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1

Energy loss reduction by critical switches  

Microsoft Academic Search

This paper presents a systematic method to derive an optimal switching plan to achieve energy loss minimization for short term and long term operation of distribution systems. The short term optimal switching criterion is developed by binary integer programming with branch and bound technique. A overall optimization problem is formulated for the optimal switching operation. It is further divided into

C.-S. Chen; M.-Y. Cho

1993-01-01

2

Critical appraisal of the fewest switches algorithm for surface hopping.  

PubMed

In this paper the authors address the problem of internal consistency in trajectory surface hopping methods, i.e., the requirement that the fraction of trajectories running on each electronic state equals the probabilities computed by the electronic time-dependent Schrodinger equation, after averaging over all trajectories. They derive a formula for the hopping probability in Tully's "fewest switches" spirit that would yield a rigorously consistent treatment. They show the relationship of Tully's widely used surface hopping algorithm with the "exact" prescription that cannot be applied when running each trajectory independently. They also bring out the connection of the consistency problem with the coherent propagation of the electronic wave function and the artifacts caused by coherent Rabi-type oscillations of the state probabilities in weak coupling regimes. A real molecule (azobenzene) and two ad hoc models serve as examples to illustrate the above theoretical arguments. Following a proposal by Truhlar's group [Zhu et al., J. Chem. Phys. 121, 7658 (2004) Zhu et al., J. Chem. Theory Comput. 1, 527 (2005)], they apply a decoherence correction to the state probabilities, in conjunction with Tully's algorithm, and they obtain satisfactory results in terms of internal consistency and of agreement with the outcomes of quantum wave packet calculations. PMID:17430023

Granucci, Giovanni; Persico, Maurizio

2007-04-01

3

To Switch, or Not to Switch: A Critical Analysis of Canada's Ban on Incandescent Light Bulbs  

Microsoft Academic Search

A critical analysis on the impacts of a ban on incandescent light bulbs is presented for different regions in Canada. The paper begins with a short history and description of incandescent light bulbs (ILBs) and compact fluorescent light bulbs (CFLBs). The notion that different regions that ban ILBs could increase greenhouse gas (GHG) emissions is introduced. A framework for a

M. Ivanco; B. W. Karney; K. J. Waher

2007-01-01

4

Generating disulfides with the quiescin sulfhydryl oxidases  

PubMed Central

The Quiescin-sulfhydryl oxidase (QSOX) family of flavoenzymes catalyzes the direct and facile insertion of disulfide bonds into unfolded reduced proteins with concomitant reduction of oxygen to hydrogen peroxide. This review discusses the chemical mechanism of these enzymes and the involvement of thioredoxin and flavin-binding domains in catalysis. The variability of CxxC motifs in the QSOX family is highlighted and attention is drawn to the steric factors that may promote efficient thiol/disulfide exchange during oxidative protein folding. The varied cellular location of these multi-domain sulfhydryl oxidases is reviewed and potential intracellular and extracellular roles are summarized. Finally, this review identifies important unresolved questions concerning this ancient family of sulfhydryl oxidases.

Heckler, Erin J.; Rancy, Pumtiwitt C.; Kodali, Vamsi K.; Thorpe, Colin

2008-01-01

5

Sulfhydryl-Reactive Metals in Autism  

Microsoft Academic Search

This study examined the difference between sulfhydryl-reactive metals (mercury, lead, arsenic, and cadmium) in the hair of 45 children with autism (1–6 yr of age) as compared to 45 gender-, age-, and race-matched typical children. Hair samples were measured with inductively coupled mass spectrometry. Some studies, such as Holmes et al. (2003), suggested that children with autism may be poor

Janet K. Kern; Bruce D. Grannemann; Madhukar H. Trivedi; James B. Adams

2007-01-01

6

Inhibition of loquat enzymatic browning by sulfhydryl compounds  

Microsoft Academic Search

The effectiveness of a series of sulfhydryl compounds in inhibiting polyphenoloxidase (PPO) activity in a model system (chlorogenic acid solution) and in loquat juices was evaluated. Application of different concentrations of sulfhydryl compounds to chlorogenic acid solution and fresh loquat juice showed that l-cysteine appeared to be an effective browning inhibitor. The required concentration of l-cysteine for 90% browning inhibition

Chang-Kui Ding; Kazuo Chachin; Yoshinori Ueda; Chien Y Wang

2002-01-01

7

Mouse liver protein sulfhydryl depletion after acetaminophen exposure.  

PubMed

Acetaminophen (APAP)-induced liver injury is the leading cause of acute liver failure in many countries. This study determined the extent of liver protein sulfhydryl depletion not only in whole liver homogenate but also in the zonal pattern of sulfhydryl depletion within the liver lobule. A single oral gavage dose of 150 or 300 mg/kg APAP in B6C3F1 mice produced increased serum alanine aminotransferase levels, liver necrosis, and glutathione depletion in a dose-dependent manner. Free protein sulfhydryls were measured in liver protein homogenates by labeling with maleimide linked to a near infrared fluorescent dye followed by SDS-polyacrylamide gel electrophoresis. Global protein sulfhydryl levels were decreased significantly (48.4%) starting at 1 hour after the APAP dose and maintained at this reduced level through 24 hours. To visualize the specific hepatocytes that had reduced protein sulfhydryl levels, frozen liver sections were labeled with maleimide linked to horseradish peroxidase. The centrilobular areas exhibited dramatic decreases in free protein sulfhydryls while the periportal regions were essentially spared. These protein sulfhydryl-depleted regions correlated with areas exhibiting histopathologic injury and APAP binding to protein. The majority of protein sulfhydryl depletion was due to reversible oxidation since the global- and lobule-specific effects were essentially reversed when the samples were reduced with tris(2-carboxyethy)phosphine before maleimide labeling. These temporal and zonal pattern changes in protein sulfhydryl oxidation shed new light on the importance that changes in protein redox status might play in the pathogenesis of APAP hepatotoxicity. PMID:23093024

Yang, Xi; Greenhaw, James; Shi, Qiang; Roberts, Dean W; Hinson, Jack A; Muskhelishvili, Levan; Davis, Kelly; Salminen, William F

2012-10-23

8

Reduction of critical current density for spin transfer magnetization switching in a spin-valve nano-pillar  

Microsoft Academic Search

Experimental results on the current induced magnetization switching of nano-patterned IrMn\\/CoFe\\/Cu\\/CoFe spin-valves are reported. The main emphasis is the increase of MR and the reduction of the critical current density through an improved fabrication process. A method using a batch-fabricated trilayer template is developed with the junction features defined by a platinum(Pt) stencil mask. Nano-pillars with the lateral dimensions (150times80

C. H. Kang; J. C. Lee; K. H. Shin; S. H. Lim

2006-01-01

9

Switching control of resistive switching devices  

Microsoft Academic Search

Switching current control plays a critical role in the operation of resistive switching devices. Both on-state resistance and maximum reset current show strong dependence on the current limit during set switching. The dependence in unipolar switching devices can be explained by the power-driven nature of reset and dynamic competition between set and reset forces. Effective switching control improves device characteristics

An Chen

2010-01-01

10

Modification of membrane sulfhydryl groups in bacteriostatic action of nitrite  

SciTech Connect

The mechanism by which nitrite inhibits outgrowing spores of bacillus cereus T was examined by using techniques developed earlier for nitrite analogs. The morphological stage of inhibition, cooperativity effects, effect of pH on inhibition, kinetics of protection against tritiated iodoacetate incorporation into membrane sulfhydryl groups, and protection against the bacteriocidal effect of carboxymethylation of iodoacetate indicate that nitrite acts as a membrane-directed sulfhydryl agent. The mechanism by which nitrite modifies the chemical reactivity of the sulfhyrdyl group could be either direct covalent modification or inactivation through communication with another modified membrane component. Profiles of pH effects suggest that the active agent is the protonated form of nitrite. The nitrite concentrations which modify membrane sulfhydryl activity coincide with those which have a bacteriostatic effect. These results are consistent with membrane sulfhydryl modification as a component of the mechanism of nitrite-induced bacteriostasis in this aerobic sporeformer.

Buchman, G.W. III; Hansen, J.N.

1987-01-01

11

Reversible activation of secretory phospholipase A 2 by sulfhydryl reagents  

Microsoft Academic Search

Secretory phospholipase A2s (sPLA2s) have been implicated in physiological and pathological events, but the regulatory mechanism(s) of their activities in cells remains to be solved. Previously, we reported that phenylarsine oxide (PAO), a sulfhydryl reagent, stimulated arachidonic acid (AA) release in rat pheochromocytoma PC12 cells. In this study, we examined the effects of thimerosal, another sulfhydryl reagent, to clarify the

Maiko Nabemoto; Keiko Ohsawa; Hiroyuki Nakamura; Tetsuya Hirabayashi; Takeshi Saito; Yasunobu Okuma; Yasuyuki Nomura; Toshihiko Murayama

2005-01-01

12

Capacitive RF MEMS switch dielectric charging and reliability: a critical review with recommendations  

NASA Astrophysics Data System (ADS)

This paper presents a comprehensive review of the reliability issues hampering capacitive RF MEMS switches in their development toward commercialization. Dielectric charging and its effects on device behavior are extensively addressed, as well as the application of different dielectric materials, improvements in the mechanical design and the use of advanced actuation waveforms. It is concluded that viable capacitive RF MEMS switches with a great chance of market acceptance preferably have no actuation voltage across a dielectric at all, contrary to the ‘standard’ geometry. This is substantiated by the reliability data of a number of dielectric-less MEMS switch designs. However, a dielectric can be used for the signal itself, resulting in a higher Con/Coff ratio than that one would be able to achieve in a switch without any dielectric. The other reliability issues of these devices are also covered, such as creep, RF-power-related failures and packaging reliability. This paper concludes with a recipe for a conceptual ‘ideal’ switch from a reliability point of view, based on the lessons learned.

van Spengen, W. M.

2012-07-01

13

CRITICAL INCIDENTS IN TOURISM: FAILURE, RECOVERY, CUSTOMER SWITCHING, AND WORD?OF?MOUTH BEHAVIORS  

Microsoft Academic Search

As an evolving area of academic investigation, service failure and recovery research is particularly relevant in the tourism field but research is still lacking. This study identifies and classifies commonly experienced service failures and recovery strategies as perceived by tourism customers that result in overall (dis)satisfying encounters. The effectiveness of service recovery strategies is assessed via behavioral responses. Specifically, switching

Scott R. Swanson; Maxwell K. Hsu

2009-01-01

14

A Flavin-dependent Sulfhydryl Oxidase in Bovine Milk†  

PubMed Central

Both metal and flavin-dependent sulfhydryl oxidases catalyze the net generation of disulfide bonds with the reduction of oxygen to hydrogen peroxide. The first mammalian sulfhydryl oxidase to be described was an iron-dependent enzyme isolated from bovine milk whey. This protein was reported to contain 0.5 atoms of iron per 89 kDa subunit and to be completely inhibited by ethylenediaminetetraacetate (EDTA). However the present work shows that a soluble 62 kDa FAD-linked and EDTA-insensitive sulfhydryl oxidase apparently constitutes the dominant disulfide bond-generating activity in skim milk. Unlike the metalloenzyme, the flavoprotein is not associated tightly with skim milk membranes. Sequencing of the purified bovine enzyme (< 70% coverage) showed it to be a member of the Quiescin-sulfhydryl oxidase (QSOX) family. Consistent with its solubility, this bovine QSOX1 paralog lacks the C-terminal transmembrane span of the long form of these proteins. Bovine milk QSOX1 is highly active towards reduced RNase and with the model substrate dithiothreitol. The significance of these new findings is discussed in relation to the earlier reports of metal-dependent sulfhydryl oxidases.

Jaje, Jennifer; Wolcott, Holly N.; Fadugba, Olajumoke; Cripps, Diane; Yang, Austin J.; Mather, Ian H.; Thorpe, Colin

2008-01-01

15

Role of sulfhydryls in in vitro growth of Mycobacterium lepraemurium.  

PubMed Central

In an attempt to evaluate various factors that influence the growth of Mycobacterium lepraemurium in NC-5 medium, the effects of sulfur and --SH compounds were investigated. Cysteine could be replaced by equimolar concentrations of other --SH compounds containing carboxyl group, and at lower concentrations by nonpolar sulfhydryl compounds. The oxidized form of sulfhydryls, as well as certain organic and inorganic reducing agents, did not support growth. The results suggest that the function of sulfhydryl compounds is to maintain low reducing potential in the medium and also to participate in metabolic or biosynthetic pathways or both. A combination of dithiothreitol and thioglycolate gave better results than when these compounds were incorporated individually in the medium. This suggests the protective action of dithiothreitol in preventing oxidation of monothiols.

Dhople, A M; Hanks, J H

1981-01-01

16

Effects of Hyperoxia on Sulfhydryl Concentration of 'Escherichia coli'.  

National Technical Information Service (NTIS)

The concentration of reduced sulfhydryl (SH) in cell-free extracts of Escherichia coli grown with air as the gas phase was 26.8 plus or minus 1.2 mnoles SH/mg soluble protein. Exposure of bacteria to 1 ata of oxygen where growth continued but at a reduced...

J. L. Stees O. R. Brown

1972-01-01

17

Paradoxical effect of reagents for sulfhydryl and disulfide groups on human sperm capacitation and superoxide production  

Microsoft Academic Search

Spermatozoa must undergo capacitation prior to fertilization. In humans, this process appears regulated by oxidoreduction reactions. We investigated the possibility that these reactions involved the sulfhydryl-disulfide pair, which offers a reversible regulation of cellular processes. The effects of reagents targeted for sulfhydryl and disulfide groups on human sperm capacitation, superoxide (O2•?) generation and protein tyrosine phosphorylation were evaluated. The sulfhydryl

Eve de Lamirande; Claude Gagnon

1998-01-01

18

Effect of Sulfhydryl and non-Sulfhydryl Angiotensin-Converting Enzyme Inhibitors on Endothelial Function in Essential Hypertensive Patients  

Microsoft Academic Search

Background: Oxidative inactivation of nitric oxide (NO) is regarded as an important cause of reduced endothelium-dependent vasodilation in essential hypertension. Because zofenopril, an angiotensin-converting enzyme (ACE) inhibitor with a sulfhydryl (SH) group, has demonstrated antioxidant properties and to reduce adhesion molecule expression in vitro, in this study we evaluated the effect of this drug in comparison with the carboxylic ACE

Anna Fratta Pasini; Ulisse Garbin; Maria Cristina Nava; Chiara Stranieri; Michele Pellegrini; Veronica Boccioletti; Maria Laura Luchetta; Paolo Fabrizzi; Vincenzo Lo Cascio; Luciano Cominacini

2007-01-01

19

Critical roles of interactions among switch I-preceding residues and between switch II and its neighboring alpha-helix in conformational dynamics of the GTP-bound Ras family small GTPases.  

PubMed

GTP-bound forms of Ras family small GTPases exhibit dynamic equilibrium between two interconverting conformations, "inactive" state 1 and "active" state 2. A great variation exists in their state distribution; H-Ras mainly adopts state 2, whereas M-Ras predominantly adopts state 1. Our previous studies based on comparison of crystal structures representing state 1 and state 2 revealed the importance of the hydrogen-bonding interactions of two flexible effector-interacting regions, switch I and switch II, with the ?-phosphate of GTP in establishing state 2 conformation. However, failure to obtain both state structures from a single protein hampered further analysis of state transition mechanisms. Here, we succeed in solving two crystal structures corresponding to state 1 and state 2 from a single Ras polypeptide, M-RasD41E, carrying an H-Ras-type substitution in residue 41, immediately preceding switch I, in complex with guanosine 5'-(?,?-imido)triphosphate. Comparison among the two structures and other state 1 and state 2 structures of H-Ras/M-Ras reveal two new structural features playing critical roles in state dynamics; interaction of residues 31/41 (H-Ras/M-Ras) with residues 29/39 and 30/40, which induces a conformational change of switch I favoring its interaction with the ?-phosphate, and the hydrogen-bonding interaction of switch II with its neighboring ?-helix, ?3-helix, which induces a conformational change of switch II favoring its interaction with the ?-phosphate. The importance of the latter interaction is proved by mutational analyses of the residues involved in hydrogen bonding. These results define the two novel functional regions playing critical roles during state transition. PMID:21388959

Matsumoto, Kousuke; Shima, Fumi; Muraoka, Shin; Araki, Mitsugu; Hu, Lizhi; Ijiri, Yuichi; Hirai, Rina; Liao, Jingling; Yoshioka, Takashi; Kumasaka, Takashi; Yamamoto, Masaki; Tamura, Atsuo; Kataoka, Tohru

2011-03-09

20

Reduction in critical current of current-induced switching in exchange-biased spin valves  

NASA Astrophysics Data System (ADS)

The current-induced magnetization reversal (CIMR) effect in nanosized exchange-biased spin valves (EBS) of IrMn/Co1/Cu/Co2 is investigated. The CIMR is studied at RT. With our EBS structure, the critical current can be lowered to 7.5×106 A/cm2, which is rather smaller than that in the conventional simple spin valves (SS) Co1/Cu/Co2. This effect can be attributed to the enhancement of spin transfer efficiency by using antiferromagnetic pinning layer in that structure. However, the absolute change in total resistance of EBS, in comparison to that of SS with similar layer thickness, is not increased, as the nearly unpatterned fixed Co layer is pinned. The results are discussed in terms of current induced spin transfer and current induced thermal activation.

Nguyen, T. H. Y.; Yi, H. J.; Joo, S. J.; Lee, J. H.; Shin, K. H.; Kim, T. W.

2005-05-01

21

A Critical Interpersonal Distance Switches between Two Coordination Modes in Kendo Matches  

PubMed Central

In many competitive sports, players need to quickly and continuously execute movements that co-adapt to various movements executed by their opponents and physical objects. In a martial art such as kendo, players must be able to skillfully change interpersonal distance in order to win. However, very little information about the task and expertise properties of the maneuvers affecting interpersonal distance is available. This study investigated behavioral dynamics underlying opponent tasks by analyzing changes in interpersonal distance made by expert players in kendo matches. Analysis of preferred interpersonal distances indicated that players tended to step toward and away from their opponents based on two distances. The most preferred distance enabled the players to execute both striking and defensive movements immediately. The relative phase analysis of the velocities at which players executed steps toward and away revealed that players developed anti-phase synchronizations at near distances to maintain safe distances from their opponents. Alternatively, players shifted to in-phase synchronization to approach their opponents from far distances. This abrupt phase-transition phenomenon constitutes a characteristic bifurcation dynamics that regularly and instantaneously occurs between in- and anti-phase synchronizations at a critical interpersonal distance. These dynamics are profoundly affected by the task constraints of kendo and the physical constraints of the players. Thus, the current study identifies the clear behavioral dynamics that emerge in a sport setting.

Okumura, Motoki; Kijima, Akifumi; Kadota, Koji; Yokoyama, Keiko; Suzuki, Hiroo; Yamamoto, Yuji

2012-01-01

22

Chemical modification and reactivity of sulfhydryls and disulfides of rat brain nicotinic-like acetylcholine receptors  

SciTech Connect

Rat central nervous system binding sites for ..cap alpha..-bungarotoxin display considerable biochemical homology with characterized nicotinic acetylcholine receptors from the periphery. They possess a critical disulfide residue(s), which is susceptible to chemical modification and consequent specific alteration in the affinity of the binding site for cholinergic agonists. After reaction with Na/sub 2/S/sub 2/O/sub 5/, as with reaction with dithiothreitol and 5,5'-dithiobis(2-nitrobenzoic acid), the binding site is frozen in a high affinity state toward acetylcholine. After reduction with dithiothreitol and alkylation with a variety of compounds of different molecular configuration or electrical charge, or both, the binding site is frozen in a low affinity state toward acetylcholine. Thus, effects of disulfide/sulfhydryl modification on agonist binding affinity appear to be attributable to the nature of the covalent modification rather than charge or steric alteration at the receptor active site brought about by chemical modification.

Lukas, R.J.; Bennett, E.L.

1980-06-25

23

Language Mixing and Code-Switching in Writing: Approaches to Mixed-Language Written Discourse. Routledge Critical Studies in Multilingualism  

ERIC Educational Resources Information Center

|"Code-switching," or the alternation of languages by bilinguals, has attracted an enormous amount of attention from researchers. However, most research has focused on spoken language, and the resultant theoretical frameworks have been based on spoken code-switching. This volume presents a collection of new work on the alternation of languages in…

Sebba, Mark, Ed.; Mahootian, Shahrzad, Ed.; Jonsson, Carla, Ed.

2011-01-01

24

Source of human ventilatory chaos: lessons from switching controlled mechanical ventilation to inspiratory pressure support in critically ill patients.  

PubMed

Ventilatory flow measured at the airway opening in humans exhibits a complex dynamics that has the features of chaos. Currently available data point to a neural origin of this feature, but the role of respiratory mechanics has not been specifically assessed. In this aim, we studied 17 critically ill mechanically ventilated patients during a switch form an entirely machine-controlled assistance mode (assist-controlled ventilation ACV) to a patient-driven mode (inspiratory pressure support IPS). Breath-by-breath respiratory variability was assessed with the coefficient of variation of tidal volume, total cycle time, inspiratory time, expiratory time, mean inspiratory flow, duty cycle. The detection of chaos was performed with the noise titration technique. When present, chaos was characterized with numerical indexes (correlation dimension, irregularity; largest Lyapunov exponent, sensitivity to initial conditions). Expectedly, the coefficients of variations of the respiratory variables were higher during IPS than during ACV. During ACV, noise titration failed to detect nonlinearities in 12 patients who did not exhibit signs of spontaneous respiratory activity. This indicates that the mechanical properties of the respiratory system were not sufficient to produce ventilatory chaos in the presence of a nonlinear command (ventilator clock). A positive noise limit was found in the remaining 5 cases, but these patients exhibited signs of active expiratory control (highly variable expiratory time, respiratory frequency higher than the set frequency). A positive noise limit was also observed in 16/17 patients during IPS (p<0.001). These observations suggest that ventilatory chaos predominantly has a neural origin (intrinsic to the respiratory central pattern generators, resulting from their perturbation by respiratory afferents, or both), with little contribution of respiratory mechanics, if any. PMID:18387347

Mangin, Laurence; Fiamma, Marie-Noëlle; Straus, Christian; Derenne, Jean-Philippe; Zelter, Marc; Clerici, Christine; Similowski, Thomas

2008-02-29

25

Thimerosal decreases TRPV1 activity by oxidation of extracellular sulfhydryl residues  

Microsoft Academic Search

TRPV1, a receptor for capsaicin, plays a key role in mediating thermal and inflammatory pain. Because the modulation of ion channels by the cellular redox state is a significant determinant of channel function, we investigated the effects of sulfhydryl modification on the activity of TRPV1. Thimerosal, which oxidizes sulfhydryls, blocked the capsaicin-activated inward current (Icap) in cultured sensory neurons, in

Yunju Jin; Dong Kwan Kim; Lee-Yong Khil; Uhtaek Oh; Jun Kim; Jiyeon Kwak

2004-01-01

26

Thimerosal A versatile sulfhydryl reagent, calcium mobilizer, and cell function-modulating agent  

Microsoft Academic Search

An overview of the literature concerning the effects of thimerosal is presented. Because of its antibacterial effect, thimerosal is used for a variety of practical purposes such as antiseptic and preservative. In biomedical studies, thimerosal is used as a sulfhydryl reagent, and as a calcium-mobilizing agent. The ability of thimerosal to act as a sulfhydryl group is related to the

Jan G. R Elferink

1999-01-01

27

Sulfhydryl Dependence in Primary Explant Hematopoietic Cells. Inhibition of Growth in vitro with Vitamin B12 Compounds  

Microsoft Academic Search

Primary explants of P388, EL-4, and L1210 murine leukemia cells and of normal mouse bone marrow are shown to require sulfhydryl compounds for proliferation in vitro. Nine established cell lines show no stimulation by these compounds. Leukemia cells can lose the sulfhydryl dependence after various periods of adaptation to in vitro culture. Various sulfhydryl compounds have widely differing potencies in

John I. Toohey

1975-01-01

28

Human erythrocyte delta-aminolevulinate dehydratase inhibition by monosaccharides is not mediated by oxidation of enzyme sulfhydryl groups.  

PubMed

The heme pathway enzyme delta-aminolevulinate dehydratase is a good marker for oxidative stress and metal intoxication. This sulfhydryl enzyme is inhibited in such oxidative pathologies as lead, mercury and aluminum intoxication, exposure to selenium organic species and diabetes. Oxidative stress is a complicating factor in diabetes, inducing non-enzymatic glucose-mediated reactions that change protein structures and impair enzyme functions. We have studied the effects of high glucose, fructose and ribose concentrations on delta-ALA-D activity in vitro. These reducing sugars inhibited delta-ALA-D with efficacies in the order fructose=ribose>glucose. The possible mechanism of glucose inhibition was investigated using lysine, DTT, and t-butylamine. Oxidation of the enzyme's critical sulfhydryl groups was not involved because DTT had no effect. We concluded that high concentrations of reducing sugars or their autoxidation products inhibit delta-ALA-D by a mechanism not related to thiol oxidation. Also, we are not able to demonstrate that the formation of a Schiff base with the critical lysine residue of the enzyme is involved in the inhibition of delta-ALA-D by hexoses. PMID:15950499

Gabriel, D; Pivetta, L; Folmer, V; Soares, J C M; Augusti, G R; Nogueira, C W; Zeni, G; Rocha, J B T

2005-08-01

29

Micromagnetic simulation of critical current density of spin transfer torque switching in a full-Heusler Co2FeAl0.5Si0.5 alloy spin valve nanopillar  

NASA Astrophysics Data System (ADS)

We investigated the critical current density of spin transfer torque switching in a full-Heusler Co2FeAl0.5Si0.5 alloy spin-valve nanopillar through micromagnetic simulations. The simulations explain the experimental results on the resistance versus external magnetic field and yield good agreement with the measured switching behavior. It is shown that different magnitudes of current densities and directions of external magnetic fields give rise to a shift of resistance hysteretic loop and a variable range of switching. We demonstrated that three critical current densities have different slopes with Gilbert damping constant ? and spin polarization constant ?, indicating that ? and ? have different contributions to the critical current densities. Furthermore, we found that the area of resistance-current hysteretic loop decreases as the nanopillar size decreases. The domain structures indicated that the magnetization reversals have different switching processes between small and large sizes of pillars.

Huang, H. B.; Ma, X. Q.; Liu, Z. H.; Meng, F. Y.; Shi, S. Q.; Chen, L. Q.

2013-03-01

30

Cro's role in the CI-Cro bistable switch is critical for ?'s transition from lysogeny to lytic development  

PubMed Central

CI represses cro; Cro represses cI. This double negative feedback loop is the core of the classical CI–Cro epigenetic switch of bacteriophage ?. Despite the classical status of this switch, the role in ? development of Cro repression of the PRM promoter for CI has remained unclear. To address this, we created binding site mutations that strongly impaired Cro repression of PRM with only minimal effects on CI regulation of PRM. These mutations had little impact on ? development after infection but strongly inhibited the transition from lysogeny to the lytic pathway. We demonstrate that following inactivation of CI by ultraviolet treatment of lysogens, repression of PRM by Cro is needed to prevent synthesis of new CI that would otherwise significantly impede lytic development. Thus a bistable CI–Cro circuit reinforces the commitment to a developmental transition.

Schubert, Rachel A.; Dodd, Ian B.; Egan, J. Barry; Shearwin, Keith E.

2007-01-01

31

Effect of thimerosal and other sulfhydryl reagents on calcium permeability in thymus lymphocytes  

Microsoft Academic Search

We have studied the effects of thimerosal, a mercurial compound extensively used as a preservative, as well as other sulfhydryl reagents (e.g. p-hydroxymercurybenzoate, hydrogen peroxide, bromophenacyl bromide, and mercuric chloride) on Ca2+ homeostasis and the redox status of sulfhydryl groups in thymus lymphocytes. They all induced an increase in [Ca2+]i which was blocked with dithiothreitol, suggesting that they act via

Elizabeth Pintado; Domingo Baquero-Leonis; Manuel Conde; Francisco Sobrino

1995-01-01

32

Effect of sulfhydryl oxidoreduction on permeability of cardiac tetrodotoxin-insensitive sodium channel  

Microsoft Academic Search

Effects of sulfhydryl oxidizing and reducing agents on permeability of the tetrodotoxin (TTX)-insensitive Na-channel were investigated in guinea-pig ventricular myocytes using the whole-cell patch-clamp technique. Mercury chloride (HgCl2) at 1–100 ?M irreversibly blocked Na+ currents with no significant changes in the gating kinetics. In contrast, the hydrophilic sulfhydryl oxidizing agent, thimerosal at 50–100 ?M little affected Na+ permeation through the

Y. Kurata; I. Hisatome; M. Tsuboi; H. Uenishi; G. Zhang; M. Oyaizu; R. Sato; S. Imanishi

1998-01-01

33

Heterogeneous Catalytic Esterification of ?-Sulfhydryl Fatty Acids: Avoidance of Thioethers, Thioesters, and Disulfides  

Microsoft Academic Search

Two mesoporous silicas functionalized with propylsulfonic (SBA-15-PSA) and arenesulfonic (SBA-15-ASA) acid groups, and a highly\\u000a acidic, functionalized styrene divinylbenzene copolymer ion exchange resin (Amberlyst-15) were examined for their ability\\u000a to catalyze the ethanolic esterification of the ?-sulfhydryl fatty acid, 11-mercaptoundecanoic acid (MUA), without catalyzing\\u000a unwanted side reactions at the sulfhydryl group. All three solid acid catalysts catalyzed the MUA esterification

David L. ComptonMichael; Michael A. Jackson

34

Unusual properties of crocodilian ovomacroglobulin shown in its methylamine treatment and sulfhydryl titration  

SciTech Connect

The inhibitory activity of chicken and crocodilian ovomacroglobulins against trypsin was measured before and after their incubation with methylamine. The result for crocodilian ovomacroglobulin showed that methylamine treatment destroyed half of its activity, in unique contrast to human alpha 2-macroglobulin and chicken ovomacroglobulin for which methylamine either destroys the inhibitory activity of the former completely or does not affect that of the latter at all. Free sulfhydryl groups of chicken and crocodilian ovomacroglobulins were titrated with 5,5'-dithiobis(2-nitrobenzoic acid) before and after incubation with trypsin. Prior to the incubation with trypsin the chicken and crocodilian proteins respectively had 0 and 1 titratable sulfhydryl per molecule of Mr 720,000. After treatment with trypsin the crocodilian protein had 3.5-4 titratable sulfhydryls, whereas there were no titratable sulfhydryls in the chicken protein. After denaturation of the crocodilian protein in sodium dodecyl sulfate at 100 degrees C the number of titratable sulfhydryls was 4. Chicken ovomacroglobulin again did not have an appreciable number of titratable sulfhydryls under similar denaturing conditions. Incubation of crocodilian protein with (14C)methylamine showed an incorporation of at least 2 mol of methylamine per molecule. The result indicated the presence of three intramolecular thiol ester bonds in crocodilian ovomacroglobulin with differential stability against external perturbations.

Arakawa, H.; Osada, T.; Ikai, A.

1986-02-01

35

Protein kinase C? is critical for the metabolic switch to glycolysis following B-cell antigen receptor engagement.  

PubMed

Signals derived from the BCR (B-cell antigen receptor) control survival, development and antigenic responses. One mechanism by which BCR signals may mediate these responses is by regulating cell metabolism. Indeed, the bioenergetic demands of naïve B-cells increase following BCR engagement and are characterized by a metabolic switch to aerobic glycolysis; however, the signalling pathways involved in this metabolic reprogramming are poorly defined. The PKC (protein kinase C) family plays an integral role in B-cell survival and antigenic responses. Using pharmacological inhibition and mice deficient in PKC?, we demonstrate an essential role of PKC? in BCR-induced glycolysis in B-cells. In contrast, mice deficient in PKC? exhibit glycolytic rates comparable with those of wild-type B-cells following BCR cross-linking. The induction of several glycolytic genes following BCR engagement is impaired in PKC?-deficient B-cells. Moreover, blocking glycolysis results in decreased survival of B-cells despite BCR engagement. The results establish a definitive role for PKC? in the metabolic switch to glycolysis following BCR engagement of naïve B-cells. PMID:22994860

Blair, Derek; Dufort, Fay J; Chiles, Thomas C

2012-11-15

36

Integrity of the AID serine-38 phosphorylation site is critical for class switch recombination and somatic hypermutation in mice.  

PubMed

Activation-induced cytidine deaminase (AID) is a single-stranded (ss) DNA-specific cytidine deaminase that initiates Ig heavy chain (IgH) class switch recombination (CSR) and Ig somatic hypermutation (SHM) by deaminating cytidines within, respectively, IgH switch (S) regions and Ig variable region (V) exons. AID that is phosphorylated on serine residue 38 interacts with replication protein A (RPA), a ssDNA binding protein, to promote deamination of transcribed double-stranded DNA in vitro, which, along with other evidence, suggests that AID may similarly gain access to transcribed S regions and V exons in vivo. However, the physiological role of AID phosphorylation at serine residue 38 (S38), and even the requirement for the S38 residue, with respect to CSR or SHM has been debated. To address this issue, we used gene targeting to generate an endogenous mouse AID locus that produces AID in which S38 is substituted with alanine (AID(S38A)), a mutant form of AID that retains similar catalytic activity on ssDNA as WT AID (AID(WT)). B cells homozygous for the AID(S38A) mutation show substantially impaired CSR and SHM, correlating with inability of AID(S38A) to interact with endogenous RPA. Moreover, mice haploinsufficient for AID(S38A) have even more severely impaired CSR when compared with mice haploinsufficient for AID(WT), with CSR levels reduced to nearly background levels. These results unequivocally demonstrate that integrity of the AID S38 phosphorylation site is required for normal CSR and SHM in mice and strongly support a role for AID phosphorylation at S38 and RPA interaction in regulating CSR and SHM. PMID:19196992

Cheng, Hwei-Ling; Vuong, Bao Q; Basu, Uttiya; Franklin, Andrew; Schwer, Bjoern; Astarita, Jillian; Phan, Ryan T; Datta, Abhishek; Manis, John; Alt, Frederick W; Chaudhuri, Jayanta

2009-02-05

37

Integrity of the AID serine-38 phosphorylation site is critical for class switch recombination and somatic hypermutation in mice  

PubMed Central

Activation-induced cytidine deaminase (AID) is a single-stranded (ss) DNA-specific cytidine deaminase that initiates Ig heavy chain (IgH) class switch recombination (CSR) and Ig somatic hypermutation (SHM) by deaminating cytidines within, respectively, IgH switch (S) regions and Ig variable region (V) exons. AID that is phosphorylated on serine residue 38 interacts with replication protein A (RPA), a ssDNA binding protein, to promote deamination of transcribed double-stranded DNA in vitro, which, along with other evidence, suggests that AID may similarly gain access to transcribed S regions and V exons in vivo. However, the physiological role of AID phosphorylation at serine residue 38 (S38), and even the requirement for the S38 residue, with respect to CSR or SHM has been debated. To address this issue, we used gene targeting to generate an endogenous mouse AID locus that produces AID in which S38 is substituted with alanine (AIDS38A), a mutant form of AID that retains similar catalytic activity on ssDNA as WT AID (AIDWT). B cells homozygous for the AIDS38A mutation show substantially impaired CSR and SHM, correlating with inability of AIDS38A to interact with endogenous RPA. Moreover, mice haploinsufficient for AIDS38A have even more severely impaired CSR when compared with mice haploinsufficient for AIDWT, with CSR levels reduced to nearly background levels. These results unequivocally demonstrate that integrity of the AID S38 phosphorylation site is required for normal CSR and SHM in mice and strongly support a role for AID phosphorylation at S38 and RPA interaction in regulating CSR and SHM.

Cheng, Hwei-Ling; Vuong, Bao Q.; Basu, Uttiya; Franklin, Andrew; Schwer, Bjoern; Astarita, Jillian; Phan, Ryan T.; Datta, Abhishek; Manis, John; Alt, Frederick W.; Chaudhuri, Jayanta

2009-01-01

38

Reusable fast opening switch  

DOEpatents

A reusable fast opening switch for transferring energy, in the form of a high power pulse, from an electromagnetic storage device such as an inductor into a load. The switch is efficient, compact, fast and reusable. The switch comprises a ferromagnetic semiconductor which undergoes a fast transition between conductive and metallic states at a critical temperature and which undergoes the transition without a phase change in its crystal structure. A semiconductor such as europium rich europhous oxide, which undergoes a conductor to insulator transition when it is joule heated from its conductor state, can be used to form the switch.

Van Devender, J.P.; Emin, D.

1983-12-21

39

Synthesis and binding characteristics of two sulfhydryl-reactive probes for vasopressin receptors.  

PubMed

The present study describes the synthesis and receptor binding affinities of the sulfhydryl-reactive vasopressin analogs deamino[Dab(N delta-N-maleoyl-beta-alanin e)4]AVP (1a) and deamino[Lys(N epsilon-N-maleoyl-beta-alanine)8VP (2a). The analogs were obtained by introducing the sulfhydryl-reactive maleoyl-beta-analyl group at the delta-amino group of Dab4 in deamino[Dab4]AVP (1) and at the epsilon-amino group of Lys8 in deamino[Lys8]VP (2), which were synthesized by the solid-phase method. Furthermore, the analog modified at Dab4 was prepared as tritium labeled compound (1b) after catalytic iodine tritium exchange at Tyr2 in deamino[Dab4]AVP. The sulfhydryl-reactive vasopressin analogs retained high binding affinity for the V2 vasopressin receptor in membranes derived from bovine kidney inner medulla. Apparent dissociation constants Kd of 45 nM (compound 1a) and 15 nM (compound 2a) were determined. Incubation of the ligand receptor complexes at pH 5.5 resulted in dissociation of the sulfhydryl-reactive vasopressin analogs from the V2 receptor. No indications of a covalent reaction between analogs 1a, 2a and 1b and sulfhydryl groups in or close to the hormone binding site of the V2 receptor were found. PMID:8422939

Pávó, I; Kojro, E; Fahrenholz, F

1993-01-18

40

THE ROLE OF SULFHYDRYL GROUPS IN THE BLEACHING AND SYNTHESIS OF RHODOPSIN  

PubMed Central

The condensation of retinene1 with opsin to form rhodopsin is optimal at pH about 6, a pH which favors the condensation of retinene1 with sulfhydryl rather than with amino groups. The synthesis of rhodopsin, though unaffected by the less powerful sulfhydryl reagents, monoiodoacetic acid and its amide, is inhibited completely by p-chloromercuribenzoate (PCMB). This inhibition is reversed in part by the addition of glutathione. PCMB does not attack rhodopsin itself, nor does it react with retinene1. Its action in this system is confined to the —SH groups of opsin. Under some conditions the synthesis of rhodopsin is aided by the presence of such a sulfhydryl compound as glutathione, which helps to keep the —SH groups of opsin free and reduced. By means of the amperometric silver titration of Kolthoff and Harris, it is shown that sulfhydryl groups are liberated in the bleaching of rhodopsin, two such groups for each retinene1 molecule that appears. This is true equally of rhodopsin from the retinas of cattle, frogs) and squid. The exposure of new sulfhydryl groups adds an important element to the growing evidence that relates the bleaching of rhodopsin to protein denaturation. The place of sulfhydryl groups in the structure of rhodopsin is still uncertain. They may be concerned directly in binding the chromophore to opsin; or alternatively they may furnish hydrogen atoms for some reductive change by which the chromophore is formed from retinene1. In the amperometric silver titration, the bleaching of rhodopsin yields directly an electrical variation. This phenomenon may have some fundamental connection with the role of rhodopsin in visual excitation, and may provide a model of the excitation process in general.

Wald, George; Brown, Paul K.

1952-01-01

41

Secreted fungal sulfhydryl oxidases: sequence analysis and characterisation of a representative flavin-dependent enzyme from Aspergillus oryzae  

Microsoft Academic Search

BACKGROUND: Sulfhydryl oxidases are flavin-dependent enzymes that catalyse the formation of de novo disulfide bonds from free thiol groups, with the reduction of molecular oxygen to hydrogen peroxide. Sulfhydryl oxidases have been investigated in the food industry to remove the burnt flavour of ultraheat-treated milk and are currently studied as potential crosslinking enzymes, aiming at strengthening wheat dough and improving

Greta Faccio; Kristiina Kruus; Johanna Buchert; Markku Saloheimo

2010-01-01

42

Effect of sulfhydryl modification on rat kidney basolateral plasma membrane transport function.  

PubMed

Transport processes are the hallmark of functioning kidney. Various nephrotoxicants disrupt the transport processes to manifest nephrotoxicity. Of several nephrotoxicants, mercuric chloride (HgCl(2)) depletes the reduced glutathione (GSH) in kidney and has been observed to affect the in vitro p-aminohippurate (PAH) transport by basolateral (BL) membrane vesicles. The role of renal nonprotein sulfhydryls such as, reduced GSH has been demonstrated to affect the PAH transport by BL membrane vesicles. The role of protein sulfhydryls in transport process of PAH by BL membrane is not known. Due to mercury mediated effects on sulfhydryls, the effects of protein-sulfhydryls (-SH) modifying reagents in the current study were investigated on PAH transport by BL membrane. It was observed that modification of -SH by p-chloromercuribenzoate sulphate (pCMBS), and mercuric chloride (HgCl(2)) decreased while recovering the protein -SH with dithiothreitol treatment provided protection against the effects of pCMBS, and HgCl(2) on PAH transport by BL membrane vesicles. PMID:22936015

Ansari, Rais A; Rizvi, Syed A A; Husain, Kazim; Lymperopoulos, Anastasios; Berndt, William O

2012-08-02

43

The Effect of Heat Treatment on the Sulfhydryl Groups in Skimmilk and Nonfat Dry Milk  

Microsoft Academic Search

At the present time, it is generally believed that cystine and cysteine are responsible for all the disulfide and sulfhydryl groups of proteins. Although a certain amount of evidence has appeared that this statement may not always be true (11), the experiments to be described on milk were carried out on the basis of this hypothesis. It is generally assumed

Gunter Zweig; Richard J. Block

1953-01-01

44

Involvement of membrane sulfhydryls in the activation and maintenance of nutrient transport in chick embryo fibroblasts.  

PubMed

At 5 microgram/ml, insulin stimulates hexose, A-system amino acid, and nucleoside transport by serum-starved chick embryo fibroblasts (CEF). This stimulation, although variable, is comparable to that induced by 4% serum. The sulfhydryl oxidants diamide (1-20 micrometer). hydrogen peroxide (500 micrometer), and methylene blue (50 micrometer) mimic the effect of insulin in CEF. PCMB-S,1 a sulfhydryl-reacting compound which penetrates the membrane slowly, has a complex effect on nutrient transport in serum- and glucose-starved CEF. Hexose uptake is inhibited by 0.1-1 mM PCMB-S in a time- and concentration-dependent manner, whereas A-system amino acid transport is inhibited maximally within 10 min of incubation and approaches control rates after 60 min. A differential sensitivity of CEF transport systems is also seen in cells exposed to membrane-impermeant glutathione-maleimide I, designated GS-Mal. At 2 mM GS-Mal reduces the rate of hexose uptake 80-100% in serum- and glucose-starved CEF; in contrast A-system amino acid uptake is unaffected. D-glucose, but not -L-glucose or cytochalasin B, protects against GS-Mal inhibition. These results are consistent with the hypothesis that sulfhydryl groups are involved in nutrient transport and that those sulfhydryls associated with the hexose transport system and essential for its function are located near the exofacial surface of the membrane in CEF. PMID:564429

Smith-Johannsen, H; Perdue, J F; Ramjeesingh, M; Kahlenberg, A

1977-01-01

45

Human erythrocyte ?-aminolevulinate dehydratase inhibition by monosaccharides is not mediated by oxidation of enzyme sulfhydryl groups  

Microsoft Academic Search

The heme pathway enzyme ?-aminolevulinate dehydratase is a good marker for oxidative stress and metal intoxication. This sulfhydryl enzyme is inhibited in such oxidative pathologies as lead, mercury and aluminum intoxication, exposure to selenium organic species and diabetes. Oxidative stress is a complicating factor in diabetes, inducing non-enzymatic glucose-mediated reactions that change protein structures and impair enzyme functions. We have

D. Gabriel; L. Pivetta; V. Folmer; J. C. M. Soares; G. R. Augusti; C. W. Nogueira; G. Zeni; J. B. T. Rocha

2005-01-01

46

Switch-on shocks  

SciTech Connect

The authors argue that parallel propagating Alfven waves steepen to second order in the wave amplitude, rather than first order, as is the case for oblique MHD waves. They derive an analytical solution for the structure of weak switch-on shocks. The Rankine-Hugoniot relations fro finite amplitude switch-on shocks are obtained in a compact form. The differential equation for resistive switch-on shocks is solved, and the resistive critical Mach number is obtained. The differential equation for resistive switch-on shocks with finite ion inertia is identical to the one obtained in the pure resistive case. They argue that efficient electron heat conduction can significantly extend the range of upstream parameters for which switch-on shocks are expected.

Kennel, C.F. (Univ. of California, Los Angeles (United States)); Edmiston, J.P. (Univ. of California, Los Angeles (United States) Univ. of Texas, Richardson (United States))

1988-10-01

47

Switch-on shocks  

NASA Astrophysics Data System (ADS)

It is argued that parallel propagating Alfven waves steepen to second order in the wave amplitude, rather than first order, as is the case for oblique MHD waves. An analytical solution for the structure of weak switch-on shocks is derived. The Rankine-Hugoniot relations for finite amplitude switch-on shocks are obtained in a compact form. The differential equation for resistive switch-on shocks is solved, and the resistive critical Mach number is obtained. The differential equation for resistive switch-on shocks with finite ion inertia is identical to the one obtained in the pure resistive case. It is argued that efficient electron heat conduction can significantly extend the range of upstream parameters for which switch-on shocks are expected.

Kennel, C. F.; Edmiston, J. P.

1988-10-01

48

A simple figure of merit for high temperature superconducting switches  

SciTech Connect

The discovery of the new high temperature superconductors has revived interest in many special applications, including superconducting switches. For comparison of switch types, a simple figure of merit based in switch performance is proposed, derived for superconducting switches, and then calculated for thyristors and vacuum switches. The figure of merit is then used to show what critical current density would be needed for superconducting switches to compete with more conventional switches. 46 refs., 1 fig.

