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1

Critical Sulfhydryl Switches, Diet, and Cancer Prevention Workshop - Executive Summary  

Cancer.gov

Critical Sulfhydryl Switches, Diet, and Cancer Prevention Workshop Executive Summary OPENING REMARKS Welcome Peter Greenwald, Director, Division of Cancer Prevention John Milner, Nutritional Sciences Research Group, Division of Cancer Prevention Peter Greenwald, M.D., Ph.D., Director, Division of Cancer Prevention (DCP), National Cancer Institute (NCI), National Institutes of Health (NIH), welcomed participants and explained that NCI has been working to enhance the field of basic nutritional science and its relationship to cancer prevention.

2

August 28, 2003: Critical Sulfhydryl Switches, Diet, and Cancer Prevention Workshop; Bethesda, MD  

Cancer.gov

Critical Sulfhydryl Switches, Diet, and Cancer Prevention Workshop Meeting Date August 28, 2003 Meeting Location Bethesda Marriott Hotel Bethesda, MD Meeting Materials Agenda Executive Summary (pdf, 96kb) Attendee List (pdf, 1kb) Speakers List

3

August 28, 2003: Critical Sulfhydryl Switches, Diet, and Cancer Prevention Workshop - Speakers List  

Cancer.gov

Critical Sulfhydryl Switches, Diet, and Cancer Prevention Workshop Speakers List Elizabeth H. Jeffery, Ph.D., Chair Professor Nutritional Sciences Research Group Division of Cancer Prevention National Cancer Institute National Institutes of Health

4

Reactions of nifurtimox with critical sulfhydryl-containing biomolecules: their potential toxicological relevance.  

PubMed

Nifurtimox (Nfx) is a drug used in the treatment of Chagas' disease, an endemic parasitic disease from Latin American countries. It produces undesirable side-effects in patients, frequently forcing the treatment to be stopped. Its toxic mechanism is not fully understood. In this work we describe purely chemical reactions of Nfx with relevant cellular sulfhydryl (SH) compounds. The compounds tested were glutathione (GSH), cysteine (RSH), lipoic acid (LA) and coenzyme A (CoA). All reacted with Nfx to give nitrite (NO(-) (2)). The relative reaction rates were CoA>LA>GSH>RSH. In studies with GSH and RSH the formation of nitrite was accompanied by decreases in Nfx concentration and increases in the formation of a reaction product revealed by HPLC. We failed to show the presence of liver cytosolic GST (GSH transferase activity)-mediated formation of NO2- from Nfx. These NO(-) (2)-releasing processes occurred under in vivo conditions in Nfx-treated Sprague-Dawley male rats (240-260 g body weight) at a dose of 100 mg Nfx kg(-1) p.o. In urine samples NO(-) (2) excretion was accompanied by unchanged drug and two unidentified more polar metabolites detectable by HPLC. The Nfx reactions with critical SH from molecules such as GSH, RSH, LA and CoA, and potentially others containing SH residues (e.g. enzymes or structural proteins), might have toxicological relevance not only for the Nfx side-effects but also for the chemotherapeutic effects on Trypanosoma cruzi. In addition, Nfx reactions with GSH might be crucial in Nfx detoxification. PMID:15211612

Díaz, E G; Montalto de Mecca, M; Castro, J A

2004-01-01

5

Sulfhydryl oxidases: sources, properties, production and applications  

Microsoft Academic Search

The formation of disulfide bonds in proteins and small molecules can greatly affect their functionality. Sulfhydryl oxidases\\u000a (SOXs) are enzymes capable of oxidising the free sulfhydryl groups in proteins and thiol-containing small molecules by using\\u000a molecular oxygen as an electron acceptor. SOXs have been isolated from the intracellular compartments of many organisms, but\\u000a also secreted SOXs are known. These latter

Greta Faccio; Outi Nivala; Kristiina Kruus; Johanna Buchert; Markku Saloheimo

2011-01-01

6

3-Terminal pMTJ reduces critical current and switching time  

NASA Astrophysics Data System (ADS)

To realize the potential of magnetic tunnel junctions (MTJs) for high-density non-volatile memory and non-volatile logic, the critical current to switch the magnetization must be lowered. This paper presents a simulation study of a new structure of perpendicular MTJs (pMTJs) which divides the fixed layer into two coupling parts. We investigate the TMR and the critical current density of this new pMTJ by micromagnetic simulation using OOMMF for various cases. The simulation results show that this new structure pMTJ has lower critical current and shorter switching time compared to the conventional three-layer MTJs.

Cheng, Lanting; Khizroev, Sakhrat; Liang, Ping

2014-05-01

7

Sulfhydryl oxidases: sources, properties, production and applications.  

PubMed

The formation of disulfide bonds in proteins and small molecules can greatly affect their functionality. Sulfhydryl oxidases (SOXs) are enzymes capable of oxidising the free sulfhydryl groups in proteins and thiol-containing small molecules by using molecular oxygen as an electron acceptor. SOXs have been isolated from the intracellular compartments of many organisms, but also secreted SOXs are known. These latter enzymes are generally active on small compounds and their physiological role is unknown, whereas the intracellular enzymes prefer proteins as substrates and are involved in protein folding. An increasing number of scientific publications and patent applications on SOXs have been published in recent years. The present mini-review provides an up-to-date summary of SOXs from various families, their production and their actual or suggested applications. The sequence features and domain organisation of the characterised SOXs are reviewed, and special attention is paid to the physicochemical features of the enzymes. A review of patents and patent applications regarding this class of enzymes is also provided. PMID:21732243

Faccio, Greta; Nivala, Outi; Kruus, Kristiina; Buchert, Johanna; Saloheimo, Markku

2011-08-01

8

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

2013-01-01

9

Mouse Liver Protein Sulfhydryl Depletion after Acetaminophen Exposure  

PubMed Central

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

2013-01-01

10

Critical analysis and remedy of switching failures in straintronic logic using Bennett clocking in the presence of thermal fluctuations  

SciTech Connect

Straintronic logic is a promising platform for beyond Moore's law computing. Using Bennett clocking mechanism, information can propagate through an array of strain-mediated multiferroic nanomagnets, exploiting the dipolar coupling between the magnets without having to physically interconnect them. Here, we perform a critical analysis of switching failures, i.e., error in information propagation due to thermal fluctuations through a chain of such straintronic devices. We solved stochastic Landau-Lifshitz-Gilbert equation considering room-temperature thermal perturbations and show that magnetization switching may fail due to inherent magnetization dynamics accompanied by thermally broadened switching delay distribution. Avenues available to circumvent such issue are proposed.

Roy, Kuntal, E-mail: royk@purdue.edu [School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907 (United States)] [School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907 (United States)

2014-01-06

11

Ligand-promoted oligomerization and sulfhydryl modification of biodegradative L-threonine dehydratase of Escherichia coli  

E-print Network

- Threonine, a competitive inhibitor. Chemical modification of the enzyme with DTNB or NEM shows that there are two classes of sulfhydryl groups which react at different rates. There are two sulfhydryl groups in the faster reacting class and one sulfhydryl... group in the slower reacting class. Modification of the faster reacting groups increases the Km for L-threonine but does not alter the Vmax. The enzyme is inactivated by the additional modification of the slower reacting group. At a given enzyme...

Cardozo, Luisa Elena

2012-06-07

12

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

13

Stretched relaxation after switching off the strong electric field in a near-critical solution under high pressure  

NASA Astrophysics Data System (ADS)

Experimental investigations of the relaxation of the nonlinear dielectric effect after switching off a strong electric field in a near-critical nitrobenzene-dodecane solution under high pressure are presented. The long-time tail of the decay is described by the stretched exponential function, with the exponent x=0.37+/-0.04. The early stages of the decay are portrayed by the power function R(t)=1-2.29(t/?)1/3, where ?OD denotes the Onuki-Doi relaxation time [Europhys. Lett. 17, 63 (1992)]. In the immediate vicinity of the critical consolute point a value ?OD~0.23 s was reached. Experimental decays observed at different pressures exhibit a scaling behavior. The pressure evolution of the scaling parameter shows a power behavior with the exponent y=1.1+/-0.2.

Rzoska, Sylwester J.; Zio?o, Jerzy; Drozd-Rzoska, Aleksandra

1997-09-01

14

Sulfhydryl reagents and energy-linked reactions in monocot thylakoids.  

PubMed

Monofunctional maleimides have been used to covalently modify the coupling factor protein of monocot thylakoid membranes. As with dicot thylakoids, incubation of the monocot thylakoids with maleimides in the light but not in the dark results in inhibition of both ATP synthesis and hydrolysis. In the dark, sites on the gamma and epsilon subunits of maize Zea mays coupling factor 1 are modified after incubation of maize mesophyll thylakoids with the fluorescent maleimide N-(anilinonaphthyl-4) maleimide. A light accessible site localized solely to the gamma subunit has also been demonstrated. In contrast to the case with dicot thylakoids (spinach [Spinacia oleracea] and pea [Pisum sativum]) treatment of monocot thylakoids (maize, barley [Hordeum vulgare], crabgrass [Digitaria sanguinalis]) with bifunctional maleimides or thiol oxidants in the light does not result in functional uncoupling, i.e the bifunctional reagents act more like energy transfer inhibitors. The lack of functional uncoupling could be due either to a failure of the reagents to cross-link key sulfhydryl residues in the gamma subunit or to the continued ability of the gamma subunit to gate proton movements through the chloroplast coupling factor complex even though its conformation has been altered by sulfhydryl reagents. PMID:16667548

Cohen, W S; Baxter, D R

1990-07-01

15

Sulfhydryl-specific probe for monitoring protein redox sensitivity.  

PubMed

Reactive oxygen species (ROS) regulate various biological processes by modifying reactive cysteine residues in the proteins participating in the relevant signaling pathways. Identification of ROS target proteins requires specific reagents that identify ROS-sensitive cysteine sulfhydryls that differ from the known alkylating agents, iodoacetamide and N-ethylmaleimide, which react nonspecifically with oxidized cysteines including sulfenic and sulfinic acid. We designed and synthesized a novel reagent, methyl-3-nitro-4-(piperidin-1-ylsulfonyl)benzoate (NPSB-1), that selectively and specifically reacts with the sulfhydryl of cysteines in model compounds. We validated the specificity of this reagent by allowing it to react with recombinant proteins followed by peptide sequencing with nanoUPLC-ESI-q-TOF tandem mass spectrometry (MS/MS), and mutant studies employed it to identify cellular proteins containing redox-sensitive cysteine residues. We also obtained proteins from cells treated with various concentrations of hydrogen peroxide, labeled them with biotinylated NPSB-1 (NPSB-B), pulled them down with streptavidin beads, and identified them with MS/MS. We grouped these proteins into four families: (1) those having reactive cysteine residues easily oxidized by hydrogen peroxide, (2) those with cysteines reactive only under mild oxidative stress, (3) those with cysteines reactive only after exposure to oxidative stress, and (4) those with cysteines that are reactive regardless of oxidative stress. These results confirm that NPSBs can serve as novel chemical probes for specifically capturing reactive cysteine residues and as powerful tools for measuring their oxidative sensitivity and can help to understand the function of cysteine modifications in ROS-mediated signaling pathways. PMID:25354229

Lee, Jae-Jin; Ha, Sura; Kim, Hee-Jung; Ha, Hyun Joo; Lee, Hee-Yoon; Lee, Kong-Joo

2014-12-19

16

A critical switch in the enzymatic properties of the Cid1 protein deciphered from its product-bound crystal structure  

PubMed Central

The addition of uridine nucleotide by the poly(U) polymerase (PUP) enzymes has a demonstrated impact on various classes of RNAs such as microRNAs (miRNAs), histone-encoding RNAs and messenger RNAs. Cid1 protein is a member of the PUP family. We solved the crystal structure of Cid1 in complex with non-hydrolyzable UMPNPP and a short dinucleotide compound ApU. These structures revealed new residues involved in substrate/product stabilization. In particular, one of the three catalytic aspartate residues explains the RNA dependence of its PUP activity. Moreover, other residues such as residue N165 or the ?-trapdoor are shown to be critical for Cid1 activity. We finally suggest that the length and sequence of Cid1 substrate RNA influence the balance between Cid1's processive and distributive activities. We propose that particular processes regulated by PUPs require the enzymes to switch between the two types of activity as shown for the miRNA biogenesis where PUPs can either promote DICER cleavage via short U-tail or trigger miRNA degradation by adding longer poly(U) tail. The enzymatic properties of these enzymes may be critical for determining their particular function in vivo. PMID:24322298

Munoz-Tello, Paola; Gabus, Caroline; Thore, Stéphane

2014-01-01

17

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

E-print Network

simulation Critical current density Spin transfer torque switching Heusler alloy Spin valve nanopillar a b with various coupling types [10­13]. According to Eq. (1), Heusler alloys with lower Ms, smaller a and higherMicromagnetic simulation of critical current density of spin transfer torque switching in a full-Heusler

Chen, Long-Qing

18

Critical Roles of Interactions among Switch I-preceding Residues and between Switch II and Its Neighboring ?-Helix in Conformational Dynamics of the GTP-bound Ras Family Small GTPases*  

PubMed Central

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

2011-01-01

19

The influence of sulfhydryl and sulfoxide on gross regeneration in the Hermit Crab (Pagurus longicarpus)  

Microsoft Academic Search

Summary and conclusion Experimental evidence is presented demonstrating that gross regeneration in the foot of the Hermit Crab (Pagurus longicarpus) is stimulated by the sulfhydryl group and retarded by the sulfoxide, a partially oxidized derivative thereof.

Frederik S. Hammett; Dorothy Wall Smith

1931-01-01

20

Protein Sulfhydryls and Their Role in the Antioxidant Function of Protein S-Thiolation  

Microsoft Academic Search

Protein S-thiolation\\/dethiolation, i.e., the oxidation of protein sulfhydryls to mixed disulfides and their reduction back to sulfhydryls, is an early cellular response to oxidative stress (1-5). This response may be elicited by oxidative phenomena of diverse origins, and the few cases that have been studied extensively give a limited insight into the metabolic roles and the molecular mechanism of the

J. A. Thomas; B. Poland; R. Honzatko

1995-01-01

21

ATM activation by a sulfhydryl-reactive inflammatory cyclopentenone prostaglandin.  

PubMed

ATM (ataxia-telangiectasia mutated) is activated by a variety of noxious agent, including oxidative stress, and ATM deficiency results in an anomalous cellular response to oxidative stress. However, the mechanisms for ATM activation by oxidative stress remain to be established. Furthermore, it is not clear whether ATM responds to oxidative DNA damage or to a change in the intracellular redox state, independent of DNA damage. We found that ATM is activated by N-methyl-N'-nitro-nitrosoguanidine (MNNG) and 15-deoxy-Delta(12,14)-prostaglandin J(2) (15d-PGJ(2)), in NBS1- or MSH6-deficient cells. We further found that ATM is activated by treating chromatin-free immunoprecipitated ATM with MNNG or 15d-PGJ(2), which modifies free sulfhydryl (SH) groups, and that 15d-PGJ(2) binds covalently to ATM. Interestingly, 15d-PGJ(2)-induced ATM activation leads to p53 activation and apoptosis, but not to Chk2 or H2AX phosphorylation. These results indicate that ATM is activated through the direct modification of its SH groups, independent of DNA damage, and this activation leads, downstream, to apoptosis. PMID:16824197

Kobayashi, Masahiko; Ono, Hirohito; Mihara, Keiko; Tauchi, Hiroshi; Komatsu, Kenshi; Shibata, Takashi; Shimizu, Hiroko; Uchida, Koji; Yamamoto, Ken-ichi

2006-07-01

22

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

23

Hemoglobin-sulfhydryls from tortoise (Geochelone carbonaria) can reduce oxidative damage induced by organic hydroperoxide in erythrocyte membrane.  

PubMed

Sulfhydryl groups are important to avoid oxidative damage to the cell. In RBC, tert-butyl hydroperoxide (tert-BOOH) and hydrogen peroxide (H2O2) are capable of oxidizing heme and promoting lipid peroxidation. H2O2 caused greater oxidation of heme than tert-BOOH, although the oxidation of sulfhydryl groups was similar. Geochelone carbonaria Hb, a rich sulfhydryl protein, inhibited the TBA-reactive substances formation of human erythrocytes exposed to tert-BOOH by about 30%; this decrease was smaller with Geochelone denticulata Hb. Sulfhydryl reagents diminished the number of reactive sulfhydryl groups in the G. carbonaria Hb resulting in a decrease of its antioxidant power, suggesting the involvement of sulfhydryls of Hb in the protection against lipid peroxidation. PMID:11026669

Torsoni, M A; Ogo, S H

2000-08-01

24

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

25

Evidence for Sulfhydryl Involvement in Regulation of Phytoalexin Accumulation in Trifolium repens Callus Tissue Cultures 1  

PubMed Central

White clover (Trifolium repens L.) callus tissue cultures accumulated the phytoalexin medicarpin after treatment with sulfhydryl reagents. After 24-hour exposures to sulfhydryl reagents, maximum obtainable levels of medicarpin, determined by high performance liquid chromatography analysis, were found with 50 millimolar N-ethyl maleimide, 25 millimolar HgCl2, 2 millimolar p-chloromercuribenzoic acid, and 0.5 millimolar iodoacetamide. Increased medicarpin levels were also observed in callus treated with p-chloromercuribenzene sulfonic acid, but the highest concentration tested (11.8 millimolar) did not produce the maximum response. After sulfhydryl treatment, medicarpin levels were unchanged for 4 to 6 hours, but steadily increased thereafter with maximum accumulation occurring by 48 to 50 hours for p-chloromercuribenzoic acid, p-chloromercuribenzene sulfonic acid, and HgCl2 treated callus. Medicarpin levels did not increase in iodoacetamide-treated callus until 8 hours after sulfhydryl exposure, and medicarpin levels were still increasing linearly after 50 hours. Three other metabolic inhibitors, KCN, NaF, and Na3AsO4, did not exhibit elicitor activity, indicating cell death was not a factor in the response. Pretreatment of callus with 20 millimolar dithiothreitol followed by 40 millimolar N-ethyl maleimide did not produce the phytoalexin response. Preincubation with dithiothreitol also prevented elicitor activity of HgCl2 and p-chloromercuribenzene sulfonic acid. These results suggested that dithiothreitol pretreatment somehow prevented sulfhydryl groups within the cell from reacting with the test compounds. These experiments established that the integrity of sulfhydryl groups is important in regulating phytoalexin accumulation in callus cells. PMID:16662101

Gustine, David L.

1981-01-01

26

Abundance of protein-bound sulfhydryl and bisulfide groups at chromosomal nucleolus organizing regions  

Microsoft Academic Search

Silver stainability of the chromosomal nucleolus organizing regions that contain the structural genes for ribosomal RNA can be abolished by proteolytic and oxidative treatments. Histone extraction has no effect. This indicates that reducing groups of non-histone chromosomal proteins are responsible for silver staining. Treatment with fluorescent sulfhydryl and disulfide specific reagents followed by silver staining demonstrates coincidence of silver dots

Charles H. C. M. Buys; Jan Osinga

1980-01-01

27

CHARACTERIZATION OF SULFHYDRYL PROTEINS INVOLVED IN THE MAINTENANCE OF FLAGELLAR STRAIGHTNESS IN HAMSTER SPERMATOZOA  

EPA Science Inventory

Hamster caput epididymal spermatozoa exhibit a marked 90-180 degree bend when induced to acquire progressive motility in vitro (Cornwall et al, 1988). lagellar bending is prevented by oxidizing sperm sulfhydryl (SH) groups with diamide. n the present study, the authors examined t...

28

The influence of fasting on liver sulfhydryl groups, glutathione peroxidase and glutathione-S-transferase activities in the rat  

Microsoft Academic Search

Sulfhydryl groups, glutathione peroxidase (GPx) and glutathione-S-transferase (GST) are important elements of the antioxidant\\u000a defence in the organism. The efficacy of their antioxidant action is influenced by many factors. In this work, the effect\\u000a of fasting on total, protein-bound and nonprotein sulfhydryl groups and on the activity of liver and serum GPx and GST in\\u000a rats were determined. Male Wistar

T. Szkudelski; M. Okulicz; I. Bialik; K. Szkudelska

2004-01-01

29

The reactivity of sulfhydryl groups of yeast DNA dependent RNA polymerase I.  

PubMed Central

The number of reactive cysteine residues of yeast RNA polymerase I was determined and their function was studied using parachloromercury benzoate (pCMB), dithiobisnitrobenzoate (DTNB) and N-ethyl-maleimide (NEM) as modifying agents. By treatment with DTNB about 45 sulfhydryl groups react in the presence of 8M urea. Under non-denaturing conditions only 20 sulfhydryl groups are reactive with pCMB and DTNB. Both reagents completely inactivate the enzyme and this effect can be reversed by reducing agents. The sedimentation coefficient and the subunit composition are not affected when the enzyme is inactivated. Two of the most reactive sulfhydryl groups are necessary for activity. The modification of these groups is partially protected by substrates and DNA, suggesting that they are involved either in catalysis or in the maintenance of the conformation of the active site. Experiments with 14C-NEM indicate that the most reactive groups are located in subunits of 185,000, 137,000 and 41,000 daltons. Images PMID:6755393

Bull, P; Wyneken, U; Valenzuela, P

1982-01-01

30

Switch of Sensitivity Dynamics Revealed with DyGloSA Toolbox for Dynamical Global Sensitivity Analysis as an Early Warning for System's Critical Transition  

PubMed Central

Systems with bifurcations may experience abrupt irreversible and often unwanted shifts in their performance, called critical transitions. For many systems like climate, economy, ecosystems it is highly desirable to identify indicators serving as early warnings of such regime shifts. Several statistical measures were recently proposed as early warnings of critical transitions including increased variance, autocorrelation and skewness of experimental or model-generated data. The lack of automatized tool for model-based prediction of critical transitions led to designing DyGloSA – a MATLAB toolbox for dynamical global parameter sensitivity analysis (GPSA) of ordinary differential equations models. We suggest that the switch in dynamics of parameter sensitivities revealed by our toolbox is an early warning that a system is approaching a critical transition. We illustrate the efficiency of our toolbox by analyzing several models with bifurcations and predicting the time periods when systems can still avoid going to a critical transition by manipulating certain parameter values, which is not detectable with the existing SA techniques. DyGloSA is based on the SBToolbox2 and contains functions, which compute dynamically the global sensitivity indices of the system by applying four main GPSA methods: eFAST, Sobol's ANOVA, PRCC and WALS. It includes parallelized versions of the functions enabling significant reduction of the computational time (up to 12 times). DyGloSA is freely available as a set of MATLAB scripts at http://bio.uni.lu/systems_biology/software/dyglosa. It requires installation of MATLAB (versions R2008b or later) and the Systems Biology Toolbox2 available at www.sbtoolbox2.org. DyGloSA can be run on Windows and Linux systems, -32 and -64 bits. PMID:24367574

Baumuratova, Tatiana; Dobre, Simona; Bastogne, Thierry; Sauter, Thomas

2013-01-01

31

Switch of sensitivity dynamics revealed with DyGloSA toolbox for dynamical global sensitivity analysis as an early warning for system's critical transition.  

PubMed

Systems with bifurcations may experience abrupt irreversible and often unwanted shifts in their performance, called critical transitions. For many systems like climate, economy, ecosystems it is highly desirable to identify indicators serving as early warnings of such regime shifts. Several statistical measures were recently proposed as early warnings of critical transitions including increased variance, autocorrelation and skewness of experimental or model-generated data. The lack of automatized tool for model-based prediction of critical transitions led to designing DyGloSA - a MATLAB toolbox for dynamical global parameter sensitivity analysis (GPSA) of ordinary differential equations models. We suggest that the switch in dynamics of parameter sensitivities revealed by our toolbox is an early warning that a system is approaching a critical transition. We illustrate the efficiency of our toolbox by analyzing several models with bifurcations and predicting the time periods when systems can still avoid going to a critical transition by manipulating certain parameter values, which is not detectable with the existing SA techniques. DyGloSA is based on the SBToolbox2 and contains functions, which compute dynamically the global sensitivity indices of the system by applying four main GPSA methods: eFAST, Sobol's ANOVA, PRCC and WALS. It includes parallelized versions of the functions enabling significant reduction of the computational time (up to 12 times). DyGloSA is freely available as a set of MATLAB scripts at http://bio.uni.lu/systems_biology/software/dyglosa. It requires installation of MATLAB (versions R2008b or later) and the Systems Biology Toolbox2 available at www.sbtoolbox2.org. DyGloSA can be run on Windows and Linux systems, -32 and -64 bits. PMID:24367574

Baumuratova, Tatiana; Dobre, Simona; Bastogne, Thierry; Sauter, Thomas

2013-01-01

32

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 insulating 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, John P. (Albuquerque, NM); Emin, David (Albuquerque, NM)

1986-01-01

33

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

34

The Trichoplusia ni single nucleopolyhedrovirus tn79 gene encodes a functional sulfhydryl oxidase enzyme that is able to support the replication of Autographa californica multiple nucleopolyhedrovirus lacking the sulfhydryl oxidase ac92 gene.  

PubMed

The Autographa californica multiple nucleopolyhedrovirus ac92 is a conserved baculovirus gene with homology to flavin adenine dinucleotide-linked sulfhydryl oxidases. Its product, Ac92, is a functional sulfhydryl oxidase. Deletion of ac92 results in almost negligible levels of budded virus (BV) production, defects in occlusion-derived virus (ODV) co-envelopment and their inefficient incorporation into occlusion bodies. To determine the role of sulfhydryl oxidation in the production of BV, envelopment of nucleocapsids, and nucleocapsid incorporation into occlusion bodies, the Trichoplusia ni single nucleopolyhedrovirus ortholog, tn79, was substituted for ac92. Tn79 was found to be an active sulfhydryl oxidase that substituted for Ac92, resulting in the production of infectious BV, albeit about 10-fold less than an ac92-containing virus. Tn79 rescued defects in ODV morphogenesis caused by a lack of ac92. Active Tn79 sulfhydryl oxidase activity is required for efficient BV production, ODV envelopment, and their subsequent incorporation into occlusion bodies in the absence of ac92. PMID:25010286

Clem, Stian A; Wu, Wenbi; Passarelli, A Lorena

2014-07-01

35

Fluorescent modification and orientation of myosin sulfhydryl 2 in skeletal muscle fibers  

SciTech Connect

The authors describe a protocol for the selective covalent labeling of the sulfhydryl 2 (SH2) on the myosin cross-bridge in glycerinated muscle fibers using the sulfhydryl-selective label 4-(N-((iodoacetoxy)ethyl)-N-methylamino)-7-nitrobenz-2-oxa-1,3-diazole (IANBD). The protocol promotes the specificity of IANBD by using the ability to protect sulfhydryl 1 (SH1) from modification by binding the cross-bridge to the actin filament and using cross-bridge-bound MgADP to promote the accessibility of SH2. They determined the specificity of the probe using fluorescence gel scanning of fiber-extracted proteins to isolate the probe on myosin subfragment 1 (S1), limited proteolysis of the purified S1 to isolate the probe on the 20-kilodalton fragment of S1, and titration of the free SH1's on purified S1 using the radiolabeled SH1-specific reagent ({sup 14}C)iodoacetamide or enzymatic activity measurements. They characterized the angular distribution of the IANBD on cross-bridges in fibers when the fibers are in rigor, in relaxation, in the presence of MgADP, and in isometric contraction using wavelength-dependent fluorescence polarization. They find that the SH2 probe distinguishes the different states of the fiber such that rigor and MgADP are ordered and maintain a similar orientation throughout the excitation wavelength domain. The relaxed cross-bridge is ordered and has an orientation that is distinct from the orientation of the cross-bridge in rigor and MgADP over the entire wavelength domain. The active isometric cross-bridge is also oriented differently from the other states, suggesting the presence of a predominant actin-bound cross-bridge state that precedes the power stroke during muscle contraction.

Ajtai, K.; Burghardt, T.P. (Mayo Foundation, Rochester, MN (USA))

1989-03-07

36

Sulfhydryl Reagents and Energy-Linked Reactions in Monocot Thylakoids 1  

PubMed Central

Monofunctional maleimides have been used to covalently modify the coupling factor protein of monocot thylakoid membranes. As with dicot thylakoids, incubation of the monocot thylakoids with maleimides in the light but not in the dark results in inhibition of both ATP synthesis and hydrolysis. In the dark, sites on the ? and ? subunits of maize Zea mays coupling factor 1 are modified after incubation of maize mesophyll thylakoids with the fluorescent maleimide N-(anilinonaphthyl-4) maleimide. A light accessible site localized solely to the ? subunit has also been demonstrated. In contrast to the case with dicot thylakoids (spinach [Spinacia oleracea] and pea [Pisum sativum]) treatment of monocot thylakoids (maize, barley [Hordeum vulgare], crabgrass [Digitaria sanguinalis]) with bifunctional maleimides or thiol oxidants in the light does not result in functional uncoupling, i.e the bifunctional reagents act more like energy transfer inhibitors. The lack of functional uncoupling could be due either to a failure of the reagents to cross-link key sulfhydryl residues in the ? subunit or to the continued ability of the ? subunit to gate proton movements through the chloroplast coupling factor complex even though its conformation has been altered by sulfhydryl reagents. Images Figure 3 Figure 4 Figure 5 Figure 6 PMID:16667548

Cohen, William S.; Baxter, Donald R.

1990-01-01

37

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

2012-10-12

38

Role of Sulfhydryl Sites on Bacterial Cell Walls in the Biosorption, Mobility and Bioavailability of Mercury and Uranium  

SciTech Connect

The goal of this exploratory study is to provide a quantitative and mechanistic understanding of the impact of bacterial sulfhydryl groups on the bacterial uptake, speciation, methylation and bioavailability of Hg and redox changes of uranium. The relative concentration and reactivity of different functional groups present on bacterial surfaces will be determined, enabling quantitative predictions of the role of biosorption of Hg under the physicochemical conditions found at contaminated DOE sites.The hypotheses we propose to test in this investigation are as follows- 1) Sulfhydryl groups on bacterial cell surfaces modify Hg speciation and solubility, and play an important role, specifically in the sub-micromolar concentration ranges of metals in the natural and contaminated systems. 2) Sulfhydryl binding of Hg on bacterial surfaces significantly influences Hg transport into the cell and the methylation rates by the bacteria. 3) Sulfhydryls on cell membranes can interact with hexavalent uranium and convert to insoluble tetravalent species. 4) Bacterial sulfhydryl surface groups are inducible by the presence of metals during cell growth. Our studies focused on the first hypothesis, and we examined the nature of sulfhydryl sites on three representative bacterial species: Bacillus subtilis, a common gram-positive aerobic soil species; Shewanella oneidensis, a facultative gram-negative surface water species; and Geobacter sulfurreducens, an anaerobic iron-reducing gram-negative species that is capable of Hg methylation; and at a range of Hg concentration (and Hg:bacterial concentration ratio) in which these sites become important. A summary of our findings is as follows- ? Hg adsorbs more extensively to bacteria than other metals. Hg adsorption also varies strongly with pH and chloride concentration, with maximum adsorption occurring under circumneutral pH conditions for both Cl-bearing and Cl-free systems. Under these conditions, all bacterial species tested exhibit almost complete removal of Hg from the experimental solutions at relatively low bacterial concentrations. ? Synchrotron based X-ray spectroscopic studies of these samples indicate that the structure and the coordination environment of Hg surface complexes on bacterial cell walls change dramatically- with sulfhydryls as the dominant Hg-binding groups in the micromolar and submicromolar range, and carboxyls and phosphoryls dominating at high micromolar concentrations. ? Hg interactions change from a trigonal or T-shaped HgS{sub 3} complex to HgS or HgS{sub 2} type complexes as the Hg concentration increases in the submicromolar range. Although all bacterial species studied exhibited the same types of coordination environments for Hg, the relative concentrations of the complexes change as a function of Hg concentration.

Myneni, Satish C.; Mishra, Bhoopesh; Fein, Jeremy

2009-04-01

39

Nucleotide-Protectable Labeling of Sulfhydryl Groups in Subunit I of the ATPhase from Halobacterium Saccharovorum  

NASA Technical Reports Server (NTRS)

A membrane-bound ATPase from the archaebacterium Halobacterium saccharovorum is inhibited by N-ethyl-maleimide in a nucleotide-protectable manner. When the enzyme was incubated with N-[C-14]jethylmaleimide, the bulk of radioactivity was as- sociated with the 87,000-Da subunit (subunit 1). ATP, ADP, or AMP reduced incorporation of the inhibitor. No charge shift of subunit I was detected following labeling with N-ethylmaleimide, indicating an electroneutral reaction. The results are consistent with the selective modification of sulfhydryl groups in subunit I at or near the catalytic site and are further evidence of a resemblance between this archaebacterial ATPase and the vacuolar-type ATPases.

Sulzner, Michael; Stan-Lotter, Helga; Hochstein, Lawrence I.

1992-01-01

40

Transmembrane Signaling Characterized in Bacterial Chemoreceptors by Using Sulfhydryl Cross-Linking in vivo  

NASA Astrophysics Data System (ADS)

Transmembrane signaling by bacterial chemoreceptors is thought to involve conformational changes within a stable homodimer. We investigated the functional consequences of constraining movement between pairs of helices in the four-helix structure of the transmembrane domain of chemoreceptor Trg. Using a family of cysteine-containing receptors, we identified oxidation treatments for intact cells that catalyzed essentially complete sulfhydryl cross-linking at selected positions and yet left flagellar and sensory functions largely unperturbed. Constraining movement by cross-links between subunits had little effect on tactic response, but constraining movement between transmembrane segments of the monomer drastically reduced function. We deduce that transmembrane signaling requires substantial movement between transmembrane helices of a monomer but not between interacting helices across the interface between subunits.

Lee, Geoffrey F.; Lebert, Michael R.; Lilly, Angela A.; Hazelbauer, Gerald L.

1995-04-01

41

Sulfhydryl oxidation reduces hippocampal susceptibility to hypoxia-induced spreading depression by activating BK channels.  

PubMed

The cytosolic redox status modulates ion channels and receptors by oxidizing/reducing their sulfhydryl (SH) groups. We therefore analyzed to what degree SH modulation affects hippocampal susceptibility to hypoxia. In rat hippocampal slices, severe hypoxia caused a massive depolarization of CA1 neurons and a negative shift of the extracellular DC potential, the characteristic sign of hypoxia-induced spreading depression (HSD). Oxidizing SH groups by 5,5'-dithiobis 2-nitrobenzoic acid (DTNB, 2 mM) postponed HSD by 30%, whereas their reduction by 1,4-dithio-dl-threitol (DTT, 2 mM) or alkylation by N-ethylmaleimide (500 microM) hastened HSD onset. The DTNB-induced postponement of HSD was not affected by tolbutamide (200 microM), dl-2-amino-5-phosphonovaleric acid (150 microM), or 6-cyano-7-nitroquinoxaline-2,3-dione (25 microM). It was abolished, however, by Ni2+ (2 mM), withdrawal of extracellular Ca2+, charybdotoxin (25 nM), and iberiotoxin (50 nM). In CA1 neurons DTNB induced a moderate hyperpolarization, blocked spontaneous spike discharges and postponed the massive hypoxic depolarization. DTT induced burst firing, depolarized glial cells, and hastened the onset of the massive hypoxic depolarization. Schaffer-collateral/CA1 synapses were blocked by DTT but not by DTNB; axonal conduction remained intact. Mitochondria did not markedly respond to DTNB or DTT. While the targets of DTT are less clear, the postponement of HSD by DTNB indicates that sulfhydryl oxidation increases the tolerance of hippocampal tissue slices against hypoxia. We identified as the underlying mechanism the activation of BK channels in a Ca(2+)-sensitive manner. Accordingly, ionic disregulation and the loss of membrane potential occur later or might even be prevented during short-term insults. Therefore well-directed oxidation of SH groups could mediate neuroprotection. PMID:15872065

Hepp, Sebastian; Gerich, Florian J; Müller, Michael

2005-08-01

42

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.

2014-05-22

43

Photoconductive switching for high power microwave generation  

SciTech Connect

Photoconductive switching is a technology that is being increasingly applied to generation of high power microwaves. Two primary semiconductors used for these devices are silicon and gallium arsenide. Diamond is a promising future candidate material. This paper discusses the important material parameters and switching modes, critical issues for microwave generation, and future directions for this high power, photoconductive switching technology.

Pocha, M.D.; Hofer, W.W.

1990-10-01

44

Diversification of Quiescin sulfhydryl oxidase in a preserved framework for redox relay  

PubMed Central

Background The enzyme family Quiescin Sulfhydryl Oxidase (QSOX) is defined by the presence of an amino-terminal thioredoxin-fold (Trx) domain and a carboxy-terminal Erv family sulfhydryl oxidase domain. QSOX enzymes, which generate disulfide bonds and transfer them to substrate proteins, are present in a wide variety of eukaryotic species including metazoans and plants, but are absent from fungi. Plant and animal QSOXs differ in their active-site amino acid sequences and content of non-catalytic domains. The question arises, therefore, whether the Trx-Erv fusion has the same mechanistic significance in all QSOX enzymes, and whether shared features distinguish the functional domains of QSOX from other instances in which these domains occur independently. Through a study of QSOX phylogeny and an analysis of QSOX sequence diversity in light of recently determined three-dimensional structures, we sought insight into the origin and evolution of this multi-domain redox alliance. Results An updated collection of QSOX enzymes was used to confirm and refine the differences in domain composition and active-site sequence motif patterns of QSOXs belonging to various eukaryotic phyla. Beyond the expected phylogenetic distinction of animal and plant QSOX enzymes, trees based on individual redox-active QSOX domains show a particular distinction of the Trx domain early in plant evolution. A comparison of QSOX domains with Trx and Erv domains from outside the QSOX family revealed several sequence and structural features that clearly differentiate QSOXs from other enzymes containing either of these domains. Notably, these features, present in QSOXs of various phyla, localize to the interface between the Trx and Erv domains observed in structures of QSOX that model interdomain redox communication. Conclusions The infrastructure for interdomain electron relay, previously identified for animal and parasite QSOXs, is found broadly across the QSOX family, including the plant enzymes. We conclude that the conserved three-dimensional framework of the QSOX catalytic domains accommodates lineage-specific differences and paralog diversification in the amino acid residues surrounding the redox-active cysteines. Our findings indicate that QSOX enzymes are characterized not just by the presence of the two defining domain folds but also by features that promote coordinated activity. PMID:23510202

2013-01-01

45

Modifications of the binding properties of the human VIP receptor of IGR39 cells by sulfhydryl reagents.  

PubMed

The effects of specific sulfhydryl reagents, N-ethylmaleimide (NEM), p-chloromercuribenzoic acid (PCMB) and 5-5'-dithiobis(2-nitrobenzoic acid) (DTNB), were tested on the vasoactive intestinal peptide (VIP) receptor binding capacity of the human superficial melanoma-derived IGR39 cells. On intact cell monolayers NEM and PCMB inhibit the specific [125I]VIP binding in a time and dose-dependent manner while DTNB has no effect at any concentration tested. Inhibitory effects of NEM and PCMB on high and low affinity VIP receptor are not identical. With NEM-treated cells, only low affinity sites remained accessible to the ligand. Their affinity constant is not modified. With PCMB-treated cells, the binding capacity of high affinity sites is reduced by 56% while the binding capacity of low affinity sites is not significantly affected. For both types of binding sites, the affinity constants remain in the same range of that of untreated cells. On cells made permeable by lysophosphatidylcholine, DTNB is able to inhibit the specific [125I]VIP binding in a time and dose-dependent manner. The three sulfhydryl reagents stabilize the preformed [125I]VIP receptor complex whose dissociation in the presence of native VIP is significantly reduced. Labeling of free SH groups with tritiated NEM after preincubation of cells with DTNB and VIP made possible the characterization of reacting SH groups which probably belong to the receptor. Taken together, these data allow us to define three classes of sulfhydryl groups. In addition, it is shown that high and low affinity sites have different sensibility to sulfhydryl reagents. PMID:1337321

Fouchier, F; Forget, P; Pic, P; Marvaldi, J; Pichon, J

1992-12-01

46

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

SciTech Connect

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.

Long, C.M. [Department of Biochemistry and Biophysics, Oregon State University, Corvallis, OR 97331 (United States); Rohrmann, G.F. [Department of Microbiology, Oregon State University, Corvallis, OR 97331 (United States); Merrill, G.F., E-mail: merrillg@onid.orst.ed [Department of Biochemistry and Biophysics, Oregon State University, Corvallis, OR 97331 (United States)

2009-06-05

47

Ethernet Switching  

NSDL National Science Digital Library

Created by Tony Castro of the Information and Communications Technologies Center (ICT), this simulation demonstrates ethernet switching. The animation depicts three separate local area networks connecting to an ethernet hub. The animation also includes descriptive text. This resource would be a helpful addition to any course on information and communications technologies as it allows students to see exactly how ethernet switching works.

Castro, Tony

2012-10-25

48

Switching Amplifiers  

NSDL National Science Digital Library

Created by Work-Ready Electronics, a project of the Advanced Technological Education, this module walks visitors through switching amplifiers. The site content is divided up into four sections: Switching Amplifiers Introduction, Class D Switching Amplifiers, Switching RF Power Amplifiers, and Troubleshooting. There is a quiz for each section to test what students learned in the module in the Knowledge Probe section, and the Learning Resources section contains four activities to help cement student understanding. There are also further resources - both print and Web based - for more information and two Questor games, a Flash quiz that reiterates the material covered. The Notebook function allows visitors to take notes and review them at any time. This is an excellent resource students and educators in electronics technician programs to introduce and explore switching amplifiers.

49

Use of sulfhydryl reagents to investigate branched chain alpha-keto acid transport in mitochondria.  

