics—marginal stability in gauge theories and little string theories at the Hagedorn temperature. The spectrum of stable supersymmetric charged particle states can change discontinuously as we change the vacuum on the Coulomb branch of four dimensional gauge theories with extended supersymmetry. This discontinuous change manifests itself via the decay of some of these states which become marginally unstable across certain submanifolds in the Coulomb branch. We describe how this decay process can be studied through semiclassical field configurations, purely within the low energy effective action on the Coulomb branch, even at strong coupling. We then describe how these semiclassical field configurations naturally give rise to and generalize the string web description of these supersyrnmetric states found in D-brane constructions for some gauge theories. After a brief study of string web interactions in theories with sixteen supercharges, we move on to study the supers...

  6. An explanation for the high stability of polycarboxythiophenes in photovoltaic devices—A solid-state NMR dipolar recoupling study

    DEFF Research Database (Denmark)

    Bierring, M.; Nielsen, J.S.; Siu, Ana

    2008-01-01

    observed in photovoltaic devices employing polythiophene substituted with carboxylic-acid moieties under oxygen free conditions. H-1 and C-13 solid-state NMR, IR, and ESR spectroscopy of unmodified and isotopically labeled polythiophenes were studied. Distances between the isotopically labeled carboxylic...... acid carbon atoms were measured by C-13 solid-state magic-angle-spinning (MAS) NMR using symmetry-based double-quantum (2Q) dipolar recoupling. This revealed the presence of C-13-C-13 distances of 3.85 angstrom, which correspond to the C-C distance in hydrogen-bonded carboxylic acid dimers. In spite...... of the presence of carboxylic groups in the polymer as demonstrated by C-13 CP/MAS NMR and IR spectroscopy, the absence of carboxylic protons in solid state H-1 NMR spectra indicate that they are mobile. We link the extraordinary stability of this system to the rigid nature, cross-linking through a hydrogen...

  7. The State Fiscal Stabilization Fund and Higher Education Spending in the States: Part 1 of 4. Issue Brief

    Science.gov (United States)

    Cohen, Jennifer

    2010-01-01

    By late 2008, the United States was in the midst of its most severe economic recession since the 1930s, brought on by a collapse in real estate prices and exacerbated by the failure of many large banks and financial institutions. Heeding calls from economists, Congress and the Obama administration passed a historic law in early 2009 to stimulate…

  8. Brazil - Poverty Reduction, Growth, and Fiscal Stability in the State of Ceara : A State Economic Memorandum, Volume 1. Policy Report

    OpenAIRE

    World Bank

    2000-01-01

    Although the State of Ceara, in Brazil, is a model of good economic, and fiscal performance given its poverty status, recent analysis show poverty remains severe, in spite of significant reductions over the last decade. The combination of good governance, and sound fiscal management, industrial promotion, and public investments have been successful, but the report questions whether differe...

  9. Compensatory interactions to stabilize multiple steady states or mitigate the effects of multiple deregulations in biological networks

    Science.gov (United States)

    Yang, Gang; Campbell, Colin; Albert, Réka

    2016-12-01

    Complex diseases can be modeled as damage to intracellular networks that results in abnormal cell behaviors. Network-based dynamic models such as Boolean models have been employed to model a variety of biological systems including those corresponding to disease. Previous work designed compensatory interactions to stabilize an attractor of a Boolean network after single node damage. We generalize this method to a multinode damage scenario and to the simultaneous stabilization of multiple steady state attractors. We classify the emergent situations, with a special focus on combinatorial effects, and characterize each class through simulation. We explore how the structural and functional properties of the network affect its resilience and its possible repair scenarios. We demonstrate the method's applicability to two intracellular network models relevant to cancer. This work has implications in designing prevention strategies for complex disease.

  10. The Indonesia’s State Budget Sustainability and Its Implication for Financial System Stability

    Directory of Open Access Journals (Sweden)

    Haryo KUNCORO

    2011-07-01

    Full Text Available This paper will examine the sustainability of the central budget and its relation to the financial stability in the case of Indonesia. The standard model of fiscal sustainability is modified to cover some financial variables. The empirical estimates are done by employing several aspects of the time series econometric literature including unit roots, co-integration, and VAR (vector auto regression. Based on the fiscal reaction function estimates of quarterly data over the period of 1999-2009, the analysis present that the government's budget is unsustainable. This finding is supported by solvency test. The impulse response test indicates that financial variables innovation has large impact both on the debt and primary balance surplus dynamics and vise versa. Eventually, the debt and primary balance have a substantial impact on financial system. Thus, the fiscal sustainability (and, of course, solvency is the key to achieve financial system stability.