Honig, E.M.

1989-01-01

49

Gene Switch  

NSDL National Science Digital Library

Regulatory "switches" are found upstream from a gene. Regulatory molecules bind to the switches and recruit RNA polymerase to bind to the gene's promoter region, increasing the transcription of the gene into messenger RNA.

Howard Hughes Medical Institute (Howard Hughes Medical Institute;)

2008-04-09

50

Electric Switches  

NSDL National Science Digital Library

In this activity, learners incorporate a simple switch into a battery/bulb circuit. Learners will use their knowledge of circuits to design and make their own switches using common materials. Learners will also identify switches found in common appliances. Note: This activity is designed to be done under the supervision of an educator familiar with electrical and electronic concepts.

Ieee

2013-07-08

51

The mitochondrial tricarboxylate carrier of silver eel: chemical modification by sulfhydryl reagents.  

PubMed

The tricarboxylate (or citrate) carrier was purified from eel liver mitochondria and functionally reconstituted into liposomes. Incubation of the proteoliposomes with various sulfhydryl reagents led to inhibition of the reconstituted citrate transport activity. Preincubation of the proteoliposomes with reversible SH reagents, such as mercurials and methanethiosulfonates, protected the eel liver tricarboxylate carrier against inactivation by the irreversible reagent N-(1-pyrenyl)maleimide (PM). Citrate and L-malate, two substrates of the tricarboxylate carrier, protected the protein against inactivation by sulfhydryl reagents and decreased the fluorescent PM bound to the purified protein. These results suggest that the eel liver tricarboxylate carrier requires a single population of free cysteine(s) in order to manifest catalytic activity. The reactive cysteine(s) is most probably located at or near the substrate binding site of the carrier protein. PMID:15479612

Capobianco, Loredana; Impagnatiello, Tecla; Ferramosca, Alessandra; Zara, Vincenzo

2004-09-30

52

Changes in Sulfhydryl Groups of Honeybee Glyceraldehyde Phosphate Dehydrogenase Associated with Generation of the Intermediate Plateau in Its Saturation Kinetics.  

National Technical Information Service (NTIS)

Honeybee and rabbit muscle GPDH were studied to obtain information at the chemical level regarding anomolous saturation kinetics of the honeybee enzyme. Results demonstrate that the enzyme's sulfhydryl groups are implicated in the process. Measured by DTN...

W. G. Gelb J. F. Brandts J. H. Nordin

1973-01-01

53

EFFECTS OF THIMEROSAL, AN ORGANIC SULFHYDRYL MODIFYING AGENT, ON SEROTONIN TRANSPORT ACTIVITY INTO RABBIT BLOOD PLATELETS  

Microsoft Academic Search

The effects of the sulfhydryl group inhibitor thimerosal on serotonin (5-HT) transport activity into rabbit blood platelets were investigated, along with its effects on the intracellular concentration of Ca2+ ([Ca2+]i). 3H-5-HT transport activity into rabbit blood platelets was inhibited by treatment with 10?5 M thimerosal for 30 min, which did not cause 5-HT release from platelets. The thimerosal-induced inhibition of

HIROAKI NISHIO; KEN-ICHI NEZASA; JUN HIRANO; YOSHIHIRO NAKATA

1996-01-01

54

Inhibitory action of thimerosal, a sulfhydryl oxidant, on sodium channels in rat sensory neurons  

Microsoft Academic Search

The effects of thimerosal, a sulfhydryl oxidizing agent, on tetrodotoxin-sensitive (TTX-S) and tetrodotoxin-resistant (TTX-R) sodium channels in rat dorsal root ganglion neurons were studied using the whole-cell patch clamp technique. Thimerosal blocked the two types of sodium channels in a dose-dependent manner. The inhibitory effect of thimerosal was much more pronounced in TTX-R sodium channels than TTX-S sodium channels. The

Jin-Ho Song; Yoon Young Jang; Yong Kyoo Shin; Moo Yeol Lee; Chung-Soo Lee

2000-01-01

55

Sulfhydryl group content of chicken progesterone receptor: effect of oxidation on DNA binding activity  

SciTech Connect

DNA binding activity of chicken progesterone receptor B form (PRB) and A form (PRA) has been examined. This activity is strongly dependent upon the presence of thiols in the buffer. Stability studies showed that PRB was more sensitive to oxidation that was PRA. Receptor preparations were fractionated by DNA-cellulose chromatography to DNA-positive and DNA-negative subpopulations, and sulfhydryl groups were quantified on immunopurified receptor by labeling with (/sup 3/H)-N-ethylmaleimide. Labeling of DNA-negative receptors with (/sup 3/H)-N-ethylmaleimide showed 21-23 sulfhydryl groups on either PRA or PRB form when the proteins were reduced and denatured. A similar number was seen without reduction if denatured DNA-positive receptor species were tested. In contrast, the DNA-negative PRB had only 10-12 sulfhydryl groups detectable without reduction. A similar number (12-13 sulfhydryl groups) was found for PRA species that lost DNA binding activity after exposure to a nonreducing environment in vitro. The authors conclude that the naturally occurring receptor forms unable to bind to DNA, as well as receptor forms that have lost DNA binding activity due to exposure to nonreducing environment in vitro, contain 10-12 oxidized cysteine residues, likely present as disulfide bonds. Since they were unable to reduce the disulfide bonds when the native DNA-negative receptor proteins were treated with dithiothreitol (DTT), they speculate that irreversible loss of DNA binding activity of receptor in vitro is due to oxidation of cysteine residues that are not accessible to DTT in the native state.

Peleg, S.; Schrader, W.T.; O'Malley, B.W.

1988-01-12

56

Altered sulfhydryl reactivity of hemoglobins and red blood cell membranes in congenital heinz body hemolytic anemia  

PubMed Central

The mechanisms of hemoglobin precipitation into Heinz bodies and hemolytic anemia that characterize congenital Heinz body hemolytic anemia (CHBHA) were studied in patients with the unstable hemoglobins, Köln (?-98 valine ? methionine) and Hammersmith (?-42 phenylalanine ? serine). The cysteines in the 93rd position of the ?-chains of CHBHA hemoglobins bound glutathione excessively in mixed disulfide linkage. The resulting diminished “free” GSH within the cell accelerated hexose monophosphate shunt metabolism. The unique precipitability of CHBHA hemoglobins when heated at 50°C could be induced in normal hemoglobin A by artificially blockading its sulfhydryl groups with paramercuribenzoate (PMB). Reflecting the previously reported excessive flux of hemes from hemoglobin Köln, the expected heme/globin ratio in this hemoglobin was reduced by 30%. The further increment in heme loss that occurs with heat (50°C) underlies the unique heat precipitability of CHBHA hemoglobins; it was retarded if detachment of heme was inhibited by cyanide or carbon monoxide. Heinz bodies were attached to red cell membrane thiol groups presumably through mixed disulfide bonds, being released by mercaptoethanol. Binding of hemoglobin Köln-59Fe to red cell ghosts, which was markedly enhanced when Heinz bodies were generated at 50°C, was inhibited if membrane thiols were preblockaded by PMB. The depletion of membrane thiols by their reaction with Heinz bodies rendered CHBHA red cells hypersusceptible to membrane sulfhydryl inhibitors, as manifested by inordinate cation leakage, osmotic fragility, and autohemolysis. We conclude that both cellular and membrane thiols bind ?-93 sulfhydryls of CHBHA hemoglobins as mixed disulfides. Concomitantly, heme avidity to ?-92 lessens, suggesting that degradation of the resulting excessively freed heme may produce the pigmented dipyrroluria of this syndrome. Heinz bodies, reflecting the heightend precipitability of heme-deficient globin, attach to, thereby depleting, membrane sulfhydryl groups. This, as shown previously, could underlie the hemolytic anemia of this syndrome by causing membrane hyperpermeability, premature splenic entrapment, and ultimately osmotic destruction of red blood cells.

Jacob, Harry S.; Brain, Michael C.; Dacie, John V.

1968-01-01

57

Significance of sulfhydryl groups in the activity of urease from pigeonpea ( Cajanus cajan L.) seeds  

Microsoft Academic Search

Titration of urease from pigeonpea (Cajanus cajan L.), a hexameric protein (mol. wt. 480?000; subunit mol. wt. 80?000), with 5,5?-dithiobis-(2-nitrobenzoate) (DTNB) reveals the presence of 5.82±0.13 ‘accessible’ sulfhydryl groups per molecule of the enzyme protein (i.e. about one ‘accessible’ SH group per subunit). Denatured enzyme was found to titrate for 12.1±0.1 SH groups per molecule (i.e. about two SH groups

Punit K Srivastava; Arvind M Kayastha

2000-01-01

58

Comparative effects of sulfhydryl inhibitors on melanosome movements within vertebrate melanophores  

Microsoft Academic Search

Résumé Dans les mélanophores des grenouilles et des lézards examinés in vitro, les inhibiteurs du groupe sulfhydryl (thiol) tels que le mérsalyle et les maléimides N-substitutés bloquent irrévocablement la dispersion des mélanosomes soumis à l'action de la MSH et provoquent même leur retrait. On étudie les conditions structurales de l'action inhibitrice d'un certain nombre de maléimides N-substitués, étroitement apparentés.

Rebecca L. Potter; M. E. Hadley

1970-01-01

59

Enhanced cytosolic delivery of plasmid DNA by a sulfhydryl-activatable listeriolysin O\\/protamine conjugate utilizing cellular reducing potential  

Microsoft Academic Search

Listeriolysin O (LLO), a sulfhydryl-activated pore-forming protein from Listeria monocytogenes, was tested and utilized for promoting plasmid DNA (pDNA) delivery into the cytosol of cells in culture. To render pDNA-complexing capability to LLO, the unique cysteine 484 of LLO was conjugated to polycationic peptide protamine (PN) at a 1:1 molar ratio through a reversible, endosome-labile disulfide bond. The sulfhydryl-oxidized LLO

G Saito; G L Amidon; K-D Lee

2003-01-01

60

Oxidative Protein Folding and the Quiescin-Sulfhydryl Oxidase Family of Flavoproteins  

PubMed Central

Abstract Flavin-linked sulfhydryl oxidases participate in the net generation of disulfide bonds during oxidative protein folding in the endoplasmic reticulum. Members of the Quiescin-sulfhydryl oxidase (QSOX) family catalyze the facile direct introduction of disulfide bonds into unfolded reduced proteins with the reduction of molecular oxygen to generate hydrogen peroxide. Current progress in dissecting the mechanism of QSOX enzymes is reviewed, with emphasis on the CxxC motifs in the thioredoxin and Erv/ALR domains and the involvement of the flavin prosthetic group. The tissue distribution and intra- and extracellular location of QSOX enzymes are discussed, and suggestions for the physiological role of these enzymes are presented. The review compares the substrate specificity and catalytic efficiency of the QSOX enzymes with members of the Ero1 family of flavin-dependent sulfhydryl oxidases: enzymes believed to play key roles in disulfide generation in yeast and higher eukaryotes. Finally, limitations of our current understanding of disulfide generation in metazoans are identified and questions posed for the future. Antioxid. Redox Signal. 13, 1217–1230.

Kodali, Vamsi K.

2010-01-01

61

Optical Switching  

Microsoft Academic Search

\\u000a Controlling the route light takes through a set of alternative fibre pathways is a basic photonic function. Optical switching\\u000a is required in all aspect s of photonics, from the manufacture of basic components to the operation of large-scale telecommunications\\u000a networks. Recent developments are placing a new importance on switching.

R. Ian MacDonald; Ken Garrett; Philip Garel-Jones; Winfried H. G. Horsthuis; Edmond J. Murphy

62

Sulfhydryl-depleting agents, but not deferoxamine, modulate EDRF action in cultured pulmonary arterial cells.  

PubMed

The potential role of intracellular sulfhydryls and iron on the biological activity of endothelium-derived relaxing factor (EDRF) released basally from bovine pulmonary arterial endothelial (BPAE) cells was investigated in a cultured cell bioassay system, by measuring N omega-nitro-L-arginine-sensitive guanosine 3',5'-cyclic monophosphate (cGMP) accumulation in rabbit pulmonary arterial smooth muscle (SM) cells. The role of sulfhydryls in the biosynthesis of EDRF was studied by selectively exposing the endothelial cells to thiol-depleting agents. Both N-ethylmaleimide (NEM) and maleic acid diethyl ester (DEM) inhibited EDRF-induced cGMP accumulation in a dose-dependent manner. To study the requirement of SM thiols in the metabolism of EDRF to a stimulator of cGMP formation, SM were selectively exposed to NEM and DEM before bioassay with control, untreated BPAE. DEM and NEM inhibited cGMP formation in response to EDRF by 30 and 68%, respectively. The requirement of SM sulfhydryls was further investigated in the stimulation of SM cGMP accumulation elicited by nitrosothiols [S-nitroso-L-cysteine, S-nitroso-mercaptoproprionic acid, and sodium nitroprusside (SNP)]. NEM pretreatment of SM cells abolished cGMP responses to all vasodilators; DEM did not affect the nitrosothiol responses but reduced by 30% the cGMP accumulation to SNP. The role of iron in the endothelial synthesis of EDRF was assessed by chelating endothelial low-molecular-weight iron compounds. Exposure of BPAE to deferoxamine mesylate had no effect on cGMP accumulation in SM, suggesting that deferoxamine-available iron is not necessary for the endothelial stimulation of SM cGMP formation.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8214082

Marczin, N; Ryan, U S; Catravas, J D

1993-09-01

63

Effect of sulfhydryl-deficient diets on hepatic metallothionein, glutathione, and adenosine 3'-phosphate 5'-phosphosulfate (PAPS) levels in rats.  

PubMed

Low dietary concentrations of methionine and cysteine are known to decrease hepatic glutathione content. However, it is not known if restricting the dietary content of these sulfur containing amino acids also affects hepatic levels of adenosine 3'-phosphate 5'-phosphosulfate (PAPS), the cofactor for sulfation, or metallothionein, a protein rich in sulfhydryl groups. Rats were fed diets lacking cysteine and containing various concentrations of methionine (0.15, 0.3, or 0.6%) for 8 days. Control diet contained 0.3% each of methionine and cysteine. Hepatic glutathione levels were decreased approximately 75% in rats fed diets containing 0.15 or 0.3% methionine. In contrast, PAPS and hepatic metallothionein concentrations were not decreased by the low sulfhydryl diets. Additionally, rats on the various diets were challenged by the administration of ZnCl2 (3 mmol/kg. sc). In both control rats and rats maintained on sulfhydryl-deficient diets, ZnCl2 increased hepatic metallothionein to the same level. However, significantly lower levels of PAPS were observed after ZnCl2 in rats receiving sulfhydryl-deficient diets than in controls. In summary, restriction of dietary sulfhydryl markedly decreases the hepatic content of glutathione and has a minor effect on PAPS concentration, but does not decrease the basal hepatic concentration of metallothionein or its induction by ZnCl2. PMID:2300970

Sendelbach, L E; White, C A; Howell, S; Gregus, Z; Klaassen, C D

1990-02-01

64

Involvement of protein sulfhydryls in the trigger reaction of rhodotorucine A, a farnesyl peptide mating pheromone of Rhodosporidium toruloides.  

PubMed

The involvement of protein sulfhydryls for the signaling of rhodotorucine A, a mating pheromone produced by mating type A cells of Rhodosporidium toruloides, was investigated by the use of sulfhydryl compounds. The sulfhydryl-blocking reagent 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB; Ellman's reagent) strongly inhibited both the biological effect of the pheromone on the recipient cell and the hydrolysis of the pheromone, which is catalyzed by the mating type-specific surface endopeptidase of the recipient cell. Conversely, the two reactions were markedly enhanced by the presence of the reducing reagent dithiothreitol. The inhibitory effect of DTNB on the pheromone response of the recipient cell was specific to an initial stage of the differentiation; once it had initiated, the reagent had no effect on its progression. The results suggested that dithiothreitol enhances and DTNB impairs the efficiency with which the pheromone triggers sexual d differentiation. The reaction of DTNB with cellular protein sulfhydryls was highly restricted to those at the exterior surface of the membrane due to the impermeability of the reagent through the membrane. Phosphorylation of endogenous proteins, which is modulated by the pheromone added to an in vitro phosphorylation system, was also blocked by DTNB. The results showed that sulfhydryl groups are involved in the pheromone hydrolysis by the surface endopeptidase of the recipient cell and that pheromone metabolism is indispensable for the signaling reaction. We suggest that the modulation of protein phosphorylation of membrane proteins by the pheromone is an initial transmembrane response coupled to pheromone metabolism. PMID:4038978

Miyakawa, T; Kaji, M; Yasutake, T; Jeong, Y K; Tsuchiya, E; Fukui, S

1985-04-01

65

Frequency dependence of critical switching asteroid of CoCrPt-SiO2 granular film under 50-ns microwave impulse  

NASA Astrophysics Data System (ADS)

Understanding the dynamic process of microwave-assisted magnetization reversal (MAMR) in a dipole-dipole coupled granular perpendicular medium is essential for its application to future magnetic storage devices. We experimentally investigated the magnetization reversal process in CoCrPt-SiO2 granular films in terms of the dependence of the switching field on the strength of an applied in-plane radio-frequency magnetic field. The reversal process changed from non-uniform rotation to uniform rotation when the frequency increased toward the ferromagnetic resonance frequency. In the resonant condition, the switching field agreed well with a model assuming uniform rotation of the magnetization in each grain. The agreement suggests that the decoherence of ferromagnetic resonance due to a dynamic dipolar field is weak in adequately exchange-coupled granular films with a saturation magnetization of 415 emu/cm3. This finding is significant for the development of the practical medium necessary for MAMR writing.

Ishida, N.; Soeno, Y.; Sekiguchi, K.; Nozaki, Y.

2013-07-01

66

Gene Switches  

NSDL National Science Digital Library

In this activity, learners explore how genetic switches function and the role of genetic switches in the process of evolution. To make these concepts less abstract and more understandable, learners first view a series of video clips and animations from the HHMI DVD (or online) "Evolution: Constant Change and Common Threads." Then, learners construct a model of a gene switch using craft materials or FridgiGears (magnetic gears). This activity can be done as a demonstration, a student inquiry activity, or a combination of the two.

Colvard, Mary

2010-01-01

67

Nanoelectromechanical switches  

NASA Astrophysics Data System (ADS)

Power dissipation is perhaps the most important problem confronting the electronics industry. To address this issue, we investigate vertical nanoelectromechanical (NEM) switches suitable for complementary logic, reconfigurable interconnects, and static power management. NEM switches have the following advantages: (i) Near elimination of source-drain static tunneling losses, (ii) Improved subthreshold characteristics [1]-- allowing lower operating voltage and hence lower dynamic power dissipation, (iii) Ability to run at much higher temperatures than Si-based CMOS. Our approach employs a carbon nanotube-based relay. We have prototyped this approach by inserting a tube into an etched gap between two contacts. Using a nanopositioner to align the tube, the prototype has demonstrated multiple switching at 5V. We will characterize this device and also integrated NEM switches. [1] Ghosh, A. W., Rakshit, T. & Datta, S. Gating of a molecular transistor: Electrostatic and Conformational. Nano Letters 4, 565-568 (2004).

Baldo, Marc

2008-03-01

68

Acceleration switch  

DOEpatents

The disclosure relates to an improved integrating acceleration switch of the type having a mass suspended within a fluid filled chamber, with the motion of the mass initially opposed by a spring and subsequently not so opposed.

Abbin, Jr., Joseph P. (Albuquerque, NM); Devaney, Howard F. (Cedar Crest, NM); Hake, Lewis W. (Albuquerque, NM)

1982-08-17

69

Magnetic switching  

SciTech Connect

Magnetic switching is a pulse compression technique that uses a saturable inductor (reactor) to pass pulses of energy between two capacitors. A high degree of pulse compression can be achieved in a network when several of these simple, magnetically switched circuits are connected in series. Individual inductors are designed to saturate in cascade as a pulse moves along the network. The technique is particularly useful when a single-pulse network must be very reliable or when a multi-pulse network must operate at a high pulse repetition frequency (PRF). Today, magnetic switches trigger spark gaps, sharpen the risetimes of high energy pulses, power large lasers, and drive high PRF linear induction accelerators. This paper will describe the technique of magnetic pulse compression using simple networks and design equations. A brief review of modern magnetic materials and of their role in magnetic switch design will be presented. 12 refs., 8 figs.

Kirbie, H.C.

1989-04-14

70

Sulfhydryl compounds reduce Staphylococcus aureus biofilm formation by inhibiting PIA biosynthesis.  

PubMed

Staphylococcus aureus is the most common opportunistic pathogen causing foreign-body-associated infections. It has been widely accepted that biofilms would help the bacteria to cope with variable environments. Here we showed that treatment with sulfhydryl compounds such as dithiothreitol, ?-mercaptoethanol or cysteine inhibited biofilm formation significantly in S. aureus. These sulfhydryl compounds at biofilm-inhibitive concentrations caused little inhibition of the growth rate and the initial adhesion ability of the cells. Real-time reverse transcriptase-PCR showed that the transcriptional level of ica, which encodes essential enzymes for polysaccharide intercellular adhesion (PIA) biosynthesis, was decreased after the treatment with thiols. Proteomic analysis revealed that Embden-Meyerhof-Parnas pathway and pentose phosphate pathway were strengthened while N-acetyl-glucosamine-associated polysaccharide metabolism was repressed in the cells treated with thiols. These changes finally resulted in the inhibition of PIA biosynthesis. We hope the discovery of this major physiological phenomenon will help in the prevention and clinical therapy of biofilm-associated problems caused by S. aureus. PMID:21204926

Wu, Xiaoqian; Wang, Yu; Tao, Liang

2011-01-17

71

Exploring ORFan Domains in Giant Viruses: Structure of Mimivirus Sulfhydryl Oxidase R596  

PubMed Central

The mimivirus genome contains many genes that lack homologs in the sequence database and are thus known as ORFans. In addition, mimivirus genes that encode proteins belonging to known fold families are in some cases fused to domain-sized segments that cannot be classified. One such ORFan region is present in the mimivirus enzyme R596, a member of the Erv family of sulfhydryl oxidases. We determined the structure of a variant of full-length R596 and observed that the carboxy-terminal region of R596 assumes a folded, compact domain, demonstrating that these ORFan segments can be stable structural units. Moreover, the R596 ORFan domain fold is novel, hinting at the potential wealth of protein structural innovation yet to be discovered in large double-stranded DNA viruses. In the context of the R596 dimer, the ORFan domain contributes to formation of a broad cleft enriched with exposed aromatic groups and basic side chains, which may function in binding target proteins or localization of the enzyme within the virus factory or virions. Finally, we find evidence for an intermolecular dithiol/disulfide relay within the mimivirus R596 dimer, the first such extended, intersubunit redox-active site identified in a viral sulfhydryl oxidase.

Hakim, Motti; Ezerina, Daria; Alon, Assaf; Vonshak, Ohad; Fass, Deborah

2012-01-01

72

Sulfhydryl-group modifications of Torpedo Californica acetylcholine receptor: subunit localization and effects on function  

SciTech Connect

The effects of thiol-group modification on acetylcholine receptor (ACHR) function were measured using purified Torpedo ACHR reconstituted into soybean lipid vesicles. N-Phenyl-maleimide (NPM) was used to modify sulfhydryl groups in ACHR in the absence of any prior reduction by dithiotheitol. Modification by NPM led to the inhibition of ion channel activity without a detectable effect on ligand binding. The ion flux inhibition by NPM primarily affected channel activation, since the initial rates of activation decreased over a wide range of carbamylcholine concentrations. The /sup 3/H-NPM subunit labelling pattern of ACHR (a multisubunit membrane protein with ..cap alpha../sub 2/..beta gamma..delta stoichiometry) revealed preferential labelling of the ..gamma.. subunit. At high NPM concentration, the number of sulfhydryl groups on the ..gamma.. subunit that could be modified with NPM was two. Detergent was required during labelling for functionally relevant thiol group modifications, and most of the label was protected from protease digestion in the reconstituted membranes. These results are consistent with the presence of the NPM modification in a bilayer and/or cytoplasmic domain. Analysis of cyanogen bromide and trypsin fragments indicates that the labeled cysteines may be located in the postulated amphipathic helix region of the ..gamma.. subunit.

McNamee, M.G.; Yee, A.S.

1986-05-01

73

DEVELOPMENT OF SULFHYDRYL-REACTIVE SILICA FOR PROTEIN IMMOBILIZATION IN HIGH-PERFORMANCE AFFINITY CHROMATOGRAPHY  

PubMed Central

Two techniques were developed for the immobilization of proteins and other ligands to silica through sulfhydryl groups. These methods made use of maleimide-activated silica (the SMCC method) or iodoacetyl-activated silica (the SIA method). The resulting supports were tested for use in high-performance affinity chromatography by employing human serum albumin (HSA) as a model protein. Studies with normal and iodoacetamide-modified HSA indicated that these methods had a high selectivity for sulfhydryl groups on this protein, which accounted for the coupling of 77–81% of this protein to maleimide- or iodacetyl-activated silica. These supports were also evaluated in terms of their total protein content, binding capacity, specific activity, non-specific binding, stability and chiral selectivity for several test solutes. HSA columns prepared using maleimide-activated silica gave the best overall results for these properties when compared to HSA that had been immobilized to silica through the Schiff base method (i.e., an amine-based coupling technique). A key advantage of the supports developed in this work is that they offer the potential of giving greater site-selective immobilization and ligand activity than amine-based coupling methods. These features make these supports attractive in the development of protein columns for such applications as the study of biological interactions and chiral separations.

Mallik, Rangan; Wa, Chunling; Hage, David S.

2008-01-01

74

Application Switching  

Microsoft Academic Search

\\u000a Application switching is a powerful feature that can extend your image creation and manipulation options. Aviary’s applications\\u000a are designed to be quick and simple to use; thus, many advanced features have been omitted to keep the applications nimble.\\u000a To offset this smaller feature set compared to the more expensive desktop applications, Aviary has added easy application\\u000a switching. For instance, if

Mike Peutz

75

Structure of yeast sulfhydryl oxidase erv1 reveals electron transfer of the disulfide relay system in the mitochondrial intermembrane space.  

PubMed

The disulfide relay system in the mitochondrial intermembrane space drives the import of proteins with twin CX(9)C or twin CX(3)C motifs by an oxidative folding mechanism. This process requires disulfide bond transfer from oxidized Mia40 to a substrate protein. Reduced Mia40 is reoxidized/regenerated by the FAD-linked sulfhydryl oxidase Erv1 (EC 1.8.3.2). Full-length Erv1 consists of a flexible N-terminal shuttle domain (NTD) and a conserved C-terminal core domain (CTD). Here, we present crystal structures at 2.0 ? resolution of the CTD and at 3.0 ? resolution of a C30S/C133S double mutant of full-length Erv1 (Erv1FL). Similar to previous homologous structures, the CTD exists as a homodimer, with each subunit consisting of a conserved four-helix bundle that accommodates the isoalloxazine ring of FAD and an additional single-turn helix. The structure of Erv1FL enabled us to identify, for the first time, the three-dimensional structure of the Erv1NTD, which is an amphipathic helix flanked by two flexible loops. This structure also represents an intermediate state of electron transfer from the NTD to the CTD of another subunit. Comparative structural analysis revealed that the four-helix bundle of the CTD forms a wide platform for the electron donor NTD. Moreover, computational simulation combined with multiple-sequence alignment suggested that the amphipathic helix close to the shuttle redox enter is critical for the recognition of Mia40, the upstream electron donor. These findings provide structural insights into electron transfer from Mia40 via the shuttle domain of one subunit of Erv1 to the CTD of another Erv1 subunit. PMID:22910915

Guo, Peng-Chao; Ma, Jin-Di; Jiang, Yong-Liang; Wang, Shu-Jie; Bao, Zhang-Zhi; Yu, Xiao-Jie; Chen, Yuxing; Zhou, Cong-Zhao

2012-08-21

76

Effects of depletion of ascorbic acid or nonprotein sulfhydryls on the acute inhalation toxicity of nitrogen dioxide, ozone, and phosgene  

Microsoft Academic Search

The effect of depleting lung ascorbic acid (AHâ) and nonprotein sulfhydryls (NPSH) on the acute inhalation toxicity of nitrogen dioxide (NOâ), ozone (Oâ), and phosgene (COClâ) was investigated in guinea pigs. The increase in bronchoalveolar lavage (BAL) fluid protein (an indicator of alveolar-capillary damage leading to increased permeability) was measured 16 to 18 hr following a 4 hr exposure to

R. Slade; J. W. Highfill; G. E. Hatch

1989-01-01

77

Effects of Redox and Sulfhydryl Reagents on the Bioelectric Properties of the Giant Axon of the Squid.  

National Technical Information Service (NTIS)

The effects of internally and externally applied sulfhydryl reagents on the bioelectric properties of the giant axon of the squid Loligo pealeii and Dosidicus gigas were studied. Cysteine-HCl (400 mM, pH 7.3) was used to remove axoplasm from the perfusion...

F. Huneeus-Cox H. L. Fernandez B. H. Smith

1965-01-01

78

Uptake of (sup 10)B in gliosarcomas following the injection of gluthathione monoethyl ester and sulfhydryl borane.  

National Technical Information Service (NTIS)

The sulfhydryl borane Na(sub 2)(sup 10)B(sub 12)H(sub 11)SH (BSH) was developed as a capture agent for BNCT about 20 years ago and is the compound currently used clinically in Japan for BNCT of malignant brain tumors. Tumor (sup 10)B concentrations follow...

D. D. Joel D. N. Slatkin J. A. Coderre

1992-01-01

79

Spatial proximity and sequence localization of the reactive sulfhydryls of porphobilinogen synthase.  

PubMed Central

The zinc metalloenzyme porphobilinogen synthase (PBGS) contains several functionally important, but previously unidentified, reactive sulfhydryl groups. The enzyme has been modified with the reversible sulfhydryl-specific nitroxide spin label derivative of methyl methanethiosulfonate (MMTS), (1-oxyl-2,2,5,5-tetramethyl-delta 3-pyrroline-3-methyl)methanethiosulfonate (SL-MMTS) (Berliner, L. J., Grunwald, J., Hankovszky, H. O., & Hideg, K., 1982, Anal. Biochem. 119, 450-455). EPR spectra show that SL-MMTS labels three groups per PBGS subunit (24 per octamer), as does MMTS. EPR signals reflecting nitroxides of different mobilities are observed. Two of the three modified cysteines have been identified as Cys-119 and Cys-223 by sequencing peptides produced by an Asp-N protease digest of the modified protein. Because MMTS-reactive thiols have been implicated as ligands to the required Zn(II), EPR spectroscopy has been used to determine the spatial proximity of the modified cysteine residues. A forbidden (delta m = 2) EPR transition is observed indicating a through-space dipolar interaction between at least two of the nitroxides. The relative intensity of the forbidden and allowed transitions show that at least two of the unpaired electrons are within at most 7.6 A of each other. SL-MMTS-modified PBGS loses all Zn(II) and cannot catalyze product formation. The modified enzyme retains the ability to bind one of the two substrates at each active site. Binding of this substrate has no influence on the EPR spectral properties of the spin-labeled enzyme, or on the rate of release of the nitroxides when 2-mercaptoethanol is added.(ABSTRACT TRUNCATED AT 250 WORDS)

Markham, G. D.; Myers, C. B.; Harris, K. A.; Volin, M.; Jaffe, E. K.

1993-01-01

80

Flow injection determination of carboxylate, phosphate, and sulfhydryl compounds using metal exchange complexation.  

PubMed

The determination of carboxylate, phosphorous, and sulfhydryl compounds has been studied using flow injection by measuring the decrease in absorbance of the Fe(III)-salicylate complex due to preferential ligand interaction with ferric ion. Targeted compounds include polycarboxylates such as sodium citrate, sodium oxalate, and EDTA, anionic phosphorous compounds such as sodium monofluoroorthophosphate, sodium trimetaphosphate, and sodium hexametaphosphate, and sulfhydryl compounds such as cysteine, glutathione, and captopril. Initial flow injection optimization has focused on citrate based on its ability to replace salicylate ion in the Fe(III)-salicylate complex causing a decrease in absorbance at 525 nm proportional to the citrate concentration. Two flow injection analysis methods are developed. In the first method, offline reaction flow injection, sodium citrate dissolved in 100 ?mol L(-1) Fe-salicylate is injected in a carrier solution of 100 ?mol L(-1) Fe-salicylate. The decrease in peak area is linear over a range of 1.36-109 ?mol L(-1) using a flow rate of 1 mL min(-1) and an injection volume of 100 ?L. The effect of pH on the Fe-salicylate complex absorbance is studied from 1 to 3.5; pH 3 shows both a high and stable complex absorbance in the visible range which provided important potential selectivity over UV detection. The limit of detection is found to be less than 57 nmol L(-1) depending on the Fe(III)-salicylate concentration used. The second method is reverse flow injection using the sample as a flowing stream in which 3 mmol L(-1) Fe(III)-salicylate is injected and the decrease in the response with increased sample concentration was monitored. The commercially available pharmaceutical product (Citroma)(®) is used to assess the accuracy and precision of the two proposed methods as compared to a reference method. PMID:22748549

Mansour, Fotouh R; Shafi, Mohammad A; Danielson, Neil D

2012-03-13

81

Switched power workshop. [Switched power electron guns  

SciTech Connect

This paper discusses the design of a switched power electron gun. Particular topics discussed are: vacuum photodiode switch; laser switched solid state diodes; gun performance; charging supply; and laser requirements. (LSP)

Palmer, R.B.

1988-01-01

82

Switching Transistor  

NASA Astrophysics Data System (ADS)

Westinghouse Electric Corporation's D60T transistors are used primarily as switching devices for controlling high power in electrical circuits. It enables reduction in the number and size of circuit components and promotes more efficient use of energy. Wide range of application from a popcorn popper to a radio frequency generator for solar cell production.

1981-01-01

83

Optical Switch.  

National Technical Information Service (NTIS)

An optical switching device is provided whereby light from a first glass fiber or a second glass fiber may be selectively transmitted into a third glass fiber. Each glass fiber is provided with a focusing and collimating lens system. In one mode of operat...

R. P. Reedy

1985-01-01

84

The regulation of party switching in Africa  

Microsoft Academic Search

The article presents a complete overview of existing regulations of party switching in Africa since the reintroduction of multiparty politics in the early 1990s. While most established democracies do not see any reason for sanctioning with legal restrictions the decision of members of parliament to change their party affiliation, in Africa many countries take a critical stance towards party switching.

Martin Goeke; Christof Hartmann

2011-01-01

85

IP switching for scalable IP services  

Microsoft Academic Search

Internet protocol (IP) switching is emerging as a critical technology for improving the speed and scalability of the Internet. This paper discusses IP Navigator, a form of IP switching developed specifically for use in core network backbones, such as Internet service provider networks and major corporate backbones. IP Navigator combines the high speed and quality of service capabilities of asynchronous

HASSAN M. AHMED; R. Gallon; ANDREW G. MALIS; JOHN MOY

1997-01-01

86

Optical switching: switch fabrics, techniques, and architectures  

Microsoft Academic Search

The switching speeds of electronics cannot keep up with the transmission capacity offered by optics. All-optical switch fabrics play a central role in the effort to migrate the switching functions to the optical layer. Optical packet switching provides an almost arbitrary fine granularity but faces significant challenges in the processing and buffering of bits at high speeds. Generalized multiprotocol label

Georgios I. Papadimitriou; Chrisoula Papazoglou; Andreas S. Pomportsis

2003-01-01

87

Increased Neuronal Glucose6-phosphate Dehydrogenase and Sulfhydryl Levels Indicate Reductive Compensation to Oxidative Stress in Alzheimer Disease  

Microsoft Academic Search

We analyzed glucose-6-phosphate dehydrogenase, the rate-controlling enzyme of the pentose phosphate pathway and free sulfhydryls, to study redox balance in Alzheimer disease. Glucose-6-phosphate dehydrogenase plays a pivotal role in homeostatic redox control by providing reducing equivalents to glutathione, the major nonenzymatic cellular antioxidant. There is a multitude of evidence that marks oxidative stress proximally in the natural history of Alzheimer

Robert L. Russell; Sandra L. Siedlak; Arun K. Raina; José M. Bautista; Mark A. Smith; George Perry

1999-01-01

88

Sulfhydryl-disulfide changes in storage proteins of developing wheat grain: influence on the SDS-unextractable glutenin polymer formation  

Microsoft Academic Search

To understand more precisely the function of free glutenin SH and SS groups in glutenins of developing wheat for UPP formation, a specific sulfhydryl probe, monobromobimane (mBBr), was used for an in vitro protein labeling. By applying this procedure to two varieties of wheat differing in high molecular weight glutenin subunit composition (2*, 7+8, 5+10 and 0, 6+8, 2+12, respectively,

L. Rhazi; R. Cazalis; T. Aussenac

2003-01-01

89

Hydrogen peroxide-induced reduction of delayed rectifier potassium current in hippocampal neurons involves oxidation of sulfhydryl groups.  

PubMed

This study examined the effect of H2O2 on the delayed rectifier potassium current (IKDR) in isolated hippocampal neurons. Whole-cell voltage-clamp experiments were performed on freshly dissociated hippocampal CA1 neurons of SD rats before and after treatment with H2O2. To reveal the mechanism behind H2O2-induced changes in IKDR, cells were treated with different oxidizing and reducing agents. External application of membrane permeable H2O2 reduced the amplitude and voltage-dependence of IKDR in a concentration dependent manner. Desferoxamine (DFO), an iron-chelator that prevents hydroxyl radical (OH) generation, prevented H2O2-induced reduction in IKDR. Application of the sulfhydryl-oxidizing agent 5,5 dithio-bis-nitrobenzoic acid (DTNB) mimicked the effect of H2O2. Sulfhydryl-reducing agents dithiothreitol (DTT) and glutathione (GSH) alone did not affect IKDR; however, DTT and GSH reversed and prevented the H2O2-induced inhibition of IKDR, respectively. Membrane impermeable agents GSH and DTNB showed effects only when added intracellularly identifying intracellular sulfhydryl groups as potential targets for hydroxyl-mediated oxidation. However, the inhibitory effects of DTNB and H2O2 at the positive test potentials were completely and partially abolished by DTT, respectively, suggesting an additional mechanism of action for H2O2, that is not shared by DTNB. In summary, this study provides evidence for the redox modulation of IKDR, identifies hydroxyl radical as an intermediate oxidant responsible for the H2O2-induced decrease in current amplitude and identifies intracellular sulfhydryl groups as an oxidative target. PMID:23688542

Hasan, Sonia M K; Redzic, Zoran B; Alshuaib, Waleed B

2013-05-18

90

Protein Substrate Discrimination in the Quiescin-sulfhydryl Oxidase (QSOX) Family†  

PubMed Central

This work explores the substrate specificity of the Quiescin-sulfhydryl oxidase (QSOX) family of disulfide-generating flavoenzymes to provide enzymological context for investigation of the physiological roles of these facile catalysts of oxidative protein folding. QSOX enzymes are generally unable to form disulfide bonds within well-structured proteins. Use of a temperature-sensitive mutant of ubiquitin-conjugating enzyme 4 (Ubc4?) as a model substrate shows that QSOX activity correlates with the unfolding of Ubc4? monitored by circular dichroism. Fusion of Ubc4? with the more stable glutathione-S-transferase domain demonstrates that QSOX can selectively introduce disulfides into the less stable domain of the fusion protein. In terms of intermolecular disulfide bond generation, QSOX is unable to crosslink well-folded globular proteins via their surface thiols. However, the construction of a septuple mutant of RNase A, retaining a single cysteine residue, demonstrates that flexible protein monomers can be directly coupled by the oxidase. Steady- and pre-steady state kinetic experiments, combined with static fluorescence approaches, indicate that while QSOX is an efficient catalyst for disulfide bond formation between mobile elements of structure, it does not appear to have a significant binding site for unfolded proteins. These aspects of protein substrate discrimination by QSOX family members are rationalized in terms of the stringent steric requirements for disulfide exchange reactions.

Codding, Jennifer A.; Israel, Benjamin A.; Thorpe, Colin

2012-01-01

91

Discovery of novel secreted fungal sulfhydryl oxidases with a plate test screen.  

PubMed

Sulfhydryl oxidases (SOX) are FAD-dependent enzymes capable of oxidising free thiol groups and forming disulphide bonds. Although the quantity of scientific papers and suggested applications for SOX is constantly increasing, only a limited number of microbial SOX have been reported and are commercially available. Hence, the aim of this study was to develop a fast and reliable qualitative plate test for screening novel secreted fungal SOX. The screening was based on the Ellman's reagent, i.e. 5,5'-dithiobis[2-nitrobenzoic acid]. Altogether, 32 fungal strains from an in-house culture collection were screened. A total of 13 SOX-producing strains were found positive in the plate test screen. The novel SOX producers were Aspergillus tubingensis, Chaetomium globusum, Melanocarpus albomyces, Penicillium aurantiogriseum, Penicillium funiculosum, Coniophora puteana and Trametes hirsuta. Six of the discovered SOX were partially characterised by determination of isoelectric point, pH optimum and substrate specificity. A. tubingensis was identified as the most efficient novel SOX producer. PMID:23417429

Nivala, Outi; Mattinen, Maija-Liisa; Faccio, Greta; Buchert, Johanna; Kruus, Kristiina

2013-02-17

92

Relationship between rubisco sulfhydryl content and relative sensitivity of potato cultivars to ozone  

SciTech Connect

Ozone (O{sub 3}) induced a reduction in quantity of rubisco in potato foliage. In vitro, O{sub 3} predisposed purified rubisco to elevated proteolysis; reagents which protected sulfhydryl (SH) groups suppressed this effect. We hypothesized that rubisco SH content correlated directly with foliar O{sub 3} sensitivity. Rubisco was purified from Solanum tuberosum L. O{sub 3}-tolerant cv. Superior (SP) and Norgold Russet (NR), and O{sub 3}-susceptible cv. Norland (NL) and Cherokee (CK). When native rubisco was titrated with DTNB, protein of NL contained 1.33 and 1.26 times more SH groups than SP and NR, respectively. Rubisco from CK also contained more SH groups than SP and NR, but the difference was not significant. Rubisco of SP, NR and CK denatured by SDS exhibited identical number of SH groups, however, NL exhibited 1.15 times more SH groups. The greater number of SH groups in rubisco from NL versus SP and NR may explain its relative sensitivity to ozone. The role of SH groups in ozone-sensitivity of CK will require further study.

Enyedi, A.J.; Pell, E.J. (Pennsylvania State Univ., University Park (USA))

1989-04-01

93

An Arabidopsis quiescin-sulfhydryl oxidase regulates cation homeostasis at the root symplast-xylem interface  

PubMed Central

A genetic screen of Arabidopsis ‘activation-tagging' mutant collection based on tolerance to norspermidine resulted in a dominant mutant (par1-1D) with increased expression of the QSO2 gene (At1g15020), encoding a member of the quiescin-sulfhydryl oxidase (QSO) family. The par1-1D mutant and transgenic plants overexpressing QSO2 cDNA grow better than wild-type Arabidopsis in media with toxic cations (polyamines, Li+ and Na+) or reduced K+ concentrations. This correlates with a decrease in the accumulation of toxic cations and an increase in the accumulation of K+ in xylem sap and shoots. Conversely, three independent loss-of-function mutants of QSO2 exhibit phenotypes opposite to those of par1-1D. QSO2 is mostly expressed in roots and is upregulated by K+ starvation. A QSO2?GFP fusion ectopically expressed in leaf epidermis localized at the cell wall. The recombinant QSO2 protein, produced in yeast in secreted form, exhibits disulfhydryl oxidase activity. A plausible mechanism of QSO2 action consists on the activation of root systems loading K+ into xylem, but different from the SKOR channel, which is not required for QSO2 action. These results uncover QSOs as novel regulators of ion homeostasis.

Alejandro, Santiago; Rodriguez, Pedro L; Belles, Jose M; Yenush, Lynne; Garcia-Sanchez, Maria J; Fernandez, Jose A; Serrano, Ramon

2007-01-01

94

Membrane-wall interrelationship in Gaffkya homari: sulfhydryl sensitivity and heat lability of nascent peptidoglycan incorporation into walls.  

PubMed Central

Membrane-walls from Gaffkya homari require a specific interrelationship between membrane and wall that functions in the incorporation of nascent peptidoglycan into the preexisting peptidoglycan of the wall. Two different methods were used to inhibit selectively this incorporation process: (i) sensitivity to sulfhydryl reagents and (ii) heat inactivation. Of the sulfhydryl reagents tested, 2.2 mM iodoacetamide inhibited the synthesis of wall peptidoglycan 50%, whereas greater than 100 mM was required to inhibit the synthesis of sodium dodecyl sulfate (SDS)-soluble peptidoglycan. Heat treatment at 37 degrees C (t 1/2 = 5.7 min) inhibited wall peptidoglycan synthesis without affecting SDS-soluble peptidoglycan synthesis. Inhibition of LD-carboxypeptidase by iodoacetamide and heat gave 50% inhibition and t 1/2 values similar to those observed for the incorporation process. Thus, it is suggested that the LD-carboxypeptidase may be one of the enzymes responsible for the sulfhydryl sensitivity and heat lability and that this enzyme may play a role in the relationship between membrane and wall in G. homari.

Neuhaus, F C; Tobin, C E; Ahlgren, J A

1980-01-01

95

Phenylethynyl-Butyltellurium Inhibits the Sulfhydryl Enzyme Na(+), K (+)-ATPase: An Effect Dependent on the Tellurium Atom.  