PubMed

The goal of this paper was to determine the contribution of the mitochondrial branched chain aminotransferase (BCATm) to branched chain alpha-keto acid transport within rat heart mitochondria. Isolated heart mitochondria were treated with sulfhydryl reagents of varying permeability, and the data suggest that essential cysteine residues in BCATm are accessible from the cytosolic face of the inner membrane. Treatment with 15 nmol/mg N-ethylmaleimide (NEM) inhibited initial rates of alpha-ketoisocaproate (KIC) uptake in reconstituted mitochondrial detergent extracts by 70% and in the intact organelle by 50%. KIC protected against inhibition suggesting that NEM labeled a cysteine residue that is inaccessible when substrate is bound to the enzyme. Additionally, the apparent mitochondrial equilibrium KIC concentration was decreased 50-60% after NEM labeling, and this difference could not be attributed to effects of NEM on matrix pH or KIC oxidation. In fact, NEM was a better inhibitor of KIC oxidation than rotenone. Measuring matrix aspartate and glutamate levels revealed that the effects of NEM on the steady-state KIC concentration resulted from inhibition of BCATm catalyzed transamination of KIC with matrix glutamate to form leucine. Furthermore, circular dichroism spectra of recombinant human BCATm with liposomes showed that the commercial lipids used in the reconstituted transport assay contain BCAT amino acid substrates. Thus BCATm is distinct from the branched chain alpha-keto acid carrier but may interact with the inner mitochondrial membrane, and it is necessary to inhibit or remove transaminase activity in both intact and reconstituted systems prior to quantifying transport of alpha-keto acids which are transaminase substrates. PMID:11018671

Drown, P M; Torres, N; Tovar, A R; Davoodi, J; Hutson, S M

2000-09-29

50

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.

2013-07-30

51

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

52

Nucleosome Switches  

NASA Astrophysics Data System (ADS)

We present a statistical-mechanical model for the positioning of nucleosomes along genomic DNA molecules as a function of the strength of the binding potential and the chemical potential of the nucleosomes. We show that a significant section of the DNA is composed of two-level nucleosome switching regions where the nucleosome distribution undergoes a localized, first-order transition. The location of the nucleosome switches shows a strong correlation with the location of gene-regulation regions.

Schwab, David J.; Bruinsma, Robijn F.; Rudnick, Joseph; Widom, Jonathan

2008-06-01

53

Human Augmenter of Liver Regeneration; probing the catalytic mechanism of a flavin-dependent sulfhydryl oxidase†  

PubMed Central

Augmenter of liver regeneration is a member of the ERV family of small flavin-dependent sulfhydryl oxidases that contain a redox-active CxxC disulfide bond in redox communication with the isoalloxazine ring of bound FAD. These enzymes catalyze the oxidation of thiol substrates with the reduction of molecular oxygen to hydrogen peroxide. This work studies the catalytic mechanism of the short, cytokine, form of augmenter of liver regeneration (sfALR) using model thiol substrates of the enzyme. The redox potential of the proximal disulfide in sfALR was found to be approximately 57 mV more reducing than the flavin chromophore, in agreement with titration experiments. Rapid reaction studies show that dithiothreitol (DTT) generates a transient mixed disulfide intermediate with sfALR signaled by a weak charge-transfer interaction between the thiolate of C145 and the oxidized flavin. The subsequent transfer of reducing equivalents to the flavin ring is relatively slow, with a limiting apparent rate constant of 12.4 s?1. However, reoxidation of the reduced flavin by molecular oxygen is even slower (2.3 s?1 at air saturation), and thus largely limits turnover at 5 mM DTT. The nature of the charge-transfer complexes observed with DTT was explored using a range of simple monothiols to mimic the initial nucleophilic attack on the proximal disulfide. While ?–mercaptoethanol is a very poor substrate of sfALR (~ 0.3 min?1 at 100 mM thiol), it rapidly generates a mixed disulfide intermediate allowing the thiolate of C145 to form a strong charge-transfer complex with the flavin. Unlike the other monothiols tested, glutathione is unable to form charge-transfer complexes and is an undetectable substrate of the oxidase. These data are rationalized on the basis of the stringent steric requirements for thiol-disulfide exchange reactions. The inability of the relatively bulky glutathione to attain the in-line geometry required for efficient disulfide exchange in sfALR may be physiologically important in preventing the oxidase from catalyzing the potentially harmful oxidation of intracellular glutathione. PMID:24147449

Schaefer-Ramadan, Stephanie; Gannon, Shawn A.; Thorpe, Colin

2013-01-01

54

Information Switching Processor (ISP) contention analysis and control  

NASA Technical Reports Server (NTRS)

In designing a satellite system with on-board processing, the selection of a switching architecture is often critical. The on-board switching function can be implemented by circuit switching or packet switching. Destination-directed packet switching has several attractive features, such as self-routing without on-board switch reconfiguration, no switch control memory requirement, efficient bandwidth utilization for packet switched traffic, and accommodation of circuit switched traffic. Destination-directed packet switching, however, has two potential concerns: (1) contention and (2) congestion. And this report specifically deals with the first problem. It includes a description and analysis of various self-routing switch structures, the nature of contention problems, and contention and resolution techniques.

Inukai, Thomas

1995-01-01

55

Internal dynamics of IGBT under zero-voltage and zero-current switching conditions  

Microsoft Academic Search

Soft switching involves turning the semiconductor device on or off with minimal switching stress. Zero voltage switching (ZVS) and zero current switching (ZCS) are the two most popular variants of soft switching schemes. The turn-off performance of insulated gate bipolar transistors (IGBT's) under ZVS and ZCS environments is critically evaluated in this paper. It is shown that the turn-off mechanism

Malay Trivedi; Krishna Shenai

1999-01-01

56

Optical switch  

DOEpatents

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 operation, light from the first glass fiber is reflected by a planar mirror into the third glass fiber. In another mode of operation, light from the second glass fiber passes directly into the third glass fiber. The planar mirror is attached to a rotatable table which is rotated to provide the optical switching. 3 figs.

Reedy, R.P.

1987-11-10

57

Optical switch  

DOEpatents

An optical switching device (10) is provided whereby light from a first glass fiber (16) or a second glass fiber (14) may be selectively transmitted into a third glass fiber (18). Each glass fiber is provided with a focusing and collimating lens system (26, 28, 30). In one mode of operation, light from the first glass fiber (16) is reflected by a planar mirror (36) into the third glass fiber (18). In another mode of operation, light from the second glass fiber (14) passes directly into the third glass fiber (18). The planar mirror (36) is attached to a rotatable table (32) which is rotated to provide the optical switching.

Reedy, Robert P. (Livermore, CA)

1987-01-01

58

Optical switch  

DOEpatents

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 operation, light from the first glass fiber is reflected by a planar mirror into the third glass fiber. In another mode of operation, light from the second glass fiber passes directly into the third glass fiber. The planar mirror is attached to a rotatable table which is rotated to provide the optical switching.

Reedy, R.P.

1985-01-18

59

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

60

Accumulation of 10Bin the Central Degenerative Areas of Human Glioma and Colon Carcinoma Spheroids after Sulfhydryl Boron Hydride Administration1  

Microsoft Academic Search

Sulfhydryl boron hydride (BSH) (IOBenriched) is presently used for boron neutron capture therapy of malignant gliomas. BSH must be close to the target cells to be effective in the inactivation of cell proliferation because of the short range of the reaction products (5-9 |tm). Clinical experience indicates that BSH is taken up in gliomas but it is not known to

Orn-Anong Pettersson; Erik Grusell

1992-01-01

61

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. PMID:23299424

Onda, Yayoi; Kawagoe, Yasushi

2013-01-01

62

Effect of magnetic film switching of crystallite interactions  

Microsoft Academic Search

Relationships among dispersion, switching thresholds, ripple theory, the switching astroid, and the Landau-Lifshitz equation are indicated. It is conjectured that film dispersion should be less than a critical value of about 2 degrees if the influence of the switching astroid is to be prominent.

J. Watson

1968-01-01

63

Ferroelectric switching of elastin  

PubMed Central

Ferroelectricity has long been speculated to have important biological functions, although its very existence in biology has never been firmly established. Here, we present compelling evidence that elastin, the key ECM protein found in connective tissues, is ferroelectric, and we elucidate the molecular mechanism of its switching. Nanoscale piezoresponse force microscopy and macroscopic pyroelectric measurements both show that elastin retains ferroelectricity at 473 K, with polarization on the order of 1 ?C/cm2, whereas coarse-grained molecular dynamics simulations predict similar polarization with a Curie temperature of 580 K, which is higher than most synthetic molecular ferroelectrics. The polarization of elastin is found to be intrinsic in tropoelastin at the monomer level, analogous to the unit cell level polarization in classical perovskite ferroelectrics, and it switches via thermally activated cooperative rotation of dipoles. Our study sheds light onto a long-standing question on ferroelectric switching in biology and establishes ferroelectricity as an important biophysical property of proteins. This is a critical first step toward resolving its physiological significance and pathological implications. PMID:24958890

Liu, Yuanming; Cai, Hong-Ling; Zelisko, Matthew; Wang, Yunjie; Sun, Jinglan; Yan, Fei; Ma, Feiyue; Wang, Peiqi; Chen, Qian Nataly; Zheng, Hairong; Meng, Xiangjian; Sharma, Pradeep; Zhang, Yanhang; Li, Jiangyu

2014-01-01

64

Vinyl sulfone bifunctional derivatives of DOTA allow sulfhydryl- or amino-directed coupling to antibodies. Conjugates retain immunoreactivity and have similar biodistributions.  

PubMed

We have synthesized a bifunctional vinyl sulfone-cysteineamido derivative of DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) that can be conjugated to the sulfhydryls of mildly reduced recombinant antibody (chimeric anti-CEA antibody cT84.66) at pH 7 or to the amino groups of lysine residues at pH 9. The conjugation is sulfhydryl specific at pH 7 (case 1), and amino specific at pH 9 (case 2) as long as the antibody has no free sulhydryl groups. At a molar ratio of 50 BCA (bifunctional chelating agent) to mAb, the number of chelates conjugated is 0.8 for case 1, and 4.6 for case 2. The resulting conjugates can be radiolabeled with (111)In to high specific activity (5 mCi/mg) with high efficiency (>95%) at 43 degrees C in 60 min. The radiolabeled conjugates retained >95% immunoreactivity and are stable in serum containing 1mM DTPA over 3 d. When the radiolabeled conjugates were injected into nude mice bearing LS174T human colon tumor xenografts, over 40% ID/g accumulated in tumors during the period 24-72h. Tumor-to-blood ratios were 4.5, 3.5, and 2.5 for the sulfhydryl coupled conjugate at 24, 48, and 72 h, respectively, and 2.7, 2.5, and 2.3 for the amino-coupled conjugate at the same time points. For other organs the biodistributions were nearly identical whether the conjugates were attached via sulfhydryl or amino groups. These novel BCAs are easy to synthesize, offer versatile conjugation options, and give equivalent biodistributions that result in high tumor uptake and good tumor-to-blood ratios. PMID:11792185

Li, Lin; Tsai, Shih-Wa; Anderson, Anne-Line; Keire, David A; Raubitschek, Andrew A; Shively, John E

2002-01-01

65

Production and characterisation of AoSOX2 from Aspergillus oryzae, a novel flavin-dependent sulfhydryl oxidase with good pH and temperature stability.  

PubMed

Sulfhydryl oxidases have found application in the improvement of both dairy and baking products due to their ability to oxidise thiol groups in small molecules and cysteine residues in proteins. A genome mining study of the available fungal genomes had previously been performed by our group in order to identify novel sulfhydryl oxidases suitable for industrial applications and a representative enzyme was produced, AoSOX1 from Aspergillus oryzae (Faccio et al. BMC Biochem 11:31, 2010). As a result of the study, a second gene coding for a potentially secreted sulfhydryl oxidase, AoSOX2, was identified in the genome of A. oryzae. The protein AoSOX2 was heterologously expressed in Trichoderma reesei and characterised with regard to both biochemical properties as well as preliminary structural analysis. AoSOX2 showed activity on dithiothreitol and glutathione, and to a lesser extent on D/L-cysteine and beta-mercaptoethanol. AoSOX2 was a homodimeric flavin-dependent protein of approximately 78 kDa (monomer 42412 Da) and its secondary structure presents alpha-helical elements. A. oryzae AoSOX2 showed a significant stability to pH and temperature. PMID:21327412

Faccio, Greta; Kruus, Kristiina; Buchert, Johanna; Saloheimo, Markku

2011-05-01

66

Fast superconducting magnetic field switch  

SciTech Connect

The superconducting magnetic switch or fast kicker magnet is employed with an 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 than 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. Magnetic switches and particularly fast kicker magnets are used in the accelerator industry to quickly deflect particle beams into and out of various transport lines, storage rings, dumps, and specifically to differentially route individual bunches of particles from a train of bunches which are injected or ejected from a given ring.

Goren, Y.; Mahale, N.K.

1995-12-31

67

Involvement of sulfhydryl oxidase QSOX1 in the protection of cells against oxidative stress-induced apoptosis  

SciTech Connect

The QSOX1 protein, belonging to a new class of FAD-linked Quiescin/Sulfhydryl oxidase, catalyzes disulfide bond formation. To give new insight into the biological function of QSOX1, we studied its involvement in oxidative stress-induced apoptosis and cell recovery of PC12 cells. By real time RT-PCR and flow cytometric analysis, we show that the QSOX1 mRNA and protein levels increased late after the beginning of oxidative treatment and were sustained for 72 h. These levels were still high when the PC12 cells were not dying but had resumed proliferation. The kinetics of QSOX1 expression suggest a more protective effect of QSOX1 rather than an involvement of this protein in apoptosis. Human breast cancer MCF-7 cell lines overexpressing the guinea pig QSOX1 protein submitted to the same treatments appeared less sensitive to cell death than the MCF-7 control cells. The protective effect is partly due to a preservation of the mitochondrial polarization generally lost after an oxidative stress. These results strengthen our hypothesis of a protective role of QSOX1 against apoptosis.

Morel, Carole; Adami, Pascale [Universite de Franche Comte, U.F.R. Sciences et Techniques, E.A.3922 Equipe Estrogenes, Expression genique et Pathologies du Systeme Nerveux Central, IFR 133 Ingenierie et Biologie Cellulaire et Tissulaire (France); Musard, Jean-Francois [Societe RD-Biotech, Besancon (France); Duval, Dominique [Universite de Caen, equipe INSERM-Avenir tPA in the working brain, Centre Cyceron (France); Radom, Jean [Universite de Franche Comte, U.F.R. Sciences et Techniques, E.A.3922 Equipe Estrogenes, Expression genique et Pathologies du Systeme Nerveux Central, IFR 133 Ingenierie et Biologie Cellulaire et Tissulaire (France); Jouvenot, Michele [Universite de Franche Comte, U.F.R. Sciences et Techniques, E.A.3922 Equipe Estrogenes, Expression genique et Pathologies du Systeme Nerveux Central, IFR 133 Ingenierie et Biologie Cellulaire et Tissulaire (France)], E-mail: michele.jouvenot@univ-fcomte.fr

2007-11-15

68

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

PubMed Central

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 channel. Oxidizing agents (1 to 60 mM) tended to increase the duration of the action potential and had a slow, irreversible blocking effect when perfused internally; the membrane potential was little affected. Reducing agents applied internally caused a decrease in the spike duration without affecting its height or the membrane potential, although at high concentrations there was reversible deterioration of the action potential. Both external and internal perfusion of mercaptide-forming reagents caused deterioration in the action and membrane potentials with conduction block occurring in 5 to 45 min. 2-mercaptoethanol reversed the effects. Thiol alkylating reagents, iodoacetate and iodoacetamide, were without effect. N-ethylmaleimide did, however, block. Tests with chelating agents for nonheme iron in the membrane brought about no change in the electrical parameters. The implications of the present findings with regard to the macromolecular mechanism of excitation are discussed. ImagesFigure 1 PMID:5970570

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

1966-01-01

69

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

70

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

71

Latching relay switch assembly  

DOEpatents

A latching relay switch assembly which includes a coil section and a switch or contact section. The coil section includes at least one permanent magnet and at least one electromagnet. The respective sections are, generally, arranged in separate locations or cavities in the assembly. The switch is latched by a permanent magnet assembly and selectively switched by an overriding electromagnetic assembly.

Duimstra, Frederick A. (Anaheim Hills, CA)

1991-01-01

72

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.

Boettcher, Gordon E. (Albuquerque, NM)

1990-01-01

73

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

74

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

2012-05-01

75

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

76

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.

Goren, Yehuda (Mountain View, CA); Mahale, Narayan K. (The Woodlands, TX)

1996-01-01

77

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

78

Free radical activity and loss of plasma antioxidants, vitamin E, and sulfhydryl groups in patients with burns: the 1993 Moyer Award.  

PubMed

This study examines the relationship of burn injury and plasma levels of conjugated dienes, total sulfhydryl groups, and vitamin E in patients with thermal injuries. Plasma neopterin levels were determined as an index of macrophage activity and serine elastase as an index of polymorphonuclear cell activation. Thirteen patients with burns, six survivors and seven nonsurvivors, were studied for the first 4 days, then every other day until postburn day 14. Twelve healthy volunteers served as the control group. Survivors had 56% +/- 4% total body surface area burned, and nonsurvivors had 63.9% +/- % total body surface area burned. The patients with burns, compared with the control group, showed elevated plasma levels of the lipid peroxidation products conjugated dienes (0.767 +/- 0.045 vs 0.269 +/- 0.013 Abs at 233 nm) and reduced levels of the natural scavengers of free radicals, vitamin E (196.2 +/- 12.6 vs 841.1 +/- 22.7 micrograms/dl) and total sulfhydryl groups (54.0 +/- 0.4 vs 15.8 +/- 1.0 mumol/dl). The total sulfhydryl groups/conjugated dienes ratio fell at a greater rate (9.8% +/- 3.2% vs 3.2% +/- 0.7%/day) in nonsurvivors than in survivors (p < 0.05 by Mann-Whitney). The levels of elastase were slightly elevated in the patients with burns, but there was no difference between survivors and nonsurvivors. Normal neopterin levels are 3 to 10 nm/L; peak levels were 119 +/- 48 nm/L in nonsurvivors and 37.4 +/- 10 nm/L in survivors. Patients with burns demonstrated evidence of increased oxygen free radical activity and activation of polymorphonuclear cell and macrophages. Nonsurvivors demonstrated increased consumption of antioxidants compared with survivors.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8300695

Nguyen, T T; Cox, C S; Traber, D L; Gasser, H; Redl, H; Schlag, G; Herndon, D N

1993-01-01

79

Protein and non-protein sulfhydryls and disulfides in gastric mucosa and liver after gastrotoxic chemicals and sucralfate: Possible new targets of pharmacologic agents  

PubMed Central

AIM: To investigate the role of major non-protein and protein sulfhydryls and disulfides in chemically induced gastric hemorrhagic mucosal lesions (HML) and the mechanism of gastroprotective effect of sucralfate. METHODS: Rats were given 1 mL of 75% ethanol, 25% NaCl, 0.6 mol/L HCl, 0.2 mol/L NaOH or 1% ammonia solutions intragastrically (i.g.) and sacrificed 1, 3, 6 or 12 min later. Total (reduced and oxidized) glutathione (GSH + GSSG), glutathione disulfide (GSSG), protein free sulfhydryls (PSH), protein-glutathione mixed disulfides (PSSG) and protein cystine disulfides (PSSP) were measured in gastric mucosa and liver. RESULTS: Reduced glutathione (GSH) was depleted in the gastric mucosa after ethanol, HCl or NaCl exposure, while oxidized glutathione (GSSG) concentrations increased, except by HCl and NaOH exposure. Decreased levels of PSH after exposure to ethanol were observed, NaCl or NaOH while the total protein disulfides were increased. Ratios of reduced to oxidized glutathione or sulfhydrils to disulfides were decreased by all chemicals. No changes in thiol homeostasis were detected in the liver after i.g. abbreviation should be spelled out the first time here administration of ethanol. Sucralfate increased the concentrations of GSH and PSH and prevented the ethanol-induced changes in gastric mucosal thiol concentrations. CONCLUSION: Our modified methods are now suitable for direct measurements of major protein and non-protein thiols/disulfides in the gastric mucosa or liver. A common element in the pathogenesis of chemically induced HML and in the mechanism of gastroprotective drugs seems to be the decreased ratios of reduced and oxidized glutathione as well as protein sulfhydryls and disulfides. PMID:17465447

Nagy, Lajos; Nagata, Miki; Szabo, Sandor

2007-01-01

80

Relationship of membrane-bound sulfhydryl groups to vitamin D-stimulated uptake of ( sup 75 Se)Selenite by the brush border membrane vesicles from chick duodenum  

SciTech Connect

The uptake of selenite by purified brush border membrane vesicles isolated from duodena of rachitic or vitamin D-treated chicks was studied by using radioactive selenite and a rapid filtration technique. Cholecalciferol treatment (500 IU at 72 h) significantly enhanced selenite uptake, a response that decreased when the vesicles were stored at room temperature for 2.5 h prior to the uptake measurement. Preincubation of the vesicles in 1.0 mmol/L H2O2 reduced (75Se)selenite uptake, indicating the involvement of oxidizable groups in the uptake reaction. Iodoacetic acid (IAA), a sulfhydryl-blocking reagent, at 1-2 mmol/L concentration eliminated the difference in selenite uptake due to cholecalciferol and had no effect on vesicles from rachitic animals. A higher concentration of IAA (10 mmol/L) enhanced selenite uptake manyfold and increased the absolute difference due to cholecalciferol treatment. Single intravenous doses of 100 IU cholecalciferol, 100 IU ergocalciferol, or 0.1 micrograms 1,25-dihydroxycholecalciferol also stimulated selenite uptake, suggesting a general response to vitamin D compounds. Normal animals given a single dose of 1,25-dihydroxycholecalciferol 12 h prior to killing also responded. Treatments that enhanced the uptake of (75Se)selenite also increased the amount of membrane-bound sulfhydryl groups, suggesting the involvement of membrane-bound sulfhydryl groups in the vitamin D response. A significant increase in selenite uptake by intravenous 1,25-dihydroxycholecalciferol occurred within 10 min. This rapid effect provides a new tool to probe early biochemical effects of vitamin D on intestinal epithelium.

Mykkanen, H.M.; Wasserman, R.H. (Cornell Univ., Ithaca, NY (USA))

1990-08-01

81

Automatic thermal switches  

NASA Technical Reports Server (NTRS)

Two automatic switches control heat flow from one thermally conductive plate to another. One switch permits heat flow to outside; other limits heat flow. In one switch, heat on conductive plate activates piston that forces saddle against plate. Heat carriers then conduct heat to second plate that radiates it away. After temperature is first plate drops, piston contracts and spring breaks thermal contact with plate. In second switch, action is reversed.

Cunningham, J. W.; Wing, L. D.

1980-01-01

82

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

83

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

84

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

85

Topology Synthesis for Low Power Cascaded Crossbar Switches  

Microsoft Academic Search

Crossbar switch network has an increasing impact on such critical measures as throughput, latency, area, and power consumption of complex system-on-chip as technology scales to deep submicrometer. With high clock frequency crossbar switch network design, global wire delay and pipeline registers inserted for throughput are important because they affect area, frequency, and power consumption of the chip. The traffic congestion

Yongho Jang; Jungsoo Kim; Chong-Min Kyung

2010-01-01

86

Purification of gastroprotective triterpenoids from the stem bark of Amphipterygium adstringens; role of prostaglandins, sulfhydryls, nitric oxide and capsaicin-sensitive neurons.  

PubMed

In this investigation three bioactive compounds, responsible for the gastroprotective property of Amphipterygium adstringens, were purified from an active dichloromethane fraction. These compounds were 3alpha-hydroxymasticadienonic acid, beta-sitosterol and 3- epi-oleanolic acid. The latter was the most active compound (88.8 % of gastroprotection) followed by 3alpha-hydroxymasticadienoic acid and beta-sitosterol (69.8 and 42.5 % of gastroprotection, respectively). Carbenoxolone was used as positive control and it showed 88.4 % of gastroprotection. Masticadienonic acid was also isolated from the active fraction, but it was unable to inhibit the ethanol-induced gastric lesions. The gastroprotection of the methanol extract was completely inhibited by the pretreatment with l-NAME and attenuated by pretreatment with indomethacin and N-ethylmaleimide. These results suggest that endogenous nitric oxide plays an important role in the gastroprotection of A. adstringens methanol extract on ethanol-induced gastric mucosal lesions and that there is partial participation by prostaglandins and endogenous sulfhydryls. The effect of 3alpha-hydroxymasticadienonic acid was attenuated only by pretreatment with N-ethylmaleimide, indicating that endogenous sulfhydryls (thiols) participate in its gastroprotective mechanism. Capsaicin-sensitive afferent neurons do not participate in the gastroprotection of either the methanol extract or 3alpha-hydroxymasticadienoic acid. PMID:14648392

Arrieta, Jesús; Benitez, Javier; Flores, Edith; Castillo, Carlos; Navarrete, Andrés

2003-10-01

87

The 3-(bromoacetamido)-propylamine hydrochloride: A novel sulfhydryl reagent and its future potential in the configurational study of S1-myosin  

NASA Technical Reports Server (NTRS)

Configurational study of S1-Myosin is an important step towards understanding force generation in muscle contraction. Previously reported NMR studies were corroborated. A new compound was synthesized, 3-(Bromoacetamido)-propylamine hydrochloride. Its potential as a sulfhydryl reagent provides an indirect but elegant approach towards future structural elucidation of S1-Myosin. The preliminary investigation has shown that this compound, BAAP, reacted with S1 in the absence of MgADP. The modified enzyme had a 2-fold increase in CaATPase activity and no detectable K-EDTA ATPase activity. Reaction of BAAP with S1 in the presence of MgADP resulted in a modified enzyme which retained a Ca-ATPase activity that was about 60 percent of the unmodified S1 and had essentially zero K-EDTA ATPase activity. Sulfhydryl titration indicated that about 1.5 and 3.5 SH groups per S1 molecule were blocked by BAAP in the absence and presence of MgADP, respectively. When coupled to a carboxyl group of EDTA, the resulting reagent could become a useful SH reagent in which chelated paramagnetic or luminescent lanthanide ions can be exploited to probe S1 conformation.

Sharma, Prasanta; Cheung, Herbert C.

1989-01-01

88

RITS-3 self-break water switch maintenance.  

SciTech Connect

The radiographic integrated test stand (RITS-3) is a 5-MV, 160-kA, 70-ns inductive voltage adder accelerator at Sandia National Laboratories used to develop critical understanding of x-ray sources and flash radiographic drivers. On RITS-3 three pulse forming lines (PFLs) are used to drive three inductive voltage adder cavities. Each PFL contains a fast-pulse-charged, self-breakdown annular water switch that is used for initial pulse shaping and timing. Low loss in the switches combined with good synchronization is required for efficient operation of the accelerator. Switch maintenance is closely monitored over time to determine the effects of wear on switch breakdown performance.

Cordova, Steve Ray; Portillo, Salvador; Puetz, Elizabeth A.; Wilkins, Frank Lee (Bechtel Nevada, Las Vegas, NV); Gignac, Raymond Edward (Bechtel Nevada, Las Vegas, NV); Johnson, David Lee (Titan Pulse Sciences Division, San Leandro, CA); Hahn, Kelly Denise; Molina, Isidro; Maenchen, John Eric

2004-06-01

89

Effective switching frequency multiplier inverter  

DOEpatents

A switching frequency multiplier inverter for low inductance machines that uses parallel connection of switches and each switch is independently controlled according to a pulse width modulation scheme. The effective switching frequency is multiplied by the number of switches connected in parallel while each individual switch operates within its limit of switching frequency. This technique can also be used for other power converters such as DC/DC, AC/DC converters.

Su, Gui-Jia (Oak Ridge, TN); Peng, Fang Z. (Okemos, MI)

2007-08-07

90

Forward-Reverse Switch  

NSDL National Science Digital Library

In this activity, learners build a switch to turn electrical circuits on and off. Learners can connect their switches to other projects they want to power and swing the popsicle stick around to control the direction of movement of the connected devices. Use this activity to introduce learners to concepts related to electrical circuits, switches, and polarity. Note: this activity requires the use of a drill, which is not included in the cost of materials.

Workshop, Fresno C.

2012-01-01

91

A nonlinear resonant switch  

Microsoft Academic Search

A resonant switch is introduced that uses linear tank elements. Zero-current switching is obtained even through the peak transistor voltage and current stresses can approach those of an equivalent ideal pulsewidth-modulated converter. Reduced switching loss without a substantial increase in conduction loss is therefore possible. An approximate analysis is outlined, and transistor peak-voltage and current stresses are shown to be

R. W. Erickson; A. F. Hernandez; A. F. Witulski; R. Xu

1989-01-01

92

30 GHz tuned MEMS switches  

Microsoft Academic Search

This paper demonstrates the use of resonant tuning in high-isolation reflective MEMS electrostatic switches. Tuned switches can achieve higher isolation and a lower pulldown voltage than a comparable single element switch. An equivalent circuit model was developed for individual shunt capacitive membrane switches and then implemented in tuned circuits. The novel cross switch was developed on a high resistivity silicon.

Jeremy B. Muldavin; Gabriel M. Rebeiz

1999-01-01

93

Wide Bandgap Extrinsic Photoconductive Switches  

NASA Astrophysics Data System (ADS)

Wide Bandgap Extrinsic Photoconductive Switches Semi-insulating Gallium Nitride, 4H and 6H Silicon Carbide are attractive materials for compact, high voltage, extrinsic, photoconductive switches due to their wide bandgap, high dark resistance, high critical electric field strength and high electron saturation velocity. These wide bandgap semiconductors are made semi-insulating by the addition of vanadium (4H and 6H-SiC) and iron (2H-GaN) impurities that form deep acceptors. These deep acceptors trap electrons donated from shallow donor impurities. The electrons can be optically excited from these deep acceptor levels into the conduction band to transition the wide bandgap semiconductor materials from a semi-insulating to a conducting state. Extrinsic photoconductive switches with opposing electrodes have been constructed using vanadium compensated 6H-SiC and iron compensated 2H-GaN. These extrinsic photoconductive switches were tested at high voltage and high power to determine if they could be successfully used as the closing switch in compact medical accelerators. The successful development of a vanadium compensated, 6H-SiC extrinsic photoconductive switch for use as a closing switch for compact accelerator applications was realized by improvements made to the vanadium, nitrogen and boron impurity densities. The changes made to the impurity densities were based on the physical intuition outlined and simple rate equation models. The final 6H-SiC impurity 'recipe' calls for vanadium, nitrogen and boron densities of 2.5 e17 cm-3, 1.25e17 cm-3 and ? 1e16 cm-3, respectively. This recipe was originally developed to maximize the quantum efficiency of the vanadium compensated 6H-SiC, while maintaining a thermally stable semi-insulating material. The rate equation models indicate that, besides increasing the quantum efficiency, the impurity recipe should be expected to also increase the carrier recombination time. Three generations of 6H-SiC materials were tested. The third generation vanadium compensated 6H-SiC has average impurity densities close to the recipe values. Extrinsic photoconductive switches constructed from the third generation vanadium compensated, 6H-SiC, 1 mm thick, 1 cm2, substrates have achieved high power operation at 16 kV with pulsed currents exceeding 1400 Amperes and a minimum on resistance of 1 ohm. The extrinsic photoconductive switch performance of the third generation 6H-SiC material was improved by a factor of up to 50 for excitation at the 532 nm wavelength compared to the initial 6H-SiC material. Switches based on this material have been incorporated into a prototype compact proton medical accelerator being developed by the Compact Particle Acceleration Corporation (CPAC). The vanadium compensated, 6H-SiC, extrinsic photoconductive switch operates differently when excited by 1064, or 532 nm, wavelength light. The 6H-SiC extrinsic photoconductive switch is a unipolar device when excited with 1064 nm light. The carriers are electrons excited from filled vanadium acceptor levels and other electron traps located within 1.17 eV of the conduction band. The switch is bipolar at 532 nm since the carriers consist of holes, as well as electrons. The holes are primarily generated by the excitation of valence band electrons into empty trap/acceptor levels and by two-photon absorption. Carrier generation by two-photon absorption becomes more important at high applied optical intensity at 532 nm and contributes to the supralinear behavior of switch conductance as a function of optical power. The 6H-SiC switch material is trap dominated at low nitrogen to vanadium ratios. The trap dominated vanadium compensated 6H-SiC exhibits low quantum efficiency when excited with 1064 and 532 nm light and has a carrier recombination time of ˜ 150 - 300 ps. The vanadium compensated 6H-SiC transitions to an impurity dominated material as the ratio of nitrogen to vanadium is increased to 0.5. The increased nitrogen doping produces a material with much higher quantum efficiency and carrier recombination time of 0.9 to 1.0 ns.

Sullivan, James Stephen

94

The Electrical Switch  

NSDL National Science Digital Library

This activity is inquiry-based in that students will perform the activity before they formally learn about how a switch works. They will use a multimeter to discover the different settings on a triple-throw switch. The teacher should show the students how

Horton, Michael

2009-05-30

95

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

96

Role of the basal ganglia in switching a planned response.  

PubMed

The ability to perform an appropriate response in the presence of competing alternatives is a critical facet of human behavioral control. This is especially important if a response is prepared for execution but then has to be changed suddenly. A popular hypothesis of basal ganglia (BG) function suggests that its direct and indirect pathways could provide a neural mechanism to rapidly switch from one planned response to an alternative. However, if one response is more dominant or 'automatic' than the other, the BG might have a different role depending on switch direction. We built upon the pro- and antisaccade tasks, two models of automatic and voluntary behavior, respectively, and investigated whether the BG are important for switching any planned response in general, or if they are more important for switching from a more automatic response to a response that is more difficult to perform. Subjects prepared either a pro- or antisaccade but then had to switch it unexpectedly on a subset of trials. The results revealed increased striatal activation for switching from a pro- to an antisaccade but this did not occur for switching from an anti- to a prosaccade. This activation pattern depended on the relative difficulty in switching, and it was distinct from frontal eye fields, an area shown to be more active for antisaccade trials than for prosaccade trials. This suggests that the BG are important for compensating for differences in response difficulty, facilitating the rapid switching of one response for another. PMID:19508693

Cameron, Ian G M; Coe, Brian C; Watanabe, Masayuki; Stroman, Patrick W; Munoz, Douglas P

2009-06-01

97

Pneumatic RF MEMS switch using a liquid metal droplet  

NASA Astrophysics Data System (ADS)

We introduce a new design for radio frequency (RF) microelectromechanical systems (MEMS) switch that uses a liquid metal (LM) droplet as a switching component. The switch uses a polymer membrane atop the droplet as a pressure transducer. Initially, a signal passes through a coplanar waveguide (CPW) line (i.e. the switch is on). Pneumatic pressure on the membrane pushes the droplet, thus reducing the gap between the bottom surface of the LM droplet and CPW line; when the gap becomes less than a critical distance, the signal is blocked (i.e. the switch is off). This switch is more stable and has better isolation than do existing RF MEMS switches that use LM droplets. We used a commercial simulation tool (CST Microwave Studio®) to confirm the feasibility of the concept, then fabricated a prototype device that has the same insertion loss as the reference configuration (i.e. a CPW line only). Applying ˜35 kPa pressure to the flexible membrane resulted in switching performances with ˜50 dB isolation at 3 GHz and when the pressure is removed, the switch insertion loss was measured ˜1.5 dB.

Baek, Seungbum; Park, Usung; Choi, In Ho; Kim, Joonwon

2013-05-01

98

The influence of switching phase and frequency of voltage on the vibration damping effect in a piezoelectric actuator  

NASA Astrophysics Data System (ADS)

In a structural system with piezoelectric actuators, a damping effect can be achieved by properly switching the voltage on the actuators. Switched voltage methods based on piezoelectric actuators, including active bang-bang control and semi-active synchronized switch damping methods, have become an important category of vibration damping approach. Since the switching phase and switching frequency are critical factors to damping performance, their influence on converted energy in a piezoelectric actuator is investigated under the condition that the switched voltage is constant. The converted energy with randomly switched voltage is also investigated theoretically and numerically. Finally an example of beam vibration with synchronized switch damping on inductor (SSDI) control and synchronized switch damping on voltage source (SSDV) control is used to illustrate how the switching frequency can affect the control performance of different modes in a multiple-degree-of-freedom system.

Ji, Hongli; Qiu, Jinhao; Xia, Pinqi; Guyomar, Daniel

2011-01-01

99

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

100

Photoconductive switch package  

DOEpatents

A photoconductive switch is formed of a substrate that has a central portion of SiC or other photoconductive material and an outer portion of cvd-diamond or other suitable material surrounding the central portion. Conducting electrodes are formed on opposed sides of the substrate, with the electrodes extending beyond the central portion and the edges of the electrodes lying over the outer portion. Thus any high electric fields produced at the edges of the electrodes lie outside of and do not affect the central portion, which is the active switching element. Light is transmitted through the outer portion to the central portion to actuate the switch.

Ca[rasp, George J

2013-10-22

101

Switching to Iloperidone.  

PubMed

Objective: To describe secondary analyses from a 12-week, randomized, open-label trial where adult schizophrenia outpatients receiving risperidone, olanzapine, or aripiprazole were switched to iloperidone. Methods: Patients switched to iloperidone were randomized into 2 groups - one group where the dose of the antecedent antipsychotic was titrated downwards and discontinued by 2 weeks, and the other group where the antecedent antipsychotic was abruptly stopped. A total of 500 patients were randomized and received open-label iloperidone (gradual switch, n=240; immediate switch, n=260), with 175, 155, and 170 patients switched from risperidone, olanzapine, and aripiprazole, respectively. All patients were titrated on iloperidone to an initial target dose of 12 mg/day (6 mg twice a day) by Day 4 after which iloperidone could be flexibly dosed between 12 to 24 mg/day (6 to 12 mg twice a day), as per clinical judgment (median dose at study end was 16 mg/day). Adaptations of the Clinical Global Impression-Severity (CGI-S) scale were used to evaluate clinical changes that occurred from baseline over 12 weeks of treatment, providing data on efficacy (E-CGI-S) and safety (ST-CGI-S), as well as on an integrated measure of severity (I-CGI-S) and change (I-CGI-C). Other assessments included the reporting of adverse events (AEs), study discontinuation, body weight, and metabolic variables. Results:Improvement was steady throughout the study for both gradual- and immediate-switch groups starting at Week 1 and continuing through Week 12. Discontinuations due to AEs in the first 2 weeks of treatment were higher for the immediate-switch group compared with the gradual-switch group (10.8% vs. 5.4%, NNT 19, 95% CI 10-151). Fewer patients in the gradual- switch group experienced dizziness as an AE, whereas a higher percentage of patients in the immediate-switch group exhibited earlier onset of a therapeutic response within the first 2 weeks; both groups were comparable thereafter with low rates of dizziness and similar efficacy outcomes. Conclusions: Switching to iloperidone can be accomplished either with a gradual crossover or immediate discontinuation of the prior antipsychotic; however, the immediate-switch method is associated with greater proportion of initial dizziness. The observed outcomes are consistent with what has been previously reported regarding iloperidone's favorable akathisia/EPS profile and modest impact on somnolence/sedation, body weight, and metabolic variables.. PMID:25367165

Citrome, Leslie; Weiden, Peter J; Gus, Alva; Glick, Ira D; Jackson, Richard; Mattingly, Greg; Kianifard, Farid; Meng, Xiangyi; Winseck, Adam

2014-11-01

102

Bi-stable resistive switching in an array of nanowires  

NASA Astrophysics Data System (ADS)

A resistive switching system comprising of metal-insulator-metal sandwich-structured nanowires embedded within polycarbonate membrane has been investigated. The system switches from non-Ohmic high resistive state (HRS) to Ohmic low resistive state on application of a critical bias of 2.5 V. The bipolar switching can be performed by applying current bias as well. Driving two suitable currents, and we observe highly reproducible switching between two stable resistive states. The switching is initiated by establishment of filamentary conduction path commonly formed in oxide materials. However, the main charge transport in the HRS is governed with modified activated behavior, which is obvious from the antisymmetric, reversible I-V characteristic following where a, b and are constants. The exponential term corresponds to charge generation by field-enhanced thermal activation process, whereas the linear term is related to mobility.

Gayen, Sirshendu; Sanyal, Milan K.; Sarma, Abhisakh; Satpati, Biswarup

2015-01-01

103

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

104

Basics of Safety Switches  

NSDL National Science Digital Library

This course is one of the quickStep series offered by Siemens in Safety Switches. These are FREE on-line industrial knowledge building tutorials. quickSTEPs are a great start for industry novices moving into technical jobs or staff in operational support rolls. They can also be very effectively used as out of class assignments for review or to build fundamental skills. Each course includes: an online tutorial organized as a number of units, lessons with self check quiz questions, a glossary of terms, a self-check final exam with scoring, an extensive downloadable PDF study guide. This course offers: current protection, fuses, enclosures, switch design, switch terminology, safety switches, a final exam, a glossary and a 72 page study guide.