  11. [Changes of the storage stability of ketones collected on activated coconut carbon in environmental ketone measurement].

    Science.gov (United States)

    Sakamroto, Takayuki; Hinoue, Mitsuo; Yoshikawa, Masahiro

    2011-06-01

    The storage stability for six ketones was studied on four activated coconut carbons commonly used for air sampling in Japan. As the ratios of the enol form of cyclohexanone and methyl ethyl ketone are high, the ketones showed drastic losses during storage (storage stability), which could be attributed to catalytic oxidation and chemisorption. Moreover, adsorbed water caused a further decrease in recoveries of the ketones from the carbons. Because keto-enol tautomerism and hydration are catalyzed by acid or base, the relationships between the recoveries of the ketones from the carbons and pH in the aqueous solution of the carbons and the ignition residue of the carbons were investigated. As a result, the intensity of acidity or basicity of the carbons correlated with the loss of the ketones during storage, but the ignition residue of the carbons did not. Therefore, these results lead us to the conclusion that a more neutral coconut carbon is more suitable for the collection of aliphatic ketones, and activated coconut carbons are not suitable for cyclohexanone.

  12. Assessment of Physical Stability and Antioxidant Activity of Polysiloxane Polyalkyl Polyether Copolymer-Based Creams

    Directory of Open Access Journals (Sweden)

    Atif Ali

    2013-01-01

    Full Text Available The purpose of the present work was to investigate the changes on physical stability (color, creaming, liquefaction, pH, conductivity, centrifugation, viscosity and rheological parameters by non-ionic surfactant polysiloxane polyalkyl polyether copolymer based creams following inclusion of plant extract containing phenolic compounds. The antioxidant activity of the plant extract alone and after addition in the cream was assessed using the stable free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH assay. Physical stability was assessed by submitting the creams to storage at 8°C, 25°C, 40°C, and at 40°C with 70% RH (relative humidity for a period of two months. Physical characteristics of polysiloxane polyalkyl polyether copolymer based creams, that is, color, creaming, liquefaction, centrifugation and pH were noted at various intervals for 2 months. The viscosities and rheological behavior of creams were determined using a rotational rheometer. Data were analyzed by using Brookfield Software Rheocalc version (2.6 with IPC Paste and Power Law (PL math models. Cream with plant extract showed pseudo plastic behaviour with decreasing on viscosity. The Acacia nilotica (AN extract alone and the cream containing this extract showed great antioxidant and free radical scavenging activities. Power Law and IPC analysis were found to fit all the rheograms.

  13. Active Stabilization of the Beam Pointing of a High- Power KrF Laser System

    Directory of Open Access Journals (Sweden)

    Barna1 A.

    2015-03-01

    Full Text Available An active beam-pointing stabilization system has been developed for a high-power KrF laser system to eliminate the long-term drift of the directional change of the beam in order to have a stable focusing to a high intensity. The control of the beam direction was achieved by a motor-driven mirror activated by an electric signal obtained by monitoring the position of the focus of the output beam. Instead of large sized UV-sensitive position sensitive detectors a simple arrangement with scatter plates and photodiodes are used to measure the directionality of the beam. After the beam stabilization the long-term residual deviation of the laser shots is ~14 μrad, which is comparable to the shot-to-shot variation of the beam (~12 μrad. This deviation is small enough to keep the focal spot size in a micrometer range when tightly focusing the beam using off-axis parabolic mirrors.