PubMed

Organotellurium compounds are known for their toxicological effects. These effects may be associated with the chemical structure of these compounds and the oxidation state of the tellurium atom. In this context, 2-phenylethynyl-butyltellurium (PEBT) inhibits the activity of the sulfhydryl enzyme, ?-aminolevulinate dehydratase. The present study investigated on the importance of the tellurium atom in the PEBT ability to oxidize mono- and dithiols of low molecular weight and sulfhydryl enzymes in vitro. PEBT, at high micromolar concentrations, oxidized dithiothreitol (DTT) and inhibited cerebral Na(+), K(+)-ATPase activity, but did not alter the lactate dehydrogenase activity. The inhibition of cerebral Na(+), K(+)-ATPase activity was completely restored by DTT. By contrast, 2-phenylethynyl-butyl, a molecule without the tellurium atom, neither oxidized DTT nor altered the Na(+), K(+)-ATPase activity. In conclusion, the tellurium atom of PEBT is crucial for the catalytic oxidation of sulfhydryl groups from thiols of low molecular weight and from Na(+), K(+)-ATPase. PMID:23955422

Quines, Caroline B; Rosa, Suzan G; Neto, José S S; Zeni, Gilson; Nogueira, Cristina W

2013-08-17

96

Potency of Michael reaction acceptors as inducers of enzymes that protect against carcinogenesis depends on their reactivity with sulfhydryl groups.  

PubMed

Induction of phase 2 enzymes and elevations of glutathione are major and sufficient strategies for protecting mammals and their cells against the toxic and carcinogenic effects of electrophiles and reactive forms of oxygen. Inducers belong to nine chemical classes and have few common properties except for their ability to modify sulfhydryl groups by oxidation, reduction, or alkylation. Much evidence suggests that the cellular "sensor" molecule that recognizes the inducers and signals the enhanced transcription of phase 2 genes does so by virtue of unique and highly reactive sulfhydryl functions that recognize and covalently react with the inducers. Benzylidene-alkanones and -cycloalkanones are Michael reaction acceptors whose inducer potency is profoundly increased by the presence of ortho- (but not other) hydroxyl substituent(s) on the aromatic ring(s). This enhancement correlates with more rapid reactivity of the ortho-hydroxylated derivatives with model sulfhydryl compounds. Proton NMR spectroscopy provides no evidence for increased electrophilicity of the beta-vinyl carbons (the presumed site of nucleophilic attack) on the hydroxylated inducers. Surprisingly, these ortho-hydroxyl groups display a propensity for extensive intermolecular hydrogen bond formation, which may raise the reactivity and facilitate addition of mercaptans, thereby raising inducer potencies. PMID:11248091

Dinkova-Kostova, A T; Massiah, M A; Bozak, R E; Hicks, R J; Talalay, P

2001-03-13

97

The conserved baculovirus protein p33 (Ac92) is a flavin adenine dinucleotide-linked sulfhydryl oxidase.  

PubMed

Open reading frame 92 of the Autographa californica baculovirus (Ac92) is one of about 30 core genes present in all sequenced baculovirus genomes. Computer analyses predicted that the Ac92 encoded protein (called p33) and several of its baculovirus orthologs were related to a family of flavin adenine dinucleotide (FAD)-linked sulfhydryl oxidases. Alignment of these proteins indicated that, although they were highly diverse, a number of amino acids in common with the Erv1p/Alrp family of sulfhydryl oxidases are present. Some of these conserved amino acids are predicted to stack against the isoalloxazine and adenine components of FAD, whereas others are involved in electron transfer. To investigate this relationship, Ac92 was expressed in bacteria as a His-tagged fusion protein, purified, and characterized both spectrophotometrically and for its enzymatic activity. The purified protein was found to have the color (yellow) and absorption spectrum consistent with it being a FAD-containing protein. Furthermore, it was demonstrated to have sulfhydryl oxidase activity using dithiothreitol and thioredoxin as substrates. PMID:19409596

Long, C M; Rohrmann, G F; Merrill, G F

2009-05-01

98

The viral oncogene Np9 acts as a critical molecular switch for co-activating ?-catenin, ERK, Akt and Notch1 and promoting the growth of human leukemia stem/progenitor cells.  

PubMed

HERV-K (human endogenous retrovirus type K) type 1-encoded Np9 is a tumor-specific biomarker, but its oncogenic role and targets in human leukemia remain elusive. We first identified Np9 as a potent viral oncogene in human leukemia. Silencing of Np9 inhibited the growth of myeloid and lymphoblastic leukemic cells, whereas expression of Np9 significantly promoted the growth of leukemia cells in vitro and in vivo. Np9 not only activated ERK, AKT and Notch1 pathways but also upregulated ?-catenin essential for survival of leukemia stem cells. In human leukemia, Np9 protein level in leukemia patients was substantially higher than that in normal donors (56% vs 4.5%). Moreover, Np9 protein level was correlated with the number of leukemia stem/progenitor cells but not detected in normal CD34(+) hematopoietic stem cells. In addition, Np9-positive samples highly expressed leukemia-specific pol-env polyprotein, env and transmembrane proteins as well as viral particles. Thus, the viral oncogene Np9 is a critical molecular switch of multiple signaling pathways regulating the growth of leukemia stem/progenitor cells. These findings open a new perspective to understand the etiology of human common leukemia and provide a novel target for treating leukemia. PMID:23307033

Chen, T; Meng, Z; Gan, Y; Wang, X; Xu, F; Gu, Y; Xu, X; Tang, J; Zhou, H; Zhang, X; Gan, X; Van Ness, C; Xu, G; Huang, L; Zhang, X; Fang, Y; Wu, J; Zheng, S; Jin, J; Huang, W; Xu, R

2013-01-11

99

A practical scheduling algorithm for input-buffered switch  

Microsoft Academic Search

Input-buffering is preferentially used in high-speed commercial and experimental routers and switches. The cell scheduling algorithms are critical components in input-buffered switches. They have a significant impact on the throughput, stability and guaranteed quality of service (QoS) of input-buffered switches. The longest queue first (LQF) algorithm can achieve 100% throughput for input-buffered switches, but is not starvation-free. That is, there

Zhang Lisheng; Han Chengdu

2000-01-01

100

Switching System Simulator.  

National Technical Information Service (NTIS)

Switching System Simulator (SSS) is a CDC 6600 computer program which simulates and evaluates networks of interconnected switching elements. SSS determines all the possible ways in which a given switching system can complete a set of input/output connecti...

C. R. Williams

1976-01-01

101

Effects of gamma-glutamylcysteine ethyl ester on heart mitochondrial creatine kinase activity: involvement of sulfhydryl groups.  

PubMed

To study the mechanism of the protective effect of gamma-glutamylcysteine ethyl ester, mitochondrial creatine kinase activity of rat heart was measured. Gamma-glutamylcysteine ethyl ester had a protective effect against the depression of creatine kinase activity induced by xanthine + xanthine oxidase or hydrogen peroxide. Gamma-glutamylcysteine ethyl ester also prevented the depression of creatine kinase activity induced by N-ethylmaleimide. It is suggested that the protective effect of gamma-glutamylcysteine ethyl ester is related to oxygen free radicals or to reduction of the sulfhydryl groups of the enzyme which were previously oxidized by oxygen free radicals. PMID:9669507

Hayashi, H; Iimuro, M; Matsumoto, Y; Kaneko, M

1998-05-15

102

Redox Factor-1 Activates Endothelial SIRTUIN1 through Reduction of Conserved Cysteine Sulfhydryls in Its Deacetylase Domain  

PubMed Central

Apurinic/Apyrmidinic Endonuclease 1/Redox Factor-1 (APE1/Ref-1) is a reductant which is important for vascular homeostasis. SIRTUIN1 (SIRT1) is a lysine deacetylase that also promotes endothelium-dependent vasorelaxation. We asked if APE1/Ref-1 governs the redox state and activity of SIRT1, and whether SIRT1 mediates the effect of APE1/Ref-1 on endothelium-dependent vascular function. APE1/Ref-1 maintains sulfhydryl (thiol) groups of cysteine residues in SIRT1 in the reduced form and promotes endothelial SIRT1 activity. APE1/Ref-1 stimulates SIRT1 activity by targeting highly conserved vicinal thiols 371 and 374 which form a zinc tetra-thiolate motif in the deacetylase domain of SIRT1. Cysteine residues in the N-terminal redox domain of APE1/Ref-1 are essential for reducing SIRT1 and stimulating its activity. APE1/Ref-1 protects endothelial SIRT1 from hydrogen peroxide-induced oxidation of sulfhydryls and from inactivation. APE1/Ref-1 also promotes lysine deacetylation of the SIRT1 target endothelial nitric oxide synthase (eNOS). SIRT1 mutated at cysteines 371 and 374, which renders it non-reducible by APE1/Ref-1, prevents lysine deacetylation of eNOS by APE1/Ref-1. SIRT1 free thiol (reduced sulfhydryl) content and deacetylase activity are diminished in all examined tissues of APE1/Ref-1+/? mice, including the vasculature. Overexpression of SIRT1 in aortas of APE1/Ref-1+/? mice restores endothelium-dependent vasorelaxation and bioavailable nitric oxide (NO) to levels similar to those observed in wild-type mice. Thus, APE1/Ref-1, by maintaining functionally important cysteine sulfhydryls in SIRT1 in the reduced form, promotes endothelial SIRT1 activity. This reductive activation of endothelial SIRT1 by APE1/Ref-1 mediates the effect of APE1/Ref-1 on eNOS acetylation, promoting endothelium-derived NO and endothelium-dependent vasorelaxation.

Naqvi, Asma; Yamamori, Tohru; Kumar, Santosh; Kumar, Ajay; Irani, Kaikobad

2013-01-01

103

An Efficient Switching Technique for NoCs with Reduced Buffer Requirements  

Microsoft Academic Search

Networks on chip (NoCs) communicate the components located inside a chip. Overall system performance depends on NoC performance, that is affected by several factors. One of them is the network clock frequency, imposed by the critical path delay. Recent works show that switch critical path includes buffer control logic. Consequently, by removing switch buffers, switch frequency can be doubled. In

Crispín Gómez Requena; María Engracia Gómez; Pedro Juan López Rodríguez; Jos ´ e Duato

2008-01-01

104

RF MEMS switches and switch circuits  

Microsoft Academic Search

MEMS switches are devices that use mechanical movement to achieve a short circuit or an open circuit in the RF transmission line. RF MEMS switches are the specific micromechanical switches that are designed to operate at RF-to-millimeter-wave frequencies (0.1 to 100 GHz). The forces required for the mechanical movement can be obtained using electrostatic, magnetostatic, piezoelectric, or thermal designs. To

G. M. Rebeiz; J. B. Muldavin

2001-01-01

105

Nanoelectromechanical contact switches.  

PubMed

Nanoelectromechanical (NEM) switches are similar to conventional semiconductor switches in that they can be used as relays, transistors, logic devices and sensors. However, the operating principles of NEM switches and semiconductor switches are fundamentally different. These differences give NEM switches an advantage over semiconductor switches in some applications--for example, NEM switches perform much better in extreme environments--but semiconductor switches benefit from a much superior manufacturing infrastructure. Here we review the potential of NEM-switch technologies to complement or selectively replace conventional complementary metal-oxide semiconductor technology, and identify the challenges involved in the large-scale manufacture of a representative set of NEM-based devices. PMID:22543427

Loh, Owen Y; Espinosa, Horacio D

2012-04-29

106

Sulfhydryl-containing agents in the treatment of gastric bleeding induced by nonsteroidal anti-inflammatory drugs.  

PubMed

In a double-blind study involving 172 patients, the author investigated the effect of sulfhydryl-containing agents (cysteine and methylmethionine sulfonium chloride [MMSC]) on hematemesis resulting from erosive gastritis induced by nonsteroidal anti-inflammatory drugs. The 56 patients who received cysteine (200 mg orally four times a day) and the 59 patients who received MMSC (500 mg orally four times a day) were significantly (p < 0.01) more hemodynamically stable, with no rebleeding, than the 57 patients who made up a control group. Endoscopy carried out 48 hours after admission demonstrated that gastric erosions were still present in a significantly (p < 0.01) higher number of patients in the control group (20 [35%]) than in patients receiving cysteine (6 [11%]) and in patients receiving MMSC (7 [12%]). Eighteen patients (32%) in the control group required blood transfusion because of continued bleeding or rebleeding compared with only 3 patients (5%) receiving cysteine and 2 patients (3%) receiving MMSC (p < 0.01). Emergency surgery was necessary in 13 patients (23%) in the control group and in 1 patient (2%) in the group receiving cysteine who had rebleeding. Four patients in the control group died postoperatively. The results show that sulfhydryl-containing agents stimulate the healing of erosive gastritis induced by nonsteroidal anti-inflammatory drugs and protect against the complications of bleeding produced by the gastritis. PMID:8443719

Salim, A S

1993-02-01

107

Staining of free sulfhydryl groups of proteins after separation by isoelectric focusing of Bio-Rad standards and lens crystallins.  

PubMed

In this study, we propose a new staining method for free sulfhydryl groups of proteins after having separated native samples by thin-layer isoelectric focusing (IEF) in absence of detergents. A comparison was made between proteins stained purple for free sulfhydryl groups (SH) and proteins stained blue by Coomassie blue (CB). A stainability factor, F = %SH/%CB, was calculated for each protein. The Bio-Rad IEF standards containing seven marker proteins for pH scale determination were stained purple, in the same way as they were designed for CB staining. To prove the validity of the currently proposed staining method for a defined protein system such as the eye lens crystallins, these proteins were also stained after IEF as described above. The factor F was calculated for all alpha-, beta-, and gamma-crystallin components that stained in both methods. We discovered that alpha-crystallins contained comparatively high amounts of free SH groups, while some beta- and gamma-crystallin components also contained considerable amounts of free SH groups. The SH staining procedure with 2,2'-dihydroxy-6,6'-dinaphthyl disulfide applied after IEF appeared to be useful, specific, and reproducible. PMID:1705395

Bours, J; Ahrend, M H

1990-11-01

108

Triggered Plasma Opening Switch.  

National Technical Information Service (NTIS)

A triggerable opening switch for a very high voltage and current pulse includes a transmission line extending from a source to a load and having an intermediate switch section including a plasma for conducting electrons between transmission line conductor...

C. W. Mendel

1986-01-01

109

Plasma Erosion Opening Switch.  

National Technical Information Service (NTIS)

The Plasma Erosion Opening Switch (PEOS) can conduct high current (approx. MA), open quickly (<10ns), and withstand high voltage (approx. MV). This switching technique has been used in inductive energy storage experiments and can be used with existing gen...

R. J. Commisso G. Cooperstein R. A. Meger J. M. Neri P. F. Ottinger

1985-01-01

110

Remote switch actuator  

DOEpatents

The invention provides a device and method for actuating electrical switches remotely. The device is removably attached to the switch and is actuated through the transfer of a user's force. The user is able to remain physically removed from the switch site obviating need for protective equipment. The device and method allow rapid, safe actuation of high-voltage or high-current carrying electrical switches or circuit breakers.

Haas, Edwin Gerard; Beauman, Ronald; Palo, Jr., Stefan

2013-01-29

111

Fast superconducting magnetic field switch  

DOEpatents

The superconducting magnetic switch or fast kicker magnet is employed with electron stream or a bunch of electrons to rapidly change the direction of flow of the electron stream or bunch of electrons. The apparatus employs a beam tube which is coated with a film of superconducting material. The tube is cooled to a temperature below the superconducting transition temperature and is subjected to a constant magnetic field which is produced by an external dc magnet. The magnetic field produced by the dc magnet is less than the critical field for the superconducting material, thus, creating a Meissner Effect condition. A controllable fast electromagnet is used to provide a magnetic field which supplements that of the dc magnet so that when the fast magnet is energized the combined magnetic field is now greater that the critical field and the superconducting material returns to its normal state allowing the magnetic field to penetrate the tube. This produces an internal field which effects the direction of motion and of the electron stream or electron bunch. The switch can also operate as a switching mechanism for charged particles. 6 figs.

Goren, Y.; Mahale, N.K.

1996-08-06

112

Is the normal content of sulfhydryl groups attributable to sparing from dystrophic pathology in dystrophin-deficient muscles?  

PubMed

Deficiency of dystrophin in skeletal muscles is supposed to be responsible for all the symptoms associated with Duchenne dystrophy (DMD) and Becker dystrophy (BMD). The dystrophin-deficient mdx mice, however, are clinically almost asymptomatic. Hence, other factor(s) might be responsible for the muscle pathology in DMD and BDM. As sulfhydryl groups are involved in maintaining the structure of membranes and the protein-phospholipid interactions, total, protein-bound and free sulfhydryl groups (-SH) in DMD, BMD, limb-girdle dystrophy (LGMD) and the mdx mice muscles have been determined. A significant decrease of total and protein-bound -SH groups content and an increased proportion of free -SH groups in DMD and BMD was found. In LGMD the changes of total and protein-bound -SH groups content were less expressed. In the mdx mice muscles the content of -SH groups was generally normal, only a higher than normal proportion of free-SH groups content in old and senile animals, especially in their diaphragm, was present. To test the sarcolemmal integrity, albumin/creatine kinase (CK) influx/efflux was determined. In early stages of DMD and BMD the albumin influx was increased. In advanced stages of these diseases albumin influx was not observed. In LGMD albumin penetration was present only in a few fibres. CK efflux in vitro was increased both in early and advanced DMD cases. In BMD and LGMD CK efflux was increased only in early stages of the diseases. In mdx mice an increased influx/efflux of albumin/CK was stated in adult animals. The changes persisted in the mdx hind limb muscles up to the senile age of the animals. In the mdx diaphragm of senile animals albumin did not penetrate the muscle cell and no increase of CK efflux was observed. It is suggested that changes in the distribution of -SH groups take part in the molecular disorganisation of the sarcolemma in course dystrophinopathies. Normal content of the sulfhydryl groups is supposed to be attributable to sparing from dystrophic pathology in dystrophin-deficient mdx mice muscles. PMID:12572920

Niebrój-Dobosz, Irena; Fidzia?ska, Anna; Glinka, Zofia; Hausmanowa-Petrusewicz, Irena

2002-01-01

113

Latching type optical switch  

NASA Astrophysics Data System (ADS)

An optical switch on yttrium orthoferrite crystal is developed. The switch is of latching type and has an operating time of 100 ns. Matrices of switches are feasible due to the dimensions of the optical rotator of less than 2 mm3.

Didosyan, Y. S.; Hauser, H.; Fiala, W.; Nicolics, J.; Toriser, W.

2002-05-01

114

ENERGY LOSSES IN SWITCHES  

Microsoft Academic Search

The authors experiments show energy losses between 2 and 10 times that of the resistive time predictions. The experiments used hydrogen, helium, air, nitrogen, SFâ polyethylene, and water for the switching dielectric. Previously underestimated switch losses have caused over predicting the accelerator outputs. Accurate estimation of these losses is now necessary for new high-efficiency pulsed power devices where the switching

T. H. Martin; J. F. Seamen; D. O. Jobe

1993-01-01

115

Integrated reed switch  

US Patent & Trademark Office Database

This invention relates to reed switches, and more particularly to micro-miniaturized reed switches and batch microfabrication techniques used to fabricate micro-miniaturized reed switches. The present invention can provide miniaturized reed switches with more consistent operating parameters, and that can be produced more efficiently than conventional reed switches. The present invention can also provide methods of making miniaturized reed switches using microfabrication techniques. The present invention can use lithographic-based fabrication to enable monolithic construction of a reed switch. Microlithography can repeatedly form micrometer dimensions with tight tolerances over large arrays of devices which, if the patterns are translated into materials appropriate for electromechanical devices, can provide for repeatable and consistent electromechanical operation. For example, tight dimensional control of the gap between two reeds in a reed switch or a reed and a fixed contact can provide consistency of performance between reed switches. Thus, the present invention can allow the commonly regarded reed switch specification of sensitivity, or "Ampere-turns" required to close a reed switch, to be tightly controlled with a commensurate reduction in spread in sensitivity across reed switch production lots.

Christenson; Todd R (Albuquerque, NM)

2012-12-11

116

Reusable Fast Opening Switch.  

National Technical Information Service (NTIS)

A reusable fast opening switch for transferring energy, in the form of a high power pulse, from an electromagnetic storage device such as an inductor into a load. The switch is efficient, compact, fast and reusable. The switch comprises a ferromagnetic se...

J. P. Van Devender D. Emin

1983-01-01

117

Triggered plasma opening switch  

DOEpatents

A triggerable opening switch for a very high voltage and current pulse includes a transmission line extending from a source to a load and having an intermediate switch section including a plasma for conducting electrons between transmission line conductors and a magnetic field for breaking the plasma conduction path and magnetically insulating the electrons when it is desired to open the switch.

Mendel, Clifford W. (Albuquerque, NM)

1988-01-01

118

Terabit burst switching  

Microsoft Academic Search

Demand for network bandwidth is growing at unprecedented rates, placing growing demands on switching and transmission technologies. Wavelength division multiplexing will soon make it possible to combine hundreds of gigabit channels on a single fiber. This paper presents an architecture for Burst Switching Systems designed to switch data among WDM links, treating each link as a shared resource rather than

Jonathan S. Turner

1999-01-01

119

Polarization switching kinetics in ultrathin ferroelectric barium titanate film  

NASA Astrophysics Data System (ADS)

The investigation of polarization switching kinetics in an ultrathin barium titanate film reveals true threshold switching at a large coercive electric field, evidence that switching is of intrinsic thermodynamic nature, rather than of extrinsic nature initiated by thermal nucleation, which has no true threshold field. The switching speed of a 7 nm thick epitaxial film exhibits a critical slowing as the threshold is approached from above, a key characteristic of intrinsic switching. In contrast, a bulk crystal exhibits nucleation-initiated switching, which has no threshold, and proceeds even at fields well below the nominal coercive field, which was determined independently from the polarization-electric field hysteresis loop. Previously, this phenomenon was only reported for ultrathin ferroelectric polymer Langmuir–Blodgett films. Since both the thermodynamic coercive field and the intrinsic switching kinetics are derived from the mean field theory of ferroelectricity, we expect that these phenomena will be found in other ferroelectric films at the nanoscale.

Gaynutdinov, R.; Minnekaev, M.; Mitko, S.; Tolstikhina, A.; Zenkevich, A.; Ducharme, S.; Fridkin, V.

2013-09-01

120

Electric-field-assisted switching in magnetic tunnel junctions  

Microsoft Academic Search

The advent of spin transfer torque effect accommodates site-specific switching of magnetic nanostructures by current alone without magnetic field. However, the critical current density required for usual spin torque switching remains stubbornly high around 106–107 A cm?2. It would be fundamentally transformative if an electric field through a voltage could assist or accomplish the switching of ferromagnets. Here we report

Mingen Li; Stephen Hageman; Wei-Gang Wang; C. L. Chien

2011-01-01

121

A distributed scheduling architecture for scalable packet switches  

Microsoft Academic Search

The continuous growth in the demand for diversified quality-of-service (QoS) guarantees in broadband networks introduces new challenges in the design of packet switches that scale to large switching capacities. Packet scheduling is the most critical function involved in the provision of individual bandwidth and delay guarantees to the switched flows. Most of the scheduling techniques proposed so far assume the

Fabio M. Chiussi; Andrea Francini

2000-01-01

122

Involvement of Sulfhydryl Groups in the Transport of L-Tyrosine and L-Tryptophan across the Human Red Cell Membrane in vitro  

Microsoft Academic Search

In previous papers, we reported a deficit in tyrosine (TYR) and tryptophan (TRP) transport across the erythrocyte membrane in depressed patients. To investigate further the transport mechanism of the two precursors of monoamines, we tested in healthy subjects the role played by sulfhydryl groups (SH). These groups, cysteine residues, are localized on the intrinsic domain such as the transporters of

J. Widmer; J.-M. Gaillard; P. Bovier; R. Tissot

1989-01-01

123

Selective labeling of the erythrocyte hexose carrier with a maleimide derivative of glucosamine: Relationship of an exofacial sulfhydryl to carrier conformation and structure  

SciTech Connect

Sulfhydryl-reactive derivatives of glucosamine were synthesized as potentially transportable affinity labels of the human erythrocyte hexose carrier. N-maleoylglycyl derivatives of either 6- or 2-amino-2-deoxy-D-glucopyranose were the most potent inhibitors of 3-O-methylglucose uptake, with concentrations of half-maximal irreversible inhibition of about 1 mM. Surprisingly, these derivatives were very poorly transported into erythrocytes. They reacted rather with an exofacial sulfhydryl on the carrier following a reversible binding step, the latter possibly to the exofacial substrate binding site. However, their reactivity was determined primarily by access to the exofacial sulfhydryl, which, as predicted by the one-site model of transport, required a carrier conformation with the exofacial substrate binding site exposed. Once reacted, the carrier was locked in a conformation unable to reorient inwardly and bind cytochalasin B. In intact erythrocytes the N-maleoylglycyl derivative of 2-({sup 3}H)glucosamine labeled predominantly an M{sub r} 45,000-66,000 protein on gel electrophoresis in a quantitative and cytochalasin B inhibitable fashion. By use of changes in carrier conformation induced by competitive transport inhibitors in a double differential labeling method, virtually complete selectivity of labeling of the carrier protein was achieved, the latter permitting localization of the reactive exofacial sulfhydryl to an M{sub r} 18,000-20,000 tryptic fragment of the carrier.

May, J.M. (Vanderbilt Univ. School of Medicine, Nashville, TN (USA))

1989-02-21

124

Asymmetrical switch costs in children  

Microsoft Academic Search

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

Michelle R. Ellefson; Laura R. Shapiro; Nick Chater

2006-01-01

125

REMOTE CONTROLLED SWITCHING DEVICE  

DOEpatents

An electrical switching device which can be remotely controlled and in which one or more switches may be accurately operated at predetermined times or with predetermined intervening time intervals is described. The switching device consists essentially of a deck, a post projecting from the deck at right angles thereto, cam means mounted for rotation around said posts and a switch connected to said deck and actuated by said cam means. Means is provided for rotating the cam means at a constant speed and the switching apparatus is enclosed in a sealed container with external adjusting means and electrical connection elements.

Hobbs, J.C.

1959-02-01

126

Switching with photodiodes  

NASA Astrophysics Data System (ADS)

The concept of optoelectronic switching is outlined, and its physical basis in photodiodes is explored. A model is developed for optoelectronic switching in p-i-n and avalanche photodiodes that agrees well with observed performance. Optoelectronic switches have demonstrated isolation is excess of 80 dB between 2 MHz and 1 GHz. The applications would range from large-scale switching of UHF or VHF signals (for example, in switched television distribution) to advanced signal routing applications in high-rate digital and high-capacity analog channels.

MacDonald, R. I.; Hara, E. H.

1980-03-01

127

Photoconductive power switches  

SciTech Connect

This paper outlines the advantages and the potential of photoconductive switches applied to high-power systems. The photoconductive effect can be used to switch large amounts of energy by changing the conductivity of a solid-state circuit element many orders of magnitude with a high-power laser. The simplicity of these devices offers many advantages in high-power applications when combined with high-power pulsed lasers. The surge capability, the switched energy gain, and the maximum average power for photoconductive power switches are discussed. In addition, the results of a 100-kV, 100-MW photoconductive switch experiment transferring 20 J in 200 ns are presented.

Nunnally, W.C.; Hammond, R.B.

1983-01-01

128

[Os(bpy)2(CO)(enIA)][OTf]2: a novel sulfhydryl-specific metal-ligand complex.  

PubMed

The synthesis and physical-chemical characterization of the metal-ligand complex [Os(bpy)2(CO)(enIA)][OTf]2 (where enIA = ethylenediamine iodoacetamide) with a sulfhydryl-specific functional group is described. The UV and visible absorption and luminescence emission, including lifetime and steady-state anisotropy, are reported for the free probe and the probe covalently linked to two test proteins. The spectroscopic properties of the probe are unaffected by chemical modification and subsequent covalent linkage to the proteins. The luminescence lifetime in aqueous buffer is approximately 200 ns and the limiting anisotropy is greater than 0.125, suggesting a potentially useful probe for biophysical investigations. PMID:15907113

Garino, Claudio; Ghiani, Simona; Gobetto, Roberto; Nervi, Carlo; Salassa, Luca; Ancarani, Valentina; Neyroz, Paolo; Franklin, Laurie; Alexander Ross, J B; Seibert, Eleanore

2005-05-30

129

P5-type sulfhydryl oxidoreductase promotes the sorting of proteins to protein body I in rice endosperm cells  

PubMed Central

In rice (Oryza sativa) endosperm cells, oxidative protein folding is necessary for the sorting of storage proteins to protein bodies, PB-I and PB-II. Here we examined the role of sulfhydryl oxidoreductase PDIL2;3 (a human P5 ortholog) in the endoplasmic reticulum (ER), using GFP-AB, a PB-I marker in which the N-terminal region (AB) of ?-globulin is fused to green fluorescent protein (GFP). RNAi knockdown of PDIL2;3 inhibited the accumulation of GFP-AB in PB-I and promoted its exit from the ER. We discuss the role of PDIL2;3 in retaining proteins within the ER and specifying their localization to PB-I through disulfide bond formation.

Onda, Yayoi; Kawagoe, Yasushi

2013-01-01

130

Hypotaurine and sulfhydryl-containing antioxidants reduce H2S toxicity in erythrocytes from a marine invertebrate.  

PubMed

Hypotaurine (HT) has been proposed to reduce sulfide toxicity in some deep-sea invertebrates by scavenging free radicals produced from sulfide oxidation or by scavenging sulfide via the reaction of HT with sulfide, forming thiotaurine (ThT). We tested whether HT or several antioxidants could reduce the total dissolved sulfide concentration in buffered seawater exposed to H(2)S, and whether HT, ThT or antioxidants could increase the viability of Glycera dibranchiata erythrocytes exposed to H(2)S in vitro. We found that 5 and 50 mmol l(-1) HT reduced the dissolved sulfide in cell-free buffer exposed to H(2)S by up to 80% whereas the antioxidants glutathione ethyl ester (GEE), N-acetylcysteine (NAC), L-ascorbic acid (ASC), Tempol and Trolox had no consistent effect. Exposure of erythrocytes to 0.10%-3.2% H(2)S (producing 0.18-4.8 mmol l(-1) sulfide) decreased the fraction of viable cells, as evidenced by loss of plasma membrane integrity, with virtually no cells remaining viable at 1.0% or more H(2)S. Addition of HT (0.5-50 mmol l(-1)) significantly increased the fraction of viable cells (e.g. from 0.01 to 0.84 at 0.32% H(2)S) whereas ThT (0.5 and 5 mmol l(-1)) decreased cell viability. GEE (0.03-3 mmol l(-1)) and NAC (0.001-1 mmol l(-1)), which contain sulfhydryl groups, increased cell viability during H(2)S exposure but to a lesser extent than HT whereas ASC, Tempol and Trolox, which do not contain sulfhydryl groups, decreased viability or had no effect. These data show that HT can protect cells from sulfide in vitro and suggest that sulfide scavenging, rather than free radical scavenging, is the most important mechanism of protection. PMID:19043054

Ortega, J A; Ortega, J M; Julian, D

2008-12-01

131

Methylation of sulfhydryl groups: a new function for a family of small molecule plant O-methyltransferases  

PubMed Central

Summary In plants, type I and II S-adenosyl-L-methionine-dependent O-methyltransferases (OMTs) catalyze most hydroxyl group methylations of small molecules. A homology-based RT-PCR strategy using Catharanthus roseus (Madagascar periwinkle) RNA previously identified six new type I plant OMT family members. We now describe the molecular and biochemical characterization of a seventh protein. It shares 56–58% identity with caffeic acid OMTs (COMTs), but it failed to methylate COMT substrates, and had no activity with flavonoids. However, the in vitro incubations revealed unusually high background levels without added substrates. A search for the responsible component revealed that the enzyme methylated dithiothreitol (DTT), the reducing agent added for enzyme stabilization. Unexpectedly, product analysis revealed that the methylation occurred on a sulfhydryl moiety, not on a hydroxyl group. Analysis of 34 compounds indicated a broad substrate range, with a preference for small hydrophobic molecules. Benzene thiol (Km 220 ?M) and furfuryl thiol (Km 60 ?M) were the best substrates (6–7-fold better than DTT). Small isosteric hydrophobic substrates with hydroxyl groups, like phenol and guaiacol, were also methylated, but the activities were at least 5-fold lower than with thiols. The enzyme was named C. roseus S-methyltransferase 1 (CrSMT1). Models based on the COMT crystal structure suggest that S-methylation is mechanistically identical to O-methylation. CrSMT1 so far is the only recognized example of an S-methyltransferase in this protein family. Its properties indicate that a few changes in key residues are sufficient to convert an OMT into a S-methyltransferase (SMT). Future functional investigations of plant methyltransferases should consider the possibility that the enzymes may direct methylation at sulfhydryl groups.

Coiner, Heather; Schroder, Gudrun; Wehinger, Elke; Liu, Chang-Jun; Noel, Joseph P.; Schwab, Wilfried; Schroder, Joachim

2010-01-01

132

Dielectric Films as Crosspoints in Switching Matrices.  

National Technical Information Service (NTIS)

A critical evaluation was made of conductor-thin insulator film-conductor structures as practical bi-stable switching elements. More than a dozen of the materials considered promising for this purpose were used to fabricate metal-thin dielectric film-p si...

P. Wang N. VanBuren

1969-01-01

133

An acoustic switch.  

PubMed

The benefits derived from the development of acoustic transistors which act as switches or amplifiers have been reported in the literature. Here we propose a model of acoustic switch. We theoretically demonstrate that the device works: the input signal is totally restored at the output when the switch is on whereas the output signal nulls when the switch is off. The switch, on or off, depends on a secondary acoustic field capable to manipulate the main acoustic field. The model relies on the attenuation effect of many oscillating bubbles on the main travelling wave in the liquid, as well as on the capacity of the secondary acoustic wave to move the bubbles. This model evidences the concept of acoustic switch (transistor) with 100% efficiency. PMID:23816529

Vanhille, Christian; Campos-Pozuelo, Cleofé

2013-06-15

134

Effects of non-ideal switches in PWM switching converters  

Microsoft Academic Search

This paper presents new models that account for the non-ideal properties of semiconductor BJT switches responsible for the switching action in PWM converters. These models can be used for both the DC and small-signal AC analyses of PWM switching regulators. Terminal voltages and currents of the switching elements of the converter are related using switching functions which account for the

WISAM M. MOUSSA; JAMES E. MORRIS

1992-01-01

135

Solid state switch  

DOEpatents

A solid state switch, with reverse conducting thyristors, is designed to operate at 20 kV hold-off voltage, 1500 A peak, 1.0 .mu.s pulsewidth, and 4500 pps, to replace thyratrons. The solid state switch is more reliable, more economical, and more easily repaired. The switch includes a stack of circuit card assemblies, a magnetic assist and a trigger chassis. Each circuit card assembly contains a reverse conducting thyristor, a resistor capacitor network, and triggering circuitry.

Merritt, Bernard T. (Livermore, CA); Dreifuerst, Gary R. (Livermore, CA)

1994-01-01

136

Bimetallic nanoparticles for surface modification and lubrication of MEMS switch contacts  

Microsoft Academic Search

Reliability continues to be a critical issue in microelectromechanical systems (MEMS) switches. Failure mechanisms include high contact resistance (R), high adhesion, melting\\/shorting, and contact erosion. Little previous work has addressed the lubrication of MEMS switches. In this study, bimetallic nanoparticles (NPs) are synthesized using a biotemplated approach and deposited on Au MEMS switch contacts as a nanoparticle-based lubricant. Bimetallic nanoparticles

Steven T. Patton; Joseph M. Slocik; Angela Campbell; Jianjun Hu; Rajesh R. Naik; Andrey A. Voevodin

2008-01-01

137

Plasma Opening Switch Experiments On Hawk With An E-beam Diode Load  

Microsoft Academic Search

Successful application of inductive energy storage depends critically on the performance of the opening switch. The new Hawk generator at NRL~ is used in plasma opening switch (POS) experiments in the 1-ps conduction time regime to study lonq conduction time Pos physics. In this experiment, different POS configurations were used, including various switch to load distances and different cathode center

P. J. Goodrich; J. R. Boller; R. J. Commisso; D. D. Hinshelwood; J. C. Kellogg; B. V. Weber

1991-01-01

138

Critical pulse power components  

SciTech Connect

Critical components for pulsed power conditioning systems will be reviewed. Particular emphasis will be placed on those components requiring significant development efforts. Capacitors, for example, are one of the weakest elements in high-power pulsed systems, especially when operation at high-repetition frequencies for extended periods of time are necessary. Switches are by far the weakest active components of pulse power systems. In particular, opening switches are essentially nonexistent for most applications. Insulaton in all systems and components requires development and improvement. Efforts under way in technology base development of pulse power components will be discussed.

Sarjeant, W.J.; Rohwein, G.J.

1981-01-01

139

Asymmetrical Switch Costs in Children  

ERIC Educational Resources Information Center

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

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

2006-01-01

140

Converting enzyme inhibitors and the role of the sulfhydryl group in the potentiation of exo- and endogenous nitrovasodilators.  

PubMed

In this study, the effect of bradykinin on coronary flow in the isolated rat heart was significantly potentiated when cysteine or the sulfhydryl-containing converting enzyme inhibitors captopril and zofenoprilat were administered simultaneously. In contrast, the effect of concomitant administration of enalaprilat only slightly increased the effect of bradykinin on coronary flow. In nitrate-tolerant hearts of rats pretreated with isosorbide dinitrate (15 mg daily), the increase in coronary flow by nitroglycerin and bradykinin was significantly less when compared to control hearts. The effect of captopril was not affected by pretreatment. The involvement of endothelium-derived relaxing factor (EDRF) in the effect of captopril was apparent from experiments with L-arginine, the precursor of EDRF, and L-NMMA, the "false" precursor of EDRF. L-Arginine increased the effect of captopril, whereas L-NMMA showed a competitive antagonism for the effect of captopril on coronary flow in the isolated rat heart. Clinically, the effect of captopril was studied in 10 patients with stable, exercise-induced angina pectoris that had been treated for 3 weeks with slow-release isosorbide dinitrate (20 mg four times daily). At day 7, a baseline exercise test was obtained. Subsequently, patients with chest pain and at least 1-mm ST-segment depression on the ECG during exercise were included. They received on day 14 and 21 either captopril (25 mg) or placebo 1 h before exercise testing in a randomized, double-blind, crossover design. Captopril significantly improved the combined score of maximal ST-segment depression, maximal workload, and time to angina when compared to placebo. No differences in the pressure-rate index at rest and during exercise were seen. These results indicate that the sulfhydryl group of certain angiotensin converting enzyme inhibitors can potentiate their effect on the endogenous nitrovasodilator EDRF. In the clinical situation, this may lead to an improved exercise performance in patients with stable angina pectoris during chronic nitrate treatment, independent of its systemic vascular effects. PMID:1720843

van Gilst, W H; de Graeff, P A; de Leeuw, M J; Scholtens, E; Wesseling, H

1991-09-01

141

Cognitive control processes during an anticipated switch of task.  

PubMed

For successful negotiation of our environment, humans must be readily able to switch from one task to another. This ability relies on 'executive control' processes and despite extensive efforts to detail the nature of these processes, there is little consensus as to how the brain achieves this critical function. Behavioural studies show that as subjects are given more time to prepare to switch task, performance improves; yet even with the longest preparation intervals, there remains an ineradicable performance cost on switch trials. As such, some elements of the switching process must wait until the stimulus to be acted upon has actually been presented. Here, using the methods of high-density mapping of brain potentials, we show that early visual processes are substantially different on switch trials than on later trials. Our data show that while there is clearly a degree of preparatory processing that occurs prior to a predictable switch of task, some elements of switching are only achieved after the switch stimulus has been presented. Our findings are discussed in the context of a new model of executive control processes that suggests that preparing to switch task may not be a separate (control) process per se, but rather, the beginning of a competition between the potentially relevant tasks, a competition that is ultimately resolved during the switch trial. PMID:12581185

Wylie, G R; Javitt, D C; Foxe, J J

2003-02-01

142

Bait and Switch  

Microsoft Academic Search

Sellers sometimes practice a form of false advertising known as bait and switch. A low-priced good is advertised but replaced by a different good at the showroom. The practice is surprising since advertising the wrong good discourages the appropriate buyers from shopping, attracting customers who will be disappointed when they see the good. Firms bait and switch to draw a

Edward P. Lazear

1995-01-01

143

Triggered plasma opening switch  

Microsoft Academic Search

A triggerable opening switch for a very high voltage and current pulse includes a transmission line extending from a source to a load and having an intermediate switch section including a plasma for conducting electrons between transmission line conductors and a magnetic field for breaking the plasma conduction path and magnetically insulating the electrons when it is desired to open

Mendel

1986-01-01

144

Triggered plasma opening switch  

Microsoft Academic Search

A triggerable opening switch for a very high voltage and current pulse includes a transmission line extending from a source to a load and having an intermediate switch section including a plasma for conducting electrons between transmission line conductors and a magnetic field for breaking the plasma conduction path and magnetically insulating the electrons when it is desired to open

Mendel; Clifford W

1988-01-01

145

Closing photoconductive semiconductor switches  

Microsoft Academic Search

One of the most important limitations of Photoconductive Semiconductor Switches (PCSS) for pulsed power applications is the high laser powers required to activate the switches. In this paper, we discuss recent developments on two different aspects of GaAs PCSS that result in reductions in laser power by a factor of nearly 1000. The advantages of using GaAs over Si are

G. M. Loubriel; F. J. Zutavern; H. P. Hjalmarson; M. W. O'Malley

1989-01-01

146

Reflective HTS switch  

DOEpatents

A HTS (High Temperature Superconductor) switch includes a HTS conductor for providing a superconducting path for an electrical signal and an serpentine wire actuator for controllably heating a portion of the conductor sufficiently to cause that portion to have normal, and not superconducting, resistivity. Mass of the portion is reduced to decrease switching time. 6 figs.

Martens, J.S.; Hietala, V.M.; Hohenwarter, G.K.G.

1994-09-27

147

Safety Selector Switch.  

National Technical Information Service (NTIS)

A safety selector switch for preventing accidental energization of an electrical circuit is described. A plurality of annular discs, each having a cut-out portion in its periphery, are mounted on a shaft of an electrical component, such as a rotary switch...

J. D. Hansen

1979-01-01

148

Reflective HTS switch  

DOEpatents

A HTS switch includes a HTS conductor for providing a superconducting path for an electrical signal and an serpentine wire actuator for controllably heating a portion of the conductor sufficiently to cause that portion to have normal, and not superconducting, resistivity. Mass of the portion is reduced to decrease switching time.

Martens, Jon S. (Albuquerque, NM); Hietala, Vincent M. (Placitas, NM); Hohenwarter, Gert K. G. (Madison, WI)

1994-01-01

149

Microelectromechanical System (MEMS) Switch Test.  

National Technical Information Service (NTIS)

Analyzing microelectromechanical system (MEMS) switch behavior is a new field of study, which guides the production of MEMS switches. I analyzed switch behavior using a digital circuit synthesized on a field-programmable gate array (FPGA) chip. The chip h...

S. Karter T. Ivanov

2011-01-01

150

Reversible blockade of the calcium-activated nonselective cation channel in brown fat cells by the sulfhydryl reagents mercury and thimerosal  

Microsoft Academic Search

We have used patch-clamp techniques to study the effect of the sulfhydryl group oxidizing agents mercury and thimerosal on calcium-activated nonselective cation channels from brown adipose tissue. 100 nmol\\/l mercury and 50 µmol\\/l thimerosal induced a complete block. Blockade could be reversed by reduction of the mercaptide by dithiotreitol (DTT). Mercury was found to be the most potent blocker (IC50-value

Ari Koivisto; Detlef Siemen; Jan Nedergaard

1993-01-01

151

Effect of excess dietary iron as ferrous sulfate and excess dietary ascorbic acid on liver zinc, copper and sulfhydryl groups and the ovary  

Microsoft Academic Search

Female guinea pigs of the NIH 13\\/N strain, weighing between 475 and 512 g, were fed diets supplemented with 50 to 2500 mg of iron per kg of diet as ferrous sulfate and 0.2 to 8.0 g of ascorbic acid per kg of diet. A significant effect was observed on tissue copper and zinc, ovary weight and liver protein sulfhydryl

C. H. Edwards; J. S. Adkins; B. Harrison

1986-01-01

152

Uptake of [sup 10]B in gliosarcomas following the injection of gluthathione monoethyl ester and sulfhydryl borane  

SciTech Connect

The sulfhydryl borane Na[sub 2][sup 10]B[sub 12]H[sub 11]SH (BSH) was developed as a capture agent for BNCT about 20 years ago and is the compound currently used clinically in Japan for BNCT of malignant brain tumors. Tumor [sup 10]B concentrations following the infusion of the oxidized BSH, a disulfide dimer (Na[sub 4][sup 10]B[sub 24]H[sub 22]S[sub 2]), are nearly twice those obtained following administration of equal amounts of boron as BSH. Also, the rate of decrease of tumor [sup 10]B concentration is slower after dimer infusion than after BSH infusion. When BNCT was administered to rats bearing intracerebral gliosarcomas, the animals infused with dimer had a significant longer median survival time. Dimer, on the other hand, induces a moderately severe, but reversible, hepatotoxicity which may complicate its use in humans. Intracellular glutathione plays an important role in defense against radical-mediated tissue injury. Glutathione monoesters have been reported to have a protective effective on cisplatin toxicity and on radical-induced acute pancreatitis. We investigated the possibility of reducing dimer-induced hepatotoxicity by pre-administration of GSH-ME. The results indicate that not only does the pre-administration of GSH-ME markedly reduce dimer-induced hepatotoxicity, but also results in nearly a doubling of tumor boron concentration. Furthermore, GSH-ME markedly increases tumor boron uptake and retention following administration of BSH.

Joel, D.D.; Slatkin, D.N.; Coderre, J.A.

1992-01-01

153

Uptake of {sup 10}B in gliosarcomas following the injection of gluthathione monoethyl ester and sulfhydryl borane  

SciTech Connect

The sulfhydryl borane Na{sub 2}{sup 10}B{sub 12}H{sub 11}SH (BSH) was developed as a capture agent for BNCT about 20 years ago and is the compound currently used clinically in Japan for BNCT of malignant brain tumors. Tumor {sup 10}B concentrations following the infusion of the oxidized BSH, a disulfide dimer (Na{sub 4}{sup 10}B{sub 24}H{sub 22}S{sub 2}), are nearly twice those obtained following administration of equal amounts of boron as BSH. Also, the rate of decrease of tumor {sup 10}B concentration is slower after dimer infusion than after BSH infusion. When BNCT was administered to rats bearing intracerebral gliosarcomas, the animals infused with dimer had a significant longer median survival time. Dimer, on the other hand, induces a moderately severe, but reversible, hepatotoxicity which may complicate its use in humans. Intracellular glutathione plays an important role in defense against radical-mediated tissue injury. Glutathione monoesters have been reported to have a protective effective on cisplatin toxicity and on radical-induced acute pancreatitis. We investigated the possibility of reducing dimer-induced hepatotoxicity by pre-administration of GSH-ME. The results indicate that not only does the pre-administration of GSH-ME markedly reduce dimer-induced hepatotoxicity, but also results in nearly a doubling of tumor boron concentration. Furthermore, GSH-ME markedly increases tumor boron uptake and retention following administration of BSH.