105

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

106

uv preilluminated gas switches  

Microsoft Academic Search

We have designed, built, and characterized uv preilluminated gas switches for a trigger circuit and a low inductance discharge circuit. These switches have been incorporated into a 54 x 76 x 150 cm pulser module to produce a 1 Ma output current rising at 5 x 10¹² amps\\/sec with 1 ns jitter. Twenty such modules will be used on the

L. P. Bradley; E. L. Orham; I. F. Stowers; J. R. Braucht

1980-01-01

107

Cygnus Water Switch Jitter  

SciTech Connect

The Cygnus Dual Beam Radiographic Facility consists of two identical radiographic sources - Cygnus 1 and Cygnus 2. Each source has the following x-ray output: 1-mm diameter spot size, 4 rad at 1 m, 50-ns Full Width Half Max. The diode pulse has the following electrical specifications: 2.25 MV, 60 kA, 60 ns. This Radiographic Facility is located in an underground tunnel test area at the Nevada Test Site (NTS). The sources were developed to produce high-resolution images on subcritical tests which are performed at NTS. Subcritical tests are single-shot, high-value events. For this application, it is desirable to maintain a high level of reproducibility in source output. The major components of the Cygnus machines are: Marx generator, water-filled pulse–forming line (PFL), water-filled coaxial transmission line, three-cell inductive voltage adder, and rod-pinch diode. A primary source of fluctuation in Cygnus shot-to-shot performance is jitter in breakdown of the main PFL switch, which is a “self-break” switch. The PFL switch breakdown time determines the peak PFL charging voltage, which ultimately affects the diode pulse. Therefore, PFL switch jitter contributes to shot-to-shot variation in source endpoint energy and dose. In this paper we will present PFL switch jitter analysis for both Cygnus machines and give the correlation with diode performance. For this analysis the PFL switch on each machine was maintained at a single gap setting which has been used for the majority of shots at NTS. In addition to this analysis, PFL switch performance for different switch gap settings taken recently will be examined. Lastly, implications of source jitter for radiographic diagnosis of subcritical shots will be discussed.

Charles V. Mitton, George D. Corrow, Mark D. Hansen, David J. Henderson, et al.

2008-03-01

108

Performance of Single and Coupled Microresonators in Photonic Switching Schemes  

Microsoft Academic Search

\\u000a Applications of single and coupled microresonators in various photonic switching schemes are considered. It is shown that\\u000a both single and coupled resonators enhance the performance of the switches based on nonlinear optical or electro-optical effect,\\u000a but the enhancement occurs at the expense of reduced bandwidth. The critical bit rates at which the enhancement is still possible\\u000a are derived for single

Jacob B. Khurgin

109

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

110

Fast deterministic switching in orthogonal spin torque devices via the control of the relative spin polarizations  

NASA Astrophysics Data System (ADS)

We model 100 ps pulse switching dynamics of orthogonal spin transfer (OST) devices that employ an out-of-plane polarizer and an in-plane polarizer. Simulation results indicate that increasing the spin polarization ratio, CP = PIPP/POPP, results in deterministic switching of the free layer without over-rotation (360° rotation). By using spin torque asymmetry to realize an enhanced effective PIPP, we experimentally demonstrate this behavior in OST devices in parallel to anti-parallel switching. Modeling predicts that decreasing the effective demagnetization field can substantially reduce the minimum CP required to attain deterministic switching, while retaining low critical switching current, Ip ˜ 500 ?A.

Park, Junbo; Ralph, D. C.; Buhrman, R. A.

2013-12-01

111

Energy losses in switches  

SciTech Connect

The authors experiments show energy losses between 2 and 10 times that of the resistive time predictions. The experiments used hydrogen, helium, air, nitrogen, SF{sub 6} 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 losses constitute the major portion of the total energy loss. They found that the switch energy losses scale as (V{sub peak}I{sub peak}){sup 1.1846}. When using this scaling, the energy losses in any of the tested dielectrics are almost the same. This relationship is valid for several orders of magnitude and suggested a theoretical basis for these results. Currents up to .65 MA, with voltages to 3 MV were applied to various gaps during these experiments. The authors data and the developed theory indicates that the switch power loss continues for a much longer time than the resistive time, with peak power loss generally occurring at peak current in a ranging discharge instead of the early current time. All of the experiments were circuit code modeled after developing a new switch loss version based on the theory. The circuit code predicts switch energy loss and peak currents as a function of time. During analysis of the data they noticed slight constant offsets between the theory and data that depended on the dielectric. They modified the plasma conductivity for each tested dielectric to lessen this offset.

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

1993-07-01

112

Optical Packet Switching  

NASA Astrophysics Data System (ADS)

This chapter provides an outline of the main concepts and issues related to optical packet switching (OPS). The basic network functions required by this paradigm are discussed and references to past and current research on the topic are provided. Optical packet switching is a transport technique that assumes information to be organized in packets formed by a payload and a header both encoded as optical signals. The payload is transferred through the network without any optical to electronic conversion. The header is processed in the early phase in the electronic domain. Optical packet switching may be considered as a long-term and more flexible alternative to the circuit-switched optical networks currently being deployed by operators. This innovative paradigm aims at optimizing the utilization of the dense wavelength division multiplexing (DWDM) channels by means of fast and highly dynamic resource allocation, overcoming the inefficiency typical of the circuit transfer modes. Traditionally, packet transfer modes have proved to be very flexible by nature, with respect to bandwidth exploitation. In fact, link capacity is shared in time by means of statistical multiplexing, while contentions occurring at each node are solved by storing packets as long as the required resources become available again. Therefore, network links are in general used more efficiently in OPS than in circuit-switching.

Raffaelli, Carla; Aleksic, Slavisa; Callegati, Franco; Cerroni, Walter; Maier, Guido; Pattavina, Achille; Savi, Michele

113

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

114

The interaction of the gamma-aminobutyric acid transporter GAT-1 with the neurotransmitter is selectively impaired by sulfhydryl modification of a conformationally sensitive cysteine residue engineered into extracellular loop IV.  

PubMed

The (Na+ + Cl-)-coupled gamma-aminobutyric acid (GABA) transporter GAT-1 keeps synaptic levels of this neurotransmitter low and thereby enables efficient GABA-ergic transmission. Extracellular loops (III, IV, and V) have been shown to contain determinants for GABA selectivity and affinity. Here we analyze the role of extracellular loop IV in transport by cysteine scanning mutagenesis. Fourteen residues of this loop have been replaced by cysteine. GABA transport by eight of the fourteen mutants is markedly more sensitive to inhibition by membrane-impermeant methane thiosulfate reagents than wild-type. Mutant A364C has high activity and is potently inhibited by the sulfhydryl reagent. GABA transport by the A364C/C74A double mutant, where the only externally accessible cysteine residue of the wild-type has been replaced by alanine, is also highly sensitive to the sulfhydryl reagents. Maximal sensitivity is observed in the presence of the cosubstrates sodium and chloride. A marked protection is afforded by GABA, provided sodium is present. This protection is also observed at 4 degrees C. The non-transportable analogue SKF100330A also protects the double mutant against sulfhydryl modification in the presence of sodium but has the opposite effect in its absence. Electrophysiological analysis shows that upon sulfhydryl modification of this mutant, GABA can no longer induce transport currents. The voltage dependence of the transient currents indicates an increased apparent affinity for sodium. Moreover, GABA is unable to suppress the transient currents. Our results indicate that part of extracellular loop IV is conformationally sensitive, and its modification selectively abolishes the interaction of the transporter with GABA. PMID:12925537

Zomot, Elia; Kanner, Baruch I

2003-10-31

115

Effects of 2- and 3tertButyl4-hydroxyanisole on Glutathione S-Transferase and Epoxide Hydrolase Activities and Sulfhydryl Levels in Liver and Forestomach of Mice1  

Microsoft Academic Search

Butylated hydroxyanisole,a food additive, has beenfound to inhibit the neoplastia effects of a wide variety of chemical carcinogens. The commercially available preparations of bu- tylated hydroxyanisole contain two isomers, 2-ferf-butyl-4-hy- droxyanisole (2-BHA) and 3-ferf-butyl-4-hydroxyanisole (3- BHA). Both isomers induce increased activities of glutathione (GSH)S-transferaseand epoxide hydrolaseand increaseacid- soluble sulfhydryl concentration in hepatic and forestomach tissues of A\\/HeJ mice. The inductions

Luke K. T. Lam; Velta L. Sparnins; J. Bradley Hochalter; Lee W. Wattenberg

116

Dynamic switch matrix for the TDMA satellite switching system  

NASA Technical Reports Server (NTRS)

Future high capacity satellite communication systems require signal processing on board satellites. The on-board signal processing includes switching of RF signals between multiple antennas to provide interconnection between the uplink and downlink beams. This paper describes the development of a dynamic switch matrix for a TDMA satellite switching system to be used in the next generation communications satellites. In this paper, a dynamic switch matrix, which includes the microwave switch matrix, the distribution control unit and the timing source, will be described. Several different microwave switch matrix architectures and switching devices were evaluated and compared. A unique coupler crossbar switch matrix architecture with dual-gate field effect transistor as switching element was developed. Experimental results of both microwave switch matrix (MSM) and distribution control unit (DCU) are presented. These test results verify the MSM with coupler crossbar architecture and dual-gate FET as switching element will meet the future SS-TDMA system requirements. Finally, the reliability of the dynamic switch matrix is addressed. The analysis shows reliability of 0.9981 for 7 year space operation can be achieved for the designed dynamic switch matrix.

Ho, P. T.; Wisniewski, J. H.; Pelose, J. R.; Perasso, H. M.

1982-01-01

117

Dynamic switch matrix for the TDMA satellite switching system  

NASA Astrophysics Data System (ADS)

Future high capacity satellite communication systems require signal processing on board satellites. The on-board signal processing includes switching of RF signals between multiple antennas to provide interconnection between the uplink and downlink beams. This paper describes the development of a dynamic switch matrix for a TDMA satellite switching system to be used in the next generation communications satellites. In this paper, a dynamic switch matrix, which includes the microwave switch matrix, the distribution control unit and the timing source, will be described. Several different microwave switch matrix architectures and switching devices were evaluated and compared. A unique coupler crossbar switch matrix architecture with dual-gate field effect transistor as switching element was developed. Experimental results of both microwave switch matrix (MSM) and distribution control unit (DCU) are presented. These test results verify the MSM with coupler crossbar architecture and dual-gate FET as switching element will meet the future SS-TDMA system requirements. Finally, the reliability of the dynamic switch matrix is addressed. The analysis shows reliability of 0.9981 for 7 year space operation can be achieved for the designed dynamic switch matrix.

Ho, P. T.; Wisniewski, J. H.; Pelose, J. R.; Perasso, H. M.

118

Optimal switching using coherent control  

NASA Astrophysics Data System (ADS)

We introduce a general framework for the analysis of coherent control in coupled optical cavity-waveguide systems. Within this framework, we use an analytically solvable model, which is validated by independent numerical calculations, to investigate switching in a micro cavity and demonstrate that the switching time, in general, is not limited by the cavity lifetime. Therefore, the total energy required for switching is a more relevant figure of merit than the switching speed, and for a particular two-pulse switching scheme we use calculus of variations to optimize the switching in terms of input energy.

Trøst Kristensen, Philip; Heuck, Mikkel; Mørk, Jesper

2013-01-01

119

The baculovirus sulfhydryl oxidase Ac92 (P33) interacts with the Spodoptera frugiperda P53 protein and oxidizes it in vitro.  

PubMed

The Autographa californica M nucleopolyhedrovirus (AcMNPV) sulfhydryl oxidase Ac92 is essential for production of infectious virions. Ac92 also interacts with human p53 and enhances human p53-induced apoptosis in insect cells, but it is not known whether any relationship exists between Ac92 and native p53 homologs from insect hosts of AcMNPV. We found that Ac92 interacted with SfP53 from Spodoptera frugiperda in infected cells and oxidized SfP53 in vitro. However, Ac92 did not interact with or oxidize a mutant of SfP53 predicted to lack DNA binding. Silencing Sfp53 expression did not rescue the ability of an ac92-knockout virus to produce infectious virus. Similarly, ac92 expression did not affect SfP53-stimulated caspase activity or the localization of SfP53. Thus, although Ac92 binds to SfP53 during AcMNPV replication and oxidizes SfP53 in vitro, we could not detect any effects of this interaction on AcMNPV replication in cultured cells. PMID:24210115

Wu, Wenbi; Clem, Rollie J; Rohrmann, George F; Passarelli, A Lorena

2013-12-01

120

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

2012-04-01

121

Microfabricated triggered vacuum switch  

DOEpatents

A microfabricated vacuum switch is disclosed which includes a substrate upon which an anode, cathode and trigger electrode are located. A cover is sealed over the substrate under vacuum to complete the vacuum switch. In some embodiments of the present invention, a metal cover can be used in place of the trigger electrode on the substrate. Materials used for the vacuum switch are compatible with high vacuum, relatively high temperature processing. These materials include molybdenum, niobium, copper, tungsten, aluminum and alloys thereof for the anode and cathode. Carbon in the form of graphitic carbon, a diamond-like material, or carbon nanotubes can be used in the trigger electrode. Channels can be optionally formed in the substrate to mitigate against surface breakdown.

Roesler, Alexander W. (Tijeras, NM); Schare, Joshua M. (Albuquerque, NM); Bunch, Kyle (Albuquerque, NM)

2010-05-11

122

Main electrical switch banks, plant switch house, looking to the ...  

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

Main electrical switch banks, plant switch house, looking to the North - Bureau of Mines Metallurgical Research Laboratory, Original Building, Date Street north of U.S. Highway 93, Boulder City, Clark County, NV

123

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

124

The structure of Plasmodium falciparum serine hydroxymethyltransferase reveals a novel redox switch that regulates its activities  

PubMed Central

Plasmodium falciparum serine hydroxymethyltransferase (PfSHMT), an enzyme in the dTMP synthesis cycle, is an antimalarial target because inhibition of its expression or function has been shown to be lethal to the parasite. As the wild-type enzyme could not be crystallized, protein engineering of residues on the surface was carried out. The surface-engineered mutant PfSHMT-F292E was successfully crystallized and its structure was determined at 3?Å resolution. The PfSHMT-F292E structure is a good representation of PfSHMT as this variant revealed biochemical properties similar to those of the wild type. Although the overall structure of PfSHMT is similar to those of other SHMTs, unique features including the presence of two loops and a distinctive cysteine pair formed by Cys125 and Cys364 in the tetrahydrofolate (THF) substrate binding pocket were identified. These structural characteristics have never been reported in other SHMTs. Biochemical characterization and mutation analysis of these two residues confirm that they act as a disulfide/sulfhydryl switch to regulate the THF-dependent catalytic function of the enzyme. This redox switch is not present in the human enzyme, in which the cysteine pair is absent. The data reported here can be further exploited as a new strategy to specifically disrupt the activity of the parasite enzyme without interfering with the function of the human enzyme. PMID:24914963

Chitnumsub, Penchit; Ittarat, Wanwipa; Jaruwat, Aritsara; Noytanom, Krittikar; Amornwatcharapong, Watcharee; Pornthanakasem, Wichai; Chaiyen, Pimchai; Yuthavong, Yongyuth; Leartsakulpanich, Ubolsree

2014-01-01

125

Plasma erosion opening switch  

NASA Astrophysics Data System (ADS)

The plasma erosion opening switch (PEOS) can conduct high current (approx. MA), open quickly ( 10 ns), and withstand high voltage (approx. MV). This switching technique has been used in inductive energy storage experiments and can be used with existing generators for pulse compression, voltage multiplication and power multiplication. The PEOS is used routinely for other types of power conditioning including prepulse suppression, pulse sharpening and multimodule jitter reduction. The PEOS work to data is reviewed. It reviews basic physics principles of the PEOS and outlines the operational limits of a system that employs a PEOS. Examples of present applications of the PEOS are also discussed.

Commisso, R. J.; Cooperstein, G.; Meger, R. A.; Neri, J. M.; Ottinger, P. F.; Weber, B. V.

1985-05-01

126

A nanophotonic switching cell  

NASA Astrophysics Data System (ADS)

We present a nanophotonic/nanometric switching cell to operate in the infrared and terahertz frequency range of telecommunications. This switching cell is based on a directional coupler made of two graphene nanoribbons separated in the vertical direction, which are embedded in a hexagonal boron nitride substrate. Theoretical analysis revealed that a graphene based nanophotonics coupler, initially working in the bar state (or cross state), can be brought into the cross state (or bar state), by modifying the graphene sheet chemical potential via the gate voltage. The analytical results are confirmed by the finite element method simulations and numerical analysis scripts.

Wirth L, A.; Sombra, A. S. B.

2014-10-01

127

How Switches Increase Speed  

NSDL National Science Digital Library

This brief interactive activity, by the Electromechanical Digital Library and Wisconsin Technical College System faculty, explains clearly the reasons to use switches in place of hubs when using an LAN. The animations and corresponding explanations are helpful as the user clicks through each slide at his or her own pace. Animations can be viewed again and navigation is simple. At the end, review questions test the userâ??s knowledge. This is a good resource for students and teachers alike to familiarize themselves with switches in this fast-paced technological world.

Bartelt, Terry L. M.

128

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

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Hand-operated switch equipped with switch...Instructions: All Systems General § 236.6 Hand-operated switch equipped with switch circuit controller. Hand-operated switch equipped...

2011-10-01

129

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...Instructions: All Systems General § 236.6 Hand-operated switch equipped with switch circuit controller. Hand-operated switch equipped...

2012-10-01

130

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

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Hand-operated switch equipped with switch...Instructions: All Systems General § 236.6 Hand-operated switch equipped with switch circuit controller. Hand-operated switch equipped...

2010-10-01

131

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

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Hand-operated switch equipped with switch...Instructions: All Systems General § 236.6 Hand-operated switch equipped with switch circuit controller. Hand-operated switch equipped...

2013-10-01

132

A delay model for noise-induced bi-directional switching  

NASA Astrophysics Data System (ADS)

Many biological systems can switch between two distinct states. Once switched, the system remains stable for a period of time and may switch back to its original state. A gene network with bistability is usually required for the switching and stochastic effect in the gene expression may induce such switching. A typical bistable system allows one-directional switching, in which the switch from the low state to the high state or from the high state to the low state occurs under different conditions. It is usually difficult to enable bi-directional switching such that the two switches can occur under the same condition. Here, we present a model consisting of standard positive feedback loops and an extra negative feedback loop with a time delay to study its capability to produce bi-directional switching induced by noise. We find that the time delay in the negative feedback is critical for robust bi-directional switching and the length of delay affects its switching frequency. This paper is published as part of a collection in honour of Todd Dupont's 65th birthday.

Lei, Jinzhi; He, Guowei; Liu, Haoping; Nie, Qing

2009-12-01

133

Coherence Switching in a Four-Level System: Quantum Switching  

NASA Astrophysics Data System (ADS)

Dark resonance switching among three-laser interactions in a four-level system is observed by using an enhanced nondegenerate four-wave mixing technique. This coherence switching mechanism is based on simultaneous suppression and enhancement of two-photon absorption and has a novel application to high-speed optical switches.

Ham, Byoung S.; Hemmer, Philip R.

2000-05-01

134

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

135

Fault-tolerant onboard digital information switching and routing for communications satellites  

NASA Technical Reports Server (NTRS)

The NASA Lewis Research Center is developing an information-switching processor for future meshed very-small-aperture terminal (VSAT) communications satellites. The information-switching processor will switch and route baseband user data onboard the VSAT satellite to connect thousands of Earth terminals. Fault tolerance is a critical issue in developing information-switching processor circuitry that will provide and maintain reliable communications services. In parallel with the conceptual development of the meshed VSAT satellite network architecture, NASA designed and built a simple test bed for developing and demonstrating baseband switch architectures and fault-tolerance techniques. The meshed VSAT architecture and the switching demonstration test bed are described, and the initial switching architecture and the fault-tolerance techniques that were developed and tested are discussed.

Shalkhauser, Mary JO; Quintana, Jorge A.; Soni, Nitin J.; Kim, Heechul

1993-01-01

136

Solid-state RF switch  

NASA Technical Reports Server (NTRS)

Consisting of NAND gates, switch can be expanded to multipole input and can switch at frequencies up to 30MHz. Device uses digital integrated circuits to provide isolation between inputs and between input and output ports.

Hanna, M. F.; Detweiler, H. K.

1977-01-01

137

Advances in integrated photonic circuits for packet-switched interconnection  

NASA Astrophysics Data System (ADS)

Sustained increases in capacity and connectivity are needed to overcome congestion in a range of broadband communication network nodes. Packet routing and switching in the electronic domain are leading to unsustainable energy- and bandwidth-densities, motivating research into hybrid solutions: optical switching engines are introduced for massive-bandwidth data transport while the electronic domain is clocked at more modest GHz rates to manage routing. Commercially-deployed optical switching engines using MEMS technologies are unwieldy and too slow to reconfigure for future packet-based networking. Optoelectronic packet-compliant switch technologies have been demonstrated as laboratory prototypes, but they have so far mostly used discretely pigtailed components, which are impractical for control plane development and product assembly. Integrated photonics has long held the promise of reduced hardware complexity and may be the critical step towards packet-compliant optical switching engines. Recently a number of laboratories world-wide have prototyped optical switching circuits using monolithic integration technology with up to several hundreds of integrated optical components per chip. Our own work has focused on multi-input to multi-output switching matrices. Recently we have demonstrated 8×8×8? space and wavelength selective switches using gated cyclic routers and 16×16 broadband switching chips using monolithic multi-stage networks. We now operate these advanced circuits with custom control planes implemented with FPGAs to explore real time packet routing in multi-wavelength, multi-port test-beds. We review our contributions in the context of state of the art photonic integrated circuit technology and packet optical switching hardware demonstrations.

Williams, Kevin A.; Stabile, Ripalta

2014-03-01

138

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

139

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

140

Multipath star switch controller  

NASA Technical Reports Server (NTRS)

Device concept permits parallel computers to scan several commonnetwork-connected data stations at maximum rate. Sequencers leap-frog to bypass ports already being serviced by another computer. Two-path system for 16-port star switch controller is cost effective if added bandwidth or increased reliability is desired. Triple-path system would be cost effective for 32-port controller.

Anderson, T. O.

1980-01-01

141

Photonic MEMS switch applications  

NASA Astrophysics Data System (ADS)

As carriers and service providers continue their quest for profitable network solutions, they have shifted their focus from raw bandwidth to rapid provisioning, delivery and management of revenue generating services. Inherently transparent to data rate the transmission wavelength and data format, MEMS add scalability, reliability, low power and compact size providing flexible solutions to the management and/or fiber channels in long haul, metro, and access networks. MEMS based photonic switches have gone from the lab to commercial availability and are now currently in carrier trials and volume production. 2D MEMS switches offer low up-front deployment costs while remaining scalable to large arrays. They allow for transparent, native protocol transmission. 2D switches enable rapid service turn-up and management for many existing and emerging revenue rich services such as storage connectivity, optical Ethernet, wavelength leasing and optical VPN. As the network services evolve, the larger 3D MEMS switches, which provide greater scalability and flexibility, will become economically viable to serve the ever-increasing needs.

Husain, Anis

2001-07-01

142

Molecular Rotors as Switches  

PubMed Central

The use of a functional molecular unit acting as a state variable provides an attractive alternative for the next generations of nanoscale electronics. It may help overcome the limits of conventional MOSFETd due to their potential scalability, low-cost, low variability, and highly integratable characteristics as well as the capability to exploit bottom-up self-assembly processes. This bottom-up construction and the operation of nanoscale machines/devices, in which the molecular motion can be controlled to perform functions, have been studied for their functionalities. Being triggered by external stimuli such as light, electricity or chemical reagents, these devices have shown various functions including those of diodes, rectifiers, memories, resonant tunnel junctions and single settable molecular switches that can be electronically configured for logic gates. Molecule-specific electronic switching has also been reported for several of these device structures, including nanopores containing oligo(phenylene ethynylene) monolayers, and planar junctions incorporating rotaxane and catenane monolayers for the construction and operation of complex molecular machines. A specific electrically driven surface mounted molecular rotor is described in detail in this review. The rotor is comprised of a monolayer of redox-active ligated copper compounds sandwiched between a gold electrode and a highly-doped P+ Si. This electrically driven sandwich-type monolayer molecular rotor device showed an on/off ratio of approximately 104, a read window of about 2.5 V, and a retention time of greater than 104 s. The rotation speed of this type of molecular rotor has been reported to be in the picosecond timescale, which provides a potential of high switching speed applications. Current-voltage spectroscopy (I-V) revealed a temperature-dependent negative differential resistance (NDR) associated with the device. The analysis of the device I–V characteristics suggests the source of the observed switching effects to be the result of the redox-induced ligand rotation around the copper metal center and this attribution of switching is consistent with the observed temperature dependence of the switching behavior as well as the proposed energy diagram of the device. The observed resistance switching shows the potential for future non-volatile memories and logic devices applications. This review will discuss the progress and provide a perspective of molecular motion for nanoelectronics and other applications.

Xue, Mei; Wang, Kang L.

2012-01-01

143

A RAILROAD SWITCHING YARD CONTROLLER  

E-print Network

A RAILROAD SWITCHING YARD CONTROLLER: DIGITAL ELECTRONICS AS AN EDUCATIONAL TOOL I. Program. Funding: NSF, DOE, CPS (~$45K / yr.) A Sample Lesson: Train Switching Yard Design #12;BUILDING A RAILROAD is then applied to building a railroad switching yard controller. STEP 1: Base 10 numbers, Base 2, TRUE or FALSE 1

Reed, Dale F.

144

Illuminated push-button switch  

NASA Technical Reports Server (NTRS)

An illuminated push-button switch is described. It is characterized by the fact that is consists of a switch group, an operator button opening and closing the switch group, and a light-emitting element which illuminates the face of the operator button.

Iwagiri, T.

1983-01-01

145

Future large broadband switched satellite communications networks  

NASA Technical Reports Server (NTRS)

Critical technical, market, and policy issues relevant to future large broadband switched satellite networks are summarized. Our market projections for the period 1980 to 2000 are compared. Clusters of switched satellites, in lieu of large platforms, etc., are shown to have significant advantages. Analysis of an optimum terrestrial network architecture suggests the proper densities of ground stations and that link reliabilities 99.99% may entail less than a 10% cost premium for diversity protection at 20/30 GHz. These analyses suggest that system costs increase as the 0.6 power of traffic. Cost estimates for nominal 20/30 GHz satellite and ground facilities suggest optimum system configurations might employ satellites with 285 beams, multiple TDMA bands each carrying 256 Mbps, and 16 ft ground station antennas. A nominal development program is outlined.

Staelin, D. H.; Harvey, R. R.

1979-01-01

146

A chemo-mechanical switch for controllable water transportation based on a thermally responsive block copolymer.  

PubMed

A smart and reversible chemo-mechanical switch was developed by synthesis of a thermally responsive block copolymer brush poly(N-isopropylacrylamide-co-hexafluoroisopropyl acrylate) (P(NIPAAm-co-HFIPA)) on a capillary plate. With the temperature changing around lower critical solution temperature (LCST), the designed chemo-mechanical switch exhibited excellent "ON-OFF" behavior for water transportation. PMID:25056637

Yang, Jianmin; Hida, Mitsuaki; Mao, Sifeng; Zeng, Hulie; Nakajima, Hizuru; Uchiyama, Katsumi

2014-09-14

147

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

148

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. PMID:22688954

Ha, Jeung-Hoi

2012-01-01

149

Plasma Opening Switch Synchronization Facility  

NASA Astrophysics Data System (ADS)

The Baikal program provides a superpower generator creation which uses a plasma opening switch for output pulse production. The MOL facility is being developed within the frames of this program to test main units and systems of the planned generator at 4-6 MV, 3 MA and 100 ns. The MOL facility is planned to use 7 parallel plasma opening switch modules placed in the relatively compact vacuum chamber of 140 cm diameter. This aims at solving two main technical issued: plasma opening switch module development with external applied magnetic field and plasma switch modules synchronization. The paper describes plasma switch module design and low inductance load synchronization experimental tests results.

Altuhov, Aleksey A.; Blinov, Petr I.; Dolgachev, Georgi I.; Maslennikov, Dmitry D.; Khodeev, Ivan A.

2002-12-01

150

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

151

Plasma opening switch  

DOEpatents

A command triggered plasma opening switch assembly using an amplification stage. The assembly surrounds a coaxial transmission line and has a main plasma opening switch (POS) close to the load and a trigger POS upstream from the main POS. The trigger POS establishes two different current pathways through the assembly depended on whether it has received a trigger current pulse. The initial pathway has both POS's with plasma between their anodes and cathodes to form a short across the transmission line and isolating the load. The final current pathway is formed when the trigger POS receives a trigger current pulse which energizes its fast coil to push the conductive plasma out from between its anode and cathode, allowing the main transmission line current to pass to the fast coil of the main POS, thus pushing its plasma out the way so as to establish a direct current pathway to the load.

Savage, Mark E. (Albuquerque, NM); Mendel, Jr., Clifford W. (Albuquerque, NM)

2001-01-01

152

Switching Power Supplies  

NSDL National Science Digital Library

Created by Work-Ready Electronics, a project of the Advanced Technological Education program, this module walks visitors through the basics of switching power supplies. The content of the site is divided into four areas: SMPS Basics and Switching Regulators; DC-DC Converters: Charge Pumps, Forwards Converters and Flyback Converters; Inverters, UPS and Hysteresis Curve, and SMPS: Advantages, Disadvantages and Troubleshooting. There is a quiz for each area in the Knowledge Probe area, and the Learning Resources section contains five activities to help cement student understanding. There are also further resources - both print and Web based - for more information and two Questors, a Flash trivia game. The Notebook function allows visitors to take notes and review them at any time. This is an excellent resource students and educators in electronics technician programs.

153

The quantum cryptographic switch  

NASA Astrophysics Data System (ADS)

We illustrate the principle of a cryptographic switch for a quantum scenario, in which a third party (Charlie) can control to a continuously varying degree the amount of information the receiver (Bob) receives, after the sender (Alice) has sent her information through a quantum channel. Suppose Charlie transmits a Bell state to Alice and Bob. Alice uses dense coding to transmit two bits to Bob. Only if the 2-bit information corresponding to the choice of the Bell state is made available by Charlie to Bob can the latter recover Alice's information. By varying the amount of information Charlie gives, he can continuously alter the information recovered by Bob. The performance of the protocol as subjected to the squeezed generalized amplitude damping channel is considered. We also present a number of practical situations where a cryptographic switch would be of use.

Srinatha, N.; Omkar, S.; Srikanth, R.; Banerjee, Subhashish; Pathak, Anirban

2014-01-01

154

SpinWave Effects in Magnetic-Film Switching  

Microsoft Academic Search

The nonlinear reaction of dispersion-induced spin waves on the uniform mode m0 has been calculated for a thin film undergoing rapid rotational magnetization reversal. It is found that if m0 rotates faster than longitudinal spin waves can relax, the magnetization goes through a transient state of high magnetostatic energy. If the pulse switching field Hp is less than a critical

K. J. Harte

1965-01-01

155

CREE: Making the Switch  

SciTech Connect

CREE, with the help of ARPA-E funding, has developed a Silicon Carbide (SIC) transistor which can be used to create solid state transformers capable of meeting the unique needs of the emerging smart grid. SIC transistors are different from common silicon computer chips in that they handle grid scale voltages with ease and their high frequency switching is well suited to the intermittent nature of renewable energy generation.

Grider, David; Palmer, John

2014-03-06

156

The Acetate Switch  

PubMed Central

To succeed, many cells must alternate between life-styles that permit rapid growth in the presence of abundant nutrients and ones that enhance survival in the absence of those nutrients. One such change in life-style, the “acetate switch,” occurs as cells deplete their environment of acetate-producing carbon sources and begin to rely on their ability to scavenge for acetate. This review explains why, when, and how cells excrete or dissimilate acetate. The central components of the “switch” (phosphotransacetylase [PTA], acetate kinase [ACK], and AMP-forming acetyl coenzyme A synthetase [AMP-ACS]) and the behavior of cells that lack these components are introduced. Acetyl phosphate (acetyl?P), the high-energy intermediate of acetate dissimilation, is discussed, and conditions that influence its intracellular concentration are described. Evidence is provided that acetyl?P influences cellular processes from organelle biogenesis to cell cycle regulation and from biofilm development to pathogenesis. The merits of each mechanism proposed to explain the interaction of acetyl?P with two-component signal transduction pathways are addressed. A short list of enzymes that generate acetyl?P by PTA-ACKA-independent mechanisms is introduced and discussed briefly. Attention is then directed to the mechanisms used by cells to “flip the switch,” the induction and activation of the acetate-scavenging AMP-ACS. First, evidence is presented that nucleoid proteins orchestrate a progression of distinct nucleoprotein complexes to ensure proper transcription of its gene. Next, the way in which cells regulate AMP-ACS activity through reversible acetylation is described. Finally, the “acetate switch” as it exists in selected eubacteria, archaea, and eukaryotes, including humans, is described. PMID:15755952

Wolfe, Alan J.

2005-01-01

157

Ultrafast gas switching experiments  

SciTech Connect

We describe 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. The highly overvolted peaking gaps produce powerful electromagnetic pulses with risetimes < 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. We have produced and accurately measured pulses with 50 to 100 ps risetimes to peak levels of 75 to 160 kV at pulse repetition frequencies (PRF) to I kHz. A unique gas switch was developed to hold off hundreds of kV with parasitic inductance less than I nH. An advanced diagnostic system using Fourier compensation was developed to measure single-shot risetimes below 35 ps. The complete apparatus is described and wave forms are presented. The measured data are compared with a theoretical model which predicts key features including dependence on gas species and pressure. We have applied this technology to practical systems driving ultrawideband radiating antennas and bounded wave simulators. For example, we have developed a thyristor/pulse transformer based system using a highly overvolted cable switch. This pulser driving a Sandia- designed TEM cell, provides an ultra wideband impulse with < 200 ps risetime to the test object at a PRF > 1 kHz at > 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.

1996-11-01

158

Ultrafast gas switching experiments  

SciTech Connect

We describe 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. The highly overvolted peaking gaps produce powerful electromagnetic pulses with risetimes < 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. We have produced and accurately measured pulses with 50 to 100 ps risetimes to peak levels of 75 to 160 kV at pulse repetition frequencies (PRF) to 1 kHz. 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 technology to practical systems antennas and bounded wave developed a thyristor/pulse transformer based system using a highly overvolted cable switch. This pulser driving a Sandia-designed TEM cell, provides an ultra wideband impulse with < 200 ps risetime to the test object at a PRF > Khz at > 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.

1993-08-01

159

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

160

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

161

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 ...

162

Investigation on properties of ultrafast switching in a bulk gallium arsenide avalanche semiconductor switch  

SciTech Connect

Properties of ultrafast switching in a bulk gallium arsenide (GaAs) avalanche semiconductor switch based on semi-insulating wafer, triggered by an optical pulse, were analyzed using physics-based numerical simulations. It has been demonstrated that when a voltage with amplitude of 5.2?kV is applied, after an exciting optical pulse with energy of 1??J arrival, the structure with thickness of 650??m reaches a high conductivity state within 110 ps. Carriers are created due to photons absorption, and electrons and holes drift to anode and cathode terminals, respectively. Static ionizing domains appear both at anode and cathode terminals, and create impact-generated carriers which contribute to the formation of electron-hole plasma along entire channel. When the electric field in plasma region increases above the critical value (?4?kV/cm) at which the electrons drift velocity peaks, a domain comes into being. An increase in carrier concentration due to avalanche multiplication in the domains reduces the domain width and results in the formation of an additional domain as soon as the field outside the domains increases above ?4?kV/cm. The formation and evolution of multiple powerfully avalanching domains observed in the simulations are the physical reasons of ultrafast switching. The switch exhibits delayed breakdown with the characteristics affected by biased electric field, current density, and optical pulse energy. The dependence of threshold energy of the exciting optical pulse on the biased electric field is discussed.

Hu, Long, E-mail: hulong-1226@126.com [Key Laboratory for Physical Electronics and Devices of the Ministry of Education, Xi'an Jiaotong University, Xi'an 710049 (China); Science and Technology on High Power Microwave Laboratory, Northwest Institute of Nuclear Technology, Xi'an 710024 (China); Su, Jiancang; Ding, Zhenjie; Hao, Qingsong; Yuan, Xuelin [Science and Technology on High Power Microwave Laboratory, Northwest Institute of Nuclear Technology, Xi'an 710024 (China)

2014-03-07

163

Investigation on properties of ultrafast switching in a bulk gallium arsenide avalanche semiconductor switch  

NASA Astrophysics Data System (ADS)

Properties of ultrafast switching in a bulk gallium arsenide (GaAs) avalanche semiconductor switch based on semi-insulating wafer, triggered by an optical pulse, were analyzed using physics-based numerical simulations. It has been demonstrated that when a voltage with amplitude of 5.2 kV is applied, after an exciting optical pulse with energy of 1 ?J arrival, the structure with thickness of 650 ?m reaches a high conductivity state within 110 ps. Carriers are created due to photons absorption, and electrons and holes drift to anode and cathode terminals, respectively. Static ionizing domains appear both at anode and cathode terminals, and create impact-generated carriers which contribute to the formation of electron-hole plasma along entire channel. When the electric field in plasma region increases above the critical value (˜4 kV/cm) at which the electrons drift velocity peaks, a domain comes into being. An increase in carrier concentration due to avalanche multiplication in the domains reduces the domain width and results in the formation of an additional domain as soon as the field outside the domains increases above ˜4 kV/cm. The formation and evolution of multiple powerfully avalanching domains observed in the simulations are the physical reasons of ultrafast switching. The switch exhibits delayed breakdown with the characteristics affected by biased electric field, current density, and optical pulse energy. The dependence of threshold energy of the exciting optical pulse on the biased electric field is discussed.

Hu, Long; Su, Jiancang; Ding, Zhenjie; Hao, Qingsong; Yuan, Xuelin

2014-03-01

164

High power switching with a V/n oil switch  

NASA Astrophysics Data System (ADS)

Accurate switching is necessary to get reproducible pulses with minimal jitter from pulse power equipment. On a 10 MV pulse power machine, Aurora, we have improved the triggering of the oil closing switch in various ways. These include suppressing fast current oscillations during capacitive charging of the switch electrodes, using a faster trigger pulse that acts only during a fraction of the switch closure time, and localization of the arc. With additional use of the machine's symmetry the output pulses are now reproducible to better than 2% over the entire pulse shape, and the jitter is reduced about twofold, to 5 ns.

Pereira, N. R.; Gondarenko, N. A.

1996-01-01

165

Multi-Port RF MEMS Switches and Switch Matrices.  

E-print Network

??Microwave and millimeter wave switch matrices are essential components in telecommunication systems. These matrices enhance satellite capacity by providing full and flexible interconnectivity between the… (more)

Daneshmand, Mojgan

2006-01-01

166

Switching efficiency improvement in spin torque majority gates  

SciTech Connect

Spin torque majority gate (STMG) is one of the promising options for beyond complementary metal-oxide-semiconductor logic. Improvement of its performance—switching speed vs. required current—is critical for its competitiveness. In this paper, (a) we identify an optimized layout of the gate comprised of thin magnetic wires with in-plane magnetization; (b) we optimize geometries of perpendicular magnetization spin torque majority gates. Micromagnetic simulations demonstrate an improvement in switching current for in-plane magnetization (with less than 1?ns switching time) from 6?mA in the original scheme to 1.5?mA in the present one. Additionally, failures of switching caused by vortex formation are eliminated and desired output magnetization is achieved. Various geometries of STMG with perpendicular magnetization are explored. The scheme with a straight cross proves to be the most advantageous. It is predicted to operate with the switching current of 50 ?A and less than 4?ns switching time.

Nikonov, Dmitri E., E-mail: dmitri.e.nikonov@intel.com; Manipatruni, Sasikanth; Young, Ian A. [Exploratory Integrated Circuits, Components Research, Intel Corporation, Hillsboro, Oregon 97124 (United States)

2014-05-07

167

Ferroelastic switching for nanoscale non-volatile magnetoelectric devices  

SciTech Connect

Multiferroics, where (anti-) ferromagnetic, ferroelectric, and ferroelastic order parameters coexist [1-5], enables manipulation of magnetic ordering by electric field through switching of the electric polarization [6-9]. It has been shown that realization of magnetoelectric coupling in single-phase multiferroic such as BiFeO3 requires ferroelastic (71o, 109o) rather than ferroelectric (180o) domain switching [6]. However, the control of such ferroleastic switching in a singlephase system has been a significant challenge as elastic interactions tend to destabilize small switched volumes, resulting in subsequent ferroelastic backswitching at zero electric field, thus disappearance of nonvolatile information storage [10, 11]. Guided by our phase-field simulations, we here report an approach to stabilize ferroelastic switching by eliminating the stress-induced instability responsible for back-switching using isolated monodomain BiFeO3islands. This work demonstrates a critical step to control and utilize nonvolatile magnetoelectric coupling at the nanoscale. Beyond magnetoelectric coupling, it provides a framework for exploring a route to control multiple order parameters coupled to ferroelastic order in other low-symmetry materials.

Baek, S. H.; Jang, H. W.; Folkman, C. M.; Li, Yulan; Winchester, B.; Zhang, J. X.; He, Q.; Chu, Y. H.; Nelson, C. T.; Rzchowski, M. S.; Pan, X. Q.; Ramesh, R.; Chen , L.Q.; Eom, C.B.

2010-04-01

168

Switched Ethernet for factory communication  

Microsoft Academic Search

Focuses on the special requirements of the control-level within factory communication systems to transmit real-time data via a switched Ethernet network. A performance evaluation of switched Ethernet is presented by providing simulation results. The simulations study the influence of different network topologies as well as the scheduling algorithms first-come-first-served and priority queuing within devices and intermediate systems, like switches. Furthermore

E. Jasperneite; Peter Neumann

2001-01-01

169

Composite Thermal Switch  

NASA Technical Reports Server (NTRS)

Lithium primary and lithium ion secondary batteries provide high specific energy and energy density. The use of these batteries also helps to reduce launch weight. Both primary and secondary cells can be packaged as high-rate cells, which can present a threat to crew and equipment in the event of external or internal short circuits. Overheating of the cell interior from high current flows induced by short circuits can result in exothermic reactions in lithium primary cells and fully charged lithium ion secondary cells. Venting of the cell case, ejection of cell components, and fire have been reported in both types of cells, resulting from abuse, cell imperfections, or faulty electronic control design. A switch has been developed that consists of a thin layer of composite material made from nanoscale particles of nickel and Teflon that conducts electrons at room temperature and switches to an insulator at an elevated temperature, thus interrupting current flow to prevent thermal runaway caused by internal short circuits. The material is placed within the cell, as a thin layer incorporated within the anode and/or the cathode, to control excess currents from metal-to-metal or metal-to-carbon shorts that might result from cell crush or a manufacturing defect. The safety of high-rate cells is thus improved, preventing serious injury to personnel and sensitive equipment located near the battery. The use of recently available nanoscale particles of nickel and Teflon permits an improved, homogeneous material with the potential to be fine-tuned to a unique switch temperature, sufficiently below the onset of a catastrophic chemical reaction. The smaller particles also permit the formation of a thinner control film layer (<50 m), which can be incorporated into commercial high-rate lithium primary and secondary cells. The innovation permits incorporation in current lithium and lithium-ion cell designs with a minimal impact on cell weight and volume. The composite thermal switch (CTS(TradeMark)) coating can be incorporated in either the anode or cathode or both. The coating can be applied in a variety of different processes that permits incorporation in the cell and electrode manufacturing processes. The CTS responds quickly and halts current flow in the hottest parts of the cell first. The coating can be applied to metal foil and supplied as a cell component onto which the active electrode materials are coated.