  14. Correlation between active layer thickness and ambient gas stability in IGZO thin-film transistors

    Science.gov (United States)

    Gao, Xu; Lin, Meng-Fang; Mao, Bao-Hua; Shimizu, Maki; Mitoma, Nobuhiko; Kizu, Takio; Ou-Yang, Wei; Nabatame, Toshihide; Liu, Zhi; Tsukagoshi, Kazuhito; Wang, Sui-Dong

    2017-01-01

    Decreasing the active layer thickness has been recently reported as an alternative way to achieve fully depleted oxide thin-film transistors for the realization of low-voltage operations. However, the correlation between the active layer thickness and device resistivity to environmental changes is still unclear, which is important for the optimized design of oxide thin-film transistors. In this work, the ambient gas stability of IGZO thin-film transistors is found to be strongly correlated to the IGZO thickness. The TFT with the thinnest IGZO layer shows the highest intrinsic electron mobility in a vacuum, which is greatly reduced after exposure to O2/air. The device with a thick IGZO layer shows similar electron mobility in O2/air, whereas the mobility variation measured in the vacuum is absent. The thickness dependent ambient gas stability is attributed to a high-mobility region in the IGZO surface vicinity with less sputtering-induced damage, which will become electron depleted in O2/air due to the electron transfer to adsorbed gas molecules. The O2 adsorption and deduced IGZO surface band bending is demonstrated by the ambient-pressure x-ray photoemission spectroscopy results.

  15. Arabidopsis HIGH PLOIDY2 sumoylates and stabilizes flowering locus C through its E3 ligase activity

    Directory of Open Access Journals (Sweden)

    Jun Soo eKwak

    2016-04-01

    Full Text Available Flowering Locus C (FLC, a floral repressor, plays an important role in flowering. The mechanisms regulating FLC gene expression and protein function have been studied extensively; however, post-translational regulation of FLC remains unclear. Here, we identified Arabidopsis HIGH PLOIDY2 (HPY2 as an E3 SUMO ligase for FLC. In vitro and vivo pull-down assays showed that FLC physically interacts with HPY2. In vitro assays showed that the stimulation of FLC sumoylation by HPY2 was dependent on SUMO-activating enzyme E1 and -conjugating enzyme E2, indicating that HPY2 was an E3 SUMO ligase for FLC. In transgenic plants, inducible HPY2 overexpression increased the concentration of FLC, indicating that HPY2 stabilized FLC through direct sumoylation. Flowering time in hpy2-2 mutants was shorter than in wild-type plants under long- and short-day conditions, with a greater effect under short-day conditions, and FLC was downregulated in hpy2-2 mutants. These data indicate that HPY2 regulates FLC function and stability at both the transcriptional and post-translational levels through its E3 SUMO ligase activity.

  16. Thermal Stability of Magnetic States in Circular Thin-Film Nanomagnets with Large Perpendicular Magnetic Anisotropy

    Science.gov (United States)

    Chaves-O'Flynn, Gabriel

    The scaling of the energy barrier to magnetization reversal in thin-film nanomagnets with perpendicular magnetization as a function of their lateral size is of great interest and importance for high-density magnetic random access memory devices. Experimental studies of such elements show either a quadratic or linear dependence of the energy barrier on element diameter. I will discuss a theoretical model we developed to determine the micromagnetic configurations that set the energy barrier for thermally activated reversal of a thin disk with perpendicular magnetic anisotropy as a function of disk diameter. We find a critical length in the problem that is set by the exchange and effective perpendicular magnetic anisotropy energies, with the latter including the size dependence of the demagnetization energy. For diameters smaller than this critical length, the reversal occurs by nearly coherent magnetization rotation and the energy barrier scales with the square of the diameter normalized to the critical length (for fixed film thickness), while for larger diameters, the transition state has a domain wall, and the energy barrier depends linearly on the normalized diameter. Simple analytic expressions are derived for these two limiting cases and verified using full micromagnetic simulations with the string method. Further, the effect of an applied field is considered and shown to lead to a plateau in the energy barrier versus diameter dependence at large diameters. Based on these finding I discuss the prospects and material challenges in the scaling of magnetic memory devices based on thin films with strong perpendicular magnetic anisotropy. In collaboration with G. Wolf, J. Z. Sun and A. D. Kent. Supported by NSF-DMR-1309202 and in part by Spin Transfer Technologies Inc. and the Nanoelectronics Research Initiative through the Institute for Nanoelectronics Discovery and Exploration.