Joel, D.D.; Slatkin, D.N.; Coderre, J.A.

1992-12-31

154

Deciphering structural and functional roles of individual disulfide bonds of the mitochondrial sulfhydryl oxidase Erv1p.  

PubMed

Erv1p is a FAD-dependent sulfhydryl oxidase of the mitochondrial intermembrane space. It contains three conserved disulfide bonds arranged in two CXXC motifs and one CX(16)C motif. Experimental evidence for the specific roles of the individual disulfide bonds is lacking. In this study, structural and functional roles of the disulfides were dissected systematically using a wide range of biochemical and biophysical methods. Three double cysteine mutants with each pair of cysteines mutated to serines were generated. All of the mutants were purified with the normal FAD binding properties as the wild type Erv1p, showing that none of the three disulfides are essential for FAD binding. Thermal denaturation and trypsin digestion studies showed that the CX(16)C disulfide plays an important role in stabilizing the folding of Erv1p. To understand the functional role of each disulfide, small molecules and the physiological substrate protein Mia40 were used as electron donors in oxygen consumption assays. We show that both CXXC disulfides are required for Erv1 oxidase activity. The active site disulfide is well protected thus requires the shuttle disulfide for its function. Although both mutants of the CXXC motifs were individually inactive, Erv1p activity was partially recovered by mixing these two mutants together, and the recovery was rapid. Thus, we provided the first experimental evidence of electron transfer between the shuttle and active site disulfides of Erv1p, and we propose that both intersubunit and intermolecular electron transfer can occur. PMID:19679655

Ang, Swee Kim; Lu, Hui

2009-08-13

155

HSF1-dependent upregulation of Hsp70 by sulfhydryl-reactive inducers of the KEAP1/NRF2/ARE pathway.  

PubMed

The KEAP1/NRF2/ARE pathway and the heat shock response are inducible cytoprotective systems regulated by transcription factors NRF2 and HSF1, respectively. We report that structurally distinct small molecule NRF2 activators, all of which react with sulfhydryl groups but differ in potency by 15,000-fold, upregulate Hsp70, a prototypic HSF1-dependent gene. Hsp70 upregulation requires HSF1 but is NRF2 independent. We further demonstrate that a sulfoxythiocarbamate inducer conjugates to the negative regulator of HSF1, Hsp90. The differential concentration dependence of the two responses suggests that activation of NRF2 precedes that of HSF1: the KEAP1/NRF2/ARE pathway is at the forefront of cellular defense, protecting against instant danger; the heat shock response closely follows to resolve subsequent potentially devastating damage, saving the proteome. This uncovered duality undoubtedly contributes to the cytoprotective effects of such molecules in models of carcinogenesis, cardiovascular disease, and neurodegeneration. PMID:22118669

Zhang, Ying; Ahn, Young-Hoon; Benjamin, Ivor J; Honda, Tadashi; Hicks, Ronald J; Calabrese, Vittorio; Cole, Philip A; Dinkova-Kostova, Albena T

2011-11-23

156

Reaction of nitroso derivatives of dinitropyrenes with sulfhydryl groups of peptides and hemoglobin in vitro and in rats.  

PubMed

Diesel engine emissions have been classified as a potential human carcinogen and may cause a variety of other health effects. Human exposure to diesel engine emissions is highly variable within the population. Therefore, specific methods for the biomonitoring of human exposure to diesel engine emissions are required for exposure assessment within epidemiological studies. Haemoglobin adducts of dinitropyrenes may serve as biomarkers for human exposures to diesel engine emissions.To characterize structures of dinitropyrene reaction products with sulfhydryl groups, glutathione was used to trap electrophilic nitroso intermediates formed from dinitropyrenes and glutathione S-conjugates were identified and characterized by Qtrap techniques using (HPLC-MS/MS) high-performance liquid chromatography coupled to triple quadrupole mass spectrometry. Nitrosonitropyrene-derived sulfinamides, sulfenamides and glutathione thioethers bound to carbon atoms in the aromatic ring, presumably formed by a rearrangement of intermediate sulfenamide cations, were formed in low yields. In haemoglobin from rats orally administered dinitropyrenes, mild alkaline hydrolysis of haemoglobin released aminonitropyrenes, which were identified by HPLC-MS/MS. The results demonstrate that dinitropyrenes undergo nitroreduction in rats and that the intermediate nitrosonitropyrenes bind to heamoglobin. The haemoglobin adducts formed from dinitropyrenes seem, in contrast to previous studies, to be hydrolysable and thus represent sulfen- and sulfinamides derived from the intermediate nitrosonitropyrenes. The developed Qtrap methods to detect and characterize glutathione S-conjugates rapidly may have wide applications in attempts to characterize reactive intermediates formed in complex mixtures in low concentrations. PMID:16418067

Straube, E; Völkel, W; Bringmann, G; Dekant, W

2005-12-01

157

Protective effect of silymarin against ethanol-induced gastritis in rats: role of sulfhydryls, nitric oxide and gastric sensory afferents.  

PubMed

Silymarin has been known to exert antioxidant, anti-carcinogenic and anti-inflammatory effects. In this study, we examined the effect of silymarin on gastritis in rats. Oral administration of silymarin dose-dependently decreased gastric lesions in ethanol-induced gastritis model. Silymarin also significantly suppressed the development of gastric lesions in aspirin- or water immersion-restraint stress-induced gastritis models. Further study demonstrated that the gastroprotective effect of silymarin was blocked by nitric oxide (NO) synthase inhibitor l-NAME, SH blocker N-ethylmaleimide or TRPV1 antagonist capsazepine in ethanol-induced gastritis model. In addition, ex vivo analysis revealed that ethanol-induced decrease in gastric mucus and non-protein sulfhydryl (NPSH) groups was significantly reversed by silymarin treatment and lipid peroxidation was also suppressed by silymarin in ethanol-induced gastritis model. Taken together, these results suggest that silymarin exerts gastroprotective effects and the gastroprotective effects of silymarin might be related to the protection of gastric mucosal NO and NP-SH and the modulation of capsaicin-sensitive gastric sensory afferents. PMID:23357565

Shin, Jung Hyu; Lee, Chang Woo; Oh, Soo Jin; Yun, Jieun; Lee, Kiho; Park, Song-Kyu; Kim, Hwan Mook; Han, Sang-Bae; Kim, Youngsoo; Kim, Hyoung-Chin; Kang, Jong Soon

2013-01-26

158

Effects of depletion of ascorbic acid or nonprotein sulfhydryls on the acute inhalation toxicity of nitrogen dioxide, ozone, and phosgene  

SciTech Connect

The effect of depleting lung ascorbic acid (AH{sub 2}) and nonprotein sulfhydryls (NPSH) on the acute inhalation toxicity of nitrogen dioxide (NO{sub 2}), ozone (O{sub 3}), and phosgene (COCl{sub 2}) was investigated in guinea pigs. The increase in bronchoalveolar lavage (BAL) fluid protein (an indicator of alveolar-capillary damage leading to increased permeability) was measured 16 to 18 hr following a 4 hr exposure to the gas in animals deficient in (AH{sub 2}) or NPSH. Gas concentrations were chosen which produced low but significant increases in BAL protein. Lung (AH{sub 2}) was lowered to about 20% of control by feeding rabbit chow for 2 weeks. Lung NPSH was lowered to about 50% of control by injecting a mixture of buthionine S,R-sulfoximine (BSO) and diethylmaleate (DEM) (2.7 and 1.2 mmol/kg respectively). BSO/DEM did not affect the lung concentrations of (AH{sub 2}) or alpha-tocopherol. AH{sub 2} depletion caused a 6 fold and a 3 fold enhancement in the toxicity of 5 ppm and 10 ppm (NO{sub 2}), and a 6 fold enhancement in the toxicity of 0.5 ppm (O{sub 3}), but did not affect toxicity of 1.0 ppm (O{sub 3}). AH{sub 2} depletion did not affect phosgene toxicity (at 0.25 ppm and 0.5 ppm).

Slade, R.; Highfill, J.W.; Hatch, G.E.

1989-01-01

159

A Sulfhydryl-Reactive Ruthenium (II) Complex and Its Conjugation to Protein G as a Universal Reagent for Fluorescent Immunoassays  

PubMed Central

To develop a fluorescent ruthenium complex for biosensing, we synthesized a novel sulfhydryl-reactive compound, 4-bromophenanthroline bis-2,2?-dipyridine Ruthenium bis (hexafluorophosphate). The synthesized Ru(II) complex was crosslinked with thiol-modified protein G to form a universal reagent for fluorescent immunoassays. The resulting Ru(II)-protein G conjugates were identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The emission peak wavelength of the Ru(II)-protein G conjugate was 602 nm at the excitation of 452 nm which is similar to the spectra of the Ru(II) complex, indicating that Ru(II)-protein G conjugates still remain the same fluorescence after conjugation. To test the usefulness of the conjugate for biosensing, immunoglobulin G (IgG) binding assay was conducted. The result showed that Ru(II)-protein G conjugates were capable of binding IgG and the more cross-linkers to modify protein G, the higher conjugation efficiency. To demonstrate the feasibility of Ru(II)-protein G conjugates for fluorescent immunoassays, the detection of recombinant histidine-tagged protein using the conjugates and anti-histidine antibody was developed. The results showed that the histidine-tagged protein was successfully detected with dose-response, indicating that Ru(II)-protein G conjugate is a useful universal fluorescent reagent for quantitative immunoassays.

Goud, Thirumani Venkatshwar; Huang, Bor-Rong; Lin, Tzu-Chau; Biellmann, Jean-Francois; Chen, Chien-Sheng

2012-01-01

160

Effects of the transverse bias field on the dynamic magnetization switching behavior  

NASA Astrophysics Data System (ADS)

The dynamic magnetization switching behavior of a nanostructured magnetic thin film under in-plane magnetic fields is well described by a switching phase diagram composed of two critical curves, one constructed at static and the other at dynamic conditions. The coherent magnetization switching occurs at high magnetic fields above the static critical curve while the incoherent magnetization switching occurs in the region enclosed by the static and the dynamic critical curves. In the incoherent switching region, an abnormal behavior of alternating non-switching/switching that cannot be explained by using the conventional switching phase diagram occurs under a strong transverse bias field. Analytically obtained energy profiles are successfully used to explain this abnormal switching behavior, and the key factor is identified to be the energy difference between the initial state and the saddle point. More extensive and systematic results for the switching phase diagram indicate that the location of the saddle point with respect to the initial state is another important factor affecting the abnormal alternating non-switching/switching behavior.

Lee, Jong Min; Lim, S. H.

2012-11-01

161

Easily reversible memory switching in Ge - As - Te glasses  

NASA Astrophysics Data System (ADS)

Electrical switching behaviour of melt-quenched 0022-3727/29/7/037/img6 and 0022-3727/29/7/037/img7 glasses have been studied in the I - V mode, using a constant current source with incremental current steps. The samples are found to stay in the high-resistance OFF state up to a critical voltage 0022-3727/29/7/037/img8 (corresponding to a critical current 0022-3727/29/7/037/img9). Above 0022-3727/29/7/037/img8, the sample switches to a low-resistance ON state with a stable negative resistance region, and lock-on to this state even if the current is reduced to zero. If the compliance voltage is turned off and switched on again, the switching transient introduced is found to reset the glasses back to the OFF state. The samples are found to switch again. The switching - resetting - switching cycle is repeated 50 times, with 0022-3727/29/7/037/img11% variation in the switching voltages.

Prakash, S.; Asokan, S.; Ghare, D. B.

1996-07-01

162

Anomalous resistive switching phenomenon  

NASA Astrophysics Data System (ADS)

Resistive switching was observed in Pt/SrTiO3/Pt capacitor devices. The switching depends on both the amplitude and polarity of the applied voltage and cannot be described as either bipolar or unipolar resistive switching. We term this behavior antipolar due to the opposite polarity of the set voltage relative to the previous reset voltage. A model based on electron injection by tunneling at interfaces and a Poole-Frenkel mechanism through the bulk is proposed. This model is quantified by use of a simple mathematical equation to simulate the experimental results.

Mojarad, Shahin A.; Goss, J. P.; Kwa, Kelvin S. K.; Petrov, Peter K.; Zou, Bin; Alford, Neil; O'Neill, Anthony

2012-12-01

163

Gene Switches: A Model  

NSDL National Science Digital Library

In this activity, learners explore how genetic switches function and the role of genetic switches in the process of evolution. To make these concepts less abstract and more understandable, learners first view a series of video clips and animations from the HHMI DVD (or online) "Evolution: Constant Change and Common Threads." Then, learners construct a model of a gene switch using craft materials or FridgiGears (magnetic gears). This activity can be done as a demonstration, a student inquiry activity, or a combination of the two.

Colvard, Mary

2010-01-01

164

Sleep State Switching  

PubMed Central

We take for granted the ability to fall asleep or to snap out of sleep into wakefulness, but these changes in behavioral state require specific switching mechanisms in the brain that allow well-defined state transitions. In this review, we examine the basic circuitry underlying the regulation of sleep and wakefulness, and discuss a theoretical framework wherein the interactions between reciprocal neuronal circuits enable relatively rapid and complete state transitions. We also review how homeostatic, circadian, and allostatic drives help regulate sleep state switching, and discuss how breakdown of the switching mechanism may contribute to sleep disorders such as narcolepsy.

Saper, Clifford B.; Fuller, Patrick M.; Pedersen, Nigel P.; Lu, Jun; Scammell, Thomas E.

2010-01-01

165

SPARK GAP SWITCH  

DOEpatents

An improved triggered spark gap switch is described, capable of precisely controllable firing time while switching very large amounts of power. The invention in general comprises three electrodes adjustably spaced and adapted to have a large potential impressed between the outer electrodes. The central electrode includes two separate elements electrically connected togetaer and spaced apart to define a pair of spark gaps between the end electrodes. Means are provided to cause the gas flow in the switch to pass towards the central electrode, through a passage in each separate element, and out an exit disposed between the two separate central electrode elements in order to withdraw ions from the spark gap.

Neal, R.B.

1957-12-17

166

Telecommunications: Switches and Hubs  

NSDL National Science Digital Library

We all know how important computers are in our every day communication, but do you know how the computer in your office transfers information between the others? This online slideshow provided by Wisc-Online and the National Science Foundation explains the difference between a switch and a hub and the reasons to use them. For example, with helpful animations and a personalized speed, one can learn that hubs often cause broadcast collisions and are less efficient than switches when trying to send information quickly among networked computers. This is great for students and teachers introducing switches and hubs to their telecommunications repertoire.

Bartelt, Terry L.

2009-10-07

167

ISS of Switched Systems and Applications to Switching Adaptive Control  

Microsoft Academic Search

In this paper we prove that a switched nonlinear system has several useful ISS-type properties under average dwell-time switching signals if each constituent dynamical system is ISS. This extends available results for switched linear systems. We apply our result to stabilization of uncertain nonlinear systems via switching supervisory control, and show that the plant states can be kept bounded in

L. Vu; D. Chatterjee; D. Liberzon

2005-01-01

168

SLOB: a switch with large optical buffers for packet switching  

Microsoft Academic Search

Recently, optical packet switch architectures, composed of devices such as optical switches, fiber delay lines, and passive couplers, have been proposed to overcome the electromagnetic interference (EMI), pinout and interconnection problems that would be encountered in future large electronic switch cores. However, attaining the buffer size (buffer depth) in optical packet switches required in practice is a major problem; in

David K. Hunter; W. David Cornwell; Tim H. Gilfedder; A. Franzen; I. Andonovic

1998-01-01

169

49 CFR 236.6 - Hand-operated switch equipped with switch circuit controller.  

Code of Federal Regulations, 2011 CFR

...Hand-operated switch equipped with switch circuit controller. 236.6 Section 236...Hand-operated switch equipped with switch circuit controller. Hand-operated switch equipped with switch circuit controller connected to the point,...

2011-10-01

170

An optical switch  

DOEpatents

The invention is a gas mixture for a diffuse discharge switch having an electron attaching gas wherein electron attachment is brought about by indirect excitation of molecules to long live states by exposure to laser light. 3 figs.

Christophorou, L.G.; Hunter, S.R.

1987-04-30

171

Plasmonic enhanced ultrafast switch.  

SciTech Connect

Ultrafast electronic switches fabricated from defective material have been used for several decades in order to produce picosecond electrical transients and TeraHertz radiation. Due to the ultrashort recombination time in the photoconductor materials used, these switches are inefficient and are ultimately limited by the amount of optical power that can be applied to the switch before self-destruction. The goal of this work is to create ultrafast (sub-picosecond response) photoconductive switches on GaAs that are enhanced through plasmonic coupling structures. Here, the plasmonic coupler primarily plays the role of being a radiation condenser which will cause carriers to be generated adjacent to metallic electrodes where they can more efficiently be collected.

Subramania,Ganapathi Subramanian; Reno, John Louis; Passmore, Brandon Scott; Harris, Tom.; Shaner, Eric Arthur; Barrick, Todd A.

2009-09-01

172

Optical Switch Evaluation Support.  

National Technical Information Service (NTIS)

Extensive testing has been done on nonlinear interface optical switch (NIOS) devices fabricated from laser deposited nonstoichiometric tungsten oxide films. A Fresnel coefficient formalism for evaluating the indices of refraction of the films has been dev...

J. Chaiken

1993-01-01

173

Microwave Switching Circuits.  

National Technical Information Service (NTIS)

The monograph is concerned with the design, exploitation, and operation of microwave antennas and equipment. It presents in monographic form a number of the most fundamental and frequently used groups of switching systems.

A. Kraszewski

1969-01-01

174

Resonant optoelectronic thyristor switches as elements for optical switching fabrics  

NASA Astrophysics Data System (ADS)

An optical switching fabric based on resonant optoelectronic switches is presented. The elements are comprised of two optoelectronic thyristors which have their own switching characteristic. Simultaneous switching of 40Gbps baseband data along with mm-wave optical signals is shown in a 4x4 fabric. The possible unique capabilities and performance advantages of implementation with thyristor-based switches in the fabric are discussed.

Pile, B. C.; Zhang, Y.; Yao, J.; Taylor, G. W.

2011-09-01

175

Task switching: a high-density electrical mapping study.  

PubMed

Flexibly switching between tasks is one of the paradigmatic functions of so-called "executive control" processes. Neuroimaging studies have implicated both prefrontal and parietal cortical regions in the processing necessary to effectively switch task. Beyond their general involvement in this critical function, however, little is known about the dynamics of processing across frontal and parietal regions. For instance, it remains to be determined to what extent these areas play a role in preparing to switch task before arrival of the stimulus to be acted upon and to what extent they play a role in any switching processes that occur after the stimulus is presented. Here, we used the excellent temporal resolution afforded by high-density mapping of brain potentials to explore the time course of the processes underlying (1) the performance of and (2) the preparation for a switch of task. We detail the contributions of both frontal and parietal processes to these two aspects of the task-switching process. Our data revealed a complex pattern of effects. Most striking was a period of sustained activity over bilateral parietal regions preceding the switch trial. Over frontal regions, activity actually decreased during this same period. Strongest sustained frontal activity was in fact seen for trials on which no switch was required. Further, we find that the first differential activity associated with switching task was over posterior parietal areas (220 ms), whereas over frontal scalp, the first differential activity is found more than 200 ms later. These and other effects are interpreted in terms of a "competition" model in which preparing to switch task is understood as the beginning of a competition between the potentially relevant tasks that is resolved during the switch trial. Our findings are difficult to account for with models that posit a strong role for frontal cortical regions in "reconfiguring" the system during switches of task. PMID:14683733

Wylie, G R; Javitt, D C; Foxe, J J

2003-12-01

176

Studies on the plasma membrane H sup + -ATPase of oat roots: Preparation and assay, cytological localization, and sulfhydryl chemistry  

SciTech Connect

Biochemical and cytological studies were performed on the plasma membrane proton pump (H{sup +}-ATPase) of oat roots (Avena sativa cv. Stout). H{sup +}-ATPase activity in oat root plasma membranes is inhibited by N-ethylmaleimide (NEM), a covalent modifier of protein sulfhydryl groups. The rate of inhibition is reduced in the presence of ADP or MgADP. An M{sub r} = 100,000 plasma membrane polypeptide showed reduced labelling by ({sup 3}H)NEM in the presence of ADP. When tryptic peptides from ({sup 3}H)NEM-labeled M{sub r} = 100,000 polypeptide were separated by reverse-phase high-pressure liquid chromatography (HPLC), only one radioactive peak consistently showed labeling in the presence of ADP. In order to determine the location and identity of the NEM-reactive residue, the radioactive peptide in this peak was further purified by HPLC. The amino acid sequence(s) in the resulting sample were then determined by Edman degradation on an automated gas-phase sequenator. The PTH-amino acids released at each cycle of the degradation were separated by HPLC. Analysis of the chromatograms suggested that the radio-labeled residue was located in a peptide of sequence V-E-N-Q-D-A-I-D-A-C{sup *}-M-V-G-M-L-A-D-P-K. The NEM-reactive residue was cysteine, based on the retention time of the radioactivity released. The ATP-hydrolyzing activity observed in electron micrographs by lead-precipitation of enzymically released inorganic phosphate was compared with that observed in in vitro assays of the soluble and plasma membrane fractions of oat root homogenates. Although an ATP-hydrolyzing activity was observed on the plasma membrane in the electron micrographs, its substrate specificity and inhibitor sensitivity was identical to that observed for phosphatase activity.

Katz, D.B.

1989-01-01

177

A radiation hard vacuum switch  

DOEpatents

A vacuum switch with an isolated trigger probe which is not directly connected to the switching electrodes. The vacuum switch within the plasmatron is triggered by plasma expansion initiated by the trigger probe which travels through an opening to reach the vacuum switch elements. The plasma arc created is directed by the opening to the space between the anode and cathode of the vacuum switch to cause conduction. 3 figs.

Boettcher, G.E.

1988-07-19

178

Innovative switching technology  

NASA Astrophysics Data System (ADS)

We have developed an all-semiconductor high-power optical switch. Potential uses include both military applications, such as ultra-wide-band impulse radar and high-frequency antenna couplers, and commercial use, such as high-power switching for utility companies. Under this three-year program, we have demonstrated various switching applications from dc to GHz frequencies. The generic switches comprise a 2-D semiconductor laser diode array and Si or GaAs devices. In the Si area (linear switches - no gain) and dc-biased network, a single two-sided PIN device, activated by two 1 kW laser arrays, has yielded a holding voltage of 1.3 kV and conducted 192 A. Similar devices have later yielded a holding voltage of 3.3 kV, demonstrating the capability of switching more than 500 kW with a single two-sided PIN device. The same generic technology was also demonstrated in high-power high-frequency antenna coupler applications as well as in mm-wave (60 GHz) attenuators and phase shifters. PIN devices tested in a RF circuit between 2-30 MHz yielded an isolation value of between 28 and 49 dB in the off-state, and insertion losses as low as 0.1 dB when illuminated with 280 W (peak) optical power at 808 nm. In the area of GaAs, PIN, and bulk devices under this project, we were able to deliver devices for experiments in both opening and closing switches. We have demonstrated a compact, all-semiconductor switch system that has switched up to 8.5 MW into a 38 (omega) load. The system uses a 2-D laser diode array with a peak power of 850 W to rigger a 1.5 cm long GaAs photoconductor into a high-gain combination mode known as 'lock on'. The highest power switch was pulse-charged to 55 kV and delivered 470 A to a 38 (omega) load in 160 ns long pulse. In the area of 2-D laser arrays, a peak power density of 7 kW/cm(exp 2) was achieved.

Rosen, A.; Stabile, P. J.; Gombar, A. M.; Janton, W. M.; Gilbert, D. B.; Herczfeld, P. R.; Bahasadri, A.

1991-03-01

179

Low inductance gas switching.  

SciTech Connect

The laser trigger switch (LTS) is a key component in ZR-type pulsed power systems. In ZR, the pulse rise time through the LTS is > 200 ns and additional stages of pulse compression are required to achieve the desired <100 ns rise time. The inductance of the LTS ({approx}500nH) in large part determines the energy transfer time through the switch and there is much to be gained in improving system performance and reducing system costs by reducing this inductance. The current path through the cascade section of the ZR LTS is at a diameter of {approx} 6-inches which is certainly not optimal from an inductance point of view. The LTS connects components of much greater diameter (typically 4-5 feet). In this LDRD the viability of switch concepts in which the diameter of cascade section is greatly increased have been investigated. The key technical question to be answered was, will the desired multi-channel behavior be maintained in a cascade section of larger diameter. This LDRD proceeded in 2 distinct phases. The original plan for the LDRD was to develop a promising switch concept and then design, build, and test a moderate scale switch which would demonstrate the key features of the concept. In phase I, a switch concept which meet all electrical design criteria and had a calculated inductance of 150 nH was developed. A 1.5 MV test switch was designed and fabrication was initiated. The LDRD was then redirected due to budgetary concerns. The fabrication of the switch was halted and the focus of the LDRD was shifted to small scale experiments designed to answer the key technical question concerning multi-channel behavior. In phase II, the Multi-channel switch test bed (MCST) was designed and constructed. The purpose of MCST was to provide a versatile, fast turn around facility for the study the multi-channel electrical breakdown behavior of a ZR type cascade switch gap in a parameter space near that of a ZR LTS. Parameter scans on source impedance, gap tilt, gap spacing and electrode diameter were conducted.

Chavez, Ray; Harjes, Henry Charles III; Wallace, Zachariah; Elizondo, Juan E.

2007-10-01

180

Switching impulse strength of compact transmission lines  

SciTech Connect

This paper summarizes test results which were carried out to investigate the influence of several parameters in the switching impulse strength of phase-to-phase insulation. As a consequence, a new formulation for the phase-to-phase critical flash over voltage is presented. Test results are also compared with those available in the literature, taking into account the differences among the various configurations used.

Vaisman, R.; Fonseca, J.R.; Andrade, V.H.G.; Almeida, M.A.; Hattori, M.K.; Melo, M.O.B.C.; Teivelis, F.; Fernandes, J.H.M.; Silva, J.T.S.; Dias, L.E.N.; Esmeraldo, P.C.V.; Samico, R.A.M.

1993-07-01

181

Free-space micromachined optical switches for optical networking  

Microsoft Academic Search

Fiber-optic switches with high port count have emerged as leading candidates for deployment in future optical transport networks, where restoration and provisioning in the optical layer will become increasingly important. This paper reviews the principle and performance of free-space micromachined optical switches (FS-MOS) featuring free-rotating hinged micromirrors. A single-chip FS-MOS that implements the critical function of bridging-essential for restoration in

L. Y. Lin; E. L. Goldstein; R. W. Tkach

1999-01-01

182

Novel synchronization technique for two parallel connected sparkgap switches  

NASA Astrophysics Data System (ADS)

In this article a novel way of synchronizing two parallel connected sparkgap switches with accuracies of 1-5 ns for high frequency pulsed power applications is described. The circuit design of a synchronized sparkgap switch circuit is discussed. The circuit uses a combination of one master sparkgap and a set of inductor and capacitors to synchronize two sparkgaps and can be controlled via an IGBT switch. Critical issues for circuit design are presented together with analytical calculations and simulations. Experimental verification of the novel topology is carried out in a prototype experimental setup. Results showing nanosecond level of accuracy in synchronization are reported in this paper along with simulations and analysis.

Kumar, Rohit; Mitra, S.; Patel, A.; Dwivedi, Rajesh; Kolge, T.; Sharma, Ranjeet Archana; Chakravarthy, D. P.

2012-08-01

183

Electrical-Thermal Switching in Carbon-Black Polymer Composites as a Local Effect  

NASA Astrophysics Data System (ADS)

Following the lack of microscopic information about the intriguing well-known electrical-thermal switching mechanism in carbon-black polymer composites, we applied atomic force microscopy in order to reveal the local nature of the process and correlated it with the characteristics of the widely used commercial switches. We conclude that the switching events take place in critical interparticle tunneling junctions that carry most of the current. The macroscopic switched state is then a result of a dynamic-stationary state of fast switching and slow reconnection of the corresponding junctions.

Azulay, D.; Eylon, M.; Eshkenazi, O.; Toker, D.; Balberg, M.; Shimoni, N.; Millo, O.; Balberg, I.

2003-06-01

184

Thermionic gas switch  

DOEpatents

The present invention is directed to an improved temperature responsive thermionic gas switch utilizing a hollow cathode and a folded emitter surface area. The folded emitter surface area of the thermionic switch substantially increases the on/off ratio by changing the conduction surface area involved in the two modes thereof. The improved switch of this invention provides an on/off ratio of 450:1 compared to the 10:1 ratio of the prior known thermionic switch, while providing for adjusting the on current. In the improved switch of this invention the conduction area is made small in the off mode, while in the on mode the conduction area is made large. This is achieved by utilizing a folded hollow cathode configuration and utilizing a folded emitter surface area, and by making the dimensions of the folds small enough so that a space charge will develop in the convolutions of the folds and suppress unignited current, thus limiting the current carrying surface in the off mode.

Hatch, G.L.; Brummond, W.A.; Barrus, D.M.

1984-04-05

185

Modifications of Sulfhydryl Groups on Phytochrome and Their Influence on Physicochemical Differences between the Red- and Far-Red-Absorbing Forms 1  

PubMed Central

Phytochrome extracted from shoots of dark-grown rye (Secale cereale cv Rymin) and oat (Avena sativa cv Garry) as the far-red-form (Pfr) and/or under conditions conducive to oxidation exhibited a blue shift in the visible absorption maximum of its red-light-absorbing form (Pr) relative to that measured in vivo. This spectral alteration could not be reversed but could be prevented by inclusion of 10 millimolar diethyldithiocarbamate and 140 millimolar 2-mercaptoethanol in homogenization buffers. Similar blue shifts were induced in purified rye phytochrome by addition of the sulfhydryl-modifying reagent, 5,5?-dithiobis-(2-nitrobenzoic acid) (DTNB). In spectrally normal phytochrome (i.e., no detectable blue shift), Pfr had three to four more sulfhydryls available for rapid reaction with DTNB than did Pr. This difference was maintained over a 2.5-hour time course. Phytochrome purified under conditions resulting in a blue-shifted Pr absorption maximum exhibited a decreased short-term reactivity of Pfr to DTNB. Comparison of the binding and elution of altered and unaltered phytochrome from agarose-immobilized Cibacron blue 3GA confirmed that the Pfr form of spectrally normal phytochrome had a greater affinity for the dye than did the Pr form but that spectral alteration of phytochrome was accompanied by a loss of this difference as evidenced by an increased binding of Pr to the dye. It was concluded that phytochrome has highly reactive sulfhydryl residues located on the portion of the protein that undergoes conformational changes on interconversion of Pr and Pfr and that these residues require rigorous protection in order to extract the native form of the protein from plant tissue. Images Fig. 3

Smith, William O.; Cyr, Karen L.

1988-01-01

186

Competitive binding interaction between Zn2+ and saxitoxin in cardiac Na+ channels. Evidence for a sulfhydryl group in the Zn2+/saxitoxin binding site.  

PubMed Central

Mammalian heart Na+ channels exhibit approximately 100-fold higher affinity for block by external Zn2+ than other Na+ channel subtypes. With batrachotoxin-modified Na+ channels from dog or calf heart, micromolar concentrations of external Zn2+ result in a flickering block to a substate level with a conductance of approximately 12% of the open channel at -50 mV. We examined the hypothesis that, in this blocking mode, Zn2+ binds to a subsite of the saxitoxin (STX) binding site of heart Na+ channels by single-channel analysis of the interaction between Zn2+ and STX and also by chemical modification experiments on single heart Na+ channels incorporated into planar lipid bilayers in the presence of batrachotoxin. We found that external Zn2+ relieved block by STX in a strictly competitive fashion. Kinetic analysis of this phenomenon was consistent with a scheme involving direct binding competition between Zn2+ and STX at a single site with intrinsic equilibrium dissociation constants of 30 nM for STX and 30 microM for Zn2+. Because high-affinity Zn2(+)-binding sites often include sulfhydryl groups as coordinating ligands of this metal ion, we tested the effect of a sulfhydryl-specific alkylating reagent, iodoacetamide (IAA), on Zn2+ and STX block. For six calf heart Na+ channels, we observed that exposure to 5 mM IAA completely abolished Zn2+ block and concomitantly modified STX binding with at least 20-fold reduction in affinity. These results lead us to propose a model in which Zn2+ binds to a subsite within or near the STX binding site of heart Na+ channels. This site is also presumed to contain one or more cysteine sulfhydryl groups.

Schild, L; Moczydlowski, E

1991-01-01

187

The Respiratory Burst and Electrolyte Leakage Induced by Sulfhydryl Blockers in Egeria densa Leaves Are Associated with H2O2 Production and Are Dependent on Ca2+ Influx1  

PubMed Central

In leaves of Egeria densa Planchon, N-ethylmaleimide (NEM) and other sulfhydryl-binding reagents induce a temporary increase in nonmitochondrial respiration (?QO2) that is inhibited by diphenylene iodonium and quinacrine, two known inhibitors of the plasma membrane NADPH oxidase, and are associated with a relevant increase in electrolyte leakage (M. Bellando, S. Sacco, F. Albergoni, P. Rocco, M.T. Marré [1997] Bot Acta 110: 388–394). In this paper we report data indicating further analogies between the oxidative burst induced by sulfhydryl blockers in E. densa and that induced by pathogen-derived elicitors in animal and plant cells: (a) NEM- and Ag+-induced ?QO2 was associated with H2O2 production and both effects depended on the presence of external Ca2+; (b) Ca2+ influx was markedly increased by treatment with NEM; (c) the Ca2+ channel blocker LaCl3 inhibited ?QO2, electrolyte release, and membrane depolarization induced by the sulfhydryl reagents; and (d) LaCl3 also inhibited electrolyte leakage induced by the direct infiltration of the leaves with H2O2. These results suggest a model in which the interaction of sulfhydryl blockers with sulfhydryl groups of cell components would primarily induce an increase in the Ca2+ cytosolic concentration, followed by membrane depolarization and activation of a plasma membrane NADPH oxidase. This latter effect, producing active oxygen species, might further influence plasma membrane permeability, leading to the massive release of electrolytes from the tissue.

Marre, Maria Teresa; Amicucci, Enrica; Zingarelli, Luisa; Albergoni, Francesco; Marre, Erasmo

1998-01-01

188

FAST ACTING CURRENT SWITCH  

DOEpatents

A high-current, fast-acting switch is designed for utilization as a crowbar switch in a high-current circuit such as used to generate the magnetic confinement field of a plasma-confining and heat device, e.g., Pyrotron. The device particularly comprises a cylindrical housing containing two stationary, cylindrical contacts between which a movable contact is bridged to close the switch. The movable contact is actuated by a differential-pressure, airdriven piston assembly also within the housing. To absorb the acceleration (and the shock imparted to the device by the rapidly driven, movable contact), an adjustable air buffer assembly is provided, integrally connected to the movable contact and piston assembly. Various safety locks and circuit-synchronizing means are also provided to permit proper cooperation of the invention and the high-current circuit in which it is installed. (AEC)

Batzer, T.H.; Cummings, D.B.; Ryan, J.F.

1962-05-22

189

Comparative Studies on Sulfhydryl Determination of Soy Protein Using Two Aromatic Disulfide Reagents and Two Fluorescent Reagents.  

PubMed

In this study, the sulfhydryl (SH) contents of unheated and heated (90 °C, 5 min) soy protein were detected under different conditions (pH, reagent addition order, SDS/GuHCl concentration, EDTA) using two aromatic disulfide reagents: 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB) and 4,4'-dithiodipyridine (DPS). Two fluorescent alkylating reagents, monobromobimane (mBBr) and N-(1-pyrenyl)maleimide (NPM), were chosen due to their high sensitivity and were also used. Amino acid analysis was used to detect the SH (cysteine) contents of unheated (7.51 ± 0.45 ?mol SH/g protein) and heated (1.47 ± 0.10 ?mol SH/g protein) soy protein, and similar results were obtained using enzymatic hydrolysis-assisted DPS. The SH content detected by DTNB was affected by pH, denaturant species, and denaturant concentration, and the best results were obtained at pH 7.0 when 6 M GuHCl was added after DTNB. These results were lower than that of the amino acid analysis, however. The SH detected by DPS was not as affected as that of DTNB by pH, denaturant species, and denaturant concentration. Additionally, the results of the amino acid analysis were similar to that of DPS at pH 7.0 in 2% SDS and 4-6 M GuHCl when SDS and GuHCl were added after DPS. EDTA did not have a significant effect on SH detection when DTNB and DPS were added before SDS and GuHCl. Finally, although mBBr and NPM can detect SH in low protein concentrations ((1)/10 of that required for DTNB and DPS), mBBr and NPM overestimated the SH content of soy protein. Therefore, using DPS at pH 7.0 when it is added before SDS and GuHCl is the most reliable method for detecting the SH content of soy protein. PMID:23432329

Ruan, Qijun; Chen, Yeming; Kong, Xiangzhen; Hua, Yufei

2013-03-11

190

Magnetic switches and circuits  

SciTech Connect

This report outlines the use of saturable inductors as switches in lumped-element, magnetic-pulse compression circuits is discussed and the characteristic use of each is defined. In addition, the geometric constraints and magnetic pulse compression circuits used in short-pulse, low-inductance systems are considered. The scaling of presaturation leakage currents, magnetic energy losses, and switching times with geometrical and material parameters are developed to aid in evaluating magnetic pulse compression systems in a particular application. Finally, a scheme for increasing the couping coefficient in saturable stripline transformers is proposed to enable their use in the short-pulse, high-voltage regime.

Nunnally, W.C.

1982-05-01

191

SHOCKPROOF MAGNETIC REED SWITCH  

DOEpatents

A shockproof magnetic reed switch is described which comprises essentially a plurality of pairs of reed contacts of magnetic, electrical conducting material which are arranged generally in circumferential spaced relationship. At least two of the pairs are disposed to operate at a predetermined angle with respect to each other, and the contacts are wired in the circuit, so that the continuity, or discontinuity, of the circuit is not affected by a shock imposed on the switch. The contacts are hermetically sealed within an outer tubular jacket. (AEC)

Medal, E.

1962-03-13

192

41. INTERIOR VIEW, GREEN SWITCH TOWER, COS COB, SHOWING SWITCH ...  

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

41. INTERIOR VIEW, GREEN SWITCH TOWER, COS COB, SHOWING SWITCH LEVER ASSEMBLAGE AND DISPLAY BOARD - New York, New Haven & Hartford Railroad, Automatic Signalization System, Long Island Sound shoreline between Stamford & New Haven, Stamford, Fairfield County, CT

193

43. OBLIQUE VIEW, GREEN SWITCH TOWER, COS COB, SHOWING SWITCH ...  

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

43. OBLIQUE VIEW, GREEN SWITCH TOWER, COS COB, SHOWING SWITCH LEVER ASSEMBLAGE AND DISPLAY BOARD - New York, New Haven & Hartford Railroad, Automatic Signalization System, Long Island Sound shoreline between Stamford & New Haven, Stamford, Fairfield County, CT

194

36. INTERIOR VIEW, BERK SWITCH TOWER, SOUTH NORWALK, SHOWING SWITCHING ...  

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

36. INTERIOR VIEW, BERK SWITCH TOWER, SOUTH NORWALK, SHOWING SWITCHING LEVERS FROM OPERATOR'S POSITION - New York, New Haven & Hartford Railroad, Automatic Signalization System, Long Island Sound shoreline between Stamford & New Haven, Stamford, Fairfield County, CT

195

35. END VIEW, INTERIOR, SHOWING SWITCHING LEVERS, BERK SWITCH TOWER, ...  

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

35. END VIEW, INTERIOR, SHOWING SWITCHING LEVERS, BERK SWITCH TOWER, SOUTH NORWALK - New York, New Haven & Hartford Railroad, Automatic Signalization System, Long Island Sound shoreline between Stamford & New Haven, Stamford, Fairfield County, CT

196

Design of Wavelength Converting Switches for Optical Burst Switching.  

National Technical Information Service (NTIS)

Optical Burst Switching (OBS) is an experimental network technology that enables the construction of very high capacity routers, using optical data paths and electronic control. In this paper, we study two designs for wavelength converting switches that a...

J. Ramamirtham J. Turner

2001-01-01

197

Packet Switching Photonic Network Switch Design and Routing Algorithms  

Microsoft Academic Search

Maturity of photonic technology makes it possible to construct all optical network switch to avoid optical-to-electrical signal conversion for routing. To realize all optical packet switching, our current network topology and routing algorithms have to be reexamined and modified to satisfy the necessities of all optical network switching such as a fast routing decision, consideration of hardware implementation, buffering etc.

Hyuk-Jun Lee; Martin M. Morf; Michael J. Flynn

198

Molecular Mechanism of the Inactivation of Tryptophan Hydroxylase by Nitric Oxide: Attack on Critical Sulfhydryls that Spare the Enzyme Iron Center  

Microsoft Academic Search

Tryptophan hydroxylase (TPH), the initial and rate-limiting en- zyme in the biosynthesis of the neurotransmitter serotonin (5- HT), is irreversibly inactivated by nitric oxide (NO). We have expressed brain TPH as a recombinant glutathione-S- transferase fusion protein and delineated the catalytic domain of the enzyme as the region spanning amino acids 99-444. Highly purified TPH catalytic core, like the native

Donald M. Kuhn; Robert Arthur Jr

1997-01-01

199

Nanosecond Spark Gap Switching Measurements.  

National Technical Information Service (NTIS)

The switching time of gas and oil dielectric spark gaps was measured in the nanosecond and subnanosecond time regime. The observed switching characteristics of the two spark gaps were compared with those predicted by empirical formulas. The formulas used ...

J. W. Ginn D. N. Hendricks M. T. Buttram

1986-01-01

200

Packet Switching with Satellites.  

National Technical Information Service (NTIS)

The beginning of the 1970's has witnessed the establishment of new forms of computer-communication networks, with clear advantages over the voice oriented point-to-point, channel switched networks of the 1960's. The paper describes some of the most import...

N. Abramson

1973-01-01

201

Capillary micro-switches  

NASA Astrophysics Data System (ADS)

A capillary surface is a liquid/liquid or liquid/gas interface whose shape is determined by surface tension. Capillary surfaces occur when the capillary length is large compared to the container scale, as happens for typical liquids against gas on the sub-millimeter scale on Earth and on the meter scale in the micro-gravity environment of space vehicles. Manipulating capillary surfaces has emerged as a leading strategy for moving liquids on the micro-scale [1]. Practitioners have yet to take advantage of capillary instability in their design of devices, though. We illustrate how the response diagram of a single switch (bi-stable device) can be constructed from that of two capillary elements, how that of a system of switches (a pair) can be built from that of a single switch and finally how understanding the response of the system guides us to observations of new behavior in the laboratory. Experiments on capillary surfaces use either a soap-film analog (10 centimeter scale) or a liquid/gas (millimeter scale) apparatus. Progress is reported on the application of an array of micro-switches to make a controllable adhesion device, with the aim of effecting droplet transport. 1. Cho, Fan, Moon and Kim, "Towards digital microfluidic circuits: creating, transporting, cutting and merging liquid droplets by electrowetting-based actuation." Proc. 15th IEEE Int'l Conf. on MEMS, January 2002.

Steen, Paul; Matalanis, Claude; Hirsa, Amir; Cox, Christhopher

2002-11-01

202

Switching with silicon  

Microsoft Academic Search

This article is a review of a new switching device currently being developed. This device, known as the thyristor controlled series capacitor, promises to provide nearly instantaneous control over the electric transmission and distribution system. It has been installed at Bonneville Power`s Slatt substation, and it is a key element in the Flexible AC Transmission Systems concept current by being

Bruce

1994-01-01

203

Hybrid Power Semiconductor Switch.  

National Technical Information Service (NTIS)

The voltage rating of a bipolar transistor may be greatly extended while at the same time reducing its switching time by operating it in conjunction with FETs in a hybrid circuit. One FET is used to drive the bipolar transistor and an inductive load. Both...

D. Y. Chen

1983-01-01

204

Tag switching architecture overview  

Microsoft Academic Search

Abstract Tag switching is a way to combine the label-swapping forwarding paradigm with network layer routing. This has several advantages. Tags can have a wide spectrum of forwarding granularities, so at one end of the spectrum a tag could be associated with a group of destinations, while at the other a tag could be associated with a single application flow.

B. Davm; D. Katz; G. Swallow; D. Famnacci

1996-01-01

205

Tag switching architecture overview  

Microsoft Academic Search

Tag switching is a way to combine the label-swapping forwarding paradigm with network-layer routing with particular application to the Internet. This has several advantages. Tags can have a wide spectrum of forwarding granularities, so at one end of the spectrum a tag could be associated with a group of destinations, while at the other end, a tag could be associated

YAKOV REKHTER; BRUCE DAVIE; ERIC ROSEN; GEORGE SWALLOW; DINO FARINACCI; DAVE KATZ

1997-01-01

206

High Speed Packet Switching.  

National Technical Information Service (NTIS)

This document constitutes the final report prepared by Proteon, Inc. of Westborough, Massachusetts under contract NAS 5-30629 entitled High-Speed Packet Switching (SBIR 87-1, Phase 2) prepared for NASA-Greenbelt, Maryland. The primary goal of this researc...