McDonald, Robert; Brawn, Shelly; Harrison, Katherine; O'Toole, Shannon; Moeller, Michael

2011-01-01

170

Power transistor switching characterization  

NASA Technical Reports Server (NTRS)

The switching properties of power transistors are investigated. The devices studied were housed in IO-3 cases and were of an n(+)-p-n(-)-n(+) vertical dopant structure. The effects of the magnitude of the reverse-base current and temperature on the reverse-bias second breakdown characteristics are discussed. Brief discussions of device degradation due to second breakdown and of a constant voltage turn-off circuit are included. A description of a vacuum tube voltage clamp circuit which reduces clamped collector voltage overshoot is given.

Blackburn, D. L.

1981-01-01

171

Hybrid switch for resonant power converters  

DOEpatents

A hybrid switch comprising two semiconductor switches connected in parallel but having different voltage drop characteristics as a function of current facilitates attainment of zero voltage switching and reduces conduction losses to complement reduction of switching losses achieved through zero voltage switching in power converters such as high-current inverters.

Lai, Jih-Sheng; Yu, Wensong

2014-09-09

172

Solid State Spark Gap Replacement Switches  

Microsoft Academic Search

Improvements in solid state high voltage switching technology now makes it feasible to replace triggered spark gap switches, used in many medical and commercial applications to switch tens of kilovolts and thousands of amperes, with compact solid state switches. The solid state switch we have developed is triggered by a single 10 V isolated trigger pulse to only one stage

S. C. Glidden; H. D. Sanders

2005-01-01

173

LCT protective dump-switch tests  

SciTech Connect

Each of the six coils in the Large Coil Task (LCT) has a separate power supply, dump resistor, and switching circuit. Each switching circuit contains five switches, two of which are redundant. The three remaining switches perform separate duties in an emergency dump situation. These three switches were tested to determine their ability to meet the LCT conditions.

Parsons, W.M.

1981-01-01

174

How Critical Is Critical Thinking?  

ERIC Educational Resources Information Center

Recent educational discourse is full of references to the value of critical thinking as a 21st-century skill. In music education, critical thinking has been discussed in relation to problem solving and music listening, and some researchers suggest that training in critical thinking can improve students' responses to music. But what exactly is…

Shaw, Ryan D.

2014-01-01

175

Critically Thinking about Critical Thinking  

ERIC Educational Resources Information Center

In this article, the author states that "critical thinking" has mesmerized academics across the political spectrum and that even high school students are now being called upon to "think critically." He furthers adds that it is no exaggeration to say that "critical thinking" has quickly evolved into a scholarly…

Weissberg, Robert

2013-01-01

176

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

177

Critical Thoughts on Critical Thinking  

ERIC Educational Resources Information Center

Scholars in many academic areas, including librarians, devote a significant amount of thought to critical thinking. Surveying views of its use and possibility, the author considers some key librarians' thoughts on critical thinking. In conclusion, the inability to define critical thinking means that librarians need to emphasize control of…

Cody, Dean E.

2006-01-01

178

Switching of ultrashort pulses in nonlinear high-birefringence two-core optical fibers  

NASA Astrophysics Data System (ADS)

We analyze the switching characteristics of ultrashort pulses in a nonlinear high-birefringence two-core optical fiber by solving a set of four generalized coupled nonlinear Schrödinger equations. In such a fiber, the critical power required for activating switching changes significantly with the polarization angle of the input pulse and, as a result, a pulse at a proper power level can be switched between the two cores of the fiber by changing the input polarization angle. This provides a simple mechanism of achieving optical switching with the fiber. We also study the effects of the group-delay difference (GDD) between the two polarization components and the coupling-coefficient dispersion (CCD) in the fiber on the switching characteristics. The GDD tends to break up the two polarization components in the input pulse and thus leads to an increase in the switching power. A larger GDD, however, can give a sharper switching contrast when the input polarization angle is varied. The CCD tends to break up the input pulse and cause pulse distortion, regardless of the polarization, so it also leads to an increase in the switching power. Unlike the GDD, a large CCD always reduces the switching contrast. To achieve high-quality switching, the fiber should have a small CCD.

Li, Jin Hua; Chiang, Kin Seng; Chow, Kwok Wing

2014-05-01

179

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

180

Thermal effects in spin torque switching  

NASA Astrophysics Data System (ADS)

We compare low temperature device behavior with room temperature behavior. We find agreement between our low temperature critical current measurements and Slonczewski theory^1. In addition, we find that the values extrapolated from the low temperature measurements were robust with respect to device size. At room temperature we find substantial variation in the hysteretic region from device to device for devices of the same nominal size. While this is not expected, it has been attributed to thermal effects having a strong influence on the response of the freelayer to applied field as well as the coercivity^2. We find that by reducing the temperature, and thus any thermal fluctuations, the device to device variations are drastically reduced. While we did observe indications of non-single domain behavior at 5 K, it is noteworthy that these did not seem to affect the critical switching current. Thus, we conclude that the room temperature device to device variations in the quasi-static switching behavior is dominated by thermal effects. 1. J. C. Slonczewski, J. Magn. Magn. Mater. 159, L1-L7 (1996) 2. D. Lacour, J. A. Katine, N. Smith, M. J. Carey, and J. R. Childress, 85, 4681-4683 (2004).

Schneider, Michael; Pufall, Mattheew; Rippard, William; Russek, Stephen; Katine, Jordan

2007-03-01

181

Exact emulation of an output queueing switch by a combined input output queueing switch  

Microsoft Academic Search

Combined input-output queueing switches (CIOQ) have better scaling properties than output queueing (OQ) switches. However, a CIOQ switch may have lower switch throughput and, more importantly, it is difficult to control delay in a CIOQ switch due to the existence of multiple queueing points. In this paper, we study the following problem: can a CIOQ switch be designed to behave

Ion Stoica; Hui Zhang

1998-01-01

182

Heat pipe thermal switch  

NASA Technical Reports Server (NTRS)

A thermal switch for controlling the dissipation of heat between a body is described. The thermal switch is comprised of a flexible bellows defining an expansible vapor chamber for a working fluid located between an evaporation and condensation chamber. Inside the bellows is located a coiled retaining spring and four axial metal mesh wicks, two of which have their central portions located inside of the spring while the other two have their central portions located between the spring and the side wall of the bellows. The wicks are terminated and are attached to the inner surfaces of the outer end walls of evaporation and condensation chambers respectively located adjacent to the heat source and heat sink. The inner surfaces of the end walls furthermore include grooves to provide flow channels of the working fluid to and from the wick ends. The evaporation and condensation chambers are connected by turnbuckles and tension springs to provide a set point adjustment for setting the gap between an interface plate on the condensation chamber and the heat sink.

Wolf, D. A. (inventor)

1983-01-01

183

A high capacity satellite switched TDMA microwave switch matrix  

NASA Technical Reports Server (NTRS)

A description is given of the conceptual design of a high-capacity satellite switched-time division multiple access (SS-TDMA) microwave switch matrix fabricated with GaAs monolithic microwave integrated circuits (MMICs), including integration of both microwave and control logic circuits into the monolithic design. The technology required for a 30/20 GHz communications system includes an on-board SS-TDMA switch matrix. A conceptual design study that has been completed for a wideband, high-capacity (typically 100 x 100) channel switch matrix using technology anticipated for 1987 is described, noting that the study resulted in a switch matrix design concept using a coupled crossbar architecture implemented with MMIC. The design involves basic building block MMIC, permitting flexible growth and efficient wraparound redundancy to increase reliability.

Cory, B. J.; Berkowitz, M.

1981-01-01

184

Robust adaptive control of switched systems  

E-print Network

In this thesis, robust adaptive controllers are developed for classes of switched nonlinear systems. Switched systems are those governed by differential equations, which undergo vector field switching due to sudden changes ...

El-Rifai, Khalid, 1979-

2007-01-01

185

14 CFR 25.1145 - Ignition switches.  

Code of Federal Regulations, 2010 CFR

... 1 2010-01-01 2010-01-01 false Ignition switches. 25.1145 Section 25.1145 ...Powerplant Controls and Accessories § 25.1145 Ignition switches. (a) Ignition switches must control each engine ignition...

2010-01-01

186

14 CFR 23.1145 - Ignition switches.  

Code of Federal Regulations, 2010 CFR

... 1 2010-01-01 2010-01-01 false Ignition switches. 23.1145 Section 23.1145 ...Powerplant Controls and Accessories § 23.1145 Ignition switches. (a) Ignition switches must control and shut off each...

2010-01-01

187

14 CFR 29.1145 - Ignition switches.  

Code of Federal Regulations, 2010 CFR

... 1 2010-01-01 2010-01-01 false Ignition switches. 29.1145 Section 29.1145 ...Powerplant Controls and Accessories § 29.1145 Ignition switches. (a) Ignition switches must control each ignition circuit...

2010-01-01

188

Performance evaluation of transoceanic switching  

Microsoft Academic Search

The method of synchronous digital hierarchy self-healing ring (SDH SHR) in submarine operation is being developed to improve the reliability of international submarine optical communications. Transoceanic switching is applied in SDH SHR because of the unique features of an international optical submarine cable network: longer distance, submarine environment and fewer terminal stations. We study the system performance of transoceanic switching.

Du Yingzi; Hao Weimin

1998-01-01

189

Corona in switching power supplies  

Microsoft Academic Search

Design literature for dealing with corona in switching power supplies for aircraft or in lamp ballasts does not contain the effects of the switching frequency on corona inception or extinguish voltages. Test data is presented showing these effects. Design techniques for corona are also discussed

A. Brockschmidt

1997-01-01

190

Audio Switch SpeakersAvotec  

E-print Network

Control Monitor Keyboard & Mouse Audio Switch Control SpeakersAvotec USB HUB USB HUB USB CAT5FORP USB Ext Stim PC Stim Mac Laptop Audio RCA RCA USB CAT5 FORPUSB Ext Video K&M Video Video Speakers Avotec Projector Video Switch VGA RCA RCA 3T Audio and Visual Stimulus Setup DVD Drive K&MSiemens RCA

Walker, Matthew P.

191

Final results from the high-current, high-action closing switch test program at Sandia National Laboratories  

Microsoft Academic Search

We tested a variety of high-current closing switches for lifetime and reliability on a dedicated 2 MJ, 500 kA capacitor bank facility at Sandia National Laboratories. Our interest was a switch capable of one shot every few minutes, switching a critically damped, DC-charged 6.2 mF bank at 24 kV, with a peak current of 500 kA. The desired lifetime is

M. E. Savage

1999-01-01

192

Final results from the high-current, high-action closing switch test program at Sandia National Laboratories  

Microsoft Academic Search

We tested a variety of high-current closing switches for lifetime and reliability on a dedicated 2-MJ, 500-kA capacitor bank facility at Sandia National Laboratories. Interest was in a switch capable of one shot every few minutes, switching a critically damped, de-charged 6.2-mF bank at 24 kV, with a peak current of over 500 kA. The desired lifetime is 24000 shots.

Mark E. Savage

2000-01-01

193

Sonic crystal acoustic switch device.  

PubMed

This study reports a wave-controlled sonic crystal switch device that exhibits a destructive interference-based wave to wave reverse switching effect. By applying control waves, this acoustic device, composed of a two-dimensional square lattice sonic crystal block, reduces acoustic wave transmission from input to output. The finite difference time domain simulation and experimental results confirm the wave-to-wave reverse switching effect at the peak frequencies of the second band. The proposed sonic crystal switch prototype provides a contrast rate of 86% at 11.3 kHz frequency. This wave-to-wave switching effect is useful for controlling wave propagation for smart structure applications. PMID:23742444

Alagoz, Serkan; Alagoz, Baris Baykant

2013-06-01

194

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)

2010-02-23

195

''Smart'' watchdog safety switch  

DOEpatents

A method and apparatus for monitoring a process having a periodic output so that the process equipment is not damaged in the event of a controller failure, comprising a low-pass and peak clipping filter, an event detector that generates an event pulse for each valid change in magnitude of the filtered periodic output, a timing pulse generator, a counter that increments upon receipt of any timing pulse and resets to zero on receipt of any event pulse, an alarm that alerts when the count reaches some preselected total count, and a set of relays that opens to stop power to process equipment. An interface module can be added to allow the switch to accept a variety of periodic output signals. 21 figures.

Kronberg, J.W.

1991-10-01

196

"Smart" watchdog safety switch  

DOEpatents

A method and apparatus for monitoring a process having a periodic output so that the process equipment is not damaged in the event of a controller failure, comprising a low-pass and peak clipping filter, an event detector that generates an event pulse for each valid change in magnitude of the filtered periodic output, a timing pulse generator, a counter that increments upon receipt of any timing pulse and resets to zero on receipt of any event pulse, an alarm that alerts when the count reaches some preselected total count, and a set of relays that opens to stop power to process equipment. An interface module can be added to allow the switch to accept a variety of periodic output signals.

Kronberg, James W. (353 Church Rd., Beech Island, SC 29842)

1991-01-01

197

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

198

Long lifetime, triggered, spark-gap switch for repetitive pulsed power applications  

NASA Astrophysics Data System (ADS)

In this article a critical component for pulsed power applications is described: the heavy-duty switch. The design of a coaxial, high repetition rate, large average power, and long lifetime spark-gap switch is discussed. The switch is used with a fail-free LCR trigger circuit. Critical issues for switch design are presented together with experimental results. It is observed that the switch has a good stability, and its lifetime is estimated to be in the order of 1010 shots (˜106C) at 10J/pulse, 60kV and 100ns pulses. Measurements were performed with 20 and 34kV average switching voltage (100ns pulses, energy per pulse 0.4 and 0.75J, respectively). For up to 450pulses/s (pps), pre-firing can be prevented by increasing the gap pressure (up to 2.5 and 7bars, respectively), no gas flush is required. Above 450pps, up to 820pps, a forced gas flow of maximal 35Nm3/h, is required for stable operation. Measurements on the time delay and jitter of the switch demonstrate that these values are influenced by pressure, flow, and pulse repetition rate. For 34kV average switching voltage the time delay and time jitter vary between 35 and 250 and 10 and 80?s, respectively. For 20kV average switching voltage these values are: 30-160 and 4-50?s. During a test run of 2.5h (at 100Hz, 0.75J/pulse) the feasibility of the switch was proved, and the switching voltage jitter was less than 0.7%.

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

2005-08-01

199

Nonisolation Soft-Switching Buck Converter With Tapped-Inductor for Wide-Input Extreme Step-Down Applications  

Microsoft Academic Search

In this paper, a new zero-voltage switching (ZVS) buck converter with a tapped inductor (TI) is proposed. This converter improves the conventional tapped inductor critical conduction mode buck converters that have the ZVS operation range determined by the TI turn ratios. It includes another soft switching range extension method, the current injection method, which gives an additional design freedom for

Joung-Hu Park; Bo-Hyung Cho

2007-01-01

200

Electrical switching in sol-gel-derived SiO2 films  

NASA Astrophysics Data System (ADS)

We have investigated electrical switching behavior of sol-gel derived SiO2 films in c-Si(p)/SiO2/metal structures. The SiO2 film is fabricated from silicafilm (a soluble Si polymer in dissolved in denatured alcohol) using spin-coating technique. The thickness of the film is in the range of 300~2000 Å which depends on both spinning speed and the degree of dilution. We find that, with Ag as the top contact, when the applied voltage reaches a critical value of 1.5 ~ 2.5 V, current increases rapidly many orders of magnitude higher, and an irreversible switching occurs. The switching is also found to be polarity-dependent. The switching occurs only when the top contact (Ag) is biased positively, indicating the switching involves diffusion or electromigration of Ag. Both switching voltage and current are found to scale with the top contact area of the device. The switching dynamics is studied using voltage-pulse over a duration of 300 ns to 500 ms and amplitude of 2 to 20 V. We find that the switching electrical field is strongly dependent of the delay time prior to switching, and not related to the film thickness.

Hu, Jian; Ward, Scott; Wang, Qi

2003-07-01

201

Alarm toe switch. [Patent application  

DOEpatents

An alarm toe switch inserted within a shoe for energizing an alarm circuit in a covert manner includes an insole mounting pad into which a miniature reed switch is fixedly molded. An elongated slot perpendicular to the reed switch is formed in the bottom surface of the mounting pad. A permanent cylindrical magnet positioned in the forward portion of the slot with a diameter greater than the pad thickness causes a bump above the pad. A foam rubber block is also positioned in the slot rearwardly of the magnet and holds the magnet in normal inoperative relation. A non-magnetic support plate covers the slot and holds the magnet and foam rubber in the slot. The plate minimizes bending and frictional forces to improve movement of the magnet for reliable switch activation. The bump occupies the knuckle space beneath the big toe. When the big toe is scrunched rearwardly the magnet is moved within the slot relative to the reed switch, thus magnetically activating the switch. When toe pressure is released the foam rubber block forces the magnet back into normal inoperative position to deactivate the reed switch.

Ganyard, F.P.

1980-11-18

202

49 CFR 236.342 - Switch circuit controller.  

Code of Federal Regulations, 2010 CFR

...342 Switch circuit controller. Switch circuit controller connected at the point to switch, derail, or movable-point frog, shall be maintained so that its contacts will not be in position corresponding to switch point closure when switch point...

2010-10-01

203

49 CFR 236.342 - Switch circuit controller.  

Code of Federal Regulations, 2011 CFR

...342 Switch circuit controller. Switch circuit controller connected at the point to switch, derail, or movable-point frog, shall be maintained so that its contacts will not be in position corresponding to switch point closure when switch point...

2011-10-01

204

49 CFR 236.342 - Switch circuit controller.  

Code of Federal Regulations, 2013 CFR

...342 Switch circuit controller. Switch circuit controller connected at the point to switch, derail, or movable-point frog, shall be maintained so that its contacts will not be in position corresponding to switch point closure when switch point...

2013-10-01

205

49 CFR 236.342 - Switch circuit controller.  

Code of Federal Regulations, 2012 CFR

...342 Switch circuit controller. Switch circuit controller connected at the point to switch, derail, or movable-point frog, shall be maintained so that its contacts will not be in position corresponding to switch point closure when switch point...

2012-10-01

206

Switch dynamics for stochastic model of genetic toggle switch  

NASA Astrophysics Data System (ADS)

Recently, more and more biological experiments have indicated that noise plays an important role in bistable systems, such as the case of the bimodal population distribution in the genetic toggle switch. In this paper, we further verify that noises in degradation rates can indeed induce switching in the genetic toggle switch. Meanwhile, we apply the theory of mean first passage time (MFPT) in high dimensional system to the above stochastic model. According to our assumption, the high order finite difference method is used to compute the MFPT (that the average time switching from one steady state to the other) and we find that the relationship between the MFPT and noise intensity is negative correlation. The result is also verified through another numerical simulation method.

Xu, Yong; Zhu, Ya-nan; Shen, Jianwei; Su, Jianbin

2014-12-01

207

Terahertz Optical Asymmetric Demultiplexer Switch with a Symmetrical Switching Window  

E-print Network

asymmetrical demultiplexer (TOAD) switch. This is achieved by saturating the semiconductor optical amplifier (SOA), located within the TOAD loop, from both directions. So that, both clockwise (CW) and counter], terahertz optical asymmetric demultiplexer (TOAD) [2], ultrafast nonlinear interferometer (UNI) [3

Haddadi, Hamed

208

Fast deterministic switching in orthogonal spin torque devices via the control of the relative spin polarizations  

SciTech Connect

We model 100 ps pulse switching dynamics of orthogonal spin transfer (OST) devices that employ an out-of-plane polarizer and an in-plane polarizer. Simulation results indicate that increasing the spin polarization ratio, C{sub P}?=?P{sub IPP}/P{sub OPP}, results in deterministic switching of the free layer without over-rotation (360° rotation). By using spin torque asymmetry to realize an enhanced effective P{sub IPP}, we experimentally demonstrate this behavior in OST devices in parallel to anti-parallel switching. Modeling predicts that decreasing the effective demagnetization field can substantially reduce the minimum C{sub P} required to attain deterministic switching, while retaining low critical switching current, I{sub p}???500??A.

Park, Junbo; Buhrman, R. A. [Cornell University, Ithaca, New York 14853 (United States)] [Cornell University, Ithaca, New York 14853 (United States); Ralph, D. C. [Cornell University, Ithaca, New York 14853 (United States) [Cornell University, Ithaca, New York 14853 (United States); Kavli Institute at Cornell, Ithaca, New York 14853 (United States)

2013-12-16

209

Molecular-based chiroptical dipole switches  

NASA Astrophysics Data System (ADS)

A series of structurally varied organic molecular switches have been prepared and their switching behavior examined. For thermally active compounds, the switching rates have been extracted from variable temperature NMR experiments and simulation studies. Additionally, chromophores have been incorporated for optical activation of thermally stable switches. Supramolecular architectures for constructing optoelectronic devices are also described.

Parakka, James P.; Schumaker, Robert R.; Kesler, Brenda S.; Thoburn, John D.

2001-05-01

210

Hobetron current regulating switch tube  

SciTech Connect

This paper describes a novel high power electron tube that can hold off voltages up to hundreds of kilovolts, and switch hundreds of amps of current. They call the divide the Hobertron since it utilizes a hollow electron beam. Unlike magnetron injection gun (MIG) switch tubes, it does not require a magnet. Further, it uses nonintercepting control laments, and a dispenser cathode for long life and reliability. Finally, it features a double walled Faraday cage collector for high power dissipation capability. Current is very tightly controlled against changes in voltage across the switch (it is an almost perfect pentode), thus this tube is ideally suited for direct series switching applications. In the paper, various Hobertron designs, and the computer codes and methods used to create them, will be described.

True, R.B.; Hansen, R.J.; Deb, D.N.; Good, G.R.; Reass, W.A.

1999-07-01

211

Cholinergic Switching Within Neocortical Inhibitory  

E-print Network

. Cholinergic activation of subsets of cortical interneurons containing the inhibitory neurotransmitter -aminobuCholinergic Switching Within Neocortical Inhibitory Networks Zixiu Xiang, John R. Huguenard, David within cortical circuits. The functional relations between inhibitory and excitatory networks

Huguenard, John R.

212

The magnetoelectrochemical switch.  

PubMed

In the field of spintronics, the archetype solid-state two-terminal device is the spin valve, where the resistance is controlled by the magnetization configuration. We show here how this concept of spin-dependent switch can be extended to magnetic electrodes in solution, by magnetic control of their chemical environment. Appropriate nanoscale design allows a huge enhancement of the magnetic force field experienced by paramagnetic molecular species in solutions, which changes between repulsive and attractive on changing the electrodes' magnetic orientations. Specifically, the field gradient force created within a sub-100-nm-sized nanogap separating two magnetic electrodes can be reversed by changing the orientation of the electrodes' magnetization relative to the current flowing between the electrodes. This can result in a breaking or making of an electric nanocontact, with a change of resistance by a factor of up to 10(3). The results reveal how an external field can impact chemical equilibrium in the vicinity of nanoscale magnetic circuits. PMID:25009179

Popa, Petru Lunca; Kemp, Neil T; Majjad, Hicham; Dalmas, Guillaume; Faramarzi, Vina; Andreas, Christian; Hertel, Riccardo; Doudin, Bernard

2014-07-22

213

The magnetoelectrochemical switch  

PubMed Central

In the field of spintronics, the archetype solid-state two-terminal device is the spin valve, where the resistance is controlled by the magnetization configuration. We show here how this concept of spin-dependent switch can be extended to magnetic electrodes in solution, by magnetic control of their chemical environment. Appropriate nanoscale design allows a huge enhancement of the magnetic force field experienced by paramagnetic molecular species in solutions, which changes between repulsive and attractive on changing the electrodes’ magnetic orientations. Specifically, the field gradient force created within a sub-100-nm-sized nanogap separating two magnetic electrodes can be reversed by changing the orientation of the electrodes’ magnetization relative to the current flowing between the electrodes. This can result in a breaking or making of an electric nanocontact, with a change of resistance by a factor of up to 103. The results reveal how an external field can impact chemical equilibrium in the vicinity of nanoscale magnetic circuits. PMID:25009179

Lunca Popa, Petru; Kemp, Neil T.; Majjad, Hicham; Dalmas, Guillaume; Faramarzi, Vina; Andreas, Christian; Hertel, Riccardo; Doudin, Bernard

2014-01-01

214

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

215

Electromagnetic Activation of Capillary Switches  

Microsoft Academic Search

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

Bernie Malouin; Rohan Dayal; Leila Parsa; Amir Hirsa

2008-01-01

216

A Piezoelectric Cryogenic Heat Switch  

NASA Technical Reports Server (NTRS)

We have measured the thermal conductance of a mechanical heat switch actuated by a piezoelectric positioner, the PZHS (PieZo electric Heat Switch), at cryogenic temperatures. The thermal conductance of the PZHS was measured between 4 K and 10 K, and on/off conductance ratios greater than 100 were achieved when the positioner applied its maximum force of 8 N. We discuss the advantages of using this system in cryogenic applications, and estimate the ultimate performance of an optimized PZHS.

Jahromi, Amir E.; Sullivan, Dan F.

2014-01-01

217

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

218

A Systematic and Unified Approach to Modeling Switches in Switch-Mode Power Supplies  

Microsoft Academic Search

This paper describes a new, systematic, and unified approach to model the low-frequency behavior of power switches in Switch-Mode Power Supplies (SMPS). This approach starts with a simplification of the switching converter circuit to a Minimum Separable Switching Configuration (MISSCO) containing all power switches but a minimum number of other components, before analysis on the MISSCO is carried out. Then

Y. S. Lee

1985-01-01

219

Electronic logic for enhanced switch reliability  

DOEpatents

A logic circuit is used to enhance redundant switch reliability. Two or more switches are monitored for logical high or low output. The output for the logic circuit produces a redundant and fail-safe representation of the switch outputs. When both switch outputs are high, the output is high. Similarly, when both switch outputs are low, the logic circuit's output is low. When the output states of the two switches do not agree, the circuit resolves the conflict by memorizing the last output state which both switches were simultaneously in and produces the logical complement of this output state. Thus, the logic circuit of the present invention allows the redundant switches to be treated as if they were in parallel when the switches are open and as if they were in series when the switches are closed. A failsafe system having maximum reliability is thereby produced.

Cooper, J.A.

1984-01-20

220

K-Band Latching Switches  

NASA Technical Reports Server (NTRS)

Design, development, and tests are described for two single-pole-double-throw latching waveguide ferrite switches: a K-band switch in WR-42 waveguide and a Ka-band switch in WR-28 waveguide. Both switches have structurally simple junctions, mechanically interlocked without the use of bonding materials; they are impervious to the effects of thermal, shock, and vibration stresses. Ferrite material for the Ka-band switch with a proper combination of magnetic and dielectric properties was available and resulted in excellent low loss, wideband performance. The high power handling requirement of the K-band switch limited the choice of ferrite to nickel-zinc compositions with adequate magnetic properties, but with too low relative dielectric constant. The relative dielectric constant determines the junction dimensions for given frequency responses. In this case the too low value unavoidably leads to a larger than optimum junction volume, increasing the insertion loss and restricting the operating bandwidth. Efforts to overcome the materials-related difficulties through the design of a composite junction with increased effective dielectric properties efforts to modify the relative dielectric constant of nickel-zinc ferrite are examined.

Piotrowski, W. S.; Raue, J. E.

1984-01-01

221

Non-latching relay switch assembly  

DOEpatents

A non-latching relay switch assembly which includes a coil section and a switch or contact section. The coil section includes a permanent magnet and an electromagnet. The respective sections are arranged in separate locations or cavities in the assembly. The switch has a "normal" position and is selectively switched by an overriding electromagnetic assembly. The switch returns to the "normal" position when the overriding electromagnetic assembly is inactive.

Duimstra, Frederick A. (Anaheim Hills, CA)

1991-01-01

222

Solid State Spark Gap Replacement Switches  

Microsoft Academic Search

Improvements in solid state high voltage switching technology now make it feasible to replace triggered spark gap switches, used in many medical and commercial applications to switch tens of kilovolts and thousands of amperes, with compact solid-state switches. We have developed a multi-stage high voltage solid-state switch that is triggered by a single 10 V isolated trigger pulse to only

S. C. Glidden; H. D. Sanders

2006-01-01

223

Optimized switching algorithm for synchronized switch damping for multimodal excitation  

NASA Astrophysics Data System (ADS)

Shunted piezoceramics can be used to dissipate vibration energy of a host structure and therefore reduce vibration amplitudes. The piezoceramic converts a portion of the mechanical energy into electric energy which is then dissipated in an electric network. One semi-active control technique is the synchronized switch damping on inductance (SSDI), which has a good damping performance and can adapt to a wide range of excitation frequencies. In the standard SSDI a switch is closed during maximum deformation for one half of the electrical period time. This results in an inversion of the electrical charge. For the rest of the half-period the switch is opened and the charge remains constant. This results in a nearly rectangular voltage signal, which is in antiphase with the deformation velocity. In case of multimodal excitation, more sophisticated switching laws are developed with the aim to extract vibration energy from higher modes (i.e. Richard). This paper describes a novel multimodal switching law for vibration damping. An observer is designed to obtain an estimation of the first two vibration modes, which are used to determine the switching times. In simulations the increase in energy dissipation is evaluated and compared to the standard SSDI technique. With the new switching algorithm an improvement in energy dissipation is observed. The theoretical results are validated by measurements carried out on a clamped-free beam. The location of the piezoceramics is chosen to optimize the electro-mechanical coupling with the first vibration mode of the beam. The modal observer is realized in a realtime environment. Measurements show a good agreement with the theoretical results.

Schwarzendahl, Sebastian M.; Han, Xu; Neubauer, Marcus; Wallaschek, Jörg

2010-04-01

224

Control for a synchronization-desynchronization switch  

NASA Astrophysics Data System (ADS)

How to freely enhance or suppress synchronization of networked dynamical systems is of great importance in many disciplines. A unified precise control method for a synchronization-desynchronization switch, called the pull-push control method, is suggested. Namely, synchronization can be achieved when the original systems are desynchronous by pulling (or protecting) one node or a certain subset of nodes, whereas desynchronization can be accomplished when the systems are already synchronous by pushing (or kicking) one node or a certain subset of nodes. With this method, the controlled nodes should be chosen by the generalized eigenvector centrality of the critical synchronization mode of the Laplacian matrix. Compared with existing control methods for synchronization, it displays high efficiency, flexibility, and precision as well.

He, Zhiwei; Wang, Xingang; Zhang, Guo-Yong; Zhan, Meng

2014-07-01

225

Control for a synchronization-desynchronization switch.  

PubMed

How to freely enhance or suppress synchronization of networked dynamical systems is of great importance in many disciplines. A unified precise control method for a synchronization-desynchronization switch, called the pull-push control method, is suggested. Namely, synchronization can be achieved when the original systems are desynchronous by pulling (or protecting) one node or a certain subset of nodes, whereas desynchronization can be accomplished when the systems are already synchronous by pushing (or kicking) one node or a certain subset of nodes. With this method, the controlled nodes should be chosen by the generalized eigenvector centrality of the critical synchronization mode of the Laplacian matrix. Compared with existing control methods for synchronization, it displays high efficiency, flexibility, and precision as well. PMID:25122362

He, Zhiwei; Wang, Xingang; Zhang, Guo-Yong; Zhan, Meng

2014-07-01

226

Switching friction with thermal- responsive gels.  

PubMed

The thermosensitive graphene oxide (GO)/poly(N-isopropyl acrylamide) (pNIPAM) composite hydrogels are prepared, and their tribological properties in response to external stimuli are evaluated. The frictional coefficient of the hydrogels is closely related to the gel composition and ambient temperature. When the gel is in swelling state below the low critical solution temperature (LCST), it shows ultra-low friction and exhibits high friction at a shrunk state above the LCST. The huge difference of frictional coefficient under two states can be reversibly switched many times by altering the temperature. The incorporation of a nonthermal sensitive monomer into pNIPAM could change the LCST and thus the transformation point of frictional coefficient can be altered. These reversible and tunable frictional hydrogels have potential application in the design of intelligent control equipment. PMID:24249089

Wu, Yang; Cai, Meirong; Pei, Xiaowei; Liang, Yongmin; Zhou, Feng

2013-11-01

227

Improved current switching symmetry of magnetic tunneling junction and giant magnetoresistance devices with nano-current-channel structure  

NASA Astrophysics Data System (ADS)

The asymmetry of the switching current in magnetic tunneling junction (MTJ) and giant magnetoresistance (GMR) spin torque transfer devices was reported in both theory and experiment. This is one of the key challenges for future magnetic random access memory applications. In this work, the switching symmetry was greatly improved by inserting a nano-current-channel (NCC) structure in both MTJ and GMR devices. With the NCC structure, the current induced magnetization switching is nonuniform with initiation cites induced by locally high current density. The critical switching current density in both switching directions was successfully reduced while the degree of switching asymmetry {[(JcP-AP-JcAP-P)/JcAP-P]×100%} was improved as well.

Yao, Xiaofeng; Meng, Hao; Zhang, Yisong; Wang, Jian-Ping

2008-04-01

228

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. PMID:24154561

Roy, Kuntal; Bandyopadhyay, Supriyo; Atulasimha, Jayasimha

2013-01-01

229

HOLLOTRON switch for megawatt lightweight space inverters  

NASA Technical Reports Server (NTRS)

The feasibility of satisfying the switching requirements for a megawatt ultralight inverter system using HOLLOTRON switch technology was determined. The existing experimental switch hardware was modified to investigate a coaxial HOLLOTRON switch configuration and the results were compared with those obtained for a modified linear HOLLOTRON configuration. It was concluded that scaling the HOLLOTRON switch to the current and voltage specifications required for a megawatt converter system is indeed feasible using a modified linear configuration. The experimental HOLLOTRON switch operated at parameters comparable to the scaled coaxial HOLLOTRON. However, the linear HOLLOTRON data verified the capability for meeting all the design objectives simultaneously including current density (greater than 2 A/sq cm), voltage (5 kV), switching frequency (20 kHz), switching time (300 ns), and forward voltage drop (less than or equal to 20 V). Scaling relations were determined and a preliminary design was completed for an engineering model linear HOLLOTRON switch to meet the megawatt converter system specifications.

Poeschel, R. L.; Goebel, D. M.; Schumacher, R. W.

1991-01-01

230

High speed packet switching  

NASA Technical Reports Server (NTRS)

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 research project is to use the results of the SBIR Phase 1 effort to develop a sound, expandable hardware and software router architecture capable of forwarding 25,000 packets per second through the router and passing 300 megabits per second on the router's internal busses. The work being delivered under this contract received its funding from three different sources: the SNIPE/RIG contract (Contract Number F30602-89-C-0014, CDRL Sequence Number A002), the SBIR contract, and Proteon. The SNIPE/RIG and SBIR contracts had many overlapping requirements, which allowed the research done under SNIPE/RIG to be applied to SBIR. Proteon funded all of the work to develop new router interfaces other than FDDI, in addition to funding the productization of the router itself. The router being delivered under SBIR will be a fully product-quality machine. The work done during this contract produced many significant findings and results, summarized here and explained in detail in later sections of this report. The SNIPE/RIG contract was completed. That contract had many overlapping requirements with the SBIR contract, and resulted in the successful demonstration and delivery of a high speed router. The development that took place during the SNIPE/RIG contract produced findings that included the choice of processor and an understanding of the issues surrounding inter processor communications in a multiprocessor environment. Many significant speed enhancements to the router software were made during that time. Under the SBIR contract (and with help from Proteon-funded work), it was found that a single processor router achieved a throughput significantly higher than originally anticipated. For this reason, a single processor router was developed and the final delivery under this contract will include a single processor CNX-500 router. The router and its interface boards (2 FDDIs and 2 dual-ethernets) are all product-quality components.

1991-01-01

231

Photoresistance switching of plasmonic nanopores.  

PubMed

Fast and reversible modulation of ion flow through nanosized apertures is important for many nanofluidic applications, including sensing and separation systems. Here, we present the first demonstration of a reversible plasmon-controlled nanofluidic valve. We show that plasmonic nanopores (solid-state nanopores integrated with metal nanocavities) can be used as a fluidic switch upon optical excitation. We systematically investigate the effects of laser illumination of single plasmonic nanopores and experimentally demonstrate photoresistance switching where fluidic transport and ion flow are switched on or off. This is manifested as a large (?1-2 orders of magnitude) increase in the ionic nanopore resistance and an accompanying current rectification upon illumination at high laser powers (tens of milliwatts). At lower laser powers, the resistance decreases monotonically with increasing power, followed by an abrupt transition to high resistances at a certain threshold power. A similar rapid transition, although at a lower threshold power, is observed when the power is instead swept from high to low power. This hysteretic behavior is found to be dependent on the rate of the power sweep. The photoresistance switching effect is attributed to plasmon-induced formation and growth of nanobubbles that reversibly block the ionic current through the nanopore from one side of the membrane. This explanation is corroborated by finite-element simulations of a nanobubble in the nanopore that show the switching and the rectification. PMID:25514824

Li, Yi; Nicoli, Francesca; Chen, Chang; Lagae, Liesbet; Groeseneken, Guido; Stakenborg, Tim; Zandbergen, Henny W; Dekker, Cees; Van Dorpe, Pol; Jonsson, Magnus P

2015-01-14

232

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

233

An explosive opening superconducting switch  

NASA Astrophysics Data System (ADS)

A superconducting YBCO tube was tested as an opening switch to demonstrate novel switching concepts for inductive energy storage. The tube was connected in series with a 1.2-mH inductor and a 4800 micro-F capacitor bank which was charged to a predetermined level and discharged through the circuit. No measurable dissipation was observed for test discharges of 8-ms duration, with maximum pulse amplitude increasing for each test while the YBCO was superconducting at 77 K. At the highest current pulse maximum of 95 A, the switch was opened by exploding a short length of detonating cord inserted into the center of the tube. The current decreased to zero, and the voltage increased to maximum in approximately 160 microsec, resulting in a voltage gain of over 25 for current commutation purposes. The data indicate that high-Tc ceramic materials have potential in this application.

Francavilla, T. L.; Ford, R. D.; Lupton, W. H.; Alford, N. Mcn.; Saunders, C. S.

1991-03-01

234

Anomalous switching of optical bistability in a Bose-Einstein condensate  

NASA Astrophysics Data System (ADS)

The nonlinear dynamics of the photon number in an optical cavity filled with a cigar-shaped Bose-Einstein condensate is investigated. We find that the way of adding the field is crucial to the switching close to the critical transition point. If the pump field is changed abruptly, the system may jump from one branch to the other even if the pump field intensity has not reached the critical transition point yet. This behavior is similar to the anomalous switching in the dispersive optical bistability.

Yang, Shuai; Al-Amri, M.; Zubairy, M. Suhail

2013-03-01

235

The plasma erosion opening switch  

NASA Astrophysics Data System (ADS)

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 generators for pulse compression, voltage multiplication and power multiplication. The PEOS is used routinely for other types of power conditioning including prepulse suppression, pulse sharpening and multimodule jitter reduction. This paper is a review of the PEOS work to date. It reviews basic physics principles of the PEOS and outlines the operational limits of a system that employs a PEOS. Examples of present applications of the PEOS are also discussed.

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

1985-05-01

236

A piezoelectric cryogenic heat switch.  

PubMed

We have measured the thermal conductance of a mechanical heat switch actuated by a piezoelectric positioner, the PZHS (PieZo electric Heat Switch), at cryogenic temperatures. The thermal conductance of the PZHS was measured between 4 K and 10 K, and on/off conductance ratios of about 100-200 at lowest and highest measures temperature were achieved when the positioner applied its maximum force of 8 N, respectively. We discuss the advantages of using this system in cryogenic applications, and estimate the ultimate performance of an ideal PZHS. PMID:24985863

Jahromi, Amir E; Sullivan, Dan F

2014-06-01

237

Optical Switch Using Risley Prisms  

SciTech Connect

An optical switch using Risley prisms and rotary microactuators to independently rotate the wedge prisms of each Risley prism pair is disclosed. The optical switch comprises an array of input Risley prism pairs that selectively redirect light beams from a plurality of input ports to an array of output Risley prism pairs that similarly direct the light beams to a plurality of output ports. Each wedge prism of each Risley prism pair can be independently rotated by a variable-reluctance stepping rotary microactuator that is fabricated by a multi-layer LIGA process. Each wedge prism can be formed integral to the annular rotor of the rotary microactuator by a DXRL process.

Sweatt, William C. (Albuquerque, NM); Christenson, Todd R. (Albuquerque, NM)

2005-02-22

238

Optical switch using Risley prisms  

SciTech Connect

An optical switch using Risley prisms and rotary microactuators to independently rotate the wedge prisms of each Risley prism pair is disclosed. The optical switch comprises an array of input Risley prism pairs that selectively redirect light beams from a plurality of input ports to an array of output Risley prism pairs that similarly direct the light beams to a plurality of output ports. Each wedge prism of each Risley prism pair can be independently rotated by a variable-reluctance stepping rotary microactuator that is fabricated by a multi-layer LIGA process. Each wedge prism can be formed integral to the annular rotor of the rotary microactuator by a DXRL process.