  17. State — Region — Field — Enterprise: Framework of Economics System Stability of Russia Part 2

    Directory of Open Access Journals (Sweden)

    Georgy Borisovich Kleiner

    2015-09-01

    Full Text Available In the article, the factors of a stability of the Russian economy are investigated from the systematic positions as a multilevel, multisubject and multidimensional socio-economic system. The concept of economics system stability as abilities to keep prerequisites for growth with the support and effective use of system structure of economy is formulated. The leading role of all economic subjects of different levels (including government as a subject of the international relations, regions as the subjects of Federation, enterprises as economic entities in economic stability is shown. The need of "extension" of a network of subjects due to strengthening of the subjectivity of economic fields is emphasized. Research of an internal basic system structure of an economic subject and external structure of its immediate environment in socioeconomic, administrative-and-managerial, and market spaces with the use of the results of the new theory of economic systems leads to a conclusion of similarity of these structures. It is shown that each of these system complexes includes (together with a subject four systems of various types — object, environmental, processed, and designed. The system environment of a subject in the administrative-and-managerial space of inter-level interactions has the same structure. It gives the chance to reduce a problem of subjects’ resistance to a question of balance of system structures of the complexes forming an internal filling and an external environment of subjects. The method of balance index of similar complexes is given. Recommendations on a choice of the measures of economic policy for providing economics system stability of Russia during the crisis are formulated. It is shown that such policy has to be developed with the principles of a subject-preservation, system balance of internal filling and external environment of subjects, a corporate solidarity of subjects despite their level in the administrative

  18. State — Region — Field— Enterprise: Framework of Economics System Stability of Russia Part 1

    Directory of Open Access Journals (Sweden)

    Georgy Borisovich Kleyner

    2015-06-01

    Full Text Available In the article, the factors of a stability of the Russian economy are investigated from the systematic positions as a multilevel, multisubject and multidimensional socio-economic system. The concept of economics system stability as abilities to keep prerequisites for growth with the support and effective use of system structure of economy is formulated. The leading role of all economic subjects of different levels (including government as a subject of the international relations, regions as subjects of Federation, enterprises as economic entities in economic stability is shown. The need of «extension» of a network of subjects due to strengthening of the subjectivity of economic fields is emphasized. Research of an internal basic system structure of an economic subject and external structure of its immediate environment in socioeconomic, administrative-and-managerial, and market spaces with the use of the results of the new theory of economic systems leads to a conclusion of similarity of these structures. It is shown that each of these system complexes includes (together with a subject four systems of various types — object, environmental, processed, and designed. The system environment of a subject in the administrative-and-managerial space of inter-level interactions has the same structure. It gives the chance to reduce a problem of subjects’ resistance to a question of balance of system structures of the complexes forming an internal filling and an external environment of subjects. The method of balance index of similar complexes is given. Recommendations on a choice of the measures of economic policy for providing economics system stability of Russia during the crisis are formulated. It is shown that such policy has to be developed with the principles of a subject-preservation, system balance of internal filling and external environment of subjects, a corporate solidarity of subjects despite their level in the administrative hierarchy

  19. Stabilization of Nonholonomic Robot Formations: A First‐state Contractive Model Predictive Control Approach

    OpenAIRE

    Xie, Feng; Fierro, Rafael

    2009-01-01

    A model predictive control algorithm is developed for stabilizing a team of nonholonomic mobile robots navigating in formation within an obstacle-populated environment. In this scenario, the {em leader} robot may need to execute abrupt maneuvers (i.e., sudden stops and backward motions) in order to avoid collisions and accomplish mission objectives. Moreover, follower robots should be capable of tracking their leaders maintaining desired relative distance and orientation. To this end, nonholo...

  20. Existence, uniqueness and stability of positive steady states to a prey-predator diffusion system

    Institute of Scientific and Technical Information of China (English)

    WANG MingXin; WANG XuBo

    2009-01-01

    In the paper, we study the positive solutions of an elliptic system coming from a prey-predator model with modified Leslie-Gower and Holling-Type Ⅱ schemes. We study the existence, non-existence, bifurcation, uniqueness and stability of positive solutions. In particular, we obtain a continuum of positive solutions connecting a semi-trivial solution to the unique positive solution of the limiting system.