1991-01-01

207

MPSS: Multiprotocol Stateless Switching  

Microsoft Academic Search

The Multiprotocol Label Switching (MPLS) architecture has become a true success story in the world of telecommunications. However, MPLS becomes cumbersome if multicast communication is needed, as aggregating of labels is not easy. Because of that, when providing Multicast VPNs, operators need to trade-off bandwidth usage with the amount of multicast state, sacrificing efficiency. Forwarding with Bloom filters in the

P. Jokela; M. Sarela; S. Ruponen; J. Kempf; P. Nikander

2010-01-01

208

Switching light with light  

Microsoft Academic Search

The basic characteristics of the light amplifying optical switch (LAOS) are explained. The LAOS, as compared to its electronic counterparts, will substantially reduce the interconnect time between components, chips, PC boards, and machines. The use of the LAOS to implement optical logic circuits with multiple input stages that invert and restore the input signal is discussed. Applications to image and

C. W. Wilmsen; S. A. Feld; X. An

1991-01-01

209

Safe LPV controller switching  

Microsoft Academic Search

Before switching to a new controller it is crucial to assure that the new closed loop will be stable. In this paper it is demonstrated how stability can be checked with limited measurement data available from the current closed loop. The paper extends an existing method to linear parameter varying plants and controllers. Rather than relying on frequency domain methods

Klaus Trangbaek

2010-01-01

210

Optoelectronic Switch Array.  

National Technical Information Service (NTIS)

The report presents the second quarter work performed in the development of an optoelectronic switch array. The report is divided into three parts. Part I describes an improved light sensing circuit which has been included in the integrated design and des...

1968-01-01

211

Kiowa Creek Switching Station  

SciTech Connect

The Western Area Power Administration (Western) proposes to construct, operate, and maintain a new Kiowa Creek Switching Station near Orchard in Morgan County, Colorado. Kiowa Creek Switching Station would consist of a fenced area of approximately 300 by 300 feet and contain various electrical equipment typical for a switching station. As part of this new construction, approximately one mile of an existing 115-kilovolt (kV) transmission line will be removed and replaced with a double circuit overhead line. The project will also include a short (one-third mile) realignment of an existing line to permit connection with the new switching station. In accordance with the Council on Environmental Quality (CEQ) regulations for implementing the procedural provisions of the National Environmental Policy Act of 1969 (NEPA), 40 CFR Parts 1500--1508, the Department of Energy (DOE) has determined that an environmental impact statement (EIS) is not required for the proposed project. This determination is based on the information contained in this environmental assessment (EA) prepared by Western. The EA identifies and evaluates the environmental and socioeconomic effects of the proposed action, and concludes that the advance impacts on the human environment resulting from the proposed project would not be significant. 8 refs., 3 figs., 1 tab.

Not Available

1990-03-01

212

Optical Switch Evaluation.  

National Technical Information Service (NTIS)

We have evaluated nonlinear interface optical switches (NIOS) based on thin films of laser deposited metal oxide clusters. Films having nominal thickness 200nm and ranging in stoichiometry from WO2.6 to WO2.5, were evaluated in at least two configurations...

J. M. Osman

1996-01-01

213

Parrondo's games with chaotic switching  

NASA Astrophysics Data System (ADS)

This paper investigates the different effects of chaotic switching on Parrondo's games, as compared to random and periodic switching. The rate of winning of Parrondo's games with chaotic switching depends on coefficient(s) defining the chaotic generator, initial conditions of the chaotic sequence and the proportion of Game A played. Maximum rate of winning can be obtained with all the above mentioned factors properly set, and this occurs when chaotic switching approaches periodic behavior.

Tang, Tze Wei; Allison, Andrew G.; Abbott, Derek

2004-05-01

214

Transparent electrode for optical switch  

DOEpatents

The invention relates generally to optical switches and techniques for applying a voltage to an electro-optical crystal, and more particularly, to transparent electodes for an optical switch. System architectures for very large inertial confinement fusion (ICF) lasers require active optical elements with apertures on the order of one meter. Large aperture optical switches are needed for isolation of stages, switch-out from regenerative amplifier cavities and protection from target retroreflections.

Goldhar, J.; Henesian, M.A.

1984-10-19

215

Gastroprotection of suaveolol, isolated from Hyptis suaveolens, against ethanol-induced gastric lesions in Wistar rats: role of prostaglandins, nitric oxide and sulfhydryls.  

PubMed

Hyptis suaveolens is a medicinal plant that is, according to traditional medicine, considered useful in the treatment of gastric ulcers. Although its gastroprotective activity was reported, the active compounds have not been identified. Therefore, the aim of the present study was to identify at least one active compound potentially responsible for the gastroprotective activity of H. suaveolens by using a bioassay guided study with an ethanol-induced gastric ulcer experimental model in rats. The results show that the hexane extract had protective activity (close to 70% when using doses between 10 and 100 mg/kg), and that the compound suaveolol, isolated from this extract, was one of the active gastroprotective agents. This is the first report about the gastroprotective activity of suaveolol. Rats treated with this compound at 3, 10, 30 and 100 mg/kg showed 12.6, 21.3, 39.6 and 70.2% gastroprotection respectively. The effect elicited by suaveolol (at 100 mg/kg) was attenuated by pretreatment with either N(G)-nitro-L-arginine methyl ester (70 mg/kg, i.p.), a nitric oxide (NO) synthase inhibitor, indomethacin (10 mg/kg, s.c.), a blocker of prostaglandin synthesis, or N-ethylmaleimide (10 mg/kg, s.c.), a blocker of sulfhydryl groups. This suggests that the gastroprotective mechanism of action of this compound involves NO, prostaglandins and sulfhydryl groups. PMID:22836211

Vera-Arzave, Carlos; Antonio, Leticia Cruz; Arrieta, Jesús; Cruz-Hernández, Gerardo; Velasquez-Mendez, Antonio Magdiel; Reyes-Ramírez, Adelfo; Sánchez-Mendoza, María Elena

2012-07-26

216

Task switching and subjective duration  

Microsoft Academic Search

Three experiments investigated the effects of switching from a nontiming task (addition of rapidly presented digits) to estimation of the duration of short tones or visual stimuli (Experiments 1 and 2), or the production of time intervals (Experiment 3). In general, compared with trials without a task-switch, trials involving a switch resulted in shorter duration estimates, but longer productions. The

J. H. Wearden; Susan C. ORourke; Claire Matchwick; Zhang Min; Sharon Maeers

2010-01-01

217

Language Switching and Language Competition  

ERIC Educational Resources Information Center

|This study examined the asymmetrical language switching cost in a word reading task (Experiment 1) and in a categorization task (Experiment 2 and 3). In Experiment 1, Spanish-English bilinguals named words in first language (L1) and second language (L2) in a switching paradigm. They were slower to switch from their weaker L2 to their more…

Macizo, Pedro; Bajo, Teresa; Paolieri, Daniela

2012-01-01

218

Development of optical multifunctional switch  

Microsoft Academic Search

A lossless, low-crosstalk and multifunction optical switch is most desirable for large-scale photonic network. To realize such a switch, we have introduced the new architecture of optical switch that embedded many functions on single device. With the use of MEMs technology has minimized the effect of crosstalk and return loss. The multifunctional device means the integration of single functional device

M. S. Ab-Rahman; M. T. M. Yusof

2008-01-01

219

High gain GaAs photoconductive semiconductor switches: Switch longevity  

SciTech Connect

Optically activated, high gain GaAs switches are being tested for many different pulsed power applications that require long lifetime (longevity). The switches have p and n contact metallization (with intentional or unintentional dopants) configured in such a way as to produce p-i-n or n-i-n switches. The longevity of the switches is determined by circuit parameters and by the ability of the contacts to resist erosion. This paper will describe how the switches performed in test-beds designed to measure switch longevity. The best longevity was achieved with switches made with diffused contacts, achieving over 50 million pulses at 10 A and over 2 million pulses at 80 A.

Loubriel, G.M.; Zutavern, F.J.; Mar, A. [and others

1998-07-01

220

Efficiency considerations of load side soft-switching inverters for electric vehicle applications  

Microsoft Academic Search

This paper critically evaluates the efficiency of load side soft-switching inverters for electric vehicle (EV) drive applications. Five types of load side soft-switching inverters are studied, including the auxiliary resonant commutated pole inverter (ARCP), the zero-current-transition (ZCT) inverter, the zero-voltage-transition (ZVT) inverter with coupled inductors (ZVTCI), the ZVT inverter with a single switch (ZVTSS), and the ZVT inverter with a

Wei Dong; Jae-Young Choi; Yong Li; Huijie Yu; Jason Lai; Dusan Boroyevich; Fred C. Lee

2000-01-01

221

Development of a heavy duty pulsed power generator with ten spark gap switches  

Microsoft Academic Search

Summary form only given. Long lifetime heavy duty (1 GW\\/1 kHz) pulsed power sources become more and more attractive for industrial applications such as gas\\/water cleaning, etc. One critical issue associated with such kind of source is the heavy switching duty. This paper describes a multiple switches based large scale prototype setup. It consists of ten high-pressure spark gap switches

Z. Liu; A. J. M. Pemen; G. J. J. Winands; E. J. M. Van Heesch; K. Yan

2007-01-01

222

Development of a heavy duty pulsed power generator with ten spark gap switches  

Microsoft Academic Search

Long lifetime heavy duty pulsed power sources become more and more attractive for industrial applications such as gas\\/water cleaning, etc. One critical issue associated with such kind of source is the heavy switching duty. This paper describes a multiple switches based large scale prototype setup. It consists of ten high-pressure spark gap switches and a ten-stage transmission-line-transformer (TLT). By means

Z. Liu; A. J. M. Pemen; G. J. J. Winands; E. J. M. Van Heesch; K. Yan

2007-01-01

223

Micromachined low-loss microwave switches  

Microsoft Academic Search

The design and fabrication of a micromechanical capacitive membrane microwave switching device is described. The switching element consists of a thin metallic membrane, which has two states, actuated or unactuated, depending on the applied bias. A microwave signal is switched on and off when the membrane is switched between the two states. These switches have a switching on speed of

Z. Jamie Yao; Shea Chen; Susan Eshelman; David Denniston; Chuck Goldsmith

1999-01-01

224

Scalable schedulers for high-performance switches  

Microsoft Academic Search

Scheduler and switching fabric are two major hardware components of a cell switch. For a switch using a nonblocking switching fabric, the performance of the switch depends on the performance of its cell scheduler. We introduce the concepts of relative and universal scheduler scalabilities. Informally, a scheduler is relatively scalable with respect to a switching fabric if its structure is

Chuanjun Li; S. Q. Zheng; Mei Yang

2004-01-01

225

Protein Conformational Switches: From Nature to Design  

PubMed Central

Protein conformational switches alter their shape upon receiving an input signal, such as ligand binding, chemical modification, or change in environment. The apparent simplicity of this transformation—which can be carried out by a molecule as small as a thousand atoms or so—belies its critical importance to the life of the cell as well as its capacity for engineering by humans. In the realm of molecular switches, proteins are unique because they are capable of performing a variety of biological functions. Switchable proteins are therefore of high interest to the fields of biology, bio-technology, and medicine. These molecules are beginning to be exploited as the core machinery behind a new generation of biosensors, functionally regulated enzymes, and “smart” biomaterials that react to their surroundings. As inspirations for these designs, researchers continue to analyze existing examples of allosteric proteins. Recent years have also witnessed the development of new methodologies for introducing conformational change into proteins that previously had none. Herein we review examples of both natural and engineered protein switches in the context of four basic modes of conformational change: rigid-body domain movement, limited structural rearrangement, global fold switching, and folding–unfolding. Our purpose is to highlight examples that can potentially serve as platforms for the design of custom switches. Accordingly, we focus on inducible conformational changes that are substantial enough to produce a functional response (e.g., in a second protein to which it is fused), yet are relatively simple, structurally well-characterized, and amenable to protein engineering efforts.

Ha, Jeung-Hoi

2012-01-01

226

Switching health insurance plans: results from a health survey.  

PubMed

The study is designed to provide an informal summary of what is known about consumer switching of health insurance plans and to contribute to knowledge about what motivates consumers who choose to switch health plans. Do consumers switch plans largely on the basis of critical reflection and assessment of information about the quality, and price? The literature suggests that switching is complicated, not always possible, and often overwhelming to consumers. Price does not always determine choice. Quality is very hard for consumers to understand. Results from a random sample survey (n = 2791) of the Alkmaar region of the Netherlands are reported here. They suggest that rather than embracing the opportunity to be active critical consumers, individuals are more likely to avoid this role by handing this activity off to a group purchasing organization. There is little evidence that consumers switch plans on the basis of critical reflection and assessment of information about quality and price. The new data reported here confirm the importance of a group purchasing organizations. In a free-market-health insurance system confidence in purchasing groups may be more important for health insurance choice than health informatics. This is not what policy makers expected and might result a less efficient health insurance market system. PMID:20640891

Lako, Christiaan J; Rosenau, Pauline; Daw, Chris

2011-12-01

227

Future switching system requirements  

SciTech Connect

What network construction and operations should a network provider expect in the future To answer this question, the author first discusses the new environment surrounding the network from two aspects: the business administration aspect, which involves the issues of competition and cooperation, reduction in labor, and new services; and the technological aspect, which involves the issues of open and global networks and the fusion of telecommunications and information processing technologies. Then, on that basis, there is clarification of what is required of the switching system in terms of architecture, connectivity, reliability, and security. Finally, there is a description of the form of the expected switching system in terms of architecture, and the enhancement of call control, operations, and the user-network interface. 3 refs., 2 figs.

Aoki, Toshiharu (NTT, Tokyo (Japan))

1993-01-01

228

MULTIPLE SPARK GAP SWITCH  

DOEpatents

A multiple spark gap switch of unique construction is described which will permit controlled, simultaneous discharge of several capacitors into a load. The switch construction includes a disc electrode with a plurality of protuberances of generally convex shape on one surface. A firing electrode is insulatingly supponted In each of the electrode protuberances and extends substantially to the apex thereof. Individual electrodes are disposed on an insulating plate parallel with the disc electrode to form a number of spark gaps with the protuberances. These electrodes are each connected to a separate charged capacitor and when a voltage ls applied simultaneously between the trigger electrodes and the dlsc electrode, each spark gap fires to connect its capacitor to the disc electrode and a subsequent load.

Schofield, A.E.

1958-07-22

229

Switching with silicon  

SciTech Connect

This article is a review of a new switching device currently being developed. This device, known as the thyristor controlled series capacitor, promises to provide nearly instantaneous control over the electric transmission and distribution system. It has been installed at Bonneville Power`s Slatt substation, and it is a key element in the Flexible AC Transmission Systems concept current by being developed by EPRI.

Bruce, B.

1994-07-01

230

A CMOS SPDT switch  

Microsoft Academic Search

In this work, a novel architecture with stacked-type CMOS device is presented. The reformed CMOS switch was implemented by the TSMC 0.18 um 1P6M standard CMOS process. In order to improve power handling capability and strengthen the isolation, the proposed circuit is inserted with an excess transistor adjacent to the receiver side. The insertion loss of the designed CMOS T\\/R

Jheng-Da Wu; Janne-Wha Wu; Chih-Ho Tu; Ching-Wen Tang; Chien-You Lai; Bing-Jiun Lai; Wei-Ju Lai; Liang-Yeh Chi; Ying-Zong Juang

2008-01-01

231

Composite Material Switches  

NASA Astrophysics Data System (ADS)

A device to protect electronic circuitry from high voltage transients is constructed from a relatively thin piece of conductive composite sandwiched between two conductors so that conduction is through the thickness of the composite piece. The device is based on the discovery that conduction through conductive composite materials in this configuration switches to a high resistance mode when exposed to voltages above a threshold voltage.

Javadi, Hamid

2002-09-01

232

Optical switch fabric design for gigabit switching router  

NASA Astrophysics Data System (ADS)

One of the key issues of high performance IP Gigabit Switching Router (GSR) design is about switching fabrics. In the traditional bus-based router architectures, the data transfer rate of copper backplanes will soon reach the speed limit because of connector reflections and crosstalk. An alternative optical switching fabric technology is necessary in order to satisfy the demand for high switching bandwidth. In this paper we firstly present a novel all-optical broadcasting switch fabric design scheme based on broadcasting bus architecture. In this section we also illustrate the advantages and disadvantages of this kind of architecture and demonstrate that this kind of switching fabric architecture have no interior block as well as none I/O block. Second, we discuss such implementation scheme of all-optical broadcasting switch fabric architecture as queuing, scheduling and multicasting. Finally, we get a conclusion that all-optical broadcasting switch fabric is one of the cost-effective solutions to design high-speed, scalable and simple switch fabrics compared with those complicated electric crossbar switch fabrics in GSR design.

Wei, Wei; Zeng, Qingji

2001-10-01

233

Study on simulation model of switched reluctance startor\\/generator system based on wavelet neural network  

Microsoft Academic Search

This paper presents a novel integrated simulation model of switched reluctance startor\\/generato r system based on wavelet neural network. The switched reluctance startor\\/generato r system is hard to obtain good simulation model due to its critical nonlinearity. Relatively accurate mathematical model would be built by the wavelet neural network due to its powerful learning, approximation and prediction abilities. The nonlinear

Xiaoshu Zan; Fangnan Xie

2011-01-01

234

Numerical simulations of all-optical switching using nonlinear semiconductor etalons  

NASA Astrophysics Data System (ADS)

Recent results in the modeling and optimization of semiconductor etalon-based devices for optical switching and signal-processing applications are reviewed. Critical device performance criteria including contrast, cascadability, switching speed and energy are evaluated for both one- and two-wavelength device concepts.

Richardson, D.; Gibbs, H. M.; Koch, S. W.

1990-07-01

235

Fibroblasts regulate the switch from acute resolving to chronic persistent inflammation  

Microsoft Academic Search

Fibroblasts are important sentinel cells in the immune system and, here, it is proposed that these cells play a critical role in the switch from acute inflammation to adaptive immunity and tissue repair. It is suggested that chronic inflammation occurs because of disordered fibroblast behaviour in which failure to switch off their inflammatory programme leads to the inappropriate survival and

Christopher D Buckley; Darrell Pilling; Janet M Lord; Arne N Akbar; Dagmar Scheel-Toellner; Mike Salmon

2001-01-01

236

High-performance multi-queue buffers for VLSI communications switches  

Microsoft Academic Search

Small nxn switches are key components of multistage interconnection networks used in multiprocessors as well as in the communication coprocessors used in multicomputers. The design of the internal buffers in these switches is of critical importance for achieving high throughput low latency communication. We discuss several buffer structures and compare them in terms of implementation complexity and their ability to

Yuval Tamir; Gregory L. Frazier

1988-01-01

237

Ultrafast gas switching experiments  

NASA Astrophysics Data System (ADS)

Recent experiments which studied the physics of ultrafast gas breakdown under the extreme overvoltages which occur when a high pressure gas switch is pulse charged to hundreds of kV in 1 ns or less are described. The highly overvolted peaking gaps produce powerful electromagnetic pulses with risetimes less than 100 ps which can be used for ultrawideband radar systems, particle accelerators, laser drivers, bioelectromagnetic studies, electromagnetic effects testing, and for basic studies of gas breakdown physics. Pulses with 50 to 100 ps risetimes to peak levels of 75 to 160 kV at pulse repetition frequencies (PRF) to 1 kHz were produced and accurately measured. A unique gas switch was developed to hold off hundreds of kV with parasitic inductance less than 1 nH. An advanced diagnostic system using Fourier compensation was developed to measure single-shot risetimes below 35 ps. The complete apparatus is described and waveforms are presented. The measured data are compared with a theoretical model which predicts key features including dependence on gas species and pressure. This technology was applied to practical systems driving ultrawideband radiating antennas and bounded wave simulators. A thyristor/pulse transformer based system using a highly overvolted cable switch was developed. This pulser driving a Sandia-designed TEM cell, provides an ultra wideband impulse with less than 200 ps risetime to the test object at a PRF greater than 1 kHz at grater tha n 100 kV/m E field.

Frost, C. A.; Martin, T. H.; Patterson, P. E.; Rinehart, L. F.; Rohwein, G. J.; Roose, L. D.; Aurand, J. F.; Buttram, M. T.

1993-06-01

238

Cygnus Diverter Switch Analysis  

SciTech Connect

The Cygnus Dual Beam Radiographic Facility consists of two 2.25-MV, 60-kA, 50-ns x-ray sources fielded in an underground laboratory at the Nevada Test Site. The tests performed in this laboratory involve study of the dynamic properties of plutonium and are called subcritical experiments. From end-to-end, the Cygnus machines utilize the following components: Marx generator, water-filled pulse-forming line (PFL), waterfilled coaxial transmission line (WTL), 3-cell inductive voltage adder (IVA), and rod-pinch diode. The upstream WTL interface to the PFL is via a radial insulator with coaxial geometry. The downstream WTL terminates in a manifold where the center conductor splits into three lines which individually connect to each of the IVA cell inputs. There is an impedance mismatch at this juncture. It is a concern that a reflected pulse due to anomalous behavior in the IVA or diode might initiate breakdown upon arrival at the upstream PFL/WTL insulator. Therefore near the beginning of the WTL a radial diverter switch is installed to protect the insulator from over voltage and breakdown. The diverter has adjustable gap spacing, and an in-line aqueous-solution (sodium thiosulfate) resistor array for energy dissipation. There are capacitive voltage probes at both ends of the WTL and on the diverter switch. These voltage signals will be analyzed to determine diverter performance. Using this analysis the usefulness of the diverter switch will be evaluated.

G. Corrow, M. Hansen, D. Henderson, C. Mitton et al.

2008-02-01

239

Organic optical bistable switch  

NASA Astrophysics Data System (ADS)

We demonstrate an organic optical bistable switch by integrating an efficient organic photodetector on top of a transparent electrophosphorescent organic light-emitting diode (TOLED). The bistability is achieved with an external field-effect transistor providing positive feedback. In the ``LOW'' state, the TOLED is off and the current in the photodetector is solely its dark current. In the ``HIGH'' state, the TOLED emits light that is directly coupled into the integrated photodetector through the transparent cathode. The photocurrent then is fed back to the TOLED, maintaining it in the HIGH state. The green electrophosphorescent material, fac tris(2-phenylpyridine) iridium [Ir(ppy)3] doped into a 4,4'-N,N'-dicarbazole-biphenyl host was used as the luminescent material in the TOLED, while alternating thin layers of copper phthalocyanine and 3,4,9,10-perylenetetracarboxylic bis-benzimidazole were used as the active region of the organic photodetector. The circuit has a 3 dB bandwidth of 25 kHz, and can be switched between HIGH and LOW using pulses as narrow as 60 ns. The bistable switch can be both electrically and optically reset, making it a candidate for image-retaining displays (e.g., electronic paper) and other photonic logic applications. The integrated organic device also has broad use as a linear circuit element in applications such as automatic brightness control.

Xue, Jiangeng; Forrest, Stephen R.

2003-01-01

240

Stochastic current switching behavior in semiconductor superlattices  

NASA Astrophysics Data System (ADS)

Numerical simulation results are presented for a discrete drift-diffusion model that describes electronic transport in weakly-coupled semiconductor superlattices under voltage bias and also includes shot noise in the tunneling currents. Sequential resonant tunneling between quantum wells is the primary conduction mechanism and noise terms are treated as delta-correlated in space and time. We study the response of this system to abrupt steps in applied voltage in a range for which the current-voltage characteristics exhibit bistability. The system switches from a metastable state to a stable state with a stochastically varying delay time, a process corresponding to relocation of charge density from one (critical) quantum well to an adjacent one. We find that the mean delay time ? varies as ?V - Vth^3/2 where V and Vth denote, respectively, the system voltage and the voltage at the boundary of the bistability range [1]; ? also depends exponentially on the cross-sectional area of the superlattice. An effective one-dimensional potential energy is constructed for the charge density in the critical quantum well. We find that noise contributions of the quantum wells far from the critical well have a significant effect on the switching process. [1] O. A. Tretiakov and K. A. Matveev, Phys. Rev. B. 71, 165326 (2005).

Teitsworth, Stephen; Xu, Huidong

2009-03-01

241

Photoconductive semiconductor switches: Laser Q-switch trigger and switch-trigger laser integration  

SciTech Connect

This report provides a summary of the Pulser In a Chip 9000-Discretionary LDRD. The program began in January of 1997 and concluded in September of 1997. The over-arching goal of this LDRD is to study whether laser diode triggered photoconductive semiconductor switches (PCSS) can be used to activate electro-optic devices such as Q-switches and Pockels cells and to study possible laser diode/switch integration. The PCSS switches we used were high gain GaAs switches because they can be triggered with small amounts of laser light. The specific goals of the LDRD were to demonstrate: (1) that small laser diode arrays that are potential candidates for laser-switch integration will indeed trigger the PCSS switch, and (2) that high gain GaAs switches can be used to trigger optical Q-switches in lasers such as the lasers to be used in the X-1 Advanced Radiation Source and the laser used for direct optical initiation (DOI) of explosives. The technology developed with this LDRD is now the prime candidate for triggering the Q switch in the multiple lasers in the laser trigger system of the X-1 Advanced Radiation Source and may be utilized in other accelerators. As part of the LDRD we developed a commercial supplier. To study laser/switch integration we tested triggering the high gain GaAs switches with: edge emitting laser diodes, vertical cavity surface emitting lasers (VCSELs), and transverse junction stripe (TJS) lasers. The first two types of lasers (edge emitting and VCSELs) did activate the PCSS but are harder to integrate with the PCSS for a compact package. The US lasers, while easier to integrate with the switch, did not trigger the PCSS at the US laser power levels we used. The PCSS was used to activate the Q-switch of the compact laser to be used in the X-1 Advanced Radiation Source.

Loubriel, G.M.; Mar, A.; Hamil, R.A.; Zutavern, F.J.; Helgeson, W.D.

1997-12-01

242

Atm switch for multi-media switching system  

Microsoft Academic Search

With the advance of the information-oriented society, research has been carried out on Broadband ISDN (B-ISDN) to enable flexible communication of various types of information, inclwiing voice, data and video. ATM is receiving much attention as a means of implementing B-ISDh? ATM is actualized by developing the self-routing switch for ATMswitching. The self-routing switch enables high-speed, highquality switching by hardware

Nobuya ARAKAWA; A. Noiri; H. Inoue

1990-01-01

243

Safety Eye Protection through Use of Fast Acting Optical Switching.  

National Technical Information Service (NTIS)

Due to the increasing use of lasers in military applications, along with their high power levels and short pulse times, there is a critical need for fast acting optical switches to protect the vision of personnel. Such devices must be economical, suitable...

R. Messier R. E. Newnham

1984-01-01

244

Microsecond plasma opening switches in externally applied magnetic field  

Microsoft Academic Search

The plasma opening switch (POS) is a key element producing nanosecond high-voltage pulses in many pulsed power systems using inductive energy storage. For POS experiments with microsecond conduction times described in the paper, an erosion regime is considered to be critical at the opening and power delivery phases. The technique to enhance the magnetic insulation of the POS gap and

Georgy I. Dolgachev; Andrey G. Ushakov

2006-01-01

245

Fault-Tolerant Array Processors Using Single-Track Switches  

Microsoft Academic Search

An array processor is a collection of many similar processing elements (PED's), which can be executed in both parallel and pipeline processing. For the implementation of arrays of large number of processors, fault tolerance has always been a very critical design issue. Very often, spare PE's and switching lattices are incorporated in the array to improve the (fabrication-time) yield and

Sun-yuan Kung; Shiann-ning Jean; Chih-wei Jim Chang

1989-01-01

246

Characterization, numerical analysis, and design of switched reluctance motors  

Microsoft Academic Search

Material productivity, design preciseness, and time to market are becoming critical in motor manufacturing and can be improved by detailed system design analysis and simulation within manufacturing tolerance. Design by analysis and simulation of switched reluctance motor (SRM) systems and the development method of a new design software are the subjects of this paper, with a focus on the main

Yifan Tang

1997-01-01

247

Task switching and the measurement of "switch costs".  

PubMed

The measurement of "switch costs" is held to be of interest because, as is widely believed, they may reflect the control processes that are engaged when subjects switch between two (or more) competing tasks. [In task-switching experiments, the reaction time (RT) switch cost is typically measured as the difference in RT between switch and non-switch (repeat) trials.] In this report we focus on the RT switch costs that remain even after the subject has had some time to prepare for the shift of task, when the switch cost may be approximately asymptotic (so-called residual switch costs). Three experiments are presented. All three experiments used Stroop colour/word, and neutral stimuli. Participants performed the two tasks of word-reading and colour-naming in a regular, double alternation, using the "alternating runs" paradigm (R. D. Rogers & S. Monsell, 1995). The experiments were designed to test the hypothesis that RT switch costs depend on a form of proactive interference (PI) arising from the performance of a prior, competing task. A. Allport, E. A. Styles and S. Hsieh (1994) suggested that these PI effects resulted from "task-set inertia", that is, the persisting activation-suppression of competing task-sets, or competing task-processing pathways. The results confirmed the existence of long-lasting PI from the competing task as a major contributor to switch costs. Non-switch trials, used as the baseline in the measurement of switch costs, were also shown to be strongly affected by similar PI effects. However, task-set inertia was not sufficient to account for these results. The results appeared inconsistent also with all other previous models of task switching. A new hypothesis to explain these between-task interference effects was developed, based on the stimulus-triggered retrieval of competing stimulus-response (S-R) associations, acquired (or strengthened) in earlier trials. Consistent with this retrieval hypothesis, switch costs were shown to depend primarily on the S-R characteristics of the preceding task (the task that was switched from) rather than the upcoming task. Further, the effects of the other, competing task were found to persist over many successive switching trials, affecting switch costs long after the stimulus overlap (and hence the principal S-R competition) between the current tasks had been removed. Switch costs were also found to be affected by recent, item-specific experience with a given stimulus, in either the same or the competing task. Finally, the results showed that switch costs were massively affected by the ratio of the number of prior trials, in response to the same stimuli, that had implemented either the currently intended or the competing S-R mappings. None of these effects are predicted by current models of residual switch costs, which appeal to the differences in control processes assumed to be engaged in switch versus non-switch trials. PMID:11004877

Wylie, G; Allport, A

2000-01-01

248

Effects of mace (Myristica fragrans, Houtt.) on cytosolic glutathione S-transferase activity and acid soluble sulfhydryl level in mouse liver.  

PubMed

The aril of plant Myristica fragrans Houtt. commonly known as mace, which is consumed as a spice as well as used as a folk-medicine, was screened for its effects on the levels of cytosolic glutathione S-transferase (GST) and acid-soluble sulfhydryl (SH) groups in the liver of young adult male and female Swiss albino mice. Animals were assorted into 4 groups comprised of either sex and received either normal diet (negative control), 1% 2,3-tert-butyl-4-hydroxyanisole (BHA) diet (positive control), 1% mace diet or 2% mace diet for 10 days. There was a significant increase in the GST activity in the liver of mice exposed to BHA or mace. In addition, there was a significant increase in the SH content in the liver of mice fed on 1% BHA and 2% mace diets. PMID:2752386

Kumari, M V; Rao, A R

1989-07-15

249

DNA-Controlled Excitonic Switches  

PubMed Central

Fluorescence resonance energy transfer (FRET) is a promising means of enabling information processing in nanoscale devices, but dynamic control over exciton pathways is required. Here, we demonstrate the operation of two complementary switches consisting of diffusive FRET transmission lines in which exciton flow is controlled by DNA. Repeatable switching is accomplished by the removal or addition of fluorophores through toehold-mediated strand invasion. In principle, these switches can be networked to implement any Boolean function.

2012-01-01

250

Dilated Networks for Photonic Switching  

Microsoft Academic Search

We present some novel architectures for rearrangeably nonblocking multistage photonic space switches implemented using arrays ofTi:LiNbO_{3}directional couplers. Multistage networks, studied mostly in the electronic domain, are obtained by minimizing the number of 2 × 2 elements needed to implement a switch. Unfortunately, straightforward extensions of these networks to the photonic domain show that the switch size has to be severely

K. Padmanabhan; A. Netravali

1987-01-01

251

Switching for electric rail guns  

Microsoft Academic Search

The switching requirements of single-stage electric railguns powered by inductive energy stores are analyzed, and the design of a 500-kA commutation switch is shown. The closed, commutation, and off states of the switch and the reclosure function at the end of the projectile acceleration are discussed in general terms, and the specific requirements of the railgun facility at Australian National

J. P. Barber; D. P. Bauer

1984-01-01

252

Virtual service switch  

US Patent & Trademark Office Database

Virtual service switching includes contracting to provide a requestor with a unit of computing capacity to a service within a specific time period, creating one or more plans based at least in part on the contracting, scheduling execution of the one or more plans using the computing capacity, and if a bid for at least part of the unit of computing capacity is received prior to the end of the specific time period, allocating at least part of the computing capacity based at least in part on the bid. Each of the one or more plans comprises software code and associated data.

Cohen; David (Ridgewood, NJ); Younan; James (Warwick, NY)

2013-10-22

253

Controlled access ATM switch  

US Patent & Trademark Office Database

An asynchronous transfer mode (ATM) switch in which access to a switchcore matrix is monitored and controlled through the logic and buffering functions of switchports connected thereto. The switchcore is greatly simplified by moving the logic and buffering functions to the switchports. The switchcore matrix comprises a plurality of rows, columns, and crosspoints thereof, providing routing paths for the routing of information cells from input points to output points on the matrix. Single-cell buffers in the switchcore matrix enable temporary storage and hand-off of individual information cells as they pass through the matrix. The simplicity of the switchcore matrix enables it to be constructed on a single integrated circuit.

Petersen; Lars-Goran (Tumba, SE)

1995-11-14

254

Neutron activated switch  

DOEpatents

A switch for reacting quickly to a neutron emission. A rod consisting of fissionable material is located inside a vacuum tight body. An adjustable contact is located coaxially at an adjustable distance from one end of the rod. Electrical leads are connected to the rod and to the adjustable contact. With a vacuum drawn inside the body, a neutron bombardment striking the rod causes it to heat and expand longitudinally until it comes into contact with the adjustable contact. This circuit closing occurs within a period of a few microseconds.

Barton, David M. (Espanola, NM)

1991-01-01

255

Neutron activated switch  

DOEpatents

A switch for reacting quickly to a neutron emission in which a rod consisting of a rod of fissionable material inside a vacuum tight body. An adjustable contact is located coaxially an adjustable distance from one end of the rod. Electrical leads are connected to the rod and to the adjustable contact. With a vacuum drawn inside the body, a neutron bombardment striking the rod will cause it to heat and expand longitudinally until it comes into contact with the adjustable contact. This closing occurs within a period of a few microseconds. 2 figs.

Barton, D.M.

1989-10-30

256

Thinking Critically about Critical Thinking  

ERIC Educational Resources Information Center

|As a philosophy professor, one of my central goals is to teach students to think critically. However, one difficulty with determining whether critical thinking can be taught, or even measured, is that there is widespread disagreement over what critical thinking actually is. Here, I reflect on several conceptions of critical thinking, subjecting…

Mulnix, Jennifer Wilson

2012-01-01

257

The respiratory burst and electrolyte leakage induced by sulfhydryl blockers in egeria densa leaves are associated with H2O2 production and are dependent on Ca2+ influx  

PubMed

In leaves of Egeria densa Planchon, N-ethylmaleimide (NEM) and other sulfhydryl-binding reagents induce a temporary increase in nonmitochondrial respiration (DeltaQO2) that is inhibited by diphenylene iodonium and quinacrine, two known inhibitors of the plasma membrane NADPH oxidase, and are associated with a relevant increase in electrolyte leakage (M. Bellando, S. Sacco, F. Albergoni, P. Rocco, M.T. Marre [1997] Bot Acta 110: 388-394). In this paper we report data indicating further analogies between the oxidative burst induced by sulfhydryl blockers in E. densa and that induced by pathogen-derived elicitors in animal and plant cells: (a) NEM- and Ag+-induced DeltaQO2 was associated with H2O2 production and both effects depended on the presence of external Ca2+; (b) Ca2+ influx was markedly increased by treatment with NEM; (c) the Ca2+ channel blocker LaCl3 inhibited DeltaQO2, electrolyte release, and membrane depolarization induced by the sulfhydryl reagents; and (d) LaCl3 also inhibited electrolyte leakage induced by the direct infiltration of the leaves with H2O2. These results suggest a model in which the interaction of sulfhydryl blockers with sulfhydryl groups of cell components would primarily induce an increase in the Ca2+ cytosolic concentration, followed by membrane depolarization and activation of a plasma membrane NADPH oxidase. This latter effect, producing active oxygen species, might further influence plasma membrane permeability, leading to the massive release of electrolytes from the tissue. PMID:9847112

Marre; Amicucci; Zingarelli; Albergoni; Marre

1998-12-01

258

Optical switch based on thermocapillarity  

NASA Astrophysics Data System (ADS)

Space-division optical switches are essential for the protection, optical cross-connects (OXCs), and optical add/drop multiplexers (OADMs) needed in future fiber-optic communication networks. For applications in these areas, we proposed a thermocapillarity switch called oil-latching interfacial-tension variation effect (OLIVE) switch. An OLIVE switch is a micro-mechanical optical switch fabricated on planar lightwave circuits (PLC) using micro-electro-mechanical systems (MEMS) technology. It consists of a crossing waveguide that has a groove at each crossing point and a pair of microheaters. The groove is partially filled with the refractive-index-matching liquid, and optical signals are switched according to the liquid's position in the groove, i.e., whether it is passing straight through the groove or reflecting at the sidewall of the groove. The liquid is driven by thermocapillarity and latched by capillarity. Using the total internal reflection to switch the optical path, the OLIVE switch exhibits excellent optical characteristics, such as high transparency (insertion loss: < 2 dB), high extinction ratio (> 50 dB), and low crosstalk (< -50 dB). Moreover, since this switch has a simple structure and bi-stability, it has wide variety of applications in wavelength division multiplexing (WDM) networks.

Sakata, Tomomi; Makihara, Mitsuhiro; Togo, Hiroyoshi; Shimokawa, Fusao; Kaneko, Kazumasa

2001-11-01

259

Modeling of rf MEMS switches  

NASA Astrophysics Data System (ADS)

The microelectromechanical system (MEMS) switch offers many benefits in radio frequency (RF) applications. These benefits include low insertion loss, high quality factor (Q), low power, RF isolation, and low cost. The ability to manufacture mechanical switches on a chip with electronics can lead to higher functionality, such as single-chip arrays, and smart switches. The MEMS switch is also used as a building block in devices such as phase shifters, filters, and switchable antenna elements. The MEMS designer needs models of these basic elements in order to incorporate them into their applications. The objective of this effort is to develop lumped element models for MEMS RF switches, which are incorporated into a CAD software. Tanner Research Inc.'s Electronic Design Automation (EDA) software is being used to develop a suite of mixed-signal RF switch models. The suite will include switches made from cantilever beams and fixed-fixed beams. The switches may be actuated by electrostatic, piezoelectric or electromagnetic forces. The effort presented in this paper concentrates on switches actuated by electrostatic forces. The lumped element models use a current-force electrical-mechanical analogy. Finite element modeling and device testing will be used to verify the Tanner models. The effects of materials, geometries, temperature, fringing fields, and mounting geometries are considered.

Robertson, Barbara; Ho, Fat D.; Hudson, Tracy D.

2001-10-01

260

Characteristics of micromachined switches at microwave frequencies  

Microsoft Academic Search

This article reviews the fundamental characteristics of micromechanical membrane switches operating at microwave frequencies. The construction and theory of operation of capacitive membrane switches is reviewed. Measurement and modeling of the electromechanical and microwave properties of these switches are presented. The inherent advantages of these switches relative to semiconductor switches is discussed

C. Goldsmith; J. Randall; S. Eshelman; T. H. Lin; D. Denniston; S. Chen; B. Norvell

1996-01-01

261

Switching Systems: Controllability and Control Design.  

National Technical Information Service (NTIS)

We consider two classes of switches: switches-on-time and switches- on-state. Switching-on-time is the simplest of the two and it can be considered as an intrinsic (or endogenous) switching scheme in the sense that it involves only changes in the tangent ...

J. Bokor P. Gaspar Z. Szabo

2009-01-01

262

Optical switch evaluation support  

NASA Astrophysics Data System (ADS)

Extensive testing has been done on nonlinear interface optical switch (NIOS) devices fabricated from laser deposited nonstoichiometric tungsten oxide films. A Fresnel coefficient formalism for evaluating the indices of refraction of the films has been developed. Three cycles of testing involving changing the tungsten-oxygen stoichiometry have not produced extremely large photorefractive effects. It was decided, after using a mathematical model to determine the required incident and reflection angles, to make the next set of NIOS devices from a film deposited on ZnS prisms. ZnS more closely matches the low light intensity index of the films. Preliminary studies of further changes to produce stronger nonlinearity have been performed. Raman spectroscopy showed that these films heated in oxygen organize themselves into octohedra, which are thought to be necessary for the photorefractive effects observed in titanates and niobates. Heating the films in vacuum produces blue films which ESCA shows contain tungsten in the +4 oxidation state. Such electron rich species might be able to provide highly polarizable charge carriers. In addition to use as optical switches, use of these films to make reconfigurable Dammann gratings has been studied. These gratings would allow optical addressing of large size S-SEED arrays.

Chaiken, Joseph

1993-07-01

263

Code-switching effects in bilingual word recognition  

PubMed Central

Two experiments tested language switching effects with bilingual participants in a priming paradigm with masked primes (duration of 50 ms in Experiment 1 and 100 ms in Experiment 2). Participants had to monitor target words for animal names, and ERPs were recorded to critical (non-animal) words in L1 and L2 primed by unrelated words from the same or the other language. Both experiments revealed language priming (switching) effects that depended on target language. For target words in L1, most of the language switch effect appeared in the N400 ERP component, with L2 primes generating a more negative going wave than L1 primes. For L2 target words, on the other hand, the effects of a language switch appeared mainly in an earlier ERP component (N250) peaking at approximately 250 ms post-target onset, and showing greater negativity following an L1 prime than an L2 prime. This is the first evidence for fast-acting language-switching effects occurring in the absence of overt task switching.

Chauncey, Krysta; Grainger, Jonathan; Holcomb, Phillip J.

2009-01-01

264

Optimal control of switching times in switched dynamical systems  

Microsoft Academic Search

This paper considers an optimal control problem for switched dynamical systems, where the objective is to minimize a cost functional defined on the state, and where the control variable consists of the switching times. The gradient of the cost functional is derived on an especially simple form, which lends itself to be directly used in gradient-descent algorithms. This special structure

M. Egerstedt; Y. Wardi; F. Delmotte

2003-01-01

265

Tuning the temperature dependence for switching in dithienylethene photochromic switches.  

PubMed

Diarylethene photochromic switches use light to drive structural changes through reversible electrocyclization reactions. High efficiency in dynamic photoswitching is a prerequisite for applications, as is thermal stability and the selective addressability of both isomers ring-opened and -closed diarylethenes. These properties can be optimized readily through rational variation in molecular structure. The efficiency with regard to switching as a function of structural variation is much less understood, with the exception of geometric requirements placed on the reacting atoms. Ultimately, increasing the quantum efficiency of photochemical switching in diarylethenes requires a detailed understanding of the excited-state potential energy surface(s) and the mechanisms involved in switching. Through studies of the temperature dependence, photoswitching and theoretical studies demonstrate the occurrence or absence of thermal activation barriers in three constitutional isomers that bear distinct ?-conjugated systems. We found that a decrease in the thermal barriers correlates with an increase in switching efficiency. The origin of the barriers is assigned to the decrease in ?-conjugation that is concomitant with the progress of the photoreaction. Furthermore, we show that balanced molecular design can minimize the change in the extent of ?-conjugation during switching and lead to optimal bidirectional switching efficiencies. Our findings hold implications for future structural design of diarylethene photochromic switches. PMID:23889496

Kudernac, Tibor; Kobayashi, Takao; Uyama, Ayaka; Uchida, Kingo; Nakamura, Shinichiro; Feringa, Ben L

2013-08-16

266

Switching behavior of a magnetically controlled superconducting switch  

SciTech Connect

This paper describes experimental and theoretical considerations of the switching behavior of a magnetically controlled superconducting switch. The experimental superconducting switch used in the experiments is composed of a superconducting gate wire (NbZr/CuNi) and a superconducting field coil (NbTi/CuNi). The experimental circuit is that the switch is connected to a load resistor and a constant current source in parallel. The experimental results show: During the switching process, where the field current increases and decreases, the gate wire has two resistive states. In one state, the gate current is determined by the field current. In the other state, the gate wire may be in the flux-flow state.

Nitta, T.; Nakata, M.; Okada, T. (Dept. of Electrical Engineering, Kyoto Univ., Yoshida-Honmachi, Kyoto 606 (JP))

1992-01-01

267

Switching languages, switching palabras (words): an electrophysiological study of code switching.  

PubMed

Switching languages has often been associated with a processing cost. In this study, the authors used event-related potentials to compare switches between two languages with within-language lexical switches as bilinguals read for comprehension. Stimuli included English sentences and idioms ending either with the expected English words, their Spanish translations (code switches), or English synonyms (lexical switches). As expected, lexical switches specifically enhanced the N400 response in both context types. Code switches, by contrast, elicited an increased negativity over left fronto-central sites in the regular nonidiomatic sentences (250-450 ms) and a large posterior positivity (450-850 ms) in both context types. In addition, both lexical and code switches elicited a late frontal positivity (650-850 ms) relative to expected completions, especially in idioms. Analysis of the individual response patterns showed correlations with vocabulary skills in English and in Spanish. Overall, the electrophysiological data suggest that for some speakers in some contexts, the processing of a code switch may actually be less costly than the processing of an unexpected within-language item. PMID:11827443

Moreno, Eva M; Federmeier, Kara D; Kutas, Marta

2002-02-01

268

Critical Care  

MedlinePLUS

Critical care helps people with life-threatening injuries and illnesses. It might treat problems such as complications from surgery, ... attention by a team of specially-trained health care providers. Critical care usually takes place in an ...

269

Switch evaluation test system for the National Ignition Facility  

SciTech Connect

Flashlamp pumped lasers use pulsed power switches to commute energy stored in capacitor banks to the flashlamps. The particular application in which the authors are interested is the National Ignition Facility (NIF), being designed by Lawrence Livermore National Laboratory, Los Alamos National Laboratory, and Sandia National Laboratories (SNL). To lower the total cost of these switches, SNL has a research program to evaluate large closing switches. The target value of the energy switched by a single device is 1.6 MJ, from a 6 mF, 24kV capacitor bank. The peak current is 500 kA. The lifetime of the NIF facility is 24,000 shots. There is no switch today proven at these parameters. Several short-lived switches (100`s of shots) exist that can handle the voltage and current, but would require maintenance during the facility life. Other type devices, notably ignitrons, have published lifetimes in excess of 20,000 shots, but at lower currents and shorter pulse widths. The goal of the experiments at SNL is to test switches with the full NIF wave shape, and at the correct voltage. The SNL facility can provide over 500 kA at 24 kV charge voltage. the facility has 6.4 mF total capacitance, arranged in 25 sub-modules. the modular design makes the facility more flexible (for possible testing at lower current) and safer. For pulse shaping (the NIF wave shape is critically damped) there is an inductor and resistor for each of the 25 modules. Rather than one large inductor and resistor, this lowers the current in the pulse shaping components, and raises their value to those more easily attained with lumped inductors and resistors. The authors show the design of the facility, and show results from testing conducted thus far. They also show details of the testing plan for high current switches.