Sweatt, William C. (Albuquerque, NM); Christenson, Todd R. (Albuquerque, NM)

2003-04-15

239

Optimized switching algorithm for synchronized switch damping for multimodal excitation  

Microsoft Academic Search

Shunted piezoceramics can be used to dissipate vibration energy of a host structure and therefore reduce vibration amplitudes. The piezoceramic converts a portion of the mechanical energy into electric energy which is then dissipated in an electric network. One semi-active control technique is the synchronized switch damping on inductance (SSDI), which has a good damping performance and can adapt to

Sebastian M. Schwarzendahl; Xu Han; Marcus Neubauer; Jörg Wallaschek

2010-01-01

240

Bilateral, Zero-Impedance Static Semiconductor Switch  

NASA Technical Reports Server (NTRS)

Static semiconductor switching circuit eliminates the undesirable features of electromechanical relays and conventional semiconductor switching circuits. There is a net zero voltage drop at the terminals and thus a zero impedance for bilateral currents there.

Doughman, C. L.

1968-01-01

241

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

242

Energy loss in spark gap switches  

SciTech Connect

The paper reports on numerical study of the energy loss in spark gap switches. The operation of the switches is analyzed using the Braginsky model which allows calculation of the time dependence of the spark channel resistance. The Braginsky equation is solved simultaneously with generator circuit equations for different load types. Based on the numerical solutions, expressions which determine both the energy released in a spark gap switch and the switching time are derived.

Oreshkin, V. I., E-mail: oreshkin@ovpe.hcei.tsc.ru; Lavrinovich, I. V. [Institute of High Current Electronics SB RAS, Akademichesky Ave. 2/3, 634055 Tomsk (Russian Federation) [Institute of High Current Electronics SB RAS, Akademichesky Ave. 2/3, 634055 Tomsk (Russian Federation); National Research Tomsk Polytechnic University, Lenin Avenue 30, 634050 Tomsk (Russian Federation)

2014-04-15

243

Voluntary Task Switching: Chasing the Elusive Homunculus  

Microsoft Academic Search

In the voluntary task switching procedure, subjects choose the task to perform on a series of bivalent stimuli, requiring top-down control of task switching. Experiments 1–3 contrasted voluntary task switching and explicit task cuing. Choice behavior showed small, inconsistent effects of external stimulus characteristics, supporting the assumption of top-down control of task choice. Switch costs were smaller when subjects chose

Catherine M. Arrington; Gordon D. Logan

2005-01-01

244

A comparison of switching energy of resonant and nonresonant electro-optic switches  

NASA Astrophysics Data System (ADS)

Optical space switching is an important functionality in dense wavelength division multiplexing (DWDM) optical communication systems, particularly within reconfigurable optical add-drop multiplexers (ROADMs) [1]. Current commercially available ROADMs are based on micro-electromechanical systems (MEMS) or liquid crystal switches but these do not have sufficient switching speed for future network requirements. Power consumption (i.e. energy per switching operation multiplied by switching rate) is a very important parameter in the selection of a switching technology. Space switches based on current injection in silicon have been reported with nanosecond switching speeds and average power consumption on the order of mW [2], which becomes significant if many switches are required in a fabric. Electro-optic (EO) switches, which utilize the Pockels effect in which the refractive index changes when an external voltage is applied [3], only dissipate power when the switch state is changed. Electro-optic switches can be implemented either as non-resonant designs (for example the Mach-Zehnder interferometer (MZI)) or as resonant designs (for example the Fabry Perot interferometer (FPI)). In this study we compare the switching energies of electro optic MZI and FPI switches by considering the capacitance of the switch, which is determined by the length of the active region of the switch. We show that for a non-resonant switch, switching energy increases linearly with device length, regardless of applied voltage, and so is simply determined by the strength of the electro-optic coefficient. We assume that the resonant switch is implemented as a switchable comb filter [4], with a free-spectral range equal to twice the wavelength spacing. This then fixes the interferometer length. As a result the resonant switch has requires significantly less switching energy for the same material parameters and is thus of interest for future ROADM implementations.

Soltani, Fatemeh; Kirk, Andrew G.

2012-10-01

245

CRITICAL REVIEW  

E-print Network

This critical review provides a processing-structure-property perspective on recent advances in cellulose nanoparticles and composites produced from them. It summarizes cellulose nanoparticles in terms of particle morphology, crystal structure, and properties. Also described are the self-assembly and rheological properties of cellulose nanoparticle suspensions. The methodology of composite processing and resulting properties are fully covered, with an emphasis on neat and high fraction cellulose composites. Additionally, advances in predictive modeling from molecular dynamic simulations of crystalline cellulose to the continuum modeling of composites made with such particles are reviewed (392 references).

Jeff Youngblood C

246

Suppression of subtelomeric VSG switching by Trypanosoma brucei TRF requires its TTAGGG repeat-binding activity.  

PubMed

Trypanosoma brucei causes human African trypanosomiasis and regularly switches its major surface antigen, VSG, in the bloodstream of its mammalian host to evade the host immune response. VSGs are expressed exclusively from subtelomeric loci, and we have previously shown that telomere proteins TbTIF2 and TbRAP1 play important roles in VSG switching and VSG silencing regulation, respectively. We now discover that the telomere duplex DNA-binding factor, TbTRF, also plays a critical role in VSG switching regulation, as a transient depletion of TbTRF leads to significantly more VSG switching events. We solved the NMR structure of the DNA-binding Myb domain of TbTRF, which folds into a canonical helix-loop-helix structure that is conserved to the Myb domains of mammalian TRF proteins. The TbTRF Myb domain tolerates well the bulky J base in T. brucei telomere DNA, and the DNA-binding affinity of TbTRF is not affected by the presence of J both in vitro and in vivo. In addition, we find that point mutations in TbTRF Myb that significantly reduced its in vivo telomere DNA-binding affinity also led to significantly increased VSG switching frequencies, indicating that the telomere DNA-binding activity is critical for TbTRF's role in VSG switching regulation. PMID:25313155

Jehi, Sanaa E; Li, Xiaohua; Sandhu, Ranjodh; Ye, Fei; Benmerzouga, Imaan; Zhang, Mingjie; Zhao, Yanxiang; Li, Bibo

2014-11-10

247

Suppression of subtelomeric VSG switching by Trypanosoma brucei TRF requires its TTAGGG repeat-binding activity  

PubMed Central

Trypanosoma brucei causes human African trypanosomiasis and regularly switches its major surface antigen, VSG, in the bloodstream of its mammalian host to evade the host immune response. VSGs are expressed exclusively from subtelomeric loci, and we have previously shown that telomere proteins TbTIF2 and TbRAP1 play important roles in VSG switching and VSG silencing regulation, respectively. We now discover that the telomere duplex DNA-binding factor, TbTRF, also plays a critical role in VSG switching regulation, as a transient depletion of TbTRF leads to significantly more VSG switching events. We solved the NMR structure of the DNA-binding Myb domain of TbTRF, which folds into a canonical helix-loop-helix structure that is conserved to the Myb domains of mammalian TRF proteins. The TbTRF Myb domain tolerates well the bulky J base in T. brucei telomere DNA, and the DNA-binding affinity of TbTRF is not affected by the presence of J both in vitro and in vivo. In addition, we find that point mutations in TbTRF Myb that significantly reduced its in vivo telomere DNA-binding affinity also led to significantly increased VSG switching frequencies, indicating that the telomere DNA-binding activity is critical for TbTRF's role in VSG switching regulation. PMID:25313155

Jehi, Sanaa E.; Li, Xiaohua; Sandhu, Ranjodh; Ye, Fei; Benmerzouga, Imaan; Zhang, Mingjie; Zhao, Yanxiang; Li, Bibo

2014-01-01

248

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

249

Switching processes in financial markets  

PubMed Central

For an intriguing variety of switching processes in nature, the underlying complex system abruptly changes from one state to another in a highly discontinuous fashion. Financial market fluctuations are characterized by many abrupt switchings creating upward trends and downward trends, on time scales ranging from macroscopic trends persisting for hundreds of days to microscopic trends persisting for a few minutes. The question arises whether these ubiquitous switching processes have quantifiable features independent of the time horizon studied. We find striking scale-free behavior of the transaction volume after each switching. Our findings can be interpreted as being consistent with time-dependent collective behavior of financial market participants. We test the possible universality of our result by performing a parallel analysis of fluctuations in time intervals between transactions. We suggest that the well known catastrophic bubbles that occur on large time scales—such as the most recent financial crisis—may not be outliers but single dramatic representatives caused by the formation of increasing and decreasing trends on time scales varying over nine orders of magnitude from very large down to very small. PMID:21521789

Preis, Tobias; Schneider, Johannes J.; Stanley, H. Eugene

2011-01-01

250

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

251

Fast all-optical switch  

NASA Technical Reports Server (NTRS)

An apparatus and method wherein polarization rotation in alkali vapors or other mediums is used for all-optical switching and digital logic and where the rate of operation is proportional to the amplitude of the pump field. High rates of speed are accomplished by Rabi flopping of the atomic states using a continuously operating monochromatic atomic beam as the pump.

Shay, Thomas M. (Inventor); Poliakov, Evgeni Y. (Inventor); Hazzard, David A. (Inventor)

2001-01-01

252

ERGODIC CONTROL OF SWITCHING DIFFUSIONS  

Microsoft Academic Search

A b st r ac t . We study the ergodic control problem of switching diffusions representing a typical hybrid system that arises in numerous applications such as fault-tolerant control systems, flexible manufacturing systems, etc. Under fairly general conditions, we establish the existence of a stable, nonrandomized Markov policy which almost surely minimizes the pathwise long-run average cost. We then

Mrinal K. Ghosh; Aristotle Arapostathis; Steven I. Marcus

253

Solar array switching power management  

NASA Technical Reports Server (NTRS)

Solar array power switching concepts are explored for a 250 kWe manned LEO platform, a 50-250 kWe load for an orbit transfer vehicle (OTV), and an unmanned platform with a 50 kWe load in GEO. A solar array switching power management (SASPM) system is under study to satisfy the switching demands. Direct connections to arrays would be implemented for voltage regulations, power distribution, and the capability of reconfiguring the arrays to meet requirements. Mission characteristics that would require the power sources were explored. The LEO platform was projected to use a concentrator, have no reconfigurability, use 250 NiH2 batteries, supply 80-0 Vdc to an ion drive, and have a 20-30 yr life. Both GEO and OTV arrays were planar, would feature reconfigurability, and supply 800 Vdc to an ion drive. NiH2 batteries would be on the OTV, while the GEO spacecraft would use AgH2 cells. A block diagram of the basic switching configuration is presented.

Cassinelli, J. E.; Smith, L. D.; Valgora, M.

1982-01-01

254

Low engine oil sensing switch  

Microsoft Academic Search

A pneumatic switch is described responsive to the vacuum in a closed crankcase of a reciprocating piston engine, the crankcase containing a volume of lubricating oil, the engine having a check valve connected for venting positive gas pressure from the crankcase to maintain an average vacuum in the crankcase, such vacuum varying as a function of the quantity of oil

M. Lenk; R. S. Podiak

1986-01-01

255

A new very high voltage semiconductor switch  

NASA Technical Reports Server (NTRS)

A new family of semiconductor switches using double injection techniques and compensated deep impurities is described. They have the potential to raise switching voltages a factor of 10 higher (up to 100 kV) than p-n junction devices while exhibiting extremely low (or zero) forward voltage. Several potential power switching applications are indicated.

Sundberg, G. R.

1985-01-01

256

Algorithmic aspects of high speed switching  

E-print Network

A major drawback of the traditional output queuing technique is that it requires a switch speedup of N, where N is the size of the switch. This dependence on N makes the switch non-scalable at high speeds. Input queuing ...

Mneimneh, Saadeddine S

2002-01-01

257

Asynchronous vs Synchronous Input-Queued Switches  

E-print Network

to their limited techno- logical requirements. Basically, IQ switches trade a lower internal data transfer capacity (i.e., very limited speed-ups of the switching fabric) for a larger complexity in switch control in fixed- size data units, which are transferred to outputs, where they are re-assembled in variable

258

Switch for serial or parallel communication networks  

DOEpatents

A communication switch apparatus and a method for use in a geographically extensive serial, parallel or hybrid communication network linking a multi-processor or parallel processing system has a very low software processing overhead in order to accommodate random burst of high density data. Associated with each processor is a communication switch. A data source and a data destination, a sensor suite or robot for example, may also be associated with a switch. The configuration of the switches in the network are coordinated through a master processor node and depends on the operational phase of the multi-processor network: data acquisition, data processing, and data exchange. The master processor node passes information on the state to be assumed by each switch to the processor node associated with the switch. The processor node then operates a series of multi-state switches internal to each communication switch. The communication switch does not parse and interpret communication protocol and message routing information. During a data acquisition phase, the communication switch couples sensors producing data to the processor node associated with the switch, to a downlink destination on the communications network, or to both. It also may couple an uplink data source to its processor node. During the data exchange phase, the switch couples its processor node or an uplink data source to a downlink destination (which may include a processor node or a robot), or couples an uplink source to its processor node and its processor node to a downlink destination.

Crosette, Dario B. (DeSoto, TX)

1994-01-01

259

Switch for serial or parallel communication networks  

DOEpatents

A communication switch apparatus and a method for use in a geographically extensive serial, parallel or hybrid communication network linking a multi-processor or parallel processing system has a very low software processing overhead in order to accommodate random burst of high density data. Associated with each processor is a communication switch. A data source and a data destination, a sensor suite or robot for example, may also be associated with a switch. The configuration of the switches in the network are coordinated through a master processor node and depends on the operational phase of the multi-processor network: data acquisition, data processing, and data exchange. The master processor node passes information on the state to be assumed by each switch to the processor node associated with the switch. The processor node then operates a series of multi-state switches internal to each communication switch. The communication switch does not parse and interpret communication protocol and message routing information. During a data acquisition phase, the communication switch couples sensors producing data to the processor node associated with the switch, to a downlink destination on the communications network, or to both. It also may couple an uplink data source to its processor node. During the data exchange phase, the switch couples its processor node or an uplink data source to a downlink destination (which may include a processor node or a robot), or couples an uplink source to its processor node and its processor node to a downlink destination. 9 figs.

Crosette, D.B.

1994-07-19

260

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

261

Voluntary Task Switching: Chasing the Elusive Homunculus  

ERIC Educational Resources Information Center

In the voluntary task switching procedure, subjects choose the task to perform on a series of bivalent stimuli, requiring top-down control of task switching. Experiments 1-3 contrasted voluntary task switching and explicit task cuing. Choice behavior showed small, inconsistent effects of external stimulus characteristics, supporting the assumption…

Arrington, Catherine M.; Logan, Gordon D.

2005-01-01

262

A computer-based substation switching scheme  

Microsoft Academic Search

This paper describes a digital computer based substation switching scheme which employs generalized rules for interlocking and sequence switching. The scheme can handle different configurations of substations which are recognized from the input data that describes the interconnections of switches. The scheme is, therefore, applicable to substations of all practical configurations. It also considers factors such as, generation and load

P. Dhakal; M. S. Sachdev

1995-01-01

263

The Octopus switch This chapter1  

E-print Network

The Octopus switch This chapter1 discusses the interconnection architecture of the Mobile Digital on the data path, where it is needed. A reconfigurable internal communication network switch called Octopus is based on a switch, called Octopus, which interconnects a general-purpose processor, (multimedia) devices

Havinga, Paul J.M.

264

Implementation of firmware on SPC switching systems  

Microsoft Academic Search

The recent trend toward distributed processing in stored-program-controlled (SPC) switching systems has resulted in increased use of firmware. The impact of firmware on SPC switching system reliability and maintainability, after sale of the product to user companies, can be substantial. The author examines both life cycle practices for firmware and the impact of firmware on switching systems, and he suggests

S. R. Ali

1988-01-01

265

A Reliability Analysis of Local Telecommunication Switches  

Microsoft Academic Search

Abstract This paper presents a reliability analysis of Local Exchange Carrier telecommunication switches in the United States, based upon empirical data. Telecommunication switch outage statistics are analyzed for a multiyear period, allowing examination into switch failure frequency, causes, and trends. Failure categories are created by reported outage cause codes, including human error, design error, hardware failure, and external factor causality

Andrew P. Snow

266

A CW Gunn Diode Switching Element.  

ERIC Educational Resources Information Center

As part of a study of the application of communication satellites to educational development, certain technical aspects of such a system were examined. A current controlled bistable switching element using a CW Gunn diode is reported on here. With modest circuits switching rates of the order of 10 MHz have been obtained. Switching is initiated by…

Hurtado, Marco; Rosenbaum, Fred J.

267

Architectural Choices in Large Scale ATM Switches  

E-print Network

, reliability and cost-effectiveness. The pressure of the competing requirements on switching systems, together networks of arbitrary size using switching systems of limited capacity, it turns out to be far more cost-effective as telephone switches require capacities of 1-10 Gb/s to provide cost/effective service to large user

Turner, Jonathan S.

268

Plug-In RF Selector Switch  

NASA Technical Reports Server (NTRS)

Short, direct link between switch and filters reduces signal loss. New switch attaches directly to filter housing, eliminating cables and connectors. As result, losses in transmitter and receiver paths reduced by about 0.4 dB. Because connectors and cables are not used, RF path loss for selected signal through switch and filter is smaller than usual.

Hwon, A. H.; Steidel, C. F.

1986-01-01

269

14 CFR 27.1145 - Ignition switches.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 false Ignition switches. 27.1145 Section 27...Controls and Accessories § 27.1145 Ignition switches. (a) There must be means to quickly shut off all ignition by the grouping of switches or by...

2010-01-01

270

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.

271

Electronic logic to enhance switch reliability in detecting openings and closures of redundant switches  

DOEpatents

A logic circuit is used to enhance redundant switch reliability. Two or more switches are monitored for logical high or low output. The output for the logic circuit produces a redundant and failsafe representation of the switch outputs. When both switch outputs are high, the output is high. Similarly, when both switch outputs are low, the logic circuit's output is low. When the output states of the two switches do not agree, the circuit resolves the conflict by memorizing the last output state which both switches were simultaneously in and produces the logical complement of this output state. Thus, the logic circuit of the present invention allows the redundant switches to be treated as if they were in parallel when the switches are open and as if they were in series when the switches are closed. A failsafe system having maximum reliability is thereby produced.

Cooper, James A. (Albuquerque, NM)

1986-01-01

272

Anisotropic high temperature superconductors as variable resistors and switches  

SciTech Connect

Several anisotropic high temperature superconductors show critical current densities which are strongly dependent on the direction of an applied external magnetic field. The resistance of a sample can change by several orders of magnitude by applying a magnetic field. The potential for using the field dependent variable resistor or switch for applications in power systems is evaluated. Test results with small samples are presented. The requirements for large scale applications are outlined. The magnetic field triggering requirement, the frequency response of the device, use in 60 Hz ac circuits and heat transfer consideration are investigated. Several application examples are discussed. Use of variable resistor as a fault current limiter, as a switching element in rectifier circuitry and as an improved dump resistor for a superconducting magnet is presented.

Boenig, H.J.; Daugherty, M.A.; Fleshler, S.; Maley, M.P.; Mueller, F.M.; Prenger, F.C.; Coulter, J.Y.

1994-12-01

273

Adaptive neural control for a class of switched nonlinear systems  

Microsoft Academic Search

In this paper, adaptive neural control is presented for a class of switched nonlinear systems with switching jumps and uncertainties in both system models and switching signals. Condition on limiting variation of the Lyapunov function is given for input-to-state asymptotic stability of switched systems with switching jumps. The control objective is achieved uniformly with respect to a class of switching

Thanh-Trung Han; Shuzhi Sam Ge; Tong Heng Lee

2009-01-01

274

A Regev-Type Fully Homomorphic Encryption Scheme Using Modulus Switching  

PubMed Central

A critical challenge in a fully homomorphic encryption (FHE) scheme is to manage noise. Modulus switching technique is currently the most efficient noise management technique. When using the modulus switching technique to design and implement a FHE scheme, how to choose concrete parameters is an important step, but to our best knowledge, this step has drawn very little attention to the existing FHE researches in the literature. The contributions of this paper are twofold. On one hand, we propose a function of the lower bound of dimension value in the switching techniques depending on the LWE specific security levels. On the other hand, as a case study, we modify the Brakerski FHE scheme (in Crypto 2012) by using the modulus switching technique. We recommend concrete parameter values of our proposed scheme and provide security analysis. Our result shows that the modified FHE scheme is more efficient than the original Brakerski scheme in the same security level. PMID:25093212

Chen, Zhigang; Wang, Jian; Song, Xinxia

2014-01-01

275

Decrease in switching voltage fluctuation of Pt /NiOx/Pt structure by process control  

NASA Astrophysics Data System (ADS)

Resistance change random access memory devices using NiOx films with resistance switching properties have immense potential for high-density nonvolatile memory exceeding currently used flash memory. The only critical failure of a NiOx film is to write wrong information due to large fluctuations of switching voltages during successive resistance switching operations. The authors show that failure-free NiOx film can be grown directly on Pt electrode just by process control. Intensive analyses show that the superior resistance switching behaviors of their simple Pt /NiOx/Pt structure may result from a very thin Ni-Pt layer self-formed at the bottom interface during deposition of NiOx.

Jung, Ranju; Lee, Myoung-Jae; Seo, Sunae; Kim, Dong Chirl; Park, Gyeong-Su; Kim, Kihong; Ahn, Seungeon; Park, Youngsoo; Yoo, In-Kyeong; Kim, Jin-Soo; Park, Bae Ho

2007-07-01

276

Universal criterion and phase diagram for switching a magnetic vortex core in soft magnetic nanodots.  

PubMed

The universal criterion for ultrafast vortex-core switching between the up- and down-core bistates in soft magnetic nanodots is investigated by micromagnetic simulations along with vortex-core switching that occurs whenever the velocity of vortex-core motion reaches its critical velocity, upsilon cri = (1.66 +/- 0.18) gamma mean square root of Aex (e.g., upsilon cri = 330 +/- 37 m/s for Permalloy), with the exchange stiffness Aex and the gyromagnetic ratio gamma. On the basis of the universality of upsilon cri, phase diagrams for the vortex-core switching event and switching time with respect to both the amplitude and frequency of a circularly rotating magnetic field are calculated. PMID:19437670

Lee, Ki-Suk; Kim, Sang-Koog; Yu, Young-Sang; Choi, Youn-Seok; Guslienko, Konstantin Yu; Jung, Hyunsung; Fischer, Peter

2008-12-31

277

A Regev-type fully homomorphic encryption scheme using modulus switching.  

PubMed

A critical challenge in a fully homomorphic encryption (FHE) scheme is to manage noise. Modulus switching technique is currently the most efficient noise management technique. When using the modulus switching technique to design and implement a FHE scheme, how to choose concrete parameters is an important step, but to our best knowledge, this step has drawn very little attention to the existing FHE researches in the literature. The contributions of this paper are twofold. On one hand, we propose a function of the lower bound of dimension value in the switching techniques depending on the LWE specific security levels. On the other hand, as a case study, we modify the Brakerski FHE scheme (in Crypto 2012) by using the modulus switching technique. We recommend concrete parameter values of our proposed scheme and provide security analysis. Our result shows that the modified FHE scheme is more efficient than the original Brakerski scheme in the same security level. PMID:25093212

Chen, Zhigang; Wang, Jian; Chen, Liqun; Song, Xinxia

2014-01-01

278

A kinetic study in vitro of the reoxidation of interchain disulfide bonds in a human immunoglobulin IgGLk. Correlation between sulfhydryl disappearance and intermediates in covalent assembly of H2L2.  

PubMed

After reduction by dithiothreitol and removal of the reductant by molecular sieve chromatography, the four interchain disulfide bonds of the human IgGlk protein Fro reoxidize in the presence of oxygen and trace metal ions. The six molecular components of the reoxidation--L (light chain), H (heavy chain), HL, H2, H2L, H2L2--are quantitatively determined from polyacrylamide gels containing sodium dodecyl sulfate and the time-dependent sulfhydryl titer is measured with 5,5'-dithiobis-(2-nitrobenzoic acid). The rates of H2L2 covalent assembly depend on pH in an unexpected way: If the reduced protein is chromatographed at pH 3.2 and then adjusted to pH 7.5 (25 degrees, ionic strength equals 0.14), H2L2 formation proceeds rapidly, with half-times ranging between 20 and 40 min. In contrast, if chromatography is carried out at pH 5.5 before adjusting to the same final conditions, the half-times for H2L2 formation are considerably longer (120-180 min). The half-times in the former case approach the somewhat faster rates of H2L2 assembly observed in pulse-chase experiments with various types of mouse, IgG-producing cells [Baumal, et al. (1971) J. Exp. Med. 134, 1316-1334]. To facilitate comparison of experiments and models, we plot the concentrations of the six components against the corresponding number of sulfhydryl equivalents per mole of Fro. The respective plots for the pH 3.2 leads to 7.5 and 5.5 leads to 7.5 experiments are very similar despite the rate differences. Moreover, these plots differ significantly from the calculated plot for a hypothetical random reoxidation in which the intrinsic probability for formation of each correct HL and H2 disulfide bond is assumed equal and independent. It is concluded that the in vitro reoxidation of Fro (i) is other than random; (ii) involved a pathway of pathways with HL, H2, and H2L precursors; and (iii) involves at least some kinetic cooperativity in bond formation, since no model bases solely on independent bond formation adequately accounts for the results. The models were used also to examine the cellular assembly pathways of mouse IgG proteins. PMID:235127

Sears, D W; Mohrer, J; Beychok, S

1975-01-01

279

T cell epitope mapping of ragweed pollen allergen Ambrosia artemisiifolia (Amb a 5) and Ambrosia trifida (Amb t 5) and the role of free sulfhydryl groups in T cell recognition.  

PubMed

Ambrosia artemisiifolia (Amb a 5; Ra5S) and Ambrosia trifida (Amb t 5; Ra5G) are homologous allergens purified from short and giant ragweed pollen, respectively. Allergic human sera and hyperimmunized animal antisera directed against Amb a 5 or Amb t 5 show a high degree of species specificity, with little or no cross-reactivity between these two allergens, suggesting that the major Ab binding epitopes of Amb a 5 and Amb t 5 are distinct. Overlapping synthetic peptides derived from the allergen sequences were used to investigate the specificity of T cell responses in four strains of mice, BALB/c (H-2d), CBA (H-2k), C57BL/6 (H-2b), and A/J (H-2a). All four strains of mice responded to purified Amb a 5 and Amb t 5. Cross-reactivity was found at the T cell level between Amb a 5 and Amb t 5 in T cells from BALB/c, A/J, and CBA mice, but not in T cells from C57BL/6 mice. A T cell epitope from Amb a 5, residues 27-36 (PWQVVCYESS), was mapped using T cell hybridomas from BALB/c mice. A T cell epitope in Amb t 5 was mapped in the same strain to residues 24-34 (KYCVCYDSKAI). Disulfide bonds in Amb a 5 and Amb t 5 were found to be involved in T cell reactivity. Conversion of disulfide bridges into free sulfhydryl (SH) forms was required for the response of T cell hybridomas to peptide t5 (residues 27-40) from Amb t 5. Reduction of peptide a4 (residues 21-37) from Amb a 5 was essential for inducing the cross-reactivity observed with Amb t 5-specific T cell hybridomas. It is concluded that free sulfhydryl groups play a major role in the T cell recognition of cross-reactivity T cell epitopes within these related allergens. PMID:7594515

Zhu, X; Greenstein, J L; Rogers, B L; Kuo, M C

1995-11-15

280

The effects of para-chloromercuribenzoic acid and different oxidative and sulfhydryl agents on a novel, non-AT1, non-AT2 angiotensin binding site identified as neurolysin  

PubMed Central

A novel, non-AT1, non-AT2 brain binding site for angiotensin peptides that is unmasked by p-chloromercuribenzoate (PCMB) has been identified as a membrane associated variant of neurolysin. The ability of different organic and inorganic oxidative and sulfhydryl reactive agents to unmask or inhibit 125I-Sar1Ile8 angiotensin II (SI-Ang II) binding to this site was presently examined. In tissue membranes from homogenates of rat brain and testis incubated in assay buffer containing losartan (10 ?M) and PD123319 (10 ?M) plus 100 ?M PCMB, 5 of the 39 compounds tested inhibited 125I-SI Ang II binding in brain and testis. Mersalyl acid, mercuric chloride (HgCl2) and silver nitrate (AgNO3) most potently inhibited 125I-SI Ang II binding with IC50’s ~1–20 ?M This HgCl2 inhibition was independent of any interaction of HgCl2 with angiotensin II (Ang II) based on the lack of effect of HgCl2 on the dipsogenic effects of intracerebroventricularly administered Ang II and 125I-SI Ang II binding to AT1 receptors in the liver. Among sulfhydryl reagents, cysteamine and reduced glutathione (GSH), but not oxidized glutathione (GSSG) up to 1 mM, inhibited PCMB-unmasked 125I-SI Ang II binding in brain and testis. Thimerosal and 4-hydroxymercuribenzoate moderately inhibited PCMB-unmasked 125I-SI Ang II binding in brain and testis at 100 ?M; however, they also unmasked non-AT1, non-AT2 binding independent of PCMB. 4-hydroxybenzoic acid did not promote 125 I-SI Ang II binding to this binding site indicating that only specific organomercurial compounds can unmask the binding site. The common denominator for all of these interacting substances is the ability to bind to protein cysteine sulfur. Comparison of cysteines between neurolysin and the closely related enzyme thimet oligopeptidase revealed an unconserved cysteine (cys650, based on the full length variant) in the proposed ligand binding channel (Brown et al., 2001) [1] near the active site of neurolysin. It is proposed that the mercuric ion in PCMB and closely related organomercurial compounds binds to cys650, while the acidic anion forms an ionic bond with a nearby arginine or lysine along the channel to effect a conformational change in neurolysin that promotes Ang II binding. PMID:23511333

Santos, Kira L.; Vento, Megan A; Wright, John W.; Speth, Robert C.

2013-01-01

281

Strain-induced polarity switching of magnetic vortex in Fe1-xGax alloys with different compositions  

NASA Astrophysics Data System (ADS)

The strain-induced polarity switching of magnetic vortex in the Fe1-xGax nanodots with different compositions is demonstrated by a real-space phase-field model, which explicitly includes the cross-coupling between magnetization and mechanical strain. The composition of Fe1-xGax nanodots has significant influence on the critical shear strain that induces the polarity switching of magnetization vortex. The critical shear strain in the Fe71Ga29 nanodot is one order of magnitude smaller than that of the Fe19Ga81 nanodot, which makes the polarity switching much easier under a mechanical shear strain. In addition, we elucidate that both the magnetostrictive coefficient and exchange stiffness that changes with compositions play the decisive role in the critical behavior; the higher magnetostrictive coefficient (or lower exchange stiffness) decreases critical shear strain.

Li, Gui-ping; Wang, Jie; Shimada, Takahiro; Fang, Hui; Kitamura, Takayuki

2014-05-01

282

CS Network Testbed Switches: Cisco, Asant, Packeteer, ...  

E-print Network

/5/06 Tornado C2 C2C2 36-port Fast Ethernet Switch 3Com SuperStack II 3900 N1 Typhoon C1 C1 C1 36-port Fast Ethernet Switch 3Com SuperStack II 3900 C1a C1aC1a 36-port Fast Ethernet Switch 3Com SuperStack II 3900 12-port Gigabit Ethernet Switch 3Com SuperStack II 9300 S2 24-port Fast Ethernet Switch Comp. Sci

Lewis, Robert Michael

283

Switch-phase distributions and stochastic resonance  

NASA Astrophysics Data System (ADS)

The de-synchronization mechanism that occurs for noise intensities above stochastic resonance is analyzed in terms of switch-time and switch-phase distributions. In particular, we observed that (i) the switch-time distributions exhibit thicker peak structures with maxima at the multiples (both odd and even) of the half forcing period; (ii) the switch-phase distributions are doubly peaked, being dominated by the in-phase and ? out-of-phase events. The appearance of these properties of the switch statistics is discussed on the grounds of numerical simulations.

Marchesoni, F.; Apostolico, F.; Santucci, S.

1998-11-01

284

Secure videoconferencing equipment switching system and method  

DOEpatents

A switching system and method are provided to facilitate use of videoconference facilities over a plurality of security levels. The system includes a switch coupled to a plurality of codecs and communication networks. Audio/Visual peripheral components are connected to the switch. The switch couples control and data signals between the Audio/Visual peripheral components and one but nor both of the plurality of codecs. The switch additionally couples communication networks of the appropriate security level to each of the codecs. In this manner, a videoconferencing facility is provided for use on both secure and non-secure networks.

Hansen, Michael E. (Livermore, CA)

2009-01-13

285

Electrical switching in cadmium boracite single crystals  

NASA Technical Reports Server (NTRS)

Cadmium boracite single crystals at high temperatures ( 300 C) were found to exhibit a reversible electric field-induced transition between a highly insulative and a conductive state. The switching threshold is smaller than a few volts for an electrode spacing of a few tenth of a millimeter corresponding to an electric field of 100 to 1000 V/cm. This is much smaller than the dielectric break-down field for an insulator such as boracite. The insulative state reappears after voltage removal. A pulse technique revealed two different types of switching. Unstable switching occurs when the pulse voltage slightly exceeds the switching threshold and is characterized by a pre-switching delay and also a residual current after voltage pulse removal. A stable type of switching occurs when the voltage becomes sufficiently high. Possible device applications of this switching phenomenon are discussed.

Takahashi, T.; Yamada, O.

1981-01-01

286

High power ferrite microwave switch  

NASA Technical Reports Server (NTRS)

A high power ferrite microwave switch was developed along with associated electronic driver circuits for operation in a spaceborne high power microwave transmitter in geostationary orbit. Three units were built and tested in a space environment to demonstrate conformance to the required performance characteristics. Each unit consisted of an input magic-tee hybrid, two non-reciprocal latching ferrite phase shifters, an out short-slot 3 db quadrature coupler, a dual driver electronic circuit, and input logic interface circuitry. The basic mode of operation of the high power ferrite microwave switch is identical to that of a four-port, differential phase shift, switchable circulator. By appropriately designing the phase shifters and electronic driver circuits to operate in the flux-transfer magnetization mode, power and temperature insensitive operation was achieved. A list of the realized characteristics of the developed units is given.

Bardash, I.; Roschak, N. K.

1975-01-01

287

Synthetic ferrimagnets with thermomagnetic switching  

NASA Astrophysics Data System (ADS)

Interlayer exchange coupling in strong/weak/strong ferromagnetic multilayers is investigated as a function of external magnetic field and temperature, with the focus on the magnetization switching near the Curie transition in the spacer composed of a diluted ferromagnet of concentration paramagnetic in the bulk. The effect of an externally applied reversing magnetic field on the width of the thermomagnetic transition is studied experimentally and explained theoretically as a result of the interplay between the proximity-induced exchange and the Zeeman effects in the system. Of high potential for applications should be the ability to switch one of the ferromagnetic outer layers using magnetic field, temperature, or a combination of the two.

Kravets, A. F.; Dzhezherya, Yu. I.; Tovstolytkin, A. I.; Kozak, I. M.; Gryshchuk, A.; Savina, Yu. O.; Pashchenko, V. A.; Gnatchenko, S. L.; Koop, B.; Korenivski, V.

2014-09-01

288

Video coding with optimal inter\\/intra-mode switching for packet loss resilience  

Microsoft Academic Search

Resilience to packet loss is a critical requirement in predictive video coding for transmission over packet-switched networks, since the prediction loop propagates errors and causes substantial degradation in video quality. This work proposes an algorithm to optimally estimate the overall distortion of decoder frame reconstruction due to quantization, error propagation, and error concealment. The method recursively computes the total decoder

Rui Zhang; Shankar L. Regunathan; Kenneth Rose

2000-01-01

289

Study of the resonance phenomenon in switching mode power supply (SMPS)  

Microsoft Academic Search

Multi resonance is highly possible to appear inside conductive and radiated frequency range. This paper presents simplified equivalent circuit model used to study the resonance phenomenon in switching mode power supply (SMPS). Indeed, the electromagnetic interference (EMI) caused by a resonance is a critical factor, and is a source of the high conducted EMI that physically affects the tested AC\\/DC

M. Kchikach; R. Lee; H. F. Weinner; Y. Zidani; Y. S. Yuan; Z. M. Qian

2004-01-01

290

MEMS-switched reconfigurable antennas  

Microsoft Academic Search

The integration and use of RF MEMS switches in microstrip patch antennas and feed structures were investigated for developing reconfigurable multi-band antennas. The current application focuses on the development of a dual L\\/X-band antenna that would support several satellite or UAV-based communications and radar applications such as SAR, terrain mapping, GMTI, AMTI, etc. A reconfigurable patch module (RPM) was designed

William H. Weedon; William J. Payne; Gabriel M. Rebeiz

2001-01-01

291

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

292

QPSK switching modulator, phase 2  

Microsoft Academic Search

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 and phase distortions. The characteristics include 8.2 GHz center frequency, 650 MHz 3 dB bandwidth, 0 dB nominal gain, emitter coupled

W. Konu; R. Bouchard

1983-01-01

293

Critical Pedagogy for Critical Mathematics Education  

ERIC Educational Resources Information Center

This article provides a brief introduction to critical pedagogy and further discussion on critical mathematics education. Critical mathematics education enables students to read the world with mathematics. Three emerging domains of mathematics education related to critical mathematics education are discussed in this manuscript: ethnomathematics,…

Tutak, Fatma Aslan; Bondy, Elizabeth; Adams, Thomasenia L.

2011-01-01

294

About Critical Care Nursing  

MedlinePLUS

About Critical Care Nursing Definition of Critical Care Nursing Critical care nursing is that specialty within nursing that deals specifically with human responses to life-threatening problems. A critical care nurse ...

295

Tactile Switch (SMD) B3FS1138 Tactile Switch (SMD)  

E-print Network

mechanism that ensures sharp switching operations D 3 actuator heights for design flexibility D Ro Dimensions Unit: mm (inch) J B3FS-1000 B3FS-1002 B3FS-1000P B3FS-1002P PCB Pad (Top View) (One-side PCB t= 1)(1) (2) 0.7 (0.03) J B3FS-1010 B3FS-1012 B3FS-1010P B3FS-1012P PCB Pad (Top View) (One-side PCB t= 1

Berns, Hans-Gerd

296

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. PMID:22960932

Rodenas-Ruano, Alma; Chávez, Andrés E.; Cossio, Maria J.; Castillo, Pablo E.; Zukin, R. Suzanne

2012-01-01

297

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

298

Pulse switching for high energy lasers  

NASA Technical Reports Server (NTRS)

A saturable inductor switch for compressing the width and sharpening the rise time of high voltage pulses from a relatively slow rise time, high voltage generator to an electric discharge gas laser (EDGL) also provides a capability for efficient energy transfer from a high impedance primary source to an intermediate low impedance laser discharge network. The switch is positioned with respect to a capacitive storage device, such as a coaxial cable, so that when a charge build-up in the storage device reaches a predetermined level, saturation of the switch inductor releases or switches energy stored in the capactive storage device to the EDGL. Cascaded saturable inductor switches for providing output pulses having rise times of less than ten nanoseconds and a technique for magnetically biasing the saturable inductor switch are disclosed.

Laudenslager, J. B.; Pacala, T. J. (inventors)

1981-01-01

299

Final Results from the High-Current, High-Action Closing Switch Test Program at Sandia National Laboratories  

SciTech Connect

We tested a variety of high-current closing switches for lifetime and reliability on a dedicated 2 MJ, 500 kA capacitor bank facility at Sandia National Laboratories. Our interest was a switch capable of one shot every few minutes, switching a critically damped, DC-charged 6.2 mF bank at 24 kV, with a peak current of 500 kA. The desired lifetime is 24 thousand shots. Typical of high-energy systems, particularly multi-module systems, the primary parameters of interest related to the switch are: (1) reliability, meaning absence of both pre-fires and no-fires, (2) total switch lifetime or number of shots between maintenance, and (3) cost. Cost was given lower priority at this evaluation stage because there are great uncertainties in estimating higher-quantity prices of these devices, most of which have been supplied before in only small quantities. The categories of switches tested are vacuum discharge, high-pressure discharge, and solid-state. Each group varies in terms of triggering ease, ease of maintenance, and tolerance to faults such as excess current and current reversal. We tested at least two variations of each technology group. The total number of shots on the switch test facility is about 50 thousand. We will present the results from the switch testing. The observed lifetime of different switches varied greatly: the shortest life was one shot; one device was still operating after six thousand shots. On several switches we measured the voltage drop during conduction and calculated energy dissipated in the switch; we will show these data also.

Savage, M.E.

1999-06-23

300

A Broadband Packet Switch for Integrated Transport  

Microsoft Academic Search

This paper gives a broadband (total throughput approaching 1 terabit\\/s) self-routing packet switch design for providing flexible multiple bit-rate broadband services for an end-to-end fiber network. The switch fabric for the slotted broadband packet switch delivers exactly one packet to each output port from one of the input ports which request packet delivery to that output port. The denied requests

J. Hui; E. Arthurs

1987-01-01

301

Vacuum switch-disconnectors : 1. Dielectric behaviour  

Microsoft Academic Search

This study on vacuum switch-disconnectors addresses two major questions: dielectric behaviour of the VI and the reliability in a practical situation. In the experimental study, the ageing of a specially designed vacuum switch-disconnector is studied. Several internal design parameters (shape of the shields, contacts and contact gap) are varied. The ageing of VIpsilas is simulated by no-load switching, by load

H. Schellekens; A. Henon; P. Picot

2008-01-01

302

Electro-optic Q-switch  

NASA Technical Reports Server (NTRS)

An electro-optic Q-switch for generating sequence of laser pulses was disclosed. The Q-switch comprises a quadratic electro-optic material and is connected with an electronic unit generating a radio frequency wave with positive and negative pulses alternatively. The Q-switch is controlled by the radio frequency wave in such a way that laser pulse is generated when the radio frequency wave changes its polarity.

Zou, Yingyin (Inventor); Chen, Qiushui (Inventor); Zhang, Run (Inventor); Jiang, Hua (Inventor)

2006-01-01

303

Magnetic switch coupling to synchronize magnetic modulators  

DOEpatents

Apparatus for synchronizing the output pulses from a pair of magnetic switches. An electrically conductive loop is provided between the pair of switches with the loop having windlings about the core of each of the magnetic switches. The magnetic coupling created by the loop removes voltage and timing variations between the outputs of the two magnetic switches caused by any of a variety of factors. The only remaining variation is a very small fixed timing offset caused by the geometry and length of the loop itself.

Reed, Kim W. (Albuquerque, NM); Kiekel, Paul (Albuquerque, NM)

1999-01-01

304

Multi-megavolt low jitter multistage switch  

DOEpatents

It is one object of the present invention to provide a multistage switch capable of holding off numerous megavolts, until triggered, from a particle beam accelerator of the type used for inertial confinement fusion. The invention provides a multistage switch having low timing jitter and capable of producing multiple spark channels for spreading current over a wider area to reduce electrode damage and increase switch lifetime. The switch has fairly uniform electric fields and a short spark gap for laser triggering and is engineered to prevent insulator breakdowns.

Humphreys, D.R.; Penn, K.J. Jr.

1985-06-19

305

Magnetic switch coupling to synchronize magnetic modulators  

DOEpatents

Apparatus for synchronizing the output pulses from a pair of magnetic switches is disclosed. An electrically conductive loop is provided between the pair of switches with the loop having windings about the core of each of the magnetic switches. The magnetic coupling created by the loop removes voltage and timing variations between the outputs of the two magnetic switches caused by any of a variety of factors. The only remaining variation is a very small fixed timing offset caused by the geometry and length of the loop itself. 13 figs.

Reed, K.W.; Kiekel, P.

1999-04-27

306

14 CFR 25.1145 - Ignition switches.  

Code of Federal Regulations, 2011 CFR

...TRANSPORT CATEGORY AIRPLANES Powerplant Powerplant Controls and Accessories § 25...Ignition switches must control each engine ignition circuit on each engine. ...by a master ignition control. (c) Each...

2011-01-01

307

14 CFR 25.1145 - Ignition switches.  

...TRANSPORT CATEGORY AIRPLANES Powerplant Powerplant Controls and Accessories § 25...Ignition switches must control each engine ignition circuit on each engine. ...by a master ignition control. (c) Each...

2014-01-01

308

14 CFR 25.1145 - Ignition switches.  

Code of Federal Regulations, 2013 CFR

...TRANSPORT CATEGORY AIRPLANES Powerplant Powerplant Controls and Accessories § 25...Ignition switches must control each engine ignition circuit on each engine. ...by a master ignition control. (c) Each...

2013-01-01

309

14 CFR 25.1145 - Ignition switches.  

Code of Federal Regulations, 2012 CFR

...TRANSPORT CATEGORY AIRPLANES Powerplant Powerplant Controls and Accessories § 25...Ignition switches must control each engine ignition circuit on each engine. ...by a master ignition control. (c) Each...

2012-01-01

310

High-index-contrast electromechanical optical switches  

E-print Network

System developers are looking to replace protocol-dependent, bandwidth-limited optical networks with intelligent optically-transparent integrated photonic networks. Several electromechanical optical switches are explored ...

Bryant, Reginald (Reginald Eugene), 1978-

2011-01-01

311

The AMOEBA switch: an optoelectronic switch for multiprocessor networking using dense-WDM  

Microsoft Academic Search

We present a single-chip asynchronous multiprocessor optoelectronic bit-sliced arrayed (AMOEBA) crossbar switch. The AMOEBA switch addresses the challenge to produce a large-scale, nonblocking packet switch through dense integration of photonic devices directly onto silicon VLSI circuits. Optoelectronic-VLSI technology is used to integrate the switch fabric, routing controller, packet buffers, line interface circuits, and optoelectronic conversion devices on a single chip.

Ashok V. Krishnamoorthy; Joseph E. Ford; Fouad E. Kiamilev; Richard G. Rozier; S. Hunsche; Keith W. Goossen; B. Tseng; James A. Walker; J. E. Cunningham; W. Y. Jan; Martin C. Nuss

1999-01-01

312

Switching losses of IGBTs under zero-voltage and zero-current switching  

Microsoft Academic Search

Turn-off switching losses of punch-through (PT) and nonpunch-through (NPT) IGBTs under hard switching (HS) and zero-voltage switching (ZVS) are presented and evaluated at 25°C, 75°C and 125°C. A comparison between PT and NPT devices based on their internal device characteristics is given for HS and ZVS. The low emitter efficiency NPT IGBTs used in this paper have smaller switching losses

Ahmed Elasser; M. J. Schutten; V. Vlatkovic; David A. Torrey; M. H. Kheraluwala

1996-01-01

313

A quadruple-anchored RF-MEMS switch for switched-line phase shifters  

Microsoft Academic Search

In the paper, the design, simulation and fabrication of a quadruple-anchored MEMS switch for switched-line phase shifters are presented. Swept inner bends were developed to lower the actuate voltage and suppress the stress of the deformed switch. Physical dimension of the MEMS switch is limited to 400?m × 400?m. The 3?m-thick polyimide membrane is spun between the bias and coplanar

Faheng Zang; Guifu Ding; Zhijuan Su; Jun Tang; Min Deng

2010-01-01

314

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

315

Multiprocessor switch with selective pairing  

DOEpatents

System, method and computer program product for a multiprocessing system to offer selective pairing of processor cores for increased processing reliability. A selective pairing facility is provided that selectively connects, i.e., pairs, multiple microprocessor or processor cores to provide one highly reliable thread (or thread group). Each paired microprocessor or processor cores that provide one highly reliable thread for high-reliability connect with a system components such as a memory "nest" (or memory hierarchy), an optional system controller, and optional interrupt controller, optional I/O or peripheral devices, etc. The memory nest is attached to a selective pairing facility via a switch or a bus

Gara, Alan; Gschwind, Michael K; Salapura, Valentina

2014-03-11

316

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

317

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

318

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

319

Using Waits, Loops and Switches  

NSDL National Science Digital Library

Students are given a difficult challenge that requires they integrate what they have learned so far in the unit about wait blocks, loops and switches. They incorporate these tools into their programming of the LEGO® MINDSTORMS® NXT robots to perform different tasks depending on input from a sound sensor and two touch sensors. This activity helps students understand how similar logic is implemented for other every day device operations via computer programs. A PowerPoint® presentation, pre/post quizzes and worksheet are provided.

GK-12 Program, Computational Neurobiology Center,

320

Switched reluctance starter/generator  

NASA Astrophysics Data System (ADS)

When operated in generator-mode, the present switched-reluctance motor (SRM) employs neither permanent magnets nor a rotor field winding; in virtue of this, the SRM precludes generating into a shorted winding, and possesses a rotor structure that is inherently simpler and more reliable than those of wound-field machines. An experimental 33-kW SRM generating system is described, and the motor/generator duality of the SRM is demonstrated. This duality exists both in the electromechanical performance of the machine and in its control techniques.

Radun, Arthur; Rulison, James; Sanza, Peter

1992-10-01

321

Fast packet switch architectures for broadband integrated services digital networks  

Microsoft Academic Search

Background information on networking and switching is provided, and the various architectures that have been considered for fast packet switches are described. The focus is solely on switches designed to be implemented electronically. A set of definitions and a brief description of the functionality required of fast packet switches are given. Three basic types of packet switches are identified: the

Fouad A. Tobagi

1990-01-01

322

Optical 2x2 switch matrix with electromechanical micromotors  

Microsoft Academic Search

In the rapidly developing optical telecommunication domain optical switch arrays lend themselves to the complex switching tasks. Therefore a prototype of an all-optical switch matrix with 2 in- and output channels has been developed in LIGA-technique. However, with the presented concept also switch arrays with more channels can be realized. The switch array has been designed for the telecommunication wavelength

Antonio Ruzzu; Dirk Haller; Juergen Mohr; Ulrike Wallrabe

2000-01-01

323

Auxiliary resonant commutated soft-switching inverter with bidirectional active switches and voltage clamping diodes  

Microsoft Academic Search

This paper presents a soft-switching PWM inverter with auxiliary resonant bridge-leg link snubbers on the basis of bidirectional active power switches and voltage clamping diodes. The voltage clamping diodes protect the bidirectional active switches from spike surge voltage caused by the stray energy of auxiliary inductors and parasitic wiring inductances. From a practical point of view, a variety of resonant

Hiroshi Takano; Takuya Domoto; Jun Takahashi; Mutsuo Nakaoka

2001-01-01

324

A Novel Saturable Reactor Reset Circuit for Optimizing Soft Switching of Resonant Reset Dual Switch Forward Converter  

Microsoft Academic Search

Resonant reset soft switching dual switch forward dc-dc topology is suitable for topology standardization in power electronics system integration since which can be used in high voltage, wide range input applications. To further meet the miniaturization requirement for system integration, the soft switching principle of resonant reset soft switching dual switch forward dc-dc topology was discussed, and an optimized circuit

Wei Chen; Zhengyu Lu; Zhaoming Qian; Shaoshi Ye

2007-01-01

325

Gastroprotective effect of desmosdumotin C isolated from Mitrella kentii against ethanol-induced gastric mucosal hemorrhage in rats: possible involvement of glutathione, heat-shock protein-70, sulfhydryl compounds, nitric oxide, and anti-Helicobacter pylori activity  

PubMed Central

Background Mitrella kentii (M. kentii) (Bl.) Miq, is a tree-climbing liana that belongs to the family Annonaceae. The plant is rich with isoquinoline alkaloids, terpenylated dihydrochalcones and benzoic acids and has been reported to possess anti-inflammatory activity. The purpose of this study is to assess the gastroprotective effects of desmosdumotin C (DES), a new isolated bioactive compound from M. kentii, on gastric ulcer models in rats. Methods DES was isolated from the bark of M. kentii. Experimental rats were orally pretreated with 5, 10 and 20 mg/kg of the isolated compound and were subsequently subjected to absolute ethanol-induced acute gastric ulcer. Gross evaluation, mucus content, gastric acidity and histological gastric lesions were assessed in vivo. The effects of DES on the anti-oxidant system, non-protein sulfhydryl (NP-SH) content, nitric oxide (NO)level, cyclooxygenase-2 (COX-2) enzyme activity, bcl-2-associated X (Bax) protein expression and Helicabacter pylori (H pylori) were also investigated. Results DES pre-treatment at the administered doses significantly attenuated ethanol-induced gastric ulcer; this was observed by decreased gastric ulcer area, reduced or absence of edema and leucocytes infiltration compared to the ulcer control group. It was found that DES maintained glutathione (GSH) level, decreased malondialdehyde (MDA) level, increased NP-SH content and NO level and inhibited COX-2 activity. The compound up regulated heat shock protein-70 (HSP-70) and down regulated Bax protein expression in the ulcerated tissue. DES showed interesting anti-H pylori effects. The efficacy of DES was accomplished safely without any signs of toxicity. Conclusions The current study reveals that DES demonstrated gastroprotective effects which could be attributed to its antioxidant effect, activation of HSP-70 protein, intervention with COX-2 inflammatory pathway and potent anti H pylori effect. PMID:23866830

2013-01-01

326

44. EXTERIOR VIEW, GREEN SWITCH TOWER, COS COB, SHOWING BARS ...  

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

44. EXTERIOR VIEW, GREEN SWITCH TOWER, COS COB, SHOWING BARS LINKING SWITCH LEVERS AND PIPES LEADING TO SWITCHES - New York, New Haven & Hartford Railroad, Automatic Signalization System, Long Island Sound shoreline between Stamford & New Haven, Stamford, Fairfield County, CT

327

IEEE Communications Magazine December 200078 Saturn: A Terabit Packet Switch  

E-print Network

IEEE Communications Magazine · December 200078 Saturn: A Terabit Packet Switch Using Dual Round second packet switch and call it the Saturn switch. It uses a simple dual round-robin arbitration scheme

Chao, Jonathan

328

30 CFR 75.519 - Main power circuits; disconnecting switches.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 false Main power circuits; disconnecting switches. 75...Equipment-General § 75.519 Main power circuits; disconnecting switches. [Statutory Provision] In all main power circuits, disconnecting switches...

2010-07-01

329

49 CFR 236.60 - Switch shunting circuit; use restricted.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Switch shunting circuit; use restricted. 236.60 Section 236...Rules and Instructions: All Systems Track Circuits § 236.60 Switch shunting circuit; use restricted. Switch shunting...

2012-10-01

330

30 CFR 75.519 - Main power circuits; disconnecting switches.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Main power circuits; disconnecting switches. 75...Equipment-General § 75.519 Main power circuits; disconnecting switches. [Statutory Provision] In all main power circuits, disconnecting switches...

2013-07-01

331

30 CFR 75.519 - Main power circuits; disconnecting switches.  

Code of Federal Regulations, 2012 CFR

...2012-07-01 false Main power circuits; disconnecting switches. 75...Equipment-General § 75.519 Main power circuits; disconnecting switches. [Statutory Provision] In all main power circuits, disconnecting switches...

2012-07-01

332

49 CFR 236.60 - Switch shunting circuit; use restricted.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Switch shunting circuit; use restricted. 236.60 Section 236...Rules and Instructions: All Systems Track Circuits § 236.60 Switch shunting circuit; use restricted. Switch shunting...

2010-10-01

333

49 CFR 236.60 - Switch shunting circuit; use restricted.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Switch shunting circuit; use restricted. 236.60 Section 236...Rules and Instructions: All Systems Track Circuits § 236.60 Switch shunting circuit; use restricted. Switch shunting...

2013-10-01

334

49 CFR 236.60 - Switch shunting circuit; use restricted.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Switch shunting circuit; use restricted. 236.60 Section 236...Rules and Instructions: All Systems Track Circuits § 236.60 Switch shunting circuit; use restricted. Switch shunting...

2011-10-01

335

30 CFR 75.519 - Main power circuits; disconnecting switches.  

...2014-07-01 false Main power circuits; disconnecting switches. 75...Equipment-General § 75.519 Main power circuits; disconnecting switches. [Statutory Provision] In all main power circuits, disconnecting switches...

2014-07-01

336

30 CFR 75.519 - Main power circuits; disconnecting switches.  

Code of Federal Regulations, 2011 CFR

...2011-07-01 false Main power circuits; disconnecting switches. 75...Equipment-General § 75.519 Main power circuits; disconnecting switches. [Statutory Provision] In all main power circuits, disconnecting switches...

2011-07-01

337

A hybrid optical packet and wavelength selective switching platform for  

E-print Network

behavior of the SOA switch, we are able to achieve fast switching transitions, high extinction ratios vortex optical packet switched interconnection network," J. Lightwave Technol. 26(13), 1777­1789 (2008

Bergman, Keren

338

Ames Lab 101: Ultrafast Magnetic Switching  

ScienceCinema

Ames Laboratory physicists have found a new way to switch magnetism that is at least 1000 times faster than currently used in magnetic memory technologies. Magnetic switching is used to encode information in hard drives, magnetic random access memory and other computing devices. The discovery potentially opens the door to terahertz and faster memory speeds.

Jigang Wang

2013-06-05

339

Ames Lab 101: Ultrafast Magnetic Switching  

SciTech Connect

Ames Laboratory physicists have found a new way to switch magnetism that is at least 1000 times faster than currently used in magnetic memory technologies. Magnetic switching is used to encode information in hard drives, magnetic random access memory and other computing devices. The discovery potentially opens the door to terahertz and faster memory speeds.

Jigang Wang

2013-04-08

340

Decoupling capacitor effects on switching noise  

Microsoft Academic Search

This paper sumnarizes the experimental results obtained for the efficiency of the decoupling capacitor schm used in the M(3M package of the IBM ES\\/9000 system in reducing the pr supply differential switching noise. It was shown that this efficiency is a function of the switching elmt and varies fran 50 to 70%. Also, the test vehicle, test system and probe

R. Downing; P. Gebler; G. Katopis

1992-01-01

341

Micromechanical electrostatic K-band switches  

Microsoft Academic Search

Two novel designs of micromechanical capacitive switches using serpentine and cantilever springs for low actuation voltage applications are reported. Both designs also incorporate an electrode situated above the switching structure in order to provide system stability. DC measurements indicate pull-in voltages of 14 and 16 V, with RF isolation of better than -30 dB up to 40 GHz

S. Pacheco; C. T. Nguyen; L. P. B. Katehi

1998-01-01

342

Stochastic Switching Circuit Synthesis Daniel Wilhelm  

E-print Network

introduce a new duality property for series-parallel stochastic switching circuits. Finally, we construct on the so-called two-terminal series-parallel circuits. A two-terminal circuit is an undirected graph. A two-terminal circuit C is series-parallel (sp) iff C is: (1) a single switch, or (2) a series

Bruck, Jehoshua (Shuki)

343

Morphological Priming Survives a Language Switch  

ERIC Educational Resources Information Center

In a long-lag morphological priming experiment, Dutch (L1)-English (L2) bilinguals were asked to name pictures and read aloud words. A design using non-switch blocks, consisting solely of Dutch stimuli, and switch-blocks, consisting of Dutch primes and targets with intervening English trials, was administered. Target picture naming was facilitated…

Verdonschot, Rinus G.; Middelburg, Renee; Lensink, Saskia E.; Schiller, Niels O.

2012-01-01

344

Lifetime characterization of capacitive RF MEMS switches  

Microsoft Academic Search

The first experimental characterization of dielectric charging within capacitive RF MEMS switches has been demonstrated. Standard devices have been inserted into a time domain setup and their lifetimes have been characterized as a function of actuation voltage. Switch lifetimes were measured using a dual-pulse waveform with 30 to 65 V of actuation voltage. Resulting lifetimes were between 104 and 108

C. Goldsmith; J. Ehmke; A. Malczewski; B. Pillans; S. Eshelman; Z. Yao; J. Brank; M. Eberly

2001-01-01

345

Realization of Nonlinearly Separable Switching Functions  

Microsoft Academic Search

In this paper CEP functions are applied to realize nonlinearly separable switching functions. It is proved that the introduction of these functions may realize all the 22nswitching functions of n binary variables. A model of a nonlinear threshold component is proposed to realize the switching functions.

M. Ali; R. Ahmed

1971-01-01

346

Programmable Ethernet Switches and Their Applications  

E-print Network

Programmable Ethernet Switches and Their Applications A DISSERTATION PRESENTED BY SRIKANT SHARMA School #12;Abstract of the Dissertation Programmable Ethernet Switches and Their Applications by Srikant effectiveness, scalability, and economies of scale make Ethernet a popular choice for (a) local area networks

Chiueh, Tzi-cker

347

A configuration independent substation switching scheme  

Microsoft Academic Search

Substations differ greatly in their configurations, sizes and importance. Substation switching schemes are, therefore, designed and developed separately for each substation. This paper describes a digital computer based substation switching scheme that can be employed in different configurations of substations. The scheme is applicable to substations of all practical configurations. It also considers factors such as, generation and load balance,

M. S. Sachdev; P. Dhakal; T. S. Sidhu

1996-01-01

348

High-frequency switching in Candida albicans.  

PubMed Central

Most strains of Candida albicans are capable of switching frequently and reversibly between a number of phenotypes distinguishable by colony morphology. A number of different switching systems have been defined according to the limited set of phenotypes in each switching repertoire, and each strain appears to possess a single system. Switching can affect many aspects of cellular physiology and morphology and appears to be a second level of phenotypic variability superimposed upon the bud-hypha transition. The most dramatic switching system so far identified is the "white-opaque transition." This system dramatizes the extraordinary effects switching can have on the budding cell phenotype, including the synthesis of opaque-specific antigens, the expression of white-specific and opaque-specific genes, and the genesis of unique cell wall structures. Switching has been demonstrated to occur at sites of infection and between episodes of recurrent vaginitis, and it may function to generate variability in commensal and infecting populations for adaptive reasons. Although the molecular mechanisms involved in the switch event are not understood, recent approaches to its elucidation are discussed and an epigenetic mechanism is proposed. Images PMID:1576587

Soll, D R

1992-01-01

349

Gas mixtures for spark gap closing switches  

DOEpatents

Gas mixtures for use in spark gap closing switches comprised of fluorocarbons and low molecular weight, inert buffer gases. To this can be added a third gas having a low ionization potential relative to the buffer gas. The gas mixtures presented possess properties that optimized the efficiency spark gap closing switches. 6 figs.

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

1987-02-20

350

Resonant switched capacitor converter with high efficiency  

Microsoft Academic Search

Conventional switched capacitor converters have an inherent drawback that their efficiency is much decreased as the output current is increased. This inherent drawback is due to a periodical forced charging and discharging operation in the internal switched capacitors accompanied by a large capacitor current, so that their efficiency can not be increased by decreasing its internal resistance. As a result,

M. Shoyama; T. Naka; T. Ninomiya

2004-01-01

351

Internal Backpressure for Terabit Switch Fabrics  

Microsoft Academic Search

This paper proposes and analyzes the efficiency of novel backpressure schemes for Terabit switch fabrics. The proposed schemes aim at buffer optimization under uniform traffic distribution with Bernoulli packet arrival process. Results show that a reduction of the needed maximum buffer capacity with up to 47% can be achieved with switch-internal backpressure mechanisms at the expense of a small control

Anna V. Manolova; Sarah Ruepp; Andreas Rytlig; Michael Berger; Henrik Wessing; Lars Dittmann

2012-01-01

352

Switched Multimegabit Data Service by Michael Iverson  

E-print Network

Switched Multimegabit Data Service by Michael Iverson Abstract: Switched Multimegabit Data Service Addressings Other SMDS Featuress r Performance Specifications Transmission Facilitiess Access Classess Quality of Service Objectivess r q SMDS Specifications: SIP Interface SIP Layer 3s SIP Layer 2s SIP Layer 1s r SIP

Jain, Raj

353

ERICA Switch Algorithm: A Complete Description  

Microsoft Academic Search

: The ERICA switch algorithm has been discussed extensively in TM group in the past. However, over the last two years, the algorithm has been substantially modified. This contribution describes the current version of ERICA switch algorithm in complete detail. The algorithm achieves both efficiency and fairness, and exhibits a fast transient response. The development of the algorithm is traced,

Raj Jain; Shiv Kalyanaraman; Rohit Goyal; Sonia Fahmy; Ram Viswanathan

1996-01-01

354

Preventing Simultaneous Conduction In Switching Transistors  

NASA Technical Reports Server (NTRS)

High voltage spikes and electromagnetic interference suppressed. Power-supply circuit including two switching transistors easily modified to prevent simultaneous conduction by both transistors during switching intervals. Diode connected between collector of each transistor and driving circuit for opposite transistor suppresses driving signal to transistor being turned on until transistor being turned off ceases to carry current.

Mclyman, William T.

1990-01-01

355

Fast and Scalable Layer Four Switching  

Microsoft Academic Search

In Layer Four switching, the route and resources allocated to a packet are determined by the destination address as well as other header fields of the packet such as source address, TCP and UDP port numbers. Layer Four switching unifies firewall processing, RSVP style resource reservation filters, QoS Routing, and normal unicast and multicast forwarding into a single framework. In

Venkatachary Srinivasan; George Varghese; Subhash Suri; Marcel Waldvogel

1998-01-01

356

Piezoelectric Diffraction-Based Optical Switches  

NASA Technical Reports Server (NTRS)

Piezoelectric diffraction-based optoelectronic devices have been invented to satisfy requirements for switching signals quickly among alternative optical paths in optical communication networks. These devices are capable of operating with switching times as short as microseconds or even nanoseconds in some cases.

Spremo, Stevan; Fuhr, Peter; Schipper, John

2003-01-01

357

Critical parameters of metals  

Microsoft Academic Search

This paper establishes the similarity relations between the critical parameters and atomic characteristics of a series of metals retaining the metallic state at the critical point. The critical parameters of these metals are interrelated. The critical parameters of some simple and transition metals are estimated on the basis of experimental data on the critical parameters of cesium.

Likalter

1985-01-01

358

First order switched-capacitor building blocks for analog circuits  

E-print Network

viii A. Nature of the Problem B. Background C. Switched Capacitor Techniques 1. Switched ckpacitor equivalent resistor 2. Switched capacitor in MOS technology a. MOS switch b. MOS capacitor c. MOS op amp d. Clock feed through effect D. Summary.... . 133 LIST OF FIGURES Figure Page 1 Switched capacitor equivalent resistor. (a. ) Continuous resistor, (b. ) Parallel SC realization of (a. ), and (c. ) Clock signals used in (b. ). 2 The MOS switch and its parasitic capacitance. 10 3 The two...

Nguyen, Liem Thanh

1983-01-01

359

Analytical and experimental investigation of the frequency ratio and switching law for piezoelectric switching techniques  

NASA Astrophysics Data System (ADS)

Piezoelectric shunt damping with mechanical structures has been an active research topic for several years. Standard passive techniques suffer from a very limited and frequency-dependent damping performance. Recently, semi-active switching techniques—namely SSDI (synchronized switch damping on inductor) and SSDV (synchronized switch damping on voltage source) techniques—have been proposed, which are capable of adapting to variations of the excitation frequency without reduction in performance. Crucial for the damping performance is the tuning of the shunt parameters and the precise switching sequence. In this paper, an analytical analysis of the switching technique is presented, which includes the influence of all shunt parameters and the switching times. New results concerning the optimal tuning of the inductance and the switching sequence are obtained, and it is shown that the enhanced SSDV technique can be equated with the SSDI technique, albeit with an increased effective piezoelectric force factor. Measurements are conducted to validate the theoretical results.

Neubauer, M.; Wallaschek, J.

2008-06-01

360

Environmental Qualification of an Actuator Torque Switch  

SciTech Connect

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 to allow normal torque switch behaviour to be observed. The present paper describes the qualification testing performed. The modified torque switch was aged to a 30-year service life at the normal service conditions for both inside and outside containment. Aging included radiation, thermal and cycle aging. A seismic test and then a combined Loss of Coolant Accident (LOCA) and Main Steam Line Break (MSLB) steam accident simulation were followed. After each stage of aging, functional tests were done to confirm normal insulation resistance, normal contact resistance and normal operation. (authors)

Chan, A.M.; Barreca, S.L. [Kinectrics, Inc., 800 Kipling Avenue Toronto, Ontario M8Z 6C4 (Canada); Kostela, T. [Ontario Power Generation, Inc., 700 University Avenue Toronto, Ontario, M5G 1X6 (Canada)

2006-07-01

361

Photonic switching devices based on semiconductor nanostructures  

E-print Network

Squeezing and guiding light into semiconductor nanostructures delivers revolutionary concepts of photonic devices, which may offer a practical pathway towards power-efficient optical networks. In this review, we consider photonic switches using semiconductor quantum dots (QDs) and photonic cavities. By intuitively introducing in a field enhancement factor, the optical nonlinearity of nano-photonic switches can be understood and this has shown their unique features to dramatically improve the power-density/speed limitation that has lain in conventional photonic switches for decades. In addition, the power consumption has been reduced due to the atom-like characterization of QDs as well as the nano-size footprint of photonic cavities. Based on this theoretical perspective, the current progress of QD/cavity switches is reviewed in terms of various optical nonlinearities which have been employed to demonstrate photonic switching at the nanoscale. Emerging functionalities enabled by cavity nonlinear effects such a...

Jin, Chao-Yuan

2013-01-01

362

Push-pull switching power amplifier  

NASA Technical Reports Server (NTRS)

A true push-pull switching power amplifier is disclosed utilizing two dc-to-dc converters. Each converter is comprised of two inductances, one inductance in series with a DC source and the other inductor in series with the output load, and an electrical energy transferring device with storage capability, namely storage capacitance, with suitable switching means between the inductances to obtain DC level conversion, where the switching means allows bidirectional current (and power) flow, and the switching means of one dc-to-dc converter is driven by the complement of a square-wave switching signal for the other dc-to-dc converter for true push-pull operation. For reduction of current ripple, the inductances in each of the two converters may be coupled, and with proper design of the coupling, the ripple can be reduced to zero at either the input or the output, but preferably the output.

Cuk, Slobodan M. (Inventor)

1980-01-01

363

Nanophotonic silicon electro-optic switch  

NASA Astrophysics Data System (ADS)

The combination of silicon and nanotechnology offers the possibility to design ultrafast silicon electro-optic switches with speeds of the order of 100 GHz. The design procedure for an ultrafast silicon electro-optic switch with the addition of photonic crystals is presented. The material medium selected for propagation of the optical signal through the switch is silicon nanocrystals in silica. A patterned slot waveguide with one-dimensional photonic crystals is proposed as the preferred slow light waveguide to be used in the design of the electro-optic switch. The ultrafast quadratic electro-optic effect or Kerr effect is the physical effect utilized, and its analysis for slot waveguides is discussed. The optical structure analysis of the electro-optic switch using a ring resonator is presented and it is shown theoretically that the use of a slow light waveguide in the ring resonator can reduce the required externally applied electric field or the radius of the ring resonator.

Simili, Deepak V.; Cada, Michael

2013-10-01

364

Molecular modeling and molecular dynamics simulation of the polarization switching phenomena in the ferroelectric polymers PVDF at the nanoscale  

NASA Astrophysics Data System (ADS)

The molecular modeling and molecular dynamics of polarization switching for the ferroelectric films model of polyvinylidene fluoride (PVDF) are investigated at the nanoscale. We consider a molecular model of PVDF film, consisting of two and four a chains [-CH2-CF2-]n limited by n=6 elementary units. The first-principle approach is applied to the switching and kinetics of these models. Two types of behavior were established for PVDF chains: simultaneous and sequential rotation in high and low electric fields. Kinetics of sequential polarization switching shows a homogeneous critical behavior in the low electric field with a critical point at Landau-Ginzburg-Devonshire (LGD) coercive field E=EC. This type of kinetics demonstrates a kink-like behavior for polarization solitary wave propagation. The simultaneous type of kinetics demonstrates the total domain-like polarization switching, corresponding to exponential behavior of switching time in high electric field as for bulk samples. Corresponding LGD intrinsic coercive field for a two-chain and four-chains model is EC~2.0 GV/m with revealing size effect. Obtained results show common quantum nature of PVDF chains switching phenomena-the quantum interaction of the PVDF molecular orbitals under applied electric field at the nanoscale level. The results obtained are compared with experimental data.

Bystrov, V. S.

2014-01-01

365

Critical Materials Institute  

ScienceCinema

Ames Laboratory Director Alex King talks about the goals of the Critical Materials Institute in diversifying the supply of critical materials, developing substitute materials, developing tools and techniques for recycling critical materials, and forecasting materials needs to avoid future shortages.

Alex King

2013-06-05

366

Comprehensive physical model of dynamic resistive switching in an oxide memristor.  

PubMed

Memristors have been proposed for a number of applications from nonvolatile memory to neuromorphic systems. Unlike conventional devices based solely on electron transport, memristors operate on the principle of resistive switching (RS) based on redistribution of ions. To date, a number of experimental and modeling studies have been reported to probe the RS mechanism; however, a complete physical picture that can quantitatively describe the dynamic RS behavior is still missing. Here, we present a quantitative and accurate dynamic switching model that not only fully accounts for the rich RS behaviors in memristors in a unified framework but also provides critical insight for continued device design, optimization, and applications. The proposed model reveals the roles of electric field, temperature, oxygen vacancy concentration gradient, and different material and device parameters on RS and allows accurate predictions of diverse set/reset, analog switching, and complementary RS behaviors using only material-dependent device parameters. PMID:24571386

Kim, Sungho; Choi, ShinHyun; Lu, Wei

2014-03-25

367

Deterministic conversion between memory and threshold resistive switching via tuning the strong electron correlation  

PubMed Central

Intensive investigations have been launched worldwide on the resistive switching (RS) phenomena in transition metal oxides due to both fascinating science and potential applications in next generation nonvolatile resistive random access memory (RRAM) devices. It is noteworthy that most of these oxides are strongly correlated electron systems, and their electronic properties are critically affected by the electron-electron interactions. Here, using NiO as an example, we show that rationally adjusting the stoichiometry and the associated defect characteristics enables controlled room temperature conversions between two distinct RS modes, i.e., nonvolatile memory switching and volatile threshold switching, within a single device. Moreover, from first-principles calculations and x-ray absorption spectroscopy studies, we found that the strong electron correlations and the exchange interactions between Ni and O orbitals play deterministic roles in the RS operations. PMID:22679556

Peng, Hai Yang; Li, Yong Feng; Lin, Wei Nan; Wang, Yu Zhan; Gao, Xing Yu; Wu, Tom

2012-01-01

368

New Insights into VEGF-A Alternative Splicing: Key Regulatory Switching in the Pathological Process.  

PubMed

Vascular endothelial growth factor (VEGF-A) is one of the most important regulatory factors in pathological and physiological angiogenesis. Alternative splicing is a complicated molecular process in VEGF-A gene expression which adds complexity to VEGF-A biology. Among all VEGF-A exons, alternative splicing of exon 8 is the key determinant of isoform switching from pro-angio-genic VEGF-xxx to anti-angiogenic VEGF-xxxb. This is known as a key molecular switching in many pathological situations. In fact, the balance between VEGF-xxx and VEGF-xxxb isoforms is a critical controlling switch in both conditions of health and disease. Here, the properties of VEGF-xxx and VEGF-xxxb isoforms were discussed and their regulatory mechanism and their roles in certain pathological processes were evaluated. In summary, it was suggested that C-terminal VEGF-A alternative splicing can provide a new treatment opportunity in angiogenic diseases. PMID:25414781

Dehghanian, Fariba; Hojati, Zohreh; Kay, Maryam

2014-10-01

369

Spin orbital torque driven magnetization switching in magnetic tunnel junction with inter-layer exchange coupling  

NASA Astrophysics Data System (ADS)

The switching processes of elliptically shaped magnetic tunnel junction bits with the structure Ta/CoFeB/MgO/CoFeB have been studied by the micromagnetic models. By comparing the tunneling magneto-resistance minor and major loops calculated by our model with related experimental results, we found that the inter-layer exchange coupling between the two CoFeB layers and a reduced saturation magnetization Ms distribution at the edge of the elliptical bit should be included. The chosen strength of the inter-layer exchange coupling also matches well with experimental observations. The current induced magnetization switching is generated from the spin Hall effect in the Ta layer. The critical switching currents calculated by our model are coincident with experiment. This shows the reliability of our micromagnetic model with the spin orbital torque term.

Xu, Lei; Ma, Zhongshui; Wei, Dan

2015-01-01

370

Plasma opening switch conduction scaling  

NASA Astrophysics Data System (ADS)

Plasma opening switch (POS) experiments performed on the Hawk generator [Commisso et al., Phys. Fluids B 4, 2368 (1992)] (750 kA, 1.2 ?s) determine the dependence of the conduction current and conduction time on plasma density, electrode dimensions, and current rise rate. The experiments indicate that for a range of parameters, conduction is controlled by magnetohydrodynamic (MHD) distortion of the plasma, resulting in a low density region where opening can occur, possibly by erosion. The MHD distortion corresponds to an axial translation of the plasma center-of-mass by half the initial plasma length, leading to a simple scaling relation between the conduction current and time, and the injected plasma density and POS electrode dimensions that is applicable to a large number of POS experiments. For smaller currents and conduction times, the Hawk data suggest a non-MHD conduction limit that may correspond to electromagnetohydrodynamic (EMH) field penetration through the POS plasma.

Weber, B. V.; Commisso, R. J.; Goodrich, P. J.; Grossmann, J. M.; Hinshelwood, D. D.; Ottinger, P. F.; Swanekamp, S. B.

1995-10-01

371

Switch: An Electronic Art Journal  

NSDL National Science Digital Library

Volume 3, number 1 of the electronic arts journal of the CADRE (Computers in Art, Design, Research & Education) Institute of the School of Art and Design at San Jose State University is now online, and focuses on "art of the world wide web." Articles include "Useless Web Pages: Conceptual Folk Art or Post Modern Web Dada?" and "The Construction of Art on the Internet and the Mediating Influence of the Search Engine." The essays are peppered with hypertext links, which may lead the reader to appendices or other websites or even personal homepages with relevance to the topic at hand. Previous issues of Switch have covered such topics as interactive narrative, virtual reality, and artificial life; as befits an arts journal, each issue has its own look and feel (though this can make navigation challenging). The next issue, due in July, will cover web-specific art.

372

Double tunneling in polarization switching  

NASA Astrophysics Data System (ADS)

We present a theory of quantum switching of polarization in hydrogen-bonded order-disorder ferroelectrics, and examine the macroscopic quantum-tunneling rate of the polarization reversal for nano-samples induced by microscopic tunneling of protons between the two wells in potentials of hydrogen bonds. We compute the rate of the electric polarization tunneling through the barrier between two minima of the free energy density of a system. By using the instanton approach, we calculate a barrier factor and a prefactor multiplying the exponential of the action integral for the tunneling splitting at zero applied electric field. We compute the tunneling rate of domain walls. We obtain the double tunneling effect, i.e., the polarization tunneling related to the proton tunneling between the two minima in potentials of hydrogen bonds.

Gordon, A.

2008-08-01

373

QPSK switching modulator, phase 2  

NASA Astrophysics Data System (ADS)

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 and phase distortions. The characteristics include 8.2 GHz center frequency, 650 MHz 3 dB bandwidth, 0 dB nominal gain, emitter coupled logics, input logic levels, 200 MHz max input data rate and 2 nsec max rise and fall time. It is shown that it is feasible to implement a QPSK modulator with a dual gate FET, but practical limits are a phase error of 2.5 deg (against 2 in specification) and an amplitude imbalance of 0.5 dB over the temperature range. Measurements on single gate FET's indicate that the dual gate FET's could contribute 1.3% phase error due to the device phase change with temperature.

Konu, W.; Bouchard, R.

1983-03-01

374

Resonant Switching Using Spin Valves  

NASA Astrophysics Data System (ADS)

Using micromagnetics we demonstrate that the r.f. field produced by a spin valve can be used to reverse the magnetization in a magnetic nanoparticle. The r.f. field is generated using a current that specifically excites a uniform spin wave in the spin valve. This current is swept such that the chirped-frequency generated by the valve matches the angular dependent resonant frequency of the anisotropy-dominated magnetic nanoparticle, as a result of which the magnetization reversal occurs. The switching is fast, requires currents similar to those used in recent experiments with spin valves, and is stable with respect to small perturbations. This phenomenon can potentially be employed in magnetic information storage devices or recently discussed magnetic computing schemes.

Rivkin, K.; Ketterson, J. B.; Saslow, W.

2007-06-01

375

Unity power factor switching regulator  

NASA Technical Reports Server (NTRS)

A single or multiphase boost chopper regulator operating with unity power factor, for use such as to charge a battery is comprised of a power section for converting single or multiphase line energy into recharge energy including a rectifier (10), one inductor (L.sub.1) and one chopper (Q.sub.1) for each chopper phase for presenting a load (battery) with a current output, and duty cycle control means (16) for each chopper to control the average inductor current over each period of the chopper, and a sensing and control section including means (20) for sensing at least one load parameter, means (22) for producing a current command signal as a function of said parameter, means (26) for producing a feedback signal as a function of said current command signal and the average rectifier voltage output over each period of the chopper, means (28) for sensing current through said inductor, means (18) for comparing said feedback signal with said sensed current to produce, in response to a difference, a control signal applied to the duty cycle control means, whereby the average inductor current is proportionate to the average rectifier voltage output over each period of the chopper, and instantaneous line current is thereby maintained proportionate to the instantaneous line voltage, thus achieving a unity power factor. The boost chopper is comprised of a plurality of converters connected in parallel and operated in staggered phase. For optimal harmonic suppression, the duty cycles of the switching converters are evenly spaced, and by negative coupling between pairs 180.degree. out-of-phase, peak currents through the switches can be reduced while reducing the inductor size and mass.

Rippel, Wally E. (Inventor)

1983-01-01

376

Thermodynamic basis for the optimization of binding-induced biomolecular switches and structure-switching biosensors  

PubMed Central

Binding-induced biomolecular switches are used throughout nature and, increasingly, throughout biotechnology for the detection of chemical moieties and the subsequent transduction of this detection into useful outputs. Here we show that the thermodynamics of these switches are quantitatively described by a simple 3-state population-shift model, in which the equilibrium between a nonbinding, nonsignaling state and the binding-competent, signaling state is shifted toward the latter upon target binding. Because of this, their performance is determined by the tradeoff inherent to their switching thermodynamics; while a switching equilibrium constant favoring the nonbinding, nonsignaling, conformation ensures a larger signal change (more molecules are poised to respond), it also reduces affinity (binding must overcome a more unfavorable conformational free energy). We then derive and employ the relationship between switching thermodynamics and switch signaling to rationally tune the dynamic range and detection limit of a representative structure-switching biosensor, a molecular beacon, over 4 orders of magnitude. These findings demonstrate that the performance of biomolecular switches can be rationally tuned via mutations that alter their switching thermodynamics and suggest a mechanism by which the performance of naturally occurring switches may have evolved. PMID:19666496

Vallée-Bélisle, Alexis; Ricci, Francesco; Plaxco, Kevin W.