Savage, M.E.; Simpson, W.W. [Sandia National Labs., Albuquerque, NM (United States). High Energy Plasma Physics Dept.; Sharpe, R.A. [Sandia National Labs., Albuquerque, NM (United States). High Energy Plasma Physics Dept.]|[Ktech Corp., Albuquerque, NM (United States); Reynolds, F.D. [Sandia National Labs., Albuquerque, NM (United States). High Energy Plasma Physics Dept.]|[Tektronix, Inc., Albuquerque, NM (United States)

1997-07-01

270

Magnetically insulated opening switch research  

Microsoft Academic Search

We examine the feasibility of an opening switch concept based on magnetic insulation in a coaxial thermionic diode. It is found that the impedance ratio between closed and open states of the diode is marginal for efficient energy transfer via this type of switch. The open, or insulated state of the diode is characterized by current leakage across the magnetic

M. W. McGeoch; R. Kraft

1987-01-01

271

SwitchEnsemble [music program  

Microsoft Academic Search

SwitchEnsemble is a music performance program written for the Apple IIGS. It provides a large variety of age-appropriate activities for students with a broad range of physical and cognitive abilities. SwitchEnsemble makes full use of the exceptional graphics and sound capabilities of the IIGS and it supports a wide variety of input devices

J. Adams

1992-01-01

272

Nonpreemptive Scheduling of Optical Switches  

Microsoft Academic Search

Many high-speed routers today use Input-Queued (IQ) architectures with a crossbar switching fabric based on op- tical technology. Packets in the input queues are divided into cells of unit length and the goal is to find a schedule of minimum makespan that forwards all packets to the output ports. The prob- lem is complicated since in optical switches so called

Alexander Kesselman; Kirill Kogan

2007-01-01

273

Task switching and multitask performance  

Microsoft Academic Search

ABSTRACT Research on task ,switching and dual-task performance ,has spawned ,two lit- eratures that have, to a surprising extent, developed independently. This tutorial reviews the principal findings of each ,tradition and considers how ,these phenomena ,may ,be related. Beginning with Jersild 1927, task-switching studies reveal that when people perform two tasks in succession, with each task requiring different responses to

H. Pashler

2000-01-01

274

Lattice-switch Monte Carlo  

Microsoft Academic Search

We present a Monte Carlo method for the direct evaluation of the differ- ence between the free energies of two crystal structures. The method is built on a lattice-switch transformation that maps a configuration of one structure onto a candidate configuration of the other by 'switching' one set of lattice vectors for the other, while keeping the displacements with respect

A. D. Bruce; A. N. Jackson; G. J. Ackland; N. B. Wilding

275

Globalization Drives Strategic Product Switching  

Microsoft Academic Search

Using firm-level data for Estonia for the years 1997-2005, we analyze the impact of international competition on firm dynamics, considering both firm closedown and product switching. We contribute to the literature in two important ways: (1) this is the first paper to study the determinants of exit and product switching in an emerging market; and (2) we consider explicitly the

Marialuz Moreno Badia; Veerle Slootmaekers; Ilke Van Beveren

2008-01-01

276

Battery switch for downhole tools  

DOEpatents

An electrical circuit for a downhole tool may include a battery, a load electrically connected to the battery, and at least one switch electrically connected in series with the battery and to the load. The at least one switch may be configured to close when a tool temperature exceeds a selected temperature.

Boling, Brian E. (Sugar Land, TX)

2010-02-23

277

Breathalyzer enabled ignition switch system  

Microsoft Academic Search

Breath alcohol detector or better known as breathalyzer plays a vital role in monitoring alcohol concentration in a person's bloodstream. This project involves the design and development of breathalyzer device which controls ignition switch. The hardware modules include the PIC16F877A microcontroller, alcohol sensor, LCD panel and ignition switch circuitry. The software component includes the programming and source code which is

H. Abdul Rahim; S. D. S. Hassan

2010-01-01

278

Satellite Up Link Diversity Switch.  

National Technical Information Service (NTIS)

The patent application relates to a satellite up link diversity switch system. A beacon or reference signal is received from the satellite at two locations separated in an east-west direction. Diversity logic compares the two signals received and switches...

P. W. Baver

1976-01-01

279

Phenotypic switching in bacteria  

NASA Astrophysics Data System (ADS)

Living matter is a non-equilibrium system in which many components work in parallel to perpetuate themselves through a fluctuating environment. Physiological states or functionalities revealed by a particular environment are called phenotypes. Transitions between phenotypes may occur either spontaneously or via interaction with the environment. Even in the same environment, genetically identical bacteria can exhibit different phenotypes of a continuous or discrete nature. In this thesis, we pursued three lines of investigation into discrete phenotypic heterogeneity in bacterial populations: the quantitative characterization of the so-called bacterial persistence, a theoretical model of phenotypic switching based on those measurements, and the design of artificial genetic networks which implement this model. Persistence is the phenotype of a subpopulation of bacteria with a reduced sensitivity to antibiotics. We developed a microfluidic apparatus, which allowed us to monitor the growth rates of individual cells while applying repeated cycles of antibiotic treatments. We were able to identify distinct phenotypes (normal and persistent) and characterize the stochastic transitions between them. We also found that phenotypic heterogeneity was present prior to any environmental cue such as antibiotic exposure. Motivated by the experiments with persisters, we formulated a theoretical model describing the dynamic behavior of several discrete phenotypes in a periodically varying environment. This theoretical framework allowed us to quantitatively predict the fitness of dynamic populations and to compare survival strategies according to environmental time-symmetries. These calculations suggested that persistence is a strategy used by bacterial populations to adapt to fluctuating environments. Knowledge of the phenotypic transition rates for persistence may provide statistical information about the typical environments of bacteria. We also describe a design of artificial genetic networks that would implement a more general theoretical model of phenotypic switching. We will use a new cloning strategy in order to systematically assemble a large number of genetic features, such as site-specific recombination components from the R64 plasmid, which invert several coexisting DNA segments. The inversion of these segments would lead to discrete phenotypic transitions inside a living cell. These artificial phenotypic switches can be controlled precisely in experiments and may serve as a benchmark for their natural counterparts.

Merrin, Jack

280

Fault Protection Circuit for Power Switching Device.  

National Technical Information Service (NTIS)

A fault protection circuit for a power switching device. The circuit comprises a driver circuit electrically connected to the power switching device, a saturation comparator electrically connected to the collector of the switching device to determine if t...

J. R. Raposa

1994-01-01

281

Switching Inverter with Sine-Wave Output.  

National Technical Information Service (NTIS)

A relatively simple method of obtaining a multiple-stepped sine-wave output using semiconductor devices as switches was developed. This circuit employs Triacs as power switches, requiring approximately one-fourth the number of switches normally required b...

J. M. Marzolf

1970-01-01

282

49 CFR 236.820 - Switch, interlocked.  

Code of Federal Regulations, 2011 CFR

... 4 2011-10-01 2011-10-01 false Switch, interlocked. 236.820 Section 236.820...DEVICES, AND APPLIANCES Definitions § 236.820 Switch, interlocked. A switch within the interlocking limits the control of...

2011-10-01

283

49 CFR 236.820 - Switch, interlocked.  

Code of Federal Regulations, 2012 CFR

... 4 2012-10-01 2012-10-01 false Switch, interlocked. 236.820 Section 236.820...DEVICES, AND APPLIANCES Definitions § 236.820 Switch, interlocked. A switch within the interlocking limits the control of...

2012-10-01

284

14 CFR 23.1145 - Ignition switches.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 2013-01-01 false Ignition switches. 23.1145 Section 23.1145 Aeronautics...Controls and Accessories § 23.1145 Ignition switches. (a) Ignition switches must control and shut off each ignition...

2013-01-01

285

30 CFR 77.1800 - Cutout switches.  

Code of Federal Regulations, 2013 CFR

... 2013-07-01 false Cutout switches. 77.1800 Section 77.1800...Feeder Wires § 77.1800 Cutout switches. Trolley wires and trolley feeder wires shall be provided with cutout switches at intervals of not more than...

2013-07-01

286

14 CFR 25.1145 - Ignition switches.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 2013-01-01 false Ignition switches. 25.1145 Section 25.1145 Aeronautics...Controls and Accessories § 25.1145 Ignition switches. (a) Ignition switches must control each engine ignition circuit on...

2013-01-01

287

14 CFR 29.1145 - Ignition switches.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 2013-01-01 false Ignition switches. 29.1145 Section 29.1145 Aeronautics...Controls and Accessories § 29.1145 Ignition switches. (a) Ignition switches must control each ignition circuit on each...

2013-01-01

288

46 CFR 111.105-19 - Switches.  

Code of Federal Regulations, 2012 CFR

...Shipping 4 2012-10-01 2012-10-01 false Switches. 111.105-19 Section 111.105-19 Shipping...REQUIREMENTS Hazardous Locations § 111.105-19 Switches. A switch that is explosionproof or flameproof, or...

2012-10-01

289

Chemical Structure and Molecular Switches.  

NASA Astrophysics Data System (ADS)

The future of molecular electronics depends on designing molecules to exhibit specific nonlinear properties such as rectification or bistable switching. In pursuit of this goal, two distinct types of switching were observed in matrix isolated and complete monolayers of bipyridyl-dinitro-oligophenylene-ethynylene (BPDN). Several groups have observed conductance state switching in this molecule. However, the mechanism of switching between the two conductance states is still not understood. Using BPDN as a starting point, chemically related structures such as bipyridyl- oligophenylene-ethynylene, dinitro-oligophenylene-ethynylene, and biphenyl- oligophenylene-ethynylene were measured in matrix isolated monolayers. By means of such comparisons to related molecules, we determine the key functional groups leading to switching in BPDN.

Blum, Amy; Long, David; Moore, Martin; Kushmerick, James; Tour, James; Ratna, Banahalli

2008-03-01

290

Optimized scalable network switch  

DOEpatents

In a massively parallel computing system having a plurality of nodes configured in m multi-dimensions, each node including a computing device, a method for routing packets towards their destination nodes is provided which includes generating at least one of a 2m plurality of compact bit vectors containing information derived from downstream nodes. A multilevel arbitration process in which downstream information stored in the compact vectors, such as link status information and fullness of downstream buffers, is used to determine a preferred direction and virtual channel for packet transmission. Preferred direction ranges are encoded and virtual channels are selected by examining the plurality of compact bit vectors. This dynamic routing method eliminates the necessity of routing tables, thus enhancing scalability of the switch.

Blumrich, Matthias A. (Ridgefield, CT); Chen, Dong (Croton On Hudson, NY); Coteus, Paul W. (Yorktown Heights, NY); Gara, Alan G. (Mount Kisco, NY); Giampapa, Mark E. (Irvington, NY); Heidelberger, Philip (Cortlandt Manor, NY); Steinmacher-Burow, Burkhard D. (Mount Kisco, NY); Takken, Todd E. (Mount Kisco, NY); Vranas, Pavlos M. (Bedford Hills, NY)

2007-12-04

291

A Reversibly Switching Surface  

NASA Astrophysics Data System (ADS)

We report the design of surfaces that exhibit dynamic changes in interfacial properties, such as wettability, in response to an electrical potential. The change in wetting behavior was caused by surface-confined, single-layered molecules undergoing conformational transitions between a hydrophilic and a moderately hydrophobic state. Reversible conformational transitions were confirmed at a molecular level with the use of sum-frequency generation spectroscopy and at a macroscopic level with the use of contact angle measurements. This type of surface design enables amplification of molecular-level conformational transitions to macroscopic changes in surface properties without altering the chemical identity of the surface. Such reversibly switching surfaces may open previously unknown opportunities in interfacial engineering.

Lahann, Joerg; Mitragotri, Samir; Tran, Thanh-Nga; Kaido, Hiroki; Sundaram, Jagannathan; Choi, Insung S.; Hoffer, Saskia; Somorjai, Gabor A.; Langer, Robert

2003-01-01

292

Experiments in magnetic switching  

SciTech Connect

Magnetic switching offers an alternative to overcoming the rep-rate and life limitations of the spark gaps in the ETA/ATA induction accelerators. The principle has been applied for many years to radar modulators but at much lower power levels and longer pulse lengths. Comparatively recent developments in magnetic materials together with some optimal circuits have made it possible to go well beyond the state of the art. A magnetic modulator has been built which steps up and compresses a 25 kV, 5 ..mu..s pulse into a 250 kV, 50 ns pulse. A second magnetic modulator has been built and installed to replace four Blumleins and spark gaps in order to provide triggers for the complete ETA injector and accelerator. The paper outlines some practical and theoretical considerations affecting the design of the magnetic pulse generator.

Birx, D.L.; Lauer, E.J.; Reginato, L.L.; Rogers, D. Jr.; Smith, M.W.; Zimmerman, T.

1981-05-29

293

Optimized scalable network switch  

SciTech Connect

In a massively parallel computing system having a plurality of nodes configured in m multi-dimensions, each node including a computing device, a method for routing packets towards their destination nodes is provided which includes generating at least one of a 2m plurality of compact bit vectors containing information derived from downstream nodes. A multilevel arbitration process in which downstream information stored in the compact vectors, such as link status information and fullness of downstream buffers, is used to determine a preferred direction and virtual channel for packet transmission. Preferred direction ranges are encoded and virtual channels are selected by examining the plurality of compact bit vectors. This dynamic routing method eliminates the necessity of routing tables, thus enhancing scalability of the switch.

Blumrich, Matthias A. (Ridgefield, CT); Chen, Dong (Croton on Hudson, NY); Coteus, Paul W. (Yorktown Heights, NY)

2010-02-23

294

Radically enhanced molecular switches.  

PubMed

The mechanism governing the redox-stimulated switching behavior of a tristable [2]rotaxane consisting of a cyclobis(paraquat-p-phenylene) (CBPQT(4+)) ring encircling a dumbbell, containing tetrathiafulvalene (TTF) and 1,5-dioxynaphthalene (DNP) recognition units which are separated from each other along a polyether chain carrying 2,6-diisopropylphenyl stoppers by a 4,4'-bipyridinium (BIPY(2+)) unit, is described. The BIPY(2+) unit acts to increase the lifetime of the metastable state coconformation (MSCC) significantly by restricting the shuttling motion of the CBPQT(4+) ring to such an extent that the MSCC can be isolated in the solid state and is stable for weeks on end. As controls, the redox-induced mechanism of switching of two bistable [2]rotaxanes and one bistable [2]catenane composed of CBPQT(4+) rings encircling dumbbells or macrocyclic polyethers, respectively, that contain a BIPY(2+) unit with either a TTF or DNP unit, is investigated. Variable scan-rate cyclic voltammetry and digital simulations of the tristable and bistable [2]rotaxanes and [2]catenane reveal a mechanism which involves a bisradical state coconformation (BRCC) in which only one of the BIPY(•+) units in the CBPQT(2(•+)) ring is oxidized to the BIPY(2+) dication. This observation of the BRCC was further confirmed by theoretical calculations as well as by X-ray crystallography of the [2]catenane in its bisradical tetracationic redox state. It is evident that the incorporation of a kinetic barrier between the donor recognition units in the tristable [2]rotaxane can prolong the lifetime and stability of the MSCC, an observation which augurs well for the development of nonvolatile molecular flash memory devices. PMID:23002805

Fahrenbach, Albert C; Zhu, Zhixue; Cao, Dennis; Liu, Wei-Guang; Li, Hao; Dey, Sanjeev K; Basu, Subhadeep; Trabolsi, Ali; Botros, Youssry Y; Goddard, William A; Stoddart, J Fraser

2012-09-24

295

Critical Thinking vs. Critical Consciousness  

ERIC Educational Resources Information Center

|This article explores four kinds of critical thinking. The first is found in Socratic dialogues, which employ critical thinking mainly to reveal logical fallacies in common opinions, thus cleansing superior minds of error and leaving philosophers free to contemplate universal verities. The second is critical interpretation (hermeneutics) which…

Doughty, Howard A.

2006-01-01

296

Foil fuses as opening switches for slow discharge circuits  

SciTech Connect

Metal foil fuses embedded in various materials are widely used as opening switches in fast discharge circuits (approx.1 ..mu..s). Several technologies of current interest require opening switches in circuits which operate on a much longer time scale (approx.100 ..mu..s). We have investigated the behavior of aluminum and copper foil fuses for conduction times of 100 to 200 ..mu..s. Reliable current interruption is obtained at the end of melting rather than at the end of vaporization. The ratio of initial to final resistance is >100. In general, the performance of slow fuses can be predicted by simple scaling from fast fuse behavior. For applications where the switching function depends critically on the resistivity versus input energy characteristic, the results presented can be used in the selection of proper fuse size and geometry.

Parker, J.V.; Parsons, W.M.

1985-01-01

297

Novel synchronization technique for two parallel connected sparkgap switches.  

PubMed

In this article a novel way of synchronizing two parallel connected sparkgap switches with accuracies of 1-5 ns for high frequency pulsed power applications is described. The circuit design of a synchronized sparkgap switch circuit is discussed. The circuit uses a combination of one master sparkgap and a set of inductor and capacitors to synchronize two sparkgaps and can be controlled via an IGBT switch. Critical issues for circuit design are presented together with analytical calculations and simulations. Experimental verification of the novel topology is carried out in a prototype experimental setup. Results showing nanosecond level of accuracy in synchronization are reported in this paper along with simulations and analysis. PMID:22938319

Kumar, Rohit; Mitra, S; Patel, A; Dwivedi, Rajesh; Kolge, T; Sharma, Ranjeet Archana; Chakravarthy, D P

2012-08-01

298

Interferometric activated X switch: IAX  

Microsoft Academic Search

High-speed phase-linear switching with low crosstalk is accomplished by using balanced bridge interferometric switches with electrooptic tunable X couplers. The devices are fabricated by titanium indiffusion into X-cut, Y-propagating LiNbO3. Lumped-element and traveling-wave electrodes of aluminum, gold, and indium-tin oxide are investigated. Devices with a 3-dB bandwidth of 6.5 GHz using coplanar traveling-wave electrodes with a switching voltage of 7.0

Thomas Pohlmann; Andreas Neyer; Edgar Voges

1989-01-01

299

Criticality Model  

SciTech Connect

The ''Disposal Criticality Analysis Methodology Topical Report'' (YMP 2003) presents the methodology for evaluating potential criticality situations in the monitored geologic repository. As stated in the referenced Topical Report, the detailed methodology for performing the disposal criticality analyses will be documented in model reports. Many of the models developed in support of the Topical Report differ from the definition of models as given in the Office of Civilian Radioactive Waste Management procedure AP-SIII.10Q, ''Models'', in that they are procedural, rather than mathematical. These model reports document the detailed methodology necessary to implement the approach presented in the Disposal Criticality Analysis Methodology Topical Report and provide calculations utilizing the methodology. Thus, the governing procedure for this type of report is AP-3.12Q, ''Design Calculations and Analyses''. The ''Criticality Model'' is of this latter type, providing a process evaluating the criticality potential of in-package and external configurations. The purpose of this analysis is to layout the process for calculating the criticality potential for various in-package and external configurations and to calculate lower-bound tolerance limit (LBTL) values and determine range of applicability (ROA) parameters. The LBTL calculations and the ROA determinations are performed using selected benchmark experiments that are applicable to various waste forms and various in-package and external configurations. The waste forms considered in this calculation are pressurized water reactor (PWR), boiling water reactor (BWR), Fast Flux Test Facility (FFTF), Training Research Isotope General Atomic (TRIGA), Enrico Fermi, Shippingport pressurized water reactor, Shippingport light water breeder reactor (LWBR), N-Reactor, Melt and Dilute, and Fort Saint Vrain Reactor spent nuclear fuel (SNF). The scope of this analysis is to document the criticality computational method. The criticality computational method will be used for evaluating the criticality potential of configurations of fissionable materials (in-package and external to the waste package) within the repository at Yucca Mountain, Nevada for all waste packages/waste forms. The criticality computational method is also applicable to preclosure configurations. The criticality computational method is a component of the methodology presented in ''Disposal Criticality Analysis Methodology Topical Report'' (YMP 2003). How the criticality computational method fits in the overall disposal criticality analysis methodology is illustrated in Figure 1 (YMP 2003, Figure 3). This calculation will not provide direct input to the total system performance assessment for license application. It is to be used as necessary to determine the criticality potential of configuration classes as determined by the configuration probability analysis of the configuration generator model (BSC 2003a).

A. Alsaed

2004-09-14

300

Nonlinear interface optical switch structure for dual mode switching revisited  

Microsoft Academic Search

There is a need for devices which will allow integration of photonic\\/optical computing subsystems into electronic computing architectures. This presentation reviews the nonlinear interface optical switch (NIOS) concept and then describes a new effect, the erasable optical memory (EOM) effect. We evaluate an extension of the NIOS device to allow simultaneous optical\\/electronic, i.e. dual mode, switching of light utilizing the

Rebecca J. Bussjager; Joseph M. Osman; Joseph Chaiken

1998-01-01

301

Shutter-based switching core for an optical packet switch  

NASA Astrophysics Data System (ADS)

Passive optical interconnection is being used in large packet switches to allow size scale up and more efficient heat dissipation from the electronic processors. The line card is the electronic island whose size is determined by thermal dissipation technology. We have selected an optical interconnection technology that is low cost, fiber ribbon, and we are working on the shutter arrays, which allow active routing. This will reduce the demands on the electronic processors. Progress on a 180 Gbps switch will be reported.

Collings, Neil; Zhang, Fan; Fan, Mark; Scarr, Robin W. A.; Wilkinson, Timothy D.; Crossland, William A.

2004-11-01

302

Dichotomously switched phase flows  

NASA Astrophysics Data System (ADS)

The general formalism for periodic dichotomous noise on nonpotential flows is considered. This uncorrelated noise process switches suddenly at integer values of period ?. The effect of additive noise of this kind on the planar FitzHugh-Nagumo ordinary differential equations [R. FitzHugh, Biophys. J. 1, 445 (1961); J. Nagumo, S. Arimoto, and Y. Yoshikawa, Proc. IRE 50, 2061 (1962)] is examined. For large ?, quasifractal attractors are observed, whereas for the white-noise limit, where ? is small, a Fokker-Planck equation describes the evolution. The magnitude of ? determines the smoothness of the transient evolution and equilibrium density of the system. Typically the stochastic equations give rise to two regions of high density near the stable fixed points of the underlying autonomous system. The stiffness parameter ? in the differential equations determines the fast variable, its associated nullcline, and the resulting flow structure. For small ? the cubic nullcline controls the motion and transitions between the high-density peaks occur along segments of a noisy limit cycle. For large ? the linear nullcline governs the transitions and the peaks are joined by a single band. The statistical behavior of the oscillatory and direct transitions is examined.

Fraser, Simon J.; Kapral, Raymond

1997-09-01

303

Electron collisions in gas switches  

SciTech Connect

Many technologies rely on the conduction/insulation properties of gaseous matter for their successful operation. Many others (e.g., pulsed power technologies) rely on the rapid change (switching or modulation) of the properties of gaseous matter from an insulator to a conductor and vice versa. Studies of electron collision processes in gases aided the development of pulsed power gas switches, and in this paper we shall briefly illustrate the kind of knowledge on electron collision processes which is needed to optimize the performance of such switching devices. To this end, we shall refer to three types of gas switches: spark gap closing, self-sustained diffuse discharge closing, and externally-sustained diffuse discharge opening. 24 refs., 15 figs., 2 tabs.

Christophorou, L.G.

1989-01-01

304

Wide Bandgap Extrinsic Photoconductive Switches  

SciTech Connect

Photoconductive semiconductor switches (PCSS) have been investigated since the late 1970s. Some devices have been developed that withstand tens of kilovolts and others that switch hundreds of amperes. However, no single device has been developed that can reliably withstand both high voltage and switch high current. Yet, photoconductive switches still hold the promise of reliable high voltage and high current operation with subnanosecond risetimes. Particularly since good quality, bulk, single crystal, wide bandgap semiconductor materials have recently become available. In this chapter we will review the basic operation of PCSS devices, status of PCSS devices and properties of the wide bandgap semiconductors 4H-SiC, 6H-SiC and 2H-GaN.

Sullivan, J S

2012-01-17

305

Electromagnetic Activation of Capillary Switches  

NASA Astrophysics Data System (ADS)

By designing coupled droplet pairs with the appropriate length scale to promote surface tension as the dominant force, one can create bi-stable capillary switches. This bi-stability can be triggered by pressure pulses, surface chemistry, electroosmosis, or body forces. To exploit the latter, we designed a capillary switch with electromagnetic activation. The resulting setup consists of a sub-millimeter tube, overfilled with a ferrofluid, surrounded by a wire coil to generate a magnetic field. Evidence of this capillary switching will be presented along with some theoretical basis in fluid- and electro-dynamics. The approach may also be used to investigate other transport phenomena in electromagnetically-coupled microfluidic systems, including the relative effects of translational motion of the ferrofluid (both particles and solvent molecules) versus the rotational effects of the individual magnetic grains. These individually addressable capillary switches offer intriguing applications including high-speed adaptive optics, actuators at the microscale, and possible PCB integration.

Malouin, Bernie; Dayal, Rohan; Parsa, Leila; Hirsa, Amir

2008-11-01

306

Theory of molecular hysteresis switch  

NASA Astrophysics Data System (ADS)

Molecular hysteresis switching has been recently observed in a series of experiments that measured the I-V spectrum of bipyridyl-dinitro oligophenylene-ethylene dithiol (BPDN) based molecular devices [1]. The experimental observations clearly show the presence of Coulomb blockade in single organic molecules that is responsible for the voltage-induced switching. We present the theory of the hysteresis switch which explains the non-linear hysteresis I-V characteristics based on the mechanisms of Coulomb blockade and the existence of two different molecular conformations of neutral and charged states of the molecule. [1] A.S. Blum, J.G. Kushmerick, D.P. Long, C.H. Patterson, J.C. Yang, J.C. Henderson, Y.X. Yao, J.M. Tour, R. Shashidhar, and B.R. Ratna, ``Molecularly inherent voltage-controlled conductance switching'' , Nature Materials 4, 167 (2005).

Kozhushner, Mortko; Oleynik, Ivan

2006-03-01

307

Qpsk Switching Modulator, Phase 2.  

National Technical Information Service (NTIS)

A breadboard QPSK modulator based on a series connected, dual gate FET switching approach was developed to meet a specification provided by ESA. Direct high level modulation immediatly prior to the downlink output on a satellite repeater avoids amplitude ...

W. Konu R. Bouchard

1983-01-01

308

High Power Mercury Switch Study.  

National Technical Information Service (NTIS)

The effort was both a theoretical and experimental program leading to the development of high voltage, high power switching devices which utilize a liquid metal cathode. A series of mercury tubes with plasma injection triggering were built and tested culm...

R. W. Waniek

1967-01-01

309

Task switching: a PDP model.  

PubMed

When subjects switch between a pair of stimulus-response tasks, reaction time is slower on trial N if a different task was performed on trial N - 1. We present a parallel distributed processing (PDP) model that simulates this effect when subjects switch between word reading and color naming in response to Stroop stimuli. Reaction time on "switch trials" can be slowed by an extended response selection process which results from (a) persisting, inappropriate states of activation and inhibition of task-controlling representations; and (b) associative learning, which allows stimuli to evoke tasks sets with which they have recently been associated (as proposed by Allport & Wylie, 2000). The model provides a good fit to a large body of empirical data, including findings which have been seen as problematic for this explanation of switch costs, and shows similar behavior when the parameters are set to random values, supporting Allport and Wylie's proposal. PMID:11971634

Gilbert, Sam J; Shallice, Tim

2002-05-01

310

Composite Transistor in Switching Regime.  

National Technical Information Service (NTIS)

Operating conditions of a composite semiconductor triode (ST) in the switching mode are analyzed. The saturation state in both triode components are achieved only when the collectors are separated by an appropriate resistor. Statistical characteristics of...

E. E. Yudin

1968-01-01

311

IGBT: a solid state switch.  

National Technical Information Service (NTIS)

A Copper Vapour Laser Power Supply has been designed using a solid state switch consisting in eighteen Isolated Gate Bipolar Transistors (IGBT), -1200 volts, 400 Amps, each-in parallel. This paper presents the Isolated Gate Bipolar Transistor (IGBTs) repl...

D. Chatroux J. Maury B. Hennevin

1993-01-01

312

CRITICAL CONSUMPTION  

Microsoft Academic Search

Critical consumption, the purchase or boycott of goods for political, ethical or environmental reasons, is regularly characterised as an example of ‘new politics’ or ‘new’ political participation. However, such analysis often neglects work from the sociology of consumption and social movement studies. This paper argues that consumers express their identity through critical consumption, in the form of a pledge of

Luke S. Yates

2011-01-01

313

Critical Muralism  

ERIC Educational Resources Information Center

|This study focuses on the development and practices of Critical Muralists--community-educator-artist-leader-activists--and situates these specifically in relation to the Mexican mural tradition of los Tres Grandes and in relation to the history of public art more generally. The study examines how Critical Muralists address artistic and…

Rosette, Arturo

2009-01-01

314

Uninterrupted Transfer Switch  

Microsoft Academic Search

Growing sophistication in critical telecommunication and other modern computerized equipment requires uninterrupted power. This necessitates an uninterrupted transfer capability between normal and alternate sources of power, such as utility and engine-generator. Such a transfer is easily accomplished between two compatible sources (for example between two sources connected to the same bus feeder) by means of make-before-break techniques. However, when the

David Mascarenhas

1986-01-01

315

Anti-ulcerogenic mechanisms of the sesquiterpene lactone onopordopicrin-enriched fraction from Arctium lappa L. (Asteraceae): role of somatostatin, gastrin, and endogenous sulfhydryls and nitric oxide.  

PubMed

Arctium lappa L. has been used in folk medicine as a diuretic, depurative, and digestive stimulant and in dermatological conditions. The mechanisms involved in the anti-ulcerogenic activity of the sesquiterpene onopordopicrin (ONP)-enriched fraction (termed the ONP fraction), obtained from A. lappa leaves, were studied. The gastroprotective mechanism of the ONP fraction was evaluated in experimental in vivo models in rodents, mimicking this disease in humans. ONP fraction (50?mg/kg, p.o.) significantly inhibited the mucosal injury induced by ethanol/HCl solution (75%), indomethacin/bethanecol (68.9%), and stress (58.3%). When the ONP fraction was investigated in pylorus ligature, it did not induce alteration in the gastric volume but did modify the pH and total acid concentration of gastric juice. ONP fraction significantly increased serum somatostatin levels (82.1±4.1 vs. control group 12.7±4?pmol/L) and decreased serum gastrin levels (62.6±6.04 vs. control group 361.5±8.2??U/mL). Mucus production was not significantly altered by the ONP fraction. Gastroprotection by the ONP fraction was completely inhibited by N-ethylmaleimide treatment and did not modify the effect in the animals pretreated with l-N(G)-nitroarginine methyl ester. These results suggest an antisecretory mechanism involved with the antiulcerogenic effect of the ONP fraction. However, only endogenous sulfhydryls play an important role in gastroprotection of the ONP fraction. PMID:22191571

de Almeida, Ana Beatriz Albino; Luiz-Ferreira, Anderson; Cola, Maíra; Di Pietro Magri, Luciana; Batista, Leonia Maria; de Paiva, Joseilson Alves; Trigo, José Roberto; Souza-Brito, Alba R M

2011-12-22

316

Sulfhydryl protection and the oxygen effect on radiation-induced inactivation of r-chromatin in vitro. Influence of an OH scavenger: t-butanol  

SciTech Connect

Transcriptionally active r-chromatin from Tetrahymena has been irradiated in dilute phosphate buffer, pH 7.2, in the presence of the sulfhydryl compound 2-mercaptoethanol (MSH). MSH was more protective against radiation-induced inactivation of transcription under N/sub 2/ than under O/sub 2/. The OH scavenger, t-butanol, on the other hand, gives significantly less protection under N/sub 2/ than under O/sub 2/, apparently due to inactivation by secondary t-butanol radicals under anoxia as shown previously. However, MSH was found to restore most of the protective effect of t-butanol under N/sub 2/. Inactivation was studied as a function of MSH concentration (0.03-10 mM) at different, fixed concentrations of t-butanol (3-300 mM). The observed protection may be explained essentially in terms of (1) OH scavenging, (2) repair of DNA radicals by H-atom transfer from MSH under N/sub 2/ in competition with fixation of damage under O/sub 2/, and (3) protection against inactivation by secondary t-butanol radicals by H-atom transfer to these radicals. The sensitizing effect of oxygen in the presence of MSH is reduced by t-butanol and may even be reversed to produce an apparently protective effect. This finding is discussed in terms of residual inactivation by secondary radicals. The significance of OH scavengers as potential modifiers of oxygen enhancement ratio values is discussed.

Herskind, C.

1988-07-01

317

Involvement of protein tyrosine phosphorylation and reduction of cellular sulfhydryl groups in cell death induced by 1' -acetoxychavicol acetate in Ehrlich ascites tumor cells.  

PubMed

Elucidation of the mechanisms underlying potential anticancer drugs continues and unraveling these mechanisms would not only provide a conceptual framework for drug design but also promote use of natural products for chemotherapy. To further evaluate the efficacy of the anticancer activity of 1'-acetoxychavicol acetate (ACA), this study investigates the underlying mechanisms by which ACA induces death of Ehrlich ascites tumor cells. ACA treatment induced loss of cell viability, and Western blotting analysis revealed that the compound stimulated tyrosine phosphorylation of several proteins with 27 and 70 kDa proteins being regulated in both dose- and time-dependent manner prior to loss of viability. Protein tyrosine kinase inhibitor herbimycin A moderately protected cells from ACA-induced toxicity. In addition, cellular glutathione and protein sulfydryl groups were also significantly reduced both dose- and time-dependently during evidence of cell death. Replenishing thiol levels by antioxidant, N-acetylcysteine (NAC), an excellent supplier of glutathione and precursor of glutathione, substantially recovered the viability loss, but the recovery being time-dependent, as late addition of NAC (at least 30 min after ACA addition to cultures) was, however, ineffective. Addition of NAC to ACA treated cultures also abolished tyrosine phosphorylation of the 27 kDa protein. These results, at least partly, identify cellular sulfhydryl groups and protein tyrosine phosphorylation as targets of ACA cytotoxicity in tumor cells. PMID:11823008

Moffatt, Jerry; Kennedy, David Opare; Kojima, Akiko; Hasuma, Tadayoshi; Yano, Yoshihisa; Otani, Shuzo; Murakami, Akira; Koshimizu, Koichi; Ohigashi, Hajime; Matsui-Yuasa, Isao

2002-02-20

318

Switching therapies in multiple sclerosis.  

PubMed

There are currently nine approved disease modifying therapies for relapsing forms of multiple sclerosis, with six distinct mechanisms of action. All have side effects, and none are cures. When a patient cannot tolerate therapy, or there is unacceptable breakthrough disease activity, the most common approach is to change drug. No universal guidelines exist for switching therapy. This overview will propose switch principles and suggestions. PMID:23508518

Coyle, Patricia K

2013-04-01

319

High PRF high current switch  

DOEpatents

A triggerable, high voltage, high current, spark gap switch for use in pu power systems. The device comprises a pair of electrodes in a high pressure hydrogen environment that is triggered by introducing an arc between one electrode and a trigger pin. Unusually high repetition rates may be obtained by undervolting the switch, i.e., operating the trigger at voltages much below the self-breakdown voltage of the device.

Moran, Stuart L. (Fredericksburg, VA); Hutcherson, R. Kenneth (College Park, MD)

1990-03-27

320

MOS switched-capacitor filters  

Microsoft Academic Search

In the past several years, much progress has been made in bringing the economies of integrated-circuit technology to bear on the realization of voiceband frequency selective filters. This paper will review one approach to this problem, the use of switched-capacitor techniques. The paper emphasizes the practical aspects of switched-capacitor filter design under the constraints imposed by MOS integrated-circuit technology. The

R. W. Brodersen; P. R. Gray; D. A. Hodges

1979-01-01

321

To burst or circuit switch?  

Microsoft Academic Search

We develop, analyze and then numerically compare performance models of a fast-adapting and centrally controlled form of optical circuit switching (OCS) with a conservative form of optical burst switching (OBS). For the first time, we consider a unified model comprising both: edge buffers at which arriving packets are aggregated and enqueued according to a vacation-type service discipline with nondeterministic set-up

Andrew Zalesky

2009-01-01

322

Computational and neural mechanisms of task switching  

Microsoft Academic Search

Switching between tasks that overlap in perceptual and response characteristics is assumed to rely upon the maintenance of task representations in prefrontal cortex (PFC). However, task-switching studies demonstrate ''switch costs,'' even when there is sufficient time to prepare for a new task. These costs suggest that task-switching performance reflects a complex interplay between priming and the updating and maintenance of

Jeremy R. Reynolds; Todd S. Braver; Joshua W. Brown; Stefan Van der Stigchel

323

Launched electrons in plasma opening switches  

Microsoft Academic Search

Plasma opening switches have provided a means to improve the characteristics of super-power pulse generators. Recent advances involving plasma control with fast and slow magnetic fields have made these switches more versatile, allowing for improved switch uniformity, triggering, and opening current levels that are set by the level of auxiliary fields. Such switches necessarily involve breaks in the translational symmetry

C. W. Mendel Jr.; G. E. Rochau; M. A. Sweeney; D. H. McDaniel; J. P. Quintenz; M. E. Savage; E. L. Lindman; J. M. Kindel

1989-01-01

324

A Comparison of High-Voltage Switches  

Microsoft Academic Search

This report summarizes our work on high-voltage switches during the past few years. With joint funding from the Department of Energy (DOE) and the Department of Defense (DOD), we tested a wide variety of switches to a common standard. This approach permitted meaningful comparisons between disparate switches. Most switches were purchased from commercial sources, though some were experimental devices. For

K. W. Chu; G. L. Scott

1999-01-01

325

Switching activity estimation of CIC filter integrators  

Microsoft Academic Search

In this work, a method for estimation of the switching activity in integrators is presented. To achieve low power, it is always necessary to develop accurate and efficient methods to estimate the switching activity. The switching activities are then used to estimate the power consumption. In our work, the switching activity is first estimated for the general purpose integrators and

Muhammad Abbas; Oscar Gustafsson

2010-01-01

326

WDM burst switching for petabit capacity routers  

Microsoft Academic Search

WDM burst switching is an approach to building very high capacity routing switches based on optical data paths and electronic control. Burst switches assign user data bursts to channels in WDM links on-the-fly in order to provide efficient statistical multiplexing of high rate data channels. The overall system architecture is designed to facilitate the introduction of optical switching components as

Yuhua Chen; Jonathan S. Turner

1999-01-01

327

Mapping L1 Ligase ribozyme conformational switch  

PubMed Central

L1 Ligase (L1L)molecular switch is an in vitro optimized synthetic allosteric ribozyme that catalyzes the regioselective formation of a 5’-to-3’ phosphodiester bond, a reaction for which there is no known naturally occurring RNA catalyst. L1L serves as a proof of principle that RNA can catalyze a critical reaction for prebiotic RNA self-replication according to the RNA World hypothesis. L1L crystal structure captures two distinct conformations that differ by a re-orientation of one of the stems by around 80 Å and are presumed to correspond to the active and inactive state, respectively. It is of great interest to understand the nature of these two states in solution, and the pathway for their interconversion. In this study, we use explicit solvent molecular simulation together with a novel enhanced sampling method that utilizes concepts from network theory to map out the conformational transition between active and inactive states of L1L. We find that the overall switching mechanism can be described as a 3-state/2-step process. The first step involves a large-amplitude swing that re-orients stem C. The second step involves the allosteric activation of the catalytic site through distant contacts with stem C. Using a conformational space network representation of the L1L switch transition, it is shown that the connection between the three states follows different topographical patterns: the stem C swing step passes through a narrow region of the conformational space network, whereas the allosteric activation step covers a much wider region and a more diverse set of pathways through the network.

Giambasu, George M.; Lee, Tai-Sung; Scott, William G.; York, Darrin M.

2012-01-01

328

Nanomechanical switch for integration with CMOS logic.  

SciTech Connect

We designed, fabricated and measured the performance of nanoelectromechanical (NEMS) switches. Initial data are reported with one of the switch designs having a measured switching time of 400 ns and an operating voltage of 5 V. The switches operated laterally with unmeasurable leakage current in the 'off' state. Surface micromachining techniques were used to fabricate the switches. All processing was CMOS compatible. A single metal layer, defined by a single mask step, was used as the mechanical switch layer. The details of the modeling, fabrication and testing of the NEMS switches are reported.

Nordquist, Christopher Daniel; Wolfley, Steven L.; Baker, Michael Sean; Czaplewski, David A.; Wendt, Joel Robert; Kraus, Garth Merlin; de Boer, Maarten Pieter; Patrizi, Gary A.

2008-11-01

329

A new resonant gate driver for switching loss reduction of high side switch in buck converter  

Microsoft Academic Search

In this paper, a new resonant gate driver circuits is proposed to reduce the switching loss of high side switch in buck converter. Hard switching causes major parts of the power loss in high side switch and limits high switching frequency application of DC-DC converter. The proposed resonant gate driver behaves more like the ideal current source driver which can

Xin Zhou; Zhigang Liang; Alex Huang

2010-01-01

330

Network Effects and Switching Costs in the Market for Routers and Switches  

Microsoft Academic Search

This research examines the impact of switching costs on vendor choice in the market for routers and switches. We show that despite the use of open standards which attempt to enhance interoperabilities for equipments from different vendors, vendors in this market are able to maintain high switching costs. Because routers and switches are networked goods, switching costs may arise from

Chris Forman; Pei-yu Chen

2003-01-01

331

The Pipeback Switch: High Performance Packet Switching with Guaranteed Delivery and Linear Buffer Complexity  

Microsoft Academic Search

A high performance packet switching archi- tecture called the Pipeback switch is proposed. This archi- tecture ensures lossless packet delivery while maintaining linear buffer complexity. The Pipeback switch improves upon the popular Knockout switch proposed by Y. Yeh et al. Both switches use an N × N space division fabric with output queuing and both designs are motivated by the

Saqib Raza; Zartash Afzal Uzmi

332

Neural correlates of establishing, maintaining, and switching brain states  

PubMed Central

Although the study of brain states is an old one in neuroscience, there has been growing interest in brain state specification owing to MRI studies tracing brain connectivity at rest. In this review, we summarize recent research on three relatively well-described brain states: the resting, alert, and meditation states. We explore the neural correlates of maintaining a state or switching between states, and argue that the anterior cingulate cortex and striatum play a critical role in state maintenance, whereas the insula has a major role in switching between states. Brain state may serve as a predictor of performance in a variety of perceptual, memory, and problem solving tasks. Thus, understanding brain states is critical for understanding human performance.

Tang, Yi-Yuan; Rothbart, Mary K.; Posner, Michael I.

2012-01-01

333

Testing results for the HCT-1400 switch  

SciTech Connect

The High Current Thyristor (HCT)-1400 was characterized for switching performance. This is a Soviet switching device that has recently become available to the U.S. community. Substantial claims have been made regarding the performance of this switch. In particular, the switch was claimed to be able to switch high currents, with very short risetime without any significant jitter. This is an independent evaluation of the high current thyristor.

Hoeberling, R.F.; Wheeler, R.B.

1996-07-01

334

A Leaky-Integrator Model as a Control Mechanism Underlying Flexible Decision Making during Task Switching  

PubMed Central

The ability to switch between tasks is critical for animals to behave according to context. Although the association between the prefrontal cortex and task switching has been well documented, the ultimate modulation of sensory–motor associations has yet to be determined. Here, we modeled the results of a previous study showing that task switching can be accomplished by communication from distinct populations of sensory neurons. We proposed a leaky-integrator model where relevant and irrelevant information were stored separately in two integrators and task switching was achieved by leaking information from the irrelevant integrator. The model successfully explained both the behavioral and neuronal data. Additionally, the leaky-integrator model showed better performance than an alternative model, where irrelevant information was discarded by decreasing the weight on irrelevant information, when animals initially failed to commit to a task. Overall, we propose that flexible switching is, in part, achieved by actively controlling the amount of leak of relevant and irrelevant information.

Mitani, Akinori; Sasaki, Ryo; Oizumi, Masafumi; Uka, Takanori

2013-01-01

335

Light Induced Soliton Switching at the Gallium-Silica Interface  

NASA Astrophysics Data System (ADS)

In the present paper, we have investigated the solitonic characteristics of a pulse passing through an interface separating two nonlinear media. The first media is a thin film of gallium nanoparticles which show switching properties under optical excitation and second is a monomode optical fiber. Soliton propagation in three different phases of gallium nanoparticles have been analyzed by using the method of phase-plane analysis. Also, the critical power required for soliton propagation has been calculated.

Naruka, Preeti; Bissa, Shivangi

336

Efficient optically switched metro Ethernet  

NASA Astrophysics Data System (ADS)

With the overwhelming success of Ethernet technology in local access networks (LANs), owing to its ease of management and its much lower line rate cost, there has been a continuous effort in migrating Ethernet technology into metro-area networks (MANs) and wide-area networks (WANs). However, current Ethernet technology has to overcome the scalability and reliability deficiencies in order to be recognized as a viable MAN/WAN technology. Recently these concerns are being addressed under the framework of Generalized-MPLS (GMPLS) and its traffic-engineering (TE) intelligence. In this paper we propose an optical Ethernet solution viable for MAN/WAN based on the concept of a reconfigurable Ethernet node, integrating reconfigurable optical cross-connects (OXCs) with traditional Ethernet switches. We subsequently proposed a dynamic TE scheme that utilizes both the simplicity of all-optical switching and the flexibility of optical-electrical-optical (OEO) traffic grooming realized by the proposed optical Ethernet node. We showed through simulations that with our proposed TE scheme, the number of OEO transceivers needed by such an optical Ethernet node is only about 20% of a fully-populated one in the extreme case (very high load) and about only 10% in normal load conditions, without degrading the performance. This actually implies a tremendous cost saving on Ethernet OEO transceivers, and on the other hand indicates that a highly efficient and scalable MAN/WAN Ethernet network system could be well achieved by using Ethernet switches of only modest switching capacity (as legacy Ethernet switches have) along with reconfigurable OXCs. To demonstrate and test our proposed ideas we have built a GMPLS testbed using MEMS-based optical cross-bar switches and legacy Gigabit Ethernet switches. The testbed consists of three core nodes and six edge nodes. Performance experiments have been conducted on the testbed as well.