2009-01-01

377

Comparison of switching control algorithms effective in restricting the switching in the neighborhood of the origin  

NASA Astrophysics Data System (ADS)

The active interaction control (AIC) system consisting of a primary structure, an auxiliary structure and an interaction element was proposed to protect the primary structure against earthquakes and winds. The objective of the AIC system in reducing the responses of the primary structure is fulfilled by activating or deactivating the switching between the engagement and the disengagement of the primary and auxiliary structures through the interaction element. The status of the interaction element is controlled by switching control algorithms. The previously developed switching control algorithms require an excessive amount of switching, which is inefficient. In this paper, the excessive amount of switching is restricted by imposing an appropriately designed switching boundary region, where switching is prohibited, on pre-designed engagement-disengagement conditions. Two different approaches are used in designing the newly proposed AID-off and AID-off2 algorithms. The AID-off2 algorithm is designed to affect deactivated switching regions explicitly, unlike the AID-off algorithm, which follows the same procedure of designing the engagement-disengagement conditions of the previously developed algorithms, by using the current status of the AIC system. Both algorithms are shown to be effective in reducing the amount of switching times triggered from the previously developed AID algorithm under an appropriately selected control sampling period for different earthquakes, but the AID-off2 algorithm outperforms the AID-off algorithm in reducing the number of switching times.

Joung, JinWook; Smyth, Andrew W.; Chung, Lan

2010-06-01

378

PZT Actuated Seesaw SPDT RF MEMS Switch  

NASA Astrophysics Data System (ADS)

A low actuation voltage and no contact stiction are important factors in applying micro-electro-mechanical-system (MEMS) RF switches to mobile communication devices. Conventional electrostatic RF MEMS switches require several tens of voltages for actuation. In this paper we propose a piezoelectric actuated seesaw (PAS) RF MEMS switch which adopts Pb(Zr, Ti)O3 (PZT) actuators and seesaw cantilevers to meet the above requirements. The fundamental structures of PAS RF MEMS switches were designed, optimized, and fabricated. Through the developed process of PAS single pole double through (SPDT), RF MEMS switches were successfully fabricated on a 4'' wafer and they showed good electrical properties. The driving voltage was less than 5 volts and the insertion loss was -0.5dB and the isolation was -35dB at 5GHz. The maximum switching speed was about 5kHz. Thus these RF MEMS switches can be applicable to mobile communication devices or wireless multi-media devices at a frequency lower than 6GHz.

Lee, Dae-Sung; Jung, Suk-Won; Cho, Nam-Kyu; Kim, Won-Hyo; Seong, Woo-Kyeong; Park, Hyo-Derk

2006-04-01

379

Language and task switching in the bilingual brain: Bilinguals are staying, not switching, experts.  

PubMed

Bilinguals' ability to control which language they speak and to switch between languages may rely on neurocognitive mechanisms shared with non-linguistic task switching. However, recent studies also reveal some limitations on the extent control mechanisms are shared across domains, introducing the possibility that some control mechanisms are unique to language. We investigated this hypothesis by directly comparing the neural correlates of task switching and language switching. Nineteen Spanish-English bilingual university students underwent a functional magnetic resonance imaging (fMRI) study employing a hybrid (event-related and blocked) design involving both color-shape switching and language switching paradigms. We compared the two switching tasks using within-subject voxel-wise t-tests for each of three trial types (single trials in single blocks, and stay and switch trials in mixed blocks). Comparing trial types to baseline in each task revealed widespread activation for single, stay, and switch trials in both color-shape and language switching. Direct comparisons of each task for each trial type revealed few differences between tasks on single and switch trials, but large task differences during stay trials, with more widespread activation for the non-linguistic than for the language task. Our results confirm previous suggestions of shared mechanisms of switching across domains, but also reveal bilinguals have greater efficiency for sustaining the inhibition of the non-target language than the non-target task when two responses are available. This efficiency of language control might arise from bilinguals' need to control interference from the non-target language specifically when not switching languages, when speaking in single- or mixed-language contexts. PMID:25446970

Weissberger, Gali H; Gollan, Tamar H; Bondi, Mark W; Clark, Lindsay R; Wierenga, Christina E

2015-01-01

380

Subnanosecond photoconductive switching in GaAs  

SciTech Connect

We are conducting research in photoconductive switching for the purpose of generating microwave pulses with amplitudes up to 50 kV. This technology has direct application to impulse radar and HPM sources. We are exploiting the very fast recombination rates of Gallium Arsenide (GaAs) to explore the potential of GaAs as an on-off switch when operating in the linear mode (the linear mode is defined such that one carrier pair is generated for each photon absorbed). In addition, we are exploring the potential of GaAs to act as a closing switch in avalanche'' mode at high fields. We have observed switch closing times of less than 200 psec with 100 psec duration laser pulse and opening times of less than 400 psec with neutron irradiated GaAs at fields of tens of kV/cm. If the field is increased and the laser energy decreased, the laser can be used to trigger photoconductive switches into an avalanche'' mode of operation in which carrier multiplication occurs. This mode of operation is quite promising since the switches close in less than 1 nsec while realizing significant energy gain (ratio of electrical energy in the pulse to optical trigger energy). We are currently investigating both large are (1 sq cm) and small area (<1 sq mm) switches illuminated by GaAlAs laser diodes at 900 nm and Nd:YAG lasers at 1.06 micrometers. Preliminary results indicate that the closing time of the avalanche switches depends primarily on the material properties of the devices with closing times of 300--1300 psec at voltages of 6-35 kV. We will present experimental results for linear, lock on and avalanche mode operation of GaAs photoconductive switches and how these pulses may be applied to microwave generation. 3 refs., 11 figs.

Druce, R.L.; Pocha, M.D.; Griffin, K.L.

1990-01-01

381

Subnanosecond photoconductive switching in GaAs  

SciTech Connect

We are conducting research in photoconductive switching for the purpose of generating microwave pulses with amplitudes up to 50 kV. This technology has direct application to impulse radar and HPM sources. We are exploiting the very fast recombination rates of Gallium Arsenide (GaAs) to explore the potential of GaAs as an on-off switch when operating in the linear mode (the linear mode is defined such that one carrier pair is generated for each photon absorbed). In addition, we are exploring the potential GaAs to act as a closing switch in avalanche'' mode at high fields. We have observed switch closing times of less than 200 psec with a 100 psec duration laser pulse and opening times of less than 400 psec with neutron irradiated GaAs at fields of tens of kV/cm. If the field is increased and the laser energy decreased, the laser can be used to trigger photoconductive switches into avalanche'' mode of operation in which carrier multiplication occurs. This mode of operation is quite promising since the switches close in less than 1 nsec while realizing significant energy gain (ratio of electrical energy in the pulse to optical trigger energy). We are currently investigating both large area (1 sq cm) and small area (< 1 sq mm) switches illuminated by GaAlAs laser diodes at 900 nm and Nd:YAG lasers at 1.06 micrometers. Preliminary results indicate that the closing time of the avalanche switches depends primarily on the material properties of the devices with closing times of 300--1300 psec at voltages of 6--35 kV. We will present experimental results for linear, lock on and avalanche mode operation of GaAs photoconductive switches and how these pulses may be applied to microwave generation. 3 refs.

Druce, R.L.; Pocha, M.D.; Griffin, K.L.

1991-04-01

382

Subnanosecond photoconductive switching in GaAs  

SciTech Connect

We are conducting research in photoconductive switching for the purpose of generating microwave pulses with amplitudes up to 50 kV. This technology has direct application to impulse radar and HPM sources. We are exploiting the very fast recombination rates of Gallium Arsenide (GaAs) to explore the potential of GaAs as an on-off switch when operating in the linear mode (the linear mode is defined such that one carrier pair is generated for each photon absorbed). In addition, we are exploring the potential GaAs to act as a closing switch in ``avalanche`` mode at high fields. We have observed switch closing times of less than 200 psec with a 100 psec duration laser pulse and opening times of less than 400 psec with neutron irradiated GaAs at fields of tens of kV/cm. If the field is increased and the laser energy decreased, the laser can be used to trigger photoconductive switches into ``avalanche`` mode of operation in which carrier multiplication occurs. This mode of operation is quite promising since the switches close in less than 1 nsec while realizing significant energy gain (ratio of electrical energy in the pulse to optical trigger energy). We are currently investigating both large area (1 sq cm) and small area (< 1 sq mm) switches illuminated by GaAlAs laser diodes at 900 nm and Nd:YAG lasers at 1.06 micrometers. Preliminary results indicate that the closing time of the avalanche switches depends primarily on the material properties of the devices with closing times of 300--1300 psec at voltages of 6--35 kV. We will present experimental results for linear, lock on and avalanche mode operation of GaAs photoconductive switches and how these pulses may be applied to microwave generation. 3 refs.

Druce, R.L.; Pocha, M.D.; Griffin, K.L.

1991-04-01

383

Still clever after all these years: searching for the homunculus in explicitly cued task switching.  

PubMed

Many researchers interpret switch costs in the explicit task-cuing procedure as reflecting endogenous task-set reconfiguration. G. D. Logan and C. Bundesen (2003) challenged this interpretation empirically and theoretically. They argued that many experiments confounded cue encoding benefits with switch costs and they showed that unconfounded switch costs could be vanishingly small. They proposed a theory in which subjects use a single task set in the explicit task-cuing procedure and switch costs reflect cue encoding benefits, not reconfiguration. S. Monsell and G. A. Mizon (2006) responded to these challenges, describing conditions under which substantial switch costs could be observed in the explicit task-cuing procedure and providing a theoretical account of performance in which reconfiguration occurred in G. D. Logan and C. Bundesen's experiments. This article is a response to S. Monsell and G. A. Mizon's challenge that highlights empirical problems with their evidence and reports an experiment that challenges critical assumptions of their theoretical account. PMID:17683241

Logan, Gordon D; Schneider, Darryl W; Bundesen, Claus

2007-08-01

384

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. PMID:23533641

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

2013-01-01

385

Resistance switching devices based on amorphous insulator-metal thin films  

NASA Astrophysics Data System (ADS)

Nanometallic resistance switching devices based on amorphous insulator-metal thin films are developed to provide a novel non-volatile resistance-switching random-access memory (RRAM) that is CMOS-compatible and meeting technological demand. In these devices, data recording/converting is controlled by a bipolar voltage, which tunes electron localization lengths, hence resistivity, through electron trapping and detrapping. The low-resistance state is a metallic state while the high-resistance state is an insulating state, as established by conductivity studies from 2K to 300K. The material is exemplified by a Si3N4 thin film with randomly dispersed Pt or Cr. It has been extended to other materials, spanning a large library of oxide and nitride insulator films, dispersed with transition and main-group metal atoms. Metallic nanoparticles, which form at metal levels greater than 10 atomic percent, are nonessential for resistance switching: nanometallicity and resistance switching in nanometer thin films start at levels well below the metal percolation threshold. Nanometallic RRAMs have superior properties that set them apart from other RRAMs. The critical switching voltage is independent of the film thickness, device area, operating temperature and switching speed. Trapped electrons are relaxed by electron-phonon interaction, adding stability which enables long-term memory retention despite a low switching voltage. As electron-phonon interaction is mechanically altered, trapped electron can be destabilized, and sub-picosecond switching has been demonstrated using an electromagnetically generated stress pulse. The resistance state is finely tunable throughout the entire continuum between the fully metallic state and the fully insulating state, by voltage, thickness and composition. AC impedance spectroscopy confirms the resistance state is spatially uniform, providing a capacitance that linearly scales with area and inversely scales with thickness. The spatial uniformity is also manifested in outstanding uniformity of switching properties. Device degradation, due to moisture, electrode oxidation and dielectrophoresis, is minimal when dense thin films are used or when a hermetic seal is provided. The potential for low power operation, multi-bit storage and complementary stacking have been demonstrated in various RRAM configurations. These studies furnish a firmer understanding of nanometallicity and nanometallic switching. They also establish nanometallic RRAM as a viable candidate for emerging memory.

Yang, Xiang

386

Nanometer Resolution Imaging by SIngle Molecule Switching  

SciTech Connect

The fluorescence intensity of single molecules can change dramatically even under constant laser excitation. The phenomenon is frequently called "blinking" and involves molecules switching between high and low intensity states.[1-3] In additional to spontaneous blinking, the fluorescence of some special fluorophores, such as cyanine dyes and photoactivatable fluorescent proteins, can be switched on and off by choice using a second laser. Recent single-molecule spectroscopy investigations have shed light on mechanisms of single molecule blinking and photoswitching. This ability to controllably switch single molecules led to the invention of a novel fluorescence microscopy with nanometer spatial resolution well beyond the diffraction limit.

Hu, Dehong; Orr, Galya

2010-04-02

387

Hybrid photonic crystal microcavity switches on SOI  

NASA Astrophysics Data System (ADS)

We report the development and characterization of 2-D photonic crystal (PC) microcavity devices on silicon on insulator. The transmission of light through a 2-D PC microcavity near resonance can be switched on and off by modulating the refractive index of the PC. Because silicon has poor electro-optical properties, it is advantageous to insert electro-optic materials inside the air holes. In this work, we report the design, fabrication, and characterization of such hybrid PC microcavity switches using liquid crystals as the electro-optic material. In addition, we demonstrate an electrode geometry that eliminates electric field screening by the more conducting silicon host, and thus enables switching. fabrication.

Anderson, Sean P.; Haurylau, Mikhail; Zhang, Jidong; Fauchet, Philippe M.

2007-02-01

388

Figuring on energy: fuel-switch mirage  

SciTech Connect

DOE's Petroleum Supply Annual: 1983 does not support the idea that the 1981-83 drop in natural gas consumption was due to industrial users switching to oil. A consumption breakdown shows a pattern of reduced oil use during the same period. The American Gas Association estimates that gas utilities lost 0.325 quads in 1982 because of dual-fuel switching, but gas consumption continued to decline even after the fuel-switching trend reversed. The author traces the problem to state rate regulators whose policies subsidize residential users at the expense of industry rather than to interfuel competition.

Schaffer, P.

1984-06-25

389

Adhesion of membranes via actively switched receptors  

E-print Network

We consider a theoretical model for membranes with adhesive receptors, or stickers, that are actively switched between two conformational states. In their 'on'-state, the stickers bind to ligands in an apposing membrane, whereas they do not interact with the ligands in their 'off'-state. We show that the adhesiveness of the membranes depends sensitively on the rates of the conformational switching process. This dependence is reflected in a resonance at intermediate switching rates, which can lead to large membrane separations and unbinding. Our results may provide insights into novel mechanisms for the controlled adhesion of biological or biomimetic membranes.

Bartosz Rozycki; Reinhard Lipowsky; Thomas R. Weikl

2005-12-20

390

SwitchEmail: Free Email Forwarding  

NSDL National Science Digital Library

For users afraid of changing email addresses for fear of not receiving messages sent to their old address, fret no longer. SwitchEmail is a free email forwarding service that can forward electronic messages to and from any ISP. Users do not have to keep old email accounts active or open, reveal their password, or have an email address with SwitchEmail. The service offers users the freedom to switch email addresses with comfort in knowing they still have access to all incoming messages.

391

How Do You Make Loops and Switches?  

NSDL National Science Digital Library

Students learn how to program using loops and switches. They see how loops enable us to easily and efficiently tell a computer to keep repeating an operation. They also see that switches permit programs to follow different instructions based on whether or not preconditions are fulfilled. Using the LEGO® MINDSTORMS® NXT robots, sensors and software, student pairs perform three mini programming activities using loops and switches individually, and then combined. With practice, they incorporate these tools into their programming skill sets in preparation for the associated activity. A PowerPoint® presentation, pre/post quizzes and worksheet are provided.

GK-12 Program, Computational Neurobiology Center,

392

Module 5: Switches, Fuses, and Circuit Breakers  

NSDL National Science Digital Library

This module on switches, fuses, and circuit breakers contains two experiments and a link to allaboutcircuits.com. The module was created by the California Regional Consortium for Engineering Advances in Technological Education (CREATE) which is “a joint effort between seven community colleges and over 30 large high tech engineering/technology employers.” This collection of study modules encourages students to learn about the basics of DC electronics and circuits. Module 5 teaches students about the Physics of Conductors and Insulators as well as Electromechanical Devices and Switches and Switching Circuits.

2014-08-15

393

Metal vapor arc switch electromagnetic accelerator technology  

NASA Technical Reports Server (NTRS)

A multielectrode device housed in an insulator vacuum vessel, the metal vapor vacuum switch has high power capability and can hold off voltages up to the 100 kilovolt level. Such switches can be electronically triggered and can interrupt or commutate at a zero current crossing. The physics of arc initiation, arc conduction, and interruption are examined, including material considerations; inefficiencies; arc modes; magnetic field effects; passive and forced extinction; and voltage recovery. Heating, electrode lifetime, device configuration, and external circuit configuration are discussed. The metal vapor vacuum switch is compared with SCRs, GTOs, spark gaps, ignitrons, and mechanical breakers.

Mongeau, P. P.

1984-01-01

394

A steroid-controlled global switch in sensitivity to apoptosis during Drosophila development  

PubMed Central

Precise control over activation of the apoptotic machinery is critical for development, tissue homeostasis and disease. In Drosophila, the decision to trigger apoptosis--whether in response to developmental cues or to DNA damage--converges on transcription of inhibitor of apoptosis protein (IAP) antagonists reaper, hid and grim. Here we describe a parallel process that regulates the sensitivity to, rather than the execution of, apoptosis. This process establishes developmental windows that are permissive or restrictive for triggering apoptosis, where the status of cells determines their capacity to die. We characterize one switch in the sensitivity to apoptotic triggers, from restrictive to permissive, that occurs during third-instar larval (L3) development. Early L3 animals are highly resistant to induction of apoptosis by expression of IAP-antagonists, DNA-damaging agents and even knockdown of the IAP diap1. This resistance to apoptosis, however, is lost in wandering L3 animals after acquiring a heightened sensitivity to apoptotic triggers. This switch in sensitivity to death activators is mediated by a change in mechanisms available for activating endogenous caspases, from an apoptosome-independent to an apoptosome-dependent pathway. This switch in apoptotic pathways is regulated in a cell-autonomous manner by the steroid hormone ecdysone, through changes in expression of critical pro-, but not anti-, apoptotic genes. This steroid-controlled switch defines a novel, physiologically-regulated, mechanism for controlling sensitivity to apoptosis and provides new insights into the control of apoptosis during development. PMID:24333635

Kang, Yunsik; Bashirullah, Arash

2014-01-01

395

Critical Thinking Skills.  

ERIC Educational Resources Information Center

This issue of a quarterly newsletter focuses on the theme of critical thinking skills. "Critical Thinking Skills: An Interview with Dr. Richard Paul" (Barbara Christopher) is the text of an interview in which the director of research at Sonoma State University's Center for Critical Thinking examines the meaning of critical thinking and the ways…

Word's Worth: A Quarterly Newsletter of the Lifelong Learning Network, 1998

1998-01-01

396

Comparative study of bolometric and non-bolometric switching elements for microwave phase shifters  

NASA Technical Reports Server (NTRS)

The performance of semiconductor and high critical temperature superconductor switches is compared as they are used in delay-line-type microwave and millimeter-wave phase shifters. Such factors as their ratios of the off-to-on resistances, parasitic reactances, power consumption, speed, input-to-output isolation, ease of fabrication, and physical dimensions are compared. Owing to their almost infinite off-to-on resistance ratio and excellent input-to-output isolation, bolometric superconducting switches appear to be quite suitable for use in microwave phase shifters; their only drawbacks are their speed and size. The SUPERFET, a novel device whose operation is based on the electric field effect in high critical temperature ceramic superconductors is also discussed. Preliminary results indicate that the SUPERFET is fast and that it can be scaled; therefore, it can be fabricated with dimensions comparable to semiconductor field-effect transistors.

Tabib-Azar, Massood; Bhasin, Kul B.; Romanofsky, Robert R.

1991-01-01

397

Design of the zero-voltage-switching quasi-square-wave resonant switch  

Microsoft Academic Search

Zero-voltage-switching, quasi-square-wave (ZVS-QSW) power converters with controllable rectifiers feature constant-frequency, PWM-like operation with low voltage and relatively low current stresses on active devices. New closed-form analytic results are derived and applied to construct a detailed design procedure for the ZVS-QSW switch. Starting with usual design constraints, resonant elements are selected so that zero-voltage switching is achieved under all operating conditions,

Dragan MaksimoviC

1993-01-01

398

Analytical and experimental investigation of the frequency ratio and switching law for piezoelectric switching techniques  

Microsoft Academic Search

Piezoelectric shunt damping with mechanical structures has been an active research topic for several years. Standard passive techniques suffer from a very limited and frequency-dependent damping performance. Recently, semi-active switching techniques---namely SSDI (synchronized switch damping on inductor) and SSDV (synchronized switch damping on voltage source) techniques---have been proposed, which are capable of adapting to variations of the excitation frequency without

M. Neubauer; J. Wallaschek

2008-01-01

399

SULFHYDRYL AND DISULFIDE GROUPS OF PROTEINS  

PubMed Central

1. In the denatured proteins of skeletal muscle, the ratio of SH to S-S groups is higher than in the mixed denatured proteins of other tissues, with a single exception—the proteins of the crystalline lens. 2. The number of active SH groups in the proteins of minced muscle or in any of the protein fractions of muscle is only a fraction of the number found after the proteins have been treated with a denaturing agent. 3. The SH groups of the native proteins of muscle are activated by a rise in pH. 4. The relation between pH and number of active SH groups in the proteins of minced muscle and in the various protein fractions of muscle shows that little, if any, denatured protein is present in minced muscle. PMID:19872947

Mirsky, A. E.

1936-01-01

400

THE SULFHYDRYL GROUPS OF EGG ALBUMIN  

PubMed Central

1. 1 cc. of 0.001 M ferricyanide, tetrathionate, or p-chloromercuribenzoate is required to abolish the SH groups of 10 mg. of denatured egg albumin in guanidine hydrochloride or Duponol PC solution. Both the nitroprusside test and the ferricyanide reduction test are used to show that the SH groups have been abolished. 2. 1 cc. of 0.001 M ferrocyanide is formed when ferricyanide is added to 10 mg. of denatured egg albumin in neutral guanidine hydrochloride or urea solution. The amount of ferricyanide reduced to ferrocyanide by the SH groups of the denatured egg albumin is, within wide limits, independent of the ferricyanide concentration. 3. Ferricyanide and p-chloromercuribenzoate react more rapidly than tetrathionate with the SH groups of denatured egg albumin in both guanidine hydrochloride solution and in Duponol PC solution. 4. Cyanide inhibits the oxidation of the SH groups of denatured egg albumin by ferricyanide. 5. Some samples of guanidine hydrochloride contain impurities which bring about the abolition of SH groups of denatured egg albumin and so interfere with the SH titration and the nitroprusside test. This interference can be diminished by using especially purified guanidine hydrochloride, adding the titrating agent before the protein has been allowed to stand in guanidine hydrochloride solution, and carrying out the nitroprusside test in the presence of a small amount of cyanide. 6. The SH groups of egg albumin can be abolished by reaction of the native form of the protein with iodine. It is possible to oxidize all the SH groups with iodine without oxidizing many of the SH groups beyond the S-S stage and without converting many tyrosine groups into di-iodotyrosine groups. 7. p-chloromercuribenzoate combines with native egg albumin either not at all or much more loosely than it combines with the SH groups of denatured egg albumin or of cysteine. 8. The compound of mercuribenzoate and SH, like the compound of aldehyde and SH and like the SH in native egg albumin, does not give a nitroprusside test or reduce ferricyanide but does reduce iodine. PMID:19873224

Anson, M. L.

1941-01-01

401

Virtual Cut-Through: A New Computer Communication Switching Technique  

Microsoft Academic Search

In this paper a new switching technique called virtual cut-through is proposed and its performance is analyzed. This switching system is very similar to message switching, with the difference that when a message arrives in an intermediate node and its selected outgoing channel is free (just after the reception of the header), then, in contrast to message switching, the message

Parviz Kermani; Leonard Kleinrock

1979-01-01

402

Minimum Delay Scheduling for Performance Guaranteed Switches With Optical Fabrics  

Microsoft Academic Search

We consider traffic scheduling in performance guaranteed switches with optical fabrics to ensure 100% throughput and bounded packet delay. Each switch reconfiguration consumes a constant period of time called reconfiguration overhead, during which no packet can be transmitted across the switch. To minimize the packet delay bound for an arbitrary traffic matrix, the number of switch configurations in the schedule

Bin Wu; Kwan L. Yeung; Pin-Han Ho; Xiaohong Jiang

2009-01-01

403

A Control and Management Plane for Large Packet Switches  

E-print Network

of a solution for the considered architecture. Finally, we consider the case of building an Ethernet switch on packet switches, such as IP routers and Ethernet switches. Several carriers cope with this growth by simply adding to their existing infrastructure more packet switches inter- connected by high-speed ports

404

An Experimental Flow-Controlled Multicast ATM Switch  

Microsoft Academic Search

BNR and Harvard have jointly designed an experimental ATM switch called CreditSwitch with sixteen 622-Mbps ports. Expected to be operational in early 1995, the switch will support credit-based flow control and full-speed multicast. This paper gives a brief over- view of the switch architecture and its design goals.

T. Blackwell; K. Chan; K. Chang; T. Charuhas; B. Karp; H. T. Kung; D. Lin; R. Morris; M. Seltzer; M. Smith; C. Young; O. Bahgat; M. Chaar; A. Chapman; G. Depelteau; K. Grimble; S. Huang; P. Hung; M. Kemp; I. Mahna; J. McLaughlin; T. Ng; J. Vincent; J. Watchorn

1994-01-01

405

Design and development of a latching micro optical switch  

Microsoft Academic Search

We will review the initial design and development of a first-of-its-kind latching micro optical switch that can be switched from one optical state to another utilizing thermal actuation. The device is designed to remain in one position or the other without the requirement for continuous external power to keep the switch in either state. The switch uses deep reactive ion

Ernest J. Garcia; Marc A. Polosky; Thomas P. Swiler; Randy J. Shul; David L. Luck

2009-01-01

406

Simultaneous switching ground noise calculation for packaged CMOS devices  

Microsoft Academic Search

Here, it is assumed that the internal switching current is small compared to the output driver switching current. In the past, it was assumed that simultaneous switching noise created by CMOS outputs was directly proportional to the number of outputs switching simultaneously. Recent studies indicate that CMOS circuits exhibit sublinear behavior (due to the negative feedback influence) of power\\/ground noise

R. Senthinathan; J. L. Prince

1991-01-01

407

Switch evaluation test system for the National Ignition Facility  

Microsoft Academic Search

Flashlamp pumped lasers use pulsed power switches to commute energy stored in capacitor banks to the flashlamps. To lower the total cost of these switches, Sandia National Laboratories has a research program to evaluate large closing switches. The particular application in which we are interested is the National Ignition Facility (NIF). The target value of the energy switched by a

M. E. Savage; W. W. Simpson; R. A. Sharpe; F. D. Reynolds

1997-01-01

408

Observation of a multiferroic critical end point  

PubMed Central

The study of abrupt increases in magnetization with magnetic field known as metamagnetic transitions has opened a rich vein of new physics in itinerant electron systems, including the discovery of quantum critical end points with a marked propensity to develop new kinds of order. However, the electric analogue of the metamagnetic critical end point, a “metaelectric” critical end point, has been rarely studied. Multiferroic materials wherein magnetism and ferroelectricity are cross-coupled are ideal candidates for the exploration of this novel possibility using magnetic-field (H) as a tuning parameter. Herein, we report the discovery of a magnetic-field-induced metaelectric transition in multiferroic BiMn2O5, in which the electric polarization (P) switches polarity along with a concomitant Mn spin–flop transition at a critical magnetic field Hc. The simultaneous metaelectric and spin–flop transitions become sharper upon cooling but remain a continuous cross-over even down to 0.5 K. Near the P = 0 line realized at ?0Hc ? 18 T below 20 K, the dielectric constant (?) increases significantly over wide field and temperature (T) ranges. Furthermore, a characteristic power-law behavior is found in the P(H) and ?(H) curves at T = 0.66 K. These findings indicate that a magnetic-field-induced metaelectric critical end point is realized in BiMn2O5 near zero temperature. PMID:19717461

Kim, Jae Wook; Haam, S. Y.; Oh, Y. S.; Park, S.; Cheong, S.-W.; Sharma, P. A.; Jaime, M.; Harrison, N.; Han, Jung Hoon; Jeon, Gun-Sang; Coleman, P.; Kim, Kee Hoon

2009-01-01

409

Clause chaining, switch reference and coordination  

E-print Network

In this thesis I ponder over a constellation of phenomena that revolve around switch reference and coordination, drawing mainly on their instantiation in Kisedje (Je, Brazil). I start by investigating Klsedje's case system. ...

Nonato, Rafael

2014-01-01

410

Visualization of spin waves during switching simulation  

NASA Astrophysics Data System (ADS)

We discuss "spin-wave switching," in which switching is triggered by a spin wave instability rather than a geometric instability mode such as buckling or curling, or end nucleation. This type of switching was reported in a simulation by Safonov and Bertram. We examine the mechanism of spin-wave switching using several visualization methods, and introduce a new method of displaying the spin-wave spectrum. We construct a three dimensional "k-space window" in which the coordinates are the wavevector components kx,ky, and kz. At each allowed k vector in this window we display only the parts of the magnetization attributable to this k vector. Initially we see magnetization only at k=0, and we can visually follow the exponential growth of the unstable Fourier components at the onset of instability.

Visscher, P. B.; Traistaru, O.; Apalkov, D. M.; Feng, Xuebing

2002-05-01

411

JANTX1N5552 switching diode  

NASA Technical Reports Server (NTRS)

Switching diodes manufactured by Micro Semidonductor and Semtech were tested. In groups 2 and 3 there were no Micro Semiconductor catastrophic failures. Testing of both lots was stopped in group 1 test because of 50% failure rate.

1980-01-01

412

46 CFR 111.105-19 - Switches.  

...105-19 Section 111.105-19 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING ELECTRIC SYSTEMS-GENERAL REQUIREMENTS Hazardous Locations § 111.105-19 Switches. A...

2014-10-01

413

46 CFR 112.43-1 - Switches.  

Code of Federal Regulations, 2013 CFR

...112.43-1 Section 112.43-1 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING EMERGENCY LIGHTING AND POWER SYSTEMS Emergency Lighting Systems § 112.43-1 Switches. An...

2013-10-01

414

Switching Dynamics and the Stress Process  

PubMed Central

This paper shows how maintaining social relationships can be a daily hassle that has implications for the stress process, depending on how often individuals transition, or “switch,” between their various social roles and social settings throughout the day. I use nationally representative time diary data on 7,662 respondents from the 2010 American Time Use Survey to measure individual rates of this switching behavior and to examine how this relates to perceived stress. Regression analysis shows that, net of how many social roles they play and settings they visit on a given day, individuals who switch more frequently between these elements report higher levels of stress. This finding holds for women but not men, suggesting that switching dynamics are disproportionately stressful for women. I close by discussing the implications of the findings for research on gender and health. PMID:25110381

Cornwell, Benjamin

2014-01-01

415

High repetition rate miniature triggered spark switch  

NASA Astrophysics Data System (ADS)

A miniature triggered spark switch designed to operate at high repetition rates has been constructed. The device, along with associated triggered circuitry, has been incorporated into a simple LC generator which produces an oscillatory discharge at a frequency of 150 MHz. The switch is operated in the pressure range 760 torr-2.6 x 10 to the 3rd torr using commercial dry nitrogen as the working gas. Both brass (70/30) and aluminum (99.95 percent) electrodes were investigated for repetition frequencies as high as 20 kHz and for gas flow rates as high as 8 cu cm/s. The effect of repetition rate on switch jitter and switch breakdown voltage is presented and discussed in terms of gas pressure and flow rate.

Rose, M. F.; Glancy, M. T.

1980-09-01

416

Structure-switching biosensors: inspired by Nature  

PubMed Central

Summary Chemosensing in nature relies on biomolecular switches, biomolecules that undergo binding-induced changes in conformation or oligomerization to transduce chemical information into specific biochemical outputs. Motivated by the impressive performance of these natural “biosensors,” which support continuous, real-time detection in highly complex environments, significant efforts have gone into the adaptation of such switches into artificial chemical sensors. Ongoing advances in the fields of protein and nucleic acid engineering (e.g., computational protein design, directed evolution, selection strategies and labeling chemistries) have greatly enhanced our ability to design new structure-switching sensors. Coupled with the development of advanced optical read-out mechanisms, including genetically encoded fluorophores, and electrochemical read-outs supporting detection directly in highly complex sample matrices, switch-based sensors have already seen deployment in applications ranging from real time, in vivo imaging to the continuous monitoring of drugs in blood. PMID:20627702

Vallée-Bélisle, Alexis; Plaxco, Kevin W.

2011-01-01

417

A mechanochemical switch to control radical intermediates.  

PubMed

B??-dependent enzymes employ radical species with exceptional prowess to catalyze some of the most chemically challenging, thermodynamically unfavorable reactions. However, dealing with highly reactive intermediates is an extremely demanding task, requiring sophisticated control strategies to prevent unwanted side reactions. Using hybrid quantum mechanical/molecular mechanical simulations, we follow the full catalytic cycle of an AdoB??-dependent enzyme and present the details of a mechanism that utilizes a highly effective mechanochemical switch. When the switch is "off", the 5'-deoxyadenosyl radical moiety is stabilized by releasing the internal strain of an enzyme-imposed conformation. Turning the switch "on," the enzyme environment becomes the driving force to impose a distinct conformation of the 5'-deoxyadenosyl radical to avoid deleterious radical transfer. This mechanochemical switch illustrates the elaborate way in which enzymes attain selectivity of extremely chemically challenging reactions. PMID:24846280

Brunk, Elizabeth; Kellett, Whitney F; Richards, Nigel G J; Rothlisberger, Ursula

2014-06-17

418

Granular acoustic switches and logic elements.  

PubMed

Electrical flow control devices are fundamental components in electrical appliances and computers; similarly, optical switches are essential in a number of communication, computation and quantum information-processing applications. An acoustic counterpart would use an acoustic (mechanical) signal to control the mechanical energy flow through a solid material. Although earlier research has demonstrated acoustic diodes or circulators, no acoustic switches with wide operational frequency ranges and controllability have been realized. Here we propose and demonstrate an acoustic switch based on a driven chain of spherical particles with a nonlinear contact force. We experimentally and numerically verify that this switching mechanism stems from a combination of nonlinearity and bandgap effects. We also realize the OR and AND acoustic logic elements by exploiting the nonlinear dynamical effects of the granular chain. We anticipate these results to enable the creation of novel acoustic devices for the control of mechanical energy flow in high-performance ultrasonic devices. PMID:25354587

Li, Feng; Anzel, Paul; Yang, Jinkyu; Kevrekidis, Panayotis G; Daraio, Chiara

2014-01-01

419

Physician switching after drug request refusal.  

PubMed

Physician switching is a barometer of the quality of the relationship between a patient and a physician. Understanding the factors associated with physician switching in the context of direct-to-consumer advertising (DTCA) of prescription drugs has been largely unexamined. A total of 818 of 2,988 participants in a national telephone survey (27.4%) who had received DTCA reported asking their physician for a prescription drug, and 196 (24.0%) reported that their physician refused to prescribe the drug. Of those whose physicians refused, 13.9% (n = 27 of 194 with data) switched doctors. We found that individuals with regular medical-seeking behavior, full prescription drug coverage, with certain chronic conditions, and of African American origin were significantly more likely to switch physicians in this context. PMID:22054027

Lee, Doohee; Begley, Charles E

2011-10-01

420

Delayed switching applied to memristor neural networks  

SciTech Connect

Magnetic flux and electric charge are linked in a memristor. We reported recently that a memristor has a peculiar effect in which the switching takes place with a time delay because a memristor possesses a certain inertia. This effect was named the ''delayed switching effect.'' In this work, we elaborate on the importance of delayed switching in a brain-like computer using memristor neural networks. The effect is used to control the switching of a memristor synapse between two neurons that fire together (the Hebbian rule). A theoretical formula is found, and the design is verified by a simulation. We have also built an experimental setup consisting of electronic memristive synapses and electronic neurons.

Wang, Frank Z.; Yang Xiao; Lim Guan [Future Computing Group, School of Computing, University of Kent, Canterbury (United Kingdom); Helian Na [School of Computer Science, University of Hertfordshire, Hatfield (United Kingdom); Wu Sining [Xyratex, Havant (United Kingdom); Guo Yike [Department of Computing, Imperial College, London (United Kingdom); Rashid, Md Mamunur [CERN, Geneva (Switzerland)

2012-04-01

421

Performance Analysis of Storage Area Network Switches  

E-print Network

of backpressure mechanisms and buffer man- agement techniques that guarantee loss-free operation and improve and reassembly. We focus mainly on the flow control and backpressure mechanisms in such CIOQ switch

422

14 CFR 23.1145 - Ignition switches.  

Code of Federal Regulations, 2012 CFR

...COMMUTER CATEGORY AIRPLANES Powerplant Powerplant Controls and Accessories...switches must control and shut off each ignition circuit on each engine...on multiengine airplanes by the grouping...master ignition control. (c)...

2012-01-01

423

14 CFR 23.1145 - Ignition switches.  

Code of Federal Regulations, 2011 CFR

...COMMUTER CATEGORY AIRPLANES Powerplant Powerplant Controls and Accessories...switches must control and shut off each ignition circuit on each engine...on multiengine airplanes by the grouping...master ignition control. (c)...

2011-01-01

424

14 CFR 23.1145 - Ignition switches.  

...COMMUTER CATEGORY AIRPLANES Powerplant Powerplant Controls and Accessories...switches must control and shut off each ignition circuit on each engine...on multiengine airplanes by the grouping...master ignition control. (c)...

2014-01-01

425

14 CFR 23.1145 - Ignition switches.  

Code of Federal Regulations, 2013 CFR

...COMMUTER CATEGORY AIRPLANES Powerplant Powerplant Controls and Accessories...switches must control and shut off each ignition circuit on each engine...on multiengine airplanes by the grouping...master ignition control. (c)...

2013-01-01

426

Circuit-switch architecture for a 30/20-GHz FDMA/TDM geostationary satellite communications network  

NASA Technical Reports Server (NTRS)

A circuit switching architecture is described for a 30/20 GHz frequency division, multiple access uplink/time division multiplexed downlink (FDMA/TDM) geostationary satellite communications network. Critical subsystems and problem areas are identified and addressed. Work was concentrated primarily on the space segment; however, the ground segment was considered concurrently to ensure cost efficiency and realistic operational constraints.

Ivancic, William D.

1992-01-01

427

The Sonic Hedgehog Signaling System as a Bistable Genetic Switch Karen Lai, Matthew J. Robertson, and David V. Schaffer  

E-print Network

The Sonic Hedgehog Signaling System as a Bistable Genetic Switch Karen Lai, Matthew J. Robertson, University of California, Berkeley, California ABSTRACT Sonic hedgehog (Shh) controls critical cellular therefore yield insights into numerous cellular processes. Drosophila hedgehog and Sonic hedgehog (Shh), one

Schaffer, David V.

428

Coaxial current transformer for test and characterization of high-power semiconductor devices under hard and soft switching  

Microsoft Academic Search

The use of a coaxial current transformer (CCT) is an interesting choice for pulsed measurement of current through power devices during switching transients. The CCT is used to reflect current for convenient external measurement with minimal insertion impedance in the critical power circuit. This paper analyzes the characteristics of the CCT and explains how it can be integrated into test

Renato O. C. Lyra; Braz J. Cardoso Filho; Vinod John; Thomas A. Lipo

2000-01-01

429

DWDM switching with network photonics CrossWave technology: the third-generation optical switching technology  

NASA Astrophysics Data System (ADS)

CrossWave$TM) multiplexed domain switches enable low cost, simple, reliable and scalable architectures for a wide variety of wavelength selective cross connects, dynamically reconfigurable add/drop multiplexers and hybrid optical core switches. As DWDM becomes ubiquitous in long haul and metro core networks, carriers are looking to optical switching to manage the ever-growing number of wavelengths and to automate wavelength routing, restoration and grooming. To meet these requirements, optical core switches (OCSs) need to scale to accommodate high wavelength counts, high TDM bit rates and various types of transport protocols such as SONET and GbE.

Georgis, Steven

2001-10-01

430

A Critical Look into Critical Pedagogy  

ERIC Educational Resources Information Center

In line with postmodern philosophy, critical pedagogy has gained considerable importance and has become a valuable educational goal. The purpose of this study is to dig into the effects of critical pedagogy in a modernist educational system. To this aim, 15 Iranian university students were asked to write down their feelings at the end of a course…

Pishghadam, Reza; Meidani, Elham Naji

2012-01-01

431

Revalorizing the Critical Attitude for Critical Education  

ERIC Educational Resources Information Center

This article argues that at a moment of crisis in education, the defence of critical pedagogy is vitally important. However, it also suggests that such a defence should be more than a "cri de coeur" that asserts principles and methods of criticality against those of neoliberal or conservative education policy. Narratives of a totalising "crisis of…

Amsler, Sarah S.

2011-01-01

432

Outlier Detecting in Fuzzy Switching Regression Models  

Microsoft Academic Search

\\u000a Fuzzy switching regression models have been extensively used in economics and data mining research. We present a new algorithm\\u000a named FCWRM (Fuzzy C Weighted Regression Model) to detect the outliers in fuzzy switching regression models while preserving\\u000a the merits of FCRM algorithm proposed by Hathaway. The theoretic analysis shows that FCWRM can converge to a local minimum\\u000a of the object

Hong-bin Shen; Jie Yang; Shi-tong Wang

2004-01-01

433

Energy Switching Threshold for Climatic Benefits  

NASA Astrophysics Data System (ADS)

Climate change is one of the great challenges facing humanity currently and in the future. Its most severe impacts may still be avoided if efforts are made to transform current energy systems (1). A transition from the global system of high Greenhouse Gas (GHG) emission electricity generation to low GHG emission energy technologies is required to mitigate climate change (2). Natural gas is increasingly seen as a choice for transitions to renewable sources. However, recent researches in energy and climate puzzled about the climate implications of relying more energy on natural gas. On one hand, a shift to natural gas is promoted as climate mitigation because it has lower carbon per unit energy than coal (3). On the other hand, the effect of switching to natural gas on nuclear-power and other renewable energies development may offset benefits from fuel-switching (4). Cheap natural gas is causing both coal plants and nuclear plants to close in the US. The objective of this study is to measure and evaluate the threshold of energy switching for climatic benefits. We hypothesized that the threshold ratio of energy switching for climatic benefits is related to GHGs emission factors of energy technologies, but the relation is not linear. A model was developed to study the fuel switching threshold for greenhouse gas emission reduction, and transition from coal and nuclear electricity generation to natural gas electricity generation was analyzed as a case study. The results showed that: (i) the threshold ratio of multi-energy switching for climatic benefits changes with GHGs emission factors of energy technologies. (ii)The mathematical relation between the threshold ratio of energy switching and GHGs emission factors of energies is a curved surface function. (iii) The analysis of energy switching threshold for climatic benefits can be used for energy and climate policy decision support.

Zhang, X.; Cao, L.; Caldeira, K.

2013-12-01

434

Lithium Niobate Devices in Switching and Multiplexing  

Microsoft Academic Search

Integrated-optics devices in lithium niobate have reached a significant maturity in recent years, and several complex devices have been demonstrated. In addition to performing modulation of light in fibre-optic transmission systems, lithium niobate devices currently offer the only components for photonic switching. Thus lithium niobate devices can be used as spatial, temporal and wavelength switches in high-speed and low-speed systems.

J. E. Midwinter; L. Thylen

1989-01-01

435

The robustness of stochastic switching networks  

Microsoft Academic Search

Many natural systems, including chemical and biological systems, can be modeled using stochastic switching circuits. These circuits consist of stochastic switches, called pswitches, which operate with a fixed probability of being open or closed. We study the effect caused by introducing an error of size. to each pswitch in a stochastic circuit. We analyze two constructions.simple series-parallel and general series-parallel

Po-Ling Loh; Hongchao Zhou; Jehoshua Bruck

2009-01-01

436

Specifying and calibrating instrumentations for wideband electronic power measurements. [in switching circuits  

NASA Technical Reports Server (NTRS)

The wideband electric power measurement related topics of electronic wattmeter calibration and specification are discussed. Tested calibration techniques are described in detail. Analytical methods used to determine the bandwidth requirements of instrumentation for switching circuit waveforms are presented and illustrated with examples from electric vehicle type applications. Analog multiplier wattmeters, digital wattmeters and calculating digital oscilloscopes are compared. The instrumentation characteristics which are critical to accurate wideband power measurement are described.

Lesco, D. J.; Weikle, D. H.

1980-01-01

437

Polarization switching and high piezoelectric response in Sn-modified BaTiO3  

NASA Astrophysics Data System (ADS)

BaTi O3 is shown to exhibit anomalous piezoelectric response, comparable to that of lead-zirconate titanate, by dilute Sn modification (1-4 mol%). Using a newly discovered powder poling technique it is shown that the mechanism associated with this anomalous strain response involves electric-field-induced switching of polarization vector from [001] towards [101] pseudocubic direction. This switchability is significantly enhanced by tuning the tetragonal-orthorhombic first-order criticality near to room temperature.

Kalyani, Ajay Kumar; Krishnan, Hari; Sen, Arijit; Senyshyn, Anatoliy; Ranjan, Rajeev

2015-01-01

438

Shared Memory Implementation of a Parallel Switch-Level Circuit Simulator  

Microsoft Academic Search

Circuit simulation is a critical bottleneck in VLSIdesign. This paper describes the implementation ofan existing parallel switch-level simulator called MIRSIMon a shared-memory multiprocessor architecture.The simulator uses a set of three different conservativeprotocols: the null message protocol, the conditionalevent protocol and the accelerated null message protocol,a combinations of the preceding two algorithms.The paper describes the implementation of these protocolsto exploit...

Yu-an Chen; Rajive Bagrodia

1998-01-01

439

Submicron bidirectional all-optical plasmonic switches  

PubMed Central

Ultra-small all-optical switches are of importance in highly integrated optical communication and computing networks. However, the weak nonlinear light-matter interactions in natural materials present an enormous challenge to realize efficiently switching for the ultra-short interaction lengths. Here, we experimentally demonstrate a submicron bidirectional all-optical plasmonic switch with an asymmetric T-shape single slit. Sharp asymmetric spectra as well as significant field enhancements (about 18 times that in the conventional slit case) occur in the symmetry-breaking structure. Consequently, both of the surface plasmon polaritons propagating in the opposite directions on the metal surface are all-optically controlled inversely at the same time with the on/off switching ratios of >6?dB for the device lateral dimension of <1??m. Moreover, in such a submicron structure, the coupling of free-space light and the on-chip bidirectional switching are integrated together. This submicron bidirectional all-optical switch may find important applications in the highly integrated plasmonic circuits. PMID:23486232

Chen, Jianjun; Li, Zhi; Zhang, Xiang; Xiao, Jinghua; Gong, Qihuang

2013-01-01

440

Microwave pulse generation by photoconductive switching  

SciTech Connect

Laser activated photoconductive semiconductor switching shows significant potential for application in high power microwave generation. Primary advantages of this concept are: small size, light weight, ruggedness, precise timing and phasing by optical control, and the potential for high peak power in short pulses. Several concepts have been suggested for microwave generation using this technology. They generally fall into two categories (1) the frozen wave generator or (2) tuned cavity modulation, both of which require only fast closing switches. We have been exploring a third possibility requiring fast closing and opening switches, that is the direct modulation of the switch at microwave frequencies. Switches have been fabricated at LLNL using neutron irradiated Gallium Arsenide which exhibit response times as short as 50 ps at low voltages. We are in the process of performing high voltage tests. So far, we have been able to generate 2.4 kV pulses with approximately 340 ps response time (FWHM) using approximately a 200..mu..J optical pulse. Experiments are continuing to increase the voltage and improve the switching efficiency. 3 refs., 6 figs.

Pocha, M.D.; Druce, R.L.

1989-03-14

441

An Optical Bypass Switch for Network Protection  

NASA Astrophysics Data System (ADS)

An innovative 2 x 2 Optical Switch has been designed by GTE Fiber Optic Products as an electromechanical bypass product for Data Communication, Local Area Network, and Telecommunication applications. The switch provides a means for easily transferring optical signals from one fiber to another in a two by two or quad port configuration. GTE's design differs from others on the market in that it uses expanded beam technology with a sliding prism oriented to reduce lateral alignment sensitivity. This tolerance of misalignment results in notably consistent throughput - a feature not always found in electromechanical switches. The design calls for two input fibers on one side of the switch with two output fibers opposite. Because a loopback fiber is unnecessary, optical throughput is similar for all four beam paths. Other advantages include beam separation flexibility and a more rugged package. Using this technology, both latching and fail safe designs have been developed. Optical switches are increasingly being used to provide system protection and to aid in network testing during installations and troubleshooting. In Local Area Networks, particularly those of a ring configuration, 2 x 2 switches are also gaining acceptance as a technologically simple and smart way of isolating or alternately connecting parts of a fiber network without introducing high losses.

Calaby, Lauren F.

1987-01-01

442

Elimination of resonance with a switching support  

NASA Astrophysics Data System (ADS)

An add-on switching support is proposed to limit the vibration of a transmission shaft. Experiments are described achieving amplitude reductions in the order of 75 percent. A simple active on/off control system to restrain the excessive transient vibrations of flexible shafts has been designed. The control can be implemented as an add-on system without interfering with the existing bearing structure. An advantage of such an add-on system is that it can be used in already existing structures which operate at supercritical speeds. A finite element analysis (FEA) technique has been utilized to simulate the dynamic response of the flexible shaft operating at sub and supercritical speeds. The results suggest that a vibration amplitude reduction of 75 percent could be obtained with the actuation of the intelligently switching extra support, which could be referred to as a switching support or a phantom support. Experimental data back up the numerical results, demonstrating the viability of the switching support technique for limiting vibration amplitude. At the motor, an amplitude reduction of 75 percent was achieved with the switching support over the simply supported case. An 80 percent reduction over the triply supported case was achieved. Thus the switching support can be used to instantaneously modify the shaft stiffness and the resonant frequencies so that the excitation speed can never approach a resonant frequency.

Turkstra, T. P.; Semercigil, S. E.

1991-05-01

443

Photonic Switching Devices Using Light Bullets  

NASA Technical Reports Server (NTRS)

The present invention is directed toward a unique ultra-fast, all-optical switching device or switch made with readily available, relatively inexpensive, highly nonlinear photonic glasses. These photonic glasses have a sufficiently negative group velocity dispersion and high nonlinear index of refraction to support stable light bullets. The light bullets counterpropagate through, and interact within the waveguide to selectively change each others' directions of propagation into predetermined channels. In one embodiment, the switch utilizes a rectangularly planar slab waveguide, and further includes two central channels and a plurality of lateral channels for guiding the light bullets into and out of the waveguide. One advantage presented by the present all-optical switching device lies in its practical use of light bullets, thus preventing the degeneration of the pulses due to dispersion and diffraction at the front and back of the pulses. Another feature of the switching device is the relative insensitivity of the collision process to the time difference in which the counter-propagating pulses enter the waveguide. since. contrary to conventional co-propagating spatial solitons, the relative phase of the colliding pulses does not affect the interaction of these pulses. Yet another feature of the present all-optical switching device is the selection of the light pulse parameters which enables the generation of light bullets in highly nonlinear glasses.

Goorjian, Peter M. (Inventor)

1997-01-01

444

Photoresolvable Compounds: Towards a Chiroptical - Crystalline Switch.  

NASA Astrophysics Data System (ADS)

The tendency for miniaturization in electronic devices has created the need for materials capable of high storage densities and high switching rates. There has been ample effort in bringing this miniaturization to the molecular level, i.e. the design of molecular switches. The possibility of using photons to address a switch at an specific site in a volume has motivated research in photoresponsive compounds. An interesting family of photoresponsive compounds are those that are sensitive to the sense of chirality of light. Compounds capable of photoresolution can be switched between a scalemic and a racemic state, this can be the basis for a chiroptical switch. Important parameters to control in the design of a photoresolvable compound are the optical properties that determine the degree of enantiomeric excess that one can attain at the photostationary state, the g value. Two strategies to increase the g value were investigated: exciton coupling and energy transfer. Energy transfer was shown to be an efficient strategy in the design of photoresolvable compounds. Specifically, a compound capable of generating a reversible enantiomeric excess of 0.4% has been design using this strategy. The implications of photoresolvable compounds in the creation of a chiroptical liquid crystalline switch are discussed.

Suarez, Mauricio

1995-11-01

445

Design and Demonstration of a 4×4 SFQ Network Switch Prototype System and 10-Gbps Bit-Error-Rate Measurement  

NASA Astrophysics Data System (ADS)

We developed a 4×4 SFQ network switch prototype system and demonstrated its operation at 10Gbps. The system's core is composed of two SFQ chips: a 4×4 switch and a 6-channel voltage driver. The 4×4 switch chip contained both a switch fabric (i. e. a data path) and a switch scheduler (i. e. a controller). Both chips were attached to a multichip-module (MCM) carrier, which was then installed in a cryocooled system with 32 10-Gbps ports. Each chip contained about 2100 Josephson junctions on a 5-mm×5-mm die. An NEC standard 2.5-kA/cm2 fabrication process was used for the switch chip. We increased the critical current density to 10kA/cm2 for the driver chip to improve speed while maintaining wide bias margins. MCM implementation enabled us to use a hybrid critical current density technology. Voltage pulses were transferred between two chips through passive transmission lines on the MCM carrier. The cryocooled system was cooled down to about 4K using a two-stage 1-W cryocooler. We correctly operated the whole system at 10Gbps. The switch scheduler, which is driven by an on-chip clock generator, operated at 40GHz. The speed gap between SFQ and room temperature devices was filled by on-chip SFQ FIFO buffers or shift registers. We measured the bit error rate at 10Gbps and found that it was on the order of 10-13 for the 4×4 SFQ switch fabric. In addition, using semiconductor interface circuitry, we built a four-port SFQ Ethernet switch. All the components except for a compressor were installed in a standard 19-inch rack, filling a space 21 U (933.5mm or 36.75 inches) in height. After four personal computers (PCs) were connected to the switch, we have successfully transferred video data between them.

Kameda, Yoshio; Hashimoto, Yoshihito; Yorozu, Shinichi

446

Non-isolation Soft-switching Buck Converter with Tapped-Inductor for Wide-input Extreme Step-down applications  

Microsoft Academic Search

In this paper, a new zero-voltage switching (ZVS) buck converter with a tapped-inductor is proposed. This converter improves the conventional tapped inductor critical conduction mode (CRM) buck converters that have the ZVS operation range determined by the tapped-inductor turn ratios. It includes another soft switching range extension method, the current injection (CI) method, which gives an additional design freedom for

J. H. Park; B. H. Cho

2005-01-01

447

Output-queued switch emulation by fabrics with limited memory  

Microsoft Academic Search

The output-queued (OQ) switch is often considered an ideal packet switching architecture for providing quality-of-service guarantees. Unfortunately, the high-speed memory requirements of the OQ switch prevent its use for large-scale devices. A previous result indicates that a crossbar switch fabric combined with lower speed input and output memory and two times speedup can exactly emulate an OQ switch; however, the

Robert B. Magill; Charles E. Rohrs; Robert L. Stevenson

2003-01-01

448

Soft switching active snubbers for dc\\/ac converters  

Microsoft Academic Search

A soft switching active snubber is proposed to reduce the switching losses of the IGBT in a DC-AC power converter. The active snubber provides zero-voltage switching for the IGBTs, thereby reducing the high turn-off losses due to current tailing. The proposed active snubber uses two auxiliary switches in order to recover the switching energy during turn-off. The snubber is itself

Ahmed Elasser; D. A. Torrey

1995-01-01

449

Soft switching active snubbers for DC\\/DC converters  

Microsoft Academic Search

A soft-switching active snubber is proposed to reduce the turn-off losses of the insulated gate bipolar transistor (IGBT) in a buck power converter. The soft-switching snubber provides zero-voltage switching for the IGBT, thereby reducing its high turn-off losses due to the current tailing. The proposed snubber uses an auxiliary switch to discharge the snubber capacitor. This auxiliary switch also operates

A. Elasser; D. A. Torrey

1996-01-01

450

Fast packet switch architectures for broadband integrated services digital networks  

NASA Technical Reports Server (NTRS)

Background information on networking and switching is provided, and the various architectures that have been considered for fast packet switches are described. The focus is solely on switches designed to be implemented electronically. A set of definitions and a brief description of the functionality required of fast packet switches are given. Three basic types of packet switches are identified: the shared-memory, shared-medium, and space-division types. Each of these is described, and examples are given.

Tobagi, Fouad A.

1990-01-01

451

False memory in bilinguals: does switching languages increase false memories?  

PubMed

People often receive and recount information in different languages. This experiment examined the impact of switching languages on false recall, recognition, and recognition confidence. We presented Spanish-English bilinguals with 10 lists of words associated to a critical non-presented lure, either in English or in Spanish. Each list was followed by free recall either in English or in Spanish. The final stage was a recognition test in either language. Results showed a higher proportion of veridical and false recall in English, the more dominant language, than in Spanish, the native language. Noncritical intrusions were equivalent in both languages. More importantly, false recall, false recognition, and false recognition confidence were higher across languages than within languages. The results are examined in relation to current research and interpretations of bilingual false memory. PMID:19353928

Marmolejo, Gloria; Diliberto-Macaluso, Kristen A; Altarriba, Jean Ette

2009-01-01

452

Mitochondrial biology. Replication-transcription switch in human mitochondria.  

PubMed

Coordinated replication and expression of the mitochondrial genome is critical for metabolically active cells during various stages of development. However, it is not known whether replication and transcription can occur simultaneously without interfering with each other and whether mitochondrial DNA copy number can be regulated by the transcription machinery. We found that interaction of human transcription elongation factor TEFM with mitochondrial RNA polymerase and nascent transcript prevents the generation of replication primers and increases transcription processivity and thereby serves as a molecular switch between replication and transcription, which appear to be mutually exclusive processes in mitochondria. TEFM may allow mitochondria to increase transcription rates and, as a consequence, respiration and adenosine triphosphate production without the need to replicate mitochondrial DNA, as has been observed during spermatogenesis and the early stages of embryogenesis. PMID:25635099

Agaronyan, Karen; Morozov, Yaroslav I; Anikin, Michael; Temiakov, Dmitry

2015-01-30

453

RF Reference Switch for Spaceflight Radiometer Calibration  

NASA Technical Reports Server (NTRS)

The goal of this technology is to provide improved calibration and measurement sensitivity to the Soil Moisture Active Passive Mission (SMAP) radiometer. While RF switches have been used in the past to calibrate microwave radiometers, the switch used on SMAP employs several techniques uniquely tailored to the instrument requirements and passive remote-sensing in general to improve radiometer performance. Measurement error and sensitivity are improved by employing techniques to reduce thermal gradients within the device, reduce insertion loss during antenna observations, increase insertion loss temporal stability, and increase rejection of radar and RFI (radio-frequency interference) signals during calibration. The two legs of the single-pole double-throw reference switch employ three PIN diodes per leg in a parallel-shunt configuration to minimize insertion loss and increase stability while exceeding rejection requirements at 1,413 MHz. The high-speed packaged diodes are selected to minimize junction capacitance and resistance while ensuring the parallel devices have very similar I-V curves. Switch rejection is improved by adding high-impedance quarter-wave tapers before and after the diodes, along with replacing the ground via of one diode per leg with an open circuit stub. Errors due to thermal gradients in the switch are reduced by embedding the 50-ohm reference load within the switch, along with using a 0.25-in. (approximately equal to 0.6-cm) aluminum prebacked substrate. Previous spaceflight microwave radiometers did not embed the reference load and thermocouple directly within the calibration switch. In doing so, the SMAP switch reduces error caused by thermal gradients between the load and switch. Thermal issues are further reduced by moving the custom, highspeed regulated driver circuit to a physically separate PWB (printed wiring board). Regarding RF performance, previous spaceflight reference switches have not employed high-impedance tapers to improve rejection. The use of open-circuit stubs instead of a via to provide an improved RF short is unique to this design. The stubs are easily tunable to provide high rejection at specific frequencies while maintaining very low insertion loss in-band.

Knuble, Joseph

2013-01-01

454

A soft switching active snubber optimized for IGBT's in single switch unity power factor three-phase diode rectifiers  

Microsoft Academic Search

This paper describes a soft switching active snubber for an IGBT operating in a single switch unity power factor three-phase diode rectifier. The soft switching snubber circuit provides zero-voltage turn-off for the main switch. The high turn-off losses of the IGBT due to current tailing are reduced by zero-voltage switching. This allows the circuit to be operated at very high

Keming Chen; A. Elasser; D. A. Torrey

1995-01-01

455

Submicrosecond Power-Switching Test Circuit  

NASA Technical Reports Server (NTRS)

A circuit that changes an electrical load in a switching time shorter than 0.3 microsecond has been devised. This circuit can be used in testing the regulation characteristics of power-supply circuits . especially switching power-converter circuits that are supposed to be able to provide acceptably high degrees of regulation in response to rapid load transients. The combination of this power-switching circuit and a known passive constant load could be an attractive alternative to a typical commercially available load-bank circuit that can be made to operate in nominal constant-voltage, constant-current, and constant-resistance modes. The switching provided by a typical commercial load-bank circuit in the constant-resistance mode is not fast enough for testing of regulation in response to load transients. Moreover, some test engineers do not trust the test results obtained when using commercial load-bank circuits because the dynamic responses of those circuits are, variously, partly unknown and/or excessively complex. In contrast, the combination of this circuit and a passive constant load offers both rapid switching and known (or at least better known) load dynamics. The power-switching circuit (see figure) includes a signal-input section, a wide-hysteresis Schmitt trigger that prevents false triggering in the event of switch-contact bounce, a dual-bipolar-transistor power stage that drives the gate of a metal oxide semiconductor field-effect transistor (MOSFET), and the MOSFET, which is the output device that performs the switching of the load. The MOSFET in the specific version of the circuit shown in the figure is rated to stand off a potential of 100 V in the "off" state and to pass a current of 20 A in the "on" state. The switching time of this circuit (the characteristic time of rise or fall of the potential at the drain of the MOSFET) is .300 ns. The circuit can accept any of three control inputs . which one depending on the test that one seeks to perform: a repetitive waveform from a signal generator, momentary closure of a push-button switch, or closure or opening of a manually operated on/off switch. In the case of a signal generator, one can adjust the frequency and duty cycle as needed to obtain the desired AC power-supply response, which one could display on an oscilloscope. Momentary switch closure could be useful for obtaining (and, if desired, displaying on an oscilloscope set to trigger on an event) the response of a power supply to a single load transient. The on/off switch can be used to switch between load states in which static-load regulation measurements are performed.

Folk, Eric N.

2006-01-01

456

Inhibition in Language Switching: What Is Inhibited when Switching between Languages in Naming Tasks?  

ERIC Educational Resources Information Center

When people switch between languages, inhibition of currently irrelevant languages is assumed to occur. The authors examined inhibition of irrelevant languages with a cued language-switching paradigm. A cue indicated in which of 3 languages (German, English, or French) a visual stimulus was to be named. In 2 experiments, the authors found that…

Philipp, Andrea M.; Koch, Iring

2009-01-01

457

Video Switching in the Panopto Editor Video Switching in the Panopto Editor  

E-print Network

Video Switching in the Panopto Editor Video Switching in the Panopto Editor In My Pitt Video (Panopto) you can control and edit which video streams the viewer sees by editing individual streams in the My Pitt Video (Panopto) Editor. Editing the primary video source will edit on all streams, editing

Benos, Panayiotis "Takis"

458

Packet switching vs. circuit switching in future integrated services digital networks  

Microsoft Academic Search

This panel presentation contains one full position paper on the user network interface in broadband ISDN, and four position summaries. Issues considered in the latter include: the impact of multimedia services, the effect of optical fiber transmission, the superiority of packet switching for diverse applications, and the potential unification of circuit-and packet-switching techniques

K. Y. Eng; A. M. Ali; C. Baradello; J. Turner; D. Vlack; S. M. Walters

1988-01-01

459

Multi-modal vibration control using a synchronized switch based on a displacement switching threshold  

NASA Astrophysics Data System (ADS)

A new semi-active method for multi-mode vibration control using the nonlinear synchronized switch damping (SSD) approach based on a displacement switching threshold is proposed in this paper. Several extensions of the SSD approach, including SSDI (SSD on inductance), SSDV (SSD on a voltage source), enhanced SSDV, and adaptive SSDV, have been developed to improve the control of the single-mode vibration, but the weakness of the SSD approach for multi-modal vibration control has not been solved. In all these extensions of the SSD approach, the switch is controlled by the same algorithm, that is, it reverses the voltage of the piezoelectric element at all extrema of displacement. This switching algorithm is effective in single-mode control, but it leads to over-frequent switching in multi-mode control. In the method proposed in this study, an improved switching algorithm based on a displacement threshold, which prevents the switch in the shunt circuit from over-frequent on-and-off actions and accordingly increases the converted energy to improve the control performance, is proposed. The switching algorithm is applied to an SSDI system and used in the vibration damping of a beam with two excited modes. Compared to the classical SSDI approach, the control performance of the first mode is improved from 3.7 to 18.2 dB, but that of the second mode is slightly worse, having changed from 3.46 to 2.6.

Ji, Hongli; Qiu, Jinhao; Zhu, Kongjun; Chen, Yuansheng; Badel, Adrien

2009-03-01

460

Silicon-based molecular switch junctions  

E-print Network

In contrast to the static operations of conventional semiconductor devices, the dynamic conformational freedom in molecular devices opens up the possibility of using molecules as new types of devices such as a molecular conformational switch or for molecular data storage. Bistable molecules, with e.g. two stable cis and trans isomeric configurations, could provide, once clamped between two electrodes, a switching phenomenon in the nonequilibrium current response. Here, we model molecular switch junctions formed at silicon contacts and demonstrate the potential of tunable molecular switches in electrode/molecule/electrode configurations. Using the non equilibrium Green function approach implemented with the density-functional-based tight-binding theory, a series of properties such as electron transmissions, I-V characteristics in the different isomer-conformations, and potential energy surfaces as a function of the reaction coordinates along the trans to cis transition were calculated. Furthermore, in order to investigate stability of molecular switches in ambient conditions, molecular dynamics (MD) simulations at room temperature were performed and time- dependent fluctuations of the conductance along the MD pathways were calculated. Our numerical results show that the transmission spectra of the cis isomers are more conductive than trans counterparts inside the bias window for all two model molecules. The current-voltage characteristics consequently show the same trends. Additionally, the calculations of time-dependent transmission fluctuations along the MD pathways have shown that the transmission in cis isomers is always significantly larger than that of trans counterparts showing that molecular switches can be expected to work as robust molecular switching components.

Daijiro Nozaki; Gianaurelio Cuniberti

2009-07-01

461

A switching cascade of hydrazone-based rotary switches through coordination-coupled proton relays  

NASA Astrophysics Data System (ADS)

Imidazole, a subunit of histidine, plays a crucial role in proton-relay processes that are important for various biological activities, such as metal efflux, viral replication and photosynthesis. We show here how an imidazolyl ring incorporated into a rotary switch based on a hydrazone enables a switching cascade that involves proton relay between two different switches. The switching process starts with a single input, zinc(II), that initiates an E/Z isomerization in the hydrazone system through a coordination-coupled proton transfer. The resulting imidazolium ring is unusually acidic and, through proton relay, activates the E/Z isomerization of a non-coordinating pyridine-containing hydrazone switch. We hypothesize that the reduction in the acid dissociation constant of the imidazolium ring results from a combination of electrostatic and conformational effects, the study of which might help elucidate the proton-coupled electron-transfer mechanism in photosynthetic bacteria.

Ray, Debdas; Foy, Justin T.; Hughes, Russell P.; Aprahamian, Ivan

2012-09-01

462

Crosstalk and Signaling Switches in Mitogen-Activated Protein Kinase Cascades  

PubMed Central

Mitogen-activated protein kinase (MAPK) cascades control cell fate decisions, such as proliferation, differentiation, and apoptosis by integrating and processing intra- and extracellular cues. However, similar MAPK kinetic profiles can be associated with opposing cellular decisions depending on cell type, signal strength, and dynamics. This implies that signaling by each individual MAPK cascade has to be considered in the context of the entire MAPK network. Here, we develop a dynamic model of feedback and crosstalk for the three major MAPK cascades; extracellular signal-regulated kinase (ERK), p38 mitogen-activated protein kinase (p38), c-Jun N-terminal kinase (JNK), and also include input from protein kinase B (AKT) signaling. Focusing on the bistable activation characteristics of the JNK pathway, this model explains how pathway crosstalk harmonizes different MAPK responses resulting in pivotal cell fate decisions. We show that JNK can switch from a transient to sustained activity due to multiple positive feedback loops. Once activated, positive feedback locks JNK in a highly active state and promotes cell death. The switch is modulated by the ERK, p38, and AKT pathways. ERK activation enhances the dual specificity phosphatase (DUSP) mediated dephosphorylation of JNK and shifts the threshold of the apoptotic switch to higher inputs. Activation of p38 restores the threshold by inhibiting ERK activity via the PP1 or PP2A phosphatases. Finally, AKT activation inhibits the JNK positive feedback, thus abrogating the apoptotic switch and allowing only proliferative signaling. Our model facilitates understanding of how cancerous deregulations disturb MAPK signal processing and provides explanations for certain drug resistances. We highlight a critical role of DUSP1 and DUSP2 expression patterns in facilitating the switching of JNK activity and show how oncogene induced ERK hyperactivity prevents the normal apoptotic switch explaining the failure of certain drugs to induce apoptosis. PMID:23060802

Fey, Dirk; Croucher, David R.; Kolch, Walter; Kholodenko, Boris N.

2012-01-01

463

Quantum dots as immobilized substrate for electrochemical detection of cocaine based on conformational switching of aptamer  

Microsoft Academic Search

A novel electrochemical cocaine aptamer biosensor based on quantum dots (QDs) as immobilized substrate, utilizing the advantage of sulfur–sulfur affinity, together with the high combination ability between heavy metal ion of quantum dots and sulfhydryl group of aptamer, has been proposed. Some intact aptamer have especial structure, such as hairpin structure and intrinsic binding site, which make the proposed electrochemical

Mei Hua; Ping Li; Li Li; Liangliang Huang; Xiaohui Zhao; Yajuan Feng; Yunhui Yang

2011-01-01

464

Interaction criticism and aesthetics  

Microsoft Academic Search

As HCI becomes more self-consciously implicated in cul-ture, theories from cultural studies, in particular aesthetics and critical theory, are increasingly working their way into the field. However, the use of aesthetics and critical theory in HCI remains both marginal and uneven in quality. This paper explores the state of the art of aesthetics and critical theory in the field, before

Jeffrey Bardzell

2009-01-01

465

Teaching Critical Reflection  

ERIC Educational Resources Information Center

Despite long-standing commitment to the notion of critical reflection across the healthcare professions it is unusual for critical theory and practice to be taught as explicit subjects in healthcare higher education. There is evidence to show that reflective techniques such as critical portfolios and reflective diaries can help students to…

Smith, Elizabeth

2011-01-01

466

Poetry: Sources for Criticism.  

ERIC Educational Resources Information Center

This handout is a guide to library resources in the J. Murrey Atkins Library at the University of North Carolina-Charlotte for the criticism of poetry. The guide enables the reader to find sources of criticism on poetry, including critical articles and essays about single poems, or writings on the work of a single author. The guide's sections…

Van Noate, Judith, Comp.

467

Anomalous critical fields in quantum critical superconductors.  

PubMed

Fluctuations around an antiferromagnetic quantum critical point (QCP) are believed to lead to unconventional superconductivity and in some cases to high-temperature superconductivity. However, the exact mechanism by which this occurs remains poorly understood. The iron-pnictide superconductor BaFe2(As(1-x)P(x))2 is perhaps the clearest example to date of a high-temperature quantum critical superconductor, and so it is a particularly suitable system to study how the quantum critical fluctuations affect the superconducting state. Here we show that the proximity of the QCP yields unexpected anomalies in the superconducting critical fields. We find that both the lower and upper critical fields do not follow the behaviour, predicted by conventional theory, resulting from the observed mass enhancement near the QCP. Our results imply that the energy of superconducting vortices is enhanced, possibly due to a microscopic mixing of antiferromagnetism and superconductivity, suggesting that a highly unusual vortex state is realized in quantum critical superconductors. PMID:25477044

Putzke, C; Walmsley, P; Fletcher, J D; Malone, L; Vignolles, D; Proust, C; Badoux, S; See, P; Beere, H E; Ritchie, D A; Kasahara, S; Mizukami, Y; Shibauchi, T; Matsuda, Y; Carrington, A

2014-01-01

468

Anomalous critical fields in quantum critical superconductors  

PubMed Central

Fluctuations around an antiferromagnetic quantum critical point (QCP) are believed to lead to unconventional superconductivity and in some cases to high-temperature superconductivity. However, the exact mechanism by which this occurs remains poorly understood. The iron-pnictide superconductor BaFe2(As1?xPx)2 is perhaps the clearest example to date of a high-temperature quantum critical superconductor, and so it is a particularly suitable system to study how the quantum critical fluctuations affect the superconducting state. Here we show that the proximity of the QCP yields unexpected anomalies in the superconducting critical fields. We find that both the lower and upper critical fields do not follow the behaviour, predicted by conventional theory, resulting from the observed mass enhancement near the QCP. Our results imply that the energy of superconducting vortices is enhanced, possibly due to a microscopic mixing of antiferromagnetism and superconductivity, suggesting that a highly unusual vortex state is realized in quantum critical superconductors. PMID:25477044

Putzke, C.; Walmsley, P.; Fletcher, J. D.; Malone, L.; Vignolles, D.; Proust, C.; Badoux, S.; See, P.; Beere, H. E.; Ritchie, D. A.; Kasahara, S.; Mizukami, Y.; Shibauchi, T.; Matsuda, Y.; Carrington, A.

2014-01-01

469

Oversized interference switches of active resonant microwave compressors  

NASA Astrophysics Data System (ADS)

Interference switches of resonant microwave compressors made of single mode waveguides provide high coupling factors after switching and rapid energy extraction. The disadvantage of these switches is low electrical strength which limits output power values. Oversized waveguides maintain higher electrical strength due to large dimensions of a cross section but mode transformation disturbs the regular operation of the switch. Operation of interference switches with a gaseous discharge gap as a switching element in oversized rectangular waveguides was studied experimentally. Conditions of their effective switching in active resonant microwave compressors were derived. It was shown that the stable microwave pulses of gigawatt power level in S-band and pulses of 0.1 GW pulse power in X- band can be produced in resonant microwave compressors with oversized interference switches. Possible switch designs are discussed.

Avgustinovich, V.; Artemenko, S.; Kaminsky, V.; Novikov, S.; Yushkov, Yu; Osipov, V.

2014-11-01

470

Low critical current density for spin-transfer torque in Fe-MgO granular film at room temperature  

NASA Astrophysics Data System (ADS)

From a practical point of view, a critical issue for the spin transfer effect is the reduction of the critical switching current density Jc. Over the past few years, the reported Jc at room temperature is in the range of 106 A cm-2. Here we report a low critical switching current density Jc of about 4.2 × 103 A cm-2 for spin transfer in Fe-MgO nanoscale granular film at room temperature, which is due to the low effective anisotropy field of the small Fe particles.

Gao, Chun Hong; Xia Yang, Yan; Xiong, Yuan Qiang; Chen, Peng

2014-01-01

471

Irreversible magnetization switching using surface acoustic waves  

NASA Astrophysics Data System (ADS)

An analytical and numerical approach is developed to pinpoint the optimal experimental conditions to irreversibly switch magnetization using surface acoustic waves (SAWs). The layers are magnetized perpendicular to the plane and two switching mechanisms are considered. In precessional switching, a small in-plane field initially tilts the magnetization and the passage of the SAW modifies the magnetic anisotropy parameters through inverse magnetostriction. The SAW triggers precession and, eventually, reversal. Using the micromagnetic parameters of a fully characterized layer of the magnetic semiconductor (Ga,Mn)(As,P), we show that there is a large window of accessible experimental conditions (SAW amplitude/wave-vector, field amplitude/orientation) allowing irreversible switching. As this is a resonant process, the influence of the detuning of the SAW frequency to the magnetic system's eigenfrequency is also explored. Finally, another—nonresonant—switching mechanism is briefly contemplated and found to be applicable to (Ga,Mn)(As,P): SAW-assisted domain nucleation. In this case, a small perpendicular field is applied opposite the initial magnetization and the passage of the SAW lowers the domain nucleation barrier.

Thevenard, L.; Duquesne, J.-Y.; Peronne, E.; von Bardeleben, H. J.; Jaffres, H.; Ruttala, S.; George, J.-M.; Lemaître, A.; Gourdon, C.

2013-04-01

472

Electromechanical modulation of electrical conduction through organic thin films for switching applications  

E-print Network

Nanoelectromechanical (NEM) switches exhibit abrupt switching behavior and near-zero leakage current making them promising alternatives to conventional semiconductor switches. However, they require high actuation voltages ...

Niroui, Farnaz

2013-01-01

473

Critical care during epidemics  

PubMed Central

We recommend several actions that could improve hospitals' abilities to deliver critical care during epidemics involving large numbers of victims. In the absence of careful pre-event planning, demand for critical care services may quickly exceed available intensive care unit (ICU) staff, beds and equipment, leaving the bulk of the infected populace without benefit of potentially lifesaving critical care. The toll of death may be inversely proportional to the ability to augment critical care capacity, so critical care health care professionals must take the lead for planning and preparing to care for numbers of seriously ill patients that far exceed available ICU beds. PMID:16137366

Rubinson, Lewis; O'Toole, Tara

2005-01-01

474

Iron Inhibits Activation-induced Cytidine Deaminase Enzymatic Activity and Modulates Immunoglobulin Class Switch DNA Recombination*  

PubMed Central

Immunoglobulin (Ig) class switch DNA recombination (CSR) and somatic hypermutation (SHM) are critical for the maturation of the antibody response. Activation-induced cytidine deaminase (AID) initiates CSR and SHM by deaminating deoxycytidines (dCs) in switch (S) and V(D)J region DNA, respectively, to generate deoxyuracils (dUs). Processing of dUs by uracil DNA glycosylase (UNG) yields abasic sites, which are excised by apurinic/apyrimidinic endonucleases, eventually generating double strand DNA breaks, the obligatory intermediates of CSR. Here, we found that the bivalent iron ion (Fe2+, ferrous) suppressed CSR, leading to decreased number of switched B cells, decreased postrecombination I?-CH transcripts, and reduced titers of secreted class-switched IgG1, IgG3, and IgA antibodies, without alterations in critical CSR factors, such as AID, 14-3-3?, or PTIP, or in general germline IH-S-CH transcription. Fe2+ did not affect B cell proliferation or plasmacytoid differentiation. Rather, it inhibited AID-mediated dC deamination in a dose-dependent fashion. The inhibition of intrinsic AID enzymatic activity by Fe2+ was specific, as shown by lack of inhibition of AID-mediated dC deamination by other bivalent metal ions, such as Zn2+, Mn2+, Mg2+, or Ni2+, and the inability of Fe2+ to inhibit UNG-mediated dU excision. Overall, our findings have outlined a novel role of iron in modulating a B cell differentiation process that is critical to the generation of effective antibody responses to microbial pathogens and tumoral cells. They also suggest a possible role of iron in dampening AID-dependent autoimmunity and neoplastic transformation. PMID:22556412

Li, Guideng; Pone, Egest J.; Tran, Daniel C.; Patel, Pina J.; Dao, Lisa; Xu, Zhenming; Casali, Paolo

2012-01-01

475

Mechanical one-to-many fiber-optic switch.  

PubMed

A mechanical multimode fiber-optic switch has been developed which uses a spherical mirror mounted on a galvanometer scanner to switch multimode light from one to many other fibers located in a linear array in the one-to-one imaging plane of the mirror. Characteristics of the switch include (1) measured optical insertion loss less than 1.5 dB; (2) optical isolation greater than 37 dB; (3) switching rate of 300 Hz; (4) potential for greater than one-to-ten fiber switching; and (5) little degradation of device characteristics after 10(6) switchings between two output fibers spaced four fiber diameters apart. PMID:20212604

Spillman, W B

1979-06-15

476

Development, implementation, and test results on integrated optics switching matrix  

NASA Technical Reports Server (NTRS)

A small integrated optics switching matrix, which was developed, implemented, and tested, indicates high performance. The matrix serves as a model for the design of larger switching matrices. The larger integrated optics switching matrix should form the integral part of a switching center with high data rate throughput of up to 300 megabits per second. The switching matrix technique can accomplish the design goals of low crosstalk and low distortion. About 50 illustrations help explain and depict the many phases of the integrated optics switching matrix. Many equations used to explain and calculate the experimental data are also included.

Rutz, E.

1982-01-01

477

On-board packet switch architectures for communication satellites  

NASA Technical Reports Server (NTRS)

NASA Lewis Research Center is developing an on-board information switching processor for a multichannel communications signal processing satellite. The information switching processor is a flexible, high-throughput, fault tolerant, on-board baseband packet switch used to route user data among user ground terminals. Through industry study contracts and in-house investigations, several packet switching architectures were examined for possible implementation. Three contention-free switching architectures were studied in detail, namely the shared memory approach, the shared bus approach, and the shared memory per beam approach. These three switching architectures are discussed and the advantages and disadvantages of each approach are examined.

Shalkhauser, Mary JO; Quintana, Jorge A.

1993-01-01

478

Critical Thinking Community: CThink  

NSDL National Science Digital Library

One of the major learning steps of young scientists is to think critically. This fascinating site offers insight into the various aspects of critical thinking. Supported by the educational nonprofit Foundation for Critical Thinking, CThink targets two levels: the college and university, and the primary and secondary education communities. The site is further organized into Library, Resources, and Events sections. Within the Library section, users may choose to browse examples of the basic elements of critical thinking, the role of questions, the critical thinking process, or a (modest) glossary of critical thinking terms, among others. Resources contains guidelines and lessons on how to integrate critical thinking into the curriculum, and Events offers information on upcoming conferences, seminars, and academies, and gives information on CThink inservices.

479

Nanoeletromechanical switch and logic circuits formed therefrom  

DOEpatents

A nanoelectromechanical (NEM) switch is formed on a substrate with a source electrode containing a suspended electrically-conductive beam which is anchored to the substrate at each end. This beam, which can be formed of ruthenium, bows laterally in response to a voltage applied between a pair of gate electrodes and the source electrode to form an electrical connection between the source electrode and a drain electrode located near a midpoint of the beam. Another pair of gate electrodes and another drain electrode can be located on an opposite side of the beam to allow for switching in an opposite direction. The NEM switch can be used to form digital logic circuits including NAND gates, NOR gates, programmable logic gates, and SRAM and DRAM memory cells which can be used in place of conventional CMOS circuits, or in combination therewith.

Nordquist, Christopher D. (Albuquerque, NM); Czaplewski, David A. (Albuquerque, NM)

2010-05-18

480

Chalcogenide Nanoionic-based Radio Frequency Switch  

NASA Technical Reports Server (NTRS)

A nonvolatile nanoionic switch is disclosed. A thin layer of chalcogenide glass engages a substrate and a metal selected from the group of silver and copper photo-dissolved in the chalcogenide glass. A first oxidizable electrode and a second inert electrode engage the chalcogenide glass and are spaced apart from each other forming a gap therebetween. A direct current voltage source is applied with positi