Guo, Aihua; Chen, Yung J.

2006-10-01

337

Critical Patriotism.  

ERIC Educational Resources Information Center

|Asserts that, post 9-11, responsibility to critical thought complicates simple-minded notions of loyalty and patriotism, and that "classics" of Western thought persist as touchstones of self-reflection and reason. (EV)|

Euben, J. Peter

2002-01-01

338

Literary Criticism.  

ERIC Educational Resources Information Center

|Reviewed in this essay are works written by and/or about women. Topics discussed include women and the literary tradition, women poets, studies of individual women novelists, and feminist criticism. (EB)|

Kaplan, Sydney Janet

1979-01-01

339

DCOS: cache embedded switch architecture for distributed shared memory multiprocessor SoCs  

Microsoft Academic Search

Shared memory is a common inter-processor com- munication paradigm for on-chip multiprocessor SoC (MPSoC) platforms. The latency overhead of switch-based interconnection networks plays a critical role in shared memory MPSoC designs. In this paper, we propose a directory-cache embedded switch architecture with distributed shared cache and distributed shared memory. It is able to reduce the number of home node cache

Daewook Kim; Manho Kim; Gerald E. Sobelman

2006-01-01

340

Flight control computer operational flight program development for the control laws switching mechanism  

Microsoft Academic Search

All new flight control law and flight control computer developments have historically been an extremely expensive and time-consuming proposition specially in a flight-critical system. To reduce and avoid these kind of problems, the switching mechanism method has been addressed. Here the switching mechanism needs two computers. One is a basic(or primary) computer already customized to the production airframe and the

Sang-Seon Park; In-Je Cho; Seung-Ha Ryu; Sang-Soo Lim

2007-01-01

341

Event-Driven Time-Domain Simulation of Closed-Loop Switched Circuits  

Microsoft Academic Search

This paper addresses the accurate time-domain simulation of closed-loop switched circuits. It is known that for such systems, conventional analog simulation can be critical due to the presence of strongly nonlinear switching devices. In order to overcome the drawback, in this paper, an in-depth investigation of the weakness points of analog simulation is first presented. On the basis of the

Paolo Maffezzoni; Lorenzo Codecasa; Dario D'amore

2006-01-01

342

49 CFR 218.103 - Hand-operated switches, including crossover switches.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Hand-operated switches, including crossover switches. 218.103 Section 218.103 Transportation...RAILROAD OPERATING PRACTICES Handling Equipment, Switches, and Fixed Derails § 218.103...

2010-10-01

343

49 CFR 218.103 - Hand-operated switches, including crossover switches.  

Code of Federal Regulations, 2010 CFR

...2009-10-01 2009-10-01 false Hand-operated switches, including crossover switches. 218.103 Section 218.103 Transportation...RAILROAD OPERATING PRACTICES Handling Equipment, Switches, and Fixed Derails § 218.103...

2009-10-01

344

Optimized Switch Allocation to Improve the Restoration Energy in Distribution Systems  

NASA Astrophysics Data System (ADS)

In distribution networks switching devices play critical role in energy restoration and improving reliability indices. This paper presents a novel objective function to optimally allocate switches in electric power distribution systems. Identifying the optimized location of the switches is a nonlinear programming problem (NLP). In the proposed objective function a new auxiliary function is used to simplify the calculation of the objective function. The output of the auxiliary function is binary. The genetic algorithm (GA) optimization method is used to solve this optimization problem. The proposed method is applied to a real distribution network and the results reveal that the method is successful.

Dezaki, Hamed H.; Abyaneh, Hossein A.; Agheli, Ali; Mazlumi, Kazem

2012-01-01

345

Polarization switching with sodium vapour  

SciTech Connect

Results are given of an experiment which demonstrates switching of the polarization state of the output of a near-concentric Fabry-Perot containing sodium vapour, excited via the homogeneously broadened Dl transition. An example of the output, for linearly polarized laser input, at 1.5 GHz below line center shows switching with hysteresis at high input power (approximately 400 mW) due to saturation, as well as the switching at lower power (approximately mW) due to optical pumping effects. Purely absorptive polarization switching at approximately 50 mW input power was observed. Polarization switching has been predicted in the context of three state atoms in an optical cavity, and the lower power switchin has been previously observed using the inhomogeneously broadened Dl transition of sodium in a Fabry-Perot with the laser detuned above line center. By using argon buffer gas at up to 100 torr, importance of hyperfine structure and inhomogeneous broadening was reduced so as to make the transition approximate a J + 1/2 to J - 1/2 transition.

Hamilton, M.W.; Sandle, W.J.

1984-01-01

346

High power solid state switches  

NASA Astrophysics Data System (ADS)

We have successfully produced an optically triggered thyristor based in Gallium Arsenide, developed a model for breakdown, and are developing two related devices, including a Gallium Arsenide based static inductor thyristor. We are getting at the basic limitations of Gallium Arsenide for these applications, and are developing models for the physical processes that will determine device limitations. The previously supported gas phase work - resulting in the back-lighted thyratron (BLT) - has actually resulted in a very changed view of how switching can be accomplished, and this is impacting the design of important machines. The BLT is being studied internationally: in Japan for laser fusion and laser isotope separation. ITT has built a BLT that has switched 30 kA at 60 kV in testing at NSWC Dahlgren and the device is being commercialized by another American company. Versions of the switch are now being tested for excimer laser and other applications. Basically, the switch, which arose from pulse power physics studies at USC, can switch more current faster (higher di/dt), with less housekeeping, and with other advantageous properties. There are a large number of other new applications, include kinetic energy weapons, pulsed microwave sources and R.F. accelerators.

Gundersen, Martin

1991-11-01

347

Phenotypic switching in Cryptococcus neoformans.  

PubMed

Phenotypic switching has been described in serotype A and D strains of Cryptococcus neoformans. It occurs in vivo during chronic infection and is associated with differential gene expression and changes in virulence. The switch involves changes in the polysaccharide capsule and cell wall that affect the yeast's ability to resist phagocytosis. In addition, the phenotypic switch variants elicit qualitatively different inflammatory responses in the host. In animal models of chronic cryptococosis, the immune response of the host ultimately determines which of the switch variants are selected and maintained. The importance of phenotypic switching is further underscored by several findings that are relevant in the setting of human disease. These include the ability of the mucoid colony variant of RC-2 (RC-2 MC) but not the smooth variant (RC-2 SM) to promote increased intracerebral pressure in a rat model of cryptococcal meningitis. Furthermore, chemotherapeutic and immunological antifungal interventions can promote the selection of the RC-2 MC variant during chronic murine infection. PMID:16385110

Guerrero, A; Jain, N; Goldman, D L; Fries, B C

2006-01-01

348

Binary switching in a 'symmetric' potential landscape  

PubMed Central

A binary switch is the basic building block for information processing. The potential energy profile of a bistable binary switch is a ‘symmetric' double well. The traditional method of switching it from one state (one well) to the other is to tilt the profile towards the desired state. Here, we present a case, where no such tilting is necessary to switch successfully, even in the presence of thermal noise. This happens because of the built-in dynamics inside the switch itself. It differs from the general perception on binary switching that in a ‘symmetric' potential landscape, the switching probability is 50% in the presence of thermal noise. Our results, considering the complete three-dimensional potential landscape, demonstrate intriguing phenomena on binary switching mechanism. With experimentally feasible parameters, we theoretically demonstrate such intriguing possibility in electric field induced magnetization switching of a shape-anisotropic single-domain magnetostrictive nanomagnet with two stable states at room-temperature.

Roy, Kuntal; Bandyopadhyay, Supriyo; Atulasimha, Jayasimha

2013-01-01

349

Satellite switch state time plan control  

NASA Astrophysics Data System (ADS)

This paper describes the basic control features of a typical satellite switch system, such as Intelsat VI. Factors are addressed pertaining to the data format that is used to express the switch plan, the timing control of the switch states comprising the satellite switch frame, the transmission of the switch plan to the satellite, storage and execution of the switch plan on board, and the coding of switch plan data for protection from radiation-induced bit errors. Also, the implementation used to achieve precision control of the on-board clock is discussed, and the influence of clock control variation on all the terrestrial interfaces that participate in the system is demonstrated. Finally, the method for achieving network-wide coordinated switch state time plan/TDMA burst time plan changes, which are essential in an operational satellite-switched (SS)-TDMA system is discussed.

Campanella, S. J.; Inukai, T.

1983-12-01

350

Binary switching in a 'symmetric' potential landscape.  

PubMed

A binary switch is the basic building block for information processing. The potential energy profile of a bistable binary switch is a 'symmetric' double well. The traditional method of switching it from one state (one well) to the other is to tilt the profile towards the desired state. Here, we present a case, where no such tilting is necessary to switch successfully, even in the presence of thermal noise. This happens because of the built-in dynamics inside the switch itself. It differs from the general perception on binary switching that in a 'symmetric' potential landscape, the switching probability is 50% in the presence of thermal noise. Our results, considering the complete three-dimensional potential landscape, demonstrate intriguing phenomena on binary switching mechanism. With experimentally feasible parameters, we theoretically demonstrate such intriguing possibility in electric field induced magnetization switching of a shape-anisotropic single-domain magnetostrictive nanomagnet with two stable states at room-temperature. PMID:24154561

Roy, Kuntal; Bandyopadhyay, Supriyo; Atulasimha, Jayasimha

2013-10-24

351

Distinct Roles of Protein Disulfide Isomerase and P5 Sulfhydryl Oxidoreductases in Multiple Pathways for Oxidation of Structurally Diverse Storage Proteins in Rice[W][OA  

PubMed Central

In the rice (Oryza sativa) endosperm, storage proteins are synthesized on the rough endoplasmic reticulum (ER), in which prolamins are sorted to protein bodies (PBs) called type-I PB (PB-I). Protein disulfide isomerase (PDI) family oxidoreductase PDIL2;3, an ortholog of human P5, contains a conserved structural disulfide in the redox-inactive thioredoxin-like (TRX) domain and was efficiently targeted to the surface of PB-I in a redox active site–dependent manner, whereas PDIL1;1, an ortholog of human PDI, was localized in the ER lumen. Complementation analyses using PDIL1;1 knockout esp2 mutant indicated that the a and a? TRX domains of PDIL1;1 exhibited similar redox activities and that PDIL2;3 was unable to perform the PDIL1;1 functions. PDIL2;3 knockdown inhibited the accumulation of Cys-rich 10-kD prolamin (crP10) in the core of PB-I. Conversely, crP10 knockdown dispersed PDIL2;3 into the ER lumen. Glutathione S-transferase-PDIL2;3 formed a stable tetramer when it was expressed in Escherichia coli, and the recombinant PDIL2;3 tetramer facilitated ?-globulin(C79F) mutant protein to form nonnative intermolecular disulfide bonds in vitro. These results indicate that PDIL2;3 and PDIL1;1 are not functionally redundant in sulfhydryl oxidations of structurally diverse storage proteins and play distinct roles in PB development. We discuss PDIL2;3-dependent and PDIL2;3-independent oxidation pathways that sustain disulfide bonds of crP10 in PB-I.

Onda, Yayoi; Nagamine, Ai; Sakurai, Mutsumi; Kumamaru, Toshihiro; Ogawa, Masahiro; Kawagoe, Yasushi

2011-01-01

352

The yin of exofacial protein sulfhydryls and the yang of intracellular glutathione in in vitro transfection with SS14 bioreducible lipoplexes.  

PubMed

Although redox-sensitive transfectants have been considered hitherto as the Holy Grail of gene delivery because of their ability to restrict the release of nucleic acids to intracellular compartments, the reasons for their sometimes lackluster performance do not seem likewise clear. To ascertain the possible influence of extracellular soluble thiols, exofacial protein sulfhydryls (EPTs) and glutathione (GSH) on the overall efficacy of bioreducible lipoplexes, we utilized a cationic gemini surfactant--SS14--in which the two single-chain amphiphiles are held together by a suitable redox-sensitive linkage. We herein draw a big picture whereby the interaction of bioreducible lipoplexes with cells and their internalization are tightly coupled events that ultimately do affect transfection. Specifically, we provide evidence that EPTs entail the reduction-triggered disruption of SS14 lipoplexes in plain Dulbecco's Modified Eagle Medium (DMEM), thereby resulting in a considerable waste (ca. 30%) of nucleic acids and low transgene expression. The DNA release from bioreducible lipoplexes can be blunted to ca. 16% by transfecting cells in complete medium and fully reverted by preincubating them for 1h before delivery in the same culture supernatant (i.e. preconditioning), thus significantly increasing transfection by ca. 3-fold and 10-fold, respectively. These results lead to the proposal of the protein corona as the central mediator in shielding SS14 bioreducible lipoplexes from the action of EPTs in the early phase of delivery and provide a smart solution as to how to increase their efficacy. Besides, we pinpoint associations between intracellular GSH levels and the extent of transfection. All these issues were unique to bioreducible lipoplexes. PMID:23123189

Pezzoli, Daniele; Zanda, Matteo; Chiesa, Roberto; Candiani, Gabriele

2012-10-30

353

Spin-transfer magnetization switching in ordered alloy-based nanopillar devices  

NASA Astrophysics Data System (ADS)

This paper reviews spin-transfer magnetization switching in ordered alloy-based nanopillar devices. L10-ordered FePt was used for one of the earliest demonstrations of spin-transfer switching in perpendicularly magnetized systems. The behaviour of magnetization switching deviates from the predictions based on a macro-spin model, suggesting incoherent magnetization switching in the system with a large perpendicular magnetic anisotropy. The effect of a 90° spin injector on spin-transfer switching was also examined using L10-ordered FePt. Full-Heusler alloys are in another fascinating material class for spin-transfer switching because of their high-spin polarization of conduction electrons and possible small magnetization damping. A B2-ordered Co2FeAl0.5Si0.5-based device showed a low intrinsic critical current density of 9.3 × 106 A cm-2 for spin-transfer switching as well as a relatively large current-perpendicular-to-plane giant-magnetoresistance (CPP-GMR) up to ~9%. The specific physical properties of ordered alloys may be useful for fundamental studies and applications in spin-transfer switching.

Mitani, S.

2011-09-01

354

"Metabolic switch" for desert survival.  

PubMed Central

Food, like water, is in short supply in the desert. We report a specialized mechanism used by a desert mouse for surviving prolonged food shortages. The key element of this adaptation is a large reduction in resting metabolism. After about 2 weeks of restricted food intake (50% of normal), the desert mouse "switched down" its resting metabolism and was able to survive and maintain its weight indefinitely on these limited rations. When food was again freely available, resting metabolism "switched up," returning to normal levels in a single day. The reduced metabolism occurred without a decrease in body temperature or in levels of activity. In marked contrast, metabolism of the laboratory white mouse increased during food restriction, and the experiments had to be terminated to avoid starvation. We think this "metabolic switch" is common among desert mammals. It may be an amplification of a general metabolic response for coping with food scarcity common to all mammals, including humans.

Merkt, J R; Taylor, C R

1994-01-01

355

Switches for use in tools  

US Patent & Trademark Office Database

A switch for use in various applications, including downhole applications, includes a first conductor and a second conductor and an insulator electrically isolating the first and second conductors. A device responsive to an applied voltage generates a plasma to perforate through the insulator to create an electrically conductive path between the first and second conductors. In another arrangement, a switch includes conductors and at least one element separating the conductors. The at least one element is adapted to electrically isolate the conductors in one state and to change characteristics in response to an applied voltage to provide an electrically conductive path between the conductors. Other types of switches may include electromechanical or mechanical elements.

Lerche; Nolan C. (Stafford, TX); Brooks; James E. (Manvel, TX)

2002-05-07

356

Liquid metal switches for electromagnetic railgun systems  

NASA Astrophysics Data System (ADS)

The need for a reliable and effective commutating switch is essential to the operation of a homopolar-generator-driven (HPG-driven) railgun system. This switch must offer the lowest possible resistance during the current build up time and then must commutate the current quickly and efficiently into the railgun barrel. The essential requirements for such a switch are discussed, and, after a brief review of the available switch technologies, a type of switch based on a liquid metal switching medium is described.

Mitcham, A. J.; Prothero, D. H.; Brooks, J. C.

1991-01-01

357

Explosive opening switch work at Westinghouse  

NASA Astrophysics Data System (ADS)

An explosive switch that commutated 315 kA into a resistor and a second version designed to switch up to 1 MA into an HPG (homopolar generator)-driven railgun system are presented. These switches are located very near the load and consist of a set of main busbars in a low-inductance configuration shorted by a thinner switch busbar. Linear-shaped charges are used to sever this switch busbar at several locations when a preselected current level is attained, commutating the current into the load. The feasibility of multishot explosive switches for electromagnetic-launch systems is also considered.

Aivaliotis, E.; Peterhans, M.

1989-01-01

358

Switching time of nanowire memory.  

PubMed

Cadmium sulfide nanowires of 10-nm diameter, electrodeposited in porous anodic alumina films, exhibit an electronic bistability that can be harnessed for non-volatile memory. The current-voltage characteristics of the wires show two stable conductance states that are well-separated (conductances differ by more than 4 orders of magnitude) and long lived (longevity > 1 year at room temperature). These two states can encode binary bits 0 and 1. Here we report measurements of the switching time to switch from the high- to the low-conductance state. These measurements also shed some light on the physical mechanisms underlying the bistability. PMID:16010934

Varfolomeev, A; Pokalyakin, V; Tereshin, S; Zaretsky, D; Bandyopadhyay, S

2005-05-01

359

Ad Critic  

NSDL National Science Digital Library

Ad Critic strives to enter every television advertisement into its database of online commercials, which can be downloaded for free and viewed with QuickTime. A complete list of advertisements is indexed by company and by ad title. There are, however, also indexes of newly added ads, most-downloaded ads, movie trailers, and music found in ads, making it easier for users to search for a new or favorite advertisement. Ad Critic includes a section on advertising news and commentary and provides services for advertising agencies including online market research and detailed viewer statistics.

360

Critical Angle  

NSDL National Science Digital Library

This website from the Exploratorium provides a demonstration of total internal reflection. The activity uses a fish aquarium to illustrate how a transparent material like water can act as a reflector. The site provides a thorough description of what to do, an explanation of what is happening, including the critical angle, and examples of its applications to optical fibers.

2008-06-23

361

Critical Load  

NSDL National Science Digital Library

In this activity, learners explore the concepts of structural engineering and how to measure the critical load, or the maximum weight a structure can bear. Learners investigate basic structures, how to reinforce, materials selection, and working as a team, design and build a prototype structure to hold increasingly greater weights.

Ieee

2013-07-08

362

Optical design of optical switches for diverse field spectroscopy  

NASA Astrophysics Data System (ADS)

Diverse field spectroscopy is a new concept in which any part of a field can be optically captured and send to the entrance slit of a spectrograph. It is more general than integral field spectroscopy, multi-object spectroscopy and even multi-integral-field spectroscopy which combine the two as in the KMOS instrument. In diverse field spectroscopy, point sources and extended sources are simultaneously optically captured in an optimal way that fully use the spectrograph for only the regions of interest; as opposed to multi-integral-field spectroscopy where rectangular or square fields are fully captured, the capturing mechanism will follow the complex shapes of the sources removing any useless field which can then be use for other sources instead or permit to observe larger sources. Optical switches can be programmed to transmit any subset of the spatial elements of a field to the spectrograph. We present the different optical designs of switches that we made, some using micromirrors arrays, others small lenses. We also present conceptual designs of low cost projects for Échelle spectrographs as the SALT HRS and for the FMOS spectrographs on SUBARU. A critical aspect of the designs is to minimize the cost so that the switches can be mass-produced while maintaining high optical performances. A general discussion will be made of the relation between the total cost of the switch system plus spectrograph and the multiplex advantage with respect to an integral-field spectrograph giving the same performances.

Content, Robert; Murray, Graham J.; Allington-Smith, Jeremy R.

2010-07-01

363

Computational and neural mechanisms of task switching  

Microsoft Academic Search

Switching between tasks that overlap in perceptual and response characteristics is assumed to rely upon the maintenance of task representations in prefrontal cor- tex (PFC). However, task-switching studies demonstrate \\

Jeremy R. Reynolds; Todd S. Braver; Joshua W. Brown; Stefan Van Der Stigchel

2006-01-01

364

Dielectric liquid pulsed-power switch  

DOEpatents

This disclosure identifies dielectric liquids for use as opening and closing switching media in pulsed power technology, and describes a dielectric-liquid-pulsed-power switch employing flashlamps. 2 figs.

Christophorou, L.; Faidas, H.

1989-08-30

365

Pulsed optical switching of junction phototransistors  

Microsoft Academic Search

This paper presents techniques for approaching the ideal theoretical waveform for switching phototransitors. Switch times of 150–250 ns have been achieved, in contrast with usual times of several microseconds. The ultimate possibilities are discussed.

M. J. Lazarus; R. W. Price

1997-01-01

366

Multi-Station Push Button Switch.  

National Technical Information Service (NTIS)

A two and ten station mechanical interlocked and manual release, illuminated, snap action, sealed, pushbutton switch assembly is being developed. Each station consists of up to six double pole miniature switch circuits, a front removable lens and lamp and...

1965-01-01

367

49 CFR 236.821 - Switch, sectionalizing.  

Code of Federal Regulations, 2011 CFR

...MAINTENANCE, AND REPAIR OF SIGNAL AND TRAIN CONTROL SYSTEMS, DEVICES, AND APPLIANCES Definitions § 236.821 Switch, sectionalizing. A switch for disconnecting a section of a power line from the source of...

2011-10-01

368

49 CFR 236.821 - Switch, sectionalizing.  

Code of Federal Regulations, 2012 CFR

...MAINTENANCE, AND REPAIR OF SIGNAL AND TRAIN CONTROL SYSTEMS, DEVICES, AND APPLIANCES Definitions § 236.821 Switch, sectionalizing. A switch for disconnecting a section of a power line from the source of...

2012-10-01

369

Design procedure for switched-reluctance motors  

Microsoft Academic Search

Some of the design aspects of the switched-reluctance motor for nonservo applications are considered. Towards this objective, a step-by-step procedure is developed for the design of switched-reluctance motors

R. Krishnan; R. Arumugan; J. F. Lindsay

1988-01-01

370

Fiber Optic Rotary Switching Device.  

National Technical Information Service (NTIS)

A fiber optic rotary switching device having a single optical fiber rotatable between a plurality of optical fibers. The arrangement for rotating the single optical fiber is designed such that the single optical fiber flexes but does not twist with respec...

S. D. Battle

1986-01-01

371

Fast latching type optical switch  

NASA Astrophysics Data System (ADS)

A magneto-optical latching switch with a yttrium orthoferrite optical rotator is described. The crystal remains in a given magnetic state for unlimited duration without energy supply. The response time is about 20 ns and the aperture of the optical rotator is 350 ?m.

Didosyan, Yuri S.; Hauser, Hans; Reider, Georg A.; Toriser, Walter

2004-06-01

372

Magnetic switching of ferromagnetic nanotubes  

NASA Astrophysics Data System (ADS)

The magnetic switching of ferromagnetic nanotubes as function of geometrical parameters has been investigated. The modes of magnetization reversal are observed to depend on the geometry of the nanotubes. Time dependent magnetization properties reveal that the nanotubes have strong magnetic viscosity effects. The values of magnetic viscosity coefficient (S) for different applied fields are high near the coercive field.

Sharif, R.; Shamaila, S.; Ma, M.; Yao, L. D.; Yu, R. C.; Han, X. F.; Khaleeq-Ur-Rahman, M.

2008-01-01

373

Magnetically Insulated Opening Switch Research.  

National Technical Information Service (NTIS)

We examine the feasibility of an opening switch concept based on magnetic insulation in a coaxial thermionic diode. It is found that the impedance ratio between 'closed' and 'open' states of the diode is marginal for efficient energy transfer via this typ...

M. W. McGeoch R. Kraft

1987-01-01

374

MOS switched capacitor ladder filters  

Microsoft Academic Search

A new technique for designing precision, fully integrated, high-order filters using standard MOS technology is described. Switched capacitor integrators have been used to realize long time constants in small areas, and by interconnecting these integrators in a `leapfrog' configuration, monolithic high-order filters have been implemented with transfer functions that are very insensitive to component variations. Experimental results are presented for

D. J. Allstot; ROBERT W. BRODERSEN; PAUL R. GRAY

1978-01-01

375

Thermoelectrically Controlled Spin-Switch  

Microsoft Academic Search

The search for novel spintronic devices brings about new ways to control switching in magnetic thin-films. In this work we experimentally demonstrate a device based on thermoelectrically controlled exchange coupling. The read out signal from a giant magnetoresistance element is controlled by exchange coupling through a weakly ferromagnetic Ni-Cu alloy. This exchange coupling is shown to vary strongly with changes

S. Andersson; V. Korenivski

2010-01-01

376

Morrison Bearingless Switched Reluctance Motor.  

National Technical Information Service (NTIS)

Switched reluctance motors typically consist of pairs of poles protruding outward from a central rotor, surrounded by pairs of coils protruding inward from a stator. The pairs of coils, positioned a short distance from opposing sides of the rotor, are con...

D. S. Wong

2004-01-01

377

Tag-switching architecture: overview  

Microsoft Academic Search

Tag switching is a way to combine the label-swapping forwarding paradigm with network layer routing. This has several advantages. Tags can have a wide spectrum of forwarding granularities, so at one end of the spectrum a tag could be associated with a group of desti-nations, while at the other a tag could be associated with a single application flow. At

Yakov Rekhter; B. Davie; E. Rosen; G. Swallow; D. Farinacci; D. Katz

1997-01-01

378

High voltage MOSFET switching circuit  

DOEpatents

The problem of source lead inductance in a MOSFET switching circuit is compensated for by adding an inductor to the gate circuit. The gate circuit inductor produces an inductive spike which counters the source lead inductive drop to produce a rectangular drive voltage waveform at the internal gate-source terminals of the MOSFET. 2 figs.

McEwan, T.E.

1994-07-26

379

Buffering in optical packet switches  

Microsoft Academic Search

This paper consists of a categorization of optical buffering strategies for optical packet switches, and a comparison of the performance of these strategies both with respect to packet loss\\/delay and bit error rate (BER) performance. Issues surrounding optical buffer implementation are discussed, and representative architectures are introduced under different categories. Conclusions are drawn about packet loss and BER performance, and

David K. Hunter; Meow C. Chia; Ivan Andonovic

1998-01-01

380

A scaffold makes the switch.  

PubMed

Protein kinase cascades are a reoccurring feature of signal transduction pathways. Recent investigations have focused on how kinase-scaffolding proteins help to convert a graded stimulus into a switch-like or binary response. New findings reveal that the graded-to-binary conversion can be turned on or off, depending on the location of the scaffold within the cell. PMID:18941137

Dohlman, Henrik G

2008-10-21

381

Spark gap switch with spiral gas flow  

DOEpatents

A spark gap switch having a contaminate removal system using an injected gas. An annular plate concentric with an electrode of the switch defines flow paths for the injected gas which form a strong spiral flow of the gas in the housing which is effective to remove contaminates from the switch surfaces. The gas along with the contaminates is exhausted from the housing through one of the ends of the switch.

Brucker, J.P.

1988-03-23

382

P-I-N Diode Switches Project  

NASA Astrophysics Data System (ADS)

The design of PIN switches in microwaves, the action of the PIN diode as a switch in the on and off states and several types of switches are described. Two SPDT (single pole double throw) switches prototypes were designed. The first, at 400 MHz, presents 40 dB isolation and 0.75 db insertion. The second, at 2.2 GHz, has 20 dB isolation and insertion low better than 0.7 dB.

Tude, E. A. P.

1984-07-01

383

A gate-controlled MISIM switch  

Microsoft Academic Search

We report the first gate-controlled MISIM switch, Its switching voltage can be controlled from 7.2 V to 2.5 V by a gate bias ranging from -5 V to +5 V. The gate-controlled MISIM switch has the capability to address individual devices. This capability is not shared by a substrate current controlled MISIM switch reported earlier. We also fabricated the first

C. L. Shieh; S. Wagner; L. D. Jackel; R. E. Howard

1982-01-01

384

Optical switching nodes: architectures and performance  

Microsoft Academic Search

We propose and describe four optical buffer-less switching node architectures studied in the European Network of Excellence e-Photon\\/ONe. We consider two possible switching scenarios: data at inputs may require either an output fiber (fiber to fiber switching) or an output fiber and a specific wavelength (wavelength to wavelength switching). We first describe the four architectures; then, we propose both heuristic

A. Bianco; F. Neri; C. Piglione

2007-01-01

385

A growable large scale ATM multicast switch  

Microsoft Academic Search

This paper focuses on designing a large N×N high performance, broadband ATM switch. Despite advances in architectural designs, practical switch dimensions continue to be severely limited by both the technological and physical constraints of packaging. Here, we focus on augmentation in a “single-switch” design: we provide ways to construct arbitrarily large switches out of modest-size components and retain overall delay\\/throughput

K. L. Law; A. Leon-Garcia

1996-01-01

386

A new architecture of photonic ATM switches  

Microsoft Academic Search

A photonic asynchronous transfer mode (ATM) switch architecture for ATM operation at throughputs greater than 1 Tbit\\/s is proposed. The switch uses vertical-to-surface transmission electrophotonic devices (VSTEPs) for the optical buffer memory, and an optical-header-driven self-routing circuit in contrast with conventional photonic ATM switches using electrically controlled optical matrix switches. The optical buffer memory using massively parallel optical interconnections is

Makoto Nishio; Shuji Suzuki; Kazuo Takagi; I. Ogura; T. Numai; K. Kasahara; K. Kaede

1993-01-01

387

Switching to “lighter” cigarettes and quitting smoking  

Microsoft Academic Search

Objective:Smokers who switch to “lighter” cigarettes may be diverted from quitting smoking. We assessed factors associated with switching and the association between switching and (1) making a quit attempt, and (2) recent quitting, yielding a measure of net quitting (attempts × recent quitting).Design:In 2003, a total of 30 800 ever-smokers who smoked in the past year provided history of switching

H A Tindle; S Shiffman; A M Hartman; J E Bost

2009-01-01

388

Carbon isotope controlled molecular switches  

NASA Astrophysics Data System (ADS)

Single molecules represent one fundamental limit to the downscaling of electronics. As a prototype element for carbon-based nanoscale science and technology, the detailed behavior of carbon monoxide (CO) on the copper surface Cu(111) has been investigated. These investigations span from individual carbon isotope resolution, to single molecules, to compact clusters assembled by molecular manipulation via a homemade scanning tunneling microscope (STM). Sub-nanoscale devices, composed of only a few molecules, which exploit both lone CO properties and molecule-molecule interaction, have been designed and assembled. The devices function as bi-stable switches and can serve as classical bits with densities > 50 Tbits/cm2. Operated in the nuclear mass sensitive regime, each switch can also function as a molecular "centrifuge" capable of identifying the isotope of a single carbon atom in real-time. A model, based on electron-vibron couping and inelastic tunneling, has been developed and explains the dynamic behavior of the switch. The interaction between pairs of switches was also explored and it was found that their behavior ranges from completely independent to strongly coupled. Larger nanostructures, which were composed of many sub-switches organized to leverage the fully coupled interaction, link two spatially separated "bits" on the surface. Such a linked system can set or read a state non-locally, which is equivalent to bidirectional information transfer. The linked system has also exhibited logic functionality. These experiments demonstrate scalable molecular cells for information storage, and for information processing through cellular automata logic schemes.

Foster, Brian K.

389

Correlated randomness and switching phenomena  

NASA Astrophysics Data System (ADS)

One challenge of biology, medicine, and economics is that the systems treated by these serious scientific disciplines have no perfect metronome in time and no perfect spatial architecture—crystalline or otherwise. Nonetheless, as if by magic, out of nothing but randomness one finds remarkably fine-tuned processes in time and remarkably fine-tuned structures in space. Further, many of these processes and structures have the remarkable feature of “switching” from one behavior to another as if by magic. The past century has, philosophically, been concerned with placing aside the human tendency to see the universe as a fine-tuned machine. Here we will address the challenge of uncovering how, through randomness (albeit, as we shall see, strongly correlated randomness), one can arrive at some of the many spatial and temporal patterns in biology, medicine, and economics and even begin to characterize the switching phenomena that enables a system to pass from one state to another. Inspired by principles developed by A. Nihat Berker and scores of other statistical physicists in recent years, we discuss some applications of correlated randomness to understand switching phenomena in various fields. Specifically, we present evidence from experiments and from computer simulations supporting the hypothesis that water’s anomalies are related to a switching point (which is not unlike the “tipping point” immortalized by Malcolm Gladwell), and that the bubbles in economic phenomena that occur on all scales are not “outliers” (another Gladwell immortalization). Though more speculative, we support the idea of disease as arising from some kind of yet-to-be-understood complex switching phenomenon, by discussing data on selected examples, including heart disease and Alzheimer disease.

Stanley, H. E.; Buldyrev, S. V.; Franzese, G.; Havlin, S.; Mallamace, F.; Kumar, P.; Plerou, V.; Preis, T.

2010-08-01

390

A new two-switch flyback battery equalizer with low voltage stress on the switches  

Microsoft Academic Search

In this paper, a new battery equalizer applying two-switch flyback topologies is proposed. Since the proposed circuit is based on two-switch flyback structure, voltage stress on the switches can be clamped at the battery stack voltage level. Furthermore, the number of active devices is minimized by using a common switch and a common clamping diode. The operational principle, theoretical analysis,

Hyoung-Suk Kim; Ki-Bum Park; Sang-Hyun Park; Gun-Woo Moon; Myung-Joong Youn

2009-01-01

391

Degree of Conversational Code-Switching Enhances Verbal Task Switching in Cantonese-English Bilinguals  

ERIC Educational Resources Information Center

|The study examined individual differences in code-switching to determine the relationship between code-switching frequency and performance in verbal and non-verbal task switching. Seventy-eight Cantonese-English bilinguals completed a semi-structured conversation to quantify natural code-switching, a verbal fluency task requiring language…

Yim, Odilia; Bialystok, Ellen

2012-01-01

392

49 CFR 236.6 - Hand-operated switch equipped with switch circuit controller.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Hand-operated switch equipped with switch circuit controller. 236.6 Section 236.6...All Systems General § 236.6 Hand-operated switch equipped with switch circuit controller....

2012-10-01

393

30 CFR 57.12002 - Controls and switches.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 false Controls and switches. 57.12002...METAL AND NONMETAL MINES Electricity Surface and Underground § 57.12002 Controls and switches. Electric...with switches or other controls. Such switches or...

2010-07-01

394

30 CFR 57.12002 - Controls and switches.  

Code of Federal Regulations, 2010 CFR

...2009-07-01 false Controls and switches. 57.12002...METAL AND NONMETAL MINES Electricity Surface and Underground § 57.12002 Controls and switches. Electric...with switches or other controls. Such switches or...

2009-07-01

395

30 CFR 56.12002 - Controls and switches.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Controls and switches. 56.12002 Section 56.12002...Electricity § 56.12002 Controls and switches. Electric equipment and circuits shall be provided with switches or other controls. Such switches...

2013-07-01

396

Light activated solid-state opening switches  

SciTech Connect

Light-activated solid-state opening switches are shown to be a viable approach for switching inductive circuits. Measured photoswitch performance indicates that light-activated opening switches have the power density ratings needed to develop compact inductive power systems.

Petr, R.A.; Kachen, G.I.; Reilly, J.P.; Schaefer, R.B. (W.J. Schafer Associates, Chelmsford, MA (United States)); Heyse, M.W. (Wright Labs., Eglin AFB, FL (United States))

1993-01-01

397

Plasma opening switch with extrinsic magnetic field  

Microsoft Academic Search

Summary form only given, as follows. We have demonstrated in series of experiments that plasma opening switch (POS) switching voltage (UPOS) is defined by energy density (w) deposited in the POS plasma. If we then consider a plasma erosion mainly responsible for the effect of POS switching (the erosion effect could be described by Hall or Child-Langmuir models) the energy

G. Dolgachev; N. Barinov; D. Maslennikov

2001-01-01

398

Minimum heat generation during fast magnetization switching  

NASA Astrophysics Data System (ADS)

Fast magnetization switching with minimum heat generation is explored based upon magnetization dynamics and optimal stochastic control method. For current spin current based magnetic device, pulse shape optimization provides significant Joule heating reduction. For future spintronic device without charge moving, the minimum amount of heat generated during magnetization switching is fundamentally constrained by magnetization switching speed and magnetization nonvolatility.

Wang, Xiaobin; Gu, Ying

2013-03-01

399

Environmental Qualification of an Actuator Torque Switch  

Microsoft Academic Search

Environmental qualification testing was performed on a modified Limitorque torque switch for the torque switch safety functions in the Limitorque type SMB actuators located inside and outside containment in a nuclear power plant. The torque switch specimen was installed in a Limitorque SMB-1 electric actuator mounted on an 8'' Velan gate valve and operated with a customized programmable logic controller

A. M. Chan; S. L. Barreca; T. Kostela

2006-01-01

400

49 CFR 236.822 - Switch, spring.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Switch, spring. 236.822 Section 236.822 Transportation...APPLIANCES Definitions § 236.822 Switch, spring. A switch equipped with a spring device which forces the points to their...

2011-10-01

401

49 CFR 236.822 - Switch, spring.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Switch, spring. 236.822 Section 236.822 Transportation...APPLIANCES Definitions § 236.822 Switch, spring. A switch equipped with a spring device which forces the points to their...

2012-10-01

402

Depletion edge translation waveguide crossing optical switch  

Microsoft Academic Search

A waveguide crossing optical switch using the depletion edge translation concept is described. By using a single AlGaAs\\/GaAs material growth and ion implantation technology, an impedance discontinuity is formed at the intersection of two waveguides. Switching operation has been observed, and a high-speed, small-device-size, and high-extinction-ratio optical switch are expected

T. C. Huang; T. Hausken; K. Lee; N. Dagli; L. A. Coldren; D. R. Myers

1989-01-01

403

Micromechanical switches fabricated using nickel surface micromachining  

Microsoft Academic Search

Micromechanical switches have been fabricated in electroplated nickel using a four-level surface micromachining process. The simplest devices are configured with three terminals, a source, a drain, and a gate and are 30 ?m wide, 1 ?m thick, and 65 ?m long. A voltage applied between the gate and source closes the switch, connecting the source to the drain. Devices switch

Paul M. Zavracky; Sumit Majumder; Nicol E. McGruer

1997-01-01

404

Memory Switches in Chemical Reaction Space  

Microsoft Academic Search

Just as complex electronic circuits are built from simple Boolean gates, diverse biological functions, including signal transduction, differentiation, and stress response, frequently use biochemical switches as a functional module. A relatively small number of such switches have been described in the literature, and these exhibit considerable diversity in chemical topology. We asked if biochemical switches are indeed rare and if

Naren Ramakrishnan; Upinder S. Bhalla

2008-01-01

405

Practical Multistage Space-Time Switching Networks  

Microsoft Academic Search

This paper discusses PCM switching networks using combined space-time (ST) nonblocking switches in multistage arrays. The interplay between switch, network, and path-search characteristics is considered and the networks chosen for the Swiss system IFS-1 are described.

J. Beesley

1973-01-01

406

Stresses in piezoceramics undergoing polarization switchings  

Microsoft Academic Search

Piezoelectric materials exhibit nonlinear behavior when subjected to large electrical or mechanical loads. This strong nonlinear material behavior is induced by localized polarization switching (i.e., change of the polarization direction) at the subgrain level. In this article, a nonlinear finite element code is described to model polarization switchings in piezoceramics subjected to large electromechanical loads. The local polarization switching criterion

Y. Fotinich; G. P. Carman

2000-01-01

407

A gain-coefficient switched Alexandrite laser  

NASA Astrophysics Data System (ADS)

We report on a gain-coefficient switched Alexandrite laser. An electro-optic modulator is used to switch between high and low gain states by making use of the polarization dependent gain of Alexandrite. In gain-coefficient switched mode, the laser produces 85 ns pulses with a pulse energy of 240 mJ at a repetition rate of 5 Hz.

Lee, Chris J.; van der Slot, Peter J. M.; Boller, Klaus-J.

2013-01-01

408

Numerical simulation of plasma opening switches  

SciTech Connect

Plasma Opening Switches have been examined numerically with the aid of the ANTHEM plasma simulation model. A generic bi-cylindrical switch is studied. The switching of generator pulses ranging from 50 ns to 1 ..mu..sec is reviewed, for a variety of plasma fill lengths and densities, and for a range of resistive loads. 7 refs., 9 figs.

Mason, R.J.; Jones, M.E.; Bergman, C.D.

1989-01-01

409

ANTHEM simulation of plasma opening switches  

SciTech Connect

Plasma Opening Switches have been examined numerically with the aid of the ANTHEM plasma simulation model. A generic bi-cylindrical switch is studied. The switching of generator pulses ranging from 50 ns to 1 /mu/sec is reviewed, for a variety of plasma fill lengths and densities, and for a range of resistive loads. 7 refs., 9 figs.

Mason, R.J.; Jones, M.E.; Bergman, C.

1989-01-01

410

30 CFR 57.9308 - Switch throws.  

Code of Federal Regulations, 2013 CFR

...Resources 1 2013-07-01 2013-07-01 false Switch throws. 57.9308 Section 57.9308 Mineral...Railroads, and Loading and Dumping Sites § 57.9308 Switch throws. Switch throws shall be installed to provide clearance to...

2013-07-01

411

49 CFR 213.135 - Switches.  

Code of Federal Regulations, 2010 CFR

...2009-10-01 2009-10-01 false Switches. 213.135 Section 213.135 Transportation...STANDARDS Track Structure § 213.135 Switches. (a) Each stock rail must be securely seated in switch plates, but care shall be used to...

2009-10-01

412

Switch Detection in Preschoolers' Cognitive Flexibility  

ERIC Educational Resources Information Center

|The current study addressed the role of switch detection in cognitive flexibility by testing the effect of transition cues (i.e., cues that directly signal the need to switch or maintain a given task goal) in a cued set-shifting paradigm at 5 years of age. Children performed better, especially on switch trials, when transition cues were combined…

Chevalier, Nicolas; Wiebe, Sandra A.; Huber, Kristina L.; Espy, Kimberly Andrews

2011-01-01

413

14 CFR 27.1145 - Ignition switches.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 2013-01-01 false Ignition switches. 27.1145 Section 27.1145 ...Accessories § 27.1145 Ignition switches. (a) There must be means to quickly shut off all ignition by the grouping of switches or by a master ignition control....

2013-01-01

414

30 CFR 56.9308 - Switch throws.  

Code of Federal Regulations, 2013 CFR

...Resources 1 2013-07-01 2013-07-01 false Switch throws. 56.9308 Section 56.9308 Mineral...Railroads, and Loading and Dumping Sites § 56.9308 Switch throws. Switch throws shall be installed to provide clearance to...

2013-07-01

415

30 CFR 75.1000 - Cutout switches.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Cutout switches. 75.1000 Section 75.1000 ...Trolley Feeder Wires § 75.1000 Cutout switches. [Statutory Provisions] Trolley...wires, shall be provided with cutout switches at intervals of not more than...

2013-07-01

416

49 CFR 213.135 - Switches.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Switches. 213.135 Section 213.135 Transportation...STANDARDS Track Structure § 213.135 Switches. (a) Each stock rail must be securely seated in switch plates, but care shall be used to...

2010-10-01

417

Switching Costs between Customer Satisfaction and Loyalty  

Microsoft Academic Search

Switching cost is becoming a popular topic in the researches of customer satisfaction and customer loyalty. There are already some deeply understandings of the relationship among switching cost, satisfaction and loyalty inside many marketing literatures. Even so, there are still two open questions have not been answered: firstly how the cost of switching service or product influences in customer loyalty

Xuecheng Yang; Jun Wu; Xiaohang Zhang; Feng Zuo; Quan Yu

2009-01-01

418

Gain switching of semiconductor injection lasers  

SciTech Connect

The limiting factors in short pulse generation by gain switching of semiconductor lasers are analyzed using an approach parallel to conventional Q switching analysis. The dependence of the gain-switched pulse width and pulse energy on various input parameters such as drive current amplitude, bias current, and spontaneous emission factor, etc., can be predicted in a simple manner.

Lau, K.Y.

1988-01-25

419

Critical Information at Critical Moments  

ERIC Educational Resources Information Center

|On a daily basis, administrators are reminded of the potential, perhaps the likelihood, of violence or natural crises on their campuses. Comprehensive studies have been conducted and point to recommendations and best practices for planning, preparing, responding to, and recovering from critical incidents. The International Association of Campus…

Fierman, Ben; Thrower, Raymond H., Jr.

2011-01-01

420

Nonlinear interface optical switch structure for dual mode switching revisited  

NASA Astrophysics Data System (ADS)

There is a need for devices which will allow integration of photonic/optical computing subsystems into electronic computing architectures. This presentation reviews the nonlinear interface optical switch (NIOS) concept and then describes a new effect, the erasable optical memory (EOM) effect. We evaluate an extension of the NIOS device to allow simultaneous optical/electronic, i.e. dual mode, switching of light utilizing the EOM effect. Specific devices involve the fabrication of thin film tungsten (VI) oxide (WO3) and tungsten (V) oxide (W2O5) on the hypotenuse of glass (BK-7), fused silica (SiO2) and zinc selenide (ZnSe) right angle prisms. Chemical reactions and temporal response tests were performed and are discussed.

Bussjager, Rebecca J.; Osman, Joseph M.; Chaiken, Joseph

1998-07-01

421

Novel Scheme of All-Optical Signal Switching in Semiconductor NLDC: Self-Induced Transparency Soliton Switch.  

National Technical Information Service (NTIS)

A novel scheme for ultrafast all-optical switching in a semiconductor NLDC has been investigated numerically. The operating characteristics of a model switch have been demonstrated: switching speed 2 Tbit/s, zero device recovery time, switching contract r...

N. Peyghambarian I. Talanina

1997-01-01

422

Grating light modulators for use as demultiplexer and switching device in wavelength-selective switching systems  

Microsoft Academic Search

All optical switches have been used with measured success in response to a high demand in all optical networks, and a dramatic increase in the Internet and communication needs over the last decade. The wavelength-selective switch is the mechanism used in various switching applications. MEMS-based wavelength-selective switches (WSS) are the most promising technology to bring all-optical switches into wide implementation

Araya Pothisorn; Alex J. Hariz

2007-01-01

423

Switching dynamics of IGBTs in soft-switching converters  

Microsoft Academic Search

Next generation of power semiconductor devices will be designed and optimized to meet the specific application requirements. Mixed-mode simulations are used to study the carrier dynamics in punch-through and nonpunch-through Insulated Gate Bipolar Transistor (IGBT) structures during soft- and hard-switching conditions. The simulation results are shown to qualitatively predict the measured bump in the tail current with varying output dv\\/dt

Imam Widjaja; A. Kurnia; Krishna Shenai; Deepakraj M. Divan

1995-01-01

424

Perpendicular magnetic anisotropy materials for reduced current switching devices  

NASA Astrophysics Data System (ADS)

Recently, spin-transfer switching of magnetic tunnel junctions (MTJs) has become a very active area of research. It is theoretically postulated that using perpendicular magnetic anisotropy materials will substantially reduce the critical current density for switching, resulting in lower energy devices, while keeping the thermal stability high. A range of perpendicular anisotropy material systems, including (i) multilayers, (ii) crystalline alloys, and (iii) amorphous alloys have been intensively studied in this dissertation. The surface and bulk anisotropy, damping parameter, and structural properties of these material systems have been investigated. Magnetic tunnel junctions based on some of these perpendicular material schemes have been fabricated, and their transport properties have been measured and related to the anisotropy. We have found several promising approaches to magnetic tunnel junctions utilized in spin-torque transfer random access memory (STT-RAM).

Tadisina, Zeenath Reddy

425

Threshold switching in chalcogenide-glass thin films  

NASA Astrophysics Data System (ADS)

The paper discusses the bias-induced threshold switching in chalcogenide-glass thin films and establishes the fundamentally electronic origin of the initiation process. An isothermal model is analyzed for filamentary ON-state solutions via a set of phenomenological kinetic equations consistent with recent advances in the understanding of the electronic structure of chalcogenide glasses. The model predictions compare favorably with experimental results; the model is basically that the switching transition develops when a critical electric field is reached in the sample, usually near an electrode. Field-induced carrier generation then causes the charged traps in the bulk to fill; when all the traps are filled, carriers can transit the sample with an enhanced mobility and the generation rate required to keep the traps filled is reduced from its threshold value.

Adler, D.; Shur, M. S.; Silver, M.; Ovshinsky, S. R.

1980-06-01

426

Evaluation of MCT in soft switching motor drive converter  

SciTech Connect

This paper evaluates the performance of a MOS-Controlled Thyristor (MCT) in a practical application. The {ital P}-type MCT is used in an AC Resonant Link Converter (ACRLC) which synthesizes three phase motor line currents from a high frequency AC (20 kHz) input. Based on the principle of discrete pulse modulation, the ACRLC operates as a current regulator. All switching transitions for line current wave-shaping occur at the AC link zero voltage crossings. Hence, in theory, switching losses are significantly reduced. This paper discusses the loss mechanisms, difficulties and solutions in using MCTs in ACRLCs. The MCT is critically evaluated, based on experimental results, on whether or not its present technology will allow the device to be utilized in resonant power conversion required for high efficiency, variable speed motor drives. {copyright} {ital 1996 American Institute of Physics.}

Langovsky, N.; Elbuluk, M. [Department of Electrical Engineering, University of Akron, Akron, Ohio 44325-3904 (United States); Kankam, D. [Power Technology Division, NASA Lewis Center, Cleveland, Ohio 44135 (United States)

1996-03-01

427

Distribution of supercurrent switching in graphene under the proximity effect.  

SciTech Connect

We study the stochastic nature of switching current in hysteretic current-voltage characteristics of superconductor-graphene-superconductor junctions. We find that the dispersion of the switching current distribution scales with temperature as {sigma}{sub I} {proportional_to} T{sup {alpha}{sub G}} with {alpha}{sub G} as low as 1/3. This observation is in sharp contrast to the known Josephson junction behavior where {sigma}{sub I} {proportional_to} T{sup {alpha}{sub J}} with {alpha}{sub J} = 2/3. We propose an explanation using a generalized version of Kurkijaervi's theory for the flux stability in rf-SQUID and attribute this anomalous effect to the temperature dependence of the critical current which persists down to low temperatures.

Coskun, U. C.; Brenner, M.; Hymel, T.; vakaryuk, V.; Levchenko, A.; Bezryadin, A. (Materials Science Division); (Univ. Illinois-Urbana); (Univ. Texas); (Michigan State Univ.)

2012-01-01

428

A microscopic model of current-induced switching of magnetization.  

PubMed

The behaviour of the magnetization in a ferromagnetic metal/nonmagnetic insulator/ferromagnetic metal/paramagnetic metal tunnel junction is studied, using the nonequilibrium Keldysh formalism. The two ferromagnets are described using the single-band Hubbard model. The left one is treated in the mean field approximation and the right ferromagnet within a (nonequilibrium) spectral density approach which takes interactions beyond the mean field into account. When a voltage is applied to the junction we observe a change of the relative orientation of the two magnetizations, which can be switched from parallel to antiparallel alignment and vice versa. This switching appears in a self-consistent way, so there is no need to use half-classical methods like the Landau-Lifshitz-Gilbert equation one. The dependence of the critical voltage at which the magnetization changes its sign on the model parameters can be studied in a systematic way. PMID:21386267

Sandschneider, N; Nolting, W

2009-12-09

429

Modeling for optically interconnected packet switches  

NASA Astrophysics Data System (ADS)

This paper studies the performance of a large-scale free-space photonic packet switch based on the generalised knockout principle. Input and output channels are grouped into sectors to make the whole switch a Clos-like three-stage architecture. The input traffic is mainly IP data packets but compatible with ATM cells. Fan-in and fan-out stages are suitable to use free-space optical interconnections with Spatial Light Modulator (SLM) as the switching element. The switch performance was studied based on the switching simulation under different traffic conditions and routing schemes.

Wang, Yalou; Crossland, William A.; Scarr, Robin W.

2000-10-01

430

Pulsed laser triggered high speed microfluidic switch  

NASA Astrophysics Data System (ADS)

We report a high-speed microfluidic switch capable of achieving a switching time of 10 ?s. The switching mechanism is realized by exciting dynamic vapor bubbles with focused laser pulses in a microfluidic polydimethylsiloxane (PDMS) channel. The bubble expansion deforms the elastic PDMS channel wall and squeezes the adjacent sample channel to control its fluid and particle flows as captured by the time-resolved imaging system. A switching of polystyrene microspheres in a Y-shaped channel has also been demonstrated. This ultrafast laser triggered switching mechanism has the potential to advance the sorting speed of state-of-the-art microscale fluorescence activated cell sorting devices.

Wu, Ting-Hsiang; Gao, Lanyu; Chen, Yue; Wei, Kenneth; Chiou, Pei-Yu

2008-10-01

431

Frequency and mode control of Q-switched Nd:YAG lasers  

SciTech Connect

This dissertation presents two experimental studies which extend the usefulness of Q-switched Nd:YAG lasers in nonlinear optical and spectroscopic applications. The major part of this dissertation describes injection locking of Q-switched Nd:YAG lasers. A transient injection locking theory is developed which describes single axial mode selection in Q-switched or gain switched laser oscillators. Comparison is made with experiments carried out for an unstable resonator Q-switched Nd:YAG oscillator. We demonstrate that injection locking provides very stable single axial mode output with Fourier transform limited bandwidth from a high power Q-switched Nd:YAG oscillator. The second part of this dissertation describes high phasematching temperature Lithium Niobate single crystals for efficient second harmonic generation of 1.064 ..mu..m Nd:YAG lasers. Growth procedures of high phasematching temperature Lithium Niobate crystals are investigated for various concentration of excessive Lithium Oxide and co-doped Magnesium Oxide in melt composition and for various growth parameters. We have grown high quality Lithium Niobate crystals with a phasematching temperature which is above the optical index damage annealing point. We have evaluated the improved Lithium Niobate crystal advantages of large nonlinearity and ability to achieve non-critical phasematching condition by efficiently doubling a TEM/sub 00/ and multitransverse mode cw lamp pumped acoustic-optic Q-switched Nd:YAG laser.

Park, Y.K.

1981-01-01

432

Two-terminal nanoelectromechanical bistable switches based on molybdenum-sulfur-iodine molecular wire bundles  

NASA Astrophysics Data System (ADS)

We demonstrate the application of Mo6S3I6 molecular wire bundles for electrically controllable two-terminal on-off switches. We investigate how changes in the contact electrode material and geometry influence the device characteristics, hysteretic switching behavior and device stability. We also determine the device operating parameters, particularly the Young's moduli (40-270 GPa), operating current densities (3.2 × 105-7 × 106 A m - 2) and force constants. Although qualitatively, the properties of Mo6S3I6 nanowires in nanoelectromechanical (NEM) switches are similar to those of carbon nanotubes (CNTs), their lower friction coefficient, higher mechanical stability and higher operation voltages give specific advantages in terms of smaller differences in on-off operating potentials, higher switching speeds and lower energy consumption than CNTs, which are critical for applications in NEM devices.

Andzane, J.; Prikulis, J.; Dvorsek, D.; Mihailovic, D.; Erts, D.

2010-03-01

433

ELECTROMAGNETIC AND THERMAL SIMULATIONS FOR THE SWITCH REGION OF A COMPACT PROTON ACCELERATOR  

SciTech Connect

A compact proton accelerator for medical applications is being developed at Lawrence Livermore National Laboratory. The accelerator architecture is based on the dielectric wall accelerator (DWA) concept. One critical area to consider is the switch region. Electric field simulations and thermal calculations of the switch area were performed to help determine the operating limits of rmed SiC switches. Different geometries were considered for the field simulation including the shape of the thin Indium solder meniscus between the electrodes and SiC. Electric field simulations were also utilized to demonstrate how the field stress could be reduced. Both transient and steady steady-state thermal simulations were analyzed to find the average power capability of the switches.

Wang, L; Caporaso, G J; Sullivan, J S

2007-06-15

434

New PWM switched-mode converter topologies  

NASA Astrophysics Data System (ADS)

Two augmented switching cells are proposed from which four novel topologies can be derived: an augmented buck converter, an augmented boost converter, a novel switching power amplifier, and a novel switching controlled rectifier. The augmented buck and the augmented boost converters realize higher step-down and step-up ratios, respectively, under a given switch duty ratio by proper design of the turn ratios of the transformer and coupled inductor. The switching power amplifier achieves four-quadrant output by the use of two bidirectional current switches and a single power supply, while the inverse converter can be used as a switching controlled rectifier. The experimental verification of the power amplifier is presented.

Hua, Gui-Chao; Huang, Shi-Peng

435

[Critical incidents].  

PubMed

In medicine real severe mishaps are rare. On the other hand critical incidents are frequent. Anonymous critical incident reporting systems allow us to learn from these mishaps. This learning process will make our daily clinical work safer Unfortunately, before these systems can be used efficiently our professional culture has to be changed. Everyone in medicine has to admit that errors do occur to see the need for an open discussion. If we really want to learn from errors, we cannot punish the individual, who reported his or her mistake. The interest is primarily in what has happened and why it has happened and not who has committed this mistake. The cause for critical incidents in medicine is in over 80% the human factor Poor communication, work under enormous stress, conflicts and hierarchies are the main cause. This has been known for many years, therefore have already 15 years ago high-tech industries, like e.g. aviation, started to invest in special courses on team training. Medicine is a typical profession were until now only the individual performance decided about the professional career Communication, conflict management, stress management, decision making, risk management, team and team resource management were subjects that have never been taught during our preor postgraduate education. These points are the most important ones for an optimal teamwork. A multimodular course designed together with Swissair (Human Aspect Development medical, HADmedical) helps to cover, as in aviation, the soft factor and behavioural education in medicine and to prepare professionals in health care to work as a real team. PMID:15801660

Scheidegger, D

2005-03-01

436

Powered oscillator using ignitron switches  

NASA Astrophysics Data System (ADS)

A 10-MVA-scale resonant oscillator, powered by a pulse-forming network and switched with a pair of commutating mercury ignitrons, was developed for the MST reversed-field pinch plasma-confinement experiment. A novel feature of this circuit is its commutation mechanism, wherein each turning on of one ignitron causes a reverse voltage transient that turns off the other. Two of these oscillators are used in oscillating-field current-drive tests, in which they are capable of nearly 1MW net input power to the plasma, with resonant frequencies of a few 100 Hz for pulse durations of a few tens of ms, being precharged for immediate full amplitude. We describe the circuit and its operation, and discuss features that allow reliable, high-current commutation of the ignitrons and exploit their low switching impedance.

Nonn, P. D.; Blair, A. P.; McCollam, K. J.; Sarff, J. S.; Stone, D. R.

2011-06-01

437

Large aperture optical switching devices  

SciTech Connect

We have developed a new approach to constructing large aperture optical switches for next generation inertial confinement fusion lasers. A transparent plasma electrode formed in low pressure ionized gas acts as a conductive coating to allow the uniform charging of the optical faces of an electro-optic material. In this manner large electric fields can be applied longitudinally to large aperture, high aspect ratio Pockels cells. We propose a four-electrode geometry to create the necessary high conductivity plasma sheets, and have demonstrated fast (less than 10 nsec) switching in a 5x5 cm aperture KD*P Pockels cell with such a design. Detaid modelling of Pockels cell performance with plasma electrodes has been carried out for 15 and 30 cm aperture designs.

Goldhar, J.; Henesian, M.A.

1983-12-12

438

A study of IGBT turn-off behavior and switching losses for zero-voltage and zero-current switching  

Microsoft Academic Search

The switching losses of insulated gate bipolar transistors (IGBTs) with zero voltage and zero current switching are compared with the switching losses of IGBTs with hard switching. The turn-off behavior of the IGBT is studied in detail for both zero voltage and zero current switching. The effect of a reverse current during turn-off is also investigated for zero current switching

Keming Chen; Thomas A. Stuart

1992-01-01

439

On calibrating enterprise switch measurements  

Microsoft Academic Search

The complexity of modern enterprise networks is ever-increasing, and our understanding of these important networks is not keeping pace. Our insight into intra-subnet traffic (staying within a single LAN) is particularly limited, due to the widespread use of Ethernet switches that preclude ready LAN-wide monitoring. We have re- cently undertaken an approach to obtaining extensive intra-subnet visibility based on tapping

Boris Nechaev; Vern Paxson; Mark Allman; Andrei Gurtov

2009-01-01

440

DNA Bending and Sugar Switching  

Microsoft Academic Search

Using high frequency antiphase NMR spectroscopy and computer simulations of the antiphase spectra, we studied the equlibria in the sugar conformations in the DNA duplex 11-mer containing the AAA tract surrounded by cytosines. We demonstrate that at the 3?-end of the A-tract, the sugar switches from the common S-conformer (B-like form) to the N-conformer (A-like form) with the probability of

Shantaram Kamath; Mukti H. Sarma; Victor B. Zhurkin; Christopher J. Turner; Ramaswamy H. Sarma

2000-01-01

441

Magnetoelectric Switching of Exchange Bias  

Microsoft Academic Search

The perpendicular exchange bias field, HEB, of the magnetoelectric heterostructure Cr2O3(111)\\/(Co\\/Pt)3 changes sign after field cooling to below the Néel temperature of Cr2O3 in either parallel or antiparallel axial magnetic and electric freezing fields. The switching of HEB is explained by magnetoelectrically induced antiferromagnetic single domains which extend to the interface, where the direction of their end spins controls the

Pavel Borisov; Andreas Hochstrat; Xi Chen; Wolfgang Kleemann; Christian Binek

2005-01-01

442

The intricate workings of a bacterial epigenetic switch.  

PubMed

Bacteria have developed epigenetic mechanisms to control the reversible Off-to-On switching of cell surface structures such as pyelonephritis-associated pili (PAP). The pap pili switch is primarily controlled by the global regulator leucine-responsive regulatory protein (Lrp), the local regulator PapI, and DNA adenine methylase (Dam). There are two sets of binding sites for Lrp in the pap regulatory region: promoter proximal sites 1,2,3 and promoter distal sites 4,5,6. The pilin promoter proximal (GATCprox) and distal (GATCdist) targets for Dam are located within Lrp binding sites 2 and 5, respectively. In the Off state, Lrp binds cooperatively to sites 1,2,3 overlapping the papBA pilin promoter, shutting off pilin transcription, and blocking methylation of GATCprox. Binding of Lrp at sites 1,2,3, together with methylation of GATCdist, reduces the affinity of Lrp for sites 4,5,6, preventing simultaneous binding of Lrp at sites 4,5,6 upstream. Switching to the phase. On state requires the environmentally regulated PapI co-regulator, which increases the affinity of Lrp for sites 5 and 2. PapI binds specifically to Lrp-pap DNA complexes via binding with Lrp as well as contact with DNA sequences within pap sites 5 and 2. Directionality in switching from Off to On appears to be due to methylation of GATCprox, which prevents formation of the PapI-Lrp-pap site 2 ternary complex. A switch model is presented in which DNA replication is proposed to play a critical role by generating a hemimethylated GATCdist site and displacing Lrp from sites 1,2,3. This facilitates methylation of GATCprox and binding of PapI-Lrp to sites 4,5,6, with subsequent activation of pap transcription. The first gene product of the pap operon, PapB, positively regulates papI transcription, resulting in a positive feedback loop that helps maintain the On state. The pap switch is environmentally regulated by a number of factors including the CpxAR two-component regulatory system, the Histone-like nucleoid structuring protein H-NS, and cAMP-Catabolite Gene Activator Protein (CAP), which all involve binding of regulatory binding proteins to pap DNA sequences with subsequent alteration of PapI and Lrp binding. The Pap switch mechanism, with interesting variations, is conserved among a number of enteric bacteria, controlling expression of many unrelated pili-adhesin complexes. PMID:15230094

Hernday, Aaron; Braaten, Bruce; Low, David

2004-01-01

443

Conductance switching in organic monolayers  

NASA Astrophysics Data System (ADS)

Self-assembled monolayers of some organic molecules, such as the bipyridyl-dinitro (BPDN) [1], present conductance switching (toggling between ON and OFF states). The switching happens upon crossing fixed threshold values in the applied bias voltage and the device can ``remember'' its previous state; thus, they have potential value as electronic memory devices. We use density-functional theory to elucidate the atomistic origins of this phenomenon. Extensive geometry relaxations revealed two adsorption states; namely, an atop and a hollow adsorption geometry. The electronic structure of both adsorption states were further recalculated using localized basis functions and the electrical currents through these devices were estimated within the Landauer approximation. The atop state shows a higher current than the hollow state, which matches the ON and OFF conductance states observed experimentally. We attribute the conductance switching to fluctuations in the adsorption geometry of the monolayers. Ab initio calculations can help us to understand the atomistic causes of the memory effect, which is essential for having a systematic approach to theory-guided molecular synthesis. Supported by DOE grant DE-FG02-02ER45995. [1] A. S. Blum, et al., Nature Materials 4, 167 (2005).

Agapito, Luis; Alkis, Sabri; Krause, Jeffrey; Cheng, Hai-Ping

2009-03-01

444

H? control for switched fuzzy systems via dynamic output feedback: Hybrid and switched approaches  

NASA Astrophysics Data System (ADS)

Fuzzy T-S model has been proven to be a practical and effective way to deal with the analysis and synthesis problems for complex nonlinear systems. As for switched nonlinear system, describing its subsystems as fuzzy T-S models, namely switched fuzzy system, naturally is an alternative method to conventional control approaches. In this paper, the H? control problem for a class of switched fuzzy systems is addressed. Hybrid and switched design approaches are proposed with different availability of switching signal information at switching instant. The hybrid control strategy includes two parts: fuzzy controllers for subsystems and state updating controller at switching instant, and the switched control strategy contains the controllers for subsystems. It is demonstrated that the conservativeness is reduced by introducing the state updating behavior but its cost is an online prediction of switching signal. Numerical examples are given to illustrate the effectiveness of proposed approaches and compare the conservativeness of two approaches.

Xiang, Weiming; Xiao, Jian; Iqbal, Muhammad Naveed

2013-06-01

445

Optimization Of Output Q-Switched Nd:YAG Laser Based On Switching Time  

NASA Astrophysics Data System (ADS)

This paper reports the optimization of output Q-switch Nd:YAG. A free running Nd:YAG laser was employed as source of light. KD*P crystal was utilized as a Pockels cell. Avalanche transistor pulser was designed to switch a high voltage power supply. The switching time was conducted via a control unit based PIC16F84A microcontroller. The pulser was able to switch the voltage within 3 ns. The optimum switching time of Q-switching is obtained at 182.34 ?s. The corresponding laser output is 40 mJ with pulse duration of 25 ns.

Tamuri, Abd Rahman; Daud, Yaacob Mat; Bidin, Noriah

2010-07-01

446

Oscillations of a capillary switch used as a miniature opto-fluidic device  

Microsoft Academic Search

A capillary switch (CS) is a continuous volume of liquid consisting of a sessile and a pendant drop that are coupled through a liquid filled hole in a plate. When capillary force is much larger than body forces such as gravity, this simple, coupled interfacial system exhibits multiple equilibrium states beyond a critical volume. Owing to its extremely small size,

Santhosh Ramalingam; Osman Basaran

2009-01-01

447

Measuring IC switching current waveforms using a GMI probe for power integrity studies  

Microsoft Academic Search

IC switching current is the main noise source of many power integrity issues in printed circuit boards. Accurate measurement of the current waveforms is critical for an effective power distribution network design. In this paper, using a giant magnetoimpedance (GMI) probe for this purpose is studied. A side-band detection and demodulation system is built up to measure various time-domain waveforms

Fan Zhou; Songping Wu; David Pommerenke; Yoshiki Kayano; Hiroshi Inoue; Kenji Tan; Jun Fan

2010-01-01

448

Developing parasitic cancellation technologies to improve EMI filter performance for switching mode power supplies  

Microsoft Academic Search

Electromagnetic interference (EMI) filters have been used for power electronics converters to attenuate switching noise and meet EMI standards for a long time. However, because of the parasitics in the filters, filters cannot attenuate high-frequency noises efficiently. In this paper, critical parasitics, which include both mutual and self-parasitics, are first identified in both differential and common mode filters. Three techniques

Shuo Wang; Rengang Chen; Jacobus Daniel Van Wyk; Fred. C. Lee; Willem Gerhardus Odendaal

2005-01-01

449

Dynamically reconfigurable optical packet switch (DROPS)  

NASA Astrophysics Data System (ADS)

A novel Dynamically Reconfigurable Optical Packet Switch (DROPS) that combines both spectral and spatial switching capabilities is proposed and experimentally demonstrated for the first time. Compared with an Arrayed Waveguide Grating Router (AWGR), the added spatial switching capability provided by the microelectromechanical systems (MEMS) enables dynamically reconfigurable routing that is not possible with an AWGR alone. This methodology has several advantages over an AWGR including scalability, additional degrees of freedom in routing a packet from an ingress port to an egress port and more flexibility in path or line card recovery. The experimental demonstration implemented with 10-Gb/s packets shows that the added spatial switching does not degrade the bit-error-rate performance, indicating the promising potential of DROPS as a versatile and ultra-high capacity switch for optical packet-switched networks.

Huang, Chi-Heng; Chou, Hsu-Feng; Bowers, John E.; Toudeh-Fallah, Farzam; Gyurek, Russ

2006-12-01

450

Plasma gate switch experiment on Pegasus II  

SciTech Connect

The plasma gate switch is a novel technique for producing a long conduction time vacuum opening switch. The switch consists of an aluminum foil which connects the cathode to the anode in a coaxial geometry. The foil is designed so that the maximum axial acceleration is in the center of the foil and that at the appropriate time, the center opens up and magnetic flux is carried down the gun to the load region. The switch is designed to minimize the amount of mass transported into the load region. We have completed the first experimental test of this design and present results from the test. These results indicate there were some asymmetry problems in the construction of the switch but that otherwise the switch performed as expected.

Wysocki, F.J.; Benage, J.F. Jr.; Shlachter, J.S. [and others

1995-09-01

451

High voltage, magnetically switched pulsed power systems  

SciTech Connect

The principles of magnetic switching are briefly described. Then the results of experiments on the following substantive topics for magnetic switching are presented: material properties and how they relate to switch performance, risetime limitations, and core insulation. Magnetic switching is then evaluated from a system perspective. An idealized pulse power system with 200 kJ or stored energy and a 40 ns output pulse is examined. The multi-megavolt electrical insulation requirements impose limitations on the switches. The cost of the magnetically switched system exceeds the cost of the conventional superpower generator system by up to 75%. The potential for reliability, reproducibility, and repetitive pulse capability must be evaluated for each application to offset the increased cost.

VanDevender, J.P.; Reber, R.A.

1981-01-01

452

Language switching in the production of phrases.  

PubMed

The language switching task has provided a useful insight into how bilinguals produce language. So far, however, the studies using this method have been limited to lexical access. The present study provides empirical evidence on language switching in the production of simple grammar structures. In the reported experiment, Polish-English unbalanced bilinguals switched between their L1 and L2 while describing pictures of ongoing and completed actions with simple SV progressive and perfective phrases. The results show asymmetrical switching costs for progressive phrases and symmetrical switching costs with reversed dominance for perfective phrases. These findings parallel those obtained in tasks requiring the production of single words, although the present study is the first in which the same bilingual participants display different patterns of switching costs depending on the characteristics of utterances they produce. These results can be explained using recently developed models of bilingual language control. PMID:22450881

Tarlowski, Andrzej; Wodniecka, Zofia; Marzecová, Anna

2013-04-01

453

Dynamically reconfigurable optical packet switch (DROPS).  

PubMed

A novel Dynamically Reconfigurable Optical Packet Switch (DROPS) that combines both spectral and spatial switching capabilities is proposed and experimentally demonstrated for the first time. Compared with an Arrayed Waveguide Grating Router (AWGR), the added spatial switching capability provided by the microelectromechanical systems (MEMS) enables dynamically reconfigurable routing that is not possible with an AWGR alone. This methodology has several advantages over an AWGR including scalability, additional degrees of freedom in routing a packet from an ingress port to an egress port and more flexibility in path or line card recovery. The experimental demonstration implemented with 10-Gb/s packets shows that the added spatial switching does not degrade the bit-error-rate performance, indicating the promising potential of DROPS as a versatile and ultra-high capacity switch for optical packet-switched networks. PMID:19529627

Huang, Chi-Heng; Chou, Hsu-Feng; Bowers, John E; Toudeh-Fallah, Farzam; Gyurek, Russ

2006-12-11

454

Molecular Switches and Motors on Surfaces  

NASA Astrophysics Data System (ADS)

Molecular switches and motors respond structurally, electronically, optically, and/or mechanically to external stimuli, testing and potentially enabling extreme miniaturization of optoelectronic devices, nanoelectromechanical systems, and medical devices. The assembly of motors and switches on surfaces makes it possible both to measure the properties of individual molecules as they relate to their environment and to couple function between assembled molecules. In this review, we discuss recent progress in assembling molecular switches and motors on surfaces, measuring static and dynamic structures, understanding switching mechanisms, and constructing functional molecular materials and devices. As demonstrative examples, we choose a representative molecule from three commonly studied classes including molecular switches, photochromic molecules, and mechanically interlocked molecules. We conclude by offering perspectives on the future of molecular switches and motors on surfaces.

Pathem, Bala Krishna; Claridge, Shelley A.; Zheng, Yue Bing; Weiss, Paul S.

2013-04-01

455

Diamond switches for high temperature electronics  

SciTech Connect

Diamond switches are well suited for use in high temperature electronics. Laboratory feasibility of diamond switching at 1 kV and 18 A was demonstrated. DC blocking voltages up to 1 kV were demonstrated. A 50 {Omega} load line was switched using a diamond switch, with switch on-state resistivity {approx}7 {Omega}-cm. An electron beam, {approx}150 keV energy, {approx}2 {mu}s full width at half maximum was used to control the 5 mm x 5 mm x 100 {mu}m thick diamond switch. The conduction current temporal history mimics that of the electron beam. These data were taken at room temperature.

Prasad, R.R.; Rondeau, G.; Qi, Niansheng [Alameda Applied Sciences Corp., San Leandro, CA (United States)] [and others

1996-04-25

456

Voltage-impulse-induced non-volatile ferroelastic switching of ferromagnetic resonance for reconfigurable magnetoelectric microwave devices.  

PubMed

A critical challenge in realizing magnetoelectrics based on reconfigurable microwave devices, which is the ability to switch between distinct ferromagnetic resonances (FMR) in a stable, reversible and energy efficient manner, has been addressed. In particular, a voltage-impulse-induced two-step ferroelastic switching pathway can be used to in situ manipulate the magnetic anisotropy and enable non-volatile FMR tuning in FeCoB/PMN-PT (011) multiferroic heterostructures. PMID:23857709

Liu, Ming; Howe, Brandon M; Grazulis, Lawrence; Mahalingam, Krishnamurthy; Nan, Tianxiang; Sun, Nian X; Brown, Gail J

2013-07-15

457

Spiro-oxazine photochromic fiber optical switch  

NASA Astrophysics Data System (ADS)

A photochromic all-optical switch in telecommunication-grade fiber is fabricated by filling a fiber Bragg grating Fabry-Pérot resonator with a spiro-oxazine solution. The narrow linewidth of the resonator allows for a high sensitivity of the resonance wavelengths to the index change. The switch is controlled by low intensity UV light exposure, and operation at infrared telecommunication wavelengths is demonstrated. The switching speed on the order of minutes has been achieved.

Huang, Yanyi; Liang, Wei; Poon, Joyce K. S.; Xu, Yong; Lee, Reginald K.; Yariv, Amnon

2006-05-01

458

Subpicosecond optical switching in polystyrene opal  

NASA Astrophysics Data System (ADS)

An ultrafast all-optical switching is demonstrated in an organic three-dimensional nonlinear photonic crystal with a response time as short as 120 fs. The operating wavelength of the optical switching is in the visible spectrum. The switching function is realized by a shift of the photonic band gap under optical pumping. It is found that the photonic band gap shifts about 10 nm with the excitation of 27.5 GW/cm2 pump laser.

Liu, Yuanhao; Hu, Xiaoyong; Zhang, Dongxiang; Cheng, Bingying; Zhang, Daozhong; Meng, Qingbo

2005-04-01

459

Design of a RF NEMS switch matrix  

Microsoft Academic Search

This paper presents for the first time, the development of a monolithic RF NEMS switch matrix. A prototype 3×3 monolithic switch matrix is designed and simulated at the nano-scale level using Ansoft HFSS and Agilent ADS. Simulation results show that the proposed NEMS switch matrices are capable of working up to 60GHz with good RF performance such as return loss

Eugene Siew; King Yuk Chan; Rodica Ramer; Andrew Dzurak

2011-01-01

460

Performance analysis of storage area network switches  

Microsoft Academic Search

This paper focuses on a switching architecture designed for storage area network (SAN) applications, with a crossbar switching fabric and an aggregate bandwidth of hundreds of Gbps. We describe the architecture and adopt an abstract model of the flow-controlled, credit-based, packet transfer around the switching fabric. The major effects on performance of the credit-based flow control are investigated under different

Andrea Bianco; Paolo Giaccone; Enrico Maria Giraudo; Fabio Neri; Enrico Schiattarella

2005-01-01

461

Improved Competitive Performance Bounds for CIOQ Switches  

Microsoft Academic Search

Combined Input and Output Queued (CIOQ) architectures with a moderate fabric speedup\\u000a S>1 have come to play a major role in the design of high performance switches. In this paper we study CIOQ switches with First-In-First-Out\\u000a (FIFO) buffers providing Quality of Service (QoS) guarantees. The goal of the switch policy is to maximize the total value\\u000a of packets sent out

Alex Kesselman; Kirill Kogan; Michael Segal

462

Improved Competitive Performance Bounds for CIOQ Switches  

Microsoft Academic Search

Combined input and output queued (CIOQ) architectures with a moderate fabric speedup\\u000a S?>?1 have come to play a major role in the design of high performance switches. In this paper we study CIOQ switches with\\u000a First-In-First-Out (FIFO) buffers providing Quality of Service (QoS) guarantees. The goal of the switch policy is to maximize\\u000a the total value of packets sent out

Alexander Kesselman; Kirill Kogan; Michael Segal

2008-01-01

463

Defense switched network technology and experiments program  

NASA Astrophysics Data System (ADS)

This report documents work performed during FY 1983 on the DCA-sponsored Defense Switched Network Technology and Experiments Program. The areas of work reported are: (1) development of routing algorithms for application in the Defense Switched Network (DSN); (2) instrumentation and integration of the Experimental Integrated Switched Network (EISN) test facility; (3) development and test of data communication techniques using DoD-standard data protocols in an integrated voice/data network; and (4) EISN system coordination and experiment planning.

Weinstein, C. J.

1983-09-01

464

Diamond switches for high temperature electronics  

SciTech Connect

This paper presents the results of switching voltages of 500 V and currents of 10 A using chemical vapor deposited (CVD) diamond as a switching material. The switching is performed by using an electron beam that penetrates the diamond, creates electron hole pairs, and lowers its resistivity to about 20 {Omega}-cm and its resistance to about 4 {Omega}. Tests were performed at room temperature but in a configuration that allows for 250 C.

Loubriel, G.M.; Zutavern, F.J.; Ruebush, M.H. [and others

1997-06-01

465

A comparative study of switching losses of IGBTs under hard-switching, zero-voltage-switching and zero-current-switching  

Microsoft Academic Search

A high power IGBT tester, based on the typical clamped inductive load circuit and incorporating zero-voltage-transition and zero-current-transition soft-switching schemes, has been developed. Both turn-on losses, including the losses associated with reverse recovery of the clamp (free-wheeling) diode, and turn-off losses are measured and compared for slow and fast IGBT devices. Benefits of zero-voltage-switching (ZVS) and zero-current-switching (ZCS) operation of

Konrong Wang; Fred C. Lee; Guichao Hua; Dum Borojevic

1994-01-01

466

Microwave-triggered laser switch  

DOEpatents

A high-repetition rate switch is described for delivering short duration, high-powered electrical pulses from a pulsed-charged dc power supply. The present invention utilizes a microwave-generating device such as a magnetron that is capable of producing high-power pulses at high-pulse repetition rates and fast-pulse risetimes for long periods with high reliability. The rail-gap electrodes provide a large surface area that reduces induction effects and minimizes electrode erosion. Additionally, breakdown is initiated in a continuous geometric fashion that also increases operating lifetime of the device.

Piltch, M.S.

1982-05-19

467

Microwave-triggered laser switch  

DOEpatents

A high-repetition rate switch for delivering short duration, high-power electrical pulses from a pulsed-charged dc power supply. The present invention utilizes a microwave-generating device such as a magnetron that is capable of producing high-power pulses at high-pulse repetition rates and fast-pulse risetimes for long periods with high reliability. The rail-gap electrodes provide a large surface area that reduces induction effects and minimizes electrode erosion. Additionally, breakdown is initiated in a continuous geometric fashion that also increases operating lifetime of the device.

Piltch, Martin S. (Los Alamos, NM)

1984-01-01

468

Laser activated diffuse discharge switch  

DOEpatents

The invention is a gas mixture for a diffuse discharge switch which is capable of changing from a conducting state to an insulating state in the presence of electrons upon the introduction of laser light. The mixture is composed of a buffer gas such as nitrogen or argon and an electron attaching gas such as C.sub.6 H.sub.5 SH, C.sub.6 H.sub.5 SCH.sub.3, CH.sub.3 CHO and CF.sub.3 CHO wherein the electron attachment is brought on by indirect excitation of molecules to long-lived states by exposure to laser light.

Christophorou, Loucas G. (Oak Ridge, TN); Hunter, Scott R. (Oak Ridge, TN)

1988-01-01

469

Laser-triggered vacuum switch  

DOEpatents

A laser-triggered vacuum switch has a material such as a alkali metal halide on the cathode electrode for thermally activated field emission of electrons and ions upon interaction with a laser beam, the material being in contact with the cathode with a surface facing the discharge gap. The material is preferably a mixture of KCl and Ti powders. The laser may either shine directly on the material, preferably through a hole in the anode, or be directed to the material over a fiber optic cable. 10 figs.

Brannon, P.J.; Cowgill, D.F.

1990-12-18

470

Laser-triggered vacuum switch  

DOEpatents

This invention pertains to a laser-triggered vacuum switch that has a material such as a alkali metal halide on the cathode electrode for thermally activated field emission of electrons and ions upon interaction with a laser beam, the material being in contact with the cathode with a surface facing the discharge gap. The material is preferably a mixture of KCl and Ti powders. The laser may either shine directly on the material, preferably through a hole in the anode, or be directed to the material over a fiber optic cable. 6 figs.

Brannon, P.J.; Cowgill, D.F.

1988-09-27

471

Laser-triggered vacuum switch  

DOEpatents

A laser-triggered vacuum switch has a material such as a alkali metal halide on the cathode electrode for thermally activated field emission of electrons and ions upon interaction with a laser beam, the material being in contact with the cathode with a surface facing the discharge gap. The material is preferably a mixture of KCl and Ti powders. The laser may either shine directly on the material, preferably through a hole in the anode, or be directed to the material over a fiber optic cable.

Brannon, Paul J. (Albuquerque, NM); Cowgill, Donald F. (Danville, CA)

1990-01-01

472

Multi-level information encoding through spectral switches and multiple FSO link formation in the phase singularity domain  

NASA Astrophysics Data System (ADS)

Spectral switching is now a well-known phenomenon. Recently, its potential applications have been explored for information encoding and transmission in free space. In this paper, we demonstrate a novel type of scheme to encode and process information at multiple levels through spectral switching. A new technique is also proposed to establish multiple parallel free-space optical (FSO) links using a single critical direction in the phase singularity domain of diffracted polychromatic light. These are contrived ideas on the basis of theoretical and experimental studies carried out so far on spectral switching. The study might find potential application in the fields of FSO interconnects and FSO communication.

Yadav, Bharat K.; Kandpal, H. C.

2011-07-01

473

CMOS off-chip driver design with simultaneous switching noise and switching time considerations  

Microsoft Academic Search

A design constraint for CMOS off-chip drivers that will meet a pre-specified normalized maximum simultaneous switching ground noise and a prespecified normalized time when the switched NMOST leaves the saturation region is provided in this paper

Yaochao Yang; J. R. Brews

1995-01-01

474

Features operation of the switching-mode UHF power amplifier with soft switching current and voltage  

Microsoft Academic Search

The bases operation of the power amplifier in a switching mode with soft switching current and voltage are presented. The addition of already existing mathematical model, including the description of commutative loss, taking place at practice (nonideal) device operation.

Aleksey M. Shingarev; Alexander V. Mikushin

2008-01-01

475

Thermooptic deflection and switching in glass.  

PubMed

New types of active optical device in glass such as deflectors and modulators/switches using the thermooptic effect originating from the temperature dependence of the refractive index are proposed and demonstrated. Thermally induced index changes for light deflection and switching are provided by applying an appropriate voltage to a small film heater deposited on the glass surface. Thermooptic waveguide switches fabricated by the ion-exchange technique successfully exhibited a switching speed of the order of 1 msec with 0.5-W driving electric power. PMID:20396258

Haruna, M; Koyama, J

1982-10-01

476

Redox-based resistive switching memories.  

PubMed

This review covers resistive random access memories which utilize redox processes and ionic motion on the nanoscale as their storage principle (ReRAM). Generic aspects are described in order to provide the physics and chemistry background for the explanation of the microscopic switching mechanism and of the high nonlinearity in the switching kinetics. The valence change memory (VCM) effect is elaborated in more detail. As common features, ReRAM typically show very short switching times, low switching energies, and long data retention times. In addition, they offer a scalability potential down to feature sizes in the order of 5 nm and below. PMID:23421124

Waser, Rainer

2012-10-01

477

A capacitor-boosted, soft-switched switched-reluctance motor drive  

Microsoft Academic Search

A resonant type soft-switched\\/switched-reluctance motor drive circuit using capacitors is proposed. Since the circuit performs soft-switching by resonating a capacitor and a motor winding, the voltage across the winding can be higher than twice the DC source voltage. Hence the circuit produces less EMI due to the application of soft-switching, and the output torque is increased by means of higher

Y. Murai; Ji Cheng; S. Sugimoto; M. Yoshida

1999-01-01

478

OBIG: the Architecture of an Output Buffered Switch with Input Groups for Large Switches  

Microsoft Academic Search

Large, fast switches require novel approaches to architecture and scheduling. In this paper, we propose the Output Buffered Switch with Input Groups (OBIG). We present simulation results, discuss the implementation, and show how our architecture can be used to build single-stage (flat) switches with multi-terabit-per-second throughput and hundreds of ports. Large switches with hundreds of ports and terabit-per- second throughput

Wladek Olesinski; Hans Eberle; Nils Gura

2007-01-01

479

Switching control of an R\\/C hovercraft: stabilization and smooth switching  

Microsoft Academic Search

This paper presents stable switching control of an radio-controlled (R\\/C) hovercraft that is a nonholonomic (nonlinear) system. To exactly represent its nonlinear dynamics, more importantly, to maintain controllability of the system, we newly propose a switching fuzzy model that has locally Takagi-Sugeno (T-S) fuzzy models and switches them according to states, external variables, and\\/or time. A switching fuzzy controller is

Kazuo Tanaka; Masaaki Iwasaki; Hua O. Wang

2001-01-01

480

Design of a single-switch-per-phase converter for switched reluctance motor drives  

Microsoft Academic Search

The main considerations in the design of a single-switch-per-phase converter for a switched reluctance motor (SRM) drive are described, with particular attention given to the choice of converter topology, the type of switching devices, the normalized rating of the power devices, and input filter design. The converter uses MOSFET switches. Experimental verification is included with a 6\\/4 pole personal-computer-controlled prototype

R. Krishnan; P. N. Materu

1990-01-01

481

A single switch boost-flyback DC-DC converter integrated with switched-capacitor cell  

Microsoft Academic Search

Without extreme duty ratio or complexity of circuits, by employing coupled-inductor and switched-capacitor cell achieved high voltage conversion ratio with a single switch is proposed in this paper. Coupled-inductor transfer source energy to secondary side through entire switching period, the leakage energy of coupled inductor is efficiently recycled; the inrush current problem on switched capacitors was restrained by leakage inductor

Tsorng-Juu Liang; Shih-Ming Chen; Lung-Sheng Yang; Jiann-Fuh Chen; Adrian Ioinovici

2011-01-01

482

Two-switch flyback-forward PWM DC-DC converter with reduced switch voltage stress  

Microsoft Academic Search

This paper introduces a two-switch flyback-forward pulse-width modulated (PWM) DC-DC converter along with the steady-state analysis, simplified design procedure, and experimental verification. The proposed converter topology is the result of integrating the secondary sides of the two-switch flyback and the two-switch forward converters in an anti-parallel connection, while retaining the two-main switches and the clamping diodes on a single winding

Dakshina Murthy-Bellur; Marian K. Kazimierczuk

2010-01-01

483

The universal criterion for switching a magnetic vortex core in soft magnetic nanodots  

SciTech Connect

The universal criterion for ultrafast vortex core switching between core-up and -down vortex bi-states in soft magnetic nanodots was empirically investigated by micromagnetic simulations and combined with an analytical approach. Vortex-core switching occurs whenever the velocity of vortex core motion reaches a critical value, which is {nu}{sub c} = 330 {+-} 37 m/s for Permalloy, as estimated from numerical simulations. This critical velocity was found to be {nu}{sub c} = {eta}{sub c}{gamma} {radical}A{sub ex} with A{sub ex} the exchange stiffness, {gamma} the gyromagnetic ratio, and an estimated proportional constant {eta}{sub c} = 1.66 {+-} 0.18. This criterion does neither depend on driving force parameters nor on the dimension or geometry of the magnetic specimen. The phase diagrams for the vortex core switching criterion and its switching time with respect to both the strength and angular frequency of circular rotating magnetic fields were derived, which offer practical guidance for implementing vortex core switching into future solid state information storage devices.

Lee, K.-S.; Kim, S.-K.; Yu, Y.-S.; Choi, Y.-S.; Guslienko, K. Y.; Jung, H.; Fischer, P.

2008-10-01

484

REST-dependent epigenetic remodeling promotes the in vivo developmental switch in NMDA receptors  

PubMed Central

N-methyl-D-aspartate receptors (NMDARs) are critical to synaptogenesis, neural circuitry and higher cognitive functions such as learning and memory. A hallmark feature of NMDARs is an early postnatal developmental switch from primarily GluN2B- to GluN2A-containing. Although the switch in phenotype has been an area of intense interest for two decades, the mechanisms that trigger it, and the link between experience and the switch are unclear. Here we show a novel role for the transcriptional repressor REST in the developmental switch of synaptic NMDARs. REST is activated at a critical window of time and acts via epigenetic remodeling to repress grin2b expression and properties at rat hippocampal synapses. Knockdown of REST in vivo prevented the decline in GluN2B and developmental switch in NMDARs. Notably, maternal deprivation impaired REST activation and acquisition of the mature NMDAR phenotype. Thus, REST is essential for experience-dependent fine-tuning of genes involved in synaptic plasticity.

Rodenas-Ruano, Alma; Chavez, Andres E.; Cossio, Maria J.; Castillo, Pablo E.; Zukin, R. Suzanne

2012-01-01

485

Switch II mutants reveal coupling between the nucleotide- and actin-binding regions in myosin V.  

PubMed

Conserved active-site elements in myosins and other P-loop NTPases play critical roles in nucleotide binding and hydrolysis; however, the mechanisms of allosteric communication among these mechanoenzymes remain unresolved. In this work we introduced the E442A mutation, which abrogates a salt-bridge between switch I and switch II, and the